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We find evidence for the formation and relaxation of large exciton polarons in 2D organic-inorganic hybrid perovskites. Using ps-scale time-resolved photoluminescence within the phenethylammonium lead iodide family of compounds, we identify a red shifting of emission that we associate with exciton polaron formation time scales of 3-10 ps. Atomic substitutions of the phenethylammonium cation allow local control over the structure of the inorganic lattice, and we show that the structural differences among materials strongly influence the exciton polaron relaxation process, revealing a polaron binding energy that grows larger (up to 15 meV) in more strongly distorted compounds.

La cultura política chilena ha contenido desde temprano nociones de excepcionalidad que han condicionado actitudes y comportamientos de diversos actores del sistema. En la época de la crisis, destrucción y reconfiguración de la democracia, entre principios de la década de 1960 y finales de la de los ochenta, estas nociones tuvieron efectos negativos y positivos en el proceso político chileno. Este artículo propone observar reflexivamente los atributos y efectos de estas nociones de excepcionalidad en la trayectoria histórica reciente de Chile, con miras a ponderar algunas de las condiciones del proceso político actualmente en curso.

We investigated Xe binding in a previously reported paramagnetic metal–organic tetrahedral capsule, [Co4L6]4–, where L2– = 4,4′-bis[(2-pyridinylmethylene)amino][1,1′-biphenyl]-2,2′-disulfonate. The...

We prove Zimmer’s conjecture for $$C^2$$ actions by finite-index subgroups of $$\mathrm {SL}(m,{\mathbb {Z}})$$ provided $$m>3$$ . The method utilizes many ingredients from our earlier proof of the conjecture for actions by cocompact lattices in $$\mathrm {SL}(m,{\mathbb {R}})$$ (Brown et al. in Zimmer’s conjecture: subexponential growth, measure rigidity, and strong property (T), 2016. arXiv:1608.04995 ) but new ideas are needed to overcome the lack of compactness of the space $$(G \times M)/\Gamma $$ (admitting the induced G-action). Non-compactness allows both measures and Lyapunov exponents to escape to infinity under averaging and a number of algebraic, geometric, and dynamical tools are used control this escape. New ideas are provided by the work of Lubotzky, Mozes, and Raghunathan on the structure of nonuniform lattices and, in particular, of $$\mathrm {SL}(m,{\mathbb {Z}})$$ providing a geometric decomposition of the cusp into rank one directions, whose geometry is more easily controlled. The proof also makes use of a precise quantitative form of non-divergence of unipotent orbits by Kleinbock and Margulis, and an extension by de la Salle of strong property (T) to representations of nonuniform lattices.

We report a family of two-dimensional hybrid perovskites (2DHPs) based on phenethylammonium lead iodide ((PEA)$_2$PbI$_4$) that show complex structure in their low-temperature excitonic absorption and photoluminescence (PL) spectra as well as hot exciton PL. We replace the 2-position (ortho) H on the phenyl group of the PEA cation with F, Cl, or Br to systematically increase the cation's cross-sectional area and mass and study changes in the excitonic structure. These single atom substitutions substantially change the observable number of and spacing between discrete resonances in the excitonic absorption and PL spectra and drastically increase the amount of hot exciton PL that violates Kasha's rule by over an order of magnitude. To fit the progressively larger cations, the inorganic framework distorts and is strained, reducing the Pb-I-Pb bond angles and increasing the 2DHP band gap. Correlation between the 2DHP structure and steady-state and time-resolved spectra suggests the complex structure of resonances arises from one or two manifolds of states, depending on the 2DHP Pb-I-Pb bond angle (as)symmetry, and the resonances within a manifold are regularly spaced with an energy separation that decreases as the mass of the cation increases. The uniform separation between resonances and the dynamics that show excitons can only relax to the next-lowest state are consistent with a vibronic progression caused by a vibrational mode on the cation. These results demonstrate that simple changes to the structure of the cation can be used to tailor the properties and dynamics of the confined excitons without directly modifying the inorganic framework., Comment: 39 pages

We construct a finitely generated subgroup of Diff ∞ ⁡ ( S 3 × S 1 ) \operatorname {Diff}^{\infty }(\mathbb {S}^3 \times \mathbb {S}^1) where every element is conjugate to an isometry but such that the group action itself is far from isometric (the group has “exponential growth of derivatives”). As a corollary, one obtains a locally constant Diff ∞ ⁡ ( S 3 × S 1 ) \operatorname {Diff}^{\infty }(\mathbb {S}^3 \times \mathbb {S}^1) valued cocycle over a hyperbolic dynamical system which has elliptic behavior over its periodic orbits but which preserves a measure with non-zero top fiber-Lyapunov exponent. Additionally, we provide new examples of Banach cocycles not satisfying the periodic approximation property as first shown in Ergodic Theory Dynam. Systems 39 (2019), pp. 689–706.

A group G is periodic of bounded exponent if there exists k∈N such that every element of G has order at most k. We show that every finitely generated periodic group of bounded exponent G

Asymptomatic SARS-CoV-2 infection of healthcare workers (HCWs) has been reported as a key player in the nosocomial spreading of COVID-19. Early detection of infected HCWs can prevent spreading of the virus in hospitals among HCWs and patients. We conducted a cross-sectional study to determine the asymptomatic infection of HCWs in a private clinic in the city of Santiago, Chile. Our study was conducted during a period of 5 weeks at the peak of transmission of SARS-CoV-2 in Chile. Nasopharyngeal samples were obtained from 413 HCWs and tested for the presence of SARS-CoV-2 using RT-qPCR. We found that a 3.14% of HCWs were positive for the presence of SARS-CoV-2 (14/413). Out of these, 7/14 were completely asymptomatic and did not develop symptoms within 3 weeks of testing. Sequencing of viral genomes showed the predominance of the GR clade; however, sequence comparison demonstrated numerous genetic differences among them suggesting community infection as the main focus of transmission among HCWs. Our study demonstrates that the protocols applied to protect HCWs and patients have been effective as no infection clusters due to asymptomatic carriers were found in the clinic. Together, these data suggest that infection with SARS-CoV-2 among HCWs of this health center is not nosocomial.

Evolution of Kondo effect in Weyl semimetal Mn3Sn leads to extraordinary terahertz and DC transport properties., Topology and strong electron correlations are crucial ingredients in emerging quantum materials, yet their intersection in experimental systems has been relatively limited to date. Strongly correlated Weyl semimetals, particularly when magnetism is incorporated, offer a unique and fertile platform to explore emergent phenomena in novel topological matter and topological spintronics. The antiferromagnetic Weyl semimetal Mn3Sn exhibits many exotic physical properties such as a large spontaneous Hall effect and has recently attracted intense interest. In this work, we report synthesis of epitaxial Mn3+xSn1−x films with greatly extended compositional range in comparison with that of bulk samples. As Sn atoms are replaced by magnetic Mn atoms, the Kondo effect, which is a celebrated example of strong correlations, emerges, develops coherence, and induces a hybridization energy gap. The magnetic doping and gap opening lead to rich extraordinary properties, as exemplified by the prominent DC Hall effects and resonance-enhanced terahertz Faraday rotation.

We investigated Xe binding in a previously reported paramagnetic metal-organic tetrahedral capsule, [Co(4)L(6)](4−), where L(2−) = 4,4'-bis[(2-pyridinylmethylene)amino]-[1,1'-biphenyl]-2,2'-disulfonate. The Xe-inclusion complex, [XeCo(4)L(6)](4−), was confirmed by (1)H NMR spectroscopy to be the dominant species in aqueous solution saturated with Xe gas. The measured Xe dissociation rate in [XeCo(4)L(6)](4−) (4.4(5) × 10(2) s(−1)) was at least forty times greater than in the analogous [XeFe(4)L(6)](4−) complex, highlighting the capability of metal-ligand interactions to tune capsule size and guest permeability. The rapid exchange of (129)Xe nuclei in [XeCo(4)L(6)](4−) produced significant hyperpolarized (129)Xe chemical exchange saturation transfer (hyper-CEST) NMR signal at 298 K, detected at a concentration of [XeCo(4)L(6)](4−) as low as 100 pM, with presaturation at −89 ppm, which was referenced to solvated (129)Xe in H(2)O. The saturation offset was highly temperature-dependent with a slope of −0.41(3) ppm/K, which is attributed to hyperfine interactions between the encapsulated (129)Xe nucleus and electron spins on the four Co(II) centers. As such, [XeCo(4)L(6)](4−) represents the first example of a paramagnetic hyper-CEST (paraHYPERCEST) sensor. Remarkably, the hyper-CEST (129)Xe NMR resonance for [XeCo(4)L(6)](4−) (δ = −89 ppm) was shifted 105 ppm upfield from the diamagnetic analog [XeFe(4)L(6)](4−) (δ = +16 ppm). The Xe inclusion complex was further characterized in the crystal structure of (C(NH(2))(3))(4)[Xe(0.7)Co(4)L(6)]·75 H(2)O (1). Hydrogen bonding between capsule-linker sulfonate groups and exogenous guanidinium cations, (C(NH(2))(3))(+), stabilized capsule-capsule interactions in the solid-state, and also assisted in trapping a Xe atom (~42 Å(3)) in the large (135 Å(3)) cavity of 1. Magnetic susceptibility measurements confirmed the presence of four non-interacting, magnetically anisotropic high-spin Co(II) centers in 1. Furthermore, [Co(4)L(6)](4−) was found to be stable towards aggregation and oxidation, and the CEST performance of [XeCo(4)L(6)](4−) was unaffected by biological macromolecules in H(2)O. These results recommend metal-organic capsules for fundamental investigations of Xe host-guest chemistry as well as applications with highly sensitive (129)Xe-based sensors.

This novel take on diplomatic history examines the involvement of the United States in Chile during the Eduardo Frei administration (1964–1970) and shows how the engagement between the two nations deepened the process of political polarization in Chile. At the heart of the book is a description of the partnership between Frei's government and that of Lyndon B. Johnson. Both leaders considered modernization to be integral to political and economic development, and the U.S. Embassy in Santiago was recognized by all parties to be the center of this modernizing agenda and the practical work of the Alliance for Progress (AFP). The book portrays the diplomatic and economic relationship between Chile and the United States in a manner that departs from the most militant and conservative interpretations of U.S. foreign policy toward Latin America. By focusing on the active participation of agents of U.S. foreign policy—particularly those associated with the AFP—and not secret operatives of the Central Intelligence Agency, the book offers a fresh narrative about a critical period in Chilean political history and a new understanding of the ways and means through which the foreign policy of the United States was carried out.

The topological kagome metal CoSn hosts orbital-selective Dirac bands and very flat bands near the Fermi energy that lead to a range of exotic phenomena, such as fractional quantum Hall states. In this work, we report the synthesis of high-quality epitaxial (0001) CoSn films by magnetron sputtering. Comprehensive structural characterizations demonstrate high crystalline quality with low disorder, sharp interfaces, and a smooth surface. Complementary magnetic and transport properties show a paramagnetic, metallic ground state as seen in bulk. Our work creates a synthetic foundation to investigate and utilize rich topological physics in CoSn thin films and heterostructures.

The topological kagome magnet (TKM) Fe3Sn2 exhibits unusual topological properties, flat electronic bands, and chiral spin textures, making it an exquisite materials platform to explore the interplay between topological band structure, strong electron correlations, and magnetism. Here we report the first synthesis of high-quality epitaxial (0001) Fe3Sn2 films with large intrinsic anomalous Hall effect close to that measured in bulk single crystals. In addition, we measured a large, anisotropic anomalous Nernst coefficient Syx of 1.26 {\mu}V/K, roughly 2-5x greater than that of common ferromagnets, suggesting the presence of Berry curvature sources near the Fermi level in this system. Crucially, the realization of high-quality Fe3Sn2 films opens the door to explore emergent interfacial physics and create novel spintronic devices based on TKMs by interfacing Fe3Sn2 with other quantum materials and by nanostructure patterning., Comment: accepted by Physical Review Materials

Topology and strong electron correlations are crucial ingredients in emerging quantum materials, yet their intersection in experimental systems has been relatively limited to date. Strongly correlated Weyl semimetals, particularly when magnetism is incorporated, offer a unique and fertile platform to explore emergent phenomena in novel topological matter and topological spintronics. The antiferromagnetic Weyl semimetal Mn3Sn exhibits many exotic physical properties such as a large spontaneous Hall effect and has recently attracted intense interest. In this work, we report synthesis of epitaxial Mn3+x Sn1-x films with greatly extended compositional range in comparison with that of bulk samples. As Sn atoms are replaced by magnetic Mn atoms, the Kondo effect, which is a celebrated example of strong correlations, emerges, develops coherence, and induces a hybridization energy gap. The magnetic doping and gap opening lead to rich extraordinary properties, as exemplified by the prominent DC Hall effects and resonance-enhanced terahertz Faraday rotation.

La investigación en psicoanálisis como partenaire de la obra que el lector tiene en sus manos, obedece a la actividad colectiva de estudiantes y asistentes del semillero de investigación LOGOS de la Universidad Santiago de Cali y de cuatro invitados nacionales e internacionales: Beatriz Elena Maya de la Universidad de Antioquia; Daniel Felipe Gómez León de la Universidad del Valle y Vanina Muraro y David Krapf de la Universidad de Buenos Aires. El interés por realizar esta compilación surge a partir de numerosas voces que, en su recorrido por las lecturas psicoanalíticas, crean inquietudes ante el lugar que ocupa el Psicoanálisis en la actualidad y que se transforman en huellas académicas que inspiraron el título de nuestro texto. La clínica como lugar insigne y de la cual se suscitan abordajes diversos, se materializan en este libro frente a los deseos de sus autores por responder a preguntas en torno al síntoma y sus manifestaciones, el lugar que ocupa lo epistemológico en Psicoanálisis y las intersecciones expresadas en el ámbito de la estética y el lazo social.

Esta propuesta es una revisión teórica alrededor de la práctica del tatuaje a modo de reflexión. El concepto de cuerpo erógeno se articula aquí a la piel como evidencia de la experiencia corporal y la mirada en tanto –en la moderna cultura del consumidor– se concibe a un sujeto a partir del cuerpo que se construye y que podría denominarse dentro de una postura deseable-deseante. La premisa lacaniana: No se es un cuerpo, sino que se posee un cuerpo se articula con lo que refiere Pierre Bourdieu acerca de la construcción social de los cuerpos en tanto se alude a un cuerpo que trasciende lo anatómico-fisiológico y se encuentra anclado al orden de la cultura.

Quantum and dielectric confinement effects in Ruddlesden-Popper 2D hybrid perovskites create excitons with a binding energy exceeding 150 meV. We exploit the large exciton binding energy to study exciton and carrier dynamics as well as electron-phonon coupling (EPC) in hybrid perovskites using absorption and photoluminescence (PL) spectroscopies. At temperatures75 K, we resolve splitting of the excitonic absorption and PL into multiple regularly spaced resonances every 40-46 meV, consistent with EPC to phonons located on the organic cation. We also resolve resonances with a 14 meV spacing, in accord with coupling to phonons with mixed organic and inorganic character. These assignments are supported by density-functional theory calculations. Hot exciton PL and time-resolved PL measurements show that vibrational relaxation occurs on a picosecond time scale competitive with that for PL. At temperatures75 K, excitonic absorption and PL exhibit homogeneous broadening. While absorption remains homogeneous, PL becomes inhomogeneous at temperatures75K, which we speculate is caused by the formation and subsequent dynamics of a polaronic exciton.

For groups of diffeomorphisms of $\T^2$ containing an Anosov diffeomorphism, we give a complete classification for polycyclic Abelian-by-Cyclic group actions on $\T^2$ up to both topological conjugacy and smooth conjugacy under mild assumptions. Along the way, we also prove a Tits alternative type theorem for some groups of diffeomorphisms of $\T^2$., Comment: To appear in Geometry & Topology, revisions according to the referee report from he old version titled "A Tits alternative for surface group diffeomorphisms and Abelian-by-Cyclic actions on surfaces containing an Anosov diffeomorphism"

Let $M$ and $N$ be two closed $C^{\infty}$ manifolds and let $\text{Diff}_c(M)$ denote the group of $C^{\infty}$ diffeomorphisms isotopic to the identity. We prove that any (discrete) group homomorphism between $\text{Diff}_c(M)$ and $\text{Diff}_c(N)$ is continuous. We also show that a non-trivial group homomorphism $\Phi: \text{Diff}_c(M) \to \text{Diff}_c(N)$ implies that $\dim(M) \leq \dim(N)$ and give a classification of such homomorphisms when $\dim(M) = \dim(N)$.

We prove several cases of Zimmer's conjecture for actions of higher-rank cocompact lattices on low dimensional manifolds. For example, if $\Gamma$ is a cocompact lattice in $\mathrm{Sl}(n, \mathbb R)$, $M$ is a compact manifold, and $\omega$ a volume form on $M$ we show that any homomorphism $\rho\colon \Gamma \rightarrow \mathrm{Diff}(M)$ has finite image if the dimension of $M$ is less than $n-1$ and that any homomorphism $\rho\colon \Gamma \rightarrow \mathrm{Diff}(M,\omega)$ has finite image if the dimension of $M$ is less than $n$. The key step in the proof is to show any such action has uniform subexponential growth of derivatives. This is established using ideas from the smooth ergodic theory of higher-rank abelian groups, structure theory of semisimple groups and results from homogeneous dynamics. Having established uniform subexponential growth of derivatives, we apply Lafforgue's strong property (T) to establish the existence of an invariant Riemannian metric., Comment: Revised and improved for referee comments

To determine the percentage of patients who would develop chronic inflammatory rheumatism (CIR) following chikungunya (CHIK) virus disease.We conducted a systematic review of the literature in 3 databases (PubMed, Science Citation Index, and Scopus) to identify studies assessing the proportion of patients who progress to CHIK-CIR. We performed a random-effects model meta-analysis to calculate the pooled prevalence and 95% confidence intervals (95% CIs). A 2-tailed alpha level of 5% was used for hypothesis testing. Measures of heterogeneity, including Cochran's Q statistic, the IUp to June 15, 2015, our literature search yielded 578 citations. The pooled prevalence of CHIK-CIR in 18 selected studies among 5,702 patients was 40.22% (95% CI 31.11-49.34; τAccording to our results in the most conservative scenario, approximately 25% of CHIK cases would develop CHIK-CIR (34% if we just consider the most representative studies), and 14% would develop chronic arthritis.

In this article, we study the smooth mapping class group of a surface S relative to a given Cantor set, that is the group of isotopy classes of orientation-preserving smooth diffeomorphisms of S which preserve this Cantor set. When the Cantor set is the standard ternary Cantor set, we prove that the subgroup consisting of diffeomorphisms which are isotopic to the identity on S does not contain any distorted elements. Moreover, we prove a weak Tits alternative for these groups., Comment: Theorem 1.1. has been improved in this version