Valley current characterization of high current density resonant tunnelling diodes for terahertz-wave applications

We report valley current characterisation of high current density InGaAs/AlAs/InP resonant tunnelling diodes (RTDs) grown by metal-organic vapour phase epitaxy (MOVPE) for THz emission, with a view to investigate the origin of the valley current and optimize device performance. By applying a dual-pass fabrication technique, we are able to measure the RTD I-V characteristic for different perimeter/area ratios, which uniquely allows us to investigate the contribution of leakage current to the valley current and its effect on the PVCR from a single device. Temperature dependent (20 – 300 K) characteristics for a device are critically analysed and the effect of temperature on the maximum extractable power (PMAX) and the negative differential conductance (NDC) of the device is investigated. By performing theoretical modelling, we are able to explore the effect of typical variations in structural composition during the growth process on the tunnelling properties of the device, and hence the device performance

Comparative Assessment of Rural Development Programs of Selected NGOs in Plateau State, North-Central, Nigeria

The study examined the extent to which the rural development programs of Evangelical Church of West Africa-People Oriented Development (ECWA-POD) and Country Women Association of Nigeria (COWAN) contribute to the development of rural communities in Plateau State. A comparison of the non-governmental organizations (NGOs) was done to examine the factors that explain variation in the organizations. A total of 150 respondents made up of community members and staff of the organizations randomly selected from four Local Government Areas responded to the structured questionnaire. The data were analyzed using descriptive and inferential statistics. The study revealed that the major rural development programs of the NGOs were agricultural programs, health programs, human resource development, community development, and industrial and trade promotion programs. Analysis carried out showed a significant relationship (P 2=0.023; p#0.05) in the program orientation of the two organizations. Majority (57.8 percent for ECWA-POD and 75.6 percent for COWAN) of the respondents considered the programs of the organizations as beneficial and benefitted more concerning potable water and community sanitation facilities. Participation of the community members at various stages of the program and type of participation was also identified. The perceived level of goal attainment of the organization was higher (t=2.72; p#0.05) in COWAN than ECWA-POD. It was recommended that government should collaborate with NGOs through the Agricultural Transformation Agenda (ATA) concerning project identification, design, and implementation of rural development programs

Comparison between two mobile absolute gravimeters: optical versus atomic interferometers

We report a comparison between two absolute gravimeters: the LNE-SYRTE cold atoms gravimeter and FG5#220 of Leibniz Universit\"at of Hannover. They rely on different principles of operation: atomic and optical interferometry. Both are movable which enabled them to participated to the last International Comparison of Absolute Gravimeters (ICAG'09) at BIPM. Immediately after, their bilateral comparison took place in the LNE watt balance laboratory and showed an agreement of 4.3 +/- 6.4 {\mu}Gal

Disparity of superconducting and pseudogap scales in low-Tc Bi-2201 cuprates

We experimentally study transport and intrinsic tunneling characteristics of a single-layer cuprate Bi(2+x)Sr(2-y)CuO(6+delta) with a low superconducting critical temperature Tc < 4 K. It is observed that the superconducting energy, critical field and fluctuation temperature range are scaling down with Tc, while the corresponding pseudogap characteristics have the same order of magnitude as for high-Tc cuprates with 20 to 30 times higher Tc. The observed disparity of the superconducting and pseudogap scales clearly reveals their different origins.Comment: 5 page

Nonequilibrium radiation measurements and modelling relevant to Titan entry

An update to a collisional-radiative model developed by Magin1 for Huygens Titan atmospheric entry is proposed. The model is designed to predict the nonequilibrium populations and the radiation emitted from cyanogen and nitrogen during the entry of the Huygens probe into the Titan atmosphere. Radiation during Titan entry is important at lower speeds (around 5 – 6 km/s) more so than other planetary entries due to the formation of cyanogen in the shock layer, which is a highly radiative species. The model has been tested against measurements obtained with the EAST shock tube of NASA Ames Research Centre.1,2 The motivation for the update is due to the large discrepancies shown in the postshock fall-off rates of the radiation when compared to the experimental EAST shock tube test results. Modifications were made to the reaction rates used to calculate the species concentrations in the flow field. The reaction that was deemed most influential for the radiation fall off rate was the dissociation of molecular nitrogen. The model with modified reaction rates showed significantly better agreement with the EAST data. This paper also includes experimental results for radiation and spectra for Titan entry. Experiments were performed on the University of Queensland's X2 expansion tube. Spectra were recorded at various positions behind the shock. This enabled the construction of radiation profiles for Titan entry, as well as wavelength plots to identify various radiating species, in this case, predominately CN violet. This paper includes radiation profiles to compare with experiments performed at NASA Ames. It is planned that further experiments will be performed to cover a larger pressure range than NASA Ames. Good qualitative agreement has so far been obtained between our data and NASA Ames, however, it should be noted at the time of printing, the experimental spectrum have not been calibrated absolutely

Overseeing oversight: governance of quality and safety by hospital boards in the English NHS

Objectives: To contribute towards an understanding of hospital Board composition and oversight of patient safety and health care quality in the NHS. Methods: A review of the theory related to hospital Board governance and two national surveys undertaken about Board management in NHS hospital trusts in England. The first was issued to 150 Trusts in 2011/12 and completed online via a dedicated web tool. A total of 145 replies were received (97% response rate). The second online survey undertaken in 2012/13 targeted individual Board members using the Board Self Assessment Questionnaire (BSAQ). A total of 334 responses were received from 165 executive and 169 non-executive board members, providing at least one response from 95 of the 144 NHS Trusts then in existence (66% response rate). Results: Around 42% of Boards had 10-12 members and around 51% had 13-15 members. We found no significant difference in Board size between Foundation and non Foundation trusts. Around 62% of Boards had three or fewer serving Board members with clinical backgrounds. For about two-thirds of the Trusts (63%), Board members with a clinical background comprised less than 30% of the Board members. Boards were using a wide range of hard performance metrics and soft intelligence to monitor their organisation with regard to patient safety. Hard, quantitative data were reportedly used at every Board meeting across most hospital Trusts (>80%), including a range of clinical outcomes measures, infection rates and process measures such as medication errors and readmission rates. A much smaller proportion of Trusts (57%) routinely report morbidity rates at every Board meeting. Softer intelligence, used organisationally and reported at all Board meetings, was more variably reported, with discussions with clinicians (in 89% of Trusts) and executive walk-arounds (88%) being most often reported, alongside use of patient stories (83%). However, in only about two-thirds of Trusts did Board members shadow clinicians and report back to the Board (65%). The BSAQ data showed general high or very high levels of agreement with desirable statements of practice in each of the six dimensions. Aggregate levels of agreement within each dimension ranged from 73% (interpersonal) to 85% (political). Conclusions: The study provides the best account to-date of English NHS Boards and their actions around health care quality and patient safety. While systematic differences between Trusts of different types were rare, there was nonetheless variation between individual Trusts on both Board composition and Board practices. These findings lay the groundwork for further empirical research exploring the dynamics, influences and impacts of Boards

Strategies for Real-Time Position Control of a Single Atom in Cavity QED

Recent realizations of single-atom trapping and tracking in cavity QED open the door for feedback schemes which actively stabilize the motion of a single atom in real time. We present feedback algorithms for cooling the radial component of motion for a single atom trapped by strong coupling to single-photon fields in an optical cavity. Performance of various algorithms is studied through simulations of single-atom trajectories, with full dynamical and measurement noise included. Closed loop feedback algorithms compare favorably to open-loop "switching" analogs, demonstrating the importance of applying actual position information in real time. The high optical information rate in current experiments enables real-time tracking that approaches the standard quantum limit for broadband position measurements, suggesting that realistic active feedback schemes may reach a regime where measurement backaction appreciably alters the motional dynamics.Comment: 12 pages, 10 figures, submitted to J. Opt. B Quant. Semiclass. Op

What physiological role(s) does the alternative oxidase perform in animals?

Although the alternative oxidase, AOX, was known to be widespread in the animal kingdom by 2004, its exact physiological role in animals remains poorly understood. Here we present what evidence has accumulated thus far, indicating that it may play a role in enabling animals to resist various kinds of stress, including toxins, abnormal oxygen or nutrient levels, protein unfolding, dessication and pathogen attack. Much of our knowledge comes from studies in model organisms, where any benefits from exogenously expressed AOX may be masked by its unregulated expression, which may itself be stressful. The further question arises as to why AOX has been lost from some major crown groups, namely vertebrates, insects and cephalopods, if it plays important roles favouring the survival of other animals. We conclude by presenting some speculative ideas addressing this question, and an outline of how it might be approached experimentally.publishedVersionPeer reviewe