Icing Characteristics and Anti-Icing Heat Requirements for Hollow and Ternally Modified Gas-Heated Inlet Guide Vanes

A two-dimensional inlet-guide-vane cascade was investigated to determine the effects of ice formations on the pressure losses across the guide vanes and to evaluate the heated gas flow and temperature required to prevent Icing at various conditions. A gas flow of approximately 0.4 percent of the inlet-air flow was necessary for anti-icing a hollow guide-vane stage at an inlet-gas temperature of 500 F under the following icing conditions: air velocity, 280 miles per hour; water content, 0.9 gram per cubic meter; and Inlet-air static temperature, 00 F. Also presented are the anti-icing gas flows required with modifications of the hollow Internal gas passage, which show heatinput savings greater than 50 percent

Renormalization of Drift and Diffusivity in Random Gradient Flows

We investigate the relationship between the effective diffusivity and effective drift of a particle moving in a random medium. The velocity of the particle combines a white noise diffusion process with a local drift term that depends linearly on the gradient of a gaussian random field with homogeneous statistics. The theoretical analysis is confirmed by numerical simulation. For the purely isotropic case the simulation, which measures the effective drift directly in a constant gradient background field, confirms the result previously obtained theoretically, that the effective diffusivity and effective drift are renormalized by the same factor from their local values. For this isotropic case we provide an intuitive explanation, based on a {\it spatial} average of local drift, for the renormalization of the effective drift parameter relative to its local value. We also investigate situations in which the isotropy is broken by the tensorial relationship of the local drift to the gradient of the random field. We find that the numerical simulation confirms a relatively simple renormalization group calculation for the effective diffusivity and drift tensors.Comment: Latex 16 pages, 5 figures ep

Dynamical transition for a particle in a squared Gaussian potential

We study the problem of a Brownian particle diffusing in finite dimensions in a potential given by $\psi= \phi^2/2$ where $\phi$ is Gaussian random field. Exact results for the diffusion constant in the high temperature phase are given in one and two dimensions and it is shown to vanish in a power-law fashion at the dynamical transition temperature. Our results are confronted with numerical simulations where the Gaussian field is constructed, in a standard way, as a sum over random Fourier modes. We show that when the number of Fourier modes is finite the low temperature diffusion constant becomes non-zero and has an Arrhenius form. Thus we have a simple model with a fully understood finite size scaling theory for the dynamical transition. In addition we analyse the nature of the anomalous diffusion in the low temperature regime and show that the anomalous exponent agrees with that predicted by a trap model.Comment: 18 pages, 4 figures .eps, JPA styl

ω-3 LCPUFA supplementation during pregnancy and risk of allergic outcomes or sensitization in offspring: A systematic review and meta-analysis

Background: Allergic diseases have increased worldwide in the last 2 decades, with children suffering the highest burden of the condition. The ω-3 long-chain poly-unsaturated fatty acid (LCPUFA) possesses anti-inflammatory properties that could lead to a reduction in inflammatory mediators in allergies. Objective: A systematic review and meta-analysis of the most recent follow-ups of randomized clinical trials (RCTs) was conducted to assess the effectiveness of ω-3 LCPUFA supplementation started during pregnancy on allergic outcomes in offspring. Methods: The RCTs with a minimum of 1-month follow-up post gestation were eligible for inclusion. The CENTRAL, MEDLINE, SCOPUS, WHO's International Clinical Trials Register, E-theses, and Web of Science databases were searched. Study quality was evaluated using the Cochrane Collaboration's risk of bias tool. Results: Ten RCTs (3,637 children), from 9 unique trials, examined the effectiveness of ω-3 LCPUFA supplementation started during pregnancy on the development of allergic outcomes in offspring. Heterogeneities were seen between the trials in terms of their sample, type, and duration of intervention and follow-up. Pooled estimates showed a significant reduction in childhood “sensitization to egg” (relative risk [RR] = 0.54, 95% confidence interval [CI] = 0.32-0.90), and “sensitization to peanut” (RR = 0.62, 95% CI = 0.40-0.96). No statistical differences were found for other allergic outcomes (eg, eczema, asthma/wheeze). Conclusion: These results suggest that intake of ω-3 LCPUFA started during pregnancy can reduce the risk of sensitization to egg and peanut; however, the evidence is limited because of the small number of studies that contributed to the meta-analyses. The current evidence on the association between supplementation with ω-3 LCPUFA started during pregnancy and allergic outcomes is weak, because of the risk of bias and heterogeneities between studies

Prenatal intake of vitamins and allergic outcomes in the offspring: a systematic review and meta-analysis

Background - Allergic diseases have seen a rise worldwide with children suffering the highest burden. Thus early prevention of allergic diseases is a public health priority. Objective - To synthesise the evidence from randomised controlled trials (RCTs) assessing the efficacy of vitamin interventions during pregnancy on developing allergic diseases in offspring. Methods - We searched CENTRAL, MEDLINE, SCOPUS, WHO’s Int. Clin. Trials Reg., E-theses and Web of Science. Study quality was evaluated using the Cochrane’s risk of bias tool. Included RCTs had a minimum of 1-month follow-up post gestation.Results - A total of five RCTs met the inclusion criteria, including 2456 children that used vitamins C+E (one study), vitamin C (one study) and vitamin D (three studies) compared with placebo/control. Two studies were judged to have a high risk of bias for performance bias or high rate of loss to follow-up. All were rated as low risk of bias for blinding of outcome assessment. We did not perform meta-analysis with vitamin C or C+E studies due to high heterogeneity between the two included studies. However we did conduct a meta-analysis with trials on vitamin D (including 1493 children) and the results showed an association between prenatal intake of vitamin D and the risk of developing recurrent wheeze in offspring (RR=0.812, 95 % CI=0.67-0.98). Conclusion - The current evidence suggests that prenatal supplementation of vitamin D, might have a beneficial effect on recurrent wheezing in children. Longer-term follow-up of these studies are needed to ascertain whether this observed effect is a sustained. There is lack of evidence on the effect of other vitamins for prevention of respiratory and/or allergic outcomes

An exploratory investigation of food choice behavior of teenagers with and without food allergies

Background - Understanding food choice behavior in adolescence is important because many core eating habits may be tracked into adulthood. The food choices of at least 2.3% of teenagers living in the United Kingdom are determined by food allergies. However, the effect of food allergies on eating habits in teenagers has not yet been studied.Objective - To provide an understanding of how teenagers with food allergies make food choice decisions and how these differ from those of non–food-allergic teenagers.Methods - One focus group discussion with non–food-allergic teenagers (n = 11) and 14 semistructured interviewers (7 with food-allergic and 7 with non–food-allergic teenagers) were performed (age range, 12-18 years). The focus group discussion and interviews were audiorecorded, transcribed verbatim, and analyzed using thematic content analysis.Results - Teenagers from both groups (food-allergic and non–food-allergic) named sensory characteristics of foods as the main reason for choosing them. Some food-allergic teenagers downplayed their allergy and frequently engaged in risk-taking behavior in terms of their food choices. However, they reported difficulties in trying new foods, especially when away from home. Parental control was experienced as protective by those with food allergies, whereas non–food-allergic teenagers felt the opposite. Most teenagers, including food-allergic ones, expressed the wish to eat similar foods to their friends. Other themes did not vary between the 2 groups.Conclusion - Food-allergic teenagers strive to be able to make similar food choices to their friends, although differences to non–food-allergic teenagers exist. It is important to address these differences to improve their dietary management

Nuclear Lattice Simulations with Chiral Effective Field Theory

We study nuclear and neutron matter by combining chiral effective field theory with non-perturbative lattice methods. In our approach nucleons and pions are treated as point particles on a lattice. This allows us to probe larger volumes, lower temperatures, and greater nuclear densities than in lattice QCD. The low energy interactions of these particles are governed by chiral effective theory and operator coefficients are determined by fitting to zero temperature few-body scattering data. Any dependence on the lattice spacing can be understood from the renormalization group and absorbed by renormalizing operator coefficients. In this way we have a realistic simulation of many-body nuclear phenomena with no free parameters, a systematic expansion, and a clear theoretical connection to QCD. We present results for hot neutron matter at temperatures 20 to 40 MeV and densities below twice nuclear matter density.Comment: 41 pages, 23 figure

Continuum Derrida Approach to Drift and Diffusivity in Random Media

By means of rather general arguments, based on an approach due to Derrida that makes use of samples of finite size, we analyse the effective diffusivity and drift tensors in certain types of random medium in which the motion of the particles is controlled by molecular diffusion and a local flow field with known statistical properties. The power of the Derrida method is that it uses the equilibrium probability distribution, that exists for each {\em finite} sample, to compute asymptotic behaviour at large times in the {\em infinite} medium. In certain cases, where this equilibrium situation is associated with a vanishing microcurrent, our results demonstrate the equality of the renormalization processes for the effective drift and diffusivity tensors. This establishes, for those cases, a Ward identity previously verified only to two-loop order in perturbation theory in certain models. The technique can be applied also to media in which the diffusivity exhibits spatial fluctuations. We derive a simple relationship between the effective diffusivity in this case and that for an associated gradient drift problem that provides an interesting constraint on previously conjectured results.Comment: 18 pages, Latex, DAMTP-96-8