538 research outputs found
Hon. Augustus F. Moulton Correspondence
Entries include brief biographical information, a humorous typed biography, handwritten letters on personal stationery, and a handwritten letter on Molton Hotel, Birmingham, Alabama, stationery
Investigation of resonant polarization radiation of relativistic electrons in gratings at small angles
The Resonant Optical Polarization Radiation (ROPR) in the Smith-Purcell
geometry and the one from the inclined grating at the Tomsk synchrotron and
6-MeV microtron have been investigated. The polarization radiation was observed
at 4.2o from the 200 MeV electron beam and at 5o from the 6.2 MeV electron
beam. Two methods of measurement of ROPR maxima in these two cases have been
used. In the first case (the experiment on synchrotron) we have fixed the
wavelength of radiation using an optical filter; the orientation dependence of
this radiation was measured. In this dependence we have observed two peaks of
radiation from electrons in gold foil grating of 0.1 mm period. The first large
peak is a zeroth order peak in direction of specular reflection, and the second
one is the 1-st order peak of resonant polarization radiation. In the
experiment on microtron the spectra of ROPR from aluminum foil strip grating of
0.2 mm period in the Smith-Purcell geometry were measured, and the peak of the
1-st order Smith-Purcell radiation in these spectra was observed. The
comparison of data obtained with the simulation results has been performed
UV and EUV Instruments
We describe telescopes and instruments that were developed and used for
astronomical research in the ultraviolet (UV) and extreme ultraviolet (EUV)
regions of the electromagnetic spectrum. The wavelength ranges covered by these
bands are not uniquely defined. We use the following convention here: The EUV
and UV span the regions ~100-912 and 912-3000 Angstroem respectively. The
limitation between both ranges is a natural choice, because the hydrogen Lyman
absorption edge is located at 912 Angstroem. At smaller wavelengths,
astronomical sources are strongly absorbed by the interstellar medium. It also
marks a technical limit, because telescopes and instruments are of different
design. In the EUV range, the technology is strongly related to that utilized
in X-ray astronomy, while in the UV range the instruments in many cases have
their roots in optical astronomy. We will, therefore, describe the UV and EUV
instruments in appropriate conciseness and refer to the respective chapters of
this volume for more technical details.Comment: To appear in: Landolt-Boernstein, New Series VI/4A, Astronomy,
Astrophysics, and Cosmology; Instruments and Methods, ed. J.E. Truemper,
Springer-Verlag, Berlin, 201
Massive stars as thermonuclear reactors and their explosions following core collapse
Nuclear reactions transform atomic nuclei inside stars. This is the process
of stellar nucleosynthesis. The basic concepts of determining nuclear reaction
rates inside stars are reviewed. How stars manage to burn their fuel so slowly
most of the time are also considered. Stellar thermonuclear reactions involving
protons in hydrostatic burning are discussed first. Then I discuss triple alpha
reactions in the helium burning stage. Carbon and oxygen survive in red giant
stars because of the nuclear structure of oxygen and neon. Further nuclear
burning of carbon, neon, oxygen and silicon in quiescent conditions are
discussed next. In the subsequent core-collapse phase, neutronization due to
electron capture from the top of the Fermi sea in a degenerate core takes
place. The expected signal of neutrinos from a nearby supernova is calculated.
The supernova often explodes inside a dense circumstellar medium, which is
established due to the progenitor star losing its outermost envelope in a
stellar wind or mass transfer in a binary system. The nature of the
circumstellar medium and the ejecta of the supernova and their dynamics are
revealed by observations in the optical, IR, radio, and X-ray bands, and I
discuss some of these observations and their interpretations.Comment: To be published in " Principles and Perspectives in Cosmochemistry"
Lecture Notes on Kodai School on Synthesis of Elements in Stars; ed. by Aruna
Goswami & Eswar Reddy, Springer Verlag, 2009. Contains 21 figure
Clinicopathological and molecular characteristics of Ku 70/80 expression in Nigerian breast cancer and its potential therapeutic implications
Ku 70/80 is a regulator of the Non-Homologous End Joining (NHEJ) roles in clinicopathological features, and has prognostic significance in breast cancer (BC) in Caucasian populations. However, its significance in the Nigerian BC population, which is characterized by a higher rate of the triple-negative and basal phenotype, p53 mutation rate and BRCA1 deficiency, still needs to be investigated. We hypothesize that Ku70/80 expression shows adverse expression in Nigerian BC and, furthermore, that it is likely to have a therapeutic implication for Black BC management.This study investigated the biological, clinicopathological and prognostic significance of Ku 70/80 expression in a BC cohort from a Nigerian population. Ku 70/80 expression was determined in 188 well-characterized formalin-fixed, paraffin-embedded (FFPE) BC samples using tissue microarray and immunohistochemistry. Ku 70/80 expression was correlated with clinicopathological, molecular and prognostic characteristics of patients.Ku 70/80 was expressed in 113 (60.1%) tumors, and was positively associated with metastatic disease, triple-negative and basal phenotype, BRCA1 down regulators (MTA-1 and ID4), p-cadherin, PI3KCA and p53 expression. It inversely correlated with BRCA1, BRCA2, BARD1 and p27. Ku 70/80 was predictive of breast cancer-specific survival in multivariate analysis, but not of disease-free interval.This study demonstrated that Ku 70/80 expression is associated with triple negativity and down-regulation of the homologous recombination pathway of DNA repair. Therefore, the development of novel drugs to target KU70/80 may improve the patients’ outcome in the treatment of Black BC
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS
The chi_b(nP) quarkonium states are produced in proton-proton collisions at
the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS
detector. Using a data sample corresponding to an integrated luminosity of 4.4
fb^-1, these states are reconstructed through their radiative decays to
Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks
corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new
structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is
also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes.
This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table,
corrected author list, matches final version in Physical Review Letter
- …