Browsing by Issue Date, starting with "2013-08"
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- Free daily newspapers : too strong incentives to print?Publication . Correia-da-Silva, João; Resende, JoanaA free daily newspaper distributes news to readers and sells ad-space to advertisers, having private information about its audience. For a given number of distributed copies, depending on the type of audience (favorable or unfavorable), the newspaper may either have a large readership or a small readership. A large readership provides a greater return to advertisers, because ads are visualized by more people. A favorable audience has also the advantage of requiring a lower distribution cost (for a given number of distributed copies), because readers are willing to exert more effort to obtain a copy of the free newspaper and are less likely to reject a copy that is handed to them. We find that when the audience is unfavorable, the number of distributed copies and the price of ad-space coincide with those of the perfect information scenario. In contrast, if the audience is favorable, the newspaper prints extra copies to send a credible signal to the advertisers that the audience is favorable. Overprinting is not necessarily welfare-detrimental since readers benefit from the existence of additional copies.
- O convencionalismo de Poincaré contextualizado: origem e significadoPublication . Paz, María de
- Heteroskedasticity testing through a comparison of Wald statisticsPublication . Murteira, José M.R.; Ramalho, Esmeralda A.; Ramalho, Joaquim J.S.This paper shows that a test for heteroskedasticity within the context of classical linear regression can be based on the difference between Wald statistics in heteroskedasticity-robust and nonrobust forms. The test is asymptotically distributed under the null hypothesis of homoskedasticity as chi-squared with one degree of freedom. The power of the test is sensitive to the choice of parametric restriction used by the Wald statistics, so the supremum of a range of individual test statistics is proposed. Two versions of a supremum-based test are considered: the first version does not have a known asymptotic null distribution, so the bootstrap is employed to approximate its empirical distribution. The second version has a known asymptotic distribution and, in some cases, is asymptotically pivotal under the null. A simulation study illustrates the use and finite-sample performance of both versions of the test. In this study, the bootstrap is found to provide better size control than asymptotic critical values, namely with heavy-tailed, asymmetric distributions of the covariates. In addition, the use of well-known modifications of the heteroskedasticity consistent covariance matrix estimator of OLS coefficients is also found to benefit the tests’ overall behaviour.
- Dynamic linkages between stock markets : the effects of crises and globalizationPublication . Doman, Małgorzata; Doman, RyszardThis paper investigates changes in the dynamics of linkages between selected national stock markets during the period 1995–2009. The analysis focuses on the possible effects of globalization and differences between crisis and non-crisis periods. We model the dynamics of dependencies between the series of daily returns on selected stock indices over different time periods, and compare strength of the linkages. Our tools are dynamic copula models and a formal sequential testing procedure based on the model confidence set methodology. We consider two types of dependencies: regular dependence measured by means of the conditional Spearman’s rho, and dependencies in extremes quantified by the conditional tail dependence coefficients. The main result consists of a collection of rankings created for the considered subperiods, which show how the mean level of strength of the dependencies have been changing in time. The rankings obtained for Spearman’s rho and tail dependencies differ, which allows us to distinguish between the results of crises and the effect of globalization.
- Myogenic oscillations in rabbit ocular vasculature are very low frequencyPublication . Delgado, E.; Marques-Neves, C.; Rocha, I.; Sales-Luís, J.; Silva-Carvalho, L.Background/Aims: In a previously described model of isolated rabbit eye, we detected myogenic intrinsic vascular tone of unknown origin in the ophthalmic artery. In order to better understand the origin of these low frequency oscillations, we analyzed their spectral characteristics using fast Fourier. Methods: Hybrid New Zealand rabbits of either sex (n = 24) were used; they were divided into 2 groups according to age. The spectral characteristics of the myogenic behaviour of the rabbit external ophthalmic artery were analyzed using the fast Fourier algorithm. Results: The frequency of the oscillations of the myogenic activity seen in the rabbit external ophthalmic artery varied between 0.033 and 0.066 Hz (mean 0.045 ± 0.012 Hz), all in the region of very low frequency (VLF) oscillations (VLF <0.07 Hz for the rabbit). The frequency of spontaneous oscillations was higher in younger animals. Conclusion: Fast Fourier analysis proved to be an adequate mathematical tool to analyze the myogenic tone oscillations, which were all in the range of VLF in the model we used. These results indicate that myogenic vascular function of ocular blood flow is composed of VLF oscillations, and they provide a new explanation for the origin of VLF in arterial spectra. They also suggest that the ocular local myogenic vascular function observed is more efficient in younger animals
- The family 6 carbohydrate-binding module (CtCBM6B) of Clostridium thermocellum alpha-L-arabinofuranosidase binds xylans and thermally stabilized by Ca2+ ionsPublication . Ahmed, Shadab; Luis, Ana Sofia; Brás, Joana L. A.; Fontes, Carlos M. G. A.; Goyal, ArunThe gene encoding CtCBM6B of Clostridium thermocellum α-L-arabinofuranosidase (Ct43Araf) was cloned in pET-21a(+) vector, over-expressed using Escherichia coli BL-21(DE3) cells and purified by immobilized metal-ion affinity chromatography (IMAC). The recombinant CtCBM6B showed a molecular size close to 15 kDa by SDS-PAGE analysis, which was close to the expected size of 14.74 kDa. The ligand-binding affinity of CtCBM6B was assessed against ligands for which the catalytic enzyme, Ct43Araf showed maximum activity. The affinity-gel electrophoresis of CtCBM6B with rye arabinoxylan showed lower equilibrium association constant (Ka, 4.0% C− 1), whereas, it exhibited higher affinity (Ka, 19.6% C− 1) with oat spelt xylan. The ligand-binding analysis of CtCBM6B by fluorescence spectroscopy also revealed similar results with low Ka (3.26% C− 1) with rye arabinoxylan and higher affinity for oat spelt xylan (Ka, 17.9% C− 1) which was corroborated by greater blue-shift in case of oat spelt xylan binding. The CtCBM6B binding with insoluble wheat arabinoxylan by adsorption isotherm analysis showed significant binding affinity as reflected by the equilibrium association constant (Ka), 9.4 × 103 M− 1. The qualitative analysis by SDS-PAGE also corroborated the CtCBM6B binding with insoluble wheat arabinoxylan. The protein-melting curve of CtCBM6B displayed the peak shift from 53°C to 59°C in the presence of Ca2+ ions indicating that Ca2+ ions impart thermal stability to the CtCBM6B structure.
- Historical embayed coastal evolution under a high energetic hydrodynamic eventPublication . Ramos Pereira, A.; Trindade, J.; Luísa-Costa, A.; Danielsen, R.; Matos Martins, J.M.The Portuguese coast of Estremadura (NW of Lisbon) is a present day cliff coast with narrow embayed beaches, most of them with estuaries of small catchment rivers. The case study covers 2100m coastline and an indentation ranging between 200m to 300m. The embayment is open to W and SW waves, but sheltered to NW dominant waves. The waves can reach 2,5m of significant height (Hs) during winter and storms (Hs>5m) are frequent. The research was developed in the framework of the FMI 5000 Project dealing with the evaluation of the balance between fluvial and marine influences, as well as the impact of extreme events.
- Rabbit muscle proteomics : a great leap forwardPublication . Almeida, André MartinhoThe rabbit is an important species as both a production animal and as a model organism in physiology, pharmaceutical, and numerous other studies. Similar to other species, the rabbit skeletal muscle proteome has been characterized, first using 2DE mapping and more recently using high-throughput shotgun proteomics. This article is a commentary on “Shotgun proteomics analysis of the sarcoplasmic reticulum preparations from rabbit skeletalmuscle” (Z. Liu et al., Proteomics, 2013, 13, 2335–2338).Herein, we present the reasons why the manuscript is of high relevance to three major fields: farm animal, rabbit, and muscle/meat proteomics.
- For host factors weddings and a Koch’s bacillus funeral: actin, lipids, phagosome maturation and inflammasome activationPublication . Anes, Elsa; Cardona, Pere-JoanThe chapter describes the 10 years research of Anes Laboratory on the interactions of M. tuberculosis with macrophages namely with the actin. modulation by lipids, phagosome maturation and inflammasome activation
- Dynamics of notch pathway expression during mouse testis post-natal development and along the spermatogenic cyclePublication . Murta, Daniel; Batista, Marta; Silva, Elisabete; Trindade, Alexandre; Henrique, Domingos; Duarte, António; Lopes da Costa, LuísThe transcription and expression patterns of Notch pathway components (Notch 1–3, Delta1 and 4, Jagged1) and effectors (Hes1, Hes2, Hes5 and Nrarp) were evaluated (through RT-PCR and IHC) in the mouse testis at key moments of post-natal development, and along the adult spermatogenic cycle. Notch pathway components and effectors are transcribed in the testis and expressed in germ, Sertoli and Leydig cells, and each Notch component shows a specific cell-type and timewindow expression pattern. This expression at key testis developmental events prompt for a role of Notch signaling in prepubertal spermatogonia quiescence, onset of spermatogenesis, and regulation of the spermatogenic cycle.