Transmission Anomalies Research Articles

3D tomographic amplitude inversion for compensating amplitude attenuation

Spatial variations in the transmission properties of the overburden cause seismic amplitude distortions on deeper horizons and hence pose problems to the AVO analysis. One of the common causes of these transmission anomalies is gas within shallow sediment. This induces anomalous amplitude decay in zones beneath the gas anomaly, often making the identification and interpretation of deeper reflectors difficult. This in turn affects the ability to accurately predict reservoir properties. Thus, there is a need to compensate the amplitude loss caused by this kind of transmission anomalies.

A new use for long-term frozen brain tissue: Golgi impregnation

The study of dendritic spine shape and number has become a standard in the analysis of synaptic transmission anomalies since a considerable number of neuropsychiatric and neurological diseases have their foundation in alterations in these structures. One of the best ways to study possible alterations of dendritic spines is the use of Golgi impregnation. Although usually the Golgi method implies the use of fresh or fixed tissue, here we report the use of Golgi–Cox for the staining of human and animal brain tissue kept frozen for long periods of time. We successfully applied the Golgi–Cox method to human brain tissue stored for up to 15 years in a freezer. The technique produced reliable and reproducible impregnation of dendrites and dendritic spines in different cortical areas. We also applied the same technique to rat brain frozen for up to 1 year, obtaining the same satisfactory results. The fact that Golgi–Cox can be successfully applied to this type of tissue adds a new value for hundreds of frozen human or animal brains kept in the freezers of the laboratories, that otherwise would not be useful for anything else. Researchers other than neuroanatomists, i.e. in fields such as biochemistry and molecular biology can also benefit from a simple and reliable technique that can be applied to tissue left from their primary experiments.

Intrinsic localized modes in photonic crystal waveguides composed of a periodic mixed array of linear and Kerr nonlinear dielectric media

A theoretical treatment is given of intrinsic localized modes in waveguides and in junctions of waveguides formed inside two-dimensional photonic crystals. Two-dimensional photonic crystals are periodic arrays of parallel-axed dielectric cylinders, and the electromagnetic modes of interest propagate in the plane perpendicular to the cylinder axes. Waveguides are formed inside the photonic crystal by replacement of a row of cylinders. The replacement cylinders are chosen so that the waveguide channels formed bind and conduct electromagnetic energy along the channel in the plane perpendicular to the cylinder axes. In the systems we study, the waveguide channels are composed of a periodic array of linear and Kerr nonlinear media in which both the linear and nonlinear dielectric materials differ from the linear dielectric materials forming the bulk photonic crystal. These waveguides are shown to support intrinsic localized modes. The intrinsic localized modes are studied by determining their scattering properties in waveguide systems. The transmission characteristics of a waveguide formed of linear dielectric media but containing a barrier that is a periodic array of linear and Kerr nonlinear dielectric is studied. Studies are also made of the transmission characteristics of waveguides of linear dielectric media that are connected at a waveguide junction that is composed of co-joined segments containing a periodic array of linear and Kerr nonlinear dielectric media. Transmission anomalies in these two types of waveguide geometries (i.e., barrier and junction geometries), associated with the development of intrinsic localized modes in the barrier or segments composing the waveguide junctions, are identified. This work is an extension of that presented in A.R. McGurn, G. Birkok. Phys. Rev. B 69 (2004) 235105, which treated the scattering characteristics of intrinsic localized modes in barriers and junctions formed solely of Kerr nonlinear dielectric media to treat other types of waveguides that can support intrinsic localized modes.

Resonant transmission near nonrobust periodic slab modes

We present a precise theoretical explanation and prediction of certain resonant peaks and dips in the electromagnetic transmission coefficient of periodically structured slabs in the presence of nonrobust guided slab modes. We also derive the leading asymptotic behavior of the related phenomenon of resonant enhancement near the guided mode. The theory applies to structures in which losses are negligible and to very general geometries of the unit cell. It is based on boundary-integral representations of the electromagnetic fields. These depend on the frequency and on the Bloch wave vector and provide a complex-analytic connection in these parameters between generalized scattering states and guided slab modes. The perturbation of three coincident zeros-those of the dispersion relation for slab modes, the reflection constant, and the transmission constant-is central to calculating transmission anomalies both for lossless dielectric materials and for perfect metals.

New hydrothermal activity and alkalic volcanism in the backarc Coriolis Troughs, Vanuatu

Research Article| January 01, 2005 New hydrothermal activity and alkalic volcanism in the backarc Coriolis Troughs, Vanuatu Timothy F. McConachy; Timothy F. McConachy 1Commonwealth Scientific and Industrial Research Organisation, Exploration and Mining, PO Box 136, North Ryde, Sydney NSW 1670, Australia Search for other works by this author on: GSW Google Scholar Richard J. Arculus; Richard J. Arculus 2Department of Earth and Marine Sciences, Australian National University, Canberra ACT 0200, Australia Search for other works by this author on: GSW Google Scholar Christopher J. Yeats; Christopher J. Yeats 3Commonwealth Scientific and Industrial Research Organisation, Exploration and Mining, PO Box 136, North Ryde, Sydney NSW 1670, Australia Search for other works by this author on: GSW Google Scholar Raymond A. Binns; Raymond A. Binns 4Commonwealth Scientific and Industrial Research Organisation, Exploration and Mining, PO Box 136, North Ryde, Sydney NSW 1670, Australia, and Department of Earth and Marine Sciences, Australian National University, Canberra ACT 0200, Australia Search for other works by this author on: GSW Google Scholar Fernando J.A.S. Barriga; Fernando J.A.S. Barriga 5Department of Geology, University of Lisbon, Edificio, Piso 5, Campo Grande, 1749-016 Lisboa, Portugal Search for other works by this author on: GSW Google Scholar Brent I.A. McInnes; Brent I.A. McInnes 6Commonwealth Scientific and Industrial Research Organisation, Petroleum Resources, PO Box 136, North Ryde, Sydney NSW 1670, Australia Search for other works by this author on: GSW Google Scholar Stephen Sestak; Stephen Sestak 6Commonwealth Scientific and Industrial Research Organisation, Petroleum Resources, PO Box 136, North Ryde, Sydney NSW 1670, Australia Search for other works by this author on: GSW Google Scholar Robina Sharpe; Robina Sharpe 7Centre for Ore Deposit Research, University of Tasmania, PO Box 252-79, Hobart, Tasmania 7001, Australia Search for other works by this author on: GSW Google Scholar Brooks Rakau; Brooks Rakau 8Department of Geology, Mines and Water Resources, Private Mail Bag 001, Port Vila, Republic of Vanuatu Search for other works by this author on: GSW Google Scholar Tony Tevi Tony Tevi 8Department of Geology, Mines and Water Resources, Private Mail Bag 001, Port Vila, Republic of Vanuatu Search for other works by this author on: GSW Google Scholar Geology (2005) 33 (1): 61–64. https://doi.org/10.1130/G20870.1 Article history received: 29 Jun 2004 rev-recd: 17 Sep 2004 accepted: 22 Sep 2004 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Timothy F. McConachy, Richard J. Arculus, Christopher J. Yeats, Raymond A. Binns, Fernando J.A.S. Barriga, Brent I.A. McInnes, Stephen Sestak, Robina Sharpe, Brooks Rakau, Tony Tevi; New hydrothermal activity and alkalic volcanism in the backarc Coriolis Troughs, Vanuatu. Geology 2005;; 33 (1): 61–64. doi: https://doi.org/10.1130/G20870.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The Vanuatu Australia Vents Expedition (VAVE) to the Coriolis Troughs in southern Vanuatu during September 2001 aboard the RV Franklin discovered a new hydrothermal vent field—herein informally named Nifonea—and recent alkalic volcanic activity. The Nifonea field in the central Vate Trough was located by coincident light transmission and CH4 anomalies in a hydrothermal plume of ∼60 km2 extent, best developed between 1600 and 1750 m depth at ∼150 m above the seafloor. Extensive hydrothermal fauna and yellow-brown crusts and mounds cover an area of ∼1 km2. Very fresh, glassy, variably vesicular, sparsely phyric and aphyric basalt, trachybasalt, and basaltic trachyandesite (with ∼5– 6 wt% combined alkalies at ∼51%–53% SiO2 and enriched light rare earth elements, Nb, and Zr) samples were dredged from youthful curtain, tube, and sheet flows, plus iron oxyhydroxide deposits. The alkalic composition of lavas in this tectonic setting is unique and attributed to thin ocean crust being developed in an incipient rifting phase involving a relatively low percentage of source-mantle melting. The Coriolis Troughs are among Earth's most youthful backarc basins and thus provide valuable insights to incipient rifting and hydrothermal processes. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Transmission anomalies in Kerr media photonic crystal circuits: Intrinsic localized modes

A study is made of the exact solutions of a system of nonlinear difference equations that model the propagation of electromagnetic radiation in photonic crystal waveguides and networks of interconnecting photonic crystal waveguides (photonic crystal circuits) containing Kerr nonlinear dielectric media. The transmission properties of a waveguide formed of linear dielectric material and containing a barrier of Kerr nonlinear material are determined and shown to exhibit anomalies similar to those due to gap solitons in layered Kerr nonlinear optical media. Similar discussions for a nonlinear segment bisected by a waveguide composed of linear dielectric media are given. The transmission properties of a junction formed from Kerr nonlinear media connecting three semi-infinite waveguides formed from linear dielectric materials are also determined. The transmission of electromagnetic energy through the junction is found to exhibit anomalies similar to those due to gap solitons in layered Kerr nonlinear media. The transmission anomalies in the systems we study are shown to arise from intrinsic localized modes that are found in the Kerr nonlinear media of the system. Intrinsic localized modes are solitonlike modes that can only exist in nonlinear systems. Previous transmission studies presented by us have concentrated on systems formed of linear media, and no previous transmission studies have been presented by us on systems supporting intrinsic localized modes. The central focus of this paper and new results presented are the study of resonant transmission anomalies in photonic crystal circuits containing Kerr media and the identification of some of these resonances with intrinsic localized modes that exist is the Kerr media.

Dynamical diffraction explanation of the anomalous transmission of light through metallic gratings

In this paper, it is pointed out that the light transmission anomalies observed for thin-film metallic gratings can be explained entirely in terms of dynamical diffraction theory. Surface plasmons are an intrinsic component of the diffracted wave field and, as such, play no independent causal role in the anomalies, as has been implied by others. The dynamical scattering matrix for the Bloch-wave modes of the diffracted photon wave field (E, H) is derived for a three-dimensionally periodic medium with arbitrary dielectric constant. A new theoretical treatment and numerical results are presented for a one-dimensional array of slits. In model metallic slit arrays, with negative dielectric constant, 100% and 0% transmission is possible at different wavelengths in the zero-order beam. In slit arrays, both propagating and evanescent modes (traditional surface plasmons) are strongly excited at both the peak and the minimum transmission conditions.

Characterization of diffraction anomalies in 2-D photonic bandgap structures

This paper deals with transmission anomalies of freestanding two-dimensional bandgap structures, which have found a large application range as filter and guiding structures in communication systems and radioastronomical applications in the far infrared region. The effect appears as a sharp breakdown of the transmission factor in the passband of quadratic patch and slot structures, first revealed by measurements. This paper outlines the numerical confirmation of these effects by computer simulations based on the method of moments combined with the Floquet theorem. The transmission and reflection behavior is examined for different structure geometries, frequency ranges, angle, and polarization of the incident wave also revealing alternative structures suppressing these effects. The modeling with electric and magnetic currents allows the characterization of both patch and slot arrays. Finally, cross shaped structures are examined allowing the complete suppression of this kind of anomalies.

Detection of cytomegalovirus in semen from a population of men seeking infertility evaluation

Objective: To determine the incidence of cytomegalovirus in the ejaculates of infertile men who were seropositive for IgG antibodies to cytomegalovirus. Design: Prospective study. Patient(s): We tested cytomegalovirus infected in the semen of men participating in an IVF-ET program. Main Outcome Measure(s): IgG and IgM antibodies to cytomegalovirus were measured in sera. We used polymerase chain reaction (PCR) and cell culture to look for both cytomegalovirus DNA and infectious virus in the semen of 70 men with cytomegalovirus-specific antibodies detected in sera. Result(s): Human cytomegalovirus was present in the semen from a population of IgG antibodies to cytomegalovirus in male serum only and not in female serum) and constituted a potential risk for cytomegalovirus transmission. Cytomegalovirus was identified in the semen of two patients who were positive for IgG antibodies to cytomegalovirus. Cytomegalovirus DNA also was detected in one positive sample after centrifugation through a three-layer Percoll gradient. Conclusion(s): Human cytomegalovirus was present in the semen from a population of infertile men. Rapid detection can be achieved by molecular techniques such as PCR combined with a hybridization assay. Even though cytomegalovirus was infrequently detected in semen, these data must be considered in determining the risk of transmission and developmental anomalies in infected fetuses.

Hydrothermal anomalies in the Lucky Strike segment on the Mid-Atlantic Ridge (37°17′N)

As part of the FARA (French-American Ridge Atlantic) project the northern Mid-Atlantic Ridge (MAR) was surveyed for hydrothermal activity between 33° and 40°N during the FAZAR cruise in August–October 1992. After detection of hydrothermal activity in the Lucky Strike segment (37°17′N) a detailed water column survey was undertaken in this region. During a follow-up cruise (with the DSRV ALVIN) several active high-temperature vents were found on the summit of an central seamount. Here we focus on the results of the water column survey undertaken during the FAZAR cruise. The influence of Mediterranean water and the site's shallow depth complicates the hydrography at Lucky Strike; background temperature and salinity gradients are usually too complex to indicate hydrothermal anomalies clearly. Light transmission anomalies within the Lucky Strike region were small, but were detected throughout the segment from mid-depth (∼ 1500 m) all the way to the valley seafloor (∼ 2300 m depth). The large depth range covered by these anomalies probably results from vertical mixing as well as the presence of multiple vent sources at various depths. Methane anomalies and a temperature anomaly observed deeper than the vents documented by ALVIN further support the idea of additional, deeper vents within this segment. Particle samples of the deep particle layer are enriched in Fe and trace metals.

Hydrothermal plumes at the Rodriguez triple junction, Indian ridge

Water column anomalies of light transmission, Mn, Fe, Al and CH 4 concentrations were searched in the central, southeastern and southwestern Indian Ridge segments centered on the Rodriguez Triple Junction (RTJ) (∼25°32′S, ∼70°02′E), for the purpose of locating hydrothermally active areas, in July to August 1993. We found an active zone in the central Indian Ridge segment (25°18–20′S) approximately 12 miles north of the RTJ, where significant hydrothermal plumes were observed at 2,200–2,400 m depth. Intensive tow-yo observations using a CTD rosette multi-sampling system equipped with a transmissometer revealed that the plumes show temporal as well as spatial variations. Discrete water samples within the plumes were enriched in Mn, Fe, and CH 4, with maximum concentrations of 9.8 n M, 40.2 n M and 3.3 n M, respectively. Judging from the spatial and chemical characteristics of the plumes, especially from transmission anomalies and C/H 4Mn ratios, we speculate that the hydrothermal venting site might be not in the rift valley but on the eastern off-axis zone, several miles distant from the rift valley.

Effect of Slab Interfaces on Diffraction of Visible Light by a Thick Volume Grating

Abstract A theory of visible light diffraction by a volume grating is given for the case when reflection at slab interfaces cannot be neglected. A method of approximate solution of the second-order coupled-wave equations, applicable over a wide range of the grating vector orientation, is proposed. An appropriate boundary-value problem is discussed and solved in the two-wave approximation. The results are analytical and expressed in matrix notation suitable for both transmission and reflection diffraction gratings. Particular attention is given to the diffraction regime that arises in a slanted grating under the total internal reflection of the diffracted wave (TIRDW). Strong transmission anomalies occurring in the vicinity of the TIRDW threshold are established and analysed.

Finite element studies of some juxtarticular stress changes due to localized subchondral stiffening

A finite element analysis was undertaken in concert with an animal model of mechanically-induced osteoarthritis. The numerical model was used to explore stress transmission anomalies associated with localized subchondral stiffening due to implantation of small cylindrical plugs immediately below the subchondral plate of sheep. The quasi-static, plane strain computational formulation included solution of the non-linear intra-articular contact problem, and was validated by comparison with a corresponding analytical solution and with the in vivo experimental results. The numerical results showed that stress aberrations due to metal implant insertion were felt most greatly in the bone immediately surrounding the implant, but that nominal compressive stress elevations up to about 50% could also be induced in the overlying deep hyaline cartilage layer. This localized cartilage stress elevation following the insertion of a metal plug could be seriously affected by a number of factors, including the positioning of the implant, variation in the area of intra-articular contact, or the elastic modulus of the cancellous bone and/or subchondral plate. Experimentally-observed fibrous encapsulation also reduced the cartilage stress elevation effect, but later bony remodelling and the development of a corticalized shell around the implant encapsulation served to re-elevate the local cartilage stresses.

A Survey of Modem Design and Performance in Digital Satellite Communications

This paper summarizes the important aspects of digital modem (modulator-demodulator) design for linear and nonlinear satellite channels using time-division multiple access (TDMA). The modem performance degradations caused by transmission anomalies, such as amplitude and delay distortions, effects of single and cascaded nonlinearities, and band-limiting effects in nonlinear channels, have been examined using the test data gathered from various field test programs using INTELSAT IV satellites and laboratory simulations using both INTELSAT IV and INTELSAT V parameters. A systematic methodology has been prescribed to reduce the effect of transmission anomalies on the performance of the modems. This paper consists of three main sections; essential features of TDMA modem design, transmission anomalies and their effects on modem performance, and optimization of modem performance in the presence of transmission deviations. The latter includes a brief description of an advanced maximum-likelihood sequence detection (MLSD) technique for application to the nonlinear channel.

Stress transmission anomalies in femoral heads altered by aseptic necrosis

The effects of aseptic necrosis upon load transmission patterns in the adult femoral head are explored by means of a two-dimensional finite element model. Experimental measurements of the modulus reductions of necrotic human cancellous bone are incorporated in the computation, by reducing the elasticity matrix values within the simulated infarct regions. Stress distribution patterns characterizing the effects of parametric variations of the stiffness deficit, and the lesion base width, depth, and apex width are presented. The data show that the intact viable bone surrounding a weakened infarct preferentially takes up additional load, but that the degree of stress relief achieved is a strong function of the infarct geometry. The results indicate that osteotomies undertaken to provide stress relief are likely to be most effective for narrow infarcts, and that achieving stress relief for the superior aspect of the lesion should be the principal objective of such procedures.

Coordinated measurements of ELF transmission anomalies and the precipitation of energetic particles into the ionosphere

Stimulated by previous findings of a positive qualitative correlation between anomalous ELF signal levels and the occurrence of significant fluxes of precipitating energetic particles, coordinated exercises were conducted between satellite measurements of the precipitating particles and ELF transmissions between the US Navy Wisconsin Test Facility and receiving stations in Maryland, Greenland, Norway, and Italy. Significant fluxes of precipitating electrons were often measured with the Lockheed pay load on the polar‐orbiting satellite 1972–076B. In March‐April 1976 the received signal strengths were found generally to increase during periods when the geomagnetic K indices were higher and when the fluxes of precipitating electrons >160 keV were greater on the average. During other coordinated exercises in March‐April 1975 the general correlations were less evident. Based on the fluxes, energy spectra, and pitch‐angle distributions of the particles, ion‐pair production profiles have been calculated and electron density profiles subsequently obtained with application of known effective electron loss rates. From the coordinated data, correlative studies between signal strengths and electron density profiles have been performed with use of an ELF waveguide mode computer program developed at the Naval Ocean Systems Center. The propagation path to each station of interest is segmented into different regions with an averaging perpendicular to the direction of propagation of the waveguide parameters. With the inclusion of data from several stations, the transmission signal strengths could be studied simultaneously under a variety of ionospheric conditions. The waveguide computer program calculations indicated that energetic electron precipitation events may cause a signal enhancement or degradation, depending upon where the disturbance is occurring along the path. The consistent occurrence during electron precipitation events of signal strength anomalies in either direction is supported by the coordinated satellite/ELF station measurements.

Variation in optical transmission and electrical resistance in a single sulfur liquid droplet during polymerization

Electrical resistance and optical transmission anomalies are observed in a single droplet of liquid sulfur during polymerization and depolymerization from 155 degrees C to 190 degrees C. Correspondence is found with some of the effects observed in electrooptic studies on bulk samples. Unlike the bulk studies, however, the single droplet shows an optical transmission of laser light that appears to follow the viscosity curve in thermal dependence. This divergence between the two studies is interpreted in terms of scattering effects at the droplet surface.

Anomalies in Daily Variation Magnetic Fields and Structure Under North-western United States and South-western Canada

Summary Thirty-one magnetometers of a large array secured records through a magnetically quiet 5-day period in July 1969, between latitudes 44 and 51 N and longitudes 100 and 121 W. The North American Central Plains variation anomaly persists in the Z component at periods 8 and 12 hr, but not in Y. Even qualitative explanation requires a channelled current of complicated geometry. Induction by Y is dominant at periods less than 2 hr but induction by 2 appears significant at daily-variation periods. The northern end of the conductive ridge in the upper mantle under the Wasatch Front produces prominent induction anomalies in Y and Z at periods 8 and 12 hr. At period 24 hr the amplitude maps show complex patterns of anomalies with features which do not correspond to those at shorter periods. The phase of 2 shows a steep gradient to the south-south-west and approaches that of X. This phase shift of over 5 hr is attributed to induction by X of currents in the highly conductive upper mantle under the Basin and Range Province, south of the array. The anomalies in 2 and Y amplitudes then arise from variable transmission of fields due to these currents through the electrically heterogeneous upper mantle and crust to the stations of the array. The use of a phase-difference test shows that anomalies in Z and Y amplitudes at period 24 hr, near the Northern Rockies, are such variable transmission (vartran) anomalies, whereas those at periods less than 2 hr are induction anomalies. West of the Northern Rockies the conductivity-depth profile which best fits the normal fields differs from the Great Plains profile by the addition of a conductive layer 15 km thick, in the depth range 50-100 km. The top of the ultimate mantle conductor is at depth 350 km. Small local anomalies near the Northern Rockies are modelled by elaborating on the conductive layer.

Heat flow and plate boundaries in Melanesia

Previous heat flow measurements in Melanesia are considered together with 23 new heat flow values. In the New Hebrides island arc, heat flow is generally normal in front (west) of the arc and high behind (east of) it. These high values are probably due in part to upwelling of asthenospheric material from the Benioff zone and volcanic activity in the interarc basins between the frontal and third arcs. Heat flow distribution behind the arc suggests that the Hazel Holme fracture zone at 15°S is a plate boundary and separates warm, newly generated Fijian lithosphere to the south from cooler, older Pacific lithosphere to the north. High heat flow in the region between Australia and the Melanesian island arcs correlates closely with seismic transmission anomalies in the area and suggests the presence of (1) a fossil island arc associated with the New Caledonia-Loyalty Islands system and (2) active sea floor spreading in the Woodlark basin.

Optical properties of transmission echelette high-pass filters

Symmetrical echelette gratings used in transmission are useful high-pass filters in the far-infrared region. Precise transmission measurements on these filters have been made in the 400 cm −1-50 cm −1 spectral range with a FIS-3 spectrophotometer. Scalar theory justifies experimental results, apart from some significant discrepancies which are related to the dichroism of the echelettes. Polarization effects have been studied in detail, showing the presence of transmission anomalies similar to the Wood anomalies in reflection echelettes. The use of a pair of crossed echelettes gives a definite improvement in the extinction at wavelengths shorter than the cut-off.