Simulation of metallic nanostructures for emission of THz radiation using the lateral photo-Dember effect

A 2D simulation for the lateral photo-Dember effect is used to calculate the THz emission of metallic nanostructures due to ultrafast diffusion of carriers in order to realize a series of THz emitters.Comment: Corrected version of a paper given at 2011 36th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz

Sources, perceived usefulness and understanding of information disseminated to families who entered home quarantine during the H1N1 pandemic in Victoria, Australia: a cross-sectional study

Background Voluntary home quarantine of cases and close contacts was the main non-pharmaceutical intervention used to limit transmission of pandemic (H1N1) 2009 influenza (pH1N1) in the initial response to the outbreak of the disease in Australia. The effectiveness of voluntary quarantine logically depends on affected families having a clear understanding of what they are being asked to do. Information may come from many sources, including the media, health officials, family and friends, schools, and health professionals. We report the extent to which families who entered home quarantine received and used information on what they were supposed to do. Specifically, we outline their sources of information; the perceived usefulness of each source; and associations between understanding of recommendations and compliance. Methods Cross-sectional survey administered via the internet and computer assisted telephone interview to families whose school children were recommended to go into home quarantine because they were diagnosed with H1N1 or were a close contact of a case. The sample included 314 of 1157 potentially eligible households (27% response rate) from 33 schools in metropolitan Melbourne. Adjusting for clustering within schools, we describe self-reported \u27understanding of what they were meant to do during the quarantine period\u27; source of information (e.g. health department) and usefulness of information. Using logistic regression we examine whether compliance with quarantine recommendations was associated with understanding and the type of information source used. Results Ninety per cent understood what they were meant to do during the quarantine period with levels of understanding higher in households with cases (98%, 95% CI 93%-99% vs 88%, 95% CI 84%-91%, P = 0.006). Over 87% of parents received information about quarantine from the school, 63% from the health department and 44% from the media. 53% of households were fully compliant and there was increased compliance in households that reported that they understood what they were meant to do (Odds Ratio 2.27, 95% CI 1.35-3.80). Conclusions It is critical that public health officials work closely with other government departments and media to provide clear, consistent and simple information about what to do during quarantine as high levels of understanding will maximise compliance in the quarantined population

Independent measurement of the total active B8 solar neutrino flux using an array of He3 proportional counters at the Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory (SNO) used an array of 3He proportional counters to measure the rate of neutral-current interactions in heavy water and precisely determined the total active (νx) 8B solar neutrino flux. This technique is independent of previous methods employed by SNO. The total flux is found to be 5.54-0.31+0.33(stat)-0.34+0.36(syst)×106  cm-2 s-1, in agreement with previous measurements and standard solar models. A global analysis of solar and reactor neutrino results yields Δm2=7.59-0.21+0.19×10-5  eV2 and θ=34.4-1.2+1.3 degrees. The uncertainty on the mixing angle has been reduced from SNO’s previous results

Quantifying Type-Specific Reproduction Numbers for Nosocomial Pathogens: Evidence for Heightened Transmission of an Asian Sequence Type 239 MRSA Clone

An important determinant of a pathogen's success is the rate at which it is transmitted from infected to susceptible hosts. Although there are anecdotal reports that methicillin-resistant Staphylococcus aureus (MRSA) clones vary in their transmissibility in hospital settings, attempts to quantify such variation are lacking for common subtypes, as are methods for addressing this question using routinely-collected MRSA screening data in endemic settings. Here we present a method to quantify the time-varying transmissibility of different subtypes of common bacterial nosocomial pathogens using routine surveillance data. The method adapts approaches for estimating reproduction numbers based on the probabilistic reconstruction of epidemic trees, but uses relative hazards rather than serial intervals to assign probabilities to different sources for observed transmission events. The method is applied to data collected as part of a retrospective observational study of a concurrent MRSA outbreak in the United Kingdom with dominant endemic MRSA clones (ST22 and ST36) and an Asian ST239 MRSA strain (ST239-TW) in two linked adult intensive care units, and compared with an approach based on a fully parametric transmission model. The results provide support for the hypothesis that the clones responded differently to an infection control measure based on the use of topical antiseptics, which was more effective at reducing transmission of endemic clones. They also suggest that in one of the two ICUs patients colonized or infected with the ST239-TW MRSA clone had consistently higher risks of transmitting MRSA to patients free of MRSA. These findings represent some of the first quantitative evidence of enhanced transmissibility of a pandemic MRSA lineage, and highlight the potential value of tailoring hospital infection control measures to specific pathogen subtypes

Characterisation of low temperature and semi-insulating GaAs lateral photo-Dember THz Emitters

Poster for IRMMW-THz conference in Mainz, Germany 201

Multiple lateral photo-Dember terahertz emitters

Pulsed terahertz time-domain systems (THz-TDS) offer many applications for spectroscopy and imaging. Typically terahertz generation is achieved by using a photoconductive antenna to generate an electric field (of about 10 kV cm-1) across a semiconductor. By creating such an electric field electro-migration occurs within the photoconductive antenna to eventually bridge the antenna electrodes. As a result photoconductive switches used for terahertz generation have a limited lifetime dependent on the voltage applied to them.This thesis investigates the lateral photo-Dember (LPD) effect as an alternative emitter that does not require an applied electric field. The photo-Dember effect relies on the difference in electron and hole mobility within semiconductors creating a current surge on photo-excitation. The lateral photo-Dember effect works by partially covering regions of the diffusion area to selectively suppresses the terahertz emission radiated by diffusion current. By selecting lateral currents the LPD emitters work in the same configuration as photoconductive antennas while only requiring a metallic boundary near photo-excitation.We investigate the mechanism of the photo-Dember effect and the suppression that causes the LPD effect. Both 1D and 2D models are demonstrated to for calculating diffusion currents within semiconductors and are used within finite element modelling to demonstrate dipole suppression. Optical fluence, beam position and polarisation are characterised within GaAs LPD emitters with SI-GaAs showing a competing generation mechanism from the Schottky barrier at high fluences. We find that the emitter dependence on optical polarisation is due to plasmonic enhancement that occurs on the metal boundary. We demonstrate a simple to fabricate multiplexed LPD emitter based on metals with different reflectivities within the terahertz regime that can be scaled over a large area and propose a design using plasmonic enhancement

School of Physics and Astronomy Logo - Vector and Raster

Logo for the school of Physics and Astronomy in Inkscape SVG, PDF and high-resolution PNG forma

QLM Quantum Light and Matter Logo

The new Physics dept Quantum Light and Matter group logo designed by Alexey Kavokin in vector format. Re-traced original bitmap logo for high quality printing. Created in inkscape and exported to PDF, EPS and high resolution PN

University Logo in Vector and Raster (Smoother Version)

These are a range of logos created in the same way as Mr Patrick McSweeny http://www.edshare.soton.ac.uk/11157. The logo has been extracted from PDF documents and is smoother and accurate to the original logo design. Many thanks to to McSweeny for publishing the logo, in SVG originally, I struggled to find it anywhere else. Files are in Inkscape SVG, PDF and PNG. From Mr Patrick McSweeney: This is a selection of University of Southampton Logos in both vector (svg) and raster (png) formats. These are suitable for use on the web or in small documents and posters. You can open the SVG files using inkscape (http://inkscape.org/download/?lang=en) and edit them directly. The University logo should not be modified and attention should be paid to the branding guidelines found here: http://www.edshare.soton.ac.uk/10481 You must always leave a space the width of an capital O in Southampton on all 4 edges of the logo. The negative space makes it appear more prominently on the page

Dataset for Temperature dependent polarity inversion in double-metal terahertz emitters

Data, code and plots used in the paper, &quot;Temperature dependent polarity inversion in double-metal terahertz emitters &quot; Submitted to be published in Electronics Letters. The temperature dependent polarity inversion in double-metal THz emitters was investigated. Double-metal emitters utilising different metal pairings and single edge metal emitters were cooled in a helium flow cryostat and their THz emission was measured over a range of temperatures. Most emitters, including those with insulating layers between the metal and semiconductor, exhibit a flip in polarity of their THz emission between 50 and 100 K. This shows the inversion is a trait intrinsic to the semiconductor and not influenced by the metallic contact on the surface.</span