bluuebunny/crossref_metadata_2025 huggingface dataset:
Recombinant human procathepsin S is capable of autocatalytic processing at neutral pH in the presence of glycosaminoglycans
Authors: Vasiljeva Olga , Dolinar Marko , Pungerčar Jerica Rozman , Turk Vito , Turk Boris
Published: January 2005

Cathepsin S is unique among mammalian cysteine cathepsins in being active and stable at neutral pH. We show that autocatalytic activation of procathepsin S at low pH is a bimolecular process that is considerably accelerated (∼20‐fold) by glycosaminoglycans and polysaccharides such as dextran sulfate, chondroitin sulfates A and E, and dermatan sulfate through electrostatic interaction with the proenzyme. Procathepsin S is also shown to undergo autoactivation at neutral pH in the presence of dextran sulfate with t
1/2 of ∼20 min at pH 7.5. This novel property of procathepsin S may have implications in pathological conditions associated with the appearance of active cathepsins outside lysosomes.
Glomerular proliferation during early stages of diabetic nephropathy is associated with local increase of sphingosine‐1‐phosphate levels
Authors: Geoffroy Karen , Troncy Lysiane , Wiernsperger Nicolas , Lagarde Michel , Bawab Samer El
Published: January 2005

In this study, the effects of short‐term diabetes (4 days) on rat renal glomerular cells proliferation and the potential involvement of sphingolipids in this process were investigated. Immunohistochemical analysis showed that streptozotocin (STZ)‐induced diabetes promoted increased intra‐glomerular hyperplasia, particularly marked for mesangial cells. This was associated with a concomitant increase in neutral ceramidase and sphingosine‐kinase activities and the accumulation of the pro‐proliferative sphingolipid sphingosine‐1‐phosphate, in glomeruli isolated from kidney cortex of STZ‐treated rats. These results suggest a possible involvement of sphingolipid metabolites in the glomerular proliferative response during the early stages of diabetic nephropathy.
Upregulation of placental growth factor by vascular endothelial growth factor via a post‐transcriptional mechanism
Authors: Yao Yong-Gang , Yang Hoseong S. , Cao Zhiming , Danielsson Jennifer , Duh Elia J.
Published: January 2005

Vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) are key angiogenic stimulators during normal development and wound healing, as well as in a variety of pathological conditions. Recent studies have demonstrated a synergistic effect of VEGF and PlGF in pathological angiogenesis and suggest a role for PlGF in amplifying VEGF action in endothelial cells. We show here in the mouse model of oxygen‐induced retinopathy that VEGF is significantly increased (P
< 0.01) in the retina at both the mRNA and protein levels. In this mouse model, PlGF was significantly upregulated in the retina at the protein level (P
< 0.01) without a corresponding change in mRNA levels. In cultured human retinal and umbilical vein endothelial cells, VEGF induced the production of PlGF protein by over 10‐fold (P
< 0.01) in a dose‐dependent manner through a post‐transcriptional mechanism. The increased PlGF expression upon VEGF treatment was significantly reduced by inhibition of the protein kinase C (PKC) and MEK signaling pathways, as well as by treatment with the calcium ionophore A23187. Taken together, our findings demonstrate that VEGF can amplify its effects on endothelial cells by inducing the production of PlGF via a post‐transcriptional mechanism in a PKC‐dependent manner, and provide a potential link between PKC inhibition and amelioration of vascular complications in the development of angiogenic diseases.
Modification of dopaminergic markers expression in the striatum by neonatal exposure to glutamate during development
Authors: López‐Pérez S.J. , Vergara P. , Ventura‐Valenzuela J.P. , Ureña‐Guerrero M.E. , Segovia J. , Beas‐Zárate C.
Published: January 2005

Monosodium l‐glutamate (MSG) was administered subcutaneously to male neonatal rats, and the effect on developmental profile of tyrosine hydroxylase (TH), D1, D2 receptors, and dopamine (DA) transporter expression in the striatum was examined using Western blot. In addition, TH‐immunopositive neurons at substantia nigra (SN) were also examined. MSG treatment (4 mg/g of body weight, administered on postnatal days 1, 3, 5, and 7) resulted in a reduction of D1 and D2 receptor expression from 30 days of age and persisted to adulthood (120 days of age), while DA transporter expression was significantly reduced from 14 days of age to adulthood. TH immunopositive neurons at SN showed a significant reduction, as well as TH expression on postnatal days 10, 30, 60, and 120 at striatum was reduced. No changes of TH were observed at 14 days of age. Results indicate that an over‐stimulation of the glutamatergic system by neonatal exposure to a high glutamate concentration induces a partial loss in TH‐positive neurons in the SN and an important reduction in dopaminergic markers expression in the striatum, suggesting that early excitotoxicity could contribute to developmental alterations in the nigrostriatal pathway, which may be associated with various disorders of the basal ganglia.
Differential Splintage for Flexor Tendon Rehabilitation: An Experimental Study of its Effect on Finger Flexion Strength
Authors: SAVAGE R. , PRITCHARD M. G. , THOMAS M. , NEWCOMBE R. G.
Published: January 2005

We conducted laboratory tests to investigate the possibility of partly de-powering flexor digitorum profundus with a view of reducing flexion force during active flexor tendon rehabilitation.

We constructed a splint and applied tapes to the proximal segments of fingers to test the hypothesis that holding three fingers more extended than the other finger would reduce the flexion strength of the more flexed finger. The splint allowed the metacarpophalangeal joint of the more flexed finger to be held in three positions of increasing flexion (15°, 30°, and 45°) compared to the remaining three fingers. We have called this ‘differential splintage’.

Healthy volunteers were tested for maximum active flexion strength at the different flexion angles. ‘Differential splintage’ of up to 45° resulted in mean decreased flexion strength of 28% in the index finger and 35% to 38% in the middle, ring and little fingers.

The results suggest that “differential splintage” of a finger after flexor tendon repair may be useful in reducing tension across the repair during a program of active tendon rehabilitation and we feel that it has potential to reduce the incidence of repair rupture before healing is complete.
Metatheatre and Character Dynamics in The Two-Headed Anomaly by Dario Fo
Authors: Scuderi Antonio
Published: January 2005

Dario Fo has developed his own brand of epic theatre by adapting principles and techniques from various forms of popular performance and the oral tradition. He stays detached from the role he plays by frequently shifting in and out of character and by calling attention to the performance as such. This, argues Antonio Scuderi, allows him to emphasize the interpretive frame – the ‘messages’ he establishes in his prologue. His most recent play, The Two-Headed Anomaly, is thus at one level a farcical romp; but a closer look reveals an intricate metatheatrical structure that allows Dario Fo and his fellow-performer Franca Rame to deliver their political satire. Antonio Scuderi is Associate Professor of Italian at Truman State University in Missouri. He is the author of Dario Fo and Popular Performance (Legas, 1998) and with Joseph Farrell edited Dario Fo: Stage, Text and Tradition (Southern Illinois University Press, 2000). His most recent articles on Fo have appeared in Theatre Journal (2003) and Modern Language Review (2004).
The Good, the Bad, and the Ugly: the Politics of Morality in Martin McDonagh's The Lieutenant of Inishmore
Authors: Rees Catherine
Published: January 2005

The recent plays of Martin McDonagh have fascinated and repelled critics for nearly a decade. His idiosyncratic blend of rural Irish mythology and ‘in-yer-face’ aggression has both caused consternation and won high praise, but the motivations and inspirations of McDonagh's work have not been widely discussed. Here, Catherine Rees addresses some of the common critical assaults on one of his most contentious plays, The Lieutenant of Inishmore (2001), and seeks to rescue the playwright from misunderstanding and heavy-handed critical treatment. She also aims to clarify some of the issues surrounding this politically charged and controversial work, and discusses it within the wider context of British and Irish drama. An earlier version of this article was given as a paper at the ‘Contemporary Irish Literature: Diverse Voices’ conference at the University of Central Lancaster in April 2003. Rees has presented on various aspects of McDonagh's work at a joint American Conference for Irish Studies and British Association of Irish Studies conference, and is currently working on a PhD about his plays at the University of Wales, Aberystwyth.
Red Lotus in the Twenty-First Century: Dilemmas in the Lao Performing Arts
Authors: Diamond Catherine
Published: January 2005

The small and sparsely populated country of Laos is squeezed between Thailand and Vietnam, and receives information, financial investment, and cultural influence from both – arguably overwhelming the development of its own modern identity. While theatre has often been a popular and important means of disseminating cultural information and values in societies with low literacy levels, in today's Laos the mass media have become the most influential source of information and influence, with Thai television dominating the Lao airwaves – and Vietnamese-style socialist realism still the model for the live performing arts. Although the troupes disseminate didactic messages deemed important by the central government, they are supported primarily by foreign aid agencies that also dictate their content. In the following article, Catherine Diamond traces the history of the three major performing arts in Laos, describes their present state, and assesses the difficulties they face in developing along their own creative and artistic paths. Catherine Diamond teaches theatre and ecology in literature at Soochow University in Taipei, Taiwan. She is a theatre reporter in Southeast Asia, and has previously written about theatre in Burma, Vietnam, Turkey, and the Czech Republic for NTQ.
Letter to an Editor: the Yesterday and Today of Poland's Teatr Ósmego Dnia
Authors: Watson Ian
Published: January 2005

Teatro Ósmego Dnia, the Theatre of the Eighth Day, has for forty years flourished in Poland, never as part of the established theatre, but as one of what Eugenio Barba calls the ‘floating islands’ – those companies which live as much as make theatre, and form part of an informal international circuit of like-minded though distinct and individual groups. Ian Watson here shapes his own memories of the group in the form of a letter to one of NTQ's co-editors, with whom he has shared experiences of Polish theatre, and in particular the work of Eighth Day, relating their history to the changing political and economic environment in Poland, and the company's relationship with the outside world. Ian Watson, who is a Contributing Editor of New Theatre Quarterly, teaches at Rutgers University, Newark, where he is the Acting Chair of the Department of Visual and Performing Arts. He is author of Towards a Third Theatre: Eugenio Barba and the Odin Teatret (Routledge, 1993) and of Negotiating Cultures: Eugenio Barba and the Intercultural Debate (Manchester University Press, 2002). He edited Performer Training across Cultures (Routledge, 2001), and has published numerous articles on theatre in scholarly journals.
‘Picture It If Yous Will’: Theatre and Theatregoing in Rural Scotland
Authors: Hamilton Christine , Scullion Adrienne
Published: January 2005

In the following article, Christine Hamilton and Adrienne Scullion review the system of theatre provision and production that exists in the rural areas of Scotland, most especially in the Highlands and Islands, assessing the policy framework that exists in the nation as a whole and in the Highlands and Islands in particular. They highlight the role and responsibilities of volunteers within the distribution of professional theatre in Scotland, challenge the response of locally based theatre-makers and nationally responsible agencies to represent rural Scotland, and raise issues fundamental to the provision of culture nationally. In doing so, they question what we expect theatre policy to deliver in rural areas, and what we expect rural agents to contribute to theatre provision and policy. Finally, they suggest that, in the system of rural arts in Scotland, there are wider lessons for the development of arts in and the arts of other sparsely populated and fragile communities. Christine Hamilton is the director and Adrienne Scullion the academic director of the Centre for Cultural Policy Research at the University of Glasgow, where Adrienne teaches in the Department of Theatre, Film, and Television Studies.
A Complementary Economy? National Markets and International Product in Early Australian Theatre Managements
Authors: Kelly Veronica
Published: January 2005

The international circulation of commercial theatre in the early twentieth century was driven not only from the centres of Great Britain and the USA, but by the specific enterprise and habitus of managers in ‘complementary’ production sites such as Australia, South Africa, and New Zealand. The activity of this period suggests a de-centred competitive trade in theatrical commodities – whether performers, scripts, or productions – wherein the perceived entertainment preferences and geographies of non-metropolitan centres were formative of international enterprise. The major producers were linked in complex bonds of partnerships, family, or common experience which crossed the globe. The fractures and commonalities displayed in the partnerships of James Cassius Williamson and George Musgrove, which came to dominate and shape the fortunes of the Australian industry for much of the century, indicate the contradictory commercial and artistic pressures bearing upon entrepreneurs seeking to provide high-quality entertainment and form advantageous combinations in competition with other local and international managements. Clarke, Meynell and Gunn mounted just such spirited competition from 1906 to 1911, and their story demonstrates both the opportunities and the centralizing logic bearing upon local managements shopping and dealing in a global market. The author, Veronica Kelly, works at the University of Queensland. She is presently undertaking a study of commercial stars and managements in late nineteenth- and early twentieth-century Australia, with a focus on the star performer as model of history, gender, and nation.
‘Big Ideas’ for Big Stages, 2004
Authors: Sierz Aleks
Published: January 2005

Report on the conference arranged by the Royal Shakespeare Company and Birmingham University, held at the Royal Shakespeare Theatre in Stratford-upon-Avon on 16 October 2004.
Decadal change of the spring dust storm in northwest China and the associated atmospheric circulation
Authors: Ding Ruiqiang , Li Jianping , Wang Shigong , Ren Fumin
Published: January 2005

The decadal variations of spring dust storms in Northwest China and the associated circulation changes are investigated by using the station observations of dust storm frequency data of China and the NCEP/NCAR reanalysis data for the period 1960–2003. The domain‐averaged, spring dust storm frequency index (DSFI) in Northwest China exhibits a decadal change, with a sharp decrease after the mid‐1980s. The decreased frequency of spring dust storms in Northwest China after the mid‐1980s is concurrent with enhanced geopotential height over the Mongolian plateau and Middle Siberia (MPMS) as well as an anomalous shift in the phase and intensity of the stationary wave over Eurasia. In addition, an increase in precipitation in the western region of Northwest China also contributed to the decrease in spring dust storms.
Role of weak zone orientation in continental lithosphere extension
Authors: van Wijk J. W.
Published: January 2005

Lithosphere extension and continental breakup axes are often (sub‐) parallel to orogenic belts and suture zones. In an attempt to understand the relation between weak zone orientation and extension direction, a 3‐D numerical model is developed with which the following aspects are studied: the relation between weak zone axis and axis of maximum crustal deformation, the amount and distribution of crustal thinning, and subsequent implications for rift (a)symmetry. The results suggest that upon oblique extension, rifts develop within the weak zone that individually cross the inherited structure, while as a group they follow the weak trend. This results in an alternating rift asymmetry; the pattern of crustal thinning, topography and thermal structure are not symmetric around the rift axes of the major rift zones and change along‐axis over such a rift. This is a possible explanation for alternating asymmetric rift structures such as observed in the East African Rift system.
Velocity and transport of the Makassar Strait throughflow
Authors: Susanto R. Dwi , Gordon Arnold L.
Published: January 2005

Analyses of ocean current measurements from two moorings in the Makassar Strait (MAK‐1, December 1996 to July 1998, and MAK‐2, December 1996 to February 1998) with newly processed acoustic Doppler current profiler (ADCP) data provide a new estimate of transport and vertical velocity structure for this important passageway of the Indonesian Throughflow. The 7‐month record of the MAK‐1 ADCP and the 3‐month record of the MAK‐2 ADCP, nominally set at depths of 150 m, are extrapolated to the end of the mooring period using a surface layer relationship to the shallowest current meter at 200 m and to the regional winds. The southward transport within Makassar Strait is confined for the most part to the upper 750 m, above the blocking topographic sill of Makassar Strait. The transport maximum occurs within the thermocline (100–300 m). After the temporal mean flow has been removed, the vertical structure of the along channel flow in the upper 750 m is decomposed using the empirical orthogonal function (EOF) method. The first two modes contain 91% of the total variance. For the entire mooring period, the total depth‐integrated transport was 8.1 ± 1.5 Sv (Sv = 1 × 106 m3/s), with 7.9 ± 1.2 Sv for calendar year1997. During the peak of 1997/1998 El Niño from September 1997 to mid‐February 1998, the first mode time series displays northward flow, enhancing the vertical shear within the thermocline and reducing the mean throughflow to 4.6 ± 0.9 Sv.
Seasonal sea surface temperature contrast between the Holocene and last glacial period in the western Arabian Sea (Ocean Drilling Project Site 723A): Modulated by monsoon upwelling
Authors: Naidu Pothuri Divakar , Malmgren Björn A.
Published: January 2005

Annual, summer, and winter sea surface temperatures (SSTs) in the western Arabian Sea were reconstructed through the last 22 kyr using artificial neural networks (ANNs) based on quantitative analyses of planktic foraminifera. Down‐core SST estimates reveal that annual, summer, and winter SSTs were 2, 1.2, and 2.6°C cooler, respectively, during the last glacial period than in the Holocene. A 2.5°C SST increase during Termination 1A (hereinafter referred as glacial to Holocene transition) in the western Arabian Sea. The study reveals a strong seasonal SST contrast between winter and summer from 18 to 14 calendar kyr owing to the combined effect of weak upwelling and strong cold northeasterly winds. Minor or no seasonal SST changes were noticed within the Holocene period, which is attributed to the intense upwelling during the summer monsoon. This causes a lowering of SST to values similar to those of the winter season in analogy with the present day. A 3°C rise in winter SSTs during the glacial to Holocene transition coincides with a strengthening of the monsoon, suggesting a link between winter SST and monsoon initiation from the beginning of the Holocene. Strikingly, annual, summer, and winter SSTs show a cooling trend from ∼8 ka to the present day, implying tropical cooling in the late Holocene.
Radiation dose along North American transcontinental flight paths during quiescent and disturbed geomagnetic conditions
Authors: Getley Ian L. , Duldig M. L. , Smart D. F. , Shea M. A.
Published: January 2005

Commercial aircraft flights across the North American continent encounter a small radiation exposure (normally <20 μSv) from galactic cosmic radiation. During October and November 2003, there was significant perturbation in the cosmic ray flux near the Earth due to extraordinary activity on the Sun. The associated sequence of solar flares and coronal mass ejections resulted in a significant decrease in the background galactic cosmic radiation levels upon which there were sudden impulsive increases from solar cosmic ray events. These fluctuations in the cosmic ray intensity were detectable at commercial aircraft cruising altitudes and at sea level cosmic ray neutron‐monitoring stations. This paper compares the in‐flight radiation dose data acquired during the disturbed conditions on 29 October 2003 with the dose data acquired over the same route in January 2004 during quiescent geomagnetic conditions. This comparison shows that during Forbush decreases or ground level cosmic ray increases, the CARI aircraft radiation dose prediction software does not adequately describe the radiation exposure from cosmic radiation.
Tracer Delay Correction of Cerebral Blood Flow with Dynamic Susceptibility Contrast-Enhanced MRI
Authors: Ibaraki Masanobu , Shimosegawa Eku , Toyoshima Hideto , Takahashi Kazuhiro , Miura Shuichi , Kanno Iwao
Published: January 2005

Cerebral blood flow (CBF) and vascular mean transit time (MTT) can be determined by dynamic susceptibility contrast-enhanced magnetic resonance imaging and deconvolution with an arterial input function. However, deconvolution by a singular value decomposition (SVD) method is sensitive to the tracer delay that often occurs in patients with cerebrovascular disease. We investigated the effect of tracer delay on CBF determined by SVD deconvolution. Simulation study showed that underestimation of CBF due to tracer delay was larger for shorter MTTs. We developed a delay correction method that determines tracer delay by means of least-squares fitting pixel-by-pixel. The corrected CBF was determined by SVD deconvolution after time-shifting of the measured concentration curve. The simulations showed that the corrected CBF was insensitive to tracer delay irrespective of the vascular model, although CBF fluctuation increased slightly. We applied the delay correction to the CBF and MTT images acquired for nine patients with hyperacute stroke and unilateral occlusion of the middle cerebral artery. We found in some patients that the delay correction modulated the contrast of CBF and MTT images. For hyperacute stroke patients, tracer delay correction is essential to obtain reliable perfusion image when SVD deconvolution is used.
Neuroprotective Efficacy of Repinotan HCl, a 5-HT1A Receptor Agonist, in Animal Models of Stroke and Traumatic Brain Injury
Authors: Mauler Frank , Horváth Ervin
Published: January 2005

Repinotan is a highly potent 5-HT1A receptor agonist with strong neuroprotective efficacy in animal models of middle cerebral artery occlusion and traumatic brain injury. In this study, we characterized the time window for neuroprotective effects of repinotan in animal models. In the permanent middle cerebral artery occlusion model, repinotan showed neuroprotective efficacy when administered as a triple bolus injection (0.3–100 μg/kg) or an intravenous infusion (0.3–100 μg/kg per hour). A 73% reduction in infarct volume was observed with a 3 μg/kg intravenous bolus, and a 65% reduction was observed with a 3 and 10 μg/kg per hour intravenous infusion. When delayed until 5 hours after occlusion, repinotan (10 μg/kg per hour) reduced infarct volume by 43%. In the transient middle cerebral artery occlusion model, repinotan (10 μg/kg per hour) administered immediately after occlusion reduced infarct volume by 97%, and a delay to 5 hours reduced infarct volume by 81%. In the acute subdural hematoma model, repinotan (3 and 10 μg/kg per hour) reduced infarct volume by 65%. In this model, repinotan (3 μg/kg per hour) administered 5 hours after occlusion reduced infarct volume by 54%. The favorable neuroprotective efficacy, broad dose–response curve, and prolonged therapeutic window observed in all models strongly suggest that repinotan is a promising candidate for treating acute ischemic stroke in humans.
Minocycline Protects against Permanent Cerebral Ischemia in Wild Type but Not in Matrix Metalloprotease-9-Deficient Mice
Authors: Koistinaho Milla , Malm Tarja M , Kettunen Mikko I , Goldsteins Gundars , Starckx Sofie , Kauppinen Risto A , Opdenakker Ghislain , Koistinaho Jari
Published: January 2005

Minocycline is protective in models of transient middle cerebral artery occlusion (MCAO). We studied whether minocycline and doxycycline, another tetracycline derivative, provide protection in permanent MCAO. Because minocycline inhibits matrix metalloprotease-9 (MMP-9), we also compared minocycline's protective effect in wild type (wt) and MMP-9 knock-out (ko) mice. Wt FVB/N, Balb/C, and two lines of MMP-9 ko and their wt C57Bl/6 control mice were subjected to 24- or 72-hour permanent MCAO. Drug administration was started either 12 hours before or 2 hours after the onset of MCAO. Infarct size was determined by triphenyltetrazolium staining or T2-weighted MRI. Zymography was used to study the expression of MMPs. In wt strains, tetracycline treatments started before MCAO reduced the infarct size by 25% to 50%, whereas the treatment started after MCAO was not protective. Minocycline inhibited ischemia-provoked pro-MMP-9 induction in wt mice, but was not protective in MMP-9 ko mice. Pro-MMP-2 was induced by MCAO in wt and MMP-9 ko mice. MCAO-induced pro-MMP-2 was downregulated by minocycline treatment in wt mice but remained in MMP-9 ko mice at the same level as in saline-treated wt mice. Tetracyclines are protective in permanent MCAO when the treatment is started before the insult. Minocycline may provide protection by interfering with MMPs.
Induction of Type 2 Iodothyronine Deiodinase in Astrocytes after Transient Focal Cerebral Ischemia in the Rat
Authors: Margaill Isabelle , Royer Julien , Lerouet Dominique , Ramaugé Martine , Goascogne Claude Le , Li Wen Wu , Plotkine Michel , Pierre Michel , Courtin Françoise
Published: January 2005

This study investigated the expression of deiodinases of thyroid hormones in the rat brain after transient occlusion of the middle cerebral artery. The activity of type 2 deiodinase (D2), which catalyzes the deiodination of thyroxine into the more active thyroid hormone 3,5,3′-triiodothyronine, was strongly increased by cerebral ischemia at 6 and 24 hours in the striatum and at 24 hours in the cerebral cortex. The activity of type 3 deiodinase, which catalyzes the inactivation of thyroid hormones, was not affected by ischemia. In situ hybridization showed, as soon as 6 hours, an upregulation of the expression of D2 mRNA in the ipsilateral striatum, which disappeared at 24 hours. In the ipsilateral cortex, the induction of D2 mRNA started at 6 hours, was increased at 24 hours and finally declined at 72 hours. These results were confirmed by reverse transcription-PCR for D2 mRNA in the striatum and cerebral cortex. The upregulation of D2 mRNA after ischemia was mainly localized in astrocytic cell bodies. These results show that D2 is rapidly induced in astrocytes after ischemic stroke. Future work will include the exploration of the role of the upregulation of this enzyme, responsible for local 3,5,3′-triiodothyronine production as a neuroprotective mechanism in the brain.
The influence of nonmagnetic seed layers on the magnetotransport properties of magnetic tunnel transistors with a silicon collector
Authors: van Dijken Sebastiaan , Jiang Xin , Parkin Stuart S. P.
Published: January 2005

The magnetotransport properties of magnetic tunnel transistors (MTTs) with a CoFe∕Cu∕NiFe spin-valve base and a Si(001) collector are studied as a function of seed layer material and thickness. The insertion of a nonmagnetic Cu or Au seed layer between the metal spin valve and the silicon is found to significantly enhance the output current and magnetic-field sensitivity of the MTT device. In contrast, the use of a Pt or Pd seed layer only slightly improves the properties of the MTT, while seed layers of Ta and Ti are found to deteriorate the output current and tunnel barrier breakdown voltage of the MTTs. Secondary-ion-mass spectroscopy is used to provide complementary information about the base∕collector interface properties of the MTTs with and without seed layers.
Topological quantization of gravitational fields
Authors: Patiño Leonardo , Quevedo Hernando
Published: January 2005

We introduce the method of topological quantization for gravitational fields in a systematic manner. First we show that any vacuum solution of Einstein’s equations can be represented in a principal fiber bundle with a connection that takes values in the Lie algebra of the Lorentz group. This result is generalized to include the case of gauge matter fields in multiple principal fiber bundles. We present several examples of gravitational configurations that include a gravitomagnetic monopole in linearized gravity, the C-energy of cylindrically symmetric fields, the Reissner–Nordström and the Kerr–Newman black holes. As a result of the application of the topological quantization procedure, in all the analyzed examples we obtain conditions implying that the parameters entering the metric in each case satisfy certain discretization relationships.
Large-time asymptotics for nonlinear diffusions: the initial-boundary value problem
Authors: Salvarani F. , Toscani G.
Published: January 2005

In this paper we investigate the large-time behavior of solutions to the first initial-boundary value problem for the nonlinear diffusion ut=(um)xx,m>0. In particular, we prove exponential decay of u(x,t) towards its own steady state in L1-norm for long times and we give an explicit upper bound for the rate of decay. The result is based on a new application of entropy estimates, and on detailed lower bounds for the entropy production in this situation.
Some remarks on locally conformally flat static space–times
Authors: Brozos-Vázquez Miguel , García-Río Eduardo , Vázquez-Lorenzo Ramón
Published: January 2005

Necessary and sufficient conditions for a static space–time to be locally conformally flat are obtained, showing some significant restrictions on the possible warping functions of the space–times. This occurs in opposition to cosmological models, where Robertson–Walker space–times are locally conformally flat for any warping function.
Approximate conditional symmetries and approximate solutions of the perturbed Fitzhugh–Nagumo equation
Authors: Shih M. , Momoniat E. , Mahomed F. M.
Published: January 2005

We consider a perturbation of the Fitzhugh–Nagumo equation. The perturbation is proportional to the electric potential across the cell membrane. The purpose of this investigation is to determine the effects of a change in electric potential across the cell membrane. Exact solutions of the perturbed equation are easily obtained from the well-known solutions of the unperturbed Fitzhugh–Nagumo equation. The method of approximate conditional symmetries is used to obtain first-order approximate solutions of the perturbed Fitzhugh-Nagumo equation. The approximate solutions are compared with the exact solutions of the perturbed equation. The exact solutions of the perturbed equation do not indicate a change in the wave front connecting one constant state to another. There is only a proportional increase or decrease in the constant nonzero state. The approximate solutions do show a change in the shape of the wave front connecting two constant states as well as a proportional increase or decrease in the constant nonzero state.
Oil-in-water microemulsions stabilized by charged diblock copolymers
Authors: Romet-Lemonne G. , Daillant J. , Guenoun P. , Yang J. , Holley D. W. , Mays J. W.
Published: January 2005

We present here oil-in-water microemulsions stabilized by charged diblock copolymers alone, along with their structural characterization by small-angle neutron scattering measurements. They consist of swollen spherical micelles containing small amounts of oil in their core, which is surrounded by a corona of stretched polyelectrolyte chains. Structural changes, including core size variations, are evidenced when using a cosurfactant, or upon addition of salt, through a contraction of the charged corona. Attempts to relate the micellar structure to the individual copolymer characteristics are also presented, and show that the size of the hydrophobic block mainly determines that of the micelles.
Defect-assisted conductivity in organic ionic plastic crystals
Authors: Pas Steven J. , Huang Junhua , Forsyth Maria , MacFarlane Douglas R. , Hill Anita J.
Published: January 2005

In order to determine the role of defects (vacancies and extended lattice defects) in the conductivity mechanism of a well studied organic ionic plastic crystal electrolyte, conductivity and mean defect volumes were measured. The ionic conductivity of the salt showed a characteristic phase dependence. Defect volumes, as measured by positron annihilation lifetime spectroscopy, showed increasing rates of expansion with increasing rotational disorder. The dependence of ionic conductivity on defect volume was observed to be phase dependent. Increases in mean defect volume size below ≈100cm3mol−1 did not always facilitate ionic conductivity. It was shown that the material undergoes a solid-solid phase transition to the most disordered phase (a plastic crystalline phase with the highest conductivity) when the mean defect volume becomes larger than the molar volume of either the rotating anionic or cationic species. Conductivity in this phase had the strongest dependence on defect volume. Critical volumes calculated from the free volume model of Cohen and Turnbull were unrealistically large.
Theoretical interpretation of the line shape of the gaseous acetic acid cyclic dimer
Authors: Blaise Paul , Wojcik Marek Janusz , Henri-Rousseau Olivier
Published: January 2005

A general quantum theoretical approach of the νX–H IR line shape of cyclic dimers of weakly H-bonded species in the gas phase is proposed. In this model, the adiabatic approximation (allowing to separate the high frequency motion from the slow one of the H-bond bridge), is performed for each separate H-bond bridge of the dimer and a strong nonadiabatic correction is introduced into the model via the resonant exchange between the fast mode excited states of the two moieties. The present model reduces satisfactorily to many models in the literature dealing with more special situations. It has been applied to the cyclic dimers (CD3CO2H)2 and (CD3CO2D)2 in the gas phase. It correctly fits the experimental line shape of the hydrogenated compound and predict satisfactorily the evolution in the line shapes, to the deuterated one by reducing simply the angular frequency of the H-bond bridge and the anharmonic coupling parameter by the factor 1∕2.
Cascading third-order Raman process and local structure formation in binary liquid mixtures of benzene and n-hexane
Authors: Shigeto Shinsuke , Kano Hideaki , Hamaguchi Hiro-o
Published: January 2005

The cascading third-order Raman process in binary mixtures of benzene and n-hexane was studied by six-wave mixing coherent anti-Stokes Raman scattering spectroscopy. By examining the concentration dependence of the cascading third-order signal intensity, we investigated the formation of local structures of benzene in the binary mixtures. A significant deviation from the dependence expected for homogeneous mixtures was observed at benzene concentrations above 7moldm−3. This deviation can be interpreted in terms of optical inhomogeneity caused by the formation of domain structures of benzene molecules. We discuss the feasibility of the cascading third-order process as a sensitive probe for the microscopic structures that are formed in liquids and solutions.
Rotational state-resolved reaction cross section in the reactions of state-selected CH with NO and with O2
Authors: Nagamachi Y. , Ohoyama H. , Ikejiri K. , Kasai T.
Published: January 2005

A pure and highly intense state-selected pulsed supersonic CH(XΠ2) radical beam source was developed by use of the C(D1)+H2 reaction with the combination of the state selection and purification by an electrostatic hexapole field. Under the beam-cell condition, the elementary reactions of CH+NO and CH+O2 were studied by using this state-selected CH beam. NH(AΠ3) [and NCO(AΣ+2)] formations and OH(AΣ+2) formation were directly identified in the elementary reaction of CH+NO and CH+O2, respectively. For the CH+NO reaction, the relative branching ratio σNCO*∕σNH of NCO(AΣ+2) formation to NH(AΠ3) formation was determined to be 0.35±0.15. The state-selected reaction cross sections were determined for each rotational state of CH. In the CH+NO reaction, a remarkable rotational state dependence of the reactive cross section was revealed, while the CH+O2 reaction showed little rotational state dependence.
Dynamic response of optical-fiber modulator by using magnetic fluid as a cladding layer
Authors: Chieh J. J. , Yang S. Y. , Chao Y. H. , Horng H. E. , Hong Chin-Yih , Yang H. C.
Published: January 2005

An in-line optical-fiber modulator that uses magnetic fluid as a cladding layer has been developed to control transmission loss generated from external magnetic fields. In this work, we investigate the instant variation in the transmission loss of an optical-fiber modulator after an external magnetic field has been turned on (referred to as the charging operation) or turned off (referred to as the discharging operation). Research showed that when the external field was turned on∕off, the transmission loss of the optical-fiber modulator did not change until after 10ms. Successively, the transmission loss varied exponentially. Thus, two kinds of characteristic time were observed to describe quantitatively the instant variation in the transmission loss: retarding time and response time. It was found that both the retarding time in a charging∕discharging operation increased with the length of the magnetic-fluid cladding over a critical level, whereas the response time in a charging∕discharging operation was cladding length independent.
Micro-Raman scattering from undoped and phosphorous-doped (111) homoepitaxial diamond films: Stress imaging of cracks
Authors: Mermoux M. , Marcus B. , Crisci A. , Tajani A. , Gheeraert E. , Bustarret E.
Published: January 2005

We report postgrowth micro-Raman stress imaging of cracks in (111) homoepitaxial diamond films. Undoped and phosphorous-doped diamond thin films grown by microwave plasma-enhanced chemical-vapor deposition on Ib (111)-oriented diamond substrates have been studied by confocal micro-Raman spectroscopy. For comparison purposes, a film grown on a (100) Ib substrate was also examined. Thanks to the confocal optics, the Raman signal arising from the epilayer could be discriminated from that arising from the substrate. As was already reported, the (111) films exhibited substantial tensile stress, indicated by a downshift in the Raman peak and by spontaneous cracking in films grown thicker than 5μm. The sixfold symmetry of the cracks supported that the films were homoepitaxial. A high compressive stress was also detected at the substrate near surface, and a partial stress relaxation was observed to occur in the vicinity of the cracks. Possible origins of the high tensile stress observed in the (111) homoepitaxial diamond films are discussed.
Electronically forbidden (5σu→kσu) photoionization of CS2: Mode-specific electronic-vibrational coupling
Authors: Rathbone G. J. , Poliakoff E. D. , Bozek John D. , Lucchese R. R.
Published: January 2005

Vibrationally resolved photoelectron spectroscopy of the CS2+(BΣu+2) state is used to show how nontotally symmetric vibrations “activate” a forbidden electronic transition in the photoionization continuum, specifically, a 5σu→kσu shape resonance, that would be inaccessible in the absence of a symmetry breaking vibration. This electronic channel is forbidden owing to inversion symmetry selection rules, but it can be accessed when a nonsymmetric vibration is excited, such as bending or antisymmetric stretching. Photoelectron spectra are acquired for photon energies 17⩽hν⩽72eV, and it is observed that the forbidden vibrational transitions are selectively enhanced in the region of a symmetry-forbidden continuum shape resonance centered at hν≈42eV. Schwinger variational calculations are performed to analyze the data, and the theoretical analysis demonstrates that the observed forbidden transitions are due to photoelectron-mediated vibronic coupling, rather than interchannel Herzberg–Teller mixing. We observe and explain the counterintuitive result that some vibrational branching ratios vary strongly with energy in the region of the resonance, even though the resonance position and width are not appreciably influenced by geometry changes that correspond to the affected vibrations. In addition, we find that another resonant channel, 5σu→kπg, influences the symmetric stretch branching ratio. All of the observed effects can be understood within the framework of the Chase adiabatic approximation, i.e., the Born–Oppenheimer approximation applied to photoionization.
Resonant and waveguiding defect modes in a two-dimensional electromagnetic band-gap slab structure for millimeter wave frequencies
Authors: Schuster M. , Antoniuk O. , Lahl P. , Klein N.
Published: January 2005

In this article we report about the investigation of two-dimensional electromagnetic band-gap structures in a slab arrangement for millimeter wave frequencies made from high resistive silicon. We investigated both waveguiding modes of a line defect and resonant modes of a point defect with respect to a possible application as passive elements in millimeter wave integrated circuits. We found that a line defect can act as a broadband waveguide comprising low transmission losses and that localized point defect modes can be excited. In accordance with recent observations at optical frequencies, the quality factor of such a defect mode was found to be affected by the local displacement of certain lattice elements near the point defect.
Growth and luminescence properties of micro- and nanotubes in sintered tin oxide
Authors: Maestre D. , Cremades A. , Piqueras J.
Published: January 2005

Sintering SnO2 under argon flow at temperatures in the range of 1350–1500°C causes the formation of wires, rods, and tubes on the sample surface. At high temperatures of the mentioned range, microwires with lengths of hundreds of microns are formed. At lower temperatures the formation of micro- and nanorods as well as micro- and nanotubes takes place. The influence of ball milling of the starting powder on the formation of tubes is investigated. The local cathodoluminescence measurements show a different defect structure in the tubes than in the sample background.
Nanostructured Co1−xNix(Sb1−yTey)3 skutterudites: Theoretical modeling, synthesis and thermoelectric properties
Authors: Stiewe Christian , Bertini Luca , Toprak Muhammet , Christensen Mogens , Platzek Dieter , Williams Simon , Gatti Carlo , Müller Eckhard , Iversen Bo B. , Muhammed Mamoun , Rowe Michael
Published: January 2005

The properties of Te-doped Co(Sb1−yTey)3 and Te-Ni double-doped Co1−xNix(Sb1−yTey)3 nanostructured skutterudites were evaluated by means of x-ray powder diffraction, and transport properties measured on the synthesized samples have been compared with ab initio theoretical modeling. Theoretical optimal dopant contents have been evaluated according to the maximum value of the power factor, calculating the electronic transport properties from the ab initio material band structure using semiclassical Boltzmann transport theory. The samples have been synthesized by chemical alloying with Te substitution for Sb up to 2.5at.% and Ni substitution for Co up to 2.0at.%. X-ray powder diffraction has been performed on all samples to reveal information about phase purity and Rietveld refinement was performed for the phase composition and cell parameter. The thermoelectric properties of the resulting consolidates were investigated in a temperature range from 300to723K using various measurement facilities. A standardization and round robin program was started among the participating evaluation laboratories in order to ensure reliability of the data obtained. The significant reduction in thermal conductivity, when compared to highly annealed CoSb3, could be proved which is caused by the nanostructuring, resulting in a high concentration of grain boundaries. A combination of substitution levels for Ni and Te has been found resulting in the largest ZT value of 0.65 at 680K among unfilled skutterudite materials.
Increased electrophosphorescent efficiency in organic light emitting diodes by using an exciton-collecting structure
Authors: Qin Dashan , Tao Ye
Published: January 2005

A phosphorescent dye, tris(1-phenylisoquinoline) iridium (III) [Ir(piq)3] doped interface of 4,4′,4″-tris(carbazol-9-yl)-triphenylamine (TCTA) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) has been studied in organic light emitting diodes. Two devices with different emissive interfaces, TCTA+6%Ir(piq)3∕BCP and TCTA+6%Ir(piq)3∕BCP+1%Ir(piq)3, exhibited nearly the same red Ir(piq)3 emissions and I–V characteristics. However, the second device showed higher efficiency and luminance than the first device over the whole voltage range. The maximum efficiency of 6.0cd∕A reached at 0.026mA∕cm2 in the second device was 30% higher than that of 4.6cd∕A reached at 0.032mA∕cm2 in the first device. The improved performance of the second device is attributed to the fact that the excitons can be formed on both sides of the TCTA/BCP interface and can be more efficiently collected with the additional 1% Ir(piq)3 doped in the BCP layer. Therefore, the exciton-collecting structure, doping phosphorescent dyes into both sides of the TCTA/BCP interface, is believed to be a very useful way to optimize the performance of phosphorescent organic light emitting diodes.
Donor-acceptor pair luminescence of nitrogen-implanted ZnO single crystal
Authors: Xiong G. , Ucer K. B. , Williams R. T. , Lee J. , Bhattacharyya D. , Metson J. , Evans P.
Published: January 2005

Donor-acceptor-pair (DAP) luminescence is a direct probe of the acceptors in ZnO. We report the near-surface doping of a ZnO single crystal by ion implantation with nitrogen and titanium. Secondary-ion-mass spectroscopy shows that the doping depth is approximately 80nm (N) and 50nm (Ti). The DAP photoluminescence centered at 3.232eV is observed from both the undoped and doped ZnO single-crystal samples. The luminescence spectrum of the nitrogen-doped sample shows enhancement of the DAP transition compared to the “pure” ZnO sample. The acceptor energy is calculated to be 177meV, consistent with nitrogen as the acceptor in DAP luminescence. The DAP recombination lifetime is found to be ∼5.5ns. The temperature evolution of spectra shows the gradual transition from DAP luminescence to electron+acceptor recombination luminescence at temperatures above 37K. Our experimental results suggest that ion implantation is an effective way of doping nitrogen into ZnO.