Designing Advanced Catalysts for Energy Conversion Based on Urea Oxidation Reaction

Urea oxidation reaction (UOR) is the underlying reaction that determines the performance of modern urea‐based energy conversion technologies. These technologies include electrocatalytic and photoelectrochemical urea splitting for hydrogen production and direct urea fuel cells as power engines. They have demonstrated great potentials as alternatives to current water splitting and hydrogen fuel cell systems with more favorable operating conditions and cost effectiveness. At the moment, UOR performance is mainly limited by the 6‐electron transfer process. In this case, various material design and synthesis strategies have recently been reported to produce highly efficient UOR catalysts. The performance of these advanced catalysts is optimized by the modification of their structural and chemical properties, including porosity development, heterostructure construction, defect engineering, surface functionalization, and electronic structure modulation. Considering the rich progress in this field, the recent advances in the design and synthesis of UOR catalysts for urea electrolysis, photoelectrochemical urea splitting, and direct urea fuel cells are reviewed here. Particular attention is paid to those design concepts, which specifically target the characteristics of urea molecules. Moreover, challenges and prospects for the future development of urea‐based energy conversion technologies and corresponding catalysts are also discussed.     

Blood Urea Nitrogen Stability: A Feasibility Study for Home Hemodialysis Adequacy Testing Through Mail

Urea kinetic modeling measures the delivered dose of hemodialysis and is used to monitor dialysis adequacy. Obtaining samples for adequacy calculations is a challenge for home hemodialysis (HHD) patients. Ideally, the urea reduction ratio (URR) should be measured at a typical dialysis session; therefore, for HHD patients test specimens should be drawn at home and transferred to a clinical laboratory. Would blood urea nitrogen (BUN) remain stable if samples were mailed to the laboratory? To answer this question, BUN was measured in pre- and postdialysis samples from 20 patients over 8 days of laboratory storage. While BUN values varied among the patient population, neither pre- nor postdialysis values showed any significant variation during the 8-day storage time. These results suggest that BUN values are sufficiently stable for specimens to be drawn at home and mailed to a testing laboratory.     

Does provision of a higher Kt/Vurea make a difference? A hemodialysis controversial issue

Background: Adequate dialysis cannot be ascertained on the sole base of a normal or even a high Kt/V_urea so the impetus of this study was to use the neurophysiologic studies as a marker of the biologic status of the hemodialysis patients to assess the optimum level of Kt/V_urea. Methods: This study was carried out on 20 patients (15 men and 5 women) on maintenance hemodialysis; their ages ranged from 18 to 66 years. Initially, the patients were subjected to thorough clinical and laboratory investigations, and their dialysis adequacy was assessed by studying their urea kinetic modeling and neurophysiologic studies (Phase I). Dialysis was optimized to achieve a target Kt/V_urea of 1.3 in Phase II and 1.5 in Phase III. The duration of each phase was six months at the end of which all patients were thoroughly reevaluated. Nutrition was not manipulated during the study. Results: A neurophysiologic study showed a significant improvement of polyphasicity pattern of both proximal and distal muscles of the upper and lower limbs concomitant with improvement of quality of life on achieving a Kt/V_urea of 1.5 (p < 0.001). There was no significant change of the duration and amplitude of all studied muscles, however. Conclusion: Achieving a Kt/V_urea of 1.5 is a more suitable target for hemodialysis patients because it may be an avenue for improving the neuromuscular functions of these patients.     

Use of Systemic Blood Urea Nitrogen Levels Obtained 30 Minutes before the End of Hemodialysis to Portray Equilibrated,Postdialysis Blood Urea Nitrogen Values

Blood urea nitrogen (BUN) levels obtained at 30 minutes before the end of dialysis were found to be closely similar to equilibrated, postdialysis BUN values obtained 30 minutes after the end of dialysis. Because of this similarity, the former BUN values can be used to derive equilibrated urea reduction ratio, or equilibrated Kt/V instead.     

Erythrocyte Toxicities of Imidazolidinyl Urea and Diazolidinyl Urea

The addition of antimicrobial preservatives to pharmaceutical and cosmetic products is necessary to prevent microbial growth. However, the use of preservatives can also produce other undesirable effects. For several years, researchers have been investigating the use of alternative methods in safety assessment of cosmetic ingredients and formulations by means of variety methods. The aim of this study was to evaluate the erythrocyte toxicities of two commercial preservatives： imidazolidinyl urea and diazolidinyl urea. Relatively few studies about the cytotoxicity of these preservative are available. The determination of their cytotoxicity is an essential step to warrant their safe use. Erythrocyte toxicities were evaluated by assessment of the amount of hemoglobin released by red blood cells after their lysis. In this study, both imidazolidinyl urea and diazolidinyl urea showed cytotoxic activity against red blood cells. The imidazolidinyl urea induce a small release of hemoglobin after 120 min of incubation. But, the diazolidinyl urea induce a massive release of hemoglobin from the imidazolidinyl urea （a rate of 83% at concentrations of 6.25 mg/mL and 12.5 mg/mL）.     

Construction of Nitrogen-Doped Biphasic Transition-Metal Sulfide Nanosheet Electrode for Energy-Efficient Hydrogen Production via Urea Electrolysis

Urea-assisted hybrid water splitting is a promising technology for hydrogen (H₂) production, but the lack of cost-effective electrocatalysts hinders its extensive application. Herein, it is reported that Nitrogen-doped Co₉S₈/Ni₃S₂ hybrid nanosheet arrays on nickel foam (N-Co₉S₈/Ni₃S₂/NF) can act as an active and robust bifunctional catalyst for both urea oxidation reaction (UOR) and hydrogen evolution reaction (HER), which could drive an ultrahigh current density of 400 mA cm⁻² at a low working potential of 1.47 V versus RHE for UOR, and gives a low overpotential of 111 mV to reach 10 mA cm⁻² toward HER. Further, a hybrid water electrolysis cell utilizing the synthesized N-Co₉S₈/Ni₃S₂/NF electrode as both the cathode and anode displays a low cell voltage of 1.40 V to reach 10 mA cm⁻², which can be powered by an AA battery with a nominal voltage of 1.5 V. The density functional theory (DFT) calculations decipher that N-doped heterointerfaces can synergistically optimize Gibbs free energy of hydrogen and urea, thus accelerating the catalytic kinetics of HER and UOR. This work significantly advances the development of the promising cobalt–nickel-based sulfide as a bifunctional electrocatalyst for energy-saving electrolytic H₂ production and urea-rich innocent wastewater treatment.     

ELISA法测定尿液中鬼臼毒素的含量

本文建立了一种利用IC-ELISA法测定尿液中的鬼臼毒素的方法。尿液样经离心沉淀,采用间接竞争酶联免疫吸附法(IC-ELISA)测定。鬼臼毒素的添加浓度在0.5 mg/L-10 mg/L时,回收率范围为78.3%-99.3%,相对标准偏差(RSD)在4.3%-11.5%之间。方法最低检测浓度为0.012μg/mL,检测范围为0.025-19.59μg/mL。方法的准确度和精密度符合残留分析要求。方法操作简捷,结果可靠稳定,比仪器方法检测成本低。     

造粒喷头工作特性探讨

本文通过对直孔与斜孔两类造粒喷头性能上优劣及其产生原因的分析，为设计或引进新型喷头提供一定的理论指导。     

尿素法制备纳米氮化锆粉体

利用尿素为固体氮源, 通过尿素分子与ZrCl₄、ZrOCl₂·8H₂O无机锆盐发生络合反应得到Z-U和ZO-U两种ZrN陶瓷的前驱体, 两种前驱体在较低温度下热裂解都可以得到ZrN陶瓷粉体。使用FT-IR对前驱体分子进行了结构分析, 采用TG-DTA跟踪了前驱体的热裂解过程, 并通过XRD和SEM对最终热裂解获得的ZrN产物进行了表征, 探讨了不同锆源制备前驱体的热裂解反应历程及其对产物ZrN的影响。结果显示: 结晶水的存在对络合反应有较大影响, 从而造成两种前驱体分子结构上存在较大差异; 尽管热裂解反应历程相似, 由于前驱体分子结构不同, 获得的ZrN粉体在纯度和形貌上存在较大差异; Z-U前驱体更容易得到纯度高的ZrN纳米粉体。     

改性硝酸脲作工业炸药敏化剂的研究

根据改性硝酸脲的性质，提出由改性硝酸脲作工业炸药敏化剂较梯恩梯有许多优点，并测试了由改性硝酸脲作敏化剂生产的工业炸药的性能。结果认为该炸药具有摩擦感度和撞击感度低，威力与铵梯炸药相同，成本低的优点。     

Indices for assessment of hemodialysis adequacy: a comparison of different formulae

Of the various indices used in the assessment of dialysis adequacy, fractional urea clearance controlled for volume of distribution "Kt/V" remains the most widely used. Its determination is best performed by formal urea kinetic modeling (UKM), which is laborious and cumbersome, and the computational softwares are largely unavailable, particularly in developing countries. Consequently, different equations have been developed that approximate the formal UKM determination. Of the available formulae, that from second-generation logarithmic equation have been found to approximate values derived from formal UKM closely. We set out to determine the clinical utility of percent reduction of urea and Kt/V formulae derived from it, using the logarithmic equation as the standard.     

复配增塑剂对聚乙烯醇薄膜性能的影响

以尿素/三乙醇胺为复配增塑剂,利用溶液共混法制备了改性PVA薄膜,通过FT-IR研究了尿素/三乙醇胺复配增塑剂与PVA间的相互作用,采用XRD,TGA,DSC表征了增塑改性PVA的结晶性能和热性能,同时分析了复配增塑剂的加入对PVA薄膜力学性能、透光性能、耐水性能的影响。实验结果表明,复配增塑剂的加入破坏了PVA分子中的氢键作用,降低了PVA的结晶度和熔点温度,热分解温度基本不变;随着复配增塑剂含量的增加,增塑改性后的PVA薄膜抗拉强度下降、断裂伸长率增加,透光性增加,溶胀率下降,溶失率增加。     

Nucleation studies in supersaturated aqueous solutions of urea and thiourea doped with inorganic dopants

Induction periods were measured for various supersaturated aqueous solutions of urea doped separately with NH₄NO₃ and NaNO₃ and thiourea doped separately with NaCl and KCI by the direct vision method. Based on classical theory for homogeneous crystal nucleation various critical nucleation parameters were calculated and the results are reported and discussed. In all the cases, the critical nucleation parameters increased with increase in doping concentration.     

Normalization of Dialysis Dose for Daily Dialysis

The equilibrated Kt/V (eKtV) is widely used in hemodialysis (HD) as a measure of the intensity (magnitude) of an individual dialysis treatment. Adequate eKt/V for thrice‐weekly hemodialysis (twHD) has been extensively studied, and a value in the range 1.0 – 1.1 per treatment (3.0 – 3.3 weekly) is generally considered to represent adequate therapy for this specific frequency of dialysis. However, for other schedules, summing eKt/V's and time‐averaging the clearance is not appropriate. This was first demonstrated several years ago by the observation that a weekly eKt/V of 2.0 in continuous ambulatory peritoneal dialysis (CAPD) is therapeutically equal to a weekly eKt/V of 3.0 in twHD. That paradox has been resolved by the standard Kt/V (stdKt/V), which accounts for the first order nature of solute removal by dialysis, and which correctly predicts a normalized weekly stdKt/V of 2.0 for both CAPD and twHD. The equivalent renal clearance (EKR) has also been advanced as a method to normalize dose for varying treatment schedules. However, mathematical consideration shows that EKR is an exact time‐averaged clearance. Analysis of data reported for daily dialysis by Piccoli et al. in the present issue of Hemodialysis International shows that the EKR_ct/V calculated for daily dialysis is identical to the sum of eKt/V's for the individual dialyses. We therefore conclude that EKR is not a suitable parameter for normalizing the dialysis dose, because it fails to reflect the effect of dialysis frequency in HD therapy.     

纤维素氨基甲酸酯的合成

以废弃的棉短绒及尿素为原料,二甲苯为溶剂合成了纤维素氨基甲酸酯。考察了各种影响因素,得到优化条件为：废弃的棉短绒经脱脂漂白后在质量分数为20％的氢氧化钠溶液中预处理6h～8h．尿素与精制的棉短绒质量比为(3～4)：1,反应温度为137℃,反应时间为4h。元素分析测得产品氮的质量分数约为9％。     

FTIR研究催化剂对半预聚物法PUU弹性体固化过程的氢键化作用及力学性能的影响

采用原位FTIR技术跟踪了半预聚物法聚醚型聚氨酯脲的固化过程,研究了催化剂对固化过程的氢键化作用及力学性能的影响。原位FTIR的光谱数据表明,随着催化剂浓度的增加,软段形成的速率逐渐增加,氢键化脲键羰基的有序性降低,微相混合度增加。催化剂决定着弹性体的微结构和力学性能,实验结果显示：当催化剂的质量浓度为2．5‰时,聚氨酯脲PUU弹性体表现出最大的拉伸强度和撕裂强度。     

甲醛/尿素/TDI三元疏水改性聚乙烯醇的制备及影响因素

采用正交实验方法,研究了甲醛、尿素和甲苯二异氰酸酯对聚乙烯醇的疏水改性,并分析了合成条件对其固含量、黏度、溶出率和交联度的影响.     

脲-异丁醛-甲醛三元缩聚树脂的合成与表征

以脲、异丁醛、甲醛为原料,在酸性条件下,合成出三元缩聚树脂(UIFR),考察了合成条件对UIFR软化点和羟基值的影响,并用FT-IR,1H-NMR,TG和GPC对其进行了表征。结果表明,在异丁醛、甲醛摩尔比为1.5,醛、脲摩尔比为6,真空蒸馏温度为140℃、时间为1 h的条件下,合成出的UIFR软化点为90℃,羟基值为32 mgKOH/g,M-n为377 g/mol,且树脂具有良好的溶解性和抗黄变性。FT-IR及1H-NMR结果说明合成反应发生在异丁醛中的α氢原子上。     

C and N doped nano-sized TiO2 for visible light photocatalytic degradation of aqueous pollutants

A facile large scale synthesis of high surface area anatase TiO₂ nano material has been carried out by using the solution combustion synthesis with very widely available urea as fuel. The as-obtained puffy powder of anatase TiO₂ was characterised by X-ray diffraction (XRD), Brunauer–Emmett–Teller surface area analysis, ultraviolet–visible (UV–vis) spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques in order to analyse the structural, optical and surface properties of the synthesised material. Diffuse UV–vis spectroscopic data show a red shift in absorption spectra which may be attributed to the possible energy levels added in between the band edges of TiO₂ due to the C and N doping as confirmed by XPS. Photocatalytic activity of the catalyst was assessed by the photocatalytic degradation of methyl orange under visible light irradiation. The effect of an electron acceptor in order to maximise the electron trapping for further inhibiting exciton recombination and thereby enhancing the oxidation of dyes has also been studied by using peroxomono sulphate(PMS) as the electron acceptor.     

尿素对UF树脂固化动力学影响的研究

为了研究尿素对弱酸性起始合成的UF树脂固化性能影响,采用DSC研究了弱酸性起始合成UF树脂中碱性加成阶段尿素添加次数和间隔时间对树脂固化反应动力学影响.计算了碱性加成阶段尿素添加次数和间隔时间不同的UF树脂的固化表观活化能和反应级数,并建立相应的固化反应动力学方程.研究结果表明:弱酸性起始合成UF树脂,碱性阶段尿素添加次数和添加间隔时间影响树脂固化,尿素添加次数增加和尿素添加次数相同而添加尿素时间间隔延长能降低UF树脂固化体系的活化能.弱酸性起始合成UF树脂的固化反应是介于0.92～0.93级之间的非基元反应.