ARTICLE | doi:10.20944/preprints201909.0093.v1
Subject: Chemistry, Analytical Chemistry Keywords: reduced graphene oxide nanosheets; gold nanoparticles; composite materials; glucose oxidase; direct electron transfer
Online: 9 September 2019 (08:14:26 CEST)
Graphene-based composites have been widely explored for electrode and electrocatalyst materials for electrochemical energy systems. In this paper, a novel composite material of the reduced graphene oxide nanosheets (rGON) with gold nanoparticles (NPs) (rGON-AuNP) is synthesized, and its morphology, structure and composition are characterized by SEM, HRTEM, XRD, EDX, FTIR, Raman, and UV-Vis techniques. To confirm this material’s electrochemical activity, a glucose oxidase (GOD) is chosen as the target reagent to modify the rGON-AuNP layer to form GOD/rGON-AuNP/glassy carbon (GC) electrode. Two pairs of distinguishable redox peaks, corresponding to the redox processes of two different conformational GOD on AuNP, are observed on the cyclic voltammograms of GOD/rGON-AuNP/GC electrode. Both cyclic voltammetry and electrochemical impedance spectroscopy are employed to study the mechanism of direct electron transfer from GOD to GC electrode on the rGON-AuNP layer. In addition, this GOD/rGON-AuNP/GC electrode shows catalytic activity toward glucose oxidation reaction.
COMMUNICATION | doi:10.20944/preprints201809.0297.v1
Subject: Chemistry, Electrochemistry Keywords: silicon nanowire (SiNW), hydrogen evolution reaction (HER), reduced graphene oxide
Online: 17 September 2018 (10:09:06 CEST)
Silicon-based photoelectrochemical (PEC) conversion system has recently gained attention with its ability to provide cost-efficient and superior photoresponsive behavior in regard to other various semiconductor photoelectrodes. Carbon-based co-catalysts have always shared the spotlight for being rendered as alternative metal-free electrocatalysts intended for hydrogen evolution reaction (HER). In particular, a representative carbon-derived material, reduced Graphene Oxide (rGO) has attracted much attention as a non-metal catalyst for efficient and durable HER. Herein, we have deposited rGO on silicon nanowire (SiNW) structure which shows the highest reduction in the overpotential for HER up to date. This could be attributed to the synergistic effects of rGO and SiNW with unique anisotropic morphology, facile tuning capabilities, and scalable fabrication methods. Combined with nanostructured photocathode, rGO deposited SiNW showed better applied bias photon to current conversion efficiency of 3.16%, which is 158 times higher than that of bare planar Si system. In regard to this development we believe that rGO-SiNW photoelectrodes would pave the way for state-of-the-art highly efficient non-metal catalysts for energy conversion technologies.
ARTICLE | doi:10.20944/preprints202107.0213.v1
Subject: Chemistry, Analytical Chemistry Keywords: laser reduced graphene oxide, grid electrode, graphene oxide, linear sweep voltammetry, carbaryl, pesticides.
Online: 9 July 2021 (10:15:49 CEST)
Laser reduced graphene oxide (LRGO) on a PET substrate was prepared in one-step to obtain the LRGO grid electrode for sensitive carbaryl determination. The grid form results in a grid distribution of different electrochemically active zones affecting the electroactive substance diffusion towards to the electrode surface and increasing the electrochemical sensitivity for carbaryl determination. Carbaryl is electrochemically irreversibly oxidized by the secondary amine moiety of the molecule with the loss of one proton and one electron in the pH range from 5 to 7 by LSV on the LRGO grid electrode with a scan rate of 300 mV/s. Some interference of the juice matrix molecules did not significantly affect the LSV oxidation current of carbaryl on the LRGO grid electrode after adsorptive accumulation without applied potential. The LRGO grid electrode can be used for LSV determination of carbaryl in fruit juices in the concentration range from 0.25 to 128 mg/L with LOD of 0.1 mg/L by. The fabrication of the LRGO grid electrode opens up possibilities for further inexpensive monitoring of carbaryl in other fruit juices and fruits.
ARTICLE | doi:10.20944/preprints202111.0209.v1
Subject: Materials Science, Nanotechnology Keywords: Graphene oxide; Green synthesis; Reduced graphene oxide; Hibiscus sabdariffa L. calyxes extracts
Online: 11 November 2021 (12:30:49 CET)
Owing to their extraordinary properties, carbon-based nanomaterials are gaining traction in biomedicine. Green synthesis is the cost-effective method for fabricating carbon-based nanomaterials due to its rapidity, renewable nature, and sustainability. This study emphasis on the graphene oxide (GO) reduction using a simple one-pot technique that does not require the use of toxic reducing agents. This article reports the green synthesis of reduced graphene oxide (RGO) using Hibiscus sabdariffa L. calyxes extract as the natural reducing agent. Additionally, this article also provides analysis RGO using X-ray diffraction (XRD), UV-Visible spectroscopy (UV-Vis), and Raman spectroscopy. XRD result showed that the GO peak at 11o diminished, and a new hump appear at 22o indicating that the GO is fully reduced when it is refluxed for 6 hours, at 100oC with 1:3 ratio of GO:PE. The UV-Vis data indicated absorption peak of GO (237 nm) and RGO (265 nm) at distinct locations. This finding shed new light on the enormous potential of Hibiscus sabdariffa L. calyxes extract for green GO reduction. As a result, this environmentally friendly method can help reduce dependence on chemical materials.
REVIEW | doi:10.20944/preprints202111.0056.v1
Subject: Materials Science, Nanotechnology Keywords: Green synthesis; Plant extract; Reduced graphene oxide; Applications; Graphene oxide
Online: 2 November 2021 (22:50:53 CET)
Graphene is a remarkable material with numerous applications. Due to its thin and lightweight design, it is ideal for a variety of applications. The synthesis of high-quality graphene in a cost-effective and environmentally friendly manner continues to be a significant challenge. Chemical reduction is considered to be the most advantageous method for preparing reduced graphene oxide (rGO). However, this process necessitates the use of toxic and harmful substances, which can have a detrimental effect on the environment and human health. Thus, to accomplish the objective, the green synthesis principle has prompted researchers worldwide to develop a simple method for green reduction of graphene oxide (GO), which is readily accessible, sustainable, economical, renewable, and environmentally friendly in nature. For example, the use of natural materials such as plants is generally considered safe. Furthermore, plants contain reducing and capping agents. The current review will focus on the discovery and application of rGO synthesis using extracts from a variety of different parts of the plant. The review aims to aid current and future researchers in their search for a novel plant extract that acts as a reductant in the green synthesis of rGO. The review aims to assist current and future researchers in their research for a novel plant extract that acts as a reductant in the green synthesis of rGO as well as their potential applications in a variety of industries.
ARTICLE | doi:10.20944/preprints201812.0275.v1
Subject: Materials Science, Nanotechnology Keywords: field emission; graphene; reduced graphene oxide; polymer composites; graphene ink; cold cathode; Fowler-Nordheim
Online: 24 December 2018 (11:31:38 CET)
Hydroiodic acid (HI) treated - reduced graphene oxide (rGO) ink/conductive polymeric composites are considered as promising cold cathodes in terms of high geometrical aspect ratio and low field emission (FE) threshold devices. In this study, four simple, cost-effective, solution-processed approaches for rGO-based field effect emitters were developed, optimized and compared; rGO layers were coated on a) n+ doped Si substrate, b) n+-Si/P3HT:rGO, c) n+-Si/PCDTBT:rGO and d) n+-Si/PCDTBT:PC71BM:rGO composites, respectively. The fabricated emitters were optimized by tailoring the concentration ratios of their preparation and field emission characteristics. In a critical composite ratio, FE performance was remarkably improved compared to the pristine Si, as well as n+-Si/rGO field emitter. In this context, the impact of various materials, such as polymers, fullerene derivatives, as well as different solvents on rGO function reinforcement and consequently on FE performance upon rGO-based composites preparation was investigated. The field emitter consisted of n+-Si/PCDTBT:PC71BM(80%):rGO(20%)/rGO displayed a field enhancement factor of ∼2850, with remarkable stability over 20h and low turn-on field in 0.6V/μm. High-efficiency graphene-based FE devices realization paves the way towards low-cost, large-scale electron sources development. Finally, the contribution of this hierarchical, composite film morphology was evaluated and discussed.
ARTICLE | doi:10.20944/preprints201810.0631.v1
Subject: Engineering, Biomedical & Chemical Engineering Keywords: E. coli O157:H7; IgG; nonspecific binding; reduced graphene oxide; linear sweep voltammetry; electrical impedance spectroscopy
Online: 26 October 2018 (12:02:15 CEST)
Immunosensors have been widely developed to use antibodies to detect a pathogen of interest; it is interesting to look at the effect of nonspecific antibody binding to E. coli using electrochemical methods. IgG antibody not specific to E. coli O157:H7 was crosslinked onto a screen-printed carbon electrode. The presence of E. coli at 4, 4 × 102, 4 × 105, and 4 × 108 CFU/mL on the electrode surface was detected via linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Current transfer at both electrodes was reduced as the concentration of bacteria increased; however, the calibration of number of cells to decreased current was nonlinear for IgG-modified electrodes. The nonlinearity is confirmed by EIS measurements which showed highest impedance at 4 CFU/mL E. coli when impedance should be the lowest. FESEM images showed higher binding of cells when IgG is present compared to electrodes with reduced graphene oxide (rGO) alone. Electrodes with rGO alone show less attachment of E. coli, with EIS showing a linear calibration profile, while LSV shows not much difference in current values for all concentrations aside from the highest concentration. These results suggest that nonspecific binding can provide false signals in electrochemical measurements, and it is crucial to provide proper controls.
COMMUNICATION | doi:10.20944/preprints201806.0452.v1
Subject: Engineering, Industrial & Manufacturing Engineering Keywords: alignments, dental pulp stem cells, nanofiber, neurogenesis, reduced graphene oxide
Online: 27 June 2018 (15:53:18 CEST)
Stem cells derived from dental tissues—dental stem cells—are flavored due to their easy acquisition. Among them, dental pulp stem cells (DPSCs) extracted from the dental pulp have many advantages such as high proliferation and highly purified population. Although their ability for neurogenic differentiation has been highlighted and neurogenic differentiation using electrospun nanofibers (NFs) has been performed, graphene-incorporated NFs have never been applied for DPSC neurogenic differentiation. Here reduced graphene oxide (RGO)-polycaprolactone (PCL) hybrid electrospun NFs were developed and applied for enhanced neurogenesis of DPSCs. First, RGO-PCL NFs were fabricated by electrospinning with incorporation of RGO and alignments, and their chemical and morphological characteristics were evaluated. Furthermore, in vitro NF properties such as influence on the cellular alignments and cell viability of DPSCs were also analyzed. The influences of NFs on DPSCs neurogenesis was also analyzed. The results confirmed that an appropriate concentration of RGO promoted better DPSC neurogenesis. Furthermore, the use of random NFs facilitated contiguous junctions of differentiated cells, whereas the use of aligned NFs facilitated aligned junction of differentiated cells along the direction of NF alignments. Our findings showed that RGO-PCL NFs can be a useful tool for DPSC neurogenesis, which will help regeneration in neurodegenerative and neurodefective diseases.
ARTICLE | doi:10.20944/preprints201811.0605.v1
Subject: Chemistry, Analytical Chemistry Keywords: cationic pillararene; host–guest recognition; reduced graphene; trinitrophenol
Online: 28 November 2018 (02:49:49 CET)
We describe a selective and sensitive fluorescence platform for the detection of trinitrophenol (TNP) based on competitive host–guest recognition between pyridine-functionalized pillararene (PCP6) and probe (acridine orange, AO) that used PCP6-functionalized reduced graphene (PCP6-rGO) as the receptor. TNP is an electron-deficient and negative molecule which is captured by PCP6 via electrostatic interactions and π-π interactions. Therefore, a selective and sensitive fluorescence sensor for TNP detection is developed. It has a low detection limit of 0.0035 μM (S/N=3) and a wider linear response of 0.01−5.0 and 5.0−125.0 for TNP. The sensing platform is also used to test TNP in two water and soil samples with satisfying results. This suggests that this approach has potential applications for the determination of TNP.
ARTICLE | doi:10.20944/preprints202201.0085.v1
Subject: Materials Science, Nanotechnology Keywords: few-layer graphene; structural defects; self-propagating high-temperature synthesis; Stone-Wales defects; graphene nanostructures, carbon nanotubes, reduced graphene oxide.
Online: 6 January 2022 (12:07:39 CET)
A quantitative method is proposed to determine of Stone-Wales defects for carbon nanostructures with sp2 hybridization of carbon atoms. The technique is based on the diene synthesis reaction (Diels-Alder reaction). The proposed method was used to determine Stone-Wales defects in the few-layer graphene (FLG) nanostructures synthesized by the self-propagating high-temperature synthesis (SHS) process, in reduced graphene oxide (rGO) synthesized based on the method of Hammers and in the single-walled carbon nanotubes (SWCNT) TUBAL trademark, Russia. Our research has shown that the structure of FLG is free of Stone-Wales defects, while the surface concentration of Stone-Wales defects in TUBAL carbon nanotubes is 1.1×10-5 mol/m2 and 3.6×10-5 mol/m2 for rGO.
ARTICLE | doi:10.20944/preprints201811.0356.v1
Subject: Medicine & Pharmacology, Pharmacology & Toxicology Keywords: crenotheraphy, reduced glutathione, rheumatoid arthritis, hydrogen sulfide
Online: 15 November 2018 (10:33:25 CET)
The tripeptide-glutathione (GSH, γ-L-glutamyl-L-cysteinyl-glycine) is one of the most important low molecular antioxidant in human body. Enhancing GSH and associated enzymes represents an aim in the search for cytoprotective strategies against cancer, neurologic degeneration, pulmonary and inflammatory conditions, as well as rheumatoid arthritis (RA).The objective of the study was to agree whether crenotherapy (drinking therapy) with sulfide/hydrogen sulfide (SHS) waters from “Zuzanna” spring located in the area of Busko-Zdrój in Poland leads to increasing of reduced glutathione (GSH) content in human blood. SHS water in distinct from mineral water is characterised by specific pharmacokinetic, invariable content and natural microbiological purity. SHS waters contain at least 1 g of total sulfur per kilogram of water and a treatment effect also depends on other bioelements. The method employing capillary electrophoresis with UV detector for the analysis of glutathione in human blood was developed. The group of 106 volunteers consisted of both women and men, in different age range. The therapy with SHS waters lasted 2 weeks. We recently demonstrated that the administration of hydrogen sulfide (H2S) in SHS waters increases GSH concentration in blood, and therefore crenotherapy could be used in therapeutics.
ARTICLE | doi:10.20944/preprints201707.0063.v1
Subject: Life Sciences, Microbiology Keywords: Sulfur reduced species; Biofilms; Chalcopyrite, Biooxidation; Hydrophobicity
Online: 21 July 2017 (17:31:25 CEST)
A bioelectrochemical study of charge transfer in the biofilm/chalcopyrite interface was performed to investigate the effect of surficial sulfur reduced species (SRS), as non-stochiometric compounds or polysulfides (Sn2-), and elemental sulfur (S0) on a biofilm structure during the earliest stages (1, 12 and 24 h) of chalcopyrite biooxidation by A. thiooxidans alone and adding Leptospirillum sp. The surface of massive chalcopyrite electrodes was exposed to the bacteria, which were analyzed electrochemically, spectroscopically, and microscopically. At the studied earlier times, charge transfer and significant differences in the biofilm structure were detected, depending on the presence of Leptospirillum sp. acting on A. thiooxidans biofilms. Such differences were a consequence of a continuous chalcopyrite pitting and promoting changes in biofilm hydropathy. A. thiooxidans modifies the reactive properties of SRS and favors an acidic dissolution, which shifts into ferric when Leptospirillum sp. is present. A. thiooxidans allows H+ and Fe3+ diffusion, and Leptospirillum sp. allows surpassing the charge transfer (reactivity) barrier between the mineral interface and the ions. The observed changes of hydropathy on the interface are associated to ions and electrons activity and transfer. Finally, a model of S0 biooxidation by A. thiooxidans alone or with Leptospirillum sp., is proposed.
ARTICLE | doi:10.20944/preprints202111.0025.v1
Subject: Engineering, Electrical & Electronic Engineering Keywords: Bandwidth Employment; Real time protocol; TCP; header reduced
Online: 1 November 2021 (15:52:52 CET)
Timeworn telecommunication are progressively being substituted by a new one that run over IP networks, which is recognized as voice over internet protocol (VoIP). VoIP has a number of qualities (e.g., inexpensive call rate), which make it progressively widespread in the telecommunication domain. However, VoIP faces plentiful obstacles that slow its growth. One of the major obstacles is poorly utilizing the network bandwidth. A number of techniques have been offered to handle this obstacle, including packet multiplexing techniques. This paper designs an original multiplexing techniques, called packet multiplexing and carrier header (PM-CH), to decrease the quantity of the bandwidth consumed by VoIP. PM-CH protect the bandwidth by multiplexing the packets in a header and using the Timestamp field in the RTP header. The achievement of the PM-CH technique was examined depends on connection capacity and payload shortening. Simulation outcomes show that the PM-CH technique outperforms the contrast technique in the two factors. For instance, the PM-CH technique’s connection capacity outperforms the comparable technique by 58.9% when the connection bandwidth is 1000 kbps. Consequently, the PM-CH technique attains its objective of reducing the unexploited bandwidth caused by VoIP.
ARTICLE | doi:10.20944/preprints202002.0430.v2
Subject: Life Sciences, Biotechnology Keywords: Co-culture; Reduced-serum; Wound bed; Fibroblasts; Keratinocytes
Online: 12 March 2020 (13:24:46 CET)
Contact-based co-culture of fibroblasts and keratinocytes is important to study the structure and functions of the wound bed. Co-culture of these two cell types in direct contact with each other has been challenging, requiring high serum concentrations (up to 10%), feeder systems and a range of supplemental factors. These approaches are not only technically demanding, but also present scientific, cost and ethical limitations associated with high-serum concentrations. We have developed two reduced-serum approaches (1-2%) to support contact-based co-culture of human dermal fibroblasts (HDFa) and human epidermal keratinocytes (HaCaT). The two approaches include (1) Specialized cell culture media for each cell type mixed in a 1:1 ratio (KGM+FGM), and (2) Minimal media supplemented with cell-specific growth factors (MEM+GF). Co-culture could be successfully achieved by co-seeding (two cell types were introduced simultaneously), or in a layered fashion (keratinocytes seeded on top of confluent fibroblasts). With wound scratch assays, the co-cultured platforms could demonstrate cell proliferation, migration and wound closure. The reduced-serum conditions developed are simple, easy to formulate and adopt, and based on commonly-available media components. These contact-based co-culture approaches can be leveraged for wound and skin studies, and tissue bioengineering applications, potentially reducing concerns with high-serum formulations.
REVIEW | doi:10.20944/preprints202301.0459.v1
Subject: Life Sciences, Biotechnology Keywords: silk, biocompatibility, reduced immune response, silk hydrogel, biodegradation, biomaterial
Online: 25 January 2023 (14:19:07 CET)
Silk is a globally renowned abundant biopolymer obtained from various sources of the Lepidoptera family, among which the most commonly used and researched are spider silk and silk worm silk. All varieties of silk have beneficial characteristics such as high tensile strength, biocompatibility, producing a reduced immune response in a biological system, biodegradability, and the ability to withstand environmental stresses as well. These features make silk suitable for a number of applications as a biomaterial. The vast potential of silk and its proteins in cosmetics, oncology, tissue engineering, TOC screenings, for preserving food, cosmetic product as a silk gel and bioremediation makes it a well-sought biopolymer among researchers. Experiments over the years have revealed that biomaterials constituting silk are very potent but are yet to be scaled up for commercial uses, but the various advantageous properties of silk biomaterial far overshadows the impeding problems of production.
ARTICLE | doi:10.20944/preprints201907.0183.v1
Subject: Chemistry, Physical Chemistry Keywords: electrophoretic deposition; photocatalysis; TiO2; reduced graphene oxide; water purification
Online: 15 July 2019 (11:59:23 CEST)
The preparation of immobilized graphene–based photocatalyst layers is highly desired for environmental applications. In this study, the preparation of an immobilized reduced graphene oxide (rGO)/TiO2 composite by electrophoretic deposition (EPD) was optimized. It enabled quantitative deposition without sintering and without the use of any dispersive additive. The presence of rGO had beneficial effects on the photocatalytic degradation of 4-chlorophenol in an aqueous solution. A marked increase in the photocatalytic degradation rate was observed, even at very low concentrations of rGO. Compared with the TiO2 and GO/TiO2 reference layers, use of the rGO/TiO2 composite (0.5 wt% of rGO) increased the first-order reaction rate constant by about 70%. This enhanced performance was due to the increased formation of hydroxyl radicals that attacked the 4-chlorophenol molecules. The direct charge transfer mechanism had only limited effect on the degradation. Thus, EPD-prepared rGO/TiO2 layers appear to be suitable for environmental application.
ARTICLE | doi:10.20944/preprints201807.0394.v1
Subject: Chemistry, Food Chemistry Keywords: reduced-alcohol wine; solid-phase microextraction; gas chromatography; chemometrics
Online: 21 July 2018 (12:47:05 CEST)
The important sampling parameters of a headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) procedure, extraction temperature, extraction time and sample volume were optimized to quantify 23 important impact odorants in reduced alcohol red and white wines. A three-factor design of Box-Behnken experiments was used to determine optimized sampling conditions for each analyte, and a global optimized condition at every ethanol concentration of interest determined using a desirability function that accounts for a low signal response for compounds. Shiraz and Chardonnay wines were dealcoholized from 13.7 and 12.2% v/v ethanol respectively, to 8 and 5% v/v, using a commercially available membrane-based technology. A sample set of the reduced alcohol wines were also reconstituted to their natural ethanol level to evaluate the effect of ethanol content reduction on volatile composition. The three-factor Box-Behnken experiment ensured an accurate determination of the headspace concentration of each compound at each ethanol concentration, allowing comparisons between wines at varying ethanol levels to be made. Overall, the results showed that the main effect of extraction temperature was considered the most critical factor when studying the equilibrium of reduced alcohol wine impact odorants. The impact of ethanol reduction upon the concentration of volatile compounds clearly resulted in losses of impact odorants from the wines. The concentration of most analytes decreased with dealcoholization compared to that of the natural samples. Significant differences were also found between the reconstituted volatile composition and 5% v/v reduced alcohol wines, revealing that the dealcoholization effect is the result of a combination between the type of dealcoholization treatment and reduction in wine ethanol content.
ARTICLE | doi:10.20944/preprints201803.0081.v1
Online: 12 March 2018 (06:46:12 CET)
The past two decades has seen a growing demand for high-power, high-voltage utility scale inverters mostly fueled by the integration of large solar PV and wind farms. Multilevel inverters have emerged as the industry choice for these megawatt range inverters because their reduced voltage stress, capable of generating an almost sinusoidal voltage, in-built redundancy, among others. This paper present a new Switched-Source Multilevel Inverter (SS MLI) architecture. The new inverter show superior over existing topologies. It has reduced voltage stress on the semiconductor, uses less number of switches –reduced size/weight/cost and increased efficiency. The new SSMLI is comprised of two voltage sources (V1, V2) and 6 switches. It is capable of generating 5-level output voltage in symmetric modes (i.e., V1 = V2), and 7-level output voltage in asymmetric modes (i.e., V1 ≠ V2). To demonstrate the validity of the proposed inverter, simulations results using MATLAB® /Simulink® for 5- and 7-level output voltages are presented . The simulations are also verified experimentally using a laboratory prototype.
ARTICLE | doi:10.20944/preprints202102.0495.v1
Subject: Materials Science, Biomaterials Keywords: Visible light; Ofloxacin; Reduced graphene oxide; photocatalytic degradation; photocurrent density
Online: 22 February 2021 (16:27:01 CET)
The ternary Bi2MoO6-reduced graphene oxide (rGO)-TiO2 catalyst were synthesized using a simple hydrothermal method. The improvement of the photocatalytic decomposition efficiency of Bi2MoO6-rGO-TiO2 composite is 92.3% than the pure and binary photocatalyst. The effects of operational parameters like catalyst ratio, the different catalyst, different ratio rGO and different pH, have been analyzed. As prepared ternary photocatalyst is low Photoluminescence and high photocurrent density responsible, it exhibited that photon-induced electron and hole-recombination were suppressed and also charged separation is effective. The present study shows the rGO is an excellent electron transfer performance and enhanced the photocatalytic reaction stability.
ARTICLE | doi:10.20944/preprints202101.0535.v1
Subject: Keywords: annual weeds; conservation agriculture; perennial weeds; reduced tillage; weed seedbank
Online: 26 January 2021 (11:35:27 CET)
When farmers first shift from conventional tillage (CT) to conservation agriculture (CA) practice the control of weeds may be more difficult due to the absence of tillage. However, in the longer term (3-5 years), CA changes to weed dynamics may alter the weed seedbank. The nature of weed seedbank changes over time in intensively cropped rice-based rotations, that are typical of the Eastern Gangetic Plain, are not well understood. Three long term CA experiments were sampled (at Rajbari after 3 years and Rajshahi after 5 years) for effects of decreased soil disturbance strip planting (SP) and bed planting (BP) at both sites and Zero tillage (ZT) at Rajbari, increased retention of standing residues of previous crops (20 vs 50 %). The weed seedbank in 0-15 cm soil was quantified by assessing emergence from trays a net-house experiment during January-December 2016. The year-round count of emerged weeds revealed the fewest number of weed species (especially broadleaf weeds) and lowest weed density in SP followed by CT, BP, and ZT with 50% crop residues. The SP, BP, and ZT produced a higher number of perennials weeds than annual weeds, which was the opposite of CT. The continuous practice of SP and increased crop residue retention for 3 or more years decreased the size of weed seedbank but increased the relative proliferation of perennial weeds compared to CT. Weed seedbank size in SP was even smaller than BP and ZT.
ARTICLE | doi:10.20944/preprints201906.0153.v1
Subject: Mathematics & Computer Science, Computational Mathematics Keywords: reduced-order model; fluid dynamics; neural network; multistep method; optimization
Online: 17 June 2019 (05:46:09 CEST)
In this effort we propose a data-driven learning framework for reduced order modeling of fluid dynamics. Designing accurate and efficient reduced order models for nonlinear fluid dynamic problems is challenging for many practical engineering applications. Classical projection-based model reduction methods generate reduced systems by projecting full-order differential operators into low-dimensional subspaces. However, these techniques usually lead to severe instabilities in the presence of highly nonlinear dynamics, which dramatically deteriorates the accuracy of the reduced-order models. In contrast, our new framework exploits linear multistep networks, based on implicit Adams-Moulton schemes, to construct the reduced system. The advantage is that the method optimally approximates the full order model in the low-dimensional space with a given supervised learning task. Moreover, our approach is non-intrusive, such that it can be applied to other complex nonlinear dynamical systems with sophisticated legacy codes. We demonstrate the performance of our method through the numerical simulation of a two-dimensional flow past a circular cylinder with Reynolds number Re = 100. The results reveal that the new data-driven model is significantly more accurate than standard projection-based approaches
ARTICLE | doi:10.20944/preprints201804.0130.v1
Subject: Medicine & Pharmacology, General Medical Research Keywords: public; tobacco; risk; modified; reduced; nicotine; non-combustible; health; smoking; harm
Online: 10 April 2018 (15:53:43 CEST)
Philip Morris International (PMI) has developed the Population Health Impact Model (PHIM) to quantify, in the absence of epidemiological data, the effects of marketing a candidate modified risk tobacco product (cMRTP) on the public health of a whole population. Various simulations were performed to understand the harm reduction impact on the U.S. population over a 20-year period under various scenarios. The overall reduction in smoking attributable deaths (SAD) over the 20-year period was estimated as 934,947 if smoking completely went away and between 516,944 and 780,433 if cMRTP use completely replaces smoking. The reduction in SADs was estimated as 172,458 for the World Health Organization (WHO) 2025 Target and between 70,274 and 90,155 for the gradual cMRTP uptake. Combining the scenarios (WHO 2025 Target and cMRTP uptake), the reductions were between 256,453 and 268,796, depending on the cMRTP effective dose. These results show how a cMRTP can reduce overall population harm additionally to existing tobacco control efforts.
ARTICLE | doi:10.20944/preprints202301.0419.v1
Subject: Chemistry, Other Keywords: Photodegradation; Ciprofloxacin; Levofloxacin; Molybdenum disulfide; Reduced Graphene Oxide; Zin oxide; Gold nanoparticles
Online: 24 January 2023 (03:02:13 CET)
November 15th, 2022 was selected as the day where the human population reached the 8 billion mark . This new reality will force the governments around the world to find ways to sustainably produce and secure food, water, and energy for their countries [2-4]. In terms of water, its quality and availability has been a matter of great concern in recent decades , especially with the emergence of new organic and inorganic pollutants . Among organic contaminants, the detection of trace amounts of fluoroquinolone antibiotics, such as ciprofloxacin (CFX) and levofloxacin (LFX), in natural water bodies, has been of great concern in the scientific community [7,8]. Some of the side effects of the consumption of these antibiotics are nausea, diarrhea, abdominal pain, rash, low sugar levels, and antibiotic resistance to bacterial infections, among others [9,10]. It was estimated that in 2019 more than 1.27 million people died due to antibiotic-resistant bacterial infections , and this number is expected to rise to 10 million by 2050, if the trend continues . Because of this, new ways to degrade antibiotics from water have been developed over the years. A method that has been implemented for some time is the use of photocatalysts for the degradation of these compounds in water . Semiconductors such as titanium oxide (TiO2), zinc oxide (ZnO), zinc sulfide (ZnS), cadmium sulfide (CdS), strontium peroxide (SnO2), or tungsten trioxide (WO3), among others, are commonly used in photocatalytic processes [14-16]. Zinc oxide has been widely used due to its low cost and stability in aqueous solution, easy production, and because it is an environmentally friendly material [17,18]. It has been identified that some of the disadvantages of ZnO as photocatalyst are photocorrosion, recombination of electron-hole pairs, fast backward reactions, and inability to use visible light . Multiple approaches have been implemented over the years to reduce these limitations. One of them is the use of noble metals such as platinum (Pt), gold (Au), or even silver (Ag) as cocatalysts [15-17,19]. These metals can increase the photocatalytic activity by reducing the recombination of electron-hole pairs, as well allowing the use of visible light . For example, Quin and coworkers  prepared a bio-inspired hierarchical assembly of carbonized spinach leaves@Au/ZnO for the degradation of CFX under visible light. The results showed a degradation of 61% of the antibiotic in a period of 180 minutes. Chankhanittha et al.  developed different Ag@ZnO composites for the complete degradation of red dye and ofloxacin antibiotic in 25 and 80 minutes, respectively. The researchers attributed the improved photoactivity to the high electron-hole separation efficiency at the photocatalyst interface, as well as the creation of the Schottky barrier at the silver-zinc oxide interface.
ARTICLE | doi:10.20944/preprints202207.0455.v1
Subject: Engineering, Control & Systems Engineering Keywords: reduced-order control; rank constraint; linear matrix inequality; alternating projection; convex optimization
Online: 29 July 2022 (09:50:27 CEST)
In this paper, we propose an efficient numerical computation method of reduced-order controller design for linear time-invariant systems. The design problem is described by linear matrix inequalities (LMIs) with a rank constraint on a structured matrix, due to which the problem is NP-hard. Instead of the heuristic method that approximates the matrix rank by the nuclear norm, we propose a numerical projection onto the rank-constrained set based on the alternating direction method of multipliers (ADMM). Then the controller is obtained by alternating projection between the rank-constrained set and the LMI set. We show the effectiveness of the proposed method compared with existing heuristic methods, by using 95 benchmark models from the COMPLeib library.
REVIEW | doi:10.20944/preprints202111.0119.v2
Subject: Life Sciences, Biotechnology Keywords: phototherapy; cancer; graphene oxide; reduced graphene oxide; graphene quantum dots; carbon dots
Online: 26 November 2021 (11:10:10 CET)
Within phototherapy, a grand challenge in clinical cancer treatments is to develop a simple, cost-effective, and biocompatible approach to treat this disease using ultra-low doses of light. Carbon-based materials (CBM), such as graphene oxide (GO), reduced GO (r-GO), graphene quantum dots (GQDs), and carbon dots (C-DOTs), are rapidly emerging as a new class of thera-peutic materials against cancer. This mini-review summarizes the progress in lasts years re-garding the applications of CBM in photodynamic (PDT) and photothermal (PTT) therapies for tumor destruction. The current understanding of the performance of modified CBM, hybrids and composites, is also addressed. This approach seeks to achieve an enhanced healing action by im-proving and modulating the properties of CBM to treat various types of cancer. Metal oxides, organic molecules, biopolymers, therapeutic drugs, among others, have been combined with CBM to treat cancer by PDT, PTT, or synergistic therapies.
ARTICLE | doi:10.20944/preprints201908.0235.v1
Subject: Biology, Agricultural Sciences & Agronomy Keywords: endophytic bacteria; indole-3-acetic acid; cadmium accumulation; phosphate solubilization; reduced glutathione
Online: 23 August 2019 (04:06:54 CEST)
Cadmium (Cd) is a heavy metal that suppresses plant growth; however, application of endophytic bacteria can increase resistance of plants against Cd, as well as improve plant growth. Two bacterial endophytic strains were isolated from Solanum nigrum and were identified as Serratia sp. AI001 and Enterobacter sp. AI002 by 16S DNA sequencing. Strains AI001 and AI002, tolerated up to 25 mg/mL Cd in broth culture and showed phosphate solubilization potential in Pikovskaya agar medium. AI001 and AI002 produced indole-3-acetic acid, which was confirmed by gas spectrometry-mass chromatography. Brassica plants stressed with 0, 5, 15, and 25 mg/L Cd showed significant decrease in plant growth, chlorophyll content and biomass, and significant increase in Cd dose-dependent electrolyte leakage. Inoculation of strain AI001 or AI002 significantly enhanced the plant growth attributes of shoot length, root length, chlorophyll content, and biomass as compared to those in uninoculated plants. Reduced glutathione contents in plants stressed with different concentrations of Cd also increased with inoculation of AI001 and AI002. The reason of Cd resistance enhancement in plants by inocula could be due to their greater plant growth promoting activities as well as their antioxidative response.
ARTICLE | doi:10.20944/preprints201801.0040.v1
Subject: Medicine & Pharmacology, Cardiology Keywords: biomarker; heart failure with reduced ejection fraction (HFrEF); cBIN1; cBIN1 Score (CS)
Online: 7 January 2018 (12:51:36 CET)
Objective: We determined, in stable ambulatory heart failure with reduced ejection fraction (HFrEF) subjects and matched controls, the capability of a novel blood based cardiac-specific cBIN1 Score (CS), which assesses the health of cardiac muscle, to identify patients with known heart failure (HF) and to prognosticate future hospitalization. Background: Limited clinical tools are available in assessing cardiac muscle health in stable ambulatory patients. Cardiac bridging integrator 1 (cBIN1) is a cardiomyocyte t-tubule membrane scaffolding protein which regulates calcium signaling in cardiomyocytes, decreases in failing muscle, and is present in plasma in levels that correlate with cardiac content. We hypothesize that CS, a normalized index of plasma cBIN1 concentration, can function as a diagnostic and prognostic biomarker of HF. Methods: Plasma cBIN1 concentration is measured by an ELISA test, and CS is calculated as the natural log of the ratio of a constant population mean cBIN1 to measured cBIN1 concentration. We determined CS among 125 clinically stable individuals with HFrEF (LVEF ≤ 40%) (mean age 56 ± 10 years old, 79% men) and 125 age, sex matched volunteers with no known history of HF. We obtained plasma concentrations of NT-proBNP, a marker of volume status, as comparison. Baseline co-morbidities and 18-month longitudinal clinical information were obtained through electronic medical records. Results: CS follows a normal distribution with a median of 0 in the control population and median is significantly increased among HFrEF patients to 1.8 (IQR 1.4 – 2.1, p < 0.0001). CS diagnosed HFrEF with a receiver operating characteristic (ROC) area under the curve (AUC) of 0.93 (AUC is 0.98 for NT-proBNP, and combined CS and NT-proBNP AUC is 0.99). Unlike NT-proBNP, CS does not correlate with body mass index (BMI) in either the control or HFrEF population (Pearson’s r = -0.15, p = 0.12; Pearson’s r = 0.003, p = 0.97, respectively). NT-proBNP significantly correlates with renal function (Pearson’s r = -0.37, p = 0.001), while CS also has no correlation (Pearson’s r = 0.03, p = 0.71). During an 18-month follow-up, a high CS ≥ 1.8 at the initial visit predicted future cardiovascular hospitalizations (38% vs. 21%, p = 0.04, hazard ratio 2.0). NT-proBNP did not predict future cardiovascular hospitalizations. Conclusions: Plasma cBIN1 based CS is insensitive to BMI and renal function and differentiates myocardial health between patients with HFrEF versus matched controls. An abnormally high CS reflected poor intrinsic myocardial health and can predict future 18-month cardiac hospitalization in stable ambulatory patients.
ARTICLE | doi:10.20944/preprints201703.0201.v1
Subject: Materials Science, General Materials Science Keywords: mesoporous TiO2; reduced graphene oxide; Ag nanoparticles; photocatalytic activity; visible light irradiation
Online: 27 March 2017 (12:01:25 CEST)
Mesoporous TiO2/reduced graphene oxide/Ag (TiO2/RGO/Ag) ternary nanocomposite with effective electrons transfer pathway is obtained by an electrostatic self-assembly method and photo-assisted treatment. Compared with bare mesoporous TiO2 (MT) and mesoporous TiO2/RGO (MTG), the ternary mesoporous TiO2/RGO/Ag (MTGA) nanocomposite exhibited superior photocatalytic performance for the degradation of MB under visible light, and the degradation rate reached 0.017 min-1, which was 3.4 times higher than that of MTG. It is proposed that Ag nanoparticles can form the local surface plasmon resonance (LSPR) to absorb the visible light and distract the electrons into MT, and RGO can accept the electrons from MT to accelerate the separation efficiency of carriers. The establishment of MTGA ternary nanocomposite make the three components act synergistic effect to enhance the photocatalytic performance.
ARTICLE | doi:10.20944/preprints202108.0027.v1
Subject: Life Sciences, Biochemistry Keywords: motor learning; fine motor coordination task; difficulty level; reduced feedback frequency; time pressure.
Online: 2 August 2021 (12:12:49 CEST)
Improving the acquisition and retention of a new motor skill is of great importance. The present study (i) investigated the effects of difficulty manipulation strategies (gradual difficulty), combined with different modalities of feedback (FB) frequency on performance accuracy and consistency when learning a novel fine motor coordination task, and (ii) examined relationships between novel fine motor task performance and executive function (EF), working memory (WM), and perceived difficulty (PD). Thirty-six, right-handed, novice physical education students volunteered to participate in this study. Participants were divided into three progressive difficulty groups (PDG), 100% visual FB (FB1), 50% FB (FB2), and 33% FB (FB3). Progressive difficulty was increased by the manipulation of the distance to the target; 2 m, 2.37 m, and 3.56 m. Three FB modalities were investigated (i.e.: 100% visual FB (100% FB), 50% reduced feedback condition (50% RFB), and 33% reduced feedback conditions (33% RFB)). Performance assessments were conducted following familiarization, acquisition, and retention learning phases. Two stress-conditions of dart throws were investigated (i.e.: free condition (FC) and time pressure condition (TPC)). After the learning intervention, data showed that, under the free condition, the 100% FB group had a significant improvement in accuracy during all learning phases. Under time pressure condition, for the 50% RFB and the 33% RFB group, the measured variable (accuracy and consistency) showed a significant linear improvement in performance. The association between the percentage of RFB frequencies and the task difficulty (50% group) may be a more appropriate and manageable cognitive load compared to the 33% RFB and the 100% FB group. The present findings could have practical implications for practitioners because, while strategies are clearly necessary for improving learning, the efficacy of the process appears to be essentially based on the characteristics of the learners.
ARTICLE | doi:10.20944/preprints202006.0320.v1
Subject: Engineering, Energy & Fuel Technology Keywords: District Heating Network; reduced-order model; building heat capacity; scalability; gray box model
Online: 28 June 2020 (08:26:31 CEST)
District heating networks have become widespread due to their ability to distribute thermal energy efficiently, which leads to reduced carbon emissions and improved air quality. The characteristics of these networks vary remarkably depending on the urban layout and system amplitude. Moreover, extensive data about the energy distribution and thermal capacity of different areas are seldom available. Design, optimization and control of these systems are enabled by the availability of fast and scalable models of district heating networks. This work addresses this issue by proposing a novel method to develop a scale-free model of large-scale district heating networks. Starting from coarse data available at the main substations, a physics-based model of the system aggregated regions is developed by identifying the heat capacity and heat loss coefficients. The model validation on the network of Västerås, Sweden, shows compatibility with literature data and can therefore be exploited for system design, optimization and control-oriented applications. In particular, the possibility to estimate the heat storage potential of network regions allows new smart management strategies to be investigated.
ARTICLE | doi:10.20944/preprints202106.0655.v1
Subject: Engineering, Automotive Engineering Keywords: Concrete; Mesoscale; Reduced order multiscale simulation; Microcracking; Micromechanics; Linear elastic fracture mechanics; Anisotropic damage
Online: 28 June 2021 (13:53:36 CEST)
Damage in concrete structures initiates as the growth of diffuse microcracks that is followed by damage localisation and eventually leads to structural failure. Weak changes such as diffuse microcracking processes are failure precursors. Identification and characterisation of these failure precursors at an early stage of concrete degradation and application of suitable precautionary measures will considerably reduce the costs of repair and maintenance. To this end, a reduced order multiscale model for simulating microcracking-induced damage in concrete at the mesoscale levelis proposed. The model simulates the propagation of microcracks in concrete using a two-scale computational methodology. First, a realistic concrete specimen that explicitly resolves the coarse aggregates in a mortar matrix was generated at the mesoscale. Microcrack growth in the mortar matrix is modelled using a synthesis of continuum micromechanics and fracture mechanics. Model order reduction of the two-scale model is achieved using clustering technique. Model predictions are calibrated and validated using uniaxial compression tests performed in the laboratory.
ARTICLE | doi:10.20944/preprints201912.0231.v2
Subject: Physical Sciences, Particle & Field Physics Keywords: four gravitational constants; electroweak fermion; reduced Planck’s constant; stellar mass limits; 3.5 keV photon; neutron life time
Online: 22 December 2019 (14:23:52 CET)
To understand the mystery of final unification, in our earlier publications, we proposed that there exist three atomic gravitational constants associated with electroweak, strong and electromagnetic interactions. During cosmic evolution, if one is willing to give equal importance to Higgs boson and Planck mass in understanding the massive origin of elementary particles, then it seems quite logical to expect a common relation in between Planck scale and Electroweak scale. Based on these two points, we noticed that, electroweak field seems to be operated by a primordial massive fermion of rest energy 585 GeV. It can be considered as the zygote of all elementary particles and galactic dark matter. H-bar seems to be a characteristic outcome of unified electroweak gravity. Electron rest mass seems to be a characteristic outcome of electroweak and strong gravity. Proton rest mass seems to be a characteristic outcome of electroweak, strong and electromagnetic gravity. Recently observed 3.5 keV photon seems to be an outcome of annihilation of charged baby lepton of rest energy 1.75 keV. Interesting point to be noted is that, Schwarzschild radius of electron is 0.48 nanometer and it needs further investigation with respect to emerging nano-science and technology. Proceeding further, by considering electromagnetic and weak gravitational constants, neutron life time can be understood.
ARTICLE | doi:10.20944/preprints201910.0107.v1
Subject: Engineering, Energy & Fuel Technology Keywords: hydrogen; methane pyrolysis; direct reduced iron; industrial decarbonization; iron and steel; electric arc furnace
Online: 9 October 2019 (11:33:17 CEST)
Reducing emissions from the iron and steel industry is essential to achieve the Paris climate goals. A new system to reduce the carbon footprint of steel production is proposed in this article by coupling hydrogen direct reduction of iron ore (H-DRI) and natural gas pyrolysis on liquid metal surface inside a bubble column reactor. If grid electricity from EU is used, the emissions would be 435 kg CO2/tls without considering methane leakage from the extraction, storage and transport of natural gas. Solid carbon, produced as a by-product of natural gas decomposition, finds applications in many industrial sectors, including as a replacement for coal in coke ovens. Specific energy consumption (SEC) of the proposed system is approximately 6.3 MWh per ton of liquid steel(tls). It is higher than other competing technologies, 3.48 MWh/tls for water electrolysis based DRI, and, 4.3-4.5 MWh/tls for natural gas based DRI and blast furnace-basic oxygen furnace (BF-BOF) respectively. Utilization of large quantities of natural gas, where the carbon remains unused, is the major reason for high SEC. Preliminary analysis of the system revealed that it has the potential to compete with existing technologies to produce CO2 free steel, if renewable electricity is used. Further studies on the kinetics of the bubble column reactor, H-DRI shaft furnace, design and sizing of components, along with building of industrial prototypes are required to improve the understanding of the system performance.
ARTICLE | doi:10.20944/preprints201808.0219.v1
Subject: Mathematics & Computer Science, Computational Mathematics Keywords: reduced order modeling; regularization; fluid dynamics; stochastic Burgers Equation; proper orthogonal decomposition; spatial filter
Online: 13 August 2018 (08:12:13 CEST)
In this paper, we introduce the evolve-then-filter (EF) regularization method for reduced order modeling of convection-dominated stochastic systems. The standard Galerkin projection reduced order model (G-ROM) yield numerical oscillations in a convection-dominated regime. The evolve-then-filter reduced order model (EF-ROM) aims at the numerical stabilization of the standard G-ROM, which uses explicit ROM spatial filter to regularize various terms in the reduced order model (ROM). Our numerical results based on a stochastic Burgers equation with linear multiplicative noise. It shows that the EF-ROM is significantly better results than G-ROM.
ARTICLE | doi:10.20944/preprints202010.0352.v1
Subject: Engineering, Control & Systems Engineering Keywords: Wind Farm Control; Axial Induction Control; Dynamic Mode Decomposition; Koopman Operator Theory; Reduced Order Model
Online: 16 October 2020 (14:29:54 CEST)
The high dimensions and governing non linear dynamics in wind farm systems make the design of numerical optimal controllers computationally expensive. A possible pathway to circumvent this challenge lies in finding reduced order models which can accurately embed the existing non linearities. The work here presented applies the ideas motivated by non linear dynamical systems theory - the Koopman Operator - to an innovative algorithm in the context of wind farm systems - Input Output Dynamic Mode Decomposition - to improve on the ability to model the aerodynamic interaction between wind turbines in a wind farm and uncover insights into the existing dynamics. It is shown that a reduced order linear state space model can reproduce the downstream turbine generator power dynamics and reconstruct the upstream turbine wake. It is further shown that the fit can be improved by judiciously choosing the Koopman observables used in the IODMD algorithm without jeopardizing the models ability to rebuild the turbine wake. The extensions to the IODMD algorithm provide an important step towards the design of linear reduced order models which can accurately reproduce the dynamics in a wind farm.
ARTICLE | doi:10.20944/preprints201911.0039.v1
Subject: Medicine & Pharmacology, Cardiology Keywords: heart failure; Sacubitril/valsartan; Neprilysin inhibition; reduced ejection fraction; echocardiography; Nt-Pro-BNP; hemodynamic; remodeling
Online: 4 November 2019 (11:20:22 CET)
Background: Sacubitril/valsartan has been shown to be superior to enalapril in reducing the risks of death and hospitalization for heart failure (HF). However the effect on cardiac performance remains unknown. We sought to evaluate the effects of sacubitril/valsartan on clinical, bioumoral and echocardiographic parameters in patients with HFrEF. Methods: Sacubitril/valsartan was administered to 205 HFrEF patients. Results: Among 230 patients (mean age 59 ± 10 years, 46% with ischemic heart disease) 205 (89%) completed the study. After a follow–up of 10.49 (2.93±18.44) months, the percentage of patients in NYHA class III changed from 40% to 17% (p<0.001). Median N–Type natriuretic peptide (Nt-proBNP) decreased from 1865 ± 2318 to 1514 ± 2205 pg/mL, (p=0.01). Furosemide dose reduced from 131.3 ± 154.5 to 120 ± 142.5 (p=0.047). Ejection fraction (from 27± 5.9% to 30 ± 7.7% (p<0.001) and E/A ratio (from 1.67 ± 1.21 to 1.42 ± 1.12 (p=0.002)) improved. Moderate to severe mitral regurgitation (from 30.1% to 17.4%; p=0.002) and tricuspid velocity decreased from 2.8 ± 0.55 m/sec to 2.64 ± 0.59 m/sec (p<0.014). CONCLUSIONS: Sacubitril/valsartan induce “hemodynamic reverse remodeling” and in association with Nt-proBNP concentrations lowering improve NYHA class despite a diuretic dose reduction.
ARTICLE | doi:10.20944/preprints202209.0425.v1
Subject: Mathematics & Computer Science, Probability And Statistics Keywords: High-dimensional time series; General Dynamic Factor Models; spiked covariance model; reduced-rank process; singular spectrum.
Online: 28 September 2022 (02:02:26 CEST)
For more than half a century, Manfred Deistler has been contributing to the construction of the rigorous theoretical foundations of the statistical analysis of time series and more general stochastic processes. Half a century of unremitting activity is not easily summarized in a few pages. In this short note, we chose to concentrate on a relatively little-known aspect of Manfred's contribution which nevertheless had quite an impact on the development of one of the most powerful tools of contemporary time series and econometrics: dynamic factor models.
ARTICLE | doi:10.20944/preprints201710.0103.v1
Subject: Mathematics & Computer Science, Information Technology & Data Management Keywords: reduced sigma set Square-Root Unscented Kalman Filter; pseudo-satellite; UAV; GPS/INS tightly-coupled system
Online: 16 October 2017 (06:35:24 CEST)
In this paper, firstly, some questionable formulas and conceptual oversights of previous reduced sigma set unscented transformation (UT) methods are revised through theoretical analysis. Then the revised UT methods based Kalman filters are used in a GPS/INS tightly-coupled system. The Kalman filter flows are the kind of square-root, since the square-root unscented Kalman filters (SRUKFs) can guarantee the stability of the system. By using the reduced sigma set SRUKFs (which contain simplex sigma set square-root unscented Kalman filter (S-SRUKF), spherical simplex sigma set square-root unscented Kalman filter (SS-SRUKF) and minimum sigma set square-root unscented Kalman filter (M-SRUKF)), the computation cost is greatly saved compared with the standard SRUKF, while the accuracy of the GPS/INS tightly-coupled system still maintained. The structure of the GPS/INS tightly-coupled system is in the form of error state, and the time updates of the state and the state covariance of SRUKFs are directly estimated without using UT, thus the computational time is also greatly saved. The pseudo-satellite is introduced to aid the system when the observation information is deficient, for example, when the GPS signal is deficient in the maneuver environment. By using the pseudo-satellite, the optimal performance of the system is guaranteed. Experiment of unmanned aerial vehicle (UAV) showed that the pseudo-satellite aided mechanism worked well.
REVIEW | doi:10.20944/preprints202202.0316.v1
Subject: Medicine & Pharmacology, Oncology & Oncogenics Keywords: Selenoprotein Glutathione Peroxidase 4 (GPX4); Reduced Glutathione (GSH); ferroptosis; lipid peroxidation; ferroptosis modulators; small molecules targeting GPX4
Online: 24 February 2022 (12:05:30 CET)
The selenoprotein glutathione peroxidase 4 (GPX4) is one of the main antioxidant mediators in the human body. Its central function involves the reduction of complex hydroperoxides into their respective alcohols often using reduced Glutathione (GSH) as a reducing agent. GPX4 has become a hotspot therapeutic target in biomedical research following its characterization as a chief regulator of ferroptosis, and its subsequent recognition as a specific pharmacological target for the treatment of an extensive variety of human diseases including cancers and neurodegenerative disorders. Several recent studies have provided insights into how GPX4 is distinguished from the rest of the glutathione peroxidase family, the unique biochemical properties of GPX4, how GPX4 is related to lipid peroxidation and ferroptosis, and how the enzyme may be modulated as a potential therapeutic target. This current report aims to review the literature underlying all these insights and present an up-to-date perspective on the current understanding of GPX4 as a potential therapeutic target.
ARTICLE | doi:10.20944/preprints202105.0213.v1
Subject: Materials Science, Biomaterials Keywords: PMMA: Polymethylmethacrylate; HRGO: Highly Reduced Graphene Oxide; DSC: Differential Scanning Calorimetry; FESEM: Field Emission Scanning Electron Microscopy.
Online: 10 May 2021 (15:27:44 CEST)
Bone cement, mainly based in PMMA, is commonly used in different arthroplasty surgical proce-dures, and its use is essential for prosthesis fixation. However, its manufacturing process reaches high temperatures that can produce necrosis in the patients' surrounding tissues. In order to con-tribute to avoid this problem, the addition of graphene could delay the polymerisation of the MMA and, simultaneously, contribute to the optimisation of the composite material's properties. This article analysed the effect of the addition of different percentages of Highly Reduced Graphene Oxide (HRGO) with different wt. % (0,10, 0,50 and 1,00) and surface densities (150, 300, 500 and 750 m2/g) on the physical, mechanical, and thermal properties of commercial PMMA-based bone cement and its processing. It was noticed that a lower sintering temperature would be reached with this addition, making it less harmful to use in surgery and as it reduces its adverse effects. In contrast, the materials' density does not show significant changes, which indicates that the addi-tion of HRGO does not significantly increase its porosity. Lastly, the mechanical properties are re-duced by almost 20 %. Nevertheless, these properties are high enough so that these new materials can still fulfil their structural function.
ARTICLE | doi:10.20944/preprints202211.0505.v1
Subject: Chemistry, Electrochemistry Keywords: hydrogen evolution reaction; hydrogen spillover; interfacial processes; supported catalysts; reduced graphene oxide; Kinetic Monte Carlo; volcano curve; hydrogen adsorption
Online: 28 November 2022 (08:37:23 CET)
The requirements for efficient replacement of fossil fuel, combined with the growing energy crisis, put hydrogen production into focus. Efficient and cost-effective electrocatalysts are needed for H2 production, and novel strategies for their discovery must be developed. Here we utilized Kinetic Monte Carlo (KMC) simulations to demonstrate that hydrogen evolution reaction (HER) can be boosted via hydrogen spillover to the support when the catalyst surface is largely covered by adsorbed hydrogen under operating conditions. Based on the insights from KMC, we synthesized a series of reduced graphene oxide-supported catalysts and compared their activities towards HER in alkaline media with that of corresponding pure metals. For Ag, Au, and Zn, the support effect is negative, but for Pt, Pd, Fe, Co, and Ni, the presence of the support enhances HER activity. The HER volcano, constructed using calculated hydrogen binding energies and measured HER activities, shows a positive shift of the strong binding branch. This work demonstrates the possibilities of metal|support interface engineering for producing effective HER catalysts and provides general guidelines for choosing novel catalyst-support combinations for electrocatalytic hydrogen production.
Subject: Medicine & Pharmacology, Allergology Keywords: Heart failure with reduced ejection fraction; Real-life practice; Sacubitril/valsartan; Left ventricular ejection fraction recovery; Implantable cardioverter defibrillator
Online: 5 May 2021 (10:30:13 CEST)
Background: our purpose is to assess the effectiveness and safety of sacubitril/valsartan (SV) in “real-world” patients with heart failure and reduced ejection fraction (HFrEF), including a broader spectrum of patients than those in clinical trials and evaluating variables not previously described in the literature. Methods: real-world study in HFrEF patients (N:204), both in and out-patients, who started SV between October 2017 and December 2018. We performed a prospective analysis with a 12-month follow-up. The study outcomes were effectiveness and safety, measured by individual parameters and combined endpoints, comparing the pre and post practice periods. Results: at the end of follow-up, an improvement of left ventricle ejection fraction (LVEF): 29.8% vs 33.7; p<0.0001, a decrease in NT-proBNP levels (3928 pg/mL vs 2902 pg/mL; p=0.012), number of hospital admissions (141 vs 35; p<0.0001) and percentage of patients with implantable cardioverter defibrillator (ICD) indication (79.9% vs 49.5%; p<0.0001) were observed. Of our population, 81.3% met a combined efficacy endpoint (defined by increase of LVEF, reduction of hospital admission or improvement in functional class). No differences were observed in parameters regarding safety. Conclusions: Sacubitril/valsartan has brought about a revolution in the therapeutic management of HFrEF patients and its use may raise questions about what is considered "optimal medical therapy" prior to implantation of cardiac devices.
ARTICLE | doi:10.20944/preprints202009.0418.v1
Subject: Engineering, Automotive Engineering Keywords: large sized lithium-ion battery; physic-based model; life prediction; scale-up model; reduced order cell model; electric vehicles
Online: 18 September 2020 (04:29:49 CEST)
Large lithium-ion batteries (LIBs) in electric vehicles and energy storage systems demonstrate different performance and lifetime compared to small LIB cells, owing to the size effects generated by the electrical configuration and property imbalance. However, the calculation time for performing life predictions with three-dimensional (3D) cell models is undesirably long. In this paper, a lumped cell model with equivalent resistances (LER cell model) is proposed as a reduced order model of the 3D cell model, which enables accurate and fast life predictions of large LIBs. The developed LER cell model is validated via the comparisons with results of the 3D cell models by simulating a 20-Ah commercial pouch cell (NCM/graphite) and the experimental values. In addition, the LER cell models are applied to different cell types and sizes, such as a 20-Ah cylindrical cell and a 60-Ah pouch cell.
CASE REPORT | doi:10.20944/preprints202210.0114.v1
Subject: Medicine & Pharmacology, Ophthalmology Keywords: CADASIL; small vessel disease; retinal and choroidal blood flow disturbance; reduced amplitude of the P50 wave in PERG; retinal drusen
Online: 10 October 2022 (07:01:45 CEST)
Abstract Aim of the study: Presentation of ophthalmic symptoms of Cerebral Autosomal Dominant Arteriopathy with Subcortical Infracts and Leucoencephalopathy (CADASIL). Material and methods: Clinical presentation of female patient with diagnosed CADASIL, manifested by transient loss of vision, migraine, convergence insufficiency, diplopia, increased deep tendon reflexes of upper left limb, subcortical infarcts, mood disturbances and dementia. Results: Confirmed NOTCH3 gene mutation (p.Cys212Gly), and presence of granular osmiophilic material (GOM) in cutaneous small vessel wall in immunohistochemistry laboratory test (IHC). Magnetic resonance imaging (MRI) revealed bilateral focal vasogenic lesions in white matter of cerebral hemisphere with single micro-focal infarct in the left external capsule. Furthermore, a left eye exophoria, a bilateral peripheral visual field loss of 20 degrees and a loss of nasolabial fold was confirmed during ophthalmic tests. An eye fundus examination as well as a fluorescein angiography (FA) revealed vessel constriction of retinal arteries and a peripheral retinal pigment epithelium (RPE) atrophy with focal drusen in the left eye. The doppler ultrasonography (USG) confirmed a decreased blood flow and an increased vascular resistance of the extraocular vessels. The pattern electroretinogram (PERG) revealed a reduced P50 wave amplitude in the patient’s left eye. Conclusions: intermittent blindness, migraine, convergence failure, diplopia with specific MRI signs, NOTCH3 mutation, and the presence of GOM in the skin of small blood vessels in a young or middle-aged patient suggests CADASIL. New observations include: atrophic changes in the RPE, hemodynamic disturbances in blood flow in the short posterior ciliary arteries and in the central retinal artery, single drusen in the retina, and a reduced amplitude of the P50 wave in PERG.
ARTICLE | doi:10.20944/preprints201911.0134.v1
Subject: Physical Sciences, Nuclear & High Energy Physics Keywords: four gravitational constants; compound reduced Planck’s constant; nuclear elementary charge; strong coupling constant; nuclear stability and binding energy; quark masses
Online: 12 November 2019 (16:53:07 CET)
To understand the mystery of final unification, in our earlier publications, we proposed two bold concepts: 1) There exist three atomic gravitational constants associated with electroweak, strong and electromagnetic interactions. 2) There exists a strong elementary charge in such a way that its squared ratio with normal elementary charge is close to reciprocal of the strong coupling constant. In this paper we propose that, can be considered as a compound physical constant associated with proton mass, electron mass and the three atomic gravitational constants. With these ideas, an attempt is made to understand nuclear stability and binding energy. In this new approach, nuclear binding energy can be fitted with four simple terms having one unique energy coefficient with a formula, where is an estimated mean stable mass number. With this new approach, Newtonian gravitational constant can be estimated in a verifiable approach with a model relation of the form, where is the Fine structure constant. Estimated and is 62 ppm higher than the CODATA recommended It needs further investigation. Proceeding further, an attempt is made to fit the recommended quark masses.
REVIEW | doi:10.20944/preprints202108.0133.v1
Subject: Chemistry, Analytical Chemistry Keywords: Carbon nanotubes, graphene, reduced graphene oxide, organic functionalization, dye, organic photovoltaics, dye sensitized solar cells, perovskite solar cells, photocatalytic hydrogen evolution
Online: 5 August 2021 (10:07:43 CEST)
This review proposes an overview on the use of organic functionalized carbon nanostructures (CNSs) into solar energy conversion schemes. Our attention has focused in particular on the contribution given by organic chemistry to the development of new hybrid materials that find application in dye sensitized solar cells (DSSC), organic photovoltaics (OPV), perovskite solar cells (PSC) and also in photocatalytic fuel production, focusing in particular on the most recent literature. The request for new materials able to accompany the green energy transition that are abundant, low cost, with low toxicity, from renewable sources has further increased the interest in CNSs that meet all these requirements. The inclusion of an organic molecule, thanks to both covalent and non-covalent interactions, into a CNS, leads to the development of a completely new hybrid material able of combining and improving the properties of both starting materials. Besides the numerical data, which unequivocally state the positive effect of the new hybrid material, we hope that these examples can be inspiring for further research in the field of photoactive materials from an organic point of view.
ARTICLE | doi:10.20944/preprints202212.0521.v1
Subject: Materials Science, Nanotechnology Keywords: multi-modal sensing devices; PDAC; reduced graphene oxide; layer-by-layer deposition; temperature monitoring; relative humidity measurements; volatile organic compounds; electrochemical sensing
Online: 28 December 2022 (01:18:48 CET)
Precise monitoring of different environmental parameters and contaminations during food processing and storage is a key factor for maintaining its safety and nutritional value. Thus, developing reliable, efficient, cost-effective sensor devices for these purposes is of utmost importance. In this paper, we show that Poly-(diallyl-dimethylammonium chloride)/reduced Graphene oxide (PDAC/rGO) films produced by a simple Layer-by-Layer deposition can be effectively used to monitor temperature, relative humidity and the presence of volatile organic compounds as indicators for spoilage odors. At the same time, they show potential for electrochemical detection of organophosphate pesticide dimethoate. By monitoring the resistance/impedance changes during temperature and relative humidity variations or upon the exposure of PDAC/rGO films to methanol, good linear responses were obtained in the temperature range of 10-100 °C, 15-95 % relative humidity, and 35 ppm - 55 ppm of methanol. Moreover, linearity in the electrochemical detection of dimethoate is shown for the concentrations in the order of 102 µmol dm−3. The analytical response to different external stimuli and analytes depends on the number of layers deposited, affecting sensors’ sensitivity, response and recovery time, and long-term stability. The presented results could serve as a starting point for developing advanced multimodal sensor devices and sensor arrays with high potential for analytical applications in food safety and quality monitoring.
ARTICLE | doi:10.20944/preprints201802.0058.v1
Subject: Engineering, Electrical & Electronic Engineering Keywords: brushless doubly fed induction generator; direct control; stand-alone; sliding-mode; resonant; reduced-order generalized integrator; variable-speed constant-frequency; wind energy conversion systems
Online: 7 February 2018 (08:39:56 CET)
In this paper, a novel voltage control strategy of stand-alone operation brushless doubly fed induction generator for variable speed constant frequency wind energy conversion systems was presented and discussed particularly. Based on the model of the generator power system, the proposed direct flux control strategy employs a nonlinear reduced-order generalized integrator based resonant sliding-mode control scheme to directly calculate and regulated the output value of converter which control winding stator required so as to eliminate the instantaneous errors of power winding stator flux, and no involving any synchronous rotating coordinate transformations. The stability, robustness and convergence capability of the proposed control strategy were described and analyzed. Owing to no extra current control loops involved, therefore simplifying the system configuration design and enhancing the transient performance. Constant converter switching frequency was achieved by using space vector pulse width modulation, which reduce the harmonic of generator terminal voltage. In addition, experimental results prove the feasibility and validity of the proposed scheme, and excellent steady and dynamic state performance is achieved.