Anion intercalated graphite: a combined electrochemical and tribological investigation by in situ AFM.

The intercalation of graphite by electrochemical methods is an efficient strategy to produce massive graphene flakes. In fact, when graphite is biased inside an acidic solution, anions enter inside the stratified structure of the electrode and reduce the layer-to-layer interaction. Consequently, a gentle sonication is sufficient to disperse the graphene flakes inside the electrolyte. In view of an optimisation of the production protocol, a detailed analysis of the intercalation mechanism at the molecular length scale is mandatory. In the last 30 years, electrochemical (EC) scanning probe microscopies (e.g. EC-STM and in situ AFM) have been widely exploited in this research topic. In fact, these techniques have the possibility of combining the EC characterisation (e.g. cyclic-voltammetry, CV) with mechanical characterisation (e.g. adhesion and friction) and topography acquisition with high (molecular) lateral resolution. In this work, we investigate the tribological properties of the basal surface of graphite before and after the anion intercalation. By comparing the results acquired after the extraction of the graphite electrode from the EC cell with those collected inside the EC cell during the CV by an in situ AFM, we show how some features deriving from anisotropic friction can be exploited to unveil the very early stage of graphite exfoliation.

Polarization properties of second-harmonic generation in AlGaAs optical nanoantennas.

Manipulating light at the nanoscale by means of dielectric nanoantennas recently received renewed attention thanks to the development of key enabling fabrication tools in semiconductor technology, combined with the extremely low losses exhibited by dielectrics in the optical regime. Nanostructures based on III-V type semiconductors, characterized by an intrinsic broken symmetry down to a single elementary cell, has already demonstrated remarkable nonlinear conversion efficiencies at scales well below the operating wavelength. In this Letter, we thoroughly investigate the emission properties of second-harmonic generation (SHG) in AlGaAs monolithic nanoantennas. Our findings point toward the pivotal role of volume susceptibility in SHG, further unraveling the physics behind the nonlinear processes in these systems. The extremely high SHG efficiency attained, together with the control over the polarized emission in these nanoantennas, constitute key ingredients for the development of tunable nonlinear metasurfaces.

Temporal analysis of blister evolution during anion intercalation in graphite.

In the currently accepted picture, when graphite is immersed and polarized in a diluted sulfuric acid electrolyte, the surface undergoes an invasive process due to the intercalation of solvated sulphate anions inside the crystal. The following evolution of CO, CO2 and O2 promotes the surface swelling and the growth of blisters. Here, we give evidence that the appearance of blisters affects the graphite surface as soon as the oxygen potential is reached, i.e. before the traditionally accepted anion intercalation stage, which instead is demonstrated slowing the blister development. These results suggest a new picture of the solvated anion intercalation in graphite with respect to the current interpretative model.

Identification of LCK mutation in a family with atypical epidermodysplasia verruciformis with T-cell defects and virus-induced squamous cell carcinoma.

BACKGROUND: Inherited epidermodysplasia verruciformis (EV) is a rare skin disorder characterized by susceptibility to specific types of human papilloma virus (HPV) and is strongly associated with skin carcinomas. Inactivating mutations in EVER1/EVER2 account for most cases of EV. However, more phenotypes related to but distinct from EV have been reported with an immunodeficiency state but without EVER1/EVER2 mutation, and the genetic basis for these atypical EV cases is poorly understood. OBJECTIVES: To identify the causative gene responsible for three siblings affected by atypical EV but without EVER1/EVER2 mutation. METHODS: Whole-exome sequencing followed by Sanger sequencing was performed to identify the gene responsible for the patients with atypical EV enrolled in our study. RESULTS: A homozygous splicing mutation was detected in LCK (c.188-2A>G). This mutation resulted in an exon 3 deletion T lymphocyte-specific protein tyrosine kinase isoform, which further led to frameshift mutation and subsequent mRNA decay. CONCLUSIONS: We demonstrate a novel mutation in LCK in a family affected by atypical EV with T-cell defects, HPV infection and virus-induced malignancy, providing new clues in the understanding of host defences against HPV and better genetic counselling of patients with the EV phenotype.

Communication: Tracking molecular structure deformation and relaxation in real time.

The CH3I structural deformation induced by strong laser fields is revealed by time- and frequency-resolved ro-vibrational spectra. The experimental results show that the CH3I molecule undergoes ultrafast structural deformation of CH3 "umbrella-closing" induced by the strong fs laser field (more than 10(11) W/cm(2)) and followed by a structural relaxation of "umbrella-opening" within an exponential decay time scale of ∼620 fs. This study provides a first glimpse of the immense potential of the time- and frequency-resolved vibrational spectra in studying molecular deformation dynamics.

Enhanced atom mobility on the surface of a metastable film.

A remarkable enhancement of atomic diffusion is highlighted by scanning tunneling microscopy performed on ultrathin metastable body-centered tetragonal Co films grown on Fe(001). The films follow a nearly perfect layer-by-layer growth mode with a saturation island density strongly dependent on the layer on which the nucleation occurs, indicating a lowering of the diffusion barrier. Density functional theory calculations reveal that this phenomenon is driven by the increasing capability of the film to accommodate large deformations as the thickness approaches the limit at which a structural transition occurs. These results disclose the possibility of tuning surface diffusion dynamics and controlling cluster nucleation and self-organization.

A versatile system for the growth of porphyrin films via electrospray and molecular sublimation in vacuum and their multi-technique characterization.

We present a system for the growth of molecular films in vacuum that exhibits high versatility with respect to the choice of molecular species. These can be either evaporated from powders or injected from solutions using an electrospray system, making it possible to handle particularly large and/or fragile molecules in a controlled environment. The apparatus is equipped with a reflectance anisotropy spectroscopy system for the in situ characterization of the optical response of the films and can be directly connected to a photoelectron spectrometer without breaking the vacuum. The system is conceived for the study and characterization of porphyrin films. Here, to showcase the range of possible analyses allowed by the experimental setup and test the operation of the system, novel results are provided on electrospray deposition on highly oriented pyrolytic graphite of Zn tetraphenyl porphyrins and Zn proto porphyrins, the latter featuring fragile side groups that make deposition from solution more attractive. In situ characterization is complemented by ex situ atomic force microscopy. Thanks to this multi-technique approach, changes in the film morphology and spectroscopic response are detected and directly related to the choice of the molecular moiety and growth method.

Laser-induced magnetic nanostructures with tunable topological properties.

We report the creation and real-space observation of magnetic structures with well-defined topological properties and a lateral size as low as about 150 nm. They are generated in a thin ferrimagnetic film by ultrashort single optical laser pulses. Thanks to their topological properties, such structures can be classified as Skyrmions of a particular type that does not require an externally applied magnetic field for stabilization. Besides Skyrmions, we are able to generate magnetic features with topological characteristics that can be tuned by changing the laser fluence. The stability of such features is accounted for by an analytical model based on the interplay between the exchange and the magnetic dipole-dipole interactions.

X-ray photoemission spectroscopy investigation of the interaction between 4-mercaptopyridine and the anatase TiO2 surface.

In polymer-metal oxide hybrid solar cells, an extremely careful engineering of the interface is required to ensure good device performances. Recently, very promising results have been obtained by functionalizing titanium dioxide (TiO2) by means of 4-mercaptopyridine (4-MPy) molecules, showing the beneficial effect of these molecules on the interface morphology. This study investigates the nature of the interaction of 4-MPy molecules with the TiO2 surface by means of X-ray photoemission spectroscopy. In order to mimic the device processing conditions, our analysis is carried out on molecules adsorbed from solution on a nanocrystalline surface. According to our analysis, 4-MPy molecules (C5H5NS) are likely bound with the oxide through the nitrogen atom. The bonding precedes either via a covalent interaction with Lewis surface sites, or via hydrogen mediation, possibly in the form of hydrogen bonds. Interestingly, in the latter case, we also observe strong changes in the spectroscopic features attributed to the thiol group.

Investigating the activation of passive metals by a combined in-situ AFM and Raman spectroscopy system: a focus on titanium.

Understanding the main steps involved in the activation of passive metals is an extremely important subject in the mechanical and energy industry and generally in surface science. The titanium-H2SO4 system is particularly useful for this purpose, as the metal can either passivate or corrode depending on potential. Although several studies tried to hypothesise the surface state of the electrode, there is no general consensus about the surface state of Ti in the active-passive transition region. Here by combining in-situ atomic force microscopy (AFM) and Raman spectroscopy, operating in an electrochemical cell, we show that the cathodic electrification of Ti electrodes causes the dissolution of the upper TiO2 portion of the passive film leaving the electrode covered by only a thin layer of titanium monoxide. Fast anodic reactions involved the acidification of the solution and accumulation of sulphur containing anions. This produces a local increase of the solution turbidity, allowing to distinguish favourable regions for the precipitation of TiOSO4·2H2O. These results give a clear answer to the long-stated question of the physical origin behind the formation of negative polarization resistances, sometimes occurring in corroding systems, and a rationale about the proton-induced degradation of passive surfaces in presence of sulphur containing species.

[Epidemiological characteristics of human rabies in China, 2016-2018].

Objective: To analyze epidemiological characteristics and explore control and prevention measures based on the rabies surveillance data in China from 2016 to 2018. Methods: The surveillance data of rabies in China from 2016-2018 were collected from the "Infectious Disease Surveillance Information Reporting Management System", eleven national surveillance sites in Hunan, Anhui, Guizhou, Jiangsu and Shandong provinces and National Bureau of Statistics. Descriptive epidemiological method was used to analyze the distributions of rabies outbreaks in China during this period, and univariate and multivariate analyses were conducted on the data using SPSS 25.0. Results: Rabies epidemics were mainly found in southern and central areas in China. Rabies mainly occurred in summer and autumn, and the majority of patients were farmers, students and children outside child care settings. The male to female ratio of the cases was 2.38∶1(1 114∶468). The cases were reported in all age groups and the incidence curve was bimodal, and more cases occurred in middle aged and old adults than in youths. In the case analysis of rabies from 2016 to 2018, the majority of the animals biting human were dogs, accounting for 91.46%(439/480). And about 71.88% (345/480) of the exposures were degree Ⅲ. The vaccination rate after exposure was only 8.13%(39/480). Age, degree of exposure, site of exposure, wound management, vaccination and injection of passive immunization product might influence the incubation period. Conclusions: The human rabies incidence in China declined consecutively from 2016 to 2018, and the affected areas decreased. No cases were reported in northwestern area. The rate of post exposure prophylaxis, vaccination and passive immunization product injection were all improved, but the level of standard wound management after exposure needs to be improved. Attention should be paid to epidemic surveillance in high-incidence provinces and neighboring provinces. It is necessary to strengthen professional treatment training in relevant medical institutions, strengthen immunization and management of dog to achieve the goal of "zero human rabies death by 2030".

Reversible metamorphosis from Fe3O4 to FeO of epitaxial iron oxide films grown on the Fe-p(1 × 1)O surface.

The reduction and oxidation of epitaxial Fe3O4 films grown by reactive deposition on a Fe-p(1 × 1)O surface have been investigated by means of Auger electron spectroscopy (AES), low energy electron diffraction (LEED) and scanning tunneling microcopy (STM). The as-grown iron oxide samples display a square LEED pattern with a lattice constant compatible with a p(1 × 1) bulk terminated Fe3O4(001) surface. STM topographic images of Fe3O4 are characterized by atomically flat terraces separated by highly oriented steps running along the (010) and (100) crystallographic directions of the substrate. Upon annealing at 800 K in an ultra-high vacuum, AES reveals that magnetite transforms to FeO. The sample exposes the (001) surface of the rock salt structure, with a lattice parameter close to that of bulk wüstite. The Fe3O4 phase can be recovered by oxidation at 10-6 mbar of molecular oxygen.

Enhanced uptake of heavy metals in municipal solid waste compost by turfgrass following the application of EDTA.

Enhancement of multiple heavy metal uptake from municipal solid waste (MSW) compost by Lolium perenne L. in a field experiment was investigated with application of EDTA. EDTA was added in solution at six rates (0-30 mmol kg( - 1)) after 50 days of plant growth. Two weeks later, plants were harvested for the first crop and then all the turfgrasses were mowed. After another 30 days of growth, EDTA was added again at above six rates to the corresponding sites and the second crop was harvested 2 weeks later. The results showed that EDTA significantly increased heavy metal accumulation in both crops of L. perenne. For the first crop, the concentrations of Mn, Ni, Cd, and Pb in the shoots increased remarkably with increasing EDTA supply, peaked at 25 mmol kg( - 1) EDTA, and shoots of 0-5 cm height (shoots from medium surface to 5 cm height) had higher metal concentrations than 5-10 cm and >10 cm shoots. The highest concentration of Mn, Ni, Cd, and Pb was 2.3-, 2.3-, 2.6-, and 3.2-fold, respectively, in 0-5 cm shoots higher than control. For the second crop, the concentrations of Mn, Cu, and Pb in shoots were, in general, less than those in the first crop. However, the second crop was significantly higher (P < 0.05) than the first crop in dry biomass, so the total amount of metals removed by the second crop was more than the first crop. In addition, EDTA significantly increased the translocation ratios of most heavy metals from roots to shoots. For the first crop, 38% of the total Zn, 51% of Cd, 49% of Pb, 60% Mn, 55% Ni, and 45% Cu taken up by the plant was translocated in the shoots of 0-5 cm height. Turfgrass would have potential for use in remediation of heavy metals in MSW compost or contaminated soils.

Near-field circular polarization probed by chiral polyfluorene.

We demonstrate that a high degree of circular polarization can be delivered to the near field (NF) of an aperture at the apex of hollow-pyramid probes for scanning optical microscopy. This result is achieved by analyzing the dichroic properties of an annealed thin polymer film containing a chiral polyfluorene derivative, placed in close proximity to the optical probe. We also prove that the degree of circular polarization in the probe NF does not depend in a significant way on the shape of the aperture, at variance with the far-field behavior. These results demonstrate the feasibility of nano-optics applications exploiting circularly polarized NFs.

[Epidemiological characteristics of human rabies in China, 2017].

Objective: To understand epidemiological characteristics of human rabies in China in 2017 and provide evidence for the development of strategy of human rabies control and prevention. Methods: The descriptive epidemiological analysis was conducted based on the epidemic data from Chinese Infectious Disease Surveillance Reporting System, sentinel surveillance system in 6 provinces (Hunan, Guangxi, Anhui, Guizhou, Jiangsu and Shandong) and National Bureau of Statistics in 2017. Results: A total of 516 human rabies cases, including 502 deaths, were reported by 27 provinces in 2017 with the morbidity rate and mortality rate of 0.037/100 000 and 0.036/100 000, respectively. The case number and death number decreased by 19.88% (128/644) and 15.20% (90/592) respectively compared with 2016. Rabies epidemics were mainly found in southern and central areas. The first 5 provinces reporting high case numbers were Hunan (71 cases), Henan (52 cases), Guangxi (41 cases), Anhui (39 cases) and Hubei (39 cases), their cases accounted for 46.90% (242/516) of the total reported cases in China. Rabies mainly occurred in summer and autumn, and the majority of patients were farmers, students and children outside child care settings. The male to female ratio of the cases was 2.46 ∶ 1 (367 ∶ 149). Cases was reported in all age groups, and more cases occurred in middle aged and old adults than in adolescents. Questionnaires survey was conducted for 186 cases, the results indicated that 94.89% (167/176) of exposures were caused by dog bites. The exposure degree was mainly category Ⅲ, accounting for 68.86% (115/167), and only 6.02% (10/166) of cases were immunized after exposure. The median of latent period of these cases was 72 days. Conclusions: By 2017, the human rabies incidence in China had declined consecutively for ten years, more cases were reported in southern area than in northern area. The case number showed downward trends in provinces with high incidences and fluctuant increase in provinces with low incidence. Rabies cases mainly occurred in rural areas, and most cases were men and farmers. Low rate of post exposure prophylaxis, low rates of vaccination and passive immunization product injection were main causes for the onset of human rabies. It is necessary to strengthen the surveillance for human rabies, especially in rural areas, health education about treatment after rabies exposure and expend the coverage of canine immunization.

Experimental demonstration of the optical Zeno effect by scanning tunneling optical microscopy.

An experimental demonstration of a classical analogue of the quantum Zeno effect for light waves propagating in engineered arrays of tunneling-coupled optical waveguides is reported. Quantitative mapping of the flow of light, based on scanning tunneling optical microscopy, clearly demonstrates that the escape dynamics of light in an optical waveguide side-coupled to a tight-binding continuum is slowed down when projective measurements, mimicked by sequential interruptions of the decay, are performed on the system.

Mapping local field enhancements at nanostructured metal surfaces by second-harmonic generation induced in the near field.

We report on an aperture scanning near-field optical microscope in which femtosecond pulses are coupled to a hollow-pyramid aperture sensor. Such probe displays high throughput and preserves pulse duration and polarization, enabling the achievement of sufficiently high peak power in the near field to perform nonlinear optics on the nanoscale. We use the system to observe the nonlinear optical response of nanostructured metal surfaces with sub-100-nm spatial resolution. We study second-harmonic generation from gold nanoparticles both isolated and in high-density patterns, highlighting a strong dependence of the generation efficiency on the shape and on the fine structure of the nanoemitter. In particular, we present results on closely packed gold triangles as well as on nanoellipsoids with different local surface plasmon resonances.

[Chemical constituents in root of Hemerocallis fulva].

OBJECTIVE: To study the chemical constituents of the root of Hemerocallis fulva. METHOD: Compounds were isolated by repeated silica gel, Sephadex LH-20, MCI gel, etc. column chromatography and their structures were determined by spectral analyses and physicochemical properties. RESULT: From the n-butanol fraction of the EtOH extract of the roots of H. fulva, 9 glycosides were isolated and identified as sweroside (1), laganin (2), picraquassioside C (3), puerarin (4), 3'-methoxypuerarin (5), 7-hydro xylnaphthalide-O-beta-D-glucopyranoside (6), orcinol-3-O-beta-glucopyranoside (7), HN saponin F (8), hederagenin-3-0-beta D-glucopyranosyl-(1-3)-alpha-L-arabinopyranoside-28-O-beta-D-glucopyranosyl ester (9). CONCLUSION: Compounds 1-9 were isolated from the genus Hemerocallis for the first time.

Spin polarized surface resonance bands in single layer Bi on Ge(1 1 1).

The spin features of surface resonance bands in single layer Bi on Ge(1 1 1) are studied by means of spin- and angle-resolved photoemission spectroscopy and inverse photoemission spectroscopy. We characterize the occupied and empty surface states of Ge(1 1 1) and show that the deposition of one monolayer of Bi on Ge(1 1 1) leads to the appearance of spin-polarized surface resonance bands. In particular, the C 3v symmetry, which Bi adatoms adopt on Ge(1 1 1), allows for the presence of Rashba-like occupied and unoccupied electronic states around the [Formula: see text] point of the Bi surface Brillouin zone with a giant spin-orbit constant [Formula: see text] eV · Å.

Direct observation of spin-resolved full and empty electron states in ferromagnetic surfaces.

We present a versatile apparatus for the study of ferromagnetic surfaces, which combines spin-polarized photoemission and inverse photoemission spectroscopies. Samples can be grown by molecular beam epitaxy and analyzed in situ. Spin-resolved photoemission spectroscopy analysis is done with a hemispherical electron analyzer coupled to a 25 kV-Mott detector. Inverse photoemission spectroscopy experiments are performed with GaAs crystals as spin-polarized electron sources and a UV bandpass photon detector. As an example, measurements on the oxygen passivated Fe(100)-p(1×1)O surface are presented.