ABSTRACT
Since the discovery of quasi-stellar objects (QSOs), also known as quasars, they have been traditionally subdivided as radio-loud and radio-quiet sources. Whether such division is a ...misleading effect from a highly heterogeneous single population of objects, or real has yet to be answered. Such dichotomy has been evidenced by observations of the flux ratio between the optical and radio emissions (usually B band and 5 GHz). Evidence of two populations in quasars and samples of a wide diversity of active galactic nuclei (AGNs) has been accumulated over the years. Other quantities beyond radio loudness also seem to show the signature of the existence of two different populations of AGNs. To verify the existence of a dichotomy through different parameters, we employed a soft clustering scheme, based on the Gaussian mixture model (GMM), to classify these objects simultaneously using the following parameters: black hole mass, colour, and R loudness index, as well as the usual radio and B-band luminosity. To investigate whether different kinds of AGNs manifest any population dichotomy, we applied GMM to four independent catalogues composed of both optical and radio information. Our results indicate the persistence of a dichotomy in all data sets, although the discriminating power differs for different choices of parameters. Although the radio loudness parameter alone does not seem to be enough to display the dichotomy, the evidence of two populations of AGNs could persist even if we consider other parameters. Our research suggests that the dichotomy is not a misleading effect but real.
ABSTRACT A high-performance liquid chromatography with ultraviolet detection (HPLC-UV) method was validated for the study of bioactive amines in chicken meat. A gradient elution system with an ...ultraviolet detector was used after extraction with trichloroacetic acid and pre-column derivatization with dansyl chloride. Putrescine, cadaverine, histamine, tyramine, spermidine, and spermine standards were used for the evaluation of the following performance parameters: selectivity, linearity, precision, recovery, limits of detection, limits of quantification and ruggedness. The results indicated excellent selectivity, separation of all amines, a coefficient of determination greater than 0.99 and recovery from 92.25 to 102.25% at the concentration of 47.2mg.kg-1, with a limit of detection at 0.3mg.kg-1 and a limit of quantification at 0.9mg.kg-1 for all amines, with the exception of histamine, which exhibited the limit of quantification, of 1mg.kg-1. In conclusion, the performance parameters demonstrated adequacy of the method for the detection and quantification of bioactive amines in chicken meat.
RESUMO Um método de cromatografia líquida de alta eficiência (CLAE) para pesquisa de aminas bioativas em carne de frango foi validado. Foi utilizado um sistema de gradiente de eluição com detector ultravioleta, após extração com ácido tricloroacético e derivação pré-coluna com cloreto de dansila. Os padrões de putrescina, cadaverina, histamina, tiramina, espermidina e espermina foram utilizados para avaliação dos seguintes parâmetros de desempenho: seletividade, linearidade, precisão, recuperação, limites de detecção, limites de quantificação e robustez. Os resultados mostraram excelente seletividade e separação de todas as aminas, coeficiente de determinação superior a 0,99, recuperação entre 92,25 e 105,25% na concentração 47,2mg.kg-1, limites de detecção de 0,3mg.kg-1 e limite de quantificação de 0,9mg.kg-1 para todas as aminas, com exceção da histamina, que apresentou o limite de quantificação mais alto, de 1mg.kg-1. Foi concluído que os parâmetros de desempenho demonstraram adequação do método para detecção e quantificação de aminas bioativas em carne de frango.
The production and physical properties of nanowires and nanoribbons formed by methylphosphonic acid (MPA)--CH3PO(OH)2--were investigated. These structures are formed on an aluminum coated substrate ...when immersed in an ethanolic solution of MPA for several days. A careful investigation of the growth conditions resulted in a narrow window of solution concentrations and temperatures for the successful development of nanowires and nanoribbons. Several different techniques were employed to characterize these nanostructures: (1) Photoluminescence experiments showed a strong emission at 2.3 eV (green), which is visible to the naked eye; (2) X-ray diffraction experiments indicated a significant cristalinity, in agreement with atomic force microscopy (AFM) and transmission electron microscopy (TEM) morphology images, which show organized nano-scale wires and ribbons, (furthermore, AFM-Phase and TEM images also suggest that nanoribbons are formed by well-aligned nanowires); (3) Conductive-AFM experiments revealed an intermediary conductivity for these structures (10(-1)/Ohm x m), which is similar to some intrinsic semiconductors and; (4) finally, Infrared, Raman, and X-Ray Photoelectron Spectroscopies produced information about the contents, structure, and composition of both wires and ribbons.
The knowledge of the phonon coherence length is of great importance for two-dimensional-based materials since phonons can limit the lifetime of charge carriers and heat dissipation. Here we use ...tip-enhanced Raman spectroscopy (TERS) to measure the spatial correlation length L c of the A1g 1 and A1g 2 phonons of monolayer and few-layer gallium sulfide (GaS). The differences in L c values are responsible for different enhancements of the A1g modes, with A1g 1 always enhancing more than the A1g 2, independently of the number of GaS layers. For five layers, the results show an L c of 64 and 47 nm for A1g 1 and A1g 2, respectively, and the coherence lengths decrease when decreasing the number of layers, indicating that scattering with the surface roughness plays an important role.
Optical studies of carbon nanotubes and nanographites Pimenta, M.A.; Gomes, A.P.; Fantini, C. ...
Physica. E, Low-dimensional systems & nanostructures,
03/2007, Volume:
37, Issue:
1
Journal Article, Conference Proceeding
Peer reviewed
Resonance Raman and photoluminescence excitation (PLE) spectroscopies are used to study the optical properties of different types of carbon nanostructures such as carbon nanotube, nanoribbons, ...nanographites and graphite edges. In the resonance Raman experiments of carbon nanotubes, the
(
n
,
m
)
assignment is obtained by comparing the experimental and theoretical diameter and chirality dependence of the optical transitions. The influence of the environment on the optical transitions of the nanotubes is also obtained in the Raman experiments. The PLE measurements in different samples of carbon nanotubes show both direct and phonon-assisted optical transitions, and the results give new evidences that the optical transitions in nanotubes have an excitonic character, which is very strong for the low energy transitions. We also analyze the Raman spectra of nanoribbons and nanographites, showing that this technique is an important tool for defect characterization in graphitic materials, and can be used to distinguish the atomic structure of the graphite edges.
Understanding soil organic matter is necessary for the development of soil amendments, which are important for sustaining agriculture in humid tropical climates. Ancient Amazonian anthrosols are ...uniquely high in black recalcitrant carbon, making them extremely fertile. In this study, we use high-resolution electron microscopy and spectroscopy to resolve the oxidation process of carbon in the nanoscale crystallites within the black carbon grains of this special soil. Most alkali and acid chemical extraction methods are known to cause chemical modifications in soil organic matter and to give poor or no information about the real spatial structure of soil aggregates. However, here we show that carbon-oxygen functional groups such as phenol, carbonyl, and carboxyl dominate over different spatial regions, with areas varying from over tens to hundreds of nm
2
. The chemical maps show that in the nanoscale grain, the surface has a tendency to be less aromatic than the grain core, where higher oxidative-degradation levels are indicated by the presence of carbonyl and carboxyl groups. A deep understanding of these structures could allow artificial reproduction of these natural events.
Carbon-oxygen functional groups dominate over different spatial regions in nanoscale carbon grains from ancient Amazonian anthrosols (
Terra Preta de Índio
).
Little is known about primary biliary cholangitis (PBC) in Latin America, where this disease is thought to be rare.
To analyze clinical and biochemical features of Brazilian PBC patients.
The ...Brazilian Cholestasis Study Group multicentre database was reviewed to assess demographics, clinical and laboratory features from PBC patients.
562 patients with PBC were included; 80 (14.2%) had overlapping syndrome with autoimmune hepatitis and were excluded. Most subjects were middle-aged women (95%; mean age 51 ± 11 years) with classical symptoms of pruritus and/or fatigue (65%) and jaundice (22%). Mean time to diagnosis was 2.5 years. Prevalence of antimitochondrial (AMA) and antinuclear antibodies was 82.8% and 72.1%, respectively. Concurrent autoimmune diseases occurred in 18.9%, mainly Hashimoto's thyroiditis and Sjogren syndrome. Celiac disease was diagnosed in 1:80 (1.2%). Osteopenia and osteoporosis were demonstrated in 42% and 26%, respectively. Liver pathology at diagnosis was available for 326 patients (67.6%). One third of them had advanced PBC. After a mean follow-up of 6.2 ± 5.3 years, 32% of the subjects had clinical, laboratory or imaging evidence of cirrhosis. Requirement for liver transplantation and liver-related deaths were reported in 6.6% and 3.2% of the patients, respectively. Hepatocarcinoma was diagnosed in 1.9% of the subjects.
A higher predominance of PBC among females, compared to other populations, was observed, while AMA positivity was lower. Concurrent autoimmune, celiac and bone diseases are common and should be adequately screened. Prolonged time to diagnosis and high prevalence of advanced liver disease might reflect difficulties in health care access in Brazil.
Primary biliary cholangitis (PBC) diagnosis is based on international criteria, which requires two of the following: (i) elevated alkaline phosphatase (AP), (ii) anti-mitochondrial antibody (AMA) and ...(iii) liver biopsy (BX) suggestive of PBC. It is still unclear if patients diagnosed by different criteria combinations present peculiarities, especially in highly-admixed populations.
To investigate if patients diagnosed with PBC by different combinations of validated criteria present clinical or laboratory particularities.
The Brazilian Cholestasis Study Group database was reviewed to compare clinical, biochemical and histological characteristics of PBC between four groups diagnosed by: (1) AP ≥2x upper limit of normality (ULN) + presence of AMA, (2) AP ≥2x ULN + BX suggestive of PBC, (3) presence of AMA + BX suggestive of PBC and (4) all criteria.
482 patients with PBC were included (Table 1). Group-1 presented with higher levels of IgG, lower frequency of arterial hypertension (AH) and lower response to ursodeoxycholic acid (UDCA), while Group-2 had lower: age at diagnosis and HDL-C levels. Group-3 had higher: age at diagnosis, frequency of neoplasms, AH and response to UDCA; and lower: frequency of pruritus and jaundice, levels of aminotransferases, GGT and bilirubin, advanced liver disease and esophageal varices. Group-4 showed higher frequency of symptoms at presentation, especially pruritus.
PBC patients diagnosed by different combinations of established criteria may present singular features that can possibly impact in disease presentation and progression.
The objective of this study was to investigate the possibility of using bioactive amines as an index of quality of fresh and stored eggs. Large white eggs from 24-wk-old Dekalb layers were randomly ...distributed in 3 groups: (i) 10 freshly laid eggs, (ii) 60 eggs stored at 25 ± 1°C and 60% RH for 30 d, and (iii) 50 eggs stored at 6 ± 1°C and 60% RH for 50 d. The eggs were weighed and the internal quality was evaluated by Haugh units (HU), pH of albumen, total solids, total volatile bases, and bioactive amines in the albumen and yolk. The fresh eggs had, on average, 56.85 g, 98.55 HU, albumen pH of 8.02, total solids of 12.17 g/100 g in the albumen and 52.43 g/100 g in the yolk, and absence of volatile bases. None of the 10 amines investigated were detected in the albumen; however, the yolk contained 0.37 mg/kg of spermidine. Throughout storage, there was a significant decrease in the weight of the egg and HU and a significant increase in the pH and in the total solids of the albumen. The decrease in HU and the increase in the total solids of the albumen were faster at 25 ± 1°C compared with 6 ± 1°C. At 50 and 30 d of storage at 6 ± 1 and 25 ± 1°C, respectively, significant levels of total volatile bases were detected. The levels of spermidine in the yolk increased significantly at the 40th and 15th days of storage at 6 ± 1 and 25 ± 1°C, respectively. At these storage times, the presence of putrescine and agmatine was also detected. Therefore, the presence of other amines besides spermidine or spermidine levels higher than 1.0 mg/kg in the yolk could be used as an index of quality of fresh eggs and throughout storage.
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