249 research outputs found
Design of three step joint typologies: review of european standardized approaches
When assessing timber roof structures on-site for any restoration project, engineers can be
faced with elements that, over time, were poorly preserved, especially damaged joints in
contact with moist masonry walls. Before dealing with any intervention technique, the
mechanical behaviour of such carpentry connections must be properly understood.
Therefore, it has to be determined how the joints fail, which parameters (i.e. geometrical
configurations and mechanical properties of the joint) influence the appearance conditions
of failure modes, and the way how the internal forces are distributed within the connection.
Therefore, the present paper aims at overviewing three different typologies of Step Joints
(SJ) which can often be encountered within traditional timber carpentries between the rafter
and the tie beam: the Single Step Joint, the Double Step Joint, and the Single Step Joint with
Tenon-Mortise. Regarding each SJ typology, some design rules and geometrical
recommendations can be gathered from European Standards and from authors of works on
the subject, but no design equation is conventionally defined. Hence, new design models
have been determined through the Analytical Campaign for the investigated Step Joints
according to their geometrical parameters and to both failure modes: the shear crack in the
tie beam and the crushing at the front-notch surface. In order to check the reliability of new
design models and the emergence conditions of both failure modes, future experiments and
numerical analysis on the three SJ typologies are going to be performed.This work was partly financed in the framework of the Portuguese Public Procurement Code, LOTE 3ES2 –
Escola Secundária de Loulé e Olhão. This work was financed by FEDER funds through the Competitively Factors Operational Programme – COMPETE and by national funds through FCT – Foundation for Science and Technology within the scope of the project PTDC/EPH-PAT/2401/2014 and PhD Scholarships SFRH/BD/128580/2017.info:eu-repo/semantics/publishedVersio
Polariton quantum boxes in semiconductor microcavities
We report on the realization of polariton quantum boxes in a semiconductor
microcavity under strong coupling regime. The quantum boxes consist of mesas
that confine the cavity photon, etched on top of the spacer of a microcavity.
For mesas with sizes of the order of a few micron in width and nm in depth, we
observe quantization, caused by the lateral confinement, of the polariton modes
in several peaks. We evidence the strong exciton-photon coupling regime through
a typical/clear anticrossing curve for each quantized level. Moreover the
growth technique is of high quality, which opens the way for the conception of
new optoelectronic devices
Reconstruction bathymétrique sonar en présence de trajets multiples et de bruit impulsif
National audienceCet article propose une méthode de poursuite de l'angle d'arrivée de l'écho principal rétrodiffusé par le fond marin pour la reconstruction bathymétrique. Cette méthode présente certains avantages par rapport aux techniques classiques d'estimation de l'angle d'arrivée et permet en particulier de régulariser la trajectoire de l'angle estimé et ainsi réduire le niveau d'interférence causé par les échos secondaires
Experimentations on the retrofitting of damaged Single Step Joints with Self-Tapping Screws
When assessing the roof of existing buildings, engineers may be confronted with structural
joints badly preserved, for instance the damaged Single Step Joint (SSJ) located at the foot of
timber trusses. Since the early appearance of failure modes in this traditional carpentry
connection may lead to the collapse of the whole timber truss, the retrofitting of damaged
SSJ is then required as an economically-viable intervention to stabilize the roof structure. In
consequence, the retrofitting of damaged SSJ with Self-Tapping Screws (STS) has been
conducted through the Experimental Campaign in order to explore further different
possibilities offered by this recent intervention technique (Sobra et al. (2016)). To this end,
two strategies, noted R1 and R2, have been proposed to retrofit the SSJ specimens with STS,
which had been previously damaged due to both failure modes, namely the crushing at the
front-notch surface and the shear crack in the tie beam (Verbist et al. (2017)). Afterwards,
the SSJ specimens retrofitted with STS have been tested under monotonic compression in
the rafter in order to pull out their mechanical behaviour encompassing the failure modes,
the force-displacement response, the stiffness of the connection, and the ultimate normal
force in the rafter. By comparing the mechanical behaviour of retrofitted SSJ specimens with
the initial ones from Verbist et al. (2017), the performances of both retrofitting strategies
with STS have been discussed. Furthermore, the impact of the shear row splitting on the
mechanical behaviour of retrofitted SSJ has been evaluated, by providing some warnings to
engineers when intervening in existing timber trusses featuring natural damage such as the
shrinkage splitting.This work was financed by FEDER funds through the Competitively Factors Operational Programme -
COMPETE and by national funds through FCT – Foundation for Science and Technology within the
scope of the research projects INVISIBLE WOODS PTDC/EPH-PAT/2401/2014, PROTIMBER
PTDC/ECM-EST/1072/2014, and the PhD Scholarships SFRH/BD/128580/2017.info:eu-repo/semantics/publishedVersio
Key to the identification of the final instar caterpillars eaten in Congo-Brazzaville
peer reviewedLa consommation humaine de lépidoptères est un thème d’actualité, mais pour lequel aucune synthèse n’a été rédigée en ce qui concerne la République du Congo-Brazzaville. Les nombreuses et récentes explorations de terrain ont montré que près d’une trentaine d’espèces de chenilles sont consommées. L’établissement d’une clef de détermination soutenue par des illustrations claires et précises apporte dès lors un outil fondamental pour un inventaire ethnozoologique efficace. La clef que nous proposons dans cet article se veut simple, complète et potentiellement évolutive
Relationship between Younger Age, Autoimmunity, Cardiometabolic Risk, Oxidative Stress, HAART, and Ischemic Stroke in Africans with HIV/AIDS
Background and Purpose. It now appears clear that both HIV/AIDS and antiretroviral therapy (HAART) use are associated with higher risk of cardiovascular disease such as stroke. In this study, we evaluated the prevalence, the risk factors, and the cardiometabolic comorbidities of stroke in HIV/AIDS Central African patients. Methods. This hospital-based cross-sectional study collected clinical, laboratory, and imaging data of black Central African heterosexual, intravenous drug nonuser, and HIV/AIDS patients. Results. There were 54 men and 62 women, with a female to male ratio of 1.2 : 1. All were defined by hypercoagulability and oxidative stress. Hemorrhagic stroke was reported in 1 patient, ischemic stroke in 17 patients, and all stroke subtypes in 18 patients (15%). Younger age <45 years (P = .003), autoimmunity (P < .0001), and metabolic syndrome defined by IDF criteria (P < .0001) were associated with ischemic stroke. Conclusions. Clustering of several cardiometabolic factors, autoimmunity, oxidative stress, and lifestyle changes may explain accelerated atherosclerosis and high risk of stroke in these young black Africans with HIV/AIDS. Prevention and intervention programs are needed
Cold-Atmospheric Plasma Induces Tumor Cell Death in Preclinical In Vivo and In Vitro Models of Human Cholangiocarcinoma
Through the last decade, cold atmospheric plasma (CAP) has emerged as an innovative therapeutic option for cancer treatment. Recently, we have set up a potentially safe atmospheric pressure plasma jet device that displays antitumoral properties in a preclinical model of cholangiocarcinoma (CCA), a rare and very aggressive cancer emerging from the biliary tree with few efficient treatments. In the present study, we aimed at deciphering the molecular mechanisms underlying the antitumor effects of CAP towards CCA in both an in vivo and in vitro context. In vivo, using subcutaneous xenografts into immunocompromised mice, CAP treatment of CCA induced DNA lesions and tumor cell apoptosis, as evaluated by 8-oxoguanine and cleaved caspase-3 immunohistochemistry, respectively. The analysis of the tumor microenvironment showed changes in markers related to macrophage polarization. In vitro, the incubation of CCA cells with CAP-treated culture media (i.e., plasma-activated media, PAM) led to a dose response decrease in cell survival. At molecular level, CAP treatment induced double-strand DNA breaks, followed by an increased phosphorylation and activation of the cell cycle master regulators CHK1 and p53, leading to cell cycle arrest and cell death by apoptosis. In conclusion, CAP is a novel therapeutic option to consider for CCA in the future
Hanging out at the club: Breeding status and territoriality affect individual space use, multi‐species overlap and pathogen transmission risk at a seabird colony
1. Wildlife movement ecology often focuses on breeders, whose territorial attachments facilitate trapping and following individuals over time. This leads to incomplete understanding of movements of individuals not actively breeding due to age, breeding failure, subordinance, and other factors. These individuals are often present in breeding populations and contribute to processes such as competition and pathogen spread. Therefore, excluding them from movement ecology studies could bias or mask important spatial dynamics.
2. Loafing areas offer an alternative to breeding sites for capturing and tracking individuals. Such sites may allow for sampling individuals regardless of breeding status, while also avoiding disturbance of sensitive breeding areas. However, little is known about the breeding status of individuals attending loafing sites, or how their movements compare to those of breeders captured at nests.
3. We captured a seabird, the brown skua, attending either nests or loafing areas (‘clubs’) at a multi-species seabird breeding site on Amsterdam Island (southern Indian Ocean). We outfitted skuas with GPS-UHF transmitters and inferred breeding statuses of individuals captured at clubs using movement patterns of breeders captured at nests. We then compared space use and activity patterns between breeders and nonbreeders.
4. Both breeding and nonbreeding skuas attended clubs. Nonbreeders ranged more widely, were more active, and overlapped more with other seabirds and marine mammals than did breeders. Moreover, some nonbreeders occupied fixed territories and displayed more restricted movements than those without territories. Nonbreeders became less active over the breeding season, while activity of breeders remained stable. Nonbreeding skuas were exposed to the agent of avian cholera at similar rates to breeders but were more likely to forage in breeding areas of the endangered endemic Amsterdam albatross, increasing opportunities for interspecific pathogen transmission.
5. Our results show that inference based only on breeders fails to capture important aspects of population-wide movement patterns. Capturing nonbreeders as well as breeders would help to improve population-level representation of movement patterns, elucidate and predict effects of external changes and conservation interventions (e.g. rat eradication) on movement patterns and pathogen spread, and develop strategies to manage outbreaks of diseases such as highly pathogenic avian influenza
Nonlinear relaxation of zero-dimension-trapped microcavity polaritons
We study the emission properties of confined polariton states in shallow zero-dimensional traps under nonresonant excitation. We evidence several relaxation regimes. For slightly negative photon-exciton detuning, we observe a nonlinear increase of the emission intensity, characteristic of carrier-carrier scattering assisted relaxation under strong-coupling regime. This demonstrates the efficient relaxation toward a confined state of the system. For slightly positive detuning, we observe the transition from strong to weak coupling regime and then to single-mode lasing
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