bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of the electrical anisotropy on the response of helicopter‐borne frequency‐domain electromagnetic systems
Authors: Yin Changchun , Fraser Douglas C. 
Published: August 2004

ABSTRACTHelicopter electromagnetic (HEM) systems are commonly used for conductivity mapping and the data are often interpreted using an isotropic horizontally layered earth model. However, in regions with distinct dipping stratification, it is useful to extend the model to a layered earth with general anisotropy by assigning each layer a symmetrical 3 × 3 resistivity tensor.The electromagnetic (EM) field is represented by two scalar potentials, which describe the poloidal and toroidal parts of the magnetic field. Via a 2D Fourier transform, we obtain two coupled ordinary differential equations in the vertical coordinate. To stabilize the numerical calculation, the wavenumber domain is divided into two parts associated with small and large wavenumbers. The EM field for small wavenumbers is continued from layer to layer with the continuity conditions. For large wavenumbers, the EM field behaves like a DC field and therefore cannot be sensed by airborne EM systems. Thus, the contribution from the large wavenumbers is simply ignored.The magnetic fields are calculated for the vertical coaxial (VCX), horizontal coplanar (HCP) and vertical coplanar (VCP) coil configurations for a helicopter EM system. The apparent resistivities defined from the VCX, VCP and HCP coil responses, when plotted in polar coordinates, clearly identify the principal anisotropic axes of an anisotropic earth. The field example from the Edwards Aquifer recharge area in Texas confirms that the polar plots of the apparent resistivities identify the principal anisotropic axes that coincide well with the direction of the underground structures.
Comparison of methods for modelling the behaviour of bubbles produced by marine seismic airguns
Authors: Cox E. , Pearson A. , Blake J.R. , Otto S.R. 
Published: August 2004

ABSTRACTThree models for the dynamics of seismic airgun‐generated bubbles and their associated far‐field signals are developed and compared with geophysical data. The first model of an airgun‐generated bubble uses a spherical approximation, the second is an approximate Lagrangian model which allows for small deformations from a spherical shape, whilst the final model is an axisymmetric boundary‐integral method which permits the bubble to evolve into highly non‐spherical geometries. The boundary‐integral method also allows both geometric interference and strong dynamic interactions in multi‐bubble studies.When comparing the spherical model to experimental data there are three apparent, significant differences: the magnitude of the primary pressure peak, which is greater in the model; the subsequent decay of the pressure peaks and motion – the experimental data demonstrating greater decay and a slower rise rate; and the frequency of oscillation, which is slower in the experimental data. It is believed that the first discrepancy is due to the initial stages of expansion where the compressed air is forced to sparge through the airgun ports. The other differences indicate that there is some other energy‐loss mechanism which is not accounted for in the spherical bubble model. Non‐spherical bubble behaviour is investigated through the use of two different deformable many‐bubble codes and their predictions are compared with the spherical model and experimental data.The Lagrangian model predicts the formation of a buoyancy‐driven liquid jet on the first collapse of a typical airgun bubble; however, the model breaks down when the bubble becomes significantly deformed, due to a low‐order spherical‐harmonic approximation for the potential. The axisymmetric boundary‐integral code models the jet shape accurately and it is found that these bubbles evolve to toroidal geometries when the jet impacts on the opposite surface of the bubble. This highly non‐spherical behaviour is readily observed on high‐speed films of airgun bubbles, and is one key source of energy loss; it damps the pulsations of the bubble and slows its rise speed.Inter‐bubble interactions are investigated using the two deformable bubble models, and the predictions are compared to field data. It was found that as the bubbles approach each other, their periods of oscillation increase in accordance with observations, and jets are formed in the direction of motion upon collapse.
The influence of induced polarization on long‐offset transient electromagnetic data
Authors: Hoheisel Andreas , Hördt Andreas , Hanstein Tilman 
Published: August 2004

ABSTRACTThe diffusion of electromagnetic fields is dependent not only on conductivity, but also on magnetic permeability, dielectric permittivity and polarizability, i.e. dispersive conductivity. The long‐offset transient electromagnetic (LOTEM) method is mainly used to determine the spatial distribution of conductivity in the subsurface. However, earlier work on loop‐loop TEM suggests that transient EM methods can also be affected by induced polarization (IP).Numerous 1D forward calculations were carried out to study the IP effect on LOTEM data, using the Cole‐Cole relaxation model to simulate the polarizability of the ground. Besides the polarizability of each layer, the IP effect depends on the LOTEM field set‐up and the spatial distribution of conductivity in the ground. In particular, near‐surface layers with high chargeabilities can significantly distort the late time transients of the electric field components in the vicinity of the transmitter. The influence of polarizable layers on the magnetic field components can be neglected under normal circumstances.In 1997 and 1999, LOTEM measurements were carried out at Mt. Vesuvius in Italy to explore the geological structure of the volcano. Sensitivity studies on the effect of polarizable layers suggest that high chargeabilities in connection with conductive layers at greater depths would result in a detectable distortion of the electric field transients. Although the simultaneous IP measurements revealed high chargeabilities in a near‐surface layer, no evidence of IP effects could be found in the measured LOTEM data. We conclude that the observed chargeabilities are local and that 3D effects are probably present in the data.Another aspect is the measurement of the system response, which is usually measured by placing a receiver very close to the transmitter. Therefore, large distortions can be expected if near‐surface polarizable layers exist. This was verified in practice by field measurements in an area with high chargeabilities in Longerich, Cologne.
Velocity model estimation for depth imaging: Comparison of three tomography methods on a 2D real data set
Authors: Bégat Soazig Le , Chauris Hervé , Devaux Vincent , Nguyen Sylvain , Noble Mark 
Published: August 2004

ABSTRACTThe estimation of velocity models is still crucial in seismic reflection imaging as it controls the quality of the depth‐migrated image, which is the basis of geological interpretation. Among the numerous existing methods for velocity determination, tomographic methods are very attractive for their efficiency and ability to retrieve heterogeneities of the medium. We present three tomographic methods in order to estimate heterogeneous velocity models from 2D prestack PP reflection data: a traveltime tomography in the time‐migrated domain, a traveltime and slope tomography in the non‐migrated time domain, and a slope tomography in the depth‐migrated domain.The first method (traveltime tomography in the time domain) is based on continuous picked events, whereas the two slope tomographic methods, one in the time domain and the other in the depth domain, are based on locally coherent events, with no assumptions about reflector geometry or the unknown velocity field. The purpose of this paper is not to describe in detail the theoretical basis and implementation of the methods, but to apply and compare their output using the same marine real data set. Based on the estimated velocity models, the migrated images and the common‐image gathers from the three processing routes, the relative strengths and weaknesses of the methods are discussed. Finally, similarities are indicated and potential alternative approaches are proposed.
Airborne EM skin depths
Authors: Beamish David 
Published: August 2004

ABSTRACTSkin depth is an electromagnetic (EM) scale length that provides a measure of the degree of attenuation experienced by a particular frequency of an EM system. As has been discussed in the literature, skin depth is not a complete measure of the depth of investigation, but the two may be related. Frequency‐domain airborne EM systems employ pairs of transmitter and receiver coils that use a frequency range from several hundred hertz to over 100 kHz. For elevated dipoles, both geometrical and frequency‐dependent attenuation of the induced fields must be considered. For airborne EM systems it is possible to define a skin depth based only on the electric field induced by the transmitter. A vertical decay scale length, here defined from the at‐surface position of maximum electric field, enables the same skin‐depth estimate to be obtained for both cases of vertical and horizontal dipolar excitation. Such dipolar skin depths associated with towed‐bird and fixed‐wing airborne systems are studied in relation to frequency, conductivity and sensor elevation. Dipolar skin depths are found to be much smaller than their plane‐wave counterparts except at high frequency (>50 kHz) and in combination with high conductivity. For the majority of airborne systems the influence of altitude on skin depth is highly significant. Dipolar skin depths increase with increasing sensor elevation. Low frequencies display the greatest sensitivity. At low elevation (<40 m), geometrical attenuation dominates the behaviour of the skin depth. The study indicates that typical low‐altitude airborne surveys provide vertically compact assessments of subsurface conductivity, well suited to near‐surface, environmental applications.
The use of vapor phase extraction in metabolic profiling of phytohormones and other metabolites
Authors: Schmelz Eric A. , Engelberth Juergen , Tumlinson James H. , Block Anna , Alborn Hans T. 
Published: August 2004

SummaryThrough complex networks of signaling interactions, phytohormones regulate growth, development, reproduction and responses to biotic and abiotic stress. Comprehensive metabolomic approaches, seeking to quantify changes in vast numbers of plant metabolites, may ultimately clarify these complex signaling interactions and consequently explain pleiotropic effects on plant metabolism. Synergistic and antagonistic phytohormone signaling interactions, referred to as crosstalk, are often considered at the level of transduction without proper consideration of synthesis or accumulation of phytohormones because of the limitation and difficulty in quantifying numerous signals. Significant progress has recently been made in the expansion of metabolic profiling and analysis of multiple phytohormones [Birkemeyer et al. (J. Chromatogr. A, 2003, 993, 89); Chiwocha et al. (Plant J., 2003, 35, 405); Müller et al. (Planta, 2002, 216, 44); Schmelz et al. (Proc. Natl Acad. Sci. USA, 2003, 100, 10552)]. We recently presented a novel metabolic profiling approach to the analysis of acidic phytohormones and other metabolites based on a simplistic preparation scheme and analysis by chemical ionization‐gas chromatography/mass spectrometry. We now provide a detailed description of this vapor phase extraction technique and use pathogen infection of Arabidopsis with Pseudomonas syringae DC3000 to illustrate metabolic changes in salicylic acid, cinnamic acid, jasmonic acid, indole‐3‐acetic acid, abscisic acid, unsaturated C18 fatty acids, 12‐oxo‐phytodienoic acid, and phytotoxin coronatine. Directions for further method expansion are provided and include issues of recovery, derivatization, range of accessible analytes, optimization, reproducibility and future directions.
ESTs, cDNA microarrays, and gene expression profiling: tools for dissecting plant physiology and development
Authors: Alba Rob , Fei Zhangjun , Payton Paxton , Liu Yang , Moore Shanna L. , Debbie Paul , Cohn Jonathan , D'Ascenzo Mark , Gordon Jeffrey S. , Rose Jocelyn K. C. , Martin Gregory , Tanksley Steven D. , Bouzayen Mondher , Jahn Molly M. , Giovannoni Jim 
Published: August 2004

SummaryGene expression profiling holds tremendous promise for dissecting the regulatory mechanisms and transcriptional networks that underlie biological processes. Here we provide details of approaches used by others and ourselves for gene expression profiling in plants with emphasis on cDNA microarrays and discussion of both experimental design and downstream analysis. We focus on methods and techniques emphasizing fabrication of cDNA microarrays, fluorescent labeling, cDNA hybridization, experimental design, and data processing. We include specific examples that demonstrate how this technology can be used to further our understanding of plant physiology and development (specifically fruit development and ripening) and for comparative genomics by comparing transcriptome activity in tomato and pepper fruit.
Effect of recombinant canine IFNγ on canine atopic dermatitis evaluated by clinical signs, histopathology and expression of Th1/Th2 cytokine mRNA
Authors: Iwasaki T. , Kagawa Y. , Park S. J. , Kanazawa N. , Momoi Y. , Tanikawa H. 
Published: August 2004

Atopic dermatitis (AD) is thought to be caused by immunologic abnormalities expressed as a Th1/Th2 cytokine imbalance in both humans and dogs. Several studies have focused on the therapeutic effects of IFNγ in human AD with successful results; however, the mechanism of action of IFNγ is not fully understood. We investigated the effect of recombinant canine interferon gamma (rCaIFNγ) on 10 dogs with AD and evaluated the ratio of IL‐4 mRNA to IFNγ mRNA in peripheral blood mononuclear cells, serum total IgE levels, and histological changes in skin. After six injections of rCaIFNγ over a span of 2 weeks, seven of the 10 dogs showed improvement, and six of these seven dogs exhibited decreased IL‐4:IFNγ mRNA ratios. Two of the three cases that did not improve had increased IL‐4:IFNγ mRNA ratios. Total serum IgE levels were significantly decreased in nine of 10 cases. The number of IgE‐positive cells detected by immunostaining and the number of mast cells in skin biopsy samples were decreased. A reduction of epidermal cell layers was demonstrated by histopathology after treatment. These results demonstrated that rCaIFNγ may be a novel safe and effective therapeutic option for the treatment of canine AD, and the mechanism of action of rCaIFNγ may be related to the modulation of Th2 cytokines to Th1 cytokines with the reduction of serum IgE production. Funding: Self‐funded.
Effects of the immunomodulatory drugs tacrolimus, rapamycin and cilomilast on dendritic cell function in a model of allergic contact dermatitis
Authors: Bäumer W. , Sülzle B. , Weigt H. , Hecht M. , Kietzmann M. 
Published: August 2004

The in vitro and in vivo immunomodulatory effects of the phosphodiesterase 4 inhibitor cilomilast were compared to tacrolimus and rapamycin, immunosuppressive drugs used in organ transplantation. Tacrolimus is also registered for treatment of human atopic dermatitis. In vitro, the effect of the substances on the mixed leucocyte reaction (dendritic cell‐mediated T‐cell activation) was tested. Cilomilast and tacrolimus, as well as rapamycin, were able to inhibit proliferation in a dose‐dependent manner. In vivo, the substances were tested in a model of allergic contact dermatitis. Toluene‐2,4‐diisocyanate (TDI)‐induced allergic contact dermatitis in BALB/c mice is characterized by a Th2‐mediated allergic inflammatory reaction, demonstrated by an increase of IL‐4 and an unchanged level of IL‐12 in inflamed tissues. It was our aim to compare the inhibitory effect of the drugs on the TDI‐induced allergic inflammatory response (ear swelling). After oral and intraperitoneal administration, only tacrolimus induced a distinct inhibition of the TDI‐mediated ear swelling 16 h after challenge. Cilomilast as well as rapamycin failed to do so. After topical administration, cilomilast and tacrolimus, but not rapamycin, inhibited the inflammatory response. Therefore, we compared the combination of topical and systemic administration of cilomilast and tacrolimus in the main experiment. Cilomilast (20 mg/kg) was administered intraperitoneally 16 and 0.5 h before challenge and topically onto mouse ears (3% in 20 μL acetone/DMSO 9:1) 2 h before challenge. Tacrolimus was given via the same routes (systemically 2.5 mg/kg and topically 0.5%) at the same time points as cilomilast. Both substances induced a significant inhibition of the ear swelling measured 16 h after TDI challenge. The mice were sacrificed, draining auricular lymph nodes were weighed, and lymph node cells were counted. Compared to vehicle‐treated mice, both lymph node weight and cell count were significantly reduced in tacrolimus‐treated mice and slightly reduced in cilomilast‐treated mice. Additionally, the dorsal half of the treated ears was cultivated for a skin dendritic cell migration assay. In contrast to a former study in which cilomilast strongly inhibited dendritic cell migration in nonsensitized skin, there was no inhibition of dendritic cell migration by cilomilast or tacrolimus in TDI‐challenged skin. In conclusion, the mixed leucocyte reaction in combination with an in vivo contact dermatitis model is a superior system to predict the efficacy of compounds for the treatment of allergic skin diseases compared to either method alone. Cilomilast and tacrolimus exert anti‐inflammatory effects in this model of allergic contact dermatitis and the mixed leucocyte reaction, but dendritic cell migration through the skin seems to be unaffected. Funding: Self‐funded.
Patch test reactions to house dust mites in dogs with atopic dermatitis
Authors: Nogueira S. A. F. , Torres S. M. F. , Horne K. , Jessen C. 
Published: August 2004

The purpose of this study was to determine the percentage of dogs with spontaneous atopic dermatitis that show a positive patch test reaction to a commercially available 20% house dust mites mixture containing equal parts of Dermatophagoides farinae and Dermatophagoides pteronyssinus in white petrolatum. In addition, we evaluated whether skin reactions induced after the epicutaneous application of house dust mites were clinically and histologically similar to naturally developed skin lesions of dogs with atopic dermatitis. Furthermore, we investigated if the reactions induced by house dust mites were true allergic reactions by comparing them to atopic lesional skin and to patch test reactions induced by an irritant substance (sodium lauryl sulphate). White petrolatum alone and nonlesional skin sites were used as negative controls. Macroscopic and microscopic evaluations of the patch test and control sites were performed in a blinded fashion at 48 and 72 h after patch test application. Microscopic results were evaluated in a qualitative and quantitative manner. A chi‐square test for homogenicity was used for the quantitative analysis to compare the proportion of each dermal inflammatory cell type among positive histopathological tested sites. P values ≤ 0.05 were considered significant. The study included 12 healthy nonatopic dogs and 13 dogs with nonseasonal atopic dermatitis. None of the nonatopic dogs reacted to house dust mites and white petrolatum. Ten (77%) of the 13 atopic dogs reacted macroscopically and histopathologically to house dust mites. Macroscopic reactions induced by house dust mites were characterized by erythema, oedema and papules. The macroscopic reactions induced by house dust mites were identical to lesional skin in 20% of the dogs and identical to reactions induced by sodium lauryl sulphate in 40% of the dogs. Qualitative histopathological findings showed that the reactions induced by house dust mites were similar to atopic lesional skin in 80% of the dogs and were similar to sodium lauryl sulphate in 20% of the dogs. Quantitative analyses showed that the proportion of neutrophils in reactions induced by sodium lauryl sulphate was significantly higher (P < 0.05) compared to house dust mites reactions, which could be a differentiator factor between an allergic and an irritant reaction. These results showed that the epicutaneous application of house dust mites in dogs with atopic dermatitis induced histopathological lesions similar to spontaneous atopic lesions in dogs. Therefore, this study demonstrated that house dust mites penetrated the skin of dogs with atopic dermatitis and induced an inflammatory response that resembled a true allergic reaction. Funding: Small Companion Animal Grant, University of Minnesota.
Conventional and rush immunotherapy in canine atopic dermatitis
Authors: Mueller R. S. , Fieseler K. V. , Zabel S. , Rosychuk R. A. W. 
Published: August 2004

The purposes of this double‐blinded, randomized study were to determine the success rate of rush immunotherapy in canine atopic dermatitis and compare it to conventional immunotherapy, and to assess if rush immunotherapy leads to a quicker reduction in clinical signs than conventional immunotherapy. Twenty‐two atopic dogs diagnosed by history, physical examination and appropriate exclusion of differential diagnoses were included in the study. Offending allergens were identified with an intradermal test. All dogs were premedicated for 3 days with an antihistamine, and then hospitalized for 1 day. Injections with prepared treatment sets were administered every 30 min subcutaneously for 7 h; dogs were then discharged and continued on immunotherapy for 1 year. All dogs were evaluated monthly by their owners for 12 months, and by clinicians prior to therapy and after 3, 6, 9 and 12 months of therapy using a standardized scoring system to measure pruritus, lesions present and any concurrent medications given. Eleven dogs were treated with rush immunotherapy, and 11 dogs with conventional immunotherapy. Significant differences in mean pruritus, medication, lesion and total scores between groups were determined by use of a repeated‐measures ANOVA. Mean pruritus scores decreased from 13.5 to 6.7 (P = 0.0333) and from 13.9 to 10.3, medication scores from 23.6 to 10.6 (P = 0.0001) and from 14.1 to 13.6, lesion scores from 5.9 to 1.6 (P = 0.0001) and from 3.0 to 1.9, and total scores from 42 to 18.1 (P = 0.001) and from 30.6 to 21.5 in the rush immunotherapy group and in the conventional immunotherapy group, respectively. Using a Tukey–Kramer Multiple Comparison test, differences between the total scores at the beginning of the study and at the various time points reached significance after 3 months. An improvement of >50% in pruritus was noted in six of 11 dogs in the rush immunotherapy group and in five of 11 dogs in the conventional immunotherapy group; similar improvements in lesion scores and total scores were observed in dogs treated with rush immunotherapy (seven of 11 and five of 11 dogs, respectively) and in dogs treated with conventional immunotherapy (seven of 11 and four of 11 dogs, respectively). Based on these results, rush immunotherapy seems to be associated with a higher success rate than conventional immunotherapy, and improvement is typically seen within the first 6 months of therapy. Funding: Morris Animal Foundation.