Showing papers by "University of Bologna published in 1996"

Ant system: optimization by a colony of cooperating agents

Abstract: An analogy with the way ant colonies function has suggested the definition of a new computational paradigm, which we call ant system (AS). We propose it as a viable new approach to stochastic combinatorial optimization. The main characteristics of this model are positive feedback, distributed computation, and the use of a constructive greedy heuristic. Positive feedback accounts for rapid discovery of good solutions, distributed computation avoids premature convergence, and the greedy heuristic helps find acceptable solutions in the early stages of the search process. We apply the proposed methodology to the classical traveling salesman problem (TSP), and report simulation results. We also discuss parameter selection and the early setups of the model, and compare it with tabu search and simulated annealing using TSP. To demonstrate the robustness of the approach, we show how the ant system (AS) can be applied to other optimization problems like the asymmetric traveling salesman, the quadratic assignment and the job-shop scheduling. Finally we discuss the salient characteristics-global data structure revision, distributed communication and probabilistic transitions of the AS.

Effect of the Angiotensin-Converting–Enzyme Inhibitor Benazepril on the Progression of Chronic Renal Insufficiency

Abstract: Background Drugs that inhibit angiotensin-converting enzyme slow the progression of renal insufficiency in patients with diabetic nephropathy. Whether these drugs have a similar action in patients with other renal diseases is not known. We conducted a study to determine the effect of the angiotensin-converting–enzyme inhibitor benazepril on the progression of renal insufficiency in patients with various underlying renal diseases. Methods In a three-year trial involving 583 patients with renal insufficiency caused by various disorders, 300 patients received benazepril and 283 received placebo. The underlying diseases included glomerulopathies (in 192 patients), interstitial nephritis (in 105), nephrosclerosis (in 97), polycystic kidney disease (in 64), diabetic nephropathy (in 21), and miscellaneous or unknown disorders (in 104). The severity of renal insufficiency was classified according to the base-line creatinine clearance: 227 patients had mild insufficiency (creatinine clearance, 46 to 60 ml per minu...

Fractional Relaxation-Oscillation and Fractional Diffusion-Wave Phenomena

Abstract: The processes involving the basic phenomena of relaxation, diffusion, oscillations and wave propagation are of great relevance in physics; from a mathematical point of view they are known to be governed by simple differential equations of order 1 and 2 in time. The introduction of fractional derivatives of order α in time, with 0

Evidence for the Conformation of the Pathologic Isoform of the Prion Protein Enciphering and Propagating Prion Diversity

Abstract: The fundamental event in prion diseases seems to be a conformational change in cellular prion protein (PrPC) whereby it is converted into the pathologic isoform PrPSc. In fatal familial insomnia (FFI), the protease-resistant fragment of PrPSc after deglycosylation has a size of 19 kilodaltons, whereas that from other inherited and sporadic prion diseases is 21 kilodaltons. Extracts from the brains of FFI patients transmitted disease to transgenic mice expressing a chimeric human-mouse PrP gene about 200 days after inoculation and induced formation of the 19-kilodalton PrPSc fragment, whereas extracts from the brains of familial and sporadic Creutzfeldt-Jakob disease patients produced the 21-kilodalton PrPSc fragment in these mice. The results presented indicate that the conformation of PrPSc functions as a template in directing the formation of nascent PrPSc and suggest a mechanism to explain strains of prions where diversity is encrypted in the conformation of PrPSc.

Effect of an Enteric-Coated Fish-Oil Preparation on Relapses in Crohn's Disease

Abstract: Background Patients with Crohn's disease may have periods of remission, interrupted by relapses. Because fish oil has antiinflammatory actions, it could reduce the frequency of relapses, but it is often poorly tolerated because of its unpleasant taste and gastrointestinal side effects. Methods We performed a one-year, double-blind, placebo-controlled study to investigate the effects of a new fish-oil preparation in the maintenance of remission in 78 patients with Crohn's disease who had a high risk of relapse. The patients received either nine fish-oil capsules containing a total of 2.7 g of n-3 fatty acids or nine placebo capsules daily. A special coating protected the capsules against gastric acidity for at least 30 minutes. Results Among the 39 patients in the fish-oil group, 11 (28 percent) had relapses, 4 dropped out because of diarrhea, and 1 withdrew for other reasons. In contrast, among the 39 patients in the placebo group, 27 (69 percent) had relapses, 1 dropped out because of diarrhea, and 1 wit...

Topology prediction for helical transmembrane proteins at 86% accuracy.

Abstract: Previously, we introduced a neural network system predicting locations of transmembrane helices (HTMs) based on evolutionary profiles (PHDhtm, Rost B, Casadio R, Fariselli P, Sander C, 1995, Protein Sci 4:521-533). Here, we describe an improvement and an extension of that system. The improvement is achieved by a dynamic programming-like algorithm that optimizes helices compatible with the neural network output. The extension is the prediction of topology (orientation of first loop region with respect to membrane) by applying to the refined prediction the observation that positively charged residues are more abundant in extra-cytoplasmic regions. Furthermore, we introduce a method to reduce the number of false positives, i.e., proteins falsely predicted with membrane helices. The evaluation of prediction accuracy is based on a cross-validation and a double-blind test set (in total 131 proteins). The final method appears to be more accurate than other methods published: (1) For almost 89% (+/-3%) of the test proteins, all HTMs are predicted correctly. (2) For more than 86% (+/-3%) of the proteins, topology is predicted correctly. (3) We define reliability indices that correlate with prediction accuracy: for one half of the proteins, segment accuracy raises to 98%; and for two-thirds, accuracy of topology prediction is 95%. (4) The rate of proteins for which HTMs are predicted falsely is below 2% (+/-1%). Finally, the method is applied to 1,616 sequences of Haemophilus influenzae. We predict 19% of the genome sequences to contain one or more HTMs. This appears to be lower than what we predicted previously for the yeast VIII chromosome (about 25%).

AI techniques in induction machines diagnosis including the speed ripple effect

Abstract: Various applications of artificial intelligence (AI) techniques (expert systems, neural networks, and fuzzy logic) presented in the literature prove that such technologies are well suited to cope with on-line diagnostic tasks for induction machines. The features of these techniques and the improvements that they introduce in the diagnostic process are recalled, showing that, in order to obtain an indication on the fault extent, faulty machine models are still essential. Moreover, by the models, that must trade off between simulation result effectiveness and simplicity, it is possible to overcome crucial points of the diagnosis. With reference to rotor electrical faults of induction machines, a new and simple procedure based on a model which includes the speed ripple effect is developed. This procedure leads to a new diagnostic index, independent of the machine operating condition and inertia value, that allows the implementation of the diagnostic system with a minimum configuration intelligence.

Influence of a lossy ground on lightning-induced voltages on overhead lines

Abstract: A comprehensive study on the effect of a lossy ground on the induced voltages on overhead power lines by a nearby lightning strike is presented The ground conductivity plays a role in both the evaluation of the lightning radiated fields and of the line parameters To be calculated by means of a rigorous theory, both fields and line constants need important computation time, which, for the problem of interest, is still prohibitive The aim of this paper is to discuss and analyze the various simplified approaches and techniques that have been proposed for the calculation of the fields and the line constants when the ground cannot be assumed as a perfectly conducting plane Regarding the radiated electromagnetic field, it is shown that the horizontal electric field, the component which is most affected by the ground finite conductivity, can be calculated in an accurate way using the Cooray-Rubinstein simplified formula The presence of an imperfectly conducting ground is included in the coupling equations by means of two additional terms: the longitudinal ground impedance and the transverse ground admittance, which are both frequency-dependent The latter can generally be neglected for typical overhead lines, due to its small contribution to the overall transverse admittance of the line Regarding the ground impedance, a comparison between several simplified expressions used in the literature is presented and the validity limits of these expressions are established It is also shown that for typical overhead lines the wire impedance can be neglected as regard to the ground impedance

Serum Sex Hormone Levels After Menopause and Subsequent Breast Cancer

Abstract: Background : High levels of androgens and estrogens have been reported to be associated with breast cancer. However, the multiplicity of factors that influence hormone levels and methodologic issues complicate the study of the relationship between steroid sex hormones and breast cancer. Purpose : Using an improved study design, we assessed prospectively the relationship between the principal steroid sex hormones in serum and the subsequent occurrence of invasive breast cancer in postmenopausal women. Methods : Four thousand fifty-three healthy postmenopausal women, aged 40-69 years, were enrolled from June 1987 through June 1992 in a prospective investigation of hormones and diet in the etiology of breast tumors (ORDET study) as part of a larger volunteer cohort of 10 788 premenopausal and postmenopausal women from Varese Province, northern Italy. At recruitment, blood samples were taken between 8 :00 AM and 9 :30 AM (after overnight fasting), and sera were preserved in -80 °C freezers. Women who had received hormone treatment in the 3 months prior to enrollment, who had a bilateral ovariectomy, or who had a history of cancer or liver disease were not recruited. Twenty-five women in the final eligible cohort of 4040 postmenopausal women developed histologically confirmed, invasive breast cancer during the first 3.5 years of follow-up for the cohort (13 537 woman-years). For each case subject, four control subjects were randomly chosen after matching for factors possibly affecting hormone preservation in serum. One case subject and eight control subjects were excluded because premenopausal hormonal patterns were found ; thus, after also excluding the four control subjects matched to the ineligible case subject, we included 24 case and 88 control subjects. In the spring of 1994, stored sera of case and control subjects were assayed in a blinded manner for dehydroepiandrosterone sulfate and estradiol (E 2 ) by in-house radioimmunoassay and for total and free testosterone and sex hormone-binding globulin by commercially available nonextraction iodination kits. Mean differences in risk factors were tested by analysis of variance for paired data. Relative risks (RRs) were estimated by conditional logistic regression analysis. All P values resulted from two-sided tests. Results : Age-adjusted mean values of total testosterone, free testosterone, and E 2 were significantly higher in case subjects than in control subjects : total testosterone, 0.34 ng/mL versus 0.25 ng/mL (P<.001) ; free testosterone, 1.07 pg/mL versus 0.77 pg/mL (P =.006) ; and E 2 , 25 pg/mL versus 22 pg/mL (P = .027). Age-adjusted RRs for breast cancer in increasing tertiles were as follows: for total testosterone, 1.0, 4.8, and 7.0 (P for trend =.026) ; for free testosterone, 1.0, 1.8, and 5.7 (P for trend =.005) ; and for total E 2 , 1.0, 7.1, and 5.5 (P for trend =.128). Conclusions and Implications : This prospective study provides further evidence in support of the already established association between elevated estrogen levels and breast cancer. Even more importantly, it provides new evidence that high serum testosterone levels precede breast cancer occurrence

Differences in Essential Oil Composition of Basil (Ocimum basilicum L.) Italian Cultivars Related to Morphological Characteristics

Abstract: Ten Italian cultivars of basil were studied to establish a possible relation between morphological characteristics and essential oil composition. The morphological parameters were recorded at the b...

Organisational learning and core capabilities development: the role of IT

Abstract: The resource-based view of the firm (RBVF) focuses on the firm's resources and capabilities to understand business strategy and to provide direction to strategy formulation. This paper emphasizes the learning aspects of capability development and explores how information technology (IT) can contribute to it. As a standardized resource widely available, IT can participate in the fundamental process that transforms resources into capabilities and eventually into core capabilities. In this way, IT can become — embedded in core capabilities — an active component of the firm's competitive advantages. The process by which resources end up being components of core capabilities in firms is a learning process that can be described and understood using RBVF concepts. Furthermore, the development of IT strategic applications (also called ‘strategic information systems’, or SIS) follows patterns that closely parallel the structure of that learning process. For this reason we propose an organizational learning model based on the RBVF, and use it to derive guidelines for management action aimed at improving IT effectiveness in organizations. The paper is organized as follows: the RBVF framework is summarized, including the concepts of capabilities and core capabilities and the organizational processes that lead to them. Next, an organizational learning model is presented: an interpretation of capability development that emphasizes situated learning and knowledge accumulation. The model is then used to show how IT can contribute to core capability formation in a firm: management action can mold the process to some extent, although it often unfolds ‘naturally’ embedded in an organizational context that is both determined by and determinant of learning. Finally, guidelines are discussed to come up and build strategic IT applications, based on the previous analysis. Short conclusions follow.

Performance of the DELPHI detector

Abstract: DELPHI (DEtector with Lepton, Photon and Hadron Identification) is a detector for e^+e^- physics, designed to provide high granularity over a 4\pi solid angle, allowing an effective particle identification. It has been operating at the LEP (Large Electron-Positron) collider at CERN since 1989. This article reviews its performance.

Hybrid I/O automata

Abstract: We propose a new hybrid I/O automaton model that is capable of describing both continuous and discrete behavior. The model, which extends the timed I/O automaton model of [12, 7] and the phase transition system models of [15, 2], allows communication among components using both shared variables and shared actions. The main contributions of this paper are: (1) the definition of hybrid I/O automata and of an implementation relation based on hybrid traces, (2) the definition of a simulation between hybrid I/O automata and a proof that existence of a simulation implies the implementation relation, (3) a definition of composition of hybrid I/O automata and a proof that it respects the implementation relation, and (4) a definition of receptiveness for hybrid I/O automata and a proof that, assuming certain compatibility conditions, receptiveness is preserved by composition.

HLA-Identical Sibling Bone Marrow Transplantation in Younger Patients with Chronic Lymphocytic Leukemia

Abstract: Objective: To characterize in detail the outcomes of HLA-identical sibling bone marrow transplantation for chronic lymphocytic leukemia (CLL) in patients younger than 60 years of age. Design: Retro...

Increased gingival dimensions. A significant factor for successful outcome of root coverage procedures? A 2-year prospective clinical study.

Abstract: The aim of this study was to evaluate whether an increased thickness of the gingiva through the use of a free connective tissue graft, in conjunction with a coronally advanced flap procedure, may positively influence the treatment outcome with respect to (i) root coverage and (ii) long-term stability of the position of the soft tissue margin following treatment of recession type defects. 67 consecutive patients having a total of 103 buccally located recession type defects of at least 3 mm were included in the study. After an initial phase of prophylaxis including instructions in a tooth brushing technique giving minimal apically directed forces to the gingival margin, the recession sites were surgically covered with a coronally advanced flap alone (control sites), or coronally advanced flap combined with a free connective tissue graft taken from the palate (test sites). Clinical examinations, including assessments of oral hygiene, gingival conditions, recession depth, gingival height, probing pocket depth and probing attachment loss, were performed before and 6, 12 and 24 months after surgical treatment. The mean initial recession depth for both treatment groups was about 4.0 mm (SD 1.0) with a gingival height apical to the recession of 1.0 mm (0.5). At the re-examination performed 6 months after surgical treatment, the mean recession depth had decreased to 0.2 mm in both the test and control groups. Complete root coverage was observed at 72% of the test sites and 74% of the control teeth. At teeth treated with the combined surgical procedure, the mean gain in probing attachment amounted to 3.7 mm and the mean gingival height had increased to 3.5 mm (0.6). The corresponding figures for control teeth were 3.6 mm and 1.5 mm (0.5), respectively. At the 24-month follow-up examination, the mean root coverage amounted to 98.9% (test) and 97.1% (control). 88% of the teeth in the test group showed complete root coverage compared to 80% for teeth in the control group. It was concluded that the 2 surgical procedures resulted in similar degree of root coverage and that changes of tooth brushing habits may be of greater importance than increased gingival thickness for long-term maintenance of the surgically established position of the soft tissue margin.

Effects of Essential Oils on Phytopathogenic Fungi In Vitro

Abstract: The essential oils of Thymus vulgaris L., of Lavandula R.C. hybrid and Mentha piperita L. were tested in vitro against the pathogenic fungi Rhizoctonia solani Kuhn, Pythium ultimum Trow var. ultimum, Fusarium solani (Mart.) Sacc, Colletotrichum lindemuthianum (Sacc. & Magn.) Briosi & Cav. All the oils tested inhibited fungal growth. The most effective oil was that of thyme, with a fungicidal activity attributable to thymol, found in a concentration of 50.06% in the oil tested. SEM observations revealed that these oils cause degeneration of the fungal hyphae which appeared emptied of their cytoplasmic content.

A New type of resistive plate chamber: The Multigap RPC

Abstract: This Letter describes the multigap resistive plate chamber (RPC). The goal is to obtain a much improved time resolution, keeping the advantages of the wide gap RPC in comparison with the conventional narrow gap RPC (smaller dynamic range and thus lower charge per avalanche which gives higher rate capability and lower power dissipation in the gas gap).

Functional demarcation of a border between areas V6 and V6A in the superior parietal gyrus of the macaque monkey

Abstract: We have compared physiological data recorded from three alert macaque monkeys with separate observations of local connectivity, to locate and characterize the functional border between two related but distinct visual areas on the caudal face of the superior parietal gyrus. We refer to these areas as V6 and V6A. The occupy almost the entire extent of the anterior bank of the parieto-occipital sulcus, V6A being the more dorsal. These two areas are strongly interconnected. Anatomically, we have defined the border as the point at which labelled axon terminals first adopt a recognizably 'descending' pattern in their laminar characteristics, after injections of wheatgerm agglutinin-horseradish peroxidase into the dorsal half of the gyrus (in presumptive V6A). A similar principle was used to recognize the same border by the pattern of input from area V5, except that in this case the relevant transition in laminar characteristics is that between an 'intermediate' pattern (in V6) and an 'ascending' pattern (in V6A). V6A was found to be distinct from V6 in a number of its physiological properties. Unlike V6, it contains visually unresponsive cells as well as units with craniotopic receptive fields ('real-position' cells), units tuned to very slow stimulus speeds, units with complex visual selectivities and units with activity related to attention. V6A was also found to have a larger mean receptive field size and scatter than V6. By contrast, response properties related to the basic orientation and direction of moving bar stimuli were indistinguishable between V6 and V6A, as was the influence of gaze direction on cell activity in the two areas. Two-dimensional maps of the recording sites allowed reconstruction of the V6/V6A border. For comparison, the anatomical results were rendered on two-dimensional maps of identical format to those used to summarize the physiological data. After normalizing for relative size, the physiological and connectional estimates of the border between V6 and V6A were found to coincide, at least within the range of individual variation between hemispheres. An architectonic map in the same format was also made from a hemisphere stained for myelin and Nissl substance. Area PO, defined by its general density of myelination was not distinct in this material, but several architectural features were traceable and one of these was also found to approximate the V6/V6A border. The particular criteria that distinguish V6 from V6A differ from a recent description of areas PO and POd in the Cebus monkey; we believe it most likely that PO and POd together may correspond to V6.

Insulin-like Growth Factor I Receptor-mediated Circuit in Ewing's Sarcoma/Peripheral Neuroectodermal Tumor: A Possible Therapeutic Target

Abstract: The disappointingly low survival rate observed in Ewing's sarcoma (ES)/peripheral neuroectodermal tumor (PNET) despite the adoption of aggressive multimodal treatments prompted us to study the existence of autocrine circuits to be used as innovative therapeutic targets. Of the several circuits analyzed, only the insulin-like growth factor receptor (IGF-IR)-mediated loop was found to be constantly present both in cell lines and clinical samples, suggesting a role for this autocrine circuit in the pathogenesis of ES/PNET. The in vitro inhibition of the IGF-IR-mediated circuit by the specific IGF-IR binding antibody alphaIR3 suppressed the growth of ES/PNET cells by decreasing the proliferative rate and increasing apoptosis. alphaIR3 also significantly inhibited the ability of ES/PNET cells to grow in soft agar and to migrate following a chemotactic stimulus. Inactivation of the IGF-IR signaling pathway may therefore be considered as an effective therapeutic modality for patients with ES/PNET.