Thinking Outside the Box : Using Stella for Reading

Students will enter the number of books they read into STELLA to keep a running log of their yearly reading activity

Modeling the solar thermal receiver for the CSPonD Project

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, June 2011."June 2011." Cataloged from PDF version of thesis.Includes bibliographical references (p. 23).The objective was to create an accurate steady state thermal model of a molten salt receiver prototype with a horizontal divider plate in the molten salt for Concentrated Solar Power on Demand (CSPonD). The purpose of the divider plate is to separate the heated salt on the top from the colder salt on the bottom while allowing some of the salt to pass around the plate. The thermal model used is a one dimensional resistance model which uses bulk temperatures for the top and bottom layers of salt. An assumption needed to be made to allow the model to be solvable, so it was modeled using two different assumptions, a given energy input and a given top salt bulk temperature. The system was solved for the maximum and minimum heights that the divider plate transverse, with the top of the plate being 2 centimeters and 5.5 centimeters from the bottom of the receiver. The given energy for the two heights was 1,598W for the 2 centimeter height and 1,512W for the 5.5 centimeter height. For the given top temperature for the two heights the temperatures were 367.2°C for 2 centimeter height and 360.0°C for 5.5 centimeter height. It was observed that both models showed correlation with the trends in the temperature gradients and heat losses as the tested experiment, varying at a maximum temperature difference of 55K to a minimum of less than 2K. The observations show that the assumed temperature models show a closer correlation with the experimental results than the assumed energy model. The experiment, however, was only run for 8000s, which suggests that it might not have reached steady state making the energy model the better model for steady state analysis.by Jennifer A. Rees.S.B

Null-space preconditioners for saddle point systems

The null-space method is a technique that has been used for many years to reduce a saddle point system to a smaller, easier to solve, symmetric positive-definite system. This method can be understood as a block factorization of the system. Here we explore the use of preconditioners based on incomplete versions of a particular null-space factorization, and compare their performance with the equivalent Schur-complement based preconditioners. We also describe how to apply the non-symmetric preconditioners proposed using the conjugate gradient method (CG) with a non-standard inner product. This requires an exact solve with the (1,1) block, and the resulting algorithm is applicable in other cases where Bramble-Pasciak CG is used. We verify the efficiency of the newly proposed preconditioners on a number of test cases from a range of applications

Green and black tea for the primary prevention of cardiovascular disease

Background: There is increasing evidence that both green and black tea are beneficial for cardiovascular disease (CVD) prevention. Objectives: To determine the effects of green and black tea on the primary prevention of CVD. Search methods: We searched the following databases on 12 October 2012 without language restrictions: CENTRAL in The Cochrane Library, MEDLINE (OVID), EMBASE (OVID) and Web of Science (Thomson Reuters). We also searched trial registers, screened reference lists and contacted authors for additional information where necessary. Selection criteria: Randomised controlled trials (RCTs) lasting at least three months involving healthy adults or those at high risk of CVD. Trials investigated the intake of green tea, black tea or tea extracts. The comparison group was no intervention, placebo or minimal intervention. The outcomes of interest were CVD clinical events and major CVD risk factors. Any trials involving multifactorial lifestyle interventions or focusing on weight loss were excluded to avoid confounding. Data collection and analysis: Two review authors independently selected trials for inclusion, abstracted data and assessed the risk of bias. Trials of green tea were analysed separately from trials of black tea. Main results: We identified 11 RCTs with a total of 821 participants, two trials awaiting classification and one ongoing trial. Seven trials examined a green tea intervention and four examined a black tea intervention. Dosage and form of both green and black tea differed between trials. The ongoing trial is examining the effects of green tea powder capsules. No studies reported cardiovascular events. Black tea was found to produce statistically significant reductions in low-density lipoprotein (LDL) cholesterol (mean difference (MD) -0.43 mmol/L, 95% confidence interval (CI) -0.56 to -0.31) and blood pressure (systolic blood pressure (SBP): MD -1.85 mmHg, 95% CI -3.21 to -0.48. Diastolic blood pressure (DBP): MD -1.27 mmHg, 95% CI -3.06 to 0.53) over six months, stable to sensitivity analysis, but only a small number of trials contributed to each analysis and studies were at risk of bias. Green tea was also found to produce statistically significant reductions in total cholesterol (MD -0.62 mmol/L, 95% CI -0.77 to - 0.46), LDL cholesterol (MD -0.64 mmol/L, 95% CI -0.77 to -0.52) and blood pressure (SBP: MD -3.18 mmHg, 95% CI -5.25 to - 1.11; DBP: MD -3.42, 95% CI -4.54 to -2.30), but only a small number of studies contributed to each analysis, and results were not stable to sensitivity analysis. When both tea types were analysed together they showed favourable effects on LDL cholesterol (MD - 0.48 mmol/L, 95% CI -0.61 to -0.35) and blood pressure (SBP: MD -2.25 mmHg, 95% CI -3.39 to -1.11; DBP: MD -2.81 mmHg, 95% CI -3.77 to -1.86). Adverse events were measured in five trials and included a diagnosis of prostate cancer, hospitalisation for influenza, appendicitis and retinal detachment but these are unlikely to be directly attributable to the intervention. Authors' conclusions: There are very few long-term studies to date examining green or black tea for the primary prevention of CVD. The limited evidence suggests that tea has favourable effects on CVD risk factors, but due to the small number of trials contributing to each analysis the results should be treated with some caution and further high quality trials with longer-term follow-up are needed to confirm this

Further Observations on Whether Host Immunodepression is Associated with Tumour Growth in Mice

In order to investigate whether the presence of a tumour was associated with immunodepression in the host, spleen cells from parent line animals with tumours were injected intravenously into F1 hybrids, half of which carried the same tumour. Further groups of F1 hybrid with and without the tumour received spleen cells from non-tumour bearing parent line animals. The G.V.H. reactions induced in the four groups of F1 hybrid were compared and no significant differences were found. This was true in separate experiments, involving two mammary carcinomata and a 3-methylcholanthrene induced sarcoma, wherein the period of tumour growth in the parent line donor and F1 hybrid recipient was varied

Observations on the Increasing Malignancy of Tumours on Prolonged Growth: The Influence of Immunological Changes in the Host

Spontaneously occurring A-strain mouse mammary carcinomata were individually passaged, at equal intervals into separate groups of isogenic hosts. The tumours showed evidence of increasing autonomy as judged either by the decreasing host lymphoid hyperplasia they evoked, or their decreased killing time, as passaging continued. However, in general, no reduction was found in the ability of spleen cells from hosts bearing succeeding passages of the same tumour to induce a graft-versus-host reaction in (A × CBA)F1 hybrid mice. It is therefore suggested that the increasing malignancy of the tumours studied was associated with a change in the tumour rather than increasing immunodepression in successive hosts

Convergence and evaluation-complexity analysis of a regularized tensor-Newton method for solving nonlinear least-squares problems

Given a twice-continuously differentiable vector-valued function r(x), a local minimizer of ∥r(x)∥2 is sought. We propose and analyse tensor-Newton methods, in which r(x) is replaced locally by its second-order Taylor approximation. Convergence is controlled by regularization of various orders. We establish global convergence to a first-order critical point of ∥r(x)∥2, and provide function evaluation bounds that agree with the best-known bounds for methods using second derivatives. Numerical experiments comparing tensor-Newton methods with regularized Gauss-Newton and Newton methods demonstrate the practical performance of the newly proposed method

Fate and pathways of dredged estuarine sediment spoil in response to variable sediment size and baroclinic coastal circulation

Most of the world’s megacities are located in estuarine regions supporting commercial ports. Such locations are subject to sedimentation and require dredging to maintain activities. Liverpool Bay, northwest UK, is a region of freshwater influence and hypertidal conditions used to demonstrate the impact of baroclinicity when considering sediment disposal. Although tidal currents dominate the time-varying current and onshore sediment movement, baroclinic processes cause a 2-layer residual circulation that influences the longer-term sediment transport. A nested modelling system is applied to accurately simulate the circulation during a three month period. The hydrodynamic model is validated using coastal observations, and a Lagrangian particle tracking model is used to determine the pathways of 2 sediment mixtures representative of locally dredged material: a mix of 70% silt and 30% medium sand and a mix of 50% fine sand and 50% medium sand. Sediments are introduced at 3 active disposal sites within the Mersey Estuary in 2 different quantities (500 and 1500 Tonnes). Following release the majority (83% or more) of the particles remain within the estuary due to baroclinic influence. However, particles able to leave follow 2 distinct pathways, which primarily depend on the sediment grain size. Typically the finer sediment moves north and the coarser sediment west. Under solely barotropic conditions larger sediment volumes (up to 5 times more) can leave the estuary in a diffuse plume moving north. This demonstrates the necessity of considering baroclinic influence even within a hypertidal region with low freshwater inflow for accurate particle tracking

Hands-On Precision Agriculture Data Management Workshops for Producers and Industry Professionals: Development and Assessment

Three Precision Agriculture Data Management workshops regarding yield monitor data were conducted in 2014, reaching 62 participants. Post-workshop surveys (n=58) indicated 73% of respondents experienced a moderate to significant increase in knowledge related to yield monitor data usage. Another 72% reported that they planned to utilize best management practices presented or would expand their current practices based on knowledge gained. One-year post-workshop survey (n=14) results indicated that far less (36%) were able to implement some of the techniques presented. However, comments indicated that accessible follow-up material would be beneficial in successfully integrating learning topics into data management systems