bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolution of Autoantibody Responses via Somatic Hypermutation Outside of Germinal Centers
Authors: William Jacqueline , Euler Chad , Christensen Sean , Shlomchik Mark J.
Published: September 2002

Somatically mutated high-affinity autoantibodies are a hallmark of some autoimmune diseases, including systemic lupus erythematosus. It has long been presumed that germinal centers (GCs) are critical in autoantibody production, because they are the only sites currently believed to sustain a high rate of somatic hypermutation. Contrary to this idea, we found that splenic autoreactive B cells in autoimmune MRL.Fas
lpr
mice proliferated and underwent active somatic hypermutation at the T zone–red pulp border rather than in GCs. Our results implicate this region as an important site for hypermutation and the loss of B cell self-tolerance.
Enhanced Tumor Formation in Mice Heterozygous for
Blm
Mutation
Authors: Goss Kathleen Heppner , Risinger Mary A. , Kordich Jennifer J. , Sanz Maureen M. , Straughen Joel E. , Slovek Lisa E. , Capobianco Anthony J. , German James , Boivin Gregory P. , Groden Joanna
Published: September 2002

Persons with the autosomal recessive disorder Bloom syndrome are predisposed to cancers of many types due to loss-of-function mutations in the
BLM
gene, which encodes a recQ-like helicase. Here we show that mice heterozygous for a targeted null mutation of
Blm
, the murine homolog of
BLM
, develop lymphoma earlier than wild-type littermates in response to challenge with murine leukemia virus and develop twice the number of intestinal tumors when crossed with mice carrying a mutation in the
Apc
tumor suppressor. These observations indicate that
Blm
is a modifier of tumor formation in the mouse and that
Blm
haploinsufficiency is associated with tumor predisposition, a finding with important implications for cancer risk in humans.
Uplift in the Fiordland Region, New Zealand: Implications for Incipient Subduction
Authors: House M. A. , Gurnis M. , Kamp P. J. J. , Sutherland R.
Published: September 2002

Low-temperature thermochronometry reveals regional Late Cenozoic denudation in Fiordland, New Zealand, consistent with geodynamic models showing uplift of the overriding plate during incipient subduction. The data show a northward progression of exhumation in response to northward migration of the initiation of subduction. The locus of most recent uplift coincides with a large positive Bouguer gravity anomaly within Fiordland. Thermochronometrically deduced crustal thinning, anomalous gravity, and estimates of surface uplift are all consistent with ∼2 kilometers of dynamic support. This amount of dynamic support is in accord with geodynamic predictions, suggesting that we have dated the initiation of subduction adjacent to Fiordland.
Cleavage of
Scarecrow-like
mRNA Targets Directed by a Class of
Arabidopsis
miRNA
Authors: Llave Cesar , Xie Zhixin , Kasschau Kristin D. , Carrington James C.
Published: September 2002

Micro-RNAs (miRNAs) are regulatory molecules that mediate effects by interacting with messenger RNA (mRNA) targets. Here we show that
Arabidopsis thaliana
miRNA 39 (also known as miR171), a 21-ribonucleotide species that accumulates predominantly in inflorescence tissues, is produced from an intergenic region in chromosome III and functionally interacts with mRNA targets encoding several members of the
Scarecrow-like
(
SCL
) family of putative transcription factors. miRNA 39 is complementary to an internal region of three
SCL
mRNAs. The interaction results in specific cleavage of target mRNA within the region of complementarity, indicating that this class of miRNA functions like small interfering RNA associated with RNA silencing to guide sequence-specific cleavage in a developmentally controlled manner.
Autocatalytic Oxidation of Lead Crystallite Surfaces
Authors: Thürmer Konrad , Williams Ellen , Reutt-Robey Janice
Published: September 2002

Growth of an ultrathin lead oxide layer causes massive changes in the shape of lead crystallites. The dynamics of this process was investigated with time-lapsed scanning tunneling microscopy. Pure lead crystallites proved extremely resistant to oxidation. Once nucleated by surface impurities, monolayer films of lead oxide grew readily on lead (111) microfacets in an autocatalytic process. The anisotropic growth of orthorhombic lead oxide films (massicot structure) was most rapid along the direction of weakest lead-oxygen bonding, which suggests that the growth edge autocatalyzes oxygen dissociation by providing proximal sites for oxygen dissociation and attachment.
What's in a Name? A Systematic Review of the Nomenclature of Chinese Medical Formulae
Authors: Park Jongbae , Park Hi-Joon , Lee Hye-Jung , Ernst Edzard
Published: September 2002

Traditional Chinese Medicine (TCM) has been modified to some extent in other Far Eastern countries such as Korea and Japan. Researchers of each of the three countries seem to use different English names for the same Chinese medicinal formulae. Lack of knowledge of the Chinese characters is destined to increase this confusion. In order to investigate this matter systematically, all investigations of Chinese medicine formulae published in the American Journal of Chinese Medicine (AJCM, 1997-March 2001) were evaluated. Moreover, PubMed (1966-June 2001) was searched using keywords differentiated by language, location and number of hyphens, and upper-or lower-case of the first letter of the English equivalent of each Chinese character. Fifty-four formulae of TCM were identified in 45 reports published in AJCM. Thirty-two were named in Chinese only (23 reports); six in Japanese (six reports); and five in Korean (five reports). Ten formulae were named in Japanese with the Chinese name in brackets (ten reports); and one in Chinese with the Japanese name in brackets (one report). By computerized literature search, different numbers of research papers were retrieved by using keywords differentiated by language, location and number of hyphens. Such confusion may prevent progress in the evaluation of TCM. To increase the efficiency of studies on Chinese medical formulae, standardization of terminology is required.
SOLUTION TO THE EXCITONIC PROBLEM OF AN ELECTRON IN A QUANTUM WIRE AND A HOLE IN A PERPENDICULAR 2D QUANTUM LAYER
Authors: DEL CASTILIO-MUSSOT MARCELO , REYES J. ADRIAN , COYOTÉCATL HONORATO A. , COCOLETZI GREGORIO H.
Published: September 2002

We calculate the states of an exciton formed by an electron confined in a 1D quantum wire (QW) and a hole confined in a 2D quantum layer (QL) perpendicular to the QW. The effective potential can be exactly calculated in the particular case where the confinement thicknesses are the same for the QW and QL. This effective potential can be used to calculate the exciton states for arbitrary confinement thicknesses, but here we show that in the limit of vanishing thickness the solution of our equation is very similar to the 3D bulk exciton equations, and therefore we can use these 3D exciton solutions as a basis for our system in a quantum perturbative approach.
AlGe ALLOY COMPOSITION CALCULATED BY AUGER ELECTRON SPECTROSCOPY
Authors: HERNÁNDEZ M. P. , PEÑA J. L. , ALONSO C. F. , BARTOLO-PÉREZ P. , FARÍAS M. H.
Published: September 2002

The Al and Ge molar fraction of a few surface atomic layers in AlGe binary alloys was calculated using Auger electron spectroscopy (AES) and the evaluation of the Auger electron matrix factor or the matrix correction. The electron backscattering correction factor (R) and the inelastic mean path (IMFP) were taken into account to calculate the matrix correction. The IMFP was obtained from experimental optical data and elastic peak electron spectroscopy (EPES) measurements. The electron backscattering correction factor was calculated using Monte Carlo simulations. The main sources of the uncertainty of the Al and Ge molar fraction of a few surface atomic layers in AlGe binary alloys is the uncertainty of Al IMFP.
THE HALL EFFECT IN HYDRIDED RARE EARTH FILMS: REMOVING BILAYER EFFECTS
Authors: KOON D. W. , AZOFEIFA D. E. , CLARK N.
Published: September 2002

We describe two new techniques for measuring the Hall effect in capped rare earth films during hydriding. In one, we simultaneously measure resistivity and the Hall coefficient for a rare earth film covered with four different thicknesses of Pd, recovering the charge transport quantities for both materials. In the second technique, we replace Pd with Mn as the covering layer. We will present results from both techniques.
SURFACE TOPOGRAPHY ON EPITAXIAL HoBa2Cu3O7-δ AND Bi2Sr2CaCu2O8+δ THIN FILMS
Authors: LOPERA W. , GIRATÁ D. , PÉREZ F. , CASTRO L. F. , BACA E. , PRIETO P. , MENDOZA A.
Published: September 2002

Surface topography on epitaxial HoBa 2 Cu 3 O 7-δ (HBCO) and Bi 2 Sr 2 CaCu 2 O 8+δ (BSCCO) thin films analysis by using the atomic force microscopy (AFM) technique was carried out. The films were deposited in situ on SrTiO 3 substrates with thicknesses ranging from 100 to 300 nm by a high-pressure sputtering process. Chemical etching with a nonaqueous solution of Br-ethanol was used to modify the surface of the samples. HBCO films showed spiral grains, while BSCCO samples exhibited a terraced growth. Etching with Br-ethanol has different effects on HBCO and BSCCO. In HBCO, etching produces clean surfaces with light changes on the surface morphology, whereas in BSCCO it conduces to strong changes in the structure and the roughness of the film surface.
SUPERCONDUCTING PROPERTIES OF BSCCO (2223) ULTRATHIN FILMS
Authors: NAVARRETE L. , MARIÑO A. , SÁNCHEZ H.
Published: September 2002

Ultrathin films of (Bi–Pb)–Sr–Ca–Cu–O (2223) were produced by ex situ RF magnetron sputtering on MgO (100) substrates. Films with different thermal treatments and thickness varying between 30 nm and 300 nm were obtained and studied systematically. A structural characterization of these samples was carried out and correlated with their electrical properties and thickness.
SOLUTION OF THE QUANTUM BOLTZMANN EQUATION IN LINEAR TRANSPORT
Authors: PAEZ B. A. , MORENO A. , MÉNDEZ H.
Published: September 2002

The one-dimensional quantum Boltzmann equation in linear transport approximation was solved using the nonequilibrium Green's function method, and based on the lifetime approximation. As an example, the effect of interactions with electric fields were included, and the thermoelectric power coefficient (α) was evaluated, based on calculations of the statistical density current in a stationary regime over the nonequilibrium distribution function, and by the Green's function method. Results are compared in order to explore the advantages of each one, in evaluating the other kinetic transport coefficients.
THERMOELECTRIC POWER COEFFICIENT IN A QUANTUM WELL
Authors: PAEZ B. A. , MÉNDEZ H. , GIRALDO J. C.
Published: September 2002

Based on the solution of the quantum Boltzmann equation, in the linear transport approximation for an isotropic low-dimensional system, the thermoelectric power coefficient, Q, in a quantum well structure was determined. These calculations are based on variational methods, taking into account especial functions which include important parameters being varied at the time of evaluating the thermoelectric power, e.g. height and width barrier. Values of Q are carried out by using a computer code written in Mathematica, which allows one to depict them easily and in this way to compare different behaviors of Q against temperature according to the scattering mechanism (phonons).
MAGNETOTRANSPORT PROPERTIES OF GdBa2Cu3O7 - δ SUPERCONDUCTING THIN FILMS
Authors: ROA-ROJAS J. , LANDÍNEZ TÉLLEZ D. A. , PRIETO P.
Published: September 2002

Systematic measurements of the Hall and longitudinal resistivities as a function of temperature in GdBa 2 Cu 3 O 7 - δ thin films were effectuated. These were performed in magnetic fields B = 0, 1, 2, 3, 4 and 5 T, applied perpendicular to the transport current orientation. Films were prepared by an in-situ high-pressure dc-sputtering technique in an atmosphere of pure oxygen. In the normal phase, the Hall coefficient is positive and varies inversely proportional to temperature. The Hall angle changes approximately as predicted by Anderson's formula. When the temperature approaches the mean-field critical temperature Tc from above, the Hall resistivity decreases abruptly in consequence of thermal fluctuations. Below Tc the Hall response changes signal, goes through a minimum and vanishes when the zero resistance is attained. We ascribe the sign-reversal feature to combined effects of thermal fluctuations and vortex motion. Close to the zero-resistance state, the Hall resistivity varies as a power law of the longitudinal resistivity, with a field-independent exponent. This result may be interpreted as evidence of a vortex-glass transition.
CALCULATION OF OPTICAL CONSTANTS IN POROUS SILICON THIN FILMS USING DIFFUSED AND SPECULAR REFLECTANCE MEASUREMENT
Authors: PEÑA C. , TORRES J.
Published: September 2002

In this work a method is proposed to calculate the optical constants of porous silicon (PS) thin films. The method is based on the theoretical simulation of the experimental reflectance spectra. In the optical system of this method the PS is considered a homogeneous, absorbing thin film, deposited on a silicon substrate of semi-infinite dimension. The theoretical form of the systems reflectance is calculated using the summation method proposed by Airy. Light scattering is included in the model by introducing the Davies–Bennett relation. The refraction index of the material is fit with the simple harmonic oscillator, proposed by Wemple–DiDomenico. The model was tested on two samples fabricated with anodization times of 25 and 35 min; the values for the refraction indexes, absorption coefficients, thickness and roughness were calculated for both samples. The PS samples were fabricated by electrochemical anodization of single crystal p-type silicon substrates in HF (25%) + isopropyl alcohol solution.
THE LOW COVERAGE PHASES OF Pb ON Ge(001): SCANNING TUNNELING MICROSCOPY AND FIRST PRINCIPLES
Authors: TAKEUCHI NOBORU , FALKENBERG G. , JOHNSON R. L.
Published: September 2002

Using scanning tunneling microscopy and first principles total energy calculations, we have studied the atomic structure of the low coverage phases of Pb on Ge(001): the (2 × 2) and the c(4 × 8)- α reconstructions. Based on the analysis of the experimental bias-dependent STM images and supported by the ab initio pseudopotential density-functional calculations, we present models for each structure. In both cases, there is a coexistence of Ge and Pb dimers. The (2 × 2) phase is formed by asymmetric Pb dimers parallel and in the trenches between the underlying Ge dimers. The Pb coverage is 0.5 ML and it corresponds to the maximum packing density of Pb dimers without breaking Ge dimers. The c(4 × 8) - α reconstruction has a Pb coverage of 0.75 ML and it is characterized by asymmetric Pb dimers forming chains along the [110] direction. However, in this case half of the Ge dimers are broken. The other half remain intact and they are perpendicular to the Pb dimers.
S ON Si(001): ADSORPTION OF A SINGLE ATOM UP TO A FULL MONOLAYER
Authors: ROMERO M. T. , ARBEY-RODRIGUEZ J. , TAKEUCHI NOBORU
Published: September 2002

We have studied the adsorption of S on the Si(001) c(4 × 2) surface by first principles total energy calculations. It is found that the first S atom is adsorbed on top of a symmetric Si dimer. Following atoms occupy similar bridge sites up to half-monolayer coverage. Increasing the amount of S atoms leads to the breaking of the underlying Si dimers. Our calculations predict that from 1/2 ML up to a full ML the growth of S is highly anisotropic. There is a preference of the S atoms to grow along the Si dimers rows. At full monolayer, all the Si dimers are broken and the surface is completely de-reconstructed with all Si atoms near bulk ideal positions.
SILICA–HYDROXYAPATITE NANOMETRIC COMPOSITES GROWN AT BOILING WATER TEMPERATURE
Authors: SÁENZ A. , MONTERO M. L. , CASTAÑO V. M.
Published: September 2002

Silica–hydroxyapatite composites have been produced with a novel method. Particle size can be selected by the pH of the solution as well as crystallite morphology which also depends on pH. An ion reservoir is built by means of the complex solution Ca/EDTA (ethylenediaminetetra-acetic acid). The formation of hydroxyapatite (HAp) at low temperatures (boiling water) and in short periods of time (around 4 h) is achieved. It is thought that the production of silica promotes the nucleation of hydroxyapatite.
Quantitative lithostratigraphic interpretation of seismic data for characterization of the Unayzah Formation in central Saudi Arabia
Authors: Fournier Frédérique , Déquirez Pierre‐Yves , Macrides Costas G. , Rademakers Marty
Published: September 2002

A lithostratigraphic interpretation of seismic data sets covering the Unayzah fluviatile formation in central Saudi Arabia has allowed us to map the sandstone distribution and to characterize the average porosity of the formation. First, sandstone distribution was predicted through seismic facies identification and interpretation with well information. Seismic facies analysis was performed with statistical pattern recognition applied to the portions of traces at the reservoir level, these traces being characterized by a series of seismic attributes. A good convergence of results from unsupervised and supervised pattern recognition was observed. This increases the confidence in the interpretation of sandprone facies.

Second, using a statistical relationship between the reservoir average porosity defined at the wells and selected amplitudes of adjacent traces, the porosity was predicted all over the area covered by the seismic information. The model was based on a multivariate linear regression, showing satisfying quality criteria (correlation coefficient, residuals, etc.). The porosity variation predicted from the seismic data complements the sandstone distribution, derived from the seismic facies analysis. In particular, some areas where sandstones are predicted do not appear as porous as could have been suspected from their lithological content, perhaps as the result of diagenetic effects.

Last, seismic facies analysis with pattern recognition applied to 2‐D exploratory lines, partly intersecting the 3‐D data set, led to the identification of potential prospects (Unayzah interval with a high sand–shale ratio).
Converted‐wave seismic exploration: Methods
Authors: Stewart Robert R. , Gaiser James E. , Brown R. James , Lawton Don C.
Published: September 2002

Multicomponent seismic recording (measurement with vertical‐ and horizontal‐component geophones and possibly a hydrophone or microphone) captures the seismic wavefield more completely than conventional single‐element techniques. In the last several years, multicomponent surveying has developed rapidly, allowing creation of converted‐wave or P‐S images. These make use of downgoing P‐waves that convert on reflection at their deepest point of penetration to upcoming S‐waves. Survey design for acquiring P‐S data is similar to that for P‐waves, but must take into account subsurface VP/VSvalues and the asymmetric P‐S ray path. P‐S surveys use conventional sources, but require several times more recording channels per receiving location. Some special processes for P‐S analysis include anisotropic rotations, S‐wave receiver statics, asymmetric and anisotropic binning, nonhyperbolic velocity analysis and NMO correction, P‐S to P‐P time transformation, P‐S dip moveout, prestack migration with two velocities and wavefields, and stacking velocity and reflectivity inversion for S‐wave velocities.

Current P‐S sections are approaching (and in some cases exceeding) the quality of conventional P‐P seismic data. Interpretation of P‐S sections uses full elastic ray tracing, synthetic seismograms, correlation with P‐wave sections, and depth migration. Development of the P‐S method has taken about 20 years, but has now become commercially viable.
A modeling study of borehole radar for oil‐field applications
Authors: Chen Yong‐Hua , Oristaglio Michael L.
Published: September 2002

This paper examines the suitability of borehole radar for near‐wellbore imaging. The maximum imaging range is primarily determined by the conductivity of the formation in which the borehole lies and the reflectivity of the targets. Under similar medium contrast, formation interfaces result in much stronger reflections than fractures. Complex horizontal borehole geometries are modeled with a 3‐D finite‐difference time‐domain (FDTD) code. Borehole effects, which are often almost insurmountable for acoustic methods, are very small for radar. As a result, the reflections in general are visually identifiable on the synthetic radar waveforms even before any signal processing. Therefore, borehole radar is a promising approach to map structures in the immediate vicinity of the borehole for a penetration depth of at least a few meters in relatively less‐conductive reservoirs (e.g., <0.03 S/m). As such, it complements borehole acoustic methods and has potential for geosteering applications.
Seismic data reconstruction by inversion to common offset
Authors: Chemingui Nizar , Biondi Biondo
Published: September 2002

Preserving amplitude information when imaging 3‐D multichannel seismic data is a challenging task. The imaging process can be described as seeking the inverse for a large matrix that relates the data to a reflectivity model. Due to irregular coverage at the surface and uneven illumination of the subsurface, the matrix is often ill‐conditioned and its coefficients are badly scaled. We present a new approach for regularizing the coverage of 3‐D surveys by partial imaging before migration. After regularization, 3‐D data become better suited for prestack migration using either “true amplitude” Kirchhoff methods or wave extrapolation techniques.

Posing partial stacking before migration as an inverse problem, we develop a new optimization technique named “inversion to common offset” (ICO) that solves for optimal partial stacks from multifold 3‐D data. The inversion approach takes advantage of the redundancy of information present in multichannel recording to recover densely and regularly sampled common‐offset common‐azimuth volumes. The reconstruction of each of these volumes combines data from multiple incomplete experiments over a common earth model to simulate the ideal data that would have been recorded from a single common‐offset common‐azimuth experiment. The method is based on the inversion of a partial prestack migration operator that maps seismic data from a given acquisition geometry to an arbitrary one. This data mapping operator is the azimuth moveout operator (AMO). The main advantage of ICO is that the AMO operator is compact and consequently cheaper to apply than other imaging operators, such as full 3‐D prestack migration.

We present a cost‐effective implementation of ICO based on a log‐stretch transformation of the time axis. After this transformation, AMO becomes time invariant, so the inversion can be performed in the Fourier domain on each temporal‐frequency slice independently. To accelerate the convergence of the iterative solution, we precondition the system of linear equations by two diagonal transformations that scale the rows and columns of the modeling operator. A stable solution is achieved by adding a penalty function that constrains the spatial variability of the model.

Results of applying ICO to a field 3‐D land survey show that we can recover the high‐frequency features of the reflectivity function from a severely undersampled data set obtained by decimating a densely sampled prestack data set. The images produced by prestack migration after regularization are superior to those produced by direct migration of the decimated data.
Interaction of a vortex ring with a piston vortex
Authors: ALLEN J. J. , AUVITY B.
Published: September 2002

Recent studies on vortex ring generation, e.g. Rosenfeld et al. (1998), have highlighted
the subtle effect of generation geometry on the final properties of rings. Experimental
generation of vortex rings often involves moving a piston through a tube, resulting in
a vortex ring being generated at the tube exit. A generation geometry that has been
cited as a standard consists of the tube exit mounted flush with a wall, with the piston
stroke ending at the tube exit, Glezer (1988). We employ this geometry to investigate
the effect of the vortex that forms in front of the advancing piston (piston vortex) on
the primary vortex ring that is formed at the tube exit. It is shown that when the
piston finishes its stroke flush with the wall, and hence forms an uninterrupted plane,
the piston vortex is convected through the primary ring and then ingested into the
primary vortex. The ingestion of the piston vortex results in an increased ring impulse
and an altered trajectory, when compared to the case when the piston motion finishes
inside the tube. As the Reynolds number of the experiments, based on the piston speed
and piston diameter, is the order of 3000, transition to turbulence is observed during
the self-induced translation phase of the ring motion. Compared to the case when
the piston is stopped inside the tube, the vortex ring which has ingested the piston
vortex transitions to turbulence at a significantly reduced distance from the orifice
exit and suggests the transition map suggested by Glezer (1988) is under question.
A secondary instability characterized by vorticity filaments with components in the
axial and radial directions, is observed forming on the piston vortex. The structure
of the instability appears to be similar to the streamwise vortex filaments that form
in the braid regions of shear layers. This instability is subsequently ingested into the
primary ring during the translation phase and may act to accelerate the growth of the
Tsai–Widnall instability. It is suggested that the origin of the instability is Görtler in
nature and the result of the unsteady wall jet nature of the boundary layer separating
on the piston face.
Modulated rotating waves in an enclosed
swirling flow
Authors: BLACKBURN H. M. , LOPEZ J. M.
Published: September 2002

The loss of axisymmetry in a swirling flow that is generated inside an enclosed
cylindrical container by the steady rotation of one endwall is examined numerically.
The two dimensionless parameters that govern these flows are the cylinder aspect
ratio and a Reynolds number associated with the rotation of the endwall. This study
deals with a fixed aspect ratio, height/radius = 2.5. At low Reynolds numbers the
basic flow is steady and axisymmetric; as the Reynolds number increases the basic
state develops a double recirculation zone on the axis, so-called vortex breakdown
bubbles. On further increase in the Reynolds number the flow becomes unsteady
through a supercritical Hopf bifurcation but remains axisymmetric. After the onset
of unsteadiness, another two unsteady axisymmetric solution branches appear with
further increase in Reynolds number, each with its own temporal characteristic: one
is periodic and the other is quasi-periodic with a very low frequency modulation.
Solutions on these additional branches are unstable to three-dimensional perturbations, leading to nonlinear modulated rotating wave states, but with the flow still
dominated by the corresponding underlying axisymmetric mode. A study of the flow
behaviour on and bifurcations between these solution branches is presented, both
for axisymmetric and for fully three-dimensional flows. The presence of modulated
rotating waves alters the structure of the bifurcation diagram and gives rise to its
own dynamics, such as a truncated cascade of period doublings of very-low-frequency
modulated states.
Dynamo mechanism in a rotating spherical shell:
competition between magnetic field and
convection vortices
Authors: ISHIHARA NORIO , KIDA SHIGEO
Published: September 2002

A strong axial magnetic dipole field with magnetic energy 15 times larger than the
kinetic energy of thermal convection is realized by a direct numerical simulation of
the magnetohydrodynamic equation of an electrically conducting Boussinesq fluid in
a rotating spherical shell which is driven by a temperature difference between the
outer and inner boundaries against a gravity force pointed towards the system centre. Cyclonic and anticyclonic convection vortices are generated and play a primary
role in the magnetic field intensification. The magnetic field is enhanced through the
stretching of magnetic lines in four particular parts of the convection fields, namely
inside anticyclones, between cyclones and their western neighbouring anticyclones at
middle as well as low latitudes, and between anticyclones and the outer boundary.
A ‘twist-turn’ loop of intense magnetic flux density is identified as a fundamental
structure which yields dominant contributions both to the toroidal and poloidal components of the longitudinally averaged magnetic field. Various types of competitive
interaction between the magnetic field and convection vortices are observed. Among
these, a creation-and-annihilation cycle in a statistically equilibrium state is particularly important. It is composed of three sequentially recurrent dynamical processes:
the generation of convection vortices by the Rayleigh–Bénard instability, the growth
of anticyclones and the intensification of magnetic field by a concentrate-and-stretch
mechanism, and the breakdown of vortices by the Lorentz force followed by diminution of the magnetic field. The energy transfer from the velocity to the magnetic fields
takes place predominantly in this dynamical cycle.
Salmonella surveillance: a global survey of public health serotyping
Authors: HERIKSTAD H. , MOTARJEMI Y. , TAUXE R. V.
Published: September 2002

To better understand the global epidemiology of salmonellosis and the national surveillance programmes used for salmonella infections in humans, we conducted a global survey of the 191 WHO Member States. We gathered information on the total number of salmonella isolates serotyped, and the 15 most commonly isolated serotypes from humans in 1990 and 1995. Of the 104 countries that responded, 76 (73.1%) conducted public health surveillance for salmonella and 69 of these (90.8%) conducted serotyping as part of the surveillance. Fifty-nine countries (56.7% of those responding) provided information about the most commonly isolated serotypes in 1995. Three serotypes, Enteritidis, Typhimurium and Typhi accounted for 76.1% of all isolates reported in 1995. One of these three was the most common serotype identified in 93.2% of countries reporting data for that year. In 1995, Enteritidis was the most frequently isolated serotype in 35 countries, followed by Typhi (12 countries) and Typhimurium (8 countries). The global pandemic of Salmonella Enteritidis continued to expand. The mean national proportion of all salmonella isolates that were Enteritidis increased globally from 25.6% in 1990 to 36.3% in 1995. Serotyping is a frequently used component of a public health response to the global challenge of salmonellosis. Support for serotyping as part of national salmonella surveillance, and for rapid international communication of the results via a new WHO electronic website will help target future prevention strategies.
Comparison of vaccination strategies for the control of dog rabies in Machakos District, Kenya
Authors: KITALA P. M. , McDERMOTT J. J. , COLEMAN P. G. , DYE C.
Published: September 2002

Demographic and epidemiological field data were used in a deterministic model to describe dog rabies transmission in Machakos District, Kenya and to predict the impact of potential vaccination strategies for its control. The basic reproduction number (R0) was estimated to be 2.44 (1.52–3.36, 95% confidence limits). There were three key model predictions. The first was that a threshold dog density (KT) of 4.5 dogs km−2 (3.8–5.2 dogs km−2, 95% confidence limits) was required to maintain transmission. The second was that the estimated annual vaccination rate of 24% failed to decrease incidence and actually increased the stability of transmission and may be counter-productive. Thirdly, to control rabies, it was predicted that 59% (34%–70%, 95% confidence limits) of dogs should be vaccinated at any one time. This requires approximately 70% coverage for annual but only 60% coverage for semi-annual vaccination campaigns. Community-level vaccination trials are needed to test these predictions.
Human salmonellosis associated with young poultry from a contaminated hatchery in Michigan and the resulting public health interventions, 1999 and 2000
Authors: WILKINS M. J. , BIDOL S. A. , BOULTON M. L. , STOBIERSKI M. G. , MASSEY J. P. , ROBINSON-DUNN B.
Published: September 2002

Although approximately 95% of disease caused by nontyphoidal salmonella is transmitted by foodborne vehicles, four documented salmonella outbreaks in the 1990s have been traced to contact with young poultry. No environmental studies of source hatcheries were completed. This case-control study was performed by comparing culture-confirmed Salmonella Infantis in Michigan residents, identified between May and July 1999, with two age- and neighbourhood-matched controls. Eighty environmental and bird tissue samples were collected from an implicated hatchery; all salmonella isolates underwent pulsed-field gel electrophoresis (PFGE) analysis. The study included 19 case-patients sharing the same PFGE subtype and 37 matched controls. Within 5 days before illness onset, 74% of case-patients resided in households raising young poultry compared with 16% of controls (matched OR 19.5; 95% CI 2.9, 378.1). Eight hatchery samples yielded Salmonella Infantis with PFGE subtypes matching the patients' isolates. This investigation identified birds from a single hatchery as the source of human illness and confirmed the link by matching PFGE patterns from humans, birds and the hatchery environment. Subsequent public health interventions reduced, but did not eliminate, transmission of poultry-associated salmonellosis. Five additional PFGE-linked cases were identified in Spring 2000, necessitating quarantine of the hatchery for depopulation, cleaning and disinfection.
Haemophilus influenzae type b and cross-reactive antigens in natural Hib infection dynamics; modelling in two populations
Authors: LEINO T. , AURANEN K. , MÄKELÄ P. H. , KÄYHTY H. , RAMSAY M. , SLACK M. , TAKALA A. K.
Published: September 2002

Natural immunity to Haemophilus influenzae type b (Hib) invasive disease is based on antibodies arising in response to encounters with Hib or cross-reactive (CR) bacteria. The relative importance of Hib and CR contacts is unknown. We applied a statistical model to estimate the total rate of immunizing infections of Hib and CR prior to wide-scale vaccinations in Finland and the UK. The average rates of these contacts were 0.7 and 1.2 per year per child in Finland and the UK, respectively. Using a rough estimate of 0.1 Hib acquisitions per year per child in the UK based on carriage rates, the proportion of Hib among all immunizing contacts was in the order of 10%, suggesting that CR bacteria have a major role. In general, varying frequency of CR contacts may explain some differences in the pre-vaccination incidence and age-distribution of invasive disease in different countries.
An outbreak of Salmonella enteritidis phage type 34a infection in primary school children: the use of visual aids and food preferences to overcome recall bias in a case control study
Authors: LINNANE E. , ROBERTS R. J. , MANNION P. T.
Published: September 2002

Outbreaks of infectious intestinal disease are common in schools. Case control studies are useful in the investigation of infectious disease outbreaks but the time interval between illness and investigation can lead to recall bias, particularly in young children. We describe an outbreak of Salmonella enteritidis phage type 34a infection involving 54 clinical cases in two adjacent schools, and a novel approach to overcome recall bias. The likely dates of infection were identified from the epidemic curve. We created a visual display of the menu from those days and asked 9 cases and 18 matched controls to identify their food preferences from this display. Preference for chocolate mouse was significantly associated with illness (P = 0.006). The results of the case control study agreed with the findings of the environmental investigation. We believe our approach could be used in other circumstances, where subjects are young children or recall bias is a concern.
Prevalence of campylobacters in chicken flocks during the summer of 1999 in Finland
Authors: PERKO-MÄKELÄ P. , HAKKINEN M. , HONKANEN-BUZALSKI T. , HÄNNINEN M.-L.
Published: September 2002

In order to determine the prevalence of campylobacter positive broiler flocks in Finland, every flock from all three major slaughterhouses was studied during the period from 1 May to 30 September 1999. Caecal samples were taken in the slaughterhouses from five birds per flock. A total of 1132 broiler flocks were tested and 33 (2.9%) of those were campylobacter positive. Thirty-one isolates were C. jejuni and two isolates were C. coli. Isolates were serotyped for heat-stable antigens (Penner) and genotyped with pulsed-field gel electrophoresis (PFGE). The most common serotypes were serotypes 6, 7, 12 and 4-complex. Together with SmaI and KpnI patterns there were 18 different PFGE genotypes. Simultaneous monitoring of chicken flocks and typing of the isolates produced data which can be used to study the epidemiology of campylobacters in chicken as well as their role in human infections.
Hypoxia Does Not Activate ATP‐Sensitive K+ Channels in Arteriolar Muscle Cells
Authors: Jackson William F.
Published: September 2002

Objective: To test the hypothesis that hypoxia activates ATP‐sensitive K+ (KATP) channels in cremasteric arteriolar muscle cells, resulting in membrane hyperpolarization and inhibition of norepinephrine‐induced contraction. Methods: Arteriolar muscle cells were isolated enzymatically from second‐ and third‐order arterioles that were surgically removed from hamster cremaster muscles. The effects of hypoxia (PO2 = 12–15 mm Hg) were then examined on norepinephrine‐induced contraction, membrane currents, and membrane potential in these cells at room temperature. Whole‐cell currents and membrane potential were recorded using the perforated patch technique. Results: Hypoxia (12–15 mm Hg PO2) reversibly inhibited norepinephrineinduced contraction to 52 ± 6% of the response in normoxic solutions (156 mm Hg, n = 12 digests, p < 0.05). These effects of hypoxia could be prevented by superfusion of the cells with either solutions containing the KATP channel antagonist glibenclamide (1 µM) or solutions containing 35 mM K+ to reduce the electrochemical gradient for K+ diffusion. Cromakalim, an activator of KATP channels, also inhibited norepinephrine‐induced contraction to a similar extent as hypoxia, and in a glibenclamide and 35 mM K+‐sensitive manner. These results are consistent with the KATP channel hypothesis. In contrast, hypoxia had no effect on estimated whole‐cell membrane conductance between −40 and −90 mV in voltage‐clamp experiments; on holding current measured at −60 mV in cells superfused with 143 mM K+ under voltage‐clamp conditions; or on membrane potential in current‐clamp experiments, despite positive effects of cromakalim in all three protocols. These electrophysiological data lead to rejection of the hypothesis that hypoxia activates KATP channels. Conclusions: Hypoxia inhibits norepinephrine‐induced contraction of cremasteric arteriolar muscle cells by a mechanism that does not involve KATP channels. It is speculated that the inhibitory effects of glibenclamide and 35 mM K+ on the effects of hypoxia on contraction resulted from depolarization induced by these treatments rather than specific inhibition of KATP channels.
Cerebral responses to pain in patients suffering acute post‐dental extraction pain measured by positron emission tomography (PET)
Authors: Derbyshire Stuart W.G. , Jones Anthony K.P. , Collins Mary , Feinmann Charlotte , Harris Malcolm
Published: September 2002

Previous studies with normal volunteers have demonstrated distributed cortical responses to experimental heat pain within a network of structures. The network includes the insula, anterior cingulate, prefrontal, inferior parietal and somatosensory cortices. Patients suffering from chronic nociceptive pain following rheumatoid arthritis (RA) have shown damped central responses to experimental heat pain applied to the back of the right hand. In this study of patients with acute, left‐sided, post‐molar‐extraction (surgical) pain, we assessed the cortical responses to experimental heat pain, applied to the back of the right hand, using positron emission tomography (PET), and compared the responses with a previously reported control group and the RA group. In response to the experimental heat pain, the surgical group indicated significantly increased regional cerebral blood flow in the prefrontal cortex [Brodman's area (BA) 44] ipsilateral to the heat stimulus. Contralateral increases were detected in the putamen and transverse temporal gyrus (BA 40/41/42) with bilateral increases in the insular cortex. Compared to the control and RA group, there were significantly reduced responses in the anterior cingulate (BA 24), pre‐frontal medial, and orbito‐frontal (BA 9/10/32/47) cortices. These results suggest that relatively discrete regions of the cerebral cortex are responsible for acute nociceptive processing during an acute inflammatory episode. The reduced frontal and anterior cingulate responses to the experimental heat pain (applied to the right hand) during acute inflammatory pain (left jaw) illustrates cortical modulation of nociceptive processing that may be related to non‐somatotopic, bilateral, nociceptive inputs to these areas.
Validation of the German version of the Fear‐Avoidance Beliefs Questionnaire (FABQ)
Authors: Pfingsten Michael , Kröner‐Herwig Birgit , Leibing Eric , Kronshage Uta , Hildebrandt Jan
Published: September 2002

Fearful avoidance of physical activities is a major factor in low back pain (LBP) and disability. In 1993 Waddell et al. developed the Fear‐Avoidance Beliefs Questionnaire (FABQ) focusing on patients’ beliefs about how physical activity and work affect LBP. The focus of our study was to analyse and validate the German version of the FABQ. Three‐hundred and two consecutive LBP outpatients participating on a functional restoration programme filled in the FABQ. Factor analysis yielded three factors which accounted for nearly 65% of the total variance of the questionnaire. Whereas the factor ‘physical activity’ (8.9% of the variance) remained the same as in the English version, the second factor of the original version split into two: one related to, ‘work as cause of pain’ (43.4% of the variance) and the other to patients’ assumptions of their probable return to work (11.8% of the variance). Both work‐related subscales showed a good internal consistency (α =0.89, resp. α =0.94), whereas the consistency of the subscale 3 ‘physical activity’ was only modest (α =0.64). Test–re‐test reliability score was fair to good for the whole scale (r =0.87;n =30). Regression analysis demonstrated that fear‐avoidance beliefs account for the highest proportion of variance (35%) regarding disability in activities of daily living and work loss. Patients out of work demonstrated more fear‐avoidance beliefs in comparison to those who were still working. It can be concluded that the German version of the FAQB is a reliable and valid instrument, but it shows a different factor structure from the original English version. The FABQ has been proven to identify patients with maladaptive beliefs which have to be focused on in proper treatment.
The development and validation of a Greek version of the short‐form McGill Pain Questionnaire
Authors: Georgoudis George , Watson Paul J. , Oldham Jacqueline A.
Published: September 2002

Background: The short form of the McGill Pain Questionnaire (SFMPQ) is a widely used instrument for assessing the quality of pain where use of the full form is not possible. To date however, this instrument has not been translated into the Greek language.

Aims: It is the aim of this study to validate an adopted Greek version of the short form of the McGill Pain Questionnaire.

Methods: A systematic translation procedure was followed before development of the final version. Sixty spinal and osteoarthritis chronic musculoskeletal pain patients completed the questionnaire. A large percentage of the subjects (43%) was of elementary educational level.

Results: The analysis of the results indicated that an internally consistent (Cronbach’s α =0.71) and content valid (all 15 descriptors were used at least by the 33% of the subjects) instrument has been developed. It has been shown to be suitable, easy to understand and administer for this sample of chronic musculoskeletal patients.

Conclusions: A Greek version of the SFMPQ (the GR‐SFMPQ) has been constructed which has the properties of internal validity and consistency. It is easy to administer, easy to understand even for an elementary educational level and it is capable of describing multidimensionally the pain experience of chronic musculoskeletal pain patients.
Age‐related changes in nociception and effect of morphine in the Lou rat
Authors: Jourdan D. , Boghossian S. , Alloui A. , Veyrat‐Durebex C. , Coudore M. A. , Eschalier A. , Alliot J.
Published: September 2002

Little is known about how the ageing process affects pain sensitivity and a relevant animal model is therefore required. The effect of age on pain reactivity in animals has been investigated by several experimenters but the results are conflicting. Four groups of male and female Lou/C/Jall rats (4–29 months old) were used for our study. Four pain tests based on evaluation of reflex or more integrated behaviours after a thermal (tail immersion test) or mechanical (paw pressure test and von Frey test) stimulation were used. With mechanical stimulus, a significant decrease in the pain threshold across age was observed, females were more sensitive than males. This increase in nociceptive sensitivity to mechanical stimulation was more pronounced on integrated behaviours (struggle reaction) than on withdrawal reflex. An age‐related increase in sensitivity was found on von Frey test. No effect on the latency of reflex induced by thermal stimulation was observed. In addition, a decrease in the spontaneous motor activity during exploration was observed across ageing; this effect was more marked for the females. The effect of morphine at doses of 1, 3 and 9 mg/kg (s.c.) decreased in intensity across ageing. These data demonstrate the need to use (1) various noxious stimuli because differences were observed in the modification of pain reactivity according to the nature of the stimulus; (2) various pain parameters and particularly integrated behaviours; (3) several age groups. In addition, Lou/C/Jall rat could be a useful model for studying of effect of age on pain.