The Born and Markov approximations for atom lasers

We discuss the use of the Born and Markov approximations in describing the dynamics of an atom laser. In particular, we investigate the applicability of the quantum optical Born-Markov master equation for describing output coupling. We derive conditions based on the atomic reservoir, and atom dispersion relations for when the Born-Markov approximations are valid and discuss parameter regimes where these approximations fail in our atom laser model. Differences between the standard optical laser model and the atom laser are due to a combination of factors, including the parameter regimes in which a typical atom laser would operate, the different reservoir state which is appropriate for atoms, and the different dispersion relations between atoms and photons. We present results based on an exact method in the regimes in which the Born-Markov approximation fails. The exact solutions in some experimentally relavent parameter regimes give non-exponential loss of atoms from a cavity.Comment: 10 pages, 3 figures. (2 new figues). Exact solutions have been included in section II. Sections IV and V have been expanded. A new section discussing the effects of gravity has been include

Interference susceptibility of satellite 136 MHz telemetry link

Interference susceptibility of satellite 136 MHz telemetry lin

A Taxonomy of Police Technology’s Racial Inequity Problems

Over the past several years, increased awareness of racial inequity in policing, combined with increased scrutiny of police technologies, have sparked concerns that new technologies may aggravate inequity in policing. To help address these concerns, some advocates and scholars have proposed requiring police agencies to seek and obtain legislative approval before adopting a new technology, or requiring the completion of “algorithmic impact assessments” to evaluate new tools. In order for policymakers, police agencies, or scholars to evaluate whether and how particular technologies may aggravate existing inequities, however, the problem must be more clearly defined. Some scholars have explored inequity in depth as it relates to specific police technologies. But to date, none have provided an explanation of how police technology aggravates inequity that can be applied across all technologies—including future technologies we have not yet encountered. This Article fills that gap. It offers a proposed new taxonomy that parses the ways in which police technology may aggravate inequity as five distinct problems: police technology may (1) replicate inequity in policing, (2) mask inequity in policing, (3) transfer inequity from elsewhere to policing, (4) exacerbate inequitable policing harms, and/or (5) compromise oversight of inequity in policing. Naming and defining these problems will help police agencies, policymakers, and scholars alike analyze proposed new police technologies through an equity lens and craft policies that respond appropriately. This framework should be built into evaluations of police tools performed in accordance with Community Control Over Police Surveillance (“CCOPS”) ordinances being passed in a growing number of cities. To assist with these practical applications of the taxonomy, this Article also offers a model equity impact assessment for proposed police technologies, and explains why the time is ripe for introduction of such an assessment. Finally, this Article explains how the proposed taxonomy and impact assessment tool can be used to evaluate new technologies through an equity lens in contexts beyond the criminal legal system. As policymakers consider requiring algorithmic impact assessments in other domains, they can draw on the framework provided in this Article for one possible model

The steady state quantum statistics of a non-Markovian atom laser

We present a fully quantum mechanical treatment of a single-mode atomic cavity with a pumping mechanism and an output coupling to a continuum of external modes. This system is a schematic description of an atom laser. In the dilute limit where atom-atom interactions are negligible, we have been able to solve this model without making the Born and Markov approximations. When coupling into free space, it is shown that for reasonable parameters there is a bound state which does not disperse, which means that there is no steady state. This bound state does not exist when gravity is included, and in that case the system reaches a steady state. We develop equations of motion for the two-time correlation in the presence of pumping and gravity in the output modes. We then calculate the steady-state output energy flux from the laser.Comment: 14 pages (twocloumn), 6 figure

How to build more equitable vaccine distribution technology

The COVID-19 pandemic and the distribution of vaccines that promise to bring it to an end have spotlighted inequities in our nation’s healthcare system. But the vaccine distribution problem illustrates a peculiar fact of our digital era: just how hard it is to ensure equitable delivery of services via the internet. This is especially the case when distributing a scarce critical resource as quickly as possible on a massive scale. In this Brookings Institution article, Professors Laura Moy and Yael Cannon argue that digital infrastructure is a critical determinant of health, and call for the restructuring of online vaccine appointment systems to ensure health equity

The sexual health needs of looked after young people; findings from qualitative interviews led through public health and health psychology.

Background - Looked after young people (LAYP) have poorer sexual health outcomes than their peers. However, research seldom examines the health needs of, or intervenes with, this group. The aim of the current study was to identify LAYP's perceived sexual health needs and explore sources of sexual health information, knowledge levels, concerns and service preferences. Methods - Looked after young people within Fife, Scotland, were recruited through their workers and carers to participate in qualitative semi-structured interviews. Those aged 12–19 years were targeted for recruitment. National Health Services ethics approval was granted. Thematic analysis was conducted using NVivo. Results - Interviews were conducted with 10 LAYP. Key themes included gaps in knowledge, and gaps between knowledge and behaviour. Being ‘looked after’ may have negative consequences on knowledge, sources of support and safer sex. A flexible, one-to-one service, aimed at several lifestyle issues, not solely sexual health, was preferred by respondents. Conclusion - Looked after young people require support to bridge the gap between knowledge and behaviour and several theories relevant to the findings have been identified. Participants desired more support around a range of health issues, which may come from school, workers and carers, as well as health professionals. Further research examining effective interventions with this group is crucial to improve outcomes

Transurethral radiofrequency collagen denaturation for the treatment of women with urinary incontinence

Peer reviewedPublisher PD

Evolution of photoionization and star formation in starbursts and HII galaxies

We analyze the stellar and nebular energy distributions of starbursts using our evolutionary synthesis model PEGASE coupled to the photoionization code CLOUDY. The originality of this study is to relate the evolution and the metallicity of the starburst to the past star formation history of the host galaxy.We compare our model predictions to an observed sample of ~750 starbursts. the most striking feature from line ratio fitting is the decreasing spread in ionization parameter U at high metallicity Z. The best fits of emission line ratios are obtained with a combination of a high- and a low-ionization components. No additional source of ionizing photons --shocks or hidden AGN -- is needed. Colors and equivalent widths are fitted in coherency with emission line ratios. An underlying population is needed, even for small-aperture observations. This evolved population not only reddens the continuum and dilutes the equivalent width of the emission lines, but also participates in the ionization process. Its main effect on line ratios is to maintain a high level of excitation when the burst stops. Models combining underlying populations typical of Hubble sequence galaxies and instantaneous starbursts with ages between 0 and 8 Myr agree satisfactorily with all the data