bluuebunny/crossref_metadata_2025 huggingface dataset:
Stability of a boundary spike layer for the Gierer–Meinhardt system
Authors: MIYAMOTO YASUHITO
Published: November 2005

We consider the activator-inhibitor Gierer–Meinhardt reaction-diffusion system of biological pattern formation in a closed bounded domain. The existence and stability of a boundary apike-layer solution to the Gierer–Meinhardt model, and it, so-called shadow limit, is analysed. In the limit of small activator diffusivity, together with a large inhibitor diffusivity, an equilibrium boundary spike-layer solution is constructed that concentrates at a non-degenerate critical point P of the boundary. By non-degenerate we mean that every principal curvature of the boundary has a local maximum at P, and hence the mean curvature at the boundary has a local maximum at P. Rigorous results for the stability of such a boundary spike-layer solution are given.
Long‐period orbital control on middle Miocene global cooling: Integrated stratigraphy and astronomical tuning of the Blue Clay Formation on Malta
Authors: Abels H. A. , Hilgen F. J. , Krijgsman W. , Kruk R. W. , Raffi I. , Turco E. , Zachariasse W. J.
Published: November 2005

Application of an astronomical age model to a bulk carbonate oxygen isotope record in the Ras il Pellegrin section on Malta indicates that the major step in the middle Miocene global cooling (13.82 Ma ± 0.03) coincides with minimum eccentricity values associated with the 400‐kyr cycle and minimum obliquity amplitudes associated with the 1.2‐Myr cycle. This orbital configuration is very similar to that found for comparable oxygen isotope enrichment events in the late Paleogene and Neogene. The stepwise character of the middle Miocene cooling event appears to be controlled by the combined influence of the 100‐kyr eccentricity cycle and the 172‐kyr cycle in obliquity amplitude. The integrated stratigraphy further allows extension of the astronomical polarity timescale to the top of chron C5ACn. The boundary between the Globigerina Limestone and the Blue Clay Formation coincides with the major step in middle Miocene global cooling and provides a level suitable for placing the physical reference point for the Langhian/Serravallian boundary.
Small‐scale heterogeneity of dissolved gas concentrations in marine continental shelf waters
Authors: Tortell Philippe D.
Published: November 2005

Marine continental shelf waters are known to contribute significantly to the global air‐sea fluxes of many gases. Biogeochemical cycles in these regions are highly dynamic, and it is thus often difficult to fully resolve the spatial and temporal distribution of gases in the upper water column. High‐frequency, real‐time gas measurements with a membrane inlet mass spectrometer (MIMS) reveal significant small‐scale heterogeneity in the distribution of CO2, O2/Ar ratios, and dimethylsulfide (DMS) in continental shelf waters of the Eastern Subarctic Pacific Ocean and Bering Sea. Decorrelation length scales for the gas distributions ranged from 15 to 25 km, with significant variability observed on subkilometer spatial scales. In the case of DMS, a number of rapid excursions were observed over distances that would be difficult to resolve with conventional methods. Across most of the sampling transects, CO2 and O2/Ar ratios were correlated, suggesting that biological processes dominated the cycling of these gases. In contrast, DMS concentrations were generally uncoupled from CO2 and O2/Ar, although concentrations often did change sharply across hydrographic and productivity fronts. The results presented here suggest that previous field studies may have underestimated the true spatial variability of dissolved gases (DMS in particular) in surface waters of highly dynamic marine systems. High‐frequency gas measurements have significant promise for unraveling complex biogeochemical cycles in these regions.
Formation of the Jinchuan ultramafic intrusion and the world's third largest Ni‐Cu sulfide deposit: Associated with the ∼825 Ma south China mantle plume?
Authors: Li X. H. , Su L. , Chung S.‐L. , Li Z. X. , Liu Y. , Song B. , Liu D. Y.
Published: November 2005

We report here SHRIMP U‐Pb geochronological, geochemical, and Nd isotopic data for the Jinchuan ultramafic intrusion (Gansu Province, China), which hosts the world's third largest magmatic Ni‐Cu sulfide deposits. U‐Pb baddeleyite analyses yield an age of 812 ± 26 Ma for the ultramafic intrusion. This age is indistinguishable within analytical uncertainties from the U‐Pb zircon ages of 827 ± 8 Ma and 828 ± 3 Ma for the sulfide‐bearing ultramafic rocks and the dolerite dykes that cut the ultramafic intrusion, respectively. These U‐Pb dating results show beyond doubt that the Jinchuan ultramafic intrusion and associated Ni‐Cu sulfide deposit were formed at ∼825 Ma, rather than ∼1500 Ma as has been widely believed. The ultramafic rocks exhibit large negative ɛNd(T) values (−8.9 to −12.0) that decrease with increasing La/Sm, suggesting that their parental magmas were derived from a long‐term enriched lithospheric mantle and experienced crustal contamination. Mineralogical, petrological, and geochemical data all indicate that the Jinchuan intrusion was generated by melting of the enriched lithospheric mantle heated by an anomalously hot plume. The U‐Pb ages of ∼825 Ma for igneous baddeleyites and zircons and ∼900–880 Ma for inherited zircons in the Jinchuan mafic‐ultramafic rocks are comparable with those in the Qaidam block and Qilian belt, the western extension of the Qinling belt that was likely derived from northern Yangtze craton. The Jinchuan Ni‐Cu sulfide‐bearing intrusion, along with coeval regional plume‐related mafic dykes and tholeiites, and mafic‐ultramafic complexes with associated V‐Ti and Ni‐Cu‐PGE mineralization, is interpreted to be genetically related to the ∼825 Ma south China mantle plume.
A Tibetan Taylor Cap and a halo of stratospheric ozone over the Himalaya
Authors: Moore G. W. K. , Semple John L.
Published: November 2005

With an average elevation in excess of 4000 m asl, the Tibetan Plateau is one of the Earth's most prominent topographic features. The plateau plays an important role in the global climate system by acting as a heat source during the summer and a heat sink during the winter. There also exists evidence that its influence extends into the upper‐troposphere and lower‐stratosphere through the existence of a region of low total column ozone over the plateau. We report on observations of ozone concentration from the Bhutanese Himalaya that support the hypothesis that a Taylor Cap exists over the plateau. We argue that the presence of this cap results in the formation of a halo of ozone‐rich air in the upper‐troposphere around the perimeter of Tibet. The Himalaya are within this halo and the higher peaks may be exposed to ozone concentrations similar to those found in industrialized cities.
Precipitation patterns alter growth of temperate vegetation
Authors: Fang Jingyun , Piao Shilong , Zhou Liming , He Jinsheng , Wei Fengying , Myneni Ranga B. , Tucker Compton J. , Tan Kun
Published: November 2005

In this paper, we use growing season Normalized Difference Vegetation Index (NDVI) as an indicator of plant growth to quantify the relationships between vegetation production and intra‐annual precipitation patterns for three major temperate biomes in China: grassland, deciduous broadleaf forest, and deciduous coniferous forest. With increased precipitation, NDVI of grassland and deciduous broadleaf forest increased, but that of deciduous coniferous forest decreased. More frequent precipitation significantly increased growth of grassland and deciduous broadleaf forest, but did not alter that of deciduous coniferous forest at low precipitation levels and constrained its growth at high precipitation levels. The relationships between NDVI and average precipitation per event were opposite to those between NDVI and precipitation frequency. Such nonlinear feedback suggests that the responses of vegetation production to changes in precipitation patterns differ by both biome type and precipitation amount.
Formation of jarosite‐bearing deposits through aqueous oxidation of pyrite at Meridiani Planum, Mars
Authors: Zolotov Mikhail Y. , Shock Everett L.
Published: November 2005

The discovery of sulfate‐rich layered deposits with hematite spherules at the landing site of the Opportunity rover is consistent with mineral deposition in an aqueous environment. We evaluate conditions responsible for the formation of a jarosite‐goethite‐gypsum assemblage with speciation calculations. The results show that the assemblage could have precipitated from acidic solutions formed through near‐surface aqueous oxidation of pyrite. Our hypothesis is that regional heating in the Meridiani Planum caused a release of sulfide‐rich hydrothermal waters, leading to formation of pyrite‐rich regional deposits in a depression. Aqueous oxidation of these deposits by atmospheric O2 created an acidic environment that allowed formation of sulfates and goethite. Partial neutralization of the solution caused further goethite precipitation and conversion of jarosite to goethite, leading to formation of goethite concretions. Subsequent dehydration of goethite to coarse‐grained hematite would also have been facilitated by regional heating.
Modeling of global biogenic emissions for key indirect greenhouse gases and their response to atmospheric CO2 increases and changes in land cover and climate
Authors: Tao Zhining , Jain Atul K.
Published: November 2005

Natural emissions of nonmethane volatile organic compounds (NMVOCs) play a crucial role in the oxidation capacity of the lower atmosphere and changes in concentrations of major greenhouse gases (GHGs), particularly methane and tropospheric ozone. In this study, we integrate a global biogenic model within a terrestrial ecosystem model to investigate the vegetation and soil emissions of key indirect GHGs, e.g., isoprene, monoterpene, other NMVOCs (OVOC), CO, and NOx. The combination of a high‐resolution terrestrial ecosystem model with satellite data allows investigation of the potential changes in net primary productivity (NPP) and resultant biogenic emissions of indirect GHGs due to atmospheric CO2 increases and changes in climate and land use practices. Estimated global total annual vegetation emissions for isoprene, monoterpene, OVOC, and CO are 601, 103, 102, and 73 Tg C, respectively. Estimated NOx emissions from soils are 7.51 Tg N. The land cover changes for croplands generally lead to a decline of vegetation emissions for isoprene OVOC, whereas temperature and atmospheric CO2 increases lead to higher vegetation emissions. The modeled global mean isoprene emissions show relatively large seasonal variations over the previous 20 years from 1981 to 2000 (as much as 31% from year to year). Savanna and boreal forests show large seasonal variations, whereas tropical forests with high plant productivity throughout the year show small seasonal variations. Results of biogenic emissions from 1981 to 2000 indicate that the CO2 fertilization effect, along with changes in climate and land use, causes the overall up‐trend in isoprene and OVOC emissions over the past 2 decades. This relationship suggests that future emission scenario estimations for NMVOCs should account for effects of CO2 and climate in order to more accurately estimate local, regional, and global chemical composition of the atmosphere, the global carbon budget, and radiation balance of the Earth‐atmosphere system.
Simultaneous mass balance inverse modeling of methane and carbon monoxide
Authors: Butler T. M. , Rayner P. J. , Simmonds I. , Lawrence M. G.
Published: November 2005

We perform a simultaneous mass‐balance inversion of atmospheric methane (CH4) and carbon monoxide (CO) using measurements from the NOAA/CMDL Cooperative Air Sampling Network and a model of tropospheric transport and background chemistry over the period 1990–2000. Our method has a spatial resolution of a semihemisphere and a temporal resolution of 1 month. The deduced CO sources show relatively low interannual variability except around the major biomass burning event in 1997–1998, when we calculate an anomalous emission between July 1997 and December 1998 of 270 Tg(CO). This is enough to suppress the modeled global air mass weighted hydroxyl radical (OH) concentration during this time by 2.2%, and account for 75% of the observed increase in CH4 mixing ratios during 1998. We compare our implied CH4/CO emissions factors with published biomass burning emissions factors, suggesting that the remainder of the increase in CH4 observed in 1998 is due to anomalously high biomass burning emissions, with CH4 emissions from wetlands showing a small negative anomaly in 1998.
Biogeochemical investigations of marine methane seeps, Hydrate Ridge, Oregon
Authors: Valentine David L. , Kastner Miriam , Wardlaw George D. , Wang Xuchen , Purdy Alexandra , Bartlett Douglas H.
Published: November 2005

A series of biogeochemical studies were conducted at the southern summit of Hydrate Ridge, offshore Oregon. Using the submersible DSV Alvin, sediment push cores were collected from two distinct seep environments characterized by the presence of clam fields (CF) or microbial mats (MM) at the sediment‐water interface; samples were also collected from a nearby reference site characterized by a barren surface at the sediment‐water interface. Sediment samples from each setting were analyzed for the depth distributions of total organic carbon (concentrations, δ13C and Δ14C), total sedimentary nitrogen, and microbial abundance. Pore fluids were extracted and analyzed for sulfate, alkalinity, sulfide, organic carbon, and volatile organic acids. These depth distributions clearly indicate the presence of three distinctive biogeochemical settings in the surface sediments of Hydrate Ridge, and provide the basis for a comparative biogeochemical analysis. Both CF and MM sites display properties indicating enhanced microbial activity in the subsurface, compared with the reference site. MM sites display evidence of net biomass production in the subsurface; however, a loss of sediment nitrogen relative to the reference site indicates that mineralization is also enhanced. Calculations based on the removal of nitrogen indicate that greater than 30% of autochthonous organic material is lost to enhanced mineralization in the top 23 cm of one MM site. An isotope mass balance of sediment‐bound organic carbon indicates a mixed source, including methane and allochthonous organic carbon dissolved in the seep fluids. The concentrations of organic carbon dissolved in seep fluids reach values of 22 mM and provide a first indication that advective transport of dissolved organic carbon from great depth may supply an important source of energy and carbon to “methane seep” communities.
Cerebral Hyperperfusion after Carotid Endarterectomy is Associated with Preoperative Hemodynamic Impairment and Intraoperative Cerebral Ischemia
Authors: Komoribayashi Nobukazu , Ogasawara Kuniaki , Kobayashi Masakazu , Saitoh Hideo , Terasaki Kazunori , Inoue Takashi , Ogawa Akira
Published: November 2005

The aim of this study was to investigate whether postoperative hyperperfusion is associated with preoperative cerebral hemodynamic impairment due to chronic ischemia and with acute cerebral ischemia during clamping of the internal carotid artery (ICA) during carotid endarterectomy (CEA). Transcranial cerebral oxygen saturation (SO2) was monitored intraoperatively using near-infrared spectroscopy in 89 patients undergoing CEA for ipsilateral ICA stenosis (> 70%). Cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) to acetazolamide were also measured using single photon emission computed tomography (SPECT) before CEA. In addition, CBF was measured immediately after CEA and on the third postoperative day. Hyperperfusion (CBF increase > 100% compared with preoperative values) was observed immediately after CEA in 10 of 18 patients (56%) with reduced preoperative CVR. Also, post-CEA hyperperfusion was observed in nine of 16 patients (56%) whose SO2 during clamping of the ICA decreased to less than 90% of the preclamping value. Logistic regression analysis showed that reduced preoperative CVR and reduced SO2 during ICA clamping were significant independent predictors of the development of hyperperfusion immediately after CEA. In fact, all patients with reduced preoperative CVR and reduced SO2 during ICA clamping developed post-CEA hyperperfusion, and two of these patients developed cerebral hyperperfusion syndrome. These data suggest that development of cerebral hyperperfusion after CEA is associated with preoperative hemodynamic impairment and intraoperative cerebral ischemia.
A theory of transport properties in molten salts
Authors: Koishi Takahiro , Tamaki Shigeru
Published: November 2005

Expressions for diffusion constants in molten salts have been obtained in terms of the inter-ionic pair potentials and the pair distribution functions. Numerical attempts for diffusion constants in molten alkali halides are carried out and results agreed fairly with those obtained by molecular-dynamics simulation and with some experimental data. Based on the coupling of generalized Langevin equation and damped Einstein oscillator equation, ions’ velocity autocorrelation functions have also been described and are numerically applied for molten potassium fluoride. The deviation from the Nernst-Einstein relation was also discussed in detail. In Appendixes A–C, the short-time expansion of velocity correlation functions in relation to the partial conductivities and the diffusion constants were obtained up to the term of t4 and these were compared with a model function described by the form of cos(ωt)∙sech(t∕τ).
Effect of flexibility on hydrophobic behavior of nanotube water channels
Authors: Andreev Stefan , Reichman David , Hummer Gerhard
Published: November 2005

Carbon nanotubes can serve as simple nonpolar water channels. Here we report computer simulations exploring the relationship between the mechanical properties of such channels and their interaction with water. We show that on one hand, increasing the flexibility of the carbon nanotubes increases their apparent hydrophobic character, while on the other hand the presence of water inside the channel makes them more resistant to radial collapse. We quantify the effect of increasing flexibility on the hydrophobicity of the nanotube water channel. We also show that flexibility impedes water transport across the nanotube channel by increasing the free-energy barriers to such motion. Conversely, the presence of water inside the nanotube is shown to affect the energetics of radial collapse in a water nanotube, an ostensibly mechanical property. We quantify the magnitude of the effect and show that it arises from the formation of energetically favorable low-dimensional water structures inside the nanotube such as one-dimensional wires and two-dimensional sheets.
The helix-coil transition in heterogeneous double stranded DNA: Microcanonical method
Authors: Badasyan A. V. , Grigoryan A. V. , Mamasakhlisov E. Sh. , Benight A. S. , Morozov V. F.
Published: November 2005

A microscopic Potts-like one-dimensional model with many-particle interactions is developed to construct a statistical mechanical description of the melting of heterogeneous sequence duplex DNA. For this model, referred as the generalized model of polypeptide chains (GMPC), a closed-form expression for the free energy is derived. The characteristic equation of the model enables estimates on the melting temperature and transition interval, consistent with results obtained from more classical approaches. From the characteristic equation of the model, the temperature-dependent statistical weight parameter for helical states is evaluated. This parameter is shown to change throughout the transition from a harmonic form in early regions of the transition to an arithmetic form in later stages. The GMPC is extended to consider the influence of sequence heterogeneity in the melting of duplex DNA.
Hartree-Fock orbitals for complex-scaled configuration interaction calculation of highly excited Feshbach resonances
Authors: Žďánská Petra R. , Moiseyev Nimrod
Published: November 2005

We examine a complex-scaled configuration interaction [(CS)CI] for highly excited Feshbach resonances, where we study the 2s2 resonance of helium as a test case. Sizable full-CI calculations are reduced by using a correctly defined minimum active space. We compare the convergence of the minimum active space for conventional Hartree-Fock (HF) orbitals obtained as solutions to Hermitian HF equations, to the convergence of minimum active space for complex orbitals obtained as solutions to complex-scaled HF equations. Ground-state optimized orbitals are compared to a simple modification of the HF method using the excited-state mean-field potential.
Differential virial theorem in relation to a sum rule for the exchange-correlation force in density-functional theory
Authors: Holas A. , March N. H. , Rubio Angel
Published: November 2005

Holas and March [Phys. Rev. A. 51, 2040 (1995)] gave a formally exact theory for the exchange-correlation (xc) force Fxc(r)=−∇υxc(r) associated with the xc potential υxc(r) of the density-functional theory in terms of low-order density matrices. This is shown in the present study to lead, rather directly, to the determination of a sum rule ⟨nFxc⟩=0 relating the xc force with the ground-state density n(r). Some connection is also made with an earlier result relating to the external potential by Levy and Perdew [Phys. Rev. A. 32, 2010 (1985)] and with the quite recent study of Joubert [J. Chem. Phys. 119, 1916 (2003)] relating to the separation of the exchange and correlation contributions.
Photon energy dependence of fragmentation of small argon clusters
Authors: Gisselbrecht Mathieu , Lindgren Andreas , Tchaplyguine Maxim , Burmeister Florian , Öhrwall Gunnar , Lundwall Marcus , Lundin Magnus , Marinho Ricardo R.T. , Naves de Brito Arnaldo , Svensson Svante , Björneholm Olle , Sorensen Stacey L.
Published: November 2005

Photofragmentation of small argon clusters with size below ten atoms is reported. In this size range significant modifications from the electronic properties and geometry take place. When tuning the photon energy through the argon 2p edge, the fragmentation pattern is changed. Specifically, cation dimer production is enhanced at the 2p3∕2→4s resonance, while above the 2p edge almost complete atomization is observed. In both cases, the widths of the peaks in the mass spectra indicate that a large amount of kinetic energy is imparted to the fragment due to the formation of multiply charged clusters. A model based on “Coulomb explosion”—charge separation, simply resulting in a complete atomization of the cluster with no dependence on the photon energy—is insufficient to explain the observed photofragmentation of small clusters.
Mechanism of “rigid-body” rotation of the superfluid and normal components during phase separation of a supersaturated He3–4He solution
Authors: Pashitskiĭ É. A. , Mal’nev V. N. , Naryshkin R. A.
Published: November 2005

It is shown that unstable hydrodynamic vortices can form inside subcritical domains in the normal component of a supersaturated decomposing He3–4He solution. A mechanism for the entrainment of the superfluid component by the normal component of the He3–4He solution into “rigid-body” rotation due to Hall–Vinen–Bekarevich–Khalatnikov forces in the equations of two-fluid hydrodynamics, which leads to the creation of quantized vortices, is considered. An increase of the average density of quantized vortices can increase the rate of heterogeneous decomposition of the He3–4He solution.
The nuclear-spin conversion effect in the thermal conduction of methane
Authors: Gorodilov B. Ya. , Krivchikov A. I. , Korolyuk O. A.
Published: November 2005

This paper discusses the thermal conduction of solid methane at temperatures below the phase-transition temperature. An increase of the thermal conduction of the samples in time is detected at temperatures below 5 K after rapid cooling. The observed effect is associated with the concentration decrease of the T modification as a result of conversion. The characteristic time of the nuclear-spin conversion of methane is determined in the 1.8–5-K temperature region.
The role of Peierls relief in the low-temperature plasticity of pure α-Ti
Authors: Moskalenko V. A. , Natsik V. D. , Kovaleva V. N.
Published: November 2005

A detailed investigation of the low-temperature plasticity of high-purity polycrystalline α-Ti (interstitial impurities O+N=0.06 at. %) is carried out. The temperature dependences of the yield strength, effective stress, rate sensitivity of the deforming stress, and activation volume are obtained in the temperature interval 0.5–450 K. A thermal-activation analysis of the experimental data is carried out in terms of a model of activated motion of a dislocation string in Peierls relief. It is shown that the plastic flow of pure α-Ti in the region of moderately low temperatures (7 K<T<150 K) results from thermally activated overcoming of Peierls barriers by the mechanism of generation, expansion, and annihilation of paired kinks. Empirical values are obtained for the parameters of the theory for {101¯0}〈112¯0〉 prismatic slip in α-Ti at low temperatures: the Peierls stress τP=72 MPa and the characteristic energy of a critical paired kink, Hc=1.5×10−19 J=0.96 eV. At T<7 K, the plasticity of pure α-Ti has a pronounced anomaly, which may be caused by a transition as the temperature is reduced, from a thermally activated regime of dislocation motion to a dynamic (over-barrier) regime. At elevated temperatures (T>150 K), the plasticity of pure α-Ti qualitatively maintains characteristic features that correspond to the mechanism of thermally activated dislocation motion in the Peierls relief for low values of the effective stresses.
Acoustic-phonon transmission and thermal conductance in a double-bend quantum waveguide
Authors: Huang Wei-Qing , Chen Ke-Qiu , Shuai Z. , Wang Lingling , Hu Wangyu , Zou B. S.
Published: November 2005

Acoustic-phonon transmission and thermal conductance in a double-bend quantum waveguide at low temperatures are investigated with the use of the scattering matrix method. The calculated results show that the total transmission coefficient versus the reduced phonon frequency exhibits a series of resonant peaks and dips. The stop-frequency gap can be observed for certain structural parameters due to the mode-mode coupling in the bend region. The universal quantum thermal conductance and the decrease of the thermal conductance at very low temperatures can be clearly observed. However, for higher temperatures where the higher transverse modes are excited, the reduced thermal conductance K∕T is proportional to temperature T. The transmission coefficient and thermal conductance sensitively depend on the geometric parameters of the double bend, which provide an efficient way to control thermal conductance artificially by adjusting the parameters of the proposed microstructures.
Surface relief gratings induced by a nanosecond pulse in a liquid-crystalline azo-polymethacrylate
Authors: Rodríguez F. J. , Sánchez C. , Villacampa B. , Alcalá R. , Cases R. , Millaruelo M. , Oriol L.
Published: November 2005

Surface relief gratings have been generated in an azobenzene side chain liquid-crystal polymer using an intensity interference pattern from two coherent laser pulses (532nm and 4ns). We elucidate whether peaks or trenches correspond to the high intensity regions of the interference pattern. For low-energy pulses, peaks are generated in the irradiated areas while trenches appear for energies above a threshold (around 100mJ∕cm2 per beam). This phenomenology, together with the lack of relief when polarization patterns are used, indicates that in this polymer surface relief has a thermal origin.
Coordinate transformation in the model of long Josephson junctions: geometrically equivalent Josephson junctions
Authors: Semerdzhieva E. G. , Boyadzhiev T. L. , Shukrinov Yu. M.
Published: November 2005

The transition from the model of a long Josephson junction of variable width to the model of a junction with a coordinate-dependent Josephson current amplitude is effected through a coordinate transformation. This establishes the correspondence between the classes of Josephson junctions of variable width and quasi-one-dimensional junctions with a variable thickness of the barrier layer. It is shown that for a junction of exponentially varying width the barrier layer of the equivalent quasi-one-dimensional junction has a distributed resistive inhomogeneity that acts as an attractor for magnetic flux vortices. The curve of the critical current versus magnetic field for a Josephson junction with a resistive microinhomogeneity is constructed with the aid of a numerical simulation, and a comparison is made with the critical curve of a junction of exponentially varying width. The possibility of replacing a distributed inhomogeneity in a Josephson junction by a local inhomogeneity at the end of the junction is thereby demonstrated; this can have certain advantages from a technological point of view.
Magnetotransport properties of Er/Sc artificial multilayer structures
Authors: Chiang Yu. N. , Shevchenko O. G. , Kolenov R. N.
Published: November 2005

Comparative studies of the transport properties—resistance, magnetoresistance, and Hall effect—of Er/Sc multilayer structures and erbium films prepared by the same deposition technology are carried out for the first time. Those properties of the structures are modified substantially in comparison with those of elemental erbium. The magnetoresistance of the samples is “giant,” although it cannot compete in absolute magnitude with the values for superlattices based on d ferromagnetic materials. In the region of helium temperatures the Hall coefficient in the multilayer systems is more than an order of magnitude greater than at room temperature. It follows from the data for the Hall coefficient and magnetoresistance in that temperature region that the zero-field magnetization of the f structure is greater than the magnetization of the bulk f material in the ferromagnetic state. The conductance of the Er/Sc multilayer structure at T>20 K is lower than at helium temperatures. The features mentioned are described in terms of a temperature-induced rearrangement of the magnetic ordering of the erbium layers in the Er/Sc structures.
Phenomenological treatment of the giant magnetoelectric effect in some ferroelectromagnets
Authors: Chupis I. E.
Published: November 2005

It is shown that the colossal changes of the dielectric constant and electric polarization observed in DyMn2O5 and TbMnO3 in magnetic fields of the order of a few tesla can occur in ferroelectromagnets in which the temperatures of the ferroelectric and magnetic transitions are close and the values of the electric polarization are small. The appearance of electric polarization in the commensurate magnetic phase of TbMnO3 and the change of its orientation in a magnetic field are interpreted as being the result of a renormalization of the ferroelectric energy by the magnetoelectric interaction. The existence of a weak ferromagnetic moment along the c axis in the commensurate phase of TbMnO3 is predicted.
Size and shape evolution of embedded single-crystal α-Fe nanowires
Authors: Mohaddes-Ardabili L. , Zheng H. , Zhan Q. , Yang S. Y. , Ramesh R. , Salamanca-Riba L. , Wuttig M. , Ogale S. B. , Pan X.
Published: November 2005

The size and shape evolution of embedded ferromagnetic α-Fe nanowires is discussed. The α-Fe nanowires are formed by pulsed-laser deposition of La0.5Sr0.5FeO3−x on single-crystal SrTiO3 (001) substrate in reducing atmosphere. The average diameter of the nanowires increases from d≈4 to 50 nm as the growth temperature increases from T=560 to 840 °C. Their in-plane shape evolves from circular to octahedral and square shape with [110] facets dominating as the growth temperature increases. A fitting to a theoretical calculation shows that the circular shape is stable when the diameter of the nanowires is smaller than 8 nm.
Electron and ion sheath effects on a microwave “hairpin” probe
Authors: Haas F. A. , Al-Kuzee J. , Braithwaite N. St. J.
Published: November 2005

A microwave measurement of electron density in low-pressure plasmas can be based on a hairpin probe. The hairpin forms a transmission line that supports a quarter-wavelength standing wave. The resonance is related to the relative permittivity of the surroundings, and hence, in a plasma, electron density can be evaluated. For improved fidelity, a general model is developed to include the effects of positive and negative space-charge sheaths formed around the hairpin wires. The former tends to lower the resonance, whereas the latter tends to raise it initially. This is qualitatively in agreement with experiments in dc argon plasmas.
Low-voltage polymer field-effect transistors for nonvolatile memories
Authors: Naber R. C. G. , de Boer B. , Blom P. W. M. , de Leeuw D. M.
Published: November 2005

We demonstrate organic nonvolatile memories based on transistors, made from spin-coated polymers, that have programming voltages of 15V and good data retention capabilities. The low-voltage programmable ferroelectric field-effect transistors were obtained by an optimized ferroelectric polymer deposition method using cyclohexanone as a solvent from which films can be obtained that are thin, smooth and defect free. The data retention characteristics were measured for 3h under constant read conditions. Extrapolation predicts that the data retention capability exceeds 10years.
Pentacene-carbon nanotubes: Semiconducting assemblies for thin-film transistor applications
Authors: Bo X.-Z. , Tassi N. G. , Lee C. Y. , Strano M. S. , Nuckolls C. , Blanchet Graciela B.
Published: November 2005

We demonstrate an alternative path for achieving high-transconductance organic transistors by assembling bilayers of pentacene onto random arrays of single-walled carbon nanotubes. We show here that, by varying the connectivity of the underlying nanotube network, the channel length of a thin-film transistor can be reduced by nearly two orders of magnitude—thus, enabling the increase of the device transconductance without reduction the on/off ratio. These field-induced percolating networks enable assembling high-transconductance transistors that, with relatively large source drain distances, can be manufactured with available commercial printing techniques.
Tuning and optical study of the ΓX and ΓL photonic pseudogaps in opals
Authors: García P. D. , Galisteo-López J. F. , López C.
Published: November 2005

In this letter we demonstrate a method to tune and optically investigate the two highest-symmetry pseudogaps in artificial opals which occur at the L an X points of the Brillouin zone and correspond to propagation along the (111) and (100) crystallographic directions, respectively. In particular we show that in artificial opals the gap at the X point, which is closed for bare opals, can be opened by controlled infiltration with a high refractive index material such as ZnO. To prove this we take advantage of the fact that, in artificial opals grown by the vertical deposition method, regions with both (100) and (111) orientations of the face centerd cubic lattice occur naturally.
Enhanced light extraction from GaN-based light-emitting diodes with holographically generated two-dimensional photonic crystal patterns
Authors: Kim Dong-Ho , Cho Chi-O , Roh Yeong-Geun , Jeon Heonsu , Park Yoon Soo , Cho Jaehee , Im Jin Seo , Sone Cheolsoo , Park Yongjo , Choi Won Jun , Park Q-Han
Published: November 2005

We observed a significant enhancement in light output from GaN-based light-emitting diodes (LEDs) in which two-dimensional photonic crystal (PC) patterns were integrated. Two-dimensional square-lattice air-hole array patterns with a period that varied from 300 to 700 nm were generated by laser holography. Unlike the commonly utilized electron-beam lithographic technique, the holographic method can make patterns over a large area with high throughput. The resultant PC-LED devices with a pattern period of ∼500nm had more than double the output power, as measured from the top of the device. The experimental observations are qualitatively consistent with the results of three-dimensional finite-difference-time-domain simulation.
Refractometric sensors based on microsphere resonators
Authors: Hanumegowda Niranjan M. , Stica Caleb J. , Patel Bijal C. , White Ian , Fan Xudong
Published: November 2005

We have developed a highly sensitive refractometric sensor based on fused silica microsphere resonators. The spectral position of the whispering gallery mode (WGM) of a sphere shifts in response to the refractive index change in the surrounding medium. The strong light-matter interaction due to the extremely high Q factor associated with the WGM results in a sensitivity of approximately 30nm∕RIU (refractive index units). This, together with the high spectral resolution of our sensor system (∼0.01pm), yields a detection limit of refractive index change on the order of 10−7RIU. Theoretical calculation is also performed and agrees well with the experimental data.
Photocarrier-injected electronic structure of VO2∕TiO2:Nb
Authors: Eguchi R. , Shin S. , Fukushima A. , Kiss T. , Shimojima T. , Muraoka Y. , Hiroi Z.
Published: November 2005

We study the effect of photocarrier injection on the electronic structure of VO2∕TiO2:Nb thin films using photoemission spectroscopy. The results indicate that the valence band and core electronic states of VO2 shift systematically to lower binding energy upon photocarrier injection, consistent with doping in a rigid-band picture. The shift in binding energy, and its saturation, follows the known photovoltage behavior. In addition, the V 3d states near EF exhibit a redistribution/transfer of spectral weight, similar to the temperature dependent insulator to metal transition in VO2. The study provides evidence for hole-doping induced electronic structure changes due to the photocarriers in VO2.
Some Approaches to Glycosylated Versions of Methyl β-Acarviosin
Authors: Fairweather Jon K. , McDonough Matthew J. , Stick Robert V. , Tilbrook D. Matthew G.
Published: November 2005

In a first approach to a glycosylated version of ‘methyl β-acarviosin’, a putative inhibitor of cellulases, cellobiose was converted into a carbocyclic enone that could not be transformed into the required amine for a subsequent alkylation. Alternatively, methyl β-acarviosin itself was glycosylated at C4′, using a ‘glycosynthase’, to provide the ‘trisaccharide’ (and some ‘tetrasaccharide’). Both of these molecules were effective inhibitors of various cellulases. In a related approach to a regioisomer of the above ‘trisaccharide’, a selectively protected derivative of 1-epivalienamine was alkylated with a carbohydrate triflate to give a ‘disaccharide’ that could not be glycosylated to give the desired ‘trisaccharide’. Another unsuccessful approach to this molecule is also reported.
Core - Shell Pd/Co Nanocrystals
Authors: Sobal Nelli S. , Giersig Michael
Published: November 2005

A method for the preparation of bimetallic Pd/Co nanoparticles with a core–shell structure is presented. The process involves synthesis of a pure Pd seed colloid using thermal decomposition of palladium acetylacetonate, Pd(acac)2. Reduction of cobalt acetate using a polyalcohol in the presence of the Pd seeds allows the formation of Pd-core/Co-shell nanocrystals. Transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDX), and superconducting quantum interference (SQUID) magnetometry were used to characterize the bimetallic system.
Tunable Luminescence of New Photochromic Bisthienylethenes Containing Triphenylamine
Authors: Luo Qianfu , Sheng Saihong , Cheng Saihe , Tian He
Published: November 2005

Two new photochromic 1,2-bisthienylethenes containing triphenylamine were conveniently prepared; large cyclization quantum yields and obvious fluorescent changes regulated by the photoisomerization were observed. The substitution effect on the photochromic process is discussed based on these systems.
Iron(II) Molecular Framework Materials with 4,4'-Azopyridine
Authors: Halder Gregory J. , Kepert Cameron J.
Published: November 2005

Three new iron(ii) molecular-framework materials incorporating the bridging ligand 4,4′-azopyridine (azpy) have been synthesized and structurally characterized: Fe2(azpy)4(NCS)4·(azpy) (A), Fe(azpy)(NCSe)2(EtOH)2·(azpy) (B), and Fe(azpy)2(NCSe)2·2(MeCN) (C). A and C consist of non-interpenetrating (4,4) grids of iron(ii) centres bridged by azpy ligands with non-coordinating azpy ligands or acetonitrile molecules occupying the spaces within and between the layers. For B, hydrogen-bonding interactions between coordinated ethanol molecules and non-coordinated azpy ligands link linear Fe–azpy chains to give a two-dimensional framework.
N,N-Dialkyl (N'-Chlorosulfonyl)chloroformamidines in Heterocyclic Synthesis. I. The Preparation of [1,2,3,5]Thiatriazole and [1,3,2,4]Oxathiadiazole Derivatives
Authors: Fallon Gary D. , Jahangiri Saba , Liepa Andris J. , Woodgate Ruth C. J.
Published: November 2005

N,N-Dialkyl (N′-chlorosulfonyl)chloroformamidines 1 react regiospecifically with hydrazine derivatives to give [1,2,3,5]thiatriazole dioxides. Reaction of 1 with hydroxamic acids and N-methyl hydroxylamine gave derivatives of [1,3,2,4]oxathiadiazole dioxide 7, a new heterocycle.
Comparison of Polarities of Room-Temperature Ionic Liquids Using FT-IR Spectroscopic Probes
Authors: Tao Guo-hong , Zou Ming , Wang Xiao-hua , Chen Zhi-yu , Evans David G. , Kou Yuan
Published: November 2005

The solvent properties, especially the polarity, of room-temperature ionic liquids (RTILs) of the general type [Cnmim]X, where [Cnmim] is the 1-CnH2n+1-3-methylimidazolium cation and X is [BF4]−, [PF6]−, [NO3]−, [SCN]−, or [NTf2]− (Tf = CF3SO2), have been investigated using Fourier-transform infrared (FTIR) spectroscopy. Comparing the experimental shifts in the νC=O stretching frequencies of acetone and N,N-dimethylformamide (DMF) as probe molecules suggests that the polarities of most common RTILs are between that of DMF and methanol. A more sensitive probe, Fe(CO)5, can distinguish small polarity differences between RTILs with similar structures. The effects of varying the structure of RTILs by introducing functional groups and different anions on their polarity are also compared.
Atrazine degradation in soils: the role of microbial communities, atrazine application history, and soil carbon
Authors: Popov V. H. , Cornish P. S. , Sultana K. , Morris E. C.
Published: November 2005

The degradation rate of atrazine in floodplain soils under natural grasslands and cropped fields in the Liverpool Plains, NSW, was studied under laboratory incubation and in glasshouse bioassays, and related to soil properties including microbial community analysis by t-RFLP. The experiments were part of a broader study aiming to manage pesticides in the environment using vegetative filters (biofilters). The soils differed in their atrazine treatment history. Degradation rate (half-life) in cropped soil was more rapid (≈2 to 7 days) than in 2 grassland soils (≈8 to ≈22 days). Bioassays in the glasshouse using oats and soybeans supported this finding. The t-RFLP analysis disclosed the presence of 2 consortia of bacterial species that are reported in the literature to degrade atrazine. These were: (i) Rhodococcus sp, Pseudomonas aeruginosa, and Clavibacter michiganense and (ii) Acinetobacter sp., Pseudomonas sp., and Streptomyces sp. Their dynamics during incubation suggested that they might have been responsible for the more rapid atrazine degradation in the cropped soil. The enhanced atrazine degradation in cropped soil was also associated with lower concentrations of soil organic C and percentage of light fraction carbon compared with grassland soils, suggesting that atrazine provided an additional source of N and C to organisms that can quickly degrade the herbicide. The finding of relatively short atrazine half-life has implications for the effectiveness of the herbicide, as well as for the loads of pesticide potentially entering the environment. The results suggest there is little risk of atrazine accumulating in biofilters and causing damage.
Lateritic soils of Kerala, India: their mineralogy, genesis, and taxonomy
Authors: Chandran P. , Ray S. K. , Bhattacharyya T. , Srivastava P. , Krishnan P. , Pal D. K.
Published: November 2005

In this study, we report the chemical and mineralogical characteristics of 4 benchmark Ultisols of Kerala to elucidate their genesis and taxonomy. The taxonomic rationale of the mineralogy class of Ultisols and other highly weathered soils on the basis of the contemporary pedogenesis is also explained. The Ultisols of Kerala have low pH, low cation exchange capacity, low effective cation exchange capacity and base saturation, with dominant presence of 1 : 1 clays and gibbsite. Presence of gibbsite along with 2 : 1 minerals discounts the hypothesis of anti-gibbsite effect. Since the kaolins are interstratified with hydroxy-interlayered vermiculites (HIV), the formation of gibbsite from kaolinite is not tenable. Thus, gibbsite is formed from primary minerals in an earlier alkaline pedo-environment. Therefore, the presence of gibbsite does not necessarily indicate an advanced stage of weathering. On the basis of a dominant amount of gibbsite, a mineralogy class such as allitic or gibbsitic does not establish a legacy between the contemporary pedogenesis and the mineralogy. The dominance of kaolin–HIV in the fine clays of Ultisols and their persistence, possibly since early Tertiary, suggests that ‘steady state’ may exist in soils developed on long-term weathered saprolite. Since the present acid environment of Ultisols does not allow desilication, the chemical transformation of Ultisols to Oxisols with time is difficult to reconcile as envisaged in the traditional model of tropical soil genesis.
Process, performance, and pollution potential: A review of septic tank - soil absorption systems
Authors: Beal C. D. , Gardner E. A. , Menzies N. W.
Published: November 2005

On-site wastewater treatment and dispersal systems (OWTS) are used in non-sewered populated areas in Australia to treat and dispose of household wastewater. The most common OWTS in Australia is the septic tank–soil absorption system (SAS)—which relies on the soil to treat and disperse effluent. The mechanisms governing purification and hydraulic performance of a SAS are complex and have been shown to be highly influenced by the biological zone (biomat) which develops on the soil surface within the trench or bed. Studies suggest that removal mechanisms in the biomat zone, primarily adsorption and filtering, are important processes in the overall purification abilities of a SAS. There is growing concern that poorly functioning OWTS are impacting upon the environment, although to date, only a few investigations have been able to demonstrate pollution of waterways by on-site systems. In this paper we review some key hydrological and biogeochemical mechanisms in SAS, and the processes leading to hydraulic failure. The nutrient and pathogen removal efficiencies in soil absorption systems are also reviewed, and a critical discussion of the evidence of failure and environmental and public health impacts arising from SAS operation is presented. Future research areas identified from the review include the interactions between hydraulic and treatment mechanisms, and the biomat and sub-biomat zone gas composition and its role in effluent treatment.