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PubMed2005

Neutron cross section measurements at ORELA for improved nuclear data and their application.

To support the Nuclear Criticality Safety Program, the Oak Ridge Electron Linear Accelerator (ORELA) has been used to measure the total and capture neutron cross sections of several nuclides in the energy range from 100 eV to -600 keV. Concerns about the use of existing cross section data in nuclear criticality calculations have been a prime motivator for the new cross-section measurements. Our new capture cross sections of aluminium, silicon, chlorine, fluorine and potassium in the energy range from 100 eV to 600 keV are substantially different from the cross sections in evaluated nuclear data files of ENDF/B-VI and JENDL-3.2.

Databases, Factual↗
PubMed1996

Measuring tree-ring increments on tree bole sections with a video-based robotic positioner.

We report on the design and performance of a system that speeds measurement of radial tree-ring increments on tree stem disks; this method replaces the usual binocular microscope with a video image, and automates the measuring and recording processes. The system was used to measure bole sections cut from stems at various heights to determine volume growth of representative trees in an old-growth ponderosa pine stand. The objective of the measurement system was to speed acquisition of annual growth increments from a large number of disks. A personal computer controls the location of a video camera in a 3-axis positioning system. The operator views the sample on a video monitor and positions the camera over each ring by selecting it with a computer-driven mouse. The computer measures and records the distance that the camera moves between each ring. Task selection is facilitated by menu-driven software that also formats, checks and organizes data files. Measurements have a resolution of 0.026 mm; however, finer resolution could be obtained with a different camera lens. Tests of measurement variability (repeated measurements by individual operators on a single radius) indicated standard errors of 0.006 mm or less for the first measurement sets for four operators. Correlation coefficients among four radii per bole section were as low as 0.66 for a whole tree, suggesting that measurements on single radii may provide poor estimates of radial growth for old trees. This system also offers the potential for automatic ring detection and measurement.

Journal Article↗
PubMed1997

Simulating the response of mature yellow poplar and loblolly pine trees to shifts in peak ozone periods during the growing season using the TREGRO model.

Multiple TREGRO simulations were conducted with meteorological data files containing different growing season peak ozone (O(3)) episodes at O(3) exposures of 1.0 and 2.0 x ambient O(3) to assess the relationship between O(3) response and the phenology of mature yellow poplar (Liriodendron tulipifera L.) and loblolly pine (Pinus taeda L.) trees. Regardless of O(3) exposure and peak O(3) episode occurrence, a peak O(3) episode in August caused the greatest reduction in carbon (C) gain in yellow poplar, whereas a peak O(3) episode in July caused the greatest reduction in C gain of loblolly pine. In both species, timing of the greatest simulated O(3) effect corresponded with the completion of the annual foliage production phenophase. Simulated C gain of yellow poplar (total tree, coarse root, and total nonstructural carbohydrate) was reduced by O(3) to a greater extent than the corresponding compartments in loblolly pine, but the opposite was true for fine roots. This differential sensitivity to O(3) reflects the fact that both C assimilation and the O(3) response of the species were parameterized according to observed field measurements of each species. The differential sensitivity to O(3) of these species may have long-term implications for species composition in southeastern USA forests.

Journal Article↗
PubMed1987

Empirical paternity exclusion rates.

We have developed an empirical method of estimating paternity exclusion rates for any genetic system by counting exclusions among fictitious "nonfather" paternity cases generated from true paternity disputes. Especially for multiallele multiloci systems, this technique has advantages over traditional formulae methods in that it replaces tedious (and, in some cases, impossible) computations with simple data file manipulations, and it avoids introducing quantities such as gametic disequilibrium and recombination fraction that are difficult to measure. Exclusion rates for standard and one-parent paternity cases are given for three racial groups (Caucasians, blacks, and Hispanics) in four genetic systems (HLA, ABO, MNSs, and Rh). Beside the method, of interest are our findings of higher HLA exclusion rates (93.25% for Caucasians, 94.62% for blacks, and 95.82% for Hispanics) compared with rates previously reported and high combined exclusion rates (89.59% for Caucasians, 91.65% for blacks, and 92.54% for Hispanics) in one-parent paternity cases.

ABO Blood-Group System↗
PubMed1991

A model of a microcomputer database system to assist medical schools in recruiting and retaining students.

A model for a microcomputer database to aid a school's efforts to recruit and retain students is presented. The model is based upon a working system developed by the author at the University of Colorado Health Sciences Center. The article discusses data needs for adequate records of the recruitment and retention efforts, especially those concerning minority students, and how these records can be used to administer and evaluate programs. The model provides a framework for microcomputer data files, record fields, relationships, and system development and maintenance considerations.

Colorado↗
PubMed2002

An analysis of students' clinical experiences in an integrated primary care clerkship.

PURPOSE: Combining complementary clinical content into an integrated clerkship curriculum should enhance students' abilities to develop skills relevant to multiple disciplines, but how educational opportunities in primary care ambulatory settings complement each other is unknown. The authors conducted an observational analytic study to explore where opportunities exist to apply clinical skills during a 16-week integrated primary care clerkship (eight weeks of family medicine, four weeks of ambulatory pediatrics, and four weeks of ambulatory internal medicine). METHOD: Using handheld computers, students recorded common problems, symptoms, and diagnoses they saw. The students also recorded information about the educational process of the clerkship. Two data files were created from the database. Descriptive statistics were used to characterize the students' clerkship experiences, and ANOVA was used to evaluate differences among these blocks within the clerkship. RESULTS: Students encountered different frequencies of presenting symptoms, the majority of which occurred in pediatrics (23.2 per student per week versus 16.3 in medicine and 16.8 in family medicine; p =.01). Students provided more behavioral change counseling in family medicine (5.2 episodes per student per week versus 4.2 and 2.0 in internal medicine and pediatrics, respectively; p =.01), and they performed more clinical procedures in family medicine (1.9 per student per week versus 0.6 and 1.1 in pediatrics and internal medicine, respectively; p =.001). Students were more likely to encounter specific conditions in internal medicine (35.3 per student per week versus 30.0 and 21.4 in family medicine and pediatrics, respectively; p =.01). Elements of the teaching and learning processes also differed by clerkship. CONCLUSIONS: Very little overlap was found in symptoms, conditions, procedures, and other educational opportunities in the ambulatory pediatrics, internal medicine, and family medicine blocks that constitute the integrated primary care clerkship. The blocks provided different and complementary learning opportunities for students. These findings will assist in clerkship planning and in guiding students to seek opportunities that will ensure educational excellence.

Ambulatory Care↗
PubMed2002

Designing tailored Web-based instruction to improve practicing physicians' chlamydial screening rates.

OBJECTIVE: To design an individualized Web-based continuing medical education (CME) program to improve practicing physicians' chlamydial screening rates. DESCRIPTION: Often unrecognized and untreated, chlamydial infections in young women may cause pelvic inflammatory disease, infertility, and ectopic pregnancy and facilitate the acquisition of HIV. The National Committee for Quality Assurance in 2001 reported chlamydia screening rates to be 23.6% for 16-20-year-olds and 18.3% for 21-26-year-olds. In a collaborative project an academic medical center and a large national managed care organization have developed four tailored Web-based modules for primary care physicians with the goal of improving rates of screening for chlamydia. Each module includes: (1) individual office chlamydial screening rates; (2) interactive cases with real-time comparison of answers with those of peers; (3) a toolbox of office support materials, including patient education materials and guideline summaries; and (4) real-time tailoring of the Web pages based on physicians' interactions with module. Readiness to change and barriers impeding change are assessed during interaction with the module and multiple pathways are created in real time for each physician. Physicians' perceptions of the prevalence of chlamydia in their patient populations and the rate of sexual activity among adolescent girls are also assessed. These variables have been correlated in other studies with low rates of chlamydial screening. Inaccurate perceptions of these variables are considered to constitute a precontemplative stage of change. Specific messages are designed to facilitate increased awareness of chlamydia prevalence, level of sexual activity, and the consequences of failure to screen. For physicians who are aware of the nature and scope of the problems related to chlamydia, messages are tailored to assist them in reducing barriers to screening. A randomized trial of a national sample of primary care physicians is being conducted to determine the effectiveness of this intervention in improving physicians' chlamydial screening rates in sexually active women 16-26 years of age. DISCUSSION: While the Internet offers an educational distribution system accessible to practicing physicians, most CME online programs are text-based and infrequently interactive or guideline-based. It is unlikely that these programs have broad impact on physicians' practice patterns. Neither the broad capacities of Web technologies nor the evidence of effective methods for influencing physicians' practice patterns has influenced the design of most CME programs. The innovative course described above provides individual office feedback on performance, compares physicians' responses with those of their peers, gathers responses to determine physicians' readiness to change practices, and provides branching pathways "on-the-fly" individualized to these responses. The module format is easily adapted to other diseases, able to be linked in an automated fashion to administrative data files, and relatively low in cost to support.

Adolescent↗
PubMed1984

Spectral and dosimetric characteristics of a D2O-moderated 252Cf calibration facility.

Calculations have been made for a D2O-moderated 252Cf assembly like that being used for the calibration of neutron dosimeters at the U.S. National Bureau of Standards and being proposed by the International Standards Organization. Leakage spectra at various distances from the assembly are given along with variations in dose-equivalent rate, average neutron energy and 235U/237Np fission ratio. The spectral shape changes rapidly near the spherical assembly and the dose-equivalent rate changes more rapidly than would be expected on the basis of the inverse-square dependence. Calibration of neutron dosimeters should therefore be made at distances greater than 15 cm from the surface. At large distances from the source, the dose equivalent per unit fluence for neutrons above 1 eV is 9.3 X 10(-9) rem cm2. The effects of the structural material, recent revisions to nuclear data files and changes in the spectrum of the source neutrons on the external field were investigated. These changes produce only about a 5% change in the neutron-dose equivalent rate. The structural material introduces negligible anisotropy in the radiation field.

Calibration↗
PubMed2003

Physical models and dose factors for use in internal dose assessment.

Internal dose assessment depends on the use of mathematical formulas for dose calculation and models of the human body and its organs. A simple, unified method for internal dose calculations is described, which brings together and simplifies concepts used in nuclear medicine and occupational internal dose systems previously described. Using the best current decay data and phantoms for internal dose calculations, dose factors for internal dose assessment are provided. Decay data for over 800 radionuclides from the data service at Brookhaven National Laboratory were combined with absorbed fraction data from a number of currently available mathematical whole body and organ models to provide the dose factors. This represents the first published update on nuclear medicine dose factors since MIRD Pamphlet No. 11 in 1975; in this paper, dose factors for many more nuclides are given (816 vs. 117 in MIRD 11), including some alpha emitters. New models are also employed, and dose factors for bone and marrow have been updated with recently suggested corrections. The good agreement of the new dose factors with previously published values for several of the models gives good confidence in their accuracy. This article gives an overview of the technical basis for these dose factors and some example tables of data, but the bulk of the data files will be distributed electronically. The use of an "electronic publishing" approach permits the publication of this kind of voluminous information in mainstream journals while facilitating rapid access and use without the need to purchase often expensive and bulky paper documents.

Adolescent↗
PubMed2002

Restraint use and injury patterns among children involved in motor vehicle collisions.

BACKGROUND: Motor vehicle collisions are the leading cause of death among children older than 1 year. Use of appropriate restraint systems is associated with reductions in morbidity and mortality in this age group. No studies have evaluated the association between specific injury patterns and restraint use among children. The purpose of this study was to evaluate differences in risks of injuries in different body regions according to restraint use among children 0 to 11 years of age. METHODS: The 1995 to 1999 National Automotive Sampling System data files were used. The National Automotive Sampling System is a national probability sample of passenger vehicles involved in police-reported tow-away collisions. Information on occupant (seating position, restraint use), collision (change in velocity, vehicle intrusion), and outcome characteristics was evaluated. Risks of injuries in different body regions (Abbreviated Injury Scale, 1990 Revision score > or = 2) were calculated and compared according to restraint use. RESULTS: Between 1995 and 1999, there were approximately 1.5 million children 0 to 11 years of age involved in police-reported tow-away MVCs who met the inclusion criteria for this study. Compared with unrestrained children, properly restrained children had significantly lower overall injury risk (risk ratio [RR], 0.37); significant risk reductions were also observed for injuries to the head (RR, 0.18), thorax (RR, 0.35), and lower extremities (RR, 0.26), and mortality (RR, 0.26). Significant risk reductions were not noted when comparing improperly restrained children with unrestrained children. CONCLUSION: Proper restraint use among children is associated with lower risk of injury. Educational initiatives should focus not only on encouraging restraint use but also on ensuring that parents know the appropriate age-dependent restraint method and how to use it properly.

Accidents, Traffic↗
PubMed2002

Incidence and characteristics of motor vehicle collision-related blunt thoracic aortic injury according to age.

BACKGROUND: Motor vehicle collision-related blunt thoracic aorta injury (BAI) is rare and highly lethal. Vascular disease as related to advancing age potentially subjects older adults to increased risk of BAI; the mechanisms associated with such injuries may be different as compared with younger adults. The goal of the present study is to test this hypothesis using population-based data. METHODS: The 1995 to 1999 National Automotive Sampling System data files were used. The National Automotive Sampling System is a national probability sample of passenger vehicles involved in police-reported tow-away crashes. BAI was defined according to the Abbreviated Injury Scale codes. Among those with BAI, information on occupant (age, seating position, restraint use), collision (collision type, delta-V, vehicle intrusion), and outcome characteristics were obtained and compared according to age. RESULTS: The overall incidence of BAI was 6.8 per 10,000 occupants and there was a steady increase in the BAI rate for advancing decades of life. The proportion of occupants with BAI who die at the scene of the collision is relatively consistent across all age groups ( approximately 85%). Among those who survive to receive medical care, ultimate survival is lowest among those aged 60 and older. Near-side collisions were responsible for more BAI among older adults than other age groups (50% vs. 20.6%, p < or = 0.05). Older adults sustained BAI in collisions with lower delta-V values compared with younger persons (p < or = 0.05). CONCLUSION: Older adults have the highest rate of motor vehicle collision-related BAI, and their injuries tend to occur in less severe collisions. A high level of suspicion for BAI among older adults should not be reserved for high-energy collisions only.

Accidents, Traffic↗
PubMed2000

Impact of individual and market factors on the timing of initiation of hospice terminal care.

CONTEXT: Hospice terminal care is now used by 10% to 15% of elderly Americans at variable points before their deaths. OBJECTIVE: By examining the duration of patient survival after enrollment in hospice care, we sought to identify individual and market factors associated with the timing of hospice use. DESIGN: We linked Medicare claims, census information, and Area Resource File data to form a national cohort of 151,410 hospice patients admitted in 1993 and followed up until late 1996. We examined this cohort with Cox regression and other means. MAIN OUTCOME MEASURE: The primary outcome measure was survival after hospice enrollment. RESULTS: The patients had a mean +/- SD age of 79.0 +/- 7.4 years; 10.2% were nonwhite; 51.4% were female; and 71.3% had cancer. Median survival after hospice enrollment was 30 days (interquartile range, 10-86 days). After adjustment for measured patient, provider, and market factors, several variables were associated with relatively earlier hospice enrollment, farther from death. Compared with complementary groups, nonwhites were enrolled in hospice 4 days earlier; women, 5 days earlier; older people, 1 day earlier; and those with substance abuse, psychiatric disease, or dementia, each 3 days earlier. After adjustment, income and education were not associated with the timing of enrollment. Patients residing in markets with more hospital beds, greater hospice capacity, or a higher proportion of generalists were enrolled earlier. CONCLUSIONS: Even after adjustment for certain clinical attributes, individual social factors and local market factors were associated with survival after hospice enrollment. Certain socially disadvantaged groups were enrolled earlier, as were those residing in areas with more medical institutions. The decision to enroll patients in hospice may depend on both nonclinical and clinical factors.

Aged↗
PubMed2005

Oral lichenoid contact reactions may occasionally transform into malignancy.

The purpose was to identify cases of squamous cell carcinoma (SCC) of the tongue, in which a biopsy taken at the site preceding the cancer could be verified to show a lichenoid contact type of reaction (LCR). We retrieved all 724 SCC of the tongue from the Swedish Cancer Registry in the period 1995-2000. These cases were cross-searched with our own oral biopsy data files from 1988 to 1994, in order to identify biopsies with LCR-type lesions preceding the cancer. We found four verified and some additional tentative cases. The study demonstrated that there is a low incidence of malignant transformation in LCR-type oral lesions, not much different from what has been previously reported in oral lichen planus.

Aged↗
PubMed1997

Occurrence of asthma and chronic bronchitis among female hairdressers. A questionnaire study.

We carried out a retrospective cohort study using a self-administered questionnaire to assess the risk of hairdressers to develop asthma and chronic bronchitis. A representative sample of 4433 female hairdressers and an equal number of shop personnel in employment in 1980 was drawn from the Longitudinal Census Data File of Statistics Finland. Physician-diagnosed asthma, chronic bronchitis, and other respiratory diseases in 1980 and 1995 were inquired about in the respiratory part of the questionnaire. The response rate to the questionnaire was 82% for the hairdressers (n = 3484) and 79% for the referents (n = 3357). The prevalence of asthma among the hairdressers was 5.6% in 1980 and 10.1% in 1995, and the prevalence of chronic bronchitis was 3.9% in 1980 and 5.6% in 1995. The relative risk for asthma (odds ratio [OR]: 1.7, 95% confidence interval [CI]: 1.3 to 2.3 in 1980; and OR: 1.7, 95% CI: 1.4 to 2.2 in 1995) and for chronic bronchitis (OR: 2.2, 95% CI: 1.5 to 3.2 in 1980; and OR: 1.9, 95% CI: 1.4 to 2.6 in 1995) among hairdressers was almost twice that in the reference group. The incidence rate of asthma in 1980 through 1995 was 2.2 and of chronic bronchitis was 1.1 cases per 1000 person-years among hairdressers, whereas the rate in the reference group was 1.3 asthma cases and 0.9 chronic bronchitis cases per 1000 person-years. The relative risk for developing asthma during the 15 years observation time was 1.7 (95% CI: 1.1 to 2.5) and for chronic bronchitis was 1.2 (95% CI: 0.7 to 1.9) among hairdressers, compared with referents. Our results indicate that hairdressers are at higher risk for developing asthma.

Adult↗
PubMed2001

Cause of death in patients with inflammatory bowel disease.

BACKGROUND: Ulcerative colitis (UC) and Crohn's disease (CD) can both result in disease-related mortality. The aim of the present study was to analyze the comorbid medical conditions that contribute to death of patients with inflammatory disease. METHODS: The United States' vital statistics offer the opportunity to study causes of death broken down by primary and contributing secondary conditions. Deaths from UC and CD were retrieved from the 1991-1996 data files of the National Center for Health Statistics. The strengths of individual associations between each comorbid condition and UC or CD were expressed as proportional mortality ratios, adjusted to the age-, gender-, and race-distribution of the general population. RESULTS: Deaths from UC and CD were found to be associated with a similar set of comorbid conditions and complications. Shock, volume depletion, protein/calorie malnutrition, and anemia were the most frequent comorbid conditions in the group of nutritional, fluid, and electrolyte disturbances. Both diseases were frequently associated with peritonitis and septicemia. Lastly, a large number of deaths were associated with complications following medical and surgical interventions. CONCLUSIONS: Deaths due to inflammatory bowel disease appear to be related to complications from multiple medical interventions and surgical procedures. In managing inflammatory bowel disease, the physician must keep in mind the potential for complications that may be associated with aggressive treatment.

Age Factors↗
PubMed2004

Perinatal mortality in first- and second-born twins in the United States.

OBJECTIVE: To evaluate the prevailing mortality paradox that second-born twins are at higher risk of perinatal mortality than first-born twins. METHODS: We used the 1995-1997 United States "matched multiple birth" data files assembled by the National Center for Health Statistics, for analysis of risk of perinatal mortality in first- and second-born twins (293788 fetuses). Perinatal mortality was defined to include stillbirths after 20 weeks of gestation and neonatal deaths (deaths within the first 28 days). Gestational age-specific risk of perinatal mortality (per 1000 total births), stillbirth (per 1000 total births), and neonatal mortality (per 1000 livebirths) by order of twin birth were based on the fetuses-at-risk approach. Associations between order of birth and mortality indices were evaluated by fitting multivariable logistic regression models based on the method of generalized estimating equations. These models were adjusted for several potential confounding factors. RESULTS: Perinatal mortality was 37% higher in second-born (26.1 per 1000 total births) than in first-born (20.3 per 1000 total births) twins (adjusted relative risk [RR] 1.37; 95% confidence interval [CI] 1.32, 1.42). The increased risk of perinatal mortality in second-born twins was chiefly driven by a 2.46-fold (95% CI 2.29, 2.63) increase in the number of stillbirths. However, the risk of neonatal mortality was very similar between first- and second-born twins (RR 0.99, 95% CI 0.95, 1.04). CONCLUSIONS: The increased risk of perinatal death in second-born twins is driven chiefly by increased rates of stillborn second twins. Thus, the increased mortality in second-born over first-born twins probably is an artifact of mortality comparisons.

Adult↗
PubMed2003

Changes in intensive care unit nurse task activity after installation of a third-generation intensive care unit information system.

UNLABELLED: OBJECTIVE To determine the percentage of time that intensive care unit (ICU) nurses spend on documentation and other nursing activities before and after installation of a third-generation ICU information system. DESIGN: Prospective data collection using real-time time-motion analysis, before and after installation of the ICU information system. SETTING: A ten-bed surgical ICU at a Veterans Affairs medical center. SUBJECTS: ICU nurses. INTERVENTIONS: Installation of a third-generation ICU information system. MEASUREMENTS AND MAIN RESULTS: Ten ICU nurses were studied before and after installation of the ICU information system. Each ICU nurse's activities and tasks, during 4-hr observation periods, were categorized in real-time by a nurse observer and recorded in a laptop computer. Each recorded task was automatically time-stamped and logged into a data file. The percentage of time spent on documentation decreased from 35.1 +/- 8.3% to 24.2 +/- 7.6% (p =.025) after the ICU information system was installed. The percentage of time providing direct patient care increased from 31.3 +/- 9.2% to 40.1 +/- 11.7% (p =.085). The percentage of time doing patient assessment, a direct patient care task, increased from 4.0 +/- 4.7% to 9.4 +/- 4.4% (p =.001). CONCLUSIONS: Installation of a third-generation ICU information system decreased the percentage of time ICU nurses spent on documentation by >30%. Almost half of the time saved on documentation was spent on patient assessment, a direct patient care task.

Hospitals, Veterans↗
PubMed2005

Trends in cigarette smoking initiation and cessation among birth cohorts of 1926-1970 in Germany.

This study examines temporal differences in cigarette smoking initiation and cessation among male and female birth cohorts of 1926-1970 born in Germany. Based on the German Federal Health Survey 1998 the sample is divided into a series of 5-year sex-birth cohorts, beginning with those born between 1926 and 1930 and extending to those born between 1966 and 1970. The final data file consists of a sample of 5110 people. Ever-smoking prevalence among men varies from 60 to 70% between the birth cohorts, while in women born 1926-1930 ever-smoking increases from 20 to about 50% in those born 1966-1970. A reduction of the median age at starting smoking also takes place between the cohorts. With 8.5 years this decrease is more incisive among women, compared with a drop of 2 years among men. Regarding cessation patterns the analysis shows a shift towards a shorter duration of smoking with succeeding birth cohorts, again this shift is more incisive in women. But even in the youngest cohort still more than 50% of ever-smokers smoke regularly for more than 25 years. In Germany tobacco-control activities are required in order to take antismoking actions that especially prevent youth from starting to smoke and that support smokers in quitting.

Adolescent↗