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PubMed2004

Scaling of prediction error does not confirm chaotic dynamics underlying irregular firing using interspike intervals from midbrain dopamine neurons.

Dopamine neurons in the substantia nigra pars compacta often fire in an irregular, single spike mode in vivo, and a similar firing pattern can be observed in vitro when small conductance calcium-activated potassium channel blockers are applied to the bath. It is not clear whether the irregular firing is due to stochastic processes or nonlinear deterministic processes. A previous study [Neuroscience 104 (2001) 829] used nonlinear forecasting methods applied to a continuous function derived from the interspike interval (ISI) data from irregularly firing dopamine neurons to show that the predictability scaled exponentially with forecast horizon and was consistent with nonlinear deterministic chaos. However, we show here that the observed exponential scaling is also consistent with a stochastic process, because it did not differ significantly from that of shuffled surrogate data. On the other hand, nonlinear forecasting directly from the ISI data using the package TISEAN provided some evidence for nonlinear deterministic structure in four of five records obtained in vitro and in two of nine records obtained in vivo. Although we cannot rule out a role for nonlinear chaotic dynamics in structuring the firing pattern, we suggest an alternate hypothesis that includes a mechanism by which the firing pattern can become more variable in the presence of a constant level of background noise.

Algorithms↗

PubMed1999

The effects of coronal holes on the propagation of solar energetic protons.

The accurate prediction of the start of a Solar Energetic Particle Event (SEP) is a high priority for space weather forecasters. The Space Environment Center (SEC) has recorded parameters related to SEPs since 1976, and that list includes a total of 134 events for the period 1976-1997. The onset times of individual events are variable, especially SEPs originating from the solar eastern hemisphere. An examination of the data shows the full set can be divided into two families--those that begin at the geosynchronous satellite at a time consistent with what would be expected for activity from a given heliolongitude, and those whose onset is later than what accepted forecast techniques would predict. There are 21 "long onset" events in this historical record. Seeking to understand what factors distinguished the slow-to-arrive events, Helium I 1083.0 nm observations were examined for the presence of coronal holes at the times of the SEPs. It was found that all SEPs with long onset times had a coronal hole situated between the flare site and the footpoint of the interplanetary magnetic field line connecting to Earth (Kunches and Zwickl, 1997 Solar-Terrestrial Predictions-V, Hiraiso Solar-Terrestrial Research Center, Ibaraki, Japan). This coronal hole configuration is important for accurate predictions, although the hole may serve as merely a proxy for the plasma conditions that actually affect the propagation and acceleration of the protons. Since coronal holes are easily identifiable using Helium I and other wavelengths, operational forecasters can employ this technique to improve their predictions of SEPs.

Cosmic Radiation↗

PubMed2004

Minimax statistical models for air pollution time series. Application to ozone time series data measured in Bordeaux.

This paper deals with the application of l(infinity) (or minimax) optimization techniques to statistical modelling of high frequency air pollution data. The method was applied to ground-level ozone time-series data measured in Bordeaux over 4 years from 1998 to 2001. The aim of model building was to develop predictive models in order to provide forecasts of the maximal daily ground-level ozone concentration. Experimental results from this case study indicate that such techniques could be more appropriate than the commonly used l2 setting if only good estimation of high levels is of interest. When the free parameters are fitted by means of l(infinity) optimization techniques, the forecasting errors are more evenly distributed amongst the data points, resulting in a better estimation of high values. The paper compares the quality of forecasts produced by both a linear and a nonlinear model, using l2 and l(infinity) parameter optimization.

Air Pollutants↗

PubMed1993

Nurse manpower demand: a review of United Kingdom methodologies.

Forecasting the demand for nurses is a complex and difficult problem. However, in a climate of economic cutbacks and disadvantageous demographic trends, it is essential that adequate methods are developed to predict both the supply and demand for nurse manpower. To this end a number of methods have been constructed, particularly in the last decade. In this paper we survey the work that has been done to provide an effective way of forecasting nurse manpower demand. The two most common approaches are from the 'top-down' or 'bottom-up'. However, an evolutionary method which allows for modification and detailed refinement is more likely to provide a means of taking into account the complexities of the system. Finally, we focus on the nursing hours per patient (NHPP) ratio as a possible tool for demand forecasting. This index is easily calculated and is readily adaptable to the bottom-up approach.

Bed Occupancy↗

PubMed2002

Prostate cancer incidence, mortality, and survival trends in the United States: 1981-2001.

The increased use of prostate-specific antigen (PSA) in screening for preclinical disease after 1985 is thought to be a major determinant of the changing patterns in prostate cancer incidence; however, the long-term effect of screening on future trends in mortality and survival is uncertain. This article reviews the temporal trends (1981-1998) for prostate cancer incidence, mortality, and survival, and projects prostate cancer incidence and mortality rates for 1999 to 2001. Autoregressive, quadratic, time-series models were used to describe prostate cancer mortality rates in the US population and prostate cancer incidence rates derived from the National Cancer Institute's (NCI) Surveillance, Epidemiology and End Results (SEER) program. These models were based on data collected from 1979 through 1998, with forecasts produced for 1999 to 2001. Prostate cancer incidence increased steadily from 1981 to 1989, with a steep increase in the early 1990s, followed by a decline. Incidence rates were forecasted to remain stable through the year 2001. Mortality rates decreased steadily and were forecasted to continue to decrease concurrently with increasing 5- and 10-year relative survival rates. The incidence, mortality, and survival trends were comparable in US blacks, who exhibited on average 2-fold higher mortality and 50% higher incidence than whites. Decreasing prostate cancer mortality and increasing relative survival trends in the United States were described after the introduction of PSA screening. However, the exaggerated rate of increase in the early 1990s in prostate cancer incidence was transient and likely a result of increased detection of preclinical disease that was prevalent in the general population.

Black People↗

PubMed1989

The hidden future supply of foreign medical graduates.

The number of foreign medical graduates (FMGs) as reported by the American Medical Association (AMA) has registered increases in recent years far exceeding the Department of Health and Human Services' (DHHS) published forecasts. The DHHS projections of new entrants have been derived from the number of postgraduate year-one positions filled by FMGs. Apparently, the FMG supply is augmented by physicians who enter by other paths. By using AMA data, this study takes the first step in attempting to shed light on the characteristics of these recent FMG additions. It then uses the DHHS model to forecast FMG supply based on a short-run continuation of the AMA-reported changes. The paper also forecasts FMG supply assuming that no new foreign national FMGs (FNFMGs) will enter the pool. The analysis suggests that some FNFMGs may be entering this country with visas granted to family members of United States citizens or permanent immigrants and then establishing practices without exiting directly from graduate medical education (GME). Further restrictions on GME participation for FMGs likely are not going to severely curtail FMG entrance into the medical care delivery system. Rather, they will likely restrict their entrance by way of the most traditional route.

Education, Medical, Graduate↗

PubMed2005

Gloom and doom? The future of marine capture fisheries.

Predicting global fisheries is a high-order challenge but predictions have been made and updates are needed. Past forecasts, present trends and perspectives of key parameters of the fisheries--including potential harvest, state of stocks, supply and demand, trade, fishing technology and governance--are reviewed in detail, as the basis for new forecasts and forecasting performance assessment. The future of marine capture fisheries will be conditioned by the political, social and economic evolution of the world within which they operate. Consequently, recent global scenarios for the future world are reviewed, with the emphasis on fisheries. The main driving forces (e.g. global economic development, demography, environment, public awareness, information technology, energy, ethics) including aquaculture are described. Outlooks are provided for each aspect of the fishery sector. The conclusion puts these elements in perspective and offers the authors' personal interpretation of the possible future pathway of fisheries, the uncertainty about it and the still unanswered questions of direct relevance in shaping that future.

Animals↗

PubMed1993

A strategic approach to human resource planning in nursing.

In Britain, Canada and the USA, a chronic shortage of registered nurses has existed since World War II. This situation is predicted to become worse. Reviews both the general and nursing literature in human resource planning, and recommends a system which can be build up step by step and individualized for each nursing department. The core planning activities are a planning database, demand forecasting, supply forecasting, variance analysis and forecasting, and recruitment policies.

Analysis of Variance↗

PubMed2006

Accounting for seasonal patterns in syndromic surveillance data for outbreak detection.

BACKGROUND: Syndromic surveillance (SS) can potentially contribute to outbreak detection capability by providing timely, novel data sources. One SS challenge is that some syndrome counts vary with season in a manner that is not identical from year to year. Our goal is to evaluate the impact of inconsistent seasonal effects on performance assessments (false and true positive rates) in the context of detecting anomalous counts in data that exhibit seasonal variation. METHODS: To evaluate the impact of inconsistent seasonal effects, we injected synthetic outbreaks into real data and into data simulated from each of two models fit to the same real data. Using real respiratory syndrome counts collected in an emergency department from 2/1/94-5/31/03, we varied the length of training data from one to eight years, applied a sequential test to the forecast errors arising from each of eight forecasting methods, and evaluated their detection probabilities (DP) on the basis of 1000 injected synthetic outbreaks. We did the same for each of two corresponding simulated data sets. The less realistic, nonhierarchical model's simulated data set assumed that "one season fits all," meaning that each year's seasonal peak has the same onset, duration, and magnitude. The more realistic simulated data set used a hierarchical model to capture violation of the "one season fits all" assumption. RESULTS: This experiment demonstrated optimistic bias in DP estimates for some of the methods when data simulated from the nonhierarchical model was used for DP estimation, thus suggesting that at least for some real data sets and methods, it is not adequate to assume that "one season fits all." CONCLUSION: For the data we analyze, the "one season fits all " assumption is violated, and DP performance claims based on simulated data that assume "one season fits all," for the forecast methods considered, except for moving average methods, tend to be optimistic. Moving average methods based on relatively short amounts of training data are competitive on all three data sets, but are particularly competitive on the real data and on data from the hierarchical model, which are the two data sets that violate the "one season fits all" assumption.

Computer Simulation↗

PubMed2001

Increasing longevity and Medicare expenditures.

Official Medicare projections forecast that the elderly population will be less healthy and more costly over the next century. This prediction stems from the use of age as an indicator of health status: increases in longevity are assumed to increase demand for health care as individuals survive to older and higher-use ages. In this paper I suggest an alternative approach, in which time until death replaces age as the demographic indicator of health status. Increases in longevity are assumed to postpone the higher Medicare use and costs associated with the final decade of life. I contrast the two approaches, using mortality forecasts consistent with recent projections from the U.S. Census Bureau and the Social Security Administration. The time-until-death method yields significantly lower-cost forecasts. The hypothetical cost savings from improved health care small, however, relative to the size of the Medicare solvency problem caused by population aging.

Accounting↗

PubMed1997

The future role of materiel management.

The objectives of this article are to review Dean Amer's forecasts and offer my personal observations as to why the forecasts were not completely accurate, review current business pressures and trends that present unprecedented opportunities for professional experts with leadership skills, and share a personal forecast as to what role materiel management can and should play in the future in manufacturing enterprises.

Consumer Behavior↗

PubMedDate not supplied

An early warning technique.

During budget preparation, forecasts of inpatient utilization for the coming year play a pivotal role. Use of ancillary services and nursing care is a function of the number of admissions and patient days expected. With DRG payment, the average length of stay has decreased, as has the amount of ancillary service per case. Utilization experience should be reviewed after the budget utilization forecast is made. If it is likely to be lower than the forecast, management should respond as soon as possible. The earlier these responses are made, the more effective they are.

Analysis of Variance↗

PubMed1987

Development of a model for predicting pharmacy personnel requirements.

The purpose of this study was to adjust current staffing based on productivity measurement and analysis of the unit dose and sterile products area of the pharmacy, and to develop a model for predicting pharmacy personnel requirements based on Pharmacy Staffing Units (PHASUs). Time measurements of the specific pharmacy procedures were performed to define baseline procedure data. A PHASU equivalency system was developed to allow comparison of all pharmacy procedures. This system was based on the time required to complete a specific procedure divided by the time required to complete the procedure most reflective of workload, a single medication order. Pharmacy personnel requirements were forecasted using the number of unit dose orders and the number of miscellaneous sterile preparations in the sterile products area. A software package used by management engineering to predict patient days and number of admissions was used to forecast workload. The PHASU system provides a means for forecasting workload and addressing personnel requirements for the next fiscal year. Pharmacy administrative personnel must adopt a contemporary business approach to meet the challenge that pharmacy will encounter in the new health care environment.

Forecasting↗

PubMed1999

[The prediction of the cancer incidence and mortality rates in Spain for the year 2000].

OBJECTIVE: To forecast the cancer incidence and mortality rates in Spain for the year 2000, and to estimate the number of new cases and the number of dead patients due to the cancer for this year. DESIGN: Ecological study with time series analysis. PATIENTS: Cancer mortality rates in Spain was obtained from 1905 to 1995. MEASUREMENTS AND RESULTS: Brow method was applied in order to forecast cancer mortality rates for the year 2000. An estimation of the incidence rates in Spain was obtained from the incidence/mortality rate (1.49 for males and 2.07 for females), given by the International Agency for Research on Cancer (IARC). INE's publications were used in order to estimate the number of new cases and the number of dead patients due to the cancer for the year 2000. The forecasting about cancer mortality rates in Spain for the year 2000 were 312.93 in men and 180.56 in women. An increasing in mortality will be produced in the following years. 90,000 men and 75,000 women will be diagnosed with cancer; 61,000 men and 36,000 women will be died due of this disease. CONCLUSION: The trends in cancer incidence and mortality are increasing. These results could be interesting in health policy in order to plan different actions in the future.

Female↗

PubMed2002

Future of medical knowledge management and decision support.

Attempts to predict the future are typically off the mark. Beyond the challenges of forecasting the stock market or the weather, dramatic instances of notoriously inaccurate prognostications have been those by the US patent office in the late 1800s about the future of inventions, by Thomas Watson in the 1930s about the market for large computers, and by Bill Gates in the early 1990s about the significance of the Internet. When one seeks to make predictions about health care, one finds that, beyond the usual uncertainties regarding the future, additional impediments to forecasting are the discontinuities introduced by advances in biomedical science and technology, the impact of information technology, and the reorganizations and realignments attending various approaches to health care delivery and finance. Changes in all three contributing areas themselves can be measured in "PSPYs", or paradigm shifts per year. Despite these risks in forecasting, I believe that certain trends are sufficiently clear that I am willing to venture a few predictions. Further, the predictions I wish to make suggest a goal for the future that can be achieved, if we can align the prevailing political, financial, biomedical, and technical forces toward that end. Thus, in a sense this is a call to action, to shape the future rather than just let it happen. This chapter seeks to lay out the direction we are heading in knowledge management and decision support, and to delineate an information technology framework that appears desirable. I believe the framework to be discussed is of importance to the health care-related knowledge management and decision making activities of the consumer and patient, the health care provider, and health care delivery organizations and insurers. The approach is also relevant to the other dimensions of academic health care institution activities, notably the conduct of research and the processes of education and learning.

Biomedical Technology↗

PubMed2002

Can 401(k) accumulations generate significant income for future retirees?

This Issue Brief develops a model that project the proportion of an individual's preretirement income that might be replaced by 401(k) plan accumulations at retirement, under several different projected scenarios. The 401(k) participant behaviors in the model are based on the year-end 2000 database collected by the Employee Benefit Research Institute (EBRI) and the Investment Company Institute (ICI) in their collaborative effort known as the EBRI/ICI Participant-Directed Retirement Plan Data Collection Project. The most significant factor affecting projected replacement rates at retirement is having access to a 401(k) plan. Projected replacement rates from 401(k) accumulations at retirement are reduced significantly when participants are not offered a 401(k) plan in all portions of their careers. Most 401(k) participants tend to have contributions in any given year. Thus, projecting that participants always have contributions (their own and/or employer contributions) every year raises projected replacement rates, but not by much compared with the importance of being offered a plan to begin with. The model simulations show that participant activities such as taking loans, taking preretirement withdrawals, or cashing out account balances at job change reduce projected 401(k) accumulations and thus replacement rates at age 65. Because loans are forecast to be paid back to the account in full, their effect on replacement rates at retirement in the model is the smallest. Even if equity returns in the future are projected to replicate the worst 50-year segment in the Standard & Poor's (S&P) 500 history (1929 to 1978), 401(k) accumulations are still projected to replace significant proportions of projected preretirement income. Another projection scenario forecasts participants experiencing a simulated three-year bear market (negative equity returns) either early in their careers, near the middle of their careers, or at the end of their careers. Forecasts of the effects of bear markets on 401(k) balances show that a bear market in equities is projected to have the largest effect the closer it occurs to age 65 (retirement), even though older participants typically have diversified their portfolios away from equities. A three-year bear market for those early in their careers would reduce median replacement rates from 401(k) accumulations by an estimated 2.9-3.7 percentage points, compared with 13.4-17.7 percentage points for those immediately before retirement. Similarly, a simulated three-year bull market (positive equity returns) is projected to have a larger positive effect on projected account balances and replacement rates the closer it occurs to retirement.

Actuarial Analysis↗

PubMed2003

Who needs budgets?

Budgeting, as most corporations practice it, should be abolished. That may sound radical, but doing so would further companies' long-running efforts to transform themselves into developed networks that can nimbly adjust to market conditions. Most other building blocks are in place, but companies continue to restrict themselves by relying on inflexible budget processes and the command-and-control culture that budgeting entails. A number of companies have rejected the foregone conclusions embedded in budgets, and they've given up the self-interested wrangling over what the data indicate. In the absence of budgets, alternative goals and measures--some financial, such as cost-to-income ratios, and some nonfinancial, such as time to market-move to the foreground. Companies that have rejected budgets require employees to measure themselves against the performance of competitors and against internal peer groups. Because employees don't know whether they've succeeded until they can look back on the results of a given period, they must use every ounce of energy to ensure that they beat the competition. A key feature of many companies that have rejected budgets is the use of rolling forecasts, which are created every few months and typically cover five to eight quarters. Because the forecasts are regularly revised, they allow companies to continuously adapt to market conditions. The forecasting practices of two such companies, both based in Sweden, are examined in detail: the bank Svenska Handelsbanken and the wholesaler Ahlsell. Though the first companies to reject budgets were located in Northern Europe, organizations that have gone beyond budgeting can be found in a range of countries and industries. Their practices allow them to unleash the power of today's management tools and realize the potential of a fully decentralized organization.

Budgets↗

PubMed2003

Climate change decreases habitat suitability for some tick species (Acari: Ixodidae) in South Africa.

Models predicting current habitat availability for four prominent tick species in Africa (Boophilus decoloratus, Amblyomma hebraeum, Rhipicephalus appendiculatus and Hyalomma truncatum) were constructed using remotely sensed information about abiotic variables and a point-to-point similarity metric. Year-to-year variations in the forecasted habitat suitability over the period 1983-2000 show a clear decrease in habitat availability, which is attributed primarily to increasing temperature in the region over this period. Climate variables were projected to the year 2015 using Fourier series analysis of the decadal abiotic data. The simulations show a trend toward the destruction of the habitats of the four tick species. In addition, a sensitivity analysis was developed to probe the changes in the habitat suitability in response to variations in temperature, vegetation availability and water vapour deficit. Four basic scenarios were studied: increasing or decreasing the temperature 1 or 2 degrees C together with correlated variations in the other abiotic variables. A decrease in temperature was predicted to promote habitat gain for every species except H. truncatum, while an increase of 1 degrees C was forecast to sustain a small but positive response in A. hebraeum and B. decoloratus. Increasing the temperature by 2 degrees C was forecast to have damaging effects on the habitat structure of all four species. The effect of climate warming on the habitat range of these ticks is considered in the light of economically sound control measures over an ecological background.

Animals↗