Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 10 de 10
Filtrar
1.
Science ; 263(5154): 1739-41, 1994 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-17795379

RESUMO

An x-ray projection microscope equipped with a charge-coupled device camera allows direct observation of zinc (Zn(2+)) ions diffusing in aqueous hydrochloric acid solution during the corrosion of zinc foil and pellets. Time series of microradiographic images with a lateral resolution on the order of 10 micrometers allow observation of the time and spatial evolution of the colorless Zn(2+) ions in solution without any previous treatment. The concentration distribution of the ions can be quantified from these images. This technique should find applications in the biology, chemistry, and electrochemistry of aqueous solutions, allowing direct observation of the behavior and concentration fluctuations of medium or heavy ions moving in a weakly absorbing medium.

2.
J Med Chem ; 43(11): 2285-9, 2000 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-10841808

RESUMO

Homocamptothecin (hCPT) is an E-ring modified camptothecin (CPT) analogue bearing a methylene spacer between the alcohol and carboxyl functions of the CPT lactone. Combining pronounced inhibitory activity of topoisomerase I (Topo I) with enhanced plasma stability, hCPT constitutes an attractive template for the elaboration of new anticancer agents. Fluorinated hCPT analogues, prepared in enantiomerically pure form, were assayed by their stimulation of Topo I-mediated DNA cleavage. Translation into cytotoxicity against tumor cells was evaluated on HT29 human colon adenocarcinoma and on the multidrug resistant lung and bladder tumor cell lines, A549 and T24r. Good correlation is observed between the ability of the drugs to stimulate Topo I-mediated DNA cleavage and the respective 50% inhibitory concentrations (IC(50) values) of the HT29, A549, and T24r cell growth. Fluorine substitution in the A-ring of hCPT was found to have a pronounced influence on biological activity, providing several compounds which are up to 100-fold more potent than CPT in terms of IC(50). Among these, 10,11-difluoro-hCPT has been selected for further development.


Assuntos
Antineoplásicos/farmacologia , Camptotecina/análogos & derivados , DNA Topoisomerases Tipo I/metabolismo , Antineoplásicos/síntese química , Antineoplásicos/química , Camptotecina/química , Camptotecina/farmacologia , DNA Topoisomerases Tipo I/efeitos dos fármacos , Relação Dose-Resposta a Droga , Células HT29 , Humanos , Concentração Inibidora 50 , Estereoisomerismo , Células Tumorais Cultivadas
3.
Scanning ; 24(3): 109-16, 2002.
Artigo em Inglês | MEDLINE | ID: mdl-12074490

RESUMO

Using primary beam energies E0 ranging from 0.2 to 15 keV and an in-lens detector, a series of images of the same region of an artificial microstructured diamond sample have been acquired in scanning electron microscopy. Next, the images were analysed by using a scatter diagram technique to underline the topographic contrast change and contrast reversal. The results obtained from 0.5 to 15 keV are discussed with the help of an expression derived from the constant loss model for the secondary electron yield delta of diamond, but including the respective roles of the angle of incidence, i, and of the angle of detection, alpha. More surprising is the quality of images obtained at a beam energy as low as 0.2 keV, and more difficult to explain is the significant contrast change between 0.2 keV and 0.5 keV. For the first time, scatter diagrams are used as a diagnostic tool in scanning electron microscopy, and after some improvements it is hoped that the experimental approach followed here may lead to quantitative estimates of the local tilts of a specimen surface.

4.
Rev Laryngol Otol Rhinol (Bord) ; 110(4): 349-53, 1989.
Artigo em Francês | MEDLINE | ID: mdl-2636730

RESUMO

This paper is an attempt to bring up to date the importance of speech therapy as regards the help given to cerebral palsy. While recognising the importance of physiotherapy, it tries to show that a new approach to the language problems of the physically handicapped child, enables one to have a greater understanding and therefore to respond better to the needs of the cerebral palsy.


Assuntos
Paralisia Cerebral/psicologia , Fonoterapia , Humanos , Recém-Nascido , Masculino , Relações Mãe-Filho , Relações Pais-Filho , Papel do Médico
5.
Ultramicroscopy ; 135: 43-9, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23872041

RESUMO

Due to the influence of refraction effects on the escape probability of the Back-Scattered Electrons (BSE), an expression of the fraction of these BSE is given as a function of the beam energy, E°, and emission angle (with respect to the normal) α. It has been shown that these effects are very sensitive to a local change of the work function in particular for low emerging angles. This sensitivity suggests a new type of contrast in Low Voltage Scanning Electron Microscopy (LVSEM for E°<2 keV): the work function contrast. Involving the change of φ with crystalline orientation, this possibility is supported by a new interpretation of a few published images. Some other correlated contrasts are also suggested. These are topographical contrasts or contrasts due to subsurface particles and cracks. Practical considerations of the detection system and its optimization are indicated.

6.
J Anim Sci ; 84(5): 1295-301, 2006 May.
Artigo em Inglês | MEDLINE | ID: mdl-16612034

RESUMO

Evaluation of skeletal muscle tolerance during development of new drug formulations for i.m. use is most often based on terminal methods performed in the target species after slaughtering. The objective of this study was to evaluate the effect of muscle damage on the pharmacokinetic parameters of the drug delivered into the muscle using an alternative, noninvasive method. Phenylbutazone (PBZ) was used as the test article. Six ewes received increasing volumes of a 20% PBZ i.m. formulation, according to a cross-over design, and an i.v. bolus of the same formulation. Serial blood samples were taken, and a pharmacokinetic analysis of the plasma activity of creatine kinase and plasma PBZ concentrations was carried out. The amount of muscle damage after i.m. administration of 2, 4, or 8 mL of PBZ, calculated from the area under the curve of plasma creatine kinase across time was 36, 76, and 178 g for a 70-kg ewe. The corresponding absolute bioavailability of PBZ was 100 +/- 32%, 96 +/- 19%, and 100 +/- 17%, and the maximal PBZ concentrations were 42 +/- 3.4, 74 +/- 8.8, and 119 +/- 18.2 microg/mL. The plasma clearance of PBZ (i.v.) was 4.2 +/- 0.94 mL.kg(-1).h(-1). In conclusion, the absolute bioavailability of PBZ after i.m. administration was not altered by the increased volume of formulation administered despite the overall increase in the extent of muscle damage.


Assuntos
Anti-Inflamatórios não Esteroides/administração & dosagem , Anti-Inflamatórios não Esteroides/efeitos adversos , Fenilbutazona/administração & dosagem , Fenilbutazona/efeitos adversos , Ovinos , Animais , Anti-Inflamatórios não Esteroides/farmacocinética , Disponibilidade Biológica , Química Farmacêutica , Creatina Quinase/sangue , Estudos Cross-Over , Relação Dose-Resposta a Droga , Feminino , Meia-Vida , Injeções Intramusculares , Músculo Esquelético , Fenilbutazona/farmacocinética , Distribuição Aleatória
7.
J Microsc ; 217(Pt 1): 16-35, 2005 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-15655059

RESUMO

In addition to improvements in lateral resolution in scanning electron microscopy, recent developments of interest here concern extension of the incident beam energy, E(0), over two decades, from approximately 20 keV to approximately 0.1-0.5 keV and the possibility of changing the take-off emission, alpha, of detected secondary electrons. These two degrees of freedom for image acquisition permit a series of images of the same field of view of a specimen to be obtained, each image of the series differing from the others in some aspect. The origins of these differences are explored in detail and they are tentatively interpreted in terms of the change in the secondary electron emission yield delta vs. E(0), delta = f(E(0)), and also of the change in delta vs. alpha, partial differentialdelta/ partial differentialalpha. Various origins for the chemical contrast and topographic contrast have been identified. Illustrated by correlating a secondary electron image and a backscattered electron image, use of the scatter diagram technique facilitates image comparison. The difference between the lateral resolution and the size of the minimum detectable detail is outlined to avoid possible errors in nanometrology. Some aspects related to charging are also considered and possible causes of contrast reversal are suggested. Finally, the suggested strategy consists of the acquisition of various images of a given specimen by changing one parameter: primary beam energy and take-off angle for conductive specimens; working distance or beam intensity for high-resolution experiments; scanning frequency for insulating specimens.


Assuntos
Microscopia Eletrônica de Varredura/tendências , Microscopia Eletrônica de Varredura/instrumentação , Microscopia Eletrônica de Varredura/métodos , Propriedades de Superfície
8.
J Microsc ; 214(Pt 3): 341-7, 2004 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-15157201

RESUMO

The relative weight, delta(Beta), of the yield of secondary electrons, SE(2), induced by the backscattered electrons, BSE, with respect to that, delta(P), of secondary electrons, SE(1), induced by the primary electrons, PE, is deduced from simple theoretical considerations. At primary energies E(0) larger than E(M) (where the total SE yield delta = delta(P) + delta(B) is maximum), the dominant role of the backscattering events is established. It is illustrated in SEM by a direct comparison of the contrast between SE images and BSE images obtained at E(0) approximately 5 keV and E(0) approximately 15 keV on a stratified specimen. At energies E(0) less than E(M), the dominant role of SE(1) electrons with respect to SE(2) (and SE(3)) is established. It is illustrated by the better practical resolution of diamond images obtained with an in-lens detection in low voltage SEM E(0) approximately 0.2-1 keV range compared with that obtained with a lateral detector. The present contribution illustrates the improved performance of LVSEM in terms of contrast and of practical resolution as well as the importance of variable voltage methods for subsurface imaging. The common opinion that the practical lateral resolution is given by the incident spot diameter is also reconsidered in LVSEM.

9.
J Electron Microsc Tech ; 11(3): 222-9, 1989 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-2723803

RESUMO

Using an instrument equipped with two electron guns, an electron analyzer, and a Si(Li) diode detector, we developed microanalytical techniques based on inner-shell electron excitations by incident electrons and X-rays, that is, electron energy-loss spectroscopy (EELS) in the reflection mode; electron probe microanalysis (EPMA) and X-ray appearance potential spectroscopy (XAPS); electron-induced Auger electron spectroscopy (e-AES); X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS); X-ray induced AES (XAES), X-ray fluorescence analysis (XRF), and scanning X-ray radiography (SXR). The corresponding characteristic images (including X-ray microradiography and X-ray photoelectron microscopy) were obtained in the scanning mode. The principle of the apparatus is described. Each spectroscopy and microscopy is illustrated by an example. Their performance and limits are discussed.


Assuntos
Microanálise por Sonda Eletrônica/métodos , Microscopia Eletrônica/métodos , Análise Espectral
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA