609 research outputs found
Fast, inexpensive, and reliable HPLC method to determine monomer fractions in poly(3-hydroxybutyrate-co-3-hydroxyvalerate)
The determination of the monomer fractions in polyhydroxyalkanoates is of great importance for research on microbial-produced plastic material. The development of new process designs, the validation of mathematical models, and intelligent control strategies for production depend enormously on the correctness of the analyzed monomer fractions. Most of the available detection methods focus on the determination of the monomer fractions of the homopolymer poly(3-hydroxybutyrate). Only a few can analyze the monomer content in copolymers such as poly(3-hydroxybutyrate-co-3-hydroxyvalerate), which usually require expensive measuring devices, a high preparation time or the use of environmentally harmful halogenated solvents such as chloroform or dichloromethane. This work presents a fast, simple, and inexpensive method for the analysis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with high-performance liquid chromatography. Samples from a bioreactor experiment for the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with Cupriavidus necator H16 were examined regarding their monomer content using the new method and gas chromatography analysis, one of the most frequently used methods in literature. The results from our new method were validated using gas chromatography measurements and show excellent agreement. Key points ∙ The presented HPLC method is an inexpensive, fast and environmentally friendly alternative to existing methods for quantification of monomeric composition of PHBV. ∙ Validation with state of the art GC measurement exhibits excellent agreement over a broad range of PHBV monomer fractions
Universality of Highly Damped Quasinormal Modes for Single Horizon Black Holes
It has been suggested that the highly damped quasinormal modes of black holes
provide information about the microscopic quantum gravitational states
underlying black hole entropy. This interpretation requires the form of the
highly damped quasinormal mode frequency to be universally of the form:
, where is an integer, and is the
black hole temperature. We summarize the results of an analysis of the highly
damped quasinormal modes for a large class of single horizon, asymptotically
flat black holes.Comment: 9 pages, 1 figure, submitted to the proceedings of Theory CANADA 1,
which will be published in a special edition of the Canadian Journal of
Physic
Assessment of Austrian contribution toward EU 2020 target sharing: Responding to the energy and climate package of the European Commission
The overarching implications of the EU 2020 targets for Austria call for a fundamental restructuring of the Austrian energy sector towards increased energy efficiency. Two guiding principles for this restructuring are required in order to be compatible with the targets for greenhouse gas emissions and renewables (RES) expected for Austria: final energy consumption needs to be stabilised at the levels of 2005; renewable energy sources need to be expanded at least by 40 percent. For the final negotiations on phase 3 of the EU Emissions Trading System we propose contributions on three issues: 1. operational procedures for dealing with carbon leakage and competitiveness in all sectors that provide criteria for allocating free allowances: 2. empowering the carbon market by extending the task of the emissions allowances issuing carbon authority to control the liquidity of the carbon market in view of stabilising the carbon price; 3. designing the auctioning mechanism by considering timing and auctioning as a strategic instrument for enhancing the carbon market and considering unified auc-tioning with revenues split among EU countries. Similarly we suggest for the final negotiations on the RES Directive improvements that overcome discrepancies between national RES targets and available resources for implementation. This requires in particular improved cooperation between EU countries for a better mapping of targets and potentials
A diquark model for baryons containing one heavy quark
We present a phenomenological ansatz for coupling a heavy quark with two
light quarks to form a heavy baryon. The heavy quark is treated in the heavy
mass limit, and the light quark dynamics is approximated by propagating scalar
and axial vector 'diquarks'. The resulting effective lagrangian, which
incorporates heavy quark and chiral symmetry, describes interactions of heavy
baryons with Goldstone bosons in the low energy region. As an application, the
Isgur--Wise form factors are estimated.Comment: 9 pages + 8 figures, both as uuencoded PS, discussion of Bjorken
limit (1 par + 1 fig) added, to appear in Z.Phys.
Fiber-optic endoscopic evaluation of swallowing to assess swallowing outcomes as a function of head position in a normal population
BACKGROUND: Head position practice has been shown to influence pill-swallowing ability, but the impact of head position on measures of swallowing outcomes has not yet been studied with fiber-optic endoscopic evaluation of swallowing (FEES). The primary purpose of this study was to determine whether head position impacts penetration-aspiration scale scores and/or post-swallow pharyngeal residue as assessed by FEES. Documenting the incidence of pharyngeal residue and laryngeal penetration and aspiration in a normal population was a secondary goal. METHODS: Adults without swallowing difficulties (N = 84) were taught a pill swallowing technique based on learning five head positions and were asked to practice with small, hard candies (e.g., TicTacs) for two weeks. Then they demonstrated swallowing in each of the head positions for two conditions, liquid and purée, while undergoing FEES. RESULTS: Out of 840 examined swallows, one event of aspiration and 5 events of penetration occurred. During practice >50% participants found positions they preferred over the center position for swallowing but head position was not associated with penetration-aspiration scores assessed by FEES. Significant associations and non-significant trends were found between pharyngeal residue and three variables: age, most preferred head position, and least preferred head position. CONCLUSION: Head position during swallowing (head up) and age greater than 40 years may result in increased pharyngeal residue but not laryngeal penetration or aspiration
Three and four current reversals versus temperature in correlation ratchets with a simple sawtooh potential
Transport of Brownian particles on a simple sawtooth potential subjected to
both unbiased thermal and nonequilibrium symmetric three-level Markovian noise
is considered. The new effects of three and four current reversals as a
function of temperature are established in such correlation ratchets. The
parameter space coordinates of the fixed points associated with these current
reversals and the necessary and sufficient conditions for the existence of the
novel current reversals are found.Comment: 4 pages, 5 figures; some changes introduced; accepted for publication
in Physical Review
Finite temperature calculations for the bulk properties of strange star using a many-body approach
We have considered a hot strange star matter, just after the collapse of a
supernova, as a composition of strange, up and down quarks to calculate the
bulk properties of this system at finite temperature with the density dependent
bag constant. To parameterize the density dependent bag constant, we use our
results for the lowest order constrained variational (LOCV) calculations of
asymmetric nuclear matter. Our calculations for the structure properties of the
strange star at different temperatures indicate that its maximum mass decreases
by increasing the temperature. We have also compared our results with those of
a fixed value of the bag constant. It can be seen that the density dependent
bag constant leads to higher values of the maximum mass and radius for the
strange star.Comment: 21 pages, 2 tables, 12 figures Astrophys. (2011) accepte
Strange Star Heating Events as a Model for Giant Flares of Soft Gamma-ray Repeaters
Two giant flares were observed on 5 March 1979 and 27 August 1998 from the
soft gamma-ray repeaters SGR 0526-66 and SGR 1900+14, respectively. The
striking similarity between these remarkable bursts strongly implies a common
nature. We show that the light curves of the giant bursts may be easily
explained in the model where the burst radiation is produced by the bare quark
surface of a strange star heated, for example, by impact of a massive
comet-like object.Comment: 5 pages, 4 figures, accepted for publication in Phys. Rev. Letter
Spectrum of rotating black holes and its implications for Hawking radiation
The reduced phase space formalism for quantising black holes has recently
been extended to find the area and angular momentum spectra of four dimensional
Kerr black holes. We extend this further to rotating black holes in all
spacetime dimensions and show that although as in four dimensions the spectrum
is discrete, it is not equispaced in general. As a result, Hawking radiation
spectra from these black holes are continuous, as opposed to the discrete
spectrum predicted for four dimensional black holes.Comment: 11 pages, Revtex4. Minor changes to match version to appear in Class.
Quant. Gra
The Highly Damped Quasinormal Modes of -dimensional Reissner-Nordstrom Black Holes in the Small Charge Limit
We analyze in detail the highly damped quasinormal modes of -dimensional
Reissner-Nordstrm black holes with small charge, paying
particular attention to the large but finite damping limit in which the
Schwarzschild results should be valid. In the infinite damping limit, we
confirm using different methods the results obtained previously in the
literature for higher dimensional Reissner-Nordstrm black holes.
Using a combination of analytic and numerical techniques we also calculate the
transition of the real part of the quasinormal mode frequency from the
Reissner-Nordstrm value for very large damping to the
Schwarzschild value of for intermediate damping. The real
frequency does not interpolate smoothly between the two values. Instead there
is a critical value of the damping at which the topology of the
Stokes/anti-Stokes lines change, and the real part of the quasinormal mode
frequency dips to zero.Comment: 18 pages, 8 figure
- …