5,255 research outputs found

### Identification and characterization of bovine regulator of telomere length elongation helicase gene (RTEL): molecular cloning, expression distribution, splice variants and DNA methylation profile

BACKGROUND: The genetic basis of telomere length heterogeneity among mammalian species is still not well understood. Recently, a gene named regulator of telomere length elongation helicase (RTEL) was identified and predicted to be an essential participant in species-specific telomere length regulation in two murine species. To obtain broader insights into its structure and biological functions and to ascertain whether RTEL is also a candidate gene in the regulation of telomere length diversity in other mammalian species, data from other mammals may be helpful. RESULTS: Here we report the cDNA cloning, genomic structure, chromosomal location, alternative splicing pattern, expression distribution and DNA methylation profile of the bovine homolog of RTEL. The longest transcript of bovine RTEL is 4440 nt, encompassing 24.8 kb of genomic sequence that was mapped to chromosome 13q2.2. It encodes a conserved helicase-like protein containing seven characterized helicase motifs in the first 750 aa and a PIP box in the C-terminus. Four splice variants were identified within the transcripts in both the coding and 5'-untranslated regions; Western blot revealed that the most abundant splice variant SV-1 was translated to a truncated isoform of RTEL. The different 5'UTRs imply alternative transcription start sites in the promoter; Bovine RTEL was transcribed at the blastocyst stage, and expression levels were highest in adult testis, liver and ovary. DNA methylation analysis of tissues that differed significantly in expression level indicated that relatively low DNA methylation is associated with higher expression. CONCLUSION: In this study, we have identified and characterized a bovine RTEL homolog and obtained basic information about it, including gene structure, expression distribution, splice variants and profile of DNA methylation around two putative transcription start sites. These data may be helpful for further comparative and functional analysis of RTEL in mammals

### Generalized Eigenvectors for Resonances in the Friedrichs Model and Their Associated Gamov Vectors

A Gelfand triplet for the Hamiltonian H of the Friedrichs model on R with
finite-dimensional multiplicity space K, is constructed such that exactly the
resonances (poles of the inverse of the Livsic-matrix) are (generalized)
eigenvalues of H. The corresponding eigen-antilinearforms are calculated
explicitly. Using the wave matrices for the wave (Moller) operators the
corresponding eigen-antilinearforms on the Schwartz space S for the unperturbed
Hamiltonian are also calculated. It turns out that they are of pure Dirac type
and can be characterized by their corresponding Gamov vector, which is uniquely
determined by restriction of S to the intersection of S with the Hardy space of
the upper half plane. Simultaneously this restriction yields a truncation of
the generalized evolution to the well-known decay semigroup of the Toeplitz
type for the positive half line on the Hardy space. That is: exactly those
pre-Gamov vectors (eigenvectors of the decay semigroup) have an extension to a
generalized eigenvector of H if the eigenvalue is a resonance and if the
multiplicity parameter k is from that subspace of K which is uniquely
determined by its corresponding Dirac type antilinearform.Comment: 16 page

### Herschel SPIRE FTS Relative Spectral Response Calibration

Herschel/SPIRE Fourier transform spectrometer (FTS) observations contain
emission from both the Herschel Telescope and the SPIRE Instrument itself, both
of which are typically orders of magnitude greater than the emission from the
astronomical source, and must be removed in order to recover the source
spectrum. The effects of the Herschel Telescope and the SPIRE Instrument are
removed during data reduction using relative spectral response calibration
curves and emission models. We present the evolution of the methods used to
derive the relative spectral response calibration curves for the SPIRE FTS. The
relationship between the calibration curves and the ultimate sensitivity of
calibrated SPIRE FTS data is discussed and the results from the derivation
methods are compared. These comparisons show that the latest derivation methods
result in calibration curves that impart a factor of between 2 and 100 less
noise to the overall error budget, which results in calibrated spectra for
individual observations whose noise is reduced by a factor of 2-3, with a gain
in the overall spectral sensitivity of 23% and 21% for the two detector bands,
respectively.Comment: 15 pages, 13 figures, accepted for publication in Experimental
Astronom

### Photon orbital angular momentum and torque metrics for single telescopes and interferometers

Context. Photon orbital angular momentum (POAM) is normally invoked in a
quantum mechanical context. It can, however, also be adapted to the classical
regime, which includes observational astronomy.
Aims. I explain why POAM quantities are excellent metrics for describing the
end-to-end behavior of astronomical systems. To demonstrate their utility, I
calculate POAM probabilities and torques from holography measurements of EVLA
antenna surfaces.
Methods. With previously defined concepts and calculi, I present generic
expressions for POAM spectra, total POAM, torque spectra, and total torque in
the image plane. I extend these functional forms to describe the specific POAM
behavior of single telescopes and interferometers.
Results. POAM probabilities of spatially uncorrelated astronomical sources
are symmetric in quantum number. Such objects have zero intrinsic total POAM on
the celestial sphere, which means that the total POAM in the image plane is
identical to the total torque induced by aberrations within propagation media &
instrumentation. The total torque can be divided into source- independent and
dependent components, and the latter can be written in terms of three
illustrative forms. For interferometers, complications arise from discrete
sampling of synthesized apertures, but they can be overcome. POAM also
manifests itself in the apodization of each telescope in an array. Holography
of EVLA antennas observing a point source indicate that ~ 10% of photons in the
n = 0 state are torqued to n != 0 states.
Conclusions. POAM quantities represent excellent metrics for characterizing
instruments because they are used to simultaneously describe amplitude and
phase aberrations. In contrast, Zernike polynomials are just solutions of a
differential equation that happen to ~ correspond to specific types of
aberrations and are typically employed to fit only phases

### Interpreting Ulysses data using inverse scattering theory: Oblique Alfv\'en waves

Solitary wave structures observed by the Ulysses spacecraft in the solar wind
were analyzed using both inverse scattering theory as well as direct numerical
integration of the derivative nonlinear Schr\"odinger (DNLS) equation. Several
of these structures were found to be consistent with soliton solutions of the
DNLS equation. Such solitary structures have been commonly observed in the
space plasma environment and may, in fact, be long-lived solitons. While the
generation of these solitons may be due to an instability mechanism, e.g., the
mirror instability, they may be observable far from the source region due to
their coherent nature.Comment: 20 pages, 3 figures, accepted by Journal of Geophysical Research:
Space Physics; typographical errors fixe

### The water supercooled regime as described by four common water models

The temperature scale of simple water models in general does not coincide
with the natural one. Therefore, in order to make a meaningful evaluation of
different water models a temperature rescaling is necessary. In this paper we
introduce a rescaling using the melting temperature and the temperature
corresponding to the maximum of the heat capacity to evaluate four common water
models (TIP4P-Ew, TIP4P-2005, TIP5P-Ew and Six-Sites) in the supercooled
regime. Although all the models show the same general qualitative behavior, the
TIP5P-Ew appears as the best representation of the supercooled regime when the
rescaled temperature is used. We also analyze, using thermodynamic arguments,
the critical nucleus size for ice growth. Finally, we speculate on the possible
reasons why atomistic models do not usually crystalize while the coarse grained
mW model do crystallize.Comment: 8 pages, 8 figure

- …