The Success of the Light Armoured Vehicle

Since the 1970s, budget constraints and debates over the tank’s relevance have prompted the Canadian Forces (CF) to pursue lighter, cheaper, and more flexible vehicles. The Light Armoured Vehicle (LAV), built in London, Ontario, has been purchased in great numbers to satisfy these demands, and it has largely succeeded. The CF has purchased the LAV as a wheeled, multi–purpose vehicle to fulfill a variety of roles (infantry carrier, medical evacuation vehicle, etc.), that is cheaper and easier to maintain than tracked alternatives. The CF has continued to purchase LAVs because they have been successful in the field, and they support a domestic producer, General Dynamics Land Systems Canada (GDLS–C), that cooperates closely with the military

Immune Functions of the Vermiform Appendix

The vermiform appendix Is purported to be the classic example of a vestigial organ, yet for nearly a century it has been known to be a specialized organ highly infiltrated with lymphoid tissue. This lymphoid tissue may help protect against local gut infections. As the vertebrate taxonomic scale increases, the lymphoid tissue of the large bowel tends to be concentrated In a specific region of the gut: the cecal apex or vermiform appendix. The rabbit appendix has the greatest relative lymphoid development. Neonatal appendectomy in rabbits results in decreased total lymphocyte counts and lower antibody response to immune challenges relative to sham-operated controls. Appendectomy in young adult rabbits subject to whole body irradiation also depresses immunocompetence. The ultrastructure of the rabbit and human appendix mirrors that of Peyer\u27s patches and the avian bursa of Fabricius. The appendix shares secondary functions of the avian bursa: it transports antigens from the intestinal lumen to the lamina propria; these antigens stimulate B cell proliferation, dissemination throughout the gut-associated lymphoid tissues, and differentiation into antibody secreting cells. In vitro studies indicate the human appendix contains immunocompetent B cells, T cells and natural killer cells. It is also a major site of IgA induction. Several epidemiologic studies suggest a correlation between appendectomy and cancer risk but these findings are inconclusive. Incidental appendectomy is often practiced by physicians despite the growing evidence that the appendix may be an Important component of the immune system

Feedforward and feedback control in apraxia of speech: effects of noise masking on vowel production

PURPOSE: This study was designed to test two hypotheses about apraxia of speech (AOS) derived from the Directions Into Velocities of Articulators (DIVA) model (Guenther et al., 2006): the feedforward system deficit hypothesis and the feedback system deficit hypothesis. METHOD: The authors used noise masking to minimize auditory feedback during speech. Six speakers with AOS and aphasia, 4 with aphasia without AOS, and 2 groups of speakers without impairment (younger and older adults) participated. Acoustic measures of vowel contrast, variability, and duration were analyzed. RESULTS: Younger, but not older, speakers without impairment showed significantly reduced vowel contrast with noise masking. Relative to older controls, the AOS group showed longer vowel durations overall (regardless of masking condition) and a greater reduction in vowel contrast under masking conditions. There were no significant differences in variability. Three of the 6 speakers with AOS demonstrated the group pattern. Speakers with aphasia without AOS did not differ from controls in contrast, duration, or variability. CONCLUSION: The greater reduction in vowel contrast with masking noise for the AOS group is consistent with the feedforward system deficit hypothesis but not with the feedback system deficit hypothesis; however, effects were small and not present in all individual speakers with AOS. Theoretical implications and alternative interpretations of these findings are discussed.R01 DC002852 - NIDCD NIH HHS; R01 DC007683 - NIDCD NIH HH

Regulation of Fruiting In Plum Production

This short overview article describes different strategies to adjust crop loads in plums in order to get regular cropping, improve fruit size and fruit quality. There are three principal methods of regulating the crop loads of plum, which can be combined: numbers of flowers on the tree can be reduced, flowers can be prevented from fruit setting and the amount of fruitlets can be reduced by thinning methods. The methods of achieving these strategies, by manual, mechanical and chemical means are described and discussed

On the appearance of internal wave attractors due to an initial or parametrically excited disturbance

In this paper we solve two initial value problems for two-dimensional internal gravity waves. The waves are contained in a uniformly stratified, square-shaped domain whose sidewalls are tilted with respect to the direction of gravity. We consider several disturbances of the initial stream function field and solve both for its free evolution and for its evolution under parametric excitation. We do this by developing a structure-preserving numerical method for internal gravity waves in a two-dimensional stratified fluid domain. We recall the linearized, inviscid Euler-Boussinesq model, identify its Hamiltonian structure, and derive a staggered finite difference scheme that preserves this structure. For the discretized model, the initial condition can be projected onto normal modes whose dynamics is described by independent harmonic oscillators. This fact is used to explain the persistence of various classes of wave attractors in a freely evolving (i.e. unforced) flow. Under parametric forcing, the discrete dynamics can likewise be decoupled into Mathieu equations. The most unstable resonant modes dominate the solution, forming wave attractors

Feedback and Feedforward Control in Speech Production in Apraxia of Speech and Aphasia

Apraxia of speech (AOS) is considered to be a speech motor planning impairment (e.g., McNeil et al., 2009), but the nature of this impairment remains poorly understood. The present study was designed to test two hypotheses about the nature of AOS, framed in the DIVA model (Guenther et al., 2006). The DIVA model assumes that speech targets are regions in auditory space, and combines two control mechanisms to reach those targets: feedback control and feedforward control. The feedback mechanism generates corrective motor commands when the actual speech sound deviates from the intended speech sound. The feedforward mechanism generates predictive motor commands based on past experiences with the speech target. In the context of the DIVA model, we developed two hypotheses about possible underlying deficits in AOS. The Feedforward Control Impairment (FF) hypothesis states that feedforward control is impaired in AOS, with consequently a greater reliance on feedback control (Jacks, 2008). The Feedback Control Impairment (FB) hypothesis states that feedback control is impaired in AOS; concurrent feedback may be disruptive (cf. Ballard & Robin, 2007). We tested these hypotheses by measuring acoustic vowel contrast in two conditions: normal listening and auditory feedback masking. Under masking conditions, unimpaired speakers maintain segmental contrast (suggesting adequate feedforward commands to support speech without auditory feedback) even though contrast is somewhat reduced (suggesting on-line use of auditory feedback) (Perkell et al., 2007). The FF hypothesis predicts a greater reduction of segmental contrast with feedback masking in speakers with AOS than in controls, because effective removal of the auditory feedback control strategy will reveal the impaired feedforward commands. The FB hypothesis, in contrast, predicts increased segmental contrast with feedback masking, because removal of auditory feedback will allow the intact feedforward commands to produce adequate contrasts. One previous study that used feedback masking in AOS examined vowel duration and found longer vowels with masking in AOS and controls (Rogers et al., 1996); the present study also examined vowel duration

Feedback and feedforward control in apraxia of speech: Noise masking effects on fricative production

The present study tested two hypotheses about apraxia of speech (AOS), framed in the DIVA model (Guenther, Ghosh, & Tourville, 2006). The DIVA model assumes that speech targets are regions in auditory space, and combines two mechanisms to reach those targets: feedback control and feedforward control. The Feedforward System Deficit (FF) hypothesis states that feedforward control is impaired in AOS, with consequently a greater reliance on feedback control (Jacks, 2008; Maas, Mailend, & Guenther, 2013). The Feedback System Deficit (FB) hypothesis states that feedback control is impaired in AOS; for example, self-generated auditory feedback may be disruptive (cf. Ballard & Robin, 2007). We tested these hypotheses by measuring acoustic fricative contrast in normal listening and noise masking conditions. The rationale is that noise masking effectively eliminates the self-generated auditory feedback signal, thus forcing a greater reliance on feedforward control. For unimpaired speakers, we predict a reduction in acoustic contrast, given evidence that speakers monitor and use auditory feedback on-line (e.g., Tourville, Reilly, & Guenther, 2008), though this reduction is expected to be small given the robust feedforward commands presumably available to unimpaired speakers (e.g., Perkell, 2012). For speakers with AOS, the FF hypothesis predicts greater reduction of contrast with masking in AOS patients than in controls, because removal of auditory feedback will reveal the impaired feedforward commands. The FB hypothesis predicts increased contrast with feedback masking, because removal of interfering auditory feedback enables intact feedforward commands to produce adequate contrasts

Peking und die Wahlen in Hongkong: Auswirkungen auf die Stabilität der ehemaligen Kronkolonie und die Taiwanfrage

"Bei den Wahlen zum Legislative Council in der Sonderverwaltungszone (SVR) Hongkong gewannen 2004 zwar erneut die Pekingtreuen Kräfte, doch nimmt dies den anhaltenden Protesten der Hongkonger gegen die unbeliebte und von der chinesischen Führung getragene Regierung Tung nichts an Vehemenz. Seit einem Jahrzehnt stehen sich in der SVR das prochinesische und das prodemokratische Parteienlager gegenüber, wobei letzterem trotz der von vielen unterstützten Forderung nach Reformen ein Sieg bislang verwehrt blieb. Die Peking-feindliche Stimmung in Hongkong hat ihre Ursachen: Die systematische Aushöhlung der Pressefreiheit und die Bevorzugung Peking-freundlicher Medien hat die Menschen ebenso erbost wie die sinkende Toleranz gegenüber Dissidentengruppen und die Zunahme der Repressionen gegenüber China-kritischen Politikern. Was die VR China zudem nervös macht - die Entwicklung in der SVR bleibt auch in Taiwan nicht unbemerkt, jener Region, deren Anschluss sich Peking so sehr wünscht. In der Tat haben die Wahlerfolge der prochinesischen Parteien den Konflikt zwischen Peking und der SVR nicht gelöst. Der Wunsch nach mehr Demokratie, aber auch die gesellschaftliche Dynamik in Hongkong sind Fakten. Beide zu unterdrücken dürfte sich Peking kaum leisten können." (Autorenreferat

SARS - eine verpasste Chance für politische Reformen in China? Eine kritische Reflexion des chinesischen Krisenmanagements im Kontext innen- und außenpolitischer Implikationen

"Die im Frühjahr 2003 in China ausgebrochene Lungenkrankheit SARS sowie die monatelangen Bestrebungen der Pekinger Führung, Verlauf, Dimension und Opferzahl der Seuche geheimzuhalten, lassen die Frage nach politischen Reformen in dem fernöstlichen Land wieder lauter werden. Als Peking nach 22 Wochen der Geheimhaltung erstmals Fehler eingestand und erste Köpfe, so die des Hauptstadtbürgermeisters und der Gesundheitsministerin, rollten, zeigte sich das Ausmaß der Folgeschäden des chinesischen Fehlverhaltens auch auf globaler Bühne - die Kehrseite der in der vernetzten Welt herrschenden Mobilität und Interdependenz hatte sich in erschreckender Klarheit geoffenbart. Die Instrumentalisierung der Katastrophe durch den auf dem 16. Parteitag der Kommunistischen Partei Chinas abtretenden Jiang Zemin bzw. dessen Nachfolger der 'Vierten Generation' machten darüber hinaus ebenso wie das mit dem Abklingen der Seuche einhergehende Ende der informationspolitischen Toleranz deutlich, wie weit das Land von einer 'chinesischen Glasnost' oder gar dem Zusammenbruch der kommunistischen Herrschaft entfernt ist. Sicher - SARS hat an den Grundfesten des Systems genagt und dessen internationaler Reputation geschadet. Dessen Ende jedoch ist, auch dank des stabilen Wirtschaftswachstums im derzeitigen China, noch lange nicht in Sicht." (Autorenreferat