6,220 research outputs found
Multiple Molecular H2 Outflows in AFGL 618
We report high spatial (0.5 arcsec) and high spectral (9 km/s) resolution
spectro-imaging of the 2.12 micron H2 1-0 S(1) line in the proto-planetary
nebula AFGL 618 using BEAR at the CFHT. The observations reveal the presence of
multiple, high-velocity, molecular outflows that align with the remarkable
optical jets seen in HST images. The structure and kinematics of the outflows
show how jets interact with circumstellar gas and shape the environment in
which planetary nebulae form.Comment: 14 pages, 5 figures. To appear in The Astrophysical Journal Letter
Electrical networks on -simplex fractals
The decimation map for a network of admittances on an
-simplex lattice fractal is studied. The asymptotic behaviour of
for large-size fractals is examined. It is found that in the
vicinity of the isotropic point the eigenspaces of the linearized map are
always three for ; they are given a characterization in terms of
graph theory. A new anisotropy exponent, related to the third eigenspace, is
found, with a value crossing over from to
.Comment: 14 pages, 8 figure
Interferometric Observations of Powerful CO Emission from the three Submillimeter Galaxies at z=2.30, 2.51 and 3.35
We report IRAM Plateau de Bure, millimeter interferometry of three z=~2.4 to
3.4, SCUBA deep field galaxies. Our CO line observations confirm the rest-frame
UV/optical redshifts, thus more than doubling the number of confirmed,
published redshifts of the faint submillimeter population and proving their
high-z nature. In all three sources our measurements of the intrinsic gas and
dynamical mass are large (1e10 to 1e11 Msun). In at least two cases the data
show that the submillimeter sources are part of an interacting system. Together
with recent information gathered in the X-ray, optical and radio bands our
observations support the interpretation that the submm-population consists of
gas rich (gas to dynamical mass ratio ~0.5) and massive, composite
starburst/AGN systems, which are undergoing a major burst of star formation and
are evolving into m*-galaxies.Comment: only minor modifications to comply with the ApJL edition rule
The phase diagram of L\'evy spin glasses
We study the L\'evy spin-glass model with the replica and the cavity method.
In this model each spin interacts through a finite number of strong bonds and
an infinite number of weak bonds. This hybrid behaviour of L\'evy spin glasses
becomes transparent in our solution: the local field contains a part
propagating along a backbone of strong bonds and a Gaussian noise term due to
weak bonds. Our method allows to determine the complete replica symmetric phase
diagram, the replica symmetry breaking line and the entropy. The results are
compared with simulations and previous calculations using a Gaussian ansatz for
the distribution of fields.Comment: 20 pages, 7 figure
Influence of conformational fluctuations on enzymatic activity: modelling the functional motion of beta-secretase
Considerable insight into the functional activity of proteins and enzymes can
be obtained by studying the low-energy conformational distortions that the
biopolymer can sustain. We carry out the characterization of these large scale
structural changes for a protein of considerable pharmaceutical interest, the
human -secretase. Starting from the crystallographic structure of the
protein, we use the recently introduced beta-Gaussian model to identify, with
negligible computational expenditure, the most significant distortion occurring
in thermal equilibrium and the associated time scales. The application of this
strategy allows to gain considerable insight into the putative functional
movements and, furthermore, helps to identify a handful of key regions in the
protein which have an important mechanical influence on the enzymatic activity
despite being spatially distant from the active site. The results obtained
within the Gaussian model are validated through an extensive comparison against
an all-atom Molecular Dynamics simulation.Comment: To be published in a special issue of J. Phys.: Cond. Mat. (Bedlewo
Workshop
Emergency planning and mitigation at Vesuvius: A new evidence-based approach
Disasters from explosive volcanic eruptions are infrequent and experience in emergency planning and mitigation for such events remains limited. The need for urgently developing more robust methods for risk assessment and decision making in volcanic crises has become increasingly apparent as world populations continue to expand in areas of active explosive volcanism. Nowhere is this more challenging than at Vesuvius, Italy, with hundreds of thousands of people living on the flanks of one of the most dangerous volcanoes in the world. We describe how a new paradigm, evidence-based volcanology, has been applied in EXPLORIS to contribute to crisis planning and management for when the volcano enters its next state of unrest, as well as in long-term land-use planning. The analytical approach we adopted enumerates and quantifies all the processes and effects of the eruptive hazards of the volcano known to influence risk, a scientific challenge that combines field data on the vulnerability of the built environment and humans in past volcanic disasters with theoretical research on the state of the volcano, and including evidence from the field on previous eruptions as well as numerical simulation modelling of eruptive processes. Formal probabilistic reasoning under uncertainty and a decision analysis approach have provided the basis for the development of an event tree for a future range of eruption types with probability paths and hypothetical casualty outcomes for risk assessment. The most likely future eruption scenarios for emergency planning were derived from the event tree and elaborated upon from the geological and historical record. Modelling the impacts in these scenarios and quantifying the consequences for the circumvesuvian area provide realistic assessments for disaster planning and for showing the potential risk–benefit of mitigation measures, the main one being timely evacuation, but include for consideration protecting buildings against dilute, low dynamic pressure surges, and temporary roof supports in the most vulnerable buildings, as well as hardening infrastructure and lifelines. This innovative work suggests that risk-based methods could have an important role in crisis management at cities on volcanoes and small volcanic islands
Optimal network topologies: Expanders, Cages, Ramanujan graphs, Entangled networks and all that
We report on some recent developments in the search for optimal network
topologies. First we review some basic concepts on spectral graph theory,
including adjacency and Laplacian matrices, and paying special attention to the
topological implications of having large spectral gaps. We also introduce
related concepts as ``expanders'', Ramanujan, and Cage graphs. Afterwards, we
discuss two different dynamical feautures of networks: synchronizability and
flow of random walkers and so that they are optimized if the corresponding
Laplacian matrix have a large spectral gap. From this, we show, by developing a
numerical optimization algorithm that maximum synchronizability and fast random
walk spreading are obtained for a particular type of extremely homogeneous
regular networks, with long loops and poor modular structure, that we call
entangled networks. These turn out to be related to Ramanujan and Cage graphs.
We argue also that these graphs are very good finite-size approximations to
Bethe lattices, and provide almost or almost optimal solutions to many other
problems as, for instance, searchability in the presence of congestion or
performance of neural networks. Finally, we study how these results are
modified when studying dynamical processes controlled by a normalized (weighted
and directed) dynamics; much more heterogeneous graphs are optimal in this
case. Finally, a critical discussion of the limitations and possible extensions
of this work is presented.Comment: 17 pages. 11 figures. Small corrections and a new reference. Accepted
for pub. in JSTA
Fatores ambientais sobre pesos em diferentes idades de ovinos da raça Santa Inês no Nordeste do Brasil.
Com o objetivo de avaliar os efeitos de ambiente sobre as características de crescimento dos cordeiros, foram analisados registros de 4094 cordeiros da raça Santa Inês provenientes de rebanhos dos estados da Paraíba, Ceará e Sergipe, coletados num período de 23 anos (1983 a 2005). Foram avaliados os efeitos da estação, do ano de nascimento, sexo do cordeiro, tipo de nascimento e idade da mãe ao parto sobre os pesos corporais ao nascimento (PN), aos 56 dias de idade (P56), aos 112 dias de idade (P112) e aos 196 dias de idade (P196). Os cordeiros nascidos na estação chuvosa e seca não apresentaram diferenças significativas para PN, P56 e P112, porém no P196 os animais nascidos em estação chuvosa apresentaram pesos maiores. Os cordeiros machos foram mais pesados que as fêmeas em todas as idades estudadas. Cordeiros nascidos de parto simples pesaram mais que os nascidos de parto duplo, entretanto, houve interação significativa entre sexo e tipo de parto em que foi observado que fêmeas nascidas de parto simples tiveram pesos maiores que os machos de parto duplo em todas as idades avaliadas. Desta forma, torna-se evidente a necessidade de inclusão e ajuste destas características, como ferramentas de auxílio na avaliação genética e seleção dos animais visando melhoria no desempenho de ovinos da raça Santa Inês. Environmental factors on weights of different ages of Santa Inês sheep in the Northeasterner of Brazil. Abstract: The aim of this study was to evaluate environmental effects on growth performance in Santa Inês lambs, were using data of 4.094 lambs proceeding from Paraíba, Ceará and Sergipe states, collected over an 23-year period (1983 to 2005). The environmental effects of season of birth (winter or summer), sex of lamb, age of dam at lambing and type of birth (single or twins), were important sources of variation to explain differences in weigth at birth (WB), at 56 (W56), 112 (W112) and 196 (W196) days of age. The lambs born in the rain and dry no observed significant differences for WB,WP112 and W56, but the W196 animals born in the rainr season showed higher weights. Males were heavier than female lambs at all ages. Lambs born as singles were heavier (P < 0.01) than lambs born as twins at all ages, however, there was significant interaction between sex and type of birth, that was observed that females lambs born as single had larger weights than the males of twins in all ages. Adjustment factors for sex of lamb, type of birth and age of ewe at lambing need to be estimated and considered in selection programs to improve growth trait of Santa Inês
SuperB: a linear high-luminosity B Factory
This paper is based on the outcome of the activity that has taken place
during the recent workshop on "SuperB in Italy" held in Frascati on November
11-12, 2005. The workshop was opened by a theoretical introduction of Marco
Ciuchini and was structured in two working groups. One focused on the machine
and the other on the detector and experimental issues.
The present status on CP is mainly based on the results achieved by BaBar and
Belle. Estabilishment of the indirect CP violation in B sector in 2001 and of
the direct CP violation in 2004 thanks to the success of PEP-II and KEKB e+e-
asymmetric B Factories operating at the center of mass energy corresponding to
the mass of the Y(4s). With the two B Factories taking data, the Unitarity
Triangle is now beginning to be overconstrained by improving the measurements
of the sides and now also of the angles alpha, and gamma. We are also in
presence of the very intriguing results about the measurements of sin(2 beta)
in the time dependent analysis of decay channels via penguin loops, where b -->
s sbar s and b --> s dbar d. Tau physics, in particular LFV search, as well as
charm and ISR physics are important parts of the scientific program of a SuperB
Factory. The physics case together with possible scenarios for the high
luminosity SuperB Factory based on the concepts of the Linear Collider and the
related experimental issues are discussed.Comment: 22 pages, 22 figures, INFN Roadmap Repor
A multi-transition HCN and HCO+ study of 12 nearby active galaxies: AGN versus SB environments
Recent studies have indicated that the HCN-to-CO(J=1-0) and
HCO+-to-HCN(J=1-0) ratios are significantly different between galaxies with AGN
(active galactic nucleus) and SB (starburst) signatures. In order to study the
molecular gas properties in active galaxies and search for differences between
AGN and SB environments, we observed the HCN(J=1-0), (J=2-1), (J=3-2),
HCO+(J=1-0) and HCO+(J=3-2), emission with the IRAM 30m in the centre of 12
nearby active galaxies which either exhibit nuclear SB and/or AGN signatures.
Consistent with previous results, we find a significant difference of the
HCN(J=2-1)-to-HCN(J=1-0), HCN(J=3-2)-to-HCN(J=1-0), HCO+(J=3-2)-to-HCO+(J=3-2),
and HCO+-to-HCN intensity ratios between the sources dominated by an AGN and
those with an additional or pure central SB: the HCN, HCO+ and HCO+-to-HCN
intensity ratios tend to be higher in the galaxies of our sample with a central
SB as opposed to the pure AGN cases which show rather low intensity ratios.
Based on an LVG analysis of these data, i.e., assuming purely collisional
excitation, the (average) molecular gas densities in the SB dominated sources
of our sample seem to be systematically higher than in the AGN sources. The LVG
analysis seems to further support systematically higher HCN and/or lower HCO+
abundances as well as similar or higher gas temperatures in AGN compared to the
SB sources of our sample. Also, we find that the HCN-to-CO ratios decrease with
increasing rotational number J for the AGN while they stay mostly constant for
the SB sources.Comment: accepted for publication in ApJ; 20 pages, 7 figures; in emulateApJ
forma
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