bluuebunny/crossref_metadata_2025 huggingface dataset:
A Review of Mathematical Models for Hydrogen and Direct Methanol Polymer Electrolyte Membrane Fuel Cells
Authors: Yao K.Z. , Karan K. , McAuley K.B. , Oosthuizen P. , Peppley B. , Xie T.
Published: April 2004

This paper presents a review of the mathematical modeling of two types of polymer electrolyte membrane fuel cells: hydrogen fuel cells and direct methanol fuel cells. Models of single cells are described as well as models of entire fuel cell stacks. Methods for obtaining model parameters are briefly summarized, as well as the numerical techniques used to solve the model equations. Effective models have been developed to describe the fundamental electrochemical and transport phenomena occurring in the diffusion layers, catalyst layers, and membrane. More research is required to develop models that are validated using experimental data, and models that can account for complex two‐phase flows of liquids and gases.
Modeling the Effects of Methanol Crossover on the DMFC
Authors: Zhang J. , Wang Y.
Published: April 2004

A mathematic model is established to simulate the effects of methanol crossover on the DMFC. The transport and reactions of both oxygen and methanol at the cathode are described and the theory of “parallel electrode reactions” is applied to calculate the cathode over‐potential caused by methanol crossover. The influence of methanol concentration, fuel cell temperature, oxygen pressure, and membrane properties on the cathode over‐potential is evaluated. Simulation results show that methanol crossover considerably increases the cathode over‐potential at low current density, but its effect is significantly reduced when the current density is increased to reasonable values. It also shows that of the two parameters characterizing a polymer electrolyte membrane, proton conductivity and methanol permeability, the former has more impact on the performance of a DMFC.
Novel CVD Techniques for Micro‐ and IT‐SOFC Fabrication
Authors: Meng G. , Song H. , Xia C. , Liu X. , Peng D.
Published: April 2004

At present, there are intensive research efforts towards intermediate temperature solid oxide fuel cells (IT‐SOFCs) with a thin film electrolyte and electrode. In view of the nature of molecular level reaction and the great potential of CVD processes for IT‐SOFCs and even Micro‐SOFC fabrication, various novel CVD techniques have been developed to prepare multi‐component oxide films and multi‐layers related to the SOFC. In this paper, novel CVD techniques are described and reviewed for possible applications in thin film electrolytes and electrodes for SOFCs, mainly based on the research activities of the author's laboratory. The techniques include metal‐organic CVD (MOCVD) with metal β‐diketonate chelates as precursors, single mixed source MOCVD, and aerosol assisted CVD (AACVD). AACVD can be operated with spray AAMOCVD, plasma‐AACVD, or oxy‐acetylene combustion AACVD. The results show their possible application in the fabrication of electrolyte and electrode thin films for SOFCs.
Development of Solid Oxide Fuel Cells by Applying DC and RF Plasma Deposition Technologies
Authors: Schiller G. , Henne R. , Lang M. , Müller M.
Published: April 2004

Based on advanced plasma deposition technology with both DC and RF plasmas DLR Stuttgart has developed a concept of a planar SOFC with consecutive deposition of all layers of a thin‐film cell onto a porous metallic substrate support. This concept is an alternative approach to conventionally used sintering techniques for SOFC fabrication without needing any sintering steps or other thermal post‐treatment. Furthermore, is has the potential to be developed into an automated continous production process. For both stationary and mobile applications, adequate stack designs and stack technologies have been developed. Future development work will focus on light‐weight stacks to be applied as an Auxillary Power Unit (APU) for on‐board electricity supply in passenger cars and airplanes.

This paper describes the plasma deposition technologies used for cell fabrication and the DLR spray concept including the resulting stack designs. The current status of development and recent progress with respect to materials development and electrochemical characterization of single cells and short‐stacks is presented.
A Study of Thermal Transient Performances of Molten Carbonate Fuel Cells
Authors: Weng S. , Weng Y. , Su M. , Zhang H.
Published: April 2004

Based on the conservation of energy and conservation of mass, as well as considering the mass transfer in the electrodes‐electrolyte interface and its effect on Molten Carbonate Fuel Cell (MCFC) thermal characteristics, this paper presents a mathematical model to modify the dynamic performance of MCFC. Using the method of weighted residuals (MWR) which possesses high precision for the solution of partial differential equations, and the Matlab system function which is efficient for numerical resolution and simulation, a dynamic simulation model of MCFC is created. The results of the simulation show that the mass transfer in the electrodes‐electrolyte interface notably affects Molten Carbonate Fuel Cell (MCFC) thermal characteristics, and there is a distribution of temperature both in the electrodes‐electrolyte and in the fuel gas as well as in the oxidant gas. The temperature of electrodes‐electrolyte increases and that of oxidant gas decreases with increments in the flow rate of both the fuel gas and oxidant gas.
Experimental Investigation of Effect of Flow Bed Design on Performance of Liquid Feed Direct Methanol Fuel Cells
Authors: Guo H. , Ma C.F. , Wang M.H. , Ye F. , Yu J. , Wang Y. , Wang C.Y.
Published: April 2004

The effect of flow bed design on the performance of a liquid feed direct methanol fuel cell was studied experimentally. The flow beds were designed and manufactured with different channel densities, channel depths, and ridge widths. The flow beds were machined on stainless steel polar plates. The experimental results showed that ridge width affects the slope of the ohmic polarization curve. A ridge width of 3.30 mm provided the highest peak power. When the contact surface area between the flow bed and electrode was constant, the effect of channel density on cell performance was minimal, under the experimental conditions of this paper. The channel depth had a considerable influence on cell performance with a 2 mm deep channel achieving the best performance. The mechanism of the experimental phenomena was analyzed in this paper.
Cross‐Linked Polyaryl Blend Membranes for Polymer Electrolyte Fuel Cells
Authors: Kerres J. , Ullrich A. , Hein M. , Gogel V. , Friedrich K.A. , Jörissen L.
Published: April 2004

The preparation and characterization of different types of proton‐conducting polymer blend membranes are presented in this paper. The investigations are focused on the determination of the thermal stability of the membranes, because thermal stability is one of the important parameters for the application of the membranes in polymer electrolyte fuel cells. In addition to the thermal stability, chemical stability, proton conductivity and mechanical strength are required. The characterization of the membranes was performed by thermogravimetry (TGA), a combined TGA and FTIR analysis where infrared spectroscopy is used for the determination of decomposition products, and experiments on the dependence of water uptake (swelling) of the membranes on temperature. Ionically cross‐linked membranes have been investigated. The TGA‐FTIR coupling experiments showed clearly, that the decomposition of the membranes starts at ≈ 230 °C, and that in some cases the principal membrane component which is sulfonated polyaryletherketone splits off SO2 at slightly lower temperature in the membrane than in the pure substance. Most of the other polymeric components of the blend membranes were slightly more stable in the membrane than in the pure form. The ionically cross‐linked membranes were tested in direct methanol fuel cells as well as in a H2/air fuel cell and exhibit a performance which compares favorably with standard membranes.
CD44 overexpression by oligodendrocytes: A novel mouse model of inflammation‐independent demyelination and dysmyelination
Authors: Tuohy Therese M.F. , Wallingford Nicholas , Liu Ying , Chan Frank H. , Rizvi Tilat , Xing Rubing , Bebo Bruce , Rao Mahendra S. , Sherman Larry S.
Published: April 2004

The CD44 transmembrane glycoprotein family has been implicated in cell‐cell adhesion and cell signaling in response to components of the extracellular matrix but its role in the nervous system is not understood. CD44 proteins are elevated in Schwann cells and oligodendrocytes following nervous system insults, in inflammatory demyelinating lesions, and in tumors. Here, we tested the hypothesis that elevated CD44 expression influences Schwann cell and oligodendrocyte functions by generating transgenic mice that express CD44 under the control of the 2′,3′‐cyclic nucleotide‐3′‐phosphodiesterase (CNPase) promoter. These mice failed to develop peripheral nerve or CNS tumors. However, they did develop severe tremors that were associated with CNS dysmyelination and progressive demyelination. Loss of CNS myelin was not due to alterations in early oligodendrocyte precursor differentiation, proliferation, or survival. Myelination in the PNS appeared normal. In no instance was there any evidence of an inflammatory response that could account for the loss of CNS myelin. These findings suggest that CNPase‐CD44 mice are a novel model for noninflammatory progressive demyelinating disease and support a potential role for CD44 proteins expressed by glial cells in promoting demyelination. © 2004 Wiley‐Liss, Inc.
Activation of P2 nucleotide receptors stimulates acid efflux from astrocytes
Authors: Dixon S. Jeffrey , Yu Rongguo , Panupinthu Nattapon , Wilson John X.
Published: April 2004

Acidification of the extracellular fluid modulates neurotransmission and ischemic injury in brain. The purpose of the present study was to investigate the effects of purine and pyrimidine transmitters on acid efflux from brain astrocytes. Using RT‐PCR, we detected transcripts for the following nucleotide receptors in rat primary astrocyte cultures: P2X1, P2X2, P2X3, P2X4, P2X6, P2X7, P2Y1, P2Y2, P2Y4, and P2Y6. Adenosine 5′‐triphosphate (ATP) was found to rapidly induce a biphasic increase in acid efflux, monitored by microphysiometry, consisting of an initial transient and a sustained plateau. Compared with ATP, the P2Y agonist uridine 5′‐triphosphate (UTP) induced a much smaller initial response but an equal plateau. The poorly hydrolyzable ATP analogue ATPγS caused the same initial response as did ATP, but a much smaller plateau, suggesting that the latter phase was due to extracellular degradation of nucleotides. The P2 receptor antagonist, suramin, blocked stimulation of acid efflux by ATP. Removal of extracellular glucose or elevation of extracellular K+ decreased the basal rate of acid efflux but not the stimulation induced by ATP. Inhibition of Na+/H+ exchange by cariporide suppressed the initial phase of ATP‐stimulated acid efflux. The intracellular Ca2+ chelator bisaminophenoxyethane‐ tetraacetic acid (BAPTA) lowered basal acid efflux and abolished the initial phase of the response to ATP. In conclusion, ATP acts through P2 nucleotide receptors on astrocytes to stimulate the Ca2+‐dependent efflux of protons, mediated in part by activation of Na+/H+ exchange. The resulting acidification of the extracellular fluid may serve as an intercellular signal in brain. © 2004 Wiley‐Liss, Inc.
Reversible disruption of tight junction complexes in the rat blood‐brain barrier, following transitory focal astrocyte loss
Authors: Willis Colin L. , Leach Lopa , Clarke Garry J. , Nolan Christopher C. , Ray David E.
Published: April 2004

Breakdown of the blood‐brain barrier is a feature of acute and chronic neurodegenerative changes, yet the relationship between astrocytes and the mature barrier remains unclear. We studied this role of astrocytes in vivo using a gliotoxin and evaluated changes in three vascular tight junction markers. Male Fisher F344 rats given systemic 3‐chloropropanediol showed astrocytic loss in the inferior colliculus from 12–24 h until the lesion was repopulated 8–28 days later. Within 6 h of astrocyte loss, microvessels in this area began to demonstrate a loss of the normal paracellular localization of the transmembrane proteins occludin and claudin‐5 and cytoplasmic zonula occludens‐1, which correlated with focal vascular leak of dextran (10 kDa) and fibrinogen. Platelet endothelial adhesion molecule‐1 staining revealed that there was no loss of the endothelial lining. Between 4–8 days, severe downregulation of tight junction protein expression was observed, which subsequently returned over the same time period as astrocytes repopulated the lesion. Unexpectedly, dextran and fibrinogen leak from vessels had ceased at 6 days, well before the return of occludin and claudin‐5 to appropriate paracellular domains. Control nonvulnerable cortical tissue showed no change in astrocyte morphology and tight junction expression over the same time course. Our data supports a primary role for astrocytic contact in the expression of occludin, claudin‐5, and zonula occludens‐1 in the mature brain vasculature in vivo. However, barrier integrity to dextran (10 kDa) and fibrinogen can be restored in the absence of astrocytes and tight junction proteins (occludin, claudin‐5, and zonula occludens‐1). © 2004 Wiley‐Liss, Inc.
Model of frequent, recurrent, and spontaneous seizures in the intact mouse hippocampus
Authors: Derchansky M. , Shahar E. , Wennberg R.A. , Samoilova M. , Jahromi S.S. , Abdelmalik P.A. , Zhang L. , Carlen P.L.
Published: April 2004

This study presents a model of chronic, recurrent, spontaneous seizures in the intact isolated hippocampal preparation from mice aged P8–P25. Field activity from the CA1 pyramidal cell layer was recorded and recurrent, spontaneous seizure‐like events (SLEs) were observed in the presence of low Mg2+ (0.25 mM) artificial cerebrospinal fluid (ACSF). Hippocampi also showed interictal epileptiform discharges (IEDs) of 0.9–4.2 Hz occurring between seizures. No age‐specific differences were found in SLE occurrence (2 SLEs per 10 min, on average), duration, and corresponding frequencies. After long exposure to low Mg2+ ACSF (>3 h), SLEs were completely reversible within minutes with the application of normal (2 mM Mg2+) ACSF. The AMPA antagonist, CNQX, blocked all epileptiform activity, whereas the NMDA antagonist, APV, did not. The γ‐aminobutyric acid (GABA)A antagonist, bicuculline, attenuated and fragmented SLEs, implicating interneurons in SLE generation. The L‐type Ca2+ blocker, nifedipine, enhanced epileptiform activity. Analysis of dual site recordings along the septotemporal hippocampus demonstrated that epileptiform activity began first in the temporal pole of the hippocampus, as illustrated by disconnection experiments. Once an SLE had been established, however, the septal hippocampus was sometimes seen to lead the epileptiform activity. The whole hippocampus with intact local circuitry, treated with low Mg2+, provides a realistic model of recurrent spontaneous seizures, which may be used, in normal and genetically modified mice, to study the dynamics of seizures and seizure evolution, as well as the mechanisms of action of anti‐epileptic drugs and other therapeutic modalities. © 2004 Wiley‐Liss, Inc.
Infant communication and the mother–infant relationship: The importance of level of risk and construct measurement
Authors: Barwick Melanie A. , Cohen Nancy J. , Horodezky Naomi B. , Lojkasek Mirek
Published: April 2004

Infants' emerging communication skills are understood to be associated with the maternal relationship, particularly for children experiencing high levels of social risk. This study attempts to determine the extent to which this association is influenced by (a) the mental health risk of the dyad and (b) different operational definitions and measurement of both the dyadic relationship and the construct of “communication.” Ninety‐six infants (10–30 months) and their mothers were recruited: A total of 46 were at‐risk dyads referred to a mental health clinic for relationship‐based emotional and/or behavioral difficulties, and 50 were nonrisk dyads not seeking mental health services and served as a normative reference or comparison group. Several factors were assessed: (a) developmental competence, (b) maternal psychopathology, (c) quality of mother–infant interaction during play, (d) attachment security classification, (e) prelinguistic and social‐affective communication, and (f) linguistic communication. In all infants studied, the quality of mother–infant interaction during play, rather than the attachment security classification, was associated with infants' prelinguistic and social‐affective communication abilities, but not with linguistic communication. Different aspects of mother–infant interaction predicted prelinguistic communication for clinic and comparison infants whereas only infant age predicted linguistic communication. All infants displayed communication abilities in the normal range, but the statistically poorer performance demonstrated by clinic‐referred infants could become clinically meaningful in later childhood. Best practices should include communication screening of infants presenting with attachment problems and screening for relational difficulties in infants presenting with communication delays. ©2004 Michigan Association for Infant Mental Health.
AQS security scores: What do they represent? A study in construct validation
Authors: Van Bakel Hedwig J.A. , Riksen‐Walraven J. Marianne
Published: April 2004

In a sample of 129 Dutch 15‐month‐old infants, attachment security was assessed both with the Attachment Q‐Set (AQS; Waters, 1995) and with a short version of Ainsworth, Blehar, Waters, and Wall's (1978) Strange Situation (SSS). Infants classified as secure using the SSS had significantly higher AQS scores than insecure and disorganized infants in particular. At the AQS item level, disorganized infants were described as significantly more noncompliant, fussy, and angry relative to secure infants. When security as assessed using the SSS was controlled, the observed quality of parental interactive behavior, parental ego‐resilience, high levels of infant task orientation and pleasure, and low levels of infant anger proneness were found to explain significant and unique portions of the variance in the AQS security scores. The apparently unfavorable set of characteristics associated with low AQS security scores suggests such scores to predict later developmental problems. ©2004 Michigan Association for Infant Mental Health.
Mothers' interactions with temperamentally frustrated infants
Authors: Calkins Susan D. , Hungerford Anne , Dedmon Susan E.
Published: April 2004

A sample of 162 six‐month‐old infants was selected from a larger sample of 346 infants on the basis of mothers' report of their infants' temperament and a laboratory assessment of temperament. Infants were classified as easily frustrated or less frustrated and observed in several types of interactions with their mothers in the laboratory. Mothers completed several measures that indicated their level of parenting stress, psychological functioning, and marital adjustment. Maternal behavior with infants was coded along the dimensions of sensitivity, intrusiveness, and physical stimulation. Results indicated that maternal intrusiveness was related to infant temperament and that maternal physical stimulation was predicted by an interaction of infant temperament and mothers' perceived parenting stress. Implications of these findings for mother–infant interaction and subsequent child adjustment are discussed. ©2004 Michigan Association for Infant Mental Health.
Interval bigraphs and circular arc graphs
Authors: Hell Pavol , Huang Jing
Published: April 2004

We prove that the complements of interval bigraphs are precisely those circular arc graphs of clique covering number two, which admit a representation without two arcs covering the whole circle. We give another characterization of interval bigraphs, in terms of a vertex ordering, that we hope may prove helpful in finding a more efficient recognition algorithm than presently known. We use these results to show equality, amongst bipartite graphs, of several classes of structured graphs (proper interval bigraphs, complements of proper circular arc graphs, asteroidal‐triple‐free graphs, permutation graphs, and co‐comparability graphs). Our results verify a conjecture of Lundgren and disprove a conjecture of Müller. © 2004 Wiley Periodicals, Inc. J Graph Theory 46: 313–327, 2004
A novel movement disorder of the lower lip
Authors: Kleopa Kleopas A. , Kyriakides Theodoros
Published: April 2004

Four patients, aged 25 to 42 years presented with acute onset of a movement disorder characterized by a tonic, sustained, lateral and outward protrusion of one half of the lower lip. The movement disorder was present at rest, while in some patients, it was also present during speech. In all cases, the abnormal lip posture could be suppressed voluntarily. Neurological examination was otherwise normal. Extensive laboratory investigation failed to reveal any causative factors for secondary focal dystonia. Treatment with oral medications and botulinum toxin was mostly ineffective. Spontaneous remissions were frequent. © 2003 Movement Disorder Society
Neutronen sehen Spinorientierung auf Nanoskala
Authors: Weissmüller Jörg , Michels Andreas
Published: April 2004

Die attraktiven magnetischen Eigenschaften nanokristalliner Weichmagnete werden darauf zurückgeführt, dass bei geringer Kristallitgröße die Orientierung der Spins den Sprüngen in den magnetisch leichten Richtungen von Kristallit zu Kristallit nicht mehr folgen kann. Physiker am Forschungszentrum Karlsruhe konnten jüngst diese Vorhersage mit Neutronenstreuung überprüfen [1].
Teamarbeit im Supraleiter
Authors: Sparn Günter
Published: April 2004

Magnetismus und Supraleitung galten lange Zeit als gegensätzlich. Die Entdeckung von Supraleitung in einem Metall, das eine dichte Anordnung von magnetischen Ionen enthält, veränderte dieses Bild Ende der 1970er‐Jahre grundlegend.
Analysis of melting transitions in extended‐chain polymer crystals
Authors: Rein Dmitry M. , Khalfin Rafail L. , Cohen Yachin
Published: April 2004

It is a well‐known experimental observation that the melting transition of polymer crystals can be affected by an external constraint, force or pressure. This effect is enhanced in cases in which chain extension is maintained. In particular, the melting temperature of extended‐chain polyethylene fibers is elevated by increased hydrostatic pressure. We use the theoretical description of Elyashevich, Baranov, and Frenkel to analyze the effect of chain extension on the relative increase in the melting temperature. This model considers explicitly the entropy difference between the crystal and melt when a given degree of chain extension is maintained. We extend this interpretation to consider the melting of different metastable phases, using the melting enthalpy as a parameter. This can explain the observed metastability of the hexagonal phase of polyethylene in extended‐chain fibers under moderate pressure, as recently observed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2238–2244, 2004
Regulation of interleukin‐6‐mediated PI3K activation and neuroendocrine differentiation by androgen signaling in prostate cancer LNCaP cells
Authors: Xie Shaozhen , Lin Hui‐Kuan , Ni Jing , Yang Lin , Wang Liang , di Sant'Agnese P. Anthony , Chang Chawnshang
Published: April 2004

BACKGROUND

Neuroendocrine (NE) differentiation in prostate cancer has been suggested to be one of the early events in the development of androgen independence. In the human prostate cancer LNCaP cell line, treatment with interleukin‐6 (IL‐6) induces NE‐like differentiation, which is similar to the phenomena observed in advanced stages of prostate cancer progression. In this study, we investigate how androgen plays a role in IL‐6‐mediated NE differentiation in LNCaP cell line.

METHODS

Western blot, co‐immunoprecipitation (co‐IP), and GST pull‐down assays were performed to detect the protein expression and protein–protein interaction. PI3K kinase assay was used to measure PI3K activity.

RESULTS

Addition of androgen blocks IL‐6‐mediated PI3K activation and NE differentiation in LNCaP cells. In vivo and in vitro protein interaction assays suggested that androgen receptor (AR) can directly interact with IL‐6 transducer gp130. In addition, androgen treatment enhances the interaction between AR and gp130, interrupts the IL‐6‐induced gp130‐mediated PI3K activation, which may lead to inhibition of IL‐6‐mediated NE differentiation in LNCaP cells.

CONCLUSIONS

Our results suggest androgen and AR can regulate IL‐6‐mediated LNCaP cell NE differentiation via directly modulating the IL‐6‐PI3K pathway. © 2004 Wiley‐Liss, Inc.
Viroids: the minimal non‐coding RNAs with autonomous replication
Authors: Flores Ricardo , Delgado Sonia , Gas Marı́a-Eugenia , Carbonell Alberto , Molina Diego , Gago Selma , De la Peña Marcos
Published: April 2004

Viroids are small (246–401 nucleotides), non‐coding, circular RNAs able to replicate autonomously in certain plants. Viroids are classified into the families Pospiviroidae and Avsunviroidae, whose members replicate in the nucleus and chloroplast, respectively. Replication occurs by an RNA‐based rolling‐circle mechanism in three steps: (1) synthesis of longer‐than‐unit strands catalyzed by host DNA‐dependent RNA polymerases forced to transcribe RNA templates, (2) processing to unit‐length, which in family Avsunviroidae is mediated by hammerhead ribozymes, and (3) circularization either through an RNA ligase or autocatalytically. Disease induction might result from the accumulation of viroid‐specific small interfering RNAs that, via RNA silencing, could interfere with normal developmental pathways.
Yeast activator proteins and stress response: an overview
Authors: Rodrigues-Pousada Claudina Amélia , Nevitt Tracy , Menezes Regina , Azevedo Dulce , Pereira Jorge , Amaral Catarina
Published: April 2004

Yeast, and especially Saccharomyces cerevisiae, are continuously exposed to rapid and drastic changes in their external milieu. Therefore, cells must maintain their homeostasis, which is achieved through a highly coordinated gene expression involving a plethora of transcription factors, each of them performing specific functions. Here, we discuss recent advances in our understanding of the function of the yeast activator protein family of eight basic‐leucine zipper trans‐activators that have been implicated in various forms of stress response.
Chemical cues and binary individual recognition in the hermit crab Pagurus longicarpus
Authors: Gherardi Francesca , Tiedemann John
Published: April 2004

The behaviour exhibited by the hermit crab Pagurus longicarpus in response to an empty shell varied in the presence of cues from conspecific individuals according to its familiarity or not with them. This binary discrimination was independent of the conspecific's relative size and was based on chemical signatures, an ability that this species shares with a few other aquatic invertebrates. From our results, olfaction appeared to be the dominant sensory channel in P. longicarpus' binary discrimination, but the combination of two signal components from visual and olfactory channels resulted in the enhancement of the response displayed by the receiver. Besides, crabs reacted differently when exposed to their own odour than to the odour of familiar (as well as unfamiliar) conspecifics, suggesting that recognition in this species can be more refined than a binary discrimination and that chemical ‘badges’ may be attributes of individual crabs.
A telemetry study of the social organization of a tawny owl (Strix aluco) population
Authors: Sunde Peter , Bølstad Mikkel S.
Published: April 2004

The spatial dispersion and social interactions were studied in 11 neighbouring pairs of radio‐tagged tawny owls Strix aluco in a deciduous wood in Denmark from 1998–2001. The numbers and shapes of territories were stable throughout the survey and similar to a mapping made 40 years earlier. The home ranges of mates were of equal size and overlapped 82% in summer and 56% in winter. The inter‐mate distances were on average 2.7% shorter than expected by chance. The activity distribution of neighbouring pairs overlapped 9% (95% CI: 2–15%) on average. Males and females did not differ in overlap with neighbours, and there was a similar overlap between neighbours of the same and opposite sex. Both sexes vocalized more often in the peripheries than in the centres of their territory. The vocal activity during May–September varied extensively among years and months in accordance with variation in the density of juvenile floaters. Males and females vocalized equally often and were involved in disputes with neighbours at similar rates. Usually, neighbouring disputes involved either one individual from each pair or all four. Disputes involving all four owls more often involved chasing and fighting than those involving one owl only from each pair. The dispute rate between neighbouring pairs correlated positively with home‐range overlap. The total annual mortality was 21% (95% CI: 6–33%). Dead owners were usually replaced within 1–2 months. Two out of four cases of radio‐tagged owls disappearing from their territory because of natural causes was due to take‐overs by invading owls, suggesting that the risk of losing fitness resulting from eviction was important. The apparent co‐operative territorial behaviour of tawny owl pairs is probably due to improved resource holding potential of pair coalitions compared to single individuals.
Enhanced vigilance in groups in Egernia stokesii, a lizard with stable social aggregations
Authors: Lanham Elvira J. , Bull C. Michael
Published: April 2004

The Australian gidgee skink Egernia stokesii is unusual among lizards in that it maintains stable social aggregations of related individuals. Experiments were conducted to investigate whether lizards living in groups gained benefits from the collective detection of approaching threats. In captive colonies, lizards living in a group detected an approaching threat earlier than lizards alone, and lizards basking in a group spent more time in a non‐vigilant, eyes‐closed, state than lizards alone. These results imply that individuals in this species gain from the enhanced vigilance associated with group membership. Since many juveniles remain within their natal groups, group vigilance may enhance inclusive fitness.
Duelling, the death wish, and the supposed suicide of Pierre Aubry
Authors: Collamore Lila
Published: April 2004

I read with special interest the article by John Haines published several years ago in Plainsong and Medieval Music on the death of Pierre Aubry (‘The ‘‘modal theory”, fencing, and the death of Aubry’, 6 [1997], 143–50). While I thank him for clearing up the rumours of a duel with Jean Beck resulting in Aubry's death, I must admit to disappointment in having to abandon the idea that Aubry and Beck fought a duel over a musicological disagreement. Haines's conclusion that the fencing accident that resulted in Aubry's death was a ‘suicide in disguise’ is, however, untenable, whatever Aubry's state of mind at the time might have been. The fact that this theory has been repeated as fact (‘Généalogies musicologiques’, Acta Musicologica, 73 [2001], 24) prompts the present communication.
The safeguards mess: a critique of WTO jurisprudence
Authors: SYKES ALAN O.
Published: April 2004

The creation of the WTO revived the use of ‘safeguard’ measures to protect troubled industries against surges in import competition. Many of these measures have now been challenged in the WTO dispute resolution process, and in each case the process has found the challenged measure to be a violation of WTO law. This paper examines the WTO rules on safeguards from an economic perspective. Among other things, it argues that the textual preconditions for the use of safeguards in the treaty text are incoherent, and that the Appellate Body has compounded the problem through a series of dubious and unhelpful rulings. The result is a situation in which nations cannot use safeguards without facing a near certainty that they will be found invalid. Those who believe that safeguard measures are wasteful protectionism may welcome these developments, but it is by no means clear that the trading system will benefit in the long run.
Nondiscrimination and the WTO Agreement on Safeguards
Authors: BOWN CHAD P. , McCULLOCH RACHEL
Published: April 2004

Most-favored-nation treatment, i.e., nondiscrimination among trading partners, is a fundamental principle of the GATT/WTO system. The WTO Agreement on Safeguards has thus been seen as encouraging use of a preferred form of contingent protection relative to antidumping and other inherently discriminatory measures. In practice, however, safeguard protection may also incorporate discriminatory elements. This paper focuses on three ways that policies conforming to the Agreement on Safeguards may nonetheless discriminate explicitly or implicitly among trading partners. First, the form of the safeguard policy matters: quantitative restrictions discriminate among foreign suppliers by preserving historical market shares more than a safeguard implemented as a tariff. Second, safeguard measures discriminate against faster-growing exporters and new entrants in import markets. Third, formal exemptions for partners in preferential trade agreements and for small developing-country suppliers allow these countries to gain market share at the expense of non-exempted exporters. We provide evidence of these discriminatory effects in actual cases of safeguard protection.
Causing problems? The WTO review of causation and injury attribution in US Section 201 cases
Authors: IRWIN DOUGLAS A.
Published: April 2004

US safeguard actions have run into problems with the WTO's panel and Appellate Body reviews for failing to ensure that injury caused by non-import factors is not attributed to imports. This paper reviews the subtle legal and economic differences between US trade law (Section 201) and the WTO's Agreement on Safeguards on the non-attribution issue. The paper then resurrects the Kelly (1988) method of attributing injury to various factors as a potential method by which the ITC can ensure that future decisions conform with the Safeguards Agreement. The method is shown to yield results that are consistent with recent ITC safeguard decisions.
Sunspot cycle‐dependent changes in the distribution of GSE latitudinal angles of IMF observed near 1 AU
Authors: Felix Pereira B. , Girish T. E.
Published: April 2004

The solar cycle variations in the characteristics of the GSE latitudinal angles of the Interplanetary Magnetic Field (θGSE) observed near 1 AU have been studied for the period 1967–2000. It is observed that the statistical parameters mean, standard deviation, skewness and kurtosis vary with sunspot cycle. The θGSE distribution resembles the Gaussian curve during sunspot maximum and is clearly non‐Gaussian during sunspot minimum. The width of the θGSE distribution is found to increase with sunspot activity, which is likely to depend on the occurrence of solar transients. Solar cycle variations in skewness are ordered by the solar polar magnetic field changes. This can be explained in terms of the dependence of the dominant polarity of the north‐south component of IMF in the GSE system near 1 AU on the IMF sector polarity and the structure of the heliospheric current sheet.
Coral radiocarbon records of Indian Ocean water mass mixing and wind‐induced upwelling along the coast of Sumatra, Indonesia
Authors: Grumet N. S. , Abram N. J. , Beck J. W. , Dunbar R. B. , Gagan M. K. , Guilderson T. P. , Hantoro W. S. , Suwargadi B. W.
Published: April 2004

Radiocarbon (14C) in the skeletal aragonite of annually banded corals track radiocarbon concentrations in dissolved inorganic carbon (DIC) in surface seawater. As a result of nuclear weapons testing in the 1950s, oceanic uptake of excess 14C in the atmosphere has increased the contrast between surface and deep ocean 14C concentrations. We present accelerator mass spectrometric (AMS) measurements of 14C/12C ratios (Δ14C) in Porites corals from the Mentawai Islands, Sumatra (0°S, 98°E) and Watamu, Kenya (3°S, 39°E) to document the temporal and spatial evolution of the 14C zonal gradient in the tropical Indian Ocean. The rise in Δ14C in the Sumatra coral, in response to the maximum in nuclear weapons testing, is delayed by 2–3 years relative to the rise in coral Δ14C from the coast of Kenya. Kenya coral Δ14C values rise quickly because surface waters are in prolonged contact with the atmosphere. In contrast, wind‐induced upwelling and rapid mixing along the coast of Sumatra entrains 14C‐depleted water from the subsurface, which dilutes the effect of the uptake of bomb‐produced 14C by the surface ocean. Bimonthly AMS Δ14C measurements on the Mentawai coral reveal mainly interannual variability with minor seasonal variability. Singular spectrum analysis of the Sumatra coral Δ14C record reveals a significant 3‐year periodicity. These results lend support to the concept that interannual variability in Indian Ocean upwelling and sea surface temperatures is related to ENSO‐like teleconnections over the Indo‐Pacific basin.
Turbulent energy production and entrainment at a highly stratified estuarine front
Authors: MacDonald Daniel G. , Geyer W. Rockwell
Published: April 2004

Rates of turbulent kinetic energy (TKE) production and buoyancy flux in the region immediately seaward (∼1 km) of a highly stratified estuarine front at the mouth of the Fraser River (British Columbia, Canada) are calculated using a control volume approach. The calculations are based on field data obtained from shipboard instrumentation, specifically velocity data from a ship mounted acoustic Doppler current profiler (ADCP), and salinity data from a towed conductivity‐temperature‐depth (CTD) unit. The results allow for the calculation of vertical velocities in the water column, and the total vertical transport of salt and momentum. The vertical turbulent transport quantities (, ) can then be estimated as the difference between the total transport and the advective transport. Estimated production is on the order of 10−3 m2 s−3, yielding a value of ɛ(νN2)−1 on the order of 104. This rate of TKE production is at the upper limit of reported values for ocean and coastal environments. Flux Richardson numbers in this highly energetic system generally range from 0.15 to 0.2, with most mixing occurring at gradient Richardson numbers slightly less than . These values compare favorably with other values in the literature that are associated with turbulence observations from regimes characterized by scales several orders of magnitude smaller than are present in the Fraser River.
Reconstructed warm season temperatures for Nome, Seward Peninsula, Alaska
Authors: D'Arrigo Rosanne , Mashig Erika , Frank David , Jacoby Gordon , Wilson Rob
Published: April 2004

Understanding of past climate variability in the Bering Strait region and adjacent land areas is limited by a paucity of long instrumental and paleoclimatic records. Here we describe a reconstruction of May–August temperatures for Nome, Seward Peninsula, Alaska based on maximum latewood density data which considerably extends the available climatic information. The reconstruction shows warm conditions in the late 1600s and middle‐20th century and cooler conditions in the 1800s. The summer of 1783, coinciding with the Laki, Iceland volcanic event, is among the coldest in the reconstruction. Statistically significant relationships with the North Pacific Index and Bering‐Chukchi sea surface temperatures indicate that the Seward tree‐ring data are potentially useful as long‐term indices of atmosphere‐ocean variability in the region.
The effect of short‐term cortisol changes on growth hormone responses to the pyridostigmine‐growth‐hormone‐releasing‐hormone test in healthy adults and patients with suspected growth hormone deficiency
Authors: Andersen Marianne , Støving Rene K. , Hangaard Jørgen , Petersen Per H. , Hagen Claus
Published: April 2004

BACKGROUND AND AIMS

The interaction between cortisol and growth hormone (GH)‐levels may significantly influence GH‐responses to a stimulation test. In order to systematically analyse the interaction in a paired design, it is necessary to use a test, which has been proven safe and reliable such as the pyridostigmine‐growth‐hormone‐releasing‐hormone (PD‐GHRH) test. Three groups of subjects with a different GH‐secretory capacity were included.

STUDY A

Eight healthy adults were tested seven times, once with placebo throughout the examination and six times with the PD‐GHRH test following no glucocorticoid pretreatment, pretreatment with hydrocortisone (HC) (30 mg/day and 80 mg/day for 1 and 3 days) or pretreatment with 15 mg prednisolone for 1 day. HC (80 mg/day for 1 day) in combination with PD significantly stimulated GH‐levels compared to PD alone, 18.9 mU/l ± 6.1 vs 3.0 mU/l ± 0.8 (P < 0.05). However, peak GH‐responses to PD in combination with GHRH were reduced during HC (80 mg/day for 1 day) compared to no glucocorticoid pretreatment in all healthy adults. Conventional HC therapy (30 mg/day for 1 and 3 days) did not significantly affect peak GH‐responses.

STUDY B

16 patients with suspected GH‐deficiency (GHD) (seven with known ACTH‐deficiency and nine with an intact pituitary‐adrenal axis) were tested five times with the PD‐GHRH test following no pretreatment or pretreatment with HC (30 mg/day and 80 mg/day for 1 and 3 days). Peak GH‐responses were not significantly affected by conventional HC therapy (30 mg/day for 1 and 3 days). However, peak GH‐responses to PD in combination with GHRH were reduced during HC (80 mg/day for 1 day) compared to no glucocorticoid pretreatment in all patients. Short‐term hypocortisolism did not significantly affect peak GH‐responses.

CONCLUSION

The GH‐responses to a PD‐GHRH test were reduced in all individuals during acute stress‐appropriate cortisol levels and the percentage reduction in GH‐levels was independent of the GH‐secretory capacity. Clinically, we found that peak GH‐responses were not significantly affected by a short break in conventional HC therapy nor by conventional HC therapy itself. However, our results also demonstrated that a GH‐stimulation test should not be performed on patients, suffering from acute stress.
Stokes flow through a channel with three-dimensional bumpy walls
Authors: Wang C. Y.
Published: April 2004

The viscous flow in a minute channel with three-dimensional bumpy walls is analyzed by perturbations using the small amplitude to channel width ratio. It is found that the bumpiness causes changes in velocity, shear stress, and vorticity. The channel resistance may be increased or decreased by the bumps. There exist optimum protrusion aspect ratios for maximum flow.
Failure analysis of the molecular block model for the direct simulation Monte Carlo method
Authors: Wang Moran , Li Zhixin
Published: April 2004

The present Brief Communication analyzed and demonstrated the failures of the molecular block (MB) model for the direct simulation Monte Carlo (DSMC) method. In the MB model, the gas viscosity and Knudsen number remained the same but the Mach number increased with the MB factor α. Therefore, the flow predicted by the MB model failed to agree with the original flow. Micro Couette flows and microchannel flows were simulated to demonstrate this point. Significant differences were found between results from the MB model and the original DSMC method. When α was large enough so that the Mach number in the MB model exceeded unity, a shock wave appeared in the channel, when there were no shocks in the original subsonic flow.
Quantitative nanofriction characterization of corrugated surfaces by atomic force microscopy
Authors: Podestà A. , Fantoni G. , Milani P.
Published: April 2004

Atomic force microscopy (AFM) is a suitable tool to perform tribological characterization of materials down to the nanometer scale. An important aspect in nanofriction measurements of corrugated samples is the local tilt of the surface, which affects the lateral force maps acquired with AFM. This is one of the most important problems of state-of-the-art nanotribology, hampering a reliable and quantitative characterization of real corrugated surfaces. In this article, we present a solution to the problem of the topographic correction of AFM lateral force maps acquired on corrugated samples in the presence of adhesion. We apply it in the specific case of multiasperity adhesive contacts, which are of common occurrence at many interfaces of technological interest. We discuss the validity and limitations of our approach.
Determination of the in-plane microwave conductivity of superconducting films
Authors: Görlitz Detlef , Dölling Dirk , Kötzler Jürgen
Published: April 2004

We report measurements of the complex resonance frequency, f̃r=fr+iΔf, of a helical resonator (fr=0.45 GHz) and a cylindrical cavity (fr=21.3 GHz), both loaded with a 50 nm thin YBa2Cu2O7−δ film (Tc=86 K) on a MgO disk, between 50 K and 250 K. The film is placed normal to the (maximum) magnetic rf field, and kept small enough for the cavity perturbation to be valid, so that the shifts δf̃r=f̃r(T)−f̃r(0) are proportional to the magnetic permeability 1+χ(ω). We employ superconducting quantum interference device susceptibilities to calibrate fr at low temperatures and, from the susceptibility χ(ω), we determine the in-plane conductivity σ(ω) by means of an exact inversion routine. The capability of this method is demonstrated: (i) by the agreements of σ′(ω,T>Tc) with the dc conductivity and of ωσ″(ω,T≲Tc) with existing low-frequency data and (ii) by the peak temperature of σ′(ω,T), which is consistent with the Arrhenius behavior, previously detected between 30 mHz and 1 MHz.
Gas-gun reverse-ballistic technique for multiple-particle impacts
Authors: Holt William H. , Mock Willis
Published: April 2004

A reverse-ballistic impact technique is described for multiple impacts of macroscopic particles on a disk of material. The disk is accelerated in a sabot. The spatial and temporal separation of the particles can be controlled by the relative positions of the particles in a frangible mechanical support. Example results for closely spaced simultaneous impacts of multiple steel spheres with steel disks show synergistic effects in the perforation response of the disks. A hollow sabot design permits the sabot to move past the disk and spheres after impact, to minimize the influence of the sabot on the perforation process. Experiments have been performed at speeds up to 970 m/s.
Double-grating polychromator for laser-aided plasma diagnostics
Authors: Mukhin E. E. , Razdobarin G. T. , Semenov V. V. , Shilnikov A. N. , Sukhanov V. L. , Tolstjakov S. Yu. , Kochergin M. M. , Mihailovskij Yu. K. , Bakh L. I.
Published: April 2004

A wide bandpass double-grating polychromator with high rejection and high transmission has been designed and manufactured for laser-aided plasma diagnostics. The special mount utilizes subtractive dispersion in the second stage of the double polychromator such that the larger dispersion of the second stage is reduced by that of the first stage. This affects the intensity of the stray light background at the laser wavelength. The background at the edge of the laser line was measured at 10−5 of the light incident on the input slit. At the short end of the 200 nm bandpass, the stray light relative intensity approached 10−7.