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Pesquisa : D01.268.150.200 [Categoria DeCS]
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  1 / 1864 MEDLINE  
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PMID:28742061
Autor:Poppinga D; Halbur J; Lemmer S; Delfs B; Harder D; Looe HK; Poppe B
Endereço:University Clinic for Medical Radiation Physics, Medical Campus Pius-Hospital, Carl von Ossietzky University, Oldenburg, Germany.
Título:Test study of boron nitride as a new detector material for dosimetry in high-energy photon beams.
Fonte:Phys Med Biol; 62(18):N436-N444, 2017 Sep 05.
ISSN:1361-6560
País de publicação:England
Idioma:eng
Resumo:The aim of this test study is to check whether boron nitride (BN) might be applied as a detector material in high-energy photon-beam dosimetry. Boron nitride exists in various crystalline forms. Hexagonal boron nitride (h-BN) possesses high mobility of the electrons and holes as well as a high volume resistivity, so that ionizing radiation in the clinical range of the dose rate can be expected to produce a measurable electrical current at low background current. Due to the low atomic numbers of its constituents, its density (2.0 g cm ) similar to silicon and its commercial availability, h-BN appears as possibly suitable for the dosimetry of ionizing radiation. Five h-BN plates were contacted to triaxial cables, and the detector current was measured in a solid-state ionization chamber circuit at an applied voltage of 50 V. Basic dosimetric properties such as formation by pre-irradiation, sensitivity, reproducibility, linearity and temporal resolution were measured with 6 MV photon irradiation. Depth dose curves at quadratic field sizes of 10 cm and 40 cm were measured and compared to ionization chamber measurements. After a pre-irradiation with 6 Gy, the devices show a stable current signal at a given dose rate. The current-voltage characteristic up to 400 V shows an increase in the collection efficiency with the voltage. The time-resolved detector current behavior during beam interrupts is comparable to diamond material, and the background current is negligible. The measured percentage depth dose curves at 10 cm × 10 cm field size agreed with the results of ionization chamber measurements within ±2%. This is a first study of boron nitride as a detector material for high-energy photon radiation. By current measurements on solid ionization chambers made from boron nitride chips we could demonstrate that boron nitride is in principle suitable as a detector material for high-energy photon-beam dosimetry.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Boron Compounds); 2U4T60A6YD (boron nitride); 7782-40-3 (Diamond); Z4152N8IUI (Silicon)


  2 / 1864 MEDLINE  
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PMID:29444056
Autor:Chen XD; Li S; Du B; Dong Y; Wang ZH; Guo GC; Sun FW
Título:High-resolution multiphoton microscopy with a low-power continuous wave laser pump.
Fonte:Opt Lett; 43(4):699-702, 2018 Feb 15.
ISSN:1539-4794
País de publicação:United States
Idioma:eng
Resumo:Multiphoton microscopy (MPM) has been widely used for three-dimensional biological imaging. Here, based on the photon-induced charge state conversion process, we demonstrated a low-power high-resolution MPM with a nitrogen vacancy (NV) center in diamond. Continuous wave green and orange lasers were used to pump and detect the two-photon charge state conversion, respectively. The power of the laser for multiphoton excitation was 40 µW. Both the axial and lateral resolutions were improved approximately 1.5 times compared with confocal microscopy. The results can be used to improve the resolution of the NV center-based quantum sensing and biological imaging.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:7782-40-3 (Diamond); N762921K75 (Nitrogen)


  3 / 1864 MEDLINE  
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PMID:29216117
Autor:Alkahtani M; Jiang L; Brick R; Hemmer P; Scully M
Título:Nanometer-scale luminescent thermometry in bovine embryos.
Fonte:Opt Lett; 42(23):4812-4815, 2017 Dec 01.
ISSN:1539-4794
País de publicação:United States
Idioma:eng
Resumo:Luminescent nanothermometry is a powerful tool that can precisely monitor temperature changes in animal embryos. Among the most sensitive nanoluminescent temperature sensors are fluorescent nanodiamonds (FNDs), having nitrogen-vacancy color centers, and lanthanide-ion-doped upconversion nanoparticles (UCNPs). Here, we investigate their use as nanothermometers inside bovine embryos. The motivation for using both FNDs and UCNPs to measure temperature is to avoid the question of sensor confusion by the local cellular environment. Specifically, by simultaneously measuring temperature using two different modalities having different physics, it is possible to greatly improve the measurement confidence, thereby directly addressing the recent controversy surrounding temperature measurements in living organisms.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:7782-40-3 (Diamond)


  4 / 1864 MEDLINE  
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PMID:29324786
Autor:Reipa V; Atha DH; Coskun SH; Sims CM; Nelson BC
Endereço:Materials Measurement Laboratory, Biosystems and Biomaterials Division, National Institute of Standards and Technology, Gaithersburg, Maryland, United States of America.
Título:Controlled potential electro-oxidation of genomic DNA.
Fonte:PLoS One; 13(1):e0190907, 2018.
ISSN:1932-6203
País de publicação:United States
Idioma:eng
Resumo:Exposure of mammalian cells to oxidative stress can result in DNA damage that adversely affects many cell processes. Lack of dependable DNA damage reference materials and standardized measurement methods, despite many case-control studies hampers the wider recognition of the link between oxidatively degraded DNA and disease risk. We used bulk electrolysis in an electrochemical system and gas chromatographic mass spectrometric analysis (GC/MS/MS) to control and measure, respectively, the effect of electrochemically produced reactive oxygen species on calf thymus DNA (ct-DNA). DNA was electro-oxidized for 1 h at four fixed oxidizing potentials (E = 0.5 V, 1.0 V, 1.5 V and 2 V (vs Ag/AgCl)) using a high surface area boron-doped diamond (BDD) working electrode (WE) and the resulting DNA damage in the form of oxidatively-modified DNA lesions was measured using GC/MS/MS. We have shown that there are two distinct base lesion formation modes in the explored electrode potential range, corresponding to 0.5 V < E < 1.5 V and E > 1.5 V. Amounts of all four purine lesions were close to a negative control levels up to E = 1.5 V with evidence suggesting higher levels at the lowest potential of this range (E = 0.5 V). A rapid increase in all base lesion yields was measured when ct-DNA was exposed at E = 2 V, the potential at which hydroxyl radicals were efficiently produced by the BDD electrode. The present results demonstrate that controlled potential preparative electrooxidation of double-stranded DNA can be used to purposely increase the levels of oxidatively modified DNA lesions in discrete samples. It is envisioned that these DNA samples may potentially serve as analytical control or quality assurance reference materials for the determination of oxidatively induced DNA damage.
Tipo de publicação: JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
Nome de substância:0 (Purines); 0 (Pyrimidines); 3352-57-6 (Hydroxyl Radical); 7782-40-3 (Diamond); 9007-49-2 (DNA); 91080-16-9 (calf thymus DNA); N9E3X5056Q (Boron)


  5 / 1864 MEDLINE  
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PMID:29254593
Autor:Veselsky T; Novotny J; Pastykova V; Koniarova I
Endereço:Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Dosimetry and Application of Ionizing Radiation, Prague, Brehova 78/7, 110 00, Czech Republic; Na Homolce Hospital, Medical Physics Department, Prague, Roentgenova 2/37, 150 30, Czech Republic;
Título:Determination of small field synthetic single-crystal diamond detector correction factors for CyberKnife, Leksell Gamma Knife Perfexion and linear accelerator.
Fonte:Phys Med; 44:66-71, 2017 Dec.
ISSN:1724-191X
País de publicação:Italy
Idioma:eng
Resumo:PURPOSE: The aim of this study was to determine small field correction factors for a synthetic single-crystal diamond detector (PTW microDiamond) for routine use in clinical dosimetric measurements. MATERIALS AND METHODS: Correction factors following small field Alfonso formalism were calculated by comparison of PTW microDiamond measured ratio M /M with Monte Carlo (MC) based field output factors Ω determined using Dosimetry Diode E or with MC simulation itself. Diode measurements were used for the CyberKnife and Varian Clinac 2100C/D linear accelerator. PTW microDiamond correction factors for Leksell Gamma Knife (LGK) were derived using MC simulated reference values from the manufacturer. RESULTS: PTW microDiamond correction factors for CyberKnife field sizes 25-5 mm were mostly smaller than 1% (except for 2.9% for 5 mm Iris field and 1.4% for 7.5 mm fixed cone field). The correction of 0.1% and 2.0% for 8 mm and 4 mm collimators, respectively, needed to be applied to PTW microDiamond measurements for LGK Perfexion. Finally, PTW microDiamond M /M for the linear accelerator varied from MC corrected Dosimetry Diode data by less than 0.5% (except for 1 × 1 cm field size with 1.3% deviation). CONCLUSIONS: Regarding low resulting correction factor values, the PTW microDiamond detector may be considered an almost ideal tool for relative small field dosimetry in a large variety of stereotactic and radiosurgery treatment devices.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:7782-40-3 (Diamond)


  6 / 1864 MEDLINE  
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PMID:29102867
Autor:Murillo-Sierra JC; Sirés I; Brillas E; Ruiz-Ruiz EJ; Hernández-Ramírez A
Endereço:Universidad Autónoma de Nuevo León, Facultad de Ciencias Químicas, Av. Universidad, Ciudad Universitaria, San Nicolás de los Garza, Nuevo León, Mexico.
Título:Advanced oxidation of real sulfamethoxazole + trimethoprim formulations using different anodes and electrolytes.
Fonte:Chemosphere; 192:225-233, 2018 Feb.
ISSN:1879-1298
País de publicação:England
Idioma:eng
Resumo:A commercial sulfamethoxazole + trimethoprim formulation has been degraded in 0.050 M Na SO at pH 3.0 by electrochemical oxidation with electrogenerated H O (EO-H O ), electro-Fenton (EF), photoelectro-Fenton with a 6-W UVA lamp (PEF) and solar photoelectro-Fenton (SPEF). The tests were performed in an undivided cell with an IrO -based, Pt or boron-doped diamond (BDD) anode and an air-diffusion cathode for H O electrogeneration. The anode material had little effect on the accumulated H O concentration. Both drugs always obeyed a pseudo-first-order decay with low apparent rate constant in EO-H O . Much higher values were found in EF, PEF and SPEF, showing no difference because the main oxidant was always OH formed from Fenton's reaction between H O and added Fe . The solution mineralization increased in the sequence EO-H O < EF < PEF < SPEF regardless of the anode. The IrO -based and Pt anodes behaved similarly but BDD was always more powerful. In SPEF, similar mineralization profiles were found for all anodes because of the rapid removal of photoactive intermediates by sunlight. About 87% mineralization was obtained as maximum for the powerful SPEF with BDD anode. Addition of Cl enhanced the decay of both drugs due to their quicker reaction with generated active chlorine, but the formation of persistent chloroderivatives decelerated the mineralization process. Final carboxylic acids like oxalic and oxamic were detected, yielding Fe(III) complexes that remained stable in EF with BDD but were rapidly photolyzed in SPEF with BDD, explaining its superior mineralization ability.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Anti-Infective Agents); 0 (Ferric Compounds); 0 (Water Pollutants, Chemical); 7782-40-3 (Diamond); AN164J8Y0X (Trimethoprim); BBX060AN9V (Hydrogen Peroxide); JE42381TNV (Sulfamethoxazole); N9E3X5056Q (Boron)


  7 / 1864 MEDLINE  
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PMID:28457668
Autor:Gonzalez R; Ludwikowski BM
Endereço:Auf der Bult Kinderkrankenhaus, Hannover, Germany. Electronic address: ricardo_gonzalez33154@yahoo.com.
Título:Re: "Stites J, Bernabé KJ, Galan D, Felsen D, Poppas DP. Urinary continence outcomes following vaginoplasty in patients with congenital adrenal hyperplasia." J Pediatr Urol 2017;13:38.e1-38.e7 and Diamond DA. 'Commentary to "Urinary continence outcome following vaginoplasty in patients with congenital adrenal hyperplasia."' J Pediatr Urol 2017;13:39.
Fonte:J Pediatr Urol; 13(5):535, 2017 10.
ISSN:1873-4898
País de publicação:England
Idioma:eng
Tipo de publicação: LETTER; COMMENT
Nome de substância:7782-40-3 (Diamond)


  8 / 1864 MEDLINE  
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PMID:28851527
Autor:Higashi K; Shibasaki M; Kuni K; Uemura T; Waragai M; Uemura K; Igarashi K; Toida T
Endereço:Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba, 260-8675, Japan.
Título:Determination of 3-hydroxypropylmercapturic acid in urine by three column-switching high-performance liquid chromatography with electrochemical detection using a diamond electrode.
Fonte:J Chromatogr A; 1517:79-85, 2017 Sep 29.
ISSN:1873-3778
País de publicação:Netherlands
Idioma:eng
Resumo:A three column-switching high-performance liquid chromatography (HPLC) using an electrochemical detector (ECD) equipped with a diamond electrode was established to determine 3-hydroxypropylmercapturic acid (3-HPMA) in urine. An extracted urine sample was consecutively fractionated using a strong anion-exchange column (first column) and a C8 column (second column) via a switching valve before application on an Octa Decyl Silyl (ODS) column (third column), followed by ECD analysis. The% recovery of 3-HPMA standard throughout the three-column process and limit of detection (LOD) were 94±1% and 0.1pmol, respectively. A solid phase extraction step is required for the sensitive analysis of 3-HPMA in urine by column-switching HPLC-ECD despite a decreased% recovery (55%) of urine sample spiked with 100pmol of 3-HPMA. To test the utility of our column-switching HPLC-ECD method, 3-HPMA levels of 27 urine samples were determined, and the correlation between HPLC-ECD and LC-Electrospray ionization (ESI)-MS/MS method was examined. As a result, the median values of µmol 3-HPMA/g Creatinine (Cre) in urine obtained by column-switching HPLC-ECD and LC-MS/MS were 2.19±2.12µmol/g Cre and 2.13±3.38µmol/g Cre, respectively, and the calibration curve (y=1.5171x-1.007) exhibited good linearity within a defined range (r =0.907). These results indicate that the combination of column-switching HPLC and ECD is a powerful tool for the specific, reliable detection of 3-HPMA in urine.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:7782-40-3 (Diamond); BFU3149V95 (S-(3-hydroxypropyl)cysteine N-acetate); WYQ7N0BPYC (Acetylcysteine)


  9 / 1864 MEDLINE  
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PMID:28839047
Autor:Silvera IF; Dias R
Endereço:Lyman Laboratory of Physics, Harvard University, Cambridge, MA 02138, USA. silvera@physics.harvard.edu.
Título:Response to Comment on "Observation of the Wigner-Huntington transition to metallic hydrogen".
Fonte:Science; 357(6353), 2017 08 25.
ISSN:1095-9203
País de publicação:United States
Idioma:eng
Resumo:Liu present negative comments on our observation of the Wigner-Huntington transition to metallic hydrogen (MH). Earlier attempts to produce MH were unsuccessful due to diamond failure before the required pressures were achieved. We produced the highest static pressures (495 gigapascals) ever on hydrogen at low temperatures. Here, we respond to their objections.
Tipo de publicação: JOURNAL ARTICLE; COMMENT
Nome de substância:7782-40-3 (Diamond); 7YNJ3PO35Z (Hydrogen)


  10 / 1864 MEDLINE  
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PMID:28672722
Autor:Fernandes A; Labiadh L; Ciríaco L; Pacheco MJ; Gadri A; Ammar S; Lopes A
Endereço:FibEnTech Unit and Department of Chemistry, University of Beira Interior, 6201-001 Covilhã, Portugal.
Título:Electro-Fenton oxidation of reverse osmosis concentrate from sanitary landfill leachate: Evaluation of operational parameters.
Fonte:Chemosphere; 184:1223-1229, 2017 Oct.
ISSN:1879-1298
País de publicação:England
Idioma:eng
Resumo:The electro-Fenton oxidation of a concentrate from reverse osmosis of a sanitary landfill leachate, with an initial chemical oxygen demand (COD) of 42 g L , was carried out using a carbon-felt cathode and a boron doped diamond anode. The influence of the applied current intensity, initial pH and dissolved iron initial concentration on the electro-Fenton process was assessed. For the experimental conditions used, results showed that the initial pH is the parameter that more strongly influences the current efficiency of the electro-Fenton process, being this influence more pronounced on the oxidation rate than on the mineralization rate of the organic matter. The increase in iron initial concentration was found to be detrimental, since the natural amount of iron present in the effluent, 73 mg L of total iron and 61 mg L of dissolved iron, was sufficient to ensure the electro-Fenton process at the applied intensities - 0.2-1.4 A. For the more favourable conditions studied, initial pH of 3 and natural iron concentration, it was found an increase in the organic load and nitrogen removals with the applied current intensity. For the highest current intensity applied, a COD removal of 16.7 g L was achieved after 8-h experiments.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:0 (Water Pollutants, Chemical); 7440-44-0 (Carbon); 7782-40-3 (Diamond); BBX060AN9V (Hydrogen Peroxide); E1UOL152H7 (Iron); N762921K75 (Nitrogen); N9E3X5056Q (Boron)



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