171 research outputs found
Analysis of indentation size effect in copper and its alloys
For describing the indentation size effect (ISE), numerous models, which relate the load or hardness to the indent dimensions, have been proposed. Unfortunately, it is still difficult to associate the different parameters involved in such relationships with physical or mechanical properties of the material. This is an unsolved problem since the ISE can be associated with various causes such as workhardening, roughness, piling-up, sinking-in, indenter tip geometry, surface energy, varying composition and crystal anisotropy. For interpreting the change in hardness with indent size, an original approach is proposed on the basis of composite hardness modelling together with the use of a simple model, which allows the determination of the hardness–depth profile. Applied to copper and copper alloys, it is shown that it is possible to determine the maximum hardness value reached at the outer surface of the material and the distance over which both the ISE and the workhardening take place
Evaluation of the VISAGE Basic Tool for Appearance and Ancestry Prediction Using PowerSeq Chemistry on the MiSeq FGx System
The study of DNA to predict externally visible characteristics (EVCs) and the biogeographical
ancestry (BGA) from unknown samples is gaining relevance in forensic genetics. Technical
developments in Massively Parallel Sequencing (MPS) enable the simultaneous analysis of hundreds of
DNA markers, which improves successful Forensic DNA Phenotyping (FDP). The EU-funded VISAGE
(VISible Attributes through GEnomics) Consortium has developed various targeted MPS-based lab
tools to apply FDP in routine forensic analyses. Here, we present an evaluation of the VISAGE Basic
tool for appearance and ancestry prediction based on PowerSeq chemistry (Promega) on a MiSeq FGx
System (Illumina). The panel consists of 153 single nucleotide polymorphisms (SNPs) that provide
information about EVCs (41 SNPs for eye, hair and skin color from HIrisPlex-S) and continental BGA
(115 SNPs; three overlap with the EVCs SNP set). The assay was evaluated for sensitivity, repeatability
and genotyping concordance, as well as its performance with casework-type samples. This targeted
MPS assay provided complete genotypes at all 153 SNPs down to 125 pg of input DNA and 99.67%
correct genotypes at 50 pg. It was robust in terms of repeatability and concordance and provided
useful results with casework-type samples. The results suggest that this MPS assay is a useful tool
for basic appearance and ancestry prediction in forensic genetics for users interested in applying
PowerSeq chemistry and MiSeq for this purpose
Robust model-based indicators of regional differences in food-web structure in the Southern Ocean
Efforts to model marine food-webs are generally undertaken by small teams working separately on specific regions (<106 km2) and making independent decisions about how to deal with data gaps and uncertainties. Differences in these largely arbitrary decisions (which we call ‘model personality’) can potentially obscure true differences between regional food-webs or lead to spurious differences. Here we explore the influence of model personality on a comparison of four Southern Ocean regional food-web models. We construct alternative model versions which sequentially remove aspects of personality (alternative model ‘currencies’, schemes for aggregating organisms into functional groups, and energetic parameter values). These alternative versions preserve regional differences in biomass and feeding relationships. Variation in a set of model metrics that are insensitive to absolute biomass and production identifies multiple regional contrasts, a subset of which are robust to differences in model personality. These contrasts imply real differences in ecosystem structure which, in conjunction with differences in primary production and consumer biomass (spanning two and four orders of magnitude respectively), underpin differences in function. Existing regional models are therefore a useful resource for comparing ecosystem structure, function and response to change if comparative studies assess and report the influence of model personality
Small Corrections to the Tunneling Phase Time Formulation
After reexamining the above barrier diffusion problem where we notice that
the wave packet collision implies the existence of {\em multiple} reflected and
transmitted wave packets, we analyze the way of obtaining phase times for
tunneling/reflecting particles in a particular colliding configuration where
the idea of multiple peak decomposition is recovered. To partially overcome the
analytical incongruities which frequently rise up when the stationary phase
method is adopted for computing the (tunneling) phase time expressions, we
present a theoretical exercise involving a symmetrical collision between two
identical wave packets and a unidimensional squared potential barrier where the
scattered wave packets can be recomposed by summing the amplitudes of
simultaneously reflected and transmitted wave components so that the conditions
for applying the stationary phase principle are totally recovered. Lessons
concerning the use of the stationary phase method are drawn.Comment: 14 pages, 3 figure
Helminth infection reactivates latent γ-herpesvirus via cytokine competition at a viral promoter
Mammals are coinfected by multiple pathogens that interact through unknown mechanisms. We found that helminth infection, characterized by the induction of the cytokine interleukin-4 (IL-4) and the activation of the transcription factor Stat6, reactivated murine γ-herpesvirus infection in vivo. IL-4 promoted viral replication and blocked the antiviral effects of interferon-γ (IFNγ) by inducing Stat6 binding to the promoter for an important viral transcriptional transactivator. IL-4 also reactivated human Kaposi's sarcoma-associated herpesvirus from latency in cultured cells. Exogenous IL-4 plus blockade of IFNγ reactivated latent murine γ-herpesvirus infection in vivo, suggesting a "two-signal" model for viral reactivation. Thus, chronic herpesvirus infection, a component of the mammalian virome, is regulated by the counterpoised actions of multiple cytokines on viral promoters that have evolved to sense host immune status
Fatigue behavior of a structural steel coated with a WC–10Co–4Cr/Colmonoy 88 deposit by HVOF thermal spraying
The fatigue behavior of a SAE 4340 steel, coated with a 50% WC–10Co–4Cr/50% Colmonoy 88 deposit, by high velocity oxygen fuel (HVOF) thermal spray, has been investigated. The change in the maximum alternating stress with the number of cycles to fracture has been described by means of the relationship advanced by Stromeyer. A fractographic analysis has been carried out on some representative fracture surfaces, by means of scanning electron microscopy (SEM) techniques. The mechanical properties of the coating were characterized by means of nanoindentation tests. The results indicate that the coating is highly heterogeneous. Its deposition gives rise to a decrease in the fatigue strength of the substrate of ∼ 30%, in comparison with the uncoated substrate. The decrease in fatigue strength is due to the presence of stress concentrators at the substrate–coating interface, as well as the intrinsic characteristics of the coating
Alterações nas propriedades químicas e microbianas de solos cultivados com videiras sob manejo orgânico e convencional no sul do Brasil
Multilocal programming and applications
Preprint versionMultilocal programming aims to identify all local minimizers of unconstrained
or constrained nonlinear optimization problems. The multilocal programming
theory relies on global optimization strategies combined with simple ideas
that are inspired in deflection or stretching techniques to avoid convergence to the
already detected local minimizers. The most used methods to solve this type of problems
are based on stochastic procedures and a population of solutions. In general,
population-based methods are computationally expensive but rather reliable in identifying
all local solutions. In this chapter, a review on recent techniques for multilocal
programming is presented. Some real-world multilocal programming problems
based on chemical engineering process design applications are described.Fundação para a Ciência e a Tecnologia (FCT
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