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Thymine hydroperoxide as a potential source of singlet molecular oxygen in DNA

PRADO, Fernanda M.; OLIVEIRA, Mauricio C. B.; MIYAMOTO, Sayuri; MARTINEZ, Glaucia R.; MEDEIROS, Marisa H. G.; RONSEIN, Graziella E.; MASCIO, Paolo Di
Fonte: ELSEVIER SCIENCE INC Publicador: ELSEVIER SCIENCE INC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
26.13%
The decomposition of organic hydroperoxides into peroxyl radicals is a potential source of singlet molecular oxygen [O(2) ((1)Delta(g))] in biological systems. This study shows that 5-(hydroperoxymethyl)uracil (5-HPMU), a thymine hydroperoxide within DNA, reacts with metal ions or HOCl, generating O(2) ((1)Delta(g)). Spectroscopic evidence for generation of O(2) ((1)Delta(g)) was obtained by measuring (i) the bimolecular decay, (ii) the monomolecular decay, and (iii) the observation of D(2)O enhancement of O(2) ((1)Delta(g)) production and the quenching effect of NaN(3). Moreover, the presence of O(2) ((1)Delta(g)) was unequivocally demonstrated by the direct characterization of the near-infrared light emission. For the sake of comparison, O(2) ((1)Delta(g)) derived from the H(2)O(2)/HOCl system and from the thermolysis of the N,N`-di(2,3-dihydroxypropyl)-1,4-naphthalenedipropanamide endoperoxide was also monitored. More evidence of O(2) ((1)Delta(g)) generation was obtained by chemical trapping of O(2) ((1)Delta(g)) with anthracene-9,10-divinylsulfonate (AVS) and detection of the specific AVS endoperoxide by HPLC/MS/MS. The detection by HPLC/MS of 5-(hydroxymethyl)uracil and 5-formyluracil, two thymine oxidation products generated from the reaction of 5-HPMU and Ce(4+) ions...

Detection and Characterization of Cholesterol-Oxidized Products Using HPLC Coupled to Dopant Assisted Atmospheric Pressure Photoionization Tandem Mass Spectrometry

RONSEIN, Graziella E.; PRADO, Fernanda M.; MANSANO, Fernando V.; OLIVEIRA, Mauricio C. B.; MEDEIROS, Marisa H. G.; MIYAMOTO, Sayuri; MASCIO, Paolo Di
Fonte: AMER CHEMICAL SOC Publicador: AMER CHEMICAL SOC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
35.82%
Oxidation of cholesterol (Ch) by a variety of reactive oxygen species gives rise mainly to hydroperoxides and aldehydes. Despite the growing interest in Ch-oxidized products, the detection and characterization of these products is still a matter of concern. In this work, the main Ch-oxidized products, namely, 3 beta-hydroxycholest-5-ene-7 alpha-hydroperoxide (7 alpha-OOH), 3 beta-5 alpha-cholest-6-ene-5-hydroperoxide (5 alpha-OOH), 3 beta-hydroxycholest-4-ene-6 alpha-hydroperoxide (6 alpha-OOH), 3 beta-hydroxycholest-4-ene-6 beta-hydroperoxide (6 beta-OOH), and 3 beta-hydroxy-5 beta-hydroxy-B-norcholestane-6 beta-carboxaldehyde (ChAld), were detected in the same analysis using high-performance liquid chromatography (HPLC) coupled to dopant assisted atmospheric pressure photoionization tandem mass spectrometry. The use of selected reaction monitoring mode (SRM) allowed a sensitive detection of each oxidized product, while the enhanced product ion mode (EPI) helped to improve the confidence of the analyses. Isotopic labeling experiments enabled one to elucidate mechanistic features during fragmentation processes. The characteristic fragmentation pattern of Ch-oxidized products is the consecutive loss of 1120 molecules, yielding cationic fragments at m/z 401...

Simultaneous voltammetric detection of ascorbic acid, dopamine and uric acid using a pyrolytic graphite electrode modified into dopamine solution

SILVA, Robson P. da; LIMA, Antonio William O.; SERRANO, Silvia H. P.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.07%
Pyrolytic graphite electrodes (PGE) were modified into dopamine solutions using phosphate buffer solutions, pH 10 and 6.5, as supporting electrolyte. The modification process involved a previous anodization of the working electrode at +1. 5 V into 0. 1 mol-L-1 NaOH followed by other anodization step, in the same experimental conditions, into dopamine (DA) solutions. pH of the supporting electrolyte performed an important role in the production of a superficial melanin polymeric film, which permitted the simultaneous detection of ascorbic acid (AA), (DA) and uric acid (UA), Delta EAA-DA = 222 mV-, Delta EAA-UA = 360 mV and Delta EDA-UA=138mV, avoiding the superficial poisoning effects. The calculated detection limits were: 1.4 x 10(-6) mol L-1 for uric acid, 1.3x10-(5) molL(-1) for ascorbic acid and 1.1 X 10(-7) mol L-1 for dopamine, with sensitivities of (7.7 +/- 0.5), (0.061 +/- 0.001) and (9.5 +/- 0.05)A mol(-1) cm(-2), respectively, with no mutual interference. Uric acid was determined in urine, blood and serum human samples after dilution in phosphate buffer and no additional sample pre-treatment was necessary. The concentration of uric acid in urine was higher than the values found in blood and serum and the recovery tests (92-102%) indicated that no matrix effects were observed. (C) 2008 Elsevier B.V. All rights reserved.

Tratamento de conflitos e detecção de deltas em atualização através de visões XML; Conflict resolution and difference detection in updates through XML views

Vargas, Andre Prisco
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
35.77%
A linguagem XML tem se tornado um padrão no intercâmbio de informações naWeb. No entanto, a maioria das organizações continua a armazenar seus dados em bancos de dados relacionais. Diante deste ambiente, surge a necessidade de se construir aplicações que permitam às empresas o intercâmbio de informações via XML, mas sem que estas empresas tenham que migrar suas bases relacionais. Neste trabalho, é apresentada uma técnica para importar e exportar documentos XML, focada em cenários entre empresas onde visões XML são extraídas de uma base de dados relacional e enviadas via Web (ou qualquer outro meio) para outra aplicação que as edita e as retorna. Através da edição da visão XML, a própria base de dados relacional é modificada, atualizando assim os dados da empresa. A base de dados relacional deve ser atualizada com as novas informações da visão XML. Neste tipo de transação tem-se as seguintes considerações: 1. A visão XML pode ser atualizada por qualquer aplicação. Editores de texto, banco de dados XML e aplicações específicas estão entre as aplicações que podematualizála. 2. A aplicação que recebe a visão XML fica de posse dela por um período não determinado, podendo inclusive não retornar a visão. Durante este período a aplicação pode ficar desconectada da base de dados geradora da visão XML. 3. Enquanto a visão XML está sendo editada...

An ELISA method using serum derived HDAg for the sorological detection of HDV antigens and antibodies

Granato,Celso; Strauss,Edna; Vitvitsky,Ludmila; Gayotto,Luiz Carlos da Costa; Trepo,Christian
Fonte: Instituto de Medicina Tropical Publicador: Instituto de Medicina Tropical
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/1987 EN
Relevância na Pesquisa
35.96%
One of the main difficulties related to the detection of the Hepatitis Delta Virus (HDV) antigen and antibody has been the source of the needed HD antigen since HDV containing human and animal livers are very difficult to obtain and since yield is low. This fact prompted us to try to use the serum of patients in the acute phase of HDV infection as a source of HDAg and turn to enzyme immunoassays (EIA) instead of RIA for the sake of easiness and economy in the amount of HDAg needed. The antigen for EIA was obtained from patients during the acute phase of HDV infection and the antibody from patients who have been carriers for many years. For the detection of the antigen, a sandwich type method was employed, whereas for the antibody a competition assay was developed. In order to assess the relative specificity and sensibility of the test, the antibody assay was compared to a commercial RIA (C. RIA, Abbott) and to a non-commercial RIA (NC RIA). Forty-two sera were tested by the two methods and only in two cases discrepant results were obtained. Its is concluded that: 1) sera from patients in the acute and chronic phases of HDV infection can be used as source of both antigen and antibody, for immunoassays; 2) EIA and RIA have comparable relative specificity and sensibility and 3) EIA is easier to perform...

Standardization of the PCR technique for the detection of delta toxin in Staphylococcus spp.

Marconi,C.; Cunha,M. L. R. S.; Araújo Jr,J. P.; Rugolo,L. M. S. S.
Fonte: Centro de Estudos de Venenos e Animais Peçonhentos - CEVAP, Universidade Estadual Paulista - UNESP Publicador: Centro de Estudos de Venenos e Animais Peçonhentos - CEVAP, Universidade Estadual Paulista - UNESP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2005 EN
Relevância na Pesquisa
36.21%
Coagulase-negative staphylococci (CNS), components of the normal flora of neonates, have emerged as important opportunistic pathogens of nosocomial infections that occur in neonatal intensive care units. Some authors have reported the ability of some CNS strains, particularly Staphylococcus epidermidis, to produce a toxin similar to S. aureus delta toxin. This toxin is an exoprotein that has a detergent action on the membranes of various cell types resulting in rapid cell lysis. The objectives of the present study were to standardize the Polymerase Chain Reaction (PCR) technique for the detection of the gene responsible for the production of delta toxin (hld gene) in staphylococcal species isolated from catheters and blood cultures obtained from neonates, and to compare the results to those obtained with the phenotypic synergistic hemolysis method. Detection of delta toxin by the phenotypic and genotypic method yielded similar results for the S. aureus isolates. However, in S. epidermidis, a higher positivity was observed for PCR (97.4%) compared to the synergistic hemolysis method (86.8%). Among CNS, S. epidermidis was the most frequent isolate and was a delta toxin producer. Staphylococcus simulans and S. warneri tested positive by the phenotypic method...

Evaluation of commercial enzyme immunoassays for detection of hepatitis delta antigen and anti-hepatitis delta virus (HDV) and immunoglobulin M anti-HDV antibodies.

Shattock, A G; Morris, M C
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1991 EN
Relevância na Pesquisa
26.14%
Panels of hepatitis B virus surface antigen-positive sera from drug abusers were used to evaluate 14 commercial enzyme immunoassays from six companies for detecting hepatitis delta virus (HDV) markers. For detecting hepatitis delta virus antigen (HDAg), the Wellcome, Pasteur and Noctech assays had 100% sensitivity for all 42 HDAg-positive serum specimens that were confirmed in-house; the Organon reagents gave 59.5% sensitivity without detergent and 64.3% sensitivity with detergent, but there were 14 discrepant results with and without detergent. The Sorin assay detected HDAg in only 10 of the positive samples (23.8% sensitivity). For the detection of antibody to HDV (anti-HDV) all six commercial enzyme immunoassays were reactive with all 36 anti-HDV-positive specimens that were confirmed in-house. There were no false-positive results with the Wellcome, Noctech, or Sorin assay, but one specimen was false positive by the Organon assay. One HDAg-positive specimen gave a false anti-HDV-positive result in the Abbott assay and an equivocal result in the Pasteur assay (97.8% specificity). For the detection of immunoglobulin M anti-HDV, the Wellcome, Noctech, and Sorin assays agreed for the 38 positives confirmed in-house, except for one false negative with the Sorin test. We conclude that there has been a substantial improvement over previously evaluated assays in sensitivity and specificity of commercial assays for anti-HDV detection...

On the separability of two mechanisms involved in the detection of grating patterns in humans.

Bodis-Wollner, I; Hendley, C D
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1979 EN
Relevância na Pesquisa
26.08%
1. The detectability of contrast modulation (M) of sinusoidal gratings was explored at the rate of 8 Hz. The luminance profile of a contrast modulated sinusoidal grating is L = L(1 + C cos 2 pi F chi). This stimulus may also be regarded as the sum of a steady grating pattern and counter phase flicker of the same spatial frequency. 2. Contrast modulation sensitivity (1/M) was established in five observers at several levels of constract and over a range of spatial frequencies, where M = delta C/C of delta C is the just detectable contrast change and C is the mean contrast of the grating. The slope of a modulation sensitivity function (C/delta C vs. C) is 1 (i.e. delta C = constant) near threshold contrast at each spatial frequency, but in the suprathreshold contrast range the slope flattens from close to 1 at 1.5 c/deg to almost 0 (delta C/C = constant) at 12 c/deg. 3. Adaptation to a high contrast steady grating of the same spatial frequency as the contrast modulated test gratings shifts each modulation sensitivity function to the right at low contrasts, but not at high. As a result the adapted curves cross their corresponding unadapted ones. At each spatial frequency the modulation sensitivity function is now fitted by a straight line of slope 1. While delta C needs to be higher than half the detection threshold of the same grating at spatial frequencies above 3 c/deg...

Mechanism of 5-hydroxytryptamine-induced coronary vasodilation assessed by direct detection of nitric oxide production in guinea-pig isolated heart.

Ellwood, A. J.; Curtis, M. J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1996 EN
Relevância na Pesquisa
26.08%
1. We assessed whether a submaximal concentration (1 microM) of 5-hydroxytryptamine (5-HT) releases nitric oxide (NO) from the coronary endothelium in guinea-pig perfused heart (n = 5 or 6/group) by direct detection of NO in coronary effluent, and determined whether this accounts for the associated coronary dilation. We also tested whether saponin is a selective and specific tool for examining the role of this mechanism in mediating agonist-induced coronary dilatation. 2. Continuous 5 min perfusion with 5-HT, or acetylcholine (ACh; 1 microM), substance P (1 nM) or sodium nitroprusside (SNP; 1 microM) increased coronary flow from baseline by 3.6 +/- 0.2, 3.4 +/- 0.2, 1.8 +/- 0.1 and 4.1 +/- 0.2 ml min-1 g-1, respectively (all P < 0.05). Coronary effluent NO content, detected by chemiluminescence, was correspondingly increased from baseline by 715 +/- 85, 920 +/- 136, 1019 +/- 58 and 2333 +/- 114 pmol min-1 g-1, respectively (all P < 0.05). 3. Continuous perfusion for 30 min with NG-nitro-L-arginine methyl ester (L-NAME) 100 microM reduced basal coronary effluent NO content by 370 +/- 32 pmol min-1 g-1 and coronary flow by 7.5 +/- 0.5 ml min-1 g-1 (both P < 0.05). Saponin (three cycles of 2 min of 30 micrograms ml-1 saponin perfusion interrupted by 2 min control perfusion) reduced basal coronary NO content by a similar amount (307 +/- 22 pmol min-1 g-1) but reduced basal coronary flow by only 0.6 +/- 0.2 ml min-1 g-1 (P < 0.05 versus the effect of L-NAME). 4. The increases in coronary flow in response to (5-HT)...

Double-Antigen Enzyme-Linked Immunosorbent Assay for Detection of Hepatitis E Virus-Specific Antibodies in Human or Swine Sera ▿

Hu, Wei Ping; Lu, Yang; Precioso, Nestor Amadeo; Chen, Hsiao Ying; Howard, Teresa; Anderson, David; Guan, Ming
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
26.07%
A new double-antigen sandwich-based enzyme-linked immunosorbent assay (ELISA) for the detection of total antibodies (immunoglobulin G [IgG] and IgM) specific for hepatitis E virus (HEV) was developed by utilizing well-characterized recombinant protein ET2.1 and its peroxidase-labeled counterpart. Our study showed that the ELISA detected all the positive patient samples (n = 265) regardless of whether they contained IgM or IgG antibodies, or both, while it maintained an excellent specificity of 98.8% with samples from various patient or healthy control groups (total number of samples, 424). The test had a detection limit for anti-HEV IgG antibodies that was equivalent to 62 mIU/ml of the international reference. Compared with the serological status of the specimens determined on the basis of tests performed at the individual collection sites, the testing outcome generated by the new ELISA had a good agreement of 99.3%, with a kappa value of 0.985. The positive predictive value and the negative predictive value for the new test reached 98.1% and 100%, respectively. This ELISA had a positive delta value of 4.836 and a negative delta value of 3.314 (where delta is a measure of the number of standard deviations by which the cutoff is separated from the mean of the sample groups) (N. Crofts...

Using sigma-delta conversion for velocity estimation in bio-inspired detection system

Guo, B.; Ng, B.; Al-Sarawi, S.
Fonte: IEEE; USA Publicador: IEEE; USA
Tipo: Conference paper
Publicado em //2010 EN
Relevância na Pesquisa
36.02%
The Sigma-Delta converter is an analog to digital converter (ADC) with oversampling pulse code modulation (PCM) integrated with noise shaping technique. The bio-inspired motion detector Reichardt Correlator has low computation complexity and is commonly used in velocity estimation for detected objects. Conventionally, the received signals in receptors in a Reichardt Correlator are often digitized at bit depths of 8 or greater and sampled at Nyquist rate. Its implementation requires relatively complicated hardware units to cope with the processing of the samples. This paper presents a new approach for using Sigma-Delta converter to pre-process the input signals to Reichardt Correlator for velocity estimation. In this new approach, the aim is to have a scheme whereby the required hardware arithmetic units can be made simpler. This is achieved by considerably reducing the bit depth of the received signals. The presented results show that the proposed approach offers good velocity estimation performance as compared to the higher bit depth representations.; Bin Guo, Brian W.-H Ng and Said Al-Sarawi

Induction of Psychosis by Delta 9-Tetrahydrocannabinol Reflects Modulation of Prefrontal and Striatal Function During Attentional Salience Processing

Bhattacharyya, Sagnik; Crippa, Jose Alexandre; Allen, Paul; Martin-Santos, Rocio; Borgwardt, Stefan; Fusar-Poli, Paolo; Rubia, Katya; Kambeitz, Joseph; O'Carroll, Colin; Seal, Marc L.; Giampietro, Vincent; Brammer, Michael; Zuardi, Antonio Waldo; Atakan,
Fonte: AMER MEDICAL ASSOC; CHICAGO Publicador: AMER MEDICAL ASSOC; CHICAGO
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.02%
Context: The aberrant processing of salience is thought to be a fundamental factor underlying psychosis. Cannabis can induce acute psychotic symptoms, and its chronic use may increase the risk of schizophrenia. We investigated whether its psychotic effects are mediated through an influence on attentional salience processing. Objective: To examine the effects of Delta 9-tetrahydrocannabinol (Delta 9-THC) and cannabidiol (CBD) on regional brain function during salience processing. Design: Volunteers were studied using event-related functional magnetic resonance imaging on 3 occasions after administration of Delta 9-THC, CBD, or placebo while performing a visual oddball detection paradigm that involved allocation of attention to infrequent (oddball) stimuli within a string of frequent (standard) stimuli. Setting: University center. Participants: Fifteen healthy men with minimal previous cannabis use. Main Outcome Measures: Symptom ratings, task performance, and regional brain activation. Results: During the processing of oddball stimuli, relative to placebo, Delta 9-THC attenuated activation in the right caudate but augmented it in the right prefrontal cortex. Delta 9-Tetrahydrocannabinol also reduced the response latency to standard relative to oddball stimuli. The effect of Delta 9-THC in the right caudate was negatively correlated with the severity of the psychotic symptoms it induced and its effect on response latency. The effects of CBD on task-related activation were in the opposite direction of those of Delta 9-THC; relative to placebo...

Implications of Muon anomalous magnetic moment for Direct detection of Neutralino Dark Matter

Kim, Yeong Gyun; Nojiri, Mihoko M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 25/04/2001
Relevância na Pesquisa
26.12%
We investigate the implications of the recent measurement of muon anomalous magnetic moment for the direct detection of neutralino dark matter in the three different SUSY models: mSUGRA, a model with non-universal Higgs mass, and an SO(10) GUT model. We consider two extreme scenario for $\Delta a_\mu$ bound, i.e. $27 \times 10^{-10} < \Delta a_\mu < 59 \times 10^{-10}$ (1$\sigma$ bound) and $0 < \Delta a_\mu < 11 \times 10^{-10}$ ($2\sigma$ below). In mSUGRA model, the counting ratio may be above the sensitivity of the future experiments when parameters are within $1\sigma$ bound of $\Delta a_{\mu}$. However, the $\Omega_{\chi}$ tends to be high compared to the currently favored value $\Omega=0.3$. For models with the non-universal scalar masses, the possibility to have the consistent $\Omega_{\chi}$ and the high counting ratio is open up in the region of parameter space where Higgsino mass $\mu$ is smaller than mSUGRA prediction. In particular, in the SO(10) model, the LSP dark matter detection rate may be enhanced by almost one order of magnitude compared to mSUGRA and the model with non-universal Higgs mass, for cosmologically acceptable $\Omega_{\chi} h^2$. The highest detection rate of LSP dark matter occurs in the region where the LSP constitutes a subdominant part of local halo DM. Implication of SUSY mass parameter measurement under the cosmological constraint is also discussed.

On the energy and baseline optimization to study effects related to the $\delta$-phase (CP-/T-violation) in neutrino oscillations at a Neutrino Factory

Bueno, A.; Campanelli, M.; Navas-Concha, S.; Rubbia, A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 21/12/2001
Relevância na Pesquisa
26.08%
In this paper we discuss the detection of CP and T-violation effects in the framework of a neutrino factory. We introduce three quantities, which are good discriminants for a non vanishing complex phase ($\delta$) in the $3\times 3$ neutrino mixing matrix. We find that these three discriminants (in vacuum) all scale with $L/E_{\nu}$. Matter effects modify the scaling, but these effects are large enough to spoil the sensitivity only for baselines larger than 5000 km. So, in the hypothesis of constant neutrino factory power, the sensitivity on the $\delta$-phase is independent of the baseline chosen. Specially interesting is the direct measurement of T-violation from the ``wrong-sign'' electron channel, which involves a comparison of the $\nue\ra\numu$ and $\numu\ra\nue$ oscillation rates. However, the $\numu\ra\nue$ measurement requires magnetic discrimination of the electron charge, experimentally very challenging in a neutrino detector: low-energy neutrino beams and hence short baselines, are preferred. In this paper we show the exclusion regions in the $\Delta m^2_{12} - \delta$ plane for two concrete cases. We obtain a similar excluded region provided that the electron detection efficiency is $\sim$20% and the charge confusion 0.1%. The $\Delta m^2_{12}$ compatible with the LMA solar data can be tested with a flux of 5$\times 10^{21}$ muons. We compare these results with the fit of the visible energy distributions.; Comment: 58 pages...

On the detection of chemically peculiar stars using Delta a photometry

Paunzen, E.; Stuetz, Ch.; Maitzen, H. M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 06/07/2005
Relevância na Pesquisa
26.13%
We have summarized all Delta a measurements for galactic field stars (1474 objects) from the literature published over more than two decades. These measurements were, for the first time, compiled and homogeneously analyzed. The Delta a intermediate band photometric system samples the depth of the 520nm flux depression by comparing the flux at the center with the adjacent regions with bandwidths of 11 to 23nm. Because it was slightly modified over the last three decades, we checked for systematic trends for the different measurements but found no correlations whatsoever. The Delta a photometric system is most suitable to detecting magnetic chemically peculiar (CP) stars with high efficiency, but is also capable of detecting a small percentage of non-magnetic CP objects. Furthermore, the groups of (metal-weak) lambda Bootis, as well as classical Be/shell stars, can be successfully investigated. In addition, we also analyzed the behaviour of supergiants (luminosity class I and II). On the basis of apparent normal type objects, the correlation of the three sigma significance limit and the percentage of positive detection for all groups was derived. We compared the capability of the Delta a photometric system with the Delta (V1 - G) and Z indices of the Geneva 7-color system to detect peculiar objects. Both photometric systems show the same efficiency for the detection of CP and lambda Bootis stars...

Modification of the surface band-bending of a silicon CCD for low-energy electron detection

Smith, Aimée L.; Yu, Qiuming; Elliot, S. T.; Tombrello, T. A.; Nikzad, Shouleh
Fonte: Materials Research Society Publicador: Materials Research Society
Tipo: Book Section; PeerReviewed Formato: application/pdf
Publicado em /12/1996
Relevância na Pesquisa
26.15%
Silicon CCDs have limited sensitivity to particles and photons with short penetration depth, due to the surface depletion caused by the inherent positive charge in the native oxide. Because of surface depletion, internally-generated electrons are trapped near the irradiated surface and therefore cannot be transported to the detection circuitry. This deleterious surface potential can be eliminated by low-temperature molecular beam epitaxial (MBE) growth of a delta-doped layer on the Si surface. This effect has been demonstrated through achievement of 100% internal quantum efficiency for UV photons detected with delta-doped CCDs. In this paper, we will discuss the modification of the band bending near the CCD surface by low-temperature MBE and report the application of delta-doped CCDs to low-energy electron detection. We show that modification of the surface can greatly improve sensitivity to low-energy electrons. Measurements comparing the response of delta-doped CCDs with untreated CCDs were made in the 50 eV-1.5 keV energy range. For electrons with energies below 300 eV, the signal from untreated CCDs was below the detection limit for our apparatus, and data are presented only for the response of delta-doped CCDs at these energies. The effects of multiple electron hole pair (EHP) production and backscattering on the observed signals are discussed.

Low-energy electron detection with delta-doped CCDs

Nikzad, Shouleh; Smith, Aimée L.; Elliott, S. Tom; Jones, Todd J.; Tombrello, T. A.; Yu, Q.
Fonte: SPIE Publicador: SPIE
Tipo: Book Section; PeerReviewed Formato: application/pdf
Publicado em //1997
Relevância na Pesquisa
26.15%
Delta-doped CCDs have achieved stable quantum efficiency, at the theoretical limit imposed by reflection from the Si surface in the near UV and visible. In this approach, an epitaxial silicon layer is grown on a fully-processed CCD using molecular beam epitaxy. During the silicon growth on the CCD, 30 percent of a monolayer of boron atoms are deposited nominally within a single atomic layer, resulting in the effective elimination of the backside potential well. In this paper, we will briefly discuss delta-doped CCDs and their application of low-energy electron detection. We show that modification of the surface this way can greatly improve sensitivity to low-energy detection. We show that modification of the surface this way can greatly improve sensitivity to low-energy electrons. Measurements comparing the response of delta-doped CCDs with untreated CCDs were made in the 50 eV-1.5 keV energy range.For electrons with energies below 300 eV, the signal from untreated CCDs was below the detection limit for our apparatus, and data are presented only for the response of delta-doped CCDs at these energies. The effects of multiple electron hole pair production and backscattering on the observed signals are discussed.

Direct detection and imaging of low-energy electrons with delta-doped charge-coupled devices

Nikzad, Shouleh; Yu, Qiuming; Smith, Aimée L.; Jones, Todd J.; Tombrello, T. A.; Elliott, S. Tom
Fonte: Instituto de Tecnologia da Califórnia Publicador: Instituto de Tecnologia da Califórnia
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 07/12/1998
Relevância na Pesquisa
26.11%
We report the use of delta-doped charge-coupled devices (CCDs) for direct detection of electrons in the 50–1500 eV energy range. We show that modification of the CCD back surface by molecular beam epitaxy can greatly improve sensitivity to low-energy electrons by introducing an atomically abrupt dopant profile to eliminate the dead layer. Using delta-doped CCDs, we have extended the energy threshold for detection of electrons by over an order of magnitude. We have also measured high gain in response to low-energy electrons using delta-doped CCDs. The effect of multiple electron hole pair production on the observed signals is discussed. Electrons have been directly imaged with a delta-doped CCD in the 250–750 eV range.

Ácido delta-aminolevulinico e estresse oxidativo hepático na fase inicial da intoxicação experimental por hexaclorobenzeno; 5-Aminolevulinic acid and the hepatic oxidative stress in the early phase of experimental hexachlorobenzene intoxication

Sawada, Tânia Cristina Higashi; Silva, Vanessa Vitoriano da; Barros, Sonia; Röpke, Cristina Dislich; Barros, Silvia Berlanga de Moraes
Fonte: Universidade de São Paulo. Faculdade de Ciências Farmacêuticas Publicador: Universidade de São Paulo. Faculdade de Ciências Farmacêuticas
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; Artigo Avaliado pelos Pares Formato: application/pdf
Publicado em 01/06/2004 ENG
Relevância na Pesquisa
35.98%
Este trabalho avaliou os níveis de ácido delta-aminolevulínico (ALA) em fígado de ratos expostos a diferentes doses de hexaclorobenzeno (HCB) (25, 50 e 100 mg/kg de peso corpóreo) durante 4 semanas e correlacionou com os parâmetros de peroxidação lipídica. Os níveis de ALA foram determinados por cromatografia líquida de alta eficiência após derivatização com acetilacetona e formaldeído, seguida de detecção de fluorescência. A metodologia foi cuidadosamente validada, apesar disso, os níveis hepáticos de ALA em todos os animais tratados ou não foram abaixo do limite de detecção do método (2,27 mg de ALA/ g de fígado). Por outro lado, para a peroxidação lipídica, avaliada como produção de reagentes ao ácido tiobarbitúrico e quimiluminescência, os resultados foram significativamente elevados em todos os animais tratados em comparação com os do grupo controle (p; This work evaluated the levels of 5-aminolevulinic acid (ALA) in the liver of rats exposed to different doses of HCB (25,50, and 100 mg/kg b.w. for 4 weeks) and correlated them with lipid peroxidation parameters. Levels of ALA were determined by high-pressure liquid chromatography after derivatization with acetylacetone and formaldehyde, followed by fluorescence detection. The methodology was carefully validated...

Método imunoenzimático usando antígeno delta derivado do soro para detecção sérica de antígeno e anticorpo do vírus da hepatite delta; An ELISA method using serum derived HDAg for the sorological detection of HDV antigens and antibodies

Granato, Celso; Strauss, Edna; Vitvitsky, Ludmila; Gayotto, Luiz Carlos da Costa; Trepo, Christian
Fonte: Universidade de São Paulo. Instituto de Medicina Tropical de São Paulo Publicador: Universidade de São Paulo. Instituto de Medicina Tropical de São Paulo
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; ; ; ; Formato: application/pdf
Publicado em 01/12/1987 ENG
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Um dos maiores problemas no desenvolvimento de metodologia para detecção de antígenos e anticorpos do vírus da hepatite delta (VHD) tem sido a fonte de antígenos, uma vez que fígados humanos e de animais infectados pelo VHD são de difícil obtenção e baixo rendimento Ao uso de soro de pacientes na fase aguda da infecção pelo VHD, como fonte de antígenos, associamos a técnica imunoenzimática, com finalidade de facilitar o manuseio e economizar antígeno. O antígeno delta foi obtido a partir do soro de indivíduo na fase aguda de infecção por VHD e o anticorpo a partir de soro de portadores crônicos de VHD. Para a detecção do antígeno foi empregado o método "sanduíche" e para a detecção do anticorpo um ensaio tipo competição. Visando testar a especificidade e a sensibilidade relativas do novo método de detecção de anticorpo, foram feitas comparações do mesmo com radio-imunoensaio comercial (C-RIE, Lab. Abbott) e um radio-imunoensaio desenvolvido na Unité 271-INSERM de Lyon, França (NC-RIA). Soros de 42 pacientes foram testados pelos três métodos, sendo observados resultados discrepantes em apenas 2 casos. Os autores concluem que: 1) soros de pacientes na fase aguda e crônica da infecção pelo VHD podem ser usados como fonte de antígeno e anticorpos em ensaios imunológicos 2) o EIE e o RIE tem especificidade e sensibilidade relativas comparáveis 3) o EIE é de fácil execução...