745 research outputs found

    The Impact of Temperature on Physical Activity Levels During a 12-Week Walking Intervention

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    Please view abstract in the attached PDF file

    Observations on the vibration of axially-tensioned elastomeric pipes conveying fluids

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    A study of the effect of axial tension on the vibration of a single-span elastomeric pipe clamped at both ends conveying fluid has been carried out both experimentally and theoretically. A new mathematical model using a penalty function technique and the method of kinematic correction and fictitious loads has been developed. The influence of flowing fluid and axial tension on natural frequencies and mode shapes of the system has been described using this model and compared with experimental observations. Linear and non-linear dynamic response of the harmonically excited pipe has also been investigated for varying flow velocities and initial axial tensions

    Application of reliability-based robustness assessment of steel moment resisting frame structures under post-mainshock cascading events

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    This paper proposes a reliability-based framework for quantifying structural robustness considering the occurrence of a major earthquake (mainshock) and subsequent cascading hazard events, such as aftershocks that are triggered by the mainshock. These events can significantly increase the probability of failure of buildings, especially for structures that are damaged during the mainshock. The application of the proposed framework is exemplified through three numerical case studies. The case studies correspond to three SAC steel moment frame buildings of three, nine, and 20 stories, which were designed to pre-Northridge codes and standards. Two-dimensional nonlinear finite-element models of the buildings are developed with the Open System for Earthquake Engineering Simulation framework (OpenSees), using a finite length plastic hinge beam model and a bilinear constitutive law with deterioration, and are subjected to multiple mainshock-aftershock seismic sequences. For the three buildings analyzed herein, it is shown that the structural reliability under a single seismic event can be significantly different from that under a sequence of seismic events. The reliability based robustness indicator shows that the structural robustness is influenced by the extent to which a structure can distribute damage

    The regeneration capacity of the flatworm Macrostomum lignano—on repeated regeneration, rejuvenation, and the minimal size needed for regeneration

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    The lion’s share of studies on regeneration in Plathelminthes (flatworms) has been so far carried out on a derived taxon of rhabditophorans, the freshwater planarians (Tricladida), and has shown this group’s outstanding regeneration capabilities in detail. Sharing a likely totipotent stem cell system, many other flatworm taxa are capable of regeneration as well. In this paper, we present the regeneration capacity of Macrostomum lignano, a representative of the Macrostomorpha, the basal-most taxon of rhabditophoran flatworms and one of the most basal extant bilaterian protostomes. Amputated or incised transversally, obliquely, and longitudinally at various cutting levels, M. lignano is able to regenerate the anterior-most body part (the rostrum) and any part posterior of the pharynx, but cannot regenerate a head. Repeated regeneration was observed for 29 successive amputations over a period of almost 12 months. Besides adults, also first-day hatchlings and older juveniles were shown to regenerate after transversal cutting. The minimum number of cells required for regeneration in adults (with a total of 25,000 cells) is 4,000, including 160 neoblasts. In hatchlings only 1,500 cells, including 50 neoblasts, are needed for regeneration. The life span of untreated M. lignano was determined to be about 10 months

    Effects of high-amylose maize starch and butyrylated high-amylose maize starch on azoxymethane-induced intestinal cancer in rats

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    Colorectal cancer (CRC) is a major cause of death worldwide. Studies suggest that dietary fibre offers protection perhaps by increasing colonic fermentative production of butyrate. This study examined the importance of butyrate by investigating the effects of resistant starch (RS) and butyrylated-RS on azoxymethane (AOM)-induced CRC in rats. Four groups (n = 30 per group) of Sprague–Dawley rats were fed AIN-93G-based diets containing a standard low-RS maize starch (LAMS), LAMS + 3% tributyrin (LAMST), 10% high-amylose maize starch (HAMS) and 10% butyrylated HAMS (HAMSB) for 4 weeks. Rats were injected once weekly for 2 weeks with 15 mg/kg AOM, maintained on diets for 25 weeks and then killed. Butyrate concentrations in large bowel digesta were higher in rats fed HAMSB than other groups (P < 0.001); levels were similar in HAMS, LAMS and LAMST groups. The proportion of rats developing tumours were lower in HAMS and HAMSB than LAMS (P < 0.05), and the number of tumours per rat were lower in HAMSB than LAMS (P < 0.05). Caecal digesta butyrate pools and concentrations were negatively correlated with tumour size (P < 0.05). Hepatic portal plasma butyrate concentrations were higher (P < 0.001) in the HAMSB compared with other groups and negatively correlated with tumour number per rat (P < 0.009) and total tumour size for each rat (P = 0.05). HAMSB results in higher luminal butyrate than RS alone or tributyrin. This is associated with reduced tumour incidence, number and size in this rat model of CRC supporting the important protective role of butyrate. Interventional strategies designed to maximize luminal butyrate may be of protective benefit in humans

    EIT Observations of the Extreme Ultraviolet Sun

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    The Extreme Ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft has been operational since 2 January 1996. EIT observes the Sun over a 45 x 45 arc min field of view in four emission line groups: Feix, x, Fexii, Fexv, and Heii. A post-launch determination of the instrument flatfield, the instrument scattering function, and the instrument aging were necessary for the reduction and analysis of the data. The observed structures and their evolution in each of the four EUV bandpasses are characteristic of the peak emission temperature of the line(s) chosen for that bandpass. Reports on the initial results of a variety of analysis projects demonstrate the range of investigations now underway: EIT provides new observations of the corona in the temperature range of 1 to 2 MK. Temperature studies of the large-scale coronal features extend previous coronagraph work with low-noise temperature maps. Temperatures of radial, extended, plume-like structures in both the polar coronal hole and in a low latitude decaying active region were found to be cooler than the surrounding material. Active region loops were investigated in detail and found to be isothermal for the low loops but hottest at the loop tops for the large loops
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