Showing papers by "University of Wisconsin–Milwaukee published in 1992"

Simple Constructions of Almost k-wise Independent Random Variables

Abstract: We present three alternative simple constructions of small probability spaces on n bits for which any k bits are almost independent. The number of bits used to specify a point in the sample space is (2 + o(1)) (log log n + k/2 + log k + log 1/ϵ), where ϵ is the statistical difference between the distribution induced on any k bit locations and the uniform distribution. This is asymptotically comparable to the construction recently presented by Naor and Naor (our size bound is better as long as ϵ < 1/(k log n)). An additional advantage of our constructions is their simplicity.

Selective transcatheter ablation of the fast and slow pathways using radiofrequency energy in patients with atrioventricular nodal reentrant tachycardia

Abstract: BACKGROUND The safety and efficacy of selective fast versus slow pathway ablation using radiofrequency energy and a transcatheter technique in patients with atrioventricular nodal reentrant tachycardia (AVNRT) were evaluated. METHODS AND RESULTS Forty-nine consecutive patients with symptomatic AVNRT were included. There were 37 women and 12 men (mean age, 43 +/- 20 years). The first 16 patients underwent a fast pathway ablation with radiofrequency current applied in the anterior/superior aspect of the tricuspid annulus. The remaining 33 patients initially had their slow pathway targeted at the posterior/inferior aspect of the right interatrial septum. The fast pathway was successfully ablated in the initial 16 patients and in three additional patients after an unsuccessful slow pathway ablation. A mean of 10 +/- 8 radiofrequency pulses were delivered; the last (successful) pulse was at a power of 24 +/- 7 W for a duration of 22 +/- 15 seconds. Four of these 19 patients developed complete atrioventricular (AV) block. In the remaining 15 patients, the post-ablation atrio-His intervals prolonged from 89 +/- 30 to 138 +/- 43 msec (p less than 0.001), whereas the shortest 1:1 AV conduction and effective refractory period of the AV node remained unchanged. Ten patients lost their ventriculoatrial (VA) conduction, and the other five had a significant prolongation of the shortest cycle length of 1:1 VA conduction (280 +/- 35 versus 468 +/- 30 msec, p less than 0.0001). Slow pathway ablation was attempted initially in 33 patients and in another two who developed uncommon AVNRT after successful fast pathway ablation. Of these 35 patients, 32 had no AVNRT inducible after 6 +/- 4 radiofrequency pulses with the last (successful) pulse given at a power of 36 +/- 12 W for a duration of 35 +/- 15 seconds. After successful slow pathway ablation, the shortest cycle length of 1:1 AV conduction prolonged from 295 +/- 44 to 332 +/- 66 msec (p less than 0.0005), the AV nodal effective refractory period increased from 232 +/- 36 to 281 +/- 61 msec (p less than 0.0001), and the atrio-His interval as well as the shortest cycle length of 1:1 VA conduction remained unchanged. No patients developed AV block. Among the last 33 patients who underwent a slow pathway ablation as the initial attempt and a fast pathway ablation only when the former failed, 32 (97%) had successful AVNRT abolition with intact AV conduction. During a mean follow-up of 6.5 +/- 3.0 months, none of the 49 patients had recurrent tachycardia. Forty patients had repeat electrophysiological studies 4-8 weeks after their successful ablation, and AVNRT could not be induced in 39 patients. CONCLUSIONS These data suggest that both fast and slow pathways can be selectively ablated for control of AVNRT: Slow pathway ablation, however, by obviating the risk of AV block, appears to be safer and should be considered as the first approach.

Stock prices and the effective exchange rate of the dollar

Abstract: The literature on the relation between stock prices and exchange rates is very poor and includes few studies that have argued that exchange rate changes do effect stock prices.By relying on the portfolio approach to exchange rate determination, it is argued that a change in stock prices could also have an impact on exchange rates, i.e. there could be a two-way relationship between exchange rates and stock prices. Granger concept of causality as well as cointegration technique are employed to support this conjecture. The empirical results show that there is bidirectional causality between stock prices measured by S&P 500 index and the effective exchange rate of the dollar, at least in the short-run. The cointegration analysis reveals that there is no long-run relationship between two variables.

Searching for a mobile intruder in a polygonal region

Abstract: The problem of searching for a mobile intruder in a simple polygon by a single mobile searcher is considered. This paper investigates the capabilities of searchers having different degrees of visibility by introducing the searcher having k flashlights whose visibility is limited to k rays emanating from his position, and the searcher having a point light source who can see in all directions simultaneously. This paper presents necessary and sufficient conditions for a polygon to be searchable by various searchers. The paper also introduces a class of polygons for which the searcher having two flashlights is as capable as the searcher having a point light source, and it gives a simple necessary and sufficient condition for such polygons to be searchable by the searcher having two flashlights. The complexity of generating a search schedule under some of these conditions is also discussed. Many of the results are proved using chord systems that represent the visibility relations among the vertices and edges o...

Reducing back stress to nursing personnel: an ergonomic intervention in a nursing home

Abstract: A prospective epidemiologic study was conducted in two units (140 beds and 57 nursing assistants) of a nursing home to demonstrate the efficacy of an ergonomic intervention strategy to reduce back stress to nursing personnel. The total programme involved the following: determining patient handling tasks perceived to be most stressful by the nursing assistants (NAs); performing an ergonomic evaluation of these tasks; and conducting a laboratory study to select patient transferring devices perceived to produce less physical stress than existing manual patient-handling methods. The intervention phase included training NAs in the use of these devices, modifying toilets and shower rooms, and applying techniques to patient care. Immediately after completing the intervention programme, a post-intervention analysis (which lasted eight months in unit 1 and four months in unit 2) was performed. A biomechanical evaluation of the physical demands required to perform stressful patient-handling tasks showed that the me...

The Impact of Representative Bureaucracies: Educational Systems and Public Policies

Abstract: Studies of representative bureaucracies are staples of public administration research; however, because of a variety of methodological problems, too few have been able to address the basic "so what?" question. Do bureaucracies with different levels of representativeness produce different policy outputs and have different policy impacts? Our research addresses these inquiries using data from the 67 public school districts in Florida. The analysis shows that when we focus on (a) bureaucrats who exercise discretion, (b) a demographic factor with a lasting impact-race, and (c) policy measures that are clearly salient to the chosen demographic factor, we can detect the relationships between bureaucratic representation and public policy outputs and outcomes. We particularly highlight the representativeness of "street-level" bureaucrats (in this case, teachers). Thus, the issue of representation in public bureaucracies possesses more than just symbolic importance.

Low-Level Temperature Inversions of the Eurasian Arctic and Comparisons with Soviet Drifting Station Data

Abstract: Seasonal and regional variations in characteristics of the Arctic low-level temperature inversion are examined using up to 12 years of twice-daily rawinsonde data from 31 inland and coastal sites of the Eurasian Arctic and a total of nearly six station years of data from three Soviet drifting stations near the North Pole. The frequency of inversions, the median inversion depth, and the temperature difference across the inversion layer increase from the Norwegian Sea eastward toward the Laptev and East Siberian seas. This effect is most pronounced in winter and autumn, and reflects proximity to oceanic influences and synoptic activity, possibly enhanced by a gradient in cloud cover. East of Novaya Zemlya during winter, inversions are found in over 95% of all soundings and tend to be surface based. For all locations, however, inversions tend to he most intense during winter due to the large deficit in surface net radiation. The strongest inversions are found over eastern Siberia, and reflect the ef...

Electoral Politics and Strategic Voting in State Supreme Courts

Abstract: This study suggests that state supreme court justices act strategically to minimize electoral opposition. In order to appease their constituencies, justices who have views contrary to those of the voters and the court majority, and who face competitive electoral conditions will vote with the court majority instead of casting unpopular dissents on politically volatile issues. Using probit, models were estimated of the effects of several types of electoral forces on death penalty votes from 1983 through 1988 in four southern state supreme courts. Results indicate that single-member districts, beginning at the end of a term, prior representational service, narrow vote margins and experience in seeking reelection encourage minority justices to be attentive to their constituencies by voting in accordance with constituent opinion. In essence, constituency influence in state supreme courts is enhanced by competitive electoral conditions and experience with electoral politics.

“I Seen My Opportunities and I Took 'Em:” Political Corruption in the American States

Abstract: This study is an empirical examination of political corruption in the American states. Using the number of public officials who are convicted of crimes involving corruption as the dependent variable, four explanations of corruption are examined--historical/cultural, political, structural, and bureaucratic. We find that corruption is associated with historical/cultural forces, political forces (especially turnout and party competition), and bureaucratic forces (government size and policies that increase bribe opportunities). Structural factors (e.g., campaign finance reporting requirements, centralization, direct democracy) are unrelated to the incidence of corruption. Finally, the study shows some evidence that prosecution of corrupt public officials was subject to partisan and racial targeting during the Reagan administration and racial targeting during the Carter administration.

Nonlinear prediction as a way of distinguishing chaos from random fractal sequences

Abstract: NONLINEAR forecasting has recently been shown to distinguish between deterministic chaos and uncorrelated (white) noise added to periodic signals1, and can be used to estimate the degree of chaos in the underlying dynamical system2. Distinguishing the more general class of coloured (autocorrelated) noise has proven more difficult because, unlike additive noise, the correlation between predicted and actual values measured may decrease with time—a property synonymous with chaos. Here, we show that by determining the scaling properties of the prediction error as a function of time, we can use nonlinear prediction to distinguish between chaos and random fractal sequences. Random fractal sequences are a particular class of coloured noise which represent stochastic (infinite-dimensional) systems with power-law spectra. Such sequences have been known to fool other procedures for identifying chaotic behaviour in natural time series9, particularly when the data sets are small. The recognition of this type of noise is of practical importance, as measurements from a variety of dynamical systems (such as three-dimensional turbulence, two-dimensional and geostrophic turbulence, internal ocean waves, sandpile models, drifter trajectories in large-scale flows, the motion of a classical electron in a crystal and other low-dimensional systems) may over some range of frequencies exhibit power-law spectra.

An ergonomic evaluation of nursing assistants' job in a nursing home.

Abstract: Thirty-eight nursing assistants (NAs) in a nursing home ranked and rated 16 different patient handling tasks for perceived stresses to the low back. The nursing assistants were observed for 79 4 h shifts and were videotaped for 14 4 h shifts to describe a typical workday and to determine the number of patient-handling tasks performed per shift, the use of assistive devices, and biomechanical stresses to the low back. In addition, data were collected on nursing assistants' and patients' characteristics. The top eight ranked tasks included transferring patient from toilet to wheelchair (WC), WC to toilet, WC to bed, bed to WC, bathtub to WC, chairlift to WC, weighing patients and lifting patients up in bed. The mean ratings of perceived exertion for these tasks were between 'somewhat hard' and 'hard'. The estimated compressive force on L5/S1 disc for the 50th percentile patient weight ranged from 3.7 to 4.9 KN. Nursing assistants worked in teams of two and performed 24 patient transfers per 8 h shift by manually lifting and carrying patients. Assistive devices (a hydraulic lift and gait belt) were used less than 2% of the time. Patient safety and comfort, lack of accessibility, physical stresses associated with the devices, lack of skill, increased transfer time, and lack of staffing were some of the reasons for not using these assistive devices. Environmental barriers (such as confined workplaces, an uneven floor surface, lack of adjustability of beds, stationary railings around the toilet, etc.) made the job more difficult. Nursing assistants had a high prevalence of low-back pain and 51% of nursing assistants visited a health care provider in the last three years for work related low-back pain.

Effects of autocorrelation on control chart performance

Abstract: In this article, we study the capability of the standard control chart for individual observations with fixed control limits to identify special causes reflected as isolated extreme points in the presence of autocorrelation. We consider both the application of standard Shewhart limits and moving-range limits and derive the risks of false positive and false negative when the control chart observations follow a general ARMA(p,q) process.

Epidemiology of low-back pain in industry.

Abstract: Low-back pain and back injuries are of such a complex nature that any one criterion cannot be applied by itself to give a valid assessment of the risk associated with manual materials-handling jobs. There is no question that low-back pain is an extremely significant cause of disability and has a major socioeconomic impact, but many different personal and job factors are associated with the incidence and prevalence of these complaints. There is a need for ongoing systematic investigations of the multiple risk factors that may be causally related to low-back pain and may possibly be amendable to preventive interventions. Knowledge of workplace and individual risk factors is far from complete. Prospective studies are needed so that factors contributing to the development of low-back pain can be separated from factors resulting from low-back pain. It is difficult to relate low-back pain to the workplace because it occurs quite often in workers employed in sedentary occupations. However, incidence, severity, and disability are all related to the physical demands of the job. In this regard, jobs involving lifting, lowering, pushing, pulling, carrying, and holding; body movements such as frequent bending, twisting, and sudden movements; and working in bent-over postures appear to have a significant potential for producing low-back pain. A combination of lifting, bending, and twisting appears to be most hazardous. It is concluded that lifting heavy loads contributes to increased frequency and severity rates for low-back pain. This is true regardless of whether the lifting is performed over a short period or throughout the day and whether it is performed a few times per day of repetitively. If, however, such lifting is performed repetitively, the medical hazard extends beyond low-back problems to other musculoskeletal strain and sprain injuries and to fatigue-related injuries, particularly for weaker workers. In this latter regard, gender, age, anthropometry, and previous history of back pain are known to modify these risks for populations of workers. The inherent variability between workers and within any worker over time precludes the use of such factors to assign risk to any particular individual.

Testing exponentiality based on Kullback-Leibler information

Abstract: In this paper a test of fit for exponentiality based on the estimated Kullback-Leibler information is proposed. The procedure is applicable when the exponential parameter is or is not specified under the null hypothesis. The test uses the Vasicek entropy estimate, so to compute it a window size m must first be fixed. A procedure for choosing m for various sample sizes is proposed and corresponding critical values are computed by Monte Carlo simulations

Rereading the Maps of the Columbian Encounter

Abstract: Maps of the Encounter have been judged by the agenda of a positivist geographical history seeking to reconstruct the pathways, landing places, and settlements of European explorers and discoverers. They were studied largely for their practical use as tools of navigation, as aids to wayfinding on land, as plans for new colonial fortifications and towns, or as public propaganda images to attract new settlers to America. This paper argues that Native American mapping belongs in the cartographic record of the Encounter, and that European maps of the period can be viewed as statements of territorial appropriation, cultural reproduction, or as devices by which a Native American presence could be silenced. Recent studies in anthropology, art history, and ethnohistory identify a corpus of indigenous maps that represent valid “alternative’ cartographies, different from European maps, yet important in the history of spatial representation. In Mesoamerica, further decoding of cartographic elements in the pr...

Heart rate response of firefighters to actual emergencies : implications for cardiorespiratory fitness

Abstract: Heart rate (HR) and oxygen consumption (VO2) responses during actual fire-suppression emergencies were monitored in 10 male firefighters. These firefighters worked at 157 +/- 8 beats per minute (bpm) for 15 +/- 7 minutes. This was 88 +/- 6% of their previously determined HR max. Based on treadmill testing, the HR x VO2 relationship was established for each firefighter. The predicted VO2 derived from HR monitoring in actual emergencies was 25.6 +/- 8.7 mL.kg-1.min-1 or 63 +/- 14% of VO2 max (40.0 +/- 6.5 mL.kg-1.min-1). These values on the cardiorespiratory response to actual emergencies are very similar to results derived from studies employing fire-suppression simulations. Recommendations for the VO2 max of firefighters ranging from 33.5 to 42.0 mL.kg-1.min-1 that have been generated from simulation testing appear appropriate given the cardiorespiratory responses to actual emergencies.

Basic counterpoint: mechanisms and pathways of gonadal steroid modulation of growth hormone secretion.

Abstract: In spite of the different patterns of GH secretion observed in male and female rats, it can be argued that there are limited differences between the mechanism of action of androgens and estrogens as reported in the literature. However, we feel that it is possible to organize the available data into a unique physiological model explaining the sex-based differences in GH secretion in the rat. Thus, it can be proposed that the greater spontaneous GH peaks observed in the male with respect to the female rat may be due to an androgen-mediated enhancement of both GHRH secretion at the hypothalamic level and GH secretion at the pituitary level. The lower GH troughs observed in the male as compared to the female rat may be due to increased interpeak somatostatin secretion induced by the androgens with respect to the estrogens. It is likely that these high GH peaks and low GH troughs establish a recycling mechanism through established feedback mechanisms. That is, the high GH peak, induced by GHRH, stimulates somatostatin secretion such that a very low GH trough follows. In turn, this low GH trough, in the high somatostatin environment, establishes the correct neuroendocrine milieu for the next high GH peak, and so on. Additional studies will help clarify this model and hopefully provide a better understanding of the mechanisms regulating the interaction between gonadal steroids and GH.

Toward a Feminist Understanding of Women and Power

Abstract: Both psychologists and feminists believe power is an important and ubiquitous concept, yet its definition and scope eludes both groups. In this introduction to a special issue on women and power, we suggest three points to help organize and interpret research in the area. First, definitions of power should center around the distinction between “power-over,” the domination and control of one person or group over another, and “power-to” or personal empowerment. Second, power can be analyzed at different levels—societal, organizational, interpersonal, and individual—and, importantly, these levels interact. Third, power differences frequently underlie what appear to be gender differences in behavior; as society is currently configured, power and gender are never independent. Although the articles in this special issue often ask more questions than they answer, the present volume adds a feminist perspective to the psychological study of power.

The Fractal Structure of Real Estate Investment Trust Returns: The Search for Evidence of Market Segmentation and Nonlinear Dependency

Abstract: This article presents a further test for market segmentation between the real estate market and the capital markets. We use rescaled range analysis developed in the fractal geometry literature to test for nonlinear trends in the returns series for different asset classes. We make three major conclusions: (1) the stock market displays tendencies consistent with a random walk, (2) portfolios of mortgage and equity REIT returns display tendencies consistent with a random walk and, (3) conditional upon the methods used, segmentation does not exist between different real estate markets and between the real estate and stock markets.

The role of glucocorticoids in the regulation of growth hormone secretion Mechanisms and clinical significance

Abstract: Glucocorticoids are well known to inhibit growth and GH secretion in humans and animals, yet in vitro these steroids stimulate GH synthesis and secretion. These opposite actions appear to be mediated at different sites. The inhibition involves modulation of hypothalamic somatostatin and the stimulation involves direct actions on the pituitary. Current evidence suggests that the predominant action in vivo is through the inhibitory influences of somatostatin.

Meta-Analysis of the Relationship between Communication Apprehension and Cognitive Performance.

Abstract: Although numerous studies have examined the relationship between communication apprehension (CA) and cognitive performance (e.g., IQ grade point averages, course grades, assignment grades, and test scores), the findings are equivocal. One area of findings suggests that students in the traditional educational environment experiencing high CA are at a distinct disadvantage when compared to their low or moderate counterparts. A second area of findings suggests that no significant relationship exists. A third area indicates that the nature of the instructional environment is a significant mediating variable that moderates the effects of CA on cognitive performance. In the present study, a meta‐analysis was conducted of 23 manuscripts containing information on 30 experiments that examined CA and cognitive performance. Results confirmed a statistically significant negative correlation between CA and cognitive performance. Implications for future research and classroom instruction are discussed.

Consent forms: how to determine and improve their readability.

Abstract: This study investigated the reading level estimates of cancer clinical trial consent forms from actively accruing studies at the Medicine Branch and the Clinical Pharmacology Branch of the National Cancer Institute Forty-four consent forms were analyzed using the SMOG formula Readability levels ranged from grade 12 to grade 175 (mean = 143) The conclusion was that these consent forms were written above most subjects' reading levels The usefulness of consent forms could be improved significantly by using readability formulas, applying rewriting techniques, and being aware of subjects' comprehension levels This paper suggests a number of strategies that nurses can use to enhance comprehension of the information contained in informed consent documents

Toward an Integrated Model of Judicial Voting Behavior

Abstract: This article is an initial step toward the development of an integrated model of judicial decision making. The study synthesizes elements derived from contextual and attitudinal perspectives by app...

Effects of manganese oxide mineralogy on microbial and chemical manganese reduction

Abstract: In this study we examine the effects of manganese oxide mineralogy and crystal structure on two types of manganese reduction: microbial manganese reduction coupled to the oxidation of organic matter, and chemical reduction of manganese oxides by Fe2+. Three synthetic manganese minerals were used: δ‐MnO2 (or vernadite), Mg‐bimessite, and pyrolusite. The δ‐MnO2 and Mg‐birnessite are relatively high‐surface‐area amorphous materials, while the pyrolusite is a low‐surface‐area crystalline solid. Studies of microbial manganese reduction were carried out using an enrichment culture isolated from sediments in the mesohaline region of the Chesapeake Bay, and with a pure culture of the organism Shewanella (formerly Alteromonas,) putrefaciens strain MR‐1. With the Chesapeake Bay enrichment culture, identical rates of manganese reduction were observed with equivalent initial suspension concentrations of all three manganese minerals. This occurred in spite of ∼ 200‐fold differences in the available surface ar...