John A. Mitchell  J. N. Reddy 《International journal for numerical methods in engineering》1998,43(8):1383-1400

In this study, a multilevel, recursively defined preconditioner, for use with the Preconditioned Conjugate Gradient (PCG) algorithm in connection with the finite element analysis of elastostatics is developed. The preconditioner is constructed from a sequence of hierarchical vector spaces arising from the p-version of the finite element method. Results from parametric studies evaluating the effects of skewed elements, orthotropic material properties, and extreme span ratios, for p=2 and 3 are given. The results indicate that the preconditioner may be used to produce an efficient solver. The efficiency of the iterative procedure is illustrated using thin elastic solids. Results indicate that the preconditioner developed herein can be used to produce an efficient iterative solver for two- and three-dimensional problems in structural mechanics. © 1998 John Wiley & Sons, Ltd.  相似文献   

    

John W. Prados  George D. Peterson  Lisa R. Lattuca 《工程教育杂志》2005,94(1):165-184

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A.K. Salem  F.R.A.J. Rose  R.O.C. Oreffo  X. Yang  M.C. Davies  J.R. Mitchell  C.J. Roberts  S. Stolnik‐Trenkic  S.J.B. Tendler  P.M. Williams  K.M. Shakesheff 《Advanced materials (Deerfield Beach, Fla.)》2003,15(3):210-213

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Wintink  Amanda J.; Young  Nicole A.; Davis  Alicia C.; Gregus  Andrea; Kalynchuk  Lisa E. 《Canadian Metallurgical Quarterly》2003,117(3):632

Modeling fear in animals is a critical approach for identifying the neural mechanisms involved in human disorders such as generalized anxiety and panic. Amygdala kindling has proven useful in this regard because it produces dramatic increases in fearful behavior. The purpose of this experiment was to compare the behavioral effects of kindling in male and female rats. Compared with the sham-stimulated rats, the kindled male and female rats showed similar increases in fearful behavior, with some sex differences in fear-related open-field activity. They also showed decreased immobility in the forced-swim test and increased sucrose consumption. These results suggest that kindling-induced fear is generally similar in male and female rats and that kindling does not appear to induce depression-like behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   

    

Johnson  Jeffrey G.; Cohen  Patricia; Kotler  Lisa; Kasen  Stephanie; Brook  Judith S. 《Canadian Metallurgical Quarterly》2002,70(5):1119

Longitudinal data were used to investigate whether anxiety, depressive, disruptive, personality, or substance use disorders are associated with risk for the development of eating disorders during adolescence or early adulthood. Psychiatric disorders were assessed among 726 youths from a random community sample during adolescence and early adulthood. Depressive disorders during early adolescence were associated with elevated risk for the onset of eating disorders, dietary restriction, purging behavior, and recurrent weight fluctuations after preexisting eating problems and other psychiatric disorders were controlled statistically. Disruptive and personality disorders were independently associated with elevated risk for specific eating or weight problems. The present findings suggest that depressive disorders during early adolescence may contribute to the development of eating disorders during middle adolescence or early adulthood. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   

    

Robinson  E. J.; Champion  H.; Mitchell  P. 《Canadian Metallurgical Quarterly》1999,35(2):535

Children between the ages of 3 years 7 months and 6 years 5 months experienced a contradiction between what they knew or guessed to be inside a box and what they were told by an adult. The authors investigated whether children believed what they were told by asking them to make a final judgment about the box's content. Children tended to believe utterances from speakers who were better informed than they themselves were and to disbelieve those from less well-informed speakers, with no age-related differences. This behavior implies an understanding of the speaker's knowledge and suggests that children can learn from oral input while being appropriately skeptical of its truth. Children also gave explicit knowledge judgments on trials on which no utterances were given. Performance on knowledge trials was less accurate than, and unrelated to, performance on utterance trials. Research on children's developing explicit theory of mind needs to be broadened to include behavioral indexes of understanding the mind. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   

    

G Bokinsky  M Miller  K Ault  P Husband  J Mitchell 《Canadian Metallurgical Quarterly》1995,108(3):625-630

STUDY OBJECTIVE: To determine whether alterations of platelet reactivity occur during obstructive sleep apnea (OSA) and, if so, whether therapy with nasal-continuous positive airway pressure (N-CPAP) alters this reactivity. DESIGN: Patients with suspected moderate to severe OSA had blood drawn for spontaneous platelet aggregation (sAGG) and activation (sACT) measurements at hourly intervals during diagnostic polysomnography (PSG) and, in those with confirmed OSA, on a separate night during which N-CPAP was applied. SETTING: Tertiary care center sleep laboratory. PATIENTS: Six patients with OSA had matched blood samples drawn on both diagnostic and N-CPAP treatment nights. Five patients without confirmed OSA served as controls. INTERVENTIONS: N-CPAP was applied to those patients with OSA and pressures adjusted with goals of eliminating apneas; N-CPAP was then maintained through the night. MEASUREMENTS AND RESULTS: sACT and sAGG were measured using flow cytometric determination of P-selectin expression using a monoclonal antibody. Platelet aggregation was assessed by measuring the proportion of platelets larger than resting platelets by light scatter techniques. Mean values for sACT and sAGG were higher on the diagnostic night compared with treatment night (p = 0.001 and p = 0.003, analysis of variance, respectively). The mean baseline supine sACT compared with completion supine sACT for both diagnostic and N-CPAP nights also revealed significant differences (mean = 16.6 +/- 3.5% vs 36.9 +/- 7.5%, p = 0.04; and 11.9 +/- 3% vs 39.5 +/- 9.1%, p = 0.04). Platelet activation during sleep in five subjects without OSA resembles that found in patients with OSA during N-CPAP. CONCLUSIONS: Increased platelet sACT and sAGG occur during sleep in patients with OSA. This effect is greatly reduced by N-CPAP.  相似文献   

    

Taylor  Shelley E.; Kemeny  Margaret E.; Aspinwall  Lisa G.; Schneider  Stephen G.; Rodriguez  Richard; Herbert  Mark 《Canadian Metallurgical Quarterly》1992,63(3):460

In a cohort of gay men responding to the threat of AIDS, dispositional optimism was associated with less distress, less avoidant coping, positive attitudes as a coping strategy, and fewer AIDS-related concerns. Men who knew they were seropositive for HIV were significantly more optimistic about not developing AIDS than men who knew they were seronegative for HIV. This AIDS-specific optimism was related to higher perceived control over AIDS and to active coping among seropositive men only and to health behaviors in both serostatus groups. There was no relation of optimism to risk-related sexual behavior. It is concluded that optimism is psychologically adaptive without necessarily compromising health behavior. It is also concluded that it is useful to distinguish between event-based optimistic expectations and dispositional optimism. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   

    

RB Vogelaar  LW Mitchell  RW Kavanagh  AE Champagne  PV Magnus  MS Smith  AJ Howard  PD Parker  HA O'Brien 《Canadian Metallurgical Quarterly》1996,53(4):1945-1949

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Siviy  Stephen M.; Fleischhauer  Anne E.; Kerrigan  Lisa A.; Kuhlman  Sandra J. 《Canadian Metallurgical Quarterly》1996,110(5):1168

By using dorsal contacts and pinning to quantify play behavior in juvenile rats, it was found that the D? agonist, quinpirole, reduced both measures of play at doses greater than 0.05 mg/kg. Eticlopride, a D? antagonist, also reduced both measures of play and blocked the reduction caused by quinpirole. The effect of quinpirole on play was largely unaffected by concurrent administration of either a D? agonist (SKF 38393) or a D? antagonist (SCH 23390), suggesting that D? and D? receptors are functionally independent with respect to play behavior. Quinpirole also reduced overall activity, suggesting that the effects on play may not be selective to neural circuitry responsible for play behavior. Although low doses of quinpirole (0.001–0.03 mg/kg) had a tendency to increase pinning, this effect was not very robust. These data suggest that D? dopamine receptors may not have a major role in the control of play behavior in juvenile rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献