323,089 research outputs found
Correlation functions of matter from galaxy rotation curves
No full textBased on the disk-halo decomposition method introduced by Persic & Salucci, we use 58 spiral rotation curves to measure the galaxy-background correlation function in the range 3-350 kpc (for H0 = 50 km s-1 Mpc-1). We find that (1) the two-point function is zeta(r) congruent-to (r0/r)1.76, with r0 congruent-to 7 Mpc (for OMEGA-0 = 1), and (2) higher order correlation functions are detected up to the sixth order and are found to fit the hierarchical expression
A physical distance indicator for spiral galaxies
No full textIn this paper we derive a Tully Fisher relation from measured I band photometry and H alpha rotation curves of a large survey of southern sky spiral galaxies, obtained in Persic & Salucci (1995) by deprojecting and folding the raw H alpha data of Mathewson, Ford & Buchhorn (1992). We calibrate the relation by combining several of the largest clusters in the survey, using an iterative maximum likelihood procedure to account for observational selection effects and Malmquist bias. We also incorporate a simple model for the line of sight depth of each cluster. Our results indicate a Tully Fisher relation of intrinsic dispersion similar to 0.3 mag, corresponding to a distance error dispersion of 13%. Application of this relation to mapping the large scale velocity field is underway
Statistics of matter distribution from halo dynamics
No full textThe galaxy-background correlation function at short distances is explored by means of the observed disk dynamics of spiral galaxies. Using both the sample of galaxies and the analytical method for dark-to-luminous mass decomposition from optical rotation curves presented by Persic and Salucci, individual sizes and mean densities are worked out for 42 extended halos (taken to be η = 10 times as massive as their respective disks) as functions of both the intensity and the gradient of the central velocity field. The statistics for the expected density enhancements within given distances from galactic centers shows simple properties which strongly tie galaxy-background and galaxy-galaxy correlation functions. In particular, we find that: (a) the two-point galaxy-background correlation function is in agreement with its galaxy-galaxy counterpart (slope γ = 1.76 +/- 0.03; clustering length r_0_ = (7.1 +/- 0.7)[η/10)gamma-2^(1/{OMEGA}_0_)]^1/γ^ h^-1^_50_ Mpc); (b) the three-point and four-point correlation functions fit the so-called hierarchical clustering expression; (c) the constants Q (for the three-point function) and R-a_ and R_b_ (for the four-point function) are found to be Q = 0.46 +/- 0.04 and R_a_ + 0.35 R_b_ = 0.19 +/- 0.05, in agreement with BBGKY hierarchy predictions. The main consideration which naturally follows is that on the scale of galaxies the statistics of matter seems to be highlighted with equal effectiveness by both the luminous point-object distribution and the dark- matter properties underlying the halo-influenced disk dynamics
Nutrition and Regulation of Muscle Protein Synthesis
No full text: Skeletal muscles are an indispensable actor for daily activities, playing an essential role in locomotion through both the control of posture and position and by joint stabilization [...]
The effect of the disc on the rotation curves of spiral galaxies
No full textWe discuss the role of the galactic disc in the interpretation of the circular velocities of spiral galaxies at large galactocentric radii. The fractional amount of mass in the disc can be shown to be an increasing function of the luminosity. As a result, the shape of the rotation curve near the edge of the optical disc is expected to vary systematically with luminosity. Using a simple disc/halo model we find that in bright, disc-dominated galaxies the rotation curve should drop by a few tens of km s−1 immediately outside the disc, even in the presence of an extended dark halo. Only in faint, halo-dominated galaxies, do we expect the rotation curve to remain flat or even to rise beyond the optical radius. We find evidence for this behaviour in several published rotation curves. In the case of the Milky Way we show that if the disc dominates the gravitational potential in the inner regions, then the low mass estimated by Little & Tremaine from the dynamics of the outer satellites is consistent with a dark halo that extends beyond the region sampled. This and other available data are well fit by a model in which the luminous component of the Galaxy contributes ∼ 70 per cent of the mass at 12 kpc from the centre and the mass at large radii increases in proportion to the radius
Morphological evaluation of liposomal iron carriers
No full textIron is one of the most important elements for human, because it plays an essential role in many metabolic processes. However, it is also recognized to be dangerous for its detrimental effect inside human cells, where, in the absence of homeostatic balance, it can induce free radicals formation. Moreover, an excessive accumulation of iron in tissues can produce iron overload, a condition incompatible with life. The use of liposomes as carriers can represent an interesting iron therapy to improve iron bioavailability and reduce its negative effects, in particular during pregnancy. In this study, a morphological analysis has been performed on commercial liposome vesicles at various drying times, both in saline solution and in distilled water. Furthermore, to highlight their possible interaction or internalization in cells, liposomes have been administered to human hemopoietic U937 cells. Ultrastructural analyses confirm that vesicle morphology and size are comparable with classical liposomal structures. Products are stable during specimen preparation and drying. Additionally, they have a good ability to penetrate into cells, interacting with cytoplasmic organelles, without inducing, at least apparently, any ultrastructural damage
A Physical Distance Indicator for Spiral Galaxies and the Determination of H0
No full textWe consider the effect of dark matter on the Tully-Fisher relation for spiral galaxies. We show that a significant fraction of the scatter in this relation could stem from a systematic dependence of the ratio of dark to luminous mass on luminosity. The dynamical effect of the dark matter can be accounted for once a mass decomposition procedure, based on photometry and rotation curve data, has been carried out. We show that the contribution to the circular velocity from the luminous disc alone correlates better with luminosity than does the total velocity, which contains an additional contribution from the dark halo. This correlation is closer to a linear law, has less scatter, and is subject to fewer biases than the conventional Tully-Fisher relation. As an illustration, we use two different sets of distance moduli for a sample of local galaxies to calibrate our relation. Applying Teerikorpi's prescription to correct for Malmquist bias, we then derive values of the Hubble constant of H0 = 61 +/- 5 and 66 +/- 6 km s-1 Mpc-1 for our two sets of calibrators respectively
Polyphenols and their potential role in preventing skeletal muscle atrophy
No full textSkeletal muscle atrophy is the consequence of various conditions, such as disuse, denervation, fasting, aging, and disease. Even if the underlying molecular mechanisms are still not fully understood, an elevated oxidative stress related to mitochondrial dysfunction has been proposed as one of the major contributors to skeletal muscle atrophy. Researchers have described various forms of nutritional supplementation to prevent oxidative stress-induced muscle wasting. Among a variety of nutrients, attention has also focused on polyphenols, a wide range of plant-based compounds with antioxidant and inflammatory properties, many of which have beneficial effects on human health and might retard skeletal muscle loss and function impairment. The purpose of this review is to describe polyphenol actions in skeletal muscle atrophy prevention. Published articles from the last 10 years were searched on PubMed and other databases. Polyphenols are important molecules that should be considered when discussing possible strategies against muscle atrophy. In particular, the collected studies describe, for each polyphenol subclass, the beneficial effect on muscle mass preservation in various skeletal muscle disorders. In these examples, the polyphenol compounds appear to mainly act by reversing mitochondrial dysfunction. Given that the current information on polyphenols is mostly restricted to basic studies, more comprehensive research and additional studies should be performed to clarify their mechanisms of action in improving skeletal muscle functions during atrophy
Dark Matter Decay and the Spiral Galaxy NGC891
No full textWe study the implications for NGC 891 of the decaying Dark matter (DDM) hypothesis which states that dark matter decays into hydrogen-ionizing photons on a time-scale of 1023 s. We are able to derive many details of the observed Hα emission of this galaxy using only its rotation curve and properties of our own very similar Galaxy. We also use the hypothesis to determine the distance and the peculiar velocity of NGC 891 and obtain agreement with an independent estimate of those quantities. The detailed agreement of the consequences of the DDM hypothesis with observations of NGC 891 provides strong support for this hypothesis. (author
Chondrocyte death involvement in osteoarthritis
No full textChondrocyte apoptosis is known to contribute to articular cartilage damage in osteoarthritis and is correlated to a number of cartilage disorders. Micromass cultures represent a convenient means for studying chondrocyte biology, and, in particular, their death. In this review, we focused the different kinds of chondrocyte death through a comparison between data reported in the literature. Chondrocytes show necrotic features and, occasionally, also apoptotic features, but usually undergo a new form of cell death called Chondroptosis, which occurs in a non-classical manner. Chondroptosis has some features in common with classical apoptosis, such as cell shrinkage, chromatin condensation, and involvement, not always, of caspases. The most crucial peculiarity of chondroptosis relates to the ultimate elimination of cellular remnants. Independent of phagocytosis, chondroptosis may serve to eliminate cells without inflammation in situations in which phagocytosis would be difficult. This particular death mechanism is probably due to the unusual condition chondrocytes both in vivo and in micromass culture. This review highlights on the morpho-fuctional alterations of articular cartilage and focus attention on various types of chondrocyte death involved in this degeneration. The death features have been detailed and discussed through in vitro studies based on tridimensional chondrocyte culture (micromasses culture). The study of this particular mechanism of cartilage death and the characterization of different biological and biochemical underlying mechanisms can lead to the identification of new potentially therapeutic targets in various joint diseases
- …
