Stability ball versus office chair: comparison of muscle activation and lumbar spine posture during prolonged sitting

OBJECTIVE: The objective of the study was to evaluate the differences between sitting on a stability ball and in an office chair in terms of trunk muscle activation and lumbar spine posture. BACKGROUND: Stability balls have become increasingly popular as an alternative to office chairs to help reduce the prevalence of low back pain; however, little research has been conducted on their use as office chairs. METHODS: The 14 participants (7 men, 7 women) were required to sit on both a stability ball and an office chair for 1 hour each while performing various computer workstation tasks throughout the sitting periods. The activation of eight muscles and lumbar spine posture were measured and analyzed. RESULTS: Increased muscle activation in thoracic erector spinae (p = .0352), decreased pelvic tilt (p = .0114), and increased perceived discomfort (p < .0001) while sitting on the stability ball were observed. CONCLUSIONS: The small changes in biological responses when sitting on a stability ball as compared with an office chair, combined with the increased reported discomfort while on the ball, suggests its use for prolonged sitting may not be advantageous. APPLICATION: Prolonged sitting on a stability ball does not greatly alter the manner in which an individual sits, yet it appears to increase the level of discomfort. Therefore, it is important to fully explore a new chair design and consult scientific research before implementing its use.     

Percolation and the resistive transition of the critical temperature Tc of Nb3Sn

The relationship between the distribution of the critical temperature, the percolation function, and the resistive transition of the critical temperature is explored for polycrystalline Nb₃Sn. In the neighborhood of the critical temperature, Nb₃Sn is assumed to be a random mixture of superconducting and normal grains. Percolation concepts are applied to a study of the resistivity. A general analysis is made showing that the onset and shape of the resistive transition for composite conductors are determined by the percolation function and the distribution of the critical temperature. An approximate form of the percolation function is determined based on a linear FEM analysis. Example resistive transitions are calculated for an assumed normal distribution of the critical temperature. An argument is presented that relates grain orientation and strain dependence in Nb₃Sn. It is noted that a dependence of the distribution of T_c with strain, in addition to the usual shift in T_c with strain, would be the result of a strain dependence that is a function of grain orientation. The analysis shows the extent to which the slope of the resistive transition is a measure of the distribution of the critical temperature, and therefore a measure of the grain orientation strain sensitivity. Finally, a method is described to determine the percolation function experimentally.     

Physical, Mental, and Social Catastrophic Cognitions as Prognostic Factors in Cognitive-Behavioral and Pharmacological Treatments for Panic Disorder.

The authors explored the prognostic value of 3 different types of catastrophic cognitions in the treatment of panic disorder with and without mild-to-moderate agoraphobia using a sample of 143 participants who received either cognitive-behavioral therapy (CBT) or imipramine in a randomized controlled trial. Stronger fears of social catastrophes both prior to and following treatment with CBT or imipramine were associated with a poorer outcome. In contrast, cognitions involving physical or mental catastrophes were unrelated to outcome, regardless of whether these thoughts were measured prior to or following treatment. These findings are consistent with the notion that although the intensity of physical catastrophe cognitions may best discriminate between panic disorder and other anxiety disorders, it is the intensity of social catastrophe cognitions that is most closely tied to success in treating this disorder. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interpreting the Good Life: Growth Memories in the Lives of Mature, Happy People.

In 2 studies, the authors examined autobiographical memories for the presence of 2 growth orientations that were expected to correspond differentially to maturity and well-being, which are considered to be key facets of "the good life" by L. A. King (2001). Mature participants emphasized integrative memories (conceptual integration and learning), whereas happy participants emphasized intrinsic memories (humanistic concerns). Both kinds of growth memories correlated more strongly with eudaimonic than with hedonic measures of well-being. Growth memories were largely independent of Big Five traits in relation to maturity and well-being. Finally, older participants were more likely than younger participants to have greater maturity (marginally) and well-being, but this was in part explained by older participants' greater tendency to have growth memories. The discussion considers the role of growth memories in the intentional cultivation of the good life. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Overconfidence in Interval Estimates.

Judges were asked to make numerical estimates (e.g., "In what year was the first flight of a hot air balloon?"). Judges provided high and low estimates such that they were X% sure that the correct answer lay between them. They exhibited substantial overconfidence: The correct answer fell inside their intervals much less than X% of the time. This contrasts with choices between 2 possible answers to a question, which showed much less overconfidence. The authors show that overconfidence in interval estimates can result from variability in setting interval widths. However, the main cause is that subjective intervals are systematically too narrow given the accuracy of one's information-sometimes only 40% as large as necessary to be well calibrated. The degree of overconfidence varies greatly depending on how intervals are elicited. There are also substantial differences among domains and between male and female judges. The authors discuss the possible psychological mechanisms underlying this pattern of findings. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Self-generated validity and other effects of measurement on belief, attitude, intention, and behavior.

Drawing from recent developments in social cognition, cognitive psychology, and behavioral decision theory, we analyzed when and how the act of measuring beliefs, attitudes, intentions, and behaviors affects observed correlations among them. Belief, attitude, or intention can be created by measurement if the measured constructs do not already exist in long-term memory. The responses thus created can have directive effects on answers to other questions that follow in the survey. But even when counterparts to the beliefs, attitudes, and intentions measured already exist in memory, the structure of the survey researcher's questionnaire can affect observed correlations among them. The respondent may use retrieved answers to earlier survey questions as inputs to response generation to later questions. We present a simple theory predicting that an earlier response will be used as a basis for another, subsequent response if the former is accessible and if it is perceived to be more diagnostic than other accessible inputs. We outline the factors that determine both the perceived diagnosticity of a potential input, the likelihood that it will be retrieved, and the likelihood that some alternative (and potentially more diagnostic) inputs will be retrieved. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of atmospheric pressure photoionization and atmospheric pressure chemical ionization for normal-phase LC/MS chiral analysis of pharmaceuticals

In this work, we compared APPI and APCI for normal-phase LC/MS chiral analysis of five pharmaceuticals. Performance was compared both by FIA and by on-column analysis using a ChiralPak AD-H column under optimized conditions. By comparison, APPI generated more reproducible signals and was less susceptible to ion suppression than APCI. APPI generated higher peak area and lower baseline noise, and therefore much higher S/N ratios. APPI sensitivity (i.e., S/N ratio) was approximately 2-130 times higher than APCI by FIA and was approximately 2.6-530 times higher than APCI by on-column analysis depending on specific compounds. The better APPI sensitivity as compared to APCI was more dramatic by on-column analysis than by FIA. APCI sensitivity was degraded by ion suppression caused by LC column bleeding components and by elevated APCI baseline noise relative to APPI. On-column APPI LODs (at S/N = 3) were 83, 16, 17, 95, and 7 pg for enantiomer #1, and 104, 23, 19, 122, and 17 pg for enantiomer #2 for benzoin, naringenin, mianserin, mephenesin, and diperodon, respectively, on a Waters ZQ. APPI offers no concern of explosion hazard relative to APCI corona needle discharge or ESI high voltage discharge when flammable solvents (e.g., hexane) are used as mobile phases. Whether APPI dopants are required depends on the IP(s) of mobile-phase solvent(s) and solvent complexes, and photon energies of VUV lamps. Dopant was not necessary for hexane-based mobile phases due to their self-doping effects. Dopants did enhance Kr lamp APPI sensitivity when MeOH was used as the mobile phase. However, dopants became unnecessary for the MeOH mobile phase when the Ar lamp was used.     

Direct sampling of chemical weapons in water by photoionization mass spectrometry

The vulnerability of water supplies to toxic contamination calls for fast and effective means for screening water samples for multiple threats. We describe the use of photoionization (PI) mass spectrometry (MS) for high-speed, high-throughput screening and molecular identification of chemical weapons (CW) threats and other hazardous compounds. The screening technology can detect a wide range of compounds at subacute concentrations with no sample preparation and a sampling cycle time of approximately 45 s. The technology was tested with CW agents VX, GA, GB, GD, GF, HD, HN1, and HN3, in addition to riot agents and precursors. All are sensitively detected and give simple PI mass spectra dominated by the parent ion. The target application of the PI MS method is as a routine, real-time early warning system for CW agents and other hazardous compounds in air and in water. In this work, we also present comprehensive measurements for water analysis and report on the system detection limits, linearity, quantitation accuracy, and false positive (FP) and false negative rates for concentrations at subacute levels. The latter data are presented in the form of receiver operating characteristic curves of the form of detection probability P(D) versus FP probability P(FP). These measurements were made using the CW surrogate compounds, DMMP, DEMP, DEEP, and DIMP. Method detection limits (3sigma) obtained using a capillary injection method yielded 1, 6, 3, and 2 ng/mL, respectively. These results were obtained using 1-microL injections of water samples without any preparation, corresponding to mass detection limits of 1, 6, 3, and 2 pg, respectively. The linear range was about 3-4 decades and the dynamic range about 4-5 decades. The relative standard deviations were generally <10% at CW subacute concentrations levels.     

Threshold voltage instability characteristics of HfO2 dielectrics n-MOSFETs

In this paper, the threshold voltage instability characteristics of HfO₂ high-k dielectric are discussed. The results from various stress bias conditions including DC and AC with variations of frequency, duty cycle, and polarity provide additional insights into the intrinsic behavior and the trapping dynamics of high-k materials. A reduced threshold voltage shift was observed at higher frequency and lower duty cycle under AC positive unipolar stress compared to DC stress. Similarly, the degradation of maximum transconductance was also reduced with AC stress. However, subthreshold swing changes were found to be negligible and fairly independent of stress frequencies and duty cycles under AC positive unipolar stress.When different polarity of stress, such as positive, negative, and bipolar stress was applied, it was observed that frequency and duty cycle dependencies were still valid in all three conditions. In contrast to positive stress, negative stress showed a decrease in the threshold voltage shift. Bipolar stress resulted in the highest threshold voltage instability, but the degradation in transconductance and subthreshold swing was actually smaller than those in negative unipolar stress. The bulk trap of HfO₂ dielectric, which is proportional to its physical thickness, is believed to be the primary factor for threshold voltage shift. AC unipolar operation would allow a higher 10-year lifetime operating voltage than the DC condition. In addition to experimental results, a plausible mechanism has been proposed.