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1.
Phys Rev E ; 109(3-1): 034202, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38632765

RESUMO

We study the multifractal behavior of coherent states projected in the energy eigenbasis of the spin-boson Dicke Hamiltonian, a paradigmatic model describing the collective interaction between a single bosonic mode and a set of two-level systems. By examining the linear approximation and parabolic correction to the mass exponents, we find ergodic and multifractal coherent states and show that they reflect details of the structure of the classical phase space, including chaos, regularity, and features of localization. The analysis of multifractality stands as a sensitive tool to detect changes and structures in phase space, complementary to classical tools to investigate it. We also address the difficulties involved in the multifractal analyses of systems with unbounded Hilbert spaces.

2.
Biomed Res Int ; 2023: 5584412, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37700878

RESUMO

Background: The resistance to antibiotics shown by some dermatological pathogenic microorganisms has increased the interest of pharmaceutical and cosmetic industries in developing natural products that possess different biological activities, including antimicrobial effects. Methods: In the present investigation, the antibacterial activity of ethanolic extracts of Dodonaea viscosa aerial part and Mammea americana leaves and seed was evaluated against resistant strains of Staphylococcus isolated from skin lesions and against S. aureus ATCC 25923 (reference strain). Column chromatography (CC) and preparative thin-layer chromatography (PTLC) were used to obtain separate fractions of the seed extract of M. americana. We also determined the antimicrobial resistance of the strains against antibiotics using the agar disc diffusion assay. In addition, phytochemical screening was performed by colorimetric standard techniques. Results: M. americana seed extract showed the highest antibacterial activity with MBC from 2.3 µg/mL to 19.5 µg/mL without differences with gentamicin (p = 0.998). The isolated strain S. epidermidis I showed the highest antimicrobial resistance against the tested antibiotics. PTLC-fractions of M. americana seed extract showed MBC from 3.2 µg/mL to 40.7 µg/mL against S. epidermidis I and S. aureus 25923 (reference), respectively, which suggests a synergistic effect of the secondary metabolites present in the crude ethanolic extract compared to its active PTLC-fractions, where only coumarins and compounds with lactone groups were detected in the phytochemical screening. Conclusion: M. americana seed extract has promising effects that should be considered in further studies as an alternative or adjuvant in treating skin infections caused by staphylococci.


Assuntos
Mammea , Dermatopatias , Staphylococcus , Staphylococcus aureus , Antibacterianos/farmacologia , Staphylococcus epidermidis , Etanol , Extratos Vegetais/farmacologia
4.
J Parasitol ; 109(2): 76-86, 2023 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-36943229

RESUMO

The French grunt, Haemulon flavolineatum, is an abundant fish and a good model for studying parasite communities. Specimens were collected at 4 localities between the Campeche Bank (within the Gulf of Mexico) and the Mexican Caribbean Sea to describe and compare the differences and similarities between localities and regions in the communities of parasitic helminths. Thus, we calculated the Hill numbers associated with species richness (q = 0) and the dominance estimator (q = 2) using rarefaction and extrapolation curves to provide asymptotic estimators of diversity. A 2-way PERMANOVA was used to determine whether there was a significant difference in parasite assemblage structure between localities or regions. A total of 11 helminth taxa (species level) were recorded in 104 individuals of H. flavolineatum, consisting of 8 digenean trematodes species, 2 acanthocephalan species, and 1 nematode species. Our findings include new reports of 7 parasite taxa and new geographical records for some parasites in H. flavolineatum. The highest dissimilarities in parasite composition were observed between the most distant locations (Banco Chinchorro vs. Cayo Arcas) that were each located in different regions. Species richness was similar between regions, although the most dominant helminths were Postmonorchis orthopristis and Dollfustrema sp. in the Mexican Caribbean and Campeche Bank regions, respectively. Future studies should explore how patterns in parasite community structure are affected by currents running south to north by the Yucatan Current through the Yucatan Channel and easterly to Campeche Bank.


Assuntos
Helmintíase Animal , Helmintos , Parasitos , Perciformes , Trematódeos , Animais , México/epidemiologia , Peixes/parasitologia , Helmintíase Animal/epidemiologia , Helmintíase Animal/parasitologia
5.
Gen Comp Endocrinol ; 330: 114150, 2023 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-36349607

RESUMO

Among all the regulatory homeostatic networks in vertebrates, the activation of the hypothalamic-pituitaryadrenal axis during the stress response, has gained considerable attention, and the measurement of fecal glucocorticoids (FGC) has become an invaluable tool to assess adrenocortical activity related to stressful events in wild and captive animals. However, the use of FGC requires the validation of measurement techniques and the proper selection of the specific hormone according to the study species. The main objective of this study was to identify the dominant glucocorticoid (GC) hormone in the stress response of black-tailed prairie dogs (Cynomys ludovicianus) in an arid grassland of Chihuahua, Mexico. A capture stress challenge in the field was developed to determine if the levels of glucocorticoids (cortisol and corticosterone) both in serum and fecal samples could be attributed to stress in Cynomys ludovicianus. The samples were analysed with the technique of liquid phase radioimmunoassay , and this study showed that both cortisol and corticosterone are present at measurable levels in serum and fecal samples of black-tailed prairie dogs. We found that both GCs were present in similar concentrations in serum, however, corticosterone concentration in fecal samples was higher than cortisol. Likewise, biochemical validations performed in this study to test the assay reached acceptable levels of reliability. Therefore, we confirm that fecal analysis can be implemented as a method to measure stress responses in wild prairie dogs.


Assuntos
Corticosterona , Glucocorticoides , Animais , Hidrocortisona , México , Reprodutibilidade dos Testes , Sciuridae
6.
Rev. ANACEM (Impresa) ; 17(1): 102-106, 2023. tab, ilus
Artigo em Espanhol | LILACS | ID: biblio-1526312

RESUMO

Introducción: La depresión es un trastorno del ánimo frecuente, cuya recurrencia altera su manejo y pronóstico. El objetivo del trabajo es describir la tasa de egreso hospitalario (TEH) por episodio depresivo recurrente (EDR) entre 2018-2021 en Chile, según sexo, edad y gravedad. Materiales y métodos: Estudio observacional y transversal que considera los egresos hospitalarios por EDR en el período 2018-2021 en Chile (N=1551). Se utilizaron las bases de datos del Departamento de Estadísticas e Información de Salud y el Instituto Nacional de Estadística. Las variables estudiadas fueron sexo, grupo etario y gravedad. No requirió aprobación de comité de ética. Resultados: Se observó la menor TEH en 2020 con 1,91 egresos por cada 100.000 habitantes. Las mujeres sobresalieron durante todo el período con una TEH de 3,68 egresos por cada 100.000 habitantes. Destacó el grupo de 15 a 19 años con la mayor TEH en ambos sexos con 5,3 egresos por cada 100.000 habitantes. Respecto a gravedad, las hospitalizaciones se concentraron en pacientes de diagnóstico no especificado. Discusión: La pandemia de COVID 19 podría explicar la disminución de la TEH en 2020, al reducirse el diagnóstico y hospitalización por EDR; presumiblemente debido al fenómeno de reconversión de camas. La TEH es mayor en el sexo femenino, lo cual es concordante con la literatura. El predominio del grupo de 15 a 19 años discrepa de la evidencia, la cual indica que suele concentrarse en individuos de 25 a 64 años. Conclusión: Las TEH por EDR se concentraron en mujeres jóvenes. Es relevante conocer la epidemiología local para focalizar los recursos en la detección oportuna de factores de riesgo, para evitar episodios graves y disminuir su recurrencia.


Introduction: Depression is a common mood disorder, whose recurrence alters its management and prognosis. The aim of the paper is to describe the hospital discharge rate (HED) for recurrent depressive episode (RDE) between 2018-2021 in Chile, according to sex, age and severity. Materials and methods: Observational and cross-sectional study considering hospital discharges due to DRE in the period 2018-2021 in Chile (N=1551). The databases of the Department of Health Statistics and Information and the National Institute of Statistics were used. The variables studied were sex, age group and severity. Ethics committee approval was not required. Results: The lowest HTE was observed in 2020 with 1.91 discharges per 100,000 inhabitants. Females stood out during the entire period with an HTE of 3.68 discharges per 100,000 population. The 15-19 years age group stood out with the highest HTE in both sexes with 5.3 admissions per 100,000 inhabitants. In terms of severity, hospitalizations were concentrated in patients with unspecified diagnosis. Discussion: The COVID 19 pandemic could explain the decrease in HTE in 2020, with a reduction in diagnosis and hospitalization for RDE, presumably due to the bed conversion phenomenon. HTE is higher in the female sex, which is consistent with the literature. The predominance of the 15 to 19 years age group disagrees with the evidence, which indicates that it tends to be concentrated in individuals aged 25 to 64 years. Conclusion: HTE due to DRE was concentrated in young women. It is important to know the local epidemiology in order to focus resources on the timely detection of risk factors to avoid serious episodes and reduce their recurrence.


Assuntos
Humanos , Masculino , Feminino , Criança , Adolescente , Adulto , Pessoa de Meia-Idade , Idoso , Idoso de 80 Anos ou mais , Adulto Jovem , Transtorno Depressivo/epidemiologia , Unidade Hospitalar de Psiquiatria , Epidemiologia Descritiva , Hospitalização/estatística & dados numéricos , Serviço Hospitalar de Registros Médicos
7.
Phys Chem Chem Phys ; 24(48): 29731-29746, 2022 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-36458515

RESUMO

An analysis of the ionic transport properties of BMIM [NTf2] in supported ionic-liquid-like phase (SILLP)-based membranes has been carried out based on experimental impedance spectroscopy measurements. The direct current (dc)-conductivity was analyzed to determine the temperature and frequency dependence. The fit of the loss tangent curve data with the Cole-Cole approximation of the electrode polarization model provides the conductivity, diffusivity, and density of charge carriers. Among these quantities, a significant increase in conductivity is observed when an ionic liquid is added to the polymeric matrix containing imidazolium fragments. The use of a recent generalization of Eyring's absolute rate theory allowed the elucidation of how the local entropy restrictions, due to the porosity of the polymeric matrix, control the conductive process. The fit of the conductivity data as a function of temperature manifests the behavior of the excess entropy with respect to the temperature. The activation entropy and enthalpy were also determined. Our results correlate the Debye length (LD) with the experimental values of conductivity, electrode polarization relaxation time, and sample relaxation time involved. Our work provides novel insights into the description of ionic transport in membranes as the diffusivity, mobility, and free charge density depend on the LD. Moreover, we discuss the behavior of the polarization relaxation time, the sample relaxation time, and the static permittivity as a function of the temperature.

8.
Rev. chil. enferm. respir ; Rev. chil. enferm. respir;38(3): 168-175, sept. 2022. tab, graf
Artigo em Espanhol | LILACS | ID: biblio-1423698

RESUMO

Introducción: Los pacientes con COVID-19 pueden evolucionar hacia una falla respiratoria aguda grave y requerir ventilación mecánica invasiva (VMI). La complicación más frecuente en estos pacientes es la neumonía asociada a ventilación mecánica (NAVM), con incidencias reportadas más altas que en la época pre-COVID. El objetivo de este estudio es reportar la incidencia, tasa de incidencia y microbiología de la NAVM en pacientes en VMI con COVID-19. Métodos: Se incluyeron a todos los pacientes con neumonía grave y PCR (+) para SARS-CoV-2 que ingresaron y requirieron VMI entre marzo y julio del 2021 en el Instituto Nacional del Tórax (INT). Se recolectaron datos demográficos, clínicos y de laboratorio de la ficha electrónica. Se registraron y caracterizaron los casos de neumonía asociado a la ventilación mecánica. Resultados: Se incluyeron 112 pacientes de los cuales el 42,8% presentó NAVM, con una tasa de incidencia de 28,8/1.000 días de VMI. Los microorganismos aislados más frecuentes fueron Klebsiella pneumoniae (29,6%), Staphylococcus aureus (21,8%) y Pseudomonas aeruginosa (12,5%). Los pacientes que cursaron NAVM estuvieron casi el doble de tiempo en VMI, pero sin presentar aumento de la mortalidad. Conclusión: La NAVM es una complicación frecuente en los pacientes con neumonía grave asociada a COVID-19. La microbiología de estas entidades no ha cambiado respecto a la era pre-pandémica. Estos resultados cobran relevancia en el inicio y suspensión de antibióticos en este grupo de pacientes.


Introduction: Patients with COVID-19 can progress to severe acute respiratory failure and require invasive mechanical ventilation (IMV). The most frequent complication in these patients is ventilator-associated pneumonia (VAP), with higher reported incidences than in the pre-COVID era. The objective of this study is to report the prevalence, incidence rate and microbiology of VAP in patients on IMV with COVID-19. Methods: Patients with severe pneumonia and PCR (+) for SARS-CoV-2 who were admitted to IMV between march and july 2021 at the Instituto Nacional del Tórax (Chile) were included. Demographic, clinical and laboratory data from electronic records were collected. Cases of pneumonia associated with mechanical ventilation were recorded and characterized. Results: 112 patients were included, 42.8% of them presented VAP with an incidence rate of 28.8/1,000 IMV days. The most frequent isolated microorganisms were Klebsiella pneumoniae (29.6%), Staphylococcus aureus (21.8%) and Pseudomonas aeruginosa (12.5%). Patients who underwent VAP spent almost twice as long on IMV, although they had not increase in mortality. Conclusion: VAP is a common complication in patients with severe pneumonia associated with COVID-19. The microbiology of these entities has not changed from the pre-pandemic era. These results become relevant in the initiation and suspension of antibiotics in this group of patients.


Assuntos
Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Idoso , Pneumonia Associada à Ventilação Mecânica/epidemiologia , COVID-19/terapia , Streptococcus pneumoniae/isolamento & purificação , Estudos Retrospectivos , Curva ROC , Legionella pneumophila/isolamento & purificação , Pneumonia Associada à Ventilação Mecânica/diagnóstico , Pneumonia Associada à Ventilação Mecânica/microbiologia , Coinfecção , SARS-CoV-2 , COVID-19/complicações , Unidades de Terapia Intensiva
9.
Acta Ortop Mex ; 36(4): 230-233, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36977642

RESUMO

INTRODUCTION: exercise programs can reduce pain and improve functionality in patients with degenerative spondylolisthesis and chronic low back pain. However, there is still no consensus surrounding the superiority of any specific routine for exercise-induced trophic changes of lumbar muscles. The aim was to compare the changes in the primary lumbar stabilizing muscle thickness after spine stabilization exercises and flexion exercises in patients with spondylolisthesis and chronic low back pain. MATERIAL AND METHODS: prospective, longitudinal and comparative study was carried out. Twenty-one treatment-naive patients with a diagnosis of both chronic low back pain and degenerative spondylolisthesis over the age of 50 were included. A physical therapist taught participants either spine stabilization exercises or flexion exercises to execute daily at home. The thickness of the primary lumbar muscles was measured through ultrasound (at rest and contraction) at baseline and three months. A Mann-Whitney U test and Wilcoxon signed-rank test were performed for comparisons, and Spearman's rank correlation coefficients were calculated for associations. RESULTS: we did not find statistically between the exercise programs: all patients presented significant changes in the thickness of the multifidus muscle but in none of the other evaluated muscles. CONCLUSION: there is no difference between spine stabilization exercises and flexion exercises after three months in terms of the changes in muscle thickness evaluated by ultrasound.


INTRODUCCIÓN: el ejercicio reduce el dolor y mejora la funcionalidad en pacientes con dolor crónico lumbar y espondilolistesis degenerativa. Sin embargo, no existe a la fecha un consenso sobre la superioridad de algún programa de ejercicio para inducir cambios tróficos de los músculos estabilizadores lumbares, por lo que el objetivo fue comparar el trofismo de estos músculos mediante ultrasonido, con dos programas de ejercicio distintos: estabilización vertebral versus ejercicios flexores. MATERIAL Y MÉTODOS: estudio prospectivo, longitudinal y comparativo, en veintiún pacientes mayores de 50 años, con dolor crónico lumbar y espondilolistesis degenerativa. Se entrenó a los pacientes para la ejecución diaria de ejercicio: estabilización lumbar o ejercicios flexores, los cuales fueron asignados por aleatorización como parte de un ECA en desarrollo. El trofismo muscular fue evaluado mediante ultrasonido al inicio y a tres meses. Las pruebas de U de Mann-Whitney y prueba de Wilcoxon se usaron para comparaciones entre grupos y para correlaciones se usaron los coeficientes de correlación de Spearman. RESULTADOS: todos los pacientes presentaron ganancia en el trofismo de los músculos multífidos a tres meses, pero sin diferencias entre grupos de tratamiento. No se detectaron cambios significativos en el resto de los músculos evaluados. CONCLUSIÓN: no encontramos diferencia significativa entre los ejercicios de estabilización lumbar y los ejercicios flexores, a tres meses de seguimiento, en términos de los cambios tróficos medidos por ultrasonido de los músculos estabilizadores lumbares.


Assuntos
Dor Lombar , Espondilolistese , Humanos , Dor Lombar/diagnóstico por imagem , Dor Lombar/terapia , Espondilolistese/diagnóstico por imagem , Estudos Prospectivos , Terapia por Exercício , Músculos
10.
Mol Genet Metab Rep ; 28: 100781, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34277356

RESUMO

We report on a Mexican mestizo with a multisystemic syndrome including neurological involvement and a type I serum transferrin isoelectric focusing (Tf IEF) pattern. Diagnosis of PMM2-CDG was obtained by clinical exome sequencing (CES) that revealed compound heterozygous variants in PMM2, the encoding gene for the phosphomannomutase 2 (PMM2). This enzyme catalyzes the conversion of mannose-6-P to mannose-1-P required for the synthesis of GDP-Man and Dol-P-Man, donor substrates for glycosylation reactions. The identified variants were c.422G>A (R141H) and c.178G>T, the former being the most frequent PMM2 pathogenic mutation and the latter a previously uncharacterized variant restricted to the Latino population with conflicting interpretations of pathogenicity and that we here report causes leaky non-functional alternative splicing (p.V60Cfs*3).

11.
Phys Rev E ; 103(5-1): 052214, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-34134277

RESUMO

Measuring the degree of localization of quantum states in phase space is essential for the description of the dynamics and equilibration of quantum systems, but this topic is far from being understood. There is no unique way to measure localization, and individual measures can reflect different aspects of the same quantum state. Here we present a general scheme to define localization in measure spaces, which is based on what we call Rényi occupations, from which any measure of localization can be derived. We apply this scheme to the four-dimensional unbounded phase space of the interacting spin-boson Dicke model. In particular, we make a detailed comparison of two localization measures based on the Husimi function in the regime where the model is chaotic, namely, one that projects the Husimi function over the finite phase space of the spin and another that uses the Husimi function defined over classical energy shells. We elucidate the origin of their differences, showing that in unbounded spaces the definition of maximal delocalization requires a bounded reference subspace, with different selections leading to contextual answers.

12.
Phys Rev Lett ; 126(21): 213602, 2021 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-34114862

RESUMO

In this Letter we introduce a novel equation addressing the effect of quantum noise in optical fibers with arbitrary frequency-dependent nonlinear profiles. To the best of our knowledge, such an endeavor has not been undertaken before despite the growing relevance of fiber optics in the design of new quantum devices. We show that the stochastic generalized nonlinear Schrödinger equation, derived from a quantum theory of optical fibers, leads to unphysical results such as a negative photon number and the appearance of a dominant anti-Stokes sideband when applied to this kind of waveguides. Starting from a recently introduced master-equation approach to propagation in fibers, we derive a novel stochastic photon-conserving nonlinear Schrödinger equation suitable for modeling arbitrary nonlinear profiles, thus greatly enhancing the study of fiber-based quantum devices.

13.
Phys Rev E ; 104(6-1): 064116, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-35030927

RESUMO

Using the Wehrl entropy, we study the delocalization in phase space of energy eigenstates in the vicinity of avoided crossings in the Lipkin-Meshkov-Glick model. These avoided crossings, appearing at intermediate energies in a certain parameter region of the model, originate classically from pairs of trajectories lying in different phase-space regions which, contrary to the low-energy regime, are not connected by the discrete parity symmetry of the model. As coupling parameters are varied, a sudden increase of the Wehrl entropy is observed for eigenstates participating in avoided crossings that are close to the critical energy of the excited-state quantum phase transition. This allows us to detect when an avoided crossing is accompanied by a superposition of the pair of classical trajectories in the Husimi function of eigenstates. This superposition yields an enhancement of dynamical tunneling, which is observed by considering initial Bloch states that evolve partially into the partner region of the paired classical trajectories, thus breaking the quantum-classical correspondence in the evolution of observables.

14.
Sci Rep ; 10(1): 16858, 2020 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-33033291

RESUMO

We have studied the Mg doping of cubic GaN grown by plasma-assisted Molecular Beam Epitaxy (PA-MBE) over GaAs (001) substrates. In particular, we concentrated on conditions to obtain heavy p-type doping to achieve low resistance films which can be used in bipolar devices. We simulated the Mg-doped GaN transport properties by density functional theory (DFT) to compare with the experimental data. Mg-doped GaN cubic epitaxial layers grown under optimized conditions show a free hole carrier concentration with a maximum value of 6 × 1019 cm-3 and mobility of 3 cm2/Vs. Deep level transient spectroscopy shows the presence of a trap with an activation energy of 114 meV presumably associated with nitrogen vacancies, which could be the cause for the observed self-compensation behavior in heavily Mg-doped GaN involving Mg-VN complexes. Furthermore, valence band analysis by X-ray photoelectron spectroscopy and photoluminescence spectroscopy revealed an Mg ionization energy of about 100 meV, which agrees quite well with the value of 99.6 meV obtained by DFT. Our results show that the cubic phase is a suitable alternative to generate a high free hole carrier concentration for GaN.

15.
Mol Genet Metab Rep ; 25: 100637, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32874916

RESUMO

Congenital Disorders of Glycosylation (CDG) are scarcely reported from Latin America. We here report on a Mexican mestizo with a multi-systemic syndrome including neurological involvement and a type I transferrin (Tf) isoelectric focusing (IEF) pattern. Clinical exome sequencing (CES) showed known compound missense variants in PMM2 c.422G > A (p.R141H) and c.395 T > C (p.I132T), coding for the phosphomanomutase 2 (PMM2). PMM2 catalyzes the conversion of mannose-6-P to mannose-1-P required for the synthesis of GDP-Man and Dol-P-Man, donor substrates for glycosylation reactions. This is the third reported Mexican CDG patient and the first with PMM2-CDG. PMM2 has been recently identified as one of the top 10 genes carrying pathogenic variants in a Mexican population cohort.

17.
Phys Chem Chem Phys ; 22(2): 437-445, 2020 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-31799568

RESUMO

The crystallographic structure of solid electrolytes and other materials determines the protonic conductivity in devices such as fuel cells, ionic-conductors, and supercapacitors. Experiments show that a rise of the temperature in a narrow interval may lead to a sudden increase of several orders of magnitude of the conductivity of some materials, a process called a superprotonic transition. Here, we use a novel macro-transport theory for irregular domains to show that the change of entropic restrictions associated with solid-solid phase or structural transitions controls the sudden change of the ionic conductivity when the superprotonic transition takes place. Specifically, we deduce a general formula for the temperature dependence on the ionic conductivity that fits remarkably well experimental data of superprotonic transitions in doped cesium phosphates and other materials reported in the literature.

18.
Materials (Basel) ; 12(19)2019 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-31574912

RESUMO

Self-assembled InN nanocolumns were grown at low temperatures by plasma-assisted molecular beam epitaxy with a high crystalline quality. The self-assembling procedure was carried out on AlN/Al layers on Si(111) substrates avoiding the masking process. The Al interlayer on the Si(111) substrate prevented the formation of amorphous SiN. We found that the growth mechanism at 400 ∘ C of InN nanocolumns started by a layer-layer (2D) nucleation, followed by the growth of 3D islands. This growth mechanism promoted the nanocolumn formation without strain. The nanocolumnar growth proceeded with cylindrical and conical shapes with heights between 250 and 380 nm. Detailed high-resolution transmission electron microscopy analysis showed that the InN nanocolumns have a hexagonal crystalline structure, free of dislocation and other defects. The analysis of the phonon modes also allowed us to identify the hexagonal structure of the nanocolumns. In addition, the photoluminescence spectrum showed an energy transition of 0.72 eV at 20 K for the InN nanocolumns, confirmed by photoreflectance spectroscopy.

19.
Phys Rev E ; 100(1-1): 012218, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31499773

RESUMO

Quantum systems whose classical counterparts are chaotic typically have highly correlated eigenvalues and level statistics that coincide with those from ensembles of full random matrices. A dynamical manifestation of these correlations comes in the form of the so-called correlation hole, which is a dip below the saturation point of the survival probability's time evolution. In this work, we study the correlation hole in the spin-boson (Dicke) model, which presents a chaotic regime and can be realized in experiments with ultracold atoms and ion traps. We derive an analytical expression that describes the entire evolution of the survival probability and allows us to determine the time scales of its relaxation to equilibrium. This expression shows remarkable agreement with our numerical results. While the initial decay and the time to reach the minimum of the correlation hole depend on the initial state, the dynamics beyond the hole up to equilibration is universal. We find that the relaxation time of the survival probability for the Dicke model increases linearly with system size.

20.
Arch Soc Esp Oftalmol (Engl Ed) ; 94(8): 367-376, 2019 Aug.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-31266666

RESUMO

INTRODUCTION: Fluctuating elevated intraocular pressure (IOP) is one of the complications of an implantable collamer lens (ICL), and its alteration is a predictive factor for the development of glaucoma. MATERIAL AND METHODS: A prospective, cross-sectional analytic study was conducted on patients suitable for ICL implantation. Complete clinical and biometric work-ups were performed, as well as night-time IOP curve, in supine position, with 4 determinations, in order to assess fluctuation, considering abnormal with a value higher than 5 mmHg. Patients underwent surgery with conventional technique and three months after the work-ups were repeated, including a night-time IOP curve to assess any changes in IOP fluctuations. RESULTS: A total of 31 eyes of 16 patients were studied. Mean IOP fluctuation in the preoperative assessment was 3.35 ± 2 mmHg, whereas the postoperative mean was 3.0 ± 2.2 mmHg, with the difference not being statistically significant. Visual acuity and capacity, as well as spheric equivalent did show a statistically significant improvement. There were 6 cases of complications, which were related to a higher vault and a greater ICL size. There was no relationship between these findings and the angle grade, pigment, and the level of training of the surgeon. CONCLUSIONS: The effect of an ICL on IOP fluctuations, has been studied for the first time, which was found to be not statistically significant. As in previous publications, the procedure was safe and reproducible, adding the fact that the level of training of the surgeon is not a determining factor in these findings.


Assuntos
Pressão Intraocular/fisiologia , Hipertensão Ocular/fisiopatologia , Lentes Intraoculares Fácicas/efeitos adversos , Complicações Pós-Operatórias/fisiopatologia , Adulto , Estudos Transversais , Feminino , Seguimentos , Glaucoma/etiologia , Humanos , Implante de Lente Intraocular/métodos , Masculino , México , Período Pós-Operatório , Período Pré-Operatório , Estudos Prospectivos , Reprodutibilidade dos Testes , Fatores de Tempo , Acuidade Visual , Adulto Jovem
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