bluuebunny/crossref_metadata_2025 huggingface dataset:
Trends and time variability in the northern continental shelf of the western Mediterranean
Authors: Vargas‐Yáñez M. , Salat J. , Luz Fernández de Puelles M. , López‐Jurado J. L. , Pascual J. , Ramírez Teodoro , Cortés Dolores , Franco Ignacio
Published: October 2005

Different works appearing during the last decade show that the western Mediterranean has suffered a temperature and salinity increase during the 20th century. Most of these works analyze long‐term trends in Levantine Intermediate Water (LIW) and Western Mediterranean Deep Water (WMDW); those dealing with changes in shallow and coastal waters are very scarce. It is still an open question whether these changes are due to meteorological factors occurring in the western Mediterranean or if they are caused by the salinity increase of the water masses contributing to deep water formation. In this work we analyze the data obtained in the last decade of the 20th century (and longer time series in some cases) within the frame of six projects aimed at the systematic collection of hydrographic data at fixed stations in the northern sector of the western Mediterranean (mainly in coastal areas). We detect strong warming trends in those stations located in the continental shelf (and probably with no influence of the LIW). This result could indicate that changes observed in the WMDW cannot be explained only on the basis of changes imported from the eastern basin. Another striking result is that these trends are an order of magnitude higher than those reported for the rest of the century, indicating that the 1990s have been an exceptionally warm decade. On the other hand, time series affected by the LIW show a salinity increase, and in some cases this is not accompanied by the corresponding temperature increment, indicating that the LIW salinity increase could also be a factor to be taken into account.
Three‐dimensional physical modeling of deep‐seated landslides: New technique and first results
Authors: Chemenda A. , Bouissou S. , Bachmann D.
Published: October 2005

A new technique for physical (experimental) modeling of landsliding and the first results are presented. The technique is based on the use of new elasto‐brittle‐plastic analogue materials and an original vertical accelerator device enabling an increase in the “gravity acceleration.” This technique allows slope stability to be addressed in a full three‐dimensional, large strain formulation involving brittle and ductile rupture of the material. Three sets of experiments on the scale of a mountain ∼1 km high are presented. The first one was designed to define the conditions and the mode of instability (deformation) in a homogeneous unfractured model. Instability occurs when the effective compressive strength σc of the mountain is as small as 107 Pa, i.e., about 1 order of magnitude lower than the typical strength of small rock samples. The deformation and rupture involve the whole mountain and correspond to well‐known, deep‐seated gravitational slope deformation. In the second set of experiments we introduced inherited “tectonic” faults, which considerably reduce mountain stability, with deformation again developing at the mountain scale. The introduction of the local small‐scale fractures and weak zones in the last set of experiments resulted in smaller‐scale shallow landslides.
Validation of ray and wave theoretical travel times in heterogeneous random media
Authors: Yang Hsin‐Ying , Hung Shu‐Huei
Published: October 2005

We investigate the validity of three theories of seismic tomography by numerical comparison of cross‐correlation travel time shifts of acoustic waves with their theoretical predictions in 3‐D heterogeneous random media. Whenever the characteristic heterogeneity scale length is shorter than half of the first Fresnel zone width, ray‐theoretical travel times yield large discrepancies from the cross‐correlation measurements. Born‐Fréchet kernel theory is valid for small‐scale structures but restricted to weak velocity perturbations. With increasing perturbation strength, neglecting the nonlinearity due to wave path bending in linearized ray and Born theories is no longer eligible. General ray theory accounts for the detour least‐time paths in strongly heterogeneous media, which prominently improves the predicted travel times for intermediate to large scale velocity variations.
The 26 December 2004 tsunami source estimated from satellite radar altimetry and seismic waves
Authors: Song Y. Tony , Ji Chen , Fu L.‐L. , Zlotnicki Victor , Shum C. K. , Yi Yuchan , Hjorleifsdottir Vala
Published: October 2005

The 26 December 2004 Indian Ocean tsunami was the first earthquake tsunami of its magnitude to occur since the advent of both digital seismometry and satellite radar altimetry. Both have independently recorded the event from different physical aspects. The seismic data has then been used to estimate the earthquake fault parameters, and a three‐dimensional ocean‐general‐circulation‐model (OGCM) coupled with the fault information has been used to simulate the satellite‐observed tsunami waves. Here we show that these two datasets consistently provide the tsunami source using independent methodologies of seismic waveform inversion and ocean modeling. Cross‐examining the two independent results confirms that the slip function is the most important condition controlling the tsunami strength, while the geometry and the rupture velocity of the tectonic plane determine the spatial patterns of the tsunami.
Structure and dynamics of the polar vortex in the Earth's core
Authors: Sreenivasan Binod , Jones Chris A.
Published: October 2005

Observations of the Earth's magnetic field suggest that there are anticyclonic polar vortices in the core (Olson and Aurnou, 1999; Hulot et al., 2002). Some geodynamo simulations have also shown the existence of an anticyclonic flow in the polar region of the Earth's outer core. The polar vortices are investigated using a spherical convection‐driven dynamo model. In a fully three‐dimensional model where no longitudinal symmetry is imposed, we find that the polar vortex core is offset from the pole itself by approximately 10° from the axis of rotation. It is therefore non‐axisymmetric, and can drift considerably in longitude during a magnetic diffusion time. We also find that the strong polar vortex depends crucially on the magnetic field in the core. The simulation results are compared with the polar core flow reconstructed from secular variation observations.
U.S. warm‐season rainfall in NCAR CAM3: An event‐oriented perspective
Authors: Collier J. Craig , Zhang Guang J.
Published: October 2005

A modified form of the Community Atmosphere Model, ver. 3 (CAM3) developed at the National Center for Atmospheric Research (NCAR) is validated in its warm‐season mean precipitation diurnal cycle for two regions of the United States. For all grid boxes of each region, simulated and observed precipitation records over four four‐month periods are separated into discrete precipitation events. These events are binned into mutually‐exclusive categories, and the diurnal harmonic for each category is estimated. In this way, the model is validated over the spectrum of precipitation episodes, and biases in the overall seasonal‐mean diurnal cycle can be attributed to particular kinds of events. The results of the study indicate that the model's total seasonal precipitation is overwhelmingly weighted in the extremely long events and that these events contain the source of any biases in the seasonal mean.
The Sun's Fury In Three Dimensions
Authors: Simpson Sarah
Published: October 2005

The Ulysses spacecraft's unique orbit over the solar poles gives scientists otherwise unattainable insight into the driving forces behind space weather.
Oxaliplatin induces hyperexcitability at motor and autonomic neuromuscular junctions through effects on voltage‐gated sodium channels
Authors: Webster Richard G , Brain Keith L , Wilson Richard H , Grem Jean L , Vincent Angela
Published: October 2005

Oxaliplatin, an effective cytotoxic treatment in combination with 5‐fluorouracil for colorectal cancer, is associated with sensory, motor and autonomic neurotoxicity. Motor symptoms include hyperexcitability while autonomic effects include urinary retention, but the cause of these side‐effects is unknown. We examined the effects on motor nerve function in the mouse hemidiaphragm and on the autonomic system in the vas deferens.

In the mouse diaphragm, oxaliplatin (0.5 mM) induced multiple endplate potentials (EPPs) following a single stimulus, and was associated with an increase in spontaneous miniature EPP frequency. In the vas deferens, spontaneous excitatory junction potential frequency was increased after 30 min exposure to oxaliplatin; no changes in resting Ca2+ concentration in nerve terminal varicosities were observed, and recovery after stimuli trains was unaffected.

In both tissues, an oxaliplatin‐induced increase in spontaneous activity was prevented by the voltage‐gated Na+ channel blocker tetrodotoxin (TTX). Carbamazepine (0.3 mM) also prevented multiple EPPs and the increase in spontaneous activity in both tissues. In diaphragm, β‐pompilidotoxin (100 μM), which slows Na+ channel inactivation, induced multiple EPPs similar to oxaliplatin's effect. By contrast, blockers of K+ channels (4‐aminopyridine and apamin) did not replicate oxaliplatin‐induced hyperexcitability in the diaphragm.

The prevention of hyperexcitability by TTX blockade implies that oxaliplatin acts on nerve conduction rather than by effecting repolarisation. The similarity between β‐pompilidotoxin and oxaliplatin suggests that alteration of voltage‐gated Na+ channel kinetics is likely to underlie the acute neurotoxic actions of oxaliplatin.

British Journal of Pharmacology (2005) 146, 1027–1039. doi:10.1038/sj.bjp.0706407
Rat tissue kallikrein releases a kallidin‐like peptide from rat low‐molecular‐weight kininogen
Authors: Hilgenfeldt Ulrich , Stannek Christina , Lukasova Martina , Schnölzer Martina , Lewicka Sabina
Published: October 2005

The kallikrein–kinin system is subdivided into the plasma and tissue–kallikrein–kinin system, with bradykinin (BK) and kallidin (KAL) (Lys0‐bradykinin) as functional peptides. This occurs in both humans and other mammals. Both peptides are released by plasma and tissue–kallikrein. BK, but not KAL, has been detected in rats until now. One can explain this observation by the structural differences found in the sequence of rat high‐ and low‐molecular kininogen containing an Arg‐residue instead of a Lys‐residue in front of the N‐terminus of the BK sequence. Nevertheless, we were able to measure a kallidin‐like peptide (KLP), in rat plasma and urine, using a specific KAL antiserum.

In order to confirm our data, we isolated low‐molecular‐weight kininogen from rat plasma and incubated it with purified rat glandular kallikrein. The generated peptide was retained on a high‐pressure liquid chromatography column and displaced by an excess of angiotensin I. The KLP‐containing fraction was identified with the KLP radioimmunoassay. A specific ion signal with a mass to charge ratio (m/z) of 1216.73 was detected with matrix‐assited laser desorption/ionization mass spectrometry.

As proposed earlier, the structure of this peptide is Arg1‐KAL, instead of Lys1‐KAL. The structural similarity between the Lys‐ and the Arg‐residue explains the high crossreactivity (80%) of KLP with the specific KAL antibody.

The incubation of KLP with angiotensin‐converting enzyme yields two molecules with masses of 913.4 and 729.3 containing the sequence H–Arg–Arg–Pro–Pro–Gly–Phe–Ser–Pro–OH and H–Arg–Arg–Pro–Pro–Gly–Phe–OH. The enzymatic cleavage could be inhibited by captopril.

The data suggest that in rats, as in other mammals, the tissue kallikrein–kinin system mediates its physiological effects via a kallidin‐like peptide, which is Arg1‐kallidin (Arg0‐bradykinin).

British Journal of Pharmacology (2005) 146, 958–963. doi:10.1038/sj.bjp.0706409
ETA and ETB receptors differentially modulate afferent and efferent arteriolar responses to endothelin
Authors: Inscho Edward W , Imig John D , Cook Anthony K , Pollock David M
Published: October 2005

The segment‐specific actions of endothelin peptides and agonists have not been thoroughly investigated in the renal microcirculation. The current studies were performed to assess the relative contribution of ETA and ETB receptors to the renal pre‐ and postglomerular arteriolar responses to ET‐1.

Experiments determined the effect of selective ETA (A‐127722; 30 nM) and ETB (A‐192621; 30 nM) receptor blockade, on arteriolar responses to ET‐1 concentrations of 1 pM to 10 nM in rat kidneys using the isolated juxtamedullary nephron technique. Renal perfusion pressure was set at 110 mmHg.

Baseline afferent arteriolar diameter was similar in all groups and averaged 17.8±0.6 μm (n=14). In control experiments (n=6), ET‐1 produced significant concentration‐dependent decreases in arteriolar diameter, with 10 nM ET‐1 decreasing diameter by 85±1%.

Selective blockade of ETA receptors (n=6) prevented ET‐1‐mediated vasoconstriction, except at concentrations of 1 and 10 nM. Similarly, the vasoconstrictor profile was right shifted during selective ETB receptor blockade (n=4). Combined ETA and ETB receptor blockade (n=5) completely abolished afferent arteriolar diameter responses to ET‐1.

ETB selective agonists (S6c and IRL‐1620) produced disparate responses. S6c produced a concentration‐dependent vasoconstriction of afferent arterioles. In contrast, S6c produced a concentration‐dependent dilation of efferent arterioles that could be blocked with an ETB receptor antagonist. IRL‐1620, another ETB agonist, was less effective at altering afferent or efferent diameter and produced a small reduction in pre‐ and postglomerular arteriolar diameter.

These data demonstrate that both ETA and ETB receptors participate in ET‐1‐mediated vasoconstriction of afferent arterioles. ETB receptor stimulation provides a significant vasodilatory influence on the efferent arteriole. Furthermore, since selective ETA and ETB receptor antagonists abolished preglomerular vasoconstrictor responses at lower ET‐1 concentrations, these data support a possible interaction between ETA and ETB receptors in the control of afferent arteriolar diameter.

British Journal of Pharmacology (2005) 146, 1019–1026. doi:10.1038/sj.bjp.0706412
Neurally released ATP mediates endothelium‐dependent hyperpolarization in the circular smooth muscle cells of chicken anterior mesenteric artery
Authors: Draid Marwan , Shiina Takahiko , El‐Mahmoudy AbuBakr , Boudaka Ammar , Shimizu Yasutake , Takewaki Tadashi
Published: October 2005

The object of the present study was to clarify the neurotransmitter(s) controlling membrane responses to electrical field stimulation (EFS) in the circular smooth muscle cells of first‐order branches of chicken anterior mesenteric artery.

EFS (five pulses at 20 Hz, 1 ms) evoked a hyperpolarization of amplitude −21.6±1.2 mV, total duration 21.8±1.2 s and latency 641.7±81.9 ms. The response was tetrodotoxin‐sensitive and nonadrenergic noncholinergic (NANC) in nature.

The NANC response was blocked by the nonspecific purinergic antagonist, suramin, indicating that the response is mediated by the neurotransmitter adenosine 5′‐triphosphate (ATP).

Either desensitization or blockade of P2Y receptor with its putative agonist 2‐methylthioATP (1 μMfor 30 min) or with its antagonist cibacron blue F3GA (10 μM), respectively, abolished the purinergic hyperpolarization. PPADS at concentrations up to 100 μMhad no effect on the EFS‐induced response, indicating that this response is mediated through P2Y, but not P2X, receptor. In addition, the response was completely abolished by two specific P2Y1 receptor antagonists, namely, MRS 2179 (300 nM) and A3P5PS (10 μM).

Removal of the endothelium abolished the purinergic hyperpolarization, which was converted, in some preparations, to a small depolarization, indicating that the hyperpolarizing response is endothelium‐dependent.

The present study suggests that in first‐order branches of chicken anterior mesenteric artery, ATP released from perivascular nerves may diffuse to the endothelium‐activating P2Y1 receptor to induce release of an inhibitory substance that mediates hyperpolarization in the circular smooth muscle.

British Journal of Pharmacology(2005)146, 983–989. doi:10.1038/sj.bjp.0706413
Endothelial dysfunction in the streptozotocin‐induced diabetic apoE‐deficient mouse
Authors: Ding Hong , Hashem Michael , Wiehler William B , Lau Winnie , Martin Jacqueline , Reid Julianne , Triggle Chris
Published: October 2005

Endothelial dysfunction plays a role in the development of atherosclerosis and diabetes‐associated vascular disease and, in the streptozotocin (STZ)‐induced apoE‐deficient diabetic mouse, we report that, when compared to the citrate (CIT)‐treated nondiabetic apoE‐deficient control, acetylcholine (Ach)‐mediated endothelium‐dependent relaxation was reduced in the small mesenteric arteries (SMA) and the plaque‐prone regions of the aorta from the STZ‐diabetic mouse.

In the SMA the component of Ach‐mediated relaxation that was attributed to nitric oxide (NO) from STZ‐treated diabetic apoE‐deficient mice was enhanced; however, the endothelium‐derived hyperpolarizing factor (EDHF)‐mediated component was reduced. The EDHF component was assessed by determining the component of the Ach‐mediated response that was resistant to the combination of the NO synthase (NOS) inhibitor N‐nitro‐L‐arginine methyl ester, cyclooxygenase inhibitor, indomethacin, and soluble guanylate cyclase inhibitor, ODQ, and inhibited by the combination of the intermediate conductance KCa (IKCa) inhibitor TRAM‐34 and the small‐conductance KCa (SKCa) inhibitor apamin.

Endothelial NOS was increased but SK2, SK3 and connexin (Cx) 37 mRNA expressions were significantly (P<0.05) decreased in the SMA from STZ‐treated apoE‐deficient mice compared to the CIT‐treated controls. There was no difference in the IKCa expression or in Cx 40, 43 and 45 mRNA levels between STZ‐ and CIT‐treated mice.

The microvasculature of STZ‐induced apoE‐deficient mice developed endothelial dysfunction, which may be linked to a decrease in the contribution of the EDHF component due to a decrease in SK2 and 3 and Cx 37 expression.

British Journal of Pharmacology (2005) 146, 1110–1118. doi:10.1038/sj.bjp.0706417
Effects of urea pretreatment on the binding properties of adenosine A1receptors
Authors: May Lauren T , Sexton Patrick M , Christopoulos Arthur
Published: October 2005

The effect of denaturation and/or extraction of nonintegral membrane proteins by 7 Murea on the binding of the antagonist [3H]cyclopentyl‐1,3‐dipropylxanthine 8 dipropyl‐2,3 ([3H]DPCPX), and the agonists adenosine, (−)‐N6‐(2‐phenylisopropyl)‐adenosine (R‐PIA) andN6‐cyclohexyladenosine (CHA), was investigated at human A1adenosine receptors stably expressed in CHO cells.

Pretreatment with urea caused a 56% reduction in membrane proteins. Compared to controls, the use of adenosine deaminase (ADA), 100 μM5′‐guanylylimidodiphosphate (Gpp(NH)p) or urea each caused equivalent increases in specific [3H]DPCPX binding.

Neither the binding kinetics nor the affinity of [3H]DPCPX were significantly different in urea‐pretreated compared to ADA‐pretreated membranes.

At 25°C in ADA‐pretreated membranes, the competition isotherms for R‐PIA and CHA were characterized by two affinity states. Gpp(NH)p (100 μM) reduced, but did not abolish, the value of the high‐affinity dissociation constant. Similar results were obtained after treatment with urea for R‐PIA, whereas the high‐affinity state for CHA was abolished.

At 37°C, urea pretreatment, but not 100 μMGpp(NH)p, abolished high‐affinity agonist competition binding. There was no significant effect of any of the treatments on the low‐affinity agonist binding state.

In urea‐pretreated membranes, exogenously added adenosine competed according to a simple mass‐action model with a pKLof 5.66±0.05 (n=3).

Compared to the more common approaches of ADA treatment and/or use of guanine nucleotides, our findings suggest that urea pretreatment represents an inexpensive and useful approach for investigating the binding properties of adenosine A1ligands (including adenosine) to the G protein‐uncoupled form of the receptor.

British Journal of Pharmacology(2005)146, 1119–1129. doi:10.1038/sj.bjp.0706419
Improvement of age‐related endothelial dysfunction by simvastatin: effect on NO and COX pathways
Authors: De Sotomayor Maria Álvarez , Pérez‐Guerrero Concepción , Herrrera Ma Dolores , Jimenez Luis , Marín Roberto , Marhuenda Elisa , Andriantsitohaina Ramaroson
Published: October 2005

The effects of oral administration of the HMG‐CoA reductase inhibitor, simvastatin (SV), on age‐related endothelial dysfunction were investigated in the aorta of male Wistar rats.

Adult (12–14 weeks) and old (60–80 weeks) rats were treated daily for 12 weeks with either vehicle or SV (1 mg kg−1). In old rats, SV treatment did not significantly affect systolic blood pressure and LDL‐cholesterol, but it reduced plasma cholesterol, triglycerides and oxidised LDL though it did not affect total antioxidant status.

SV improved endothelium‐dependent relaxation to acetylcholine and A‐23187 in vessels from aged, but not adult, rats. This effect was linked to a greater NO vasodilatation via an increased expression of endothelial NO‐synthase. A mechanism sensitive to superoxide dismutase and catalase also accounts for enhanced endothelial vasodilatation.

Finally, SV did not affect the release of prostacyclin, but it inhibited the generation of thromboxane (TX) A2 from COX‐2 isoform. The effect of the latter was sensitive to the Tp receptor antagonist, ICI‐192,605.

The present study provides evidence that oral administration of SV improves endothelial dysfunction in the aorta from aged rats by mechanisms associated with enhanced NO vasodilatation, reduced release of TXA2 from cyclo‐oxygenase, and increased antioxidant properties of the vessel wall. These data underscore a new therapeutic perspective for SV in age‐related endothelial dysfunction.

British Journal of Pharmacology (2005) 146, 1130–1138. doi:10.1038/sj.bjp.0706420
Nongenomic responses to 17β‐estradiol in male rat mesenteric arteries abolish intrinsic gender differences in vascular responses
Authors: Keung Wendy , Vanhoutte Paul M , Man Ricky Y K
Published: October 2005

The aim of the present study was to investigate the gender differences in the acute effects of 17β‐estradiol on the rat superior mesenteric artery.

Isometric tension was measured in rings of mesenteric arteries from both male and female Sprague–Dawley rats.

Relaxation to acetylcholine was not significantly different between arteries (with endothelium) from male and female rats in the absence or presence of 17β‐estradiol. After blockade of endothelium‐dependent hyperpolarizations with apamin (0.3 μM) plus charybdotoxin (0.1 μM), acute exposure to 17β‐estradiol (1 nM) for 30 min resulted in enhancement of relaxation to acetylcholine in arteries from male but not female rats.

After acute exposure to 17β‐estradiol, mesenteric arteries from male rats were more sensitive to sodium nitroprusside than arteries from female rats.

Contractions of mesenteric arteries to phenylephrine and 9,11‐dideoxy‐11α,9α‐epoxymethanoprostaglandin F2α (U46619) were greater in arteries from male rats than female rats. This difference was not detected after acute exposure to 17β‐estradiol.

In preparations without endothelium, the enhancement of relaxation and reduction in contraction in arteries from male rats were preserved.

These results suggest that there exists a gender difference in the response to the acute nongenomic modulatory effect of 17β‐estradiol in rat mesenteric arteries. Arteries from male rats seem to be more sensitive to the modulatory effects of 17β‐estradiol than arteries from female rats. The effect appears to be mainly at the level of the vascular smooth muscles.

British Journal of Pharmacology (2005) 146, 1148–1155. doi:10.1038/sj.bjp.0706422
Hydrogen peroxide is an endothelium‐dependent contracting factor in rat renal artery
Authors: Gao Yu‐Jing , Lee Robert M K W
Published: October 2005

In addition to endothelium‐derived relaxing factor and hyperpolarizing factor, vascular endothelium also modulates smooth muscle tone by releasing endothelium‐derived contracting factor(s) (EDCF), but the identity of EDCF remains obscure. We studied here the involvement of hydrogen peroxide (H2O2) in endothelium‐dependent contraction (EDC) of rat renal artery to acetylcholine (ACh).

ACh (10−6, 10−5, and 10−4 M) induced a transient contraction of rat renal artery with intact endothelium in a concentration‐related manner, but not in the artery with endothelium removed. In phenylephrine‐precontracted renal arteries, ACh induced an endothelium‐dependent relaxation response at lower concentrations (10−8–10−6 M), and a relaxation followed by a contraction at higher concentrations (10−5 M). Inhibition of nitric oxide synthase by Nω‐nitro‐L‐arginine (10−4 M) enhanced the EDC to ACh.

Catalase (1000 U ml−1) reduced the EDC to ACh. H2O2 (10−6, 10−5, and 10−4 M) induced a similar transient contraction of the renal arteries as ACh, but in an endothelium‐independent manner. Inhibition of NAD(P)H oxidase and cyclooxygenase by diphenylliodonium chloride and diclofenac greatly attenuated ACh‐induced EDC, while inhibition of xanthine oxidase (allopurinol) and cytochrome P450 monooxygenase (17‐octadecynoic acid) did not affect the contraction. Antagonist of thromboxane A2 and prostaglandin H2 receptors (SQ 29548) and thromboxane A2 synthase inhibitor (furegrelate) attenuated the contraction to ACh and to H2O2.

In isolated endothelial cells, ACh (10−5 M) induced a transient H2O2 production detected with a fluorescence dye sensitive to H2O2 (2′,7′‐dichlorofluorescein diacetate). The peak concentration of H2O2 was 5.1 × 10−4 M at 3 min and was prevented by catalase.

Taken together, these results show that ACh triggers H2O2 production through NAD(P)H oxidase activation in the endothelial cells, and that ACh and H2O2 share the same signaling pathway in causing smooth muscle contraction. Therefore, H2O2 is most likely the EDCF in rat renal artery in response to ACh stimulation.

British Journal of Pharmacology (2005) 146, 1061–1068. doi:10.1038/sj.bjp.0706423
Contractile effects of 5‐hydroxytryptamine and 5‐carboxamidotryptamine in the equine jejunum
Authors: Delesalle Cathérine , Deprez Piet , Schuurkes Jan A J , Lefebvre Romain A
Published: October 2005

The use of human prokinetic drugs in colic horses leads to inconsistent results. This might be related to differences in gastrointestinal receptor populations. The motor effects of 5‐hydroxytryptamine (5‐HT; serotonin) on the equine mid‐jejunum were therefore studied. Longitudinal muscle preparations were set up for isotonic measurement.

5‐HT induced tonic contractions with superimposed phasic activity; these responses were not influenced by tetrodotoxin and atropine, suggesting a non‐neurogenic, non‐cholinergic pathway.

The 5‐HT receptor antagonists GR 127935 (5‐HT1B,D), ketanserin (5‐HT2A), SB 204741 (5‐HT2B), RS 102221 (5‐HT2C), granisetron (5‐HT3), GR 113808 (5‐HT4) and SB 269970 (5‐HT7) had no influence on the 5‐HT‐induced response; the 5‐HT1Areceptor antagonists NAN 190 (pKb=8.13±0.06) and WAY 100635 (pKb=8.69±0.07), and the 5‐HT1,2,5,6,7receptor antagonist methysergide concentration‐dependently inhibited the 5‐HT‐induced contractile response.

The 5‐HT1,7receptor agonist 5‐carboxamidotryptamine (5‐CT) induced a contractile response similar to that of 5‐HT; its effect was not influenced by tetrodotoxin and atropine, and SB 269970, but antagonised by WAY 100635. 8‐OHDPAT, buspiron and flesinoxan, which are active at rat and human 5‐HT1Areceptors, had no contractile influence.

These results suggest that the contractile effect of 5‐HT in equine jejunal longitudinal muscle is due to interaction with muscular 5‐HT receptors, which cannot be characterised between the actually known classes of 5‐HT receptors.

British Journal of Pharmacology(2006)147, 23–35. doi:10.1038/sj.bjp.0706431
The polymerization of actin: Structural changes from small-angle neutron scattering
Authors: Norman Alexander I. , Ivkov Robert , Forbes Jeffrey G. , Greer Sandra C.
Published: October 2005

We present a new analysis of small-angle neutron-scattering data from rabbit muscle actin in the course of the polymerization from G-actin to F-actin as a function of temperature. The data, from Ivkov et al. [J. Chem. Phys. 108, 5599 (1998)], were taken in D2O buffer with Ca2+ as the divalent cation on the G-actin in the presence of ATP and with KCl as the initiating salt. The new analysis of the data using modeling and the method of generalized indirect fourier transform (O. Glatter, GIFT, University of Graz, Austria, http://physchem.kfunigraz.ac.at/sm/) provide shapes and dimensions of the G-actin monomer and of the growing actin oligomer in solution as a function of temperature and salt concentration. This analysis indicates that the G-actin monomer, under the conditions given above, is a sphere 50–54Å in diameter as opposed to the oblate ellipsoid seen by x-ray crystallography. The F-actin dimensions are consistent with x-ray crystal structure determinations.
Tetrads in geometrodynamics
Authors: Garat Alcides
Published: October 2005

A new tetrad is introduced within the framework of geometrodynamics for non-null electromagnetic fields. This tetrad diagonalizes the electromagnetic stress-energy tensor and allows for maximum simplification of the expression of the electromagnetic field. The Einstein-Maxwell equations will also be simplified.
Gel mechanics: A comparison of the theories of Biot and Tanaka, Hocker, and Benedek
Authors: Hui Chung-Yuen , Muralidharan Vijayanand
Published: October 2005

This article compares the Biot [J. Appl. Phys. 12, 155 (1941)] and Tanaka, Hocker, and Benedek (THB) [J. Chem. Phys. 59, 5151 (1973)] theories of gel deformation. Biot’s theory treats the gel as a continuum with the pore pressure as a state variable whereas the THB theory treats the gel as a mixture of solid and liquid phases. We revisit the problem of gel deswelling and use this example to show that there can be substantial differences between the two theories. The THB theory is not a complete mixture theory since the displacements of the liquid are assumed to be negligibly small in comparison with the displacements of the network. We propose a simple extension of the THB model, which takes into account the momentum transfer of the liquid phase. We show that with this simple addition and some very reasonable assumptions, the extended THB theory is identical to the Biot theory.
First-principles study of band-gap change in deformed nanotubes
Authors: Shan Bin , Lakatos Gregory W. , Peng Shu , Cho Kyeongjae
Published: October 2005

The effects of cross-sectional deformation and bending on the electronic structures of single-wall carbon nanotubes (SWNTs) are examined. Upon increasing the deformation, semiconducting SWNTs undergo semiconductor-metal transition, and the conduction band and valence band show asymmetric response to the deformation. The metallic tubes’ electronic structures are relatively insensitive to similar mechanical deformation. Using the properties of deformed nanotubes, we propose a conceptual design of SWNT-based single-electron quantum-well devices.
Brownian motion near a partial-slip boundary: A local probe of the no-slip condition
Authors: Lauga Eric , Squires Todd M.
Published: October 2005

Motivated by experimental evidence of violations of the no-slip boundary condition for liquid flow in micrometer-scale geometries, we propose a simple, complementary experimental technique that has certain advantages over previous studies. Instead of relying on externally induced flow or probe motion, we suggest that colloidal diffusivity near solid surfaces contains signatures of the degree of fluid slip exhibited on those surfaces. To investigate, we calculate the image system for point forces (Stokeslets) oriented perpendicular and parallel to a surface with a finite slip length, analogous to Blake’s solution for a Stokeslet near a no-slip wall. Notably, the image system for the point source and perpendicular Stokeslet contain the same singularities as Blake’s solution; however, each is distributed along a line with a magnitude that decays exponentially over the slip length. The image system for the parallel Stokeslet involves a larger set of fundamental singularities, whose magnitude does not decay exponentially from the surface. Using these image systems, we determine the wall-induced correction to the diffusivity of a small spherical particle located “far” from the wall. We also calculate the coupled diffusivities between multiple particles near a partially slipping wall. Because, in general, the diffusivity depends on “local” wall conditions, patterned surfaces would allow differential measurements to be obtained within a single experimental cell, eliminating potential cell-to-cell variability encountered in previous experiments. In addition to motivating the proposed experiments, our solutions for point forces and sources near a partial-slip wall will be useful for boundary integral calculations in slip systems.
Evolution of zero-mean magnetic fields in cellular flows
Authors: Silvers L. J.
Published: October 2005

This paper presents the results of numerical simulations to examine the evolution of a zero-mean magnetic field in a steady cellular flow. In the kinematic model the evolution consists of two phases. In general, the time scale for decay in these two phases are those presented by Rhines and Young [“How rapidly is a passive scalar mixed within closed streamlines,” J. Fluid Mech. 133, 135 (1983)]. However, we show that there is a case for which the magnetic energy does not decay on these time scales. In the dynamic model, the evolution is dependent on the strength of the imposed field. For weak fields, the evolution can be satisfactorily approximated by that for the kinematic model. However, as the field strength is increased the approximation ceases to be valid. For stronger fields, there are three primary phases to the decay. For such fields there is an additional phase, in between those for the kinematic model, where the field decays at the ohmic rate.
Monte Carlo calculations of static and dynamic electron transport in nitrides
Authors: Starikov E. , Shiktorov P. , Gruinskis V. , Varani L. , Vaissière J. C. , Palermo C. , Reggiani L.
Published: October 2005

Monte Carlo simulation of high-field transport in semiconductor nitrides GaN and InN is used to calculate the velocity field and the high-frequency behavior of differential mobility, spectral density of velocity fluctuations, and noise temperature. The spectra of hot-carrier differential mobility and velocity noise are found to exhibit a plateau in the low-frequency region, a peak at intermediate frequencies, and a 1∕f2 decay at the highest frequencies. The comparison with standard A3B5 compounds shows that the characteristic frequencies associated with extreme and cutoff decay of the negative differential mobility, etc., are shifted to a higher-frequency range for the case of nitrides. This property is favorable for applications of nitrides in the terahertz frequency range.
Measuring flow resistivity of porous material via acoustic reflected waves
Authors: Sebaa N. , Fellah Z. E. A. , Fellah M. , Lauriks W. , Depollier C.
Published: October 2005

An acoustic reflectivity method is proposed for measuring flow resistivity of porous materials having rigid frame. The flow resistivity of porous material is defined as the ratio between the pressure difference across a sample and the velocity of flow of air through that sample per unit cube. It is important as one of the several parameters required by acoustical theory to characterize porous materials like plastic foams and fibrous or granular materials. The proposed method is based on a temporal model of the direct and inverse scattering problem for the diffusion of transient low-frequency waves in a homogeneous isotropic slab of porous material having a rigid frame. This time domain model of wave propagation was initially introduced by the authors [Z.E.A. Fellah and C. Depollier, J. Acoust. Soc. Am. 107, 683 (2000)]. The viscous losses of the medium are described by the model devised by Johnson et al. [D. L. Johnson, J. Koplik, and R. Dashen, J. Fluid. Mech. 176, 379 (1987)]. Reflection and transmission scattering operators for a slab of porous material are derived from the responses of the medium to an incident acoustic pulse. The flow resistivity is determined from the expression of the reflection operator. Experimental and numerical validation results of this method are presented. A guide (pipe) is used in the experiment for obtaining a plane wave. This method has the advantage of being simple, rapid, and efficient.
Instability and transition of flow past two tandem circular cylinders
Authors: Mizushima Jiro , Suehiro Norihisa
Published: October 2005

The instability and transition of flow past two circular cylinders arranged in tandem are investigated numerically. A steady symmetric flow is realized at small Reynolds numbers, but the flow becomes unstable above a critical Reynolds number and makes a transition to an oscillatory flow. We obtained the symmetric flow numerically and analyze its stability by applying linear stability theory. The nonlinear oscillatory flow arising from the instability is obtained not only by numerical simulation but also by direct numerical calculation of the equilibrium solution, and the bifurcation diagram for the nonlinear equilibrium solution is depicted. We focused our attention on the effect of the gap spacing between the two cylinders on the stability and transition of the flow. The transition of the flow from a steady state to an oscillatory state is clarified to occur due to a supercritical or subcritical Hopf bifurcation depending upon the gap spacing. We found that there is a certain range of the gap spacing where physical quantities such as the drag and lift coefficients and the Strouhal number show an abrupt change when the gap spacing is continuously changed. We identified the origin of the abrupt change as the existence of multiple stable solutions for the flow.
Atomically flat aluminum-oxide barrier layers constituting magnetic tunnel junctions observed by in situ scanning tunneling microscopy
Authors: Mizuguchi M. , Suzuki Y. , Nagahama T. , Yuasa S.
Published: October 2005

Observation using in situ scanning tunneling microscopy of the layers constituting a magnetic tunnel junction with a naturally oxidized aluminum barrier layer revealed an extremely flat aluminum-oxide surface. It was clarified from line-scan images that the aluminum-oxide barrier layer has atomic steps. This flatness, which is surprising given that the aluminum-oxide film is amorphous, reduced electron scattering within the barrier, leading to momentum-dependent tunneling, which should enable the fabrication of advanced devices, such as spin-polarized resonant tunneling transistors.
Onset of erosion and avalanche for an inclined granular bed sheared by a continuous laminar flow
Authors: Loiseleux Thomas , Gondret Philippe , Rabaud Marc , Doppler Delphine
Published: October 2005

The transport inception of immersed grains is studied experimentally with laminar flow conditions in a Hele-Shaw cell when varying the tilt angle of the cell and the water flow rate. Varying these two parameters, grains are either motionless, rolling on the bed surface, or avalanching downwards. This paper focuses on the determination of the onset for grain motion either by erosion or by avalanche. For a horizontal interface, onset for erosion corresponds to a constant critical Shields number θc=0.14 at small particle Reynolds number (Red<1) but decreases as Red−1 at larger particle Reynolds number (Red>1). For tilted bed, the onset of erosion increases when the flow is opposed to gravity. Both results are compared to a standard model based on a balance of the forces acting on a single grain lying on a tilted plane. When tilt angles are large, avalanches occur. The maximum angle of stability is modified by the flow and increases slightly when the flow acts against gravity. This behavior is compared to a continuous model where a few layers of grains are about to slide.
The antimony-vacancy defect in p-type germanium
Authors: Lindberg C. E. , Hansen J. Lundsgaard , Bomholt P. , Mesli A. , Nielsen K. Bonde , Larsen A. Nylandsted , Dobaczewski L.
Published: October 2005

Ge - n + p mesa diodes have been produced in 2-Ωcm single crystals using a molecular-beam epitaxy (MBE) process to grow the Sb-doped epitaxial Ge n+-top layer. The diodes are characterized by a leakage current at room temperature of 8×10−4A∕cm2 at a reverse bias of 3 V. The diodes have been used to study irradiation-induced defects in p-type Ge, in particular Sb-related defects, where Sb stems from in-diffusion during the MBE growth. Two lines in the deep level transient spectroscopy (DLTS) spectra are related to the presence of Sb. One of these lines originates from the single-acceptor state of the SbV pair with an enthalpy of ionization of ΔHp=(0.309±0.007)eV, the other from a state with an enthalpy of ionization of ΔHp=(0.095±0.006)eV, which is concluded to be the single donor-charge state of the SbV pair.
Application of carbon nanotube field emission effect to an ionization gauge
Authors: Choi In-Mook , Woo Sam-Yong
Published: October 2005

Using the field emission effect of a carbon nanotube (CNT), we characterized a new type of technology for detecting low pressure. The fabricated low pressure sensor is of a triode type, consisting of a cathode (carbon nanotubes field emitter arrays), a grid, and a collector. The gauge described here has a triode configuration similar to that of a conventional hot cathode ionization gauge but also has a cold emission source. Due to the excellent field emission characteristics of CNT, it is possible to make a cost effective cold cathode type ionization gauge. For an effective CNT cathode, we used the screen-printing method and also, we controlled the collector and the grid potentials in order to obtain a high ionization current. We found that the ratio of the ionization current to the CNT cathode current changes according to the pressure in the chamber. In short, we elaborate the various metrological characteristics of a home-made pressure sensor that uses CNTs.
Guided modes in a planar anisotropic biaxial slab with partially negative permittivity and permeability
Authors: Cheng Qiang , Cui Tie Jun
Published: October 2005

We have investigated the guidance conditions for both bulk and surface modes in a anisotropic biaxial slab whose permittivity and permeability tensors can be partially negative under the excitation of a two-dimensional line source. We have shown that such guidance conditions will vary greatly with the change of the tensor components. We also show that infinite bulk modes are excited under some specific conditions in the anisotropic slab, unlike the case in the traditional dielectric waveguide. An efficient graphical method has been proposed to determine the propagation constants of the guided modes in the anisotropic slab.
Structural control of vertically aligned multiwalled carbon nanotubes by radio-frequency plasmas
Authors: Menda Jitendra , Ulmen Benjamin , Vanga Lakshman K. , Kayastha Vijaya K. , Yap Yoke Khin , Pan Zhengwei , Ivanov Ilia N. , Puretzky Alex A. , Geohegan David B.
Published: October 2005

Plasma-enhanced chemical vapor deposition is the only technique for growing individual vertically aligned multiwalled carbon nanotubes (VA-MWCNTs) at desired locations. Inferior graphitic order has been a long-standing issue that has prevented realistic applications of these VA-MWCNTs. Previously, these VA-MWCNTs were grown by a one-plasma approach. Here, we demonstrate the capability of controlling graphitic order and diameters of VA-MWCNTs by decoupling the functions of the conventional single plasma into a dual-plasma configuration. Our results indicate that the ionic flux and kinetic energy of the growth species are important for improving graphitic order of VA-MWCMTs.
Charge storage in nitrided nanocrystalline silicon dots
Authors: Huang Shaoyun , Oda Shunri
Published: October 2005

Nitrided nanocrystalline silicon (nc-Si) dots are proposed to be a candidate of memory nodes for nonvolatile memory device applications to make good use of advantages of both silicon quantum dots and silicon nitride films. The stored charges in the memory nodes are identified not only in nc-Si dots (electron delocalized states) but also in defect states at the nc-Si/silicon-nitride interface (electron localized states) by current-voltage (I-V) spectrum. Temperature dependences of the I-V characteristics demonstrate an evolution of stored charges in the combined system and clarify its storage mechanisms.
High radiation tolerance of InAs∕AlSb high-electron-mobility transistors
Authors: Weaver B. D. , Boos J. B. , Papanicolaou N. A. , Bennett B. R. , Park D. , Bass R.
Published: October 2005

In As ∕ Al Sb -based high-electron-mobility transistors (HEMTs) were irradiated with 2MeV protons. Radiation damage caused the source-drain current Ids to decrease nearly linearly with fluence Φ at a rate of Δ[Ids(Φ)∕Ids(0)]∕ΔΦ≈7×10−16cm2. Radiation-induced decreases in Ids have been observed for other HEMT material systems, and have been attributed to high-efficiency defect-induced scattering of carriers out of the two-dimensional electron gas. However, in the InAs∕AlSb system the rate of decrease of Ids is about 140 times less than that for typical GaAs∕AlGaAs HEMTs. An explanation is presented in which the high radiation tolerance of InAs∕AlSb HEMTs is related to carrier reinjection and the unusually large energy offset between the AlSb barriers and the InAs quantum well.
Ultraflexible organic field-effect transistors embedded at a neutral strain position
Authors: Sekitani Tsuyoshi , Iba Shingo , Kato Yusaku , Noguchi Yoshiaki , Someya Takao , Sakurai Takayasu
Published: October 2005

We fabricated ultraflexible pentacene field-effect transistors (FETs) with a mobility of 0.5cm2∕Vs and an on/off ratio of 105, which are functional at the bending radius less than 1mm. The transistors are manufactured on a 13-μm-thick polyimide film and covered by a 13-μm-thick poly-chloro-para-xylylene encapsulation layer so that transistors can be embedded at a neutral position. This sandwiched structure can drastically suppress strain-induced changes in transistor characteristics. Furthermore, the FETs show no significant change after bending cycles of 60 000 times on inward and outward bending stresses.
Electroluminescence from two fluorinated organic emitters embedded in polyvinylcarbazole
Authors: Giovanella Umberto , Botta Chiara , Papagni Antonio , Tubino Riccardo , Miozzo Luciano
Published: October 2005

Electroluminescence and photoluminescence of two fluorinated dyes emitting in the blue and in the green, blended with polyvinylcarbazole and an oxadiazole compound, are reported. Organic light-emitting diodes realized with about 0.1wt% dye concentration show interesting performances. Excited state complexes reduce the effectiveness of energy transfer in the blue-emitting device while, for the green-emitting device, the main mechanism of exciton generation is based on charge trapping at the emissive dye.
Cylindrical nanopores in NiO induced by swift heavy ions
Authors: Schattat B. , Bolse W. , Klaumünzer S. , Zizak I. , Scholz R.
Published: October 2005

NiO single crystals and polycrystalline films of about 100nm thickness have been irradiated at liquid-nitrogen temperature with 90MeV Ar, 140MeV Kr, 230MeV Xe, and 350MeV Au ions. After bombardment with Xe or Au ions, transmission electron microscopy and small angle x-ray scattering reveal empty ion tracks with diameters between 2 and 4nm. These nanopores extend through the specimens and are terminated by spherical nanoparticles containing the material which is missing in the pores.