ARTICLE | doi:10.20944/preprints201801.0025.v1
Subject: Earth Sciences, Environmental Sciences Keywords: freezing/melting desalination process; aqueous solutions of sodium chloride; theoretical diffusive models
Online: 4 January 2018 (07:08:51 CET)
Considering the important demand of fresh water and its scarce availability, water desalination is an interesting technology, producing about 44 Mm3/year worldwide, but, in general the most common desalination techniques are highly energy demanding. Freezing-Melting (F/M) desalination uses just up to 70% less thermal energy, but is the least used process mainly, due to the difficulty of the salt separation. This study proposes a model able to analyses the thermodynamic potential that allows the salt diffusion during the F/M process, using an aqueous solution of sodium chloride. This should allow to obtain a sensitive analysis of the process to promote the separation between the high concentration brine and the ice with liquid separation by physical process. The unidimensional model is based on the evolution of both processes: thermal and mass diffusions, depending on temperature and saline gradients, predicting whether the salt will remain inside the ice or not. Thus, the thermal potential is adjusted to frozen only when the salt has been "pushed" towards the brine. Mostly models have base their results on the assumption of a “certain value of saline concentration of the liquid fraction”, value in which there is great disagreement. In this paper the calculations are based on the concentration in the solid-liquid interface, which has been extensively studied and there is a coincidence in those results, being the main advantage of the proposed model.
ARTICLE | doi:10.20944/preprints202106.0140.v2
Subject: Physical Sciences, Acoustics Keywords: aqueous electrolyte solution; UHF wave; polarization direction; Debye ionic vibrational potential; giant relaxation time
Online: 9 December 2021 (13:17:07 CET)
In this paper, we considered two phenomena in acoustically excited aqueous solutions of a strong electrolyte. These are the well-known Debye ionic vibrational potential (IVP), and radiofrequency anisotropy we discovered earlier , apparently, for the first time. Since both occur due to the accelerated motion of the solution, we have tried to combine them in one simple model. We have established that for a polarized UHF radio wave passed through a NaCl aqueous solution excited by an acoustic pulse the rotation angle of its vector E is proportional to the integral of the square of the observing IVP over time. An equivalent electrical circuit simulating the observed phenomena has been proposed and tested for physical feasibility. Several arguments are given in favour of the fluid-gyroscopic mechanism of RF anisotropy-related effects. We also found out that the IVP is practically independent of the vibrational velocity for frequencies below 10 kHz and it tends to zero at zero frequency. The latter is consistent with the law of conservation of energy but contradicts the incomplete existing theory.
ARTICLE | doi:10.20944/preprints201909.0319.v1
Subject: Earth Sciences, Atmospheric Science Keywords: secondary organic aerosol; isoprene epoxydiol; aqueous aerosol; cloudwater
Online: 29 September 2019 (02:50:17 CEST)
Chemical processing of organic material in aqueous atmospheric aerosols and cloudwater is known to form secondary organic aerosols (SOA), although the extent to which each of these processes contributes to total aerosol mass is unclear. In this study, we use GAMMA 5.0, a photochemical box model with coupled gas and aqueous-phase chemistry, to consider the impact of aqueous organic reactions in both aqueous aerosols and clouds on isoprene epoxydiol (IEPOX) SOA over a range of pH for both aqueous phases, including cycling between cloud and aerosol within a single simulation. Low-pH aqueous aerosol, in the absence of organic coatings or other morphology which may limit uptake of IEPOX, is found to be an efficient source of IEPOX SOA, consistent with previous work. Cloudwater at pH 4 or lower is also found to be a potentially significant source of IEPOX SOA. This phenomenon is primarily attributed to the relatively high uptake of IEPOX to clouds as a result of higher water content in clouds as compared to aerosol. For more acidic cloudwater, the aqueous organic material is comprised primarily of IEPOX SOA and lower-volatility organic acids. For both cloudwater and aqueous aerosol, pH is the most significant factor considered in this study in determining the mass of aqueous phase organic acids and IEPOX SOA. Other factors, such as the time of day or sequence of aerosol-to-cloud or cloud-to-aerosol transitions, contribute to less than 15% difference in the final aqSOA fractional composition. The potential significance of cloud processing as a contributor to IEPOX SOA production could account for discrepancies between predicted IEPOX SOA mass from atmospheric models and measured ambient IEPOX SOA mass, or observations of IEPOX SOA in locations where mass transfer limitations are expected in aerosol particles.
REVIEW | doi:10.20944/preprints202211.0202.v1
Subject: Physical Sciences, Optics Keywords: terahertz; Kerr effect; liquid water; hydrogen bond; aqueous solution
Online: 10 November 2022 (11:16:36 CET)
In recent years, various optical measurement technologies such as far-infrared spectroscopy, low-frequency Raman spectroscopy, optical Kerr effect spectroscopy, and two-dimensional Raman-terahertz spectroscopy have developed vigorously. By comparing the complementary aspects detected by various linear and nonlinear spectroscopic techniques, a coherent picture emerges from studies of dynamics in water. Numerous molecular dynamics experiments and theoretical investigations have demonstrated low-frequency molecular motions in liquid water. For example, intermolecular hydrogen bond vibration, molecular reorientation motion, and the interaction between molecule/ionic solute and hydrogen bond all occur in the THz region, which are closely related to their physical/chemical properties and structural dynamics. However, precise probing of various modes of motion is difficult due to the complexity of the collective and cooperative motion of molecules and the spectral overlap of related modes. With the development of THz optical technology, current state-of-the-art THz sources can generate pulsed electric fields with peak intensities on the order of ~MV/cm. Such strong fields make it possible to use THz waves as the driving light source for nonlinear polarization of the medium, which in turn leads to the development of the emerging terahertz Kerr effect (TKE) spectroscopy technique. Many low-frequency molecular motion modes, such as the collective directional motion of molecules and the cooperative motion under the constraint of weak intermolecular interactions, are resonantly excited to unprecedentedly strong amplitudes driven by the THz electric field. Thereby the collected responses are increased. The TKE technique thus creates an interesting prospect for investigating low-frequency dynamics in these media. In view of this, this paper firstly summarizes the research work on the measurement mechanism of TKE spectroscopy by taking the solid material without low-frequency molecular dynamics process as an example. Starting from the principle of TKE technology and the exploration of the properties of solid matter using this technology, its application in the exploration of low-frequency molecular dynamics of liquid water and aqueous solutions is introduced. Liquid water is considered the building block of life and possesses many extraordinary physical and biochemical properties. Its hydrogen bonding network plays a crucial role in these properties. It is generally believed that the ability of water to form complex hydrogen-bonding networks is the main reason for its various kinetic and thermodynamic properties that are different from other liquids. However, the exact structure of the hydrogen-bonding network, the spatial extent of its existence, and the associated timescale are not known. And the relevant spectral information of the basic properties of the reaction water is still not known. Therefore, it is of great significance to evaluate the hydrogen bond-related kinetic properties of liquid water by optical means.
Subject: Chemistry, Analytical Chemistry Keywords: Fullerene; Endofullerene; Aqueous Fullerene Dispersion; Antioxidant Potential; Kinetic Chemiluminometry
Online: 26 May 2021 (14:19:39 CEST)
The antioxidant potential (capacity and activity) of aqueous fullerene dispersions (AFD) of non-functionalized C60, C70, and Gd@C82 endofullerene (in micromolar concentration range) was estimated based on chemiluminescence measurements of the model of luminol and generation of organic radicals by 2,2’-azobis(2-amidinopropane) dihydrochloride (ABAP). The antioxidant capacity was estimated by the TRAP method, from the concentration of half-suppression, and from the suppression area in the initial period. All three approaches agree and show that the antioxidant capacity of AFDs increased in the row Gd@C82 < C70 < C60. Mathematical modeling of the long-term kinetics data was used for antioxidant activity estimation. The effect of C60 and C70 is found to be quenching of the excited product of luminol with ABAP-generated radical and not an actual antioxidant effect; quenching constants differ insignificantly. Apart from quenching with a similar constant, the AFD of Gd@C82 exhibits actual antioxidant action. The antioxidant activity in Gd@C82 is 300-fold higher than quenching constants.
COMMUNICATION | doi:10.20944/preprints202003.0377.v2
Subject: Physical Sciences, Applied Physics Keywords: contactless cardiography; polarization vector; polarimetry; aqueous electrolyte solution; relaxation time
Online: 13 July 2020 (03:05:48 CEST)
In the present work, a novel conductive liquids method of study has been proposed. It is based on the phenomenon of radiofrequency anisotropy of electrolyte solution discovered by us. It arises in response to mechanical or acoustic excitation of the solution. We have observed the phenomenon during the development of an RF polarimetric contactless cardiograph. The electric field vector of the transmitted 433.82 MHz signal rotated after its transition through the pericardial region. That rotation depends on the change of blood acceleration when passing through the chambers of the heart and large vessels. It has also been revealed that rotation occurs after RF wave passage through the physiological saline (0.9% NaCl) subjected to any mechanical excitation inside it like a jet appearing or soundwave passing. No significant difference was detected experimentally between NaCl and KCl solutions behavior. It means that the mechanism of hydrodynamic separation of ions is apparently not suitable to explain the phenomenon. The response we have registered resembles the magnetization process of spin glasses. From the nature of the observed response, we have concluded that a fundamentally new physical effect is discovered. It may provide wide opportunities for remote measurement of the electrolyte solution parameters with polarized radio-frequency signals.
REVIEW | doi:10.20944/preprints201902.0238.v1
Subject: Chemistry, Analytical Chemistry Keywords: hydride surface; silicon-carbon bond; aqueous normal phase; retention mechanism
Online: 26 February 2019 (11:33:15 CET)
The development of a stationary phase material for high performance liquid chromatography based on a surface of silica hydride as opposed to silanols on ordinary silica is discussed including synthetic approaches, characterization and applications. There are several synthetic approaches available to create a silica hydride surface. Modification of the Si-H moiety on the silica surface can be accomplished through use of a hydrosilation reaction. Both the intermediate silica hydride and the material modified with an organic moiety can be characterized by a number of spectroscopic as well as a variety of other methods. Further insights into the retention mechanism are provide through chromatographic measurements. The ultimate utility of any chromatographic stationary phase material is determined by its success for solving challenging analytical problems. A broad range of applications are reviewed to illustrate the versatility and usefulness of silica hydride-based stationary phases.
ARTICLE | doi:10.20944/preprints201808.0123.v1
Subject: Chemistry, Other Keywords: HCT-116, WS1, water dispersive QDs, aqueous synthesis, cytotoxicity of QDs.
Online: 6 August 2018 (13:56:16 CEST)
Semiconductor nanocrystals or quantum dots (QDs), have unique optical and physical properties that make them potential imaging tools in biological and medical applications. However, concerns such as the aqueous dispersivity, toxicity to cells and stability in biological environments may limit the use of QDs in bioapplications. Here, we report an investigation into the cytotoxicity of aqueously dispersed CdSe(S) and CdSe(S)/ZnO core/shell QDs in the presence of human colorectal carcinoma cells (HCT-116) and a human skin fibroblast cell line (WS-1). The cytotoxicity of the precursor solutions used in the synthesis of the CdSe(S) QDs was also determined in the presence of HCT-116 cells and compared to that of the heat-shock protein (Hsp90) inhibitor, 17-AAG. CdSe(S) QDs were found to have a low toxicity at concentrations up to 100 µg/ml, with a decreased cell viability at higher concentrations, indicating a highly dose-dependent response. Meanwhile, CdSe(S)/ZnO core/shell QDs exhibited lower toxicity than uncoated QDs at higher concentrations. Confocal microscopy images of HCT-116 cells after incubation with CdSe(S) and CdSe(S)/ZnO QDs showed that the cells were stable in aqueous concentrations of 100 µg of QDs per ml, with no sign of cell necrosis, confirming the cytotoxicity data. Key words: HCT-116, WS1, water dispersive QDs, aqueous synthesis, cytotoxicity of QDs.
Subject: Engineering, Industrial & Manufacturing Engineering Keywords: non-aqueous electrolysis; TiN-MCx; precipitation; bearings; high carbon chromium bearing steel
Online: 28 May 2019 (11:06:35 CEST)
Nitride and carbide are the second phases which play an important role in the performance of bearing steel, and their precipitation behavior is complicated. In this study, TiN-MCx precipitations in GCr15 bearing steels were obtained by non-aqueous electrolysis, and their precipitation mechanisms were studied. TiN is the effective heterogeneous nucleation site for Fe7C3 and Fe3C, therefore, MCx can precipitate on the surface of TiN easily, its chemistry component consists of M3C and M7C3 (M = Fe, Cr, Mn) and Cr3C2. TiN-MCx with high TiN volume fraction, TiN forms in early stage of solidification, and MCx precipitates on TiN surface after TiN engulfed by the solidification advancing front. TiN-MCx with low TiN volume fraction, TiN and MCx form in late stage of solidification, TiN can not grow sufficiently and is covered by a large number of precipitated MCx particles.
ARTICLE | doi:10.20944/preprints201808.0054.v1
Subject: Materials Science, Nanotechnology Keywords: few layer graphene production; aqueous suspension; pyrene derivative; molecular modelling
Online: 2 August 2018 (23:52:47 CEST)
The search for graphene or few layer graphene production methods that are simple, allow mass production and yield good quality material continues to provoke intense investigation. The present work contributes through the study of the aqueous exfoliation of four types of graphene sources, namely graphite and graphite nanoflakes with different morphologies and geographical origin. The exfoliation was achieved in an aqueous solution of a soluble pyrene derivative that was synthesized to achieve maximum interaction with the graphene surface at low concentration (5 x 10-5 M). The yield of bilayer and few layer graphene obtained was quantified by Raman spectroscopic analysis and the adsorption of the pyrene derivative on the graphene surface was studied by thermogravimetric analysis and X-ray diffraction. The whole procedure was rationalized with the help of molecular modeling.
ARTICLE | doi:10.20944/preprints202201.0243.v1
Subject: Chemistry, Food Chemistry Keywords: aqueous micellar system; trypsin inhibitor; isoflavone extraction; non-ionic surfactant; multifactorial optimization
Online: 17 January 2022 (16:01:53 CET)
Simultaneous extraction of trypsin inhibitors and soy isoflavones from soybean meal was investigated using the non-destructive phytochemical extraction process, namely aqueous micellar system. The ethoxylated aliphatic alcohols Genapol X-080, Tergitol 15-S-7, and Tergitol 15-S-9, all non-toxic and biodegradable surfactants, were assessed as potential extractants. A Box-Behnken multifactorial design with the application of the Derringer desirability was used to determine the conditions that maximized the trypsin inhibitors and isoflavone extraction while minimizing the protein extraction. The optimum condition of 5% m/m of surfactant in 50 mM aqueous sodium citrate solution pH 4.5, at 45 °C for 45 min, was established for the three surfactants. The novel methodology would allow the extraction of the main soybean antinutritional factors, trypsin inhibitors, and the valuable isoflavones, preserving the nutritional quality of the treated material. This represents a sustainable alternative methodology for industrial purposes due to its low cost, biodegradability, non-toxicity, and easy scaling up.
ARTICLE | doi:10.20944/preprints201806.0075.v1
Subject: Biology, Physiology Keywords: glaucoma; nitric oxide; spectral domain optical coherence tomography; aqueous humor outflow tract; physiology
Online: 6 June 2018 (06:09:24 CEST)
Purpose: To correlate outflow function and outflow tract vessel diameter changes induced by nitric oxide (NO). Methods: In a porcine anterior segment perfusion model, the effects of a nitric oxide donor (100 µM DETA-NO) on outflow facility were compared to controls (n=8 per group) with trabecular meshwork (TM) and after circumferential ab interno trabeculectomy (AIT). Outflow structures were assessed with spectral domain optical coherence tomography (SD-OCT) before and after NO, or an NO synthase inhibitor (100 µM L-NAME) and the vasoconstrictor, endothelin-1 (100 pg/mL ET-1). Scans were processed with a custom macro script and aligned for automated reslicing and quantification of cross-sectional outflow tract areas (CSA). Results: The facility increased after DETA-NO (0.189±0.081 μL/min·mmHg, p=0.034) and AIT (0.251±0.094 μL/min·mmHg, p=0.009), respectively. Even after AIT, DETA-NO increased the facility by 61.5% (0.190±0.074 μL/min·mmHg, p=0.023) and CSA by 13.9% (p<0.001). L-NAME + ET-1 decreased CSA by -8.6% (p<0.001). NO increased the diameter of focal constrictions 5.0±3.8 fold. Conclusions: NO can dilate vessels of the distal outflow tract and increase outflow facility in a TM-independent fashion. There are short, focally constricting vessel sections that display large diameter changes and may have a substantial impact on outflow.
REVIEW | doi:10.20944/preprints201906.0077.v1
Subject: Chemistry, Electrochemistry Keywords: aqueous electrolyte; corrosion; iron-air; metal-air batteries; silicon-air; stationary energy storage
Online: 10 June 2019 (11:24:23 CEST)
Abstract: Metal-air batteries provide a most promising battery technology given their outstanding potential energy densities, which are desirable for both stationary and mobile applications in a ‘beyond lithium-ion’ battery market. Silicon- and iron-air batteries underwent less research and development compared to lithium- and zinc-air batteries. Nevertheless, in the recent past, the two also-ran battery systems made considerable progress and attracted rising research interest due to the excellent resource-efficiency of silicon and iron. Silicon and iron are among the top five of the most abundant elements in the earth’s crust, which ensures almost infinite material supply of the anode materials, even for large scale applications. Furthermore, primary silicon-air batteries are set to provide one of the highest energy densities among all batteries, while iron-air batteries are frequently considered as a highly rechargeable system with decent performance characteristics. Considering fundamental aspects for the anode materials, i.e., the metal electrodes, in this review, we will first outline the challenges, which explicitly apply to silicon- and iron-air batteries and prevented them from a broad implementation so far. Afterwards, we provide an extensive literature survey regarding state-of-the-art experimental approaches, which are set to resolve the aforementioned challenges and might enable the introduction of silicon- and iron-air batteries into the battery market in the future.
ARTICLE | doi:10.20944/preprints201806.0478.v1
Subject: Earth Sciences, Environmental Sciences Keywords: allophane; adsorption; precipitation; interface processes; environment; heavy metals; nano-structure; short-range order aluminosilicate; wastewater treatment; aqueous geochemistry
Online: 28 June 2018 (15:39:12 CEST)
The capacity and the mechanism of the adsorption of aqueous barium (Ba), cobalt (Co), strontium (Sr) and zinc (Zn) by Ecuadorian (NatAllo) and synthetic (SynAllo-1 and SynAllo-2) allophanes were studied as a function of contact time, pH and metal ion concentration using kinetic and equilibrium experiments. The mineralogy, nano-structure and chemical composition of the allophanes were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and specific surface area analyses. The evolution of adsorption fitted to a pseudo-first-order reaction kinetics, where equilibrium between aqueous metal ions and allophane was reached within < 10 min. The metal ion removal efficiencies varied from 0.7 to 99.7 % at pH 4.0 to 8.5. At equilibrium, the adsorption behavior is better described by the Langmuir model than by the Dubinin-Radushkevich model, yielding sorption capacities of 10.6, 17.2 and 38.6 mg/g for Ba^(2+), 12.4, 19.3 and 29.0 mg/g for HCoO_2^-, 7.2, 15.9 and 34.4 mg/g for Sr^(2+) and 20.9, 26.9 and 36.9 mg/g for Zn^(2+), respectively, by NatAllo, SynAllo-2 and SynAllo-1. The uptake mechanism is based on a physical adsorption process. Allophane holds great potential to remove aqueous metal ions and could be used instead of zeolites, montmorillonite, carbonates and phosphates for wastewater treatment.
ARTICLE | doi:10.20944/preprints201809.0078.v1
Subject: Engineering, Energy & Fuel Technology Keywords: Ethanol; corn; dry-grind process; bolt-on process; corn fiber; soaking in aqueous ammonia pretreatment; cellulase; cellulosic ethanol.
Online: 5 September 2018 (01:40:11 CEST)
Corn fiber is a co-product of commercial ethanol dry-grind plants, which is processed into distillers dried grains with solubles (DDGS) and used as animal feed, yet it holds high potential to be used as feedstock for additional ethanol production. Due to the tight structural make-up of corn fiber, a pretreatment step is necessary to make the cellulose and hemicellulose polymers in the solid fibrous matrix more accessible to the hydrolytic enzymes. A pretreatment process was developed in which whole corn kernels were soaked in aqueous solutions of 2.5, 5.0, 7.5 and 10.0 wt% ammonia at 105oC for 24 h. The pretreated corn then was subjected to a conventional mashing procedure and subsequently ethanol fermentation using a commercial strain of natural Saccharomyces cerevisiae with addition of a commercial cellulase. Pretreatment of the corn with 7.5 wt% ammonia solution plus cellulase addition gave highest ethanol production, which improved the yield in fermentation using 25 wt% solid from 334 g ethanol/kg corn obtained in the control (no pretreatment and no cellulase addition) to 379 g ethanol/kg corn (a 14% increase). The process developed can potentially be implemented in existing dry-grind ethanol facilities as a “bolt-on” process for additional ethanol production from corn fiber, and this additional ethanol can then qualify as “cellulosic ethanol” by the EPA’s Renewable Fuels Standard and thereby receive RINS (Renewable Identification Numbers).
ARTICLE | doi:10.20944/preprints202105.0132.v1
Subject: Life Sciences, Biochemistry Keywords: aqueous fullerene dispersions; pristine fullerenes; metallofullerenes; ROS homeostasis; oxidative stress; NOX4; Nrf2; PRAR-γ; heme oxygenase 1; NAD(P)H quinone dehydrogenase 1; an-ti-inflammatory pathways
Online: 7 May 2021 (09:38:38 CEST)
Background: Fullerenes and metallofullerenes can be considered promising nanopharmaceuticals themselves and as a basis for chemical modification. As reactive oxygen species homeostasis plays a vital role in cells, the study of their effect on genes involved in oxidative stress and anti-inflammatory response is of particular importance. Methods: Human fetal lung fibroblasts were incubated with aqueous dispersions of C60, C70, and Gd@C82 in concentrations of 5 nM and 1.5 µM for 1, 3, 24, and 72 hours. Cell viability, intracellular ROS, NOX4, NFκB, PRAR-γ, NRF2, heme oxygenase 1, and NAD(P)H quinone dehydrogenase 1 expression have been studied. Results & conclusion: The aqueous dispersions of C60, C70, and Gd@C82 fullerenes are active participants in ROS homeostasis. Low and high concentrations of AFDs have similar effects. C70 was the most inert substance, C60 was the most active substance. All AFDs have both a “prooxidant” and “antioxidant” effect, but with a different balance. Gd@C82 was a substance with more pronounced antioxidant and anti-inflammatory properties, while C70 had more pronounced “prooxidant” properties.