Very Low Frequency Electromagnetics

Analysis of heart rate variability (HRV) is a valuable, non-invasive method for quantifying autonomic cardiac control in humans. Frequency-domain analysis of HRV involving myocardial ischaemic episodes should take into account its non-stationary behaviour. The wavelet transform is an alternative tool for the analysis of non-stationary signals. Fourteen patients have been analysed, ranging from 40 to 64 years old and selected from the European Electrocardiographic ST-T Database (ESDB).

The history of electrochemical impedance spectroscopy (EIS) is briefly reviewed, starting with the foundations laid by Heaviside in the late 19th century in the form of Linear Systems Theory (LST). Warburg apparently was the first to extend the concept of impedance to electrochemical systems at the turn of the 19th century, when he derived the impedance function for a diffusional process that still bears his name. Impedance spectroscopy was next employed extensively using reactive bridges to measure the capacitance of ideally polarizable electrodes (mostly mercury), leading to the development of models for the electrified interface. However, it was the invention of the potentiostat in the 1940s and the development of frequency response analyzers in the 1970s that led to the use of EIS in exploring electrochemical and corrosion mechanisms, primarily because of their ability to probe electrochemical systems at very low frequencies. These inventions have led to an explosion in the use of EIS for exploring a wide range of systems and processes, ranging from conduction in the solid and liquid states, ionic and electronic conduction in polymers, heterogeneous reaction mechanisms, and the important phenomenon of passivity. It is evident that the use of EIS in identifying reaction mechanisms makes use of pattern recognition, currently through inspection. It is argued that, in the future development of EIS, reaction mechanism analysis (RMA) would be most efficiently done by using artificial neural networks operating in the pattern recognition mode. This strategy would require the creation of libraries of reaction mechanisms for which the theoretical impedance functions are known.

During the last decade, Very Low Frequency (VLF) testing for extruded distribution cables has gained interest among the North American utilities. The increasing interest is evidenced by recent research publications and discussions inside the expert community in which standards are being proposed and continuously discussed. While there is a general consensus as to the meaning of insulation dielectric properties, many open issues still remain for discussion in order to produce a more accurate evaluation. Consequently, this paper will discuss a number of the practical issues that arise when making these measurements at VLF on field aged and non-aged cables, particularly Tan δ measurements. The discussion is based on data from laboratory experiments and field testing.

A conductivity relaxation experiment has been conducted on an SrFeCo0.5Ox sample by abruptly changing the oxygen partial pressure in the atmosphere and monitoring the change of conductivity as a function of time. The re-equilibrium process obeys Fick's second law. By fitting the relaxation data to the solution of the diffusion equation with appropriate boundary conditions, we could determine the oxygen chemical diffusion coefficient and the activation energy. The oxygen diffusion coefficient is 8.9 × 10−7 cm2/s at 900 °C and it increases with increase in temperature. Measured activation energy is 0.92 eV, which is slightly lower than that of other oxides in the system SrFe1 − xCoxOy.

The VLF-E.M. (Very Low Frequency-Electro Magnetics) method was first used for geophysical surveying in 1964. Since then many hundreds of surveys have been carried out; several variations on the original design have been introduced; and the method has become airborne.The VLF instrument is a directional radio receiver, which can be tuned to distant radio transmitters in the 15–25 kHz band. The first VLF instrument and the one most widely used to date measures the vertical real and imaginary components of the magnetic field vector.The imaginary component has been found useful in distinguishing between conductors lying at different depths below ground. Ground conductivity is also interpretable. Relative conductivity-thickness of a buried conductor affects the VLF response but is harder to interpret.The VLF-E.M. method has established its usefulness in geophysical surveying for massive sulphides and for geological mapping. Field results suggest that it may also play a useful role in exploring for the more disseminated ores, where suitable conductivity contrasts at these frequencies exist.

Integrated electrical and electromagnetic surveys were carried out in hard rock areas of Purulia district (West Bengal), India, for delineation of groundwater-bearing zones that would be suitable for construction of deep tube-wells for large amounts of water. Groundwater movement that occurs through fractures in hard rocks is suitable to be delineated by very low frequency (VLF) electromagnetic surveys. A detailed survey of the area was done using a VLF-WADI instrument and appropriate locations were selected for further study using Schlumberger resistivity sounding. Hence, the entire area was surveyed in a relatively short time by the combined use of resistivity and electromagnetic surveys.

Early embryonic development is characterized by dramatic modifications in chromatin organization. These contribute to the formation of the totipotent cells that will differentiate into the embryonic and extra-embryonic lineages. However, some groups of genes are not affected by these global changes. Amongst these, are the genes controlled by genomic imprinting, an epigenetic mechanism that makes the maternal and the paternal genomes functionally non-equivalent in development. Somatic cell nuclear transfer (SCNT), used to clone animals, mimics the chromatin reprogramming that occurs in the post-fertilization embryo. However, SNCT leads to aberrant development, particularly of the extra-embryonic tissues. As a consequence, live-born animals are obtained at very low frequency. Here, we review how different steps in the SCNT procedure may give rise to aberrant development. Imprinted genes are amongst the frequently affected genes, and their perturbed expression explains in part the abnormal developmental phenotypes. The future challenge will be to modify currently used cloning procedures, in order to increase the efficiency of nuclear reprogramming, without affecting the gene loci at which chromatin is normally not altered during development.

The details of digital recording and computer processing of a 12-lead electrocardiogram (ECG) remain a source of confusion for many health care professionals. A better understanding of the design and performance tradeoffs inherent in the electrocardiograph design might lead to better quality in ECG recording and better interpretation in ECG reading. This paper serves as a tutorial from an engineering point of view to those who are new to the field of ECG and to those clinicians who want to gain a better understanding of the engineering tradeoffs involved. The problem arises when the benefit of various electrocardiograph features is widely understood while the cost or the tradeoffs are not equally well understood. An electrocardiograph is divided into 2 main components, the patient module for ECG signal acquisition and the remainder for ECG processing which holds the main processor, fast printer, and display. The low-level ECG signal from the body is amplified and converted to a digital signal for further computer processing. The Electrocardiogram is processed for display by user selectable filters to reduce various artifacts. A high-pass filter is used to attenuate the very low frequency baseline sway or wander. A low-pass filter attenuates the high-frequency muscle artifact and a notch filter attenuates interference from alternating current power. Although the target artifact is reduced in each case, the ECG signal is also distorted slightly by the applied filter. The low-pass filter attenuates high-frequency components of the ECG such as sharp R waves and a high-pass filter can cause ST segment distortion for instance. Good skin preparation and electrode placement reduce artifacts to eliminate the need for common usage of these filters.

Low frequency noise measurements are among the most sensitive tools for the investigation of the quality and of the reliability of semiconductor devices. The sensitivity that can be obtained depends on the background noise of the low noise preamplifier coupled to the device under test (DUT) that, at very low frequencies, is dominated by flicker noise. The low frequency noise produced by the DUT, on the other end, is very often the most interesting signal to be detected and analyzed. In this work we propose a very simple topology for the realization of a general purpose low noise preamplifier whose noise performances, at very low frequencies (below 10 Hz), are significantly better than those that can be obtained by the most popular commercial instrumentation. Indeed, a gain of 80 dB with a pass band extending from a few tens of mHz up to a few kHz with an equivalent input voltage noise as low as 14 nV/square root(Hz) (100 mHz), 1.4 nV/square root(Hz) (1 Hz), 1.0 nV/square root(Hz) (10 Hz), and 0.8 nV/square root(Hz) (1 kHz) are consistently obtained by using quite standard electronic components and with no need for trimming and/or calibration steps. Moreover, the junction field-effect transistor input stage of the amplifier is characterized by an equivalent input current noise below 4 fA/square root(Hz) in the entire bandwidth, resulting in negligible background noise degradation for DUT impedances in excess of 100 kohms.

ABSTRACT This paper investigates the benefits of a multisensor fusion methodology for underwater navigation using location-dependent signatures, or geotags. The proposed coordinate-free system uses both natural and man-made signals, as well as transient events to extract location-dependent signatures for navigation and guidance. Natural signals include the geomagnetic field, gravity field, bathymetric features, and naturally-occurring very low frequency radio signals. Man-made acoustic sources of opportunity include drainage outlets and pump stations in littoral zones and particularly in harbors, which can be explored to serve as underwater beacons for navigation. This paper models a multisensor coordinate-free system, characterizes various signals for underwater navigation, and evaluates the Multisensor Underwater Signature-based Navigation (MUSNav) system in terms of accuracy, availability, and continuity of the navigation solution.

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.

During the International Polar Year (IPY), one area of great interest is co-coordinated, multi-instrument probing of the ionosphere at high latitudes. This region is important not only for the applications that rely upon our understanding of it, but also because it contains the footprints of processes that have their origin in the interplanetary space. Many different techniques are now available for probing the ionosphere, from radar measurements to the analysis of very low frequency (VLF) wave paths. Combining these methods provides the ability to study the ionosphere from high in the F-region to the bottom of the D-layer. Thus, coupling processes from the magnetosphere and to the neutral atmosphere can be considered. An additional dimension is through comparisons of the response of the two polar ionospheres to similar (or the same) geomagnetic activity. With more instruments available at the South Pole inter-hemispheric, studies have become easier to accomplish such that a fuller picture of the global response to Sun-Earth coupling can be painted. This paper presents a review of the current state of knowledge in ionospheric probing. It cannot provide a comprehensive guide of the work to date due to the scale of the topic. Rather it is intended to give an overview of the techniques and recent results from some of the instruments and facilities that are a part of the IPY cluster 63-Heliosphere Impact on Geospace. In this way it is hoped that the reader will gain a flavor of the recent research performed in this area and the potential for continuing collaboration and capabilities during the IPY

Abstrak-Kelongsoran sering terjadi pada tanah yang memiliki topografi curam. Salah satunya adalah yang terjadi di Desa Jombok, Kecamatan Ngantang, Kabupaten Malang, Jawa Timur. Pada areal seluas satu hektar dijumpai penurunan permukaan tanah (longsor). Daerah longsoran ini diteliti dengan menggunakan salah satu metoda Geofisika, yaitu Very Low Frequency-Electromagnetic (VLF-EM). Data lapangan yang didapatkan dari hasil pengukuran metode VLF-EM biasanya tercampur dengan noise dan outlier. Pada penelitian ini digunakan filter NA-MEMD untuk menghilangkan noise dan outlier. Digunakan Filter Karous-Hjelt untuk menganalisa data secara kualitatif. Sedangkan analisa secara kuantitatif diperoleh dengan melakukan pemodelan inversi menggunakan INV2DVLF. Hasil analisis VLF-EM dengan menggunakan filter NA-MEMD mampu mereduksi noise dan outlier dari data pengukuran. Sedangkan hasil inversi 2D menunjukkan bahwa terdapat zona anomali yang menunjukkan zona lemah atau rawan longsor di area penelitian.
Abstract-Landslide often occurs in a steep topography ground. One of them is happened in the Jombok village, Ngantang, Malang, East Java. Land subsidence (landslides) often occur in this area. The landslide area investigated using one of the Geophysics methods, the Very Low Frequency-Electromagnetic (VLF-EM). The field datas obtained from measurement results of VLF-EM method are usually mixed with noise and outliers. In this research, NA-MEMD filter.is used to eliminate the noise and outliers. Karous-Hjelt (K-Hjelt) filter is udes to qualitative analyze of the data. While quantitative analysis is obtained by performing inversion modeling using INV2DVLF. VLF-EM analysis results using the NA-MEMD filter is able to reduce the noise and outliers of measurement data. While the 2D inversion results indicate that there is an anomalous zone which indicates weak or landslide-prone zones in the study area.

This study examined the theoretical controversy on the impact of syllables and bigrams in handwriting production. French children and adults wrote words on a digitizer so that we could collect data on the local, online processing of handwriting production. The words differed in the position of the lowest frequency bigram. In one condition, it coincided with the word's syllable boundary. In the other condition, it was located before the syllable boundary. The results yielded higher movement durations at the position where the low-frequency bigram coincided with the syllable boundary compared to where the low-frequency bigram appeared before the syllable boundary. Syllable-oriented strategies failed with the presence of a very low-frequency bigram within the initial syllable. Further analysis showed that children in grades 3 and 4 privileged syllable-oriented programming strategies. The production times of children in grade 4 were also affected by syllable frequency and, to a lesser extent, bigram frequency. The adults writing durations were modulated by bigram frequency. Therefore, both bigrams and syllables regulate handwriting production although the influence of bigrams was stronger in adults than children. In the light of these results, we propose a psycholinguistic model of handwriting production. We are grateful to Lucie Hérault for her help in the experimental part of this work. We would also like to thank an anonymous reviewer for his/her enlightening comments that improved considerably the quality of this paper. This research was supported by a grant from the Région Rhône-Alpes (Cluster 11: Handicap, Viellissement et Neurosciences) attributed to Sonia Kandel.

Collapse and overtopping repeatedly occur in LUSI Embankment. Discontinuities (crack or fracture) in the embankment are major reasons for embankment failures or collapses. Very-low frequency electromagnetic (VLF-EM) measurement is essentially a non-destructive technique which displays subsurface 2-D cross section of resistivity. The cross section result has the possibility of detecting discontinuities and liquid saturation in embankment before it collapsed by observing which part of it in the cross section has low resistivity. This paper presents results of a survey conducted at the LUSI embankment in Eastern Java, Indonesia in a part of potential collapse. VLF-EM profiles measured along the embankment crest provided an overview of the whole embankment and served to detect anomalous zones. The noise assisted multivariate empirical mode decomposition (NA-MEMD) is applied to reject unwanted VLF-EM noise and Inv2DVLF software is applied to obtain result of 2-D resistivity models. In the selected area, the drill log and the standard penetration test (SPT) value gave detailed information about subsurface layer below embankment. This information is valuable for supporting 2-D resistivity image obtained from VLF-EM data inversion. Furthermore, the low resistivity in embankment layer is associated to discontinuities (fracture, crack or fault) along the embankment which caused its collapse.

1] Six different geophysical investigations, (1) ground-penetrating radar, (2) DC resistivity sounding, (3) seismic refraction, (4) very low frequency (VHF) electromagnetic, (5) helicopter borne electromagnetic (HEM), and (6) transient electromagnetic (TEM) techniques, were employed to obtain information on the ice body properties of pingos near Fairbanks, Alaska. The surface nuclear magnetic resonance (NMR) data were also compared from similar sites near one of the study pingos. The geophysical investigations were undertaken, along with core sampling and permafrost drilling, to enable measurement of the ground temperature regime. Drilling (ground truthing) results support field geophysical investigations, and have led to the development of a technique for distinguishing massive ice and overburden material of the permafrost. The twodimensional DC resistivity sounding tomography and ground-penetrating radar profiling are useful for ice detection under heterogeneous conditions. However, the DC resistivity sounding investigation required high-quality ground contact and less area coverage. The active layer thickness and the homogeneous horizontal structure of the overburden material are important parameters influencing detection of massive ice in permafrost for most methods such as seismic, TEM, or surface NMR.

This background paper on rural labour markets and migration in South Asia has been prepared for the 2008 World Development Report. The paper focuses on the question of how rural labour markets and migration can be made to work better for poverty reduction. Using select case studies and longitudinal studies from five parts of India and Bangladesh we first discuss the key processes that shape rural labour markets and how these have evolved over time with the changing macroeconomic, policy, agro-ecological and infrastructural context. Each region is discussed separately to draw out the influence of location specific factors and illustrate the complexity of labour markets in South Asia. Under each we examine factors that have enabled rural labouring households to improve their asset base and wealth status. We find that while agricultural wages have remained relatively low, a few rural labouring households have been able to break out of poverty through household diversification strategies that use a combination of two or more of the following: accessing regular work (not necessarily well-paid) inside or outside the village; leasing in land or being given a land by a patron for cultivating; and starting up a small business. Skills, education, strong intra-family cooperation with pooling of labour and resources; being able to use social networks to one's advantage and the capacity to "shift" occupations from traditional to modern ones are critical in accessing better paid jobs and more work. The stage in the lifecycle of the household and the number of dependents play an important role in enabling households to establish themselves on an upward trajectory of accumulation. Ultimately the prospects for achieving an "exit" from poverty depend very much on the political, social and natural resource context which shape the institutions that allocate resources and set the terms of trade and exchange for the poor.

The seismic hazard presented by slow subduction zones is not well known. While there is a widely accepted apparent relation between “fast-young plate” subduction and great earthquake generation (e.g., Chile, 1960), the seismic record indicates that slow subduction zones are also capable of generating mega-thrust earthquakes (M > 8.2). Available data on the recurrence interval for slow subduction margins, suggests that repeat times are longer than for more rapid convergence margins (on the order of several hundred to a few thousand years). For several of these margins, however, no shallow dipping thrust earthquake focal mechanisms are observed and no mega-thrust earthquakes known either. Slow subduction zones (v ≥ 4 cm/year) are typically characterized by thick sedimentary sections on the incoming plate (2–6 km) and by a broad accretionary wedge (100–250 km). The “taper” of these accretionary wedges is mechanically related to the basal and internal friction and ranges from about 2̆ to 12̆. Some wedges have extremely shallow mean surface and basal slopes (about 1–2̆ each, taper <4̆) indicating a very weak decollement layer. These include: Barbados Ridge, Makran, Hikurangi, Mediterranean Ridge, Calabria, Gibraltar/Cadiz, and Cascadia/Washington. Nankai, Sumatra and E. Alaska have slightly higher tapers of about 5–7̆. Most of these low-taper wedges have very slow to slow convergence rates (0.5–4 cm/year). The presence of these wide accretionary wedges strongly affects the type and amount of deformation above the “up-dip limit” of the seismogenic zone. The thermally insulating effect of a wide and thick wedge of sediment produces a wide, shallow transition zone (between the 100̆C and 150̆C isotherms) as well as a substantial (up to 80 km wide) region between this and the front of the wedge, where the amount and timing of deformation is poorly understood. Indeed, recent seismological data from Nankai indicate “very-low-frequency” shallow-thrust earthquakes beneath the accretionary wedge, long considered to be “aseismic,” underscoring the unusual mechanical behavior in the transition zone. As the rigidity of the high-porosity wedge sediments is low, for an earthquake of a given seismic moment, more co-seismic slip will occur and for a longer duration, than for a deeper earthquake in more consolidated units. Thus shallow earthquakes in the wedge are more effi cient at generating a strong tsunami. Many of the margins with very broad accretionary wedges have produced extremely strong earthquakes (M9) in the past, as well as giant tsunamis.

The energy transfer due to non-linear interactions between the components of a gravity-wave spectrum discussed in Parts 1 and 2 of this paper is evaluated for a fully and partially developed Neumann spectrum with various spreading factors. The characteristic time scales of the energy transfer are found to be typically of the order of a few hours. I n all cases the high frequencies and the low-frequency peak are found to gain energy from an intermediate range of frequencies. The transfer of energy to very low frequencies and to waves travelling at large angles to the main propagation direction of the spectrum is negligible. Computations are presented also for the rate of decay of swell interacting with local windgenerated seas (represented by a Neumann spectrum). An appreciable decay is found only for swell frequencies in the same range as those of the local sea.

Several efforts by the local authority to fix the bad portions of Ijebu-Ode-Erunwon road, southwest Nigeria have yielded no meaningful result, as the road often get deteriorated shortly after repairs. Geophysical investigation integrated with geotechnical studies were undertaken to determine causes of the consistent failure of the highway. Very Low Frequency Electromagnetic (VLF-EM) and Electrical Resistivity (ER) methods were employed to map sections of the road with anomalous electrical responses and interpreted in-terms of structures, lithology and water saturation. VLF-EM plots identified positive peaks of filtered real amplitudes greater than 30 % which correspond to major and minor linear fractures within the basement rocks. High current density >30 and low resistivity <10 Ω m delineated rock units underlying the failed pavement to be water saturated. Liquid limit, linear shrinkage and plastic limit index results; 24.0-48.5 %, 2.1-12.9 %, 7.5-27.4 % respectively, indicate excellent to good engineering index properties. However, soaked and unsoaked CBR results; 70.3-83.9 %, and 12.9-31.6 % respectively, indicate percentage reduction in strength with wetness up to 80 %. 144 oSinowo, o. o., akanji, o. a., akinMoSin a.

Erosion of rock cliffs has been considered to be relatively unpredictable. This perceived stochastic nature of the erosional processes often occurs through collapses along fractures in the rock-mass. The prediction of catastrophic cliff failures and collapses remains very difficult. For advancing in this field, it is important to understand the processes through which a crack is initiated, how it develops and propagates until the final failure. This paper examines the micro-seismic signals recorded 15 h prior to a rock-fall located at Mesnil-Val, France. The results lead to the hypothesis that several phases of failure mechanisms contribute to rock-fall occurrence. The most important phases were associated with micro-seismic event families identified by multiplet selection. Each event family contained one specific frequency spectrum showing a progressive decrease of the frequencies as the rock approached failure suggesting the following phases: 1) the micro-seismic events recorded 15 h before the rock-fall were characterised by the highest frequencies in a large spectrum-band, between ~100 and 1000 Hz (family 1), suggesting a crack initiation mechanism or the opening of existing fractures; 2) the micro-seismic events recorded several minutes before the rock-fall were associated with a clear decrease in the highest frequency components (family 2) suggesting that the mechanism was related to the growing and development (or coalesce) of existing micro-cracks into larger fractures; 3) micro-seismic events recorded just before the rock-fall were associated with a lower frequency spectrum than families 1 and 2, the highest frequency components were absent (family 3), the frequency emission source mechanism could be related to the shearing or opening of the existing large fractures permitting the complete detachment of the blocky rock-mass; 4) finally, micro-seismic events with a very low frequency spectrum (lower than 100 Hz) characterized the rock-fall impact on the ground. These encouraging results offer the possibility of using the micro-seismic system to monitor high risk sections of coastline and to advance understanding of cliff failure mechanisms.

Surface geophysical survey was conducted around Aarada refuse dumpsite, Ogbomosho, Oyo State, Nigeria to locate leachate plumes migration pathways using the very low frequency electromagnetic and vertical electrical sounding techniques. Eight VLF-EM profiles of length 70 to 150m with 10m interstation spacing and seven Vertical Electrical Soundings with current electrode separation varying from 150 to 200m were established. The analyzed VLF-EM data revealed the presence of conductive pollutants (leachate plumes) at the subsurface while the geoeletric sections generated from the processed VES data showed that the leachate plumes have actually migrated to a depth of 5.4m in the area which confirmed the VLF-EM results.

An integrated suite of environmental methods was used to characterize the hydrogeological, geological and tectonic regime of the largest waste disposal landfill of Crete Island, the Fodele municipal solid waste site (MSW), to determine the geometry of the landfill (depth and spatial extent of electrically conductive anomalies), to define the anisotropy caused by bedrock fabric fractures and to locate potential zones of electrically conductive contamination. A combination of geophysical methods and chemical analysis was implemented for the characterization and management of the landfill. Five different types of geophysical surveys were performed: (1) 2D electrical resistance tomography (ERT), (2) electromagnetic measurements using very low frequencies (VLF), (3) electromagnetic conductivity (EM31), (4) seismic refraction measurements (SR), and (5) ambient noise measurements (HVSR). The above geophysical methods were used with the aim of studying the subsurface properties of the landfill and to define the exact geometrical characteristics of the site under investigation.

The very low frequency-electromagnetic (VLF-EM) technique was used to delineate two sub-parallel lava tubes, faults and dikes in Umm El-Quttein area, NE Jordan. The investigation of the lava tubes was conducted through 22 VLF-EM profiles across lava strike; the length of profiles ranged from 700 to 1700 m. The lava tubes outcrop at two sites: Azzam cave and Al-Howa tunnel, characterized by slightly weathered basalt, columnar joints and fissure zones; qualitative interpretation of Fraser and Karous-Hjelt maps differentiate those zones as linear, elongated and circular anomalous zones. The 2-D tipper inversion of VLF-EM data and resistivity imaging had the potential to screen out three anomalous zones of likely resistivity contrast: the lava tube body with resistivity over 2500 Θ·m, the fractured zones with resistivity less than 500 Θ·m, and the host vesicular basalt with resistivity of 1500 Θ·m. The strike of lava tubes varied from SW to NE direction with depth less than 20 m and width from 10 to 30 m.

In this paper we study the energy of ULF electromagnetic waves that were recorded by the satellite DEMETER, during its passing over Haiti before and after a destructive earthquake. This earthquake occurred on 12 January 2010, at geographic Latitude 18.46° and Longitude 287.47°, with Magnitude 7.0 R. Specifically, we are focusing on the variations of energy of Ez-electric field component concerning a time period of 100 days before and 50 days after the strong earthquake. In order to study these variations, we have developed a novel method that can be divided in two stages: first we filter the signal, keeping only the ultra low frequencies and afterwards we eliminate its trend using techniques of Singular Spectrum Analysis (SSA), combined with a third-degree polynomial filter. As it is shown, a significant increase in energy is observed for the time interval of 30 days before the earthquake. This result clearly indicates that the change in the energy of ULF electromagnetic waves could be related to strong precursory earthquake phenomena. Moreover, changes in energy associated with strong aftershock activity were also observed 25 days after the earthquake. Finally, we present results concerning the comparison between changes in energy during night and day passes of the satellite over Haiti, which showed differences in the mean energy values, but similar results as far as the rate of the energy change is concerned.

1] A composite model of wave propagation from terrestrial very low frequency (VLF) transmitters has been constructed to estimate the wave normal angles and fields of whistler mode waves in the plasmasphere. The model combines a simulation of the fields in the Earth-ionosphere waveguide, ionospheric absorption estimates, and geomagnetic field and plasma density models with fully three-dimensional ray tracing that includes refraction, focusing, and resonant damping. The outputs of this model are consistent with those of several previous, simpler simulations, some of which have underlying component models in common. A comparison of the model outputs to wavefield data from five satellites shows that away from the magnetic equator, all of the models systematically overestimate the median field strength in the plasmasphere owing to terrestrial VLF transmitters by about 20 dB at night and at least 10 dB during the day. In addition, wavefield estimates at L < 1.5 in the equatorial region appear to be about 15 dB too low, although measured fields there are extremely variable. Consideration of the models' similarities and differences indicates that this discrepancy originates in or below the ionosphere, where important physics (as yet not conclusively identified) is not being modeled. Adjustment of the low-altitude field estimates downward by constant factors brings the model outputs into closer agreement with satellite observations. It is concluded that past and future use of these widely employed trans-ionospheric VLF propagation models should be reevaluated.

A morphologically conspicuous bacterium that constituted a very small fraction (< 0.01%) of the total microbial community of activated sludge was enriched and analysed phylogenetically by a combination of cultivation-independent molecular and physical methods. The large, corkscrew-shaped, filamentous bacteria were first detected in municipal activated sludge by light microscopy owing to their unusual rotating gliding motility. Various attempts at microbiological enrichment and pure culture isolation with traditional techniques failed, as did attempts to retrieve the morphotype of interest by micromanipulation. In situ hybridization with the group-specific, rRNA-targeted oligonucleotide probe CF319a indicated a phylogenetic affiliation to the Cytophaga-Flexibacter group of the Cytophaga-Flavobacterium-Bacteroides phylum. Based on strong morphological resemblance to members of the genus Saprospira, additional 16S rRNA-targeted oligonucleotides with more narrow specificity were designed and evaluated for in situ hybridization to the morphotype of interest. Flow cytometric cell sorting based on the fluorescence conferred by probe SGR1425 and forward scatter enabled a physical enrichment of the helical coiled cells. Subsequent polymerase chain reaction (PCR) amplification of 16S rDNA fragments from whole fixed sorted cells with a primer pair based on probes CF319a and SGR1425 resulted in the retrieval of 12 almost identical partial 16S rDNA fragments with sequence similarities among each other of more than 99.2%. In situ hybridizations proved that the sequences that showed the highest similarity (88.4%) to the 16S rRNA of Saprospira grandis were indeed retrieved from the corkscrewshaped filaments. The bacterium is likely to be a member of a genus of which no species has been cultured hitherto. It was consequently tentatively named 'Magnospira bakii' and has the taxonomic rank of Candidatus Magnospira bakii, as the ultimate taxonomic placement has to await its cultivation. In this study, it was demonstrated that even bacteria occurring at very low frequencies in highly complex environmental samples can be retrieved selectively without cultivation for further molecular analysis.

We propose a mechanism to explain suggested links between seismic activity and ionospheric changes detected overhead. Specifically, we explain changes in the natural extremely low-frequency (ELF) radio noise recently observed in the topside ionosphere aboard the DEMETER satellite at night, before major earthquakes. Our mechanism utilises increased electrical conductivity of surface layer air before a major earthquake, which reduces the surface-ionosphere electrical resistance. This increases the vertical fair weather current, and (to maintain continuity of electron flow) lowers the ionosphere. Magnitudes of crucial parameters are estimated and found to be consistent with observations. Natural variability in ionospheric and atmospheric electrical properties is evaluated, and may be overcome using a hybrid detection approach. Suggested experiments to investigate the mechanism involve measuring the cut-off frequency of ELF "tweeks", the amplitude and phase of very low frequency radio waves in the Earth-ionosphere waveguide, or medium frequency radar, incoherent scatter or rocket studies of the lower ionospheric electron density.

The measurement of Very Low Frequency Electromagnetic (VLF-EM) is important in many different applications, i.e, environmental, archeological, geotechnical studies, etc. In recent years, improving and enhancing VLF-EM data containing complex numbers (bivariate) was presented by several authors in order to produce reliable models, generally using univariate empirical mode decomposition (EMD). Applying univariate EMD separately on each data is problematic. This results in a different number of misaligned Intrinsic Mode Functions (IMFs) which can complicate the selection of some IMFs for denoising process. Thus, a filtering method based on the multivariate empirical mode decomposition (MEMD) approach to decompose simultaneously bivariate data is proposed. In this paper we address two issues by employing the recently introduced noise assisted MEMD (N-A MEMD) for improving bivariate VLF-EM data. Firstly, the N-A MEMD to decompose bivariate measurement of the VLF-EM data into IMFs and a residue is defined as VLF-EM signal or unwanted noise. Secondly, the proposed method is used to enhance VLF-EM data and to reject unwanted noise. Finally, the proposed method is applied to a synthetic data with two added sinusoids. To demonstrate the robustness of the N-A MEMD method, the method was tested on added-noise synthetic data sets and the results were compared to the Ensemble EMD (EEMD) and Bivariate EMD (BEMD). The N-A MEMD gave more robust and accurate results than the EEMD and BEMD methods and the method required less CPU time to obtain the IMFs compared to EEMD.

Large cell lymphomas (LCLs) are heterogeneous in morphology, clinical presentation, and behavior. We studied 52 de novo LCLs of B-cell type for rearrangements of the bcl-2 and c-myc oncogenes by Southern blot analysis and related these data to the primary site of presentation, stage, and cytomorphology. Thirteen tumors had comigrating rearrangements of JH and bcl-2, indicative of a t(14;18). Far more primary nodal lymphomas than extranodal lymphomas carried a t(14;18) (40% v less than 5%). Additionally, almost all lymphomas with a t(14;18) versus 41% of the tumors without a bcl-2 rearrangement presented with lymphadenopathy. c-myc rearrangements were seen in 35% of the extranodal lymphomas and 5% of the nodal lymphomas. No differences were observed in bone marrow involvement and staging according to Ann Arbor. bcl-2 rearrangements were found in 50% of the LCLs with cleaved nuclei, whereas c-myc rearrangements were relatively frequent (25%) in the noncleaved subtype. Our data support...

Species composition and diversity of bryophyte communities occurring on dead beech trees were analyzed in five European countries (Slovenia, Hungary, The Netherlands, Belgium and Denmark). Altogether 1.009 trees were inventoried in 19 beech dominated forest reserves. The differences in the composition of bryophyte communities were high among countries and it overwhelms the effect of decay stages, which affect the species composition at local scale. Well decayed trees were dominated by epixylic species in Slovenia, while in other countries the proportion of opportunistic bryophytes was much higher and in Atlantic countries uproot species are also common. In Slovenia hepatics, in Hungary and Denmark pleurocarps, and in The Netherlands and Belgium acrocarps were the most frequent. Diversity of communities differed considerably among regions. Slovenian sites were the hotspot of bryophyte diversity characterized by high species richness (both tree and country level) and a high fraction of rare and threatened species. This richness is most likely caused by the combination of high air humidity combined with a very high degree of naturalness of the Slovenian sites. The diversity of Hungarian stands was intermediate reflecting the relatively high naturalness of the study sites, as well as a rather continental climate sub-optimal for epixylic liverworts. Atlantic forests have deteriorated bryophyte communities on dead trees, dominated by a few opportunistic species. This is partly a result of habitat fragmentation and past and recent management of forest. Most of the stands the amount and quality of dead wood is not suitable for species rich epixylic bryophyte communities.

Expressions tabulated for the effective antenna noise figure F a usually assume an electric field antenna, since most measurements of radio noise are made on the electric field of the noise. Furthermore, the International Radio Consultative Committee (CCIR) noise model predictions for F a are made only for electrically short grounded vertical monopoles over a perfect ground. However, at frequencies lower than those traditionally used for communications, i.e., at extremely low frequencies (ELF; frequencies in the range 3 Hz to 3 kHz) and very low frequencies (VLF; frequencies in the range 3-30 kHz), it is common for magnetic field loop antennas to be used, and the tabulated expressions for F a do not apply. This communication reports the derivation of an expression for F a as measured by a small vertical magnetic loop antenna and its subsequent application to ELF/VLF radio noise measurements made at a variety of locations around the world. There is good agreement between the measured F a values and estimates of maximum and minimum F a values for the ELF/VLF range published by Spaulding and Hagn in 1978, but an improved fit to the measurements can be obtained by making moderate adjustments to the maximum and minimum values at both the low (10-100 Hz) and high (8-32 kHz) frequency limits. Citation: Fraser-Smith, A. C. (2007), The effective antenna noise figure F a for a vertical loop antenna and its application to extremely low frequency/very low frequency atmospheric noise, Radio Sci., 42, RS4026,

Interspecific hybrids of various Epilobium species have been produced in order to analyse plastid inheritance using restriction fragment polymorphisms of plastid DNA as markers. This analysis reveals that interspecific hybrids exhibit only the fragment pattern of the maternal plastome. Southern hybridization experiments using cloned species-specific plastid DNA fragments as markers confirm the maternal type of plastid inheritance in Epilobium, while providing at least a tenfold increase of sensitivity to detect restriction polymorphisms. Within the limit of detection even young seedlings contain no plastid DNA from the paternal parent. However, investigations of plastomes of large populations have provided evidence that a very low frequency of paternal plastid transmission can occur. Thus, the mechanism which ensures the elimination of paternal plastids is not 100% efficient. This suggestion is also supported by intraspecific reciprocal crosses between plants carrying mutant white and normal green plastids. While the offspring usually exhibit the maternal plastid type, a few cases indicate an apparent paternal plastid transmission.

1] This paper reports multiplatform observations of leader radiation preceding initial cloud-to-ground lightning return strokes by <6 ms. Specifically, we present multistation ground-based LF/VLF recordings of events with large-amplitude leader activity (comparable in amplitude to the return stroke amplitude). The events were selected for their coincidence with VHF observations by the FORTE satellite. Some FORTE VHF leader step observations have obvious direct and ground reflection components. For these steps, which temporally correspond to specific features in the ground LF/VLF field change records, we calculate a source height based on event satellite geometry. We determine source heights between 4.0 and 5.5 km. For FORTE records with multiple reflected events we calculate vertical leader propagation velocities on the order of 10 6 m/s. The determined vertical leader propagation speeds are an order of magnitude greater than those reported as typical values for stepped leader velocities associated with initial return strokes.

This study utilized the very low frequency-electromagnetic (VLF-EM) technique, a passive electromagnetic prospecting method working in the very low frequency range (15–30 KHz) to investigate the geo-environmental problems of shallow, low conductivity sedimentary layers in Taiwan. Field examples successfully demonstrate the advantages of using this method in locating non-mineralized shallow fault zones. The zero-crossings of in-phase and quadrature measurements in 2-D contour maps clearly locate the position of subsurface anomalous source bodies. Further analysis of the measured VLF single profile peaks reveals that this method is useful in determining subsurface structures and conductivity. The advantages of nondestructive, noninvasive, and low consumption of power make this method extremely friendly to the environment. The authors anticipate this method will have more profound impacts on the interactions between prospecting technology and the earth.

Low grade wastes produced by mining activities particularly in the sulphide deposits may cause detrimental impacts on the environment. In this situation, the remaining sulphide minerals within the waste dump may cause various toxic elements due to oxidation processes. The transportation of such elements into the surface and groundwater flow systems has serious impacts on the human being, aquatic life and other creatures. As the transportation of metallic pollutants by different physical and geochemical mechanisms could considerably change the conductivity of the polluted zone, so the electric and electromagnetic geophysical methods could successfully be used to map these zones. In this research, it is attempted the pollution potential of a sulphide mine located at the north-east of Iran to be investigated using the very low frequency electromagnetic (VLF- EM), resistivity (RES) and induced polarization (IP) geophysical methods. In addition, it is also aimed to perform a suitable num...

This paper investigates the electric and magnetic fields created due to the operation of roof-mounted photovoltaic units. For this purpose the most recent reference levels for safe general public and occupational exposure given in the guidelines of the International Commission on Non-Ionizing Radiation Protection are first presented. Basic constructional and operational data of the rooftop photovoltaic installations are examined follow, as well as a description of the measurement process. Electric and magnetic field measurements in typical photovoltaic units with different nominal powers and inverter types (single or three-phase) are performed under convenient weather conditions that ensure maximum electricity production. The main measurement results are evaluated according to the reference levels for safe public exposure, and the conclusion finally derived is that the examined fields are not dangerous and, therefore, are no cause for concern among the public.

Genetic hemochromatosis is an autosomal recessive disorder characterized by iron overload and a variety of clinical manifestations such as liver cirrhosis and arthropathy. It is the most common genetic disease of northern European populations. The principal gene responsible for hereditary hemochromatosis, designated HFE, is located on chromosome 6 in the HLA region. The single point mutation 845A, changing cysteine at position 282 to tyrosine (C282Y), in this gene has been identified as the main genetic basis of hereditary hemochromatosis. Two other mutations, 187G, a histidine to aspartate at amino acid 63 (H63D), and 193T, a serine to cysteine at amino acid 65 (S65C), appear to be associated with milder forms of hereditary hemochromatosis. There is a high prevalence of the C282Y mutation in northern European populations, whereas in those of the Mediterranean basin the prevalence seems low and almost absent in Far East countries. This mutation seems usually to occur on the ancestral haplotype 7.1. Accordingly, a Celtic origin of this mutation has been suggested. The aim of this study was to determine the frequency of HFE gene mutations in five geographic regions in Italy. Samples were tested for C282Y, H63D, and S65C mutations of the HFE gene according to methods of each laboratory and the results were standardized with the exchange of typed samples between the different laboratories. In addition, C282Ypositive DNA samples were typed for D6S105 allele 8 and HLA-A3 by ARMS-PCR. We have found that the allele frequency of the C282Y mutation decreases from northeast Italy (Friuli, 6%) to northwest Italy (Piedmont, 4.8%) and to central Italy (Emilia-Romagna, 1.7%). However, this mutation is lacking in the two regions of the Mediterranean basin's center (Sicily and Sardinia). Accordingly, a significant difference in the frequency of the mutation was observed between these Italian regions (P ϭ 0.07 ϫ 10 Ϫ3). In contrast, no difference was observed in allele frequency of H63D in the five Italian regions. Finally, as regards the S65C mutation a very low frequency was observed in Friuli, Emilia-Romagna, and Sardinia, whereas in Sicily and Piedmont we have not found this mutation. In conclusion, these data are consistent with the hypothesis that the C282Y mutation occurred in Caucasian populations of Celtic origin, whereas the H63D mutation is more ancient as demonstrated by the ubiquitous distribution.

While exercise heat stress and hydration status are known to independently influence heart rate variability (HRV), the combined effect of these physiological stressors is unknown. Thus, heat-acclimated subjects (n ¼ 5) performed exercise heat trials (40 1C, 20% relative humidity) in the euhydrated and hypohydrated state (3.970.7% body weight loss). During each trial, cardiac cycle R-R interval data were collected for 45 min at rest (pre-) and after (post-) completing 90 min of cycle ergometer exercise. Pre-and post-exercise RRI data were analyzed by Fast Fourier Power Spectral analysis to determine the high-frequency (HF), low-frequency (LF), very low-frequency (VLF), and total power (TP) components of HRV. Overall HRV was decreased by both hypohydration and exercise heat stress. Hypohydration reduced TP, LF, VLF, and LF:HF ratio ðPo0:05Þ while HF was significantly higher. The change in both LF and HF power (pre-vs. post-exercise) were blunted during hypohydration compared to euhydration. These data suggest that dehydration alone positively influences the parasympathetic (HF) control of HRV, but the reduction in overall HRV and the blunted oscillations in LF and HF power following exercise heat stress support an overall deleterious effect of dehydration on autonomic cardiac stability. Published by Elsevier Ltd.