Middle-atmospheric response to a future increase in humidity arising from increased methane abundance

The response of the middle atmosphere to an increase in humidity arising from a possible future increase in CH4 is examined in a general circulation model with interactive H2O and O3. A chemical parameterization allows the middle-atmospheric H2O change to evolve naturally from an imposed change in tropospheric CH4. First, a simulation of the year 2060 using postulated loadings of the radiatively active gases is compared with a control simulation of the present-day atmosphere. Then, the particular contribution of the CH4 (and hence H2O) change to the observed difference is isolated by repeating the 2060 simulation without the projected CH4 change. Under the Intergovernmental Panel on Climate Change Special Report on Emission Scenarios (SRES) B2 scenario, the middle atmosphere in 2060 cools by up to ∼5 K relative to 1995, with the CH4-derived increase in H2O accounting for ∼10% of the change. The cooling is accompanied by a strengthened general circulation, intensified dynamic heating rates, and a reduction in the mean age of middle-atmospheric air. The component of the circulation change attributable solely to the H2O change differs somewhat from the net response: The H2O change causes a greater increase in the descent rate in the north than in the south, ages the stratospheric air, and has a distinct effect on age/N2O correlations. Around 20% of the increased prevalence of polar stratospheric clouds (PSCs) in 2060 is due to the microphysical effect of the extra H2O, with the remainder attributable to the reduced vortex temperatures. Although the PSC increase facilitates release of reactive chlorine, this positive impact on chemical O3 destruction is outweighed by the negative impact of the reduced total chlorine in 2060. Nonetheless, the H2O increase does make the 2060 Arctic O3 loss ∼15% greater than it would otherwise be

Radar multipath study for rain-on-radome experiments at the Aircraft Landing Dynamics Facility

An analytical study to determine the feasibility of a rain-on-radome experiment at the Aircraft Landing Dynamics Facility (ALDF) at the Langley Research Center is described. The experiment would measure the effects of heavy rain on the transmission of X-band weather radar signals, looking in particular for sources of anomalous attenuation. Feasibility is determined with regard to multipath signals arising from the major structural components of the ALDF. A computer program simulates the transmit and receive antennas, direct-path and multipath signals, and expected attenuation by rain. In the simulation, antenna height, signal polarization, and rainfall rate are variable parameters. The study shows that the rain-on-radome experiment is feasible with regard to multipath signals. The total received signal, taking into account multipath effects, could be measured by commercially available equipment. The study also shows that horizontally polarized signals would produce better experimental results than vertically polarized signals

A K_ATP channel opener inhibited myocardial reperfusion action potential shortening and arrhythmias

Low concentrations of certain K<sub>ATP</sub> channel openers have been reported to exert a moderate inhibitory effect on arrhythmias during post-ischaemic early myocardial reperfusion, but the accompanying effects on the time course of changes in action potentials in intact hearts have not yet been studied. We report that in rat isolated hearts, reperfusion following 10 min of regional no-flow ischaemia was associated with both an acute, marked, but transient, shortening of ventricular repolarisation (by 63%) during reperfusion, and a high incidence (90%) of ventricular tachyarrhythmias. The K<sub>ATP</sub> channel opener Ro 31-6930 [2-(6-cyano-2,2-dimethyl-2H-1-benzopyran-4-yl)-pyridine 1-oxide], delivered prior to ischaemia at a relatively low concentration (0.5 μM), significantly reduced the incidence and duration of reperfusion arrhythmias, and prevented the associated acute action potential shortening during reperfusion, each in a glibenclamide (1 μM)-sensitive manner (P<0.05, <i>n</i>=10–15 hearts). This was associated with a moderate and non-arrhythmogenic action potential shortening during ischaemia (a potentially “cardioprotective” effect). However, these data highlight the potential harm these drugs may cause, since a higher concentration of Ro 31-6930 caused marked shortening of action potentials and significant pro-arrhythmia during ischaemia

Coupling Poisson and Jacobi structures on foliated manifolds

Let M be a differentiable manifold endowed with a foliation F. A Poisson structure P on M is F-coupling if the image of the annihilator of TF by the sharp-morphism defined by P is a normal bundle of the foliation F. This notion extends Sternberg's coupling symplectic form of a particle in a Yang-Mills field. In the present paper we extend Vorobiev's theory of coupling Poisson structures from fiber bundles to foliations and give simpler proofs of Vorobiev's existence and equivalence theorems of coupling Poisson structures on duals of kernels of transitive Lie algebroids over symplectic manifolds. Then we discuss the extension of the coupling condition to Jacobi structures on foliated manifolds.Comment: LateX, 38 page

Windshear radar calibration: Transmitter power and receiver gain stability

An experimental windshear Doppler radar was flown on 27 occasions during a series of flight experiments in 1991. Radar calibrations were performed by the flight team to monitor the transmitter power and receiver gain from pre-flight to post-flight and from one day to another. From the recorded calibration data, the receiver gain and effective receiver system noise were calculated and tabulated, together with the transmitter power. These quantities of interest are compared for two receiver/transmitter (R/T) units and two intermediate frequency (IF) bandwidths that were tested in various modes. It was found that, in most operating modes, gain stayed within a 2.5-dB range and transmitter power stayed within a 20-watt range. R/T number 1 had 0.8 dB more gain and 1.2 dBm less noise power than R/T number 2. The 7-MHz IF bandwidth resulted in 1 dB more gain and 1 dBm less noise than the 2-MHz IF bandwidth. Depending on the R/T unit and IF bandwidth, the effective system noise power averaged between -107.3 dBm and -109.5 dBm

Do K_ATP channels open as a prominent and early feature during ischaemia in the Langendorff-perfused rat heart?

The objective was to investigate whether myocardial adenosine triphosphate-sensitive K<sup>+</sup> (K<sub>ATP</sub>) channels open during the first 10 min of regional ischaemia in Langendorff-perfused rat hearts. Changes in monophasic action potentials and arrhythmias were studied during myocardial ischaemia in both the presence and absence of pharmacological K<sub>ATP</sub> modulation. Ligation of the left main coronary artery for 10 min did not shorten the action potential duration (APD). The APD<sub>50</sub> and APD<sub>80</sub> (15.5 +/- 1.0 and 38.1 +/- 2.3 ms, respectively [mean +/- S.E., n = 15 hearts], immediately prior to ligation) increased transiently during the first 4 min of ligation (by 160 and 79% respectively, P < 0.05), before returning to pre-ligation values, but without a significant below-baseline-shortening. The cardiac electrogram showed no accompanying ventricular tachyarrhythmia (VT). These results raised the possibility that the myocardial K<sub>ATP</sub> channels had not opened during the ligation. The K<sub>ATP</sub> opener Ro 31-6930 (0.5 and 5 microM) shortened the APD50 and APD80 during coronary ligation, to significantly below both their control and pre-occlusion values (P < 0.05), and caused a concentration-dependent increase in both the incidence and duration of VT during the ligation. Ro 31-6930 at 5 microM also shortened APD50 and APD80 even before ligation (by 50 and 62% respectively, P < 0.05), and abolished the normal APD-lengthening seen during ischaemia. The K<sub>ATP</sub> blocker glibenclamide (1 μM) abolished both the APD-shortening and pro-arrhythmic effects of the K<sub>ATP</sub> opener, both before and during coronary ligation, yet when delivered on its own, at the same concentration which abolished the effects of K<sub>ATP</sub> activation, it had no significant effect on the APD changes seen during the coronary ligation alone. These results suggest that, in Langendorff-perfused rat hearts in the absence of drugs, K<sub>ATP</sub> channels do not open during early myocardial ischaemia

On prescriptivism and ideology

In this article we explore the prescriptive approach to language use in its relation to ideology, past and present. Before Saussure, prescriptivists formulated rules from an instrumental perspective, which saw formal language as a means to persuade, partly by borrowing authority from august sources. We can now see this view as an ideology, and by analysing the mental components of ideology further we argue that the modern prescriptive approach to language appeals to a hierarchical view of society, and hence of language. This view is in conflict with the more recent ideology of equality, and contemporary processes of standardisation need to be understood by reference to this conflict. We argue at the same time that modern ‘descriptive’ linguistics, by taking the standard as its model, risks contamination from prescriptivism

Laser operation of a Tm:Y₂O₃ planar waveguide

We demonstrate the first Tm-doped yttria planar waveguide laser to our knowledge, grown by pulsed laser deposition. A maximum output power of 35 mW at 1.95 µm with 9% slope efficiency was achieved from a 12 µm-thick film grown on a Y3Al5O12 substrate

Interprofessional learning in practice: The student experience

Interprofessional learning and the development of teamworking skills are recognised as essential for patient care and are also a government priority for undergraduate education. Sixteen occupational therapy students worked on an interprofessional training ward as part of their practice placement and three of them participated in an evaluation using the nominal group technique. Despite this small number, the evaluation identifies the value of this learning experience in giving the students an opportunity to appreciate the importance of interpersonal skills; to learn about other team members’ roles; and to experience the challenges of working on a busy rehabilitation ward for older people