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The author presents 12 theories which try to evaluate the significance of paranasal sinuses. A vast amount of references on this subject and additionally this paper do not explain the role of paranasal sinuses in human. In the author's opinion the most probable is the amortizative and constructive theory based on antropometric studies and experimental head traumas.
Bruno de Finetti is possibly the best known Italian applied mathematician of the 20th century, but was he really just a mathematician? Looking at his papers it is always possible to find original and pioneering contributions to the various fields he was interested in, where he always put his mathematical "formamentis" and skills at the service of the applications, often extending standard theories and models in order to achieve more general results. Many contributions are also devoted to educational issues, in mathematics in general and in probability and statistics in particular.He really thought that mathematics and, in particular, those topics related to uncertainty, should enter in everyday life as a useful support to everyone's decision making. He always imagined and lived mathematics as a basic tool both for better understanding and describing complex phenomena and for helping decision makers in assuming coherent and feasible actions. His many important contributions to the theory of probability and to mathematical statistics are well known all over the world, thus, in the following, minor, but still pioneering, aspects of his work, related both to theory and to applications of mathematical tools, and to his work in the field of education and training of teachers, are presented.
INTRODUCTION: Patients with hip fractures are usually frail and elderly with a 30-day mortality in excess of 10% in European series. Perioperative morbidity is often multifactorial in nature, and unimodal interventions will not necessarily decrease mortality. The purpose of this prospective study was to analyse causes of mortality, and thereby the potential and limitations to decrease mortality after hip fracture surgery. METHODS: 300 consecutive, unselected hip fracture patients were treated in a multimodal rehabilitation programme with continuous perioperative epidural analgesia and anaesthesia, early surgery, standardized fluid and transfusion therapy, enforced oral nutrition and early mobilization and physiotherapy. All deaths within 30 days of surgery or during primary hospitalization were analysed and classified according to whether death was unavoidable, probably unavoidable, or potentially avoidable. RESULTS: Thirty-day mortality was 13.3% (40 patients) and the total perioperative mortality was 15.6% (47 patients). Death was definitely unavoidable in 28%, probably unavoidable in 15%, and in theory potentially avoidable in 57%. In the patients where death was potentially avoidable, active care was curtailed in 16 of 27 (59%) patients. CONCLUSION: About a quarter of the total mortality in hip fracture patients is definitely unavoidable, and death is probably only avoidable in about half of the unselected patients. These results have important implications for the design of future outcome studies, which should focus on other relevant outcomes than mortality per se.
We study how interactions affect the quantum reflection of Bose-Einstein condensates. A patterned silicon surface with a square array of pillars resulted in high reflection probabilities. For incident velocities greater than 2.5 mm/s, our observations agreed with single-particle theory. At velocities below 2.5 mm/s, the measured reflection probability saturated near 60% rather than increasing towards unity as predicted by the accepted theoretical model. We extend the theory of quantum reflection to account for the mean-field interactions of a condensate which suppresses quantum reflection at low velocity. The reflected condensates show collective excitations as recently predicted.
Assessment of the reliability of a given phylogenetic hypothesis is an important step in phylogenetic analysis. Historically, the nonparametric bootstrap procedure has been the most frequently used method for assessing the support for specific phylogenetic relationships. The recent employment of Bayesian methods for phylogenetic inference problems has resulted in clade support being expressed in terms of posterior probabilities. We used simulated data and the four-taxon case to explore the relationship between nonparametric bootstrap values (as inferred by maximum likelihood) and posterior probabilities (as inferred by Bayesian analysis). The results suggest a complex association between the two measures. Three general regions of tree space can be identified: (1) the neutral zone, where differences between mean bootstrap and mean posterior probability values are not significant, (2) near the two-branch corner, and (3) deep in the two-branch corner. In the last two regions, significant differences occur between mean bootstrap and mean posterior probability values. Whether bootstrap or posterior probability values are higher depends on the data in support of alternative topologies. Examination of star topologies revealed that both bootstrap and posterior probability values differ significantly from theoretical expectations; in particular, there are more posterior probability values in the range 0.85-1 than expected by theory. Therefore, our results corroborate the findings of others that posterior probability values are excessively high. Our results also suggest that extrapolations from single topology branch-length studies are unlikely to provide any general conclusions regarding the relationship between bootstrap and posterior probability values.
A theory has been developed to quantify the reduction of subsample variance of aflatoxin contamination, which is observed when granular materials are wet slurried, rather than dry ground, during subsample homogenization. A coefficient of variation, based on particle size distribution, subsample size, and probability of contamination, is predicted. The theory is tested with dry ground and with wet slurried pistachios, and excellent quantitative agreement is obtained. A 32% increase in the mean aflatoxin level is observed as well when wet slurrying is applied. Although no statistical explanation for this effect can be found, it is suggested that it is related to physiochemical binding between the nut matrix, which is (partly) broken by wet slurrying, and aflatoxin, making the extraction of more toxin possible. Other parameters that may affect slurrying results have been investigated as well.
A fundamental goal of cognitive neuroscience is to explain how mental decisions originate from basic neural mechanisms. The goal of the present study was to investigate the neural correlates of perceptual decisions in the context of emotional perception. To probe this question, we investigated how fluctuations in functional MRI (fMRI) signals were correlated with behavioral choice during a near-threshold fear detection task. fMRI signals predicted behavioral choice independently of stimulus properties and task accuracy in a network of brain regions linked to emotional processing: posterior cingulate cortex, medial prefrontal cortex, right inferior frontal gyrus, and left insula. We quantified the link between fMRI signals and behavioral choice in a whole-brain analysis by determining choice probabilities by means of signal-detection theory methods. Our results demonstrate that voxel-wise fMRI signals can reliably predict behavioral choice in a quantitative fashion (choice probabilities ranged from 0.63 to 0.78) at levels comparable to neuronal data. We suggest that the conscious decision that a fearful face has been seen is represented across a network of interconnected brain regions that prepare the organism to appropriately handle emotionally challenging stimuli and that regulate the associated emotional response.
From the steady-state theory of mutation rates we have the probability, q, of the occurrence of a critical change at some site in a cell that leads to genetic alternation, and the probability, p = 1 - q, that the site either is not changed or that it has been repaired. In this paper the formal theory is extended to include survival of biological systems. Single and multiple mechanisms of nonsurvival, and multiple factors acting on a single mechanism, are considered. The number of sites that must be altered to lead to nonsurvival is examined and found to be greater than one. The effect of independent action on separate sets of sites, and the relationship between dose size and survival time are given.
PURPOSE OF THE STUDY: Mucoid pseudocysts are infrequent benign tumors which can develop on all peripheral nerves near joints. The origin of these cysts remains to be determined. We searched for arguments favoring an articular origin which would have an impact on management and risk of recurrence. MATERIALS AND METHODS: Twenty-three patients (21 men and 2 women, mean age 38 years, age range 13-56 years) presented mucoid pseudocysts and were followed for a mean six years. The mucoid pseudocyst was located on the common fibular nerve at the neck of the fibula in 16 patients, on the tibial nerve at the knee in one, on the median nerve in one, on the ulnar nerve in one, and on the suprascapular nerve in two. Pain was local in 18 patients and irradiated to the concerned nerve territory in 20. Motor deficit was the inaugural feature in 17 patients. EMG was performed in all patients, ultrasound exploration in 15, computed tomography in 7 and magnetic resonance imaging in 10. All patients included in this series underwent surgery: pathological diagnosis of mucoid intra-neural pseudocyst was established in all. Systematic search for communication with the neighboring joint was performed in all cases. RESULTS: An articular communication was found in 17 patients. Mean time to recovery of muscle force (scored 5) and/or normal sensitivity was seven months in 17 patients. One patient did not achieve full recovery. Three patients experienced recurrence and required tibiofibular arthrodesis. DISCUSSION: Three theories have been proposed (cystic degeneration of schwannoma, degeneration of nerve sheath connective tIssue, and an articular origin). The articular theory appears to be the most probable. The presence of an articular pedicle in 60% of the patients, the anatomic juxtaposition between the nerves involved and neighboring joints, and occasional migration along the articular nerve as well as the cyst's mucoid content argue in favor of the articular theory. The notion of recurrence after complete minute excision is also in favor of an articular pathogenic mechanism. The diagnosis of mucoid cyst should be retained as a possibility in patients with rapidly progressive signs of nerve compression near a joint. It is important to search for articular communication before and during the surgical excision in order to limit the risk of recurrence.
A longstanding problem in the study of sediment transport in gravel-bed rivers is related to the physical mechanisms governing bed resistance and particle motion. To study this problem, we investigated the motion of coarse spherical glass beads entrained by a steady shallow turbulent water flow down a steep two-dimensional channel with a mobile bed. This experimental facility is the simplest representation of sediment transport on the laboratory scale, with the tremendous advantages that boundary conditions are perfectly controlled and a wealth of information can be obtained using imaging techniques. Flows were filmed from the side by a high-speed camera. Using image processing software made it possible to determine the flow characteristics such as particle trajectories, their state of motion (rest, rolling, or saltating motion), and flow depth. In accordance with earlier investigations, we observed that over short time periods, sediment transport appeared as a very intermittent process. To interpret these results, we revisited Einstein's theory on sediment and derived the statistical properties (probability distribution and autocorrelation function) of the key variables such as the solid discharge and the number of moving particles. Analyzing the autocorrelation functions and the probability distributions of our measurements revealed the existence of long-range correlations. For instance, whereas theory predicts a Binomial distribution for the number of moving particles, experiments demonstrated that a negative binomial distribution best fit our data, which emphasized the crucial role played by wide fluctuations. These frequent wide fluctuations stemmed particle entrainment and motion being collective phenomena rather than individual processes, contrary to what is assumed in most theoretical models.
According to the theory of developmental tasks the mastery of a developmental task leads to happiness and increases the probability of competence in the following tasks. This theory may be the roof under which theories of life crises, continuity, stress, learned helplessness, and socialization may be specific models to explain satisfaction and/or competence in managing developmental tasks. -- By applying the theory of developmental tasks to the process of aging this process in the negative sense may be seen as a consequence of not mastering developmental tasks.
The adsorption of proteins and other large molecules at the liquid-solid interface often involves a surface-induced transition in either internal conformation or molecular orientation. Recently, Van Tassel et al. modeled this adsorption/transition process as the sequential surface placement of spreading disks. In this work, we employ the scaled particle theory (SPT) to derive approximate analytical expressions for the probability functions appearing in the kinetic equations for this model system. Specifically, the probability functions governing the adsorption and spreading events are calculated in terms of the reversible work required to create cavities in a binary system of spread and unspread disks. Compared to those derived earlier via a density expansion theory (DET), the SPT approximated probability functions are simpler and more accurate (compared to simulation), and are applicable over a wider set of parameter values. Copyright 1999 Academic Press.
When people have access to information sources such as newspaper weather forecasts, drug-package inserts, and mutual-fund brochures, all of which provide convenient descriptions of risky prospects, they can make decisions from description. When people must decide whether to back up their computer's hard drive, cross a busy street, or go out on a date, however, they typically do not have any summary description of the possible outcomes or their likelihoods. For such decisions, people can call only on their own encounters with such prospects, making decisions from experience. Decisions from experience and decisions from description can lead to dramatically different choice behavior. In the case of decisions from description, people make choices as if they overweight the probability of rare events, as described by prospect theory. We found that in the case of decisions from experience, in contrast, people make choices as if they underweight the probability of rare events, and we explored the impact of two possible causes of this underweighting--reliance on relatively small samples of information and overweighting of recently sampled information. We conclude with a call for two different theories of risky choice.
Pigeons obtained food by responding in a discrete-trials two-choice probability-learning experiment involving temporal stimuli. A given response alternative, a left- or right-key peck, had 11 associated reinforcement probabilities within each session. Reinforcement probability for a choice was an increasing or a decreasing function of the time interval immediately preceding the choice. The 11 equiprobable temporal stimuli ranged from 1 to 11 sec in 1-sec classes. Preference tended to deviate from probability matching in the direction of maximizing; i.e., the percentage of choices of the preferred response alternative tended to exceed the probability of reinforcement for that alternative. This result was qualitatively consistent with probability-learning experiments using visual stimuli. The result is consistent with a molecular analysis of operant behavior and poses a difficulty for molar theories holding that local variations in reinforcement probability may safely be disregarded in the analysis of behavior maintained by operant paradigms.
Statistical decision theory can provide useful support for climate change decisions made under conditions of uncertainty. However, the probability distributions used to calculate expected costs in decision theory are themselves subject to uncertainty, disagreement, or ambiguity in their specification. This imprecision can be described using sets of probability measures, from which upper and lower bounds on expectations can be calculated. However, many representations, or classes, of probability measures are possible. We describe six of the more useful classes and demonstrate how each may be used to represent climate change uncertainties. When expected costs are specified by bounds, rather than precise values, the conventional decision criterion of minimum expected cost is insufficient to reach a unique decision. Alternative criteria are required, and the criterion of minimum upper expected cost may be desirable because it is consistent with the precautionary principle. Using simple climate and economics models as an example, we determine the carbon dioxide emissions levels that have minimum upper expected cost for each of the selected classes. There can be wide differences in these emissions levels and their associated costs, emphasizing the need for care when selecting an appropriate class.
The role of quantum processes in brain activity has been discussed intensively in recent years. Some authors regard the indeterminacy of quantum events as key property to relate brain activity and consciousness on a scientific basis. Here we ask the question where quantum events could be effective in the complex cortical structure. We argue that only elementary microscopic processes like electron transfer in protein complexes are able to survive thermal fluctuations. A model for the quantal emission process at the synaptic cleft is presented and related to the mechanism of electron transfer between different molecular states, as described by Marcus theory.
Acquired drug resistance is a major limitation for successful treatment of cancer. Resistance emerges due to drug exclusion, drug metabolism and alteration of the drug target by mutation or overexpression. Depending on therapy, the type of cancer and its stage, one or several genetic or epigenetic alterations are necessary to confer resistance to treatment. The fundamental question is the following: if a genetically diverse population of replicating cancer cells is subjected to chemotherapy that has the potential to eradicate it, what is the probability of emergence of resistance? Here, we review a general mathematical framework based on multi-type branching processes designed to study the dynamics of escape of replicating organisms from selection pressures. We apply the general model to evolution of resistance of cancer cells and discuss examples for diverse mechanisms of resistance. Our theory shows how to estimate the probability of success for any treatment regimen.
The idea of perturbation independent decay (PID) has appeared in the context of survival-probability studies, and lately has emerged in the context of quantum irreversibility studies. In both cases the PID reflects the Lyapunov instability of the underlying semiclassical dynamics, and it can be distinguished from the Wigner-type decay that holds in the perturbative regime. The theory of the survival probability is manifestly related to the parametric theory of the local density of states (LDOS). In contrast to that the physics of quantum irreversibility requires subtle cross correlations, which are not captured by the LDOS alone, to be taken into account.