Biomedical subjects

S Peysson

Publications and source records attributed to S Peysson.

5 recordsLinked to original sources

PubMed2003

[Cerebral amyloid angiopathy revealed by transient ischemic events: contribution of MRI to diagnosis and pathophysiology study].

We report the case of a 72-year-old left-handed woman presenting with episodes of paresthesias of the left arm and dysarthria consistent with transient ischemic attacks. The diffusion MRI showed hypersignals of the right corona radiata suggesting recent ischemic process whereas gradient-echo MRI revealed multiple small hypointense regions consistent with petechial hemorrhages restricted to the corticosubcortical regions. Gadolinium-enhanced, T1-weighted MRI showed focal meningeal enhancement. The diagnosis of cerebral amyloid angiopathy was supported by leptomeningeal biopsy. The association of ischemic suffering, petechial haemorrhage and meningeal enhancement as demonstrated by multisequence MRI highly suggest a cerebral amyloid angiopathy.

Aged↗

PubMed2001

Magnetic fluctuations in the classical XY model: the origin of an exponential tail in a complex system.

We study the probability density function for the fluctuations of the magnetic order parameter in the low-temperature phase of the XY model of finite size. In two dimensions, this system is critical over the whole of the low-temperature phase. It is shown analytically and without recourse to the scaling hypothesis that, in this case, the distribution is non-Gaussian and of universal form, independent of both system size and critical exponent eta. An exact expression for the generating function of the distribution is obtained, which is transformed and compared with numerical data from high-resolution molecular dynamics and Monte Carlo simulations. The asymptotes of the distribution are calculated and found to be of exponential and double exponential form. The calculated distribution is fitted to three standard functions: a generalization of Gumbel's first asymptote distribution from the theory of extremal statistics, a generalized log-normal distribution, and a chi(2) distribution. The calculation is extended to general dimension and an exponential tail is found in all dimensions less than 4, despite the fact that critical fluctuations are limited to D=2. These results are discussed in the light of similar behavior observed in models of interface growth and for dissipative systems driven into a nonequilibrium steady state.

Journal Article↗

PubMed2000

Random bond XXZ chains with modulated couplings

The magnetization behavior of q-periodic antiferromagnetic spin- 1/2 Heisenberg chains under uniform magnetic fields is investigated in a background of disorder exchange distributions. By means of both real space decimation procedures and numerical diagonalizations in XX chains, it is found that for binary disorder the magnetization exhibits wide plateaus at values of 1+2(p-1)/q, where p is the disorder strength. In contrast, no spin gaps are observed in the presence of continuous exchange distributions. We also study the magnetic susceptibility at low magnetic fields.

Journal Article↗

PubMed1986

[Detection of endotoxins in radiopharmaceutical preparations--II. Comparison of the sensitivity of methods using the rabbit and the Limulus amoebocyte lysate for the detection of endotoxins].

The rise of the rabbit internal temperature after i.v. injection of an endotoxin solution is proportional to concentration. Gelation of Limulus amoebocyte, when in presence of an endotoxin solution, is also related to concentration. We compared the sensitivity of these two methods. With our experimental procedure, the rabbit is sensitive to a 0.40 ng/mL solution and the Limulus amoebocyte lysate to a 0.14 ng/mL solution. The rabbit sensitivity increase is related to the per kilogramme injected volume, whereas sensitivity is not related to the volume to check in the case of the lysate.

Animals↗

PubMed1986

[Detection of endotoxins in radiopharmaceutical preparations--III. Limulus test assessment using radiopharmaceutical preparations; correlation with the rabbit pyrogen test].

Experiments using 17 radiopharmaceuticals containing known amounts of added endotoxin show that none of them inhibits the pyrogenic reaction of the rabbit. Gelation of the Limulus amoebocyte lysate (LAL) is inhibited by 4 of them: colloidal erbium 169Er citrate, colloidal rhenium 186Re sulfide, colloidal technetium 99mTc (Re) sulfide for liver scintigraphy and the colloidal technetium 99mTc (Re) sulfide for lymphography. This inhibition is cancelled, either by dilution or after neutral pH adjustment. Both controls were performed on 313 batches of various radiopharmaceuticals, 95% of results were identical (93% negative, 2% positive). The remaining 5% correspond to positive LAL tests vs negative rabbit tests on the same batches. No negative LAL test vs positive rabbit test was observed.

Animals↗