bluuebunny/crossref_metadata_2025 huggingface dataset:
A model for calculating resputter rates in codeposition
Authors: Gregoire J. M. , van Dover R. B.
Published: September 2008

The ability to calculate composition in composition spread thin films is a powerful tool in combinatorial research. This ability is pivotal in high-throughput studies, where the time and effort required to determine elemental compositions using standard techniques can be prohibitive. Calculating codeposited film composition from single-source deposition profiles requires a model for film growth in codeposition. In dc magnetron sputtering, modeling film growth as the simple addition of individual rates can lead to significant errors, primarily due to resputtering of film atoms by energetically reflected gas atoms. We develop a model which includes the definition of a resputter coefficient that is used to calculate resputtering rates in the codeposition of an arbitrary number of sources. The accuracy of the model is demonstrated for the codeposition of Pt and Pb. In the development of the model, useful parametrizations of fundamental quantities of sputter dynamics are presented, and the authors also present tabulated values of the resputter coefficient for 27 commonly sputtered elements at select sputter voltages.
Effect of annealing temperature on the photocatalytic activity of sol-gel derived TiO2 thin films
Authors: Biswas S. , Majumder Arpi , Hossain M. F. , Takahashi T. , Kubota Y. , Fujishima A.
Published: September 2008

Transparent TiO2 thin films were deposited on glass substrates by a sol-gel dip coating technique, where crystallinity can be achieved at a relatively low annealing temperature. In this sol-gel preparation technique, acetic acid was used as a catalyst. Repetitive dip coating and drying, with a single annealing has made this technique easier to prepare TiO2 thin film with desired thickness within a short period of time. The crystallographic and optical properties of TiO2 films were investigated in detail. The photocatalytic activity was evaluated by the measurement of decomposition of methanol under UV-visible irradiation. The rate of decomposition of gaseous methyl alcohol depends on the structures and surface properties of the TiO2 films. The structure of the TiO2 films, prepared at various annealing temperatures, shows different crystallinities. Although crystallinity has been observed for 300°C annealing temperature, it improved with increasing annealing temperature. The average transmittances of the TiO2 films slightly decrease with the increase of the annealing temperature in the range of 900–380nm. The optical transmission edge of the TiO2 films, annealed at different annealing temperatures shifts toward higher wavelength with higher annealing temperature. All the as-deposited TiO2 films successfully photocatalyzed methanol to CO2 and H2O, measured by Fourier transform infrared spectrometer. The decomposition efficiency of TiO2 films increased with decrease of annealing temperature. The surface morphology of all the samples was investigated by field emission scanning electron microscopy and atomic force microscopy measurements. The higher photocatalytic activity of the sample prepared at lower annealing temperature was explained by the effect of more porous structure with smaller grains and open surface morphology of the sample.
Conducting polymer nanofilm growth on a nanoscale linked-crater pattern fabricated on an Al surface
Authors: Kato H. , Takemura S. , Ishii A. , Takarai Y. , Watanabe Y. , Sugiyama T. , Hiramatsu T. , Nanba N. , Nishikawa O. , Taniguchi M.
Published: September 2008

A linked-crater structure was fabricated on an Al surface by chemical and electrochemical combination processes. The surface of an Al plate was treated with semiClean and was successively processed in anodization in H2SO4. Dynamic force microscopy image showed that a linked-crater structure was formed on the Al surface. The crater size ranged from 80to200nm. It turned out that a lot of pores with 9nm in diameter were created inside each crater. The depth of each crater was approximately 7–17nm. At the next stage, the thin film growth of polythiophene on the linked-crater structured Al surface was conducted by an electrochemical synthetic method. The electrochemical polymerization on the Al surface was performed in acetonitrile containing thiophene monomer and (Et)4NBF4 as a supporting electrolyte. After being electrochemically processed, the contour image of each crater was still recognized implying that the polymer nanofilm was grown on the nanoscale structured Al surface. The cross section analysis demonstrated that the nanofilm was grown along the linked-crater structure because the contour of each crater became thick. The average thickness of the polymer film was estimated as 10–20nm. Furthermore, copper phthalocyanine molecules were successfully injected into the polymer nanofilm on the Al surface in order to functionalize the nanoscale material.
Global plasma simulations using dynamically generated chemical models
Authors: Munro James J. , Tennyson Jonathan
Published: September 2008

Extensive molecular data are a key requirement in understanding modern technical plasmas. A method for coupling molecular data with chemical models in a global plasma simulation to enable rapid testing and evaluation of new plasmas is presented. A global plasma model (GLOBALKIN) is extended using an expert system (Quantemol-P) to enable ad hoc simulations using new plasma recipes. A set of atomic and molecular species to be considered in the plasma simulation is specified by the user. The expert system generates a complete set of reaction pathways for both the gas and surface reactions in a plasma. This set is pruned by discarding unphysical reactions and reaction data not appropriate to technical plasmas (such as autodetachment). The species, gas phase reactions, surface reactions, and plasma properties can be adjusted to control the simulation. The reaction list is populated through a database of molecular parameters and cross sections; missing data can be calculated through molecular cross sections using a further expert system (Quantemol-N) which applies the R-matrix method to electron-molecule collisions. For cases where the R-matrix method is not appropriate, other methods are used to maximize the range of cross-section data available. The Quantemol-P expert system allows rapid creation of new plasma recipes and investigation of their effects allowing a greater level of flexibility than previously achievable.
Study on the amorphous Ta–Zr films as diffusion barrier in Cu metallization
Authors: Li Chuan , Hsieh J. H. , Tang Z. Z.
Published: September 2008

An amorphous Ta–Zr binary alloy diffusion barrier was studied in the Cu metallization. A Cu∕Ta50Zr50∕Si stack with 50nm thick amorphous film was prepared by cosputtering can effectively suppress the penetration of Cu atoms into substrate upon annealing up to 650°C. Examining the thermal stability of the barrier revealed that the crystallization of these amorphous Ta50Zr50 films occurred at 800°C, higher than its failure temperature. The results show that the existence of Cu layer first induced the formation of TaSi2 and ZrSi2 crystalline phases at 650°C, followed by the formation of Cu3Si. A failure mechanism of the diffusion barrier is proposed based on the relation between the thermal stress and the activation energy of barrier/substrate interface reaction.
Effects of hydrogen ambient and film thickness on ZnO:Al properties
Authors: Duenow Joel N. , Gessert Timothy A. , Wood David M. , Dillon Anne C. , Coutts Timothy J.
Published: September 2008

Undoped ZnO and ZnO:Al (0.1, 0.2, 0.5, 1.0, and 2.0wt.% Al2O3) films were deposited by rf magnetron sputtering. Controlled incorporation of H2 in the Ar sputtering ambient for films grown at substrate temperatures up to 200°C results in mobilities exceeding 50cm2V−1s−1 when using targets containing 0.1 and 0.2wt.% Al2O3. Temperature-dependent Hall measurements show evidence of phonon scattering as the dominant scattering mechanism in these lightly Al-doped films, while ionized impurity scattering appears increasingly dominant at higher doping levels. A combination of compositional and structural analysis shows that hydrogen expands the ZnO lattice normal to the plane of the substrate and desorbs from ZnO at ∼250°C according to temperature-programmed desorption and annealing experiments.
Effects of annealing on antiwear and antibacteria behaviors of TaN–Cu nanocomposite thin films
Authors: Hsieh J. H. , Cheng M. K. , Chang Y. K. , Li C. , Chang C. L. , Liu P. C.
Published: September 2008

TaN–Cu nanocomposite films were deposited by reactive cosputtering on Si and tool steel substrates. The films were then annealed using rapid thermal annealing (RTA) at 400°C for 2, 4, and 8min, respectively, to induce the nucleation and growth of Cu particles in TaN matrix and on film surface. Field emission scanning electron microscopy was applied to characterize Cu nanoparticles emerged on the surface of TaN–Cu thin films. The effects of annealing on the antiwear and antibacterial properties of these films were studied. The results reveal that annealing by RTA can cause Cu nanoparticles to form on the TaN surface. Consequently, the tribological behaviors, as well as the antibacterial behavior may vary depending on particle size, particle distribution, and total exposed Cu amount. For the samples with large Cu particles, the reduction of averaged friction and wear rate is obvious. Apparently, it is due to the smeared Cu particles adhered onto the wear tracks. This Cu layer may act as a solid lubricant. From the antibacterial testing results, it is found that both Cu particle size and total exposed Cu amount are critical in making short-term antibacterial effect. Overall, all the annealed TaN–Cu samples can reach >99% antibacterial efficiency in 24h, with respect to uncoated Si substrate.
Influence of a post–chemical mechanical polishing cleaning process on the ferroelectric properties of a Pb(Zr,Ti)O3 thin film capacitor fabricated by the damascene process
Authors: Kim Nam-Hoon , Jun Young-Kil , Ko Pil-Ju , Lee Woo-Sun
Published: September 2008

The author first applied a chemical mechanical polishing (CMP) process to fabricate a ferroelectric Pb(Zr,Ti)O3 (PZT) capacitor instead of using a plasma etching process for the vertical profile without plasma damage in their previous study. The post-CMP cleaning process was very important in this CMP process. In this study, they investigated the effects of the post-CMP cleaning process on the ferroelectric properties of a PZT thin film capacitor. They proposed an optimized post-CMP cleaning process that uses a SC-1 chemical, diluted HF treatment, and an ultrasonic cleaning process. The slurry residues on the surface of the PZT thin films were removed. The polarization-voltage (P-V) characteristics showed the typical hysteresis loop of PZT thin films after a post-CMP cleaning process with the optimized conditions, while the ferroelectric characteristics could not be observed in the specimen without the post-CMP cleaning process. The remanent polarization (Pr) and coercive voltage (Vc) of the PZT thin films after the post-CMP process with the optimized condition were 17.092μC∕cm2 and 3.252V, respectively.
Dry etching of extreme ultraviolet lithography mask structures in inductively coupled plasmas
Authors: Kim D. Y. , Lee H. J. , Jung H. Y. , Lee N.-E. , Kim T. G. , Kim B. H. , Ahn Jinho , Kim C. Y.
Published: September 2008

Extreme ultraviolet lithography (EUVL) is currently being examined for its potential use in the next generation of lithography techniques. Among the core EUVL technologies, mask fabrication is of considerable importance due to the use of new reflective optics. This study investigated the etching properties of EUVL mask materials, such as Al2O3 antireflection coating (ARC), TaN (absorber layer) and Ru (buffer/capping layer), by varying the Cl2∕Ar gas flow ratio, dc self-bias voltage (Vdc) and top electrode power in inductively coupled plasma. The Al2O3 (ARC) layer could be etched with an etch selectivity approaching 0.5 over the TaN absorber layer. The ARC/TaN stack could be etched with an infinitely high etch selectivity over the Ru layer. Etching of the stacked mask structures with a 200nm line/space hydrogen silsesquioxane e-beam resist pattern showed a profile angle of 85° and an etch stop on the Ru buffer/capping layer.
Gate oxide process control optimization by x-ray photoelectron spectroscopy in a semiconductor fabrication line
Authors: Le Gouil A. , Cabuil N. , Dupeyrat P. , Dickson B. , Kwan M. , Barge D. , Gurer E. , Doclot O. , Royer J.-C.
Published: September 2008

X-ray photoelectron spectroscopy is a metrology technique that is used for in-line control of decoupled plasma nitridation processes in the fabrication of logic devices. This article shows XPS results of thickness and composition obtained on two types of gate oxide nitrided by a decoupled plasma nitridation process. Measurements are performed in specific test structures with an x-ray spot which can be focused down to 35μm, enabling process control directly on products. First, XPS is used to characterize and quantify the chemical composition of a SiON layer. The Results show that the nitrogen composition in a SiON layer decreases at a fast rate during the initial days after nitridation processing and stabilizes with time. Second, measurements are performed on products with the objective of transferring process control from monitor to product wafers. In this regard, comparison of nitrogen dose and thickness uniformity on monitor and pattern wafers show similar trends, indicating that measurements of nitrogen dose and thickness on monitor and product wafers give the same information. Third, different mapping protocols are studied on products to identify the best compromise between throughput and an optimized mapping representative of the process distribution. An optimized process control strategy of gate oxides with results is discussed in this article.
Characterization of electrospray ion-beam-deposited CdSe/ZnS quantum dot thin films from a colloidal solution
Authors: Tani Yuki , Kobayashi Satoshi , Kawazoe Hiroshi
Published: September 2008

Colloidal semiconductor quantum dot (QD) nanocrystals can be deposited in the form of inorganic thin films using the ion beam direct deposition method. To simultaneously preserve the nanocrystal configuration and remove the organics derived from the ligand and solvent, the authors used an electrospray technique and an ion beam technique. These techniques provided a soft-ionization process to obtain nanocrystalline ions and a collision process to attain a nonequilibrium state of the deposits, respectively. Because of the nature of the soft-ionization process, the electrospray phenomenon resulted in various forms of QD ions that depended on the preparation of the colloidal solution source and spraying conditions. The authors concentrated on finding operational conditions of the system that deposited thin films with reduced organics concentrations by examining the correlation between fast Fourier transform infrared absorption spectroscopy and photoluminescence intensity. The morphology of the deposited films was observed using an atomic force microscope.
Fabrication of metal-based high-aspect-ratio microscale structures by compression molding
Authors: Jiang J. , Mei Fanghua , Meng W. J.
Published: September 2008

Metal-based high-aspect-ratio microscale structures (HARMSs) are basic building blocks for metallic microdevices such as microelectromagnetic relays and microchannel heat exchangers. Metallic microdevices may have advantages over Si-based devices when subjected to high stresses, high temperatures, and other harsh conditions. In this article, the authors summarize our recent results on molding replication of metal-based HARMS. The micromolding response was experimentally measured in Al and Cu, and rationalized with companion high-temperature tensile testing and finite element analysis. Successful replication of Ni-based and NiTi-based HARMS was demonstrated.
Low-damage low-k etching with an environmentally friendly CF3I plasma
Authors: Soda Eiichi , Kondo Seiichi , Saito Shuichi , Ichihashi Yoshinari , Sato Aiko , Ohtake Hiroto , Samukawa Seiji
Published: September 2008

The feasibility of etching Cu/low-k interconnects by using a low global warming potential CF3I plasma was studied. Low-damage etching was done and porous SiOC (p-SiOC, k<2.6) film with low roughness was produced. Exposing p-SiOC film to CF3I plasma was found to suppress the decrease in the CH3 group and the increase in the k value compared to those of conventional CF4 and C4F6 plasmas. These effects are due to the low UV intensity and small amount of F radicals of CF3I plasma. The authors also found that the etching profile of CF3I plasma was comparable with that of CF4 plasma. Since the etching selectivity (p-SiOC∕ArF photoresist) of CF3I plasma is higher than that of CF4 plasma, the remaining photoresist thickness increases after etching, thus suppressing line edge roughness (LER). The decreased LER mitigated degradation of IV and time dependent dielectric breakdown characteristics in Cu interconnects. They also found that the roughness on the bottom surface of the p-SiOC trench was reduced. These benefits are due to CF3I plasma’s low reactivity with the carbon in photoresists and p-SiOC films. Based on these findings, they believe that the environmentally friendly CF3I gas has great promise as a p-SiOC etching material.
Silicon carbonitrides: On the attainability of stable compounds with high nitrogen content
Authors: Rudolphi M. , Baumann H. , Geckle U. , Bruns M.
Published: September 2008

Thin stoichiometric SiCN thin films and layers along selected tie lines of the phase diagram have been synthesized from the elements by means of ion implantation of carbon and nitrogen ions into silicon wafer substrates as well as rf magnetron cosputtering of targets with different Si∕C area ratios by using Ar∕N2 sputter gas with successive variation of the N2 content. After synthesis, the samples were heat treated under high vacuum conditions utilizing an electron beam annealing system. Resonant nuclear reaction analysis, non-Rutherford backscattering spectrometry and Auger electron spectroscopy have been used to perform an elemental analysis of the films and layers, respectively. The chemical binding states were investigated with x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy.
Can the throttling of a perfect gas through a free molecular orifice produce a cooling effect?
Authors: Young Robert M. , Braggins Timothy T. , Kirby Christopher F. , Adam J. Douglas , Petach Michael B. , Tward Emanuel
Published: September 2008

A novel refrigeration cycle using throttling through free molecular orifice(s) was explored experimentally and theoretically, attempting to exploit the heat transfer that occurs by the entropy shift across a discontinuous system formed by a wall containing tens of thousands of micron or submicron free molecular throttling (FMT) orifices. Single stage free molecular throttle cooling is compared in terms of figure of merit and coefficient of performance (COP) against the analogous isothermal entropy shift cooling effect in thermoelectric junctions. Unlike thermoelectric materials, free molecular throttling is predicted to perform increasingly better as the temperature drops below 200K. Experimentally, the authors have shown in three rounds of progressively smaller dimensions and hence larger heat flux vector magnitude that the simple, isothermal movement of heat, taken in analogy with thermoelectric (Peltier junction) refrigerators, is not valid. By using this information, the authors then show that solid state heat conduction across the orifice wall controls the degree of temperature reduction. This was described in a new dimensionless number which gives the relative importance of the backward thermal leakage due to solid state conduction through the wall thickness, against that of the FMT heat flow, and is thus the means by which a designer would direct the design space toward a functional and practical wall. The largest theoretical temperature drop per stage was found to be ΔT=T0∕6, and thus staging would be required to reach cryogenic temperatures from ambient. Single stage FMT refrigeration was derived theoretically to have a peak second law efficiency of 5%–10% of the Carnot COP. The low pressures involved and lack of the regenerative heat exchanger in this new cycle means that it is scalable to very small dimensions, and indeed, since it operates in a regime where the characteristic size of the orifices must be smaller than the mean free path length of the gas molecules, it is already scaled to microscopic dimensions. FMT cooling would appear to have future applications in subwatt heat lift systems with the ultimate lowest temperature of ∼10K being only dictated by the perfect gas limit of He.
Characterization of molecular nitrogen in III-V compound semiconductors by near-edge x-ray absorption fine structure and photoemission spectroscopies
Authors: Bozanic A. , Majlinger Z. , Petravic M. , Gao Q. , Llewellyn D. , Crotti C. , Yang Y.-W.
Published: September 2008

Formation of molecular nitrogen under low-energy nitrogen bombardment of III-V compound semiconductor surfaces has been studied by photoemission spectroscopy around N 1s core-level and near-edge x-ray absorption fine structure (NEXAFS) around NK edge. Interstitial molecular nitrogen N2 has been formed in all of the samples under consideration. The presence of N2 produces a sharp resonance in low-resolution NEXAFS spectra, showing the characteristic vibrational fine structure in high-resolution measurements, and at the same time, a new peak, shifted toward higher binding energies for several eV, in all N 1s photoemission spectra.
Plasma modification of CoPt3 nanoparticle arrays: A route to catalytic coatings of surfaces
Authors: Gehl Bernhard , Flege Jan Ingo , Aleksandrovic Vesna , Schmidt Thomas , Kornowski Andreas , Bernstorff Sigrid , Falta Jens , Weller Horst , Bäumer Marcus
Published: September 2008

Two-dimensional layers of bimetallic cobalt-platinum nanoparticles were prepared from colloidal suspension to serve as model systems for catalytic surface coatings with well-defined chemistry and geometry. After deposition, the particle surfaces were exposed to mild rf plasmas in order to remove the passivating shell of organic ligands that covered their surfaces after preparation. X-ray photoelectron spectroscopy subsequently carried out without exposing the samples to air revealed that all carbon species can be quantitatively removed due to the treatment and that selective oxidation/reduction of the particles is possible. Grazing-incidence small-angle x-ray scattering was used to study plasma-induced changes in the particle ordering with high precision. The measurements prove that even for closely packed layers with lateral distances of less than 2nm, changes in the mean diameters of the particles can be kept in the order of just 1%–2%.
Design and fabrication of a multilayer micro-/nanofluidic device with an electrically driven nanovalve
Authors: Li Hao , Ocola Leonidas E. , Auciello Orlando , Firestone Millicent
Published: September 2008

A device containing microfluidic and nanofluidic channels was designed and fabricated to study the performance of an electrically driven nanovalve controlled by induced polarization of a ferroelectric substrate. The microfluidic component was fabricated in polydimethylsiloxane and designed to provide adequate driving pressure and flow rate for fluid flow in the nanofluidic component using only a common syringe pump. The nanofluidic component was fabricated on a glass substrate, coated with a thin film of lead-zirconium-titanate (PZT) substrate, and integrated with nanoelectrodes to induce surface polarization. The experimental concept is to use the polarizable surface of the PZT layers to control the motion of a nanovalve made of charged nanowires or biological molecules. The function of the nanovalve would be demonstrated by observing the fluid mixing behavior variation in the nanofluidic channels before and after the polarization of the PZT substrate. A successful device will prove useful for many applications including laboratory on a chip and release-on-demand drug delivery systems. This device can also be used to study the basic science of fluid flow and heat transfer at the nanoscale with the purpose of improvement in flow and heat transfer efficiency in nanoscale devices.
Nanometer-scaled triangular platinum islands fabricated using the bridge phenomenon of polystyrene beads
Authors: Lee Byoung-Kyu , Kim Kyoung Seob , Lee Ji-Hye , Kim Nam-Hoon , Roh Yonghan
Published: September 2008

The authors optimized the fabrication of nanometer-scaled triangular platinum islands using the bridge phenomenon of polystyrene beads. Both the mixture ratio of polystyrene beads and the spin coating process were optimized to array a uniform monolayer of polystyrene beads at a high density over a large area. The length of the bridge between the adjacent polystyrene beads as well as the size of polystyrene beads could be controlled using the oxygen plasma ashing process with an adjustment in the ashing time. Platinum was deposited on the ashed polystyrene beads with the bridges as a mask, and the hexagonally arrayed triangular platinum islands were obtained through the dense and uniform triangular structures surrounded by the polystyrene bead bridges with dimensions of less than 45nm2 on the silicon substrate.
Etching characteristics and application of physical-vapor-deposited amorphous carbon for multilevel resist
Authors: Kim H. T. , Kwon B. S. , Lee N.-E. , Park Y. S. , Cho H. J. , Hong B.
Published: September 2008

For the fabrication of a multilevel resist (MLR) based on a very thin, physical-vapor-deposited (PVD) amorphous carbon (a-C) layer, the etching characteristics of the PVD a-C layer with a SiOx hard mask were investigated in a dual-frequency superimposed capacitively coupled plasma etcher by varying the following process parameters in O2∕N2∕Ar plasmas: high-frequency/low-frequency combination (fHF∕fLF), HF/LF power ratio (PHF∕PLF), and O2 and N2 flow rates. The very thin nature of the a-C layer helps to keep the aspect ratio of the etched features low. The etch rate of the PVD a-C layer increased with decreasing fHF∕fLF combination and increasing PLF and was initially increased but then decreased with increasing N2 flow rate in O2∕N2∕Ar plasmas. The application of a 30nm PVD a-C layer in the MLR structure of ArF PR∕BARC∕SiOx∕PVD a-C∕TEOS oxide supported the possibility of using a very thin PVD a-C layer as an etch-mask layer for the TEOS-oxide layer.
Mechanisms and selectivity for etching of HfO2 and Si in BCl3 plasmas
Authors: Wang Chunyu , Donnelly Vincent M.
Published: September 2008

The authors have investigated plasma etching of HfO2, a high dielectric constant material, and poly-Si in BCl3 plasmas. Etching rates were measured as a function of substrate temperature (Ts) at several source powers. Activation energies range from 0.2to1.0kcal∕mol for HfO2 and from 0.8to1.8kcal∕mol for Si, with little or no dependence on source power (20–200W). These low activation energies suggest that product removal is limited by chemical sputtering of the chemisorbed Hf or Si-containing layer, with a higher Ts only modestly increasing the chemical sputtering rate. The slightly lower activation energy for HfO2 results in a small improvement in selectivity over Si at low temperature. The surface layers formed on HfO2 and Si after etching in BCl3 plasmas were also investigated by vacuum-transfer x-ray photoelectron spectroscopy. A thin boron-containing layer was observed on partially etched HfO2 and on poly-Si after etching through HfO2 films. For HfO2, a single B(1s) feature at 194eV was ascribed to a heavily oxidized species with bonding similar to B2O3. B(1s) features were observed for poly-Si surfaces at 187.6eV (B bound to Si), 189.8eV, and 193eV (both ascribed to BOxCly). In the presence of a deliberately added 0.5% air, the B-containing layer on HfO2 is largely unaffected, while that on Si converts to a thick layer with a single B(1s) peak at 194eV and an approximate stoichiometry of B3O4Cl.
Survey on measurement of tangential momentum accommodation coefficient
Authors: Agrawal Amit , Prabhu S. V.
Published: September 2008

The value of tangential momentum accommodation coefficient (TMAC) is required while prescribing the boundary condition for flow of gases in the slip and transition flow regimes. The precise determination of its value is important for several other applications as well. This article reviews the experimental techniques employed by researchers over the decades to measure this coefficient and the values reported in the literature, with relevance to calculation of the slip velocity. The review shows that the value of TMAC is dependent on a number of parameters including nature of the gas, pressure of the gas, material of the surface, surface cleanliness and roughness, and surface temperature. For monatomic gases, the TMAC at about 0.93 is almost constant with respect to the Knudsen number, and this value can be employed for most commonly available surface materials. However, for nonmonatomic gases, TMAC decreases with an increase in Knudsen number; a correlation of TMAC with Knudsen number for this class of gases, is proposed based on the available data. It is also revealed that TMAC depends strongly on the surface cleanliness and roughness, while temperature has an influence although it may not be very important for values greater than the room temperature.
X-ray photoelectron spectroscopy studies of water-induced surface reorganization of amphiphilic poly(2-hydroxyethyl methacrylate-g-dimethylsiloxane) copolymers using cryogenic sample handling techniques
Authors: Chen Lu , Hook Daniel J. , Valint Paul L. , Gardella Joseph A.
Published: September 2008

A series of amphiphilic graft copolymers having a hydrophilic poly(2-hydroxyethyl methacrylate) (HEMA) backbone and hydrophobic polydimethylsiloxane (PDMS) side chains were studied by x-ray photoelectron spectroscopy (XPS) in both dry and hydrated states using cryogenic sample handling techniques. The polymers were synthesized using anionic methods for the PDMS side chains, yielding a tightly controlled PDMS graft chain length in a polymer brush surface configuration. The effects of hydration time and polymer bulk structure (e.g., PDMS graft length) and composition on surface reorganization were examined. XPS studies provided direct quantitative data on the extent of polymer surface reorganization between dry and hydrated states. The dry surface was enriched with PDMS while the hydrated surface was enriched with HEMA. The surface reorganization reaches equilibrium when copolymers were hydrated for 24 h. In the dry state, PDMS graft length and bulk composition have a strong effect on surface composition; while in the hydrated state, the polymer surface composition was nearly independent of bulk structure or composition.
Structural study of TiO2-based transparent conducting films
Authors: Hitosugi T. , Yamada N. , Nakao S. , Hatabayashi K. , Shimada T. , Hasegawa T.
Published: September 2008

We have investigated microscopic structures of sputter and pulsed laser deposited (PLD) anatase Nb-doped TiO2 transparent conducting films, and discuss what causes the degradation of resistivity in sputter-deposited films. Cross-sectional transmission electron microscope and polarized optical microscope images show inhomogeneous intragrain structures and small grains of ∼10μm in sputter-deposited films. From comparison with PLD films, these results suggest that homogeneous film growth is the important factor to obtain highly conducting sputter-deposited film.
Study on plasma assisted metal-organic chemical vapor deposition of Zr(C,N) and Ti(C,N) thin films and in situ plasma diagnostics with optical emission spectroscopy
Authors: Cho S. J. , Nam S.-H. , Jung C.-K. , Jee H.-G. , Boo J.-H. , Kim S. , Han J. G.
Published: September 2008

Zr(C,N) and Ti(C,N) films were synthesized by pulsed dc plasma assisted metal-organic chemical vapor deposition method using metal-organic compounds of tetrakis diethylamido titanium and tetrakis diethylamido zirconium at 200–300°C. To change the plasma characteristics, different carrier gases such as H2 and He∕H2 were used and, as the reactive gas, N2 and NH3 were added to the gas mixture. The effect of N2 and NH3 gases was also evaluated in the reduction of C content of the films. Radical formation and ionization behaviors in plasma were analyzed by optical emission spectroscopy and mass spectrometry at various pulsed biases and gas conditions. The gas mixture of He and H2 as the carrier gas was very effective in enhancing the dissociation of molecular gases. In the case of N2 addition, N2 as reactive gas resulted in higher hardness. However, NH3 as reactive gas highly reduced the formation of CN radical, thereby greatly decreasing the C content of Zr(C,N) and Ti(C,N) films. The hardness of the film is 1400–1700HK depending on gas species and bias voltage. Higher hardness can be obtained for a H2 and N2 gas atmosphere and bias voltage of −600V. Plasma surface cleaning using N2 gas prior to deposition appeared to increase the adhesion of films on steel. The changes of plasmas including radicals and film properties are illustrated in terms of carrier and reactive gases, as well as pulsed power variation.
Ancient Permafrost and a Future, Warmer Arctic
Authors: Froese Duane G. , Westgate John A. , Reyes Alberto V. , Enkin Randolph J. , Preece Shari J.
Published: September 2008

Climate models predict extensive and severe degradation of permafrost in response to global warming, with a potential for release of large volumes of stored carbon. However, the accuracy of these models is difficult to evaluate because little is known of the history of permafrost and its response to past warm intervals of climate. We report the presence of relict ground ice in subarctic Canada that is greater than 700,000 years old, with the implication that ground ice in this area has survived past interglaciations that were warmer and of longer duration than the present interglaciation.
Political Attitudes Vary with Physiological Traits
Authors: Oxley Douglas R. , Smith Kevin B. , Alford John R. , Hibbing Matthew V. , Miller Jennifer L. , Scalora Mario , Hatemi Peter K. , Hibbing John R.
Published: September 2008

Although political views have been thought to arise largely from individuals' experiences, recent research suggests that they may have a biological basis. We present evidence that variations in political attitudes correlate with physiological traits. In a group of 46 adult participants with strong political beliefs, individuals with measurably lower physical sensitivities to sudden noises and threatening visual images were more likely to support foreign aid, liberal immigration policies, pacifism, and gun control, whereas individuals displaying measurably higher physiological reactions to those same stimuli were more likely to favor defense spending, capital punishment, patriotism, and the Iraq War. Thus, the degree to which individuals are physiologically responsive to threat appears to indicate the degree to which they advocate policies that protect the existing social structure from both external (outgroup) and internal (norm-violator) threats.
Comment on "Age and Evolution of the Grand Canyon Revealed by U-Pb Dating of Water Table–Type Speleothems"
Authors: Pederson Joel , Young Richard , Lucchitta Ivo , Beard L. Sue , Billingsley George
Published: September 2008

Polyak
et al
. (Reports, 7 March 2008, p. 1377) reported speleothem data leading to their inference that the western Grand Canyon incised much earlier than previously thought. This contradicts several lines of published geological knowledge in the region, hinges upon unjustified hydrogeological assumptions, and is based on two anomalous data points for which we offer alternative explanations.
Can Catch Shares Prevent Fisheries Collapse?
Authors: Costello Christopher , Gaines Steven D. , Lynham John
Published: September 2008

Recent reports suggest that most of the world's commercial fisheries could collapse within decades. Although poor fisheries governance is often implicated, evaluation of solutions remains rare. Bioeconomic theory and case studies suggest that rights-based catch shares can provide individual incentives for sustainable harvest that is less prone to collapse. To test whether catch-share fishery reforms achieve these hypothetical benefits, we have compiled a global database of fisheries institutions and catch statistics in 11,135 fisheries from 1950 to 2003. Implementation of catch shares halts, and even reverses, the global trend toward widespread collapse. Institutional change has the potential for greatly altering the future of global fisheries.
Reward-Predictive Cues Enhance Excitatory Synaptic Strength onto Midbrain Dopamine Neurons
Authors: Stuber Garret D. , Klanker Marianne , de Ridder Bram , Bowers M. Scott , Joosten Ruud N. , Feenstra Matthijs G. , Bonci Antonello
Published: September 2008

Using sensory information for the prediction of future events is essential for survival. Midbrain dopamine neurons are activated by environmental cues that predict rewards, but the cellular mechanisms that underlie this phenomenon remain elusive. We used in vivo voltammetry and in vitro patch-clamp electrophysiology to show that both dopamine release to reward predictive cues and enhanced synaptic strength onto dopamine neurons develop over the course of cue-reward learning. Increased synaptic strength was not observed after stable behavioral responding. Thus, enhanced synaptic strength onto dopamine neurons may act to facilitate the transformation of neutral environmental stimuli to salient reward-predictive cues.
Molecular Coupling of
Xist
Regulation and Pluripotency
Authors: Navarro Pablo , Chambers Ian , Karwacki-Neisius Violetta , Chureau Corinne , Morey Céline , Rougeulle Claire , Avner Philip
Published: September 2008

During mouse embryogenesis, reversion of imprinted X chromosome inactivation in the pluripotent inner cell mass of the female blastocyst is initiated by the repression of
Xist
from the paternal X chromosome. Here we report that key factors supporting pluripotency—Nanog, Oct3/4, and Sox2—bind within
Xist
intron 1 in undifferentiated embryonic stem (ES) cells. Whereas
Nanog
null ES cells display a reversible and moderate up-regulation of
Xist
in the absence of any apparent modification of Oct3/4 and Sox2 binding, the drastic release of all three factors from
Xist
intron 1 triggers rapid ectopic accumulation of
Xist
RNA. We conclude that the three main genetic factors underlying pluripotency cooperate to repress
Xist
and thus couple X inactivation reprogramming to the control of pluripotency during embryogenesis.
Clusters of Hyperactive Neurons Near Amyloid Plaques in a Mouse Model of Alzheimer's Disease
Authors: Busche Marc Aurel , Eichhoff Gerhard , Adelsberger Helmuth , Abramowski Dorothee , Wiederhold Karl-Heinz , Haass Christian , Staufenbiel Matthias , Konnerth Arthur , Garaschuk Olga
Published: September 2008

The neurodegeneration observed in Alzheimer's disease has been associated with synaptic dismantling and progressive decrease in neuronal activity. We tested this hypothesis in vivo by using two-photon Ca
2+
imaging in a mouse model of Alzheimer's disease. Although a decrease in neuronal activity was seen in 29% of layer 2/3 cortical neurons, 21% of neurons displayed an unexpected increase in the frequency of spontaneous Ca
2+
transients. These “hyperactive” neurons were found exclusively near the plaques of amyloid β–depositing mice. The hyperactivity appeared to be due to a relative decrease in synaptic inhibition. Thus, we suggest that a redistribution of synaptic drive between silent and hyperactive neurons, rather than an overall decrease in synaptic activity, provides a mechanism for the disturbed cortical function in Alzheimer's disease.
Evaluation of a Commercial
Echinococcus
Western Blot Assay for Serological Follow-Up of Patients with Alveolar Echinococcosis
Authors: Tappe Dennis , Grüner Beate , Kern Peter , Frosch Matthias
Published: September 2008

A total of 20 patients with alveolar echinococcosis in different clinical stages according to the WHO-PNM staging system (P, parasitic mass in the liver; N, involvement of neighboring organs; M, metastasis) were followed up serologically with the commercial
Echinococcus
Western Blot IgG assay and a crude antigen extract enzyme-linked immunosorbent assay (ELISA). The cohort included patients after curative resection and patients who had unresectable lesions with stable disease or progressive infection. There were visible correlations of the crude antigen ELISA index and the presence and intensity of diagnostic bands in the Western blot. In most patients after curative resection, bands at 7, 16, and 18 kDa markedly decreased or vanished after 1 to 4 years. In a patient with a nonviable lesion (it died out), bands at 16 and 18 kDa vanished after 4 years. Among individuals with unresectable lesions but stable disease under antiparasitic chemotherapy, a decrease of all diagnostic bands was visible after 2 to 3 years in half of the patients, whereas the other half had unchanged blot results after 4 to 6 years. Patients with progressive disease showed increasing intensities of bands at 16, 18, and 7 kDa. The change of banding patterns was not influenced by the PNM stage in patients after curative surgery or with unresectable lesions. Our data indicate a correlation of the 7-, 16-, and 18-kDa-Western blot bands with disease activity independent of the PNM stage. This study demonstrated the usefulness of the
Echinococcus
Western Blot IgG assay as an additional serological test for the follow-up of patients with alveolar echinococcosis.
Development of Natural Culture Media for Rapid Induction ofFonsecaea pedrosoiSclerotic Cells In Vitro
Authors: da Silva Moises Batista , da Silva Jorge Pereira , Sirleide Pereira Yamano Suellen , Salgado Ubirajara Imbiriba , Diniz José Antonio Picanço , Salgado Claudio Guedes
Published: September 2008

Fonsecaea pedrosoiis the main agent of chromoblastomycosis, a skin disease presenting verrucous lesions, in which round, thick-walled sclerotic cells are found. In vitro induction of sclerotic cells is time-consuming (20 to 45 days) and temperature dependent. We present two new natural media that reduce the sclerotic-cell induction time to only 2 days.
Fatal Wound Infection Caused by
Chromobacterium violaceum
in Ho Chi Minh City, Vietnam
Authors: Baker Stephen , Campbell James I. , Stabler Richard , Nguyen Hoang V. M. , To Diep S. , Nguyen Dung V. , Farrar Jeremy
Published: September 2008

Chromobacterium violaceum
is a proteobacterium found in soil and water in tropical regions which rarely causes infection in humans. Here, we report a fatal bacteremia caused by
Chromobacterium violaceum
in Vietnam. We describe a number of clinical, microbiological, and molecular aspects associated with this bacterial infection.
Analysis of Human Papillomavirus Type 16 (HPV16) DNA Load and Physical State for Identification of HPV16-Infected Women with High-Grade Lesions or Cervical Carcinoma
Authors: Saunier Maëlle , Monnier-Benoit Sylvain , Mauny Frédéric , Dalstein Véronique , Briolat Jenny , Riethmuller Didier , Kantelip Bernadette , Schwarz Elisabeth , Mougin Christiane , Prétet Jean-Luc
Published: September 2008

Integration of human papillomavirus (HPV) DNA into the host cell genome is a frequent event in cervical carcinogenesis, even though this phenomenon does not seem to be mandatory for cervical cancer development. Our objective was to describe the load and physical state of HPV type 16 (HPV16) DNA in a series of cervical samples representative of the natural history of cervical cancer. We used a combination of three real-time PCR assays targeting E6, E2, and albumin genes to calculate HPV16 load (E6 and albumin) and the E2/E6 ratio as a surrogate of integration. This method was applied to 173 HPV16-positive cervical samples. Results show that viral load increases with the lesion grade (from 102 HPV16 DNA copies per 10
3
cells in normal samples up to 56,354 copies per 10
3
cells in cancers), while E2/E6 ratio decreases (from 1 in normal samples down to 0.36 in cancers). We propose that, according to this technique, an HPV16 viral load of higher than 22,000 copies/10
3
cells or an E2/E6 ratio of lower than 0.50 allows the identification of women with prevalent high-grade lesions or worse with a high specificity. In conclusion, both viral load and E2/E6 ratio, used in combination with an appropriate cutoff value, are suitable to screen women with prevalent cervical intraepithelial neoplasia grade 2 or 3 or cancer. Therefore, these assays would be useful in addition to routine HPV testing to more accurately identify women with (pre)cancerous lesions.
Comparison of Carrot Broth- and Selective Todd-Hewitt Broth-Enhanced PCR Protocols for Real-Time Detection of
Streptococcus agalactiae
in Prenatal Vaginal/Anorectal Specimens
Authors: Block Timothy , Munson Erik , Culver Anne , Vaughan Katharine , Hryciuk Jeanne E.
Published: September 2008

The reporting of accurate
Streptococcus agalactiae
screening results in a short time frame is of tremendous clinical benefit. A total of 203 consecutive primary vaginal/anorectal specimens were cultured in selective Todd-Hewitt broth (LIM broth) and with the StrepB carrot broth kit (carrot broth). One-day broth cultures were subjected to both centrifugation and clarification of a 500-μl aliquot prior to sample lysis (protocol A) and direct lysis of a 50-μl aliquot (protocol B). The lysates were subsequently analyzed by the BD GeneOhm StrepB assay. The results were compared to the carrot broth culture results derived from visualization of pigment on day 1 or from a subculture of carrot broth. Thirty-four carrot broth cultures (16.7%) generated diagnostic pigment following overnight incubation; an additional 26 (12.8%) were positive for
S. agalactiae
upon subculture. Carrot broth-enhanced PCR by the use of either protocol A or protocol B trended toward a higher rate of positive results (33.0%) than the rate observed by either the LIM broth-enhanced PCR (30.5%) or full carrot broth culture analysis (29.6%). In the context of the result on day 1, both carrot broth- and LIM broth-enhanced PCRs generated more true-positive results (
P
< 0.001) than carrot broth culture visualization. The predictive values for both protocols of carrot broth- or LIM broth-enhanced PCR were ≥95.4%. Whereas protocol A resolved the results for 99.8% of the specimens in the evaluation upon initial testing, a 5.7% initial unresolved rate and a 1.5% final unresolved rate were determined by the use of protocol B. The use of carrot broth within a rapid and highly accurate molecular reflex testing algorithm can limit follow-up testing to cultures without evidence of pigmentation.