bluuebunny/crossref_metadata_2025 huggingface dataset:
A case of valgus ankle in an early Pleistocene hominin
Authors: DeSilva J. M. , Papakyrikos A.
Published: June 2010

Bipedal locomotion is a defining character of the hominin lineage. A skeletal correlate of bipedality is a perpendicularly oriented tibia relative to the plane of the ankle joint, positioning the foot directly under the centre of mass. Non‐human primates, in contrast, possess a tibial shaft that tilts laterally away from the plane of the ankle joint (valgus ankle), which positions the foot in inversion and is adaptive for arboreal climbing. KNM‐ER 2596 is a small distal tibia from 1.9 mya sediments at Koobi Fora, Kenya. Though it possesses some morphologies functionally linked to bipedality, such as an expanded metaphysis, it also possesses a valgus tilt to the ankle. We test the competing hypotheses that the KNM‐ER 2596 tibia is from a cercopithecoid, a non‐human hominoid, or a pathological hominin. A survey of the orthopaedic literature and a comparative study of modern human and non‐human primate tibiae support the hypothesis that KNM‐ER 2596 is from a hominin. In order to investigate the non‐phylogenetic causes of valgus ankle, we examined human skeletal tibiae with valgus tilt secondary to fracture of the distal fibula. Untreated breaks of the lower third portion of the fibula during childhood can result in a valgus tilt to the distal tibia and occasionally other peculiar morphologies found in the KNM‐ER 2596 tibia such as a superoinferiorly atrophied medial malleolus. The morphology of this tibia is incompatible with hypotheses that it is from a cercopithecoid or a hominoid, and instead, we suggest that KNM‐ER 2596 belonged to a hominin that may have suffered a fracture of the lower left fibula as a juvenile. Copyright © 2010 John Wiley & Sons, Ltd.
Zum Bifurkationsverhalten stochastischer Systeme
Authors: Cichon Martin , Wedig Walter
Published: June 2010

Untersucht werden nichtlineare stochastisch parametererregte Systeme mit Berechnung stationärer Verteilungsdichten durch Lösung der zugehörigen Fokker‐Planck‐Kolmogorow‐Gleichungen (FPK).

Die Lösung kann nur in wenigen Sonderfällen exakt analytisch angegeben werden, andernfalls sind geeignete Methoden zur analytischen Näherung erforderlich. Die so erhaltenen Verteilungsdichten werden mit denjenigen aus Monte Carlo Simulationen verglichen und dienen zusätzlich der physikalischen Deutung der Ränder.
Adaptive finite element procedures for elastoplastic problems at finite strains
Authors: Koch A. , Miehe C.
Published: June 2010

A major difficulty in the context of adaptive analysis of geometrically nonlinear problems is to provide a robust remeshing procedure that accounts both for the error caused by the spatial discretization and for the error due to the time discretization. For stability problems, such as strain localization and necking, it is essential to provide a step–size control in order to get a robust algorithm for the solution of the boundary value problem. For this purpose we developed an easy to implement step–size control algorithm. In addition we will consider possible a posteriori error indicators for the spatial error distribution of elastoplastic problems at finite strains. This indicator is adopted for a density–function–based adaptive remeshing procedure. Both error indicators are combined for the adaptive analysis in time and space. The performance of the proposed method is documented by means of representative numerical examples.
Fitting Yield Curve Models Using the Kalman Filter
Authors: Walther B. , May A. , Fischer T.
Published: June 2010

We consider several stochastic interest rate models relying on the classes of Gaussian and square root processes. In particular, we introduce both, the Vasicek and the Cox‐Ingersoll‐Ross model, with k factors. Kalman filter methods are applied in order to estimate the parameters of these models. A detailed empirical analysis based on data from the German debt securities market is performed. The models are compared with respect to the number of factors and the different model classes. As a result, we suggest the application of the Vasicek model with at least two factors and the Cox‐Ingersoll‐Ross model with two factors.
Enhancement of a hyperbranched charring and foaming agent on flame retardancy of polyamide 6
Authors: Ke Chenhao , Li Juan , Fang Keyi , Zhu Qiliang , Zhu Jin , Yan Qing
Published: June 2010

A hyperbranched polyamine was prepared using an A2 + B3 approach. It acted as a hyperbranched charring and foaming agent (HCFA) in combination with ammonium polyphosphate (APP) to form a new intumescent flame retardant (IFR) system for polyamide 6 (PA6). Effect of HCFA on flame retardant and thermal degradation properties of IFR‐PA6 was investigated by limiting oxygen index (LOI), UL‐94 vertical burning, cone calorimeter, and thermogravimetric analysis (TGA) tests. The IFR system presented the most effective flame retardancy in PA6 when the weight ratio of APP to HCFA was 2:1. The LOI value of IFR‐PA6 could reach 36.5 with V‐0 rating when the IFR loading was 30 wt%. Even if the loading decreased to 25 wt%, IFR‐PA6 could still maintain V‐0 rating with an LOI value of 31. TGA curves indicated that APP would interact with both PA6 and HCFA in PA6/APP/HCFA composite under heating. The interaction between APP and HCFA improved the char formation ability of IFR system and then much more char was formed for PA6/APP/HCFA composite than for PA6/APP. Therefore, better flame retardancy was achieved. Moreover, the structure and morphology of char residue were studied by Fourier transform infrared (FTIR), X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results indicated that compact and foaming char layer containing P‐O‐C structure was formed for PA6/APP/HCFA system during combustion. Copyright © 2010 John Wiley & Sons, Ltd.
Nitride semiconductors as terahertz sources based on spontaneous and piezoelectric polarization
Authors: Metcalfe Grace D. , Shen Hongen , Wraback Michael , Hirai Asako , Koblmüller Gregor , Gallinat Chad S. , Speck James S.
Published: June 2010

We investigate the effects of internal polarization‐related drift and diffusion on the emitted THz radiation from m ‐plane (1$ \bar 1 $00), a ‐plane (11$ \bar 2 $0), and c ‐plane (0001) nitride semiconductors. Enhanced THz radiation is observed from c ‐plane InN/InGaN multiple quantum wells as compared to c ‐plane bulk InN at 800 nm excitation wavelength. THz generation in the quantum well structure is due to surface normal transport in electric fields due to the termination of spontaneous and piezoelectric polarization at the well/barrier interfaces. From high stacking fault density nonpolar GaN, we observe further enhanced THz emission as compared to stacking fault free m ‐plane GaN. THz generation from the high stacking fault density m ‐plane GaN is attributed to in‐plane transport in built‐in fields due to stacking fault‐terminated internal polarization. A similar effect is observed in m ‐plane as well as a ‐plane InN. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimizing performance to achieve multi‐terahertz operating frequencies in pseudomorphic HEMTs
Authors: Akis R. , Faralli N. , Goodnick S. M. , Ferry D. K. , Saraniti M.
Published: June 2010

High‐electron mobility transistors (HEMTs) are important for high frequency applications, and they now operate in the range of several hundred GHz for the cut‐off frequency, fT and even higher for the maximum frequency of oscillation, fmax. To study the question of how much higher these frequencies can be pushed, we have used a full‐band, cellular Monte Carlo transport program to study scaled pseudomorphic HEMTs and their response at high frequency. Building on a previous study on fT, we have obtained the unilateral power gain for gate lengths ranging from 10 to 50 nm, extracted the corresponding fmax's and extrapolated the results to determine an ultimate frequency limit for the 300 nm long device shown here.. We find that fmax can exceed 4 THz, ∼25% higher than the limit for fT that was previously obtained. We also examine the effect of varying the gate to channel spacing has on the operation of these devices. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tunneling current of GaAs ultrashallow sidewall n+p+n+ and p+n+in+ structure prepared by area‐selective molecular layer epitaxy
Authors: Ohno Takeo , Oyama Yutaka
Published: June 2010

Sidewall n+p+n+ and p+n+in+ structures were fabricated by area‐selective molecular layer epitaxy of GaAs, and electrical evaluation was carried out on the structures by J ‐V measurement. In the n+p+n+ structure, tunneling current decreased as the thickness of the p+ layer increased. An Esaki peak was also observed when the p+ layer was thicker than the depletion layer. The J ‐V characteristic of the p+n+in+ structure depended on the thickness of the n+ layer, and its curve at the reverse bias shifted to the low voltage side when the n+ layer became thick. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Recent advances in Ge/Si PIN and APD photodetectors
Authors: Bowers John E. , Ramaswamy Anand , Dai Daoxin , Zaoui Wissem Sfar , Kang Yimin , Yin Tao , Morse Mike
Published: June 2010

Photodetectors on a Si platform are important because of the opportunity to manufacture literally millions of photodetectors per wafer and because the use of a mature CMOS (Complementary Metal‐Oxide‐Semiconductor) process results in low cost and high uniformity. In this paper, we review recent results on Ge‐Si‐based PIN‐type photodetectors and avalanche photodetectors (APD). We show several exciting advantages of SiGe photodetectors namely, the higher thermal conductivity of Si and Ge, resulting in higher power capability, and the lower k factor, resulting in higher gain bandwidth products in APDs (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Equivalent circuit modeling of triple‐barrier resonant tunneling diodes taking nonlinear quantum inductance and capacitance into account
Authors: Asakawa Kiyoto , Naoi Mamoru , Iki Yuichi , Shinada Masaaki , Suhara Michihiko
Published: June 2010

Focusing on compound semiconductor triple‐barrier (or coupled‐quantum well) resonant tunneling diodes (TBRTD), equivalent circuit topology and elements are expressed in terms of negative quantum inductance (LQ) and quantum capacitance (CQ) as well as negative differential conductance G. The circuit model is theoretically derived on the basis of rate equation approach and validity of the model was experimentally confirmed by impedance measurement up to 30 GHz and nonlinear bias‐voltage‐dependent. LQ and CQ were evaluated with electron quasi‐lifetime and escape time as tentative fitting parameters in the particular In0.52Al0.48As/In0.53Ga0.47As TBRTD grown by MBE. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Insertion loss and linearity of III‐nitride microwave switches
Authors: Deng Jianyu , Yang Jinwei , Hu Xuhong , Gaska Remis , Khan Bilal , Simin Grigory , Shur Michael
Published: June 2010

We report the insertion loss and linearity characteristics of novel microwave switches based on III‐Nitride heterostructure field‐effect transistors (HFETs) and Metal‐Oxide‐Semiconductor HFETs (MOSHFETs). The high mobility and large sheet carrier density make nitride‐based microwave switches ideal candidates for high power, low loss and high linearity microwave switching applications. The demonstrated SPDT switch achieved the third order intermodulation power of ‐68 dBm for 250 micron devices at 1 GHz and 10 dBM input power and the extrapolated IP3 of >80 dBm with <0.25 dB insertion loss and >35 dB isolation for 2GHz operation for 3mm devices. Further improvements of the insertion loss and linearity are expected from new material and contact development, which will achieve lower 2DEG sheet resistance and contact resistance. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nuclear spin polarization and relaxation probed by spin phase transition peak
Authors: Watanabe S. , Fauzi M. H. , Kumada N. , Hirayama Y.
Published: June 2010

We perform resistively‐detected nuclear‐spin relaxation measurements by using the spin phase transition (SPT) peak in the fractional quantum Hall system at the flling factor ν = 2/3. We investigate nuclear spin relaxation for several electronic systems under a spatially inhomogeneous nuclear spin polarization.

When Skyrmions are introduced in the ground state, the position of the SPT peak shifts to higher magnetic feld. This result indicates that Skyrmions relax nuclear spins polarized anti‐parallel to the external magnetic feld more effectively than those parallel to the magnetic feld. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High efficiency violet to blue light emission in porous SiC produced by anodic method
Authors: Nishimura T. , Miyoshi K. , Teramae F. , Iwaya M. , Kamiyama S. , Amano H. , Akasaki I.
Published: June 2010

Porous fluorescent (f‐) SiC containing N and B was produced by anodic oxidation. The average crystal size can be controlled by adding K2S2O8 as an oxidant to dilute HF solution during the anodic process. With the reduction of the average crystal size of the porous crystal, the PL peak wavelength becomes shorter, and its intensity increases. Such behavior can be explained by the quantum size effect of donor‐acceptor‐pair recombination. Finally, we confirmed the superior fluorescent property of blue light emission in porous f‐SiC crystal (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wurtzite InP nanowire arrays grown by selective area MOCVD
Authors: Chu Hyung‐Joon , Yeh Ting‐Wei , Stewart Lawrence , Dapkus P. Daniel
Published: June 2010

InP nanowires are a unique material phase because this normally zincblende material forms in the wurtzite crystal structure below a critical diameter owing to the contribution of sidewalls to the total formation energy. This may allow control of the carrier transport and optical properties of InP nanowires for applications such as nano scale transistors, lasers and detectors. In this work, we describe the fabrication of InP nanowire arrays by selective area growth using MOCVD in the diameter range where the wurtzite structure is formed. The spatial growth rate in selective area growth is modeled by a diffusion model for the precursors. The proposed model achieves an average error of 9%. Electron microscopy shows that the grown InP nanowires are in the wurtzite crystal phase with many stacking faults. The threshold diameter of the crystal phase transition of InP nanowires is larger than the thermodynamic estimation. In order to explain this tendency, we propose a surface kinetics model based on a 2×2 reconstruction. This model can explain the increased tendency for wurtzite nanowire formation on InP (111)A substrates and the preferred growth direction of binary III‐V compound semiconductor nanowires. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigating the effect of aqueous extract of Chicorium intybus L. leaves on offspring sex ratio in rat
Authors: Behnam‐Rassouli Morteza , Aliakbarpour Ali , Hosseinzadeh Hossein , Behnam‐Rassouli Fatemeh , Chamsaz Mahmood
Published: June 2010

A traditional belief in Iranian culture indicates that parental consumption of chicory leaves (Chicorium intybus L.) affects the gender of newborns. The aim of this study was to investigate the effect of aqueous extract of chicory on offspring sex ratio in rat. All rats in experimental groups 1 and 2 were i.p. injected with either 1.0 or 0.7 g/kg body weight (LD50 = 2.244 g/kg) of an aqueous extract of chicory leaves for 30 days at 72 h intervals. The control rats were injected with distilled water in the same manner. After the 8th injection, blood pH, and Na+, K+, Ca2+ and Mg2+ serum levels, were measured in all groups. On day 30, all the rats were mated within and between groups. The results revealed that in comparison with the control group, there were significant increases (p < 0.01) in Na+ and K+ levels, as well as the sex ratio of male to female offspring (10.23%) in experimental group 1. Therefore, it can be concluded that the administration of chicory leaf extract has a significant effect on the sex ratio of the rat offspring. Copyright © 2010 John Wiley & Sons, Ltd.
Molecular ions in cluster bombardment: what clues do the molecular dynamics simulations provide?
Authors: Garrison Barbara J.
Published: June 2010

Molecular dynamics simulations of C60 bombardment of molecular solids suggest that there is a space–time divide between the fragmentation/ion creation process and the ejection of intact molecules via fluid flow physics. This space–time divide leads to the conclusion that molecular ions are preformed prior to ejection. Consequently, to increase the ion yield significantly, the sample must be altered to create more preformed ions. Copyright © 2010 John Wiley & Sons, Ltd.
RIMS analysis of Ca and Cr in Genesis solar wind collectors
Authors: Veryovkin I. V. , Tripa C. E. , Zinovev A. V. , King B. V. , Pellin M. J. , Burnett D. S.
Published: June 2010

RIMS depth profiles have been measured for Cr and Ca in Genesis solar wind collector made from Si and compared to such measurements for ion‐implanted Si reference material. The presence of surface contamination has been shown to be a significant factor influencing the total Ca and Cr fluence measured in the Genesis collectors. A procedure to remove the contaminant signal from these depth profiles using the reference material implanted with a minor isotope demonstrated that 36% of the measured Ca fluence in our Genesis sample comes from terrestrial contamination. Copyright © 2010 John Wiley & Sons, Ltd.
Investigations of secondary ion yield‐enhancing methods in combination
Authors: Heile A. , Muhmann C. , Lipinsky D. , Arlinghaus H. F.
Published: June 2010

Today, several methods are used for secondary ion yield enhancement in time‐of‐flight SIMS (ToF‐SIMS). Some deal with the modification of sample properties, e.g. with monolayer preparation of analytes on metal substrates instead of thick layers, or the metalization of thick‐layer samples with noble metals like gold or silver (MetA‐SIMS). Other methods deal with primary ion beam parameters, e.g. the use of heavier ions or the use of polyatomic instead of monoatomic primary ions.

To investigate the yield‐enhancing effects of the combination of these techniques, (sub‐) monolayers of polyethylene imine, both pristine and metalized with different amounts of gold, were prepared on substrate materials with different stopping powers. For primary ion (PI) bombardment, monoatomic (Ne+, Ar+, Kr+, Xe+, Bi+) and polyatomic (Bin+, Bin++) primary ions were used.

It was found that all techniques used in this contribution increase the secondary ion yield mainly by increasing the stopping power, thereby increasing the amount of PI energy that is deposited near the sample surface (upper 5 nm). Only a small additional yield enhancement was observed when to a yield‐enhancing technique such as polyatomic PI bombardment, which deposits nearly all the PI energy near the surface, another technique was added that is based on the same mechanism for yield enhancement. In other words, the yield enhancement achieved by two enhancement techniques used in combination was much smaller than the product of the yield enhancements obtainable with each technique taken by itself. Copyright © 2010 John Wiley & Sons, Ltd.
Examination of individual nanoparticles with cluster SIMS
Authors: Rajagopalachary S. , Verkhoturov S. V. , Schweikert E. A.
Published: June 2010

We report on nanoprojectile–nanoparticle (NP) interaction when the two collision partners are in the same size range. The experiments involved C60+ accelerated to 26 keV impacting isolated NPs of Ag and Au, both ∼5 nm in diameter, deposited as single layers on an organic substrate. A direct ‘bulls‐eye’ impact of one C60+ onto one NP can result in two processes: fragmentation of the NP and emission of metallic ions, or fragmentation of the NP with fragmentation of substrate molecule followed by recombination and emission of ions. The NPs were covered with self assembled monolayers (SAMs), grazing impacts were readily observed via emission of fragments of SAMs. A mix of Ag and Au NPs showed that emission can be affected by surrounding NPs. Mass spectrometric data from vanishingly small objects reflect size‐dependant processes and effects. Copyright © 2010 John Wiley & Sons, Ltd.
Present State of Development of Laser‐Assisted Wide Angle Three‐Dimensional Atom Probe
Authors: Mayama Norihito , Iwata Tatsuo , Yamashita Chikanori , Ito Satoko , Kaneko Tetsuya , Mikami Sunao , Hanaoka Yuya , Kajiwara Yasuko , Kaito Takashi , Adachi Tatsuya , Hoshino Hitoshi , Nikawa Kiyoshi , Nojima Masashi , Taniguchi Masahiro , Owari Masanori
Published: June 2010

Three‐dimensional atom probe (3DAP) has been developed in our laboratory. In our instrument, the position‐sensitive detector with a diameter of 120 mm following a pair of microchannel plates (MCP) was set up at a distance of 110 mm in front of the apex of the sample. Our original preset‐type sample stage with a local microelectrode was adopted. The pulse laser, or voltage pulse, was used as a trigger for field evaporation. The pulse width of the laser was 180 fs at a wavelength of 1030 nm. The pulse width of the voltage pulse was less than 10 ns. The performance of our instrument was widely tested with the pure tungsten samples fabricated by the electropolishing and focused ion beam methods. The flight path compensation of detected ions, including the small inclination of MCP assembly, led to the good mass resolution approximately 220 (FWHM). By this compensation, we realized full 0.75 sr acceptable angle 3DAP. The detection efficiency of emitted ions was estimated to be about 50% from the three‐dimensional reconstruction images of samples. Copyright © 2010 John Wiley & Sons, Ltd.
Oxygen Influence on the Growth of Thin Hf Films on the 6H‐SiC(0001) Surfaces
Authors: Mazur Piotr , Markowski Leszek
Published: June 2010

Initial stages of Hf growth on the SiC(0001) surface and the influence of annealing on the evolution of microstructure of the formed Hf films were investigated by XPS and scanning tunneling microscopy (STM). The character of XPS spectra and the shifts of the binding energies of Hf 4f, Si 2p, C 1s, O 1s levels, observed with increasing Hf depositions, indicate that even at room temperature a hafnium oxide in the form of HfO2 was created. The registered band bending created at the HfO2/SiC interface is about 0.4 eV. Hafnium tended to grow irregularly with a tendency to form nanocrystalline grains near terraces edges, and preferably on the surface regions not covered by additional graphite carbon layers which together with oxygen were present on the virgin SiC(0001) surface. The grain sizes were sensitive to annealing and efficiently increased during heating the sample at 1100 °C. These surface morphology changes proceeded through merging smaller nanoparticels into clusters. For longer Hf depositions, with average thickness over 10 monolayers, excess carbon segregated and migrated towards the surface, with simultaneous formation of Hf–C and O‐C‐O bonds. Copyright © 2010 John Wiley & Sons, Ltd.
Attenuation lengths in organic materials
Authors: Seah M. P. , Spencer S. J.
Published: June 2010

Measurements are reported for attenuation lengths in overlayers of guanine, poly(styrene), poly(methyl methacrylate) and poly(2‐vinylpyridine) in the energy range 700–1400 eV to evaluate the accuracy of theoretical computations and generic equations. The layers are deposited on gold, either by evaporation and condensation or by spin casting. Measurements are made by X‐ray photoelectron spectroscopy (XPS) for the substrate Au 4f, 4d and 4p peaks as well as the overlayer N 1s peak in guanine and poly(2‐vinylpyridine). These measurements all correlate with the theory of Tanuma, Powell and Penn, to an RMS deviation of 11%. Correlations with the predictions using the generic equation known as TPP‐2M exhibit a poorer RMS deviation of 20%. Use of an ‘average’ organic material for the inelastic mean free paths for the four materials also leads to a 20% RMS deviation. Additional data are also presented for Irganox 1010 that is used, increasingly, as a reference sample for secondary ion mass spectrometry. Comparisons for 5 materials with the Gries G1 formula gives an RMS deviation of 13%, but a small change to interpolate between Gries' classes of organic materials with H/C being around either 1 or 2, leads to a reduced RMS deviation of 10%. This final version, G1‐SS, requiring only the material density and chemical formula, is very simple to use for all organic materials where these data are known or can be estimated. © Crown copyright 2010. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.
D‐SIMS analysis supporting SiOxNy film in‐line metrology
Authors: Budri Thanas , Getchell Donald
Published: June 2010

D‐SIMS is used in conjunctions with in‐line metrology techniques to better monitor SiOxNy films. Different D‐SIMS analytical conditions are chosen in order to properly measure the nitrogen dose and profile since proper evaluation of both characteristics plays a major role on the performance of the device. Copyright © 2010 John Wiley & Sons, Ltd.
Sputtered and laser recrystalized phosphorus‐doped zinc oxide
Authors: Sämann Marc , Eisele Sebastian , Bilger Gerhard
Published: June 2010

Phosphorus‐doped zinc oxide (ZnO:P) films with red phosphorus as dopant were grown in a radio‐frequency target‐to‐intermediate‐target sputtering process. As‐grown ZnO:P films were annealed at 500 °C for relaxing the mechanical strain in the films, and subsequently laser irradiated. X‐ray diffraction and SIMS reveal surface melting of the thin films due to laser irradiation and a subsequent strain relaxation during their recrystalization in (0002) direction. X‐ray photoelectron spectroscopy hints at the formation of stable complexes, such as PZn–2VZn, with phosphorus occupying a zinc site (PZn) and zinc vacancies (VZn). Copyright © 2010 John Wiley & Sons, Ltd.
Investigation of molecular surfaces with time‐of‐flight secondary ion mass spectrometry
Authors: Aoyagi Satoka , Namekawa Koki , Yamamoto Kenichiro , Sakai Kiyotaka , Kato Nobuhiko , Kudo Masahiro
Published: June 2010

TOF‐SIMS is a promising technique for evaluating biodevices due to its ultrahigh surface sensitivity. Since a cluster ion source such as C60+ provides low collision energy per atom, time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) with the cluster ion is useful for detecting the uppermost surface of molecules immobilized on a substrate, and therefore, enables the evaluation of the orientation of these immobilized biomolecules. Effects of TOF‐SIMS with C60+ were investigated in this study. A relatively small protein, lysozyme, and polypeptides having five amino acid residues, Leu‐enkephalin and Met‐enkephalin, were employed as model samples. The protein and the polypeptides were immobilized on aminosilanized‐indium‐tin oxide (ITO) coated glass plates at their N‐terminal residues by covalent bonding. The aminosilanized‐ITO plate without protein or polypeptide was also prepared as a control sample. After freeze‐drying, the samples were measured with TOF‐SIMS using gallium and C60+ cluster ion sources, and then TOF‐SIMS spectra were analyzed to select peaks specific to each biomolecule by a comparison between the samples. As a result, the C60+ primary ion source showed advantages in evaluating biomolecules, because more peaks at a higher mass generated from the biomolecules can be obtained using C60+ than Ga+ or Au3+ as the primary ion source, although no difference was detected between the two polypeptide samples under the current measurement conditions. Copyright © 2010 John Wiley & Sons, Ltd.
Zero‐energy SIMS depth profiling: the role of surface roughness development with XeF2‐based etching
Authors: Vanhove N. , Lievens P. , Vandervorst W.
Published: June 2010

To obtain monolayer depth resolution in the zero‐energy SIMS concept, an almost atomically flat surface during the electron beam‐induced etching (EBIE) is crucial. However, the surface roughness observed with Si EBIE and XeF2 shows the same characteristics as observed during spontaneous etching of Si with XeF2. The subsurface fluorine concentration in a Si EBIE process (even in a mass transport limited regime) can influence the unactivated formation of the SiFx reaction layer as well, and therefore, contribute to observed roughness development. SiO2 EBIE leads to extreme pit formation due to preferential etching of Si at the SiO2/Si interface. In general, preferential etching can deteriorate or enhance the depth resolution as shown on a SiGe epilayer structure. Finally, the capabilities of zero‐energy SIMS are shown on an ultra‐shallow SiGe structure demonstrating a narrow surface transient and a very good depth resolution in the surface region. Copyright © 2010 John Wiley & Sons, Ltd.
Investigation of imaging ToF‐SIMS as a means to study coatings on wood
Authors: Nejad Mojgan , Cooper Paul , Sodhi Rana
Published: June 2010

Measurement of the penetration of coatings into wood may be performed by SEM analysis with OsO4 or other markers used for post‐treatment labeling. However, there are indications that the Os only binds with the uncured components of the resin. Since these are mainly located at the surface of the coating, the use of Os could thus misinterpret the actual penetration of the coatings into the wood surface. Time‐of‐Flight Secondary Ion Mass Spectrometry (ToF‐SIMS) provides a unique means by which the penetration depths of the various components of the coating (resin + pigments) into the wood microstructure can be visualized. This arises from both the high spatial resolution (<100 nm) and high mass resolution achievable with the technique (albeit not at the same time). The latter feature is of importance to resolve different molecular fragments of similar molecular weight which could be needed as markers for the various components in the complex hydrocarbon systems constituting wood and the coating materials, whilst the former is required to ascertain differences in penetration depth of the components.

In this work, imaging ToF‐SIMS spectra are obtained on cross‐sections of coated wood samples using a Bi cluster ion source. Coating distribution is followed by identifying fragments associated more with the coating and with the wood respectively. Sample preparation techniques are of importance and thus results are compared for cross‐sections prepared both by microtoming, as well as by mounting in epoxy resin and polishing. Copyright © 2010 John Wiley & Sons, Ltd.
SIMS quantification of SiGe composition with low‐energy ion beams
Authors: Zhu Zhengmao , Ronsheim Paul , Turansky Andrew , Hatzistergos Michael , Madan Anita , Pinto Teresa , Holt Judson , Reznicek Alexander
Published: June 2010

Systematic SIMS analyses with low‐energy (250 eV ∼1 keV) oxygen, cesium and krypton primary beams have been carried out on a set of fully strained uniform epitaxial Si1−xGex films (x = 5 ∼ 60%), as well as a germanium ion‐implanted silicon standard to investigate the matrix effect under various conditions. It is shown that preferential ion yield enhancement of one matrix component over the other can occur as the result of primary ion incorporation. Through defining a matrix yield factor, this work demonstrated that constant secondary ion yield ratios between Si ion and Ge ion over a large concentration range are only valid under some very specific analysis conditions. Emphases were placed on oxygen beam analyses with regard to steady‐state ion yields and surface transients. Both show some unique features only accessible under low‐energy conditions. Copyright © 2010 John Wiley & Sons, Ltd.
Size control of MnZn ferrite nanoparticles and their XAFS spectra
Authors: Moro Yuki , Katayanagi Hikaru , Kimura Shinji , Shigeoka Daiki , Hiroki Tomoyuki , Mashino Toshiyuki , Ichiyanagi Yuko
Published: June 2010

MnZn ferrite (Mn0.5Zn0.5Fe2O4) nanoparticles in amorphous SiO2 were prepared using the chemical wet method. On the basis of the X‐ray diffraction peaks, the particle sizes were estimated to be between 17 and 41 nm, depending on the flow rate of Ar gas. The particle size increased with the flow rate of Ar gas. From magnetization measurements, the magnetization values varied in accordance with the conditions of Ar gas. To clarify the electronic state of metal ions of nanoparticles, X‐ray absorption fine structure (XAFS) measurements were performed, and the results were compared with X‐ray diffraction patterns. Copyright © 2010 John Wiley & Sons, Ltd.
Comparison of Reprogramming Efficiency Between Transduction of Reprogramming Factors, Cell–Cell Fusion, and Cytoplast Fusion
Authors: Hasegawa Kouichi , Zhang Peilin , Wei Zong , Pomeroy Jordan E. , Lu Wange , Pera Martin F.
Published: June 2010

Reprogramming human somatic cells into pluripotent cells opens up new possibilities for transplantation therapy, the study of disease, and drug screening. In addition to somatic cell nuclear transfer, several approaches to reprogramming human cells have been reported: transduction of defined transcription factors to generate induced pluripotent stem cell (iPSC), human embryonic stem cell (hESC)–somatic cell fusion, and hESC cytoplast–somatic cell fusion or exposure to extracts of hESC. Here, we optimized techniques for hESC–human fibroblast fusion and enucleation and cytoplast fusion, and then compared the reprogramming efficiency between iPSC generation, cell-fusion and cytoplast-fusion. When compared with iPSC, hESC-fusion provided much faster and efficient reprogramming of somatic cells. The reprogramming required more than 4 weeks and the efficiency was less than 0.001% in iPSC generation, and it was less than 10 days and more than 0.005% in hESC-fusion. In addition, fusion yielded almost no partially reprogrammed cell colonies. However, the fused cells were tetraploid or aneuploid. hESC cytoplast fusion could initiate reprogramming but was never able to complete reprogramming. These data indicate that in cell fusion, as in nuclear transfer, reprogramming through direct introduction of a somatic nucleus into the environment of a pluripotent cell provides relatively efficient reprogramming. The findings also suggest that the nucleus of the host pluripotent cell may contain components that accelerate the reprogramming process.
Epithelial-Mesenchymal Transition-Derived Cells Exhibit Multilineage Differentiation Potential Similar to Mesenchymal Stem Cells
Authors: Battula Venkata Lokesh , Evans Kurt William , Hollier Brett George , Shi Yuexi , Marini Frank C. , Ayyanan Ayyakkannu , Wang Rui-yu , Brisken Cathrin , Guerra Rudy , Andreeff Michael , Mani Sendurai A.
Published: June 2010

The epithelial-to-mesenchymal transition (EMT) is an embryonic process that becomes latent in most normal adult tissues. Recently, we have shown that induction of EMT endows breast epithelial cells with stem cell traits. In this report, we have further characterized the EMT-derived cells and shown that these cells are similar to mesenchymal stem cells (MSCs) with the capacity to differentiate into multiple tissue lineages. For this purpose, we induced EMT by ectopic expression of Twist, Snail, or transforming growth factor-β in immortalized human mammary epithelial cells. We found that the EMT-derived cells and MSCs share many properties including the antigenic profile typical of MSCs, that is, CD44+, CD24−, and CD45−. Conversely, MSCs express EMT-associated genes, such as Twist, Snail, and mesenchyme forkhead 1 (FOXC2). Interestingly, CD140b (platelet-derived growth factor receptor-β), a marker for naive MSCs, is exclusively expressed in EMT-derived cells and not in their epithelial counterparts. Moreover, functional analyses revealed that EMT-derived cells but not the control cells can differentiate into alizarin red S-positive mature osteoblasts, oil red O-positive adipocytes and alcian blue-positive chondrocytes similar to MSCs. We also observed that EMT-derived cells but not the control cells invade and migrate towards MDA-MB-231 breast cancer cells similar to MSCs. In vivo wound homing assays in nude mice revealed that the EMT-derived cells home to wound sites similar to MSCs. In conclusion, we have demonstrated that the EMT-derived cells are similar to MSCs in gene expression, multilineage differentiation, and ability to migrate towards tumor cells and wound sites.
How can the current CDM deliver sustainable development?
Authors: Bumpus Adam G. , Cole John C.
Published: June 2010

The two aims of the clean development mechanism (CDM) were to reduce greenhouse gases cost effectively and contribute to sustainable development (SD) in developing countries. So far, however, SD components of the mechanism have been questionable. In this opinion article, we argue for a more theoretically informed engagement with the CDM that could be empowered through the better provision of transparent and clear information in the project implementation processes. Drawing on our work in Latin America, we concur with other authors that the CDM as it stands does not ‘deliver’ SD, but that improved information and a research agenda that focuses on the multi‐level political economy of project‐based CDM could assist in the mechanism delivering on multiple forms of SD in local contexts. Copyright © 2010 John Wiley & Sons, Ltd.

This article is categorized under:

Climate and Development > Decoupling Emissions from Development

Policy and Governance > International Policy Framework
Synthesis and Structure of Ag4Te(SO4) – a New Compound Featuring a Silver‐Telluride Framework
Authors: Shestimerova Tatiana A. , Mitiaev Alexander S. , Davliatshin Dmitry I. , Shevelkov Andrei V.
Published: June 2010

Tetrasilver telluride sulfate was obtained as a black air‐stable polycrystalline powder; its structure was determined from X‐ray powder diffraction data. The new compound crystallizes in the cubic space group P213, with the unit cell parameter a = 8.6263(2) Å and Z = 4. The crystal structure of Ag4Te(SO4) is composed of a positively charged silver‐telluride three‐dimensional framework, in which the isolated tetrahedral SO42– anions are embedded. The framework features an irregular coordination for tellurium atoms with a coordination number of six and manifold Ag–Ag contacts ranging from 2.99 to 3.14 Å. The distortion of the SO42– anion as well as the interactions within the framework and between the framework and the SO42– anions are analyzed with the help of the structural data, vibrational spectra, and band structure calculations.
Phosphane Copper(I) Dicarboxylates: Synthesis and Their Potential Use as Precursors for the Spin‐coating Process in the Deposition of Copper
Authors: Jakob Alexander , Rüffer Tobias , Ecorchard Petra , Walfort Bernhard , Körbitz Kathrin , Frühauf Swantje , Schulz Stefan E. , Gessner Thomas , Lang Heinrich
Published: June 2010

Dicopper dicarboxylates [(R3P)mCuXCu(PR3)m] (5a, X = O2CCO2, R = Ph, m = 2; 5b, X = O2CCO2, R = nBu, m = 3) were prepared by treatment of [Cu2O] (1a) with HO2CCO2H (2a) in presence of PR3 (4a, R = Ph; 4b, R = nBu). A further synthesis approach to mono‐ and dicopper dicarboxylates is given using an electrolysis cell equipped with Cu electrodes and charged with acids H2X and phosphanes R3P. Without addition of a base mononuclear [(nBu3P)mCuXH] (6a, m = 3, XH = O2CCO2H, 6b, m = 3, XH = O2CCH2CO2H, 6c, m = 3, XH = O2CCH2CH2CO2H, 6d, m = 2, XH = O2C‐2‐C5H4N‐6‐CO2H) was formed, whereas in presence of NEt3 (3), the dicopper systems [(R3P)mCuXCu(PR3)m] (5a, X = O2CCO2, R = Ph, m = 2; 5b, X = O2CCO2, R = nBu, m = 3; 5c, X = O2CCH2CO2, R = nBu, m = 3; 5d, X = O2CCH2CH2CO2, R = nBu, m = 3; 5e, X = O2C‐2‐C5H4N‐6‐CO2, R = nBu, m = 3) were produced. When 6a reacted with [(tmeda)Zn(nBu)2] (7), trimetallic [(tmeda)Zn((nBu3P)3CuO2CCO2)2] (8) was accessible. In this heterobimetallic complex the Zn(tmeda) unit spans two CuO2CCO2 entities. The molecular structures of 5a, 6a and 6d in the solid state were determined by single X‐ray structure analysis. Complexes 5a and 6a are monomers, whereas 6d creates in the solid state a linear open chain coordination polymer by hydrogen bridge formation. Characteristic for 6d is the somewhat distorted trigonal bipyrimidal arrangement around the copper atom with the nBu3P ligands in axial and the C5H3NCO2H oxygen and nitrogen atoms in equatorial positions. In 5a the oxalate connectivity binds in a μ‐1,2,3,4 fashion being part of a planar Cu2(oxalate) core. TG studies of several mono‐ and dicopper dicarboxylates were carried out. Release of the PR3 ligands is recognized and the remaining Cu‐(di)carboxylate unit decomposes to afford elemental copper and CO2. The deposition of copper onto pieces of PVD‐Cu oxidized silicon wafers by applying the spin‐coating process and using 5c and 5d as precursors is discussed.
Magnetic Properties of Mixed Ligand NiII2 and NiII4 Complexes Composed of Macrocyclic Hexaamine‐Dithiophenolato and Bridging Tetrazolato Ligands
Authors: Lach Jochen , Voitekhovich Sergei V. , Lozan Vasile , Gaponik Pavel N. , Ivashkevich Oleg A. , Lincke Jörg , Lässig Daniel , Kersting Berthold
Published: June 2010

The magnetic properties of the dinuclear and tetranuclear nickel(II) tetrazolato complexes [Ni2L(RCN4)][BPh4] (R = H (4), Me (5), Ph (6)) and [(Ni2L)2(1,4‐(CN4)2‐C6H4)][BPh4]2 (7), where (L)2– represents a 24‐membered macrocyclic N6S2 supporting ligand, are reported. Analysis of temperature‐dependent magnetic susceptibility measurements over the temperature range from 2 to 300 K revealed the presence of weak ferromagnetic exchange interactions between the NiII ions in the binuclear [Ni2L(μ‐L′)]+ subunits with magnetic exchange coupling constant values of J1 = 13.5 cm–1 for 4, J1 = 20.0 cm–1 for 5, J1 = 19.2 cm–1 for 6, and J1 = 15.2 cm–1 for 7 (H = –2JS1S2). The exchange coupling J2 across the bistetrazolato bridge in 7 is less than 0.1 cm–1, which suggests that no significant interdimer coupling occurs in this compound. The synthesis and crystal structure of the new complex 7·2MeCN is also reported.
Synthesis of Rare Earth (Oxo)nitridocarbonates by Employment of Supercritical Carbon Dioxide, Single‐source Precursor, Solid‐State, and Ion Exchange Reactions
Authors: Pagano Sandro , Zeuner Martin , Baisch Ulrich , Schnick Wolfgang
Published: June 2010

Novel synthetic approaches to rare earth nitrido‐ and oxonitridocarbonates are described. Dioxy mono‐carbodiimides (Ln2O2CN2) from the second half of the lanthanide series are accessible by insertion of supercritical CO2 into lanthanide amido compounds (e.g. [(Cp2ErNH2)2]), forming single‐source precursors. Ammonolyses of amorphous carbamate compounds afford phase pure Ln2O2CN2, which are also accessible via the crystalline carbamate compound [Ln2{μ‐η1:η2‐OC(OtBu)NH}Cp4] (Ln = Y, Ho, Er, Yb). Urea complexes and homoleptic cyanates of europium and strontium were synthesized by solid‐state reaction of urea with the respective metals. Subsequent thermal treatment (160–240 °C) results in formation of solvent‐free homoleptic cyanates. The Eu2+‐doped compounds [Sr(OCN)2(urea)]:Eu2+ and Sr(OCN)2:Eu2+ as well as the respective pure europium compounds exhibit strong broad band emissions due to 4f65d1–4f7 transitions in the bluish green region. Furthermore, rare earth dicyanamides Ln[N(CN)2]3·2H2O as well as Ln[N(CN)2]3 (with Ln = Eu, Tb, and Gd) were prepared by ion exchange in aqueous solution, followed by evaporation of the solvent at room temperature. Condensed nitridocarbonates such as rare earth tricyanomelaminates [NH4]Ln[HC6N9]2[H2O]7·H2O (Ln = La–Nd, Sm–Dy) were obtained through ion exchange reactions. The luminescence properties of the europium and terbium dicyanamides as well as the tricyanomelaminates have been explored in detail.
Insight in Structures of Superbulky Metallocenes with the CpBIG Ligand: Theoretical Considerations of Decaphenyl Metallocenes
Authors: Kuchenbecker Dennis , Harder Sjoerd , Jansen Georg
Published: June 2010

The structures of a series of decaphenyl metallocenes (Ph5Cp)2M, which model superbulky metallocenes, are calculated by means of density functional theory including a semi‐empirical correction for dispersion interactions (DFT+D). Through a detailed investigation of the calcocene it is shown that the interactions between the phenyl substituents of the two cyclopentadienyl ligands lead to a preference of S10 symmetrical structures and that dispersion interactions contribute to the overall stability of superbulky metallocenes. Whereas the Ph substituents of the two ligands bend away from each other with standard DFT, inclusion of the dispersion correction reproduces the experimentally observed slight inclination towards each other. The experimentally observed linear correlation between the out‐of‐plane bending angle of the phenyl substituents and the size of the metal atom M (M = Fe, Ni, Cr, W, Ca, Yb, Sn, Sm, Sr, Ba) is also confirmed at the DFT+D level.
Mitochondrial medicine: to a new era of gene therapy for mitochondrial DNA mutations
Authors: Cwerman‐Thibault Hélène , Sahel José‐Alain , Corral‐Debrinski Marisol
Published: June 2010

Mitochondrial disorders can no longer be ignored in most medical disciplines. Such disorders include specific and widespread organ involvement, with tissue degeneration or tumor formation. Primary or secondary actors, mitochondrial dysfunctions also play a role in the aging process. Despite progresses made in identification of their molecular bases, nearly everything remains to be done as regards therapy. Research dealing with mitochondrial physiology and pathology has >20 years of history around the world. We are involved, as are many other laboratories, in the challenge of finding ways to fight these diseases. However, our main limitation is the scarcety of animal models required for both understanding the molecular mechanisms underlying the diseases and evaluating therapeutic strategies. This is especially true for diseases due to mutations in mitochondrial DNA (mtDNA), since an authentic genetic model of mtDNA mutations is technically a very difficult task due to both the inability of manipulating the mitochondrial genome of living mammalian cells and to its multicopy nature. This has led researchers in the field to consider the prospect of gene therapy approaches that can roughly be divided into three groups: (1) import of wild‐type copies or relevant sections of DNA or RNA into mitochondria, (2) manipulation of mitochondrial genetic content, and (3) rescue of a defect by expression of an engineered gene product from the nucleus (allotopic or xenotropic expression). We briefly introduce these concepts and indicate where promising progress has been made in the last decade.