A comparison of CFD‐simulations and measurements of the temperature stratification in a mixing box of an air‐handling unit

This paper presents a comparison between CFD‐simulations and measurements of the temperature stratification in a mixing box of an air‐handling unit. We have used data from field measurements during a period of over a year for different outside temperatures. We performed two‐dimensional CFD‐simulations for four different outside temperatures with commercially available software. The measurements as well as the simulations show that the temperature difference between the upper part and the lower part of the duct downstream of the mixing box is considerable. It increases, as the outside temperature decreases. However, the discrepancies between the measurements and the simulations are large. The reasons for this are uncertain boundary conditions and modelling errors leading to an inaccurate simulation result. The stratification downstream of the mixing box implies large sensor errors and the use of the mixed air temperature for control and fault detection must therefore be questioned. Averaging sensors, which take a mean value over the duct section, can be used but do not consider differences in velocities and are therefore not accurate either. In order to, for example, use CFD as a tool to decide the optimal sensor location a more accurate model and more information regarding the boundary conditions is needed. Copyright © 2001 John Wiley & Sons, Ltd.     

Temporal and spatial associations of oestrogen receptor alpha and progesterone receptor in the endometrium of cyclic and early pregnant mares

Uterine function is primarily controlled by the combined actions of oestrogen and progesterone working through their cognate nuclear receptors. The mechanism of establishment of pregnancy in the mare is of interest because it involves prolonged pre-attachment and conceptus migration phases, and both invasive and non-invasive placental cell types, and as such has been an important comparative model. This study characterised regulation of oestrogen (ER) and progesterone (PR) receptors in the endometrium of the mare during the oestrous cycle and early pregnancy. Endometrial tissues collected during the oestrous cycle and early pregnancy were analysed for steady-state levels of ER and PR mRNA and protein. Steady-state levels of ER and PR mRNA were highest on days 0, 17 and 20 in cyclic mares and lowest on days 11 and 14. A day-by-status interaction was detected, indicating that day 17 and day 20 pregnant mares exhibited low levels of ER and PR compared with the corresponding days of the oestrous cycle. In situ hybridisation analyses showed receptor mRNA localisation primarily in the luminal epithelium (LE), glandular epithelium (GE) and stroma around oestrus. During dioestrus and early pregnancy, receptors were not detected in the LE, and were lower in the stroma and deeper GE. Changes in hybridisation intensity in these cell types were consistent with changes in mRNA levels detected by slot-blot hybridisation. ER and PR proteins were detected in the nuclei of LE, GE and stromal cells. Consistent with results from in situ hybridisation, levels of ER and PR immunoreactivity were higher around oestrus, declined to low levels during dioestrus and remained low during early pregnancy. Results described here for temporal and spatial changes in steroid receptor gene expression in mares show the greatest similarities with those described for cattle and sheep.     

The alpha1 and alpha2 isoforms of the AMP-activated protein kinase have similar activities in rat liver but exhibit differences in substrate specificity in vitro

The AMP-activated protein kinase (AMPK) is a heterotrimeric complex composed of a catalytic subunit (alpha) and two regulatory subunits (beta and gamma). Two isoforms of the catalytic subunit (alpha1 and alpha2) have been identified. We show here that the alpha1- and alpha2-containing complexes contribute approximately equally to total AMPK activity in rat liver. Furthermore, expression of alpha1 or alpha2 with beta and gamma in mammalian cells demonstrates that both complexes have equal specific activity measured with the SAMS peptide. Using variant peptides, however, we show that alpha1 and alpha2 exhibit slightly different substrate preferences, which suggest that the two isoforms could play different physiological roles within the cell.     

Filaments as optical waveguides in gallium-arsenide lasers

Experimental evidence is given in support of a dielectric-waveguide model for filaments in gallium-arsenide lasers. Measurements of the variation with current of the spectral-mode frequencies of a single-heterojunction gallium-arsenide laser have been carried out both below and above threshold. It is suggested that the frequency shifts above threshold are due to the formation of filaments in the laser. Changes in the far-field pattern support this theory.     

The impact of fine sediment accumulation on the survival of incubating salmon progeny: implications for sediment management

This paper draws on results from a recent research programme on the impact of fine sediment transport through catchments to present a case for the development of new approaches to improving the quality of salmonid spawning and incubation habitats. To aid the development of these programmes, this paper summarises the mechanisms by which fine sediment accumulation influences the availability of oxygen (O2) to incubating salmon embryos. The results of the investigation indicate that incubation success is inhibited by: (i) the impact of fine sediment accumulation on gravel permeability and, subsequently, the rate of passage of oxygenated water through the incubation environment; (ii) reduced intragravel O2 concentrations that occur when O2 consuming material infiltrates spawning and incubation gravels; and (iii) the impact of fine particles (clay) on the exchange of O2 across the egg membrane. It is concluded that current granular measures of spawning and incubation habitat quality do not satisfactorily describe the complexity of factors influencing incubation success. Furthermore, an assessment of the trends in fine sediment infiltration indicates that only a small proportion of the total suspended sediment load infiltrates spawning and incubation gravels. This casts doubt over the ability of current catchment-based land use management strategies to adequately reduce fine sediment inputs.     

Normal housing with specialized supports: A psychiatric rehabilitation approach to living in the community.

Presents a conceptual and historical overview of residential services for Ss with psychiatric disability and challenges the appropriateness and effectiveness of the "continuum of services" model. The authors propose that the goal of residential services should be to assist all people with psychiatric disabilities to choose, obtain, and maintain normal housing and that rehabilitation technology is currently available to accomplish this goal. Data indicate that despite high costs, most state mental health systems are continuing to make large scale investments in facility-based residential programs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Channel change and sediment transport in regulated U.K. rivers

The history of investigations of channel change consequent upon river regulation is traced from the late 1960s until the present. The associated sediment transport and depositional processes are also reviewed. Conveniently the approaches adopted historically have fallen into three basic groups, these are: (1) analyses of the changes in channel networks as evident in adjustments to hydraulic geometry related to catchment area; (2) analyses concerned with sediment transport processes and channel adjustments at the reach scale (typically utilizing regime-type concepts), and finally; (3) more recent attempts at an integrated approach utilizing holistic concepts of channel change over extended time periods. A major conclusion drawn from this review is that each reservoir-catchment system is unique, producing singular responses that cannot easily be integrated into a basic general model except at a facile level. The continuing lack of complete theoretical models of channel adjustment is a hindrance in predicting regulation effects and may be related to limited understanding of such factors as sediment supply dynamics and bank collapse mechanisms. Emphasis is placed on: the importance of the aggregational as well as the well-known degradational response of channels below dams; the recognition of suitable temporal frameworks; the potentially destabilizing effect of rare large floods; and the local effects of unregulated tributary inflows. In addition more sophisticated theory and analysis needs applying to the transport and subsequent deposition of suspended sediments in gravel-beds whilst the three-dimensional facies relationships of regulated river alluvial suites need clarification in the light of recent initiatives concerning the sedimentary architecture of other alluvial systems.