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Resonance Peaks (resonance + peak)
Selected AbstractsGold Nanocages for Biomedical Applications,ADVANCED MATERIALS, Issue 20 2007E. Skrabalak Abstract Nanostructured materials provide a promising platform for early cancer detection and treatment. Here we highlight recent advances in the synthesis and use of Au nanocages for such biomedical applications. Gold nanocages represent a novel class of nanostructures, which can be prepared via a remarkably simple route based on the galvanic replacement reaction between Ag nanocubes and HAuCl4. The Au nanocages have a tunable surface plasmon resonance peak that extends into the near-infrared, where the optical attenuation caused by blood and soft tissue is essentially negligible. They are also biocompatible and present a well-established surface for easy functionalization. We have tailored the scattering and absorption cross-sections of Au nanocages for use in optical coherence tomography and photothermal treatment, respectively. Our preliminary studies show greatly improved spectroscopic image contrast for tissue phantoms containing Au nanocages. Our most recent results also demonstrate the photothermal destruction of breast cancer cells in vitro by using immuno-targeted Au nanocages as an effective photo-thermal transducer. These experiments suggest that Au nanocages may be a new class of nanometer-sized agents for cancer diagnosis and therapy. [source] Chemical modification of polystyrene by low-energy (<100 eV) electron irradiation studied by mass spectrometryJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008S. Massey Abstract Dip-coated thin films of polystyrene were chemically modified (degraded) by low-energy electron irradiation (0,100 eV). The resulting degradation was studied by mass spectrometry with variable electron energy. In the negative-ion mode, H, was observed and was associated with two phenomena. The resonant structure at 9.1 ± 0.4 eV was associated with dissociative electron attachment. The energy of the resonance peak agreed with the results obtained for organic molecules. At a higher energy, a monotonic rise of the emission yield was observed and was associated with nonresonant dipolar dissociation. More mass fragments were observed in the positive-ion mode. The predominant ion was H+ at 100 eV of electron irradiation, and alkyl ions were detected at higher masses. Emission thresholds were measured for the most predominant positive ions. The shape of the emission curve showed that there was no resonant process in the formation of these ions. The energy threshold was measured at about 20 eV, and this meant that the carbon structure of the polymer broke with a recombination of the degradation products with hydrogen atoms before the emission occurred. Below 19 eV, there was only hydrogen loss; this implied that the possible degradation mechanisms did not break the general carbon structure of the material, leading to crosslinking. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Electronic transport through large quantum dots in the Kondo regimePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2003P. Stefa Abstract Conductance through a large two-level quantum dot is investigated theoretically in the strong coupling regime. In large quantum dots the separation between discrete levels becomes smaller than the level width due to strong hybridization with electrodes. In such circumstances, apart from strong electronic correlations in the quantum dot, the indirect interaction between both the spatial levels comes into play. It takes place in lateral quantum dots, where the spatial level index is not conserved during the hybridization process with electrodes. This interaction shifts the Kondo resonance peak in the density of states out of the Fermi surface and alters its intensity. This feature can be observed in the differential conductance dependence vs. bias voltage. The virtual inter-level mixing is suppressed for temperatures above the Kondo temperature of the system. The results of theoretical predictions are compared with the results of experimental conductance measurements performed on large quantum dots and some non-typical conductance features are clarified. [source] Optical effect of diamond-like carbon film coating of long-period optical fiber gratingsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2007M. Smietana Abstract The paper presents diamond-like carbon (DLC) film as a coating for long-period grating (LPG) optical fiber structure. The spectral response of a DLC-coated LPG structure is strictly dependent on Radio Frequency Plasma Chemical Vapour Deposition (RF PCVD) process parameters. The paper discusses the influence of DLC deposition time and self-bias voltage to shift of the LPG resonance peak and explores the possibility of using the structure as a refractometric sensor. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Three-dimensional models of reservoir sediment and effects on the seismic response of arch damsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 10 2004O. Maeso Abstract The important effects of bottom sediments on the seismic response of arch dams are studied in this paper. To do so, a three-dimensional boundary element model is used. It includes the water reservoir as a compressible fluid, the dam and unbounded foundation rock as viscoelastic solids, and the bottom sediment as a two-phase poroelastic domain with dynamic behaviour described by Biot's equations. Dynamic interaction among all those regions, local topography and travelling wave effects are taken into account. The results obtained show the important influence of sediment compressibility and permeability on the seismic response. The former is associated with a general change of the system response whereas the permeability has a significant influence on damping at resonance peaks. The analysis is carried out in the frequency domain considering time harmonic excitation due to P and S plane waves. The time-domain results obtained by using the Fourier transform for a given earthquake accelerogram are also shown. The possibility of using simplified models to represent the bottom sediment effects is discussed in the paper. Two alternative models for porous sediment are tested. Simplified models are shown to be able to reproduce the effects of porous sediments except for very high permeability values. Copyright © 2004 John Wiley & Sons, Ltd. [source] Analytical solutions for dynamic pressures of coupling fluid,porous medium,solid due to SV wave incidenceINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 12 2009Jin-Ting Wang Abstract This paper presents the results of theoretical investigation on the dynamic coupling of an ideal fluid-porous medium-elastic half-space system subjected to SV waves to study the effect of sediment on the seismic response of dams for reservoirs that are deposited with a significant amount of sediment after a long period of operation. The effects of the porous medium and the incident wave angle on dynamic pressures in the overlying ideal fluid are analyzed, and the reflection and transmission coefficients of the wave at the material interfaces are derived using an analytical solution in terms of displacement potentials. The numerical test of modeling shows that the dynamic pressures significantly depend on the properties of porous medium. The fully saturated porous medium reduces the response peaks slightly, while the partially saturated porous medium causes a considerable increase in the resonance peaks. Copyright © 2009 John Wiley & Sons, Ltd. [source] NMR-based analysis of structure of heteroleptic triple-decker (phthalocyaninato) (porphyrinato) lanthanides in solutionsMAGNETIC RESONANCE IN CHEMISTRY, Issue 7 2010Kirill P. Birin Abstract A novel approach for the structural analysis of heteroleptic triple-decker (porphyrinato)(phthalocyaninato) lanthanides(III) in solutions is developed. The developed approach consists in molecular mechanics (MM+) optimization of the geometry of the complex taking into account the lanthanide-induced shift (LIS) datasets. LISs of the resonance peaks in 1H NMR spectra of a series of symmetric complexes [An4P]Ln[(15C5)4Pc]Ln[An4P], where An4P2, is 5,10,15,20-tetrakis(4-methoxyphenyl)porphyrinato-dianion, [(15C5)4Pc]2, is 2,3,9,10,16,17,24,25-tetrakis(15-crown-5)phthalocyaninato-dianion and Ln = La, Ce, Pr, Nd, Sm, Eu, are analyzed. Analysis of LISs showed two sets of protons in the molecule with opposite signs of shift. Two-nuclei analysis of LISs testifies isostructurality of the whole series of investigated complexes in solution despite contraction of the lanthanide ions. Model-free separation of contact and dipolar contributions of LISs was performed with one-nucleus technique and did not show changes in contact and dipolar terms within the investigated series. MM+ optimization of the molecular structure allowed the interpretation of features of LIS for each particular group of protons. Parameterization of MM + -optimized model of molecule with values of structure-dependent dipolar contributions of LIS allows the development of the precise structural model of the triple-decker complex in solution. This approach allows the determination of the geometry and structure of the sandwich macrocyclic tetrapyrrolic complexes together with conformational analysis of flexible peripheral substituents in solutions. The developed method can be applied with minor modifications for the determination of structural parameters of other types of lanthanides(III) complexes with tetrapyrrolic ligands and also supramolecular systems based on them. Copyright © 2010 John Wiley & Sons, Ltd. [source] Solid-state NMR studies of the molecular structure of TaxolMAGNETIC RESONANCE IN CHEMISTRY, Issue 6 2006Yu Ho Abstract Solid-state 13C{1H} cross-polarization/magic angle spinning spectroscopy (CP/MAS) has been utilized to extract the molecular structure information of Taxol, which is an anti-tumor therapeutic medicine extracted from the yew bark. The 13C signals have chemical shift values quite consistent with those measured in solution phase, and the overall chemical shift range is over 200 ppm. Notably, most of the 13C resonances of the taxane ring have two clearly resolved spectral components except the resonance peaks of C-15, C-16 and C-17, which are located at the central part of the taxane ring. On the basis of our NMR data, we propose that these doublets originate from two slightly different molecular conformations of the taxane ring and still the central part of the ring remains structurally similar. Furthermore, it is demonstrated that the 13C chemical shift difference deduced from the doublet splittings can serve as a direct measure of the structural difference between the two conformations, which could possibly correlate with the anti-tumor activity of Taxol. Copyright © 2006 John Wiley & Sons, Ltd. [source] Spectrum separation resolves partial-volume effect of MRSI as demonstrated on brain tumor scansNMR IN BIOMEDICINE, Issue 10 2008Yuzhuo Su Abstract Magnetic resonance spectroscopic imaging (MRSI) is currently used clinically in conjunction with anatomical MRI to assess the presence and extent of brain tumors and to evaluate treatment response. Unfortunately, the clinical utility of MRSI is limited by significant variability of in vivo spectra. Spectral profiles show increased variability because of partial coverage of large voxel volumes, infiltration of normal brain tissue by tumors, innate tumor heterogeneity, and measurement noise. We address these problems directly by quantifying the abundance (i.e. volume fraction) within a voxel for each tissue type instead of the conventional estimation of metabolite concentrations from spectral resonance peaks. This ,spectrum separation' method uses the non-negative matrix factorization algorithm, which simultaneously decomposes the observed spectra of multiple voxels into abundance distributions and constituent spectra. The accuracy of the estimated abundances is validated on phantom data. The presented results on 20 clinical cases of brain tumor show reduced cross-subject variability. This is reflected in improved discrimination between high-grade and low-grade gliomas, which demonstrates the physiological relevance of the extracted spectra. These results show that the proposed spectral analysis method can improve the effectiveness of MRSI as a diagnostic tool. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||||||||