860 resultados para STEPPING-STONES


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Natural stone has been a popular and reliable building material throughout history appearing in many historic monuments and in more recent buildings. Research into the intrinsic properties of specific stones is important because it gives us a greater understanding of the factors that limit and act on them. This can help prevent serious problems from occurring in our buildings bringing both esthetic benefits and financial savings. To this end, the main objective of this research has been to study the influence of the fabric and the mineral composition of two types of sandstone on their durability. The first is a red continental sandstone from the Buntsandstein Age called “Molinaza Roja”, which is quarried in Montoro (Cordoba). The second is quarried in Ronda (Malaga) and is sold under the trade name of “Arenisca Ronda”. It is a light pink-whitish calcarenite deposited during the Late Tortonian to Late Messinian. We characterized their petrological and petrophysical properties by studying their rock fabrics, porous systems and mechanical properties. In order to obtain a complete vision of the behavior of their rock fabrics, we also carried out two decay tests, the salt crystallization and the freeze–thaw tests. We then measured the effects on the textures of the altered samples during and after the decay tests and we evaluated the changes in the porous system. By comparing the results between intact and altered samples, we found that Arenisca Ronda is less durable because it has a high quantity of expandable clays (smectites) and a high percentage of pores in the 0.1–1 μm range, in which the pressure produced by salt crystallization is strongest. In Molinaza Roja the decay agents caused significant sanding due to loss of cohesion between the clasts, especially during the salt crystallization test. In both stones, the anisotropies (oriented textures) have an important role in their hydric and dynamic behavior and also affect their mechanical properties (especially in the compression resistance). No changes in color were detected.

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Plants belonging to Berberis are reported in several folklore medicinal pharmacopeias and are used in traditional medicines in Asia and European countries. The plants have been used in the preparation of various traditional and synthetic medicines since pre-historic times for wound healing, fever, eye disease, jaundice, vomiting during pregnancy, rheumatism, kidney and gall balder stones, and several other illnesses. Their healing properties are appear to be due to the presence of secondary metabolites and important alkaloids with different pharmacological activities. Their antibacterial, antifungal, antiviral, anti-diabetic, and anti-tumor activities as well as positive effects on the cardiovascular and body immune systems have been reported. Root extracts of some species of the plant genus contain quinine which acts as a powerful anti-malarial agent. The main chemical constituents of Berberis plants are alkaloids, steroids, glycosides, flavonoids, saponins, terpenoids and reducing sugars. Of these alkaloids, berberine is the most important. The present review focuses on recent advances in phytopharmacological and ethnomedicinal uses of plants belonging to Berberis genus.

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Acanthopagrus butcheri completes its entire life history within estuaries and coastal lakes of southern Australia, although adults occasionally move between estuaries via the sea. Consequently, it is expected that populations of A. butcheri in different estuaries will be genetically distinct, with the magnitude of genetic divergence increasing with geographic isolation. However, previous genetic studies of A. butcheri from southeast Australia yielded conflicting results; allozyme variation exhibited minimal spatial structuring (θ = 0.012), whereas mitochondrial DNA distinguished the majority of populations analyzed (θ = 0.263) and genetic divergence was positively correlated with geographic isolation. This discrepancy could reflect high male gene flow, which impacts nuclear but not mitochondrial markers. Here we estimated allele frequencies at five nuclear microsatellite loci across 11 southeast Australian populations (595 individuals). Overall structuring of microsatellite variation was weaker (θ = 0.088) than that observed for mitochondrial DNA, but was able to distinguish a greater number of populations and was positively correlated with geographic distance. Therefore, we reject high male gene flow and invoke a stepping-stone model of infrequent gene flow among estuaries for both sexes. Likewise, management of A. butcheri within the study range should be conducted at the scale of individual or geographically proximate estuaries for both sexes. The lack of allozyme structuring in southeast Australia reflects either the large variance in structuring expected among loci under neutral conditions and the low number of allozymes surveyed or a recent colonization of estuaries such that some but not all nuclear loci have approached migration-drift equilibrium.

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PURPOSE: To evaluate, compared to usual practice, the initial and long-term effectiveness of a workplace intervention targeting reducing sitting on activity outcomes.

METHODS: Office worksites (≥1km apart) from a single organization in Victoria, Australia were cluster randomized to intervention (n=7) or control (n=7). Participants were 231 desk-based office workers (5 to 39 participants per worksite) working at least 0.6 full time equivalent. The workplace-delivered intervention addressed organizational, physical environment, and individual behavioural change to reduce sitting time. Assessments occurred at baseline, three-, and 12-months, with the primary outcome participants' objectively measured (activPAL3 device) workplace sitting time (mins/8-h workday). Secondary activity outcomes were: workplace time spent standing, stepping (light, moderate-vigorous and total) and in prolonged (≥30min) sitting bouts (h/8-h workday); usual duration of workplace sitting bouts; and, overall sitting, standing and stepping time (mins/16-h day). Analysis was by linear mixed models, accounting for repeated measures and clustering and adjusting for baseline values and potential confounders.

RESULTS: At baseline, on average, participants (68% women; mean±SD age = 45.6±9.4 years) sat, stood and stepped for 78.8±9.5%, 14.3±8.2%, and 6.9±2.9% of work hours respectively. Workplace sitting time was significantly reduced in the intervention group compared to the controls at three months (-99.1 [95% CI -116.3 to -81.8] min/8-h workday) and 12 months (-45.4 [-64.6 to -26.2] min/8-h workday). Significant intervention effects (all favoring intervention) were observed for standing, prolonged sitting, and usual sitting bout duration at work, as well as overall sitting and standing time, with no significant nor meaningful effects observed for stepping.

CONCLUSIONS: This workplace-delivered multicomponent intervention was successful at reducing workplace and overall daily sitting time in both the short- and long- term.

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Biological invasions often occur through expansion of satellite populations that become established at 'invasion hubs'. Invasion hubs can result from random dispersal events, but frequently arise when invading individuals actively choose habitats using cues that signify high-quality environments where the fitness consequences are positive. Theoretical studies suggest that targeted control at invasion hubs can effectively suppress the populations and impacts of invaders. In arid Australia, small dams that provide water for livestock function as invasion hubs by providing an invasive vertebrate, the cane toad Rhinella marina, with refuge from extreme aridity during the annual dry season. Toads are attracted to dams and use them as stepping stone habitats from which they disperse during rainy periods. Here, we ask whether sustained control of this invasive vertebrate can be achieved by converting invasion hubs into ecological traps. We did this by manipulating invasion hub habitats to induce a mismatch between toads' habitat preference and the fitness consequences of their habitat choice to cause high mortality. We constructed fences to exclude toads from dams and maintained these fences for 1 year. This period encompassed periods of dry and wet seasonal climatic conditions. Our manipulation did not alter the attractive cues for invading toads which died en masse while attempting to settle at fenced dams that prevented toads from reaching water. Toad populations at the fenced dams were suppressed by 1-2 orders of magnitude compared to unfenced controls and procedural controls. Toad populations remained suppressed for a year after exclusion. By excluding toads from dams, we converted invasion hubs into ecological traps and effectively thwarted the reinvasion of cane toads. Our research suggests that water exclusion devices could be used to prevent toad invasion or to control cane toad populations in arid landscapes colonized by toads. Synthesis and applications. Our study demonstrates that sustained control of invader populations can be achieved by restricting their access to invasion hubs. Control of invasive species via elimination of invasion hubs could be conducted reactively, to control established populations of invaders, or conducted strategically, by rendering invasion hubs unsuitable for colonization ahead of the invasion front to prevent further population spread.

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Excursion of cathodic protection (CP) potential from the designed "safe" CP level resulting from various forms of electrical interference signals are observed rather frequently in industrial applications, in particular in the pipeline industry; however, the influence of such potential fluctuations on the corrosion behavior of steel under CP conditions does not yet appear to be fully understood. In this work, the effects of anodic transients that periodically shift the potential of a CP protected steel electrode from-1,200 mVAg/AgCl to-750 mVAg/AgCl on the corrosion of a steel electrode in aqueous media was investigated using square wave polarization. Anodic currents were measured that lasted for significant periods of time upon stepping the CP potential up to a less cathodic potential at various frequencies (1 h, 30 s, 10 s, 5 s, and 1 s). Part of such anodic currents is found to cause steel corrosion, and this is explained on the basis of understanding the Fe/H2O equilibrium.

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Cette étude vise à caractériser le «crampage», une entité relativement nouvelle dans l’industrie ovine au Québec. Les signes cliniques se manifestent au pas, par une hyperflexion (hanche, grasset, jarret), d’un ou des deux membres pelviens. Cinq agneaux naturellement affectés et cinq agneaux appariés cliniquement normaux ont été soumis à des examens physique, neurologique et orthopédique, à des techniques d’imagerie avancée (tomodensitométrie, résonance magnétique), à des tests électrodiagnostiques (électromyogramme, vitesses de conduction nerveuse motrice et sensitive) puis à une nécropsie. Des hématologies, biochimies ainsi que des analyses du liquide céphalorachidien ont également été réalisées. Les résultats ont été comparés entre les groupes (affectés/cliniquement normaux). Il a été constaté à la tomodensitométrie que la surface du canal vertébral mesurée au niveau de la deuxième vertèbre lombaire était inférieure dans le groupe des agneaux affectés (p=0.045). Aucune répercussion n’a été constatée sur le segment de moelle épinière correspondant. La racine S2, quant à elle, était plus grêle dans le groupe des agneaux affectés (p=0.01). À l’issue de cette étude, une cause orthopédique, musculaire ou neurologique consécutive à une lésion structurale de la moelle épinière a été écartée. Il pourrait s‘agir d’une atteinte sensitive de la racine S2 altérant la sensation dans le membre affecté, toutefois, une anomalie fonctionnelle cérébrale ou de la moelle épinière dans le renflement lombaire, est également à considérer. Sans anomalie musculaire, l’appellation «crampage» est inexacte. Nous proposons de la remplacer par des termes plus descriptifs comme «syndrome d’hyperflexion» ou «high stepping gait».

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Cette étude vise à caractériser le «crampage», une entité relativement nouvelle dans l’industrie ovine au Québec. Les signes cliniques se manifestent au pas, par une hyperflexion (hanche, grasset, jarret), d’un ou des deux membres pelviens. Cinq agneaux naturellement affectés et cinq agneaux appariés cliniquement normaux ont été soumis à des examens physique, neurologique et orthopédique, à des techniques d’imagerie avancée (tomodensitométrie, résonance magnétique), à des tests électrodiagnostiques (électromyogramme, vitesses de conduction nerveuse motrice et sensitive) puis à une nécropsie. Des hématologies, biochimies ainsi que des analyses du liquide céphalorachidien ont également été réalisées. Les résultats ont été comparés entre les groupes (affectés/cliniquement normaux). Il a été constaté à la tomodensitométrie que la surface du canal vertébral mesurée au niveau de la deuxième vertèbre lombaire était inférieure dans le groupe des agneaux affectés (p=0.045). Aucune répercussion n’a été constatée sur le segment de moelle épinière correspondant. La racine S2, quant à elle, était plus grêle dans le groupe des agneaux affectés (p=0.01). À l’issue de cette étude, une cause orthopédique, musculaire ou neurologique consécutive à une lésion structurale de la moelle épinière a été écartée. Il pourrait s‘agir d’une atteinte sensitive de la racine S2 altérant la sensation dans le membre affecté, toutefois, une anomalie fonctionnelle cérébrale ou de la moelle épinière dans le renflement lombaire, est également à considérer. Sans anomalie musculaire, l’appellation «crampage» est inexacte. Nous proposons de la remplacer par des termes plus descriptifs comme «syndrome d’hyperflexion» ou «high stepping gait».

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Aquatic macrophytes can successfully colonise and re-colonise areas separated by space and time. The mechanisms underlying such “mobility” are not well understood, but it has often been hypothesised that epizoochory (external dispersal) plays an important role. Yet, there is only limited, and mostly anecdotal, evidence concerning successful epizoochorous dispersal of aquatic macrophytes, particularly in the case of short-distance dispersal. Here we examine in situ and ex situ dispersal of aquatic macrophytes, including three invasive alien species. A high frequency of Lemna minor Linnaeus dispersal was observed in situ, and this was linked to bird-mediated epizoochory. We concluded that wind had no effect on dispersal. Similarly, in an ex situ examination Lemna minuta Kunth and Azolla filiculoides Lamarck, were found to be dispersed with a high frequency by mallard ducks (Anas platyrhynchos). No dispersal was measured for Elodea nuttalli (Planchon) H. St. John. It is concluded that short-distance or “stepping-stone” dispersal via bird-mediated epizoochory can occur with high frequencies, and therefore can play an important role in facilitating colonisation, range expansion and biological invasion of macrophytes.

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BACKGROUND: Few studies have investigated the accuracy of the ActiGraph (AG) GTX3 accelerometer for assessing children's sitting and standing time. The activPAL (aP) has an inclinometer function that enables it to distinguish between sitting/lying and standing; however, its accuracy for assessing sitting and standing in older children is unknown. This study validated the accuracy of these devices for estimating sitting and standing time in a school classroom against a criterion measure of direct observation (DO).

FINDINGS: Forty children in grades 5-7 wore both devices while being video recorded during two school lessons. AG and aP data were simultaneously collected in 15-s epochs. Individual participant DO and aP data were recorded as total time spent sitting/lying, standing and stepping. AG data were converted into time spent sitting and standing using previously established cut-points. Compared with DO, the aP underestimated sitting time (mean bias = -1.9 min, 95 % LoA = -8.9 to 5.2 min) and overestimated standing time (mean bias = 1.8 min, 95% LoA = -9.6 to 13.3 min). The best-performing AG cut-point across both sitting and standing (<75 counts/15 s) was more accurate than the aP, underestimating sitting time (mean bias = -0.8 min, 95 % LoA = -10.5 to 9.9 min) and standing time (mean bias = -0.4 min, 95% LoA = -9.8 to 9.1 min), but was less precise as evidenced by wider LoAs and poorer correlations with DO (sitting r = 0.86 aP vs 0.80 AG; standing r = 0.78 aP vs 0.60 AG).

CONCLUSIONS: The aP demonstrated good accuracy and precision for assessing free-living sitting and standing time in classroom settings. The AG was most accurate using a cut-point of < 75 counts/15 s. Further studies should validate the monitors in settings with greater inter- and intra-individual variation in movement patterns.

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OBJECTIVES: To validate activPAL3™ (AP3) for classifying postural allocation, estimating time spent in postures and examining the number of breaks in sedentary behaviour (SB) in 5-12 year-olds. DESIGN: Laboratory-based validation study. METHODS: Fifty-seven children completed 15 sedentary, light- and moderate-to-vigorous intensity activities. Direct observation (DO) was used as the criterion measure. The accuracy of AP3 was examined using a confusion matrix, equivalence testing, Bland-Altman procedures and a paired t-test for 5-8y and 9-12y. RESULTS: Sensitivity of AP3 was 86.8%, 82.5% and 85.3% for sitting/lying, standing, and stepping, respectively, in 5-8y and 95.3%, 81.5% and 85.1%, respectively, in 9-12y. Time estimates of AP3 were equivalent to DO for sitting/lying in 9-12y and stepping in all ages, but not for sitting/lying in 5-12y and standing in all ages. Underestimation of sitting/lying time was smaller in 9-12y (1.4%, limits of agreement [LoA]: -13.8 to 11.1%) compared to 5-8y (12.6%, LoA: -39.8 to 14.7%). Underestimation for stepping time was small (5-8y: 6.5%, LoA: -18.3 to 5.3%; 9-12y: 7.6%, LoA: -16.8 to 1.6%). Considerable overestimation was found for standing (5-8y: 36.8%, LoA: -16.3 to 89.8%; 9-12y: 19.3%, LoA: -1.6 to 36.9%). SB breaks were significantly overestimated (5-8y: 53.2%, 9-12y: 28.3%, p<0.001). CONCLUSIONS: AP3 showed acceptable accuracy for classifying postures, however estimates of time spent standing were consistently overestimated and individual error was considerable. Estimates of sitting/lying were more accurate for 9-12y. Stepping time was accurately estimated for all ages. SB breaks were significantly overestimated, although the absolute difference was larger in 5-8y. Surveillance applications of AP3 would be acceptable, however, individual level applications might be less accurate.

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During school hours, children can sit for prolonged and unbroken periods of time. This study investigated the impact of an 8-month classroom-based intervention focusing on reducing and breaking-up sitting time on children's cardio-metabolic risk factors (i.e., body mass index, waist circumference, blood pressure) and perceptions of musculoskeletal discomfort. Two Year-6 classes (24 students per class) in one primary school were assigned to either an intervention or control classroom. The intervention classroom was equipped with height-adjustable desks and the teacher was instructed in the delivery of pedagogical strategies to reduce and break-up sitting in class. The control classroom followed standard practice using traditional furniture. At baseline, and after 8-months, time spent sitting, standing, stepping, and sitting-bouts (occasions of continuous sitting) as well as the frequency of sit-to-stand transitions were obtained from activPAL inclinometers and the time spent in light-intensity physical activity was obtained from ActiGraph accelerometers. Demographics and musculoskeletal characteristics were obtained from a self-report survey. Hierarchical linear mixed models found that during class-time, children's overall time spent sitting in long bouts (>10 min) were lower and the number of sit-to-stand transitions were higher in the intervention group compared to the control group, while no changes were observed for musculoskeletal pain/discomfort. No significant intervention effects were found for the anthropometrics measures and blood pressure. Height-adjustable desks and pedagogical strategies to reduce/break-up sitting can positively modify classroom sitting patterns in children. Longer interventions, larger and varied sample size may be needed to show health impacts; however, these desks did not increase musculoskeletal pain/discomfort.

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Résumé : Cette juxtaposition de matériaux solides -blocs, pierres ou briques,...- liés ou non entre eux que nous appelons maçonnerie ne se comporte pas très bien vis-à-vis des forces latérales, surtout si elle n’a pas été réalisée suivant les normes parasismiques ou de façon adéquate. Cette vulnérabilité (glissement, cisaillement, déchirure en flexion, ou tout autre) vient souvent du fait même de ce processus d’empilement, des problèmes d’interaction avec le reste de la structure et aussi à cause des caractéristiques mécaniques peu fiables de certains éléments utilisés. Malgré cette défaillance structurale, la maçonnerie est encore utilisée aujourd’hui grâce à son côté traditionnel, sa facilité de mise en œuvre et son coût d’utilisation peu élevé. Depuis quelques années, la maçonnerie s’est enrichie de documents qui ont été publiés par divers chercheurs dans le but d’une meilleure compréhension des caractéristiques mécaniques des éléments et aussi, et surtout, des mécanismes de rupture des murs de maçonnerie pour une meilleure réponse face aux sollicitations sismiques. Beaucoup de programmes expérimentaux ont alors été effectués et tant d’autres sont encore nécessaires. Et c’est dans ce contexte que cette recherche a été conduite. Elle présentera, entre autres, le comportement sous charges latérales d’un mur en maçonnerie armée entièrement rempli de coulis. Ce projet de recherche fait partie d’un programme plus large visant à une meilleure connaissance du comportement sismique de la maçonnerie pour une amélioration des techniques de construction et de réparation des ouvrages en maçonnerie.

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The Selvagens Islands are located in the northeastern Atlantic between the Canary Islands and Madeira Island. As a result of their small size, remote location and harsh sea conditions only a few studies have been conducted to describe their marine species diversity. We were able to identify 29 new coastal fish species, an increase of 33% in the ichthyofauna described for these islands (n = 88). There is a prevalence of species with tropical affinities and only 2.3% (n = 2) are endemic to Macaronesia. Considered a stepping-stone colonization vector from the nearest continental shore, as proposed by other authors for this region, the Selvagens Islands host 34.1% of the ichthyofauna described for the much larger Canary Islands (nspecies = 258, submerged area nSelvagensIs. = 2.3%) and 47.3% of the ichthyofauna described for the more distantly located Madeira Island (nspecies = 186, submerged area nSelvagensIs. = 17.9%). Interestingly, 6.8% (n = 6) of the species failed to bridge the gap between the Selvagens Islands and Madeira Island. Data collected so far showed no trend toward an increasing number of species with high dispersal capability. The Selvagens Islands are an example of a high coastal species diversity occurring even in very small areas of the northeastern Atlantic Ocean.

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An inventory of benthic and benthopelagic fishes is presented as a result of two exploratory surveys around Ampe`re Seamount, between Madeira and the Portuguese mainland, covering water depths from 60 to 4,400 m. A total of 239 fishes were collected using different types of sampling gear. Three chondrichthyan species and 31 teleosts in 21 families were identified. The collections showed a vertical zonation with little overlap, but indications for an affinity of species to certain water masses were only vague. Although most of the species present new records for Ampe`re Seamount, all of them have been known for the NE Atlantic; endemic species were not found. The comparison with fish communities at other NE Atlantic seamounts indicates that despite a high ichthyofaunal similarity, which supports the ‘‘stepping stone’’ hypothesis of species dispersal, some differences can be attributed to the local features of the seamounts.