Scaling the temperature-dependent boson peak of vitreous silica with the high-frequency bulk modulus derived from Brillouin scattering data

The position and strength of the boson peak in silica glass vary considerably with temperature T. Such variations cannot be explained solely with changes in the Debye energy. New Brillouin-scattering measurements are presented which allow determining the T dependence of unrelaxed acoustic velocities. Using a velocity based on the bulk modulus, scaling exponents are found which agree with the soft-potential model. The unrelaxed bulk modulus thus appears to be a good measure for the structural evolution of silica with T and to set the energy scale for the soft potentials.

[A tool to predict the resources necessary for the whole hemodialysis population]

Predicting the resources necessary for the treatment of terminal renal insufficiency requires an understanding of the needs of the whole dialysis population. This study evaluates the advantages of a complete evaluation grid for care needs (CG, 47 items) compared with a simplified version (SG) and with the data obtained from REIN (R) as a tool for predicting the required resources. Compared to CG, the two other classifications under-estimate the level of care needed and the prevalence of patients who have at least one condition resulting in an 'excess' of needs. In a system with three types of structures, the theoretical distribution of patients according to the CG is: in structure A (permanent medical presence): 43.4% (vs 39 for SG and 21% for R); in structure B (intermediate): 34% (vs 31.5 and 24.7% respectively); and in structure C (independent): 22.3% (vs 29.5 and 53.5%) of patients. The care needs scores of populations assigned by R to home dialysis are incompatible with the resources allocated to it. With a certain number of adjustments and qualifications, a population study using a simplified needs grid could enable a prediction of the resources which need to be provided. The patients' records which take precedence in the future REIN should be modified in order to make possible a regular evaluation of the appropriateness of the resources allocated.

[Evaluation of the needs of a population of hemodialysis patients in Rhône-Alpes]

The evaluation of the needs of patients with terminal renal insufficiency is necessary to determine the appropriate care programme. An evaluation of the medical and nursing needs, as well as those related to handicap (a total of 47 items) was undertaken on all hemodialysis patients in the Rhône-Alpes region. Only 34.4% were free of co-morbidity and 35.7% of significant handicap, 63.7% needed no other nursing care than that related to supervision of the dialysis and 16.9% were free of all the conditions studied. The patients treated in the centre required care needs than those treated in all other structures. The autodialysis population differs from that treated at home by a greater need for care due to handicaps, and from that treated in a dialysis centre by a lesser degree of handicap and less need for medical treatment. A level of theoretical unsuitability (needs incompatible with the statutory provisions for each type of treatment) was defined: it concerns 5% of the population in a dialysis centre and to 33% of the population on home dialysis. The needs evaluation grid could be used to quantify the requirements of a dialysis population and to arrange for the necessary resources.

Observation of the onset of strong scattering on high frequency acoustic phonons in densified silica glass

The linewidth of longitudinal acoustic waves in densified silica glass is obtained by inelastic x-ray scattering. It increases with a high power alpha of the frequency up to a crossover where the waves experience strong scattering. We find that alpha is at least 4, and probably larger. Resonance and hybridization of acoustic waves with the boson-peak modes seems to be a more likely explanation for these findings than Rayleigh scattering from disorder.

Olmsted syndrome: report of two new cases and literature review

Olmsted syndrome is a rare keratinization disorder; 18 cases have been published so far. It associates a mutilating cogenital palmoplantar keratoderma with periorificial erythematokeratotic lesions. We report herein two new unrelated male children with Olmsted syndrome (OS), one of whom was studied by light and electron microscopy. Our histological, immunohistochemical, and ultrastructural findings suggest that this disease is related to epidermal hyperproliferation. We present herein a review of the twenty cases published so far and discuss the major clinicopathological and genetic features of this disease.

Direct determination of blood recirculation rate in hemodialysis by a conductivity method

Blood recirculation is one of the key factors of decreasing dialysis efficiency. Determination of recirculation rate (R) is necessary to optimize effective dialysis delivery and to monitor vascular access function. R can be directly measured by a conductivity method in paired filtration dialysis (PFD), a double-compartment hemodiafiltration system that permits direct access to plasma water via the ultrafiltration stream. Measurement of R, in this system, involves the first of two conductivity sensors integrated in a urea monitor (UMS, BelIco-Sorin, Mirandola, Italy), and two saline injections. The rise in conductivity (deltaC1) induced by a 2.7 ml bolus of hypertonic saline 20% (mg/dl) in the arterial line serves for calibration, and is followed by an equivalent injection into the venous line, giving rise to deltaC2. The ratio deltaC2/deltaC1 equals R. A comparison between R values obtained with this method and with the low-flow technique in 31 chronic dialysis patients during 138 PFD sessions is reported. Mean R+/-SD by the conductivity method was 5.1+/-2.0 and 5.7+/-2.0% after 65 and 155 minutes of PFD (correlation coefficient, r = 0.75), whereas it was 6.4+/-4.9% and 5.5+/-4.6% after 30 sec of low blood pump flow for urea and creatinine markers, respectively (r = 0.35). After 120 sec of low flow, mean R increased to 9.0+/-5.1 and 8.8+/-4.6% for urea and creatinine, respectively (r = 0.45). Considerable discrepancies were found in R values measured simultaneously with the two blood markers. Statistically significant differences were found between the two measurement modalities (blood-side and conductivity); the correlation coefficients (r) varied between 0.28 and 0.41. The observed differences in mean R results do not seem considerable from a clinical perspective. The best agreement between blood-side and conductivity R measurements was obtained with Rcreat after 30 sec of low flow. Overall, a wider distribution was found in R values from blood-side determinations, most likely consequent to variability in the dosing method. The conductivity method appears more accurate and simple in assessing total R, and can be readily automated and integrated into the dialysis machine. The authors, therefore, recommend evaluation of R using methods not based on chemical blood concentration values.

Trace elements and lipid peroxidation abnormalities in patients with chronic renal failure

Plasma selenium (Se), zinc (Zn) and copper (Cu) levels and antioxidant metalloenzymes, glutathione peroxidase (GPX) and superoxide dismutase (SOD), were studied in 17 patients on maintenance hemodialysis (HD) (group I), 14 uremic patients (group II) and 14 healthy subjects (group III). Plasma Se levels and erythrocyte GPX were significantly lower in the HD group (for Se: 0.69 +/- 0.12 vs. 1.05 +/- 0.13 mumol/l in controls; for erythrocyte GPX: 34.4 +/- 6.4 vs. 49.2 +/- 9 IU/g hemoglobin in controls) and a significant correlation was found between the two parameters (r = 0.66, p less than 0.005). There was also a correlation between decreased plasma Zn and erythrocyte SOD activity (r = 0.58, p less than 0.02) and between decreased plasma Cu and erythrocyte SOD (r = 0.60, p less than 0.02). Plasma malondialdehyde levels were augmented in HD patients (5.08 +/- 0.26 vs. 2.55 +/- 0.15 mumol/l in controls and 2.79 +/- 0.40 mumol/l in the uremic group). The catalase activity was increased in HD patients (202 +/- 24 vs. 140 +/- 40 IU/mg hemoglobin in group III). A defective antioxidant activity may thus contribute to increased peroxidative damage to cells in the course of dialysis.

[Arthropathy of the fingers in hemodialyzed patients with chronic renal failure. Apropos of a study of 44 patients]

Arthropathy affecting the small joints of the hand are one of the osteo-articular complications of chronic renal failure treated by hemodialysis. Amongst the 44 patients studied, there were 9 cases of arthropathy of the fingers. The clinical characteristics (age, duration of hemodialysis) and paraclinical characteristics (oxygenated free radical activity indicators, serum levels of aluminium and beta-2-microglobulins) appear to be specific to this population and may help us to understand the pathogenesis of the joint lesions.

Interconversion and uptake of nucleotides, nucleosides, and purine bases by the marine bacterium MB22

Whole cells and isolated membranes of the marine bacterium MB22 converted nucleotides present in the external medium rapidly into nucleosides and then into bases. Nucleosides and purine bases formed were taken up by distinct transport systems. We found a high-affinity common transport system for adenine, guanine, and hypoxanthine, with a Km of 40 nM. This system was inhibited noncompetitively by purine nucleosides. In addition, two transport systems for nucleosides were present: one for guanosine with a Km of 0.8 microM and another one for inosine and adenosine with a Km of 1.4 microM. The nucleoside transport systems exhibited both mixed and noncompetitive inhibition by different nucleosides other than those translocated; purine and pyrimidine bases had no effect. The transport of nucleosides and purine bases was inhibited by dinitrophenol or azide, thus suggesting that transport is energy dependent. Inside the cell all of the substrates were converted mainly into guanosine, xanthine, and uric acid, but also anabolic products, such as nucleotides and nucleic acids, could be found.