bluuebunny/crossref_metadata_2025_split huggingface dataset:
All II‐VI magnetic resonant tunneling diodes as voltage controlled spin filters
Authors: Supp D. , Slobodskyy T. , Slobodskyy A. , Gould C. , Schmidt G. , Molenkamp L. W. 
Published: June 2007

AbstractWe have fabricated resonant tunneling diodes based ZnSe/(Zn,Be)Se with Mn added in the quantum well. The I/V characteristics show a clear resonance which, when an external magnetic field is applied splits into two separate peaks. The splitting can be explained by a giant Zeeman splitting of the quantized levels in the well and can be fitted by a simple model using two independent spin channels. The experiments demonstrate resonant transport through spin split levels and indicate that the device may be suitable as a voltage controlled spin filter. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
In‐situ X‐ray diffraction during epitaxial growth of ZnSe‐based heterostructures on (001)GaAs
Authors: Benkert Andreas , Schumacher Claus , Neder Reinhard B. , Brunner Karl 
Published: June 2007

AbstractWe developed a real‐time in‐situ X‐ray (RIX) diffraction technique for the detailed layer characterisation during epitaxial deposition of ZnSe‐based alloys on (001)GaAs substrates. A conventional molecular beam epitaxy chamber was equipped with a Cu X‐ray tube. The 113 reflection of the deposited structure is detected in static geometry by a CCD and is immediately analyzed in terms of strain, composition, thickness and strain relaxation behavior of the deposited layer. The in‐situ monitoring of ZnCdSe layers reveals a delay of heteroepitaxial growth start on GaAs, a gradual layer degradation due to dislocation formation, and a critical thickness for plastic relaxation which depends on the Cd content, consistent with an energy‐balance model. ZnCrSe alloy layers can be deposited with Cr content up to 2% at low substrate temperature TS = 210 °C. The layers appear to be epitaxial alloys with good quality, but a broadening of the Bragg peaks without a significant plastic relaxation is observed. Epitaxial growth and layer properties are studied as function of deposition conditions. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic structure of zinc‐blende MnTe within the GW approximation
Authors: Fleszar A. , Potthoff M. , Hanke W. 
Published: June 2007

AbstractUsing the local spin‐density approximation (LSDA) and the (non self‐consistent) GWapproach, the (quasiparticle) band structure is calculated forMnTe in zinc‐blende geometry. Different parameters characterizing the electronic structure are computed for an antiferromagnetic and the ferromagnetic phase and compared with the experiment. The strong Hubbard‐type repulsion on the Mn‐3d orbitals and the p ‐d hybridization are seen to be responsible for substantial defects found in the LSDA picture. It is discussed to which extent these can be improved upon by means of the GW approach. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of lattice dynamics and magnetic properties of II‐VI layers and interfaces by Raman spectroscopy
Authors: Geurts J. , Bass U. , Lentze M. , Wagner V. 
Published: June 2007

AbstractWe report on the lattice dynamics of abrupt and intermixed interfaces of II‐VI‐layers and quantum dots, studied by Raman spectroscopy from embedded CdSe monolayers in BeTe, and from CdSe quantum dots in ZnSe. It is demonstrated that the best CdSe/BeTe interface quality is achieved, when CdTe interface bonds are applied. The corresponding vibration modes are described very well by density functional calculations, and they also reveal the onset of CdSe quantum dot formation. For these interfaces, the reduced symmetry (i.e. non‐equivalence of [011] and [01‐1] in‐plane axes) is analyzed from the polarization dependent Raman scattering intensity. Similar results are presented for Raman scattering from Te surface dimers on BeTe(100). Furthermore, the (s,p)‐d exchange energy of diluted magnetic II‐VI semiconductors is studied by spin flip Raman spectroscopy. For n‐doped (Zn,Mn)Se, a doping‐induced reduction of the exchange energy and enhancement of the spin relaxation time T is demonstrated. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical characterization of thermally annealed self‐assembled ZnCdSe quantum dots
Authors: Margapoti E. , Worschech L. , Mahapatra S. , Slobodskyy T. , Tribu A. , Aichele T. , Brunner K. , Schmidt G. , Molenkamp L. W. , André R. , Kheng K. , Bougerol C. , Forchel A. 
Published: June 2007

AbstractPost‐growth thermal annealing, (TA) in combination with mesa‐fabrication technologies, was applied to tune the shape and material composition of ZnCdSe quantum dots (QDs). The QDs were studied by means of photoluminescence spectroscopy. An enhancement of QD homogeneity due to TA is demonstrated by substantial narrowing of the QD emission, observed from large QD ensembles. Energy shifts of QD luminescence, exceeding 100 meV after thermal annealing, were observed. Tracing the evolution of single exciton lines, the activation energy of an enhanced diffusion process in small mesas was determined. Distinct changes of quantum dot symmetries were identified through a reduction of the exciton fine structure splitting. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experiments on single levitated particles: a novel approach for investigations of electronic properties of structured II‐VI‐semiconductor nanoparticles in selected environments
Authors: Graf C. , Lewinski R. , Dembski S. , Langer B. , Rühl E. 
Published: June 2007

AbstractA novel approach for investigations of the electronic structure of II‐VI semiconductor nanoparticles in selected environments is presented. CdSe/ZnS core shell nanoparticles are dispersed in a liquid non‐volatile siloxane graft/block copolymer and injected in an electrodynamic trap, where a single liquid microdroplet is stably stored under ultra high vacuum conditions. In this way, it is possible to investigate quantum dots by soft X‐ray spectroscopies in a liquid environment, which is not influenced by any outer surface. NEXAFS spectra of stored nanoparticles were recorded at the Zn 2p‐, S 2p‐, and Cd 3d‐edge by measuring X‐ray excited optical luminescence or the element‐selective charging current of single, trapped microdroplets. The spectra are compared to those of similar CdSe/ZnS nanoparticles, which are dispersed in a controlled way in solid silica colloids as well as to those of matrix materials. An analysis of the data reveals that the electronic structure of the ZnS shell is significantly influenced by the outer functionalization and the dispersive media whereas the electronic structure of the core is shown to be independent from the surroundings. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamical symmetries and quantum transport through nanostructures
Authors: Kiselev M. N. 
Published: June 2007

AbstractWe discuss the manifestation of dynamical symmetries in quantum transport through nanostructures. The dynamical symmetry SO (4) manifested in the singlet‐triplet excitations is shown to be responsible for several exotic effects in nano‐devices: non‐equilibrium Kondo effect in T‐shape Double Quantum Dots, phonon‐induced Kondo effect in transition‐metal‐organic complexes, Kondo shuttling in Nano‐Electromechanical Single Electron Transistor. We consider the interplay between charge U (1) and spin SU (2) fluctuations in the vicinity of Stoner instability point and a non‐monotonic behavior of a Tunneling Density of States in metallic quantum dots. The experiments showing important role of dynamical symmetries in nanostructures are briefly reviewed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure and relaxation effects in thin semiconducting films and quantum dots
Authors: Kumpf Christian , Stahl Andreas , Gierz Isabella , Schumacher Claus , Mahapatra Suddhasatta , Lochner Florian , Brunner Karl , Schmidt Georg , Molenkamp Laurens W. , Umbach Eberhard 
Published: June 2007

AbstractThe structural properties of two epitaxial model systems were investigated, NiMnSb thin films on a (In,Ga)As/InP(001) substrate and free‐standing CdSe quantum dots on a ZnSe(001) surface. For the first system the influence of surface‐oxidation on the relaxation behavior of the entire film was investigated by a comparison of capped and uncapped samples. We found that the critical thickness for pseudomorphic growth is more than doubled by the protective capping layers. For the second system under investigation a determination of the size and shape of the quantum dots was performed. They have a cylindrical shape with an almost constant diameter of ≈10 nm and a height of about 2 nm, whereby the lowermost region widens up to about 14 nm. The entire quantum dots are strained. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Angle‐resolved photoemission on ZnSe(001): determination of conduction band quasiparticle shifts
Authors: Fleszar A. , Hanke W. , Weigand W. , Kumpf C. , Heske C. , Umbach E. , Plucinski L. , Johnson R. L. 
Published: June 2007

AbstractAngle‐resolved photoemission measurements have been performed on the ZnSe(001) surface and analyzed using ab initio LDA and GW calculations. The key point of this analysis consists of a comparison between measured and calculated photoemission spectra. We suggest that matching the main dispersive peaks in experiment and theory leads to the determination of quasiparticle shifts of the conduction bands relative to their LDA position. It is found that these experimental shifts largely exceed the calculated GW‐quasiparticle shifts leading to an increased free‐electron‐like character of the photoemission final states as compared to the LDA calculations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Movement and pinning of dislocations in SiC
Authors: Eberlein T. A. G. , Jones R. , Blumenau A. T. , Öberg S. , Briddon P. R. 
Published: June 2007

AbstractSiC bipolar devices show a degradation under forward‐biased operation due to the formation and rapid propagation of stacking faults in the active region of the device. It is believed that the observed rapid stacking fault growth is due to a recombination‐enhanced dislocation glide (REDG) mechanism at the bordering partial dislocations having either Si or C core atoms. We investigated the effect of charge on the dislocation kinks and found that only silicon kinks have a deep filled band above the valence band. Trapping of holes into this band permits dislocation glide at room temperature. This mechanism is distinct from REDG as it requires only holes to be trapped at a Si partial and not in addition electrons in stacking fault states. We furthermore looked at the pinning of dislocations by nitrogen and boron and found a strong pinning of the C core by N and of the Si core by B. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantitative Structure–Activity Relationship Study of Binding Affinity of Azole Compounds with CYP2B and CYP3A
Authors: Itokawa Daisuke , Nishioka Tomoki , Fukushima Junji , Yasuda Tomoyo , Yamauchi Aiko , Chuman Hiroshi 
Published: June 2007

AbstractAn azole compound is considered to be a good probe for analyzing the binding affinity with various cytochrome P450 (CYP) proteins because of its coordination ability regarding the heme iron in the proteins. Eighteen azole compounds including commercial fungicides were examined for their binding to rat liver microsomal CYP2B and CYP3A using a type II spectral change. The binding affinities determined were analyzed in relation to the molecular properties of the azole compounds. Good correlation with the bilinear model was observed between the binding affinities and the partition coefficient (log P). The model suggested that the optimum log P values of the azole compounds were nearly the same for these two CYPs. The sequence homology of amino acid residues around the substrate recognition site is significantly high between CYP2B and CYP3A. It was reported that sizes of the binding pocket in CYP2B and CYP3A are not much different. These explain why the optimum log P values in the correlation equations for CYP2B and CYP3A was nearly the same.
Doped helium clusters analyzed through quantum chemistry methods
Authors: de Lara–Castells M. P. , Prosmiti R. , López–Durán D. , Delgado–Barrio G. , Villarreal P. , Gianturco F. A. , Jellinek J. 
Published: June 2007

AbstractA quantum‐chemistry‐like methodology developed recently to study molecules solvated in atomic clusters is reviewed, and the results of its application to diatomic molecules immersed in helium clusters are presented and discussed. The methodology is based on treating the atoms of the solvent cluster as the “electrons” and the solvated molecule (“BC”) as a structured “nucleus” of the combined solvent‐solute system. The “electron”‐“electron” and “electron”‐“nucleus” interactions are represented by parametrized two‐body and ab initio three‐body potentials, respectively. The “intranuclear” (intramolecular) energy is mimicked by a parametrized pair potential energy function. The methodology furnishes the wave functions, and thereby it allows for computation of the infrared or Raman spectra of the solvated molecules. The computed spectra are then compared with the measured ones. In agreement with the experimental observations, the computed spectra of the solvated molecule show considerable differences depending on whether the solvent cluster is comprised of pure bosonic (4He), pure fermionic (3He), or both bosonic and fermionic helium atoms. The differences in the spectra are explained in terms of the differences in the spin‐statistics of the solvent clusters. The bosonic vs fermionic nature of the solvent is also reflected in the selection rules. In the case of a polar molecule, the Q‐branch of the spectrum is forbidden when the molecule is solvated in a bosonic cluster, and it becomes allowed when the solvent is a fermionic cluster. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
On‐column tryptic mapping of proteins using metal‐ion‐chelated magnetic silica microspheres by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Li Yan , Yan Bo , Xu Xiuqing , Deng Chunhui , Yang Pengyuan , Shen Xizhong , Zhang Xiangmin 
Published: June 2007

AbstractPeptide mapping analysis, utilizing an easily replaceable and regenerable on‐column enzymatic microreactor with metal‐ion‐chelated adsorption of enzyme on magnetic silica microspheres, combined with matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS), was developed. Firstly, magnetic microspheres of small size and strong magnetism were prepared through solvothermal reaction. Thereafter, by introducing tetraethyl orthosilicate (TEOS), magnetic silica (MS) microspheres were formed. Trypsin could then be immobilized onto the MS microspheres based on the Lewis acid‐base interaction through the divalent cation chelators such as iminodiacetic acid (IDA), which was chemically bound to the microspheres through the introduction of glycidoxypropyltrimethoxysilane (GLYMO). The trypsin‐immobilized MS microspheres were then locally packed into the capillary by the application of a strong magnetic field using a magnet. The performance of the method was exemplified with digestion of bovine serum albumin for 5 min at 50°C and the result was comparable to the 12 h in‐solution digestion. The ability of regeneration of the prepared on‐column microreactor and good reproducibility of microreactor before and after regeneration were also demonstrated. Copyright © 2007 John Wiley & Sons, Ltd.
Evaluation of high‐field asymmetric waveform ion mobility spectrometry coupled to nanoelectrospray ionization for bioanalysis in drug discovery
Authors: Hatsis Panos , Brockman Adam H. , Wu Jing‐Tao 
Published: June 2007

AbstractThe potential of high‐field asymmetric waveform ion mobility spectrometry (FAIMS) coupled to nanoelectrospray ionization (nanoESI) as a method to improve sample throughput for bioanalysis in a discovery pharmaceutical setting was explored in this work. The ability of FAIMS to separate gas‐phase ions in the millisecond timescale was exploited to eliminate the need for liquid chromatography. Samples were introduced into the FAIMS electrodes/mass spectrometer using offline nanoESI at 20 nL/min and 1.5 kV. Signals were averaged for 30 s after which the next sample could be analyzed. The separation of simple mixtures, e.g., the removal of metabolite and endogenous interferences from parent drug, was demonstrated. Moreover, the application of nanoESI attenuated the ion suppression effects that normally plague conventional electrospray. On average, approximately two‐thirds of the neat sample signal intensity was preserved in extracted plasma samples. Standard curves were prepared for several compounds and linearity was obtained over approximately two to three orders of magnitude. This methodology was further tested with the analysis of plasma samples from a mouse pharmacokinetic study. Concentration values determined using nanoESI‐FAIMS were comparable to those determined using conventional LC/MS as demonstrated by percent differences of less than 30%. This work demonstrated the proof of concept that the combination of FAIMS and nanospray ionization can be a potentially useful tool to improve the throughput of discovery bioanalysis. Copyright © 2007 John Wiley & Sons, Ltd.
Meta‐analysis of genetic association studies under different inheritance models using data reported as merged genotypes
Authors: Salanti Georgia , Higgins Julian P. T. 
Published: June 2007

AbstractMeta‐analysis of population‐based genetic association studies is often challenged by obstacles associated with the underlying inheritance model. For a simple genetic variant with two alleles, a recessive, dominant or co‐dominant model is typically assumed. In the absence of a strong biological rationale for a particular inheritance model, a recently suggested inheritance‐model‐free approach can be implemented. To enable a flexible choice among these models, summary results from each of the three genotypes are required. Incompatibility of the data across studies because of different inheritance models is a common problem. For instance, if the underlying model is dominant, studies that have assumed the recessive model and presented the results accordingly, have so far been excluded from the meta‐analysis.We show how to combine data and make inferences under any inheritance model, irrespective of the models assumed within each study and the way that data are presented. Within a Bayesian framework we describe prospective models for binary
and continuous outcomes, and retrospective models for binary outcomes. The methods exploit an assumption of Hardy–Weinberg equilibrium, prior information about genotype prevalence or assumption of a specific inheritance model. On application to meta‐analyses of the associations between a polymorphism in the lipoprotein lipase gene and coronary heart disease or high‐density lipoprotein cholesterol, we observe substantial gains in precision when there is a large proportion of studies in which different inheritance models have been assumed. Copyright © 2007 John Wiley & Sons, Ltd.
Sequential analysis of latent variables using mixed‐effect latent variable models: Impact of non‐informative and informative missing data
Authors: Sébille Véronique , Hardouin Jean‐Benoit , Mesbah Mounir 
Published: June 2007

AbstractSequential methods allowing for early stopping of clinical trials are widely used in various therapeutic areas. These methods allow for the analysis of different types of endpoints (quantitative, qualitative, time to event) and often provide, in average, substantial reductions in sample size as compared with single‐stage designs while maintaining pre‐specified type I and II errors. Sequential methods are also used when analysing particular endpoints that cannot be directly measured, such as depression, quality of life, or cognitive functioning, which are often measured through questionnaires. These types of endpoints are usually referred to as latent variables and should be analysed with latent variable models. In addition, in most
clinical trials studying such latent variables, incomplete data are not uncommon and the missing data process might also be non‐ignorable. We investigated the impact of informative or non‐informative missing data on the statistical properties of the double triangular test (DTT), combined with the mixed‐effects Rasch model (MRM) for dichotomous responses or the traditional method based on observed patient's scores (S) to the questionnaire. The achieved type I errors for the DTT were usually close to the target value of 0.05 for both methods, but increased slightly for the MRM when informative missing data were present. The DTT was very close to the nominal power of 0.95 when the MRM was used, but substantially underpowered with the S method (reduction of about 23 per cent), irrespective of whether informative missing data were present or not. Moreover, the DTT using the MRM allowed for reaching a conclusion (under H0 or H1) with fewer patients than the S method, the average sample number for the latter increasing importantly when the proportion of missing data increased. Incorporating MRM in sequential analysis of latent variables might provide a more powerful method than the traditional S method, even in the presence of non‐informative or informative missing data. Copyright © 2007 John Wiley & Sons, Ltd.
A composite design for transition from a preliminary to a full‐scale study
Authors: Lachin John M. , Younes Naji 
Published: June 2007

AbstractIn drug development, a sequence of studies are conducted to evaluate effectiveness (or efficacy) and safety, such as a Phase II study to assess pharmacological activity or safety that is then followed by a definitive Phase III study to assess clinical effectiveness. Rather than conducting separate successive studies, we describe a design in which the patients enrolled in a preliminary (e.g. Phase II) study are continued into a subsequent full‐scale (e.g. Phase III) study. This design also applies to a study that uses an internal pilot with a preliminary assessment of efficacy or safety. The combined preliminary to full‐scale design potentially reduces the total numbers of patients required and the total duration of the program. The design allows a futility or safety stopping boundary for the preliminary study result that is specified in terms of a lower critical Z‐value
(ZL) and the pursuant type II error probability incurred under a specified alternative hypothesis of a beneficial effect or no toxicity at that stage. This boundary also leads to a deflation of the type I error probability for the final test at the completion of the full‐scale study, such that a critical value for the final test
(ZF) can be determined that provides the desired level of the type I error probability exactly. Thus, it is possible to determine sample sizes at the two stages, and critical values
ZL and
ZF that provide specified type I and II error probabilities for the combined study. We describe the design using large‐sample normally distributed Z‐tests at the two phases, including a test for means, or proportions or survival times, or combinations thereof, such as a test for means at Phase II followed by a test for proportions at Phase III.We compare the properties of this design versus the conduct of two successive studies, and explore the factors that influence the operating characteristics of the design. We also discuss the practical considerations in the implementation of the design. Copyright © 2007 John Wiley & Sons, Ltd.