Showing papers by "University of Bologna published in 1988"

State of the art and present trends in nonlinear microwave CAD techniques

Abstract: The authors present a survey of modern nonlinear CAD (computer-aided design) techniques as applied to the specific field of microwave circuits. A number of fundamental aspects of the nonlinear CAD problem, including simulation, optimization, intermodulation, frequency conversion, stability, and noise, are addressed and developed. For each one it is shown that either well-established CAD solutions are available, or at least a solution approach suitable for implementation in a general-purpose CAD environment can be outlined. Also, the discussion shows that the various subjects are not just separate items, but rather can be chained in a strictly logical sequence. Finally, an elementary treatment of vector processing is given, to show that supercomputers can handle the involved large-size numerical problems efficiently. >

High-field-induced degradation in ultra-thin SiO/sub 2/ films

Abstract: Very thin thermal oxides are shown to exhibit a failure mode that is undetected by conventional breakdown tests. This failure mode appears in the form of excessive leakage current at low field and is induced by high-field stresses. The stress-induced oxide leakage is permanent and stable with time and thermal annealing. It becomes the dominant failure mode of thin oxides because it always precedes destructive breakdown. Experimental results and theoretical calculations show that the leakage current is not caused by positive charge generation and accumulation in the oxide. It is proposed that the oxide leakage originates from localized defect-related weak spots where the insulator has experienced significant deterioration from electrical stress. The leakage conduction mechanism appears to be thermally assisted tunneling through the locally reduced injection barrier, and the model seems to be consistent with both I-V measurements at temperatures from 77 K to 250 degrees C and theoretical calculations. >

Physical database design for relational databases

Abstract: This paper describes the concepts used in the implementation of DBDSGN, an experimental physical design tool for relational databases developed at the IBM San Jose Research Laboratory. Given a workload for System R (consisting of a set of SQL statements and their execution frequencies), DBDSGN suggests physical configurations for efficient performance. Each configuration consists of a set of indices and an ordering for each table. Workload statements are evaluated only for atomic configurations of indices, which have only one index per table. Costs for any configuration can be obtained from those of the atomic configurations. DBDSGN uses information supplied by the System R optimizer both to determine which columns might be worth indexing and to obtain estimates of the cost of executing statements in different configurations. The tool finds efficient solutions to the index-selection problem; if we assume the cost estimates supplied by the optimizer are the actual execution costs, it finds the optimal solution. Optionally, heuristics can be used to reduce execution time. The approach taken by DBDSGN in solving the index-selection problem for multiple-table statements significantly reduces the complexity of the problem. DBDSGN's principles were used in the Relational Design Tool (RDT), an IBM product based on DBDSGN, which performs design for SQL/DS, a relational system based on System R. System R actually uses DBDSGN's suggested solutions as the tool expects because cost estimates and other necessary information can be obtained from System R using a new SQL statement, the EXPLAIN statement. This illustrates how a system can export a model of its internal assumptions and behavior so that other systems (such as tools) can share this model.

Entry of herpes simplex virus 1 in BJ cells that constitutively express viral glycoprotein D is by endocytosis and results in degradation of the virus.

Abstract: The BJ cell line which constitutively expresses herpes simplex virus 1 glycoprotein D is resistant to infection with herpes simplex viruses. Analysis of clonal lines indicated that resistance to superinfecting virus correlates with the expression of glycoprotein D. Resistance was not due to a failure of attachment to cells, since the superinfecting virus absorbed to the BJ cells. Electron microscopic studies showed that the virions are juxtaposed to coated pits and are then taken up into endocytic vesicles. The virus particles contained in the vesicles were in various stages of degradation. Viral DNA that reached the nucleus was present in fewer copies per BJ cell than that in the parental BHKtk- cells infected at the same multiplicity. Moreover, unlike the viral DNA in BHKtk- cells which was amplified, that in BJ cells decreased in copy number. The results suggest that the glycoprotein D expressed in the BJ cell line interfered with fusion of the virion envelope with the plasma membrane but not with the adsorption of the virus to cells and that the viral proteins that mediate adsorption to and fusion of membranes appear to be distinct.

A mathematical study of human intracranial hydrodynamics part 1—The cerebrospinal fluid pulse pressure

Abstract: An original mathematical model of human intracranial hydrodynamics is proposed. Equations able to mimic the behavior of the intracranial arterial vascular bed, intracranial venous vascular bed, cerebrospinal fluid absorption and production processes, and the constancy of overall intracranial volume are separately presented and discussed. The model parameters were given normal values computed using physiological considerations and recent anatomical data. In this paper the model is used to simulate the genesis and morphology of the intracranial pressure pulse wave. In particular, dependence of the intracranial pressure pulse amplitude on mean intracranial pressure, obtained from the model, shows excellent agreement with recent experimental findings. The model explains the intracranial pressure pulse wave as the result of the pulsating changes in cerebral blood volume (related to cerebrovascular compliance) which occur within a rigid space (i.e., the craniospinal compartment). At low and medium values of intracranial pressure, the intracranial pressure pulse amplitude mainly reflects the cerebral pressure-volume relationship. However, during severe intracranial hypertension, an abrupt increase in the cerebrovascular compliance becomes evident, which is reflected in an abrupt increase in the intracranial pressure pulse wave.

Global-fit approach to the analysis of limb-scanning atmospheric measurements.

Abstract: A method for the retrieval of concentration profiles of atmospheric constituents from spectra, recorded by balloon-borne spectrometers with the limb-scanning technique, is presented. The method uses a nonlinear least-squares fit procedure to fit simultaneously the whole concentration profile on a limb-scanning sequence of spectra. A use in interferometric measurements of the stratospheric emission is shown and a comparison is discussed with the results obtained from the analysis of the same data set, by using the onion-peeling method in which the error propagation, over concentrations, is taken into account. With the global-fit, error bars smaller than with the onion-peeling analysis are obtained. Computational details are also discussed.

MELAS syndrome: Characteristic migrainous and epileptic features and maternal transmission

Abstract: Severe prolonged migrainous symptoms and prolonged partial status epilepticus are characteristic features of the MELAS syndrome (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes). Maternal transmission previously found in myoclonus epilepsy and ragged-red fibers (MERRF), another mitochondrial disease, is suggested in this disorder as well.

Polyamine inhibition of lipoperoxidation. The influence of polyamines on iron oxidation in the presence of compounds mimicking phospholipid polar heads.

Abstract: Polyamines appear to inhibit peroxidation of vesicles containing acidic phospholipids. A correlation exists between polyamine binding to phospholipid vesicles and its protective effect. However, phosphatidylinositol-containing vesicles which bind spermine are not protected by the polyamine [Tadolini, Cabrini, Landi, Varani & Pasquali (1985) Biogenic Amines 3, 97-106]. In the present paper I tested the hypothesis that polyamines, in particular spermine, by forming a ternary complex with iron and the phospholipid polar head may change the susceptibility of Fe2+ to autoxidation and thus its ability to generate free oxygen radicals. Different compounds mimicking phospholipid polar heads were studied, namely AMP, mimicking phosphatidic acid, CDP-choline, mimicking phosphatidylcholine, and glycerophosphoinositol, mimicking phosphatidylinositol. The results support the proposed hypothesis. In the presence of CDP-choline or of glycerophosphoinositol, spermine poorly affects Fe2+ autoxidation, whereas a considerable inhibition is observed in the presence of AMP. The ability of other phosphorus-containing compounds (ATP, ADP, cyclic AMP, sodium phosphate) to affect Fe2+ autoxidation in the presence of polyamines was also evaluated to understand the molecular mechanism of this phenomenon. It is proposed that polyamines may be part of the passive cellular defence mechanism against the oxidative damage caused by Fe2+.

Algorithms and codes for the assignment problem

Abstract: This paper analyzes the most efficient algorithms for the Linear Min-Sum Assignment Problem and shows that they derive from a common basic procedure. For each algorithm, we evaluate the computational complexity and the average performance on randomly-generated test problems. Efficient FORTRAN implementations for the case of complete and sparse matrices are given.

A new discretization strategy of the semiconductor equations comprising momentum and energy balance

Abstract: A discretization scheme is applied to the hydrodynamic model for semiconductor devices that generalizes the Scharfetter-Gummel method to both the momentum-conservation and the energy-conservation equations. The major advantages of the scheme are: (1) the discretization is carried out without neglecting any terms, thus providing a satisfactory description of such effects as velocity overshoot and carrier heating; and (2) the resulting equations lend themselves to a self-consistent solution procedure similar to those currently used to solve the simpler drift-diffusion equations. Two-dimensional steady-state simulations of an n-channel MOSFET and of an n-p-n BJT (bipolar junction transistor) have been carried out by means of an improved version of the program HFIELDS. Carrier-temperature plots have been obtained with a reasonable computational effort, demonstrating the efficiency of this technique. The results have been compared with those obtained with the standard drift-diffusion model and significant differences in the electron concentration have been found, especially at the drain end of the MOSFET channel. >

Endoscopic demonstration of loss of duodenal folds in the diagnosis of celiac disease.

Abstract: Among 873 patients undergoing upper gastrointestinal endoscopy for various reasons over a two-year period, four had a loss of Kerckring's folds in the descending duodenum. Endoscopic duodenal biopsy in all four patients revealed subtotal villous atrophy due to celiac disease. We undertook a prospective study to evaluate the extent to which this finding predicted celiac disease in 65 consecutive patients referred for intestinal biopsy. Duodenal folds were absent or markedly decreased in 15 of 17 patients with subtotal villous atrophy and in 8 of 48 patients with partial villous atrophy or normal duodenal mucosa, giving a sensitivity of 88 percent and a specificity of 83 percent for this endoscopic finding with respect to celiac disease. We recommend that all patients undergoing upper gastrointestinal endoscopy be examined for the loss or reduction of duodenal folds and, should this be found, that the examination include duodenal biopsy. The value of this procedure as an aid in the diagnosis of cel...

A New Algorithm for the 0-1 Knapsack Problem

Abstract: We present a new algorithm for the optimal solution of the 0-1 Knapsack problem, which is particularly effective for large-size problems. The algorithm is based on determination of an appropriate small subset of items and the solution of the corresponding "core problem": from this we derive a heuristic solution for the original problem which, with high probability, can be proved to be optimal. The algorithm incorporates a new method of computation of upper bounds and efficient implementations of reduction procedures. The corresponding Fortran code is available. We report computational experiments on small-size and large-size random problems, comparing the proposed code with all those available in the literature.

Desmin and actin in the identification of Ito cells and in monitoring their evolution to myofibroblasts in experimental liver fibrosis

Abstract: It has been reported that myofibroblasts contain actin and that Ito cells are positive for desmin. The distribution of desmin and actin detected by immunofluorescence, of vitamin A autofluorescence and of Sudan III staining of lipid droplets has been evaluated in sequential stages of experimental liver fibrosis induced in rats by intraperitoneal injections of swine serum. In the normal rat liver Ito cells were positive for desmin and weakly positive for actin. Prior to the development of hepatic fibrosis a clearcut increase in number and desmin staining of lobular Ito cells was observed in treated rats, but the overall actin pattern was unchanged. In the fibrotic rat livers, highly cellular septa contained large numbers of strongly desmin-positive, actin-weakly positive Ito cells and strongly desmin- and actin-positive myofibroblasts. These observations indicate that both Ito cells and myofibroblasts are positive for desmin, but only myofibroblasts contain large amounts of actin. Visualization of actin and desmin using relatively simple techniques, allows the monitoring of Ito cells proliferation, the accumulation of these cells in fibrous septa and their evolution into myofibroblasts as characterized by their increased desmin and actin content; it also allows an indirect evaluation of the process of fibrogenesis.

General-purpose harmonic balance analysis of nonlinear microwave circuits under multitone excitation

Abstract: A powerful software tools for the simulation of nonlinear microwave circuits under single- or multiple-frequency excitation is described. The program operates in a truly general-purpose fashion, both circuit topology and active-device equivalent circuits being arbitrarily established by the user at the data entry level. Built-in facilities based on the multidimensional Fourier transform allow a straightforward and unrestricted treatment of mixer and intermodulation problems. The capabilities of the program are illustrated by a number of practical examples. >

Prodromal symptoms in panic disorder with agoraphobia.

Abstract: Of 20 patients suffering from panic disorder with agoraphobia, 18 reported experiencing agoraphobic avoidance, generalized anxiety, and/or hypochondriacal fears and beliefs before the first panic attack. The prevalence of these symptoms in the patients was significantly higher than the prevalence in 20 healthy control subjects. The results indicate that phobic avoidance in panic disorder with agoraphobia may not be secondary to the panic attacks, a finding that runs counter to the current DSM-III-R classification of anxiety disorders.

Epidemiology of headache in the Republic of San Marino.

Abstract: An epidemiological survey on headache was performed in the Republic of San Marino, which is the smallest independent State in the world, located near the Adriatic Coast, within Italy. Among a random sample of 1500 inhabitants over 7 years of age the frequency of headache, severe headache and migraine in the previous year was 35.3%, 12.2%, 9.3% respectively for men, and 46.2%, 20.6%, 18% for women. The most common factors reported to provoke headache were emotional stress, physical strain, lack of sleep, particular foods or drinks and for women menstruation. Migraine patients differed from people without headache in that they had a higher consumption of coffee, more frequently reported bad sleep, allergic disease and previous appendectomy. Furthermore, migraine patients and severe headache sufferers had a higher diastolic blood pressure than non headache subjects.

Epirubicin and doxorubicin comparative metabolism and pharmacokinetics. A cross-over study.

Abstract: The pharmacokinetics and metabolism of doxorubicin (DX) and epirubicin (epiDX) were investigated in eight cancer patients who received 60 mg/m2 of both drugs independently by intravenous (i.v.) bolus at 3-week intervals according to a balanced cross-over design. Unchanged DX and epiDX plasma levels followed a triexponential decay. Half-lives (t/2) of the three decay phases were longer for DX (t/2α: 4.8 vs. 3 min; t/2β 2.57 h vs. 1.09 h; t/2γ 48.4 vs. 31.2 h). According to a model-independent analysis, the different plasma disposition kinetics of the two compounds appears to be related to a higher plasma clearance (PlCl) and to a lower mean residence time (MRT) of epiDX (PlCl: 75.0 l/h, range: 35.6–133.4 l/h; MRT: 31.6 h, range: 7.0–41.5 h;) compared to DX (PlCl: 56.8 l/h, range: 24.4–119.5; MRT: 45.6 h, range: 26.0–83.1 h). No statistically significant differences could be detected for the volume of distribution at steady state (Vss) (epiDX, 31.8 l/kg; DX, 33.3 l/kg). Metabolites common to both compounds were detected in plasma: the 13-dihydro derivatives doxorubicinol (DXol) and epirubicinol (epiDXol), together with monor amounts of four aglycones (7-deoxy adriamycinone, adriamycinone, 7-deoxy 13-dihydro adriamycinone, and 13-dihydro adriamycinone). Following epiDX administration, two additional major metabolites were detected: the glucuronic acid conjugates of epiDX (4′-O-β-d-glucuronyl-4′-epiDX) and epiDXol (4′-O-β-d-glucuronyl 13-dihydro-4′-epiDX). This additional detoxication route appears to account for the more efficient and faster elimination of epiDX than of DX. In the urine collected in the 6 days after treatment, 12.2% of the DX and 11.9% of the epiDX dose was excreted as unchanged drug and fluorescent metabolites. A comparable renal clearance was calculated for DX (4.7 l/h, range 1.4–7.0 l/h) and epiDX (4.4 l/h, range 1.7–7.0 l/h). One patient with hepatic metastates and abnormal bilirubin serum level had percutaneous biliary drainage because of extrahepatic obstruction. The elimination of both drugs was significantly impaired in this patient; nevertheless, elimination of epiDX was still more efficient and faster than that of DX (PlCl: 35.6 vs. 24.4 l/h; MRT: 39.0 vs. 83.1 h; t/2γ: 47 vs. 74 h). This patient's biliary excretion accounted for 35.4% of the epiDX dose and 18.2% of the DX dose.

Order of the deconfining phase transition in pure-gauge QCD.

Abstract: We study the behavior of the string tension in the SU(3) lattice pure-gauge theory close to the deconfining critical point. We find very large correlation lengths, increasing with the lattice size. This result is strongly suggestive of a second-order phase transition, and excludes the presence of a strong first-order transition.

Developmental transitions of myosin isoforms and organisation of the lateral muscle in the teleost Dicentrarchus labrax (L.).

Abstract: InDicentrarchus labrax (the sea bass) the differentiation of lateral muscle fibres occurs at different stages and in different ways in the superficial (red), intermediate (pink) and deep (white) regions of the myotome. At hatching the myotomes are composed of presumptive white and red fibres, the latter forming a superficial monolayer present only near the transverse septum. At this stage, differences between the fibre types are mainly ultrastructural. From their different reactions with isoform-specific antibodies to mullet myosin, and the appearance of histochemical mATPase activity, it appears that in both red and white muscle fibres there is a transition in myosin composition from an early larval form (L1R and L1W respectively) to a late larval form (L2R and L2W) and then to the isoforms typical of adult red and white muscle. The transition from L1W to L2W in the deep muscle occurs very rapidly and early in larval life (between 10 and 28 days), whereas the equivalent transition in the superficial muscle (from L1R to L2R) is a gradual process beginning in fibres near the trasverse septum and spreading hypo- and epi-axially as this layer grows around the deep muscle. The definitive adult forms (AR and AW), distinguishable by the appearance of characteristic histochemical myosin ATPase activity, are present in the superficial red muscle by 80 days, but later in the deep white muscle (by 20 months), respectively. Compared to the superficial red and deep white muscle, the intermediate (pink) muscle layer first appears relatively late (80 days), but then acquires the histo- and immunohistochemical profile characteristic of the adult form much more rapidly. The mosaic appearance of the deep white muscle is first seen during larval life. However, at this stage the smaller fibres of the mosaic have a different histo- and immunohistochemical profile from that seen in the adult small white fibres, which may indicate different mechanisms of histogenesis of new fibres in the deep muscle layer in the early and adult stages.

Zolpidem-polysomnographic study of the effect of a new hypnotic drug in sleep apnea syndrome

Abstract: Clinical studies have shown that zolpidem, an original imidazopyridine derivative, induces and maintains sleep and does not have daytime side-effects. Polysomnography has revealed that this drug has several interesting qualities that benzodiazepines do not possess: stages 3-4 increase, stage 2 is unchanged or slightly reduced and no abnormal changes are detected on the EEG tracing. Like benzodiazepines, zolpidem slightly reduces REM sleep. The Multiple Sleep Latency Test confirmed that the drug does not cause daytime drowsiness. All the hypnotic drugs studied up to now worsen heavy snoring and obstructive sleep apnea syndrome. A controlled double blind cross-over trial assessed the effects of a single dose of zolpidem 20 mg on nocturnal breathing in patients with mild forms of sleep apnea syndrome. The results indicate that, at this dose, the drug does not overcome the existing contraindications to the use of hypnotics in this syndrome.