18,569 research outputs found
Comparison of Torpedograss and Pickerelweed Susceptibility to Glyphosate
Torpedograss (Panicum repens L.) is one of the most invasive
exotic plants in aquatic systems. Repeat applications of
(N-phosphonomethyl) glycine (glyphosate) herbicides provide
limited control of torpedograss; unfortunately, glyphosate
often negatively impacts most non-target native species
that grow alongside the weed. This experiment studied the
effect of glyphosate on pickerelweed (Pontederia cordata L.), a native plant that shares habitats with torpedograss. Actively growing plants of torpedograss and pickerelweed were cultured in 8-liter containers and sprayed to wet with one of four rates of glyphosate: 0%, 0.75%, 1.0%, or 1.5%. Each treatment included a surfactant to aid in herbicide uptake and a surface dye to verify uniform application of the treatments. All herbicide treatments were applied with a backpack sprayer to intact plants and to cut stubble of both species. Four replicates were treated for each species-rategrowth combination during each of two experiment periods. Plant dry weights 8 weeks after herbicide application suggest that torpedograss was effectively controlled by the highest rate of glyphosate applied to cut stubble. Pickerelweed was unaffected when the highest rate of glyphosate was applied as a cut-and-spray treatment. These data suggest that a cut-and-spray application of a 1.5% solution of glyphosate may be an effective strategy to control torpedograss without deleteriously affecting pickerelweed. (PDF contains 4 pages.
Plants for predators - a participatory experiment
Encouraging natural enemies by growing attractant plants is a highly effective method of pest control in organic systems. However, it is important to establish which plants are most effective at attracting benefi cial insects. Experiments were carried out by 179 HDRA members, who grew four plant species (Coriander, Corn Marigold, Fennel and Phacelia) in their gardens and allotments. Over the course of the growing season, assessments were made on the growth and flowering of the plants and the presence of four key groups of beneficial insect (ladybirds, hoverflies, lacewings and parasitic wasps). Phacelia established quickly and its long flowering period meant it attracted insects throughout the summer. However, Phacelia was only the most attractive plant at the end of the season and insects preferred the other trial plants when they were in flower. Results highlight the importance of growing a range of flowering plants to provide resources for beneficials throughout their activity period
Hybrid mean field and real space model for vacancy diffusion-mediated annealing of radiation defects
In a fusion or advanced fission reactor, high energy neutrons induce the
formation of extended defect clusters in structural component materials,
degrading their properties over time. Such damage can be partially recovered
via a thermal annealing treatment. Therefore, for the design and operation of
fusion and advanced fission nuclear energy systems it is critical to estimate
and predict the annealing timescales for arbitrary configurations of defect
clusters. In our earlier paper [I. Rovelli, S. L. Dudarev, and A. P. Sutton, J.
Mech. Phys. Solids 103, 121 (2017)] we extended the Green function formulation
by Gu, Xiang et al. [Y. Gu, Y. Xiang, S. S. Quek, and D. J. Srolovitz, J. Mech.
Phys. Solids 83, 319 (2015)] for the climb of curved dislocations, to include
the evaporation and growth of cavities and vacancy clusters, and take into
account the effect of free surfaces. In this work, we further develop this
model to include the effect of radiation defects that are below the
experimental detection limit, via a mean field approach coupled with an
explicit treatment of the evolution of discrete defect clusters distributed in
real space. We show that randomly distributed small defects screen diffusive
interactions between larger discrete clusters. The evolution of the coupled
system is modelled self-consistently. We also simulate the evolution of defects
in an infinite laterally extended thin film, using the Ewald summation of
screened Yukawa-type diffusive propagators
Analytical fuel property effects--small combustors
The consequences of using broad-property fuels in both conventional and advanced state-of-the-art small gas turbine combustors are assessed. Eight combustor concepts were selected for initial screening, of these, four final combustor concepts were chosen for further detailed analysis. These included the dual orifice injector baseline combustor (a current production 250-C30 engine combustor) two baseline airblast injected modifications, short and piloted prechamber combustors, and an advanced airblast injected, variable geometry air staged combustor. Final predictions employed the use of the STAC-I computer code. This quasi 2-D model includes real fuel properties, effects of injector type on atomization, detailed droplet dynamics, and multistep chemical kinetics. In general, fuel property effects on various combustor concepts can be classified as chemical or physical in nature. Predictions indicate that fuel chemistry has a significant effect on flame radiation, liner wall temperature, and smoke emission. Fuel physical properties that govern atomization quality and evaporation rates are predicted to affect ignition and lean-blowout limits, combustion efficiency, unburned hydrocarbon, and carbon monoxide emissions
Heterodyne detection of CO2 emission lines and wind velocities in the atmosphere of Venus
Strong 10 micrometer line emission from (c-12)(o-16)2 in the upper atmosphere of Venus was detected by heterodyne techniques. Observations of the absolute Doppler shift of the emission features indicate mean zonal wind velocities less than 10 m/sec in the upper atmosphere near the equator. No evidence was found of the 100 m/sec wind velocity implied by the apparent 4-day rotation period of ultraviolet cloud features
Heterodyne detection of CO2 emission lines and wind velocities in the atmosphere of Venus
Strong 10 micrometer line emission from (C-12)(O-16)2 in the upper atmosphere of Venus was detected by heterodyne techniques. Observations of the absolute Doppler shift of the emission features indicate mean zonal wind velocities less than 10 m/sec in the upper atmosphere near the equator. No evidence was found of the 100 m/sec wind velocity implied by the apparent 4-day rotation period of ultraviolet cloud features
Case study of a female ocean racer: prerace preparation and nutritional intake during the Vendee Globe 2008.
The Vendée Globe is a solo round-the-world sailing race without stopovers or assistance, a physically demanding challenge for which appropriate nutrition should maintain energy balance and ensure optimum performance. This is an account of prerace nutritional preparation with a professional and experienced female racer and assessment of daily nutritional intake (NI) during the race using a multimethod approach. A daily energy intake (EI) of 15.1 MJ/day was recommended for the race and negotiated down by the racer to 12.7 MJ/day, with carbohydrate and fluid intake goals of 480 g/day and 3,020 ml/day, respectively. Throughout the 99-day voyage, daily NI was recorded using electronic food diaries and inventories piloted during training races. NI was assessed and a postrace interview and questionnaire were used to evaluate the intervention. Fat mass (FM) and fat-free mass (FFM) were assessed pre- (37 days) and postrace (11 days) using dual-energy X-ray absorptiometry, and body mass was measured before the racer stepped on the yacht and immediately postrace. Mean EI was 9.2 MJ/day (2.4-14.3 MJ/day), representing a negative energy balance of 3.5 MJ/day under the negotiated EI goal, evidenced by a 7.9-kg loss of body mass (FM -7.5 kg, FFM -0.4 kg) during the voyage, with consequent underconsumption of carbohydrate by ~130 g/day. According to the postrace yacht food inventory, self-reported EI was underreported by 7%. This intervention demonstrates the practicality of the NI approach and assessment, but the racer's nutrition strategy can be further improved to facilitate meeting more optimal NI goals for performance and health. It also shows that evaluation of NI is possible in this environment over prolonged periods, which can provide important information for optimizing nutritional strategies for ocean racing
The brightness distribution of IRC +10216 at 11 microns
The brightness distribution of IRC +10216 at a wavelength of 11 microns was measured in detail using a spatial interferometer. This brightness distribution appears to have azimuthal symmetry; an upper limit of 1.1 may be set to the ellipticity at 11 microns if the object has a major axis oriented either along or perpendicular to the major axis of the optical image. The radial distribution shows both compact and extended emission. The extended component, which is due to thermal emission from circumstellar dust, contributes 91% of the total flux and has a 1/e diameter of 0.90 minutes. The tapered shape of this component is consistent with a l/r squared dust density dependence. The compact component is unresolved (less than 0.2 minutes in diameter) and represents emission from the central star seen through the circumstellar envelope
Disease and psychological status in ankylosing spondylitis.
Objectives. Psychological factors may be important in the assessment and management of ankylosing spondylitis (AS). Our primary objective was to describe associations between disease and psychological status in AS, using AS-specific assessment tools and questionnaires. Our secondary objectives were to identify patient subgroups based on such associations and to determine the stability of the measures over time.
Methods. A total of 110 patients were assessed at 6-monthly intervals up to four times using tools to measure disease [Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI) and the Bath Ankylosing Spondylitis Metrology Index (BASMI)], psychological [Hospital Anxiety and Depression Questionnaire (HADS), Health Locus of Control—Form C Questionnaire (HLC-C)] and generic health [Short form (SF)-36] status.
Results. Eighty-nine participants completed all four assessments. Throughout the study, BASDAI, BASFI and BASMI scores correlated significantly with anxiety, depression, internality and health status, but not with levels of belief in chance or powerful others. Clinically anxious or depressed subgroups had significantly worse BASDAI and BASFI, but not BASMI, scores. BASMI scores were the least closely linked to psychological status. Mean scores for disease, psychological and health status were clinically stable over the 18 months period.
Conclusions. Disease status scores in AS correlated significantly with anxiety, depression, internality and health status. Interpretation of AS disease scores should take an account of psychological status and the choice of measures used. These findings have important potential applications in AS management and monitoring, including the identification of patients for biological therapies
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