Asymmetric Synthesis of Pochonin E and F,Revision of Their Proposed Structure,and Their Conversion to Potent Hsp90 Inhibitors

A concise and modular synthesis of pochonin E and F, and their epimers at C‐6 established the correct stereochemistry of these two natural products. Several members of the pochonin family have been shown to bind the heat shock protein 90 (Hsp90), which has been the focus of intense drug discovery efforts. Pochonin E and F as well as their epimers were derivatized into the corresponding pochoximes and further modified at the C‐6 position. Molecular dynamics simulations, docking studies, and Hsp90 affinity measurements were performed to evaluate the impact of these modifications.     

Electrochemical Sensing of Chemical Warfare Agent Based on Hybrid Material Silver‐aminosilane Graphene Oxide

The threat from chemical warfare agents (CWAs) imparts an alarming call for the global community not limited to human being but also extends as unprecedented environmental threat, hence, timely detection and degradation in the event of CWAs attack is very crucial. Herein, we describe a hybrid material of 3‐aminopropyltriethoxysilane (APTES) modified graphene oxide (GO) on glassy carbon (GC) electrode along with electrodeposited silver nanodendrimers (AgNDs) for the electrochemical detection and degradation of CWA sulphur mustard (HD). The AgNDs/APTES‐GO hybrid material was characterized by SEM, EDX, BET, TGA, Raman, UV‐Vis, XPS and XRD techniques. The AgNDs/APTES‐GO modified GC electrode was also characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Electrochemical studies indicated presence of electrocatalysis owing to the synergistic effect of AgNDs and GO for sensing CWA HD via reductive dehalogenation. The AgNDs/APTES‐GO modified GC electrode exhibited linearity for CWA HD from 5.3 μM to 42.4 μM. Constant potential electrolysis was performed with modified electrode and degradation products were analysed using GC‐MS, highlighting the great potential of graphene based hybrid material. This new strategy provides an opportunity for the development of “detect and destroy” system for the CWAs and other environmental toxic pollutant, which could help in mitigation of on‐ site events for first responders.     

Controlling the solid-state luminescence of gold(I) <Emphasis Type="Italic">N</Emphasis>-heterocyclic carbene complexes through changes in the structure of molecular aggregates

Thermally stable, solid-state luminescent organic materials are highly desired for the development of practical applications. Herein we synthesized new gold(I) complexes with N-heterocyclic carbene ligands, which have the ability to form strong metal-organic bond. Consequently, their thermochemical stability is enhanced at temperatures around 300 °C. Precise design of the molecular structure of the ligands, with a focus on ensuring low steric hindrance around Au atoms in order to limit disturbances to Au/Au interactions, provided a complex with a densely packed crystal with a shorter intermolecular Au–Au distance (3.17 Å) than the typical distance. In the solid state, this complex exhibited strong aurophilic interactions, which generated intense phosphorescence even in air at room temperature (quantum yield=16%) in spite of absence of any phosphorescence in solution. This behavior is characteristic for solid-state luminescence referred to as aggregation-controlled emission. Furthermore, the gold (I) complex displays capacity for mechano- and vapo-chromism—that is, the ability to change color reversibly in response to the application of external stimuli. We believe that the proposed design framework, which involves controlling thermal stability and luminescence property separately, provides a new opportunity for the development of practical applications using solid-state luminescent organic molecules.     

Generalized local projection stabilized nonconforming finite element methods for Darcy equations

Numerical Algorithms - An a priori analysis for a generalized local projection stabilized finite element solution of the Darcy equations is presented in this paper. A first-order nonconforming...     

Experimental Determination of Transmittance of Porous Cerium Dioxide Media in the Spectral Range of 300–1,100 nm

Abstract

A spectroscopy system is developed to measure radiative characteristics of participating media in the spectral range of 300–1,100 nm. The system incorporates a short-arc radiation source, double monochromator, optical chopper synchronized with a lock-in amplifier, and a silicon detector. Measurements of overall spectral transmittance are performed with two types of cerium dioxide samples with average porosities of 0.08 and 0.72, respectively. For both sample types, the spectral variation of the transmittance indicates mixed contribution by absorption and scattering to the observed attenuation in the considered spectral range. All samples are characterized by high opacity to radiation up to approximately 400 nm.     

Chemical and electrochemical investigations of high carbon steel corrosion inhibition in 10 % HCl medium by quinoline chalcones

The corrosion inhibitive effect of 3-(3-oxo-3-phenyl-propenyl)-1H-quinolin-2-one (PPQ) and 3-(3-oxo-3-phenyl-propenyl)-1H-benzoquinolin-2-one (PPBQ) on high carbon steel (HCS) in 10 % HCl media was evaluated by chemical (weight loss) and electrochemical (electrochemical impedance spectroscopy and potentiodynamic polarization technique) measurements. The inhibition efficiencies obtained from weight loss and electrochemical measurements were in good agreement. The inhibition efficiency was found to increase with the increase in inhibitor concentration but decreased with rise in temperature. Potentiodynamic polarization studies revealed the mixed mode inhibition of inhibitors. The adsorption behavior of these inhibitors on the HCS surface was found to obey the Langmuir adsorption isotherm. The thermodynamic parameter values of free energy of adsorption (?G _ads) and enthalpy of adsorption (?H _ads) revealed that the inhibitor was adsorbed on the HCS surface via both chemisorption and physisorption mechanisms. The adsorption mechanism of inhibition was supported by spectroscopic techniques (UV–visible, FT-IR, and wide-angle X-ray diffraction), surface analysis (SEM–EDS), and adsorption isotherms.     

Annealing induced transformations in structural and optical properties of Ge30Se70−xBix thin films

ABSTRACT

Thin films of Ge₃₀Se_70?xBi_x (x?=?5, 15, 20) were prepared by thermal evaporation method on glass substrates with thickness 800?nm. The films were annealed at 250°C and 320°C for 2?h to study the annealing-induced structural and optical change. The X-ray diffraction characterization revealed the amorphous to crystalline phase transformation with annealing. The indirect optical band gap decreased with annealing which is explained on the basis of phase transformation and density of localized states. The formation of surface dangling bonds around the crystallites during crystallization process reduced the band gap. The Tauc parameter and Urbach energy change show the degree of chemical disorderness in the films. The transmitivity decreased while the absorption coefficient increased with the annealing process. The microstructural study done by Field emission scanning electron microscopy shows the formation of crystallites upon annealing. Atomic force microscopy investigation on these films shows the influence of annealing on surface topography.     

Mechanical and magnetic properties of nanostructured CoNiP films

The electroplating technique is especially interesting due to its low cost, high throughput and high quality of deposit. Magnetic thin films are extensively used in various electronic devices including high-density recording media and micro electromechanical (MEMS) devices. Due to these potential applications, deposition of magnetic film draws special attention and it needs a cost-effective process. Electro-deposition being cost-effective, in the present work cobalt-based magnetic films were deposited electrochemically and deposition characteristics were studied. Effect of concentration of organic additives such as urea and thiourea in the presence of sodium hypophosphite was studied. Surface characterisation was carried out using X-ray diffractometer (XRD) and scanning electron microscope (SEM). Elemental compositions of the films were studied using atomic absorption spectrometer (AAS) and showed phosphorous content was less than 1%. Samples were subjected to vibrating sample magnetometer (VSM) and studies showed that organic additive has altered magnetic properties of these films. The reason for change in magnetic properties and structural characteristics because of the additives were discussed. Mechanical properties such as residual stress, hardness and adhesion of the films were also examined and reported.     

Free convection effects on the flow of water at 4°C past a semi-infinite inclined plate

Free convection flow of water at its maximum density past a semi-infinite inclined plate has been studied by using an implicit-finite difference technique. The steady-state velocity and temperature profiles, local and average skin friction and the Nusselt number are shown graphically. It is observed that velocity decreases owing to a fall in temperature of water from 20°C to 4°C.     

Characterization of new cellulosic fiber from the stem of Sida rhombifolia

Natural fibers play a vital role in the field of composites mainly due to their environmental friendliness, the nature of their disposal, and low energy requirement for processing. Recently, research ideas have focused on exploration of promising natural fibers with superior mechanical properties. Sida rhombifolia is one such perennial shrub from which high stiffness natural fibers can be extracted. The physico-chemical properties of Sida rhombifolia fibers (SRFs), crystallinity index (56.6%), higher cellulose (75.09 wt.%) content, and lower density (1320.7 kg/m³) were revealed and compared to those properties of other natural fibers.