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Spectrum Analysis (spectrum + analysis)
Selected AbstractsNeural responses to uninterrupted natural speech can be extracted with precise temporal resolutionEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2010Edmund C. Lalor Abstract The human auditory system has evolved to efficiently process individual streams of speech. However, obtaining temporally detailed responses to distinct continuous natural speech streams has hitherto been impracticable using standard neurophysiological techniques. Here a method is described which provides for the estimation of a temporally precise electrophysiological response to uninterrupted natural speech. We have termed this response AESPA (Auditory Evoked Spread Spectrum Analysis) and it represents an estimate of the impulse response of the auditory system. It is obtained by assuming that the recorded electrophysiological function represents a convolution of the amplitude envelope of a continuous speech stream with the to-be-estimated impulse response. We present examples of these responses using both scalp and intracranially recorded human EEG, which were obtained while subjects listened to a binaurally presented recording of a male speaker reading naturally from a classic work of fiction. This method expands the arsenal of stimulation types that can now be effectively used to derive auditory evoked responses and allows for the use of considerably more ecologically valid stimulation parameters. Some implications for future research efforts are presented. [source] Multicarrier analysis of magnetotransport data at low and high electric fieldsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2009O. V. S. N. Murthy Abstract We present some results on multicarrier analysis of magnetotransport data. Both synthetic as well as data from narrow gap Hg0.8Cd0.2Te samples are used to demonstrate applicability of various algorithms vs. nonlinear least square fitting, Quantitative Mobility Spectrum Analysis (QMSA) and Maximum Entropy Mobility Spectrum Analysis (MEMSA). Comments are made from our experience on these algorithms, and, on the inversion procedure from experimental R/,-B to S-, specifically with least square fitting as an example. Amongst the conclusions drawn are: (i) Experimentally measured resistivity (Rxx, Rxy) should also be used instead of just the inverted conductivity (,xx, ,xy) to fit data to semiclassical expressions for better fits especially at higher B. (ii) High magnetic field is necessary to extract low mobility carrier parameters. (iii) Provided the error in data is not large, better estimates to carrier parameters of remaining carrier species can be obtained at any stage by subtracting highest mobility carrier contribution to , from the experimental data and fitting with the remaining carriers. (iv)Even in presence of high electric field, an approximate multicarrier expression can be used to guess the carrier mobilities and their variations before solving the full Boltzmann equation. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Low-Temperature Synthesis of Nanocrystalline Yttrium Aluminum Garnet Powder Using TriethanolamineJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2003Yangqiao Liu Nanocrystalline yttrium aluminum garnet (YAG, Y3Al5O12) was synthesized by pyrolysis of complex compounds of aluminum and yttrium with triethanolamine [(HOCH2CH2)3N, (TEA)]. Loose and porous precursor was obtained on complete dehydration of the metal ion,triethanolamine complexes. Pure YAG powder was obtained by calcination of the precursor at 950°C. The precursor was characterized by simultaneous thermogravimetry, differential scanning calorimetry, and mass spectra analyses (TG,DSC,MS). The heat-treated powders were characterized by X-ray diffractometry (XRD), specific surface area measurements, and transmission electron microscopy (TEM). The average crystallite size as determined from X-ray line broadening and transmission electron microscopy studies was ,40 nm. The effects of the calcination temperature and the ratio of triethanolamine to mixed metal ions were also studied. [source] Application of carbon arc-generated Mo- and W-based catalyst systems to the ROMP of norborneneAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 9 2009Bülent Düz Abstract This study focuses on the application of the carbon arc-generated molybdenum- and tungsten-based catalyst systems, MoCl5C and WCl6C, to effect ring-opening metathesis polymerization (ROMP) of bicyclo[2.2.1]hept-2-ene (norbornene). The results are compared with those previously obtained by the electrochemically generated MoCl5,AlCH2Cl2 and WCl6,AlCH2Cl2 systems. The polymer products are characterized using 1H and 13C NMR, gel permeation chromatography, differential scanning calorimetry and thermo gravimetric analysis. According to NMR spectra analyses, the molybdenum-based catalyst system produced polynorbornene with ca 48% cis structure whereas tungsten system produced ca 56% cis structure polynorbornene and in both cases the polynorbornene had a blocky distribution. Copyright © 2009 John Wiley & Sons, Ltd. [source] Synthesis, growth and characterization of single crystals of pure and thiourea doped L-glutamic acid hydrochlorideCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1 2007R. Sathyalakshmi Abstract L(+)Glutamic acid hydrochloride [HOOC (CH2)2CH(NH2) COOH·HCl], a monoamino dicarboxylic acid salt of L-Glutamic acid was synthesized and the synthesis was confirmed by FTIR analysis. Solubility of the material in water was determined. Pure and Thiourea doped L-Glutamic acid hydrochloride crystals were grown by low temperature solution growth using solvent evaporation technique. XRD, UV-Vis-NIR analyses were carried out for both pure and thiourea doped crystals. The crystals were qualitatively analyzed by EDAX analysis and the presence of thiourea was confirmed. The cell parameters of L-Glutamic acid hydrochloride have been determined as a = 5.151 Å, b = 11.79 Å, c = 13.35 Å by X-ray diffraction analysis and it crystallizes in orthorhombic space group P212121. UV-Vis-NIR spectra analysis showed good optical transmission in the entire visible region for both pure and doped crystals. Micro hardness of both pure and doped crystals has been determined using Vickers micro hardness tester. The SHG efficiencies of both pure and doped crystals were determined using Kurtz powder test and pure L-Glutamic acid hydrochloride crystal was found to possess better efficiency than thiourea doped L-Glutamic acid hydrochloride crystals. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Spectral analysis and design approach for high force-to-volume extrusion damper-based structural energy dissipationEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 2 2008Geoffrey W. Rodgers Abstract High force-to-volume extrusion damping devices can offer significant energy dissipation directly in structural connections and significantly reduce seismic response. Realistic force levels up to 400,kN have been obtained experimentally validating this overall concept. This paper develops spectral-based design equations for their application. Response spectra analysis for multiple, probabilistically scaled earthquake suites are used to delineate the response reductions due to added extrusion damping. Representative statistics and damping reduction factors are utilized to characterize the modified response in a form suitable for current performance-based design methods. Multiple equation regression analysis is used to characterize reduction factors in the constant acceleration, constant velocity, and constant displacement regions of the response spectra. With peak device forces of 10% of structural weight, peak damping reduction factors in the constant displacement region of the spectra are approximately 6.5,×, 4.0,×, and 2.8,× for the low, medium, and high suites, respectively. At T,=,1,s, these values are approximately 3.6,×, 1.8,×, and 1.4,×, respectively. The maximum systematic bias introduced by using empirical equations to approximate damping reduction factors in design analyses is within the range of +10 to ,20%. The seismic demand spectrum approach is shown to be conservative across a majority of the spectrum, except for large added damping between T,=,0.8 and 3.5,s, where it slightly underestimates the demand up to a maximum of approximately 10%. Overall, the analysis shows that these devices have significant potential to reduce seismic response and damage at validated prototype device force levels. Copyright © 2007 John Wiley & Sons, Ltd. [source] Two New Aporphine Alkaloids from Litsea glutinosaHELVETICA CHIMICA ACTA, Issue 9 2005Jing-Hua Yang Chemical examination of the BuOH extract of the leaves and twigs of Litsea glutinosa collected from Xishuangbanna resulted in the isolation of two new aporphine alkaloids, namely litseglutine,A (1) and B (2), along with two known aporphine alkaloids, boldine (3) and laurolitsine (4). The structures of the new alkaloids have been elucidated on the basis of spectra analysis as 6-demethyl-9-methoxy-1,2-(methylenedioxy)aporphin-10-ol (=6,7,7a,8-tetrahydro-10-methoxy-5H -benzo[g]-1,3-benzodioxolo[6,5,4- de]quinolin-11-ol; 1) and 1,10,11-trimethoxyaporphin-2-ol (=5,6,6a,7-tetrahydro-1,10,11-trimethoxy-6-methyl-4H -dibenzo[de,g]quinolin-2-ol; 2). [source] Preparation and characterization of interpenetration polymer network films based on poly(vinyl alcohol) and poly(acrylic acid) for drug deliveryJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Yu-Mei Yue Abstract A series of full interpenetrating polymer network (full-IPN) films of poly(acrylic acid) (PAA)/poly (vinyl alcohol) (PVA) were prepared by radical solution polymerization and sequential IPN technology. Attenuated total reflectance-Fourier transform infrared spectroscopy, swelling properties, mechanical properties, morphology, and glass transition temperature of the films were investigated. FTIR spectra analysis showed that new interaction hydrogen bonds between PVA and PAA were formed. Swelling property of the films in distilled water and different pH buffer solution was studied. Swelling ratio increased with increasing PAA content of IPN films in all media, and swelling ratio decreased with increasing PVA crosslink degree. Tensile strength and elongation at break related not only to the constitution of IPNs but also to the swelling ratio of IPNs. Mechanical property of glutaraldehyde (0.5%) for poly(vinyl alcohol) crosslinking was better than that of glutaraldehyde (1.0%). DSC of the IPN films showed only a single glass transition temperature (Tg) for each sample, and Tg data showed a linear relationship with network composition. Morphology was observed a homogeneous structure, indicating the good compatibility and miscibility between PAA and PVA. Potential application of the IPN films in controlled drug delivery was also examined using crystal violet as a model drug. The release rate of the drug was higher at 37°C than 25°C for all IPNs and also increased slightly with decreasing of poly(acrylic acid) content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Low-Temperature Growth of Rutile Nanorod Thin Films and their Photon-Induced PropertyJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2008Jin-Ming Wu Thin films of well-crystallized pure rutile nanorods were deposited on Ti substrates through a simple solution approach at a low temperature of 353 K. Field emission scanning electron microscopic and atomic force microscopic investigations revealed topographies of both quasi-aligned and less-aligned nanorod arrays, depending on Ti grain facets. X-ray diffraction and Raman spectra analysis verified that the deposited nanorod thin film was phase-pure rutile. This rutile nanorod was identified to be single crystalline growing along the [001] direction by high-resolution transmission electron microscopy. UV-Vis diffuse reflectance spectra estimated a remarkable red shift in responsive light for the nanorods when compared with that of bulk rutile. Under illumination of artificial solar light, the ability of the rutile nanorod film to aid photodegradation of rhodamine B in water was argued to be superior to the rutile nanoparticles isolated from commercial Degussa P25, which was attributed to the unique rod-like nanostructure. [source] Targeted destruction of the polymerized human serum albumin binding site within the preS2 region of the HBV surface antigen while retaining full immunogenicity for this epitopeJOURNAL OF VIRAL HEPATITIS, Issue 1 2003J.-H. Park summary. The 55-amino acid (a.a.) preS2 region of the hepatitis B virus (HBV) envelope protein is highly immunogenic, and antibodies against this epitope confer seroprotection against HBV infections. Accordingly, various experimental and clinical studies for developing and evaluating HBV vaccines that include this particular epitope have been reported. However, a pitfall in using preS2 epitopes as part of a vaccinating antigen is that polymerized human serum albumin (pHSA), which is a normal constituent of the human serum, binds to and makes complexes with this particular region. Consequently, it is most likely that the antigen epitope is masked by serum pHSA and subsequently not detected by the immune system. To overcome these limitations, a novel single a.a substitute of the preS2 region was designed that corresponds to a tyrosine to serine exchange at position 140 of preS2. Competitive enzyme-linked immunosorbent assay showed that this substitution completely abolishes pHSA-binding activities in the mutated preS2 peptide, and CD spectra analysis revealed that this property might have been induced by slight conformational changes in its secondary structure. Nevertheless, the original B-cell epitope was still preserved in the mutated preS2 as determined by experimental immunization in mice. In this regard, the preS2(120,145/Y140S) sequence may be an HBV vaccine where epitopes, with intrinsic properties have been deleted without affecting the immunogenicity of the epitope itself. It is expected that the inclusion of this point mutated preS2 epitope will improve the efficacy of conventional preS2-containing HBV vaccines. [source] Flame retardancy and toughening of high impact polystyrenePOLYMER COMPOSITES, Issue 4 2007Wenguang Cui Flame retardant high impact polystyrene (HIPS) was prepared by melt blending HIPS, nano-modified aluminum trihydrate (nano-CG-ATH), red phosphorus masterbatch (RPM), and modified polyphenylene oxide (MPPO). Styrene-butadiene-styrene (SBS) was used as a toughener in this research. The effects of nano-CG-ATH, RPM, MPPO, and SBS on properties of HIPS composites were studied by combustion test, mechanical tests, and thermogravimetric analysis. The morphologies of fracture surfaces and char layers were characterized through scanning electron microscopy (SEM). The HIPS/nano-CG-ATH/RPM/MPPO (60/6/9/25) composite and its combustion residues at various temperatures were characterized by Fourier transform infrared (FTIR) spectra analysis. The results showed that the UL-94 rating of the HIPS/nano-CG-ATH/RPM/MPPO (60/6/9/25) composite reached V-0 and its char layer after flame test was integrated, but its impact strength was low. Addition of SBS improved its impact property and did not influence its thermal and flame retardant properties but lowered its tensile strength and flexural modulus to some extent. The FTIR spectra confirmed that the POC group was present in the charred substance. POLYM. COMPOS., 28:551,559, 2007. © 2007 Society of Plastics Engineers [source] Synthesis and magnetic properties of poly(p-phthaloyl-disacetylaceton-ethylenediimine) metal complexes,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 1 2002Yun-Pu Wang Abstract Macrocyclic Schiff-base ligand, bisacetylaceton-ethylenediimine (BAE) and its transition metal complexes M(BAE) (M,=,Cu2+, Ni2+) were synthesized. The complexes having characteristics of aromatic systems and well-defined one-dimensional structures, reacted with p-phthaloyl chloride, to obtain polymer complexes. The complexes were characterized by elemental analysis, inductively coupled plasma (ICP), FT-IR, and thermal analysis and show good thermal stability. ESR spectra analysis discovered that there are free radicals in the chain of polymers, indicating that a weak magnetic spin-exchange interaction operates between the metal ions and free radicals. It is found that, as the bridging p -phthaloyl group is able to propagate the magnetic exchange interaction, the polymer complexes show paramagnetic properties by measurement of temperature dependence of the magnetic property, and obey Curie,Weiss law. Copyright © 2001 John Wiley & Sons, Ltd. [source] Proteome analysis of the responses of Panax ginseng C. A. Meyer leaves to high light: Use of electrospray ionization quadrupole-time of flight mass spectrometry and expressed sequence tag dataPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 12 2003Myung Hee Nam Abstract We performed comparative proteomic analyses in order to understand the physiological responses of ginseng (Panax ginseng C. A. Meyer) to high light (HL). As a first step, we analyzed the proteins expressed in ginseng leaves. Proteins extracted from leaves were separated by two-dimensional polyacrylamide gel electrophoresis. Protein spots were identified by tandem mass spectra analysis using electrospray ionization quadrupole-time of flight mass spectrometry (ESI Q-TOF MS). We used a ginseng expressed sequence tag (EST) database as well as a nonredundant protein database from NCBI to identify proteins. Eighty-one proteins were identified using the nr protein database, 51 of which were also verified from the ginseng EST database. An additional 66 proteins were identified only from the ginseng EST database. Proteins that function in energy metabolism, protein stabilization, and protection against oxidative stress were abundant. To understand the light responses of ginseng leaves, we studied time dependent changes in expressed proteins produced by 0,4 h of HL exposure. Six HL-responsive proteins were identified: three proteins were up-regulated (cytosolic small heat-shock protein, cytosolic ascorbate peroxidase, and putative major latex-like protein) and three proteins were down-regulated (Rieske Fe/S protein, putative 3-beta hydroxysteroid dehydrogenase/isomerase-like protein, and oxygen-evolving enhancer-like protein). Our results show that the ginseng EST database combined with ESI Q-TOF MS analysis can be used to identify ginseng proteins and to elucidate the protective mechanism of ginseng against HL induced damage. [source] Quality assessment of Cortex Phellodendri by high-performance liquid chromatography coupled with electrospray ionization mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 4 2010Yong Mei Hu Abstract A simple method based on liquid chromatography coupled with diode array detection and electrospray ionization mass spectrometry (LC-DAD-ESI-MS) was developed for the quality assessment of Cortex Phellodendri (CP), which was mainly derived from two species of Phellodendron chinense Schneid and Phellodendron amurense Rupr. Total 41 compounds, including 14 phenols, 24 alkaloids and three liminoidal triterpenes were identified or tentatively characterized from the 75% methanol extract of CP samples by online ESI-MSn fragmentation and UV spectra analysis. Among them, two phenols and six alkaloids were simultaneously quantified using HPLC-DAD method. The validated HPLC-DAD method showed a good linearity, precision, repeatability and accuracy for the quantification of eight marker compounds. Furthermore, the plausible fragmentation pathway of the representative compounds were proposed in the present study. The differences of the chemical constituents content and the comprehensive HPLC profiles between the two CP species using LC-DAD-ESI-MS method are reported for the first time, indicating that the CP drugs from different resources should be used separately in the clinic. Copyright © 2009 John Wiley & Sons, Ltd. [source] Structural determinations by circular dichroism spectra analysis using coupled oscillator methods: An update of the applications of the DeVoe polarizability model,CHIRALITY, Issue 7 2004Stefano Superchi Abstract The exciton (coupled oscillator) model for optical activity is a very useful and powerful method which allows to analyze a circular dichroism (CD) spectrum in a nonempirical way, arriving at a safe assignment of the absolute configuration of organic and inorganic compounds. Usually in this model only the exciton coupling of two electrically allowed transitions (oscillators) is taken into account. This approach has the important advantage of an easy application but, sometimes, it may lead to wrong results. Thus, in this review article a more general treatment, which allows considering the simultaneous coupling of several oscillators, i.e., the DeVoe model, is presented and critically analyzed, discussing in detail the latest applications reported in the literature. In the authors opinion, since the DeVoe model joins generality and reliability requiring an almost negligible computational effort, it represents the method of choice for stereochemical assignments, even by nonspecialists. Chirality 16:422,451, 2004. © 2004 Wiley-Liss, Inc. [source] Cyclicity analysis of precipitation regimes in the Yangtze River basin, ChinaINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 5 2008S. Becker Abstract Daily precipitation data of 148 weather stations located in the Yangtze River basin (P.R. China) are analysed to detect cycles in the annual frequency of occurrence of precipitation events of 1-, 5- and 10 days duration. These events were defined in terms of exceedances of some selected thresholds. The events corresponding to 10, 25 and 30 mm thresholds for 1-, 5- and 10-day precipitation totals, respectively, are analysed in detail. For the identification of cycles, basin-wide averaged standardized time series of frequency of precipitation events are used. It is found that peaks in the smoothed time series occurred around 1974, 1982 and 1991. The Fourier, autoregressive and wavelet analyses reveal distinct cycles of 7,9 and 2,3 year periods, which dominate large parts of the time series. In addition, a shift towards a 4,5 year period in the annual frequency of precipitation events is noticed since the mid- to late-nineties. Major peaks in the annual frequency of occurrence of precipitation events are expected to occur around 2012, 2015 and 2018 according to the spectrum analyses. Copyright © 2007 Royal Meteorological Society [source] Functional and structural properties and in vitro digestibility of acylated hemp (Cannabis sativa L.) protein isolatesINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 12 2009Shou-Wei Yin Summary The effects of succinylation and acetylation on some functional, structural properties and in vitro trypsin digestibility of hemp protein isolate (HPI) were investigated. The extent of acylation gradually increased from 0 to 60,70%, with the anhydride-to-protein ratio increasing from 0 to 1.0 g g,1. Size exclusion chromatography showed that succinylation led to formation of more soluble protein aggregate than acetylation, especially at anhydride levels higher than 0.1 g g,1. Succinylation led to gradual increase in protein solubility (PS) from 30 to 85,90%, while in the acetylation case, the PS was improved only at low anhydride levels, increasing from 30 to about 50% with anhydride-to-protein ratio increasing from 0 to 0.2 g g,1. At neutral pH, the emulsifying activity indexes (EAI) of HPI was 22.1 m2 g,1, and the EAI linearly and significantly increased with the extent of acylation. The EAIs of succinylated and acetylated HPI (1.0 g g,1) were 119.0 and 54.4 m2 g,1, respectively. Differential scanning calorimetry (DSC) and intrinsic fluorescence spectrum analyses indicated gradual structural unfolding of proteins, or exposure of hydrophobic clusters to the solvent, especially at higher anhydride levels. Additionally, the in vitro trypsin digestibility was significantly improved by the succinylation. The results indicated that the chemical acylation treatment (especially succinylation) could be applied to modify some selected functional properties of hemp proteins, especially PS and emulsifying ability. [source] Climatic influence on the inter-annual variability of late-Holocene minerogenic sediment supply in a boreal forest catchmentEARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2010Gunilla Petterson Abstract Processes controlling sediment yield vary over a range of timescales, although most process-based observations are extremely short. Lake sediments, however, can be used to extend the observational timescale and are particularly useful when annually laminated (varved) sediment is present. The sediment record at Kassjön (N. Sweden) consists of ,6400 varves, each 0·5,1 mm thick. Image analysis was used to determine grey-scale variation and varve thickness from which annual minerogenic accumulation rate (MinAR) (mg cm,2 year,1) was inferred for the period 4486 BC , AD 1900. MinAR varies on annual to centennial scales and mainly reflects channel bank erosion by the inflow streams. The mineral input reflects the intensity of the spring run-off, which is dependent on the amount of snow accumulated during the winter, and hence MinAR is a long-term record of variability in past winter climate; other factors will be a variable response to catchment uplift, vegetation succession and pedogenesis. A major shift from low to high MinAR occurred ,250 BC, and peaks occurred around AD 250, 600, 1000, 1350 and 1650. Wavelet power spectrum analysis (confirmed by Fourier analyses) indicated significantly different periodicities throughout the period 4000 BC , AD 1700, including 275 years for the period 4000 BC , 2900 BC, 567 years for the period 2901 BC , 1201 BC, and 350 and 725 years for the period 1200 BC , AD 1700. The long-term, centennial scale variability (,350 years) may reflect solar forcing (cf the 385-year peak in tree-ring calibrated 14C activity) but interestingly, there is no obvious link to high frequency forcing, such as the North Atlantic Oscillation. The high resolution component of the record highlights the relevance of varved lake sediment records for understanding erosion dynamics in undisturbed forested catchments and their link to long-term climate dynamics and future climate change. Copyright © 2010 John Wiley & Sons, Ltd. [source] Applicability of pushover methods for the seismic analysis of single-column bent viaductsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2008Tatjana Isakovi Abstract An overview of the applicability of a typical single-mode pushover method (the N2 method) and two typical multi-mode pushover methods (the modal pushover analysis (MPA) and incremental response spectrum analysis (IRSA) methods) for the analysis of single column bent viaducts in the transverse direction is presented. Previous research, which was limited to relatively short viaducts supported by few columns, has been extended to longer viaducts with more bents. The single-mode N2 method is accurate enough for bridges where the effective modal mass of the fundamental mode is at least 80% of the total mass. The applicability of this method depends on (a) the ratio of the stiffness of the superstructure to that of the bents and (b) the strength of the bents. In short bridges with few columns, the accuracy of the N2 method increases as the seismic intensity increases, whereas in long viaducts (e.g. viaducts with lengths greater than 500,m) the method is in general less effective. In the case of the analyzed moderately irregular long viaducts, which are common in construction design practice, the MPA method performed well. For the analysis of bridges where the modes change significantly, depending on the seismic intensity, the IRSA method is in principle more appropriate, unless a viaduct is torsionally sensitive. In such cases, all simplified methods should be used with care. Copyright © 2008 John Wiley & Sons, Ltd. [source] A modal pushover analysis procedure to estimate seismic demands for unsymmetric-plan buildingsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 8 2004Anil K. Chopra Abstract An Erratum has been published for this article in Earthquake Engng. Struct. Dyn. 2004; 33:1429. Based on structural dynamics theory, the modal pushover analysis (MPA) procedure retains the conceptual simplicity of current procedures with invariant force distribution, now common in structural engineering practice. The MPA procedure for estimating seismic demands is extended to unsymmetric-plan buildings. In the MPA procedure, the seismic demand due to individual terms in the modal expansion of the effective earthquake forces is determined by non-linear static analysis using the inertia force distribution for each mode, which for unsymmetric buildings includes two lateral forces and torque at each floor level. These ,modal' demands due to the first few terms of the modal expansion are then combined by the CQC rule to obtain an estimate of the total seismic demand for inelastic systems. When applied to elastic systems, the MPA procedure is equivalent to standard response spectrum analysis (RSA). The MPA estimates of seismic demand for torsionally-stiff and torsionally-flexible unsymmetric systems are shown to be similarly accurate as they are for the symmetric building; however, the results deteriorate for a torsionally-similarly-stiff unsymmetric-plan system and the ground motion considered because (a) elastic modes are strongly coupled, and (b) roof displacement is underestimated by the CQC modal combination rule (which would also limit accuracy of RSA for linearly elastic systems). Copyright © 2004 John Wiley & Sons, Ltd. [source] A unified formulation of the piecewise exact method for inelastic seismic demand analysis including the P -delta effectEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 6 2003M. N. Ayd Abstract The non-linear analysis of single-degree-of-freedom (SDOF) systems provides the essential background information for both strength-based design and displacement-based evaluation/design methodologies through the development of the inelastic response spectra. The recursive solution procedure called the piecewise exact method, which is efficiently used for the response analysis of linear SDOF systems, is re-formulated in this paper in a unified format to analyse the non-linear SDOF systems with multi-linear hysteresis models. The unified formulation is also capable of handling the P-delta effect, which generally involves the negative post-yield stiffness of the hysteresis loops. The attractiveness of the method lies in the fact that it provides the exact solution when the loading time history is composed of piecewise linear segments, a condition that is perfectly satisfied for the earthquake excitation. Based on simple recursive relationships given for positive, negative and zero effective stiffnesses, the unified form of the piecewise exact method proves to be an extremely powerful and probably the best tool for the SDOF inelastic time-history and response spectrum analysis including the P-delta effect. A number of examples are presented to demonstrate the implementation of the method. Copyright © 2003 John Wiley & Sons, Ltd. [source] Isolating endogenous visuo-spatial attentional effects using the novel visual-evoked spread spectrum analysis (VESPA) techniqueEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2007Edmund C. Lalor Abstract In natural visual environments, we use attention to select between relevant and irrelevant stimuli that are presented simultaneously. Our attention to objects in our visual field is largely controlled endogenously, but is also affected exogenously through the influence of novel stimuli and events. The study of endogenous and exogenous attention as separate mechanisms has been possible in behavioral and functional imaging studies, where multiple stimuli can be presented continuously and simultaneously. It has also been possible in electroencephalogram studies using the steady-state visual-evoked potential (SSVEP); however, it has not been possible in conventional event-related potential (ERP) studies, which are hampered by the need to present suddenly onsetting stimuli in isolation. This is unfortunate as the ERP technique allows for the analysis of human physiology with much greater temporal resolution than functional magnetic resonance imaging or the SSVEP. While ERP studies of endogenous attention have been widely reported, these experiments have a serious limitation in that the suddenly onsetting stimuli, used to elicit the ERP, inevitably have an exogenous, attention-grabbing effect. Recently we have shown that it is possible to derive separate event-related responses to concurrent, continuously presented stimuli using the VESPA (visual-evoked spread spectrum analysis) technique. In this study we employed an experimental paradigm based on this method, in which two pairs of diagonally opposite, non-contiguous disc-segment stimuli were presented, one pair to be ignored and the other to be attended. VESPA responses derived for each pair showed a strong modulation at 90,100 ms (during the visual P1 component), demonstrating the utility of the method for isolating endogenous visuo-spatial attention effects. [source] Spatio-temporal climatic change of rainfall in East Java IndonesiaINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2008Edvin Aldrian Abstract Spatial and temporal rainfall analysis of the Brantas Catchment Area (DAS Brantas), East Java, from 1955 to 2005 based on 40 rainfall stations with monthly rainfall data derived from daily rainfall data has been performed. To identify the climatic trend and annual changes in the area over the last five decades, we use the empirical orthogonal function (EOF) method based on multivariate statistics, followed by the fast Fourier transform (FFT) method for the power density spectrum analysis, the non-parametric Mann-Kendall trend test and the wavelet transform method. With EOF, we found the monsoonal rainfall pattern as the most dominant in this area, which explains about 72% of all variances. Without the annual signal, the leading EOF shows significant ENSO-modulated inter-annual and seasonal variabilities, especially during the second transitional period. We found a common and significant negative trend of accumulated rainfall and a negative trend of the monsoonal strength and dominance. This finding leads to changes in the annual pattern, which are increase in the ratio of rainfall during the wet season and increase of the dry spell period or the imbalance of the annual pattern. The increased ratio of the rainfall in the wet season has led to an increased threat of drought in the dry season and extreme weather in the wet season in recent decades. The role of the orographic effect had been detected from the decadal pattern, in which the high-altitude areas have greater rainfall amount all year round. From the decadal isohyets in December/January/February (DJF) and June/July/August (JJA), the rainfall amount decreased significantly during the last five decades as shown by a persistent increase of areas with low rainfall amount. By comparing the time series of rainfall data in two locations, the mountain and coastal areas, we discovered that the dry periods have increased, mainly in the low altitude area. Copyright © 2007 Royal Meteorological Society [source] Application of k -space energy spectrum analysis for inherent and dynamic B0 mapping and deblurring in spiral imagingMAGNETIC RESONANCE IN MEDICINE, Issue 4 2010Trong-Kha Truong Abstract Spiral imaging is vulnerable to spatial and temporal variations of the amplitude of the static magnetic field (B0) caused by susceptibility effects, eddy currents, chemical shifts, subject motion, physiological noise, and system instabilities, resulting in image blurring. Here, a novel off-resonance correction method is proposed to address these issues. A k -space energy spectrum analysis algorithm is first applied to inherently and dynamically generate a B0 map from the k -space data at each time point, without requiring any additional data acquisition, pulse sequence modification, or phase unwrapping. A simulated phase evolution rewinding algorithm and an automatic residual deblurring algorithm are then used to correct for the blurring caused by both spatial and temporal B0 variations, resulting in a high spatial and temporal fidelity. This method is validated against conventional B0 mapping and deblurring methods, and its advantages for dynamic MRI applications are demonstrated in functional MRI studies. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc. [source] Cluster analysis of BOLD fMRI time series in tumors to study the heterogeneity of hemodynamic response to treatmentMAGNETIC RESONANCE IN MEDICINE, Issue 6 2003Christine Baudelet Abstract BOLD-contrast functional MRI (fMRI) has been used to assess the evolution of tumor oxygenation and blood flow after treatment. The aim of this study was to evaluate K-means-based cluster analysis as a exploratory, data-driven method. The advantage of this approach is that it can be used to extract information without the need for prior knowledge concerning the hemodynamic response function. Two data sets were acquired to illustrate different types of BOLD fMRI response inside tumors: the first set following a respiratory challenge with carbogen, and the second after pharmacological modulation of tumor blood flow using flunarizine. To improve the efficiency of the clustering, a power density spectrum analysis was first used to isolate voxels for which signal changes did not originate from noise or linear drift. The technique presented here can be used to assess hemodynamic response to treatment, and especially to display areas of the tumor with heterogeneous responses. Magn Reson Med 49:985,990, 2003. © 2003 Wiley-Liss, Inc. [source] Quantitative analysis of spatial proteoglycan content in articular cartilage with Fourier transform infrared imaging spectroscopy: Critical evaluation of analysis methods and specificity of the parametersMICROSCOPY RESEARCH AND TECHNIQUE, Issue 5 2010L. Rieppo Abstract Objective: To evaluate the specificity of the current Fourier transform infrared imaging spectroscopy (FT-IRIS) methods for the determination of depthwise proteoglycan (PG) content in articular cartilage (AC). In addition, curve fitting was applied to study whether the specificity of FT-IRIS parameters for PG determination could be improved. Methods: Two sample groups from the steer AC were prepared for the study (n = 8 samples/group). In the first group, chondroitinase ABC enzyme was used to degrade the PGs from the superficial cartilage, while the samples in the second group served as the controls. Samples were examined with FT-IRIS and analyzed using previously reported direct absorption spectrum techniques and multivariate methods and, in comparison, by curve fitting. Safranin O-stained sections were measured with digital densitometry to obtain a reference for depthwise PG distribution. Results: Carbohydrate region-based absorption spectrum methods showed a statistically weaker correlation with the PG reference distributions than the results of the curve fitting (subpeak located approximately at 1,060 cm,1). Furthermore, the shape of the depthwise profiles obtained using the curve fitting was more similar to the reference profiles than with the direct absorption spectrum analysis. Conclusions: Results suggest that the current FT-IRIS methods for PG analysis lack the specificity for quantitative measurement of PGs in AC. The curve fitting approach demonstrated that it is possible to improve the specificity of the PG analysis. However, the findings of the present study suggest that further development of the FT-IRIS analysis techniques is still needed. Microsc. Res. Tech. 2010. © 2009 Wiley-Liss, Inc. [source] Studies on dimerisation of tocopherols under the influence of methyl linoleate peroxidesMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 2 2003Marek Gogolewski Abstract The stability of plant oils is related to the level of polyunsaturated fatty acids and the presence of native antioxidants , especially tocopherols. During storage, lipids or the fat products undergo oxidation and tocopherol dimers and trimers are formed. These compounds possess reducing and antioxidant properties and participate in oxidation clearly inhibiting this process. In the present study, the correlation between levels of peroxides formed during autoxidation of methyl linoleate and simultaneous decomposition of tocopherols was examined. The peroxide value was investigated. Quantities of decomposed tocopherols and formation of their dimers were determined by high-performance liquid chromatography (HPLC). Mass spectrum analysis confirmed that the analysed compounds were dimers. Dimerisation of ,-T begins at the smaller quantity of the methyl linoleate peroxides than dimerisation of ,-T. At the beginning of methyl linoleate autoxidation dimerization of ,-T in relation to its loss was smaller. The quantity of ,-T dimers with ether bonds in total dimers pointed to faster binding of phenoxy radicals than transformation into the phenyl ones. ,-T dimers with phenyl bonds constitute about 65% of the total. The quantity of peroxides in methyl linoleate, necessary for quantitative and qualitative changes of homologous tocopherols, decreased from ,-T to ,-T. [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] Technical Note: Effect of contact lenses on measurement of the accommodation microfluctuationsOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 1 2008Mhairi Day Abstract Aim:, Dynamic measurement of accommodation in subjects with myopia usually involves recording through soft contact lenses (CLs) to correct the refractive error. Conversely, dynamic accommodation measurement in emmetropic control subjects is generally undertaken without any corrective lenses. The aim of this experiment was to determine whether CL correction affects the measurement of accommodation microfluctuations using infrared refractometry, and whether this needs to be considered in studies which attempt to compare accommodation responses between the two groups. Methods:, Ten young emmetropic subjects viewed a high contrast Maltese cross target monocularly using the right eye at a target vergence of 0 D. The subjects viewed the target under two conditions: with CL condition and without CL condition, where the subjects viewed the target with the eye only. Accommodation responses of the right eye were recorded continuously for 2 min at a sampling rate of 52 Hz using the Shin-Nippon SRW-5000 autorefractor. Results:, No significant difference (two-tailed paired t -test, t9 = ,1.499, p = 0.168) was found in mean accommodation response between the with CL (mean ± S.D. = ,0.02 ± 0.24 D) and without CL conditions (mean ± S.D. = +0.01 ± 0.25 D). No significant (two-tailed paired t -test, t9 = 0.151, p = 0.883) difference in the magnitude of the accommodation microfluctuations was found between the with CL (mean ± S.D. = 0.162 ± 0.04 D) and without CL condition (mean ± S.D. = 0.169 ± 0.04 D). Power spectrum analysis revealed no differences in the characteristics of the microfluctuations waveform between the two conditions. A control experiment carried out on a subgroup of five subjects using a negative (,3 D) CL demonstrated that there was no significant effect of the dioptric power of the CL on the magnitude of the accommodation microfluctuations (anova: F3,15 = 0.254, p = 0.782). Conclusion:, Thin soft CLs do not affect the magnitude or frequency characteristics of accommodation microfluctuations when measured using the Shin-Nippon SRW-5000. [source] The contribution of accommodation and the ocular surface to the microfluctuations of wavefront aberrations of the eyeOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 5 2006Mingxia Zhu Abstract We have used videokeratoscopy and wavefront sensing to investigate the contribution of the ocular surface and the effect of stimulus vergence on the microfluctuations of the wavefront aberrations of the eye. The fluctuations of the wavefront aberrations were quantified by their variations around the mean and by using power spectrum analysis. Integrated power was determined in two regions: 0.1,0.7 Hz (low frequencies) and 0.8,1.8 Hz (high frequencies). Changes in the ocular surface topography were measured using high-speed videokeratoscopy and variations in the ocular wavefront aberrations were measured with a wavefront sensor. The microfluctuations of wavefront aberrations of the ocular surface were found to be considerably smaller than the microfluctuations of the wavefront aberrations of the total eye. The fluctuations in defocus while viewing a closer target at 2 or 4 D were found to be significantly greater than fluctuations in defocus when viewing a far target. This increase in defocus fluctuations (p , 0.001) occurred in both the low- and high-frequency regions of the power spectra. [source] | |||||||||||||||||||||||||