bluuebunny/crossref_metadata_2025 huggingface dataset:
Increase in oxide hole trap density associated with nitrogen incorporation at the SiO2/SiC interface
Authors: Rozen John , Dhar Sarit , Dixit S. K. , Afanas’ev V. V. , Roberts F. O. , Dang H. L. , Wang Sanwu , Pantelides S. T. , Williams J. R. , Feldman L. C.
Published: June 2008

Nitrogen incorporation at the SiO2/SiC interface via high temperature nitric oxide annealing leads to the passivation of electrically active interface defects, yielding improved inversion mobility in the semiconductor. However, we find that such nitrided oxides can possess a larger density of hole traps than as-grown oxides, which is detrimental to the reliability of devices (e.g., can lead to large threshold voltage instabilities and to accelerated failure). Three different charge injection techniques are used to characterize this phenomenon in metal–oxide–semiconductor structures: x-ray irradiation, internal photoemission and Fowler–Nordheim tunneling. Some nitrogen-based atomic configurations that could act as hole traps in nitrided SiO2 are discussed based on first-principles density functional calculations.
Soft x-ray emission from a pulsed gas discharge in a pseudosparklike electrode geometry
Authors: Bergmann Klaus , Küpper Felix , Benk Markus
Published: June 2008

The mechanism of the soft x-ray generation in a pulsed high current discharge is investigated by means of time and space resolved characterization of the extreme ultraviolet emitting regions and discussion of the related electrical circuit parameters. The plasma is ignited in a pseudosparklike electrode geometry. In a discharge of 15 J, stored electrical energy characteristic emission of different gases (oxygen, argon, and nitrogen) is excited in the spectral range from 2 to 5 nm. Special interest is devoted to the 2.88 nm line emission of heliumlike nitrogen ions within the spectral range of the water window to be used for x-ray microscopy. For the nitrogen discharge, an admixture of xenon leads to axial shorter plasma emission as well as to a smaller diameter below 300 μm of the short wavelength emission. Investigation of the xenon related emission in the range of 10–16 nm indicates that radiative cooling is a possible reason for the observed decrease in the radius. Time and spatial resolved images show that the x-ray emission exhibits an axial dynamic in addition to the usual compression occurring in pinch plasmas.
Effects of nitrogen content on the structure and electrical properties of high-k NdOxNy gate dielectrics
Authors: Pan Tung-Ming , Hou Sung-Ju , Wang Chih-Hwa
Published: June 2008

This paper describes the structure and electrical properties of thin NdOxNy gate dielectrics deposited on Si(100) substrates through reactive rf sputtering. Atomic force microscopy and x-ray photoelectron spectroscopy were used to study the morphological and chemical features of these films as functions of the growth conditions (argon-to-nitrogen flow ratios of 20∕5, 15∕10, 10∕15, and 5∕20; temperatures ranging from 600to800°C). The NdOxNy gate dielectric prepared under an Ar∕N2 flow ratio of 10∕15 with subsequent annealing at 700°C exhibited the smallest capacitance equivalent thickness and the best electrical characteristics (gate leakage current, interface-trapped charge, and hysteresis voltage in the capacitance-voltage curves). We attribute this behavior to the optimal nitrogen content in this metal oxide film suppressing the amorphous silica and silicate at the NdOxNy∕Si interface and forming a smooth surface.
Role of solvent in protein phase behavior: Influence of temperature dependent potential
Authors: Li Jianguo , Rajagopalan Raj , Jiang Jianwen
Published: June 2008

Among many factors that affect protein phase separation, solvent plays a pivotal role in the possible structuring of the solvent molecules around the protein. The effect of solvent structuring is influenced strongly by temperature because of the relative stability of hydrogen bonding at low temperatures. As a result, quantitative as well as qualitative changes in protein phase separation may be expected with change in temperature. Here, we use a temperature dependent pair potential to examine the effect of water in the phase separation of protein solutions. Using Gibbs ensemble Monte Carlo simulations, we observe both a lower critical solution temperature and an upper critical solution temperature, in good agreement with the experimental observations for a number of proteins and phenomenological, statistical thermodynamic arguments. It is found that the effect of solvent is significant at low temperatures as a result of the highly structured shell of water molecules around the protein molecules. Radial distribution functions also indicate that a thick shell of structured water exists around the protein molecules due to the formation of strong hydrogen bonds when temperature is low. The findings of this study suggest that a simple model with a reasonable physical basis can capture the general phase behavior of some proteins or biopolymers.
Fe catalytic growth, microstructure, and low-threshold field emission properties of open ended tubular graphite cones
Authors: Shang N. G. , Papakonstantinou P. , McLaughlin J. , Chen W. C. , Chen L. C. , Chu M. , Stamboulis A.
Published: June 2008

Large-area tubular graphite cones (TGCs) with an open end were successfully synthesized on Si substrates by microwave plasma assisted chemical vapor deposition using a thin Fe film as catalyst. As-grown TGCs are uniformly distributed on the Si surface with a density of 5.8×105∕cm2 and an average growth rate of 0.6μm∕min. Some of them are very sharp with an apex angle as small as 2°–3°. Combined observations by transmission electron microscopy and cross-sectional scanning electron microscopy clarified that the TGCs possess a hollow nanotube core, a metal-free open tip and that the Fe catalyst is located in the root, strongly supporting the base-growth mechanism of TGCs. Scanning confocal micro-Raman spectroscopy along an individual TGC shows that the integrated intensity ratio of D to G band of individual TGC at tips (0.12) is an order of magnitude less than that at roots (1.2), confirming that the tip is highly crystalline whereas the root is of poor quality. Their field emission performance exhibits a turn-on field as low as 1.8V∕μm and highly stable emission characteristics. The present study opens the way to site selective growth of TGCs and demonstrates its use as a potentially excellent emitter.
Absorption and emission lineshapes and ultrafast solvation dynamics of NO in parahydrogen
Authors: Egorov S. A. , Larrégaray P.
Published: June 2008

We perform a theoretical study on the electronic spectroscopy of dilute NO impurity embedded in parahydrogen (p-H2). Absorption and emission lineshapes for the A Σ2+←X Π2 Rydberg transition of NO in parahydrogen have been previously measured and simulated, which yielded results for the NO/p-H2 ground and excited state pair potentials [L. Bonacina et al., J. Chem. Phys. 125, 054507 (2006)]. Using these potentials, we performed molecular dynamics simulation, theoretical statistical mechanical calculations of absorption and emission lineshapes, and both equilibrium and nonequilibrium solvation correlation functions for NO chromophore in parahydrogen. Theory was shown to be in good agreement with simulation. Linear response treatment of solvation dynamics was shown to break down due to a dramatic change in the solute-solvent microstructure upon solute excitation to the Rydberg state and the concomitant increase of the solute size.
Bipolar high-repetition-rate high-voltage nanosecond pulser
Authors: Tian Fuqiang , Wang Yi , Shi Hongsheng , Lei Qingquan
Published: June 2008

The pulser designed is mainly used for producing corona plasma in waste water treatment system. Also its application in study of dielectric electrical properties will be discussed. The pulser consists of a variable dc power source for high-voltage supply, two graded capacitors for energy storage, and the rotating spark gap switch. The key part is the multielectrode rotating spark gap switch (MER-SGS), which can ensure wider range modulation of pulse repetition rate, longer pulse width, shorter pulse rise time, remarkable electrical field distortion, and greatly favors recovery of the gap insulation strength, insulation design, the life of the switch, etc. The voltage of the output pulses switched by the MER-SGS is in the order of 3–50kV with pulse rise time of less than 10ns and pulse repetition rate of 1–3kHz. An energy of 1.25–125J per pulse and an average power of up to 10–50kW are attainable. The highest pulse repetition rate is determined by the driver motor revolution and the electrode number of MER-SGS. Even higher voltage and energy can be switched by adjusting the gas pressure or employing N2 as the insulation gas or enlarging the size of MER-SGS to guarantee enough insulation level.
A mimetic porous carbon model by quench molecular dynamics simulation
Authors: Shi Yunfeng
Published: June 2008

A mimetic porous carbon model is generated using quench molecular dynamics simulations that reproduces experimental radial distribution functions of activated carbon. The resulting structure is composed of curved and defected graphene sheets. The curvature is induced by nonhexagonal rings. The quench conditions are systematically varied and the final porous structure is scrutinized in terms of its pore size distribution, pore connectivity, and fractal dimension. It is found that the initial carbon density affects the fractal dimension but only causes a minor shift in the pore size distribution. On the other hand, the quench rate affects the pore size distribution but only causes a minor shift in the fractal dimension.
Spontaneous compliance of the InP∕SrTiO3 heterointerface
Authors: Saint-Girons G. , Priester C. , Regreny P. , Patriarche G. , Largeau L. , Favre-Nicolin V. , Xu G. , Robach Y. , Gendry M. , Hollinger Guy
Published: June 2008

The lattice mismatch between a growing layer and its substrate is a major limitation for heteroepitaxy. Finding solutions to overcome this limitation has given rise to many researches that have up to now not come out any satisfying solution. Here we demonstrate the compliant behavior of the InP∕SrTiO3 (STO) heterointerface. InP islands grown on STO substrates and STO/Si crystalline layers are defect-free, oriented with respect to STO, and have their InP bulk lattice parameter. This contrasts with plastic relaxation mechanisms observed for III-V, Si, or Ge mismatched heterostructures. Compliance occurs spontaneously during the growth and does not require any substrate patterning.
Facet dependent reactivity and selective deposition of nanometer sized β-SiC on diamond surfaces
Authors: Jiang X. , Srikanth V. V. S. S. , Zhao Y. L. , Zhang R. Q.
Published: June 2008

Selective deposition of nano-β-SiC on non-{100} diamond faces has been observed in a microwave plasma chemical vapor deposition process due to the presence of Si(CH3)4 in the gas phase. The process allows only the growth of diamond starting crystals whose [001] is normal to the film surface and interrupts the growth of otherwise oriented grains; this is due to the preferential deposition of SiH3 on {111} diamond but not on {001} diamond according to additional theoretical reactivity analysis of the gas species on the exposed diamond surfaces. The facet dependent reactivity facilitates control of diamond/β-SiC nanocomposite film growth.
Evidence of an isomeric pair in furan…HCl: Fourier transform infrared spectroscopy and ab initio calculations
Authors: Asselin P. , Madebène B. , Soulard P. , Reinhardt P. , Alikhani M. E.
Published: June 2008

For the first time the coexistence of a σ- and a π-complex in the C4H4O:HCl system has been observed, in the same supersonic expansion of a molecular jet seeded with argon (or helium) or in a flow-cooled cell at 240K. This is an exception to the third of the Legon–Miller rules which claims the σ-structure to be the only one to exist. On the grounds of energetic considerations and band contour simulations, two observed bands at 2787.7 and 2795.5cm−1 of the νs HCl stretching frequency are assigned to the two complexes, recorded as Fourier transform infrared spectra with a resolution between 0.2 and 0.5cm−1. Complementary calculations show that the use of the standard second-order Møller–Plesset perturbation theory may be erroneous for such a complex, due of the overestimation of the dispersion contribution with respect to the electrostatic term. It is finally established that only a balanced version of the second-order Møller–Plesset perturbation method, spin-component scaled-MP2, or a higher level of theory like a coupled-cluster approach, can provide a reliable energetic analysis for this complex.
Strong light-matter coupling in ultrathin double dielectric mirror GaN microcavities
Authors: Bejtka K. , Réveret F. , Martin R. W. , Edwards P. R. , Vasson A. , Leymarie J. , Sellers I. R. , Duboz J. Y. , Leroux M. , Semond F.
Published: June 2008

Strong light-matter coupling is demonstrated at low temperature in an ultrathin GaN microcavity fabricated using two silica/zirconia Bragg mirrors, in addition to a three-period epitaxial (Al,Ga)N mirror serving as an etch stop and assuring good quality of the overgrown GaN. The λ∕2 cavity is grown by molecular beam epitaxy on a Si substrate. Analysis of angle-resolved data reveal key features of the strong coupling regime in both reflectivity and transmission spectra at 5K: anticrossing with a normal mode splitting of 43±2 meV and 56±2meV for reflectivity and transmission, respectively, and narrowing of the lower polariton linewidth near resonance.
Side electron emission device using carbon nanofiber/elastomer composite sheet
Authors: Nakamura Hironao , Yanagi Hisao , Kita Takashi , Magario Akira , Noguchi Toru
Published: June 2008

A side electron emission device was made of a carbon nanofiber/elastomer composite sheet. Instead of a conventional field emission configuration, electron emitters consisting of cross-sectional sides of the composite sheet were put in position perpendicular to the phosphor/anode surface by inserting an insulating spacer. Light emission of 4200cd∕m2 at 1kV was achieved by intense electron emission from the cross section since the carbon nanofibers preferentially orient parallel to the sheet plane and stick out of the cross section. This simple device structure enabled us to fabricate a flexible, transparent field emission device.
Photoemission study of Cs–NF3 activated GaAs(100) negative electron affinity photocathodes
Authors: Liu Zhi , Sun Yun , Peterson Samuel , Pianetta Piero
Published: June 2008

GaAs based negative electron affinity photocathodes activated with Cs and NF3 are used as polarized electron sources for linear accelerators. It is generally believed that the activation layer consists of CsF. The activation layers of Cs–NF3 on GaAs photocathodes are herein investigated using synchrotron radiation photoelectron spectroscopy. F1s, N1s, and other core levels are recorded at photon energies ranging from 70to820eV. Surprisingly, a significant amount of nitrogen is observed in the activation layers. Two distinct species of nitrogen are observed, one of which decreases along with the fluorine signal as the yield of the photocathode decays with time.
Thermally tunable polymer microlenses
Authors: Huang Xian , Cheng Chao-Min , Wang Li , Wang Bin , Su Chih-Chuan , Ho Mon-Shu , LeDuc Philip R. , Lin Qiao
Published: June 2008

Polymer microlenses capable of using heat to control its focal length are presented. The microlenses are created by exposing droplets of the polymer SU-8 to UV light. By altering the temperature of the microlenses via on-chip heating, their curvature and focal length are actively controlled without mechanical movements. By directly and indirectly measuring temperature-dependent changes of the focal length, we test the ability of the microlenses as a tunable imaging component. The microlenses have potential use in applications such as laser systems, functional biomimetics, and endoscopy.
Experimental investigation of nanofluid shear and longitudinal viscosities
Authors: Schmidt Aaron J. , Chiesa Matteo , Torchinsky Darius H. , Johnson Jeremy A. , Boustani Avid , McKinley Gareth H. , Nelson Keith A. , Chen Gang
Published: June 2008

Dilute nanoparticle suspensions of alumina in decane and isoparaffinic polyalphaolefin (PAO) exhibit thermal conductivity and shear viscosity that are enhanced compared to continuum models that assume well-dispersed particles. An optical technique has been used to measure the longitudinal viscosity of these suspensions at frequencies from 200to600MHz and evaluate an effective hydrodynamic particle size. The measurements indicate that for the decane-based nanofluids the nanoparticles do not form clusters. In the case of PAO nanofluids, the measurements of longitudinal viscosity and the corresponding values of the particle size are consistent with a picture of nonclustered particles in a weakly shear-thinning viscous oligomeric oil.
Dielectric evidences of core-shell-like effects in nanosized relaxor PbMg1∕3Nb2∕3O3
Authors: Carreaud Julie , Bogicevic Christine , Dkhil Brahim , Kiat J. M.
Published: June 2008

Temperature and frequency dependence of dielectric permittivity in nanotextured ceramics of PbMg1∕3Nb2∕3O3 has been performed in a wide range of grain sizes and shown to display strong variation. In particular, frequency relaxation follows the Vögel Fulcher law for the high grain sizes, whereas for intermediate sizes, two Debye processes are evidenced. This behavior as well as a diminution of the maximum of the real dielectric constant εmax could be explained within the mechanism of relaxation based on the existence of polar nanoregions with a core-shell structure for each grain.
Waves in a cylindrical borehole filled with micropolar fluid
Authors: Singh Dilbag , Tomar S. K.
Published: June 2008

Dispersion equation is derived for the propagation of surface waves in a cylindrical borehole filled with a micropolar viscous fluid and hosted in an infinite micropolar elastic solid medium. These waves are found to be dispersive and attenuated. The effects of fluid viscosity, micropolarity of the fluid, and radius of the borehole on the dispersion curve are noticed and depicted graphically. For a particular model, the dispersion curve is found to be significantly affected by the fluid viscosity and radius of the borehole, but not much by the micropolarity of the fluid.
On the effect of the electrical contact resistance in nanodevices
Authors: Schwamb Timo , Burg Brian R. , Schirmer Niklas C. , Poulikakos Dimos
Published: June 2008

We have investigated the effect of the electric contact resistance in nano devices by manufacturing dedicated chips with four-point contacted platinum nanowires and individual, suspended, and four-point contacted carbon nanotubes. For both cases, we measured the intrinsic electrical resistance and the electrical contact resistance. Our results indicate that the electrical contact resistance of the platinum nanowires and the carbon nanotubes can be one to three orders of magnitude higher than the intrinsic electrical resistance of the sample itself. Subsequently, we tested the platinum nanowires as pressure sensors to quantify the impact of the electrical contact resistance on the performance of micro- and nanodevices.
Electrical detection of photoinduced spins both at room temperature and in remanence
Authors: Hövel S. , Gerhardt N. C. , Hofmann M. R. , Lo F.-Y. , Reuter D. , Wieck A. D. , Schuster E. , Keune W. , Wende H. , Petracic O. , Westerholt K.
Published: June 2008

We demonstrate a photodetector with ferromagnetic contacts which can electrically detect the polarization degree of incoming light using spin filtering of photoinduced spin-polarized electron currents. Our structure is a pin diode with a single GaAs quantum well as active region and a Fe∕Tb multilayer on top of a MgO tunnel barrier as n-contact where the spin-polarized electron current is filtered. The photocurrent depends on the magnetization of the contacts and on the polarization of the injected light. We prove that even in remanence and at room temperature the degree of circular polarization of the incident light can be unambiguously determined by the photocurrent intensity.
Heterogeneous nucleation in a glass-forming alloy
Authors: Wall J. J. , Liu C. T. , Rhim W.-K. , Li J. J. Z. , Liaw P. K. , Choo H. , Johnson W. L.
Published: June 2008

Nucleation in the undercooled liquid state in the bulk metallic glass-forming composition Zr52.5Cu17.9Ni14.6Al10Ti5 (VIT-105), produced using high purity (PA) and commercial purity (CA) raw materials was investigated using electrostatic levitation and ex situ neutron diffraction. The CA material was observed to have a lower density than the PA sample and crystallized at relatively shallow undercooling. The densities of the samples at temperatures above the solidus showed an oxygen-dependent hysteresis associated with the state change, indicating the presence of oxygen-stabilized intermetallics. The PA alloy exhibited three distinct crystallization modes dependent on the thermal history of the melt, one of which showed a net volume expansion.
Effect of screening on the sensitivity of field-effect devices used to detect oligonucleotides
Authors: Landheer D. , McKinnon W. R. , Jiang W. H. , Aers G.
Published: June 2008

The effect of screening and the establishment of the Donnan potential at the floating gate of field-effect transistors (BioFETs) are calculated for a model that includes proton site binding on metal oxides used as gate insulators. Variations of response with pH, electrolyte concentration, and the fixed charge density of oligonucleotides are calculated assuming the charge is distributed homogenously in an ion-permeable membrane of finite thickness. Derived expressions describe the change in threshold voltage with electrolyte concentration and pH. These could be used to predict the sensitivity of the BioFET to hybridization, and provide a means of calibration prior to use.
Oxygen etching mechanism in carbon-nitrogen (CNx) domelike nanostructures
Authors: Acuña J. J. S. , Figueroa C. A. , Biggemann D. , Kleinke M. U. , Alvarez F.
Published: June 2008

We report a comprehensive study involving the ion beam oxygen etching purification mechanism of domelike carbon nanostructures containing nitrogen. The CNx nanodomes were prepared on Si substrate containing nanometric nickel islands catalyzed by ion beam sputtering of a carbon target and assisting the deposition by a second nitrogen ion gun. After preparation, the samples were irradiated in situ by a low energy ion beam oxygen source and its effects on the nanostructures were studied by x-ray photoelectron spectroscopy in an attached ultrahigh vacuum chamber, i.e., without atmospheric contamination. The influence of the etching process on the morphology of the samples and structures was studied by atomic force microscopy and field emission gun–secondary electron microscopy, respectively. Also, the nanodomes were observed by high resolution transmission electron microscopy. The oxygen atoms preferentially bond to carbon atoms by forming terminal carbonyl groups in the most reactive parts of the nanostructures. After the irradiation, the remaining nanostructures are grouped around two well-defined size distributions. Subsequent annealing eliminates volatile oxygen compounds retained at the surface. The oxygen ions mainly react with nitrogen atoms located in pyridinelike structures.
High-yield TiO2 nanowire synthesis and single nanowire field-effect transistor fabrication
Authors: Baik Jeong Min , Kim Myung Hwa , Larson Christopher , Chen Xihong , Guo Shujing , Wodtke Alec M. , Moskovits Martin
Published: June 2008

We report a facile method for synthesizing single-crystal rutile TiO2 nanowires using atmospheric-pressure, chemical vapor deposition with Ti and TiO as precursors. The synthesis is found to depend critically on the predeposition of a layer of metallic Ti on the Ni catalysts layer. The omission of this step seems previously to have impeded the efficient synthesis of titania nanowires. Single-nanowire field-effect transistors showed the TiO2 nanowires to be n-type semiconductors with conductance activation energy of ∼58meV.
Activation and carrier mobility in high fluence B implanted germanium
Authors: Mirabella S. , Impellizzeri G. , Piro A. M. , Bruno E. , Grimaldi M. G.
Published: June 2008

High doping regimes of B implanted Ge have been accurately characterized combining Hall effect technique and nuclear reaction analysis. Preamorphized Ge was implanted with B at 35keV (spanning the 0.25–25×1020B∕cm3 concentration range) and recrystallized by solid phase epitaxy at 360°C. The Hall scattering factor and the maximum concentration of active B resulted rH=1.21 and ∼5.7×1020B∕cm3, respectively. The room-temperature carrier mobility was accurately measured, decreasing from ∼300to50cm2∕Vs in the investigated dopant density, and a fitting empirical law is given. These results allow reliable evaluation for Ge application in future microelectronic devices.
High-performance 4H-SiC based metal-semiconductor-metal ultraviolet photodetectors with Al2O3∕SiO2 films
Authors: Zhang Feng , Yang Weifeng , Huang Huolin , Chen Xiaping , Wu Zhengyun , Zhu Huili , Qi Hongji , Yao Jianke , Fan Zhengxiu , Shao Jianda
Published: June 2008

4H-silicon carbide (SiC) metal-semiconductor-metal (MSM) ultraviolet (UV) photodetectors with Al2O3∕SiO2 (A/S) films employed as antireflection/passivation layers have been demonstrated. The devices showed a peak responsivity of 0.12A∕W at 290nm and maximum external quantum efficiency of 50% at 280nm under 20V electrical bias, which were much larger than conventional MSM detectors. The redshift of peak responsivity and response restriction effect were found and analyzed. The A/S/4H-SiC MSM photodetectors were also shown to possess outstanding features including high UV to visible rejection ratio, large photocurrent, etc. These results demonstrate A/S/4H-SiC photodetectors as a promising candidate for OEIC applications.
Polarization-dependent sensing of a self-assembled monolayer using biaxial nanohole arrays
Authors: Eftekhari F. , Gordon R. , Ferreira J. , Brolo A. G. , Sinton D.
Published: June 2008

We demonstrate surface plasmon resonance (SPR) sensing based on the polarization-dependent extraordinary optical transmission through a biaxial nanohole array. The biaxial array has two periodicities in a single array that can be individually probed by varying polarization. Here, the SPR polarization-spectral dependence is demonstrated for the detection of a self-assembled monolayer for four sets of biaxial array periodicities. By monitoring the polarization dependence of transmission through the nanohole arrays with biaxial periodicity, surface-sensitive refractive index induced intensity variations may be separated from other effects such as absorption, scattering, and intensity fluctuations, while using a single wavelength source. Biaxial sensing is useful for ongoing microfluidic integration of nanohole SPR, where the light source is transmitted through a microfluidic channel.
A transparent cell-culture microchamber with a variably controlled concentration gradient generator and flow field rectifier
Authors: Cheng Ji-Yen , Yen Meng-Hua , Kuo Ching-Te , Young Tai-Horng
Published: June 2008

Real-time observation of cell growth provides essential information for studies such as cell migration and chemotaxis. A conventional cell incubation device is usually too clumsy for these applications. Here we report a transparent microfluidic device that has an integrated heater and a concentration gradient generator. A piece of indium tin oxide (ITO) coated glass was ablated by our newly developed visible laser-induced backside wet etching (LIBWE) so that transparent heater strips were prepared on the glass substrate. A polymethylmethacrylate (PMMA) microfluidic chamber with flow field rectifiers and a reagent effusion hole was fabricated by a CO2 laser and then assembled with the ITO heater so that the chamber temperature can be controlled for cell culturing. A variable chemical gradient was generated inside the chamber by combining the lateral medium flow and the flow from the effusion hole. Successful culturing was performed inside the device. Continuous long-term (>10 days) observation on cell growth was achieved. In this work the flow field, medium replacement, and chemical gradient in the microchamber are elaborated.
Modeling time-dependent phosphate buffering capacity in different soils as affected by bicarbonate and silicate ions
Authors: De Nirmal , Datta Samar Chandra
Published: June 2008

The aim of this paper was to establish a relationship between phosphate buffering capacity and time in the presence of specifically sorbed anions like bicarbonate and silicate. P sorption isotherms were obtained at different times of equilibration for 3 surface soil samples, namely, Typic Haplustept, Calcic Chromustert, and Ultic Paleustalf in 3 different systems namely, bicarbonate (0.001 m), silicate (0.001 m), and a control system without any bicarbonate or silicate and having a common concentration of 0.1 m NaCl. Phosphate sorption data at different times could be fitted very closely to a modified Freundlich equation of the form: X/m = KCntp, where X/m is the amount of phosphate sorbed at solution phosphate concentration C and time t in hours. The values of n and p were positive fractions (mostly) and found to vary with soils and ionic medium. The silicate system was more effective in decreasing P sorption. Phosphate buffering capacity, defined as the first-order partial derivative of X/m with respect to C, KntpCn–1, was calculated at a particular concentration of 0.3 mg/L (usual P concentration of soil solution) at different times from the optimised value of K, n, and p. Phosphate buffering capacity was maximum in the control system and found to increase with time. Bicarbonate and, particularly, silicate ion decreased buffering capacity drastically and also the rate of change of buffering capacity with time. The practical implications of this decrease in buffering capacity by bicarbonate and silicate ions is discussed.
Changes in soil microbial biomass and community composition along vegetation zonation in a coastal sand dune
Authors: Yoshitake Shinpei , Nakatsubo Takayuki
Published: June 2008

We used phospholipid fatty acid (PLFA) analysis to examine the relation of microbial biomass and community composition to vegetation zonation on a coastal sand dune. Soil samples were collected along 3 line transects established from the shoreline to the inland bush. Total PLFA content and PLFA composition of soils were used as indices of total microbial biomass and community composition, respectively. The microbial biomass was much higher in the inland Vitex rotundifolia zone than in the seaside plots. The microbial community composition also differed among the vegetation zones, with a higher contribution of fungal biomarkers in the inland plots. The microbial biomass increased significantly with increasing soil organic matter (SOM) content, but was not correlated with soil salinity. These results suggest that microbial biomass in the coastal sand dune was controlled primarily by the accumulation of SOM. The microbial community composition also changed with SOM content in the seaside plots, but SOM had little effect in the inland plots. These results suggest that the factors limiting the microbial community composition differed with location on the dune.
Salmonella uptake in sheep exposed to pastures after biosolids application to agricultural land
Authors: Eamens G. J. , Waldron A. M.
Published: June 2008

Young adult sheep grazing pasture on land treated with dewatered biosolids 1–3 weeks before pasture sowing were used to assess the risk of transfer of Salmonella spp. from biosolids to the food chain. Monthly determinations of Salmonella spp. concentrations in the biosolids after land application showed survival for at least 7 months, with concentrations fluctuating between 104/g and below detection limits at various time points. Low concentrations were measured 4–5 months after application, followed by a return to 102–103/g on subsequent samplings. Sheep introduced at 3 or 6 months after biosolids applications of 0, 10, or 15 dry t/ha were assessed monthly for faecal shedding of salmonellae, and at slaughter, 8 months after biosolids application, for intestinal carriage of Salmonella spp. None of 80 sheep grazing the biosolids-treated land were found to excrete salmonellae. A single sheep among those grazing treated land showed Salmonella carriage in slaughter tissues, but the serovar isolated from this animal was different from the 6 serovars of Salmonella detected in the applied biosolids. Use of dewatered biosolids on land later sown for pasture and grazed by sheep thus posed no risk to animal uptake or faecal shedding of Salmonella spp. This in part relates to a low risk of direct pathogen ingestion by grazing sheep and the period of several months necessary for pasture establishment before grazing stock can be introduced.
The fate of phosphorus under contrasting border-check irrigation regimes
Authors: McDowell R. W. , Rowley D.
Published: June 2008

Flood-irrigation, to the extent that outwash (runoff from border-check bays) occurs, is a major cause of P loss from grazed pastures and has potential to harm surface water quality. We used a combination of rainfall simulation to produce runoff and field sampling of outwash to investigate processes of P loss from treatments receiving no irrigation and irrigation at 10%, 15%, and 20% soil moisture and every 21 days (3w). Intact soil blocks were removed from each treatment, dung removed, soils wetted to about 32% soil moisture, and runoff produced via rainfall simulation. This indicated that P losses were proportional to soil Olsen P concentrations (29.8–51.4 mg Olsen P/kg; 0.096–0.541 mg dissolved reactive P/L). Olsen P concentration was less in those treatments receiving a greater number of irrigations due to increased pasture production and, presumably, loss via outwash. When soil blocks were allowed to dry, concentrations in runoff more than doubled and were paralleled by a decrease in soil microbial biomass P. However, when outwash was sampled in the field, P loss was greater in more frequently irrigated treatments. This was attributed to increased stocking rates and P-release from dung masking any soil effect. However, differences in P loss in outwash from 2 treatments (without recent grazing) were attributed to different soil moisture before irrigation. Assuming 25% of irrigation is lost as outwash, annual loads were estimated to range from 0.7 kg P/ha in the 10% treatment, irrigated 2.6 times a year, to 12.6 kg P/ha in the 3w treatment, irrigated 6.5 times per year. This suggests that the frequency of irrigation and stocking rate dictate the majority of P lost in this system (not soil P concentration). Hence, mitigation practices should be promoted to minimise outwash in intensively sheep-grazed pastures and potential surface water quality impacts.
Prospects of improving efficiency of fertiliser nitrogen in Australian agriculture: a review of enhanced efficiency fertilisers
Authors: Chen D. , Suter H. , Islam A. , Edis R. , Freney J. R. , Walker C. N.
Published: June 2008

Fertiliser nitrogen use in Australia has increased from 35 Gg N in 1961 to 972 Gg N in 2002, and most of the nitrogen is used for growing cereals. However, the nitrogen is not used efficiently, and wheat plants, for example, assimilated only 41% of the nitrogen applied. This review confirms that the efficiency of fertiliser nitrogen can be improved through management practices which increase the crop’s ability to compete with loss processes. However, the results of the review suggest that management practices alone will not prevent all losses (e.g. by denitrification), and it may be necessary to use enhanced efficiency fertilisers, such as controlled release products, and urease and nitrification inhibitors, to obtain a marked improvement in efficiency. Some of these products (e.g. nitrification inhibitors) when used in Australian agriculture have increased yield or reduced nitrogen loss in irrigated wheat, maize and cotton, and flooded rice, but most of the information concerning the use of enhanced efficiency fertilisers to reduce nitrogen loss to the environment has come from other countries. The potential role of enhanced efficiency fertilisers to increase yield in the various agricultural industries and prevent contamination of the environment in Australia is discussed.
Comparing the effects of continuous and time-controlled grazing systems on soil characteristics in Southeast Queensland
Authors: Sanjari Gholamreza , Ghadiri Hossein , Ciesiolka Cyril A. A. , Yu Bofu
Published: June 2008

Grazing by livestock has a great influence on soil characteristics with major effects on soil carbon and nitrogen cycling in grazing lands. Grazing practices affect soil properties in different ways depending on the prescribed stocking rate and grazing periods. The new grazing system of short, intensive grazing followed by a long period of rest, referred to as time-controlled grazing (TC grazing), has become popular among many graziers in Australia and elsewhere. However, little research has been carried out on the impacts of this grazing system on the physical and chemical health of the soil. To address this issue, a comprehensive field study was carried out on a sheep-grazing property in the south-eastern region of Queensland, Australia, where the 2 grazing systems of continuous and TC grazing were compared. Results over the period 2001–2006 showed an increase in soil organic carbon and nitrogen in the areas with favourable soil condition compared with continuous grazing. There was also an increase in ground-litter accumulation over time and no compaction in TC grazing. Nitrate and extractable P concentrations were reduced by increased grass growth under TC grazing, which in turn decreased the contamination potential for downstream water bodies. This reduction was much more pronounced on a historical sheep aggregation camp, where a large amount of faecal material had been deposited prior to conversion to TC grazing. The smaller size of the paddocks, along with the long rest period provided by TC grazing in this area, are recognised to be the major contributors to both physical and chemical recovery of the soil after each grazing operation.
Land-use effects on soil properties on the north-western slopes of New South Wales: Implications for soil condition assessment
Authors: Wilson B. R. , Growns Ivor , Lemon J.
Published: June 2008

In Australia, as elsewhere, there is a growing need for information relating to soil condition, its current status, and the nature and direction of change in response to management pressures. This information is required by land managers, and regional, State and, national agencies to inform modified land-use practices and investment to maintain and improve the soil resource. Here, we present data relating to soils under 3 land-use types at 6 properties the north-western slopes of New South Wales. We aimed to quantify the range of soil condition states that exist across the region and to test a range of potential soil condition indicators and their suitability to detect differences in soil condition between these land-use types. A range of soil properties showed no significant difference between land-uses and could be rejected as indicators. However, significant differences existed between the land-uses and soil depths for a range of the other soil parameters determined (bulk density, C, N, P, EC, and Na). Soil C, N, P, and Na concentration and total soil C were typically higher in woodland soils compared with other land-uses, while bulk density, pH, and EC were lower in the woodland soils. The depth at which these differences existed varied between soil parameters. Correlation and principal components analysis suggested that a minimum dataset of soil parameters including soil bulk density, pH, C, P, and Na would discern much of the difference in soil condition between the land-uses studied. It is proposed that these parameters be used as a minimum dataset of indicators for soil condition assessment on soils of the type across this region. Work continues under the New South Wales Land and Soil Condition Monitoring Program to further refine the selection of appropriate soil indicators in this and other regions of New South Wales.
Assessing mitigation of wildfire severity by fuel treatments - an example from the Coastal Plain of Mississippi
Authors: Martinson Erik J. , Omi Philip N.
Published: June 2008

Fuel treatments such as prescribed fire are a controversial tenet of wildfire management. Despite a well-established theoretical basis for their use, scant empirical evidence currently exists on fuel treatment effectiveness for mitigating the behaviour and effects of extreme wildfire events. We report the results of a fire severity evaluation of an escaped prescribed fire that burned into an area previously treated with repeated prescribed fires. We observed significantly lower scorch heights, crown damage, and ground char in the treated area. We attribute the moderated fire severity in the treated area to a significantly altered fuel profile created by the repeated prescribed fires. Though our results represent just one treatment area in a single wildfire, they add to a depauperate database and bring us a step closer to defining the conditions under which fuel treatments are an effective pre-suppression strategy.
Using visual obstruction to estimate heathland fuel load and structure
Authors: Davies G. M. , Hamilton A. , Smith A. , Legg C. J.
Published: June 2008

We present a simple non-destructive technique for assessing fuel load and critical aspects of vegetation structure that play important roles in determining fire behaviour. The method is tested in a Scottish Calluna vulgaris (L.) Hull heathland but could be applied to any vegetation up to ~1 m high. Visual obstruction of a banded measurement stick (the FuelRule) placed vertically through a stand of vegetation is governed by a combination of the height of the vegetation and its density. The vertical distribution of visual obstruction is calibrated to give estimates of total fuel loading, the loading of separate size categories and the vertical distribution and horizontal heterogeneity of fuels. The present paper provides a quick and simple method for estimating total aboveground biomass and structure that may be useful not just in studies of fire behaviour but where non-destructive assessment of biomass, vegetation density or canopy structure is needed. Calibration equations can be rapidly created for use in other vegetation or fuel types.
Dendroclimatic inference of wildfire activity in Quebec over the 20th century and implications for natural disturbance-based forest management at the northern limit of the commercial forest
Authors: Le Goff Héloïse , Girardin Martin P. , Flannigan Mike D. , Bergeron Yves
Published: June 2008

We examined the fire–climate relationship at the northern limit of commercial forest in western Quebec, a region where forest management is currently competing with fires for mature stands. The main objective was to determine if a particular climate signal would control the fire activity in this region when compared with other parts of the Quebec boreal forest. We used 500-hPa spatial correlation maps to compare the atmospheric patterns associated with the annual area burned (AAB) in the study area, the entire province of Quebec, the intensive (southern Quebec), and the restricted (northern Quebec) fire management zones. Next, dendroclimatic analyses were used to obtain tree-ring estimates of the AAB back to 1904 and to investigate the temporal stability of the fire–climate relationship. The climate controls associated with the AAB of the study area are intermediate between those associated with the AAB of the intensive and restricted fire management zones. The 500-hPa correlation patterns for the 1948–71 and 1972–2001 periods were relatively stable through time for the study area and for the restricted fire management zone. Our results provide a plausible mechanism for explaining the link between sea surface temperature and regional fire activity established in previous studies. They also provide information complementary to the Canadian fire danger rating system that uses daily weather data.
Differential function of the NACHT-LRR (NLR) members Nod1 and Nod2 in arthritis
Authors: Joosten Leo A. B. , Heinhuis Bas , Abdollahi-Roodsaz Shahla , Ferwerda Gerben , LeBourhis Lionel , Philpott Dana J. , Nahori Marie-Anne , Popa Calin , Morre Servaas A. , van der Meer Jos W. M. , Girardin Stephen E. , Netea Mihai G. , van den Berg Wim B.
Published: June 2008

The pathogenesis of chronic joint inflammation remains unclear, although the involvement of pathogen recognition receptors has been suggested recently. In the present article, we describe the role of two members of the NACHT-LRR (NLR) family, Nod1 (nucleotide-binding oligomerization domain) and Nod2 in a model of acute joint inflammation induced by intraarticular injection ofStreptococcus pyogenescell wall fragments. Here, we show that Nod2 deficiency resulted in reduced joint inflammation and protection against early cartilage damage. In contrast, Nod1 gene-deficient mice developed enhanced joint inflammation with concomitant elevated levels of proinflammatory cytokines and cartilage damage, consistent with a model in which Nod1 controls the inflammatory reaction. To explore whether the different function of Nod1 and Nod2 occurs also in humans, we exposed peripheral blood mononuclear cells (PBMCs) carrying either Nod1ins/del or Nod2fs mutation with SCW fragmentsin vitro. Production of both TNFα and IL-1β was clearly impaired in PBMCs carrying the Nod2fs compared with PBMCs isolated from healthy controls. In line with results in Nod1 gene-deficient mice, PBMCs from individuals bearing a newly described Nod1 mutation produced enhanced levels of proinflammatory cytokines after 24-h stimulation with SCW fragments. These data indicate that the NLR family members Nod1 and Nod2 have different functions in controlling inflammation, and that intracellular Nod1–Nod2 interactions may determine the severity of arthritis in this experimental model. Whether a distorted balance between the function of Nod1 and/or Nod2 is involved in the pathogenesis of human autoinflammatory or autoimmune disease, such as rheumatoid arthritis, remains to be elucidated.
A defined transposon mutant library and its use in identifying motility genes in
Vibrio cholerae
Authors: Cameron D. Ewen , Urbach Jonathan M. , Mekalanos John J.
Published: June 2008

Defined mutant libraries allow for efficient genome-scale screening and provide a convenient collection of mutations in almost any nonessential gene of interest. Here, we present a near-saturating transposon insertion library in
Vibrio cholerae
strain C6706, a clinical isolate belonging to the O1 El Tor biotype responsible for the current cholera pandemic. Automated sequencing analysis of 23,312 mutants allowed us to build a 3,156-member subset library containing a representative insertion in every disrupted ORF. Because uncharacterized mutations that affect motility have shown utility in attenuating
V. cholerae
live vaccines, we used this genome-wide subset library to define all genes required for motility and to further assess the accuracy and purity of the library. In this screen, we identified the hypothetical gene VC2208 (
flgT
) as essential for motility. Flagellated cells were very rare in a
flgT
mutant, and transcriptional analysis showed it was specifically stalled at the class III/IV assembly checkpoint of the
V. cholerae
flagellar regulatory system. Because FlgT is predicted to have structural homology to TolB, a protein involved in determining outer membrane architecture, and the sheath of the
V. cholerae
flagellum appears to be derived from the cell's outer membrane, FlgT may play a direct role in flagellar sheath formation.