485 research outputs found
Multivector Field Formulation of Hamiltonian Field Theories: Equations and Symmetries
We state the intrinsic form of the Hamiltonian equations of first-order
Classical Field theories in three equivalent geometrical ways: using
multivector fields, jet fields and connections. Thus, these equations are given
in a form similar to that in which the Hamiltonian equations of mechanics are
usually given. Then, using multivector fields, we study several aspects of
these equations, such as the existence and non-uniqueness of solutions, and the
integrability problem. In particular, these problems are analyzed for the case
of Hamiltonian systems defined in a submanifold of the multimomentum bundle.
Furthermore, the existence of first integrals of these Hamiltonian equations is
considered, and the relation between {\sl Cartan-Noether symmetries} and {\sl
general symmetries} of the system is discussed. Noether's theorem is also
stated in this context, both the ``classical'' version and its generalization
to include higher-order Cartan-Noether symmetries. Finally, the equivalence
between the Lagrangian and Hamiltonian formalisms is also discussed.Comment: Some minor mistakes are corrected. Bibliography is updated. To be
published in J. Phys. A: Mathematical and Genera
MODELO DE VIVIENDA AUTO SOSTENIBLE PARA MEJORAR LA HABITABILIDAD Y CONFORT DE LAS VIVIENDAS DE PUNO.
El presente trabajo abordó la problemática de determinar en qué medida los materiales constructivos con cualidades térmicas y energías alternativas influyen sobre los niveles de habitabilidad y confort. Con este objetivo, se buscó identificar las características de un modelo de vivienda autosostenible que haga uso de estos materiales y sistemas alternativos de energía para influir en los niveles de habitabilidad y confort de las viviendas en la ciudad de Puno. Para ello, se realizó un estudio cuantitativo y se utilizaron métodos descriptivos explicativos para analizar las viviendas de la ciudad en términos de hogar, vivienda y población. Se utilizaron datos estadísticos provenientes del INEI (censo de vivienda 2017) como fuente de información de primer orden. En un primer momento, la investigación tuvo un alcance descriptivo, recopilando la información documental y estadística necesaria para dimensionar las variables de estudio. Luego, se procedió al procesamiento y análisis de los datos recolectados, con el fin de identificar las características de diseño del modelo de vivienda auto sostenible propuesto y dimensionar los niveles de influencia en la habitabilidad y confort de las viviendas. Como resultado, se identificaron las características constructivas y funcionales de un modelo de vivienda auto sostenible, adaptado a las condiciones climáticas y geográficas de la ciudad de Puno, que contribuirían a mejorar la eficiencia térmica y energética de las viviendas de la ciudad. En conclusión, se comprueba que estos elementos influyen positivamente en los niveles de habitabilidad y confort de las viviendas de la ciudad de Puno
Non-standard connections in classical mechanics
In the jet-bundle description of first-order classical field theories there
are some elements, such as the lagrangian energy and the construction of the
hamiltonian formalism, which require the prior choice of a connection. Bearing
these facts in mind, we analyze the situation in the jet-bundle description of
time-dependent classical mechanics. So we prove that this connection-dependence
also occurs in this case, although it is usually hidden by the use of the
``natural'' connection given by the trivial bundle structure of the phase
spaces in consideration. However, we also prove that this dependence is
dynamically irrelevant, except where the dynamical variation of the energy is
concerned. In addition, the relationship between first integrals and
connections is shown for a large enough class of lagrangians.Comment: 17 pages, Latex fil
Stereodynamical studies of velocity aligned photofragments
The state resolved stereodynamics of bimolecular reactions can be probed using velocity aligned photofragments as reagents, and polarised, Doppler resolved laser detection techniques for the products. The new strategy and its application to the reaction O(1D) + N2O→ NO + NO are outlined
The host of the Type I SLSN 2017egm: A young, sub-solar metallicity environment in a massive spiral galaxy
Here we present an integral-field study of the massive, high-metallicity
spiral NGC 3191, the host of SN 2017egm, the closest SLSN Type I to date. We
use data from PMAS/CAHA and the public MaNGA survey to shed light on the
properties of the SLSN site and the origin of star-formation in this
non-starburst spiral galaxy. We map the physical properties different
\ion{H}{II} regions throughout the galaxy and characterize their stellar
populations using the STARLIGHT fitting code. Kinematical information allows to
study a possible interaction with its neighbouring galaxy as the origin of
recent star formation activity which could have caused the SLSN. NGC 3191 shows
intense star-formation in the western part with three large SF regions of low
metallicity. The central regions of the host have a higher metallicity, lower
specific star-formation rate and lower ionization. Modeling the stellar
populations gives a different picture: The SLSN region has two dominant stellar
populations with different ages, the youngest one with an age of 2-10 Myr and
lower metallicity, likely the population from which the SN progenitor
originated. Emission line kinematics of NGC 3191 show indications of
interaction with its neighbour MCG+08-19-017 at 45 kpc, which might be
responsible for the recent starburst. In fact, this galaxy pair has in total
hosted 4 SNe, 1988B (Type Ia), SN 2003ds (Type Ic in MCG+08-19-017), PTF10bgl
(SLSN-Type II) and 2017egm, underlying the enhanced SF in both galaxies due to
interaction. Our study shows that one has to be careful interpreting global
host and even gas properties without looking at the stellar population history
of the region. SLSNe seem to still be consistent with massive stars ( 20
M) requiring low () metallicity and those environments
can also occur in massive, late-type galaxies but not necessarily starbursts.Comment: Accepted for publication in A&A, 13 pages, 11 figures, 7 tables.
Abstract has been reduced to match arXiv form requirement
Higher-order Mechanics: Variational Principles and other topics
After reviewing the Lagrangian-Hamiltonian unified formalism (i.e, the
Skinner-Rusk formalism) for higher-order (non-autonomous) dynamical systems, we
state a unified geometrical version of the Variational Principles which allows
us to derive the Lagrangian and Hamiltonian equations for these kinds of
systems. Then, the standard Lagrangian and Hamiltonian formulations of these
principles and the corresponding dynamical equations are recovered from this
unified framework.Comment: New version of the paper "Variational principles for higher-order
dynamical systems", which was presented in the "III Iberoamerican Meeting on
Geometry, Mechanics and Control" (Salamanca, 2012). The title is changed. A
detailed review is added. Sections containing results about variational
principles are enlarged with additional comments, diagrams and summarizing
results. Bibliography is update
Influence of collision energy on the dynamics of the reaction O(1D) + CH4(X1A 1) → OH(X2Π) + CH3(X2 A2'')
We studied the effects of collision energy (ET) on the dynamics of the title reaction using the quasiclassical trajectory method on an analytical triatomic potential energy surface we had derived for this system. We compared the dependence of the scalar and two-vector properties of the reaction on ET with experimental data and obtained a quite good agreement. The results can be explained in terms of the coexistence of two microscopic reaction mechanisms: insertion and abstraction. The former mechanism is the most important one, although the contribution of the latter increases with ET
Classical field theory on Lie algebroids: Variational aspects
The variational formalism for classical field theories is extended to the
setting of Lie algebroids. Given a Lagrangian function we study the problem of
finding critical points of the action functional when we restrict the fields to
be morphisms of Lie algebroids. In addition to the standard case, our formalism
includes as particular examples the case of systems with symmetry (covariant
Euler-Poincare and Lagrange Poincare cases), Sigma models or Chern-Simons
theories.Comment: Talk deliverd at the 9th International Conference on Differential
Geometry and its Applications, Prague, September 2004. References adde
Altered Env conformational dynamics as a mechanism of resistance to peptide‑triazole HIV‑1 inactivators.
Background: We previously developed drug-like peptide triazoles (PTs) that target HIV-1 Envelope (Env) gp120,
potently inhibit viral entry, and irreversibly inactivate virions. Here, we investigated potential mechanisms of viral
escape from this promising class of HIV-1 entry inhibitors.
Results: HIV-1 resistance to cyclic (AAR029b) and linear (KR13) PTs was obtained by dose escalation in viral passaging
experiments. High-level resistance for both inhibitors developed slowly (relative to escape from gp41-targeted
C-peptide inhibitor C37) by acquiring mutations in gp120 both within (Val255) and distant to (Ser143) the putative PT
binding site. The similarity in the resistance profiles for AAR029b and KR13 suggests that the shared IXW pharmacophore
provided the primary pressure for HIV-1 escape. In single-round infectivity studies employing recombinant virus,
V255I/S143N double escape mutants reduced PT antiviral potency by 150- to 3900-fold. Curiously, the combined
mutations had a much smaller impact on PT binding affinity for monomeric gp120 (four to ninefold). This binding
disruption was entirely due to the V255I mutation, which generated few steric clashes with PT in molecular docking.
However, this minor effect on PT affinity belied large, offsetting changes to association enthalpy and entropy. The
escape mutations had negligible effect on CD4 binding and utilization during entry, but significantly altered both
binding thermodynamics and inhibitory potency of the conformationally-specific, anti-CD4i antibody 17b. Moreover,
the escape mutations substantially decreased gp120 shedding induced by either soluble CD4 or AAR029b.
Conclusions: Together, the data suggest that the escape mutations significantly modified the energetic landscape of
Env’s prefusogenic state, altering conformational dynamics to hinder PT-induced irreversible inactivation of Env. This
work therein reveals a unique mode of virus escape for HIV-1, namely, resistance by altering the intrinsic conformational
dynamics of the Env trimerpost-print4093 K
Characteristics and large bulk density of the C-type main-belt triple asteroid (93) Minerva
From a set of adaptive optics (AO) observations collected with the W.M. Keck telescope between August and September 2009, we derived the orbital parameters of the most recently discovered satellites of the large C-type asteroid (93) Minerva. The satellites of Minerva, which are approximately 3 and 4 km in diameter, orbit very close to the primary (∼5 and ∼8 × R_p and ∼1% and ∼2% × R_(Hill)) in a circular manner, sharing common characteristics with most of the triple asteroid systems in the main-belt. Combining these AO observations with lightcurve data collected since 1980 and two stellar occultations in 2010 and 2011, we removed the ambiguity of the pole solution of Minerva’s primary and showed that it has an almost regular shape with an equivalent diameter D_(eq) = 154 ± 6 km in agreement with IRAS observations. The surprisingly high bulk density of 1.75 ± 0.30 g/cm3 for this C-type asteroid, suggests that this taxonomic class is composed of asteroids with different compositions, For instance, Minerva could be made of the same material as dry CR, CO, and CV meteorites. We discuss possible scenarios on the origin of the system and conclude that future observations may shine light on the nature and composition of this fifth known triple main-belt asteroid
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