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Abstract: Memantine hydrochloride (MH) is a first-line therapeutic drug approved by the US FDA for the management of moderate to severe Alzheimer's disease. This study involves the synthesis of memantine hydrochloride from 1-bromo-3,5-dimethyladamantane through a reaction with thiourea. The research results showed that the solvent reaction was propylene glycol (PG); the total time reaction was 5.5 hours, the temperature reaction in the first stage was 160oC and in the second stage was 80oC; the overall yield was 82.44%. The reaction intermediates were confirmed by the IR, MS,1HNMR, and 13C-NMR spectra.

PurposeThis study aims to achieve two objectives: First, to investigate the moderating influences of Coronavirus-19 (Covid-19)-related psychological distress on the process of entrepreneurial cognition; and second, to close the gap between entrepreneurial intention and behavior of higher education institutions students.Design/methodology/approachScales from previous studies have been adopted to develop a questionnaire survey. An online survey questionnaire then is carried out to collect the data; the final sample includes 405 university students. The validity and reliability of scales are tested throughout Cronbach's alpha and confirmatory factor analysis. Hypothesized correlations were then tested via structural equation modeling.FindingsThe results confirm the important roles of perceived behavioral control and entrepreneurial intention in encouraging entrepreneurial behavior, whereas attitude toward entrepreneurship is strongly and positively related to intention to engage in a business venture. Yet, subjective norms are not found to have an impact on entrepreneurial intention. Entrepreneurial attitude-intention link has been negatively moderated by Covid-19-related psychological distress. Also, Covid-19-related psychological distress can lessen the entrepreneurial intention–behavior linkage of higher education institutions students.Practical implicationsThe study provides useful recommendations for practitioners such as educators and policymakers to promote higher education institutions students' entrepreneurship, especially in the global crisis context of the spread of Covid-19.Social implicationsBeing aware of the effects of the Covid-19 pandemic on the entrepreneurship process and translations from intention into behavior to become entrepreneurs provide useful insights to nascent entrepreneurs, community and our society to limit the negative influence of the Covid-19 pandemic and help us overcome this crisis.Originality/valueAddressing the entrepreneurial intention–behavior gap is considered as the biggest contribution of this study. Moreover, the association between perceived behavioral control and entrepreneurial behavior, overlooked by previous studies, is also tested in this study. Furthermore, the findings confirm that psychological distress caused by Covid-19 can inhibit the cognitive process of entrepreneurship.

This work presents a predominant cost-saving process for the industrial scale synthesis of memantine hydrochloride (1) from 1,3-dimethyladamantane (2) by a two-step method in which both steps were carried out in one-pot. The conversion of 2 to N-(3,5-dimethyladamantane-1-yl)acetylamide (3) was synthesized first in mixture of sulfuric acid 96-98% and nitric acid 64-65% at 25 ºC for 2.5 h and then in acetonitrile at 40 ºC for 3.5 h as a key step. The yield of this process reached to 98%. Next, the deacetylation of 3 with potasium hydroxide in mixture of water-ethylene glycol at 140 ºC for 15 h to get memantine base which was then converted into memantine hydrochloride (1) by aq. HCl 14% (yield of 93%). Overall yield of this synthetic route was 91.65%. The advantages of this process is saving time, solvents, reagents and giving a higher yield as compared to reported procedures.

In this study, gold nanostars (AuNSs) were prepared by a facile and environmentally friendly method through the one-step reduction process with collagen as the stabilizing agent. The use of collagen, a highly biocompatible protein with many functional amines groups, can facilitate the simultaneous controlled synthesis and surface protecting of gold nanoparticles in one step. This synthetic process was operated in the aqueous solution of tetrachloroauric acid (HAuCl4) at room temperature, in which ascorbic acid serves as a reductive agent. The influence of collagen concentration (0.02-0.06 mM) on the morphology of AuNSs was carefully studied to clarify its dual roles as stabilizing and controlling agents for the growth of the particles. Besides that, by simply adjusting reaction components such as the molar ratio of ascorbic acid to HAuCl4 and pH value, the length of the AuNS tips was also controlled. This study could offer a novel modified approach in the controlled synthesis process of AuNSs with the biomolecules collagen. The resulting AuNSs were then characterized by ultraviolet-visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), zeta potential, Fourier transform-infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and circular dichroism (CD), as well as selected area electron diffraction (SAED). UV-Vis spectroscopy showed the formation of AuNSs with the maximum surface plasmon resonance peak at 600-639 nm. TEM results revealed that the average particle size of the AuNSs stabilized by the collagen ranged from 27.39 nm to 41.55 nm, depending on the experimental composition and the pH values. HRTEM, EDS, and SAED results prove a more precise insight into the formation of pure gold nanocrystals. Analysis of the current results may also help better understand the growth mechanism of AuNSs during the synthesis process in the presence of collagen. The Au concentration quantified by the inductively coupled plasma mass spectrometry (ICP-MS) technique after separating and decomposing with microwave-assisted digestion exhibits that the synthesis of AuNSs has a high yield of 88.62%. Additionally, the colloidal stability of AuNS-collagen against different NaCl concentrations, pH, temperatures, and storage time was also examined through UV-Vis spectroscopy. The investigation results reveal that AuNS-collagen remains stable in NaCl 2.0% (w/v), from mildly acidic to neutral pH (4-7), below the temperature of 40°C, and within 21 days postsynthesis. The AuNS synthesized by this eco-friendly method is promising for many potential applications in biomedical field.

To overcome the disadvantages of commercial carbonaceous catalysts in direct methanol fuel cells (DMFCs), novel Pt/Ti1–xIrxO2 catalysts are fabricated in this study. Simultaneously, the influence of the Ir composition in the support on the electrocatalytic activities and physicochemical properties of Pt/Ti1–xIrxO2 catalysts is also evaluated. Ti1–xIrxO2 materials with the tunable Ir composition (x = 0.1, 0.2, 0.3) synthesized via a simple and green hydrothermal route exhibited much higher electrical conductivity and surface area than the undoped TiO2. Furthermore, the well-distributed Pt nanoparticles (NPs) with small sizes (∼3 nm) over supports were obtained by using a modified chemical reduction route. Electrochemical results revealed that a series of 20 wt. % Pt/Ti1–xIrxO2 catalysts exhibited superior durability and electrochemical activity toward the methanol oxidation reaction to the commercial 20 wt. % Pt/C (E-TEK) catalyst. According to these results, Ti1–xIrxO2 materials seem to be very promising as a stable catalyst support in the harsh medium of DMFCs.

This field study was performed to demonstrate that Bacillus aquimaris SH6 spores administered as a feed supplement in adequate amounts confer beneficial effects to the whiteleg shrimp. Shrimps were administered either B. aquimaris SH6 spores at 1×106CFU g-1 pellet (SH6 group) or a mixture of SH6 and B. subtilis SH23 spores at 5×105 CFU g-1 pellet for each strain (SH6-SH23 group). After a 28-day feeding period, the number of SH6 spores in the gut of whiteleg shrimp in the SH6 group and the SH6-SH23 group were 5.7×103 CFU gut-1 and 7.7×103 CFU gut-1, respectively. The total bacterial population of these two experimental groups increased about 10-75% compared to that of the control group. The astaxanthin level and red colour score were the highest in the SH6-SH23 group (1.66 μg.g-1 shrimp; 28-29), followed by the SH6 spore group (1.42 μg.g-1 shrimp; 27-28), and were the lowest in the control group (0.61 μg.g-1 shrimp; 26-27). Nevertheless, the growth rate of shrimps was similar (7.8-8%) among the three groups. In conclusion, feed supplements containing SH6 and SH23 spores co-effectively improved live counts and diversity of microbiota in shrimp guts, as well as improved astaxanthin level and red colour of whiteleg shrimps.