bluuebunny/crossref_metadata_2025 huggingface dataset:
Higher‐harmonic atomic force microscopy
Authors: Giessibl Franz J.
Published: November 2006

To 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

By 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

The 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

We 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

Nanowires 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

When 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

It 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

Intensity 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

The 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

The 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

In 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

Protonated 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

This 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

Small 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

The 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.
Kinetic regime of step motion on the Si(111) (1 × 1) surface
Authors: Man K. L. , Tang W. X. , Jin X. F. , Altman M. S.
Published: November 2006

The kinetic regime of step motion on the Si(111) (1 × 1) surface is determined from observations of island decay with low‐energy electron microscopy (LEEM). We have investigated the island decay on the tops of mounds fabricated by a photolithographic method. Prefabricated mounds serve as controllable and reproducible island sources and platforms for decay. Island area during decay exhibits the expected power‐law dependence on time, with exponent, α, that is indicative of the kinetic regime. In order to overcome the basic problem of realizing the thermodynamic limit of island decay on an infinite terrace, the power‐law decay exponent is extrapolated to vanishing island (r)—to—terrace (R) radius ratio, r/R = 0. The dependence of α upon r/R suggests that island decay kinetics is intermediate between the diffusion‐limited (DL) and attachment/detachment‐limited (ADL) regimes. Copyright © 2006 John Wiley & Sons, Ltd.
Electronically induced surface chemistry: localised bond breaking versus delocalisation
Authors: Menzel Dietrich
Published: November 2006

Surface photochemistry can be considerably different from the corresponding molecular photochemistry. This is due to the fact that bonding of reactants to a surface induces modifications also in reaction paths via electronically excited states. These changes are of importance in respect of both fundamental and applied research. The past 40 years have seen the development of quite detailed understanding of the underlying effects, in particular in the case of bond breaking, which shows up by desorption of neutral and charged molecules and/or fragments. Recent developments in laser technology and nanostructuring have brought renewed interest to this field. Here a survey is given of the important facts and ideas in this realm. It will be argued that the counterplay between localisation of excitations and their delocalisation by coupling is the decisive effect to be understood. Copyright © 2006 John Wiley & Sons, Ltd.
Microscopy of mesoscopic ferromagnetic systems with slow electrons
Authors: Bauer E. , Belkhou R. , Cherifi S. , Hertel R. , Heun S. , Locatelli A. , Pavlovska A. , Zdyb R. , Agarwal N. , Wang H.
Published: November 2006

Mesoscopic ferromagnetic systems are not only of practical interest for high density recording and storage devices but also as models of cooperative phenomena in low dimensions. The magnetization distribution in such systems is studied in this paper by X‐ray Magnetic Circular Dichroism Photo Emission Microscopy (XMCDPEEM), using thin rectangular and ring‐shaped patterned Co films and by Spin‐Polarized Low Energy Electron Microscopy (SPLEEM), using epitaxial Fe nanostructures. Copyright © 2006 John Wiley & Sons, Ltd.
The early history and future of the SEM
Authors: Wells Oliver C. , Joy David C.
Published: November 2006

The basic principles of the scanning electron microscope (SEM) were established in the 1930's and early 1940's by Knoll, and then by von Ardenne in Germany and by Zworykin, Hillier and others in America. The SEM was revived by Charles Oatley in a series of PhD projects in the Electrical Engineering Department of Cambridge University in England. The first industrial application followed from the early work of McMullan and Smith in Cambridge and was at the Pulp and Paper Institute in Canada. This was soon followed by the application of the SEM to integrated circuits at Westinghouse in America and by the availability of commercial SEMs in England and Japan. At the present time, the SEM and other microscopic and microanalytical techniques are in a worldwide state of development and are being applied in an increasing number of application areas. Copyright © 2006 John Wiley & Sons, Ltd.
Spectroscopic analysis of the process‐dependent microstructure of ultra‐thin high‐k gate dielectric film systems
Authors: Lysaght Patrick S. , Bersuker Gennadi , Tseng Hsing‐Huang , Jammy Raj
Published: November 2006

HfO2 gate dielectric thin films have been exposed to anneal processing in NH3 and N2 ambient in order to decouple the influence of N incorporation from that of the thermal cycle alone. We report on the effectiveness of NH3 processing to introduce N into the dielectric film system during intermediate temperature annealing. Several high‐resolution techniques including electron microscopy with electron energy loss spectra (EELS), rotationally averaged selective area electron diffraction, grazing incidence X‐ray diffraction and synchrotron X‐ray photoelectron spectroscopy (XPS) have been utilized to elucidate chemical composition and crystalline structure differences between samples annealed in NH3 and N2 ambient as a function of temperature. Copyright © 2006 John Wiley & Sons, Ltd.
PEEM with high time resolution—imaging of transient processes and novel concepts of chromatic and spherical aberration correction
Authors: Schönhense G. , Elmers H. J.
Published: November 2006

The potential of time‐resolved photoemission electron microscopy (PEEM) for imaging ultrafast processes and for aberration correction in full‐field imaging is discussed. In particular, we focus on stroboscopic imaging of precessional magnetic excitations via XMCD‐PEEM exploiting the time structure of synchrotron radiation (magnetic field pulse pump–X‐ray probe). In a special bunch‐compression mode at BESSY, a time resolution of about 15 ps has been obtained. Further, we discuss an all‐optical pump–probe technique using femtosecond laser excitation. A highly promising alternative to stroboscopic imaging is an approach using time‐resolved image detection. As a second application of time‐resolved PEEM we discuss potential ways of aberration correction. These approaches go back to the old ideas of Scherzer in the light of state‐of‐the‐art equipment. The excellent time structure of synchrotron radiation or pulsed lasers along with advanced methods of time‐resolved image detection and fast electronic pulsers opens ways for driving the resolution limit of a PEEM into the range of a few nanometers. Copyright © 2006 John Wiley & Sons, Ltd.
Electronic structure of ultrathin Si oxynitrides
Authors: Jin Hua , Oh Suhk Kun , Kang Hee Jae
Published: November 2006

We have investigated the chemical states and the band gap of ultrathin Si oxynitrides on Si(100) by X‐ray photoemission spectroscopy (XPS) and reflection electron energy loss spectroscopy (REELS). Silicon oxynitride thin films were grown by plasma‐nitridation and annealed‐nitridation treatment. XPS results show that for the annealed‐nitride SiON thin films, Si3N and N(SiOx)3 states exist at the interface, while for the plasma‐nitride SiON thin films, Si3N, N(SiOx)3 and SiNO states exist at the surface with trapped N2 molecules. The band gap for the annealed‐nitride SiON thin film is 8.9 eV at the surface but it is reduced to about 8.45 eV at the interface. Meanwhile, the band gap for the plasma‐nitride SiON thin film is 7.4 eV. In addition, REELS turns out to be an excellent method to obtain the band gap and electronic structure in oxide thin films. Copyright © 2006 John Wiley & Sons, Ltd.
Shave‐off depth profiling of transparent conductive films and data analysis of the profile
Authors: Nakamura K. , Ishikawa Y. , Utsumi K. , Iigusa H. , Tanaka R. , Ishizaki Y. , Yamamoto T. , Maekawa A. , Owari M. , Nojima M. , Nihei Y.
Published: November 2006

Aluminum doped zinc oxide (ZAO) is a promising material for transparent conductive films, but higher conductivity is needed for its use in flat‐panel displays. Its conductivity depends on the deposition conditions, and the segregation of aluminum is suspected as one of causes for its low conductivity. But it has not been confirmed yet because of the low aluminum content in ZAO films.

‘Shave‐off depth profiling’ is one of the methods that can be used to analyze such samples. By applying this method, multiple elements can be detected simultaneously and with high sensitivity. Furthermore, even samples with surface roughness can be analyzed accurately.

We have acquired the shave‐off depth profile of a ZAO thin film and attempted to obtain depth information. However, when the film thickness is insufficient, it is difficult to obtain the depth information directly from the profile. To solve this problem, we now propose a new data analysis method for the shave‐off depth profile, and apply the method to the depth profiling of the ZAO thin film. Copyright © 2006 John Wiley & Sons, Ltd.
Adsorbed hydrogens and their behavior on Ni(111) surface studied by slow‐positron beam
Authors: Kanazawa I. , Oishi Y. , Hirota K. , Fukutani K. , Nozawa K. , Komori F.
Published: November 2006

Reemitted slow positrons from the clean Ni(111) surface and the hydrogen‐saturated Ni(111) surface were measured. We suggest that the disordered hydrogen adsorbed structure of the β1 phase contains vacancy‐type defects, and that the number of these defects will grow with time in the case of hydrogen‐saturated Ni(111) surface at 180 K. Copyright © 2006 John Wiley & Sons, Ltd.
Surface structural analysis of h‐BN/Ni (111) by X‐ray photoelectron diffraction excited by Al Kα and Cr Lα lines
Authors: Mochizuki Hidehiro , Amano Kentaro , Nojima Masashi , Owari Masanori , Nihei Yoshimasa
Published: November 2006

Using the Cr Lα (hν = 572.8 eV) line, which has energy lower than conventional lines, X‐ray photoelectron spectroscopy (XPS) and X‐ray photoelectron diffraction (XPED) can be used to achieve surface‐sensitive and light‐element‐sensitive measurements. We prepared hexagonal boron nitride (h‐BN), which is a light‐element material, grown in a monolayer on a Ni (111) surface, and measured h‐BN/Ni(111) by XPS/XPED excited by the Al Kα (hν = 1486.6 eV) line and the Cr Lα line. Finally, we investigated the excitation‐energy dependence of the XPED method with respect to energy of the photoelectrons and discuss the effectiveness of the XPED method using Cr Lα excitation. Copyright © 2006 John Wiley & Sons, Ltd.
Surface modification of industrial alloys induced by long‐term interaction with an ionic liquid
Authors: Bardi U. , Chenakin S. P. , Caporali S. , Lavacchi A. , Perissi I. , Tolstogouzov A.
Published: November 2006

The surface modification of Inconel 600, Naval Brass and AISI 1018 carbon steel after immersion into the [C4mim][Tf2N] ionic liquid (IL) at 225 °C for 20 days has been studied using SIMS, XPS and by surface topography measurements. The trace concentration of alloys' components in the IL solution after the immersion test was measured by inductively coupled plasma‐optical emission spectroscopy (ICP‐OES). Appreciable amounts of carbon, nitrogen, oxygen, sulphur and fluorine were detected on the surface of the alloys after the immersion test because of thermal decomposition of the IL. The corrosion layer formed onto the surface of Inconel was found to be rather thick (ca 400–500 nm) and rough (Ra∝ 100–200 nm) due to the dominant adsorption of the IL decomposition products. At the same time, Inconel exhibited minor weight loss (2.5 × 10−5 g × cm−2) after the immersion test. On the contrary, for Brass, the thickness (70–100 nm) and roughness (Ra∝ 80–100 nm) of the corrosion layer were the smallest among the alloys studied, and the weight loss was the greatest (1.3 × 10−2 g × cm−2). It is assumed that IL decomposition might be catalysed by some metallic atoms, for instance Ni, that, in turn, could slow down the surface corrosion and migration of metal atoms into the ionic liquid. Copyright © 2006 John Wiley & Sons, Ltd.
Developments in cluster randomized trials and Statistics in Medicine
Authors: Campbell M. J. , Donner A. , Klar N.
Published: November 2006

The design and analysis of cluster randomized trials has been a recurrent theme in Statistics in Medicine since the early volumes. In celebration of 25 years of Statistics in Medicine, this paper reviews recent developments, particularly those that featured in the journal. Issues in design such as sample size calculations, matched paired designs, cohort versus cross‐sectional designs, and practical design problems are covered. Developments in analysis include modification of robust methods to cope with small numbers of clusters, generalized estimation equations, population averaged and cluster specific models. Finally, issues on presenting data, some other clustering issues and the general problem of evaluating complex interventions are briefly mentioned. Copyright © 2006 John Wiley & Sons, Ltd.
A boosting approach to flexible semiparametric mixed models
Authors: Tutz G. , Reithinger F.
Published: November 2006

In linear mixed models the influence of covariates is restricted to a strictly parametric form. With the rise of semi‐ and non‐parametric regression also the mixed model has been expanded to allow for additive predictors. The common approach uses the representation of additive models as mixed models. An alternative approach that is proposed in the present paper is likelihood based boosting. Boosting originates in the machine learning community where it has been proposed as a technique to improve classification procedures by combining estimates with reweighted observations. Likelihood based boosting is a general method which may be seen as an extension of L2 boost. In additive mixed models the advantage of boosting techniques in the form of componentwise boosting is that it is suitable for high dimensional settings where many explanatory variables are present. It allows to fit additive models for many covariates with implicit selection of relevant variables and automatic selection of smoothing parameters. Moreover, boosting techniques may be used to incorporate the subject‐specific variation of smooth influence functions by specifying ‘random slopes’ on smooth effects. This results in flexible semiparametric mixed models which are appropriate in cases where a simple random intercept is unable to capture the variation of effects across subjects. Copyright © 2006 John Wiley & Sons, Ltd.
A statistical comparison of different family history scores
Authors: Murad H. , Kalter‐Leibovici O. , Chetrit A. , Freedman L. S.
Published: November 2006

Family history (FH) scores are used for estimating the familial risk (FR), i.e. the level of risk for a particular disease among members of that family. An FH score is created from reports about the disease status of the relatives in each family. The most commonly used score is the dichotomous score (positive when at least one relative is affected), which does not consider the family size, number of affected relatives nor each relative's risk factor profile. Authors have proposed many other FH scores that overcome these deficiencies by using external expected risks adjusted for important risk factors. We consider the use of FH scores in studies, which investigate risk factors for a disease and where family risk is considered as a confounder, and examine through simulations the performance of a variety of FH scores in controlling the FR status. We also examine performance in predicting true FR status.

For both criteria, only small differences were found between most of the FH scores, although the dichotomous score performed the poorest. Since the proportion score (the proportion of first‐degree relatives of the index who have the disease) is the simplest to calculate, use of this score seems to be justified. Copyright © 2006 John Wiley & Sons, Ltd.
Computerized adaptive testing for measuring development of young children
Authors: Jacobusse Gert , Buuren Stef van
Published: November 2006

Developmental indicators that are used for routine measurement in The Netherlands are usually chosen to optimally identify delayed children. Measurements on the majority of children without problems are therefore quite imprecise. This study explores the use of computerized adaptive testing (CAT) to monitor the development of young children. CAT is expected to improve the measurement precision of the instrument. We do two simulation studies—one with real data and one with simulated data—to evaluate the usefulness of CAT. It is shown that CAT selects developmental indicators that maximally match the individual child, so that all children can be measured to the same precision. Copyright © 2006 John Wiley & Sons, Ltd.
Pseudoscore‐based estimation from biased observations
Authors: Hu X. Joan , Schroeder R. Jason , Wang Winfred C. , Boyett James M.
Published: November 2006

There are many practical situations where observation of the primary variableYfor individuals in a population is incomplete and depends on some auxiliary variablesXthat are potentially correlated withY. We consider parameter estimation for the distribution ofYwith the incomplete data, without specifying the underlying association betweenYandX. The approach is based on a class of pseudoscore functions using available information ofX. We demonstrate the consistency and asymptotic normality of the estimators and study their finite‐sample properties in various situationsviasimulation. The methodology is illustrated by an example involving kindergarten readiness skills in children with sickle cell disease. Copyright © 2006 John Wiley & Sons, Ltd.
Adaptive design method based on sum of p‐values
Authors: Chang Mark
Published: November 2006

Bauer and Kohne proposed an adaptive design using Fisher's combination of independent p‐values based on subsamples from different stages (Biometrics 1994; 50(4):1029–1041). Their method provides great flexibility in the selection of statistical methods for hypothesis testing of subsamples. However, the choices for the stopping boundaries are not flexible enough to meet practical needs (Biometrics 2001; 57(3): 886–891). In this paper, an adaptive design method is proposed using linear combination of the independent p‐values. The method provides great flexibility in the selection of stopping boundaries and no numerical integration is required for the two‐stage designs. The stopping boundaries and p‐values can be calculated manually. The operating characteristics of the adaptive designs are studied using computer simulations with and without sample size adjustment. Examples are presented for superiority and non‐inferiority trials with different endpoints (normal, binary, and survival) under different adaptations. The statistical efficiency of the proposed method is compared with other methods based on conditional power. Copyright © 2006 John Wiley & Sons, Ltd.
Pooling batches in drug stability study by using constant‐width simultaneous confidence bands
Authors: Liu W. , Jamshidian M. , Zhang Y. , Bretz F. , Han X. L.
Published: November 2006

One important study objective in drug stability studies is to estimate the shelf‐life of a drug. A key statistical problem involved in this is how to assess the practical equivalence of different batches of the same drug so that different batches can be subgrouped to produce a single shelf‐life for the drug. In this paper constant‐width simultaneous confidence bands are proposed to quantify the magnitude of difference between different batches, with a particular view to establish the practical equivalence of different batches. This approach is suitable for the situation that the intercepts and slopes of the regression lines for the batches cannot be assumed to be equal. It is shown how constant‐width simultaneous confidence bands can be easily constructed for the multiple comparison of several general linear regression models. In particular, it is shown that constant‐width simultaneous confidence bands have a better chance to establish the equivalence than, and so are preferable to, the hyperbola‐shaped simultaneous confidence bands considered (J. Am. Stat. Assoc. 2004; 99:395–403). Copyright © 2006 John Wiley & Sons, Ltd.
Regression models for mixed Poisson and continuous longitudinal data
Authors: Yang Ying , Kang Jian , Mao Kai , Zhang Jie
Published: November 2006

In this article we develop flexible regression models in two respects to evaluate the influence of the covariate variables on the mixed Poisson and continuous responses and to evaluate how the correlation between Poisson response and continuous response changes over time. A scenario for dealing with regression models of mixed continuous and Poisson responses when the heterogeneous variance and correlation changing over time exist is proposed. Our general approach is first to jointly build marginal model and to check whether the variance and correlation change over timevialikelihood ratio test. If the variance and correlation change over time, we will do a suitable data transformation to properly evaluate the influence of the covariates on the mixed responses. The proposed methods are applied to the interstitial cystitis data base (ICDB) cohort study, and we find that the positive correlations significantly change over time, which suggests heterogeneous variances should not be ignored in modelling and inference. Copyright © 2006 John Wiley & Sons, Ltd.
Influences of top management team incentives on firm risk taking
Authors: Wright Peter , Kroll Mark , Krug Jeffrey A. , Pettus Michael
Published: November 2006

In our work, the influences on subsequent firm risk taking of fixed incentives relative to variable incentives as well as the separate effects on subsequent corporate risk taking of variable incentives are examined. Focusing on the top management team members, we find a higher proportion of incentives that are devoted to fixed incentives relative to variable incentives tend to be inversely associated with subsequent firm risk taking. Managerial stock options are directly and uniformly associated with subsequent corporate risk taking. Executive shareholdings, however, display a curvilinear relationship with subsequent enterprise risk taking. Copyright © 2007 John Wiley & Sons, Ltd.
Are joint venture partners more opportunistic in a more volatile environment?
Authors: Luo Yadong
Published: November 2006

This study examines how joint venture partners' opportunism is influenced by environmental volatility in a drastically changing emerging economy. Building on transaction cost and information‐processing theories, we develop the hypothesis that opportunism increases to cope with industry structural instability, information unverifiability, and law unenforceability, the three interrelated yet distinct characteristics that jointly describe environmental volatility in an emerging economy. Our analysis of 188 foreign joint ventures in an emerging market suggests that opportunism increases with information unverifiability and law unenforceability. These relationships are even stronger when joint ventures depend more on the host country environment, but weaker when joint ventures operate in faster‐growing industries. Finally, opportunism is found to play a mediating role in the relationship between environmental volatility and joint venture performance. Copyright © 2007 John Wiley & Sons, Ltd.
Innovations and the role of complementarities in a strategic theory of the firm
Authors: Stieglitz Nils , Heine Klaus
Published: November 2006

In the resource‐based view of strategy and in evolutionary economics, complementary assets play a crucial role in explaining sustainable competitive advantages and innovations. Despite the apparent importance of complementary assets for the understanding of corporate strategy, their creation and the associated managerial problems have been much less discussed. We believe this to be a major weakness in the strategic theory of the firm. Interestingly, problems of coordination and cooperation are center stage in the contract‐based theories of the firm, and we try to integrate some of their insights into a resource‐based perspective. Specifically, we show how complementary assets raise the need for strategic direction by a firm's top management. Moreover, complementary assets magnify internal incentive problems, and their management has an impact on the innovativeness of a firm. Lastly, complementary assets play a crucial role in the internal appropriation of innovative rents. We demonstrate the fruitfulness of our integrated framework by relating some of our findings to the literature on corporate strategy, industry evolution, and organizational structures. Copyright © 2007 John Wiley & Sons, Ltd.
The significance of network resources in the race to enter emerging product markets: the convergence of telephony communications and computer networking, 1989–2001
Authors: Lee Gwendolyn K.
Published: November 2006

This paper focuses on the role of network resources and examines the associated mechanisms that affect the timing of entry into an emerging product market. Linking network theory to market entry research, I analyze the pattern in the structure, relation, and composition of 517 firms' strategic alliances as the firms face the decision of whether and when to enter the networking switches market over a 13‐year period from 1989 to 2001. The context for empirical testing is the voice/data convergence between telephony communications and computer networking technologies during which the industry boundary blurs. Firms that have access to information of high quality, large quantity, and compositional heterogeneity are likely to enter the newly developed market more quickly. However, network configuration lock‐in and network costs may counterbalance the benefits derived from network resources. I discuss the implications of these findings for research on social networks and the timing of market entry. Copyright © 2007 John Wiley & Sons, Ltd.
When is more better? The impact of business scale and scope on long‐term business survival, while controlling for profitability
Authors: Bercovitz Janet , Mitchell Will
Published: November 2006

Empirical research shows that larger businesses tend to survive longer than smaller companies. Little research, though, shows whether size confers survival advantages in addition to the survival benefits of baseline profitability. Moreover, no prior research attempts to disentangle the benefits of organizational capital that accrue from greater scale from those that arise from greater business scope. Thus, we lack a conceptual understanding of the underlying benefits of business size for long‐term survival. We expect business scale and business scope to reflect organizational capital that offers survival benefits, where we conceptualize scale in terms of annual sales revenue and scope in terms of product line breadth and sub‐sector participation within a related business context. We first argue that greater business scale and business scope each enhance long‐term survival, independent of baseline profitability, owing to greater availability of financial resources, organizational routines, and external ties. We then argue that the benefits of scale are greatest for multi‐product businesses, stemming from positive interactive effects of breadth and depth. We find support for these hypotheses with data from 618 firms that operated in the U.S. medical sector between 1978 and 1995. Copyright © 2007 John Wiley & Sons, Ltd.
Investor activism, managerial responsiveness, and corporate social performance
Authors: David Parthiban , Bloom Matt , Hillman Amy J.
Published: November 2006

We study relationships between shareholder proposal activism, managerial response, and corporate social performance (CSP). We find that shareholder proposal activism reduces CSP. We infer that rather than pressuring firms to improve CSP, activism may engender diversion of resources away from CSP into political activities used by managers to resist external pressures and retain discretion. We also find that managers are more likely to settle proposals filed by ‘salient’ shareholders (i.e., those with power, legitimacy, and urgency). Settlement with salient shareholders, however, also reduces CSP, suggesting that managers' responses are symbolic; i.e., they settle with salient shareholders to demonstrate conformance but continue to resist making the substantive changes to core policies that may compromise their discretion. Copyright © 2007 John Wiley & Sons, Ltd.
The passage to adulthood: Challenges of late adolescence
Authors: Zarrett Nicole , Eccles Jacquelynne
Published: November 2006

This chapter outlines the major developmental challenges likely to affect overall well‐being during adolescence and emerging adulthood and discusses the personal and social assets needed to facilitate a successful passage through adolescence and into adulthood.
Designing for diversity: Incorporating cultural competence in prevention programs for urban youth
Authors: Goldstein Marion J. , Noguera Pedro A.
Published: November 2006

If prevention programs are going to be effective in appealing to the sensibilities of urban youth and ultimately alter their behavior, they need to place diversity with respect to culture, class, and environment at the center of prevention efforts.
Teens and technology: Preparing for the future
Authors: Hall Georgia
Published: November 2006

We must prioritize the integration of technology skill building into youth development experiences in order to better prepare older youth for the challenges and responsibilities ahead.
First Things First: A framework for successful secondary school reform
Authors: Connell James P. , Klem Adena M.
Published: November 2006

Secondary schools can improve the academic achievement of all students by using a reform frame‐work grounded in research about how young people develop and how schools can promote students' engagement and learning.
Young people and social action: Youth participation in the United Kingdom and United States
Authors: Arches Joan , Fleming Jennie
Published: November 2006

Social action theory provides a valuable youth engagement strategy that emphasizes youth voice, participatory practice, and community building.
Workforce development for older youth
Authors: Brown David E. , Thakur Mala B.
Published: November 2006

Recent research and evaluation of youth development and employment programs suggests that the demands of the knowledge economy and the emerging digital economy are causing employers to expect higher levels of skills from older youth.
Going the distance: Serving the needs of older youth at scale
Authors: Ouellette Mark
Published: November 2006

Communities that want to build a system of supports to meet the unique developmental and programmatic needs of the older youth population must do so in the context of a communitywide strategy as opposed to fragmented, individually operating programs and services.
Arabidopsis thaliana CHX17 gene complements the kha1 deletion phenotypes in Saccharomyces cerevisiae
Authors: Maresova Lydie , Sychrova Hana
Published: November 2006

AtChx17p is a putative K+/H+ exchanger from Arabidopsis thaliana, expressed in the roots and probably involved in K+ acquisition and homeostasis. AtCHX17 cDNA complements the phenotypes of the kha1Δ mutation in S. cerevisiae cells: a growth defect at increased pH and hygromycin sensitivity. The localization of GFP‐tagged AtChx17 protein in yeast cells is similar to that of ScKha1p: a bold dotted pattern inside the cells resembling the Golgi fluorescence markers. These results show that (a) the proteins AtChx17 and ScKha1 could have similar functions and (b) S. cerevisiae kha1 deletion mutants could serve for the heterologous expression and characterization of plant transporters. The results of this work are evidence that a S. cerevisiae strain with deletions of genes encoding alkali–metal–cation/H+ antiporters (i.e. Nha1p, Nhx1p, Kha1p) could be an ideal tool for expression and functional analysis of any type of similar plant antiporters (plasma membrane, endosomal/prevacuolar and Golgi). Copyright © 2006 John Wiley & Sons, Ltd.