Cost-effective modeling strategies for the analysis of spliced steel connections

The paper presents several cost-effective modeling strategies that can be used by structural engineers in practice to determine the stresses in the spliced members. The computational efficiency and the modeling effort required for the several modeling options are also discussed. The deformation mechanisms and load transfer for several types of connections are illustrated. Optimization techniques are also presented to economize the computer time for connections with large number of bolts. Results are presented to compare the accuracy of several modeling strategies commonly used in practice. It is shown that for eccentric connections, the flexural bending largely affect the maximum tensile and compressive stresses within the joint. The difference may reach up to 54%. Finally, Experimental comparisons are made with the numerical procedures for typical connection model.     

Kinetics and mechanism of oxidation of N,N-bis(salicylaldehyde-1,2-diaminoethane) cobalt(II) by N-bromosuccinimide in aqueous acidic medium

The kinetics of oxidation of N,N-bis(salicylaldehyde-1,2-diaminoethane) cobalt(II) complex by N-bromosuccinimide (NBS) in aqueous acid and H₂O–MeOH solvent mixtures were studied spectrophotometrically over the 20–40 °C range, 0.1–0.5 mol dm^?3 ionic strength, 2.2–2.8 pH range and 0–40 wt% MeOH–H₂O solvent mixtures for a range of NBS and complex concentrations. The rate shows first-order dependence on both [NBS] and [complex] and decreases with pH over the range studied. The protonated form of N-bromosuccinimide was identified as the main reactive species. An inner-sphere mechanism involving free radicals is proposed.     

Synthesis, reactions and biological evaluation of some new naphtho[2,1-b]furan derivatives bearing a pyrazole nucleus

Vilsmeier formylation of 2-(1-phenylhydrazonoethyl)naphtho[2,1-b]furan (2) gave 3-naphtho[2,1-b]furan-2-yl-1-phenyl-1H-pyrazole-4-carbaldehyde (3), which was reacted with C- and N-nucleophiles to afford naphthofuranpyrazol derivatives 4-8. Treatment of 2-[(3-(naphtho[2,1-b]furan-2-yl)-1-phenyl-1H-pyrazol-4-yl)methylene]-malononitrile (4a) with reactants having active hydrogen and Et?N gave the corresponding pyrazoline, pyran and chromene addition product derivatives 10, 12 and 13, consisting of three different connected heterocyclic moieties. Reaction of 1-((3-(naphtho[2,1-b]furan-2-yl)-1-phenyl-1H-pyrazol-4-yl) methylene)-2-phenylhydrazone (6b) with AcONa and ethyl bromoacetate or chloroacetone afforded the thiazolidinone and methylthiazole derivatives 14 and 15, respectively. In addition, intramolecular cyclization of 6d with Ac?O afford the corresponding 1,3,4-thiadiazol-2-yl acetamide derivative 16. The structures of the synthesized compounds were confirmed by IR, 1H-NMR/13C-NMR and mass spectral studies. Compound 14 showed promising effects against the tested Gram positive and negative bacteria and fungi.     

Cytotoxic cembranoids from the Red Sea soft coral Sarcophyton glaucum

One new cembrane diterpene, 2R,7R,8R-dihydroxydeepoxysarcophine (1), together with three known compounds, 7alpha,8beta-dihydroxydeepoxysarcophine (2), 7beta-acetoxy-8alpha-hydroxydeepoxysarcophine (3), and sarcophine (4), have been isolated from the Red Sea soft coral Sarcophyton glaucum. Their structures were determined using 1D and 2D NMR spectroscopy. 7beta-Acetoxy-8alpha-hydroxydeepoxysarcophine (3) exhibits cytotoxic activity against HepG2, HCT-116, and HeLa cells with IC50 values of 3.6, 2.3, and 6.7 microg/mL, respectively.     

A Spectrophotometric Method for the Determination of Buclizine Hydrochloride Using the Charge-Transfer Spectrum of Buclizine-Iodine Complex

Abstract

A simple and sensitive spectrophotometric method is described for the determination of buclizine hydrochloride in bulk and tablets form. The method is based on the formation of charge-transfer complex between buclizine, as n-donor, and iodine, as Δ acceptor, which measured spectrophotometrically at 295 and 355 nm. A Job's plot indicated a 1:1 complex between the drug and iodine and Beer's law was obeyed in a concentration range of 4–30 μg ml^?1. A more detailed investigation of the complex was made with respect to its association constant and the free energy change. The method is simple and sensitive and has been applied successfully to the analysis of laboratory-made tablets without any interference from the tablet excipients. To validate the method, the results obtained were compared statistically with a newly developed uv-derivative spectrophotometric method. The charge-transfer method was favored due to its higher sensitivity, cheap coast and available equipments.     

Solvent and substituent effects on spectroscopical changes of some diazoaminobenzene derivatives

A series of diazoaminobenzene derivatives (seven) in which the substituents have a wide range of electronic characters are set out to understand the involvement of the substituent identity in controlling the changes in their electronic absorption spectra. The interactions between the diazoamino group and the different groups account for some spectral shifts. The UV-vis spectrum of each compound is measured in several solvents with wide variations of solvent polarity parameters to examine the role of the chemistry of the solvent in these spectroscopical changes. The electronic transitions are assigned and the solvent induced spectral shifts are analyzed in relation to the different solute-solvent interaction mechanisms using computational chemistry. The regression analysis is applied for correlating the different parameters. The results help to assign the solute-solvent interactions and the solvatochromic potential of the investigated compounds. It is concluded that the electronic character of the substituent and the chemical nature of the solvent are the major factors for the observed solvatochromism.     

Remarks on the asymptotic behavior of scalar auxiliary variable (SAV) schemes for gradient-like flows

We introduce a time semi-discretization of a damped wave equation by a SAV scheme with second order accuracy. The energy dissipation law is shown to hold without any restriction on the time step. We prove that any sequence generated by the scheme converges to a steady state (up to a subsequence). We notice that the steady state equation associated to the SAV scheme is a modified version of the steady state equation associated to the damped wave equation. We show that a similar result holds for a SAV fully discrete version of the Cahn-Hilliard equation and we compare numerically the two steady state equations.     

Thermally and optically induced effects on sub-band gap absorption in nanocrystalline CdSe (nc-CdSe) thin films

Nanocrystalline cadmium selenide (nc-CdSe) thin films have been prepared by thermal evaporation using the inert gas condensation (IGC) technique. Transmission electron microscopy (TEM) studies show that the CdSe nanocrystals (NCs) are spherical in shape. Constant photocurrent method (CPM) is used to determine the value of absorption coefficient in low absorption region of as-deposited, annealed and light soaked nc-CdSe thin films. Values of optical band gap (E_g) have been determined by using Tauc's relation for as-deposited, annealed and light soaked nc-CdSe thin films from the α values evaluated from reflection and transmission measurements. We have used a derivative procedure to sub-gap absorption spectra in order to get information on the energetic distribution of the occupied density of states below Fermi level. Constants such as optical gap E_g, Urbach edge E_u have been obtained from CPM spectra in as-deposited, annealed and light soaked nc-CdSe thin films. Concentration of defect states has also been calculated in as-deposited, annealed and light soaked nc-CdSe thin films.     

Reactive intermediates in the reaction of hydrazinecarbothioamides with 2-(bis(methylthio)methylene)malononitrile and ethyl 2-cyano-3,3-bis(methylthio)acrylate

Research on Chemical Intermediates - The reaction of N-substituted hydrazinecarbothioamides with both 2-(bis(methylthio)methylene)malononitrile and ethyl 2-cyano-3,3-bis(methylthio)acrylate...