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Anisotropy Value (anisotropy + value)
Selected AbstractsAccounting for velocity anisotropy in seismic traveltime tomography: a case study from the investigation of the foundations of a Byzantine monumental buildingGEOPHYSICAL PROSPECTING, Issue 1 2006L. Polymenakos ABSTRACT We estimate velocity anisotropy factors from seismic traveltime tomographic data and apply a correction for anisotropy in the inversion procedure to test possible improvements on the traveltime fit and the quality of the resulting tomographic images. We applied the anisotropy correction on a traveltime data set obtained from the investigation of the foundation structure of a monumental building: a Byzantine church from the 11th century AD, in Athens, Greece. Vertical transverse isotropy is represented by one axis of symmetry and one anisotropy magnitude for the entire tomographic inversion grid. We choose the vertical direction for the symmetry axis by analysing the available data set and taking into account information on the character of the foundations of the church from the literature and past excavations. The anisotropy magnitude is determined by testing a series of values of anisotropy and examining their effect on the tomographic inversion results. The best traveltime fit and image quality are obtained with an anisotropy value (Vmax/Vmin) of 1.6, restricted to the high velocity structures in the subsurface. We believe that this anisotropy value, which is significantly higher than the usual values reported for near-surface geological material, is related to the fabric of the church foundations, due to the shape of the individual stone blocks and the layout of the stonework. Inversion results obtained with the correction for anisotropy indicate that both the traveltime fit and the image quality are improved, providing an enhanced reconstruction of the velocity field, especially for the high-velocity features. Based on this enhanced and more reliable reconstruction of velocity distribution, an improved image of the subsurface material character was made possible. In particular, the pattern and state of the church foundations and possible weak ground material areas were revealed more clearly. This improved subsurface knowledge may assist in a better design of restoration measures for monumental buildings such as Byzantine churches. [source] Synthesis of poly(cystine bisamide)-PEG block copolymers grafted with 1-(3-aminopropyl)imidazole and their phase transition behaviorsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11 2008Byung Suk Jin Abstract New biodegradable and pH-sensitive block copolymers were prepared by grafting 1-(3-aminopropyl) imidazole onto a backbone polymer formed via condensation polymerization between l -cystine and EDTA-dianhydride. The copolymer with a graft ratio of 79% exhibited a good buffering capacity and pH sensitivity. These are attributed to protonation,deprotonation of the imidazole ring at around pH 7. The copolymers with less imidazole content did not show any apparent responses to changes in pH. The particle size of the copolymer aggregate formed under basic conditions was around 200,nm and increased with decreasing pH. The critical aggregation values at pH 6.0 and 8.0, derived from the changes of intensity ratios (I1/I3) in the emission spectrums of pyrene, were approximately 0.17 and 0.05,mg/ml, respectively. The surface charge of the aggregates increased with the decreasing pH as a result of the increase in protonation of imidazole and the tertiary amine in the polymer chain. The microviscosity of hydrophobic domains was estimated using 1,6-diphenyl-1,3,5-hexatriene. The decrease of the anisotropy value under acidic conditions reflects a disruption of hydrophobic interaction. Copyright © 2008 John Wiley & Sons, Ltd. [source] A Sensitive Fluorescence Anisotropy Method for Point Mutation Detection by Using Core,Shell Fluorescent Nanoparticles and High-Fidelity DNA LigaseCHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2007Ting Deng Dr. Abstract The present study reports a proof-of-principle for a sensitive genotyping assay approach that can detect single nucleotide polymorphisms (SNPs) based on fluorescence anisotropy measurements through a core,shell fluorescent nanoparticles assembly and ligase reaction. By incorporating the core,shell fluorescent nanoparticles into fluorescence anisotropy measurements, this assay provided a convenient and sensitive detection assay that enabled straightforward single-base discrimination without the need of complicated operational steps. The assay was implemented via two steps: first, the hybridization reaction that allowed two nanoparticle-tagged probes to hybridize with the target DNA strand and the ligase reaction that generated the ligation between perfectly matched probes while no ligation occurred between mismatched ones were implemented synchronously in the same solution. Then, a thermal treatment at a relatively high temperature discriminated the ligation of probes. When the reaction mixture was heated to denature the duplex formed, the fluorescence anisotropy value of the perfect-match solution does not revert to the initial value, while that of the mismatch again comes back as the assembled fluorescent nanoparticles dispart. The present approach has been demonstrated with the discrimination of a single base mutation in codon 12 of a K-ras oncogene that is of significant value for colorectal cancers diagnosis, and the wild type and mutant type were successfully scored. Due to its ease of operation and high sensitivity, it was expected that the proposed detection approach might hold great promise in practical clinical diagnosis. [source] Characterization of site I of human serum albumin using spectroscopic analyses: Locational relations between regions Ib and Ic of site IJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2004Keishi Yamasaki Abstract Site I of human serum albumin is an important and complex region for high-affinity binding of drugs. Equilibrium dialysis showed independent binding of dansyl- L -asparagine (DNSA) and n -alkyl p -aminobenzoates (p -ABEs) to regions Ib and Ic, respectively, in the pH range 6.0,9.0. However, individual binding of DNSA increased with pH in the same range. Binding of the four n -alkyl p -ABEs strongly perturbed the circular dichroism spectrum of bound DNSA, and the effect increased with concentration and the number of carbon atoms in the alkyl moiety. A similar effect was observed by increasing pH from 6.0 to 9.0, a pH range in which human serum albumin is known to undergo the neutral-to-base transition. The spectral changes propose spatial orientation changes of DNSA at region Ib. This proposal was supported by increased fluorescence anisotropy values: n -alkyl p -ABEs binding and the pH-dependent conformational change each restricted the mobility of the naphthalene ring of bound DNSA. Despite the similar effects on the spatial orientation of DNSA, clear differences were observed between the effects of n -alkyl p -ABEs and neutral-to-base transition. The former hardly changed the affinity and maximum fluorescence emission wavelength of bound DNSA; in contrast, the latter significantly affected them. The results give new information about site I and, according to our knowledge, represent a new type of ligand interaction, because the binding site of DNSA could be changed by simultaneous binding of the n -alkyl p -ABEs without affecting the binding constant. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:3004,3012, 2004 [source] Ortho-aminobenzoic acid-labeled bradykinins in interaction with lipid vesicles: Fluorescence studyBIOPOLYMERS, Issue 5 2002R. F. Turchiello Abstract The peptide hormone bradykinin (BK) (Arg1 -Pro2 -Pro3 -Gly4 -Phe5 -Ser6 -Pro7 -Phe8 -Arg9) and its shorter homolog BK1,5 (Arg1 -Pro2 -Pro3 -Gly4 -Phe5) were labeled with the extrinsic fluorescent probe ortho -aminobenzoic acid (Abz) bound to the N-terminal and amidated in the C-terminal carboxyl group (Abz-BK-NH2 and Abz-BK1,5 -NH2). The fragment des-Arg9 -BK was synthesized with the Abz fluorescent probe attached to the 3-amino group of 2,3-amino propionic acid (DAP), which positioned the Abz group at the C-terminal side of BK sequence, constituting the peptide des-Arg9 -BK-DAP(Abz)-NH2. The spectral characteristics of the probe were similar in the three peptides, and their fluorescent properties were monitored to study the interaction of the peptides with anionic vesicles of dimyristoylphosphatidylglycerol (DMPG). Time-resolved fluorescence experiments showed that the fluorescence decay of the peptides was best described by double-exponential kinetics, with mean lifetimes values around 8.0 ns in buffer pH 7.4 that increased about 10% in the presence of DMPG vesicles. About a 10-fold increase, compared with the values in aqueous solution, was observed in the steady-state anisotropy in the presence of vesicles. A similar increase was also observed for the rotational correlation times obtained from time-resolved anisotropy decay profiles, and related to the overall tumbling of the peptides. Equilibrium binding constants for the peptide,lipid interaction were examined monitoring anisotropy values in titration experiments and the electrostatic effects were evaluated through Gouy,Chapman potential calculations. Without corrections for electrostatic effects, the labeled fragment Abz-BK1,5 -NH2 presented the major affinity for DMPG vesicles. Corrections for the changes in peptide concentration due to electrostatic interactions suggested higher affinity of the BK fragments to the hydrophobic phase of the bilayer. © 2002 Wiley Periodicals, Inc. Biopolymers 65: 336,346, 2002 [source] | ||||||||||