2,754 research outputs found
Operator product expansion of the energy momentum tensor in 2D conformal field theories on manifolds with boundary
Starting from the well-known expression for the trace anomaly we derive the
operator product expansion of the energy-momentum tensor in 2D
conformal theories defined in the upper halfplane making use of the
additional condition of no energy-momentum flux across the boundary. The OPE
turns out to be the same as in the absence of the boundary. For this result it
is crucial that the trace anomaly is proportional to the Gau\ss-Bonnet density.
Some relations to the - model approach for open strings are discussed.Comment: 8 pages, Latex, HU Berlin-IEP-93/
Is the physics within the Solar system really understood?
A collection is made of presently unexplained phenomena within our Solar
system and in the universe. These phenomena are (i) the Pioneer anomaly, (ii)
the flyby anomaly, (iii) the increase of the Astronomical Unit, (iv) the
quadrupole and octupole anomaly, and (v) Dark Energy and (vi) Dark Matter. A
new data analysis of the complete set of Pioneer data is announced in order to
search for systematic effects or to confirm the unexplained acceleration. We
also review the mysterious flyby anomaly where the velocities of spacecraft
after Earth swing--bys are larger than expected. We emphasize the scientific
aspects of this anomaly and propose systematic and continuous observations and
studies at the occasion of future flybys. Further anomalies within the Solar
system are the increase of the Astronomical Unit and the quadrupole and
octupole anomaly. We briefly mention Dark Matter and Dark Energy since in some
cases a relation between them and the Solar system anomalies have been
speculated.Comment: 22 pages, 3 figures, submitted for the proceedings of the 359th
WE-Heraeus Seminar on "Lasers, Clocks, and Drag-Free: Technologies for Future
Exploration in Space and Tests of Gravity
Bayesian analysis of magnetic island dynamics
We examine a first order differential equation with respect to time coming up
in the description of magnetic islands in magnetically confined plasmas. The
free parameters of this equation are obtained by employing Bayesian probability
theory. Additionally a typical Bayesian change point is solved in the process
of obtaining the data.Comment: 10 pages, 4 figures, submitted to be included in MaxEnt 2002
proceeding
The local dust foregrounds in the microwave sky: I. Thermal emission spectra
Analyses of the cosmic microwave background (CMB) radiation maps made by the
Wilkinson Microwave Anisotropy Probe (WMAP) have revealed anomalies not
predicted by the standard inflationary cosmology. In particular, the power of
the quadrupole moment of the CMB fluctuations is remarkably low, and the
quadrupole and octopole moments are aligned mutually and with the geometry of
the Solar system. It has been suggested in the literature that microwave sky
pollution by an unidentified dust cloud in the vicinity of the Solar system may
be the cause for these anomalies. In this paper, we simulate the thermal
emission by clouds of spherical homogeneous particles of several materials.
Spectral constraints from the WMAP multi-wavelength data and earlier infrared
observations on the hypothetical dust cloud are used to determine the dust
cloud's physical characteristics. In order for its emissivity to demonstrate a
flat, CMB-like wavelength dependence over the WMAP wavelengths (3 through 14
mm), and to be invisible in the infrared light, its particles must be
macroscopic. Silicate spheres from several millimetres in size and carbonaceous
particles an order of magnitude smaller will suffice. According to our
estimates of the abundance of such particles in the Zodiacal cloud and
trans-neptunian belt, yielding the optical depths of the order of 1E-7 for each
cloud, the Solar-system dust can well contribute 10 microKelvin (within an
order of magnitude) in the microwaves. This is not only intriguingly close to
the magnitude of the anomalies (about 30 microKelvin), but also alarmingly
above the presently believed magnitude of systematic biases of the WMAP results
(below 5 microKelvin) and, to an even greater degree, of the future missions
with higher sensitivities, e.g. PLANCK.Comment: 33 pages, 9 figures, 1 table. The Astrophysical Journal, 2009,
accepte
Comparative gene mapping in Arabidopsis lyrata chromosomes 1 and 2 and the corresponding A. thaliana chromosome 1: recombination rates, rearrangements and centromere location
Decomposition of multicomponent mass spectra using Bayesian probability theory
We present a method for the decomposition of mass spectra of mixture gases
using Bayesian probability theory. The method works without any calibration
measurement and therefore applies also to the analysis of spectra containing
unstable species. For the example of mixtures of three different hydrocarbon
gases the algorithm provides concentrations and cracking coefficients of each
mixture component as well as their confidence intervals. The amount of
information needed to obtain reliable results and its relation to the accuracy
of our analysis are discussed
The determination and distribution of precise time
Methods for time determination including atomic clocks and distribution of timing signal
Transient transfection induces different intracellular calcium signaling in CHO K1 versus HEK 293 cells
For the controlled production of recombinant proteinsin mammalian cells by transient transfection, it maybe desirable not only to manipulate, but also todiagnose the expression success early. Here, weapplied laser scanning confocal microscopy to monitortransfection induced intracellular Ca2+responses. We compared Chinese hamster ovary (CHO K1)versus human embryo kidney (HEK) 293 cell lines, whichdiffer largely in their transfectability. An improvedcalcium phosphate transfection method was used for itssimplicity and its demonstrated upscale potential.Cytosolic Ca2+ signaling appeared to inverselyreflect the cellular transfection fate. Virtually allCHO cells exhibited asynchronous, cytosolicCa2+ oscillations, which peaked 4 h afteraddition of the transfecting solution. Yet, most ofthe HEK cells displayed a slow and continuousCa2+ increase over the time of transfection. CHOcells, when exposed to a transfection-enhancingglycerol shock, strongly downregulated their Ca2+response, including its oscillations. When treatedwith thapsigargin, a Ca2+ store depleting drug,the number of successfully transfected CHO cells was significantly reduced. Our result points tointracellular store release as a critical componentfor the transfection fate of CHO cells, and its early detection before product visualizatio
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