bluuebunny/crossref_metadata_2025 huggingface dataset:
Tunable near-infrared optical properties of three-layered metal nanoshells
Authors: Wu DaJian , Xu XiaoDong , Liu XiaoJun
Published: August 2008

The extinction spectra of a three-layered metal nanoshell, which consists of a particle with a dielectric core, a middle Ag (Au) layer, and an outer Au (Ag) shell, have been investigated by means of the Mie theory. With a decrease in the outer shell thickness or the middle layer thickness, the wavelengths of the localized surface plasmon resonance (LSPR) for SiO2–Ag–Au (SiO2–Au–Ag) nanoshells show distinct redshifts and the full widths at half maximum (FWHMs) for the dipole peaks in the extinction spectra decrease first and then increase. We have further investigated the influence of the embedding medium on the LSPRs for SiO2–Ag–Au and SiO2–Au–Ag nanoshells and found that the resonance wavelengths of the particles show redshift and the FWHM of the dipole peak increases with increasing the dielectric constant of the embedding medium. The calculated results indicate that the LSPR of the three-layered gold-silver nanoshells can be controlled to the near-infrared region by changing the geometry, which has practical biomedical application.
Fabrication of three-dimensional photonic crystal structures by interferometric lithography and nanoparticle self-assembly
Authors: Xia Deying , Zhang Jingyu , He Xiang , Brueck S. R. J.
Published: August 2008

We report a simple approach to fabrication of three-dimensional photonic crystal structures. One-dimensional photoresist patterns (lines) are defined as templates using interferometric lithography and silica nanoparticles are self-assembled around the photoresist patterns using spin coating. Multiple-layer structures are formed by repeating these processing steps. The photoresist patterns are removed through high temperature calcination to fabricate three-dimensional photonic crystals with void channels in a woodpile structure. The optical properties of as-prepared photonic crystal structures are in good agreement with simulation results. This approach provides a versatile and facile technology to fabricate photonic bandgap materials and photonic crystals with defects.
Influence of top surface passivation on bottom-channel hole mobility of ultrathin SiGe- and Ge-on-insulator
Authors: Yang Haigui , Wang Dong , Nakashima Hiroshi , Gao Hongye , Hirayama Kana , Ikeda Ken-ichi , Hata Satoshi , Nakashima Hideharu
Published: August 2008

Bottom-channel hole mobility was examined by a pseudo-metal-oxide-semiconductor field-effect transistors method for ultrathin SiGe-on-insulator (SGOI) and Ge-on-insulator (GOI), which were fabricated using Ge condensation by dry oxidation. By comparing samples with and without a top SiO2 layer, we investigated the influence of top surface passivation on bottom-channel hole mobility. Mobility degradation was found in an ultrathin SGOI/GOI layer without top SiO2 and became more serious with a decrease in the thickness of the SGOI/GOI layer, which strongly suggested that top surface passivation is necessary to evaluate accurate channel mobility. A 13-nm-thick GOI with passivation showed a high mobility value of 440 cm2/V s.
Linear and nonlinear stability analyses of thermal convection for Oldroyd-B fluids in porous media heated from below
Authors: Zhang Zhiyong , Fu Ceji , Tan Wenchang
Published: August 2008

Based on a modified Darcy–Brinkman–Oldroyd model, linear and nonlinear thermal stability analyses of a horizontal layer of an Oldroyd-B fluid in a porous medium heated from below were performed. By using the linear stability theory, the critical Rayleigh number, wave number, and frequency for stationary and oscillatory convections were determined. The effects of the viscoelastic parameters and the porous parameter on the critical Rayleigh number for oscillatory convection were analyzed. Based on the results of the linear stability analysis, a nonlinear stability analysis was also conducted. It is shown that the onset of stationary convection has the form of a supercritical and stable bifurcation independent of the viscoelastic parameters. However, the onset of oscillatory convection has the forms of supercritical or subcritical bifurcations. The nature of the oscillatory mode depends strongly on the viscoelastic parameters. The variation of the Nusselt number with respect to the Rayleigh number is derived for stationary and oscillatory convection modes. Although the critical Rayleigh number for stationary convection is independent of the viscoelastic parameters, the Nusselt number depends on the viscoelastic parameters of the fluids, which is different from that for the modified Darcy–Oldroyd model.
Balanced ambipolar charge carrier mobility in mixed layers for application in hybrid white organic light-emitting diodes
Authors: Schwartz Gregor , Ke Tung-Huei , Wu Chung-Chih , Walzer Karsten , Leo Karl
Published: August 2008

We investigate the electron and hole mobility in mixed layers of N,N′-di(naphthalen-1-yl)-N,N′-diphenyl-benzidine and bis(2-methyl-8-quinolinato)-4-phenylphenolate aluminum with different mix ratios, using both space-charge limited currents of single-carrier devices with electrically doped charge transport layers and time-of-flight measurements. Both experimental methods yield consistent results. The 1:1 blend shows balanced ambipolar charge carrier transport, which is advantageous for the application as exciton blocking interlayer in hybrid white organic light-emitting diodes: The electroluminescence spectrum is rather stable against changes in interlayer thickness and driving current. Moreover, the external quantum efficiency is enhanced by a factor of 2.5 as compared to a device without interlayer.
Controlled surface distribution and luminescence of YVO4:Eu3+ nanophosphor layers
Authors: Khan A. F. , Haranath D. , Yadav Ravishanker , Singh Sukhvir , Chawla S. , Dutta V.
Published: August 2008

A method of dispersing YVO4:Eu quantum dots (QDs) as uniform two-dimensional (2D) layers with a high degree of homogeneity is presented. Annealing at 773 K resulted in coalescence of QDs to form nanoclusters with size of ∼25 nm with an improved photoluminescence and ∼80% transmittance at 800 nm. An efficient D50-F72 transition and lifetimes of ∼1038 μs for the characteristic Eu3+ emission were observed. The absorption and emission peaks showed a slight blueshift, due to quantum-size effect, as compared to that for the bulk counterpart. Our method of 2D layer deposition is useful to enhance spectral response of the solar cells.
Spectroscopic research of underwater electrical wire explosion
Authors: Fedotov A. , Sheftman D. , Gurovich V. Tz. , Efimov S. , Bazilitski G. , Krasik Ya. E. , Oreshkin V. I.
Published: August 2008

Results of spectroscopic research in the visible range of light of the radiation generated by underwater electrical wire explosions (UEWE) are presented. A pulsed generator with an output voltage of ∼110kV, current of ∼70kA, and rise time of ∼60ns was used for electrical explosion of Cu wires 0.1mm in diameter and 50mm in length. It was shown that UEWE is not governed by the “polarity” effect, which plays an important role in electrical wire explosions in vacuum. The results of detailed space- and time-resolved spectroscopic measurements show that the radiation spectrum differs significantly of the spectrum expected from the exploding wire. A model is suggested based on the formation of a few μm “water” plasma layer in the vicinity of the exploding wire plasma which efficiently absorbs the radiation of the exploding wire.
Observation of Ti4+ ions in a high power impulse magnetron sputtering plasma
Authors: Andersson Joakim , Ehiasarian Arutiun P. , Anders André
Published: August 2008

Multiply charged titanium ions including Ti4+ were observed in high power impulse magnetron sputtering discharges. Mass/charge spectrometry was used to identify metal ion species. Quadruply charged titanium ions were identified by isotope-induced broadening at mass/charge 12. Due to their high potential energy, Ti4+ ions give a high yield of secondary electrons, which in turn are likely to be responsible for the generation of multiply charged states.
The nature of dielectric breakdown
Authors: Li X. , Tung C. H. , Pey K. L.
Published: August 2008

Dielectric breakdown is the process of local materials transiting from insulating to conductive when the dielectric is submerged in a high external electric field environment. We show that the atomistic changes of the chemical bonding in a nanoscale breakdown path are extensive and irreversible. Oxygen atoms in dielectric SiO2 are washed out with substoichiometric silicon oxide (SiOx with x<2) formation, and local energy gap lowering with intermediate bonding state of silicon atoms (Si1+, Si2+, and Si3+) in the percolation leakage path. Oxygen deficiency within the breakdown path is estimated to be as high as 50%–60%.
Exchange coupling assisted FePtC perpendicular recording media
Authors: Hu J. F. , Chen J. S. , Ding Y. F. , Lim B. C. , Phyoe W. L. , Liu B.
Published: August 2008

Exchange coupling assisted perpendicular recording media consisting of a 10 nm magnetically hard FePtC layer with a FePtC soft overlayer of a different thickness were investigated. Both the coercivity and the saturation field of the FePtC film decreased after introducing a magnetically soft FePtC overlayer. The soft FePt grains were located on top of the underlying FePt grains and at the grain boundaries. Some of the hard and soft grains were separated by a C layer accumulated on the hard magnetic FePtC layer surface. The strength of the exchange coupling between soft and hard grains depended on the C layer thickness.
Determination of the adsorption mechanism of imidazolium-type ionic liquids onto kaolinite: implications for their fate and transport in the soil environment
Authors: Mrozik Wojciech , Jungnickel Christian , Skup Michał , Urbaszek Piotr , Stepnowski Piotr
Published: August 2008

Environmental context. The present paper looks at the possible spreading of a new class of chemicals, namely, ionic liquids in soils. These ionic liquids have gained increasing attention, and their environmental impact and fate needs to be determined before accidental release. The paper specifically focusses on the adhesion mechanisms of these chemicals onto a type of clay, kaolinite. It was found that a multilayer adhesion mechanism occurs. Sorption of ionic liquids on kaolinite indicates that these chemicals can modify the clay surfaces, which may lead to changes in its natural geochemical cycles. Abstract. In the present study, the mechanism of sorption of ionic liquids onto kaolinite clay mineral has been investigated in detail. Results obtained indicate a multilayer type of adsorption. At final saturations, the highest distribution coefficients were found for the long alkyl chain molecules. The mean free energy values obtained are below values of a typical ion-exchange process, which thus suggests that the adsorption mechanism is a combination of electrostatic interaction and physical sorption. At the beginning of the binding process (formation of a monolayer), ion-exchange and van der Waals interactions are predominantly responsible for the process, whereas at higher concentrations of ionic liquids, dispersive interactions become dominant. Thermodynamic parameters were also calculated from graphical interpretation of experimental data. Negative values of ΔG indicate a spontaneous sorption process for ionic liquids. Standard heats of adsorption were found to be exothermic and entropy contributions were negative in all cases studied.
Effects of a barley (Hordeum vulgare) chromosome 6 grain protein content locus on whole-plant nitrogen reallocation under two different fertilisation regimes
Authors: Heidlebaugh Nancy M. , Trethewey Brian R. , Jukanti Aravind K. , Parrott David L. , Martin John M. , Fischer Andreas M.
Published: August 2008

A large fraction of protein N harvested with crop seeds is derived from N remobilisation from senescing vegetative plant parts, while a smaller fraction stems from de novo N assimilation occurring after anthesis. This study contrasts near-isogenic barley (Hordeum vulgare L.) germplasm, varying in the allelic state of a major grain protein content (GPC) locus on chromosome 6. Plant material was grown under both low- and high-N fertilisation levels. The analyses indicated that leaf N remobilisation occurred earlier in high-GPC germplasm under both fertilisation regimes, as indicated by an earlier decrease of total leaf N, chlorophylls, soluble- and membrane-proteins. At the same time, kernel free amino acid levels were enhanced, while leaf free amino acid levels were lower in high-GPC barleys, suggesting enhanced retranslocation of organic N to the developing sinks. Enhanced or longer availability of leaf nitrates was detected in high-GPC varieties and lines, at least under high N fertilisation, indicating that the GPC locus profoundly influences whole-plant N allocation and management. Results presented here, together with data from a recent transcriptomic analysis, make a substantial contribution to our understanding of whole-plant N storage, remobilisation and retranslocation to developing sinks.
Alternative oxidase: an inter-kingdom perspective on the function and regulation of this broadly distributed 'cyanide-resistant' terminal oxidase
Authors: McDonald Allison E.
Published: August 2008

Alternative oxidase (AOX) is a terminal quinol oxidase located in the respiratory electron transport chain that catalyses the oxidation of quinol and the reduction of oxygen to water. However, unlike the cytochrome c oxidase respiratory pathway, the AOX pathway moves fewer protons across the inner mitochondrial membrane to generate a proton motive force that can be used to synthesise ATP. The energy passed to AOX is dissipated as heat. This appears to be very wasteful from an energetic perspective and it is likely that AOX fulfils some physiological function(s) that makes up for its apparent energetic shortcomings. An examination of the known taxonomic distribution of AOX and the specific organisms in which AOX has been studied has been used to explore themes pertaining to AOX function and regulation. A comparative approach was used to examine AOX function as it relates to the biochemical function of the enzyme as a quinol oxidase and associated topics, such as enzyme structure, catalysis and transcriptional expression and post-translational regulation. Hypotheses that have been put forward about the physiological function(s) of AOX were explored in light of some recent discoveries made with regard to species that contain AOX. Fruitful areas of research for the AOX community in the future have been highlighted.
Photoprotection of PSII in Hawaiian lobeliads from diverse light environments
Authors: Montgomery Rebecca A. , Goldstein Guillermo , Givnish Thomas J.
Published: August 2008

Excess irradiance can reduce the quantum yield of photosynthesis via photoprotective energy dissipation, inactivation or downregulation of PSII. We examined variation in photoprotection as part of a study of adaptive radiation in photosynthetic light responses by Hawaiian lobeliads. We measured the maximum efficiency of PSII (Fv/Fm) and recovery of Fv/Fm after high light stress in field populations of 11 lobeliad species and in four species growing under common-garden greenhouse conditions. Species showed no difference in Fv/Fm (0.82 ± 0.02 (mean ± s.e.)) or in their ability to recover from light stress under field conditions. Average recovery was 74 ± 1.4% within 1 h of removal of the stress suggesting that all species maintain the ability to recover from high light stress, at least in the short-term. In contrast, the results from the common-garden indicate that long-term exposure to high irradiance and associated higher temperatures can cause a sustained reduction in PSII function. Species showed decreased Fv/Fm and percentage recovery as treatment irradiance increased. Fv/Fm and percentage recovery were positively related to native habitat PFD across species, suggesting that there has been a diversification in high light tolerance, with species from sunnier environments better able to avoid sustained declines in PSII function.
Silicon-mediated improvement in the salt resistance of wheat (Triticum aestivum) results from increased sodium exclusion and resistance to oxidative stress
Authors: Saqib Muhammad , Zörb Christian , Schubert Sven
Published: August 2008

Silicon (Si) is reported to reduce the effect of salinity on wheat (Triticum aestivum L.) and other crops. In the present study, Si decreased plant Na+ uptake and shoot : root Na+ distribution of a salt-resistant as well as a salt-sensitive wheat genotype. Reduced shoot Na+ concentration and increased shoot K+ : Na+ ratio led to improved plant growth. Silicon increased cell-wall Na+ binding from 49% in SARC-1 and 37% in 7-Cerros under salinity to 87% in SARC-1 and 79% in 7-Cerros under salinity + silicon. It may also have resulted in decreased potentially toxic leaf sap Na+ concentration. The concentration of glutathione, an important antioxidant in plants, was increased due to the addition of Si under saline conditions. The salt-resistant wheat genotype SARC-1 was less Si-responsive in terms of shoot fresh weight, having a 39% increase compared with a 49% increase in 7-Cerros, as well as root fresh weight, having a 12% increase compared with a 22% in 7-Cerros. It is concluded that Si may have improved shoot growth of the salt-resistant as well as the salt-sensitive wheat genotype by decreasing plant Na+ uptake and shoot : root Na+ distribution as well as by increasing glutathione concentration. Silicon may have also improved in-plant Na+ detoxification by increasing cell-wall Na+ binding.
Using traditional age and growth techniques in endangered species management: eastern freshwater cod, Maccullochella ikei
Authors: Butler Gavin L. , Rowland Stuart J.
Published: August 2008

Age and growth estimates can be difficult to obtain for endangered fishes owing to their relative low abundance and the ethics associated with sampling threatened populations. The eastern freshwater cod, Maccullochella ikei Rowland 1985, is an endangered freshwater fish endemic to the Clarence and Richmond Rivers of New South Wales, Australia. Bony parts were gathered from archival collections and hatcheries, as well as opportunistically from the wild, to determine age and growth. Examination of opercular bones and dorsal spine sections revealed no consistent annuli. Sectioned otoliths exhibited consistent bipartite rings throughout the structures and 106 otoliths were used to estimate the age of cod from 0+ to 15+ years. Edge increment analysis and known-age cod were used to validate the age estimates. The von Bertalanffy growth equation for M. ikei is Lt = 704.9 (1–exp (–0.20 (t + 0.14))). A length–weight relationship of W = 2.80 × 10–6 × L3.2467 was established from 372 cod collected using non-destructive techniques. Significant differences were found in the relative condition of cod in summer (Kn = 0.999) and winter (Kn = 1.026). The information presented in this paper will assist in the conservation of M. ikei and will provide a guide for future age and growth studies of threatened species.
Temporal dynamics in coral bioindicators for water quality on coastal coral reefs of the Great Barrier Reef
Authors: Cooper Timothy F. , Ridd Peter V. , Ulstrup Karin E. , Humphrey Craig , Slivkoff Matthew , Fabricius Katharina E.
Published: August 2008

There is a need to identify effective coral bioindicators that provide quantifiable links between changes in water quality and the condition of coastal coral reefs. Temporal variation in a range of coral bioindicators including symbiont density, concentration of chlorophyll a, skeletal density and colony brightness of Pocillopora damicornis, as well as colony brightness and density of macro-bioeroders of massive Porites spp. was examined for 2 years on a coastal coral reef of the Great Barrier Reef. The specificity to changes in water quality varied among bioindicators. For example, a 2.5-fold variation in symbiont density of P. damicornis was related strongly to mean 14-day sea surface temperature and seasonal changes in water quality, suggesting medium specificity to changes in water quality. In contrast, the density of macro-bioeroders in Porites did not vary seasonally but there were consistently more macro-bioeroders at the coastal than mid-shelf reference locations, suggesting high specificity of spatial differences in water quality. In situ measurements of benthic irradiance and turbidity allowed the quantification of potential stress thresholds for coastal corals. Our data suggest long-term turbidity >3 NTU leads to sublethal stress, whereas long-term turbidity >5 NTU corresponds to severe stress effects on corals at shallow depths.
Freshwater fishes and aquatic habitats in Peru: Current knowledge and conservation
Authors: Ortega Hernán , Hidalgo Max
Published: August 2008

Peruvian freshwater fishes and their habitats were investigated by the Natural History Museum of San Marcos University (MHNSM) as part of a long-term project. Fishes were inventoried by sampling in main drainage basins, including coastal rivers, highland rivers, and Peru's Amazonian waters. To date, the MHNSM fish collection has approximately 300,000 specimens comprising 1000 valid species in 168 families and 8 orders. The greatest diversity lies within the Ostariophysi (80% of all species) with the dominant orders being Characiformes and Siluriformes. Characidae is the most diverse family with 22.5% of all species.

Protected areas (i.e. Parks, Reserved Zones or National Reserves) have been sampled intensively providing a reasonable estimates of their fish diversity. However, our knowledge is still poor for less accessible areas. More fieldwork is needed in all of the large river basins before we can have a fuller understanding of total fish diversity. As an example of ongoing efforts, we discuss specific fish inventories in both Peruvian coastal rivers and highlands and in river systems shared with neighboring countries.

In addition to Peruvian fish diversity; we discuss the state of aquatic resources and habitats in Peru's principal river basins, and current problems facing such aquatic systems (e.g. inland fisheries and extractive activities such as deforestation and gold mining). Near large cities, such as Iquitos and Pucallpa, fishing effort has increased considerably in the last decade, whereas catch per unit effort appears to have decreased considerably indicating that over-fishing has become locally problematic. An overview is presented of main conservation problems, including exotic species that confront aquatic ecosystems in Peru. Finally, an environmental education program is recommended to inform the general public about the value of freshwater fishes and aquatic ecosystems and the main problems such resources are facing.
Processing ambiguous Spanish se in a minimal chain
Authors: Meseguer Enrique , Acuña-Fariña Carlos , Carreiras Manuel
Published: August 2008

The recovery of pieces of information that are not linguistically expressed is a constant feature of the process of language comprehension. In the processing literature, such missing information is generally referred to as “gaps”. Usually, one resolves gaps by finding “fillers” in either the sentence or the context. For instance, in Peter seemed to be upset, Peter is really the subject of being upset but appears as surface subject of seems. Sometimes constituents move, leaving gaps behind. Various Romance languages such as Spanish or Italian have a grammatical particle se/si, which, as it is extremely ambiguous, licenses different sorts of gaps. In Spanish, se can encode at least reflexive, impersonal, and passive meanings. In an eye-tracking experiment we contrast reflexive structures containing postverbal subjects with impersonal structures with no subjects (GAP se vendó apresuradamente el corredor/“the runner bandaged himself hurriedly” vs. GAP se vendó apresuradamente al corridor/“(someone) bandaged the runner hurriedly”). In a second manipulation we contrast the presence of an extra argument with se-passives (GAP se vendó el tobillo el corredor/“the runner bandaged his ankle” vs. GAP se vendó el tobillo al corridor/“the runner's ankle was bandaged”). Our comparisons involve contrasting standard transitive structures with nonstandard word order (postverbal subject and a preverbal subject gap) against inherently complex and less habitual structures such as impersonals (with no subject) or se-passives (with subjects in canonical object position). We evaluate the minimal chain principle (de Vincenzi, 1991), according to which displacement is costly because it entails complex (derivational) “chains” that must be undone before phrasal packaging can commence. We show the minimal chain principle to be essentially correct when contrasting more complex but more frequent structures with less complex but less frequent structures. A noteworthy feature of this research is that the gaps appear before the fillers in the structures that we analyse.
Equilibrium properties at very low aspect ratio in the Pegasus toroidal experiment
Authors: Sontag A.C. , Diem S.J. , Fonck R.J. , Garstka G.D. , Unterberg E.A. , Thorson T.A.
Published: August 2008

Equilibrium reconstructions of low-aspect ratio (A < 1.3) discharges in the Pegasus toroidal experiment have been performed. Magnetic diagnostics are used for equilibrium constraint and a filament code is used to estimate the significant currents flowing in the vacuum vessel walls. This technique is able to fit the global plasma parameters of plasma current and major radius to within 5%, internal inductance to within 10% and plasma pressure to within 15% as determined by Monte Carlo estimation of the uncertainties in the fit parameters. Determination of the equilibrium properties of the plasma allows an understanding of the dynamics of internal tearing modes and external ideal kink modes that limit plasma performance. Internal tearing modes were found to degrade plasma confinement when rational surfaces are located in regions of low magnetic shear early in the discharge when temperature is lower and resistivity is higher. This confinement degradation limits the maximum achievable plasma current and pressure. Disruptions with precursors growing with a time of ∼90 µs have been found to be consistent with ideal external kink modes with a hybrid growth time.
Effect of Atmospheric Interfering Absorption on Measurement of BTX by DOAS
Authors: Peng Fu-min , Xie Pin-hua , Li Hai-yang , Zhang Ying-hua , Wang Jun-de , Liu Wen-qing
Published: August 2008

It was reported on the elimination of interfering absorption of BTX. the absorption of O2 includes different absorption bands, which change differently when the partial pressure of oxygen is varied. These cause the nonlinear absorption of O2 and the observed band shape to vary with the column density of O2. The absorption ratios of molecular absorption in each of the Herzberg bands and dimer absorptions, as well as the contribution to the correction error of molecular absorption, are studied based on the characteristic of these absorption bands. The optimized way to eliminate the interfering absorption is obtained in the end and the effectiveness of using interpolation proposed by Volkamer et al. to remove O2 absorption is proved again. As to O3 and SO2, the effect of the thermal effect of characteristic spectra on the elimination error of their absorption is studied. Solutions to these problems are discussed and demonstrated together with methods to optimize the interpolation of spectra. As a sample application, differential optical absorption spectroscopy (DOAS) measurements of BTX are carried out. Results show a low detection limit and the good correlation with point instruments are achieved. All these prove the feasibility of using spectral interpolation to improve the accuracy of DOAS measurements of aromatic hydrocarbons for practical purposes.
Internal Conversion Process of Chlorophyll a in Solvents in Femtosecond Pump-Probe Laser Fields
Authors: Niu Kai , Dong Li-qing , Cong Shu-lin
Published: August 2008

The internal conversion (IC) processes of chlorophyll a (chl-a) in solvents are studied based on the reduced density matrix theory. The IC times can be obtained by simulating the experimental fluorescence depletion spectra (FDS). The calculated IC times of chl-a in ethyl acetate, tetrahydrofuran and dimethyl formamide are 141, 147, and 241 fs, respectively. The oscillation feature of the FDS results from the forward and backward transfer of the population between coupled electronic states. The effects of diabatic coupling between two electronic states on the IC time and the FDS are described. The influence of molecule-reservoir coupling on the IC time is also investigated.
All-atom Molecular Dynamic Simulations and NMR Spectra Study on Intermolecular Interactions of N,N-dimethylacetamide-Water System
Authors: Zhang Rong , Tan Zai-you , Luo San-lai
Published: August 2008

N,N-dimethylacetamide (DMA) has been investigated extensively in studying models of peptide bonds. An all-atom MD simulation and the NMR spectra were performed to investigate the interactions in the DMA-water system. The radial distribution functions (RDFs) and the hydrogen-bonding network were used in MD simulations. There are strong hydrogen bonds and weak CHO contacts in the mixtures, as shown by the analysis of the RDFs. The insight structures in the DMA-water mixtures can be classified into different regions by the analysis of the hydrogen-bonding network. Chemical shifts of the hydrogen atom of water molecule with concentration and temperatures are adopted to study the interactions in the mixtures. The results of NMR spectra show good agreement with the statistical results of hydrogen bonds in MD simulations.
Spectroscopic Properties and Three-photon Absorption Induced Optical Limiting of Series of Novel Nonlinear Chromophores
Authors: Guo Fu-quan , Sun Xiao-lao , Liang Hao , Hu Zhi-yuan , Zhang Qi-jin , Ming Hai
Published: August 2008

Three novel nonlinear chromophores with symmetric D--D molecular structure and extended conjugated length were synthesized. Solvatochromism analysis shows great symmetric intramolecular charge transfer occurring in chromophores by the enhancement in the dipole moment between the ground and excited states. The properties of optical power limiting induced by three-photon absorption (3PA) are demonstrated. Large 3PA coeficients and the corresponding molecular cross sections as high as 1074 cm6 s2 were obtained for nanosecond laser pulses at 1.06 m from nonlinear transmission measurements.
Theoretical Study on Reaction Mechanism of Aluminum-Water System
Authors: Sun Yun-lan , Tian Yan , Li Shu-fen
Published: August 2008

A theoretical study on the reaction of aluminum with water in the gas phase was performed using the hybrid density functional B3LYP and QCISD(T) methods with the 6-311+G(d,p) and the 6-311++G(d,p) basis sets. The results show that there are three possible reaction pathways that involve four isomers, seven transition structures, and two possible products for the reaction of aluminum with water. The two most favorable reaction pathways were found, whose intermediates and products agreed quite well with experimental results. The enthalpy and Gibbs free energy change of the reaction between Al and H2O at 298 and 2000 K were calculated. Some results are also in good agreement with the previous calculations or experimental results.
Theoretical Study of Haloacetonitrile Anions: CH2XCN (X = F, Cl)
Authors: Zhang Xin-wen , Li Mei , Tian Shan-xi
Published: August 2008

Haloacetonitrile anions CH2XCN(X = F, Cl) were studied by HF-SCF, Becke3-LYP, and MP2 methods together with the Dunning's basis set aug-cc-PVTZ. The vertical electron attachments to the neutral are endothermic. The geometrically optimized CH2FCN is mainly a valence-bounded anion and CH2FCNCH2CN+F is a nonadiabatic dissociation. This theoretical study in good agreement with the experimental results shows that the Becke3-LYP method is reasonable in describing the electronic structures of anions and dissociative attachment dynamics, while significant differences between MP2 and Becke3-LYP results are shown for the dissociation potential curves of CH2ClCNCH2CN+Cl.
Theoretical Studies on the Ground State and Excited State of 2,7-(Ethylene)-bis-8-hydroxyquinoline
Authors: Li Hui-xue , Pan Su-juan , Wang Xiao-feng , Xiao Tai
Published: August 2008

2,7-(Ethylene)-bis-8-hydroxyquinoline was optimized with DFT/B3LYP and ab initio HF methods, so ionization potential and electron affinity could be determined. Absorption spectrum was calculated by ZINDO and TD-DFT. CIS method was used to calculate the S1 excited states of the compound and afterwards the emission spectrum was computed. When the solvent effect was taken into account, the computed results show encouraging agreement with known experimental data. The results of analyzing the relationship between the energies and absorption spectra indicate that the ability to transporting electrons is strengthened compared with 8-hydroxyquinoline and that absorption and emission spectra are red-shifted. The intramolecular reorganization energy of tris(2,7-(ethylene)-bis-8-hydroxyquinoline)-aluminum implies its electron transporting property is worse than tris(8-hydroxyquinoline)-aluminum. The predicted maximum emission wavelength is red-shifted compared with tris(8-hydroxyquinoline)-aluminum.
Mixed Conduction in BaCe0.8Pr0.2O3- Ceramic
Authors: Wang Mao-yuan , Qiu Li-gan
Published: August 2008

BaCe0.8Pr0.2O3- ceramic was synthesized by high temperature solid-state reaction. The structural characteristics and the phase purity of the crystal were determined using powder X-ray diffraction analysis. By using the methods of AC impedance spectroscopy, gas concentration cell and electrochemical pumping of hydrogen, the conductivity and ionic transport number of BaCe0.8Pr0.2O3- were measured, and the electrical conduction behavior of the material was investigated in different gases in the temperature range of 500-900 C. The results indicate that the material was of a single perovskite-type orthorhombic phase. From 500 C to 900 C, electronic-hole conduction was dominant in dry and wet oxygen, air or nitrogen, and the total conductivity of the material increased slightly with increasing oxygen partial pressure in the oxygen partial pressure range studied. Ionic conduction was dominant in wet hydrogen, and the total conductivity was about one or two orders of magnitude higher than that in hydrogen-free atmosphere (oxygen, air or nitrogen).
A Novel Functional Screen in Human Cells Identifies MOCA as a Negative Regulator of Wnt Signaling
Authors: Caspi Elanite , Rosin-Arbesfeld Rina
Published: August 2008

Aberrant Wnt signal transduction is involved in many human diseases such as cancer and neurodegenerative disorders. The key effector protein of the canonical Wnt pathway is β-catenin, which functions with T-cell factor/lymphoid enhancer factor (TCF/LEF) to activate gene transcription that leads to expression of Wnt target genes. In this study we provide results obtained from a novel functional screen of a human brain cDNA library used to identify 63 genes that are putative negative Wnt regulators. These genes were divided into eight functional groups that include known canonical and noncanonical Wnt pathway components and genes that had not yet been assigned to the Wnt pathway. One of the groups, the presenilin-binding proteins, contains the modifier of cell adhesion (MOCA) gene. We show that MOCA is a novel inhibitor of Wnt/β-catenin signaling. MOCA forms a complex with β-catenin and inhibits transcription of known Wnt target genes. Epistasis experiments indicate that MOCA acts to reduce the levels of nuclear β-catenin, increase the levels of membrane-bound β-catenin, and enhances cell–cell adhesion. Therefore, our data indicate that MOCA is a novel Wnt negative regulator and demonstrate that this screening approach can be a rapid means for isolation of new Wnt regulators.
Assembly and Misassembly of Cystic Fibrosis Transmembrane Conductance Regulator: Folding Defects Caused by Deletion of F508 Occur Before and After the Calnexin-dependent Association of Membrane Spanning Domain (MSD) 1 and MSD2
Authors: Rosser Meredith F. N. , Grove Diane E. , Chen Liling , Cyr Douglas M.
Published: August 2008

Cystic fibrosis transmembrane conductance regulator (CFTR) is a polytopic membrane protein that functions as a Cl−channel and consists of two membrane spanning domains (MSDs), two cytosolic nucleotide binding domains (NBDs), and a cytosolic regulatory domain. Cytosolic 70-kDa heat shock protein (Hsp70), and endoplasmic reticulum-localized calnexin are chaperones that facilitate CFTR biogenesis. Hsp70 functions in both the cotranslational folding and posttranslational degradation of CFTR. Yet, the mechanism for calnexin action in folding and quality control of CFTR is not clear. Investigation of this question revealed that calnexin is not essential for CFTR or CFTRΔF508 degradation. We identified a dependence on calnexin for proper assembly of CFTR's membrane spanning domains. Interestingly, efficient folding of NBD2 was also found to be dependent upon calnexin binding to CFTR. Furthermore, we identified folding defects caused by deletion of F508 that occurred before and after the calnexin-dependent association of MSD1 and MSD2. Early folding defects are evident upon translation of the NBD1 and R-domain and are sensed by the RMA-1 ubiquitin ligase complex.
Lysosomal Localization of Ubiquitinated Jun Requires Multiple Determinants in a Lysine-27–Linked Polyubiquitin Conjugate
Authors: Ikeda Hiromi , Kerppola Tom K.
Published: August 2008

Ubiquitination regulates many cellular functions, including protein localization and degradation. Each function is specified by unique determinants in the conjugate. Ubiquitinated Jun is localized to lysosomes for degradation. Here, we characterized determinants of Jun ubiquitination and lysosomal localization by using ubiquitin-mediated fluorescence complementation (UbFC) in living cells and analysis of the stoichiometry of ubiquitin linked to Jun extracted from cells. The δ region of Jun and isoleucine-44 in ubiquitin were required for lysosomal localization of the conjugate. Ubiquitin containing only lysine-27, but no other single-lysine ubiquitin, mediated Jun ubiquitination, albeit at lower stoichiometry than wild-type ubiquitin. These conjugates were predominantly nuclear, but coexpression of lysine-27 and lysine-less ubiquitins enhanced the mean stoichiometry of Jun ubiquitination and lysosomal localization of the conjugate. Hepatocyte growth factor-regulated tyrosine kinase substrate (HRS) and tumor susceptibility gene 101 (TSG101) colocalized with ubiquitinated Jun. Knockdown of HRS or TSG101 inhibited lysosomal localization of ubiquitinated Jun and reduced Jun turnover. Ubiquitination of other Fos and Jun family proteins had distinct effects on their localization. Our results indicate that Jun is polyubiquitinated by E3 ligases that produce lysine-27–linked chains. Lysosomal localization of the conjugate requires determinants in Jun and in ubiquitin that are recognized in part by TSG101 and HRS, facilitating selective translocation and degradation of ubiquitinated Jun.
First Report of Tomato Yellow Leaf Curl Virus in Greenhouse Tomatoes in Kentucky
Authors: de Sá P. B. , Seebold K. W. , Vincelli P.
Published: August 2008

Tomato yellow leaf curl virus (TYLCV), genus Begomovirus in the family Geminiviridae, was identified for the first time in the United States in Florida in 1997 and since then has been reported in other states on tomato in greenhouse and in field production environments. During 2005 symptoms typical of geminivirus infection were observed on tomato plants grown in a greenhouse production system in Jefferson Co., KY. A nucleic acid-based pathogen detection approach was used and TYLCV infection was confirmed in tomato plants collected from the greenhouse and in symptomless Acalypha ostryifolia growing outside the greenhouse. To our knowledge, A. ostryifolia has not been previously described as a host of this virus. This find raises concerns regarding the introduction of TYLCV to the state in infected transplants or in viruliferous whiteflies transported on infested plants, and its potential impact on economically important crops in the state.

Accepted for publication 17 June 2008. Published 19 August 2008.
Maximal frustration as an immunological principle
Authors: de Abreu F. Vistulo , Mostardinha P
Published: August 2008

A fundamental problem in immunology is that of understanding how the immune system selects promptly which cells to kill without harming the body. This problem poses an apparent paradox. Strong reactivity against pathogens seems incompatible with perfect tolerance towards self. We propose a different view on cellular reactivity to overcome this paradox: effector functions should be seen as the outcome of cellular decisions which can be in conflict with other cells' decisions. We argue that if cellular systems are frustrated, then extensive cross-reactivity among the elements in the system can decrease the reactivity of the system as a whole and induce perfect tolerance. Using numerical and mathematical analyses, we discuss two simple models that perform optimal pathogenic detection with no autoimmunity if cells are maximally frustrated. This study strongly suggests that a principle of maximal frustration could be used to build artificial immune systems. It would be interesting to test this principle in the real adaptive immune system.
Enhancement of the antituberculosis activity of weak acids by inhibitors of energy metabolism but not by anaerobiosis suggests that weak acids act differently from the front-line tuberculosis drug pyrazinamide
Authors: Gu Peihua , Constantino Luis , Zhang Ying
Published: August 2008

Mycobacterium tuberculosis is uniquely susceptible to weak acids compared with other mycobacteria or bacteria. The antituberculosis activity of the front-line drug pyrazinamide (PZA), a weak acid (pyrazinoic acid) precursor, can be enhanced by inhibitors of energy metabolism and anaerobiosis. Here, we investigated the effect of inhibitors of energy metabolism and anaerobiosis on weak acid activity against M. tuberculosis in general. The susceptibility of M. tuberculosis to benzoic acid (BA) esters and amides was determined alone and in the presence of inhibitors of energy metabolism such as N,N′-dicyclohexylcarbodiimide (DCCD) and azide and also under anaerobic conditions in the form of MIC and drug exposure followed by colony count. Some BA esters such as propyl hydroxybenzoic acid and 4-dodecyloxylbenzoic acid had significant activity whereas amides of BA had no activity. As for PZA, inhibitors of energy metabolism DCCD and azide enhanced the antituberculosis activity of weak acids under normal atmospheric oxygen tension. However, unlike PZA, weak acids did not show antituberculosis activity and the inhibitors of energy metabolism did not enhance the weak acid activity under anaerobic conditions. The enhancement of weak acid activity by inhibitors of energy metabolism for M. tuberculosis was not seen in other bacterial species such as Helicobacter pylori. These results suggest that while the antituberculosis activity of weak acids can be enhanced by inhibitors of energy metabolism as for PZA, weak acids act differently from PZA in that they were inactive against M. tuberculosis under anaerobic conditions. The significance of these findings is discussed in the context of the unique physiology of M. tuberculosis and the development of new tuberculosis drugs.
Human recombinant lactoferrin acts synergistically with antimicrobials commonly used in neonatal practice against coagulase-negative staphylococci and Candida albicans causing neonatal sepsis
Authors: Venkatesh Mohan Pammi , Rong Liang
Published: August 2008

Neonatal sepsis causes significant mortality and morbidity. Coagulase-negative staphylococci (CoNS) andCandidafrequently cause neonatal sepsis at >72 h of age. Lactoferrin, which is present in human milk, is a component of innate immunity and has broad-spectrum antimicrobial activity. The synergistic effects of lactoferrin with antibiotics against neonatal isolates have not been systematically evaluated. Here, eight clinical strains (seven neonatal) of CoNS and three strains (two neonatal) ofCandidaalbicanswere studied. MIC50and MIC90values of human recombinant lactoferrin (talactoferrin; TLF), vancomycin (VAN) and nafcillin (NAF) against CoNS, and of TLF, amphotericin B (AMB) and fluconazole (FLC) againstC. albicans, were evaluated according to established guidelines. Antimicrobial combinations of TLF with NAF or VAN against CoNS, and TLF with AMB or FLC againstC. albicans, were evaluated by a chequerboard method with serial twofold dilutions. Synergy was evaluated by the median effects principle, and combination indices and dose reduction indices were reported at 50, 75 and 90 % inhibitory effect at several drug-dose ratios. It was found that TLF acted synergistically with NAF and VAN against CoNS, and with AMB and FLC againstC. albicans, at multiple dose effects and drug-dose ratios with few exceptions. In synergistic combinations, drug reduction indices indicated a significant reduction in doses of antibiotics, which may be clinically relevant. Thus TLF acts synergistically with anti-staphylococcal and anti-Candidaagents commonly used in neonatal practice and is a promising agent that needs to be evaluated in clinical studies.
Enteroaggregative Escherichia coli associated with a foodborne outbreak of gastroenteritis
Authors: Scavia Gaia , Staffolani Monica , Fisichella Stefano , Striano Gianluca , Colletta Stefano , Ferri Giovanni , Escher Martina , Minelli Fabio , Caprioli Alfredo
Published: August 2008

This study investigated two foodborne outbreaks of gastroenteritis that occurred 10 days apart among individuals who had meals at the restaurant of a farm holiday resort. Mild gastrointestinal symptoms were reported and none of the patients needed hospitalization. Mean incubation times were 45 and 33 h, and the overall attack rates were 43.5 and 58.3 %, respectively. Stool sample examination was negative for common enteric pathogens in both outbreaks. Specimens from 13 people involved in the second outbreak and 3 restaurant staff were examined for diarrhoeagenic Escherichia coli. An enteroaggregative E. coli (EAEC) strain of serotype O92 : H33 was isolated from six participants and one member of staff. In particular, the EAEC strain was isolated from five of the six cases of diarrhoea examined. The strain showed an aggregative pattern of adherence to HEp-2 cells, did not produce a biofilm and possessed the virulence-related genes aat, aggR, aap and set1A, but not the astA gene. A retrospective cohort study indicated a pecorino cheese made with unpasteurized sheep milk as the possible source (P<0.001). Samples of the cheese had E. coli counts higher than 106 c.f.u. g−1, but the outbreak EAEC strain was not isolated. This report confirms that EAEC infections are probably underdiagnosed because of the limited availability of laboratories capable of identifying this group of pathogenic E. coli.