Influence of Ti additions on the martensitic phase transformation and mechanical properties of Cu–Al–Ni shape memory alloys

The effect of Ti additions on the microstructure and mechanical properties of Cu–Al–Ni shape memory alloys (SMA) was studied by means of a differential scanning calorimeter, field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction (XRD), a tensile test, a hardness test, and a shape memory effect test. The experimental results show that the Ti additions have an effective influence on the phase transformation behavior through generating a new phase into the microstructure, which is known as X-phase and/or controlling the grain size. The results of the XRD confirmed that the X-phase is a combination of two compounds, AlNi₂Ti and Ti₃·3Al. Nevertheless, it was found that with 0.7 mass% of Ti, the best phase transformation temperatures and mechanical properties were obtained. These improvements were due to the highest existence of the X-phase into the alloy along with a noticeable decrement of grain size. The Ti additions to the Cu–Al–Ni SMA were found to increase the ductility from 1.65 to 3.2 %, corresponding with increasing the strain recovery by the shape memory effect from 50 to 100 %; in other words, a complete recovery occurred after Ti additions.     

Reactions of halobenzenes with methanol on the microporous solid acids hbeta, HZSM-5, and HSAPO-5: halogenation does not improve the hydrocarbon pool

The reactions of fluorobenzene, 3-fluorotoluene, and three isomers of difluorotoluene, chlorobenzene, and bromobenzene with excesses of methanol were investigated on the large-pore catalysts HBeta (*BEA) and HSAPO-5 (AFI), and on the medium-pore HZSM-5 (MFI). Flow reactor studies in pulse mode with GC-MS detection revealed that the fluorobenzene derivatives were readily methylated at, for example, 375 degrees C, but not even pentamethylfluorobenzene was obviously active as a reaction center for methanol-to-olefin (MTO) catalysis. Carbon-labeling studies revealed that small amounts of methylbenzenes were formed by defluorination, and these aromatic hydrocarbons seemed to account for the small yields of olefins (and their secondary reaction products) observed. Loss of one fluorine was also evident in the products for one of the difluorotoluene isomers. On HSAPO-5 the activity order for ring-methylation of halobenzenes was F > Cl > Br. On HZSM-5, chlorobenzene and especially bromobenzene lost halogen through a route forming halomethane. These largely negative results will nevertheless be useful in testing theoretical models of the detailed reaction steps in the hydrocarbon pool mechanism for MTO catalysis.     

Preparation,characterization and catalytic activity of biomaterial-supported copper nanoparticles

Synthesis of copper nanoparticles was carried out with nanocrystalline cellulose (NCC) as a support by reducing CuSO₄·5H₂O ions using hydrazine. Ascorbic acid and aqueous NaOH were also used as an antioxidant and pH controller, respectively. The synthesized copper nanoparticles supported on NCC (CuNPs@NCC) were characterized by UV–vis, XRD, TEM, XRF, TGA, DSC, N₂ adsorption-desorption method at 77 K and FTIR. The UV–vis confirmed the formation and stability of the CuNPs, which indicated that the maximum absorbance of CuNPs@NCC was at 590 nm due to the surface plasmon absorption of CuNPs. Morphological characterization clearly showed the formation of a spherical structure of the CuNPs with the mean diameter and standard deviation of 2.71 ± 1.12 nm. Similarly, XRD showed that the synthesized CuNPs@NCC was of high purity. The thermal analysis showed that the CuNPs@NCC exhibited better thermal behaviors than NCC. BET surface area revealed that the N₂ adsorption–desorption isotherms of CuNPs@NCC featured a type IV isotherm with an H3 hysterisis loop. This chemical method is simple, cost effective, and environmentally friendly. Compared to NCC-supported CuNPs and unsupported CuNPs, the as-prepared CuNPs@NCC exhibit a superior catalytic activity and high sustainability for the reduction of methylene blue with NaBH₄ in aqueous solution at room temperature. The CuNPs@NCC achieved complete reduction of MB with completion time, rate constant and correlation coefficient (R ²) of 12 min, 0.7421 min^?1 and 0.9922, respectively.     

Metal Negatrode Supercapatteries: Advancements,Challenges, and Future Perspectives for High-Performance Energy Storage

Metal negatrode supercapattery (MNSC) is an emerging technology that combines the high energy storage capabilities of batteries with the high-power delivery of supercapacitors, thereby offering promising solutions for various applications, such as energy storage systems, electric vehicles, and portable electronics. This review article presents a comprehensive analysis of the potential of MNSCs as a prospective energy storage technology. MNSCs utilize a specific configuration in which the negatrode consists of a metal or metal-rich electrode, such as sodium, aluminum, potassium, or zinc, whereas the positrode functions as a supercapacitor electrode. The utilization of negatrodes with low electrochemical potential and high electrical conductivity is crucial for achieving high specific energy in energy storage devices, despite facing numerous challenges. The present study discusses the design and fabrication aspects of MNSCs, including the selection of appropriate metal negatrodes, electrolytes, and positrodes, alongside the fundamental operational mechanisms. Additionally, this review explores the challenges encountered in MNSCs and proposes solutions to enhance their performance, such as addressing dendrite formation and instability of metal electrodes.     

The Role of Genetic Polymorphism and Other Factors on Clopidogrel Resistance (CR) in an Asian Population with Coronary Heart Disease (CHD)

Clopidogrel is a widely-used antiplatelet drug. It is important for the treatment and prevention of coronary heart disease. Clopidogrel can effectively reduce platelet activity and therefore reduce stent thrombosis. However, some patients still have ischemic events despite taking the clopidogrel due to the alteration in clopidogrel metabolism attributable to various genetic and non-genetic factors. This review aims to summarise the mechanisms and causes of clopidogrel resistance (CR) and potential strategies to overcome it. This review summarised the possible effects of genetic polymorphism on CR among the Asian population, especially CYP2C19 *2 / *3 / *17, where the prevalence rate among Asians was 23.00%, 4.61%, 15.18%, respectively. The review also studied the effects of other factors and appropriate strategies used to overcome CR. Generally, CR among the Asian population was estimated at 17.2–81.6%. Therefore, our overview provides valuable insight into the causes of RC. In conclusion, understanding the prevalence of drug metabolism-related genetic polymorphism, especially CYP2C19 alleles, will enhance clinical understanding of racial differences in drug reactions, contributing to the development of personalised medicine in Asia.     

Kinetics of Oxidative Cracking of n-Hexane to Light Olefins using Lattice Oxygen of a VOx/SrO-γAl2O3 Catalyst

The kinetics of oxidative cracking of n-hexane to light olefins using the lattice oxygen of VO_x/SrO-γAl₂O₃ catalysts has been investigated. Kinetic experiments were conducted in a CREC Riser Simulator (CERC: Chemical Reactor Engineering Center), which mimics fluidized bed reactors. The catalyst's performance is partly attributed to the moderate interaction between active VO_x species and the SrO-γAl₂O₃ support. This moderate interaction serves to control the release of lattice oxygen to curtail deep oxidation. The incorporation of basic SrO component in the support also helped to moderate the catalyst's acidity to checkmate excessive cracking. Langmuir-Hinshelwood model was applied to formulate the rate equations. The intrinsic kinetic parameters were obtained by fitting the experimental data to the kinetic model using a nonlinear regression algorithm at a 95% confidence interval, implemented in MATLAB. n-Hexane transforms to olefins at a specific reaction rate of 1.33 mol/gcat.s and activation energy of 119.2 kJ/mol. These values when compared with other duplets (i. e., ki° and E_A) for paraffins to olefins, show that indeed olefins are stable products of the oxidative conversion of n-hexane over VO_x/SrO-γAl₂O₃ under a fluidized bed condition. Values of activation energy for all CO_x formation routes indicate that intermediate paraffins are likely to be cracked to form CH₄ than to be converted directly to CO_x. On the other hand, olefins may transform partly, and directly to CO_x (E₉=9.65 kJ/mol) than to form CH₄ (E₈=89.1 kJ/mol) in the presence of excess lattice oxygen. Overall, olefins appear to be stable to deep oxidation due to the role of SrO in controlling the amount of lattice oxygen of the catalyst at the reaction temperature.     

Low-Lying Isomers of (TiO\begin{document}$_{2}$\end{document})\begin{document}$_{n}$\end{document} (\begin{document}${n}$\end{document}=2-8) Clusters

Although there are diverse bond features of Ti and O atoms, so far only several isomers have been reported for each (TiO\begin{document}$_2$\end{document})\begin{document}$_n$\end{document} cluster. Instead of the widely used global optimization, in this work, we search for the low-lying isomers of (TiO\begin{document}$_2$\end{document})\begin{document}$_n$\end{document} (\begin{document}$n$\end{document}=2\begin{document}$-$\end{document}8) clusters with up to 10000 random sampling initial structures. These structures were optimized by the PM6 method, followed by density functional theory calculations. With this strategy, we have located many more low-lying isomers than those reported previously. The number of isomers increases dramatically with the size of the cluster, and about 50 isomers were found for (TiO\begin{document}$_2$\end{document})\begin{document}$_7$\end{document} and (TiO\begin{document}$_2$\end{document})\begin{document}$_8$\end{document} with the energy within kcal/mol. Furthermore, new lowest isomers have been located for (TiO\begin{document}$_2$\end{document})\begin{document}$_5$\end{document} and (TiO\begin{document}$_2$\end{document})\begin{document}$_8$\end{document}, and isomers with three terminal oxygen atoms, five coordinated oxygen atoms as well as six coordinated titanium atoms have been located. Our work highlights the diverse structural features and a large number of isomers of small TiO\begin{document}$_2$\end{document} clusters.     

The Prospect for O.R. in the Nigerian Government Service—An Administrators' Viewpoint

The paper reports the results of interviews with senior government administrators in Nigeria in which they were asked a range of questions about their own work and about the problems that are likely to be encountered in trying to introduce operational research into the government service. It is thus in contrast with most papers on O.R. in developing countries, which are written primarily from the viewpoint of practitioners. The administrators confirmed that there was a wide range of problems recognized as being suitable for the O.R. approach, and identified some of the barriers to the introduction of an effective O.R. service.