bluuebunny/crossref_metadata_2025 huggingface dataset:
“Plate‐like” subsidence of the East Pacific Rise–South Pacific superswell system
Authors: Hillier J. K. , Watts A. B.
Published: October 2004

In previous studies the removal of small‐scale features such as seamounts and oceanic islands from bathymetry has revealed a large and unusually shallow region in the South Pacific Ocean, which, at 3000 km wide and up to 1 km high, has been dubbed a “superswell.” These studies use statistical techniques based on finding the modal depth of the bathymetry. Such an analysis, however, does not completely isolate these features, or their associated oceanic plateaus and localized hot spot swells, from the ridge‐generated regional bathymetry upon which they are superimposed. Accordingly, a technique is required that passes beneath topographic constructs rather than through them, as is the tendency of the mean, median, or mode. We have developed an algorithm, MiMIC, that reproducibly removes all these features and reveals the large‐scale bathymetric trends in a manner based upon and consistent with manual interpretation. Application of the algorithm to bathymetry data in the southwest Pacific shows that the depth anomaly with respect to a cooling plate model changes steadily from being too deep at the East Pacific Rise (EPR) crest to being too shallow at the superswell. The largest shallow anomaly of 712 ± 66 m occurs at 98 Ma, not 1300 m at 65 Ma, as has been previously suggested. Most significantly, the superswell appears to be part of a large‐scale, “plate‐like,” subsidence that extends to the EPR crest, rather than an isolated shallowing that reverses the subsidence and causes uplift. We interpret the plate‐like subsidence as due in part to cooling of the oceanic lithosphere and in part to a lateral temperature gradient in the underlying asthenosphere which is maintained by the flow of relatively hot material from beneath the superswell toward the relative cold material beneath the EPR. The best fit model implies a lateral temperature gradient of 0.014°C km−1 and is in general accord with the available effective elastic thickness, crustal thickness, heat flow, and seismic tomography data.
Constructing the crust along the Galapagos Spreading Center 91.3°–95.5°W: Correlation of seismic layer 2A with axial magma lens and topographic characteristics
Authors: Blacic T. M. , Ito G. , Canales J. P. , Detrick R. S. , Sinton J.
Published: October 2004

Multichannel seismic reflection data are used to infer crustal accretion processes along the intermediate spreading Galapagos Spreading Center. East of 92.5°W, we image a magma lens beneath the ridge axis that is relatively shallow (1.0–2.5 km below the seafloor) and narrow (∼0.5–1.5 km, cross‐axis width). We also image a thin seismic layer 2A (0.24–0.42 km) that thickens away from the ridge axis by as much as 150%. West of 92.7°W, the magma lens is deeper (2.5–4.5 km) and wider (0.7–2.4 km), and layer 2A is thicker (0.36–0.66 km) and thickens off axis by <40%. The positive correlation between layer 2A thickness and magma lens depth supports the interpretation of layer 2A as the extrusive volcanic layer with thickness controlled by the pressure on the magma lens and its ability to push magma to the surface. Our findings also suggest that narrower magma lenses focus diking close the ridge axis such that lava flowing away from the ridge axis will blanket older flows and thicken the extrusive crust off axis. Flow of lava away from the ridge axis is probably promoted by the slope of the axial bathymetric high, which is largest east of 92.5°W. West of ∼94°W the “transitional” axial morphology lacks a prominent bathymetric high and layer 2A no longer thickens off axis. We detect no magma lens west of 94.7°W where a small axial valley appears. The above changes can be linked to the westward decrease in the magma and heat flux associated with the fading influence of the Galapagos hot spot on the Galapagos Spreading Center.
Ductile Precambrian fabric control of seismic anisotropy in the Açu dam area, northeastern Brazil
Authors: do Nascimento Aderson F. , Bezerra Francisco H. R. , Takeya Mario K.
Published: October 2004

In the João Câmara area, NE Brazil, seismic anisotropy has been interpreted as the result of either Precambrian ductile fabric or stress‐aligned, fluid‐filled grain boundary caused by high pore fluid pressures. The first interpretation is based on the fact that the direction of the fastest S wave splitting agrees with the north‐south trending Precambrian fabric. The second interpretation, related to the extensive dilatancy anisotropy (EDA), is based on the stress field orientation and on the assumption that the pore fluid pressure in the region is high enough to modify microcrack distribution and cause S wave polarization to become parallel to the north‐south oriented minimum horizontal stress SHmin. Here we address this question by investigating this ambiguity. We have analyzed the seismicity in the Açu dam area, ∼150 km west of João Câmara, over a 3‐year period. In the Açu area, the northeast‐southwest trending ductile Precambrian fabric is not parallel or orthogonal to the east‐west trending, maximum horizontal stress SHmax. We combined the interpretation of fastest S wave polarizations, their time delays, and fabric orientation measured in the field with side‐looking airborne radar imagery taken before the lake impoundment. Thus we discriminate between (1) stress‐aligned fluid‐filled cracks, (2) high pore pressure fluids modifying the microcrack distribution and therefore causing 90° flips, and (3) fabric or “paleostrain” as causes for the observed S wave anisotropy. Our main result indicates that the direction of the fastest S wave polarization in the Açu dam area agrees with the northeast‐southwest trending fabric (∼N40°E). EDA or 90°Flips control of seismic anisotropy, if occurring in Açu, have minor effects.
Spring phytoplankton photosynthesis, growth, and primary production and relationships to a recurrent coastal sediment plume and river inputs in southeastern Lake Michigan
Authors: Lohrenz Steven E. , Fahnenstiel Gary L. , Millie David F. , Schofield Oscar M. E. , Johengen Tom , Bergmann Trisha
Published: October 2004

A recurrent coastal sediment plume (RCP) is an episodic event in the southern basin of Lake Michigan that typically coincides with the spring diatom bloom. Strong winter storm activity during El Niño conditions in 1998 resulted in a large and intense RCP event. Consistently higher values of the light‐saturated rate of photosynthesis, PmaxB, were observed in spring 1998 compared to 1999 and 2000. Higher values of PmaxB in 1998 appeared to be related to increased availability of phosphorus, as evidenced by significant correlations of PmaxB with soluble reactive phosphorus (SRP). Light‐saturated growth rates were also significantly correlated with SRP concentrations. These findings were consistent the view that the RCP was a source of enrichment. However, incubation experiments involving lake water enriched with sediments showed relatively small increases in growth and photosynthetic parameters, while enrichments with river water exhibited elevated rates. This result, along with increased levels of river discharge in 1998 and high levels of dissolved phosphorus in river water, supported the view that riverine inputs rather than the RCP were responsible for the higher photosynthetic parameters and growth seen for coastal margin assemblages. Despite the higher levels of PmaxB in 1998, model analyses revealed that reduced light availability resulting from the intense RCP event constrained phytoplankton growth rates and primary production during this season and apparently suppressed the development of a typical spring bloom. These findings indicate a potential for reduced ecosystem productivity in response to extreme storm events, the frequency of which may increase with projected long‐term climate changes.
Bifurcation of synchronous oscillations into torus in a system of two reciprocally inhibitory silicon neurons: Experimental observation and modeling
Authors: Bondarenko Vladimir E. , Cymbalyuk Gennady S. , Patel Girish , DeWeerth Stephen P. , Calabrese Ronald L.
Published: October 2004

Oscillatory activity in the central nervous system is associated with various functions, like motor control, memory formation, binding, and attention. Quasiperiodic oscillations are rarely discussed in the neurophysiological literature yet they may play a role in the nervous system both during normal function and disease. Here we use a physical system and a model to explore scenarios for how quasiperiodic oscillations might arise in neuronal networks. An oscillatory system of two mutually inhibitory neuronal units is a ubiquitous network module found in nervous systems and is called a half-center oscillator. Previously we created a half-center oscillator of two identical oscillatory silicon (analog Very Large Scale Integration) neurons and developed a mathematical model describing its dynamics. In the mathematical model, we have shown that an in-phase limit cycle becomes unstable through a subcritical torus bifurcation. However, the existence of this torus bifurcation in experimental silicon two-neuron system was not rigorously demonstrated or investigated. Here we demonstrate the torus predicted by the model for the silicon implementation of a half-center oscillator using complex time series analysis, including bifurcation diagrams, mapping techniques, correlation functions, amplitude spectra, and correlation dimensions, and we investigate how the properties of the quasiperiodic oscillations depend on the strengths of coupling between the silicon neurons. The potential advantages and disadvantages of quasiperiodic oscillations (torus) for biological neural systems and artificial neural networks are discussed.
Heating effect on steady and unsteady horizontal laminar flow of air past a circular cylinder
Authors: Shi J.-M. , Gerlach D. , Breuer M. , Biswas G. , Durst F.
Published: October 2004

Extensive numerical experiments were carried out to study the effect of cylinder heating on the characteristics of the flow and heat transfer in a two-dimensional horizontal laminar flow of air past a heated circular cylinder for the range of Reynolds numbers 0.001⩽Re⩽170. The fluid was treated as incompressible (density is independent of the pressure) while the variation of the fluid properties with temperature was taken into account. By including the transient density term of the continuity equation, which was neglected in a previous study by Lange, Durst, and Breuer [Int. J. Heat Mass Transfer 41, 3409 (1998)], we were able to predict correctly the vortex shedding frequency at various overheat ratios using an incompressible flow solver. The effect of dynamic viscosity and density variations on the flow dynamics occurring with the cylinder heating was analyzed separately. Another emphasis of the work was to investigate the physical mechanism behind the “effective Reynolds number” concept widely applied in engineering correlations. Similarity was discovered for the distribution of the local dimensionless viscous force, the vorticity and the Nusselt number at the cylinder surface and the pressure force in the rear part of the cylinder. Two characteristic temperatures, Teff=T∞+0.28(TW−T∞) for the flow dynamics and Tf=T∞+0.5(TW−T∞) for the heat transfer, were identified.
On the simulation of particle trajectories in turbulent flows
Authors: Reynolds A. M. , Lo Iacono G.
Published: October 2004

A different class of stochastic model, comprising of the Langevin equation with a random time scale, for the simulation of fluid velocities along particle trajectories in high Reynolds-number turbulent flows is formulated. These velocities are neither purely Lagrangian nor purely Eulerian in character. The distribution of time scales is chosen to ensure that the modeled form of the fluid-velocity structure function and spectral functions are compatible with Kolmogorov similarity scaling and with the scaling analysis of Fung, Hunt, and Perkins [Proc. R. Soc. London, Ser. A 459, 445 (2003)]. It is shown that the model accounts naturally for the crossing trajectory effect and integral time scales are compatible with the much used parameterizations advocated by Csanady [J. Atmos. Sci. 20, 201 (1963)] and by Frenkiel [Adv. Appl. Mech. 3, 61 (1953)]. Model predictions for particle dispersion in grid generated turbulence are shown to be in close accord with the experimental data of Snyder and Lumley [J. Fluid Mech. 48, 41 (1971)].
Scalar decay in two-dimensional chaotic advection and Batchelor-regime turbulence
Authors: Fereday D. R. , Haynes P. H.
Published: October 2004

This paper considers the decay in time of an advected passive scalar in a large-scale flow. The relation between the decay predicted by “Lagrangian stretching theories,” which consider evolution of the scalar field within a small fluid element and then average over many such elements, and that observed at large times in numerical simulations, associated with emergence of a “strange eigenmode” is discussed. Qualitative arguments are supported by results from numerical simulations of scalar evolution in two-dimensional spatially periodic, time aperiodic flows, which highlight the differences between the actual behavior and that predicted by the Lagrangian stretching theories. In some cases the decay rate of the scalar variance is different from the theoretical prediction and determined globally and in other cases it apparently matches the theoretical prediction. An updated theory for the wavenumber spectrum of the scalar field and a theory for the probability distribution of the scalar concentration are presented. The wavenumber spectrum and the probability density function both depend on the decay rate of the variance, but can otherwise be calculated from the statistics of the Lagrangian stretching history. In cases where the variance decay rate is not determined by the Lagrangian stretching theory, the wavenumber spectrum for scales that are much smaller than the length scale of the flow but much larger than the diffusive scale is argued to vary as k−1+ρ, where k is wavenumber, and ρ is a positive number which depends on the decay rate of the variance γ2 and on the Lagrangian stretching statistics. The probability density function for the scalar concentration is argued to have algebraic tails, with exponent roughly −3 and with a cutoff that is determined by diffusivity κ and scales roughly as κ−1/2 and these predictions are shown to be in good agreement with numerical simulations.
Higher modes of the mixed buoyant-Marangoni unstable convection originated from a droplet dissolving in a liquid/liquid system with miscibility gap
Authors: Lappa Marcello , Piccolo Chiara
Published: October 2004

Some phenomena, never observed before, concerning a system composed by two organic-liquid bicomponent phases with a miscibility gap, used as transparent surrogates for immiscible metal alloys, are discussed and elucidated in the framework of experimental analyses and numerical simulations. It is shown that a single dissolving droplet at the bottom of a test cell behaves as an intriguing pattern-forming dynamical system leading to a wealth of different spatiotemporal modes of convection when the imposed temperature gradient is increased. The last part of the analysis is devoted to comparison with other similar phenomena (the flow instability pertaining to the Marangoni convection around bubbles surrounded by a liquid heated from above, and the case of rising buoyant jets), showing analogies and differences. Such a comparison is also used as a means to focus on the intrinsic nature of the present instability.
Probing the instabilities in the dynamics of helical fragments from mouse PrP
C
Authors: Dima Ruxandra I. , Thirumalai D.
Published: October 2004

The first step in the formation of the protease resistant form (PrP
Sc
) of prion proteins involves a conformational transition of the monomeric cellular form of PrP
C
to a more stable aggregation prone state PrP
C*
. A search of PDBselect and
Escherichia coli
and yeast genomes shows that the exact pattern of charges in helix 1 (H1) is rare. Among the 23 fragments in PDBselect with the pattern of charges that match H1, 83% are helical. Mapping of the rarely found (in
E. coli
and yeast genomes) hydrophobicity patterns in helix 2 (H2) to known secondary structures suggests that the PrP
C
→ PrP
C*
transition must be accompanied by alterations in conformations in second half of H2. We probe the dynamical instability in H1 and in the combined fragments of H2 and helix 3 (H3) from mPrP
C
(H2+H3), with intact disulfide bond, using all atom molecular dynamics (MD) simulations totaling 680 ns. In accord with recent experiments, we found that H1 is helical, whereas the double mutant H1[D147A–R151A] is less stable, implying that H1 is stabilized by the (
i
,
i
+ 4) charged residues. The stability of H1 suggests that it is unlikely to be involved in the PrP
C
→ PrP
C*
transition. MD simulations of H2+H3 shows that the second half of H2 (residues 184–194) and parts of H3 (residues 200–204 and 215–223) undergo a transition from α-helical conformation to a β and/or random coil state. Simulations using two force fields (optimized potentials for liquid simulations and
charmm
) give qualitatively similar results. We use the MD results to propose tentative structures for the PrP
C*
state.
Development of hydrocephalus in mice lacking SOCS7
Authors: Krebs Danielle L. , Metcalf Donald , Merson Tobias D. , Voss Anne K. , Thomas Tim , Zhang Jian-Guo , Rakar Steven , O'Bryan Moira K. , Willson Tracy A. , Viney Elizabeth M. , Mielke Lisa A. , Nicola Nicos A. , Hilton Douglas J. , Alexander Warren S.
Published: October 2004

SOCS7 is a member of the suppressor of cytokine signaling (SOCS) family of proteins (SOCS1-SOCS7 and CIS). SOCS proteins are composed of an N-terminal domain of variable length, a central Src homology 2 domain, and a C-terminal SOCS box. Biochemical and genetic studies have revealed that SOCS1, SOCS2, SOCS3, and CIS play an important role in the termination of cytokine and growth factor signaling. However, the biological actions of other SOCS proteins are less well defined. To investigate the physiological role of SOCS7, we have used gene targeting to generate mice that lack expression of the
Socs7
gene.
Socs7
-/-
mice were born in expected numbers, were fertile, and did not exhibit defects in hematopoiesis or circulating glucose or insulin concentrations. However,
Socs7
-/-
mice were 7-10% smaller than their wild-type littermates, and within 15 weeks of age ≈50% of the
Socs7
-/-
mice died as a result of hydrocephalus that was characterized by cranial distortion, dilation of the ventricular system, reduced thickness of the cerebral cortex, and disorganization of the subcommissural organ.
In situ
hybridization studies revealed prominent expression of
Socs7
in the brain, suggestive of an important functional role of SOCS7 in this organ.
Task Rule-Congruency and Simon-Like Effects in Switching between Spatial Tasks
Authors: Meiran Nachshon
Published: October 2004

In task switching, a response indicated as correct by both task rules is executed more quickly than one for which the rules disagree. This rule-congruency, so far demonstrated unequivocally only in nonspatial tasks, shows that the currently irrelevant task set is kept active. However, in spatial task-switching, rule-congruency could potentially reflect a preexperimental tendency that contributes to a Simon-like effect. In the present study, participants switched between RIGHT–LEFT and UP–DOWN tasks with either a standard key arrangement (e.g., upper key = UP) or a mapping-reversed arrangement (e.g., up = DOWN), which reverses the direction of the potential Simon-like effect but leaves potential rule-congruency effects unchanged. Mapping-reversal did not modulate any other effect, including rule-congruency, and therefore indicated rule-congruency unequivocally. Finally, implications concerning generality versus domain specificity of control processes in task switching are discussed.
Assessment of coronary arterial stents by multislice-CT angiography
Authors: Maintz D. , Gride M. , Fallenberg E. M. , Heindel W. , Fischbach R.
Published: October 2004

Purpose: To assess patency and lumen visibility of coronary artery stents by multislice-CT angiography (MSCTA) in comparison with conventional coronary angiography as the standard of reference.

Material and Methods: 47 stents of 13 different types were evaluated in 29 patients. MSCTA was performed on a 4-slice scanner with a standard coronary protocol (detector collimation 4 × 1 mm; table feed 1.5 mm/rotation, 400 mAs, 120 kV). Image evaluation was performed by two readers who were blinded to the reports from the catheter angiography. MIP reconstructions were evaluated for image quality on a 4-point scale (1 = poor, 4 = excellent) and stent patency (contrast distal to the stent as an indirect patency sign). Axial images and multiplanar reformations through the stents were used for assessment of stent lumen visibility (measurement of the visible stent lumen diameter) and detection of relevant in-stent stenosis (≥50%).

Results: Image quality was fair to good on average (score 2.64 ± 1.0) and depended on the heart rate (heart rate 45–60: average score 3.2, heart rate 61–70: average score 2.8, heart rate >71: average score 1.4). Thirty-seven stents were correctly classified as patent, 1 was correctly classified as occluded and 9 stents were not assessible due to insufficient image quality because of triggering artifacts. Parts of the stent lumen could be visualized in 30 cases. On average, 20–40% of the stent lumen diameter was visible. Twenty-five stents were correctly classified as having no stenosis, 1 was falsely classified as stenosed, 1 was correctly classified as occluded. In 20 stents lumen visibility was not sufficient for stenosis evaluation.

Conclusion: Although the stent lumen may be partly visualized in most stents, a reliable evaluation of in-stent stenoses does not seem practical by 4-slice MSCT. Nevertheless, for stent patency evaluation, MS-CTA might provide valuable clinical information. With submillimeter MSCT (e.g., 16-slice scanners) and more sophisticated reconstruction algorithms, further improvements may be expected.
Comparison of indirect CsI/a:Si and direct a: SE digital radiography: An assessment of contrast and detail visualization
Authors: Fischbach F. , Freund T. , Pech M. , Werk M. , Bassir C. , Stoever B. , Felix R. , Ricke J.
Published: October 2004

Purpose: To assess and quantify the image quality at two dose levels for an amorphous Silicon (a:Si) Cesium Iodide (CsI) flat panel system compared with a direct amorphous Selenium (a:Se) digital radiography system.

Material and Methods: A contrast detectability test was performed employing the CDRAD-phantom at mAs-values leading to approximately equal phantom entrance doses of 41.4, 57.9, 75.1 and 120.8 µGy for the a:Se and 39.9, 58.4, 75.6 and 117.9 µGy for the CsI system. Images were presented to 4 independent observers. For quantitative comparison, the image quality figure (IQF) was calculated. Statistical analysis was performed using Pearson's correlation and the Wilcoxon test. A ROC-analysis was performed employing the TRG-phantom in a high- and a low-dose setting leading to entrance doses of 126.2 and 35 µGy for the direct, and 125.9 and 34.4 µGy for the indirect system. Statistical significance was evaluated using the Wilcoxon test

Results: The flat panel a:Si digital system provided superior results compared with the a:Se drum digital system with respect to low-dose settings for CDRAD-phantom and ROC-analysis, ensuring a better image quality with respect to contrast and detail detectability. Higher-dose settings provided similar results for both systems.

Conclusion: Image quality of a:Si flat panel digital radiography proved to be superior to a:Se drum digital radiography using low-dose settings. If the primary target is dose reduction indirect flat panel technology should be used.
MR findings of desmoplastic cerebral astrocytoma of infancy: A case report
Authors: Kim J.-H. , Kim I.-O. , Kim W. S. , Kim K. H. , Park C. M. , Yeon K.-M.
Published: October 2004

Desmoplastic cerebral astrocytoma of infancy (DCAI) presents as a large supratentorial mass consisting of a central cystic component and an enhancing solid component associated with peripheral dural attachment. We report the unusual MR findings of a DCAI that differed from previously reported cases in terms of the presence of calcification, which is not considered a feature of this tumor, and the absence of an enhancing peripheral dural component.
Cushing's disease and sphenoidal aspergilloma: A case report
Authors: Gondim J. , Quidute A. R. , Maciel M. , Carneiro A. , Taveres C. , Fontenele E. , Montenegro R.
Published: October 2004

A rare case of isolated sphenoid sinus aspergillosis in a 51-year-old patient, with the clinical and laboratory diagnosis of Cushing's disease but no radiologically confirmed tumor is presented. The patient made a complete recovery after treatment. The radiologic findings and the management of this potential disease are discussed.
Sclerosing stromal tumor of the ovary with torsion: MRI features
Authors: Yerli H. , Agildere A. M. , Bilezikci B. , Karadeli E.
Published: October 2004

Sclerosing stromal tumors are rare benign ovarian neoplasms that are usually diagnosed in the second or third decade of life. Most patients with these tumors present with menstrual irregularities and pelvic pain. We present the magnetic resonance imaging (MRI) findings of a left ovarian sclerosing stromal tumor with torsion that was located in the right parauterine area, and discuss the differential diagnosis for this entity based on MRI findings. In this case, MRI demonstrated a well-defined, predominantly solid mass with a pseudolobular pattern, and showed a shift of the uterus to the left. The surgical and histopathologic aspects of the case are also described.
Does high income buffer the association between adverse working conditions and ill health?
Authors: Hemström Örjan
Published: October 2004

Aim: A study was undertaken to analyse the possible interaction between work environment and income for the probability of self-rated health being less than good. Methods: Data from the Swedish Survey of Living Conditions for the years 1998 and 1999 were analysed. Employed 20- to 64-year-olds with a registered wage were included (n=5982). The synergy index (SI) was applied, using odds ratios from logistic regressions for men, women, and all. Low and high levels of physical demands, decision authority, skill discretion and psychological demands were separately combined with low- and high-wage income (median split). Full-time work and four sociodemographic factors were controlled for. Results: Significant synergy was found for women when they were exposed to low income and a low level of skill discretion (SI=1.46 [1.01—2.13]), although this was attenuated by education level (SI=1.47 [0.96—2.25]). In general (both sexes), poor health caused by low income and unfavourable work is additive rather than multiplicatively exaggerating the risk among the jointly exposed. Conclusion: Work exposures in the form of high physical load, low levels of decision authority and skill discretion, or a high level of psychological demands were significantly related to poor health also when income was high, suggesting that high income does not seem to buffer the detrimental effects of adverse working conditions. As nearly half of employed women were found to be in circumstances marked by synergy, it seems a relevant public health issue to improve these women's conditions at work, by simultaneously increasing, for example, job variety and wages.
Non-additivity for triple point numbers on the connected sum of surface-knots
Authors: Satoh Shin
Published: October 2004

Any surface-knot

F
F

in 4-space can be projected into 3-space with a finite number of triple points, and its triple point number,

t

(
F
)

\textrm {t}(F)

, is defined similarly to the crossing number of a classical knot. By definition, we have

t

(

F
1

#

F
2

)
≤

t

(

F
1

)
+

t

(

F
2

)

\textrm {t}(F_1\# F_2)\leq \textrm {t}(F_1)+\textrm {t}(F_2)

for the connected sum. In this paper, we give infinitely many pairs of surface-knots for which this equality does not hold.
The single-valued extension property for bilateral operator weighted shifts
Authors: Bourhim A. , Chidume C.
Published: October 2004

In this paper, we give necessary and sufficient conditions for a bilateral operator weighted shift to enjoy the single-valued extension property.
The Cayley transform of linear relations
Authors: Miranda Mercedes , Labrousse Jean-Philippe
Published: October 2004

This paper extends the definition of the Cayley transform defined for symmetric linear operators to any linear relation.
Tietze extension theorem for Hilbert 𝐶*-modules
Authors: Bakić Damir
Published: October 2004

We prove the following generalization of the noncommutative Tietze extension theorem: if

V
V

is a countably generated Hilbert

C
∗

C^*

-module over a

σ
\sigma

-unital

C
∗

C^*

-algebra, then the canonical extension

Φ
¯

\overline {\Phi }

of a surjective morphism

Φ
:
V
→
W

\Phi : V \rightarrow W

of Hilbert

C
∗

C^*

-modules to extended (multiplier) modules,

Φ
¯

:

V
d

→

W
d

\overline {\Phi } : V_d \rightarrow W_d

, is also surjective.
The number of planar central configurations for the 4–body problem is finite when 3 mass positions are fixed
Authors: Alvarez Martha , Corbera Montserrat , Delgado Joaquin , Llibre Jaume
Published: October 2004

In the

n
n

–body problem a central configuration is formed when the position vector of each particle with respect to the center of mass is a common scalar multiple of its acceleration vector. Lindstrom showed for

n
=
3

n=3

and for

n
>
4

n>4

that if

n
−
1

n-1

masses are located at fixed points in the plane, then there are only a finite number of ways to position the remaining

n
n

th mass in such a way that they define a central configuration. Lindstrom leaves open the case

n
=
4

n=4

. In this paper we prove the case

n
=
4

n=4

using as variables the mutual distances between the particles.
A note on meromorphic operators
Authors: Schmoeger Christoph
Published: October 2004

Let

X
X

be a complex Banach space and

T
T

a bounded linear operator on

X
X

.

T
T

is called meromorphic if the spectrum

σ
(
T
)

\sigma (T)

of

T
T

is a countable set, with

0
0

the only possible point of accumulation, such that all the nonzero points of

σ
(
T
)

\sigma (T)

are poles of

(
λ
I
−
T

)

−
1

(\lambda I-T)^{-1}

. By means of the analytical core

K
(
T
)

K(T)

we give a spectral theory of meromorphic operators. Our results are a generalization of some results obtained by Gong and Wang (2003).
Lagrange multipliers for functions derivable along directions in a linear subspace
Authors: An Le , Du Pham , Duc Duong , Tuoc Phan Van
Published: October 2004

We prove a Lagrange multipliers theorem for a class of functions that are derivable along directions in a linear subspace of a Banach space where they are defined. Our result is available for topological linear vector spaces and is stronger than the classical one even for two-dimensional spaces, because we only require the differentiablity of functions at critical points. Applying these results we generalize the Lax-Milgram theorem. Some applications in variational inequalities and quasilinear elliptic equations are given.
An improved Mordell type bound for exponential sums
Authors: Cochrane Todd , Pinner Christopher
Published: October 2004

For a sparse polynomial
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="f left-parenthesis x right-parenthesis equals sigma-summation Underscript i equals 1 Overscript r Endscripts a Subscript i Baseline x Superscript k Super Subscript i Baseline element-of double-struck upper Z left-bracket x right-bracket">

f
(
x
)
=

∑

i
=
1

r

a
i

x

k
i

∈

Z

[
x
]

f(x)=\sum _{i=1}^r a_ix^{k_i}\in \mathbb Z [x]

, with

p
∤

a
i

p\nmid a_i

and

1
≤

k
1

>
⋯
>

k
r

>
p
−
1

1\leq k_1>\cdots >k_r>p-1

, we show that
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartAbsoluteValue sigma-summation Underscript x equals 1 Overscript p minus 1 Endscripts e Superscript 2 pi i f left-parenthesis x right-parenthesis slash p Baseline EndAbsoluteValue less-than-or-equal-to 2 Superscript StartFraction 2 Over r EndFraction Baseline left-parenthesis k 1 midline-horizontal-ellipsis k Subscript r Baseline right-parenthesis Superscript StartFraction 1 Over r squared EndFraction Baseline p Superscript 1 minus StartFraction 1 Over 2 r EndFraction Baseline comma">

|

∑

x
=
1

p
−
1

e

2
π
i
f
(
x
)

/

p

|

≤

2

2
r

(

k
1

⋯

k
r

)

1

r
2

p

1
−

1

2
r

,

\left |\sum _{x=1}^{p-1} e^{2\pi i f(x)/p} \right | \leq 2^{\frac {2}{r}} (k_1\cdots k_r)^{\frac {1}{r^2}}p^{1-\frac {1}{2r}},

\]
thus improving upon a bound of Mordell. Analogous results are obtained for Laurent polynomials and for mixed exponential sums.
On the algebra of functions 𝒞^{𝓀}-extendable for each 𝓀 finite
Authors: Pawłucki Wiesław
Published: October 2004

For each positive integer

l
l

we construct a

C

l

\mathcal C^l

-function of one real variable, the graph

Γ
\Gamma

of which has the following property: there exists a real function on

Γ
\Gamma

which is

C

k

\mathcal C^k

-extendable to

R

2

\mathbb {R}^2

, for each

k
k

finite, but it is not

C

∞

\mathcal C^{\infty }

-extendable.
Positive scalar curvature for manifolds with elementary abelian fundamental group
Authors: Botvinnik Boris , Rosenberg Jonathan
Published: October 2004

The statement often called the Gromov-Lawson-Rosenberg Conjecture asserts that a manifold with finite fundamental group should admit a metric of positive scalar curvature except when theKO∗KO_*-valued index of some Dirac operator with coefficients in a flat bundle is non-zero. We prove spin and oriented non-spin versions of this statement for manifolds (of dimension≥5\ge 5) with elementary abelian fundamental groupsπ\pi, except for “toral” classes, and thus our results are automatically applicable once the dimension of the manifold exceeds the rank ofπ\pi. The proofs involve the detailed structure ofBP∗(Bπ)BP_*(B\pi ), as computed by Johnson and Wilson.
Normal Biogenesis and Cycling of Empty Synaptic Vesicles in Dopamine Neurons of Vesicular Monoamine Transporter 2 Knockout Mice
Authors: Croft Benjamin G. , Fortin Gabriel D. , Corera Amadou T. , Edwards Robert H. , Beaudet Alain , Trudeau Louis-Eric , Fon Edward A.
Published: October 2004

The neuronal isoform of vesicular monoamine transporter, VMAT2, is responsible for packaging dopamine and other monoamines into synaptic vesicles and thereby plays an essential role in dopamine neurotransmission. Dopamine neurons in mice lacking VMAT2 are unable to store or release dopamine from their synaptic vesicles. To determine how VMAT2-mediated filling influences synaptic vesicle morphology and function, we examined dopamine terminals from VMAT2 knockout mice. In contrast to the abnormalities reported in glutamatergic terminals of mice lacking VGLUT1, the corresponding vesicular transporter for glutamate, we found that the ultrastructure of dopamine terminals and synaptic vesicles in VMAT2 knockout mice were indistinguishable from wild type. Using the activity-dependent dyes FM1-43 and FM2-10, we also found that synaptic vesicles in dopamine neurons lacking VMAT2 undergo endocytosis and exocytosis with kinetics identical to those seen in wild-type neurons. Together, these results demonstrate that dopamine synaptic vesicle biogenesis and cycling are independent of vesicle filling with transmitter. By demonstrating that such empty synaptic vesicles can cycle at the nerve terminal, our study suggests that physiological changes in VMAT2 levels or trafficking at the synapse may regulate dopamine release by altering the ratio of fillable-to-empty synaptic vesicles, as both continue to cycle in response to neural activity.
Autopoiesis with or without cognition: defining life at its edge
Authors: Bitbol Michel , Luisi Pier Luigi
Published: October 2004

This paper examines two questions related to autopoiesis as a theory for minimal life: (i) the relation between autopoiesis and cognition; and (ii) the question as to whether autopoiesis is the necessary and sufficient condition for life. First, we consider the concept of cognition in the spirit of Maturana and Varela: in contradistinction to the representationalistic point of view, cognition is construed as interaction between and mutual definition of a living unit and its environment. The most direct form of cognition for a cell is thus metabolism itself, which necessarily implies exchange with the environment and therefore a simultaneous coming to being for the organism and for the environment. A second level of cognition is recognized in the adaptation of the living unit to new foreign molecules, by way of a change in its metabolic pattern. We draw here an analogy with the ideas developed by Piaget, who recognizes in cognition the two distinct steps of assimilation and accommodation. While
assimilation
is the equivalent of uptake and exchange of usual metabolites,
accommodation
corresponds to biological adaptation, which in turn is the basis for evolution. By comparing a micro-organism with a vesicle that uptakes a precursor for its own self-reproduction, we arrive at the conclusion that (a) the very lowest level of cognition is the condition for life, and (b) the lowest level of cognition does not reduce to the lowest level of autopoiesis. As a consequence, autopoiesis alone is only a necessary, but not sufficient, condition for life. The broader consequences of this analysis of cognition for minimal living systems are considered.
Role of anti-CD3 in modulation of Th1-type immune response in Shigella dysenteriae infection
Authors: Sinha A K , Bagchi A K
Published: October 2004

A murine model was used to evaluate the role of anti-CD3 in modulating a Th1-type response by restimulation of T-cells after immunization with the 57 kDa immunodominant antigen ofShigella dysenteriae1 outer-membrane proteins (OMPs), followed byShigellainfection after immunization. To observe the effect of anti-CD3, other T-cell cultures were also established following anti-CD1, anti-IL2 and phytohaemagglutinin stimulation. Anti-CD3 stimulation of reconstituted T-cells showed ‘mean’ levels of CD4 and CD25 were enhanced by 34.5 and 31.1 % in immunized mice, which was comparable to 53.2 and 50.7 %, respectively, in challenged-immunized mice, and were dominant over CD8+T-cells. Levels of IL2 generated by anti-CD3-stimulated T-cells of immunized mice were greater than those of unstimulated T-cells and were significantly elevated in challenged-immunized mice. The reactivity of T-cells indicated their complete responsiveness, as anti-CD3 antibody might not inhibit the migration of the macrophages but rather inhibit IL4. These macrophage factors synergistically act with anions towards an activated response, which in turn provokes IL2 secretion with a low degree of internalization of its receptor. Thus, sharing of IL2 to form a high-affinity receptor complex with CD4+T-cells through motive signals suggested a generalized T-cell activation with increased humoral responses. Macrophage migration inhibition factor (MIF) and IL4 responses during anti-CD3 stimulation of immunized mice indicated that the role of anti-CD3 in generation of O−2is due to a synergistic effect by Th1 subsets of Th0 cells. The above findings should have implications for understanding the immunoregulatory role of anti-CD3 associated with 57 kDa antigen in immunoprophylactic measures.
Occurrence of virulence-associated genes in clinical Enterococcus faecalis strains isolated in Londrina, Brazil
Authors: Bittencourt de Marques Elisa , Suzart Sérgio
Published: October 2004

Epidemiological studies have reinforced the importance of Enterococcus faecalis in causing serious infections, and to date, our understanding of how certain virulence factors are involved in the pathogenesis of enterococcal infections is still limited. The aim of the present study was to examine the occurrence of known virulence determinants in a group of E. faecalis strains isolated from different clinical sources in Brazil. A total of 95 E. faecalis strains were investigated for the presence of nine virulence genes including aggA, cylA, cylB, cylM, eep, efaA, enlA, esp and gelE by using PCR. The data showed a relatively wide distribution of the virulence genes among the investigated strains. The clinical strains carried at least one and concomitantly up to as many as eight virulence markers, with two or three being the most common pattern. Most of the strains carried efaA (58.9 %), eep (58.9 %) and esp (57.9 %) genes, whereas the remaining virulence markers were detected in variable percentages ranging from 9.5 to 45 %. Simultaneous presence of virulence markers was observed among clinical strains regardless of their sources. In this study, the efaA
+
esp
+
gelE
+ profile was the virulence genotype most frequently detected among E. faecalis strains. Finally, there was no significant association between virulence markers and clinical sources.
Role of quorum sensing in the pathogenicity of Burkholderia pseudomallei
Authors: Ulrich Ricky L , DeShazer David , Brueggemann Ernst E , Hines Harry B , Oyston Petra C , Jeddeloh Jeffrey A
Published: October 2004

Burkholderia pseudomallei is the causative agent of human and animal melioidosis. The role of quorum sensing (QS) in the in vivo pathogenicity of B. pseudomallei via inhalational exposure of BALB/c mice and intraperitoneal challenge of Syrian hamsters has not been reported. This investigation demonstrates that B. pseudomallei encodes a minimum of three luxI and five luxR homologues that are involved in animal pathogenicity. Mass spectrometry analysis of culture supernatants revealed that wild-type B. pseudomallei and the luxI mutants synthesized numerous signalling molecules, including N-octanoyl-homoserine lactone, N-decanoyl-homoserine lactone, N-(3-hydroxyoctanoyl)-l-homoserine lactone, N-(3-hydroxydecanoyl)-l-homoserine lactone and N-(3-oxotetradecanoyl)-l-homoserine lactone, which was further confirmed by heterologous expression of the B. pseudomallei luxI alleles in Escherichia coli. Mutagenesis of the B. pseudomallei QS system increased the time to death and reduced organ colonization of aerosolized BALB/c mice. Further, intraperitoneal challenge of Syrian hamsters with the B. pseudomallei QS mutants resulted in a significant increase in the LD50. Using semi-quantitative plate assays, preliminary analysis suggests that QS does not affect lipase, protease and phospholipase C biosynthesis/secretion in B. pseudomallei. The findings of the investigation demonstrate that B. pseudomallei encodes multiple luxIR genes, and disruption of the QS alleles reduces animal pathogenicity, but does not affect exoproduct secretion.
Association of atypical enteropathogenic Escherichia coli (EPEC) with prolonged diarrhoea
Authors: Afset Jan E , Bevanger Lars , Romundstad Pål , Bergh Kåre
Published: October 2004

The aim of the present case control study was to investigate the prevalence of atypical enteropathogenic Escherichia coli (EPEC) and its possible role in causing diarrhoea among children < 5 years of age in Norway. Stool specimens received in the laboratory from children with suspected gastroenteritis (n = 251) were, in addition to routine testing, analysed for the presence of EPEC by PCR of the eae, bfpA and stx genes. Specimens from healthy children (n = 210) recruited from Maternal and Child Health Centres were analysed for EPEC only. EPEC isolates (eae
+, stx
−) were classified as typical (bfpA
+) or atypical (bfpA
−), and were tested for O : K serogroup. Information on duration of diarrhoea was recorded in a questionnaire and from referral forms. Atypical EPEC was diagnosed in 37 patients (14.7 %) compared to 21 (10.0 %) of the healthy controls [Odds ratio (OR) = 1.4, P = 0.3]. Only three isolates, all from patients, belonged to EPEC serogroups. One patient had typical EPEC. Twenty (22.5 %) of 89 patients with diarrhoea lasting ⩾14 days had atypical EPEC. The association between atypical EPEC and prolonged diarrhoea (OR = 2.1, P = 0.04) was caused by a high prevalence among female patients (40.6 %). In conclusion, atypical EPEC was found to be slightly more prevalent in patients than controls, without any overall significant association with diarrhoea. However, a significant association was observed with diarrhoea lasting 14 days or more, a finding that may indicate a role for atypical EPEC in prolonged disease.
Erythromycin resistance in invasive serotype 14 pneumococci is highly related to clonal type
Authors: Clarke S C , Scott K J , McChlery S M
Published: October 2004

Sixty-seven serotype 14 pneumococci, isolated from invasive disease in Scotland during the first 6 months of 2003, were characterized. Serotype 14 pneumococci accounted for 18.2 % of the total number of cases. Serotyping, multilocus sequence typing and antibiotic susceptibility testing revealed 10 different sequence types (STs), predominantly ST 9 and ST 124; most ST 9 pneumococci were erythromycin-resistant whilst those of ST 124 were not.
Solvent effects on the conformational transition of a model polyalanine peptide
Authors: Nguyen Hung D. , Marchut Alexander J. , Hall Carol K.
Published: October 2004

We have investigated the folding of polyalanine by combining discontinuous molecular dynamics simulation with our newly developed off‐lattice intermediate‐resolution protein model. The thermodynamics of a system containing a single Ac‐KA14K‐NH2 molecule has been explored by using the replica exchange simulation method to map out the conformational transitions as a function of temperature. We have also explored the influence of solvent type on the folding process by varying the relative strength of the side‐chain's hydrophobic interactions and backbone hydrogen bonding interactions. The peptide in our simulations tends to mimic real polyalanine in that it can exist in three distinct structural states: α‐helix, β‐structures (including β‐hairpin and β‐sheet–like structures), and random coil, depending upon the solvent conditions. At low values of the hydrophobic interaction strength between nonpolar side‐chains, the polyalanine peptide undergoes a relatively sharp transition between an α‐helical conformation at low temperatures and a random‐coil conformation at high temperatures. As the hydrophobic interaction strength increases, this transition shifts to higher temperatures. Increasing the hydrophobic interaction strength even further induces a second transition to a β‐hairpin, resulting in an α‐helical conformation at low temperatures, a β‐hairpin at intermediate temperatures, and a random coil at high temperatures. At very high values of the hydrophobic interaction strength, polyalanines become β‐hairpins and β‐sheet–like structures at low temperatures and random coils at high temperatures. This study of the folding of a single polyalanine‐based peptide sets the stage for a study of polyalanine aggregation in a forthcoming paper.