Measuring valley polarization in two-dimensional materials with second-harmonic spectroscopy

A population imbalance at different valleys of an electronic system lowers its effective rotational symmetry. We introduce a technique to measure such imbalance - a valley polarization - that exploits the unique fingerprints of this symmetry reduction in the polarization-dependent second-harmonic generation (SHG). We present the principle and detection scheme in the context of hexagonal two-dimensional crystals, which include graphene-based systems and the family of transition metal dichalcogenides, and provide a direct experimental demonstration using a 2H-MoSe$_{2}$ monolayer at room temperature. We deliberately use the simplest possible setup, where a single pulsed laser beam simultaneously controls the valley imbalance and tracks the SHG process. We further developed a model of the transient population dynamics which analytically describes the valley-induced SHG rotation in very good agreement with the experiment. In addition to providing the first experimental demonstration of the effect, this work establishes a conceptually simple, com-pact and transferable way of measuring instantaneous valley polarization, with direct applicability in the nascent field of valleytronics

Prediction of sarcomere mutations in subclinical hypertrophic cardiomyopathy.

BACKGROUND: Sarcomere protein mutations in hypertrophic cardiomyopathy induce subtle cardiac structural changes before the development of left ventricular hypertrophy (LVH). We have proposed that myocardial crypts are part of this phenotype and independently associated with the presence of sarcomere gene mutations. We tested this hypothesis in genetic hypertrophic cardiomyopathy pre-LVH (genotype positive, LVH negative [G+LVH-]). METHODS AND RESULTS: A multicenter case-control study investigated crypts and 22 other cardiovascular magnetic resonance parameters in subclinical hypertrophic cardiomyopathy to determine their strength of association with sarcomere gene mutation carriage. The G+LVH- sample (n=73) was 29 ± 13 years old and 51% were men. Crypts were related to the presence of sarcomere mutations (for ≥1 crypt, β=2.5; 95% confidence interval [CI], 0.5-4.4; P=0.014 and for ≥2 crypts, β=3.0; 95% CI, 0.8-7.9; P=0.004). In combination with 3 other parameters: anterior mitral valve leaflet elongation (β=2.1; 95% CI, 1.7-3.1; P<0.001), abnormal LV apical trabeculae (β=1.6; 95% CI, 0.8-2.5; P<0.001), and smaller LV end-systolic volumes (β=1.4; 95% CI, 0.5-2.3; P=0.001), multiple crypts indicated the presence of sarcomere gene mutations with 80% accuracy and an area under the curve of 0.85 (95% CI, 0.8-0.9). In this G+LVH- population, cardiac myosin-binding protein C mutation carriers had twice the prevalence of crypts when compared with the other combined mutations (47 versus 23%; odds ratio, 2.9; 95% CI, 1.1-7.9; P=0.045). CONCLUSIONS: The subclinical hypertrophic cardiomyopathy phenotype measured by cardiovascular magnetic resonance in a multicenter environment and consisting of crypts (particularly multiple), anterior mitral valve leaflet elongation, abnormal trabeculae, and smaller LV systolic cavity is indicative of the presence of sarcomere gene mutations and highlights the need for further study

From bound states to resonances: analytic continuation of the wave function

Single-particle resonance parameters and wave functions in spherical and deformed nuclei are determined through analytic continuation in the potential strength. In this method, the analyticity of the eigenvalues and eigenfunctions of the Schroedinger equation with respect to the coupling strength is exploited to analytically continue the bound-state solutions into the positive-energy region by means of Pade' approximants of the second kind. The method is here applied to single-particle wave functions of the $^{154}Sm$ and $^{131}Eu$ nuclei. A comparison of the results with the direct solution of the Schroedinger equation shows that the method can be confidently applied also in coupled-channel situations requiring high numerical accuracy.Comment: 13 pages, 3 figure

Non-hermiticity in spintronics: oscillation death in coupled spintronic nano-oscillators through emerging exceptional points

The emergence of exceptional points (EPs) in the parameter space of a non-hermitian (2D) eigenvalue problem is studied in a general sense in mathematical physics, and has in the last decade successively reached the scope of experiments. In coupled systems, it gives rise to unique physical phenomena, which enable novel approaches for the development of seminal types of highly sensitive sensors. Here, we demonstrate at room temperature the emergence of EPs in coupled spintronic nanoscale oscillators and hence exploit the system's non-hermiticity. We describe the observation of amplitude death of self-oscillations and other complex dynamics, and develop a linearized non-hermitian model of the coupled spintronic system, which properly describes the main experimental features. Interestingly, these spintronic nanoscale oscillators are deployment-ready in different applicational technologies, such as field, current or rotation sensors, radiofrequeny and wireless devices and, more recently, novel neuromorphic hardware solutions. Their unique and versatile properties, notably their large nonlinear behavior, open up unprecedented perspectives in experiments as well as in theory on the physics of exceptional points. Furthermore, the exploitation of EPs in spintronics devises a new paradigm for ultrasensitive nanoscale sensors and the implementation of complex dynamics in the framework of non-conventional computing

Developing pressure swing adsorption process for biogas upgrading using shaped MIL-160(Al)

In this study, regarding the increasing interest on renewable sources of energy as well as considering the challenges of climate changes, the potential of shaped MOF MIL-160 (Al) for biogas upgrading has been evaluated. Accordingly, firstly the breakthrough assessments of CO2 and CH4 adsorption onto this sorbents were studied. Afterwards, a pressure swing adsorption (PSA) process to this end was designed and developed. The results showed MIL-160(Al) has an excellent potential for biogas upgrading concerning CO2 and CH4 separation.info:eu-repo/semantics/publishedVersio

Sludge characterization by image analysis

In wastewater treatment plants by activated sludge, a complex ecosystem constituted mainly of bacteria, protozoa and metazoa is degrading the pollution. Bacteria are agglomerated as flocs, exopolymers helping to bind zoogleal bacteria to filamentous bacteria which constitute the backbone of the flocs. When a good equilibrium is not maintained between these two bacterial groups, problems occur such as pin-floc (when filamentous bacteria are not present), filamentous bulking (when too many filamentous bacteria are present) or viscous bulking (when exopolymers are produced in excess). The protozoa, which contribute to a decrease of the effluent turbidity (by consumption of free bacteria and suspended matter) and stimulate the bacterial growth (by grazing on the flocs) are very sensitive to the plant operation conditions. They can be classified as amoebae, flagellates and ciliated. Generally speaking the species identification and the counting of filamentous bacteria and protozoa are performed manually, which is rather tedious and requires experts for the identification. Image-based procedures have been developed to try to solve this problem. A fully automated procedure has been tested and validated at pilot scale and full-scale: a drop of sludge is examined with an optical microscope (no fixation or staining, brightfield examination), a series of monochrome images is grabbed and analysed to provide information on the number and total length of filamentous bacteria and the size and shape of flocs. More recently this analysis has been coupled to a Gram-staining procedure to evaluate the ratio of Gram-positive to Gram-negative bacteria, as an indication of the species distribution. A semi-automated procedure has been developed in parallel for protozoa. The recognition rate is actually higher than 80% for some species. As the protozoa may be in contact with the flocs, the image segmentation is performed manually by the operator who defines a area of interest around the micro-organism. To improve the classification rate, new morphological descriptors are presently included

Insulator-Superfluid transition of spin-1 bosons in an optical lattice in magnetic field

We study the insulator-superfluid transition of spin-1 bosons in an optical lattice in a uniform magnetic field. Based on a mean-field approximation we obtained a zero-temperature phase diagram. We found that depending on the particle number the transition for bosons with antiferromagnetic interaction may occur into different superfluid phases with spins aligned along or opposite to the field direction. This is qualitatively different from the field-free transition for which the mean-field theory predicts a unique (polar) superfluid state for any particle number.Comment: 10 pages, 2 eps figure

Combination of Pneumococcal Surface Protein A (PspA) with Whole Cell Pertussis Vaccine Increases Protection Against Pneumococcal Challenge in Mice

Streptococcus pneumoniae is the leading cause of respiratory acute infections around the world. In Latin America, approximately 20,000 children under 5 years of age die of pneumococcal diseases annually. Pneumococcal surface protein A (PspA) is among the best-characterized pneumococcal antigens that confer protection in animal models of pneumococcal infections and, as such, is a good alternative for the currently available conjugated vaccines. Efficient immune responses directed to PspA in animal models have already been described. Nevertheless, few low cost adjuvants for a subunit pneumococcal vaccine have been proposed to date. Here, we have tested the adjuvant properties of the whole cell Bordetella pertussis vaccine (wP) that is currently part of the DTP (diphtheria-tetanus-pertussis) vaccine administrated to children in several countries, as an adjuvant to PspA. Nasal immunization of BALB/c mice with a combination of PspA5 and wP or wPlow – a new generation vaccine that contains low levels of B. pertussis LPS – conferred protection against a respiratory lethal challenge with S. pneumoniae. Both PspA5-wP and PspA5-wPlow vaccines induced high levels of systemic and mucosal antibodies against PspA5, with similar profile, indicating no essential requirement for B. pertussis LPS in the adjuvant properties of wP. Accordingly, nasal immunization of C3H/HeJ mice with PspA5-wP conferred protection against the pneumococcal challenge, thus ruling out a role for TLR4 responses in the adjuvant activity and the protection mechanisms triggered by the vaccines. The high levels of anti-PspA5 antibodies correlated with increased cross-reactivity against PspAs from different clades and also reflected in cross-protection. In addition, passive immunization experiments indicated that antibodies played an important role in protection in this model. Finally, subcutaneous immunization with a combination of PspA5 with DTPlow protected mice against challenge with two different pneumococcal strains, opening the possibility for the development of a combined infant vaccine composed of DTP and PspA

Measuring the perception of quality physical education in Latin American professionals

Um plano instável para o desenvolvimento de currículos e questões de apoio na educac¸ão física (PE) criou confusão entre os profissionais. O objetivo desta pesquisa é investigar os fatores percebidos como importantes no desenvolvimento da educac¸ão física de qualidade (QPE) por profissionais de países da América Latina (AL). Um questionário composto por 24 itens com base no QPE foi respondido por 468 profissionais coletados em 6 cidades da América Latina. Uma análise fatorial exploratória dos 24 itens usando extrac¸ão ML e rotac¸ão obliminar direta foram aplicados, e os 17 itens retidos foram agrupados em uma soluc¸ão de três fatores denominada Elementos de Desenvolvimento e Suporte para QPE na Escola (DSFQPE) ( = 0,935), Valor essencial do QPE (CVPE) ( = 0,890) e Arranjo Curricular das Atividades Físicas (CAPA) ( = 0,850). Os itens retidos indicaram propriedades excelentes e o referencial básico percebido pelos profissionais de EF em países da América Latina como importante na investigac¸ão do PEQ. © 2018 Colegio ´ Brasileiro de Ciencias ˆ do Esporte. Publicado por Elsevier Editora Ltda. Este e´ um artigo Open Access sob uma licenc¸a CC BY-NC-N