13,439 research outputs found
FCNCs in supersymmetric multi-Higgs doublet models
We conduct a general discussion of supersymmetric models with three families
in the Higgs sector. We analyse the scalar potential, and investigate the
minima conditions, deriving the mass matrices for the scalar, pseudoscalar and
charged states. Depending on the Yukawa couplings and the Higgs spectrum, the
model might allow the occurrence of potentially dangerous flavour changing
neutral currents at the tree-level. We compute model-independent contributions
for several observables, and as an example we apply this general analysis to a
specific model of quark-Higgs interactions, discussing how compatibility with
current experimental data constrains the Higgs sector.Comment: 30 pages, 9 figures. Comments and references added. Final version
published in Physical Review
Colheita de sementes de Brachiaria humidicola pelo método de sucção.
Colheita pelo método de sucção. Etapas da colheita. Vantagens do método. Desvantagens do método.bitstream/CNPGC-2010/13277/1/COT117.pd
The ionizing sources of luminous compact HII regions in the RCW106 and RCW122 clouds
Given the rarity of young O star candidates, compact HII regions embedded in
dense molecular cores continue to serve as potential sites to peer into the
details of high-mass star formation. To uncover the ionizing sources of the
most luminous and compact HII regions embedded in the RCW106 and RCW122 giant
molecular clouds, known to be relatively nearby (2-4 kpc) and isolated, thus
providing an opportunity to examine spatial scales of a few hundred to a
thousand AU in size. High spatial resolution (0.3"), mid-infrared spectra
(R=350), including the fine structure lines [ArIII] and [NeII], were obtained
for four luminous compact HII regions, embedded inside the dense cores within
the RCW106 and RCW122 molecular cloud complexes. At this resolution, these
targets reveal point-like sources surrounded by nebulosity of different
morphologies, uncovering details at spatial dimensions of <1000AU. The
point-like sources display [ArIII] and [NeII] lines - the ratios of which are
used to estimate the temperature of the embedded sources. The derived
temperatures are indicative of mid-late O type objects for all the sources with
[ArIII] emission. Previously known characteristics of these targets from the
literature, including evidence of disk or accretion suggest that the identified
sources may grow more to become early-type O stars by the end of the star
formation process
Crafting a Systematic Literature Review on Open-Source Platforms
This working paper unveils the crafting of a systematic literature review on
open-source platforms. The high-competitive mobile devices market, where
several players such as Apple, Google, Nokia and Microsoft run a platforms- war
with constant shifts in their technological strategies, is gaining increasing
attention from scholars. It matters, then, to review previous literature on
past platforms-wars, such as the ones from the PC and game-console industries,
and assess its implications to the current mobile devices platforms-war. The
paper starts by justifying the purpose and rationale behind this literature
review on open-source platforms. The concepts of open-source software and
computer-based platforms were then discussed both individually and in unison,
in order to clarify the core-concept of 'open-source platform' that guides this
literature review. The detailed design of the employed methodological strategy
is then presented as the central part of this paper. The paper concludes with
preliminary findings organizing previous literature on open-source platforms
for the purpose of guiding future research in this area.Comment: As presented in 10th IFIP WG 2.13 International Conference on Open
Source Systems, OSS 2014, San Jos\'e, Costa Rica, May 6-9, 201
The challenging modelling of kLa in a periodic constricted small-scale tube
An extensive use in chemistry, biological and pharmaceutical laboratories is envisaged for a novel continuous screening reactor based on the oscillatory flow technology (Harvey, 2001). The basic unit of this reactor was recently presented by Harvey et al. (2003) and Reis et al. (2004) and consists in a 4.4 mm internal diameter and 350 mm long jacketed glass small-scale tube provided
with smooth periodic constrictions, SPCs (Figure 1). Prediction of fluid mixing and residence time within this tube were successfully achieved with CFDs (Harvey et al. (2003) and Reis et al. (2004)), but modelling of oxygen mass-transfer coefficient forecast as a very challenging task.
Physical properties, sparger and column configuration, agitation/oscillation intensity, superficial gas velocity, all affects kLa, controlling the properties of gas-phase: bubble size, bubble velocity/residence time and gas hold-up. In all, the the overall volumetric mass transfer coefficient, kLa can
be affected by the mass transfer coefficient, kL or by the interfacial area, a.
Previous work with this novel reactor (Reis et al., in Proceedings of 16th CHISA, 2004)
demonstrated improved oxygen mass transfer rates. The modelling of kLa requires a good understand of liquid and gas-phase behaviours. The application of oscillatory flow motion to the constricted tube induced significant modification in bubbles trajectories, resulting in complex liquid-bubble mixing pattern, and made breakage and coalescence of bubbles become regular events in each cavity. Those patterns switch with the increase of mixing intensity (either by increasing the oscillation frequency and/or amplitude) in several regimes (Figure 2), in the same way as in conventional oscillatory flow reactors (OFRs): initially, bubbles move upward, but with the increase of oscillation intensity bubbles start to move downwards in certain phases of the oscillation cycle.
At intensive levels of oscillation, rising bubbles are trapped within each cell for several seconds thus staying in each cavity longer due to the motion of vortices as compared with a bubble column.
It was found that bubble size and hold-up contribute to the measured mass transfer enhancement but is the combination of small bubbles with the tortuous routes for bubbles to travel that promotes enhanced mass transfer. Moreover, the small-scale of the tube associated with the 1.6 mm internal
diameter of the constriction walls, makes the Taylor flow of gas bubbles contribution an important variable, requiring (or not) to be considered in kLa modelling. This question is bringing into discussion
A rapide method for separation of adults in a mixed population of Steinernema carpocapsae (Nematoda : Steinernematidae)
La sélection d'un grand nombre de nématodes viables est une condition impérative pour les études sur la physiologie de #Steinernema carpocapsae$. Est décrite ici une méthode rapide et pratique permettant la séparation des mâles et des femelles de ce nématode à partir d'une suspension contenant une population brute. Pour l'utilisation de cette méthode, la densité des mâles et des femelles est déterminée par application de la loi de Stokes modifiée. Les adultes sont séparés dans un gradient discontinu de saccharose s'étageant de 10 et 20%. Quatre-vingt quinze pour cent des mâles et des femelles isolés grâce à cette méthode restent viables. (Résumé d'auteur
Process intensification using a meso-scale oscillatory flow reactor
Meso-technologies are currently triggering a paradigm change in the design of chemical and
biochemical processes. Mass and heat transfer rates can readily be maximised in smaller,
sustainable, cheaper and safer plants, whilst virtually reducing the design of (bio) process
unit operations to the intrinsic kinetics of the system.
A novel meso-scale reactor running with oscillatory flow mixing was recently developed in the
University of Minho in collaboration with the University of Cambridge, UK. The oscillatory
meso-reactor (OMR) has shown an outstanding performance for gas-liquid contacting [1] and
particles suspension, and a fine control of the residence time distribution due to a superior
combination of the internal reactor geometry (OMR is composed of 5 mm internal diameter
tube provided with smooth periodic constrictions) and a well-proved mixing technology (i.e.
oscillatory flow).
Proof-of-concept experiments were carried out demonstrating the potential of the OMR in the
bioprocess intensification. The time scale for the production of -decalactone by Yarrowia
lipolytica in a gas-liquid-liquid system was halved and the yield of biomass on glucose nearly
doubled for the aerobic growth of Saccharomyces cerevisiae in comparison with parallel
trials in an aerated stirred tank fermentor [2].
The OMR is currently finding potential applications in the kg-per-day production of valueadded
pharmaceutical and biopharmaceuticals. Commercial computational fluid dynamics
tools have shown capable of predicting the flow patterns within the OMR, thus being valuable
tools in the design of unit operations based on this new technology
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