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https://www.readbyqxmd.com/read/28433865/high-sensitivity-hplc-method-for-analysis-of-in-vivo-extracellular-gaba-using-optimized-fluorescence-parameters-for-o-phthalaldehyde-opa-sulfite-derivatives
#1
Shannon L Zandy, James M Doherty, Nathan D Wibisono, Rueben A Gonzales
Reversed-phase HPLC with derivatization using o-phthalaldehyde (OPA) and sulfite allows electrochemical detection of γ-aminobutyric acid (GABA) in microdialysis samples. However, OPA/sulfite derivatives have been reported to produce lower fluorescent yield than OPA derivatives using organic thiols as the nucleophile. To overcome this limitation we examined excitation and emission spectra, reaction time, pH, and concentration of reagents in the derivatization solution. Optimal detection parameters were determined as λex=220nm and λem=385nm for maximal fluorescence...
April 3, 2017: Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences
https://www.readbyqxmd.com/read/28433589/low-dose-out-of-field-radiotherapy-part-1-measurement-of-scattered-doses
#2
M Kruszyna, S Adamczyk, A Skrobała, M Skórska, W Suchorska, K Zaleska, A Kowalik, W Jackowiak, J Malicki
PURPOSE: To measure out-of-field doses in a phantom model to better quantify this radiation. MATERIAL AND METHODS: The individual contribution of photons and neutrons to the total out-of-field dose for 6 MV and 20 MV photons at open beam were measured in a purpose-designed water phantom. Radiation doses were measured at seven separate points (P1-P7) in the phantom with thermoluminescent detectors (TLD 100, 600, and 700) and GAFchromic™ EBT films. RESULTS: At a prescribed dose of 75Gy to the isocentre, the photon dose level in the close-to-field area (P2) ranged from 2...
April 19, 2017: Cancer Radiothérapie: Journal de la Société Française de Radiothérapie Oncologique
https://www.readbyqxmd.com/read/28432828/quantitative-contrast-enhanced-spectral-mammography-based-on-photon-counting-detectors-a-feasibility-study
#3
Huanjun Ding, Sabee Molloi
PURPOSE: To investigate the feasibility of accurate quantification of iodine mass thickness in contrast-enhanced spectral mammography. MATERIALS AND METHODS: A computer simulation model was developed to evaluate the performance of a photon-counting spectral mammography system in the application of contrast-enhanced spectral mammography. A figure-of-merit (FOM), which was defined as the decomposed iodine signal-to-noise ratio (SNR) with respect to the square root of the mean glandular dose (MGD), was chosen to optimize the imaging parameters, in terms of beam energy, splitting energy, and pre-filtrations for breasts of various thicknesses and densities...
April 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28432820/the-impact-of-small-motion-on-the-visualization-of-coronary-vessels-and-lesions-in-cardiac-ct-a-simulation-study
#4
Francisco Contijoch, J Webster Stayman, Elliot R McVeigh
PURPOSE: Coronary x-ray computed tomography angiography (CCTA) is used to non-invasively assess coronary artery geometry and has, combined with computational modeling, demonstrated the potential to identify physiologically significant lesions. These measurements require robust and accurate coronary imaging and delineation of vessels in the presence of small motion. This simulation study characterizes the impact of small, uncorrected vessel drifts during data acquisition on the assessment of vessel intensity, diameter, and shape...
April 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28432786/the-comprehensive-connectome-of-a-neural-substrate-for-on-motion-detection-in-drosophila
#5
Shin-Ya Takemura, Aljoscha Nern, Dmitri B Chklovskii, Louis K Scheffer, Gerald M Rubin, Ian A Meinertzhagen
Analysing computations in neural circuits often uses simplified models because the actual neuronal implementation is not known. For example, a problem in vision, how the eye detects image motion, has long been analysed using Hassenstein-Reichardt (HR) detector or Barlow-Levick (BL) models. These both simulate motion detection well, but the exact neuronal circuits undertaking these tasks remain elusive. We reconstructed a comprehensive connectome of the circuits of Drosophila's motion-sensing T4 cells using a novel EM technique...
April 22, 2017: ELife
https://www.readbyqxmd.com/read/28432760/determination-of-ochratoxin-a-in-black-and-white-pepper-nutmeg-spice-mix-cocoa-and-drinking-chocolate-by-high-performance-liquid-chromatography-coupled-with-fluorescence-detection-collaborative-study
#6
Elena Cubero-Leon, Katrien Bouten, Hamide Senyuva, Joerg Stroka
A method validation study for the determination of ochratoxin A in black and white pepper (Piper spp.), nutmeg (Myristica fragrans), spice mix (blend of ginger, turmeric, pepper, nutmeg, and chili), cocoa powder, and drinking chocolate was conducted according to the International Harmonized Protocol of the International Union of Pure and Applied Chemistry. The method is based on the extraction of samples with aqueous methanol, followed by a cleanup of the extract with an immunoaffinity column. The determination is carried out by reversed-phase LC coupled with a fluorescence detector...
April 22, 2017: Journal of AOAC International
https://www.readbyqxmd.com/read/28432685/chiral-analysis-of-%C3%AE-diimine-ru-ii-and-fe-ii-complexes-by-capillary-electrophoresis-using-sulfated-cyclodextrins-as-stereoselectors
#7
Petra Sázelová, Dušan Koval, Lukáš Severa, Filip Teplý, Václav Kašička
Capillary electrophoresis (CE) using randomly highly sulfated α-, β-, and γ-cyclodextrins (S-α-CD, S-β-CD, S-γ-CD), sulfobutylether-β-CD (SBE-β-CD), single isomer (6-O-sulfo) α-, β-, and γ-CDs and their derivatives as stereoselectors was applied to chiral analysis of polypyridyl complexes of [Ru(bpy)3 ](2+) , [Ru(phen)3 ](2+) , and [Fe(phen)3 ](2+) (bpy = 2,2'-bipyridine; phen = 1,10 phenanthroline). The best separations of Δ- and Λ-enantiomers of the these complexes with high resolution (up to R1,2  = 7...
April 22, 2017: Electrophoresis
https://www.readbyqxmd.com/read/28432000/determination-of-thiol-to-protein-ratio-and-drug-to-antibody-ratio-by-in-line-size-exclusion-chromatography-with-post-column-reaction
#8
Kenichiro Furuki, Toshimasa Toyo'oka
An in-line size-exclusion (SE) ultra-high-performance liquid chromatography (UHPLC)- 5,5-dithio-bis-(2-nitrobenzoic acid) (DTNB) method to quantify thiols in monoclonal antibodies (mAb) when manufacturing antibody-drug conjugates (ADCs) was developed. The mAbs are separated on an SE-UHPLC column and monitored with a UV detector at a wavelength of 280 nm. Eluents are channeled into a reaction coil and mixed with DTNB to form 5-thio-2-nitrobenzoic acid (TNB). Thiol concentration is calculated using absorption at 412 nm...
April 18, 2017: Analytical Biochemistry
https://www.readbyqxmd.com/read/28431893/proficiency-testing-with-uncertainty-evaluation-for-measuring-activities-per-unit-mass-of-134-cs-and-137-cs-in-brown-rice-in-japan
#9
R Furukawa, Y Unno, T Miura, A Yunoki, M Hachinohe, S Hamamatsu, H Itadzu, M Mizui
In Japan, we conducted proficiency testing of activity measurement by using high-purity germanium detectors for (134)Cs and (137)Cs in brown rice grains. Among 176 reported results, 86 % (for (134)Cs) and 93 % (for (137)Cs) of the results satisfied |En| ≦ 1. However, 58 reports for (134)Cs and 51 reports for (137)Cs had some failures in their evaluations of uncertainties. The proficiency testing was effective to improve the ability of uncertainty evaluation.
March 30, 2017: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/28431822/detecting-bursts-in-the-eeg-of-very-and-extremely-premature-infants-using-a-multi-feature-approach
#10
John M O'Toole, Geraldine B Boylan, Rhodri O Lloyd, Robert M Goulding, Sampsa Vanhatalo, Nathan J Stevenson
AIM: To develop a method that segments preterm EEG into bursts and inter-bursts by extracting and combining multiple EEG features. METHODS: Two EEG experts annotated bursts in individual EEG channels for 36 preterm infants with gestational age < 30 weeks. The feature set included spectral, amplitude, and frequency-weighted energy features. Using a consensus annotation, feature selection removed redundant features and a support vector machine combined features...
April 18, 2017: Medical Engineering & Physics
https://www.readbyqxmd.com/read/28431206/phase-transfer-ligand-exchange-of-lead-chalcogenide-quantum-dots-for-direct-deposition-of-thick-highly-conductive-films
#11
Qianglu Lin, Hyeong Jin Yun, Wenyong Liu, Hyung-Jun Song, Nikolay S Makarov, Oleksandr Isaienko, Tom Nakotte, Gen Chen, Hongmei Luo, Victor I Klimov, Jeffrey M Pietryga
The use of semiconductor nanocrystal quantum dots (QDs) in optoelectronic devices typically requires post-synthetic chemical surface treatments to enhance electronic coupling between QDs and allow for efficient charge transport in QD films. Despite their importance to solar cells, and infrared (IR) light-emitting diodes and photodetectors, advances in these chemical treatments for lead chalcogenide (PbE, E = S, Se, Te) QDs have lagged behind those of, for instance, II-VI semiconductor QDs. Here, we introduce a method for fast and effective ligand exchange for PbE QDs in solution, resulting in QDs completely passivated by a wide range of small anionic ligands...
April 21, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28430991/development-toward-high-resolution-x-ray-phase-imaging
#12
Atsushi Momose
Since the 1990s, the use of X-ray phase contrast has been extensively studied for imaging weakly absorbing objects consisting of low-Z elements such as biological soft tissues and polymers. The development of X-ray microscopy was also progressing during this time, although absorption contrast was only available. It was straightforward and important to develop phase-contrast X-ray microscopy. One characteristic in the development is that quantitative phase measurement is possible through the acquisition of phase-contrast images under a specific procedure, thanks to digital X-ray image detectors...
April 18, 2017: Microscopy
https://www.readbyqxmd.com/read/28430990/three-dimensional-dose-prediction-and-validation-with-the-radiobiological-gamma-index-based-on-a-relative-seriality-model-for-head-and-neck-imrt
#13
Noriaki Hamatani, Iori Sumida, Yutaka Takahashi, Michio Oda, Yuji Seo, Fumiaki Isohashi, Keisuke Tamari, Kazuhiko Ogawa
This study proposes a quality assurance (QA) method incorporating radiobiological factors based on the QUANTEC-determined tumor control probability and the normal tissue complication probability (NTCP) of head-and-neck intensity-modulated radiation therapy (HN-IMRT). Per-beam measurements were conducted for 20 cases using a 2D detector array. Three-dimensional predicted dose distributions within targets and organs at risk were reconstructed based on the per-beam QA results derived from differences between planned and measured doses...
April 19, 2017: Journal of Radiation Research
https://www.readbyqxmd.com/read/28430507/beating-the-standard-sensitivity-bandwidth-limit-of-cavity-enhanced-interferometers-with-internal-squeezed-light-generation
#14
M Korobko, L Kleybolte, S Ast, H Miao, Y Chen, R Schnabel
The shot-noise limited peak sensitivity of cavity-enhanced interferometric measurement devices, such as gravitational-wave detectors, can be improved by increasing the cavity finesse, even when comparing fixed intracavity light powers. For a fixed light power inside the detector, this comes at the price of a proportional reduction in the detection bandwidth. High sensitivity over a large span of signal frequencies, however, is essential for astronomical observations. It is possible to overcome this standard sensitivity-bandwidth limit using nonclassical correlations in the light field...
April 7, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28430400/highly-sensitive-hplc-method-for-the-determination-of-galantamine-in-human-plasma-and-urine-through-derivatization-with-dansyl-chloride-using-fluorescence-detector
#15
Elif Özdemir, Sevgi Tatar Ulu
A new method based on fluorescence derivatization with 5-(dimethylamino) naphthalene-1-sulfonyl chloride (dansyl chloride) was developed for the quantitative determination of galantamine in human plasma and urine using high-performance liquid chromatography. The reaction between galantamine and dansyl chloride was optimally realized in 30 min at room temperature and pH 10.5, with a reagent to galantamine molar ratio of 2.13. The derivative was extracted with dichloromethane, and the extract was dried under a nitrogen stream and dissolved in the mobile phase...
April 21, 2017: Luminescence: the Journal of Biological and Chemical Luminescence
https://www.readbyqxmd.com/read/28430258/transparency-measurement-of-thin-films-with-one-sided-optical-access-using-fluorescence-imaging
#16
A F Forughi, B Stoeber, S I Green
Optical transparency can be determined by passing light through an object and comparing the intensity of the transmitted light with the intensity of the incident light. This measurement needs optical access to both sides of the object for illumination and measurement. Optical access to both sides of the object may be restricted in some situations due to the presence of an opaque obstacle, lack of physical access, etc. A novel technique of transmittance measurement is presented that is able to determine the transparency of thin-film objects with optical access limited to just one side...
April 20, 2017: Applied Optics
https://www.readbyqxmd.com/read/28430253/nanoscale-schottky-contact-surface-plasmon-point-detectors-for-optical-beam-scanning-applications
#17
Naema Othman, Pierre Berini
We propose and investigate a Schottky contact detector where the contact metal is a nanoscale metal stripe waveguide supporting surface plasmons with strong localization along the Schottky contact. We consider Au for the metal stripe, p-doped silicon for the semiconductor, operation in the infrared (at λ<sub>0</sub>=1550  nm), and internal photoemission as the sub-bandgap detection mechanism. We find that the main surface plasmon mode of operation of the Au stripe exhibits diverging real and imaginary parts of n<sub>eff</sub> with decreasing stripe dimensions, commensurate with increasing confinement...
April 20, 2017: Applied Optics
https://www.readbyqxmd.com/read/28430230/compact-multichannel-high-resolution-micro-electro-mechanical-systems-based-interrogator-for-fiber-bragg-grating-sensing
#18
D Ganziy, B Rose, O Bang
We propose a novel type of compact high-resolution multichannel micro-electro-mechanical systems (MEMS)-based interrogator, where we replace the linear detector with a digital micromirror device (DMD). The DMD is typically cheaper and has better pixel sampling than an InGaAs detector used in the 1550 nm range, which leads to cost reduction and better performance. Moreover, the DMD is a 2D array, which means that multichannel systems can be implemented without any additional optical components in the interrogator...
April 20, 2017: Applied Optics
https://www.readbyqxmd.com/read/28429745/high-temperature-terahertz-detectors-realized-by-a-gan-high-electron-mobility-transistor
#19
H W Hou, Z Liu, J H Teng, T Palacios, S J Chua
In this work, a high temperature THz detector based on a GaN high electron mobility transistor (HEMT) with nano antenna structures was fabricated and demonstrated to be able to work up to 200( )°C. The THz responsivity and noise equivalent power (NEP) of the device were characterized at 0.14 THz radiation over a wide temperature range from room temperature to 200 °C. A high responsivity Rv of 15.5 and 2.7 kV/W and a low NEP of 0.58 and 10 pW/Hz(0.5) were obtained at room temperature and 200 °C, respectively...
April 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28429391/technical-note-direct-measurement-of-continuous-tmr-data-with-a-1d-tank-and-automated-couch-movements
#20
Nels C Knutson, Matthew C Schmidt, Matthew D Belley, Ngoc Nguyen, H Harold Li, Erno Sajo, Michael Price
PURPOSE: Real-time dynamic control of the linear accelerator, couch, and imaging parameters during radiation delivery was investigated as a novel technique for acquiring tissue maximum ratio (TMR) data. METHODS: TrueBeam Developer Mode (Varian Medical Systems, Palo Alto, CA) was used to control the linear accelerator using the Extensible Markup Language (XML). A single XML file was used to dynamically manipulate the machine, couch, and imaging parameters during radiation delivery...
April 21, 2017: Medical Physics
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