Browsing by Issue Date, starting with "2015-08"
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- Resonant energy transfer in Si Nanocrystal SolidsPublication . Limpens, Rens; Lesage, Arnon; Stallinga, Peter; Poddubny, Alexander N.; Fujii, Minoru; Gregorkiewicz, TomEnergy exchange between closely packed semiconductor quantum dots allows for long-range transfer of electronic energy and enables new functionalities of nanostructured materials with a huge application potential in photonics, optoelectronics, and photovoltaics. This is illustrated by impressive advances of quantum-dot solids based on nanocrystals (NCs) of direct bandgap materials, where this effect has been firmly established. Regretfully, the (resonant) energy transfer in close-packed ensembles of NCs remains elusive for silicon the main material for electronic and photovoltaic industries. This is the subject of the present study in which we conclusively demonstrate this process taking place in dense dispersions of Si NCs in an SiO2 matrix. Using samples with different NC configurations, we can directly determine the wavelength dependent energy transfer rate and show that it (i) can be modulated by material parameters, and (ii) decreases with the NCs size, and thus being consistent with the energy flow proceeding from smaller to larger NCs. This result opens the way to new applications of Si NCs, requiring energy transport and extraction. In particular, it forms a fundamental step toward development of an excitonic all-Si solar cell, operating in some analogy to polymer devices.
- Induction of defence responses by cinnamomins against Phytophthora cinnamomi in Quercus suber and Quercus ilex subs. rotundifoliaPublication . Cravador, A.; Martins, JorgeThe strong association between Phytophthora cinnamomi and the mortality and decline of Quercus suber and Q. ilex subsp. rotundifolia has been known for two decades. The ability of elicitins secreted by this pathogen to trigger defence responses in these Quercus against itself was evaluated in this work. Biomass quantification by quantitative real-time PCR revealed a significant decrease in pathogen colonization of Q. suber roots after 24 h pre-treatment with α- and β-cinnamomin. In Q. suber and Q. ilex roots pre-treated with α-cinnamomin, hyphae were unable to reach and colonize the vascular cylinder and showed cytoplasmic disorganization in all the roots observed as contrasted with non-pre-treated roots. The pathogen was restricted to the intercellular spaces of the cortical parenchyma and the concomitant accumulation of electron dense materials was observed in contact with the hyphae. Furthermore, ROS (reactive oxygen species) production and the enzymatic activities of superoxide dismutase, catalase and peroxidase were compared in infected and non-infected Quercus roots in time course trials. There was a significant increase in the production of hydrogen peroxide (H2O2) and superoxide anion (O2 •-) and an enhanced activity of the enzymes in infected roots was observed at each time point. When comparing with elicitin non-treated roots, the α-cinnamomin-treated roots in interaction with P. cinnamomi showed a decrease in ROS accumulation and an increase of the enzyme activities. The overall results were consistent with an induction by the cinnamomins which initiated defence responses against the pathogen invasion of roots. Finally, elicitins were immunolocalized in the contact zone of P. cinnamomi hyphae with epidermal host cells, plasmalemma outer cytoplasm and around the intracellular hyphae in the vacuoles of invaded epidermal cells.
- Xenopus Pkdcc1 and Pkdcc2 Are Two New Tyrosine Kinases Involved in the Regulation of JNK Dependent Wnt/PCP Signaling PathwayPublication . Vitorino, Marta; Silva, Ana Cristina; Inacio, Jose Manuel; Ramalho, Jose Silva; Gur, Michal; Fainsod, Abraham; Steinbeisser, Herbert; Belo, José A.Protein Kinase Domain Containing, Cytoplasmic (PKDCC) is a protein kinase which has been implicated in longitudinal bone growth through regulation of chondrocytes formation. Nevertheless, the mechanism by which this occurs remains unknown. Here, we identified two new members of the PKDCC family, Pkdcc1 and Pkdcc2 from Xenopus laevis. Interestingly, our knockdown experiments revealed that these two proteins are both involved on blastopore and neural tube closure during gastrula and neurula stages, respectively. In vertebrates, tissue polarity and cell movement observed during gastrulation and neural tube closure are controlled by Wnt/Planar Cell Polarity (PCP) molecular pathway. Our results showed that Pkdcc1 and Pkdcc2 promote the recruitment of Dvl to the plasma membrane. But surprisingly, they revealed different roles in the induction of a luciferase reporter under the control of Atf2 promoter. While Pkdcc1 induces Atf2 expression, Pkdcc2 does not, and furthermore inhibits its normal induction by Wnt11 and Wnt5a. Altogether our data show, for the first time, that members of the PKDCC family are involved in the regulation of JNK dependent Wnt/PCP signaling pathway.
- In vitro susceptibility of Leishmania infantum to Artemisinin derivatives and selected trioxolanesPublication . Cortes, Sofia; Albuquerque, Andreia; Cabral, Lília; Lopes, Liliana; Campino, Lenea; Cristiano, Maria L. S.Leishmaniasis is among the world's most neglected diseases. Currently available drugs for treatment present drawbacks, urging the need for more effective, safer, and cheaper drugs. A small library of artemisinin-derived trioxanes and synthetic trioxolanes was tested against promastigote and intramacrophage amastigote forms of Leishmania infantum. The trioxolanes LC50 and LC95 presented the best activity and safety profiles, showing potential for further studies in the context of leishmanial therapy. Our results indicate that the compounds tested exhibit peroxide-dependent activity.
- Primary fallopian tube carcinoma: review of MR imaging findingsPublication . Veloso Gomes, Filipe; Dias, Joao Lopes; Lucas, Rita; CUNHA, TERESA MARGARIDAObjectives To review the epidemiological and clinical features of primary fallopian tube carcinoma (PFTC), and to illustrate the spectrum of MRI findings, with pathological confirmation. Methods This article reviews the relevant literature on the epidemiological, clinical, and imaging features of primary fallopian tube carcinoma, with pathological confirmation, using illustrations from the authors' teaching files. Results Primary fallopian tube carcinoma came under focus over the last few years due to its possible role on the pathogenesis of high-grade serous epithelial ovarian and peritoneal cancers. Typical symptoms, together with the presence of some of the most characteristic MRI signs, such as a "sausage-shaped" pelvic mass, hydrosalpinx, and hydrometra, may signal the presence of primary fallopian cancer, and allow the radiologist to report it as a differential diagnosis. Conclusions Primary fallopian tube carcinoma has a constellation of clinical symptoms and magnetic resonance imaging features, which may be diagnostic. Although these findings are not present together in the majority of cases, radiologists who are aware of them may include the diagnosis of primary fallopian tube cancer in their report more frequently and with more confidence. Teaching Points PFTC may be more frequent than previously thought PFTC has specific clinical and MRI characteristics Knowledge of typical PFTC signs enables its inclusion in the differential diagnosis PFTC is currently staged under the 2013 FIGO system PFTC is staged collectively with ovarian and peritoneal neoplasms
- Spatial distribution patterns and movements of Holothuria arguinensis in the Ria Formosa (Portugal)Publication . Siegenthaler, Andjin; Canovas, Fernando; Gonzalez-Wangueemert, MercedesHolothurian populations are under pressure worldwide because of increasing demand for beche-de-mer, mainly for Asian consumption. Importations to this area from new temperate fishing grounds provide economic opportunities but also raise concerns regarding future over-exploitation. Studies on the habitat preferences and movements of sea cucumbers are important for the management of sea cucumber stocks and sizing of no-take zones, but information on the ecology and behavior of temperate sea cucumbers is scarce. This study describes the small-scale distribution and movement patterns of Holothuria arguinensis in the intertidal zone of the Ria Formosa national park (Portugal).Mark/recapture studieswere performed to record theirmovements over time on different habitats (sand and seagrass). H. arguinensis preferred seagrass habitats and did not show a size or life stage-related spatial segregation. Its density was 563 ind. ha−1 and mean movement speed was 10 m per day. Movement speed did not differ between habitats and the direction of movement was offshore during the day and shoreward during the night. Median home range size was 35 m2 and overlap among home ranges was 84%. H. arguinensis' high abundance, close association with seagrass and easy catchability in the intertidal zone, indicate the importance of including intertidal lagoons in future studies on temperate sea cucumber ecology since those systems might require different management strategies than fully submerged habitats.
- Role stress and job satisfaction: examining the mediating role of work engagementPublication . Orgambidez-Ramos, Alejandro; Perez-Moreno, Pedro J.; Borrego Alés, YolandaThe aim of this study is to examine the relationship between role stress, work engagement, and job satisfaction according to the Job Demands-Resources Model. The proposed model hypothesizes that work engagement mediates the relationship between role ambiguity, role conflict, and role overload on one hand, and job satisfaction on the other. To test the model, data was collected from 586 workers from southern Spain (M-age = 37.11, 50% women). Model fit and mediation test were examined using structural equation modeling (path analysis). Results showed that role conflict, role ambiguity, and work engagement were significant predictors of job satisfaction. However, work engagement did not mediate the relationship between role stress and job satisfaction. Role stress as a hindrance job demand would explain the most direct impact on job satisfaction than through work engagement. Implications for practice and future research are considered. (C) 2015 Colegio Oficial de Psicologos de Madrid. Published by Elsevier Espana, S.L.U.
- Rapid automatized naming and reading performance: a meta-analysisPublication . Araújo, Susana; Reis, Alexandra; Petersson, Karl Magnus; Faisca, LuisEvidence that rapid naming skill is associated with reading ability has become increasingly prevalent in recent years. However, there is considerable variation in the literature concerning the magnitude of this relationship. The objective of the present study was to provide a comprehensive analysis of the evidence on the relationship between rapid automatized naming (RAN) and reading performance. To this end, we conducted a meta-analysis of the correlational relationship between these 2 constructs to (a) determine the overall strength of the RAN-reading association and (b) identify variables that systematically moderate this relationship. A random-effects model analysis of data from 137 studies (857 effect sizes; 28,826 participants) indicated a moderate-to-strong relationship between RAN and reading performance (r = .43, I-2 = 68.40). Further analyses revealed that RAN contributes to the 4 measures of reading (word reading, text reading, non-word reading, and reading comprehension), but higher coefficients emerged in favor of real word reading and text reading. RAN stimulus type and type of reading score were the factors with the greatest moderator effect on the magnitude of the RAN-reading relationship. The consistency of orthography and the subjects' grade level were also found to impact this relationship, although the effect was contingent on reading outcome. It was less evident whether the subjects' reading proficiency played a role in the relationship. Implications for future studies are discussed.
- Model of polarization selectivity of the intermediate filament optical channelsPublication . Khmelinskii, Igor; Zueva, Lidia; Inyushin, Michail; Makarov, VladimirRecently we have analyzed light transmission and spectral selectivity by optical channels in Muller cells and other transparent cells, proposing a model of their structure, formed by specialized intermediate filaments [1,2]. Our model represents each optical channel by an axially symmetric tube with conductive walls. Presently, we analyze the planar polarization selectivity in long nanostructures, using the previously developed approach extended to structures of the elliptic cross-section. We find that the output light polarization degree depends on the a/b ratio, with a and b the semiaxes of the ellipse. Experimental tests used a Cr nano-strip device to evaluate the transmitted light polarization. The model adapted to the experimental geometry provided an accurate fit of the experimental results. Published by Elsevier B.V.
- Behind the mask: cryptic genetic diversity of Mytilus galloprovincialis along southern European and northern African shoresPublication . Lourenço, Carla R.; Nicastro, Katy; Serrao, Ester A.; Castilho, Rita; Zardi, GerardoMorphological uniformity in geographically widespread species may cause genetically distinct entities to pass unnoticed if they can only be detected by molecular approaches. The importance of uncovering such cryptic diversity is prompted by the need to understand the putative adaptive potential of populations along species ranges and to manage biodiversity conservation efforts. In this study, we aim to assess cryptic intraspecific genetic diversity and taxonomic status of the widely distributed intertidal mussel Mytilus galloprovincialis, along Atlantic southwestern (SW) Iberian, Atlantic northwestern (NW) Moroccan and Mediterranean Tunisian shores. By using mitochondrial (16S restriction-fragment length polymorphism) and nuclear (polyphenolic adhesive protein gene, Glu-5') markers, we discovered a more complex taxonomic diversity of M. galloprovincialis than previously known. Both Atlantic and Mediterranean haplogroups of M. galloprovincialis were detected along Atlantic SW Iberian shores along with M. galloprovincialis/edulis hybrids (92.2% Atlantic, 3.9% Mediterranean and 3.9% hybrids). In contrast, NW Moroccan populations consisted solely of Atlantic M. galloprovincialis. The Mediterranean populations did not include M. galloprovincialis/ edulis hybrids, but both Atlantic (58%) and Mediterranean (42%) lineages were detected. Divergent selection between coastlines and/or indirect larval dispersal by human activities may be the drivers of this geographically structured genetic diversity.