Units of relativistic time scales and associated quantities

This note suggests nomenclature for dealing with the units of various astronomical quantities that are used with the relativistic time scales TT, TDB, TCB and TCG. It is suggested to avoid wordings like "TDB units" and "TT units" and avoid contrasting them to "SI units". The quantities intended for use with TCG, TCB, TT or TDB should be called "TCG-compatible", "TCB-compatible", "TT-compatible" or "TDB-compatible", respectively. The names of the units second and meter for numerical values of all these quantities should be used with out any adjectives. This suggestion comes from a special discussion forum created within IAU Commission 52 "Relativity in Fundamental Astronomy"

Relativistic Celestial Mechanics with PPN Parameters

Starting from the global parametrized post-Newtonian (PPN) reference system with two PPN parameters $\gamma$ and $\beta$ we consider a space-bounded subsystem of matter and construct a local reference system for that subsystem in which the influence of external masses reduces to tidal effects. Both the metric tensor of the local PPN reference system in the first post-Newtonian approximation as well as the coordinate transformations between the global PPN reference system and the local one are constructed in explicit form. The terms proportional to $\eta=4\beta-\gamma-3$ reflecting a violation of the equivalence principle are discussed in detail. We suggest an empirical definition of multipole moments which are intended to play the same role in PPN celestial mechanics as the Blanchet-Damour moments in General Relativity. Starting with the metric tensor in the local PPN reference system we derive translational equations of motion of a test particle in that system. The translational and rotational equations of motion for center of mass and spin of each of $N$ extended massive bodies possessing arbitrary multipole structure are derived. As an application of the general equations of motion a monopole-spin dipole model is considered and the known PPN equations of motion of mass monopoles with spins are rederived.Comment: 71 page

The field high-amplitude SX Phe variable BL Cam: results from a multisite photometric campaign. II. Evidence of a binary - possibly triple - system

Short-period high-amplitude pulsating stars of Population I ($\delta$ Sct stars) and II (SX Phe variables) exist in the lower part of the classical (Cepheid) instability strip. Most of them have very simple pulsational behaviours, only one or two radial modes being excited. Nevertheless, BL Cam is a unique object among them, being an extreme metal-deficient field high-amplitude SX Phe variable with a large number of frequencies. Based on a frequency analysis, a pulsational interpretation was previously given. aims heading (mandatory) We attempt to interpret the long-term behaviour of the residuals that were not taken into account in the previous Observed-Calculated (O-C) short-term analyses. methods heading (mandatory) An investigation of the O-C times has been carried out, using a data set based on the previous published times of light maxima, largely enriched by those obtained during an intensive multisite photometric campaign of BL Cam lasting several months. results heading (mandatory) In addition to a positive (161 $\pm$ 3) x 10$^{-9}$ yr$^{-1}$ secular relative increase in the main pulsation period of BL Cam, we detected in the O-C data short- (144.2 d) and long-term ($\sim$ 3400 d) variations, both incompatible with a scenario of stellar evolution. conclusions heading (mandatory) Interpreted as a light travel-time effect, the short-term O-C variation is indicative of a massive stellar component (0.46 to 1 M_{\sun}) with a short period orbit (144.2 d), within a distance of 0.7 AU from the primary. More observations are needed to confirm the long-term O-C variations: if they were also to be caused by a light travel-time effect, they could be interpreted in terms of a third component, in this case probably a brown dwarf star ($\geq$ 0.03 \ M_{\sun}), orbiting in $\sim$ 3400 d at a distance of 4.5 AU from the primary.Comment: 7 pages, 5 figures, accepted for publication in A&

Astrometry and geodesy with radio interferometry: experiments, models, results

Summarizes current status of radio interferometry at radio frequencies between Earth-based receivers, for astrometric and geodetic applications. Emphasizes theoretical models of VLBI observables that are required to extract results at the present accuracy levels of 1 cm and 1 nanoradian. Highlights the achievements of VLBI during the past two decades in reference frames, Earth orientation, atmospheric effects on microwave propagation, and relativity.Comment: 83 pages, 19 Postscript figures. To be published in Rev. Mod. Phys., Vol. 70, Oct. 199

Sex-dimorphism in Cardiac Nutrigenomics: effect of Trans fat and/or Monosodium Glutamate consumption

<p>Abstract</p> <p>Background</p> <p>A paucity of information on biological sex-specific differences in cardiac gene expression in response to diet has prompted this present nutrigenomics investigation.</p> <p>Sexual dimorphism exists in the physiological and transcriptional response to diet, particularly in response to high-fat feeding. Consumption of <it>Trans</it>-fatty acids (TFA) has been linked to substantially increased risk of heart disease, in which sexual dimorphism is apparent, with males suffering a higher disease rate. Impairment of the cardiovascular system has been noted in animals exposed to Monosodium Glutamate (MSG) during the neonatal period, and sexual dimorphism in the growth axis of MSG-treated animals has previously been noted. Processed foods may contain both TFA and MSG.</p> <p>Methods</p> <p>We examined physiological differences and changes in gene expression in response to TFA and/or MSG consumption compared to a control diet, in male and female C57BL/6J mice.</p> <p>Results</p> <p>Heart and % body weight increases were greater in TFA-fed mice, who also exhibited dyslipidemia (P < 0.05). Hearts from MSG-fed females weighed less than males (P < 0.05). 2-factor ANOVA indicated that the TFA diet induced over twice as many cardiac differentially expressed genes (DEGs) in males compared to females (P < 0.001); and 4 times as many male DEGs were downregulated including <it>Gata4</it>, <it>Mef2d </it>and <it>Srebf2</it>. Enrichment of functional Gene Ontology (GO) categories were related to transcription, phosphorylation and anatomic structure (P < 0.01). A number of genes were upregulated in males and downregulated in females, including pro-apoptotic histone deacetylase-2 (HDAC2). Sexual dimorphism was also observed in cardiac transcription from MSG-fed animals, with both sexes upregulating approximately 100 DEGs exhibiting sex-specific differences in GO categories. A comparison of cardiac gene expression between all diet combinations together identified a subset of 111 DEGs significant only in males, 64 DEGs significant in females only, and 74 transcripts identified as differentially expressed in response to dietary manipulation in both sexes.</p> <p>Conclusion</p> <p>Our model identified major changes in the cardiac transcriptional profile of TFA and/or MSG-fed mice compared to controls, which was reflected by significant differences in the physiological profile within the 4 diet groups. Identification of sexual dimorphism in cardiac transcription may provide the basis for sex-specific medicine in the future.</p

Mechanisms of hypoxic up-regulation of versican gene expression in macrophages

Hypoxia is a hallmark of many pathological tissues. Macrophages accumulate in hypoxic sites and up-regulate a range of hypoxia-inducible genes. The matrix proteoglycan versican has been identified as one such gene, but the mechanisms responsible for hypoxic induction are not fully characterised. Here we investigate the up-regulation of versican by hypoxia in primary human monocyte-derived macrophages (HMDM), and, intriguingly, show that versican mRNA is up-regulated much more highly (&gt;600 fold) by long term hypoxia (5 days) than by 1 day of hypoxia (48 fold). We report that versican mRNA decay rates are not affected by hypoxia, demonstrating that hypoxic induction of versican mRNA is mediated by increased transcription. Deletion analysis of the promoter identified two regions required for high level promoter activity of luciferase reporter constructs in human macrophages. The hypoxia-inducible transcription factor HIF-1 has previously been implicated as a key potential regulator of versican expression in hypoxia, however our data suggest that HIF-1 up-regulation is unlikely to be principally responsible for the high levels of induction observed in HMDM. Treatment of HMDM with two distinct specific inhibitors of Phosphoinositide 3-kinase (PI3K), LY290042 and wortmannin, significantly reduced induction of versican mRNA by hypoxia and provides evidence of a role for PI3K in hypoxic up-regulation of versican expression