Gender Differences in Risk-Taking Behavior and their Relationship to SAT-Mathematics Performance

This study focused on the relationship of an individual's risk-taking behavior and his/her performance on the mathematics section of the Scholastic Aptitude Test (SAT-M). Previous research in this area has found that on multiple choice tests, calculated guessing (risk-taking) plays a role in the score one obtains. Risk-taking behavior was defined by the number of items omitted by the student on the instrument designed for the purpose of assessing this behavior. The data were obtained from 89 students who were attending two colleges in upstate New York. The data consisted of SAT-M scores and performance scores on a mathematics test designed to assess risk-taking. A t-test performed on the number of omissions revealed that females omit more items and thus manifest less risk-taking behavior. A significant difference in favor of females omitting more items was found at the p < .01 level. A multiple regression design was employed, and gender and risk-taking behavior were found to be significantly related at the p<.01 level to a student's performance on the SAT-M.     

Unified formulation of numerical methods. I. Green's formulas for operators in discontinuous fields

Applying the method of weighted residuals and then interpreting the resulting equations by means of Green's formulas for discontinuous functions, a direct method of analysis is developed. The scheme includes finite differences, finite elements, and boundary methods. This is the first of a sequence of articles in which the methodology is presented. A fundamental ingredient of the procedure are general Green's formulas for operators defined in discontinuous fields. They are developed in this first article.     

Identification of peptides that neutralize bacterial endotoxins using β-hairpin conformationally restricted libraries

Bacterial endotoxins are the major mediator of septic shock; therefore, endotoxin-neutralizing molecules could have biomedical applications. The septic shock cascade relies in a series of molecular recognition processes. The large contact-surface described for the interacting macromolecules, in most cases, prevents the identification of small molecules that could modulate such recognition events. Here we report on a beta-hairpin conformationally restricted combinatorial library that has been generated and screened towards the identification of new peptides that neutralize bacterial endotoxins. Starting with a de novo designed linear peptide that shows a beta-hairpin structure population of around 30%, (Ramirez-Alvarado, M., Blanco, F. J. and Serrano, L. Nat. Struc. Biol., 7, 604-612 (1996)), we selected four positions to build up a combinatorial library of 20(4) sequences. Deconvolution of the library reduced such a sequence complexity to 8 defined sequences. The newly identified peptides have a biological activity equivalent to that reported for peptides derived from natural endotoxin-binding proteins.     

Globally convergent DC trust-region methods

In this paper, we investigate the use of DC (Difference of Convex functions) models and algorithms in the application of trust-region methods to the solution of a class of nonlinear optimization problems where the constrained set is closed and convex (and, from a practical point of view, where projecting onto the feasible region is computationally affordable). We consider DC local models for the quadratic model of the objective function used to compute the trust-region step, and apply a primal-dual subgradient method to the solution of the corresponding trust-region subproblems. One is able to prove that the resulting scheme is globally convergent to first-order stationary points. The theory requires the use of exact second-order derivatives but, in turn, the computation of the trust-region step asks only for one projection onto the feasible region (in comparison to the calculation of the generalized Cauchy point which may require more). The numerical efficiency and robustness of the proposed new scheme when applied to bound-constrained problems is measured by comparing its performance against some of the current state-of-the-art nonlinear programming solvers on a vast collection of test problems.     

Sigmatropic rearrangements in 5-allyloxytetrazoles

Mechanisms of thermal isomerization of allyl tetrazolyl ethers derived from the carbocyclic allylic alcohols cyclohex-2-enol and 3-methylcyclohex-2-enol and from the natural terpene alcohol nerol were investigated. In the process of the syntheses of the three 1-aryl-5-allyloxytetrazoles, their rapid isomerization to the corresponding 1-aryl-4-allyltetrazol-5-ones occurred. The experiments showed that the imidates rearrange exclusively through a [3,3']-sigmatropic migration of the allylic system from O to N, with inversion. Mechanistic proposals are based on product analysis and extensive quantum chemical calculations at the DFT(B3LYP) and MP2 levels, on O-allyl and N-allyl isomers and on putative transition state structures for [1,3']- and [3,3']-sigmatropic migrations. The experimental observations could be only explained on the basis of the MP2/6-31G(d,p) calculations that favoured the [3,3']-sigmatropic migrations, yielding lower energies both for the transition states and for the final isomerization products.     

Anchoring effects on the electrically controlled optical band gap in twisted photonic liquid crystals

We study a one-dimensional twisted photonic liquid crystal (TPLC), consisting of various nematic liquid crystal cells adopting a twisted configuration intercalated by isotropic dielectric layers, submitted to a dc electric field (E^dc ) aligned along the periodicity axis. We write the corresponding Euler–Lagrange equations describing the nematic layer configuration. By assuming arbitrary anchoring quasi-planar boundary conditions, we calculate the equilibrium textures for the nematic, parametrized by the two types of strength of its interaction (polar and azimuthal) with the plane walls. We write the electromagnetic equations in a 4?×?4 matrix representation and using the transfer matrix formalism, we obtain the transmittance and reflectance coefficients for normal incidence as functions of the external electric field and anchoring strengths. We have observed a remarkable dependence of the electric field on the transmission and reflection spectra in opening and closing band gaps.     

Chemical oxidative polymerization of m-phenylenediamine and its derivatives using aluminium triflate as a co-catalyst

Aromatic diamine monomers, including m-phenylenediamine (mPD), 2-methyl-m-phenylenediamine (2Me-mPD), 4-methyl-m-phenylenediamine (4Me-mPD) and trimethyl-m-phenylenediamine (tMe-mPD), were polymerized by chemical oxidation using ammonium persulfate as an oxidant. Aluminium triflate (Al(OTf)₃) was also used for the first time as a co-catalyst under various polymerization conditions. The polymerization yield was improved when Al(OTf)₃ was introduced to the polymerization reaction for most polymers. The poly(2-methyl-m-phenylenediamine) (P(2Me-mPD)), poly(4-methyl-m-phenylenediamine) (P(4Me-mPD)) and poly(trimethyl-m-phenylenediamine) (P(tMe-mPD)) polymers exhibited better solubility than poly(m-phenylenediamine) (P(mPD)) polymers in most common solvents. The homopolymers obtained were characterized by FT-IR, ¹H and ¹³C NMR, WAXD and TGA. The results showed that the yield, solubility and structure of the polymers are significantly dependent on the polymerization conditions. TGA measurements indicated that the polymers have good thermal stability and decompose above 400 °C in nitrogen.     

Microwave‐Assisted One‐Pot Synthesis of 2‐(Substituted phenyl)‐1H‐benzimidazole Derivatives

A series of 2‐(substituted phenyl)‐1H‐benzimidazole derivatives with various 5‐and 6‐position substituents (‐H, ‐CH₃, ‐CF₃) were synthesized via microwave irradiation using a short synthetic route and Na₂S₂O₅ as oxidant. This simple, fast, and efficient preparation of benzimidazole derivatives has been developed using readily available and inexpensive reagents (aldehydes and 1,2‐phenylenediamines) under solvent‐free conditions.     

Blue‐to‐Orange Color‐Tunable Laser Emission from Tailored Boron‐Dipyrromethene Dyes

A series of meso‐substituted boron‐bipyrromethene (BODIPY) dyes are synthesized and their laser and photophysical properties systematically studied. Laser emission covering a wide visible spectral region (from blue to orange) is obtained by just changing the electron donor character of the heteroatom at position 8. The additional presence of methyl groups at positions 3 and 5 results in dyes with a photostability similar to that of the unsubstituted dye but with much improved efficiency. Correlation of the lasing properties of the different dyes to their photophysical properties provides inklings to define synthetic strategies of new BODIPY dyes with enhanced efficiency and modulated wavelength emission over the visible spectral region.     

Synthesis of new vinylpyridinium salts

This article reports the reactions of salts of 4‐ureylmethylpyridinium and 4‐ethoxycarbonylaminomethylpyridinium with carbonylic compounds, performed with the aim of obtaining new vinylpyridinium salts. These reactions can lead to the formation of both condensation and dimerization products. The type of products formed is conditioned by the nature of the salts and carbonyl groups involved. The interest generated by the condensation products formed lies in their potential cholinergic activity. J. Heterocyclic Chem., 2011.