Urea Loading Research Articles

Characterization of blends of virgin nitrile rubber and compounded nitrile rubber latex waste reclaimed with urea. Part 1: Cure characteristics

The objectives of this study were to develop a cost-effective, environmental-friendly, mechanochemical reclaiming process for compounded nitrile rubber (NBR) latex waste generated from the dipping and treatment plants of the glove manufacturing process and evaluate properties of reclaimed NBR and virgin NBR/reclaimed NBR blend compounds. Initially, compounded NBR latex waste containing NBR latex mixed with compounding ingredients was dried and reclaimed mechanically by varying the milling time from 0 min to 12.5 min at 2.5-min time interval. Properties such as initial plasticity, Mooney viscosity, swelling, and cross-link density of the mechanically reclaimed NBR samples were evaluated. Also, a series of mechanochemically reclaimed NBR samples were produced using urea and varying its amount from 0 phr to10 phr at 2 phr intervals and milling according to the selected milling time. The mechanochemically reclaimed NBR samples were also tested for the above properties. Finally, a reclaimed NBR sample was prepared by applying the best urea loading and the optimum milling time. Further, a series of virgin NBR/reclaimed NBR blend compounds was prepared by varying the reclaimed NBR from 0% to 70% at 10% interval. Cure characteristics of the above blend compounds were evaluated and compared with those of the 100% virgin NBR (control) compound. Initial plasticity and Mooney viscosity of mechanochemically reclaimed NBR revealed that urea is effective as a reclaiming agent for dried compounded NBR latex waste. Results in overall indicated that 5 min is the optimum milling time and 6 phr is the optimum loading of urea required to produce the best reclaimed NBR in terms of properties and energy consumption. Minimum torque and cure time of the 50:50 virgin NBR/reclaimed rubber blend compound were higher compared to the control, whereas scorch time, maximum torque, and cure rate index of the former were lower compared to the latter.

Urea-silica nanohybrids with potential applications for slow and precise release of nitrogen

The adoption of nanoparticles as carrier matrices in the production of hybrid functional materials is futuristic in agriculture applications. In this study, a greener, modified in-situ sol-gel route was employed to synthesize urea-silica nanohybrids with a high urea loading of 36% (w/w) and a loading efficiency of ~83%. Characterization studies indicated the successful incorporation of urea into silica nanoparticles and the formation of strong bonds between the nanoparticles and urea molecules without any substantial modification to the structure and morphology of silica nanoparticles. Aforesaid observations were further corroborated by the slow and sustained release behavior exhibited by nanohybrids in water for more than ten days. The developed urea-silica nanohybrids could be utilized as a potential candidate for slow-release nitrogen fertilizers.

Effect of urea loading on the anodic synthesis of titania nanotube arrays photoanode to enhance photoelectrochemical performance

The development of efficient photoanode to improve the photoelectrochemical performance under UV light was investigated. The nitrogen-doped titania nanotube array was prepared by one step anodic oxidation of titanium foil in a solution of electrolyte-containing urea as nitrogen precursor at 50 V for 2h. During the process, the urea was added to the electrolyte solution with different concentrations, 0.1%, 0.2%, and 0.4% based on the weight of electrolyte that containing 25% water, 0.5% ammonium fluoride, and glycerol. The synthesis was followed by annealing at 500°C for 3h under 60ml/min of N2 gas to induce the crystalline phase. SEM analysis showed that titania nanotube was successfully synthesized with average diameter is 72 - 153 nm. Refer to XRD analysis titania nanotube mostly have anatase phase with the crystallite size of 27-37 nm depending on loading of urea. Bandgap energy was determined by UV-DRS analysis and showed that nitrogen-doped titania nanotube arrays have smaller bandgap energy. The photoelectrochemical responses of titania nanotube before and after nitrogen doping were examined by linear sweep voltammetry method. Photocurrent density measurements showed better activity on nitrogen-doped titania nanotube. Nitrogen-doped titania nanotube caused the flatband potential shifted to a negative value and the smaller space charge layer, resulting in the higher photocurrent density and photoconversion efficiency.

Epac1 null mice have nephrogenic diabetes insipidus with deficient corticopapillary osmotic gradient and weaker collecting duct tight junctions.

The cAMP-mediator Epac1 (RapGef3) has high renal expression. Preliminary observations revealed increased diuresis in Epac1-/- mice. We hypothesized that Epac1 could restrict diuresis by promoting transcellular collecting duct (CD) water and urea transport or by stabilizing CD paracellular junctions to reduce osmolyte loss from the renal papillary interstitium. In Epac1-/- and Wt C57BL/6J mice, renal papillae, dissected from snap-frozen kidneys, were assayed for the content of key osmolytes. Cell junctions were analysed by transmission electron microscopy. Urea transport integrity was evaluated by urea loading with 40% protein diet, endogenous vasopressin production was manipulated by intragastric water loading and moderate dehydration and vasopressin type 2 receptors were stimulated selectively by i.p.-injected desmopressin (dDAVP). Glomerular filtration rate (GFR) was estimated as [14 C]inulin clearance. The glomerular filtration barrier was evaluated by urinary albumin excretion and microvascular leakage by the renal content of time-spaced intravenously injected 125 I- and 131 I-labelled albumin. Epac1-/- mice had increased diuresis and increased free water clearance under antidiuretic conditions. They had shorter and less dense CD tight junction (TJs) and attenuated corticomedullary osmotic gradient. Epac1-/- mice had no increased protein diet-induced urea-dependent osmotic diuresis, and expressed Wt levels of aquaporin-2 (AQP-2) and urea transporter A1/3 (UT-A1/3). Epac1-/- mice had no urinary albumin leakage and unaltered renal microvascular albumin extravasation. Their GFR was moderately increased, unless when treated with furosemide. Our results conform to the hypothesis that Epac1-dependent mechanisms protect against diabetes insipidus by maintaining renal papillary osmolarity and the integrity of CD TJs.

Correlation Between Gel Strength of Starch-Based Hydrogel and Slow Release Behavior of Its Embedded Urea

Starch-based hydrogels have attracted increasingly attention for application in controlled release fertilizers. However, there is currently a lack of knowledge on ways to characterize this system. In this work, we employed a hot-compression vulcanizer to in-situ synthesize monolithic urea-embedded grafted starch hydrogels with a slab geometry, which facilitates the subsequent measurement of gel strength and urea release kinetics. The results revealed that the greater the gel strength induced by a decreased urea load, an increased graft content, and an increased cross-linking density of starch-based hydrogels, the less the initial burst release of embedded urea. The unavoidable burst release could be ascribed to the heterogeneous network structure of starch-based hydrogels. The network of the hydrogels also afforded an zero-order, or at least time-independent, release kinetics of urea at intermediate stable stage, regardless of their microstructural parameters. Our results could provide a guideline to the design of hydrogel-based fertilizer delivery systems.

Bioconversion of post-culture wastewater from farm fisheries for the production of high-value algal biomass

Post-consumption water from inland fisheries possesses a tremendous environmental impact on aquatic ecosystems due to their high load of nutrients such as Nitrates, Phosphates, Urea and organic load. Due to the high cost of current water treatment systems, most of the waters from inland fisheries are discharged without any treatment, thus generating a significant environmental impact in rivers of different localities. Cyanobacteria are a group of photosynthetic microorganisms that can grow in different environments including wastewater. Among the most industrially exploited cyanobacteria, Spirulina (Arthrospira) maxima is the most relevant microorganism, due to its capacity to produce large quantities of protein and colourants (especially phycocyanins) for the food and feed industry. The objective of this project is to determine the maximum production capacity of Spirulina in post-consumption waters of fish farming as a system for the treatment of this type of water through the biological capture of the various nutrients and the production of biomass of industrial interest. S. maxima was produced on 3 different media (wastewater + Zarouk, wastewater + K2HPO4, NaNO3, NaHCO3 and wastewater without any modification) for 30 days. Results shown that S. maxima can effectively grow on wastewater supplemented with NaNO3 (2.5 g/L), NaHCO3 (16.8 g/L) and K2HPO4 (0.5 g/L) to obtain up to 1.18 g/L of total biomass and 0.23 g/L of phycocianins. The scaling of culture at 10 L showed a minimal reduction on final biomass and phycocyanin (1.05 and 0.21 g/L respectively), this result indicates that the production of biomass and phycobiliproteins from S. maxima in wastewater from inland fisheries can be a possible candidate for the simplification of biomass and high-value metabolites process production.

Impact of alkaline–acid and strongly acid process on the synthesis of urea–formaldehyde resins and derived composites: a comparison study

This paper presents the impact of different processes for producing urea–formaldehyde resins and their roles on the physico-mechanical properties and the formaldehyde emission of the resulting particleboards. Five resins were produced: four via the alkaline–acid process (Resin A to D) and one using the strongly acid process (Resin E). The differences between the syntheses are mainly related to different formaldehyde/urea molar ratios during the synthesis, temperatures, and the number of urea load addition. The molecular weight distribution of the resins was monitored by gel permeation chromatography/size exclusion chromatography and the unreacted oligomers were followed by high-performance liquid chromatography. The shear strength of adhesive joints was evaluated using automated bonding evaluation system. Particleboards produced with these resins were analyzed according to the usual standards for mechanical tests and formaldehyde emission. The resins differ in some characteristics, namely percentage of unreacted oligomers, chemical composition, viscosity, and reactivity. At a pressing time of 120 s, the internal bond of the particleboards was similar for all the resins produced using the alkaline–acid process (≈ 0.60 N mm−2) but differed from that obtained using the strongly acid process (≈ 0.40 N mm−2). However, formaldehyde emissions were apparently independent of the synthesis process.

Activated carbon-supported catalyst loading of CH4N2O for selective reduction of NO from flue gas at low temperatures

Selective catalytic reduction of nitrogen oxides with loaded CH4N2O (low-temperature urea-SCR) is a novel and promising technology to remove nitrogen oxides from low-temperature oxygen-containing flue gas, which can avoid the problem of NH3 escape. In the present study, a series of industrial-grade biomass-based activated carbon (AC)-supported transition metal oxide catalysts with urea loading were prepared by ultrasound-assisted impregnation, and the physicochemical properties of the catalysts were observed by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), graphite furnace atomic absorption spectroscopy (GFAAS), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) analysis, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The influences of the AC type, reaction temperature, AC particle size, metal oxide loading, urea load level and loaded active element type on the catalytic activity were studied through experiments. Moreover, the NO adsorption capacities of the AC carrier at different temperatures were also tested and calculated. The results of NO adsorption tests show that the adsorption capacity of AC decreased with increasing temperature. The results of the catalytic performance tests indicate that the copper- and manganese-based catalysts with 6 wt% urea exhibited better activity than the other catalysts. The copper-based catalyst, in particular, yielded better than 93% NO conversion at low temperatures (50–100 °C). Finally, on the basis of the combined characterization results and thermodynamics analysis, a NO removal mechanism of the copper- and manganese-based catalysts was proposed and discussed; the electron transfers of Mn4+ ⇌ Mn2+ and Cu2+ ⇌ Cu0 promoted the low-temperature urea-SCR method.

Effect of Magnetized Water on Urea-Loading Efficiency of Mesoporous Nano-Silica: A Seed Germination Study on Wheat Crop.

Efficiently-loaded, controlled-release nanofertilizer systems improve fertilizer use efficiency, germination percentage, root and shoot length, seedling growth, and can overcome the problem of the ever-increasing cost of agrochemicals and their inherent post-application losses, which lead to severe soil, water, and eatable commodity pollution. In this study, magnetized distilled waters (MDWs) with various physicochemical characteristics have been used to enhance the urea loading efficiency into mesoporous nano silica (mNS). The mNS was in-house synthesized by a sol-gel method and characterized by UV-visible spectrophotometer (UV-Vis), Fourier Transform Infrared Spectroscopy (FTIR), Energy-dispersive X-ray (EDX) spectroscopy, X-ray powder diffractometer (XRD), and thermogravimetric (TGA)/differential thermal analyzer (DTA) and Field Emission Scanning Electron Microscope (FESEM). We then compared the effects of magnetized and normal water, mNS, urea-loaded mNS, and bare urea on the germination of wheat seeds under laboratory conditions. Comparing to mNS in DW, we detected an increase in root (4-fold) and shoot (1.85-fold) lengths when using mNS in MDW. The root and shoot length in case of urea loaded mNS in normal DW and MDW were 2.05 and 1.77 times more, respectively. The germination percentage and root and shoot length increased significantly in accordance to the exposure to 0.5% (w/v) mNS in magnetized water (mNS-MDW) and urea loaded mNS in magnetized water (mNSU-MDW) as compared to same treatment with mNS in distilled water (mNS-DW). Our findings show that the unfavorable effects of urea fertilizer on seed germination, seedling growth, and early plant growth on paper towels can be ameliorated, at least partially, by supplementation with mNSU-MDW. We conclude that mNS-MDW and mNSU-MDW might be effective alternatives for sustained and effective means of fertilizer use efficiency during wheat seed germination.

Inner Medullary Urea Transporters Contribute to Development of Renal Fibrosis in Mice With Unilateral Ureteral Obstruction

Fourteen percent of the population of the United States is affected by chronic kidney disease (CKD). Although the mechanisms that are responsible for CKD remain unclear, there are many clinical and animal studies showing that low protein diets reduce the long term effects of CKD. One possible explanation for these benefits is the restricted urea load of the low protein diet suggesting a role for the urea transporters in this process. Unilateral ureteral obstruction (UUO) is a well known model to produce fibrogenic responses such as increased capillary macrophages, pro‐fibrogenic proteins, interstitial matrix, myofibroblasts, etc. in CKD rodents. We hypothesized that the urea transporters contribute to the development of renal fibrosis. We used UUO mice receiving a maximal urea load (high protein diet) to investigate contributions of urea transporters to renal fibrosis. C57Bl6 mice ± genetic ablation of UT‐A1 and UT‐A3 urea transporters (UT‐A1/A3 KO) underwent UUO surgery (ligation of the left proximal ureter). Four days after surgery mice were given a high (40%) protein diet for 10 further days. Mice were killed and obstructed kidneys collected for protein and histochemical analysis. All of the obstructed kidneys showed evidence of hydronephrosis after 14 days. BUN was unchanged by UUO: WT control: 44.2 mg/dl, WT UUO: 46.8 mg/dl, KO control: 43.4, KO UUO: 47.1. TGF‐b was increased in both WT and UT‐A1/A3 KO mice with UUO (302% and 389% respectively). WT with UUO showed a 320% increase in α‐SMA vs mice without UUO. UT‐A1/A3 KO mice with UUO showed a blunted 271% increase in α‐SMA vs unobstructed UT‐A1/A3 KO mice. Vimentin, another marker of fibrosis, was significantly increased 555% by UUO (vs no UUO). UUO in UT‐A1/A3 KO mice did not increase vimentin. H&E staining revealed similar infiltration of inflammatory cells in both UUO WT and UUO UT‐A1/A3 KO mice. Trichrome staining showed higher collagen levels in UUO WT vs UUO UT‐A1/A3 KO mice. Immunohistochemical staining for αSMA and vimentin revealed higher levels in UUO WT vs UUO UT‐A1/A3 KO mice. These data suggest that urea transporters do not prevent inflammation caused by UUO. However, the overall development of fibrosis in UUO mice fed a high protein diet is attenuated by the absence of urea transporters suggesting that urea reabsorption by urea transporters contributes to renal fibrosis. If urea transport inhibitors replicate the effects of genetic knock out, they may represent a promising future therapy.Support or Funding InformationRelypsa Nephrology and Cardiology Fellowship Grant;NIH RO1 DK41707This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Impact of the Synthesis Procedure on Urea-Formaldehyde Resins Prepared by Alkaline–Acid Process

In this work, two synthesis procedures for the preparation of urea-formaldehyde (UF) resins, based on the alkaline–acid process, are studied in order to better understand the chemical reactions involved. For that purpose, the number of urea loads and the methyolation temperature were varied. The molecular weight distribution of the resins was monitored by gel permeation chromatography/size exclusion chromatography and the unreacted oligomers by high-performance liquid chromatography, during the synthesis processes. Chemical modifications were investigated using quantitative analysis by carbon-13 nuclear magnetic resonance of samples taken during the synthesis. The largest difference identified between the procedures regards the methylene linkages and methylol groups determined by 13C NMR. With the results of this study, it is possible to optimize the process and the properties of particleboards produced.

PRELIMINARY RESULTS OF THE CREATION OF A ROBOTIC COMPLEX IN THE ORGANIZATION OF PRIMARY DIAGNOSIS OF RISK FACTORS AND EARLY FORMS OF CANCER

On the basis of the created robotic complex with a program for a survey with illustrations (by the type of whether there are similar forms of pathology) of major tumors, a portable USB microscope built into a flexible hose and the body of the complex for transmitting to the touch screen pathological changes in visible localizations (skin, oral cavity). The survey was conducted in 38 patients with a certain trajectory for men and women on the touch screen. The use of the robotic complex allowed patients to suspect tumors of the skin, oral cavity, thyroid gland, lymph node enlargement in 39.4%±1.7%, of which 53.4%±1.9 with further examination of cancer was confirmed, including 2 patients with melanoma and 4 basal cell carcinoma. In the presence of complaints from the stomach, heartburn or belching with a smell on an empty stomach, 17 patients underwent a “breathing test” (basal and with a load of urea) on the Helik-Scan of AMA LLC, built into the program of the robotic complex. The color change in the “breathing tubes” was scanned with fixation on the touch screen, 7 of them had Helicobacter pylori above 10 units with load. In 5 patients with FGS, metaplasia (MP-1 and MP-2) was established, in 2 gastric ulcer and one of them with malignancy. After examination of the patient and processing of the results with a robotic complex, recommendations for further tactics were sent via the confidential Internet to the doctor of the prevention Cabinet.

Activity and stability of titanosilicate supported Au catalyst for propylene epoxidation with H2 and O2

Highly dispersed Au catalysts supported on amorphous titanosilicate supports with three-dimensional wormhole-like mesoporosity were prepared by deposition–precipitation method, which show excellent performance in propylene epoxidation with H2 and O2. The best catalytic performance, propylene conversion of 12.8%, propylene oxide selectivity of 76.2% and PO space-time yield of 160.9 gpo/Kgcat/h, was obtained at the reaction temperature of 300 °C. The Ti/Si molar ratio of the supports and some experimental parameters, such as the urea amount, loading temperature and Au loading on the as-produced catalyst are optimized. In addition, with the assistance of in-situ Fourier transform infrared spectroscopy (In-situ FT-IR), adsorption and desorption of PO, propylene and the reaction mixture on the catalyst are conducted to further explore the deactivation mechanism. It suggests that propylene and PO can be irreversibly and strongly adsorbed on the catalyst surface and finally transform to carbonate adsorbed on the active sites Ti-OH, resulting in catalyst deactivation.

Methane recovery from anaerobic digestion of urea-pretreated wheat straw

Pretreatment is necessary to improve methane production from lignocellulosic biomass. Urea was adopted to pretreat wheat straw with the advantages of structure deconstruction, its nitrogen source, and prevention of pH drop in subsequent anaerobic digestion (AD). Scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) and Fourier transform infrared spectroscopy (FTIR) spectra measurements indicated that urea pretreatment is able to degrade the lignocellulosic structure, which was beneficial for the improvement of methane production. Urea pretreatment led to the satisfactory performance of AD with wheat straw as substrate. The maximum methane production of 305.5 L/kg volatile solids (VS) was obtained using 1% (w/w) urea loading, which was 45.2% higher than the untreatment. After 1%- and 3%-urea treatment, time used for achieving stable status (≥50%) was 2 days earlier compared to untreatment. Reductions of total solids (49.4%), VS (54.5%), cellulose (50.4%) and hemicelluloses (47.3%) on the optimal condition were the highest, which were 36.8%, 46.5%, 33.3% and 47.4% higher compared to untreatment. Higher levels of urea pretreatment (3% and 5%) were less efficient and resulted in the formation of pseudo-lignin according to FTIR. These results indicate that wheat straw can be used to produce methane significantly with urea pretreatment.

Urea Controlled-Release Fertilizer Based on Gelatin Microspheres

Gelatin microsphere, as a sustained release urea carrier, was prepared by an emulsion–cross linking method with glutaraldehyde (GA) as a cross-linking agent. The influence of urea/gelatin ratio, emulsifier, GA concentration, and cross-linking time on the urea loading and encapsulation efficiency was investigated using response surface methodology. It was found that the urea/gelatin ratio had greater impact on urea loading and encapsulation efficiency than other factors. Equilibrium swelling of microspheres were performed in distilled water, and as expected, the water uptake decreased with the increase of GA as well as the reaction time. The cumulative release of urea from the microspheres decreased with the increase of reaction time and urea release presented a Fickian trend, indicating a diffusion controlled urea release mechanism. The insight from this study is useful to the design and process of controlled release urea fertilizers.

Generation and phenotypic analysis of mice lacking all urea transporters

Urea transporters (UT) are a family of transmembrane urea-selective channel proteins expressed in multiple tissues and play an important role in the urine concentrating mechanism of the mammalian kidney. UT inhibitors have diuretic activity and could be developed as novel diuretics. To determine if functional deficiency of all UTs in all tissues causes physiological abnormality, we established a novel mouse model in which all UTs were knocked out by deleting an 87 kb of DNA fragment containing most parts of Slc14a1 and Slc14a2 genes. Western blot analysis and immunofluorescence confirmed that there is no expression of urea transporter in these all-UT-knockout mice. Daily urine output was nearly 3.5-fold higher, with significantly lower urine osmolality in all-UT-knockout mice than that in wild-type mice. All-UT-knockout mice were not able to increase urinary urea concentration and osmolality after water deprivation, acute urea loading, or high protein intake. A computational model that simulated UT-knockout mouse models identified the individual contribution of each UT in urine concentrating mechanism. Knocking out all UTs also decreased the blood pressure and promoted the maturation of the male reproductive system. Thus, functional deficiency of all UTs caused a urea-selective urine-concentrating defect with little physiological abnormality in extrarenal organs.

Macro- and Micronutrient Simultaneous Slow Release from Highly Swellable Nanocomposite Hydrogels.

Clay-loaded hydrogels have been arousing great interest from researchers and academics due to their unique properties and broad applicability range. Here we developed hydrogel-based nanocomposites intended for slow/controlled release of macro- and micronutrients into independent or concurrent systems. The produced nanocomposites underwent a hydrolysis treatment that improved their physicochemical properties. We obtained materials capable of absorbing water contents 5000 times greater than their weights, an outcome that makes them promising, particularly if compared with commercially available materials. Though swelling degree was affected by the presence of calcium montmorillonite (MMt), MMt has increased nutrient (urea and boron) loading capacity and, as a consequence of its interaction with the studied nutrients, has led to a slower release behavior. By evaluating the simultaneous release behavior, we observed that both the ionic (sodium octaborate) and the nonionic (urea) sources competed for the same active sites within the nanocomposites as suggested by the decreased loading and release values of both nutrients when administrated simultaneously. Because of its great swelling degree, higher than 2000 times in water, the nanocomposites formulated with high MMt contents (approximately 50.0% wt) as well as featuring high loading capacity and individual (approximately 74.2 g of urea g(-1) of nanocomposite and 7.29 g of boron g(-1) of nanocomposite) and simultaneous release denote interesting materials for agricultural applications (e.g., carriers for nutrient release).

Fabrication and properties of a novel superabsorbent composite based on coco peat and poly (acrylic acid) cross-linked trimethylolpropane trimaleate under ultraviolet irradiation

A series of novel poly(acrylic acid)/coco peat (PAA/CP) superabsorbent composites were prepared via the ultraviolet irradiation copolymerization of acrylic acid monomer (PAA) and coco peat cellulose (CP) in the presence of the cross-linker trimethylolpropane trimaleate. The physico-chemical structures of obtained PAA/CP were characterized by Fourier transform infrared spectroscopy, thermogravimetry/derivative thermogravimetry, X-ray diffraction, and scanning electron microscopy, respectively. The critical parameters of affecting the water absorbency of PAA/CP, including the cross-linker level, amount of CP and reaction time, were studied in detailed. The experimental results showed that the PAA/CP samples exhibited the maximum swelling value of 523.09 g/g in distilled water and 40.52 g/g in 0.9 wt % NaCl solution. The swelling behaviors of PAA/CP were significantly relied on the concentration of salt solution and the pH of external solution. The effect of ions species on the swelling performance was in the order: Na+ > Ca2+ > Fe3+ , and in pH 2.2 and 7.2 aqueous solutions PAA/CP composites displayed better pH-responsiveness and reversible on-off switching characteristics. Urea, as an agrochemical model, was loaded into PAA/CP substrate to supply with nitrogen nutrient. The test of their loading and releasing diffusion performance of urea suggested that the urea loading percentage of PAA/CP was remarkably dependent on the concentration of aqueous urea solutions and the release of urea from loaded PAA/CP samples in water followed a non-Fickian mechanism. Owing to their considerable good water absorption capacity, slow urea release, economical and environment-friendly merits, PAA/CP composites could be exploited for the agriculture applications. Copyright © 2016 John Wiley & Sons, Ltd.

Catalytic hydrogenation of carbon monoxide over Rh–Mn–Li/SiO2 catalyst for the synthesis of C2+ oxygenates: the remarkable effect of urea on the particle size of Rh

A series of Rh-Mn-Li/SiO2 catalysts were prepared by the impregnation of a silica support with solutions containing metal precursors with different amounts of urea. Catalyst performance was investigated by the hydrogenation of carbon monoxide. The catalysts were characterized by X-ray diffraction, transmission electron microscopy, hydrogen chemisorption, diffuse reflectance ultraviolet-visible (DR UV-Vis) spectroscopy, and thermogravimetric analysis. The results revealed that the amount of urea had a significant effect on the particle size of Rh, which increased from approximately 2-5 nm with the increase in urea loading from 0 to 2.0 wt%. DR UV-Vis spectra indicated that the increase in the Rh particle size with increasing urea loading might be attributed to the coordination of Rh3+ with urea or its derivatives during calcination. At a urea loading of 1.0 wt%, the particle size of Rh was 3.7 nm, and the space time yield of C2+ oxygenates reached a maximum of 560.0 g kg(-1) h(-1).

Effect of physiological stress on expression of glucose transporter 2 in liver of the wood frog, Rana sylvatica.

Glucose transporters (GLUTs) have been implicated in the survival of various physiological stresses in mammals; however, little is known about the role of these proteins in stress tolerance in lower vertebrates. The wood frog (Rana sylvatica), which survives multiple winter-related stresses by copiously mobilizing hepatic glycogen stores, is an interesting subject for the study of glucose transport in amphibians. We examined the effects of several physiological stresses on GLUT2 protein and mRNA levels in the liver of R. sylvatica. Using immunoblotting techniques to measure relative GLUT2 abundance, we found that GLUT2 numbers increased in response to organismal freezing, hypoxia exposure, and glucose loading; whereas, experimental dehydration and urea loading did not affect GLUT2 abundance. GLUT2 mRNA levels, assessed using quantitative real-time polymerase chain reaction, changed in accordance with protein abundance for most stresses, indicating that transcriptional regulation of GLUT2 occurs in response to stress. Overall, hepatic GLUT2 seems to be important in stress survival in R. sylvatica and is regulated to meet the physiological need to accumulate glucose.