High-Stakes Testing: Barrier to Gifted Girls in Mathematics and Science?

The gender gap in scores on the mathematics section of the Scholastic Assessment Test (SAT-M) is currently approximately 30 points for academically gifted middle school students who take the SAT as part of Talent Search participation. This paper explores possible reasons for the gap, including test bias, variability in scores, the timed nature of the test, and environmental factors. When the SAT-M is used as the sole criterion for admission, gender differences in scores mean that disparate numbers of boys and girls are identified for high-level mathematics and science programs. Solutions to the problem are proposed, taking the perspective that the goal of the special programs is to identify and serve students who are likely to benefit from and be successful in such programs.     

Experimental assessment of a nonlinear turbulent stress relation in a complex reciprocating engine flow

A nonlinear turbulent stress relationship, based on an explicit algebraic Reynolds stress closure, is compared against experimental data obtained in a swirl-supported, light-duty engine motored at constant speed. The model relationship is applied to measured mean velocity gradients and turbulence scales, and the predictions compared against the measured shear stress and normal stress anisotropy. Significant improvement over the linear stress relationship typically used in two-equation turbulence models is observed. Conditions under which the model predictions are poor are identified and the reasons for the poor performance discussed.     

Modeling of aspheric,diverging hydrodynamic instability experiments on the National Ignition Facility

One branch of work in the laboratory astrophysics community has been focused on developing the understanding of hydrodynamic mixing in core-collapse supernovae (ccSNe) by the Rayleigh–Taylor instability. Experiments studying these processes in the past have been limited to planar systems in large part due to limitations of drive energy. The National Ignition Facility (NIF) is now capable of providing experiments with far more energy than has been previously available on laser facilities, enabling supernova-relevant hydrodynamics in a diverging system. This paper focuses on a proposed design in which hydrodynamic instabilities develop from an aspheric blast-wave driven through multiple, coupled interfaces in a hemispheric target in which the relative masses of the layers are scaled to those within the ccSNe progenitor star. The simulations investigate the diagnosability and experimental value of different designs using a variety of drive conditions.     

Through‐space 19F–15N couplings for the assignment of stereochemistry in flubenzimine

Through‐space ¹⁹F–¹⁵N couplings revealed the configuration of flubenzimine, with the CF₃ group on N4 pointing towards the lone pair of N5. The ¹⁹F–¹⁵N coupling constants were measured at natural abundance using a spin‐state selective indirect‐detection pulse sequence. As ¹⁵N‐labelled proteins are routinely synthesized for NMR studies, through‐space ¹⁹F–¹⁵N couplings have the potential to probe the stereochemistry of these proteins by ¹⁹F labelling of some amino acids or can reveal the site of docking of fluorine‐containing drugs. Copyright © 2016 John Wiley & Sons, Ltd.     

Midkine Interaction with Chondroitin Sulfate Model Synthetic Tetrasaccharides and Their Mimetics: The Role of Aromatic Interactions

Midkine (MK) is a neurotrophic factor that participates in the embryonic central nervous system (CNS) development and neural stem cell regulation, interacting with sulfated glycosaminoglycans (GAGs). Chondroitin sulfate (CS) is the natural ligand in the CNS. In this work, we describe the interactions between a library of synthetic models of CS-types and mimics. We did a structural study of this library by NMR and MD (Molecular Dynamics), concluding that the basic shape is controlled by similar geometry of the glycosidic linkages. Their 3D structures are a helix with four residues per turn, almost linear. We have studied the tetrasaccharide-midkine complexes by ligand observed NMR techniques and concluded that the shape of the ligands does not change upon binding. The ligand orientation into the complex is very variable. It is placed inside the central cavity of MK formed by the two structured beta-sheets domains linked by an intrinsically disordered region (IDR). Docking analysis confirmed the participation of aromatics residues from MK completed with electrostatic interactions. Finally, we test the biological activity by increasing the MK expression using CS tetrasaccharides and their capacity in enhancing the growth stimulation effect of MK in NIH3T3 cells.     

Design, synthesis and evaluation of β-lactam antigenic peptide hybrids; unusual opening of the β-lactam ring in acidic media

β-Lactam peptides were envisioned as conformational constraints in antigenic peptides (APs). Three different β-lactam tripeptides of varying flexibility were prepared in solution and incorporated in place of the central part of the altered melanoma associated antigenic peptide Leu(27)-Melan-A(26-35) using solid phase synthesis techniques. Upon TFA cleavage from the solid support, an unexpected opening of the β-lactam ring occurred with conservation of the amide bond. After adaptation of the solid phase synthesis strategy, β-lactam peptides were successfully obtained and both opened and closed forms were evaluated for their capacity to bind to the antigen-presenting class-I MHC HLA-A2 protein system. None of the closed β-lactam peptides bound to HLA-A2, but their opened variants were shown to be moderate to good HLA-A2 ligands, one of them being even capable of stimulating a Melan-A-specific T cell line.     

Polyhedral approximation in mixed-integer convex optimization

Generalizing both mixed-integer linear optimization and convex optimization, mixed-integer convex optimization possesses broad modeling power but has seen relatively few advances in general-purpose solvers in recent years. In this paper, we intend to provide a broadly accessible introduction to our recent work in developing algorithms and software for this problem class. Our approach is based on constructing polyhedral outer approximations of the convex constraints, resulting in a global solution by solving a finite number of mixed-integer linear and continuous convex subproblems. The key advance we present is to strengthen the polyhedral approximations by constructing them in a higher-dimensional space. In order to automate this extended formulation we rely on the algebraic modeling technique of disciplined convex programming (DCP), and for generality and ease of implementation we use conic representations of the convex constraints. Although our framework requires a manual translation of existing models into DCP form, after performing this transformation on the MINLPLIB2 benchmark library we were able to solve a number of unsolved instances and on many other instances achieve superior performance compared with state-of-the-art solvers like Bonmin, SCIP, and Artelys Knitro.     

Stabilization and functionalization of single-walled carbon nanotubes with polyvinylpyrrolidone copolymers for applications in aqueous media

In spite of their useful electronic and mechanical properties, the utility of single-walled carbon nanotubes (SWNT) is limited by their inherent insolubility in aqueous environments and the difficulty in functionalizing the material while retaining opto-electric properties. In this article, the synthesis of polyvinylpyrrolidone (PVP) copolymers for wrapping SWNTs is described. Studies include the effect of polymer composition and charge on SWNT stability in aqueous solution and the variation of the stability of wrapped SWNTs during high-dilution conditions using dialysis studies. Finally, the PVP-copolymer strategy is used to create polymer wrappers with functional handles for the incorporation of useful chemical functionality. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 337–343     

Lateral pull-in instability of electrostatic MEMS transducers employing repulsive force

Nonlinear Dynamics - We report on the lateral pull-in in capacitive MEMS transducers that employ a repulsive electrostatic force. The moving element in this system undergoes motion in two...     

Diels–Alder Reactions of β-Acylacrylic Acids

The Diels–Alder reaction of β-acylacrylic acids with dienes gave good yields and good regio- or stereoselectivity of the corresponding cycloaddition products with the use of Lewis acids.