Essentially translation invariant pseudodifferential operators on manifolds with cylindrical ends

We study two classes (or calculi) of pseudodifferential operators defined on manifolds with cylindrical ends: the class of pseudodifferential operators that are ``translation invariant at infinity'' and the class of ``essentially translation invariant operators'' that have appeared in the study of layer potential operators on manifolds with straight cylindrical ends. Both classes are close to the $b$-calculus considered by Melrose and Schulze and to the $c$-calculus considered by Melrose and Mazzeo-Melrose. Our calculi, however, are different and, while some of their properties follow from those of the $b$- or $c$-calculi, many of their properties do not. In particular, the ``essentially translation invariant calculus'' is spectrally invariant, a property not enjoyed by the ``translation invariant at infinity'' calculus or the $b$-calculus. For our calculi, we provide easy, intuitive proofs of the usual properties: stability for products and adjoints, mapping and boundedness properties for operators acting between Sobolev spaces, regularity properties, existence of a quantization map and topological properties of our algebras, the Fredholm property. Since our applications will be to the Stokes operator, we systematically work in the setting of Agmon-Douglis-Nirenberg-elliptic operators.Comment: 39 page

Exchange stiffness in ultrathin perpendicularly-magnetized CoFeB layers determined using spin wave spectroscopy

We measure the frequencies of spin waves in nm-thick perpendicularly magnetized FeCoB systems, and model the frequencies to deduce the exchange stiffness of this material in the ultrathin limit. For this, we embody the layers in magnetic tunnel junctions patterned into circular nanopillars of diameters ranging from 100 to 300 nm and we use magneto-resistance to determine which rf-current frequencies are efficient in populating the spin wave modes. Micromagnetic calculations indicate that the ultrathin nature of the layer and the large wave vectors used ensure that the spin wave frequencies are predominantly determined by the exchange stiffness, such that the number of modes in a given frequency window can be used to estimate the exchange. For 1 nm layers the experimental data are consistent with an exchange stiffness A= 20 pJ/m, which is slightly lower that its bulk counterpart. The thickness dependence of the exchange stiffness has strong implications for the numerous situations that involve ultrathin films hosting strong magnetization gradients, and the micromagnetic description thereof.Comment: 5 pages, 4 figures, submitted to PR

Examining the Relationship Between Math Scores and English Language Proficiency

Multiple studies propose that English proficiency dictates English language learners’ (ELLs) performances on mathematics assessments. The current study investigates the predictive power of English proficiency on mathematics scores, while controlling for gender, socioeconomic status (SES), and grade level among ELLs at a south Florida elementary school. Krashen’s theory of comprehensible input as a precursor to second language acquisition provides the framework for this quantitative, correlation study. Mathematics scores from the Florida Comprehensive Assessment Test for Grade 3–5 ELLs (N = 177) were analyzed using multiple linear regression. Analysis reveals English proficiency as a statistically significant predictor of mathematics scores. Mathematics scores increase simultaneously with English proficiency but inversely with grade level. Grade level moderates the influence of English proficiency on mathematics scores. Gender and SES have no significant moderating influence

Social Mobility Through Mathematics Proficiency for English Language Learners

College admission is contingent upon students’ high school performances, especially mathematics proficiency that is crucial in qualifying for the projected science, technology, engineering, and mathematics professions of the future. This paper reviews some concerns that hinder the efforts of English language learners (ELLs), often the children of immigrants, to achieve social mobility through a college education. ELLs consistently fail to achieve proficiency on mathematics assessments as measured by the National Assessment for Educational Progress and local assessments such as the Florida Comprehensive Assessment Test. Consequently, many ELLs do not attend college. The article examines implications for educators and policymakers for resolving some of the issues that impede transforming ELLs into academic and societal achievers. Actions taken by educators and policymakers might assist ELLs in navigating the challenges encountered in their pursuit of a college education

Androgenic alopecia; the risk–benefit ratio of Finasteride

Finasteride is currently approved and largely used as a therapeutic option for androgenetic alopecia. Apparently a safe drug and effective at the onset of its application, several concerns have since appeared over the years regarding the frequency and magnitude of finasteride adverse effects, which in some cases appear irreversible even after drug termination. This paper discusses the use of finasteride for androgenic alopecia from two distinct perspectives. On the one hand, androgenic alopecia is a condition that especially affects a person’s self-image and esteem, aspects that are subjectively-constructed and thus relative and changeable. On the other hand, this condition involves a multifactorial etiology, with androgens being only partly responsible. Because androgens have important and unique physiological roles within the body, any procedure that results in androgenic suppression should be advised with caution. Furthermore, adverse effects induced by finasteride are neither fully documented nor easily treated. Finally, as alternative therapeutic approaches (such as topical finasteride) become available, the oral administration of finasteride for androgenic alopecia should, in our opinion, be reevaluated. Due to such concerns, a detailed and informed discussion should take place with patients considering therapy with finasteride for androgenic alopecia

Spin injection in Silicon at zero magnetic field

In this letter, we show efficient electrical spin injection into a SiGe based \textit{p-i-n} light emitting diode from the remanent state of a perpendicularly magnetized ferromagnetic contact. Electron spin injection is carried out through an alumina tunnel barrier from a Co/Pt thin film exhibiting a strong out-of-plane anisotropy. The electrons spin polarization is then analysed through the circular polarization of emitted light. All the light polarization measurements are performed without an external applied magnetic field \textit{i.e.} in remanent magnetic states. The light polarization as a function of the magnetic field closely traces the out-of-plane magnetization of the Co/Pt injector. We could achieve a circular polarization degree of the emitted light of 3 % at 5 K. Moreover this light polarization remains almost constant at least up to 200 K.Comment: accepted in AP

Novel types of anti-ecloud surfaces

In high power RF devices for space, secondary electron emission appears as the main parameter governing the multipactor effect and as well as the e-cloud in large accelerators. Critical experimental activities included development of coatings with low secondary electron emission yield (SEY) for steel (large accelerators) and aluminium (space applications). Coatings with surface roughness of high aspect ratio producing the so-call secondary emission suppression effect appear as the selected strategy. In this work a detailed study of the SEY of these technological coatings and also the experimental deposition methods (PVD and electrochemical) are presented. The coating-design approach selected for new low SEY coatings include rough metals (Ag, Au, Al), rough alloys (NEG), particulated and magnetized surfaces, and also graphene like coatings. It was found that surface roughness also mitigate the SEY deterioration due to aging processes.Comment: 4 pages, contribution to the Joint INFN-CERN-EuCARD-AccNet Workshop on Electron-Cloud Effects: ECLOUD'12; 5-9 Jun 2012, La Biodola, Isola d'Elba, Italy; CERN Yellow Report CERN-2013-002, pp.153-15

Muon capture on light nuclei

This work investigates the muon capture reactions 2H(\mu^-,\nu_\mu)nn and 3He(\mu^-,\nu_\mu)3H and the contribution to their total capture rates arising from the axial two-body currents obtained imposing the partially-conserved-axial-current (PCAC) hypothesis. The initial and final A=2 and 3 nuclear wave functions are obtained from the Argonne v_{18} two-nucleon potential, in combination with the Urbana IX three-nucleon potential in the case of A=3. The weak current consists of vector and axial components derived in chiral effective field theory. The low-energy constant entering the vector (axial) component is determined by reproducting the isovector combination of the trinucleon magnetic moment (Gamow-Teller matrix element of tritium beta-decay). The total capture rates are 393.1(8) s^{-1} for A=2 and 1488(9) s^{-1} for A=3, where the uncertainties arise from the adopted fitting procedure.Comment: 6 pages, submitted to Few-Body Sys