Investigation of 500 keV Si ion induced surface structuring of Ni and Ti for enhancement of field emission properties

The present paper reports the investigation of surface morphology, elemental composition, phase changes and field emission properties of Si ion irradiated nickel (Ni) and titanium (Ti). The Ni and Ti targets have been irradiated with 500 keV Si ions generated by Pelletron accelerator at various fluences ranging from 6.9 × 10¹³ to 77.1 × 10¹³ ions/cm². Stopping range of ions in matter analysis revealed higher values of electronic stopping and sputtering yield for Ni as compared with Ti. For both irradiated metals, electronic energy loss dominant over the nuclear stopping. The growth of induced surface structures have been analysed by using field emission scanning electron microscopy (FESEM) analysis. In case of Ni, as the ion fluence increases from 6.9 × 10¹³ to 65.8 × 10¹³ ions/cm², the formation of spherical particulates, agglomers and sputtering is observed. Although in the case of Ti, with the increase of Si ion fluence from 11.6 × 10¹³ to 77.1 × 10¹³ ions/cm², the formation of irregular-shaped particulates along with crater and sputtered channels is observed. X-ray diffraction (XRD) analysis shows that no new phase is identified. However, a significant increase in peak intensity is observed with increasing ion fluence. The variation in crystallite size and dislocation line density is also observed as a function of Si ion fluence. Fourier transform infrared spectroscopy analysis shows that no bands are formed after the Si ion irradiation. Field emission properties of ion-structured Ni and Ti are well correlated with the growth of surface structures observed by SEM and dislocation line density evaluated by XRD analysis.     

Vertical Phase Separation in Small Molecule:Polymer Blend Organic Thin Film Transistors Can Be Dynamically Controlled

Blending of small‐molecule organic semiconductors (OSCs) with amorphous polymers is known to yield high performance organic thin film transistors (OTFTs). Vertical stratification of the OSC and polymer binder into well‐defined layers is crucial in such systems and their vertical order determines whether the coating is compatible with a top and/or a bottom gate OTFT configuration. Here, we investigate the formation of blends prepared via spin‐coating in conditions which yield bilayer and trilayer stratifications. We use a combination of in situ experimental and computational tools to study the competing effects of formulation thermodynamics and process kinetics in mediating the final vertical stratification. It is shown that trilayer stratification (OSC/polymer/OSC) is the thermodynamically favored configuration and that formation of the buried OSC layer can be kinetically inhibited in certain conditions of spin‐coating, resulting in a bilayer stack instead. The analysis reveals here that preferential loss of the OSC, combined with early aggregation of the polymer phase due to rapid drying, inhibit the formation of the buried OSC layer. The fluid dynamics and drying kinetics are then moderated during spin‐coating to promote trilayer stratification with a high quality buried OSC layer which yields unusually high mobility >2 cm² V^?1 s^?1 in the bottom‐gate top‐contact configuration.     

A new curvularin glycoside and its cytotoxic and antibacterial analogues from marine actinomycete Pseudonocardia sp. HS7

Five curvularin macrolides (1–5) were isolated from the cultured broth of marine actinomycete Pseudonocardia sp. HS7 that was obtained from the cloacal aperture of sea cucumber Holothuria moebii. The structures of these isolates were characterized as (11S,15R)-11-hydroxycurvularin (1), (11R,15R)-11-hydroxycurvularin (2), curvularin-7-O-α-D-glucopyranoside (3), trans-dehydrocurvularin (4) and curvularin (5) based on their NMR and HRESIMS data as well as chemical degradation. Compound 3 is a new macrolide with a rare α-D-glucopyranose substituent. Compounds 1–4, 5a and 5c (the acyl products of 5), suppressed the proliferation of all six tested cancer cell lines and 4 is the most active compound with IC₅₀ values ranging from 0.59 to 3.39 μM. The 11-hydroxycurvularins 1 and 2 also showed antibacterial activity inhibiting the growth of Escherichia coli.     

Pregnane‐Type Steroidal Alkaloids of Sarcococca saligna: a New Class of Cholinesterase Inhibitors

Phytochemical investigation of Sarcococca saligna by extensive bioassay‐guided fractionation resulted in the isolation of the pregnane‐type steroidal alkaloids 1 – 15 , i.e. of the five new compounds 1 – 5 and the ten known alkaloids 6 – 15 . The structures of the new alkaloids salignenamide C ( 1 ), salignenamide D ( 2 ), 2β‐hydroxyepipachysamine D ( 3 ), salignenamide E ( 4 ), and salignenamide F ( 5 ) were elucidated with the help of modern spectroscopic techniques, while the known alkaloids axillarine C ( 6 ), axillarine F ( 7 ), sarcorine ( 8 ), N³‐demethylsaracodine ( 9 ), saligcinnamide ( 10 ), salignenamide A ( 11 ), vaganine A ( 12 ), axillaridine A ( 13 ), sarsalignone ( 14 ), and sarsalignenone ( 15 ) were identified by comparing their spectral data with those reported earlier. Inhibition of electric‐eel acetylcholinesterase (EC 3.1.1.7) and horse‐serum butyrylcholinesterase (EC 3.1.1.8) by alkaloids 1 – 15 were investigated. These new cholinesterase inhibitors may act as potential leads in the discovery of clinically useful inhibitors for nervous‐system disorders, particularly by reducing memory deficiency in Alzheimer's disease patients by potentiating and effecting the cholinergic transmission process. These compounds were found to inhibit both enzymes in a concentration‐dependent fashion with the IC₅₀ values ranging from 5.21–227.92 μM against acetylcholinesterase and 2.18–38.36 μM against butyrylcholinesterase.     

Ginsenoside Rb1 Mitigates Escherichia coli Lipopolysaccharide-Induced Endometritis through TLR4-Mediated NF-κB Pathway

Endometritis is the inflammatory response of the endometrial lining of the uterus and is associated with low conception rates, early embryonic mortality, and prolonged inter-calving intervals, and thus poses huge economic losses to the dairy industry worldwide. Ginsenoside Rb1 (GnRb1) is a natural compound obtained from the roots of Panax ginseng, having several pharmacological and biological properties. However, the anti-inflammatory properties of GnRb1 in lipopolysaccharide (LPS)-challenged endometritis through the TLR4-mediated NF-κB signaling pathway has not yet been researched. This study was planned to evaluate the mechanisms of how GnRb1 rescues LPS-induced endometritis. In the present research, histopathological findings revealed that GnRb1 ameliorated LPS-triggered uterine injury. The ELISA and RT-qPCR assay findings indicated that GnRb1 suppressed the expression level of pro-inflammatory molecules (TNF-α, IL-1β and IL-6) and boosted the level of anti-inflammatory (IL-10) cytokine. Furthermore, the molecular study suggested that GnRb1 attenuated TLR4-mediated NF-κB signaling. The results demonstrated the therapeutic efficacy of GnRb1 in the mouse model of LPS-triggered endometritis via the inhibition of the TLR4-associated NF-κB pathway. Taken together, this study provides a baseline for the protective effect of GnRb1 to treat endometritis in both humans and animals.     

Investigations of Viscous Dissipation in Stagnation Point Flow Past a Stretchable Riga Wall: Modern Analysis of Heat Transport

This article scrutinizes the features of viscous dissipation in the stagnation point flow past through a linearly stretched Riga wall by implementing Cattaneo-Christov heat flux model. Viscous dissipation is carried out in Cattaneo-Christov diffusion analysis for the first time in this letter. As a result of Cattaneo-Christov model, some extra terms of viscous dissipation are appeared in the energy equation. These extra terms of viscous dissipation are missing in the literature. On the utilization of suitable transformations, the equations governing the problem are reduced under the boundary layer approximation into the non-linear and dimensionless ordinary differential equations. Convergent approach is utilized to solve the dimensionless governing equations. The solution thus acquired is used to highlight the effects of emerging parameters on velocity distribution and fluid's temperature through the graphs. Features of the drag force (or skin friction co-efficient) are graphically interpreted. It is noticed that the presence of modified Hartman number helps to reduce the fluid's temperature but enhances the velocity profile. Further an enlargement in the value of thermal time relaxation parameter helps to decrease the temperature distribution.     

Cu(OTf)2/Cu-catalyzed four-component reaction: a facile synthesis of α-alkoxytriazoles via click chemistry

Aldehyde, alcohol, azide, and alkyne undergo smooth coupling by means of acetal formation, azidation, and a subsequent ‘click reaction’ in the presence of copper(II) triflate and copper metal in acetonitrile to furnish α-alkoxy-1,2,3-triazoles in good yields. The method provides a convenient route to prepare a wide range of triazoles in a one-pot operation via a four-component reaction.     

Study of the Degradation Kinetics of Carvedilol by Use of a Validated Stability-Indicating LC Method

The objectives of this investigation were to establish a validated stability-indicating LC method for assay of carvedilol and to study the degradation behaviour of the drug under different ICH-recommended stress conditions. Chromatographic separation was achieved on a C₁₈ column with 55:45 (%, v/v) acetonitrile–0.02 m phosphate buffer, pH 3.5, as mobile phase at a flow rate of 1.0 mL min^?1; detection was by UV absorbance at 242 nm. The method was validated for linearity, precision, accuracy, robustness, specificity, and sensitivity, with the bulk drug. The drug was subjected to forced degradation and peaks of all the degradation products were well resolved from that of the pure drug, with significantly different retention times, which indicates the specificity and stability-indicating properties of the method. First-order degradation kinetics of carvedilol were observed under acidic and alkaline conditions. When the utility of the method was verified by analysis of the drug in marketed tablets and a nano-emulsion formulation, the assay was found to be 98.60–99.61 and 99.52–99.87, respectively. These results indicate the method can be successfully used for routine analysis of carvedilol in the bulk drug and in pharmaceutical dosage forms.     

Analysis of Heat and Mass Transfer in a Vertical Annular Porous Cylinder Using FEM

The present study is intended to study heat and mass transfer in a vertical annular cylinder embedded with saturated porous medium. The inner surface of cylinder is maintained at uniform wall temperature and uniform wall concentration. The governing partial differential equations are non-dimensionalised and solved by using finite element method (FEM). The porous medium is discritised using triangular elements with uneven element size. Large number of smaller-sized elements are placed near the walls of the annulus to capture the smallest variation in solution parameters. The results are reported for both aiding and opposing flows. The effects of various non-dimensional numbers such as buoyancy ratio, Lewis number, Rayleigh number, aspect ratio, etc on heat and mass transfer are discussed. The temperature and concentration profiles are presented.     

The role of metal contacts in the stability of n-type organic field effect transistors

We are presenting a long-time bias stress stability of C₆₀-based n-type organic field effect transistors (OFETs), in bottom gate, top contacts configuration, with aluminium (Al), silver (Ag) and gold (Au) source–drain contacts. The results clearly shows that the bias stress effects in C₆₀-based n-type OFETs is similar to p-type OFETs and it can be reduced by using an appropriate metal for the source–drain contacts. During the bias stress time, the threshold voltage shift and an increase in the contacts resistance have also been measured. On the basis of the stability of the device parameters, it is proposed that the Al source–drain contact-based devices gives better stability as compared to the devices with Ag and Au source–drain contacts. Our results show that the bias stress-induced threshold voltage shift is due to the trapping of charges in the channel region and in the vicinity of the source–drain contacts.