Should I Say Something? Dating and Sexual Aggression Bystander Intervention Among High School Youth

Using data from a sample of 218 high school youth from three high schools in New England (one rural, two urban), this brief discusses dating and sexual aggression bystander intervention among high school youth. Authors Katie Edwards, Robert Eckstein, and Kara Anne Rodenhizer-Stämpfli report that an overwhelming majority (93.6 percent) of high school students reported having the opportunity to intervene during the past year in situations of dating aggression or sexual aggression; however, in over one-third of the episodes (37.4 percent) students reported not intervening. Girls were more likely to intervene in situations of dating and sexual aggression than boys, and youth with histories of dating and sexual aggression were more likely to intervene than youth without these histories. Focus group data revealed that barriers to bystander intervention included avoidance of drama or a desire to fuel drama, social status and personal repercussions, closeness with the victim and/or perpetrator, the victim being male and the perpetrator female, the failure of the dating or sexual aggression to meet a certain threshold, the dating and sexual aggression occurring online, anticipated negative reactions from the perpetrator or victim, and an inability to relate to the situation. Given the mounting evidence that bystander education is a critical component of dat­ing and sexual aggression prevention, the authors urge policy makers and educators to enhance the presence of this type of education in high school health curricula and related course curricula

A model metal potential exhibiting polytetrahedral clusters

Putative global minima have been located for clusters interacting with an aluminium glue potential for N<190. Virtually all the clusters have polytetrahedral structures, which for larger sizes involve an ordered array of disclinations that are similar to those in the Z, H and sigma Frank-Kasper phases. Comparisons of sequences of larger clusters suggest that the majority of the global minima will adopt the bulk face-centred-cubic structure beyond N=500.Comment: 14 pages, 7 figure

Calculations of the A_1 phonon frequency in photoexcited Tellurium

Calculations of the A_1 phonon frequency in photoexcited tellurium are presented. The phonon frequency as a function of photoexcited carrier density and phonon amplitude is determined. Recent pump probe experiments are interpreted in the light of these calculatons. It is proposed that, in conjunction with measurements of the phonon period in ultra-fast pump-probe reflectivity experiments, the calculated frequency shifts can be used to infer the evolution of the density of photoexcited carriers on a sub-picosecond time-scale.Comment: 15 pages Latex, 3 postscript figure

Direct AFM observation of individual micelles, tile decorations and tiling rules of a dodecagonal liquid quasicrystal.

We performed an atomic force microscopy study of the dendron-based dodecagonal quasicrystal, the material that had been reported in 2004 as the first soft quasicrystal. We succeeded in orienting the 12-fold axis perpendicular to the substrate, which allowed imaging of the quasiperiodic xy plane. Thus for the first time we could obtain direct real-space information not only on the arrangement of the tiles, but also on their "decorations" by the individual spherical micelles or "nanoatoms". The high-resolution patterns recorded confirm the square-triangle tiling, but the abundance of the different nodes corresponds closely to random tiling rather than to any inflation rule. The previously proposed model of three types of decorated tiles, two triangular and one square, has been confirmed, and the basic Frank-Kasper mode of alternating dense-sparse-dense-sparse layer stacking along z is confirmed too, each of the four sublayers being 2 nm thick. The consecutive dense layers are seen to be rotated by 90°, as expected. The 2 nm steps on the surface correspond to one layer of spheres, however with a dense layer always remaining on top, which implies a layer slip underneath and possibly the existence of screw dislocations

Theory for the ultrafast ablation of graphite films

The physical mechanisms for damage formation in graphite films induced by femtosecond laser pulses are analyzed using a microscopic electronic theory. We describe the nonequilibrium dynamics of electrons and lattice by performing molecular dynamics simulations on time-dependent potential energy surfaces. We show that graphite has the unique property of exhibiting two distinct laser induced structural instabilities. For high absorbed energies (> 3.3 eV/atom) we find nonequilibrium melting followed by fast evaporation. For low intensities above the damage threshold (> 2.0 eV/atom) ablation occurs via removal of intact graphite sheets.Comment: 5 pages RevTeX, 3 PostScript figures, submitted to Phys. Re

Formation of dodecagonal quasicrystals in two-dimensional systems of patchy particles

The behaviour of two-dimensional patchy particles with 5 and 7 regularly-arranged patches is investigated by computer simulation. For higher pressures and wider patch widths, hexagonal crystals have the lowest enthalpy, whereas at lower pressures and for narrower patches, lower-density crystals with five nearest neighbours and that are based on the (3^2,4,3,4) tiling of squares and triangles become lower in enthalpy. Interestingly, in regions of parameter space near to that where the hexagonal crystals become stable, quasicrystalline structures with dodecagonal symmetry form on cooling from high temperature. These quasicrystals can be considered as tilings of squares and triangles, and are probably stabilized by the large configurational entropy associated with all the different possible such tilings. The potential for experimentally realizing such structures using DNA multi-arm motifs are discussed.Comment: 12 pages, 12 figure

An Alternative Active Site Architecture for O2 Activation in the Ergothioneine Biosynthetic EgtB from Chloracidobacterium thermophilum

Sulfoxide synthases are nonheme iron enzymes that catalyze oxidative carbon-sulfur bond formation between cysteine derivatives and N-α-trimethylhistidine as a key step in the biosynthesis of thiohistidines. The complex catalytic mechanism of this enzyme reaction has emerged as the controversial subject of several biochemical and computational studies. These studies all used the structure of the γ-glutamyl cysteine utilizing sulfoxide synthase, MthEgtB from Mycobacterium thermophilum (EC 1.14.99.50), as a structural basis. To provide an alternative model system, we have solved the crystal structure of CthEgtB from Chloracidobacterium thermophilum (EC 1.14.99.51) that utilizes cysteine as a sulfur donor. This structure reveals a completely different configuration of active site residues that are involved in oxygen binding and activation. Furthermore, comparison of the two EgtB structures enables a classification of all ergothioneine biosynthetic EgtBs into five subtypes, each characterized by unique active-site features. This active site diversity provides an excellent platform to examine the catalytic mechanism of sulfoxide synthases by comparative enzymology, but also raises the question as to why so many different solutions to the same biosynthetic problem have emerged

On the 3n+l Quantum Number in the Cluster Problem

It has recently been suggested that an exactly solvable problem characterized by a new quantum number may underlie the electronic shell structure observed in the mass spectra of medium-sized sodium clusters. We investigate whether the conjectured quantum number 3n+l bears a similarity to the quantum numbers n+l and 2n+l, which characterize the hydrogen problem and the isotropic harmonic oscillator in three dimensions.Comment: 8 pages, revtex, 4 eps figures included, to be published in Phys.Rev.A, additional material available at http://radix2.mpi-stuttgart.mpg.de/koch/Diss

A Single Cluster Covering for Dodecagonal Quasiperiodic Structure

Single cluster covering approach provides a plausible mechanism for the formation and stability of octagonal and decagonal quasiperiodic structures. For dodecagonal quasiperiodic pattern such a single cluster covering scheme is still unavailable. Here we demonstrated that the ship tiling, one of the dodecagonal quasiperioidic structures, can be constructed from one single prototile with matching rules. A deflation procedure is devised by assigning proper orientations to the tiles present in the ship tiling including regular triangle, 30{\deg}-rhombus and square, and fourteen types of vertical configurations have been identified in the deflated pattern, which fulfill the closure condition under deflation and all result in a T-cluster centered at vertex. This result can facilitate the study of physical properties of dodecagonal quasicrystals.Comment: 5 pigs ;11page