Urea Solution Research Articles

STUDY OF SOLUBILITY OF CO(NH2)2 - HOOC - COOH · NH2C2H4OH - H2O SYSTEM

In this work, the interaction of components in the CO(NH2)2 - HOOC - COOH ·NH2C2H4OH - H2O system was studied by visual polythermic method in the temperature range from -11.2 to 61°C. A polythermal solubility diagram of the system was constructed and the crystallization sites of ice, urea, monoethanolammonium oxalate, and the new phase ureamonoethanolammonium oxalate were determined.During the addition of monoethanolammonium oxalate to urea solutions of different concentrations, changes in rheological properties (pH, density, refractive index, viscosity) were recorded, and the results were found to be consistent with the polythermal solubility diagram. A new phase formed during the study of the CO(NH2)2 - HOOC-COOH · NH2C2H4OH - H2O system, ureamonoethanolammonium oxalate, was isolated and analyzed by confirmed using appropriate analytical methods (IR, Thermal, X-ray phase).

STUDY OF SOLUBILITY PROPERTIES OF COMPONENTS IN ACETATE UREA - TRIETHANOLAMINE - WATER SYSTEM

In this work, in order to synthesize new physiologically active substances, the solubility properties of the components in the acetate urea triethanolamine water ternary system were studied by observational polythermal method at a wide range of concentration and a temperature range from -43°C to 18°C. The solubility diagram of the studied system was constructed and the crystallization areas of all substances acetateurea, triethanolamine, ice and the new compound С3Н8O3N2∙N(C2H4OH)3 acetate ureatriethanolammonium were separated. The composition of the new substance С3Н8O3N2∙N(C2H4OH)3 was determined using the chemical analysis method. In order to determine optimal conditions for the synthesis of С3Н8O3N2∙N(C2H4OH)3 acetate ureatriethanolammonium, which has a new physiologically active property, the rheological properties of the solution were studied by adding triethanolamine to 60, 70 and 80 % acetateurea. A “composition-property” diagram was constructed based on the rheological properties of the studied system, the рH indicator, the density and viscosity of the solution, and the refractive index. The optimal conditions for the synthesis of the new substance С3Н8O3N2∙N(C2H4OH)3 acetate ureatriethanolammonium, obtained by the ratio of components, were determined by adding triethanolamine to a 60 % acetate urea solution.

Preparation and characterization of cellulose fluorescent material: Experiment and simulation

The extensive use of fossil based materials has caused serious pollution problems, the full utilization of biomass resources to prepare high value-added new materials is of great significance for the environmental protection and sustainable social development. For this purpose, this study explored the preparation process and molecular dynamics simulation of cellulose fluorescent materials. Firstly, bacterial cellulose was dissolved in a solution of NaOH and urea at low temperature, followed by a solution blending and hot pressing with hyperbranched polyamide. It was found that the addition of hyperbranched polyamide could effectively filled in the internal pores of cellulose hydrogel, thereby enhancing the fluorescence effects and tensile properties, especially the elongation at break of cellulose materials. The optimal amount of hyperbranched polyamide added was 5 wt%. Molecular dynamics simulation showed that the hydrogen bonds and interaction with cellulose increased as the concentration of hyperbranched polyamide increased.

Influence of bacterial biomineralization conditions on the microstructural characteristics of cement mortar

Bacterial concrete is considered an effective self-healing material due to its capacity to repair damages such as cracks autonomously throughout microbially induced calcium carbonate precipitation (MICP). This study aimed to evaluate the direct incorporation of bacteria into mortar within the framework of concrete damage repairing technol-ogy. Sporosarcina pasteurii, a bacterium capable of surviving in alkaline conditions and inducing biomineralization by precipitating calcium carbonate, was selected for this purpose. Cement mortars with and without bacteria were prepared, and these samples were cured in different solutions to examine bacterial reactivity: a media solution for bacterial growth and calcium carbonate precipitation, a urea solution for calcium carbonate precipitation, and normal water. Mechanical properties and microstructural characteristics were investigated using various approaches. The out-comes revealed that the calcium carbonate precipitated by bacteria in cement mortar exhibited varying phases, such as calcite and vaterite, depending on the specific curing solutions employed. Particularly, the presence of properly precipitated calcium carbonate was found to significantly enhance the durability and mechanical properties of the cement mortar.

Comparison of the efficiency of traditional MICP and two-step MICP method for immobilizing heavy metals in aquatic environments

The application of the microbially induced carbonate precipitation (MICP) method for remediating heavy metals (i.e., HMs) has recently garnered significant attention. Nevertheless, the inhibition of urease activity by toxic Cd2+, Pb2+, Zn2+, and Cu2+ poses a challenge for MICP-based remediation of HMs contamination. This study: (1) first performed the traditional MICP tests (in which the bacterial solution, urea solution, and HMs were mixed simultaneously), and investigated the toxic effect of HMs on the urease activity and the immobilization efficiency, (2) analyzed the toxicity and immobilization mechanism during the MICP process by combining the simulation and XRD tests, (3) conducted the two-step MICP tests (which initially mixed the bacterial solution and urea solution to promote urea hydrolysis, then added the HMs solutions for HMs precipitation) to improve the immobilization efficiency. The tube experiments and simulations were investigated in the HMs concentration range from 1 to 10 mmol/L. Indicators including ammonium concentration, HMs concentrations, and pH were measured/recorded during the tests. The results show that soluble HMs exhibit a concentration-dependent inhibition of urea hydrolysis during the traditional MICP process, resulting in a decreasing immobilization efficiency. The two-step MICP method can effectively immobilize almost the Cd2+ and Zn2+ when the initial urea hydrolysis period exceeds 1–2 h. In addition, a high immobilization rate of over 90% can be achieved for Cu-contaminated solutions at the optimal first-step reaction time. Compared with the traditional MICP procedure, the effective two-step MICP method exhibits more promising application prospects for the immobilization of soluble HMs in aquatic environments.

Elevated blood pressure follows physiological body-water conservation

Background: Pre-clinical evidence suggests that blood pressure (BP) increase is part of an adaptive physiological body response designed to prevent under-hydration. This idea challenges established thinking that hypertension is caused by initial salt-driven over-hydration. We tested the hypothesis that this alternative view also holds true in humans. Methods: In a mechanistic study, we investigated the interrelation between daily Na+ and water intake, renal solute and water excretion, renal water conservation, and body Na+ balance with BP in 6 healthy men living in a controlled environment for 205 days. In an additional daily-life observational study we investigated the interrelation between BP and adaptive-physiological water and Na+ conservation in 108 Singaporeans. Results: In participants living under controlled conditions, BP increased when urine osmolality was high, and fluid intake or urine volume was low. This BP-increasing water conservation response was not caused by body Na+ retention. Similarly, participants living under daily-life conditions showed a BP-elevating adaptive body water conservation response with increased plasma solute concentration, increased plasma vasopressin levels, and reduced urine volume production due to reduced renal free-water excretion. Participants with higher BP relied on more urea and glucose solutes, but on less Na+ solutes, to maintain their hydration status. Participants with essential hypertension showed more pronounced adaptive-physiological water conservation. None of these hypertension-specific water conservation responses were accompanied by differences in 24-h Na+ excretion. Conclusions: BP increase in humans is part of a systemic body water conservation response that occurs largely independent of body Na+ balance. The Mars500 Salt and Water Homeostasis Project was realized by grant support from the German Federal Ministry for Economics and Technology/DLR Forschung unter Weltraumbedingungen (50WB1624-50WB2024) and the Interdisciplinary Centre for Clinical Research (IZKF Junior Research Group 2), Friedrich-Alexander-University of Erlangen-Nuremberg to JT. The food products were donated by APETITO, Coppenrath und Wiese, ENERVIT, HIPP, Katadyn, Kellogg, Molda, and Unilever. The Sodium Storage in Singaporeans Project was realized with grant support from Duke NUS Medical School (Duke-NUS-KBrFA/2019/0026) to JT. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Enhanced Predictability of Urea Crystallization by an Optimized Laser Repetition Rate.

Laser-induced crystallization is a novel alternative to classical methods for crystallizing organic molecules but requires a judicious choice of experimental parameters for the onset of crystallization to be predictable. This study investigated the impact of the laser repetition rate on the time delay from the start of the pulsed laser illumination to the initiation of crystallization, the so-called induction time. A supersaturated urea solution was irradiated with near-infrared (λ = 1030 nm) laser pulses of pulse duration τ = 5 ps at a pulse energy of approximately E = 340 μJ while varying the repetition rate from 10 to 20,000 Hz. The optimal rate discovered ranged from 500 Hz to 1 kHz, quantified by the measured induction time (median 2-5 s) and the mean probability of inducing a successful crystallization event (5 × 10-2%). For higher repetition rates (5-20 kHz), the mean probability dropped to 3 × 10-3%. The reduced efficiency at high repetition rates is likely due to an interaction between an existing thermocavitation bubble and subsequent pulses. These results suggest that an optimized pulse repetition rate can be a means to gain further control over the laser-induced crystallization process.

The Effect of Bacteria-to-Calcium Ratio on Microbial-Induced Carbonate Precipitation (MICP) under Different Sequences of Calcium-Source Introduction.

To explore the effects of the introduction order of calcium sources and the bacteria-to-calcium ratio on the microbially induced calcium carbonate precipitation (MICP) product CaCO3 and to achieve the regulation of CaCO3 crystal morphology, the mineralisation products of MICP were compared after combining bacteria and calcium at ratios of 1/9, 2/9, 3/9, 4/9, 5/9, and 6/9. A bacterial solution was combined with a urea solution in two calcium addition modes: calcium-first and calcium-later modes. Finally, under the calcium-first addition method, the output of high-purity vaterite-type CaCO3 was achieved at bacteria-to-calcium ratios of 2/9 and 3/9; under the calcium-later addition method, the output of calcite-type CaCO3 could be stabilised, and the change in the bacteria-to-calcium ratio did not have much effect on its crystalline shape.

Simultaneously converting synthetic fresh urine into high-quality artificial phosphate ores and urea solution: A novel coupled system of electrochemical selective separation plus induced precipitation

Both the sustainable development and environmental protection urge a demand of new paradigm to recover high-quality nutrients from source-separated urine, but the simultaneous recovery of phosphorus and nitrogen is difficult due to the complex composition. Herein, a coupled system consisting of a flow-electrode capacitive desalination and magnesium-air fuel cell (FCDI-MAFC) was proposed to accomplish electrochemical selective separation plus induced precipitation. The results showed that ionic species in urine were effectively separated from the non-ionic components to generate a urea solution with purity up to 99.7%. Ionic species were converted into artificial phosphate ores (APOs) with a phosphate content of 98.2%. The mass proportion of struvite in the APOs exceeded 90%. The energy consumption also decreased by 13% over five batches of operation. The overall results provide a novel method for the electrochemical selective separation and recovery of high-quality nutrients from complex wastewater.

Changes in the avids of IgG antibodies to the S protein of SARS-CoV-2 after coronavirus infection in medical workers of a temporary infections hospital

BACKGROUND: The effector capabilities of humoral immunity are determined not only by the amount of specific antibodies produced in response to an antigenic effect, but also by their qualitative characteristics, which include avidity ― the total strength of binding to the antigen, which determines the duration and effectiveness of post-infectious immunity to SARS-CoV-2.
 AIM: Is a selective study of the quantity and avidity of IgG antibodies to SARS-CoV-2 over time among medical workers of a temporary infectious diseases hospital in Kazan ― convalescents of COVID-19, during the period from July 2020 to July 2021.
 MATERIALS AND METHODS: Determination of IgG to the S antigen of SARS-CoV-2 by ELISA was carried out using the test system SARS-CoV-2-IgG quantitative-ELISA-BEST (Vector-Best, Russia) and expressed in BAU/ml (binding antibody units). Antibody avidity was determined using a 4.0 M urea solution and expressed as avidity indices. 1, 4 and 7 months after COVID-19 asymptomatic (n=34); mild severity (n=42); moderate severity (n=29); reinfected (n=34). When statistically processing the data, descriptive statistics methods and the Wilcoxon matched data test were used. Differences were considered significant at p 0.05.
 RESULTS: IgG avidity to SARS-CoV-2 depended on the severity of COVID-19. The highest rates of avidity indices were found in the group of those who had a moderate form of COVID-19. If in mild and asymptomatic forms there was a parallel decrease in avidity indices and IgG titer, then in moderate forms an increase in antibody titer was accompanied by a decrease in their avidity 4 months after the infection. 7 months after seroconversion, the IgG level decreased almost twofold, both in mild, asymptomatic and moderate forms. In the group of medical workers who had COVID-19 repeatedly, the initially low levels of avidity indices and antibody titers increased in parallel, while avidity indices after 7 months did not decrease, but remained high. Differences in avidity indices determined the subsequent formation of different trends in the development of the humoral immune response, which were mainly characterized by an uneven decrease in IgG and persistence of IgM antibodies for more than 1 month.
 CONCLUSIONS: The research results expand the understanding of the mechanisms of formation of the humoral immune response and the avidity of IgG antibodies against SARS-CoV-2 in the risk group ― medical workers. The level of humoral immunity decreases in the first six months and varies depending on the severity of COVID-19. The data obtained can be used to identify categories of increased risk of SARS-CoV-2 infection among healthcare workers, make decisions about immunorehabilitation and revaccination against COVID-19.

Innovative Fertiliser Based on Urea and Ammonium Nitrate Solution with Potassium Thiosulphate as a Crucial Factor in Shaping Plant Yield and Its Parameters

In the cultivation of crops in recent times, in addition to taking care of the balanced supply of nutrients to plants and the protection of soil resources, it is also important to take into account the non-productive factor by implementing production systems based on balanced fertilisation. The aim of this study was to demonstrate the effect of soil kind and the application of a new fertiliser based on a urea and ammonium nitrate solution with potassium thiosulphate (UAN-KTS) on the yielding and biometric characteristics of spring wheat, spring rape, and maize to determine the optimal N:K:S ratio. An increase in the soil kind increased the weight of 1000 spring rape seeds, the yield of maize fresh matter, a reduction in the height of spring wheat and maize plants, a reduction in the yield of spring wheat grains and straw, and the yield of the fresh and dry matter of spring rape straw. A higher nitrogen dose promoted the growth of spring rape at the later growing stage and maize and had a positive effect on the yield of spring wheat grains and straw, spring rape seeds and straw, and the above-ground parts of maize. The application of potassium fertilisers caused a significant increase in the spring rape plant height, an increase in the yield of spring wheat grains and straw and spring rape seeds and straw, the above-ground parts of maize, a reduction in the plant height at the beginning of the spring wheat growing period, and a reduction in the weight of 1000 spring rape seeds (only on the soil with rich quality). The fertiliser with the N:K2:S2 ratio had a particularly favourable effect on the yielding of spring wheat. In the cultivation of maize, the same effect was most often obtained under the influence of fertiliser in the ratio of N:K1:S1 on the weaker soil fertilised at the same time as a higher dose of nitrogen (N 1) and N:K2:S2 (in other cases). In the case of spring rape, generally, fertiliser with N:K1:S1 was the strongest, although, in some objects, a higher yield was achieved under the influence of N:K2:S2. The existence of statistically confirmed correlations (expressed as the percentage of the variability observed) between the soil kind and the fertilisers applied and the yielding and biometric characteristics of the plants were observed.

Fabrication and characterization of TiO2‐hydroxyapatite composite‐loaded Polysulfone membranes with integrated biocompatibility for dialysis application

AbstractBackgroundThe use of Polysulfone (PSf) as membrane material for dialysis therapy is becoming more common. However, the PSf membrane can cause the adsorption of blood proteins followed by the adhesion of platelets, destruction of red blood cells, and thrombus formation. One of the biggest challenges in creating membranes for hemodialysis (HD) applications is ensuring biocompatibility. Therefore, to maintain the biocompatibility of PSf membranes, further modifications are necessary.MethodsIn this study, the performance and biocompatibility of PSf membranes were improved by the impregnation of TiO2‐hydroxyapatite composite as an additive. The TiO2‐hydroxyapatite composite was first synthesized via sintering at 1200°C, and then a dope solution composed of pristine PSf polymer solution in N‐Methyl‐2‐pyrrolidone solvent (NMP) and different wt% ratios of the synthesized composite were prepared, and resultant membranes were fabricated using a film applicator via a phase inversion scheme using water as a non‐solvent exchange medium. The synthesized composite was characterized using SEM, EDX, and XRD techniques.ResultsThe FTIR analysis confirmed the weak interaction of PSf polymer with the hydroxyapatite moiety of the composite. The interaction of the synthesized composite within the membrane matrix was evaluated via leaching ratio results. The hydrophilicity, pore profile, and pure water permeation flux rates were also determined. The results of the biocompatibility study showed that membranes based on TiO2‐hydroxyapatite composite had reduced adsorption of BSA protein by 34.41% as well as less than 5% hemolysis ratio. Additionally, the study displayed thrombus formation ranging from 2.08% to 8.69%, respectively. The dialysis results indicated that compared with the original PSf membrane, the TiO2‐hydroxyapatite composite showed high clearance rates for urea (73.81%) and creatinine (72.13%) solutes, respectively.ConclusionTherefore, blending TiO2‐hydroxyapatite composite in the PSf membrane significantly improved the biocompatibility and removal ability of uremic solutes.

Effective Method of Improving the Performance Properties of Wall Products On the Basis of the Gypsum Binder

The basis of the conducted research was the goal of modifying composite gypsum-containing binders for the manufacture of wall products with increased water resistance, strength, frost resistance, and durability by developing a hydrophobizing solution for processing products based on gypsum binder. The article presents the results of research on the modification of artificial gypsum stone with a developed hydrophobizing chemical solution based on calcium polysulfide and titanium dioxide. Comparative indicators of water absorption of original and solution-impregnated samples, which were exposed to the frontal influence of water, are given. The water absorption of the modified samples is within 9...21% and does not change after the frontal impact of rain. Indicators of chemical resistance of impregnated samples in solutions of magnesium sulfate, urea, acetic and oxalic acids, which are characteristic components for aggressive environments of livestock complexes, food and chemical industry, are presented. The test results of the samples showed that the developed chemical solution provides a chemical resistance factor of 0.7, that is, they are chemically stable in such environments. It is shown that, depending on the number of applied layers of the solution or the time of impregnation, hydrophobization gives high indicators of the softening coefficient of the products, which is in the range of 0.6...0.82. The research results showed that thanks to the developed hydrophobizing solution, the construction and technical characteristics of the artificial gypsum stone are significantly increased. Wall products made of this material have high operational characteristics, and it is advisable to use them both indoors and outdoors.

Sustained-release nitrogen fertilizer delivery systems based on carboxymethyl cellulose-grafted polyacrylamide: Swelling and release kinetics

Sustained or controlled-release delivery systems can enhance functions such as nutrient usage; minimize soil contamination, and reduce the required fertilizer dose. This paper reports the development of a carboxymethyl cellulose-g-polyacrylamide copolymer (CMC-g-PAM) as a sustained and slow-release fertilizer carrier for urea. The developed copolymer was characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and thermo gravimetric analysis (TG). The grafting process increased the activation energy of CMC from 0.1521 to 0.5952 J/mol with a higher loading percentage of 72.140.85% using a 15% urea solution. The swelling ratio is significantly dependent on the pH. The maximum swelling ratio of 1199.58% at pH 9. However, Swelling follows a pseudo-first-order reaction with the maximum swelling ratio in a saline of 349.76%.The CMC-g-PAM copolymer loaded with urea exhibited sustained and slow release, with the maximum cumulative percentage of 69.12% at pH 9 and 38.94% in saline. Urea release from the CMC-g-PAM copolymer followed the first-order, Fickian, and biexponential biphasic release mechanisms. The release of the CMC-g-PAM copolymer loaded with urea is a complicated process governed by diffusion and a biphasic releasing profile.

Using Borax as a Cross-Linking Agent in Poly(Vinyl Alcohol)/Hemp-Extracted Cellulose Hydrogels

This study focused on the preparation of hydrogels of poly (vinyl alcohol) and cellulose extracted from hemp fibers with the aid of borax as a cross-linking agent. Cellulose extracted from hemp fibers was initially dissolved in a mixed solution of urea and NaOH to obtain a cellulose solution. In the meantime, PVA was also dissolved in the urea and NaOH. These two solutions were mixed, and various loadings of borax were introduced. Moreover, the effect of borax loadings on equilibrium water content (EWC) and compression properties of the cross-linked hydrogels was investigated. The cross-linked hydrogels showed an EWC of 95.76% and a compression set of 9.71%, compared to those of the physical cross-linked hydrogels which had an EWC of 92.40% and a compression set of 29.96%. It was found that the chemically crosslinked hydrogels exhibited greater stability compared with physical ones owing to the stronger interaction induced by borax. Therefore, The PVA/cellulose hydrogels cross-linked with borax hold potential in various applications such as wound dressing, wastewater treatment, and agricultural fields.

Thermo‐responsive polymer to clean fouled forward osmosis membrane after wastewater treatment: Excellent flux recovery

AbstractThermally responsive polymers (TRPs) have gained significant attention in the past decade due to their unique phase transition behavior, those exhibiting changes in properties with temperature variations. In water, hydrophilic block copolymers form helical structures that can transform into hydrophobic globules above the lower critical solution temperature (LCST). Fouling is one of the limiting issues for the forward osmosis (FO) process in wastewater treatment. In this work, after the treatment of wastewater from the paper and pulp industries, foulants were removed from the surface of the commercial polyamide thin‐film composite membrane of the FO process using polyvinyl methyl ether (PVME), a TRP with an LCST of 35–37°C. PVME was mixed with different aqueous solutions to form cleaning solutions. Foulant cleaning experiments utilized a 1% PVME (w/v) solution in 300 mL of de‐ionized (DI) water, while 1 M NaCl solution served as the draw solution (DS) in the FO process. Comparing the water flux (J) and change in membrane hydraulic resistance (Rf) among pristine, fouled, and cleaned membranes revealed a 56.67% increase in water flux and a 51.68% decrease in membrane resistance after PVME mixed with DI water cleaning solution showcasing its effectiveness in improving membrane performance and reducing fouling. The cleaning efficiency of two solutions, that is, 1% PVME mixed in DI water and 1% PVME mixed in 1 M aqueous urea solution, is compared. Results showed that the former cleaning solution helped to obtain 32.62% higher water flux and 56.05% less membrane resistance. Various membrane characterizations are performed, such as field emission scanning electron microscopy (FE‐SEM), which characterizes the membrane's pore structure and surface morphology, while a contact angle analyzer assesses hydrophilicity. This research highlights the use of TRPs as effective cleaning agents, enhancing membrane performance by effectively removing foulants on the membrane surface. Investigating alternative cleaning solutions also provides insights for optimizing water treatment processes.Highlights Cleaning of fouled thin‐film composite membrane using thermal‐responsive polymers (TRPs). Polyvinyl methyl ether, a TRP with an lower critical solution temperature of 35–37°C used as a cleaning agent. 60% increase in water flux was observed after the single‐step cleaning process. Multiple uses of TRP for cleaning performed with no membrane damage.

Assessing site-specificity of the biomechanical properties of hamstring aponeuroses using MyotonPRO: A cadaveric study

BackgroundHamstring muscles are the most frequently reported sites of muscle strain injuries, especially near the bi-articular muscles' myotendinous junction, where aponeurosis provides a connective tissue network linking muscle fibers to the tendon. This study aimed to investigate the reliability and site-specific differences of hamstring aponeuroses under different conditions (formalin and urea) using MyotonPRO. MethodsEight hamstring muscle groups were dissected from four human cadavers (two males and two females) aged 83–93 years. Measurements of the mechanical properties of the aponeuroses from the superficial and deep regions of biceps femoris long head, semitendinosus, and semimembranosus (after formalin solution immersion) were done using MyotonPRO (intra-rater reliability was examined within a 24-h interval), following which the hamstring aponeuroses were measured using a similar procedure after urea solution immersion. FindingsTest-retest (intra-rater) results revealed that the MyotonPRO measurement of tone, stiffness, relaxation, and creep of cadaveric aponeuroses presented good to excellent reliability (ICC: 0.86 to 0.98). There were no significant differences in tone, stiffness, elasticity, relaxation, and creep among the six sites of hamstring aponeuroses under both formalin and urea conditions. Significant differences between formalin and urea conditions were found in the tone, stiffness, relaxation, and creep of hamstring aponeuroses (P < 0.05). InterpretationThese results suggested that the biomechanical properties of hamstring aponeuroses showed homogeneity between the sites using MyotonPRO. Urea solution could potentially neutralize the effect of formalin on the biomechanical properties of cadaveric muscle-aponeurosis-tendon units. The present findings might influence the design of subsequent cadaveric studies on hamstring muscle strains.

Improving electrochemical performance of Ni-rich layered cathode material with combining Co-enriched compositional gradient and radial microstructure

Ni-rich complex layered oxides LiNixMnyCozO2 (x > 0.85) with a combined Ni/Co concentration gradient and radially oriented elongated plate-like primary particles were synthesized with hydrothermal microwave-assisted treatment of an as-prepared mixed hydroxide precursor with aqueous solution of Co source and urea followed by a high temperature annealing with a Li source. The radial distribution of plate-like primary crystallites in microwave-treated materials was achieved through Co-enrichment at the surface, which likely triggered the surface-to-bulk growth of plate-like particles rather than isotropic octahedral crystallites. The Co-modified cathode materials demonstrate greatly improved cycling stability (capacity fade per cycle of 0.04 ± 0.01%) compared to unmodified Ni-rich NMCs (capacity fade per cycle of 0.13 ± 0.02%) with similar Ni concentration, as well as good rate capability (215, 210, 199, 189, 178 and 160 mAh/g at C/10, C/5, C/2, 1C, 2C, and 5C rates at 2.7–4.3V vs Li/Li+). Enhanced electrochemical performance is linked to the improved mechanical integrity, which was achieved through radial microstructure organization of the agglomerates triggered by Co concentration gradient, suppressing the intragranular crack formation.

Research on Urea Oxidation Coupled with Electrolysis of Water to Produce Hydrogen Based on (NiFe)2P Catalyst

Hydrogen production at low potential was realized by urea oxidation coupled water electrolysis. Transition metal phosphides ((NiFe)2P) were prepared by regulating polyvinylpyrrolidone (PVP) addition during the materials preparation, and their electrocatalytic performance for urea oxidation coupled hydrogen production was investigated. It was found that the material prepared with the PVP addition of 300 mg shows the best catalytic activity. The potential required to reach 100 mA cm−2 in KOH+urea solution is only 1.433 V with an impedance value of 4.128 Ω, which is 103 mV lower than that in KOH solution. Hydrogen evolution in KOH solution required 414 mV to reach −100 mA cm−2 with an impedance value of 48.75 Ω, while the potential required to reach the same current density in KOH+urea solution is only 343 mA with an impedance value of 5.65 Ω. As a result, the energy barrier and electron transfer resistance of electrocatalytic reaction can be significantly reduced by urea oxidation, and it provides a strategy for large-scale application of water electrolysis.

Evaluation of urea hydrolysis for MICP technique applied in recycled aggregate: Concentration of urea and bacterial spores

Aggregate is an indispensable raw material for concrete. Microbial induced carbonate precipitation (MICP) is an environmentally friendly aggregate modification method, which could modify recycled aggregate (RA) to replace natural aggregate for the preparation of concrete in the future. The urea hydrolysis is the key to modified RA by MICP. Biological calcium carbonate is generated during mineralization reaction in modification solution to fill the weak part of aggregate, which will enhance the performance of RA. The bacterial solution and urea solution, as the sources of CO32- in biological CaCO3, jointly affect the modification effect of RA. In this paper, the different ratios of bacterial solution concentration (×108 cells/mL) to urea concentration (mg urea/mL) are used for exploring the improvement effect and the cooperative enhancement mechanism of recycled coarse aggregate (4.75 mm-9.5 mm). The results show that the bacterial mineralization efficiency is most improved when bacterial solution concentration/urea concentration (B/U) is in the optimal interval of 5–6 because 1 mg urea provides a moderate number of bacteria during the modification period. In the interval, the precipitation amount of biological CaCO3 and effective CaCO3 that could modify RA is larger, and the pores of the attached mortar of RA are better filled and blocked. Therefore, the macro performance of RA is greatly improved in the internal. When the B/U is outside the optimal interval, the modification effect is poor because the amount of biological CaCO3 and effective CaCO3 is too less to fill pores or too more to enter pores.