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PubMed1987

Forecasting parasitic gastroenteritis in lambs.

Incorporating estimated temperature data and assuming non-limiting rainfall, a simulation model was used to compare forecast and actual pasture counts of sheep nematode larvae over a 2-year period. The results indicate that the first possible date of the summer larval rise can be predicted up to 6 weeks in advance of its actual occurrence, enabling control measures to be planned and implemented. Rainfall variation had a marked effect on the degree of disparity between the predicted and actual timing of the rise, indicating the importance of this factor.

Animals↗

PubMed2005

Interpreting hippocampal function as recoding and forecasting.

A model of hippocampal function, centered on region CA3, reproduces many of the cognitive and behavioral functions ascribed to the hippocampus. Where there is precise stimulus control and detailed quantitative data, this model reproduces the quantitative behavioral results. Underlying the model is a recoding conjecture of hippocampal computational function. The expanded conjecture includes a special role for randomization and, as recoding progresses with experience, the occurrence of sequence learning and sequence compression. These functions support the putative higher-order hippocampal function, i.e. production of representations readable by a linear decoder and suitable for both neocortical storage and forecasting. Simulations confirm the critical importance of randomly driven recoding and the neurocognitive relevance of sequence learning and compression. Two forms of sequence compression exist, on-line and off-line compression: both are conjectured to support neocortical encoding of context and declarative memory as described by .

Cognition↗

PubMed2006

Neural network forecasts of the tropical Pacific sea surface temperatures.

A nonlinear forecast system for the sea surface temperature (SST) anomalies over the whole tropical Pacific has been developed using a multi-layer perceptron neural network approach, where sea level pressure and SST anomalies were used as predictors to predict the five leading SST principal components at lead times from 3 to 15 months. Relative to the linear regression (LR) models, the nonlinear (NL) models showed higher correlation skills and lower root mean square errors over most areas of the domain, especially over the far western Pacific (west of 155 degrees E) and the eastern equatorial Pacific off Peru at lead times longer than 3 months, with correlation skills enhanced by 0.10-0.14. Seasonal and decadal changes in the prediction skills in the NL and LR models were also studied.

Computer Simulation↗

PubMed1995

EEG predictability: adequacy of non-linear forecasting methods.

The predictive properties of EEG segments were analyzed. The sample included alpha, delta as well as spike and wave EEG activity recordings. Most of these segments are better described with non-linear autoregressive models, and a non-linear forecasting algorithm is routinely required. In terms of their predictive properties, segments can be divided into unpredictable, predictable and very predictable, these three groups being similarly represented among the alpha activity EEG segments. In EEG segments with alpha activity, poor predictability is associated with poor organization of the rhythmic pattern. Concerning dynamic properties, it was found that cyclic skeletons were highly represented among the very predictable segments, which reflect a contribution of the deterministic component of the autoregressive model to the predictability of the segments. Notable contributions of the noise component may explain the properties of unpredictable segments. These results point to a great diversity of predictive patterns among EEG recordings. Other factors besides the existence of chaotic dynamics must be regarded.

Algorithms↗

PubMed2001

Forecasting habitat suitability for ticks and prevention of tick-borne diseases.

Climate and vegetation are the major factors affecting the distribution of ticks. Consequently, spatial distributions can be analysed by statistical methods that look for correlations between abiotic factors and known data about tick presence/absence. Remote sensing features can be obtained from a wide database of sensors with different characteristics, then applied to the problem of mapping prediction of tick distribution. Some studies had demonstrated that the use of these abiotic variables from satellite imagery has biological significance, therefore statistical accuracy of these distribution models can be interpreted under an ecological framework. Furthermore, models can be linked to these predictive maps, enabling the forecast of spatial and temporal dynamics of ticks, looking for seasonal patterns of activity and accurate use of acaricide treatments.

Animals↗

PubMed2005

Chronomics, neuroendocrine feedsidewards and the recording and consulting of nowcasts--forecasts of geomagnetics.

A multi-center four-hourly sampling of many tissues for 7 days (00:00 on April 5-20:00 to April 11, 2004), on rats standardized for 1 month in two rooms on antiphasic lighting regimens happened to start on the day after the second extremum of a moderate double magnetic storm gauged by the planetary geomagnetic Kp index (which at each extremum reached 6.3 international [arbitrary] units) and by an equatorial index Dst falling to -112 and -81 nT, respectively, the latter on the first day of the sampling. Neuroendocrine chronomes (specifically circadian time structures) differed during magnetically affected and quiet days. The circadian melatonin rhythm had a lower MESOR and lower circadian amplitude and tended to advance in acrophase, while the MESOR and amplitude of the hypothalamic circadian melatonin rhythm were higher during the days with the storm. The circadian parameters of circulating corticosterone were more labile during the days including the storm than during the last three quiet days. Feedsidewards within the pineal-hypothalamic-adrenocortical network constitute a mechanism underlying physiological and probably also pathological associations of the brain and heart with magnetic storms. Investigators in many fields can gain from at least recording calendar dates in any publication so that freely available information on geomagnetic, solar and other physical environmental activity can be looked up. In planning studies and before starting, one may gain from consulting forecasts and the highly reliable nowcasts, respectively.

Animals↗

PubMed2002

TDM coupled with Bayesian forecasting should be considered an invaluable tool for optimizing vancomycin daily exposure in unstable critically ill patients.

A randomized two-arm prospective study was planned to assess the role of therapeutic drug monitoring (TDM) coupled with a Bayesian approach in tailoring vancomycin dosages in unstable critically ill patients. Group A (n=16) had their regimen adjusted day-by-day according to TDM and Bayesian forecasting (D(a)); group B (n=16) had their regimen adjusted day-by-day according to Moellering's nomogram (D(M)). Blood samples were collected every 1-2 days to assess the trough and peak plasma concentrations. In group A, the tailored D(a) required for optimizing vancomycin exposure were considerably higher than the D(M) in 7/16 cases, and lower than the D(M) in 1/16 cases. In group B, standard D(M) caused under-treatment in 3/16 cases and over-treatment in 4/16 cases. Most of these patients concomitantly had some conditions that might have altered vancomycin disposition. The TDM-guided Bayesian-based approach should be considered an invaluable tool for clinicians to handle appropriately on real-time vancomycin therapy in critically ill patients.

Adult↗

PubMed1989

The value of skin temperature measurements in forecasting the healing of a below-knee amputation for end-stage ischaemia of the leg in peripheral vascular disease.

In order to forecast the healing of a Burgess type below-knee amputation the skin temperature of the leg has been studied before operation in 39 instances using infra-red thermography in a 26 degrees C environment. Healing bore no relation to the mean skin temperature of the calf or that of the skin at the site of the anterior incision. However, when the skin temperature at the site of the incision for the long posterior flap was greater than 30.4 degrees C or when the ratio of the temperatures at the posterior and anterior incision sites (P/A) was greater than 0.98 healing was significantly more likely to occur. It is proposed that the temperatures at these sites should be used to assess the prospect of such an amputation healing.

Aged↗

PubMedDate not supplied

An atlas of forecasted molecular data. 1. Internuclear separations of main-group and transition-metal neutral gas-phase diatomic molecules in the ground state.

Needed spectroscopic data on diatomic molecules can often be found in the superb critical tables of Huber and Herzberg or in the literature published since 1979. Unfortunately, these sources apply to only a fraction of the diatomic species that can exist and so investigators have had to rely on interpolation, additivity, or ad hoc rules to estimate needed values, all of which require other information that is often lacking. This Atlas presents 1001 additional internuclear separations for use until critical tables are available to fill the needs more precisely. The Atlas was produced by mining the data from Huber and Herzberg for trends with least-squares analysis and with neural network software. There are 162 molecules about whose data Huber and Herzberg had no qualifications and whose data were employed for this work; 248 copies of data with low and high magnitudes were added to reduce the effects of frequency. Internuclear separations for 1001 species not found in Huber and Herzberg are presented, and least-squares predictions supplement some of them. The results, i.e., the Atlas, are presented as Table A, Supporting Information. The average error, based on the average of the absolute differences between the predicted values and tabulated values for the molecules having Huber and Herzberg data, is 0.074 A; if each error is expressed as a percent of the forecast to which it pertains, the average of these errors is 2.94%. There are 25 "questionable" data from Huber and Herzberg, not used in the preparation of the Atlas, for which predictions are included in the Atlas. Of these, 14 agree with the predicted internuclear separations to within twice the stated errors. Additional atlases for other properties of diatomic molecules are in preparation.

Journal Article↗

PubMed2000

Forecasting physicochemical variables by a classification tree method. Application to the Berre Lagoon (south France).

The dynamics of the "Etang de Berre", a brackish lagoon situated close to the French Mediterranean sea coast, is strongly disturbed by freshwater inputs coming from an hydroelectric power station. The system dynamics has been described as a sequence of daily typical states from a set of physicochemical variables such as temperature, salinity and dissolved oxygen rates collected over three years by an automatic sampling station. Each daily pattern summarizes the evolution, hour by hour of the physicochemical variables. This article presents results of forecasts of the states of the system subjected to the simultaneous effects of meteorological conditions and freshwater releases. We recall the main step of the classification tree method used to build up the predictive model (Classification and Regression Trees, Breiman et al., 1984) and we propose a transfer procedure in order to test the stability of the model. Results obtained on the Etang de Berre data set allow us to describe and predict the effects of the environmental variables on the system dynamics with a margin of error. The transfer procedure applied after the tree building process gives a maximum gain in prediction accuracy of about 15%.

Environmental Monitoring↗

PubMed1998

Immune neglect: a source of durability bias in affective forecasting.

People are generally unaware of the operation of the system of cognitive mechanisms that ameliorate their experience of negative affect (the psychological immune system), and thus they tend to overestimate the duration of their affective reactions to negative events. This tendency was demonstrated in 6 studies in which participants overestimated the duration of their affective reactions to the dissolution of a romantic relationship, the failure to achieve tenure, an electoral defeat, negative personality feedback, an account of a child's death, and rejection by a prospective employer. Participants failed to distinguish between situations in which their psychological immune systems would and would not be likely to operate and mistakenly predicted overly and equally enduring affective reactions in both instances. The present experiments suggest that people neglect the psychological immune system when making affective forecasts.

Adaptation, Psychological↗

PubMed2005

Earth science: microseismicity data forecast rupture area.

On 28 September 2004 there was an earthquake of magnitude 6.0 at Parkfield, California. Here we show that the size distribution of the micro-earthquakes recorded in the decades before the main shock occurred allowed an accurate forecast of its eventual rupture area. Applying this approach to other well monitored faults should improve earthquake hazard assessment in future.

Journal Article↗

PubMed2000

Forecasting the growth of multicell tumour spheroids: implications for the dynamic growth of solid tumours.

The growth dynamics of multicell tumour spheroids (MTS) were analysed by means of mathematical techniques derived from signal processing theory. Volume vs. time trajectories of individual spheroids were fitted with the Gompertz growth equation and the residuals (i.e. experimental volume determinations minus calculated values by fitting) were analysed by fast fourier transform and power spectrum. Residuals were not randomly distributed around calculated growth trajectories demonstrating that the Gompertz model partially approximates the growth kinetics of three-dimensional tumour cell aggregates. Power spectra decreased with increasing frequency following a 1/f(delta) power-law. Our findings suggest the existence of a source of 'internal' variability driving the time-evolution of MTS growth. Based on these observations, a new stochastic Gompertzian-like mathematical model was developed which allowed us to forecast the growth of MTS. In this model, white noise is additively superimposed to the trend described by the Gompertz growth equation and integrated to mimic the observed intrinsic variability of MTS growth. A correlation was found between the intensity of the added noise and the particular upper limit of volume size reached by each spheroid within two MTS populations obtained with two different cell lines. The dynamic forces generating the growth variability of three-dimensional tumour cell aggregates also determine the fate of spheroid growth with a strong predictive significance. These findings suggest a new approach to measure tumour growth potential.

Animals↗

PubMed1992

Nonlinear forecasting and iterated function systems.

The theory of dynamical forecasting can be extended to iterated function systems. An unordered set of iterates may be sufficient to construct a simulation of the unknown dynamics. The underlying dynamical system may be nondeterministic: A random element may be allowed in the dynamics, and retrieved by our proposed procedures. A first application of these extensions pertains to the reconstruction of fractal attractors, and allows us to solve the so-called inverse problem in Iterated Functions Systems.

Journal Article↗

PubMed1991

Identification of naturally processed viral nonapeptides allows their quantification in infected cells and suggests an allele-specific T cell epitope forecast.

Virus-specific cytotoxic T lymphocytes (CTL) recognize virus-derived peptides presented by major histocompatibility complex (MHC) class I molecules on virus-infected cells. Such peptides have been isolated from infected cells and were compared to synthetic peptides. We found previously the Kd- or Db-restricted natural influenza nucleoprotein peptides to coelute on reversed phase high performance liquid chromatography columns with certain peptidic by-products present in synthetic peptide preparations. Here we show by extensive biochemical and immunological comparison that the natural peptides in all respects behave as the surmised synthetic nonapeptides, and thus, must be identical to them. The absolute amounts of these natural peptides contained in infected cells could be determined to be between 220 and 540 copies by comparing with defined amounts of pure synthetic nonapeptides. The comparison of the natural Kd-restricted peptide with published synthetic peptides known to contain other Kd-restricted CTL epitopes suggested a new MHC allele-specific T cell epitope forecast method, based on the defined length of nine amino acid residues and on critical amino acid residues at the second and the last position.

Alleles↗

PubMed2006

Forecasting mortality: dynamic assessment of risk in ST-segment elevation acute myocardial infarction.

AIMS: To demonstrate the feasibility and clinical utility of developing dynamic risk assessment models for ST-segment elevation myocardial infarction (STEMI) patients. METHODS AND RESULTS: In 6066 STEMI patients enrolled in the Assessment of the Safety and Efficacy of a New Thrombolytic-3 (ASSENT-3) trial with complete electrocardiographic data, we assessed the probability of 30-day mortality over the following forecasting periods beginning at day 0 (baseline), 3 h, day 2, and day 5 using multiple-logistic regression. These models were validated and simplified in independent samples of 1622 similar fibrinolytic-treated patients from the ASSENT-3 PLUS trial and in 814 STEMI patients undergoing primary percutaneous coronary intervention in the COMplement inhibition in Myocardial infarction treated with Angioplasty (COMMA) trial. The discriminatory power of these predictive models, from baseline to day 5, was excellent (c-statistics 0.80 to 0.87); and their predictive ability was supported by strong gradients in mortality outcomes as the risk score increased. Dynamic modelling also provided information on the change in prognosis over time which may be used to advise more appropriate therapeutic decisions, e.g. the identification of high-risk patients for possible co-interventions. CONCLUSION: Dynamic modelling for STEMI patients enhances the risk assessment and stratification and should provide valuable ongoing guidance for their management.

Adult↗

PubMed2003

Economic impact of extended time on peritoneal dialysis as a result of using polyglucose: the application of a Markov chain model to forecast changes in the development of the ESRD programme over time.

BACKGROUND: The use of polyglucose as a peritoneal dialysis (PD) fluid extends time on PD treatment. It is anticipated, therefore, that the share of patients treated with PD will be positively influenced. The relationship between extension of PD treatment time and an increase of the PD treatment share, however, is complex and needs further investigation. In this paper, a Markov chain model was applied to investigate the impact of extended time on PD treatment for the PD share in all dialysis patients in The Netherlands. Furthermore, the economic impact of the extended time on treatment (ETOT) was explored. METHODS: Scenarios were forecast over a 10 year period using aggregate data from the End-Stage Renal Registry in The Netherlands (Renine). Three scenarios were simulated in which the median PD technique survival was extended by 8, 10 and 12 months. Two other scenarios explored the impact of the combined effect of ETOT of 10 months together with a 10% and 20% increase of PD inflow shares. Reductions of costs to society due to ETOT were estimated using Dutch cost data on renal replacement therapies. RESULTS: PD share increases from 30.0% in the null scenario to 34.5% in the scenario with an ETOT of 10 months and an increased PD inflow share of 20%. The reduction in total costs to society of the renal replacement therapies is 0.96%. The average societal costs per discounted patient year for haemodialysis (HD) are 84 100 euros. For PD, these costs are 60 300 euros. A shift from HD to PD results in average cost savings of 28% per patient year. CONCLUSIONS: In view of high dialysis costs to society, a reduction of 0.96% can be considered to be relevant for healthcare policy makers.

Adolescent↗

PubMed1985

Bayesian pharmacokinetic/pharmacodynamic forecasting of prothrombin response to warfarin therapy: preliminary evaluation.

The ability of a pharmacokinetic/pharmacodynamic Bayesian forecasting computer program to predict prothrombin response to warfarin therapy was investigated. The performance of the program was evaluated retrospectively in an inpatient study population of 45 subjects. Predictions of prothrombin response at discharge, based on zero to five serially measured prothrombin ratios, were compared. Precision of prediction was measured by root mean squared error (rmse), bias was measured by average prediction error, and significance (p less than 0.05) was determined by 95% confidence intervals and correlation coefficients. Eleven (3.8%) predictions exceeded established limitations of the pharmacokinetic/pharmacodynamic model and were excluded from data analysis. Correlations between measured and predicted prothrombin ratios for all methods were significant. The five prothrombin ratio feedbacks provided the most accurate predictions (rmse 0.219). These predictions were significantly better than the population parameter (rmse 0.418), one (rmse 0.401), and two (rmse 0.459) prothrombin ratio feedback predictions. The predictions based on population parameters and one prothrombin ratio feedback were significantly biased. When provided with sufficient feedback, the bias was not apparent and the predictive performance improved with each additional prothrombin ratio. The predictive performance of the four and five prothrombin ratio feedbacks is sufficient to provide clinically useful dosage guidelines early in the course of warfarin therapy. The population parameter estimates require further delineation in order to improve the performance of limited prothrombin ratio feedback predictions.

Bayes Theorem↗