Exponential Stability of Slowly Time-Varying Nonlinear Systems

Let be a time-varying vector field depending on t containing a regular and a slow time scale (α large). Assume there exist a k (τ)≥1 and a γ(τ) such that ∥x _τ(t, t ₀, x ₀)∥≤k(τ) e ^{−γ(τ)(t−t0)}∥x ₀∥, with x _τ(t, t ₀, x ₀) the solution of the parametrized system with initial state x ₀ at t ₀. We show that for α sufficiently large is exponentially stable when “on average”γ(τ) is positive. The use of this result is illustrated by means of two examples. First, we extend the circle criterion. Second, exponential stability for a pendulum with a nonlinear slowly time-varying friction attaining positive and negative values is discussed. Date received: January 22, 2000. Date revised: April 14, 2001.     

Psychological consequences of an exercise training program for a paraplegic man: A case study.

Examined the effects of a 12-wk exercise training program on the mood states (assessed via the Profile of Mood States [POMS]) of a 27-yr-old spinal-cord-injured male in a rehabilitation hospital. S was administered the POMS immediately before and after the program and once each week during the program. S demonstrated major mood changes following exercise training, indicating a significant decrease in tension, depression, anger, fatigue, and confusion and a significant increase in vigor. Findings support the hypothesis that vigorous physical exercise can be a useful therapeutic strategy with the disabled. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Classroom context and teachers' perceptions of problem behaviors.

73 teachers of kindergarten to 8th grade viewed disruptive- or nondisruptive-context videotaped vignettes and rated each portrayal in terms of severity, manageability, tolerance, and contagion to investigate the effects of context on Ss' perceptions of 5 problem behaviors (blaming, poor peer cooperation, negative aggression, inattention, and failure anxiety). ANCOVA showed that contagion yielded significant differences (stronger within the disruptive context), suggesting that the target child was held responsible for the classroom disorder. Correlational data explained the relationship between the 4 areas, suggesting a dichotomy between quality (type of behavior) and quantity (degree or severity of behavior) for interpreting perceptions. Low tolerance was associated with higher levels of severity and more outer-directed behaviors. Contagion had more active, observable components and was related more to the qualitative dimension. Manageability (also active, observable, and teacher centered) was strongly influenced by quantitative factors (greater extremes of atypical behavior). (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lipoprotein lipase activity and its relationship to high milk fat transfer during lactation in grey seals

Lipoprotein lipase regulates the hydrolysis of circulating triglyceride and the uptake of fatty acids by most tissues, including the mammary gland and adipose tissue. Thus, lipoprotein lipase is critical for the uptake and secretion of the long-chain fatty acids in milk and for the assimilation of a high-fat milk diet by suckling young. In the lactating female, lipoprotein lipase appears to be regulated such that levels in adipose tissue are almost completely depressed while those in the mammary gland are high. Thus, circulating fatty acids are directed to the mammary gland for milk fat production. Phocid seals serve as excellent models in the study of lipoprotein lipase and fat transfer during lactation because mothers may fast completely while secreting large quantities of high fat milks and pups deposit large amounts of fat as blubber. We measured pup body composition and milk fat intake by isotope (deuterium oxide) dilution and plasma post-heparin lipoprotein lipase activity in six grey seal (Halichoerus grypus) mother-pup pairs at birth and again late in the 16-day lactation period. Maternal post-heparin lipoprotein lipase activity increased by an average of four-fold by late lactation (P = 0.027), which paralleled an increase in milk fat concentration (from 38 to 56%; P = 0.043). Increasing lipoprotein lipase activity was correlated with increasing milk fat output (1.3-2.1 kg fat per day) over lactation (P = 0.019). Maternal plasma triglyceride (during fasting) was inversely correlated to lipoprotein lipase activity (P = 0.027) and may be associated with the direct incorporation of long-chain fatty acids from blubber into milk. In pups, post-heparin lipoprotein lipase activity was already high at birth and increased as total body fat content (P = 0.028) and the ratio of body fat: protein increased (P = 0.036) during lactation. Although pup plasma triglyceride increased with increasing daily milk fat intake (P = 0.023), pups effectively cleared lipid from the circulation and deposited 70% of milk fat consumed throughout lactation. Lipoprotein lipase may play an important role in the mechanisms involved with the extraordinary rates of fat transfer in phocid seals.     

Secretarial attitudes towards word processors as a function of familiarity and locus of control

The purpose of the present study was to investigate dimensions of secretarial anxiety, eagerness, and curiosity with respect to word processing equipment. Such variables as familiarity, formal training, physical proximity to the equipment, degree of influence in the decision to acquire a word processor, and frequency of use were seen as potential predictors of such attitudes. Additionally, two trait-like dimensions were measured, locus of control and complexity. Questionnaires were sent to 408 secretaries employed at a mid-western university. The response rate was 59 per cent (n = 241). People who had not used word processing equipment were more anxious than those individuals who had. Moreover, frequency of use for people with experience was related to greater change in anxiety levels. While familiarity reduced anxiety, it also tended to reduce curiosity. Frequency of word processor use was related to several variables. For instance, frequency of use was related to how positively the person evaluated the processor as affecting their work capabilities. Heavy users felt that the manuals were less helpful. Internally controlled individuals were more eager, curious and less anxious, while cognitively complex individuals were more curious about word processors. The applied implications of the findings are discussed.     

Injuries to the phrenic nerve resulting in diaphragmatic paralysis with special reference to stretch trauma

The effectiveness of purines and purine analogues as inducers of erythroid differentiation in cultured murine erythroleukemia cells has been investigated. These cell lines have previously been shown to differentiate in vitro in response to dimethylsulfoxide (DMSO) and a number of other polar solvents. Two purine analogues, 6-thioguanine and 6-mercaptopurine, as well as the naturally occuring purine, purine, hypoxanthine, are shown to be extremely potent inducers. 6-Thioguanine is effective at a concentration of 0.06 mM, 750 fold lower than the DMSO concentration required for equivalent induction. 6-Mercaptopurine and hypoxanthine are effective inducers at a concentration of approximately 2 mM. Accumulation of globin mRNA was monitored during induction with purine inducers and shown to be similar in amount to globin mRNA levels reached in DMSO-induced cultures. Induction of differentiation by all three compounds follows a similar time course to induction with DMSO. All three compounds are potent inducers of HGPRT (hypoxanthine-guanine phosphoribosyltransferase)-negative cell lines; hence incorporation of purines into DNA is not required for induction of differentiation. Comparison of these compounds with other purines and purine analogues suggests a high degree of specificity in their interaction with a cellular target.     

Subdoctoral education in psychology: A study of issues and attitudes.

Discusses several psychological conferences and committee's attitudes toward the desirability of "programs to train for psychological service at less than the doctoral level." 7 central areas of contention concerning subdoctoral training are (1) type of training, (2) level of training, (3) responsibility for training, (4) locus of training, (5) degree and/or title, (6) roles and duties, and (7) implications for psychology. The 7 issues served as the basis of the specific questions in a large scale survey. The sample (N = 4308) included American Psychological Association members of the Clinical, School, and Counseling Divisions of Psychology and chairmen of graduate departments of psychology. Results indicate that "the large majority of psychologists recognize the need for and approve the training of people at less than the doctoral level to do psychological work." A consensus as to how this is to be implemented was not reached. (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Redox speciation of copper in rainwater: temporal variability and atmospheric deposition

Copper speciation was determined in 68 rainwater samples collected in Wilmington, NC, from August 25, 2000, to September 24, 2002. Volume-weighted average concentrations of Cu(total), dissolved Cu(II), and dissolved Cu(I) were 5.3, 3.2, and 1.4 nM, respectively, with a significantly higher ratio of Cu(II)/Cu(I) in summer relative to winter events. The concentrations of all Cu species were higher in storms of continental origin relative to marine-dominated events, suggesting anthropogenic and/or terrestrial sources are important contributors of Cu in precipitation. Concentrations of strong Cu-complexing ligands were consistently lower than dissolved Cu concentrations, indicating a significant portion, but not all, of the dissolved Cu in rainwater is strongly complexed. A portion of these ligands, in addition to the sulfite and chloride in precipitation, may be Cu(I)-complexing ligands, which may explain the resistance of Cu(I) against oxidation in rainwater. Using our rainwater concentration data along with other published rainwater Cu concentrations and an estimate for total global annual rain, the total global flux of Cu removed from the atmosphere via wet deposition is 150 x 106 kg yr(-1). This represents complete removal of the estimated Cu input into the troposphere and indicates essentially all Cu released into the global atmosphere is removed by rain.     

Monitoring particle adsorption by use of laser reflectometry near the critical angle

We investigate the use of laser reflectometry near the critical angle to monitor particle adsorption onto a flat glass surface. Experimental results show that positive particles are adsorbed onto the glass surface and that their adsorption kinetics depend strongly on the volume fraction occupied by the particles in suspension but not appreciably on the particle size. The reflectance near the critical angle is dominated by the particles on the surface, with the contribution of the particles in suspension being very low. We compare the reflectance change near the critical angle with the change in reflectance near the Brewster angle when particles are adsorbed onto the glass surface. We find that reflectometry near the critical angle is 3000 times more sensitive than it is near the Brewster angle. Some optical images are presented to validate our results.     

Detection of trace fatty acids in fats and oils by urea fractionation and gas-liquid chromatography

The detection of trace fatty acids (<0.1%) in a fat or oil by gas-liquid chromatography is possible when the methyl esters are fractionated with urea to provide a number of less complex fractions. Identification and estimation of trace fatty acids is simplified by quantitative removal of other fatty acids having similar gas chromatographic retention times. A detailed knowledge of the order in which inclusion compounds are formed was obtained by fractionating a complex mixture of marine and vegetable fatty acids. In addition, lanolin was fractionated to determine the preferential order in which saturated, branched chain (iso-, anteiso-) and hydroxy acids form inclusion compounds. Using urea fractionation and gas chromatography, 52 trace fatty acids were tentatively identified in butter, 30 in lard, and 26 in walnut oil. Presented at the AOCS Meeting in New Orleans, 1964.