1,321 research outputs found
A nonparametric analysis of the U.S. earnings distribution
This paper examines the change in the earnings distribution and in the earnings distribution conditional on years of schooling and experience for white male full-time, year-round workers in the United States from 1967 to 1992. Ginther uses nonparametric kernel estimators to examine changes in the unconditional and conditional earnings distributions and to estimate measures of conditional earnings inequality. Ginther compares estimates from parametric wage equations to nonparametric estimates and finds that parametric estimates are biased: earnings inequality did not change in equal proportions within cohorts and experience groups. Instead, inequality increased the most among workers with 10 and 12 years of schooling at all experience levels and among workers with both 16 years of schooling and less than 15 years experience. Inequality decreased among people with graduate levels of schooling. Controlled for levels of schooling and experience, real wages have declined drastically for all workers except those with more than 16 years of schooling or more than 25 years experience. Groups experiencing the largest increase in earnings inequality are also those with the largest decline in real wages.
Advancing biomedical science through investments in elite training
How can governments invest in the public good of science in a way that accelerates advancement and encourages innovation at the frontier of science–all the while acknowledging that investing in science means investing in scientists? The Ruth L. Kirschstein National Research Service Award (NRSA) program is a research-training program administered by the National Institutes of Health (NIH) that makes such investments. This study examines the impact of NRSA postdoctoral fellowships on subsequent career outcomes using NIH administrative records on applicants for the fellowship from 1996 to 2008. It finds that fellowships increased the probability of receiving subsequent research awards from 4.0 to 6.3 percentage points and of achieving a major independent research award from 2.6 to 4.6 percentage points. The findings demonstrate that federally funded fellowships promote the retention of scientists in the biomedical research workforce
Can Mentoring Help Female Assistant Professors? Interim Results from a Randomized Trial
While much has been written about the potential benefits of mentoring in academia, very little research documents its effectiveness. We present data from a randomized controlled trial of a mentoring program for female economists organized by the Committee for the Status of Women in the Economics Profession and sponsored by the National Science Foundation and the American Economics Association. To our knowledge, this is the first randomized trial of a mentoring program in academia. We evaluate the performance of three cohorts of participants and randomly-assigned controls from 2004, 2006, and 2008. This paper presents an interim assessment of the program’s effects. Our results suggest that mentoring works. After five years the 2004 treatment group averaged .4 more NSF or NIH grants and 3 additional publications, and were 25 percentage points more likely to have a top-tier publication. There are significant but smaller effects at three years post-treatment for the 2004 and 2006 cohorts combined. While it is too early to assess the ultimate effects of mentoring on the academic careers of program participants, the results suggest that this type of mentoring may be one way to help women advance in the Economics profession and, by extension, in other male-dominated academic fields.
Cosmic ray tests of the D0 preshower detector
The D0 preshower detector consists of scintillator strips with embedded
wavelength-shifting fibers, and a readout using Visible Light Photon Counters.
The response to minimum ionizing particles has been tested with cosmic ray
muons. We report results on the gain calibration and light-yield distributions.
The spatial resolution is investigated taking into account the light sharing
between strips, the effects of multiple scattering and various systematic
uncertainties. The detection efficiency and noise contamination are also
investigated.Comment: 27 pages, 24 figures, submitted to NIM
Measurement of direct photon production at Tevatron fixed target energies
Measurements of the production of high transverse momentum direct photons by
a 515 GeV/c piminus beam and 530 and 800 GeV/c proton beams in interactions
with beryllium and hydrogen targets are presented. The data span the kinematic
ranges of 3.5 < p_T < 12 GeV/c in transverse momentum and 1.5 units in
rapidity. The inclusive direct-photon cross sections are compared with
next-to-leading-order perturbative QCD calculations and expectations based on a
phenomenological parton-k_T model.Comment: RevTeX4, 23 pages, 32 figures, submitted to Phys. Rev.
mTOR Controls Ovarian Follicle Growth by Regulating Granulosa Cell Proliferation
We have shown that inhibition of mTOR in granulosa cells and ovarian follicles results in compromised granulosa proliferation and reduced follicle growth. Further analysis here using spontaneously immortalized rat granulosa cells has revealed that mTOR pathway activity is enhanced during M-phase of the cell cycle. mTOR specific phosphorylation of p70S6 kinase and 4E-BP, and expression of Raptor are all enhanced during M-phase. The predominant effect of mTOR inhibition by the specific inhibitor Rapamycin (RAP) was a dose-responsive arrest in the G1 cell cycle stage. The fraction of granulosa cells that continued to divide in the presence of RAP exhibited a dose-dependent increase in aberrant mitotic figures known as anaphase bridges. Strikingly, estradiol consistently decreased the incidence of aberrant mitotic figures. In mice treated with RAP, the mitotic index was reduced compared to controls, and a similar increase in aberrant mitotic events was noted. RAP injected during a superovulation regime resulted in a dose-dependent reduction in the numbers of eggs ovulated. Implications for the real-time regulation of follicle growth and dominance, including the consequences of increased numbers of aneuploid granulosa cells, are discussed
Evidence for Parton kT Effects in High pT Particle Production
Inclusive pizero and direct-photon cross sections in the kinematic range 3.5
< pT < 12 GeV/c with central rapidities are presented for 530 and 800 GeV/c
proton beams and a 515 GeV/c pi- beam incident on beryllium targets. Current
Next-to-Leading-Order perturbative QCD calculations fail to adequately describe
the data for conventional choices of scales. Kinematic distributions from these
hard scattering events provide evidence that the interacting partons carry
significant initial-state parton transverse momentum (kT). Incorporating these
kT effects phenomenologically greatly improves the agreement between
calculations and the measured cross sections.Comment: 11 pages including 6 pages of figures with caption
Precise measurement of the top quark mass in the dilepton channel at D0
We measure the top quark mass (mt) in ppbar collisions at a center of mass
energy of 1.96 TeV using dilepton ttbar->W+bW-bbar->l+nubl-nubarbbar events,
where l denotes an electron, a muon, or a tau that decays leptonically. The
data correspond to an integrated luminosity of 5.4 fb-1 collected with the D0
detector at the Fermilab Tevatron Collider. We obtain mt = 174.0 +- 1.8(stat)
+- 2.4(syst) GeV, which is in agreement with the current world average mt =
173.3 +- 1.1 GeV. This is currently the most precise measurement of mt in the
dilepton channel.Comment: 7 pages, 4 figure
A search for charged massive long-lived particles
We report on a search for charged massive long-lived particles (CMLLPs),
based on 5.2 fb of integrated luminosity collected with the D0 detector
at the Fermilab Tevatron collider. We search for events in which one
or more particles are reconstructed as muons but have speed and ionization
energy loss inconsistent with muons produced in beam collisions.
CMLLPs are predicted in several theories of physics beyond the standard model.
We exclude pair-produced long-lived gaugino-like charginos below 267 GeV and
higgsino-like charginos below 217 GeV at 95% C.L., as well as long-lived scalar
top quarks with mass below 285 GeV.Comment: submitted to Phys. Rev. Letter
Measurement of Leptonic Asymmetries and Top Quark Polarization in ttbar Production
We present measurements of lepton (l) angular distributions in ttbar -> W+ b
W- b -> l+ nu b l- nubar bbar decays produced in ppbar collisions at a
center-of-mass energy of sqrt(s)=1.96TeV, where l is an electron or muon. Using
data corresponding to an integrated luminosity of 5.4fb^-1, collected with the
D0 detector at the Fermilab Collider, we find that the angular distributions of
l- relative to anti-protons and l+ relative to protons are in agreement with
each other. Combining the two distributions and correcting for detector
acceptance we obtain the forward-backward asymmetry A^l_FB = (5.8 +- 5.1(stat)
+- 1.3(syst))%, compared to the standard model prediction of A^l_FB (predicted)
= (4.7 +- 0.1)%. This result is further combined with the measurement based on
the analysis of the l+jets final state to obtain A^l_FB = (11.8 +- 3.2)%.
Furthermore, we present a first study of the top-quark polarization.Comment: submitted versio
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