Contribution of the Upper-Body in Skate Cross-Country Skiing

The skate technique in cross-country skiing has a unique gait transition. Typically, skiers will use the two-skate technique at low speeds, transition to the one-skate technique at intermediate speeds, then return to the two-skate technique at high speeds. We hypothesize that this unique gait transition can be explained by differences in the contribution of the arms to propulsion and the associated metabolic cost of upper-body and arm work. In one-skate, poles are planted simultaneously with every skate stride, while in two-skate, poles are planted with every second skate stride (Smith, 2000). Using four trained cross-country ski racers, two separate tests were performed for each technique of skate skiing. First, subjects skied at 6, 15, and 30 km/h on a rollerski treadmill. During the entire test VO2, pole force, lactate, and video were recorded for one technique and repeated on another day using the second technique. In the second phase of testing, the poling motion only was simulated on a pole ergometer with subjects matching their stroke rate and poling forces using video and force feedback. Upper-body VO2 and lactate were measured and compared to the treadmill test values. The average metabolic cost associated with the upper-body work was 60% of the total metabolic cost when skiing on the treadmill. The upper-body metabolic cost was always higher for the one skate compared to the two skate technique. At slow speeds the difference between the two techniques was small (3%), but this difference increased at higher speeds from 10% at 15km/h to 14% at 30km/h. The poling motion associated with one-skate becomes more metabolically costly than two-skate as speed increases. A skier’s regressive transition from one-skate to two-skate at high speeds may be explained by a need to transfer impulse generation to the legs, since the sliding limbs remain effective at high speeds while the fixed limbs (poles) become less effective

Mechanical Properties of the Poling Motion in Cross Country Skiing

Skate cross-country skiing is a unique gait with the skis acting as sliding limbs and poles acting as fixed limbs. As skiers increase their speed, the sliding limbs (skis) remain relatively unrestricted in their ability to generate forward impulse. The poles, however, are fixed and thus the poling action depends on the skier’s speed. Since muscles generate less force at higher shortening velocity (Hill, 1938), the arms become limited in their ability to generate force through the poles. Also, muscles ability to generate force depends on their length, or the configuration of joints the muscles cross (Gordon et al., 1966). Therefore, it might be expected that the forces of arm and trunk muscles contributing to the poling action change as a function of the poling cycle. The purpose of this study was to relate maximum isometric force of the muscles contributing to poling as a function of the poling cycle, and quantify the dynamic force of these muscles as a function of skiing speed. Maximal isometric force was measured at 11 points in the poling stride of ten nationally ranked skiers. Five of these subjects were also tested for their maximal dynamic poling force at skiing speeds ranging from 6 to 36 km/h, increasing by 6km/h increments. Maximal isometric poling force was maximal (223N) at 20% of the poling cycle. The component of the pole force in the direction of travel was highest (117N) at 30% of the poling cycle. Toward the end of the poling cycle, the propulsive force approaches the total force and the total force decreases to 50 N. The dynamic poling force was maximal for the two slowest speeds tested (236 N at 6km/h and 254 N at 12km/h), and then decreased force almost linearly with increasing speeds and reached 102 N at 36 km/h. The results of this study suggest that the propulsive forces in poling depend greatly on the position of arms and trunk and the speed of skiing

Summary report on excavations at Tell Khaiber, an administrative centre of the Sealand period, 2013-2017

Excavations at Tell Khaiber by the Ur Region Archaeological Project have revealed a substantial building (hereafter the Public Building) dating to the mid-second millennium BC. The results are significant for several reasons: they shed light on Babylonian provincial administration; they reveal a previously unknown type of fortified monumental building; and they produced a provenanced, dated archive of the little-understood Sealand Dynasty. Here we give a summary of the main results, including the architecture and the material culture. There are also comments on the historical background, and a discussion of the form and function of the Public Building

Correction to: Wnt3a induces exosome secretion from primary cultured rat microglia

Correction to: BMC Neuroscience 2012, 13:144 http://www.biomedcentral.com/1471-2202/13/14

Intercultural ethics: questions of methods in language and intercultural communication

This paper explores how questions of ethics and questions of method are intertwined and unavoidable in any serious study of language and intercultural communication. It argues that the focus on difference and solution orientations to intercultural conflict has been a fundamental driver for theory, data collection and methods in the field. These approaches, the paper argues, have created a considerable consciousness raising industry, with methods, trainings and ‘critical incidents’, which ultimately focus intellectual energy in areas which may be productive in terms of courses and publications but which have a problematic basis in their ethical terrain. Dieser Artikel untersucht wie ethische und methodische Fragen nicht nur ineinander greifen, sondern in keiner ernstzunehmenden Studie ueber Sprache und interkulturelle Kommunikation ausgelassen werden duerfen. Es wird hier argumentiert, dass der Schwerpunkt auf Verschiedenheit und Problemorientierung im interkulturellen Konflikt einen wesentlichen Einfluss auf theoretische Entwicklungen, Datenerhebung und Methoden in diesem Bereich hatte. Dieser Artikel legt auch dar, wie diese Ansaetze eine betraechtliche ‘Bewusstseinsbildungs – Branche' erzeugt haben, mit Methoden, Trainings, und ‘kritischen Interaktionssituationen’, welche letztendlich allen intellektuellen Arbeitseifer auf Bereiche konzentriert hat, die zwar ertragreich sind in Bezug auf Kurse und Publikationen, jedoch eine problematische Grundlage im ethischen Bereich aufweisen

E1A Activates Transcription of p73 and Noxa to Induce Apoptosis

p73, a member of the p53 family of proteins, transcriptionally activates a number of genes involved in the control of cell cycle and apoptosis. Overexpression of p73 was detected in a large number of primary head and neck cancers, and in the established cell lines examined, these all contained inactivating p53 mutations. The significance of p73 overexpression in the pathogenesis of head and neck cancer is currently unclear. We have shown that the expression of adenovirus 5 E1A in a panel of head and neck cancer cell lines induces apoptosis independently of their p53 status. In this study we examined the role of p73 and its transcriptional targets in E1A-mediated induction of apoptosis. E1A expression resulted in significant activation of the TAp73 promoter but had no effect on the alternative, DeltaNp73 promoter. E1A also increased expression of endogenous TAp73 mRNA and protein. E1A mutants lacking the p300- and/or pRB-binding sites showed reduced ability to activate the TAp73 promoter. Additionally, mutations in the E2F1-binding sites in the TAp73 promoter impaired activation by E1A. Importantly, expression of the 13S isoform of E1A substantially induced the p53 apoptotic target Noxa in several p53-deficient cancer cell lines. Our results indicate that E1A activation of p73 and the p53 apoptotic target Noxa can occur in the absence of a functional p53. This activation is likely to play a key role in the mechanism of p53-independent apoptosis induced by E1A in some cancers and may provide an avenue for future cancer therapies

Convection enhanced delivery of panobinostat (LBH589)-loaded pluronic nano-micelles prolongs survival in the F98 rat glioma model

BACKGROUND: The pan-histone deacetylase inhibitor panobinostat is a potential therapy for malignant glioma, but it is water insoluble and does not cross the blood–brain barrier when administered systemically. In this article, we describe the in vitro and in vivo efficacy of a novel water-soluble nano-micellar formulation of panobinostat designed for administration by convection enhanced delivery (CED). MATERIALS AND METHODS: The in vitro efficacy of panobinostat-loaded nano-micelles against rat F98, human U87-MG and M059K glioma cells and against patient-derived glioma stem cells was measured using a cell viability assay. Nano-micelle distribution in rat brain was analyzed following acute CED using rhodamine-labeled nano-micelles, and toxicity was assayed using immunofluorescent microscopy and synaptophysin enzyme-linked immunosorbent assay. We compared the survival of the bioluminescent syngenic F98/Fischer344 rat glioblastoma model treated by acute CED of panobinostat-loaded nano-micelles with that of untreated and vehicle-only-treated controls. RESULTS: Nano-micellar panobinostat is cytotoxic to rat and human glioma cells in vitro in a dose-dependent manner following short-time exposure to drug. Fluorescent rhodamine-labelled nano-micelles distribute with a volume of infusion/volume of distribution (Vi/Vd) ratio of four and five respectively after administration by CED. Administration was not associated with any toxicity when compared to controls. CED of panobinostat-loaded nano-micelles was associated with significantly improved survival when compared to controls (n=8 per group; log-rank test, P<0.001). One hundred percent of treated animals survived the 60-day experimental period and had tumour response on post-mortem histological examination. CONCLUSION: CED of nano-micellar panobinostat represents a potential novel therapeutic option for malignant glioma and warrants translation into the clinic