Short Wavelength Components Research Articles

Localization of geoid anomalies and the evolution of oceanic lithosphere: A case study from the Mendocino Fracture Zone

The thermal evolution of oceanic lithosphere is investigated by focusing on geoid offsets occurring across the Mendocino Fracture Zone, where plates with different ages are juxtaposed. Various processing techniques have been devoted to separate the geoid signal of the age contrast from regional and shorter wavelength components unrelated to the thermal structure of lithosphere. Nevertheless, due to processing differences, estimates of geoid offsets vary, and no agreement on the thermal evolution of oceanic lithosphere has been found so far. In this study, we propose to use a continuous wavelet analysis to accurately characterize the components of the geoid at different spatial scales and to estimate a new geoid slope‐age relationship from localized signals. We also apply the same wavelet transform on a set of synthetic geoid calculated with different assumptions on plate cooling. The comparison of the observed geoid offsets with those predicted from cooling models indicates that our approach can successfully remove unwanted regional contributions and isolate the geoid signature due to lithospheric cooling. Our results suggest that, contrary to previous studies, geoid slopes measured at the Mendocino Fracture Zone are compatible with both the half‐space cooling model and the plate model.

Greenland uplift and regional sea level changes from ICESat observations and GIA modelling

We study the implications of a recently published mass balance of the Greenland ice sheet (GrIS), derived from repeated surface elevation measurements from NASA’s ice cloud and land elevation satellite (ICESat) for the time period between 2003 and 2008. To characterize the effects of this new, high-resolution GrIS mass balance, we study the time-variations of various geophysical quantities in response to the current mass loss. They include vertical uplift and subsidence, geoid height variations, global patterns of sea level change (or fingerprints), and regional sea level variations along the coasts of Greenland. Long-wavelength uplifts and gravity variations in response to current or past ice thickness variations are obtained solving the sea level equation, which accounts for both the elastic and the viscoelastic components of deformation. To capture the short-wavelength components of vertical uplift in response to current ice mass loss, which is not resolved by satellite gravity observations, we have specifically developed a high-resolution regional elastic rebound (ER) model. The elastic component of vertical uplift is combined with estimates of the viscoelastic displacement fields associated with the process of glacial-isostatic adjustment (GIA), according to a set of published ice chronologies and associated mantle rheological profiles. We compare the sensitivity of global positioning system (GPS) observations along the coasts of Greenland to the ongoing ER and GIA. In notable contrast with past reports, we show that vertical velocities obtained by GPS data from five stations with sufficiently long records and from one tide gauge at the GrIS margins can be reconciled with model predictions based on the ICE-5G deglaciation model and the ER associated with the new ICESat-derived mass balance.

A Model with Two Elastically Coupled Reaction Coordinates for the Internal Friction of Proteins

The rates of protein conformational changes are usually not only limited by external but also internal friction, however, the origin and significance of this latter phenomenon is poorly understood. It is often found experimentally that a linear fit to the reciprocal of the reaction rate as a function of the viscosity of the external medium has a non-zero value at zero viscosity, signifying the presence of internal friction. Furthermore, some of the experiments performed at different temperatures indicate that the internal friction follows an Arrhenius-like temperature dependence. To explain these phenomena we suggest a simple model for protein conformational changes in terms of two elastically coupled reaction coordinates, one of which being in contact with the external medium, and the other one experiencing the rough energy landscape of the protein. Our analytical calculations, supplemented with numerical simulations demonstrate that depending on the coupling strength (which is related to the flexibility of the protein) the short-wavelength components of the energy landscape roughness can be observed as an increased apparent internal friction with an apparent activation energy.

Effect of the difference between surface and terrain models on gravity field related quantities

Topographic masses have a strong impact on the medium and short wavelength components of the gravitational signal generated by the mass of the Earth, thus digital terrain models (DTM) are routinely involved in gravity field modelling. In this study the verification of the Shuttle Radar Topographic Mission (SRTM) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM) which is a joint product of METI (Ministry of Economy, Trade and Industry of Japan) and NASA has been done by comparing them to the points of the horizontal and vertical control networks of Hungary. SRTM data fit better to geodetic ground control points than ASTER GDEM, since some artefacts have been found in ASTER elevation set which impede further use of the latter without any pre-processing. Since SRTM is an “unclassified” surface model including all those points which reflected the scanning radar signal thus tree canopy height has been compared to the differences of SRTM and DTM elevations in a hilly test area in Hungary where a local and accurate DTM having 20 m × 20 m horizontal resolution was available. Considerable agreement was indicated between forest height and model differences. Model differences were evaluated to determine their effect synthetically on gravity related quantities. Their influence on geoid height is insignificant, but the change of the investigated second derivatives of the potential is considerable.

Wave Intensity Distributions in Complex Structures

The vibro-acoustic response of mechanical structures can in general be well approximated in terms of linear wave equations. Standard numerical solution methods comprise the nite or boundary element method in the low frequency regime and statistical energy analysis in the high-frequency limit. Major computational challenges are posed by the so-called mid-frequency problem that is, composite structures where the local wavelength may vary by orders of magnitude across the components. Recently, a new approach towards determining the distribution of mechanical and acoustic wave energy in complex built-up structures improving on standard statistical energy analysis has been proposed. The technique interpolates between statistical energy analysis and ray tracing containing both these methods as limiting cases. The method has its origin in studying solutions of wave equation with an underlying chaotic ray-dynamics often referred to as wave chaos. Within the new theory dynamical energy analysis statistical energy analysis is identi ed as a low resolution ray tracing algorithm and typical statistical energy analysis assumptions can be quanti ed in terms of the properties of the ray dynamics. We have furthermore developed a hybrid statistical energy analysis/ nite element method based on random wave model assumptions for the short-wavelength components. This makes it possible to tackle mid-frequency problems under certain constraints on the geometry of the structure. Dynamical energy analysis and statistical energy analysis/ nite element method calculations for a range of multi-component model systems will be presented. The results are compared with both statistical energy analysis results and nite element method as well as boundary element method calculations. Dynamical energy analysis emerges as a numerically e cient method for calculating mean wave intensities with a high degree of spatial resolution and capturing long range correlations in the ray dynamics.

A hybrid approach for predicting the distribution of vibro-acoustic energy in complex built-up structures

Finding the distribution of vibro-acoustic energy in complex built-up structures in the mid-to-high frequency regime is a difficult task. In particular, structures with large variation of local wavelengths and/or characteristic scales pose a challenge referred to as the mid-frequency problem. Standard numerical methods such as the finite element method (FEM) scale with the local wavelength and quickly become too large even for modern computer architectures. High frequency techniques, such as statistical energy analysis (SEA), often miss important information such as dominant resonance behavior due to stiff or small scale parts of the structure. Hybrid methods circumvent this problem by coupling FEM/BEM and SEA models in a given built-up structure. In the approach adopted here, the whole system is split into a number of subsystems that are treated by either FEM or SEA depending on the local wavelength. Subsystems with relative long wavelengths are modeled using FEM. Making a diffuse field assumption for the wave fields in the short wave length components, the coupling between subsystems can be reduced to a weighted random field correlation function. The approach presented results in an SEA-like set of linear equations that can be solved for the mean energies in the short wavelength subsystems.

Darkening enhancement in SK3 glass with quartz under irradiation of femtosecond laser pulses

In this paper, the femtosecond laser-induced darkening in SK3 glass is investigated. A sample with 3-mm thickness is irradiated with 200 fs laser pulses (FLP) at 800 nm wavelength and 1 kHz repetition rate. When a piece of quartz or sapphire, which does not show darkening effect under IR irradiations, is placed in front of the sample, the laser-induced darkening is enhanced. The directly darkened region in the sample gets darker on placing a piece of quartz or sapphire in front of the sample. When a piece of ULE glass that shows darkening effect by IR-FLP irradiations is placed in front of the sample, SK3 sample does not get that dark. We believe the enhancement of the darkening in SK3 glass sample by the quartz or sapphire is related to the absorption of the short wavelength component of the white light, which is generated and not absorbed in the quartz or sapphire.

Bathymetry enhancement by altimetry-derived gravity anomalies in the East Sea (Sea of Japan)

The gravity-geologic method (GGM) was used to enhance the bathymetry of the East Sea (Sea of Japan) with satellite altimetry-derived free-air gravity anomalies and shipborne depth measurements. By comparison with the bathymetry model of Smith and Sandwell’s (SAS) approach (1994), GGM was found to have an advantage with short wavelength (≤12 km) components, while SAS better predicts longer wavelength (≥25 km) components, despite its dependency on density contrast. To mitigate this limitation, a tuning density contrast of 10.25 g/cm3 between seawater and the seafloor was primarily estimated by the downward continuation method and then validated by the check points method with GGM. Similarly, SAS is limited by the “A” value in low-pass part of the Wiener filter, which defines the effective range of the wavelength components on bathymetry. As a final result, we present an enhanced GGM bathymetry model by integrating all available data.

UV emission line shifts of symbiotic binaries

Relative and absolute emission line shifts have been previously found for symbiotic binaries, but their cause was not clear. This work aims to better understand the emission line shifts. Positions of strong emission lines were measured on archival UV spectra of Z And, AG Dra, RW Hya, SY Mus and AX Per and relative shifts between the lines of different ions compared. Profiles of lines of RW Hya and Z And were also examined. The reality of the relative shift between resonance and intercombination lines of several times ionised atoms was clearly shown except for AG Dra. This redshift shows a well defined variation with orbital phase for Z And and RW Hya. In addition the intercombination lines from more ionised atoms and especially OIV are redshifted with respect to those from less ionised atoms. Other effects are seen in the profiles. The resonance-intercombination line shift variation can be explained in quiescence by P Cygni shorter wavelength component absorption, due to the wind of the cool component, which is specially strong in inferior conjunction of this cool giant. The velocity stratification permits absorption of line emission. The relative intercombination line shifts may be connected with varying occultation of line emission near an accretion disk, which is optically thick in the continuum.

A Chemometric Analysis of Ligand-Induced Changes in Intrinsic Fluorescence of Folate Binding Protein Indicates a Link between Altered Conformational Structure and Physico-Chemical Characteristics

Ligand binding alters the conformational structure and physico-chemical characteristics of bovine folate binding protein (FBP). For the purpose of achieving further information we analyzed ligand (folate and methotrexate)-induced changes in the fluorescence landscape of FBP. Fluorescence excitation and emission two-dimensional (2D) spectra were recorded over a wide range of wavelengths on a Perkin-Elmer LS 55 spectrofluorometer at varying pH in different buffers, and the resulting three-dimensional data were subjected to a chemometric analysis, parallel factor analysis (PARAFAC). The most important finding was the occurrence of two maximum intensity emission wavelengths of tryptophan, 350 nm (component one) and 330 nm (component two). In contrast to the first component, the score of the short wavelength component increased with increasing ligation of FBP. Since the emission wavelengths of indole groups in tryptophan shorten with increasing distance from the solvent surface of proteins, an increasing number of the 11 tryptophan residues seem to reorientate from the solvent surface to the interior of FBP with increasing ligation. The sharp decrease in hydrophobicity at pI=7-8 following binding of folate accords fairly well with the disappearance of strongly hydrophobic tryptophan residues from the solvent-exposed surface of FBP. The PARAFAC has thus proven useful to establish a hitherto unexplained link between parallel changes in conformational structure and physico-chemical characteristics of FBP induced by folate binding. Parameters for ligand binding derived from PARAFAC analysis of the fluorescence data were qualitatively and quantitatively similar to those obtained from binding of radiofolate to FBP. Herein, methotrexate exhibited a higher affinity for FBP than in competition with radiofolate. This could suggest a rapid and firm complexation of folate to FBP, blocking access of competing ligands.

Investigating the influence of wavelength, light intensity and macular pigmentation on retinal straylight

Abstract Purpose To investigate the influence of wavelength, light intensity and macular pigmentation on retinal straylight. This will be tested in both phakic and pseudophakic eyes by means of color filters, as well as by comparing postoperative straylight results of eyes implanted with either clear or blue‐blocking IOLs. It has also been suggested in the literature that the yellow macular pigment reduces the effects of the short wavelength components of retinal straylight. Methods In this prospective study the straylight is measured on two groups of pseudophakic subjects: one group of 25 subjects implanted with a clear IOL (Alcon AcrySof SA60AT) and another group of 25 subjects implanted with a yellow IOL (AcrySof Natural SN60AT) using white light as well as with blue, green and red filters. These measurements are repeated on a group of age matched 25 phakic subjects. All retinal straylight measurements will be performed using the Oculus C‐Quant straylight meter. In the normal and clear IOL subjects the macular pigment is measured as well using the Tinsley M|Pod device. Results The first, preliminary results demonstrate that in healthy eyes the retinal straylight measured by the Oculus C‐Quant depends on the wavelength of the stimulus light. Measurements performed with blue light were lower than those performed in green or red light. Conclusion Stimulus light wavelength appears to have an influence on straylight measurements. Further study on a larger population is required to confirm this trend and to study how IOL color may influence this result in pseudophakic eyes. The possible influence of macular pigment on retinal straylight will be studied simultaneously.

Detection of heavy-metal lines in the spectrum of the circumstellar envelope of a post-AGB star

Splitting of the strongest absorption lines with a lower-level excitation potential χlow < 1 eV has been detected for the first time in the optical spectra of the post-AGB star V354 Lac obtained with a spectral resolution R = 60 000 at the 6-m BTA telescope. Analysis of the kinematics shows that the short-wavelength component of the split line originates in the star’s thick gas-dust envelope. Disregarding the splitting of strong lines when the chemical composition is calculated leads to overestimated overabundances of s-process elements (Ba, La, Ce, Nd) in the stellar atmosphere. The profiles of strong absorption lines have been found to be variable. The available radial-velocity data suggest the absence of any changes in the velocity field in the atmosphere and circumstellar envelope of V354 Lac over 15 years of its observations.

Development of a roughness measurement standard with irregular surface topography for improving 3D surface texture measurement

In this study, measurement standards with irregular surface topography which can be used for surface texture measuring instruments of various measurement principles are proposed, and the verification system for surface texture measuring instruments is established using the measurement standard. We have generated the software gauge data with 3D irregular surface texture using the non-causal 2D auto-regressive model (2D AR model). This model can generate periodic irregular surface topography data from specified surface texture parameters, and based on the generated software gauge data, the measurement standards were manufactured by machining with a diamond ball end mill. The short wavelength components which cannot be processed by the ball end mill were removed from the original machining data by the morphological filter. Manufactured measurement standards were measured using three types of surface texture measuring instruments. Proposed measurement standards can be used for various types of measuring instruments.

Diffusion Behavior of Isobornyl Acrylate into Photopolymerized Urethane Acrylate Films: Influence of Surface Oxidation during Curing

The diffusion of liquid isobornyl acrylate (iBoA) into photopolymerized films of urethane acrylate was shown to be strongly dependent on curing conditions. Fourier transform infrared (FTIR) monitoring of iBoA sorption into films photopolymerized in oxygen-free conditions reveals that diffusion proceeds according to Fick's laws. The diffusion coefficient and the total amount of absorbed monomer are dependent on the degree of cure of the polymer network. When polymerized in air, the films exhibit an anomalous behavior, with a lag time increasing with the dose of applied radiation. At a comparable degree of cure, films photopolymerized in air showed a retarded diffusion with a characteristic diffusion constant close or equal to the Fickian diffusion coefficient observed with the film polymerized under nitrogen, suggesting that the retardation phenomenon was due to differences in surface interactions with liquid the monomer. X-ray photoelectron spectroscopy (XPS) measurements clearly revealed the occurrence of surface oxidation attributed to direct photolysis of urethane functions by the short wavelength component of the incident UV light. The lag time observed in samples polymerized in aerobic conditions is interpreted by the existence of H-bonded hydroperoxides forming a temporary barrier retarding monomer diffusion.

Integrating long and short wavelength time and amplitude statics

The single most important parameter for accurate statics corrections is an accurate time model of the weathering, when the replacement statics model is used. Representative seismic velocities in the weathering are generally adequate. The resolution achieved with the generalized reciprocal method (GRM) and the refraction convolution section (RCS) is comparable to that achieved with the delay time method (DTM) together with one application of residual statics. It is proposed that the long wavelength components of the statics represent gross variations in the thickness of the weathered layer, and that the short wavelength components represent variations in the surface soil layers. The head wave amplitudes are inverted to generate a model of the head coefficients. Like the time model, the head coefficient model is separated into a long wavelength component which is representative of the seismic parameters at the base of the weathering, and a short wavelength component representative of the surface soil layers. In the study area, the inhomogeneities in the surface soil layer produce static variations of ±3 ms and ±2 db. It is concluded that the surface soil layer is as important a source of intra-array statics as variations in topography and thickness of the weathered layer.

Effect of conjugation with biomolecules on photoluminescence and structural characteristics of CdSe/ZnS quantum dots

The photoluminescence and photoluminescence excitation spectra, the X-ray diffraction patterns, and the effect of conjugation with biomolecules upon these characteristics are studied for silanized CdSe/ZnS quantum dots. Along with the band of annihilating excitons in the quantum dots, the luminescence spectra exhibit emission associated with defects. It is established that the emission spectrum of defects involves at least two components. It is shown that the defects are located mainly at the small-sized quantum dots; the defects responsible for the long-wavelength component are located mainly at the quantum dots larger in size than the quantum dots, at which the defects responsible for the short-wavelength component are located. It is found that conjugation with biomolecules induces not only the blue shift of the excitonic band, but transformation of the emission spectra of defects and an increase in the contribution of defects to the luminescence spectrum as well. The changes observed in the emission spectrum of defects are attributed to the formation of certain emission centers. It is shown that, when conjugated with biomolecules, the quantum dots experience increasing compression strains. This effect is responsible for the blue shift of the luminescence band of the quantum dots.

Management Method for Large Wheel Loads and Lateral Forces Using Axle-box Acceleration and Track Irregularity

Very large wheel loads and lateral forces are frequently caused by short-wavelength track irregularities. These large loads are undesirable, as they have a significant effect on the deterioration of the track material and necessitate additional track maintenance. This study focused on correlation between wheel load, lateral force, axle-box acceleration and track irregularity. First, we analyzed the frequency characteristics of the relationship between wheel loads, lateral forces, axle-box acceleration and track irregularities. Then, we proposed a technique to estimate wheel loads and lateral forces that involves a shortwavelength component using axle-box acceleration and track irregularity waveforms.

Effects of Light With Reduced Short Wavelength Components on Parameters of Circadian Rhythm and Performance in an Experimental Night Shift Model

Shift work is associated with alterations in physiological circadian patterns resulting in chronic diseases, e.g. cardiovascular disorders or major depression. The intensity and spectral composition of light is known to affect the 24 h- rhythm of our body. We investigated the effects of two different lighting environments on parameters of circadian rhythm and performance in healthy volunteers during an experimental night shift. Test light with a low color temperature was compared to normal light with a higher color temperature. Melatonin synthesis, red and white blood count, blood pressure, heart rate and indicators of performance were analyzed. Nocturnal increases in melatonin were more pronounced under low color temperature lighting conditions. This was not associated with limited degrees of arousal or vigilance. Mainte- nance of a normal nocturnal rhythm of melatonin with adapted illumination may provide a benefit for employees well- being without affecting their productivity.

Integrating long- and short-wavelength statics with the generalized reciprocal method and the refraction convolution section

Statics, the corrections for variations in the elevation of the ground surface and for the weathered layer, represent the major challenge to improving the resolution of land seismic reflection data. This study describes a simple approach to determining long- and short-wavelength refraction statics that are generally accurate to a few milliseconds with good quality data. The approach employs the generalized reciprocal method (GRM) and the refraction convolution section (RCS).The resolution achieved with the GRM and RCS is comparable to that achieved with the delay-time method (DTM) together with one application of residual statics. Furthermore, a comparison with a coincident set of data recorded with different acquisition parameters shows that there is a long-wavelength static error with the DTM but not the GRM.There is a limit in the lateral resolution of variations in the base of the weathering, which is demonstrated with triplications or ‘frowns’ in the shot records. However, the statics model also exhibits short-wavelength variations, which suggest a resolution considerably greater than that indicated to be possible by the ‘frowns’. This study proposes that the long-wavelength component represents the variations in the time model of the weathering, which are caused by gross variations in the thickness of the weathered layer, while the short-wavelength components represent the variations in the surface soil layers.With the data used in this study, variations of more than 10 ms in the time model of the weathering were observed over distances of 10 m. Such variations result in similar intra-array statics with receiver arrays over comparable distances. These intra-array statics are a major cause of reduced resolution of reflection data and poor signal-to-noise ratios with first-break refraction data, especially in arid regions. Poor quality refraction data are the major impediment to obtaining accurate refraction statics.

In vivo hyperspectral confocal fluorescence imaging to determine pigment localization and distribution in cyanobacterial cells.

Hyperspectral confocal fluorescence imaging provides the opportunity to obtain individual fluorescence emission spectra in small ( approximately 0.03-microm(3)) volumes. Using multivariate curve resolution, individual fluorescence components can be resolved, and their intensities can be calculated. Here we localize, in vivo, photosynthesis-related pigments (chlorophylls, phycobilins, and carotenoids) in wild-type and mutant cells of the cyanobacterium Synechocystis sp. PCC 6803. Cells were excited at 488 nm, exciting primarily phycobilins and carotenoids. Fluorescence from phycocyanin, allophycocyanin, allophycocyanin-B/terminal emitter, and chlorophyll a was resolved. Moreover, resonance-enhanced Raman signals and very weak fluorescence from carotenoids were observed. Phycobilin emission was most intense along the periphery of the cell whereas chlorophyll fluorescence was distributed more evenly throughout the cell, suggesting that fluorescing phycobilisomes are more prevalent along the outer thylakoids. Carotenoids were prevalent in the cell wall and also were present in thylakoids. Two chlorophyll fluorescence components were resolved: the short-wavelength component originates primarily from photosystem II and is most intense near the periphery of the cell; and the long-wavelength component that is attributed to photosystem I because it disappears in mutants lacking this photosystem is of higher relative intensity toward the inner rings of the thylakoids. Together, the results suggest compositional heterogeneity between thylakoid rings, with the inner thylakoids enriched in photosystem I. In cells depleted in chlorophyll, the amount of both chlorophyll emission components was decreased, confirming the accuracy of the spectral assignments. These results show that hyperspectral fluorescence imaging can provide unique information regarding pigment organization and localization in the cell.