Application of spectral phase shaping to high resolution CARS spectroscopy

By spectral phase shaping of both the pump and probe pulses in coherent anti-Stokes Raman scattering (CARS) spectroscopy we demonstrate the extraction of the frequencies, bandwidths and relative cross sections of vibrational lines. We employ a tunable broadband Ti:Sapphire laser synchronized to a ps-Nd:YVO mode locked laser. A high resolution spectral phase shaper allows for spectroscopy with a precision better than 1 cm-1 in the high frequency region around 3000 cm-1. We also demonstrate how new spectral phase shaping strategies can amplify the resonant features of isolated vibrations to such an extent that spectroscopy and microscopy can be done at high resolution, on the integrated spectral response without the need for a spectrograph

Biophysical modelling of a drosophila photoreceptor

It remains unclear how visual information is co-processed by different layers of neurons in the retina. In particular, relatively little is known how retina translates vast environmental light changes into neural responses of limited range. We began examining this question in a bottom-up way in a relatively simple °y eye. To gain understanding of how complex bio-molecular interactions govern the conversion of light input into voltage output (phototransduction), we are building a biophysical model of the Drosophila R1-R6 photoreceptor. Our model, which relates molecular dynamics of the underlying biochemical reactions to external light input, attempts to capture the molecular dynamics of phototransduction gain control in a quantitative way

Resonant tunneling in a Luttinger liquid for arbitrary barrier transmission

A numerically exact dynamical quantum Monte Carlo approach has been developed and applied to transport through a double barrier in a Luttinger liquid with arbitrary transmission. For strong transmission, we find broad Fabry-Perot Coulomb blockade peaks, with a lineshape parametrized by a single parameter, but at sufficiently low temperatures, non-Lorentzian universal lineshapes characteristic of coherent resonant tunneling emerge, even for strong interactions. For weak transmission, our data supports the recently proposed correlated sequential tunneling picture and is consistent with experimental results on intrinsic nanotube dots.Comment: 4 pages, 4 figure

Genetic Variation in FADS Genes and Plasma Cholesterol Levels in 2-Year-Old Infants

Single nucleotide polymorphisms (SNPs) in genes involved in fatty acid metabolism (FADS1 FADS2 gene cluster) are associated with plasma lipid levels. We aimed to investigate whether these associations are already present early in life and compare the relative contribution of FADS SNPs vs traditional (non-genetic) factors as determinants of plasma lipid levels. Information on infants' plasma total cholesterol levels, genotypes of five FADS SNPs (rs174545, rs174546, rs174556, rs174561, and rs3834458), anthropometric data, maternal characteristics, and breastfeeding history was available for 521 2-year-old children from the KOALA Birth Cohort Study. For 295 of these 521 children, plasma HDLc and non-HDLc levels were also known. Multivariable linear regression analysis was used to study the associations of genetic and non-genetic determinants with cholesterol levels. All FADS SNPs were significantly associated with total cholesterol levels. Heterozygous and homozygous for the minor allele children had about 4% and 8% lower total cholesterol levels than major allele homozygotes. In addition, homozygous for the minor allele children had about 7% lower HDLc levels. This difference reached significance for the SNPs rs174546 and rs3834458. The associations went in the same direction for non-HDLc, but statistical significance was not reached. The percentage of total variance of total cholesterol levels explained by FADS SNPs was relatively low (lower than 3%) but of the same order as that explained by gender and the non-genetic determinants together. FADS SNPs are associated with plasma total cholesterol and HDLc levels in preschool children. This brings a new piece of evidence to explain how blood lipid levels may track from childhood to adulthood. Moreover, the finding that these SNPs explain a similar amount of variance in total cholesterol levels as the non-genetic determinants studied reveals the potential importance of investigating the effects of genetic variations in early life

MSSM Higgses as the source of reheating and all matter

We consider the possibility that the dark energy responsible for inflation is deposited into extra dimensions outside of our observable universe. Reheating and all matter can then be obtained from the MSSM flat direction condensate involving the Higgses $H_u$ and $H_d$, which acquires large amplitude by virtue of quantum fluctuations during inflation. The reheat temperature is $T_{RH} \lesssim 10^9$ GeV so that there is no gravitino problem. We find a spectral index $n_s\approx 1$ with a very weak dependence on the Higgs potential.Comment: 4 page

Risk of pneumonia in obstructive lung disease : A real-life study comparing extra-fine and fine-particle inhaled corticosteroids

The study received institutional support from Teva Pharmaceuticals Europe B.V. Teva did not contribute either in part or in whole, to the collection, analysis, or interpretation of study data, manuscript writing, or the decision to submit the manuscript for publication. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Electron-hole symmetry in a semiconducting carbon nanotube quantum dot

Optical and electronic phenomena in solids arise from the behaviour of electrons and holes (unoccupied states in a filled electron sea). Electron-hole symmetry can often be invoked as a simplifying description, which states that electrons with energy above the Fermi sea behave the same as holes below the Fermi energy. In semiconductors, however, electron-hole symmetry is generally absent since the energy band structure of the conduction band differs from the valence band. Here we report on measurements of the discrete, quantized-energy spectrum of electrons and holes in a semiconducting carbon nanotube. Through a gate, an individual nanotube is filled controllably with a precise number of either electrons or holes, starting from one. The discrete excitation spectrum for a nanotube with N holes is strikingly similar to the corresponding spectrum for N electrons. This observation of near perfect electron-hole symmetry demonstrates for the first time that a semiconducting nanotube can be free of charged impurities, even in the limit of few-electrons or holes. We furthermore find an anomalously small Zeeman spin splitting and an excitation spectrum indicating strong electron-electron interactions.Comment: 12 pages, 4 figure

Interference effects in electronic transport through metallic single-wall carbon nanotubes

In a recent paper Liang {\it et al.} [Nature {\bf 411}, 665 (2001)] showed experimentally, that metallic nanotubes, strongly coupled to external electrodes, may act as coherent molecular waveguides for electronic transport. The experimental results were supported by theoretical analysis based on the scattering matrix approach. In this paper we analyze theoretically this problem using a real-space approach, which makes it possible to control quality of interface contacts. Electronic structure of the nanotube is taken into account within the tight-binding model. External electrodes and the central part (sample) are assumed to be made of carbon nanotubes, while the contacts between electrodes and the sample are modeled by appropriate on-site (diagonal) and hopping (off-diagonal) parameters. Conductance is calculated by the Green function technique combined with the Landauer formalism. In the plots displaying conductance {\it vs.} bias and gate voltages, we have found typical diamond structure patterns, similar to those observed experimentally. In certain cases, however, we have found new features in the patterns, like a double-diamond sub-structure.Comment: 15 pages, 4 figures. To apear in Phys. Rev.

Hooge's Constant of Carbon Nanotube Field Effect Transistors

The 1/f noise in individual semiconducting carbon nanotubes (s-CNT) in a field effect transistor configuration has been measured in ultra-high vacuum and following exposure to air. The amplitude of the normalized current spectral noise density is independent of source-drain current, indicating the noise is due to mobility rather than number fluctuations. Hooge's constant for s-CNT is found to be 9.3 plus minus 0.4x10^-3. The magnitude of the 1/f noise is substantially degreased by exposing the devices to air

Identifying the curvaton within MSSM

We consider inflaton couplings to MSSM flat directions and the thermalization of the inflaton decay products, taking into account gauge symmetry breaking due to flat direction condensates. We then search for a suitable curvaton candidate among the flat directions, requiring an early thermally induced start for the flat direction oscillations to facilitate the necessary curvaton energy density dominance. We demonstrate that the supersymmetry breaking $A$-term is crucial for achieving a successful curvaton scenario. Among the many possible candidates, we identify the ${\bf u_1dd}$ flat direction as a viable MSSM curvaton.Comment: 9 pages. Discussion on the evaporation of condensate added, final version published in JCA