Structure of self-assembled Mn atom chains on Si(001)

Mn has been found to self-assemble into atomic chains running perpendicular to the surface dimer reconstruction on Si(001). They differ from other atomic chains by a striking asymmetric appearance in filled state scanning tunneling microscopy (STM) images. This has prompted complicated structural models involving up to three Mn atoms per chain unit. Combining STM, atomic force microscopy and density functional theory we find that a simple necklace-like chain of single Mn atoms reproduces all their prominent features, including their asymmetry not captured by current models. The upshot is a remarkably simpler structure for modelling the electronic and magnetic properties of Mn atom chains on Si(001).Comment: 5 pages, 4 figure

Electronic coupling between Bi nanolines and the Si(001) substrate: An experimental and theoretical study

Atomic nanolines are one dimensional systems realized by assembling many atoms on a substrate into long arrays. The electronic properties of the nanolines depend on those of the substrate. Here, we demonstrate that to fully understand the electronic properties of Bi nanolines on clean Si(001) several different contributions must be accounted for. Scanning tunneling microscopy reveals a variety of different patterns along the nanolines as the imaging bias is varied. We observe an electronic phase shift of the Bi dimers, associated with imaging atomic p-orbitals, and an electronic coupling between the Bi nanoline and neighbouring Si dimers, which influences the appearance of both. Understanding the interplay between the Bi nanolines and Si substrate could open a novel route to modifying the electronic properties of the nanolines.Comment: 6 pages (main), 2 pages (SI), accepted by Phys. Rev.

Brownian motion meets Riemann curvature

The general covariance of the diffusion equation is exploited in order to explore the curvature effects appearing on brownian motion over a d-dimensional curved manifold. We use the local frame defined by the so called Riemann normal coordinates to derive a general formula for the mean-square geodesic distance (MSD) at the short-time regime. This formula is written in terms of $O(d)$ invariants that depend on the Riemann curvature tensor. We study the n-dimensional sphere case to validate these results. We also show that the diffusion for positive constant curvature is slower than the diffusion in a plane space, while the diffusion for negative constant curvature turns out to be faster. Finally the two-dimensional case is emphasized, as it is relevant for the single particle diffusion on biomembranes.Comment: 16 pages and 3 figure

Axially symmetric membranes with polar tethers

Axially symmetric equilibrium configurations of the conformally invariant Willmore energy are shown to satisfy an equation that is two orders lower in derivatives of the embedding functions than the equilibrium shape equation, not one as would be expected on the basis of axial symmetry. Modulo a translation along the axis, this equation involves a single free parameter c.If c\ne 0, a geometry with spherical topology will possess curvature singularities at its poles. The physical origin of the singularity is identified by examining the Noether charge associated with the translational invariance of the energy; it is consistent with an external axial force acting at the poles. A one-parameter family of exact solutions displaying a discocyte to stomatocyte transition is described.Comment: 13 pages, extended and revised version of Non-local sine-Gordon equation for the shape of axi-symmetric membrane

Casimir-like tunneling-induced electronic forces

We study the quantum forces that act between two nearby conductors due to electronic tunneling. We derive an expression for these forces by calculating the flux of momentum arising from the overlap of evanescent electronic fields. Our result is written in terms of the electronic reflection amplitudes of the conductors and it has the same structure as Lifshitz's formula for the electromagnetically mediated Casimir forces. We evaluate the tunneling force between two semiinfinite conductors and between two thin films separated by an insulating gap. We discuss some applications of our results.Comment: 8 pages, 3 figs, submitted to Proc. of QFEXT'05, to be published in J. Phys.

The Relationship between Sexual Orientation Outness, Heterosexism, Emotion Dysregulation, and Alcohol Use among Lesbian, Gay, and Bisexual Emerging Adults

Introduction Research demonstrates that both proximal personal characteristics (e.g., outness, emotion dysregulation) and distal stressors (e.g., heterosexism) may be associated with harmful alcohol use among lesbian, gay, and bisexual (LGB) individuals. No study has systematically examined the factors linking LGB identity outness to harmful alcohol use. The current cross-sectional study bridges this gap by testing a sequential mediation model wherein heterosexist experiences (HE) and emotion dysregulation (ER) were hypothesized to mediate the relationship between outness and alcohol use. Method Participants were 264 LGB emerging adults in the age range of 18-29 years (M/SD = 25.46/2.74; 16.7% lesbian, 23.1% gay, 60.2% bisexual). Result Findings showed that 8.3% scored above a cutoff indicating harmful alcohol use. Findings supported the hypothesized serial mediation linking low levels of outness with harmful alcohol use via HE and ER, with a significant serial indirect effect (B = −.002, CI = −.004 — −.0004) and indirect effects via both HE (B = −.01, CI = −.02 – −.002) and ER (B = −.01, CI = −.02 – −.003). Conclusion Heterosexist experiences and emotion dysregulation are potential links in the association between outness and harmful alcohol use

Patterns of childhood maltreatment and intimate partner violence, emotion dysregulation, and mental health symptoms among lesbian, gay, and bisexual emerging adults: A three-step latent class approach

Background: Childhood abuse and neglect (CAN) and intimate partner violence victimization (IPV) is prevalent among lesbian, gay, and bisexual individuals (LGB). Identification of distinct patterns of childhood and adult victimization, including technology-mediated and face-to-face IPV, and their cumulative relations to mental/behavioral health challenges, among LGB people is needed to facilitate identification of at-risk individuals. Objective: Using latent class analysis, we first sought to identify patterns of lifetime interpersonal victimization, primarily five types of CAN and IPV in LGB emerging adults. Second, we examined if LGB-status and race/ethnicity predicted classmembership; third, we assessed differences between the latent classes on emotion dysregulation, depressive and anxiety symptoms, and alcohol use. Participants: Participants were 288 LGB adults between 18-29 years (M = 25.35, SD = 2.76; 41.7% gay/lesbian) recruited via Amazon MTurk. Methods and Results: The 3-step LCA identified five-latent classes: high victimization, childhood emotional abuse and neglect, cybervictimization, adult face-to-face IPV, and lower victimization. People of color (including Hispanics) were more likely to be in the high victimization class, and bisexual individuals, especially bisexual women, in the childhood emotional abuse and neglect class. High victimization and childhood emotional abuse and neglect classes had elevated emotion dysregulation levels and depression and anxiety symptoms, and the high victimization class reported the highest levels of alcohol use. Conclusion: Findings suggest a detrimental effect of cumulative interpersonal victimization on emotion dysregulation and the mental/behavioral health of LGB emerging adults, with bisexuals and LGB-people of color at heightened risk of cumulative victimization and of related mental/behavioral health challenges

Responses Of Lipids And Lipoproteins Following Acute And Training Resistance Exercise In Obese Postmenopausal Women

A single aerobic session and aerobic training can favorably modify lipids and lipoproteins in postmenopausal women, but the effects of a single resistance exercise session (RE) and resistance training (RT) remain equivocal. PURPOSE: To determine the acute effects of RE and chronic effects of 12 weeks of RT on lipid and lipoprotein-cholesterol concentrations in obese, postmenopausal women. METHODS: Sedentary, obese, non-smoking, postmenopausal women, not taking HRT, were divided into either an exercise group (E, n = 10; age = 65.7 ± 1.8 y; BMI = 32.6 ± 3.5 kg/m2) or control group (C, n = 11; age = 66.1 ± 3.0 y; BMI = 32.9 ± 4.3 kg/m2). Fasting (12 hr) blood samples were collected prior to and 24 hr after the first (BT) and last (AT) exercise session, and at the same time points for C. E performed ten upper and lower body resistance exercises (3 sets, 8 rep/set, 80% 1-RM) 3 times per week for 12 weeks; while C attended education classes twice per week for 12 weeks. Serum was assayed for total cholesterol, triglycerides, LDL-C, HDL-C, HDL2-C, HDL3-C concentrations. A 2 x 2 x 2 (group x training period x time) MANOVA was to determine changes in lipid and lipoprotein variables. A 2 x 2 (group x time) repeated measures ANOVA was used to assess body composition. RESULTS: The MANOVA revealed no significant changes in serum lipids or lipoproteins following RE or RT. No changes in body composition were observed post-training (P \u3e 0.05). Variable Pre-BT 24 hr BT Pre-AT 24 hr AT TC (mg/dl) C E 189 ± 28 217 ± 55 205 ± 40 212 ± 49 201 ± 48 207 ± 105 206 ± 42 195 ± 106 Tg (mg/dl) C E 107 ± 42 114 ± 40 96 ± 49 103 ± 25 116 ± 49 129 ± 92 112 ± 45 102 ± 48 LDL-C (mg/dl) C E 112 ± 26 140 ± 51 129 ± 37 137 ± 41 118 ± 40 127 ± 89 124 ± 41 120 ± 88 HDL-C (mg/dl) C E 55 ± 16 55 ± 12 57 ± 14 55 ±16 60 ± 13 53 ± 15 60 ± 16 54 ± 17 HDL2-C (mg/dl) C E 36 ± 12 36 ± 10 35 ± 10 34 ± 13 35 ± 12 33 ± 14 33 ± 16 35 ± 13 HDL3-C (mg/dl) C E 19 ± 9 19 ± 5 21 ± 7 21 ± 6 25 ± 6 20 ± 5 26 ± 6 20 ± 7 CONCLUSION: These data suggest that a single RE session and a 12-week RT program have no effect on lipids and lipoproteins. Compared to the effects of aerobic training, resistance exercise related changes in body composition may be necessary to modify lipids and lipoproteins in obese postmenopausal women