79 research outputs found
Litter growth and waning characteristics in two generations of straightbred and cross bred rabbits
No full textNo Abstract.Nigerian Journal of Genetics Vol. 18 2003: pp. 68-7
Cytogenic analysis of branching traits and inheritance pattern in a cross of branching and non-branching cowpea (Vigna unguiculata L. Walp)
No full textNo Abstract.Nigerian Journal of Genetics Vol. 18 2003: pp. 44-4
Advanced camera for surveys photometry of the cluster RDCS 1252.9-2927: The color-magnitude relation at z=1.24
No full textWe investigate the color-magnitude (CM) relation of galaxies in the distant X-ray-selected cluster RDCS 1252.9 - 2927 z = 1.24 at using images obtained with the Advanced Camera for Surveys on the Hubble Space Telescope in the F775W and F850LP bandpasses. We select galaxies based on morphological classifications extending about 3.5 mag down the galaxy luminosity function, augmented by spectroscopic membership information. At the core of the cluster is an extensive early-type galaxy population surrounding a central pair of galaxies that show signs of dynamical interaction. The early-type population defines a tight sequence in the CM diagram, with an intrinsic scatter in observed (i(775)-z(850)) of 0.029 +/- 0.007 mag based on 52 galaxies or 0.024 +/- 0.008 mag for similar to30 elliptical galaxies. Simulations using the latest stellar population models indicate an age scatter for the elliptical galaxies of about 34%, with a mean age tau(L) greater than or similar to 2.6 Gyr (corresponding to z(L) greater than or similar to 2.7), and the last star formation occurring at z(end) greater than or similar to 1.5 Transforming to rest-frame (U-B), we conclude that the slope end and scatter in the CM relation for morphologically selected early-type galaxies show little or no evidence of evolution out to z approximate to 1.2. Thus, elliptical galaxies were already well established in X-ray - luminous clusters when the universe was a third of its present age
Recommended from our members
Geothermal play typing in Germany, case study Molasse Basin: A modern concept to categorise geothermal resources related to crustal permeability
No full textThe majority of running geothermal plants worldwide are located in geological settings with convection- or advection-dominant heat transport. In Germany as in most regions in Europe, conduction is the dominating heat transport mechanism, with a resulting average geothermal gradient. The geothermal play type concept is a modern methodology to group geothermal resources according to their geological setting, and characteristic heat transport mechanisms. In particular, the quantity of heat transport is related to fluid flow in natural or engineered geothermal reservoirs. Hence, the permeability structure is a key element for geothermal play typing. Following the existing geothermal play type catalogue, four major geothermal play types can be identified for Germany: intracratonic basins, foreland basins and basement/crystalline rock provinces as conduction-dominated play types, and extensional terrains as the convection-dominated play type. The installed capacity of geothermal facilities sums up to 397.1 MWth by the end of 2018. District heating plants accounted for the largest portion, with about 337.0 MWth. The majority of these installations are located in the play type 'foreland basin', namely the Molasse Basin in southern Germany. The stratigraphic unit for geothermal use is the Upper Jurassic, also known as 'Malm' formation, a carbonate reservoir with high variability in porosity and permeability. Recently drilled wells in the southernmost Molasse Basin indicate the Upper Jurassic as a tight, fracture-controlled reservoir, not usable for conventional hydrothermal well doublets. Our new data compilation including the recently drilled deep geothermal well Geretsried reveals the relation of porosity and permeability to depth. The results suggest that obviously diagenetic processes control permeability with depth in carbonate rock, diminishing the predictability of reservoir porosity and permeability. The play type concept helps to delineate these property variations in play type levels because it is based on geological constraints, common for exploration geology. Following the general idea of play typing, the results from this play analysis can be transferred to geological analogues as carbonate rock play levels in varying depth. © The Author(s) 2020
THE ROLE OF DIFFERENT TYPES OF CORTICOSTEROIDS ON THE INFLAMMATORY MEDIATORS IN CARDIOPULMONARY BYPASS
No full textIn a placebo-controlled double-blind study on patients undergoing cardiopulmonary bypass (CPB) we studied the inhibited effects of dexamethasone, a high dose of methylprednisolone, and a low dose of prednisolone on the inflammatory reaction induced by CPB. During CPB two episodes of blood activation were noticed. First, the blood-material interaction caused a significant increase in complement C3a and elastase concentrations after the start of bypass (p <0.01). Secondly, the reperfusion of the ischemic heart, lungs, and peripheral tissue, after the release of the aortic cross-clamp, caused an additional increase in C3a and elastase concentration and a statistically significant increase in leukotriene B4 (LTB4) concentration and tissue plasminogen activator (t-PA) activity (p <0.01, p <0.05, respectively). Dexamethasone treatment effectively inhibited the increase in LTB4 concentration and t-PA activity after release of the cross-clamp (significant differences to the placebo group, p <0.01, p <0.05, respectively). High-dose methylprednisolone treatment was almost as effective as dexamethasone treatment, whereas low-dose prednisolone treatment was less effective that methylprednisolone in the inhibition of the inflammatory mediators (DM > MP > P). None of the corticosteroid regimens was able to inhibit the increase in complement C3a and elastase. We therefore conclude that corticosteroids do not have an effect on complement activation during CPB. However, leukocyte activation and t-PA activity after release of the aortic cross-clamp are effectively inhibited by corticosteroid treatment, in a dose-dependent way. The inhibition of this inflammatory reaction will have a favourable effect on the postoperative course in patients who have undergone CPB.</p
Ultracompact dwarf galaxies in Abell 1689: A photometric study with the advanced camera for surveys
No full textThe properties of ultracompact dwarf (UCD) galaxy candidates in Abell 1689 (z = 0.183) are investigated, based on deep high-resolution images from the Hubble Space Telescope Advanced Camera for Surveys. A UCD candidate has to be unresolved, have i < 28 mag (M-V < -11.5 mag), and satisfy color limits derived from Bayesian photometric redshifts. We find 160 UCD candidates with 22 mag < i < 28 mag. We estimate that about 100 of these are cluster members, based on their spatial distribution and photometric redshifts. For i greater than or similar to 26.8 mag, the radial and luminosity distribution of the UCD candidates can be explained well by Abell 1689's globular cluster ( GC) system. For i less than or similar to 26.8 mag, there is an overpopulation of 15 +/- 5 UCD candidates with respect to the GC luminosity function. For i less than or similar to 26 mag, the radial distribution of UCD candidates is more consistent with the dwarf galaxy population than with the GC system of Abell 1689. The UCD candidates follow a color-magnitude trend with a slope similar to that of Abell 1689's genuine dwarf galaxy population, but shifted fainter by about 2-3 mag. Two of the three brightest UCD candidates (M-V similar or equal to -17 mag) are slightly resolved. At the distance of Abell 1689, these two objects would have King profile core radii of similar or equal to35 pc and r(eff) similar or equal to 300 pc, implying luminosities and sizes 2-3 times those of M32's bulge. Additional photometric redshifts obtained with late-type stellar and elliptical galaxy templates support the assignment of these two resolved sources to Abell 1689 but also allow for up to four foreground stars among the six brightest UCD candidates. Our findings imply that in Abell 1689 there are greater than or equal to10 UCDs with M-V < -12.7 mag, probably created by stripping "normal" dwarf or spiral galaxies. Compared with the UCDs in the Fornax Cluster - the location of their original discovery - they are brighter, larger, and have colors closer to normal dwarf galaxies. This suggests that they may be in an intermediate stage of the stripping process. Checking the photometric redshifts of the brightest UCD candidates with spectroscopy would be the next step to definitely confirm the existence of UCDs in Abell 1689
A Lightweight Spherical Generalized Luneburg Lens Antenna With Low Cross-Polarization Over a Wide Range in Azimuth and Elevation
No full textIn this paper, a novel dual-slant polarized three-dimensional (3D) periodic Luneburg lens with a diameter of 390 mm ( at 3.55 GHz) is presented. Copper-plated cubes with truncated corners are placed in a body-centered cubic (BCC) lattice and held together with layers of Rohacell foam. The sizes of the cubes are varied to realize the gradient refractive index (GRIN) profile of a generalized Luneburg lens at a low cost, with a low weight and loss. The designed Luneburg lens operates from 3.3 to 3.8 GHz with a total weight of 1 kg. The quasi-isotropic response of the proposed periodic structure allows a wide angle coverage. Measured results show that the lens antenna can achieve a peak gain of 22 dBi with a scanning loss of less than 0.4 dB in a wide angular range in both the azimuth and the elevation plane. Importantly, the proposed lens antenna design achieves a cross-polarization level below peak gain of less than −19 dB at all angles for the two slant polarizations of the feed, while comparable designs report up to −11 dB at given angular directions. This high-gain multi-beam antenna with a commercially viable design is suitable for wireless communications at low microwave frequencies
Faint galaxies in deep advanced camera for surveys observations
No full textWe present the analysis of the faint galaxy population in the Advanced Camera for Surveys (ACS) Early Release Observation fields VV 29 ( UGC 10214) and NGC 4676. These observations cover a total area of 26.3 arcmin(2) and have depths close to that of the Hubble Deep Fields in the deepest part of the VV 29 image, with 10 sigma detection limits for point sources of 27.8, 27.6, and 27.2 AB magnitudes in the g(F475W), V-F606W, and I-F814W bands, respectively. Measuring the faint galaxy number count distribution is a difficult task, with different groups arriving at widely varying results even on the same data set. Here we attempt to thoroughly consider all aspects relevant for faint galaxy counting and photometry, developing methods that are based on public software and that are easily reproducible by other astronomers. Using simulations we determine the best SExtractor parameters for the detection of faint galaxies in deep Hubble Space Telescope observations, paying special attention to the issue of deblending, which significantly affects the normalization and shape of the number count distribution. We confirm, as claimed by Bernstein, Freedman, & Madore, that Kron-like magnitudes, such as the ones generated by SExtractor, can miss more than half of the light of faint galaxies, what dramatically affects the slope of the number counts. We show how to correct for this effect, which depends sensitively not only on the characteristics of the observations, but also on the choice of SExtractor parameters. We present catalogs for the VV 29 and NGC 4676 fields with photometry in the F475W, F606W, and F814W bands. We also show that combining the Bayesian software BPZ with superb ACS data and new spectral templates enables us to estimate reliable photometric redshifts for a significant fraction of galaxies with as few as three filters. After correcting for selection effects, we measure slopes of 0.32 +/- 0.01 for 22 25.5 can be well approximated in all our filters by a passive luminosity evolution model based on the COMBO-17 luminosity function (alpha = -1.5), with a strong merging rate following the prescription of Glazebrook et al., phi* proportional to / (1 + Qz), with Q = 4
Star formation at z~6: i-dropouts in the advanced camera for surveys guaranteed time observation fields
No full textUsing an i - z dropout criterion, we determine the space density of z similar to 6 galaxies from two deep ACS GTO fields with deep optical-IR imaging. A total of 23 objects are found over 46 arcmin(2), or similar to0.5 +/- 0.1 objects arcmin(-2) down to z(AB) similar to 27.3 (6 sigma), or a completeness-corrected similar to0.5 +/- 0.2 objects arcmin(-2) down to z(AB) similar to 26.5 (including one probable z similar to 6 active galactic nucleus). Combining deep ISAAC data for our RDCS 1252-2927 field (J(AB) similar to 25.7 and K-s;AB similar to 25.0; 5 sigma) and NICMOS data for the Hubble Deep Field North (J(110;AB) and H-160; AB similar to 27.3, 5 sigma), we verify that these dropouts have relatively. at spectral slopes, as one would expect for star-forming objects at z similar to 6. Compared with the average-color (beta = -1.3) U-dropout in the Steidel et al. z similar to 3 sample, i-dropouts in our sample range in luminosity from similar to1.5L(*) (z(AB) similar to 25.6) to similar to0.3L(*) (z(AB) similar to 27.3) with the exception of one very bright candidate at z(850; AB) similar to 24.2. The half-light radii vary from 0."09 to 0."21, or 0.5 kpc to 1.3 kpc. We derive the z similar to 6 rest-frame UV luminosity density (or star formation rate density) by using three different procedures. All three procedures use simulations based on a slightly lower redshift (z similar to 5) V-606-dropout sample from Chandra Deep Field-South ACS images. First, we make a direct comparison of our findings with a no-evolution projection of this V-dropout sample, allowing us to automatically correct for the light lost at faint magnitudes or lower surface brightnesses. We find 23% +/- 25% more i-dropouts than we predict, consistent with no strong evolution over this redshift range. Adopting previous results to z similar to 5, this works out to a mere 20% +/- 29% drop in the luminosity density from z similar to 3 to z similar to 6. Second, we use the same V-dropout simulations to derive a detailed selection function for our i-dropout sample and compute the UV-luminosity density [7.2 +/- 2.5) _x 10(25) ergs s(-1) Hz(-1) Mpc(-3) down to z(AB) similar to 27]. We find a 39% +/- 21% drop over the same redshift range (z similar to 3-6), consistent with the first estimate. This is our preferred value and suggests a star formation rate of 0.0090 +/- 0.0031 M-. yr(-1) Mpc(-3) to z(AB) similar to 27, or similar to 0.036 +/- 0.012 M-. yr(-1) Mpc(-3) by extrapolating the luminosity function to the faint limit, assuming alpha = - 1.6. Third, we follow a very similar procedure, except that we assume no incompleteness, and find a rest-frame continuum luminosity that is similar to2-3 times lower than our other two determinations. This final estimate is to be taken as a lower limit and is important if there are modest changes in the colors or surface brightnesses from z similar to 5 to z similar to 6 (the other estimates assume no large changes in the intrinsic selectability of objects). We note that all three estimates are well within the canonical range of luminosity densities necessary for reionization of the universe at this epoch by star-forming galaxies
Hubble Space Telescope ACS coronagraphic imaging of the circumstellar disk around HD 141569A
No full textMulticolor coronagraphic images of the circumstellar disk around HD 141569A have been obtained with the Hubble Space Telescope Advanced Camera for Surveys. The B, V, and I images show that the disk's previously described multiple-ring structure is actually a continuous distribution of dust with a tightly wound spiral structure. Extending from the disk are two, more open spiral arms, one of which appears to reach the nearby binary star HD 141569BC. Diffuse dust is seen up to 1200 AU from HD 141569A. Although planets may exist in the inner region of the disk, tidal interaction with HD 141569BC seems more likely to be the cause of these phenomena. The disk appears redder than the star ( B - V = 0.21 and V - I = 0.25), and its color is spatially uniform. A scattering asymmetry factor of g = 0.25 - 0.35 is derived. The azimuthal density distribution is asymmetric, varying by a factor of similar to3 at some radii
- …
