Showing papers by "Polytechnic University of Milan published in 1988"
TL;DR: In diabetics, besides a reduced RR variance at rest, an altered response of spectral indices of sympathetic activation and vagal withdrawal is observed during passive tilt, suggestive of a complex modification in the neural control activities.
Abstract: We studied heart rate variability in 49 uncomplicated diabetics (27 with insulin therapy; 22 with oral hypoglycemic agents) and in 40 age-matched controls. An automatic autoregressive algorithm was used to compute the power spectral density (PSD) of beat by beat RR variability derived from the surface ECG. The PSD contains two major components (a low frequency approximately 0.1 Hz (LF) and a high frequency, respiratory linked, approximately 0.25 Hz (HF] that provide, respectively, quantitative markers of sympathetic and vagal modulatory activities and of their balance. As compared to controls, in diabetics, besides a reduced RR variance at rest (2722 +/- 300 and 1436 +/- 241 ms2, respectively), we observed during passive tilt an altered response of spectral indices of sympathetic activation and vagal withdrawal, suggestive of a complex modification in the neural control activities. In addition, we compared this approach to the commonly used clinical tests score, and observed that the latter provides overall results similar to those obtained with spectral changes induced by tilt (r = 0.42; P less than 0.01). Of potential clinical importance is that the data obtained with spectral analysis appear more thoroughly quantifiable and do not require the active collaboration of the patients.
407 citations
TL;DR: In this article, the Amplitude Mode Theory worked out for obtaining a unified interpretation of the vibrational spectra of Polyacetylene can be reformulated in a simpler and more complete way in terms of straightforward concepts of moleculare dynamics.
206 citations
TL;DR: It is shown how complex update programs can be built from primitive update operators and how view update programs are translated into database update programs and shows that consistent views have a number of interesting properties with respect to the concurrency of (high-level) update transactions.
Abstract: The problem of translating view updates to database updates is considered. Both databases and views are modeled as data abstractions. A data abstraction consists of a set of states and of a set of primitive update operators representing state transition functions. It is shown how complex update programs can be built from primitive update operators and how view update programs are translated into database update programs. Special attention is paid to a class of views that we call “consistent.” Loosely speaking, a consistent view is a view with the following property: If the effect of a view update program on a view state is determined, then the effect of the corresponding database update is unambiguously determined. Thus, in order to know how to translate a given view update into a database update, it is sufficient to be aware of a functional specification of such a program. We show that consistent views have a number of interesting properties with respect to the concurrency of (high-level) update transactions. Moreover we show that the class of consistent views includes as a subset the class of views that translate updates under maintenance of a constant complement. However, we show that there exist consistent views that do not translate under constant complement. The results of Bancilhon and Spyratos [6] are generalized in order to capture the update semantics of the entire class of consistent views. In particular we show that the class of consistent views is obtained if we relax the requirement of a constant complement by allowing the complement to decrease according to a suitable partial order.
163 citations
TL;DR: In this article, the authors analyzed the symmetric periodic positive semidefinite (SPPS) solution of the DPRE under appropriate assumptions of stabilizability and detectability of the periodic system.
Abstract: Gives a comprehensive treatment of several important aspects of the discrete-time periodic Riccati equation (DPRE) arising from the prediction problem for linear discrete-time periodic systems. The authors analyze the symmetric periodic positive semidefinite (SPPS) solution of the DPRE under appropriate assumptions of stabilizability and detectability of the periodic system. Among the results obtained are necessary and sufficient conditions for the existence and uniqueness of the SPPS solution and the stability of the resulting closed-loop system. Some of these results can be seen as extensions of the corresponding results for the time-invariant case; however, a number of them contain contributions to the time-invariant case as well. The paper also gives a numerical algorithm based on an iterative linearization procedure for computing the SPPS solution. The algorithm is a periodic version of Kleinman's algorithm for the time-invariant case. >
158 citations
TL;DR: The simulations as well as the experimental results confirm the capability of the model of drastically improving the S/N (signal-to-noise) ratio in each single trial and satisfactorily identifying the contributions of signal and noise to the overall recording.
Abstract: A parametric method of identification of event-related (or evoked) potentials on a single-trial basis through an ARX (autoregressive with exogenous input) algorithm is discussed. The basic estimation of the information contained in the single trial is taken from an average carried out on a sufficient number of trials, while the noise sources, EEG and EOG, are characterized as exogenous inputs in the model. The simulations as well as the experimental results confirm the capability of the model of drastically improving the S/N (signal-to-noise) ratio in each single trial and satisfactorily identifying the contributions of signal and noise to the overall recording. A particularly efficient reduction of ocular artifacts is also achieved. >
149 citations
01 Jan 1988
TL;DR: In this article, the problem of describing the state of thermal equilibrium of a monatomic perfect gas can be nicely solved; in particular, they found a very simple formula for the one-particle distribution P (1) in the form of a Maxwellian.
Abstract: In the previous chapter we saw that the problem of describing the state of thermal equilibrium of a monatomic perfect gas can be nicely solved; in particular, we found a very simple formula for the one-particle distribution P (1) in the form of a Maxwellian. This result has a large variety of applications in the statistical description of matter in the gaseous state.
139 citations
TL;DR: In this article, the effectiveness of the vulnerability index as a measure of the health status of buildings is discussed on the basis of regional surveys of vulnerability index versus reported damage, carried out in various Italian areas such as Friuli and the city of Gubbio.
Abstract: The evaluation of the seismic damageability of existing buildings is a primary element in the planning for mitigation of earthquake effects. To this purpose, the use of the vulnerability index has been recently proposed and adopted in various surveys in Italy. The index results from grading the status of various structural and non-structural components exposed to damage in a seismic event. The effectiveness of the vulnerability index as a measure of the health status of buildings is discussed on the basis of regional surveys of vulnerability index versus reported damage, carried out in various Italian areas such as Friuli and the city of Gubbio. Also, investigation of the items most effective in describing damageability among those contributing to the index is performed, in view of formulating a reduced survey procedure. A damage versus vulnerability index database collected in these surveys is presented as well. Finally, a vulnerability index based procedure to evaluate the expected damage in a territory is proposed.
101 citations
TL;DR: In this paper, the surface segregation in transition metal binary alloys is compared and theoretical predictions are discussed referring also to an updated collection of experimental results, both semi-empirical and first-principle.
85 citations
TL;DR: In this article, the authors examined speech enhancement techniques to be applied in a mobile radio environment and compared the performance of a noise-cancelling microphone approach and signal processing methods.
79 citations
TL;DR: In this article, a single-photon avalanche diode (SPAD) with epitaxial structure is presented, where the carrier diffusion effect is strongly reduced and the resolution is less than 30ps full width at half-maximum.
Abstract: A new silicon single-photon avalanche diode (SPAD) with epitaxial structure is presented. The carrier diffusion effect, which has plagued the time response of previous SPADs, is strongly reduced. The resolution obtained, less than 30ps full width at half-maximum, is the highest so far reported in single-photon timing.
64 citations
TL;DR: It is shown that the basic topology and access scheme of Tree-Net can be extended so that a family of tree-structured fiber-optic MANs (metropolitan area networks) can be defined to suit different needs, including data, voice, and video integration.
Abstract: A fiber-optic architecture, Tree-Net, is introduced that does not require intermediate processing components and supports a large number of stations. Tree-Net is based on a tree topology, passive station taps, and implicit token protocol. The properties and performance of Tree-Net are evaluated. It is shown that the basic topology and access scheme of Tree-Net can be extended so that a family of tree-structured fiber-optic MANs (metropolitan area networks) can be defined to suit different needs, including data, voice, and video integration. >
TL;DR: Results show that both FFT and MESE are adequate to estimate the SMG Power Spectrum; both the mean and the median frequency are suitable parameters, the mean frequency being the more favourable one; and the SMg Power Spectrum is a promising tool to study the muscle activation modalities.
Abstract: The activated muscle generates a low frequency rumbling noise, which is known as the Sound-MyoGram (SMG). Spectral analysis of the SMG is carried out in this work, in order to: (i) check the adequacy of both the Fast Fourier Transform (FFT) and the Maximum Entropy Spectrum Estimation (MESE). Because it is a well known technique, the FFT method is only briefly described, while the philosophy of the MESE method is given in more detail and completed with a description of the recursive algorithm; (ii) select a frequency parameter suitable to describe the SMG. For this purpose two well-defined physiological conditions (20% and 80% Maximal Voluntary Contraction) have been adopted in order to provide a safe reference for the interpretation of the findings. The results show that: (a) both FFT and MESE are adequate to estimate the SMG Power Spectrum; (b) both the mean and the median frequency are suitable parameters, the mean frequency being the more favourable one; (c) the SMG Power Spectrum is a promising tool to study the muscle activation modalities.
TL;DR: In this paper, a numerical scheme is presented aimed at computing shakedown load safety factors in elastic-plastic structures discretized by finite elements, which allows the prescription of a maximum violation of the constitutive law, and the use of a physically oriented solution algorithm to the linear complementarity problem.
TL;DR: The direct escape widths of the giant monopole resonance populating the lowest five valence hole states of /sup 207/Pb are determined, and compared with the results obtained from complex collective states.
Abstract: The neutron decay of the giant monopole resonance region between 13 and 15 MeV in $^{208}\mathrm{Pb}$ is analyzed in terms of collective and statistical doorway states. The direct escape widths of the giant monopole resonance populating the lowest five valence hole states of $^{207}\mathrm{Pb}$ are determined, and compared with the results obtained from complex collective states. This comparison discriminates sharply between different model Hamiltonians which predict similar energies and collectivities for the resonance.
TL;DR: A photon-counting optical-time-domain reflectometer (OTDR) operating at a wavelength of 0.85 microm at room temperature with high sensitivity and high sensitivity at high resolution is demonstrated.
Abstract: We demonstrate a photon-counting optical-time-domain reflectometer (OTDR) operating at a wavelength of 0.85 microm at room temperature with high sensitivity (3 x 10(-15) W) at high resolution (1.5 cm, 150 psec). Measurements of splice losses and Rayleigh scattering losses less then 0.1 dB with centimeter resolution are demonstrated to be possible with such an OTDR.
TL;DR: In this paper, a comparison between countercurrent separation and simulated countercurrent operation is performed through suitable mathematical models in the context of adsorption separation, including non linear multicomponent equilibria, finite mass transport rates and axial dispersion.
TL;DR: The revised Enskog equation for a dense gas of rough spheres is considered in this paper, where the H theorem and the conservation equations are discussed as well as the conservation equation.
Abstract: The revised Enskog equation for a dense gas of rough spheres is considered. TheH theorem and the conservation equations are discussed.
TL;DR: In this article, the photochemical behavior of 3,5-disubstituted 1,2,4-oxadiazoles in methanol at 254 nm has been investigated.
TL;DR: In this article, the dependence of peak ground acceleration and velocity on seismic moment is studied for a set of small earthquakes recorded digitally at distances of a few km in the Campi Flegrei volcanic area near Naples, Italy, during the ground uplift episode of 1982-1984.
Abstract: The dependence of peak ground acceleration and velocity on seismic moment is studied for a set of small earthquakes (0.7
TL;DR: A method is described which allows the determination of the causal relationship existing between two biological signals which carry information about the role of control elicited by the autonomic nervous system to provide a more precise evaluation of the complex mechanisms involved in the control of heart rate and blood pressure in numerous physiopathological situations.
Abstract: A method is described which allows the determination of the causal relationship existing between two biological signals (heart rate and arterial blood pressure variability signals) which carry information about the role of control elicited by the autonomic nervous system. This method assumes an autoregressive (AR) model for the two signals to check the cross-correlation of the two residuals after AR identification. This information, together with the classical parameters of the spectral analysis (mean, variance, frequency and power in two typical bands, gain, phase and coherence) may provide a more precise evaluation of the complex mechanisms involved in the control of heart rate and blood pressure in numerous physiopathological situations.
TL;DR: 1H-nuclear magnetic resonance spectroscopy is used to show that succinate is produced by rice seedlings subjected to anoxic conditions, suggesting its involvement in rice coleoptile elongation under anoxia.
Abstract: Anaerobic production of succinate, a common feature in animals able to sustain anoxia, has seldom been reported in plants. By the use of 1H-nuclear magnetic resonance spectroscopy we show here that succinate is produced by rice seedlings (Oryza sativa L. cv. Arborio) subjected to anoxic conditions. Starting from levels below I μmol (g fresh weight)−1 in air, after 48 h of anoxia the levels of alanine, succinate and lactate had increased to 23.8, 5.2 and 1.0 μmol (g fresh weight) −1, respectively, in shoot tissues. Succinate was accumulated in shoots, notably in the coleoptiles, but not in roots of the rice seedlings, suggesting its involvement in rice coleoptile elongation under anoxia. Other possible functions of succinate production in rice seedling, an organism highly tolerant to anoxia, are discussed.
TL;DR: It is found that BLC (which improves power margins) is easier to implement than FDV, but FDV ( which improves outage probability and retains most of its advantages at higher frequencies) is more effective in reducing built-in power margins in ‘unassisted’ conditions.
Abstract: Adaptive shared resource methods may be the only available effective countermeasure to rain-induced attenuation in satellite communication systems above 20 GHz Two of these methods, frequency diversity (FDV) and burst length control (BLC) are examined and compared by using a unified approach The fundamental statistical relationships between unassisted and assisted conditions are derived, and optimum values are identified It is found that BLC (which improves power margins) is easier to implement than FDV, but FDV (which improves outage probability and retains most of its advantages at higher frequencies) is more effective in reducing built-in power margins in ‘unassisted’ conditions From a large database at 116 GHz collected in the Sirio experiment, some realistic FDV results are derived for systems using 20/30 GHz bands for unassisted conditions and 12/14 GHz bands for assisted conditions As the ESA Olympus satellite will carry both 20/30 GHz and 12/14 GHz transponders, an FDV experiment with Olympus has been proposed by CSTS; the characteristics of the three earth-stations planned to be built in Italy for the experiment are described
Journal Article•
TL;DR: Results show that direct irradiation of the retina is, to some extent, present especially near threshold, and that shielding between subsequent pulses in a train is likely to occur only to a very limited extent.
Abstract: Shielding of laser pulses by plasmas generated in ocular media has been experimentally investigated using single Nd:YAG laser pulses of different durations, ranging from several nanoseconds (ns) to a few tens of picoseconds (ps), both in saline solution and extracted calf vitreous. At the respective threshold radiant exposures for breakdown in saline (259 mJ/cm2 for 7 ns, 20.5 mJ/cm2 for 220 ps and 4.7 mJ/cm2 for 30 ps pulses) the single pulse energy transmission is found to be about 74% for 7 ns, 55% for 220 ps and 50% for 30 ps, thus showing that shielding of laser-induced plasmas is more effective for shorter pulses than for longer pulses. Moreover, the decrease in transmission with increasing radiant exposure is faster in the picosecond case than in the nanosecond case. These results show that direct irradiation of the retina is, to some extent, present especially near threshold. In the case of picosecond pulses, a comparison with published results indicates that shielding between subsequent pulses in a train is likely to occur only to a very limited extent.
TL;DR: An automatic procedure for improving the extraction of parameters in heart rate (HR) and arterial blood pressure (ABP) beat-to-beat variability signals is described and parameters seem to validate significantly the capability of such models to describe the physiological interactions existing between the two considered signals.
TL;DR: A line-shape analysis of these spectra allows one to recognize a partial filling up of the Yb 5d states along with the formation of Si 3p\char21{}Yb 5D hybrids when Si and Yb atoms chemically interact.
Abstract: We present Si ${L}_{2}$,3VV Auger and Yb Coster-Kronig and super-Coster-Kronig spectra for the Si(111)/Yb interface as a function of the Yb coverage. A line-shape analysis of these spectra allows one to recognize a partial filling up of the Yb 5d states along with the formation of Si 3p--Yb 5d hybrids when Si and Yb atoms chemically interact. Analogies with other Si-metal chemical bonds are discussed.
15 Dec 1988-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, a large-area (∼ 4 × 4 cm2) silicon drift chamber has been designed and constructed in order to investigate its possible use in the UA6 experiment.
Abstract: A large-area (∼ 4 × 4 cm2) silicon drift chamber has been designed and constructed in order to investigate its possible use in the UA6 experiment. The drift chamber will supply unambiguously (x, y) space points on each track; each arm of the UA6 spectrometer could be provided with two layers of drift detectors.
Journal Article•
TL;DR: An original method of processing heart rate variability (HRV) and respiration signals as detected respectively through chest electrodes and thoracic belt in dogs under different experimental conditions is introduced, to be used both in physiological and clinical research.
Abstract: The present paper introduces an original method of processing heart rate variability (HRV) and respiration signals as detected respectively through chest electrodes and thoracic belt in dogs under different experimental conditions. Signals are processed as time series synchronous with the occurrence of QRS complexes on ECG signal and auto and cross spectra are accordingly calculated. Two particular bands appear mainly of interest on the spectrum of HRV signal: one in correspondence with the respiration rate and another one at a lower frequency value. Values of power at these frequency bands together with coherence and phase between HRV signal and respiration complete the parameters which try to quantify a few aspects of the complex dynamic relationships between the original signals. In particular, controlled respiration in dogs was studied through the connection with an automatic ventilator, as well as the effects of drugs which interact with the neural regulatory systems (i.e. sympathetic and parasympathetic nervous system). Gain and phase relationships between heart rate variability and respiration, obtained with spectral analysis, could be used to provide a better understanding of the neural control mechanisms linking heart rate and respiration in various experimental conditions. The method described in this study is to be used both in physiological and clinical research.
TL;DR: An existence theorem for the Enskog equation with small initial data was proved in anL 1 setting as mentioned in this paper, which is not available for the Boltzmann equation with large initial data.
Abstract: An existence theorem for the Enskog equation with small initial data is proved in anL1 setting. This type of result is not available for the Boltzmann equation.
TL;DR: On donne des theorems d'existence et de regularite pour les equations de Navier-Stokes dans un domaine Ω T =U/0≤t≤T Ω(t)x{t} ou chaque Ω (t) est un ouvert borne de R 3 and T>0 est un nombre fini as mentioned in this paper.
Abstract: On donne des theorems d'existence et de regularite pour les equations de Navier-Stokes dans un domaine Ω T =U/0≤t≤T Ω(t)x{t} ou chaque Ω(t) est un ouvert borne de R 3 et T>0 est un nombre fini
TL;DR: In this paper, a functional interpretation of the Verhulst-Pearl (logistic) equation is presented, and it is shown that the optimal growth is logistic if the functional to be minimized is defined over an infinite time horizon.