bluuebunny/crossref_metadata_2025 huggingface dataset:
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

Recently, 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

In 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

In 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

A 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

Visible 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

Microbeam 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

ZnO 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

The 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

Stretched 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)
Distribution of chloroquine in ocular tissue of pigmented rat using matrix‐assisted laser desorption/ionization imaging quadrupole time‐of‐flight tandem mass spectrometry
Authors: Yamada Yasuhiro , Hidefumi Kaji , Shion Henry , Oshikata Motoji , Haramaki Yukari
Published: May 2011

In pharmacology and toxicology, localization of the distribution of a drug molecule in its target tissue provides very important in vivo biological information. Traditionally, this has been examined using autoradiography (ARG). However, there are significant limitations in this application. One is the synthesis and use of radiolabeled compounds, the other is that the image generated expresses an undifferentiated mixture of the parent drug and/or its metabolites. The objective of the study was to define the specific distribution of the parent drug in rat ocular tissue containing melanin (e.g. the retina) using non‐labeled chloroquine by MALDI Imaging tandem mass spectrometry (MS/MS). After single oral administration (at 20 mg/kg) of chloroquine, sections (10 µm) of rat eye tissue were prepared at 24 h. The MS system used was a quadrupole time‐of flight (Q‐TOF) tandem mass spectrometer (MALDI Synapt™, Waters, Milford, MA, USA). Tissue sections were sprayed with CHCA (α‐cyano‐4‐hydroxycinnamic acid, 5 mg/mL) in 80% acetonitrile (ACN) containing 5% formic acid (FA) using either a manual sprayer (airbrush) or an automated sprayer (TM‐Sprayer™, HTX Technologies, Carrboro, NC, USA). Chloroquine was readily detected in the MS/MS mode by monitoring one of its major fragment ions (m/z 247.10) and imaged through the rat eye tissue. The image of the specific distribution within the retina in the rat eye tissue was confirmed, and found to be similar to autoradiograms after oral administration of 14C‐chloroquine reported previously. Copyright © 2011 John Wiley & Sons, Ltd.
Selected reaction monitoring (SRM) mass spectrometry without isotope labeling can be used for rapid protein quantification
Authors: Zhi Wenbo , Wang Meiyao , She Jin‐Xiong
Published: May 2011

The validation of putative biomarker candidates has become the major bottle‐neck in protein biomarker development. Conventional immunoaffinity methods are limited by the availability of antibodies and kits. Here we demonstrate the feasibility of using selected reaction monitoring (SRM) without isotope labeling to achieve fast and reproducible quantification of serum proteins. The SRM/MRM assays for three standard serum proteins, including ceruloplasmin (CP), serum aymloid A (SAA) and sex hormone binding globulin (SHBG), have good linear ranges, generally 103 to 104. There are almost perfect correlations between SRM intensities and the loaded peptide amounts (R2 is usually ~0.99). Our data suggest that SRM/MRM is able to quantify proteins within the range of 0.2–2 fmol, which is comparable to the commercial ELISA/LUMINEX kits for these proteins. Excellent correlations between SRM/MRM and ELISA/LUMINEX assays were observed for SAA and SHBG (R2 = 0.928 and 0.851, respectively). However, the correlation between SRM/MRM and ELISA for CP is less desirable (R2 = 0.565). The reproducibility for SRM/MRM assays is generally very good but may depend on the proteins/peptides being analyzed (R2 = 0.931 and 0.882 for SAA and SHBG, and 0.723 for CP). The SRM/MRM assay without isotope labeling is a rapid and useful method for protein biomarker validation in a modest number of samples and is especially useful when other assays such as ELISA or LUMINEX are not available. Copyright © 2011 John Wiley & Sons, Ltd.
Convertible ring signatures with gradual revelation of non‐signers
Authors: Tso Raylin
Published: May 2011

A 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

Synthetic 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

Starch 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

This 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.117

This 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

While 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.123

This 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

Sociolinguistics 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.152

This 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

As 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.
Hair of the dog: Obtaining samples from coyotes and wolves noninvasively
Authors: Ausband David E. , Young Julie , Fannin Barbara , Mitchell Michael S. , Stenglein Jennifer L. , Waits Lisette P. , Shivik John A.
Published: May 2011

Canids can be difficult to detect and their populations difficult to monitor. We tested whether hair samples could be collected from coyotes (Canis latrans) in Texas, USA and gray wolves (C. lupus) in Montana, USA using lure to elicit rubbing behavior at both man‐made and natural collection devices. We used mitochondrial and nuclear DNA to determine whether collected hair samples were from coyote, wolf, or nontarget species. Both coyotes and wolves rubbed on man‐made barbed surfaces but coyotes in Texas seldom rubbed on hanging barbed surfaces. Wolves in Montana showed a tendency to rub at stations where natural‐material collection devices (sticks and debris) were present. Time to detection was relatively short (5 nights and 4 nights for coyotes and wolves, respectively) with nontarget and unknown species comprising approximately 26% of the detections in both locations. Eliciting rubbing behavior from coyotes and wolves using lures has advantages over opportunistic genetic sampling methods (e.g., scat transects) because it elicits a behavior that deposits a hair sample at a fixed sampling location, thereby increasing the efficiency of sampling for these canids. Hair samples from rub stations could be used to provide estimates of abundance, measures of genetic diversity and health, and detection–nondetection data useful for cost‐effective population monitoring. © 2011 The Wildlife Society.
Design of an underwater telemetry antenna for locating and retrieving submerged radiocollars
Authors: Webb Stephen L. , Gaskamp Joshua A. , Gee Kenneth L. , Demarais Stephen , Little Andrew R.
Published: May 2011

Radiocollars represent a significant investment of financial resources, particularly global positioning system (GPS) collars, and loss of data imposes analytical limitations from reduced sample sizes. Radiocollars on large, terrestrial mammals are seldom lost in the water. However, several instances in Oklahoma, USA necessitated a reliable and cost‐effective technique for retrieving GPS collars from underwater to salvage the financial investment and data. We designed an underwater telemetry antenna to find and retrieve collars in ≤3 m of water. We describe field simulations under varying environmental and water conditions, and provide a list of materials along with instructions and considerations for building and using an underwater telemetry antenna. We successfully used our underwater antenna to locate and retrieve our submerged collar that was disposed of in a pond after illegal harvest; we also located and retrieved all collars used for field simulation (n = 11). On average, search time for collars was 30 min. The design of our underwater antenna was inexpensive (US$30), easy to build, and effective at locating submerged collars in 0.6–3.0 m of water, with varying water turbidity and substrates. Although our underwater telemetry antenna was designed to meet our needs, it could be modified for more specific or alternative circumstances. © 2011 The Wildlife Society.
Structural Aspects of Chlorine‐Aluminium Alkoxides
Authors: Veith Michael , Ullah Wazir Hameed , Kirs Tatjana , Huch Volker , Zimmer Michael
Published: May 2011

LiAlH4 and AlCl3 reacted in a ratio 1:3 to obtain Cl2AlH, which is stabilised by the addition of two equivalents of N‐methylpiperidine (nmp) to form dichloroalane (1) as bis adduct of nmp. Compound 1 was allowed to react with 2,6‐tBu‐4‐MeC6H2OH and HOcHex in a 1:1 ratio to get compounds 2 and 3, respectively. Cl2Al(2,6‐tBu‐4‐MeC6H2O)(nmp) (2) is a monomer in which the central aluminium atom is tetracoordinate. Contrary to the parent compound 1, compound 2 is stabilised by only one nmp molecule. The larger bulk of the alkoxide in 2 prevents the second nmp molecule to reach the aluminium atom. Compound 3 crystallises as unique anionic tri‐nuclear aluminium entity [Al3Cl6(OR)4]– [nmp2H]+ with a protonated nmp as countercation. The lesser bulk of the cyclohexanolate leads to a higher oligomerisation of ROAlCl2 (R = cyclohexyl). When a relatively bulkier alcohol, 1‐methylcyclohexanol, was allowed to react with mixtures of LiAlH4 and AlCl3 prepared in 1:1 and 1:3 ratios in solution, compounds 4 and 5, respectively, were obtained. Both compounds ((HClAlOR)2 (4) and (Cl2AlOR)2 (5), R = cHexMe‐1)) are dimers with oxygen as bridging atom in the Al2O2 rings. All compounds 2, 3, 4, and 5 were structurally characterised by X‐ray diffraction on single crystals.
Anthraquinone‐2,6‐disulfonate as Versatile Ligand for the Synthesis of Hydrogen‐Bonded Supramolecules
Authors: Fu Feng , Hou Xiang‐Yang , Wang Xiao , Gao Zi‐Wei , Li Dong‐Sheng
Published: May 2011

The reactions of anthraquinone‐2,6‐disulfonic acid disodium salt (Na2a‐2,6‐dad) with CuII, MnII, and ZnII with 1,10‐phenanthroline (phen) or 2,2′‐dipyridyl (bipy) under hydrothermal conditions formed two or three‐dimensional supramolecules of stoichiometries [Cu(a‐2,6‐dad)(phen)(H2O)3](H2O)4 (1), [Mn(a‐2,6‐dad)(bipy)2(H2O)](H2O)2 (2), and [Zn(a‐2,6‐dad)(bipy)2(H2O)](H2O)2 (3), which were synthesized and characterized. The arrangement around each metal atom is distorted octahedral. The ligands in all the compounds are engaged in intermolecular hydrogen bonding leading to the formation of hydrogen‐bonded networks, the compounds show novel π–π stacking interactions. Photoluminescence measurements indicate that the compound [Zn(a‐2,6‐dad)(bipy)2(H2O)](H2O)2 (3) shows strong blue luminescence in the solid state at room temperature.
Development and Validation of a Surgical Workload Measure: The Surgery Task Load Index (SURG‐TLX)
Authors: Wilson Mark R. , Poolton Jamie M. , Malhotra Neha , Ngo Karen , Bright Elizabeth , Masters Rich S. W.
Published: May 2011

Background

The purpose of the present study was to develop and validate a multidimensional, surgery‐specific workload measure (the SURG‐TLX), and to determine its utility in providing diagnostic information about the impact of various sources of stress on the perceived demands of trained surgical operators. As a wide range of stressors have been identified for surgeons in the operating room, the current approach of considering stress as a unidimensional construct may not only limit the degree to which underlying mechanisms may be understood but also the degree to which training interventions may be successfully matched to particular sources of stress.

Methods

The dimensions of the SURG‐TLX were based on two current multidimensional workload measures and developed via focus group discussion. The six dimensions were defined as mental demands, physical demands, temporal demands, task complexity, situational stress, and distractions. Thirty novices were trained on the Fundamentals of Laparoscopic Surgery (FLS) peg transfer task and then completed the task under various conditions designed to manipulate the degree and source of stress experienced: task novelty, physical fatigue, time pressure, evaluation apprehension, multitasking, and distraction.

Results

The results were supportive of the discriminant sensitivity of the SURG‐TLX to different sources of stress. The sub‐factors loaded on the relevant stressors as hypothesized, although the evaluation pressure manipulation was not strong enough to cause a significant rise in situational stress.

Conclusions

The present study provides support for the validity of the SURG‐TLX instrument and also highlights the importance of considering how different stressors may load surgeons. Implications for categorizing the difficulty of certain procedures, the implementation of new technology in the operating room (man–machine interface issues), and the targeting of stress training strategies to the sources of demand are discussed. Modifications to the scale to enhance clinical utility are also suggested.
Late Recurrence of Hepatocellular Carcinoma after Liver Transplantation
Authors: Chok Kenneth S. H. , Chan See Ching , Cheung Tan To , Chan Albert C. Y. , Fan Sheung Tat , Lo Chung Mau
Published: May 2011

Background

Long‐term survival of patients with hepatocellular carcinoma (HCC) after liver transplantation is affected mainly by recurrence of HCC. There is the opinion that the chance of recurrence after 2 years post‐transplantation is remote, and therefore lifelong surveillance is not justified because of limited resources. The aims of the present study were to determine the rate of late HCC recurrence (≥2 years after transplantation) and to compare the long‐term patient survival outcomes between cases of early recurrence (<2 years after transplantation) and late recurrence.

Patients

A total of 139 adult HCC patients having liver transplantation during the period from July 1994 to December 2007 were included in the analysis. The median follow‐up period was 55 months. Thirty‐two patients received deceased‐donor grafts and 107 received living‐donor grafts.

Results

Hepatocellular carcinoma recurrence occurred in 24 (17.3%) patients, among them 22 (86%) had living‐donor grafts and 7 (5%) developed late recurrence. Patients in the early recurrence group and patients in the late recurrence group had comparable demographics and disease pathology. The former group, when compared with the latter, had significantly worse overall survival at 3 years (13.3 versus 100%) and 5 years (6.67 versus 71.4%) (log‐rank test; p < 0.001).

Conclusions

Both early recurrence and late recurrence of HCC after liver transplantation were not uncommon, mostly detected at a subclinical stage. Regular and long‐term surveillance with imaging and blood tests is essential for early detection.
Thymic involution and corticosterone level in Sandhoff disease model mice: new aspects the pathogenesis of GM2 gangliosidosis
Authors: Matsuoka Kazuhiko , Tsuji Daisuke , Taki Takao , Itoh Kohji
Published: May 2011

Sandhoff disease (SD) is a lysosomal disease caused by a mutation of the HEXB gene associated with excessive accumulation of GM2 ganglioside (GM2) in lysosomes and neurological manifestations. Production of autoantibodies against the accumulated gangliosides has been reported to be involved in the progressive pathogenesis of GM2 gangliosidosis, although the underlying mechanism has not been fully elucidated. The thymus is the key organ in the acquired immune system including the development of autoantibodies. We showed here that thymic involution and an increase in cell death in the organ occur in SD model mice at a late stage of the pathogenesis. Dramatic increases in the populations of Annexin‐V+ cells and terminal deoxynucletidyl transferase dUTP nick end labeling (TUNEL) + cells were observed throughout the thymuses of 15‐week old SD mice. Enhanced caspase‐3/7 activation, but not that of caspase‐1/4, ‐6 ,‐8, or −9, was also demonstrated. Furthermore, the serum level of corticosterone, a potent inducer of apoptosis of thymocytes, was elevated during the same period of apoptosis. Our studies suggested that an increase in endocrine corticosterone may be one of the causes that accelerate the apoptosis of thymocytes leading to thymic involution in GM2 gangliosidosis, and thus can be used as a disease marker for evaluation of the thymic condition and disease progression.
Direct numerical simulation of the flow over a sphere at Re = 3700
Authors: RODRIGUEZ IVETTE , BORELL RICARD , LEHMKUHL ORIOL , PEREZ SEGARRA CARLOS D. , OLIVA ASSENSI
Published: May 2011

The direct numerical simulation of the flow over a sphere is performed. The computations are carried out in the sub-critical regime at Re = 3700 (based on the free-stream velocity and the sphere diameter). A parallel unstructured symmetry-preserving formulation is used for simulating the flow. At this Reynolds number, flow separates laminarly near the equator of the sphere and transition to turbulence occurs in the separated shear layer. The vortices formed are shed at a large-scale frequency, St = 0.215, and at random azimuthal locations in the shear layer, giving a helical-like appearance to the wake. The main features of the flow including the power spectra of a set of selected monitoring probes at different positions in the wake of the sphere are described and discussed in detail. In addition, a large number of turbulence statistics are computed and compared with previous experimental and numerical data at comparable Reynolds numbers. Particular attention is devoted to assessing the prediction of the mean flow parameters, such as wall-pressure distribution, skin friction, drag coefficient, among others, in order to provide reliable data for testing and developing statistical turbulence models. In addition to the presented results, the capability of the methodology used on unstructured grids for accurately solving flows in complex geometries is also pointed out.
Stabilization of gas-fluidized beds of magnetic powders by a cross-flow magnetic field
Authors: ESPIN M. J. , VALVERDE J. M. , QUINTANILLA M. A. S. , CASTELLANOS A.
Published: May 2011

In this paper we present an experimental study of the stabilization of gas-fluidized beds of magnetic powders by application of a cross-flow magnetic field. The powders tested consist of magnetite and steel powders in a range of particle size dp between 35 and 110 μm, allowing us to investigate the effect of particle size and material properties on magnetic stabilization. In the operation mode employed by us the magnetic field is applied to the unstable bubbling bed and the gas velocity is slowly decreased. According to our observations, the bed is stabilized at a critical gas velocity by the jamming of particle chains formed during bubbling because of the attractive forces induced between the magnetized particles, which are thus responsible for stabilization. Although the magnetic field is applied in the horizontal direction, these chains are mechanically stable at orientations close to the gas flow direction, in agreement with the prediction of an unconfined chain model based on the balance between gas flow shear and interparticle magnetic force fm. Since fm is increased as dp is increased, the critical gas velocity at marginal stability vc for a fixed field strength B is seen to increase with dp. As the gas velocity v0 is decreased below vc, there is a rearrangement of the structure depending on particle size. Restructuring of the bed depends on particle size as derived from measurements of its permeability to the gas flow, which causes the yield stress to be a function of particle size. It is also inferred from our results that natural agglomeration of fine particles (in the absence of a magnetic field) due to van der Waals forces enhances the yield stress of the magnetically stabilized bed. From our experimental results it is concluded that structural effects, as affected by operating conditions and material properties, play a main role in the rheology of the stabilized magnetofluidized bed (MFB).
Freely decaying, homogeneous turbulence generated by multi-scale grids
Authors: KROGSTAD P.-Å. , DAVIDSON P. A.
Published: May 2011

We investigate wind-tunnel turbulence generated by both conventional and multi-scale grids. Measurements were made in a tunnel which has a large test section, so that possible side wall effects are very small and the length ensures that the turbulence has time to settle down to a homogeneous shear-free state. The conventional and multi-scale grids were all designed to produce turbulence with the same integral scale, so that a direct comparison could be made between the different flows. Our primary finding is that the behaviour of the turbulence behind our multi-scale grids is virtually identical to that behind the equivalent conventional grid. In particular, all flows exhibit a power-law decay of energy, u2 ~ t−n, where n is very close to the classical Saffman exponent of n = 6/5. Moreover, all spectra exhibit classical Kolmogorov scaling, with the spectra collapsing on the integral scales at small k, and on the Kolmogorov microscales at large k. Our results are at odds with some other experiments performed on similar multi-scale grids, where significantly higher energy decay exponents and turbulence levels have been reported.
Structural variation along the Zagros and the nature of the Dezful Embayment
Authors: ALLEN MARK B. , TALEBIAN MORTEZA
Published: May 2011

Structure varies along strike in the Zagros fold-and-thrust belt of Iran, which is a principal element in the Arabia–Eurasia continental collision. Pre-collision, Late Cretaceous ophiolite nappes (Kermanshah, Neyriz) and related nappes of deep marine sediments (Radiolarite Series) were emplaced next to two regions (Pusht-e Kuh arc, Fars) which later developed a consistent structural style across the range from the High Zagros Fault to the foreland limit of deformation. The intervening area has a zone of highly imbricated Arabian plate strata (the Bakhtyari Culmination) thrust southwest towards and over a low relief, low elevation region (the Dezful Embayment). There are no ophiolite nappes northeast of the Bakhtyari Culmination. Isopachs reflect these different structural patterns from Late Cretaceous time but not earlier. In Late Cretaceous time the Dezful Embayment recorded less deposition than adjacent areas to the northwest and southeast. In the Palaeogene there was little net difference between the Dezful Embayment and its margins. The Dezful Embayment has been a depocentre since roughly 35 Ma, which is the likely time of initial collision between Arabia and Eurasia. We propose that the syn-collision structure and stratigraphy of the Zagros is therefore strongly influenced by the variation in Late Cretaceous ophiolite emplacement, but the original cause of this variation is not clear.
Human ethology: concepts and implications for the sciences of man
Authors: Eibl-Eibesfeldt Irenäus
Published: May 2011

Human ethology is defined as the biology of human behavior. The methods it employs and the questions it poses are elaborations of those generally used in the various fields of biology, but especially adapted to the study of man. Observation and experimentation in the natural and seminatural setting as well as the comparative method derived from morphology play important roles in human ethology, and the exploration of phylogenetic adaptations constitutes one of its focal interests. On the basis of observations on experientially deprived and nondeprived children, comparative primate and animal behavior studies, and cross-cultural investigations, certain universal phylogenetic adaptations (in terms of fixed action patterns, innate releasing mechanisms, releasers, innate motivating mechanisms, and innate learning dispositions) have been found to occur. However, human ethology does not restrict itself to the investigation of phylogenetic adaptations. The question as to how a behavior pattern contributes to survival can be posed with respect to cultural patterns as well. Similar selection pressures have shaped both culturally and phylogenetically evolved patterns. Through cross-cultural studies a number of universal social interaction strategies have been discovered.
Motor-sensory feedback and geometry of visual space: an attempted replication
Authors: Gyr John , Willey Richmond , Henry Adele
Published: May 2011

This study involved a partial replication of an experiment performed by Held & Rekosh (1963) on the relation between prism-induced changes in visuomotor feedback and shifts in the perception of straightness. The Held & Rekosh study is important because its methodology makes it possible to clearly separate changes in perception due to visuomotor feedback from those due to other perceptual factors. Thus it bears unambiguously on the hypothesis that the neurological processing of sensory input is dependent on the organization of motor activity. The present paper consists of a brief review of theory and experiment on sensorimotor phenomena in perception, followed by a detailed consideration of the Held & Rekosh study and the present replication. For greater effectiveness, Held & Rekosh should have used base-up and base-down prism orientations rather than the base-left and base-right orientations that they employed, but in any case our replication yielded negative results for both base-up and base-right. It is concluded that, given the minimally effective prism orientation and the attentional loads characterizing the Held & Rekosh study, there is need for further experimentation with these two variables. A more drastic suggestion is that there may be a need to confront anew the evidence for sensorimotor processes in perception.
Absolute timing of mental activities
Authors: Wasserman Gerald S. , Kong King-Leung
Published: May 2011

A new tool that may measure certain absolute temporal properties of information processing in intact organisms is suggested by. investigations of temporal summation in single nerve cells. Two findings have led to this suggestion: One, the form of the temporal summation function (relating the intensity and duration required to evoke a criterion neural signal) depends on the analysis used by the investigator. Corresponding form variations occur in behavioral studies when the observer's task is varied. Two, the critical durations of fixed neural signals depend on the latency of the feature of the signal chosen as criterion; early features yield short critical durations and vice versa. The critical duration also varies in behavioral studies if one varies the observer's task, keeping the stimulus ensemble fixed.

These data lead to two inferences: One, the form of a behavioral temporal-summation function expresses the kind of hidden mental analysis mediating that behavior. Two, a behavioral critical duration is an indicator of the absolute timing of the hidden mental analysis mediating that behavior.
The neuropsychology of schizophrenia
Authors: Gray J. A. , Feldon J. , Rawlins J. N. P. , Hemsley D. R. , Smith A. D.
Published: May 2011

A model is proposed for integrating the neural and cognitive aspects of the positive symptoms of acute schizophrenia, using evidence from postmortem neuropathology and neurochemistry, clinical and preclinical studies of dopaminergic neurotransmission, anatomical connections between the limbic system and basal ganglia, attentional and other cognitive abnormalities underlying the positive symptoms of schizophrenia, specific animal models of some of these abnormalities, and previous attempts to model the cognitive functions of the septohippocampal system and the motor functions of the basal ganglia. Anatomically, the model emphasises the projections from the septohippocampal system, via the subiculum, and the amygdala to nucleus accumbens, and their interaction with the ascending dopaminergic projection to the accumbens. Psychologically, the model emphasises a failure in acute schizophrenia to integrate stored memories of past regularities of perceptual input with ongoing motor programs in the control of current perception. A number of recent experiments that offer support for the model are briefly described, including anatomical studies of limbic-striatal connections, studies in the rat of the effects of damage to these connections, and of the effects of amphetamine and neuroleptics, on the partial reinforcement extinction effect, latent inhibition and the Kamin blocking effect; and studies of the latter two phenomena in acute and chronic schizophrenics.