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R Pieri

Publications and source records attributed to R Pieri.

At least 19 recordsLinked to original sources
PubMed2005

Small-angle neutron scattering of ionic perfluoropolyether micellar solutions: role of counterions and temperature.

This paper reports a small-angle neutron scattering (SANS) characterization of perfluoropolyether (PFPE) aqueous micellar solutions with lithium, sodium, cesium and diethanol ammonium salts obtained from a chlorine terminated carboxylic acid and with two perfluoroisopropoxy units in the tail (n(2)). The counterion and temperature effects on the micelle formation and micellar growth extend our previous work on ammonium and potassium salts n(2) micellar solutions. Lithium, sodium, cesium and diethanol ammonium salts are studied at 0.1 and 0.2 M surfactant concentration in the temperature interval 28-67 degrees C. SANS spectra have been analyzed by a two-shell model for the micellar form factor and a screened Coulombic plus steric repulsion potential for the structure factor in the frame of the mean spherical approximation of a multicomponent system reduced to a generalized one component macroions system (GOCM). At 28 degrees C, for all the salts, the micelles are ellipsoidal with an axial ratio that increases from 1.6 to 4.2 as the counterion volume increases. The micellar core short axis is 13 A and the shell thickness 4.0 A for the alkali micelles, and 14 and 5.1 A for the diethanol ammonium micelles. Therefore, the core short axis mainly depends on the surfactant tail length and the shell thickness on the carboxylate polar head. The bulky diethanol ammonium counterion solely influences the shell thickness. Micellar charge and average aggregation number depend on concentration, temperature and counterion. At 28 degrees C, the fractional ionization decreases vs the counterion volume (or molecular weight) increase at constant concentration for both C = 0.1 M and C = 0.2 M. The increase of the counterion volume leads also to more ellipsoidal shapes. At C = 0.2 M, at 67 degrees C, for sodium and cesium micelles the axial ratio changes significantly, leading to spherical micelles with a core radius of 15 A, lower average aggregation number, and larger fractional ionization.

Journal Article↗
PubMed2000

Electroencephalography in infants with periventricular leukomalacia: prognostic features at preterm and term age.

Cystic periventricular leukomalacia represents the most severe white-matter lesion in preterm infants and its occurrence accounts for most cases of neurologic impairment in these subjects. Electroencephalographic (EEG) findings and their prognostic value in relation to motor and cognitive outcome were investigated in a group of preterm infants affected by different degrees of cystic periventricular leukomalacia. EEG recordings were carried out in the early postnatal period (first 2 weeks of life) on 24 infants and at term age on 29. In the early postnatal period, background EEG abnormalities ("dysmaturity") were significantly more apparent in affected infants than in a control group, and, among infants with cystic periventricular leukomalacia, this parameter related to the occurrence of cerebral palsy; moreover, at the same age, the incidence of abnormal EEG transients seemed to show a correlation with cognitive outcome. At term age, these latter abnormalities were significantly more apparent in neonates with cystic periventricular leukomalacia than in control subjects, but they did not show any prognostic value. In conclusion, these data indicate that, during the early postnatal period, the EEG is a useful diagnostic and prognostic tool for preterm infants with white-matter lesions, whereas at term age, the role of EEG tracings appears secondary.

Brain Damage, Chronic↗
PubMed1999

Constantly discontinuous EEG patterns in full-term neonates with hypoxic-ischaemic encephalopathy.

OBJECTIVES: Selected EEG features were evaluated in 21 constantly discontinuous tracings recorded on the same number of full-term neonates with hypoxic-ischaemic encephalopathy. METHODS: The tracings were examined without using interval amplitude as the basis for distinguishing between burst-suppression and nonburst-suppression patterns. RESULTS: The results were related to outcomes and other clinical parameters (severity of hypoxic-ischaemic encephalopathy, pO2 levels and drug intake). CONCLUSIONS: Features defining the grade of EEG discontinuity (i.e. maximum interval duration, minimum burst duration and interval amplitude) significantly related to outcome and, in most cases, to the grade of hypoxic-ischaemic encephalopathy. Other features (amplitude of slow waves within the burst and incidence of abnormal EEG transients) related to PO2 levels. The consumption of anticonvulsant drugs increased EEG discontinuity, but this effect did not seem dose-related. Finally, the persistence of a constantly discontinuous EEG pattern after the first week of life is a sign of unfavourable prognosis. In full-term neonates with hypoxic-ischaemic encephalopathy quantitative analysis of all constantly discontinuous EEGs seems more useful than only describing burst-suppression patterns on the basis of interval amplitude.

Brain↗
PubMed1996

Prognostic value of abnormal EEG transients in preterm and full-term neonates.

The prognostic value of abnormal EEG transients was investigated in 362 subjects submitted to EEG recording during the neonatal age and followed-up at least until the 12th month of corrected age. The incidence of negative and positive spikes and sharp waves, of rhythmic sharp theta and delta activities and of alpha discharges were evaluated by means of a quantitative score. These abnormal EEG transients appeared to be generally rare and even absent in a large number of subjects. In infants with normal outcome their incidence tends to increase from low postmenstrual ages towards term period. Full-term newborns with abnormal neurological outcome presented a significantly higher incidence of these transients. Preterm infants with unfavourable evolution showed a higher incidence only when submitted to EEG recording at around term age. However, no difference between subjects with normal and abnormal outcome was detected in preterm infants when evaluated at low postmenstrual ages. The hypothesis that at low postmenstrual ages brain damage might, on the one hand, give rise to abnormal transients and, on the other, alter the "capability' of manifesting them (together with other EEG maturational aspects), might explain these results.

Brain↗
PubMed1996

Electroencephalographic dysmaturity in preterm infants: a prognostic tool in the early postnatal period.

The aim of the study was to assess the prognostic value of maturational abnormalities in the electroencephalogram (EEG) of preterm infants. 63 subjects (mean gestational age: 32.7 weeks; range 28-34) were submitted to EEG recording within the first two weeks of life and subsequently followed up until at least 12 months of corrected age. Maturational features of background EEG were analysed and the occurrence of different degrees of maturational anomalies ("dysmaturity") was scored, according to standardised criteria. The results were compared to neurological outcome and to cranial ultrasound (US) findings. EEG maturational features significantly related to the outcome. When the EEG background activity was normal all but one patient showed a favourable outcome; the incidence of neurological sequelae became higher according to the degree of dysmaturity detected. However, some infants had a normal evolution, despite severe EEG dysmaturity in the early postnatal period. The correlation between EEG and US findings was low, although US also significantly related to the outcome. Background EEG maturational features seem to be a reliable prognostic tool in the early postnatal period of preterm infants, complementary to serial US scans.

Brain Diseases↗
PubMed1983

A polygraph study of ischemic heart disease: behavior of systolic times in acute myocardial infarction.

The authors investigated systolic time intervals in 28 cases of acute myocardial infarction (AMI). Polygraph recordings were made on the first day of illness and repeated at two, three, five, and seven hospital days. The patients were divided into two groups: one with a contributory history of ischemic and/or hypertensive heart disease (Group PH for "positive history") and one without such history (Group NH for "negative history"). The influence of numerous variables on systolic times were explored in both groups, and the emerging data were processed by multiple stepwise regression analysis. The results show that the left ventricular ejection time (LVET) is invariably shortened in AMI, whereas the pre-ejection indices (PEP and ICT) afford definite differentiation of patients of Group PH (with lengthened PEP and ICT values) from those of Group NH (shortened PEP and ICT). The authors emphasize the importance of obtaining polygraph recordings very early in the course of AMI and of taking into account the patient's history in view of a correct assessment of pre-ejection times.

Aged↗