745 research outputs found
A dynamic programming approach for evaluating a portfolio of R&D projects with a budget
The Real Options approach has proved to be a suitable methodology for capturing the flexibility in the investment decision process. This is very useful for the financial evaluation of R&D projects where there are several possible decisions concerning to the investment – delaying, improving or abandoning. Since the risk of an R&D project is usually due to singular characteristics of the project and is uncorrelated with the financial markets, the contingent claims analysis may be not adequate to value R&D projects. Based on a dynamic programming evaluation model, presented in Huchzermeier and Loch [1], we propose an approach to valuing a portfolio of R&D projects with a budget. Specifically, considering a budget constraint, we make an extension of the model mentioned above for assessing the projects in the portfolio simultaneously. To test the proposed evaluation procedure, we generated several R&D portfolios with different dimensions and characteristics. According to our computational experience, the main conclusions are presented
Molecular structure and charge density analysis of p-methoxybenzoic acid (anisic acid)
A concerted X-ray and ab initio SCF-MO study of the structure and charge density of p-methoxybenzoic acid (anisic acid) is reported. An extensive X-ray data set (7401 reflections) was measured on a single crystal using Mo Kα radiation and the structure refined with 2121 unique reflections, leading to a final R(F)-factor of 0.047 calculated for reflections with I>2σ. The molecular geometry of crystalline anisic acid, where the molecules dimerize via a moderately strong CO–H⋯O hydrogen bond, is compared with that of the isolated molecule, resulting from SCF-MO ab initio calculations. A topological analysis of the molecular charge density was performed using Bader's method to gain insight into the dominant intra- and intermolecular interactions in this compound. In particular, the effects of the substituents on the observed distortions of the benzene ring were investigated as well as the internal rotation of the methyl group
Magnetostructural correlations in BiFeO3-based multiferroics
This work was supported by funds from FEDER (Programa Operacional Factores de Competitividade COMPETE) and from FCT-Fundaça˜o para a Cieˆncia e a Tecnologia under the project UID/FIS/04564/2016. V. A. K. is grateful to Fundaça˜o para a Cieˆncia e a Tecnologia for financial support through the FCT Investigator Programme (project IF/00819/2014). D. V. K. is grateful to BRFFR (grant F16R-066). Access to the TAIL-UC facility funded under QREN-Mais Centro project ICT_2009_02_012_1890 is gratefully acknowledged
3β-Acetoxy-lup-20(29)-en-28-yl 1H-1,2,4-triazole-1-carboxylate
The title triterpene, C35H53N3O4, is a C-28 carbamate derivative of 3β-acetoxybetulin prepared in a one-step reaction from the commercially available 1,1′-carbonyl-di(1,2,4-triazole) (CDT), crystallized from acetone/n-hexane. All rings are trans fused. The carbamate and acetate substituents are in axial and equatorial positions, respectively. A quantum chemical ab initio Roothaan Hartree–Fock calculation of the equilibrium geometry of the isolated molecule gives values for bond lengths and valency angles in close agreement with experimental values. The calculation also reproduces the observed molecular conformation, with puckering parameters that agree well with those determined from the crystallographic study
Spin exchange in elastic e-O_2 collisions
Recent experiments using polarized electron beams have shown that spin exchange effects for elastic collisions with O_2 and NO are much smaller than for Na atoms. We report calculated spin-flip differential cross sections for elastic collisions of polarized electrons with O_2 in agreement with experiment. In general, we can attribute the large variation of the spin-flip differential cross sections to resonances and interference effects. Such features arising from interference, however, may be washed out in the molecular case due to the average over orientations. Calculations with oriented O_2 molecules show strong exchange effects as for Na
Investigar e inovar na educação em ciências para um futuro sustentável
No pico de uma real situação de emergência planetária, a educação torna-se a melhor
aliada de uma luta global com vista a um desenvolvimento sustentável. Para
concretizar a Década da Educação para um Futuro Sustentável, a investigação em
educação em ciências e a correspondente inovação na formação de professores e no
ensino, apresentam-se entre os contributos mais fortes, amplos e eficazes. Parte do
nosso contributo, que se apresenta neste artigo, tem passado pelo desenvolvimento
de alguns estudos situados no quadro teórico que sustenta a educação CTS e assentes
em temáticas centrais para a educação para a sustentabilidade ambiental: os
transportes e a mobilidade, o uso da água, a fome no mundo, a preservação da
biodiversidade. A aposta tem-se dirigido para o ensino nos primeiros anos através do
desenho de propostas didácticas validadas por especialistas e em sala de aula e
utilizadas quer no ensino quer como ferramentas de formação inicial e contínua de
professores
Probing the interference between non-linear, axionic and space-time-anisotropy effects in the QED vacuum
We pursue the investigation of a generic non-linear extension of axionic
electrodynamics (ED) in a Carroll-Field-Jackiw (CFJ) scenario that implements
Lorentz-symmetry violation (LSV). The model consists of an arbitrary non-linear
ED action coupled to the axion field in presence of an anisotropy four-vector
that realizes the breaking of Lorentz symmetry under the particle point of
view. The non-linear electromagnetic field is expanded around a constant and
uniform magnetic background up to second order in the propagating photon field.
Our attention is the study of the material properties of the vacuum in the
particular case of a space-like CFJ -vector. The dispersion relations
associated to the plane wave solutions are explicitly worked out in two
situations: the magnetic background perpendicular and parallel to the wave
direction. We extend these results to consider the analysis of the
birefringence phenomenon in presence of non-linearity, the axion and the LSV
manifested through the spatial anisotropy. Three specific proposals of
non-linear ED are contemplated: Euler-Heisenberg, Born-Infeld and the Modified
Maxwell ED. Throughout the paper, we shall justify why we follow the unusual
path of connecting, in a single Lagrangian density, three pieces of physics
beyond the Standard Model, namely, non-linearity, axions and LSV. We anticipate
that we shall not be claiming that the simultaneous introduction of these three
topics beyond the Standard Model will bring new insights or clues for the
efforts to detect axions or to constrain parameters associate to both
non-linear ED and LSV physics . Our true goal is to actually inspect and
describe how axionic, non-linear and LSV effects interfere with one another
whenever physical entities like refraction indices and birefringence are
computed in presence of an external constant and homogeneous magnetic
background.Comment: 27 pages, no figure
The axion-photon mixing in non-linear electrodynamic scenarios
In this contribution, we re-assess some aspects of axionic electrodynamics by
coupling non-linear electromagnetic effects to axion physics. We present a
number of motivations to justify the coupling of the axion to the photon in
terms of a general non-linear extension of the electromagnetic sector. Our
emphasis in the paper relies on the investigation of the constitutive
permittivity and permeability tensors, for which the axion contributes by
introducing dependence on the frequency and wave vector of the propagating
radiation. Also, we point out how the axion mass and the axion-photon-photon
coupling constant contribute to a dispersive behavior of the electromagnetic
waves, in contrast to what happens in the case of non-linear extensions, when
effective refractive indices appear which depend only on the direction of the
propagation with respect to the external fields. The axion changes this picture
by yielding refractive indices with dependence on the wavelength. We apply our
results to the special case of the Born-Infeld Electrodynamics and we show that
it becomes birefringent whenever the axion is coupled. The paper is
supplemented by an Appendix, where we approach the recent discussion on the
controversy in defining the Poynting vector of axionic electrodynamics. We
present our path to tackle the question and give the expressions we work out
for both the Poynting vector and the momentum density transported by the waves.Comment: 30 pages, no figure
Influence of temperature and fat content on ideal sucrose concentration, sweetening power, and sweetness equivalence of different sweeteners in chocolate milk beverage
CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOThe introduction of new products catering to specific dietary needs and the corresponding changes in the consumer profile reflect a growing demand for diet and "light" products. However, little information is available regarding the sensory effects of different sweeteners in products consumed at different temperatures and with varying fat contents. In this regard, this study aimed to determine the influence of temperature and fat content on the ideal sucrose concentration and the sweetness equivalence and sweetening power of different sweeteners: Neotame (NutraSweet Corp., Chicago, IL), aspartame, neosucralose, sucralose, and stevia (95% rebaudioside A), with sucrose as reference, in a chocolate milk beverage using a just-about-right (JAR) scale and magnitude estimation. Increasing temperature of consumption had an inverse effect on the ideal sucrose concentration in whole milk beverages, whereas no difference was noted in beverages made skim milk. In addition, a decrease in sweetening power was observed for all of the sweeteners analyzed considering the same conditions. The findings suggest that different optimal conditions exist for consumption of chocolate milk beverage related to sweetness perception, which depends on the fat level of milk used in the formulation. This information can be used by researchers and dairy processors when developing chocolate milk beverage formulations.New products catering to specific dietary needs and the corresponding changes in the consumer profile reflect a growing demand for diet and “light” products. However, little information is available regarding the sensory effects of different sweeteners in products consumed at different temperatures and with varying fat contents. In this regard, this study aimed to determine the influence of temperature and fat content on the ideal sucrose concentration and the sweetness equivalence and sweetening power of different sweeteners: Neotame (NutraSweet Corp., Chicago,IL), aspartame, neosucralose, sucralose, and stevia (95% rebaudioside A), with sucrose as reference, in a chocolate milk beverage using a just-about-right (JAR) scale and magnitude estimation. Increasing temperature of consumption had an inverse effect on the ideal sucrose concentration in whole milk beverages, whereas no difference was noted in beverages made skim milk. In addition, a decrease in sweetening power was observed for all of the sweeteners analyzed considering the same conditions. The findings suggest that different optimal conditions exist for consumption of chocolate milk beverage related to sweetness perception, which depends on the fat level of milk used in the formulation. This information can be used by researchers and dairy processors when developing chocolate milk beverage formulations971273447353CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGIC
Pharmacogenetic: screening relevant polymorphisms on antiretroviral therapy in a HIV Portuguese population
Poster presented at the 15th European AIDS Conference. Barcelona, 21-24 October 2015"Several factors cause heterogeneity of response to antiretroviral therapy. Genetic polymorphisms, particularly in metabolizing enzyme, cytochrome P450 isoenzymes and transport proteins MDR, MRP and SLC, may cause pharmacokinetic variability in some ARVs, leading to viral failure, drug toxicity and may explain the interpatient variability for drug absorption pathways.
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