7,469 research outputs found
TRIAD - Preliminary design of an operational earth resources survey system. 1969 summer faculty fellowship program in engineering systems design
TRIAD, preliminary design of operational earth resources survey syste
TRIAD - Preliminary design of an operational earth resources survey system Final report
Design of operational earth resources survey syste
Latent heat flux and canopy conductance based on Penman-Monteith and Bouchet’s complementary hypothesis:validation over diverse biomes
Abstract
A novel method is presented to analytically resolve the terrestrial latent heat flux (λE) and conductances (boundary layer gB and surface gS) using net radiation (RN), ground heat flux (G), air temperature (Ta), and relative humidity (RH). This method consists of set of equations where the two unknown internal state variables (gB and gS) were expressed in terms of the known core variables, combining diffusion equations, the Penman–Monteith equation, the Priestley–Taylor equation, and Bouchet’s complementary hypothesis. Estimated λE is validated with the independent eddy covariance λE observations over Soil Moisture Experiment 2002 (SMEX-02); the Global Energy and Water Cycle Experiment (GEWEX) Continental-Scale International Project (GCIP) selected sites from FLUXNET and tropics eddy flux, representing four climate zones (tropics, subtropics, temperate, and cold); and multiple biomes. The authors find a RMSE of 23.8–54.6 W m−2 for hourly λE over SMEX-02 and GCIP and 23.8–29.0 W m−2 for monthly λE over the FLUXNET and tropics. Observational and modeled evidence in the reduction in annual evaporation (E) pattern on the order of 33% from 1999 to 2006 was found in central Amazonia. Retrieved gS responded to vapor pressure deficit, measured λE, and gross photosynthesis in a theoretically robust behavior. However, the current scheme [Penman–Monteith–Bouchet–Lhomme (PMBL)] showed some overestimation of λE in limited soil moisture regimes. PMBL provides similar results when compared with another Priestley–Taylor–based λE estimation approach [Priestley–Taylor–Jet Propulsion Laboratory (PT-JPL)] but with the advantage of having the conductances analytically recovered.</jats:p
An international prospective general population-based study of respiratory work disability
Background: Previous cross-sectional studies have shown that job change due to breathing problems at the workplace (respiratory work disability) is common among adults of working age. That research indicated that occupational exposure to gases, dust and fumes was associated with job change due to breathing problems, although causal inferences have been tempered by the cross-sectional nature of previously available data. There is a need for general population-based prospective studies to assess the incidence of respiratory work disability and to delineate better the roles of potential predictors of respiratory work disability.Methods: A prospective general population cohort study was performed in 25 centres in 11 European countries and one centre in the USA. A longitudinal analysis was undertaken of the European Community Respiratory Health Survey including all participants employed at any point since the baseline survey, 6659 subjects randomly sampled and 779 subjects comprising all subjects reporting physician-diagnosed asthma. The main outcome measure was new-onset respiratory work disability, defined as a reported job change during follow-up attributed to breathing problems. Exposure to dusts (biological or mineral), gases or fumes during follow-up was recorded using a job-exposure matrix. Cox proportional hazard regression modelling was used to analyse such exposure as a predictor of time until job change due to breathing problems.Results: The incidence rate of respiratory work disability was 1.2/1000 person-years of observation in the random sample (95% CI 1.0 to 1.5) and 5.7/1000 person-years in the asthma cohort (95% CI 4.1 to 7.8). In the random population sample, as well as in the asthma cohort, high occupational exposure to biological dust, mineral dust or gases or fumes predicted increased risk of respiratory work disability. In the random sample, sex was not associated with increased risk of work disability while, in the asthma cohort, female sex was associated with an increased disability risk (hazard ratio 2.8, 95% CI 1.3 to 5.9).Conclusions: Respiratory work disability is common overall. It is associated with workplace exposures that could be controlled through preventive measures
A comparison of animal output and nitrogen leaching losses recorded from drained fertilized grass and grass/clover pasture
Annual liveweight gain of beef cattle (steers) grazing grass pasture
fertilized with 200 kg N/ha was
compared over a period of 7 years (1989–95) with that of
steers grazing grass/white clover pasture
given no artificial N fertilizer at North Wyke, Devon, UK. Nitrogen lost
by leaching over the ensuing
winter drainage periods was monitored from both pastures. Nitrogen leaching
loss from the fertilized
pasture over an extended period of 13 years (1983–95) is also reported.The average annual liveweight gain of the steers grazing the
grass/clover pasture (0·81 t/ha) was
19% lower than that of the steers grazing the N-fertilized
grass pasture (1·00 t/ha). The average
annual loss of nitrate-N by leaching in winter drainage from
the grass/clover pasture (13 kg/ha) was
only 26% of that recorded from the fertilized grass (50 kg/ha).
A possible reason for this difference
may arise from the previous history of the grass/clover
pasture which had been ploughed in 1982,
causing a flush of N mineralization and consequently greater immobilization
of N in the soil in subsequent years.Losses of N each winter by leaching measured over a 13-year period from
the fertilized grass were
highly correlated (P<0·001) with the preceding
summer's soil moisture deficit, with the highest losses
following dry summers. The nitrate-N concentration in
the drainage water exceeded the European
Union limit in drinking water (11·3 mg/l) in the
initial 25 mm of drainage during 11 of the 13
autumns. The average loss of N each winter (53 kg/ha) was
equivalent to 26% of the fertilizer-N
applied annually. Immediate losses of N by leaching of fertilizer applied
in early spring and
throughout one very wet summer (1993) were minimal.</jats:p
Classification of Singular Fibres on Rational Elliptic Surfaces in Characteristic Three
We determine and list all possible configurations of singular fibres on
rational elliptic surfaces in characteristic three. In total, we find that 267
distinct configurations exist. This result complements Miranda and Persson's
classification in characteristic zero, and Lang's classification in
characteristic two.Comment: 40 Pages. Minor typos correcte
A kinematical approach to gravitational lensing using new formulae for refractive index and acceleration
This paper uses the Schwarzschild metric to derive an effective refractive
index and acceleration vector that account for relativistic deflection of light
rays, in an otherwise classical kinematic framework. The new refractive index
and the known path equation are integrated to give accurate results for travel
time and deflection angle, respectively. A new formula for coordinate
acceleration is derived which describes the path of a massless test particle in
the vicinity of a spherically symmetric mass density distribution. A standard
ray-shooting technique is used to compare the deflection angle and time delay
predicted by this new formula with the previously calculated values, and with
standard first order approximations. Finally, the ray shooting method is used
in theoretical examples of strong and weak lensing, reproducing known
observer-plane caustic patterns for multiple masses.Comment: 11 pages, 7 figures, MNRAS accepte
Pinnipeds, people and photo identification: the implications of grey seal movements for effective management of the species
This is the author accepted manuscript. The final version is available from Cambridge University Press via the DOI in this record.Grey seals (Halichoerus grypus) of the North-east Atlantic are protected at designated European Marine Sites (Special Areas of Conservation, SACs) typically during their reproductive periods and in the UK at Sites of Special Scientific Interest (SSSI). As a mobile marine species, grey seals spend other parts of their annual life cycle in non-designated habitat. There is limited information on individual grey seal movements in south-west England. Citizen science photo identification (PID) revealed the movements of 477 grey seals at a regional scale (54 haul-outs up to 230 km apart) for over a decade. Reconstructed movements showed considerable individual variability. Four SACs were linked to up to 18 non-designated sites and two SSSIs in Cornwall were linked to a maximum of 41 non-designated sites. Observations support the value of existing SSSIs at both the well-connected West and North Cornwall sites. Thirteen Marine Protected Areas (MPAs) were visited by grey seals from four SACs and two SSSIs in Cornwall. As a mobile species, grey seals could be included in English MPA management plans. The application of functional linkage from SACs and SSSIs, informed by the movements evidenced in this research, could aid management efforts. This analysis reveals grey seal movements occur across a complex network of interconnected designated and non-designated sites that need to be managed holistically for this species for which the UK has a special responsibility
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