bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of the Gould‐Shih procedure for sample size re‐estimation
Authors: Waksman Joel A. 
Published: November 2006

AbstractThe power of a clinical trial is partly dependent upon its sample size. With continuous data, the sample size needed to attain a desired power is a function of the within‐group standard deviation. An estimate of this standard deviation can be obtained during the trial itself based upon interim data; the estimate is then used to re‐estimate the sample size. Gould and Shih proposed a method, based on the EM algorithm, which they claim produces a maximum likelihood estimate of the within‐group standard deviation while preserving the blind, and that the estimate is quite satisfactory. However, others have claimed that the method can produce non‐unique and/or severe underestimates of the true within‐group standard deviation. Here the method is thoroughly examined to resolve the conflicting claims and, via simulation, to assess its validity and the properties of its estimates. The results show that the apparent non‐uniqueness of the method's estimate is due to an apparently innocuous alteration that Gould and Shih made to the EM algorithm. When this alteration is removed, the method is valid in that it produces the maximum likelihood estimate of the within‐group standard deviation (and also of the within‐group means). However, the estimate is negatively biased and has a large standard deviation. The simulations show that with a standardized difference of 1 or less, which is typical in most clinical trials, the standard deviation from the combined samples ignoring the groups is a better estimator, despite its obvious positive bias. Copyright © 2006 John Wiley & Sons, Ltd.
Potential cytotoxic activity of some Brazilian seaweeds on human melanoma cells
Authors: Rocha Fabíola Dutra , Soares Angélica Ribeiro , Houghton Peter John , Pereira Renato Crespo , Kaplan Maria Auxiliadora Coelho , Teixeira Valéria Laneuville 
Published: November 2006

AbstractIn vitro screening of the crude extracts of some Brazilian coastal seaweeds for cytotoxic activity against a cultured human melanoma cancer cell line using the sulphorhodamine B assay was performed. The crude dichloromethane:chloroform extract of Stypopodium zonale showed good cytotoxic activity against the C32 cell line. The crude acetone extract and aqueous phase of Lobophora variegata did not show any activity, but semi‐purified fractions XAD LOB I and II could inhibit the growth of melanoma cells. The crude acetone extract of Caulerpa racemosa showed some cytotoxicity, but caulerpin isolated from this extract did not show any such activity. The crude acetone extract of Spatoglossum schroederi was not able to inhibit the growth of C32 melanoma cells. Copyright © 2006 John Wiley & Sons, Ltd.
Quantification of D‐amino acids in the central nervous system of Aplysia californica by liquid chromatography/tandem mass spectrometry
Authors: Song Yaru , Liang Fei , Liu Yi‐Ming 
Published: November 2006

AbstractA sensitive, specific and reliable liquid chromatography/tandem mass spectrometry (LC/MS/MS) method has been developed for simultaneous determination of D‐amino acids in the central nervous system (CNS) of Aplysia californica. In order to correct for any potential matrix effects on measured signals, deuterium‐labeled L‐Asp‐d3 was used as an internal standard. Pre‐column derivatization of the sample with 7‐fluoro‐4‐nitrobenzoxadiazole (NBD‐F) allowed both effective in‐line pre‐concentration and sensitive MS/MS detection of the analytes. An extraction column (50 × 0.25 mm, 5 µm C18 silica particles) was used to pre‐concentrate/stack samples. Enantiomeric separation of amino acid enantiomers was achieved on a chiral column packed with teicoplanin aglycone bonded silica particles (170 × 0.25 mm, 5 µm) with an MS‐friendly mobile phase. The characteristic precursor to product ion transitions, m/z 297 → 279 (for NBD‐Asp), m/z 269 → 223 (For NBD‐Ser), m/z 311 → 293 (for NBD‐Glu) and m/z 300 → 282 (for NBD‐L‐Asp‐d3) were monitored for the quantification. Samples from the CNS of A. californica and heart tissues were analyzed. D‐Asp was detected at high levels in all the ganglia and nerve tissues, but not in the heart tissue. Further, neither D‐Ser nor D‐Glu was detected in Aplysia, a widely used neuronal model. Copyright © 2006 John Wiley & Sons, Ltd.
Evaluation of an on‐target sample preparation system for matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry in conjunction with normal‐flow peptide high‐performance liquid chromatography for peptide mass fingerprint analyses
Authors: McComb Mark E. , Perlman David H. , Huang Hua , Costello Catherine E. 
Published: November 2006

AbstractLarge‐scale mass spectrometry (MS)‐based proteomic analyses require high‐throughput sample preparation techniques due to the increasing numbers of samples that make up a typical proteomics experiment. Moreover, extensive sample pre‐treatment steps are necessary prior to MS acquisition for even the most rapid and robust MS‐based proteomics methodology, matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) MS followed by peptide mass fingerprinting (PMF) analysis. These include sample purification and fractionation, removal of digestion buffers or solvents, and spotting of sample with matrix onto the MALDI target. These multiple steps of time‐consuming sample handling can result in high overall analysis costs and the likelihood of sample contamination and loss. In order to overcome some of these limitations in sample processing, we have investigated the use of a novel, simple, inexpensive 96‐well elastomeric array that affixes to a MALDI target to create an on‐target 96‐well plate that accommodates a high solution volume (ca. 200 µL), thereby enabling the on‐target processing of samples for MALDI‐TOFMS. We explored several factors that influence MALDI sample preparation: type of matrix, solution volume, solution organic composition, solution drying rates and matrix/analyte co‐crystallization methods. We also investigated the use of the 96‐well elastomeric device for coupling MALDI‐TOFMS analysis directly to high flow rate (1 mL/min) reversed‐phase (rp)‐HPLC. By developing an optimized, robust sample preparation protocol, we were able to obtain mass spectra with a high signal‐to‐noise ratio from peptide standards present at the 50‐fmol level in large starting volumes of solution. PMF analyses were possible from 1‐pmol and 500‐fmol protein‐digest standards. Coupling the device to high‐flow HPLC (750 µL/min) yielded a robust and semi‐automated means to obtain enhanced MALDI‐TOFMS data at 500 ng of protein digest. These methodologies developed for this simple, on‐target, elastomeric device show promise for streamlining the sample preparation process from HPLC to MALDI‐MS. Copyright © 2006 John Wiley & Sons, Ltd.
Higher‐harmonic atomic force microscopy
Authors: Giessibl Franz J. 
Published: November 2006

AbstractTo maximize the spatial resolution of atomic force microscopy (AFM), it is helpful to isolate the spurious short‐range components from the plethora of force contributions acting between AFM tips and samples. It is shown theoretically and experimentally that higher‐harmonic AFM, a technique that utilizes the anharmonic deflection contributions that arise when a cantilever oscillates in the highly nonlinear force field of a sample, is a suitable technique for maximizing spatial resolution. The qPlus sensor, a quartz cantilever that utilizes the piezoelectric effect for deflection detection, is particularly well suited for higher harmonic AFM because the physics of piezoelectric detection inherently magnifies the signal level of higher harmonics. Experimental results for W on graphite (0001), Si (111)‐(7 × 7), NiO (100) and CaF2(111) are presented. Copyright © 2006 John Wiley & Sons, Ltd.
High‐temperature diffusion barriers from Si‐rich silicon‐nitride
Authors: Bilger G. , Voss T. , Schlenker T. , Strohm A. 
Published: November 2006

AbstractBy radiotracer diffusion experiments, it is shown that the 31Si diffusivity in Si‐rich nonstoichiometric amorphous silicon‐nitride layers (Si3+xN4−x) sharply drops to low values at a temperature of 1075 °C and is unmeasurable at lower temperatures. A similar behavior was found for Au and Ge diffusion in Si3+xN4−x, however, at lower temperatures. Utilizing this diffusion‐blocking effect, thin films of Si3+xN4−x were employed as efficient diffusion barriers for preventing the diffusion of Fe and other constituents from a steel substrate into a Cu(In,Ga)Se2 absorber layer of a thin‐film solar cell. The reduced diffusion consequently allows the employment of higher process temperatures, which can lead to larger grains and an improved cell performance. Copyright © 2006 John Wiley & Sons, Ltd.
Influence of d.c. bias on characteristic X‐ray emission from Al2O3 targets bombarded with 30‐keV Ga+ ions
Authors: Rao J. C. , Song M. , Che R. C. , Takeguchi M. , Furuya K. 
Published: November 2006

AbstractThe present paper presents the low‐energy characteristic X‐ray emission from monocrystalline Al2O3 insulator samples in an electric field during positive, low‐energy ion (30 keV Ga+ and 100 keV Xe+) bombardment. The electric field built up by the direct current (d.c.) bias was parallel to the surface of the samples. The results show that the characteristic O Kα and Al Kα X rays increased with increase in applied d.c. bias, and that the X‐ray yield from the lighter element was more sensitive to the d.c. bias than that from the heavier element. Copyright © 2006 John Wiley & Sons, Ltd.
Pin point depth profiling for unit device or several nano‐devices
Authors: Maekawa Ayaka , Yamamoto Takeshi , Ishizaki Yasuhiro , Tanaka Risa , Sakamoto Tetsuo , Owari Masanori , Nojima Masashi , Nihei Yoshimasa 
Published: November 2006

AbstractWe have been developing a new depth profiling method named ‘the shave‐off depth profiling’. This method aims to acquire a depth profile by a shave‐off mode, in which the fast horizontal sweep is combined with a very slow vertical sweep of the focused ion beam (FIB). Shave‐off depth profiling is a unique and powerful quantitative analytical method for structured samples: particles, rough surfaces, and/or micro‐machined structures. In this paper, we describe the results of shave‐off depth profiling for the TiN barrier metal structured in an SRAM chip. By shave‐off depth profiling, we were able to evaluate a manufacturing process of practical nano‐devices. Furthermore, we have established that shave‐off depth profiling is a unique methodology for the acquisition of material information in various nano‐devices. Copyright © 2006 John Wiley & Sons, Ltd.
Electron holographic study of the effect of contact resistance of connected nanowires on resistivity measurement
Authors: Takeguchi M. , Shimojo M. , Tanaka M. , Che R. , Zhang W. , Furuya K. 
Published: November 2006

AbstractNanowires were formed on a tungsten tip and on an edge of a metal substrate by electron beam induced deposition (EBID), and were made to come in contact with each other in a specially designed transmission electron microscope (TEM) sample holder to perform the measurement of the resistivity of the nanowires. The resistivity of the contacted nanowires was very high (>0.01 Ωm) immediately after making contact. During the resistivity measurement, potential distribution around the contacted nanowires was observed by electron holography, and it was revealed that electric field concentrated on the contact point. It was due to the insulative character of the contact. The irradiation of an intense electron beam decreased such high contact resistance, and electron holographic observation showed that the electric field distribution became uniform. Copyright © 2006 John Wiley & Sons, Ltd.
A microcalorimeter EDS system suitable for low acceleration voltage analysis
Authors: Tanaka Keiichi , Odawara Akikazu , Nagata Atsushi , Ikeda Masanori , Baba Yukari , Nakayama Satoshi 
Published: November 2006

AbstractWhen a scanning electron microscope (SEM) is used for analysis, a low acceleration voltage must be used to reduce damage to the sample and to obtain information near the sample surface. Here, a microcalorimeter energy dispersive spectrometer (EDS) system without external cryogen was developed to analyze material samples under low acceleration voltages (<5 kV) with high energy resolution (<20 eV). This EDS system can maintain the operating temperature of the transition edge X‐ray sensor (TES) composing of the microcalorimeter system continuously at 100 mK to measure the X‐ray spectrum with high reproducibility and with high energy resolution. This system resembles a conventional EDS system, but also has a snout to allow the X‐ray detector to be close to the sample. The measured energy resolution was 19 eV (5.9 keV) and the count rate was 300 cps. A thin X‐ray window of aluminum/polyimide bilayer was designed to transmit the X rays at a low acceleration voltage (5 keV). When SUS‐304 was analyzed using this EDS system at an acceleration voltage less than 3 kV, the Cr Lα (573 eV) was distinguished between the closely spaced O Kα (525 eV) and Fe Ll (615 eV)lines, whereas when a solid‐state detector(SSD) was used, it was not distinguished owing to inadequate energy resolution (130 eV). Copyright © 2006 John Wiley & Sons, Ltd.
Formation of Fe–Pt intermetallic phase in nanostructures by electron‐beam‐induced deposition and postdeposition alloying processes
Authors: Zhang W. , Che R. , Takeguchi M. , Shimojo M. , Furuya K. 
Published: November 2006

AbstractIt was found that Fe and Pt can be successfully alloyed in rod‐like nanostructures by electron‐beam‐induced deposition (EBID) using a Fe(CO)5 precursor in an ultrahigh vacuum scanning electron microscope (SEM), followed by a 600 °C vacuum heating of the deposit and a subsequent surface platinum coating and a further 600–700 °C annealing treatment. By using high‐resolution transmission electron microscopy (HRTEM), image simulation and energy dispersion X‐ray spectra analysis, L12‐type intermetallic FePt3 phase occurred in the nanostructure formed by the aforementioned EBID and postdeposition alloying processes. Copyright © 2006 John Wiley & Sons, Ltd.
Estimation of crystal grain size near surface using X‐ray scattering at small glancing angles of incidence
Authors: Fujii Yoshikazu , Nakayama Takenori 
Published: November 2006

AbstractIntensity distributions of the diffracted X rays on a polycrystalline surface were investigated as a function of incidence angles for the surface. In the previous study, we derived the intensity of X‐ray propagation in surface layer materials characterized by a complex refractive index that changes continuously with depth. Using that result, we now analyzed the method for evaluating the distribution of crystal grain size in the surface layer by using X‐ray diffraction at small glancing angles of incidence. The dependence of the peak width of diffracted X‐rays on the incidence angle lead to the depth profile of the crystal grain size in the surface layer. Using the calculation to reproduce the experimental result, the depth profile of the crystal grain size in the surface polycrystalline layers was evaluated. The evaluated result shows that the crystal grain under the mechanically polished iron surface is very small. Copyright © 2006 John Wiley & Sons, Ltd.
Handling of the ice protective film for potential use in the 3D microscale analysis of biological samples
Authors: Iwanami T. , Liu YuJing , Okazaki M. , Nojima M. , Sakamoto T. , Owari M. 
Published: November 2006

AbstractThe improvement of bioanalytical imaging techniques for biological samples such as single cells is an important theme in biological research. We have investigated handling of the ice protective film in techniques such as gallium focused ion beam (Ga‐FIB) fabrication, SIMS analysis and microscopic observation, which is necessary for the three‐dimensional (3D) microscale analysis of freeze‐non‐dried biological samples in its freshly frozen state. To bring about this 3D microscale analysis, we carried out the following four experiments: (i) Microscopic observation by Ga‐FIB under a water vapor environment; (ii) Evaluation of the balance between the growth rate of the protection film and the sputtering rate in SIMS analysis; (iii) Fabrication of an ice grain with shave‐off scan with no water vapor jet on the sample; (iv) Secondary ion mapping of the ice. The results show that it is possible to carry out the study of 3D microscale analysis of biological samples in their fresh frozen state with the ice protective film. Copyright © 2006 John Wiley & Sons, Ltd.
Effects of oxygen atmosphere on surface properties of ScO/W(100) system as Schottky emitter at high temperature
Authors: Nakanishi Y. , Nagatomi T. , Takai Y. 
Published: November 2006

AbstractThe dependence of properties of the ScO/W(100) system on the partial pressure of oxygen was investigated by means of Auger electron spectroscopy, low‐energy electron diffraction and work function measurement. The (1 × 1)‐ScO/W(100) surface having a low work function, which was prepared by heating at 1700 K under ultrahigh vacuum (UHV) conditions, hardly showed any changes in surface properties at 1500 K, the operating temperature of the ScO/W(100) emitter, in a UHV of ∼5 × 10−10 Torr. In contrast, the (1 × 1) ScO/W(100) surface was changed to the (2 × 1)‐(1 × 2) ScO/W(100) surface having a high work function by heating at 1500 K in an oxygen atmosphere of even 5 × 10−9 Torr. The present results revealed that the partial pressure of oxygen around the ScO/W(100) tip is one of the most important factors for determining the optimum preparation and operating conditions of the ScO/W(100) emitter. Copyright © 2006 John Wiley & Sons, Ltd.
An application of cesium–xenon co‐sputtering: quantitative study of a Pd–Rh thin film by ToF‐SIMS
Authors: Brison J. , Hubert R. , Lucas S. , Houssiau L. 
Published: November 2006

AbstractIn this work, the ionization processes and the formation mechanisms of monoatomic and molecular ions were studied by co‐sputtering cesium and xenon on a RhPd layer. Firstly, the relative concentrations of Rh and Pd and the thickness of the RhPd layer were measured by PIXE and by RBS, respectively. Secondly, the total sputtering yield was measured by ToF‐SIMS for different cesium beam concentrations, varying from a pure xenon beam to a pure cesium beam. The sputtering yield was found to decrease linearly with cesium beam concentration, from 4.6 atoms/ion for the pure xenon to 4.0 atoms/ion for the pure cesium. The positive signals were then monitored with respect to the cesium surface concentration. As predicted by the tunneling model, the M+ signals decrease exponentially with the cesium surface concentration and the MCs+ yields exhibit a maximum for a well‐defined Cs/Xe ratio. Copyright © 2006 John Wiley & Sons, Ltd.
Mass spectrometric and theoretical studies on the fragmentation mechanism of protonated molecules and molecular radical cations of organometallic compounds with SiC, SiSi, GeC and GeGe bonds
Authors: Takeuchi Takae , Shirai Yuko , Matsumura Yuriko , Iwai Kaoru , Matsutani Takaomi , Oshita Joji , Naka Akinobu 
Published: November 2006

AbstractProtonated hexamethyldigermane [HMDG]H+ and protonated hexamethyldisilane [HMDS]H+ were generated in the gas phase by nanoelectrospray ionization (nano‐ESI) and atmospheric pressure chemical ionization (APCI). The fragmentation mechanisms of [HMDG]H+ and [HMDS]H+ were investigated by analyzing the collision‐induced dissociation (CID). In CID spectra of [HMDG]H+, the fragment ions due to a CH4 elimination from the protonated hexamethyldigermane were observed. The potential energy curves were calculated using the ab initio method (B3LYP/6–31G(2df,p)). The calculated optimal geometries of [HMDG]H+ and [HMDS]H+ were the proton‐bound structures and the ion‐neutral complexes. The results of ab initio calculations showed that C2H4 elimination occurred more easily than C2H6 elimination in both (CH3)3Ge+ and (CH3)3Si+. This was consistent with the experimental results of the CID spectrum of (CH3)3Si+. Copyright © 2006 John Wiley & Sons, Ltd.
Electron spectrometers for inelastic scattering from magnetic surface excitations
Authors: Ibach Harald , Etzkorn Markus , Kirschner Jürgen 
Published: November 2006

AbstractThis paper compares the performance of two different designs for electron spectrometers to be used for inelastic scattering of spin‐polarized electrons from surface magnons and Stoner excitations. The recently proposed combination of monochromators with 90° and 180° deflection angles ensures a maximum spin asymmetry signal while providing still a good quality of the monochromatic beam. Higher intensities, however, are obtained with the classical 146° /146° combination, which features a spin polarization longitudinal to the beam direction at the target. We present calculations for the monochromatic current for both combinations and argue that the use of the classical spectrometer type may be advantageous. Copyright © 2006 John Wiley & Sons, Ltd.
Stereoisomeric influence on 2D lattice structure: achiral meso‐tartaric acid versus chiral tartaric acid
Authors: Parschau Manfred , Behzadi Bahar , Romer Sara , Ernst Karl‐Heinz 
Published: November 2006

AbstractSmall changes in molecular structure have consequences on long‐range lattice structure formation. We compare and discuss two‐dimensional lattice structures of achiral (R,S)‐tartaric acid (TA) with structures of chiral (R,R)‐ and (S,S)‐TA, both generated on a Cu(110) surface. These diasteriomers are only distinguished by the relative position of hydroxyl groups at the C2 and C3 carbon atoms. Two‐dimensional crystal structures of both species have been identified via low energy electron diffraction (LEED) and characterized by XPS. The impact on two‐dimensional pattern formation due to small differences in intermolecular interaction is discussed. Copyright © 2006 John Wiley & Sons, Ltd.
Incident angle dependence in the transient sputtering of an amorphous Si surface by sub‐keV O2+ ion bombardment
Authors: Lee Hyung‐Ik , Kang Hee Jae , Oh Suhk Kun , Moon Dae Won 
Published: November 2006

AbstractThe transient sputtering of an amorphous Si surface with sub‐keV oxygen ion bombardment was studied with medium energy ion scattering (MEIS) spectroscopy and dynamic Monte Carlo simulation. The in‐depth composition profiles of the incorporated oxygen and sputtering yield change in Si were obtained from in situ medium energy ion scattering spectroscopy. As ion doses increase, the Si surface is thickly oxidized, and the sputtering yield is rapidly reduced. At the initial stage of the sputtering, the surface is continuously swelled owing to an incorporation rate of oxygen higher than the sputtering rate of Si. A dynamic Monte Carlo calculation, which takes into account swelling and diffusion effects, describes the experimental results for the in‐depth composition profiles and the transient Si sputtering yield very well. At normal incidence, the surface is swelled rather than etched due to incorporation rate of oxygen atoms higher than surface etching rate, but at grazing incidence, the transient effect can be minimized. Copyright © 2006 John Wiley & Sons, Ltd.