Spectrophotometric Methods for the Determination of Chloramphenicol,Dexamethasone Sodium Phosphate,and Tetrahydrozoline HCl in their Pure and Ophthalmic Dosage Forms

Journal of Applied Spectroscopy - Chloramphenicol (CHL), dexamethasone sodium phosphate (DSP), and tetrahydrozoline HCl (THZ) are co-formulated for conjunctivitis treatment. The ternary mixture...     

A Heroin Epidemic Model: Very General Non Linear Incidence,Treat-Age,and Global Stability

The aim of this work is to establish the existence of multi-peak solutions for the following class of quasilinear problems

$$ - \mbox{div} \bigl(\epsilon^{2}\phi\bigl(\epsilon|\nabla u|\bigr)\nabla u \bigr) + V(x)\phi\bigl(\vert u\vert\bigr)u = f(u)\quad\mbox{in } \mathbb{R}^{N}, $$

where \(\epsilon\) is a positive parameter, \(N\geq2\), \(V\), \(f\) are continuous functions satisfying some technical conditions and \(\phi\) is a \(C^{1}\)-function.

     

Modeling of MIG/MAG welding with experimental validation using an active contour algorithm applied on high speed movies

This paper investigates some issues in physical modeling of metal inert gas/metal active gas (MIG/MAG) welding process in the short arc mode. In this mode, a metal supply is molten in the arc state and then transferred to the weld pool during the short-circuit state. A hybrid model having two distinct continuous states whose switchings are controlled by two guard conditions is proposed. Due to the complexity of the physical phenomena involved in the welding process, simplifications are used to obtain a model accounting for the main physical contributions but simple enough to yield an efficient, fast and numerically tractable simulator which can be used intensively for evaluating different control strategies. In an attempt to validate the proposed model, different measurements have been made including supply voltage and current sampled synchronously with high speed digital video. In order to extract some relevant quantities representative of the metal transfer from image sequences, an active contour algorithm is developed and tested. The effectiveness of the proposed model in the prediction of major tendencies of a welding process, especially in the arc state, is shown using experimental data. Some limitations of the model during the metal transfer are also stressed and possible remedies are then proposed.     

Steric substituent effect on the resin catalyzed hydrolysis of alkyl acetate esters

The rates of hydrolysis of seven acetate esters substituted in the alkyl group have been studied in the presence of a sulfonated cation exchange resin in 70% aqueous acetone solution. the slower hydrolysis rates with increasing size of substituent are related to increasing steric influence, as determined by decreasing values of the steric substituent parameter, E_s. The efficiency of the resin catalyst is related to the entropy of substituents. Influence caused by steric hindrance on reaction rates accounts satisfactorily for observed variations of the enthalpies and entropies of activation with alkyl group substituents. The entropy, S^x, values increase in the order: n-octyl-

, , 70%- . , , E_S. . , . , S^*, : --<-<, .

     

Natural radioactivity and their radiological effects for different types of rocks from Egypt

The present work investigated the radioactivity level of the rocks samples collected from different sites in Egypt. Twenty one rocks samples were analyzed by gamma-ray spectrometry using NaI(Tl) detector with specially designed shield. The concentration of three natural radionuclides namely ²²⁶Ra, ²³²Th and ⁴⁰K has been determined and compared with chemical data obtained by XRF analysis. The results showed that these radionuclides were present in concentration ranges (3.4-99, 7.5-134 and 93-3382 Bq kg⁻¹), (54.9-211.6, 20.71-170.5 and 2068-2344 Bq kg⁻¹) and (13-106, 29.25-106.1 and 682-755 Bq kg⁻¹) for gneiss, granite and basalt rocks, respectively, while the values were (7.5, 12.5 and 263.9 Bq kg⁻¹) and (113, 148.5 and 1672 Bq kg⁻¹) for ²²⁶Ra, ²³²Th and ⁴⁰K in sandstone and siltstone rocks, respectively. Also radium equivalent activity, total dose rates and external hazard index of the rocks samples under consideration were calculated. The results showed that granite rocks contain a high proportion of natural radioactive elements, while sandstone rocks have lesser radioactivity concentration compared with other types of rocks.     

Influence of microcrystalline cellulose fiber (MCCF) on the morphology of poly(3-hydroxybutyrate) (PHB)

Biopolymer composites were prepared from poly(3-hydroxybutyrate) (PHB)/microcrystalline cellulose fiber (MCCF)/plastiziers/poly(vinyl acetate) by melt extrusion. The morphology, crystal structure, and non-isothermal crystallization of these composites were investigated by polarized optical microscopy (POM), differential scanning calorimetry, Fourier transform infrared spectrometer, and wide-angle X-ray diffraction. The results of DSC indicate that the addition of small amount of MCCF improved the crystallization rate. Non-isothermal crystallization shows that the composites 1 and 2 have lower crystallization half time (t _{0 .5}) than that of pure PHB. Higher MCCF contents in PHB (composite 4) lead to a decrease in the crystallization rate. POM micrographs show that the MCCF were well dispersed in the PHB matrix and served as a nucleating agent with a strong change in PHB morphology. Increasing the isothermal crystallization temperature above 120 °C, leads to the formation of banded spherulites with large regular band spacing. Decreasing the isothermal crystallization temperature below 100 °C produces more and small spherulites.     

Influence of operating conditions on the rejection of cobalt and lead ions in aqueous solutions by a nanofiltration polyamide membrane

The potential use of nanofiltration polyamide membrane for removing cobalt and lead ions from wastewater was investigated. Rejection experiments were conducted with Pb(NO₃)₂ and Co(NO₃)₂ in both single-salt solutions and mixtures. Experimental rejection rates were corrected for concentration polarization phenomenon by means of film theory. The structural features of the membrane (pore radius and thickness-to-porosity ratio) were first estimated from the fitting of glucose rejection rates. Its surface charge properties were then investigated in single-salt solutions at pH values between 3 and 7. Rejection of both heavy metal ions was found to be influenced by operating conditions such as permeate flux, solution pH and feed salt concentration. In single-salt solutions, rejection of lead was higher than that of cobalt at pH ≥ 5. This behavior may be explained by (i) higher normalized volume charge density in the Pb(NO₃)₂ than in the Co(NO₃)₂ solution and (ii) lower ionic strength of the Pb(NO₃)₂ solution as compared with the Co(NO₃)₂ solution. At pH < 5, the dielectric exclusion would be more important for Co(NO₃)₂ than for Pb(NO₃). Lead rejection was almost the same in both single-salt solutions and ternary mixtures, whereas cobalt rejection was strongly affected by the presence of lead. Cobalt was found to be rejected much more than lead in mixtures at equal mass concentrations, the difference between rejections of the two cations being greater as pH increased.     

Gamma Ray Interaction with Some High-Lead Glasses Containing Chromium Ions

Optical absorption of some selected high-lead borate glasses containing chromium exposed to different doses of gamma-irradiation was studied. The results obtained showed that the absorption bands before and after irradiation exhibited changes with the radiation dose and chemical composition of the glass. The response of the glass to gamma irradiation was related to the creation and spread of defects “color centers,” the approach of a saturation condition after a certain irradiation dose, and the possible photochemical effect on the transition metal present in the glass.     

A new adaptive subband decomposition approach for automatic analysis of NMR data

This paper presents a non-iterative, fast, and almost automated time-data analysis method for NMR spectroscopy, based on a new adaptive implementation of high resolution methods used in spectral subbands. It is intended to avoid the choice of the decimation factor (or the width of the spectral windows) which, in the case of a uniform decomposition, strongly conditions the estimation results, and to diminish the computational burden. It is achieved through successive decimation/estimation stages each followed by a test procedure in order to decide whether or not the process should continue. The proposed test is based on a local spectral flatness measure of the estimation residuals. This stop-criterion involves an a posteriori validation of the estimation, thus the method proposed allows one to obtain a better detection rate at a lower complexity comparatively to other stopping rules, while preserving a reasonable estimation variance. Moreover, the reliability of the fitting algorithms considered is improved, by decreasing the influence of the model order and the number of false detections. Finally, the method is more efficient than Fourier transform (FT) at low signal-to-noise ratio (SNR). The effectiveness of the method is demonstrated by analyzing a simulation signal and raw carbon-13 experimental data.