@inproceedings{2746,
abstract = {We consider random Schrödinger equations on Rd or Zd for d ≥ 3 with uncorrelated, identically distributed random potential. Denote by λ the coupling constant and ψt the solution with initial data ψ0.},
author = {László Erdös and Salmhofer, Manfred and Yau, Horng-Tzer},
pages = {233 -- 257},
publisher = {World Scientific Publishing},
title = {{Towards the quantum Brownian motion}},
doi = {10.1007/3-540-34273-7_18},
volume = {690},
year = {2006},
}
@article{2747,
abstract = {Consider a system of N bosons on the three-dimensional unit torus interacting via a pair potential N 2V(N(x i - x j)) where x = (x i, . . ., x N) denotes the positions of the particles. Suppose that the initial data ψ N,0 satisfies the condition 〈ψ N,0, H 2 Nψ N,0) ≤ C N 2 where H N is the Hamiltonian of the Bose system. This condition is satisfied if ψ N,0 = W Nφ N,t where W N is an approximate ground state to H N and φ N,0 is regular. Let ψ N,t denote the solution to the Schrödinger equation with Hamiltonian H N. Gross and Pitaevskii proposed to model the dynamics of such a system by a nonlinear Schrödinger equation, the Gross-Pitaevskii (GP) equation. The GP hierarchy is an infinite BBGKY hierarchy of equations so that if u t solves the GP equation, then the family of k-particle density matrices ⊗ k |u t?〉 〈 t | solves the GP hierarchy. We prove that as N → ∞ the limit points of the k-particle density matrices of ψ N,t are solutions of the GP hierarchy. Our analysis requires that the N-boson dynamics be described by a modified Hamiltonian that cuts off the pair interactions whenever at least three particles come into a region with diameter much smaller than the typical interparticle distance. Our proof can be extended to a modified Hamiltonian that only forbids at least n particles from coming close together for any fixed n.},
author = {László Erdös and Schlein, Benjamin and Yau, Horng-Tzer},
journal = {Communications on Pure and Applied Mathematics},
number = {12},
pages = {1659 -- 1741},
publisher = {Wiley-Blackwell},
title = {{Derivation of the Gross-Pitaevskii hierarchy for the dynamics of Bose-Einstein condensate}},
doi = {10.1002/cpa.20123},
volume = {59},
year = {2006},
}
@article{2791,
abstract = {Generally, the motion of fluids is smooth and laminar at low speeds but becomes highly disordered and turbulent as the velocity increases. The transition from laminar to turbulent flow can involve a sequence of instabilities in which the system realizes progressively more complicated states, or it can occur suddenly. Once the transition has taken place, it is generally assumed that, under steady conditions, the turbulent state will persist indefinitely. The flow of a fluid down a straight pipe provides a ubiquitous example of a shear flow undergoing a sudden transition from laminar to turbulent motion. Extensive calculations and experimental studies have shown that, at relatively low flow rates, turbulence in pipes is transient, and is characterized by an exponential distribution of lifetimes. They also suggest that for Reynolds numbers exceeding a critical value the lifetime diverges (that is, becomes infinitely large), marking a change from transient to persistent turbulence. Here we present experimental data and numerical calculations covering more than two decades of lifetimes, showing that the lifetime does not in fact diverge but rather increases exponentially with the Reynolds number. This implies that turbulence in pipes is only a transient event (contrary to the commonly accepted view), and that the turbulent and laminar states remain dynamically connected, suggesting avenues for turbulence control.},
author = {Björn Hof and Westerweel, Jerry and Schneider, Tobias M and Eckhardt, Bruno},
journal = {Nature},
number = {7107},
pages = {59 -- 62},
publisher = {Nature Publishing Group},
title = {{Finite lifetime of turbulence in shear flows}},
doi = {10.1038/nature05089},
volume = {443},
year = {2006},
}
@article{2792,
abstract = {Transition to turbulence in pipe flow has posed a riddle in fluid dynamics since the pioneering experiments of Reynolds[1]. Although the laminar flow is linearly stable for all flow rates, practical pipe flows become turbulent at large enough flow speeds. Turbulence arises suddenly and fully without distinct steps and without a clear critical point. The complexity of this problem has puzzled mathematicians, physicists and engineers for more than a century and no satisfactory explanation of this problem has been given. In a very recent theoretical approach it has been suggested that unstable solutions of the Navier Stokes equations may hold the key to understanding this problem. In numerical studies such unstable states have been identified as exact solutions for the idealized case of a pipe with periodic boundary conditions[2, 3]. These solutions have the form of waves extending through the entire pipe and travelling in the streamwise direction at a phase speed close to the bulk velocity of the fluid. With the aid of a recently developed high-speed stereoscopic Particle Image Velocimetry (PIV) system, we were able to observe transients of such unstable solutions in turbulent pipe flow[4].},
author = {Björn Hof and van Doorne, Casimir W and Westerweel, Jerry and Nieuwstadt, Frans T},
journal = {Fluid Mechanics and its Applications},
pages = {109 -- 114},
publisher = {Springer},
title = {{Observation of nonlinear travelling waves in turbulent pipe flow}},
doi = {10.1007/1-4020-4159-4_11},
volume = {78},
year = {2006},
}
@article{2894,
abstract = {IL-10 is a potent anti-inflammatory and immunomodulatory cytokine, exerting major effects in the degree and quality of the immune response. Using a newly generated IL-10 reporter mouse model, which easily allows the study of IL-10 expression from each allele in a single cell, we report here for the first time that IL-10 is predominantly monoallelic expressed in CD4+ T cells. Furthermore, we have compelling evidence that this expression pattern is not due to parental imprinting, allelic exclusion, or strong allelic bias. Instead, our results support a stochastic regulation mechanism, in which the probability to initiate allelic transcription depends on the strength of TCR signaling and subsequent capacity to overcome restrictions imposed by chromatin hypoacetylation. In vivo Ag-experienced T cells show a higher basal probability to transcribe IL-10 when compared with naive cells, yet still show mostly monoallelic IL-10 expression. Finally, statistical analysis on allelic expression data shows transcriptional independence between both alleles. We conclude that CD4+ T cells have a low probability for IL-10 allelic activation resulting in a predominantly monoallelic expression pattern, and that IL-10 expression appears to be stochastically regulated by controlling the frequency of expressing cells, rather than absolute protein levels per cell.},
author = {Calado, Dinis P and Tiago Paixao and Holmberg, Dan and Haury, Matthias},
journal = {Journal of Immunology},
number = {8},
pages = {5358 -- 5364},
publisher = {American Association of Immunologists},
title = {{Stochastic Monoallelic Expression of IL 10 in T Cells}},
doi = {10.4049/jimmunol.177.8.5358 },
volume = {177},
year = {2006},
}
@inbook{2921,
abstract = {Most binocular stereo algorithms assume that all scene elements are visible from both cameras. Scene elements that are visible from only one camera, known as occlusions, pose an important challenge for stereo. Occlusions are important for segmentation, because they appear near discontinuities. However, stereo algorithms tend to ignore occlusions because of their difficulty. One reason is that occlusions require the input images to be treated symmetrically, which complicates the problem formulation. Worse, certain depth maps imply physically impossible scene configurations, and must be excluded from the output. In this chapter we approach the problem of binocular stereo with occlusions from an energy minimization viewpoint. We begin by reviewing traditional stereo methods that do not handle occlusions. If occlusions are ignored, it is easy to formulate the stereo problem as a pixel labeling problem, which leads to an energy function that is common in early vision. This kind of energy function can he minimized using graph cuts, which is a combinatorial optimization technique that has proven to be very effective for low-level vision problems. Motivated by this, we have designed two graph cut stereo algorithms that are designed to handle occlusions. These algorithms produce promising experimental results on real data with ground truth.},
author = {Vladimir Kolmogorov and Zabih, Ramin},
booktitle = {Handbook of Mathematical Models in Computer Vision},
pages = {423 -- 427},
publisher = {Springer},
title = {{Graph cut algorithms for binocular stereo with occlusions}},
doi = {10.1007/0-387-28831-7_26},
year = {2006},
}
@article{8488,
abstract = {We demonstrate for different protein samples that three-dimensional HNCO and HNCA correlation spectra may be recorded in a few minutes acquisition time using the band-selective excitation short-transient sequences presented here. This opens new perspectives for the NMR structural investigation of unstable protein samples and real-time site-resolved studies of protein kinetics.},
author = {Schanda, Paul and Van Melckebeke, Hélène and Brutscher, Bernhard},
issn = {0002-7863},
journal = {Journal of the American Chemical Society},
keywords = {Colloid and Surface Chemistry, Biochemistry, General Chemistry, Catalysis},
number = {28},
pages = {9042--9043},
publisher = {American Chemical Society},
title = {{Speeding up three-dimensional protein NMR experiments to a few minutes}},
doi = {10.1021/ja062025p},
volume = {128},
year = {2006},
}
@article{8489,
abstract = {Structure elucidation of proteins by either NMR or X‐ray crystallography often requires the screening of a large number of samples for promising protein constructs and optimum solution conditions. For large‐scale screening of protein samples in solution, robust methods are needed that allow a rapid assessment of the folding of a polypeptide under diverse sample conditions. Here we present HET‐SOFAST NMR, a highly sensitive new method for semi‐quantitative characterization of the structural compactness and heterogeneity of polypeptide chains in solution. On the basis of one‐dimensional 1H HET‐SOFAST NMR data, obtained on well‐folded, molten globular, partially‐ and completely unfolded proteins, we define empirical thresholds that can be used as quantitative benchmarks for protein compactness. For 15N‐enriched protein samples, two‐dimensional 1H‐15N HET‐SOFAST correlation spectra provide site‐specific information about the structural heterogeneity along the polypeptide chain.},
author = {Schanda, Paul and Forge, Vincent and Brutscher, Bernhard},
issn = {0749-1581},
journal = {Magnetic Resonance in Chemistry},
number = {S1},
pages = {S177--S184},
publisher = {Wiley},
title = {{HET-SOFAST NMR for fast detection of structural compactness and heterogeneity along polypeptide chains}},
doi = {10.1002/mrc.1825},
volume = {44},
year = {2006},
}
@article{8490,
abstract = {We demonstrate the feasibility of recording 1H–15N correlation spectra of proteins in only one second of acquisition time. The experiment combines recently proposed SOFAST-HMQC with Hadamard-type 15N frequency encoding. This allows site-resolved real-time NMR studies of kinetic processes in proteins with an increased time resolution. The sensitivity of the experiment is sufficient to be applicable to a wide range of molecular systems available at millimolar concentration on a high magnetic field spectrometer.},
author = {Schanda, Paul and Brutscher, Bernhard},
issn = {1090-7807},
journal = {Journal of Magnetic Resonance},
keywords = {Nuclear and High Energy Physics, Biophysics, Biochemistry, Condensed Matter Physics},
number = {2},
pages = {334--339},
publisher = {Elsevier},
title = {{Hadamard frequency-encoded SOFAST-HMQC for ultrafast two-dimensional protein NMR}},
doi = {10.1016/j.jmr.2005.10.007},
volume = {178},
year = {2006},
}
@article{8513,
author = {Kaloshin, Vadim and Saprykina, Maria},
issn = {1553-5231},
journal = {Discrete & Continuous Dynamical Systems - A},
number = {2},
pages = {611--640},
publisher = {American Institute of Mathematical Sciences (AIMS)},
title = {{Generic 3-dimensional volume-preserving diffeomorphisms with superexponential growth of number of periodic orbits}},
doi = {10.3934/dcds.2006.15.611},
volume = {15},
year = {2006},
}
@article{8514,
abstract = {We study the extent to which the Hausdorff dimension of a compact subset of an infinite-dimensional Banach space is affected by a typical mapping into a finite-dimensional space. It is possible that the dimension drops under all such mappings, but the amount by which it typically drops is controlled by the ‘thickness exponent’ of the set, which was defined by Hunt and Kaloshin (Nonlinearity12 (1999), 1263–1275). More precisely, let $X$ be a compact subset of a Banach space $B$ with thickness exponent $\tau$ and Hausdorff dimension $d$. Let $M$ be any subspace of the (locally) Lipschitz functions from $B$ to $\mathbb{R}^{m}$ that contains the space of bounded linear functions. We prove that for almost every (in the sense of prevalence) function $f \in M$, the Hausdorff dimension of $f(X)$ is at least $\min\{ m, d / (1 + \tau) \}$. We also prove an analogous result for a certain part of the dimension spectra of Borel probability measures supported on $X$. The factor $1 / (1 + \tau)$ can be improved to $1 / (1 + \tau / 2)$ if $B$ is a Hilbert space. Since dimension cannot increase under a (locally) Lipschitz function, these theorems become dimension preservation results when $\tau = 0$. We conjecture that many of the attractors associated with the evolution equations of mathematical physics have thickness exponent zero. We also discuss the sharpness of our results in the case $\tau > 0$.},
author = {OTT, WILLIAM and HUNT, BRIAN and Kaloshin, Vadim},
issn = {0143-3857},
journal = {Ergodic Theory and Dynamical Systems},
number = {3},
pages = {869--891},
publisher = {Cambridge University Press},
title = {{The effect of projections on fractal sets and measures in Banach spaces}},
doi = {10.1017/s0143385705000714},
volume = {26},
year = {2006},
}
@inproceedings{8515,
abstract = {We consider the evolution of a set carried by a space periodic incompressible stochastic flow in a Euclidean space. We
report on three main results obtained in [8, 9, 10] concerning long time behaviour for a typical realization of the stochastic flow. First, at time t most of the particles are at a distance of order √t away from the origin. Moreover, we prove a Central Limit Theorem for the evolution of a measure carried by the flow, which holds for almost every realization of the flow. Second, we show the existence of a zero measure full Hausdorff dimension set of points, which
escape to infinity at a linear rate. Third, in the 2-dimensional case, we study the set of points visited by the original set by time t. Such a set, when scaled down by the factor of t, has a limiting non random shape.},
author = {Kaloshin, Vadim and DOLGOPYAT, D. and KORALOV, L.},
booktitle = {XIVth International Congress on Mathematical Physics},
isbn = {9789812562012},
location = {Lisbon, Portugal},
pages = {290--295},
publisher = {World Scientific},
title = {{Long time behaviour of periodic stochastic flows}},
doi = {10.1142/9789812704016_0026},
year = {2006},
}
@article{854,
abstract = {Phylogenetic relationships between the extinct woolly mammoth (Mammuthus primigenius), and the Asian (Elephas maximus) and African savanna (Loxodonta africana) elephants remain unresolved. Here, we report the sequence of the complete mitochondrial genome (16,842 base pairs) of a woolly mammoth extracted from permafrost-preserved remains from the Pleistocene epoch - the oldest mitochondrial genome sequence determined to date. We demonstrate that well-preserved mitochondrial genome fragments, as long as ∼1,600-1700 base pairs, can be retrieved from pre-Holocene remains of an extinct species. Phylogenetic reconstruction of the Elephantinae clade suggests that M. primigenius and E. maximus are sister species that diverged soon after their common ancestor split from the L. africana lineage. Low nucleotide diversity found between independently determined mitochondrial genomic sequences of woolly mammoths separated geographically and in time suggests that north-eastern Siberia was occupied by a relatively homogeneous population of M. primigenius throughout the late Pleistocene.},
author = {Rogaev, Evgeny I and Moliaka, Yuri K and Malyarchuk, Boris A and Fyodor Kondrashov and Derenko, Miroslava V and Chumakov, Ilya M and Grigorenko, Anastasia P},
journal = {PLoS Biology},
number = {3},
pages = {0403 -- 0410},
publisher = {Public Library of Science},
title = {{Complete mitochondrial genome and phylogeny of pleistocene mammoth Mammuthus primigenius}},
doi = {10.1371/journal.pbio.0040073},
volume = {4},
year = {2006},
}
@article{868,
abstract = {Background: The glyoxylate cycle is thought to be present in bacteria, protists, plants, fungi, and nematodes, but not in other Metazoa. However, activity of the glyoxylate cycle enzymes, malate synthase (MS) and isocitrate lyase (ICL), in animal tissues has been reported. In order to clarify the status of the MS and ICL genes in animals and get an insight into their evolution, we undertook a comparative-genomic study. Results: Using sequence similarity searches, we identified MS genes in arthropods, echinoderms, and vertebrates, including platypus and opossum, but not in the numerous sequenced genomes of placental mammals. The regions of the placental mammals' genomes expected to code for malate synthase, as determined by comparison of the gene orders in vertebrate genomes, show clear similarity to the opossum MS sequence but contain stop codons, indicating that the MS gene became a pseudogene in placental mammals. By contrast, the ICL gene is undetectable in animals other than the nematodes that possess a bifunctional, fused ICL-MS gene. Examination of phylogenetic trees of MS and ICL suggests multiple horizontal gene transfer events that probably went in both directions between several bacterial and eukaryotic lineages. The strongest evidence was obtained for the acquisition of the bifunctional ICL-MS gene from an as yet unknown bacterial source with the corresponding operonic organization by the common ancestor of the nematodes. Conclusion: The distribution of the MS and ICL genes in animals suggests that either they encode alternative enzymes of the glyoxylate cycle that are not orthologous to the known MS and ICL or the animal MS acquired a new function that remains to be characterized. Regardless of the ultimate solution to this conundrum, the genes for the glyoxylate cycle enzymes present a remarkable variety of evolutionary events including unusual horizontal gene transfer from bacteria to animals.},
author = {Fyodor Kondrashov and Koonin, Eugene V and Morgunov, Igor G and Finogenova, Tatiana V and Kondrashova, Marie N},
journal = {Biology Direct},
publisher = {BioMed Central},
title = {{Evolution of glyoxylate cycle enzymes in Metazoa Evidence of multiple horizontal transfer events and pseudogene formation}},
doi = {10.1186/1745-6150-1-31},
volume = {1},
year = {2006},
}
@article{869,
abstract = {The impact of synonymous nucleotide substitutions on fitness in mammals remains controversial. Despite some indications of selective constraint, synonymous sites are often assumed to be neutral, and the rate of their evolution is used as a proxy for mutation rate. We subdivide all sites into four classes in terms of the mutable CpG context, nonCpG, postC, preG, and postCpreG, and compare four-fold synonymous sites and intron sites residing outside transposable elements. The distribution of the rate of evolution across all synonymous sites is trimodal. Rate of evolution at nonCpG synonymous sites, not preceded by C and not followed by G, is ∼10% below that at such intron sites. In contrast, rate of evolution at postCpreG synonymous sites is ∼30% above that at such intron sites. Finally, synonymous and intron postC and preG sites evolve at similar rates. The relationship between the levels of polymorphism at the corresponding synonymous and intron sites is very similar to that between their rates of evolution. Within every class, synonymous sites are occupied by G or C much more often than intron sites, whose nucleotide composition is consistent with neutral mutation-drift equilibrium. These patterns suggest that synonymous sites are under weak selection in favor of G and C, with the average coefficient s∼0.25/Ne∼10-5, where Ne is the effective population size. Such selection decelerates evolution and reduces variability at sites with symmetric mutation, but has the opposite effects at sites where the favored nucleotides are more mutable. The amino-acid composition of proteins dictates that many synonymous sites are CpGprone, which causes them, on average, to evolve faster and to be more polymorphic than intron sites. An average genotype carries ∼107 suboptimal nucleotides at synonymous sites, implying synergistic epistasis in selection against them.},
author = {Fyodor Kondrashov and Ogurtsov, Aleksey Yu and Kondrashov, Alexey S},
journal = {Journal of Theoretical Biology},
number = {4},
pages = {616 -- 626},
publisher = {Elsevier},
title = {{Selection in favor of nucleotides G and C diversifies evolution rates and levels of polymorphism at mammalian synonymous sites}},
doi = {10.1016/j.jtbi.2005.10.020},
volume = {240},
year = {2006},
}
@article{873,
abstract = {New genes commonly appear through complete or partial duplications of pre-existing genes. Duplications of long DNA segments are constantly produced by rare mutations, may become fixed in a population by selection or random drift, and are subject to divergent evolution of the paralogous sequences after fixation, although gene conversion can impede this process. New data shed some light on each of these processes. Mutations which involve duplications can occur through at least two different mechanisms, backward strand slippage during DNA replication and unequal crossing-over. The background rate of duplication of a complete gene in humans is 10-9-10-10 per generation, although many genes located within hot-spots of large-scale mutation are duplicated much more often. Many gene duplications affect fitness strongly, and are responsible, through gene dosage effects, for a number of genetic diseases. However, high levels of intrapopulation polymorphism caused by presence or absence of long, gene-containing DNA segments imply that some duplications are not under strong selection. The polymorphism to fixation ratios appear to be approximately the same for gene duplications and for presumably selectively neutral nucleotide substitutions, which, according to the McDonald-Kreitman test, is consistent with selective neutrality of duplications. However, this pattern can also be due to negative selection against most of segregating duplications and positive selection for at least some duplications which become fixed. Patterns in post-fixation evolution of duplicated genes do not easily reveal the causes of fixations. Many gene duplications which became fixed recently in a variety of organisms were positively selected because the increased expression of the corresponding genes was beneficial. The effects of gene dosage provide a unified framework for studying all phases of the life history of a gene duplication. Application of well-known methods of evolutionary genetics to accumulating data on new, polymorphic, and fixed duplication will enhance our understanding of the role of natural selection in the evolution by gene duplication.},
author = {Fyodor Kondrashov and Kondrashov, Alexey S},
journal = {Journal of Theoretical Biology},
number = {2},
pages = {141 -- 151},
publisher = {Elsevier},
title = {{Role of selection in fixation of gene duplications}},
doi = {10.1016/j.jtbi.2005.08.033},
volume = {239},
year = {2006},
}
@article{1715,
abstract = {Background: Cell-to-cell communication at the synapse involves synaptic transmission as well as signaling mediated by growth factors, which provide developmental and plasticity cues. There is evidence that a retrograde, presynaptic transforming growth factor-β (TGF-β) signaling event regulates synapse development and function in Drosophila. Results: Here we show that a postsynaptic TGF-β signaling event occurs during larval development. The type I receptor Thick veins (Tkv) and the R-Smad transcription factor Mothers-against-dpp (Mad) are localized postsynaptically in the muscle. Furthermore, Mad phosphorylation occurs in regions facing the presynaptic active zones of neurotransmitter release within the postsynaptic subsynaptic reticulum (SSR). In order to monitor in real time the levels of TGF-β signaling in the synapse during synaptic transmission, we have established a FRAP assay to measure Mad nuclear import/export in the muscle. We show that Mad nuclear trafficking depends on stimulation of the muscle. Conclusions: Our data suggest a mechanism linking synaptic transmission and postsynaptic TGF-β signaling that may coordinate nerve-muscle development and function.},
author = {Dudu, Veronika and Bittig, Thomas and Entchev, Eugeni V and Anna Kicheva and Julicher, Frank and González-Gaitán, Marcos A},
journal = {Current Biology},
number = {7},
pages = {625 -- 635},
publisher = {Cell Press},
title = {{Postsynaptic mad signaling at the Drosophila neuromuscular junction}},
doi = {10.1016/j.cub.2006.02.061},
volume = {16},
year = {2006},
}
@article{1716,
author = {Dudu, Veronika and Bittig, Thomas and Entchev, Eugeni V and Anna Kicheva and Julicher, Frank and González-Gaitán, Marcos A},
journal = {Current Biology},
number = {12},
publisher = {Cell Press},
title = {{Erratum: Postsynaptic mad signaling at the Drosophila neuromuscular junction}},
doi = {10.1016/j.cub.2006.06.020},
volume = {16},
year = {2006},
}
@article{1745,
abstract = {SiGe islands grown by deposition of 10 monolayers of Ge on Si(0 0 1) at 740 °C were investigated by using a combination of selective wet chemical etching and atomic force microscopy. The used etchant, a solution consisting of ammonium hydroxide and hydrogen peroxide, shows a high selectivity of Ge over SixGe1-x and is characterized by relatively slow etching rates for Si-rich alloys. By performing successive etching experiments on the same sample area, we are able to gain a deeper insight into the lateral displacement the islands undergo during post growth annealing.},
author = {Georgios Katsaros and Rastelli, Armando and Stoffel, Mathieu and Isella, Giovanni and Von Känel, Hans and Bittner, Alexander M and Tersoff, Jerry and Denker, Ulrich and Schmidt, Oliver G and Costantini, Giovanni and Kern, Klaus},
journal = {Surface Science},
number = {12},
pages = {2608 -- 2613},
publisher = {Elsevier},
title = {{Investigating the lateral motion of SiGe islands by selective chemical etching}},
doi = {10.1016/j.susc.2006.04.027},
volume = {600},
year = {2006},
}
@article{1746,
abstract = {A microscopic picture for the GaAs overgrowth of self-organized InAs/GaAs(001) quantum dots is developed. Scanning tunneling microscopy measurements reveal two capping regimes: the first being characterized by a dot shrinking and a backward pyramid-to-dome shape transition. This regime is governed by fast dynamics resulting in island morphologies close to thermodynamic equilibrium. The second regime is marked by a true overgrowth and is controlled by kinetically limited surface diffusion processes. A simple model is developed to describe the observed structural changes which are rationalized in terms of energetic minimization driven by lattice mismatch and alloying.},
author = {Costantini, Giovanni and Rastelli, Armando and Manzano, Carlos and Acosta-Diaz, P and Songmuang, Rudeeson and Georgios Katsaros and Schmidt, Oliver G and Kern, Klaus},
journal = {Physical Review Letters},
number = {22},
publisher = {American Physical Society},
title = {{Interplay between thermodynamics and kinetics in the capping of InAs/GaAs (001) quantum dots}},
doi = {10.1103/PhysRevLett.96.226106},
volume = {96},
year = {2006},
}
@article{1747,
abstract = {We report on recent advances in the understanding of surface processes occurring during growth and post-growth annealing of strained islands which may find application as self-assembled quantum dots. We investigate the model system SiGe/Si(0 0 1) by a new approach based on "reading the footprints" which islands leave on the substrate during their growth and evolution. Such footprints consist of trenches carved in the Si substrate. We distinguish between surface footprints and footprints buried below the islands. The former allow us to discriminate islands which are in the process of growing from those which are shrinking. Islands with steep morphologies grow at the expense of smaller and shallower islands, consistent with the kinetics of anomalous coarsening. While shrinking, islands change their shape according to thermodynamic predictions. Buried footprints are investigated by removing the SiGe epilayer by means of selective wet chemical etching. Their reading shows that: (i) during post-growth annealing islands move laterally because of surface-mediated Si-Ge intermixing; (ii) a tree-ring structure of trenches is created by dislocated islands during their "cyclic" growth. This allows us to distinguish coherent from dislocated islands and to establish whether the latter are the result of island coalescence.},
author = {Rastelli, Armando and Stoffel, Mathieu and Georgios Katsaros and Tersoff, Jerry and Denker, Ulrich and Merdzhanova, Tsvetelina and Kar, Gouranga S and Costantini, Giovanni and Kern, Klaus and Von Känel, Hans and Schmidt, Oliver G},
journal = {Microelectronics Journal},
number = {12},
pages = {1471 -- 1476},
publisher = {Elsevier},
title = {{Reading the footprints of strained islands}},
doi = {10.1016/j.mejo.2006.05.029},
volume = {37},
year = {2006},
}
@article{1748,
abstract = {The authors apply selective wet chemical etching and atomic force microscopy to reveal the three-dimensional shape of SiGeSi (001) islands after capping with Si. Although the "self-assembled quantum dots" remain practically unaffected by capping in the temperature range of 300-450 °C, significant morphological changes take place on the Si surface. At 450 °C, the morphology of the capping layer (Si matrix) evolves toward an intriguing semifacetted structure, which we call a "ziggurat," giving the misleading impression of a stepped SiGe island shape.},
author = {Georgios Katsaros and Rastelli, Armando and Stoffel, Mathieu and Costantini, Giovanni and Schmidt, Oliver G and Kern, Klaus and Tersoff, Jerry and Müller, Elisabeth and Von Känel, Hans},
journal = {Applied Physics Letters},
number = {25},
publisher = {American Institute of Physics},
title = {{Evolution of buried semiconductor nanostructures and origin of stepped surface mounds during capping}},
doi = {10.1063/1.2405876},
volume = {89},
year = {2006},
}
@article{1796,
abstract = {Drugs that block the entry of human immunodeficiency virus type 1 (HIV-1) into host cells abrogate the establishment of a productive infection and should ideally diminish the chances of HIV-1 developing resistance. This review will give an overview of the mechanism by which the envelope glycoprotein mediates HIV-1 entry and will summarize current drug developments.},
author = {Sandra Siegert and Schnierle, Peter and Schnierle, Barbara S},
journal = {Mini-Reviews in Medicinal Chemistry},
number = {5},
pages = {557 -- 562},
publisher = {Bentham Science Publishers},
title = {{Novel anti-viral therapy: Drugs that block HIV entry at different target sites}},
doi = {10.2174/138955706776876267},
volume = {6},
year = {2006},
}
@article{1961,
abstract = {Respiratory complex I plays a central role in cellular energy production in bacteria and mitochondria. Its dysfunction is implicated in many human neurodegenerative diseases, as well as in aging. The crystal structure of the hydrophilic domain (peripheral arm) of complex I from Thermus thermophilus has been solved at 3.3 angstrom resolution. This subcomplex consists of eight subunits and contains all the redox centers of the enzyme, including nine iron-sulfur clusters. The primary electron acceptor, flavin-mononucleotide, is within electron transfer distance of cluster N3, leading to the main redox pathway, and of the distal cluster Nia, a possible antioxidant. The structure reveals new aspects of the mechanism and evolution of the enzyme. The terminal cluster N2 is coordinated, uniquely, by two consecutive cysteines. The novel subunit Nqo15 has a similar fold to the mitochondrial iron chaperone frataxin, and it may be involved in iron-sulfur cluster regeneration in the complex.
},
author = {Leonid Sazanov and Hinchliffe, Philip },
journal = {Science},
number = {5766},
pages = {1430 -- 1436},
publisher = {American Association for the Advancement of Science},
title = {{Structure of the hydrophilic domain of respiratory complex I from Thermus thermophilus}},
doi = {10.1126/science.1123809},
volume = {311},
year = {2006},
}
@article{1966,
abstract = {The hydrophilic domain (peripheral arm) of the proton-translocating NADH:quinone oxidoreductase (complex I) from the thermophilic organism Thermus thermophilus HB8 has been purified and characterized. The subcomplex is stable in sodium dodecyl sulfate up to 80 °C. Of nine iron-sulfur clusters, four to five (one or two binuclear and three tetranuclear) could be detected by EPR in the NADH-reduced enzyme. The preparation consists of eight different polypeptides. Seven of them have been positively identified by peptide mass mapping and N-terminal sequencing as known hydrophilic subunits of T. thermophilus complex I. The eighth polypeptide copurified with the subcomplex at all stages, is strongly associated with the other subunits, and is present in crystals of the subcomplex, used for X-ray data collection. Therefore, it has been identified as a novel complex I subunit and named Nqo15. It is encoded in a locus separate from the nqo operon, containing the 14 other known complex I genes. ORFs encoding Nqo15 homologues are present in the genomes of the closest relatives of T. thermophilus. Our data show that, contrary to previous assumptions, bacterial complex I can contain proteins in addition to a "core" complement of 14 subunits.},
author = {Hinchliffe, Philip and Carroll, Joe D and Leonid Sazanov},
journal = {Biochemistry},
number = {14},
pages = {4413 -- 4420},
publisher = {ACS},
title = {{Identification of a novel subunit of respiratory complex I from Thermus thermophilus}},
doi = {10.1021/bi0600998},
volume = {45},
year = {2006},
}
@article{2066,
abstract = {Although the X chromosome is usually similar to the autosomes in size and cytogenetic appearance, theoretical models predict that its hemizygosity in males may cause unusual patterns of evolution. The sequencing of several genomes has indeed revealed differences between the X chromosome and the autosomes in the rates of gene divergence, patterns of gene expression and rates of gene movement between chromosomes. A better understanding of these patterns should provide valuable information on the evolution of genes located on the X chromosome. It could also suggest solutions to more general problems in molecular evolution, such as detecting selection and estimating mutational effects on fitness},
author = {Beatriz Vicoso and Charlesworth, Brian},
journal = {Nature Reviews Genetics},
number = {8},
pages = {645 -- 653},
publisher = {Nature Publishing Group},
title = {{Evolution on the X chromosome: Unusual patterns and processes}},
doi = {10.1038/nrg1914},
volume = {7},
year = {2006},
}
@inproceedings{2077,
abstract = {We present an adaptive animation method for electrical discharges. Electrical discharges can be simulated using the dielectric breakdown model. Regular discretization of the governing Laplace equation leads to huge equation systems, and the computational cost of solving the equations quickly becomes prohibitive at high resolutions, especially for simulations in 3D. In contrast, our method discretizes the Laplace equation on an adaptive octree, reducing the size of the problem significantly, and making simulations of high resolution 3D datasets and even 3D animations feasible. In order to enhance realism for lightning animations, we propose a particle simulation that animates the residual positive charge. Thus, interaction of electrical discharges with their surroundings
can be simulated.},
author = {Bernd Bickel and Wicke, Martin and Gross, Markus},
publisher = {IOS Press},
title = {{Adaptive simulation of electrical discharges}},
year = {2006},
}
@inproceedings{2088,
abstract = {We have measured 3D face geometry, skin reflectance, and subsurface scattering using custom-built devices for 149 subjects of varying age, gender, and race. We developed a novel skin reflectance model whose parameters can be estimated from measurements. The model decomposes the large amount of measured skin data into a spatially-varying analytic BRDF, a diffuse albedo map, and diffuse subsurface scattering. Our model is intuitive, physically plausible, and - since we do not use the original measured data - easy to edit as well. High-quality renderings come close to reproducing real photographs. The analysis of the model parameters for our sample population reveals variations according to subject age, gender, skin type, and external factors (e.g., sweat, cold, or makeup). Using our statistics, a user can edit the overall appearance of a face (e.g., changing skin type and age) or change small-scale features using texture synthesis (e.g., adding moles and freckles). We are making the collected statistics publicly available to the research community for applications in face synthesis and analysis. },
author = {Weyrich, Tim and Matusik, Wojciech and Pfister, Hanspeter and Bernd Bickel and Donner, Craig and Tu, Chien and McAndless, Janet M and Lee, Jinho and Ngan, Addy and Jensen, Henrik W and Groß, Markus S},
pages = {1013 -- 1024},
publisher = {ACM},
title = {{Analysis of human faces using a measurement-based skin reflectance model}},
doi = {10.1145/1179352.1141987},
year = {2006},
}
@article{2089,
abstract = {We have measured 3D face geometry, skin reflectance, and subsurface scattering using custom-built devices for 149 subjects of varying age, gender, and race. We developed a novel skin reflectance model whose parameters can be estimated from measurements. The model decomposes the large amount of measured skin data into a spatially-varying analytic BRDF, a diffuse albedo map, and diffuse subsurface scattering. Our model is intuitive, physically plausible, and - since we do not use the original measured data - easy to edit as well. High-quality renderings come close to reproducing real photographs. The analysis of the model parameters for our sample population reveals variations according to subject age, gender, skin type, and external factors (e.g., sweat, cold, or makeup). Using our statistics, a user can edit the overall appearance of a face (e.g., changing skin type and age) or change small-scale features using texture synthesis (e.g., adding moles and freckles). We are making the collected statistics publicly available to the research community for applications in face synthesis and analysis.},
author = {Weyrich, Tim and Matusik, Wojciech and Pfister, Hanspeter and Bernd Bickel and Donner, Craig and Tu, Chien and McAndless, Janet M and Lee, Jinho and Ngan, Addy and Jensen, Henrik W and Groß, Markus S},
journal = {ACM Transactions on Graphics},
number = {3},
pages = {1013 -- 1024},
publisher = {ACM},
title = {{Analysis of human faces using a measurement-based skin reflectance model}},
doi = {10.1145/1141911.1141987},
volume = {25},
year = {2006},
}
@inproceedings{2090,
author = {Bernd Bickel and Weyrich, Tim and Matusik, Wojciech and Pfister, Hanspeter and Donner, Craig and Tu, Chien and McAndless, Janet M and Lee, Jinho and Ngan, Addy and Jensen, Henrik W and Groß, Markus S},
publisher = {ACM},
title = {{Processing and editing of faces using a measurement-based skin reflectance model}},
doi = {10.1145/1179849.1180059},
year = {2006},
}
@article{213,
abstract = {For any integers d,n ≥2, let X ⊂ Pn be a non‐singular hypersurface of degree d that is defined over the rational numbers. The main result in this paper is a proof that the number of rational points on X which have height at most B is O(Bn − 1 + ɛ), for any ɛ > 0. The implied constant in this estimate depends at most upon d, ɛ and n. 2000 Mathematics Subject Classification 11D45 (primary), 11G35, 14G05 (secondary).},
author = {Timothy Browning and Heath-Brown, Roger and Starr, Jason M},
journal = {Proceedings of the London Mathematical Society},
number = {2},
pages = {273 -- 303},
publisher = {John Wiley and Sons Ltd},
title = {{The density of rational points on non-singular hypersurfaces, II}},
doi = {https://doi.org/10.1112/S0024611506015784},
volume = {93},
year = {2006},
}
@article{2134,
abstract = {Predissociation of the N+2 C 2Σ+u(v') vibrational levels with v' ≥ 3 was observed via dispersed C 2Σ+u → X 2Σ+g fluorescence in the spectral range of 165–208 nm after resonant 1s−1π*(vr) excitation of N2 and its subsequent autoionization into the N+2 C state. This range is dominated by lines in atomic nitrogen, by overlapped C 2Σ+u(v') → X 2Σ+g(v'') vibrational band sequences with Δv = const and broad unresolved band systems (D, (2))2Πg(v') → A2Πu(v'') in the N+2 molecular ion. With very high fluorescence resolution of about 0.1 nm FWHM individual C 2Σ+u(v') → X 2Σ+g(v'') vibrational bands have been resolved. Calculation of the observed fluorescence spectra by taking into account predissociation and molecular rotation describes well the shape of both individual vibrational bands C 2Σ+u(v') → X 2Σ+g(v'') and the whole band system.},
author = {Ehresmann, Arno and Werner, Lutz and Klumpp, Stefan and Demekhin, Ph V and Mikhail Lemeshko and Sukhorukov, V. L and Schartner, Karl H and Schmoranzer, Hans P},
journal = {Journal of Physics B: Atomic, Molecular and Optical Physics},
number = {6},
pages = {L119 -- L126},
publisher = {IOP Publishing Ltd.},
title = {{Predissociation of the N+2(C 2Σ+u) state observed via C 2Σ+u → X 2Σ+g fluorescence after resonant 1s−1π* excitation of N2 molecule}},
doi = {10.1088/0953-4075/39/6/L03},
volume = {39},
year = {2006},
}
@article{2142,
abstract = {Fluorescence from fragments formed after the de-excitation of the N*2(1s−1π*) resonance has been measured in the spectral range of 135–190 nm. This range is dominated by lines in atomic nitrogen and lines formed by overlapping C2Σ+u(v') → X2Σ+g(v'') bands with Δv = const in the N+2 molecular ion which result from the spectator Auger decays of the N*2(1s−1π*(vr)) resonances. Ab initio calculations of the corresponding potential curves and transition probabilities showed that the observed irregular intensity dependence of the C2Σ+u(v') → X2Σ+g(v'')(Δv = const) fluorescence lines on the vibrational quantum number vr is due to transitions between vibrational levels during the reaction N2(v0 = 0)→ N*2(1s−1π*(vr)) Longrightarrow C2Σ+u(v') → X2Σ+g(v'').},
author = {Ehresmann, Arno and Werner, Lutz and Klumpp, Stefan and Lucht, S and Schmoranzer, Hans P and Mickat, Sascha and Schill, Rüdiger H and Schartner, Karl H and Demekhin, Philipp and Mikhail Lemeshko and Sukhorukov, Victor L},
journal = {Journal of Physics B: Atomic, Molecular and Optical Physics},
number = {2},
pages = {283 -- 304},
publisher = {IOP Publishing Ltd.},
title = {{Studying the N+2(C2Σ+u → X2Σ+g) fluorescence excited via the 1s−1π* resonance}},
doi = {10.1088/0953-4075/39/2/006},
volume = {39},
year = {2006},
}
@article{2144,
abstract = {Temperature dependent preedge and extended x-ray absorption fine structure measurements at the Zr K edge for the perovskite-type zirconates Pb Zr0.515 Ti0.485 O3 (PZT), PbZr O3 (PZ), and BaZr O3 are performed. To carry out a more accurate study of the weak reconstruction of the local atomic structure we employed a combination of two techniques: (i) analysis of the preedge fine structure, and (ii) analysis of the Fourier transform of the difference between χ (k) functions obtained at different temperatures. A detailed investigation of local atomic structure in the cubic phase for all the crystals is also performed. It is shown that neither the displacive nor the order-disorder model can describe correctly the changes of local atomic structure during phase transitions in PZ and PZT. A spherical model describing the local atomic structure of perovskite-type crystals suffering structural phase transitions is proposed.},
author = {Vedrinskiǐ, Rostislav V and Nazarenko, Elena S and Mikhail Lemeshko and Nassif, Vivian M and Proux, Olivier and Novakovich, Alexander A and Joly, Yves},
journal = {Physical Review B - Condensed Matter and Materials Physics},
number = {13},
publisher = {American Physical Society},
title = {{Temperature dependent XAFS studies of local atomic structure of the perovskite-type zirconates}},
doi = {10.1103/PhysRevB.73.134109},
volume = {73},
year = {2006},
}
@article{215,
abstract = {For any n≥3, let F ∈ Z[X0,...,Xn ] be a form of degree d *≥5 that defines a non-singular hypersurface X ⊂ Pn . The main result in this paper is a proof of the fact that the number N (F ; B) of Q-rational points on X which have height at most B satisfiesN (F ; B) = Od,ε,n (Bn −1+ε ), for any ε > 0. The implied constant in this estimate depends at most upon d, ε and n. New estimates are also obtained for the number of representations of a positive integer as the sum of three dth powers, and for the paucity of integer solutions to equal sums of like polynomials.*},
author = {Timothy Browning and Heath-Brown, Roger},
journal = {Bulletin of the London Mathematical Society},
number = {3},
pages = {401 -- 410},
publisher = {Wiley-Blackwell},
title = {{The density of rational points on non-singular hypersurfaces, I}},
doi = {10.1112/S0024609305018412},
volume = {38},
year = {2006},
}
@article{216,
abstract = {For any N ≥ 2, let Z ⊂ ℙN be a geometrically integral algebraic variety of degree d. This article is concerned with the number Nz(B) of ℚ-rational points on Z which have height at most B. For any ε > 0, we establish the estimate NZ(B) = O d,ε,N(Bdim Z+ε), provided that d ≥ 6. As indicated, the implied constant depends at most on d, ε, and N.},
author = {Timothy Browning and Heath-Brown, Roger and Salberger, Per},
journal = {Duke Mathematical Journal},
number = {3},
pages = {545 -- 578},
publisher = {Unknown},
title = {{Counting rational points on algebraic varieties}},
doi = {10.1215/S0012-7094-06-13236-2},
volume = {132},
year = {2006},
}
@article{218,
abstract = {This paper is concerned with the average order of certain arithmetic functions, as they range over the values taken by binary forms.},
author = {de la Bretèche, Régis and Timothy Browning},
journal = {Acta Arithmetica},
number = {3},
pages = {291 -- 304},
publisher = {Instytut Matematyczny},
title = {{Sums of arithmetic functions over values of binary forms}},
doi = {10.4064/aa125-3-6},
volume = {125},
year = {2006},
}
@inproceedings{7326,
abstract = {Often the properties of a single cell are considered as representative for a complete polymer electrolyte fuel cell stack or even a fuel cell system. In some cases this comes close, however, in many real cases differences on several scales become important. Cell interaction phenomena in fuel cell stacks that arise from inequalities between adjacent cells are investigated in detail experimentally. For that, a specialized 2-cell stack with advanced localized diagnostics was developed. The results show that inequalities propagate by electrical coupling, inhomogeneous cell polarization and inducing in-plane current in the common bipolar plate. The effects of the different loss-mechanisms are analyzed and quantified. },
author = {Büchi, Felix N. and Freunberger, Stefan Alexander and Santis, Marco},
booktitle = {ECS Transactions},
location = {Cancun, Mexico},
number = {1},
pages = {963--968},
publisher = {ECS},
title = {{What is learned beyond the scale of single cells?}},
doi = {10.1149/1.2356215},
volume = {3},
year = {2006},
}
@article{7327,
abstract = {Propagation of performance changes to adjacent cells in polymer electrolyte fuel cell stacks is studied by means of voltage monitoring and local current density measurements in peripheral cells of the stack. A technical fuel cell stack has been modified by implementing two independent reactant and coolant supplies in order to deliberately change the performance of one cell (anomalous cell) and study the coupling phenomena to adjacent cells (coupling cells), while keeping the working conditions of the later cell-group unaltered.
Two anomalies are studied: (i) air starvation and (ii) thermal anomaly, in a single anomalous cell in the stack and their coupling to adjacent cells. The results have shown that anomalies inducing considerable changes in the local current density of the anomalous cell (such as air starvation) propagate to adjacent cells affecting their performance. The propagation of local current density changes takes place via the common bipolar plate due to its finite thickness and in-plane conductivity. Consequently, anomalies which do not strongly influence the local current density distribution (such as a thermal anomaly under the studied working conditions) do not propagate to adjacent cells.},
author = {Santis, Marco and Freunberger, Stefan Alexander and Papra, Matthias and Wokaun, Alexander and Büchi, Felix N.},
issn = {0378-7753},
journal = {Journal of Power Sources},
number = {2},
pages = {1076--1083},
publisher = {Elsevier},
title = {{Experimental investigation of coupling phenomena in polymer electrolyte fuel cell stacks}},
doi = {10.1016/j.jpowsour.2006.06.007},
volume = {161},
year = {2006},
}
@article{7328,
abstract = {An experimental technique for measuring the current density distribution with a resolution smaller than the channel/rib scale of the flow field in polymer electrolyte fuel cells (PEFCs) is presented. The electron conductors in a plane perpendicular to the channel direction are considered as two-dimensional resistors. Hence, the current density is obtained from the solution of Laplace's equation with the potentials at current collector and reaction layer as boundary conditions. Using ohmic drop for calculating the local current, detailed knowledge of all resistances involved is of prime importance. In particular, the contact resistance between the gas diffusion layer (GDL) and flow field rib, as well as GDL bulk conductivity, are strongly dependent on clamping pressure. They represent a substantial amount of the total ohmic drop and therefore require careful consideration. The detailed experimental setup as well as the concise procedure for quantitative data evaluation is described. Finally, the method is applied successfully to a cell operated on pure oxygen and air up to high current densities. The results show that electrical and ionic resistances seem to govern the current distribution at low current regimes, whereas mass transport limitations locally hamper the current production at high loads.},
author = {Freunberger, Stefan Alexander and Reum, Mathias and Evertz, Jörg and Wokaun, Alexander and Büchi, Felix N.},
issn = {0013-4651},
journal = {Journal of The Electrochemical Society},
number = {11},
publisher = {The Electrochemical Society},
title = {{Measuring the current distribution in PEFCs with sub-millimeter resolution}},
doi = {10.1149/1.2345591},
volume = {153},
year = {2006},
}
@article{7329,
abstract = {A novel measurement principle for measuring the current distribution in polymer electrolyte fuel cells (PEFCs) is introduced. It allows, in contrast to all other known techniques, for the first time for a resolution smaller than the channel/rib scale of the flow field in PEFCs. The current density is obtained by considering the electron conductors in the cell as a two-dimensional resistor with the voltage drop caused by the current. The method was applied to a cell operated on oxygen up to high current densities. The results show that the ohmic resistances govern the current distribution in the low current regime, whereas mass transport limitations hamper the current production under the land at high loads.},
author = {Freunberger, Stefan Alexander and Reum, Mathias and Wokaun, Alexander and Büchi, Felix N.},
issn = {1388-2481},
journal = {Electrochemistry Communications},
number = {9},
pages = {1435--1438},
publisher = {Elsevier},
title = {{Expanding current distribution measurement in PEFCs to sub-millimeter resolution}},
doi = {10.1016/j.elecom.2006.05.032},
volume = {8},
year = {2006},
}
@article{7330,
abstract = {Polymer electrolyte fuel cells (PE fuel cells) working with air at low stoichiometries (<2.0) and standard electrochemical components show a high degree of inhomogeneity in the current density distribution over the active area. An inhomogeneous current density distribution leads to a non-uniform utilization of the active area, which could negatively affect the time of life of the cells. Furthermore, it is also believed to lower cell performance. In this work, the homogenization of the current density, realized by means of tailored cathodes with along-the-air-channel redistributed catalyst loadings, is investigated. The air stoichiometry range for which a homogenization of the current density is achieved depends upon the gradient with which the catalyst is redistributed along the air channel. A gentle increasing catalyst loading profile homogenizes the current density at relatively higher air stoichiometries, while a steeper profile is suited better for lower air stoichiometries. The results show that a homogenization of the current density by means of redistributed catalyst loading has negative effects on cell performance. Model calculations corroborate the experimental findings on homogenization of the current density and deliver an explanation for the decrease in cell performance.},
author = {Santis, M. and Freunberger, Stefan Alexander and Reiner, A. and Büchi, F.N.},
issn = {0013-4686},
journal = {Electrochimica Acta},
number = {25},
pages = {5383--5393},
publisher = {Elsevier},
title = {{Homogenization of the current density in polymer electrolyte fuel cells by in-plane cathode catalyst gradients}},
doi = {10.1016/j.electacta.2006.02.008},
volume = {51},
year = {2006},
}
@article{7331,
abstract = {A previously developed mathematical model for water management and current density distribution in a polymer electrolyte fuel cell (PEFCs) is employed to investigate the effects of cooling strategies on cell performance. The model describes a two-dimensional slice through the cell along the channels and through the entire cell sandwich including the coolant channels and the bipolar plate. Arbitrary flow arrangements of fuel, oxidant, and coolant stream directions can be described. Due to the serious impact of temperature on all processes in the PEFC, both the relative direction of the coolant stream to the gas streams and its mass flow turns out to significantly affect the cell performance. Besides influencing the electrochemical reaction and all kinds of mass transfer temperature, variations predominantly alter the local membrane hydration distribution and subseqently its conductivity.},
author = {Freunberger, Stefan Alexander and Wokaun, Alexander and Büchi, Felix N.},
issn = {0013-4651},
journal = {Journal of The Electrochemical Society},
number = {5},
publisher = {The Electrochemical Society},
title = {{In-plane effects in large-scale PEFCs: II. The influence of cooling strategy on cell performance}},
doi = {10.1149/1.2185282},
volume = {153},
year = {2006},
}
@article{7332,
abstract = {A quasi-two-dimensional, along-the-channel mass and heat-transfer model for a proton exchange membrane fuel cell (PEFC) is described and validated against experimental current distribution data. The model is formulated in a dimensional manner, i.e., local transport phenomena are treated one-dimensional in through-plane direction and coupled in-plane by convective transport in the gas and coolant channels. Thus, a two-dimensional slice running through the repetitive unit of a cell from the anode channel via membrane-electrode assembly (MEA) and cathode channel to the coolant channel and from inlet to outlet is modeled. The aim of the work is to elucidate the influence of operating conditions such as feed gas humidities and stoichiometric ratios on the along-the-channel current density distribution and to identify the distinct underlying voltage loss mechanisms. Furthermore, a complicated technical flow field is modeled by a combination of co- and counterflow subdomains and compared with experimental current densities.},
author = {Freunberger, Stefan Alexander and Santis, Marco and Schneider, Ingo A. and Wokaun, Alexander and Büchi, Felix N.},
issn = {0013-4651},
journal = {Journal of The Electrochemical Society},
number = {2},
publisher = {The Electrochemical Society},
title = {{In-plane effects in large-scale PEMFCs}},
doi = {10.1149/1.2150150},
volume = {153},
year = {2006},
}
@unpublished{573,
abstract = {Mitchison and Jozsa recently suggested that the "chained-Zeno" counterfactual computation protocol recently proposed by Hosten et al. is counterfactual for only one output of the computer. This claim was based on the existing abstract algebraic definition of counterfactual computation, and indeed according to this definition, their argument is correct. However, a more general definition (physically adequate) for counterfactual computation is implicitly assumed by Hosten et. al. Here we explain in detail why the protocol is counterfactual and how the "history tracking" method of the existing description inadequately represents the physics underlying the protocol. Consequently, we propose a modified definition of counterfactual computation. Finally, we comment on one of the most interesting aspects of the error-correcting protocol. },
author = {Hosten, Onur and Rakher, Matthew and Barreiro, Julio and Peters, Nicholas and Kwiat, Paul},
pages = {12},
publisher = {ArXiv},
title = {{Counterfactual computation revisited}},
year = {2006},
}
@unpublished{574,
abstract = {Vaidman, in a recent article adopts the method of 'quantum weak measurements in pre- and postselected ensembles' to ascertain whether or not the chained-Zeno counterfactual computation scheme proposed by Hosten et al. is counterfactual; which has been the topic of a debate on the definition of counterfactuality. We disagree with his conclusion, which brings up some interesting aspects of quantum weak measurements and some concerns about the way they are interpreted. },
author = {Hosten, Onur and Kwiat, Paul},
pages = {2},
publisher = {ArXiv},
title = {{Weak measurements and counterfactual computation}},
year = {2006},
}
@inproceedings{577,
abstract = {Visible light photon counters (VLPCs) and solid-state photomultipliers (SSPMs) are high-efficiency single-photon detectors which have multi-photon counting capability. While both the VLPCs and the SSPMs have inferred internal quantum efficiencies above 93%, the actual measured values for both the detectors were in fact limited to less than 88%, attributed to in-coupling losses. We are currently improving this overall detection efficiency via a) custom anti-reflection coating the detectors and the in-coupling fibers, b) implementing a novel cryogenic design to reduce transmission losses and, c) using low-noise electronics to obtain a better signal-to-noise ratio.},
author = {Rangarajan, Radhika and Altepeter, Joseph B and Jeffrey, Evan R and Stoutimore, Micah J and Peters, Nicholas A and Onur Hosten and Kwiat, Paul G},
publisher = {SPIE},
title = {{High-efficiency single-photon detectors}},
doi = {10.1117/12.686117},
volume = {6372},
year = {2006},
}
@inproceedings{578,
abstract = {A source of single photons allows secure quantum key distribution, in addition, to being a critical resource for linear optics quantum computing. We describe our progress on deterministically creating single photons from spontaneous parametric downconversion, an extension of the Pittman, Jacobs and Franson scheme [Phys. Rev A, v66, 042303 (2002)]. Their idea was to conditionally prepare single photons by measuring one member of a spontaneously emitted photon pair and storing the remaining conditionally prepared photon until a predetermined time, when it would be "deterministically" released from storage. Our approach attempts to improve upon this by recycling the pump pulse in order to decrease the possibility of multiple-pair generation, while maintaining a high probability of producing a single pair. Many of the challenges we discuss are central to other quantum information technologies, including the need for low-loss optical storage, switching and detection, and fast feed-forward control.},
author = {Peters, Nicholas A and Arnold, Keith J and VanDevender, Aaron P and Jeffrey, Evan R and Rangarajan, Radhika and Onur Hosten and Barreiro, Julio T and Altepeter, Joseph B and Kwiat, Paul G},
publisher = {SPIE},
title = {{Towards a quasi-deterministic single-photon source}},
doi = {10.1117/12.684702},
volume = {6305},
year = {2006},
}
@article{579,
abstract = {The logic underlying the coherent nature of quantum information processing often deviates from intuitive reasoning, leading to surprising effects. Counterfactual computation constitutes a striking example: the potential outcome of a quantum computation can be inferred, even if the computer is not run 1. Relying on similar arguments to interaction-free measurements 2 (or quantum interrogation3), counterfactual computation is accomplished by putting the computer in a superposition of 'running' and 'not running' states, and then interfering the two histories. Conditional on the as-yet-unknown outcome of the computation, it is sometimes possible to counterfactually infer information about the solution. Here we demonstrate counterfactual computation, implementing Grover's search algorithm with an all-optical approach4. It was believed that the overall probability of such counterfactual inference is intrinsically limited1,5, so that it could not perform better on average than random guesses. However, using a novel 'chained' version of the quantum Zeno effect6, we show how to boost the counterfactual inference probability to unity, thereby beating the random guessing limit. Our methods are general and apply to any physical system, as illustrated by a discussion of trapped-ion systems. Finally, we briefly show that, in certain circumstances, counterfactual computation can eliminate errors induced by decoherence. },
author = {Onur Hosten and Rakher, Matthew T and Barreiro, Julio T and Peters, Nicholas A and Kwiat, Paul G},
journal = {Nature},
number = {7079},
pages = {949 -- 952},
publisher = {Nature Publishing Group},
title = {{Counterfactual quantum computation through quantum interrogation}},
doi = {10.1038/nature04523},
volume = {439},
year = {2006},
}
@inproceedings{583,
abstract = {Visible light photon counters (VLPCs) and solid-state photomultipliers (SSPMs) facilitate efficient single-photon detection. We are attempting to improve their efficiency, previously limited to < 88% by coupling losses, via anti-reflection coatings, better electronics and cryogenics.},
author = {Rangarajan, Radhika and Peters, Nicholas A and Onur Hosten and Altepeter, Joseph B and Jeffrey, Evan R and Kwiat, Paul G},
publisher = {IEEE},
title = {{Improved single-photon detection}},
doi = {10.1109/CLEO.2006.4628641},
year = {2006},
}