3,263 research outputs found
Sensitive High-Frequency Hearing in Earless and Partially Eared Harlequin Frogs (Atelopus)
Harlequin frogs, genus Atelopus, communicate at high frequencies despite most species lacking a complete tympanic middle ear that facilitates high-frequency hearing in most anurans and other tetrapods. Here, we tested whether Atelopus are better at sensing high-frequency acoustic sound compared with other eared and earless species in the Bufonidae family, determined whether middle ear variation within Atelopus affects hearing sensitivity and tested potential hearing mechanisms in Atelopus. We determined that at high frequencies (2000â4000â
Hz), Atelopus are 10â34â
dB more sensitive than other earless bufonids but are relatively insensitive to mid-range frequencies (900â1500â
Hz) compared with eared bufonids. Hearing among Atelopus species is fairly consistent, evidence that the partial middle ears present in a subset of Atelopus species do not convey a substantial hearing advantage. We further demonstrate that Atelopus hearing is probably not facilitated by vibration of the skin overlying the normal tympanic membrane region or the body lung wall, leaving the extratympanic hearing pathways in Atelopus enigmatic. Together, these results show Atelopus have sensitive high-frequency hearing without the aid of a tympanic middle ear and prompt further study of extratympanic hearing mechanisms in anurans
Stable Biological Production in the Eastern Equatorial Pacific Across the Plio-Pleistocene Transition (âŒ3.35â2.0 Ma)
Upwelling within the Eastern Equatorial Pacific (EEP) Ocean is a key factor for the Earth's climate because it supports >10% of the present-day biological production. The dynamics of upwelling in the EEP across the Plio-Pleistocene transitionâan interval particularly relevant for understanding near-future warming due to Anthropocene-like atmospheric carbon-dioxide levelsâhave been intensively studied for the region east of the East Pacific Rise. In contrast, changes of the equatorial upwelling regime in the open Pacific Ocean west of this oceanographic barrier have received markedly less attention. We therefore provide new proxy records from Ocean Drilling Program Site 849 located within the EEP open-ocean upwelling regime. Our target interval (âŒ3.35â2.0 Ma) covers the Plio-Pleistocene transition characterized by the intensification of Northern Hemisphere Glaciation (iNHG). We use benthic ÎŽ18O values to generate a new, high-resolution age model for Site 849, and sand-accumulation rates together with benthic ÎŽ13C values to evaluate net export production. Although showing temporary substantial glacial-interglacial variations, our records indicate stability in net export production on secular timescales across the iNHG. We suggest the following processes to have controlled the long-term evolution of primary productivity at Site 849. First, nutrient export from the high latitudes to the EEP; second, a successive shoaling of the Pacific nutricline during the studied interval; and third, a simultaneous reduction in dust-borne iron input.publishedVersio
Submillimeter Line Emission from LMC 30Dor: The Impact of a Starburst on a Low Metallicity Environment
(Abridged) The 30 Dor region in the Large Magellanic Cloud (LMC) is the most
vigorous star-forming region in the Local Group. Star formation in this region
is taking place in low-metallicity molecular gas that is exposed to an extreme
far--ultraviolet (FUV) radiation field powered by the massive compact star
cluster R136. We used the NANTEN2 telescope to obtain high-angular resolution
observations of the 12CO 4-3, 7-6, and 13CO 4-3 rotational lines and [CI]
3P1-3P0 and 3P2-3P1 fine-structure submillimeter transitions in 30Dor-10, the
brightest CO and FIR-emitting cloud at the center of the 30Dor region. We
derived the properties of the low-metallicity molecular gas using an
excitation/radiative transfer code and found a self-consistent solution of the
chemistry and thermal balance of the gas in the framework of a clumpy cloud PDR
model. We compared the derived properties with those in the N159W region, which
is exposed to a more moderate far-ultraviolet radiation field compared with
30Dor-10, but has similar metallicity. We also combined our CO detections with
previously observed low-J CO transitions to derive the CO spectral-line energy
distribution in 30Dor-10 and N159W. The separate excitation analysis of the
submm CO lines and the neutral carbon fine structure lines shows that the mid-J
CO and [CI]-emitting gas in the 30Dor-10 region has a temperature of about 160
K and a H2 density of about 10^4 cm^-3. We find that the molecular gas in
30Dor-10 is warmer and has a lower beam filling factor compared to that of
N159W, which might be a result of the effect of a strong FUV radiation field
heating and disrupting the low--metallicity molecular gas. We use a clumpy PDR
model (including the [CII] line intensity reported in the literature) to
constrain the FUV intensity to about chi_0 ~ 3100 and an average total H
density of the clump ensemble of about 10^5 cm^-3 in 30Dor-10.Comment: 11 pages, 8 figures. Accepted for publication in A&
Interaction between Obesity and the NFKB1 - 94ins/delATTG Promoter Polymorphism in Relation to Incident Acute Coronary Syndrome: A Follow Up Study in Three Independent Cohorts
Introduction: The NF-ÎșB transcription factor family regulates several genes encoding pro-inflammatory and anti-inflammatory proteins in adipose tissues and in atherosclerotic plaques. The deletion variant allele of the NFKB1 - 94ins/delATTG promoter polymorphism leads to lower transcript levels of the p50 subunit, and the variant allele has been associated with the risk of several inflammatory diseases as well as coronary heart disease where inflammation is important in the pathogenesis. The objective of this study was to explore the potential interaction between the NFKB1-94ins/delATTG promoter polymorphism and general, abdominal, and gluteofemoral obesity in relation to the risk of incident acute coronary syndrome (ACS) in three large independent cohorts. Methods and Results: The analyses were conducted in the Danish prospective study Diet, Cancer and Health and the two US based cohorts; Nursesâ Health Study and Health Professionals Follow-up Study. We conducted sex stratified analyses that included 1202 male and 708 female cases of incident ACS. We observed a positive association for general and abdominal obesity with risk of incident ACS, independent of genotype in both genders. Gluteofemoral obesity was negatively associated with ACS risk in women independent of genotype, whereas there was no clear association for men. We calculated the relative excess risk due to interaction (RERI) and observed a statistically significant excess risk among men jointly exposed to general or abdominal obesity and the variant allele of the NFKB1-94ATTG polymorphism, whereas there was a tendency towards sub-additivity for gluteofemoral obesity. The excess risks in all analyses were, however, small and could not clearly be demonstrated in women. Conclusion: The variant allele of the NFKB1-94ins/delATTG promoter polymorphism did not substantially modify the association between obesity and incident ACS
Quantitative conditional quantum erasure in two-atom resonance fluorescence
We present a conditional quantum eraser which erases the a priori knowledge
or the predictability of the path a photon takes in a Young-type double-slit
experiment with two fluorescent four-level atoms. This erasure violates a
recently derived erasure relation which must be satisfied for a conventional,
unconditional quantum eraser that aims to find an optimal sorting of the system
into subensembles with particularly large fringe visibilities. The conditional
quantum eraser employs an interaction-free, partial which-way measurement which
not only sorts the system into optimal subsystems with large visibility but
also selects the appropriate subsystem with the maximum possible visibility. We
explain how the erasure relation can be violated under these circumstances.Comment: Revtex4, 12pages, 4 eps figures, replaced with published version,
changes in Sec. 3, to appear in Physical Review
Enabling low-carbon development in poor countries
The challenges associated with achieving sustainable development goals and stabilizing the worldâs climate cannot be solved without significant efforts by developing and newly-emerging countries. With respect to climate change mitigation, the main challenge for developing countries lies in avoiding future emissions and lock-ins into emission-intensive technologies, rather than reducing todayâs emissions. While first best policy instruments like carbon prices could prevent increasing carbonization, those policies are often rejected by developing countries out of a concern for negative repercussions on development and long-term growth. In addition, policy environments in developing countries impose particular challenges for regulatory policy aiming to incentivize climate change mitigation and sustainable development. This chapter first discusses how climate policy could potentially interact with sustainable development and economic growth. It focuses, in particular, on the role of industrial sector development. The chapter then continues by discussing how effective policy could be designed, specifically taking developing country circumstances into account
Length Scale of the Spin Seebeck Effect
We investigate the origin of the spin Seebeck effect in yttrium iron garnet (YIG) samples for film thicknesses from 20 nm to 50ââÎŒm at room temperature and 50 K. Our results reveal a characteristic increase of the longitudinal spin Seebeck effect amplitude with the thickness of the insulating ferrimagnetic YIG, which levels off at a critical thickness that increases with decreasing temperature. The observed behavior cannot be explained as an interface effect or by variations of the material parameters. Comparison to numerical simulations of thermal magnonic spin currents yields qualitative agreement for the thickness dependence resulting from the finite magnon propagation length. This allows us to trace the origin of the observed signals to genuine bulk magnonic spin currents due to the spin Seebeck effect ruling out an interface origin and allowing us to gauge the reach of thermally excited magnons in this system for different temperatures. At low temperature, even quantitative agreement with the simulations is found.United States. Dept. of Energy. Office of Science (Solid-State Solar-Thermal Energy Conversion Center Grant DE-SC0001299)National Science Foundation (U.S.) (Award ECCS1231392
Jet production in charged current deep inelastic eâșp scatteringat HERA
The production rates and substructure of jets have been studied in charged current deep inelastic eâșp scattering for QÂČ > 200 GeVÂČ with the ZEUS detector at HERA using an integrated luminosity of 110.5 pbâ»Âč. Inclusive jet cross sections are presented for jets with transverse energies E_{T}^{jet} > 5 GeV. Measurements of the mean subjet multiplicity, â©n_{sbj}âȘ, of the inclusive jet sample are presented. Predictions based on parton-shower Monte Carlo models and next-to-leading-order QCD calculations are compared to the measurements. The value of α_{s} (M_{z}), determined from â©n_{sbj}âȘ at y_{cut} = 10â»ÂČ for jets with 25 < E_{T}^{jet} < 119 GeV, is α_{s} (M_{z}) = 0.1202 ± 0.0052 (stat.)_{-0.0019}^{+0.0060} (syst.)_{-0.0053}^{+0.0065} (th.). The mean subjet multiplicity as a function of QÂČ is found to be consistent with that measured in NC DIS
Evidence for SU(3) symmetry breaking from hyperon production
We examine the SU(3) symmetry breaking in hyperon semileptonic decays (HSD)
by considering two typical sets of quark contributions to the spin content of
the octet baryons: Set-1 with SU(3) flavor symmetry and Set-2 with SU(3) flavor
symmetry breaking in HSD. The quark distributions of the octet baryons are
calculated with a successful statistical model. Using an approximate relation
between the quark fragmentation functions and the quark distributions, we
predict polarizations of the octet baryons produced in annihilation
and semi-inclusive deeply lepton-nucleon scattering in order to reveal the
SU(3) symmetry breaking effect on the spin structure of the octet baryons. We
find that the SU(3) symmetry breaking significantly affects the hyperon
polarization. The available experimental data on the polarization
seem to favor the theoretical predictions with SU(3) symmetry breaking. We
conclude that there is a possibility to get a collateral evidence for SU(3)
symmetry breaking from hyperon production. The theoretical errors for our
predictions are discussed.Comment: 3 tables, 14 figure
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