bluuebunny/crossref_metadata_2025 huggingface dataset:
Alanine Scanning of Arp1 Delineates a Putative Binding Site for Jnm1/Dynamitin and Nip100/p150Glued
Authors: Clark Sean W. , Rose Mark D.
Published: June 2005

Arp1p is the only actin-related protein (ARP) known to form actin-like filaments. Unlike actin, Arp1p functions with microtubules, as part of the dynein regulator, dynactin. Arp1p's dissimilar functions imply interactions with a distinct set of proteins. To distinguish surface features relating to Arp1p's core functions and to identify the footprint of protein interactions essential for dynactin function, we performed the first complete charge-cluster-to-alanine scanning mutagenesis of an ARP and compared the results with a similar study of actin. The Arp1p mutations revealed three nonoverlapping surfaces with distinct genetic properties. One of these surfaces encompassed a region unique to Arp1p that is crucial for Jnm1p (dynamitin/p50) and Nip100p (p150Glued) association as well as pointed-end associations. Unlike the actin mutations, none of the ARP1 alleles disrupt filament formation; however, one pointed-end allele delayed the elution of Arp1p on gel filtration, consistent with loss of additional subunits.
Abl Tyrosine Kinase and Its Substrate Ena/VASP Have Functional Interactions with Kinesin-1
Authors: Martin MaryAnn , Ahern-Djamali Shawn M. , Hoffmann F. Michael , Saxton William M.
Published: June 2005

Relatively little is known about how microtubule motors are controlled or about how the functions of different cytoskeletal systems are integrated. A yeast two-hybrid screen for proteins that bind to Drosophila Enabled (Ena), an actin polymerization factor that is negatively regulated by Abl tyrosine kinase, identified kinesin heavy chain (Khc), a member of the kinesin-1 subfamily of microtubule motors. Coimmunoprecipitation from Drosophila cytosol confirmed a physical interaction between Khc and Ena. Kinesin-1 motors can carry organelles and other macromolecular cargoes from neuronal cell bodies toward terminals in fast-axonal-transport. Ena distribution in larval axons was not affected by mutations in the Khc gene, suggesting that Ena is not itself a fast transport cargo of Drosophila kinesin-1. Genetic interaction tests showed that in a background sensitized by reduced Khc gene dosage, a reduction in Abl gene dosage caused distal paralysis and axonal swellings. A concomitant reduction in ena dosage rescued those defects. These results suggest that Ena/VASP, when not inhibited by the Abl pathway, can bind Khc and reduce its transport activity in axons.
HIV-1-infected Blood Mononuclear Cells Form an Integrin- and Agrin-dependent Viral Synapse to Induce Efficient HIV-1 Transcytosis across Epithelial Cell Monolayer
Authors: Alfsen Annette , Yu Huifeng , Magérus-Chatinet Aude , Schmitt Alain , Bomsel Morgane
Published: June 2005

The heparan sulfate proteoglycan agrin and adhesion molecules are key players in the formation of neuronal and immune synapses that evolved for efficient communication at the sites of cell-cell contact. Transcytosis of infectious virus across epithelial cells upon contact between HIV-1-infected cells and the mucosal pole of the epithelial cells is one mechanism for HIV-1 entry at mucosal sites. In contrast, transcytosis of cell-free HIV-1 is not efficient. A synapse between HIV-1-infected cells and the mucosal epithelial surface that resembles neuronal and immune synapses is visualized by electron microscopy. We have termed this the “viral synapse.” Similarities of the viral synapse also extend to the functional level. HIV-1-infected cell-induced transcytosis depends on RGD-dependent integrins and efficient cell-free virus transcytosis is inducible upon RGD-dependent integrin cross-linking. Agrin appears differentially expressed at the apical epithelial surface and acts as an HIV-1 attachment receptor. Envelope glycoprotein subunit gp41 binds specifically to agrin, reinforcing the interaction of gp41 to its epithelial receptor galactosyl ceramide.
Role of the Regulatory Domain of Protein Kinase D2 in Phorbol Ester Binding, Catalytic Activity, and Nucleocytoplasmic Shuttling
Authors: Auer Alexandra , von Blume Julia , Sturany Sabine , von Wichert Götz , Van Lint Johan , Vandenheede Jackie , Adler Guido , Seufferlein Thomas
Published: June 2005

Protein kinase D2 (PKD2) belongs to the PKD family of serine/threonine kinases that is activated by phorbol esters and G protein-coupled receptors (GPCRs). Its C-terminal regulatory domain comprises two cysteine-rich domains (C1a/C1b) followed by a pleckstrin homology (PH) domain. Here, we examined the role of the regulatory domain in PKD2 phorbol ester binding, catalytic activity, and subcellular localization: The PH domain is a negative regulator of kinase activity. C1a/C1b, in particular C1b, is required for phorbol ester binding and gastrin-stimulated PKD2 activation, but it has no inhibitory effect on the catalytic activity. Gastrin triggers nuclear accumulation of PKD2 in living AGS-B cancer cells. C1a/C1b, not the PH domain, plays a complex role in the regulation of nucleocytoplasmic shuttling: We identified a nuclear localization sequence in the linker region between C1a and C1b and a nuclear export signal in the C1a domain. In conclusion, our results define the critical components of the PKD2 regulatory domain controlling phorbol ester binding, catalytic activity, and nucleocytoplasmic shuttling and reveal marked differences to the regulatory properties of this domain in PKD1. These findings could explain functional differences between PKD isoforms and point to a functional role of PKD2 in the nucleus upon activation by GPCRs.
Na/K-ATPase Tethers Phospholipase C and IP3 Receptor into a Calcium-regulatory Complex
Authors: Yuan Zhaokan , Cai Ting , Tian Jiang , Ivanov Alexander V. , Giovannucci David R. , Xie Zijian
Published: June 2005

We have shown that the caveolar Na/K-ATPase transmits ouabain signals via multiple signalplexes. To obtain the information on the composition of such complexes, we separated the Na/K-ATPase from the outer medulla of rat kidney into two different fractions by detergent treatment and density gradient centrifugation. Analysis of the light fraction indicated that both PLC-γ1 and IP3 receptors (isoforms 2 and 3, IP3R2 and IP3R3) were coenriched with the Na/K-ATPase, caveolin-1 and Src. GST pulldown assays revealed that the central loop of the Na/K-ATPase α1 subunit interacts with PLC-γ1, whereas the N-terminus binds IP3R2 and IP3R3, suggesting that the signaling Na/K-ATPase may tether PLC-γ1 and IP3 receptors together to form a Ca2+-regulatory complex. This notion is supported by the following findings. First, both PLC-γ1 and IP3R2 coimmunoprecipitated with the Na/K-ATPase and ouabain increased this interaction in a dose- and time-dependent manner in LLC-PK1 cells. Depletion of cholesterol abolished the effects of ouabain on this interaction. Second, ouabain induced phosphorylation of PLC-γ1 at Tyr783and activated PLC-γ1 in a Src-dependent manner, resulting in increased hydrolysis of PIP2. It also stimulated Src-dependent tyrosine phosphorylation of the IP3R2. Finally, ouabain induced Ca2+release from the intracellular stores via the activation of IP3 receptors in LLC-PK1 cells. This effect required the ouabain-induced activation of PLC-γ1. Inhibition of Src or depletion of cholesterol also abolished the effect of ouabain on intracellular Ca2+.
Abnormal maturation of the retinal vasculature in type XVIII collagen/endostatin deficient mice and changes in retinal glial cells due to lack of collagen types XV and XVIII
Authors: Hurskainen Merja , Eklund Lauri , Hägg Pasi O. , Fruttiger Marcus , Sormunen Raija , Ilves Mika , Pihlajaniemi Taina
Published: June 2005

Type XVIII collagen is important in the early phase of retinal vascular development and for the regression of the primary vasculature in the vitreous body after birth. We show here that the retina in Col18a1−/− mice becomes densely vascularized by anomalous anastomoses from the persistent hyaloid vasculature by day 10 after birth. In situ hybridizations revealed normal VEGF mRNA expression, but the phenotype of collagen XVIII deficient mice closely resembled that of mice expressing VEGF120 and VEGF188 isoforms only, suggesting that type XVIII collagen may be involved in VEGF function. Type XVIII collagen was found to be indispensable for angiogenesis in the eye, as also oxygen‐induced neovascularization was less intense than normal in the Col18a1−/− mice. We observed a marked increase in the amount of retinal astrocytes in the Col18a1−/− mice. Whereas the retinal vessels of wild‐type mice are covered by astrocytes and the regressing, thin hyaloid vessels are devoid of astrocytes, the retinal vessels in the Col18a1−/− mice were similarly covered by astrocytes but not the persistent hyaloid vessels in the vitreous body. Interestingly, double null mice lacking type XVIII collagen and its homologue type XV collagen had the persistent hyaloid vessels covered by astrocytes, including the parts located in the vitreous body. We thus hypothesize that type XV collagen is a regulator of glial cell recruitment around vessels and that type XVIII collagen regulates their proliferation.
Hyperasymptotics for nonlinear ODEs I. A Riccati equation
Authors: Olde Daalhuis A.B
Published: June 2005

We illustrate how one can obtain hyperasymptotic expansions for solutions of nonlinear ordinary differential equations. The example is a Riccati equation. The main tools that we need are transseries expansions and the Riemann sheet structure of the Borel transform of the divergent asymptotic expansions. Hyperasymptotic expansions determine the solutions uniquely. A numerical illustration is included.
Observations of nanoindents via cross-sectional transmission electron microscopy: a survey of deformation mechanisms
Authors: Lloyd S.J , Castellero A , Giuliani F , Long Y , McLaughlin K.K , Molina-Aldareguia J.M , Stelmashenko N.A , Vandeperre L.J , Clegg W.J
Published: June 2005

Examination of cross-sections of nanoindents with the transmission electron microscope has recently become feasible owing to the development of focused ion beam milling of site-specific electron transparent foils. Here, we discuss the development of this technique for the examination of nanoindents and survey the deformation behaviour in a range of single crystal materials with differing resistances to dislocation flow. The principal deformation modes we discuss, in addition to dislocation flow, are phase transformation (silicon and germanium), twinning (gallium arsenide and germanium at 400 °C), lattice rotations (spinel), shear (spinel), lattice rotations (copper) and lattice rotations and densification (TiN/NbN multilayers). The magnitude of the lattice rotation, about the normal to the foil, was measured at different positions under the indents. Indents in a partially recrystallized metallic glass Mg
66
Ni
20
Nd
14
were also examined. In this case a low-density porous region was formed at the indent tip and evidence of shear bands was also found. Further understanding of indentation deformation will be possible with three-dimensional characterization coupled with modelling which takes account of the variety of competing deformation mechanisms that can occur in addition to dislocation glide. Mapping the lattice rotations will be a particularly useful way to evaluate models of the deformation process.
Introducing the use of positive and negative inertial functions in asymptotic modelling
Authors: Ilanko Sinniah
Published: June 2005

The work presented here shows that the natural frequencies of constrained systems may be obtained from asymptotic models of corresponding systems where the constraints are replaced by artificial mass or moment of inertia of very large positive and negative values. This offers a convenient alternative to the current practice of using artificial elastic restraints of large stiffness, a concept introduced by Courant in 1943, to remove a limitation on the choice of admissible functions. Recent publications show that in order to control the error caused by approximating constraints with restraints of large stiffness, it is necessary to use both positive and negative stiffness values. However, the negative stiffness introduces instability near the lower modes of vibration and the magnitude of negative stiffness parameter used must be greater than the highest critical stiffness to ensure bounded results are obtained. The use of positive and negative artificial inertial parameters overcomes this problem as they do not introduce instability near the lower modes, allowing the natural frequencies of constrained systems to be delimited to any desired accuracy.
The power potential of tidal currents in channels
Authors: Garrett Chris , Cummins Patrick
Published: June 2005

Interest in sources of renewable energy has led to increasing attention being paid to the potential of strong tidal currents. There is a limit to the available power, however, as too many turbines will merely block the flow, reducing the power generated. The maximum average power available from a tidal stream along a channel, such as that between an island and the mainland, is estimated and found to be typically considerably less than the average kinetic energy flux in the undisturbed state through the most constricted cross-section of the channel. A general formula gives the maximum average power as between 20 and 24% of the peak tidal pressure head, from one end of the channel to the other, times the peak of the undisturbed mass flux through the channel. This maximum average power is independent of the location of the turbine ‘fences’ along the channel. The results may also be used to evaluate the power potential of steady ocean currents.
Home‐Based Asthma Self‐Management Education for Inner City Children
Authors: Butz Arlene M. , Syron Laura , Johnson Betty , Spaulding Joanne , Walker Melissa , Bollinger Mary Elizabeth
Published: June 2005

Abstract  Optimal home self‐management in young children with asthma includes accurate symptom identification followed by timely and appropriate treatment. The objective of this study was to evaluate a home‐based asthma educational intervention targeting symptom identification for parents of children with asthma. Two hundred twenty‐one children with asthma were enrolled into an ongoing home‐based clinical trial and randomized into either a standard asthma education (SAE) or a symptom/nebulizer education intervention (SNEI). Data included home visit records and parent's self‐report on questionnaires. Symptom identification and self‐management skills significantly improved from preintervention to postintervention for parents in both groups with the exception of checking medications for expiration dates and the frequency of cleaning nebulizer device and equipment. However, significantly more parents of children in the SNEI group reported treating cough symptoms as compared with the SAE group (p = 0.05). Of concern is that only 38% of all parents reported having an asthma action plan in the home. A targeted home‐based asthma education intervention can be effective for improving symptom identification and appropriate use of medications in children with asthma. Home asthma educational programs should address accurate symptom identification and a demonstration of asthma medication delivery devices.
The Role of “Envisioning the Future” in the Development of Resilience Among At‐Risk Youth
Authors: Aronowitz Teri
Published: June 2005

Abstract  The objective was to explore the process by which adolescents develop resilience and change their risk behaviors despite multiple stressors in their environment. The design was exploratory using grounded theory to understand the process from the teens’ perspectives. Semistructured interviews were conducted with 32 individuals—28 adolescents (age range 16–21 years) and 4 adults (age range 32 and 72)—on two occasions. The participants used the basic social process “envisioning the future” to become resilient and stop engaging in risk behaviors. Envisioning the future included two processes “feeling competent” and “elevating expectations” that were facilitated within the context of a relationship with a reliable, caring, and competent adult. Participants in this study became resilient despite environmental stressors by setting higher expectations for themselves and feeling self‐confident. The findings of this study provide information regarding the specific behaviors that promote positive outcomes in at‐risk youth and suggest ways in which public health nurses can facilitate these behaviors in both the youth and their mentors.
Health‐Promoting Behaviors and Psychosocial Well‐Being of University Students in Hong Kong
Authors: Lee Regina L. T. , Loke Alice J. T. Yuen
Published: June 2005

Abstract The objective of this study was to examine health‐promoting behaviors and psychosocial well‐being of university students in Hong Kong. A cross‐sectional study was conducted using convenience sample (n = 247) of students recruited at various locations on campus. The Chinese version of the Health Promotion Lifestyle Profile II (HPLP‐II; S. Walker, K. Sechrist, & N. Pender, 1995) was given to students as a questionnaire. Relatively few university students had a sense of “health responsibility” (6.5–27.1%), engaged in any form of physical activity (31.2%), or exercised regularly (13.8%). Less than half ate fruits (35.2%) and vegetables (48.9%) every day. Positive personal growth was reported by 50.6% of the students; 42.5% used stress‐management skills and 74.1% rated their interpersonal relationships as meaningful and fulfilling. Students' scores on the health responsibility, nutritional habits, spiritual growth, interpersonal relations, or stress‐management subscales of the HPLP‐II did not differ significantly by gender, but males scored better than females (p = 0.001) on the physical exercise subscale. This study provides information on gender differences and specific needs of students which can help university administrators, curriculum planners, and community health professionals design guidelines for structuring a healthier environment and developing health education programs that support healthy choices among university students.
Korean Male Smokers’ Perceptions of Tobacco Control Policies in the United States
Authors: Kim Sun Seog , Nam Kyoung A.
Published: June 2005

Abstract  The purpose of this secondary data analysis is to report Korean male smokers’ perceptions of tobacco control policies in the United States. Descriptive data from four focus groups held in New York City in 2003 are presented. Focus group interviews were used to collect data, and the two investigators independently analyzed all four recorded group sessions. Korean male immigrants living in New York City area were recruited, and 22 volunteered to participate. Exclusion criteria included immigration to the United States before age 12, no smoking history, and use of chemical substance other than tobacco. Korean men differed in perceptions of the policies based on smoking status and length of U.S. residency. Among current smokers, recent immigrants had difficulty understanding smoking restrictions, whereas longtime residents complained of price increases. Both groups suggested that policies target the tobacco industry and do not target smokers. In contrast, former smokers supported more regulation of public smoking and suggested use of more aggressive antismoking campaigns. Public policymakers should take into consideration cultural attitudes and beliefs about smoking behavior in the design and implementation of tobacco control policies that affect ethnic groups whose cultural and value orientations may differ from the mainstream.
Actions and Beliefs Related to Hepatitis B and Influenza Immunization Among Registered Nurses in Texas
Authors: McEwen Melanie , Farren Elizabeth
Published: June 2005

Abstract  Studies indicate that roughly half of health care workers are not immunized against hepatitis B and influenza. Findings from a survey of 1,000 registered nurses (RNs) conducted to analyze their beliefs and actions related to immunization recommendations are reported. Only 8% of the responding RNs chose not to receive vaccination against hepatitis B. The primary reasons that nurses declined hepatitis B vaccination were because they were not working in nursing or did not believe they were at risk of exposure. Similarly, 86% of the RNs reported they had ever received a flu shot, and 69% reported of being immunized during 2 of the previous 4 years. Rationale for receiving immunization included belief in its effectiveness, belief that they were at risk of exposure, and that it was provided free of charge. Reasons for declining included concerns about side effects, lack of concern about getting the illness, and doubts about effectiveness. The nurses who responded to the survey appear to value immunizations and generally adhere to immunization recommendations. Further study needs to be conducted on related issues, including follow‐up for assessment of long‐term protection of hepatitis B immunization and adherence to guidelines for postexposure prophylaxis. Ongoing monitoring and further study of serious complications of hepatitis B immunizations are also needed.
Self‐Reported Napping and Nocturnal Sleep in Taiwanese Elderly Insomniacs
Authors: Lai Hui‐Ling
Published: June 2005

Abstract  The aim of this study was to investigate the relationships between self‐reported nocturnal sleep quality and napping patterns in elderly persons with insomnia and to compare the nocturnal sleep quality between napping and non‐napping groups. Convenience sampling was used to recruit 60 community‐dwelling elderly residents of Taichung City, Taiwan (age range 60–83 years, mean 67.1 years) who reported insomnia. All participants scored greater than 5 on the Pittsburgh Sleep Quality Index (PSQI) questionnaire. Napping prevalence, frequency, and duration were assessed by participant interview. Self‐reported sleep quality, sleep latency, sleep duration, sleep efficiency, sleep disturbance, use of sleep medication, and daytime dysfunction were measured with the PSQI. Sixty‐four percentage of participants (n = 38) reported napping. There were no age, gender, and ethnicity differences on napping patterns. Global sleep quality, sleep efficiency, and sleep disturbance were significantly associated with prevalence of napping (r = 0.24–0.26, p < 0.05). A significant correlation was also found between global sleep quality and nap duration (r = 0.31, p < 0.05). Elders in the napping group reported better global sleep quality (t = 2.2, p < 0.05) and sleep efficiency (t = 2.1, p < 0.05) than those in the non‐napping group. The findings suggest that there is no need for health care providers to restrict elderly insomniacs’ daytime napping.
Emergency Preparedness and Bioterrorism Response: Development of an Educational Program for Public Health Personnel
Authors: Baldwin Karen , LaMantia Joanne , Proziack Linda
Published: June 2005

Abstract  Public health departments are under increasing pressure to provide emergency preparedness and bioterrorism response education to public health personnel. The challenge that health departments face is to provide cost‐efficient, timely education to a large number of multidisciplinary personnel. This article describes an innovative strategy for providing this education to public health personnel using the health department's intranet system. The intranet system provided confidential information specific to the staff role and allowed for concurrent access to the program by multiple individuals at different service sites. Knowledge acquisition was tested through short multiple‐choice questions that followed the specific information modules. The intranet system faced a number of challenges during the pilot‐testing phase, primarily related to changes in the role of the public health nurse and limitations in funding and public health staff to maintain and monitor the bioterrorism response program and the intranet system. The design of the program may prove useful for other public health organizations when a need exists for quick delivery of information to a large number of personnel. It may especially be useful in providing basic emergency preparedness and bioterrorism education to new personnel in health departments.
Sustained Nurse Home Visiting in Early Childhood: Exploring Australian Nursing Competencies
Authors: Kemp Lynn , Anderson Teresa , Travaglia Joanne , Harris Elizabeth
Published: June 2005

Abstract  There is strong evidence that a comprehensive model of sustained nurse home visiting (SNHV) in early childhood can improve child and family outcomes for vulnerable and at‐risk families. There is also evidence that nurse home visitors experience challenges in delivering SNHV. This article aims to identify the nursing competencies needed for delivering a comprehensive model of SNHV and highlight the areas where further competency development is required. Qualitative analysis compared the content and language of published registered generalist and child and family nursing competency statements for Australian nurses with the work experiences of a team of community‐based nurses delivering SNHV. Development of competencies is needed in the areas of (a) enhanced knowledge of child development, social determinants of health, and broader outcomes for individuals and populations; (b) advanced skills in fine observation, anticipatory guidance, negotiating, modelling and experimentation, holistic case management, and working in interdisciplinary teams; and (c) attitudinal competency for working “with” and supporting risk taking. The current published competencies for general and child and family nurses do not encompass the different and advanced competencies required for performing SNHV. Competency development and associated nurse training and support are needed for delivery of quality SHNV services.
Student Nurses Participate in Public Health Research and Practice Through a School‐Based Screening Program
Authors: Brosnan Christine A. , Upchurch Sandra L. , Meininger Janet C. , Hester Lynne E. , Johnson Gwen , Eissa Mona A.
Published: June 2005

Abstract  Obesity has reached epidemic proportions among children in minority populations, placing them at risk for diabetes and hypertension. The importance of educating a generation of nurses who have the knowledge, skills, and passion to address this public health need is crucial to the profession and to America's health. This article describes the use of a Community Partnership Model to frame baccalaureate nursing students' (B.S.N.) service learning within the context of a research study to screen middle‐ and high‐school students for health risks. The missions of education, research, and practice are linked together in the model by three processes: evidence‐based practice, service learning, and scholarly teaching. The aim of the project was early identification of obesity, hypertension, and type 2 diabetes and their predictors in a high‐risk student population, between 12 and 19 years of age. Early evidence indicates that the model is feasible and effective for directing student learning and addressing public health problems in the community.
Acoustic and petrophysical relationships in low‐shale sandstone reservoir rocks
Authors: Khazanehdari Jalal , McCann Clive
Published: June 2005

This paper describes the measurements of the acoustic and petrophysical properties of two suites of low‐shale sandstone samples from North Sea hydrocarbon reservoirs, under simulated reservoir conditions. The acoustic velocities and quality factors of the samples, saturated with different pore fluids (brine, dead oil and kerosene), were measured at a frequency of about 0.8 MHz and over a range of pressures from 5 MPa to 40 MPa.

The compressional‐wave velocity is strongly correlated with the shear‐wave velocity in this suite of rocks. The ratio VP/VS varies significantly with change of both pore‐fluid type and differential pressure, confirming the usefulness of this parameter for seismic monitoring of producing reservoirs.

The results of quality factor measurements were compared with predictions from Biot‐flow and squirt‐flow loss mechanisms. The results suggested that the dominating loss in these samples is due to squirt‐flow of fluid between the pores of various geometries. The contribution of the Biot‐flow loss mechanism to the total loss is negligible. The compressional‐wave quality factor was shown to be inversely correlated with rock permeability, suggesting the possibility of using attenuation as a permeability indicator tool in low‐shale, high‐porosity sandstone reservoirs.
The estimation of shear‐wave statics using in situ measurements in marine near‐surface sediments
Authors: Winsborrow Gavin , Huws Dei G. , Muyzert Everhard
Published: June 2005

Shear‐wave statics in marine seismic exploration data are routinely too large to be estimated using conventional techniques. Near‐surface unconsolidated sediments are often characterized by low values of Vs and steep velocity gradients. Minor variations in sediment properties at these depths correspond to variations in the shear‐wave velocity and will produce significant static shifts. It is suggested that a significant proportion of the shear‐wave statics solution can be estimated by performing a separate high‐resolution survey to target near‐surface unconsolidated sediments. Love‐wave, shear‐wave refraction and geotechnical measurements were individually used to form high‐resolution near‐surface shear‐wave velocity models to estimate the shear‐wave statics for a designated survey line. Comparisons with predicted statics revealed that shear‐wave statics could not be estimated using a velocity model predicted by substituting geotechnical measurements into empirical relationships. Empirical relationships represent a vast simplification of the factors that control Vs and are therefore not sufficiently sensitive to estimate shear‐wave statics. Refraction measurements are potentially sensitive to short‐wavelength variations in sediment properties when combined with accurate navigational data. Statics estimated from Love‐wave data are less sensitive, and sometimes smoothed in appearance, since interpreted velocity values represent an average both laterally and vertically over the receiver array and the frequency–depth sensitivity range, respectively.

For the survey site, statics estimated from near‐surface irregularities using shear‐wave refraction measurements represent almost half the total statics solution. More often, this proportion will be greater when bedrock relief is less.
Simple relative space–time scaling of electrical and electromagnetic depth sounding arrays: implications for electrical static shift removal and joint DC‐TEM data inversion with the most‐squares criterion
Authors: Meju Max A.
Published: June 2005

A simple scaling relationship is shown to facilitate comparison, correlation and integration of data recorded using the common experimental configurations in electrical and electromagnetic depth sounding. Applications of the scheme to field data from typical geological and landfill environments show that it is robust and, where transient electromagnetic (TEM) data are available, enables easy identification and quantification of electrical static shift (galvanic distortion) in magnetotelluric and direct current (DC) sounding curves. TEM‐based procedures are suggested for both the direct removal of static shift in DC sounding curves and effective joint data inversion with the most‐squares criterion in the presence of static shift. A case study of aquifer characterization using sounding data from borehole sites in the Vale of York in England shows that static shift is a common problem in this glacial‐covered terrain and demonstrates the effectiveness of the proposed joint DC‐TEM inversion strategy in handling distorted soundings.
3D modelling and sensitivity in DC resistivity using charge density
Authors: Boulanger Olivier , Chouteau Michel
Published: June 2005

A three‐dimensional (3D) electrical resistivity modelling code is developed to interpret surface and subsurface data. Based on the integral equation, it calculates the charge density caused by conductivity gradients at each interface of the mesh, allowing the estimation of the potential everywhere without the need to interpolate between nodes. Modelling generates a huge matrix, made up of Green's functions, which is stored by using the method of pyramidal compression. The potential is compared with the analytical and the numerical solutions obtained by finite‐difference codes for two models: the two‐layer case and the vertical contact case. The integral method is more accurate around the source point and at the limits of the domain for the potential calculation using a pole‐pole array. A technique is proposed to calculate the sensitivity (Jacobian) and Hessian matrices in 3D. The sensitivity is based on the derivative with respect to the block conductivity of the potential computed using the integral equation; it is only necessary to compute the electrical field at the source location. A direct extension of this technique allows the determination of the second derivatives. The technique is compared with the analytical solutions and with the calculation of the sensitivity according to the method using the inner product of the current densities calculated at the source and receiver points. Results are very accurate when the Green's function that includes the source image is used. The calculation of the three components of the electric field on the interfaces of the mesh is carried out simultaneously and quickly, using matrix compression.
Ultrasonic velocities of North Sea chalk samples: influence of porosity, fluid content and texture
Authors: Røgen Birte , Fabricius Ida L. , Japsen Peter , Høier Christian , Mavko Gary , Pedersen Jacob M.
Published: June 2005

We have studied 56 unfractured chalk samples of the Upper Cretaceous Tor Formation of the Dan, South Arne and Gorm Fields, Danish North Sea. The samples have porosities of between 14% and 45% and calcite content of over 95%. The ultrasonic compressional‐ and shear‐wave velocities (VP and VS) for dry and water‐saturated samples were measured at up to 75 bar confining hydrostatic pressure corresponding to effective stress in the reservoir. The porosity is the main control of the ultrasonic velocities and therefore of the elastic moduli. The elastic moduli are slightly higher for samples from the South Arne Field than from the Dan Field for identical porosities. This difference may be due to textural differences between the chalk at the two locations because we observe that large grains (i.e. filled microfossils and fossil fragments) that occur more frequently in samples from the Dan Field have a porosity‐reducing effect and that samples rich in large grains have a relatively low porosity for a given P‐wave modulus. The clay content in the samples is low and is mainly represented by either kaolinite or smectite; samples with smectite have a lower P‐wave modulus than samples with kaolinite at equal porosity. We find that ultrasonic VP and VS of dry chalk samples can be satisfactorily estimated with Gassmann's relationships from data for water‐saturated samples. A pronounced difference between the VP/VS ratios for dry and water‐saturated chalk samples indicates promising results for seismic amplitude‐versus‐offset analyses.
Piecewise 1D laterally constrained inversion of resistivity data
Authors: Auken Esben , Christiansen Anders V. , Jacobsen Bo H. , Foged Nikolaj , Sørensen Kurt I.
Published: June 2005

In a sedimentary environment, layered models are often capable of representing the actual geology more accurately than smooth minimum structure models. Furthermore, interval thicknesses and resistivities are often the parameters to which non‐geophysicist experts can relate and base decisions on when using them in waste site remediation, groundwater modelling and physical planning.

We present a laterally constrained inversion scheme for continuous resistivity data based on a layered earth model (1D). All 1D data sets and models are inverted as one system, producing layered sections with lateral smooth transitions. The models are regularized through laterally equal constraints that tie interface depths and resistivities of adjacent layers. Prior information, e.g. originating from electric logs, migrates through the lateral constraints to the adjacent models, making resolution of equivalences possible to some extent. Information from areas with well‐resolved parameters will migrate through the constraints in a similar way to help resolve the poorly constrained parameters. The estimated model is complemented by a full sensitivity analysis of the model parameters, supporting quantitative evaluation of the inversion result.

Examples from synthetic 2D models show that the model recognition of a sublayered 2D wedge model is improved using the laterally constrained inversion approach when compared with a section of combined 1D models and when compared with a 2D minimum structure inversion. Case histories with data from two different continuous DC systems support the conclusions drawn from the synthetic example.
Parsimonious 3D post‐stack Kirchhoff depth migration
Authors: Hua Biaolong , McMechan George A.
Published: June 2005

Parsimonious post‐stack migration is extended to three dimensions. By tracing single rays back along each incident wave direction (as determined by a local slant stack at the receivers), the ray tracing can be embedded in the migration. This approach significantly reduces the computer time and disk space needed because it is not necessary to build and save image time maps; 3D migration can be performed on a workstation or personal computer rather than using a supercomputer or cluster.

The location of a reflector in the output image is defined by tracing a zero‐offset ray to the one‐way traveltime (the image condition); the orientation of the reflector is defined as a surface perpendicular to the raypath. The migration impulse response operator is confined to the first Fresnel zone around the estimated reflection point, which is much smaller than the large isochronic surface in traditional Kirchhoff depth migration. Additional efficiency is obtained by applying an amplitude threshold to reduce the amount of data to be migrated. Tests on synthetic data show that the proposed implementation of parsimonious 3D post‐stack Kirchhoff depth migration is at least two orders of magnitude faster than traditional Kirchhoff migration, at the expense of slightly degraded migration image coherence. The proposed migration is expected to be a useful complement to conventional time migrations for fast initial imaging of subsurface structures and for real‐time imaging of near‐offset sections during data acquisition for quality control.
2.5D finite‐difference solution of the acoustic wave equation
Authors: Novais Amélia , Santos Lúcio T.
Published: June 2005

The finite‐difference method applied to the full 3D wave equation is a rather time‐consuming process. However, in the 2.5D case, we can take advantage of the medium symmetry. By taking the Fourier transform with respect to the out‐of‐plane direction (the symmetry axis), the 3D problem can be reduced to a repeated 2D problem. The third dimension is taken into account by a sum over the corresponding wave‐vector component. A criterion for where to end this theoretically infinite sum derives from the stability conditions of the finite‐difference schemes employed. In this way, the computation time of the finite‐difference calculations can be considerably reduced. The quality of the modelling results obtained with this 2.5D finite‐difference scheme is comparable to that obtained using a standard 3D finite‐difference scheme.
Semi‐automatic detection of faults in 3D seismic data
Authors: Tingdahl Kristofer M. , De Rooij Matthijs
Published: June 2005

The semi‐automated detection of objects has been quite successful in detecting various types of seismic object, such as chimneys. The same technique can be applied successfully to detect faults in 3D seismic data. We show that several different attributes – among others, similarity, frequency and curvature, all of which potentially enhance the visibility of faults – can be combined successfully by an artificial neural network. This results in a fault ‘probability’ cube in which faults are more continuous and noise is suppressed compared with single‐attribute cubes. It is believed that the fault‐cube can be improved further by applying image‐processing techniques to enhance the fault prediction.
Analytic expressions for the velocity sensitivity to the elastic moduli for the most general anisotropic media
Authors: Zhou B. , Greenhalgh S.A.
Published: June 2005

For non‐linear kinematic inversion of elastic anisotropy parameters and related investigations of the sensitivity of seismic data, the derivatives of the wavespeed (phase velocity and group velocity) with respect to the individual elastic moduli are required. This paper presents two analytic methods, called the eigenvalue and eigenvector methods, to compute the derivatives of the wavespeeds for wave propagation in a general anisotropic medium, which may be defined by up to 21 density‐normalized elastic moduli. The first method employs a simple and compact form of the eigenvalue (phase velocity) and a general form of the group velocity, and directly yields general expressions of the derivatives for the three wave modes (qP, qS1, qS2). The second method applies simple eigenvector solutions of the three wave modes and leads to other general forms of the derivatives. These analytic formulae show that the derivatives are, in general, functions of the 21 elastic moduli as well as the wave propagation direction, and they reflect the sensitivity of the wavespeeds to the individual elastic moduli. Meanwhile, we give results of numerical investigations with some examples for particular simplified forms of anisotropy. They show that the eigenvalue method is suitable for the qP‐, qS1‐ and qS2‐wave computations and mitigates the singularity problem for the two quasi‐shear waves. The eigenvector method is preferable to the eigenvalue method for the group velocity and the derivative of the phase velocity because it involves simpler expressions and independent computations, but for the derivative of the group velocity the derivative of the eigenvector is required. Both methods tackle the singularity problem and are applicable to any degree of seismic anisotropy for all three wave modes.
Radiation from flexural vibrations of the baseplate and their effect on the accuracy of traveltime measurements
Authors: Lebedev A. , Beresnev I.
Published: June 2005

We analyse the problem of radiation of seismic waves by a vibroseis source when the baseplate is subject to flexure. A theoretical model is proposed to account for baseplate flexure, generalizing the well‐known model of the vibroseis source of Sallas and Weber, which was developed for a rigid plate. Using the model proposed, we analyse the effect of flexure on the properties of seismic waves. We show that the flexure does not contribute to the far‐field and mainly affects the readings of the reference accelerometer that is used to measure the force applied to the ground; these readings generally become dependent on the location of the sensor on the plate. For muddy and sandy soils, the effect of flexure on baseplate‐acceleration measurements is nonetheless pronounced at the high end of the vibroseis frequency band only (∼100 Hz), and is negligible at all frequencies for stiffer soils. The corresponding phase lags introduced by the flexural vibrations at high frequencies lead to errors in the traveltime measurements (through the cross‐correlation function) of up to 0.6 ms for muddy soils and less for denser soils. We show the existence of an optimal position of the reference sensor on the baseplate and also propose a general method of eliminating the phase lag due to the baseplate flexure in acceleration measurements.
Structure and genetic diversity inColliguaja odoriferaMol. (Euphorbiaceae), a shrub subjected to Pleisto‐Holocenic natural perturbations in a mediterranean South American region
Authors: Bull‐Hereñu Kester , Martínez Enrique A. , Squeo Francisco A.
Published: June 2005

Aim Colliguaja odoriferaMol., a Euphorbiaceous shrub of central Chile, inhabits the matorral formation, growing at low altitudes on both Andean and coastal mountain range slopes. In the recent geological past, this region was subjected to climatic changes and geological disturbances that most probably caused population shrinkages on the Andean mountain slopes. This study tested the hypothesis that under such a scenario, existing populations should show lower genetic diversity in the Andean than in the coastal areas; these coastal populations being the potential source populations for recolonization.

Location The study was carried out in central Chile by comparing the genetic diversity between the Andean and coastal areas, each represented by five localities distributed from 32°30′ S to 34° S.

Methods Genetic diversity was estimated by DNA analysis using 18 dominant multilocus Random Amplified Polymorphic DNA (RAPD) loci, characterizing 73 genetic phenotypes.

Results The comparison of the two matorral areas showed that Andean populations ofC. odoriferahave a subset of the genetic diversity found in the coastal populations. Andean populations also show a consistently lower genetic diversity, lower genetic distances and higher genetic structure, coincident with expectations based on the Pleisto‐Holocenic perturbation regime.

Main conclusions This first genetic analysis for South American mediterranean populations confirms the findings of previous floristic and palynological studies that identified refuge zones in the coastal mountain range of central Chile, a situation analogous with that occurring during periods of inter‐glacial northward migration in Southern Europe.
Development of individual recognition of female southern elephant seals, Mirounga leonina, from Punta Norte Península Valdés, applying principal components analysis
Authors: Caiafa Cesar F. , Proto Araceli N. , Vergani Daniel , Stanganelli Zulma
Published: June 2005

Aim  The development of software able to provide individual recognition of southern elephant seals, as a tool to study colonies. This analysis was performed within a framework of studies concerning environmental dispersion produced by the El Niño Southern Oscillation effect in the Southern Ocean Ecosystem.

Location  Digital photographs of reproductive female elephant seals were taken at Punta Norte (Península Valdés, Patagonia; 42°05′ S, 63°45′ W) during the 2002 breeding season (August to November). The data set under analysis is composed of 96 elephant seal images for a population of 56 individuals.

Method  Identification of specimens was carried out using digital pictures taken with a digital video camera, and processed through the ‘Eigenfaces’ method, which is based on principal components analysis. Special care was taken to control possible variations among images of the same individual, like distance, angle, light intensity, etc. To deal with these variations, an initial alignment procedure is proposed to have all images framed; in addition an initial histogram equalization was used which attenuates any potential variation in light intensity. The software was developed in IDL5.5 language.

Results  A complete set of empirical results is displayed showing the potential effectiveness of this technique. Individual recognition and pertinence to different population subsets (harems) tests have been carried out. A principal result of this work is that all 96 elephant seal images (representing 56 individuals) were correctly identified.

Conclusion  The Eigenfaces method can be used successfully for identification of elephant seals. With the appropriate preparatory treatment of images, high performance results can be expected.