bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Polymerisation and Autoxidation of Technical Grade Linoleic Acid
Authors: Tolvanen P. , Mäki‐Arvela P. , Eränen K. , Wärnå J. , Holmbom B. , Salmi T. , Murzin D. Yu.
Published: March 2008

Oligomerisation of technical grade linoleic acid was studied over a broad temperature range. Effects of water and air were specifically addressed. The products were analysed by size‐exclusion chromatography to give directly the concentrations of dimers and trimers. Oligomerisation of technical grade linoleic acid was seen to be dependent on temperature and the activation energy for monomer disappearance was 109 kJ/mol. A phenomenological kinetic model was proposed for the linoleic acid oligomerisation giving good model predictions. The presence of water inhibited the oligomerisation reaction. Extensive dimerisation and trimerisation occurred under a continuous air flow, whereas introduction of air pulses resulted in only a minor enhancement of trimerisation.
Modelling alternative strategies for delivering hepatitis B vaccine in prisons: the impact on the vaccination coverage of the injecting drug user population
Authors: SUTTON A. J. , GAY N. J. , EDMUNDS W. J. , GILL O. N.
Published: March 2008

Since 2001 hepatitis B vaccination has been offered to prisoners on reception into prisons in England and Wales. However, short campaigns of vaccinating the entire population of individual prisons have achieved high vaccination coverage for limited periods, suggesting that short campaigns may be a preferable way of vaccinating prisoners. A model is used that describes the flow of prisoners through prisons stratified by injecting status to compare a range of vaccination scenarios that describe vaccination on prison reception or via regular short campaigns. Model results suggest that vaccinating on prison reception can capture a greater proportion of the injecting drug user (IDU) population than the comparable campaign scenarios (63% vs. 55·6% respectively). Vaccination on prison reception is also more efficient at capturing IDUs for vaccination than vaccination via a campaign, although vaccination via campaigns may have a role with some infections for overall control.
The unexpected discovery of a focus of hepatitis C virus genotype 5 in a Syrian province
Authors: ANTAKI N. , HADDAD M. , KEBBEWAR K. , ABDELWAHAB J. , HAMED O. , AARAJ R. , ALHAJ N. , HAFFAR S. , ASSIL M. , FTAYEH M. , ASSAAD F. , DOGHMAN D. , ALI T. , NASSERELDDINE M. , ALI A. , ANTAKI F. ,   the Syrian Working Group for the Study of Viral Hepatitis
Published: March 2008

Genotype 5 (G5) was initially discovered and is still mainly diagnosed in South Africa. No cases of G5 have ever been reported from the Middle East countries. The aim of the study was to determine the hepatitis C virus (HCV) genotype distribution in Syria and the prevalence of G5 in this country. Genotyping of HCV was performed in 636 consecutive HCV patients referred to eight medical centres in Syria over a 3-year period. Genotype 4 was the most frequent genotype (375 patients, 59%) followed by genotype 1 (181 patients, 28·5%) and G5 (64 patients, 10%). The majority of G5 patients (56 cases, 87%) live in the north of Syria, including 21 cases (33%) from Azaz, a small city close to Turkey. No obvious epidemiological reason for such high prevalence of G5 was found.
GROUNDS OF LAW AND LEGAL THEORY: A Response
Authors: Finnis John
Published: March 2008

Linking theses of Plato, Wittgenstein, and Weber, section I argues that identification of central cases and settling of focal meanings depend upon the theorist's purpose(s) and, in the case of theory about human affairs—theory adequately attentive to the four irreducible orders in which human persons live and act—upon the purposes for which we intelligibly and intelligently act. Among these purposes, primacy (centrality) is to be accorded (by acknowledgement, not fiat) to purposes which are, as best the theorist can judge, reasonable and fit to be adopted by anyone, the theorist included. Section II defends the reasonableness (and hence entitlement to universal assent) of practical and moral judgments, against Michael Perry's ultimately nihilist claims that egoism's challenge to moral normativity has gone unanswered and that “reason for A” does not entail “reason for” anyone else. Section III takes up Steven Smith's suggestion that such subjectivism is encouraged by the talk in Natural Law and Natural Rights of “pursuing goods,” talk which (he argues) is individualistic and neglectful of (other) persons, inimical to an understanding of friendship, and impotent in the face of egoism. Here as elsewhere the key is to grasp that understanding any basic or intrinsic human good is to understand it as good for anyone like me and thus—since as I instantiate and embody a universal, viz. human being—as a good common to (good for) anyone and everyone. Section IV argues that common good (which includes respect for human rights, and the Rule of Law) gives reason for exercise and acceptance of authority, and for allegiance, even (and in a sense, especially) in time of breakdown. Section V argues that natural law theory is no more dependent on affirming God's existence than any other theory is, in any of the four orders of theory, but equally that is not safe for atheists. For, like any other sound theory, it suggests and is consistent with questions and answers about its grounds, in this case about the source of its normativity and of the human nature that its normative universals presuppose and affirm; and the answers are those argued for, too abstemiously, in the last chapter of NLNR and, more adequately, in the equivalent chapter of Aquinas.
TRANSACTION SERVICES AND ASSET-PRICE BUBBLES
Authors: KOBAYASHI KEIICHIRO
Published: March 2008

This paper examines asset-price bubbles in an economy where a nondepletable asset (e.g., land) can provide transaction services, using a variant of the cash-in-advance model. When a landowner can borrow money immediately using land as collateral, one can say that land essentially provides a transaction service. The transaction services that such an asset can provide increase as its price rises, as the asset owner can borrow more money against the asset's increased value. Thus, an asset-price bubble can emerge due to the externality of self-reference, wherein the asset price reflects the transaction services that it can provide, whereas the amount of the transaction services reflects the asset price. If the collateral ratio of the asset (θ) and money supply (m) are not very large, a steady-state equilibrium exists where the asset price has a bubble component and resource allocation is inefficient; if θ and/or m become large, the bubble component of the asset price vanishes and the equilibrium allocation becomes efficient. The paper shows that in the case where the equilibrium concept is relaxed to allow for sticky prices and a temporary supply-demand gap, an equilibrium exists where a bubble develops temporarily and eventually bursts.
Eddy heat fluxes from direct current measurements of the Antarctic Polar Front in Shag Rocks Passage
Authors: Walkden Graham J. , Heywood Karen J. , Stevens David P.
Published: March 2008

Determining meridional heat flux in the Southern Ocean is critical to the accurate understanding and model simulation of the global ocean. Mesoscale eddies provide a significant but poorly‐defined contribution to this transport. An eighteen‐month deep‐water current meter array deployment in Shag Rocks Passage (53°S, 48°W) between May 2003 and November 2004 provides estimates of the eddy flux of heat across the Polar Front. We calculate a statistically nonzero (99% level), vertically coherent local poleward heat flux of 12.0 ± 5.8 kW m−2 within the eddy frequency band at ∼2750 m depth. Exceeding previous deep‐water estimates by up to an order of magnitude, this highlights the large spatial variation in flux estimates and illustrates that constriction of circumpolar fronts facilitates large eddy transfers of heat southwards.
Model evaluation of CO2 and SF6 in the extratropical UT/LS region
Authors: Bönisch H. , Hoor P. , Gurk Ch. , Feng W. , Chipperfield M. , Engel A. , Bregman B.
Published: March 2008

We evaluate the transport of three‐dimensional chemical transport models in the upper troposphere and lower stratosphere applying observed distributions of CO2 and SF6. The data consist of high‐resolution in situ observations, obtained during all seasons at subtropical, middle and high latitudes over Western Europe within the SPURT (Spurenstofftransport in der Tropopausenregion) project (2001–2003). We show that the combination of the two passive tracers SF6 and CO2 with their different tropospheric characteristics and the propagation of the temporal trends of these two gases into the lower stratosphere is a powerful diagnostic for evaluation of model transport. The model evaluation shows that all models are able to capture the general features in the tracer distributions including the vertical and horizontal propagation of the CO2 seasonal cycle. However, the modeled CO2 cycles are a few months out of phase in the lowermost stratosphere due to tropospheric mixing. Two models show a too strong Brewer‐Dobson circulation causing an overestimation of the tracers in the lowermost stratosphere during winter and spring. One model displays a too strong tropical isolation leading to an underestimation of the tracers in the lowermost stratosphere during winter. All models suffer to some extend from diffusion and/or too strong mixing across the tropopause. In addition, the models show too weak vertical upward transport into the upper troposphere during the boreal summer. Sensitivity studies show that our initial conditions and boundary constraints are realistic and that a horizontal resolution higher than 2 degrees and an increase of the meteorology update frequency (from 6 to 3‐hourly) have negligible impact on the modeled CO2 and SF6 distributions.
Geologic implications of new zircon U‐Pb ages from the White Mountain Peak Metavolcanic Complex, eastern California
Authors: Scherer Hannah H. , Ernst W. G. , Brooks Hanson R.
Published: March 2008

The NNW‐trending White‐Inyo Range includes intrusive and volcanic rocks on the eastern flank of the Sierran volcano‐plutonic arc. The NE‐striking, steeply SE‐dipping Barcroft reverse fault separates folded, metamorphosed Mesozoic White Mountain Peak mafic and felsic volcanic flows, volcanogenic sedimentary rocks, and minor hypabyssal plugs on the north from folded, well‐bedded Neoproterozoic‐Cambrian marble and siliciclastic strata on the south. The 163 ± 2 Ma Barcroft Granodiorite rose along this fault, and thermally recrystallized its wall rocks. However, new SHRIMP‐RG ages of magmatic zircons from three White Mountain Peak volcanogenic metasedimentary rocks and a metafelsite document stages of effusion at ∼115–120 Ma as well as at ∼155–170 Ma. The U‐Pb data confirm the interpretation by Hanson et al. (1987) that part of the metasedimentary‐metavolcanic pile was laid down after Late Jurassic intrusion of the Barcroft pluton. The Lower Cretaceous, largely volcanogenic metasedimentary section lies beneath a low‐angle thrust fault, the upper plate of which includes interlayered Late Jurassic mafic and felsic metavolcanic rocks and the roughly coeval Barcroft pluton. Late Jurassic and Early Cretaceous volcanism in this sector of the Californian continental margin, combined with earlier petrologic, structural, and geochronologic studies, indicates that there was no gap in igneous activity at this latitude of the North American continental margin.
Acetazolamide prevents vacuolar myopathy in skeletal muscle of K+‐depleted rats
Authors: Tricarico D , Lovaglio S , Mele A , Rotondo G , Mancinelli E , Meola G , Camerino D C
Published: March 2008

Background and purpose: Acetazolamide and dichlorphenamide are carbonic anhydrase (CA) inhibitors effective in the clinical condition of hypokalemic periodic paralysis (hypoPP). Whether these drugs prevent vacuolar myopathy, which is a pathogenic factor in hypoPP, is unknown. The effects of these drugs on the efflux of lactate from skeletal muscle were also investigated.

Experimental approach: For 10 days, K+‐depleted rats, a model of hypoPP, were administered 5.6 mg kg−1 day−1 of acetazolamide, dichlorphenamide or bendroflumethiazide (the last is not an inhibitor of CA). Histological analysis of vacuolar myopathy and in vitro lactate efflux measurements were performed in skeletal muscles from treated and untreated K+‐depleted rats, and also from normokalemic rats.

Key results: About three times as many vacuoles were found in the type II fibres of tibialis anterioris muscle sections from K+‐depleted rats as were found in the same muscle from normokalemic rats. In ex vivo experiments, a higher efflux of lactate on in vitro incubation was found in muscles of K+‐depleted rats compared with that found in muscles from normokalemic rats. After treatment of K+‐depleted rats with acetazolamide, the numbers of vacuoles in tibialis anterioris muscle decreased to near normal values. Incubation with acetazolamide in vitro inhibited efflux of lactate from muscles of K+‐depleted rats. In contrast, bendroflumethiazide and dichlorphenamide failed to prevent vacuolar myopathy after treatment in vivo and failed to inhibit lactate efflux in vitro.

Conclusions and implications: Acetazolamide prevents vacuolar myopathy in K+‐depleted rats. This effect was associated with inhibition of lactate transport, rather than inhibition of CA.
Neuroplasticity in the mesolimbic dopamine system and cocaine addiction
Authors: Thomas M J , Kalivas P W , Shaham Y
Published: March 2008

The main characteristics of cocaine addiction are compulsive drug use despite adverse consequences and high rates of relapse during periods of abstinence. A current popular hypothesis is that compulsive cocaine use and cocaine relapse is due to drug‐induced neuroadaptations in reward‐related learning and memory processes, which cause hypersensitivity to cocaine‐associated cues, impulsive decision making and abnormal habit‐like learned behaviours that are insensitive to adverse consequences. Here, we review results from studies on the effect of cocaine exposure on selected signalling cascades, growth factors and physiological processes previously implicated in neuroplasticity underlying normal learning and memory. These include the extracellular signal‐regulated kinase (ERK) signalling pathway, brain‐derived neurotrophic factor (BDNF), glutamate transmission, and synaptic plasticity (primarily in the form of long‐term potentiation and depression, LTP and LTD). We also discuss the degree to which these cocaine‐induced neuroplasticity changes in the mesolimbic dopamine system mediate cocaine psychomotor sensitization and cocaine‐seeking behaviours, as assessed in animal models of drug addiction. Finally, we speculate on how these factors may interact to initiate and sustain cocaine psychomotor sensitization and cocaine seeking.

British Journal of Pharmacology (2008) 154, 327–342; doi:fn1; published online 17 March 2008
Caspase activation cascades in apoptosis
Authors: Logue Susan E. , Martin Seamus J.
Published: March 2008

Apoptosis, a highly controlled mode of cell death, is utilized to eliminate superfluous, aged, injured or infected cells from the body. Caspases, a family of aspartic acid-specific proteases, are the major effectors of apoptosis. To curtail their activity, caspases are normally synthesized as inactive precursors, but become activated at the onset of apoptosis by activation signals. Once active, caspases preside over the ordered dismantling of the cell through restricted proteolysis of hundreds of substrate proteins. Over the last 10 years, intense research has focused upon the pathways that control caspase activation. Although some, such as the apoptosome and death receptor-mediated pathways to caspase activation, are well established, others are less clearly defined. In this review, we discuss current perspectives concerning the diverse pathways to caspase activation.
Coarse-grained simulation: a high-throughput computational approach to membrane proteins
Authors: Sansom Mark S.P. , Scott Kathryn A. , Bond Peter J.
Published: March 2008

An understanding of the interactions of membrane proteins with a lipid bilayer environment is central to relating their structure to their function and stability. A high-throughput approach to prediction of membrane protein interactions with a lipid bilayer based on coarse-grained Molecular Dynamics simulations is described. This method has been used to develop a database of CG simulations (coarse-grained simulations) of membrane proteins (http://sbcb.bioch.ox.ac.uk/cgdb). Comparison of CG simulations and AT simulations (atomistic simulations) of lactose permease reveals good agreement between the two methods in terms of predicted lipid headgroup contacts. Both CG and AT simulations predict considerable local bilayer deformation by the voltage sensor domain of the potassium channel KvAP.
Managing and sharing experimental data: standards, tools and pitfalls
Authors: Paton Norman W.
Published: March 2008

Experimental processes in the life sciences are becoming increasingly complex. As a result, recording, archiving and sharing descriptions of these processes and of the results of experiments is becoming ever more challenging. However, validation of results, sharing of best practice and integrated analysis all require systematic description of experiments at carefully determined levels of detail. The present paper discusses issues associated with the management of experimental data in the life sciences, including: the different tasks that experimental data and metadata can support, the role of standards in informing data sharing and archiving, and the development of effective databases and tools, building on these standards.
AAA+ proteins: diversity in function, similarity in structure
Authors: Snider Jamie , Houry Walid A.
Published: March 2008

The AAA+ (ATPases associated with various cellular activities) superfamily of proteins represents a distinct lineage of the larger class of P-loop NTPases. Members of this superfamily use the power of nucleotide binding and hydrolysis to direct molecular remodelling events. All AAA+ proteins share a common core architecture, which, through various sequence and structural modifications, has been adapted for use in a remarkably diverse range of functions. The following mini-review provides a concise description of the major structural elements common to all AAA+ proteins in the context of their mechanistic roles. In addition, the evolutionary and functional diversity of this superfamily is described on the basis of recent classification studies.
Roles for the AAA+ motifs of DnaA in the initiation of DNA replication
Authors: Katayama Tsutomu
Published: March 2008

The cell-cycle-co-ordinated initiation of chromosomal replication is highly regulated. The ordered assembly and conformational change of specific proteins at the replication origin are crucial to the process of replication initiation. In Escherichia coli, ATP–DnaA molecules form multimeric complexes with the chromosomal origin of replication (oriC), and unwind the duplex DNA within oriC, resulting in initiation of replication. DnaA is a common protein in bacterial species and plays a main and crucial role in the initiation of chromosomal replication. Unlike well-characterized AAA+ (ATPase associated with various cellular activities) proteins such as chaperons and proteases, DnaA molecules stably take on a monomeric form and form homomultimers in a manner dependent on binding to oriC. The oriC region carries several DnaA-binding sites with various affinities. Recent progress in the analysis of DnaA and related proteins has revealed specific roles for the AAA+ unique motifs of DnaA. These results suggest mechanisms for recognition of ATP bound to DnaA, the co-operative binding of ATP–DnaA molecules on oriC, the formation of an ATP–DnaA-specific oriC complex, an initiation complex and regulatory hydrolysis of DnaA-bound ATP.
Regulation and action of the bacterial enhancer-binding protein AAA+ domains
Authors: Chen Baoyu , Sysoeva Tatyana A. , Chowdhury Saikat , Nixon B. Tracy
Published: March 2008

Bacterial EBPs (enhancer-binding proteins) play crucial roles in regulating cellular responses to environmental changes, in part by providing efficient control over σ54-dependent gene transcription. The AAA+ (ATPase associated with various cellular activites) domain of the EBPs, when assembled into a ring, uses energy from ATP binding, hydrolysis and product release to remodel the σ54–RNAP (RNA polymerase) holoenzyme so that it can transition from closed to open form at promoter DNA. The assembly, and hence activity, of these ATPases are regulated by many different signal transduction mechanisms. Recent advances in solution scattering techniques, when combined with high-resolution structures and biochemical data, have enabled us to obtain mechanistic insights into the regulation and action of a subset of these σ54 activators: those whose assembly into ring form is controlled by two-component signal transduction. We review (i) experimental considerations of applying the SAXS (small-angle X-ray scattering)/WAXS (wide-angle X-ray scattering) technique, (ii) distinct regulation mechanisms of the AAA+ domains of three EBPs by similar two-component signal transduction receiver domains, and (iii) major conformational changes and correlated σ54-binding activity of an isolated EBP AAA+ domain in the ATP hydrolysis cycle.
Roles of VCP in human neurodegenerative disorders
Authors: Kakizuka Akira
Published: March 2008

Abnormal protein aggregates are commonly observed in affected neurons in many neurodegenerative disorders. We have reported that VCP (valosin-containing protein) co-localizes with protein aggregates in neurons of patients and in cultured cells expressing diseased proteins. However, the significance of such co-localization remains to be elucidated. In the present paper, I discuss the involvement of VCP in the processes of both the formation and re-solubilization of abnormal protein aggregates. In the study, VCP recognized and accumulated on to pre-formed protein aggregates created by proteasome inhibition. VCP knockdown or expression of dominant-negative VCP both significantly delayed the elimination of ubiquitin-positive aggregates. VCP was also involved in the clearance of pre-formed polyglutamine aggregates. Paradoxically, VCP knockdown also diminished polyglutamine aggregate formation. Furthermore, its ATPase activity is required for the re-solubilization and reactivation of heat-denatured proteins, such as luciferase, from insoluble aggregates. We thus propose that VCP functions as a mediator for both aggregate formation and clearance, depending on the concentration of soluble aggregate-prone proteins, indicating that VCP has dual functions as an aggregate formase and an unfoldase. We then examined the potentially elevated aggregate formase activities of mutant VCPs, which have been found to cause IBMPFD (inclusion body myopathy, Paget disease of bone and front-temporal dementia). Indeed, all IBMPFD VCPs showed elevated aggregate formase activities on both polyglutamine and proteasome inhibitor-mediated aggregates. Biochemically, all IBMPFD VCPs showed elevated ATPase activities as well as elevated binding affinities not only for several VCP cofactors, but also for ubiquitinated proteins. Thus controlling the function of VCP, namely decreasing aggregate formase activities and/or increasing unfoldase activities, is expected to be of great benefit for the treatment of IBMPFD and also several neurodegenerative disorders with intracellular protein inclusions.
Common and specific mechanisms of AAA+ proteins involved in protein quality control
Authors: Mogk Axel , Haslberger Tobias , Tessarz Peter , Bukau Bernd
Published: March 2008

A protein quality control system, consisting of molecular chaperones and proteases, controls the folding status of proteins and mediates the refolding or degradation of misfolded proteins. Ring-forming AAA+ (ATPase associated with various cellular activities) proteins play crucial roles in both processes by co-operating with either peptidases or chaperone systems. Peptidase-associated AAA+ proteins bind substrates and thread them through their axial channel into the attached proteolytic chambers for degradation. In contrast, the AAA+ protein ClpB evolved independently from an interacting peptidase and co-operates with a cognate Hsp70 (heat-shock protein 70) chaperone system to solubilize and refold aggregated proteins. The activity of this bi-chaperone system is crucial for the survival of bacteria, yeast and plants during severe stress conditions. Hsp70 acts at initial stages of the disaggregation process, enabling ClpB to extract single unfolded polypeptides from the aggregate via a threading activity. Although both classes of AAA+ proteins share a common threading activity, it is apparent that their divergent evolution translates into specific mechanisms, reflecting adaptations to their respective functions. The ClpB-specific M-domain (middle domain) represents such an extra feature that verifies ClpB as the central disaggregase in vivo. M-domains act as regulatory devices to control both ClpB ATPase activity and the Hsp70-dependent binding of aggregated proteins to the ClpB pore, thereby coupling the Hsp70 chaperone activity with the ClpB threading motor to ensure efficient protein disaggregation.
A silicon radio-frequency single electron transistor
Authors: Angus S. J. , Ferguson A. J. , Dzurak A. S. , Clark R. G.
Published: March 2008

We report the demonstration of a silicon radio-frequency single electron transistor. The island is defined by electrostatically tunable tunnel barriers in a narrow channel field effect transistor. Charge sensitivities of better than 10μe∕Hz are demonstrated at megahertz bandwidth. These results demonstrate that silicon may be used to fabricate fast, sensitive electrometers.
Magnetic properties of epitaxial Fe–Pd films measured at elevated temperatures
Authors: Buschbeck J. , Heczko O. , Ludwig A. , Fähler S. , Schultz L.
Published: March 2008

Magnetic properties of disordered Fe–Pd films with 28 and 33at.% Pd epitaxially grown at room temperature were measured at room and elevated temperatures up to 900 and 600K, respectively. Thermomagnetic measurements of the film with 28at.% Pd having a body-centered-tetragonal structure in the as-deposited state show that, due to their metastability, disordered Fe–Pd phases can decompose at elevated temperatures. For a film with 33at.% Pd having a face-centered-tetragonal (fct) structure in the as-deposited state, no indication of decomposition or first order transformation is observed up to 600K, suggesting that the fct phase required for the magnetic shape memory effect is quite stable in epitaxial films.
Magnetic properties and quantum phase transitions of purely organic molecule-based ferrimagnets based on Green’s function theory
Authors: Fu Hua-Hua , Yao Kai-Lun , Liu Zu-Li
Published: March 2008

Magnetic properties of a Heisenberg diamondlike spin chain model for purely organic molecule-based ferrimagnets are investigated by means of the many-body Green’s function method within random phase approximation. The molecule-based ferrimagnet is composed of S=1 biradical and S=1∕2 monoradical molecules alternating with intermolecular antiferromagnetic (AF) interactions, and the S=1 site is composed of two S=1∕2 spins by a finite intramolecular ferromagnetic (F) interaction. The numerical results reveal that occurrence of ferrimagnetic spin alignments along the chain is determined by the intermolecular AF interactions. Owing to the very small intermolecular AF interactions, the curves of the product of magnetic susceptibility and temperature (χT) against temperature display as a round peak at low temperatures, and the ferrimagnetic phase transition could only be detected at ultralow temperatures in practical organic compounds. Temperature- and magnetic-field-induced magnetic phase transitions are discussed, which are consistent with the experimental findings. The lower spatial symmetry of intermolecular interactions makes it easy to form spin pairs with a singlet (S=0) ground state along the chain and to reduce Curie temperature. The formations of molecular dimers and trimers along the chain have contributions to bring about F alignments with effective S=1∕2 magnetic supramolecules and to enhance Curie temperature. In addition, the experimental data of the magnetic susceptibility measurements for a molecule-based ferrimagnet are also fairly compared with our theoretical results.
Absorption and emission lineshapes and solvation dynamics of NO in supercritical Ar
Authors: Tiftickjian Christopher N. , Egorov S. A.
Published: March 2008

We perform a theoretical study of electronic spectroscopy of dilute NO in supercritical Ar fluid. Absorption and emission lineshapes for the AΣ+2←XΠ2 Rydberg transition of NO in argon have been previously measured and simulated, which yielded results for the NO/Ar ground- and excited-state pair potentials [Larrégaray et al., Chem. Phys. 308, 13 (2005)]. Using these potentials, we have performed molecular dynamics simulations and theoretical statistical mechanical calculations of absorption and emission lineshapes and nonequilibrium solvation correlation functions for a wide range of solvent densities and temperatures. Theory was shown to be in good agreement with simulation. Linear response treatment of solvation dynamics was shown to break down at near-critical temperature due to dramatic change in the solute-solvent microstructure upon solute excitation to the Rydberg state and the concomitant increase of the solute size.
Direct correlation between the internal quantum efficiency and photoluminescence lifetime in undoped ZnO epilayers grown on Zn-polar ZnO substrates by plasma-assisted molecular beam epitaxy
Authors: Takamizu D. , Nishimoto Y. , Akasaka S. , Yuji H. , Tamura K. , Nakahara K. , Onuma T. , Tanabe T. , Takasu H. , Kawasaki M. , Chichibu S. F.
Published: March 2008

The equivalent internal quantum efficiency (ηinteq) at 300K of the near-band-edge excitonic photoluminescence (PL) peak in ZnO epilayers grown by plasma-assisted molecular beam epitaxy on Zn-polar ZnO substrates was directly correlated with the PL lifetime (τPL) for the first time. This relation seems to be universal for O-polar ZnO films grown by other methods. Present homoepitaxial ZnO epilayers grown above 800°C exhibited atomically flat surfaces, and the best full-width-at-half-maximum value of (0002) ZnO x-ray diffraction ω-rocking curves was 17.6arcsec. The high-temperature growth also led to a long τPL of 1.2ns at 300K. As a result, a record high ηinteq value (9.6%) was eventually obtained under an excitation density of 5W∕cm2 (He–Cd, 325.0nm). The homoepitaxial Zn-polar ZnO films grown by molecular beam epitaxy are coming to be used for p-n junction devices.
Microwave resonators based on single-crystal yttrium iron garnet and lead magnesium niobate-lead titanate layered structures
Authors: Ustinov Alexey B. , Srinivasan G. , Fetisov Yuri K.
Published: March 2008

Electrically and magnetically tunable microwave resonators based on ferrite-piezoelectric layered structure have been investigated. The structure consisted of bonded layers of single-crystal yttrium iron garnet film and single-crystal lead magnesium niobate-lead titanate (PMN-PT) slab. The frequency of the resonator was tuned over a wide frequency range, from 3to10GHz, by varying the bias magnetic field (magnetic tuning) and over a narrow range, up to 45MHz, by the application of an electric field (electric tuning) to the PMN-PT layer. Performance characteristics of the resonator are discussed. The data are in good agreement with theory.
Current versus voltage characteristics of GaN∕AlGaN∕GaN double heterostructures with varying AlGaN thickness and composition under hydrostatic pressure
Authors: Steinke I. P. , Ruden P. P. , Ni X. , Morkoç H. , Son K.-A.
Published: March 2008

We have studied current versus voltage characteristics of n-GaN∕u-AlGaN∕n-GaN double heterostructure devices under hydrostatic pressure up to 500MPa. Devices were grown on c-plane sapphire substrates by organometallic vapor phase epitaxy using epitaxial layer overgrowth. The effect of AlGaN layer thickness and composition on the pressure sensitivity was investigated. For a fixed applied bias, we found that the current decreases approximately linearly in magnitude with increasing hydrostatic pressure over the range of voltages and pressures applied. The decrease in current magnitude can be attributed to piezoelectric effects and is consistent with model calculations. The polarization charge densities at the GaN∕AlGaN interfaces change with hydrostatic pressure, which in turn modifies the internal potential barrier. Changes in the AlGaN layer thickness and composition also modify the interfacial polarization, with thicker AlGaN layers and higher AlN content increasing the effect of pressure on the observed current versus voltage characteristics. The strain gauge factors obtained for these devices range from ∼200 to 800.
A relation on round-off error, attractor size and its dynamics in driven or coupled logistic map system
Authors: Shi Pengliang
Published: March 2008

In this paper, we investigate three kinds of numerical artifacts: period-like, strange-nonchaotic-attractor-like, and chaos-like behaviors in an extended logistic map system. These artificial behaviors appear in double precision and change into other real attractors in high-precision simulations. All of them are generated by a complicated dynamical process of the system and round-off truncation errors in numerical computations. A quantity β, which is closely related to the local Lyapunov exponent, is proposed to measure the extremum of large expansion or contraction dynamical capability. Eventually, we find the artifacts will emerge if the relation is not kept: αβ<γ, where γ is the attractor size of the system and α is the computational precision digit, for instance, α=2×10−16 for double precision, which has a unit round-off of 2×10−16.
Te-induced modulation of the Mo∕HfO2 interface effective work function
Authors: Xiong Ka , Delugas Pietro , Hooker Jacob C. , Fiorentini Vincenzo , Robertson John , Liu Dameng , Pourtois Geoffrey
Published: March 2008

First principles calculations of the impact of Te local doping on the effective work function of a Mo∕HfO2 interface are presented. The undoped interface has a p-type effective work function. We find that interstitial Te and Te in the metal both make the effective work function more p-type. More importantly, Te substituting for O or Hf in the dielectric near the interface—energetically stable for all growth conditions—decreases the effective work function, making it more n-type.
Current constriction of high-current vacuum arc in vacuum interrupters
Authors: Wang Lijun , Jia Shenli , Zhang Ling , Yang Dingge , Shi Zongqian , Gentils Francois , Jusselin Benoît
Published: March 2008

Compared with previous paper [L. Wang et al., J. Appl. Phys. 100, 113304 (2006)], higher-current vacuum arc is simulated and analyzed based on magnetohydrodynamics model, and current constriction phenomenon in arc column is mainly paid attention to and analyzed in this paper. According to simulation results, it can be found that significant current constriction only appears near anode regions for lower-current vacuum arc. However, with the increase of arc current, current constriction also appears near the cathode side, and with the further increase of arc current, current constriction near the cathode side can become more significant than that near the anode side. The current constriction near the cathode side can be mainly caused by very high current level. The increase of axial magnetic field (AMF) strength will inhibit current constriction in the whole arc column. For influence of AMF distribution, saddle-shaped distributed AMF can more efficiently inhibit current constriction of arc column than bell-shaped AMF. The phenomenon of current constriction near the cathode side has also been found by many experiments, which also can verify the correctness of simulation results.
Kinetics of docking in postnucleation stages of self-assembly
Authors: Garza-López Roberto A. , Bouchard Philippe , Nicolis Gregoire , Sleutel Mike , Brzezinski Jack , Kozak John J.
Published: March 2008

In a previous study, the early stages of self-assembly in nanophase materials were explored by coupling a kinetic mean-field analysis with a lattice-based stochastic theory [J. J. Kozak et al., J. Chem. Phys. 126, 154701 (2007)]. Recent experimental results on the postnucleation stages of zeolite assembly and protein crystallite formation have suggested a new study, presented here, in which the docking of a platelet on the existing surface of a structured crystallite is similarly investigated. A model is designed which allows the quantification of factors affecting docking efficiency; principal among these is the structure of the template itself, which here is assumed to be either unstructured or bifurcated into terraces and edges/ledges. Going beyond our earlier study (in which diffusion was restricted to d=2 dimensions), the diffusion space here is enlarged to consider both d=2 and d=3 dimensional flows. By expanding the external diffusion space systematically, we are able to document the consequences (as regards docking efficiency) of diffusive flows in the near neighborhood of a developing crystallite versus surface-only processes. Particularly in regimes where the barriers to surface diffusion are high, and/or the probability of desorption significant, we find that d=3 dimensional processes (leading to a “direct hit”) can compete kinetically with surface-only mediated processes. Although the crystallite model studied here is simple, it can be diffeomorphically distorted into a manifold of possible geometries; in analogy with the classical theory of corresponding states, we argue that the familial relationship among these structures suggests that the generic results obtained provide a qualitatively correct description of the kinetics of docking on structured surfaces.
Lattice vibration characterization and magnetic properties of M-type barium hexaferrite with excessive iron
Authors: Zhao W. Y. , Wei P. , Wu X. Y. , Wang W. , Zhang Q. J.
Published: March 2008

Nonstoichiometric M-type barium hexaferrite compounds, with nominal compositions BaFe12+xO19+1.5x (0⩽x⩽0.4), have been synthesized by spark plasma sintering technique. The electron probe microanalysis shows that the excessive trivalent iron (Fe3+) ions are in the lattices of BaFe12+xO19+1.5x compounds. Both Raman and FTIR spectra reveal that the excessive Fe3+ ions spin upward. They occupy the octahedron interstices similar to the FeO6 octahedron at the 12k site and the bipyramid interstices similar to the FeO5 bipyramid at the 2b site, in the x range of 0–0.3 and x=0.4, respectively. This explains well significant enhancement in the specific saturation magnetizations for BaFe12+xO19+1.5x with increasing the x in the range of 0–0.4. The gradual increase in the coercivities has been interpreted with the augment of Fe3+ concentration in unit cell.
A model for the thermal degradation of metal/(p-GaN) interface in GaN-based light emitting diodes
Authors: Meneghini M. , Rigutti L. , Trevisanello L. R. , Cavallini A. , Meneghesso G. , Zanoni E.
Published: March 2008

This paper analyzes the thermal degradation of GaN-based light emitting diodes with hydrogen-rich passivation layer by combined capacitance and current measurements. The decrease of optical power arising during thermal treatment at T=250°C is well related to a decrease in the high-frequency capacitance and to the generation of a further peak in the conductance/frequency curves. Deep level transient spectroscopy measurements excluded the role of further deep levels introduced/generated in the p-n junction region. Transmission line method analysis showed that stress induces nonlinearity of the characteristics of the contacts, related to the increase of Ohmic contact resistivity. All these modifications are explained using a small-signal model in which a parasitic impedance arises as a consequence of stress in the portion of metal/(p-GaN) interface exposed to diffusion of hydrogen from the passivation layer. Therefore, degradation is shown to be related to the worsening of the properties of the metal/semiconductor interface at the p side of the diode, due to the interaction between the hydrogen-rich passivation layer and the acceptor dopant. This interaction is well confined to the immediate proximity of the interface, leaving the activated acceptor concentration in the bulk almost unaffected.
Highly efficient laser action in femtosecond-written Nd:yttrium aluminum garnet ceramic waveguides
Authors: Torchia G. A. , Rodenas A. , Benayas A. , Cantelar E. , Roso L. , Jaque D.
Published: March 2008

We report continuous wave 1.06μm laser operation in an optical waveguide fabricated in a Nd:YAG ceramic by femtosecond laser writing. Single mode and stable laser oscillation have been achieved by using the natural Fresnel reflection for optical feedback. Output laser power in excess of 80mW and a laser slope efficiency of 60% have been demonstrated.
Observation and modeling of fast trapped ion losses due to neoclassical tearing modes
Authors: Poli Emanuele , García-Muñoz Manuel , Fahrbach Hans-Ulrich , Günter Sibylle ,   ASDEX Upgrade Team
Published: March 2008

Losses of trapped fast ions in the presence of low-frequency modes are observed in the ASDEX Upgrade tokamak [Fusion Science and Technology 44, 569 (2003), Special Issue on ASDEX Upgrade] during ion-cyclotron heated discharges by means of a new fast-ion-losses detector. The expulsion is explained in terms of the magnetic drift induced by the perturbation field when the ratio between the bounce frequency and the toroidal precession frequency equals the toroidal mode number.
Microwave permeability spectra of flake-shaped FeCuNbSiB particle composites
Authors: Qiao Liang , Wen Fusheng , Wei Jianqiang , Wang Jianbo , Li Fashen
Published: March 2008

The effective permeability of flake-shaped FeCuNbSiB particles/nonmagnetic matrix composition in high frequency was measured and calculated. In contrast to the relatively larger size and irregular shape particles, the flake particles have higher permeability. The results are attributed to the different magnetic loss mechanisms. According to the skin-effect criterion, we find that the magnetic loss in flake particles is mainly caused by the natural resonance, compared with the eddy current effect in the larger size and irregular shape particles. Using the shape anisotropy, the flake soft magnetic particles overcome the difficulty of the relatively small intrinsic anisotropies and increase the natural resonant frequencies to the gigahertz range, leading to the higher real part and imaginary part of the permeability. The resonance peak of flake particles was simulated using the combination of the Landau–Lifshitz–Gilbert equation and Bruggeman’s effective medium theory considering a random spatial distribution of magnetic easy axes. Our theory simulation agrees well with the experimental data.
Comment on “Exponential stabilization of chaotic systems with delay by periodically intermittent control” [Chaos 17, 013103 (2007)]
Authors: Deng Shaojiang , Xiao Di
Published: March 2008

In the referenced paper, there is a technical carelessness in the second lemma, and it is highlighted here to avoid possible failure when the result is used to design the intermittent controller for nonlinear systems.
Submillisecond response nematic liquid crystal modulators using dual fringe field switching in a vertically aligned cell
Authors: Jiao Meizi , Ge Zhibing , Wu Shin-Tson , Choi Wing-Kit
Published: March 2008

A fast response nematic liquid crystal (LC) modulator using dual fringe field switching (DFFS) mode is demonstrated. Both top and bottom substrates have pixel and common electrodes to generate complementary fringing fields. The cell consists of a vertically aligned LC layer whose dielectric anisotropy is positive. In a voltage-on state, self-imposed thin LC walls near the center of the slits and electrodes are formed and the surrounding LC molecules exert a strong restoring force. As a result, submillisecond gray-to-gray response time is achieved. Two DFFS cells are used as examples to illustrate the design principles for display and photonic applications.
Real-time spectroscopy with subgigahertz resolution using amplified dispersive Fourier transformation
Authors: Chou Jason , Solli Daniel R. , Jalali Bahram
Published: March 2008

Dispersive Fourier transformation is a powerful technique in which spectral information is mapped into the time domain using chromatic dispersion. It replaces a spectrometer with an electronic digitizer and enables real-time spectroscopy. The fundamental problem in this technique is the trade-off between the detection sensitivity and spectral resolution, a limitation set by the digitizer’s bandwidth. This predicament is caused by the power loss associated with optical dispersion. We overcome this limitation using Raman-amplified spectrum-to-time transformation. An extraordinary lossless −11.76ns∕nm dispersive device is used to demonstrate single-shot gas absorption spectroscopy with a 950MHz resolution—a record in real-time spectroscopy.
The interface effect of the magnetic anisotropy in ultrathin epitaxial Fe3O4 film
Authors: Huang Z. C. , Zhai Y. , Lu Y. X. , Li G. D. , Wong P. K. J. , Xu Y. B. , Xu Y. X. , Zhai H. R.
Published: March 2008

The magnetic anisotropy of epitaxial layered structures of Fe3O4(tFe=4nm)∕GaAs(100), MgO(3nm)∕Fe3O4(tFe=4nm)∕GaAs(100), and Fe3O4(tFe=4nm)∕MgO(3nm)∕Fe3O4(tFe=4nm)∕GaAs(100) was studied by ferromagnetic resonance. It was shown that a predominant in-plane uniaxial magnetic anisotropy and a small fourfold cubic magnetocrystalline anisotropy existed. The in-plane uniaxial anisotropy constant decreased when the MgO layer was covered on Fe3O4∕GaAs, while the cubic anisotropy increased. In the sandwich structures, two resonance peaks were observed. One is similar to that in Fe3O4∕GaAs layer, while another corresponding to Fe3O4 on MgO showed more remarkable fourfold anisotropy and lower uniaxial anisotropy due to smaller mismatch between Fe3O4 and MgO. The interface the Fe3O4 layer is deposited on has dominant effect.
Excimer-based red/near-infrared organic light-emitting diodes with very high quantum efficiency
Authors: Cocchi M. , Kalinowski J. , Virgili D. , Williams J. A. G.
Published: March 2008

Various light output measures of red/near-infrared (NIR) excimer-based organic light-emitting diodes (LEDs) are reported for different cathodes (Al, Al∕LiF, Ca, and Ca∕PbO2). By using a selected phosphor (PtL2Cl) from a series of terdentate cyclometallated efficient phosphorescent Pt(II) complexes, PtLnCl, as the neat film emitting layer and a Ca∕Pb(IV)O2 cathode, the authors achieve unusually high forward viewing external quantum efficiencies of up to 14.5% photons/electron and a power conversion efficiency of up to 6% at a high emission forward output of 25mW∕cm2. These are the highest efficiencies reported for a NIR organic LED. Electron tunneling through thin insulating layers of LiF and Pb(IV)O2 and the difference in band bending at the organic electron transporting layer and the cathode between the samples are used to explain this performance achievement.
Two-dimensional electromagnetic cloak having a uniform thickness for elliptic cylindrical regions
Authors: Kwon Do-Hoon , Werner Douglas H.
Published: March 2008

A two-dimensional electromagnetic cloak recipe having a uniform thickness is presented for cloaked regions of elliptic cylindrical shape. The cloak material parameters are obtained from the spatial transformation approach. The effectiveness of the cloak design is verified by full-wave simulations of plane wave scattering from uncloaked and cloaked conducting elliptic cylinders. The proposed design provides a more practical cloak geometry when compared to previous designs that have the outer boundary limited only to a scaled version of the inner boundary.