bluuebunny/crossref_metadata_2025 huggingface dataset:
Total Hip Arthroplasty After Periacetabular Osteotomy
Authors: Baqué François , Brown Antony , Matta Joel
Published: August 2009

Patients with hip dysplasia often endure multiple surgical interventions, first in attempts to preserve their biologic hips and later for total hip arthroplasty (THA). Each different surgical approach traumatizes the musculoligamentous complex of the hip. These cumulative insults can significantly affect THA success.

We retrospectively reviewed 8 patients who underwent THA after previous periacetabular osteotomy via the same anterior approach. Acetabular bone stock required no augmentation for implant coverage. No complication occurred during surgery. All patients increased their functional score at last follow-up. No dislocation or implant loosening occurred. Leg-length restoration was excellent.

Periacetabular osteotomy is a proven conservative procedure in dysplastic hips that can be realized through a Smith-Petersen incision. Restoration of the acetabular anatomy is achieved with limited muscle detachment. Good results have been achieved with periacetabular osteotomy; however, some patients develop increasing pain from progression of osteoarthritis and require a THA to allow relief of symptoms. The anterior-approach THA is a well-established procedure using the same Smith-Petersen interval as periacetabular osteotomy. Using this approach for both procedures optimizes the patient's immediate and ultimate functional recovery and hip stability. Instead of compromising subsequent THA, periacetabular osteotomy may improve THA results in dysplastic hips.
Classification of Pelvic Fractures: Analysis of Inter- and Intraobserver Variability Using the Young-Burgess and Tile Classification Systems
Authors: Furey Andrew J. , O'Toole Robert V. , Nascone Jason W. , Sciadini Marcus F. , Copeland Carol E. , Turen Clifford
Published: August 2009

Classification systems for pelvic ring injuries have been developed to assist in understanding the anatomy of the injury, predicting prognosis, and helping define treatment. Despite the frequent clinical use of the Young-Burgess and Tile classification systems, to our knowledge little work has been conducted to validate either system. We assessed the degree of inter- and intraobserver variability when using both the Young-Burgess and Tile classification systems and thereby assessed their validity for clinical use.

Eighty-nine isolated pelvic ring disruptions were selected. Sets of injury images were randomly ordered and distributed to 5 orthopedic trauma surgeons blinded to the patients' names, attending surgeons, dates of injury, and eventual treatments. The surgeons were asked to independently classify each pelvic ring disruption based on the Young-Burgess and Tile classifications. Eight weeks later, the same images were randomly ordered and redistributed to the same 5 surgeons, who were again asked to classify the pelvic injuries. A kappa analysis was conducted to analyze agreement among surgeons. A moderate degree of agreement was shown among orthopedic trauma surgeons when using both the Young-Burgess and Tile classification systems. Intraobserver agreement was found to be substantial for the Young-Burgess classification and moderate for the Tile classification. The degree of inter- and intraobserver variability may limit the usefulness of the 2 classification systems, both clinically and for research purposes.
Nonunion of Fractures in Pediatric Patients: 15-Year Experience at a Level I Trauma Center
Authors: Shrader M. Wade , Stans Anthony A. , Shaughnessy William J. , Haidukewych George J.
Published: August 2009

There is little data evaluating the risk factors, demographics, and prognoses for non-unions in children. Previous literature has reviewed time periods when contemporary techniques of internal fixation and management of open injuries had not been available. The purpose of this retrospective study was to evaluate a large consecutive series of pediatric nonunions treated at a level I trauma center. Between 1985 and 2000, 43 nonunions in 42 pediatric patients with a mean age of 9 years and 9 months (range, 3–14 years) were identified at our level I trauma center. Eleven of the original 43 fractures were open and 5 presented with active infection. Patients were observed until union or a minimum of 1 year with a mean follow-up of 50 months. Twenty of 43 nonunions (47%) were located around the elbow. Seventeen of 43 nonunions (39%) were diaphyseal. The operative fractures required a mean of 3.6 surgeries (range, 1–19 surgeries) to achieve bony union. All secondary attempts to achieve union were successful at last follow-up. Although nonunions in the pediatric population are rare, these data underscore the importance of careful evaluation and treatment of these fractures at risk for nonunion.
The Use of a Biplanar Construct in Pelvic External Fixation
Authors: Noda Mitsuaki , Yamakawa Takayoshi , Fujii Tsuyoshi
Published: August 2009

Inserting pins at a single location of the iliac crest temporarily provides an effective splint for emergency patients with pelvic ring fractures. For a longer application, however, this procedure frequently causes infection and pin loosening and does not effectively stabilize the pelvic construct. We presumed biplanar pelvic constructs may provide better stability than a uniplanar construct.

Two patients were treated with inserting pins at the lateral side of the supra-acetabulum as well as the iliac crest. Postoperatively, they demonstrated significant improvement in pain relief. The biplanar pelvic constructs showed sufficient stability during the procedure and at the time of pin removal several months postoperatively. Another pinning location for pelvic external fixation is the anteroinferior iliac spine toward the posteroinferior iliac spine. Inserting pins from this spot and the iliac crest does not create a biplanar construct, since anatomically these pins share a similar plane. Thus, the biplanar method in which pins were introduced at the lateral side of the supra-acetabulum and at the iliac crest was selected.

Despite the pins' application for several months, pin-site infection was not critical in our cases. We concluded that stability of the biplanar construct helped minimize pin-site infection.
A Rare Case of Intraosseous Benign Notochordal Cell Tumor of the Coccyx
Authors: Uglialoro Anthony D. , Beebe Kathleen S. , Hameed Meera , Benevenia Joseph
Published: August 2009

This article presents a case of a 53-year-old woman who presented with intermittent, dull, poorly localized lower back and buttock pain. The pain worsened in a seated position or after long periods of standing. A T1-weighted magnetic resonance image (MRI) of the sacrum and coccyx revealed a well-demarcated intraosseous lesion with homogeneous low signal intensity, while T2-weighted MRIs demonstrated homogeneous high signal intensity. An excisional biopsy revealed benign notochord cell tumor. The biopsy proved to be effective, as it relieved the patient's coccydynia.

Due to the rarity of intraosseous benign notochordal cell tumors, it is essential to document and review this type of tumor. Only 2 benign notochordal cell tumors involving the coccyx have been previously reported, both of which presented with the same clinical symptoms of chronic coccydynia as our patient, likely due to the location of the involved lesion. The other leading diagnosis in our patient was chordoma, a malignant and locally aggressive neoplasm that is important to consider and exclude. Although chordomas have been well characterized in the surgery, pathology, and radiology literature, the benign notochordal cell tumor is a relative newcomer.
Ceramic Hemi-unicondylar Arthroplasty in an Adolescent Patient With Idiopathic Tibial Chondrolysis
Authors: Dombroski Derek , Garino Jonathan , Lee Gwo-Chin
Published: August 2009

Despite recent advances in cartilage regeneration and restoration procedures, isolated, large, full-thickness cartilage lesions in young patients continue to pose significant challeneges to patients and orthopedic surgeons. Treatment options for this difficult problem have traditionally included arthrodesis, osteotomy, osteochondral allograft, and prosthetic reconstruction. We present a case of an adolescent patient with isolated idiopathic lateral tibial chondrolysis treated with a custom ceramic hemi-unicondylar hemiarthroplasty.

Preoperatively, a 3-dimensional computed tomography scan of the patient's knee was obtained to begin manufacturing a conforming custom ceramic insert that would articulate between the tibial base plate and the patient's native lateral femoral cartilage. Through a lateral parapatellar approach, the tibial preparation was carried out using the Zimmer M/G unicompartmental knee system (Warsaw, Indiana), and the tibial base plate was cemented into position in the standard fashion. A custom, conforming, prefabricated ceramic insert (CeramTec, Memphis, Tennessee) was then inserted onto the tibial base plate.

At 5-year follow-up, this salvage procedure was successful in relieving pain and restoring function in this young patient. There were no signs of implant loosening or lysis. Magnetic resonance imaging of the knee at last follow-up revealed that the cartilage thickness of the patient's lateral femoral condyle remained unchanged.

Unicondylar hemiarthroplasty performed in patients with large unipolar lesions in the knee can provide durable and reliable pain relief. Ceramic is a viable material that can be considered for articulation with native cartilage.
Metabolic Derangement After Injection of Triamcinolone Into the Hip of an HIV-infected Patient Receiving Ritonavir
Authors: Danaher Patrick J. , Salsbury Thomas L. , Delmar Judith A.
Published: August 2009

Iatrogenic Cushing syndrome with secondary adrenal insufficiency is a rare but recognized complication of intra-articular corticosteroid injection. Recent reports suggest that the risk of this serious complication is significantly higher in human immunodeficiency virus (HIV)-infected patients receiving ritonavir-based antiretroviral regimens. This article describes a case of a 44-year-old HIV-infected man taking ritonavir who required admission to the intensive care unit (ICU) for hyperosmolar hyperglycemic state following injection of triamcinolone acetonide 80 mg into his right hip for osteoarthritis. Within 3 days of the injection, he developed polydipsia, polyphagia, polyuria, fatigue, and malaise and lost 10 lbs. Laboratory evaluation revealed a blood glucose of 766 mg/dL, and serum pH was 7.36 (normal, 7.31–7.41). After 3 days in the ICU, he was discharged on detemir insulin 15 units subcutaneously daily and sliding scale insulin aspart. Seven weeks after the injection, his detemir insulin had been titrated to 41 units daily, and his serum triamcinolone acetonide concentration was 0.39 mcg/dL (normal, <0.03 mcg/dL). His morning plasma cortisol level was 1.6 mcg/dL (normal, 4–24 mcg/dL), and his adrenocorticotropic hormone concentration was <5 pg/mL (normal, 7–50 pg/mL), consistent with suppression of his hypothalamic-pituitary-adrenal axis. We believe that systemic absorption of triamcinolone and decreased metabolism of triamcinolone due to ritonavir caused this profound and persistent hyperglycemia and hypothalamic-pituitary-adrenal axis suppression. This case highlights the need for heightened awareness of potential interactions to avoid important adverse effects in patients who receive intra-articular corticosteroids.
Transpedicular Bone Grafting Following Short-Segment Posterior Instrumentation for Acute Thoracolumbar Burst Fracture
Authors: Liao Jen-Chung , Fan Kuo-Fon , Chen Wen-Jer , Chen Lih-Hui , Kao Hsuan-Kai
Published: August 2009

Posterior short-segment instrumentation for thoracolumbar burst fracture is known for a high implant failure rate because of the lack of anterior support. Anterior body augmentation by transpedicular bone grafting has been developed as an alternative to overcome this failure. However, the efficacy of transpedicular bone grafting remains debatable.

Between August 2002 and August 2006, 31 patients with a single-level thoracolumbar fracture underwent insertion of posterior short-segment pedicle screws and transpedicular bone grafting. Twenty-one men and 10 women had a mean age of 39.7 years at the time of surgery. All patients were followed up for at least 2 years; the mean follow-up period was 52.7 months. Preoperative computed tomography showed that the mean canal encroachment was 48.1%. The kyphotic angle improved from 20.9° to 3.7° immediately postoperatively. Loss of kyphosis correction was 2.7° before implant removal and 6.2° at final follow-up. The anterior body height was corrected from 50.9% to 86.9% by surgery, but collapsed to 82.2% before implant removal and became 78.1% at final follow-up. The failure of the surgery was defined as an increase of ⩾10° in local kyphosis and/or implant breakage. At last follow-up, no implants had failed, but 3 patients had a loss of correction >10°; the failure rate was 9.7%. According to the Dennis functional scales, the mean pain score was 1.7, and the mean work score was 2.2 at final follow-up. All 8 patients with partial neurological deficit initially had improvement.

Analysis of the results indicated that this technique effectively corrects deformities, restores vertebral height, prevents early implant failure, and provides satisfactory clinical results.
Calcific Tendinitis of the Rectus Femoris
Authors: Yun Ho Hyun , Park Jung Ho , Park Jong Woong , Lee Jae Wook
Published: August 2009

This article describes calcific tendinitis of the rectus femoris treated with a local injection of a mixture of steroid and local anesthetic under C-arm control. From March 2004 to May 2005, 6 patients were treated for calcific tendinitis of the rectus femoris at our institution and followed for at least 2 years. The male:female ratio was 1:5, and mean patient age was 41 years (range, 33–49 years). Calcifications were located in the direct head in 1 patient and in the reflected head of the rectus femoris in 5. One patient underwent open surgical removal and 5 were treated with a local steroid and anesthetic injection. The patient undergoing surgical removal obtained immediate pain relief but reported discomfort in the wound area for 10 days postoperatively. The 5 patients receiving injections achieved dramatic pain relief within 2 days; follow-up radiographs revealed complete calcification disappearance within 16 weeks of treatment in all 5. No patient had experienced recurrence or complications at >2-year follow-up. Prompt diagnosis and early treatment with a local injection of a mixture of steroid and local anesthetic under C-arm control successfully relieved symptoms and facilitated a return to normality.
Arthroscopic Split Transpositional Repair for Torn Complete Discoid Lateral Meniscus
Authors: Ahn Jin Hwan , Chang Moon Jong , Lee Yong Seuk , Yoo Jae Chul , Pae Young Ryeol
Published: August 2009

A 20-year-old man presented with a 5-year history of pain in his left knee. He reported intermittent swelling and pain, especially after sporting activities. Arthroscopic surgery revealed that the entire anterior and mid-body of the discoid meniscus had been lost, and the remaining portion was shifted to posterocentral direction. Considering his age, resection of the entire meniscus was initially thought to be undesirable, although there was strong possibility of a re-tear. Although there was considerable anterocentral loss of the meniscus, the thickened inner portion of meniscus, which was displaced to the intercondylar notch, had remained relatively intact. Therefore, the lost part of the meniscus was reconstructed by transposing the remaining inner fragment. Margins of the torn side were freshened and abraded. The thick inner portion of remnant meniscus was reshaped by trimming the inferior portion. Subsequently, the posteromedial corner of remnant discoid meniscus was divided. The inner portion of the torn discoid meniscus was then flipped to the position of anterior and mid-body of the meniscus. The transposed portion was repaired using outside-in sutures and augmented with an exogenous blood clot. Surprisingly, follow-up magnetic resonance images at 40 months confirmed healing, and the patient was satisfied with the surgical outcome.
Chondroblastoma With Geographic Bone Destruction and a Sclerotic Rim
Authors: Kennedy Nicholas , Demos Terrence C. , Lomasney Laurie M.
Published: August 2009

The case:

A 16-year-old boy presented with right hip pain of 3 months' duration.
Five Recommendations for Prelicensure Clinical Nursing Education
Authors: MacIntyre Richard C. , Murray Teri A. , Teel Cynthia S. , Karshmer Judith F.
Published: August 2009

The acute shortage of RNs is both well established and projected to continue. Two primary factors contributing to the nursing shortage are insufficient numbers of faculty and insufficient clinical sites for students. Innovative academic-service partnerships are realigning these scarce resources to improve the quality of clinical education and build cultures of safety. Relationships among students, staff nurses, faculty, and the institutions where they practice are central to students' socialization, professional role development, and transition to practice. Five recommendations to strengthen these professional relationships are suggested to: reenvision nursing student-staff nurse relationships, reconceptualize the clinical faculty role, enhance development for school-based faculty and staff nurses working with students, reexamine the depth and breadth of the clinical component, and strengthen the evidence for best practices in clinical nursing education. Five key outcomes are suggested to evaluate both traditional and emerging approaches to clinical nursing education.
Adolescent Depression: Assessment and Treatment
Authors: Callan Judith A. , Howland Robert H. , Puskar Kathryn
Published: August 2009

Kayla is a 17 year old who came to the attention of her teachers and the school nurse, Mrs. Austen. During the past 6 months, she made numerous trips to the nurse's office complaining of headaches, stomach pain, and feeling “achy.” She was usually an A student, but her grades were dropping. Some teachers commented on her “attitude and motivation.” Kayla's parents were also concerned that she rarely comes out of her room, complains about being tired all the time, has been eating little, and has lost weight. Kayla has become increasingly emotional, sometimes bursting into tears for no apparent reason or “snapping out.” She sleeps more than usual, goes to bed early, and has difficulty waking up. Her parents thought some of these changes might be related to the breakup with her boyfriend.
Understanding Chirality and Stereochemistry: Three-Dimensional Psychopharmacology
Authors: Howland Robert H.
Published: August 2009

Drugs and the places in the body they bind to are each three-dimensional molecular structures. Stereoisomers are compounds that possess the same molecular and structural formula but differ in their three-dimensional configuration. Chiral compounds have two mirror-image stereoisomer forms called
enantiomers
. Compounds that contain both mirror-image enantiomers in equal proportions are referred to as
racemic mixtures
or
racemates
. The presence of a second enantiomer in racemic mixtures can be associated with various problems. The second enantiomer may be less biologically active but could interfere with the more biologically active enantiomer by binding to the same site. Adverse reactions can sometimes be attributed to one of the enantiomers. Each enantiomer may bind to metabolic enzymes differently, resulting in different rates of metabolism and clearance. They may interact differently with other drugs. The investigation, development, and use of stereochemically pure drugs have been encouraged by the U.S. Food and Drug Administration to improve the efficacy, tolerability, and safety of marketed drugs.
Common Ground, Not A Battle Ground: Violence Prevention at a Detoxification Facility
Authors: Adamson Mary A. , Vincent Audrey A. , Cundiff Jeff
Published: August 2009

This article evaluates the results of a workplace violence prevention program implemented in a Colorado detoxification facility. The program interventions are modeled after federal Occupational Safety and Health Administration guidelines and use theories from both nursing and criminology for philosophy and direction. Serving as its own control, the detoxification facility shares data measured over a 4-year period, demonstrating a sharp decline in assault rates after program implementation. The importance of administrative controls, environmental adjustments, recordkeeping and evaluation, and education and training are emphasized as key components of success.
Treatment of Conversion Disorder: A Clinical and Holistic Approach
Authors: Tocchio Sandra L.
Published: August 2009

Conversion disorder is rare, but when it affects a young woman on the verge of adulthood, it can be devastating. The intent of this article is to encourage others by describing the success that psychiatry and alter native medicine can offer to patients with conversion disorder and to emphasize the value of nursing as a part of that team. This article will explore the attitude change in both staff and patient that was needed to achieve the ultimate goal of wellness.
Clinical Implications of Chirality and Stereochemistry in Psychopharmacology
Authors: Howland Robert H.
Published: August 2009

Chirality, the concept of nonsuperimposable mirror images, is a fundamental property of biological systems and can be observed on a molecular, cellular, or organism level. Stereoisomer compounds possess the same molecular and structural formula, but they differ in their three-dimensional configurations. Chiral compounds have two mirror-image stereoisomer forms called
enantiomers
. Com pounds containing mirror-image enantiomers in equal proportions are referred to as
racemic mixtures
or
racemates
. Racemates and their individual enantiomers can have very different pharmacological properties that are relevant in clinical psychopharmacology. Various examples of drug therapies that show the clinical importance of chirality and stereochemistry are described.
Benefits and Challenges of Electronic Surveillance in Nursing Home Research
Authors: Sifford K. Susan , Bharucha Ashok
Published: August 2009

Cognitive impairment and frailty associated with dementia renders residents of long-term care (LTC) facilities particularly vulnerable to physical and emotional harm. Resident-to-resident violence affects not only the target of the aggression, but also the aggressor, as well as the formal and informal caregivers who must intervene. To date, little research has been conducted on resident-to-resident violence despite preliminary but emerging evidence that it is a common (and likely growing) problem in LTC settings. Exploration of this phenomenon presents multiple pragmatic and ethical challenges. This article presents a rationale for implementing newer technological methods to collect data in investigations of resident-to-resident violence associated with dementia. The advantages and disadvantages of electronic surveillance in LTC research and the ethical principles involved are discussed, and an argument is developed for using electronic surveillance in both the shared, as well as private, spaces of the facility.
New logging tool for measuring azimuth of the ground‐water flow
Authors: Mares Stanislav , Henzl Tomas , Woltaer Leo , Lux Karl‐Norbert , Stump Uwe
Published: August 2009

In hydrogeological research for ground water as well as in many contamination studies, the direction of the subhorizontal ground water flow is an important information influencing further decisions in exploitation of the ground water resources or in application of remediation measures.

New construction of the logging tool for determining azimuth of the ground water flow in a single well and its laboratory and field testing is presented. The sophisticated logging tool ‐ combination of an electronic compass with a special circular photometric sensor detecting the time changes of the tracer plume in the measuring slot ‐ offers the information on direction of subhorizontal ground water flow in a single well for velocities ranging between 10‐6 to 10‐1 m/s. The diameter of the tool is 76 mm, length 1.12 m and weight 13 kg. The tool is operating together with current logging systems.
Geophysical Study of an Landslide in Northern Sicily
Authors: Cosentino P. , Martorana R. , Perniciaro M. , Terranova L.M.
Published: August 2009

The San Fratello area in the Nebrodi Mountains (northern Sicily) is a region of high instability. It has suffered many devastating occurrences, which have hit and destroyed the village of San Fratello. At present the area is still subject to a high landslide risk.

A series of geophysical surveys have been carried out with the aim of determining the thickness and dimensions of the landslide body as well as some tectonic features, in order to gain insight into the evolution of the landslide. The following geophysical techniques have been used: borehole seismic tomography, i.e. down‐hole tomographic seismic soundings (DH TSS), time‐domain electromagnetic (TDEM) soundings and georadar profiling (GPR). An additional objective was to compare the efficiency of the geophysical methods used in real geological, morphological and logistic situations.

The data obtained using seismic tomography outlined the shape and the thickness of the body of the landslide in the scar and track area, as well as some mechanical characteristics of the formations involved in the movement. TDEM soundings provided a little additional information on the upper 5–10 m. Georadar profiles supplied some information about the locations of some lateral lithological changes.

Finally the information obtained with the various geophysical techniques was used to provide an outline of the history of the area.
Two‐dimensional electrical imaging for detection of hydrocarbon contaminants
Authors: Godio A. , Naldi M.
Published: August 2009

The effects of a long‐term diesel oil pollution due to leakage from buried tanks have been investigated using electrical resistivity tomography. The reliability of 2D electrical resistivity imaging of the subsoil was assessed using a numerical modelling approach that simulated the different behaviour of the contaminated zone. The effects of inversion parameters, such as the damping factor and smoothing matrix, have been studied in order to evaluate the optimal parameters to process real data.

The results of the field test indicated that highly conductive anomalies can be related to the biological degradation of hydrocarbons: geochemical analysis performed on several groundwater samples confirmed the presence of biodegradation activity. Chemical analysis pointed out an anomalous concentration of iron and manganese cations dissolved in the groundwater. Very low values of resistivity can be associated with a marked modification of the cation exchange capacity of the soil mixture due to degradation of these hydrocarbons. Chemical and physical interactions due to hydrocarbon pollution affect the electrical properties of soils and groundwater.
Investigation of a fractured limestone cliff (Chartreuse Massif, France) using seismic tomography and ground‐penetrating radar
Authors: Dussauge‐Peisser Carine , Wathelet Marc , Jongmans Denis , Hantz Didier , Couturier Bernard , Sintes Michel
Published: August 2009

Evaluating the stability state of a rock slope is a complex problem, mainly due to the lack of knowledge of the real state of the rock mass. Geophysical methods appear to be useful for investigating the deep discontinuity pattern, which may be poorly interpreted from surface observations. However, they have seldom been applied on steep rock slopes. The aim of this study is to test seismic tomography and ground‐penetrating radar on near‐vertical cliffs, and assess the quality of information that they can provide when investigating the characteristics of the fracture pattern inside the massif.

The test site is located in the Chartreuse massif, 20 km north‐west of Grenoble, France. It is a 15 m high limestone cliff, characterized by one main near‐vertical discontinuity set, including some wide open fractures.

Seismic tomography has been conducted between the vertical free surface and the plateau above, along three parallel profiles. Results show strong velocity gradients, from 800 to 3500 m/s. Some triangular low‐velocity zones can be correlated with field observation of open fractures, but different tests on synthetic models and on real data show that the method is too sensitive to such heterogeneous conditions to provide accurate information on the fracture pattern.

Ground‐penetrating radar surveys have also been acquired along vertical profiles on the cliff. We used three different antennae with centre frequencies of 35, 120 and 500 MHz. The penetration depth varied from 10 m (500 MHz) to about 20 m (35 MHz). The main reflectors are near‐vertical and most of them can be correlated with fractures observed on the site. The reflectivity varies strongly along one single reflector, indicating changes in the aperture and/or filling characteristics.
Seismic reflection imaging of an ultrashallow interface from a P‐wave data set with a poor signal‐to‐noise ratio
Authors: Balia Roberto , Gavaudo Enrico
Published: August 2009

It is well known that pitfalls are commonly encountered in the acquisition and processing of shallow reflection data. Although they can often lead to misinterpretations, the obsession with these difficulties can generate an excessively pessimistic attitude and ultimately lead to rejecting data that contain genuine reflections. The authors revisited a data set acquired during an ultrashallow P‐wave reflection experiment conducted in December 1996 on a subsurface model characterized by one main, complex interface. The model had been purpose‐built to control acquisition and processing decisions, and to contribute to clarifying at least some of the critical aspects inherent in the ultrashallow seismic reflection method. For the experiment, the acquisition geometry was purposely designed regardless of the known characteristics of the model, considering only a target depth of less than ten metres. The data, which had been acquired with CMP techniques, were generally characterized by a poor signal‐to‐noise ratio and had been considered completely useless. Initially, inexperience in acquiring and, above all, processing ultrashallow reflection data, in conjunction with mise‐valuations, had led to disappointing failures. Velocity analysis on reflection data had proved very difficult and standard processing sequences were inadequate. However, in this case a good result was obtained by modelling the near‐surface velocity using direct‐wave traveltimes analysis and by adopting a simple but segregated processing sequence, which proved necessary due to significant velocity gradients and large relative variations of the reflector depth. Time‐to‐depth conversion afforded a more than acceptable result.
Three‐dimensional GPR imaging in the horizontal wavenumber domain for different heights of source and receiver antennae
Authors: van der Kruk J.
Published: August 2009

For imaging ground‐penetrating radar (GPR) data, three of the most important parameters are the wave speed, polarization and amplitude of the propagating electromagnetic wave‐field. Choosing an appropriate forward model that incorporates these three parameters is a critical aspect of imaging. Also, the height of the antennae above the surface influences the scattered field significantly and should be taken into account. As the height of the antennae above the surface is increased, the widths of the antenna patterns decrease, resulting in decreasing horizontal spatial bandwidths of the scattered electric fields. Imaging is carried out in the horizontal wavenumber domain using the spatial bandwidths of the scattered data. Decreased spatial resolution is obtained for increasing heights. The far‐field expressions do not account for geometrical spreading in air above the surface, resulting in anomalously low image amplitudes for elevated antennae. Experimental data measured with 900 MHz antennae also show reductions in spatial bandwidth as the height of the source and receiver antennae is increased. For heights and , similar spatial bandwidths as predicted by the synthetic results are obtained. For , this reduction in bandwidth is not as strong as predicted by the synthetic results, primarily because of limitations of the far‐field expressions. For stability reasons, the imaging could only be carried out using the limited bandwidth for the forward far‐field model. Images of a spherical metal sphere for measurements at and were almost identical, whereas those at were similar to those at low heights. In one direction, a higher spatial resolution was observed for the antennae with zero height and decreasing spatial resolution for increasing height. In the other direction, the difference in spatial resolution was not very obvious.
Subsurface imaging using measured near‐field antenna footprints
Authors: van Dongen Koen W.A. , van den Berg Peter M. , Nicolaescu Ioan
Published: August 2009

Images of the subsurface are made for the detection of land‐mines using a bistatic stepped‐frequency continuous‐wave spiral‐antenna system. While the system moves along the surface, the emitted electromagnetic wavefields are scattered by objects in the subsurface and cause changes in the voltages measured at the receiver. These changes are formulated as a convolution of a sensitivity function and a complex contrast function. Within the Born approximation, this sensitivity function is equal to the inner product of the wavefield emitted by the transmitter and the field from the receiver operating in transmitting mode. For true amplitude imaging purposes, knowledge of the wavefields in the subsurface is needed. Since it is difficult to obtain a model which describes the radiation characteristics accurately, we measure the footprints of the antennae at one level in the near‐field region and propagate the emitted wavefields using Huygens’ principle. We use both synthetic and experimental data to localize objects in a homogeneous space. First, we apply time‐domain synthetic‐aperture‐radar (SAR) imaging in its most basic appearance. Next, we apply a single‐step inversion algorithm to the data, where we use the measured radiation characteristics of the antenna system. This results in an increase in resolution. We refer to this method as ‘minimized back‐propagation’.
Finite‐difference modelling for tunnel seismology
Authors: Kneib Guido , Leykam Alice
Published: August 2009

The diagonal differencing algorithm, which takes spatial derivatives along the diagonals of the finite‐difference grid, is well suited to solve the elastodynamic equations for tunnel seismic modelling because it is accurate and stable at strong low‐order discontinuities of the elastic medium. Spatial high‐order finite‐difference operators increase the accuracy and efficiency of the algorithm except at steps in the elastic properties, where these operators fail. A solution is to use high‐order finite differences in most of the grid but to employ two‐point second‐order operators at low‐order discontinuities. This keeps memory requirements and computational effort on a level that allows 3D simulations on moderately priced PC hardware. Measurements with the commercial tunnel seismic prediction method yield complex seismic common‐receiver gathers with long direct‐wave pulses. Finite‐difference simulations in two and three dimensions reveal that these long pulses are due to P‐wave reverberations in and around the water‐filled shothole. Direct S‐waves originate close to the detonation point by conversion at the shothole–rock boundary. A dispersive, low‐frequency guided wave reverberates with the average S‐wave velocity inside the excavation damaged zone around the tunnel. The guided wave creates multiple body waves inside the undisturbed rock as it reverberates. It carries useful information about the degree and depth of the rock excavation damage but the guided wave often overlaps tunnel surface‐wave modes and may be difficult to extract from seismograms. Receivers should be buried deeper than the extent of the excavation damaged zone so that the guided waves and tunnel surface waves, which circulate around the tunnel, do not dominate seismic records and hide direct S‐waves, reflections or other late arrivals.
Propagation of errors due to incorrect positions of sources and detectors in wave‐field tomography
Authors: Cosentino P.L. , Sanfratello V.
Published: August 2009

Tomographic data processed by 2D inversion programs can produce fairly large distortions due to incorrect source and/or detector positions. This problem is very serious in high‐frequency electromagnetic tomography (GPR), due to the dimensions of the transmitter and receiver antennae. The errors can even be larger when coupled antennae are used (receiver and transmitter inside the same box) whose positions are not clearly known. Similar errors can be involved in seismic tomography, for instance when the mechanical connection between transducers and sample is defective.

In this paper the problem has been studied using synthetic data which were calculated for different acquisition geometries. Synthetic data have been distorted assuming a position error in the whole set of sensors, transmitters or receivers. Tests have been carried out using a homogeneous, isotropic medium and various simple inhomogeneous models, characterized by different geometric boundaries.

The responses for all the models have been calculated (both forward and inverse problems) assuming straight raypaths, also in the case of velocity variations. The calculated traveltimes were processed using an LSQR algorithm implemented in an iterative inversion program, containing two damping factors to reduce total and local velocity contrasts. The inversion results have been reproduced graphically and the analysis of residuals has been carried out. Finally, propagation of these residuals, both in time and velocity, is discussed.
An investigation into the use of geophysical methods in the study of aquifer contamination by graveyards
Authors: Senos Matias M.J. , Marques da Silva M. , Goncalves L. , Peralta C. , Grangeia C. , Martinho E.
Published: August 2009

Graveyards are the traditional way of dealing with the deceased and often their location is unsuitable so that there is a potential contamination danger for local aquifers and soils. Such a contamination is complex as organic, inorganic and biological pollutants will be present. This problem has been studied by direct methods, i.e. boreholes. However borehole location can be difficult and so it is proposed here to use geophysical multiparameter surveys, as well as hydrochemistry studies, to investigate the contamination in the vicinity of two graveyards located in very porous and permeable formations. Based on the geophysical interpretation, two shallow boreholes were drilled and groundwater sampling confirmed local aquifer contamination. The geophysical response is shown to depend on the water table depth, and when this is close to the ground surface, it is demonstrated that geophysical methods can be used to map contamination plumes originated in the graveyards and, therefore, assist borehole location.
Surface waves in inversely dispersive media
Authors: Ryden N. , Park C.B.
Published: August 2009

The dispersion of surface waves in inversely dispersive media where the shear‐wave velocity decreases with depth is studied. Theoretical dispersion curves are calculated in the complex wavenumber domain. Excitability and attenuation due to leakage are calculated for each point on the dispersion curves. These additional parameters are critical for a correct understanding of the dispersion properties of surface waves. Mode shapes are included in the study to visualize displacements inside the medium. The results of the study show that, for inversely dispersive media, the Rayleigh‐wave assumption is not valid, and other types of interface waves and leaky Lamb waves contribute to the surface wavefield. They also show that, in this case, true theoretical dispersion curves can be approximated by Lamb‐wave dispersion curves for a free plate in a vacuum, provided that the stiffness contrast between the top layer and the underlying half‐space is large, and also that the shear‐wave velocity of the stiff layer is greater than the compressional‐wave velocity in the underlying media. The error in the phase velocity resulting from this approximation is investigated and it is shown that the error does not exceed 5% for the fundamental antisymmetric Lamb‐wave dispersion curve. Because of the numerical simplicity of calculating its theoretical dispersion curves, the Lamb‐wave approximation can provide an effective evaluation method to resolve the thickness and elastic parameters of the stiff top layer. This is exemplified using a set of field data.
Surface‐wave inversion using a direct search algorithm and its application to ambient vibration measurements
Authors: Wathelet M. , Jongmans D. , Ohrnberger M.
Published: August 2009

Passive recordings of seismic noise are increasingly used in earthquake engineering to measure in situ the shear‐wave velocity profile at a given site. Ambient vibrations, which are assumed to be mainly composed of surface waves, can be used to determine the Rayleigh‐wave dispersion curve, with the advantage of not requiring artificial sources. Due to the data uncertainties and the non‐linearity of the problem itself, the solution of the dispersion‐curve inversion is generally non‐unique. Stochastic search methods such as the neighbourhood algorithm allow searches for minima of the misfit function by investigating the whole parameter space. Due to the limited number of parameters in surface‐wave inversion, they constitute an attractive alternative to linearized methods. An efficient tool using the neighbourhood algorithm was developed to invert the one‐dimensional profile from passive or active source experiments. As the number of generated models is usually high in stochastic techniques, special attention was paid to the optimization of the forward computations. Also, the possibility of inserting a priori information into the parametrization was introduced in the code.

This new numerical tool was successfully tested on synthetic data, with and without a priori information. We also present an application to real‐array data measured at a site in Brussels (Belgium), the geology of which consists of about 115 m of sand and clay layers overlying a Palaeozoic basement. On this site, active and passive source data proved to be complementary and the method allowed the retrieval of a profile consistent with borehole data available at the same location.
Using transfer function for estimating dissipative properties of soils from surface‐wave data
Authors: Foti S.
Published: August 2009

The quality factor (or damping ratio) can be estimated by analysing the spatial attenuation of surface‐wave data. However, because of the link between geometrical and material dispersion, a coupled analysis of dispersion and attenuation curves is preferable. Using a transfer‐function approach, it is possible to estimate the dispersion and attenuation curves simultaneously, provided the seismic source is known. A formulation based on the deconvolution of seismic traces is used to extend the transfer‐function approach to ordinary seismic gathers in which the source wavelet is not known. The measured transfer function is used in a regression analysis to obtain estimates of the complex wavenumbers, which, in the framework of viscoelasticity, contain all the information relating to phase velocity and attenuation of surface waves for a layered medium. Application of this procedure to experimental data leads to results consistent with those obtained using conventional techniques (e.g. analysis and amplitude regression).
Mechanical characterization of heterogeneous soils with surface waves: experimental validation on reduced‐scale physical models
Authors: Abraham O. , Chammas R. , Cote Ph. , Pedersen H.A. , Semblat J.‐F.
Published: August 2009

The characterization of heterogeneous soils using common geotechnical techniques often proves impossible when the size of the heterogeneity is larger than a few tens of centimetres. Geophysical investigation techniques based on seismic wave propagation can help engineers to characterize the mechanical properties of such materials. In this paper, both refracted and surface waves are used to estimate the mechanical properties of an equivalent homogeneous medium.

A summary of the main results obtained numerically using finite‐element computations and homogenization theory is presented. It is shown that, for first‐mode surface‐wave wavelengths larger than 7.5 times the nominal size of the heterogeneity and within certain heterogeneity concentration ranges (up to 50% for matrix dominant soils), surface waves homogenize the soil in accordance with classical homogenization theory.

To validate these numerical results, a reduced‐scale model was built and seismograms, generated with a falling weight, were recorded. The phase‐velocity dispersion curve of the generated surface waves is inverted in order to obtain the shear‐wave velocity of the heterogeneous layer. The compressional‐wave velocity is calculated by means of seismic refraction analysis. Velocities obtained on the reduced‐scale model correspond to those predicted by homogenization theory from individual measurements of matrix and inclusion velocities.
Modelling azimuthal resistivity sounding over a laterally changing resistivity subsurface
Authors: Watson Kathryn A. , Barker Ron D.
Published: August 2009

Rotational or azimuthal resistivity sounding is frequently employed for determining the electrical anisotropy of the subsurface. From this, the orientation of fracturing which might give rise to the anisotropy is interpreted. However, 4‐electrode arrays, such as the Wenner or Schlumberger, are strongly ambiguous and will produce an anisotropy‐style signature also over dipping strata or a gra‐dational lateral change in rock resistivity. However, this problem may be overcome by use of a 5‐electrode offset Wenner array. Simple computer modelling of rotational soundings is sufficient to demonstrate that azimuthal Wenner surveys, conducted on ground where there is a lateral variation in resistivity, will produce results similar to those recorded on truly anisotropic ground, whereas alternative techniques, such as offset Wenner azimuthal sounding, will successfully differentiate the two models.
Magnetic, GPR and geoelectrical measurements for studying the archaeological site of ‘Masseria Nigro’ (Viggiano, southern Italy)
Authors: Rizzo E. , Chianese D. , Lapenna V.
Published: August 2009

The results of a geophysical survey carried out at the archaeological site of Masseria Nigro, located on a fluvial terrace on the north‐eastern flank of the Agri valley (Viggiano, Basilicata Region), are presented and discussed. The site includes an important ancient structure, developed in successive phases between the 4th and 3rd centuries BC and destroyed after the Roman conquest. Magnetic mapping, GPR profiling and electrical resistivity tomography were applied in the course of geophysical exploration in the archaeological area. The application of these methods revealed information about buried ancient walls, helping to define the boundaries of the whole building. During the first phase of the excavation, archaeologists targeted only the western part of the ancient structure (about 1000 m2), but the geophysical survey performed in a second phase was able to cover the entire ancient structure (1400 m2), enabling the archaeologists to define the extent of the buried structures. Our findings confirmed the hypothesis of the larger extent of the archaeological area in the eastern part and revealed the complete plan of the ancient building.