Evaluation and Modelling of the Material Properties for Analysis of Cold-formed Steel Sections

The results of two series of experimental investigations to evaluate the mechanical properties and the residual stresses of cold-formed steel (CFS) sections are reported in this paper. These investigations were performed on channel-shaped CFS sections manufactured using cold-roll forming technique. Tensile coupon tests were used to evaluate the mechanical properties at different positions of the channel sections. Electrical resistance strain gauges with an Electrical Discharge Machining cutting technique were used to establish the magnitudes and the distributions of residual stresses within the channel sections. Based on the experimental results, appropriate analysis models for the stress-strain relationship, the variation of the yield strength, and the residual stresses in CFS channel sections are established. These models are incorporated within a large deformation shell finite element to form a model for cold-formed steel sections. The finite element model is evaluated against experimental results of CFSsections in compression

Reaction of nitrilimines and nitrile oxides with hydrazines, hydrazones and oximes

This review article discusses the reaction of nitrilimines and nitrile oxides with hydrazines, hydrazones, and oximes. Three reaction modes were observed. The article mainly covers our work published over the last fifteen years, in which interesting heterocyles such as oxadiazoles, triazoles, and tetrazines were synthesized and fully characterized. View Full-Text Keywords

Determination of Oral or Dermal Benzene Exposure from Contaminated Soils

Soil contamination with dangerous, toxic chemicals remains one of the most difficult problems in this era. Health risk assessments often do not consider the amount of chemicals in soil that are absorbed and their disposition (kinetics). The aim of these studies was to compare the extent to which adsorption to either a sand or clay content soil affects the kinetics and manner which benzene is subsequently handled in orally or dermally exposed rats. Dermal exposure increased absorption half-lives (t1/2) by 25, 60 and 44-fold compared with oral exposure to benzene alone, or in the presence of sandy or clay soil, respectively. The elimination t1/2 following dermal versus oral exposure were increased about 2-fold in benzene alone and sandy soil groups, while in the clay soil group the increase was 13-fold. The area under the blood concentration versus time curve (AUC) of benzene in the presence of either soil was increased after oral and decreased after dermal exposure compared with exposure to benzene alone. The urinary recovery, 48 hours following dermal exposure to benzene alone, was 3-fold greater than following oral exposure. Tissue distribution after all oral exposures resulted in the highest concentrations of radioactivity in gastric contents \u3e stomach \u3e fat \u3e duodenum \u3e adrenal. The highest tissue concentrations of radioactivity after dermal exposure to benzene alone were kidney \u3e liver \u3e treated skin; however, after exposure in the presence of either soil the highest tissue concentrations were treated skin \u3e kidney \u3e liver. The results of these studies reveal that the presence of sand or clay content soil produced qualitative and quantitative differences in the disposition of benzene in the body following oral or dermal exposures. These differences will impact the risk assessment of benzene

Implications of a Quantum Mechanical Treatment of the Universe

We attempt to treat the very early Universe according to quantum mechanics. Identifying the scale factor of the Universe with the width of the wave packet associated with it, we show that there cannot be an initial singularity and that the Universe expands. Invoking the correspondence principle, we obtain the scale factor of the Universe and demonstrate that the causality problem of the standard model is solved.Comment: LaTex, 5 pages, 1 figure, to be published in Mod. Phys. Lett.

Investigations on the action mode of Bacillus thuringiensis Cyt2Aa1 toxin

B. thuringiensis is a Gram-positive bacterium that, while quite otherwise closely related to the soil saprophyte Bacillus cereus, is unique in producing a large variety of membrane-damaging, insecticidal protein toxins. These toxins, which are widely used as biopesticides, fall into two major structural families, named Cry and Cyt. This thesis reports experiments that characterize the activity and membrane specificity of Cyt2Aa1 toxin, which is a member of the Cyt family. This toxin is shown to have a low degree of antibacterial activity against Gram-positive bacteria; the growth of the model organism Bacillus megaterium is inhibited in the presence of approximately 700 μg/mL of the toxin. The toxin readily binds to the bacterial cell surface, and marker release experiments show that the bactericidal effect arises through permeabilization of the bacterial membrane. In contrast, the Gram-negative organism E. coli is not inhibited by Cyt2Aa1, and the toxin fails to bind to the bacterial cells. Furthermore, it is shown that the cytolytic activity of the toxin is inhibited by cholesterol. The extent of inhibition is greater on model liposomes, in which virtually complete suppression is observed above a molar fraction of 20% or greater of cholesterol, than with red blood cells that were subjected to partial cholesterol extraction with methyl- β- cyclodextrin. Since cholesterol inhibits rather than activates Cyt2Aa1, its absence from bacterial membranes does not account for the low susceptibility of bacterial cells to the toxin. In previous studies, two different mechanisms have been proposed for the permeabilization of membranes by Cyt2Aa1, namely, the formation of discrete, oligomeric transmembrane pores, and the diffuse disruption of the target membrane in a detergent-like manner. A series of experiments that used both wild-type toxin and several point mutants with impaired hemolytic activity provides evidence for the formation of toxin oligomers that precedes the permeabilization of the target membrane. Moreover, osmotic protection experiments with polyethyleneglycol suggest the formation of pores with limited, but possibly heterogeneous size. Collectively, these findings support the notion that Cyt2Aa1 acts through the formation of discrete oligomeric pores

Cloning and expression of Cyt2Aa1 toxin and characterization of its mode of action

The discovery of the pore-forming toxins produced by Bacillus thuringiensis, which are toxic to insects but not to mammalians, has provided a new successful means to control harmful plant-feeding insects biologically. The toxins are also used on insects that don’t feed on plants, for example on Anopheles. The Bacillus thuringiensis toxins fall into two structural families, named cry and cyt. All of these toxins act by damaging the cell membranes in the mid gut of the insect. In this study, a reliable system for expression and purification of the recombinant Cyt2Aa1 toxin has been developed. The recombinant Cyt2Aa1 toxin has been produced, characterized, followed by the construction of the cysteine mutants V186C and L189C by site directed mutagenesis. The new expression system yields 0.4 g of protein per litre of culture. The activated Cyt2Aa1 toxin is active in the hemolysis assay. Of note, the hemolytic activity of the V186C mutant exceeds that of wild type Cyt2Aa1 toxin and of the L189C mutant. Calcein release assay experiments have been done to examine the activity of the toxin with different artificial liposomes. It was found that Cyt2Aa1 toxin is very active with DMPC, DMPC+DMPG unilamellar liposomes. Surprisingly, however, Cyt2Aa1 toxin showed no activity with liposomes containing cholesterol. With both erythrocytes and sensitive liposomes, the toxin shows a “pro-zone effect”, that is the activity decreases at very high concentrations. The findings are discussed in the context of the toxin’s putative mode of action

SYNTHESIS AND X-RAY CRYSTAL STRUCTURE ANALYSIS OF SUBSTITUTED 2,3-DIHYDRO-1,3,4-OXADIAZOLES VIA REACTION OF ACETONE- AND CYCLOALKANONE BENZOYLHYDRAZONES WITH PHENYLISOCYANATE

Oximic 1,2,4-triazole ligands 2a-e were prepared from the reaction of 3-acetyl–4,5-dihydro-1H-1,2,4-triazoles 1a-e with hydroxylamine hydrochloride at room temperature. At higher temperatures, the reaction afforded, however, the novel ring transformation product 4-amino-2-(4-chlorophenyl)-5-methyl-2H-1,2,3,6-oxatriazine 3. The reaction of the ligands 2a-e with nickel(II) and palladium(II) acetates in ethanol at room temperature yielded the respective square planar complexes 5a-e, 6a,e rather than the simple bis oximato metal(II) complexes that have been suggested before. X-ray structure determination of one of these complexes (5a) revealed that metallation led to unexpected ring transformation of the triazole ligand. It is probable that such ring transformation generated the imidazole-N-oxide intermediate 4a which coordinated to Ni(II) ion, and the 4N-donor set comprises both imidazole nitrogen and arylhydrazone nitrogen. The whole process is associated with loss of one hydrogen molecule and formation of one new -bond. The new compounds were characterized by elemental analysis, IR, 1H NMR, 13C NMR and HRMS data

Radiological evaluation of postoperative complications after non-sleeve gastrectomy bariatric procedures

Background: Obesity is a medical condition, which may lead to serious related diseases, ultimately, resulting in many morbidities and early mortality. Its management involves many approaches of which bariatric surgery is considered nowadays as one of the most effective treatment for it. However, follow up of postoperative complications of this surgery by effective radiological method as computed tomography (CT) is important for assessment of its success.Objective: The aim of this study was to illuminate the radiological signs and features of postoperative complications after non sleeve bariatric procedures and stressing the importance of using multi-slice CT (MSCT), and fluoroscopic study for detection of these complications. Patients and methods: An observational cohort study for 275 patients with suspected complications after non sleeve gastrectomy bariatric procedures, including 195 patients after Roux-en-Y gastric bypass (RYGB), 76 patients after laparoscopic adjustable gastric banding (LAGB) and 4 patients after intragastric balloon placement was done. These patients were subjected to either multi-slice CT and or fluoroscopy. Results: We detected complications in 21 patients out of the 195 patients who underwent RYGB: leakage, abscess, intestinal obstruction, internal hernia, port site ventral hernia, intussusception, fistula between the gastric pouch and the excluded stomach and hiatus hernia. On the other hand, 8 out of 76 patients operated by LAGB developed complications: band slippage, band erosion, pouch dilatation and tubal disconnection. Lastly two out of the 4 patients who placed intra-gastric balloon encountered other complications: gastric outlet obstruction, spontaneous balloon deflation and distal migration with intestinal obstruction.Conclusion: It could be concluded that bariatric procedures may be followed by many complications and accurate diagnosis of these problems by proper radiological procedures as MSCT is imperative