995 research outputs found
On the usefulness of finding charts Or the runaway carbon stars of the Blanco & McCarthy field 37
We have been recently faced with the problem of cross--identifying stars
recorded in historical catalogues with those extracted from recent fully
digitized surveys (such as DENIS and 2MASS). Positions mentioned in the old
catalogues are frequently of poor precision, but are generally accompanied by
finding charts where the interesting objects are flagged. Those finding charts
are sometimes our only link with the accumulated knowledge of past literature.
While checking the identification of some of these objects in several
catalogues, we had the surprise to discover a number of discrepancies in recent
works.The main reason for these discrepancies was generally the blind
application of the smallest difference in position as the criterion to identify
sources from one historical catalogue to those in more recent surveys. In this
paper we give examples of such misidentifications, and show how we were able to
find and correct them.We present modern procedures to discover and solve
cross--identification problems, such as loading digitized images of the sky
through the Aladin service at CDS, and overlaying entries from historical
catalogues and modern surveys. We conclude that the use of good finding charts
still remains the ultimate (though time--consuming) tool to ascertain
cross--identifications in difficult cases.Comment: 4 pages, 1 figure, accepted by A&
On The 5D Extra-Force according to Basini-Capozziello-Leon Formalism and five important features: Kar-Sinha Gravitational Bending of Light, Chung-Freese Superluminal Behaviour, Maartens-Clarkson Black Strings, Experimental measures of Extra Dimensions on board International Space Station(ISS) and the existence of the Particle due to a Higher Dimensional spacetime
We use the Conformal Metric as described in Kar-Sinha work on Gravitational
Bending of Light in a 5D Spacetime to recompute the equations of the 5D Force
in Basini-Capozziello-Leon Formalism and we arrive at a result that possesses
some advantages. The equations of the Extra Force as proposed by Leon are now
more elegant in Conformal Formalism and many algebraic terms can be simplified
or even suppressed. Also we recompute the Kar-Sinha Gravitational Bending of
Light affected by the presence of the Extra Dimension and analyze the
Superluminal Chung-Freese Features of this Formalism describing the advantages
of the Chung-Freese BraneWorld when compared to other Superluminal spacetime
metrics(eg:Warp Drive) and we describe why the Extra Dimension is invisible and
how the Extra Dimension could be made visible at least in theory.We also
examine the Maartens-Clarkson Black Holes in 5D(Black Strings) coupled to
massive Kaluza-Klein graviton modes predicted by Extra Dimensions theories and
we study experimental detection of Extra Dimensions on-board LIGO and LISA
Space Telescopes.We also propose the use of International Space Station(ISS) to
measure the additional terms(resulting from the presence of Extra Dimensions)
in the Kar-Sinha Gravitational Bending of Light in Outer Space to verify if we
really lives in a Higher Dimensional Spacetime.Also we demonstrate that
Particle can only exists if the 5D spacetime exists.Comment: Withdrawn: author no longer wishes to post work on arXi
A streamwise-constant model of turbulent pipe flow
A streamwise-constant model is presented to investigate the basic mechanisms
responsible for the change in mean flow occuring during pipe flow transition.
Using a single forced momentum balance equation, we show that the shape of the
velocity profile is robust to changes in the forcing profile and that both
linear non-normal and nonlinear effects are required to capture the change in
mean flow associated with transition to turbulence. The particularly simple
form of the model allows for the study of the momentum transfer directly by
inspection of the equations. The distribution of the high- and low-speed
streaks over the cross-section of the pipe produced by our model is remarkably
similar to one observed in the velocity field near the trailing edge of the
puff structures present in pipe flow transition. Under stochastic forcing, the
model exhibits a quasi-periodic self-sustaining cycle characterized by the
creation and subsequent decay of "streamwise-constant puffs", so-called due to
the good agreement between the temporal evolution of their velocity field and
the projection of the velocity field associated with three-dimensional puffs in
a frame of reference moving at the bulk velocity. We establish that the flow
dynamics are relatively insensitive to the regeneration mechanisms invoked to
produce near-wall streamwise vortices and that using small, unstructured
background disturbances to regenerate the streamwise vortices is sufficient to
capture the formation of the high- and low-speed streaks and their segregation
leading to the blunting of the velocity profile characteristic of turbulent
pipe flow
Variability and spectral classification of LMC giants: results from DENIS and EROS
We present the first cross-identifications of sources in the near-infrared
DENIS survey and in the micro-lensing EROS survey in a field of about 0.5
square degrees around the optical center (OC) of the Large Magellanic Cloud. We
analyze the photometric history of these stars in the EROS data base and obtain
light-curves for about 800 variables. Most of the stars are long period
variables (Miras and Semi-Regulars), a few Cepheids are also present. We also
present new spectroscopic data on 126 asymptotic giant branch stars in the OC
field, 30 previously known and 96 newly discovered by the DENIS survey. The
visible spectra are used to assign a carbon- (C-) or oxygen-rich (O-rich)
nature to the observed stars on the basis of the presence of molecular bands of
TiO, VO, CN, C2. For the remaining of the stars we used the (J-Ks) color to
determine whether they are O-rich or C-rich. Plotting Log(period) versus Ks we
find three very distinct period-luminosity relations, mainly populated by
Semi-Regular of type a (SRa), b (SRb) and Mira variables. Carbon-rich stars
occupy mostly the upper part of these relations. We find that 65% of the
asymptotic giant branch population are long period variables (LPVs).Comment: 9 pages, 7 figures, 4 tables (2 via CDS), accepted by A&A journa
L-arginine uptake, the citrulline-NO cycle and arginase II in the rat brain: an in situ hybridization study
Nitric oxide (NO) is synthesized from a unique precursor, arginine, by nitric oxide synthase (NOS). In brain cells, arginine is supplied by protein breakdown or extracted from the blood through cationic amino acid transporters (CATs). Arginine can also be recycled from the citrulline produced by NOS activity, through argininosuccinate synthetase (AS) and argininosuccinate lyase (AL) activities, and metabolized by arginase. NOS, AS and AL constitute the so-called citrulline-NO cycle. In order to better understand arginine transport, recycling and degradation, we studied the regional distribution of cells expressing CAT1, CAT3, AS, AL, neuronal NOS (nNOS) and arginase II (AII) in the adult rat brain by non-radioisotopic in situ hybridization (ISH). CAT1, AL and AII presented an ubiquitous neuronal and glial expression, whereas CAT3 and AS were confined to neurons. nNOS was restricted to scattered neurons and a few brain nuclei and layers. We demonstrate by this study that cells expressing nNOS all appear to express the entire citrulline-NO cycle, whereas numerous cells expressing AL do not express AS. The differential expression of these genes within the same anatomical structure could indicate that intercellular exchanges of citrulline-NO cycle metabolites are relevant. Thus vicinal interactions should be taken into account to study their regulatory mechanisms
Differential expression of the cationic amino acid transporter 2(B) in the adult rat brain
L-Arginine is a substrate for the synthesis of proteins, nitric oxide (NO), creatine, urea, proline, glutamate, polyamines and agmatine. In the central nervous system (CNS), arginine is extracted from the blood and exchanged by cells through carriers called cationic amino acid transporters (CAT) and belonging to the so-called system y+. In order to better understand the arginine transport in the CNS, we studied in detail the regional distribution of the cells expressing the CAT2(B) transcript in the adult rat brain by non-radioisotopic in situ hybridization. We show that CAT2(B) is expressed in neurons and oligodendrocytes throughout the brain, but is not detected in astrocytes. The pattern of localization of CAT2(B) in the normal adult rat brain fits closely that of CRT1, a specific creatine transporter. Our study demonstrates that the in vivo expression of CAT2(B) differs from that reported in vitro, implying that local cellular interactions should be taken into account in studies of gene regulation of the CAT2(B) gene. Our work suggests that CAT2(B) may play a role in case of increased NO production as well as arginine or creatine deficiency in the brain
- …