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Deformability
Kinds of Deformability Terms modified by Deformability Selected AbstractsSlit-flow ektacytometry: Laser diffraction in a slit rheometerCYTOMETRY, Issue 1 2005Sehyun Shin Abstract Background Deformability of red blood cells (RBCs) is a determinant of blood flow resistance as RBCs pass through small capillaries of the microcirculation. Available techniques for measuring RBC deformability often require a washing process after each measurement, which is not optimal for day-to-day clinical use. Methods A laser diffraction technique has been combined with slit-flow rheometry, which shows significant advances in ektacytometric design, operation, and data analysis. The essential features of this design are its simplicity (ease of operation and no moving parts) and a disposable element that is in contact with the blood sample. Results With slit ektacytometry, the deformation of RBCs subjected to continuously decreasing shear stress in a slit flow can be quickly measured with extremely small quantities of blood. The measurements with the slit ektacytometer were compared with those of LORCA and a strong correlation was apparent. The deformability of the hardened RBCs was markedly lower than that of the normal RBCs. In addition, the young cells showed higher values of the elongation index than did the old cells. Conclusions The newly developed slit ektacytometer can measure RBC deformability with ease and accuracy. In addition, the slit ektacytometer can be easily used in a clinical setting owing to the incorporation of a disposable element that holds the blood sample. © 2005 Wiley-Liss, Inc. [source] Changes in mu opioid receptors and rheological properties of erythrocytes among opioid abusersADDICTION BIOLOGY, Issue 2 2002ALLEN R. ZEIGER The high prevalence of anemia among chronic opioid users leads us to propose that chronic opiate use results in elevated mu opioid receptor levels on human erythrocytes and that these receptor changes may affect erythrocyte membrane properties. Blood samples from 17 opioid-dependent subjects (based on the Diagnostic and Statistical Manual of Mental Disorders, 4th edition or DSM-IV) and 15 drug-free controls were assayed for mu opioid receptors on erythrocytes using a flow cytometry immunoassay. Deformability and the hydration status of erythrocytes were studied by ektacytometry. Data were analyzed by independent t-tests, tests of correlation, chi square and cluster analyses. As expected, the percentage of erythrocytes from opioiddependent subjects with opioid receptors (opioid receptor levels) was significantly higher (47.4 ± 38.3%) than controls (22.8 ± 30.1%) (t = 2.01, df = 30, p < 0.05). Also, the opioid-dependent patients showed a wide variation in the percentage of erythrocytes bearing opioid receptors and data analyses of these patients showed two strongly defined clusters. One subgroup consisted of nine individuals with very high receptor levels (mean = 81.5%) while the other had eight patients with low receptor levels (mean = 9.1%) that were not significantly different than the receptor levels of controls. Ektacytometry of opioid dependent patients with high opioid receptor levels showed changes in rheological parameters of erythrocytes, such as deformability index and cellular hydration. For example, a positive correlation was observed between opioid receptor levels and deformability indices among opioid-dependent patients (r = 0.74, p < 0.005). Our findings indicate that the mu opioid receptor is present on human erythrocytes, although with considerable variation in receptor levels, and that the levels of this receptor are significantly elevated with chronic opioid exposure. Moreover, erythrocytes with high opioid receptor levels from chronic opiate users seem to have high deformability. This study may offer clues to the biological properties of peripheral blood cells that may be mediated by mu opioid receptors and lead to a better understanding of some of the clinical effects of opioid use. [source] Experimental Investigation of Pulsatility Effect on the Deformability and Hemolysis of Blood CellsARTIFICIAL ORGANS, Issue 4 2010Yang Jun Kang Abstract In this study, we investigated the differences between pulsatile cardiopulmonary bypass (CPB) procedure and nonpulsatile CPB procedure in terms of their effects on hemolysis and deformability of red blood cells (RBCs) under various shear stress conditions. In order to research the effects on hemolysis and deformability, four parameters,free hemoglobin (fHb) concentration, normalized index of hemolysis (NIH), deformability index (DI) of RBCs, and elongation index of RBCs,have been deeply investigated. For these investigations, two randomly assigned adult mongrel dog groups,nonpulsatile group (NP, n = 6) and pulsatile group (P, n = 6),were examined. According to our results, both types of perfusion did not show any statistical differences in terms of the concentrations of fHb as well as NIH. In addition, there were no significant differences in RBC deformability between perfusion types within an operation time of 3 h. Therefore, our studies suggest that pulsatile perfusion has no significant difference from nonpulsatile perfusion in terms of hemolysis and deformability of RBCs. [source] Role of erythrocyte deformability during capillary wettingBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2006Ronghui Zhou Abstract Deformability of erythrocyte was found to fundamentally alter the wetting dynamics of red blood cell (RBC) suspensions during their invasion into capillaries. Normal RBC suspensions failed to penetrate more than 1 cm into a glass capillary when the capillary radius was smaller than a critical value that is dependent on the erythrocyte concentration (about 50 µm for whole blood). In contrast, suspensions of rigidified RBCs, after cross-linking with different concentrations of glutaraldehyde or incubating with 100 ng/mL of an endotoxin, could penetrate any capillary larger than the erythrocyte dimension. The effect of RBC deformability on penetration was attributed to the enhanced shear-induced migration of normal deformable RBCs toward the capillary centreline, which imparted a higher average velocity to the RBCs than the average plasma velocity. As a result, the erythrocytes advanced into the capillary faster than the wetting meniscus, packing behind it to form a concentrated slug. This tightly packed slug had a high hydrodynamic resistance that could arrest the penetrating flow of concentrated suspensions into the small capillaries. © 2005 Wiley Periodicals, Inc. [source] Slit-flow ektacytometry: Laser diffraction in a slit rheometerCYTOMETRY, Issue 1 2005Sehyun Shin Abstract Background Deformability of red blood cells (RBCs) is a determinant of blood flow resistance as RBCs pass through small capillaries of the microcirculation. Available techniques for measuring RBC deformability often require a washing process after each measurement, which is not optimal for day-to-day clinical use. Methods A laser diffraction technique has been combined with slit-flow rheometry, which shows significant advances in ektacytometric design, operation, and data analysis. The essential features of this design are its simplicity (ease of operation and no moving parts) and a disposable element that is in contact with the blood sample. Results With slit ektacytometry, the deformation of RBCs subjected to continuously decreasing shear stress in a slit flow can be quickly measured with extremely small quantities of blood. The measurements with the slit ektacytometer were compared with those of LORCA and a strong correlation was apparent. The deformability of the hardened RBCs was markedly lower than that of the normal RBCs. In addition, the young cells showed higher values of the elongation index than did the old cells. Conclusions The newly developed slit ektacytometer can measure RBC deformability with ease and accuracy. In addition, the slit ektacytometer can be easily used in a clinical setting owing to the incorporation of a disposable element that holds the blood sample. © 2005 Wiley-Liss, Inc. [source] Haemorheology in Gaucher diseaseEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 3 2005Bridget E. Bax Abstract:, In Gaucher disease, a deficiency of glucocerebrosidase results in the accumulation of glucocerebroside within the lysosomes of the monocyte,macrophage system. Prior to the availability of enzyme replacement therapy (ERT), splenectomy was often indicated for hypersplenism. Haemorheological abnormalities could be expected in view of the anaemia and abnormal lipid metabolism in these patients and the role of the spleen in controlling erythrocyte quality. Objectives: To investigate the effect of Gaucher disease on blood and plasma viscosity, erythrocyte aggregation and erythrocyte deformability, and to determine whether observed rheological differences could be attributed to splenectomy. Methods: Haematological and haemorheological measurements were made on blood collected from 26 spleen-intact patients with Gaucher disease, 16 splenectomised patients with Gaucher disease, 6 otherwise healthy asplenic non-Gaucher disease subjects and 15 healthy controls. Results: No haemorheological differences could be demonstrated between spleen-intact patients with Gaucher disease and the control group. Compared to controls, both asplenic Gaucher disease and asplenic non-Gaucher disease study groups had a reduced MCHC (P = 0.003 and 0.005, respectively) and increased whole blood viscosity at 45% haematocrit (Hct), relative viscosity and red cell aggregation index , all measured at low shear (P < 0.05 for all). Additionally, asplenic patients with Gaucher disease alone showed an increased MCV (P = 0.006), an increased whole blood viscosity at 45% Hct measured at high shear (P = 0.019), and a reduced relative filtration rate (P = 0.0001), compared to controls. Conclusion: These observations demonstrate a direct and measurable haemorheological abnormality in Gaucher disease only revealed when there is no functioning spleen to control erythrocyte quality. [source] Protein deficiency balance as a predictor of clinical outcome in hereditary spherocytosisEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 5 2005S. Rocha Abstract:, Vertical and horizontal interactions between membrane constituents account for integrity, strength and deformability of the erythrocyte. Disruption of vertical interactions caused by membrane protein deficiencies in hereditary spherocytosis (HS), favor membrane vesiculation with development of spherocytic cells. Our aim was to evaluate the hematological and clinical presentation of HS according to the type and amount of protein deficiency. We studied 81 Portuguese individuals, 71 belonging to 21 families plus 10 unrelated subjects, and found that 51 of them were HS patients. Patients were classified as presenting mild, typical or severe HS, according to laboratory results and clinical follow-up. We performed screening tests and the standardized electrophoretic membrane protein analysis to identify and quantify protein deficiencies. We found band 3 and ankyrin deficiencies as the major causes for HS. The ratios between the value of the primary and/or secondary protein deficiencies showed significantly different values according to the severity of HS, and a significant inverse correlation with the severity of HS was observed. In mild HS, the ratios between protein deficiencies reflected equivalent protein deficiencies, while an unbalance was observed in typical HS, which was enhanced in severe HS. Our data suggest that the relative quantification of each major membrane protein and of the ratios between the values of protein deficiencies may be helpful in providing additional data about the clinical outcome of HS. [source] Optical tweezers for measuring red blood cell elasticity: application to the study of drug response in sickle cell diseaseEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 4 2003M. M. Brandão Abstract: The deformability of erythrocytes is a critical determinant of blood flow in microcirculation. By capturing red blood cells (RBC) with optical tweezers and dragging them through a viscous fluid we were able to measure their overall elasticity. We measured, and compared, the RBC deformability of 15 homozygous patients (HbSS) including five patients taking hydroxyurea (HU) for at least 6 months (HbSS/HU), 10 subjects with sickle cell trait (HbAS) and 35 normal controls. Our results showed that the RBC deformability was significantly lower in haemoglobin S (HbS) subjects (HbSS and HbAS), except for HbSS/HU cells, whose deformability was similar to the normal controls. Our data showed that the laser optical tweezers technique is able to detect differences in HbS RBC from subjects taking HU, and to differentiate RBC from normal controls and HbAS, indicating that this is a very sensitive method and can be applied for detection of drug-response in sickle cell disease. [source] Erythrocytes as targets for gamma-glutamyltranspeptidase initiated pro-oxidant reactionEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 5 2002Hayet Aberkane Abstract: Gamma-glutamyltranspeptidase (GGT) is a well known cell plasma membrane and serum circulating enzyme. In clinical chemistry, GGT is used as a marker of alcohol consumption and drug uptake. Serum GGT activity varies in hepatobiliary diseases and cancer. This enzyme is involved in glutathione (GSH) metabolism, which is generally associated with antioxidant properties. However, in recent years, findings from our group and from others showed that GGT-catalysed extracellular metabolism of GSH leads, in the presence of iron, to the generation of reactive oxygen species (ROS). It was demonstrated that those highly reactive species oxidise lipids, cell surface protein thiols or activate transcriptional factors such as Nuclear Factor ,B (NF,B). The objective of the present work is to determine whether the red blood cells are targets for plasma GGT-initiated pro-oxidant reaction. The results obtained demonstrate that the GGT/GSH/iron system oxidises isolated erythrocyte membranes. A significant release of haemoglobin and a decrease of erythrocyte deformability are also observed. In addition, in vivo studies showed a relationship between plasma GGT activity and erythrocyte deformability in 20 studied subjects. In conclusion, GGT-mediated ROS production is able to oxidise erythrocytes and thus disturbs their functions. [source] Changes in mu opioid receptors and rheological properties of erythrocytes among opioid abusersADDICTION BIOLOGY, Issue 2 2002ALLEN R. ZEIGER The high prevalence of anemia among chronic opioid users leads us to propose that chronic opiate use results in elevated mu opioid receptor levels on human erythrocytes and that these receptor changes may affect erythrocyte membrane properties. Blood samples from 17 opioid-dependent subjects (based on the Diagnostic and Statistical Manual of Mental Disorders, 4th edition or DSM-IV) and 15 drug-free controls were assayed for mu opioid receptors on erythrocytes using a flow cytometry immunoassay. Deformability and the hydration status of erythrocytes were studied by ektacytometry. Data were analyzed by independent t-tests, tests of correlation, chi square and cluster analyses. As expected, the percentage of erythrocytes from opioiddependent subjects with opioid receptors (opioid receptor levels) was significantly higher (47.4 ± 38.3%) than controls (22.8 ± 30.1%) (t = 2.01, df = 30, p < 0.05). Also, the opioid-dependent patients showed a wide variation in the percentage of erythrocytes bearing opioid receptors and data analyses of these patients showed two strongly defined clusters. One subgroup consisted of nine individuals with very high receptor levels (mean = 81.5%) while the other had eight patients with low receptor levels (mean = 9.1%) that were not significantly different than the receptor levels of controls. Ektacytometry of opioid dependent patients with high opioid receptor levels showed changes in rheological parameters of erythrocytes, such as deformability index and cellular hydration. For example, a positive correlation was observed between opioid receptor levels and deformability indices among opioid-dependent patients (r = 0.74, p < 0.005). Our findings indicate that the mu opioid receptor is present on human erythrocytes, although with considerable variation in receptor levels, and that the levels of this receptor are significantly elevated with chronic opioid exposure. Moreover, erythrocytes with high opioid receptor levels from chronic opiate users seem to have high deformability. This study may offer clues to the biological properties of peripheral blood cells that may be mediated by mu opioid receptors and lead to a better understanding of some of the clinical effects of opioid use. [source] Martensite Formation in a Ductile Cu47.5Zr47.5Al5 Bulk Metallic Glass Composite,ADVANCED ENGINEERING MATERIALS, Issue 6 2007S. Pauly A Cu47.5Zr47.5Al5 alloy was solidified into rods of 2, 3 and 5 mm diameter and the microstructures as well as the elastic and plastic properties were investigated along the length of each rod. It was found that neither the microstructure nor the mechanical properties vary significantly along the length of the specimens, except for the 5 mm diameter rod where the top part was proved to be fully crystalline containing cubic B2 CuZr (austenite) and monoclinic CuZr (martensite) phases. The differently solidified alloys show high strength and a distinct deformability under uniaxial compression and a work hardening-like behavior. [source] Effects of host mineral re-equilibration during uplift and cooling on the fidelity of primary hydrothermal fluid inclusions: a theoretical example using Mississippi Valley-type ore fluidsGEOFLUIDS (ELECTRONIC), Issue 2 2009M. A. McKIBBEN Abstract At the moment of its trapping as a primary fluid inclusion, a hydrothermal fluid is typically at or near equilibrium with multiple mineral species at depth and temperature. After trapping, however, the isolated inclusion fluid can re-equilibrate only with its own host mineral species during later uplift and cooling to surface conditions. Because the solubility versus temperature behavior is unique for each host mineral species, identical inclusions trapped at the same time within different species may re-equilibrate in a disparate manner upon cooling and become variably less representative of the original trapped fluid once they reach ambient temperature. To test the significance of this effect, a series of theoretical equilibrium reaction models was constructed in which a trapped hydrothermal fluid characteristic of Mississippi Valley-type ore deposits is cooled in contact with silicate, sulfide and carbonate hosts, respectively, from 100 to 25°C. Dissolved base metal concentrations are predicted to decline by two to four orders of magnitude in inclusions in all hosts, due to the precipitation of optically undetectable masses of sulfide daughter minerals. Fluids in the calcite host show the greatest decline in dissolved base metals upon cooling, due to its retrograde solubility and consequent shift in the pH and aqueous C speciation of the fluid. ,13C values for CO2 in all hosts become depleted by 2,7, relative to the original trapped fluid, with depletions again being the greatest for the calcite host due to its retrograde dissolution. Analytical techniques that extract and analyze the complete contents of fluid inclusions at room temperature can account for the predicted precipitation of microscopic daughter minerals during cooling, but may not compensate for chemical changes caused by the retrograde dissolution of calcite. Such solubility effects are another reason to be cautious in using carbonate minerals for fluid inclusion studies, in addition to their undesirable physical properties of softness, deformability and perfect cleavage. [source] Calibration of a discrete element model for intact rock up to its peak strengthINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 5 2010Yuannian Wang Abstract When three dimensional, bonded discrete element models (DEMs) are deployed to model intact rock, a basic question is how to determine the micro parameters that control macro properties of the modeled rock. After briefly describing the authors' DEM code, this paper describes algorithms to calibrate the model's micro parameters against standard laboratory tests, such as uniaxial and triaxial tests. Sensitivity analysis is used to identify the deformability micro parameters by obtaining relationships between microscopic and macroscopic deformability properties. The strength model parameters are identified by a global optimization process aimed at minimizing the difference between computed and experimental failure envelopes. When applied to the experimental results of Lac du Bonnet granite, this calibration process produced a good agreement between simulated and experimental results for both deformability and strength properties. Copyright © 2009 John Wiley & Sons, Ltd. [source] Surgical correction of scoliosis: Numerical analysis and optimization of the procedureINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 9 2010J. F. Aguilar Madeira Abstract A previously developed model is used to numerically simulate real clinical cases of the surgical correction of scoliosis. This model consists of one-dimensional finite elements with spatial deformation in which (i) the column is represented by its axis; (ii) the vertebrae are assumed to be rigid; and (iii) the deformability of the column is concentrated in springs that connect the successive rigid elements. The metallic rods used for the surgical correction are modeled by beam elements with linear elastic behavior. To obtain the forces at the connections between the metallic rods and the vertebrae geometrically, non-linear finite element analyses are performed. The tightening sequence determines the magnitude of the forces applied to the patient column, and it is desirable to keep those forces as small as possible. In this study, a Genetic Algorithm optimization is applied to this model in order to determine the sequence that minimizes the corrective forces applied during the surgery. This amounts to find the optimal permutation of integers 1, ,, n, n being the number of vertebrae involved. As such, we are faced with a combinatorial optimization problem isomorph to the Traveling Salesman Problem. The fitness evaluation requires one computing intensive Finite Element Analysis per candidate solution and, thus, a parallel implementation of the Genetic Algorithm is developed. Copyright © 2010 John Wiley & Sons, Ltd. [source] Towards a comprehensive computational model for the respiratory system,INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 7 2010Wolfgang A. Wall Abstract This paper is concerned with computational modeling of the respiratory system against the background of acute lung diseases and mechanical ventilation. Conceptually, we divide the lung into two major subsystems, namely the conducting airways and the respiratory zone represented by lung parenchyma. Owing to their respective complexity, both parts are themselves out of range for a direct numerical simulation resolving all relevant length scales. Therefore, we develop detailed individual models for parts of the subsystems as a basis for novel multi-scale approaches taking into account the unresolved parts appropriately. In the tracheobronchial region, CT-based geometries up to a maximum of approximately seven generations are employed in fluid,structure interaction simulations, considering not only airway wall deformability but also the influence of surrounding lung tissue. Physiological outflow boundary conditions are derived by considering the impedance of the unresolved parts of the lung in a fully coupled 3D-1D approach. In the respiratory zone, an ensemble of alveoli representing a single ventilatory unit is modeled considering not only soft tissue behavior but also the influence of the covering surfactant film. Novel nested multi-scale procedures are then employed to simulate the dynamic behavior of lung parenchyma as a whole and local alveolar ensembles simultaneously without resolving the alveolar micro-structure completely. Copyright © 2010 John Wiley & Sons, Ltd. [source] Modification of cellulose acetate with oligomeric polycaprolactone by reactive processing: Efficiency, compatibility, and propertiesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2009Szilvia Klébert Abstract Oligomeric polycaprolactone (oPCL) was used for the modification of cellulose acetate by reactive processing in an internal mixer at 180°C, 50 rpm, 60 min reaction time, and 45 wt % caprolactone (CL) content. The product of the reaction was characterized by several analytical techniques and its mechanical properties were determined by dynamic mechanical thermal analysis and tensile testing. The synthesized oPCL contained small and large molecular weight components. The small molecular weight fraction plasticized cellulose acetate externally and helped fusion. Although composition and structure did not differ considerably from each other when CL monomer or polycaprolactone oligomer was used for modification, the grafting of a few long chains had considerable effect on some properties of the product. The large molecular weight chains attached to CA increased the viscosity of the melt considerably and resulted in larger deformability. oPCL homopolymer is not miscible with cellulose acetate and migrates to the surface of the polymer. Exuded polycaprolactone oligomers crystallize on the surface but can be removed very easily. More intense conditions may favor the grafting of long chains leading to polymers with advantageous properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Factorial designed experiment to study the effects of excipients on the mechanical properties of pelletsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 10 2006Abraham B. Bashaiwoldu The aim of this work was to determine the effects of formulation factors on the mechanical properties of pellets produced by the process of extrusion and spheronisation. A range of properties from a simple fracture load to detailed load/displacement curves were used to study the effects of the levels of lactose monohydrate and glyceryl monostearate on the mechanical properties of pellets in terms of their surface tensile strength, pellet deformability and linear strain. A series of independent 22 -factorial designs were employed to establish the relationships between composition of the formulations and pellet properties, whereby the concept of an excess variable was explored. It was found that the spheronisation aid used, microcrystalline cellulose, is the domineering factor in most mechanical properties studied, except for the surface tensile strength, which decreased significantly with an increase in glyceryl monostearate concentration. The change in binder liquid from water to a water/ethanol mixture further changed the behaviour of the systems significantly. The assumption of an excess variable being less critical for the statistical outcome of a factorial experiment has not been found feasible for the systems studied. [source] Skin permeation of retinol in Tween 20-based deformable liposomes: in-vitro evaluation in human skin and keratinocyte modelsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 2 2006Yu-Kyoung Oh To develop a more effective transdermal delivery method for lipophilic functional cosmetic compounds such as retinol, we formulated various deformable liposomes and compared their transdermal delivery efficiency with those of neutral or negatively-charged conventional liposomes. We tested the deformability of liposomes containing edge activators such as bile salts, polyoxyethylene esters and polyoxyethylene ethers. As indicators of deformability, we used the passed volume and phospholipid ratios during extrusion, as well as the deformability index. We found that the type of edge activator significantly affected the extent of deformability, and that Tween 20 provided the highest level of deformability. Accordingly, we used Tween 20 to formulate deformable liposomes containing retinol in the membrane bilayers, and conducted a skin permeation study in Franz diffusion cells, using dermatomed human skin and three-dimensional human keratinocyte layers. As compared with the use of conventional neutral or negatively-charged liposomes, the use of Tween 20-based deformable liposomes significantly increased the skin permeation of retinol. These results suggested that deformable liposomes might be of potential use for the formulation of retinol and other lipophilic functional cosmetic compounds. [source] Melatonin increases glutathione peroxidase activity and deformability of erythrocytes in septic ratsJOURNAL OF PINEAL RESEARCH, Issue 2 2003M.B. Yerer No abstract is available for this article. [source] MECHANICAL PROPERTIES OF A FRIED CRUST,JOURNAL OF TEXTURE STUDIES, Issue 1 2001ISABEL LIMA A restructured potato model system was fried in canola oil for 5, 10, or 15 min at 170, 180, or 190C and tested in a Dynamic Mechanical Analyzer. Selected mechanical properties were measured using puncture and three-point bending cells. Forces involved in puncture were a combination of tension, compression, and shear, while the three-point bend test studied the crust flexural properties. Crust deformability seemed to be governed by internal structural yielding. Maximum force at rupture increased significantly with both frying time and temperature. Failure criteria identified and standardized types of failure observed during bending tests. [source] INFLUENCE OF UNIAXIAL COMPRESSION RATE ON RHEOLOGICAL PARAMETERS AND SENSORY TEXTURE PREDICTION OF COOKED POTATOESJOURNAL OF TEXTURE STUDIES, Issue 1 2000ANETTE KISTRUP THYBO ABSTRACT The effect of uniaxial compression rate (20,1000 mm/min) on the parameters: Stress (,ftrue), strain (,fHencky) and work to fracture (Wf), modulus of deformability (Ed), maximum slope before fracture (Emax) and work during 75% compression (Wtotal) was investigated for ten potato varieties. Multivariate data analysis was used to study the correlation between and within the sensory and nonsensory measurements by Principal Component Analysis (PCA) which showed ,ftrue, Emax, Wf, and Wtotal to explain the same type of information in the data, and ,fHencky versus Ed another type of information in the data. The deformation rate had a large effect on ,fHencky. Nine sensory texture attributes covering the mechanical, geometrical and moistness attributes were evaluated. Relationships between uniaxial compression data at various deformation rates and the sensory texture attributes were studied by Partial Least Squares Regression (PLSR). A minor effect of deformation rate on the correlation with the sensory texture properties was obtained. Mechanical properties were predicted to a higher extent than the geometrical attributes and moistness. The prediction of the mechanical, geometrical and moistness attributes increased largely by using uniaxial compression supplemented by chemical measures such as dry matter and pectin methylesterase, but here no relevant effect of deformation rate was obtained. [source] Favorable Impact of a Vegan Diet with Exercise on Hemorheology: Implications for Control of Diabetic NeuropathyJOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 2 2003MF McCarty A little-noticed clinical report indicates that a low-fat, whole-food vegan diet, coupled with daily walking exercise, leads to rapid remission of neuropathic pain in the majority of type 2 diabetics expressing this complication. Concurrent marked improvements in glycemic control presumably contribute to this benefit, but are unlikely to be solely responsible. Consideration should be given to the possibility that improved blood rheology , decreased blood viscosity and increased blood filterability , plays a prominent role in mediating this effect. There is considerable evidence that neural hypoxia, secondary to impaired endoneurial microcirculatory perfusion, is a crucial etiologic factor in diabetic neuropathy; the unfavorable impact of diabetes on hemorheology would be expected to exacerbate endoneurial ischemia. Conversely, measures which improve blood fluidity would likely have a beneficial impact on diabetic neuropathy. There is indeed evidence that vegan diets, as well as exercise training, tend to decrease the viscosity of both whole blood and plasma; reductions in hematocrit and in fibrinogen may contribute to this effect. The fact that vegan diets decrease the white cell count is suggestive of an improvement in blood filterability as well; filterability improves with exercise training owing to an increase in erythrocyte deformability. Whether these measures influence the activation of leukocytes in diabetics , an important determinant of blood filterability , remains to be determined. There are various reasons for suspecting that a vegan diet can reduce risk for other major complications of diabetes , retinopathy, nephropathy, and macrovascular disease , independent of its tendency to improve glycemic control in type 2 patients. The vegan diet/exercise strategy represents a safe, ,low-tech' approach to managing diabetes that deserves far greater attention from medical researchers and practitioners. [source] Superplasticity and high temperature deformation behaviour in nano grain Tungsten compactsMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 4-5 2008K. Ameyama Abstract Nano grain tungsten is fabricated by Mechanical Milling (MM) process, and its grain growth behavior and high temperature deformability is investigated. As a result, a nano grain structure, whose grain size is approximately 20 nm or less, is obtained after MM for 360ks. Those nano grains demonstrate an irregular grain boundary structure, i.e., "non-equilibrium grain boundary", and they change to a smooth grain boundary structure by annealing at 1023 K for 3.6 ks. Compacts with nano grain structure indicate superior sintering property even at 1273 K (0.35 Tm). Rhenium addition prevents grain growth during sintering and thus the compacts indicate a further improvement in deformability. The compact is composed of equiaxed grain, whose grain size is 420 nm, and has low dislocation density even after the large deformation. The strain rate sensitivity, i.e., m-value, of 0.41 is obtained in the W-Re compact at 1473 K. Those results strongly imply that the nano grain W-Re compacts show superplasticity at less than half of the melting temperature, i.e., 1473 K (0.42 of the solidus temperature). [source] Microvascular Rheology and HemodynamicsMICROCIRCULATION, Issue 1 2005HERBERT H. LIPOWSKY ABSTRACT The goal of elucidating the biophysical and physiological basis of pressure,flow relations in the microcirculation has been a recurring theme since the first observations of capillary blood flow in living tissues. At the birth of the Microcirculatory Society, seminal observations on the heterogeneous distribution of blood cells in the microvasculature and the rheological properties of blood in small bore tubes raised many questions on the viscous properties of blood flow in the microcirculation that captured the attention of the Society's membership. It is now recognized that blood viscosity in small bore tubes may fall dramatically as shear rates are increased, and increase dramatically with elevations in hematocrit. These relationships are strongly affected by blood cell deformability and concentration, red cell aggregation, and white cell interactions with the red cells and endothelium. Increasing strength of red cell aggregation may result in sequestration of clumps of red cells with either reductions or increases in microvascular hematocrit dependent upon network topography. During red cell aggregation, resistance to flow may thus decrease with hematocrit reduction or increase due to redistribution of red cells. Blood cell adhesion to the microvessel wall may initiate flow reductions, as, for example, in the case of red cell adhesion to the endothelium in sickle cell disease, or leukocyte adhesion in inflammation. The endothelial glycocalyx has been shown to result from a balance of the biosynthesis of new glycans, and the enzymatic or shear-dependent alterations in its composition. Flow-dependent reductions in the endothelial surface layer may thus affect the resistance to flow and/or the adhesion of red cells and/or leukocytes to the endothelium. Thus, future studies aimed at the molecular rheology of the endothelial surface layer may provide new insights into determinants of the resistance to flow. [source] Protective effects of selected medicinal plants against protein degradation, lipid peroxidation and deformability loss of oxidatively stressed human erythrocytesPHYTOTHERAPY RESEARCH, Issue 4 2004S. M. Suboh Abstract The effects of seven medicinal plants including Artemisia herba-alba, Ferula hermonis, Hibiscus sabdariffa, Nigella sativa, Teucrium polium, Trigonella foenum-graecum, and Allium sativum on protein degradation, lipid peroxidation, erythrocyte deformability and osmotic fragility of erythrocytes exposed in vitro to 10 mM H2O2 for 60 min at 37 °C have been examined. Preincubation of erythrocytes with Nigella sativa and Allium sativum protected erythrocytes against protein degradation, loss of deformability and increased osmotic fragility caused by H2O2, while the other plants failed to protect erythrocytes against these damages. Artemisia herba-alba did not protect erythrocytes against lipid peroxidation, while Trigonella foenum-graecum unexpectedly increased lipid peroxidation of erythrocytes exposed to H2O2. Ferula hermonis, Hibiscus sabdariffa, Nigella sativa, Teucrium polium and Allium sativum protected erythrocytes against lipid peroxidation. The results indicate the importance of oxidatively damaged cellular proteins in compromising the rheologic behaviour of the erythrocytes, and that the medicinal plants which have anti-protein-oxidant activity (e.g. Nigella sativa and Allium sativum) could be rheologically useful, particularly in pathological conditions related to free radicals. Copyright © 2004 John Wiley & Sons, Ltd. [source] Correction of haemorheological disturbances in myocardial infarction by diquertin and ascorbic acidPHYTOTHERAPY RESEARCH, Issue 1 2003M. B. Plotnikov Abstract In a model of the high blood viscosity syndrome, developed after myocardial infarction in rats, it was observed that a therapy of a combination of diquertin (20,mg/kg) and ascorbic acid (50,mg/kg) for a period of 6 days, resulted in an improvement of haemorheological indices. The decrease in blood viscosity was primarily due to an improved deformability of erythrocytes, and to some extent, due to a decrease in the content of plasma fibrinogen and erythrocyte aggregation. Copyright © 2003 John Wiley & Sons, Ltd. [source] The effect of interface characteristics on the static and dynamic mechanical properties of three-component polymer alloysPOLYMER COMPOSITES, Issue 3 2002I. Fisher The effect of interfacial characteristics on the structure-property relationships of ternary polymer alloys and blends comprising polypropylene (PP), ethylene-vinyl alcohol copolymer (EVOH) and glass beads (GB) or fibers (GF) was investigated. The systems studied were based on a binary PP/EVOH immiscible blend, representing a blend of a semi-crystalline apolar polymer with a semi-crystalline highly polar copolymer. The ternary systems studied consisted of filler particles encapsulated by EVOH, with some of the minor EVOH component separately dispersed within the PP matrix. Modification of the interfacial properties was done using silane coupling agents for the EVOH/glass interface and compatibilization using a maleic anhydride grafted PP (MA-g-PP) for the PP/EVOH interface. Both glass fillers increased the dynamic modulus and decreased the damping of the neat polymers and of their binary blends, especially in the rubbery region. GF has a more profound effect on both the modulus and the damping. Glass surface treatments and compatibilization have only a marginal effect on the dynamic mechanical behavior of the ternary blends. Yet, compatibilization shifted the polymers' TgS to higher temperatures. Both glass fillers increased the elastic modulus of the binary blends, where GF performed better than GB as a reinforcing agent. GF slightly increased the strength of the binary blends while, GB reduced it. Both fillers reduced the ductility of the binary blends. The blends' mechanical properties were related to the morphology and their components' crystallinity. The compatibilizer increases both stiffness and strength and reduces deformability. [source] Extension rheology of liquid-crystalline solution/layered silicate hybridsPOLYMER ENGINEERING & SCIENCE, Issue 4 2010Gleb B. Vasilyev The extension rheology of polymer/layered silicate composites based on liquid-crystalline (LC) solution of hydroxypropylcellulose (HPC) in oligomeric polyethyleneglycole (PEG) was studied. The HPC concentration was 60 wt%. Extension experiments have been carried out for materials in the different phase states. Compositions containing Na-montmorillonite (MMT) were prepared by a two-stage method. Final systems may be attributed to solutions of HPC in PEG, which intercalates into MMT galleries. The ordered domain structure of the LC matrix as well as hydrogen-bonded network between HPC and PEG molecules significantly reduce deformation at break and provide a strong nonlinear viscoelastic behavior at extension. Appearance of isotropic phase in solutions leads to a sharp drop of the elongation viscosity. The introduction of clay into LC solution only slightly affects the viscosity value but significantly suppresses the strain-hardening scale. In contrast, loading in biphasic state of HPC-PEG solution with even small amount (1 wt%) of MMT leads to the drastic viscosity increase that does not change in further growth of the filler concentration. Elastic properties of the systems under study demonstrate the similar behavior. This effect likely is caused by the interrelationship between deformability of the LC domain structure and the network strength formed by the clay particles. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source] Formation of a fibrillar morphology of crosslinked epoxy in a polystyrene continuous phase by reactive extrusionPOLYMER ENGINEERING & SCIENCE, Issue 4 2004Françoise Fenouillot An immiscible polymer blend where the dispersed phase is fibrillar was prepared by in situ crosslinking of the minor phase. A model polystyrene/epoxy-amine blend was selected on the basis of rheological (achievement of the fibrillar structure) and reactivity (fast crosslinking) criteria. The system was a polystyrene/diglycidyl ether of bisphenol A (DGEBA)-aminoethyl piperazine (AEP) blend. At the temperature of extrusion, 180°C, the DGEBA is immiscible in PS and heterogeneous material is obtained. The elongational flow imposed by drawing the extrudate at the die exit permitted controlled generation of a fibrillar morphology of the dispersed epoxy phase, with a fiber diameter of 1 ,m and an aspect ratio greater than 100. It was shown that when the amine comonomer was injected into the extruder, its reactivity with DGEBA at high temperature was high enough to ensure partial crosslinking of the epoxy. The fibrils were formed even though the gel point of the epoxy phase was exceeded. However, above a certain critical insoluble fraction that we estimated to be between 45% and 70%, a coarsening of the structure appeared, caused by the decreasing deformability of the domains and their coalescence. Finally, for our system, the crosslinking of the dispersed phase up to 90% of insoluble fraction did not totally stabilize the morphology after the second processing step (injection molding). Polym. Eng. Sci. 44:625,637, 2004. © 2004 Society of Plastics Engineers. [source] Hemorheologic profile in systemic sclerosis: Role of NOS3 ,786T>C and 894G>T polymorphisms in modulating both the hemorheologic parameters and the susceptibility to the diseaseARTHRITIS & RHEUMATISM, Issue 7 2006Cinzia Fatini Objective Microvascular disorders are relevant in systemic sclerosis (SSc). Hyperviscosity, due to alterations of blood cells and plasma components, may play a role in the pathogenesis of microcirculatory disorders. An impaired availability of nitric oxide, related to polymorphisms in NOS3, the gene for endothelial cell nitric oxide synthase, might influence erythrocyte deformability. We undertook this study to investigate the hemorheologic profile in SSc and the role of NOS3 polymorphisms in modulating the hemorheologic status of SSc patients. Methods We studied 113 consecutive SSc patients (75 with limited cutaneous SSc [lcSSc] and 38 with diffuse cutaneous SSc [dcSSc]) and 113 healthy controls. The hemorheologic profile was obtained by assessing whole blood viscosity (WBV; at shear rates of 0.512 and 94.5 seconds,1), plasma viscosity (PLV; at a shear rate of 94.5 seconds,1), and erythrocyte deformability index (DI). We determined NOS3 polymorphisms by molecular analysis. Results A marked alteration of hemorheologic parameters was found both in patients with lcSSc and in those with dcSSc compared with controls (P < 0.0001). In multivariate analysis, rheologic variables were significantly associated with the disease (for WBV at a shear rate of 94.5 seconds,1, odds ratio [OR] 5.4, 95% confidence interval [95% CI] 1.4,19.9, P = 0.01; for PLV, OR 2.8, 95% CI 1.2,6.5, P = 0.01; for DI, OR 3.9, 95% CI 1.4,10.8, P = 0.007), and NOS3 ,786C and 894T alleles significantly affected the DI (for ,786C allele, OR 2.3, 95% CI 1.01,5.4, P = 0.04; for 894T allele, OR 2.2, 95% CI 1.01,4.8, P = 0.04). The simultaneous presence of the ,786C and 894T alleles represented a susceptibility factor for SSc (OR 2.8, 95% CI 1.4,5.7, P = 0.004). Conclusion Our findings document an altered rheologic profile in SSc and demonstrate a relationship between this alteration and NOS3 polymorphisms, thus shedding light on a potential novel mechanism influencing the microcirculation in this disease. [source] | ||||||||||||||||||||||