Efficient Tests of the Seasonal Unit Root Hypothesis*

In this paper we derive, under the assumption of Gaussian errors with known error covariance matrix, asymptotic local power bounds for seasonal unit root tests for both known and unknown deterministic scenarios and for an arbitrary seasonal aspect. We demonstrate that the optimal test of a unit root at a given spectral frequency behaves asymptotically independently of whether unit roots exist at other frequencies or not. We also develop modified versions of the optimal tests which attain the asymptotic Gaussian power bounds under much weaker conditions. We further propose near-efficient regression-based seasonal unit root tests using pseudo-GLS de-trending and show that these have limiting null distributions and asymptotic local power functions of a known form. Monte Carlo experiments indicate that the regression-based tests perform well in finite samples.Point optimal invariant (seasonal) unit root tests, asymptotic local power bounds, near seasonal integration

Design of a Microengineered Electrostatic Lens

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Les fourmis (Hymenoptera, Formicidae) de l’enclos d’acclimatation de Katané de la réserve de faune du Ferlo nord (Sénégal)

Les fourmis (Hymenoptera, Formicidae), de par leur biomasse, et leur diversité spécifique, jouent un rôle fondamental dans les écosystèmes terrestres tropicaux. Néanmoins, elles sont très peu étudiées et mal connues au Sénégal. Pour contribuer à combler cette lacune nous avons étudié le peuplement des fourmis de l’enclos d’acclimatation de Katané, un site se trouvant dans la Réserve de Faune du Ferlo Nord en zone de savane sahélienne (région de Matam, Sénégal). Les fourmis ont été échantillonnées à l’aide de pièges à fosse et par la chasse à vue. La richesse spécifique (S) est de 21 espèces. Les espèces les plus remarquables par leur abondance et leur distribution sont Crematogaster senegalensis, Monomorium areniphilum, Trichomyrmex abyssinicus, Monomorium bicolor, Pheidole andrieui, Brachyponera sennaarensis, Tetramorium angulinode papyri et Tetramorium sericeiventre. Elles appartiennent toutes à la sous-famille des Myrmicinae sauf B. sennaarensis qui est de la sous-famille des Ponerinae. L’indice de fourragement (9,79), l’indice de Shannon (0,95), l’indice d’équitabilité de Piélou (0,77), l’indice de Simpson (0,14) et l’indice de diversité de Simpson (0,86) peuvent être utilisés comme référentiels pour le suivi de l’évolution des habitats de l’enclos et pour les études de l’état de dégradation des habitats dans le Ferlo en général.© 2016 International Formulae Group. All rights reserved.Mots clés: Fourmis, écosystèmes, diversité, abondance, Ferlo nord, SénégalEnglish Title: Ants (Hymenoptera, Formicidae) of the acclimatization enclosure of Katane in the north Ferlo wildlife reserve (Senegal)English AbstractAnts (Hymenoptera, Formicidae), by their biomass and species diversity, play a fundamental role in the terrestrial ecosystems of the tropical area. Nevertheless, they are very little studied and poorly known in Senegal. To fill this gap we have chosen to study them in the acclimatization enclosure of Katane in the north Ferlo Reserve Wildlife situated in the Sahel savanna in Matam region (Senegal). They were sampled using pitfall traps and hand collecting. Species richness (S) is 21 species. The most remarkable for their abundances and distributions are Crematogaster senegalensis, Monomorium areniphilum, Trichomyrmex abyssinicus, Monomorium bicolor, Pheidole andrieui, Brachyponera sennaarensis, Tetramorium angulinode papyri and Tetramorium sericeiventre. They all belong to the subfamily Myrmicinae except B. sennaarensis which belongs to the subfamily Ponerinae. The foraging index (9.79), the Shannon index (0.95), the index of Pielou equitability (0.77), the Simpson index (0.14) and the Simpson's index diversity (0.86) can be used as reference for monitoring the biotopes evolution in the enclosure of Katané and for the studies of land degradation in the Ferlo in general.© 2016 International Formulae Group. All rights reserved.Keywords: Ants, ecosystems, diversity, abundance, northern Ferlo, Senega

Silicon micromachined mass filter for a low power, low cost quadrupole mass spectrometer

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The impact of freight transport capacity limitations on supply chain dynamics

We investigate how capacity limitations in the transportation system affect the dynamic behaviour of supply chains. We are interested in the more recently defined, 'backlash' effect. Using a system dynamics simulation approach, we replicate the well-known Beer Game supply chain for different transport capacity management scenarios. The results indicate that transport capacity limitations negatively impact on inventory and backlog costs, although there is a positive impact on the 'backlash' effect. We show that it is possible for both backlog and inventory to simultaneous occur, a situation which does not arise with the uncapacitated scenario. A vertical collaborative approach to transport provision is able to overcome such a trade-off. © 2013 Taylor & Francis

Inward propagating chemical waves in Taylor vortices

Advection-reaction-diffusion (ARD) waves in the Belousov-Zhabotinsky reaction in steady Taylor-Couette vortices have been visualized using magnetic-resonance imaging and simulated using an adapted Oregonator model. We show how propagating wave behavior depends on the ratio of advective, chemical and diffusive time scales. In simulations, inward propagating spiral flamelets are observed at high Damköhler number (Da). At low Da, the reaction distributes itself over several vortices and then propagates inwards as contracting ring pulses—also observed experimentally

A practical gauge invariant regularization of the SO(10) grand unified model

It is shown that a simple modification of the dimensional regularization allows to compute in a consistent and gauge invariant way any diagram with less than four loops in the SO(10) unified model. The method applies also to the Standard Model generated by the symmetry breaking $SO(10) \to SU(3)\times SU(2)\times U(1)$. A gauge invariant regularization for arbitrary diagram is also described.Comment: 10 pages, uses linedraw.st

Nuttier Bubbles

We construct new explicit solutions of general relativity from double analytic continuations of Taub-NUT spacetimes. This generalizes previous studies of 4-dimensional nutty bubbles. One 5-dimensional locally asymptotically AdS solution in particular has a special conformal boundary structure of $AdS_3\times S^1$. We compute its boundary stress tensor and relate it to the properties of the dual field theory. Interestingly enough, we also find consistent 6-dimensional bubble solutions that have only one timelike direction. The existence of such spacetimes with non-trivial topology is closely related to the existence of the Taub-NUT(-AdS) solutions with more than one NUT charge. Finally, we begin an investigation of generating new solutions from Taub-NUT spacetimes and nuttier bubbles. Using the so-called Hopf duality, we provide new explicit time-dependent backgrounds in six dimensions.Comment: 32 pages, 1 figure; v.3. typos corrected. Matches the published versio