10,210 research outputs found
Starburst Intensity Limit of Galaxies at z~5-6
The peak star formation intensity in starburst galaxies does not vary
significantly from the local universe to redshift z~6. We arrive at this
conclusion through new surface brightness measurements of 47 starburst galaxies
at z~5-6, doubling the redshift range for such observations. These galaxies are
spectroscopically confirmed in the Hubble Ultra Deep Field (HUDF) through the
GRism ACS program for Extragalactic Science (GRAPES) project. The starburst
intensity limit for galaxies at z~5-6 agree with those at z~3-4 and z~0 to
within a factor of a few, after correcting for cosmological surface brightness
dimming and for dust. The most natural interpretation of this constancy over
cosmic time is that the same physical mechanisms limit starburst intensity at
all redshifts up to z~6 (be they galactic winds, gravitational instability, or
something else). We do see two trends with redshift: First, the UV spectral
slope of galaxies at z~5-6 is bluer than that of z~3 galaxies, suggesting an
increase in dust content over time. Second, the galaxy sizes from z~3 to z~6
scale approximately as the Hubble parameter 1/H(z). Thus, galaxies at z~6 are
high redshift starbursts, much like their local analogs except for slightly
bluer colors, smaller physical sizes, and correspondingly lower overall
luminosities. If we now assume a constant maximum star formation intensity, the
differences in observed surface brightness between z~0 and z~6 are consistent
with standard expanding cosmology and strongly inconsistent with tired light
model.Comment: Accepted for publication in ApJ (23 pages, 5 figures). Minor changes
to tex
Treatment of central nervous system complications of renal dialysis and transplantation
Purpose of review Most clinical neurologists will have come across individuals receiving renal replacement therapy who have developed a neurological complication, and neurologists working in, or close to, hospitals with a Renal Unit will be very aware of the range of central nervous system (CNS) complications that may develop in these patients. These can often be difficult to differentiate from disorders relating to renal failure or systemic conditions leading to kidney disease and can in fact arise from the interaction between underlying disease and the side effects of treatment. Patients with renal disease frequently have multiple comorbidities, and it is necessary to take a generally inclusive approach to diagnosis and treatment. Recent findings Unfortunately, there is a lack of specific high-quality evidence for a number of CNS complications of renal replacement therapy. Here, we review the major CNS complications of dialysis and transplantation, discussing evidence for treatments where available and detailing standard management approaches where evidence is scarce. Summary Given the lack of specific evidence for interventions in the treatment of CNS complications of renal replacement therapy, it is often necessary to take an individualised approach based on comorbidities and applying findings from the general population. In these complex patients, we must stress the importance of collaborative working between neurologists and renal physicians when treating this complex patient group
Redshifts of the Gravitational Lenses MG0414+0534 and MG0751+2716
We report redshifts in two gravitational lens systems, MG0414+0534 and
MG0751+2716. The lens galaxy in MG0414+0534 lies at z_l=0.9584+/-0.0002. The
luminosity and extreme red color of the lens are then typical of a passively
evolving, early-type, ~2L* galaxy. The galaxy cannot have a significant global
mean extinction without being anomalously luminous. The lens galaxy in
MG0751+2716 has a redshift of z_l=0.3502+/-0.0003 and it is a member of a small
group. The group includes the nearby, bright companion galaxy whose redshift we
confirmed to be z=0.3501+/-0.0001 and a nearby emission line galaxy with
z=0.3505+/-0.0003. A second emission line galaxy with z=0.5216+/-0.0001 was
found nearly superposed on the first emission line galaxy. The source in
MG0751+2716 is a z_s=3.200+/-0.001 radio quasar. For flat universes with
Omega_0=1.0 (0.3), 96% (87%) of lenses like MG0414+0534 and 7% (3%) of lenses
like MG0751+2716 are expected to have lower lens redshifts than observed.Comment: 9 pages, AASTeX Latex, including 5 Postscript figures, submitted to
Astronomical Journa
Clustering of Lyman alpha emitters at z ~ 4.5
We present the clustering properties of 151 Lyman alpha emitting galaxies at
z ~ 4.5 selected from the Large Area Lyman Alpha (LALA) survey. Our catalog
covers an area of 36' x 36' observed with five narrowband filters. We assume
that the angular correlation function w(theta) is well represented by a power
law A_w = Theta^(-beta) with slope beta = 0.8, and we find A_w = 6.73 +/- 1.80.
We then calculate the correlation length r_0 of the real-space two-point
correlation function xi(r) = (r/r_0)^(-1.8) from A_w through the Limber
transformation, assuming a flat, Lambda-dominated universe. Neglecting
contamination, we find r_0 = 3.20 +/- 0.42 Mpc/h. Taking into account a
possible 28% contamination by randomly distributed sources, we find r_0 = 4.61
+/- 0.6 Mpc/h. We compare these results with the expectations for the
clustering of dark matter halos at this redshift in a Cold Dark Matter model,
and find that the measured clustering strength can be reproduced if these
objects reside in halos with a minimum mass of 1-2 times 10^11 Solar masses/h.
Our estimated correlation length implies a bias of b ~ 3.7, similar to that of
Lyman-break galaxies (LBG) at z ~ 3.8-4.9. However, Lyman alpha emitters are a
factor of ~ 2-16 rarer than LBGs with a similar bias value and implied host
halo mass. Therefore, one plausible scenario seems to be that Lyman alpha
emitters occupy host halos of roughly the same mass as LBGs, but shine with a
relatively low duty cycle of 6-50%.Comment: 23 pages in preprint format, 4 figures, ApJ accepte
Marketing innovation: a consequence of competitiveness
This research uses complexity theory to probe the relationship between competiveness and innovation in the marketing practices of large manufacturing firms that offer their branded products in a foreign market by engaging a network of local small-and medium-sized enterprises (SMEs) as resellers of their brand. A deductive, quantitative research approach was employed and data was collected over a nine-month period from resellers of international IT firms in India using a questionnaire. A structural equation modelling technique and fuzzy-set qualitative comparative analysis (fsQCA) were employed on a sample of 649 respondents to find answers to the questions raised. This research suggests that a successful business relationship between a brand and its resellers can enable both parties to compete in a competitive market. This study finds that innovativeness in the marketing initiatives of the brand can be a function of the contributions made by the brand to its competitiveness. Nevertheless, the findings are also subject to some limitations and provide direction for future research on the topic
The local brand representative in reseller networks
This study investigates the characteristics of local individuals who represent a brand to its resellers by first conceptualizing these characteristics by employing complexity theory and then testing the conceptualization. This research revealed that four characteristics ‘native’, ‘entrepreneurial’, ‘advisor’, and ‘compatible’ are the main ones that influence reseller brand preferences. The study finds a link between reseller brand preference and reseller brand loyalty which is useful for managing business-to-business markets. The study closes with implications, limitations, and directions for future research
IRAC Observations of M81
IRAC images of M81 show three distinct morphological constituents: a smooth
distribution of evolved stars with bulge, disk, and spiral arm components; a
clumpy distribution of dust emission tracing the spiral arms; and a pointlike
nuclear source. The bulge stellar colors are consistent with M-type giants, and
the disk colors are consistent with a slightly younger population. The dust
emission generally follows the blue and ultraviolet emission, but there are
large areas that have dust emission without ultraviolet and smaller areas with
ultraviolet but little dust emission. The former are presumably caused by
extinction, and the latter may be due to cavities in the gas and dust created
by supernova explosions. The nucleus appears fainter at 8 um than expected from
ground-based 10 um observations made four years ago.Comment: ApJS in press (Spitzer special issue); 15 pages, 3 figures. Changes:
unused references removed, numbers and labels in Table 1 change
Evaluation of the performance of microprocessor-based colorimeter
Colorimetric estimations have an important role in quantitative
studies. An inexpensive and portable microprocessor-based colorimeter
developed by the authors is described in this paper. The
colorimeter uses a light emitting diode as the light source; a pinphotodiode
as the detector and an 8085A microprocessor. Blood
urea, glucose, total protein, albumin and bilirubin from patient
blood samples were analysed with the instrument and results
obtained were compared with assays of the same blood using a
Spectronic 21. A good correlation was found between the results
from the two instruments
- …