bluuebunny/crossref_metadata_2025_split huggingface dataset:
Limitations on dynamic excess carrier lifetime calibration methods
Authors: Sinton Ronald A. , Trupke Thorsten 
Published: May 2011

ABSTRACTComparison of minority carrier lifetime measurements carried out in transient mode with measurements performed under steady‐state conditions allows determination of the calibration constants needed in non‐transient measurements. In this letter, we point out practical scenarios in which the assumptions underlying this approach break down, resulting in significant experimental errors. Specific examples for crystalline silicon wafers will be discussed to provide some guidelines on practical limitations of this calibration approach. Large errors are possible for wafers with high surface recombination velocity as might be the case for incoming wafers for a solar cell production line. Copyright © 2011 John Wiley & Sons, Ltd.
Eukaryotic cell lines as a sensitive layer for direct monitoring of carbon monoxide
Authors: Bohrn Ulrich , Stütz Evamaria , Fleischer Maximilian , Schöning Michael J. , Wagner Patrick 
Published: May 2011

AbstractIn the past years, whole cell gas toxicity assays have been developed in order to study the harmful effects of gaseous chemicals. Cells are incubated with nutrition medium supplemented with the gaseous substances to be tested. These methods are not feasible for the examination of toxic gases, which are insoluble in water. Carbon monoxide (CO), a poorly soluble and toxic gas (lethal dose 1 vol% for some minutes) has been chosen as a model gas. Besides its binding to hemoglobin, it also leads to an inhibition of cytochrome c oxidase in the mitochondrial respiratory chain of living cells. Thus, a decrease in the respiratory behavior of eukaryotic cells indicates the presence of CO in a gaseous phase. Based on the Bionas® 2500 analyzing system, a device to measure the metabolic and morphological effects, caused by direct gas exposure on eukaryotic cells was established. The gaseous substances directly contact the eukaryotic cell line V79 (Chinese hamster lung fibroblast) without interfering liquid phase in between. Beside the measurement of oxygen consumption also acidification and impedance changes of the cell culture are detected by a metabolic sensor chip. In order to increase the stability different chip surface coatings like collagen A and poly‐L‐lysin (PLL) were used. Adhesion coating leads to a tighter junction of the cells to the sensor chip surface and thus enables higher stability of the confluent cell monolayer towards the gaseous flow during the gas exposure. The method reported here has the potential to become a valuable means for rapid monitoring of toxic compounds in gaseous phases.
Comment on “Paramagnetic and ferromagnetic resonance studies on dilute magnetic semiconductors based on GaN” [Phys. Status Solidi A 205, 1872 (2008)]
Authors: Gehlhoff W. , Salameh B. , Hoffmann A. 
Published: May 2011

AbstractRecently, Kammermeier et al. (KD) reported on electron paramagnetic resonance (EPR) and ferromagnetic resonance (FMR) studies in the diluted magnetic semiconductor GaN:Gd (Kammermeier et al., Phys. Status Solidi A 205, 1872 (2008) 1). They observed several broad resonance signals at temperatures below 50 K in samples grown by molecular beam epitaxy on 6H SiC. The angular dependence of two FMR‐like lines was measured and reveal uniaxial behavior with opposite anisotropy. From the temperature dependence of the resonance field and the line width as well as the uniaxial behavior of the line positions the authors suggest a ferromagnetic origin. The discussed resonance lines are supposed to originate from GdN clusters with the same orientation to the crystal environment. Several observed weaker signals which were not discussed in detail were attributed to Gd clusters of different orientations. Further, it is believed that signatures of isolated, paramagnetic Gd impurities are not visible in the resonance experiment, in particular, because the resonance field is presumable covered by the observed cavity and substrate signals. The authors did not perform a rigorous analysis of the observed angular dependence of the EPR line positions and their intensities with the corresponding Hamiltonian for the considered defect. In addition they overlooked some well‐known findings on the feature of high‐spin systems in strong crystal fields. Most of their conclusions and interpretations turn out to be erroneous. Here, we show by computer simulation of the EPR spectrum that all observed Gd‐related lines can be successfully explained by isolated Gd3+ on the two inequivalent Ga sites of the hexagonal GaN lattice considering the fine‐structure of the S = 7/2 system and the strain in the epitaxial layer.
Reply to “Comment on 'Paramagnetic and ferromagnetic resonance studies on dilute magnetic semiconductors based on GaN' ” [Phys. Status Solidi A 205, 1872 (2008)]
Authors: Kammermeier T. , Ney A. , Wieck A. D. 
Published: May 2011

AbstractIn a comment by Gehlhoff et al. on our work on “Paramagnetic and ferromagnetic resonance studies on dilute magnetic semiconductors based on GaN” [Phys. Status Solidi A 205, 1872 (2008)] the authors claim a contradictory explanation of angular dependent magnetic resonance measurements. Here we discuss their – solely based on computer simulations – claims. We show that an interpretation limited on magnetic impurities can hardly be used to explain the complex magnetic behavior.
Silicon in AlN: shallow donor and DX behaviors
Authors: Son N. T. , Bickermann M. , Janzén E. 
Published: May 2011

AbstractIn unintentionally Si‐doped AlN bulk samples, an electron paramagnetic resonance (EPR) spectrum with characteristics of a shallow donor, previously assigned to the shallow Si donor, was observed at room temperature in darkness. Temperature dependent studies of the EPR signal showed that Si is a DX center in AlN. However, with the negatively charged DX– state determined to be only ∼78 meV below the neutral shallow donor state, Si should behave as a shallow dopant in AlN at normal device operating temperatures. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fully‐coupled electromechanical analysis of stress‐related failure in GaN HEMTs
Authors: Ancona M. G. , Binari S. C. , Meyer D. 
Published: May 2011

AbstractA multi‐dimensional model for simulating the electromechanics of GaN HEMTs under bias is presented and illustrated. The model’s equations are those of linear electroelasticity and diffusion‐drift transport with full coupling of all variables included. The important benefit of not being restricted to one‐dimension is that these simulations capture various field/stress concentrations that occur especially near corners. To illustrate the simulation tool, we discuss the potential importance of electron injection, the inverse piezoelectric effect, and SiN intrinsic stress in triggering electrical and mechanical failure. Among other things, we argue that stress concentration makes it likely that cracks, once initiated, will propagate and fracture the AlGaN barrier (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
CuBr blue light emitting electroluminescent thin film devices
Authors: Lucas Francis Olabanji , Cowley A. , Daniels S. , McNally P. J. 
Published: May 2011

AbstractVisible blue cathodoluminescence (CL), photoluminescence (PL), x‐ray excited optical luminescence (XEOL) and electroluminescence (EL) via Zf free excitonic emission have been obtained from CuBr thin films deposited on glass, Cr coated glass, GaAs and Si substrates. In addition to the Zf emission several peaks corresponding to Cu+ emissions via 3d94s ↔ d10 transitions were observed on the AC EL spectrum at 2.10, 2.7, 3.03, 3.07 and 3.80 eV. X‐ray diffraction (XRD) measurements confirmed that the vacuum evaporated CuBr thin films grow preferentially with a (111) orientation irrespective of the substrate. While the AC voltage source was found to have no detrimental effects on CuBr thin films, cathodic deposition of Cu metal via electrolytic decomposition was observed under steady state DC voltage stresses. The results from the various luminescence experiments suggest that CuBr thin films may be used as a phosphor layer in blue emitting AC thin film electroluminescent devices (ACTFELD) (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Valency conversion of samarium ions under high dose synchrotron generated X‐ray radiation
Authors: Belev George , Okada Go , Tonchev Dancho , Koughia Cyril , Varoy Chris , Edgar Andy , Wysokinski Tomasz , Chapman Dean , Kasap Safa 
Published: May 2011

AbstractMicrobeam Radiation Therapy (MRT) is a synchrotron based technique for cancer treatment. During MRT tumours are irradiated with micro‐planar arrays of synchrotron‐generated X‐rays. The quality assurance of such a technique depends on the accurate measurement of very high dose levels (>1000 Gy) together with a precise measurement of the dose distribution over a scale of a few microns. For such applications we need to have a high dynamic range, high‐dose detector with very high spatial resolution. As part of the work towards the development of such a detector we have examined the X‐ray radiation induced conversion of rare‐earth ions, especially Sm3+ to Sm2+, embedded in suitable media. We have exposed a variety of Sm3+ doped media, from single crystals to glass‐ceramics, to a high dose radiation at the Canadian Light Source to examine whether we could convert the rare‐earth ion valency. The irradiation was carried out at a bending magnet beamline using filtered white beam with a spectrum peaking at 50 keV. We have used the distinctly different signatures in the photoluminescence emission spectra of the two valency states to identify the rare‐earth ions and whether a valency conversion has taken place. We report the results from these experiments, which show that the conversion of Sm3+ to Sm2+ is not universal and depends very much on the host material. We discuss possible reasons for the presence and lack of radiation induced valency conversion of Sm‐ions, and identify the challenges that must be overcome to develop a high‐resolution, high‐dose detector. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cobalt doping, etching, and attachment of gold nanoparticles and quantum dots on ZnO nanorods
Authors: Hari Parameswar , Spencer Daryl , Hor Amy , Liang Huan , Roberts Ken , Teeters Dale 
Published: May 2011

AbstractZnO is an important material for optoelectronic applications such as solar cells and sensors due to its wide band gap and functional properties. Optimizing the growth mechanisms of ZnO nanorods as grown in a low temperature, wet chemical method will allow for an enhancement of material, optical, and electronic properties in a low cost production method. Our group fabricated nanorods on indium tin oxide (ITO) and glass substrates. The alignment and optical properties of the ZnO nanorods depend greatly on the initial seed layer of (doped) ZnO as well as the growth parameters. In this study we investigated the changes in the optical absorption properties of ZnO nanorods doped with cobalt. Cobalt doping was achieved by adding a percentage of cobalt chloride to the total volume of chemical bath precursor solution of Zinc nitrate and hexamethylentramine. Optical and energy dispersive X‐ray measurements reveal that the optical absorption of ZnO nanorods extends from 385 nm to 700 nm when doped with cobalt from 0.1 at.% to 9.7 at.%. In addition, we investigated the selective etching of ZnO with 3 molar concentrations of potassium chloride solution. Etching under 3 molar solution concentration produced ZnO nanotube structures that can be used for enhancing optical and chemical sensitivity. We also present absorption profiles of ZnO nanorods decorated with metallic nano particles of gold as well as CdSe quantum dots (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical rectification for terahertz generation
Authors: Lee Cameron , Lewis R. A. 
Published: May 2011

AbstractThe applications of terahertz‐frequency electromagnetic radiation are growing rapidly, driven by developments in sources, detectors and optics suited to the THz‐frequency region. Much of the advance is in the field of THz time‐domain spectroscopy in which ultrashort pulses of near‐infrared radiation are used in a pulse‐probe arrangement to realise both the emission and detection of the THz radiation. Methods for ultrafast THz pulse generation include photoconductivity, transient currents or optical rectification. While optical rectification has been known for some time, earlier theoretical and experimental results have been limited to simple crystallographic directions. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stretched exponential relaxation processes in hydrogenated amorphous and polymorphous silicon
Authors: Morigaki Kazuo , Hikita Harumi 
Published: May 2011

AbstractStretched exponential relaxation has been observed in various phenomena of hydrogenated amorphous silicon (a‐Si:H) and hydrogenated polymorphous silicon (pm‐Si:H). As an example, we take light‐induced defect creation in a‐Si:H and pm‐Si:H, in which defect‐creation process and defect‐annihilation process via hydrogen movement play important roles. We have performed the Monte Carlo simulation for hydrogen movement. Hydrogen movement exhibits anomalous diffusion. In our model of light‐induced defect creation in a‐Si:H, a pair of two types of dangling bonds, i.e., a normal dangling bond and a hydrogen‐related dangling bond, that is a dangling bond having hydrogen in the nearby site, are created under illumination, and hydrogen dissociated from the hydrogen‐related dangling bond terminates a normal dangling bond via hydrogen movement. The amorphous network reflects on the dispersive parameter of the stretched exponential function in the light‐induced defect creation. We discuss this issue, taking into account the difference in the amorphous network between a‐Si:H and pm‐Si:H (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Convertible ring signatures with gradual revelation of non‐signers
Authors: Tso Raylin 
Published: May 2011

ABSTRACTA ring signature enables a member of a group to sign any message on behalf of the group while hiding the identity of the real signer. On the other hand, a convertible ring signature is a kind of ring signature in which the real signer can convert it into an ordinary signature. In this way, the real signer can prove the ownership of a ring signature if necessary. In this paper, we introduce a new convertible ring signature with an additional property. That is, before converting a ring signature into an ordinary signature, we allow the real signer to reveal the identity of non‐signers gradually. In other words, if there are n possible signers in a ring, then, by revealing one non‐signer, it will become a ring signature with n − 1 possible signers. By revealing n − 1 non‐signers, then, the ring signature comes to an ordinary signature, and anyone can verify who is the real signer. This property is useful when some non‐signers of a ring signature are not trusted by a verifier (i.e., the signature will not be accepted if someone is a possible signer). Rivest, Shamir, and Tauman first mentioned this problem and gave a solution as their modified ring signature scheme. However, their modified scheme can only guarantee computational anonymity. Our new scheme provides the same property on one hand and still guarantees unconditional anonymity on the other hand. The security is rigorously proved in the random oracle model according to the formal definition. Copyright © 2011 John Wiley & Sons, Ltd.
Synthesis of Biomolecule‐Modified Mesoporous Silica Nanoparticles for Targeted Hydrophobic Drug Delivery to Cancer Cells
Authors: Ferris Daniel P. , Lu Jie , Gothard Chris , Yanes Rolando , Thomas Courtney R. , Olsen John‐Carl , Stoddart J. Fraser , Tamanoi Fuyuhiko , Zink Jeffrey I. 
Published: May 2011

AbstractSynthetic methodologies integrating hydrophobic drug delivery and biomolecular targeting with mesoporous silica nanoparticles are described. Transferrin and cyclic‐RGD peptides are covalently attached to the nanoparticles utilizing different techniques and provide selectivity between primary and metastatic cancer cells. The increase in cellular uptake of the targeted particles is examined using fluorescence microscopy and flow cytometry. Transferrin‐modified silica nanoparticles display enhancement in particle uptake by Panc‐1 cancer cells over that of normal HFF cells. The endocytotic pathway for these particles is further investigated through plasmid transfection of the transferrin receptor into the normal HFF cell line, which results in an increase in particle endocytosis as compared to unmodified HFF cells. By designing and attaching a synthetic cyclic‐RGD, selectivity between primary cancer cells (BT‐549) and metastatic cancer cells (MDA‐MB 435) is achieved with enhanced particle uptake by the metastatic cancer cell line. Incorporation of the hydrophobic drug Camptothecin into these two types of biomolecular‐targeted nanoparticles causes an increase in mortality of the targeted cancer cells compared to that caused by both the free drug and nontargeted particles. These results demonstrate successful biomolecular‐targeted hydrophobic drug delivery carriers that selectively target specific cancer cells and result in enhanced drug delivery and cell mortality.
Physicochemical and functional properties of fern rhizome (Pteridium aquilinum) starch
Authors: Zhang Shurong , Zhong Geng , Liu Beiyu , Wang Bo 
Published: May 2011

AbstractStarch isolated from fern rhizome was studied for physicochemical and functional properties. The recrystallization method was used for separation and purification of AM and AP from the starches. The fern rhizome starch contained 25.38 ± 0.40% AM. XRD studies showed that fern rhizome starch exhibited a C‐type diffraction pattern. SEM showed that granule shape was oval mostly, and the size ranged from 7 to 28 µm. The gelatinization temperature was from 58.94 ± 0.11°C to 71.73 ± 0.22°C, and the melting enthalpy was 12.86 ± 0.53 J/g. According to the viscosity measurement with Brabender viscograph, fern rhizome starch presented higher peak viscosity, which showed that it had more swelling power. Compared with corn and potato starches, fern rhizome starch had a lower transparency. The RS in the fern rhizome starch vermicelli prepared with extrusion method was around 10.49 ± 0.46%.
Climate change and the imagination
Authors: Yusoff Kathryn , Gabrys Jennifer 
Published: May 2011

AbstractThis review article surveys the complex terrain of the imagination as a way of understanding and exploring the manifestations of anthropogenic climate change in culture and society. Imagination here is understood as a way of seeing, sensing, thinking, and dreaming that creates the conditions for material interventions in, and political sensibilities of the world. It draws upon literary, filmic, and creative arts practices to argue that imaginative practices from the arts and humanities play a critical role in thinking through our representations of environmental change and offer strategies for developing diverse forms of environmental understanding from scenario building to metaphorical, ethical, and material investigations. The interplay between scientific practices and imaginative forms is also addressed. Thematically, this review addresses the modalities of climate futures, adaptive strategies, and practices of climate science in its study of key imaginative framings of climate change.WIREs Clim Change2011 2 516–534 DOI: 10.1002/wcc.117This article is categorized under:Trans‐Disciplinary Perspectives > Humanities and the Creative Arts
Markets for SO2 and NOx—what can we learn for carbon trading?
Authors: Hansjürgens Bernd 
Published: May 2011

AbstractWhile the pros and cons of CO2 emissions trading are discussed intensively in climate policies, it has rarely been acknowledged that emissions trading schemes already exist in other policy fields. This holds true in particular for noncarbon‐related air quality management policies in the United States that have existed for almost 20 years. There have been (and still are) many lessons learned from these existing emissions trading markets for the functioning and the design of carbon trading schemes. This article describes the history and design features of the three most important noncarbon US programs in air quality management: the domestic SO2 Acid Rain Program, the Regional Clean Air Incentives Market (RECLAIM) in Southern California addressing SO2 and NOx, and the NOx Budget Program in the Northeastern states of the United States focusing on the decrease of summer ozone. Special attention is given to the question as to whether these programs were successful with respect to (1) the functioning of the markets, (2) their cost‐effectiveness, and (3) their environmental effectiveness. This article addresses lessons learned that were found in the literature based on the assessments of these policies for carbon policies. Lessons learned include, inter alia, rules to increase companies' flexibility (e.g., banking of allowances); grandfathering as political‐motivated allocation rule; design options to reduce uncertainties, transaction costs, and rent seeking of special interest groups; monitoring and enforcement regulation; and the idea of focusing on learning and flexible systems. WIREs Clim Change 2011 2 635–646 DOI: 10.1002/wcc.123This article is categorized under:

The Carbon Economy and Climate Mitigation > Policies, Instruments, Lifestyles, Behavior
Sociolinguistic variables and cognition
Authors: Thomas Erik R. 
Published: May 2011

AbstractSociolinguistics has examined mental organization of language only sporadically. Meanwhile, areas of linguistics that deal with cognitive organization seldom delve deeply into language variation. Variation is essential for understanding how language is structured cognitively, however. Three kinds of evidence are discussed to illustrate this point. First, style shifting demonstrates that language users develop detailed associations of when to produce specific linguistic forms, depending on the pragmatic context. Second, variation in fine‐grained phonetic cues shows that cognitive organization applies to linguistic forms not otherwise known to be under speakers' control. Finally, experiments on dialect comprehension and identification demonstrate that listeners have detailed cognitive associations of language variants with groups of people, whether or not they can produce the same variants themselves. A model is presented for how sociolinguistic knowledge can be viewed in relation to other parts of language with regard to cognitive and neural representations.WIREs Cogni Sci2011 2 701–716 DOI: 10.1002/wcs.152This article is categorized under:Linguistics > Language in Mind and Brain
Fault handling for a wind farm with an internal DC collection grid
Authors: Max Lena , Thiringer Torbjörn , Carlson Ola 
Published: May 2011

ABSTRACTAs a result of the increased wind power penetration, there are increased requirements for robustness of the wind farms during disturbances and faults. The wind farms are required to stay connected during short grid faults, and also, the disturbances as a result of internal faults should be minimized. In this paper, the fault ride‐through properties during external faults for a wind farm with an internal direct current (DC) grid are investigated. A safe detection of the fault is derived, as well as the reconnection procedure after the fault has been cleared. Also, the operation during internal faults has been investigated, focusing on the faults in the DC bus. It has been shown that the wind farm with an internal DC grid can operate through faults in the external grid and reconnect well within the requirements stated in the grid codes. Further, methods for detection of internal faults are derived, and it was shown that a faulted part can be disconnected and the non‐faulted parts can be back in operation within 100 ms using a DC breaker in each radial and within 300 ms without DC breakers. Copyright © 2011 John Wiley & Sons, Ltd.