36,754 research outputs found
Quantifying the tension between the Higgs mass and (g-2)_mu in the CMSSM
Supersymmetry has been often invoqued as the new physics that might reconcile
the experimental muon magnetic anomaly, a_mu, with the theoretical prediction
(basing the computation of the hadronic contribution on e^+ e^- data). However,
in the context of the CMSSM, the required supersymmetric contributions (which
grow with decreasing supersymmetric masses) are in potential tension with a
possibly large Higgs mass (which requires large stop masses). In the limit of
very large m_h supersymmetry gets decoupled, and the CMSSM must show the same
discrepancy as the SM with a_mu . But it is much less clear for which size of
m_h does the tension start to be unbearable. In this paper, we quantify this
tension with the help of Bayesian techniques. We find that for m_h > 125 GeV
the maximum level of discrepancy given current data (~ 3.3 sigma) is already
achieved. Requiring less than 3 sigma discrepancy, implies m_h < 120 GeV. For a
larger Higgs mass we should give up either the CMSSM model or the computation
of a_mu based on e^+ e^-; or accept living with such inconsistency
Natural history of Belonuchus Nordmann spp. and allies (Coleoptera: Staphylinidae) in Heliconia L. (Zingiberales: Heliconiaceae) flower bracts
Adults, and in some species larvae, of several members of Belonuchus Nordmann (Coleoptera: Staphylinidae: Staphylininae) and a few related genera seem to be to various degrees consistently associated with flower bracts of the genus Heliconia (Zingiberales: Heliconiaceae). They are predators and eat various dipterous and lepidopterous larvae in that habitat. Adults of at least Belonuchus cephalotes (Sharp) and Odontolinus fasciatus Sharp are able to immerse completely in water to capture larvae and/or pupae of mosquitoes (Culicidae). Adults and larvae of Belonuchus satyrus Erichson, and adults of B. cacao Blackwelder and B. rufipennis (F.) were found in water-filled flower bracts of Heliconia bihai (L.) L. in northern, lowland Venezuela. The bracts also contained mosquito larvae and semiaquatic coleopterous (Chrysomelidae: Hispinae), lepidopterous (Crambidae: Pyraustinae) and dipterous (Syrphidae, Stratiomyidae, Psychodidae, Richardiidae) larvae, and Annelida. In feeding trials, B. satyrus adults and larvae did not feed on hispine larvae or annelids, but did feed on all the lepidopterous and dipterous larvae available to them; adults dragged larvae and pupae of the mosquito genus Toxorhynchites Theobald from shallow water and thus seemed to be the top predators of the food pyramid within bracts. Records are compiled of association of Belonuchus and relatives with Heliconia bracts in the neotropics. We correct the names used for Heliconia spp. by earlier entomological authors working in Venezuela. Their ‘Heliconia caribaea Lamarck’ is H. bihai (L.) L. and their ‘H. aurea Rodríguez’ is H. bihai cv. Aurea.Los adultos y en algunos casos también las larvas de varias especies de Belonuchus spp. (Coleoptera: Staphylinidae: Staphylininae) y algunos géneros relacionados están consistentemente asociados con las espatas florales del género Heliconia (Zingiberales: Heliconiaceae). Estos coleópteros son depredadores y comen larvas de varios tipos de dípteros y lepidópteros en ese hábitat. Los adultos de Belonuchus cephalotes (Sharp) y Odontolinus fasciatus Sharp pueden sumergirse completamente en el agua para capturar las larvas y pupas de mosquitos (Culicidae). Larvas y adultos de Belonuchus satyrus Erichson, así como adultos de B. cacao Blackwelder y B. rufipennis (F.) fueron encontrados en las brácteas florales de Heliconia bihai (L.) L. de las partes bajas del norte de Venezuela. Las brácteas también contenían larvas de mosquitos y coleópteros semi-acuáticos (Chrysomelidae: Hispinae), larvas de lepidópteros (Crambidae: Pyraustinae) y de dípteros (Syrphidae, Stratiomyidae, Psychodidae, Richardiidae), y anélidos. En experimentos de alimentación, las larvas y los adultos de B. satyrus no se alimentaron de larvas de Hispinae ni de anélidos, sin embargo todas las larvas de lepidópteros y de dípteros que se les ofrecieron fueron ingeridas; los adultos de B. satyrus también extraen larvas de mosquitos del género Toxorhynchites Theobald del agua, por lo cual parecen ser los depredadores del tope de la pirámide alimentaria en las brácteas. Los registros de asociaciones de Belonuchus y géneros afines con las brácteas de Heliconia en el Neotrópico fueron recopiladas. Corregimos los nombres de Heliconia spp.utilizados anteriormente por entomólogos que trabajaron en Venezuela. Su ‘Heliconia caribaea Lamarck’ corresponde a H. bihai (L.) L. y su ‘H. aurea Rodríguez’ corresponde a H. bihai cv. Aurea
A CASE AGAINST THE SIMULTANEOUS USE OF MARKET ACCESS RESTRICTIONS, DOMESTIC SUPPORT, AND EXPORT SUBSIDIES
The Uruguay Round of GATT introduced market disciplines to international trade in agricultural commodities. However, in cases where countries negotiated the right to limit market access, support domestic production at high levels and subsidize exports, the spirit of the WTO rules have been violated. The Norwegian meat market (beef, pork, lamb and mutton, and chicken) situations are studied in terms of the policy implications and WTO commitments. If Norway's policy objective is to target some level of production that satisfies its non-trade concerns, then semi-decoupled income support could be an improvement over a policy mix that simultaneously restricts market access, provides domestic support and applies export subsidies.Norway, meat, market access limitations, domestic support, export subsidies, International Relations/Trade,
Highly nondegenerate four-wave mixing efficiency of an asymmetric coupled quantum well structure
An asymmetric coupled quantum well structure is theoretically investigated as a means of tailoring the conversion efficiency of the four-wave mixing process at terahertz detuning rates. In this structure, a coherent electronic oscillation between the two wells can be excited that introduces a resonance peak in the four-wave mixing frequency response. A calculation based on the density matrix formalism shows that an increase in the power conversion efficiency on the order of 10 dB can be attained at the selected resonance frequency for low temperature operation. Finally, we propose a novel technique for exciting the interwell oscillations that takes advantage of the polarization dependence of the interband optical transitions in alternating strain quantum wells
The cosmological evolution of the QSO luminosity density and of the star formation rate
We demonstrate that the evolution of the QSO luminosity density with epoch
displays a striking similarity to the cosmological evolution of the field
galaxy star formation rate, recently derived from a number of independent
surveys. The QSO luminosity density at 2800A is approximately one-fortieth that
implied by the star formation rate in galaxies throughout the past 11 Gigayears
(z<4). This similarity suggests that a substantial fraction of the QSO
luminosity may be closely linked to the star formation process and its
evolution with cosmic time.Comment: 3 pages, TeX, 1 figure, MNRAS in pres
Crop intensification, land use, and on-farm energy-use efficiency during the worldwide spread of the green revolution
We analyzed crop production, physical inputs, and land use at the country level to assess technological changes behind the threefold increase in global crop production from 1961 to 2014. We translated machinery, fuel, and fertilizer to embedded energy units that, when summed up, provided a measure of agricultural intensification (human subsidy per hectare) for crops in the 58 countries responsible for 95% of global production. Worldwide,there was a 137% increase in input use per hectare, reaching 13 EJ, or 2.6% of the world´s primary energy supply, versus only a 10% increase in land use. Intensification was marked in Asia and Latin America, where input-use levels reached those that North America and Europe had in the earlier years of the period; the increase was more accentuated, irrespective of continent, for the 12 countries with mostly irrigated production. Half of the countries (28/58), mainly developed ones, had an average subsidy >5 GJ/ha/y (with fertilizers accounting for 27% in 1961 and 45% in 2014), with most of them (23/28) using about the same area or less than in 1961 (net land sparing of 31 Mha). Most of the remaining countries (24/30 with inputs <5 GJ/ha/y), mainly developing ones, increased their cropped area (net land extensification of 135 Mha). Overall, energy-use efficiency (cropoutput/inputs) followed a U-shaped trajectory starting at about 3 and finishing close to 4. The prospects of a more sustainable intensification are discussed, and the inadequacy of the land-sparing model expectation of protecting wilderness via intensified agriculture is highlighted.Fil: PELLEGRINI, PEDRO. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; ArgentinaFil: FERNANDEZ, Roberto J.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentin
Element sets for high-order Poincar\'e mapping of perturbed Keplerian motion
The propagation and Poincar\'e mapping of perturbed Keplerian motion is a key
topic in celestial mechanics and astrodynamics, e.g. to study the stability of
orbits or design bounded relative trajectories. The high-order transfer map
(HOTM) method enables efficient mapping of perturbed Keplerian orbits over many
revolutions. For this, the method uses the high-order Taylor expansion of a
Poincar\'e or stroboscopic map, which is accurate close to the expansion point.
In this paper, we investigate the performance of the HOTM method using
different element sets for building the high-order map. The element sets
investigated are the classical orbital elements, modified equinoctial elements,
Hill variables, cylindrical coordinates and Deprit's ideal elements. The
performances of the different coordinate sets are tested by comparing the
accuracy and efficiency of mapping low-Earth and highly-elliptical orbits
perturbed by with numerical propagation. The accuracy of HOTM depends
strongly on the choice of elements and type of orbit. A new set of elements is
introduced that enables extremely accurate mapping of the state, even for high
eccentricities and higher-order zonal perturbations. Finally, the high-order
map is shown to be very useful for the determination and study of fixed points
and centre manifolds of Poincar\'e maps.Comment: Pre-print of journal articl
Four-wave mixing and generation of terahertz radiation in an alternating-strain coupled quantum-well structure
We propose a scheme for exciting steady-state tunneling oscillations of an electronic wave packet in a semiconductor coupled quantum-well structure with strain of the opposite polarity in the two wells. A detailed study of the four-wave mixing process in this structure is then presented, based on the density matrix formalism. Our results show that a resonance peak is introduced in the four-wave mixing frequency response at the tunneling frequency, leading to a significant enhancement in the wavelength conversion efficiency for low temperature operation. Furthermore, we consider this structure under the same excitation condition as a potential source of coherent radiation in, the terahertz frequency band
Continual reproduction of self-assembling oligotriazole peptide nanomaterials.
Autocatalytic chemical reactions, whereby a molecule is able to catalyze its own formation from a set of precursors, mimic nature's ability to generate identical copies of relevant biomolecules, and are thought to have been crucial for the origin of life. While several molecular autocatalysts have been previously reported, coupling autocatalytic behavior to macromolecular self-assembly has been challenging. Here, we report a non-enzymatic and chemoselective methodology capable of autocatalytically producing triskelion peptides that self-associate into spherical bioinspired nanostructures. Serial transfer experiments demonstrate that oligotriazole autocatalysis successfully leads to continual self-assembly of three-dimensional nanospheres. Triskelion-based spherical architectures offer an opportunity to organize biomolecules and chemical reactions in unique, nanoscale compartments. The use of peptide-based autocatalysts that are capable of self-assembly represents a promising method for the development of self-synthesizing biomaterials, and may shed light on understanding life's chemical origins.Molecules that act as both autocatalysts and material precursors offer exciting prospects for self-synthesizing materials. Here, the authors design a triazole peptide that self-replicates and then self-assembles into nanostructures, coupling autocatalytic and assembly pathways to realize a reproducing supramolecular system
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