Quantifying Finite Temperature Effects in Atom Chip Interferometry of Bose-Einstein Condensates

We quantify the effect of phase fluctuations on atom chip interferometry of Bose-Einstein condensates. At very low temperatures, we observe small phase fluctuations, created by mean-field depletion, and a resonant production of vortices when the two clouds are initially in anti-phase. At higher temperatures, we show that the thermal occupation of Bogoliubov modes makes vortex production vary smoothly with the initial relative phase difference between the two atom clouds. We also propose a technique to observe vortex formation directly by creating a weak link between the two clouds. The position and direction of circulation of the vortices is subsequently revealed by kinks in the interference fringes produced when the two clouds expand into one another. This procedure may be exploited for precise force measurement or motion detection.Comment: 7 pages, 5 figure

Estimating marine reservoir effects in archaeological chronologies: Comparing ΔR calculations in Prince Rupert Harbour, British Columbia, Canada

The best method for quantifying the marine reservoir effect (MRE) using the global IntCal Marine13 calibration curve remains unresolved. Archaeologists frequently quantify uncertainty on MRE values as errors computed from single pairs of marineterrestrial radiocarbon ages, which we argue significantly overstates their accuracy and precision. Here, we review the assumptions, methods, and applications of estimating MRE via an estimate of the additional regional offset between the marine and terrestrial calibration curves (ΔR) for the Prince Rupert Harbour (PRH) region of British Columbia, Canada.We acknowledge the influence on ΔR of MRE variation as (1) a dynamic oceanographic process, (2) its variable expression in biochemical and geochemical pathways, and (3) compounding errors in sample selection, measurement, and calculation. We examine a large set of marine-terrestrial pairs (n = 63) from PRH to compare a common archaeological practice of estimating uncertainty from means that generate an uncertainty value of ±49 years with a revised, more appropriate estimate of error of ± 230 years. However, we argue that the use of multiple-pair samples estimates the PRH ΔR as 273 ± 38 years for the last 5,000 years. Calculations of error that do not consider these issues may generate more inaccurate age estimates with unjustifiable precision

A qualitative study of men’s recollections of growing up with father absence: childhood father figures and family resilience

© 2017 Informa UK Limited, trading as Taylor & Francis Group. Background: Families come in many forms and single parent women headed households are common with nurses being well positioned to provide support for these women and their children. For children growing up in lone parent households, the nature of family relationships and the availability of a social support network are important factors in reducing developmental risks. Aim: The aim of this study was to explore adult men’s recollections of growing up in a father-absent home. Design: This study utilised a qualitative methodology. Methods: Semi-structured interviews were conducted with 21 adult men who grew up in a father-absent home due to family discord. Interview transcripts were thematically analysed using an inductive approach. Findings: Analysis of the interview transcripts revealed two themes relating to childhood father figures and family relational networks. For some men, ambivalent, violent or unavailable father figures stepped into the void created by the absent father. Others experienced positive father figures or multigenerational relationships, which provided positive relational supports and attachments. Conclusion: The findings illuminate the dynamics of family resilience and provide important insights for nurses and other family healthcare workers

“Being a father”: constructions of fatherhood by men with absent fathers

© 2018 Informa UK Limited, trading as Taylor & Francis Group Family dynamics and parenting styles are influential on children's wellbeing [Walsh, F. (2016). Strengthening family resilience (3rd ed.). New York: Guilford Press]. Additionally, childhood experiences and how an individual experienced being parented can impact on how individuals as mothers and fathers choose to parent their own children [Herland, M. D., Hauge, M.-I., & Helegland, I. M. (2015). Balancing fatherhood: Experiences of fatherhood among men with a difficult past. Qualitative Social Work, 14(2), 242–258]. However, growing up in a home with an absent parent may create challenges associated with parenting for individuals, due to not having these experiences themselves. Therefore, the article reports findings on men who grew up in a father-absent household and how their experiences influenced their understanding of fatherhood and becoming a father. Twenty-one men participated in this qualitative study. Findings revealed that although men felt unprepared for fatherhood they attempted to learn to be a father and expressed the importance of not wanting their children to experience father absence. The study findings provide important insights in the provision of support for fathers who have experienced father absence

Gapless finite-TT theory of collective modes of a trapped gas

We present predictions for the frequencies of collective modes of trapped Bose-condensed $^{87}$Rb atoms at finite temperature. Our treatment includes a self-consistent treatment of the mean-field from finite-$T$ excitations and the anomolous average. This is the first gapless calculation of this type for a trapped Bose-Einstein condensed gas. The corrections quantitatively account for the downward shift in the $m=2$ excitation frequencies observed in recent experiments as the critical temperature is approached.Comment: 4 pages Latex and 2 postscript figure

Kinetic Theory of Collective Excitations and Damping in Bose-Einstein Condensed Gases

We calculate the frequencies and damping rates of the low-lying collective modes of a Bose-Einstein condensed gas at nonzero temperature. We use a complex nonlinear Schr\"odinger equation to determine the dynamics of the condensate atoms, and couple it to a Boltzmann equation for the noncondensate atoms. In this manner we take into account both collisions between noncondensate-noncondensate and condensate-noncondensate atoms. We solve the linear response of these equations, using a time-dependent gaussian trial function for the condensate wave function and a truncated power expansion for the deviation function of the thermal cloud. As a result, our calculation turns out to be characterized by two dimensionless parameters proportional to the noncondensate-noncondensate and condensate-noncondensate mean collision times. We find in general quite good agreement with experiment, both for the frequencies and damping of the collective modes.Comment: 10 pages, 8 figure

A tool for simulating and communicating uncertainty when modelling species distributions under future climates

Tools for exploring and communicating the impact of uncertainty on spatial prediction are urgently needed, particularly when projecting species distributions to future conditions. We provide a tool for simulating uncertainty, focusing on uncertainty due to data quality. We illustrate the use of the tool using a Tasmanian endemic species as a case study. Our simulations provide probabilistic, spatially explicit illustrations of the impact of uncertainty on model projections. We also illustrate differences in model projections using six different global climate models and two contrasting emissions scenarios. Our case study results illustrate how different sources of uncertainty have different impacts on model output and how the geographic distribution of uncertainty can vary. Synthesis and applications: We provide a conceptual framework for understanding sources of uncertainty based on a review of potential sources of uncertainty in species distribution modelling; a tool for simulating uncertainty in species distribution models; and protocols for dealing with uncertainty due to climate models and emissions scenarios. Our tool provides a step forward in understanding and communicating the impacts of uncertainty on species distribution models under future climates which will be particularly helpful for informing discussions between researchers, policy makers, and conservation practitioners

Holes in my memories: A qualitative study of men affected by father absence

This qualitative study explored adult men's experiences of father absence. Interviews with 21 men between the ages of 24 and 70 explored narratives of father absence and how the men perceived this influenced their life trajectory. Thematic analysis revealed that these men experienced a range of difficulties and challenges, including episodes of sadness and depression associated with loss and grief for the paternal relationship, self-esteem issues, feelings of anger and rejection, and difficulty forming trusting relationships particularly with other men. This study contributes to understanding mental health issues that can be associated with paternal absence for men. © 2014 Informa Healthcare USA, Inc

Bivariate tt-distribution for transition matrix elements in Breit-Wigner to Gaussian domains of interacting particle systems

Interacting many-particle systems with a mean-field one body part plus a chaos generating random two-body interaction having strength $\lambda$, exhibit Poisson to GOE and Breit-Wigner (BW) to Gaussian transitions in level fluctuations and strength functions with transition points marked by $\lambda=\lambda_c$ and $\lambda=\lambda_F$, respectively; $\lambda_F >> \lambda_c$. For these systems theory for matrix elements of one-body transition operators is available, as valid in the Gaussian domain, with $\lambda > \lambda_F$, in terms of orbitals occupation numbers, level densities and an integral involving a bivariate Gaussian in the initial and final energies. Here we show that, using bivariate $t$-distribution, the theory extends below from the Gaussian regime to the BW regime up to $\lambda=\lambda_c$. This is well tested in numerical calculations for six spinless fermions in twelve single particle states.Comment: 7 pages, 2 figure