bluuebunny/crossref_metadata_2025 huggingface dataset:
Progress of remote sensing in Australia
Authors: Furlong V.L.R.
Published: November 2007

During the past year multispectral photography and thermal infra-red scanning have been introduced to the region. The Cartwright multilens camera and the Daedalus thermal scanner have opened entirely new remote sensing horizons to consumers including government agencies, mining companies, forestry departments and municipal authorities. Much of the introduction has been via comprehensive test programmes over well known and documented features. Multispectral photography has been successfully used in several Queensland and Tasmanian mining areas as an aid to geological mapping, and by highway authorities in New South Wales. Thermal infra-red scanning has been carried out in the Territory of Papua New Guinea in search for geothermal areas and has proved highly successful in the search for upwelling fresh water into the ocean along coastal areas ultimately for a source of fresh water. Pollution studies involving oil slicks, sewerage, thermal pollution and illegal releasing of industrial waste have taken place in and around major population centres on the east coast using thermal detection techniques. Undoubtedly one of the major contributions thermal infra-red scanning has achieved is in the mineral exploration field. The large arid regions of Australia lend themselves well to presunrise scanning, where as a direct result of the work undertaken, significantly large new mineral discoveries have been made. Additional research and development further into the remote sensing field are taking place in Universities, quasi-governmental agencies and in the private sector like ourselves. The future looks bright for remote sensing in this part of the world and through same are continuing to further improve the environment we live in.
Hydrogeological applications of the empirical approach to water resistivity - salinity relationships
Authors: Haines B.M. , Emerson D.W. , Smith M.J.
Published: November 2007

Hydrogeological evaluation of subsurface aquifers involves measurement of electrolyte resistivity and subsequent determination of solution salinity. Resistivity of the water may be evaluated by quantitative interpretation of electrical well logs or by direct measurement on recovered samples. Determination of a reliable relationship between electrolyte resistivity and salinity presents a more difficult problem. Approximate solutions have been attempted frequently on theoretical and experimental bases. An empirical relationship derived from previously collected data provides the most satisfactory solution for any particular situation (be it region, valley, basin or aquifer).
On the electrochemical nature of I.P.
Authors: Lynam J.T.
Published: November 2007

Although the measurement of induced polarization effects has been universally accepted as a viable technique of geophysical prospection, the underlying electrochemical phenomena which contribute to the measured effect are less well understood. The present paper reviews the various phenomena which are thought to contribute to induced polarization and the contribution of univalent interfacial electrochemical reactions is considered in detail for both metallic I.P. and the normal effect. The treatment gives rise naturally to the presence of secondary current generators at the metal/electrolyte interface and the time characteristics of such generators are exhibited by the I.P. voltage decay.
Sign conventions in magnetometry for southern hemisphere - discussion
Authors: Shalley M.J.
Published: November 2007

I would like to add to the discussions on sign conventions in magnetometry for the southern hemisphere which were published in the last issue of the ASEG bulletin.
Data integration of exploration data using colour space on an image processor
Authors: Spencer G.A. , Pridmore D.F. , Isles D.J.
Published: November 2007

lmage processing in exploration has rapidly evolved into the field of data integration, whereby independent data sets which coincide in space are displayed concurrently. Interrelation-ships between data sets which may be crucial to exploration can thus be identified much more effectively than with conventional hard copy overlays. The use of perceptual colour space; hue, saturation and luminosity (HSL) provides an effective means for integrating raster data sets, as illustrated with the multi-spectral scanner and airborne geophysical data from the Kambalda area in Western Australia. The integration process must also cater for data in vector format, which is more appropriate for geological, topographic and cultural information, but to date, image processing systems have poorly captured and managed such data. As a consequence, the merging of vector data management software such as GIS (geographic information system) with existing advanced image enhancement packages is an area of active development in the exploration industry.
Geophysical methods of oil and gas exploration in cambrian and precambrian sedimentary rocks of the Siberian Platform
Authors: Mandelbaum M.M. , Shamal A.I.
Published: November 2007

The Siberian Platform is the largest hydrocarbon-bearing sedimentary basin in the USSR. The conditions encountered in geophysical exploration in this basin are uniquely difficult. This very old sedimentary complex is characterised by abrupt changes in physical properties reflecting the presence of dolerites and tuffs, changes in salt thickness, and complex structure. Petroleum traps are controlled by low amplitude structures in the salt complex, although reservoir properties are variable, so that most traps are stratigraphic. This leads to the use of frequency content of seismic data to identify traps and electrical and time domain EM techniques to confirm the presence of the traps.
Airborne spectral sensing of hydrothermal alteration minerals
Authors: Lee J.B. , Osborne P.R. , Williams J.C. , Woodyatt A.S.
Published: November 2007

Remote sensing infrared spectrometer data were collected with the Geophysical and Environmental Research Corp. 64 channel scanning spectrometer. These have been used to delineate geological units and, subject to some ambiguity, identify their mineralogy. Results are given for a survey area near Coppin Gap in the Pilbara region of Western Australia. Here, clear distinction was obtained between the sericite mineralogy of the Hardey Sandstone and some members of the Marble Bar belt, and the carbonate or epidote/chlorite mineralogy of the Kylena Basalt and other units in the Marble Bar belt.From the airborne spectrometer data it was also possible to identify and map the occurrence of the mineral pyrophyllite. Analysis of field samples confirmed the identification and provided evidence that the technique was indeed mapping the occurrence of this mineral.The applicability of this technique has been assessed from other surveys in Australia, and it appears to require good geological exposure and sparse vegetation. There is some scope for extension of its applicability through further instrumental developments.
The application of airborne geophysics to epithermal gold exploration in Eastern Misima Island, Papua New Guinea
Authors: Logan K.
Published: November 2007

Misima Island is situated 625 km east southeast of Port Moresby in Papua New Guinea. A detailed airborne magnetic and radiometric survey was carried out over the eastern portion of the island which contains the Umuna epithermal gold deposit.The purpose of the survey was to improve the understanding of surface and underlying geology and assist the regional mineral exploration of the area.In situ magnetic susceptibility measurements were taken within the survey area to determine the magnetic properties of the various Palaeocene-Miocene metasedimentary sequences and Miocene porphyritic felsic intrusives.The interpretation of the airborne magnetic data was constrained by susceptibility measurements, magnetic modelling and regional geological mapping. Computer processing included the use of reduction to the pole and pseudo gravimetric transforms.Variable density and type of vegetation cover on the island limited previous interpretations of the airborne radiometric data. The data was reprocessed using principal components analysis of the potassium and total count radiometric data.
Interpretation and removal of EM coupling in IP data
Authors: Grant T.W. , Hohmann G.W.
Published: November 2007

We have computed EM coupling responses for the dipole-dipole IP array over realistic 3-D bodies using a volume integral equation approach. The objectives of these simulations are to gain insight regarding negative EM coupling over good conductors, to analyze the phase extrapolation method of removing EM coupling, and to determine whether interpretation of the EM coupling can help resolve the resistivity structure. Our results show that a good conductor, especially if it is shallow, can produce a complex pattern of negative and positive coupling in a pseudosection. Extrapolating three-frequency phase data to zero frequency eliminates EM coupling in most cases; however, residual EM effects may be present in extremely low-resistivity environments. We are studying ways of utilizing EM coupling to provide information about 3-D bodies beyond that produced by DC resistivity data.
Results of geoelectrical soundings for mapping of a marine clay along the Tangkak-Pagoh highway Johor, Malaysia
Authors: Rafek A.G. , Samsudin A.R.
Published: November 2007

Geoelectrical resistivity soundings conducted along the north-south expressway in the Tangkak-Pagoh area during its construction enabled the mapping of a marine clay which was present in alluvium. The apparent resistivity curves of the marine clay area, were characterised by low apparent resistivity values falling to almost zero, and a characteristic shape which was different from areas of weathered metasediments and weathered granite adjacent to this area. Apparent resistivities for both metasediments and granite were intermediate to high, with a distinct upward convex curve for metasediments and a flat upward convex curve for granite. Quantitative interpretation was able to distinguish between an upper and a lower clay horizon, which have differentconsistency and fine sand content. The thickness of the upper clay horizon, which varies between 8.0 m to 9.0 m according to borehole data showed good agreement with that obtained by resistivity soundings. The base of the lower clay horizon remained undetected by the resistivity soundings because of its very low specific resistivity. Using the thickness of weathered layers as observed along the road cuttings as a guide, good agreement between field data and calculated values was obtained in determining the specific resistivities and individual layer thicknesses for the granite and metasediment weathering profiles.
Case histories and modelling interpretation in CSAMT
Authors: van Reed E. , Maclnnes S. , Smith M.
Published: November 2007

Two CSAMT case history studies are presented in which modelling has been applied to data in order to produce geo-electric depth sections. These sections then assist in developing an idealized geologic model used as part of a geological exploration programme. At the geological planning level, one can define certain key geologic features which need to be identified as part of an exploration programme. Modelling may give some indication as to the success of a particular planned geophysical programme.At the interpretation level, modelling can be used to confirm or disprove geologic ideas previously developed, and aid in quantifying features that survive the test. In addition, modelling may give new insights on how to get more information from the geophysical data and give rise to new ideas.The case history information comes from the Golden Cross mine development programme near Waihi, New Zealand, and from the Togi exploration programme conducted near Kanazawa on the island of Honshu, Japan. While the distance separating the two survey sites is great, they are both epithermal gold prospects. CSAMT was used to obtain high resolution structural mapping both for near-surface geology and geology at depth, which are two important tasks.Modelling of the CSAMT data obtained at Golden Cross and Togi is provided by three different computer programmes: CSINV is a one-dimensional general EM field approach using a finite number of layers where the survey geometry is specified; a variation of CSINV uses an infinite number of one-dimensional layers; and EM2D is a two-dimensional approach using a finite number of bodies/layers based on plane-wave EM theory. All three modelling approaches provide resistivity values varying as a function of depth, however useful results with EM2D are limited to modelling frequencies where data satisfies plane-wave criteria.Modelling at Golden Cross provides cross-sectional geoelectric information which extends known drill-hole geology. This provides broader detail to known information, and suggests additional potentially interesting features. Modelling at Togi was directed at providing plan view coverage of certain geologic structures. Here one survey objective of the CSAMT survey was to provide structurally related control to be used with interpretation of geochemical data.Even though targets are geologically similar, planning and interpretational goals differed. CSAMT modelling optimized the interpretational use of CSAMT data in each case history.
Seismic reflection survey by the crooked line method applied to a coalfield in a mountainous region
Authors: Nakano O. , Tamari A. , Tobe Y.
Published: November 2007

In the past, seismic reflection surveys on land in Japan have usually been carried out along straight lines irrespective of surface terrain. However in Japan, where most of the areas are covered by mountainous terrain, it may require considerable time and cost to carry out field operations by the straight line method.From August to October in 1988, a reflection seismic survey was carried out at the Sarufutsu area in Hokkaido, Japan. The area is in a mountainous region where the straight line method was very difficult to conduct. A trial of the crooked line method was introduced to the area by laying out seismic lines along roads and valleys.Four test borings with VSP and extensive field geological surveys were carried out in this area by NEDO (New Energy and Industrial Technology Development Organization) prior to 1987, and the results show that there is a north-south trending syncline in the area and that the maximum depth of the main coal seam is approximately 600 m below the surface.The data acquisition system adopted was a 48-trace IFP digital recording system with one-millisecond sample interval.The result of the survey gives a good correlation with existing geological information.It has been concluded that seismic reflection surveys by the crooked line method are applicable for coal exploration in such a mountainous terrain.
Borehole radar applied to characterization of fracture zones
Authors: Olsson O. , Falk L. , Forslund O. , Niva B. , Sandberg E.
Published: November 2007

A new short-pulse radar system (RAMAC) developed by ABEM AB has now been in operation for three years during which more than 100 km of borehole logging has been performed. The bulk of the surveys have been in granites and gneisses.The RAMAC system operates at centre frequencies in the interval 20 to 60 MHz. At those frequencies single-hole reflection ranges of 50 to 150 m are normally obtained in gneissic and granitic rock. Cross-hole ranges have in some cases exceeded 300 m. The large probing range in combination with resolution of the order of a few metres makes borehole radar a unique technique for investigation of fracture zones in crystalline rock.Case histories illustrate application of the RAMAC system in three different configurations (single-hole reflection, cross-hole reflection, and cross-hole tomography) and demonstrate how combination of these three can yield consistent 3D models of fracture zones and other structures.
Diffraction tomography applied to crosshole and VSP seismic data
Authors: Young J.A.
Published: November 2007

Diffraction tomography is an approach to seismic inversion which is analogous to f-k migration. It differs from f-k migration in that it attempts to obtain a more quantitative rather than qualitative image of the Earth's subsurface. Diffraction tomography is based on the generalized projection-slice theorem which relates the scattered wave field to the Fourier spectrum of the scatterer. Factors such as the survey geometry and the source bandwidth determine the data coverage in the spatial Fourier domain which in turn determines the image resolution. Limited view-angles result in regions of the spatial Fourier domain with no data coverage, causing the solution to the tomographic reconstruction problem to be nonunique. The simplistic approach is to assume the missing samples are zero and perform a standard reconstruction but this can result in images with severe artefacts. Additional a priori information can be introduced to the problem in order to reduce the nonuniqueness and increase the stability of the reconstruction. This is the standard approach used in ray tomography but it is not commonly used in diffraction tomography applied to seismic data.This paper shows the application of diffraction tomography to crosshole and VSP seismic data. Using synthetic data, the effects on image resolution of the survey geometry and the finite source bandwidth are examined and techniques for improving image quality are discussed.
The effect of vertical crustal fractures on the rifting process
Authors: Anfiloff V.
Published: November 2007

In the past, rifts have mainly been identified in terms of sediment troughs. They account for many of the elongate gravity lows distributed in a coherent rectilinear manner over the continent. Other gravity lows can be attributed to granites intruding rift compartments, and some gravity highs can be attributed to basic volcanics in compartments. The total number of rifts which can be thus inferred from gravity and magnetics is very large, and suggests rifting is pervasive over the whole continent and controlled by a systematically distributed "Cardinal" system of ancient vertical crustal fractures.The extensional concept of rifting is based on a finite number of rifts, all of which have "failed" to split the continent. When a far greater number of rifts is recognised, it becomes difficult to accept that all these rifts have "failed" to reach full opening by extensional processes. In view of the known horizontal compressive forces acting in the crust, it is more probable that rifting is caused by compression. The compartmentalization of rifts, clearly observed in gravity data, also implies compression.Closely spaced rectilinear dyke systems in shield areas may also represent the pervasive "Cardinal" fracture system. In general, this system of orthogonal fractures poses problems for the detatchment rifting concept which assumes that transfer faults are formed at the time a rift forms, whereas they in all probability predate the rift, and owe their existence to a fundamental process operating when continental crust first formed.Two types of compressive rift models are discussed. One is associated with shear couples between widely spaced parallel fractures. The other is based on the concept of a crust cut by closely spaced fractures in which compression is propagated along a network of linked blocks. In both cases the development of basement ridges is a key issue.
Production of a residual gravity field map for Tasmania and some implications
Authors: Leaman D.E. , Richardson R.G.
Published: November 2007

The substantial gravity data base in Tasmania has been used to formulate a regional crustal model. This was derived by array modelling techniques for geological sources of crustal scale. A simultaneous solution for mantle, basement and granite forms was created by this means within a framework of realistic and internally consistent assumptions. The regional field derived from this geological model (including the ocean basins) is not dependent on any filtering or smoothing procedure and thus the magnitude and sign of any residuals is absolute. The residual map was produced by removing the effect of the crustal model at individual data points. The resultant map enables detailed and reliable modelling of upper crustal features as well as revealing crustal character hitherto concealed beneath post Carboniferous cover. An important example of the value of the residual separation is shown by the structural relationships exposed in NE Tasmania which involve gold mineralisation.
A 3D isochronal modelling technique and its applications
Authors: Cao S. , Kennett B.L.N. , Goleby B.R.
Published: November 2007

Reflection seismic datasets are obtained in both the exploration of oil and mineral resources and the probing of the deep crust and the upper mantle. To interpret the datasets, considerable effort has been spent on the understanding of seismic wave propagation phenomena by simulating seismic wave propagations in some a priori physical models. A rather simple and efficient modelling technique has been developed to study elastic wave reflections with full inclusion of diffractions.This modelling technique employs an integral representation of reflections from a surface or a scatterer. High frequency asymptotic approximations are used for the propagation between the seismic source or receiver and a surface or a scatterer. At a scatterer, first order scattering is assumed. At a surface, reflection and transmission effects are estimated using the assumption of a locally plane interface and plane incident wave. With these approximations, the reflected seismograms are calculated by convolving the time derivative of a source function with a model weight function for a particular source-receiver pair. The weight function at a particular time is evaluated by a line integral along a contour of equal total travel time from source to receiver via the scattering surface (an isochron). The kernel of this integral at a reflecting point is the local reflection coefficient which which represents the effects of the amplitude of material parameter contrasts at the reflecting point, the angles between the incoming and outgoing waves and the local surface normal and the local speed of advance of the isochron on the surface, and the geometrical spreading factors from the source and receiver to the reflecting point.This modelling technique is used to investigate the validity of some of the interpretations of a deep crustal reflection profile collected in central Australia. The modelling results confirm that even with a relatively short (4 km) field spread it would be possible to pick up the reflected energy from faults with dips of about 40�. The largest fault, the Redbank Zone, has significant displacement of the crust-mantle boundary and within the fault zone, it is conceivable to have considerable variability in physical properties.The deep seismic section shows this boundary as a thick (0.5s) band of complex reflections and diffractions at the reflection time appropriate to the crust-mantle transition. Two possible structures for the crust-mantle boundary were investigated, one where the crustal faults have displaced this interface and created a 'block-faulted' geometry and the other where the crustal faults are listric near the boundary and appear to sole out on the crust-mantle interface, giving rise to an undulation of the Moho. The modelling results (Figure 1) for an undulating boundary show a band of reflections which strongly resemble the observed seismic reflection data.
Practical 3D refraction statics
Authors: Dent B.
Published: November 2007

Analysis of refracted first breaks has traditionally assumed that the data have been collected using special geometries that enhance the results, e.g. reversed profiles with regularly spaced geophones in-line between two shots. The geometries used to collect most 3D reflection data are quite different. Thus refraction analysis to obtain statics using traditional methods requires both approximations and selection of a subset of the data. The surface-consistent method allows use of nearly all the data, thus providing the high redundancy required for statistical robustness. A large survey incorporating both a new 3D survey and older 2D lines yielded refraction statics that greatly improved the final results.The surface-consistent method assumes that the refractor can be approximated by a horizontal plane under each station. When the refracting surface is steeply dipping, this assumption may break down. The Generalized Reciprocal Method is a traditional refraction analysis technique that gives improved results for steeply-dipping refracting surfaces. The surface-consistent method can also be made less sensitive to dip by a generalization, i.e. assume a dipping plane under each station. The refracting surface between the stations can be approximated by interpolation of these planes using the "linear projection" technique. A comparison of results using the two surface-consistent methods on synthetic data generated from a model of a buried, steep-walled valley shows the superior results obtainable.
The instantaneous-phase time slice: A crucial display for enhancing 3-D interpretation
Authors: Duff B.A. , Mason D.J.
Published: November 2007

Instantaneous-phase is the optimum attribute to use in horizontal seismic time slices for rapid, accurate 3-D structural mapping, because of its enhancement of event continuity. Instantaneous-phase slices also provide the interpreter with the most precise display for directly interpreting spatial relationships between seismic sequences, by reasoning analagous to that used to interpret geological maps. In contrast, amplitude time slices lack precision because weak events are lost by scaling, and wavelet phase points can only be crudely estimated.
A case history of a cost effective 3D seismic survey over the Perth Basin, Western Australia
Authors: Stewart S.C. , Evans B.J.
Published: November 2007

As part of an industry funded research project into the application of the technique of LOFOLD3D land seismic surveying, a four fold three dimensional seismic survey was performed in the Perth Basin at Moora, Western Australia in July 1987. The volume covered an area of four kilometres by just under two kilometres, producing a total of 23,000 common midpoint traces. The objective was to collect and process the data in such a manner that a three dimensional structural interpretation would result, which would be the same as that resulting from a conventional three dimensional survey. A cost comparison indicates that a commercial LOFOLD3D survey would reduce the cost of performing a land 3D survey to an estimated 20% of the full fold equivalent, and the technique therefore offers potential for substantial savings if it is adopted on a commercial basis.
Gathering good seismic data from the Otway Basin
Authors: Heath A.M. , Culver A.L. , Luxton C.W.
Published: November 2007

Cultus Petroleum N.L. began exploration in petroleum permit EPP 23 of the offshore Otway Basin in December 1987. The permit was sparsely explored, containing only 2 wells and poor quality seismic data. A regional study was made taking into account the shape of the basin and the characteristics of the major seismic sequences. A prospective trend was recognised, running roughly parallel to the present shelf edge of South Australia. A new seismic survey was orientated over this prospective trend. The parameters were designed to investigate the structural control of the prospects in the basin. To improve productivity during the survey, north-south lines had to be repositioned due to excessive swell noise on the cable. The new line locations were kept in accordance with the structural model. Field displays of the raw 240 channel data gave encouraging results. Processing results showed this survey to be the best quality in the area. An FK filter was designed on the full 240 channel records. Prior to wavelet processing, an instrument dephase was used to remove any influence of the recording system on the phase of the data. Close liaison was kept with the processing centre over the selection of stacking velocities and their relevance to the geological model. DMO was found to greatly improve the resolution of steeply dipping events and is now considered to be part of the standard processing sequence for Otway Basin data. Seismic data of a high enough quality for structural and stratigraphic interpretation can be obtained from this basin.
Three-component amplitude versus offset analysis
Authors: Miles D.R. , Gassaway G. , Bennett L. , Brown R.
Published: November 2007

Three-component (3-C) amplitude versus offset (AVO) inversion is the AVO analysis of the three major energies in the seismic data, P-waves, S-waves and converted waves. For each type of energy the reflection coefficients at the boundary are a function of the contrast across the boundary in velocity, density and Poisson's ratio, and of the angle of incidence of the incoming wave. 3-C AVO analysis exploits these relationships to analyse the AVO changes in the P, S, and converted waves. 3-C AVO analysis is generally done on P, S, and converted wave data collected from a single source on 3-C geophones. Since most seismic sources generate both P and S-waves, it follows that most 3-C seismic data may be used in 3-C AVO inversion. Processing of the P-wave, S-wave and converted wave gathers is nearly the same as for single-component P-wave gathers. In split-spread shooting, the P-wave and S-wave energy on the radial component is one polarity on the forward shot and the opposite polarity on the back shot. Therefore to use both sides of the shot, the back shot must be rotated 180 degrees before it can be stacked with the forward shot. The amplitude of the returning energy is a function of all three components, not just the vertical or radial, so all three components must be stacked for P-waves, then for S-waves, and finally for converted waves. After the gathers are processed, reflectors are picked and the amplitudes are corrected for free-surface effects, spherical divergence and the shot and geophone array geometries. Next the P and S-wave interval velocities are calculated from the P and S-wave moveouts. Then the amplitude response of the P and S-wave reflections are analysed to give Poisson's ratio. The two solutions are then compared and adjusted until they match each other and the data. Three-component AVO inversion not only yields information about the lithologies and pore-fluids at a specific location; it also provides the interpreter with good correlations between the P-waves and the S-waves, and between the P and converted waves, thus greatly expanding the value of 3-C seismic data.
A new approach to signature analysis in seismic interpretation using an interactive workstation
Authors: Paterson G.A.D.
Published: November 2007

Initial hydrocarbon discoveries normally lead to a succession of wells on the same or similiar seismic trends, sometimes with a succession of dry holes. The problem posed is, given some initial success, to what extent can seismic be used to predict lithology and prevent these occurrences. Satellite technologists already utilize similar methods to quickly identify similar terrain features using an image 'bench mark', and multiple signals. The bench mark for the seismic interpreter is the well, and the multiple signals are the seismic attributes. The tool used to bring these together is the interpretation workstation. A demonstration of the technique on synthetic data displays good results, dependent on several factors. Future work will be directed at evaluating the method on field data and together with other lithology prediction methods.
Depth conversion problems of the SKUA field
Authors: Cowley R.G.
Published: November 2007

Before oil volumes and economics can be calculated for an oil field, the seismic time map must be converted to a depth map. The Skua Field, located in Permit AC/P2 in the Timor Sea, has proved particularly difficult to depth convert. Velocity anomalies and inconsistencies in the seismic times, termed 'lags', have created distortions in the seismic time map which require compensation. Beneath a velocity anomaly, both seismic undershoot and increased velocity, which are difficult to determine, must be compensated for during depth conversion. The current depth map was produced by smoothing through the pull-up regions on the time map, which required judgement, then depth, converting using a regional average velocity field. The seismic lag, which is the difference between the seismic time and an ideal vertical path travel time, can only be measured at the wells and appears to be unpredictable. The seismic lag between Skua-4 and Skua-5 was assumed to change linearly in order to produce the depth map. Large lags can be introduced into the data in the common depth point stack stage of data processing. The stacking velocity with the largest stack response does not necessarily result in the smallest lag error.
Sediment compaction and magnetotelluric data in the Eromanga Basin
Authors: Cull J.P. , Gray J.D.
Published: November 2007

Magnetotelluric data obtained in the Eromanga Basin can be interpreted using one-dimensional models to describe plane layers consistent with geological mapping. Interpretations are based on the results of non-linear inversions generating a minimum least-squares error between the observations and the model. However there is no statistical justification for selecting highly complex starting models. In particular adequate solutions can be generated using models based on 2, 3 or 4 layers over basement; additional layers defining fine structure can only be retained using external geological constraints. Solutions based on random starting models suggest gradations in resistivity (1?4 ohm m) consistent with sediment compaction. Major discontinuities in all models (4?30 ohm m) are assumed to indicate a basement contact at depths of 7?8 km.
Effect of highway construction on plant diversity of grassland communities in the permafrost regions of the Qinghai - Tibet plateau
Authors: Guo Zheng Gang , Long Rui Jun , Niu Fu Jun , Wu Qing Bo , Hu Yu Kun
Published: November 2007

During 2002–2004, a broad-scale survey on the plant diversity of grassland communities along a natural elevation gradient in the permafrost regions of the Qinghai–Tibet plateau, China, was conducted to investigate the effect of highway construction nearly 30 years ago. Richness index was not significantly different among undisturbed communities (Kobresia pygmaea meadow, K. humilis meadow, Stipa purpurea steppe, Carex moorcroftii steppe), but significant differences (P < 0.05) were observed for evenness and diversity indices among four undisturbed communities. Three indices significantly decreased from communities 100 m (lightly disturbed communities), 200 m (undisturbed communities), and 50 m (severely disturbed communities) from the Qinghai–Xicang Highway, and three indices of severely disturbed communities were similar to that of 30 m communities (extremely-severely disturbed communities). Diversity and richness indices peaked at intermediate elevations of 4720 m in undisturbed communities and lightly disturbed communities, but were uniform in the severely disturbed communities and extremely-severely disturbed communities along with the increase of elevation. β-Diversity decreased in communities at 30, 50, and 100–200 m distance from the highway. This indicated that β-diversity of communities was enhanced with the increase of disturbance for each grassland type in the study region. Both undisturbed and disturbed communities showed the same changeable bell-shaped trend with elevation increase, increasing from 4320–4620 m, decreasing from 4720 to 4920 m, and peaking at 4620 to ~4720 m, indicating that elevation from 4620–4720 m was a transition zone in permafrost region.
Global positioning systems indicate landscape preferences of cattle in the subtropical savannas
Authors: Tomkins N. , O'Reagain P.
Published: November 2007

Large paddocks, a heterogeneous landscape and widely dispersed water points provide challenges for the sustainable grazing management of northern Australian beef properties. Determining grazing animal distribution and relating this to features in the landscape, including artificial water points, can assist in the sustainable management of these environments. This case study describes the distribution and landscape association of cattle for part of a single wet season. Twelve Brahman cows were fitted with global positioning system (GPS) collars for 8 weeks in a 1530 ha paddock that contained a diversity of land-types and a single artificial water point. Grazing preferences were initially limited to a 250-ha cleared area of clay soil sown with Cenchrus ciliaris. Thereafter, animals moved on to less fertile outlying areas of Eucalyptus and Acacia agyrodendron native pasture woodland. Mean convex polygon, the smallest polygon that contained 90% of positional data, increased from 229 ± 37.6 ha to 449 ± 80.3 ha over the first 3 weeks of the study. Animals avoided areas dominated by steep terrain and the preference index (proportion of GPS locations that occurred in a land-type divided by its relative cover) was less than unity for 71% of the paddock area. Although the performance of the GPS units was disappointing, the study verifies that GPS telemetry and satellite imagery can be used to quantify cattle distribution and probable grazing preferences in the extensive, spatially heterogeneous paddocks of northern Australia.
Distinct roles of Wnt/β-catenin and Bmp signaling during early cardiogenesis
Authors: Klaus Alexandra , Saga Yumiko , Taketo Makoto M. , Tzahor Eldad , Birchmeier Walter
Published: November 2007

Heart formation requires the coordinated recruitment of multiple cardiac progenitor cell populations derived from both the first and second heart fields. In this study, we have ablated the Bmp receptor 1a and the Wnt effector β-catenin in the developing heart of mice by using MesP1-cre, which acts in early mesoderm progenitors that contribute to both first and second heart fields. Remarkably, the entire cardiac crescent and later the primitive ventricle were absent in
MesP1-cre
;
BmpR1a

lox/lox

mutants. Although myocardial progenitor markers such as
Nkx2-5
and
Isl1
and the differentiation marker
MLC2a
were detected in the small, remaining cardiac field in these mutants, the first heart field markers,
eHand
and
Tbx-5
, were not expressed. We conclude from these results that Bmp receptor signaling is crucial for the specification of the first heart field. In
MesP1-cre;
β
-catenin

lox/lox

mutants, cardiac crescent formation, as well as first heart field markers, were not affected, although cardiac looping and right ventricle formation were blocked. Expression of
Isl1
and
Bmp4
in second heart field progenitors was strongly reduced. In contrast, in a gain-of-function mutation of β-catenin using MesP1-cre, we revealed an expansion of
Isl1
and
Bmp4
expressing cells, although the heart tube was not formed. We conclude from these results that Wnt/β-catenin signaling regulates second heart-field development, and that a precise amount and/or timing of Wnt/β-catenin signaling is required for proper heart tube formation and cardiac looping.
Selective inhibition of NF-κB activation prevents dopaminergic neuronal loss in a mouse model of Parkinson's disease
Authors: Ghosh Anamitra , Roy Avik , Liu Xiaojuan , Kordower Jeffrey H. , Mufson Elliott J. , Hartley Dean M. , Ghosh Sankar , Mosley R. Lee , Gendelman Howard E. , Pahan Kalipada
Published: November 2007

Parkinson's disease (PD) is the second most common neurodegenerative disorder. Despite intense investigations, no effective therapy is available to stop its onset or halt its progression. The present study evaluates the ability of peptide corresponding to the NF-κB essential modifier-binding domain (NBD) of IκB kinase α (IKKα) or IKKβ to prevent nigrostriatal degeneration in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD and establish a role for NF-κB in human parkinsonism. First, we found that NF-κB was activated within the substantia nigra pars compacta of PD patients and MPTP-intoxicated mice. However, i.p. injection of wild-type NBD peptide reduced nigral activation of NF-κB, suppressed nigral microglial activation, protected both the nigrostriatal axis and neurotransmitters, and improved motor functions in MPTP-intoxicated mice. These findings were specific because mutated NBD peptide had no effect. We conclude that selective inhibition of NF-κB activation by NBD peptide may be of therapeutic benefit for PD patients.
Blood-borne soluble protein antigen intensifies T cell activation in autoimmune CNS lesions and exacerbates clinical disease
Authors: Odoardi F. , Kawakami N. , Klinkert W. E. F. , Wekerle H. , Flügel A.
Published: November 2007

We explored the effect of i.v. soluble antigen on autoaggressive, myelin basic protein-specific effector T cells within their target organ during acute experimental autoimmune encephalomyelitis (EAE). Intravital two-photon imaging revealed that i.v. autoantigen reached the CNS and was taken up and processed by antigen-presenting cells within 30 min after injection. The exogenous autoantigen dramatically changed the motility and function of autoreactive effector T cells within the EAE lesions: T cells that had been cruising through the tissue slowed down and became tethered to local antigen-presenting cells within 1 h. One hour later, the effector T cells massively produced proinflammatory cytokines and up-regulated membranous activation markers. This strong activation of the T cells boosted CNS inflammation and aggravated clinical disease. Postactivated effector and resting memory T cells specific for a non-CNS antigen (ovalbumin) were recruited to EAE lesions and moved there without contacting antigen-presenting cells. These cells were similarly arrested and activated after i.v. infusion of ovalbumin, and they also exacerbated clinical disease. Our data are relevant for autoantigen-based therapies of autoimmune disorders. Further, the study indicates how brain unrelated antigens (microbial components) leaking into the chronically inflamed CNS through the bloodstream might trigger relapses in multiple sclerosis.
Circadian rhythms of superhelical status of DNA in cyanobacteria
Authors: Woelfle Mark A. , Xu Yao , Qin Ximing , Johnson Carl Hirschie
Published: November 2007

The cyanobacterium
Synechococcus elongatus
expresses robust circadian (daily) rhythms under the control of the KaiABC-based core clockwork. Unlike eukaryotic circadian systems characterized thus far, the cyanobacterial clockwork modulates gene expression patterns globally and specific clock gene promoters are not necessary in mediating the circadian feedback loop. The oscilloid model postulates that global rhythms of transcription are based on rhythmic changes in the status of the cyanobacterial chromosome that are ultimately controlled by the KaiABC oscillator. By using a nonessential, cryptic plasmid (pANS) as a reporter of the superhelical state of DNA in cyanobacteria, we show that the supercoiling status of this plasmid changes in a circadian manner
in vivo
. The rhythm of topological change in the plasmid is conditional; this change is rhythmic in constant light and in light/dark cycles, but not in constant darkness. In further support of the oscilloid model, cyanobacterial promoters that are removed from their native chromosomal locations and placed on a plasmid preserve their circadian expression patterns.
A cold phase of the East Pacific triggers new phytoplankton blooms in San Francisco Bay
Authors: Cloern James E. , Jassby Alan D. , Thompson Janet K. , Hieb Kathryn A.
Published: November 2007

Ecological observations sustained over decades often reveal abrupt changes in biological communities that signal altered ecosystem states. We report a large shift in the biological communities of San Francisco Bay, first detected as increasing phytoplankton biomass and occurrences of new seasonal blooms that began in 1999. This phytoplankton increase is paradoxical because it occurred in an era of decreasing wastewater nutrient inputs and reduced nitrogen and phosphorus concentrations, contrary to the guiding paradigm that algal biomass in estuaries increases in proportion to nutrient inputs from their watersheds. Coincidental changes included sharp declines in the abundance of bivalve mollusks, the key phytoplankton consumers in this estuary, and record high abundances of several bivalve predators: Bay shrimp, English sole, and Dungeness crab. The phytoplankton increase is consistent with a trophic cascade resulting from heightened predation on bivalves and suppression of their filtration control on phytoplankton growth. These community changes in San Francisco Bay across three trophic levels followed a state change in the California Current System characterized by increased upwelling intensity, amplified primary production, and strengthened southerly flows. These diagnostic features of the East Pacific “cold phase” lead to strong recruitment and immigration of juvenile flatfish and crustaceans into estuaries where they feed and develop. This study, built from three decades of observation, reveals a previously unrecognized mechanism of ocean–estuary connectivity. Interdecadal oceanic regime changes can propagate into estuaries, altering their community structure and efficiency of transforming land-derived nutrients into algal biomass.
Sustainable and efficient biohydrogen production via electrohydrogenesis
Authors: Cheng Shaoan , Logan Bruce E.
Published: November 2007

Hydrogen gas has tremendous potential as an environmentally acceptable energy carrier for vehicles, but most hydrogen is generated from nonrenewable fossil fuels such as natural gas. Here, we show that efficient and sustainable hydrogen production is possible from any type of biodegradable organic matter by electrohydrogenesis. In this process, protons and electrons released by exoelectrogenic bacteria in specially designed reactors (based on modifying microbial fuel cells) are catalyzed to form hydrogen gas through the addition of a small voltage to the circuit. By improving the materials and reactor architecture, hydrogen gas was produced at yields of 2.01–3.95 mol/mol (50–99% of the theoretical maximum) at applied voltages of 0.2 to 0.8 V using acetic acid, a typical dead-end product of glucose or cellulose fermentation. At an applied voltage of 0.6 V, the overall energy efficiency of the process was 288% based solely on electricity applied, and 82% when the heat of combustion of acetic acid was included in the energy balance, at a gas production rate of 1.1 m
3
of H
2
per cubic meter of reactor per day. Direct high-yield hydrogen gas production was further demonstrated by using glucose, several volatile acids (acetic, butyric, lactic, propionic, and valeric), and cellulose at maximum stoichiometric yields of 54–91% and overall energy efficiencies of 64–82%. This electrohydrogenic process thus provides a highly efficient route for producing hydrogen gas from renewable and carbon-neutral biomass resources.