Respiratory virus detection among healthcare professionals in Brazil: work-related contact and episode recurrence during the COVID-19 pandemic.

OBJECTIVES: Since the beginning of the COVID-19 pandemic, changes in the circulation of respiratory viruses have been observed after measures to control the spread of SARS-CoV-2 were implemented. In this sense, we aimed to understand the circulation of the respiratory virus and its impact in a controlled healthy population of healthcare professional (HCP) volunteers in phase III of the clinical trial of the ChadOx nCoV1 conducted in São Paulo, Brazil. STUDY DESIGN: This was a nested observational cohort study within a clinical trial. METHODS: We performed RT-qPCR to detect SARS-CoV-2, influenza virus A and B (IVA and IVB), respiratory syncytial virus (RSV), human rhinovirus (HRV), human metapneumovirus (hMPV), human coronaviruses (hCoVs: HKU-1, NL63, OC43, and 229-E), parainfluenza virus (PiV) I-IV, and q-PCR for adenovirus in nasopharyngeal and oropharyngeal samples obtained from HCP enrolled in the clinical trial to assess respiratory viruses infection among vaccinated and non-vaccinated. RESULTS: From July 2020 to January 2022, 876 samples were included from 737 volunteers (median age: 33 years, 62.9% female). New episodes were registered for 119 individuals. We observed an overall positivity of 37.7% for SARS-CoV-2 and 16.4% for other respiratory viruses; HRV was the second most detected virus (8%), followed by RSV (2.4%). Fully vaccinated individuals accounted for 53.3% of collected samples, and 52.9% presented at least one respiratory virus infection, with SARS-CoV-2 being the most predominant etiologic agent (62.3%). Influenza and hMPV were not detected among the tested samples. Among the subjects that presented more than one episode, SARS-CoV-2 and HRV infections were related to direct contact with patients (P < 0.002). CONCLUSIONS: Data show high infection rates among HCPs even under mask policies and contact precautions, highlighting the need for improvement in infection control measures in this population regardless of the vaccination program.

Factors that Influence Placement of Gastrostomy Tube in Infants with Complex Congenital Heart Disease: A Single Center Study.

BACKGROUND: Factors that determine the need for Gastrostomy tube (G-tube) placement in infants with complex congenital heart defects (CHD) are variable. We aim to identify factors that improve counseling of expectant parents regarding postnatal outcomes and management. METHODS: We performed a retrospective review of medical record of infants with prenatal diagnoses of complex CHD between 2015-2019 in a single tertiary care center and assessed risk factors for G-tube placement with linear regression. RESULTS: Of the 105 eligible infants with complex CHD, 44 infants required G-tube (42%). No significant association was observed between G-tube placement and chromosomal abnormalities, cardiopulmonary bypass time or type of CHD. Median days on noninvasive ventilation (4 [IQR 2-12] vs. 3 [IQR 1-8], p = 0.035), time at which gavage-tube feeds were started postoperatively (3 [IQR 2-8] vs. 2 [IQR 0-4], p = 0.0013), time to reach full-volume gavage-tube feeds (6 [IQR 3-14] vs. 5 [IQR 0-8], p = 0.038) and intensive care unit (ICU) length of stay (LOS) (41 [IQR: 21 - 90] vs. 18 [IQR: 7 - 23], p < 0.01) were associated with G-tube placement. Infants with ICU LOS duration longer than median had almost 7 times the odds of requiring a G-tube (OR: 7.23, 95% CI: 2.71-19.32; by regression). CONCLUSIONS: Delay in initiation and in reaching full-volume gavage-tube feeds after cardiac surgery, increased number of days spent on non-invasive ventilation and in the ICU were found to be significant predictors for G-tube placement. The type of CHD and the need for cardiac surgery were not significant predictors for G-tube placement.

Distinctive g-Factor of Moiré-Confined Excitons in van der Waals Heterostructures.

We investigated the valley Zeeman splitting of excitonic peaks in the microphotoluminescence (µPL) spectra of high-quality hBN/WS2/MoSe2/hBN heterostructures under perpendicular magnetic fields up to 20 T. We identify two neutral exciton peaks in the µPL spectra; the lower-energy peak exhibits a reduced g-factor relative to that of the higher energy peak and much lower than the recently reported values for interlayer excitons in other van der Waals (vdW) heterostructures. We provide evidence that such a discernible g-factor stems from the spatial confinement of the exciton in the potential landscape created by the moiré pattern due to lattice mismatch or interlayer twist in heterobilayers. This renders magneto-µPL an important tool to reach a deeper understanding of the effect of moiré patterns on excitonic confinement in vdW heterostructures.

In vitro digestibility of four high moisture grains used in liquid pig feeding.

One of the main challenges in the livestock sector is the need to increase sustainability and production efficiency. In pig production, feed is the main production cost. High moisture grains (HMGs) have recently emerged as an interesting alternative to conventional feedstuffs. In this study, the nutritional value for pigs of eight HMGs was determined considering the chemical composition and the in vitro digestibility. We have used four seeds (lupine, barley, wheat, and corn) and two substrates (water and whey). Lupine HMG showed higher values of crude fat (2.12%) and crude protein (8.59%). Within cereal HMGs, corn HMG showed higher DM (34.37%), OM (36.27%), and starch (27.17%) values; wheat HMG stood out for crude protein content (4.23%) and barley for NDF (5.68%). The pH values were low for all HMG, with lupine having the highest value (4.39). Ammoniacal nitrogen had the highest value for wheat HMG (6.10%). When whey was used as substrate, it improved the characteristics of the HMG. Regarding in vitro digestibility, of the four HMGs studied, wheat showed the highest value for DM (89.93%), while lupine showed the highest value for crude protein (96.12%). When considering the substrates, whey showed better results for all in vitro digestibility's parameters (87.48%, 90.95%, and 90.59%, for DM, OM, and crude protein, respectively). Overall, all HMGs showed good conservation of nutritional value and high in vitro digestibility. The use of whey as a substrate was beneficial for HMG quality. Results show that the analyzed HMG can be efficiently used in the framework of swine production.

Modulation of persistent current in graphene quantum rings.

We investigate the effect of long-range impurity potentials on the persistent current of graphene quantum rings in the presence of an uniform perpendicular magnetic field. The impurity potentials are modeled as finite regions of the ring with a definite length. We show that, due to the relativistic and massless character of the charge carriers in graphene, the effect of such non-uniform potentials on the energy spectrum and on the persistent current of the rings can be reliably modeled by assuming a non-perturbed ring and including an additional phase due to the interaction of the charge carriers with the potential. In addition, the results show the presence of localized states in the impurity regions. Moreover, we show that for the case of a potential created by a p-n-p junction, the persistent current can be modulated by controlling the voltage at the junction.

Zitterbewegung of Moiré Excitons in Twisted MoS_{2}/WSe_{2} Heterobilayers.

The moiré pattern observed in stacked noncommensurate crystal lattices, such as heterobilayers of transition metal dichalcogenides, produces a periodic modulation of their band gap. Excitons subjected to this potential landscape exhibit a band structure that gives rise to a quasiparticle dubbed the moiré exciton. In the case of MoS_{2}/WSe_{2} heterobilayers, the moiré trapping potential has honeycomb symmetry and, consequently, the moiré exciton band structure is the same as that of a Dirac-Weyl fermion, whose mass can be further tuned down to zero with a perpendicularly applied field. Here we show that, analogously to other Dirac-like particles, the moiré exciton exhibits a trembling motion, also known as Zitterbewegung, whose long timescales are compatible with current experimental techniques for exciton dynamics. This promotes the study of the dynamics of moiré excitons in van der Waals heterostructures as an advantageous solid-state platform to probe Zitterbewegung, broadly tunable by gating and interlayer twist angle.

Apical hypertrophic cardiomyopathy: A case series at a Brazilian referral center with a maximal follow-up of 15 years.

BACKGROUND: Apical hypertrophic cardiomyopathy (AHCM) is a rare cardiomyopathy, in which hypertrophy occurs predominantly in the ventricular apex, and in some cases with a high risk of sudden cardiac death. OBJECTIVE: The aim of this paper is to present a case series of patients with AHCM and describe their main clinical, echocardiographic and electrocardiographic characteristics, the recommendation for an implantable cardioverter-defibrillator (ICD) and the frequency of sudden cardiac death (SCD). METHODS: A retrospective case series was conducted at the referral center of a federal teaching hospital, between the years 2005 to 2020, involving patients with an echocardiographic diagnosis of AHCM. The parameters of the American College of Cardiology and the European Society of Cardiology were used to assess the risk of SCD. RESULTS: A total of 11 individuals were assessed with a mean age of 55.3 years, mean follow-up of 41.2 months, most of whom were symptomatic at diagnosis (72.7%). The most frequent symptom was dyspnea (27.3%). A family history of SCD was described in 45.5% of cases. Due to a high risk of SCD, four patients received ICDs. One patient presented sudden cardiac death after having refused the ICD. CONCLUSIONS: Symptoms and alterations in the imaging exams are significant factors in the clinical and prognostic assessment of patients with AHCM.

Factores asociados al fracaso de la terapia con cánulas nasales de alto flujo en pacientes pediátricos con insuficiencia respiratoria en dos unidades de cuidados críticos pediátricos a gran altitud / Factors associated to high-flow nasal cannula treatment failure in pediatric patients with respiratory failure in two pediatric intensive care units at high altitude

Introducción: El fallo respiratorio agudo es la principal causa de hospitalización en pediatría. Las cánulas nasales de alto flujo (CNAF) ofrecen una nueva alternativa, pero sigue existiendo debate en torno a la evidencia e indicaciones. No se ha descrito su comportamiento en gran altitud. Objetivo Describir el uso de CNAF en pacientes pediátricos que ingresan con insuficiencia respiratoria y explorar los factores asociados al fracaso de la terapia. Metodología Estudio de cohortes prospectivo. Pacientes entre un mes y 18 años manejados con CNAF. Se describieron datos demográficos y se evaluó la respuesta al inicio, 1.a, 6.a y 24.a horas. Se determinó el número de fracasos, así como estancia, complicaciones y mortalidad. Se compararon los pacientes con fracaso al tratamiento. Resultados Ingresaron 539 pacientes. Fueron más frecuentes los lactantes (70,9%) de sexo masculino (58,4%) con afecciones respiratorias como asma y bronquiolitis (61,2%). Se presentaron 53 fracasos (9,8%), 21 en las primeras 24 horas. La mediana de estancia fue de 4 días (RIQ 4), hubo 5 éxitus (0,9%) y 13 eventos adversos –epistaxis– (2,2%). Se observó mejoría de signos vitales y gravedad en el tiempo con diferencias en el grupo que fracasó, pero sin interacciones. El modelo logístico final estimó una relación independiente del fracaso, entre el hospital (OR 2,78; IC95% 1,48-5,21) y la frecuencia respiratoria inicial (OR 1,56; IC95% 1,21-2,01). Conclusión La CNAF es un sistema con buena respuesta clínica, pocas complicaciones y una baja tasa de fracasos. Las diferencias entre las instituciones sugieren una relación subjetiva de la decisión del fracaso. (AU)

Introduction: Acute respiratory failure is the leading cause of hospitalization in pediatrics. High-flow nasal cannulas (HFNCs) offer a new alternative, but the evidence and indications are still debated. The performance of HFNCs at high altitude has not been described to date. Objective To describe the use of HFNCs in pediatric patients admitted with respiratory failure and explore the factors associated with treatment failure. Methodology A prospective cohort study was carried out in patients between 1 month and 18 years of age managed with HFNCs. The demographic and treatment response data were recorded at baseline and after 1, 6 and 24hours. The number of failures was determined, as well as the length of stay, complications and mortality. Patients with treatment failure were compared with the rest. Results A total of 539 patients were enrolled. Infants (70.9%) of male sex (58.4%) and airway diseases such as asthma and bronchiolitis (61.2%) were more frequent. There were 53 failures (9.8%), with 21 occurring in the first 24hours. The median length of stay was 4 days (IQR 4); there were 5 deaths (0.9%) and 13 adverse events (epistaxis) (2.2%). Improvement was observed in vital signs and severity over time, with differences in the group that failed, but without interactions. The final logistic model established an independent relationship of failure between the hospital (OR 2.78, 95%CI 1.48-5.21) and the initial respiratory rate (OR 1.56, 95%CI 1.21-2.01). Conclusions HFNCs afford good clinical response, with few complications and a low failure rate. The differences found between institutions suggest a subjective relationship in the decision of therapy failure. (AU)

[Factors associated to high-flow nasal cannula treatment failure in pediatric patients with respiratory failure in two pediatric intensive care units at high altitude]. / Factores asociados al fracaso de la terapia con cánulas nasales de alto flujo en pacientes pediátricos con insuficiencia respiratoria en dos unidades de cuidados críticos pediátricos a gran altitud.

INTRODUCTION: Acute respiratory failure is the leading cause of hospitalization in pediatrics. High-flow nasal cannulas (HFNCs) offer a new alternative, but the evidence and indications are still debated. The performance of HFNCs at high altitude has not been described to date. OBJECTIVE: To describe the use of HFNCs in pediatric patients admitted with respiratory failure and explore the factors associated with treatment failure. METHODOLOGY: A prospective cohort study was carried out in patients between 1 month and 18 years of age managed with HFNCs. The demographic and treatment response data were recorded at baseline and after 1, 6 and 24hours. The number of failures was determined, as well as the length of stay, complications and mortality. Patients with treatment failure were compared with the rest. RESULTS: A total of 539 patients were enrolled. Infants (70.9%) of male sex (58.4%) and airway diseases such as asthma and bronchiolitis (61.2%) were more frequent. There were 53 failures (9.8%), with 21 occurring in the first 24hours. The median length of stay was 4 days (IQR 4); there were 5 deaths (0.9%) and 13 adverse events (epistaxis) (2.2%). Improvement was observed in vital signs and severity over time, with differences in the group that failed, but without interactions. The final logistic model established an independent relationship of failure between the hospital (OR 2.78, 95%CI 1.48-5.21) and the initial respiratory rate (OR 1.56, 95%CI 1.21-2.01). CONCLUSIONS: HFNCs afford good clinical response, with few complications and a low failure rate. The differences found between institutions suggest a subjective relationship in the decision of therapy failure.

Gap opening in graphene nanoribbons by application of simple shear strain and in-plane electric field.

The effects of shear strain and applied in plane electric field on the electronic properties of monolayer graphene nanoribbons (GNRs) are theoretically investigated. Band structures and the probability densities are calculated within the tight-binding model and the mechanical stresses submitted to the GNRs are taken into account by using the theory of linear elasticity with joint modifications in the elongation of the nearest-neighbor vectors and the modification of the hopping parameters. The energy gaps for specific widths of (semiconducting) armchair nanoribbons are verified also in the presence of either strain or field, whereas zigzag nanoribbons are metallic for any value of strain and exhibit a small gap for any value of field. However, our results demonstrate that when both strain and electric field are combined, a significant energy gap is always observed in the band structure, for any width or edge type of the ribbon. Moreover, the obtained total wave function is asymmetric along the ribbon width due to the applied electric field that pushes the electrons to one side of the ribbon and, under shear strain, a peak at the center of the ribbon in the spatial distribution is also observed owing to the preferable localization around the almost undeformed carbon bonds at ribbon center.

Magnetic field induced vortices in graphene quantum dots.

The energy spectrum and local current patterns in graphene quantum dots (QD) are investigated for different geometries in the presence of an external perpendicular magnetic field. Our results demonstrate that, for specific geometries and edge configurations, the QD exhibits vortex and anti-vortex patterns in the local current density, in close analogy to the vortex patterns observed in the probability density current of semiconductor QD, as well as in the order parameter of mesoscopic superconductors.

Real-world data from the Portuguese Nivolumab Expanded Access Program (EAP) in previously treated Non Small Cell Lung Cancer (NSCLC).

OBJECTIVE: The main aim of the study was to evaluate the efficacy and safety profile of Nivolumab, an immune-checkpoint-inhibitor antibody, in advanced, previously treated, Non-Small Cell Lung Cancer (NSCLC) patients, in a real world setting. METHODS: We performed a retrospective, multicentre data analysis of patients who were included in the Portuguese Nivolumab Expanded Access Program (EAP). Eligibility criteria included histologically or citologically confirmed NSCLC, stage IIIB and IV, evaluable disease, sufficient organ function and at least one prior line of chemotherapy. The endpoints included Overall Response Rate (ORR), Disease Control Rate (DCR), Progression Free Survival (PFS) and Overall Survival (OS). Safety analysis was performed with the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE), version 4.0, and immune-related Adverse Events (irAEs) were treated according to protocol treatment guidelines. Tumour response was assessed using the Response Evaluation Criteria in Solid Tumours (RECIST) version 1.1. Data was analysed using SPSS, version 21.0 (IBM Statistics). RESULTS: From June 2015 to December 2016, a total of 229 patients with advanced NSCLC were enrolled at 30 Portuguese centres. Clinical data were collected up to the end of July 2018. The baseline median age was 64 years (range 37-83) and the majority of patients were males (70.3%) and former/current smokers (69.4%). Patients with non-squamous histology predominated (88.1%), and 67.6% of the patients had received 2 or more prior lines of chemotherapy. Out of 229 patients, data was available for 219 patients (3 patients did not start treatment, while data was unavailable in 7 patients); of the 219 patients, 15.5% were not evaluated for radiological tumour assessment, 1.4% had complete response (CR), 21% partial response (PR), 31% stable disease (SD) and 31.1% progressive disease (PD). Thus, the ORR was 22.4% and DCR was 53.4% in this population. At the time of survival analysis the median PFS was 4.91 months (95% CI, 3.89-6.11) and median OS was 13.21 months (95% CI, 9.89-16.53). The safety profile was in line with clinical trial data. CONCLUSIONS: Efficacy and safety results observed in this retrospective analysis were consistent with observations reported in clinical trials and from other centres.

Effects of the inclusion of Moringa oleifera seed on rumen fermentation and methane production in a beef cattle diet using the rumen simulation technique (Rusitec).

Moringa oleifera seeds are currently being used as a livestock feed across tropical regions of the world due to its availability and palatability. However, limited knowledge exists on the effects of the raw seeds on ruminant metabolism. As such, the rumen stimulation technique was used to evaluate the effects of substituting increasing concentrations of ground Moringa seeds (0, 100, 200 and 400 g/kg concentrate dry matter (DM)) in the diet on rumen fermentation and methane production. Two identical, Rusitec apparatuses, each with eight fermenters were used with the first 8 days used for adaptation and days 9 to 16 used for measurements. Fermenters were fed a total mixed ration with Urochloa brizantha as the forage. Disappearance of DM, CP, NDF and ADF linearly decreased (P<0.01) with increasing concentrations of Moringa seeds in the diet. Total volatile fatty acid production and the acetate to propionate ratio were also linearly decreased (P<0.01). However, only the 400 g/kg (concentrate DM basis) treatment differed (P<0.01) from the control. Methane production (%), total microbial incorporation of 15N and total production of microbial N linearly decreased (P<0.01) as the inclusion of Moringa seeds increased. Though the inclusion of Moringa seeds in the diet decreased CH4 production, this arose from an unfavourable decrease in diet digestibility and rumen fermentation parameters.

Influence of feeding supplements of almond hulls and ensiled citrus pulp on the milk production, milk composition, and methane emissions of dairy cows.

Almond hulls and citrus pulp have been fed to dairy cows with variable responses for milk production, but no information exists on their effect on enteric methane emissions. This experiment examined the effects of dietary supplementation with either almond hulls or ensiled citrus pulp on the milk yield, milk composition, and enteric methane emissions of dairy cows. Thirty-two Holstein dairy cows in mid lactation were offered 1 of 3 diets over a 28-d experiment. Twelve cows received a control (CON) diet, 10 cows a diet containing almond hulls (ALH), and 10 cows a diet containing ensiled citrus pulp (CIT). All cows were offered 6.0 kg of dry matter (DM)/d of crushed corn, 2.0 kg of DM/d of cold-pressed canola, and 0.2 kg of DM/d of a mineral mix. In addition, cows fed the CON diet were offered 14.5 kg of DM/d of alfalfa cubes; cows fed the ALH diet were offered 10.5 kg of DM/d of alfalfa cubes and 4.0 kg of DM/d of almond hulls; and cows on the CIT diet were offered 11.5 kg of DM/d of alfalfa cubes and 3.0 kg of DM/d of ensiled citrus pulp. Milk yield was measured daily and milk composition was measured on 4 d of each week. Individual cow methane emissions were measured by a sulfur hexafluoride tracer technique on d 24 to 28 of the experiment. The mean milk yield of cows fed the CON diet (27.4 kg/d) was greater than the mean milk yield of cows fed the ALH diet (24.6 kg/cow per day), whereas the mean milk yield of cows fed the CIT diet (26.2 kg/cow per day) was not different from the mean milk yield from cows fed the other 2 diets. Dietary treatment did not influence the concentrations of milk fat, protein, and lactose or fat yields, but the mean protein yield from cows fed the CON diet (0.87 kg/d) was greater than that from cows fed the ALH diet (0.78 kg/d) but not different to those fed the CIT diet (0.85 kg/d). In general, we found no differences in the proportion of individual fatty acids in milk. The mean pH of ruminal fluid from cows offered the CON diet was not different to the pH in the ruminal fluids of cows offered the ALH or the CIT diets. The mean methane emissions (g/d) and yields (g/kg of DM intake) were not influenced by dietary treatment. These findings indicate that, although almond hulls and ensiled citrus pulp can be used as a low-cost feed supplement, almond hulls did negatively affect milk production and neither inhibited enteric methane emissions.

Efecto de las bacterias uropatógenas y de los factores solubles de su metabolismo sobre la calidad espermática: Escherichia coli y Enterococcus faecalis / Effect of uropathogenic bacteria and soluble factors produced by their metabolism on sperm quality: Escherichia coli and Enterococcus faecalis

Objetivo: El contacto de los espermatozoides con algunas especies bacterianas y sus factores solubles tiene un efecto negativo en la calidad seminal, alterando la función reproductiva del hombre. El objetivo de este trabajo fue determinar el efecto de 2 bacterias enteropatógenas (Escherichia coli [E. coli] y Enterococcus faecalis [E. faecalis]) y sus factores solubles sobre la calidad espermática. Metodología: Las cepas bacterianas de E. coli sensible y resistente a ampicilina/sulbactam y piperacilina/tazobactam, las cepas de E. faecalis sensible y resistente a gentamicina y estreptomicina de alto nivel, además de los factores solubles producto del metabolismo bacteriano de cada cepa, se incubaron con las muestras de semen de voluntarios. Posteriormente, se cuantificó la movilidad por microscopia y los parámetros funcionales espermáticos (potencial de membrana mitocondrial, integridad de la membrana, detección de especies reactivas del oxígeno e índice de fragmentación del ADN) por citometría de flujo. Resultados: Las cepas de E. coli, E. faecalis y los factores solubles de su metabolismo alteran la movilidad espermática y algunos de los parámetros funcionales evaluados luego de 3 h de incubación con los espermatozoides humanos, sin que estos cambios sean estadísticamente significativos. Conclusión: La interacción de las bacterias E. coli y E. faecalis o los factores solubles producto de su metabolismo con los espermatozoides humanos alteran la calidad seminal, por lo que se debe evaluar el impacto de las infecciones urogenitales por estos microorganismos en la fertilidad masculina

Objective: Interactions between sperm and bacteria or soluble factors have a negative effect on semen quality and male fertility. The aim of this study was to determine the effect of 2 enteropathogenic bacteria (Escherichia coli [E. coli] and Enterococcus faecalis [E. faecalis]) and their soluble factors on sperm quality. Methodology: E. coli-sensitive and -resistant strains to ampicillin/sulbactam and piperacillin/tazobactam, E. faecalis-sensitive and -resistant strains to gentamicin and high level streptomycin and soluble factors produced by bacterial metabolism of each strain were incubated with semen samples from volunteers. Subsequently, motility was quantified by light microscopy and sperm function parameters (mitochondrial membrane potential, membrane integrity, reactive oxygen species, and chromatin integrity) by flow cytometry. Results: E. coli and E. faecalis strains and their soluble factors altered sperm motility and some of the sperm function parameters evaluated after 3h of incubation with human sperm but these changes were not statistically significant. Conclusion: Semen quality is affected by the interaction between E. coli and E. faecalis or their soluble factors. Therefore, there is a need to assess the impact of urogenital infections by these microorganisms on male fertility

Valley filtering in graphene due to substrate-induced mass potential.

The interaction of monolayer graphene with specific substrates may break its sublattice symmetry and results in unidirectional chiral states with opposite group velocities in the different Dirac cones (Zarenia et al 2012 Phys. Rev. B 86 085451). Taking advantage of this feature, we propose a valley filter based on a transversal mass kink for low energy electrons in graphene, which is obtained by assuming a defect region in the substrate that provides a change in the sign of the substrate-induced mass and thus creates a non-biased channel, perpendicular to the kink, for electron motion. By solving the time-dependent Schrödinger equation for the tight-binding Hamiltonian, we investigate the time evolution of a Gaussian wave packet propagating through such a system and obtain the transport properties of this graphene-based substrate-induced quantum point contact. Our results demonstrate that efficient valley filtering can be obtained, provided: (i) the electron energy is sufficiently low, i.e. with electrons belonging mostly to the lowest sub-band of the channel, and (ii) the channel length (width) is sufficiently long (narrow). Moreover, even though the transmission probabilities for each valley are significantly affected by impurities and defects in the channel region, the valley polarization in this system is shown to be robust against their presence.

Electronic properties of superlattices on quantum rings.

We present a theoretical study of the one-electron states of a semiconductor-made quantum ring (QR) containing a series of piecewise-constant wells and barriers distributed along the ring circumference. The single quantum well and the superlattice cases are considered in detail. We also investigate how such confining potentials affect the Aharonov-Bohm like oscillations of the energy spectrum and current in the presence of a magnetic field. The model is simple enough so as to allow obtaining various analytical or quasi-analytical results. We show that the well-in-a-ring structure presents enhanced localization features, as well as specific geometrical resonances in its above-barrier spectrum. We stress that the superlattice-in-a-ring structure allows giving a physical meaning to the often used but usually artificial Born-von-Karman periodic conditions, and discuss in detail the formation of energy minibands and minigaps for the circumferential motion, as well as several properties of the superlattice eigenstates in the presence of the magnetic field. We obtain that the Aharonov-Bohm oscillations of below-barrier miniband states are reinforced, owing to the important tunnel coupling between neighbour wells of the superlattice, which permits the electron to move in the ring. Additionally, we analysis a superlattice-like structure made of a regular distribution of ionized impurities placed around the QR, a system that may implement the superlattice in a ring idea. Finally, we consider several random disorder models, in order to study roughness disorder and to tackle the robustness of some results against deviations from the ideally nanostructured ring system.

Electronic confinement in graphene quantum rings due to substrate-induced mass radial kink.

We investigate localized states of a quantum ring confinement in monolayer graphene defined by a circular mass-related potential, which can be induced e.g. by interaction with a substrate that breaks the sublattice symmetry, where a circular line defect provides a change in the sign of the induced mass term along the radial direction. Electronic properties are calculated analytically within the Dirac-Weyl approximation in the presence of an external magnetic field. Analytical results are also compared with those obtained by the tight-binding approach. Regardless of its sign, a mass term [Formula: see text] is expected to open a gap for low-energy electrons in Dirac cones in graphene. Both approaches confirm the existence of confined states with energies inside the gap, even when the width of the kink modelling the mass sign transition is infinitely thin. We observe that such energy levels are inversely proportional to the defect line ring radius and independent on the mass kink height. An external magnetic field is demonstrated to lift the valley degeneracy in this system and easily tune the valley index of the ground state in this system, which can be polarized on either K or [Formula: see text] valleys of the Brillouin zone, depending on the magnetic field intensity. Geometrical changes in the defect line shape are considered by assuming an elliptic line with different eccentricities. Our results suggest that any defect line that is closed in a loop, with any geometry, would produce the same qualitative results as the circular ones, as a manifestation of the topologically protected nature of the ring-like states investigated here.

Avaliação endoscópica das vias aéreas, do perfil de gases, dos eletrólitos e do equilíbrio ácido-base em equinos submetidos ao treinamento de três tambores / Endoscopic airway, blood gas, electrolytes, and acid-base in equine submitted to three-barrel training

O objetivo deste estudo foi avaliar as vias aéreas por endoscopia, o perfil de gases, de eletrólitos e o equilíbrio ácido-base de equinos da raça Quarto de Milha (QM) antes e após o exercício de três tambores. Dezesseis cavalos, divididos em dois grupos de oito animais, treino regular (TR - cinco vezes) e treino esporádico (TE - duas vezes por semana), foram utilizados no experimento. A endoscopia foi realizada antes e 90 min após o exercício. Foram realizadas duas coletas de sangue por punção da artéria facial transversa antes do aquecimento (M0) e imediatamente após o exercício (M1), e as leituras foram realizadas com o I-Stat(r). Foram determinadas PCO2, PO2, SO2, pH, BE, HCO3 e TCO2, Na+, K+, iCa, glicose, Hg e Ht. Foi utilizada ANOVA com medidas repetidas no tempo para comparações dos grupos e dos momentos (P<0,05). A HFL acometeu em grau leve (1-2) os animais de ambos os grupos, com 8/8 (100%) no TR e 5/8 (62,5%) no TE. Observou-se presença de secreção serosa na traqueia em 4/8 (50%) para ambos os grupos. A HPIE acometeu em grau leve (1-2) os animais de ambos os grupos, com 4/8 (50%) no grupo TR e 3/8 (37,5%) no grupo TE. Os animais com grau 2 de HPIE apresentaram leve hipoxemia e hipercapnia pós-exercício. SO2, PCO2, pH, HCO3, BE, K e iCa+ não diferiram estatisticamente (P>0,05) entre os grupos. Os cavalos da raça QM submetidos ao exercício de TT apresentam HPIE e acidose metabólica.(AU)

The aim of this study was to evaluate the airways by endoscopy, gas profile, electrolytes and acid-base balance of horses in the Quarter Horse (QM) race before and after training three drums. Sixteen horses divided into two groups of 8 animals, with regular training (RT - 5 times a week) and sporadic training (ET - 2 times a week) were used in the experiment. Endoscopy was performed before and 90 min after training. Two blood samples were taken by puncturing the transverse facial artery before heating (M0) and immediately after training (M1), and the readings were performed with the I-Stat(r). PCO2, PO2, SO2, pH, BE, HCO3 and TCO2, Na +, K +, iCa, Glucose, Hg, and Ht were determined. ANOVA was used with repeated measures over time for comparisons of groups and time (P<0.05). The HFL befell was mild (1-2), the animals from both groups with 8/8 (100%) in the TR and 5/8 (62.5%) for the TE. There was presence of serous trachea 4/8 (50%) for both groups. The EIPH befell was mild (1-2) in the animals from both groups with 4/8 (50%) in the RT group and 3/8 (37.5%) for the TE group. Animals with grade 2 EIPH had mild hypoxemia and hypercapnia after exercise. The SO2, PCO2, pH, HCO3, BE, K, and iCa did not differ P <0.05 between groups. QM race submitted to TT exercise have EIPH and metabolic acidosis.(AU)