Driver scheduling problem modelling

The Drivers Scheduling Problem (DSP) consists of selecting a set of duties for vehicle drivers, for example buses, trains, plane or boat drivers or pilots, for the transportation of passengers or goods. This is a complex problem because it involves several constraints related to labour and company rules and can also present different evaluation criteria and objectives. Being able to develop an adequate model for this problem that can represent the real problem as close as possible is an important research area.The main objective of this research work is to present new mathematical models to the DSP problem that represent all the complexity of the drivers scheduling problem, and also demonstrate that the solutions of these models can be easily implemented in real situations. This issue has been recognized by several authors and as important problem in Public Transportation. The most well-known and general formulation for the DSP is a Set Partition/Set Covering Model (SPP/SCP). However, to a large extend these models simplify some of the specific business aspects and issues of real problems. This makes it difficult to use these models as automatic planning systems because the schedules obtained must be modified manually to be implemented in real situations. Based on extensive passenger transportation experience in bus companies in Portugal, we propose new alternative models to formulate the DSP problem. These models are also based on Set Partitioning/Covering Models; however, they take into account the bus operator issues and the perspective opinions and environment of the user.We follow the steps of the Operations Research Methodology which consist of: Identify the Problem; Understand the System; Formulate a Mathematical Model; Verify the Model; Select the Best Alternative; Present the Results of theAnalysis and Implement and Evaluate. All the processes are done with close participation and involvement of the final users from different transportation companies. The planner s opinion and main criticisms are used to improve the proposed model in a continuous enrichment process. The final objective is to have a model that can be incorporated into an information system to be used as an automatic tool to produce driver schedules. Therefore, the criteria for evaluating the models is the capacity to generate real and useful schedules that can be implemented without many manual adjustments or modifications. We have considered the following as measures of the quality of the model: simplicity, solution quality and applicability. We tested the alternative models with a set of real data obtained from several different transportation companies and analyzed the optimal schedules obtained with respect to the applicability of the solution to the real situation. To do this, the schedules were analyzed by the planners to determine their quality and applicability. The main result of this work is the proposition of new mathematical models for the DSP that better represent the realities of the passenger transportation operators and lead to better schedules that can be implemented directly in real situations.

Research joint ventures and optimal R&D policy with asymmetric information

When to allow Research Joint Ventures (RJVs) or not is an importantinstrument in the development of an optimal R&D policy. Theregulator, however, is unlikely to know all the relevant informationto regulate R&D optimally. The extent to which there existappropriability problems between the firms is one such variable thatis private information to the firms in the industry. In a duopolysetting we analyze the characteristics of a second-best R&D policywhere the government can either allow RJVs or not and give lump-sumsubsidies to the parties involved. The second-best R&D policy withoutsubsidies will either block some welfare improving RJVs or allow somewelfare reducing ones. With lump-sum subsidies, the second-best policytrades off the expected subsidy cost with allowing welfare decreasingRJVs or blocking welfare increasing ones.

Current trends in illegal drug use and drug related health problems in Switzerland.

As part of the evaluation of the Confederation's measures to reduce drug related problems, a review of available data on drug use and drug related problems in Switzerland has been conducted. Source of data included: population surveys (adults and teenagers), surveys among drug users, health statistics (drug related and AIDS related deaths, HIV case reporting, drug treatments) police statistics (denunciations for consumption). The aims of reducing the number of dependent hard drug users have been achieved where heroin is concerned. In particular, there seems to have been a decrease in the number of people becoming addicted to this substance. For all other illegal substances, especially cannabis, the trend is towards an increased use, as in many European countries. As regards dependent drug users, especially injecting drug users, progress has been made in the area of harm reduction and treatment coverage. This epidemiological assessment can be used in the discussions currently engaged about the revision of the Law governing narcotics and will be a baseline for future follow up of the situation.

Neural control of vascular reactions: impact of emotion and attention.

This study investigated the neural regions involved in blood pressure reactions to negative stimuli and their possible modulation by attention. Twenty-four healthy human subjects (11 females; age = 24.75 ± 2.49 years) participated in an affective perceptual load task that manipulated attention to negative/neutral distractor pictures. fMRI data were collected simultaneously with continuous recording of peripheral arterial blood pressure. A parametric modulation analysis examined the impact of attention and emotion on the relation between neural activation and blood pressure reactivity during the task. When attention was available for processing the distractor pictures, negative pictures resulted in behavioral interference, neural activation in brain regions previously related to emotion, a transient decrease of blood pressure, and a positive correlation between blood pressure response and activation in a network including prefrontal and parietal regions, the amygdala, caudate, and mid-brain. These effects were modulated by attention; behavioral and neural responses to highly negative distractor pictures (compared with neutral pictures) were smaller or diminished, as was the negative blood pressure response when the central task involved high perceptual load. Furthermore, comparing high and low load revealed enhanced activation in frontoparietal regions implicated in attention control. Our results fit theories emphasizing the role of attention in the control of behavioral and neural reactions to irrelevant emotional distracting information. Our findings furthermore extend the function of attention to the control of autonomous reactions associated with negative emotions by showing altered blood pressure reactions to emotional stimuli, the latter being of potential clinical relevance.

Optimal information transmission in organizations: Search and congestion

We propose a stylized model of a problem-solving organization whoseinternal communication structure is given by a fixed network. Problemsarrive randomly anywhere in this network and must find their way to theirrespective specialized solvers by relying on local information alone.The organization handles multiple problems simultaneously. For this reason,the process may be subject to congestion. We provide a characterization ofthe threshold of collapse of the network and of the stock of foatingproblems (or average delay) that prevails below that threshold. We buildupon this characterization to address a design problem: the determinationof what kind of network architecture optimizes performance for any givenproblem arrival rate. We conclude that, for low arrival rates, the optimalnetwork is very polarized (i.e. star-like or centralized ), whereas it islargely homogenous (or decentralized ) for high arrival rates. We also showthat, if an auxiliary assumption holds, the transition between these twoopposite structures is sharp and they are the only ones to ever qualify asoptimal.

A finite-population revenue management model and a risk-ratio procedure for the joint estimation of population size and parameters

Many dynamic revenue management models divide the sale period into a finite number of periods T and assume, invoking a fine-enough grid of time, that each period sees at most one booking request. These Poisson-type assumptions restrict the variability of the demand in the model, but researchers and practitioners were willing to overlook this for the benefit of tractability of the models. In this paper, we criticize this model from another angle. Estimating the discrete finite-period model poses problems of indeterminacy and non-robustness: Arbitrarily fixing T leads to arbitrary control values and on the other hand estimating T from data adds an additional layer of indeterminacy. To counter this, we first propose an alternate finite-population model that avoids this problem of fixing T and allows a wider range of demand distributions, while retaining the useful marginal-value properties of the finite-period model. The finite-population model still requires jointly estimating market size and the parameters of the customer purchase model without observing no-purchases. Estimation of market-size when no-purchases are unobservable has rarely been attempted in the marketing or revenue management literature. Indeed, we point out that it is akin to the classical statistical problem of estimating the parameters of a binomial distribution with unknown population size and success probability, and hence likely to be challenging. However, when the purchase probabilities are given by a functional form such as a multinomial-logit model, we propose an estimation heuristic that exploits the specification of the functional form, the variety of the offer sets in a typical RM setting, and qualitative knowledge of arrival rates. Finally we perform simulations to show that the estimator is very promising in obtaining unbiased estimates of population size and the model parameters.

Insurance with frequent trading

This paper looks at the dynamic management of risk in an economy with discrete time consumption and endowments and continuous trading. I study how agents in such an economy deal with all the risk in the economy and attain their Pareto optimal allocations by trading in a few natural securities: private insurance contracts and a common set of derivatives on the aggregate endowment. The parsimonious nature ofthe implied securities needed for Pareto optimality suggests that insuch contexts complete markets is a very reasonable assumption.

Three essays on liquidity risk

Preface In this thesis we study several questions related to transaction data measured at an individual level. The questions are addressed in three essays that will constitute this thesis. In the first essay we use tick-by-tick data to estimate non-parametrically the jump process of 37 big stocks traded on the Paris Stock Exchange, and of the CAC 40 index. We separate the total daily returns in three components (trading continuous, trading jump, and overnight), and we characterize each one of them. We estimate at the individual and index levels the contribution of each return component to the total daily variability. For the index, the contribution of jumps is smaller and it is compensated by the larger contribution of overnight returns. We test formally that individual stocks jump more frequently than the index, and that they do not respond independently to the arrive of news. Finally, we find that daily jumps are larger when their arrival rates are larger. At the contemporaneous level there is a strong negative correlation between the jump frequency and the trading activity measures. The second essay study the general properties of the trade- and volume-duration processes for two stocks traded on the Paris Stock Exchange. These two stocks correspond to a very illiquid stock and to a relatively liquid stock. We estimate a class of autoregressive gamma process with conditional distribution from the family of non-central gamma (up to a scale factor). This process was introduced by Gouriéroux and Jasiak and it is known as Autoregressive gamma process. We also evaluate the ability of the process to fit the data. For this purpose we use the Diebold, Gunther and Tay (1998) test; and the capacity of the model to reproduce the moments of the observed data, and the empirical serial correlation and the partial serial correlation functions. We establish that the model describes correctly the trade duration process of illiquid stocks, but have problems to adjust correctly the trade duration process of liquid stocks which present long-memory characteristics. When the model is adjusted to volume duration, it successfully fit the data. In the third essay we study the economic relevance of optimal liquidation strategies by calibrating a recent and realistic microstructure model with data from the Paris Stock Exchange. We distinguish the case of parameters which are constant through the day from time-varying ones. An optimization problem incorporating this realistic microstructure model is presented and solved. Our model endogenizes the number of trades required before the position is liquidated. A comparative static exercise demonstrates the realism of our model. We find that a sell decision taken in the morning will be liquidated by the early afternoon. If price impacts increase over the day, the liquidation will take place more rapidly.

Rabies postexposure prophylaxis in routine practice in view of the new centers for disease control and prevention and world health organization recommendations.

Background. New recommendations for rabies postexposure prophylaxis (PEP) were published by the Centers for Disease Control and Prevention and the World Health Organization in 2010. In view of these new recommendations, we investigated the adequacy of rabies PEP among patients consulting our travel clinic. Methods. A retrospective analysis of the files of all patients who consulted for rabies PEP at the Travel Clinic of the University Hospital in Lausanne, Switzerland, between January 2005 and August 2011 was conducted. Results. A total of 110 patients who received rabies PEP were identified. The median age of the patients was 34 years (range, 2-79 years), and 53% were women. Ninety subjects were potentially exposed to rabies while travelling abroad. Shortcomings in the management of these patients were (1) late initiation of rabies PEP in travelers who waited to seek medical care until returning to Switzerland, (2) administration of human rabies immunoglobulin (HRIG) to only 7 of 50 travelers (14%) who sought care abroad and for whom HRIG was indicated, and (3) antibody levels <0.5 IU/mL in 6 of 90 patients (6.7%) after 4 doses of vaccine. Conclusions. Patients do not always receive optimal rabies PEP under real-life conditions. A significant proportion of patients did not develop adequate antibody levels after 4 doses of vaccine. These data indicate that the measurement of antibody levels on day 21 of the Essen PEP regimen is useful in order to verify an adequate immune response.

Role of substrate utilization and thermogenesis on body-weight control with particular reference to alcohol.

Alcohol (ethanol; EtOH) provides fuel energy to the body (29.7 kJ (7. 1 kcal)/g, 23.4 kJ (5.6 kcal)/ml), as do other macronutrients, but no associated essential nutrients. The thermogenic effect of EtOH (on average 15 % of its metabolizable value) is much greater than that of the main substrates utilized by the body, i.e. fat and carbohydrates (CHO), suggesting a lower net efficiency of energy utilization for EtOH than for fat and CHO. EtOH cannot be stored in the body and is toxic, so that there is an obligatory continuous oxidation of EtOH and it becomes the priority fuel to be metabolized. In contrast to CHO, its rate of oxidation does not depend on the dose ingested. As with CHO intake, it engenders a shift in postprandial substrate utilization (decrease in fat oxidation), but by a non-insulin-mediated mechanism. A limited amount of EtOH can be converted to fatty acids by hepatic de novo lipogenesis (as occurs with high levels of CHO feeding) from acetate production, which inhibits lipolysis in peripheral tissues. There is no evidence that EtOH consumed under normoenergetic conditions (i.e. isoenergetically replacing CHO or fat) leads to greater body fat storage than fat or CHO. However, there is still a lack of experimental studies on the influence of EtOH on the level of spontaneous physical activity in man. This effect may well depend on the dose of EtOH consumed as well as other intrinsic factors.

Control d'una bobinadora automàtica

Un dels problemes típics de regulació en el camp de l’automatització industrial és el control de velocitat lineal d’entrada del fil a les bobines, ja que com més gruix acumulem a igual velocitat de rotació de la bobina s’augmenta notablement la velocitat lineal d’entrada del fil, aquest desajust s’ha de poder compensar de forma automàtica per aconseguir una velocitat d’entrada constant. Aquest problema de regulació de velocitats és molt freqüent i de difícil control a la indústria on intervé el bobinat d’algun tipus de material com cablejat, fil, paper, làmines de planxa, tubs, etc... Els dos reptes i objectius principals són, primer, la regulació de la velocitat de rotació de la bobina per aconseguir una velocitat lineal del fil d’entrada, i segon, mitjançant el guiatge de l’alimentació de fil a la bobina, aconseguir un repartiment uniforme de cada capa de fil. El desenvolupament consisteix amb l’automatització i control d’una bobinadora automàtica mitjançant la configuració i programació de PLC’s, servomotors i encoders. Finalment es farà el muntatge pràctic sobre una bancada per verificar i simular el seu correcte funcionament que ha de donar solució a aquests problemes de regulació de velocitats. Com a conclusions finals s’han aconseguit els objectius i una metodologia per fer una regulació de velocitats de rotació per bobines, amb accionaments de servomotors amb polsos, i a nivell de coneixements he aconseguit dominar les aplicacions d’aquest tipus d’accionaments aplicats a construccions mecàniques.

Phytochrome interacting factors 4 and 5 redundantly limit seedling de-etiolation in continuous far-red light.

Phytochromes are red/far-red photosensors that regulate numerous developmental programs in plants. Among them, phytochrome A (phyA) is essential to enable seedling de-etiolation under continuous far-red (FR) light, a condition that mimics the environment under a dense canopy. The ecological relevance of this response is demonstrated by the high mortality rate of phyA mutant plants that germinate in deep vegetational shade. phyA signaling involves direct interaction of the photoreceptor with phytochrome-interacting factors PIF1 and PIF3, members of the bHLH transcription factor family. Here we investigated the involvement of PIF4 and PIF5 in phyA signaling, and found that they redundantly control de-etiolation in FR light. The pif4 pif5 double mutant is hypersensitive to low fluence rates of FR light. This phenotype is dependent on FR light perception by phyA, but does not rely on alterations in the phyA level. Our microarray analysis shows that PIF4 and PIF5 are part of an inhibitory mechanism that represses the expression of some light-responsive genes in the dark, and that they are also needed for full expression of several growth-related genes in the light. Unlike PIF1 and PIF3, PIF4 and PIF5 are not degraded in response to FR light, indicating that they are light-regulated by a different mechanism. Our genetic analysis suggests that this is achieved through sequestration of these PIFs by the closely related bHLH transcription factor HFR1 (long hypocotyl in FR light).

Parental post-traumatic reactions after premature birth: implications for sleeping and eating problems in the infant.

BACKGROUND: Progress in perinatal medicine has made it possible to increase the survival of very or extremely low birthweight infants. Developmental outcomes of surviving preterm infants have been analysed at the paediatric, neurological, cognitive, and behavioural levels, and a series of perinatal and environmental risk factors have been identified. The threat to the child's survival and invasive medical procedures can be very traumatic for the parents. Few empirical reports have considered post-traumatic stress reactions of the parents as a possible variable affecting a child's outcome. Some studies have described sleeping and eating problems as related to prematurity; these problems are especially critical for the parents. OBJECTIVE: To examine the effects of post-traumatic reactions of the parents on sleeping and eating problems of the children. DESIGN: Fifty families with a premature infant (25-33 gestation weeks) and a control group of 25 families with a full term infant participated in the study. Perinatal risks were evaluated during the hospital stay. Mothers and fathers were interviewed when their children were 18 months old about the child's problems and filled in a perinatal post-traumatic stress disorder questionnaire (PPQ). RESULTS: The severity of the perinatal risks only partly predicts a child's problems. Independently of the perinatal risks, the intensity of the post-traumatic reactions of the parents is an important predictor of these problems. CONCLUSIONS: These findings suggest that the parental response to premature birth mediates the risks of later adverse outcomes. Preventive intervention should be promoted.

When "enough" is not enough: new perspectives on optimal methadone maintenance dose.

Some methadone maintenance treatment (MMT) programs prescribe inadequate daily methadone doses. Patients complain of withdrawal symptoms and continue illicit opioid use, yet practitioners are reluctant to increase doses above certain arbitrary thresholds. Serum methadone levels (SMLs) may guide practitioners dosing decisions, especially for those patients who have low SMLs despite higher methadone doses. Such variation is due in part to the complexities of methadone metabolism. The medication itself is a racemic (50:50) mixture of 2 enantiomers: an active "R" form and an essentially inactive "S" form. Methadone is metabolized primarily in the liver, by up to five cytochrome P450 isoforms, and individual differences in enzyme activity help explain wide ranges of active R-enantiomer concentrations in patients given identical doses of racemic methadone. Most clinical research studies have used methadone doses of less than 100 mg/day [d] and have not reported corresponding SMLs. New research suggests that doses ranging from 120 mg/d to more than 700 mg/d, with correspondingly higher SMLs, may be optimal for many patients. Each patient presents a unique clinical challenge, and there is no way of prescribing a single best methadone dose to achieve a specific blood level as a "gold standard" for all patients. Clinical signs and patient-reported symptoms of abstinence syndrome, and continuing illicit opioid use, are effective indicators of dose inadequacy. There does not appear to be a maximum daily dose limit when determining what is adequately "enough" methadone in MMT.

Yield of intermittent versus continuous EEG in comatose survivors of cardiac arrest treated with hypothermia.

INTRODUCTION: Electroencephalography (EEG) has a central role in the outcome prognostication in subjects with anoxic/hypoxic encephalopathy following a cardiac arrest (CA). Continuous EEG monitoring (cEEG) has been consistently developed and studied; however, its yield as compared to repeated standard EEG (sEEG) is unknown. METHODS: We studied a prospective cohort of comatose adults treated with therapeutic hypothermia (TH) after a CA. cEEG data regarding background activity and epileptiform components were compared to two 20 minute sEEG extracted from the cEEG recording (one during TH, and one in early normothermia). RESULTS: In this cohort, 34 recordings were studied. During TH, the agreement between cEEG and sEEG was 97.1% (95% CI: 84.6 - 99.9%) for background discontinuity and reactivity evaluation, while it was 94.1% (95% CI 80.3 - 99.2%) regarding epileptiform activity. In early normothermia, we did not find any discrepancies. Thus, concordance was very good during TH (kappa 0.83), and optimal during normothermia (kappa=1). The median delay between CA and the first EEG reactivity testing was 18 hours (range: 4.75 - 25) for patients with perfect agreement and 10 hours (range: 5.75 - 10.5) for the three patients in whom there were discordant findings (P=0.02, Wilcoxon). CONCLUSION: Standard intermittent EEG has comparable performance than continuous EEG both for variables important for outcome prognostication (EEG reactivity) and identification of epileptiform transients in this relatively small sample of comatose survivors of CA. This finding has an important practical implication, especially for centers where EEG resources are limited.