Testing Critical Slowing Down as a Bifurcation Indicator in a Low-Dissipation Dynamical System.

We study a two-dimensional low-dissipation nonautonomous dynamical system, with a control parameter that is swept linearly in time across a transcritical bifurcation. We investigate the relaxation time of a perturbation applied to a variable of the system and we show that critical slowing down may occur at a parameter value well above the bifurcation point. We test experimentally the occurrence of critical slowing down by applying a perturbation to the accessible control parameter and we find that this perturbation leaves the system behavior unaltered, thus providing no useful information on the occurrence of critical slowing down. The theoretical analysis reveals the reasons why these tests fail in predicting an incoming bifurcation.

Synthesis and dispersion of Ni(OH)2 platelet-like nanoparticles in water.

Synthesis of nanometric platelet-like Ni(OH)2 particles is described. The role of several experimental parameters on the particle size is investigated. A colloidal dispersion of particles is produced by adsorbing ionizable organic ligands (trisodium citrate) on the particle surface. The stability of this colloidal dispersion and the particle charge density are determined for different citrate ions concentrations.

Central vein catheter-related thrombosis in intensive care patients: incidence, risks factors, and relationship with catheter-related sepsis.

OBJECTIVE: To evaluate the incidence and risk factors for catheter-related central vein thrombosis in ICU patients. DESIGN: Observational prospective multicenter study. SETTING: An 8-bed surgical ICU, a 10-bed surgical cardiovascular ICU, and a 10-bed medical-surgical ICU. PATIENTS: During an 18-month period, 265 internaljugular or subclavian catheters were included. Veins were explored by duplex scanning performed just before or < 24 h after catheter removal. Suspected risk factors of catheter-related central vein thrombosis were recorded. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Fifty-seven catheters were excluded from the analysis. Therefore 208 catheters were analyzed. Mean age of patients was 64+/-15 years, simplified acute physiologic score was 12+/-5, organ system failure score at insertion was 1+/-1, and mean duration of catheterization was 9+/-5 days. A catheter-related internal jugular or subclavian vein thrombosis occurred in 33% of the cases (42% [95% confidence interval (CI), 34 to 49%] and 10% [95% CI, 3 to 18%], respectively). Thrombosis was limited in 8%, large in 22%, and occlusive in 3% of the cases. Internal jugular route (relative risk [RR], 4.13; 95% CI, 1.72 to 9.95), therapeutic heparinization (RR 0.47; 95% CI, 0.23 to 0.99), and age >64 years (RR, 2.44; 95% CI, 2.05 to 3.19) were independently associated with catheter-related thrombosis. Moreover, the risk of catheter-related sepsis was 2.62-fold higher when thrombosis occurred (p=0.011). CONCLUSIONS: Catheter-related central vein thrombosis is a frequent complication of central venous catheterization in ICU patients and is closely associated with catheter-related sepsis.

[Blood saving in pediatric orthopedics. A study of 145 posterior vertebral arthrodesis]. / Les économies de sang en orthopédie pédiatrique. Etude à propos de 145 arthrodèses vertébrales postérieures.

The authors review 145 operations utilizing the Cotrel-Dubousset technique for scoliosis and/or cyphosis over a period of 4 years. From 1985 to 1989, the number of patients who received no homologous blood rose from 0% to 85% for the totality of cases. Inversely, the average quantity per patient of homologous blood used for transfusion decreased from 3,564 ml to 194 ml, ie. -94%. Among the 145 operated patients, 47 (33%) have never received a transfusion, whether or not an autotransfusion procedure was planned; out of the 41 children prepared with preoperative autologous sampling, 39 (97%) received no homologous blood. The authors study the various means used to achieve these results in a particularly hemorrhagic surgical procedure: low blood pressure techniques, intraoperative installation and warming, peroperative recovery of blood, decrease in duration and bleeding using natural coral to avoid removing an iliac bone graft, study of evoked potentials to prevent intraoperative awakening, better postoperative control of bleeding by means of an original drain tube. As a conclusion, they state that, owing to better coordination between surgery, anesthesiology and blood biology, such definite progress may be extended to other operations in future.

Root growth potential, seedling morphology and bud dormancy correlate with survival of loblolly pine seedlings planted in December in Alabama.

First-year survival of December-planted loblolly pine seedlings sampled from 20 nurseries ranged from 36 to 86%. Various characteristics of the seedlings including root growth potential (RGP), shoot/root ratio, root weight and stem length were correlated with survival. A regression model using the number of new roots >/= 0.5 cm and the shoot/root ratio accounted for 80% of the variation in first-year survival. Alone, the number of new roots >/= 0.5 cm accounted for 76% of the variation in survival. Foliar nutrients were not correlated with survival. Seedlings with a high proportion of quiescent buds at planting had a higher RGP and better survival than seedlings with dormant (endodormant) buds. The data suggest that seedlings with dormant buds should not be planted on sites where rapid new root growth is needed for survival.

Lipid composition and activity of a lytic factor isolated from Plasmodium berghei.

A fraction was obtained from Plasmodium berghei which induced hemolysis of the erythrocytes of mice and hamsters. This fraction, called lytic factor (LF), was found to be composed of a large amount of lipid material. An examination of the lipids showed the major lipids to be monoglycerides, diglycerides, triglycerides, fatty acids, long-chain alcohol, sterol, sterol ester, sterol glycoside, and two cerebrosides. The most abundant component found in the LF was sterol ester, followed in order by cerebrosides, sterol, and sterol glycoside. Lytic activity was found to be lost when samples were boiled for 5 min. An examination of the lipid composition of LF before and after boiling showed changes which may be useful in studies on the mechanism of activity of this factor. The fatty acid composition of the total lipid fraction of LF was examined by gas-liquid chromatography. The major fractions were 18:1 and 16:0 in unheated LF and 16:0 in the heated LF.

Biochemical characterization of anaerobic bacteria by an impregnated disk method.

An impregnated disk method was used to characterize 20 clinical isolates of anaerobic bacteria by utilization of substrate. The procedure was easy to perform, reliable, and economical.