5,704 research outputs found
Probing supernova physics with neutrino oscillations
We point out that solar neutrino oscillations with large mixing angle as
evidenced in current solar neutrino data have a strong impact on strategies for
diagnosing collapse-driven supernova (SN) through neutrino observations. Such
oscillations induce a significant deformation of the energy spectra of
neutrinos, thereby allowing us to obtain otherwise inaccessible features of SN
neutrino spectra. We demonstrate that one can determine temperatures and
luminosities of non-electron flavor neutrinos by observing bar{nu}_{e} from
galactic SN in massive water Cherenkov detectors by the charged current
reactions on protons.Comment: 6 pages. Typos corrected and references added. Version to be
published in Physics Letters
Polygons on a Rotating Fluid Surface
We report a novel and spectacular instability of a fluid surface in a
rotating system. In a flow driven by rotating the bottom plate of a partially
filled, stationary cylindrical container, the shape of the free surface can
spontaneously break the axial symmetry and assume the form of a polygon
rotating rigidly with a speed different from that of the plate. With water we
have observed polygons with up to 6 corners. It has been known for many years
that such flows are prone to symmetry breaking, but apparently the polygonal
surface shapes have never been observed. The creation of rotating internal
waves in a similar setup was observed for much lower rotation rates, where the
free surface remains essentially flat. We speculate that the instability is
caused by the strong azimuthal shear due to the stationary walls and that it is
triggered by minute wobbling of the rotating plate. The slight asymmetry
induces a tendency for mode-locking between the plate and the polygon, where
the polygon rotates by one corner for each complete rotation of the plate
Assessing the Impacts of the Prescription Drug User Fee Acts (PDUFA) on the FDA Approval Process
Congress enacted and renewed the Prescription Drug User Fee Acts (PDUFA) in 1992, and renewed it in 1997 and 2002, mandating FDA performance goals in reviewing and acting on drug applications within specified time periods. In turn, the FDA was permitted to levy user fees on drug sponsors submitting applications to the FDA. While PDUFA mandated action or review times, its ultimate impacts on actual final drug approval times are unknown. We model and quantify the impact of PDUFA-I and II on drug approval times, since these approval dates are the ones most directly related to new medicines becoming available to benefit patients. In assessing the impacts of PDUFA on drug approval times, it is noteworthy that approval times were trending downwards at 1.7% percent per year prior to implementation of PDUFA. Assuming continuation of that time trend, approval times post-PDUFA would have fallen even in the absence of PDUFA. Our principal finding is that PDUFA accelerated this downward trend so that instead of a counterfactual 6% reduction in approval times from 24.2 to 20.4 months in absence of these acts between 1991 and 2002, there was an observed decline of about 42%, from 24.2 to 14.2 months, following implementation of PDUFA. Thus, of the total observed decline in approval times between 1991 and 2002, approximately two-thirds can be attributed to PDUFA. However, much of this impact occurred in the initial years between 1992 and 1997 (PDUFA-I) rather than during the subsequent 1997-2002 time frame (PDUFA-II). We discuss implications of these findings and how future research might quantify the social value of the observed acceleration in the FDA drug approvals.
Assessing the Safety and Efficacy of the FDA: The Case of the Prescription Drug User Fee Acts
The US Food and drug Administration (FDA) is estimated to regulate markets accounting for about 20% of consumer spending in the US. This paper proposes a general methodology to evaluate FDA policies, in general, and the central speed-safety tradeoff it faces, in particular. We apply this methodology to estimate the welfare effects of a major piece of legislation affecting this tradeoff, the Prescription Drug User Fee Acts (PDUFA). We find that PDUFA raised the private surplus of producers, and thus innovative returns, by about 13 billion. Dependent on the market power assumed of producers while having patent protection, we find that PDUFA raised consumer welfare between 19 billion; thus the combined social surplus was raised between 31 billions. Converting these economic gains into equivalent health benefits, we find that the more rapid access of drugs on the market enabled by PDUFA saved the equivalent of 180 to 310 thousand life-years. Additionally, we estimate an upper bound on the adverse effects of PDUFA based on drugs submitted during PDUFA I/II and subsequently withdrawn for safety reasons, and find that an extreme upper bound of about 56 thousand life-years were lost. We discuss how our general methodology could be used to perform a quantitative and evidence-based evaluation of the desirability of other FDA policies in the future, particularly those affecting the speed-safety tradeoff.
Parameter Degeneracy in Flavor-Dependent Reconstruction of Supernova Neutrino Fluxes
We reexamine the possibility of reconstructing the initial fluxes of
supernova neutrinos emitted in a future core-collapse galactic supernova
explosion and detected in a Megaton-sized water Cherenkov detector. A novel key
element in our method is the inclusion, in addition to the total and the
average energies of each neutrino species, of a "pinching" parameter
characterizing the width of the distribution as a fit parameter. We uncover in
this case a continuous degeneracy in the reconstructed parameters of supernova
neutrino fluxes at the neutrinosphere. We analyze in detail the features of
this degeneracy and show how it occurs irrespective of the parametrization used
for the distribution function. Given that this degeneracy is real we briefly
comment on possible steps towards resolving it, which necessarily requires
going beyond the setting presented here.Comment: 28 pages, 37 figures, version with some improvements in the text and
some new references, conclusions unchanged, to appear in JCA
TĂ©cnicas de levantamento e monitoração de populações de carnĂvoros
Diferentes tĂ©cnicas vĂŞm sendo utilizadas em levantamentos de carnĂvoros, e o principal fator que influencia as estimativas Ă© a detectabilidade. Raramente todos os animais presentes em uma dada área sĂŁo detectados num levantamento, e a maioria das estimativas sĂŁo baseadas em contagens incompletas. Por outro lado, nem sempre se faz necessário a obtenção de estimativas de abundĂŁncia absoluta ou de densidade absoluta, e um Ăndice de abundância pode ser o suficiente para, por exemplo, avaliar as tendĂŞncias da população. ĂŤndices de abundância precisam ter uma forte correlação com a abundância absoluta ou com a densidade, para que sejam Ăşteis. ĂŤndices podem ser obtidos de contagens incompletas, em relação ao esforço empregado, usando sinais da presença de animais, fotografia remota e outras tĂ©cnicas. MĂ©todos para estimar a densidade ou abundância absoluta podem ser divididos em diretas e indiretas.bitstream/CPAP/55978/1/DOC73.pdfFormato EletrĂ´nic
Supreme Court Amicus Brief Regarding Wyeth v. Diana Levine
Prominent in arguments opposing preemption of state tort law liability for alleged inadequacies in prescription drug labeling is the argument that such liability can complement FDA regulation by improving on a regulatory scheme that fails to provide adequate deterrence against the marketing of unsafe or inadequately labeled drugs. The premise of this argument is faulty. Fundamental principles of economics and numerous studies of FDA drug regulation reveal that FDA in fact errs on the side of overregulation of prescription drugs. Product liability litigation focused solely on one side of the prescription drug public health equation leads to further distortions of the drug approval and labeling process and exacerbates FDA's inherent overly cautious approach. Preemption of state tort law where it conflicts with FDA requirements will minimize these distortions and thereby maximize public health.Health and Safety, Other Topics
Interactive extraction of diverse vocal units from a planar embedding without the need for prior sound segmentation
Annotating and proofreading data sets of complex natural behaviors such as vocalizations are tedious tasks because instances of a given behavior need to be correctly segmented from background noise and must be classified with minimal false positive error rate. Low-dimensional embeddings have proven very useful for this task because they can provide a visual overview of a data set in which distinct behaviors appear in different clusters. However, low-dimensional embeddings introduce errors because they fail to preserve distances; and embeddings represent only objects of fixed dimensionality, which conflicts with vocalizations that have variable dimensions stemming from their variable durations. To mitigate these issues, we introduce a semi-supervised, analytical method for simultaneous segmentation and clustering of vocalizations. We define a given vocalization type by specifying pairs of high-density regions in the embedding plane of sound spectrograms, one region associated with vocalization onsets and the other with offsets. We demonstrate our two-neighborhood (2N) extraction method on the task of clustering adult zebra finch vocalizations embedded with UMAP. We show that 2N extraction allows the identification of short and long vocal renditions from continuous data streams without initially committing to a particular segmentation of the data. Also, 2N extraction achieves much lower false positive error rate than comparable approaches based on a single defining region. Along with our method, we present a graphical user interface (GUI) for visualizing and annotating data
Triplet Leptogenesis in Left-Right Symmetric Seesaw Models
We discuss scalar triplet leptogenesis in a specific left-right symmetric
seesaw model. We show that the Majorana phases that are present in the model
can be effectively used to saturate the existing upper limit on the
CP-asymmetry of the triplets. We solve the relevant Boltzmann equations and
analyze the viability of triplet leptogenesis. It is known for this kind of
scenario that the efficiency of leptogenesis is maximal if there exists a
hierarchy between the branching ratios of the triplet decays into leptons and
Higgs particles. We show that triplet leptogenesis typically favors branching
ratios with not too strong hierarchies, since maximal efficiency can only be
obtained at the expense of suppressed CP-asymmetries.Comment: 16 pages, 5 figures, published versio
Neutrino signatures of supernova shock and reverse shock propagation
A few seconds after bounce in a core-collapse supernova, the shock wave
passes the density region corresponding to resonant neutrino oscillations with
the ``atmospheric'' neutrino mass difference. The transient violation of the
adiabaticity condition manifests itself in an observable modulation of the
neutrino signal from a future galactic supernova. In addition to the shock wave
propagation effects that were previously studied, a reverse shock forms when
the supersonically expanding neutrino-driven wind collides with the slower
earlier supernova ejecta. This implies that for some period the neutrinos pass
two subsequent density discontinuities, giving rise to a ``double dip'' feature
in the average neutrino energy as a function of time. We study this effect both
analytically and numerically and find that it allows one to trace the positions
of the forward and reverse shocks. We show that the energy dependent neutrino
conversion probabilities allow one to detect oscillations even if the energy
spectra of different neutrino flavors are the same as long as the fluxes
differ. These features are observable in the \bar\nu_e signal for an inverted
and in the \nu_e signal for a normal neutrino mass hierarchy, provided the
13-mixing angle is ``large'' (sin^2\theta_{13}\gg 10^{-5}).Comment: 23 pages, 27 eps figures (high resolution plots are available on
request), JCAP style; v2: figure 8 extended, matches published versio
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