bluuebunny/crossref_metadata_2025 huggingface dataset:
Template‐directed self‐assembly and growth of insulin amyloid fibrils
Authors: Ha Chanki , Park Chan Beum
Published: April 2005

The formation of amyloid aggregates in tissue is a pathological feature of many neurodegenerative diseases and type II diabetes. Amyloid deposition, the process of amyloid growth by the association of individual soluble amyloid molecules with a pre‐existing amyloid template (i.e., plaque), is known to be critical for amyloid formation in vivo. The requirement for a natural amyloid template, however, has made amyloid deposition study difficult and cumbersome. In the present work, we developed a novel, synthetic amyloid template by attaching amyloid seeds covalently onto an N‐hydroxysuccinimide‐activated surface, where insulin was chosen as a model amyloidogenic protein. According to ex situ atomic force microscopy observations, insulin monomers in solution were deposited onto the synthetic amyloid template to form fibrils, like hair growth. The fibril formation on the template occurred without lag time, and its rate was highly accelerated than in the solution. The fibrils were long, over 2 μm, and much thinner than those in the solution, which was caused by limited nucleation sites on the template surface and lack of lateral twisting between fibrils. According to our investigations using thioflavin T‐induced fluorescence, birefringent Congo red binding, and circular dichroism, fibrils grown on the template were identified to be amyloids that formed through a conformational rearrangement of insulin monomers upon interaction with the template. The amyloid deposition rate followed saturation kinetics with respect to insulin concentration in the solution. The characteristics of amyloid deposition on the synthetic template were in agreement with previous studies performed with human amyloid plaques. It is demonstrated that the synthetic amyloid template can be used for the screening of inhibitors on amyloid deposition in vitro. © 2005 Wiley Periodicals, Inc.
Interactions between self‐assembled polyelectrolyte shells and tumor cells
Authors: Ai Hua , Pink John J. , Shuai Xintao , Boothman David A. , Gao Jinming
Published: April 2005

Layer‐by‐layer self‐assembled polyelectrolyte shells are a new class of micro/nanocapsules with unique physicochemical properties for potential applications in drug/gene delivery. The objective of this study was to investigate the interactions of polyelectrolyte shells (∼1 μm in diameter) with MCF‐7 breast cancer cells and identify key parameters that affect such interactions. Tailoring of surface properties of polyelectrolyte shells was achieved by choosing different outermost layer materials, including cationic polymers, anionic polymers, and lipid bilayers. Different surface compositions led to a wide range of electrostatic potentials from −46 to +47 mV in phophate‐buffered saline buffer. Confocal microscopy studies showed that the polyelectrolyte shells were internalized into the cell cytoplasm, but not into the nuclei. Correlation of cell uptake with shell surface compositions was complicated by the adsorption of serum proteins on the surface of polyelectrolyte shells, particularly polycation‐coated shells. To prevent protein adsorption, poly(ethylene glycol) (PEG) grafted poly(ethyleneimine) (PEI) copolymers (1:1, 1:5, 1:10 graft ratios) were synthesized and introduced on the shell surface. Shells coated with PEI‐PEG copolymers effectively reduced protein adsorption whereas PEI‐PEG copolymers with lower graft ratios achieved higher cell uptake efficiency after 24 h of incubation with MCF‐7 cells. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res 73A: 303–312, 2005
Analysis of glutathione and immunoglobulin G inside chromatographic beads using surface‐enhanced Raman scattering spectroscopy
Authors: Larsson Mina , Lindgren Jan
Published: April 2005

Gold‐containing chromatographic beads were used to record spectra of the tripeptide glutathione and the protein immunoglobulin G (IgG) by surface‐enhanced Raman scattering (SERS) spectroscopy. SERS spectra were recorded from glutathione in solution at three different pH values, 2, 6 and 10. It was found that the SERS spectra are strongly dependent on pH, which indicates that the adsorption mode of glutathione changes with the pH value of the solution. Assignment of some of the observed bands and a suggestion for adsorption modes at the different pH were made. A SERS spectrum of human IgG in ethanolamine was also recorded. No complete assignment of the bands in this spectrum was performed, but the results indicate adsorption to the gold nanoparticles by aromatic amino acids and cystine residues. Copyright © 2005 John Wiley & Sons, Ltd.
Molecular imprinting technology in capillary electrochromatography
Authors: Turiel Esther , Martin‐Esteban Antonio
Published: April 2005

Molecularly imprinted polymers (MIPs) are tailor‐made synthetic polymers with a predetermined selectivity for a given analyte, or group of structurally related compounds, that make them ideal materials for use as stationary phases in affinity chromatography. However, extensive peak broadening and tailing, especially of the more retained compound (normally the template) are often observed. Thus, huge efforts have been made during recent years to use MIPs in capillary electrochromatography, which is inherently a more efficient chromatographic technique than conventional HPLC. Accordingly, this paper gives an overview of the attempts carried out in the recent past to improve the chromatographic performance of MIPs in capillary electrochromatography as well as more recent applications. It is concluded that MIPs are very promising materials for use as selective stationary phases in CEC.
Spectral and dynamical properties of random models with nonlocal and singular interactions
Authors: Hislop Peter D. , Kirsch Werner , Krishna M.
Published: April 2005

We give a spectral and dynamical description of certain models of random Schrödinger operators onL2(ℝd) for which a modified version of the fractional moment method of Aizenman and Molchanov [3] can be applied. One family of models includes Schrödinger operators with random nonlocal interactions constructed from multidimensional wavelet bases. The second family includes Schrödinger operators with random singular interactions randomly located on sublattices of ℤd, ford= 1, 2, 3. We prove that these models are amenable to Aizenman‐Molchanov‐type analysis of the Green's function, thereby eliminating the use of multiscale analysis. The basic technical result is an estimate on the expectation of fractional moments of the Green's function. Among our results, we prove a Wegner estimate, Hölder continuity of the integrated density of states, and spectral and Hilbert‐Schmidt dynamical localization at negative energies. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bases and quasi‐reflexivity in Fréchet spaces
Authors: Valdivia Manuel
Published: April 2005

A Fréchet space E is quasi‐reflexive if, either dim(E″/E) < ∞, or E″[β(E″,E′)]/E is isomorphic to ω. A Fréchet space E is totally quasi‐reflexive if every separated quotient is quasi‐reflexive. In this paper we show, using Schauder bases, that E is totally quasi‐reflexive if and only if it is isomorphic to a closed subspace of a countable product of quasi‐reflexive Banach spaces. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On a class of Besicovitch functions to have exact box dimension: A necessary and sufficient condition
Authors: Zhou S. P. , He G. L.
Published: April 2005

Let 1 < s < 2, λk > 0 with λk → ∞ satisfy λk+1/λk ≥ λ > 1. For a class of Besicovich functions B(t) = $ \sum ^{\infty} _{k=1} \, \lambda ^{s-2} _{k} $ sin λkt, the present paper investigates the intrinsic relationship between box dimension of their graphs and the asymptotic behavior of {λk}. We show that the upper box dimension does not exceed s in general, and equals to s while the increasing rate is sufficiently large. An estimate of the lower box dimension is also established. Then a necessary and sufficient condition is given for this type of Besicovitch functions to have exact box dimensions: for sufficiently large λ, dimBΓ(B) = dimBΓ(B) = s holds if and only if limn→∞ $ { { {\rm log} \lambda _{n+1}} \over { {\rm log} \lambda _{n} } } $ = 1. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reply: Diagnosis and management of pergolide‐induced fibrosis
Authors: Frucht Steven , Agarwal Pinky , Fahn Stanley
Published: April 2005

The original letter to which this reply refers was published in Movement DisordersMov Disord (2005) 20 (4) 512–513.
Visual system side effects caused by parasympathetic dysfunction after botulinum toxin type B injections
Authors: Dubow Jordan , Kim Angela , Leikin Jerrold , Cumpston Kirk , Bryant Sean , Rezak Michael
Published: April 2005

Botulinum toxin type B (BTX‐B) has been approved by the Food and Drug Administration for the treatment of cervical dystonia. However, as with botulinum toxin type A (BTX‐A) it has off‐label uses, such as for hyperhidrosis, focal dystonias, spasticity, and facial wrinkles. BTX‐B has also been shown to be a safe and effective alternative for patients who are resistant to BTX‐A. The most commonly reported side effects include dry mouth and dysphagia. To date, there have been few reports of visual disturbances associated with BTX‐B use. In this study, we report on three individual patients who received BTX‐B and who subsequently developed parasympathetic dysfunction of the visual system after injections of BTX‐B at remote sites. © 2005 Movement Disorder Society
Impact of pro‐oxidant agents on the morula‐blastocyst transition in bovine embryos
Authors: Feugang Jean‐Magloire , Donnay Isabelle , Mermillod Pascal , Marchandise Joelle , Lequarre Anne‐Sophie
Published: April 2005

Exposing day 5 bovine morulae to reactive oxygen species induces a delayed degeneration of some blastocysts on day 8 post‐insemination (pi) but without affecting the blastocyst rates. The aim of this study was to characterize the resisting and the degenerating population of blastocysts. The kinetics of degeneration of the embryos exposed to the two pro‐oxidant agents: 2,2′‐azobis (2‐amidinopropane) dihydrochloride (AAPH) and buthionine sulfoximine (BSO) was evaluated using time‐lapse cinematography. With both agents the first signs of degeneration appeared at day 7.5 pi but the duration of the degeneration process was shorter in presence of AAPH than BSO (4.2 vs. 12.5 hr, ANOVA, P < 0.05). The resisting blastocysts derived from morulae with a larger diameter (mean diameter: 161 vs. 154 μm, ANOVA, P < 0.05) and showed an earlier cavitation (135 vs. 142 hpi, P < 0.05) than the degenerating ones. The profile of protein neosynthesis at day 7 was not affected by the treatment. The proportion of male embryos was more important in the resisting than in the degenerating population (70 vs. 55%, χ2, P < 0.05) especially when the stress was induced by AAPH. The quality of the resisting embryos, measured by the total cell number and the rate of apoptosis, did not seem to be affected when compared to control embryos. In conclusion, resistance to oxidative stress seems related to the kinetics of development and/or the sex of the embryos. Resisting embryos apparently display a quality similar to untreated embryos. Mol. Reprod. Dev. © 2005 Wiley‐Liss, Inc.
Effects of duration, concentration, and timing of ionomycin and 6‐dimethylaminopurine (6‐DMAP) treatment on activation of goat oocytes
Authors: Lan Guo‐Cheng , Han Dong , Wu Yan‐Guanng , Han Zheng‐Bin , Ma Suo‐Feng , Liu Xin‐Yong , Chang Chong‐Le , Tan Jing‐He
Published: April 2005

The protocol of ionomycin followed by 6‐dimethylaminopurine (6‐DMAP) is commonly used for activation of oocytes and reconstituted embryos. Since numerous abnormalities and impaired development were observed when oocytes were activated with 6‐DMAP, this protocol needs optimization. Effects of concentration and treatment duration of both drugs on activation and development of goat oocytes were examined in this study. The best oocyte activation (87–95%), assessed by pronuclear formation, was obtained when oocytes matured in vitro for 27 hr were treated with 0.625–20 μM ionomycin for 1 min before 6‐hr incubation in 2 mM 6‐DMAP. Progressional reduction of time for 6‐DMAP‐exposure showed that the duration of 6‐DMAP treatment can be reduced to 1 hr from the second up to the fourth hour after ionomycin, to produce activation rates greater than 85%. Activation rates of oocytes in vitro matured for 27, 30, and 33 hr were higher (P < 0.05) than that of oocytes matured for 24 hr when treated with ionomycin plus 1‐hr (the third hour) 6‐DMAP, but a 4‐hr incubation in 6‐DMAP enhanced activation of the 24‐hr oocytes. Goat activated oocytes began pronuclear formation at 3 hr and completed it by 5‐hr post ionomycin. An extended incubation in 6‐DMAP (a) impaired the development of goat parthenotes, (b) quickened both the release from metaphase arrest and the pronuclear formation, and (c) inhibited the chromosome movement at anaphase II (A‐II) and telophase II (T‐II), leading to the formation of one pronucleus without extrusion of PB2. In conclusion, duration, concentration, and timing of ionomycin and 6‐DMAP treatment had marked effects on goat oocyte activation, and to obtain better activation and development, goat oocytes matured in vitro for 27 hr should be activated by 1 min exposure to 2.5 μM ionomycin followed by 2 mM 6‐DMAP treatment for the third hour. Mol. Reprod. Dev. © 2005 Wiley‐Liss, Inc.
Involvement of superficial peroneal sensory nerve in common peroneal neuropathy
Authors: Kang Peter B. , Preston David C. , Raynor Elizabeth M.
Published: April 2005

Motor involvement in common peroneal neuropathy (CPN) frequently shows a selective pattern with regard to deep and superficial divisions of the peroneal nerve, by clinical examination and needle electromyography. The involvement of the sensory branch of the superficial peroneal nerve (SPN) has not been well established using nerve conduction studies. Among 42 cases of electrophysiologically defined CPN in 35 patients, 37 (88%) had clinical or electrophysiologic evidence for SPN involvement, but only 20 had diminished superficial peroneal sensory response (SPSR) amplitudes. Many of the cases involving normal SPSRs had significant axonal loss involving deep peroneal motor fibers. Sparing of the superficial peroneal sensory fibers provides further evidence for the selective vulnerability of different nerve fascicles to injury. This is an important pattern to recognize; from a practical standpoint, focal segmental conduction abnormalities in the motor nerve and EMG findings can help to differentiate these lesions from L‐5 radiculopathy. Muscle Nerve 31, 2005
Beta 2 adrenergic receptor polymorphisms in cystic fibrosis
Authors: Hart Meeghan A. , Konstan Michael W. , Darrah Rebecca J. , Schluchter Mark D. , Storfer‐Isser Amy , Xue Lintong , Londono Douglas , Goddard Katrina A.B. , Drumm Mitchell L.
Published: April 2005

There has been a recent emphasis on identifying modifier genes that influence the severity of cystic fibrosis (CF) lung disease. The beta‐2‐adrenergic receptor is expressed on airway smooth muscle, is the target for inhaled beta agonists, and has several common polymorphisms in its gene, ADRB2. Polymorphisms changing glycine to arginine or glutamate to glutamine in codons 16 and 27, respectively, were associated with differences in clinical response to inhaled beta agonists in individuals with asthma. We compared acute airway responsiveness and 5‐year decline in pulmonary function in CF patients with different ADRB2 genotypes. One hundred and six subjects performed spirometry before and after the administration of an inhaled bronchodilator, and had ADRB2 genotype determined for codons 16 and 27. Comparing the percent change in FEV1 and FEF25–75 continuously revealed differences in the degree of airway responsiveness to bronchodilator between ADRB2‐genotyped groups. However, there was no significant relationship between the ADRB2 genotype at positions 16 and 27 and bronchodilator response when defined as 12% improvement in FEV1. Five‐year decline in percent predicted FEV1 showed no association with ADRB2 genotype. These data are consistent with variants of the ADRB2 gene having different responses to bronchodilator, but the long‐term effects, if any, are not apparent over a 5‐year period. Pediatr Pulmonol © 2005 Wiley‐Liss, Inc.
Investigation of limiting metabolic steps in the utilization of xylose by recombinant Saccharomyces cerevisiae using metabolic engineering
Authors: Karhumaa Kaisa , Hahn‐Hägerdal Bärbel , Gorwa‐Grauslund Marie‐F.
Published: April 2005

A Saccharomyces cerevisiae screening strain was designed by combining multiple genetic modifications known to improve xylose utilization with the primary objective of enhancing xylose growth and fermentation in xylose isomerase (XI)‐expressing strains. Strain TMB 3045 was obtained by expressing the XI gene from Thermus thermophilus in a strain in which the GRE3 gene coding for aldose reductase was deleted, and the genes encoding xylulokinase (XK) and the enzymes of the non‐oxidative pentose phosphate pathway (PPP) [transaldolase (TAL), transketolase (TKL), ribose 5‐phosphate ketol‐isomerase (RKI) and ribulose 5‐phosphate epimerase (RPE)] were overexpressed. A xylose‐growing and fermenting strain (TMB 3050) was derived from TMB 3045 by repeated cultivation on xylose medium. Despite its low XI activity, TMB 3050 was capable of aerobic xylose growth and anaerobic ethanol production at 30 °C. The aerobic xylose growth rate reached 0.17 l/h when XI was replaced with xylose reductase (XR) and xylitol dehydrogenase (XDH) genes expressed from a multicopy plasmid, demonstrating that the screening system was functional. Xylose growth had not previously been detected in strains in which the PPP genes were not overexpressed or when overexpressing the PPP genes but having XR and XDH genes chromosomally integrated. This demonstrates the necessity to simultaneously increase the conversion of xylose to xylulose and the metabolic steps downstream of xylulose for efficient xylose utilization in S. cerevisiae. Copyright © 2005 John Wiley & Sons, Ltd.
Estimation of aboveground biomass and net biomass increment in a cool temperate forest on a landscape scale
Authors: Hiura Tsutom
Published: April 2005

I clarified aboveground biomass (AGB), net biomass increment (NBI) and its spatial heterogeneity in a cool temperate forest on a landscape scale (>2,200 ha). The relationships among AGB, NBI, and the size frequency distribution of trees of each stand were examined by combining an analysis of vegetation using aerial photographs, and data from 146 inventory plots (28.8 ha in total). This area included natural broad‐leaved stands, harvested broad‐leaved stands, and artificial conifer plantations. A −3/2 power distribution density function was applied to the individual mass frequency distribution of each plot. Estimated AGB in carbon (C) equivalent was 480–5,615 g C m−2 (3,130 g C m−2 on average), and NBI was −98 to 436 g C m−2 year−1 (83.0 g C m−2 year−1 on average). NBI had a single significant relationship with the reciprocal of theoretical maximum individual mass, while NBI was not significantly related to AGB. My results showed that, on a landscape scale, AGB and NBI strongly depend on the size structure of forest stands.
Interseismic strain accumulation and anthropogenic motion in metropolitan Los Angeles
Authors: Argus Donald F. , Heflin Michael B. , Peltzer Gilles , Crampé Fréderic , Webb Frank H.
Published: April 2005

We use global positioning system (GPS) geodesy and synthetic aperture radar (SAR) interferometry to distinguish between interseismic strain accumulation and anthropogenic motion in metropolitan Los Angeles. We establish a relationship between horizontal and vertical seasonal oscillations of the Santa Ana aquifer, use this relationship to infer cumulative horizontal anthropogenic motions from cumulative vertical motions caused by water and oil resource management, and estimate horizontal interseismic velocities corrected for anthropogenic effects. Vertical anthropogenic rates from 1992 to 1999 are slower than 3 mm yr−1 in the Santa Ana and San Gabriel aquifers and faster than 5 mm yr−1 in the Chino aquifer and in many oil fields. Inferred horizontal anthropogenic velocities are faster than 1 mm yr−1 at 18 of 46 GPS sites. Northern metropolitan Los Angeles is contracting, with the 25 km south of the San Gabriel Mountains shortening at 4.5 ± 1 mm yr−1 (95% confidence limits). The thrust fault in an elastic edge dislocation model of the observed strain is creeping at 9 ± 2 mm yr−1 beneath and north of a position 6 ± 2 km deep and 8 ± 8 km north of downtown Los Angeles. The model fault is near the Los Angeles segment of the Puente Hills thrust but south of the Sante Fe Springs segment of the thrust. Disagreement between the 6 km locking depth in the model and the 15 km seismogenic depth inferred from earthquakes suggests that the elastic continuum model may be unsatisfactory; models with different stiffnesses of sedimentary basin and crystalline basement must be investigated.
Effect of thinning on surface fluxes in a boreal forest
Authors: Vesala T. , Suni T. , Rannik Ü. , Keronen P. , Markkanen T. , Sevanto S. , Grönholm T. , Smolander S. , Kulmala M. , Ilvesniemi H. , Ojansuu R. , Uotila A. , Levula J. , Mäkelä A. , Pumpanen J. , Kolari P. , Kulmala L. , Altimir N. , Berninger F. , Nikinmaa E. , Hari P.
Published: April 2005

Thinning is a routine forest management operation that changes tree spacing, number, and size distribution and affects the material flows between vegetation and the atmosphere. Here, using direct micrometeorological ecosystem‐scale measurements, we show that in a boreal pine forest, thinning decreases the deposition velocities of fine particles as expected but does not reduce the carbon sink, water vapor flux, or ozone deposition. The thinning decreased the all‐sided leaf area index from 8 to 6, and we suggest that the redistribution of sources and sinks within the ecosystem compensated for this reduction in foliage area. In the case of water vapor and O3, changes in light penetration and among‐tree competition seem to increase individual transpiration rates and lead to larger stomatal apertures, thus enhancing also O3 deposition. In the case of CO2, increased ground vegetation assimilation and decreased autotrophic respiration seem to cancel out opposite changes in canopy assimilation and heterotrophic respiration. Current soil‐vegetation‐atmosphere transfer models should be able to reproduce these observations.
Tropical and extratropical tropospheric air in the lowermost stratosphere over Europe: A CO‐based budget
Authors: Hoor P. , Fischer H. , Lelieveld J.
Published: April 2005

We present a new approach to calculate a trace gas budget for the lowermost stratosphere based on airborne CO measurements. The measurements were obtained during the SPURT‐project (SPURT in German: Trace gas transport in the tropopause region) and covered the tropopause region over Europe from 35°–75°N during different seasons. Using CO as a tracer for tropospheric air we quantified the contribution of three source regions to the composition of the lowermost stratosphere. Influence from the extratropical troposphere mainly contributes to the mixing layer above the local tropopause, where it decreases rapidly to less than 25% within a potential temperature range of 25 K above the local tropopause. With increasing distance from the tropopause mixing layer, the tropospheric fraction is dominated by influence from the tropics. During winter and spring the latter contributes about 35% to the chemical composition of the lowermost stratosphere over Europe, increasing to about 55% in summer and autumn.
Long-period martensitic structures of Ni-Mn-Ga alloys studied by high-resolution transmission electron microscopy
Authors: Pons Jaume , Santamarta Rubén , Chernenko Volodymyr A. , Cesari Eduard
Published: April 2005

The layered martensitic structures formed in Ni-Mn-Ga alloys have been investigated by high-resolution transmission electron microscopy (including image simulations) in order to discern from two structural models reported in the literature. For the seven-layer martensite, the observations discard the model based on shuffling of the atomic positions (modulation) by a function with a period of seven planes and confirm its nanotwinned nature, which is inherent to the description as stacking of nearly close-packed planes derived from {110}aust with (52¯) sequence, that is, the so-called 14M structure. The observed stacking sequence, however, is notably distorted [the perfect (52¯) sequence is present only in small areas], although it preserves a predominant periodicity of seven planes. For another alloy composition, a nanotwinned martensite with periodicity of twelve planes and (75¯) average stacking sequence has also been observed. In case of the five-layer martensite, the image simulations and atom projections obtained from the two structural models fit well with the experimental images, which makes it very difficult to discern between them.
Size-dependent optical properties of sputter-deposited nanocrystalline p-type transparent CuAlO2 thin films
Authors: Banerjee A. N. , Chattopadhyay K. K.
Published: April 2005

Nanocrystalline, p-type semiconducting, transparent CuAlO2 thin films were deposited by direct current sputtering of a prefabricated polycrystalline CuAlO2 target, with deposition time as a variable parameter. Transmission electron micrographs reveal the formation of CuAlO2 nanoparticles. For the films deposited in 3, 9, and 15min, the average particle sizes are determined to be around 10, 20, and 30nm, respectively. The interplaner spacings calculated from selected area electron-diffraction patterns obtained from transmission electron microscopy confirmed the proper phase formation of the material. X-ray diffraction measurements of the films deposited for 15 and 45min show some diffraction peaks, which depict the rhombohedral crystal structure of the material. The band-gap values obtained from the optical transmission and reflection data, for the films deposited in 3 and 9min, are 3.94 and 3.84eV, respectively, whereas for those films deposited in 15 and 45min, the band-gap values lie in the range of 3.72–3.60eV. These values are quite larger than that of bulk material, which is around 3.34eV. The particle sizes in these cases are, respectively, 30 and 60nm. It is well known that quantum confinement in semiconductor nanocrystals leads to the band-gap widening with respect to the bulk material. In this report we have observed an increase in the band gap of the nanostructured p-type semiconducting CuAlO2 thin film with the decrease in the particle size. Room-temperature photoluminescence measurements of this material are reported, which showed an ultraviolet near-band-edge emission around 3.60eV, which originates from the generation and recombination of electron-hole pairs, namely, excitons. From the semiquantitative arguments it is supposed that the natural layered structure of delafossite CuAlO2 is responsible for the stability of the excitons. Also a blueshift of the emission peaks is observed with a decrease in the particle size, which may be described as another experimental indication of the quantum confinement effect within our nanocrystalline CuAlO2 thin films. The p-type nature of the films was established by hot-probe and thermopower measurements.
Truncation of the correlation consistent basis sets: Extension to third-row (Ga–Kr) molecules
Authors: Mintz Benjamin , Wilson Angela K.
Published: April 2005

The systematic reduction of the commonly used correlation consistent basis sets [cc-pVnZ where n=D(2), T(3), Q(4), and 5] as a means to reduce computational cost has been extended to hydrogen-containing third-row (Ga–Kr) molecules of the G2 test suite. Coupled cluster with singles, doubles, and quasiperturbative triple excitations [CCSD(T)] calculations were performed using both the full correlation consistent basis sets and a series of truncated basis sets in order to assess the impact of basis set reduction upon the structures and energies of the species. The impact that truncation of the basis sets for hydrogen has upon extrapolation of energies to the complete basis set limit also has been examined, and the cost savings that can be achieved are discussed. Overall, basis set reduction can be accomplished which preserves the systematic convergence behavior of the full correlation consistent basis sets.
Potential-step amplified nonequilibrium thermal-electric converters
Authors: Chen Gang
Published: April 2005

We predict a large thermoelectric effect at properly designed electrical potential steps that can be exploited to design thermoelectric coolers and power generators. A large nonequilibrium between electrons and phonons can be created at a potential step either by a heat flux (for power generation) or an electrical current. This effect can only exist in a forward structural configuration, which consists of a short region with low doping and a long region with high doping, and a potential step from the short to the long region. Electron temperature discontinuity is amplified at such an interface, leading to a large Seebeck voltage drop at the interface. A similar effect does not exist in a reverse structure. Modeling shows that higher thermal-electric power generation and cooling efficiency can be realized using the effect.
Experimental and theoretical analyses of PrAl2 and NdAl2 composite for use as an active magnetic regenerator
Authors: Carvalho A. Magnus G. , Campoy J. C. P. , Coelho A. A. , Plaza E. J. R. , Gama S. , von Ranke P. J.
Published: April 2005

We report the theoretical and experimental investigations on the magnetocaloric effect in the PrAl2 and NdAl2 compounds and a composite of these compounds for use as an active magnetic regenerator. The theoretical calculations were performed considering the crystalline electrical field anisotropy and the magnetocaloric potentials were calculated in the three main crystallographic directions. The experimental data, obtained for the polycrystalline samples, are in good agreement with the theoretical results. Also, an optimum molar fraction of the PrAl2 and NdAl2 composite was determined theoretically and experimentally and discussed in the framework of the optimum regeneration Ericsson cycle.
Incompatibility of the exponential scaling law for a zero pressure gradient boundary layer flow with Reynolds averaged turbulence models
Authors: Guenther S. , Oberlack M.
Published: April 2005

Analyzing the multipoint-correlation equations for parallel turbulent shear flows and zero pressure gradient turbulent boundary layer flows with the help of Lie symmetry methods, a new exponential scaling law has been derived in the work by Oberlack [“A unified approach for symmetries in plane parallel turbulent shear flows,” J. Fluid Mech. 427, 299 (2001)]. In the frame work of Lie group methods these solutions are called invariant solutions. From experiments [B. Lindgren, J. M. Österlund, and A. Johansson, “Evaluation of scaling laws derived from Lie group symmetry methods in zero-pressuere-gradient turbulent boundary layers,” J. Fluid Mech. 502, 127 (2004)] and direct numerical simulations [G. Khujadze and M. Oberlack, “DNS and scaling laws from new symmetry groups of ZPG turbulent boundary layer flow,” Theor. Comput. Fluid Dyn. 18, 5 (2004)] the exponential velocity profile was clearly validated in the mid-wake region of high Reynolds number flat-plate boundary layers. It was identified as an explicit analytic form of the velocity defect law. Implementing the latter invariant solution into various Reynolds stress models it was found that none of the investigated models are in accordance with the exponential velocity law.
Observation of bound-free transitions of the linear Ar⋯I2(X,v″=) complex in and above the I2B-X spectral region
Authors: Darr Joshua P. , Glennon John J. , Loomis Richard A.
Published: April 2005

Laser-induced fluorescence and action spectroscopy experiments were performed to identify the origin of the Ar⋯I2 continuum signals observed in and above the I2B-X spectral region. We have verified that these signals arise from transitions of the linear Ar⋯I2(X,v″=0) complex. The data provides no evidence that the excited state complexes undergo a one-atom caging mechanism when prepared above the I2(B) dissociation limit, Ar⋯I2(B)*→Ar+I+I*→Ar+I2(B,v′). Instead, our results indicate that the continuum signals result from bound-free transitions of the linear Ar⋯I2(X,v″=0) complex to the inner repulsive walls of numerous Ar+I2(B,v′) intermolecular potentials. The bound-free continuum signal associated with transitions to each Ar+I2(B,v′) potential spans an energy region >700cm−1. We have found that the continuum signals turn-on 250(2)cm−1 above the corresponding I2B-X,v′-0 band origin, and this energy represents the binding energy of the linear Ar⋯I2(X,v″=0) conformer, D0″(L)=250(2)cm−1.
Magnetic domain walls in T-shaped permalloy microstructures
Authors: Haug T. , Back C. H. , Raabe J. , Heun S. , Locatelli A.
Published: April 2005

The magnetic domain wall width of T-shaped permalloy structures has been measured using a photoemission electron microscope and x-ray magnetic dichroism. The results are compared to micromagnetic simulations. The shape of the structures allows us to analyze 90° Néel walls. We find a decrease in domain wall width with decreasing contact dimensions as expected by theory and in good agreement with our micromagnetic simulations.
Intensity-modulated blue light generated by frequency doubling of wavelength-modulated high-power diode-laser radiation
Authors: Woll Dirk , Tremont Marc A. , Fuchs Harry , Casel Oliver , Wallenstein Richard
Published: April 2005

A scheme for the generation of modulated blue laser radiation is demonstrated. The 923nm radiation of a high-power diode-laser master-oscillator power-amplifier system is wavelength modulated within a range of 0.2nm by modulating the injection current of the distributed feedback (DFB) diode oscillator. Single-pass frequency doubling of the generated radiation in periodically poled potassium titanyl phospate converts the wavelength modulation into an intensity modulation with a contrast ratio exceeding 700:1. The 3dB modulation bandwidth of 35kHz is limited by the speed of the wavelength tuning of the DFB oscillator.
Hf
O
2
and Al2O3 gate dielectrics on GaAs grown by atomic layer deposition
Authors: Frank Martin M. , Wilk Glen D. , Starodub Dmitri , Gustafsson Torgny , Garfunkel Eric , Chabal Yves J. , Grazul John , Muller David A.
Published: April 2005

High-performance metal-oxide-semiconductor field effect transistors (MOSFETs) on III–V semiconductors have long proven elusive. High-permittivity (high-κ) gate dielectrics may enable their fabrication. We have studied hafnium oxide and aluminum oxide grown on gallium arsenide by atomic layer deposition. As-deposited films are continuous and predominantly amorphous. A native oxide remains intact underneath HfO2 during growth, while thinning occurs during Al2O3 deposition. Hydrofluoric acid etching prior to growth minimizes the final interlayer thickness. Thermal treatments at ∼600°C decompose arsenic oxides and remove interfacial oxygen. These observations explain the improved electrical quality and increased gate stack capacitance after thermal treatments.
Postannealing of magnetic tunnel junctions with ion-bombardment-modified exchange bias
Authors: Höink V. , Sacher M. D. , Schmalhorst J. , Reiss G. , Engel D. , Junk D. , Ehresmann A.
Published: April 2005

The influence of a postannealing procedure on the transport properties of magnetic tunnel junctions with ion-bombardment-manipulated exchange bias is investigated. The controlled manipulation of the direction of the exchange bias field in magnetic tunnel junctions by He ion bombardment usually is accompanied by a reduction of the tunneling magnetoresistance and an increase in the resistance. Here, we demonstrate that it is possible to reduce these negative effects of the ion bombardment considerably by postannealing without a magnetic field. For optimized combinations of ion dose and postannealing temperature, the tunneling magnetoresistance recovers completely (>50% resistance change) while the exchange bias direction set by the ion bombardement is preserved.
Magnetic directed assembly of molecular junctions
Authors: Long David P. , Patterson Charles H. , Moore Martin H. , Seferos Dwight S. , Bazan Guillermo C. , Kushmerick James G.
Published: April 2005

We present a technique for fabricating molecular junctions for molecular electronic devices. Silica microspheres are rendered magnetically susceptible and electrically conductive by the sequential deposition of nickel and gold films. The metallized microspheres undergo directed assembly into lithographically defined magnetic arrays functionalized with self-assembled monolayers of prototypical molecular wire candidates. We characterize the resulting junctions by scanning electron microscopy and measure their current-voltage characteristics. Magnetic directed assembly provides a wafer-level route for the fabrication of molecular junctions and opens up the potential for hybrid complementary metal-oxide semiconductor∕molecular electronic applications.
Optical modulation processes in thin films based on thermal effects of surface plasmons
Authors: Lereu A. L. , Passian A. , Goudonnet J-P. , Thundat T. , Ferrell T. L.
Published: April 2005

Experimental results are presented for light-on-light modulation at low rates using coupling to nonradiative surface plasmons and their associated thermal effects in a thin gold foil. It is first shown that several modulated Gaussian beams simultaneously exciting surface plasmons in the same region of a thin gold film, will result in a coupling that is revealed in the reflected beams. The observed effects result in the reflected beams undergoing changes in both spatial distribution and intensity levels. A brief study is then presented of the coupling between surface plasmons and an electrical current in the excitation region to further support the role of the surface plasmon induced thermal processes in the gold foil.
The phasevarion: A genetic system controlling coordinated, random switching of expression of multiple genes
Authors: Srikhanta Yogitha N. , Maguire Tina L. , Stacey Katryn J. , Grimmond Sean M. , Jennings Michael P.
Published: April 2005

Several host-adapted bacterial pathogens contain methyltransferases associated with type III restriction-modification (R-M) systems that are subject to reversible, high-frequency on/off switching of expression (phase variation). To investigate the role of phase-variable expression of R-M systems, we made a mutant strain lacking the methyltransferase (
mod
) associated with a type III R-M system of
Haemophilus influenzae
and analyzed its phenotype. By microarray analysis, we identified a number of genes that were either up- or down-regulated in the
mod
mutant strain. This system reports the coordinated random switching of a set of genes in a bacterial pathogen and may represent a widely used mechanism.
Multipotent nestin-positive, keratin-negative hair-follicle bulge stem cells can form neurons
Authors: Amoh Yasuyuki , Li Lingna , Katsuoka Kensei , Penman Sheldon , Hoffman Robert M.
Published: April 2005

We have recently shown that the expression of nestin, the neural stem cell marker protein, is expressed in bulge-area stem cells of the hair follicle. We used transgenic mice with GFP expression driven by the nestin regulatory element [nestin-driven GFP (ND-GFP)]. The ND-GFP stem cells give rise to the outer-root sheath of the hair follicle as well as an ND-GFP interfollicular vascular network. In this study, we demonstrate that ND-GFP stem cells isolated from the hair-follicle bulge area that are negative for the keratinocyte marker keratin 15 can differentiate into neurons, glia, keratinocytes, smooth muscle cells, and melanocytes
in vitro
. These pluripotent ND-GFP stem cells are positive for the stem cell marker CD34, as well as keratin 15-negative, suggesting their relatively undifferentiated state. The apparent primitive state of the ND-GFP stem cells is compatible with their pluripotency. Furthermore, we show that cells derived from ND-GFP stem cells can differentiate into neurons after transplantation to the subcutis of nude mice. These results suggest that hair-follicle bulge-area ND-GFP stem cells may provide an accessible, autologous source of undifferentiated multipotent stem cells for therapeutic application.
Independent perceptual learning in monocular and binocular motion systems
Authors: Lu Zhong-Lin , Chu Wilson , Dosher Barbara Anne , Lee Sophia
Published: April 2005

Eye-transfer tests, external noise manipulations, and observer models were used to systematically characterize learning mechanisms in judging motion direction of moving objects in visual periphery (Experiment 1) and fovea (Experiment 2) and to investigate the degree of transfer of the learning mechanisms from trained to untrained eyes. Perceptual learning in one eye was measured over 10 practice sessions. Subsequent learning in the untrained eye was assessed in five transfer sessions. We characterized the magnitude of transfer of each learning mechanism to the untrained eye by separately analyzing the magnitude of subsequent learning in low and high external noise conditions. In both experiments, we found that learning in the trained eye reduced contrast thresholds uniformly across all of the external noise levels: 47 ± 10% and 62 ± 8% in experiments 1 and 2, respectively. Two mechanisms, stimulus enhancement and template retuning, accounted for the observed performance improvements. The degree of transfer to the untrained eye depended on the amount of external noise added to the signal stimuli: In high external noise conditions, learning transferred completely to the untrained eye in both experiments. In low external noise conditions, there was only partial transfer of learning: 63% in experiment 1 and 54% in experiment 2. The results suggest that template retuning, which is effective in high external noise conditions, is mostly binocular, whereas stimulus enhancement, which is effective in low external noise displays, is largely monocular. The two independent mechanisms underlie perceptual learning of motion direction identification in monocular and binocular motion systems.
Interaction strength combinations and the overfishing of a marine food web
Authors: Bascompte Jordi , Melián Carlos J. , Sala Enric
Published: April 2005

The stability of ecological communities largely depends on the strength of interactions between predators and their prey. Here we show that these interaction strengths are structured nonrandomly in a large Caribbean marine food web. Specifically, the cooccurrence of strong interactions on two consecutive levels of food chains occurs less frequently than expected by chance. Even when they occur, these strongly interacting chains are accompanied by strong omnivory more often than expected by chance. By using a food web model, we show that these interaction strength combinations reduce the likelihood of trophic cascades after the overfishing of top predators. However, fishing selectively removes predators that are overrepresented in strongly interacting chains. Hence, the potential for strong community-wide effects remains a threat.
A simple model for the within-host dynamics of a protozoan parasite
Authors: Klinkenberg D , Heesterbeek J.A.P
Published: April 2005

The dynamics of parasite–host systems can be complicated if the parasite life cycle contains an obligatory environmental stage and if the hosts' immunity increases upon re-infection. The dynamics then greatly depend on the relation between infection history and parasite uptake and excretion of individual hosts. In an effort to better understand such systems, we studyEimeriaspp. in chickens as our model. In this paper we take a first step and study the within-host dynamics ofEimeriaspp., transmitted through oocysts in the environment, with a mathematical model for the parasite life cycle in discrete time, interacting with a single variable describing the immune response. The model can explain various types of oocyst input–output behaviour as described in previous experiments, in particular the characteristic crowding effect, which causes a decreasing oocyst production with increasing single dose oocyst uptake. Oocyst excretion during constant oocyst uptake (trickle infection) and the immunizing effect of single and trickle infections also appears in accordance with published experiments. The model seems a good description of oocyst input–output behaviour in individual hosts; it provides a solid basis for the study of between-host dynamics, where individuals interact in a common environment, thereby affecting their own and each other's infection pattern.
The effect of the Neolithic expansion on European molecular diversity
Authors: Currat Mathias , Excoffier Laurent
Published: April 2005

We performed extensive and realistic simulations of the colonization process of Europe by Neolithic farmers, as well as their potential admixture and competition with local Palaeolithic hunter–gatherers. We find that minute amounts of gene flow between Palaeolithic and Neolithic populations should lead to a massive Palaeolithic contribution to the current gene pool of Europeans. This large Palaeolithic contribution is not expected under the demic diffusion (DD) model, which postulates that agriculture diffused over Europe by a massive migration of individuals from the Near East. However, genetic evidence in favour of this model mainly consisted in the observation of allele frequency clines over Europe, which are shown here to be equally probable under a pure DD or a pure acculturation model. The examination of the consequence of range expansions on single nucleotide polymorphism (SNP) diversity reveals that an ascertainment bias consisting of selecting SNPs with high frequencies will promote the observation of genetic clines (which are not expected for random SNPs) and will lead to multimodal mismatch distributions. We conclude that the different patterns of molecular diversity observed for Y chromosome and mitochondrial DNA can be at least partly owing to an ascertainment bias when selecting Y chromosome SNPs for studying European populations.
Environmental influences during development and their later consequences for health and disease: implications for the interpretation of empirical studies
Authors: Gluckman Peter D , Hanson Mark A , Spencer Hamish G , Bateson Patrick
Published: April 2005

Early experience has a particularly great effect on most organisms. Normal development may be disrupted by early environmental influences; individuals that survive have to cope with the damaging consequences. Additionally, the responses required to cope with environmental challenges in early life may have long-term effects on the adult organism. A further set of processes, those of developmental plasticity, may induce a phenotype that is adapted to the adult environment predicted by the conditions of early life. A mismatch between prediction and subsequent reality can cause severe health problems in those human societies where economic circumstances and nutrition are rapidly improving. Understanding the underlying mechanisms of plasticity is, therefore, clinically important. However, to conduct research in this area, developmental plasticity must be disentangled from disruption and the adverse long-term effects of coping. The paper reviews these concepts and explores ways in which such distinctions may be made in practice.