Resonant tunneling through ultrasmall quantum dots: zero-bias anomalies, magnetic field dependence, and boson-assisted transport

We study resonant tunneling through a single-level quantum dot in the presence of strong Coulomb repulsion beyond the perturbative regime. The level is either spin-degenerate or can be split by a magnetic field. We, furthermore, discuss the influence of a bosonic environment. Using a real-time diagrammatic formulation we calculate transition rates, the spectral density and the nonlinear $I-V$ characteristic. The spectral density shows a multiplet of Kondo peaks split by the transport voltage and the boson frequencies, and shifted by the magnetic field. This leads to zero-bias anomalies in the differential conductance, which agree well with recent experimental results for the electron transport through single-charge traps. Furthermore, we predict that the sign of the zero-bias anomaly depends on the level position relative to the Fermi level of the leads.Comment: 27 pages, latex, 21 figures, submitted to Phys. Rev.

Cardiovascular and metabolic determinants of quality of life in patients with cancer

AIMS: Maintaining quality of life (QoL) in patients with cancer has gathered significant interest, but little is known about its major determinants. We sought to identify determinants of QoL in patients undergoing cancer treatment as well as in treatment-naïve patients about to commence such therapy. METHODS AND RESULTS: QoL was assessed in 283 patients with cancer using the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 questionnaire. All patients underwent a battery of tests including physical examination, resting electrocardiogram, hand grip strength, and biochemistry assessment. Using multivariable logistic regression, we found that age [odds ratio (OR) 0.954, 95% confidence interval (CI) 0.916-0.994], resting heart rate (OR 1.036, 95% CI 1.004-1.068), hand grip strength (OR 0.932, 95% CI 0.878-0.990), and the presence of cachexia (OR 4.334, 95% CI 1.767-10.631) and dyspnoea (OR 3.725, 95% CI 1.540-9.010; all P < 0.05) remained independently predictive of reduced QoL. CONCLUSIONS: Therefore, it may be reasonable to address circumstances that are affecting muscle mass, body weight, and heart rate to maintaining QoL; however, prospective studies to test these endpoints are required

Chloroplast DNA variation of oaks in western Central Europe and genetic consequences of human influences

Oak chloroplast DNA (cpDNA) variation was studied in a grid-based inventory in western Central Europe, including Belgium, The Netherlands, Luxembourg, Germany, the Czech Republic, and the northern parts of Upper and Lower Austria. A total of 2155 trees representing 426 populations of Quercus robur L. and Q. petraea (Matt.) Liebl. were screened for polymorphism in up to four PCR-amplified cpDNA fragments. Eleven haplotypes belonging to four lineages were detected; these lineages were formerly restricted to glacial refugia in the Iberian Peninsula, the Apennine Peninsula and the Balkan Peninsula. The haplotypes originating from the Apennines are particularly well represented in the study region, but there is also a significant contribution from the other refugia, which explain the high overall level of cpDNA diversity. The strong human impact in western Central Europe during the past centuries, which has resulted in the clearance of most forests, was followed by reforestation, sometimes involving seed transfers. Despite this strong human impact, broad geographic patterns of lineages and haplotypes could still be detected. To evaluate further the consequences of the former human activities on the present day oak cpDNA genetic structure, four regions where increasingly strong human impact was anticipated (ranging from hilly regions in southern Germany to roadsides plantations in The Netherlands) were selected. There, a comparison of the levels of intrapopulation cpDNA diversity and spatial structuring was made. Over the whole area, within stand diversity was significantly higher in Q. robur than in Q. petraea (h[sub]S = 0.24 vs. 0.16). Since total diversity is identical for both species, this results in a significantly lower level of fixation for Q.robur than for Q. petraea (G[sub]ST = 0.68 vs. 0.79). The analyses also reveal a decrease of fixation with increasing human impact on oak populations. The Dutch roadside plantations (Q. robur) exhibit a very low level of fixation (GST = 0.28) as comparedto Q. petraea in southern Germany (GST=0.91). The significance of the spatial genetic structure was tested using geostatistical methods. For the complete data set, a strong spatial genetic structure is confirmed, with higher than average genetic similarities between populations distant from up to 270 km, whereas there is no spatial structure in the roadside plantations in The Netherlands or in the northern German lowlands. These results should help to differentiate introduced from autochthonous populations, and provide a framework for the identification of the geographic origin of seed lots

Identification of refugia and post-glacial colonisation routes of European white oaks based on chloroplast DNA and fossil pollen evidence

The geographic distribution throughout Europe of each of 32 chloroplast DNA variants belonging to eight white oak species sampled from 2613 populations is presented. Clear-cut geographic patterns were revealed by the survey. These distributions, together with the available palynological information, were used to infer colonisation routes out of the glacial period refugia. In western Europe in particular, movements out of the Iberian and the Italian Peninsulas can be clearly identified. Separate refugia are also present in eastern Balkans, whereas further west in this peninsula similarities with Italy were evident. Movements resulting in the exchange of haplotypes between refugia both during the present interglacial and probably also during earlier glacial cycles were therefore inferred. The consequences of these past exchanges is that phylogenetically divergent haplotypes have sometimes followed very similar colonisation routes, limiting somewhat the phylogeographic structure. Cases of geographic disjunction in the present-day distribution of haplotypes are also apparent and could have been induced by the existence of rapid climatic changes at the end of the glacial period (specifically the Younger Dryas cold period), which resulted in range restriction following an early warm period during which oak first expanded from its primary refugia. This cold phase was followed by a new period of expansion at the outset of the Holocene, involving in some cases ‘secondary’ refugia. It is expected that these short climate oscillations would have led to a partial reshuffling of haplotype distribution. Early association between haplotypes and oak species are also suggested by the data, although extensive introgression among species has ultimately largely blurred the pattern. This implies that colonisation routes may have been initially constrained by the ecological characteristics of the species hosting each chloroplast variant. We suggest for instance that two oak species distributed in the north of the Iberian Peninsula (Quercus petraea and Q. pubescens) are recent post-glacial immigrants there. When considered together, conclusions on the location of glacial period refugia and the colonisation routes derived from molecular information and fossil pollen data appear to be both largely compatible and complementary.Rémy J. Petit; Simon Brewer; Sándor Bordács; Kornel Burg; Rachid Cheddadi; Els Coart; Joan Cottrell; Ulrike M. Csaikl; Barbara van Dam; John D. Deans; Santiago Espinel; Silvia Fineschi; Reiner Finkeldey; Izabela Glaz; Pablo G. Goicoechea; Jan Svejgaard Jensen; Armin O. König; Andrew J. Lowe; Søren Flemming Madsen; Gabor Mátyás; Robert C. Munro; Flaviu Popescu; Danko Slade; Helen Tabbener; Sven G. M. de Vries; Birgit Ziegenhagen; Jacques-Louis de Beaulieu and Antoine Kremerhttp://www.elsevier.com/wps/find/journaldescription.cws_home/503310/description#descriptio

Chloroplast DNA variation in European white oaks: Phylogeography and patterns of diversity based on data from over 2600 populations

A consortium of 16 laboratories have studied chloroplast DNA (cpDNA) variation in European white oaks. A common strategy for molecular screening, based on restriction analysis of four PCR-amplified cpDNA fragments, was used to allow comparison among the different laboratories. A total of 2613 oak populations (12,214 individual trees from eight species) weresampled from 37 countries, and analysed with the four fragments. They belong to eight related oak species: Quercus robur, Q. petraea, Q. pubescens, Q. frainetto, Q. faginea, Q. pyrenaica, Q. canariensis and Q. macranthera. During this survey, 45 chloroplast variants were detected and are described together with their phylogenetic relationships, but several of these haplotypes were pooled when there were some risks of confusion across laboratories during the survey, and finally 32 remained that were mapped and used in diversity analyses. A strong phylogeographic structure is apparent from the data, where related haplotypes have broadly similar geographic distributions. In total, six cpDNA lineages are identified, which have distinct geographic distributions, mainly along a longitudinal gradient. Most haplotypes found in northern Europe are also present in the south, whereas the converse is not true, suggesting that the majority of mutations observed were generated prior to postglacial recolonisation, corroborating the conclusions of earlier studies. The description of a new western European lineage constitutes a major finding, compared to earlier phylogenetic treatments. Although the eight oak species studied systematically share cpDNA variants when in sympatry, they partition cpDNA diversity differently, as a consequence of their different ecology and life history attributes. Regional differences in levels of differentiation also exist (either species-specific or general); these seem to be related to the intensity of past and present management of the forests across Europe but also to the level of fragmentation of the range within these regions. © 2002 Elsevier Science B.V. All rights reserved.Remy J. Petit, Ulrike M. Csaikl, Sandor Bordacs, Kornel Burg, Els Coart, Joan Cottrell, Barbara van Dam, John D. Deans, Sylvie Dumolin-Lapegue, Silvia Fineschi, Reiner Finkeldey, Amanda Gillies, Izabela Glaz, Pablo G. Goicoechea Jan S. Jensen Armin O. Konig, Andrew J. Lowe, Søren F. Madsen, Gabor Matyas, Robert C. Munro, Maria Olalde, Marie-Helene Pemonge, Flaviu Popescu, Danko Slade, Helen Tabbener, Daniela Taurchini, Sven G.M. de Vries, Birgit Ziegenhagen, Antoine Kremerhttp://www.elsevier.com/wps/find/journaldescription.cws_home/503310/description#descriptio