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1.
Osteoporos Int ; 32(12): 2533-2541, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34137899

RESUMO

Our human observational study showed that elevated arginine vasopressin levels by heavy exercise, not catecholamines, were associated with elevated serum tartrate-resistant acid phosphatase 5b (TRACP-5b). The increase in serum calcium was positively associated with percent changes of TRACP-5b, implying the involvement of bone resorption in the pathogenesis of exercise-induced hypercalcemia. INTRODUCTION: It remains unclear whether enhanced bone resorption explains exercise-induced hypercalcemia. An experimental study demonstrated that arginine vasopressin (AVP) stimulated osteoclast activity. METHODS: We conducted a prospective observational study, enrolling 65 trained healthy male officers of the Japan Self-Defense Forces (34 and 31 in waves 1 and 2, respectively). Before and after a 5-h heavy exercise, we collected laboratory data including bone markers, symptoms, and ionized calcium (iCa; wave 2 only). As blood calcium levels change after exercise, we estimated calcium (corrected calcium) levels immediately after the exercise using the correlation between blood calcium and time from the end of exercise in another cohort. RESULTS: Body weight decreased by 6.9% after the exercise. Corrected post-exercise serum total calcium (tCa) and iCa levels were significantly higher than pre-exercise levels, and 18% of participants showed hypercalcemia defined as corrected tCa >10.4 mg/dL or iCa >1.30 mmol/L. Serum tartrate-resistant acid phosphatase 5b (TRACP-5b), plasma three fractions of catecholamines, and AVP elevated significantly (median 14.3 pg/mL), while procollagen type 1 N-terminal propeptide and whole parathyroid hormone showed significant decreases. Corrected tCa increase showed a non-linear positive association with percent changes of TRACP-5b (%ΔTRACP-5b) even after adjustment for confounders. In addition, %ΔTRACP-5b was not associated with catecholamines, but with post-exercise AVP levels after adjustment for pre-exercise TRACP-5b. Symptoms of nausea or vomiting (observed in 20%) were positively associated with corrected post-exercise iCa after adjustment for post-exercise blood pH. CONCLUSION: AVP elevation may explain bone resorption and the following hypercalcemia in the setting of heavy exercise.


Assuntos
Reabsorção Óssea , Hipercalcemia , Fosfatase Ácida , Biomarcadores , Reabsorção Óssea/etiologia , Humanos , Hipercalcemia/etiologia , Isoenzimas , Masculino , Fosfatase Ácida Resistente a Tartarato , Vasopressinas
2.
Poult Sci ; 99(4): 1914-1920, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32241471

RESUMO

In avian species, maternal immunoglobulin Y (IgY) is transferred from the blood to the yolks of maturing oocytes; however, the mechanism underlying this transfer is unknown. To gain insight into the mechanisms of maternal IgY transfer into egg yolks, IgY-depleted chickens were generated by removing the bursa of Fabricius (bursectomy) during egg incubation, and their egg production and IgY transport ability into egg yolks were determined. After hatching, blood IgY concentrations of the bursectomized chickens decreased gradually until sexual maturity, whereas those of IgA remained low from an early stage of growth (from at least 2 wk of age). Chickens identified as depleted in IgY through screening of blood IgY and IgA concentrations were raised to sexual maturity. At 20 wk of age, both blood and egg yolk IgY concentrations in the IgY-depleted group were 600-fold lower than those of the control group, whereas egg production did not differ between the groups. Intravenously injected, digoxigenin-labeled IgY uptake into the egg yolk was approximately 2-fold higher in the IgY-depleted chickens than in the controls, suggesting that IgY depletion may enhance IgY uptake in maturing oocytes. DNA microarray analysis of the germinal disc, including the oocyte nucleus, revealed that the expression levels of 73 genes were upregulated more than 1.5-fold in the IgY-depleted group, although we could not identify a convincing candidate gene for the IgY receptor. In conclusion, we successfully raised IgY-depleted chickens presenting a marked reduction in egg yolk IgY. The enhanced uptake of injected IgY into the egg yolks of the IgY-depleted chickens supports the existence of a selective IgY transport mechanism in maturing oocytes and ovarian follicles in avian species.


Assuntos
Proteínas Aviárias/metabolismo , Galinhas/metabolismo , Gema de Ovo/metabolismo , Imunoglobulinas/metabolismo , Animais , Proteínas Aviárias/deficiência , Bolsa de Fabricius/cirurgia , Galinhas/cirurgia , Feminino , Imunoglobulinas/deficiência
3.
Radiat Prot Dosimetry ; 183(1-2): 280-284, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-30726975

RESUMO

Neutron fields produced by an accelerator-driven neutron source are generally mixed radiation fields that consist of fast neutrons and gamma rays. To estimate the biological effects of fast neutrons precisely, the gamma ray dose contamination must be evaluated in neutron fields. In this work, we developed a discrimination technique for absorbed doses (60Co gamma-ray equivalent) of fast neutrons and gamma rays using an ionization chamber. The filter thickness dependences of the absorbed doses of fast neutrons and gamma rays are different for a given filter material. Thus, the absorbed doses of each type of radiation were distinguished by fitting the dose attenuation curve, which was measured with an ionization chamber and attenuation filters, with a two-component exponential function. The absorbed dose of fast neutrons and gamma rays with no attenuation filter was evaluated from the y-intercept of the fitting function. This technique was demonstrated in two neutron fields produced by 4 MeV proton and deuteron bombardment of a 9Be target. The thicknesses of the polyethylene attenuation filters were 0-350 mm. The dose attenuation coefficients of fast neutrons obtained by the two-component exponential fitting function for the 9Be(p,n)9 and 9Be(d,n) reactions showed differences of 1.5 and 1.7%, respectively, from the reference measurements using a CR-39 plastic nuclear track detector. The absorbed dose contributions of gamma rays in neutrons fields of the 9Be(p,n)9B and 9Be(d,n) reactions were evaluated as 30.2 ± 3.24% and 20.4 ± 5.16%, respectively, without polyethylene filters.


Assuntos
Nêutrons Rápidos , Raios gama , Radiometria/instrumentação , Absorção de Radiação
5.
J Intern Med ; 283(3): 314-327, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29044764

RESUMO

BACKGROUND: The Systolic Blood Pressure Intervention Trial (SPRINT; ClinicalTrials.gov, NCT01206062) reported reduced cardiovascular events by intensive blood pressure (BP) control amongst hypertensive patients without diabetes. However, the risk-benefit profile of intensive BP control may differ across estimated glomerular filtration rate (eGFR) levels. METHODS: This is a post hoc analysis of the SPRINT. Nondiabetic hypertensive adults (n = 9361) with eGFR >20 mL per min per 1.73 m2 were enrolled from 102 US facilities between November 2010 and March 2013 and were followed up until August 2015 (median follow-up, 3.26 years). Patients were randomly assigned to either a systolic BP target of <120 or <140 mmHg (for intensive or standard treatment, respectively). The outcomes of interests were the development of (i) fatal and nonfatal major cardiovascular events and (ii) acute kidney injury (AKI). RESULTS: The cardiovascular benefit from intensive treatment was attenuated with lower eGFR (Pinteraction  = 0.019), whereas eGFR did not modify the adverse effect on AKI (Pinteraction  = 0.179). Amongst 891 participants with eGFR <45 mL per min per 1.73 m2 , intensive treatment did not reduce the cardiovascular outcome (54/446 vs. 54/445 events in the standard group, respectively; hazard ratio [HR], 0.92; 95% CI, 0.62-1.38) with an absolute rate difference (ARD) of -0.02 (95% CI, -0.07 to +0.03) per 100 patient-years, whereas it increased AKI (62/446 vs. 38/445 events in the standard group; HR, 1.73; 95% CI, 1.12-2.66) with an ARD of +1.93 (95% CI, +1.88 to +1.97) per 100 patient-years. CONCLUSIONS: Intensive BP control may provide little or no benefit and even be harmful for patients with moderate-to-advanced chronic kidney disease.


Assuntos
Injúria Renal Aguda/fisiopatologia , Anti-Hipertensivos/administração & dosagem , Determinação da Pressão Arterial/métodos , Pressão Sanguínea/fisiologia , Taxa de Filtração Glomerular/fisiologia , Hipertensão/tratamento farmacológico , Injúria Renal Aguda/etiologia , Idoso , Pressão Sanguínea/efeitos dos fármacos , Diabetes Mellitus , Relação Dose-Resposta a Droga , Feminino , Humanos , Hipertensão/complicações , Hipertensão/fisiopatologia , Masculino , Pessoa de Meia-Idade , Prognóstico , Resultado do Tratamento
6.
Clin Genet ; 92(3): 274-280, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28244113

RESUMO

BACKGROUND: Mutations in GDAP1 are responsible for heterogeneous clinical and electrophysiological phenotypes of Charcot-Marie-Tooth disease (CMT), with autosomal dominant or recessive inheritance pattern. The aim of this study is to identify the clinical and mutational spectrum of CMT patients with GDAP1 variants in Japan. MATERIALS AND METHODS: From April 2007 to October 2014, using three state-of-art technologies, we conducted gene panel sequencing in a cohort of 1,030 patients with inherited peripheral neuropathies (IPNs), and 398 mutation-negative cases were further analyzed with whole-exome sequencing. RESULTS: We identified GDAP1 variants from 10 patients clinically diagnosed with CMT. The most frequent recessive variant in our cohort (5/10), c.740C>T (p.A247V), was verified to be associated with a founder event. We also detected three novel likely pathogenic variants: c.928C>T (p.R310W) and c.546delA (p.E183Kfs*23) in Case 2 and c.376G>A (p.E126K) in Case 8. Nerve conduction study or sural nerve biopsy of all 10 patients indicated axonal type peripheral neuropathy. CONCLUSION: We identified GDAP1 variants in approximately 1% of our cohort with IPNs, and established a founder mutation in half of these patients. Our study originally described the mutational spectrum and clinical features of GDAP1-related CMT patients in Japan.


Assuntos
Doença de Charcot-Marie-Tooth/diagnóstico , Doença de Charcot-Marie-Tooth/genética , Mutação , Proteínas do Tecido Nervoso/genética , Fenótipo , Adolescente , Adulto , Alelos , Criança , Pré-Escolar , Análise Mutacional de DNA , Feminino , Efeito Fundador , Estudos de Associação Genética , Genótipo , Haplótipos , Humanos , Japão , Masculino , Pessoa de Meia-Idade , Proteínas da Mielina/genética , Linhagem , Reprodutibilidade dos Testes , Sequenciamento do Exoma , Adulto Jovem
7.
Endosc Ultrasound ; 3(Suppl 1): S4-5, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26425529

RESUMO

INTRODUCTION: We report a case of low-risk stomach gastrointestinal stromal tumor (GIST) which has been under a long-term observation, obtaining from this experience knowledge useful in determining the treatment formula for this disease. RESULTS: During the observation for 6 years, no such change as ulcer formation was observed in the appearance of the tumor. The measurement of tumor diameter, however, showed gradual growth of maximum tumor diameter from 2.7 to 5.0 cm. When the changes in the diameter of tumor during this period is plotted, taking the timeon the horizontal axis and the tumor diameter on the vertical axis, the growth of the tumor can be approximated with a secondary function, making it possible to estimate the developmental period of the GIST concerned from the approximated secondary function. Thus, the developmental period in this case was estimated to go back 19 years before the time when it was discovered for the 1(st) time. Further, it was considered that the coefficient of the secondary function represents the rate of tumor growth, and that comparison with this coefficient contributed to the evaluation of malignancy stage of the GIST concerned. CONCLUSION: The growth curve predicting the growth of tumor could be depicted by measuring the diameter of the tumor in GIST twice or more at an interval of 6-12 months with EUS, and it was thought that this was utilizable for determining treatment formula for GISTs.

8.
Endosc Ultrasound ; 3(Suppl 1): S7, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26425534

RESUMO

Aberrant pancreas is used to describe ectopic pancreatic tissue lying outside its normal location with no anatomic or vascular connection to the pancreas proper. Patients with aberrant pancreas are usually asymptomatic, so aberrant pancreas are typically discovered incidentally during endoscopy, surgery, or autopsy. This time, we report a case of gastric aberrant pancreas bleeding was repeated and endoscopic hemostasis was difficult. A 22-year-old man was admitted to a hospital with a complaint of epigastric pain and melena. Upper gastrointestinal endoscopy and endoscopic ultrasonography (EUS) revealed a submucosal tumor with a bleeding ulcer at the anterior wall of the antrum in the stomach, and diagnosed it as an aberrant pancreas. It was hard to stop bleeding by in total 7 times endoscopic hemostasis and anemia was gradually progressed, so partial gastrectomy was performed. This gastric tumor measured 40 mm × 30 mm × 20 mm and had a severe ulcerative change. The pathological diagnosis was aberrant pancreas with Langerhans islet, acinous cells and excretory duct. (Heinrich type) Until December 2013 in Japan, 13 cases of gastric aberrant pancreas with bleeding have been reported and in these, a surgery was done in 11 cases. In gastric aberrant pancreas cases with ulcer formation like this case, endoscopic hemostasis is expected to be difficult, and surgery is necessary. Hence, early accurate diagnosis by EUS is a very important to decide better treatment plan.

10.
Rev Sci Instrum ; 84(9): 093506, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-24089827

RESUMO

Collection optics for core measurements in a JT-60SA Thomson scattering system were designed. The collection optics will be installed in a limited space and have a wide field of view and wide wavelength range. Two types of the optics are therefore suggested: refraction and reflection types. The reflection system, with a large primary mirror, avoids large chromatic aberrations. Because the size limit of the primary mirror and vignetting due to the secondary mirror affect the total collection throughput, conditions that provide the high throughput are found through an optimization. A refraction system with four lenses forming an Ernostar system is also employed. The use of high-refractive-index glass materials enhances the freedom of the lens curvatures, resulting in suppression of the spherical and coma aberration. Moreover, sufficient throughput can be achieved, even with smaller lenses than that of a previous design given in [H. Tojo, T. Hatae, T. Sakuma, T. Hamano, K. Itami, Y. Aida, S. Suitoh, and D. Fujie, Rev. Sci. Instrum. 81, 10D539 (2010)]. The optical resolutions of the reflection and refraction systems are both sufficient for understanding the spatial structures in plasma. In particular, the spot sizes at the image of the optics are evaluated as ~0.3 mm and ~0.4 mm, respectively. The throughput for the two systems, including the pupil size and transmissivity, are also compared. The results show that good measurement accuracy (<10%) even at high electron temperatures (<30 keV) can be expected in the refraction system.

11.
Rev Sci Instrum ; 83(2): 02A332, 2012 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-22380179

RESUMO

The National Institute of Radiological Sciences (NIRS) maintains various ion accelerators in order to study the effects of radiation of the human body and medical uses of radiation. Two electrostatic tandem accelerators and three cyclotrons delivered by commercial companies have offered various life science tools; these include proton-induced x-ray emission analysis (PIXE), micro beam irradiation, neutron exposure, and radioisotope tracers and probes. A duoplasmatron, a multicusp ion source, a penning ion source (PIG), and an electron cyclotron resonance ion source (ECRIS) are in operation for these purposes. The Heavy-Ion Medical Accelerator in Chiba (HIMAC) is an accelerator complex for heavy-ion radiotherapy, fully developed by NIRS. HIMAC is utilized not only for daily treatment with the carbon beam but also for fundamental experiments. Several ECRISs and a PIG at HIMAC satisfy various research and clinical requirements.


Assuntos
Academias e Institutos , Radiometria/instrumentação , Carbono/uso terapêutico , Ciclotrons , Nêutrons
12.
Rev Sci Instrum ; 81(10): 10D539, 2010 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21033891

RESUMO

This paper presents designs of collection optics for a JT-60SA Thomson scattering system. By using tangential (to the toroidal direction) YAG laser injection, three collection optics without strong chromatic aberration generated by the wide viewing angle and small design volume were found to measure almost all the radial space. For edge plasma measurements, the authors optimized the channel number and wavelength ranges of band-pass filters in a polychromator to reduce the relative error in T(e) by considering all spatial channels and a double-pass laser system with different geometric parameters.

13.
Colorectal Dis ; 12(10 Online): e200-5, 2010 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-19912287

RESUMO

AIM: Inguinal lymph node (ILN) metastasis occurs with high frequency in some of the patients with lower rectal cancer. The aim of this study was to identify risk factors for ILN metastasis in patients with low rectal adenocarcinoma. METHOD: We retrospectively analysed 156 patients with lower rectal adenocarcinoma who underwent radical resection (R0) at a single institution. RESULTS: Twenty-five (16%) patients had a tumour that invaded the dentate line, seven of whom had ILN metastasis. Invasion of the dentate line was significantly associated with a high rate of ILN metastasis, worse prognosis and local recurrence than with a tumour not invading the dentate line (P = 0.03). A Cox proportional hazard regression analysis revealed the histological characteristics at the invading front (Hif) also to be a risk factor for ILN metastasis. CONCLUSION: Tumours which invade the dentate line have a high rate of ILN metastases and worse cancer specific end-points. The presence of poorly differentiated or mucinous adenocarcinoma components is an indication for bilateral groin irradiation.


Assuntos
Adenocarcinoma/secundário , Linfonodos/patologia , Neoplasias Retais/patologia , Adenocarcinoma/patologia , Adenocarcinoma/cirurgia , Idoso , Feminino , Humanos , Canal Inguinal , Metástase Linfática , Masculino , Pessoa de Meia-Idade , Invasividade Neoplásica , Recidiva Local de Neoplasia , Modelos de Riscos Proporcionais , Neoplasias Retais/cirurgia , Estudos Retrospectivos , Fatores de Risco
14.
Pharmacogenomics J ; 9(2): 137-46, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19104505

RESUMO

Biomedical researchers usually test the null hypothesis that there is no difference of the population mean of pharmacokinetics (PK) parameters between genotypes by the Kruskal-Wallis test. Although a monotone increasing pattern with a number of alleles is expected for PK-related genes, the Kruskal-Wallis test does not consider a monotonic response pattern. For detecting such patterns in clinical and toxicological trials, a maximum contrast method has been proposed. We show how that method can be used with pharmacogenomics data to a develop test of association. Further, using simulation studies, we compare the power of the modified maximum contrast method to those of the maximum contrast method and the Kruskal-Wallis test. On the basis of the results of those studies, we suggest rules of thumb for which statistics to use in a given situation. An application of all three methods to an actual genome-wide pharmacogenomics study illustrates the practical relevance of our discussion.


Assuntos
Estudo de Associação Genômica Ampla/estatística & dados numéricos , Modelos Genéticos , Modelos Estatísticos , Farmacogenética/estatística & dados numéricos , Farmacocinética , Polimorfismo de Nucleotídeo Único , Simulação por Computador , Genótipo , Humanos , Método de Monte Carlo , Fenótipo
15.
J Oral Rehabil ; 35(9): 700-5, 2008 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-18793354

RESUMO

The present study aimed to examine the effect of custom tray designs on the displacement of mobile tooth and local impression pressures during the impression procedure, using partially edentulous simulation models with six anterior teeth containing a mobile tooth prepared in previous studies. The custom trays were designed by altering the thickness of the respective spaces on the labial and lingual sides of the remaining tooth arch. In previous studies, the mobile tooth was displaced in the labial direction and local impression pressures of the mobile tooth were greater against the lingual side than the labial side for all custom tray designs. Furthermore, the custom trays perforated with holes on the lingual side were effective to reduce mobile tooth displacement, labial and lingual impression pressures against the mobile tooth, and the differences between them. Therefore, the present study was performed focusing on the labial and lingual thickness of spaces in custom tray designs. It was found that mobile tooth displacement, labial and lingual impression pressures against the mobile teeth and their differences were less in trays with spaces>3.0 mm thick on both the labial and lingual sides, but markedly greater in trays with a 1.5 mm-thick space on the labial side. These results indicate that the thickness of spaces on the labial side in the tray should not be reduced to prevent mobile tooth displacement.


Assuntos
Materiais para Moldagem Odontológica , Técnica de Moldagem Odontológica/instrumentação , Avulsão Dentária/complicações , Mobilidade Dentária/etiologia , Dente Canino/fisiologia , Técnica de Moldagem Odontológica/efeitos adversos , Análise do Estresse Dentário , Humanos , Incisivo/fisiologia , Arcada Parcialmente Edêntula , Maxila/fisiologia , Modelos Dentários
16.
Pharmacogenomics J ; 6(6): 388-96, 2006.
Artigo em Inglês | MEDLINE | ID: mdl-16550209

RESUMO

TZT-1027 is an antimicrotubule agent targeting beta-tubulin that is undergoing clinical development. The genomic response of cancer cells to TZT-1027 was profiled to evaluate its biochemical activity. A lung cancer cell line, PC-14, was exposed to antimicrotubule agents including dolastatins, Vinca alkaloids and taxanes at an equivalent toxicity level. Alterations in the TZT-1027-induced gene expression of approximately 600 genes were then examined using microarray technology and the resulting gene profiles were compared with those for cells exposed to the other antimicrotubule agents. A principle component analysis using the whole gene set demonstrated that TZT-1027 produced similar gene profiles to those produced by dolastatin 10, but that these gene profiles differed from those produced by other agents. The agents were classified according to their induced genomic response in a molecular structure-dependent manner. Genes whose expression profiles differed according to drug class included intermediate filaments, extracellular matrix protein and Rho regulatory genes that may be involved in cytoskeletal and angiogenesis processes that are regulated by microtubule dynamics. TZT-1027 produces a unique genomic response profile distinct from that of Vinca alkaloids and taxanes, suggesting that this agent has a different mechanism of action. The selected genes may act as pharmacodynamic biomarkers allowing the unique mode of action of TZT-1027 to be discriminated from those of other antimicrotubule agents.


Assuntos
Antineoplásicos/farmacologia , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Oligopeptídeos/farmacologia , Linhagem Celular Tumoral , Depsipeptídeos , Regulação para Baixo , Humanos , Microtúbulos/efeitos dos fármacos , Análise de Sequência com Séries de Oligonucleotídeos , Taxoides/farmacologia , Sais de Tetrazólio , Tiazóis , Testes de Toxicidade , Regulação para Cima , Alcaloides de Vinca/farmacologia
18.
Cell Mol Biol (Noisy-le-grand) ; 50(5): 613-24, 2004 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-15559978

RESUMO

The Rbp proteins in cyanobacteria are RNA-binding proteins with a single RNA recognition motif or RRM. A comprehensive assembly of genomic data suggests that there are two major classes of Rbp proteins (classes I and II) that diverged before the diversification of cyanobacteria. Class I proteins are further classified into two types with or without a C-terminal glycine-rich domain. The results of selection from a random RNA pool suggest that RbpA1 (class I) has affinity to C-rich and G-rich sequences. In vitro RNA binding assay with homopolymers indicated that class II protein has low affinity to poly(G) in contrast with class I proteins. Site-specific mutagenesis analysis of the RRM in RbpA1 showed that the aromatic residues Tyr4 or Phe46 are important in RNA binding as well as maintenance of secondary structure. We also tested various truncated proteins lacking the C-terminal domain as well as point mutants. Most of these proteins exhibited decreased affinity to RNA. Circular dichroism analysis as well as chromatographic analysis showed that Tyr4 and Phe46 are also important in maintaining the structure of RbpA1 protein. The C-terminal glycine-rich domain itself does not contribute much to the RNA-binding, but Arg83 which is located close to the C-terminal end of RRM is important in the RNA-binding.


Assuntos
Anabaena/metabolismo , Proteínas de Ligação a RNA/metabolismo , RNA/metabolismo , Sequência de Aminoácidos , Dados de Sequência Molecular , Fenilalanina/metabolismo , Filogenia , Ligação Proteica/fisiologia , Estrutura Terciária de Proteína , Proteínas de Ligação a RNA/química , Alinhamento de Sequência
19.
Opt Express ; 12(24): 5962-7, 2004 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-19488237

RESUMO

The high frequency operation of a low-voltage electrooptic modulator based on a strip-loaded BaTiO3 thin film waveguide structure has been demonstrated. The epitaxial BaTiO3 thin film on an MgO substrate forms a composite structure with a low effective dielectric constant of 20.8 at 40 GHz. A 3.9 V half-wave voltage with a 3.7 GHz 3-dB bandwidth and a 150 pm/V effective electrooptic coefficient is obtained for the 3.2mm-long modulator at 1.55 ?m. Broadband modulation up to 40 GHz is measured with a calibrated detection system. Numerical simulations indicate that the BaTiO3 thin film modulator has the potential for a 3-dB operational bandwidth in excess of 40 GHz through optimized design.

20.
J Oral Rehabil ; 29(9): 827-34, 2002 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-12366536

RESUMO

In order to investigate the thermal stability, the physical and mechanical, and dynamic viscoelastic properties of glass-fibre reinforced composite materials were measured. The G' of the seven materials examined was within 5;20 +/- 14; 55 and 4;50-14; 35 GPa for dry and wet specimens in air at 37 degrees C, respectively, and decreased with increasing temperature. The G' values of dry specimens decreased by 7;74-15;4% when heated to 60 degrees C. The value of tan delta ranged from 0;0102 to 0;0295 and from 0.0181 to 0.0406 for dry and wet specimens in air at 37 degrees C, respectively. The coefficient of linear thermal expansion between 30 and 60 degrees C ranged from 0;557 to 3; 95 x 10-5/ degrees C. Moreover, the filler content ranged from 56; 36 to 88; 87 wt%. These results showed that the magnitudes of G', tan delta, and the coefficient of linear thermal expansion and water absorption depend on the inorganic filler or glass-fibre content; i.e. the amount of resin matrix. Moreover, for all the materials examined, the G' values were thermostable in the temperature range encountered in the oral cavity.


Assuntos
Resinas Compostas/química , Vidro , Absorção , Coroas , Análise do Estresse Dentário , Prótese Parcial Fixa , Análise Diferencial Térmica , Elasticidade , Teste de Materiais , Tamanho da Partícula , Resistência ao Cisalhamento , Viscosidade , Água
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