Collective Light Emission of a Finite Size Atomic Chain

Radiative properties of collective electronic states in a one dimensional atomic chain are investigated. Radiative corrections are included with emphasize put on the effect of the chain size through the dependence on both the number of atoms and the lattice constant. The damping rates of collective states are calculated in considering radiative effects for different values of the lattice constant relative to the atomic transition wave length. Especially the symmetric state damping rate as a function of the number of the atoms is derived. The emission pattern off a finite linear chain is also presented. The results can be adopted for any chain of active material, e.g., a chain of semiconductor quantum dots or organic molecules on a linear matrix.Comment: 10 pages, 20 figure

Hybrid Quantum System of a Nanofiber Mode Coupled to Two Chains of Optically Trapped Atoms

A tapered optical nanofiber simultaneously used to trap and optically interface of cold atoms through evanescent fields constitutes a new and well controllable hybrid quantum system. The atoms are trapped in two parallel 1D optical lattices generated by suitable far blue and red detuned evanescent field modes very close to opposite sides of the nanofiber surface. Collective electronic excitations (excitons) of each of the optical lattices are resonantly coupled to the second lattice forming symmetric and antisymmetric common excitons. In contrast to the inverse cube dependence of the individual atomic dipole-dipole interaction, we analytically find an exponentially decaying coupling strength with distance between the lattices. The resulting symmetric (bright) excitons strongly interact with the resonant nanofiber photons to form fiber polaritons, which can be observed through linear optical spectra. For large enough wave vectors the polariton decay rate to free space is strongly reduced, which should render this system ideal for the realization of long range quantum communication between atomic ensembles.Comment: 9 pages, 9 figure

Trust, regulatory processes and NICE decision-making: Appraising cost-effectiveness models through appraising people and systems.

This article presents an ethnographic study of regulatory decision-making regarding the cost-effectiveness of expensive medicines at the National Institute for Health and Care Excellence (NICE) in England. We explored trust as one important mechanism by which problems of complexity and uncertainty were resolved. Existing studies note the salience of trust for regulatory decisions, by which the appraisal of people becomes a proxy for appraising technologies themselves. Although such (dis)trust in manufacturers was one important influence, we describe a more intricate web of (dis)trust relations also involving various expert advisors, fellow committee members and committee Chairs. Within these complex chains of relations, we found examples of both more blind-acquiescent and more critical-investigative forms of trust as well as, at times, pronounced distrust. Difficulties in overcoming uncertainty through other means obliged trust in some contexts, although not in others. (Dis)trust was constructed through inferences involving abstract systems alongside actors’ oral and written presentations-of-self. Systemic features and ‘forced options’ to trust indicate potential insidious processes of regulatory capture

Secure Proximity-Based Identity Pairing using an Untrusted Signalling Service

New protocols such as WebRTC promise seamless in-browser peer-to-peer communications that in theory remove the need for third-party services. In practice, widespread use of Firewalls, NATS and dynamic IP addresses mean that overlay addressing or use of some fixed rendezvous point is still needed. In this paper we describe a proximity-based pairing scheme that uses a signalling service to minimise the trust requirements on the third party, achieving anonymity and avoiding the need for PKI, while still requiring only a simple asymmetric pairing protocol

Longitude : a privacy-preserving location sharing protocol for mobile applications

Location sharing services are becoming increasingly popular. Although many location sharing services allow users to set up privacy policies to control who can access their location, the use made by service providers remains a source of concern. Ideally, location sharing providers and middleware should not be able to access users’ location data without their consent. In this paper, we propose a new location sharing protocol called Longitude that eases privacy concerns by making it possible to share a user’s location data blindly and allowing the user to control who can access her location, when and to what degree of precision. The underlying cryptographic algorithms are designed for GPS-enabled mobile phones. We describe and evaluate our implementation for the Nexus One Android mobile phone

High-Spatial-Resolution OH PLIF Visualization in a Cavity-Stabilized Ethylene-Air Turbulent Flame

High-spatial-resolution OH planar laser-induced fluorescence was measured for a premixed ethylene-air turbulent flame in an electrically-heated Mach 2 continuous-flow facility (University of Virginia Supersonic Combustion Facility, Configuration E.) The facility comprised a Mach 2 nozzle, an isolator with flush-wall fuel injectors, a combustor with optical access, and an extender. The flame was anchored at a cavity flameholder with a backward-facing step of height 9 mm. The temperature-insensitive Q1(8) transition of OH was excited using laser light of wavelength 283.55 nm. A spatial filter was used to create a laser sheet approximately 25 microns thick based on full-width at half maximum (FWHM). Extension tubes increased the magnification of an intensified camera system, achieving in-plane resolution of 40 microns based on a 50% modulation transfer function (MTF). The facility was tested with total temperature 1200 K, total pressure 300 kPa, local fuel/air equivalence ratios of approximately 0.4, and local Mach number of approximately 0.73 in the combustor. A test case with reduced total temperature and another with reduced equivalence ratio were also tested. PLIF images were acquired along a streamwise plane bisecting the cavity flameholder, from the backward facing step to 120 mm downstream of the step. The smallest observed features in the flow had width of approximately 110 microns. Flame surface density was calculated for OH PLIF images

High-Resolution OH and CH2O Visualization in a Premixed Cavity-Anchored Ethylene-Air Flame in a M = 0.6 Flowfield

OH and CH2O were imaged in a premixed, cavity-anchored, ethylene-air turbulent flame using a high resolution planar laser-induced fluorescence (PLIF) system. The electrically-heated, continuous flow facility (UVa Supersonic Combustion Facility, Configuration E) consisted of a Mach 2 nozzle, an isolator with fuel injectors, a test section with a cavity flame holder and optical access, and an extender. Standard test conditions comprised total temperature 1200 K, total pressure 300 kPa, local equivalence ratio near 0.4, and local Mach number near 0.6. OH PLIF data was also collected for a case with reduced total temperature and another with reduced equivalence ratio. OH and CH2O were excited in separate experiments with light sheets at 283.55 nm and 352.48 nm, respectively. A light sheet of approximate thickness 25 ?m illuminated the stream-wise midplane. This plane was imaged for 120 mm downstream of the backward-facing step. The intensified camera system imaged OH with magnification 1.97, a square 6.67 mm field of view, and in-plane resolution of 39 ?m. The smallest observed OH structures observed were approximately 100 ?m wide. The CH2O PLIF image signal was much weaker; the smallest observed structures were approximately 200 ?m wide. Composite fluorescence images were computed for the observed area

Phenotype variability of infantile-onset multisystem neurologic, endocrine, and pancreatic disease IMNEPD

Infantile-onset multisystem neurologic, endocrine, and pancreatic disease (IMNEPD) has been recently linked to biallelic mutation of the peptidyl-tRNA hydrolase 2 gene PTRH2. Two index patients with IMNEPD in the original report had multiple neurological symptoms such as postnatal microcephaly, intellectual disability, developmental delay, sensorineural deafness, cerebellar atrophy, ataxia, and peripheral neuropathy. In addition, distal muscle weakness and abnormalities of thyroid, pancreas, and liver were found. Here, we report five further IMNEPD patients with a different homozygous PTRH2 mutation, broaden the phenotypic spectrum of the disease and differentiate common symptoms and interindividual variability in IMNEPD associated with a unique mutation. We thereby hope to better define IMNEPD and promote recognition and diagnosis of this novel disease entity

Associations between objectively assessed and questionnaire-based sedentary behaviour with body mass index and systolic blood pressure in Kuwaiti adolescents.

OBJECTIVE: Kuwait has one of the highest obesity rates in the world. This study examined the associations between sedentary behaviour (objectively measured and self-reported), adiposity and systolic blood pressure in a sample of adolescents residing in Kuwait. Data was obtained from the Study of Health and Activity among adolescents in Kuwait (2012-2013). The sample included a total of 435 adolescents (201 boys). Outcomes were age- and sex specific body mass index Z-scores and systolic blood pressure. Exposures were total sedentary behaviour measured by accelerometry and time spent in some sedentary behaviours (television viewing, video games, computer use and total screen-time). We used multiple linear regression analyses, adjusted for age, governorate, maternal education and physical activity, to examine associations between sedentary behaviour and adiposity and systolic blood pressure. RESULTS: Only 2 statistically significant associations were found between sedentary behaviour and the study outcomes: body mass in boys was directly associated with higher sedentary time [β (95% CIs) 0.003 (0.00 to 0.06)]; body mass index was inversely associated with videogames in both sexes [girls: β (95% CIs) - 0.17 (- 0.48 to - 0.04); boys: - 0.24 (- 0.57 to - 0.12)]. In this sample of Kuwaiti adolescents, sedentary behaviour showed limited deleterious associations with adiposity and systolic blood pressure