Biomedical subjects

G Gregori

Publications and source records attributed to G Gregori.

At least 19 recordsLinked to original sources

PubMed2006

Generalized x-ray scattering cross section from nonequilibrium plasmas.

We propose a modified x-ray form factor that describes the scattering cross section in warm dense matter valid for both the plasma and the solid (crystalline) state. Our model accounts for the effect of lattice correlations on the electron-electron dynamic structure, as well as provides a smooth transition between the solid and the plasma scattering cross sections. In addition, we generalize the expression of the dynamic structure in the case of a two-temperature system (with different electron and ion temperatures). This work provides a unified description of the x-ray scattering processes in warm and dense matter, as the one encountered in inertial confinement fusion, laboratory astrophysics, material science, and high-energy density physics and it can be used to verify temperature relaxation mechanisms in such environments.

Journal Article↗

PubMed2005

Intensity limits for propagation of 0.527 microm laser beams through large-scale-length plasmas for inertial confinement fusion.

We have established the intensity limits for propagation of a frequency-doubled (2omega, 527 nm) high intensity interaction beam through an underdense large-scale-length plasma. We observe good beam transmission at laser intensities at or below 2x10(14) W/cm(2) and a strong reduction at intensities up to 10(15) W/cm(2) due to the onset of parametric scattering instabilities. We show that temporal beam smoothing by spectral dispersion allows a factor of 2 higher intensities while keeping the beam spray constant, which establishes frequency-doubled light as an option for ignition and burn in inertial confinement fusion experiments.

Journal Article↗

PubMed2004

Observation of the parametric two-ion decay instability with thomson scattering.

We present the first direct experimental observation of the parametric two-ion decay instability of ion-acoustic waves driven by a high intensity (5 x 10(15) W cm(-2)) laser beam in a laser produced high-Z plasma. Using two separate Thomson scattering diagnostics simultaneously, we directly measure the scattering from thermal ion-acoustic fluctuations, the primary ion waves that are driven to large amplitudes by the high intensity beam, and the two-ion decay products. The decay products are shown to be present only where the interaction takes place and their k spectrum is broad.

Journal Article↗

PubMed2004

Direct observation of the saturation of stimulated Brillouin scattering by ion-trapping-induced frequency shifts.

We report the first measurement of the saturation of stimulated Brillouin scattering (SBS) by an ion-trapping-induced frequency shift, which was achieved by directly measuring the amplitude and absolute frequency of SBS-driven ion-acoustic waves (IAW). A frequency shift of up to 30% and a simultaneous saturation of driven IAW and SBS reflectivity were observed. The scaling of the frequency shift with the IAW amplitude compares well with theoretical calculations. We have further measured fast 30 ps oscillations of the SBS-driven IAW amplitude induced by the frequency shift.

Journal Article↗

PubMed2004

Effect of nonlocal transport on heat-wave propagation.

We present the first direct measurements of spatially and temporally resolved temperature and density profiles produced by nonlocal transport in a laser plasma. Absolutely calibrated measurements have been performed by Rayleigh scattering and by resolving the ion-acoustic wave spectra across the plasma volume with Thomson scattering. We find that the electron temperature and density profiles disagree with flux-limited models, but are consistent with nonlocal transport modeling.

Journal Article↗

PubMed2003

Demonstration of spectrally resolved x-ray scattering in dense plasmas.

We present the first spectrally resolved x-ray scattering measurements from solid-density plasmas. The scattering spectra show the broadened Compton down-shifted feature allowing us to determine the electron temperature and density with high accuracy. In the low temperature limit, our data indicate that the ionization balance reflects the electrons in the conduction band consistent with calculations that include quantum mechanical corrections to the interaction potential.

Journal Article↗

PubMed2003

Direct observation of stimulated-Brillouin-scattering detuning by a velocity gradient.

We report the first direct evidence of detuning of stimulated Brillouin scattering (SBS) by a velocity gradient, which was achieved by directly measuring the frequency shift of the SBS-driven acoustic wave relative to the local resonant acoustic frequency. We show that in the expanding part of the plasma, ion-acoustic waves are driven off resonance which leads to the saturation of the SBS instability. These measurements are well reproduced by fluid simulations that include the measured flow.

Journal Article↗

PubMed2003

Theoretical model of x-ray scattering as a dense matter probe.

We present analytical expressions for the dynamic structure factor, or form factor S(k,omega), which is the quantity describing the x-ray cross section from a dense plasma or a simple liquid. Our results, based on the random phase approximation for the treatment on the charged particle coupling, can be applied to describe scattering from either weakly coupled classical plasmas or degenerate electron liquids. Our form factor correctly reproduces the Compton energy down-shift and the known Fermi-Dirac electron velocity distribution for S(k,omega) in the case of a cold degenerate plasma. The usual concept of scattering parameter is also reinterpreted for the degenerate case in order to include the effect of the Thomas-Fermi screening. The results shown in this work can be applied to interpreting x-ray scattering in warm dense plasmas occurring in inertial confinement fusion experiments or for the modeling of solid density matter found in the interior of planets.

Journal Article↗

PubMed2002

Analysis of Thomson scattered light from an arc plasma jet.

In this paper we present an analysis of Thomson scattered light from an arc plasma jet. Our approach goes beyond the standard random-phase approximation (RPA) and provides more consistent data for the electron temperature and density in plasmas that are weakly nonideal and collisional. The theory is based on a memory function formalism for the spectral density function with the use of the three lowest-order frequency-moment sum rules. These moments are then corrected for temperature inhomogeneities in the scattering volume. The proposed interpretation of scattering data is compared with the RPA result and with the standard Bhatnagar-Gross-Krook collisional model for the dynamic structure factor. It is shown that the obtained electron temperature values are closer but not equal to local thermodynamic equilibrium temperature values extracted from spectroscopic measurements.

Journal Article↗

PubMed2002

HCMV pp67-mRNA detection by nucleic acid sequence-based amplification in renal transplant patients.

CMV infection is a major cause of morbidity and mortality following renal transplantation. Clinical diagnosis is difficult, and rapid and sensitive diagnostic methods are needed since antiviral therapy is available. The determination of the presence of viral transcripts is considered a direct marker of HCMV replication in vivo. In particular, it seems that the expression of late transcripts might better reflect active HCMV replication, dissemination and disease, and should cease upon effective blockage of viral polymerase by antiviral agents, such as gancyclovir. The unspliced pp67-mRNA can be specifically amplified using nucleic acid sequence-based amplification (NASBA) in a background of DNA. In the present study blood samples of forty-two renal transplant patients with active HCMV infection, demonstrated by pp65-antigenaemia, were investigated to detect pp67-mRNA using the NASBA technique. Thirty-one pp65-antigenaemia positive patients resulted NASBA positive (73.8%) also in case of very low levels of antigenaemia; in 9/42 (21.4%) pp67-m-RNA was detected between 6 and 15 days before antigenaemia. Our results indicate that pp67-mRNA NASBA is a useful tool for the early diagnosis of active HCMV infection and for starting and modulating antiviral therapy, in addition to quantitative techniques such as antigenaemia, in renal transplant patients.

Cytomegalovirus↗

PubMed1999

Enhanced Cloud Disruption by Magnetic Field Interaction.

We present results from the first three-dimensional numerical simulations of moderately supersonic cloud motion through a tenuous, magnetized medium. We show that the interaction of the cloud with a magnetic field perpendicular to its motion has a great dynamical impact on the development of instabilities at the cloud surface. Even for initially spherical clouds, magnetic field lines become trapped in surface deformations and undergo stretching. The consequent field amplification that occurs there and, in particular, its variation across the cloud face then dramatically enhance the growth rate of Rayleigh-Taylor unstable modes, hastening the cloud disruption.

Journal Article↗

PubMed1992

[A computer program to retrieve and record ISTAT codes related to pediatric diagnosis].

The paper describes a computer program that retrieves ISTAT codes increasing the efficiency of the retrieving time spent with traditional methods storing the obtained information in a suitable data-base, which may be lately explored by means of commercial programs. To increase the detail of the stored data, many of the official codes have been expanded with an extra character. Some results obtained from an experience conducted at the Pediatric Division of Crema Hospital are also reported.

Age Factors↗

PubMed1991

How can storage time and temperature affect enzymic activities in urines?

We measured a tubular brush-border enzyme (alanine aminopeptidase, AAP) and a lysosomal hydrolase (N-acetyl-beta-D-glucosaminidase, NAG) in morning urines from 15 healthy normal subjects to check if different storage times and temperatures could modify enzyme concentrations. Short-term (24 h) storage time at room temperature or 4 degrees C does not affect AAP and NAG activities. Both enzymes are well preserved at -70 degrees C. AAP dramatically falls after 1 month at -20 degrees C, lowering to about 8% of the initial value after only 4 days of storage. On the contrary, NAG is well preserved at these storage conditions. Centrifugation has revealed not critical for measurement of these two enzymes.

Acetylglucosaminidase↗

PubMed1991

Effects of storage time and temperature on urinary enzymes.

We measured three renal tubular brush-border enzymes (lactate dehydrogenase, LDH, EC 1.1.1.27; gamma-glutamyltransferase, GGT, EC 2.3.2.2; and alkaline phosphatase, AP, EC 3.1.3.1) in morning urine samples from 48 healthy subjects to check whether different storage times and temperatures could modify enzyme concentrations. Short-term (24 h) storage time at room temperature or 4 degree C does not affect urinary enzyme activity. A few days of freezing, at -20 or -70 degrees C, dramatically lowers LDH and AP values; GGT is partially preserved only at -70 degrees C, if the sample has been previously centrifuged. Urinary enzymes investigated in this study are extremely labile at low temperatures.

Alkaline Phosphatase↗

PubMed1990

Exercise-induced proteinuria in well-trained athletes.

We studied the rate of urinary excretion of albumin, alpha 1-microglobulin (as an indicator of the renal tubular involvement), sodium, potassium, and creatinine in the basal state (overnight urine collection) and after physical exercise (training session) in 10 professional cyclists, to verify whether protein excretion is increased even in well-trained athletes after physical effort. In addition, we wanted to understand whether the origin of exercise-induced proteinuria was glomerular, tubular, or both. Compared with the basal state (overnight collection), exercise significantly (P less than 0.01) increased the excretion rate of albumin (4.2 +/- 2.6 micrograms/min vs 18.1 +/- 10.6 micrograms/min, mean +/- SD), Na, and K, and also the urinary volume. Creatinine output was not affected by exercise. The mean (+/- SD) overnight excretion rate of albumin by athletes was quite similar to that found for 91 healthy nonathletes at rest (4.6 +/- 2.7 micrograms/min). The mean exercise-related excretion of alpha 1-microglobulin by the athletes significantly exceeded the overnight value (6.6 vs 0.3 mg/L, P = 0.037). Our study indicates that (a) albuminuria furnishes the greater contribution to the increase in exercise-induced proteinuria; (b) the exercise proteinuria is both glomerular and tubular in origin, and is reversible; (c) the enhanced protein requirement of athletes may in part be due to the recurrent excretion of proteins in the urine after physical effort.

Adult↗

PubMed1990

[Clinico-hematological evaluation of 57 patients undergoing antiaggregant treatment with indobufen].

A long-term administration of Indobufen, 400 mg daily, was evaluated in 57 patients with cardiovascular diseases. Aggregation waves induced by ADP, collagen and epinephrine showed a significant and persistent inhibition of platelet function. Minor side effects were observed and in 6 patients the drug was withdrawn: 4 patients began to experience gastric troubles, 1 patient had positive occult test for blood, 1 patient developed an allergic rush. Clinical evaluation and platelet aggregation study before starting indobufen and during the follow up period seem to be useful in the evaluation of effectiveness, safety, compliance and suitable daily dose.

Cardiovascular Diseases↗

PubMed1988

Increased urinary excretion of digoxin-like immunoreactive substance by insulin-dependent diabetic patients: a linkage with hypertension?

Excretion of digoxin-like immunoreactivity (DLIS) was measured by RIA in timed overnight urine collections from 91 normotensive nondiabetic subjects and 104 normotensive insulin-dependent diabetic (IDDM) patients. The mean +/- SD DLIS excretion rate for the diabetic patients significantly exceeded that for the controls (73 +/- 41 vs 63 +/- 36 pg/min, P = 0.024). In both groups, the mean DLIS excretion rates for men were significantly higher (P = 0.0014, P = 0.006) than for women. In the controls, the DLIS excretion rate significantly correlated with the urinary excretion rate of creatinine (P less than 0.01), Na+ (P less than 0.05), and K+(P less than 0.05), and with the subjects' body weight (P less than 0.01), body mass index (P less than 0.05), and systolic blood pressure (P less than 0.05). In the diabetics, the DLIS excretion rate was significantly correlated with body weight (P less than 0.05) and with urinary excretion rates for albumin (P less than 0.01), creatinine (P less than 0.01), Na+ (P less than 0.05), and K+(P less than 0.05). Our data indicate that: (a) increased amounts of a cardiac glycoside-like substance (or a group of substances) are excreted in the urine of IDDM patients; (b) the urinary excretion of DLIS seems to depend on glomerular filtration rate and physiocochemical properties of glomerular membrane, as well as on subjects' body mass; and (c) because cardiac glycoside-like substances may increase peripheral vascular resistance, increased urinary excretion of DLIS by IDDM patients may indicate a tendency to develop hypertension.

Adult↗

PubMed1988

Excretion of digoxin-like immunoreactivity in urine of normal subjects: correlations with excretion of creatinine and electrolytes.

To verify whether there is a variation in the 24-h urinary excretion of digoxin-like immunoreactivity (DLIS) in humans, we studied 18 normal adults, who collected their urines for 24-h in several portions. We then measured DLIS (by means of a sensitive RIA method), creatinine, sodium, and potassium concentrations in the urine samples. The mean urinary excretion rate for DLIS in the complete 24-h collection was 84.8 (SD 31.3) pg/min. The mean DLIS urinary excretion rate calculated for overnight collections was significantly lower than those of afternoon collections (P less than 0.01) and the 24-h collection (P less than 0.05). Significant positive correlations were found between urinary DLIS and excretion rates for creatinine (r = 0.347, P = 0.0016), Na+ (r = 0.232, P = 0.038), and K+ (r = 0.323, P = 0.003), respectively. Our data suggest that urinary excretion of DLIS is higher during "active" hours of the day, especially in the afternoon, than at rest, during the night.

Adult↗