207 research outputs found
Mathisson-Papapetrou equations in metric and gauge theories of gravity in a Lagrangian formulation
We present a simple method to derive the semiclassical equations of motion
for a spinning particle in a gravitational field. We investigate the cases of
classical, rotating particles (pole-dipole particles), as well as particles
with intrinsic spin. We show that, starting with a simple Lagrangian, one can
derive equations for the spin evolution and momentum propagation in the
framework of metric theories of gravity and in theories based on a
Riemann-Cartan geometry (Poincare gauge theory), without explicitly referring
to matter current densities (spin and energy-momentum). Our results agree with
those derived from the multipole expansion of the current densities by the
conventional Papapetrou method and from the WKB analysis for elementary
particles.Comment: 28 page
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Empowering Studentsâ Learning Achievement Through Project-Based Learning As Perceived By Electrical Instructors And Students
Purposes of this research were to find out factors empowering electrical studentsâ learning achievement through Project-Based Learning (PBL) as perceived by instructorsâ and studentsâ opinions. The sample chosen for this study were 247 electrical power instructors at vocational education institutes and 161 electrical students in the 3 rd and 4th year who were studying in the 1st semester of academic year 2006 at Electrical Education Department, Faculty of Industrial Education and Technology, King Mongkutâs University of Technology Thonburi by using simple random sampling. The instrument used for data collection was 7 rating scales questionnaire. The reliability of the instrument calculated by Cronbach Alpha Coefficient was 0.8185 and 0.9839, respectively. The data were analysed by using mean ( ), Standard Deviation (S.D.) and Analysis of Factors by Principal Component Analysis technique: PCA, orthogonal rotation axis by Varimax Method. The results of the study on factors empowering electrical studentsâ learning achievement through Project-Based Learning (PBL) were as follows: both instructors and students agreed on Interesting/Attention(0.799 and 0.885, respectively) while other factors such as Planning(0.722), Sharing Ideas(0.582), Thinking(0.576), Facilitating (0.547), Constructionism (0.540), Scientific Process (0.525), Multiple Intelligence (0.479), and Goal Setting(0.453) were perceived by instructors, and studentsâ opinions were on Advising/Guiding(0.863), Thinking(0.661), Goal Setting (0.634), Multiple Intelligence(0.553), Scientific Process(0.528), Assisting(0.524), and Sharing Ideas (0.492), if not more so
Rheological Characteristics of Municipal Thickened Excess Activated Sludge (TEAS): Impacts of pH, Temperature, Solid Concentration and Polymer Dose
Rheological characterization of sludge is known to be an essential tool to optimize flow, mixing and other process parameters in wastewater treatment plants. This study deals with the characterization of thickened excess activated sludge in comparison to raw primary sludge and excess activated sludge. The effects of key parameters (total solid concentration, temperature, and pH) on the rheology and flow behavior of thickened excess activated sludge were studied. The rheological investigations were carried out for total solid concentration range of 0.9â3.7 %w/w, temperature range of 23â55 °C, and pH range of 3.6â10.0. Different rheological model equations were fitted to the experimental data. The model equations with better fitting were used to calculate the yield stress, apparent, zero-rate, infinite-rate viscosities, flow consistency index, and flow index. The decrease in concentration from 3.7 to 3.1 %w/w resulted in a drastic reduction of yield stress from 27.6 to 11.0 Pa, while a further reduction of yield stress to 1.3 Pa was observed as solid concentration was reduced to 1.3 %w/w. The viscosity at higher shear rate (>600 sâ1) decreased from 0.05 Pa·s down to 0.008 Pa·s when the total solid concentration was reduced from 3.7 to 0.9 %. Yield stress decreased from 20.1 Pa down to 8.3 Pa for the Bingham plastic model when the temperature was raised from 25 to 55 °C. Activation energy and viscosity also showed decreasing trends with increasing temperature. Yield stress of thickened excess activated sludge increased from a value of 6.0 Pa to 8.3 Pa when the pH was increased from 3.6 to 10.0. The effect of polymer dose on the rheological behavior of the thickening of excess activated sludge was also investigated, and the optimum polymer dosage for enhanced thickener performance was determined to be 1.3 kg/ton DS
The elusive role of soil quality in nutrient cycling: a review
peer-reviewedCycling of nutrients, including nitrogen and phosphorus, is one of the ecosystem services we expect
agricultural soils to deliver. Nutrient cycling incorporates the reuse of agricultural, industrial and
municipal organic residues that, misleadingly, are often referred to as âwastesâ. The present review
disentangles the processes underlying the cycling of nutrients to better understand which soil
properties determine the performance of that function. Four processes are identified (i) the capacity to
receive nutrients, (ii) the capacity to make and keep nutrients available to crops, (iii) the capacity to
support the uptake of nutrients by crops and (iv) the capacity to support their successful removal in
harvested crop. Soil properties matter but it is imperative that, as constituents of âsoil qualityâ, they
should be evaluated in the context of management options and climate and not as ends in their own
right. The effect of a soil property may vary depending on the prevailing climatic and hydrologic
conditions and on other soil properties. We recognize that individual soil properties may be enhancing
one of the processes underlying the cycling of nutrients but simultaneously weakening others.
Competing demands on soil properties are even more obvious when considering other soil functions
such as primary production, purification and flow regulation of water, climate modification and
habitat provision, as shown by examples. Consequently, evaluations of soil properties and
management actions need to be site-specific, taking account of local aspects of their suitability and
potential challenges.Horizon 202
Effects of the Veterinary Pharmaceutical Ivermectin in Indoor Aquatic Microcosms
The effects of the parasiticide ivermectin were assessed in plankton-dominated indoor microcosms. Ivermectin was applied once at concentrations of 30, 100, 300, 1000, 3000, and 10,000Â ng/l. The half-life (dissipation time 50%; DT50) of ivermectin in the water phase ranged from 1.1 to 8.3Â days. The lowest NOECcommunity that could be derived on an isolated sampling from the microcosm study by means of multivariate techniques was 100Â ng/l. The most sensitive species in the microcosm study were the cladocerans Ceriodaphnia sp. (no observed effect concentration, NOECÂ =Â 30Â ng/l) and Chydorus sphaericus (NOECÂ =Â 100Â ng/l). The amphipod Gammarus pulex was less sensitive to ivermectin, showing consistent statistically significant reductions at the 1000-ng/l treatment level. Copepoda taxa decreased directly after application of ivermectin in the highest treatment but had already recovered at day 20 posttreatment. Indirect effects (e.g., increase of rotifers, increased primary production) were observed at the highest treatment level starting only on day 13 of the exposure phase. Cladocera showed the highest sensitivity to ivermectin in both standard laboratory toxicity tests as well as in the microcosm study. This study demonstrates that simple plankton-dominated test systems for assessing the effects of ivermectin can produce results similar to those obtained with large complex outdoor systems
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