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Tension Measurements (tension + measurement)
Kinds of Tension Measurements Selected AbstractsBlood pressure and vascular reactivity to endothelin-1, phenylephrine, serotonin, KCl and acetylcholine following chronic alcohol consumption in vitroFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 3 2001Tijen Utkan Ethanol has been reported to cause hypertension, the mechanism of which is unknown. Therefore, the effect of chronic ethanol consumption on vascular responsiveness and blood pressure was investigated. Systolic blood pressure was recorded weekly by tail-cuff method. Aortic rings from rats fed chow ad libitum or pair-fed liquid diets containing either ethanol (7.2% v/v) or isocaloric carbohydrate for 4 weeks were placed in organ chambers for isometric tension measurement. There was a mild but significant elevation of the systolic blood pressure in the alcohol-fed rats by week 1 compared to baseline measurements and this remained higher. No significant changes in reactivity of rat isolated aortas to phenylephrine, serotonin, endothelin-1 (ET-1) and KCl were seen in chronic ethanol consumption. In addition, the sensitivity (i.e. pD2) of alcohol-fed aortic rings to the vasoconstrictors was also unchanged compared to controls. Chronic ethanol consumption, however, increased relaxation to acetylcholine with increased pD2 values, but did not alter relaxation to sodium nitroprusside, a cyclic guanosine monophosphate (cGMP)-dependent direct smooth muscle dilator. The results indicate that chronic ethanol consumption significantly potentiates endothelium-dependent relaxations in aortic rings, probably through interference with the production and/or the release of nitric oxide (NO) or adaptive alterations in muscarinic receptors on the endothelial cells, and that increased vascular responsiveness to several vasoconstrictors is not a mechanism responsible for the blood pressure elevation in the chronic alcohol consumption in rats. [source] Identifying rotation and oscillation in surface tension measurement using an oscillating droplet methodHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 7 2008Shumpei Ozawa Abstract We proposed a new approach to identify the frequencies of droplet rotation and m=±2 oscillation that degrade the accuracy of surface tension measurement by an oscillating droplet method. Frequencies of droplet rotation and m=±2 oscillation can be identified by a phase unwrapping analysis of time dependence of the deflection angle for the maximum diameter of the droplet image observed from above. The present method was validated, using test data with given frequencies. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(7): 421,430, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20214 [source] The effect of viscosity on surface tension measurements by the drop weight methodJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007T. Kaully Abstract Viscosity is one of the parameters affecting the measured surface tension, as fluid mechanics affects the measurement process using conventional methods. Several methods including the selected planes (SPM) and WDSM which combines the weight drop method (WDM) and SPM, are applied to surface tension measurement of high viscous liquids. Yet, none of them treats the viscosity effect separately. The current publication presents a simple, easy to apply empirical approach of satisfactory accuracy, for evaluation of surface tension of liquids having wide range of viscosities up to 10 Pa s. The proposed method is based on Tate's law and the "drop weight" method using calibration curves of known liquids having similar surface tensions but different viscosities. Drop weight of liquids having viscosity ,0.05 Pa s, was found to be significantly affected by the liquid viscosity. The shape factor, f, of high viscosity liquids was found to correlate linearly with the logarithm of viscosity, pointing the importance of viscosity correction. The experimental correlation presented in the current work can be used as a tool for the evaluation of surface tension for high viscosity liquids such as prepolymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Erectile Function in Two-Kidney, One-Clip Hypertensive Rats is Maintained by a Potential Increase in Nitric Oxide ProductionTHE JOURNAL OF SEXUAL MEDICINE, Issue S3 2009A. Elizabeth Linder PhD ABSTRACT Introduction., Hypertension is closely associated with erectile dysfunction (ED) as it has been observed in many experimental models of hypertension. Additionally, epidemiological studies show that approximately a third of hypertensive patients have ED. Aim., To test the hypothesis that the two-kidney, one-clip (2K-1C) rat model of hypertension displays normal erectile function due to increased nitric oxide (NO) production in the penis. Methods., Ganglionic-induced increase in intracavernosal pressure (ICP)/mean arterial pressure (MAP) ratio was used as an index of erectile function in 2K-1C and in normotensive sham-operated (SHAM) anesthetized rats. Cavernosal strips from hypertensive and normotensive rats were used for isometric tension measurement. The contraction induced by alpha-adrenergic agonist phenylephrine and the relaxation induced by the NO donor sodium nitroprusside (SNP) and by the Rho-kinase inhibitor Y-27632 were performed in the absence and in the presence of the NO synthase inhibitor N, -nitro-L-arginine (L-NNA). Results., Changes in ICP/MAP induced by ganglionic stimulation were not different between 2K-1C and SHAM rats. The contractile response induced by phenylephrine as well as the relaxation induced by SNP or the Y-27632 were similar in cavernosal strips from both groups. However, in the presence of L-NNA, the relaxation induced by Y-27632 was significantly impaired in 2K-1C compared to SHAM. Conclusions., These data suggest that hypertension and ED could be dissociated from high levels of blood pressure in some animal models of hypertension. Erectile function in 2K-1C hypertensive rats is maintained in spite of the increased Rho-kinase activity by increased NO signaling. Linder AE, Dorrance AM, Mills TM, Webb RC, and Leite R. Erectile function in two-kidney, one-clip hypertensive rats is maintained by a potential increase in nitric oxide production. J Sex Med 2009;6(suppl 3):279,285. [source] cGMP-enhancing- and ,1A/,1D -adrenoceptor blockade-derived inhibition of Rho-kinase by KMUP-1 provides optimal prostate relaxation and epithelial cell anti-proliferation efficacyTHE PROSTATE, Issue 13 2007Chi-Ming Liu Abstract Background Soluble guanylyl cyclase (sGC)/cyclic guanosine monophosphate (cGMP)/protein kinase G (PKG) and Rho kinase (ROCK2) pathways are important in the regulation of prostate smooth muscle tone. This study is aimed to examine the relaxation activities of a sGC activator and PDE5A/ROCK2 inhibitor KMUP-1 in rat prostate and associated anti-proliferation activity in human prostatic epithelial cells. Methods The action characteristics of KMUP-1 were identified by isometric tension measurement, receptor binding assay, Western blotting and radioimmunoassay in rat prostate. Anti-proliferation activity of KMUP-1 in human prostatic epithelial PZ-HPV-7 cells was identified using flow cytometry and real time QRT-PCR. Results KMUP-1 inhibited phenylephrine-induced contractility in a concentration-dependent manner. KMUP-1 possessed potent ,1A/,1D -adrenoceptor binding inhibition activity, increased cAMP/cGMP levels and increased the expression of sGC, PKG, and PKA protein in rat prostate. Moreover, KMUP-1 inhibited phenylephrine-induced ROCK2 expression. KMUP-1 inhibited cell growth, arrested the cell cycle at G0/G1 phase and increased the expression of p21 in PZ-HPV-7 cells. Conclusions These results broaden our knowledge of sGC/cGMP/PKG and ROCK2 regulation on the relaxation and proliferation of prostate, which may help in the design of benign prostate hyperplasia (BPH) therapies that target these signaling pathways. KMUP-1 possesses the potential benefit in the treatment of BPH by its ,1A/,1D -adrenoceptor blockade, sGC activation, inhibition of PDE5A and ROCK2 and p21 protein enhancement, leading to attenuation of the smooth muscle tone and the proliferation of epithelial PZ-HPV-7 cells. The synergistic contribution of these pathways by KMUP-1 may benefit BPH patients with lower urinary tract symptoms. Prostate 67: 1397,1410, 2007. © 2007 Wiley-Liss, Inc. [source] Solubilities and surface activities of phthalates investigated by surface tension measurementsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2001Marianne Thomsen Abstract Aueous solutions of DEP (di-ethyl), DnBP (di- n -butyl), DnH(6)P (di- n -hexyl), and DEHP (di-[2-ethyl-hexyl])phthalates have been investigated by use of surface tension measurements at temperatures between 10 and 35°C. A tensiometric approach allows for the determination of unimeric solubilities and ,G°, which is the standard Gibbs free energy change, for the dissolution of phthalates in water. The unimeric solubility of the phthalates increase with decreasing temperature. The ,G° shows a linear increase with increasing phthalate alkyl chain length. The contribution of enthalpy (,H°) and entropy (,S°) to ,G° were calculated from the temperature-dependent solubilities. The contributions of both ,H° and ,S° are negative and increase in magnitude with increasing alkyl chain length, suggesting hydrophobic interactions between phthalates and water. The ability of different phthalates to lower the surface tension decreases with increasing alkyl chain length, whereas the relative affinity for adsorption in the air-water interface increases drastically for long-chain phthalates. Despite the low surface activity of phthalates compared with that of common surfactants, they show significant affinity for adsorption in air-water interfaces of natural surface waters. This property, combined with their low solubilities, may affect the fate of these compounds within the natural environment, because they form emulsions above unimeric saturation in aqueous media. [source] The effect of viscosity on surface tension measurements by the drop weight methodJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007T. Kaully Abstract Viscosity is one of the parameters affecting the measured surface tension, as fluid mechanics affects the measurement process using conventional methods. Several methods including the selected planes (SPM) and WDSM which combines the weight drop method (WDM) and SPM, are applied to surface tension measurement of high viscous liquids. Yet, none of them treats the viscosity effect separately. The current publication presents a simple, easy to apply empirical approach of satisfactory accuracy, for evaluation of surface tension of liquids having wide range of viscosities up to 10 Pa s. The proposed method is based on Tate's law and the "drop weight" method using calibration curves of known liquids having similar surface tensions but different viscosities. Drop weight of liquids having viscosity ,0.05 Pa s, was found to be significantly affected by the liquid viscosity. The shape factor, f, of high viscosity liquids was found to correlate linearly with the logarithm of viscosity, pointing the importance of viscosity correction. The experimental correlation presented in the current work can be used as a tool for the evaluation of surface tension for high viscosity liquids such as prepolymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Electrospinning of cellulose-based nanofibersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Audrey Frenot Abstract Cellulose derivatives of carboxymethyl cellulose sodium salt (CMC), hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), and enzymatically treated cellulose have been electrospun, and the microstructure of the resulting nanofibers has been analyzed by scanning electron microscopy (SEM). Before electrospinning, the solutions were characterized by viscometry and surface tension measurements, and the results were correlated with spinnability. Four different CMC derivatives, varying in molecular weight (Mw), degree of substitution (DS), and substitution pattern, have been electrospun in mixtures with poly(ethylene oxide) (PEO), and nanofibers of various characteristics have formed. The CMC-based nanostructures, i.e., the nonwoven sheet and individual nanofibers, proved to be independent of Mw and DS but largely dependent on the substitution pattern. The nonwoven sheets varied in homogeneity, and beads appeared on the individual fibers. Depending on the chemical nature of the CMC, the extraction of PEO resulted in pure CMC nanostructures of varying appearance, indicating that the distribution of PEO and CMC in the nanofibers also varied. Two different HPMC derivatives, varying in DS, were electrospun into nanofibers. Homogeneous nonwoven sheets based on nanofibers of similar appearance are formed, independent of the substitution content of the HPMC sample. Preliminary fibers were obtained from enzymatically treated cellulose in a solvent system based on lithium chloride dissolved in dimethyl acetamide (LiCl: DMAc). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1473,1482, 2007 [source] The Dynamic Interaction of Water with Four Dental Impression Materials During CureJOURNAL OF PROSTHODONTICS, Issue 4 2009Dariush Hosseinpour PhD Abstract Purpose: The purpose of this work was to investigate the interaction of water with four different dental impression materials: Aquasil (Ultra XLV Type 3), Take 1 (Wash Regular Set), Genie (Light Body, Standard Set), and Impregum Garant (Soft Light Bodied Consistency). Materials and Methods: Apparent contact angles of de-ionized water made against thin horizontal sample films of the different materials under different conditions were measured from analysis of profile images of symmetrical sessile drops of water placed on the sample films using a Model FTÅ200 dynamic drop shape analysis system, which included a JAI M30 high speed CCD camera combined with a zoom microscope. Data were taken for specimens of dry ages (times following mixing) from a minimum of 20 seconds up to 1220 seconds. Imaging was started before the initial water/impression material contact, and lasted for at least 420 seconds in each case. The interval at the beginning of each run was 0.033 second, and then increased by a factor of 1.012 to the end. During the initial 3 seconds following the drop deposition, the drop's shape oscillated due to inertial effects, so apparent contact angle data during this period were neglected in all cases. All measurements were made at room temperature. The drops were enclosed in a humidified chamber that suppressed evaporation. All data were repeated at least five times, and results were analyzed where appropriate using one-way ANOVA. Microscopic images of the water/impression material interactions for fresh (uncured) materials were acquired to reveal the destructive interactions that resulted from such contact. Finally, surface tension measurements were made of water that had been contacted with material of varying dry age using the pendant drop method capability of the drop shape analysis system. These helped to assess the origin of hydrophilicity development for the different materials. Results: For short curing times (dry ages), water showed a destructive effect on the integrity of all of the impression materials, as evidenced by the formation of a crater beneath the water drop and a scum of material at its surface. These effects diminished with dry age until a critical curing time was reached, beyond which such destructive interactions were no longer detectable. These critical curing times were determined to be 80, 140, 110, and 185 seconds for Aquasil, Take 1, Genie, and Impregum, respectively. The initial contact angle following the respective critical curing time was lowest for Impregum, at 66°; while values for Aquasil, Genie, and Take 1 were 93°, 104°, and 110°, respectively. Beyond the critical curing times for the different materials, different degrees of hydrophilicity were observed. Aquasil showed the lowest final contact angle (<10°), with Impregum, Take 1, and Genie showing 31°, 34°, and 40°, respectively. Measurements of the surface tension of water after contact with the different materials suggested that for Aquasil, hydrophilicity appears to be developed through the leaching of surfactant from the material, whereas for Impregum, Take 1, and Genie, hydrophilicity is developed at least in part through a change in surface structure in contact with water. Impregum and Aquasil materials of dry ages well beyond the critical curing time exhibited a stick-slip behavior in their interline movement or contact angle evolution. This was believed to be due to the slowness in the leaching of surfactant (in the case of Aquasil) or the re-orientation of unleachable surface groups (in the case of the other materials) in comparison to the inherent kinetics of water drop spreading. Conclusions: All materials investigated in the fresh, uncured state showed qualitative decomposition when put in contact with water through the formation of a crater beneath the water drop and a scum of material at its surface. These effects diminished with curing time until beyond a critical value, no such effects were evident. The initial hydrophilicity of the materials as determined by the contact angles obtained at their respective critical dry ages was greatest for Impregum. Beyond the critical curing time, different degrees of hydrophilicity were observed, with Aquasil showing the lowest final contact angle. [source] Comparison of relaxation responses to multiple vasodilators in TxA2 -analog and endothelin-1-precontracted pulmonary arteriesACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 6 2007C. Piamsomboon Background:, Peri-operative pulmonary hypertension can lead to right ventricular dysfunction and to an increase in morbidity and mortality. Altered function of the pulmonary vascular endothelium and vasoconstriction play a crucial role in the development of elevated pulmonary vascular resistance. Because pulmonary artery vasoreactivity is dependent on many factors including the constricting agent that precipitated the event therefore the aim of the current study was to investigate the effectiveness of different classes of vasodilator agents to reverse endothelin-1 (ET-1) or thromboxane A2 (TxA2)-induced vasoconstriction in porcine pulmonary artery (PA) in vitro. Methods:, Relaxation responses to vasodilatory drugs were studied in PA precontracted with ET-1 (1 × 10,8 M) or TxA2 analog (U46619, 1 × 10,8 M). All vasodilating drugs were added in a cumulative fashion and isometric tension measurements were obtained using an organ chamber technique. Results:, In both groups relaxation responses to the vasodilators were dose dependent. When ET-1 was used as a constrictor nitroglycerin and milrinone caused nearly complete (80,100%) relaxation, whereas other agents were of limited effectiveness (40,50%). On the other hand, in the vessels constricted with U46619, olprinone, indomethacin, prostaglandin E1 (PGE1), nitroglycerin, milrinone and clevidipine induced complete (90,110%) vasodilatation but brain natriuretic peptide (BNP), l -arginine, and isoproterenol relaxed the vessels maximally by 45,60%. Conclusions:, Nitroglycerin and milrinone are very effective in reversing ET-1 and U46619-induced pulmonary vasoconstriction in vitro. The effectiveness of other drugs studied was dependent on the type of constrictor used. BNP, l -arginine and isoproterenol were shown to have minimal vasodilatory effects in porcine PA. [source] Surface activity,thermodynamic properties and light scattering studies for some novel aliphatic polyester surfactantsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2004R. A. El-Ghazawy Abstract The preparation of 12 new polyester surfactants based on aliphatic amines and different ethylene oxide content is described. These surfactants were characterized by determining their molecular weights and polydispersity by gel permeation chromatography (GPC) and nitrogen content. Drop volume tensiometry (DVT) was used to measure the surface tension at 25, 35, 45 and 55°C. The surface tension isotherms were used to determine critical micelle concentration (CMC), maximum Gibb's adsorption (,max), minimum area per molecule (Amin), the effectiveness of surface tension reduction (,cmc) and the efficiency (pC20). The thermodynamic parameters of micellization (,Gmic, ,Hmic, ,Smic) and of adsorption (,Gad, ,Had, ,Sad) were calculated and the data showed that these surfactants favor micellization to adsorption. The static scattered light intensity measurements provide the calculation of the molecular weight of micelle and the aggregation number (N°), while the dynamic light scattering provide the hydrodynamic radius of micelle (RH) and the diffusion coefficient at different surfactant concentrations. The hydrodynamic radius of micelle (RH) at different surfactant concentrations could be used also to determine the CMC giving results that are comparable to those obtained by surface tension measurements. All the data are discussed regarding the chemical structure of the polymeric surfactants. Copyright © 2004 John Wiley & Sons, Ltd. [source] Exploring the interactions of gliadins with model membranes: Effect of confined geometry and interfacesBIOPOLYMERS, Issue 8 2009Amélie Banc Abstract Mechanisms leading to the assembly of wheat storage proteins into proteins bodies within the endoplasmic reticulum (ER) of endosperm cells are unresolved today. In this work, physical chemistry parameters which could be involved in these processes were explored. To model the confined environment of proteins within the ER, the dynamic behavior of ,-gliadins inserted inside lyotropic lamellar phases was studied using FRAP experiments. The evolution of the diffusion coefficient as a function of the lamellar periodicity enabled to propose the hypothesis of an interaction between ,-gliadins and membranes. This interaction was further studied with the help of phospholipid Langmuir monolayers. ,- and ,-gliadins were injected under DMPC and DMPG monolayers and the two-dimensional (2D) systems were studied by Brewster angle microscopy (BAM), polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS), and surface tension measurements. Results showed that both gliadins adsorbed under phospholipid monolayers, considered as biological membrane models, and formed micrometer-sized domains at equilibrium. However, their thicknesses, probed by reflectance measurements, were different: ,-gliadins aggregates displayed a constant thickness, consistent with a monolayer, while the thickness of ,-gliadins aggregates increased with the quantity of protein injected. These different behaviors could find some explanations in the difference of aminoacid sequence distribution: an alternate repeated - unrepeated domain within ,-gliadin sequence, while one unique repeated domain was present within ,-gliadin sequence. All these findings enabled to propose a model of gliadins self-assembly via a membrane interface and to highlight the predominant role of wheat prolamin repeated domain in the membrane interaction. In the biological context, these results would mean that the repeated domain could be considered as an anchor for the interaction with the ER membrane and a nucleus point for the formation and growth of protein bodies within endosperm cells. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 610,622, 2009. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Site-Selective Formation of Optically Active Inclusion Complexes of Alkoxo-Subphthalocyanines with ,-Cyclodextrin at the Toluene/Water InterfaceCHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2006Kenta Adachi Abstract Several subphthalocyanine derivatives that contain an alkoxo substituent as an axial ligand (RO-Subpc, R = 9-anthracenemethyl, benzyl, phenyl, 3,5-dimethylbenzyl, 3,5-dimethylphenyl, 4-methylbenzyl, and 4-methylphenyl) were synthesized. The formation of inclusion complexes of RO-Subpc with ,-CD in DMSO and at the toluene/water interface was investigated by UV/Vis absorption spectroscopy, induced circular dichroism (ICD), and nuclear magnetic resonance (NMR) measurements. Interfacial tension measurements suggested that ,-CD adsorbed as a monolayer at the toluene/water interface and probably orientated towards the toluene phase with its primary face. The 1:1 composition of ,-CD,RO-Subpc inclusion complexes was confirmed in DMSO and at the toluene/water interface for BzO-Subpc, PhO-Subpc, MeBzO-Subpc, and MePhO-Subpc. A 2:1 inclusion complex of AnO-Subpc formed in DMSO. The observed ICD spectra of ,-CD,RO-Subpc inclusion complexes are discussed with respect to molecular modeling and the simulation based on Tinoco,Kirkwood theory. Interestingly, the ICD spectra of ,-CD,BzO-Subpc and ,-CD,MeBzO-Subpc inclusion complexes exhibited a negative sign in DMSO and a positive sign at the toluene/water interface. This reversal of the ICD sign strongly suggests a difference in the structure of the inclusion complexes: ,-CD at the interface formed the inclusion complex with its primary face, whereas the secondary face of ,-CD bound favorably to RO-Subpc in DMSO. 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