Creation of spin-triplet Cooper pairs in the absence of magnetic ordering

In superconducting spintronics, it is essential to generate spin-triplet Cooper pairs on demand. Up to now, proposals to do so concentrate on hybrid structures in which a superconductor (SC) is combined with a magnetically ordered material (or an external magnetic field). We, instead, identify a novel way to create and isolate spin-triplet Cooper pairs in the absence of any magnetic ordering. This achievement is only possible because we drive a system with strong spin-orbit interaction--the Dirac surface states of a strong topological insulator (TI)--out of equilibrium. In particular, we consider a bipolar TI-SC-TI junction, where the electrochemical potentials in the outer leads differ in their overall sign. As a result, we find that nonlocal singlet pairing across the junction is completely suppressed for any excitation energy. Hence, this junction acts as a perfect spin triplet filter across the SC generating equal-spin Cooper pairs via crossed Andreev reflection.Comment: 12 pages, 8 figure

Appearance of the universal value e2/he^{2}/h of the zero-bias conductance in a Weyl semimetal-superconductor junction

We study the differential conductance of a time-reversal symmetric Weyl semimetal-superconductor (N-S) junction with an s-wave superconducting state. We find that there exists an extended regime where the zero-bias differential conductance acquires the universal value $e^{2}/h$ per unit channel, independent of the pairing and chemical potentials on each side of the junction, due to a perfect cancellation of Andreev and normal reflection contributions. This universal conductance can be attributed to the interplay of the unique spin/orbital-momentum locking and s-wave pairing that couples Weyl nodes of the same chirality. We expect that the universal conductance can serve as a robust and distinct signature for time-reversal symmetric Weyl fermions, and be observed in the recently discovered time-reversal symmetric Weyl semimetals.Comment: 12 pages, 4 figure

Identification of homogeneos units of the pampa biome using sentinel-2 imagery: Capim-annoni-2 infestation

O objetivo deste trabalho foi o de identificar e classificar as unidades homogêneas presentes nos campos naturais do bioma Pampa pelo uso das imagens Sentinel-2, fundamentado pelas distintas composições dos campos naturais da região da Campanha e pela presença de áreas invadidas com Eragrostis plana Nees (capim-anonni-2). A área de estudo compreendeu a região do Complexo Eólico Cerro Chato em Santana do Livramento- RS. A análise utilizou imagens, uma contendo apenas as bandas de 10 metros e a outra composta pelas bandas de 10 e 20 metros de resolução espacial. Para a classificação foi utilizado o classificador multiestágio ECHO, com suporte de amostras levantadas no campo. Os resultados mostraram que o classificador foi eficiente na discriminação das classes. O valor do coeficiente kappa de 74% para a imagem composta pelas bandas de 10 metros e 84,7% para a imagem de 10 e 20 metros. O desempenho da imagem com 9 bandas apresentou resultados mais fidedignos com a verdade de campo. A boa performance deste produto deu-se em razão da maior variabilidade espectral, onde destacaram-se as bandas localizadas na região da red edge, que tiveram alta contribuição na discriminação do capim-annoni-2.The aim of this study was to identify and classify the homogeneous units present in the natural fields of the Pampa biome by using Sentinel-2 images, based on the different compositions of the natural fields of the Campanha region and on the presence of areas invaded by Eragrostis plana Nees. The study area comprised the Cerro Chato Wind Complex in Santana do Livramento, RS. The analysis used 2 images, one containing only the bands of 10 meters and the other composed by bands of 10 and 20 meters of spatial resolution. For classification, the multi-stage classifier ECHO was used, with support of samples collected in the field. The results showed that the classifier was efficient in class discrimination. The kappa coefficient of 74% for the image composed by the bands of ten meters and 84.7% for the image of 10 and 20 meters. the performance of the image with 9 bands presented more consistent results with the field truth. The good performance of this product was due to the higher spectral variability, where the bands located in the red edge region, which had a high contribution in the discrimination of the capim-annoni-2

IDENTIFICAÇÃO DE UNIDADES HOMOGÊNEAS DO BIOMA PAMPA COM USO DE IMAGENS SENTINEL-2: INFESTAÇÃO DO CAPIM-ANNONI-2

O objetivo deste trabalho foi o de identificar e classificar as unidades homogêneas presentes nos campos naturais do bioma Pampa pelo uso das imagens Sentinel-2, fundamentado pelas distintas composições dos campos naturais da região da Campanha e pela presença de áreas invadidas com Eragrostis plana Nees (capim-anonni-2). A área de estudo compreendeu a região do Complexo Eólico Cerro Chato em Santana do Livramento- RS. A análise utilizou imagens, uma contendo apenas as bandas de 10 metros e a outra composta pelas bandas de 10 e 20 metros de resolução espacial. Para a classificação foi utilizado o classificador multiestágio ECHO, com suporte de amostras levantadas no campo. Os resultados mostraram que o classificador foi eficiente na discriminação das classes. O valor do coeficiente kappa de 74% para a imagem composta pelas bandas de 10 metros e 84,7% para a imagem de 10 e 20 metros. O desempenho da imagem com 9 bandas apresentou resultados mais fidedignos com a verdade de campo. A boa performance deste produto deu-se em razão da maior variabilidade espectral, onde destacaram-se as bandas localizadas na região da red edge, que tiveram alta contribuição na discriminação do capim-annoni-2

Distribution of Gold Nanoparticles in the Anterior Chamber of the Eye after Intracameral Injection for Glaucoma Therapy

In glaucoma therapy, nanoparticles (NPs) are a favorable tool for delivering drugs to the outflow tissues of the anterior chamber of the eye where disease development and progression take place. In this context, a prerequisite is an efficient enrichment of NPs in the trabecular meshwork with minimal accumulation in off-target tissues such as the cornea, lens, iris and ciliary body. We evaluated the optimal size for targeting the trabecular meshwork by using gold NPs of 5, 60, 80 and 120 nm with a bare surface (AuNPs) or coated with hyaluronic acid (HA-AuNPs). NPs were compared regarding their colloidal stability, distribution in the anterior chamber of the eye ex vivo and cellular uptake in vitro. HA-AuNPs demonstrated an exceptional colloidal stability. Even after application into porcine eyes ex vivo, the HA coating prevented an aggregation of NPs inside the trabecular meshwork. NPs with a diameter of 120 nm exhibited the highest volume-based accumulation in the trabecular meshwork. Off-target tissues in the anterior chamber demonstrated an exceptionally low gold content. Our findings are particularly important for NPs with encapsulated anti-glaucoma drugs because a higher particle volume would be accompanied by a higher drug payload

Giant magnetochiral anisotropy from quantum-confined surface states of topological insulator nanowires

Wireless technology relies on the conversion of alternating electromagnetic fields into direct currents, a process known as rectification. Although rectifiers are normally based on semiconductor diodes, quantum mechanical non-reciprocal transport effects that enable a highly controllable rectification were recently discovered1,2,3,4,5,6,7,8,9. One such effect is magnetochiral anisotropy (MCA)6,7,8,9, in which the resistance of a material or a device depends on both the direction of the current flow and an applied magnetic field. However, the size of rectification possible due to MCA is usually extremely small because MCA relies on inversion symmetry breaking that leads to the manifestation of spin–orbit coupling, which is a relativistic effect6,7,8. In typical materials, the rectification coefficient γ due to MCA is usually ∣γ∣ ≲ 1 A−1 T−1 (refs. 8,9,10,11,12) and the maximum values reported so far are ∣γ∣ ≈ 100 A−1 T−1 in carbon nanotubes13 and ZrTe5 (ref. 14). Here, to overcome this limitation, we artificially break the inversion symmetry via an applied gate voltage in thin topological insulator (TI) nanowire heterostructures and theoretically predict that such a symmetry breaking can lead to a giant MCA effect. Our prediction is confirmed via experiments on thin bulk-insulating (Bi1−xSbx)2Te3 (BST) TI nanowires, in which we observe an MCA consistent with theory and ∣γ∣ ≈ 100,000 A−1 T−1, a very large MCA rectification coefficient in a normal conductor

A Comparative Study of Efficient Initialization Methods for the K-Means Clustering Algorithm

K-means is undoubtedly the most widely used partitional clustering algorithm. Unfortunately, due to its gradient descent nature, this algorithm is highly sensitive to the initial placement of the cluster centers. Numerous initialization methods have been proposed to address this problem. In this paper, we first present an overview of these methods with an emphasis on their computational efficiency. We then compare eight commonly used linear time complexity initialization methods on a large and diverse collection of data sets using various performance criteria. Finally, we analyze the experimental results using non-parametric statistical tests and provide recommendations for practitioners. We demonstrate that popular initialization methods often perform poorly and that there are in fact strong alternatives to these methods.Comment: 17 pages, 1 figure, 7 table

Fasudil Loaded PLGA Microspheres as Potential Intravitreal Depot Formulation for Glaucoma Therapy

Rho-associated protein kinase (ROCK) inhibitors allow for causative glaucoma therapy. Unfortunately, topically applied ROCK inhibitors suffer from high incidence of hyperemia and low intraocular bioavailability. Therefore, we propose the use of poly (lactide-co-glycolide) (PLGA) microspheres as a depot formulation for intravitreal injection to supply outflow tissues with the ROCK inhibitor fasudil over a prolonged time. Fasudil-loaded microspheres were prepared by double emulsion solvent evaporation technique. The chemical integrity of released fasudil was confirmed by mass spectrometry. The biological activity was measured in cell-based assays using trabecular meshwork cells (TM cells), Schlemm's canal cells (SC cells), fibroblasts and adult retinal pigment epithelium cells (ARPE-19). Cellular response to fasudil after its diffusion through vitreous humor was investigated by electric cell-substrate impedance sensing. Microspheres ranged in size from 3 to 67 mu m. The release of fasudil from microspheres was controllable and sustained for up to 45 days. Released fasudil reduced actin stress fibers in TM cells, SC cells and fibroblasts. Decreased collagen gel contraction provoked by fasudil was detected in TM cells (similar to 2.4-fold), SC cells (similar to 1.4-fold) and fibroblasts (similar to 1.3-fold). In addition, fasudil readily diffused through vitreous humor reaching its target compartment and eliciting effects on TM cells. No negative effects on ARPE-19 cells were observed. Since fasudil readily diffuses through the vitreous humor, we suggest that an intravitreal drug depot of ROCK inhibitors could significantly improve current glaucoma therapy particularly for patients with comorbid retinal diseases