bluuebunny/crossref_metadata_2025 huggingface dataset:
Biodistribution of Cyclosporin Encapsulated in Liposomes Modified with Bioadhesive Polymer
Authors: Yoshikawa Yukako , Miyazaki Masaya , Houjou Takeshi , Komuta Yutaka , Yoshikawa Hiroshi , Takada Kanji
Published: April 2011

The purpose of this investigation was to study the possibility of renewing the immunosuppressive activity of cyclosporin by formulating the compound in liposomes modified with bioadhesive polymers. The liposomes prepared were evaluated both pharmacokinetically and pharmacodynamically. Tissue distribution and plasma pharmacokinetics of cyclosporin and model dye, sudan black, which is as hydrophobic as cyclosporin, were studied in rats after intravenous infusion (10 mg kg−). The immunosuppressive efficacy of liposomal cyclosporin preparations was studied in the allogenic rat-heart-transplantation model, where cyclosporin therapy (10 mg kg−) continued for one week.

The entrapment of sudan black in liposomes modified with bioadhesive polymers resulted in higher sudan black delivery to the spleen and the liver than with standard sudan-black-loaded liposomes. Among the modified liposomes, those modified with carbopol 941 showed the most remarkable enhancing effect on the delivery of sudan black to these organs and total plasma clearance of sudan black decreased to 38.6 ± 7.8 mL h− kg− (standard liposomes, 58.9 ± 64 mL h− kg−). Delivery of cyclosporin to the spleen and the liver was increased approximately twofold by modifying the liposomes with carbopol 941. In the preliminary study on the allogenic rat-heart-transplantation model, the mean survival days of the graft were 18.8 ± 2.9 days for the group receiving cyclosporin liposomes modified with carbopol 941, 14.2 ± 4.4 days for the group receiving standard cyclosporin liposomes and 7.6 ± 0.5 days for the group receiving cyclosporin solution.

The encapsulation of cyclosporin in liposomes modified with bioadhesive polymer enhanced the residence time of cyclosporin in the systemic circulation, resulting in approximately twofold greater delivery of cyclosporin to the spleen and liver. However, in the allogenic rat-heart-transplantation model no significant difference was detected between the immunosuppressive efficacy of cyclosporin encapsulated in bioadhesive polymer-modified liposomes and that encapsulated in standard liposomes.
Antiplatelet Effects of Some Aporphine and Phenanthrene Alkaloids in Rabbits and Man
Authors: Teng Che-Ming , Hsueh Cheung-Mei , Chang Ya-Ling , Ko Feng-Nien , Lee Shoei-Sheng , Liu Karin Chiung-Sheue
Published: April 2011

Two aporphines (boldine and laurolitsine) and five phenanthrene alkaloids (litebamine, secoboldine, N-cyanosecoboldine, N-methylsecoglaucine and N-methylsecopredicentrine) were evaluated in-vitro for their ability to inhibit platelet aggregation.

All seven alkaloids inhibited aggregation of rabbit platelets and inhibited the release of ATP induced by arachidonic acid and collagen in rabbit platelets. Those aggregations induced by platelet-activating factor (PAF), thrombin, U46619 and ADP were inhibited by the three N-substituted secoboldine derivatives only. Thromboxane B2 formation caused by arachidonic acid was also suppressed by these compounds. They did not affect the generation of [3H]inositol monophosphate caused by collagen, PAF and thrombin in the presence of indomethacin. Platelet cyclic AMP level was unaffected by litebamine, but was increased by N-methyl-secoglaucine. Litebamine suppressed the secondary aggregation, but not the primary aggregation, induced by ADP and adrenaline in platelet-rich plasma from man, whereas N-methylsecoglaucine inhibited both primary and secondary aggregation.

It is concluded that the antiplatelet effect of these seven aporphine and phenanthrene alkaloids is mainly a result of inhibition of thromboxane A2 formation; N-methylsecoglaucine has additional antiplatelet activity as a result of increasing the levels of platelet cyclic AMP.
A Comparison of the Standard Approach and the NONMEM Approach in the Estimation of Bioavailability in Man
Authors: Combrink M , McFadyen M L , Miller R
Published: April 2011

There has recently been concern about confidence intervals calculated using the standard error of parameter estimates from NONMEM, a computer program that uses a non-linear mixed-effects model to calculate relative bioavailability (F), because of possible downward bias of these estimates. In this study an alternate approach, the log-likelihood procedure, was used to calculate the confidence intervals for F from NONMEM. These were then compared with those calculated using the standard error of the parameter estimates, the traditional NONMEM approach, and the standard model-independent method, to determine whether bias exists.

By use of data from a single dose, open cross-over study of ibuprofen using 14 healthy male volunteers, NONMEM was shown to give results consistent with those obtained using the standard model-independent method of analysis and could be a useful tool in the determination of F where conditions for using the standard method of analysis are not optimum. The width of the confidence interval for F using the log-likelihood procedure was narrower and non-symmetrical when compared with that obtained using the traditional NONMEM approach. The width of the confidence interval obtained using the traditional NONMEM method was similar to that from the standard approach, however the parameter estimate for F was higher than that obtained from the standard method. This could have been because of an outlier in the data set to which the standard approach is more sensitive.

No downward bias was found in the confidence intervals from NONMEM. The bioavailability data set was of relatively low variability and more research with highly variable data is necessary before it can be concluded that the confidence intervals calculated from NONMEM can be used for hypothesis testing.
The Synergistic Purgative Action of Aloe-emodin Anthrone and Rhein Anthrone in Mice: Synergism in Large Intestinal Propulsion and Water Secretion
Authors: Yagi Teruyo , Yamauchi Kazuko , Kuwano Shigeaki
Published: April 2011

This study aimed to explore the mechanism involved in the synergistic purgative action of aloe-emodin anthrone and rhein anthrone, the active metabolites of sennoside C.

Aloe-emodin anthrone and rhein anthrone, and their equimolar mixture, induced excretion of an approximately equal number of faeces by intracaecal administration at a dose of 23.2 μmol kg−1 in mice (= 10 standard dose). The number of wet faeces induced by aloe-emodin anthrone was less than those of rhein anthrone and the mixture. At the same dose, rhein anthrone and the mixture significantly stimulated large intestinal propulsion, though aloe-emodin anthrone had little stimulatory effect. Aloe-emodin anthrone and rhein anthrone decreased net water absorption but could not reverse it to the net secretion at 1/2 dose. The mixture significantly decreased net water absorption and reversed it to the net secretion at this dose. These anthrones did not stimulate mucus secretion in the colon at 1/2 dose.

We concluded that the synergistic purgative effect of aloe-emodin anthrone and rhein anthrone in mice results from synergistic stimulation of large intestinal transit and large intestinal water secretion.
VB20B7, a Novel 5-HT-ergic Agent with Gastrokinetic Activity. II. Evaluation of the Gastroprokinetic Activity in Rats and Dogs
Authors: García-Garayoa E , Monge A , Roca J , Del Río J , Lasheras B
Published: April 2011

The gastrokinetic activity of 2[l-(4-piperonyl)piperazinyl]benzothiazole (VB20B7), a new compound with 5-HT4 receptor agonist and weak 5-HT3 receptor antagonist properties has been studied in rats and dogs.

The effects of VB20B7 were investigated in physiological conditions and in a model of gastroparesis induced by the α2-adrenergic agonist UK-14304 and compared with cisapride.

In rats, both VB20B7 and cisapride enhanced gastric emptying of indigestible solids (steel spheroids) and liquids (phenol red) at doses of 5–10 mg kg−1 by mouth. Gastric emptying of solid radiopaque markers in fasted beagle dogs was enhanced significantly by VB20B7 (0.25–1 mg kg−1 p.o.) whereas the effect of cisapride (0.5–2 mg kg−1 p.o.) did not reach statistical significance. Similar results were found when the radiopaque markers were given to the dogs following a standard solid meal The delayed gastric emptying of indigestible solids and radiopaque markers by UK-14304 was reversed by oral administration of VB20B7 in both rats and dogs. Cisapride, however, was only effective in rats. In addition, gastric emptying of a digestible solid/liquid meal was assessed by quantitating the rate of appearance of the radioactive markers in the duodenum of dogs. VB20B7 (0.2–1 mg kg−1, i.v.) enhanced gastric emptying of both solid and liquid phases while cisapride only enhanced emptying of the solid phase.

The present study indicates that acute oral and intravenous administration of VB20B7 accelerates gastric emptying of both solids and liquids in different animal models.
Portal Hypotensive Effects of Tetrandrine and Verapamil in Portal Hypertensive Rats
Authors: Liu Tsun-Bin , Lin Han-Chieh , Huang Yi-Tsau , Sun Chang-Ming , Hong Chuang-Ye
Published: April 2011

The portal hypotensive effects of tetrandrine and verapamil (both calcium-channel blockers) were assessed in portal hypertensive rats.

Portal hypertension was induced by partial portal vein ligation in Sprague–Dawley rats. Both tetrandrine (4, 8, 16 and 24 mg kg−1) and verapamil (0.5, 10, 1.5 and 2.0 mg kg−1) induced dose-dependent decreases of portal venous pressure and mean arterial pressure after intravenous infusion. For example, infusion of tetrandrine (16 mg kg−1) induced a maximum reduction of portal venous pressure and mean arterial pressure approximately 1 min after the start of infusion. Portal venous pressure decreased from baseline (12.5 mmHg) to 100 mmHg, and mean arterial pressure from baseline (90 mmHg) to 80 mmHg. Heart rate decreased from 250 to 240 beats min−1. At 24 mg kg−1, tetrandrine reduced portal venous pressure and mean arterial pressure to 20.3 ± 2.4% and 28.4 ± 1.4% of baseline, respectively.

Our results show that both tetrandrine and verapamil induce portal pressure reduction in portal hypertensive animals.
The Effects of Aminorex and Related Compounds on Brain Monoamines and Metabolites in CBA Mice
Authors: Zheng Yiwen , Russell Bruce , Schmierer David , Laverty Richard
Published: April 2011

Acute and long-term neurochemical effects of aminorex, an appetite-suppressing drug related to amphetamine in chemical structure, and stereoisomers of its analogues were examined and compared with those of 3,4-methylenedioxymethylarnphetamine (MDMA) and fenfluramine.

Aminorex and its analogues, with exception of 45, 5S-dimethylaminorex, did not cause the long-term neurotransmitter depletion in either the dopaminergic or 5-HT-ergic systems that was observed after MDMA or fenfluramine in CBA mice. These results are discussed in terms of possible structurally related mechanisms of neurotoxicity.

The acute neurochemical effects showed that aminorex and analogues all produced increases in 5-hydroxytryptamine (5-HT) levels, unlike fenfluramine and MDMA in the present study or in published data. This suggests that inhibition of 5-HT metabolism, rather than direct 5-HT release, may be involved in their anorectic effect. The parallel study of acute dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) changes suggest that in CBA mice MDMA may be a better dopamine releaser and this may contribute to its dopaminergic neurotoxicity. However the ability to release dopamine or 5-HT, or both, may be important, but not the only factor involved in causing the long-term neurotoxicity observed with amphetamine derivatives.
Nitric Oxide Scavenging by Curcuminoids
Authors: Sreejayan  , Rao M N A
Published: April 2011

Because curcumin, a compound with anti-inflammatory and anticancer activity, inhibits induction of nitric oxide synthase in activated macrophages and has been shown to be a potent scavenger of free radicals we have investigated whether it can scavenge nitric oxide directly.

Curcumin reduced the amount of nitrite formed by the reaction between oxygen and nitric oxide generated from sodium nitroprusside. Other related compounds, e.g. demethoxycurcumin, bisdemethoxycurcumin and diacetylcurcumin were as active as curcumin, indicating that the methoxy and the phenolic groups are not essential for the scavenging activity.

The results indicate curcumin to be a scavenger of nitric oxide. Because this compound is implicated in inflammation and cancer, the therapeutic properties of curcumin against these conditions might be at least partly explained by its free-radical scavenging properties, including those toward nitric oxide.
Some Effects of Cassia italica on the Central Nervous System in Mice
Authors: Ali B H , Bashir A K , Tanira M O M
Published: April 2011

This work examines some effects of the crude ethanolic extract of the medicinal plant Cassia italica, given at single oral doses of 0.25, 0.5 or 1 g kg−1, on the central nervous system in mice. Several models of nociception have been used to examine the analgesic effect of the extract. HPLC fingerprinting of the extract was performed to ensure uniformity of the extract material used.

In treated mice, the extract caused dose-related inhibition of acetic acid-induced abdominal constriction, and in the formalin test of antinociception the extract reduced formalin-induced pain in the second (late) but not in the first (early) phase of the pain. Treatment with the extract at doses of 0.5 and 1 g kg−1 significantly increased the reaction time in the hot-plate and warm-water tail-flick tests. Naloxone was ineffective in antagonizing the analgesic effect of C. italica on tail-flick and abdominal constriction tests, possibly indicating that the effect occurs via non-opiate pathways. The C. italica extract caused slight dose-related impairment of motor control which was significant only at a dose of 1 g kg−1. Treatment at the three doses used did not affect the rectal temperature of normothermic mice, but was effective in significantly reducing the rectal temperature of hyperthermic rats, 0.5 and 1 h (but not 6 h) after administration of the extract at doses of 0.5 and 1 g kg−1. The extract also produced progressive diminution in the ambulatory and total activity of treated mice for up to 2 h after administration.

It is concluded that the crude ethanolic extract of C. italica has CNS depressant properties, manifested as antinociception and sedation.
Characteristics of Cefdinir Uptake by Rabbit Small Intestinal Brush-border Membrane Vesicles
Authors: Kitagawa Shuji , Sugaya Yoshio , Kaseda Yoshihiko , Sato Shinji
Published: April 2011

Aminocephalosporins with peptide-like structures have been shown to be absorbed by the intestinal peptide carrier. We investigated the transport mechanism of cefdinir, an oral monocarboxylic acid cephalosporin, using rabbit small intestinal brush-border membrane vesicles.

Transport of cefdinir showed a slow and almost linear uptake rate for concentrations up to 30 mm with and without an inward H+ gradient. No overshoot phenomenon was observed in the presence of an inward H+ gradient. The uptake rate increased only slightly with decreasing extravesicular pH, and a protonophore had little effect on the uptake. Aminocephalosporins such as cephalexin only slightly inhibited cefdinir uptake even in the presence of an inward H+ gradient, and vice-versa. Monocarboxylic acids such as acetic acid and salicylic acid had little effect on cefdinir uptake.

These findings suggest that in contrast with other oral cephalosporins cefdinir uptake through the brush-border membrane is slow and involves a mechanism similar to passive diffusion.
Effect of a Chymotrypsin-like Inhibitor, TPCK, on Histamine Release from Cultured Human Mast Cells
Authors: Yanagida Makoto , Fukamachi Hiromi , Takei Masao , Uzumaki Hiroya , Saito Tomonobu Tokiwa Hirohisa , Iikura Yoji , Nakahata Tatsutoshi
Published: April 2011

The involvement of endogenous proteases in the secretory process from human mast cells remains to be clarified.

A chymotrypsin-like protease inhibitor, N-tosyl-l-phenylalanylchloromethyl ketone (TPCK), blocked both FcεRI- and A23187-mediated histamine release from cultured human mast cells at concentrations above 1 μm. At 10 μm, the concentration that completely inhibited FcεI-mediated histamine release, TPCK did not inhibit the chymase activity of the lysate or that in intact cells. The addition of TPCK to cells 30 min before challenge did not affect FcεRI- or A23187-mediated Ca2+ mobilization.

These findings suggest that a TPCK-sensitive molecule distinct from chymase is involved in a late stage of the process of histamine release from mast cells in man.
Contribution of Cytochrome P450 3A Pathway to Bromocriptine Metabolism and Effects of Ferrous Iron and Hypoxia-re-oxygenation on its Elimination in the Perfused Rat Liver
Authors: Matsubayashi Keiko , Matsumoto Hiroshi , Fukui Yuko
Published: April 2011

The contribution of the cytochrome P450 3A pathway to bromocriptine metabolism, and the effects of ferrous iron and hypoxia-re-oxygenation on its elimination, were evaluated with the perfused rat liver. Outflow profiles of bromocriptine after bolus administration were estimated by moment analysis and dispersion model analysis.

Kinetic parameters were not significantly changed by troleandomycin, a P450 3A inhibitor. The inhibition of bromocriptine metabolism by troleandomycin was 5.7 ± 2.4%. These findings indicate that cytochrome P450 3A does not play an important role in bromocriptine elimination with the perfused rat liver. Elimination rate constant (ke) values were significantly increased by ferrous iron perfusion or hypoxia-re-oxygenation. Free-radical generation can, therefore, affect bromocriptine elimination.

Our observations suggest that bromocriptine might be eliminated by scavenging of free radicals in the liver.
Polyhedral Non-ionic Surfactant Vesicles
Authors: Uchegbu Ijeoma F , Schätzlein Andreas , Vanlerberghe Guy , Morgatini Nicola , Florence Alexander T
Published: April 2011

Large polyhedral (2–10 μm) non-ionic surfactant vesicles (niosomes) formed from mixtures of a hexadecyl diglycerol ether (C16G2), a cholesteryl poly-24-oxyethylene ether (solulan C24) and a low level of cholesterol are being investigated as slow-release systems for ophthalmic, subcutaneous or intramuscular administration.

The phase-diagram of this three-component system has been constructed and these polyhedral vesicles are found to be in the gel (Lβ) phase. Confocal laser-scanning microscopy was used to confirm the complex morphology of these vesicles. The thermo-responsive nature of release of entrapped carboxyfluorescein and nicotinamide adenine dinucleotide has been studied; release is increased with increase in temperature (37°C) even though the polyhedral vesicles still maintain their polyhedral shape at this temperature.

The results indicate that the thermo-responsive features of the niosomes are a result of reversible changes in bi-layer permeability caused by temperature-mediated alteration in the membrane-packing characteristics of the polyethoxylated cholesterol ether.
Does it take one to know one? Endorsement of conspiracy theories is influenced by personal willingness to conspire
Authors: Douglas Karen M. , Sutton Robbie M.
Published: April 2011

We advance a new account of why people endorse conspiracy theories, arguing that individuals use the social–cognitive tool of projection when making social judgements about others. In two studies, we found that individuals were more likely to endorse conspiracy theories if they thought they would be willing, personally, to participate in the alleged conspiracies. Study 1 established an association between conspiracy beliefs and personal willingness to conspire, which fully mediated a relationship between Machiavellianism and conspiracy beliefs. In Study 2, participants primed with their own morality were less inclined than controls to endorse conspiracy theories – a finding fully mediated by personal willingness to conspire. These results suggest that some people think ‘they conspired’ because they think ‘I would conspire’.
Transmission of colour and acuity signals by parvocellular cells in marmoset monkeys
Authors: Martin Paul R. , Blessing Esther M. , Buzás Péter , Szmajda Brett A. , Forte Jason D.
Published: April 2011

Non‐technical summary  Colour gets a free ride, according to our study of visual nerve cell responses in marmoset monkeys. All male marmosets are red–green colour‐blind (dichromatic), but most female marmosets have normal trichromatic colour vision. It is known that signals for high‐acuity daytime vision are carried in the parvocellular (P) pathway, and the P pathway also carries signals for red–green colour vision in trichromats. Here we compared P cell responses with patterned stimuli in dichromatic and trichromatic marmosets, and found no detectable difference in resolving power for fine patterns. These results indicate that red–green colour vision does not come at a cost for spatial vision. The ‘piggyback ride’ for colour signals in the P pathway may have encouraged the evolution of full colour vision in primates, including great apes, monkeys and humans.
Pathophysiology of tissue fluid accumulation in inflammation
Authors: Wiig Helge
Published: April 2011

Abstract  The potential role of extravascular factors for the local as well as systemic response to an inflammatory stimulus is addressed here in light of recent data from the trachea, serving as a surrogate for lower airways, and spleen, because of its role in the immune response and fluid volume regulation. From analysis of interstitial fluid from trachea it is apparent that the colloid osmotic pressure is high relative to plasma, suggesting a significant buffering capacity against oedema formation, and also that there is a significant local production of proinflammatory mediators to a systemic inflammatory stimulus. Inflammatory stimuli may furthermore result in a rapid reduction in interstitial fluid pressure, thus leading to increased filtration and oedema formation. Knowledge regarding the fluid phase within the spleen microenvironment can be gathered via analysis of drained lymph. During a septic response induced by lipopolysaccharide injection, the spleen contributes significantly to the production of pro‐ and anti‐inflammatory cytokines, and may induce protracted inflammation because of a dominant role in IL‐6 production. Significant amounts of immune cells exit via lymph, and acquire specific activation signatures having been exposed to the spleen microenvironment. Although often overlooked, extravascular or interstitial factors may therefore contribute significantly to the inflammatory process and thus the ensuing oedema associated with inflammation.
Volume regulation in mammalian skeletal muscle: the role of sodium–potassium–chloride cotransporters during exposure to hypertonic solutions
Authors: Lindinger Michael I. , Leung Matthew , Trajcevski Karin E. , Hawke Thomas J.
Published: April 2011

Non‐technical summary  During moderate to high intensity exercise, there is a net flux of solute‐poor fluid into contracting skeletal muscle. This raises plasma osmolarity, and non‐contracting skeletal muscle and other tissues lose water to the vascular compartment to help maintain blood volume. The loss of water from these non‐contracting tissues causes the cells to shrink. For many tissues the shrinkage of the cells activates the sodium–potassium–chloride cotransporter (NKCC) which is situated in the plasma membrane. Activation of the NKCC reduces the volume loss and functions to restore cell volume in order to prevent cell damage and maintain cellular function. We show that this is also the case for mammalian skeletal myocytes and that the necessary sodium and chloride gradients to maintain NKCC activity depend on the continued activity of the sodium pump (Na+,K+‐ATPase).
Adenosine A2A receptor induces protein kinase A‐dependent functional modulation of human α3β4 nicotinic receptor
Authors: Di Angelantonio Silvia , Piccioni Alessio , Moriconi Claudia , Trettel Flavia , Cristalli Gloria , Grassi Francesca , Limatola Cristina
Published: April 2011

Non‐technical summary  In many brain regions, adenosine regulates the function of the nicotinic acetylcholine receptor–channel, which allows the movement of ions across neuronal membrane if nicotine or acetylcholine is present. In this work we use a very controlled experimental system to study the details of adenosine action. We show that adenosine enhances the function of the receptor–channel when it is repeatedly stimulated. The intracellular signalling molecule protein kinase A mediates the effects of adenosine on the nicotinic receptor–channel. Our results contribute to understanding the function of receptor proteins involved in the normal function of the brain, but also in pathologies such as nicotine addiction.
Extreme Dynamic Structural Response Analysis of Catenary Moored Spar Wind Turbine in Harsh Environmental Conditions
Authors: Karimirad Madjid , Moan Torgeir
Published: April 2011

Proper performance of structures requires among other things that their failure probability is sufficiently small. This would imply design for survival in extreme conditions. The failure of a system can occur when the ultimate strength is exceeded (ultimate limit state (ULS)) or fatigue limit (fatigue limit state) is exhausted. The focus in this paper is on the determination of extreme responses for ULS design checks, considering coupled wave and wind induced motion and structural response in harsh condition up to 14.4 m significant wave height and 49 m/s 10 min average wind speed (at the top of the tower, 90 m) for a parked floating wind turbine of a spar type concept. In the survival condition, the wind induced resonant responses (mainly platform pitch resonance) are dominant. Due to the platform resonant motion responses, the structural responses are close to Gaussian, but wide banded. The critical structural responses are determined by coupled aerohydro-elastic time domain simulation. Based on different simulations (20 1 h, 20 2 h, 20 3 h, and 20 5 h), the mean up-crossing rate has been found in order to predict the extreme structural responses. The most probable maximum of the bending moment and the bending moment having an up-crossing rate of 10−4 are found to be close in the present research. The minimum total simulation time in order to get accurate results is highly correlated with the needed up-crossing rate. The 1 h and 2 h raw data cannot provide any information for 10−4 up-crossing rate. Comparison of different simulation periods shows that the 20 1 h simulations can be used in order to investigate the 3 h extreme bending moment if the proper extrapolation of up-crossing rate is used.
Source Seeking With Very Slow or Drifting Sensors
Authors: Ghods Nima , Krstic Miroslav
Published: April 2011

Slow sensors arise in many applications, including sensing chemical concentrations in tracking of contaminant plumes. Slow sensors are often the cause of poor performance and a potential cause of instability. In this paper, we design a modified extremum seeking scheme to account and exploit slow sensor dynamics. We also consider the worst case, which is sensor dynamics governed by a pure integrator. We provide stability results for several distinct variations of an extremum seeking scheme for one-dimensional optimization. Then we develop a design for source seeking in a plane using a fully actuated vehicle, prove its closed-loop convergence, and present simulation results. We use metal oxide microhotplate gas sensors as a real world example of slow sensor dynamics, model the sensor based on experimental data, and employ the identified sensor model in our source seeking simulations.
Surface Instabilities in Linear Orthotropic Half-Spaces With a Frictional Interface
Authors: Agwa M. A. , Pinto da Costa A.
Published: April 2011

This paper studies the friction induced vibrations that may develop in the neighborhood of steady sliding states of elastic orthotropic half-spaces compressed against a rigid plane moving tangentially with a prescribed speed. These vibrations may lead to flutter instability associated to a surfacelike oscillation. The system of dynamic differential equations and boundary conditions that governs the small plane oscillations of the half-space about the steady sliding state is established. The general form of the surface solutions to the plane strain case is given. The way how the coefficient of friction varies with changes in some of the system’s parameters is investigated. It is shown that for certain combinations of material data, low coefficients of friction are found for surface flutter instability (lower than in the isotropic case).
Estimation of In Vivo ACL Force Changes in Response to Increased Weightbearing
Authors: Hosseini Ali , Gill Thomas J. , Van de Velde Samuel K. , Li Guoan
Published: April 2011

Accurate knowledge of in vivo anterior cruciate ligament (ACL) forces is instrumental for understanding normal ACL function and improving surgical ACL reconstruction techniques. The objective of this study was to estimate the change in ACL forces under in vivo loading conditions using a noninvasive technique. A combination of magnetic resonance and dual fluoroscopic imaging system was used to determine ACL in vivo elongation during controlled weightbearing at discrete flexion angles, and a robotic testing system was utilized to determine the ACL force-elongation data in vitro. The in vivo ACL elongation data were mapped to the in vitro ACL force-elongation curve to estimate the change in in vivo ACL forces in response to full body weightbearing using a weighted mean statistical method. The data demonstrated that by assuming that there was no tension in the ACL under zero weightbearing, the changes in in vivo ACL force caused by full body weightbearing were 131.4±16.8 N at 15 deg, 106.7±11.2 N at 30 deg, and 34.6±4.5 N at 45 deg of flexion. However, when the assumed tension in the ACL under zero weightbearing was over 20 N, the change in the estimated ACL force in response to the full body weightbearing approached an asymptotic value. With an assumed ACL tension of 40 N under zero weightbearing, the full body weight caused an ACL force increase in 202.7±27.6 N at 15 deg, 184.9±22.5 N at 30 deg, and 98.6±11.7 N at 45 deg of flexion. The in vivo ACL forces were dependent on the flexion angle with higher force changes at low flexion angles. Under full body weightbearing, the ACL may experience less than 250 N. These data may provide a valuable insight into the biomechanical behavior of the ACL under in vivo loading conditions.
Study on the Identification of Experimental Chaotic Vibration Signal for Nonlinear Vibration Isolation System
Authors: Liu Shuyong , Shijian Zhu , Qingchao Yang , Qiwei He
Published: April 2011

In order to identify experimental chaotic vibration signals correctly, the measured data were analyzed by applying the methods of Poincaré section, return map, and phase space reconstruction. However, the nonlinear time series analysis based on phase space reconstruction is complex and time-consuming for large quantities of experimental signals. Besides, especially when the signal identification process should be completed online, the conventional method is unable to meet the requirements. The energy distribution features of signals in different frequency bands were extracted with the wavelet package analysis method, and the important characteristic vectors for chaos identification were provided. These methods were verified with numerical simulation first in this paper. Then, the nonlinear vibration system based on an air spring isolator was designed, which exhibits different responses with different parameters. In the experiment, the wavelet package technology and neural network were applied to identify the system behavior; results showed that the vibration system exhibited chaotic responses under special parameter ranges, and the parameter variation law was concluded, which is the foundation of linear spectra isolation for chaotic vibration control technology.
Ageing Assessment, Condition Inspection and Lifetime Evaluation for Safety Related Fuse in Nuclear Power Plant
Authors: Shi Jie , Jin Xinming , Liu Zhiming , Shi Haining , Yao Jianlin , Tu Fengsheng
Published: April 2011

This paper presents the ageing mechanism of fuse in nuclear power plant in detail. Metal Electromigration is identified as the dominant ageing mechanism. On this basis, the dominant status indicators, temperature and resistance of fuse were ensured, and current-temperature curve was proposed. The infrared thermal imaging technology was used to inspect the ageing condition and prove the current-temperature curve. Finally, the accelerated ageing testing was conducted abiding by the dominant ageing mechanism, and the lifetime was evaluated.
Fluid-Elastic Instability of Normal Square Tube Bundles in Two-Phase Cross Flow
Authors: Sim Woo Gun , Park Mi Yeon
Published: April 2011

Some knowledge on damping and fluid-elastic instability is necessary to avoid flow-induced-vibration problems in shell and tube heat exchanger such as steam generator. Fluid-elastic instability is the most important vibration excitation mechanism for heat exchanger tube bundles subjected to the cross flow. Experiments have been performed to investigate fluid-elastic instability of normal square tube bundles, subjected to two-phase cross flow. The test section consists of cantilevered flexible cylinder(s) and rigid cylinders of normal square array. From a practical design point of view, fluid-elastic instability may be expressed simply in terms of dimensionless flow velocity and dimensionless mass-damping parameter. For dynamic instability of cylinder rows, added mass, damping and critical flow velocity are evaluated. The Fluid-elastic instability coefficient is calculated and then compared to existing results given for tube bundles in normal square array.
Interaction of a Nuclear Power Plant With the Egyptian Electrical Grid Based on PSS/E
Authors: Othman S. , Mahmoud H. M. , Kotb S. A.
Published: April 2011

The capacity of the electrical power system in Egypt will increase rapidly in the coming twenty years. In year 2018, nuclear power generation will be connecting to the Egyptian electrical grid. Consequently, the interaction of nuclear power plants and other systems becomes a very important issue, and a detailed nuclear power model for the medium-term and long-term power system stability should be developed. However, there is no nuclear unit model that can describe the detailed characteristics of the nuclear unit in the available commercial power system simulation software. In this paper, a detailed pressurized water reactor (PWR) nuclear unit model for medium-term and long-term power system transient stability is proposed. The model is implemented by a user defined program in PSS/E through PSS/E Matlab Simulink Interface. This model can be used to analyze the interaction of nuclear power plants and other power systems. The simulation results show that the proposed model is valid.
Output-Feedback Load-Following Control of Nuclear Reactors Based on a Dissipative High Gain Filter
Authors: Dong Zhe , Huang Xiaojin , Zhang Liangju
Published: April 2011

Due to the existing serious climate and environment problems caused by burning fossil fuels, nuclear energy is now rapidly developed. Power-level control for nuclear reactors is significant for not only regular operating but also safety issues. The advances in computer technology, information processing, and control theory in the past decades allow the applications of advanced controllers with higher performance. In this paper, the separation principle for the recently established dissipation based high gain filter (DHGF) is presented, which guarantees the closed-loop stability of the system interconnected with a state-feedback controller and the DHGF. Then, the feasibility of applying the DHGF to the load-following control of nuclear reactors has then been verified. Finally, the DHGF with a well designed state-feedback power-level controller has been successfully applied to realize the load-following control for a nuclear heating reactor (NHR). Numerical simulation results has shown the high performance of the DHGF and the feasibility of the DHGF-based output feedback control strategy, and influence of the observer gain to the control and observation performance has also been analyzed.
Sump Influence on Containment Thermal Hydraulic: Results of the TOSQAN Tests
Authors: Porcheron Emmanuel , Lemaitre Pascal , Nuboer Amandine
Published: April 2011

This paper presents the results of the TOSQAN tests performed in the field of the TOSQAN sump program undertaken by the Institut de Radioprotection et de Suˆrete´ Nucle´aire (IRSN). This work is devoted to study the heat and mass transfers induced by the water sump towards the containment atmosphere, for typical accidental thermal hydraulic conditions in PWR.
The Experimental Study on the Impact of the Target Film Thickness to the Properties of the Neutron Tube
Authors: Jing Shiwei , Zhang Mingri , Qiao Shuang
Published: April 2011

Neutron tube is a kind accelerator neutron source, which has been applied extensively. It is mainly composed of an ion source system, an accelerator system, and a target system. The target system is one of the most important parameters of the neutron tube, and it impacts directly the yield, the lifetime, and the stability. The pure titanium film was evaporated on the ceramic target by using the evaporation technique. The impact of the thickness of the titanium film on the yield of the neutron tube was studied, and the yield of the neutron tube was on optimistic state if the thickness of titanium film was 2.2μm. The properties of training and stability of neutron tubes with different thick titanium film target were also present in this paper.
Corrosion Resistance of Mo-Fe-Ti Alloy for Overpack in Simulating Underground Environment
Authors: Nishimura Toshiyasu
Published: April 2011

In order to examine the application of Mo-Fe-Ti alloy for overpak, the corrosion resistance of heat-treated its alloys was investigated by Electrochemical impedance spectroscopy (EIS), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM) and Energy dispersive X-ray analysis (EDAX). Considering the welding, the sample subjected to solution heat treatment (ST) had a single β phase and samples subjected to aging heat treatment at 600–700°C had a-phase precipitation in b-phase. EIS results showed that the corrosion resistance of the aging heat-treated samples was lower than that of the ST sample, but much higher than that of pure Ti in long term immersion test in 10% NaCl solution of pH 0.5 at 97°C which simulating the crevice solution. Laser micrographs of the aging heat-treated samples indicated that a-phase at the grain boundary and in the grain was selectively corroded and caused selective dissolution in NaCl solution. The results of TEM combined with EDAX analyses showed that there were b-phase matrix composed of 2.7 wt% of Mo and 4.8wt% of Fe, and a-phase composed of 0.7 wt% of Mo and 0.1 wt% of Fe in sample aged at 600°C. Thus, Mo-poor a-phase was selectively dissolved in in 10% NaCl solution of pH 0.5 at 97°C. In a result, the ST sample of only b-phase showed the highest resistance, and aging heat-treated samples containing a-phase (0.7 wt% of Mo) showed higher values than pure Ti in the corrosion test. Addition of Fe did not decrease the resistance of alloy in the case of ST condition. Moreover, as Fe was involved in b-phase with Mo which increased remarkably the corrosion resistance, the addition of Fe did not decrease the corrosion resistance of aging heat-treated Mo-Fe-Ti alloy. Finally, it was concluded that Mo-Fe-Ti alloy had excellent resistance for overpack in simulating underground environment.
Application of Interval Method in Reliability Analysis of Nuclear Plant Off-Site Power Supply
Authors: Zheng Zhijie , Sha Zhicheng , Li Lei
Published: April 2011

The loss of off-site power supply for nuclear power plants may lead to a core melt accident, with large potential risk. So the evaluation of loss of off-site power is important for the PSA (Probabilistic Safety Assessment). Uncertainty of the original parameters of electric grid components may be caused by the shortage of the statistical information, the approximation to model parameters or the statistic error. In order to deal with the uncertainty problem in electric grids, interval analysis method is introduced in this paper. The original reliability parameters that are changing in a certain range are treated with interval number. Thereby the uncertainty of the parameters can be calculated in the whole process of the probabilistic assessment. The proposed method has been tested on the reliability analysis evaluation of T power plant loss of off-site power. The results demonstrated the effectiveness and practical value of the interval analysis method.
Random Seismic Response Analysis of Coupling Structure Interconnected by Hysteretic Dampers
Authors: Huang Qian , Zang Fenggang , Zhang Yixiong
Published: April 2011

Coupling structure interconnected by hysteretic dampers appears to be an effective method to mitigate structural seismic response. In the paper, the random seismic response is evaluated through the pseudo-excitation principle incorporated with stochastic equivalent linearization method without by solving the Lyapunov differential equation. For which, the seismic excitation is limited to be shot noise process and the computation burden should not be neglected while structural freedoms are large. In the paper, it is supposed that the structures keep elastic all the time and the hysteretic dampers are represented with versatile Bouc-Wen model. With the participation of assistant augment and reduced matrices which are correlated with the location of hysteretic dampers, the unidirectional excitation of one component and spatial excitation of multiple components are derived and the relationship between the pseudo-excitation and pseudo-response is deduced. Then, a pseudo-excitation closed-form expression for the system random response is established. Consequently, the stationary random seismic response of two shear type structure interconnected with hysteretic dampers is analyzed. The structural stationary seismic responses for two methods agree well. parametric studies for the hysteretic dampers and the optimum way to install the hysteretic dampers are also discussed.
Application of Oil-Gas Hybrid Bearing Turbine-Expander in EAST Helium Cryogenic System
Authors: Wang X. M. , Bai Hong Yu , Xu G. F. , Zhang Q. Y. , Zhuang M.
Published: April 2011

Fusion energy with much more advantages could become a serious option for the future energy. The EAST (Experimental Advanced Superconducting Tokomak) device is aiming to study the physical and technical issues involved in stead-state tokamak nuclear fusion. Cryogenic system is one of the most important sub-systems in EAST device, and turbine-expanders are the key components of cryogenic system. In this paper, turbine-expanders with specific configuration in EAST cryogenic system were introduced, and the problem of instability of turbine-expanders in actual refrigerating process was pointed out. Three different refrigerating methods (Using T3, No-using T3 and using a two-phase turbine) were analyzed, and the results showed that the instability of turbine-expander, especially the coldest turbine (T3), will influence the normal operation, even the whole physical experiment of EAST device. The liquefaction capacity will be increased largely by using a two-phase turbine-expander instead of the JT-throttling.
Investigation of Pressure Drop for Fluid Flow Through Porous Media: Application to a Pebble-Bed Reactor
Authors: Cai Xiaoyu , Su Guanghui , Qiu Suizheng , Tian Wenxi
Published: April 2011

The present studied Pebble-Bed Reactor is a light-water cooled reactor that consists of millions of Micro-Fuel Elements, and the TRISO-coated fuel particles (MFE) fill the fuel assembly disorderly and form a porous media with internal heat source. Papers on porous media continue to be published at the rate of about 150 per year and the domain of application is wide spread, ranging from chemical particle beds, mass separator units, debris beds, soil investigations, heat pipes and fluidized beds etc. In this paper, investigation is performed on the press drop under conditions of both single-phase and two-phase flow through porous media. Large number of relations are studied and the relational expressions, which generalize the available data of experiments, are suggested for pressure drop calculation in a pebble bed of spheres at random distribution. Finally, the relational expressions are applied to analyze the flow characteristics of the Pebble-Bed Reactor, such as the influence of pressure on two phase friction factor in the core etc.
High-Cycle Thermal Fatigue in Mixing Zones: Investigations on Heat Transfer Coefficient and Temperature Fields in PWR Mixing Configurations
Authors: Fontes Jean-Philippe , Braillard Olivier , Cartier Olivier , Dupraz Sylvain
Published: April 2011

Piping systems of nuclear power plants include connections of branches conveying fluids at different temperatures. Thermal-hydraulic fluctuations arising from the turbulent mixing of the flows can affect the inner wall of the pipes and lead to fatigue damage. In order to assess the high-cycle thermal fatigue damages risks of the NPP mixing zones, knowledge of the temperature fluctuations and heat transfer from fluid to structure is necessary. In order to have a better knowledge of the thermal loadings in the several kinds of mixing zones of a NPP, a multi-annual R&D program has been initiated by EDF, AREVA and CEA. The experimental program uses two kinds of representative small-scale mock-ups which are called “Skin of Fluid” and “Stainless Steel FATHERINO”, for different mixing configurations. “Skin of Fluid” mock-ups are very thin ones, made of brass material, allowing visualization with an infrared camera of the fluid temperature field in the mixing zone, with minimized thermal attenuation. As a consequence, “Skin of Fluid” mock-ups allow detecting areas of interest in the mixing zone. “Stainless Steel FATHERINO” mock-ups are then used to evaluate quantitatively the thermal fluctuations and the heat transfer coefficient in the mixing zone. “Stainless Steel FATHERINO” mock-ups are made of 304L stainless steel and are 9.5mm thick. The mock-ups are instrumented with specific sensors named “Coefh”. These sensors allow measuring simultaneously the fluid and structure temperature time-histories and thus determining the heat transfer coefficient. This paper describes the experimental program and the approach used to evaluate the thermal load in the mixing zones. As an example, the application of this approach to an equal T-junction is presented hereafter.