Biaspartimide-diamines as Curing Agents for Epoxy Resins

Various 4,4′ -bis(N²-[4-(4-aminophenoxy)phenyl]aspartimido)diphenylmethane-type bisaspartimide-diamines have been used as solventless curing agents for epoxy resins. The thermal curing was performed at 170, 190, and 230°C to give a tough brown polymer. Thermogravimetric analysis of the polymer obtained showed thermal stability up to 330°C and char yields of 45% in N₂ at 800°C and 12% in air at 700°C. The thermal curing reaction was monitored using FT-IR. The synthesized polymers are useful for making composites, laminates, and adhesives.     

Antifertility and biocidal activities of organometallics of silicon,germanium, titanium and zirconium derived from 2-acetylthiophene thiosemicarbazone

A comparative biochemical study of four Group IV element compounds with specific sulphur-containing organic substrates has been carried out and discussed. The structural characterizations of these organometallics, viz. Me₂SiLCl, Me₂SiL₂, Me₃SiL, Ph₂SiLCl, Ph₂SiL₂, Ph₃SiL, Ph₃GeL, Cp₂TiLCl, Cp₂TiL₂, Cp₂ZrLCl and Cp₂ZrL₂ (where LH?2-acetylthiophene thiosemicarbazone) had been deduced on the basis of various physico-chemical and instrumental techniques, viz., IR, UV, ¹H NMR, ¹³C NMR AND ²⁹SI NMR spectral studies. All the organometallics and the parent thiomine have been screened against a number of microbes and their sterilizing power in male mice tested. The results of these biocidal studies show that the organosilicon(IV) and organogermanium(IV) compounds are more active than the organotitanium(IV) and organozirconium(IV) derivatives. An attempt has also been made to correlate the structural aspects of the molecule with its biological activity.     

Generalized growth and best approximation of entire functions in <Emphasis Type="Italic">L</Emphasis><Superscript><Emphasis Type="Italic">p</Emphasis></Superscript>-norm in several complex variables

The paper deals with the characterization of generalized order and generalized type of entire functions in several complex variables in terms of the coefficients of the development with respect to the sequence of extremal polynomials and the best L ^p -approximation and interpolation errors, 0 < p ≤ ∞, on a compact set K with respect to the set

$K_r = \left\{z \in \mathbb{C}^n, {\rm exp} (V_K (z)) \leq r\right\}$

where V _K is the Siciak extremal function of a L-regular compact set K or V _K is the pluricomplex Green function with a pole at infinity. It has been noticed that in the study of growth of entire functions, the set K _r has not been used so extensively in comparison to disk. Our results apply satisfactorily for slow growth in \({\mathbb{C}^n}\) , replacing the circle \({\{z \in \mathbb{C}; |z| = r\}}\) by the set K _r and improve and extend various results of Harfaoui (Int J Maths Math Sci 2010:1–15, 2010), Seremeta (Am Math Soc Transl 88(2):291–301, 1970), Shah (J Approx Theory 19:315–324, 1977) and Vakarchuk and Zhir (Ukr Math J 54(9):1393–1401, 2002).

     

Effect of 100 MeV O7+ ion beam irradiation on structural,optical and electronic properties of SnO2 thin films

In this paper, we present the impact of swift heavy ion beam irradiation on the structural, optical and electronic properties of SnO₂ thin films. Thin films were deposited using the pulsed laser deposition technique on Al₂O₃ substrates. Atomic force microscopy, X-ray diffraction, UV–visible absorption and temperature-dependent resistivity measurements were performed to explore the morphological, structural, optical and electronic properties of the as-deposited and irradiated samples. The peak intensity of the (200) peak was found to decrease monotonously with increasing irradiation fluence. The band gap energy of the 1×10¹¹ ion/cm² irradiated sample was found to increase. The electrical resistivity of the samples showed a continuous increase with the irradiation fluence.     

Comparative evaluation of magnetization transfer MR imaging and in-vivo proton MR spectroscopy in brain tuberculomas

We have compared and analyzed the value of in vivo proton MR spectroscopy (PMRS) and T1 weighted magnetization transfer (MT) MR imaging in tissue characterization of brain tuberculomas. We studied 33 cases of proven intracranial tuberculomas with in vivo PMRS and T1 weighted MT MR imaging. MT ratios from the rim and core of the tuberculomas were calculated and compared with metabolites seen on PMRS. Final diagnosis of tuberculoma was based on histopathology (n = 26) and/or associated tuberculous meningitis (n = 7) in all the cases. Out of the 33 patients who underwent both PMRS and T1 weighted MT MR imaging, spectroscopy showed only lipids at 0.9 ppm, 1.3 ppm, 2.0 ppm, and 2.80 ppm in 26 cases while lipids at 0.9 ppm, 1.3 ppm, 2.0 ppm and 2.80 ppm along with choline at 3.22 ppm was seen in remaining 7 patients. MT ratios from the core or solid necrosis varied from 21-29% while from the rim or cellular region varied from 16-24%. MT ratios from all the 33 lesions were consistent with tuberculomas while PMRS showed choline along with lipids in 7 predominantly cellular lesions simulating a neoplasm. We conclude that T1 weighted MT MR imaging appears to be more consistent in the tissue characterization of brain tuberculomas.     

Microwave-assisted rapid synthesis of tetragonal Cu2SnS3 nanoparticles for solar photovoltaics

A simple and rapid process for the synthesis of Cu₂SnS₃ (CTS) nanoparticles by microwave heating of metal–organic precursor solution is described. X-ray diffraction and Raman spectroscopy confirm the formation of tetragonal CTS. X-ray photoelectron spectroscopy indicates the presence of Cu, Sn, S in +1, +4, ?2 oxidation states, respectively. Transmission electron microscopy divulges the formation of crystalline tetragonal CTS nanoparticles with sizes ranging 2–25 nm. Diffuse reflectance spectroscopy in the 300–2,400 nm wavelength range suggests a band gap of 1.1 eV. Pellets of CTS nanoparticles show p-type conduction and the carrier transport in temperature range of 250–425 K is thermally activated with activation energy of 0.16 eV. Thin film solar cell (TFSC) with architecture: graphite/Cu₂SnS₃/ZnO/ITO/SLG is fabricated by drop-casting dispersion of CTS nanoparticles which delivered a power conversion efficiency of 0.135 % with open circuit voltage, short circuit current and fill factor of 220 mV, 1.54 mA cm^?2, 0.40, respectively.     

A parameter‐uniform scheme for the parabolic singularly perturbed problem with a delay in time

In this paper, a parameter‐uniform numerical scheme for the solution of singularly perturbed parabolic convection–diffusion problems with a delay in time defined on a rectangular domain is suggested. The presence of the small diffusion parameter ? leads to a parabolic right boundary layer. A collocation method consisting of cubic B ‐spline basis functions on an appropriate piecewise‐uniform mesh is used to discretize the system of ordinary differential equations obtained by using Rothe's method on an equidistant mesh in the temporal direction. The parameter‐uniform convergence of the method is shown by establishing the theoretical error bounds. The numerical results of the test problems validate the theoretical error bounds.     

A computational method for singularly perturbed nonlinear differential-difference equations with small shift

This paper is devoted to the numerical study of the boundary value problems for nonlinear singularly perturbed differential-difference equations with small delay. Quasilinearization process is used to linearize the nonlinear differential equation. After applying the quasilinearization process to the nonlinear problem, a sequence of linearized problems is obtained. To obtain parameter-uniform convergence, a piecewise-uniform mesh is used, which is dense in the boundary layer region and coarse in the outer region. The parameter-uniform convergence analysis of the method has been discussed. The method has shown to have almost second-order parameter-uniform convergence. The effect of small shift on the boundary layer(s) has also been discussed. To demonstrate the performance of the proposed scheme two examples have been carried out. The maximum absolute errors and uniform rates of convergence have been presented in the form of the tables.     

In situ Study Unravels Bio‐Nanomechanical Behavior in a Magnetic Bacterial Nano‐cellulose (MBNC) Hydrogel for Neuro‐Endovascular Reconstruction

Surgical clipping and endovascular coiling are well recognized as conventional treatments of Penetrating Brain Injury aneurysms. These clinical approaches show partial success, but often result in thrombus formation and the rupture of aneurysm near arterial walls. The authors address these challenging brain traumas with a unique combination of a highly biocompatible biopolymer hydrogel rendered magnetic in a flexible and resilient membrane coating integrated to a scaffold stent platform at the aneurysm neck orifice, which enhances the revascularization modality. This work focuses on the in situ diagnosis of nano‐mechanical behavior of bacterial nanocellulose (BNC) membranes in an aqueous environment used as tissue reconstruction substrates for cerebral aneurysmal neck defects. Nano‐mechanical evaluation, performed using instrumented nano‐indentation, shows with very low normal loads between 0.01 to 0.5 mN, in the presence of deionized water. Mechanical testing and characterization reveals that the nano‐scale response of BNC behaves similar to blood vessel walls with a very low Young´s modulus, E (0.0025 to 0.04 GPa), and an evident creep effect (26.01 ± 3.85 nm s^?1). These results confirm a novel multi‐functional membrane using BNC and rendered magnetic with local adhesion of iron‐oxide magnetic nanoparticles.     

Design,Synthesis, and Biological and In Silico Study of Fluorine‐Containing Quinoline Hybrid Thiosemicarbazide Analogues

A novel series of fluorine‐containing quinoline hybrid thiosemicarbazide analogues ( 8a–8l ) were synthesized and tested for their biological activities. The antibacterial results demonstrated that compounds 8d and 8l [minimal inhibitory concentration (MIC) 62.5 μg/mL] were shown to have higher biological activity than ampicillin against Escherichia coli. Compound 8b (MIC 25 μg/mL) was shown to have the highest activity than was ampicillin against Staphylococcus aureus. The antifungal results demonstrated that compound 8j (MIC 100 μg/mL) has shown good activity. Most of the targeted compounds have shown potent antimalarial activity. Compounds 8d (0.19 μg/mL), 8g (0.30 μg/mL), 8h (0.36 μg/mL), 8k (0.10 μg/mL), 8l (0.28 μg/mL), 8k (0.10 μg/mL), and 8l (0.28 μg/mL) have notable activity than does the reference drug quinine. Compounds 8d (0.27 μg/mL), 8g (0.30 μg/mL), and 8k (0.17 μg/mL) have shown excellent activity against chloroquine‐resistant strain. The MTT assay performed on peripheral blood lymphocyte cultures showed a high percentage of lymphocyte viability [ 8d (99.64), 8g (99.46), 8h (98.83), and 8k (99.51)] at a maximum dose (10 μg/mL), depicting no cytotoxicity of these compounds on human lymphocytes in vitro. A molecular docking study was performed on Pf‐DHFR‐TS inhibitor. A molecular dynamics study has shown compound 8g to have better affinity with protein. ADME‐Tox and pharmacophore study of synthesized compounds suggested prediction of active site.