4,067 research outputs found
Access to undergraduate research experiences at a large research university
The American Physical Society recently released a statement calling on all
university physics departments to provide or facilitate access to research
experiences for all undergraduate students. In response, we investigated the
current status of access to undergraduate research at University of Colorado
Boulder (CU), a large research institution where the number of undergraduate
physics majors outnumber faculty by roughly ten to one. We created and
administered two surveys within CU's Physics Department: one probed
undergraduate students' familiarity with, and participation in, research; the
other probed faculty members' experiences as research mentors to
undergraduates. We describe the development of these instruments, our results,
and our corresponding evidence-based recommendations for improving local access
to undergraduate research experiences. Reflecting on our work, we make several
connections to an institutional change framework and note how other
universities and colleges might adapt our process.Comment: 4 pages, 3 figures, 1 table; Submitted to 2015 PERC Proceeding
Dynamical Realization of Macroscopic Superposition States of Cold Bosons in a Tilted Double Well
We present exact expressions for the quantum sloshing of Bose-Einstein
condensates in a tilted two-well potential. Tunneling is suppressed by a small
potential difference between wells, or tilt. However, tunneling resonances
occur for critical values of the tilt when the barrier is high. At resonance,
tunneling times on the order of 10-100 ms are possible. Furthermore, such
tilted resonances lead to a dynamical scheme for creating few-body NOON-like
macroscopic superposition states which are protected by the many body
wavefunction against potential fluctuations.Comment: 6 pages, 5 figures, final version, only minor changes from previous
arXiv versio
Rituximab with chemotherapy in children and adolescents with central nervous system and/or bone marrow-positive Burkitt lymphoma/leukaemia: a childrens oncology group report
pre-printApproximately 1 in 4 children and adolescents with de-novo mature and Burkitt lymphoma (BL) present with high-risk disease that is either mature B-cell leukaemia (bone marrow ≥ 25% blasts [BM]) and/or have central nervous system (CNS) involvement. Both the Berlin-Frankfurt- Münster (BFM) and French-American-British (FAB) international cooperative studies have unsuccessfully attempted to reduce the overall burden of chemotherapy in this high risk group of patients. In the FAB 96 study, a randomized attempt to reduce the dose of cytarabine during consolidation and eliminate three final cycles of maintenance was halted early due to inferior event-free survival (EFS) (Cairo, et al 2012, Cairo, et al concluded that reducing the infusion duration of methotrexate from 24 to 4 hours led to significantly inferior EFS in high risk (R3/R4) patients.(Woessmann, et al 2005) Subsets of children with BL, such as those with poor response to initial reduction, complex karyotypes, and those with combined BM and CNS disease, have a significantly worse prognosis (Cairo, et al 2012, Cairo, et al 2007, Poirel, et al 2009)
Generic but Expensive: Why Prices Can Remain High for Off-Patent Drugs
Brand-name prescription drugs are sold at extremely high prices in the US because patents and other market exclusivities provided by the government allow manufacturers to exclude direct competition. This period of market exclusivity was intended for pharmaceutical manufacturers to recoup costs associated with research and development of those products and make profits. The other intended outcome of this system is that the market exclusivity period for brand-name drugs should be self-limited, with competition being able to flourish after the market exclusivities end. Such competition has been most effectively supplied by generic drug manufacturers that produce Food and Drug Administration (FDA)-approved bioequivalent versions of the brand-name product. The market entry of these generic drugs—with market uptake augmented by automatic substitution of brand-name prescriptions at the pharmacy— remains the only market intervention that lowers prescription drug prices consistently and substantially.
Generic manufacturers can make their drugs available at considerably lower cost because of various market advantages they have over brand-name drugs. When this process does not operate as intended, drug prices do not fall after market exclusivity expiration, or prices for generic drugs may actually increase. In this paper, we examine the variety of factors that mitigate the cost savings associated with introduction of interchangeable generic drugs, especially older, off-patent drugs. We then consider policy solutions that may help stabilize the generic drug marketplace, diminishing the frequency and impact of generic price increases
Observation of a Large Atomic Parity Violation Effect in Ytterbium
Atomic parity violation has been observed in the 6s^2 1S0 - 5d6s 3D1 408-nm
forbidden transition of ytterbium. The parity-violating amplitude is found to
be two orders of magnitude larger than in cesium, where the most precise
experiments to date have been performed. This is in accordance with theoretical
predictions and constitutes the largest atomic parity-violating amplitude yet
observed. This also opens the way to future measurements of neutron skins and
anapole moments by comparing parity-violating amplitudes for various isotopes
and hyperfine components of the transition
The Metallicity of Pre-Galactic Globular Clusters: Observational consequences of the first stars
We explore a scenario where metal-poor globular clusters (GCs) are enriched
by the first supernovae in the Universe. If the first stars in a 10^7 Msun dark
halo were very massive (>180 Msun), then a pair instability supernova from a
single massive star can produce sufficient iron to enrich 10^6 Msun of
pristine, primordial gas to [Fe/H] ~ -2. In such a scenario, where a single
massive star acts as a seed for halo GCs, the accurate abundance analysis of GC
stars would allow a direct measurement of the Population III initial mass.
Using the latest theoretical yields for zero metallicity stars in the mass
range 140-260 Msun, we find that the metals expelled from a ~230 Msun star are
consistent with [Si/Fe] and [Ca/Fe] observed in GC stars. However, no single
star in this mass range can simultaneously explain all halo GC heavy-element
abundance ratios, such as [V/Fe], [Ti/Fe] and [Ni/Fe]. These require a
combination masses for the Population III stellar progenitors. The various
observational consequences of this scenario are discussed.Comment: 5 pages, 2 figures, accepted for publication in ApJ Lette
Evaluating the Potential Efficacy of Invasive Lionfish (Pterois volitans) Removals
The lionfish, Pterois volitans (Linnaeus) and Pterois miles (Bennett), invasion of the Western Atlantic Ocean, Caribbean Sea and Gulf of Mexico has the potential to alter aquatic communities and represents a legitimate ecological concern. Several local removal programs have been initiated to control this invasion, but it is not known whether removal efforts can substantially reduce lionfish numbers to ameliorate these concerns. We used an age-structured population model to evaluate the potential efficacy of lionfish removal programs and identified critical data gaps for future studies. We used high and low estimates for uncertain parameters including: length at 50% vulnerability to harvest (Lvul), instantaneous natural mortality (M), and the Goodyear compensation ratio (CR). The model predicted an annual exploitation rate between 35 and 65% would be required to cause recruitment overfishing on lionfish populations for our baseline parameter estimates for M and CR (0.5 and 15). Lionfish quickly recovered from high removal rates, reaching 90% of unfished biomass six years after a 50-year simulated removal program. Quantifying lionfish natural mortality and the size-selective vulnerability to harvest are the most important knowledge gaps for future research. We suggest complete eradication of lionfish through fishing is unlikely, and substantial reduction of adult abundance will require a long-term commitment and may be feasible only in small, localized areas where annual exploitation can be intense over multiple consecutive years
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