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PubMed1999

On the theory of partially inbreeding finite populations. VI. The survival probability of a two-locus allele combination when there is partial selfing.

Consider a large population with two loci that may be linked, with one having alleles A and a and the second alleles B and b. Let there be initially one individual with genotype AB/ab in a population otherwise consisting of ab/ab individuals. We assume that AB/ab, Ab/aB, AB/aB, AB/Ab and AB/AB individuals have higher probabilities of survival to adulthood than individuals with genotype ab/ab. The probability that AB ultimately survives, if there is a positive probability of selfing, is calculated. To simplify calculations, it is assumed that the number of offspring produced by any individual follows a Poisson distribution and that genotypes of separate offspring are independent. If recombination is possible, we conclude that a population with a high probability of selfing is more likely to accumulate epistatically favorable genes than one reproducing largely by random mating. This advantage of selfing becomes more pronounced as the strength of selection in favor of AB increases.

Alleles↗

PubMed2003

Low-level predictive inference in reading: the influence of transitional probabilities on eye movements.

We report the results of an investigation into the ability of transitional probability (word-to-word contingency statistics) to account for reading behaviour. Using a corpus of eye movements recorded during the reading of newspaper text, we demonstrate both the forward [P(n/n-1)] and backward [P(n/n+1)] transitional probability measures to be predictive of first fixation and gaze durations: the higher the transitional probability, the shorter the fixation time. Initial fixation position was also affected by the forward measure; we observed a small rightward shift for words that were highly predictable from the preceding word. Although transitional probability is sensitive to word class, with function words being generally more predictable from their context than content words, the measures accounted equally well for the data for both classes.

Eye Movements↗

PubMed2001

Age, prostate-specific antigen, and digital rectal examination as determinants of the probability of having prostate cancer.

OBJECTIVES: The decision to perform prostate biopsy has traditionally been based on an abnormal prostate-specific antigen (PSA) level or abnormal digital rectal examination (DRE) findings. For example, a 60-year-old man with a benign DRE and PSA level of 4.1 ng/mL would be counseled for biopsy, and the same man with a PSA level of 3.9 ng/mL might be counseled against biopsy. However, the difference in these PSA levels and in the likelihood of these two men having prostate cancer is not significant. We constructed a probability nomogram for the likelihood of detecting prostate cancer, thus aiding in the decision of whether to perform a prostate biopsy. METHODS: Using multivariate logistic regression analysis and data from 2054 men (mean age 64 years) participating in the Tyrol Screening Project between January 9, 1993 and January 9, 1997, patient age, PSA level, and DRE findings were analyzed for their ability to determine the likelihood of finding prostate cancer on transrectal ultrasound-guided biopsy. RESULTS: DRE was suspicious in 278 men (13.5%). Overall, 498 (24.5%) of 2054 men biopsied had prostate cancer. The probability of discovering cancer on biopsy was calculated using patient age, DRE findings, and PSA level. CONCLUSIONS: DRE status had a large influence on the likelihood of positive biopsy across all PSA and age ranges. A combination of PSA, DRE result, and age better defined the probability of a positive biopsy than any factor alone. Using this nomogram, the decision to proceed with or defer prostate biopsy can be based on an actual probability of discovering prostate cancer rather than a single PSA-based cutpoint. These data may aid physicians and patients in decision-making.

Age Factors↗

PubMed1996

Using proportions of free to total prostate-specific antigen, age, and total prostate-specific antigen to predict the probability of prostate cancer.

OBJECTIVES: This study was undertaken to define the probability of prostate cancer as a function of the proportion of free to total prostate-specific antigen (FTPSA), total PSA, and age for those patients with total PSA levels between 2.5 and 20.0 ng/mL. METHODS: Prebiopsy serums were obtained from 428 untreated patients (165 malignant, 263 benign) who had undergone sextant six-core biopsy. Each patient had no prior history of prostate cancer and a prebiopsy total PSA value between 2.5 and 20.0 ng/mL. Total PSA levels were determined using the PA immunoassay performed on the TOSOH AIA-1200 automated immunoassay instrument. Free PSA levels were determined using a monoclonal-polyclonal antibody sandwich radioimmunoassay. RESULTS: In men with total PSA values between 2.5 and 20.0 ng/mL, the FTPSA significantly differentiated between patients with benign and malignant histologic states. Log linear modeling indicated distinct differences in the risk for cancer as a function of FTPSA, total PSA, and age. The highest probability for cancer was observed in men greater than 70 years of age who had a FTPSA less than 7% and total PSA more than 10.0 ng/mL. Conversely, the lowest probability for cancer was observed in patients less than 60 years of age who had a FTPSA more than 25% and a total PSA less than 4 ng/mL. CONCLUSIONS: The probability that prostate cancer will be found on biopsy has a marked gradient that is associated with age, total PSA, and FTPSA. The extreme ends of FTPSA of less than 7% and more than 25% are diagnostic for prostate cancer and benign prostatic disease, respectively.

Adult↗

PubMedDate not supplied

The precise time course of lexical activation: MEG measurements of the effects of frequency, probability, and density in lexical decision.

Visually presented letter strings consistently yield three MEG response components: the M170, associated with letter-string processing (Tarkiainen, Helenius, Hansen, Cornelissen, & Salmelin, 1999); the M250, affected by phonotactic probability, (Pylkkänen, Stringfellow, & Marantz, 2002); and the M350, responsive to lexical frequency (Embick, Hackl, Schaeffer, Kelepir, & Marantz, 2001). Pylkkänen et al. found evidence that the M350 reflects lexical activation prior to competition among phonologically similar words. We investigate the effects of lexical and sublexical frequency and neighborhood density on the M250 and M350 through orthogonal manipulation of phonotactic probability, density, and frequency. The results confirm that probability but not density affects the latency of the M250 and M350; however, an interaction between probability and density on M350 latencies suggests an earlier influence of neighborhoods than previously reported.

Adolescent↗

PubMed1998

Stimulus probability and event-related potentials of the brain in 6-month-old human infants: a parametric study.

The effects of a priori stimulus probability and local-stimulus sequences on the Nc, NSW and Pc components of the event-related brain potentials were studied in six groups of 6-month-old human infants. Predictions from memory, expectancy and attentional accounts of the Nc, NSW and Pc components were examined using an infant-control oddball paradigm in which visual stimuli were presented across groups, at 0.90/0.10, 0.80/0.20, 0.70/0.30, 0.60/0.40, 0.50/0.50 (alternation) and 0.50/0.50 (random) probabilities. The main results indicated that stimulus probabilities and local-stimulus sequences affected Nc amplitude and latency, NSW amplitude but not the Pc component. Concurrent visual fixation performance was also found to be influenced by stimulus probabilities. The results were discussed in terms of the predictions from memory, expectancy and attentional accounts of the infant late components.

Analysis of Variance↗

PubMed2000

Time-dependent transition probabilities and the assessment of seasonal effects on within-day variations in chewing behaviour of housed sheep.

State transitions in the chewing behaviour of six half-breed (Île de FrancexTexel) yearling female sheep (Ovis aries L.) were studied by using jaw movements recorded continuously over 5 days at the end of a number of experimental periods from 21 September 1992 to 4 April 1993. The sheep were housed in individual pens. Each of them received the same diet, that is, 250 g/day of concentrate mix (15.5% crude protein (CP), 36.5% neutral detergent fibre (NDF)) fed at 0900 h and natural grass hay (6.7% CP, 69.1% NDF) fed ad libitum at 0915 and 1600 h. Mineral salt blocks and water were continuously available. The main objective was to assess seasonal effects on within-day variations in the chewing behaviour of sheep, at small to large time scales within a day. We therefore focused on two experimental periods characterised by contrasting conditions of daylength and temperature (i.e., 'Period 1': 610 min daylight, mean temperature of 10.9 degrees C, and 'Period 4': 550 min daylight, mean temperature of 7.2 degrees C). In particular, differences between periods in the nycterohemeral pattern of chewing behaviour and the quality of forecasts of chewing states were tested. We submitted our data to a new method of analysis that we developed: the method of time-dependent transition probabilities, and compared the results to those obtained using other methods that were available in the literature.Overall, the sheep spent more time eating in Period 1 than in Period 4. Specifically, a secondary peak in eating activity, which was observed in the early afternoon in Period 1, was absent in Period 4. The nycterohemeral pattern of eating activity showed significant differences between periods, at the main rhythmic component of 24 h and at short components around 2 h. Such differences were not observed for ruminating and idling activities. The quality of forecasts of chewing states decreased from Periods 1 to 4, in terms of accuracy (based on R(2)) and lead of reliable forecasts (i.e., &z.sfnc;forecast-observation&z.sfnc;<0.1). The most (least) accurate forecasts were obtained for the ruminating (eating) state in both periods. We have attributed the differences that we found between periods to daylength instead of temperature because the sheep were mostly within the thermoneutral zone in our study. By comparison, using mean hourly times of eating activity, significant differences between periods were detected for the 24-h rhythmic component and the 4-h component, instead of the 2-h component, probably because of aliasing (i.e., when the sampling time interval used is longer than suited; the minute was found to be a suitable interval length in the calculation of time-dependent transition probabilities). Using the age-dependent model of Rook and Penning, minor differences between periods were detected. On that basis, the method of time-dependent transition probabilities may be brought forward as a complement of value to existing methods of behavioural data analysis.

Journal Article↗

PubMed2004

Predictive model of diagnosing probable cases of severe acute respiratory syndrome in febrile patients with exposure risk.

STUDY OBJECTIVE: Since the World Health Organization issued a global alert about severe acute respiratory syndrome (SARS) on March 12, 2003, the illness has become a major public health challenge worldwide. The objective of this study is to identify the clinical risk factors of SARS and to develop a scoring system for early diagnosis. METHODS: The detailed clinical data of all patients presenting to the emergency department (ED) with a temperature higher than 38.0 degrees C (100.3 degrees F), documented at home or at the ED, and risks of exposure to SARS within 14 days were assessed. The diagnosis of probable SARS was made according to the definition of the Centers for Disease Control and Prevention. Items with significant differences among symptoms, signs, and laboratory tests on presentation between SARS and non-SARS groups were determined and used to develop the scoring system. RESULTS: Seventy patients were enrolled and 8 were diagnosed as probably having SARS. None of the initially discharged patients or their relatives developed SARS. Compared with the non-SARS group, the SARS group was younger (33.9+/-15.9 years versus 44+/-9.8 years; P=.02), had a higher percentage of fever prolonged more than 5 days (87.5% versus 6.5%; P<.01), myalgia (75% versus 27.4%; P=.01), and diarrhea (50% versus 9.7%; P=.02); had less occurrence of cough before or during fever (0% versus 64.5%; P=.01); and had lower absolute lymphocyte (0.9+/-0.3x10(9)/L versus 1.5+/-1.1x10(9)/L; P<.01) and platelet counts (144.1+/-36.3x10(9)/L versus 211.6+/-78.8x10(9)/L; P=.02). A 4-item symptom score based on the presence of cough before or concomitant with fever, myalgia, diarrhea, and rhinorrhea or sore throat detects SARS with 100% sensitivity and 75.9% specificity; a 6-item clinical score based on lymphopenia (<1.0x10(9)/L), thrombocytopenia (<150x10(9)/L) and the 4 symptom items detects SARS with 100% sensitivity and 86.3% specificity. CONCLUSION: Certain symptoms and laboratory tests indicate higher risk of febrile probable SARS. In nonendemic areas, the febrile patients with recent contact with SARS or travel history to endemic areas could be screened for the probability of SARS by the use of clinical and symptom scores.

Adolescent↗

PubMed2000

Effects of auditory stimuli correlated with different probabilities of water delivery in a limited-hold temporal schedule.

Four rats were exposed to two different tone frequencies, each tone being correlated with independent probabilities of water delivery in a temporally defined schedule. The schedule consisted of a 60-s T cycle, with 30-s t(D) and t(Delta) succesive subcycles. t(D) and t(Delta) were assigned complementary probabilities of water delivery (1.0-0, 0.75-0.25, 0.5-0.5 and 1.0-0) in succesive phases. Each of the first three experimental phases was followed by five consecutive probe sessions using the same probability values, and in which water was delivered independently of responding at the end of each subcycle. Three additional rats were exposed to the same conditions, except that only one tone was used in t(D) and t(Delta). The highest frequencies of responding were observed in two of the rats exposed to differential tone frequencies, an effect that was correlated with lower percentages of lost water deliveries, shorter response latencies, and less variability in the intervals between successive water presentations. In the last phase in which probabilities of water delivery in t(D) and t(Delta) were 1.0 and 0, respectively, response frequency was always higher in t(Delta). These results suggest that the number of water deliveries obtained in the early cycles of every session were responsible for the total number of responses and its correlated effects.

Journal Article↗

PubMed2001

Comparison of measured and calculated emission probabilities for K and L X-rays following radioactive disintegration processes.

The program EMISSION has been developed at the Physikalisch-Technische Bundesanstalt (PTB). It allows emission probabilities to be calculated for K and L X-rays following radioactive disintegration processes. This program was already applied to the calculation of total K X-ray emission probabilities for six radionuclides. The results are found to be in reasonable agreement with measured values. In order to check the validity of this program also for the individual components of K and L X-rays, calculated emission probabilities of K X-ray components (139Ce, 203Hg) and L X-ray components (139Ce, 203Hg, 241Am) were compared with remeasured (139Ce, 203Hg) and already available (241Am) emission probabilities, measured earlier at the PTB. In most cases there is an agreement within the standard uncertainties of the measured and calculated values, usually within 1-5%. Larger deviations, not covered by three times the standard uncertainty have been found for some weak lines.

Journal Article↗

PubMed2003

"Probable" versus "confirmed" leptospirosis: an epidemiologic and clinical comparison utilizing a surveillance case classification.

PURPOSE: For surveillance purposes, the Centers for Disease Control and Prevention and Council of State and Territorial Epidemiologists (CDC/CSTE) have defined two case classifications for leptospirosis: "confirmed" and "probable." The objective of this study was to provide data to refine the current surveillance case classifications. METHODS: All reported leptospirosis infections from exposures within the State of Hawaii, 1974 to 1998 meeting CDC/CSTE "confirmed" and "probable" case classifications were compared on a number of clinical and epidemiologic parameters. RESULTS: Confirmed cases (n = 276) had more severe clinical manifestations than probable cases (n = 180); however, probable cases with higher peak microscopic agglutination test (MAT) titers (> or =1:800) were clinically and epidemiologically comparable to confirmed cases. In addition, 77 cases demonstrating fourfold or greater MAT titer increases in paired serum collected less than two weeks apart (currently excluded from the "confirmed" case classification) were also comparable to confirmed cases. CONCLUSIONS: Our findings support amending the current CDC/CSTE surveillance confirmed case classification to include demonstration of a fourfold or greater MAT titer increase in paired serum, irrespective of the interval between specimen collection. Consideration should also be given to including single MAT titer > or =1:800 as a criterion for "confirmation." These changes would both simplify and expedite the surveillance confirmation of leptospirosis.

Diagnosis, Differential↗

PubMed2006

Calculation of vertical correlation probability in Ge/Si(001) shallow island quantum dot multilayer systems.

We investigate the behavior of the island vertical pairing probability in multilayer systems of Ge island quantum dots (QDs) in Si(001). By combining a simple kinetic rate model with our previously reported atomistic simulation results on the nature of the stress field from buried shallow Ge islands having {105}-oriented sidewalls, we derive an analytical expression for correlation probability as a function of the parameters characterizing the multi-QD systems. The approach is based upon continuum mechanochemical potential model, which allows one to introduce necessary elements of the kinetics of island formation in a simple way. We compare the model predictions with available experimental data and find that the model provides a satisfactory description of the coupling probability. The correlation probability behavior as a function of capping layer thickness, Ge island size, interisland distance, and Ge adatom diffusion length is investigated within the framework of the developed model.

Computer Simulation↗

PubMed2002

S-state dependence of the miss probability in Photosystem II.

The oxygen production of dark-adapted Photosystem II upon illumination by a series of single-turnover flashes shows a damped period four oscillation with flash number. The damping is attributed to 'misses' resulting from a statistical probability that a reaction center fails to produce a stable charge separation after a saturating flash. The origin of misses is of interest because its probable dependence on flash number, in principle, affects the quantitative interpretation of all measurements on phenomena associated with the period four oscillation. We show that the kinetics of chlorophyll fluorescence yield transients induced by a flash series can be used to estimate the relative amplitudes of the miss probability on each flash. It is concluded that a major part of the misses must be caused by failure of the reduction of the oxidized primary electron donor chlorophyll P680(+) by the secondary donor tyrosine Y(Z) before the charge separation is lost by recombination. The probability of this failure is found to increase with the oxidation state of the oxygen-evolving complex: more than half of it occurs upon charge separation in the S(3) state, which is attributed to the presence of Y(Z) (ox) S(2) in Boltzmann equilibrium with Y(Z)S(3).

Journal Article↗

PubMed2004

Marijuana odor perception: studies modeled from probable cause cases.

The 4th Amendment of the United States Constitution protects American citizens against unreasonable search and seizure without probable cause. Although law enforcement officials routinely rely solely on the sense of smell to justify probable cause when entering vehicles and dwellings to search for illicit drugs, the accuracy of their perception in this regard has rarely been questioned and, to our knowledge, never tested. In this paper, we present data from two empirical studies based upon actual legal cases in which the odor of marijuana was used as probable cause for search. In the first, we simulated a situation in which, during a routine traffic stop, the odor of packaged marijuana located in the trunk of an automobile was said to be detected through the driver's window. In the second, we investigated a report that marijuana odor was discernable from a considerable distance from the chimney effluence of diesel exhaust emanating from an illicit California grow room. Our findings suggest that the odor of marijuana was not reliably discernable by persons with an excellent sense of smell in either case. These studies are the first to examine the ability of humans to detect marijuana in simulated real-life situations encountered by law enforcement officials, and are particularly relevant to the issue of probable cause.

Adult↗

PubMed2000

Probabilities and polarity biases in conditional inference.

A probabilistic computational level model of conditional inference is proposed that can explain polarity biases in conditional inference (e.g., J. St. B. T. Evans, 1993). These biases are observed when J. St. B. T. Evans's (1972) negations paradigm is used in the conditional inference task. The model assumes that negations define higher probability categories than their affirmative counterparts (M. Oaksford & K. Stenning, 1992); for example, P(not-dog) > P(dog). This identification suggests that polarity biases are really a rational effect of high-probability categories. Three experiments revealed that, consistent with this probabilistic account, when high-probability categories are used instead of negations, a high-probability conclusion effect is observed. The relationships between the probabilistic model and other phenomena and other theories in conditional reasoning are discussed.

Humans↗

PubMed1994

The role of probability of reinforcement in models of choice.

A general account of choice behavior in animals, the cumulative effects model, has been proposed by Davis, Staddon, Machado, and Palmer (1993). Its basic assumptions are that choice occurs in an all-or-none fashion for the response alternative with the highest probability of reinforcement and that the probability of reinforcement for each response alternative is calculated from the entire history of training (total number of reinforced responses/total number of reinforced and nonreinforced responses). The model's reliance on probability of reinforcement as the fundamental variable controlling choice behavior subjects the cumulative effects model to the same criticisms as have been directed toward other related models of choice, notably melioration theory. Several different data sets show that the relative value of a response alternative is not predicted by the obtained probability of reinforcement associated with that alternative. Alternative approaches to choice theory are considered.

Animals↗

PubMed2005

Spread of human cancer cells occurs with probabilities indicative of a nongenetic mechanism.

There has been much uncertainty as to whether metastasis requires mutation at the time of spread. Here, we use clinical data to calculate the probability of the spread of melanoma and breast cancer cells. These calculations reveal that the probability of the spread of cancer cells is relatively high for small tumours (approximately 1 event of spread for every 500 cells for melanomas of 0.1 mm) and declines as tumours increase in size (approximately 1 event of spread for every 10(8) cells for melanomas of 12 mm). The probability of spread of breast cancer cells from the lymph nodes to the periphery is approximately 1 event of spread for every 10(8) cells in the nodal masses, which have a mean diameter of 5 mm, while the probability of spread of cancer cells from the breast to the periphery when the primary masses are 5 mm is also approximately 1 event of spread for every 10(8) cells. Thus, the occurrence of an event of spread from the breast to the lymph nodes appears not to increase the propensity of the progeny of those cells to spread from the lymph nodes to the periphery. These values indicate that the spread of human breast cancer and melanoma cells is unlikely to occur by a mechanism requiring mutation at the time of spread.

Breast Neoplasms↗

PubMed2004

Spasms in children with definite and probable mitochondrial disease.

The diagnosis of mitochondrial encephalomyopathies is complex and a system for classification of the diagnosis as definite, probable, and possible has been proposed. The objective of this study was to explore the spectrum of epileptic disorders associated with probable and definite mitochondrial disease in children using this classification system. The patient population with mitochondrial disease and epilepsy was selected from a tertiary care children's hospital. Interictal electroencephalograms and video-EEG recordings were used to characterize seizure types. Ten children fulfilled the criteria for probable or definite mitochondrial disease and had epilepsy. Four had siblings with a similar clinical phenotype. Spasms were the most common seizure type and were the initial seizure type in seven patients and two siblings. Four patients had only partial seizures, with or without generalization, and one patient had seizures that were difficult to classify. Blood lactate concentrations were elevated consistently in patients with partial seizures alone but were occasionally normal in children with spasms. Spasms were the most common presenting seizure type in children with probable and definite mitochondrial disease.

Child↗