4,039 research outputs found
Recommended from our members
Predominant variable region gene usage by gamma/delta T cell receptor-bearing cells in the adult thymus.
Previous studies have indicated that the diversity of gamma genes expressed by gamma/delta-bearing murine T cells is limited, but comparable information concerning the expressed diversity of delta genes is lacking. In this study, we have investigated the rearrangement and expression of delta and gamma genes in T cell hybridomas that express gamma/delta T cell receptors. Three productive delta chain cDNA clones were isolated (delta 7.3, delta 7.1, and delta 2.3) that encode new variable region sequences. Two of the delta cDNAs differ significantly from those observed in the V alpha repertoire. In addition, one cDNA expressed a new J delta region (J delta 2), which was localized between J delta 1 and C delta genes. Using these and other delta gene probes and gamma gene probes, we found that five independent hybridomas expressed four different V delta s and three different V gamma s. However, analysis of an enriched population of gamma/delta-expressing cells from the adult thymus suggests that only a few V delta genes and one V gamma gene are used by the majority of the cells. These results suggest that important components of receptor chain that contribute to specificity (i.e., the germline V gene sequences) are relatively nondiverse in the thymic gamma/delta population
Photometric and spectroscopic study of the intermediate age open cluster NGC 3960
We present CCD UBVI photometry and high-resolution spectroscopy of the
intermediate age open cluster NGC 3960. The colour - magnitude diagrams (CMDs)
derived from the photometric data and interpreted with the synthetic CMD method
allow us to estimate the cluster parameters. We derive: age = 0.9 or 0.6 Gyr
(depending on whether or not overshooting from convective regions is included
in the adopted stellar models), distance (m-M)0 = 11.6 +/- 0.1, reddening
E(B-V) = 0.29 +/- 0.02, differential reddening Delta E(B-V) = 0.05 and
approximate metallicity between solar and half of solar. We obtained high
resolution spectra of three clump stars, and derived an average [Fe/H] = -0.12
(rms 0.04 dex), in very good agreement with the photometric determination. We
also obtained abundances of alpha-elements, Fe-peak elements, and of Ba. The
reddenings toward individual stars derived from the spectroscopic temperatures
and the Alonso et al. calibrations give further support to the existence of
significative variations across the cluster.Comment: Accepted for publication on MNRAS; fig. 3, 4, 5, 6 at degraded
resolutio
870 micron observations of nearby 3CRR radio galaxies
We present submillimeter continuum observations at 870 microns of the cores
of low redshift 3CRR radio galaxies, observed at the Heinrich Hertz
Submillimeter Telescope. The cores are nearly flat spectrum between the radio
and submillimeter which implies that the submillimeter continuum is likely to
be synchrotron emission and not thermal emission from dust. The emitted power
from nuclei detected at optical wavelengths and in the X-rays is similar in the
submillimeter, optical and X-rays. The submillimeter to optical and X-ray power
ratios suggest that most of these sources resemble misdirected BL Lac type
objects with synchrotron emission peaking at low energies. However we find
three exceptions, the FR I galaxy 3C264 and the FR II galaxies 3C390.3 and
3C338 with high X-ray to submillimeter luminosity ratios. These three objects
are candidate high or intermediate energy peaked BL Lac type objects. With
additional infrared observations and from archival data, we compile spectral
energy distributions (SEDs) for a subset of these objects. The steep dips
observed near the optical wavelengths in many of these objects suggest that
extinction inhibits the detection and reduces the flux of optical continuum
core counterparts. High resolution near or mid-infrared imaging may provide
better measurements of the underlying synchrotron emission peak.Comment: accepted for publication in A
On the origin of X-ray emission in some FR Is: ADAF or jet?
We investigate the X-ray origin in FR Is using the radio, submillimetre,
optical, and {\em Chandra} X-ray data of a small sample consisting of eight FR
I sources. These sources are very dim, with X-ray luminosities ( is the X-ray luminosity
between 2-10 keV). We try to fit the multiwaveband spectrum using a coupled
accretion-jet model. In this model, the accretion flow is described by an
advection-dominated accretion flow (ADAF) while in the innermost region of ADAF
a fraction of accretion flow is transferred into the vertical direction and
forms a jet. We find that X-ray emission in the source with the highest () is from the ADAF. The results for
the four sources with moderate ( several ) are complicated. Two are mainly from the ADAFs, one from
the jet, and the other from the sum of the jet and ADAF. The X-ray emission in
the three least luminous sources () is dominated by the jet although for one source it can also be
interpreted by the ADAF since the quality of X-ray data is low. We conclude
that these results roughly support the predictions of Yuan & Cui (2005) where
they predict that when the X-ray luminosity of the system is below a critical
value, the X-radiation will not be dominated by the emission from the ADAF any
longer, but by the jet. We also investigate the fuel supply in these sources.
We find that the accretion rates in four sources among the five in which we can
have good constraints to their accretion rates must be higher than the Bondi
rates. This implies that other fuel supply, such as the gas released by the
stellar population inside the Bondi radius, should be important.Comment: 31 pages, 8 figures, accepted for publication in Ap
Kenoyn News Bulletin March 31, 2020
Kenyon News Bulletin: COVID-19 Update from Provost Klesner to employees/studentshttps://digital.kenyon.edu/covid19words/1035/thumbnail.jp
Recommended from our members
Human resource management practices and organizational performance. The mediator role of immaterial satisfaction in Italian Social Cooperatives
The paper deals with the mediating role of immaterial satisfaction between substantive human resources (HR) features and organizational performance. We address this relationship in the Italian social service sector using a survey dataset that includes 4134 workers and 320 not-for-profit social cooperatives. The obtained results show that human resource management (HRM) practices influence immaterial satisfaction and, satisfaction positively impacts on firm performance. However, the impact of the different HRM practices is not the same. In this sense, worker involvement and workload pressure have a positive impact on firm performance; but task autonomy or collaborative teamwork do not have impact on organizational performance
- …