A critical appraisal of empirical equations and models for the prediction of the coefficient of reaeration of deoxygenated water

Existing equations for the prediction of the reaeration coefficient of deoxygenerated water are reviewed, and checked for agreement with a wide range of data, covering widely different physical and hydraulic conditions.It is demonstrated that none of these equations permits reliable prediction of reaeration rate. sufficiently accurate for purposes of effluent control. It appears likely that this is because none of the published relations correctly or fully describes the mechanism of mass transfer pertaining to the open-channel flow situation. This is borne out by the dimensionally inhomogeneous, and hence incomplete, nature of those equations which provide the best general prediction of reaeration coefficient.     

Assessing the influence of climate variability on atmospheric concentrations of polychlorinated biphenyls using a global-scale mass balance model (BETR-global)

We introduce a new global-scale multimedia contaminant fate model (the Berkeley-Trent Global Model; BETR-Global) that integrates global climate data from the National Centers for Environmental Prediction (NCEP). BETR-Global represents the global environment as a connected set of 288 multimedia regions on a 15 degrees grid. We evaluate the model by simulating the global fate and transport of seven PCB congeners over a 70 year period and find satisfactory agreement between model output and observations of atmospheric PCB concentrations at 11 long-term monitoring stations in the Northern Hemisphere. We demonstrate the use of the model as a tool for understanding global pollutant dynamics by examining the hypothesis that variability in global-scale climate conditions, as reflected bythe North Atlantic Oscillation (NAO), influences atmospheric PCB concentrations in the Northern Hemisphere. We estimate that the maximum variability in atmospheric PCB concentrations attributable to NAO variability is approximately a factor of 2. The influence of variability in the NAO on PCB concentrations in air is most likely to be observed in the winter and spring at monitoring sites in Northern Europe and the Arctic. Analysis of long-term monitoring data from 11 sites shows some statistically significant relationships between NAO indices and atmospheric PCB concentrations during the winter and spring. Giving consideration to competing factors that influence atmospheric PCB concentrations, longer time series of monitoring data are required to fully evaluate the modeling results and to improve our understanding of the role of climate variability on the long-term fate of persistent semivolatile pollutants.     

An empirical study of a CDC 844-41 disk subsystem

Three methods (seek overlap, seek arm scheduling, static file repositioning) for improvement of disk subsystem performance are reviewed. Detailed measured data are reported for seek time, probability of zero-length seek, latency, and transfer time, for a 12-spindle CDC 844-41 disk subsystem shared between two CDC Cyber 170/750 central processors. The probability of zero-length seeks is shown to be high, and the spindle queue lengths are observed to be low. The transfer time data are very different from the data published by others for IBM systems. A detailed simulation model of the measured system is shown to validate. This model is then used to demonstrate that seek arm scheduling is unlikely to produce much improvement, that static file repositioning can improve performance by about 20%, and that seek overlap can almost double the interactive capacity of the system measured.     

Glucocorticoids: Fuelling the Fire of Atherosclerosis or Therapeutic Extinguishers?

Glucocorticoids are steroid hormones with key roles in the regulation of many physiological systems including energy homeostasis and immunity. However, chronic glucocorticoid excess, highlighted in Cushing’s syndrome, is established as being associated with increased cardiovascular disease (CVD) risk. Atherosclerosis is the major cause of CVD, leading to complications including coronary artery disease, myocardial infarction and heart failure. While the associations between glucocorticoid excess and increased prevalence of these complications are well established, the mechanisms underlying the role of glucocorticoids in development of atheroma are unclear. This review aims to better understand the importance of glucocorticoids in atherosclerosis and to dissect their cell-specific effects on key processes (e.g., contractility, remodelling and lesion development). Clinical and pre-clinical studies have shown both athero-protective and pro-atherogenic responses to glucocorticoids, effects dependent upon their multifactorial actions. Evidence indicates regulation of glucocorticoid bioavailability at the vasculature is complex, with local delivery, pre-receptor metabolism, and receptor expression contributing to responses linked to vascular remodelling and inflammation. Further investigations are required to clarify the mechanisms through which endogenous, local glucocorticoid action and systemic glucocorticoid treatment promote/inhibit atherosclerosis. This will provide greater insights into the potential benefit of glucocorticoid targeted approaches in the treatment of cardiovascular disease.     

Visual word recognition: A dissociation of lexical and semantic processing.

These experiments illustrate 2 new dissociations in word-recognition tasks. In one, relatedness facilitated lexical decision but impaired searching for a common letter in the same pairs of words (a cross-over interaction between relatedness and task). In the other dissociation, lexicality facilitated performance (words processed faster than nonwords) while relatedness impaired performance (related words processed slower than unrelated words) in the letter search task. Two classes of explanation are discussed. In the first, the perception of relatedness serves to focus attention to the word level, thereby making explicit letter level processing more difficult and/or increasing the number of competing lexical entries via priming. In the second, spreading inhibition makes related words more difficult to process than unrelated words. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

PASAT performance and the pattern of uptake of 99mTc-exametazime in brain estimated with single photon emission tomography

The effect of the paced auditory serial addition test (PASAT) on the regional uptake of 99mTc-exametazime was determined by single photon emission computed tomography. Twenty insulin-treated diabetic outpatients were scanned at rest and during the performance of the PASAT task using split-dose injection of tracer. When resting and activation scans were compared there were significant decreases in tracer uptake in the right anterior cingulate and left posterior cingulate areas during PASAT activation. The findings are compared with previous studies which had implicated the anterior cingulate area in the mechanisms of attention in humans and other animals. The potentially confounding role of anxiety during attentional tasks is discussed.     

Word frequency effects on recall, recognition, and word fragment completion tests.

In 3 experiments, the effect of word frequency on an indirect word fragment completion test and on direct free-recall and Yes–no recognition tests was investigated. In Experiment 1, priming in word fragment completion was substantially greater for low-frequency words than for high-frequency words, but free recall was unaffected. Experiment 2 replicated the word fragment completion result and showed a corresponding effect in recognition. Experiment 3 replicated the low-frequency priming advantage in word fragment completion with the set of words that P. L. Tenpenny and E. J. Shoben (1992) had used in reporting the opposite pattern in word fragment completion. Using G. Mandler's (1980) dual-process theory, the authors argue that recognition and word fragment completion tests both rely on within-item integration that influences familiarity, whereas recall hinges on elaboration that influences retrievability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recognition memory in depression.

Research suggests that the poor performance of depressed patients on memory tests reflects cautious response criteria rather than reduced accessibility of memories. Studies of recognition memory enable this issue to be addressed. The present experiment provides the first clear demonstration of a deficit in recognition memory in depression that is not explicable in terms of response bias. A subsidiary concern was to examine the effect of requiring subjects to vocalize words on presentation. This had no significant effects on "hits," but it interacted with depression on "false alarms," suggesting that discrepant claims in the literature regarding the effects of depression on false alarms may be attributable to procedural variations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Free flaps in the aged and infirm

Some of the most dramatic advances in reconstructive surgery have involved microvascular free-flap transfers. Although initial studies stressed the need for the procedures to be restricted to the healthy, with no evidence of vascular disease, it has become apparent that such restrictions need not apply if adequate patient care is available. Refinements of technique and development of new operations have made the free flap available to all. In particular, the procedure has been found to have unique benefits in the elderly and infirm population.