不同种类羧酸钠对草酸钙结晶过程中晶相的影响

采用X射线衍射法研究了水溶液中不同种类羧酸钠对尿结石主要成份草酸钙结晶的影响，这些羧酸钠分别为含有一、二、三和四个羧基的羟基乙酸钠（NaGly）、酒石酸钠（Na2Tart）、柠檬酸钠（Na3Cit）和EDTA二钠盐（Na2EDTA）.结果表明，随着羧酸钠浓度的增加，草酸钙的晶相均发生规律性的变化：从最稳定的一水草酸钙（COM），到不稳定的二水草酸钙（COD），最后转化为次稳定的三水草酸钙（COT）.不同结构羧酸钠抑制COM生长、促进COD生成的顺序为:Na3Cit >Na2Tart >Na2EDTA >NaGly.该结果将为临床上选择防结石药物提供新的思路.     

Effects of temperature and sodium carboxylate additives on mineralization of calcium oxalate in silica gel systems

Urolithiasis remains a major medical problem in China, especially in Guangdong Province in the southest of China[1]. A survey in Shenzhen city, the most southern city in China, showed the incidence of renal calculus was 4.87%, being 6.12% in the males and 4.07% in the females[2]. The prevalence of renal calculus has been more as the age advances and in the male population and so was in the less-educated population. The recurrence rate is more than 80%, with a moderate improvement by conventi…     

Z‐bpy,a New C2‐Symmetric Bipyridine Ligand and Its Application in Enantioselective Copper(I)‐Catalyzed Cyclopropanation of Olefins

A rigid C₂‐symmetric chiral bipyridine ligand Z‐bpy with a triptycene‐like backbone was designed and synthesized from simple chemicals in a scalable route. Using this new ligand, copper(I) catalyzed cyclopropanation of styrenes with commercial ethyl diazoacetate produced various corresponding cyclopropanes in high yields, diastereoselectivity and enantioselectivity up to 97% ee.     

Immobilization of carboxyl-modified multiwalled carbon nanotubes in chitosan-based composite membranes for U(VI) sorption

Journal of Radioanalytical and Nuclear Chemistry - The carboxyl-modified multiwalled carbon nanotubes were immobilized in chitosan-based composite membranes (CS-CNTs) which were used as efficient...     

The MAP/PH/N retrial queue in a random environment

We consider the MAP/PH/N retrial queue with a finite number of sources operating in a finite state Markovian random environment. Two different types of multi-dimensional Markov chains are investigated describing the behavior of the system based on state space arrangements. The special features of the two formulations are discussed. The algorithms for calculating the stationary state probabilities are elaborated, based on which the main performance measures are obtained, and numerical examples are presented as well.     

Filling the Charge–Discharge Voltage Gap in Flexible Hybrid Zinc-Based Batteries by Utilizing a Pseudocapacitive Material

The high charge–discharge voltage gap is one of the main bottlenecks of zinc–air batteries (ZABs) because of the kinetically sluggish oxygen reduction/evolution reactions (ORR/OER) on the oxygen electrode side. Thus, an efficient bifunctional catalyst for ORR and OER is highly desired. Herein, honeycomb-like MnCo₂O_4.5 spheres were used as an efficient bifunctional electrocatalyst. It was demonstrated that both ORR and OER catalytic activity are promoted by Mn^IV-induced oxygen vacancy defects and multiple active sites. Importantly, the multivalent ions present in the material and its defect structure endow stable pseudocapacitance within the inactive region of ORR and OER; as a result, a low charge–discharge voltage gap (0.43 V at 10 mA cm⁻²) was achieved when it was employed in a flexible hybrid Zn-based battery. This mechanism provides unprecedented and valuable insights for the development of next-generation metal–air batteries.     

In Situ Nitrogen Retention of Carbon Anode for Enhancing the Electrochemical Performance for Sodium-Ion Battery

Retaining nitrogen for polyacrylonitrile (PAN) based carbon anode is a cost-effective way to make full use of the advantages of PAN for sodium-ion batteries (SIBs). Here, a simple strategy has been successfully adopted to retain N atoms in situ and increase production yield of a novel composite PAZ by mixing 3 wt % of zinc borate (ZB) with poly (acrylonitrile-co-itaconic acid) (PANIA). Among the prepared carbonised fibre (CF) samples, PAZ-CF-700 maintains the highest N content, retaining 90 % of the original N from PANIA. It represents the highest capacity storage contribution (80.55 %) and the lowest impedance R_ct (117 Ω). Consequently, the specific capacity increases from 60 mAh g⁻¹ of PANIA-CF-700 to 190 mAh g⁻¹ of PAZ-CF-700 at a current density of 100 mA g⁻¹. At the same time, PAZ-CF-700 exhibits a good rate performance and excellent long-term cycling stability with a specific capacity of 94 mAh g⁻¹ after 4000 cycles at 1.6 A g⁻¹.     

Steganography and authentication in image sharing without parity bits

Recently, a polynomial-based (k, n) steganography and authenticated image sharing (SAIS) scheme was proposed to share a secret image into n stego-images. At the same time, one can reconstruct a secret image with any k or more than k stego-images, but one cannot obtain any information about the secret from fewer than k stego-images. The beauty of a (k, n)-SAIS scheme is that it provides the threshold property (i.e., k is the threshold value), the steganography (i.e., stego-images look like cover images), and authentication (i.e., detection of manipulated stego-images). All existing SAIS schemes require parity bits for authentication. In this paper, we present a novel approach without needing parity bits. In addition, our (k, n)-SAIS scheme provides better visual quality and has higher detection ratio with respect to all previous (k, n)-SAIS schemes.     

Nanostructures for Electrocatalytic CO2 Reduction

One of the most effective ways to cope with the problems of global warming and the energy shortage crisis is to develop renewable and clean energy sources. To achieve a carbon-neutral energy cycle, advanced carbon sequestration technologies are urgently needed, but because CO₂ is a thermodynamically stable molecule with the highest carbon valence state of +4, this process faces many challenges. In recent years, electrochemical CO₂ reduction has become a promising approach to fix and convert CO₂ into high-value-added fuels and chemical feedstock. However, the large-scale commercial use of electrochemical CO₂ reduction systems is hindered by poor electrocatalyst activity, large overpotential, low energy conversion efficiency, and product selectivity in reducing CO₂. Therefore, there is an urgent need to rationally design highly efficient, stable, and scalable electrocatalysts to alleviate these problems. This minireview also aims to classify heterogeneous nanostructured electrocatalysts for the CO₂ reduction reaction (CDRR).