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2.
Lupus ; 22(11): 1174-7, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23886639

RESUMO

Lupus associated protein loosing enteropathy (LUPLE) is a rare gastrointestinal manifestation of SLE. We presented a case of painless ascites from serve hypoalbuminaemia secondary to LUPLE. The patient responded to a course of intravenous cyclophosphamide. The remission was maintained by azathioprine and low dose prednisolone.


Assuntos
Ascite/etiologia , Antígeno Ca-125/sangue , Lúpus Eritematoso Sistêmico/complicações , Enteropatias Perdedoras de Proteínas/diagnóstico , Azatioprina/uso terapêutico , Ciclofosfamida/uso terapêutico , Feminino , Humanos , Pessoa de Meia-Idade , Prednisolona/uso terapêutico , Enteropatias Perdedoras de Proteínas/tratamento farmacológico , Enteropatias Perdedoras de Proteínas/etiologia
4.
J Clin Microbiol ; 50(9): 3084-8, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22760048

RESUMO

A variable-number tandem-repeat (VNTR) typing assay for the differentiation of Mycobacterium abscessus strains was developed. This assay showed complete reproducibility, locus stability, and a discriminatory power (Hunter-Gaston discriminatory index [HGDI] of 0.9563) that is superior to that of multilocus sequencing. It is a promising tool for the investigation of Mycobacterium abscessus epidemiology and nosocomial outbreaks.


Assuntos
Repetições Minissatélites , Tipagem Molecular/métodos , Mycobacterium/classificação , Mycobacterium/genética , DNA Bacteriano/genética , Humanos , Epidemiologia Molecular/métodos , Mycobacterium/isolamento & purificação , Infecções por Mycobacterium não Tuberculosas/microbiologia , Polimorfismo Genético , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
5.
J Clin Invest ; 100(11): 2783-92, 1997 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-9389743

RESUMO

Mucin 1 (MUC1) is a large complex glycoprotein that is highly expressed in breast cancer, and as such could be a target for immunotherapy. In mice, human MUC1 is highly immunogenic, particularly when conjugated to mannan, where a high frequency of CD8(+) MHC-restricted cytotoxic T lymphocytes is induced, accompanied by tumor protection. On this basis, a clinical trial was performed in which 25 patients with advanced metastatic carcinoma of breast, colon, stomach, or rectum received mannan-MUC1 in increasing doses. After 4 to 8 injections, large amounts of IgG1 anti-MUC1 antibodies were produced in 13 out of 25 patients (with antibody titers by ELISA of 1/320-1/20,480). Most of the antibodies reacted to the epitopes STAPPAHG and PAPGSTAP. In addition, T cell proliferation was found in 4 out of 15 patients, and CTL responses were seen in 2 out of 10 patients. Mannan-MUC1 can immunize patients, particularly for antibody formation, and to a lesser extent, cellular responses. It remains to be seen whether such responses have antitumor activity.


Assuntos
Adenocarcinoma/imunologia , Anticorpos/imunologia , Neoplasias da Mama/imunologia , Vacinas Anticâncer/imunologia , Neoplasias do Colo/imunologia , Mananas/imunologia , Mucina-1/imunologia , Neoplasias Retais/imunologia , Neoplasias Gástricas/imunologia , Linfócitos T/imunologia , Adenocarcinoma/fisiopatologia , Idoso , Sequência de Aminoácidos , Neoplasias da Mama/fisiopatologia , Divisão Celular , Neoplasias do Colo/fisiopatologia , Testes Imunológicos de Citotoxicidade , Epitopos de Linfócito B/imunologia , Feminino , Humanos , Isotipos de Imunoglobulinas , Masculino , Mananas/administração & dosagem , Dados de Sequência Molecular , Mucina-1/administração & dosagem , Proteínas Recombinantes de Fusão/administração & dosagem , Proteínas Recombinantes de Fusão/imunologia , Neoplasias Retais/fisiopatologia , Neoplasias Gástricas/fisiopatologia , Linfócitos T/citologia
7.
Med Phys ; 42(12): 7078-89, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26632061

RESUMO

PURPOSE: Focal therapy has been proposed as an alternative method to whole-gland treatment for prostate cancer when aiming to reduce treatment side effects. The authors recently validated a radiobiological model which takes into account tumor location and tumor characteristics including tumor cell density, Gleason score, and hypoxia in order to plan optimal dose distributions for focal therapy. The authors propose that this model can be informed using multiparametric MRI (mpMRI) and in this study present a registration framework developed to map prostate mpMRI and histology data, where histology will provide the "ground truth" data regarding tumor location and biology. The authors aim to apply this framework to a growing database to develop a prostate biological atlas which will enable MRI based planning for prostate focal therapy treatment. METHODS: Six patients scheduled for routine radical prostatectomy were used in this proof-of-concept study. Each patient underwent mpMRI scanning prior to surgery, after which the excised prostate specimen was formalin fixed and mounted in agarose gel in a custom designed sectioning box. T2-weighted MRI of the specimen in the sectioning box was acquired, after which 5 mm sections of the prostate were cut and histology sections were microtomed. A number of image processing and registration steps were used to register histology images with ex vivo MRI and deformable image registration (DIR) was applied to 3D T2w images to align the in vivo and ex vivo MRI data. Dice coefficient metrics and corresponding feature points from two independent annotators were selected in order to assess the DIR accuracy. RESULTS: Images from all six patients were registered, providing histology and in vivo MRI in the ex vivo MRI frame of reference for each patient. Results demonstrated that their DIR methodology to register in vivo and ex vivo 3D T2w MRI improved accuracy in comparison with an initial manual alignment for prostates containing features which were readily visible on MRI. The average estimated uncertainty between in vivo MRI and histology was 3.3 mm, which included an average error of 3.1 mm between in vivo and ex vivo MRI after applying DIR. The mean dice coefficient for the prostate contour between in vivo and ex vivo MRI increased from 0.83 before DIR to 0.93 after DIR. CONCLUSIONS: The authors have developed a registration framework for mapping in vivo MRI data of the prostate with histology by implementing a number of processing steps and ex vivo MRI of the prostate specimen. Validation of DIR was challenging, particularly in prostates with few or mostly linear rather than spherical shaped features. Refinement of their MR imaging protocols to improve the data quality is currently underway which may improve registration accuracy. Additional mpMRI sequences will be registered within this framework to quantify prostate tumor location and biology.


Assuntos
Técnicas Histológicas/métodos , Imageamento por Ressonância Magnética/métodos , Próstata/patologia , Próstata/cirurgia , Neoplasias da Próstata/patologia , Neoplasias da Próstata/cirurgia , Idoso , Atlas como Assunto , Contagem de Células , Fixadores , Formaldeído , Géis , Humanos , Imageamento Tridimensional , Masculino , Microtomia , Pessoa de Meia-Idade , Prostatectomia , Sefarose
8.
Endocrinology ; 142(7): 2985-95, 2001 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-11416020

RESUMO

A complementary DNA, uterine-ovarian-specific gene 44 (UO-44), has been isolated from tamoxifen-induced rat uterine complementary DNA library using differential display techniques. UO-44 transcripts are found to be abundant in the uterus and ovary. UO-44 gene expression in the uterus is strictly regulated by estrogens, tamoxifen, and GH, whereas the pure antiestrogen ICI 182780 is inhibitory. Treatment of ovariectomized rats and hypophysectomized rats with tamoxifen and GH, respectively, resulted in up-regulation of UO-44 expression in a dose-dependent manner. In situ hybridization revealed that UO-44 gene expression was restricted to the luminal and glandular epithelial cells of the uterus and to granulosa cells of medium-size ovarian follicles. Transfection studies showed that UO-44 was a membrane-associated protein. Because estrogens, tamoxifen, and GH are stimulators of uterine luminal epithelial cell growth in vivo, UO-44 protein may serve as a mediator of the effect of these compounds in inducing epithelial proliferation and differentiation in these tissues.


Assuntos
DNA Complementar/genética , Estradiol/análogos & derivados , Antagonistas de Estrogênios/farmacologia , Regulação da Expressão Gênica , Ovário/efeitos dos fármacos , Tamoxifeno/farmacologia , Útero/efeitos dos fármacos , Animais , DNA Complementar/isolamento & purificação , DNA Complementar/metabolismo , Estradiol/farmacologia , Feminino , Fulvestranto , Humanos , Ovariectomia , Ovário/metabolismo , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Frações Subcelulares/metabolismo , Distribuição Tecidual , Células Tumorais Cultivadas , Útero/metabolismo
9.
Medicine (Baltimore) ; 73(4): 215-23, 1994 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-8041244

RESUMO

The lipid profiles of 192 patients with functioning renal transplants and their etiologic associations and response to therapy, in particular simvastatin, were assessed. Hypercholesterolemia was present in 71.3% of patients within 3 years following transplantation. There were independent associations of serum cholesterol with prednisone dosage (p < 0.05), renal function (p < 0.05), and smoking (p < 0.05) in the early posttransplant period (up to 3 months posttransplant). Those patients whose immunosuppression included cyclosporin had lower serum cholesterol levels than those receiving azathioprine and prednisone (p < 0.02). Plasma triglyceride levels reflected a marked interindividual variation, and no independent correlations were observed. The presence of diabetes mellitus, hypertension (or the use of antihypertensive agents), or the form or duration of prior dialysis did not independently influence the lipid profiles. During the study period 22 patients died, 54.5% due to vascular causes. Those who died of vascular causes had higher serum cholesterol levels than those who died of other causes, which reached statistical significance at 3 years posttransplant (7.74 +/- 0.4 versus 5.5 +/- 0.52 mmol/L; p < 0.02). Cholestyramine was introduced in 30 patients, only 2 of whom continued with therapy beyond 3 months. Simvastatin was used in 43 patients, 20 of whom were receiving cyclosporin, resulting in a mean reduction in serum cholesterol of 16.5% (p < 0.001) and in serum triglycerides of 21% (p < 0.05). No clinical or biochemical evidence of muscle, liver, or renal toxicity occurred in 15.4 +/- 0.9 months of follow-up.


Assuntos
Hiperlipidemias/etiologia , Transplante de Rim , Adolescente , Adulto , Idoso , Colesterol/sangue , Feminino , Humanos , Inibidores de Hidroximetilglutaril-CoA Redutases , Hiperlipidemias/tratamento farmacológico , Hipolipemiantes/uso terapêutico , Lovastatina/análogos & derivados , Lovastatina/uso terapêutico , Masculino , Pessoa de Meia-Idade , Sinvastatina , Fatores de Tempo , Triglicerídeos/sangue
10.
Immunol Lett ; 25(1-3): 77-81, 1990 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-1704351

RESUMO

Antibody and cell-mediated immune responses to the transmission-blocking target antigens of Plasmodium falciparum, Pfs 48/45, were determined in infected non-immune patients and in immune individuals from an endemic area. Characterization of the B cell epitopes with monoclonal antibodies showed that there were five regions identifiable but there could be interactions between them causing either competitive or enhancing effects. Sera from infected non-immune patients contained antibodies that would compete with one or more of the mAbs to the different epitopes. Immune responsiveness to purified Pfs 48/45 in P. falciparum-immune adults measured as lymphoproliferation, production of interferon-gamma, or as Pfs 48/45-specific antibody was very limited. This did not appear to be due to MHC class II restriction, to diversity in structure of the parasite antigens or to a failure of immunological memory. The antibody-response data were more consistent with down-regulation of immunity as a result of prolonged exposure to infection.


Assuntos
Antígenos de Protozoários/imunologia , Plasmodium falciparum/imunologia , Proteínas de Protozoários/imunologia , Adulto , Animais , Anticorpos Monoclonais , Anticorpos Antiprotozoários/análise , Linfócitos B/imunologia , Criança , Regulação para Baixo , Epitopos/imunologia , Células Germinativas/imunologia , Humanos , Imunidade Celular , Memória Imunológica , Complexo Principal de Histocompatibilidade/imunologia , Malária/imunologia , Recidiva
11.
AIDS Res Hum Retroviruses ; 10(8): 977-82, 1994 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-7811549

RESUMO

Neurological manifestations of HIV disease occur in most adults and children with AIDS. Many of those affected will inevitably suffer clinical neurological deficits involving mental function, movement, and sensation. Surprisingly, there are not as yet adequate monitoring systems to predict the onset and/or progression of HIV infection of the CNS. Neurological, neuropsychological, CSF, and magnetic resonance imaging (MRI) analyses cannot accurately detect mental deterioration during advancing HIV disease. Reports suggest that in vivo proton MR spectroscopy (1H MRS) of the brain could be a predictor of virus-induced neurological deterioration. H MRS can measure N-acetylaspartate (NAA), a metabolite present only in neurons. Decreased NAA reflects neuronal loss seen during HIV infection of brain. To uncover possible associations between NAA levels and HIV-induced neurological disease we performed serial 1H MRS brain tests in HIV-infected patients with or at risk for encephalopathy. Serial testing, for 1 year, of 10 patients showed that brain NAA levels decreased in all HIV-infected subjects. The most severe NAA reductions were associated with progressive neurological impairment. These findings suggest that NAA can be used as a noninvasive measure of neuronal loss in patients with HIV disease. Most important, the results suggest that 1H MRS could be used to monitor therapeutics directed against HIV infection within the CNS.


Assuntos
Complexo AIDS Demência/diagnóstico , Ácido Aspártico/análogos & derivados , Espectroscopia de Ressonância Magnética , Complexo AIDS Demência/metabolismo , Adulto , Ácido Aspártico/análise , Biomarcadores/análise , Criança , Colina/análise , Creatina/análise , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Neurônios/patologia , Estudos Prospectivos , Prótons
12.
Am J Trop Med Hyg ; 60(4): 578-83, 1999 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-10348231

RESUMO

This study was carried out to compare cryptosporidiosis and giardiasis seroprevalence rates in residents of three communities. Community (Com 1) uses drinking water from deep wells, community 2 (Com 2) uses surface water from a protected watershed, and community 3 (Com 3) uses surface water frequently containing Cryptosporidium oocysts and Giardia cysts. Unfiltered drinking water from each community was collected at the tap and tested for Cryptosporidium oocysts and Giardia cysts during the 12 months in which sera were collected for testing. No oocysts or cysts were detected in the water from the Com 1 deep wells; oocysts and cysts were detected intermittently in the drinking water from the other two communities. A waterborne outbreak of cryptosporidiosis occurred in a municipality adjacent to Com 3 six months into this 12-month study. Sera from residents of each of the communities were collected proportionately by month and by population size. Coded sera were tested for IgG to Cryptosporidium using a previously developed Western blotting method. The presence or absence of bands at 15-17 kD and/or 27 kD was recorded for the 1,944 sera tested. Definite bands at 15-17 kD and/or 27 kD were detected in 981 (50.5%) of the sera. A total of 33.2% of sera from Com 1 (community using deep wells) were positive using the same criteria compared with 53.5% (Com 2) and 52.5% (Com 3) of sera from the two communities using surface drinking water. Both bands (15-17 kD plus 27 kD) were detected in 582 sera (29.9%) from the three communities: 14.1% of sera from Com 1 compared with 32.7% from Com 2 and 31.5% from Com 3. These findings are consistent with a lower risk of exposure to Cryptosporidium from drinking water obtained from deep well sources. However, analysis of results by calendar quarter showed a significant (P < 0.001) increase in the number of Com 3 positive sera (compared with Com 1) following the waterborne outbreak. Without this outbreak-related observation, a significant overall difference in seropositivity would not have been seen. We also observed that in sera from the community affected by the outbreak, the presence on immunoblots of both Cryptosporidium bands appeared to be the best indicator of recent infection. Seroprevalence rates using an ELISA to detect IgG to Giardia were estimated using the same sera. Overall 30.3% (590 of 1,944) of sera were positive by the ELISA. A total of 19.1% of sera from Com 1, 34.7% from Com 2 and 16.0% from Com 3 were seropositive. Rates for both Com 3 and Com 1 did not change significantly over time. In Com 2, rates decreased significantly (P < 0.001) during the last half of the study period (third and fourth calendar quarters). The reasons for the decrease in seroprevalence in Com 2 sera are presently not known. These studies show intriguing associations between seroprevalence, outbreak-related laboratory serologic data, and patterns of parasite contamination of drinking water. Further studies are required to validate the serologic approach to risk assessment of waterborne parasitic infections at a community level.


Assuntos
Anticorpos Antiprotozoários/sangue , Criptosporidiose/epidemiologia , Cryptosporidium parvum/imunologia , Giardia/imunologia , Giardíase/epidemiologia , Abastecimento de Água , Animais , Antígenos de Protozoários/imunologia , Colúmbia Britânica/epidemiologia , Cryptosporidium parvum/isolamento & purificação , Surtos de Doenças , Doenças Endêmicas , Ensaio de Imunoadsorção Enzimática , Giardia/isolamento & purificação , Humanos , Immunoblotting , Estações do Ano , Estudos Soroepidemiológicos , Água/parasitologia , Poluição da Água
13.
Am J Trop Med Hyg ; 61(1): 63-9, 1999 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-10432058

RESUMO

Isolates from 25 (13 sporadic and 12 outbreak) cryptosporidiosis cases, 24 of which were from British Columbia, Canada, were characterized using nested polymerase chain reaction amplification of the polymorphic internal transcribed spacer 1 locus. Two predominant Cryptosporidium parvum genotypes were found. Twelve (8 sporadic and 4 outbreak) isolates amplified with the cry7/cry21 primer pair and 12 (5 sporadic and 7 outbreak) isolates amplified with the cry7/cryITS1 primer pair. Multi-locus gene analysis using sequence polymorphisms on 3 other loci, i.e., the thrombospondin-related adhesion protein gene, the dihydrofolate reductase gene, and the 18S rRNA gene on 8 (4 outbreak and 4 sporadic) isolates showed non-random association among the human and animal alleles of the 4 different C. parvum gene loci. Associations between these 2 parasite genotypes and different routes of cryptosporidiosis transmission such as zoonotic, anthroponotic, and waterborne transmission were studied using municipal population and agricultural information, as well as detection of C. parvum oocysts in municipal drinking water specimens of the residential communities of sporadic and outbreak cases.


Assuntos
Criptosporidiose/transmissão , Cryptosporidium parvum/genética , Surtos de Doenças , Polimorfismo Genético/genética , Microbiologia da Água , Animais , Anticorpos Monoclonais , Colúmbia Britânica/epidemiologia , Criptosporidiose/epidemiologia , Criptosporidiose/genética , Primers do DNA/química , DNA de Helmintos/química , Eletroforese em Gel de Ágar , Fezes/parasitologia , Imunofluorescência , Humanos , Microscopia de Fluorescência , Reação em Cadeia da Polimerase
14.
Trans R Soc Trop Med Hyg ; 88(4): 395-9, 1994.
Artigo em Inglês | MEDLINE | ID: mdl-7570815

RESUMO

A waterborne outbreak of giardiasis which occurred 5 years after another in the same town in Canada was investigated. Sera from residents defined as cases or non-cases were tested by enzyme-linked immunosorbent assay (ELISA) and compared with sera from symptomatic and asymptomatic control groups. The outbreak-associated Giardia isolate was retrieved from contaminated drinking water and antigen from this strain was used in the serological investigation. Up to 84% of cases were identified by ELISA. More cases were identified by elevated immunoglobulin (Ig) G than by either elevated anti-Giardia IgA or IgM levels. Residents of the community infected during the first outbreak were significantly less likely to have been reinfected during the second outbreak. This is the first report of a second waterborne outbreak occurring in a community and results of the investigations are consistent with an acquired, protective immunity lasting at least 5 years.


Assuntos
Surtos de Doenças , Giardíase/epidemiologia , Abastecimento de Água , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Anticorpos Antiprotozoários/biossíntese , Colúmbia Britânica/epidemiologia , Criança , Pré-Escolar , Ensaio de Imunoadsorção Enzimática , Feminino , Giardia/isolamento & purificação , Giardíase/imunologia , Humanos , Imunoglobulinas/análise , Lactente , Masculino , Pessoa de Meia-Idade
15.
J Parasitol ; 86(1): 172-7, 2000 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-10701587

RESUMO

Twenty-seven Giardia duodenalis cyst-positive specimens (human, animal, or drinking water) were obtained from a waterborne outbreak in a community in British Columbia, western Canada. Parasite isolates were characterized using molecular techniques at 4 different steps of organism retrieval. None of the drinking water samples (n = 20) infected gerbils and none was successfully amplified using polymerase chain reaction (PCR). We were able to genotype 4 of 7 (human and animal) isolates by amplification of DNA from original specimens at the triosephosphate isomerase (tpi) gene locus using PCR followed by restriction fragment length polymorphism (RFLP) analysis. Five of the original specimens inoculated into Mongolian gerbils (Meriones unguiculatus) were infective and genotyped at the tpi locus using parasite material collected from the gerbil (cysts and trophozoites). Pulsed field gel electrophoresis (PFGE) was used to biotype trophozoites collected from the gerbils as well as trophozoites from the 4 isolates that adapted to culture. Four of these 5 isolates displayed the same (designated outbreak) biotype at all parasite retrieval steps with all molecular techniques including the originally amplified isolates. PCR-RFLP identified an additional biotype group. The 4 isolates that adapted to in vitro culture were also characterized by isoenzyme electrophoresis (IE). Biotype groups identified in these axenized isolates were all the same with each molecular technique (PCR-RFLP, PFGE, IE) tested. Results of this study demonstrate a need for more sensitive molecular methods to detect and characterize Giardia in original host and environmental samples. Results are also consistent with evidence of biotype changes that occur during the presently used process of isolate retrieval.


Assuntos
DNA de Protozoário/análise , Surtos de Doenças , Giardia/classificação , Giardíase/parasitologia , Animais , Colúmbia Britânica/epidemiologia , DNA de Protozoário/química , DNA de Protozoário/isolamento & purificação , Eletroforese , Eletroforese em Gel de Campo Pulsado , Genótipo , Gerbillinae , Giardia/enzimologia , Giardia/genética , Giardíase/epidemiologia , Humanos , Isoenzimas/análise , Fenótipo , Reação em Cadeia da Polimerase , Polimorfismo de Fragmento de Restrição , Roedores
16.
Proc Inst Mech Eng H ; 212(1): 65-9, 1998.
Artigo em Inglês | MEDLINE | ID: mdl-9529938

RESUMO

An ultrasonic non-destructive evaluation process is established to observe cracks and delaminations that occur below the surface of retrieved ultra-high molecular weight polyethylene joints. The result from the ultrasonic evaluation is compared with destructive (optical) test results of the actual cracks. Feasibility of characterizing different grades of bulk polyethylene is also established by means of ultrasonic attenuation measurements in the materials. This ultrasonic data can be used to give a better understanding of the failure mechanisms in the UHMWPE material.


Assuntos
Processamento de Imagem Assistida por Computador/métodos , Prótese do Joelho , Teste de Materiais/métodos , Polietilenos/análise , Ultrassonografia , Humanos , Articulação do Joelho/diagnóstico por imagem , Transdutores
17.
Ann Acad Med Singap ; 17(2): 205-7, 1988 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-3408222

RESUMO

A series of monoclonal antibodies (mAb) were produced against the hepatitis B surface antigen (HBsAg) and their specificity tested against 2 separate panels of known HBsAg subtypes. Using an enzymeimmunoassay, mAbs that specifically bind to the 'a', 'd' and 'w' epitopes were identified. There were also a number of mAbs that expressed binding patterns that do not correspond to the standard serological classification--which is not unusual since the mAbs were of murine origin. These mAbs are at present being used to replace the conventional goat or guinea-pig derived HBsAg subtyping antisera which are available in limited quantities and often vary in titer.


Assuntos
Anticorpos Monoclonais/imunologia , Anticorpos Anti-Hepatite B/imunologia , Antígenos de Superfície da Hepatite B/imunologia , Animais , Antígenos de Superfície da Hepatite B/classificação , Camundongos
19.
Sci Rep ; 2: 587, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22905318

RESUMO

Coexistence of polarization and resistance-switching characteristics in single compounds has been long inspired scientific and technological interests. Here, we report the non-volatile resistance change in noncentrosymmetric compounds investigated by using defect nanotechnology and contact engineering. Using a noncentrosymmetric material of ZnO as example, we first transformed ZnO into high resistance state. Then ZnO electrical polarization was probed and its domains polarized 180° along the [001]-axis with long-lasting memory effect (>25 hours). Based on our experimental observations, we have developed a vacancy-mediated pseudoferroelectricity model. Our first-principle calculations propose that vacancy defects initiate a spontaneous inverted domains nucleation at grain boundaries, and then they grow in the presence of an electrical field. The propagation of inverted domains follows the scanning tip motion under applied electrical field, leading to the growth of polarized domains over large areas.

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