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Metals are canonical plasmonic media at infrared and optical wavelengths, allowing one to guide and manipulate light at the nanoscale. A special form of optical waveguiding is afforded by highly anisotropic crystals revealing the opposite signs of the dielectric functions along orthogonal directions. These media are classified as hyperbolic and include crystalline insulators, semiconductors, and artificial metamaterials. Layered anisotropic metals are also anticipated to support hyperbolic waveguiding. However, this behavior remains elusive, primarily because interband losses arrest the propagation of infrared modes. Here, we report on the observation of propagating hyperbolic waves in a prototypical layered nodal-line semimetal ZrSiSe. The observed waveguiding originates from polaritonic hybridization between near-infrared light and nodal-line plasmons. Unique nodal electronic structures simultaneously suppress interband loss and boost the plasmonic response, ultimately enabling the propagation of infrared modes through the bulk of the crystal.

Twisted bilayer graphene near the magic angle exhibits remarkably rich electron correlation physics, displaying insulating, magnetic, and superconducting phases. Here, using measurements of the local electronic compressibility, we reveal that these phases originate from a high-energy state with an unusual sequence of band populations. As carriers are added to the system, rather than filling all the four spin and valley flavors equally, we find that the population occurs through a sequence of sharp phase transitions, which appear as strong asymmetric jumps of the electronic compressibility near integer fillings of the moire lattice. At each transition, a single spin/valley flavor takes all the carriers from its partially filled peers, "resetting" them back to the vicinity of the charge neutrality point. As a result, the Dirac-like character observed near the charge neutrality reappears after each integer filling. Measurement of the in-plane magnetic field dependence of the chemical potential near filling factor one reveals a large spontaneous magnetization, further substantiating this picture of a cascade of symmetry breakings. The sequence of phase transitions and Dirac revivals is observed at temperatures well above the onset of the superconducting and correlated insulating states. This indicates that the state we reveal here, with its strongly broken electronic flavor symmetry and revived Dirac-like electronic character, is a key player in the physics of magic angle graphene, forming the parent state out of which the more fragile superconducting and correlated insulating ground states emerge., 42 pages, 22 figures

The link between crystal and electronic structure is crucial for understanding structure-property relations in solid-state chemistry. In particular, it has been instrumental in understanding topological materials, where electrons behave differently than they would in conventional solids. Herein, we identify 1D Bi chains as a structural motif of interest for topological materials. We focus on Sm$_3$ZrBi$_5$, a new quasi-one-dimensional (1D) compound in the Ln$_3$MPn$_5$ (Ln = lanthanide; M = metal; Pn = pnictide) family that crystallizes in the P$6_{3}$/mcm space group. Density functional theory calculations indicate a complex, topologically non-trivial electronic structure that changes significantly in the presence of spin-orbit coupling. Magnetic measurements show a quasi-1D antiferromagnetic structure with two magnetic transitions at 11.7 and 10.7 K that are invariant to applied field up to 9 T, indicating magnetically frustrated spins. Heat capacity, electrical, and thermal transport measurements support this claim and suggest complex scattering behavior in Sm$_3$ZrBi$_5$. This work highlights 1D chains as an unexplored structural motif for identifying topological materials, as well as the potential for rich physical phenomena in the Ln$_3$MPn$_5$ family., 43 pages, 13 figures. Updated to add one reference and correct error in Figure 3

Metals are canonical plasmonic media at infrared and optical wavelengths allowing one to guide and manipulate light at sub-diffractional length scales. A special form of optical waveguiding is offered by highly anisotropic crystals revealing different signs of the dielectric function along orthogonal directions. These latter types of media are classified as hyperbolic and many crystalline insulators, semiconductors and artificial metal-based metamaterials belong to that class. Layered anisotropic metals are also anticipated to support hyperbolic waveguiding. Yet this behavior remains elusive primarily because interband processes introduce extreme losses and arrest light propagation. Here, we report on the observation of propagating hyperbolic waves in a prototypical layered nodal-line semimetal ZrSiSe. The unique electronic structure with touching energy bands at nodal points/lines suppresses losses and enables a hyperbolic regime at the telecommunications frequencies. The observed waveguiding in metallic ZrSiSe is a product of polaritonic hybridization between near-infrared light and long-lived nodal-line plasmons. By mapping the energy-momentum dispersion of the nodal-line hyperbolic modes in ZrSiSe we inquired into the role of additional screening associated with the surface states.

Confining two dimensional Dirac fermions on the surface of topological insulators has remained an outstanding conceptual challenge. Here we show that Dirac fermion confinement is achievable in topological crystalline insulators (TCI), which host multiple surface Dirac cones depending on the surface termination and the symmetries it preserves. This confinement is most dramatically reflected in the flux dependence of these Dirac states in the nanowire geometry, where different facets connect to form a closed surface. Using SnTe as a case study, we show how wires with all four facets of the type display novel Aharonov-Bohm oscillations, while nanowires with the four facets of the type such oscillations are absent due to a strong confinement of the Dirac states to each facet separately. Our results place TCI nanowires as versatile platform for confining and manipulating Dirac surface states., 13 pages, 7 figures

Stroke is defined by the sudden onset of signs and / or symptoms caused by the loss of focal brain function, divided into ischemic stroke (iC) and hemorrhagic stroke (h). Pregnancy and the puerperium confer an increased risk of hs and hs, and the main risk factors are preeclampsia and eclampsia. This study aims to analyze the risk factors and the pathogenesis of stroke during pregnancy and puerperium. This is a systematic review of the databases: VHL / LILACS; PubMed; Science Direct, using stroke, pregnancy and puerperium as descriptors. Original articles in Portuguese, English and Spanish, published on human beings published from 2014 to 2019, were included. Of the 569 articles accessed, 13 were evaluated for eligibility. After analyzing the articles, it was found that stroke in pregnant women and in the puerperium is multifactorial, in which pregnant women may have circulatory complications. Physiological changes lead to the state of hypercoagulability, and those of connective tissue increase the distensibility of the vessels, leading to the occurrence of stroke. Stroke and stroke. When they occur, they confer a great risk of disability and death. The incidence is possibly increasing due to the increase in hypertensive young women.

Photodynamic therapy (PDT) appears as a promising alternative in the treatment of breast cancer since it can be highly effective in curing cancer while preserving normal tissue. However, predicting outcomes in PDT still constitutes a great challenge. One of the parameters that are usually empirically determined is the rate of photon flux delivered to the tissue (light fluence rate). In the present study, we intended to understand why monolayers of human cells derived from mammary adenocarcinomas (MDA-MB-231 and MCF-7) respond quite differently to fluence rates (cells were irradiated either for 6 or for 16 min) at a fixed light dose (4.5 J cm-2 ) delivered with an array of LEDs in a typical methylene blue PDT protocol. While death rates of MDA-MB-231 cells were insensitive to the fluence rate, MCF-7 cells showed a quite impressive (three times) decrease in cell death levels in the shorter irradiation protocol. Independent on cell type cell death was invariably correlated with the depletion of reduced glutathione intracellular levels and consequently with widespread redox misbalance. Our data show the potential to optimize fluence rates to provide exhaustion of the cell antioxidant responses in order to circumvent therapy resistance of breast tumors.

A classificação dos sinais eletroencefalográficos (EEG) é um problema fundamental nos sistemas de Interface Cérebro-Computador (BCI). Os sinais de EEG podem ser vistos como um conjunto de séries temporais, sendo interessante o uso das Redes Neurais Recorrentes (RNNs) para seu processamento, em particular a rede LSTM (Long Short-Term Memory). Neste artigo é proposto uma estrutura de classificação baseada em LSTM utilizando o Algoritmo Genético (GA) e o Algoritmo de Seleção Clonal (CSA) para realizar a seleção do número de canais em um conjunto de dados de EEG artificiais.

During type 1 diabetes mellitus (T1DM) development, beta-cells undergo intense endoplasmic reticulum (ER) stress that could result in apoptosis through the failure of adaptation to the unfolded protein response (UPR). Islet transplantation is considered an attractive alternative among beta-cell replacement therapies for T1DM. To avoid the loss of beta-cells that will jeopardize the transplant’s outcome, several strategies are being studied. We have previously shown that prolactin induces protection against proinflammatory cytokines and redox imbalance-induced beta-cell death by increasing heat-shock protein B1 (HSPB1) levels. Since the role of HSPB1 in beta cells has not been deeply studied, we investigated the mechanisms involved in unbalanced protein homeostasis caused by intense ER stress and overload of the proteasomal protein degradation pathway. We tested whether HSPB1-mediated cytoprotective effects involved UPR modulation and improvement of protein degradation via the ubiquitin-proteasome system. We demonstrated that increased levels of HSPB1 attenuated levels of pro-apoptotic proteins such as CHOP and BIM, as well as increased protein ubiquitination and the speed of proteasomal protein degradation. Our data showed that HSPB1 induced resistance to proteotoxic stress and, thus, enhanced cell survival via an increase in beta-cell proteolytic capacity. These results could contribute to generate strategies aimed at the optimization of beta-cell replacement therapies.

Orientador: Gun Birgitta Bergsten Mendes Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas Resumo: A atuação do farmacêutico nas comissões de controle de infecção hospitalar (CCIH), tem sido de grande importância na tentativa de conseguir um uso racional de antimicrobiano em hospitais. Apesar dos princípios básicos da antibiótico- profilaxia estarem bem estabelecidos, este constitui ainda uma parcela alta de uso inadequado quanto a sua indicação e principalmente duração, geralmente superior à determinada. O uso adequado destes fármacos contribui para diminuir o tempo de internação do paciente, prevenir infecção do sítio cirúrgico (ISC), diminuir a seleção de microrganismos resistentes e os custos para a farmácia. Neste estudo foi realizado a implantação de um protocolo para o uso de antibiótico- profilaxia no Serviço de Ortopedia e Traumatologia do Hospital do Servidor Público Estadual de São Paulo. Os objetivos do estudo foram: promover uma antibiótico- profilaxia cirúrgica racional, através da implantação de um protocolo para o uso destes fármacos em uma unidade cirúrgica, com a colaboração direta de um farmacêutico em conjunto com a CCIH, avaliar a adesão da equipe de saúde ao protocolo em três períodos distintos ( pré- protocolo, pós- protocolo e um ano após) e definir o consumo e custos dos antimicrobianos utilizados em dose diária definida para os três períodos. Consideramos "erro" qualquer item discordante do protocolo. Analisamos um total de 290 cirurgias para os três períodos. Os itens avaliados foram: indicação da profilaxia, escolha do antibiótico utilizado, dose, início da primeira dose, repetição no intra- operatório, duração da profilaxia e infecção do sítio cirúrgico. O número de itens em não conformidade ("erros") passou de 93.4% para 42.4% após a padronização. A freqüência de zero "erros" para os itens analisados passou de 3.3% para 50% após implantação do protocolo. Houve também uma diminuição no consumo e custos demonstrados através da dose diária definida (DDD) e média de custo por procedimento profilático. . A padronização implantada promoveu a adequação da antibiótico- profilaxia neste serviço de ortopedia, tendo ficado clara a importância de se manter a participação de membro da ccm e do. farmacêutico nas visitas à enfermaria junto com a equipe médica a fim de estimular a utilização correta de antibióticos como profilaxia em cirurgias Abstract: The inappropriateness of surgical antibiotic prophylaxis has been extensively reported, documenting wrong dosing, for toa long, and with toa broad a spectmm of antimicrobial activity. To describe a multidisciplinary experience in implanting a protocol for prophylactic antibiotic prescription in the orthopedic department of a general hospital. A consensus protocol was developed. Prophylactic antibiotics were dispensed only with a proper fonn, and the phannacist provided for each surgery the antibiotic kit assuring that the patient received the correct intra - and postoperative doses of the indicated antibiotic. AlI surgeries in three study periods were evaluated (pre protocol, early post-protocol, and a late post-protocol) and compared. Cost of the prophylactic antibiotics was determined before and after the implemented protocol. Two hundred and ninety nine surgeries were evaluated. Forty percent of the patients were male, and the mean age of all the patients was 52.5 :t 25.7 years. More than 95% of the surgeries were elective and clean. The frequency of the appropriateness of the antibiotic prophylaxis according to the agreed protocol for the three study was evaluated. The number of times there were items in each patient's prescription which disagreed with the established protocol ("error") showed a significant shift. In the pre-protocol period, only 3.3% of the surgeries with antibiotic prophylaxis had no "errors", but this value reached 50.0% in the late post-protocol period (p < .0001). Combining educational and restrictive interventions can markedly improve the surgical antibiotic prophylaxis Mestrado Mestre em Farmacologia

The Borborema Plateau is characterized by different stages of relief evolution, which modify the climate and vegetation, and where high-altitude tropical forests can be seen surrounded by caatinga. The aim of this study was to characterize the soils of a topo-climosequence in the Agreste region of the State of Pernambuco, and evaluate the influence of the relief and climate on the pedogenesis. A topo-climosequence was selected, and trenches were opened in the geomorphological features of high-altitude forest (P1), between forest and pediplane (P2) and on a pediplanation surface (P3 and P4). A morphological description and a physical, chemical and micromorphological characterization were carried out. In general, the soils are sandy, with the predominance of a single-grain structure or weak aggregation. Higher values for pH, S, V% and assimilable P were found on the lower parts of the landscape. From the micromorphological analysis, the incipient development of pedogenic structures was detected in the C horizon in P1 and P3, clay translocation in P2 and the degradation of iron micronodules in P4. The P1 and P3 profiles were classified as Neossolos Regolíticos Distróficos espessarênicos (Regolsols), the P2 profile as a Argissolo Amarelo Distrófico típico (Alisol), and P4 as an Planossolo Háplico Eutrófico arênico (Planosol). Soil variation in the landscape was determined by climate, relief and parent material. Micromorphology was efficient in detecting attributes not seen in the field, such as incipient aggregation in the Neossolos Regolíticos (Regosols) and the degradation of iron micronodules in the Planossolo Háplico (Planosol). O Planalto da Borborema é caracterizado pelos diferentes estágios de evolução do relevo, modificando o clima e a vegetação, sendo observadas florestas tropicais, (brejos de altitude), circundado por caatinga. O objetivo deste trabalho foi caracterizar os solos de uma topoclimossequência no agreste pernambucano, avaliandoa influência do relevo e do clima na pedogênese. Foi selecionada uma topoclimossequência e abertas trincheiras nas feições geomorfológicas de brejo de altitude (P1), entre brejo de altitude e pediplano (P2) e em superfície de pediplanação (P3 e P4). Foi realizada a descrição morfológica e a caracterização física, química e micromorfológica. De maneira geral, os solos são arenosos, com predomínio da estrutura grão simples ou fraca agregação. Maiores valores de pH, S, V% e P assimilável foram quantificados nas partes mais baixas da paisagem. Na análise micromorfológica detectou-se o desenvolvimento pedogenético incipiente de estrutura nos horizontes C de P1 e P3; translocação de argila em P2; e degradação de micronódulos de ferro em P4. Os perfis P1 e P3 foram classificados como Neossolos Regolíticos Distróficos espessarênicos (Regosols); P2 como Argissolo Amarelo Distrófico típico (Alisol); P4 como Planossolo Háplico Eutrófico arênico (Planosol). A variação dos solos na paisagem foi determinada pelo clima, relevo e material de origem. A micromorfológica foi eficiente na detecção de atributos não observados em campo, como agregação incipiente nos Neossolos Regolíticos e degradação de micronódulos de ferro no Planossolo Háplico. Made available in DSpace on 2019-01-14T23:50:50Z (GMT). No. of bitstreams: 1 2019001.pdf: 310039 bytes, checksum: 93ad41d2b74ed52b3ecf8924df73ba31 (MD5) Previous issue date: 2019-01-14

The axion insulator is a higher-order topological insulator protected by inversion symmetry. We show that under quenched disorder respecting inversion symmetry {\it on average}, the topology of the axion insulator stays robust, and an intermediate metallic phase in which states are delocalized is unavoidable at the transition from an axion insulator to a trivial insulator. We derive this conclusion from general arguments, from classical percolation theory, and from the numerical study of a 3D quantum network model simulating a disordered axion insulator through a layer construction. We find the localization length critical exponent near the delocalization transition to be $\nu=1.42\pm 0.12$. We further show that this delocalization transition is stable even to weak breaking of the average inversion symmetry, up to a critical strength. We also quantitatively map our quantum network model to an effective Hamiltonian and we find its low energy k$\cdot$p expansion., Comment: 8+11 pages, 4+6 figures, some references added

Correlations in topological states of matter provide a rich phenomenology, including a reduction in the topological classification of the interacting system compared to its non-interacting counterpart. This happens when two phases that are topologically distinct on the non-interacting level become adiabatically connected once interactions are included. We use a quantum Monte Carlo method to study such a reduction. We consider a 2D charge-conserving analog of the Levin-Gu superconductor whose classification is reduced from $\mathbb{Z}$ to $\mathbb{Z}_4$. We may expect any symmetry-preserving interaction that leads to a symmetric gapped ground state at strong coupling, and consequently a gapped symmetric surface, to be sufficient for such reduction. Here, we provide a counter example by considering an interaction which (i) leads to a symmetric gapped ground state at sufficient strength and (ii) does not allow for any adiabatic path connecting the trivial phase to the topological phase with $w=4$. The latter is established by numerically mapping the phase diagram as a function of the interaction strength and a parameter tuning the topological invariant. Instead of the adiabatic connection, the system exhibits an extended region of spontaneous symmetry breaking separating the topological sectors. Frustration reduces the size of this long-range ordered region until it gives way to a first order phase transition. Within the investigated range of parameters, there is no adiabatic path deforming the formerly distinct free fermion states into each other. We conclude that an interaction which trivializes the surface of a gapped topological phase is necessary but not sufficient to establish an adiabatic path within the reduced classification. In other words, the class of interactions which trivializes the surface is different from the class which establishes an adiabatic connection in the bulk., 10 pages, 6 figures

One challenge in point-of-care diagnostics is the lack of room-temperature methods for RNA detection based on enzymatic amplification and visualization steps. Here we perform a reverse transcription ligase chain reaction using our isothermal lesion induced DNA amplification (LIDA) technique that can be tuned to operate at any desired temperature. Using RNA-triggered LIDA, we can detect as little as ~100 attomoles target RNA and can distinguish RNA target from total cellular RNA. Finally, we demonstrate that the resulting DNA amplicons can be detected colorimetrically, also at room temperature, by rapid, target-triggered disassembly of DNA-modified gold nanoparticles. This integrated amplification/detection platform requires no heating or visualization instrumentation, which is an important step towards realizing instrument-free POC testing.

Este artigo procura reunir diversas discussões a respeito do uso da tradução no ensino de línguas a fim de compreender melhor a relação entre ambas as áreas. Ao longo da história do ensino-aprendizagem de línguas, a tradução exerceu diferentes papéis, às vezes marcada pelo protagonismo, como na Metodologia Gramática Tradução (MGT) e às vezes pelo esquecimento nas abordagens decorrentes do Método Direto. Atualmente, no entanto, vem ganhando espaço nas discussões sobre as novas perspectivas da abordagem comunicativa, tendo, inclusive, nomenclatura própria: a Tradução Pedagógica. Com o aumento de sua popularidade, fazem-se necessários o estudo e a definição desse termo. O objetivo desse artigo é contribuir para o esclarecimento do que é a Tradução Pedagógica e como vem sendo compreendida pelos estudiosos, bem como discorrer sobre as contribuições dessa ferramenta para as áreas de ensino de línguas e da formação de tradutores.

Symmetries crucially underlie the classification of topological phases of matter. Most materials, both natural as well as architectured, possess crystalline symmetries. Recent theoretical works unveiled that these crystalline symmetries can stabilize fragile Bloch bands that challenge our very notion of topology: while answering to the most basic definition of topology, one can trivialize these bands through the addition of trivial Bloch bands. Here, we fully characterize the symmetry properties of the response of an acoustic metamaterial to establish the fragile nature of the low-lying Bloch bands. Additionally, we present a spectral signature in the form of spectral flow under twisted boundary conditions., Comment: 4 pages, 3 figures + supplementary information (21 pages, 13 figures, 7 tables). Note the accompanying paper by Zhi-Da Song et al. "Real Space Invariants: Twisted Bulk-Boundary Correspondence of Fragile Topology"' posted on the same day on the arXiv

Lack of effective treatments for aggressive breast cancer is still a major global health problem. We have previously reported that photodynamic therapy using methylene blue as photosensitizer (MB-PDT) massively kills metastatic human breast cancer, marginally affecting healthy cells. In this study, we aimed to unveil the molecular mechanisms behind MB-PDT effectiveness and specificity towards tumor cells. Through lipidomics and biochemical approaches, we demonstrated that MB-PDT efficiency and specificity rely on polyunsaturated fatty acid-enriched membranes and on the better capacity to deal with photo-oxidative damage displayed by non-tumorigenic cells. We found out that, in tumorigenic cells, lysosome membrane permeabilization is accompanied by ferroptosis and/or necroptosis. Our results also pointed at a cross-talk between lysosome-dependent cell death (LDCD) and necroptosis induction after photo-oxidation, and contributed to broaden the understanding of MB-PDT-induced mechanisms and specificity in breast cancer cells. Therefore, we demonstrated that efficient approaches could be designed on the basis of lipid composition and metabolic features for hard-to-treat cancers. The results further reinforce MB-PDT as a therapeutic strategy for highly aggressive human breast cancer cells.

Drumhead surface states that link together loops of nodal lines arise in Dirac nodal-line semimetals as a consequence of the topologically non-trivial band crossings. We used low-temperature scanning tunneling microscopy and Fourier-transformed scanning tunneling spectroscopy to investigate the quasiparticle interference (QPI) properties of ZrSiTe. Our results show two scattering signals across the drumhead state resolving the energy-momentum relationship through the occupied and unoccupied energy ranges it is predicted to span. Observation of this drumhead state is in contrast to previous studies on ZrSiS and ZrSiSe, where the QPI was dominated by topologically trivial bulk bands and surface states. Furthermore, we observe a near $\mathbf{k} \rightarrow -\mathbf{k}$ scattering process across the $\Gamma$-point, enabled by scattering between the spin-split drumhead bands in this material., Comment: 7 pages, 3 figures

We study the effects of pseudo-magnetic fields on Weyl semimetals with over-tilted Weyl cones, or type II cones. We compare the phenomenology of the resulting pseudo-Landau levels in the type II Weyl semimetal to the known case of type I cones. We predict that due to the nature of the chiral Landau level resulting from a magnetic field, a pseudo-magnetic field, or their combination, the optical conductivity can be utilized to detect a type II phase and deduce the direction of the tilt. Finally, we discuss ways to engineer homogeneous and inhomogeneous type II semimetals via generalizations of known layered constructions in order to create controlled pseudo-magnetic fields and over-tilted cones., Comment: 12 pages, 8 figures

We study the electronic structure of the nodal line semimetal ZrSiTe both experimentally and theoretically. We find two different surface states in ZrSiTe—topological drumhead surface states and trivial floating band surface states, which can be easily distinguished in ARPES experiments. Using the spectra of Wilson loops, we show that a nontrivial Berry phase that exists in a confined region within the Brillouin zone gives rise to the topological drumhead-type surface states. The Z_{2} structure of the Berry phase induces a Z_{2} “modular arithmetic” of the surface states, allowing surface states derived from different nodal lines to hybridize and gap out, which can be probed by a set of Wilson loops. Our findings are confirmed by ab initio calculations and angle-resolved photoemission experiments, which are in excellent agreement with each other and the topological analysis. This work is the first complete characterization of topological surface states in the family of square-net-based nodal line semimetals, and thus it fundamentally increases the understanding of the topological nature of this growing class of topological semimetals.

Hydrodynamics is a general description for the flow of a fluid, and is expected to hold even for fundamental particles such as electrons when inter-particle interactions dominate. While various aspects of electron hydrodynamics were revealed in recent experiments, the fundamental spatial structure of hydrodynamic electrons, the Poiseuille flow profile, has remained elusive. In this work, we provide the first real-space imaging of Poiseuille flow of an electronic fluid, as well as visualization of its evolution from ballistic flow. Utilizing a scanning nanotube single electron transistor, we image the Hall voltage of electronic flow through channels of high-mobility graphene. We find that the profile of the Hall field across the channel is a key physical quantity for distinguishing ballistic from hydrodynamic flow. We image the transition from flat, ballistic field profiles at low temperature into parabolic field profiles at elevated temperatures, which is the hallmark of Poiseuille flow. The curvature of the imaged profiles is qualitatively reproduced by Boltzmann calculations, which allow us to create a 'phase diagram' that characterizes the electron flow regimes. Our results provide long-sought, direct confirmation of Poiseuille flow in the solid state, and enable a new approach for exploring the rich physics of interacting electrons in real space.

We used screw dislocations as a tool to probe spectroscopically the topological classification of electronic matter in bismuth., The growing diversity of topological classes leads to ambiguity between classes that share similar boundary phenomenology. This is the status of bulk bismuth. Recent studies have classified it as either a strong or a higher-order topological insulator, both of which host helical modes on their boundaries. We resolve the topological classification of bismuth by spectroscopically mapping the response of its boundary modes to a screw-dislocation. We find that the one-dimensional mode, on step-edges, extends over a wide energy range and does not open a gap near the screw-dislocations. This signifies that this mode binds to the screw-dislocation, as expected for a material with nonzero weak indices. We argue that the small energy gap, at the time reversal invariant momentum L, positions bismuth within the critical region of a topological phase transition between a higher-order topological insulator and a strong topological insulator with nonzero weak indices.

In absence of time-reversal symmetry, viscous electron flow hosts a number of interesting phenomena, of which we focus here on the Hall viscosity. Taking a step beyond the hydrodynamic definition of the Hall viscosity, we derive a generalized relation between Hall viscosity and transverse electric field using a kinetic equation approach. We explore two different geometries where the Hall viscosity is accessible to measurement. For hydrodynamic flow of electrons in a narrow channel, we find that the viscosity may be measured by a local probe of the transverse electric field near the center of the channel. Ballistic flow, on the other hand, is dominated by boundary effects. In a Corbino geometry viscous effects arise not from boundary friction but from the circular flow pattern of the Hall current. In this geometry we introduce a viscous Hall angle which remains well defined throughout the crossover from ballistic to hydrodynamic flow, and captures the bulk viscous response of the fluid., Comment: 5 pages, 2 figures, supplementary material

Symmetry protected topological (SPT) phases are gapped phases of matter that cannot be deformed to a trivial phase without breaking the symmetry or closing the bulk gap. Here, we introduce a new notion of a topological obstruction that is not captured by bulk energy gap closings in periodic boundary conditions. More specifically, we say two bulk Hamiltonians belong to distinct boundary obstructed topological `phases' (BOTPs) if they can be deformed to each other on a system with periodic boundaries, but cannot be deformed to each other for symmetric open boundaries without closing the gap at at least one high symmetry region on the surface. BOTPs are not topological phases of matter in the standard sense since they are adiabatically deformable to each other on a torus but, similar to SPTs, they are associated with boundary signatures in open systems such as surface states or fractional corner or hinge charges. We show that the double-mirror quadrupole model of [Science, 357(6346), 2018] is a prototypical example of such phases, and present a detailed analysis of several aspects of boundary obstructions in this model. In addition, we introduce several three-dimensional models having boundary obstructions, which are characterized either by surface states or fractional corner or hinge charges. We also provide a general framework to study boundary obstructions in free-fermion systems in terms of Wannier band representations (WBR), an extension of the recently-developed band representation formalism to Wannier bands. WBRs capture the notion of topological obstructions in the Wannier bands which can then be used to study topological obstructions in the boundary spectrum by means of the correspondence between the Wannier and boundary spectra. This establishes a form of bulk-boundary correspondence for BOTPs by relating the bulk band representation to the boundary topology., 30 pages, 21 figures

The surface of a higher order topological insulator (HOTI) comprises a two-dimensional topological insulator (TI) with broken inversion symmetry, whose mass is determined by the microscopic details of the surface such as surface potentials and termination. It hosts a helical mode pinned to selected hinges where the surface gap changes its sign. We study the effect of perturbations that break time-reversal and particle-conservation on this helical mode, such as a Zeeman field and a proximate superconductor. We find that in contrast to the helical modes of inversion symmetric TIs, which are gapped by these couplings, the helical modes at the hinges can remain gapless and spatially split. When this happens, the Zeeman field splits the helical mode into a chiral mode surrounding the magnetized region; and a superconductor results in a helical Majorana mode surrounding the superconducting region. The combination of the two might lead to the gapping of one of the chiral Majorana modes, and leave a single one-dimensional chiral Majorana around the superconducting island. We propose that the different topological states can be measured in electrical transport., Comment: added supplementary information

Photodynamic therapy (PDT) has been clinically applied to cure various diseases including cancer. Indeed, photophrin (porfimer sodium, Axcan Pharma, Montreal, Canada), a heterogenous mixture of porphyrins, was the first photosensitizer (PS) approved for the treatment of human bladder cancer in 1993 in Canada. Over the past 10 years the use of PDT in the treatment of benign and malignant lesions has increased dramatically. However, PDT is still considered as an adjuvant strategy due to its limitations, primarily including low tissue penetration by light and inaccurate lesion selectivity by the PSs. To overcome this scenario, new technologies and approaches including nanotechnology have been incorporated into the concept of PS formulations as PS delivery systems, as PSs per se or as energy transducers. The ideal nanophotosensitizer (NPS) for cancer therapy should possess the following characteristics: biocompatibility and biodegradability without toxicity, stability in physiological conditions, tumor specific targeting, strong near infrared absorption for efficient and sufficient light absorbance and large singlet oxygen quantum yield for PDT. To fulfill these requirements, several nanoscale delivery platforms and materials have been developed. In this review we will focus on the state of the art of nanotechnology contributions to the optimization of PDT as a therapeutic alternative to fight against cancer. For this purpose we will start from the basic concepts of PDT, discuss the versatility in terms of NPS formulations and how to tackle the deficiencies of the current therapy. We also give our critical view and suggest recommendations for improving future research on this area.