5,649 research outputs found
Deterministic model to evaluate the impact of lactational treatment of subclinical mastitis due to coagulase-negative staphylococci
Coagulase-negative staphylococci (CNS) are the most frequently isolated bacteria from milk samples in several studies worldwide. Despite their relative frequency, specific measures aiming at their control are not well established. One possible measure to include in a control programme is lactational antimicrobial treatment. The decision to perform such treatment, as well as other actions on farm, should be based on the likelihood of financial return. A deterministic model was used to evaluate whether performing an antimicrobial treatment during the lactation for quarters infected with CNS was financially justifiable. Input variables for the impact of CNS on udder health were based on a previous study by the same authors and on available literature on the subject. Prices included in the model were based on 2009/2010 conditions in Portugal. The average result per antimicrobial treated quarter was a net loss of (sic)38.74. Performing a sensitivity analysis to evaluate how systematic variation of the input variables of the model would lead to outcome changes showed that variation in input variables nearly always led to a negative outcome, with the greatest variation in losses observed for variation in the length of treatment and milk withdrawal period (-(sic)46.26 to -(sic)28.49). The situations in which a net benefit was to be expected included the bulk tank somatic cell count decreasing to a level corresponding to a premium payment or to penalties being avoided, and the prevention of transmission of CNS in the milking parlour when the possibility of transmission was at its highest level. For most situations, lactational treatment of CNS subclinical mastitis was not financially justifiable
Geometry, stochastic calculus and quantum fields in a non-commutative space-time
The algebras of non-relativistic and of classical mechanics are unstable
algebraic structures. Their deformation towards stable structures leads,
respectively, to relativity and to quantum mechanics. Likewise, the combined
relativistic quantum mechanics algebra is also unstable. Its stabilization
requires the non-commutativity of the space-time coordinates and the existence
of a fundamental length constant. The new relativistic quantum mechanics
algebra has important consequences on the geometry of space-time, on quantum
stochastic calculus and on the construction of quantum fields. Some of these
effects are studied in this paper.Comment: 36 pages Latex, 1 eps figur
Eficiência de colhedeiras de forragem tipo Taarup na produção de feno de capim brachiaria (Brachiaria decumbens Stapf).
Avaliação do desempenho de colhedeira de forragem tipo Taarup como equipamento alternativo para a produção de feno.Resumo
Can aerosols be trapped in open flows?
The fate of aerosols in open flows is relevant in a variety of physical
contexts. Previous results are consistent with the assumption that such
finite-size particles always escape in open chaotic advection. Here we show
that a different behavior is possible. We analyze the dynamics of aerosols both
in the absence and presence of gravitational effects, and both when the
dynamics of the fluid particles is hyperbolic and nonhyperbolic. Permanent
trapping of aerosols much heavier than the advecting fluid is shown to occur in
all these cases. This phenomenon is determined by the occurrence of multiple
vortices in the flow and is predicted to happen for realistic particle-fluid
density ratios.Comment: Animation available at
http://www.pks.mpg.de/~rdvilela/leapfrogging.htm
Área do piquete e taxa de lotação no pastejo rotacionado.
ABSTRACT: During the last two decades, rotational grazing has been increasingly adopted in cattle farms in the Cerrado Region. However, many farmers and extensionists are still having problems in designing efficient pastoral systems based on rotational grazing. This paper briefly describes the basic concepts of this grazing method and provides key steps to be followed in planning pasture area and stocking rate in rotational grazing.bitstream/CPAC-2009/27320/1/comtec_101.pd
Propriedades calorimétricas da água e vidros citoplasmáticos associados à tolerância a dessecação em sementes de Coffee arabica L.
Silk bilayer scaffolds can induce fast integration with subchondral bone and support cartilage repair
Publicado em : J Tissue Eng Regen Med 2014; 8 (Suppl. 1)Introduction: Osteochondral defect (OCD) regeneration presents major
challenges in orthopedics. Since healing of cartilage and bone should
be simultaneously considered, ideal scaffolds should be those that can
mimic both tissues properties. In this study, bilayered silk and silk-nano
calcium phosphate (Silk/Silk-NanoCaP) scaffolds with tailored
mechanical properties were developed for OCD tissue engineering
application.
Materials and methods: Aqueous silk solution (16%) was prepared.1
Nano calcium phosphate particles (16%) were synthesized in the silk
solution (Silk-NanoCaP).2 The bony layer was prepared by addition of
NaCl particles (500–1000 lm) into the Silk-NanoCaP suspension. After
drying for 2 days and salt-leaching overnight, silk solution was added
on top of the bony layer using the same procedure to produce the chondral
layer. The !nal scaffolds were evaluated through in vitro culture of
rabbit bone marrow stromal cells (RBMSCs) for 2 weeks, and in vivo
implantation in a rabbit knee OCD for 4 weeks.
Results: The RBMSCs cultured in the scaffolds presented increasing
viability from day 1 to day 7 by MTS assay. Good adhesion and migration
of the RBMSCs in the scaffolds were achieved, as observed under
the scanning electron microscope. Cell proliferation was observed from
day 7 to day 14 as determined by DNA quanti!cation. The bony layer
induced higher alkaline phosphatase level as compared to the chondral
layer, in osteogenic condition. Histological analysis (H&E) showed that
the bilayered scaffolds integrated well with the host tissue, after
4 weeks of implantation in a critical size OC defect (Fig. 1). Abundant
new bone formation was detected in the Silk-NanoCaP layer. Cartilage
regeneration occurred in the silk layer.
Discussion and conclusions: The bilayered scaffolds favored the attachment,
proliferation, and differentiation of RBMSCs. The bony layer of
the bilayered scaffolds possessed osteoconductive properties. The bilayered
scaffolds were biocompatible in vitro and in vivo. These scaffolds
also induced both subchondral bone regeneration and supported cartilage
regeneration, thus showing great promise in OCD regeneration.
Acknowledgments: The authors thank FCT projects Tissue2Tissue and
OsteoCart, and the FP7 Programme POLARIS. Yan LP was awarded a
FCT PhD scholarship. Investigador FCT program (IF/00423/2012) and
(IF/00411/2013) are also greatly acknowledged.
Disclosure: The authors declare that there is no con"ict of interest
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