Sound radiation from randomly vibrating beams of finite circular cross section

The radiation of sound from vibrating cylindrical beams is analyzed based on the frequency of the beam vibrations and the physical characteristics of the beam and its surroundings. A statistical analysis of random beam vibrations allows this result to be independent of the boundary conditions at the ends of the beam. The acoustic power radiated by the beam can be determined from a knowledge of the frequency band vibration data without a knowledge of the individual modal vibration amplitudes. A practical example of the usefulness of this technique is provided by the application of the theoretical calculations to the prediction of the octave band acoustic power output of the picking sticks of an automatic textile loom. Calculations are made of the expected octave band sound pressure levels based on measured acceleration data. These theoretical levels are subsequently compared with actual sound pressure level measurements of loom noise

Flipping the Kill-Switch: Why Governments Shut Down the Internet

In the last decade, governments have begun more frequently cutting internet and mobile services as a response to real or potential threats. Both democratic and autocratic regimes use internet shutdowns to maintain security and suppress dissent. Why do governments intentionally shut down the internet? This paper focuses on complete blackouts of online communications, known as “kill-switch” shutdowns, and examines the factors that contribute to a regime’s choice to enact such extreme measures. Using a mixed-methods analysis, this paper evaluates multiple potential causes of internet shutdowns. Results from both cross-national, quantitative analysis and qualitative process tracing present several findings. First, government internet shutdowns follow a strong path dependency: once a government enacts a shutdown, the chances they will do so again are high. Second, there is surprisingly no apparent link between violent protest and internet shutdowns. This thesis finds strong support, on the other hand, for violent conflict and competitive elections as factors that lead governments to shut down internet services. Finally, this paper finds a negative relationship between U.S. foreign assistance and internet shutdowns in the data, suggesting that greater linkages with the West may be a way to curb government-mandated internet shutdowns in the future

Introduction to the Eastern Arctic Marine Environmental Studies Program

The primary objective of the EAMES program was to collect, collate and interpret environmental data in order to prepare Environmental Impact Statements to be submitted to the Federal Environmental Assessment and Review Process. A secondary objective was to provide data to be used in the development of oil spill contingency plans. Within this context, two basic approaches emerge regarding the acquisition of environmental data: (1) survey techniques and (2) process-oriented studies. ... Most of the studies carried out were either comprehensive ship-borne operations or aerial surveys. Work was also undertaken from shore-based camps. Extensive use was made of remote sensing, by radar and satellites. ... The physical studies ... [comprised] three principal disciplines: oceanography, meteorology and geomorphology. ... The biological studies were primarily large-scale surveys, although there were several smaller-scale studies of specific features such as ice edges. The larger-scale studies were designed to document the distribution and abundance of organisms in all trophic levels .... Given the fact that the original reports were far too voluminous for distribution ... the decision was made to ask each of the scientists who contributed to the EAMES program to write up the essence of his or her study(s) as a scientific manuscript and subject it to the peer review system. The papers favourably evaluated would be published together in a single number of Arctic. ... This edition of Arctic contains that series of papers. ... The content of this issue is a reflection of the integrated, multi-disciplinary approach of the EAMES program and will permit the reader to see the ecosystem of the Baffin Bay/Lancaster Sound area as a whole, as well as the sum of its component parts. ..

Associations between BMI, Body Composition, Sleep and Physical Activity in College Students

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Implication de MMP-9 dans le phénotype invasif des cellules souches cancéreuses et dans l'endothélium vasculaire cérébral tumoral

Le traitement des tumeurs cérébrales représente un défi d'envergure, puisqu'elles sont isolées du reste du corps par la barrière hémato-encéphalique. Il est donc impératif d'accroître nos connaissances sur les cellules composant ces tumeurs. L'une des hypothèses émergentes concerne la présence d'une sous-population spécifique de cellules au sein de la tumeur, les cellules souches cancéreuses (CSC), impliquées dans l'initiation et la récurrence des cancers. Les marqueurs de surfaces des CSC varient largement selon le tissu d'intérêt, mais il semble que CD133, une glycoprotéine membranaire, soit une signature commune à plusieurs CSC. S'il est courant de traiter le cancer en ciblant les cellules cancéreuses elles-mêmes, cibler le microenvironnement dans lequel évolue la tumeur est une avenue thérapeutique prometteuse. En effet, les cellules endothéliales (CE) au sein d'une tumeur sont connues pour avoir des propriétés différentes des CE normales. Ces cellules endothéliales tumorales (CET) peuvent donc constituer une cible supplémentaire pour inhiber sélectivement la croissance tumorale. À l'aide d'une lignée de médulloblastome (DAOY), nous avons identifié et évalué de nouvelles caractéristiques cellulaires et moléculaires impliquées dans la régulation du phénotype invasif associé à la formation de structures comparables aux neurosphères formées par les CSC CD133(+). De plus, nous avons apporté de nouvelles informations concernant les propriétés chimiopréventives du sulforaphane (SFN), un composé naturel retrouvé principalement dans le brocoli, en ciblant spécifiquement les CET cérébrales possiblement impliquées dans la cooption vasculaire. En utilisant la technologie de \ud l'ARN interférant, nous avons montré que MMP-9 et MT1-MMP, deux métalloprotéinases matricielles importantes pour l'invasion cellulaire, les métastases et la résistance à la radiation, avaient un rôle crucial dans la formation par les DAOY de \ud structures apparentées aux neurosphères CD133(+). De plus, nous avons mis en évidence une inhibition presque complète (> 90 %) de la migration des HBMEC (human brain microvascular endothelial cell) activées par un carcinogène, le phorbol 12-myristate 13-acétate (PMA). Ainsi, nos résultats suggèrent que les molécules présentes dans notre diète pourraient cibler les CET cérébrales composant la masse tumorale. En somme, nous proposons que MMP-9 constitue une cible de choix pour le traitement du cancer, que ce soit au niveau du compartiment tumoral ou vasculaire. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Cellule souche cancéreuse (CSC), Cellule endothéliale tumorale (CET), Sulforaphane (SFN), Métalloprotéinase matricielle-9 (MMP-9), Tumeur cérébrale