bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of deposition and synthesis parameters on size, density, structure, and field emission properties of Pd-catalyzed carbon nanotubes synthesized by thermal chemical vapor deposition
Authors: Wei S. , Kang W. P. , Hofmeister W. H. , Davidson J. L. , Wong Y. M. , Huang J. H.
Published: April 2005

The effects of deposition parameters and NH3 pretreatment on the size and distribution of Pd catalytic particles and subsequently their effects on the characteristics of the synthesized carbon nanotubes (CNTs) were systematically investigated. It was found that the size of Pd particles decreases and the particle density (total number of Pd particles per unit area) increases as the Pd film thickness decreases. Moreover, pretreatment of Pd film in NH3 gas promotes smaller Pd particles and higher particle density which is beneficial for CNT growth. The CNTs were synthesized by thermal chemical vapor deposition at 750 °C using methane (CH4) as the carbon source, and a mixture of Ar/H2 (80 vol %: 20 vol %) as a carrier gas with NH3 serving as a processing reagent. The incorporation of NH3 in CNT synthesis, per the specific pretreatment of catalytic film, has a distinct effect on the size and morphology of CNTs produced. The interrelation between processing, structure and emission behavior of CNTs produced with different synthesis conditions was examined by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and field emission measurements.
Ferromagnetic properties of (Ga,Mn)N nanowires grown by a chemical vapor deposition method
Authors: Baik Jeong Min , Lee Jong-Lam
Published: April 2005

Ferromagnetic (Ga,Mn)N nanowires were grown on sapphire substrates at 900 °C by a chemical vapor deposition. Synchrotron radiation photoemission spectroscopy revealed that no secondary phases were found in the grown nanowire, meaning the dissolution of Mn atoms to form a solid solution in GaN nanowire. Fermi level was apart by 3.0 eV in the GaN nanowire (n-type), and it shifted toward the valance band maximum with ammonia flow rate. The Ga–to–N ratio decreased with the increase of ammonia flow rate, leading to the increase of Ga vacancies. From this, it is suggested that both increases in magnetic moment and Curie temperature with ammonia flow rate originated from the solid solution of Mn and Ga vacancies.
Universe Interactive: Static Displays with Active Components
Authors: Larson Michelle B.
Published: April 2005

As the World Year of Physics (WYP) approaches, the AAPT WYP Committee would like to encourage everyone to consider ways to engage those around us in celebrating the science that makes us the proud geeks we are. The geek sentiment is my own, and does not necessarily reflect the views and opinions of the committee. This paper offers simple and inexpensive astronomy-related ideas for a bulletin-board-type display. The particular ideas presented below are hands-on classroom activities that I've adapted for display purposes. The display is static in that once constructed it does not require a personal facilitator, but each component invites interaction. At the end of the paper I revisit the idea of building a sundial1 as a highly visible and artistic way to engage students and communities in physics. The activities presented here are available for use when constructing your own display. In addition, these examples are meant to illustrate how instructional products might be modified for display purposes, and I encourage others to consider their favorite activities for an interactive display.
Newton's Zeroth Law: Learning from Listening to Our Students
Authors: Scherr Rachel E. , Redish Edward F.
Published: April 2005

Modern instructional advice encourages us to not just tell our students what we want them to know, but to listen to them carefully. This helps us to find out “where they are” in order to better understand what tasks to offer them that might help them learn the physics most effectively. Sometimes, listening to students and trying to understand their intuitions not only helps them, it helps us—giving us new insights into the physics we are teaching. We had such an experience in the fall of 2003 in our algebra-based physics class at the University of Maryland.
Maximizing the Range of a Projectile Launched by a Simple Pendulum
Authors: Bittel D.
Published: April 2005

Maximizing the range of a projectile is a common problem. For a projectile launched at angle θ, with fixed speed v from ground level, the range equation is R(θ)=v2gsin 2θ. The angle that maximizes this range, θm, is 45°. Calculations for the more realistic, and complicated, case of a projectile launched from a height h have appeared in a number of places.1–4 The range equation is R(θ) = v22g[ sin 2θ + (sin2 2θ + (8ghv2)cos2θ)12]. The angle that maximizes this range is θm =12cos−1(ghv2+ gh).
Inductively Modeling Parallel, Normal, and Frictional Forces
Authors: Wyrembeck Edward P.
Published: April 2005

This year, instead of resolving the weight mg of an object resting on an incline into force components parallel and perpendicular to the surface of the incline, I asked my students to actually measure these forces at various angles of inclination and graph the data. I wanted my students to inductively discover mg sin θ and mg cos θ, and to use these graphs to confront the passive nature of the static frictional force.1 I believe the graphs themselves are very powerful conceptual tools that are often never discovered and used by students who only learn to use equations at specific angles to solve specific quantitative problems.
Using the Alsos Digital Library for Nuclear Issues
Authors: Settle Frank A. , Blackmer Elizabeth R. , Whaley Thomas P.
Published: April 2005

A valuable resource for physics, the Alsos Digital Library for Nuclear Issues1 (see Fig. 1) is well worth an exploratory visit by teachers of introductory physics and their students. It provides a searchable collection of vetted annotations of references including books, articles, films, websites, and CD-ROMs. While many of those resources focus on the history of nuclear physics and its applications to weapons and nuclear power production, the library also contains materials on the military, social, geopolitical, and cultural consequences of those applications.
Evidence for Autotrophic CO2Fixation via the Reductive Tricarboxylic Acid Cycle by Members of the ε Subdivision of Proteobacteria
Authors: Hügler Michael , Wirsen Carl O. , Fuchs Georg , Taylor Craig D. , Sievert Stefan M.
Published: April 2005

Based on 16S rRNA gene surveys, bacteria of the ε subdivision of proteobacteria have been identified to be important members of microbial communities in a variety of environments, and quite a few have been demonstrated to grow autotrophically. However, no information exists on what pathway of autotrophic carbon fixation these bacteria might use. In this study,Thiomicrospira denitrificansandCandidatusArcobacter sulfidicus, two chemolithoautotrophic sulfur oxidizers of the ε subdivision of proteobacteria, were examined for activities of the key enzymes of the known autotrophic CO2fixation pathways. Both organisms contained activities of the key enzymes of the reductive tricarboxylic acid cycle, ATP citrate lyase, 2-oxoglutarate:ferredoxin oxidoreductase, and pyruvate:ferredoxin oxidoreductase. Furthermore, no activities of key enzymes of other CO2fixation pathways, such as the Calvin cycle, the reductive acetyl coenzyme A pathway, and the 3-hydroxypropionate cycle, could be detected. In addition to the key enzymes, the activities of the other enzymes involved in the reductive tricarboxylic acid cycle could be measured. Sections of the genes encoding the α- and β-subunits of ATP citrate lyase could be amplified from both organisms. These findings represent the first direct evidence for the operation of the reductive tricarboxylic acid cycle for autotrophic CO2fixation in ε-proteobacteria. Since ε-proteobacteria closely related to these two organisms are important in many habitats, such as hydrothermal vents, oxic-sulfidic interfaces, or oilfields, these results suggest that autotrophic CO2fixation via the reductive tricarboxylic acid cycle might be more important than previously considered.
Two Distinct Functions of ComW in Stabilization and Activation of the Alternative Sigma Factor ComX inStreptococcus pneumoniae
Authors: Sung Chang Kyoo , Morrison Donald A.
Published: April 2005

Natural genetic transformation inStreptococcus pneumoniaeis controlled by a quorum-sensing system, which acts through the competence-stimulating peptide (CSP) for transient activation of genes required for competence. More than 100 genes have been identified as CSP regulated by use of DNA microarray analysis. One of the CSP-induced genes required for genetic competence iscomW. As the expression of this gene depended on the regulator ComE, but not on the competence sigma factor ComX (σX), and as expression of several genes required for DNA processing was affected in acomWmutant,comWappears to be a new regulatory gene. Immunoblotting analysis showed that the amount of the σXprotein is dependent on ComW, suggesting that ComW may be directly or indirectly involved in the accumulation of σX. As σXis stabilized inclpPmutants, acomWmutation was introduced into theclpPbackground to ask whether the synthesis of σXdepends on ComW. TheclpP comWdouble mutant accumulated an amount of σXhigher (threefold) than that seen in the wild type but was not transformable, suggesting that whilecomWis not needed for σXsynthesis, it acts both in stabilization of σXand in its activation. Modification of ComW with a histidine tag at its C or N terminus revealed that both amino and carboxyl termini are important for increasing the stability of σX, but only the N terminus is important for stimulating its activity.
Synthesis of Autoinducer 2 by the Lyme Disease Spirochete,Borrelia burgdorferi
Authors: Babb Kelly , von Lackum Kate , Wattier Rachel L. , Riley Sean P. , Stevenson Brian
Published: April 2005

Defining the metabolic capabilities and regulatory mechanisms controlling gene expression is a valuable step in understanding the pathogenic properties of infectious agents such asBorrelia burgdorferi. The present studies demonstrated thatB. burgdorferiencodes functional Pfs and LuxS enzymes for the breakdown of toxic products of methylation reactions. Consistent with those observations,B. burgdorferiwas shown to synthesize the end product 4,5-dihydroxy-2,3-pentanedione (DPD) during laboratory cultivation. DPD undergoes spontaneous rearrangements to produce a class of pheromones collectively named autoinducer 2 (AI-2). Addition of in vitro-synthesized DPD to culturedB. burgdorferiresulted in differential expression of a distinct subset of proteins, including the outer surface lipoprotein VlsE. Although many bacteria can utilize the other LuxS product, homocysteine, for regeneration of methionine,B. burgdorferiwas found to lack such ability. It is hypothesized thatB. burgdorferiproduces LuxS for the express purpose of synthesizing DPD and utilizes a form of that molecule as an AI-2 pheromone to control gene expression.
Impact of Global Transcriptional Regulation by ArcA, ArcB, Cra, Crp, Cya, Fnr, and Mlc on Glucose Catabolism in
Escherichia coli
Authors: Perrenoud Annik , Sauer Uwe
Published: April 2005

Even though transcriptional regulation plays a key role in establishing the metabolic network, the extent to which it actually controls the in vivo distribution of metabolic fluxes through different pathways is essentially unknown. Based on metabolism-wide quantification of intracellular fluxes, we systematically elucidated the relevance of global transcriptional regulation by ArcA, ArcB, Cra, Crp, Cya, Fnr, and Mlc for aerobic glucose catabolism in batch cultures of
Escherichia coli
. Knockouts of ArcB, Cra, Fnr, and Mlc were phenotypically silent, while deletion of the catabolite repression regulators Crp and Cya resulted in a pronounced slow-growth phenotype but had only a nonspecific effect on the actual flux distribution. Knockout of ArcA-dependent redox regulation, however, increased the aerobic tricarboxylic acid (TCA) cycle activity by over 60%. Like aerobic conditions, anaerobic derepression of TCA cycle enzymes in an ArcA mutant significantly increased the in vivo TCA flux when nitrate was present as an electron acceptor. The in vivo and in vitro data demonstrate that ArcA-dependent transcriptional regulation directly or indirectly controls TCA cycle flux in both aerobic and anaerobic glucose batch cultures of
E. coli
. This control goes well beyond the previously known ArcA-dependent regulation of the TCA cycle during microaerobiosis.
Autoinduction in
Erwinia amylovora
: Evidence of an Acyl-Homoserine Lactone Signal in the Fire Blight Pathogen
Authors: Molina Lázaro , Rezzonico Fabio , Défago Geneviève , Duffy Brion
Published: April 2005

Erwinia amylovora
causes fire blight disease of apple, pear, and other members of the Rosaceae. Here we present the first evidence for autoinduction in
E. amylovora
and a role for an
N
-acyl-homoserine lactone (AHL)-type signal. Two major plant virulence traits, production of extracellular polysaccharides (amylovoran and levan) and tolerance to free oxygen radicals, were controlled in a bacterial-cell-density-dependent manner. Two standard autoinducer biosensors,
Agrobacterium tumefaciens
NTL4 and
Vibrio harveyi
BB886, detected AHL in stationary-phase cultures of
E. amylovora
. A putative AHL synthase gene,
eamI
, was partially sequenced, which revealed homology with autoinducer genes from other bacterial pathogens (e.g.,
carI
,
esaI
,
expI
,
hsII
,
yenI
, and
luxI
).
E. amylovora
was also found to carry
eamR
, a convergently transcribed gene with homology to
luxR
AHL activator genes in pathogens such as
Erwinia carotovora
. Heterologous expression of the
Bacillus
sp. strain A24 acyl-homoserine lactonase gene
aiiA
in
E. amylovora
abolished induction of AHL biosensors, impaired extracellular polysaccharide production and tolerance to hydrogen peroxide, and reduced virulence on apple leaves.
Dynamics of FtsZ Assembly during Sporulation in
Streptomyces coelicolor
A3(2)
Authors: Grantcharova Nina , Lustig Ulrika , Flärdh Klas
Published: April 2005

FtsZ, the bacterial tubulin homologue, is the main player in at least two distinct processes of cell division during the development of
Streptomyces coelicolor
A3(2). It forms cytokinetic rings and is required for the formation of both the widely spaced hyphal cross walls in the substrate mycelium and the specialized septation that converts sporogenic aerial hyphae into spores. The latter developmentally controlled septation involves the coordinated assembly of large numbers of FtsZ rings in each sporulating hyphal cell. We used an FtsZ-enhanced green fluorescent protein (EGFP) translational fusion to visualize the progression of FtsZ ring assembly in vivo during sporulation of aerial hyphae. This revealed that the regular placement of multiple FtsZ rings and initiation of cytokinesis was preceded by a protracted phase during which spiral-shaped FtsZ intermediates were detected along the length of the aerial hyphal cell. Time course experiments indicated that they were remodeled and gradually replaced by regularly spaced FtsZ rings. Such spiral-shaped filaments could also be detected with immunofluorescence microscopy using an antiserum against FtsZ. Based on our observations, we propose a model for the progression of Z-ring assembly during sporulation of
S. coelicolor
. Furthermore, mutants lacking the developmental regulatory genes
whiA
,
whiB
,
whiG
,
whiH
, and
whiI
were investigated. They failed in up-regulation of the expression of FtsZ-EGFP in aerial hyphae, which is consistent with the known effects of these genes on
ftsZ
transcription.
Requirement of the Receiver and Phosphotransfer Domains of ArcB for Efficient Dephosphorylation of Phosphorylated ArcA In Vivo
Authors: Peña-Sandoval Gabriela R. , Kwon Ohsuk , Georgellis Dimitris
Published: April 2005

The Arc two-component system, comprising the ArcB sensor kinase and the ArcA response regulator, modulates the expression of numerous genes in response to the respiratory conditions of growth. Under anoxic growth conditions, ArcB autophosphorylates and transphosphorylates ArcA, which in turn represses or activates its target operons. Under aerobic growth conditions, phosphorylated ArcA (ArcA-P) dephosphorylates and its transcriptional regulation is released. The dephosphorylation of ArcA-P has been shown to occur, at least in vitro, via an ArcA
Asp54
-P → ArcB
His717
-P → ArcB
Asp576
-P → P
i
reverse phosphorelay. In this study, the physiological significance of this pathway was assessed. The results demonstrate that the receiver and phosphotransfer domains of the tripartite sensor kinase ArcB are necessary and sufficient for efficient ArcA-P dephosphorylation in vivo.
Organisational and occupational risk factors associated with work related injuries among public hospital employees in Costa Rica
Authors: Gimeno D , Felknor S , Burau K D , Delclos G L
Published: April 2005

Aims:To explore the relation between occupational and organisational factors and work related injuries (WRI) among public hospital employees in Costa Rica.

Methods:A cross-sectional survey was conducted among a stratified random sample of 1000 employees from 10 of the 29 public hospitals in Costa Rica. A previously validated, self-administered questionnaire which included occupational and organisational factors and sociodemographic variables was used. From the final eligible sample (n = 859), a total of 842 (response rate 98%) questionnaires were returned; 475 workers were analysed after excluding not-at-risk workers and incomplete questionnaires. WRI were computed for the past six months.

Results:Workers exposed to chemicals (RR = 1.36) and physical hazards (RR = 1.26) had higher WRI rate ratios than non-exposed workers. Employees reporting job tasks that interfered with safety practices (RR = 1.46), and a lack of safety training (RR = 1.41) had higher WRI rate ratios than their counterparts. Low levels of safety climate (RR = 1.51) and safety practices (RR = 1.27) were individually associated with an increased risk of WRI. Also, when evaluated jointly, low levels of both safety climate and safety practices showed the highest association with WRI (RR = 1.92).

Conclusions:When evaluated independently, most of the occupational exposures and organisational factors investigated were significantly correlated with an increased injury risk. As expected, some of these associations disappeared when evaluated jointly. Exposure to chemical and physical hazards, lack of safety training, and low levels of safety climate and safety practices remained significant risk factors for WRI. These results will be important to consider in developing future prevention interventions in this setting.
"V-MICS",ADVANCED TPSFOR STRATEGIC PRODUCTION ADMINISTRATION: INNOVATIVE MAINTENANCE COMBINING DB AND CG
Authors: SAKAI HIROHISA , AMASAKA KAKURO
Published: April 2005

To achieve worldwide high productivity and quality assurance of global production, the authors considered the necessity of including the above with strategic application of the TPS, and clarified the Advanced TPS as the global production by manufacturing technology for the strategic administration of production facilities. Nowadays, we have established manufacturing technology by innovative maintenance of Toyota, a most advanced automotive manufacturing enterprise. Therefore, we propose the V-MICS (utilizing Visualization-Maintenance Innovated Computer System) consisting of five steps (AML-1 to AML-5). Concretely for transfer of the maintenance skill, in particular we will accomplish a procedure combining DB (database) and CG (computer graphics). With regard to the former we will construct a DB for easier accumulation of know-how for parts replacement and other jobs. As regards to the latter, we will provide the instructions to enable even a person not familiarized with machine-drawings to carry out dairy inspection. As a result, we will not only attain considerable reduction of the maintenance cost, but also realize a lot of benefits such as more improved availability when we start up the global production in the world.
FEA APPLICATIONS IN MILLING CHATTER STABILITY ANALYSIS
Authors: LIU EYSION A. , HO SIMON , WEHRLY MITCHEL , RESH WILLIAM F.
Published: April 2005

Regenerative chatter is a major hurdle to the productivity and quality of machining operations. This is because of the undesirable surface finish, excessive tool wear and deteriorated dimensional accuracy. Machining chatter analysis techniques examine the stability of a closed-loop model of machining forces and tool-workpiece system. This model is based on mathematical manipulations of machining forces and the dynamic responses of machining tooling. Almost all techniques derive the dynamic responses from physical test. In this paper, a novel approach of milling chatter stability analysis is introduced by using FEA applications to obtain the dynamic responses of the machine tool. The accuracy of this methodology is validated by machine shop tests.
ONTOLOGICAL MACHINING PROCESS DATA MODELLING FOR POWERTRAIN PRODUCTION IN EXTENDED ENTERPRISE
Authors: CAI JING , WEYRICH MICHAEL , BERGER ULRICH
Published: April 2005

As a new CAx concept, Digital Factory points out digital design of product & virtual planning of production. In this context, feature technology builds up the entire CAx process chain in Digital Factory, and facilitates STEP based engineering data generation and exchange.

The collaborative computer-aided machining process planning of a transfer line is an element in process chain of extended enterprises Automotive Engineering. In practice, it is an approach engaged by both OEMs and their long-term machine suppliers. Application of a CAD-based Digital Factory planning system to design a virtual transfer line needs planning standard data and exchange with supplier.

This paper highlights STEP-referenced ontological data modeling approach in the standardized data exchange for collaborative machining process planning, discusses the aspects of its prospective application advantages in machining process planning by OEMs and suppliers for Powertrain production in Automotive Industry.
HYBRID GENETIC — ANT COLONY ALGORITHMS FOR SOLVING AGGREGATE PRODUCTION PLAN
Authors: KUMAR G. MOHAN , HAQ A. NOORUL
Published: April 2005

It is necessary for the management of any industry to workout an intermediate range plan also known as aggregate production plan, consistently with the long range policies and resources allocated by long range decisions. It is a procedure of translating the expected demand and production capacity of the available facilities into future manufacturing plans for a family of products. It includes decisions on production quantity, work force and inventory to workout a low cost product and timely delivery. Ant colony optimization algorithm finds its extensive application in solving job shop scheduling, assignment problems, transportation problems, etc. Genetic algorithms are proposed to solve the problem, already by the authors. In this paper, an attempt is made to solve an aggregate production-planning problem for obtaining an effective solution using ant colony algorithm. Also a hybrid algorithm that combines genetic algorithm and ant colony algorithm is proposed and its effectiveness over the models developed using genetic algorithms and ant colony algorithm is also analyzed.
Distribution of Rab GTPases in Mouse Kidney and Comparison with Vacuolar H+-ATPase
Authors: Curtis Lisa M. , Gluck Stephen
Published: April 2005

Background: Vacuolar H+-ATPases (V-ATPases) are essential for renal bicarbonate transport in both the proximal and distal nephron. Regulation of proton transport occurs, in part, by vesicle-mediated traffic of V-ATPases between intracellular vacuoles and the plasma membrane. Although the proteins involved in regulated V-ATPase traffic are largely unknown, Rab GTPases have a central role in the traffic and recycling of other membrane proteins. Methods: To identify candidate Rab GTPases potentially involved in V-ATPase traffic, immunocytochemical and subcellular fractionation studies were used to evaluate the distribution to sites of abundant V-ATPase of 5 Rab GTPases expressed in kidney, Rab5a, Rab11, Rab13, Rab18, and Rab20. Results: The immunocytochemical distribution of Rab5a and Rab13 and the subcellular distribution of Rab18 were not compatible with a role in V-ATPase traffic. In contrast, Rab11 colocalized with V-ATPase in apical regions of proximal tubule, and Rab20 colocalized with the enzyme in intercalated cells. Rab11 and Rab20 were enriched in membrane fractions that were also enriched in V-ATPase B2 and B1 subunit isoforms, respectively. Conclusions: The immunohistochemical data in combination with the membrane fractionation studies are consistent with a potential role for Rab11 and Rab20 in regulating V-ATPase traffic in specific segments of the nephron.
The Surgical Management of Haemorrhoids – A Review
Authors: Hardy A. , Chan C.L.H. , Cohen C.R.G.
Published: April 2005

A number of new surgical treatments have led to a reappraisal of haemorrhoid disease over the last few decades. Despite a range of treatment modalities, the options are limited in their effectiveness and can lead to a number of complications. An inadequate classification system based on appearance rather than symptoms makes the choice of appropriate therapy difficult. More recent techniques have led to a move away from surgical excision. However, further research is required to establish their precise indications and long-term efficacy.
Laparoscopy for Colorectal Malignancy
Authors: Pillinger Stephen H. , Monson John R.T.
Published: April 2005

Laparoscopy for colorectal pathology is technically demanding with a steep learning curve. In expert hands, there is no doubt that there is a place for laparoscopy in the operative armamentarium for the treatment of benign disease. The question of its application in the treatment of carcinoma is more difficult to address. The evidence available suggests that laparoscopic resection is a feasible and appropriate option for the treatment of colorectal carcinoma. The skill and technology to perform the procedure are developing apace, and level 1 evidence to support it is tantalizingly close. This paper will outline the development of the technique, the operative approach, and the available evidence for its use in the treatment of carcinoma.
Physical Function and Quality of Life after Thoracoabdominal Oesophageal Resection
Authors: Fagevik Olsén Monika , Larsson Malin , Hammerlid Eva , Lundell Lars
Published: April 2005

Background: The long-term functional outcome after thoracoabdominal resection has to be better evaluated. A study was performed to evaluate patients after a similar operation both in terms of physical function and health-related quality of life (HRQL). Methods: Eighteen patients were evaluated 2 years after a thoracoabdominal resection. Respiratory function, physical performance and range of motion in shoulder, thorax and spine were recorded. HQRL was assessed by EORTC QLQ-C30 (European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30) and EORTC QLQ-OES18 (Oeophageal module). Results: Two years after surgery, respiratory function (forced vital capacity and forced expiratory volume in 1 s) was significantly impaired compared to preoperative values (p < 0.05). The physical performance was significantly reduced as measured by a functional stand-up test (p < 0.05) and the handgrip force (p < 0.001). Shoulder range of motion, thoracic lateral flexion and C7 to wall were within normal ranges, thoracic flexion significantly greater (p < 0.01) but chest expansion significantly decreased (p < 0.01) compared to controls. HQRL was comparable to age- and sex-matched population norms for most of the functions. A clinical significant difference was, however, found for diarrhoea, dyspnoea, appetite loss and fatigue. Conclusion: Within a 2-year period, each individual regains most of the respiratory and physical performances and HRQL after a thoracoabdominal resection.
Progression of Subclinical Coronary Atherosclerosis
Authors: Cassidy Andrea E. , Bielak Lawrence F. , Zhou Yan , Sheedy Patrick F. , Turner Stephen T. , Breen Jerome F. , Araoz Philip A. , Kullo Iftikhar J. , Lin Xihong , Peyser Patricia A.
Published: April 2005

Background—

Obesity is associated with coronary artery calcification (CAC), a marker of the presence and extent of subclinical coronary atherosclerosis. Obesity adds incremental information in identifying those at higher risk of coronary heart disease to traditional risk factor assessment. The present study examined associations between obesity measures and progression of CAC in those at higher (≥10%) and lower (<10%) 10-year coronary heart disease risk according to the Framingham risk equation.

Methods and Results—

In this study, 443 asymptomatic white individuals >30 years of age (243 men) had baseline and follow-up CAC measurements an average of 8.9 years apart. Multivariable linear regression models were fit to determine associations of obesity measures at baseline with progression of CAC defined as log
e
of the difference between follow-up and baseline CAC area plus 1 divided by time (in years) between examinations, adjusting for baseline CAC quantity, age, sex, baseline hypertension status, and baseline cholesterol level. Among 329 participants (74.3%) in the lower-risk group, waist circumference (
P
=0.024), waist-to-hip ratio (
P
<0.001), body mass index (
P
=0.036), and being overweight compared with being underweight or of normal weight (
P
=0.008) were each significantly positively associated with progression of CAC. Among those at higher coronary heart disease risk, no baseline obesity measures were associated with CAC progression.

Conclusions—

Various measures of obesity were associated with increased progression of CAC in those at lower risk of coronary heart disease. Future studies examining the effectiveness of weight reduction strategies in reducing CAC progression among those with an otherwise favorable risk factor profile may be warranted.
Factor Analysis of Clustered Cardiovascular Risks in Adolescence
Authors: Goodman Elizabeth , Dolan Lawrence M. , Morrison John A. , Daniels Stephen R.
Published: April 2005

Background—

Clustering of cardiovascular (CV) risks begins in childhood, yet studies of the factor structure underlying this clustering have focused on adults. The increasing rates of obesity and type 2 diabetes and the growing importance of metabolic syndrome among adolescents make assessment of CV risk clustering even more urgent in this age group.

Methods and Results—

Exploratory factor analysis (principal components analysis) was performed with data from 1578 healthy seventh to 12th graders from the Princeton School District Study, a school-based study in Cincinnati, Ohio. Measured CV risks included cholesterol, triglycerides, fasting insulin and glucose, body mass index (BMI), waist circumference, fibrinogen, and blood pressure. Factor analysis yielded 4 uncorrelated factors (adiposity [BMI, waist, fibrinogen, insulin], cholesterol [LDL and total cholesterol], carbohydrate-metabolic [glucose, insulin, HDL cholesterol, triglycerides], and blood pressure [systolic and diastolic blood pressure]). These factors explained approximately 67% of the total variance. A summary cumulative risk scale was derived from factor scores, and high risk was defined as scoring in the top 5%. Although insulin loaded onto both the adiposity and carbohydrate-metabolic factors, obesity was a much stronger correlate of high cumulative risk (odds ratio=19.2; 95% CI, 7.6 to 48.5) than hyperinsulinemia (odds ratio=3.5; 95% CI, 1.8 to 6.8). A sizable proportion (18.5%; n=12) of those who were at high cumulative risk were not at high risk for any of the individual factors.

Conclusions—

The patterning of CV risk clustering seen among adults is present in healthy adolescents. Among youth, obesity is the predominant correlate of cumulative risk.
A one-way dual-domain propagator for scalar qP-waves in VTI media
Authors: Han Qiyu , Wu Ru-Shan
Published: April 2005

In this paper, we present an anisotropic one-way propagator for modeling and imaging quasi-P (qP) waves in transversely isotropic media with a vertically symmetric axis (VTI media). We derive the dispersion relation for a scalar qP-wave using elastic wave equations for anisotropic media. By applying a rational approximation to the dispersion relation, we obtain a one-way, dual-domain, scalar qP-wave propagator for heterogeneous VTI media. The propagator includes a phase-shift term and both phase-screen and large-angle correction terms. The phase-shift term is implemented in the wavenumber domain, while the other terms are implemented in the space domain. Fourier transformations are used to shuttle the wavefield between the two domains. This propagator can be used to propagate qP-wavefields within an isotropic or a VTI medium, with either medium containing lateral heterogeneities. Error analysis of the impulse response and dispersion relations demonstrates that the propagator is accurate and stable and has a wide-angle capability. The application of the propagator to the imaging of qP-wave data with VTI models which contain complex structures and large perturbations of velocity and anisotropy results in excellent image quality. This demonstrates the potential value of the propagator for use in modeling and imaging qP-wavefields within strongly heterogeneous VTI media.
Comparison of seismic attenuation models using zero-offset vertical seismic profiling (VSP) data
Authors: Toverud Tommy , Ursin Bjørn
Published: April 2005

For seismic frequencies it is common to use an empirical equation to model attenuation. Usually the attenuation coefficient is modeled with linear frequency dependence, a model referred to as the Kolsky-Futterman model. Other models have been suggested in the geophysical literature. We compare eight of these models on a zero-offset vertical seismic profiling (VSP) data set: the Kolsky-Futterman, the power law, the Kjartansson, the Müller, the Azimi second, the Azimi third, the Cole-Cole, and the standard linear solid (SLS) models. For three separate depth zones we estimate velocities and Q-values for all eight models. A least-squares model-fitting algorithm gives almost the same normalized misfit for all models. Thus, none of the models can be preferred or rejected based on the given data set. Slightly better overall results are obtained for the Kolsky-Futterman model; for one depth zone, the SLS model gave the best result.
Refraction traveltime tomography using damped monochromatic wavefield
Authors: Pyun Sukjoon , Shin Changsoo , Min Dong-Joo , Ha Taeyoung
Published: April 2005

For complicated earth models, wave-equation–based refraction-traveltime tomography is more accurate than ray-based tomography but requires more computational effort. Most of the computational effort in traveltime tomography comes from computing traveltimes and their Fréchet derivatives, which for ray-based methods can be computed directly. However, in most wave-equation traveltime-tomography algorithms, the steepest descent direction of the objective function is computed by the backprojection algorithm, without computing a Fréchet derivative directly. We propose a new wave-based refraction-traveltime–tomography procedure that computes Fréchet derivatives directly and efficiently. Our method involves solving a damped-wave equation using a frequency-domain, finite-element modeling algorithm at a single frequency and invoking the reciprocity theorem. A damping factor, which is commonly used to suppress wraparound effects in frequency-domain modeling, plays the role of suppressing multievent wavefields. By limiting the wavefield to a single first arrival, we are able to extract the first-arrival traveltime from the phase term without applying a time window. Computing the partial derivative of the damped wave-equation solution using the reciprocity theorem enables us to compute the Fréchet derivative of amplitude, as well as that of traveltime, with respect to subsurface parameters. Using the Marmousi-2 model, we demonstrate numerically that refraction traveltime tomography with large-offset data can be used to provide the smooth initial velocity model necessary for prestack depth migration.
Imaging and suppressing near-receiver scattered surface waves
Authors: Campman Xander H. , van Wijk Kasper , Scales John A. , Herman Gérard C.
Published: April 2005

When traveling through a complex overburden, upcoming seismic body waves can be disturbed by scattering from local heterogeneities. Currently, surface-consistent static and amplitude corrections correct for rapid variations in arrival times and amplitudes of a reflector, but these methods impose strong assumptions on the near-surface model. Observations on synthetic and laboratory experiments of near-surface scattering with densely sampled data suggest that removing noise from near-receiver scattering requires multichannel approaches rather than single-channel, near-surface corrections. In this paper we develop a wavefield-based imaging method to suppress surface waves scattered directly beneath the receivers. Using an integral-equation formulation, we account for near-surface heterogeneities by a surface impedance function. This impedance function is used to model scattered surface waves, excited by upcoming wavefronts. The final step in our algorithm is to subtract the scattered surface waves. We successfully apply this method to laboratory data of scattered surface waves, excited and monitored with a noncontacting acquisition system.
Refraction across an angular unconformity between nonparallel TI media
Authors: Hodgkinson John , Brown R. James
Published: April 2005

Assuming elliptical wavefronts, we reformulate refraction theory for transversely isotropic (TI) media based on the use of the auxiliary angle, α, which is intermediate between the phase angle, θ, and the group angle, ϕ. When considering the application of stretching to transform elliptically anisotropic media into isotropic media, the auxiliary angle is a natural one to use because both θ and ϕ → α under such stretching. Our present formulation for TI media makes the assumption of elliptical anisotropy, which is valid generally for SH-waves but only as a special case for P-and SV-waves, where, in the SV case, the only possible ellipses are circles. Nevertheless, the theory has useful applications for P-waves over limited ranges of propagation direction (e.g., in the short-spread approximation). Our formulation provides explicit results for all angles of incidence and for what we term an angular unconformity between two TI media, that is, for all orientations of the axes of symmetry for each of the media, and for all orientations of the interface, assuming these two axes and the interface normal to lie in the same vertical plane. Our conclusions have been verified by showing that the phase angles and phase velocities of the incident and refracted waves obey Snell's law across the interface. We also demonstrate, using auxiliary angles, that the description of refraction between elliptically anisotropic media by stretching the media to make them isotropic, then applying isotropic refraction, is also valid for our general angular-unconformity case. However, both stretching (1D) and either scaling (2D) or shearing must be applied correctly and separately to the two media. The refraction algorithm developed from this theory and another developed by Byun in terms of phase-velocity theory are currently the only published noniterative algorithms known to us for refraction across an angular unconformity where the axes of anisotropy are parallel neither to each other nor to the interface. Based on this theory, we have developed a demonstration program, AUXDEMOC, that computes the refracted-ray angles for any combination of parameters by the two equivalent methods: (1) anisotropic refraction and (2) stretching plus isotropic refraction. This program can be downloaded from http://www.crewes.org/under Free Software.
Multipole acoustic responses of a prestressed formation: An effective medium approach
Authors: Wang Tsili , Tang Xiaoming
Published: April 2005

Acoustic waveforms have been simulated for monopole, dipole, and quadrupole sources in a prestressed formation. The prestressed medium is modeled as an unstressed medium with the stress effect replaced by effective elastic moduli. The effective, unstressed medium is acoustically anisotropic. Because the medium is inhomogeneous due to the local stress concentrations around the borehole, the anisotropy tensor varies in space. To avoid the use of a full anisotropy tensor, the effective medium is assumed to be transversely isotropic (TI) with a symmetry axis parallel to the minimum stress direction. The elastic moduli of the TI medium are determined from the shear velocities of the unstressed medium using an empirical relation between static stress and shear velocities. The effective medium is then modeled with the conventional finite-difference time-domain method. The effective-medium approach successfully predicts the known first-order effects of stress; that is, shear-wave splitting for a monopole source and dispersion crossover for cross-dipole sources. It also shows that the dipole wave-dispersion crossover frequency decreases linearly with increasing borehole radius. With the effective medium model, we study the interaction of quadrupole waves excited and recorded in a vertical well with static formation stress. It is shown that the quadrupole wave in a prestressed formation splits into a fast wave and a slow wave. The velocities of the waves are similar to those of crossed-dipole waves in the same formation. Both waves are faster than quadrupole waveforms without stress. Moreover, the wave splitting is observed for different tool orientations in the borehole and different borehole sizes. Therefore, the wave splitting may be used as an indication of static formation stress if the medium without stress is isotropic.
Impact factors, citations, and GEOPHYSICS
Authors: Peltoniemi Markku
Published: April 2005

This review assesses the contributions and impact that GEOPHYSICS journal has made to both the theory and the applications of exploration geophysics during its publication life span. The contributions are evaluated first on the basis of Journal Citation Reports data, which summarize information available since 1975 about the impact factor of our journal. The impact factor for GEOPHYSICS in 1975–2002 has ranged between 1.461 and 0.591, with an average of 0.924 and with a relative ranking between 16 and 45 for all journals in its category. The journal receiving the highest impact factor for the period 2000–2003 in the “Geochemistry and Geophysics” category is Reviews of Geophysics, with an average impact factor of 7.787 and which ranged between 9.226 and 6.083. A second and important criterion is the frequency with which individual papers published in GEOPHYSICS have been cited elsewhere. This information is available for the entire publication history of GEOPHYSICS and supports the choices made for the early classic papers. These were listed in both the Silver and the Golden Anniversary issues of GEOPHYSICS. In August 2004, the five most-cited papers in GEOPHYSICS published in the time period 1936 to February 2003 are Thomsen (1986) with 423 citations, Constable et al. (1987) with 380 citations, Cagniard (1953) with 354 citations, Sen et al. (1981) with 313 citations, and Stolt (1978) with 307 citations. Fifteen more papers exceed a threshold value of 200 citations. During 2000–2002, GEOPHYSICS, Geophysical Prospecting, Geophysical Journal International, and Journal of Applied Geophysics were the four journals with the highest number of citations of papers published in GEOPHYSICS. In the same 2000–2002 period, those journals in which papers published in GEOPHYSICS are cited most are GEOPHYSICS, Geophysical Prospecting, Geophysical Journal International, and Journal of Geophysical Research. During 1985, the total number of citations in all journals in the Science Citation Index database to papers published in GEOPHYSICS was 2657. By 2002, this same citation count for GEOPHYSICS had increased to 4784.
Intellectual Property
Authors: Walker David A.
Published: April 2005

The Intellectual Property department in each issue of Geophysics provides U.S. patent abstracts, published patent abstracts of U.S. patent applications, and published abstracts filed under the Patent Cooperation Treaty (PCT).
Genetic Causes of Mental Retardation
Authors: MOSER HUGO W.
Published: April 2005

Abstract: Mental retardation has been categorized into severe mental retardation where genetics plays a very important role and mild mental retardation, in which genetics in some instances plays a role but in which cultural factors also matter a great deal. The pathogenetic, clinical and behavioral characteristics of genetically determined disorders associated with mental retardation differ greatly—as exemplified by two genetic disorders that have been clarified recently, namely Rett syndrome and the Williams syndrome. In the work‐up of the developmentally disabled child, previous studies have shown that genetic studies are of have great importance and high yield. Early biochemical diagnosis in newborn screening has tremendous potential and has been strongly supported by NICHD—the PKU story being so much part of what NICHD has done. We must gain a better understanding of structure/function relationships, which becomes more and more possible with neuroimaging. A better understanding of neural plasticity can lead to correction by early intervention.
Developmental Biology of Zebrafish
Authors: DAWID IGOR B.
Published: April 2005

Abstract: The biology and genetics of zebrafish has become a very popular system in developmental biology especially because of their suitability for genetics and the transparent embryo of this small tropical fish. Studies reported briefly here demonstrate that one can use gene expression in the zebrafish embryo to find new components of important and well‐studied developmental mechanisms and signal transduction pathways. The study of zebrafish developmental genetics has proven invaluable in determining many aspects of vertebrate development. Further use of this model organism promises to generate many interesting and useful data.
Dynamics of Secretory Membrane Trafficking
Authors: LIPPINCOTT‐SCHWARTZ JENNIFER
Published: April 2005

Abstract: The study of intracellular membrane trafficking and organelle dynamics has been revolutionized with the advent of GFP technology, which allows individual proteins to be tagged with GFP and monitored in living cells. Using GFP‐based techniques such as selective photobleaching and time‐lapse imaging of different GFP color variants, it is now possible to address a host of questions related to protein retention within the organelles, the origin and fate of transport intermediates, and the extent of trafficking through different transport pathways. This has provided unexpected new insights into the organization and function of secretory and endocytic pathways within cells.
Activins and Inhibins and Their Signaling
Authors: VALE WYLIE , WIATER EZRA , GRAY PETER , HARRISON CRAIG , BILEZIKJIAN LOUISE , CHOE SENYON
Published: April 2005

Abstract: Activins and inhibins, which were discovered by virtue of their abilities to stimulate or inhibit, respectively, the secretion of FSH, are members of the transforming growth factor‐β (TGFβ) superfamily and exert a broad range of effects on the diffentiation, proliferation and functions of numerous cell types. Activins interact with two structurally related classes of serine/threonine kinase receptors (type I and type II). Inhibin antagonizes activin by binding to the proteoglycan, betaglycan, and forming a stable complex with and, thereby, sequestering type II activin receptors while excluding type I receptors. If betaglycan is present, inhibin can also antagonize those bone morphogenic proteins (BMPs) whose signaling is dependent upon access to type II activin receptors. Recent insights regarding the structures of ligands, receptors and their signaling complexes are providing the basis for the development of therapeutics capable of modulating fertility and numerous pathophysiologic processes.