538,503 research outputs found
Generalised connections and higher-spin equations
We consider high-derivative equations obtained setting to zero the divergence
of the higher-spin curvatures in metric-like form, showing their equivalence to
the second-order equations emerging from the tensionless limit of open string
field theory, which propagate reducible spectra of particles with different
spins. This result can be viewed as complementary to the possibility of setting
to zero a single trace of the higher-spin field strengths, which yields an
equation known to imply Fronsdal's equation in the compensator form. Higher
traces and divergences of the curvatures produce a whole pattern of
high-derivative equations whose systematics is also presented.Comment: 12 pages, minor change
Low-spin models for higher-spin Lagrangians
Higher-spin theories are most commonly modelled on the example of spin 2.
While this is appropriate for the description of free irreducible spin-s
particles, alternative options could be equally interesting. In particular
Maxwell's equations provide the effective model for maximally reducible
theories of higher spins inspired by the tensionless limit of the open string.
For both options, as well as for their fermionic counterparts, one can extend
the analogy beyond the equations for the gauge potentials, formulating the
corresponding Lagrangians in terms of higher-spin curvatures. The associated
non-localities are effectively due to the elimination of auxiliary fields and
do not modify the spectrum. Massive deformations of these theories are also
possible, and in particular in this contribution we propose a generalisation of
the Proca Lagrangian for the Maxwell-inspired geometric theories.Comment: 12 pages, PTPTeX. Contribution to the proceedings of the 3rd
International Conference on String Field Theory and Related Aspects (SFT
2010), Kyoto, Japan, 18-22 Oct 201
Size-assortative mating in simultaneous hermaphrodites: an experimental test and a meta-analysis
Assortative mating by size has been argued to be widespread in the animal kingdom. However, the strength of size-assortative mating is known to vary considerably between species and the underlying mechanisms promoting this inter-specific variation remain largely unexplored. Size-assortative mating has been proposed to be particularly strong in simultaneous hermaphrodites, i.e. organisms that produce male and female gametes at the same time. Here, we build on this hypothesis by arguing that size-assortative mating mediated by sexual selection is generally stronger in reciprocally mating hermaphrodites compared with unilaterally mating species and separate-sexed organisms. We report a series of empirical tests suggesting that size-assortative mating in the unilaterally copulating freshwater snail Physa acuta is caused by spatial clustering of similar-sized individuals and not by mate choice. In addition, we present a meta-analysis testing, for the first time, the hypothesis that sexual selection-mediated size-assortative mating is stronger in reciprocally copulating simultaneous hermaphrodites. Overall, we found significant size-assortative mating across 18 tested species and substantial inter-specific variation. Importantly, part of this variation can be explained by mating type, providing support for the hypothesis that size-assortative mating is stronger in reciprocally mating hermaphrodites compared with unilaterally mating species. We highlight potential pitfalls when testing for sexual selection-mediated size-assortative mating and discuss the need for more experimental and comparative approaches in order to resolve the observed variation in the strength of size-assortative mating among species.Fil: Graham, Stuart. UniversitĂ© de Montpellier. Centre dâEcologie Fonctionnelle et Evolutive; Francia. UniversitĂ© Paul-ValĂ©ry Montpellier; Francia. Centre National de la Recherche Scientifique; FranciaFil: Chapuis, Elodie. UniversitĂ© de Montpellier. Centre dâEcologie Fonctionnelle et Evolutive; Francia. Centre National de la Recherche Scientifique; Francia. Institut de Recherche pour le DĂ©veloppement,. IntĂ©ractions Plantes-Microrganismes-Environement; Francia. UniversitĂ© Paul-ValĂ©ry Montpellier; FranciaFil: Meconcelli, Stefania. UniversitĂ© de Montpellier. Centre dâEcologie Fonctionnelle et Evolutive; Francia. Centre National de la Recherche Scientifique; Francia. UniversitĂ di Torino; ItaliaFil: Bonel, NicolĂĄs. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - BahĂa Blanca; Argentina. Universidad Nacional del Sur. Departamento de BiologĂa, BioquĂmica y Farmacia. Laboratorio de ZoologĂa de Invertebrados I; Argentina. UniversitĂ© de Montpellier. Centre dâEcologie Fonctionnelle et Evolutive; Francia. UniversitĂ© Paul-ValĂ©ry Montpellier; FranciaFil: Sartori, Kevin. UniversitĂ© de Montpellier. Centre dâEcologie Fonctionnelle et Evolutive; Francia. Centre National de la Recherche Scientifique; Francia. UniversitĂ© Paul-ValĂ©ry Montpellier; FranciaFil: Christophe, Ananda. UniversitĂ© de Montpellier. Centre dâEcologie Fonctionnelle et Evolutive; Francia. Centre National de la Recherche Scientifique; Francia. UniversitĂ© Paul-ValĂ©ry Montpellier; FranciaFil: Alda, Maria del Pilar. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Centro de Estudios ParasitolĂłgicos y de Vectores. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Estudios ParasitolĂłgicos y de Vectores; ArgentinaFil: Patrice David. UniversitĂ© de Montpellier. Centre dâEcologie Fonctionnelle et Evolutive; Francia. Centre National de la Recherche Scientifique; Francia. UniversitĂ© Paul-ValĂ©ry Montpellier; FranciaFil: Janicke, Tim. UniversitĂ© de Montpellier. Centre dâEcologie Fonctionnelle et Evolutive; Francia. Centre National de la Recherche Scientifique; Francia. UniversitĂ© Paul-ValĂ©ry Montpellier; Franci
Structure and magnetism of orthorhombic epitaxial FeMnAs
The molecular beam epitaxy growth of Fe on MnAs/GaAs(001) leads to the formation of an epitaxial FeMnAs phase at the Fe/MnAs interface. The investigation of the structure by high angle annular dark field imaging in a scanning transmission electron microscope reveals an unusual orthorhombic structure, with vacancy ordering. Ab initio calculations show an antiferromagnetic ground state for this orthorhombic FeMnAs.Fil: Demaille, Dominique. Laboratorio Internacional Franco-Argentino en Nanociencias; Francia. Universite Pierre et Marie Curie. Institut des Nanosciences de Paris; FranciaFil: Patriarche, Gilles. Centre National de la Recherche Scientifique; FranciaFil: Helman, Christian. ComisiĂłn Nacional de EnergĂa AtĂłmica; Argentina. Laboratorio Internacional Franco-Argentino en Nanociencias; FranciaFil: Eddrief, Mahmoud. Laboratorio Internacional Franco-Argentino en Nanociencias; Francia. Universite Pierre et Marie Curie. Institut des Nanosciences de Paris; FranciaFil: Etgens, Hugo. Laboratorio Internacional Franco-Argentino en Nanociencias; Francia. Universite Pierre et Marie Curie. Institut des Nanosciences de Paris; FranciaFil: Sacchi, Maurizio. Laboratorio Internacional Franco-Argentino en Nanociencias; Francia. Universite Pierre et Marie Curie. Institut des Nanosciences de Paris; Francia. LâOrme des merisiers Saint-Aubin. Synchrotron SOLEIL; FranciaFil: Llois, Ana Maria. ComisiĂłn Nacional de EnergĂa AtĂłmica; Argentina. Laboratorio Internacional Franco-Argentino en Nanociencias; Francia. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Marangolo, Massimiliano. Laboratorio Internacional Franco-Argentino en Nanociencias; Francia. Universite Pierre et Marie Curie. Institut des Nanosciences de Paris; Franci
String theory triplets and higher-spin curvatures
Unconstrained local Lagrangians for higher-spin gauge theories are bound to
involve auxiliary fields, whose integration in the partition function generates
geometric, effective actions expressed in terms of curvatures. When applied to
the triplets, emerging from the tensionless limit of open string field theory,
the same procedure yields interesting alternative forms of geometric
Lagrangians, expressible for both bosons and fermions as squares of
field-strengths. This shows that higher-spin curvatures might play a role in
the dynamics, regardless of whether the Fronsdal-Labastida constraints are
assumed or forgone.Comment: 14 pages. Eqs. (2.13) and (3.7) added. Footnotes 8 and 14 and
corresponding references included. Additional minor changes. To appear in
Phys. Lett.
Performance of Hispanic-Owned Businesses in Nacogdoches, Texas
Hypothesis
The Hispanic business owners have an increasing potential to become big businesses in the East Texas town because of the growth of the Hispanic population in tow
Synergistic effects of cardiac resynchronization therapy and drug up-titration in heart failure. is this enough?
This editorial refers to âOptimization of heart failure medication after cardiac resynchronization therapy and the impact on long-term survivalâ, by C.T. Witt et al., on
page 18
Cubic interactions of massless higher spins in (A)dS: metric-like approach
Cubic interactions of higher-spin gauge fields in (A)dS are studied in the
metric-like approach. Making use of the traceless and transverse constraints
together with the ambient-space formalism, all consistent parity-invariant
cubic vertices are obtained for d>3 in closed form pointing out the key role of
their flat-space counterparts.Comment: 33 pages, LaTex. Final version to appear in NP
Steroid profiling in male wobbler mouse, a model of Amyotrophic Lateral Sclerosis
The Wobbler mouse is an animal model for human motoneuron diseases, especially amyotrophic lateral sclerosis (ALS), used in the investigation of both pathology and therapeutic treatment. ALS is a fatal neurodegenerative disease, characterized by the selective and progressive death of motoneurons, leading to progressive paralysis. Previous limited studies have reported steroidal hormone dysregulation in Wobbler mouse and in ALS patients, suggesting endocrine dysfunctions which may be involved in the pathogenesis of the disease. In this study, we established a steroid profiling in brain, spinal cord, plasma, adrenal glands, and testes in 2-month-old male Wobbler mice and their littermates by gas chromatography coupled to mass spectrometry. Our results show in Wobbler mice the following: 1) a marked up-regulation of corticosterone levels in adrenal glands, plasma, spinal cord regions (cervical, thoracic, lumbar) and brain; 2) a strong decrease in T levels in the testis, plasma, spinal cord, and brain; and 3) increased levels of progesterone and especially of its reduced metabolites 5α-dihydroprogesterone, allopregnanolone, and 20α-dihydroprogesterone in the brain, spinal cord, and adrenal glands. Furthermore, Wobbler mice showed a hypothalamic-pituitary-gonadal hypoactivity. Interestingly, plasma concentrations of corticosterone and T correlate well with their respective levels in cervical spinal cord in both control and Wobbler mice. T down-regulation is probably the consequence of adrenal hyperactivity, and the up-regulation of progesterone and its reduced metabolites may correspond to an endogenous protective mechanism in response to motoneuron degeneration. Our findings suggest that increased levels of corticosterone and decreased levels of T in plasma could be a signature of motoneuron degeneration.Fil: Gonzalez Deniselle, Maria Claudia. Universidad de Buenos Aires. Facultad de Medicina; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto de BiologĂa y Medicina Experimental. FundaciĂłn de Instituto de BiologĂa y Medicina Experimental. Instituto de BiologĂa y Medicina Experimental; ArgentinaFil: Liere, Philippe. Inserm; Francia. UniversitĂ© Paris Saclay; FranciaFil: Pianos, Antoine. Inserm; Francia. UniversitĂ© Paris Saclay; FranciaFil: Meyer, Maria. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto de BiologĂa y Medicina Experimental. FundaciĂłn de Instituto de BiologĂa y Medicina Experimental. Instituto de BiologĂa y Medicina Experimental; ArgentinaFil: Aprahamian, Fanny. Inserm; Francia. UniversitĂ© Paris Saclay; FranciaFil: Cambourg, Annie. Inserm; Francia. UniversitĂ© Paris Saclay; FranciaFil: Di Giorgio, Noelia Paula. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto de BiologĂa y Medicina Experimental. FundaciĂłn de Instituto de BiologĂa y Medicina Experimental. Instituto de BiologĂa y Medicina Experimental; ArgentinaFil: Schumacher, Michael. Inserm; Francia. UniversitĂ© Paris Saclay; Francia. Universite Paris Sud; FranciaFil: de Nicola, Alejandro Federico. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Instituto de BiologĂa y Medicina Experimental. FundaciĂłn de Instituto de BiologĂa y Medicina Experimental. Instituto de BiologĂa y Medicina Experimental; ArgentinaFil: Guennoun, Rachida. UniversitĂ© Paris Saclay; Francia. Inserm; Francia. Universite Paris Sud; Franci
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