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PubMed1995

The decline and rise of the medical school applicant pool.

The authors characterize the demographic changes that transpired with the decline and rise of the medical school applicant pool over the past decade, and describe the variations in academic antecedents, attrition, and graduation rates of students matriculated during that time. Data over the ten-year cycle, derived from the AAMC's Student and Applicant Information Management System (SAIMS), were examined in the context of published education and employment statistics. The contraction and expansion of the applicant pool were related to changes in the number and pattern of undergraduate majors and to changes in the employment conditions for college-educated youth. Furthermore, a significant part of the variations in size of the applicant pool is an artifact of changes in the number of repeat applications. Matriculants' pre-medical grades and MCAT scores dropped slightly during the period of applicant decline, and rebounded as admission committees were able to exercise greater selection when the pool expanded. The attrition of medical students rose and fell during this time, but the changes were small and of little discrete influence on graduation rates during the period. The downturn and rebound in applications over the past decade appear to be more related to cycles in the employment market for college graduates than to applicants' perceptions of unfavorable/favorable conditions in medical education and practice.

College Admission Test↗
PubMed1980

Covariance of affective and schizophrenic symptoms in schizoaffective psychosis.

A case report of a patient with schizophrenic and affective symptoms in remarkable correlations (r = .94) is presented to highlight difficulties in documenting the diagnosis of schizoaffective disorder. Proposed solutions include the frequent use of appropriate rating scales, recognizing that postpsychotic depression is common and may mimic primary affective disorders, and employing statistical methods applicable to the individual case.

Adult↗
PubMed2003

A new algorithm for border description of polarized light surface microscopic images of pigmented skin lesions.

The aim of this study was to provide mathematical descriptors for the border of pigmented skin lesion images and to assess their efficacy for distinction among different lesion groups. New descriptors such as lesion slope and lesion slope regularity are introduced and mathematically defined. A new algorithm based on the Catmull-Rom spline method and the computation of the gray-level gradient of points extracted by interpolation of normal direction on spline points was employed. The efficacy of these new descriptors was tested on a data set of 510 pigmented skin lesions, composed by 85 melanomas and 425 nevi, by employing statistical methods for discrimination between the two populations.

Algorithms↗
PubMed2004

Storage capacity diverges with synaptic efficiency in an associative memory model with synaptic delay and pruning.

It is known that storage capacity per synapse increases by synaptic pruning in the case of a correlation-type associative memory model. However, the storage capacity of the entire network then decreases. To overcome this difficulty, we propose decreasing the connectivity while keeping the total number of synapses constant by introducing delayed synapses. In this paper, a discrete synchronous-type model with both delayed synapses and their prunings is discussed as a concrete example of the proposal. First, we explain the Yanai-Kim theory by employing statistical neurodynamics. This theory involves macrodynamical equations for the dynamics of a network with serial delay elements. Next, considering the translational symmetry of the explained equations, we rederive macroscopic steady-state equations of the model by using the discrete Fourier transformation. The storage capacities are analyzed quantitatively. Furthermore, two types of synaptic prunings are treated analytically: random pruning and systematic pruning. As a result, it becomes clear that in both prunings, the storage capacity increases as the length of delay increases and the connectivity of the synapses decreases when the total number of synapses is constant. Moreover, an interesting fact becomes clear: the storage capacity asymptotically approaches 2/pi due to random pruning. In contrast, the storage capacity diverges in proportion to the logarithm of the length of delay by systematic pruning and the proportion constant is 4/pi. These results theoretically support the significance of pruning following an overgrowth of synapses in the brain and may suggest that the brain prefers to store dynamic attractors such as sequences and limit cycles rather than equilibrium states.

Action Potentials↗
PubMedDate not supplied

A statistical wisp model and pseudophysical approaches for interactive hairstyle generation.

This paper presents an interactive technique that produces static hairstyles by generating individual hair strands of the desired shape and color, subject to the presence of gravity and collisions. A variety of hairstyles can be generated by adjusting the wisp parameters, while the deformation is solved efficiently, accounting for the effects of gravity and collisions. Wisps are generated employing statistical approaches. As for hair deformation, we propose a method which is based on physical simulation concepts, but is simplified to efficiently solve the static shape of hair. On top of the statistical wisp model and the deformation solver, a constraint-based styler is proposed to model artificial features that oppose the natural flow of hair under gravity and hair elasticity, such as a hairpin. Our technique spans a wider range of human hairstyles than previously proposed methods and the styles generated by this technique are fairly realistic.

Acceleration↗
PubMed2006

Ventilation and performance in office work.

Outdoor air ventilation rates vary considerably between and within buildings, and may be too low in some spaces. The purpose of this study was to evaluate the potential work performance benefits of increased ventilation. We analyzed the literature relating work performance with ventilation rate and employed statistical analyses with weighting factors to combine the results of different studies. The studies included in the review assessed performance of various tasks in laboratory experiments and measured performance at work in real buildings. Almost all studies found increases in performance with higher ventilation rates. The studies indicated typically a 1-3% improvement in average performance per 10 l/s-person increase in outdoor air ventilation rate. The performance increase per unit increase in ventilation was bigger with ventilation rates below 20 l/s-person and almost negligible with ventilation rates over 45 l/s-person. The performance increase was statistically significant with increased ventilation rates up to 15 l/s-person with 95% CI and up to 17 l/s-person with 90% CI. Practical Implications We have demonstrated a quantitative relationship between work performance and ventilation within a wide range of ventilation rates. The model shows a continuous increase in performance per unit increase in ventilation rate from 6.5 l/s-person to 65 l/s-person. The increase is statistically significant up to 15 l/s-person. This relationship has a high level of uncertainty; however, use of this relationship in ventilation design and feasibility studies may be preferable to the current practice, which ignores the relationship between ventilation and productivity.

Air Pollution, Indoor↗
PubMed2004

Effect of physical activity levels on bone strength.

The present study employs statistical analysis using age as the covariate and seeks to provide cross-sectional data concerning the relationship between bone strength and levels of physical activities among Japanese.

Adolescent↗
PubMed2000

Line bisection judgments implicate right parietal cortex and cerebellum as assessed by fMRI.

OBJECTIVE: To use functional MRI (fMRI) to determine which brain regions are implicated when normal volunteers judge whether pretransected horizontal lines are correctly bisected (the Landmark test). BACKGROUND: Manual line bisection and a variant thereof involving perceptual judgments of pretransected lines (the Landmark test) are widely used to assess unilateral visuospatial neglect in patients with neurologic disease. Although unilateral (left) neglect most often results from lesions to right temporoparietal cortex, the normal functional anatomy of the Landmark test has not been convincingly demonstrated. METHODS: fMRI was carried out in 12 healthy right-handed male volunteers who judged whether horizontal lines were correctly prebisected. In the control task, subjects detected whether the horizontal lines contained a transection mark irrespective of the position of that mark. Response was by two-choice key press: on half the trials, subjects used the right, and on half, the left hand. Statistical analysis of evoked blood oxygenation level-dependent responses, measured with echoplanar imaging, employed statistical parametric mapping. RESULTS: Performing the Landmark task showed neural activity (p < 0.05, corrected) in the right superior posterior and right inferior parietal lobe, early visual processing areas bilaterally, the cerebellar vermis, and the left cerebellar hemisphere. Only the latter area showed a significant interaction with hand used. CONCLUSIONS: The right hemispheric dominance observed in inferior parietal cortex is consistent with the results of lesion studies. Right superior parietal cortex, vermis, and left cerebellar hemisphere have not been implicated in neglect, but all appear to play a cognitive role in the Landmark task.

Adult↗
PubMedDate not supplied

A brief primer on automated signal detection.

BACKGROUND: Statistical techniques have traditionally been underused in spontaneous reporting systems used for postmarketing surveillance of adverse drug events. Regulatory agencies, pharmaceutical companies, and drug monitoring centers have recently devoted considerable efforts to develop and implement computer-assisted automated signal detection methodologies that employ statistical theory to enhance screening efforts of expert clinical reviewers. OBJECTIVE: To provide a concise state-of-the-art review of the most commonly used automated signal detection procedures, including the underlying statistical concepts, performance characteristics, and outstanding limitations, and issues to be resolved. DATA SOURCES: Primary articles were identified by MEDLINE search (1965-December 2002) and through secondary sources. STUDY SELECTION AND DATA EXTRACTION: All of the articles identified from the data sources were evaluated and all information deemed relevant was included in this review. DATA SYNTHESIS: Commonly used methods of automated signal detection are self-contained and involve screening large databases of spontaneous adverse event reports in search of interestingly large disproportionalities or dependencies between significant variables, usually single drug-event pairs, based on an underlying model of statistical independence. The models vary according to the underlying model of statistical independence and whether additional mathematical modeling using Bayesian analysis is applied to the crude measures of disproportionality. There are many potential advantages and disadvantages of these methods, as well as significant unresolved issues related to the application of these techniques, including lack of comprehensive head-to-head comparisons in a single large transnational database, lack of prospective evaluations, and the lack of gold standard of signal detection. CONCLUSIONS: Current methods of automated signal detection are nonclinical and only highlight deviations from independence without explaining whether these deviations are due to a causal linkage or numerous potential confounders. They therefore cannot replace expert clinical reviewers, but can help them to focus attention when confronted with the difficult task of screening huge numbers of drug-event combinations for potential signals. Important questions remain to be answered about the performance characteristics of these methods. Pharmacovigilance professionals should take the time to learn the underlying mathematical concepts in order to critically evaluate accumulating experience pertaining to the relative performance characteristics of these methods that are incompletely defined.

Automation↗
PubMed2004

Statistical-mechanics theory of active mode locking with noise.

Actively mode-locked lasers with noise are studied employing statistical mechanics. A mapping of the system to the spherical model (related to the Ising model) of ferromagnets in one dimension that has an exact solution is established. It gives basic features, such as analytical expressions for the correlation function between modes, and the widths and shapes of the pulses [different from the Kuizenga-Siegman expression; IEEE J. Quantum Electron. QE-6, 803 (1970)] and reveals the susceptibility to noise of mode ordering compared with passive mode locking.

Journal Article↗
PubMed2004

Cosine histogram analysis for spectral image data classification.

Conventional multivariate strategies for making qualitative estimates of sample composition rely chiefly on identifying subtle differences in spectral shape. In some instances, such as in biological tissues, the spectra obtained from a single sample class may consist of many shapes. Likewise, two distinctly different sample classes, such as normal and abnormal tissue, may produce similar variations in spectral shape. In our work, we employ statistical analysis of the set of cosine correlation scores obtained from multispectral visible absorption images of stained cervical Papanicolaou samples. By analyzing the cosine correlation score frequency for spectra obtained from the cell nuclei, abnormal cells can be differentiated from the background of normal cells, which vary considerably in their optical properties and morphology. Our method, called cosine histogram analysis (CHA), returns the percent likelihood of abnormality for each pixel in the field of view and is presented here for the first time.

Female↗
PubMed2006

Modeling and optimization of biopolymer (polyhydroxyalkanoates) production from ice cream residue by novel statistical experimental design.

Polyhydroxyalkanoates (PHAs) are thermoplastic polyesters synthesized by Ralstonia eutropha and other bacteria as a form of intracellular carbon and energy storage and are accumulated as lipid inclusions in the cytoplasm of these bacteria. The modeling and optimization of PHA production by fermentation from industrial waste (ice cream residue) was studied by employing statistical experimental design methods. A series of iterative experimental designs was used to find optimal factor conditions (medium components and fermentation process time) in the order of fractional factorial design, path of steepest ascent, and full factorial augmented with axial design (rotational central composite design). An optimal range characterized by lipid (15 mg/mL) and % lipid (88%) values was found and further investigated to verify the optimal conditions for PHA production from ice cream (56.68 mL of ice cream or 56.68% ice cream in water [v/v], 5.03 mL of buffer, 1 mL of mineral salts solution, 100 muL of trace element solution, 100 mL of seed culture, and 213.76 h of fermentation time).

Analysis of Variance↗
PubMed1994

Systematic reviews--theory and practice.

The consumer of health care services experts that medical practice is based on scientific evidence with regard to efficacy and effectiveness. Randomized controlled trials provide the most valid basis for comparison of interventions in health care and offer the most reliable information to guide clinical practice. The need for well-designed and performed systematic reviews of the available information to address a specific clinical question should be obvious both to the practicing clinician and the consumer. A systematic review is defined as "the application of scientific strategies that limits bias to the systematic assembly, critical appraisal, and synthesis of all relevant studies on a specific topic". "Meta-analysis (quantitative overview) is a systematic review that employs statistical methods to combine and summarize the results of several trials". In a meta-analysis the individual studies are weighted according to the inverse of the variance; that is more weight is given to studies with more events. The pooling of data allows for an increase in power and thus a more precise estimate of the effect size. Systematic reviews that meet explicit criteria for validity offer the reader information that as a rule is less biased than the unstructured overview which has traditionally been performed by one or several experts in a specific content area. Recently statistical methods have been developed to summarize data from studies of diagnostic tests. Cumulative meta-analyses offer the caregiver and the health-care consumer with answers regarding the effectiveness of a certain intervention at the earliest possible date in time.

Humans↗
PubMed2006

Does money really matter? A review of the literature on the relationships between healthcare organization finances and quality.

The authors review empirical literature from 1980 to 2005 on relationships between healthcare organizations' finances and quality of care. They found only 16 studies of this topic that employed statistical methods. This research indicates cumulatively that expenses, fiscal margin, and asset and liability management all affect healthcare outcome quality. There is less evidence about how organizational finance factors affect structural or process quality, and there is no information about how structural or process quality mediates between finances and outcomes. The authors note what patterns have emerged from previous studies and make specific suggestions about what future research is necessary and why.

Financial Management, Hospital↗
PubMed2000

Image-processing algorithms for behavior analysis of group-housed pigs.

Computational algorithms of image processing were developed and evaluated to select, by motion detection, images of resting artificial pigs and to segment the pigs (mixture of black and white pigs) from their background. Motion detection of the pigs was implemented by detecting interframe differences of postural behavioral images. This algorithm combines the advantages of likelihood ratio method and shading model method and shows a stable performance under noisy and dynamic illumination conditions. Segmentation of the pigs from their background was implemented by employing multilevel thresholding and background reference techniques. The algorithm automatically determines the number of thresholds needed and produces satisfactory segmentation when both black and white pigs with different image intensities are present at the same time (the most complicated situation). The reference background image is updated so that temporal changes in illumination and/or spatial changes of the pen condition have little effect on the performance of image segmentation. The algorithm employs statistical models of the pigs and background and Bayes hypothesis testing to obtain and update the exposed portion of the reference background. Linear filters were used in this process for updating the parameters. These algorithms will serve as essential components for a novel, behavior-based, interactive approach to assess and control thermal comfort of group-housed pigs, which is expected to result in enhanced animal health and well-being.

Algorithms↗
PubMed1978

Using statistics in employment discrimination cases.

Statistics play an important role in employment discrimination cases, and this role will expand as the legal profession becomes increasingly aware of the utility of the increasingly sophisticated statistical methods available. Historically, plaintiffs in employment discrimination cases have used statistics to establish prima facie cases concerning inequities in areas such as wage rates, personnel selection, promotion, layoff, and termination decisions. Defendants have also employed statistics to demonstrate the fairness of employment practices and policies--for example, by providing statistical evidence of the validity of a test used in personnel selection. This article provides an overview of the role of statistics and the major statistical techniques employed in discrimination cases.

Black or African American↗
PubMed1999

The Danish Prevention Register. A comprehensive health and socio-economic, individual based register.

The Danish Prevention Register has been created recently as a very comprehensive national individual based register, based on register linkage. The Prevention Register currently comprises eight registers, which have been linked together using the unique personal identification number. The register contains data from 1977 and onwards. From an international research perspective this register offers unique opportunities to the researchers. The eight registers can be divided into three groups: health-related registers, registers on living conditions and a Register of Population Statistics. The health-related registers are: Register of Causes of Death, National Patient Register (in-patients and out-patients) and Register of Health Insurance Statistics (primary health care, GPs). Within the next few years the register will be expanded with The Medical Birth Register. The Abortion Register and The Malformation Register. The registers on living conditions are: Longitudinal Register of Social and Employment Statistics, Employment Classification Module, Educational Classification Module and Register of Population and Housing Censuses. The Register allows for cross-sectional and follow-up studies and is used for administrative purposes as well as research purposes. An overview of the register is presented in the article. Earlier articles in the Danish Register series in DMB explain details of the registers.

Adolescent↗
PubMed1999

[Primary neoplasms of the parapharyngeal space in material from the Otolaryngology Department, Karol Marcinkowski University of Medical Sciences in Poznan].

Primary neoplasms of parapharyngeal space are rare. In this location the so called non-malignant tumors occur many times more than the malignant ones. In our paper, employing statistics, objective symptoms and complaints connected with these tumors were ordered according to frequency. In recent five years in ENT Department of Karol Marcinkowski University of Medical Sciences in Poznań 9 persons were surgically treated. The differentiated histopathological picture is discussed and described (6 malignant and 3 non-malignant). It can be claimed that MR is more useful in diagnosis than CT. The treatment is usually surgical; both external and oral approaches are used.

Adolescent↗