Capillary Tubes (capillary + tubes)

Distribution by Scientific Domains


Selected Abstracts


Self-Assembly of Rodlike Bio-nanoparticles in Capillary Tubes,

ANGEWANDTE CHEMIE, Issue 5 2010
Yuan Lin Dr.
Richtungsweisend: Unterschiedliche Muster resultieren beim Trocknen einer Lösung von Tabakmosaikvirus(TMV)-Partikeln in einer Glaskapillare (siehe AFM-Bilder). Die Eigenschaften der hierarchischen Struktur können über die Partikelkonzentration, den Trocknungsprozess und die Beschaffenheit der Röhrchenwand gesteuert werden. Die inwändig gemusterten Röhren wurden genutzt, um glatte Muskelzellen aus der Mausaorta auszurichten. [source]


An assessment of friction factor and viscosity correlations for model prediction of refrigerant flow in capillary tubes

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2005
Zhang Yufeng
Abstract In this paper, a homogeneous model including the metastable liquid and metastable two-phase region is presented to assess the effects of various friction factor equations and two-phase viscosity correlations on simulating the behaviour of capillary tubes. Both straight and coiled capillary tubes are considered and R-22 is used for comparison. The predicted pressure distribution, tube lengths or mass flow rates are compared with experimental data reported in literature. It is confirmed that the predicting accuracy with homogeneous model can be improved by employing the suitable correlations of friction factor and two-phase viscosity. For straight capillaries, the Churchill and Colebrook friction factor correlations give almost the same simulating results. However, the numerical results show that the optimum combination of correlations of friction factor and two-phase viscosity may be different when compared with different experimental data. For coiled capillaries, the Mori and Nakayama friction factor correlation agrees well with Ito's formula for single liquid-phase flow. Together with Giri's friction factor equation for two-phase flow, Cicchitti viscosity model best predicts the measured mass flow rate with an average error of 4.88%. Copyright © 2004 John Wiley & Sons, Ltd. [source]


Experimental analysis of capillary tubes behaviour with some HCFC-22 alternative refrigerants

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 14 2001
Samuel M. Sami
Abstract In this paper, an experimental study is presented to enhance our understanding of the capillary tube behaviour using some new alternative refrigerants to HCFC-22. An experimental setup fully instrumented was used to gather the behaviour of three different capillary tube geometries with R-410B, R-407C, and R-410A under various conditions; saturated, sub-cooled and two-phase. Experimental data showed that R-410B has the highest pressure drop along the capillary tubes compared to the alternatives under question and also has the highest temperature drop along the capillary tube. The data also showed that R-407C has similar capillary behaviour to that of R-22. The results clearly demonstrated that the pressure drop is significantly influenced by the diameter of the capillary tube, the type of refrigerant and inlet conditions to the capillary tube. The data also showed that the capillary pressure drop decreases with the increase of the capillary diameter. There is clear evidence that the component concentration of the refrigerant mixture significantly affects the capillary tube behaviour and particularly the pressure drop along the capillary tube length. Copyright © 2001 John Wiley & Sons, Ltd. [source]


Prediction of capillary tubes with alternative refrigerants to CFC-502

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 14 2001
Samuel M. Sami
Abstract A numerical model is presented in this paper, for predicting capillary tube performance using new alternative refrigerants to CFC-502. The model has been established after the fluid flow conservation equations written for a homogeneous azeotropic refrigerant fluid flow under saturated, sub-cooled and two-phase conditions. The study was limited to the following azeotropic mixtures; R-507, R-404A, and quaternary mixture (R32/R125/R134a/R143a). Numerical results showed that the proposed model in question fairly simulated our experimental data and fairly predicted the capillary tube behaviour under different conditions. The results also indicated that a system using R-507 would experience smaller pressure drop across the capillary compared to the other alternatives under question. Copyright © 2001 John Wiley & Sons, Ltd. [source]


Demonstration of Flexible Freestanding All-Polymer Integrated Optical Ring Resonator Devices,

ADVANCED MATERIALS, Issue 1 2004
Y. Huang
A simple method to fabricate thin freestanding all-polymer integrated optical devices and the transfer of the devices to various substrates, such as the curved surfaces of capillary tubes, is reported. A passive microring resonator optical filter device (see Figure) with a ,27,dB notch extinction for wavelengths in the telecommunication band, which is within the range of requirements for practical telecommunications applications, is also shown. [source]


An improved method for detecting red cells with hemoglobin H inclusions that does not require glass capillary tubes

INTERNATIONAL JOURNAL OF LABORATORY HEMATOLOGY, Issue 2 2003
D.E. Sabath
Summary, -Thalassemia trait is the most common inherited abnormality worldwide. Diagnosis of , -thalassemia trait can be difficult as there are no abnormalities detectable by hemoglobin electrophoresis or high-performance liquid chromatography. Detection of individuals with , -thalassemia trait, particularly the type present in many Asian populations, is important for genetic counseling purposes, because these individuals are at risk for having offspring with hemoglobin Bart's hydrops fetalis, a fatal condition. The best routine diagnostic method to detect individuals with , -thalassemia trait is staining reticulocyte-enriched red cell preparations with brilliant cresyl blue to detect hemoglobin H inclusions. Current methods use centrifugation of microhematocrit tubes to enrich for reticulocytes, which presents a laboratory safety hazard. In this report, we describe an alternative technique to enrich for reticulocytes that does not require glass capillary tubes, but is as effective as the capillary tube method for reticulocyte enrichment and detection of cells containing hemoglobin H inclusions. [source]


Lack of inhibitory effects of the anti-fibrotic drug imatinib on endothelial cell functions in vitro and in vivo

JOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 10 2009
Paulius Venalis
Abstract Systemic sclerosis (SSc) is a systemic autoimmune disease that is characterized by microangiopathy with progressive loss of capillaries and tissue fibrosis. Imatinib exerts potent anti-fibrotic effects and is currently evaluated in clinical trials. The aim of the present study was to exclude that the anti-fibrotic effects of imatinib are complicated by inhibitory effects on endothelial cell functions, which might augment vascular disease in SSc. Endothelial cells and mice were treated with pharmacologically relevant concentrations of imatinib. The expression of markers of vascular activation was assessed with real-time PCR. Proliferation was analysed with the cell counting experiments and the MTT assay. Apoptosis was quantified with caspase 3 assays, annexin V in vitro and with TUNEL staining in vivo. Migration was studied with scratch and transwell assays. Tube forming was investigated with the matrigel assay. Imatinib did not alter the expression of markers of vascular activation. Imatinib did not increase the percentage of annexin V positive cells or the activity of caspase 3. No reduction in proliferation or metabolic activity of endothelial cells was observed. Imatinib did not affect migration of endothelial cells and did not reduce the formation of capillary tubes. Consistent with the in vitro data, no difference in the number of apoptotic endothelial cells was observed in vivo in mice treated with imatinib. Imatinib does not inhibit activation, viability, proliferation, migration or tube forming of endothelial cells in vitro and in vivo. Thus, treatment with imatinib might not augment further endothelial cell damage in SSc. [source]


Hypoxia-induced apoptosis and tube breakdown are regulated by p38 MAPK but not by caspase cascade in an in vitro capillary model composed of human endothelial cells

JOURNAL OF CELLULAR PHYSIOLOGY, Issue 3 2007
Toshiro Ohta
In order to improve medical treatment of ischemic injury such as myocardial infarction, it is important to elucidate hypoxia-induced changes to endothelial cells. An in vitro blood vessel model, in which HUVECs are stimulated to form a network of capillary-like tubes, was used to analyze hypoxia-induced morphological and biochemical changes. When exposed to hypoxia, the network of capillary tubes broke down into small clusters. This tube breakdown was accompanied by chromatin condensation and cell nuclear fragmentation, morphological markers of apoptosis, and activation of two apoptotic signals, caspase-3 and p38. We investigated what roles caspase cascade and p38 play in hypoxia-induced apoptosis and tube breakdown by using zVAD-fmk and SB203580, specific inhibitors of these two apoptotic signals, respectively. Chromatin condensation and cell nuclear fragmentation and tube breakdown were effectively inhibited by SB203580, but not by zVAD-fmk. SB203580 caused dephosphorylation of p38, which indicates that p38 was autophosphorylated. Inhibition by zVAD-fmk caused slight MW increase in p17 and emergence of p19, which indicates that the inhibitor caused partial processing of caspase-3. Inhibition of p38 suppressed activation of caspase-3 but not vice versa. In addition, these two inhibitors were shown to differentially inhibit cleavage of so-called caspase substrates. SB203580 inhibited cleavage of PARP and lamin A/C, while zVAD-fmk inhibited cleavage of lamin A/C but not that of PARP. Taken together, these results show that p38 is located upstream of caspase cascade and that, although caspase-3 is activated, a p38-regulated caspase-independent pathway is crucial for the execution of hypoxia-induced apoptosis and tube breakdown. J. Cell. Physiol. 211: 673,681, 2007. © 2007 Wiley-Liss, Inc. [source]


Snap-off of a liquid drop immersed in another liquid flowing through a constricted capillary

AICHE JOURNAL, Issue 8 2009
T. J. Peña
Abstract Emulsions are encountered at different stages of oil production processes, often impacting many aspects of oilfield operations. Emulsions may form as oil and water come in contact inside the reservoir rock, valves, pumps, and other equipments. Snap-off is a possible mechanism to explain emulsion formation in two-phase flow in porous media. Quartz capillary tubes with a constriction (pore neck) served to analyze snap-off of long ("infinite") oil droplets as a function of capillary number and oil-water viscosity ratio. The flow of large oil drops through the constriction and the drop break-up process were visualized using an optical microscope. Snap-off occurrence was mapped as a function of flow parameters. High oil viscosity suppresses the breakup process, whereas snap-up was always observed at low dispersed-phase viscosity. At moderate viscosity oil/water ratio, snap-off was observed only at low capillary number. Mechanistic explanations based on competing forces in the liquid phases were proposed. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]


Cryoimmobilization and three-dimensional visualization of C. elegans ultrastructure

JOURNAL OF MICROSCOPY, Issue 1 2003
T. Müller-Reichert
Summary Caenorhabditis elegans is one of the most important genetic systems used in current biological research. Increasingly, these genetics-based research projects are including ultrastructural analyses in their attempts to understand the molecular basis for cell function. Here, we present and review state-of-the-art methods for both ultrastructural analysis and immunogold localization in C. elegans. For the initial cryofixation, high-pressure freezing is the method of choice, and in this article we describe two different strategies to prepare these nematode worms for rapid freezing. The first method takes advantage of transparent, porous cellulose capillary tubes to contain the worms, and the second packs the worms in E. coli and/or yeast paste prior to freezing. The latter method facilitates embedding of C. elegans in a thin layer of resin so individual worms can be staged, selected and precisely orientated for serial sectioning followed by immunolabelling or electron tomography. [source]


Distributed intraclot thrombolysis: mechanism of accelerated thrombolysis with encapsulated plasminogen activators

JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 9 2004
J. K. Leach
Summary.,Background: The delivery of encapsulated plasminogen activators has demonstrated enhanced thrombolysis in vivo in several models. The mechanism of such improvement has not previously been established. Objectives We explored in vitro the mechanism by which microencapsulation of streptokinase in polymeric microparticles accelerates clot digestion and reduces reperfusion times by as much as an order of magnitude in vivo. Methods: The efficacy of microencapsulated streptokinase (MESK) was directly compared with identical dosages of unencapsulated streptokinase (FREE SK) at three initial pressure drops using clots formed of plasma or whole blood in 0.2-cm inner diameter glass capillary tubes. Results: MESK demonstrated accelerated flow restoration compared with FREE SK for each condition in plasma (23.8 ± 4.5% faster) and whole blood clots (17.2 ± 9.2% faster). Images collected by light microscopy show sites of thrombolysis internal to the clot only with MESK while the spatial distribution of fluorescently labeled streptokinase by confocal microscopy confirms greater penetration of the encapsulated agent compared with unencapsulated streptokinase. Digestion thus proceeds in three dimensions rather than restricted to a two-dimensional lysis front. Conclusions: The improved clot penetration with MESK establishes enhanced transport with encapsulation and the concept of distributed intraclot thrombolysis as a basis for the accelerated dissolution observed with encapsulated plasminogen activators in vivo. [source]


The influence of an internal electric field upon protein crystallization using the gel-acupuncture method

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2003
N. Mirkin
In this work, the influence of an internal electric field upon the crystallization of lysozyme and thaumatin is explored using a modified design of the gel-acupuncture setup. From a crystallographic point of view, the orientation of crystals that grow preferentially over different types of electrodes inside capillary tubes is also evaluated. Finally, the crystal quality and the three-dimensional structure of these proteins grown with and without the electric field influence are analyzed by means of X-ray diffraction methods. [source]


Retinal vessel oximetry using sequential and 'snapshot' hyperspectral imaging

ACTA OPHTHALMOLOGICA, Issue 2009
A MCNAUGHT
Purpose Use of sequential, and 'snapshot' hyperspectral imagers to measure oxygen saturation in retinal vessels in normals, and examples of eye disease, eg glaucoma, and retinovascular diseases. Validation of estimated oximetry values using a model eye. Methods A sequential hyperspectral imager was constructed using a fundus camera with built-in liquid-crystal tuneable filter. Images of normals,and ocular disease are presented. A novel 'snapshot' hyperspectral imager is also described: this produces images in a single exposure. Validation of both devices using an artificial eye with capillary tubes containing human blood of known oxygen saturation, placed in front of an 'artificial retina' is described. The image analysis used to detect retinal vessels, and generate oximetric values is detailed. Results Both the sequential, and 'snapshot' retinal imagers produced accurate estimations of retinal vessel oxygen saturation, when compared with the model eye. Imaging of a small group of glaucoma eyes showed abnormally elevated venous oxygen saturation. In proliferative diabetic retinopathy, abnormally elevated venular saturation was found in areas of capillary loss on FFA. In vein occlusion, elevated venous saturation was found in eyes with ischaemic FFAs. Conclusion Both the sequential and 'snapshot' hyperspectral imagers deliver useful oximetric maps of the retina. The 'snapshot' device allows more rapid imaging. The elevated venular oxygen saturation seen in both glaucoma, and retinovascular disease, is perhaps evidence of reduced oxygen consumption in damaged inner retina in glaucoma, and/or vascular 'shunting' in retinovascular disease. [source]


Morphological and biochemical effects of immunosuppressive drugs in a capillary tube assay for endothelial dysfunction

CLINICAL TRANSPLANTATION, Issue 2003
Chumpon Wilasrusmee
Abstract: Immunosuppressive drugs common in clinical transplantation are known to have untoward effects on the vascular system. The effects of some drugs, notably cyclosporin A (CyA), have been studied on the vascular system, while those of others have not. In the vascular system, endothelial cells are the predominant cell type exposed to intravascular concentrations of immunosuppressive drugs. We therefore studied the effects of drugs common in clinical transplantation on endothelial cells in a capillary tube assay. The endothelial cells in the capillary tubes are morphologically more similar to those in the microvasculature than endothelial cells in monolayers. We studied the kinetics and extent of capillary tube formation and prostacyclin (PGI2) and endothelin-1 (ET-1) release from the in vitro capillaries to determine the morphological and biochemical effects of five immunosuppressive agents on endothelial function. We found a significant difference in the morphological and biochemical effects of the two common calcineurin inhibitors, CyA and tacrolimus (FK506) on capillary morphology in vitro. The former had a pronounced injurious effect on the morphology of the in vitro capillaries, while the latter did not. CyA also significantly increased ET-1 release by the capillaries, but FK506 did not. Mycophenolate mofetil (MMF) was the only other agent that had a moderately injurious effect on the morphology of the in vitro capillaries. Sirolimus (rapamycin) and dexamethasone, similar to FK506, had no effect on the capillary morphology. All these agents, except dexamethasone, increased PGI2 release. Our data suggest that CyA adversely affects the morphology of the microvasculature and that this is mediated, at least partly, by an increased ET-1 release by endothelial cells exposed to CyA. These findings describe a novel effect of CyA and MMF on endothelial cells that could be relevant to understanding the mechanisms of immunosuppressive drug-mediated endothelial injury in clinical transplantation. [source]