Thermal entrance effects in a thermoacoustic stacked screen regenerator

Thermoacoustic cryocoolers are of raising interest because they are cost effective and reliable. The underlying heat pumping process occurs in the regenerator, where a sound wave interacts with a solid matrix material. Stacked screens are frequently used to build regenerators for thermoacoustic applications because of their favorable thermal properties and vast mesh sizes. One dimensional codes are commonly used for estimating the performance of thermoacoustic cryocoolers. While these codes are a useful tool in thermoacoustic device design, they do not incorporate entrance effects at the extremities of the regenerator or the resulting convective effects. In this paper these effects are investigated by means of a full Navier-Stokes solution of the flow and heat transfer in a geometrical reduced model of a regenerator. It is shown that convective effects play a role at low pressure amplitudes. A convection driven heat pumping process occurring at the extremities of the regenerator is described. Furthermore, a geometrical study is conducted to estimate the optimal opening of the stacked screen for ideal heat transfer

The influence of poultry litter biochar on early season cotton growth

Cotton is known for being sensitive to cool, wet soils, especially in the early stages of growth. Amendments to soil can aid cotton seedlings in development and nutrient uptake. However, soil amendments can be costly and detrimental to the environment, and alternatives such as the addition of biochar have been considered. Biochar is produced from biomass that has gone through pyrolysis and has been shown to improve plant yield, microbial response, soil structure, soil cation–exchange capacity, and water use efficiency. This study was conducted to evaluate the effect of biochar on early season cotton growth. The aim of this study was to determine whether biochar aids nutrient uptake and seedling development during the seedling’s life cycle. The study was established in October 2013 in the greenhouse at the University of Arkansas using a randomized complete block design with three replications. Treatments included a control with no fertilizer or biochar, a control with fertilizer (56 kg N/ ha) and no biochar, and two fertilizer treatments (0 or 56 kg N/ ha) each with 1500 or 3000 kg/ha biochar. Plants were grown for eight weeks then harvested to collect plant height, plant fresh weight, plant dry weight, and leaf area. Data showed that the highest level of biochar with additional fertilizer provided the best growth response in plant height, fresh weight dry weight, and leaf area at 27.52 cm, 14.7g, 1.87 g, and 419.48 cm2 , respectively

Vulnerability to xylem cavitation and the distribution of sonoran desert vegetation

Journal ArticleWe studied 15 riparian and upland Sonoran desert species to evaluate how the limitation of xylem pressure (Vx) by cavitation corresponded with plant distribution along a moisture gradient. Riparian species were obligate riparian trees (Fraxinus velutina, Populus fremontii, and Salix gooddingii), native shrubs (Baccharis spp.), and an exotic shrub (Tamarix ramosissima). Upland species were evergreen (Juniperus monosperma, Larrea tridentata), drought-deciduous (Ambrosia dumosa, Encelia farinosa, Fouquieria splendens, Cercidium microphyllum), and winter-deciduous (Acacia spp., Prosopis velutina) trees and shrubs

Allelic losses in carcinoma in situ and testicular germ cell tumours of adolescents and adults: evidence suggestive of the linear progression model

Testicular germ cell tumours (TGCTs) may arise through a process of multi-step carcinogenesis, and loss of heterozygosity (LOH) at specific loci is likely to be an important early event, although this has not been studied in detail. In order to explore the pathogenetic relationships among TGCTs, we investigated the genetic changes in testicular tumours that exhibit a disease continuum through the precursor carcinoma in situ (CIS) to either seminoma (SE) and/or non-seminomatous germ cell tumour (NSGCT). Universal amplification has been performed on 87 TGCT specimens and 36 samples of CIS cells microdissected from single paraffin-embedded tumour sections from 40 patients, including multiple specimens of CIS and TGCT cells of varied histology microdissected from 24 individual patients. Seventy-seven microsatellite markers were used to assay these samples for LOH at candidate regions selected from the literature, mapping to 3q, 5q, 9p, 11p, 11q, 12q, 17p and 18q. Construction of deletion maps for each of these regions identified common sites of deletion at 3q27–q28, 5q31, 5q34–q35, 9p22–p21 and 12q22, which correlate with allelic losses we have also observed in the precursor CIS cells. Evidence for allelic loss at 3q27–q28 was observed in all of the embryonal carcinoma samples analysed. We conclude that inactivation of gene(s) within these regions are likely to be early events in the development and progression of TGCTs. These results also provide molecular evidence in support of the hypothesis that SE is an intermediate stage of development within a single neoplastic pathway of progression from CIS precursor cells to NSGCT. © 2000 Cancer Research Campaig