Showing papers by "University of Konstanz published in 2006"
TL;DR: It is found that gold particles can be produced in a wide range of sizes, from 9 to 120 nm, with defined size distribution, following the earlier work of Turkevich and Frens.
Abstract: The growth of gold nanoparticles by reduction by citrate and ascorbic acid has been examined in detail to explore the parameter space of reaction conditions. It is found that gold particles can be produced in a wide range of sizes, from 9 to 120 nm, with defined size distribution, following the earlier work of Turkevich and Frens. The reaction is initiated thermally or in comparison by UV irradiation, which results in similar final products. The kinetics of the extinction spectra show the multiple steps of primary and secondary clustering leading to polycrystallites.
1,906 citations
TL;DR: It is concluded that ERP measures are useful to assess the emotion-attention interface at the level of distinct processing stages in response to stimulus novelty, emotional prime pictures, learned stimulus significance, and in the context of explicit attention tasks.
Abstract: Emotional pictures guide selective visual attention. A series of event-related brain potential (ERP) studies is reviewed demonstrating the consistent and robust modulation of specific ERP components by emotional images. Specifically, pictures depicting natural pleasant and unpleasant scenes are associated with an increased early posterior negativity, late positive potential, and sustained positive slow wave compared with neutral contents. These modulations are considered to index different stages of stimulus processing including perceptual encoding, stimulus representation in working memory, and elaborate stimulus evaluation. Furthermore, the review includes a discussion of studies exploring the interaction of motivated attention with passive and active forms of attentional control. Recent research is reviewed exploring the selective processing of emotional cues as a function of stimulus novelty, emotional prime pictures, learned stimulus significance, and in the context of explicit attention tasks. It is concluded that ERP measures are useful to assess the emotion-attention interface at the level of distinct processing stages. Results are discussed within the context of two-stage models of stimulus perception brought out by studies of attention, orienting, and learning.
863 citations
TL;DR: It is shown that in the unicellular eukaryote Paramecium tetraurelia, a ciliate, most of the nearly 40,000 genes arose through at least three successive whole-genome duplications.
Abstract: The duplication of entire genomes has long been recognized as having great potential for evolutionary novelties, but the mechanisms underlying their resolution through gene loss are poorly understood. Here we show that in the unicellular eukaryote Paramecium tetraurelia, a ciliate, most of the nearly 40,000 genes arose through at least three successive whole-genome duplications. Phylogenetic analysis indicates that the most recent duplication coincides with an explosion of speciation events that gave rise to the P. aurelia complex of 15 sibling species. We observed that gene loss occurs over a long timescale, not as an initial massive event. Genes from the same metabolic pathway or protein complex have common patterns of gene loss, and highly expressed genes are over-retained after all duplications. The conclusion of this analysis is that many genes are maintained after whole-genome duplication not because of functional innovation but because of gene dosage constraints.
732 citations
TL;DR: It is found that the minimum conductivity of order e2/h at the Dirac point (when the electron and hole excitations are degenerate) is associated with a maximum of the Fano factor (the ratio of noise power and mean current).
Abstract: We calculate the mode-dependent transmission probability of massless Dirac fermions through an ideal strip of graphene (length $L$, width $W$, no impurities or defects) to obtain the conductance and shot noise as a function of Fermi energy. We find that the minimum conductivity of order ${e}^{2}/h$ at the Dirac point (when the electron and hole excitations are degenerate) is associated with a maximum of the Fano factor (the ratio of noise power and mean current). For short and wide graphene strips the Fano factor at the Dirac point equals $1/3$, 3 times smaller than for a Poisson process. This is the same value as for a disordered metal, which is remarkable since the classical dynamics of the Dirac fermions is ballistic.
724 citations
TL;DR: A convincing case of sympatric speciation is presented in the Midas cichlid species complex (Amphilophus sp.) in a young and small volcanic crater lake in Nicaragua and it is found that the two species in Lake Apoyo are reproductively isolated and eco-morphologically distinct.
Abstract: One of the hottest controversies in evolutionary biology is sympatric speciation, the formation of new species in the absence of geographical boundaries. The controversy is about whether it happens or not: it ‘should’ in theory but it is difficult to prove it. Two new examples of the phenomenon are reported this week, one in fish and one (online) in plants, convincing evidence that as Darwin suggested, sympatric speciation is likely to be common. The fishy example is the formation of Amphilophus zaliosus from A. citrinellus in a volcanic crater lake in Nicaragua. And in plants, the curly palm Howea belmoreana and the thatch palm H. forsteriana diverged on Lord Howe Island, a volcanic island 480 km east of Australia in the Tasman Sea. Sympatric speciation, the formation of species in the absence of geographical barriers, remains one of the most contentious concepts in evolutionary biology. Although speciation under sympatric conditions seems theoretically possible1,2,3,4,5, empirical studies are scarce and only a few credible examples of sympatric speciation exist6. Here we present a convincing case of sympatric speciation in the Midas cichlid species complex (Amphilophus sp.) in a young and small volcanic crater lake in Nicaragua. Our study includes phylogeographic, population-genetic (based on mitochondrial DNA, microsatellites and amplified fragment length polymorphisms), morphometric and ecological analyses. We find, first, that crater Lake Apoyo was seeded only once by the ancestral high-bodied benthic species Amphilophus citrinellus, the most common cichlid species in the area; second, that a new elongated limnetic species (Amphilophus zaliosus) evolved in Lake Apoyo from the ancestral species (A. citrinellus) within less than ∼10,000 yr; third, that the two species in Lake Apoyo are reproductively isolated; and fourth, that the two species are eco-morphologically distinct.
680 citations
TL;DR: In both studies, need for recovery mediated the effects of job characteristics and off-job activities on fatigue and poor well-being, respectively.
Abstract: Two empirical studies examined need for recovery (i.e., a person's desire to be temporarily relieved from demands in order to restore his or her resources) as a mediator in the relationship between poor job characteristics (high job demands, low job control) and high off-job demands, on the one hand, and fatigue and poor individual well-being, on the other hand. Multilevel data from a daily survey study in the health service sector (Study 1) showed that high job demands, low job control, and unfavorable off-job activities predicted a high need for recovery. Need for recovery in turn was negatively related to individual well-being. A large-scale survey with a representative sample of the Dutch working population (Study 2) confirmed these findings for fatigue. In both studies, need for recovery mediated the effects of job characteristics and off-job activities on fatigue and poor well-being, respectively.
611 citations
TL;DR: In this article, it is shown that sustainability research for sustainable development has to be issue oriented and reflect the diversity, complexity and dynamics of the processes involved as well as their variability between specific problem situations.
590 citations
TL;DR: A crystallographic structure of trimeric AcrB determined at 2.9 and 3.0 angstrom resolution in space groups reveals three different monomer conformations representing consecutive states in a transport cycle, implying an alternating access mechanism and a novel peristaltic mode of drug transport by this type of transporter.
Abstract: The AcrA/AcrB/TolC complex spans the inner and outer membranes of Escherichia coli and serves as its major drug-resistance pump. Driven by the proton motive force, it mediates the efflux of bile salts, detergents, organic solvents, and many structurally unrelated antibiotics. Here, we report a crystallographic structure of trimeric AcrB determined at 2.9 and 3.0 angstrom resolution in space groups that allow asymmetry of the monomers. This structure reveals three different monomer conformations representing consecutive states in a transport cycle. The structural data imply an alternating access mechanism and a novel peristaltic mode of drug transport by this type of transporter.
536 citations
TL;DR: Results showed changes in well-being and self-reported effort expenditure from before to after vacation, revealing vacation effects and partial fade-out effects.
Abstract: On the basis of theoretical assumptions regarding resource gain and loss (S. E. Hobfoll, 1998), the authors used a longitudinal study to examine effects of vacation on well-being and performance-related outcomes. University employees (N = 221) completed measures of well-being (health complaints and burnout) and performance-related outcomes (self-reported task performance and effort expenditure) 1 week before and 2 days and 2 weeks after vacation and measures of workload 2 days after vacation. Specific vacation experiences (positive and negative work reflection, relaxation, mastery experience, and nonwork hassles) were assessed during vacation. Results showed changes in well-being and self-reported effort expenditure from before to after vacation, revealing vacation effects and partial fade-out effects. In addition, vacation experiences and workload significantly predicted some of the outcomes. The authors discuss applicability of the theoretical approach in the context of vacation and fade-out effects, implications for future research on recovery processes, and practical implications.
522 citations
TL;DR: In this paper, the authors examined the relationship between routinization and four work character istics (job control, job complexity, time pressure, and supervisor support) and a range of creative and proactive behaviors on the other hand.
Abstract: Summary Researchers have claimed that routinization hinders creativity. However, empirical evidence for this assumption is sparse. In this study, we argue that routinization may be beneficial for creativity and related behavior due to available resources that can be used to develop new ideas while working. We examine the relationship between routinization and four work character istics (job control, job complexity, time pressure, and supervisor support) on the one hand and a range of creative and proactive behaviors on the other hand in a randomly selected sample of 278 employees of a German high tech company. Regression analyses reveal that in addition to work characteristics, routinization is generally positively related to creative and proactive behaviors. Ways to enhance routinization and thereby creative and proactive behaviors are discussed.
500 citations
05 Jul 2006
TL;DR: This paper aims at providing an overview of visual analytics, its scope and concepts, and details the most important technical research challenges in the field.
Abstract: In todays applications data is produced at unprecedented rates. While the capacity to collect and store new data grows rapidly, the ability to analyze these data volumes increases at much lower pace. This gap leads to new challenges in the analysis process, since analysts, decision makers, engineers, or emergency response teams depend on information "concealed" in the data. The emerging field of visual analytics focuses on handling massive, heterogenous, and dynamic volumes of information through integration of human judgement by means of visual representations and interaction techniques in the analysis process. Furthermore, it is the combination of related research areas including visualization, data mining, and statistics that turns visual analytics into a promising field of research. This paper aims at providing an overview of visual analytics, its scope and concepts, and details the most important technical research challenges in the field.
TL;DR: The data show that TLR2 forms heterodimers with TLR1 and TLR6 and that these heterodimer pre-exist and are not induced by the ligand, and that heterotypic associations ofTLR2/6 with CD36 are not preformed and are ligand-induced.
TL;DR: Time resolved measurements of light transport through strongly scattering samples with kl* values as low as 2.5 constitute an experimental realization of the critical regime in the approach to Anderson localization.
Abstract: In this paper we present time resolved measurements of optical transmission, which show clear deviations from classical diffusion. These deviations increase with increasing turbidity, providing experimental evidence for the onset of Anderson localization of light.
TL;DR: The ability of southern killifish to upregulate hsc70 in response to heat shock suggests a possible role for these hsps in whole-organism differences in thermal tolerance, and highlights the importance of considering the complexity of the heat shock response across multiple isoforms when attempting to make linkages to whole- Organism traits such as thermal tolerance.
Abstract: Populations of common killifish, Fundulus heteroclitus, are distributed along the Atlantic coast of North America through a steep latitudinal thermal gradient. We examined intraspecific variation in whole-animal thermal tolerance and its relationship to the heat shock response in killifish from the northern and southern extremes of the species range. Critical thermal maxima were significantly higher in southern than in northern fish by approximately 1.5 degrees C at a wide range of acclimation temperatures (from 2-34 degrees C), and critical thermal minima differed by approximately 1.5 degrees C at acclimation temperatures above 22 degrees C, converging on the freezing point of brackish water at lower acclimation temperatures. To determine whether these differences in whole-organism thermal tolerance were reflected in differences in either the sequence or regulation of the heat shock protein genes (hsps) we obtained complete cDNA sequences for hsc70, hsp70-1 and hsp70-2, and partial sequences of hsp90alpha and hsp90beta. There were no fixed differences in amino acid sequence between populations in either hsp70-1 or hsp70-2, and only a single conservative substitution between populations in hsc70. By contrast, there were significant differences between populations in the expression of many, but not all, of these genes. Both northern and southern killifish significantly increased hsp70-2 levels above control values (T(on)) at a heat shock temperature of 33 degrees C, but the magnitude of this induction was greater in northern fish, suggesting that northern fish may be more susceptible to thermal damage than are southern fish. In contrast, hsp70-1 mRNA levels increased gradually and to the same extent in response to heat shock in both populations. Hsc70 mRNA levels were significantly elevated by heat shock in southern fish, but not in northern fish. Similarly, the more thermotolerant southern killifish had a T(on) for hsp90alpha of 30 degrees C, 2 degrees C lower than that of northern fish. This observation combined with the ability of southern killifish to upregulate hsc70 in response to heat shock suggests a possible role for these hsps in whole-organism differences in thermal tolerance. These data highlight the importance of considering the complexity of the heat shock response across multiple isoforms when attempting to make linkages to whole-organism traits such as thermal tolerance.
TL;DR: Data suggest that the enhanced positive slow wave seen over posterior sites during emotional picture processing represents activity in a circuit of visual cortical structures, reflecting a perceptual sensitivity to the motivational relevance of visual scenes.
Abstract: Dense-array electrocortical and functional hemodynamic measures of human brain activity were collected to assess the relationship between 2 established neural measures of emotional reactivity. Recorded in parallel sessions, the slow-wave late positive potential (LPP) and visual cortical blood oxygen level-dependent (BOLD) signals were both modulated by the rated intensity of picture arousal. The amplitude of the LPP correlated significantly with BOLD intensity in lateral occipital, inferotemporal, and parietal visual areas across picture contents. Estimated strength of modeled regional sources did not correlate significantly with regional BOLD intensity. These data suggest that the enhanced positive slow wave seen over posterior sites during emotional picture processing represents activity in a circuit of visual cortical structures, reflecting a perceptual sensitivity to the motivational relevance of visual scenes.
TL;DR: In the development of modern nation states, the state has not only been the guarantor of civil rights, e.g. the right to own property, to enter into private contracts, and to engage in market activity, but also provided political participation rights, the right of the citizen to take part in the processes that determine public rules and issues of public concern as discussed by the authors.
Abstract: Economic activities require the existence of rules and their enforcement as preconditions that the market cannot generate itself. Property rights, and contractual rights and obligations, are minimal prerequisites for modern societies that are provided and enforced by the state. Without such prerequisites, the market cannot flourish. The state thus determines regulations and delineates the sphere of private freedom, within which individual citizens and private institutions are entitled to conclude contracts with one another, to which the system of property and contractual rights compels obedience. In the development of modern nation states, the state has not only been the guarantor of civil rights, e. g. the right to own property, to enter into private contracts, and to engage in market activity. In its role as a democratic constitutional state, it has also been the guarantor of political participation rights, the right of the citizen to take part in the processes that determine public rules and issues of public concern. Finally, in its role as a welfare state, it has provided social rights for citizens, such as the right to education, to health care, and to other forms of welfare (Marshall 1965). The combination of state-guaranteed civil, political, and social rights has provided legitimacy, solidarity, and welfare to modern society, thereby contributing to peaceful, stable communities of anonymous individuals (Habermas 2001). Following Matten and Crane (Matten/Crane 2005) we refer to this triad of rights as citizenship rights.
TL;DR: In vivo cell lineage analysis in mice demonstrates the presence of a common progenitor of cortical and medullary TECs after birth, suggesting that cell-based therapies could be developed for thymus disorders.
Abstract: The thymus is essential for the generation of self-tolerant effector and regulatory T cells. Intrathymic T-cell development requires an intact stromal microenvironment, of which thymic epithelial cells (TECs) constitute a major part. For instance, cell-autonomous genetic defects of forkhead box N1 (Foxn1) and autoimmune regulator (Aire) in thymic epithelial cells cause primary immunodeficiency and autoimmunity, respectively. During development, the thymic epithelial rudiment gives rise to two major compartments, the cortex and medulla. Cortical TECs positively select T cells, whereas medullary TECs are involved in negative selection of potentially autoreactive T cells. It has long been unclear whether these two morphologically and functionally distinct types of epithelial cells arise from a common bi-potent progenitor cell and whether such progenitors are still present in the postnatal period. Here, using in vivo cell lineage analysis in mice, we demonstrate the presence of a common progenitor of cortical and medullary TECs after birth. To probe the function of postnatal progenitors, a conditional mutant allele of Foxn1 was reverted to wild-type function in single epithelial cells in vivo. This led to the formation of small thymic lobules containing both cortical and medullary areas that supported normal thymopoiesis. Thus, single epithelial progenitor cells can give rise to a complete and functional thymic microenvironment, suggesting that cell-based therapies could be developed for thymus disorders.
TL;DR: A route and mechanism for translocation of the capsular polysaccharide of Wza, an integral outer membrane lipoprotein, which is essential for group 1 capsule export in Escherichia coli is proposed and may provide insight into the export of other large polar molecules such as DNA and proteins.
Abstract: Many types of bacteria produce extracellular polysaccharides (EPSs). Some are secreted polymers and show only limited association with the cell surface, whereas others are firmly attached to the cell surface and form a discrete structural layer, the capsule, which envelopes the cell and allows the bacteria to evade or counteract the host immune system. EPSs have critical roles in bacterial colonization of surfaces, such as epithelia and medical implants; in addition some EPSs have important industrial and biomedical applications in their own right. Here we describe the 2.26 A resolution structure of the 340 kDa octamer of Wza, an integral outer membrane lipoprotein, which is essential for group 1 capsule export in Escherichia coli. The transmembrane region is a novel alpha-helical barrel. The bulk of the Wza structure is located in the periplasm and comprises three novel domains forming a large central cavity. Wza is open to the extracellular environment but closed to the periplasm. We propose a route and mechanism for translocation of the capsular polysaccharide. This work may provide insight into the export of other large polar molecules such as DNA and proteins.
TL;DR: Forward and reverse genetics in the mouse now provide powerful novel models to elucidate the action of CEACAM family members in vivo.
TL;DR: The view of evolution of N2O respiration prior to the separation of the domains Bacteria and Archaea is supported, with the paradigm of Z-type N2OR described.
Abstract: N2O is a potent greenhouse gas and stratospheric reactant that has been steadily on the rise since the beginning of industrialization. It is an obligatory inorganic metabolite of denitrifying bacteria, and some production of N2O is also found in nitrifying and methanotrophic bacteria. We focus this review on the respiratory aspect of N2O transformation catalysed by the multicopper enzyme nitrous oxide reductase (N2OR) that provides the bacterial cell with an electron sink for anaerobic growth. Two types of Cu centres discovered in N2OR were both novel structures among the Cu proteins: the mixed-valent dinuclear CuA species at the electron entry site of the enzyme, and the tetranuclear CuZ centre as the first catalytically active Cu–sulfur complex known. Several accessory proteins function as Cu chaperone and ABC transporter systems for the biogenesis of the catalytic centre. We describe here the paradigm of Z-type N2OR, whose characteristics have been studied in most detail in the genera Pseudomonas and Paracoccus. Sequenced bacterial genomes now provide an invaluable additional source of information. New strains harbouring nos genes and capability of N2O utilization are being uncovered. This reveals previously unknown relationships and allows pattern recognition and predictions. The core nos genes, nosZDFYL, share a common phylogeny. Most principal taxonomic lineages follow the same biochemical and genetic pattern and share the Z-type enzyme. A modified N2OR is found in Wolinella succinogenes, and circumstantial evidence also indicates for certain Archaea another type of N2OR. The current picture supports the view of evolution of N2O respiration prior to the separation of the domains Bacteria and Archaea. Lateral nos gene transfer from an e-proteobacterium as donor is suggested for Magnetospirillum magnetotacticum and Dechloromonas aromatica. In a few cases, nos gene clusters are plasmid borne. Inorganic N2O metabolism is associated with a diversity of physiological traits and biochemically challenging metabolic modes or habitats, including halorespiration, diazotrophy, symbiosis, pathogenicity, psychrophily, thermophily, extreme halophily and the marine habitat down to the greatest depth. Components for N2O respiration cover topologically the periplasm and the inner and outer membranes. The Sec and Tat translocons share the task of exporting Nos components to their functional sites. Electron donation to N2OR follows pathways with modifications depending on the host organism. A short chronology of the field is also presented.
TL;DR: Mapping the interplay between cortical and subcortical mechanisms that give rise to amplified cortical responses to emotional words will be of highest priority for future research.
Abstract: The event-related brain potential (ERP) literature concerning the impact of emotional content on visual word processing is reviewed and related to general knowledge on semantics in word processing: emotional connotation can enhance cortical responses at all stages of visual word processing following the assembly of visual word form (up to 200 ms), such as semantic access (around 200 ms), allocation of attentional resources (around 300 ms), contextual analysis (around 400 ms), and sustained processing and memory encoding (around 500 ms). Even earlier effects have occasionally been reported with subliminal or perceptual threshold presentation, particularly in clinical populations. Here, the underlying mechanisms are likely to diverge from the ones operational in standard natural reading. The variability in timing of the effects can be accounted for by dynamically changing lexical representations that can be activated as required by the subjects' motivational state, the task at hand, and additional contextual factors. Throughout, subcortical structures such as the amygdala are likely to contribute these enhancements. Further research will establish whether or when emotional arousal, valence, or additional emotional properties drive the observed effects and how experimental factors interact with these. Meticulous control of other word properties known to affect ERPs in visual word processing, such as word class, length, frequency, and concreteness and the use of more standardized EEG procedures is vital. Mapping the interplay between cortical and subcortical mechanisms that give rise to amplified cortical responses to emotional words will be of highest priority for future research.
TL;DR: The startle tone interrupted processing of particularly pleasant adjectives and caused re-alerting to environmental stimuli and specific effects for pleasant material may arise from a "positivity offset," favoring responses to pleasant material at lower arousal levels.
Abstract: Affective startle modulation in the electromyographic (EMG) response, auditory startle evoked potentials, and visually evoked potentials (VEPs) were assessed while subjects evaluated pleasant, unpleasant, and neutral adjectives. Acoustic startle probes were presented at random time points 2.5–4.0 s after word onset. The visual P2 and P3 potentials were generally larger during processing of emotional than of neutral adjectives. In contrast, the late positive component was enhanced and was correlated with larger EMG startle responses and auditory startle evoked potential P3 amplitudes for pleasant words only. During internal cognitive activity, the startle reflex represents a measure of ’’processing interrupt.’’ Thus the startle tone interrupted processing of particularly pleasant adjectives and caused realerting to environmental stimuli. Specific effects for pleasant material may arise from a ’’positivity offset,’’ favoring responses to pleasant material at lower arousal levels.
TL;DR: Results of this study argue for the presence of a deafferentation also in tinnitus subjects with audiometrically normal thresholds and therefore favour the deAfferentation assumption posed by most neuroscientific theories.
TL;DR: In this article, the authors examined job stressors, job involvement, and recovery-related selfefficacy as predictors of psychological detachment in a sample of 148 school teachers, assessed by self-reports and by ratings provided by family members.
Abstract: Previous research has suggested that psychological detachment from work during off-job time is important in order to recover from stress encountered at the job. Psychological detachment refers to an individual's experience of being mentally away from work, to make a pause in thinking about work-related issues, thus to “switch off”. This study examines job stressors, job involvement, and recovery-related self-efficacy as predictors of psychological detachment in a sample of 148 school teachers. Psychological detachment was assessed by self-reports and by ratings provided by family members. Multiple regression analysis showed that workload, job involvement, and recovery-related self-efficacy were significant predictors of both self-rated and family-rated psychological detachment. The study findings suggest that with respect to practical implications it is crucial to manage workload and to increase recovery-related self-efficacy.
TL;DR: In this article, the authors analyze whether globalization has indeed influenced the composition of government expenditures and conclude that globalization did not influence the composition at the level of government expenditure in 108 countries.
Abstract: According to the disciplining hypothesis, globalization restrains governments by inducing increased budgetary pressure. As a consequence, governments shift their expenditures in favour of transfers and subsidies and away from capital expenditures. This expenditure shift is potentially enhanced by citizens' preferences to be compensated for the risks of globalization ("compensation hypothesis"). Employing two different datasets and various measures of globalization, we analyze whether globalization has indeed influenced the composition of government expenditures. For a sample of 108 countries, we examine the development of four broad expenditure categories for the period 1970-2001: capital expenditures; expenditures for goods and services; interest payments; and subsidies and other current transfers. A second dataset provides a much more detailed classification: public expenditures, expenditures for defence, order, economic environment, housing, health, recreation, education, and social expenditures. However, this second data set is only available since 1990 - and only for the OECD countries. Our results show that globalization did not influence the composition of government expenditures.
TL;DR: Diatoms can be considered as one of the most successful taxonomic groups with respect to evolution and ecology, however, the genetic andphysiological basis why diatoms became soecologically successful is still a matter of debate.
TL;DR: In this article, a step-by-step guideline is developed to assess the chances of submerged macrophyte re-establishment in shallow lakes in Germany, taking into account the complex factors and interrelations that determine their occurrence, abundance and diversity.
TL;DR: It is shown that the water temperature rises to near the critical temperature and the water undergoes an explosive evaporation in the subnanosecond range, and the formation of vapor bubbles shows a threshold dependence on laser fluence.
Abstract: Intense nonequilibrium femtosecond laser excitation of gold nanoparticles in water leads to a transient heating of the nanoparticles, which decays via heat transfer to the water phase. It is shown that the water temperature rises to near the critical temperature and the water undergoes an explosive evaporation in the subnanosecond range. The formation of vapor bubbles shows a threshold dependence on laser fluence. The nascent nanoscale vapor bubbles change the heat dissipation drastically. The nanoscale structure is resolved directly with a combination of x-ray scattering methods sensitive to the particle lattice expansion and the change in the water structure factor.
TL;DR: In this article, the Dirac equation was used to determine the maximal supercurrent that can flow through an undoped strip of graphene with heavily doped superconducting electrodes, and the result was shown to be the same as in this paper.
Abstract: We solve the Dirac\char21{}Bogoliubov\char21{}de Gennes equation in an impurity-free superconductor\char21{}normal-metal\char21{}superconductor junction, to determine the maximal supercurrent ${I}_{c}$ that can flow through an undoped strip of graphene with heavily doped superconducting electrodes. The result ${I}_{c}\ensuremath{\simeq}(W∕L)e{\ensuremath{\Delta}}_{0}∕\ensuremath{\hbar}$ is determined by the superconducting gap ${\ensuremath{\Delta}}_{0}$ and by the aspect ratio of the junction (length $L$ small relative to the width $W$ and to the superconducting coherence length). Moving away from the Dirac point of zero doping, we recover the usual ballistic result ${I}_{c}\ensuremath{\simeq}(W∕{\ensuremath{\lambda}}_{F})e{\ensuremath{\Delta}}_{0}∕\ensuremath{\hbar}$, in which the Fermi wavelength ${\ensuremath{\lambda}}_{F}$ takes over from $L$. The product ${I}_{c}{R}_{\mathrm{N}}\ensuremath{\simeq}{\ensuremath{\Delta}}_{0}∕e$ of the critical current and normal-state resistance retains its universal value (up to a numerical prefactor) on approaching the Dirac point.
18 Sep 2006
TL;DR: A novel sampling-based approximation technique for classical multidimensional scaling that yields an extremely fast layout algorithm suitable even for very large graphs, and is among the fastest methods available.
Abstract: We present a novel sampling-based approximation technique for classical multidimensional scaling that yields an extremely fast layout algorithm suitable even for very large graphs. It produces layouts that compare favorably with other methods for drawing large graphs, and it is among the fastest methods available. In addition, our approach allows for progressive computation, i.e. a rough approximation of the layout can be produced even faster, and then be refined until satisfaction.