Wavelength

Large-scale periodic undulations within the oceanic and continental lithospheres revealed by a number of observations, are often treated as compressive instabilities, i.e. lithospheric buckling or folding. These undulations are normally associated with intensive faulting, which raises questions on the role of faulting in the folding process, and even on the possibility of folding in highly faulted media. In this study, we demonstrate that folding can "survive" faulting and that both processes may develop concurrently, so that faulting may serve as a mechanism of folding in the brittle domain. We support this hypothesis by direct numerical modeling. The results are compared with the data on three most prominent and well-known cases of the oceanic and continental folding-like deformation ("Indian Ocean" type, "Western Gobi (central Asia)" type and "Central Australian" type). We demonstrate that under reasonable tectonic stresses, folds can develop from faults cutting through the brittle parts of the lithosphere. The predicted wavelengths and nite growth rates are in agreement with the observations. We also show that within a continental lithosphere with thermotectonic age greater than 400 My, either a bi-harmonic mode (two superimposed wavelengths, crustal and mantle one) or a coupled mode (mono-layer deformation) of inelastic folding can develop, depending on the strength and thickness of the lower crust.

This study proposes a simplified methodology to determine coal ash emissivity for the thermal design of coal-fired boilers. For this purpose, the Konopelko equation expressing spectral emissivities in relation to the wavelength and iron content in ash was modified. Spectral emissivity of coal ash is known to have a positive wavelength dependence; it is low at short wavelengths and increases with a rise in wavelengths which then remains constant (e max) over a certain wavelength (k max). In the modified equation, input parameters are e max , k max and spectral emissivity in the shorter wavelength:1.6 lm(e 1.6(T)). Based on spectral emissivity data from early studies, we determined e max , k max as 0.85 and 8 lm, respectively. To verify our modification, we compared total emissivities obtained by calculated spectral emissivities with those obtained by measured spectral emissivity for several literature. The modified equation predicts 90% of data records with an error of 15%. Additionally, to obtain e 1.6(T) without measurements, we investigated dependences of iron content in ash and temperature on e 1.6(T) using a shield tube emissometer. With reflecting these results, our equation requires only iron content in ash to obtain spectral emissivity of coal ashes. This simplified equation determines total emissivities obtained in different studies with an error of almost 20%.

A series of experiments was conducted to study the effect of twisted-tape width on the heat transfer and pressure drop with laminar flow in tubes. Data for three twisted-tape wavelengths, each with five different widths, have been collected with constant wall temperature boundary condition. Correlations for the friction factor and Nusselt number are also available. The correlations predict the experimental data to within 10 to 15 percent for the heat transfer and friction factor, respectively. The presence of the twisted tape has caused the friction factor to increase by a factor of 3 to 7 depending on Reynolds number and the twisted-tape geometry. Heat transfer results have shown an increase of 1.5 to 3 times that of plain tubes depending on the flow conditions and the twisted-tape geometry. The width shows no effect on friction factor and heat transfer in the low range of Reynolds number but has a more pronounced effect on heat transfer at the higher range of Reynolds number. It i...

... and small scale fading in indoor wireless communication channels. Reinaldo A. Valenzuela, Dmitry Chizhik and Jonathan Ling ... References [I] R. A. Valenzuela, 0. Landron, DL Jacobs, "Estimating Local Mean Signal Strength of Indoor Multipath Propagation", IEEE Trans. ...

A lattice Boltzmann model which simulates and predicts, on a massively parallel computer, wave propagation in urban environments is presented. This technique takes into account complicated boundary conditions. Two-dimensional simulations are performed starting from a city map and a renormalisation scheme is proposed to extend the results to three dimensions and adjust the wave length. The method, which is simple and easy to implement, provides good path loss predictions when compared with in situ measurements.

This paper focuses on the estimation of tsunami-wave parameters (propagation direction, propagation speed, and wavelength) using the Global Navigation Satellite System (GNSS) reflectometry (GNSS-R)-based sea surface height (SSH) measurements. By exploiting multiple surface specular reflection tracks of GNSS signals as well as the geometry of wave propagation direction and the multiple tracks, concise mathematical expressions are derived to determine the propagation direction and speed and wavelength of a tsunami wave. Real tsunami-wave data measured by buoy sensors are employed to model GNSS-R-based SSH measurements by adding Gaussian measurement noise. The simulation results demonstrate that the proposed method can achieve a propagation direction estimation accuracy of about 4.4 • and 5.9 • when the SSH error standard deviations are 10 and 20 cm, respectively. The propagation speed estimation accuracies are about 12.7 and 17.7 m/s, respectively, under the same conditions when the speed ground truth is 200 m/s. The results also show that the wavelength estimation error can be as large as 100 km when the wavelength ground truth is about 400 km. Better filtering methods are needed to improve the wavelength estimation accuracy by mitigating the effect of the SSH estimation error particularly on the wave trailing edge of small negative magnitudes.

Synthetic Aperture Radar (SAR) is an active microwave imaging method. It operates independently of Sun illumination and cloud coverage. Current spaceborne systems use wavelengths of 3 to 25 cm and achieve resolutions of 10 to 50 m. The paper attempts to explain the basic SAR imaging principles using a minimum of mathematics. Emphasis is put on the particular properties of SAR images that should be understood before interpreting these data.

ABSTRACTDue to the wave nature of light, optical microscopy has a lower-bound lateral resolution limit of about half of the wavelength of the detected light, i.e., within the range of 200 to 300 nm. The Fluorescence Fluctuation based Super Resolution Microscopy (FF-SRM) encompases a collection of image analysis techniques which rely on the statistical processing of temporal variations of fluorescence to reduce the uncertainty about the fluorophore positions within a sample, hence, bringing spatial resolution down to several tens of nm. The FF-SRM is known to be suitable for live-cell imaging due to its compatibility with most fluorescent probes and lower instrumental and experimental requirements, which are mostly camera-based epifluorescence instruments. Each FF-SRM approach has strengths and weaknesses, which depend directly on the underlying statistical principles through which enhanced spatial resolution is achieved. In this review, the basic concepts and principles behind a ran...

Elastic full waveform inversion of seismic reflection data represents a data-driven form of analysis leading to quantification of sub-surface parameters in depth. In previous studies attention has been given to P-wave data recorded in the marine environment, using either acoustic or elastic inversion schemes. In this paper we exploit both P-waves and mode-converted S-waves in the marine environment in the inversion for both P- and S-wave velocities by using wide-angle, multi-component, ocean-bottom cable seismic data. An elastic waveform inversion scheme operating in the time domain was used, allowing accurate modelling of the full wavefield, including the elastic amplitude variation with offset response of reflected arrivals and mode-converted events. A series of one- and two-dimensional synthetic examples are presented, demonstrating the ability to invert for and thereby to quantify both P- and S-wave velocities for different velocity models. In particular, for more realistic low velocity models, including a typically soft seabed, an effective strategy for inversion is proposed to exploit both P- and mode-converted PS-waves. Whilst P-wave events are exploited for inversion for P-wave velocity, examples show the contribution of both P- and PS-waves to the successful recovery of S-wave velocity.

The spectral sensitivities of middle-(M-) and long-(L-) wavelength-sensitive cones have been measured in dichromats of known genotype: M-cone sensitivities in nine protanopes, and L-cone sensitivities in 20 deuteranopes. We have used these dichromat cone spectral sensitivities, along with new luminous efficiency determinations, and existing spectral sensitivity and color matching data from normal trichromats, to derive estimates of the human M-and L-cone spectral sensitivities for 2 and 10°dia. central targets, and an estimate of the photopic luminosity function [V(u)] for 2°dia. targets, which we refer to as V 2 *(u). These new estimates are consistent with dichromatic and trichromatic spectral sensitivities and color matches.

Two different configurations of a shortwave infrared water stress index (SIWSI) are derived from the MODIS near-and shortwave infrared data. A large absorption by leaf water occurs in the shortwave infrared wavelengths (SWIR) and the reflectance from plants thereby is ...

Different nitrogen (N) treatments of four common green-leafy vegetable varieties with different leaf color: lettuce (Lactuca sativa L. var. crispa L.) with yellow green leaves, pakchoi (Brassica chinensis L.) var. aijiaohuang in Chinese (AJH) with middle green leaves, spinach (Spinacia oleracea L.) with green leaves and pakchoi (B. chinensis L.) var. shanghaiqing in Chinese (SHQ) with dark green leaves, were carried out to achieve a wide range of chlorophyll content. The relationship of vegetable leaf hyperspectral response to its chlorophyll content was examined in this study. Almost all reported successful leaf chlorophyll indices in the literature were evaluated for their ability to predict the chlorophyll content in vegetable leaves. Some new indices based on the first derivative curve were also developed, and compared with the chlorophyll indices published. The results showed that most of the indices showed a strong relation with leaf chlorophyll content. In general, modified indices with the blue or near red edge wavelength performed better than their simple counterpart without modification, ratio indices performed a little better than normalized indices when chlorophyll expressed on area basis and reversed when chlorophyll expressed on fresh weight basis. A normalized derivative difference ratio (BND: (D 722 − D 700 )/(D 722 + D 700 ) calibrated by Maire et al. [Maire, G., Francois, C., Dufrene, E., 2004. Towards universal broad leaf chlorophyll indices using PROSPECT simulated database and hyperspectral reflectance measurements. Remote Sensing of Environment 89 (1), 1-28]) gave the best results among all published indices in this study (RMSE = 22.1 mg m −2 ), then the mSR-like indices with the RMSE between 22.6 and 23.0 mg m −2 .

A new hydrophilic interaction liquid chromatographic (HILIC) method for the simultaneous determination of isoascorbic (IAA) and ascorbic acid (AA) was developed. The separation of IAA and AA was studied in various HILIC stationary phases and the influence of the composition of the mobile phase, the ionic strength and the column temperature to the chromatographic characteristics is presented. The final method used an aminopropyl column under isocratic elution with acetonitrile-100 mM ammonium acetate solution (90:10, v/v) at a flow rate of 0.4 mL/min and a detection wavelength of 240 nm. This method was validated and the calibration curves were found to be linear in the range of 1.0-65 μg/mL for both IAA and AA. The method limit of detection for IAA determination in fish tissue was 2.3 μg/g. Inter-day precision (as %RSD R ) was ranged between 0.56% and 8.3% at three concentration levels, whereas the respected recoveries ranged between 82% and 98%. This method was applied to the determination of IAA (as additive E315) in frozen redfish samples. The hyphenation of the HILIC separation with a tandem mass spectrometer was also studied and the problems encountered with negative electrospray ionization under HILIC separation conditions are discussed.

Plants have adapted very efficiently to their natural light habitat. Artificial plant illumination, therefore, requires careful design. Not only the quantity of radiation per area or volume (intensity) but also the spectral quality has to match seasonal and diurnal variations of natural global radiation as close as possible. The GSF Research Center has developed a phytotron system especially devoted to plant stress research, where these requirements are of particular importance. The phytotron consists of seven closed chambers (4 walk-in size chambers, two medium and one small sun simulator). Our contribution outlines the basic design of the lighting and presents spectral data.

Full-waveform inversion ͑FWI͒ is a challenging data-fitting procedure based on full-wavefield modeling to extract quantitative information from seismograms. High-resolution imaging at half the propagated wavelength is expected. Recent advances in high-performance computing and multifold/multicomponent wide-aperture and wide-azimuth acquisitions make 3D acoustic FWI feasible today. Key ingredients of FWI are an efficient forward-modeling engine and a local differential approach, in which the gradient and the Hessian operators are efficiently estimated. Local optimization does not, however, prevent convergence of the misfit function toward local minima because of the limited accuracy of the starting model, the lack of low frequencies, the presence of noise, and the approximate modeling of the wave-physics complexity. Different hierarchical multiscale strategies are designed to mitigate the nonlinearity and ill-posedness of FWI by incorporating progressively shorter wavelengths in the parameter space. Synthetic and real-data case studies address reconstructing various parameters, from V P and V S velocities to density, anisotropy, and attenuation. This review attempts to illuminate the state of the art of FWI. Crucial jumps, however, remain necessary to make it as popular as migration techniques. The challenges can be categorized as ͑1͒ building accurate starting models with automatic procedures and/or recording low frequencies, ͑2͒ defining new minimization criteria to mitigate the sensitivity of FWI to amplitude errors and increasing the robustness of FWI when multiple parameter classes are estimated, and ͑3͒ improving computational efficiency by data-compression techniques to make 3D elastic FWI feasible.

A simple filter is developed which transforms VLF-EM real magnetic field transfer functions into apparent resistivities. It is based on the relationship between the horizontal derivative of the surface electric field and the vertical magnetic field at the surface of a two-dimensional earth model. The performance of this simple autoregressive filter is tested for modelled and real survey data. The technique yields profiles of apparent resistivity very similar, both in magnitude and in wavelength, to those which would have been obtained using VLF-EM resistivity measurements or d.c. resistivity profiling. This low-pass filter has the advantage of reducing high-wavenumber noise in the data; therefore only the major features of the VLF-EM profile are displayed.

BACKGROUND AND OBJECTIVES A major cause of skin aging is a chronic microinflammation created by environmental conditions and ultraviolet exposures. The hand-free application on the skin of a new intense light combining a narrowband blue-light (405- to 420-nm) antiinflammatory emission and a near-infrared (850- to 890-nm) emission inducing self-defense mechanisms provides a new component to photorejuvenation and antiaging treatment protocols.STUDY DESIGN An innovative skin rejuvenation schedule is presented in this study. It includes skin exposure to the light, with concomitant glycolic peels and daily vitamin C cream regimen for group A and only topical vitamin C cream and glycolic peels for control group B.RESULTS Results show a significant improvement on pore size, rhytids, and radiance in group A. Conversely no improvement is noticed in group B except for a brief increase of skin radiance. Mechanisms of action of that specific light source are discussed.CONCLUSION The exposure to this device can clinically enhance conventional antiaging protocols in skin rejuvenation.

The photosynthetic microalga Haematococcus pluvialis, a potential source of astaxanthin, was cultivated under illumination with LEDs emitting red (λ max = 625 nm), green (λ max = 525 nm), blue (λ max = 470 nm), blue-purple (λ max = 410 nm) and purple (λ max = 380 nm) light and a fluorescent lamp, and the effects of wavelength on cell growth and astaxanthin accumulation were studied. LEDs emitting light of short wavelengths (380-470 nm) were found to induce astaxanthin accumulation of up to 5-6% per dry cell, although the induction caused the suppression of cell growth. From these results, we proposed a new strategy of cultivating H. pluvialis under illumination with red LEDs without inducing a high level of astaxanthin accumulation, and then switching to illumination with blue LEDs at a high light intensity to induce a high level of astaxanthin accumulation.

The study shows that leaf area index (LAI), leaf chlorophyll content (LCC) and canopy chlorophyll content (CCC) can be mapped in a heterogeneous Mediterranean grassland from canopy spectral reflectance measurements. Canopy spectral measurements were made in the field using a GER 3700 spectroradiometer, along with concomitant in situ measurements of LAI and LCC. We tested the utility of univariate techniques involving narrow band vegetation indices and the red edge inflection point, as well as multivariate calibration techniques, including stepwise multiple linear regression and partial least squares regression. Among the various investigated models, CCC was estimated with the highest accuracy (R 2 cv = 0.74, nRMSE cv = 0.35). All methods failed to estimate LCC (R 2 cv ≤ 0.40), while LAI was estimated with intermediate accuracy (R 2 cv values ranged from 0.49 to 0.69). Compared with narrow band indices and red edge inflection point, stepwise multiple linear regression generally improved the estimation of LAI. The estimations were further improved when partial least squares regression was used. When a subset of wavelengths was analyzed, it was found that partial least squares regression had reduced the error in the retrieved parameters. The results of the study highlight the significance of multivariate techniques, such as partial least squares regression, rather than univariate methods such as vegetation indices in estimating heterogeneous grass canopy characteristics.

Ultrasonic measurements of acoustic wavefields scattered by single spheres placed in a homogenous background medium ͑water͒ are presented. The dimensions of the spheres are comparable to the wavelength and the wavelength and represent both positive ͑rubber͒ and negative ͑teflon͒ velocity anomalies with respect to the background medium. The sensitivity of the recorded wavefield to scattering in terms of traveltime delay and amplitude variation is investigated. The results validate a linear ͑first-order͒ diffraction theory for wavefields propagating in heterogeneous media with anomaly contrasts on the order of ±15%. The diffraction theory is compared further with the exact results known from literature for scattering from an elastic sphere, formulated in terms of Legendre polynomials. To investigate the 2D case, the firstorder scattering theory is tested against 2D elastic finite-difference calculations. As the presented theory involves a volume integral, it is applicable to any geometric shape, and the scattering object does not need to be spherical or any other specific symmetrical shape. Furthermore, it can be implemented easily in seismic data inversion schemes, which is illustrated with examples from seismic crosswell tomography and a reflection experiment.

A multi-wavelength Brillouin erbium fiber laser (BEFL) with a Q-switching characteristic is demonstrated using a piece of non-zero dispersion shifted fiber (NZ-DSF) as a Brillouin gain medium (BGM) in conjunction with relaxation oscillation technique. The performance of the multi-wavelength short pulse generation is investigated for two different BEFL configurations for single and double Brillouin spacing outputs. The Q-switched BEFL generates a pulse train with repetition rates of 10.36 and 20.41 kHz whose corresponding pulse widths are 13.21 and 3.84 μs for the single and double Brillouin spacing outputs, respectively. The self-starting pulses are obtained within a low 1480-nm pump power region at a slightly higher power than the lasing threshold power. This pulse laser based on stimulated Brillouin scattering (SBS) is fairly stable at room temperature. © 2009-2012 IEEE.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6548080

One major cause of elastic wave attenuation in heterogeneous porous media is wave-induced flow of the pore fluid between heterogeneities of various scales. It is believed that for frequencies below 1 kHz, the most important cause is the wave-induced flow between mesoscopic inhomogeneities, which are large compared with the typical individual pore size but small compared to the wavelength. Various laboratory experiments in some natural porous materials provide evidence for the presence of centimeter-scale mesoscopic heterogeneities. Laboratory and field measurements of seismic attenuation in fluid-saturated rocks provide indications of the role of the wave-induced flow. Signatures of wave-induced flow include the frequency and saturation dependence of P-wave attenuation and its associated velocity dispersion, frequency-dependent shear-wave splitting, and attenuation anisotropy. During the last four decades, numerous models for attenuation and velocity dispersion from wave-induced flow have been developed with varying degrees of rigor and complexity. These models can be categorized roughly into three groups according to their underlying theoretical framework. The first group of models is based on Biot's theory of poroelasticity. The second group is based on elastodynamic theory where local fluid flow is incorporated through an additional hydrodynamic equation. Another group of models is derived using the theory of viscoelasticity. Though all models predict attenuation and velocity dispersion typical for a relaxation process, there exist differences that can be related to the type of disorder ͑periodic, random, space dimension͒ and to the way the local flow is incorporated. The differences manifest themselves in different asymptotic scaling laws for attenuation and in different expressions for characteristic frequencies. In recent years, some theoretical models of wave-induced fluid flow have been validated numerically, using finite-difference, finite-element, and reflectivity algorithms applied to Biot's equations of poroelasticity. Application of theoretical models to real seismic data requires further studies using broadband laboratory and field measurements of attenuation and dispersion for different rocks as well as development of more robust methods for estimating dissipation attributes from field data.

Sprites are a spectacular type of transient luminous events (TLE) which occur above thunderstorms immediately after lightning. They have shapes of giant jellyfish, carrots or columns and last tens of milliseconds. In Earth's atmosphere, sprites mostly emit in red and blue wavelengths from excited N 2 and N 2 + and span a vertical range between 50 and 90 km above the surface. The emission spectra, morphology and occurrence heights of sprites reflect the properties of the planetary atmosphere they inhabit and are related to the intensity of the initiating parent lightning.. This paper presents results of theoretical calculations of the expected occurrence heights of sprites above lightning discharges in the CO 2 atmosphere of Venus, the N 2 atmosphere of Titan and the H 2 -He atmosphere of Jupiter. The expected emission features are presented and the potential of detecting sprites in planetary atmospheres by orbiting spacecraft is discussed.

In dating applications, detection of thermal or optically stimulated (IR & visible) luminescence is overwhelmingly biased towards the UV-blue portions of the electromagnetic spectrum. This bias is based on a number of factors including the generally good performance of UV-blue emission luminescence as an integrating dosimeter for quartz over the time range ca. 0 -150 ka, the historical development of blue-sensitive photomultiplier tubes and problems in the separation of longer wavelength emissions from thermal and other background contributions. Research into the use of orange-red and far-red luminescence emissions has, however, also progressed.

Cherchant à utiliser au maximum les données provenant d'un pseudo-profil et à développer de façon accrue le concept d'indice de rugosité international (IRI), une nouvelle approche d'interprétation de l'IRI est présentée. Elle est basée sur la décomposition du pseudo-profil initial d'une chaussée en pseudo-profils élémentaires selon différentes longueurs d'onde bien déterminées. L'hypothèse sous-jacente à cette approche est que l'IRI calculé sur ces pseudoprofils élémentaires est proportionnel à la contribution de chacun d'eux à l'état de la chaussée. À partir de cette hypothèse, différentes techniques d'analyse du pseudo-profil sont présentées. Quelques définitions et mises en contexte sont d'abord présentées. L'approche est ensuite décrite : (i) La technique de filtrage; (ii) Le calcul de l'IRI des pseudoprofils élémentaires; (iii) Les outils d'analyse complémentaires. Finalement, un exemple d'application décrit la démarche.

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Airborne Visible/IR Image Spectrometer (AVIRIS) data were used to characterize hot spring deposits in the Lower, Midway, and Upper Geyser Basins of Yellowstone National Park from the visible/near infrared (VNIR) to thermal infrared (TIR) wavelengths. Field observations of these basins provided the critical ground-truth for comparison with the remote sensing results. Fourteen study sites were selected based on diversity in size, deposit type, and thermal activity. Field work included detailed site surveys such as land cover analysis, photography, Global Positioning System (GPS) data collection, radiometric analysis, and VNIR spectroscopy. Samples of hot spring deposits, geyser deposits, and soil were also collected. Analysis of ASTER data provided broad scale characteristics of the hot springs and their deposits, including the identification of thermal anomalies. AVIRIS high spectral resolution short-wave infrared (SWIR) spectroscopy provided the ability to detect hydrothermally altered minerals as well as a calibration for the multispectral SWIR ASTER data. From the image analysis, differences in these basins were identified including the extent of thermal alteration, the location and abundance of alteration minerals, and a comparison of active, nearextinct, and extinct geysers. We determined the activity level of each region using a combination of the VNIR-SWIR-TIR spectral differences as well as the presence of elevated temperatures, detected by the TIR subsystem of ASTER. The results of this study are applicable to the exploration of extinct mineralized hydrothermal deposits on both Earth and Mars. D

En este laboratorio se analiza el comportamiento de una onda estacionaria en un modelo real de laboratorio donde se nota la relación entre la frecuencia y la tensión, la velocidad de la onda y la tensión, la longitud de la cuerda y la frecuencia; además de otros aspectos importantes en el estudio del movimiento de una onda que nos ayudaron a comprender mejor fenómenos cotidianos asociados con dicho tema como lo son el análisis de la importancia de las cuerdas en los instrumentos musicales, el eco; entre otras.

An UV-sensitive class of photoreceptors exists in all regions of the retinas of mantis shrimps. UV photosensitivity apparently resides in rhabdomeres of the eighth retinular cell (RS) that lies atop each rhabdom; and in ommatidia where the Rg rhabdomere consists of microvilli parallel in a single direction, ~nsiti~~ is maximal when the e-vector of plainly light is parallel to the mi~ro~Ui, Spectral sensitivity of the UV ~otor~eptor peaks at 345 um and is best explained by the presence of a photopigment with I.,,,,., near 325 nm overlain by material that absorbs UV light at wavelengths below z 350 nm. Rhabdomeres of RS cells in several different retinal regions of a variety of species examined contain a photopigment absorbing maximally below 340 nm. Under appropriate conditions, a metapigment with A

A 2D finite-difference, frequency-domain method was developed for modeling viscoacoustic seismic waves in transversely isotropic media with a tilted symmetry axis. The medium is parameterized by the P-wave velocity on the symmetry axis, the density, the attenuation factor, Thomsen's anisotropic parameters ␦ and ⑀ , and the tilt angle. The finite-difference discretization relies on a parsimonious mixed-grid approach that designs accurate yet spatially compact stencils. The system of linear equations resulting from discretizing the time-harmonic wave equation is solved with a parallel direct solver that computes monochromatic wavefields efficiently for many sources. Dispersion analysis shows that four grid points per P-wavelength provide sufficiently accurate solutions in homogeneous media. The absorbing boundary conditions are perfectly matched layers ͑PMLs͒. The kinematic and dynamic accuracy of the method was assessed with several synthetic examples which illustrate the propagation of S-waves excited at the source or at seismic discontinuities when ⑀ Ͻ ␦ . In frequency-domain modeling with absorbing boundary conditions, the unstable S-wave mode is not excited when ⑀ Ͻ ␦ , allowing stable simulations of the P-wave mode for such anisotropic media. Some S-wave instabilities are seen in the PMLs when the symmetry axis is tilted and ⑀ Ͼ ␦ .

Simple methods for HPTLC peak purity assessment and identification of the HPTLC peaks were presented. The spectrodensitograms -selected at different time intervals across the elution time of the HPTLC peak -were extracted and digital algorithms for manipulating the data were carried out in the wavelength domain. Three different methods were developed for testing the HPTLC peak purity using the mathematically transformed data of the spectrodensitograms. These included the method of relative absorption, the method of log A versus the wavelength plots and the derivative (first, second, third and fourth) method. The identification of the HPTLC peaks was based on the use of the derivative profile of the spectrodensitogram and the derivative ratios as fingerprints for the compounds. The wavelengths of absorbance and derivative (first, second, third and fourth) optima of the extracted spectrodensitograms were allocated. The data were compared with those obtained using the corresponding reference standard. The validity of the proposed methods was performed by chromatography of a mixture containing mebendazole and methylparaben as a model versus the winCATS ® spectral correlation method as a reference method. The study indicated that the proposed concept is a reliable non-confusing valuable tool for testing the purity and identity of the HPTLC peaks as the results are easily and rigorously interpreted.

For various reasons, aerial archaeologists use(d) film when studying their objects in the Near InfraRed (NIR). However, even the use of colour InfraRed (CIR) emulsions remained severely restricted till today due to some ignorance or a severe lack of knowledge about the subject and – not at least – the critical imaging process. This error-prone film-based workflow belongs now to the past, thanks to the advent of digital cameras. In this article, two new approaches will be outlined, both in an attempt to overcome the constraints on the common archaeological interpretation of varying visible colours in vegetation: the use of modified hand-held digital cameras to photograph the NIR spectrum on the one hand, as well as future plans to digitally capture both Red and NIR wavelengths simultaneously on the other. Besides additional technical background information on NIR photography, the paper treats the advantages (and disadvantages) of NIR to normal archaeological aerial imaging. In the end, an introduction of a new, remotely controlled system to support (aerial) archaeologists in their (NIR) photography is given together with several approaches to NIR image processing.

Elastic full waveform inversion of seismic reflection data represents a data-driven form of analysis leading to quantification of sub-surface parameters in depth. In previous studies attention has been given to P-wave data recorded in the marine environment, using either acoustic or elastic inversion schemes. In this paper we exploit both P-waves and mode-converted S-waves in the marine environment in the inversion for both P-and S-wave velocities by using wide-angle, multi-component, ocean-bottom cable seismic data. An elastic waveform inversion scheme operating in the time domain was used, allowing accurate modelling of the full wavefield, including the elastic amplitude variation with offset response of reflected arrivals and mode-converted events. A series of one-and two-dimensional synthetic examples are presented, demonstrating the ability to invert for and thereby to quantify both P-and S-wave velocities for different velocity models. In particular, for more realistic low velocity models, including a typically soft seabed, an effective strategy for inversion is proposed to exploit both P-and mode-converted PS-waves. Whilst P-wave events are exploited for inversion for P-wave velocity, examples show the contribution of both P-and PS-waves to the successful recovery of S-wave velocity.

Percent reflectance of corals is perhaps the most important remotely sensed data that can be related to their biophysical properties. Because most of the biophysical variables of corals (i.e., pigment content, live cover and algal overgrowth) are related to their reflectance spectra, the analysis and inversion of the spectra may provide an account of these variables. Our research was aimed at determining the relationship between the percent live cover and reflectance of corals. Two wavelength bands (405-425 nm, and 590-600 nm) were identified to establish the relationship. A linear relationship was observed, which showed higher correlation (R 2 = 0.886) at 405-425 nm when compared to 590-600 nm (R 2 = 0.602). Validation methods revealed that 405-425 nm wavelength range provided a better relationship than 590-600 nm in predicting percent live cover of corals.

Electrical, seismic, and electromagnetic methods can be used for noninvasive determination of subsurface physical and chemical properties. In particular, we consider the evaluation of water salinity and the detection of surface contaminants. Most of the relevant properties are represented by electric conductivity, P-wave velocity, and dielectric permittivity. Hence, it is important to obtain relationships between these measurable physical quantities and soil composition, saturation, and frequency. Conductivity in the geoelectric frequency range is obtained with Pride's model for a porous rock. (The model considers salinity and permeability.) White's model of patchy saturation is used to calculate the P-wave velocity and attenuation. Four cases are considered: light nonaqueous phase liquid (LNAPL) pockets in water, dense nonaqueous phase liquid (DNAPL) pockets in water, LNAPL pockets in air, and DNAPL pockets in air. The size of the pockets (or pools), with respect to the signal wavelength, is modeled by the theory. The electromagnetic properties in the GPR frequency range are obtained by using the Hanai–Bruggeman equation for two solids (sand and clay grains) and two fluids (LNAPL or DNAPL in water or air). The Hanai–Bruggeman exponent (1/3 for spherical particles) is used as a fitting parameter and evaluated for a sand/clay mixture saturated with water.Pride's model predicts increasing conductivity for increasing salinity and decreasing permeability. The best-fit exponent of the Hanai–Bruggeman equation for a sand/clay mixture saturated with water is 0.61, indicating that the shape of the grains has a significant influence on the electromagnetic properties. At radar frequencies, it is possible to distinguish between a water-saturated medium and a NAPL-saturated medium, but LNAPL- and DNAPL-saturated media have very similar electromagnetic properties. The type of contaminant can be better distinguished from the acoustic properties. P-wave velocity increases with frequency, and has dissimilar behaviour for wet and dry soils.

Optical absorbance measurements are presented for discontinuous films of gold, aluminum, and copper as a function of wavelength, polarization, and angle. Anomolous peaks in the absorbance spectra are observed for all three metals. Two peaks are detected for gold, and one peak is detected for both aluminum and copper. Comparison with electromagnetic theory is made on the basis that the microstructures can be modeled as prolate spheroids.

The finite nature of typical small seismic arrays used in conjunction with spatial autocorrelation (SPAC) processing for observing the microtremor wavefield gives rise to predictable perturbations of the SPAC spectrum when sources of seismic noise are confined to a restricted range of azimuths. Such perturbations are especially evident at higher frequencies where wavelengths are of the order of the array radius. The effects are readily modeled and show that the triangular array geometries in common usage for microtremor studies require azimuthal distributions of wave energy of order 60! or greater in order to have a high probability of being free of such perturbations. The imaginary component of the SPAC spectrum, which is ideally zero for a sufficiently dense circular array and/or a sufficiently isotropic wave field, is in practice often non-zero and provides three quality-control indicators: 1) an indication of insufficient spatial averaging, 2) an empirical measure of the level of statistical uncertainty in SPAC spectral estimates, and 3) an indication of departures from planewave stationarity of the seismic noise wave field.

María Belén Muñoz-García is an assistant professor of stratigraphy in the Universidad Complutense de Madrid where she obtained her Ph.D. in 2007. Her research interests include the sedimentology of continental depositional settings and the geochemistry of recent speleothems with the aim of obtaining paleoclimatic proxies.

"Stoneley guided waves in a fluid-filled fracture generally
have larger amplitudes than other waves; therefore, their
properties need to be incorporated into more realistic models.
A fracture is modeled as an infinite layer of viscous fluid
bounded by two elastic half-spaces with identical parameters.
For small fracture thickness, a simple dispersion equation
for wave-propagation velocity is obtained. This velocity
is much smaller than the velocity of a fluid wave in a Biottype
solution, in which fracture walls are assumed to be rigid.
At seismic prospecting frequencies and realistic fracture
thicknesses, the Stoneley guided wave has wavelengths on
the order of several meters and a quality factor Q exceeding
10, which indicates the possibility of resonance excitation in
fluid-bearing rocks. The velocity and attenuation of Stoneley
guided waves are distinctly different at low frequencies for
water and for oil. The predominant role of fractures in fluid
flow at field scales is supported by permeability data, showing
an increase of several orders of magnitude when compared
with values obtained at laboratory scales. The data suggest
that Stoneley guided waves should be taken into account
in theories describing seismic wave propagation in fluid-saturated
rocks."

Experiments were performed to measure the various sound-wave propagation parameters of two kinds of gravel, a crushed limestone and a stream-formed ''pea gravel", at frequencies between 25 and 200 Hz. The apparatus was a very large standing-wave tube with an array of microphones along its entire length. Measurements were made with the tube in the vertical position, filled to various depths, with a pressuredoubling barrier at the bottom. Values were determined for wavelength and attenuation in the gravel and for input impedance at the boundary between gravel and air. The basic analysis method was to fit the parameters of a presumed Green's function representing the standing wave in the tube to the measured sound pressure amplitudes measured by the microphones. This worked well for some frequencies and some depths of gravel. In other cases, various modifications of the method gave more consistent results. For crushed limestone, the estimates of phase velocity and attenuation increased monotonically with frequency, ranging between 150 and 250 m/s and 0.1 and 0.8 Np/m, respectively. For pea gravel, the estimates increased monotonically with frequency, with values between 160 and 205 m/s and 0.4 and 1.1 Np/m, respectively.

A simple technique for achieving multi-wavelength tunable multi-wavelength Brillouin fiber laser (BFL) based on dual-pass configuration is demonstrated. The BFL uses a piece of 10 km long non-zero dispersion shifted fiber (NZ-DSF) as a Brillouin gain medium to obtain odd-order Brillouin Stokes waves as an output with the line spacing of 0.16 nm (20 GHz) between each two consecutive waves by employing even-order Brillouin Stokes to improve output performance of the laser. With a BP of 15.3 dBm, at least 15 odd-order Brillouin Stokes and anti-Stokes lines are generated. The laser is room temperature stable, tunable over 50 nm wavelength range and has an optical signal to noise ratio of more than 30 dB at 1560 nm region. This Brillouin fiber laser can operate at any wavelength depending on the Brillouin pump (BP) wavelength used. © 2011 Pleiades Publishing, Ltd.

http://link.springer.com/article/10.1134/S1054660X11010166

Yagi-Uda Antenna is a widely used roof top DVB-T2 receiver antenna due to its high forward gain capability, low cost and ease in construction. In Tanzania, there have been some complaints which were logged to Tanzania Communications Regulatory Authority (TCRA) by the customers on the poor reception of DVB-T2 signals which may be caused by signal degradation. In this paper we propose enhancement of the gain of the Yagi antenna so as to improve the reception signals of the DVB-T2. This will help solve those complaints. It is well known that the increase in radiation pattern causes the increase in directivity and hence gain which will have an impact on good quality of reception for DVB-T2 signals coming from the transmitter. After carefully design and simulation in FEKO simulating software by adding the number of director elements and making some adjustments on the length and spacing between the elements, we managed to increase the gain of the antenna by 4.7dB. This is significant impr...