7,896 research outputs found
Traumatic appendicitis is probably not real:an illustrative analysis of coincidental occurrences in nature
On conjectures of Hovey-Strickland and Chai
We prove the height two case of a conjecture of Hovey and Strickland that provides a -local analogue of the Hopkins--Smith thick subcategory theorem. Our approach first reduces the general conjecture to a problem in arithmetic geometry posed by Chai. We then use the Gross--Hopkins period map to verify Chai's Hope at height two and all primes. Along the way, we show that the graded commutative ring of completed cooperations for Morava -theory is coherent, and that every finitely generated Morava module can be realized by a -local spectrum as long as . Finally, we deduce consequences of our results for descent of Balmer spectra
The influence of expertise on brain activation of the action observation network during anticipation of tennis and volleyball serves
In many daily activities, and especially in sport, it is necessary to predict the effects of others' actions in order to initiate appropriate responses. Recently, researchers have suggested that the action-observation network (AON) including the cerebellum plays an essential role during such anticipation, particularly in sport expert performers. In the present study, we examined the influence of task-specific expertise on the AON by investigating differences between two expert groups trained in different sports while anticipating action effects. Altogether, 15 tennis and 16 volleyball experts anticipated the direction of observed tennis and volleyball serves while undergoing functional magnetic resonance imaging (fMRI). The expert group in each sport acted as novice controls in the other sport with which they had only little experience. When contrasting anticipation in both expertise conditions with the corresponding untrained sport, a stronger activation of AON areas (SPL, SMA), and particularly of cerebellar structures, was observed. Furthermore, the neural activation within the cerebellum and the SPL was linearly correlated with participant's anticipation performance, irrespective of the specific expertise. For the SPL, this relationship also holds when an expert performs a domain-specific anticipation task. Notably, the stronger activation of the cerebellum as well as of the SMA and the SPL in the expertise conditions suggests that experts rely on their more fine-tuned perceptual-motor representations that have improved during years of training when anticipating the effects of others' actions in their preferred sport. The association of activation within the SPL and the cerebellum with the task achievement suggests that these areas are the predominant brain sites involved in fast motor predictions. The SPL reflects the processing of domain-specific contextual information and the cerebellum the usage of a predictive internal model to solve the anticipation task. © 2014 Balser, Lorey, Pilgramm, Naumann, Kindermann, Stark, Zentgraf, Williams and Munzert
On the search for the chiral anomaly in Weyl semimetals: The negative longitudinal magnetoresistance
Recently, the existence of massless chiral (Weyl) fermions has been
postulated in a class of semi-metals with a non-trivial energy dispersion.These
materials are now commonly dubbed Weyl semi-metals (WSM).One predicted property
of Weyl fermions is the chiral or Adler-Bell-Jackiw anomaly, a chirality
imbalance in the presence of parallel magnetic and electric fields. In WSM, it
is expected to induce a negative longitudinal magnetoresistance (NMR), the
chiral magnetic effect.Here, we present experimental evidence that the
observation of the chiral magnetic effect can be hindered by an effect called
"current jetting". This effect also leads to a strong apparent NMR, but it is
characterized by a highly non-uniform current distribution inside the sample.
It appears in materials possessing a large field-induced anisotropy of the
resistivity tensor, such as almost compensated high-mobility semimetals due to
the orbital effect.In case of a non-homogeneous current injection, the
potential distribution is strongly distorted in the sample.As a consequence, an
experimentally measured potential difference is not proportional to the
intrinsic resistance.Our results on the MR of the WSM candidate materials NbP,
NbAs, TaAs, TaP exhibit distinct signatures of an inhomogeneous current
distribution, such as a field-induced "zero resistance' and a strong dependence
of the `measured resistance" on the position, shape, and type of the voltage
and current contacts on the sample. A misalignment between the current and the
magnetic-field directions can even induce a "negative resistance".
Finite-element simulations of the potential distribution inside the sample,
using typical resistance anisotropies, are in good agreement with the
experimental findings. Our study demonstrates that great care must be taken
before interpreting measurements of a NMR as evidence for the chiral anomaly in
putative Weyl semimetals.Comment: 13 pages, 6 figure
Spinaler Infarkt
Zusammenfassung: Die durch einen RĂŒckenmarkinfarkt verursachte Symptomatik kann aufgrund der komplexen Blutversorgung des Myelons zu unterschiedlichen neurologischen AusfĂ€llen fĂŒhren. Dabei steht hĂ€ufig die durch eine arterielle Minderperfusion des Myelons bedingte Querschnittssymptomatik im Vordergrund. Venös induzierte Mikrozirkulationsstörungen sind anhand des neurologischen Befundes klinisch nicht immer von arteriellen Infarkten zu unterscheiden. Die moderne Bildgebung unter Einsatz der CT- (CTA) und MR-Angiographie (MRA) dient dem Ausschluss nichtvaskulĂ€rer Ursachen fĂŒr die Symptomatik wie EntzĂŒndungen und Tumoren sowie der prĂ€operativen Planung vor der Aortenchirurgie zum Nachweis der fĂŒr die Myelondurchblutung entscheidenden A.Adamkiewicz. Im Gegensatz zur CT kann mittels MRT ein Infarkt im Myelon mit hoher VerlĂ€sslichkeit nachgewiesen werde
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