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PubMedDate not supplied

Orbit selection and its impact on radiation warning architecture for a human mission to Mars.

With the recent announcement of the discovery of the possibility of life on Mars, there is renewed interest in Mars missions, perhaps eventually in human missions. Astronauts on such missions are at risk to occasional periods of enhanced high energy particle flux from the sun known as Solar Particle Events. These events can pose a substantial risk to the health of the astronauts and to the on-board electronics. Effective forecast and warning of these events could provide time to take steps to minimize the risk (retreating to a safe haven, shutting down sensitive equipment, etc.) Providing that forecast capability, will require additional monitoring capability. The extent of this architecture is sensitive to the orbit selected for the transfer to and from Mars. This paper looks at the major classes of Mars missions (Conjunction and Opposition) and sub-categories of these classes and draws conclusions on the number of monitoring satellites needed for each, with a goal to reducing total system cost through optimum orbit selection.

Forecasting↗

PubMed1997

Neural network and linear regression models in residency selection.

For many years, multiple linear regression models have been used at a residency program to generate preliminary rank lists of residency applicants. These lists are then used by the admissions committee as an aid in developing a final ranking to submit to the National Residency Match Program (NRMP). A study was undertaken to compare predictions made using linear regression with those generated by a newer technique, an artificial neural network. A prospective cohort design was used. Seventy-four applicants to an emergency medicine program were evaluated by faculty and resident interviewers with regard to medical school grades, autobiography, interviews, letters of recommendation, and National Board scores. Normalization of these scores (by linear transformation of interviewer means) was used to correct for differences among interviewers. Multivariate linear regression and neural network models were developed using data from the previous 5 years' applicants. These models were used to forecast provisional rank orderings of the candidates. These rankings were combined into a single hybrid list that was used by the admissions committee as the starting point for development of the final rank list by consensus. Each model's predictions were tested for goodness of fit against the final NRMP rank using Wilks' test. Using the final submitted NRMP rank order as the dependent variable, the neural network yielded a correlation coefficient of 0.77 and an R2 of 59.4%. The linear regression model exhibited a correlation coefficient of 0.74 and an R2 of 54.0%. No significant difference was found (chi 2 = 1.08, P = .7). A neural network performs as well as a linear regression model when used for forecasting the rank order of residency applicants.

Cohort Studies↗

PubMed1998

Multivariate prediction of skeletal Class II growth.

Prediction of craniofacial growth is one of the keys to successful orthodontic treatment and stability. Despite numerous attempts at growth forecasting, our ability to accurately predict growth is limited. The present study outlines a possible new approach to prediction of craniofacial growth that differs from any previous attempt because of both the methods used and type of patients studied. The purpose of this study is to create and test prediction equations for forecasting favorable or unfavorable patterns of growth in skeletal Class II preadolescents. The subjects for this study include 19 females and 12 males from the Bolton growth center in Cleveland, Ohio. The patients were all untreated orthodontically, had lateral cephalometric headfilms taken biannually from the ages of 6 through 18 and had a Class II skeletal relationship at age 8. Twenty-six skeletal and dental landmarks were identified and digitized, and 48 linear, angular, and proportional measurements were calculated. The subjects were divided into two groups based on anterior-posterior changes in the relationship between the maxilla and mandible. Eleven patients were in the favorable growth group, with an average improvement of 4.13 degrees in the ANB angle; 20 patients were in the unfavorable growth group with an average increase of 0.16 degrees in the ANB angle. The following prediction formula was created with Bayes theorem and assuming a multivariate Gaussian distribution: P(Good¿Fn) = ke (-(0.5)) ¿Fn - mu(ng)¿sigma(g)(-1)¿Fn - mu(ng)¿T. The equation's sensitivity and specificity was calculated from serial cephalometric data from ages 6, 8, 10, and 12. The results obtained with this equation indicate 82.2% sensitivity, 95% specificity with a overall positive predictive value of 91%. This corresponds to 17.8% of patients being incorrectly identified as Poor Growers and only 5% of our patients were incorrectly identified as Good Growers. We conclude that this prediction formula improves the ability to predict favorable or unfavorable patterns of growth in this sample of skeletal Class II preadolescents.

Adolescent↗

PubMed2004

Assessing development pressure in the Chesapeake Bay watershed: an evaluation of two land-use change models.

Natural resource lands in the Chesapeake Bay watershed are increasingly susceptible to conversion into developed land uses, particularly as the demand for residential development grows. We assessed development pressure in the Baltimore-Washington, DC region, one of the major urban and suburban centers in the watershed. We explored the utility of two modeling approaches for forecasting future development trends and patterns by comparing results from a cellular automata model, SLEUTH (slope, land use, excluded land, urban extent, transportation), and a supply/demand/allocation model, the Western Futures Model. SLEUTH can be classified as a land-cover change model and produces projections on the basis of historic trends of changes in the extent and patterns of developed land and future land protection scenarios. The Western Futures Model derives forecasts from historic trends in housing units, a U.S. Census variable, and exogenously supplied future population projections. Each approach has strengths and weaknesses, and combining the two has advantages and limitations.

Baltimore↗

PubMed1995

Reliability of computer-generated prediction tracing.

The reliability of a commercially available computer prediction program (Quick Ceph II) was evaluated using pretreatment and posttreatment cephalograms of 30 patients who were treated during an active period of growth. The computer prediction was compared with the actual treatment result, and the growth forecast with the computer program was compared with the growth forecast using a manual method. Using paired student's t-tests, predictions for 5 of the 10 variables measured were found to be statistically reliable. Comparing the relative accuracy of growth prediction in terms of absolute values, the computer came closer to the actual result in four of the nine variables, while the manual method came closer in three variables. Predictions for the other two variables were virtually the same using both methods. The manual method of prediction was sufficient to give a reasonably good graphic representation of growth changes to create a VTO. However, the computer offers the added advantages of quicker access to information and somewhat greater accuracy in producing the tracing, as well as its use in patient education.

Adolescent↗

PubMed1999

Are women carrying "basketballs" really having boys? Testing pregnancy folklore.

BACKGROUND: Antenatal ascertainment of fetal sex is a common feature of modern pregnancies. Women who opt not to learn fetal sex typically employ a variety of methods to forecast it. This study investigated the validity of prevalent folklore used to identify fetal sex before birth. METHOD: One hundred four pregnant women, who did not know the sex of the fetus, were administered a questionnaire to explore their perceptions of fetal sex and the basis for these predictions. RESULTS: Fetal sex was not systematically related to the shape of the woman's abdomen, prevalence of morning sickness, or comparisons with previous pregnancies. However, women who had more than twelve years of education correctly predicted fetal sex greater than chance (71% correct), in contrast to less educated women (43% correct). Contrary to expectations, women whose forecasts were based on psychological criteria (i.e., dreams or feelings) were more likely to be correct than those employing prevalent folklore criteria (i.e., the way a woman was carrying the pregnancy). CONCLUSIONS: In general, women were not good predictors of fetal sex. The mechanisms that promote maternal accuracy in predicting fetal sex for highly educated women are unknown. It is reasonable to expect that maternal perceptions of fetal sex contribute to the process of fetal attachment.

Adult↗

PubMed2003

Spatiotemporal stochastic forcing effects in an ensemble consisting of arrays of diffusively coupled Lorenz cells.

Spatiotemporal stochastic forcing of an ensemble system consisting of chaotic Lorenz cells diffusively coupled is analyzed. The nontrivial effects of time and length correlations on the ensemble mean error and spread are studied and the implications to new trends in weather forecast methodologies are discussed. A maximum for the forecast scores is observed to occur for specific values of time and length correlations. This maximum is studied in terms of an interplay between the natural scales occurring in the system and the noise parameters.

Forecasting↗

PubMed2000

Neural network model for predicting peak photochemical pollutant levels.

In this paper, an attempt is made for the 24-hr prediction of photochemical pollutant levels using a neural network model. For this purpose, a model is developed that relates peak pollutant concentrations to meteorological and emission variables and indexes. The analysis is based on measurements of O3 and NO2 from the city of Athens. The meteorological variables are selected to cover atmospheric processes that determine the fate of the airborne pollutants while special care is taken to ensure the availability of the required input data from routine observations or forecasts. The comparison between model predictions and actual observations shows a good agreement. In addition, a series of sensitivity tests is performed in order to evaluate the sensitivity of the model to the uncertainty in meteorological variables. Model forecasts are generally rather insensitive to small perturbations in most of the input meteorological data, while they are relatively more sensitive in changes in wind speed and direction.

Air Pollutants↗

PubMed2001

Ozone predictions in Atlanta, Georgia: analysis of the 1999 ozone season.

Ozone prediction has become an important activity in many U.S. ozone nonattainment areas. In this study, we describe the ozone prediction program in the Atlanta metropolitan area and analyze the performance of this program during the 1999 ozone-forecasting season. From May to September, a team of 10 air quality regulators, meteorologists, and atmospheric scientists made a daily prediction of the next-day maximum 8-hr average ozone concentration. The daily forecast was made aided by two linear regression models, a 3-dimensional air quality model, and the no-skill ozone persistence model. The team's performance is compared with the numerical models using several numerical indicators. Our analysis indicated that (1) the team correctly predicted next-day peak ozone concentrations 84% of the time, (2) the two linear regression models had a better performance than a 3-dimensional air quality model, (3) persistence was a strong predictor of ozone concentrations with a performance of 78%, and (4) about half of the team's wrong predictions could be prevented with improved meteorological predictions.

Air Pollution↗

PubMed2006

Field data: a study on trend and prediction of fatal traffic injuries prevalence in Shanghai.

OBJECTIVE: The main objectives of the study are to analyze fatal traffic-injury trends in 1987-2003 in Shanghai and predict its prevalence in near future and provide scientific data for the local governmental decision on developing practical working methods on traffic-injury prevention and control. METHODS: In this study, epidemiological method and Grey dynamic model GM (1,1) were introduced to analyze and forecast traffic-injury mortality rates respectively. RESULTS: There was an apparent increasing trend of traffic-related injuries in Shanghai from 1987 to 2003 with the rate of growth in motorization. The average rates of annual increase are 3.59% in fatalities (from 7.78 per 100,000 population to 14.18 per 100,000 population) during the period. Pedestrians were the most common type of victims (29.6%), followed by bicyclists (25.1%), and motorcyclists (24.1%). Males accounted for the majority of all victims, over 69%. The population of high-school and lower high-school education level represented 66.4% victims of total road-traffic injuries. And if no special factors effect its development, the traffic fatalities would be up to 17.84 per 100,000 population in 2010, when calculating from equations we found and validated Y(t) = 359.90 x e0.027(t-1)-352.13, (t = 1, 2, ..., N) for Shanghai. CONCLUSION: Our data indicate the risk of fatal traffic injuries has increased in recent years and will go on growing in the near future in Shanghai. The findings showed that Grey dynamic model GM (1,1) is eligible on the prediction and can be a tool for injuries forecasting, implementing effective policies, programs, and interventions for reducing traffic injuries in the big cities.

Accidents, Traffic↗

PubMed2003

Cancer mortality trends in the EU and acceding countries up to 2015.

BACKGROUND: Examination of trends in cancer mortality in Europe over the past 30 years has shown that, after long-term rises, age-standardised mortality from most common cancer sites has fallen in the EU since the late 1980s. This study aimed to examine trends in the age-specific and age-standardised cancer mortality rates and numbers of cancer deaths up to 2020 for all cancers and various specific sites for all 15 EU countries, the 10 acceding countries, Bulgaria and Romania (currently applicant countries, along with Turkey), and Iceland, Norway and Switzerland of the four EEA countries. PATIENTS AND METHODS: Mortality rates were modelled as a function of age, calendar period and birth cohort. Birth cohort was calculated as age subtracted from calendar period. RESULTS: As a consequence of the generally decreasing trends in the age-standardised rates, the best estimate is that there will be approximately 1.25 million cancer deaths in 2015, which is almost 130,000 (11%) more deaths than in 2000, but 155,000 (11%) fewer deaths than the 1.4 million projected in 2015 on the basis of demographic changes alone. The increases in the forecast numbers of cancer deaths in 2015 are proportionally larger in males than in females (13% and 10%, respectively) and proportionally larger in the acceding countries than in the current EU member countries (14% and 11%, respectively). CONCLUSIONS: Our forecasts are conservative best estimates of future cancer mortality. There is clearly scope for large improvements in survival, and hence reductions in cancer mortality, in some countries, through eliminating these differences using existing knowledge and treatment regimes.

Adolescent↗

PubMed2001

The widening social class gap of preventive health behaviours in Spain.

As a way of forecasting future evolution of inequalities in disease burden and mortality, trends in preventive health behaviours by social class were examined. Using the Spanish National Health Survey from 1987 to 1997 the evolution of the Health Practices Index (smoking, alcohol consumption, physical exercise, sleep hours and the Quetelet index) is described for the Spanish non-institutionalised adult population. In the last 10 years the disadvantaged population of Spain (social class groups IV and V) has not opted for healthier behavioural choices. On the contrary the Health Practices Index figures have worsened during the study period. Conversely, the more affluent groups (social class groups I, II and III) have exhibited a net gain in the index. Due to this, an increase in the existing gap in health inequalities in Spain in terms of morbidity and mortality can be forecast for the near future. As time trends of a summary indicator of preventive health behaviours by social class have not been described in other countries, a replication of this study in different cultural, social and economic milieus could produce valuable information.

Adult↗

PubMed1993

Transient periodicity and episodic predictability in biological dynamics.

Biological time series often contain passing episodes of nearly periodic dynamics. In chaotic systems, such transient periodicity can reflect the existence of semiperiodic saddles--nonstable invariant sets--contained in the attractor. Motion in the vicinity of such objects has a prominent periodic component. In addition, trajectories can become temporarily trapped in these neighbourhoods before exiting. The immediate dynamical antecedents (low-order preimages) of transient periodicity are well defined and, along with the saddles to which they map, correspond to regions of enhanced predictability under nonlinear forecasting. This suggests that it may be possible to forecast the onset of transient periodicity in systems for which overall predictability is low. The present paper reviews these concepts and applies them to biological phenomena at different levels of organization.

Child↗

PubMed1996

Application of exponential smoothing for nosocomial infection surveillance.

Detection of outbreaks of infection or increases in bacterial resistance to antimicrobial agents is an essential component of hospital infection control surveillance. The authors applied the method of exponential smoothing to microbiology data from 1987-1992 to investigate a suspected outbreak of gentamicin resistance among Pseudomonas aeruginosa bacteria at the Department of Veterans Affairs Medical Center, San Francisco, California, in 1991-1992. The years 1987-1990 were used to develop the baseline for the forecast model. Application of the model indicated that two observed prominent peaks in the annual cumulative incidence of gentamicin-resistant P. aeruginosa were within the upper bounds of their respective 95% confidence intervals as estimated by the forecast model--i.e., that no epidemic was in progress. This prediction was supported by investigations by the hospital's infection control team which indicated that the apparent increases were due to readmission of patients previously known to harbor these organisms. In contrast, application of a typically employed method that ignores the time series data structure indicated that there were 6 months in which incidence rates exceeded the upper bounds of their respective 95% confidence intervals, thereby erroneously suggesting that an epidemic was in progress. Recursive algorithms and some simplifying assumptions that do not affect the validity of inferences make the application of this method practical for nosocomial infection control programs.

Anti-Bacterial Agents↗

PubMedDate not supplied

Black-white inequalities in mortality and life expectancy, 1933-1999: implications for healthy people 2010.

OBJECTIVES: Optimistic predictions for the Healthy People 2010 goals of eliminating racial/ethnic disparities in health have been made based on absolute improvements in life expectancy and mortality. This study sought to determine whether there is evidence of relative improvement (a more valid measure of inequality) in life expectancy and mortality, and whether such improvement, if demonstrated, predicts future success in eliminating disparities. METHODS: Historical data from the National Center for Health Statistics and the Census Bureau were used to predict future trends in relative mortality and life expectancy, employing an Autoregressive Integrated Moving Average (ARIMA) model. Excess mortality and time lags in mortality and life expectancy for blacks relative to whites were also estimated. RESULTS: Based on data for 1945 to 1999, forecasts for relative black:white age-adjusted, all-cause mortality and white:black life expectancy at birth showed trends toward increasing disparities. From 1979, when the Healthy People initiative began, to 1998, the black:white ratio of age-adjusted, gender-specific mortality increased for all but one of nine causes of death that accounted for 83.4% of all US mortality in 1998. From 1980 to 1998, average numbers of excess deaths per day among American blacks relative to whites increased by 20%. American blacks experienced 4.3 to 4.5 million premature deaths relative to whites in 1940-1999. CONCLUSIONS: The rationale that underlies the optimistic Healthy People 2010 forecasts, that future success can be built on a foundation of past success, is not supported when relative measures of inequality are used. There has been no sustained decrease in black-white inequalities in age-adjusted mortality or life expectancy at birth at the national level since 1945. Without fundamental changes, most probably related to the ways medical and public health practitioners are trained, evaluated, and compensated for prevention-related activities, as well as further research on translating the findings of prevention studies into clinical practice, it is likely that simply reducing disparities in access to care and/or medical treatment will be insufficient. Millions of premature deaths will continue to occur among African Americans.

Adolescent↗

PubMed2004

Can the confidence in long range atmospheric transport models be increased? The pan-european experience of ensemble.

Is atmospheric dispersion forecasting an important asset of the early-phase nuclear emergency response management? Is there a 'perfect atmospheric dispersion model'? Is there a way to make the results of dispersion models more reliable and trustworthy? While seeking to answer these questions the multi-model ensemble dispersion forecast system ENSEMBLE will be presented.

Air Movements↗

PubMed1992

The trade-off between hospital cost and quality of care. An exploratory empirical analysis.

The debate concerning quality of care in hospitals, its "value" and affordability, is increasingly of concern to providers, consumers, and purchasers in the United States and elsewhere. We undertook an exploratory study to estimate the impact on hospital-wide costs if quality-of-care levels were varied. To do so, we obtained costs and service output data regarding 300 U.S. hospitals, representing approximately a 5% cross section of all hospitals operating in 1983; both inpatient and outpatient services were included. The quality-of-care measure used for the exploratory analysis was the ratio of actual deaths in the hospital for the year in question to the forecasted number of deaths for the hospital; the hospital mortality forecaster had earlier (and elsewhere) been built from analyses of 6 million discharge abstracts, and took into account each hospital's actual individual admissions, including key patient descriptors for each admission. Such adjusted death rates have increasingly been used as potential indicators of quality, with recent research lending support for the viability of that linkage. The authors then utilized the economic construct of allocative efficiency relying on "best practices" concepts and peer groupings, built using the "envelopment" philosophy of Data Envelopment Analysis and Pareto efficiency. These analytical techniques estimated the efficiently delivered costs required to meet prespecified levels of quality of care. The marginal additional cost per each death deferred in 1983 was estimated to be approximately $29,000 (in 1990 dollars) for the average efficient hospital. Also, over a feasible range, a 1% increase in the level of quality of care delivered was estimated to increase hospital cost by an average of 1.34%. This estimated elasticity of quality on cost also increased with the number of beds in the hospital.

Comorbidity↗

PubMed1999

Development and estimation of a pediatric chronic disease score using automated pharmacy data.

BACKGROUND: Although risk assessment models for specific adult populations such as the elderly have been developed, little work has focused on developing pediatric-specific models. The lack of pediatric models may result in incorrect estimates of relative disease severity among children, in reduced reimbursement for health plans and providers, and in inadequate health care for chronically ill children. OBJECTIVES: To develop and to evaluate a pediatric risk assessment model using automated pharmacy data. DESIGN: Retrospective, case-cohort study using automated data. SUBJECTS: All children continuously enrolled in Group Health Cooperative of Puget Sound during 1992 and 1993. MEASURES: The Pediatric Chronic Disease Score (PCDS), an algorithm that classified children into chronic disease categories by prescription drug fills, was compared with the ICD-9-CM-based Ambulatory Care Groups (ACG) model and a demographic model for prediction of total, ambulatory, or primary care costs and primary care visits. Forecast models were estimated using linear regression and they were evaluated with R2, mean prediction error, mean squared prediction error, and Mincer-Zarnowitz tests. RESULTS: The pharmacy-based PCDS performed significantly better on each of the four forecasting accuracy tests than did a demographic model (eg, R2s averaging fourfold higher). Compared with the ACG model, the PCDS model performed similarly on mean squared prediction error tests; however, the ACG generally had higher validation R2 values. CONCLUSIONS: A pharmacy-based pediatric risk assessment model performs better than a demographic model and represents a viable alternative to ICD-9-CM-based models. Further research is necessary to determine if children must be considered separately from adults when conducting population-based risk assessments.

Adolescent↗