Collimated, single-pass atom source from a pulsed alkali metal dispenser for laser-cooling experiments

We have developed an improved scheme for loading atoms into a magneto-optical trap (MOT) from a directed alkali metal dispenser in < 10^-10 torr ultra-high vacuum conditions. A current-driven dispenser was surrounded with a cold absorbing "shroud" held at < 0 C, pumping rubidium atoms not directed into the MOT. This nearly eliminates background alkali atoms and reduces the detrimental rise in pressure normally associated with these devices. The system can be well-described as a current-controlled, rapidly-switched, two-temperature thermal beam, and was used to load a MOT with 3 x 10^8 atoms.Comment: 5 pages, 4 figure

Manifestation of classical wave delays in a fully quantized model of the scattering of a single photon

We consider a fully quantized model of spontaneous emission, scattering, and absorption, and study propagation of a single photon from an emitting atom to a detector atom both with and without an intervening scatterer. We find an exact quantum analog to the classical complex analytic signal of an electromagnetic wave scattered by a medium of charged oscillators. This quantum signal exhibits classical phase delays. We define a time of detection which, in the appropriate limits, exactly matches the predictions of a classically defined delay for light propagating through a medium of charged oscillators. The fully quantized model provides a simple, unambiguous, and causal interpretation of delays that seemingly imply speeds greater than c in the region of anomalous dispersion.Comment: 18 pages, 4 figures, revised for clarity, typos corrrecte

Ponderomotive light squeezing with atomic cavity optomechanics

Accessing distinctly quantum aspects of the interaction between light and the position of a mechanical object has been an outstanding challenge to cavity-optomechanical systems. Only cold-atom implementations of cavity optomechanics have indicated effects of the quantum fluctuations in the optical radiation pressure force. Here we use such a system, in which quantum photon-number fluctuations significantly drive the center of mass of an atomic ensemble inside a Fabry-Perot cavity. We show that the optomechanical response both amplifies and ponderomotively squeezes the quantum light field. We also demonstrate that classical optical fluctuations can be attenuated by 26 dB or amplified by 20 dB with a weak input pump power of < 40 pW, and characterize the optomechanical amplifier's frequency-dependent gain and phase response in both the amplitude and phase-modulation quadratures

CanadiEM: Accessing a Virtual Community of Practice to Create a Canadian National Medical Education Institution

Background: The rise of free open-access medical education (FOAM) has led to a wide range of online resources in emergency medicine. Canadian physicians have been active contributors to FOAM. Objectives: We aimed to create a virtual community of practice that would serve as a national platform for collaboration, learning, and knowledge dissemination. Methods: CanadiEM was formed in 2016 from the merger of two Canadian websites and a podcast. Using a community-of-practice model, we introduced two training programs to support junior community members in becoming core editorial team members and employed asynchronous Web technologies to facilitate collaboration. We also introduced a coached peer review process and formed strategic alliances that aim to ensure a high quality of publication. Results: CanadiEM has become a portal for readers to access a broad range of FOAM content. The website has published 782 articles. Of these, 71 have undergone a coached peer review process. The website has received over 2.5 million page views from 217 countries, and the associated CRACKCast podcast has been downloaded over 750,000 times. Conclusions: CanadiEM has succeeded in building a national multi-interface dissemination network that fosters collaboration and knowledge sharing in emergency medicine while fostering junior digital scholars. The construction of a community of practice has been facilitated by quality assurance, training programs, and the use of asynchronous Web technologies. Ongoing challenges in sustainability include a volunteer workforce with high turnover

Contested childhoods across borders and boundaries: Insights from curriculum provisions in Northern Ireland and the Irish Free State in the 1920s

Conceptualisations and constructs of children and childhood are temporally and contextually grounded. Historical documents are rich sources of insight and understanding regarding how children were understood, valued and treated at various times by particular societies. This article explores the conceptualisation of children and childhood in the 26-county Irish Free State (South) and the 6-county Northern Ireland (North) in the 1920s following the partition of Ireland, through the lens of educational documentation, primarily national primary school curricula. The focus on both jurisdictions is interesting in the context of partition, exploring the sometimes divergent and often convergent ways in which children were conceptualised across borders and boundaries. This article reveals, using Sorin and Galloway’s framework as a conceptual and analytical tool, that conceptualisations of children were broadly similar in the North and South but differed in their focus and enactment in both fledgling states. These disparities are largely attributable to the very different political, social and religious orientations of both jurisdictions and the use of education as a vehicle for nation-building, as well as identity and gender formation. The article also explores alternative conceptualisations of children in education policy in the North and South by presenting case study ‘outliers’ of educational provision. A century since partition, conclusions and implications are noted that resonate with contemporary elements of convergence and divergence on educational policy and the conceptualisation of children across the island of Ireland