Modeling and simulation of long-wave infrared InAs/GaSb strained layer superlattice photodiodes with different passivants

Current–voltage characteristics of long-wave infrared (LWIR) InAs/GaSb strained layer superlattice photodiodes (cut-off wavelength ∼10 μm), passivated with different surface passivants, have been modeled and simulated using ATLAS software from SILVACO. The simulated results are fitted to previous experimental results obtained on unpassivated devices and those passivated by silicon-dioxide (SiO₂), silicon nitride (Si_xN_y) and zinc sulfide (ZnS). Surface parameters in terms of surface recombination velocity, shunt resistance and interface trap density are extracted for different passivants. The performance of silicon-dioxide passivated diode is solely dominated by a shunt leakage path with a shunt resistance value of 0.56 Ω-cm². Extracted electron and hole surface recombination velocities have values of 10⁵ cm/s and 10⁷ cm/s for unpassivated, 10³ cm/s and 10⁵ cm/s for Si_xN_y passivated and 10² cm/s and 10³ cm/s for ZnS passivated devices. Interface trap density follows a similar trend with values of 10¹⁵ cm⁻², 8.5 × 10¹⁴ cm⁻² and 10¹⁰ cm⁻² for unpassivated, Si_xN_y passivated and ZnS passivated devices respectively. The suitability and limitations of the simulation tool are discussed.     

Application of high performance liquid chromatography coupled to on-line solid-phase extraction-nuclear magnetic resonance spectroscopy for the analysis of degradation products of V-class nerve agents and nitrogen mustard

The detection and identification of the degradation products of nitrogen mustard and nerve agent VX by high performance liquid chromatography coupled to on-line solid-phase extraction-nuclear magnetic resonance spectroscopy (HPLC-UV-SPE-NMR) were demonstrated. The analytes selected for the study were N,N-dimethylaminoethanol (DMAE), N,N-diethylaminoethanol (DEAE), N,N-diisopropylaminoethanol (DIAE) and triethanolamine (TEA). Offline solid-phase extraction (SPE) followed by derivatization was applied to eliminate the interferents and make the analytes amenable for UV detection. Thereafter, chromatographically separated derivatives were trapped on on-line SPE cartridges. They were subsequently eluted and ¹H NMR and COSY spectra were obtained. The overall detection limits of the LC-UV-SPE-NMR method for the mentioned analytes were found to be 18, 23, 25, and 32 mg/L respectively. Applicability of the method to real samples was demonstrated by the analysis of samples provided during the 22nd OPCW official proficiency test. The method gave reproducible NMR spectra devoid of intense background signals.     

Synthesis of Optically Active 2- and 3- Indolylglycine Derivatives and their Oxygen Analogues

2-Indolylglycine derivative and its oxygen analogue have been synthesized by Sonogashira coupling followed by cyclization in one pot between 2-iodoheteroarenes and ethynyloxazolidinone where 3-indolylglycine derivative and its oxygen analogue have been synthesized from silylated internal alkyne using Larock's heteroannulation as the key reaction.     

Self‐Coupling of a 4‐H‐Butatrienylidene Tungsten Complex

Tungsten tryst : A 4‐H‐butatrienylidene complex of tungsten was successfully isolated and structurally characterized. It undergoes a unique self‐coupling, which leads to a dimer (see picture; P pink, O red) with a cross‐conjugated π system and with electrochemically and magnetically active metal centers.

     

Coordination-driven self-assembly of truncated tetrahedra capable of encapsulating 1,3,5-triphenylbenzene

The design and synthesis of coordinative truncated tetrahedra is described. The coordination-driven self-assembly of a truncated tetrahedron was achieved using 90° organoplatinum acceptors and a hexapyridyl ligand with six-fold symmetry under mild conditions. This tetrahedron can act as a host toward 1,3,5-triphenylbenzene. The truncated tetrahedral structures and the host-guest complex were identified using multinuclear ((31)P and (1)H) NMR spectroscopy, electrospray ionization mass spectrometry, X-ray crystallography, and pulsed-field-gradient spin-echo NMR, along with computational simulations.     

A high-resolution phosphorus-31 nuclear magnetic resonance (NMR) spectroscopic method for the non-phosphorus markers of chemical warfare agents

A high-resolution phosphorus-31 nuclear magnetic resonance (NMR) spectroscopic method has been developed for detection, identification and quantification of non-phosphorus markers of toxic nerve agents (soman and V-class), vesicants (HD, HN-2, HN-3), and incapacitating agent (Bz). These analytes were converted to phosphorus-containing derivatives via phosphitylation reaction of their hydroxyl and sulfhydryl functions (using 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane). This was followed by ³¹P{¹H} and ³¹P NMR analysis of these derivatives. The chemical shifts (δ) and coupling constants (³ J _P–H) of derivatives were used for their specific detection and identification. The method allowed clear distinction between the alcohols and thiols. The lower limits of detection of these analytes were found to be between 12 and 28 μg obtained from 128 transients of ³¹P{¹H} quantitative NMR experiments. Utility of the method was ensured by the detection and identification of triethanolamine present (at an original concentration of 5 μg/mL) in an aqueous sample from 28th OPCW Official Proficiency Tests.     

FRW Cosmological Model with Modified Chaplygin Gas and Dynamical System

The Friedmann-Robertson-Walker (FRW) model with dynamical Dark Energy (DE) in the form of modified Chaplygin gas (MCG) has been investigated. The evolution equations are reduced to an autonomous system on the two dimensional phase plane and it can be interpreted as the motion of the particle in an one dimensional potential. Also the dynamical system analysis has been extended to examine the critical points at infinity with will exist provided the equation of state parameter $\omega<-\frac{1}{3}$ . Finally, theoretical points are asymptotically stable or unstable.     

Antimicrobial potentiality of Phyllanthus amarus against drug resistant pathogens

The antimicrobial potentiality of the methanolic extract of Phyllanthus amarus (Family: Euphorbiaceae) was studied against some drug resistant pathogenic bacterial strains by disc diffusion and agar dilution method. The extract showed significant concentration-dependent antibacterial activity particularly against gram-negative microbes. The study illustrated the claim of the usefulness of the plant in dysenteric and diarrheal infections and also suggested its use in fever. The antibacterial action was mainly due to the isolated phyllanthin.     

Updates on synthesis and biological activities of 1,3,4-oxadiazole: A review

The new era of heterocyclic moieties which are developed in the decades plays a very important role in the treatment of various diseases. Among them are 1,3,4-oxadiazoles, a heterocyclic five-membered ring which plays an vital role in the development of newer medicinal compounds for treating various biological activities, such as proliferation of cells, tuberculosis, allergy, viral diseases, etc. The present review will summarize the various synthetic approaches which will be correlated with the biological activities so that the information in future may be used by many researches to give a path breaking lead in the field of medicinal chemistry.