1,101 research outputs found
Redshift-Space Distortions and the Real-Space Clustering of Different Galaxy Types
We study the distortions induced by peculiar velocities on the redshift-space
correlation function of galaxies of different morphological types in the
Pisces-Perseus redshift survey. Redshift-space distortions affect early- and
late-type galaxies in different ways. In particular, at small separations, the
dominant effect comes from virialized cluster cores, where ellipticals are the
dominant population. The net result is that a meaningful comparison of the
clustering strength of different morphological types can be performed only in
real space, i.e., after projecting out the redshift distortions on the
two-point correlation function xi(r_p,pi). A power-law fit to the projected
function w_p(r_p) on scales smaller than 10/h Mpc gives r_o =
8.35_{-0.76}^{+0.75} /h Mpc, \gamma = 2.05_{-0.08}^{+0.10} for the early-type
population, and r_o = 5.55_{-0.45}^{+0.40} /h Mpc, \gamma =
1.73_{-0.08}^{+0.07} for spirals and irregulars. These values are derived for a
sample luminosity brighter than M_{Zw} = -19.5. We detect a 25% increase of r_o
with luminosity for all types combined, from M_{Zw} = -19 to -20. In the
framework of a simple stable-clustering model for the mean streaming of pairs,
we estimate sigma_12(1), the one-dimensional pairwise velocity dispersion
between 0 and 1 /h Mpc, to be 865^{+250}_{-165} km/s for early-type galaxies
and 345^{+95}_{-65} km/s for late types. This latter value should be a fair
estimate of the pairwise dispersion for ``field'' galaxies; it is stable with
respect to the presence or absence of clusters in the sample, and is consistent
with the values found for non-cluster galaxies and IRAS galaxies at similar
separations.Comment: 17 LaTeX pages including 3 tables, plus 11 PS figures. Uses AASTeX
macro package (aaspp4.sty) and epsf.sty. To appear on ApJ, 489, Nov 199
Southern Sky Redshift Survey: Clustering of Local Galaxies
We use the two-point correlation function to calculate the clustering
properties of the recently completed SSRS2 survey. The redshift space
correlation function for the magnitude-limited SSRS2 is given by xi(s)=(s/5.85
h-1 Mpc)^{-1.60} for separations between 2 < s < 11 h-1 Mpc, while our best
estimate for the real space correlation function is xi(r) = (r/5.36 h-1
Mpc)^{-1.86}. Both are comparable to previous measurements using surveys of
optical galaxies over much larger and independent volumes. By comparing the
correlation function calculated in redshift and real space we find that the
redshift distortion on intermediate scales is small. This result implies that
the observed redshift-space distribution of galaxies is close to that in real
space, and that beta = Omega^{0.6}/b < 1, where Omega is the cosmological
density parameter and b is the linear biasing factor for optical galaxies. We
also use the SSRS2 to study the dependence of xi on the internal properties of
galaxies. We confirm earlier results that luminous galaxies (L>L*) are more
clustered than sub-L* galaxies and that the luminosity segregation is
scale-independent. We find that early types are more clustered than late types,
but that in the absence of rich clusters, the relative bias between early and
late types in real space, is not as strong as previously estimated.
Furthermore, both morphologies present a luminosity-dependent bias, with the
early types showing a slightly stronger dependence on luminosity. We also find
that red galaxies are significantly more clustered than blue ones, with a mean
relative bias stronger than that seen for morphology. Finally, we find that the
relative bias between optical and iras galaxies in real space is b_o/b_I
1.4.Comment: 43 pages, uses AASTeX 4.0 macros. Includes 8 tables and 16 Postscript
figures, updated reference
Some remarks on the chemical potential of a system in an external field
The chemical potential change provides a criterion for predicting the spontaneity of any physical and chemical process. If asked to calculate the chemical potential change of a system in which several forces vary, a student might find the task quite complicate at first glance. However, the chemical potential is a state function. This property permits a precise definition of the contribution of each force to the chemical potential when all other relevant parameters are kept constant. The total chemical potential change can easily be calculated by summing up the above contributions. After a brief review of the role played by some parameters of the system, like activity (a) of the components, temperature (T), pressure (p) and surface tension (gamma), as well as of external fields, i.e. gravitational (Mgh), centrifugal (Mcp) and electric field (Fz(i) Phi), an equation for the computation of the chemical potential (mu) including all the above contributes is reported:-, where refers not only to p = p degrees = 1 bar but also to a chosen value of T, h, rho, Phi and r. Finally, applicative examples are illustrated.The chemical potential change provides a criterion for predicting the spontaneity of any physical and chemical process. If asked to calculate the chemical potential change of a system in which several forces vary, a student might find the task quite complicate at first glance. However, the chemical potential is a state function. This property permits a precise definition of the contribution of each force to the chemical potential when all other relevant parameters are kept constant. The total chemical potential change can easily be calculated by summing up the above contributions. After a brief review of the role played by some parameters of the system, like activity ( of the components, temperature (T), pressure (p) and surface tension (), as well as of external fields, i.e. gravitational (ℎ, centrifugal () and electric field (Φ), an equation for the computation of the chemical potential (µ) including all the above contributes is reported: °′ ° ° ℎ Φ 2 , where ° refers not only to p = p° =1 bar but also to a chosen value of T, h, ρ, Φ and r. Finally, applicative examples are illustrated
Prevalence Of Functional Gastrointestinal Disorders According To Rome III Criteria In Italian Morbidly Obese Patients
The relationship between GI symptoms and obesity has yet to be completely clarified. Aim. To determine in a morbidly obese southern Italy adult population the prevalence of Functional Gastrointestinal Disorders (FGID) and its association with the presence of a Binge Eating (BE) behavior pattern. Methods. Consecutive obese patients eligible for bariatric surgery and 100 Healthy Controls (HC) were recruited. All participants were questioned and scored for the presence of FGID according to Rome III criteria and for the presence or the frequency-intensity of a number of upper and lower GI symptoms. BE behavior pattern was assessed. Results. One-hundred obese patients met the inclusion criteria. The prevalence of FGID was similar between obese patients and HC. There was a significant association between obese patients with BE behavior and postprandial distress syndrome (P = 0.04). Moreover, a significantly higher frequency-intensity score for epigastric fullness (1.23 ± 0.45 versus 0.35 ± 0.13, P = 0.01) was found in obese patients with BE behavior compared to obese patients without. Conclusions. Obese patients with a BE behavior pattern showed a significantly higher prevalence of postprandial distress syndrome. A greater knowledge of the GI symptoms associated with obesity along with the pathophysiological mechanisms underlying will be important in the clinical management of these patients
Infiltration Measurements for Soil Hydraulic Characterization
This book summarises the main results of many contributions from researchers worldwide who have used the water infiltration process to characterize soil in the field. Determining soil hydrodynamic properties is essential to interpret and simulate the hydrological processes of economic and environmental interest. This book can be used as a guide to soil hydraulic characterization and in addition it gives a complete description of the treated techniques, including an outline of the most significant research results, with the main points that still needing development and improvement
Acetylcholine downregulates the cough reflex in the caudal nucleus tractus solitarii of the rabbit
Essential Role of the cVRG in the Generation of Both the Expiratory and Inspiratory Components of the Cough Reflex.
As stated by Korpáš and Tomori (1979), cough is the most important airway protective reflex which provides airway defensive responses to nociceptive stimuli. They recognized that active expiratory efforts, due to the activation of caudal ventral respiratory group (cVRG) expiratory premotoneurons, are the prominent component of coughs. Here, we discuss data suggesting that neurons located in the cVRG have an essential role in the generation of both the inspiratory and expiratory components of the cough reflex. Some lines of evidence indicate that cVRG expiratory neurons, when strongly activated, may subserve the alternation of inspiratory and expiratory cough bursts, possibly owing to the presence of axon collaterals. Of note, experimental findings such as blockade or impairment of glutamatergic transmission to the cVRG neurons lead to the view that neurons located in the cVRG are crucial for the production of the complete cough motor pattern. The involvement of bulbospinal expiratory neurons seems unlikely since their activation affects differentially expiratory and inspiratory muscles, while their blockade does not affect baseline inspiratory activity. Thus, other types of cVRG neurons with their medullary projections should have a role and possibly contribute to the fine tuning of the intensity of inspiratory and expiratory efforts
The Effect of Heating on Properties of Sandy Soils
Although burning grass and crop residues is prohibited in many countries, farmers perceive
it as a quick and inexpensive way to eliminate unwanted biomass. The aim of this study was to
estimate the impact of heating temperature (simulation of biomass burning) on the studied properties
(soil organic carbon (SOC) content, pH(H2O), water drop penetration time, WDPT, and contact
angle, CA) of acidic sandy soils. Soil samples were taken from the experimental sites S1, S2, and
S3 at Studienka village in the Borská nížina lowland (southwestern Slovakia). Experimental site S1
was arable land, experimental site S2 was arable land abandoned for approximately 10 years, and
experimental site S3 was arable land abandoned for approximately 30 years with scattered Scots pine
(Pinus sylvestris L.) trees. It was found that all the soil properties studied were strongly affected by
heating. A drop in SOC was observed in all the soils for the heating temperature between 20 and
600 °C. Due to the incomplete combustion of SOC, a small (0.1–0.7%) SOC content was recorded
even in soils heated to between 600 and 900 °C. An increase in pH(H2O) was observed in all the
soils for the heating temperature higher than 300 °C. Soil from the experimental site S1 was wettable
(WDPT < 5 s) for all of the heating temperatures. WDPT vs. heating temperature relationships for
the soils from the experimental sites S2 and S3 were more complex. After a decrease in the heating
temperature of 50 °C, an increase in WDPT for the heating temperature between 50 °C and 300 °C
(for S3 soil) and 350 C (for S2 soil) was registered. Finally, the WDPT dramatically dropped to 0 for
the heating temperature of 350 °C (for S3 soil) and 400 °C (for S2 soil). CA started to decrease at
300 °C in all the soils and dropped to 0° for all the soils at 800 °C. CA > 0° measured in soils for the
heating temperature between 400 and 800 °C, as a consequence of the small SOC contents due to
the incomplete combustion of SOC, is a novelty of this study which demonstrates that CA is more
sensitive to the changes in subcritical water repellency than WDPT
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