bluuebunny/crossref_metadata_2025 huggingface dataset:
Scaphoid Nonunion in Break-Dancers: A Report of 3 Cases
Authors: Cho Chul-Hyun , Song Kwang-Soon , Min Byung-Woo , Bae Ki-Cheor , Lee Kyung-Jae , Kim Sang-Hyon
Published: August 2009

Most injuries resulting from break-dancing are minor, such as sprains and strains, but there is great potential for dance participants to sustain severe and life-threatening conditions, such as cervical cord injuries. Break-dancing carries many of the risks of conventional dance and gymnastics, but unlike those forms of activity, it is usually performed without trained supervision, as is supplied by coaches in other sports. The pleasure of break-dancing carries with it the responsibility of proper and thorough preparation. It is essential that break-dancers wear protective devices and perform proper warm-up and cool-down exercises.

Break-dancing has become a popular youth subculture. Its complex acrobatic moves, such as splits, handstands, spins, and tumbling, have important medical implications. We report 3 cases of scaphoid nonunion in a break-dancer, the first such report in the English literature to our knowledge. Accordingly, we believe that the clinician must inquire more thoroughly into the nature of patients' activities that result in both unusual and common injuries and educate those who are break-dancers about the hazards of this activity. Careful screening, instruction, and coaching of break-dancers will help prevent injuries.
Acute Isolated Lateral Compartment Syndrome of the Leg After a Noncontact Sports Injury
Authors: Rehman Saqib , Joglekar Siddharth B.
Published: August 2009

Compartment syndrome of the leg typically affects the anterior compartment or multiple compartments and can be traumatic or exertional (chronic) in nature. Isolated lateral (peroneal) compartment syndrome of the leg is a less typical and lesser-known condition that can potentially escape diagnosis if not considered in the workup of a painful leg.

This article presents a case of isolated lateral compartment syndrome of the leg without gross muscle rupture or hematoma. The patient presented 21 hours after injury while playing soccer. Isolated lateral compartment syndrome was diagnosed based on history, physical examination, and a compartment pressure measurement of 130 mm Hg. Emergent surgical decompressive fasciotomy was performed. The peroneal longus and brevis muscle tissue was not lost. Superficial peroneal nerve sensation, which was initially impaired, was recovered at 1 month postoperatively. The patient recovered and was able to participate in sports again by 2 months postoperatively.
Computer-Assisted for Depression & Anxiety: Increasing Accessibility to Evidence-Based Mental Health Treatment
Authors: Stuhlmiller Cynthia , Tolchard Barry
Published: August 2009

Cognitive-behavioral therapy (CBT) is the most effective nonpharmacological treatment for almost all mental disorders, especially anxiety and depression. The treatment is time limited, encourages self-help skills, is problem focused, is inductive, and requires that individuals develop and practice skills in their own environment through homework. However, most of those with mental health issues are unable to seek help because of factors related to treatment availability, accessibility, and cost. CBT is well suited to computerization and is easy to teach to nurses. In this article we describe outcome studies of computer-assisted CBT (cCBT), outline the current technologies available, discuss concerns and resistance associated with computerized therapy, and consider the role of nurses in using cCBT.
Loss of a Companion Animal: Understanding and Helping the Bereaved
Authors: Durkin Anne
Published: August 2009

Pet owners may face numerous animal losses in a lifetime. Grief following pet loss is often misunderstood and devalued. Nurses are likely to encounter patients and families mourning the loss of a companion animal. This article outlines the grief process and offers practical suggestions for assisting those who are bereaved.
Disorder or Delusion?: Living with Morgellons Disease
Authors: Simpson Lindsay , Baier Marjorie
Published: August 2009

Whether Morgellons disease is a delusional disorder or even a disease has been a mystery for more than 300 years. Symptoms of Morgellons include crawling and stinging sensations, feeling of “bugs” and/or fiber-like material beneath the skin, disabling fatigue, and memory loss. The cause, transmission, and treatment are unknown. Research about Morgellons is staggeringly sparse and limited in scope. However, in recent years, discussion about Morgellons has become more common because of the Internet and online support groups. Mental health professionals and the general public need to be aware of the signs, symptoms, and treatment of this disease. Focusing on the disease and listening to patients can make a difference in the way health care professionals provide the best possible care for people with Morgellons.
Understanding and Promoting Attachment
Authors: Wilson Samantha L.
Published: August 2009

Interest in early relationships has led to increased use of terms such as
attachment disorder, attachment problems,
and
attachment therapy
when describing behavioral/emotional regulation in young children. Unfortunately, such terms are vague and lead to clinical confusion and diagnostic inaccuracies. This article will introduce attachment theory, with a discussion of reactive attachment disorder and implications for treatment of children who have problems with social-emotional development.
Comparison of LASIK with the OPDCAT or OATz Algorithm Using the NIDEK EC-5000CXII Excimer Laser
Authors: Hori-Komai Yoshiko , Toda Ikuko , Yamamoto Takahiro , Tsubota Kazuo
Published: August 2009

Purpose:

To compare refractive outcomes, higher order aberrations, visual quality, and patient satisfaction between aspheric and whole-eye wavefront aspheric LASIK algorithms.

Methods:

Two hundred seventy-four eyes of 152 patients undergoing LASIK for myopia and myopic astigmatism were divided into two groups: eyes that underwent treatment using either the OPD-guided customized aspheric treatment (OPDCAT) or optimized aspheric treatment zone (OATz). Both groups were subdivided into two groups based on preoperative manifest refraction spherical equivalent (MRSE) <−6.00 diopters (D) and eyes with MRSE ≥−6.00 D. Both groups were additionally subdivided into eyes with preoperative ocular higher order aberrations <0.40
μ
m and eyes with higher order aberrations ≥0.40
μ
m. A
P
value <.05 was considered statistically significant.

Results:

At 3 months postoperatively, 88.3% (242/274) of eyes were available for follow-up. Postoperatively, 91.4% of eyes in the OPDCAT group and 90.6% of eyes in the OATz group were within 0.50 D. No difference in refractive outcomes and patient satisfaction among groups or subgroups was noted (
P
>.05). A significantly less change in asphericity (less oblate) was noted for the OPDCAT group (0.31±0.30) compared with the OATz group (0.51±0.35) (
P
<.05). A lower induction of aberrations in the OPDCAT group compared with the OATz group was noted (
P
<.05). Mesopic contrast sensitivity was significantly higher for the OPDCAT groups and subgroups (
P
<.05).

Conclusions:

Refractive outcomes between groups or subgroups were equivalent. A significantly lower induction of higher order aberrations and less change in asphericity in the OPDCAT group was noted. The OPD-CAT algorithm was more likely to maintain mesopic contrast sensitivity.
Women's and Men's Exercise Adherence After a Cardiac Event: Does Age Make a Difference?
Authors: Dolansky Mary A. , Stepanczuk Beth , Charvat Jacqueline M. , Moore Shirley M.
Published: August 2009

The purpose of this secondary analysis was to determine whether age affects women's and men's exercise adherence after a cardiac event. In a convenience sample of 248 adults ages 38 to 86 who had a cardiac event, exercise adherence (three exercise sessions per week) was compared between men and women in three age groups (younger than 60, 61 to 70, and older than 70). Exercise patterns were recorded by heart rate monitors worn during exercise. No differences were found in adherence between the age groups for women; older men were nonadherent sooner than younger men when controlling for fitness level, pain, comorbidity, self-efficacy, depressed mood, and social support. Exercise adherence after a cardiac event was higher for younger men compared with older men. For all age groups, less than 37% of the total sample adhered to a three-times-per-week exercise regimen after 1 year, suggesting that interventions to maintain exercise adherence are needed.
The use of electrical conductivity mapping in the definition of an aquifer vulnerability index
Authors: Kirsch Reinhard , Sengpiel Klaus‐Peter , Voss Wolfgang
Published: August 2009

There is an increasing demand for vulnerability maps which show the degree of exposure of aquifers against pollution. Parameters shown in these maps are generally cation exchange capacity or clay content of the near surface layers, or quantities related to the infiltration time of surface water. Instead of determining these parameters by means of drillings and geological investigation, we propose the use of geophysical techniques for vulnerability mapping and for the interpolation between drillings. A geophysical quantity which is closely related to these parameters is the electrical conductivity. In this paper the relation between clay content and electrical conductivity is shown and used for vulnerability mapping. It is demonstrated that ground and airborne electromagnetic (EM) techniques are suited for large scale data acquisition.
MCS data processing for the interpretation of ancient ice sheet movements
Authors: Stucchi E.
Published: August 2009

The paper deals with the analysis and reprocessing of data from a 30‐km section of the IT88A‐01 seismic line acquired in the Ross Sea Basin during the Italian 1988 PNRA project (National Program for Antarctic Research). The purpose of this study was to achieve an improved data quality for a better geophysical and geological interpretation of the area. Field data were subjected to a processing sequence aimed at enhancing the S/N ratio and at recovering reliable acoustic impedances. Acoustic impedance recovery calls for the estimation of both the velocity field and the pseudo‐acoustic impedance in the wavelet frequency band. At the end of the study, a time‐migrated stack section and a time impedance map were produced. The migrated section shows, quite clearly, an event previously hidden by a strong sea‐bottom multiple; furthermore reflections that can be related to proximal debris left by ice expansion and regression are now visible. The impedance map shows impedance inversion along the whole length of the processed section, possibly denoting different sedimentary conditions due to ice‐sheet loading and unloading in the Ross Sea.

The processing sequence described and the recovery of the absolute acoustic impedance as outlined here could be adopted to determine, by means of seismic reflection, the position and movement of the ice sheet in the remote past.
Time‐frequency representation of strong‐motion records for damage appraisal: examples from the Düzce earthquake (Turkey)
Authors: Basokur Ahmet T. , Dikmen Unal , Tokgoz O. Engin
Published: August 2009

The Düzce (Turkey) earthquake, which struck on 12th November 1999, caused serious damage and loss of life in the town of Düzce, 8 km from the Düzce fault. However, the strong‐motion records indicate that the peak acceleration values were almost twice as high in the town of Bolu, 34 km from the epicentre, compared with those in Düzce. In the earthquake‐affected region, the peak acceleration values are not well correlated with the damage to buildings. For this reason, the use of Fourier spectra leads to some confusion when comparing the quality of the civil engineering work carried out in Düzce and in Bolu. Fourier spectra provide a complete description of amplitudes versus frequency, but they do not contain information about the dynamic characteristics of waveforms. This difficulty may be overcome by considering the time‐duration effect of an earthquake, which is the main cause of damage to buildings. The Stockwell transform of acceleration records offers a means of representing the variation of spectral components with time. This makes possible an unambiguous visualization of the time‐duration effect of an earthquake and consequently an easy correlation of strong‐motion records with damage to structures.
Experiments of joint acquisition of seismic refraction and surface wave data
Authors: Foti Sebastiano , Sambuelli Luigi , Socco Valentina L. , Strobbia Claudio
Published: August 2009

Dispersive Rayleigh waves, contained in conventional P‐wave refraction records, can be used to determine the shear‐wave velocity profile. In the present paper, the synergies of a cross interpretation of refraction and surface wave data are exploited using data collected at sites where other geotechnical and geophysical information was available.

Selected examples are presented to emphasize the relative advantages and limitations of the two techniques in the cases of hidden layer, velocity inversions and shallow water table.

Surface wave analysis was performed to estimate the experimental dispersion curves in thef–kdomain and the results of the dispersion curves inversion were compared with refraction results in terms of velocity profiles.

The experimental results prove that many advantages, in terms of resolution and reliability, can be obtained with joint acquisition and cross interpretation of P‐wave refraction and surface wave data, without a significant increase in testing time.
Improving the resolution of shallow seismic sections using eigenimage analysis
Authors: Shtivelman Vladimir
Published: August 2009

The basic limitation of geophysical techniques used for imaging various shallow localized subsurface inhomogeneities is their spatial resolution, that is, the ability of the methods to detect small‐scale objects. This is especially true for low‐resolution techniques, such as recently developed methods using seismic surface waves. The objective of this work is to improve the spatial resolution and to enhance the detectability of small‐scale objects on seismic sections. For this purpose, a method of eigenimage analysis, based on singular value decomposition of seismic sections, was used. The method effectively separates events with different horizontal coherence. Since shallow subsurface inhomogeneities are characterized by poor horizontal coherence on seismic sections, such a separation can serve as a tool for detecting the inhomogeneous areas in the subsurface.

Application of the method to synthetic and real seismic data shows that it can significantly improve the spatial resolution of the subsurface imaging.
Realistic modelling of surface ground‐penetrating radar antenna systems: where do we stand?
Authors: Holliger Klaus , Lampe Bernhard , Meier Ueli , Lambert Marc
Published: August 2009

The generation and recording of electromagnetic waves by ground‐penetrating radar (GPR) systems are complex phenomena. To investigate the characteristics of typical surface GPR antennae operating in realistic environments, we have developed an antenna simulation tool based on a finite‐difference time‐domain (FDTD) approximation of Maxwell’s equations in 3D Cartesian coordinates. The accuracy of the algorithm is validated with respect to laboratory measurements for comparable antenna systems. Numerically efficient and accurate modelling of small antenna structures and high permittivity materials is achieved through a grid‐refinement procedure. We simulate the radiation characteristics of a wide range of common surface GPR antenna types ranging from thin‐wire antennae to bow‐tie antennae with arbitrary flare angles based on the assumption of perfect electrical conductivity (PEC) of the metal parts. Due to the modular structure of the algorithm, additional planar antenna designs can readily be added. Shielding is achieved by placing a metal box immediately above the antenna. To enhance the damping effects, this metal box can be filled with a dielectric absorber and/or connected to the antenna panels through discrete resistors. Finally, we also consider the effects of continuous resistive loading of the antenna panels using a sub‐cell algorithm. We find that GPR antennae with Wu–King‐type resistivity profiles radiate compact, broadband pulses and, as opposed to PEC antennae, are largely insensitive to their operating environment. Unfortunately, these favourable radiation characteristics are accompanied by a dramatic loss in radiation efficiency compared to the corresponding PEC antennae.
Geophysical investigation of antique iron furnaces: insights from modelling magnetic and VLF data
Authors: Darnet Mathieu , Sailhac Pascal , Marquis Guy
Published: August 2009

Magnetic and very low frequency electromagnetics (VLF) surveys at an Antique iron mine near Saales (France) revealed several large magnetic anomalies (of the order of a few hundred nT), strong electrical conductivity contrasts (10–1000 Ωm) and out‐of‐quadrant VLF phases (φ >90°).To define both the location and the vertical extent of the underground artefacts, we interpret our magnetic data with Euler deconvolution and a 2D wavelet transform that combines maps of the total field and its gradient. We also explain out‐of‐quadrant VLF phases using simple 3D EM forward modelling. A joint interpretation of magnetic, VLF and topography data enables us to locate iron‐ore exploitation trenches, Antique iron furnaces and their surrounding slags at depths between 1 and 3 m, in good agreement with results obtained during a recent road construction.
Geophysical study of the industrial waste land in Mortagne‐du‐Nord (France) using electrical resistivity
Authors: Guérin Roger , Bégassat Philippe , Benderitter Yves , David Jacques , Tabbagh Alain , Thiry Médard
Published: August 2009

The industrial waste land in Mortagne‐du‐Nord (France) has been the site of a zinc smelter unit and a lead smelter unit linked to sulphuric acid production. It has been systematically explored by drillings and pits. Geophysical data have led to the location of mineralized soil and water, and to the identification of water seepage towards the river drain. Various geophysical devices are used for subsurface exploration and for studies with higher spatial resolution. The prospect area covers a surface of 4.5 ha. Data obtained from trenches has been used to calibrate and to validate the geophysical interpretation. It has been found that variations in the depth of the interface between resistive and conductive layers are due to two types of waste: ‘non‐active’ (carbonates and oxides) and ‘active’ (sulphides and sulphates) materials. Lower resistivities than expected are due to the presence of mineralized water in all geological formations.
On the correspondence between resistivity and texture of loose sediments, saturated with salt water
Authors: Abu‐Zeid N. , Santarato G.
Published: August 2009

Electrical resistivity tomography (ERT) has been applied to characterize coastal aquifers heavily affected by the problem of groundwater salinization. With the help of a number of resistivity data sets and control boreholes, separate resistivity ranges were related to sand‐grained sediments, saturated with salt water, and fine‐grained sediments, silts and clays, deposited in a sub‐marine environment.

Frequency‐domain electromagnetic soundings (FDEM) were then used to map the spatial resistivity variations in a selected site of the study area. One‐dimensional inversion of FDEM real and imaginary parts provided a quantitative resistivity–depth model that was consistent with the ERT model section and direct borehole observations. The successful application of the FDEM technique supports its use for mapping shallow fluid pathways of salt‐water intrusion over large areas.
Lithological interpretation of the spectral dielectric properties of limestone
Authors: Fechner T. , Börner F.D. , Richter T. , Yaramanci U. , Weihnacht B.
Published: August 2009

Limestone is a raw material used in the building and chemical industries. To guarantee good quality, it is important to investigate the limestone before mining to get information about the lithology and the mineral content. The chemical properties of rock cannot be measured directly by geophysical methods. Therefore extensive laboratory work was carried out to find relationships between the chemical, mineralogical, petrophysical and spectral dielectric properties of artificially mixed and natural limestone rock samples. A comprehensive interpretation is possible by using a complex dielectric parameter model. An interpretation scheme was developed. It is based on the fact that the specific internal surface area and the water saturation have the most influence on the spectral properties of rock at constant water salinities. These results were applied to field data measured with a borehole radar system. In order to interpret the field data directly using the results of the laboratory investigations, a new spectral interpretation method was developed. The method is focused on in‐hole and cross‐hole measurements with one receiving and one transmitting antenna. It was shown that all impurities causing an increase in the specific internal surface area compared to that of pure limestone could be detected by spectral dielectric measurements.
Surface‐wave method for near‐surface characterization: a tutorial
Authors: Socco L.V. , Strobbia C.
Published: August 2009

Surface‐wave methods (SWMs) are very powerful tools for the near‐surface characterization of sites. They can be used to determine the shear‐wave velocity and the damping ratio overcoming, in some cases, the limitations of other shallow seismic techniques.

The different steps of SWM have to be optimized, taking into consideration the conditions imposed by the small scale of engineering problems. This only allows the acquisition of apparent dispersion characteristics: i.e. the high frequencies and short distances involved make robust modelling algorithms necessary in order to take modal superposition into account.

The acquisition has to be properly planned to obtain quality data over an adequate frequency range. Processing and inversion should enable the interpretation of the apparent dispersion characteristics, i.e. evaluating the local quality of the data, filtering coherent noise due to other seismic events and determining energy distribution, higher modes and attenuation.

The different approaches that are used to estimate and interpret the dispersion characteristics are considered. Their potential and limits with regard to sensitivity to noise, reliability and capability of extracting significant information present in surface waves are discussed. The theory and modelling algorithms, and the acquisition, processing and inversion procedures suitable for providing stiffness and damping ratio profiles are illustrated, with particular attention to reliability and resolution.
A case study of two and three‐dimensional inversion of dipole‐dipole data: the Enfermarías Zn‐Pb (Ag, Sb, Au) Prospect (Moura, Portugal)
Authors: Represas P. , Monteiro Santo F. A. , Mateus A. , Figueiras J. , Barroso M. , Martins R. , Oliveira V. , Nolasco da Silva M. , Matos J.X.
Published: August 2009

The Enfermarías Zn‐Pb(Ag, Sb, Au) prospect, located in the Moura‐Ficalho region (Alentejo, Portugal), was intensively explored during 1980s. A drilling programme was successful, intersecting massive and disseminated sulphide mineralizations. The geological and geophysical data set available for Enfermarias is quite vast and comprises 13 borehole geological logs, as well as gravity, magnetic and resistivity data. In this paper, the dipole‐dipole resistivity surveys are re‐examined and interpreted using both 2D and 3D inversion to provide an interesting comparison of the two different approaches. Results from gravity data modelling and data from borehole logs are used as independent validity tests on the quality of the results.

The 2D and 3D models indicate a conductive overburden covering more resistive bedrock, which appears at a depth of 70–100 m in the western part of the profiles. Results obtained from 3D inversion, however, show a very clear separation of the most resistive domains in the two different bodies, whereas this separation does not appear in the 2D models. The 3D model also shows a higher degree of spatial continuity than the partial 2D models, which are, in general, richer in short‐wavelength anomalies, and show a higher variation from profile to profile.

Comparison of the resistivity results with gravity in two coincident profiles reveals an excellent agreement between the main shallow features of both 2D and 3D models. This suggests that the resistivity model does indeed satisfy the main features of the available geological and geophysical data.
MRS contribution to hydrogeological system parametrization
Authors: Lubczynski M. , Roy J.
Published: August 2009

The contribution of magnetic resonance sounding (MRS) to hydrogeological system parametrization is based on the hydrogeological interpretation of the two MRS output parameters, MRS water content () and decay‐time constant (). An overview of the hydrogeological parameters that can be defined with MRS is presented and is followed by a discussion on the nature, applicability and limitations of the relationships between MRS and hydrogeological parameters. The most important contributions to hydrogeological system parametrization are the estimations of effective porosity, specific yield and specific retention. The most important contributions are the estimations of hydraulic conductivity and aquifer transmissivity. The hydrogeological parameters obtained from parametrization are relatively well physically defined but insufficiently verified, where as the parameters obtained from have already largely been verified but they are based on an empirical relationship. All the hydrogeological parameters derived from and and obtained from a 1D MRS experiment, are integrated over a large subsurface volume of up to 106 m3.
Stability of MRS signal and estimation of data quality
Authors: Girard J.F. , Legchenko A. , Boucher M.
Published: August 2009

Based on the principle of nuclear magnetic resonance (NMR), the magnetic resonance sounding (MRS) method is used to measure the magnetic resonance signal from groundwater via a surface loop. The accuracy of the measurements depends on both the stability of the magnetic resonance signal under varying experimental conditions (geomagnetic field, electromagnetic noise, etc.) and the accuracy of the measuring device. The efficiency of the signal processing algorithms adopted by the NUMISPlus device, as well as sensitivity to the signal‐to‐noise (S/N) ratio (), are numerically investigated. The results are shown to be stable when .

Numerical simulation of the magnetic resonance signal shows that with a fluctuating geomagnetic field and within a few Hertz of the frequency offset, amplitude remains stable whereas phase follows the geomagnetic field variations. An anti‐correlation is observed between phase and frequency shift.

The numerical results were validated experimentally using the NumisPlus system at St‐Cyr‐en‐Val near the city of Orleans, France. For filtered data with and a frequency offset within ±0.5 Hz, the relative standard deviation of the measurements was found to lie within ±12% for amplitude and ±10° for phase. The standard deviation of the signal, which is strongly weighted by the S/N ratio, is higher for lower pulses than for higher pulses. Analysis of the stability of the current transmitted by NumisPlus reveals that for weak currents (<5 A), the standard deviation of the pulse amplitude is 3.7%, whereas for stronger currents (>100 A), it is only 1.3%. We thus conclude that for currents greater than 5 A, the instrumental instability of NumisPlus is significantly less than the electromagnetic noise, which can be considered as the major source of error. The S/N ratio can be significantly improved by stacking, which is efficient but time consuming. Note that the accuracy of measurements carried out over a long time (due to stacking) may decrease as measuring conditions can change during any one sounding.

The accuracy of the field measurements for enables the complex MRS signal to be used in the inversion process instead of only amplitude. Nevertheless, any variation in the geomagnetic field with time must be taken into consideration during inversion of the MRS signal.
SNMR measurements in Thailand to investigate low‐porosity aquifers
Authors: Lange G. , Mohnke O. , Grissemann C.
Published: August 2009

Integrated geophysical surveys have been carried out at two different locations in Thailand in the context of the Thai‐German Research Project “Investigation of Waste Disposal Sites ‐ WADIS”. Surface nuclear magnetic resonance (SNMR, MRS) was used in addition to conventional geophysics. Although a high total intensity of the earth’s magnetic field (TMI) offers advantageous physical conditions for SNMR, only very low signal amplitudes could be measured. Due to the long acquisition times caused by high stacking rates, diurnal variations in TMI may have had a considerable influence on the SNMR signal.

The two investigated sites are characterized by different geological and physical ground conditions. An unusual feature is an extremely high local magnetic anomaly caused by magnetic landfill material at the Nong Harn dump site in northern Thailand. Because of strong field inhomogeneities, SNMR measurements were impractical in the sphere of influence of this anomaly. The Dan Khun Thot site in central Thailand is characterized by very high ground conductivities, obviously due to saline pore fluids. Despite the evidence of water occurring in several narrow sand layers observed in shallow holes, the water content deduced from the SNMR measurements turns out to be very low. An explanation for the apparent discrepancy is the irregular distribution of the water in lens‐shaped confined aquifers. Forward modelling of an elementary 3D situation and its comparison with 1D inversion illustrate that this hydrogeological situation cannot be treated correctly using the usual 1D data collection and 1D interpretation algorithms.
3D inversion of VES data from the Saqqara archaeological area, Egypt: a case study
Authors: El‐Qady G.M. , Monteiro Santos F.A. , Hassaneen A. Gh. , Trindade L.
Published: August 2009

Saqqara is one of the most important archaeological sites in Egypt. The monuments in this area are suffering from the effects of urbanization and temporal and spatial variations in the groundwater level. In an attempt to understand better the problems associated with the groundwater, a geoelectrical DC resistivity survey, comprising 47 vertical electrical soundings using a Schlumberger array, has been conducted. These data have been inverted using a 3D code based on a smoothness‐constrained least‐squares method. To determine the reliability of the inversion results, a range of tests has been performed. The final 3D resistivity model obtained for the study area provides useful new subsurface geological and hydrogeological information. The new model allows a more integrated image and interpretation of the complex hydrogeological conditions. It also depicts the mutual relationship between the two water‐bearing units in the area that was not clear in the previous 1D and 2D interpretations.
Seismic prospecting in archaeology: a 3D shear‐wave study of the ancient harbour of Miletus (Turkey)
Authors: Woelz Susanne , Rabbel Wolfgang
Published: August 2009

A 3D multicomponent shear‐wave survey was performed in the area of the ancient city of Miletus (western Turkey). To achieve high spatial resolution of near‐surface targets, data were acquired with a geophone array of 1 m grid spacing. The survey served: to investigate archaeologically important details of the basement of one of the silted harbours of Miletus, and to evaluate the potential of close‐meshed shear‐wave seismics for shallow high‐resolution prospecting in a more general sense. Methodically, we could show that isotropic radiation patterns of compressional shear‐ and surface waves can be reconstructed with simple vector arithmetic even if hand‐driven hammer blows are applied as a horizontal seismic source. Presenting time‐slices of S‐wave propagation, we demonstrate that side‐swipe may significantly affect the propagation of refracted waves. It is shown that the wavefronts of surface waves may be far from circular in the case of typical near‐surface lateral heterogeneity. As a further phenomenon of wave propagation, we could visualize the coda of a ground‐coupled air wave probably caused by mud cracks. Regarding the archaeological background of our study, we could show that the basement of the Milesian Lions’ Harbour is shallow enough to provide appropriate ground for ancient construction work. However, by ‘true 3D’ refraction mapping, we could image small‐scale topographic details of the harbour basement, proving that no large ancient stone walls are hidden under the ground. Magnetic anomalies were found to coincide with a lateral increase in Rayleigh‐wave velocity. The rectangular shape of this velocity contrast may indicate the remnants of an artificially shaped rock platform or an embankment. Spectral analysis of the surface wavefield shows that this seismic anomaly will be found at a depth of 3–6 m.
Nuclear magnetic resonance (NMR) properties of unconsolidated sediments in field and laboratory
Authors: Müller Martin , Kooman Stefan , Yaramanci Ugur
Published: August 2009

Surface nuclear magnetic resonance (SNMR) is a geophysical technique that has proved to be a useful tool for the investigation of hydrological properties of aquifers (porosity , saturated hydraulic conductivity ) in the past 10–15 years. Until recently, laboratory NMR has focused on consolidated sediments. In this research, an attempt is made to investigate unconsolidated sediments. To enable an enhanced understanding and interpretation of SNMR data, laboratory nuclear magnetic resonance (NMR) properties of synthetic and natural unconsolidated samples (glass beads, sand mixtures, bore‐core samples from a Quaternary environment west of Berlin (Germany) and coarse sand samples with a varying clay content) were analysed. To verify the NMR measurements, pore‐space properties (specific surface, porosity, pore‐size distribution) were analysed. Finally, hydraulic conductivity measurements were conducted to verify both the hydraulic conductivity derived from NMR relaxation times and the hydraulic conductivity estimates based on grain size. The laboratory data were compared to SNMR field data to assess scaling effects due to the dispersion of relaxation.

The results show that the relationship used to obtain hydraulic conductivity from NMR relaxation is suitable for predicting the saturated hydraulic conductivity of samples composed of clay, silt and coarse sand. Furthermore, it is found that the predictions of hydraulic conductivity of intermediate grain sizes with differing clay content vary over a wide range. A more individual approach with regard to the paramagnetic properties of the material might be needed to achieve successful estimations.

Clay (because of its high specific surface and large surface‐to‐pore‐volume (S/V) ratio) has a strong influence on NMR relaxation and the associated saturated hydraulic conductivity. The NMR relaxation of a series of coarse sand samples (d=1.0–0.5 mm) with a clay content in the range 3–20% shows an exponential decay for the hydraulic conductivity.
Multi‐electrode measurements at Thai Binh dikes (Vietnam)
Authors: Weller Andreas , Canh Tran , Breede Katrin , Trong Vu Nguyen
Published: August 2009

The province of Thai Binh is located in the delta of the Red River in Vietnam where an extensive system of river and sea dikes protects the population and infrastructure from flooding in the rainy season. The integrity of the river dikes is affected by a diversity of problems. Importantly, various termite species dig their nests in the dikes causing water leakage. Leakage can also occur near sluices and passages.

Geoelectrical multi‐electrode profiling has been applied to locate defects in the dikes. Surveys carried out on several dikes demonstrated that a combined half‐Wenner configuration yields high‐resolution images in which termite nests are indicated by resistive anomalies. Petrophysical investigations of soil samples and density logs yield additional information on the dike material. Elsewhere, imaging surveys confirmed the subsurface extent of a buried sluice structure in the dike body.
GPR studies in the Piano di Pezza area of the Ovindoli‐Pezza fault, central Apennines, Italy: Extending palaeoseismic trench investigations with high‐resolution GPR profiling
Authors: Jewell Chris J. , Bristow Charles
Published: August 2009

A high‐resolution 200 MHz frequency GPR profile with 0.1 m station spacing was collected using a Pulse EKKO 100 system, adjacent to a trench site that had been previously excavated and interpreted. The profile intersected the fault scarp on one of the alluvial fans on the northern slope of the Piano di Pezza; this fault scarp was thought to be associated with repeated earthquake activity along the Ovindoli‐Pezza fault. The GPR profile was conducted to evaluate the effectiveness of the technique in radar mapping and in extending the trenching information laterally and in depth in this environment. The work was carried out as part of a wider research programme of GPR profiling along the Ovindoli‐Pezza fault system. The GPR data were processed using Win EKKO radar data processing software and time–depth conversion was facilitated using field‐derived CMP velocity analysis. The results provided a detailed image of the GPR data, which shows a generally high spatial correlation with the mapped fault and 14C‐dated lithologic/pedologic units. Furthermore, the GPR data has provided a framework for estimating the extent of extensional and episodic catastrophic activity along the fault, and has elucidated the geometric relationship between the faulting in response to recent tectonic events.
Electrical resistivity imaging of tree trunks
Authors: al Hagrey S.A.
Published: August 2009

An electrical resistivity technique using a ring array of needle electrodes is applied to image the internal electrical structures of the trunks of living standing trees and trunk disks. Measured electrical resistance data are inverted using a 2D iterative finite‐element algorithm which incorporates the cylindrical geometry of the trunk. The technique is successfully tested using synthetic models showing that the resolution obtained when mapping anomalous zones inside the trunk is higher for the dipole‐dipole configuration than for the Wenner configuration. Measurements on a trunk column show a well‐established inverse relationship between the imaged resistivity and the moisture content determined from wood cores.

Healthy tree trunks always show a concentric ring structure with a central maximum of resistivity, which decreases towards the outside, corresponding to an increase in moisture from the inner dry heartwood to the outer wet ring of sapwood. Asymmetry in the ring structure is interpreted as the influence of branching or the direction of sunshine and wind. Strong local resistivity anomalies are related to infections causing wet, rotting or dry cavities. The resistivity of the heartwood is a maximum in olive and oak trunks, intermediate in young fruit trees and a minimum in cork oak trunks that are considered to be wet. The resistivity imaging technique can also monitor the dynamic process of sapflow if adequate tracers are used.
Karst investigations using microgravity and MASW; Application to Orléans, France
Authors: Debeglia Nicole , Bitri Adnand , Thierry Pierre
Published: August 2009

An integrated geophysical approach to detecting and characterizing karst structures in an urban environment was applied experimentally to partially explored karst conduits located in Orléans, France. Microgravity was performed to detect voids, in conjunction with multichannel analysis of surface waves (MASW) for the purpose of identifying areas of mechanical weakness.

Microgravity detected negative anomalies corresponding to known conduits and succeeded in identifying the probable extensions of this network in unexplored areas. Control boreholes located on these extensions encountered several levels of water‐saturated voids, probably belonging to the shallowest part of the karst system, overlying the main conduits. Buried urban networks, accurately located by ground‐penetrating radar (GPR), were shown to have no significant gravity effect. Simulations using the compact inversion approach to characterize the size and density of environmental disturbances confirmed this conclusion. In this context, the gravity method has been shown to be suitable for detecting near‐surface (<25 m deep) karst features.

The MASW method, which analyses Rayleigh‐wave propagation, can determine the mechanical behaviour of superficial formations and serve as an indicator for subsurface heterogeneities such as voids or fractures. At the Orléans site, MASW provided evidence of perturbed zones superimposed on gravity anomalies, characterized by the appearance of several dispersion modes, velocity inversions and the attenuation of seismic markers. One of these features was characterized by low velocities and was interpreted as an area of mechanical weakness, confirmed by pressure measurements in the boreholes.

Repeated gravity measurements, or time‐lapse microgravity, were conducted on the anomalous areas to ascertain gravity reproducibility and detect possible temporal variations due to subsurface mass redistribution that may indicate site instability. A two‐year experiment revealed low‐amplitude gravity changes that were recorded in the two sensitive zones. However, their significance is still unclear and these changes need to be validated by further repeat experiments.
Analysis of multi‐offset GPR data: a case study in a coarse‐grained gravel aquifer
Authors: Becht A. , Appel E. , Dietrich P.
Published: August 2009

Multi‐offset ground‐penetrating radar (GPR) data were collected in a coarse‐grained gravel aquifer located in a glacial delta environment within dipping foresets (at the Tettnang aquifer test site, SW Germany). We apply prestack processing techniques and normal‐moveout (NMO) velocity analysis in preparation for stacking. The estimation of propagation velocities is of considerable importance for converting time‐domain radargrams into depth‐sections and for an interpretation in terms of petrophysical properties. In our case, interval velocity determination is difficult because reflector dip angles are variable, and stacking and NMO velocities differ significantly since the antenna offset is comparable to the reflector depth. Using a synthetic two‐layer model, we systematically study possible errors in interval velocity determination. We compare the cases of decreasing velocity with depth (typical for ground‐penetrating (GPR) surveys of aquifers) and increasing velocity with depth (typical for seismic surveys). In the case of decreasing velocity with depth, the discrepancy between stacking and NMO velocity is considerable and, consequently, interval velocities calculated with the Dix equation or the more accurate 2D NMO approximation for dipping layers show unacceptably high errors. The errors are much smaller in comparable models with increasing velocity with depth. Thus, the small‐offset approximation inherent in the NMO concept is not appropriate for the first case. Consequently, it is necessary to model the true common‐midpoint (CMP) raypaths to determine realistic interval velocities from our GPR field data.

Stacked GPR sections of multi‐offset data show significant improvements in imaging of reflectors and depth of investigation compared with a standard constant‐offset section. This allows a more reliable interpretation of geological structures. Simultaneous acquisition of four channels, which is possible with some commercial GPR systems, yields significantly better results than constant‐offset standard acquisition without increasing the efforts for data acquisition. Major reflectors in the GPR section can be correlated with distinct contrasts of porosity, represented by the base of open‐framework gravels and sand beds within poorly sorted gravels.
Velocity spectra and seismic‐signal identification for surface‐wave analysis
Authors: Dal Moro G. , Forte E. , Pipan M. , Sugan M.
Published: August 2009

Rayleigh‐wave dispersion is observed every time acoustic‐impedance stratification occurs, and its analysis is suitable for vertical shear‐wave profile reconstruction. Accurate dispersion‐curve identification is essential in order to properly determine the shear‐wave velocity distribution of a medium. Data sets characterized by several events generate complex velocity spectra that can lead to possible misinterpretations. We analyse a real data set by taking into account theoretical dispersion curves and synthetic data obtained from numerical simulations in order to avoid possible pitfalls that could arise from the complex trends exhibited in the (frequency–wavenumber) and (velocity–frequency) domains. In the domain in particular, we show that reflection events and their multiples generate coherences that could be misinterpreted because of their similarity to typical higher‐mode dispersion curves. Another observed signal is interpreted in terms of guided waves and related phenomena. The results of the fundamental‐mode dispersion curve inversion performed via genetic algorithms indicate a sedimentary cover stratification that simple reflection analysis cannot reveal.

The present case study highlights the importance of a synergic approach, based on integrated synthetic and field data analysis, for correct interpretation of all the wavefield components in the velocity spectrum.
Fresnel reflection coefficients for GPR‐AVA analysis and detection of seawater and NAPL contaminants
Authors: Carcione José M. , Gei Davide , Botelho Marco A.B. , Osella Ana , de la Vega Matias
Published: August 2009

We obtain the transverse electric (TE) and transverse magnetic (TM) Fresnel reflection coefficients for different interfaces in the subsoil: air/fresh‐water, air/seawater, fresh‐water/seawater, air/NAPL (non‐aqueous phase liquid), NAPL/water and water/NAPL. We consider a range of NAPL saturations, where the complementary fluid is water with 0.65 ppt (parts per thousand) of NaCl. The common feature is that the TM mode (parallel polarization) has a negative anomaly and the TE mode (perpendicular polarization) has a positive anomaly. For the cases studied in this work, pseudo‐Brewster angles appear beyond 40° for the air/NAPL and NAPL/water interfaces and at near offsets (below 40°) for the water/NAPL interface. Pseudo‐critical angles are present for the water/NAPL interface. Besides the reflection strength, the phase angle can be used to discriminate between low‐ and high‐conductivity NAPL, when the properties of the upper medium are known. A wavenumber–frequency domain method is used to compute the reflection coefficient and phase angle from synthetic radargrams. This method and the curves can be used to interpret the amplitude variations with angle (AVA) of reflection events in radargrams obtained with ground‐penetrating radar (GPR).