University of Texas - Pan American

The aim of this paper is to determine the optimal shape of a viscoelastic damping layer within a constrained layer plate that is undergoing harmonic excitation at its midpoint. The optimization objective is to minimize the peak displacement of the plate at the first resonant frequency. The material loss factor is monitored as well to determine the improvement in performance between an initial, uniform layer shape and the optimized shape. A fine mesh validation model is also created to verify the optimized shape. As manufacturing costs would be reduced for a uniform shape, the optimized shape is used as a guide to create a new, uniform damping layer, which is compared with the previous results. Several geometries and boundary conditions are examined. The ABAQUS finite element code is used to model the structures. Elasticity theory based continuum elements are used so that all stress effects are taken into account in the models. The optimization code uses a Sequential Quadratic Programming algorithm. Results show significant improvement in the loss factor for optimized shapes. For most models, the optimal shape tends towards being a thin, uniform damping layer, which indicates shearing effects dominate in producing the optimal shape. In one case, however, it appears that some normal stress effects also have some influence.

Doppler radar installation by the National Weather Service (NWS) improved tornado warning performance, raising the probability of detection and mean lead time while reducing the false alarm ratio. Research on tornado casualties has established that a warning reduces tornado injuries while lead times of up to fifteen minutes also reduce tornado fatalities. In this paper we estimate the decrease in tornado casualties attributable to the observed change in the distribution of warning lead times, and thus provide evidence on the benefit to society of weather warning systems. We find that increases in warning lead times accounts for 30–50 percent of the reduction in injuries but no more than 1/4 of the reduction in fatalities which occurred with the installation of Doppler radar by the NWS. Future improvements in warning performance to further reduce tornado fatalities by 18 percent and injuries by 24 percent.

The history of the Pizarros, conquerors of Peru, is inseparably bound with images of swine. If we are to believe the chronicler Gómara, the Pizarro-pig association began when the illegitimate infant Francisco was abandoned at a church door, where he survived by suckling a sow for several days. Later, according to Gómara, the young Francisco's father recognized his offspring, but only to make him his swineherd. Though the former of these two stories is probably fantasy, the latter should not be rejected out of hand, as will become clear later. But whether true or not, the legend of the swineherd-turned-conquistador has sparked the historian's imagination for centuries.

Aims The aim of this study is to investigate the p-toluene sulphonic acid (p-Ts.OH)- catalyzed reaction of racemic-azetidine-2,3-diones with enantiomerically pure cis and trans-4- hydroxy-L-proline in refluxing ethanol culminating in a synthesis of substituted novel 3-(pyrrol-1- yl)-azetidin-2-ones at the C-3 position. Methods This work describes an alternative synthetic route enabling the tandem transformation of proline to pyrrole, followed by intramolecular chirality transfer to the β -lactams ring. Results All four diastereomers of 3-(pyrrol-1-yl)-azetidin-2-ones could be achieved in good to excellent yield with high diastereoselectivity in a single-pot operation. Conclusion This method can be applied to other activated carbonyl compounds and functionalized pyrroles can be obtained through an expeditious process.

A cost effective, operationally simple and environmentally benign one-pot access to 1,4-dihydropyridine (DHP) derivatives was achieved through the successful utilization of vitamin C as catalyst under microwave irradiation. The applicability of this method was fairly demonstrated through implementation of reaction conditions on diversified substrates. A plausible mechanistic interpretation for this reaction has been outlined based on Hantzsch reaction.

Computational-experimental analysis has allowed determining that the stereochemistry of the Staudinger reaction between ketenes and imines is strongly associated with the nature of the imine, which affects the two steps of the reaction. The first step, namely the nucleophilic attack of the sp2-hybridized nitrogen atom of the imine on the sp-hybridized carbon atom of the ketene, is affected by the energetically accessible in situ isomerization patterns of the imine. The second step consists of a conrotatory electrocyclization of the zwitterionic intermediate formed in the previous step. This latter pericyclic step depends on the inward/outward torquoelectronic effects generated by the substituents of the imine. The impact of these factors on the stereochemistry of this reaction has been analyzed kinetically by numerical methods. The results of these simulations are compatible with the experimental results and support these conclusions.

Metformin is one of the most widely prescribed medications for type 2 diabetes. While extremely rare, metformin has been reported to cause hemolysis in patients with glucose-6-phosphate dehydrogenase deficiency. In this paper, we present a case of a patient with previously undiagnosed glucose-6-phosphate dehydrogenase deficiency who presented with hemolysis likely induced by metformin. The patient concurrently presented with idiopathic Steven-Johnson syndrome/toxic epidermal necrolysis (SJS/TEN). Metformin causing hemolysis is extremely rare but considering the severe outcomes, it is something that medical practitioners need to be aware of.

This work was mainly aimed to synthesize new ceramic composites based on nano-bioactive glass (nBG) and magnesium phosphate ceramic (MgP) with different ratios using the sol-gel approach in order to overcome the limitations of both materials. The glass was based on 85SiO2-10CaO-5P2O5 (mole %), and MgP was based on the formula; Mg3(PO4)2. The obtained composites were characterized by DTA, XRD, FTIR, SEM/EDX and Zeta potential techniques. The in vitro bioactivity test was carried out in SBF, and the cell viability test was conducted by culturing the composites with human normal fibroblast cell line (BJ1). The results of XRD analyses showed that there were often no strong diffraction peaks detected which indicated the amorphous nature of the ceramic composites. Moreover, soaking of the ceramic composites in SBF exhibited that addition of MgP to nBG was increased the degradation of the latter one, and nBG was improved the formation of apatite crystals on MgP ceramic. Moreover, the cell viability results showed that MgP was showed significant higher viability than nBG at high concentrations, and it improved the viability of nBG in the ceramic composites.

An expeditious base assisted highly diastereoselective intramolecular oxy-Michael addition reaction in the synthesis of enantiomerically pure 1,4-dioxepane fused β-lactam has been described. This present study has been portrayed a rapid intramolecular 7-exo-trig oxy-Michael reaction involving chemoselective nucleophilic addition of 2⁰ alcohol of the vic-diols to an α β-unsaturated ester. Furthermore, the developed methodology elaborates an extremely atom-economical approach in constructing the C-O bond in stereoselective fashion under mild reaction conditions.

Herein, CoFe2O4 nanoparticles were directly synthesized through a solution combustion method using ferric nitrate, cobalt nitrate, and glycine as raw materials. The effects of glycine on the phase composition and magnetic properties of the CoFe2O4 products were investigated. When the fuel/ferric nitrate ratio was 0.8, the obtained product was pure CoFe2O4 with an average particle size of 25 nm. Furthermore, the saturation magnetization is 77.3 emu/g, which is about 95.7% that of CoFe2O4 bulk materials at room temperature and good for recycling. The photo-Fenton catalytic properties of CoFe2O4 were investigated for assessing its efficacy in removing dyes. It could degrade the 20 ppm MB in 75 min. To improve the photo-Fenton catalytic performance, NH4HCO3 and glucose were employed as additives. Due to the pores formed by NH4HCO3 and glucose, the G-CoFe2O4 and N-CoFe2O4 could degrade the 20 ppm MB in 40 and 25 min, respectively. The results indicated that these additives can effectively improve the catalytic activity of CoFe2O4. The modified CoFe2O4 is a promising alternative recyclable photo-Fenton catalyst for removing organic dyes.

To explore barriers to specialty substance abuse treatment programs among women with recent substance use disorders by race/ethnicity. Qualitative interviews were conducted with 28 women of White, Black, and Latino racial/ethnic descent who reported a substance use disorder in the past 5 years. Interviews were conducted by telephone and were audio-recorded. A codebook was developed using the Theory of Planned Behavior to code and identify barriers within the domains of attitudes, subjective norms, and perceived control toward specialty treatment. Frequencies for coded themes were then compared across all participants and by race/ethnicity. We identified several key differences in barriers to treatment by race/ethnicity. Attitudinal barriers were more pervasive among the narratives of Latinas relative to Black and White women. Latinas were more likely to report not needing treatment and that treatment would not be effective; Latinas were the only group to describe cultural barriers to treatment. Within the subjective norms domain, namely stigma and lack of support, were key barriers. Stigma was more pervasive among the narratives of Latinas and Black women than White women; Latinas were more likely to report a lack of social support for using treatment than both Black and White women. Findings provide deeper insight into barriers that may be contributing to racial/ethnic disparities in the use of substance abuse treatment among women.

A copper-free intramolecular azide–alkyne cycloaddition reaction of 4-hydroxymethyl-β-lactam with sodium azide has been described. The present approach involves the incorporation of an alkyne moiety through O-alkynylation of 3-hydroxy β-lactam with various propargylic halides. The generality of the method has been demonstrated by treating the corresponding tosylates or mesylates of the hydroxymethyl functionality of a variety of β-lactam-tethered terminal and internal alkynes with sodium azide in a one-pot three-step reaction to furnish novel oxazepane-β-lactam fused triazole scaffolds of diverse interest in good yield.