Showing papers by "University of Bologna published in 2000"

The International Registry of Acute Aortic Dissection (IRAD): new insights into an old disease.

Abstract: ContextAcute aortic dissection is a life-threatening medical emergency associated with high rates of morbidity and mortality. Data are limited regarding the effect of recent imaging and therapeutic advances on patient care and outcomes in this setting.ObjectiveTo assess the presentation, management, and outcomes of acute aortic dissection.DesignCase series with patients enrolled between January 1996 and December 1998. Data were collected at presentation and by physician review of hospital records.SettingThe International Registry of Acute Aortic Dissection, consisting of 12 international referral centers.ParticipantsA total of 464 patients (mean age, 63 years; 65.3% male), 62.3% of whom had type A dissection.Main Outcome MeasuresPresenting history, physical findings, management, and mortality, as assessed by history and physician review of hospital records.ResultsWhile sudden onset of severe sharp pain was the single most common presenting complaint, the clinical presentation was diverse. Classic physical findings such as aortic regurgitation and pulse deficit were noted in only 31.6% and 15.1% of patients, respectively, and initial chest radiograph and electrocardiogram were frequently not helpful (no abnormalities were noted in 12.4% and 31.3% of patients, respectively). Computed tomography was the initial imaging modality used in 61.1%. Overall in-hospital mortality was 27.4%. Mortality of patients with type A dissection managed surgically was 26%; among those not receiving surgery (typically because of advanced age and comorbidity), mortality was 58%. Mortality of patients with type B dissection treated medically was 10.7%. Surgery was performed in 20% of patients with type B dissection; mortality in this group was 31.4%.ConclusionsAcute aortic dissection presents with a wide range of manifestations, and classic findings are often absent. A high clinical index of suspicion is necessary. Despite recent advances, in-hospital mortality rates remain high. Our data support the need for continued improvement in prevention, diagnosis, and management of acute aortic dissection.

Artificial Molecular Machines.

Abstract: The miniaturization of components used in the construction of working devices is being pursued currently by the large-downward (top-down) fabrication. This approach, however, which obliges solid-state physicists and electronic engineers to manipulate progressively smaller and smaller pieces of matter, has its intrinsic limitations. An alternative approach is a small-upward (bottom-up) one, starting from the smallest compositions of matter that have distinct shapes and unique properties-namely molecules. In the context of this particular challenge, chemists have been extending the concept of a macroscopic machine to the molecular level. A molecular-level machine can be defined as an assembly of a distinct number of molecular components that are designed to perform machinelike movements (output) as a result of an appropriate external stimulation (input). In common with their macroscopic counterparts, a molecular machine is characterized by 1) the kind of energy input supplied to make it work, 2) the nature of the movements of its component parts, 3) the way in which its operation can be monitored and controlled, 4) the ability to make it repeat its operation in a cyclic fashion, 5) the timescale needed to complete a full cycle of movements, and 6) the purpose of its operation. Undoubtedly, the best energy inputs to make molecular machines work are photons or electrons. Indeed, with appropriately chosen photochemically and electrochemically driven reactions, it is possible to design and synthesize molecular machines that do work. Moreover, the dramatic increase in our fundamental understanding of self-assembly and self-organizational processes in chemical synthesis has aided and abetted the construction of artificial molecular machines through the development of new methods of noncovalent synthesis and the emergence of supramolecular assistance to covalent synthesis as a uniquely powerful synthetic tool. The aim of this review is to present a unified view of the field of molecular machines by focusing on past achievements, present limitations, and future perspectives. After analyzing a few important examples of natural molecular machines, the most significant developments in the field of artificial molecular machines are highlighted. The systems reviewed include 1) chemical rotors, 2) photochemically and electrochemically induced molecular (conformational) rearrangements, and 3) chemically, photochemically, and electrochemically controllable (co-conformational) motions in interlocked molecules (catenanes and rotaxanes), as well as in coordination and supramolecular complexes, including pseudorotaxanes. Artificial molecular machines based on biomolecules and interfacing artificial molecular machines with surfaces and solid supports are amongst some of the cutting-edge topics featured in this review. The extension of the concept of a machine to the molecular level is of interest not only for the sake of basic research, but also for the growth of nanoscience and the subsequent development of nanotechnology.

Self‐categorization, affective commitment and group self‐esteem as distinct aspects of social identity in the organization

Abstract: The purpose of this study is to distinguish between cognitive, affective and evaluative components of social identity in the organization and to show how the components instigate behaviours that benefit in-group members. A new scale for measuring cognitive organizational identification (i.e. self-categorization) is developed and compared to a leading scale. Internal consistency, convergent validity, predictive validity and generalizability of the two scales are established on a sample of Italian (N = 409) and Korean (N = 283) workers. Next, convergent and discriminant validity for measures of organizational identification, affective commitment and group self-esteem are demonstrated. Then, two antecedents of these components of social identity are examined: organization prestige and organization stereotypes. Finally, the mediating role of the components of social identity are investigated between the antecedents and five forms of citizenship behaviours. The last three analyses are performed on the Italian (N = 409) workers. Among other findings, the results show that affective commitment and self-esteem are the primary motivators of citizenship behaviours. Moreover, cognitive identification performs as a central mediator between prestige and stereotypes on the one hand, and affective commitment and self-esteem on the other. Identification is thus an indirect determinant of citizenship behaviours.

A survey of design techniques for system-level dynamic power management

Abstract: Dynamic power management (DPM) is a design methodology for dynamically reconfiguring systems to provide the requested services and performance levels with a minimum number of active components or a minimum load on such components DPM encompasses a set of techniques that achieves energy-efficient computation by selectively turning off (or reducing the performance of) system components when they are idle (or partially unexploited) In this paper, we survey several approaches to system-level dynamic power management We first describe how systems employ power-manageable components and how the use of dynamic reconfiguration can impact the overall power consumption We then analyze DPM implementation issues in electronic systems, and we survey recent initiatives in standardizing the hardware/software interface to enable software-controlled power management of hardware components

High-precision calculation of multiloop feynman integrals by difference equations

Abstract: We describe a new method of calculation of generic multiloop master integrals based on the numerical solution of systems of difference equations in one variable. We show algorithms for the construction of the systems using integration-by-parts identities and methods of solutions by means of expansions in factorial series and Laplace transformation. We also describe new algorithms for the identification of master integrals and the reduction of generic Feynman integrals to master integrals, and procedures for generating and solving systems of differential equations in masses and momenta for master integrals. We apply our method to the calculation of the master integrals of massive vacuum and self-energy diagrams up to three loops and of massive vertex and box diagrams up to two loops. Implementation in a computer program of our approach is described. Important features of the implementation are: the ability to deal with hundreds of master integrals and the ability to obtain very high precision results expanded at will in the number of dimensions.

Efficacy of Implantable Cardioverter–Defibrillators for the Prevention of Sudden Death in Patients with Hypertrophic Cardiomyopathy

Abstract: Background Hypertrophic cardiomyopathy is a genetic disease associated with a risk of ventricular tachyarrhythmias and sudden death, especially in young patients. Methods We conducted a retrospective multicenter study of the efficacy of implantable cardioverter–defibrillators in preventing sudden death in 128 patients with hypertrophic cardiomyopathy who were judged to be at high risk for sudden death. Results At the time of the implantation of the defibrillator, the patients were 8 to 82 years old (mean [±SD], 40±16), and 69 patients (54 percent) were less than 41 years old. The average follow-up period was 3.1 years. Defibrillators were activated appropriately in 29 patients (23 percent), by providing defibrillation shocks or antitachycardia pacing, with the restoration of sinus rhythm; the average age at the time of the intervention was 41 years. The rate of appropriate defibrillator discharge was 7 percent per year. A total of 32 patients (25 percent) had episodes of inappropriate discharges. In the g...

Spin-orbit matrix elements for internally contracted multireference configuration interaction wavefunctions

Abstract: An efficient method for the calculation of Breit-Pauli spin-orbit matrix elements for internally contracted multireference configuration interaction wavefunctions is presented. Instead of taking all two-electron contributions of the wavefunction explicitly into account, the most important two-electron contributions of the spin-orbit operator are incorporated by means of an effective one-electron Fock operator. As a further refinement, explicit two-electron contributions can be reinstated for the dominant all-internal parts of the wavefunctions.

Fractional calculus and continuous-time finance

Abstract: In this paper we present a rather general phenomenological theory of tick-by-tick dynamics in financial markets Many well-known aspects, such as the Levy scaling form, follow as particular cases of the theory The theory fully takes into account the non-Markovian and non-local character of financial time series Predictions on the long-time behaviour of the waiting-time probability density are presented Finally, a general scaling form is given, based on the solution of the fractional diffusion equation

Multiple versus Single Banking Relationships: Theory and Evidence

Abstract: A theory of the optimal number of banking relationships is developed and tested using matched bank-firm data. According to the theory, relationship banks may be unable to continue funding profitable projects owing to internal problems and a firm may thus have to refinance from nonrelationship banks. The latter, however, face an adverse selection problem, as they do not know the quality of the project, and may refuse to lend. In these circumstances, multiple banking can reduce the probability of an early liquidation of the project. The empirical evidence supports the predictions of the model.

When Far Becomes Near: Remapping of Space by Tool Use

Abstract: Far (extrapersonal) and near (peripersonal) spaces are behaviorally defined as the space outside the hand-reaching distance and the space within the hand-reaching distance. Animal and human studies have confirmed this distinction, showing that space is not homogeneously represented in the brain. In this paper we demonstrate that the coding of space as "far" and "near" is not only determined by the hand-reaching distance, but it is also dependent on how the brain represents the extension of the body space. We will show that when the cerebral representation of body space is extended to include objects or tools used by the subject, space previously mapped as far can be remapped as near. Patient P.P., after a right hemisphere stroke, showed a dissociation between near and far spaces in the manifestation of neglect. Indeed, in a line bisection task, neglect was apparent in near space, but not in far space when bisection in the far space was performed with a projection lightpen. However, when in the far space bisection was performed with a stick, used by the patient to reach the line, neglect appeared and was as severe as neglect in the near space. An artificial extension of the patient's body (the stick) caused a remapping of far space as near space.

A theoretical characterization of nonlinear distortion effects in OFDM systems

Abstract: This paper presents a theoretical characterization of nonlinear distortion effects in orthogonal frequency division multiplexing (OFDM) transmission systems. In the theoretical framework developed, it is shown that the effects on the decision variables of the in-band distortion introduced by a bandpass memoryless nonlinearity can be described by means of a complex gain and an additive Gaussian term with zero mean and suitable variance; analytical expressions for gain and variance are given. The conditions which allow this description are emphasized and discussed. As a consequence, a completely analytical procedure to evaluate error probability is also obtained and illustrated using OFDM/discrete multitone modulation (DMT) systems with rectangular pulse shaping; for the soft-envelope limiter nonlinearity, a closed form is derived. A comparison with simulation results is carried out to verify the accuracy of this method.

Effect of long-term treatment with metformin added to hypocaloric diet on body composition, fat distribution, and androgen and insulin levels in abdominally obese women with and without the polycystic ovary syndrome.

Abstract: Abdominal obesity and hyperinsulinemia play a key role in the development of the polycystic ovary syndrome (PCOS). Dietary-induced weight loss and the administration of insulin-lowering drugs, such as metformin, are usually followed by improved hyperandrogenism and related clinical abnormalities. This study was carried out to evaluate the effects of combined hypocaloric diet and metformin on body weight, fat distribution, the glucose-insulin system, and hormones in a group of 20 obese PCOS women[ body mass index (BMI) > 28 kg/m2] with the abdominal phenotype (waist to hip ratio >0.80), and an appropriate control group of 20 obese women who were comparable for age and pattern of body fat distribution but without PCOS. At baseline, we measured sex hormone, sex hormone-binding globulin (SHBG), and leptin blood concentrations and performed an oral glucose tolerance test and computerized tomography (CT) at the L4-L5 level, to measure sc adipose tissue area (SAT) and visceral adipose tissue area. All women were...

Adhesion, autoaggregation and hydrophobicity of 13 strains of Bifidobacterium longum

Abstract: To identify bacterial traits related to adhesion ability in human bifidobacteria, 13 strains of Bifidobacterium longum isolated from human gastric juice and intestine were studied. Strains were tested for their capability to adhere to Caco-2 cells and classified as adhesive (Adh+) or non-adhesive (Adh-). Adh+ and Adh- strains were then investigated for their autoaggregation ability and surface hydrophobicity. Comparing the properties of Adh+ and Adh-, we observed that strains were able to adhere to cell monolayers if they autoaggregate and manifest a good degree of hydrophobicity as determined by microbial adhesion to hydrocarbons. These two traits could be used for preliminary screening to identify potentially adherent isolates.

Insights into the reasons for discontinuation of the first highly active antiretroviral therapy (HAART) regimen in a cohort of antiretroviral naïve patients.

Abstract: Objective: To evaluate the frequency of discontinuation of the first highly active antiretroviral regimen (HAART) and the factors predictive of discontinuing for toxicity and failure in a population-based cohort of HIV-positive individuals in Italy, naive from antiretrovirals at enrolmentMethods: The study population consisted of individuals who initiated HAART and had at least one follow-up visit The primary end-points were discontinuation of any component of HAART for drug toxicity and discontinuation for failure Survival analyses were performed to identify predictive factors for reaching the two end pointsResults: Eight hundred and sixty-two individuals initialed HAART; in 727 of them (843%) this consisted of two nucleoside reverse transcriptase inhibitors (NRTI) and one protease inhibitor (PI) Over a median follow-up of 45 weeks, 312 patients (362%) discontinued therapy: 182 (211%) discontinued due to toxicity, 44 (51%) due to failure The probability of discontinuing HAART at 1 year was 255% [95% confidence interval (Cl), 219-289] due to toxicity and 76% (95% Cl, 49-103) due to failure Independent factors associated with discontinuation for toxicity were: gender [relative hazard (RH) = 051; 95% Cl, 032-080 for men versus women], type of treatment (indinavir-containing regimens, RH = 194; 95% Cl, 110-341 and ritonavir-containing regimens, RH = 383; 95% Cl, 209-703 versus hard-gell saquinavir) and time spent on treatment (RH = 089; 95% Cl, 080-098 for each additional month) Discontinuation due to failure was independently associated with the most recent HIV-RNA (RH = 320; 959/0 Cl, 174-588 for log(10) copies/ml higher), and with type of treatment (indinavir-containing regimens, RH = 021; 95% Cl, 006-078 and ritonavir-containing regimens, RH = 023; 95% Cl, 004-126 Versus hard-gell saquinavir)Conclusions: If the current HAART regimen caused no toxicity, less than 10% of naive patients discontinue their first HAART regimen because of failure after 1 year from starting therapy (C) 2000 Lippincatt Williams & Wilkins

The Three-Dimensional Bin Packing Problem

Abstract: The problem addressed in this paper is that of orthogonally packing a given set of rectangular-shaped items into the minimum number of three-dimensional rectangular bins. The problem is strongly NP-hard and extremely difficult to solve in practice. Lower bounds are discussed, and it is proved that the asymptotic worst-case performance ratio of the continuous lower bound is ?. An exact algorithm for filling a single bin is developed, leading to the definition of an exact branch-and-bound algorithm for the three-dimensional bin packing problem, which also incorporates original approximation algorithms. Extensive computational results, involving instances with up to 90 items, are presented: It is shown that many instances can be solved to optimality within a reasonable time limit.

Recent developments of induction motor drives fault diagnosis using AI techniques

Abstract: This paper presents a review of the developments in the field of diagnosis of electrical machines and drives based on artificial intelligence (AI). It covers the application of expert systems, artificial neural networks (ANNs), and fuzzy logic systems that can be integrated into each other and also with more traditional techniques. The application of genetic algorithms is considered as well. In general, a diagnostic procedure starts from a fault tree developed on the basis of the physical behavior of the electrical system under consideration. In this phase, the knowledge of well-tested models able to simulate the electrical machine in different fault conditions is fundamental to obtain the patterns characterizing the faults. The fault tree navigation performed by an expert system inference engine leads to the choice of suitable diagnostic indexes, referred to a particular fault, and relevant to build an input data set for specific AI (NNs, fuzzy logic, or neuro-fuzzy) systems. The discussed methodologies, that play a general role in the diagnostic field, are applied to an induction machine, utilizing as input signals the instantaneous voltages and currents. In addition, the supply converter is also considered to incorporate in the diagnostic procedure the most typical failures of power electronic components. A brief description of the various AI techniques is also given; this highlights the advantages and the limitations of using AI techniques. Some applications examples are also discussed and areas for future research are also indicated.

Fractional calculus and continuous-time finance II: the waiting-time distribution

Abstract: We complement the theory of tick-by-tick dynamics of financial markets based on a continuous-time random walk (CTRW) model recently proposed by Scalas et al [4], and we point out its consistency with the behaviour observed in the waiting-time distribution for BUND future prices traded at LIFFE, London.

Implementation of a direct control algorithm for induction motors based on discrete space vector modulation

Abstract: The basic concept of direct torque control of induction machines is investigated in order to emphasize the effects produced by a given voltage vector on stator flux and torque variations. The low number of voltage vectors which can be applied to the machine using the basic DTC scheme may cause undesired torque and current ripple. An improvement of the drive performance can be obtained using a new DTC algorithm based on the application of the space vector modulation (SVM) for prefixed time intervals. In this way a sort of discrete space vector modulation (DSVM) is introduced. Numerical simulations and experimental tests have been carried out to validate the proposed method.