778 research outputs found
Recommended from our members
Impact of tsetse control on land use in the semi-arid zone of Zimbabwe. Phase 2: Analysis of land use change by remote sensing imagery (NRI Bulletin 70)
Tsetse control is carried out to facilitate the expansion of livestock-based production systems in areas cleared of the threat of bovine trypanosomiasis. There is a growing awareness of the need for tsetse control to be considered an integral component of rural development and of the importance of monitoring and evaluating both the causes and consequences of potential land-use changes as a prerequisite for planning control operations. As part of an international programme to evaluate the environmental and socio-economic effects of tsetse control in southern Africa, changes in land cover over a 20-year period are being assessed in an area of Zimbabwe with a long and varied history of tetse control and agricultural development. The study area, adjacent to Lake Kariba, covers approximately 8300 km2 and comprises Reserved, Communal and State Lands. The first phase of the study established the baseline land-use and vegetation patterns, using satellite imagery. In Phase 2, changes in land cover, particularly human-dominated land use (HDLU), are examined from 1972 to 1993, using four Landsat TM and five MSS images, integrated with other datasets in ARC/INFO GIS
Crustal carbonate build-up as a driver for Earthâs oxygenation
Oxygenation of Earthâs atmosphere and oceans played a pivotal role in the evolution of the surface environment and life. It is thought that the rise in oxygen over Earthâs history was driven by an increasing availability of the photosynthetic limiting nutrient phosphate combined with declining oxygen-consuming inputs from the mantle and crust. However, it has been difficult to assess whether these processes alone can explain Earthâs oxygenation history. Here we develop a theoretical framework for the long-term global oxygen, phosphorus and carbon cycles, incorporating potential trajectories for the emergence of continents, the degassing of mantle volatiles and the resulting increase in the size of the crustal carbonate reservoir. We find that we can adequately simulate the Earthâs oxygenation trajectory in both the atmosphere and oceans, alongside reasonable reconstructions of planetary temperature, atmospheric carbon dioxide concentration, phosphorus burial records and carbon isotope ratios. Importantly, this is only possible when we include the accumulation of carbonates in the crust, which permits ever-increasing carbon recycling rates through weathering and degassing. This carbonate build-up is a missing factor in models of Earthâs coupled climate, nutrient and oxygen evolution and is important for reconstructing Earthâs history and potential exoplanet biogeochemistry
Application of the pMHC array to characterise tumour antigen specific T cell populations in leukaemia patients at disease diagnosis
Immunotherapy treatments for cancer are becoming increasingly successful, however to further improve our understanding of the T-cell recognition involved in effective responses and to encourage moves towards the development of personalised treatments for leukaemia immunotherapy, precise antigenic targets in individual patients have been identified. Cellular arrays using peptide-MHC (pMHC) tetramers allow the simultaneous detection of different antigen specific T-cell populations naturally circulating in patients and normal donors. We have developed the pMHC array to detect CD8+ T-cell populations in leukaemia patients that recognise epitopes within viral antigens (cytomegalovirus (CMV) and influenza (Flu)) and leukaemia antigens (including Per Arnt Sim domain 1 (PASD1), MelanA, Wilmsâ Tumour (WT1) and tyrosinase). We show that the pMHC array is at least as sensitive as flow cytometry and has the potential to rapidly identify more than 40 specific T-cell populations in a small sample of T-cells (0.8â1.4 x 106). Fourteen of the twenty-six acute myeloid leukaemia (AML) patients analysed had T cells that recognised tumour antigen epitopes, and eight of these recognised PASD1 epitopes. Other tumour epitopes recognised were MelanA (n = 3), tyrosinase (n = 3) and WT1126-134 (n = 1). One of the seven acute lymphocytic leukaemia (ALL) patients analysed had T cells that recognised the MUC1950-958 epitope. In the future the pMHC array may be used provide point of care T-cell analyses, predict patient response to conventional therapy and direct personalised immunotherapy for patients
Circadian rhythm of urinary pH in man with and without chronic antacid administration
In normal human volunteers, when urinary pH was plotted versus time, the circadian sine-wave type curve was not altered by chronic administration of a commercially available suspension containing a mixture of magnesium and aluminum hydroxides, although the antacid perturbed the entire curve in a more alkaline direction. A single dose of the antacid had little effect on urinary pH. There was a highly significant linear relationship between the change in hydrogen ion concentration during chronic antacid treatment and the initial control urinary hydrogen ion concentration, but there was no significant correlation between change in urinary pH and initial control urinary pH as has been previously reported. The above results were based on the evaluation of the hydrogen ion concentrations of 1562 separate urine samples collected from 24 normal subjects in a three treatment crossover study. It is recommended that: (1) research studies involving drug-drug interactions with antacids be designed to consider the effect of the antacid on the circadian rhythm of urinary pH, and (2) pH values not be averaged as commonly reported in the literature, but rather the pH values be converted to hydrogen ion concentrations before statistical analysis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46636/1/228_2004_Article_BF00561060.pd
Synthesizing greenhouse gas fluxes across nine European peatlands and shrublands: responses to climatic and environmental changes
In this study, we compare annual fluxes of methane
(CH4), nitrous oxide (N2O) and soil respiratory carbon dioxide
(CO2) measured at nine European peatlands (n = 4) and
shrublands (n = 5). The sites range from northern Sweden
to Spain, covering a span in mean annual air temperature
from 0 to 16 ïżœC, and in annual precipitation from 300 to
1300mmyrâ1. The effects of climate change, including temperature
increase and prolonged drought, were tested at five
shrubland sites. At one peatland site, the long-term (>30 yr)
effect of drainage was assessed, while increased nitrogen deposition
was investigated at three peatland sites.
The shrublands were generally sinks for atmospheric CH4,
whereas the peatlands were CH4 sources, with fluxes ranging
from â519 to +6890 mgCH4-Cmâ2 yrâ1 across the studied
ecosystems. At the peatland sites, annual CH4 emission
increased with mean annual air temperature, while
a negative relationship was found between net CH4 uptake
and the soil carbon stock at the shrubland sites. Annual
N2O fluxes were generally small ranging from â14
to 42 mgN2O-Nmâ2 yrâ1. Highest N2O emission occurred
at the sites that had highest nitrate (NOâ
3 ) concentration
in the soil water. Furthermore, experimentally increased
NOâ
3 deposition led to increased N2O efflux, whereas prolonged
drought and long-term drainage reduced the N2O efflux.
Soil CO2 emissions in control plots ranged from 310
to 732 gCO2-Cmâ2 yrâ1. Drought and long-term drainage generally reduced the soil CO2 efflux, except at a hydric
shrubland where drought tended to increase soil respiration.
In terms of fractional importance of each greenhouse gas
to the total numerical global warming response, the change in
CO2 efflux dominated the response in all treatments (ranging
71â96 %), except for NOâ
3 addition where 89% was due to
change in CH4 emissions. Thus, in European peatlands and
shrublands the effect on global warming induced by the investigated
anthropogenic disturbances will be dominated by
variations in soil CO2 fluxes
Disordered eating behaviour is associated with blunted cortisol and cardiovascular reactions to acute psychological stress
Research suggests a potential dysregulation of the stress response in individuals with bulimia nervosa. This study measured both cardiovascular and cortisol reactions to a standardised laboratory stress task in individuals identified as showing disordered eating behaviour to determine whether dysregulation of the stress response is characteristic of the two branches of the stress response system. Female students (N = 455) were screened using two validated eating disorder questionnaires. Twelve women with disordered eating, including self-induced vomiting, and 12 healthy controls were selected for laboratory stress testing. Salivary cortisol and cardiovascular activity, via Doppler imaging and semi-automatic blood pressure monitoring, were measured at resting baseline and during and after exposure to a 10-min mental arithmetic stress task. Compared to controls the disordered eating group showed blunted cortisol, cardiac output, heart rate, and stroke volume reactions to the acute stress, as well as an attenuated vasodilatory reaction. These effects could not be accounted for in terms of group differences in stress task performance, subjective task impact/engagement, age, BMI, neuroticism, cardiorespiratory fitness, or co-morbid exercise dependence. Our findings suggest that disordered eating is characterised by a dysregulation of the autonomic stress-response system. As such, they add further weight to the general contention that blunted stress reactivity is characteristic of a number of maladaptive behaviours and states
The necessity for multiphoton processes in the 193-nm photochemistry of sulphuric acid aerosols
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in âs = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fbâ1 of protonâproton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC
Measurements of inclusive jet suppression in heavy ion collisions at the LHC
provide direct sensitivity to the physics of jet quenching. In a sample of
lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated
luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with
a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the
transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the
anti-kt algorithm with values for the distance parameter that determines the
nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of
the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp.
Jet production is found to be suppressed by approximately a factor of two in
the 10% most central collisions relative to peripheral collisions. Rcp varies
smoothly with centrality as characterized by the number of participating
nucleons. The observed suppression is only weakly dependent on jet radius and
transverse momentum. These results provide the first direct measurement of
inclusive jet suppression in heavy ion collisions and complement previous
measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables,
submitted to Physics Letters B. All figures including auxiliary figures are
available at
http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
- âŠ