Performance evaluation of optical attocells configuration in an indoor visible light communication

Visible light communication VLC is deemed as futuristic technology applied for both illumination and data communication due to the low-cost energy consumption, long life expectancy, huge bandwidth, and high security compared to radio frequency RF. Uncovered area, minimum signal-to-noise ratio (SNR) and received power results from the non-uniform distribution of small base stations (i.e. Optical attocells) in the room. In this paper, the researchers propose a new LEDs distribution of five optical attocells configuration model in order to optimize the received power distribution and SNR at the center of the room for indoor VLC system. The optical attocells configuration in terms of received power to fill the uncovered area at the center of the room has been investigated. The simulation results showed that the proposed attocells configuration saved 24.9% of the transmitted power. Besides that, the whole room was covered uniformly. As a result, the received power and SNR are improved

Device independent state estimation based on Bell's inequalities

The only information available about an alleged source of entangled quantum states is the amount $S$ by which the Clauser-Horne-Shimony-Holt (CHSH) inequality is violated: nothing is known about the nature of the system or the measurements that are performed. We discuss how the quality of the source can be assessed in this black-box scenario, as compared to an ideal source that would produce maximally entangled states (more precisely, any state for which $S=2\sqrt{2}$). To this end, we introduce several inequivalent notions of fidelity, each one related to the use one can make of the source after having assessed it; and we derive quantitative bounds for each of them in terms of the violation $S$. We also derive a lower bound on the entanglement of the source as a function of $S$ only.Comment: 8 pages, 2 figures. Added appendices containing proof

Retinitis pigmentosa-associated cystoid macular oedema: pathogenesis and avenues of intervention

Hereditary retinal diseases are now the leading cause of blindness certification in the working age population (age 16-64 years) in England and Wales, of which retinitis pigmentosa (RP) is the most common disorder. RP may be complicated by cystoid macular oedema (CMO), causing a reduction of central vision. The underlying pathogenesis of RP-associated CMO (RP-CMO) remains uncertain, however, several mechanisms have been proposed, including: (1) breakdown of the blood-retinal barrier, (2) failure (or dysfunction) of the pumping mechanism in the retinal pigment epithelial, (3) Müller cell oedema and dysfunction, (4) antiretinal antibodies and (5) vitreous traction. There are limited data on efficacy of treatments for RP-CMO. Treatments attempted to date include oral and topical carbonic anhydrase inhibitors, oral, topical, intravitreal and periocular steroids, topical non-steroidal anti-inflammatory medications, photocoagulation, vitrectomy with internal limiting membrane peel, oral lutein and intravitreal antivascular endothelial growth factor injections. This review summarises the evidence supporting these treatment modalities. Successful management of RP-CMO should aim to improve both quality and quantity of vision in the short term and may also slow central vision loss over time

Cardiovascular risk scores do not account for the effect of treatment: a review

OBJECTIVE: To compare the strengths and limitations of cardiovascular risk scores available for clinicians in assessing the global (absolute) risk of cardiovascular disease. DESIGN: Review of cardiovascular risk scores. DATA SOURCES: Medline (1966 to May 2009) using a mixture of MeSH terms and free text for the keywords 'cardiovascular', 'risk prediction' and 'cohort studies'. ELIGIBILITY CRITERIA FOR SELECTING STUDIES: A study was eligible if it fulfilled the following criteria: (1) it was a cohort study of adults in the general population with no prior history of cardiovascular disease and not restricted by a disease condition; (2) the primary objective was the development of a cardiovascular risk score/equation that predicted an individual's absolute cardiovascular risk in 5-10 years; (3) the score could be used by a clinician to calculate the risk for an individual patient. RESULTS: 21 risk scores from 18 papers were identified from 3536 papers. Cohort size ranged from 4372 participants (SHS) to 1591209 records (QRISK2). More than half of the cardiovascular risk scores (11) were from studies with recruitment starting after 1980. Definitions and methods for measuring risk predictors and outcomes varied widely between scores. Fourteen cardiovascular risk scores reported data on prior treatment, but this was mainly limited to antihypertensive treatment. Only two studies reported prior use of lipid-lowering agents. None reported on prior use of platelet inhibitors or data on treatment drop-ins. CONCLUSIONS: The use of risk-factor-modifying drugs-for example, statins-and disease-modifying medication-for example, platelet inhibitors-was not accounted for. In addition, none of the risk scores addressed the effect of treatment drop-ins-that is, treatment started during the study period. Ideally, a risk score should be derived from a population free from treatment. The lack of accounting for treatment effect and the wide variation in study characteristics, predictors and outcomes causes difficulties in the use of cardiovascular risk scores for clinical treatment decision

On the effective plate thickness of monolayer graphene from flexural wave propagation

We utilize classical molecular dynamics to study flexural, or transverse wave propagation in monolayer graphene sheets and compare the resulting dispersion relationships to those expected from continuum thin plate theory. In doing so, we determine that regardless of the chirality for monolayer graphene, transverse waves exhibit a dispersion relationship that corresponds to the lowest order antisymmetric (A0) mode of wave propagation in a thin plate with plate thickness of h = 0.104 nm. Finally, we find that the achievable wave speeds in monolayer graphene are found to exceed those reported previously for single walled carbon nanotubes, while the frequency of wave propagation in the graphene monolayer is found to reach the terahertz range, similar to that of carbon nanotubes.open9

The Effect of Element Types on Force Analogy Method Analysis

In this study, the seismic performance of a 2D portal frame subjected to the recorded seismic ground motions of the Northridge 1994 earthquake was evaluated by the force analogy method (FAM) with different element types. To increase the accuracy of FAM, Timoshenko (TS) elements were employed instead of the classical Euler Bernoulli (EB) elements, to revert the shear deformations that are neglected in EB elements. To perform evaluation, the same material and section properties were considered and the same portal frame was analyzed with different element lengths, from 0.5 to 7.0 m in 0.5 m steps

Studies of monomer impregnation and polymerised in situ in wood using dynamic mechanical thermal analyser.

Ten tropical hardwoods are impregnated with methyl methacrylate and polymerised in‐situ by use of catalysts and heat techniques. Treatability of the wood, as determined from the fractional volumetric retentions of monomers that are a fraction of voids filled by the impregnant, showed that the mean retention range from 15·03% (Acacia Mangium) to 56·59% (Cratoxylum Arborescens). The penetration of the monomer evaluated using ultrasonic waves showed that the treated wood had higher velocities which indicated significant increase in density. The present paper deals with the viscoelastic relaxation of polymerised treated wood. The efficiency of the monomer as a plasticiser is studied through the temperature dependence of the storage modulus (E′) and loss tangent (tan δ) of treated and untreated wood by dynamic mechanical thermal analysis (DMTA) over a temperature in the range from −100 to 200°C. The storage modulus E′ decreased with temperature and as the maximum mechanical damping developed, the glass transition temperature (T g) of the plasticised wood decreased with the plasticiser content

Operation speed of polariton condensate switches gated by excitons

We present a time-resolved photoluminescence (PL) study in real- and momentum-space of a polariton condensate switch in a quasi-1D semiconductor microcavity. The polariton flow across the ridge is gated by excitons inducing a barrier potential due to repulsive interactions. A study of the device operation dependence on the power of the pulsed gate beam obtains a satisfactory compromise for the ON/OFF-signal ratio and -switching time of the order of 0.3 and $\thicksim50$ ps, respectively. The opposite transition is governed by the long-lived gate excitons, consequently the OFF/ON-switching time is $\thicksim200$ ps, limiting the overall operation speed of the device to $\thicksim3$ GHz. The experimental results are compared to numerical simulations based on a generalized Gross-Pitaevskii equation, taking into account incoherent pumping, decay and energy relaxation within the condensate.Comment: 11 pages, 11 figure

Optical control of spin textures in quasi-one-dimensional polariton condensates

We investigate, through polarization-resolved spectroscopy, the spin transport by propagating polariton condensates in a quasi one-dimensional microcavity ridge along macroscopic distances. Under circularly polarized, continuous-wave, non-resonant excitation, a sinusoidal precession of the spin in real space is observed, whose phase depends on the emission energy. The experiments are compared with simulations of the spinor-polariton condensate dynamics based on a generalized Gross-Pitaevskii equation, modified to account for incoherent pumping, decay and energy relaxation within the condensate.Comment: 10 pages, 9 figure