First-principles calculations of the structural, electronic and optical properties of cubic BxGa1−xAs alloys

Density functional calculations are performed to study the structural, electronic and optical properties of technologically important B_xGa_1−xAs ternary alloys. The calculations are based on the total-energy calculations within the full-potential augmented plane-wave (FP-LAPW) method. For exchange-correlation potential, local density approximation (LDA) and the generalized gradient approximation (GGA) have been used. The structural properties, including lattice constants, bulk modulus and their pressure derivatives, are in very good agreement with the available experimental and theoretical data. The electronic band structure, density of states for the binary compounds and their ternary alloys are given. The dielectric function and the refractive index are also calculated using different models. The obtained results compare very well with previous calculations and experimental measurements.     

Labeling of new formulation of tin–sucralfate freeze-dried kit with technetium-99m and its biological evaluation

The present investigation deals with a simple preparation of new formulation of tin?Csucralfate freeze-dried kit (F.D.K.), to be directly labeled with ^99mTc at optimal pH value of 7.0. The lyophilized form containing 100?mg sucralfate and 11.3?mg dihydrated stannous chloride. Other optimal pH values of the preparation were found to be from 4.0 to 11.0. The range of sucralfate amount studied (50?C500?mg) not affected the radiochemical purity of the labeled complex. The radiochemical purity and the stability of the labeled preparation that assessed by filtration were more than 95%. ^99mTc sucralfate was radiochemical stable up to a specific activity of 1,000?mCi per gram which was more stable than earlier published value (700?mCi per gram) without any radiolytic decomposition. The biological behavior of ^99mTc-pertechnetate was evaluated in two groups of animals, the first group (neither fasted nor ulcerated) and the second group (fasted and ulcerated mice). The data of organ distribution of ^99mTc?Csucralfate in ulcerated fasted mice showed that more than 99% of the administered dose was accumulated in the stomach (87.92%) and intestine (11.43%). The radioanalytical results together with the in vivo-biological behavior of the labeled preparation demonstrate it??s stability, efficacy and usefulness in medical applications for the detection of gastrointestinal ulcers.     

Nonlinear analytical multi-dimensional convolution solution of the second order system

In this paper, a procedure to analytically develop an approximate solution for the prototypical nonlinear mass–spring–damper system based on multi-dimensional convolution expansion theory is offered. The nonlinearity herein is mathematically considered in quadratic and bilinear terms. A variational expansion methodology, one of the most efficient analytical Volterra techniques, is used to develop an analytical two-term Volterra series. The resultant model is given in the form of first and second kernels. This analytical solution is visualized in the time domain followed by a parametric study for understanding the influence of each nonlinear/linear term appearing in the kernel structure. An analytical nonlinear step response is also conducted to characterize the overall system response from the fundamental components. The developed analytical step response provides an illumination for the source of differences between nonlinear and linear responses such as initial departure time, settling time, and steady value. Feasibility of the proposed implementation is assessed by numerical examples. The developed kernel-based model shows the ability to predict, understand, and analyze the system behavior beyond that attainable by the linear-based model.     

Kinetics of isothermal decomposition of γ-irradiated and unirradiated Co(II) succinato complex

A kinetic study of the dehydration and decomposition of -irradiated and unirradiated Na₂[Co(C₄H₄O₄)₂]·7H₂O has been studied using isothermal and dynamic thermogravimetric methods. The thermal dehydration occurs in one step regulated by a random nucleation model (A₃), while the decomposition of anhydrous salt is controlled by a phase boundary controlled model (R₃). The kinetic parameters obtained at three heating rates are in good agreement; however, the values of the kinetic parameters estimated isothermally are slightly different from those estimated dynamically. Irradiation enhanced both the dehydration and the decomposition reactions but did not modify their mechanisms. The activation energy decreases as the irradiation dose increases.

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Zusammenfassung Unter Anwendung von isothermen und dynamischen thermogravimetrischen Methoden wurde eine kinetische Untersuchung der Dehydratation und der Zersetzung von -bestrahltem und unbestrahltem Na₂[Co(C₄H₄O₄)₂]·7H₂O durchgeführt. Die thermische Dehydratation erfolgt in einem Schritt, bestimmt durch ein Random-Keimbildungsmodell (A₃), während die Zersetzung der wasserfreien Salze durch ein phasengrenzenkontrolliertes Modell bestimmt wird (R₃). Die bei drei Aufheizgeschwindigkeiten erhaltenen kinetischen Parameter stehen in guter Übereinstimmung; jedoch weichen die isotherm geschätzten kinetischen Parameter etwas von den dynamisch ermittelten ab. Bestrahlung mehrt sowohl die Dehydratations- als auch die Zersetzungsreaktionen, beläßt deren Mechanismus jedoch unverändert. Die Aktivierungsenergie sinkt mit zunehmender Strahlungsdosis.

     

Synthesis and extraction properties of preorganized host molecules based on tetraamides of thiacalix[4]arene

Template effect of alkali metal ions was employed to prepare three isomers of tetraamide of p-tert-butylthiacalix[4]arene: cone, partial cone and 1,3-alternate. It was demonstrated that pre-organization of four amide fragments attached to the calix[4]arene platform has a strong macrocyclic cooperative effect on the extraction ability of the title hosts.     

Synthesis of polyfunctionally substituted heteroaromatic compounds via benzotriazolyl chalcones with antimicrobial and antifungal activities

The utility of both 3‐(1‐benzotriazolyl) chalcone derivatives 3a‐c and 2‐(1‐benzotriazolyl)‐1,4‐pentadien‐3‐one (18) in the synthesis of some new 2‐(1H)‐pyridone, pyridine, pyrazole and isoxazole derivatives is reported. Antimicrobial and antifungal screening of some selected examples from the synthesized products were carried out. The structure of the newly synthesized compounds was elucidated by elemental analysis, ir, ¹H and ¹³C nmr investigations.     

Simultaneous kinetic determination of sulfite and sulfide using artificial neural networks

Artificial neural networks (ANNs) are proposed for the determination of sulfite and sulfide simultaneously. The method is based on the reaction between Brilliant Green (BG) as a colored reagent and sulfite and/or sulfide in buffered solution (pH 7.0) and monitoring the changes of absorbance at maximum wavelength of 628 nm. Experimental conditions such as pH, reagents concentrations, and temperature were optimized and training the network was performed using principal components (PCs) of the original data. The network architecture (number of input, hidden and output nodes), and some parameters such as learning rate (η) and momentum (α) were also optimized for getting satisfactory results with minimum errors. The measuring range was 0.05-3.6 μg ml⁻¹ for both analytes. The proposed method has been successfully applied to the quantification of the sulfite and sulfide in different water samples.     

Synthesis and Characterization of New Thiacalix[4]arenes Bearing Semicarbazide and Thiosemicarbazide Fragments at the Lower Rim

Starting from thiacalixarene tetraacetates, tetraacetohydrazides have been prepared and then used for the introduction of semicarbazide and thiosemicarbazide fragments into the lower rim by the reaction with phenyl isocyanate and phenyl isothiocyanate in dry toluene. The structures of the prepared compounds were investigated by FT‐IR, FAB‐MS, ¹H NMR, and X‐ray crystallography, and their receptor properties were examined by liquid liquid extraction of dichromate anions.     

Well-Defined Ni(0) and Ni(II) Complexes of Bicyclic (Alkyl)(Amino)Carbene (MeBICAAC): Catalytic Activity and Mechanistic Insights in Negishi Cross-Coupling Reaction

Negishi cross-coupling reaction of organozinc compounds as nucleophiles with aryl halides has drawn immense focus for C−C bond formation reactions. In comparison to the well-established library of Pd complexes, the C−C cross-coupling of this particular approach is largely primitive with nickel-complexes. Herein, we describe the syntheses of Ni(II) complexes, [(^MeBICAAC)₂NiX₂] (X=Cl ( 1 ), Br ( 2 ), and I ( 3 )) by employing the bicyclic (alkyl)(amino)carbene (^MeBICAAC) ligand. The reduction of complexes 1 – 3 using KC₈ afforded the two coordinate low valent, Ni(0) complex, [(^MeBICAAC)₂Ni(0)] ( 4 ). Complexes 1 – 4 have been characterized by spectroscopic techniques and their solid-state structures were also confirmed by X-ray crystallography. Furthermore, complexes 1 – 4 have been applied in a direct and convenient method to catalyze the Negishi cross-coupling reaction of various aryl halides with 2,6-difluorophenylzinc bromide or phenylzinc bromide as the coupling partner in the presence of 3 mol % catalyst. Comparatively, among all-pristine complexes, 1 exhibit high catalytic potential to afford value-added C−C coupled products without the use of any additive. The UV-vis studies and HRMS measurements of controlled stochiometric reactions vindicate the involvement of Ni(I)−NI(III) cycle featured with a penta-coordinated Ni(III)-aryl species as the key intermediate for 1 whereas Ni(0)/Ni(II) species are potentially involved in the catalytic cycle of 4 .     

Ligational,DFT modeling and biological properties of some new metal complexes with 3-(bromoacetyl)coumarin and 1,10-phenanthroline

The synthesis and characterization of Mn (II), Fe (II), Co (II), Ni (II), Cu (II) and Zn (II) complexes with 3-(bromoacetyl)coumarin (BAC) in presence of 1,10-phenanthroline (Phen) were reported and described by elemental analysis, molar conductivity, FT-IR, UV–Vis and effective magnetic moments. TG and DTG have been applied to study the decomposition mechanisms for BAC, Phen and their complexes. The analytical results and spectral studies showed that BAC and Phen act as bidentate ligands via oxygen of α, β-unsaturated ketone and oxygen of lactone carbonyl of coumarin and two pyridyl nitrogen atoms of Phen. Octahedral geometries have been proposed for all complexes and the kinetic parameter (E*, ΔH*, ΔS* and ΔG*) were calculated using Coats-Redfern (CR) and Horowitz-Metzeger (HM) methods. DFT calculations (bond lengths, bond angles, total energy, heat of formation, dipole moment and the lowest energy model structures) have been determined. The antibacterial activities for synthesized complexes were assayed against some selected bacterial and the complexes displayed a very highly significant against L. monocytogens.