3,038 research outputs found
Structural stability of the two-fold singularity
At a two-fold singularity, the velocity vector of a flow switches discontinuously across a codimension one switching manifold, between two directions that both lie tangent to the manifold. Particularly intricate dynamics arises when the local flow curves toward the switching manifold from both sides, a case referred to as the Teixeira singularity. The flow locally performs two different actions: it winds around the singularity by crossing repeatedly through, and passes through the singularity by sliding along, the switching manifold. The case when the number of rotations around the singularity is infinite has been analyzed in detail. Here we study the case when the flow makes a finite, but previously unknown, number of rotations around the singularity between incidents of sliding. We show that the solution is remarkably simple: the maximum and minimum numbers of rotations made anywhere in the flow differ only by one and increase incrementally with a single parameter -the angular jump in the flow direction across the switching manifold at the singularity
Experiencia clĂnica del tratamiento con onabotulinumtoxin A en pacientes con migraña refractaria
To analyse our experience in the treatment of refractory chronic migraine,
episodic frequent refractory migraine (>= 10 days/month), with onabotulinumtoxin
A (OnabotA). PATIENTS AND METHODS. Retrospective analysis of patients with
refractory migraine who underwent, at least two sessions of OnabotA pericranial
injections following the PREEMPT protocol between 2008 and 2012. The efficacy of
OnabotA was evaluated comparing the basal situation with 12-16 weeks after the
second session. We analysed the subjective improvement of the patients, number of
days with headache, preventive and abortive drugs consumption, and adverse
effects. RESULTS. Forty-one patients (37 women, 4 male) were identified. 65.8%
patients experienced subjective improvement after OnabotA treatment. 36.58%
responded (reduction of > 50% in headache days). Differences between days with
headache before the first session (24.5 +/- 7.3), and 12-16 weeks after the
second session (17.4 +/- 11.6), as well as the differences between the number of
abortive drugs taken before the first session (26.8 +/- 23.1) and 12-16 weeks
after the second session (16.7 +/- 19.3), were statistically significant (p <
0.001). Subgroups analysis showed that all differences were significant, except
for the reduction of the number of days with headache in patients with episodic
frequent refractory migraine. CONCLUSION. Our work shows that treatment with
OnabotA is safe and useful in patients with episodic and chronic refractory
migraine, including those patients with medication overuse headache
Solutions of the Strominger System via Stable Bundles on Calabi-Yau Threefolds
We prove that a given Calabi-Yau threefold with a stable holomorphic vector
bundle can be perturbed to a solution of the Strominger system provided that
the second Chern class of the vector bundle is equal to the second Chern class
of the tangent bundle. If the Calabi-Yau threefold has strict SU(3) holonomy
then the equations of motion derived from the heterotic string effective action
are also satisfied by the solutions we obtain.Comment: 19 pages, late
Metalloprotease OMA1 Fine-tunes Mitochondrial Bioenergetic Function and Respiratory Supercomplex Stability
Mitochondria are involved in key cellular functions including energy production, metabolic homeostasis, and apoptosis. Normal mitochondrial function is preserved by several interrelated mechanisms. One mechanism – intramitochondrial quality control (IMQC) – is represented by conserved proteases distributed across mitochondrial compartments. Many aspects and physiological roles of IMQC components remain unclear. Here, we show that the IMQC protease Oma1 is required for the stability of the respiratory supercomplexes and thus balanced and tunable bioenergetic function. Loss of Oma1 activity leads to a specific destabilization of respiratory supercomplexes and consequently to unbalanced respiration and progressive respiratory decline in yeast. Similarly, experiments in cultured Oma1-deficient mouse embryonic fibroblasts link together impeded supercomplex stability and inability to maintain proper respiration under conditions that require maximal bioenergetic output. Finally, transient knockdown of OMA1 in zebrafish leads to impeded bioenergetics and morphological defects of the heart and eyes. Together, our biochemical and genetic studies in yeast, zebrafish and mammalian cells identify a novel and conserved physiological role for Oma1 protease in fine-tuning of respiratory function. We suggest that this unexpected physiological role is important for cellular bioenergetic plasticity and may contribute to Oma1- associated disease phenotypes in humans
Quantification of titanium dioxide (TiO2) anatase and rutile polymorphs in binary mixtures by Raman spectroscopy: an interlaboratory comparison
This article presents an interlaboratory comparison (ILC) on Raman spectroscopy as a technique for relative quantification of the two most common polymorphs of titanium dioxide (TiO2)-anatase and rutile-in binary mixtures. Some standard methods are currently employed internationally for the determination of TiO2 content in samples (ISO 591-1, ASTM D3720-90), but require extensive sample preparation, do not distinguish between the two polymorphs or are accurate only for small fractions of either polymorph. Raman spectroscopy is a well-suited characterization technique for measuring and differentiating TiO2 in a fast, non-invasive way, while requiring no particular reagent or sample preparation. Eleven international participants conducted the study under the framework of Versailles Project on Advanced Materials and Standards. The collected data was analyzed by means of partial least squares regression after spectral preprocessing. The resulting models all show discrepancies of lower than 2% from the nominal values in the quantitative analysis over the concentration range of 5%-95% mixture fractions, with many datasets showing substantial improvement margins on this figure. The results of this ILC provide validation of Raman spectroscopy as a reliable method for quantification of TiO2 phases
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