MANAGEMENT EFFECTS OF SPATIALLY DISPERSED LAND TRACTS: A SIMULATION ANALYSIS

A sequential simulation model is used to test a way to study the relationship between net farm income and land tract dispersion, total acres, machinery size and rainfall. The model simulates the day-to-day sequence of field work on a hypothetical farm simulation varying crop acreage, machinery size and for a wet and dry rainfall situation. Data generated by this model are then analyzed using a regression equation estimating the influence of studied variables on net farm income.Land Economics/Use,

Modeling desorption kinetics of a persistent organic pollutant from field aged sediment using a bi-disperse particle size distribution

Purpose With the predicted climate change, it is expected that the chances of river flooding increase. During flood events, sediments will resuspend and when sediments are polluted, contaminants can be transferred to the surrounding water. In this paper we discuss a numerical intraparticle diffusion model that simulates desorption of dieldrin from a suspension of contaminated porous sediment particles with a well-characterized particle size distribution. The objective of this study was to understand the desorption rate (flux) of dieldrin from a suspension of field-aged sediment at different hydraulic retention times (HRT) of the aqueous phase and to elaborate the effect of particle-size distribution on mass transfer. Materials and methods Desorption kinetics of dieldrin, a persistent organic pollutant (POP), were experimentally measured and described in a separate paper using field-contaminated sediment. A radial diffusion model, accommodating intraparticle reversible sorption kinetics, aqueous phase pore diffusion, and a sink term for bulk aqueous phase refreshment was used to describe the experimental data. Results and discussion We observed rapid equilibrium of contaminants between small particles (10 µm) and the surrounding water even though the sorption affinity of dieldrin towards organic matter was high. On the contrary, for the larger particles (84 µm), calculations show that desorption was limited by intraparticle diffusion. Combining small and larger particles in our radial diffusion model resulted in the biphasic desorption behavior often observed even when using a linear isotherm. Conclusions Flood events will result in an increase of desorption rate of POPs from sediments to the surrounding water. HRT and the particle-size distribution determine the desorption rate. We conclude that nonstationary diffusion within organic matter is the main process of mass transfer. Particle size distributions are very valuable to understand the phenomenology related to mass transfer limitations often described as limited bioavailability and can be used as basis to develop engineering options to limit contaminant mass fluxes into the environmen

Detection of differential rotation in psi Cap with profile analysis

We report detection of differential rotation on the F5 dwarf psi Cap using line profile analysis. The Fourier transform of both FeI lambda 5775 and SiI lambda 5772 are used to obtain a projected rotational velocity of v sini = (42+-1)km/s. Modelling of the Fourier transformed profiles shows that the combined effects of equatorial velocity, inclination and differential rotation dominate the line profile while limb darkening and turbulence velocities have only minor effects. Rigid rotation is shown to be inconsistent with the measured profiles. Modelling the line profiles analogous to solar differential rotation we find a differential rotation parameter of alpha = 0.15+-0.1 (15+-10%) comparable to the solar case. To our knowledge this is the first successful measurement of differential rotation through line profile analysis.Comment: 4 pages, 4 figures, accepted for publication in A&A Letter

Exploring Self-regulation of More or Less Expert College-Age Video Game Players: A Sequential Explanatory Design

This study examined differences in self-regulation among college-age expert, moderately expert, and non-expert video game players in playing video games for fun. Winnie\u27s model of self-regulation (Winne, 2001) guided the study. The main assumption of this study was that expert video game players used more processes of self-regulation than the less-expert players. We surveyed 143 college students about their game playing frequency, habits, and use of self-regulation. Data analysis indicated that while playing recreational video games, expert gamers self-regulated more than moderately expert and non-expert players and moderately expert players used more processes of self-regulation than non-experts. Semi-structured interviews also were conducted with selected participants at each of the expertise levels. Qualitative follow-up analyses revealed five themes: (1) characteristics of expert video gamers, (2) conditions for playing a video game, (3) figuring out a game, (4) how gamers act and, (5) game context. Overall, findings indicated that playing a video game is a highly self-regulated activity and that becoming an expert video game player mobilizes multiple sets of self-regulation related skills and processes. These findings are seen as promising for educators desiring to encourage student self-regulation, because they indicate the possibility of supporting students via recreational video games by recognizing that their play includes processes of self-regulation

Using Responsive Evaluation to Evaluate a Professional Conference

In a statewide conference on alternative methods for assessing students’ learning, we incorporated responsive evaluation methods into the structure of the conference. The application of these interactive evaluation techniques serves as a pilot study that illustrates the possible utility of these tech-niques in evaluating conferences. This paper provides a brief review of the literature surrounding responsive evaluation, a description of the responsive evaluation methods applied to this conference, and a discussion of the results and implications of this pilot study

Turning drops into bubbles: Elastic cavitation by diffusion

Some members of the vegetal kingdom can achieve surprisingly fast movements making use of a clever combination of evaporation, elasticity and cavitation. In this process, enthalpic energy is transformed into elastic energy and suddenly released in a cavitation event which produces kinetic energy. Here we study this uncommon energy transformation by a model system: a droplet in an elastic medium shrinks slowly by diffusion and eventually transforms into a bubble by a rapid cavitation event. The experiments reveal the cavity dynamics over the extremely disparate timescales of the process, spanning 9 orders of magnitude. We model the initial shrinkage as a classical diffusive process, while the sudden bubble growth and oscillations are described using an inertial-(visco)elastic model, in excellent agreement with the experiments. Such a model system could serve as a new paradigm for motile synthetic materials.Comment: 6 pages, 5 figure

Diffusion due to the Beam-Beam Interaction and Fluctuating Fields in Hadron Colliders

Random fluctuations in the tune, beam offsets and beam size in the presence of the beam-beam interaction are shown to lead to significant particle diffusion and emittance growth in hadron colliders. We find that far from resonances high frequency noise causes the most diffusion while near resonances low frequency noise is responsible for the large emittance growth observed. Comparison of different fluctuations shows that offset fluctuations between the beams causes the largest diffusion for particles in the beam core.Comment: 5 pages, 3 postscript figure

Rationale and design of PROSPECT-CONKO 004: a prospective, randomized trial of simultaneous pancreatic cancer treatment with enoxaparin and chemotherapy

BACKGROUND: Advanced pancreatic cancer, in addition to its high mortality, is characterized by one of the highest rates of venous thromboembolic events (VTE) as compared to other types of cancer. Enoxaparin, a low molecular weight heparin (LMWH), has proven to be effective for the prevention and treatment of VTE in surgical and general medical patients. Results of some small studies suggest that this benefit might extend to patients with cancer, however, enoxaparin is not currently indicated for this use. This phase IIb study was designed to analyze the efficacy of enoxaparin in patients with locally advanced or metastatic pancreatic cancer undergoing systemic chemotherapy. METHODS: The aim of this prospective multicenter trial is to compare concomitant treatment with enoxaparin to no anticoagulation in 540 patients. Primary endpoint is the incidence of clinically relevant VTE (symptomatic deep venous thrombosis (DVT) of the leg and / or pelvic and / or pulmonary embolism (PE)) within the first 3 months. Secondary endpoints include the incidence of symptomatic and asymptomatic VTE after 6, 9 and 12 months as well as remission at 3, 6, 9 and 12 months, overall survival and bleeding. Trial registration: isrctn.org identifier CCT-NAPN-16752, controlled-trials.com identifier: ISRCTN02140505. RESULTS: An interim analysis for safety performed after inclusion of 152 patients revealed no increased risk of bleeding (5 pts vs. 6 pts, Chi2: 0.763). CONCLUSIONS: PROSPECT is a pivotal study in elucidating the role of low molecular weight heparins in advanced pancreatic cancer. Its results will lead to a new understanding of the role of heparins in the prevention of venous thromboembolism and of their effect on survival, remission rates and toxicity of chemotherapeutic regimens