Stark ladders as tunable far-infrared emitters

A superlattice of GaAs/Ga(1 – x)Al(x)As quantum wells forms a Stark ladder under the influence of a perpendicular electric field. A two level incoherent emitter system, formed by radiative intersubband transitions between adjacent wells, is investigated as a tunable far-infrared radiation source. Intersubband transition rates are calculated at 4, 77, and 300 K for applied fields from 0 to 40 kV cm(–1). It is shown that the quantum efficiency of the radiative emission reaches a maximum at low temperatures for a field of 32 kV cm(–1). Under these conditions the emission wavelength is 38 µm with an estimated power output of 1.1 mW. © 1998 American Institute of Physics

Assessment of the environmental toxicity and carcinogenicity of tungsten-based shot.

The toxicity of elemental tungsten released from discharged shot was assessed against previous studies that established a 1% toxic threshold for soil organisms. Extremely heavy theoretical shot loadings of 69,000 shot/ha were used to generate estimated environmental concentrations (EEC) for two brands of tungsten-based shot containing 51% and 95% tungsten. The corresponding tungsten EEC values were 6.5–13.5 mg W/kg soil, far below the 1% toxic threshold. The same shot loading in water produced tungsten EEC values of 2.1–4.4 mg W/L, levels that are not toxic under experimental conditions. Pure tungsten has not been shown to exhibit carcinogenic properties when ingested or embedded in animal tissues, but nickel, with which it is often alloyed, has known carcinogenicity. Given the large number of waterfowl that carry shot embedded in their body, it is advisable to screen lead shot substitutes for their carcinogenic potential through intra-muscular implantation

Mechanisms of Thermal Stability during Flight in the Honeybee Apis Mellifera

Thermoregulation of the Thorax Allows Honeybees (Apis Mellifera) to Maintain the Flight Muscle Temperatures Necessary to Meet the Power Requirements for Flight and to Remain Active Outside the Hive Across a Wide Range of Air Temperatures (T(A)). to Determine the Heat-Exchange Pathways through Which Flying Honeybees Achieve Thermal Stability, We Measured Body Temperatures and Rates of Carbon Dioxide Production and Water Vapor Loss between T(A) Values of 21 and 45°C for Honeybees Flying in a Respirometry Chamber. Body Temperatures Were Not Significantly Affected by Continuous Flight Duration in the Respirometer, indicating that Flying Bees Were at Thermal Equilibrium. Thorax Temperatures (T(Th)) during Flight Were Relatively Stable, with a Slope of T(Th) on T(A) of 0.39. Metabolic Heat Production, Calculated from Rates of Carbon Dioxide Production, Decreased Linearly by 43% as T(A) Rose from 21 to 45°C. Evaporative Heat Loss Increased Nonlinearly by over Sevenfold, with Evaporation Rising Rapidly at T(A) Values above 33°C. at T(A) Values above 43°C, Head Temperature Dropped Below T(A) by Approximately 1-2°C, Indicating that Substantial Evaporation from the Head Was Occurring at Very High T(A) Values. the Water Flux of Flying Honeybees Was Positive at T(A) Values Below 31°C, But Increasingly Negative at Higher T(A) Values. at All T(A) Values, Flying Honeybees Experienced a Net Radiative Heat Loss. Since the Honeybees Were in Thermal Equilibrium, Convective Heat Loss Was Calculated as the Amount of Heat Necessary to Balance Metabolic Heat Gain Against Evaporative and Radiative Heat Loss. Convective Heat Loss Decreased Strongly as T(A) Rose Because of the Decrease in the Elevation of Body Temperature above T(A) Rather Than the Variation in the Convection Coefficient. in Conclusion, Variation in Metabolic Heat Production is the Dominant Mechanism of Maintaining Thermal Stability during Flight between T(A) Values of 21 and 33°C, But Variations in Metabolic Heat Production and Evaporative Heat Loss Are Equally Important to the Prevention of overheating during Flight at T(A) Values between 33 and 45°C

Design and performance of a multicentre, randomized controlled trial of teleconsulting.

We have designed and performed a multicentre, randomized controlled trial of teleconsulting. The trial investigated the effectiveness and cost implications in rural and inner-city settings of using videoconferencing as an alternative to general practitioner referral to a hospital specialist. The participating general practitioners referred a total of 3170 patients who satisfied the entry criteria. Of these, 1040 (33%) failed to provide consent or otherwise refused to participate in the trial. Of the patients recruited to the trial, a total of 1902 (91%) completed and returned the baseline questionnaire. Although the trial was successful in recruiting sufficient patients and in obtaining high questionnaire response rates, the findings will require careful interpretation to take account of the limits which the protocol placed on the ability of general practitioners to select patients for referral

Flight Respiration and Energetics

We Use a Comparative Approach to Examine Some of the Physiological Traits that Make Flight Possible. Comparisons of Related Fliers and Runners Suggest that Fliers Generally Have Higher Aerobic Metabolic Capacities Than Runners But that the Difference is Highly Dependent on the Taxa Studied. the High Metabolic Rates of Fliers Relative to Runners, Especially in Insects, Are Correlated with High Locomotory Muscle Cycle Frequencies and Low Efficiencies of Conversion of Metabolic Power to Mechanical Power. We Examine Some Factors that Produce Variation in Flight Respiration and Energetics. Air Temperature Strongly Affects the Flight Metabolic Rote of Some Insects and Birds. Flight Speed Interacts with Flier Mass, So that Small Fliers Tend to Exhibit a J-Shaped Power Curve and Larger Fliers a U-Shaped Power Curve. as Body Size Increases, Mass-Specific Aerobic Flight Metabolism Decreases in Most Studies, But Mass-Specific Power Output is Constant or Increases, Leading to an Increase in Efficiency with Size. Intraspecific Studies Have Revealed Specific Genetically based Effects on Flight Metabolism and Power Output and Multiple Ecological Correlates of Flight Capabilities

Allometry of Kinematics and Energetics in Carpenter Bees (Xylocopa Varipuncta) Hovering in Variable-Density Gases

We Assessed the Energetic and Aerodynamic Limits of Hovering Flight in the Carpenter Bee Xylocopa Varipuncta. using Normoxic, Variable-Density Mixtures of O2, N2 and He, We Were Able to Elicit Maximal Hovering Performance and Aerodynamic Failure in the Majority of Bees Sampled. Bees Were Not Isometric Regarding Thorax Mass and Wing Area, Both of Which Were Disproportionately Lower in Heavier Individuals. the Minimal Gas Density Necessary for Hovering (MGD) Increased with Body Mass and Decreased with Relative Thoracic Muscle Mass. Only the Four Bees in Our Sample with the Highest Body Mass-Specific Thorax Masses Were Able to Hover in Pure Heliox. Wingbeat Frequency and Stroke Amplitude during Maximal Hovering Were Significantly Greater Than in Normodense Hovering, Increased Significantly with Body Mass during Normodense Hovering But Were Mass Independent during Maximal Hovering. Reserve Capacity for Wingbeat Frequency and Stroke Amplitude Decreased Significantly with Increasing Body Mass, Although Reserve Capacity in Stroke Amplitude (10-30%) Exceeded that of Wingbeat Frequency (0-8%). Stroke Plane Angle during Normodense Hovering Was Significantly Greater Than during Maximal Hovering, Whereas Body Angle Was Significantly Greater during Maximal Hovering Than during Normodense Hovering. Power Production during Normodense Hovering Was Significantly Less Than during Maximal Hovering. Metabolic Rates Were Significantly Greater during Maximal Hovering Than during Normodense Hovering and Were Inversely Related to Body Mass during Maximal and Normodense Hovering. Metabolic Reserve Capacity Averaged 34% and Was Independent of Body Mass. Muscle Efficiencies Were Slightly Higher during Normodense Hovering. the Allometry of Power Production, Power Reserve Capacity and Muscle Efficiency Were Dependent on the Assumed Coefficient of Drag (CD), with Significant Allometries Most Often at Lower Values of CD. Larger Bees Operate Near the Envelope of Maximal Performance Even in Normodense Hovering Due to Smaller Body Mass-Specific Flight Muscles and Limited Reserve Capacities for Kinematics and Power Production

Propagation of sausage soliton in the solar lower atmosphere observed by Hinode/SOT

Acoustic waves and pulses propagating from the solar photosphere upwards may quickly develop into shocks due to the rapid decrease of atmospheric density. However, if they propagate along a magnetic flux tube, then the nonlinear steepening may be balanced by tube dispersion effects. This may result in the formation of sausage soliton. The aim of this letter is to report an observational evidence of sausage soliton in the solar chromosphere. Time series of Ca II H line obtained at the solar limb with the Solar Optical Telescope (SOT) on the board of Hinode is analysed. Observations show an intensity blob, which propagates from 500 km to 1700 km above the solar surface with the mean apparent speed of 35 km s$^{-1}$. The speed is much higher than expected local sound speed, therefore the blob can not be a simple pressure pulse. The blob speed, length to width ratio and relative intensity correspond to slow sausage soliton propagating along a magnetic tube. The blob width is increased with height corresponding to the magnetic tube expansion in the stratified atmosphere. Propagation of the intensity blob can be the first observational evidence of slow sausage soliton in the solar atmosphere.Comment: 5 pages, 4 figures, accepted in MNRA

Joint teleconsultations (virtual outreach) versus standard outpatient appointments for patients referred by their general practitioner for a specialist opinion: a randomised trial.

BACKGROUND: The current model of general practitioner referral of patients to hospital specialists in the UK is sometimes associated with unnecessary duplication of investigations and treatments. We aimed to compare joint teleconsultations between general practitioners, specialists, and patients (virtual outreach) with standard outpatient referral. METHODS: Virtual outreach services were established in London and Shrewsbury. The general practitioners referred 3170 patients, of whom 2094 consented to participate in the study and were eligible for inclusion. 1051 patients were randomly assigned virtual outreach, and 1043 standard outpatient appointments. We followed up the patients for 6 months after their index consultation. The primary outcome measure was the offer of a follow-up outpatient appointment. Analysis was by intention to treat. FINDINGS: More patients in the virtual outreach group than the standard group were offered a follow-up appointment (502 [52%] vs 400 [41%], odds ratio 1.52 [95% CI 1.27-1.82], p<0.0001). Significant differences in effects were observed between the two sites (p=0.009) and across different specialties (p<0.0001). Virtual outreach increased the offers of follow-up appointments more in Shrewsbury than in London, and more in ear, nose, and throat surgery and orthopaedics than in the other specialties. Fewer tests and investigations were ordered in the virtual outreach group by an average of 0.79 per patient (0.37-1.21, p=0.0002). Patients' satisfaction (analysed per protocol) was greater after a virtual outreach consultation than after a standard outpatient consultation (mean difference 0.33 scale points [95% CI 0.23-0.43], p<0.0001), with no heterogeneity between specialties or sites. INTERPRETATION: The trial showed that allocation of patients to virtual outreach consultations is variably associated with increased offers of follow-up appointments according to site and specialty, but leads to significant increases in patients' satisfaction and substantial reductions in tests and investigations. Efficient operation of such services will require appropriate selection of patients, significant service reorganisation, and provision of logistical support

Tri-bimaximal Neutrino Mixing and Quark Masses from a Discrete Flavour Symmetry

We build a supersymmetric model of quark and lepton masses based on the discrete flavour symmetry group T', the double covering of A_4. In the lepton sector our model is practically indistinguishable from recent models based on A_4 and, in particular, it predicts a nearly tri-bimaximal mixing, in good agreement with present data. In the quark sector a realistic pattern of masses and mixing angles is obtained by exploiting the doublet representations of T', not available in A_4. To this purpose, the flavour symmetry T' should be broken spontaneously along appropriate directions in flavour space. In this paper we fully discuss the related vacuum alignment problem, both at the leading order and by accounting for small effects coming from higher-order corrections. As a result we get the relations: \sqrt{m_d/m_s}\approx |V_{us}| and \sqrt{m_d/m_s}\approx |V_{td}/V_{ts}|.Comment: 27 pages, 1 figure; minor correction