bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of nickel nanoparticles and their catalytic activity in the cracking of methane
Authors: De Jesús Juan Carlos , González Ismael , García Miguel , Urbina Caribay
Published: September 2008

Metallic nickel nanoparticles are excellent catalysts for the cracking of methane into carbon nanotubes and hydrogen. Decomposition of tetrahydrate nickel acetate proceeds readily in inert or hydrocarbon streams to produce metallic nickel agglomerates (average size of 10–80nm) at around 350°C. In the present study, this parent salt is thermally treated in methane streams in situ in a thermogravimetric analyzer (TGA), and weight changes corresponding to the carbon buildup in the metallic nickel particles are analyzed to provide some insight into the nickel-catalyzed cracking process. C to Ni atomic ratios (C∕Ni) estimated directly from TGA data provided a systematic approach to study the catalytic activity of the nickel nanoparticles. Methane cracking starts at temperatures as low as 400°C and continues efficiently until approximately 600°C. Between 600 and 660°C, methane decomposition momentarily breaks off, while presumably the catalytic system undergoes a self-reorganization. Cracking resumes at 660°C and continues slowly up to 950°C. The amount of carbon deposited in the 600–660°C interval shows a linear dependence with methane concentrations, with C∕Ni ratios ranging from 6 to 31. Transmission-electron microscopy images of the different C∕Ni residues collected at 660°C show, that during cracking, narrower carbon nanotubes are produced at elevated methane concentrations, suggesting dispersion of nickel nanoparticles.
Fabrication and characterization of a pentacene thin film transistor with a polymer insulator as a gate dielectric
Authors: Lee Chulwoo , Ko Jungmin , Lee Junyoung , Chung Ilsub
Published: September 2008

An organic thin film transistor (OTFT) with a back gate structure on a patterned pentacene active region was fabricated. The variations of electrical properties as a function of polyvinylcinnamate (PVCN) concentration used as a gate dielectric were evaluated. In addition, the morphology of the pentacene thin film was characterized by scanning probe microscope by simultaneously obtaining the topology and current image. Within the pentacene thin film, the current was observed to flow through grain rather than through the grain boundaries. Within marginal variations, an OTFT fabricated using 8% PVCN revealed the best electrical properties in terms of mobility, threshold voltage (VT), subthreshold swing, and on/off ratio.
Microstructure and tribological behavior of tungsten-containing diamondlike carbon coated rubbers
Authors: Pei Y. T. , Bui X. L. , Zhou X. B. , De Hosson J. Th. M.
Published: September 2008

Tungsten-containing diamondlike carbon (W-DLC) coatings have been deposited on FKM (fluorocarbon), ACM (acrylate), and HNBR (hydrogenated nitrile butadiene) rubbers via unbalanced magnetron reactive sputtering from a WC target in C2H2/Ar plasma. The surface morphology and fracture cross sections of coated rubbers have been scrutinized by high resolution scanning electron microscopy (SEM). The random crack networks formed due to the large difference in the coefficients of thermal expansion break down the W-DLC coatings into segments of a couple of hundred micrometers in size, facilitating good flexibility if the interfacial adhesion between the coating and a rubber substrate is strong enough. The size and density of growth defects in the W-DLC coatings strongly depend on the surface roughness of the rubber sheets. The tribological behavior of uncoated and coated rubbers has been investigated with ball-on-disk tribotest under dry sliding condition against a 6 mm 100Cr6 ball. Uncoated rubbers exhibited a very high coefficient of friction (>0.9). W-DLC coated FKM did not considerably reduce the friction because the coating was damaged due to poor adhesion. W-DLC coated HNBR and ACM exhibited excellent tribological performance, and very low coefficients of friction (<0.24) were achieved even at high normal load of 5 N. After tribotests, the W-DLC coatings on HNBR and ACM were intact and no serious damage was observed on the wear tracks.
Silicate formation and thermal stability of ternary rare earth oxides as high-k dielectrics
Authors: Van Elshocht S. , Adelmann C. , Conard T. , Delabie A. , Franquet A. , Nyns L. , Richard O. , Lehnen P. , Swerts J. , De Gendt S.
Published: September 2008

Hf-based dielectrics are currently being introduced into complementary metal oxide semiconductor transistors as replacement for SiON to limit gate leakage current densities. Alternative materials such as rare earth based dielectrics are of interest to obtain proper threshold voltages as well as to engineer a material with a high thermal stability. The authors have studied rare earth based dielectrics such as Dy2O3, DyHfOx, DyScOx, La2O3, HfLaOx, and LaAlOx by means of ellipsometry, time of flight secondary ion mass spectroscopy x-ray diffraction, and x-ray photoelectron spectroscopy. The authors show that ellipsometry is an easy and powerful tool to study silicate formation. For ternary rare earth oxides, this behavior is heavily dependent on the composition of the deposited layer and demonstrates a nonlinear dependence. The system evolves to a stable composition that is controlled by the thermal budget and the rare earth content of the layer. It is shown that silicate formation can lead to a severe overestimation of the thermal stability of ternary rare earth oxides.
Self-limiting deposition of aluminum oxide thin films by pulsed plasma-enhanced chemical vapor deposition
Authors: Szymanski Scott F. , Rowlette Pieter , Wolden Colin A.
Published: September 2008

Self-limiting deposition of aluminum oxide (Al2O3) thin films was accomplished by pulsed plasma-enhanced chemical vapor deposition using a continuous delivery of trimethyl aluminum (TMA) and O2. Film characterization included spectroscopic ellipsometry and Fourier transform infrared (FTIR) spectroscopy. Deposition rates scaled with TMA exposure and could be controlled over a large range of 1–20Å∕pulse. For fixed conditions, digital control over film thickness is demonstrated. Deposition rates initially decreased with substrate temperature before becoming constant for Ts>100°C. Higher growth rates at low temperature are attributed to the thermal reaction between H2O, produced during the plasma on step, with TMA during the plasma off step. Gas-phase analysis confirms the coexistence of these species, and their degree of overlap is a strong function of the chamber wall temperature. With both the substrate and chamber wall temperature elevated, impurities related to carbon and hydroxyl groups are attenuated below the detection limit of FTIR.
Cluster primary ions: Spikes, sputtering yields, secondary ion yields, and interrelationships for secondary molecular ions for static secondary ion mass spectrometry
Authors: Seah Martin P.
Published: September 2008

A framework is provided to describe the enhanced sputtering yields and secondary ion yields of molecular fragments, from molecules on substrates, achieved when using cluster primary ions. Analysis of published sputtering yield measurements shows that one particular model of sputtering, which includes the thermal spike, is an excellent quantitative description of the yields for a wide range of monatomic and polyatomic primary ions. The model is valid for describing clusters of up to more than ten atoms over three orders of magnitude in sputtering yield. Using data from one primary ion, extremely good descriptions of measurements reported with other primary ions are achieved. This is then used to evaluate the important molecular ion yield behavior for static secondary ion mass spectrometry based on data for Irganox 1010. Universal dependences for the deprotonated molecular ion yields, valid for all the primary ions studied, both single atom and cluster, over five decades of emission intensity are obtained. This permits the prediction of the (M−H)− secondary ion yield for different, or new, cluster primary ions, e.g., Bin+ and C70+, for the analysis of organic materials. Optimal primary ion sources are predicted and discussed. For analyzing materials, raising the molecular secondary ion yield is extremely helpful but it is the ratio of this yield to the disappearance cross section that is critical for obtaining the maximum useful molecular yield and/or the best spatial resolution for molecular signals from molecular monolayers. Data are evaluated and a description is given to show how this ratio varies with the cluster to provide further universal dependences.
Atomic-scale investigation of graphene formation on 6H-SiC(0001)
Authors: Guisinger N. P. , Rutter G. M. , Crain J. N. , Heiliger C. , First P. N. , Stroscio J. A.
Published: September 2008

The growth of graphene on the silicon-terminated face of 6H-SiC(0001) was investigated by scanning tunneling microscopy (STM) measurements. The initial stages of ultrahigh vacuum graphitization resulted in the growth of individual graphene sheets on random SiC terraces. These initial graphene sheets contained few defects, and the regions of clean SiC were free of contamination, exhibiting a 63×63R30° surface reconstruction. However, graphitization to multilayer thickness resulted in multiple defects, as observed with the STM. A high density of defects was observed, which may be attributed to the initial treatment of the SiC wafer. We characterize these defects, showing that they are located predominantly below the first layer of graphene.
Thermoplasmonic shift and dispersion in thin metal films
Authors: Lereu A. L. , Passian A. , Farahi R. H. , van Hulst N. F. , Ferrell T. L. , Thundat T.
Published: September 2008

In 2004, the authors reported two coupling schemes based on the thermo-optic properties of thin metallic films and their associated sub- and superstrates, by utilizing surface plasmons. These studies showed a potential for all-optical modulation at low rates that may be used for sensing purposes. In this article, they continue by investigating thermal processes involved in thin metallic films with different approaches. They first experimentally imaged the shift of the surface plasmon dispersion relation in the visible spectrum, as the thin film temperature is externally varied. They then reinforce the previous observations by collecting the absorption curves at selected visible photon energies of excitation, as the film temperature in the excitation region increases. Utilizing the absorption measurements, they briefly address how one may obtain the real and imaginary parts of the index of refraction of the thin film as a function of temperature for each involved wavelength. Finally, they investigate the local physical state of the film by optically profiling the surface plasmon excitation region.
Investigation of thin-oxide-free protective coatings on chromium and 316L stainless steel formed by treatment with etidronic acid
Authors: Johnson S. L. , Sherwood P. M. A.
Published: September 2008

In this article, the authors report how thin (10nm or less) oxide-free phosphorus containing films can be formed on chromium and stainless steel on treatment with an organophosphorus acid (etidronic acid) using an anaerobic cell and a “bench” treatment. Core level and valence band x-ray photoelectron spectroscopy were used to study the films formed. Compositional variations were interpreted through the use of band structure and X-alpha calculations. The chromium study indicates that the etidronate at least partially decomposed to form phosphate. Some phosphide was observed for the bench treatment. Polished 316L chromium containing stainless steel treated in 3M etidronic acid formed a thin phosphate containing film when using the bench treatment, but a film characteristic of etidronate when the anaerobic cell was used. Film changes during air exposure and exposure to 1M sodium chloride solution showed decomposition, the most resistant film being that of the etidronate on stainless steel. This thin etidronate film result shows that oxide-free etidronate films can be formed on stainless steel and these films have corrosion inhibition properties, which may find application in implant fabrication.
Main determinants for III–V metal-oxide-semiconductor field-effect transistors (invited)
Authors: Ye Peide D.
Published: September 2008

Lacking a suitable gate insulator, practical GaAs metal-oxide-semiconductor field-effect transistors (MOSFETs) have remained all but a dream for more than four decades. The physics and chemistry of III–V compound semiconductor surfaces or interfaces are problems so complex that our understanding is still limited even after enormous research efforts. Most research is focused on surface pretreatments, oxide formation, and dielectric materials; less attention is paid to the III–V substrate itself. The purpose of this article is to show that device physics more related to III–V substrates is as important as surface chemistry for realizing high-performance III–V MOSFETs. The history and present status of III–V MOSFET research are briefly reviewed. A model based on the charge neutrality level is proposed to explain all experimental work he performed on III–V MOSFETs using ex situ atomic-layer-deposited high-k dielectrics. This model can also explain all reported experimental observations on III–V MOSFETs using in situ molecular-beam-expitaxy-grown Ga2O3(Gd2O3) as a gate dielectric. Related perspectives are also discussed to understand III–V MOS capacitance-voltage measurements.
Optical characterization of InN layers grown by high-pressure chemical vapor deposition
Authors: Alevli M. , Atalay R. , Durkaya G. , Weesekara A. , Perera A. G. U. , Dietz N. , Kirste R. , Hoffmann A.
Published: September 2008

The optical properties of InN layers grown by high-pressure chemical vapor deposition have been studied. Raman, infrared reflection, and transmission spectroscopy studies have been carried out to investigate the structural and optical properties of InN films grown on sapphire and GaN/sapphire templates. Results obtained from Raman and IR reflectance measurements are used to estimate the free carrier concentrations, which were found to be varying from mid 1018 to low 1020cm−3. The values for free carrier concentrations are compared to optical absorption edge estimates obtained from optical transmission spectra analysis. The analysis shows that optical absorption edge for InN shifts below 1.1eV as the free carrier concentration decreases to low 1018cm−3.
Thermal stability of synthetic antiferromagnet and hard magnet coupled spin valves
Authors: Tadisina Zeenath R. , Gupta Subhadra , LeClair Patrick , Mewes Tim
Published: September 2008

The magnetic properties of current-in-plane (CIP) giant magnetoresistive (GMR) spin valves employing synthetic antiferromagnet (SAF) pinning have been investigated. The conventional spin valve structure, with a ferromagnetic (FM) layer pinned by an antiferromagnet (AFM) layer, exhibits high electrical resistance, the AFM typically being a high resistivity material. We have investigated pinning with a Co∕Ru∕Co SAF trilayer only, with no additional AFM pinning. We have also investigated spin valves employing a hard magnet layer in three different configurations as the pinning/pinned layer. Elimination of the AFM-induced parasitic resistance has the potential for yielding a higher GMR ratio in current-perpendicular-to-the-plane (CPP) structures. The full-film properties have been optimized by using vibrating sample magnetometry and CIP magnetotransport measurements. The thermal stability of SAF-pinned spin valves and hard magnet-pinned spin valves has been characterized through magnetotransport measurements of up to 400K, and found to have measurable MR even at that temperature. A study of the M-H loops for the SAF spin valve showed no change up to 500K. Therefore, these non-AFM-containing spin valves appear to be usable in CPP devices under practical head operating temperatures, representing a significant advance in reduced stack resistance, increased MR ratio, and reduced coupling between free and pinned layers in a small-dimensional patterned structure.
Photoluminescence and electroluminescence from Eu-activated CaAl2O4-based multicomponent oxide thin-film phosphors
Authors: Fukada Haruki , Matsui Shun , Miyata Toshihiro , Minami Tadatsugu
Published: September 2008

Photoluminescence (PL) and electroluminescence (EL) from newly developed Eu-activated CaAl2O4 -based multicomponent oxide phosphor thin films prepared by rf magnetron sputtering are described. Yellowish green and blue emissions in PL were obtained in as-deposited and postannealed ((CaAl2O4)1−x–(BaAl2O4)x):Eu and ((CaAl2O4)1−x–(MgAl2O4)x):Eu thin films, respectively. In addition, blue emission in EL was observed from thin-film electroluminescent (TFEL) devices fabricated by using ((CaAl2O4)1−x–(BaAl2O4)x):Eu thin films postannealed at 1000°C in an Ar+H2(5%) gas atmosphere. A luminance of 3.2cd∕m2 for blue emission was obtained in a ((CaAl2O4)0.44–(BaAl2O4)0.56):Eu TFEL device driven by a 1kHz sinusoidal wave ac voltage; the blue EL emission corresponds to the CIE color coordinates of (x=0.24, y=0.13).
Evaluation of bond quality and heat transfer of Cu-based microchannel heat exchange devices
Authors: Mei Fanghua , Jiang J. , Meng W. J.
Published: September 2008

Metal-based microchannel heat exchangers (MHEs) promise high heat transfer coefficients together with mechanical robustness, and are of interest for a wide range of applications. Fabrication technologies capable of creating high-aspect-ratio microscale structures in metals such as Cu at low cost and high throughput are of particular interest. Likewise, simple and reliable bonding and assembly techniques are critical for building functional metal-based microfluidic devices. In this article, the authors report successful fabrication, bonding, and assembly of Cu-based MHE prototypes. Bonding of Cu specimens was achieved through Al thin foil intermediate layers. Quantitative evaluation of bond strengths was carried out as a function of various bonding parameters. Results of preliminary heat transfer testing carried out on assembled Cu-based MHE prototypes are reported.
W chemical-vapor deposition using (i-C3H7C5H4)2WH2
Authors: Ogura Atsushi , Imai Satoshi , Kagawa Taihei , Kurozaki Hirotaka , Ishikawa Masato , Muramoto Ikuyo , Machida Hideaki , Ohshita Yoshio
Published: September 2008

One of the most popular refractory metals is tungsten or W. Therefore, W chemical-vapor deposition (CVD) is expected to be useful for nanotechnology applications. In some cases, the residual atoms, such as halogen and oxygen, in films may degrade their quality. The authors therefore propose (i-C3H7C5H4)2WH2, i.e., (i-PrCp)2WH2, as a new W precursor because the authors expect some advantages from the absence in this molecule of the F and O that exist in the popular W precursors, WF6 and W(CO2)6. The melting point of (i-PrCp)2WH2 is 30°C and the precursor has a high vapor pressure of 0.1torr at 110°C. The authors conducted W CVD with the (i-PrCp)2WH2 as a precursor and obtained conformal W thin film. The deposition rate was 69nm∕min at 750°C, and the deposited film had resistivity of 2.3×10−4Ωcm. However, the deposited film included a tremendous amount of C. Therefore, investigating the possibility of reducing the C contamination is necessary.
Experiments and modeling of dual reactive magnetron sputtering using two reactive gases
Authors: Kubart T. , Trinh D. H. , Liljeholm L. , Hultman L. , Högberg H. , Nyberg T. , Berg S.
Published: September 2008

Reactive sputtering from two elemental targets, aluminum and zirconium, with the addition of two reactive gases, oxygen and nitrogen, is studied experimentally as well as theoretically. The complex behavior of this process is observed and explained. It is shown that the addition of oxygen to a constant supply of nitrogen significantly changes the relative content of aluminum with respect to zirconium in the film. Moreover, it is concluded that there is substantially more oxygen than nitrogen in the films even when the oxygen supply is significantly lower than the nitrogen supply. It is further shown that the addition of a certain minimum constant flow of nitrogen reduces, and eventually eliminates, the hysteresis with respect to the oxygen supply. It is concluded that the presented theoretical model for the involved reactions and mass balance during reactive sputtering of two targets in two reactive gases is in qualitative agreement with the experimental results and can be used to find optimum processing conditions for deposition of films of a desired composition.
Exotic shapes of gold nanoparticles synthesized using plasma in aqueous solution
Authors: Hieda Junko , Saito Nagahiro , Takai Osamu
Published: September 2008

Gold nanoparticles with exotic shapes, such as triangle, pentagon, and hexagon, have been synthesized by glow discharge in aqueous solutions. A pulsed power supply was used to generate discharges in the aqueous solutions. Pulse width and frequency were 2 μs and 15 kHz, respectively. Discharges were generated at applied voltages of 1600 and 3200 V. The shapes of the gold nanoparticles and electron diffraction patterns were observed by transmission electron microscopy. The nanoparticles obtained were about 20 nm in diameter. In particular, at the higher voltage of 3200 V, nanoparticles with anisotropic shapes were synthesized. In the initial stages of synthesis, diameter decreased with discharge time as the nanoparticles redissolved in the solution. After discharge for 25 min, nanoparticles with anisotropic shapes appeared. This discharge led to the generation of H2O2 and a decrease in pH as a result of the consumption of OH radicals during the generation of H2O2 and electron donation of H radicals to the solution. After the pH stopped decreasing, H radicals mainly reacted as a reducing agent. The decrease in pH allowed redissolution of the gold nanoparticles. The gold dust particles that were not completely dissolved acted as new seeds for nucleation. Thus, the two reaction steps, nucleation and nuclear growth, occur during the formation of gold nanoparticles with exotic shapes.
Effect of substrate temperatures on amorphous carbon nitride films prepared by reactive sputtering
Authors: Aono Masami , Akiyoshi Hidenobu , Kikuchi Shunsuke , Kitazawa Nobuaki , Watanabe Yoshihisa
Published: September 2008

Amorphous carbon nitride, a-CNx, films were deposited by reactive radio frequency magnetron sputtering of a graphite target in nitrogen gas. This kind of films could be used as novel electric and optical devices. The authors investigated effects of the substrate temperature up to 873 K on the films in this study. The films were characterized with x-ray photoelectron spectroscopy (XPS), ellipsometry, atomic force microscopy, and nanoindentation tests. XPS studies show that the decreasing tendency in the composition ratio of carbon to nitrogen in a-CNx films with the substrate temperature is observed; however, the bonding fraction of sp3C–N increases depending on the substrate temperature. The nanoindentation tests reveal that the film hardness increases from 2 to 12 GPa as the substrate temperature increases from room temperature to 823 K. These results suggest that the film hardness is closely related to the bonding states between carbon and nitrogen.
Top-emitting organic light-emitting diodes with Ba∕Ag/indium tin oxide cathode and built-in potential analyses in these devices
Authors: Lim J. T. , Lee J. H. , Yeom G. Y. , Lee E. H. , Kim T. W.
Published: September 2008

Top-emitting organic light-emitting diodes (TEOLEDs) with a thin semitransparent conducting cathode (STCC) of Ba∕Ag/indium tin oxide (ITO) were fabricated and their electric/optical characteristics were investigated. At the wavelength of 520nm, optical properties of STCC of the Ba(3nm)∕Ag(15nm)/ITO (100nm) structure showed the transmittance of 63% and the reflectance of 37%. The light out-coupling properties of the TEOLED, which is composed of glass/Ag(150nm)/ITO (130nm)∕4,4′,4″-tris[2-naphthylphenyl-1-phenylamino]triphenylamine (2-TNATA, 30nm)/4,4′-bis[N-(1-napthyl)-N-phenyl-amino]-biphenyl (18nm)/tris(8-quinolinolato)aluminum (III) (62nm)∕Ba (xnm,x=3,2,and1nm)∕Ag(15nm)/ITO (100nm), was increased as the deposition thickness of Ba is increased. This driving performance of the devices could be interpreted on the base of carrier injection barrier by measuring built-in voltage as well as both the optical properties and electric properties of the cathode. The optical properties (e.g., transmittance and reflectance) and electric properties of all STCCs (Ba∕Ag/ITO) used in this study were nearly equal. However, built-in voltage studied using modulated photocurrent technique was increased as the thickness of barium composing of STCC was increased. This rising of a built-in voltage means a lowering of barrier height for electron injection in the devices.
Effect of capacitive to inductive coupling transition in multiple linear U-type antenna on silicon thin film deposition from pure SiH4 discharges
Authors: Kim Hong Bum , Lee Hyoung Cheol , Kim Kyong Nam , Yeom Geun Young
Published: September 2008

Using a large area internal-type inductively coupled plasma (ICP) source called “multiple U-type ICP source” having the size of 1020×830mm2, the electrical properties of the antennas and the dissociation characteristics were investigated as a function of rf power using pure SiH4 and their influence on the deposited silicon films was studied. With increasing rf power, the plasma mode has changed from capacitively coupled plasma (E mode) to inductively coupled plasma (H mode), and the change of plasma mode increased the ratios of HFulcher*∕SiH* and Si*∕SiH* by changing the electron energy distribution function. In addition, the increase in HFulcher*∕SiH* changed the microstructure of a silicon thin film deposited on glass substrates from amorphous to microcrystalline. At the high rf power regime of 4000W, a silicon films having the crystalline volume fraction of 53% with optical band gap (Tauc’) of about 2.1eV and dark conductivity of 2.4×10−5Ω−1cm−1 could be obtained at 20mTorr of SiH4 [70SCCM (SCCM denotes cubic centimeter per minute at STP)].
Study of electron beam evaporated compositionally modulated Fe/Al multilayers
Authors: Brajpuriya R. , Tripathi S. , Sharma A. , Chaudhari S. M. , Shripathi T. , Lakshmi N.
Published: September 2008

This article presents temperature dependent magnetic and electronic properties of compositionally modulated electron beam evaporated Fe/Al multilayer samples (MLSs) with an average composition of Fe0.70A10.30 (MLS-A) and Fe0.50Al0.50 (MLS-B). Structural studies show a large amount of intermixing, leading to alloying at the interfaces as a result of annealing. Both multilayer samples show soft ferromagnetic behavior at room temperature with an in-plane easy axis of magnetization. In both cases, coercivity as well as saturation field continuously increase and magnetization decreases with an increase in temperature. The Curie temperature (TC) is found to decrease from ∼561 °C for MLS-A to ∼288 °C for MLS-B. These modifications can be attributed to the continuous change in electronic structure brought about by the strong hybridization of Fe 3d and Al 3sp states near Fermi level leading to the formation of different Fe–Al phases (Fe3Al in MLS-A) and (FeAl in MLS-B), as seen from valence band photoemission measurements. The formation of these phases is also supported by resistivity measurement.
Effects of manganese oxide–mixed abrasive slurry on the tetraethyl orthosilicate oxide chemical mechanical polishing for planarization of interlayer dielectric film in the multilevel interconnection
Authors: Seo Yong-Jin , Park Sung-Woo , Lee Woo-Sun
Published: September 2008

In this article, the authors have studied the chemical mechanical polishing (CMP) characteristics of mixed abrasive slurry (MAS) retreated by adding of manganese oxide (MnO2) abrasives within 1:10 diluted silica slurry. The slurry designed for optimal performance should produce reasonable removal rates, acceptable polishing selectivity with respect to the underlying layer, low surface defects after polishing, and good slurry stability. The modified abrasives in MAS are evaluated with respect to their particle size distribution, surface morphology, and CMP performances such as removal rate and nonuniformity. As an experimental result, the authors obtained the comparable slurry characteristics compared to original silica slurry in the viewpoint of high removal rate and low nonuniformity.
Comparative study of photocatalytic activity in CdS–TiO2 thin films prepared by two different techniques
Authors: Biswas S. , Hossain M. F. , Takahashi T. , Kubota Y. , Fujishima A.
Published: September 2008

In this study, CdS layer in CdS–TiO2 bilayer films was fabricated by two different chemical bath deposition techniques: one with an ammonium complex as complexing agent and the other with sodium citrate as a substitute for the ammonium complex. The TiO2 upper layer was deposited by dc magnetron sputtering technique for both the CdS underlayers. The effect of postdeposition vacuum annealing was studied for both samples. The photocatalytic activity was evaluated by measuring the decomposition of methanol in gas phase under ultraviolet-visible irradiation. The CdS thin films, prepared by both techniques, show a highly oriented hexagonal structure. The optical transmission edge of the CdS thin films deposited by the ammonia-free technique is in lower wavelength than that of the other technique. For both techniques, vacuum annealing extends the absorption edge to higher wavelength, but this effect is more pronounced for the ammonia-content technique. The decomposition efficiency of the as-deposited CdS–TiO2 thin film prepared by the ammonia-free technique is much higher than the as-deposited CdS–TiO2 prepared by ammonia-content technique. In case of the ammonia-content technique, high-vacuum annealing improves the photocatalytic activity but it has minimal influence in the other technique. The surface morphology of all the CdS thin films was studied by field emission scanning electron microscopy and atomic force microscopy in order to find out the possible inherent reason that leads to a huge difference in the photocatalytic decomposition activity of CdS–TiO2 thin films.
Optical properties of organic and inorganic capped CdS nanoparticles and the effects of x-ray irradiation on organic capped CdS nanoparticles
Authors: Hullavarad Nilima V. , Hullavarad Shiva S.
Published: September 2008

In this article, the authors report synthesis of CdS nanoparticles using a simple, inexpensive and straightforward chemical colloidal method using organic and inorganic capping agents. 1-6 hexanedithiol, mercaptoethanol, thioglycerol, tetraethyl orthosilicate, and tetraethyl orthotitaniate are used as the capping agents. The optical absorption spectra of CdS nanoparticles synthesized using the same parameters are found to depend on the nature of capping agents. The infrared absorption measurements provided important information about the nature of bonding. The optical studies on effect of x-ray irradiation on thioglycerol-capped CdS nanoparticle are also discussed.
Morphological analysis of TiB2 thin film prepared by rf magnetron sputtering
Authors: Dai Wei , Zhang Tongjun , Yang Junyou , Sun Rongxing , Xu Juliang
Published: September 2008

Superhard TiB2 thin films were deposited on steel substrates using the radio-frequency magnetron-sputtering technique with a low normalized substrate temperature (0.1<Ts∕Tm<0.2). The microstructure of these films was observed by a field-emission scanning-electron microscope (FESEM) and grazing-incidence x-ray diffraction (GIXRD), while the composition of films was obtained using Auger electron spectroscopy (AES). It was found that the TiB2 thin films were overstoichiometric and that the diffusion of Ti and B atoms on the substrate surface was greatly improved at a temperature of 350°C. Moreover, a new dense structure, named the “equiaxed” grain structure, was observed by FESEM at this substrate temperature. GIXRD was carried out at different directions with same the grazing-incidence method and the variation of diffraction intensity of the nonrandom textured grains was confirmed. Combined with FESEM and AES analysis, it is suggested that the equiaxed grain structure was located in zone 2 at the normalized substrate temperature as low as 0.18.
Structural and electronic properties of bilayer epitaxial graphene
Authors: Rutter G. M. , Crain J. N. , Guisinger N. P. , First P. N. , Stroscio J. A.
Published: September 2008

Scanning tunneling microscopy and scanning tunneling spectroscopy (STS) are used to study the structural and electronic properties of bilayer epitaxial graphene on SiC(0001). Topographic images reveal that graphene conforms to the SiC interface morphology and is observed to be continuous across steps separating adjoining terraces. Bilayer epitaxial graphene is shown to be Bernal stacked as is evidenced by bias-dependent topographic imaging. STS maps of the differential conductance show that graphene lattice defects cause scattering of charge carriers near the Fermi level. An analysis of stationary scattering patterns observed in the conductance maps determines the energy-momentum dispersion relation within 100meV of the Fermi level. In contrast to lattice defects, disorder at the SiC interface and at subsurface steps plays a much lesser role in the scattering of charge carriers.
Apoptotic Force and Tissue Dynamics During
Drosophila
Embryogenesis
Authors: Toyama Yusuke , Peralta Xomalin G. , Wells Adrienne R. , Kiehart Daniel P. , Edwards Glenn S.
Published: September 2008

Understanding cell morphogenesis during metazoan development requires knowledge of how cells and the extracellular matrix produce and respond to forces. We investigated how apoptosis, which remodels tissue by eliminating supernumerary cells, also contributes forces to a tissue (the amnioserosa) that promotes cell-sheet fusion (dorsal closure) in the
Drosophila
embryo. We showed that expression in the amnioserosa of proteins that suppress or enhance apoptosis slows or speeds dorsal closure, respectively. These changes correlate with the forces produced by the amnioserosa and the rate of seam formation between the cell sheets (zipping), key processes that contribute to closure. This apoptotic force is used by the embryo to drive cell-sheet movements during development, a role not classically attributed to apoptosis.
Response to Comments on the "Age and Evolution of the Grand Canyon Revealed by U-Pb Dating of Water Table–Type Speleothems"
Authors: Polyak Victor , Hill Carol , Asmerom Yemane
Published: September 2008

Pederson
et al
. and Pearthree
et al
. offer critical comments on our study of the age and evolution of the Grand Canyon. Both sets of authors question our use of incision rates from two sample sites located outside the canyon and present alternative interpretations of our data. As we explain, even without the sites in question, our data support a “precursor” western Grand Canyon older than 6 million years.
An Inhibitor of FtsZ with Potent and Selective Anti-Staphylococcal Activity
Authors: Haydon David J. , Stokes Neil R. , Ure Rebecca , Galbraith Greta , Bennett James M. , Brown David R. , Baker Patrick J. , Barynin Vladimir V. , Rice David W. , Sedelnikova Sveta E. , Heal Jonathan R. , Sheridan Joseph M. , Aiwale Sachin T. , Chauhan Pramod K. , Srivastava Anil , Taneja Amit , Collins Ian , Errington Jeff , Czaplewski Lloyd G.
Published: September 2008

FtsZ is an essential bacterial guanosine triphosphatase and homolog of mammalian Î²-tubulin that polymerizes and assembles into a ring to initiate cell division. We have created a class of small synthetic antibacterials, exemplified by PC190723, which inhibits FtsZ and prevents cell division. PC190723 has potent and selective in vitro bactericidal activity against staphylococci, including methicillin- and multi-drugâresistant
Staphylococcus aureus
. The putative inhibitor-binding site of PC190723 was mapped to a region of FtsZ that is analogous to the Taxol-binding site of tubulin. PC190723 was efficacious in an in vivo model of infection, curing mice infected with a lethal dose of
S. aureus
. The data validate FtsZ as a target for antibacterial intervention and identify PC190723 as suitable for optimization into a new anti-staphylococcal therapy.
An Alternative Menaquinone Biosynthetic Pathway Operating in Microorganisms
Authors: Hiratsuka Tomoshige , Furihata Kazuo , Ishikawa Jun , Yamashita Haruyuki , Itoh Nobuya , Seto Haruo , Dairi Tohru
Published: September 2008

In microorganisms, menaquinone is an obligatory component of the electron-transfer pathway. It is derived from chorismate by seven enzymes in
Escherichia coli
. However, a bioinformatic analysis of whole genome sequences has suggested that some microorganisms, including pathogenic species such as
Helicobacter pylori
and
Campylobacter jejuni
, do not have orthologs of the
men
genes, even though they synthesize menaquinone. We deduced the outline of this alternative pathway in a nonpathogenic strain of
Streptomyces
by bioinformatic screening, gene knockouts, shotgun cloning with isolated mutants, and in vitro studies with recombinant enzymes. As humans and commensal intestinal bacteria, including lactobacilli, lack this pathway, it represents an attractive target for the development of chemotherapeutics.
Suppression of Cotton Bollworm in Multiple Crops in China in Areas with Bt Toxin–Containing Cotton
Authors: Wu Kong-Ming , Lu Yan-Hui , Feng Hong-Qiang , Jiang Yu-Ying , Zhao Jian-Zhou
Published: September 2008

Transgenic cotton that has been engineered to produce insecticidal toxins from
Bacillus thuringiensis
(Bt) and so to resist the pest cotton bollworm (
Helicoverpa armigera
) has been widely planted in Asia. Analysis of the population dynamics of
H. armigera
from 1992 to 2007 in China indicated that a marked decrease in regional outbreaks of this pest in multiple crops was associated with the planting of Bt cotton. The study area included six provinces in northern China with an annual total of 3 million hectares of cotton and 22 million hectares of other crops (corn, peanuts, soybeans, and vegetables) grown by more than 10 million resource-poor farmers. Our data suggest that Bt cotton not only controls
H. armigera
on transgenic cotton designed to resist this pest but also may reduce its presence on other host crops and may decrease the need for insecticide sprays in general.
Shape Changes of Supported Rh Nanoparticles During Oxidation and Reduction Cycles
Authors: Nolte P. , Stierle A. , Jin-Phillipp N. Y. , Kasper N. , Schulli T. U. , Dosch H.
Published: September 2008

The microscopic insight into how and why catalytically active nanoparticles change their shape during oxidation and reduction reactions is a pivotal challenge in the fundamental understanding of heterogeneous catalysis. We report an oxygen-induced shape transformation of rhodium nanoparticles on magnesium oxide (001) substrates that is lifted upon carbon monoxide exposure at 600 kelvin. A Wulff analysis of high-resolution in situ x-ray diffraction, combined with transmission electron microscopy, shows that this phenomenon is driven by the formation of a oxygen–rhodium–oxygen surface oxide at the rhodium nanofacets. This experimental access into the behavior of such nanoparticles during a catalytic cycle is useful for the development of improved heterogeneous catalysts.
Chondrulelike Objects in Short-Period Comet 81P/Wild 2
Authors: Nakamura Tomoki , Noguchi Takaaki , Tsuchiyama Akira , Ushikubo Takayuki , Kita Noriko T. , Valley John W. , Zolensky Michael E. , Kakazu Yuki , Sakamoto Kanako , Mashio Etsuko , Uesugi Kentaro , Nakano Tsukasa
Published: September 2008

The Stardust spacecraft returned cometary samples that contain crystalline material, but the origin of the material is not yet well understood. We found four crystalline particles from comet 81P/Wild 2 that were apparently formed by flash-melting at a high temperature and are texturally, mineralogically, and compositionally similar to chondrules. Chondrules are submillimeter particles that dominate chondrites and are believed to have formed in the inner solar nebula. The comet particles show oxygen isotope compositions similar to chondrules in carbonaceous chondrites that compose the middle-to-outer asteroid belt. The presence of the chondrulelike objects in the comet suggests that chondrules have been transported out to the cold outer solar nebula and spread widely over the early solar system.
The Life of a Magus and Martyr
Authors: Dirda Michael
Published: September 2008

Giordano Bruno
. Philosopher/Heretic.
By Ingrid D. Rowland
. Farrar, Straus and Giroux, New York, 2008. 345 pp. $27. ISBN 9780809095247.

The author discusses the nomadic life of the 16th-century philosopher and former priest whose execution in Rome in 1600 made him an early martyr for science.
Evaluation of Leptospiral Recombinant Antigens MPL17 and MPL21 for Serological Diagnosis of Leptospirosis by Enzyme-Linked Immunosorbent Assays
Authors: Oliveira Tatiane R. , Longhi Mariana T. , de Morais Zenaide M. , Romero Eliete C. , Blanco Roberta M. , Kirchgatter Karin , Vasconcellos Silvio A. , Nascimento Ana L. T. O.
Published: September 2008

Leptospirosis is a zoonosis of multisystem involvement caused by pathogenic strains of the genus
Leptospira
. In the last few years, intensive studies aimed at the development of a vaccine have provided important knowledge about the nature of the immunological mechanisms of the host. The purpose of this study was to analyze the immune responses to two recombinant proteins, MPL17 and MPL21 (encoded by the genes LIC10765 and LIC13131, respectively) of
Leptospira interrogans
serovar Copenhageni in individuals during infection. The recombinant proteins were expressed in
Escherichia coli
as six-His tag fusion proteins and were purified from the soluble bacterial fraction by affinity chromatography with Ni
2+
-charged resin. The recombinant proteins were used to evaluate their ability to bind to immunoglobulin G (IgG) (and IgG subclass) or IgM antibodies in serum samples from patients in the early and convalescent phases of leptospirosis (
n
= 52) by enzyme-linked immunosorbent assays. The prevalences of total IgG antibodies against MPL17 and MPL21 were 38.5% and 21.2%, respectively. The titers achieved with MPL17 were statistically significantly higher than those obtained by the reference microscopic agglutination test. The specificity of the assay was estimated to be 95.5% for MPL17 and 80.6% for MPL21 when serum samples from individuals with unrelated febrile diseases and control healthy donors were tested. The proteins are conserved among
Leptospira
strains that cause human and animal diseases. MPL17 and MPL21 are most likely new surface proteins of leptospires, as revealed by liquid-phase immunofluorescence assays with living organisms. Our results demonstrate that these recombinant proteins are highly immunogenic and, when they are used together, might be useful as a means of diagnosing leptospirosis.
Specificity of L1 Peptides versus Virus-Like Particles for Detection of Human Papillomavirus-Positive Cervical Lesions in Females Attending Engativa Hospital, Bogota, Colombia
Authors: Urquiza Mauricio , Sánchez Ricardo , Amaya Jairo , León Sandra , Acosta Jenny , Patarroyo Manuel A. , Camargo Milena , Patarroyo Manuel E.
Published: September 2008

A serological test for the detection of human papillomavirus (HPV) infection in females at risk of developing cervical cancer could be based on conserved L1 peptides with low levels of antigenicity specifically recognized by antibodies from patients with cervical lesions infected with high-risk HPV (HR-HPV) types. The aim was to assess the ability of L1 peptides 18283, 18294, and 18301 compared with the ability of virus-like particles (VLPs) to identify these infections in females. A total of 391 HPV-infected female volunteers were interviewed, and peripheral blood and cervical cells were obtained for detection of anti-HPV antibodies and HPV DNA; all of the patients had a Pap smear test; 287 patients were referred for colposcopy or biopsy, according to gynecological criteria. The level of agreement, as determined by the use of the Lin coefficient (rho value), showed that 75 to 83% of females with HR-HPV DNA-positive cervical lesions had antibodies that recognized VLPs and peptide 18283, 18294, or 18301, while 15 to 23% of the HPV DNA-negative females with a normal cytology had antibodies that recognized these three peptides and 45% had antibodies that recognized VLPs. The rate of agreement between peptides and VLPs for antibody detection was higher for patients with HPV DNA-positive cervical lesions. Peptides 18283, 18294, and 18301 showed similar sensitivities for the detection of HR-HPV DNA-positive cervical lesions and were more specific than VLPs. Peptide 18301 might be detecting protective antibodies in HPV DNA-negative females with atypical squamous cells of undetermined significance. These peptides could be useful for the design of a serology test for the detection of HR-HPV infection in females with cervical lesions and at risk of cervical cancer.
Differences between Two Real-Time PCR-Based Hepatitis C Virus (HCV) Assays (RealTime HCV and Cobas AmpliPrep/Cobas TaqMan) and One Signal Amplification Assay (Versant HCV RNA 3.0) for RNA Detection and Quantification
Authors: Vermehren Johannes , Kau Annika , Gärtner Barbara C. , Göbel Reinhild , Zeuzem Stefan , Sarrazin Christoph
Published: September 2008

Hepatitis C virus (HCV) RNA detection and quantification are the key diagnostic tools for the management of hepatitis C. Commercially available HCV RNA assays are calibrated to the HCV genotype 1 (gt1)-based WHO standard. Significant differences between assays have been reported. However, it is unknown which assay matches the WHO standard best, and little is known about the sensitivity and linear quantification of the assays for non-gt1 specimens. Two real-time reverse transcriptase PCR-based assays (RealTime HCV and Cobas Ampliprep/Cobas TaqMan HCV [CAP/CTM]) and one signal amplification-based assay (the Versant HCV RNA, version 3.0, branched DNA [bDNA] assay) were compared for their abilities to quantify HCV RNA in clinical specimens (
n
= 65) harboring HCV isolates of gt1 to g5. The mean differences in the amounts detected by RealTime HCV in comparison to those detected by the bDNA assay and CAP/CTM were −0.02 and 0.72 log
10
IU/ml HCV RNA, respectively, for gt1; −0.22 and 0.03 log
10
IU/ml HCV RNA, respectively, for gt2; −0.27 and −0.22 log
10
IU/ml HCV RNA, respectively, for gt3; −0.19 and −1.27 log
10
IU/ml HCV RNA, respectively, for gt4; and −0.03 and 0.09 log
10
IU/ml HCV RNA, respectively, for gt5. The lower limits of detection for RealTime HCV and CAP/CTM were 16.8 and 10.3 IU/ml, respectively, for the WHO standard and in the range of 4.7 to 9.0 and 3.4 to 44.4 IU/ml, respectively, for clinical specimens harboring gt1 to gt6. Direct comparison of the two assays with samples of the WHO standard (code 96/798) with high titers yielded slightly smaller amounts by RealTime HCV (−0.2 log
10
at 1,500 IU/ml and −0.3 log
10
at 25,000 IU/ml) and larger amounts by CAP/CTM (0.3 log
10
at 1,500 IU/ml and 0.2 log
10
at 25,000 IU/ml). Finally, all three tests were linear between 4.0 × 10
3
and 1.0 × 10
6
IU/ml (correlation coefficient, ≥0.99). In conclusion, the real-time PCR based assays sensitively detected all genotypes and showed comparable linearities for the quantification of HCV RNA, with the exception of gt1 and gt4. The previously reported differences in the absolute quantification of samples harboring gt1 were confirmed and may be explained by different calibrations to the WHO standard.