5,356 research outputs found
Physician-scientists in the United States at 2020: Trends and concerns
Physician-scientists comprise a unique and valuable part of the biomedical workforce, but for decades there has been concern about the number of physicians actively engaged in research. Reports have outlined the challenges facing physician-scientists, and programs have been initiated to encourage and facilitate research careers for medically trained scientists. Many of these initiatives have demonstrated successful outcomes, but there has not been a recent summary of the impact of the past decade of effort. This report compiles available data from surveys of medical education and physician research participation to assess changes in the physician-scientist workforce from 2011-2020. Several trends are positive: rising enrollments in MD-PhD programs, greater levels of interest in research careers among matriculating medical students, more research experience during medical school and rising numbers of physicians in academic medicine, and an increase in first R01 grants to physician-scientists. However, there are now decreased levels of interest in research careers among graduating medical students, a steady decline in MDs applying for NIH loan repayment program support, an increased age at first R01 grant success for physicians, and fewer physicians reporting research as their primary work activity: all of these indicators create concern for the stability of the career path. Despite a recommendation by the Physician-Scientist Workforce in 2014 to create real-time reporting on NIH grants and grantees to help the public assess trends, this initiative has not been completed. Better information is still needed to fully understand the status of the physician-scientist workforce, and to assess efforts to stabilize this vulnerable career path
Molecular epidemiologic investigations of Mycoplasma gallisepticum conjunctivitis in songbirds by random amplified polymorphic DNA analyses.
An ongoing outbreak of conjunctivitis in free-ranging house finches (Carpodacus mexicanus) began in 1994 in the eastern United States. Bacterial organisms identified as Mycoplasma gallisepticum (MG) were isolated from lesions of infected birds. MG was also isolated from a blue jay (Cyanocitta cristata) that contracted conjunctivitis after being housed in a cage previously occupied by house finches with conjunctivitis, and from free-ranging American goldfinches (Carduelis tristis) in North Carolina in 1996. To investigate the molecular epidemiology of this outbreak, we produced DNA fingerprints of MG isolates by random amplification of polymorphic DNA (RAPD). We compared MG isolates from songbirds examined from 1994 through 1996 in 11 states, representing three host species, with vaccine and reference strains and with contemporary MG isolates from commercial poultry. All MG isolates from songbirds had RAPD banding patterns identical to each other but different from other strains and isolates tested. These results indicate that the outbreak of MG in songbirds is caused by the same strain, which suggests a single source; the outbreak is not caused by the vaccine or reference strains analyzed; and MG infection has not been shared between songbirds and commercial poultry
The reaction 2H(p,pp)n in three kinematical configurations at E_p = 16 MeV
We measured the cross sections of the H(p,pp)n breakup reaction at
E=16 MeV in three kinematical configurations: the np final-state
interaction (FSI), the co-planar star (CST), and an intermediate-star (IST)
geometry. The cross sections are compared with theoretical predictions based on
the CD Bonn potential alone and combined with the updated 2-exchange
Tucson-Melbourne three-nucleon force (TM99'), calculated without inclusion of
the Coulomb interaction. The resulting excellent agreement between data and
pure CD Bonn predictions in the FSI testifies to the smallness of three-nucleon
force (3NF) effects as well as the insignificance of the Coulomb force for this
particular configuration and energy. The CST also agrees well whereas the IST
results show small deviations between measurements and theory seen before in
the pd breakup space-star geometries which point to possible Coulomb effects.
An additional comparison with EFT predictions (without 3NF) up to order NLO
shows excellent agreement in the FSI case and a rather similar agreement as for
CD Bonn in the CST and IST situations.Comment: 20 pages, 11 figure
Factors Associated with the Diversification of the Gut Microbial Communities within Chimpanzees from Gombe National Park.
The gastrointestinal tract harbors large and diverse populations of bacteria that vary among individuals and within individuals over time. Numerous internal and external factors can influence the contents of these microbial communities, including diet, geography, physiology, and the extent of contact among hosts. To investigate the contributions of such factors to the variation and changes in gut microbial communities, we analyzed the distal gut microbiota of individual chimpanzees from two communities in Gombe National Park, Tanzania. These samples, which were derived from 35 chimpanzees, many of whom have been monitored for multiple years, provide an unusually comprehensive longitudinal depth for individuals of known genetic relationships. Although the composition of the great-ape microbiota has been shown to codiversify with host species, indicating that host genetics and phylogeny have played a major role in its differentiation over evolutionary timescales, the geneaological relationships of individual chimpanzees did not coincide with the similarity in their gut microbial communities. However, the inhabitants from adjacent chimpanzee communities could be distinguished based on the contents of their gut microbiota. Despite the broad similarity of community members, as would be expected from shared diet or interactions, long-term immigrants to a community often harbored the most distinctive gut microbiota, suggesting that individuals retain hallmarks of their previous gut microbial communities for extended periods. This pattern was reinforced in several chimpanzees sampled over long temporal scales, in which the major constituents of the gut microbiota were maintained for nearly a decade
Quantum Communication with Phantom Photons
We show that quantum information may be transferred between atoms in
different locations by using ``phantom photons'': the atoms are coupled through
electromagnetic fields, but the corresponding field modes do not have to be
fully populated. In the case where atoms are placed inside optical cavities,
errors in quantum information processing due to photon absorption inside the
cavity are diminished in this way. This effect persists up to intercavity
distances of about a meter for the current levels of cavity losses, and may be
useful for distributed quantum computing.Comment: 6 pages RevTex, 4 eps figures included. Revised calculation with more
details about mode structure calculation and the introduction of losse
Connection Between Type A and E Factorizations and Construction of Satellite Algebras
Recently, we introduced a new class of symmetry algebras, called satellite
algebras, which connect with one another wavefunctions belonging to different
potentials of a given family, and corresponding to different energy
eigenvalues. Here the role of the factorization method in the construction of
such algebras is investigated. A general procedure for determining an so(2,2)
or so(2,1) satellite algebra for all the Hamiltonians that admit a type E
factorization is proposed. Such a procedure is based on the known relationship
between type A and E factorizations, combined with an algebraization similar to
that used in the construction of potential algebras. It is illustrated with the
examples of the generalized Morse potential, the Rosen-Morse potential, the
Kepler problem in a space of constant negative curvature, and, in each case,
the conserved quantity is identified. It should be stressed that the method
proposed is fairly general since the other factorization types may be
considered as limiting cases of type A or E factorizations.Comment: 20 pages, LaTeX, no figure, to be published in J. Phys.
Full capacitance-matrix effects in driven Josephson-junction arrays
We study the dynamic response to external currents of periodic arrays of
Josephson junctions, in a resistively capacitively shunted junction (RCSJ)
model, including full capacitance-matrix effects}. We define and study three
different models of the capacitance matrix : Model A
includes only mutual capacitances; Model B includes mutual and self
capacitances, leading to exponential screening of the electrostatic fields;
Model C includes a dense matrix that is constructed
approximately from superposition of an exact analytic solution for the
capacitance between two disks of finite radius and thickness. In the latter
case the electrostatic fields decay algebraically. For comparison, we have also
evaluated the full capacitance matrix using the MIT fastcap algorithm, good for
small lattices, as well as a corresponding continuum effective-medium analytic
evaluation of a finite voltage disk inside a zero-potential plane. In all cases
the effective decays algebraically with distance, with
different powers. We have then calculated current voltage characteristics for
DC+AC currents for all models. We find that there are novel giant capacitive
fractional steps in the I-V's for Models B and C, strongly dependent on the
amount of screening involved. We find that these fractional steps are quantized
in units inversely proportional to the lattice sizes and depend on the
properties of . We also show that the capacitive steps
are not related to vortex oscillations but to localized screened phase-locking
of a few rows in the lattice. The possible experimental relevance of these
results is also discussed.Comment: 12 pages 18 Postscript figures, REVTEX style. Paper to appear in July
1, Vol. 58, Phys. Rev. B 1998 All PS figures include
- …