C.R. Xllle Colloque Européen d'Arachnologie, Neuchâtel, 2 - 6 septembre 1991 [Rezension]

Das 13. Europäische Arachnologische Kolloquium fand vom 2.-6. September 1991 in Neuchâtel (Schweiz) statt. Die in Neuchâtel vorgetragenen wissenschaftlichen Ergebnisse liegen nun gedruckt als Tagungsbericht vor

On bounds and algorithms for frequency synchronization for collaborative communication systems

Cooperative diversity systems are wireless communication systems designed to exploit cooperation among users to mitigate the effects of multipath fading. In fairly general conditions, it has been shown that these systems can achieve the diversity order of an equivalent MISO channel and, if the node geometry permits, virtually the same outage probability can be achieved as that of the equivalent MISO channel for a wide range of applicable SNR. However, much of the prior analysis has been performed under the assumption of perfect timing and frequency offset synchronization. In this paper, we derive the estimation bounds and associated maximum likelihood estimators for frequency offset estimation in a cooperative communication system. We show the benefit of adaptively tuning the frequency of the relay node in order to reduce estimation error at the destination. We also derive an efficient estimation algorithm, based on the correlation sequence of the data, which has mean squared error close to the Cramer-Rao Bound.Comment: Submitted to IEEE Transaction on Signal Processin

List of endangered harvestmen species of Germany (Red Data Book) (Arachnida: Opiliones)

Erstmals wird hiermit eine Rote Liste der Weberknechte vorgelegt, die sich auf das vereinigte Deutschland bezieht. Die beiden ersten Fassungen der Roten Liste (MARTENS 1977, 1984) waren auf die BRD in ihren alten Grenzen beschränkt; in der DDR gab es ein entsprechendes Verzeichnis nicht. Wegen des veränderten territorialen Bezuges und des besseren faunistischen Kenntnisstandes waren gegenüber der vorhergehenden Liste Veränderungen in den Einstufungen der Arten erforderlich. Sie ergaben sich z.T. zwangsläufig mit den aktuellen Definitionen für die Gefährdungskategorien bzw. den neu eingeführten Rubriken "R" (Arten mit geographischer Restriktion) und ,,u" (Arten, deren Gefährdungsstatus unsicher ist)

FDA Actions Against Health Economic Promotions, 2002–2011

AbstractObjectiveTo investigate Food and Drug Administration (FDA) regulatory actions against drug companies' health economic promotions from 2002 through 2011 to understand how frequently and in what circumstances the agency has considered such promotions false or misleading.MethodsWe reviewed all warning letters and notices of violation (“untitled letters”) issued by the FDA's Division of Drug Marketing, Advertising and Communications (DDMAC) to pharmaceutical companies from January 2002 through December 2011. We analyzed letters containing a violation related to “health economic promotion,” defined according to one of several categories (e.g., implied claims of cost savings due to work productivity or economic claims containing unsupported statements about effectiveness or safety). We also collected information on factors such as the indication and type of media involved and whether the letter referenced Section 114 of the Food and Drug Administration Modernization Act.ResultsOf 291 DDMAC letters sent to pharmaceutical companies during the study period, 35 (12%) cited a health economic violation. The most common type of violation cited was an implied claim of cost savings due to work productivity or functioning (found in 20 letters) and economic claims containing unsubstantiated comparative claims of effectiveness, safety, or interchangeability (7 letters). The violations covered various indications, mostly commonly psychiatric disorders (6 letters) and pain (6 letters). No DDMAC letter pertained to Food and Drug Administration Modernization Act Section 114.ConclusionThe FDA has cited inappropriate health economic promotions in roughly 12% of the letters issued by the DDMAC. The letters highlight drug companies' interest in promoting the value of their products and the FDA's concerns in certain cases about the lack of supporting evidence

Twitter reciprocal reply networks exhibit assortativity with respect to happiness

The advent of social media has provided an extraordinary, if imperfect, 'big data' window into the form and evolution of social networks. Based on nearly 40 million message pairs posted to Twitter between September 2008 and February 2009, we construct and examine the revealed social network structure and dynamics over the time scales of days, weeks, and months. At the level of user behavior, we employ our recently developed hedonometric analysis methods to investigate patterns of sentiment expression. We find users' average happiness scores to be positively and significantly correlated with those of users one, two, and three links away. We strengthen our analysis by proposing and using a null model to test the effect of network topology on the assortativity of happiness. We also find evidence that more well connected users write happier status updates, with a transition occurring around Dunbar's number. More generally, our work provides evidence of a social sub-network structure within Twitter and raises several methodological points of interest with regard to social network reconstructions.Comment: 22 pages, 21 figures, 5 tables, In press at the Journal of Computational Scienc

Negative Activism

Shareholder activism has become one of the most important and widely studied topics in law and finance. To date, popular and academic accounts have focused on what we call “positive activism,” where activists seek to profit from positive changes in the share prices of targeted firms. In this Article, we undertake the first comprehensive study of positive activism’s mirror image, which we term “negative activism.” Whereas positive activists focus on increasing share prices, negative activists take short positions to profit from decreasing share prices. We develop a descriptive typology of three categories of negative activism and use a private database of activist activity and other hand-collected information to provide empirical evidence about the frequency and manner with which each category occurs. First, informational negative activism seeks to uncover and then communicate the truth about companies whose shares the activists believe are overvalued. We show that the announcement of this kind of activism is associated with a statistically significant abnormal decline in share prices. Second, operational negative activism involves dismantling or disabling sources of value at companies. We document a range of actual and potential instances of operational negative activism and associated abnormal share price declines. Third, unintentionally negative activists are failed positive activists: their announcements of ownership stakes in companies they target are met with immediate negative abnormal returns. Using this typology and the related evidence, we explore the policy and regulatory implications for each category of negative activism. We show a range of areas where policy and regulatory goals either conflict with or seemingly ignore the effects from negative activism. We also offer several ways that existing regulatory approaches could be improved to account for negative activism. In general, we advocate less regulation, and even subsidization, of informational negative activism; tighter regulation of operational negative activism; and a more nuanced approach to unintentional negative activism

Negative Activism

Shareholder activism has become one of the most important and widely studied topics in law and finance. To date, popular and academic accounts have focused on what we call “positive activism,” where activists seek to profit from positive changes in the share prices of targeted firms. In this Article, we undertake the first comprehensive study of positive activism’s mirror image, which we term “negative activism.” Whereas positive activists focus on increasing share prices, negative activists take short positions to profit from decreasing share prices. We develop a descriptive typology of three categories of negative activism and use a private database of activist activity and other hand-collected information to provide empirical evidence about the frequency and manner with which each category occurs. First, informational negative activism seeks to uncover and then communicate the truth about companies whose shares the activists believe are overvalued. We show that the announcement of this kind of activism is associated with a statistically significant abnormal decline in share prices. Second, operational negative activism involves dismantling or disabling sources of value at companies. We document a range of actual and potential instances of operational negative activism and associated abnormal share price declines. Third, unintentionally negative activists are failed positive activists: their announcements of ownership stakes in companies they target are met with immediate negative abnormal returns. Using this typology and the related evidence, we explore the policy and regulatory implications for each category of negative activism. We show a range of areas where policy and regulatory goals either conflict with or seemingly ignore the effects from negative activism. We also offer several ways that existing regulatory approaches could be improved to account for negative activism. In general, we advocate less regulation, and even subsidization, of informational negative activism; tighter regulation of operational negative activism; and a more nuanced approach to unintentional negative activism

Die Weberknechte (Arachnida, Opiliones) der Naturschutzgebiete Großer und Kleiner Rakel und angrenzender Waldgebiete

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