We present a Raman study of Ar+-bombarded graphene samples with increasing ion doses. This allows us to have a controlled, increasing, amount of defects. We find that the ratio between the D and G ...peak intensities, for a given defect density, strongly depends on the laser excitation energy. We quantify this effect and present a simple equation for the determination of the point defect density in graphene via Raman spectroscopy for any visible excitation energy. We note that, for all excitations, the D to G intensity ratio reaches a maximum for an interdefect distance ∼3 nm. Thus, a given ratio could correspond to two different defect densities, above or below the maximum. The analysis of the G peak width and its dispersion with excitation energy solves this ambiguity.
Changes in climate and air pollutant emissions will affect future air quality from global to urban scale. In this study, regional air quality simulations for historical and future periods are ...conducted, with CAMx version 6.0, to investigate the impacts of future climate and anthropogenic emission projections on air quality over Portugal and the Porto metropolitan area in 2050. The climate and the emission projections were derived from the Representative Concentrations Pathways (RCP8.5) scenario. Modelling results show that climate change will impact NO2, PM10 and O3 concentrations over Portugal. The NO2 and PM10 annual means will increase in Portugal and in the Porto municipality, and the maximum 8-hr daily O3 value will increase in the Porto suburban areas (approximately 5%) and decrease in the urban area (approximately 2%). When considering climate change and projected anthropogenic emissions, the NO2 annual mean decreases (approximately 50%); PM10 annual mean will increase in Portugal and decrease in Porto municipality (approximately 13%); however PM10 and O3 levels increase and extremes occur more often, surpassing the currently legislated annual limits and displaying a higher frequency of daily exceedances. This air quality degradation is likely to be related with the trends found for the 2046–2065 climate, which implies warmer and dryer conditions, and with the increase of background concentrations of ozone and particulate matter. The results demonstrate the need for Portuguese authorities and policy-makers to design and implement air quality management strategies that take climate change impacts into account.
•Air quality under RCP8.5 climate change scenario for multi-years.•Evaluation of climate change and emissions changes effects.•Impacts of climate change at regional and urban scale.•Emissions changes have stronger effects on air quality than climate change alone.•Increase in the occurrence, duration and intensity of extreme values of PM10 and O3.
Raman scattering is used to study disorder in graphene subjected to low energy (90eV) Ar+ ion bombardment. The evolution of the intensity ratio between the G band (1585cm−1) and the disorder-induced ...D band (1345cm−1) with ion dose is determined, providing a spectroscopy-based method to quantify the density of defects in graphene. This evolution can be fitted by a phenomenological model, which is in conceptual agreement with a well-established amorphization trajectory for graphitic materials. Our results show that the broadly used Tuinstra-Koenig relation should be limited to the measure of crystallite sizes, and allows extraction of the Raman relaxation length for the disorder-induced Raman scattering process.
known for its medicinal value, is officially accepted in many countries. The flowers and leaves are used globally in homeopathy. In Brazilian folk medicine,
has been used to treat diabetes mellitus. ...This study evaluated the hypoglycemic activity of an infusion extract (RosCE) of commercially available
leaves in alloxan-induced diabetic rats. Oral administration of RosCE resulted in the reduction of blood glucose levels after the first day of treatment, compared to the diabetic control group. These results showed that RosCE displays hypoglycemic activity, which may be due to the combined effect of rosmarinic acid, and other minor compounds. Reversed phase-high performance liquid chromatography-diode array detection was used to identify and quantify the major constituents of RosCE. This study presents evidence that supports the folkloric use of
for the treatment of hyperglycemia, confirming the use of its infusion as an antidiabetic herbal medicine.
This work reports Ga+ focused ion beam nanopatterning to create amorphous defects with periodic square arrays in highly oriented pyrolytic graphite and the use of Raman spectroscopy as a new protocol ...to test and compare progresses in ion beam optics, for low fluence bombardment or fast writing speed. This can be ultimately used as a metrological tool for comparing different FIB machines and can contribute to Focused Ion Beam (FIB) development in general for tailoring nanostructures with higher precision. In order to do that, the amount of ion at each spot was varied from about 106 down to roughly 1 ion per dot. These defects were also analyzed by using high resolution scanning electron microscopy and atomic force microscopy. The sensitivities of these techniques were compared and a geometrical model is proposed for micro-Raman spectroscopy in which the intensity of the defect induced D band, for a fixed ion dose, is associated with the diameter of the ion beam. In addition, the lateral increase in the bombarded spot due to the cascade effect of the ions on graphite surface was extracted from this model. A semi-quantitative analysis of the distribution of ions at low doses per dot or high writing speed for soft modification of materials is discussed.
► Highly oriented pyrolytic graphite surface is bombarded using a focused ion beam. ► Raman spectroscopy is used to propose a new protocol to test focused ion beam optics. ► Scattering diameter of the ions on HOPG surface is experimentally obtained. ► Optical limitations of the ion column in fast writing speed are discussed. ► Small level of modifications is considered for changing graphene conductive properties.
Background
The Nucleus accumbens (Acc) is the main structure of the ventral striatum. It acts as a motor-limbic interface, being involved in emotional and psychomotor functions, frequently disturbed ...in neuropsychiatric disorders such as obsessive compulsive disorder and addiction. Most of the studies concerning the Acc were made in animals and those performed in humans are contradictory. Nevertheless, it has become a target for stereotactic deep brain stimulation for some of those diseases, when refractory to medical treatment. Previous studies performed by our group have established the localization, limits and dimensions of the human Acc and its stereotactic coordinates. Now it is our purpose to perform the Acc anatomical three-dimensional (3D) reconstruction in order to clarify its shape and topography and to render this nucleus a safer target for stereotactic procedures.
Methods
Anatomical coronal slicing of ten Acc from human brains was performed, perpendicular to the anterior commissure-posterior commissure line and to the midline; then the Acc contours were traced and its dimensions and 3D stereotactic coordinates measured, on each slice. Finally a 3D computerized model was created.
Results
The human Acc was identified as a distinct brain structure, with clear-cut limits on its posterior half. It lies parallel to the midline, descends caudally, and progresses from a globose to a flattened and dorsolateral concave shape. Its main expression is subcomissural.
Conclusion
This study defined more accurately the 3D anatomy of the human Acc, providing new tools for stereotactic procedures.
Electron beam induced deposition using ethylene as precursor gas is used to generate carbonaceous films on Cu(111). The study was performed in an ultrahigh vacuum chamber for two different precursor ...gas pressures, and two substrate temperatures. Auger electron spectroscopy and reflection electron energy loss spectroscopy were used to characterize the film growth process in-situ. These techniques allowed us to determine how the deposited film covers the Cu(111) substrate as a function of the ethylene exposure, obtaining a final coverage of up to 0.8 monolayer, depending on the growing conditions. Based on the CKLL Auger line shape and on the reflection electron energy loss (REELS) spectra we can conclude on the graphitic characteristics of the grown film and on the optimum growing conditions: lower substrate temperature and higher ethylene pressure. Raman spectroscopy and scanning tunneling spectroscopy were used as ex-situ techniques to assess the properties of the grown film. Results from both techniques indicate that the film consists of small (10–20 nm in size) nanocrystals of few (1–2) layers graphene. Once optimized, this method may allow growing graphene with a predesigned pattern, without the need to heat the substrate at high temperatures.
•Carbon films can be grown on Cu via electron irradiation in an ethylene atmosphere.•Auger and energy-loss spectroscopy reveal graphitic characteristics of grown films.•Raman and STM show the grown films are 10–20 nm patches of few layers graphene.•The method may allow growing graphene without the need of heating the substrate.
The increasing interaction between laboratories from universities and research institutes with other society sectors, such as industries and government agencies, has led a growing number of those ...laboratories to adopt quality management systems based on international requirements standards. As a consequence, there is a crescent interest on practical information related to implementation of quality management systems in laboratories that provide testing services and carry out research activities. In this context, this article presents the practical approach applied for implementing a quality management system based on ISO/IEC 17025 at the materials metrology division (Dimat)—Inmetro and at its laboratories. The approach is consistent with a hierarchical implementation, where the laboratory quality management system must fulfill ISO/IEC 17025 requirements as well as internal requirements from the upper layers of the quality management system. The implementing approach discussed here was specifically developed to be applied inside a particular hierarchical quality management structure. However, due to its general characteristics, it can be useful for diverse implementing cases.
► Interdisciplinary nanotechnology approach to study Amazonian Dark Earth carbon. ► Electron microscopy/diffraction gives the chemical contents and morphology. ► Electron and optical spectroscopy ...elucidates the primary structure. ► Comparative analysis with charcoal and turf shows structural differences. ► We discuss the importance of the 2–12-nm-scaled morphological aspects.
The anthropogenic Amazonian soil “Terra Preta de Índio” (Amazonian Dark Earth) provides a potential model for a sustainable land-use system in the humid tropics. A large amount of carbon-based materials in this soil is responsible for its high fertility over long periods of usage, and soil scientists are trying to create “Terra Preta Nova” (New Dark Earth) by adding charcoal as a soil conditioner. By applying materials science tools, including scanning and transmission electron microscopy, energy dispersive X-ray, electron energy loss spectroscopy and Raman spectroscopy, we show that these millenary carbon materials exhibit a complex morphology, with particles ranging in size from micro- to nanometers, from the core to the surface of the carbon grains. From one side, our results might elucidate how nature solved the problem of keeping high levels of ion exchange capacity in these soils. From the other side, morphology and dimensionality are the key issues in nanotechnology, and the structural aspects revealed here may help generating the Terra Preta Nova, effectively improving world agriculture and ecosystem sustainability.