Spatially Resolved Excitation of Rydberg Atoms and Surface Effects on an Atom Chip

We demonstrate spatially resolved, coherent excitation of Rydberg atoms on an atom chip. Electromagnetically induced transparency (EIT) is used to investigate the properties of the Rydberg atoms near the gold coated chip surface. We measure distance dependent shifts (~10 MHz) of the Rydberg energy levels caused by a spatially inhomogeneous electric field. The measured field strength and distance dependence is in agreement with a simple model for the electric field produced by a localized patch of Rb adsorbates deposited on the chip surface during experiments. The EIT resonances remain narrow (< 4 MHz) and the observed widths are independent of atom-surface distance down to ~20 \mum, indicating relatively long lifetime of the Rydberg states. Our results open the way to studies of dipolar physics, collective excitations, quantum metrology and quantum information processing involving interacting Rydberg excited atoms on atom chips

Three-dimensional character of atom-chip-based rf-dressed potentials

We experimentally investigate the properties of radio-frequency-dressed potentials for Bose-Einstein condensates on atom chips. The three-dimensional potential forms a connected pair of parallel waveguides. We show that rf-dressed potentials are robust against the effect of small magnetic-field variations on the trap potential. Long-lived dipole oscillations of condensates induced in the rf-dressed potentials can be tuned to a remarkably low damping rate. We study a beam-splitter for Bose-Einstein condensates and show that a propagating condensate can be dynamically split in two vertically separated parts and guided along two paths. The effect of gravity on the potential can be tuned and compensated for using a rf-field gradient.Comment: 9 pages, 7 figure

Sub-Poissonian atom number fluctuations by three-body loss in mesoscopic ensembles

We show that three-body loss of trapped atoms leads to sub-Poissonian atom number fluctuations. We prepare hundreds of dense ultracold ensembles in an array of magnetic microtraps which undergo rapid three-body decay. The shot-to-shot fluctuations of the number of atoms per trap are sub-Poissonian, for ensembles comprising 50--300 atoms. The measured relative variance or Fano factor $F=0.53\pm 0.22$ agrees very well with the prediction by an analytic theory ($F=3/5$) and numerical calculations. These results will facilitate studies of quantum information science with mesoscopic ensembles.Comment: 4 pages, 3 figure

Box traps on an atom chip for one-dimensional quantum gases

We present the implementation of tailored trapping potentials for ultracold gases on an atom chip. We realize highly elongated traps with box-like confinement along the long, axial direction combined with conventional harmonic confinement along the two radial directions. The design, fabrication and characterization of the atom chip and the box traps is described. We load ultracold ($\lesssim1 \mu$K) clouds of $^{87}$Rb in a box trap, and demonstrate Bose-gas focusing as a means to characterize these atomic clouds in arbitrarily shaped potentials. Our results show that box-like axial potentials on atom chips are very promising for studies of one-dimensional quantum gases.Comment: 9 pages 4 figure

Quantitative Genetic Effects of Bottlenecks: Experimental Evidence from a Wild Plant Species, Nigella degenii

Understanding the genetic consequences of changes in population size is fundamental in a variety of contexts, such as adaptation and conservation biology. In the study presented here, we have performed a replicated experiment with the plant Nigella degenii to explore the quantitative genetic effects of a single-founder bottleneck. In agreement with additive theory, the bottleneck reduced the mean (co)variance within lines and caused stochastic, line-specific changes in the genetic (co)variance structure. However, a significant portion of the (co)variance structure was conserved, and 2 characters—leaf and flower (sepal) size—turned out to be positively correlated in all data sets, indicating a potential for correlated evolution in these characters, even after a severe bottleneck. The hierarchical partitioning of genetic variance for flower size was in good agreement with predictions from additive theory, whereas the remaining characters showed an excess of within-line variance and a deficiency of among-line variance. The latter discrepancies were most likely a result of selection, given the small proportion of lines (23%) that remained viable until the end of the experiment. Our results suggest that bottlenecked populations of N. degenii generally have a lower adaptive potential than the ancestral population but also highlight the idiosyncratic nature of bottleneck effects

Evolutionary dynamics on degree-heterogeneous graphs

The evolution of two species with different fitness is investigated on degree-heterogeneous graphs. The population evolves either by one individual dying and being replaced by the offspring of a random neighbor (voter model (VM) dynamics) or by an individual giving birth to an offspring that takes over a random neighbor node (invasion process (IP) dynamics). The fixation probability for one species to take over a population of N individuals depends crucially on the dynamics and on the local environment. Starting with a single fitter mutant at a node of degree k, the fixation probability is proportional to k for VM dynamics and to 1/k for IP dynamics.Comment: 4 pages, 4 figures, 2 column revtex4 format. Revisions in response to referee comments for publication in PRL. The version on arxiv.org has one more figure than the published PR

Daily mood, partner support, sexual interest, and sexual activity among adolescent women

This is a post print version of the article. The official published version can be accessed from the link below.Objective: to examine day-to-day associations of coitus, sexual interest, partner emotional support, negative mood and positive mood among adolescent women. Methods: Women (ages 14 – 17 at enrollment; N=146) enrolled from one of three adolescent primary care clinics completed up to five 84-day diaries over a 27-month period. The diaries assessed partner interactions, sexual activity, substance use and mood. Partner-specific measures assessed on each day included partner emotional support (4 items; alpha = 0.94), argument with a partner (no/yes) and coitus (no/yes). Within-day measures assessed marijuana use (no/yes), Positive Mood (3-items; alpha = 0. 86); Negative Mood (3-items; alpha = 0.82) and Sexual Interest (1-item). Lagged measures of mood and sexual activity were included in multivariate models to control for recent mood and sexual behavior effects on current day mood and coitus. Two main analyses were conducted: coitus as a predictor of positive and negative mood; and the role of positive and negative mood as predictors of coitus. Analyses were conducted by multivariate mixed effect regression and mixed effect logistic regression models. Results: Data represent 28,376 days from 146 participants. The average number of diary days was 194 days per participant. Sexual activity was reported on 8.3% of days, with condoms used for 27.0% of these coital events. Marijuana was used on 11% of days. Significant predictors of positive mood on a given day included partner support, marijuana use, and coitus. Negative mood was associated with having an argument with a partner and with prior day coitus. Predictors of coitus on a given day included age (Odds ratio = 1.22), increased coital frequency in previous week (OR = 1.49), coitus on the previous day (1.21), increased same-day sexual interest (OR = 2.8) and decreased same-day negative mood (OR = 0.92). Conclusions: The data demonstrate complex associations of sexual interest, mood, partner interactions and sexual activity

Non-suicidal self-injury in adolescence: a longitudinal study of the relationship between NSSI, psychological distress and perceived parenting

Objective: The present study investigates whether either adolescents' psychological distress and/or perceived parenting predicted the occurrence of NSSI. Furthermore, the consequences of NSSI are examined in a three-wave longitudinal study. Design: The sample at time 1 (age 12) consisted of 1396 adolescent reports and 1438 parent reports. At time 2 (age 13), 827 adolescent reports and 936 parent reports were obtained. Time 3 (age 14) included 754 adolescent reports and 790 parent reports. Psychological distress of adolescents was measured using the Strengths and Difficulties Questionnaire. Perceived parenting behaviors were examined by the Parental Behavior Scale and the Psychological Control Scale. Results: A total of 10% of the adolescents engaged in NSSI at least once before age 15. Higher psychological distress of adolescents at time 1 was associated with the presence of NSSI at time 2 or 3. The association between psychological distress at time 1 and perception of decreased parental rule setting at time 3 was mediated by the presence of NSSI at time 2. Conclusions: The present study showed that psychological distress at age 12 predicts NSSI over time and that parental awareness of NSSI changes the perception of parenting behaviors. (C) 2014 The Foundation for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved

Test purchase, synthesis, and characterization of 2-methoxydiphenidine (MXP) and differentiation from its meta- and para-substituted isomers

The structurally diverse nature of the 1,2-diphenylethylamine template provides access to a range of substances for drug discovery work but some have attracted attention as ‘research chemicals’. The most recent examples include diphenidine, i.e. 1-(1,2-diphenylethyl)piperidine and 2-methoxydiphenidine, i.e. 1-[1-(2-methoxyphenyl)-2-phenylethyl]piperidine (MXP, methoxyphenidine, 2-MXP) that have been associated with uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist activity. Analytical challenges encountered during chemical analysis include the presence of positional isomers. Three powdered samples suspected to contain 2-MXP were obtained from three Internet retailers in the United Kingdom and subjected to analytical characterization by gas chromatography (GC) and high performance liquid chromatography (HPLC) coupled to various forms of mass spectrometry (MS). Nuclear magnetic resonance spectroscopy, infrared spectroscopy and thin layer chromatography were also employed. This was supported by the synthesis of all three isomers (2-, 3- and 4-MXP) by two different synthetic routes. The analytical data obtained for the three purchased samples were consistent with the synthesized 2-MXP standard and the differentiation between the isomers was possible. Distinct stability differences were observed for all three isomers during in-source collision-induced dissociation of the protonated molecule when employing detection under HPLC selected-ion monitoring detection, which added to the ability to differentiate between them. Furthermore, the analysis of a 2-MXP tablet by matrix assisted inlet ionization Orbitrap mass spectrometry confirmed that it was possible to detect the protonated molecule of 2-MXP directly from the tablet surface following addition of 3-nitrobenzonitrile as the matrix

Restless quiescence: thermonuclear flashes between transient X-ray outbursts

For thermonuclear flashes to occur on neutron-star surfaces, fuel must have been accreted from a donor star. However, sometimes flashes are seen from transient binary systems when they are thought to be in their quiescent phase, during which no accretion, or relatively little, is expected to occur. We investigate the accretion luminosity during several such flashes, including the first-ever and brightest detected flash from Cen X-4 in 1969. We infer from observations and theory that immediately prior to these flashes the accretion rate must have been between about 0.001 and 0.01 times the equivalent of the Eddington limit, which is roughly 2 orders of magnitude less than the peak accretion rates seen in these transients during an X-ray outburst and 3-4 orders of magnitude more than the lowest measured values in quiescence. Furthermore, three such flashes, including the one from Cen X-4, occurred within 2 to 7 days followed by an X-ray outburst. A long-term episode of enhanced, but low-level, accretion is predicted near the end of the quiescent phase by the disk-instability model, and may thus have provided the right conditions for these flashes to occur. We discuss the possibility of whether these flashes acted as triggers of the outbursts, signifying a dramatic increase in the accretion rate. Although it is difficult to rule out, we find it unlikely that the irradiance by these flashes is sufficient to change the state of the accretion disk in such a dramatic way.Comment: 9 pages, 3 figures, accepted for publication in A&A; referee comments included plus improved text; results unchange