On the determination of the impulsive Sturm–Liouville operator with the eigenparameter-dependent boundary conditions

In the present work, we consider the inverse problem for the impulsive Sturm–Liouville equations with eigenparameter-dependent boundary conditions on the whole interval (0,π) from interior spectral data. We prove two uniqueness theorems on the potential q(x) and boundary conditions for the interior inverse problem, and using the Weyl function technique, we show that if coefficients of the first boundary condition, that is, h₁,h₂, are known, then the potential function q(x) and coefficients of the second boundary condition, that is, H₁,H₂, are uniquely determined by information about the eigenfunctions at the midpoint of the interval and one spectrum or partial information on the eigenfunctions at some internal points and some of two spectra.     

Convenient stereoselective synthesis of some 3-aminosteroid scaffolds

Abstract

An efficient stereoselective synthesis 3α- and 3β-aminoandrostan-17-one and 3α-amino dehydroepiandrosten-17-one based on a Mitsunobu reaction has been developed, using azide as the ammonia equivalent. All the products were isolated in high yield.     

Spectrophotometric study of etodolac complexes with copper (II) and iron (III)

A rapid, simple, and selective method was developed for the determination of etodolac. The method depends on complexation of etodolac with copper (II) acetate and iron (III) chloride followed by extraction of complexes with dichloromethane and then measuring the extracted complexes spectrophotometrically at 684 and 385 nm in case of Cu (II) or Fe (III), respectively. Different factors affecting the reaction, such as pH, reagent concentration, and time, were studied. By use of Job's method of continuous variation, the molar ratio method, and elemental analysis, the stoichiometry of the reaction was found to be in the ratio of 1:2 and 1:3, metal:drug in the case of Cu (II) and Fe (III), respectively. The method obeys Beer's law in a concentration range of 2.00-9.00 and 0.50-2.00 mg/mL in case of Cu (II) and Fe (III), respectively. The stability of the complexes formed was also studied, and the reaction products were isolated for further investigation. The complexes have apparent molar absorptivities of about 32.14 +/- 0.97 and 168.32 +/- 1.12 for Cu (II) and Fe (III), respectively. The suggested procedures were successfully applied to the analysis of pure etodolac and its pharmaceutical formulations. The validity of the procedures was further ascertained by the method of standard additions, and the results were compared with other reported spectrophotometric methods and showed no significant difference in accuracy and precision.     

New cytotoxic flavonoids from aerial parts of Platycladus orientalis L.

Abstract

Investigation of Platycladus orientalis yielded five flavonoids, including aglycone flavone 1 (apigenin), flavone glycoside 2 (apigenin 7-O-β-D-glucopyranoside), new gernaylated flavone glycoside 3 (apigenin 8-gernayl-4′-O-α-gluco pyranoside) and two new pernylated flavonoid glycosides 4 & 5 (apigenin 8-pernyl-4′-glucopyranosyl-7-O-α-glucopyranoside and apigenin 5-pernyl-7-glucopyranosyl-4′-O-β-D-glucopyranoside). Their structures were elucidated on the basis of spectroscopic evidence. The cytotoxicity of compounds 1–5 were tested against Lung adenocarcinoma (A549), human hepatocellular liver carcinoma (HepG2), human breast carcinoma (MCF-7) cell lines and mouse fibroblast cell line NIH/3T3 as normal cells. This assay gave spot on structure activity relationship which, showed that cytotoxicity of compounds (1) and (2) against three cell lines was weak as IC₅₀?>?15. Compounds (4) and (5) had moderate cytotoxic and no toxic effect on normal cell. Compound (3) showed high cytotoxic activity against tested three cell lines with no toxic effect of normal cells.

     

Chemical modification of the alkaloid 2,3-tetramethylene-3,4-dihydroquinazol-4-one

The 1,2-dihydro derivative of 2,3-tetramethylene-3,4-dihydroquinazol-4-one was produced by reduction and characterized using NMR spectra. 1-Acyl-1,2,3,4-tetrahydroquinazol-4-ones and ureas were synthesized by acylation of 2,3-tetramethylene-1,2,3,4-tetrahydroquinazol-4-one with acid chlorides and arylisocyanates, respectively. The molecular structures of 1-acetyl-and-m-chlorophenylaminocarbonyl-2,3-tetramethylene-1,2,3,4-tetrahydroquinazol-4-ones were established using x-ray structure analyses. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 364–370, July–August, 2007.     

Carbon modified (CM)-n-TiO2 thin films for efficient water splitting to H2 and O2 under xenon lamp light and natural sunlight illuminations

Visible light-active carbon modified n-type titanium oxide (CM-n-TiO₂) thin films were synthesized by both flame oxidation and a combination of spray pyrolysis and flame oxidation. An undoped reference sample was also synthesized in an electric oven for comparison. Photoresponse of CM-n-TiO₂ and n-TiO₂ was evaluated by measuring the rates of water splitting to hydrogen and oxygen, in terms of observed photocurrent densities. Under monochromatic illumination from a xenon lamp, the integrated photocurrent densities from 300 nm to wavelengths corresponding to band gaps were found to be 1.12, 7.7, and 12.7 mA cm⁻² for optimized oven-made n-TiO₂ (sample 1), flame-made (sample 2), and spray pyrolysis flame-made CM-n-TiO₂ (sample 3) thin films at 0.48, 0.24, and 0.215 V biases, respectively. The corresponding maximum photoconversion efficiencies for these thin films were 0.84%, 7.62%, and 12.89%, respectively. Under actual natural global AM 1.5 sunlight illumination of 1 sun, the photocurrent densities for water splitting were 0.85, 5.89, and 12.27 mA cm⁻² for samples 1, 2, and 3, respectively. These photocurrent densities generated the maximum photoconversion efficiencies of 0.67%, 5.63%, and 12.26% for samples 1, 2, and 3, respectively, under global sunlight illuminations. These values compared well with those found under monochromatic light illumination from the xenon lamp. The increasing efficiencies were found to be consistent with lowering of main band gap from 3.0 eV to 2.65 eV and the generation of mid-gap bands at 1.6 eV and 1.4 eV above the valence band for samples 2 and 3, respectively. Carbon contents were found to be 0.0, 17.60, and 23.23 atom% for samples 1, 2, and 3, respectively. Dedicated to the 85th birthday of John O’ M. Bockris.     

Crystallization kinetics of Li2O-PbO-V2O5 glasses

Lead vanadate glasses of the system 5Li₂O−(45−x) PbO−(50+x) V₂O₅, with x=0, 5, 10, and 15 mol% have been prepared and studied by differential scanning calorimetry (DSC). The crystallization kinetics of the glasses were investigated under non-isothermal conditions applying the formal theory of transformations for heterogeneous nucleation to the experimental data obtained by DSC using continuous-heating techniques. In addition, from dependence of the glass-transition temperature (T_g) on the heating rate, the activation energy for the glass transition was derived. Similarly the activation energy of the crystallization process was determined and the crystallization mechanism was characterized. The results reveal the increase of the activation energy for glass transition which was attributed to the increase in the rigidity, the cross-link density and the packing density of these glasses. The phases into which the glass crystallizes have been identified by X-ray diffraction. Diffractograms of the transformed material indicate the presence of microcrystallites of Li_0.30V₂O₅, Li_0.67O₅V₂, LiV₆O₁₅, Li₄O₄Pb, and O₇Pb₂V₂ in a remaining amorphous matrix.     

Measurement of neutron spectrum parameters for NAA irradiation holes in the Jordan research and training reactor

Three irradiation holes coupled to a pneumatic transfer system were installed for neutron activation analysis in the Jordan Research and Training Reactor (JRTR), which is the first research reactor in Jordan. To perform instrumental neutron activation analysis, neutron spectrum parameters, such as thermal neutron flux, α and f for the irradiation holes, should be measured. The Cd-ratio method was applied for the determination of the aforementioned parameters. For this purpose, 0.1% Au–Al wires and Zr foils were irradiated with and without Cd-cover, and the Cd ratios were determined for Au-198, Zr-95, and Zr-97/Nb-97m nuclides. Then, the parameters were calculated and determined at three irradiation holes.

     

Development of constitutive laws for thermomechanical behaviors of composites containing multi-type ellipsoidal reinforcements

Composite materials are widely used in industrial applications because of their excellent properties and behaviors. While a composite material is defined as a mixture of two or more different materials, many research works in the literature dealt with composites of only two constituents, which are matrix and one type of particles. On the other hand, the theoretical research works that dealt with more than two constituents are rare. Using some additives affects the sintering behavior, the tribological behavior and the fracture mechanics behavior of composites. For example, a suitable amount of additives as sintering aids, in the sintering process, could lower the sintering temperature, enhance phase wettability and bonding strength and improve the interlaminar fracture resistance of a composite. Therefore, it is worthwhile to develop the constitutive laws that describe the behavior of such composite materials. Accordingly, the aim of this paper is to modify the previous paper, Shabana (2003) [Shabana, Y.M., 2003. Incremental constitutive equation for discontinuously reinforced composites considering reinforcement damage and thermoelastoplasticity. Computational Materials Science 28, 31–40], in order to propose constitutive laws that predict the thermomechanical behavior of composites containing multi-type ellipsoidal reinforcements. This includes reinforcements with different materials and/or different shapes that are represented by aspect ratios. These constitutive laws not only predict the macroscopic and microscopic thermoelastoplastic behaviors of composites containing multi-type ellipsoidal reinforcements, but also characterize their different overall effective properties such as modulus of elasticity, Poison’s ratio and thermal expansion coefficient in different directions. Beside this, they are applicable for porous materials and composites with multiple reinforcements and porosities of different shapes and distributions. In the present numerical analyses, composites with two, three and four constituents considering different materials and aspect ratios as well as reinforcement damage are discussed.     

Stokeslets-meshfree computations and theory for flow in a collapsible microchannel

We present both a theoretical model and Stokeslets-meshfree computations to study the induced flow motions and transport in a 2D microchannel with moving multiple prescribed dynamic collapses (contractions) along the upper wall. The channel is assumed to have a length that is much greater than its width, i.e., ${(\delta = W/L \ll1)}$ . The wall contractions are set to move with or without time (phase) lags with respect to each other. The theoretical analysis presented is based on the quasi-steady state approximations and the lubrication theory at the low Reynolds number flow regime. The meshfree numerical method is based on the method of fundamental solutions MFS, which uses a set of singularized force elements called Stokeslets to induce the flow motions. The flow field developments and structures induced by these wall contractions are given at various time snapshots during the collapsing cycle. The effect of the wall contractions amplitudes and the phase lags between individual contractions on the flow variables and on the time-averaged net flow over a complete cycle of contractions motions is studied. The present study is motivated by pumping mechanisms observed in insects, physiological systems that use multiple contractions to transport fluid, and the emerging novel microfluidic devices that mimic these systems.