bluuebunny/crossref_metadata_2025_split huggingface dataset:
The partition‐of‐unity method for linear diffusion and convection problems: accuracy, stabilization and multiscale interpretation
Authors: Munts E. A. , Hulshoff S. J. , des Borst R. 
Published: August 2003

AbstractWe investigate the effectiveness of the partition‐of‐unity method (PUM) for convection–diffusion problems. We show that for the linear diffusion equation, an exponential enrichment function based on an approximation of the analytic solution leads to improved accuracy compared to the standard finite‐element method. It is illustrated that this approach can be more efficient than using polynomial enrichment to increase the order of the scheme. We argue that the PUM enrichment, can be interpreted as a subgrid‐scale model in a multiscale framework, and that the choice of enrichment function has consequences for the stabilization properties of the method. The exponential enrichment is shown to function as a near optimal subgrid‐scale model for linear convection. Copyright © 2003 John Wiley & Sons, Ltd.
A substructure‐based iterative inner solver coupled with Uzawa's algorithm for the Stokes problem
Authors: Zsaki Attila , Rixen Daniel , Paraschivoiu Marius 
Published: August 2003

AbstractA domain decomposition method with Lagrange multipliers for the Stokes problem is developed and analysed. A common approach to solve the Stokes problem, termed the Uzawa algorithm, is to decouple the velocity and the pressure. This approach yields the Schur complement system for the pressure Lagrange multiplier which is solved with an iterative solver. Each outer iteration of the Uzawa procedure involves the inversion of a Laplacian in each spatial direction. The objective of this paper is to effectively solve this inner system (the vector Laplacian system) by applying the finite‐element tearing and interconnecting (FETI) method. Previously calculated search directions for the FETI solver are reused in subsequent outer Uzawa iterations. The advantage of the approach proposed in this paper is that pressure is continuous across the entire computational domain. Numerical tests are performed by solving the driven cavity problem. An analysis of the number of outer Uzawa iterations and inner FETI iterations is reported. Results show that the total number of inner iterations is almost numerically scalable since it grows asymptotically with the mesh size and the number of subdomains. Copyright © 2003 John Wiley & Sons, Ltd.
Preparation of Gas Diffusion Electrodes with Silver Catalysts for Alkaline Fuel Cells
Authors: Gülzow E. , Wagner N. , Schulze M. 
Published: August 2003

AbstractIn alkaline fuel cells (AFC) silver can be used as the cathode catalyst in gas diffusion electrodes. To prepare the gas diffusion electrodes, the metal catalyst was mixed with polytetraflourethylene (PTFE), as the organic binder, in a knife mill and rolled onto a metal web in a calender. The electrodes are manufactured as an endless tape with a thickness of approx. 0.4 mm and widths of up to 20 cm. Raney‐silver, carbon supported silver, or silver deposited as a closed film on PTFE are used as the catalyst. In the gas diffusion electrode preparation process the silver catalyst can be used in this oxidized form. Before using the gas diffusion silver cathodes in the alkaline fuel cell the catalyst will be reduced to the metallic form.
Optical Measurements of Platinum Based Electrocatalysts for the Electrooxidation of Methanol
Authors: Gruber K. , Kronberger H. , Fafilek G. , Nauer G. , Besenhard J.‐O. 
Published: August 2003

AbstractIn a combinatorial electrochemistry experiment quinine was used as a pH sensitive fluorescing indicator to detect the catalytic activity of methanol oxidation catalysts. During electrochemical experiments the surface of the electrode array was monitored with a CCD camera. The dependence of the intensity of the fluorescence on the applied potential was used as an analytical tool; to investigate the electrochemical performance of Pt based electrocatalysts, for the electrooxidation of methanol, in both short and long term tests.
Progress in DMFC Development Using the Dry Spraying Preparation Technique
Authors: Gülzow E. , Reissner R. , Weisshaar S. , Kaz T. 
Published: August 2003

AbstractA dry MEA (membrane electrode assembly) preparation technique developed at DLR was applied to DMFC (direct methanol fuel cell) MEAs using different preparation parameters. It turned out that for cathode and anode backings with high hydrophobicity the high current density performance of the MEA at low cathode airflow and thus low stoichiometry is better than for backings with low hydrophobicity. The anode reaction layer does not need to contain Nafion™. It has been demonstrated that at catalyst loadings similar to or lower than generally reported, power densities of technical interest are within reach.
Membrane Durability in a PEM Fuel Cell Studied Using PVDF Based Radiation Grafted Membranes
Authors: Gode P. , Ihonen J. , Strandroth A. , Ericson H. , Lindbergh G. , Paronen M. , Sundholm F. , Sundholm G. , Walsby N. 
Published: August 2003

AbstractThe durability testing of membranes for use in a polymer electrolyte fuel cell (PEFC) has been studied in situ by a combination of galvanostatic steady‐state and impedance measurements. The PEFC measurements, which are time consuming, have been compared to fast ex situ testing in 3% H2O2 solution. For the direct assessment of membrane degradation micro‐Raman spectroscopy and determination of ion exchange capacity (IEC) have been used. PVDF based membranes, radiation grafted with styrene and sulfonated, were used as model membranes. By using low degrees of grafting, below about 35%, the durability of this type of membrane can be increased. Degradation in the fuel cell was found to be highly localised. It was found that in situ measurements in the PEFC alone are not sufficient. Measurement of the cell resistance via impedance is not always a reliable indicator of changes in membrane resistance because other resistance changes in the cell can easily interfere and cannot be separated from those caused by the membrane. Micro‐Raman is an ideal complementary method to in situ testing, but it is time consuming. For fast pre‐screening of membrane durability mass loss measurements during exposure to 3% H2O2 solution combined with the determination of changes in the IEC can be performed.
Hydrogen Evolution on Zeolite Supported Platinum Clusters
Authors: Mentus S. , Mojovic Z. , Cvjeticanin N. , Tesic Z. 
Published: August 2003

AbstractNaX type zeolite was loaded with platinum, by the thermal decomposition of Pt(II) acetylacetonate, up to the Pt/NaX mass ratio of 0.174. The sample, dispersed on a glassy carbon rotating disc, was used in slightly acidic solution to observe the kinetics of the hydrogen evolution reaction. A comparison was made with the rate of hydrogen evolution on smooth polycrystalline platinum, and both slower and faster evolution rates were observed, depending on the percentage of carbon black added to the zeolite sample.
Electro‐Oxidation of Methanol and Ethanol on Poly(3,4‐Ethylenedioxythiophene) with Dispersed Pt, Pt + Sn, and Pt + Pb Particles
Authors: Biallozor S. , Kupniewska A. , Jasulaitene V. 
Published: August 2003

AbstractThe influence of tin and lead additives on the catalytic activity of platinum particles dispersed on a poly(3,4‐dioxyethylenethiophene) (PEDT) layer deposited on gold or steel towards anodic oxidation of methanol and ethanol was studied. It was found that these additives increase the rate of anodic oxidation of both alcohols. It was also found that the electro‐catalytic properties of PEDT depend on the kind of support used for its deposition.The authors have shown that these additives (Pb and Sn) increase the rate of anodic oxidation of both alcohols on platinum deposited on PEDT, but tin was evidently more effective than lead. In the presence of Sn, the steady‐state current density of methanol oxidation increases about 100 times, while Pb only promotes the platinum catalyst activity by about 2 times. In the authors opinion the most probable mechanism for the tin promotion effect seems to be a homogenous catalytic reaction with the participation of the Sn (IV) and Sn (II) ions as mediators.
A Method for Characterizing CO Transients in a PEMFC
Authors: Lee W.‐k. , Van Zee J.W. , Murthy M. 
Published: August 2003

AbstractA method for characterizing the response of a PEMFC to transients in the CO concentration in the fuel is presented. The method uses the well‐known First Order Plus Dead Time (FOPDT) model to separate the system effects from the poisoning characteristics of CO as a function of concentration and dosage. The method is more representative of the data and should be used as an alternative to a simple slope measurement for reporting the experimental data of the poisoning and recovery processes. The results characterize a specific MEA by showing that the time constant for the poisoning process is extended from 4 – 48 s when 15% air was injected with an anode stream of 3,000 ppm CO/H2. For the recovery process, a 15% air‐bleed reduces the dead time from 122 – 36 s and the time constant from 89 – 18 s. In addition, the gain is shown to be relatively independent of the high CO concentrations but it is affected by air bleeding. The gain changes from –0.10 to –0.08 mV/ppm CO for a poisoning process and from 0.09 – 0.08 mV/ppm CO for a recovery process with 15% air bleeding in the 3,000 ppm CO/H2. In general, the dead times and time constants for the poisoning process decreased as the CO concentrations increased at equal CO dosage. On the other hand, these parameters (dead time and time constant) for the recovery process increased as the CO concentration increased at equal CO dosage. The method is critical for comparison of the dynamic response of MEAs between laboratories and for the design of reformate fuel‐processing systems.
Operation of Direct Methanol Fuel Cell in a Centrifugal Field
Authors: Cheng H. , Scott K. , Ramshaw C. 
Published: August 2003

AbstractDirect methanol fuel cells were operated and evaluated in a centrifugal field. It was observed that the methanol oxidation was significantly intensified in a centrifugal field. The application of centrifugal fields greatly enhanced mass transfer and accelerated gas bubble disengagement from the electrode surfaces, the electrolytes and the membrane during the methanol oxidation. The high acceleration field caused a significant reduction in the anode potential up to 500 mV at 300 mA cm–2 at a relative acceleration rate of 190 g and 80 °C. Increases in methanol concentration and operating temperature contributed to increase the methanol oxidation rate. These beneficial effects were improved further in a centrifugal field, compared to the gravitational field. A beneficial effect of the centrifugal field on the direct methanol fuel cell performance was observed. More effort is required to guarantee efficient oxygen supply to the cathode under the centrifugal acceleration conditions and thus to increase power output by this particular approach.
Looking for contagion in currency futures markets
Authors: Tai Chu‐Sheng 
Published: August 2003

AbstractThis article tests whether there are pure contagion effects in both conditional means and volatilities among
British pound, Canadian dollar, Deutsche mark, and Swiss franc futures markets during the 1992 ERM crisis. A
conditional version of international capital asset pricing model (ICAPM) in the absence of purchasing
power parity (PPP) is used to control for economic fundamentals. The empirical results indicate that
overall there are no mean spillovers among those futures markets, but they are detected during the crisis
period. That is, past return shocks originating in any one of the four markets have no impact on the other three
markets during the entire sample period, suggesting that these markets are weak‐form efficient. However,
this weak‐form market efficiency fails to hold during the market turmoil, especially for British pound
and Swiss franc, and the sources of contagion‐in‐mean effects are mainly due to the return shocks
originating in three European currency futures markets. As for the contagion‐in‐volatility, it is
detected for British pound only because its conditional volatility is influenced by the negative volatility
shocks from Canadian dollar, Deutsche mark, and Swiss franc, with Deutsche mark playing the dominant role in
generating these shocks. JEL Classifications: C32; F31; G12. © 2003 Wiley Periodicals, Inc. Jrl Fut Mark
23:957–988, 2003
A first look at the empirical relation between spot and futures electricity prices in the United States
Authors: Shawky Hany A. , Marathe Achla , Barrett Christopher L. 
Published: August 2003

AbstractIn this article we investigate the statistical properties of wholesale electricity spot and futures prices
traded on the New York Mercantile Exchange for delivery at the California–Oregon Border. Using daily data
for the years 1998 and 1999, we find that many of the characteristics of the electricity market can be viewed to
be broadly consistent with efficient markets. The futures risk premium for 6‐month futures contracts is
estimated to be 0.1328% per day or about 4% per month. Using a GARCH specification, we estimate
minimum variance hedge ratios for electricity futures. Finally, we study the dynamic relation between spot and
futures prices using an Exponential GARCH model and between the spot and futures returns series using a vector
autoregression. © 2003 Wiley Periodicals, Inc. Jrl Fut Mark 23:931–955, 2003
On the adequacy of single‐stock futures margining requirements
Authors: Dutt Hans R. , Wein Ira L. 
Published: August 2003

AbstractUnlike the traditional futures contract risk‐based approach to margining, new security futures
contracts
are margined under a strategy‐based margining system similar to that which applies in the equity options
markets. As a result, these new margin requirements are potentially much less sensitive to changes in market
conditions. This article performs a simulation to evaluate whether these alternative margining methodologies can
be
expected to produce comparable outcomes. The analysis suggests that a 1‐day settlement period will likely
lead to collection of customer margins that are virtually always greater than that which its traditional
risk‐based counterpart would require. A 4‐day settlement period would lead to margin requirements
that both significantly under‐ and overmargin relative to a comparable risk‐based system. This
study
argues that exchanges may approach the preferred probability of customer exhaustion by managing margin
settlement
intervals. Thus, the new strategy‐based rules, in and of themselves, will not necessarily inhibit new
security futures trading activity. © 2003 Wiley Periodicals, Inc. Jrl Fut Mark 23:989–1002, 2003
Commodity trading advisors' leverage and reported margin‐to‐equity ratios
Authors: Diz Fernando 
Published: August 2003

AbstractWe investigate the effect of leverage on Commodity Trading Advisors' (CTAs) performance
measurement. We find that leverage has important effects on the cross section of CTA returns, volatility, and
survival experience. On average, a 100‐basis points increase in leverage is associated with a
27‐basis points increase in returns. After performance is adjusted for leverage, volatility, and survival
experience, CTAs' style variables have no significant effect on performance. The amount of leverage used by a
CTA is found to reduce the likelihood of survival. However, the total effect of leverage on survival is much
smaller than its partial effect. Contrary to common beliefs, we find that CTA diversification leads to higher
levels of leverage and volatility. This apparent contradiction is related to how the diversification process
affects the use of leverage. The findings in this study have implications for measuring and comparing
managers' performance track records. © 2003 Wiley Periodicals, Inc. Jrl Fut Mark 23:1003–1017,
2003
Approximating American option prices in the GARCH framework
Authors: Duan Jin‐Chuan , Gauthier Geneviève , Sasseville Caroline , Simonato Jean‐Guy 
Published: August 2003

AbstractThis article proposes an efficient approach for computing the prices of American style options in the GARCH
framework. Rubinstein's (1998) Edgeworth tree idea is combined with the analytical formulas for
moments of the cumulative return under GARCH developed in Duan et al. (1999, 2002) to yield a simple
recombining binomial tree for option valuation in the GARCH context. Because the resulting tree is univariate, the
proposed approach represents a convenient approximation of the bivariate GARCH system. Numerical analysis is used
to demonstrate the speed and accuracy of the proposed approximation. © 2003 Wiley Periodicals, Inc. Jrl Fut
Mark 23:915–929, 2003
Disruption of a novel gene, DIRC3, and expression of DIRC3‐HSPBAP1 fusion transcripts in a case of familial renal cell cancer and t(2;3)(q35;q21)
Authors: Bodmer Daniëlle , Schepens Marga , Eleveld Marc J. , Schoenmakers Eric F.P.M. , Geurts van Kessel Ad 
Published: August 2003

AbstractPreviously, we identified a family with renal cell cancer and a t(2;3)(q35;q21). Positional cloning of the chromosome 3 breakpoint led to the identification of a novel gene, DIRC2, that spans this breakpoint. Here we have characterized the chromosome 2 breakpoint in detail and found that another novel gene, designated DIRC3, spans this breakpoint. In addition, we found that the first two exons of DIRC3 can splice to the second exon of HSPBAP1, a JmjC‐Hsp27 domain gene that maps proximal to the breakpoint on chromosome 3. This splice results in the formation of DIRC3‐HSPBAP1 fusion transcripts. We propose that these fusion transcripts may affect normal HSPBAP1 function and concomitant chromatin remodeling and/or stress response signals within t(2;3)(q35;q21)‐positive kidney cells. As a consequence, familial renal cell cancer may develop. © 2003 Wiley‐Liss, Inc.
High‐resolution comparative genomic hybridization detects extra chromosome arm 12p material in most cases of carcinoma in situ adjacent to overt germ cell tumors, but not before the invasive tumor development
Authors: Ottesen Anne Marie , Skakkebæk Niels E. , Lundsteen Claes , Leffers Henrik , Larsen Jacob , Rajpert‐De Meyts Ewa 
Published: August 2003

AbstractHigh‐resolution comparative genomic hybridization (HR‐CGH) analysis was performed on DNA purified from laser‐capture microdissected carcinoma in situ (CIS) cells from nine cases of CIS, either from tissue without any invasive tumor or from testicular parenchyma adjacent to seminoma, nonseminoma, or a combined germ cell tumor. Before CGH analysis, DNA was amplified by degenerate oligonucleotide primed PCR (DOP‐PCR) and directly labeled with a mixture of FITC‐dUTP and FITC‐dCTP. CGH analysis revealed extra chromosome arm 12p material in six out of seven cases with CIS adjacent to overt tumors, but only a diminutive gain of 12q was noted in one of the two cases of CIS without invasive elements. In addition, gains of parts of chromosome 8 (3/7) and losses of chromosome 5 (2/7) were demonstrated in CIS adjacent to invasive tumors. Gains of parts of chromosome 7 were found in CIS adjacent to seminoma (4/4), whereas relative gains of chromosome 15 were identified in some cases of CIS adjacent to seminoma and in isolated CIS in comparison to CIS adjacent to nonseminoma. Our data seem to indicate that extra 12p material is not present in the “dormant” CIS cell before development of an invasive tumor. The gain of extra chromosome 12 material may not be an early event in the neoplastic transformation, but is most likely associated with a more malignant progression of the CIS cell. © 2003 Wiley‐Liss, Inc.
Heterogeneity of the 7q36 breakpoints in the t(7;12) involving ETV6 in infant leukemia
Authors: Tosi Sabrina , Hughes Jim , Scherer Stephen W. , Nakabayashi Kazuhiko , Harbott Jochen , Haas Oskar A. , Cazzaniga Giovanni , Biondi Andrea , Kempski Helena , Kearney Lyndal 
Published: August 2003

AbstractThe t(7;12)(q36;p13) is a recurrent chromosome abnormality in infant leukemia. In these cases, the involvement of ETV6, with disruption of the gene consistently at its 5′ end, has been reported by several groups. A fusion transcript between ETV6 and HLXB9 has been detected in some, but not all, reported cases of t(7;12). We report here a study based on fluorescence in situ hybridization (FISH) mapping of the translocation breakpoints in seven patients and detailed molecular studies using Southern blotting on two of these patients. The FISH studies have shown a cluster of breakpoints within a cosmid contig proximal to the HLXB9 gene. Southern blotting analysis enabled us to define two distinct breakpoints within the area covered by the cosmid contig in two patients. The analysis of an unusual case of t(7;12)(q22;p13) [full karyotype: 46,XX,der(7)t(7;12)(q22;p13)del(7)(q22q36)] also revealed a break in 7q36, although in a region proximal to the overlapping cosmids. 5′ RACE PCR in one patient has shown a rearrangement involving the ETV6 allele not involved in the t(7;12), suggesting that no functional ETV6 allele might be present in this case. These data show some heterogeneity in the distribution of breakpoints in 7q36, indicating that the generation of a fusion gene might not be the mechanism responsible for leukemogenesis in the t(7;12), at least in some cases. © 2003 Wiley‐Liss, Inc.
Site‐directed mutagenesis of the ATM promoter: Consequences for response to proliferation and ionizing radiation
Authors: Gueven Nuri , Keating Karen , Fukao Toshiyuki , Loeffler Heidi , Kondo Naomi , Rodemann H. Peter , Lavin Martin F. 
Published: August 2003

AbstractAlthough ATM, the protein defective in ataxia‐telangiectasia (A‐T), is activated primarily by radiation, there is also evidence that expression of the protein can be regulated by both radiation and growth factors. Computer analysis of the ATM promoter proximal 700‐bp sequence reveals a number of potentially important cis‐regulatory sequences. Using nucleotide substitutions to delete putative functional elements in the promoter of ATM, we examined the importance of some of these sites for both the basal and the radiation‐induced activity of the promoter. In lymphoblastoid cells, most of the mutations in transcription factor consensus sequences [Sp1(1), Sp1(2), Cre, Ets, Xre, γIre(2), a modified AP1 site (Fse), and GCF] reduced basal activity to various extents, whereas others [γIre(1), NF1, Myb] left basal activity unaffected. In human skin fibroblasts, results were generally the same, but the basal activity varied up to 8‐fold in these and other cell lines. Radiation activated the promoter approximately 2.5‐fold in serum‐starved lymphoblastoid cells, reaching a maximum by 3 hr, and all mutated elements equally blocked this activation. Reduction in Sp1 and AP1 DNA binding activity by serum starvation was rapidly reversed by exposure of cells to radiation. This reduction was not evident in A‐T cells, and the response to radiation was less marked. Data provided for interaction between ATM and Sp1 by protein binding and co‐immunoprecipitation could explain the altered regulation of Sp1 in A‐T cells. The data described here provide additional evidence that basal and radiation‐induced regulation of the ATM promoter is under multifactorial control. © 2003 Wiley‐Liss, Inc.