931 research outputs found
Combining filter method and dynamically dimensioned search for constrained global optimization
In this work we present an algorithm that combines the filter technique and the dynamically dimensioned search (DDS) for solving nonlinear and nonconvex constrained global optimization problems. The DDS is a stochastic global algorithm for solving bound constrained problems that in each iteration generates a randomly trial point perturbing some coordinates of the current best point. The filter technique controls the progress related to optimality and feasibility defining a forbidden region of points refused by the algorithm. This region can be given by the flat or slanting filter rule. The proposed algorithm does not compute or approximate any derivatives of the objective and constraint functions. Preliminary experiments show that the proposed algorithm gives competitive results when compared with other methods.The first author thanks a scholarship supported by the International
Cooperation Program CAPES/ COFECUB at the University of Minho.
The second and third authors thanks the support given by FCT (Funda¸c˜ao para
Ciˆencia e Tecnologia, Portugal) in the scope of the projects: UID/MAT/00013/2013
and UID/CEC/00319/2013. The fourth author was partially supported by CNPq-Brazil
grants 308957/2014-8 and 401288/2014-5.info:eu-repo/semantics/publishedVersio
ruvA Mutants that resolve Holliday junctions but do not reverse replication forks
RuvAB and RuvABC complexes catalyze branch migration and resolution of Holliday junctions (HJs) respectively. In addition to their action in the last steps of homologous recombination, they process HJs made by replication fork reversal, a reaction which occurs at inactivated replication forks by the annealing of blocked leading and lagging strand ends. RuvAB was recently proposed to bind replication forks and directly catalyze their conversion into HJs. We report here the isolation and characterization of two separation-of-function ruvA mutants that resolve HJs, based on their capacity to promote conjugational recombination and recombinational repair of UV and mitomycin C lesions, but have lost the capacity to reverse forks. In vivo and in vitro evidence indicate that the ruvA mutations affect DNA binding and the stimulation of RuvB helicase activity. This work shows that RuvA's actions at forks and at HJs can be genetically separated, and that RuvA mutants compromised for fork reversal remain fully capable of homologous recombination
Semi-Holographic Fermi Liquids
We show that the universal physics of recent holographic non-Fermi liquid
models is captured by a semi-holographic description, in which a dynamical
boundary field is coupled to a strongly coupled conformal sector having a
gravity dual. This allows various generalizations, such as a dynamical exponent
and lattice and impurity effects. We examine possible relevant deformations,
including multi-trace terms and spin-orbit effects. We discuss the matching
onto the UV theory of the earlier work, and an alternate description in which
the boundary field is integrated out.Comment: 26 pages, 4 figures; v2: typos corrected and report number adde
The origin of dust in galaxies revisited: the mechanism determining dust content
The origin of cosmic dust is a fundamental issue in planetary science. This
paper revisits the origin of dust in galaxies, in particular, in the Milky Way,
by using a chemical evolution model of a galaxy composed of stars, interstellar
medium, metals (elements heavier than helium), and dust. We start from a review
of time-evolutionary equations of the four components, and then, we present
simple recipes for the stellar remnant mass and yields of metal and dust based
on models of stellar nucleosynthesis and dust formation. After calibrating some
model parameters with the data from the solar neighborhood, we have confirmed a
shortage of the stellar dust production rate relative to the dust destruction
rate by supernovae if the destruction efficiency suggested by theoretical works
is correct. If the dust mass growth by material accretion in molecular clouds
is active, the observed dust amount in the solar neighborhood is reproduced. We
present a clear analytic explanation of the mechanism for determining dust
content in galaxies after the activation of accretion growth: a balance between
accretion growth and supernova destruction. Thus, the dust content is
independent of the uncertainty of the stellar dust yield after the growth
activation. The timing of the activation is determined by a critical metal mass
fraction which depends on the growth and destruction efficiencies. The solar
system formation seems to have occurred well after the activation and plenty of
dust would have existed in the proto-solar nebula.Comment: 12 pages, 11 figure
Phronetic workplace: a step forward into a practically wise Company
Phronesis (practical wisdom) is introduced in the management field as a possible solution to the problems associated with wild capitalism. Although its highly sustainable performance characterizes a phronetic company through innovativeness and shared value creation, there is yet a gap in the literature concerning workplace phronesis' perspective in management. We propose integrating organizational spirituality and organizational phronesis theories in management research to address the phronetic workplace. This study contributes to shedding light on the understanding of phronesis in management addressing group behavior and how individual phronesis spreads into the workplace towards the phronetic organization
Organizational spirituality and knowledge management supporting organizational practical wisdom
This study aims to understand how knowledge management and organizational spirituality support organizational practical wisdom. There is a growing aspiration among some organizations to do good to society while measuring sufficient profits for its innovation and evolution. Practical wisdom has pillars related to spirituality (by seeking the best result from their actions, doing as little harm as possible) and knowledge management (by needing social and technical knowledge to weigh decision making). Practical wisdom needs action, and the best result. A systematic literature review was developed to understand the state of the art. It was not enough to propose a theoretical framework. So, an integrative literature review was developed. The scrutiny was successful in producing a theoretical framework with propositions. The present article has two main contributions, the systematization of the state of the art and the suggestion of a theoretical framework
Aortic valvuloplasty of calcific aortic stenosis with monofoil and trefoil balloon catheters: practical considerations
In order to evaluate the relation between balloon design (monofoil, trefoil) and valvular configuration, experimental aortic valvuloplasty was performed in four post-mortem hearts with calcific aortic sten
Carcass persistence and detectability : reducing the uncertainty surrounding wildlife-vehicle collision surveys
Carcass persistence time and detectability are two main sources of uncertainty on roadkill surveys. In this study, we evaluate the influence of these uncertainties on roadkill surveys and estimates. To estimate carcass persistence time, three observers (including the driver) surveyed 114km by car on a monthly basis for two years, searching for wildlife-vehicle collisions
(WVC). Each survey consisted of five consecutive days. To estimate carcass detectability, we randomly selected stretches of 500m to be also surveyed on foot by two other observers (total 292 walked stretches, 146 km walked). We expected that body size of the carcass, road type, presence of scavengers and weather conditions to be the main drivers influencing the carcass persistence times, but their relative importance was unknown. We also expected detectability to be highly dependent on body size. Overall, we recorded low
median persistence times (one day) and low detectability (<10%) for all vertebrates. The results indicate that body size and landscape cover (as a surrogate of scavengers' presence) are the major drivers of carcass persistence. Detectability was lower for animals with body mass less than 100g when compared to carcass with higher body mass. We estimated that our recorded mortality rates underestimated actual values of mortality by 2±10 fold. Although persistence times were similar to previous studies, the detectability rates here described are very different from previous studies. The results suggest that detectability is the main source of bias across WVC studies. Therefore, more than persistence times, studies should carefully account for differing detectability when comparing WVC studies
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Effects of conversion of native cerrado vegetation to pasture on soil hydro-physical properties, evapotranspiration and streamflow on the Amazonian agricultural frontier
Understanding the impacts of land-use change on landscape-hydrological dynamics is one of the main challenges in the Northern Brazilian Cerrado biome, where the Amazon agricultural frontier is located. Motivated by the gap in literature assessing these impacts, we characterized the soil hydro-physical properties and quantified surface water fluxes from catchments under contrasting land-use in this region. We used data from field measurements in two headwater micro-catchments with similar physical characteristics and different land use, i.e. cerrado sensu stricto vegetation and pasture for extensive cattle ranching. We determined hydraulic and physical properties of the soils, applied ground-based remote sensing techniques to estimate evapotranspiration, and monitored streamflow from October 2012 to September 2014. Our results show significant differences in soil hydro-physical properties between the catchments, with greater bulk density and smaller total porosity in the pasture catchment. We found that evapotranspiration is smaller in the pasture (639 ± 31% mm yr-1) than in the cerrado catchment (1,004 ± 24% mm yr-1), and that streamflow from the pasture catchment is greater with runoff coefficients of 0.40 for the pasture and 0.27 for the cerrado catchment. Overall, our results confirm that conversion of cerrado vegetation to pasture causes soil hydro-physical properties deterioration, reduction in evapotranspiration reduction, and increased streamflow
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