1,591 research outputs found
Raman Fingerprint of Charged Impurities in Graphene
We report strong variations in the Raman spectra for different single-layer
graphene samples obtained by micromechanical cleavage, which reveals the
presence of excess charges, even in the absence of intentional doping. Doping
concentrations up to ~10^13 cm-2 are estimated from the G peak shift and width,
and the variation of both position and relative intensity of the second order
2D peak. Asymmetric G peaks indicate charge inhomogeneity on the scale of less
than 1 micron.Comment: 3 pages, 5 figure
Influence of magnetic field and ferromagnetic film thickness on domain pattern transfer in multiferroic heterostructures
Domains in BaTiO induces a regular modulation of uniaxial magnetic
anisotropy in CoFeB via an inverse magnetostriction effect. As a result, the
domain structures of the CoFeB wedge film and BaTiO substrate correlate
fully and straight ferroelectric domain boundaries in BaTiO pin magnetic
domain walls in CoFeB. We use x-ray photoemission electron microscopy and
magneto-optical Kerr effect microscopy to characterize the spin structure of
the pinned domain walls. In a rotating magnetic field, abrupt and reversible
transitions between two domain wall types occur, namely, narrow walls where the
magnetization vectors align head-to-tail and much broader walls with
alternating head-to-head and tail-to-tail magnetization configurations. We
characterize variations of the domain wall spin structure as a function of
magnetic field strength and CoFeB film thickness and compare the experimental
results with micromagnetic simulations.Comment: 5 pages, 5 figure
Circadian and Metabolic Effects of Light: Implications in Weight Homeostasis and Health
Daily interactions between the hypothalamic circadian clock at the suprachiasmatic nucleus (SCN) and peripheral circadian oscillators regulate physiology and metabolism to set temporal variations in homeostatic regulation. Phase coherence of these circadian oscillators is achieved by the entrainment of the SCN to the environmental 24-h light:dark (LD) cycle, coupled through downstream neural, neuroendocrine, and autonomic outputs. The SCN coordinate activity and feeding rhythms, thus setting the timing of food intake, energy expenditure, thermogenesis, and active and basal metabolism. In this work, we will discuss evidences exploring the impact of different photic entrainment conditions on energy metabolism. The steady-state interaction between the LD cycle and the SCN is essential for health and wellbeing, as its chronic misalignment disrupts the circadian organization at different levels. For instance, in nocturnal rodents, non-24 h protocols (i.e., LD cycles of different durations, or chronic jet-lag simulations) might generate forced desynchronization of oscillators from the behavioral to the metabolic level. Even seemingly subtle photic manipulations, as the exposure to a "dim light" scotophase, might lead to similar alterations. The daily amount of light integrated by the clock (i.e., the photophase duration) strongly regulates energy metabolism in photoperiodic species. Removing LD cycles under either constant light or darkness, which are routine protocols in chronobiology, can also affect metabolism, and the same happens with disrupted LD cycles (like shiftwork of jetlag) and artificial light at night in humans. A profound knowledge of the photic and metabolic inputs to the clock, as well as its endocrine and autonomic outputs to peripheral oscillators driving energy metabolism, will help us to understand and alleviate circadian health alterations including cardiometabolic diseases, diabetes, and obesity.Fil: Plano, Santiago AndrĂ©s. Pontificia Universidad CatĂłlica Argentina "Santa MarĂa de los Buenos Aires". Instituto de Investigaciones BiomĂ©dicas. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Houssay. Instituto de Investigaciones BiomĂ©dicas; ArgentinaFil: Casiraghi, Leandro Pablo. Universidad Nacional de Quilmes. Departamento de Ciencia y TecnologĂa. Laboratorio de CronobiologĂa; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Garcia Moro, Paula. Universidad Nacional de Quilmes. Departamento de Ciencia y TecnologĂa. Laboratorio de CronobiologĂa; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Paladino, Natalia. Universidad Nacional de Quilmes. Departamento de Ciencia y TecnologĂa. Laboratorio de CronobiologĂa; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Golombek, Diego AndrĂ©s. Universidad Nacional de Quilmes. Departamento de Ciencia y TecnologĂa. Laboratorio de CronobiologĂa; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Chiesa, Juan JosĂ©. Universidad Nacional de Quilmes. Departamento de Ciencia y TecnologĂa. Laboratorio de CronobiologĂa; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentin
Raman Spectroscopy of Graphene Edges
Graphene edges are of particular interest since their orientation determines the electronic properties. Here we present a detailed Raman investigation of graphene flakes with edges oriented at different crystallographic directions. We also develop a real space theory for Raman scattering to analyze the general case of disordered edges. The position, width, and intensity of G and D peaks are studied as a function of the incident light polarization. The D-band is strongest for polarization parallel to the edge and minimum for perpendicular. Raman mapping shows that the D peak is localized in proximity of the edge. For ideal edges, the D peak is zero for zigzag orientation and large for armchair, allowing in principle the use of Raman spectroscopy as a sensitive tool for edge orientation. However, for real samples, the D to G ratio does not always show a significant dependence on edge orientation. Thus, even though edges can appear macroscopically smooth and oriented at well-defined angles, they are not necessarily microscopically ordered
tuppence-based SERS for the detection of illicit materials
Deposition of silver onto British 2p coins has been demonstrated as an
efficient and cost effective approach to producing substrates capable of
promoting surface enhanced Raman scattering (SERS). Silver application to the
copper coins is undemanding taking just 20 s, and results in the formation of
multiple hierarchial dendritic structures. To demonstrate that the silver
deposition sites were capable of SERS the highly fluorescent Rhodamine 6G
(R6G) probe was used. Analyses indicated that Raman enhancement only occurs at
the silver deposition sites and not from the roughened copper surface. The
robustness of the substrate in the identification and discrimination of
illegal and legal drugs of abuse was then explored. Application of the drugs
to the substrates was carried out using spotting and soaking methodologies.
Whilst little or no SERS spectra of the drugs were generated upon spotting,
soaking of the substrate in a methanolic solution of the drugs yielded a vast
amount of spectral information. Excellent reproducibility of the SERS method
and classification of three of the drugs, 4-methylmethcathinone (mephedrone),
5,6-methylenedioxy-2-aminoindane (MDAI) and
3,4-methylenedioxy-N-methylamphetamine (MDMA) were demonstrated using
principal components analysis and partial least squares
Regulatory framework of pharmaceutical compounding and actual developments of legislation in Europe
Pharmaceutical preparations are medicines that the pharmacist makes for the special needs of the patients that the pharmaceutical industry cannot comply for economic and logistic reasons. Pharmacy compounding is still an important component of pharmacy practice and a valuable therapeutical service that is an integrant part of the modern health care system, but its legislation is not harmonized among European and US countries.In 2011 the Committee of Ministers of the Council of Europe has adopted a Resolution on quality and safety assurance requirements for medicinal products prepared in pharmacies for the special needs of patients. Aim of this resolution is to harmonize quality assurance and standards for pharmacy-made medicinal products among European countries and to pass the gap in quality assurance and standards between preparation in pharmacies and medicines prepared by the pharmaceutical industry. This article will analyze the actual rules and technical norms that regulate compounding activity and the expectations resultants from the new European and US laws
Intrinsic Dimension Estimation: Relevant Techniques and a Benchmark Framework
When dealing with datasets comprising high-dimensional points, it is usually advantageous to discover some data structure. A fundamental information needed to this aim is the minimum number of parameters required to describe the data while minimizing the information loss. This number, usually called intrinsic dimension, can be interpreted as the dimension of the manifold from which the input data are supposed to be drawn. Due to its usefulness in many theoretical and practical problems, in the last decades the concept of intrinsic dimension has gained considerable attention in the scientific community, motivating the large number of intrinsic dimensionality estimators proposed in the literature. However, the problem is still open since most techniques cannot efficiently deal with datasets drawn from manifolds of high intrinsic dimension and nonlinearly embedded in higher dimensional spaces. This paper surveys some of the most interesting, widespread used, and advanced state-of-the-art methodologies. Unfortunately, since no benchmark database exists in this research field, an objective comparison among different techniques is not possible. Consequently, we suggest a benchmark framework and apply it to comparatively evaluate relevant state-of-the-art estimators
Targeting bacterial cell division: A binding site-centered approach to the most promising inhibitors of the essential protein FtsZ
Binary fission is the most common mode of bacterial cell division and is mediated by a multiprotein complex denominated the divisome. The constriction of the Z-ring splits the mother bacterial cell into two daughter cells of the same size. The Z-ring is formed by the polymerization of FtsZ, a bacterial protein homologue of eukaryotic tubulin, and it represents the first step of bacterial cytokinesis. The high grade of conservation of FtsZ in most prokaryotic organisms and its relevance in orchestrating the whole division system make this protein a fascinating target in antibiotic research. Indeed, FtsZ inhibition results in the complete blockage of the division system and, consequently, in a bacteriostatic or a bactericidal effect. Since many papers and reviews already discussed the physiology of FtsZ and its auxiliary proteins, as well as the molecular mechanisms in which they are involved, here, we focus on the discussion of the most compelling FtsZ inhibitors, classified by their main protein binding sites and following a medicinal chemistry approach
A cockpit of multiple measures for assessing film restoration quality
In machine vision, the idea of expressing the quality of a films by a single value is very popular. Usually this value is computed by processing a set of image features with the aim of resembling as much as pos- sible a kind of human judgment of the film quality. Since human quality assessment is a complex mech- anism involving many different perceptual aspects, we believe that such approach may scarcely provide a comprehensive analysis. Especially in the field of digital movie restoration, a single score can hardly provide reliable information about the effects of the various restoring operations. For this reason we in- troduce an alternative approach, where a set of measures, describing over time basic global and local visual properties of the film frames, is computed in an unsupervised way and delivered to expert evalu- ators for checking the restoration pipeline and results. The proposed framework can be viewed as a car or airplane cockpit , whose parameters (i.e. the computed measures) are necessary to control the machine status and performance. This cockpit, which is publicly available online, would like to support the digital restoration process and its assessment
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