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Magnetic Data (magnetic + data)
Selected AbstractsSynthesis, Structural, Thermal and Magnetic Characterization of a Pyrophosphato-Bridged Cobalt(II) ComplexEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2008Oluwatayo F. Ikotun Abstract The reaction in water of CoII sulfate heptahydrate with 1,10-phenanthroline (phen) and sodium pyrophosphate (Na4P2O7) in a 2:4:1 stoichiometric ratio resulted in the crystallization of a neutral dinuclear CoII complex, {[Co(phen)2]2(,-P2O7)}·6MeOH (1), as revealed by a single-crystal X-ray diffraction study. The bridging pyrophosphato ligand between the two [Co(phen)2]2+ units in a bis(bidentate) coordination mode places the adjacent metal centers at 4.857 Å distance, and its conformation gives rise to intramolecular ,,, stacking interaction between adjacent phen ligands. Indeed, intermolecular ,,, stacking interactions between phen ligands from adjacent dinuclear complexes create a supramolecular 2D network in 1. Magnetic susceptibility measurements on a polycrystalline sample of 1 in the temperature range 1.9,295 K are typical of an overall antiferromagnetic coupling with a maximum of the magnetic susceptibility at 3.0 K. The analysis of the magnetic data in the whole temperature range allows the determination of the value of the intramolecular magnetic coupling (J = ,1.23 cm,1). The ability of the pyrophosphato ligand to mediate magnetic interactions between different first-row transition-metal ions when adopting the bis(bidentate) bridging mode is analyzed and discussed in the light of the small number of magneto-structural reports on this type of compound, bearing in mind the number of unpaired electrons and type of magnetic orbitals on each metal center. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Tetracyanoquinodimethanido Derivatives of (Terpyridine)- and (Phenanthroline)metal Complexes , Structural and Magnetic Studies of Radical-Ion SaltsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2005Cristina Alonso Abstract Several derivatives of formulae [M(terpy)2](TCNQ)2 or [M(terpy)2](TCNQ)3 (M = Ni, Cu, Zn; terpy = 2,2,:6,,2"-terpyridine; TCNQ= 7,7,8,8-tetracyanoquinodimethane) and [M(phen)3](TCNQ)2 or [M(phen)3](TCNQ)4 (M = Fe, Ni; phen = 1,10-phenanthroline) have been obtained. The crystal structures of [M(terpy)2](TCNQ)2 (M = Ni, Cu) show that the metal is surrounded by the terpyridine nitrogen atoms in a closed octahedral environment and the TCNQ anions are dimerised by , overlap. The cationic [M(terpy)2]2+ and the anionic [TCNQ]22, groups alternate in the crystal. For the derivatives with three TCNQ groups, the existence of a stack of trimeric [TCNQ]32, ions having electronic delocalisation is proposed. The compound [Fe(phen)3](TCNQ)2, which shows a strong interaction between TCNQ anions, led to the formation of a , bond in the diamagnetic species [TCNQ,TCNQ], while the nickel analogue is expected to have a localised structure formed by alternation of cationic metal complexes and dimeric [TCNQ]22, anions similar to those observed in the analogous terpy derivatives. The derivatives having four TCNQ groups also show electronic delocalisation and a 1D stack based on the magnetic data is proposed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Using analytic signal to determine magnetization/density ratios of geological structuresGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2009Wen-Bin Doo SUMMARY The Poisson theorem provides a simple relationship between the gravity and magnetic potentials, which is useful in interpreting joint data sets of gravity and magnetic data. Based on the simple Poisson theorem, magnetization/density ratio (MDR) can be estimated. However, potential field data is often ambiguous in datum level and multisources interference that may cause bias in interpretation. Here, we propose an improved Poisson theorem to estimate MDR by using analytic signals of gravity and magnetic data. The major advantage of using the analytic signal is that we can also determine the sources locations and boundaries supposing that we know the ambient magnetic parameters. Besides, we can also avoid the determination error from uncertain datum levels. We demonstrate the feasibility of the proposed method in 2-D and 3-D synthetic models. The proposed method is also applied to a profile across the offshore area of northern Taiwan. Comparing with the reflection seismic profile, our result can help identify the existence of a deep-seated igneous body beneath the area of Mienhuayu and Pengchiagu islands off northern Taiwan. [source] The SGR 1806-20 magnetar signature on the Earth's magnetic fieldGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2006M. Mandea SUMMARY SGRs denote ,soft ,-ray repeaters', a small class of slowly spinning neutron stars with strong magnetic fields. On 2004 December 27, a giant flare was detected from magnetar SGR 1806-20. The initial spike was followed by a hard-X-ray tail persisting for 380 s with a modulation period of 7.56 s. This event has received considerable attention, particularly in the astrophysics area. Its relevance to the geophysics community lies in the importance of investigating the effects of such an event on the near-Earth electromagnetic environment. However, the signature of a magnetar flare on the geomagnetic field has not previously been investigated. Here, by applying wavelet analysis to the high-resolution magnetic data provided by the CHAMP satellite, a modulated signal with a period of 7.5 s over the duration of the giant flare appears in the observed data. Moreover, this event was detected by the energetic ion counters onboard the DEMETER satellite. [source] An enhanced method for source parameter imaging of magnetic data collected for mineral explorationGEOPHYSICAL PROSPECTING, Issue 5 2005Richard S. Smith ABSTRACT We have developed a method for imaging magnetic data collected for mineral exploration to yield the following structural information: depth, model type (structural index) and susceptibility. The active nature of mineral exploration data requires we derive the structural information from a robust quantity: we propose that the first- or second-order analytic-signal amplitude is suitably stable. The procedure is to normalize the analytic-signal amplitude by the peak value and then use non-linear inversion to estimate the depth and the structural index for each anomaly. In our field example, different results are obtained depending on whether we inverted for the first- or second-order analytic-signal amplitude. This is probably because the two-dimensional contact, thin sheet or horizontal cylinder models we have assumed are not appropriate. In cases such as these, when our model assumptions are not correct, the results should not be interpreted quantitatively, but they might be useful for giving a qualitative indication of how the structure might vary. With a priori information, it is possible to assume a model type (i.e. set the structural index) and generate estimates of the depth and susceptibility. These data can then be gridded and imaged. If a contact is assumed, the susceptibility contrast is estimated; for the dike model, the susceptibility-thickness is estimated; for the horizontal cylinder, the susceptibility-area is estimated. To emphasize that the results are dependent on our assumed model, we advocate prefixing any derived quantity by the term ,apparent'. [source] Euler deconvolution of the analytic signal and its application to magnetic interpretationGEOPHYSICAL PROSPECTING, Issue 3 2004P. Keating ABSTRACT Euler deconvolution and the analytic signal are both used for semi-automatic interpretation of magnetic data. They are used mostly to delineate contacts and obtain rapid source depth estimates. For Euler deconvolution, the quality of the depth estimation depends mainly on the choice of the proper structural index, which is a function of the geometry of the causative bodies. Euler deconvolution applies only to functions that are homogeneous. This is the case for the magnetic field due to contacts, thin dikes and poles. Fortunately, many complex geological structures can be approximated by these simple geometries. In practice, the Euler equation is also solved for a background regional field. For the analytic signal, the model used is generally a contact, although other models, such as a thin dike, can be considered. It can be shown that if a function is homogeneous, its analytic signal is also homogeneous. Deconvolution of the analytic signal is then equivalent to Euler deconvolution of the magnetic field with a background field. However, computation of the analytic signal effectively removes the background field from the data. Consequently, it is possible to solve for both the source location and structural index. Once these parameters are determined, the local dip and the susceptibility contrast can be determined from relationships between the analytic signal and the orthogonal gradients of the magnetic field. The major advantage of this technique is that it allows the automatic identification of the type of source. Implementation of this approach is demonstrated for recent high-resolution survey data from an Archean granite-greenstone terrane in northern Ontario, Canada. [source] Complex attributes of the magnetic signal for multiple sources: Application to signals from buried ditchesARCHAEOLOGICAL PROSPECTION, Issue 2 2010Christian M. Milea Abstract Complex attributes of the magnetic signal are computed using a multiple source approach. Polygonal bodies are considered and the attributes of each corner are summed to produce the overall response; that is a decomposition of the polygonal body into magnetized steps to simulate the vertices. The method is tested on synthetic examples of buried ditches, as well as on real magnetic data. This type of target was selected because it comprises a common objective in ,archaeological geophysics'. The resolution of the method in detecting the edges of the buried ditches depends on their lateral dimensions with respect to the sampling interval used. In general, the signal of the shallowest edges of the buried targets obscures the signal from the deeper corners, thus prohibiting their detection. In some extreme cases, the signals from the deeper corners posed a recognizable signature. The analytic signal may be seen as an anomaly rectification technique. In this context, it is suitable for the presentation of ,archaeological prospection' data since it provides an image that resembles the plane view of the buried antiquities better than the total field anomaly itself. Copyright © 2010 John Wiley & Sons, Ltd. [source] Magnetic survey at Venta Icenorum, Caistor St Edmund: Survey strategies and initial resultsARCHAEOLOGICAL PROSPECTION, Issue 4 2009D. Bescoby Abstract This short report summarizes two seasons of magnetic surveying at the Roman town of Venta Icenorum at Caistor St Edmund, Norfolk. Survey strategies have been developed utilizing caesium vapour magnetometers mounted on a wheeled platform with a global positioning system to map former areas of settlement and their immediate hinterlands. The resulting survey system has enabled the rapid collection of high-resolution magnetic data over an area of 30,ha, providing a detailed magnetic map of the former town. Details of the system configuration and survey strategy are described and data from the survey presented. Copyright © 2009 John Wiley & Sons, Ltd. [source] Multimethodological approach to investigate chamber tombs in the Sabine Necropolis at Colle del Forno (CNR, Rome, Italy)ARCHAEOLOGICAL PROSPECTION, Issue 2 2009Salvatore Piro Abstract Non-destructive geophysical prospecting methods are increasingly used for the investigation of archaeological sites, especially where a detailed physical and geometrical reconstruction of structures is required prior to any excavation work. Often, due to the limited size and depth of an archaeological structure, it may be rather difficult to single out its position and extent because of the generally low signal-to noise (S/N) ratio. This can be overcome by improving data acquisition and processing techniques and integrating different geophysical methods. In this work the results of a multimethodological surveys, used with the aim of detecting sharp discontinuities (boundary of cavities and fractures in the host medium) at the Archaeological Test Site of Sabine Necropolis at Research Area of National Research Council of Rome (Montelibretti, Italy) are shown. For the survey a combination of passive and active methods (magnetic, ground-penetrating radar (GPR), and dipole,dipole geoelectric (DDG)), topographical and three-dimensional laser scanner surveys and archaeological excavations were used to study the state of conservation of underground tombs. With all geophysical methods a high-resolution data acquisition was adopted with the aim of reconstructing a global vision of the study area. Signal processing and amplitude time-slice representation techniques were used for the analysis of GPR data. The bi-dimensional cross-correlation technique was applied to enhance the S/N ratio of the magnetic data. An example of the integration (both qualitative and quantitative) of these results is presented for a portion of the investigated area in the Sabine Necropolis at Colle del Forno (Rome, Italy). Archaeological excavations were then conducted systematically after completing the geophysical surveys and interpretations (from 2000 to 2006), which confirmed the location and shape of the individual chamber tombs with associated corridors. Copyright © 2009 John Wiley & Sons, Ltd. [source] Geophysical investigation of the Environs of Rattin Castle Tower House, County Westmeath, IrelandARCHAEOLOGICAL PROSPECTION, Issue 1 2009T. O'Rourke Abstract No visible archaeological features are today associated with Rattin Castle Tower House in County Westmeath, Ireland located near the boundary of the Pale, the area around Dublin and adjoining counties where English control prevailed. However, both magnetic and resistance data show that Rattin Castle was surrounded by a substantial bawn wall, which has since been removed. Interpretation of two-dimensional resistivity shows a deep trench at the site of the bawn wall. A small (12 by 16,m) rectangular low-resistance anomaly located outside the northern section of the bawn wall but connected to it, is interpreted as a possible gatehouse providing access to the castle. Less than 20,m from this anomaly, the course of an old military road is delineated by magnetic data but is seen most clearly on the resistance data where it is represented by two parallel low-resistance anomalies 230,m long. This road is possibly older than the castle. Rattin is associated with an extensive network of subrectangular field boundaries and enclosures, most noticeably west of the castle. The presence of the military road, potential gatehouse, substantial bawn wall and geographical location all suggest that Rattin Castle was an important strategic fortification in Ireland. Copyright © 2009 John Wiley & Sons, Ltd. [source] Determination of grave locations in Dedemezari Necropolis (Western Turkey) using magnetic field derivativesARCHAEOLOGICAL PROSPECTION, Issue 4 2008A. Büyüksaraç Abstract The location of the study area for this research of a Middle Bronze Age Necropolis is situated in the west of Turkey near Afyonkarahisar. Magnetic surveying was carried out in two adjacent areas (Areas 4 and 5). Four trenches have been excavated so far and graves were located in positions interpreted from a magnetic survey carried out in 2005. Initial excavations have shown that cist, pithos and simple graves were placed randomly and it is suggested that Dedemezari Necropolis is similar to the well known necropoleis of Gordion and Sariket. This paper compares the results of some phase-based filters which show improved performance as edge detectors in different ways. The filters are demonstrated on synthetic magnetic data and magnetic field data from Dedemezari Necropolis. Magnetic field derivatives, both vertical and horizontal, are common and useful tools for interpretation of the magnetic anomalies. Interpretation of magnetic field derivatives, separately or together, provide images of shallow bodies from magnetic data. The horizontal derivatives of the total magnetic field were computed in the space domain by means of finite-difference relationships, and the vertical derivative was computed in the frequency domain by using fast Fourier transform filtering. Derivatives of the magnetic anomalies have been used for detection of causative bodies. The analytic signal (AS), the enhanced horizontal derivative (EHD), tilt derivative (TD), theta map, hyperbolic tilt angle (HTA) and total horizontal derivative (THDR) methods were applied not only to synthetic anomalies but also to the measured magnetic anomalies of Areas 4 and 5. However, AS and EHD produced the best results as the other methods created edge effects. Copyright © 2008 John Wiley & Sons, Ltd. [source] New approach to the study of city planning and domestic dwellings in the ancient Near EastARCHAEOLOGICAL PROSPECTION, Issue 2 2007Christophe BenechArticle first published online: 8 MAY 200 Abstract This paper presents the results of a magnetic survey on the Hellenistic and Roman site of Doura- Europos in Syria. The interpretation of the magnetic data is based on an original approach by considering the use of space in a domestic unit. This type of study has been developed for sociological research but is adapted to the information carried within geophysical data. After a brief presentation of the role of geophysical methods for the study of city planning, the most important components of the ,space syntax' will be presented and applied to two blocks of Doura-Europos, one that has been excavated in the twentieth century by the Yale University and another surveyed using the magnetic method. Copyright © 2007 John Wiley & Sons, Ltd. [source] 3D seismic imaging of a Tertiary Dyke Swarm in the Southern North Sea, UKBASIN RESEARCH, Issue 2 2010Mostyn Wall ABSTRACT We use three-dimensional (3D) seismic reflection and magnetic data to interpret and describe the 3D geometry of igneous dykes in the southern North Sea. The dykes were emplaced into Paleozoic and Mesozoic sediments and have a common upper termination in Early Tertiary sediments. We interpret the dykes to be part of the British Tertiary volcanic province and estimate the age of the dykes to be 58 Ma. The dykes are characterized by a narrow 0.5,2 km wide vertical disturbance of seismic reflections that have linear plan view geometry. Negative magnetic anomalies directly align with the vertical seismic disturbance zones and indicate the presence of igneous material. Linear coalesced collapse craters are found above the dykes. The collapse craters have been defined and visualized in 3D. Collapse craters have formed above the dyke due to the release of volatiles at the dyke tip and resulting volume loss. Larger craters have potentially formed due to explosive phreatomagmatic interaction between magma and pore water. The collapse craters are a new Earth analogue to Martian pit chain craters. [source] A New Hydroxo-bridged Chromium(III) Dimer [Cr(saltn)OH]2·4H2O: Synthesis, Crystal Structure and Magnetic PropertiesCHINESE JOURNAL OF CHEMISTRY, Issue 6 2005Ni Zhong-Hai Abstract A new hydroxo-bridged dimeric Cr(III) complex [Cr(saltn)OH]2·4H2O [H2saltn=N,N,-bis(salicylidene)trimethylenediamine] has been synthesized and its structural and magnetic properties have been investigated. The complex crystallizes in the triclinic space group P -1 with one dimeric formula unit in a cell of dimensions a=0.95828(19) nm, b=0.95926(19) nm, c=1.0437(2) nm, ,=86.77(3)°, ,=82.48(3)°, and ,=64.93(3)°. The geometry around each chromium(III) center is six-coordinate, distorted-octahedral. The bridging Cr2O2 unit is strictly planar, as required by the crystallographic symmetry. The CrOCr, bridging angle is 99.94(16)°, and the distance between Cr,Cr, is 0.3019 nm. The magnetic susceptibility of the complex has been examined in the range of 2-300 K. By using the spin-spin coupled model for an S1=S2=3/2 dimeric system , the magnetic data were fitted to give the parameters of g=2.01(1), J=-0.85(2) cm -1, and zJ' =0.18(3)cm -1, indicating the presence of a weak antiferromagnetic spin-exchange interaction between the Cr(III) ions in the binuclear complex. [source] | |||||||||||||