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Background Signal (background + signal)
Selected AbstractspH-Activated Near-Infrared Fluorescence Nanoprobe Imaging Tumors by Sensing the Acidic MicroenvironmentADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Cong Li Abstract Imaging tumors in their early stages is crucial to increase the surviving rate of cancer patients. Currently most fluorescence probes visualize the neoplasia by targeting the tumor-associated receptor over-expressed on the cancer cell membrane. However, the expression level of these receptors in vivo is hard to predict, which limits their clinical translation. Furthermore, the signal output of these receptor-targeting probes usually stays at a high level, which leads to a strong background signal in normal tissue due to non-specific binding. In contrast to receptors, characteristics of the tumor microenvironment , such as acidosis , are pervasive in almost all solid tumors and can be easily accessed. In this work, a novel biodegradable nanoprobe InNP1 that demonstrates pH-activated near-infrared (NIR) fluorescence in both human glioblastoma U87MG cancer cells in vitro and the subcutaneous U87MG tumor xenografts in vivo is developed. Bio-distribution, in vivo optical imaging, and autoradiography studies demonstrate that the pH-activated NIR fluorescence is the dominant factor responsible for the high tumor/normal tissue (T/N) ratio of InNP1 in vivo. Overall, the work provides a nanoprobe prototype to visualize the solid tumor in vivo with high sensitivity and minimal systemic toxicity by sensing the tumor acidic microenvironment. [source] Influence of Device Geometry on Sensor Characteristics of Planar Organic Electrochemical TransistorsADVANCED MATERIALS, Issue 9 2010Fabio Cicoira The response of PEDOT:PSS planar electrochemical transistors to H2O2 can be tuned by varying the ratio between the areas of the channel and the gate electrode. Devices with small gates show lower background signal and higher sensitivity. The detection range, on the other hand, is found to be rather independent of the gate/channel area ratio. [source] A 100-position robotic sample changer for powder diffraction with low-background vacuum chamberJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2010S. R. Olsen At the new Australian OPAL research reactor, experiments carried out at room temperature use a substantial fraction of beam time on the high-resolution powder diffractometer, Echidna. With an average data collection time of 2,h and a complicated safety interlock system to protect users, the need for a fully automated and remotely controlled system was quickly realized. This report presents a solution based on a commercial four-axis robot capable of loading samples from two 50-position sample trays, in any order, into an automatically evacuated chamber. This chamber significantly reduced background signal arising from air scattering, with the effect being especially pronounced at low and high 2, angles. In the case of textured or inhomogeneous samples, the system may be re-configured so that the robot rotates the sample in the beam or translates it vertically through the beam. [source] A high sensitivity pinhole camera for soft condensed matterJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-1 2003Thomas Zemb A significant improvement in the sensitivity of a Huxley-Holmes design for a small angle X-ray scattering camera is obtained by separating the mirror and the monochromator. The "separated optics" camera described in this paper involves a long X-ray mirror close to a point X-ray source associated with a curved focusing crystal located close to the sample. The sample area is located at half the distance between the source and detector planes. Diffuse scattering produced by the mirror is not incident on the focusing crystal, thus reducing the background signal. Complete elimination of hard X-rays allows precise calibration and hence absolute determination of sample cross-section by means of a semi-transparent beam-stop. In pinhole geometry, the flux corresponds to a ca. 107 photons/s through the sample, collimated to q=10 -2 Å -1 in scattering vector range. This allows determination of scattered intensities of the order of 10 -3 cm -1, corresponding to the scattering related to isothermal compressibility of less than 0.1 mm of pure water. Values of absolute intensities for water as well as convenient widespread buffer solutions are shown, in order to be usable for calibration as secondary standards. As solid reference sample, the widely studied Lupolentm, a semi-crystalline polymer- is calibrated. The high- q limit (q, 4.5 nm,1 ) of a porous calcite sample can be used as a secondary standard for specific area determination of solid/solid or solid-liquid dispersions. [source] Cosmic microwave background signal in Wilkinson Microwave Anisotropy Probe three-year data with fasticaMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007D. Maino ABSTRACT We present an application of the fast Independent Component Analysis (fastica) to the Wilkinson Microwave Anisotropy Probe (WMAP) three-year data with the goal of extracting the cosmic microwave background (CMB) signal. We evaluate the confidence of our results by means of Monte Carlo simulations including the CMB, foreground contaminations and instrumental noise specific to each WMAP frequency band. We perform a complete analysis involving all or a subset of the WMAP channels in order to select the optimal combination for CMB extraction, using the frequency scaling of the reconstructed component as a figure of merit. We find that the combination KQVW provides the best CMB frequency scaling, indicating that the low-frequency foreground contamination in Q, V and W bands is better traced by the emission in the K band. The CMB angular power spectrum is recovered up to the degree scale; it is consistent within errors for all WMAP channel combinations considered, and in close agreement with the WMAP three-year results. A power spectrum analysis is made of the sky map divided into two hemispheres that have been previously reported as showing evidence of an asymmetric ratio of power on large angular scales. We then confirm the findings of several previous works with independent techniques. [source] Kell and XK immunohistochemistry in McLeod myopathyMUSCLE AND NERVE, Issue 10 2001Hans H. Jung MD Abstract The McLeod syndrome is an X-linked neuroacanthocytosis manifesting with myopathy and progressive chorea. It is caused by mutations of the XK gene encoding the XK protein, a putative membrane transport protein of yet unknown function. In erythroid tissues, XK forms a functional complex with the Kell glycoprotein. Here, we present an immunohistochemical study in skeletal muscle of normal controls and a McLeod patient with a XK gene point mutation (C977T) using affinity-purified antibodies against XK and Kell proteins. Histological examination of the affected muscle revealed the typical pattern of McLeod myopathy including type 2 fiber atrophy. In control muscles, Kell immunohistochemistry stained sarcoplasmic membranes. XK immunohistochemistry resulted in a type 2 fiber-specific intracellular staining that was most probably confined to the sarcoplasmic reticulum. In contrast, there was only a weak background signal without a specific staining pattern for XK and Kell in the McLeod muscle. Our results demonstrate that the lack of physiological XK expression correlates to the type 2 fiber atrophy in McLeod myopathy, and suggest that the XK protein represents a crucial factor for the maintenance of normal muscle structure and function. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 1346,1351, 2001 [source] 5-Ethynyl-2,-deoxyuridine labeling detects proliferating cells in the regenerating avian cochlea,THE LARYNGOSCOPE, Issue 9 2009Christina L. Kaiser PhD Abstract Objectives/Hypothesis: The avian cochlea regenerates hair cells following aminoglycoside treatment through supporting cell proliferation. Immunocytochemical labeling of 5-bromo-2,-deoxyuridine (BrdU), a thymidine analog, is a popular nonradioactive marker for identifying cells in the DNA synthesis (S phase) of the cell cycle. However, it requires harsh treatments to denature double-stranded DNA for the antibody to bind BrdU. We explored a new method using 5-ethynyl-2,-deoxyuridine (EdU) as a thymidine analog and a nonantibody azide/alkyne reaction between EdU and the fluorescent probe. We propose that EdU is as effective as BrdU, but without the requirement for harsh denaturation or the use of antibodies for detection. Study Design: Two-week-old chicks received a single gentamicin injection followed by a single EdU injection 72 hours later. Cochleae were extracted 4,8 hours later, fixed, and processed for fluorescent detection of EdU. Methods: Cochleae were processed for detection of incorporated EdU using the Click-iT Imaging Kit (Invitrogen/Molecular Probes, Carlsbad, CA) and colabeled with Sox2, myosin VI, or myosin VIIa antibodies. Whole-mount cochlear preparations were examined with confocal microscopy. Results: Supporting cells incorporated EdU into their newly synthesized DNA during the 4,8 hours following the EdU injection and were readily detected with little background signal. The intensity and quantity of cells labeled were similar to or better than that seen for BrdU. Conclusions: The EdU method is as effective as BrdU, without requiring harsh denaturation or secondary antibodies to identify proliferating cells. Thus, the nonantibody EdU system allows more flexibility by enabling colabeling with multiple antibodies to other cellular proteins involved in regeneration. Laryngoscope, 2009 [source] Coprecipitation with calcium hydroxide for determination of iron in fish otoliths by collision cell ICP-MS,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2007Stephanie L. Daniels Abstract A method has been described for the determination of iron from fish otoliths containing high levels of calcium by collision cell technology (CCT) ICP-MS. Iron (Fe) in otolith solutions was quantitatively coprecipitated with small amounts of calcium hydroxide by adding 1.0 M sodium hydroxide solution. The performance of CCT-ICP-MS pressurized with He/H2 cell gas was investigated on the elimination of Ca-based spectral interferences at m/z 54, 56 and 57. Molecular ion interferences at m/z 54 and 56 were reduced by 2 orders of magnitude. However, the interferences at m/z 57 increased by the same amount in the presence of Ca in solutions owing to the formation of 40Ca16 OH+ through reactions with H2 in collision cell, indicating that 57Fe was not suitable for the determination of Fe from otoliths. Results for 56Fe suffered significantly from interferences of Ca-based molecular ions when the Ca concentration in solution exceeded 100 µg ml,1, for which matrix-matched calibration was required for accurate determination. CCT with the aid of He/H2 cell gas proved to be very effective in eliminating the interferences (40Ar14N+ and 40Ca14N+) at m/z 54. Presence of Ca up to 300 µg ml,1 had virtually no effect on the ion signals of 54Fe, which with low background signals, afforded accurate determination of Fe from otoliths by using aqueous external standards. Copyright © 2007 John Wiley & Sons, Ltd. [source] A versatile method for stable carbon isotope analysis of carbohydrates by high-performance liquid chromatography/isotope ratio mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2008H. T. S. Boschker We have developed a method to analyze stable carbon isotope (13C/12C) ratios in a variety of carbohydrates using high-performance liquid chromatography/isotope ratio mass spectrometry (HPLC/IRMS). The chromatography is based on strong anion-exchange columns with low strength NaOH eluents. An eluent concentration of 1,mM resulted in low background signals and good separation of most of the typical plant neutral carbohydrates. We also show that more strongly bound carbohydrates such as acidic carbohydrates can be separated by inclusion of NO as an inorganic pusher ion in the eluent. Analyses of neutral carbohydrate concentrations and their stable carbon isotope ratios are shown for plant materials and marine sediment samples both at natural abundance and for 13C-enriched samples. The main advantage of HPLC/IRMS analysis over traditional gas chromatography based methods is that no derivatization is needed resulting in simple sample treatment and improved accuracy and reproducibility. Copyright © 2008 John Wiley & Sons, Ltd. [source] High-resolution magic-angle spinning NMR for the identification of reaction products directly from thin-layer chromatography spotsMAGNETIC RESONANCE IN CHEMISTRY, Issue 10 2007Scott A. Bradley Abstract We have investigated the prospect of identifying organic reaction products directly from separated thin-layer chromatography (TLC) spots with high-resolution magic-angle spinning (HRMAS) NMR. The concept is to use the TLC spots for NMR analysis so that spectra can be obtained before the reaction is worked up, but without having to elute the product from the TLC stationary phase. Thus, the separated spot is scraped from the plate, transferred to an HRMAS sample rotor, and suspended with a deuterated solvent. Herein, we describe the effects of having the stationary phase present during NMR acquisition. Using a Varian 4 mm gHX Nanoprobe and rotenone as a test compound, we found that the presence of the stationary phase during NMR acquisition resulted in (i) a large, broad ,background' signal near 4.6 ppm and (ii) a decrease in the signal-to-noise ratio due to the adsorption of the product molecules to the adsorbent. However, both effects could be adequately and conveniently eliminated. The background signal was removed by using either a CPMG pulse sequence or chemical exchange. The adsorption was avoided by using a more polar solvent system. Finally, we found that spectra with good signal-to-noise ratio and resolution could be acquired in a matter of minutes even for cases of limited product concentration. Therefore, we believe the technique has value and provides the organic chemist with another option to obtain NMR data critical for structural elucidation or verification. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||||||||