9,298 research outputs found
Photospheric activity, rotation, and star-planet interaction of the planet-hosting star CoRoT-6
The CoRoT satellite has recently discovered a hot Jupiter that transits
across the disc of a F9V star called CoRoT-6 with a period of 8.886 days. We
model the photospheric activity of the star and use the maps of the active
regions to study stellar differential rotation and the star-planet interaction.
We apply a maximum entropy spot model to fit the optical modulation as observed
by CoRoT during a uninterrupted interval of about 140 days. Photospheric active
regions are assumed to consist of spots and faculae in a fixed proportion with
solar-like contrasts. Individual active regions have lifetimes up to 30-40
days. Most of them form and decay within five active longitudes whose different
migration rates are attributed to the stellar differential rotation for which a
lower limit of \Delta \Omega / \Omega = 0.12 \pm 0.02 is obtained. Several
active regions show a maximum of activity at a longitude lagging the
subplanetary point by about 200 degrees with the probability of a chance
occurrence being smaller than 1 percent. Our spot modelling indicates that the
photospheric activity of CoRoT-6 could be partially modulated by some kind of
star-planet magnetic interaction, while an interaction related to tides is
highly unlikely because of the weakness of the tidal force.Comment: 9 pages, 7 figures, accepted to Astronomy & Astrophysic
Design for Low-Cost Country Sourcing: Motivation, Basic Principles and Design Guidelines
Organised by: Cranfield UniversityNot every product can be successfully sourced in low-cost countries. Disadvantageous cost structures or
extremely complex workpiece designs are the most frequent reasons for failures. A design that has been
tailored to low-cost country sourcing offers the possibility of increasing potentials while reducing risks and
costs at the same time. The wbk Institute of Production Science at the Universität Karlsruhe (TH) developed
a new approach which ensures that the product design meets the requirements of the supplier. This paper
identifies the factors influencing the design, deduces basic principles and illustrates guidelines for an
adapted product design.Mori Seiki – The Machine Tool Compan
Event generator to construct cross sections for the multiphonon excitation of a set of collective vibrational modes
The construction of differential cross sections as a function of excitation
energy for systems with a collection of low- and high-lying intrinsic
vibrational modes has been attempted in the past. A prescription is proposed
that simplifies the implementation of such calculation schemes with a
remarkable reduction in computational time.Comment: 6 pages, 3 figures, to be published in Phys. Rev.
Population of dipole states via isoscalar probes: the splitting of pygmy dipole resonance in Sn}
Inelastic -scattering excitation cross sections are calculated for
electric dipole excitations in Sn based on the transition densities
obtained from the relativistic quasiparticle time-blocking approximation
(RQTBA) in the framework of a semiclassical model. The calculation provides the
missing link to directly compare the results from the microscopic RQTBA
calculations to recent experimental data measured via the reaction, which show a structural splitting of the low-lying E1
strength often denoted as pygmy dipole resonance (PDR). The experimentally
observed splitting is reproduced by the cross section calculations, which
allows to draw conclusion on the structure of the PDR.Comment: 6 pages, 7 figures; accepted in Phys. Rev C as Rapid Communicatio
Mass Formula for a Stationary Axisymmetric Configuration and the Physical Realization of the Kerr Metric
We analyse the expression for the mass of a stationary axisymmetric
configuration in general relativity obtained in our previous work [1]. From the
generality of our formula and its incompatibility with the corresponding
expression in Kerr space-time we argue that a stationary equilibrium
distribution of a real matter cannot be a source of the Kerr metric.Comment: RevTex, 5 pages, no figure
Microscopic description of Coulomb and nuclear excitation of multiphonon states in Ca + Ca collisions
We calculate the inelastic scattering cross sections to populate one- and
two-phonon states in heavy ion collisions with both Coulomb and nuclear
excitations. Starting from a microscopic approach based on RPA, we go beyond it
in order to treat anharmonicities and non-linear terms in the exciting field.
These anharmonicities and non-linearities are shown to have important effects
on the cross sections both in the low energy part of the spectrum and in the
energy region of the Double Giant Quadrupole Resonance. By properly introducing
an optical potential the inelastic cross section is calculated semiclassically
by integrating the excitation probability over all impact parameters. A
satisfactory agreement with the experimental results is obtained.Comment: 20 pages, 2 figures, revtex, to be published in Phys. Rev.
A condition-specific codon optimization approach for improved heterologous gene expression in Saccharomyces cerevisiae
All authors are with the Department of Chemical Engineering, The University of Texas at Austin, 200 E Dean Keeton St. Stop C0400, Austin, TX 78712, USA -- Hal S. Alper is with the Institute for Cellular and Molecular Biology, The University of Texas at Austin, 2500 Speedway Avenue, Austin, TX 78712, USA
-- Amanda M. Lanza Current Address: Bristol-Myers Squibb, Biologics Development, 35 South Street, Hopkinton, MA 01748, USABackground: Heterologous gene expression is an important tool for synthetic biology that enables metabolic engineering and the production of non-natural biologics in a variety of host organisms. The translational efficiency of heterologous genes can often be improved by optimizing synonymous codon usage to better match the host organism. However, traditional approaches for optimization neglect to take into account many factors known to influence synonymous codon distributions. Results: Here we define an alternative approach for codon optimization that utilizes systems level information and codon context for the condition under which heterologous genes are being expressed. Furthermore, we utilize a probabilistic algorithm to generate multiple variants of a given gene. We demonstrate improved translational efficiency using this condition-specific codon optimization approach with two heterologous genes, the fluorescent protein-encoding eGFP and the catechol 1,2-dioxygenase gene CatA, expressed in S. cerevisiae. For the latter case, optimization for stationary phase production resulted in nearly 2.9-fold improvements over commercial gene optimization algorithms. Conclusions: Codon optimization is now often a standard tool for protein expression, and while a variety of tools and approaches have been developed, they do not guarantee improved performance for all hosts of applications. Here, we suggest an alternative method for condition-specific codon optimization and demonstrate its utility in Saccharomyces cerevisiae as a proof of concept. However, this technique should be applicable to any organism for which gene expression data can be generated and is thus of potential interest for a variety of applications in metabolic and cellular engineering.Chemical EngineeringInstitute for Cellular and Molecular [email protected]
Excitation of Pygmy Dipole Resonance in neutron-rich nuclei via Coulomb and nuclear fields
We study the nature of the low-lying dipole strength in neutron-rich nuclei,
often associated to the Pygmy Dipole Resonance. The states are described within
the Hartree-Fock plus RPA formalism, using different parametrizations of the
Skyrme interaction. We show how the information from combined reactions
processes involving the Coulomb and different mixtures of isoscalar and
isovector nuclear interactions can provide a clue to reveal the characteristic
features of these states.Comment: 9 Pages, 8 figures, contribution to International Symposium On
Nuclear Physics, December 8-12, 2009,Bhabha Atomic Research Centre, Mumbai,
Indi
Transparency in Global Production Networks: Improving Disruption Management by Increased Information Exchange
Modern companies operate in global production networks. The operational performance of production networks is hampered by disrupting events. Digitalization and the horizontal interlinkage of production networks may increase information exchange and lead to more transparency. It is propagated as being an enabler for a faster identification and reaction to disruptions. This paper presents a metamodeling approach that maps disruptions as systematic parameter variations and analyzes their impact on the performance of production networks under different level of information exchange. The method aims for the determination of cause-effect relationships and contributes to the determination of the appropriate level of information exchange in production networks
Neurofibromatosis type I: Case report
We present a case of neurofibromatosis type 1 (NF-1) discussing how cutaneous manifestations of disorders or syndromes can be difficult to identify, especially when they are present since birth, present also in a percentage of normal population, and especially when these are isolated findings, not accompanied by other clinical relevant signs or symptoms. It is well known that NF-1 is a rather heterogeneous condition, with different degrees of expression and including cutaneous manifestations. Although there are some life threatening complications clearly associated, for most patients the primary concern and main clinical impact remains the disfigurement caused by the presence and growth of cutaneous-dermal neurofibromas. These lesions can be underestimated especially in the impact on quality of life and sequelae that can cause if abnormally large and not removed. We present a clinical history spanning several years, before managing to properly diagnose our patient with neurofibromatosis type 1 and treat the relevant skin manifestation causing significant deformity and quality of life consequences
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