The implementation of an autoregressive model with exogenous input in a single sweep visual evoked potential analysis.

Based on a model of signal-noise interaction, we present a method for single-sweep analysis of Visual Evoked Potentials. The EEG is represented as an autoregressive process and the single-sweep VEP as a filtered version of a reference signal taken as the running average of 20 consecutive sweeps. The algorithm for model identification and filtering is an ARX (AutoRegressive with eXogenous input) which provides a fast and efficient solution by means of a least squares approach. The choice of reference signal, as well as the complexity of the model, is also discussed. A further advantage of this approach is parameter reduction: all the single-sweep information is contained in 18 model coefficients and the reference signal.

[Quick's time and derived times in the study of the extrinsic course of the coagulation process. The PIVKA (protein induced by vitamin K absence or antagonists) in states of chronic disseminated intravascular coagulation]. / Il tempo di quick e tempi derivati nello studio della via estrinseca del processo coagulativo. i PIVKA (protein induced by vitamin k absence or antagonists) in condizioni di coagulazione intravascolare disseminata cronica

After reviewing the available methods for the clinical study of the extrinsec way of the coagulative process (Quick's time, Owren's Thrombotest and Normotest), the AA. explain what is the significance that the most of hte researchers ascribe to time-value discrepancies between Thrombotest and Normotest. The AA. remember that while the former is sensitive to the presence of certain inhibitors called PIVKA (Protein Induced by Vitamin K Absence or Antagonists), just as Quick's original time; the latter is on the contrary insensitive to them. Then it provides more significant data about the real rate of factors II, VII, and X. Such inhibitors have been found also in subjects that did not undergo any anti-vitamin K therapy and peculiarly in cases in which a Intravascular Coagulation occurred. Therefore the AA. thought to verify the hypothesis that the detection of a discrepancy between TT and NT could be useful in the clinical diagnosis of I.C. which is a serious and often hardly detectable disorder of haemostasis. The AA. have therefore tested 72 patients, 65 of which showed the evidence of I.C. and 7 with I.C. probabilities. The discrepancy values that were obtained are showed in Table I. The first group (65 cases) was furtherly divided into four subgroups, according to the positivities obtained from SDPS test, as shown in Table II. The AA. can therefore come to the following conclusions: a) In human Intravascular Coagulation, the discrepancy between NT/TT may occur with a frequency of 57 per cent but it is not a constant event. b) The discrepancy rate is generally of low degree, being of high degree only in twelve cases (18.5 per cent. c) Analyzing the discrepancy presence and rate in relation to the number of SDPS test positivities, we can notice that the values are remarkably scattered and it is not possible, only on the basis of these data to make a statistical evaluation of their significativity because the groups are not comparable among them, being in exc3ss the cases in which paracoagulation occurs in a low degree. We can only state that the absence of discrepancy predominates in the cases in which a low number of positivities of SDPS test occurs, and on the contrary the discrepancy is a constant event in the cases in which SDPS test shows a large number of positivities. In consitive test to detect Intravascular Coagulation, but we think the positivity of this test may be a support in doubtful cases.