567 research outputs found
Iteration Method to Derive Exact Rotation Curves from Position-Velocity Diagrams of Spiral Galaxies
We present an iteration method to derive exact rotation curves (RC) of spiral
galaxies from observed position-velocity diagrams (PVD), which comprises the
following procedure. An initial rotation curve, RC0, is adopted from an
observed PV diagram (PV0), obtained by any simple method such as the
peak-intensity method. Using this rotation curve and an observed radial
distribution of intensity (emissivity), we construct a simulated PV diagram
(PV1). The difference between a rotation curve obtained from this PV1 and the
original RC (e.g., difference between peak-intensity velocities) is used to
correct the initial RC to obtain a corrected rotation curve, RC1. This RC1 is
used to calculated another PVD (PV2) using the observed intensity distribution,
and to obtain the second iterated RC (RC2). This iteration is repeated until
PV converges to PV0, so that the differences between PV and PV0 becomes
minimum. Finally RC is adopted as the most reliable rotation curve. We apply
this method to some observed PVDs of nearby galaxies, and show that the
iteration successfully converges to give reliable rotation curves. We show that
the method is powerful to detect central massive objects.Comment: To appear in ApJ.Letters, 5 pages Latex with 4 figure
The immune response of allophenic mice to the synthetic polymer L-glutamic acid, L-lysine, L-phenylalanine. II. Lack of gene complementation in two nonresponder strains
The genetic control of the immune response of inbred strains of mice to certain antigens has been demonstrated to be governed by a set of Ir genes linked to the major histocompatibility complex (H-2) of mice (1,2). Until recently, the control was thought to be governed by single, dominant genes, located within the I region of the H-2 complex. Merryman et al. (3) originally demonstrated that the immune response to the synthetic terpolymer L-glutamic acid, L-lysine, L-phenylaline (GLÏ) is under dominant, H-2-linked Ir gene control (4-7). This was shown both by crossing two nonresponder parental strains to produce responder offspring in the F(1) generation, and by the analysis of appropriate recombinant stains of mice. The two complementing genes have been mapped in the IA and IC regions of the H-2 complex, and have been termed ÎČ and α, respectively (5,6). Thus, any strain of mouse may contain neither, one, or both genes. Only mice containing both genes are capable of responding to GLÏ. It has been shown using F(1) hybrid and recombinant strains of mice, that the α- and ÎČ-genes can complement each other in either the cis (on the same chromosome) or in the trans (on different chromosomes) position (8). In this paper we report the results of studies aimed at answering the question of whether or not the α- and ÎČ- genes can complement each other when they are present in different lymphoid cells. To this end we have constructed allophenic mice composed of two nonresponder strains (A and C57BL/6), which show gene complementation in the F(1) generation. Allophenic mice are chimeras containing two cell types coexisting in a ânormalâ environment. The mice were tested for the specific cellular composition of the two parental cell types and were found to possess a complete range in the relative proportion of the two cell types. This report demonstrates that regardless of the mixture of cell types present in the allophenic mice, none of them were responders to GLÏ. Thus no complementation of the α- and ÎČ-genes is seen when the two genes are present in different cells
Classical novae from the POINT-AGAPE microlensing survey of M31 -- I. The nova catalogue
The POINT-AGAPE survey is an optical search for gravitational microlensing
events towards the Andromeda Galaxy (M31). As well as microlensing, the survey
is sensitive to many different classes of variable stars and transients. Here
we describe the automated detection and selection pipeline used to identify M31
classical novae (CNe) and we present the resulting catalogue of 20 CN
candidates observed over three seasons. CNe are observed both in the bulge
region as well as over a wide area of the M31 disk. Nine of the CNe are caught
during the final rise phase and all are well sampled in at least two colours.
The excellent light-curve coverage has allowed us to detect and classify CNe
over a wide range of speed class, from very fast to very slow. Among the
light-curves is a moderately fast CN exhibiting entry into a deep transition
minimum, followed by its final decline. We have also observed in detail a very
slow CN which faded by only 0.01 mag day over a 150 day period. We
detect other interesting variable objects, including one of the longest period
and most luminous Mira variables. The CN catalogue constitutes a uniquely
well-sampled and objectively-selected data set with which to study the
statistical properties of classical novae in M31, such as the global nova rate,
the reliability of novae as standard-candle distance indicators and the
dependence of the nova population on stellar environment. The findings of this
statistical study will be reported in a follow-up paper.Comment: 21 pages, 13 figures, re-submitted for publication in MNRAS, typos
corrected, references updated, figures 5-9 made cleare
Effectiveness of interventions to promote healthy diet in primary care: systematic review and meta-analysis of randomised controlled trials
Background
A diet rich in fruit, vegetables and dietary fibre and low in fat is associated with reduced risk of chronic disease. This review aimed to estimate the effectiveness of interventions to promote healthy diet for primary prevention among participants attending primary care.<p></p>
Methods
A systematic review of trials using individual or cluster randomisation of interventions delivered in primary care to promote dietary change over 12 months in healthy participants free from chronic disease or defined high risk states. Outcomes were change in fruit and vegetable intake, consumption of total fat and fibre and changes in serum cholesterol concentration.<p></p>
Results
Ten studies were included with 12,414 participants. The design and delivery of interventions were diverse with respect to grounding in behavioural theory and intervention intensity. A meta-analysis of three studies showed an increase in fruit consumption of 0.25 (0.01 to 0.49) servings per day, with an increase in vegetable consumption of 0.25 (0.06 to 0.44) serving per day. A further three studies that reported on fruit and vegetable consumption together showed a pooled increment of 0.50 (0.13 to 0.87) servings per day. The pooled effect on consumption of dietary fibre, from four studies, was estimated to be 1.97 (0.43 to 3.52) gm fibre per day. Data from five studies showed a mean decrease in total fat intake of 5.2% of total energy (1.5 to 8.8%). Data from three studies showed a mean decrease in serum cholesterol of 0.10 (-0.19 to 0.00) mmol/L.<p></p>
Conclusion
Presently-reported interventions to promote healthy diet for primary prevention in primary care, which illustrate a diverse range of intervention methods, may yield small beneficial changes in consumption of fruit, vegetables, fibre and fat over 12 months. The present results do not exclude the possibility that more effective intervention strategies might be developed.<p></p>
What is the clinical relevance of different lung compartments?
The lung consists of at least seven compartments with relevance to immune reactions. Compartment 1 - the bronchoalveolar lavage (BAL), which represents the cells of the bronchoalveolar space: From a diagnostic point of view the bronchoalveolar space is the most important because it is easily accessible in laboratory animals, as well as in patients, using BAL. Although this technique has been used for several decades it is still unclear to what extent the BAL represents changes in other lung compartments. Compartment 2 - bronchus-associated lymphoid tissue (BALT): In the healthy, BALT can be found only in childhood. The role of BALT in the development of the mucosal immunity of the pulmonary surfaces has not yet been resolved. However, it might be an important tool for inhalative vaccination strategies. Compartment 3 - conducting airway mucosa: A third compartment is the bronchial epithelium and the submucosa, which both contain a distinct pool of leukocytes (e.g. intraepithelial lymphocytes, IEL). This again is also accessible via bronchoscopy. Compartment 4 - draining lymph nodes/Compartment 5 - lung parenchyma: Transbronchial biopsies are more difficult to perform but provide access to two additional compartments - lymph nodes with the draining lymphatics and lung parenchyma, which roughly means "interstitial" lung tissue. Compartment 6 - the intravascular leukocyte pool: The intravascular compartment lies between the systemic circulation and inflamed lung compartments. Compartment 7 - periarterial space: Finally, there is a unique, lung-specific space around the pulmonary arteries which contains blood and lymph capillaries. There are indications that this "periarterial space" may be involved in the pulmonary host defense
Hypothalamic over-expression of VGF in the Siberian hamster increases energy expenditure and reduces body weight gain
VGF (non-acronymic) was first highlighted to have a role in energy homeostasis through experiments involving dietary manipulation in mice. Fasting increased VGF mRNA in the Arc and levels were subsequently reduced upon refeeding. This anabolic role for VGF was supported by observations in a VGF null (VGF-/-) mouse and in the diet-induced and gold-thioglucose obese mice. However, this anabolic role for VGF has not been supported by a number of subsequent studies investigating the physiological effects of VGF-derived peptides. Intracerebroventricular (ICV) infusion of TLQP-21 increased resting energy expenditure and rectal temperature in mice and protected against diet-induced obesity. Similarly, ICV infusion of TLQP-21 into Siberian hamsters significantly reduced body weight, but this was due to a decrease in food intake, with no effect on energy expenditure. Subsequently NERP-2 was shown to increase food intake in rats via the orexin system, suggesting opposing roles for these VGF-derived peptides. Thus to further elucidate the role of hypothalamic VGF in the regulation of energy homeostasis we utilised a recombinant adeno-associated viral vector to over-express VGF in adult male Siberian hamsters, thus avoiding any developmental effects or associated functional compensation. Initially, hypothalamic over-expression of VGF in adult Siberian hamsters produced no effect on metabolic parameters, but by 12 weeks post-infusion hamsters had increased oxygen consumption and a tendency to increased carbon dioxide production; this attenuated body weight gain, reduced interscapular white adipose tissue and resulted in a compensatory increase in food intake. These observed changes in energy expenditure and food intake were associated with an increase in the hypothalamic contents of the VGF-derived peptides AQEE, TLQP and NERP-2. The complex phenotype of the VGF-/- mice is a likely consequence of global ablation of the gene and its derived peptides during development, as well as in the adult
Changing sex at the same relative body size
Sex change occurs in a variety of animals,
including fish, echinoderms,crustaceans, molluscs and polychaete worms. Here we show that the relative timing
of sex change is surprisingly invariant
across all animals: 91â97% of the variation
in size at sex change across species can be
explained by the simple rule that individuals
change sex when they reach 72% of their
maximum size. This suggests that there is a
fundamental similarity across all animals,
from a 2-mm-long crustacean to a 1.5-mlong
fish in the underlying forces
that select for sex change
Asteroseismology and Interferometry
Asteroseismology provides us with a unique opportunity to improve our
understanding of stellar structure and evolution. Recent developments,
including the first systematic studies of solar-like pulsators, have boosted
the impact of this field of research within Astrophysics and have led to a
significant increase in the size of the research community. In the present
paper we start by reviewing the basic observational and theoretical properties
of classical and solar-like pulsators and present results from some of the most
recent and outstanding studies of these stars. We centre our review on those
classes of pulsators for which interferometric studies are expected to provide
a significant input. We discuss current limitations to asteroseismic studies,
including difficulties in mode identification and in the accurate determination
of global parameters of pulsating stars, and, after a brief review of those
aspects of interferometry that are most relevant in this context, anticipate
how interferometric observations may contribute to overcome these limitations.
Moreover, we present results of recent pilot studies of pulsating stars
involving both asteroseismic and interferometric constraints and look into the
future, summarizing ongoing efforts concerning the development of future
instruments and satellite missions which are expected to have an impact in this
field of research.Comment: Version as published in The Astronomy and Astrophysics Review, Volume
14, Issue 3-4, pp. 217-36
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