A check on the numerical stability of frame analysis solutions

A method of checking numerical instability in a frame solution is to compare the values of ‘decomposed’ loading diagonal elements of the structural stiffness matrix with their original values. Using this comparison a number of practical cases are studied to indicate how situations in which numerical instability is likely can be identified.     

THE EMBRYO OF BARLEY IN RELATION TO MODIFICATION OF THE ENDOSPERM

Differential dissection of the embryo of barley grains, followed by observation of the extent of modification and assessment of α-amylase production in the endosperm, has shown that the various organs of the embryo make the following different contributions to modification. The isolated scutellum has a very limited ability to produce α-amylase and its powers of enzyme secretion are largely restricted to the peripheral region where aleurone cells are present. The stimulus which initiates enzyme formation in the aleurone is largely derived from the nodal region of the embryo, especially from the base of the node where subsidiary rootlets are formed; the scutellum apparently lacks the means of producing this stimulus. Translocation of the enzyme-inducing hormone from embryo to aleurone takes place through the apical half of the scutellum in which vascular tissue develops; this preferred route of translocation partially accounts for the asymmetric pattern of modification normally observed. Removal of the first foliar leaf from within the coleoptile allows increased production of α-amylase in the endosperm: this leaf can be regarded as a natural consumer of gibberellin.     

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)     

Lexical decision as an indirect test of memory: Repetition priming and list-wide priming as a function of type of encoding.

Two experiments examined priming in the lexical decision task, an indirect test of memory. Experiment 1 manipulated type of processing during study of unrelated word pairs. Recognition of individual words benefited more from semantic than from nonsemantic processing. Repetition priming in lexical decision depended on the context in which the target appeared. Targets preceded at test by unstudied primes showed greater repetition priming if processed nonsemantically during study; targets preceded at test by studied primes were not affected by type of processing at study. Interestingly, studied targets were facilitated more by studied than by unstudied primes regardless of whether the prime came from the same pair as the target. This list-wide episodic priming occurred under all four processing conditions in Experiment 1 (consonant counting, rote rehearsal, pleasantness rating, and sentence generation) with a 250-ms stimulus onset asynchrony. Experiment 2 showed that this list-wide episodic priming disappeared by 1,000 ms, suggesting that it had resulted from relatively transient activation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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.     

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.