Monodisperse nickel-nanoparticles for stereo- and chemoselective hydrogenation of alkynes to alkenes

Here, we report the use of monosaccharides for the preparation of novel nickel nanoparticles (NP), which constitute selective hydrogenation catalysts. For example, immobilization of fructose and Ni(OAc)2 on silica and subsequent pyrolysis under inert atmosphere produced graphitic shells encapsulated Ni-NP with uniform size and distribution. Interestingly, fructose acts as structure controlling compound to generate specific graphitic layers and the formation of monodisperse NP. The resulting stable and reusable catalysts allow for stereo- and chemoselective semihydrogenation of functionalized and structurally diverse alkynes in high yields and selectivity. © 2019 The Author(s

Production of Silver Nanoparticles with Strong and Stable Antimicrobial Activity against Highly Pathogenic and Multidrug Resistant Bacteria

Aims. To synthesize, characterize, and analyze antimicrobial activity of AgNPs of Escherichia hermannii (SHE), Citrobacter sedlakii (S11P), and Pseudomonas putida (S5). Methods. The synthesized AgNPs were examined using ultraviolet-visible spectroscopy (UV-vis) and, zeta potential, and the size and the morphology obtained from the three different isolates were also confirmed by TEM. Results. Among the three isolates tested, SHE showed the best antimicrobial activity due to the presence of small (4–12 nm) and stable (−22 mV) AgNPs. Stability of AgNPs was also investigated and found to be dependent on the nature of isolates. Conclusion. Produced AgNPs showed particle stability and antimicrobial efficacy up to 90 days of production. Our AgNPs exhibited greater antimicrobial activity compared with gentamicin against P. aeruginosa isolates and vancomycin against S. aureus and MRSA isolates at very low concentration (0.0002 mg per Microliters)

The Benign Prostatic Hyperplasia and Its Aetiologies

This study aimed at investigating the Benign Prostatic Hyperplasia and Its Aetiologies, therefore th prostatic hyperplasia predominantly involves the stromal compartment of the gland and affects more than 70% of men of 70 years or older with or without obstructive symptoms of benign prostatic hyperplasia. A consensus view is emerging concerning the factors and control systems that modulate cell proliferation and connective tissue biology in the prostate. The purpose of this review is to discuss some of the recent work contributing to the latter in the context of the aetiology of benign prostatic hyperplasia. The current study also reviews the most important findings regarding the key mechanisms involved in the pathophysiology of BPH. The study concluded that although the pathogenesis of BPH is not yet fully understood, several mechanisms seem to be involved in the development and progression of the disease. These mainly include systemic and local hormonal and vascular alterations as well as prostatic inflammation that would stimulate cellular proliferation

The Usability of E-learning Platforms in Higher Education: A Systematic Mapping Study

The use of e-learning in higher education has increased significantly in recent years, which has led to several studies being conducted to investigate the usability of the platforms that support it. A variety of different usability evaluation methods and attributes have been used, and it has therefore become important to start reviewing this work in a systematic way to determine how the field has developed in the last 15 years. This paper describes a systematic mapping study that performed searches on five electronic libraries to identify usability issues and methods that have been used to evaluate e-learning platforms. Sixty-one papers were selected and analysed, with the majority of studies using a simple research design reliant on questionnaires. The usability attributes measured were mostly related to effectiveness, satisfaction, efficiency, and perceived ease of use. Furthermore, several research gaps have been identified and recommendations have been made for further work in the area of the usability of online learning

Heterogeneous Gold Catalysis: From Discovery to Applications

In the present review, the important and current developments of gold catalysts for a wide range of applications are comprehensively summarized. This review also provides a detailed study of the literature data concerning the preparation, characterization, and catalytic applications of gold catalysts. Additionally, the main aspects of using supported gold nanoparticles (AuNPs) as catalysts for oxidation reactions are considered. In particular, the oxidation of benzyl alcohol to benzaldehyde and the production of adipic acid from cyclohexane are discussed in detail. Lastly, the key properties of gold catalysts are described, and an outlook on the application of gold catalysts is presented

Molecular Retrofitting Adapts a Metal-Organic Framework to Extreme Pressure.

Despite numerous studies on chemical and thermal stability of metal-organic frameworks (MOFs), mechanical stability remains largely undeveloped. To date, no strategy exists to control the mechanical deformation of MOFs under ultrahigh pressure. Here, we show that the mechanically unstable MOF-520 can be retrofitted by precise placement of a rigid 4,4'-biphenyldicarboxylate (BPDC) linker as a "girder" to afford a mechanically robust framework: MOF-520-BPDC. This retrofitting alters how the structure deforms under ultrahigh pressure and thus leads to a drastic enhancement of its mechanical robustness. While in the parent MOF-520 the pressure transmitting medium molecules diffuse into the pore and expand the structure from the inside upon compression, the girder in the new retrofitted MOF-520-BPDC prevents the framework from expansion by linking two adjacent secondary building units together. As a result, the modified MOF is stable under hydrostatic compression in a diamond-anvil cell up to 5.5 gigapascal. The increased mechanical stability of MOF-520-BPDC prohibits the typical amorphization observed for MOFs in this pressure range. Direct correlation between the orientation of these girders within the framework and its linear strain was estimated, providing new insights for the design of MOFs with optimized mechanical properties