bluuebunny/crossref_metadata_2025 huggingface dataset:
Aerosol distribution in the Northern Hemisphere during ACE‐Asia: Results from global model, satellite observations, and Sun photometer measurements
Authors: Chin Mian , Chu Allen , Levy Robert , Remer Lorraine , Kaufman Yoram , Holben Brent , Eck Tom , Ginoux Paul , Gao Qingxian
Published: December 2004

We analyze the aerosol distribution and composition in the Northern Hemisphere during the Asian Pacific Regional Aerosol Characterization Experiment (ACE‐Asia) field experiment in spring 2001. We use the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model in this study, in conjunction with satellite retrieval from the Moderate‐Resolution Imaging Spectroradiometer (MODIS) on EOS‐Terra satellite and Sun photometer measurements from the worldwide Aerosol Robotic Network (AERONET). Statistical analysis methods including histograms, mean bias, root‐mean‐square error, correlation coefficients, and skill scores are applied to quantify the differences between the MODIS 1° × 1° gridded data, the daytime average AERONET data, and the daily mean 2° × 2.5° resolution model results. Both MODIS and the model show relatively high aerosol optical thickness (τ) near the source regions of Asia, Europe, and northern Africa, and they agree on major features of the long‐range transport of aerosols from their source regions to the neighboring oceans. The τ values from MODIS and from the model have similar probability distributions in the extratropical oceans and in Europe, but MODIS is approximately 2–3 times as high as the model in North/Central America and nearly twice as high in Asia and over the tropical/subtropical oceans. Comparisons with the AERONET measurements in the Northern Hemisphere demonstrate that in general the model and the AERONET data have comparable values and similar probability distributions of τ, whereas MODIS tends to report higher values of τ over land, particularly North/Central America. The MODIS high bias is primarily attributed to the difficulties in land algorithm dealing with surface reflectance over inhomogeneous and bright land surfaces, including mountaintops, arid areas, and areas of snow/ice melting and with land/water mixed pixels. The model estimates that on average, sulfate, carbon, dust, and sea salt comprise 30%, 25%, 32%, and 13%, respectively, of the 550‐nm τ in April 2001 in the Northern Hemisphere, with ∼46% of the total τ from anthropogenic activities and 66% from fine mode aerosols.
Extreme floods in central Europe over the past 500 years: Role of cyclone pathway “Zugstrasse Vb”
Authors: Mudelsee M. , Börngen M. , Tetzlaff G. , Grünewald U.
Published: December 2004

Anthropogenically induced climate change has been hypothesized to add to the risk of extreme river floods because a warmer atmosphere can carry more water. In the case of the central European rivers Elbe and Oder, another possibility that has been considered is a more frequent occurrence of a weather situation of the type “Zugstrasse Vb,” where a low‐pressure system travels from the Adriatic region northeastward, carrying moist air and bringing orographic rainfall in the mountainous catchment areas (Erzgebirge, Sudeten, and Beskids). Analysis of long, homogeneous records of past floods allows us to test such ideas. M. Mudelsee and co‐workers recently presented flood records for the middle parts of the Elbe and Oder, which go continuously back to A.D. 1021 and A.D. 1269, respectively. Here we review the reconstruction and assess the data quality of the records, which are based on combining documentary data from the interval up to 1850 and measurements thereafter, finding both the Elbe and Oder records to provide reliable information on heavy floods at least since A.D. 1500. We explain that the statistical method of kernel occurrence rate estimation can overcome deficiencies of techniques previously used to investigate trends in the occurrence of climatic extremes, because it (1) allows nonmonotonic trends, (2) imposes no parametric restrictions, and (3) provides confidence bands, which are essential for evaluating whether observed trends are real or came by chance into the data. We further give a hypothesis test that can be used to evaluate monotonic trends. On the basis of these data and methods, we find for both the Elbe and Oder rivers (1) significant downward trends in winter flood risk during the twentieth century, (2) no significant trends in summer flood risk in the twentieth century, and (3) significant variations in flood risk during past centuries, with notable differences between the Elbe and Oder. The observed trends are shown to be both robust against data uncertainties and only slightly sensitive to land use changes or river engineering, lending support for climatic influences on flood occurrence rate. In the case of winter floods, regional warming during the twentieth century has likely reduced winter flood risk via a reduced rate of strong river freezing (breaking ice at the end of winter may function as a water barrier and enhance a high water stage severely). In the case of summer floods, correlation analysis shows a significant, but weak, relation between flood occurrence and meridional airflow, compatible with a “Zugstrasse Vb” weather situation. The weakness of this relation, together with the uncertainty about whether this weather situation became more frequent, explains the absence of trends in summer flood risk for the Elbe and Oder in the twentieth century. We finally draw conclusions about flood disaster management and modeling of flood occurrence under a changed climate.
Regulation of eukaryotic translation by the RACK1 protein: a platform for signalling molecules on the ribosome
Authors: Nilsson Jakob , Sengupta Jayati , Frank Joachim , Nissen Poul
Published: December 2004

The receptor for activated C‐kinase (RACK1) is a scaffold protein that is able to interact simultaneously with several signalling molecules. It binds to protein kinases and membrane‐bound receptors in a regulated fashion. Interestingly, RACK1 is also a constituent of the eukaryotic ribosome, and a recent cryo‐electron microscopy study localized it to the head region of the 40S subunit in the vicinity of the messenger RNA (mRNA) exit channel. RACK1 recruits activated protein kinase C to the ribosome, which leads to the stimulation of translation through the phosphorylation of initiation factor 6 and, potentially, of mRNA‐associated proteins. RACK1 therefore links signal‐transduction pathways directly to the ribosome, which allows translation to be regulated in response to cell stimuli. In addition, the fact that RACK1 associates with membrane‐bound receptors indicates that it promotes the docking of ribosomes at sites where local translation is required, such as focal adhesions.
Monodromy of the quantum 1:1:2 resonant swing spring
Authors: Giacobbe A. , Cushman R. H. , Sadovskií D. A. , Zhilinskií B. I.
Published: December 2004

We describe the qualitative features of the joint spectrum of the quantum 1:1:2 resonant swing spring. The monodromy of the classical analogue of this problem is studied in Dullin et al. [Physica D 190, 15–37 (2004)]. Using symmetry arguments and numerical calculations we compute its three-dimensional (3D) lattice of quantum states and show that it possesses a codimension 2 defect characterized by a nontrivial 3D-monodromy matrix. The form of the monodromy matrix is obtained from the lattice of quantum states and depends on the choice of an elementary cell of the lattice. We compute the quantum monodromy matrix, that is the inverse transpose of the classical monodromy matrix. Finally we show that the lattice of quantum states for the 1:1:2 quantum swing spring can be obtained—preserving the symmetries—from the regular 3D-cubic lattice by means of three “elementary monodromy cuts.”
Wide-field surface plasmon microscopy with solid immersion excitation
Authors: Zhang J. , See C. W. , Somekh M. G. , Pitter M. C. , Liu S. G.
Published: December 2004

This letter shows how an aplanatic solid immersion lens system may be used for high-resolution wide-field surface plasmon microscopy. The lens configuration means that no fluid couplant is required; it has the additional advantage that very high refractive indices may be used to reduce the incident angle at which surface plasmons are excited. A transmission spatial light modulator is incorporated conjugate with the back focal plane; this allows the image contrast to be controlled in a precise and flexible manner. Its use also provides definitive demonstration that the image contrast arises from surface plasmon excitation.
Imaging optical near-fields of nanostructures
Authors: Leiderer P. , Bartels C. , König-Birk J. , Mosbacher M. , Boneberg J.
Published: December 2004

We present a method for imaging the optical near-fields of nanostructures, which is based on the local ablation of a smooth silicon substrate by means of a single, femtosecond laser pulse. At those locations, where the field enhancement due to a nanostructure is large, substrate material is removed. The resulting topography, imaged by scanning electron or atomic force microscopy, thus reflects the intensity distribution caused by the nanostructure at the substrate surface. With this method one avoids a possible distortion of the field distribution due to the presence of a probe tip, and reaches a resolution of a few nanometers. Several examples for the optical near-field patterns of dielectric and metallic nanostructures are given.
A differential mechanical profilometer for thickness measurement
Authors: Alves J. Maia , Brito M. C. , Serra J. M. , Vallêra A. M.
Published: December 2004

A low cost differential profilometer based on standard commercial displacement transducers is fully described. Unlike most common profilometers this device can be used to measure the thickness profile of samples having both surfaces irregular. A sensitivity of about 0.2 μm, independent of the sample thickness is achieved.
A top-emission organic light-emitting diode with a silicon anode and an Sm∕Au cathode
Authors: Qin G. G. , Xu A. G. , Ma G. L. , Ran G. Z. , Qiao Y. P. , Zhang B. R. , Chen W. X. , Wu S. K.
Published: December 2004

A top-emission organic light-emitting diode (TEOLED) with a p-type silicon anode and a semitransparent samarium/gold cathode has been constructed and studied. With a structure of Al∕p-Si∕SiOx∕N,N′-bis-(1-naphthl)-diphenyl-1,1′-biphenyl-4,4′-diamine(NPB)∕Tris-(8-hydroxyquinoline)aluminum(Alq)∕LiF∕Al, we have found that compared to indium-tin-oxide, the p-Si anode enhances the unbalance between electron- and hole-injection, which is a disadvantage factor for the light-emitting efficiency of the TEOLED. Selecting p-Si wafers with suitable electric resistivities and inserting an ultrathin low temperature grown SiOx layer of about 1.5nm between the anode and NPB can effectively restrict hole-injection. Moreover, a low work function Sm∕Au cathode was used to enhance electron-injection. The electroluminescence efficiency of the TEOLED depends on the thickness of the Sm layer in the cathode. A current efficiency of 0.55cd∕A and a power efficiency of 0.07lm∕W have been reached.
IV
–
VI
device arrays: Microfabrication and specific contact resistivity
Authors: Taylor P. J. , Harman T. C. , Dhar N. K. , Wijewarnasuriya P. S. , Fraser J. C. , Tidrow M. Z.
Published: December 2004

Techniques for the preparation of highly integrated arrays of IV–VI semiconductors are presented. PbSnTeSe films were grown by molecular-beam epitaxy and array structures are fabricated by photolithography, electrical contact formation, and etching. The rationale for forming electrical contacts with low specific contact resistivity is provided. Characterization of the specific contact resistivity was performed using a transmission line technique. Using a procedure discussed in this letter, specific contact resistivity measurements as low as 7×10−8Ωcm2 have been obtained and demonstrate the feasibility of a class of highly integrated IV–VI device technology.
Nonpolar InGaN∕GaN emitters on reduced-defect lateral epitaxially overgrown a-plane GaN with drive-current-independent electroluminescence emission peak
Authors: Chakraborty Arpan , Haskell B. A. , Keller S. , Speck J. S. , DenBaars S. P. , Nakamura S. , Mishra U. K.
Published: December 2004

Nonpolar (112¯0) a-plane InGaN∕GaN multiple-quantum-well light-emitting diodes were grown by metalorganic chemical vapor deposition on reduced-defect density hydride-vapor-phase-epitaxy lateral epitaxially overgrown a-plane GaN templates. Direct current output power of 240 μW was measured at 20 mA for a 300×300μm2 device, and dc output powers as high as 1.5 mW were measured at 250 mA. DC electroluminescence (EL) measurements yielded a peak at 413.5 nm, corresponding with the room-temperature photoluminescence peak. The EL peak position was independent of drive current and a 23.5 nm linewidth was realized at 20 mA. The current–voltage characteristics of these diodes showed a forward voltage (Vf) of 3.3 V with a series resistance of 7.8 Ω.
Characterization of quantum wells by cross-sectional Kelvin probe force microscopy
Authors: Douhéret O. , Anand S. , Glatzel Th. , Maknys K. , Sadewasser S.
Published: December 2004

Cross-sectional Kelvin probe force microscopy (KPFM) in ultrahigh vacuum is used to characterize the electronic structure of InGaAs∕InP quantum wells. The KPFM signal shows clear peaks at the position of the quantum wells and exhibits a systematic trend for different wells. It is demonstrated that KPFM is capable of detecting quantum wells as narrow as 5nm. Evidence for carrier accumulation in the quantum wells is observed. A complete quantitative analysis of the quantum well properties is shown to be impeded by tip averaging effects and due to surface/interface states.
A nanomechanical device based on linear molecular motors
Authors: Huang Tony Jun , Brough Branden , Ho Chih-Ming , Liu Yi , Flood Amar H. , Bonvallet Paul A. , Tseng Hsian-Rong , Stoddart J. Fraser , Baller Marko , Magonov Sergei
Published: December 2004

An array of microcantilever beams, coated with a self-assembled monolayer of bistable, redox-controllable [3]rotaxane molecules, undergoes controllable and reversible bending when it is exposed to chemical oxidants and reductants. Conversely, beams that are coated with a redox-active but mechanically inert control compound do not display the same bending. A series of control experiments and rational assessments preclude the influence of heat, photothermal effects, and pH variation as potential mechanisms of beam bending. Along with a simple calculation from a force balance diagram, these observations support the hypothesis that the cumulative nanoscale movements within surface-bound “molecular muscles” can be harnessed to perform larger-scale mechanical work.
Preparation and magnetic properties of hollow nano-spheres of cobalt and cobalt oxide: Drastic cooling-field effects on remnant magnetization of antiferromagnet
Authors: Yoshikawa Hirofumi , Hayashida Kenta , Kozuka Yasuharu , Horiguchi Asami , Awaga Kunio , Bandow Shunji , Iijima Sumio
Published: December 2004

We investigate the making of magnetic hollow spheres of Co3O4 (2) and fcc Co (3) with diameter 500 nm and thickness 40 nm, using polystyrene-bead templates. The spheres are characterized by scanning electron microscope, transmission electron microscope, electron diffraction, and x-ray diffraction. Magnetic measurements on 2 reveal a drastic enhancement of remnant magnetization below TN induced by cooling-field, while measurements on 3 indicate a soft ferromagnetism similar to that of bulk fcc Co.
Quantum and transport lifetimes in a tunable low-density AlGaN∕GaN two-dimensional electron gas
Authors: Manfra M. J. , Simon S. H. , Baldwin K. W. , Sergent A. M. , West K. W. , Molnar R. J. , Caissie J.
Published: December 2004

We experimentally determine the density dependence of the transport lifetime (τt) obtained from low-field Hall measurements and the quantum lifetime (τq) derived from analysis of the amplitude of Shubnikov–de Haas oscillations in a tunable high mobility two-dimensional electron gas (2DEG) in a Al0.06Ga0.94N∕GaN heterostructure. Using an insulated gate structure, we are able to tune the 2DEG density from 2×1011 to 2×1012cm−2, and thus, monitor the evolution of the scattering times in a single sample at T=0.3K in a previously unexplored density regime. The transport lifetime τt is a strong function of electron density, increasing from ∼2.7ps at ne=2×1011cm−2 to ∼11ps at ne=1.75×1012cm−2. Conversely, we find that the quantum scattering time τq is relatively insensitive to changes in electron density over this range. The data suggest that dislocation scattering accounts for the density dependence of τq as well as τt in our low-density sample.
Improving exchange-spring nanocomposite permanent magnets
Authors: Jiang J. S. , Pearson J. E. , Liu Z. Y. , Kabius B. , Trasobares S. , Miller D. J. , Bader S. D. , Lee D. R. , Haskel D. , Srajer G. , Liu J. P.
Published: December 2004

We demonstrate a counterintuitive approach for improving exchange-spring magnets. Contrary to the general belief that the exchange–spring interface must be ideal and atomically coherent, we thermally process, by annealing or high-temperature deposition, epitaxial Sm–Co∕Fe thin-film bilayers to induce interfacial mixing. Synchrotron x-ray scattering and electron microscopy elemental mapping confirm the formation of a graded interface. The thermal processing enhances the nucleation field and the energy product. The hysteresis loop becomes more single-phase-like yet the magnetization remains fully reversible. Model simulations produce demagnetization behaviors similar to experimental observations.
Enhanced vertical transport in p-type AlGaN∕GaN superlattices
Authors: Kauser M. Z. , Osinsky A. , Dabiran A. M. , Chow P. P.
Published: December 2004

We report on p-type AlGaN∕GaN superlattice designs with significantly improved vertical and lateral electrical conductivities (σV and σL). Composition-graded p-AlGaN layers produce a polarization charge distribution, which together with an appropriate Mg doping in the structure leads to more than an eightfold reduction of barrier height and a ∼50% increase in the sheet hole density in the p-GaN wells compared to typical modulation-doped superlattice structures. Using the optimized structure, more than 13 orders of magnitude and 35 times improvement is shown for σV, compared to typical superlattice and σL, compared to bulk p-GaN, respectively. Both σV and σL are found to improve significantly at higher temperatures in the optimized structure.
Enhanced thermal stability of the two-dimensional electron gas in GaN∕AlGaN∕GaN heterostructures by Si3N4 surface-passivation-induced strain solidification
Authors: Feng Z. H. , Zhou Y. G. , Cai S. J. , Lau Kei May
Published: December 2004

The plasma-enhanced chemical-vapor-deposited Si3N4 surface passivation layers with high rf (13.56MHz) and low rf (380KHz), were investigated, using the annealing experiment at 500°C in N2 ambient, for their effectiveness in regard to the stability of the two-dimensional electron gas (2DEG) in GaN∕AlGaN∕GaN high-electron-mobility transistor structures. When the unpassivated sample was annealed, as observation using the Hall and high-resolution x-ray diffraction measurements, an irreversible degradation of the 2DEG behavior and a strain relaxation of the AlGaN epilayer occurred. The Si3N4 deposited with high frequency provided superior long-term stability for the sample and showed no change in the 2DEG conductivity and the strain state in AlGaN epilayer after 170h of aging. However, a significant degradation after deposition and a partial recovery of the 2DEG behavior after annealing due to the Si3N4 densification, was found in sample passivated by low-frequency Si3N4. The enhancement of the long-term stability can be explained as a consequence of the strain solidification of the AlGaN epilayer induced by a denser Si3N4 passivation.
A longitudinal-longitudinal mode TERFENOL-D∕Pb(Mg1∕3Nb2∕3)O3–PbTiO3 laminate composite
Authors: Dong Shuxiang , Li Jie-Fang , Viehland D.
Published: December 2004

We have found that laminates of longitudinally magnetized magnetostrictive TERFENOL-D layersand a longitudinally poled piezoelectric Pb(Mg1∕3Nb2∕3)O3-PbTiO3 crystal have a giant magnetoelectric voltage coefficient of >430mV∕Oe under a low magnetic bias. Under a resonant drive operation at a frequency of 82.1 kHz, the magnetoelectric coefficient was dramatically increased to ∼18.5V∕Oe. In addition, an ultrahigh magnetic field sensitivity of <10−11T has been observed.
Ruthenium-coated ruthenium oxide nanorods
Authors: Ducati Caterina , Dawson Darryl H. , Saffell John R. , Midgley Paul A.
Published: December 2004

The role of ruthenium and its oxides in catalysis, electrochemistry, and electronics is becoming increasingly important because of the high thermal and chemical stability, low resistivity, and unique redox properties of this metallic system. We report an observation of RuO2 nanorods decorated with nanometer size Ru metal clusters. We identify precise crystallographic relationships between metal and oxide, and provide a simple model for the synthesis of these structures, based on the theory of columnar growth. The high aspect ratio, high surface area, and quantum size crystalline decorations of these nanostructures make them particularly attractive candidates for further fundamental research and for advanced catalytic and electronic applications.
Magnetization distribution in Nd4.5Fe77B18.5 nanocomposite magnets studied by electron holography
Authors: Park Y.-G. , Shindo D. , Kanekiyo H. , Hirosawa S.
Published: December 2004

Magnetic nanostructures at demagnetized and remanent states in Nd4.5Fe77B18.5 nanocomposite magnets are investigated by electron holography, utilizing the specially designed electromagnet. The quantitative mapping of magnetization distribution at a nanometer scale using a polar diagram has been reported for both the demagnetized and remanent states. Through the polar diagrams for the remanent state, the homogeneous distribution of magnetic flux is found in the specimen annealed at a low temperature, while the fluctuated distribution is found in the specimen annealed at a high temperature. The difference is considered to be responsible for their magnetic properties, i.e., remanence and coercivity.
Ultrasound detection using polymer microring optical resonator
Authors: Ashkenazi Shai , Chao Chung-Yen , Guo L. Jay , O’Donnell Matthew
Published: December 2004

Application of polymer waveguide microring resonators for high-frequency ultrasound detection is presented. The device consists of a microring optical resonator coupled to a straight optical waveguide which serves as input and output ports. Acoustic waves irradiating the ring waveguide induce strain modifying the waveguide cross section. As a consequence, the effective refractive index of optical waves propagating along the ring is modified. The sharp wavelength dependence of the high Q-factor resonator enhances the optical response to acoustic strain. High sensitivity is demonstrated experimentally in detecting broadband ultrasound pulses from a 10MHz transducer. Methods of extending the technique to form multi-element ultrasonic arrays for imaging applications are proposed.
Hot-electron transport in AlGaN∕GaN two-dimensional conducting channels
Authors: Danilchenko B. A. , Zelensky S. E. , Drok E. , Vitusevich S. A. , Danylyuk S. V. , Klein N. , Lüth H. , Belyaev A. E. , Kochelap V. A.
Published: December 2004

We report on experimental studies of high-field electron transport in AlGaN∕GaN two-dimensional electron gas. The velocity–electric field characteristics are extracted from 10to30ns pulsed current–voltage measurements for 4.2 and 300K. An electron drift velocity as high as 1.7×107cm∕s was obtained in the fields 150kV∕cm. Estimates of thermal budget of the system show that overheating of the electrons exceeds 1700K at highest electric fields achieved in the experiment.
Regulation of behavioral maturation by a primer pheromone produced by adult worker honey bees
Authors: Leoncini Isabelle , Le Conte Yves , Costagliola Guy , Plettner Erika , Toth Amy L. , Wang Mianwei , Huang Zachary , Bécard Jean-Marc , Crauser Didier , Slessor Keith N. , Robinson Gene E.
Published: December 2004

Previous research showed that the presence of older workers causes a delayed onset of foraging in younger individuals in honey bee colonies, but a specific worker inhibitory factor had not yet been identified. Here, we report on the identification of a substance produced by adult forager honey bees, ethyl oleate, that acts as a chemical inhibitory factor to delay age at onset of foraging. Ethyl oleate is synthesized
de novo
and is present in highest concentrations in the bee's crop. These results suggest that worker behavioral maturation is modulated via trophallaxis, a form of food exchange that also serves as a prominent communication channel in insect societies. Our findings provide critical validation for a model of self-organization explaining how bees are able to respond to fragmentary information with actions that are appropriate to the state of the whole colony.
Water clusters in nonpolar cavities
Authors: Vaitheeswaran Subramanian , Yin Hao , Rasaiah Jayendran C. , Hummer Gerhard
Published: December 2004

We explore the structure and thermodynamics of water clusters confined in nonpolar cavities. By calculating the grand-canonical partition function term by term, we show that small nonpolar cavities can be filled at equilibrium with highly structured water clusters. The structural and thermodynamic properties of these encapsulated water clusters are similar to those observed experimentally in the gas phase. Water filling is highly sensitive to the size of the cavity and the strength of the interactions with the cavity wall. Water penetration into pores can thus be modulated by small changes in the polarity and structure of the cavity. Implications on water penetration into proteins are discussed.
A dot-blot ELISA comparable to immunoblot for the specific diagnosis of human parastrongyliasis
Authors: Eamsobhana P. , Yoolek A. , Punthuprapasa P. , Suvouttho S.
Published: December 2004

A dot-blot enzyme-linked immunosorbent assay (dot-blot ELISA) using an electroeluted 31-kDa glycoprotein from adult worms of Parastrongylus cantonensis as the specific antigen was evaluated for the immunological diagnosis of patients infected with P. cantonensis. The sensitivity and specificity for the detection of serum antibody to P. cantonensis in dot-blot ELISA were both 100%, as determined with serum samples of ten P. cantonensis-infected patients, 60 patients with other related parasitic infections, and 20 uninfected controls. The test was as sensitive and specific as the immunoblot test which revealed a reactive band of 31 kDa. Both the dot-blot ELISA and immunoblot detected all sera from ten P. cantonensis-infected individuals, but not with those of other heterologous parasitoses (gnathostomiasis, toxocariasis, filariasis, paragonimiasis, cysticercosis and malaria) or sera from healthy controls. The dot-blot ELISA is much simpler to perform than the immunoblot technique, and the test can be applied under field conditions where sophisticated facilities are lacking.
Density Modulation Experiments on HT-7 Tokamak
Authors: K. Tanaka  , Gao Xiang  , Jie Yin-Xian  , R. Sakamoto  , K. Toi
Published: December 2004

Density modulation experiments are successfully conducted on HT-7 ohmic discharge to investigate particle transport coefficients: diffusion coefficients D and convection velocity V. The particle transport is studied at low (1.5×1019 m−3) and high (3×1019 m−3) density regimes. The clear differences are observed that D is 0.42 m2 /s and 0.17 m2/s,Vis 4.7 m/s (outward) and 1.6 m/s (inward) for low and high density plasmas respectively, where spatially constant D andV(r) = (r/a)V0were assumed for the analysis.
Long-time behavior for a nonlinear fourth-order parabolic equation
Authors: Cáceres María , Carrillo J. , Toscani G.
Published: December 2004

We study the asymptotic behavior of solutions of the initial- boundary value problem, with periodic boundary conditions, for a fourth-order nonlinear degenerate diffusion equation with a logarithmic nonlinearity. For strictly positive and suitably small initial data we show that a positive solution exponentially approaches its mean as time tends to infinity. These results are derived by analyzing the equation verified by the logarithm of the solution.
Gröbner bases of associative algebras and the Hochschild cohomology
Authors: Kobayashi Yuji
Published: December 2004

We give an algorithmic way to construct a free bimodule resolution of an algebra admitting a Gröbner base. It enables us to compute the Hochschild (co)homology of the algebra. Let

A
A

be a finitely generated algebra over a commutative ring

K
K

with a (possibly infinite) Gröbner base

G
G

on a free algebra

F
F

, that is,

A
A

is the quotient

F

/

I
(
G
)

F/I(G)

with the ideal

I
(
G
)

I(G)

of

F
F

generated by

G
G

. Given a Gröbner base

H
H

for an

A
A

-subbimodule

L
L

of the free

A
A

-bimodule

A
⋅
X
⋅
A
=

A
K

⊗
K
⋅
X

⊗
K

A

A \cdot X \cdot A = A_K \otimes K \cdot X \otimes _KA

generated by a set

X
X

, we have a morphism

∂
\partial

of

A
A

-bimodules from the free

A
A

-bimodule

A
⋅
H
⋅
A

A \cdot H \cdot A

generated by

H
H

to

A
⋅
X
⋅
A

A \cdot X \cdot A

sending the generator

[
h
]

[h]

to the element

h
∈
H

h \in H

. We construct a Gröbner base

C
C

on

F
⋅
H
⋅
F

F \cdot H \cdot F

for the

A
A

-subbimodule Ker(

∂
\partial

) of

A
⋅
H
⋅
A

A \cdot H \cdot A

, and with this

C
C

we have the free

A
A

-bimodule

A
⋅
C
⋅
A

A \cdot C \cdot A

generated by

C
C

and an exact sequence

A
⋅
C
⋅
A
→
A
⋅
H
⋅
A
→
A
⋅
X
⋅
A

A \cdot C \cdot A \rightarrow A \cdot H \cdot A \rightarrow A \cdot X \cdot A

. Applying this construction inductively to the

A
A

-bimodule

A
A

itself, we have a free

A
A

-bimodule resolution of

A
A

.
Brownian motion in twisted domains
Authors: DeBlassie Dante , Smits Robert
Published: December 2004

The tail behavior of a Brownian motion’s exit time from an unbounded domain depends upon the growth of the “inner radius” of the domain. In this article we quantify this idea by introducing the notion of a twisted domain in the plane. Roughly speaking, such a domain is generated by a planar curve as follows. As a traveler proceeds out along the curve, the boundary curves of the domain are obtained by moving out

±
g
(
r
)

\pm g(r)

units along the unit normal to the curve when the traveler is

r
r

units away from the origin. The function

g
g

is called the growth radius. Such domains can be highly nonconvex and asymmetric. We give a detailed account of the case

g
(
r
)
=
γ

r
p

g(r) = \gamma r^p

,

0
>
p
≤
1

0>p\le 1

. When

p
=
1

p=1

, a twisted domain can reasonably be interpreted as a “twisted cone.”
Weakly compact approximation in Banach spaces
Authors: Odell Edward , Tylli Hans-Olav
Published: December 2004

The Banach space

E
E

has the weakly compact approximation property (W.A.P. for short) if there is a constant

C
>
∞

C > \infty

so that for any weakly compact set

D
⊂
E

D \subset E

and

ε
>
0

\varepsilon > 0

there is a weakly compact operator

V
:
E
→
E

V: E \to E

satisfying

sup

x
∈
D

‖
x
−
V
x
‖
>
ε

\sup _{x\in D} \Vert x - Vx \Vert > \varepsilon

and

‖
V
‖
≤
C

\Vert V\Vert \leq C

. We give several examples of Banach spaces both with and without this approximation property. Our main results demonstrate that the James-type spaces from a general class of quasi-reflexive spaces (which contains the classical James’ space

J
J

) have the W.A.P, but that James’ tree space

J
T

JT

fails to have the W.A.P. It is also shown that the dual

J

∗

J^{*}

has the W.A.P. It follows that the Banach algebras

W
(
J
)

W(J)

and

W
(

J

∗

)

W(J^{*})

, consisting of the weakly compact operators, have bounded left approximate identities. Among the other results we obtain a concrete Banach space

Y
Y

so that

Y
Y

fails to have the W.A.P., but

Y
Y

has this approximation property without the uniform bound

C
C

.
Resultants and discriminants of Chebyshev and related polynomials
Authors: Dilcher Karl , Stolarsky Kenneth
Published: December 2004

We show that the resultants with respect to

x
x

of certain linear forms in Chebyshev polynomials with argument

x
x

are again linear forms in Chebyshev polynomials. Their coefficients and arguments are certain rational functions of the coefficients of the original forms. We apply this to establish several related results involving resultants and discriminants of polynomials, including certain self-reciprocal quadrinomials.
On the construction of certain 6-dimensional symplectic manifolds with Hamiltonian circle actions
Authors: Li Hui
Published: December 2004

Let

(
M
,
ω
)

(M, \omega )

be a connected, compact 6-dimensional symplectic manifold equipped with a semi-free Hamiltonian

S
1

S^1

action such that the fixed point set consists of isolated points or surfaces. Assume dim

H
2

(
M
)
>
3

H^2(M)>3

. In an earlier paper, we defined a certain invariant of such spaces which consists of fixed point data and twist type, and we divided the possible values of these invariants into six “types”. In this paper, we construct such manifolds with these “types”. As a consequence, we have a precise list of the values of these invariants.
Chromatin remodeling and histone modification in the conversion of oligodendrocyte precursors to neural stem cells
Authors: Kondo Toru , Raff Martin
Published: December 2004

We showed previously that purified rat oligodendrocyte precursor cells (OPCs) can be induced by extracellular signals to convert to multipotent neural stem-like cells (NSLCs), which can then generate both neurons and glial cells. Because the conversion of precursor cells to stem-like cells is of both intellectual and practical interest, it is important to understand its molecular basis. We show here that the conversion of OPCs to NSLCs depends on the reactivation of the sox2 gene, which in turn depends on the recruitment of the tumor suppressor protein Brca1 and the chromatin-remodeling protein Brahma (Brm) to an enhancer in the sox2 promoter. Moreover, we show that the conversion is associated with the modification of Lys 4 and Lys 9 of histone H3 at the same enhancer. Our findings suggest that the conversion of OPCs to NSLCs depends on progressive chromatin remodeling, mediated in part by Brca1 and Brm.
Marking of specific sequences in double-stranded DNA molecules—SNP detection and direct observation
Authors: Shigemori Yasushi , Haruta Hirotaka , Okada Takao , Oishi Michio
Published: December 2004

In this study, we describe a simple method to mark specific sequences in double-stranded DNA molecules. For the marking, we used two specifically designed oligonucleotides, one of which is complementary to the sequence to be marked and the other, serving as a splint, to make the marking stable and detectable by subsequent various analytical means. In the presence of the two deoxyoligonucleotides, whereas RecA protein-mediated reaction converts the sequence to be marked to a regional triple-stranded structure with the complementary (probing) oligonucleotide, DNA ligase transforms it to a stable multi- (possibly quintuple) stranded structure with the splint oligonucleotide. The whole marking process is simple and completed in a single reaction mixture. Because RecA protein makes the marking to proceed with high fidelity, we were able to mark (detect) SNPs in complex genomes like human's. Furthermore, the structure of the marked sequence is stable and quite distinct enough to be readily detectable by biochemical means or direct observation by scanning probe microscopy.
Hiring and Dismissal Costs in Theory and Practice: A Comparison of Institutional Constraints and Employment Adjustment Patterns in Six OECD Countries
Authors: Kraft Kornelius
Published: December 2004

This paper reports the results of a comparison of employment adjustment in Japan, the United States and four major EC countries. Output and real wages are used in explaining the optimal employment level and change in employment. Short‐ and long run responses to alterations of the exogenous variables are estimated and compared. Surprisingly, Germany has a quite rapid adjustment of labor while France and Italy show a much slower adjustment pattern. Even in comparison with the United States. Great Britain demonstrates the fastest adjustment to changes in the economic environment. By far the slowest adjustment pattern is realized in Japan. Overall the difference between the US and Europe seems not to be too large and European labor markets are not as sclerotic as occasionally assumed.

ZUSAMMENFASUNG

Dieser Artikel gibt die Ergebnisse eines Vergleichs der Beschäftigungsanpassung in Japan, den Vereinigten Staaten und den vier wichtigsten EU‐Landern wieder. Das Produktionsniveau und der Reallohn sind die erklarenden Variablen für das optimale Beschaftigungsniveau wie auch Veranderungen der Beschäftigung. Es werden kurz‐ und langfnstige Beziehungen zwischen den exogenen und der endogenen Vanablen geschatzt und verglichen Uberraschenderweise hat Deutschland eine relativ rasche Beschaftigungsanpassung, während Frankreich und Italien eine viel langsamere Anpassung aufweisen. Großbntannien hat auch im Vergleich zu den USA die schnellste Reaktion auf Veränderungen der ökonomischen Umwelt. Das bei weitem inflexibelste Anpassungsverhalten wird für Japan registriert. Zusammenfassend scheinen die Unterschiede zwischen den Vereinigten Staaten und Europa nicht so groß und der europaische Arbeitsmarkt nicht so sklerotisch zu sein wie erwartet.

Cet article présente les résultats d'une comparaison de la vitesse d'adaptation de l'emploi au Japon, aux Etats‐Unis et dans les quatre pays les plus importants de l'UE. Le niveau de l'emploi optimal ***ainsi que les variations de l'emploi sont expliquées par le niveau de production et les salaires réels. Les variations à court et long terme des changements des variables exogènes ont été estimés et comparés. Étonnamment, l'Allemagne a une vitesse d'adaptation de l'emploi relativement rapide par rapport à celles de la France et de l'Italie. L'Angleterre montre měme, en comparaison avec les Etats‐Unis, une plus grande flexibilité envers les modifications de l'environnement économique. L'adaptation la plus lente est observée au Japon. Pour conclure les différences concernant la vitesse d'adaptation de l'emploi entre les Etats‐Unis et l'Europe ne semblent pas si grandes et les marchés de travail européens sont moins sclérosés que ce que l'on attendait.
Review article: Barrett's oesophagus and associated adenocarcinoma – a UK perspective
Authors: Fitzgerald R. C.
Published: December 2004

In the UK and across the Western world there has been a rapid increase in oesophageal adenocarcinoma, such that this cancer is now more common than squamous cell carcinoma. The 5‐year mortality from oesophageal adenocarcinoma is >80% and therefore there has been increasing interest in the pre‐malignant condition Barrett's oesophagus. Barrett's oesophagus is defined by a visible columnar‐lined segment with histopathological evidence of a glandular epithelium, which typically contains intestinal metaplasia. Once Barrett's oesophagus is diagnosed, most centres in the UK offer endoscopic surveillance with the aim to detect early, curable lesions. Surveillance in its current form is cumbersome and expensive, and new endoscopic and molecular developments are hoped to improve the yield of such procedures. The current treatments are symptomatic control of reflux symptoms, with more definitive treatments usually reserved for patients with at least high‐grade dysplasia. There is interest in chemoprevention strategies, including proton‐pump inhibitors, cyclo‐oxygenase‐2 inhibitors and aspirin, but to date none of these have proven effective. Treatment options for high‐grade dysplasia include surgery, endoscopic mucosal resection (in the context of a visible lesion) and photodynamic therapy. Comparative studies between various geographical regions, as the predominant histopathological subtypes of oesophageal cancer change, may give us some clues about the pathogenesis of Barrett's adenocarcinoma.
Polyorchidism: a case report and review of the literature
Authors: Lawrentschuk Nathan , MacGregor Robert J.
Published: December 2004

Polyorchidism is defined as the presence of two or more testes. It is a rare anomaly with approximately 77 cases reported in the literature. Polyorchidism is frequently associated with additional urological pathologies such as undescended testis, inguinal hernia, testicular torsion, hydrocoele, malignancy and infertility. Differential diagnosis includes spermatocoele, hydrocoele, epididymal cysts or aberrant epididymis. We report on an interesting case of polyorchidism in a 15‐year‐old man diagnosed on ultrasound and we review the literature and current management of polyorchidism.
Evidence‐based risk factors for postoperative deep vein thrombosis
Authors: Edmonds Michael J. R. , Crichton Timothy J. H. , Runciman William B. , Pradhan Malcolm
Published: December 2004

Background:  Deep vein thrombosis (DVT) is a common postoperative complication that is associated with significant morbidity and mortality. Thromboprophylaxis has been shown to be underused. In the absence of prophylaxis, rates as high as 50% have been reported following orthopaedic surgery, and 25% following general surgery. Many risk factors have been suggested but there is often little evidence to support these claims.

Methods:  A systematic review was performed to determine the evidence base behind each suggested risk factor, and, where sufficient data were available, a random‐effects meta‐analysis was performed.

Results:  There is evidence to support a significant association between increased age, obesity, a past history of thromboembolism, varicose veins, the oral contraceptive pill, malignancy, Factor V Leiden gene mutation, general anaesthesia and orthopaedic surgery, with higher rates of postoperative DVT, although there remain some variables within the study designs that may lead to overestimation of effect. There is no evidence to support the suggested risk factors of hormone replacement therapy, gender, ethnicity or race, chemotherapy, other thrombophilias, cardiovascular factors, smoking and blood type.

Conclusions:  An accurate knowledge of evidence‐based risk factors is important in predicting and preventing postoperative DVT, and can be incorporated into a decision support system for appropriate thromboprophylaxis use.
Teaching subfascial perforator veins surgery: survey on a 2‐day hands‐on course
Authors: Rulli Francesco , Cina Gregorio , Galatà Gabriele , Cina Alesssandro , Vincenzoni Claudio , Fiorentino Alessandro , Farinon Attilio Maria
Published: December 2004

Background : The present paper describes a training method with objective evaluation to enhance video‐assisted surgical skills in subfascial endoscopic perforator veins surgery (SEPS). Training was scheduled during a 2‐day intensive course.

Methods : Hands‐on exercises were performed (i) on a simulator to assess whether specific training exercises were helpful in attainment of skills; (ii) on a known animal model that uses the swine abdominal wall and which allows practice in endoscopic dissection and perforator veins (PV) using appropriate instrumentation in an environment that is a reasonable surrogate for the human calf; and (iii) assisting a senior surgeon performing SEPS. Thirty surgeons without experience in SEPS were trained to perform a sequence of standardized drills connected with the SEPS technique. The SEPS simulator consisted of an artificially constructed subfascial space of the leg in which false perforator veins had to be localized, and cut. The participants performed a sequence of drills three times in order to improve their dexterity. The same exercises were then performed on a swine model. The model consisted of the arteries and veins penetrating the rectus fascia and passing into the overlying cutaneous trunci muscle and hypodermis on either side of the midline between the arch of the ribs cranially and the umbilicus caudally. Trainees were required to achieve operative space in the animal subcutaneous fat, to reach and identify the ‘perforating’ subcutaneous vessels, and to interrupt some of them with a 5‐mm clamp coagulator ultrasonic scalpel. The time required to perform each dexterity drill was recorded in seconds. Finally, the day after, trainees were asked to drive the senior operator during clinical SEPS performed on eight patients, suggesting the following manoeuvres in order to: (i) enter the subfascial space of the leg; (ii) make operative space; (iii) identify the incompetent perforator vein(s); and (iv) coagulate and divide them with the ultrasonic scalpel. Each of these four steps scored 1 point.

Results : All the trainees showed a steady improvement in skill acquisition on the SEPS simulator (P < 0.001), and on the animal model with the single‐port technique (P < 0.001). These results reflect positively on the animal model using the dual‐port technique, and on the scores achieved in the operating theatre during clinical SEPS.

Conclusions : The validity of the 2‐day course was demonstrated by significant improvement in performance with increasing skill on the training models, and in clinical practice.
Mitochondrial Ca2+ transport in frog early distal tubule
Authors: Fowler Mark R. , Hunter Malcolm
Published: December 2004

A global and transient rise of intracellular Ca2+ (Ca2+i) is central to the operation of pump–leak coupling in the frog early distal tubule (EDT). The endoplasmic reticulum (ER) is the site of this Ca2+ release and reuptake; however, it is likely that other intracellular pools, such as mitochondria, also contribute to cellular Ca2+ homeostasis. The present study was performed to seek evidence of mitochondrial Ca2+ transport in the frog EDT. Experiments were performed on isolated and permeabilized EDT segments from the frog kidney loaded with the low‐affinity, Ca2+‐sensitive fluorescent indicator, mag‐fura‐2. Ca2+ uptake in the absence of SarcoEndoplasmic Reticulum Calcium ATPase (SERCA) activity (inhibition by 2,5‐di‐t‐butyl hydroquinone, TBQ) was evident at a bath [Ca2+] of 1 μm, but not at 200 nm, in the presence of ATP. This uptake was sensitive to the protonophore FCCP and the ATP‐synthase inhibitor oligomycin. Ca2+ uptake was also stimulated by respiratory substrates; this uptake was enhanced by oligomycin and reversed by the application of FCCP. These findings provide the first evidence of mitochondrial Ca2+ transport in renal tubules, which appears to occur via a low‐affinity pathway and which will act as a physiological Ca2+ buffer, protecting the cell from large increases in Ca2+i.
Parallel Hybrid Algorithm for Three-Dimensional Elastic Wave Scattering in Steel Pipes
Authors: Mahmoud A. , Shah A. H. , Popplewell N.
Published: December 2004

A parallel computational algorithm that models three-dimensional elastic wave scattering in an infinite pipe is introduced. The algorithm combines two procedures: a Wave Function Expansion (WFE) and a Finite Element Discretization (FED). The WFE represents a flawless unbounded region while the FED idealizes a bounded region containing the defects. Unknown amplitudes in the WFE are determined by imposing continuity between the two regions; they are then used to calculate the reflection and transmission coefficients. The inversion of a large stiffness matrix resulting from the FED has been overcome in the current formulation by sub-structuring the finite element mesh. The algorithm is implemented in Fortran 90™ on a shared-memory, parallel computing platform using OpenMP™ directives. The algorithm is validated against available numerical and experimental results. Agreement with previous three-dimensional results for a radial crack in a steel pipe and a two-dimensional hybrid model of an axisymmetric cracked, welded steel pipe are shown to be excellent. New results are presented for an inclined crack in a steel pipe as well as for a non-axisymmetric cracked welded steel pipe.