High resolution forecast models of water vapour over mountains: comparison of results from the UM and MERIS

Propagation delay due to variable tropospheric water vapor (WV) is one of the most intractable problems for radar interferometry, particularly over mountains. The WV field can be simulated by an atmospheric model, and the difference between the two fields is used to correct the radar interferogram. Here, we report our use of the U.K. Met Office Unified Model in a nested mode to produce high-resolution forecast fields for the 3-km-high Mount Etna volcano. The simulated precipitablewater field is validated against that retrieved from the Medium Resolution Imaging Spectrometer (MERIS) radiometer on the Envisat satellite, which has a resolution of 300 m. Two case studies, one from winter (November 24, 2004) and one from summer (June 25, 2005), show that the mismatch between the model and the MERIS fields (rms = 1.1 and 1.6 mm, respectively) is small. One of the main potential sources of error in the models is the timing of the WV field simulation. We show that long-wavelength upper tropospheric troughs of low WV could be identified in both the model output and Meteosat WV imagery for the November 24, 2004 case and used to choose the best time of model output. © 2007 IEEE

Role of COX-1 and COX-2 in the release of prostanoids in murine lung and isolated lung fibroblasts

Cyclooxygenase (COX) is the first enzyme in the conversion of arachidonic acid to prostanoids. There are two isoforms of COX; COX-1, which is constitutively expressed with a homeostatic role in most tissues, and COX-2, which while constitutively expressed in some discreet sites is generally inducible by growth factors and during inflammation. In the current study, we have used tissues and cells from knock-out mice to investigate the relative contributions of COX-1 and COX-2 to PGE2 production by lung tissue ex vivo and by proliferating lung fibroblasts in vitro. Lung tissues from WT (C57Bl6), COX-1-/- and COX-2-/- mice were immediately dissected (<15 min after death) and incubated (37 °C) for 30 min in DMEM containing 50 µM calcium ionophore (A23187). Release of PGE2 was determined by competitive immunoassay. In parallel studies, murine lung fibroblasts from COX-1-/- and COX-2-/- mice were explanted and cultured before being seeded in 96-well plates at sub-confluence (5000-8000/well) and incubated for 24-48 hours in the presence of 10% FCS. Accumulated release of PGE2 was then measured as above. Over 30 min PGE2 was released by lung pieces from wild type (1117 ± 55 pg/ml) and COX-2-/- (2013 ± 255 pg/ml) but not from COX-1-/- (<61pg/ml) mice (n=4). In contrast, proliferating lung fibroblasts from COX-1-/- (4978.9 ± 1392 pg/ml) mice released higher levels of PGE2 than cells from COX-2-/- (1194 ± 617 ng/ml) mice (n=4 using cells from 2-3 separate mice for each genotype). These results show that COX-1 activity underpins the stimulated release of PGE2 in healthy mouse lung tissue. Conversely, COX-2 activity predominates in proliferating lung fibroblasts, which may be important as COX-derived PGE2 mediates proliferation of lung fibroblasts (Trends Immunol.2004;25(1):40-6). Our results suggest a switch in COX isoform in lung cells during proliferation which could be relevant to our understanding of conditions such as idiopathic pulmonary fibrosis.Non peer reviewedFinal Accepted Versio

Characterising a solid state qubit via environmental noise

We propose a method for characterising the energy level structure of a solid-state qubit by monitoring the noise level in its environment. We consider a model persistent-current qubit in a lossy resevoir and demonstrate that the noise in a classical bias field is a sensitive function of the applied field.Comment: 3 Figure

Pyrrolo- and pyridomorphinans:Non-selective opioid antagonists and delta opioid agonists/mu opioid partial agonists

Opioid ligands have found use in a number of therapeutic areas, including for the treatment of pain and opiate addiction (using agonists) and alcohol addiction (using antagonists such as naltrexone and nalmefene). The reaction of imines, derived from the opioid ligands oxymorphone and naltrexone, with Michael acceptors leads to pyridomorphinans with structures similar to known pyrrolo- and indolomorphinans. One of the synthesized compounds, 5e, derived from oxymorphone had substantial agonist activity at delta opioid receptors but not at mu and/or kappa opioid receptors and in that sense profiled as a selective delta opioid receptor agonist. The pyridomorphinans derived from naltrexone and naloxone were all found to be non-selective potent antagonists and as such could have utility as treatments for alcohol abuse

Weak energy condition violation and superluminal travel

Recent solutions to the Einstein Field Equations involving negative energy densities, i.e., matter violating the weak-energy-condition, have been obtained, namely traversable wormholes, the Alcubierre warp drive and the Krasnikov tube. These solutions are related to superluminal travel, although locally the speed of light is not surpassed. It is difficult to define faster-than-light travel in generic space-times, and one can construct metrics which apparently allow superluminal travel, but are in fact flat Minkowski space-times. Therefore, to avoid these difficulties it is important to provide an appropriate definition of superluminal travel.Comment: 15 pages, 3 figures, LaTeX2e, Springer style files -included. Contribution to the Proceedings of the Spanish Relativity Meeting-2001 (Madrid, September 2001

Regeneration in gap models: priority issues for studying forest responses to climate change

Recruitment algorithms in forest gap models are examined with particular regard to their suitability for simulating forest ecosystem responses to a changing climate. The traditional formulation of recruitment is found limiting in three areas. First, the aggregation of different regeneration stages (seed production, dispersal, storage, germination and seedling establishment) is likely to result in less accurate predictions of responses as compared to treating each stage separately. Second, the relatedassumptions that seeds of all species are uniformly available and that environmental conditions are homogeneous, are likely to cause overestimates of future species diversity and forest migration rates. Third, interactions between herbivores (ungulates and insect pests) and forest vegetation are a big unknown with potentially serious impacts in many regions. Possible strategies for developing better gap model representations for the climate-sensitive aspects of each of these key areas are discussed. A working example of a relatively new model that addresses some of these limitations is also presented for each case. We conclude that better models of regeneration processes are desirable for predicting effects of climate change, but that it is presently impossible to determine what improvements can be expected without carrying out rigorous tests for each new formulation

Exploring Explanations of Subglacial Bedform Sizes Using Statistical Models

Sediments beneath modern ice sheets exert a key control on their flow, but are largely inaccessible except through geophysics or boreholes. In contrast, palaeo-ice sheet beds are accessible, and typically characterised by numerous bedforms. However, the interaction between bedforms and ice flow is poorly constrained and it is not clear how bedform sizes might reflect ice flow conditions. To better understand this link we present a first exploration of a variety of statistical models to explain the size distribution of some common subglacial bedforms (i.e., drumlins, ribbed moraine, MSGL). By considering a range of models, constructed to reflect key aspects of the physical processes, it is possible to infer that the size distributions are most effectively explained when the dynamics of ice-water-sediment interaction associated with bedform growth is fundamentally random. A ‘stochastic instability’ (SI) model, which integrates random bedform growth and shrinking through time with exponential growth, is preferred and is consistent with other observations of palaeo-bedforms and geophysical surveys of active ice sheets. Furthermore, we give a proof-of-concept demonstration that our statistical approach can bridge the gap between geomorphological observations and physical models, directly linking measurable size-frequency parameters to properties of ice sheet flow (e.g., ice velocity). Moreover, statistically developing existing models as proposed allows quantitative predictions to be made about sizes, making the models testable; a first illustration of this is given for a hypothesised repeat geophysical survey of bedforms under active ice. Thus, we further demonstrate the potential of size-frequency distributions of subglacial bedforms to assist the elucidation of subglacial processes and better constrain ice sheet models

Seasonal Antarctic pressure variability during the twentieth century from spatially complete reconstructions and CAM5 simulations

As most permanent observations in Antarctica started in the 1950s, understanding Antarctic climate variations throughout the twentieth century remains a challenge. To address this issue, the non-summer multi-decadal variability in pressure reconstructions poleward of 60°S is evaluated and assessed in conjunction with climate model simulations throughout the twentieth and early twenty-first centuries to understand historical atmospheric circulation variability over Antarctica. Austral autumn and winter seasons show broadly similar patterns, with negative anomalies in the early twentieth century (1905–1934), positive pressure anomalies in the middle twentieth century (1950–1980), and negative pressure anomalies in the most recent period (1984–2013), consistent with concurrent trends in the SAM index. In autumn, the anomalies are significant in the context of estimates of interannual variability and reconstruction uncertainty across most of the Antarctic continent, and the reconstructed patterns agree best with model-generated patterns when the simulation includes the forced response to tropical sea surface temperatures and external radiative forcing. In winter and spring, the reconstructed anomalies are less significant and are consistent with internal atmospheric variability alone. The specific role of tropical SST variability on pressure trends in these seasons is difficult to assess due to low reconstruction skill in the region of strongest tropical teleconnections, the large internal atmospheric variability, and uncertainty in the SST patterns themselves. Indirect estimates of pressure variability, whether through sea ice reconstructions, proxy records, or improved models and data assimilation schemes, will help to further constrain the magnitude of internal variability relative to the forced responses expected from SST trends and external radiative forcing

Event-related potential correlates of spatiotemporal regularities in vision

Spatiotemporal regularities in stimulus structure have been shown to influence visual target detection and discrimination. Here we investigate whether the influence of spatiotemporal regularity is associated with the modulation of early components (P1/N1) in Event-Related Potentials (ERP). Stimuli consisted of five horizontal bars (predictors) appearing successively towards the fovea followed by a target bar at fixation, and participants performed a key-press on target detection. Results showed that compared to the condition where five predictors were presented in a temporally regular but spatially randomised order, target detection-times were faster and contralateral N1 peak latencies were shorter when the predictors and the target were presented with spatial and temporal regularity. Both measures were most prolonged when only the target was presented. In this latter condition, an additional latency prolongation was observed for the P1 peak compared to the conditions where the target was preceded by the predictors. The latency shifts associated with early ERP components provides additional support for involvement of early visual processing stages in the coding of spatiotemporal regularities in humans

Measurements of Hard-Scattering by PHENIX at RHIC

Hard-scattering in p-p collisions was discovered in 1972 at the CERN-ISR, the first hadron collider. Techniques were developed and several hard-processes were discovered which form the basis for many of the measurements made in p-p and Au+Au collisions at RHIC. Recent measurements of hard-scattering and related reactions by the PHENIX experiment at RHIC are presented in this context.Comment: 6 pages, 12 figures, Proceedings of Hadron Collider Physics Symposium 2007, La Biodola, Isola d'Elba (Italy), May 20-26, 200