Search results for "Viscosity."
showing 10 items of 537 documents
Synthesis and solution properties of star-shaped poly(tert-butyl acrylate)
2000
A series of star polymers consisting of poly(tert-butyl acrylate) arms and an ethyleneglycol dimethacrylate (EGDMA) microgel core were synthesized using anionic polymerization. The effect of various parameters (precursor length, ratio [[EGDMA]/[Initiator], reaction time, and overall concentrations) on the average number of arms was investigated. Molecular weights were determined using GPC coupled with an online viscometer and MALLS. The exponents for the relation between intrinsic viscosity or radius of gyration and molecular weight, respectively, are extremely low, indicating that the dimensions of the star polymers only slightly increase with the number of arms. After a certain number of …
Adsorptionseffekte als Fehlerquellen bei Lichtzerstreuungsmessungen
1956
Es werden die Einflusse der Adsorption von Hochpolymeren aus den Losungen auf Lichtzerstreuungsmessungen untersucht. Zunachst wird die Adsorption aus Losung an Glaswolle und Glaspulver in verschiedenen Losungsmitteln gemessen. Es zeigt sich, das sowohl Konzentrationserniedrigung, bestimmt im Differentialrefraktometer, wie auch eine Abnahme des Molekulargewichtes, aus der Lichtzerstreuung bestimmt, infolge selektiver Adsorption auftreten. Beim Schutteln der Losungen tritt als weiterer Effekt ein Abbau der Kettenmolekule ein. Beim Filtrieren von Losungen nehmen durch Adsorption im Filter Konzentration und Molekulargewicht ab. Die Abnahme wachst mit der Feinheit des Filters, d. h. mit seiner O…
Rheological blood behavior is not only influenced by cardiovascular risk factors but also by aging itself. Research into 927 healthy Spanish Mediterr…
2013
It is not well-established whether the alterations that the hemorheological profile undergoes with aging are an effect of concomitant cardiovascular risk factors or are due to age itself. To clarify this issue, we investigated the effect of age on blood rheology in a population of 927 healthy subjects from eastern Spain aged between 16-85 years, divided into four age groups (<30, 30-44, 45-50, ≥60 years) with and without cardiovascular risk factors. We determined blood viscosity, corrected blood viscosity (BVc), plasma viscosity (PV), erythrocyte aggregation (EA), erythrocyte deformability (EEI60) and fibrinogen, along with glucose and plasma lipids. We found that corrected blood viscosity …
Plasma viscosity and related cardiovascular risk factors in a Spanish Mediterranean population
2006
Plasma viscosity (PV) constitutes an independent important predictor of initial and recurrent cardiac events and mortality. It has been suggested that there is a geographical variation in PV values related to coronary event rates. Little information exists regarding PV in Spain. Therefore, our objective was to determine PV in a large sample of randomly selected subjects from the Spanish population and to study which demographic or cardiovascular risk factors (CVRF) influence levels of PV in this population.1277 subjects (503 males, 774 females) aged 43+/-14 years (range: 20-70) were randomly selected from an Eastern Spanish population. These subjects were free of cardiovascular diseases and…
Effects of sorbinicate and nicotinic acid on blood viscosity, red cell deformation and platelet function
1982
Summary Nicotinic acid (NA) and a retard derivative, sorbinicate, were investigated for their effects on blood rheology and platelet function, after oral administration, in two groups of patients with lower limb atherosclerosis obliterans — the second group having diabetes also. Red cell deformation and blood plasma viscosity were studied in the nondiabetic group (single dose of NA, 100 mg, and sorbinicate, 400 mg); release of platelet malondialdehyde (MDA) (single dose of NA, 100 mg, and sorbinicate, 800 mg), and the platelet regeneration time (before and after sorbinicate 400 mg × 3/die for 7 days) were studied in the diabetic group. Both drugs induced a significant improvement in red cel…
Haemorheological parameters in young patients with acute myocardial infarction
2008
The role played by hemorheological alterations on acute myocardial infarction (AMI) in young patients remains a question of debate. We have carried out a case-control study of 84 AMI patients aged45 years and 135 sex and age matched controls, in which blood viscosity (BV), plasma viscosity (PV), erythrocyte aggregation (EA) performed with the Myrenne (EA0, EA1) and the Sefam aggregometer (Ta, AI10, gammaD), erythrocyte deformability (ED) along with fibrinogen (Fbg), C-reactive protein (CRP) and plasmatic lipids i.e. total cholesterol (T-Chol) and triglycerides (TG) were determined. AMI patients showed higher, Fbg, TG, EA0, EA1, IA10, gammaD and lower Ta than controls (p=0.029, p0.001, p=0.0…
Metabolic alterations in morbid obesity. Influence on the haemorheological profile.
2011
There are few studies on haemorheological disturbances in morbidly obese patients. The role played by the metabolic syndrome on the rheological profile of morbidly obese subjects has not yet been established, and it is not clear whether morbidly obese, but "metabolically healthy", show rheological alterations. We aimed to determine the whole rheological profile in 136 morbidly obese patients and 136 normo-weight volunteers, along with plasma lipids, inflammatory and insulin resistance parameters. Patients had statistically higher glucose, triglycerides, HbA1c, leptin, insulin, HOMA, CRP, leucocytes, fibrinogen, plasma viscosity (p0.001, respectively), erythrocyte aggregation at 3 s-1 (p = 0…
Influence of lipids and obesity on haemorheological parameters in patients with deep vein thrombosis.
2007
It is not well established whether haemorheological alterations constitute independent risk factors for deep vein thrombosis (DVT).We have determined in 149 DVT patients and in 185 control subjects the body mass index (BMI), the haemorheological profile: blood viscosity (BV), plasma viscosity (PV), fibrinogen (Fg), erythrocyte aggregation (EA), erythrocyte deformability (ED) and plasma lipids. In the crude analysis BMI, Fg, PV, EA, triglycerides (TG) and ApoB were statistically higher and HDL cholesterol (HDL-Chol) statistically lower in DVT patients than in controls. No differences in BV and ED were observed.After BMI adjustment, Fg, PV and EA remained statistically higher in DVT cases tha…
Plasma viscosity pattern and erythrocyte aggregation in two patients with congenital afibrinogenemia
2020
: In this case report, we examine the behavior of plasma viscosity, explored at high and low shear rates, and erythrocyte aggregation in two patients with congenital afibrinogenemia, a clinical disorder firstly described in 1920 and that has an estimated incidence of 1 : 1-200 0000. The two hemorheological parameters examined by us showed a marked decrease in both patients, in one of whom erythrocyte aggregation was even undetectable. Keeping in mind that spontaneous thrombosis (venous and arterial) has been often described in congenital afibrinogenemia, it can be hypothesized that the decrease in plasma viscosity and erythrocyte aggregation might cause a reduction of the endothelial synthe…
Blood rheology during chemotherapy in patients with ovarian cancer.
1998
The use of platinum based chemotherapy in ovarian malignancy and other cancer types is known to be associated with deep vein thrombosis. In a prospective study of 47 patients with ovarian cancer of International Federation of Gynecology and Obstetrics stage Ib-IV, serial rheological parameters were determined (plasma viscosity, red blood cell aggregation under conditions of stasis and low shear) in addition to hemoglobin, hematocrit, leukocytes, platelets, and fibrinogen. At the same time the incidence of deep vein thrombosis was recorded before, during six cycles of first line cisplatinum/epirubicin/cyclophosphamide chemotherapy, and 2 months thereafter (two-months check-up). Only six pati…