A novel method for determining the optical constantn λ of metallic films

Optical changes of visible radiation in transmission through evaporated manganese and bismuth thin films were determined using the Rayleigh-Lowe refractometer. The variation of the phase change in transmission with thicknesst>t _c was utilized to determine directly the refractive indexn _λ.     

Adsorption of tartrazine from an aqueous solution by octadecyltrimethylammonium bromide-modified bentonite: Kinetics and isotherm modeling

A modified bentonite was prepared at different surfactant (ODTMA) loadings through ion exchange. The obtained organobentonite adsorbent materials were then used for the removal of an anionic dye, tartrazine, from an aqueous solution. The bentonite was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and Brunauer- Emmett-Teller (BET) method. The modification of organophilic bentonite by ODTMA increases the basal spacing d₀₀₁ from 24.1 to 39.1 Å when the cation exchange capacity increases from 1 to 4. The increase in the spacing, due to the basic organic modifications, was confirmed by the results of thermogravimetric analysis, Fourier transform infrared spectroscopy, and BET. The effects of contact time, initial concentration, and solution pH onto an adsorbed amount of tartrazine were investigated. To predict adsorption isotherm, the experimental data were analyzed using the Langmuir and Freundlich isotherm equations. It was determined that the isotherm data were fitted to the Langmuir isotherm. The adsorption process was also found to follow a pseudo-second-order kinetic model.     

An algorithm for finding the shortest element of a polyhedral set with application to lagrangian duality

An algorithm is developed which finds the point in a compact polyhedral set with smallest Euclidean norm. At each iteration the algorithm requires knowledge of only those vertices of the set which are adjacent to a current reference vertex. This feature is shown to permit the adoption of the technique to find iteratively the shortest subgradient (i.e. the direction of steepest ascent) of the lagrangian dual function for large scale linear programs. Procedures are presented for finding the direction of steepest ascent in both the equality constraint and the inequality constraint cases of lagrangian duality.     

Thermal transfer simulation regarding the rotational moulding of polyamide 11

Simulation of thermal phenomena in rotational moulding is very important to follow the evolution of the temperature in various zones of this process. It was a question of modelling heat gradients developing in rotational moulding part. Thermal model tested take into account the temperature change (thermal transfer mechanism) of melting and crystallization pseudo-stages (enthalpy method). Series of tests in polyamide 11 (PA11) were carried out by means of rotational moulding STP LAB, and non-isothermal crystallization kinetics of rotational moulding PA11 grade are measured and analysed by DSC technique type TAQ20. A result of non-isothermal crystallization of the studied polyamide was confronted with Ozawa model. In order to test the validity degree of enthalpy method (layer to layer), another approach based on Ozawa model has also been used in the case of cooling pseudo-stage. As results, the rotational moulding of PA11 was successfully carried out. The simulation of the fusion and crystallization stages, by application of Ozawa model coupled with enthalpy method gave a good representation of experimental data.     

Structure and intercalation behavior of copper II on the layered sodium silicate magadiite material

In this work, the ion-exchange reaction of the sodium silicate Na-magadiite with cupric ions was studied and the mode of interaction of the intercalated Cu²⁺ ions with silicate sheet was investigated. To do this, Na-magadiite was first synthesized using a hydrothermal method and characterized. It is then used to prepare Cu-exchanged magadiite materials with different copper contents by an ion-exchange reaction. The solids obtained were characterized by chemical and thermogravimetric analyses, powder X-ray diffraction, UV–Visible diffuse reflectance and Fourier transform spectroscopy, scanning electron microscopy and transmission electron microscopy. The results show that magadiite has a high affinity to copper ions and that the experimental exchange rate can be easily predicted. They show also that the intercalated Cu²⁺ ions are non-hydrated and are in direct interactions with the terminal interlayer ≡Si–O^? groups, to which they are also probably strongly linked. Furthermore, the interlayer copper oxide species phase formed are in form of small particles homogeneously dispersed. Finally, the introduction of Cu²⁺ ions into the interlayer space does not substantially affect the structure of the Cu-exchanged materials but rather tends to stabilize it by increasing the decomposition temperature of the silanol groups .     

Inhibition of Human Immunodeficiency Type 1 Virus (HIV-1) Life Cycle by Different Egg White Lysozymes

Lysozyme is a relatively small enzyme with different biological activities, which is found in tears, saliva, egg white, and human milk. In the study, the anti-HIV-1 activity of lysozymes purified from quail, Meleagris, and hen egg white has been determined. For this end, a time-of-drug-addition assay was performed to identify the target of anti-HIV-1 agents and for determination of probable anti HIV-1 mechanism of the studied lysozyme, the binding affinity of the lysozymes to the human CD4 receptor was studied by molecular docking method. To define structural differences between studied lysozymes, structural motifs of them were predicted by MEME tool. Quail, hen, and Meleagris lysozymes showed potent anti-HIV-1 activity with EC₅₀ of 7.5, 10, and 55 nM, respectively. The time-of-drug-addition study demonstrated that the inhibitory effect of all purified lysozymes is before HIV-1 infection. The frequency and intensity of CD4 expression in PBMCs decreased in the presence of all mentioned lysozymes. Also, the expression level of C-C chemokine receptor type 5 (CCR5) and chemokine receptor type 4 (CXCR4) on CD4+ T cells was not changed in cells treated with these lysozymes. The results of in silico study confirmed that the binding energy of quail lysozyme with CD4 was more than that of other studied lysozymes. The results revealed that these lysozymes restrict HIV-1 attachment to host cell CD4.     

Speciation of manganese in fresh water-I Use of EPR studies

The process of standardization of the use of electron paramagnetic resonance (EPR) spectrometry in the determination of Mn(II) species in aqueous solution by comparison with atomic absorption spectrometry (AAS) is discussed. It is shown that EPR signals obtained from standardized aqueous solutions of manganese(II) perchlorate and nitrate in the concentration range of 0.05-2 mg/l. do not vary significantly over the pH range 2.1-7.0. Study of the effect (on the manganese EPR signals) of the addition of inorganic ions commonly found in significant concentrations in natural waters, viz. chloride, sulphate and bicarbonate, has shown that such ions, at the levels reported to occur in surface fresh waters, will not complex manganese(II); however, evidence is obtained that humic acid/manganese complexes could be present in such waters. The EPR signals are not affected by ionic strengths of the levels found in fresh waters.     

Gas‐Phase Interactions between Lead(II) Ions and Cytosine: Tandem Mass Spectrometry and Infrared Multiple‐Photon Dissociation Spectroscopy Study

Gas‐phase interactions between Pb²⁺ ions and cytosine (C) were studied by combining tandem mass spectrometry, infrared multiple photon dissociation spectroscopy, and density functional theory (DFT) calculations. Both singly and doubly charged complexes were generated by electrospray. The [Pb(C)?H]⁺ complex was extensively studied, and this study shows that two structures, involving the interaction of the metal with the deprotonated canonical keto‐amino tautomer of cytosine, are generated in the gas phase; the prominent structure is the bidentate form involving both the N1 and O2 electronegative centers. The DFT study also points out a significant charge transfer from the nucleobase to the low‐lying p orbitals of the metal and a strong polarization of the base upon complexation. The various potential energy surfaces explored to account for the fragmentation observed are consistent with the high abundance of the [PbNH₂]⁺ fragment ion.     

Determination of the polyphenolic content of a Capsicum annuum L. extract by liquid chromatography coupled to photodiode array and mass spectrometry detection and evaluation of its biological activity

The present study was aimed to investigate the polyphenolic profile of a pepper (Capsicum annuum L.) extract from Algeria and evaluate its biological activity. The total polyphenol content of the extract was determined as 1.373 mg of gallic acid equivalents (±0.0046), whereas the flavonoids were determined as 0.098 mg of quercetin (±0.0015). The determination of the complete polyphenolic profile of the extract was achieved by liquid chromatography with an RP‐amide column in combination with photodiode array and mass spectrometry detection through an electrospray ionization interface. A total of 18 compounds were identified, of which five were reported for the first time in the sample tested. Quercetin rhamnoside was the most abundant compound (82.6 μg/g of fresh pepper) followed by quercetin glucoside (19.86 μg/g). The antioxidant activity and antimicrobial effects were also determined. For the antimicrobial tests assessed against Gram‐positive and Gram‐negative bacteria, kaempferol showed the strongest inhibitory effect followed by quercetin and caffeic acids. In the study of the cytotoxicity of the extract, the cancer cells (U937) were more affected than the normal cells (peripheral blood mononucleated cells), with more than 62% inhibition at the highest concentration.