An Interaction Value Perspective on Firms of Differing Size

We present a general model of a network of interacting individuals, each of whom derives a known, real-valued benefit from each possible dyadic interaction. The model views interactions as knowledge-transfer exchanges that add value to the organization. We use this model to derive interaction patterns within an organization. We assume that the value of dyadic interaction benefits is distributed as a randomly permuted geometric series. Moreover, interactions only add value when a large enough waiting period is observed between interaction attempts. We show that an organization optimized for knowledge transfer has a distribution of interaction frequencies which correlates well with observations. Organizations of differing sizes can have similar optimal structures as long they have similar normalized levels of interdependence between interactions, and distribution of interaction benefit values. This research has implications for the design of communication infrastructure in a growing organization, as well as for the predictive value of modeling organizations at different scales.     

Spectrophotometric Determination of Some Phenolic Antibiotics in Dosage Forms

 A simple and sensitive spectrophotometric method is described for the determination of some phenolic antibiotics namely: cefadroxil, amoxicillin and vancomycin. The method is based on the measurement of the orange yellow species produced when the drugs are coupled with diazotized benzocaine in triethylamine medium. The method is applicable over the range of 0.8–12 μg/ml for cefadroxil, 2–16 μg/ml for amoxicillin and 2–18 μg/ml for vancomycin. The formed compounds absorb at 455 nm for both cefadroxil and amoxicillin and at 442 nm for vancomycin. The proposed method has detection limits of 0.018 μg for cefadroxil, 0.0034 μg for amoxicillin and 0.0156 μg for vancomycin. The stoichiometric ratio for the studied compounds was found to be 1:1 and a proposal of the reaction pathway was made. The proposed method was applied for the analysis of the cited drugs in their pharmaceutical preparations. The results are in good agreement with those obtained by the official methods. Received February 7, 2000. Revision June 14, 2000.     

On the Quasi-Static Evolution of Nonequilibrium Steady States

The quasi-static evolution of steady states far from equilibrium is investigated from the point of view of quantum statistical mechanics. As a concrete example of a thermodynamic system, a two-level quantum dot coupled to several reservoirs of free fermions at different temperatures is considered. A novel adiabatic theorem for unbounded and nonnormal generators of evolution is proven and applied to study the quasi-static evolution of the nonequilibrium steady state (NESS) of the coupled system. Submitted: April 23, 2006. Accepted: October 4, 2006.     

GC-MS and LC-MS Identification of the Phenolic Compounds Present in the ethyl Acetate Fraction Obtained from Senna tora,L. Roxb. seeds

The aim of this work is to characterize the active constituents present in the ethyl acetate fraction of Senna tora, L. Roxb. seeds. Due to the fact that the main biological activity of S. tora, L seeds is attributed to its phenolic compounds which are mainly isolated from Ethyl acetate fraction, to avoid repetition of work and to save time, it was deemed necessary to confirm the identity of these phenolic compounds. This was done by GC-MS and LC-MS analysis of the ethyl acetate fraction where the structures of the isolated compounds were established on the basis of molecular ion peak and their fragmentation pattern. They were identified as Chrysophanol, Chrysarobin, 10-hydroxy-5-methoxy-2-methyl-1, 4-anthracenedione, Rubrofusarin, Parietin, Griseoxanthone-B, Isotorachrysone, and Cumbiasin B.

     

A Comparative Study of Fluorescein Isothiocyanate-Encapsulated Silica Nanoparticles Prepared in Seven Different Routes for Developing Fingerprints on Non-Porous Surfaces

Preparation of fluorescein isothiocyanate (FITC)-encapsulated silica nanoparticles (F-SiNPs) via seven different approaches to be used as developing agents for fingerprints detection is presented in this report. In this study, the suitability of each synthesis route toward incorporation of the selected fluorophore into silica matrix and its efficiency in fingerprints detection were systematically studied. The composition of the particles was designed to examine the hydrophobic and dipole-dipole interactions between the silicate backbone and both of the fluorescent reporter molecules and the fingerprint residues. F-SiNPs were prepared with two conventional sol-gel approaches; the Stöber method and the water in oil reverse microemulsion (WORM) method. The alkoxysilane precursor, tetraethoxyorthosilicate (TEOS) and its binary mixtures with phenyltriethoxysilane (PTEOS) or 3-aminopropyl triethoxysilane (APTES) have been used in preparing the F-SiNPs to study the effect of nanoparticles composition on fingerprints development. In addition, FITC was conjugated with APTES so it can be covalently bonded to the silica matrix and to be compared with non-covalently FITC-doped SiNPs. Moreover, the enhancement effect of introducing polyvinylpyrrolidone (PVP) onto the surface of the less hydrophobic F-SiNP on fingerprints detection on different non-porous surfaces was also investigated. The mean diameters of the F-SiNPs were between 4.1?±?0.6 and 110.4?±?31.1 nm as obtained from the TEM size measurement for the nanoparticles prepared by the WORM and Stöber methods, respectively. The obtained results clearly highlight the advantages of using a mixture of TEOS and PTEOS alkoxysilane precursors in preparing F-SiNPs with remarkable encapsulation efficiency and clear detection of fingerprints due to efficient embedding of the fluorophore inside the silica network even without conjugation. It was also observed that both the Stöber and WORM methods can be used in preparing the F-SiNPs developing agents and that PVP coated particles did not show any significant enhancement in fingerprints visualization.     

Assessment of the Effects of Glycosylation on the Pattern and Kinetics of Degradation of Lenograstim in Comparison to Filgrastim Using a Stability-Indicating Orthogonal Testing Protocol

In the biopharmaceutical industry, protein aggregation and/or degradation has profound pathological implications and is encountered routinely during production, shipping, storage and administration. Lenograstim (glycosylated recombinant human granulocyte colony-stimulating factor) was subjected to stress conditions, namely, oxidation, pH, temperature, agitation and repeated freeze–thaw to generate all possible degradation products. An orthogonal stability-indicating testing protocol (RP-HPLC, SE-HPLC, ELISA and SDS-PAGE) was developed and validated for assessment of the pattern and kinetics of aggregation/degradation, under the studied experimental conditions. Results indicated clearly that Lenograstim is susceptible to degradation induced by the studied stress conditions. However, Lenograstim was found relatively more stable than Filgrastim (non-glycosylated recombinant human granulocyte colony-stimulating factor) which was attributed to the effect of glycosylation. Oxidized forms and high molecular weight aggregates of Lenograstim and Filgrastim were detected in all samples subjected to stress conditions to different degrees. ELISA assay and SDS-PAGE results were generally in agreement to those obtained using SE-HPLC assay which confirmed its selectivity to the intact drug. However, formation of soluble aggregates of both drugs was found to occur via physical adsorption and formation of intermolecular disulfide bonds. Results confirmed the need for an orthogonal testing protocol since it was impossible to reveal all types of degradation products using a single technique. Results raised a concern about the efficacy and safety of such sensitive products and highlighted the need for simple tools to inspect biologics for soluble aggregates and sub-visible particles before administration.

     

Synthesis,characterization, and evaluation of biological activities of new 4′‐substituted ruthenium (II) terpyridine complexes: Prospective anti‐inflammatory properties

The synthesis and characterization of Ru (II) terpyridine complexes derived from 4′ functionalized 2,2′:6′,2″‐terpyridine (tpy) ligands are reported. The heteroleptic complexes comprise the synthesized ligands 4′‐(2‐thienyl)‐ 2,2′:6′,2″‐terpyridine) or (4′‐(3,4‐dimethoxyphenyl)‐2,2′:6′,2″‐terpyridine and (dimethyl 5‐(pyrimidin‐5‐yl)isophthalate). The new complexes [Ru(4′‐(2‐thienyl)‐2,2′:6′,2″‐terpyridine)(5‐(pyrimidin‐5‐yl)‐isophthalic acid)Cl₂] ( 9 ), [Ru(4′‐(3,4‐dimethoxyphenyl)‐2,2′:6′,2″‐terpyridine)(5‐(pyrimidin‐5‐yl)‐isophthalic acid)Cl₂] ( 10 ), and [Ru(4′‐(2‐thienyl)‐2,2′:6′,2″‐terpyridine)(5‐(pyrimidin‐5‐yl)‐isophthalic acid)(NCS)₂] ( 11 ) were characterized by ¹H‐ and ¹³C‐NMR spectroscopy, C, H, N, and S elemental analysis, UPLC‐ESI‐MS, TGA, FT‐IR, and UV‐Vis spectroscopy. The biological activities of the synthesized ligands and their Ru (II) complexes as anti‐inflammatory, antimicrobial, and anticancer agents were evaluated. Furthermore, the toxicity of the synthesized compounds was studied and compared with the standard drugs, namely, diclofenac potassium and ibuprofen, using hemolysis assay. The results indicated that the ligands and the complex 9 possess superior anti‐inflammatory activities inhibiting albumin denaturation (89.88–100%) compared with the standard drugs (51.5–88.37%) at a concentration of 500 μg g^?1. These activities were related to the presence of the chelating N‐atoms in the ligands and the exchangeable chloro‐ groups in the complex. Moreover, the chloro‐ and thiophene groups in complex 9 produce a higher anticancer activity compared with its isothiocyanate derivative in the complex 11 and the 3,4‐dimethoxyphenyl moiety in complex 10 . Considering the toxicity results, the synthesized ligands are nontoxic or far less toxic compared with the standard drugs and the metal complexes. Therefore, these newly synthesized compounds are promising anti‐inflammatory agents in addition to their moderate unique broad antimicrobial activity.     

Green and sustainable carboxymethyl cellulose-chitosan composite hydrogels: Effect of crosslinker on microstructure

Cellulose - The toxicity level of conventional hydrogels is considerably high for most applications. To date, very few studies on hydrogels synthesized using only safe materials and simple,...     

Synthesis, Crystal Structure and Characterization of a New Dabcodiium Hexaaquacobalt(II) Bis(Selenate), (C6H14N2)[Co(H2O)6](SeO4)2

Abstract  

The new hybrid material, cobalt selenate templated by 1,4-diazabicyclo[2.2.2]octane (abbreviated dabco), has been synthesised by the slow evaporation method at room temperature. Its crystal structure was investigated using single crystal X-ray diffraction data. It crystallises in the monoclinic system (space group P2₁/c) with the following unit-cell parameters: a = 12.9169(2) ?, b = 11.9101(2) ?, c = 12.4951(2) ?, β = 108.484(1)°, V = 1823.10(5) ?³ and Z = 4. The supramolecular structure of (C₆H₁₄N₂)[Co(H₂O)₆](SeO₄)₂ consists of isolated [Co(H₂O)]²⁺ and (C₆H₁₄N₂)²⁺ cations and (SeO₄)²⁻ anions linked together by three dimensional hydrogen-bond network. The infrared spectroscopy confirmed the presence of these different entities. The thermal behaviour of the precursor, studied by thermodiffractometry and thermogravimetric analyses, indicates that its decomposition proceeds through three stages giving rise to the cobalt oxide.