bluuebunny/crossref_metadata_2025 huggingface dataset:
Peroxisomes Start Their Life in the Endoplasmic Reticulum
Authors: Tabak Henk F. , Murk Jean L. , Braakman Ineke , Geuze Hans J.
Published: November 2010

Peroxisomes belong to the ubiquitous organelle repertoire of eukaryotic cells. They contribute to cellular metabolism in various ways depending on species, but a consistent feature is the presence of enzymes to degrade fatty acids. Due to the pioneering work of DeDuve and coworkers, peroxisomes were in the limelight of cell biology in the sixties with a focus on their metabolic role. During the last decade, interest in peroxisomes has been growing again, this time with focus on their origin and maintenance. This has resulted in our understanding how peroxisomal proteins are targeted to the organelle and imported into the organellar matrix or recruited into the single membrane surrounding it. With respect to the formation of peroxisomes, the field is divided. The long‐held view formulated in 1985 by Lazarow and Fujiki (Lazarow PB, Fujiki Y. Biogenesis of peroxisomes. Annu Rev Cell Biol 1985; 1: 489–530) is that we are dealing with autonomous organelles multiplying by growth and division. This view is being challenged by various observations that call attention to a more active contribution of the ER to peroxisome formation. Our contribution to this debate consists of recent observations using immuno‐electronmicroscopy and electron tomography in mouse dendritic cells that show the peroxisomal membrane to be derived from the ER.
Altered13C Glucose Metabolism in the Cortico—Striato—Thalamo—Cortical Loop in the MK-801 Rat Model of Schizophrenia
Authors: Eyjolfsson Elvar M , Nilsen Linn Hege , Kondziella Daniel , Brenner Eiliv , Håberg Asta , Sonnewald Ursula
Published: November 2010

Using a modified MK-801 (dizocilpine) N-methyl-d-aspartic acid (NMDA) receptor hypofunction model for schizophrenia, we analyzed glycolysis, as well as glutamatergic, GABAergic, and monoaminergic neurotransmitter synthesis and degradation. Rats received an injection of MK-801 daily for 6 days and on day 6, they also received an injection of [1-13C]glucose. Extracts of frontal cortex (FCX), parietal and temporal cortex (PTCX), thalamus, striatum, nucleus accumbens (NAc), and hippocampus were analyzed using13C nuclear magnetic resonance spectroscopy, high-performance liquid chromatography, and gas chromatography—mass spectrometry. A pronounced reduction in glycolysis was found only in PTCX, in which13C labeling of glucose, lactate, and alanine was decreased.13C enrichment in lactate, however, was reduced in all areas investigated. The largest reductions in glutamate labeling were detected in FCX and PTCX, whereas in hippocampus, striatum, and Nac,13C labeling of glutamate was only slightly but significantly reduced. The thalamus was the only region with unaffected glutamate labeling. γ-Aminobutyric acid (GABA) labeling was reduced in all areas, but most significantly in FCX. Glutamine and aspartate labeling was unchanged. Mitochondrial metabolites were also affected. Fumarate labeling was reduced in FCX and thalamus, whereas malate labeling was reduced in FCX, PTCX, striatum, and NAc. Dopamine turnover was decreased in FCX and thalamus, whereas that of serotonin was unchanged in all regions. In conclusion, neurotransmitter metabolism in the cortico—striato—thalamo—cortical loop is severely impaired in the MK-801 (dizocilpine) NMDA receptor hypofunction animal model for schizophrenia.
Chronic Hyperperfusion and Angiogenesis Follow Subacute Hypoperfusion in the Thalamus of Rats with Focal Cerebral Ischemia
Authors: Hayward Nick MEA , Yanev Pavel , Haapasalo Annakaisa , Miettinen Riitta , Hiltunen Mikko , Gröhn Olli , Jolkkonen Jukka
Published: November 2010

Cerebral blood flow (CBF) is disrupted after focal ischemia in rats. We examined long-term hemodynamic and cerebrovascular changes in the rat thalamus after focal cerebral ischemia. Cerebral blood flow quantified by arterial spin labeling magnetic resonance imaging was decreased in the ipsilateral and contralateral thalamus 2 days after cerebral ischemia. Partial thalamic CBF recovery occurred by day 7, then the ipsilateral thalamus was chronically hyperperfused at 30 days and 3 months compared with its contralateral side. This contrasted with permanent hypoperfusion in the ipsilateral cortex. Angiogenesis was indicated by endothelial cell (RECA-1) immunohistochemistry that showed increased blood vessel branching in the ipsilateral thalamus at the end of the 3-month follow-up. Only transient thalamic IgG extravasation was observed, indicating that the blood–brain barrier was intact after day 2. Angiogenesis was preceded by transiently altered expression levels of cadherin family adhesion molecules, cadherin-7, protocadherin-1, and protocadherin-17. In conclusion, thalamic pathology after focal cerebral ischemia involved long-term hemodynamic changes and angiogenesis preceded by altered expression of vascular adhesion factors. Postischemic angiogenesis in the thalamus represents a novel type of remote plasticity, which may support removal of necrotic brain tissue and aid functional recovery.
Recent trends in computational photochemistry
Authors: Serrano-Andrés Luis , Roca-Sanjuán Daniel , Olaso-González Gloria
Published: November 2010

Recent advances in theoretical photophysics and photochemistry derive from the improved capabilities of ab initio quantum-chemical methods to deal with different types of excited states phenomena in molecules of increasing size and complexity. Whereas the widespread use of time-dependent density functional (TD-DFT) based techniques for the excited state have extended the study of absorption and emission processes to large molecular systems and coupled-cluster (CC) methods have increased the accuracy of spectroscopic studies in medium-size compounds, multiconfigurational ab initio approaches such as CASPT2 and MRCI are now able to cope accurately with all types of photochemical processes in medium to relatively large systems, including nonadiabatic processes involving conical intersections, i.e., energy degeneracies, between potential energy hypersurfaces (PEHs), which are out of reach for the other single reference approaches. The coupling of accurate electronic structure calculations based on PEHs with reaction dynamic procedures is starting to make available the theoretical determination of both static and dynamic, time-dependent and statistical, photoinduced properties in systems of different type and complexity. Examples of the studied processes and the most commonly used approaches are given below.
Dynamics and photophysics of oligomers and polymers
Authors: Pina João , Costa Telma , de Melo J. Sérgio Seixas
Published: November 2010

Recent advances in the photophysics of two different type of organic (conjugated and hydrophobically modified) polymers are reviewed. Three major issues are considered in this report. With conjugated organic oligomers and polymers, the first one involves the advancement in the comprehensive investigation of the solution and solid state photophysics of several oligomers in view of the particular relevance of the information obtained in this way for rationalizing the behaviour of polymers. A second consideration is related to the decay mechanisms in conjugated polymers. Indeed, with p-phenylene-vinylene (PPV) polymers, different oligomeric structures have been investigated with the aim of differentiating between the relaxation decay processes; in conjugated organic polymers the decay to the ground state can take place through energy migration along the chain (in a ladder-type mechanism involving segments of gradually increasing conjugation), isomerization, or conformational relaxation into a more relaxed structure with subsequent decay to the ground state. Finally, in the case of hydrophobically modified water soluble polymers, a particular emphasis will be put on the kinetics of excimer formation and on the presence of ground-state dimers. It will be discussed in which way the solution of the kinetic schemes, with the determination of all the rate constants and fractions of species present in the ground-state, can be used for the understanding of the polymer behaviour in solution.
Alkenes, alkynes, dienes, polyenes
Authors: Tsuno Takashi
Published: November 2010

This chapter deals with the photochemistry of alkenes, alkynes, dienes, polyenes, and related compounds through a choice of the literature published during the period July 2007–December 2009. This chapter also covers the large area of isomerization/electrocyclization/cycloaddition reactions of stilbene derivatives as well as its heterocyclic analogues such as dithienylethenes.
Photophysics of transition metal complexes
Authors: Barigelletti Francesco
Published: November 2010

This chapter deals with studies reporting the photophysical properties of selected transition-metal complexes, as extracted from journal articles appeared in the period July 2007 to December 2009. The transition metal species considered here belong to families of complexes featuring largely studied optical properties, in particular luminescence. The complexes are from the following metal centres: d6 Ru(II), Os(II), Re(I), Ir(III), and Rh(III), d8 Pt(II) and Pd(II), d10 Cu(I) and Au(I), d3 Cr(III); finally some mention is given of lanthanide (Ln) complexes.
Photochemical and photocatalytic properties of transition-metal compounds
Authors: Maldotti Andrea
Published: November 2010

This contribution covers important developments on the photochemical and photocatalytic properties of transition-metal compounds for the period between July 2007 and December 2009. The emphasis is on photoactive molecular-based systems of interest in the following major areas:water splitting and H2 production;CO2 reduction;photoreactivity and applications in synthesis;biomimetic activity of enzyme active site models, including bioinspired photosynthetic systems;biomedical applications such as DNA cleavage.
New materials for sensitized photo-oxygenation
Authors: Lacombe Sylvie , Pigot Thierry
Published: November 2010

A variety of photosensitizers has been included, adsorbed or grafted onto different supports. This review focuses on original new materials designed for photoinduced oxygenation reactions, using light as the activation method and oxygen as the reactant. Such materials find widespread applications for the oxidation of fine chemicals under mild conditions, for water treatment, for photodynamic bactericidal inactivation or photodynamic therapy. The generation, diffusion and reactivity of Reactive Oxygen Species (ROS), and particularly of singlet oxygen 1O2 in these heterogeneous media are discussed.
Prebiotic photochemistry
Authors: Dondi Daniele , Merli Daniele , Pretali Luca
Published: November 2010

The role of photochemistry in the synthesis of prebiotic compounds is briefly reviewed.
Trends in photolithography materials
Authors: Conley Will , Garza Cesar
Published: November 2010

New trends on materials for photolithography are presented
Streptococcal pyogenic exotoxin B (SpeB) boosts the contact system via binding of α-1 antitrypsin
Authors: Meinert Niclasen Louise , Olsen Johan G. , Dagil Robert , Qing Zhang , Sørensen Ole E. , Kragelund Birthe B.
Published: November 2010

The Streptococcus pyogenes cysteine protease SpeB (streptococcal pyrogenic exotoxin B) is important for the invasive potential of the bacteria, but its production is down-regulated following systemic infection. This prompted us to investigate if SpeB potentiated the host immune response after systemic spreading. Addition of SpeB to human plasma increased plasma-mediated bacterial killing and prolonged coagulation time through the intrinsic pathway of coagulation. This effect was independent of the enzymatic activity of SpeB and was mediated by a non-covalent medium-affinity binding and modification of the serpin A1AT (α-1 antitrypsin). Consequently, addition of A1AT to plasma increased bacterial survival. Sequestration of A1AT by SpeB led to enhanced contact system activation, supported by increased bacterial growth in prekallikrein deficient plasma. In a mouse model of systemic infection, administration of SpeB reduced significantly bacterial dissemination. The findings reveal an additional layer of complexity to host–microbe interactions that may be of benefit in the treatment of severe bacterial infections.
Research Ethics III: Publication Practices and Authorship, Conflicts of Interest, and Research Misconduct
Authors: Horner Jennifer , Minifie Fred D.
Published: November 2010

Purpose

In this series of articles—
Research Ethics I,
Research Ethics II,
and
Research Ethics III
—the authors provide a comprehensive review of the 9 core domains for the responsible conduct of research (RCR) as articulated by the Office of Research Integrity.

Method

In
Research Ethics III,
they review the RCR domains of publication practices and authorship, conflicts of interest, and research misconduct. Whereas the legal definition of research misconduct under federal law pertains mainly to intentional falsification, fabrication, and plagiarism, they discuss a host of research practices that raise ethical concerns.

Conclusions

The integrity of the scientific record—its accuracy, completeness, and value—ultimately impacts the health and well-being of society. For this reason, scientists are both entrusted and obligated to use the highest standards possible when proposing, performing, reviewing, and reporting research or when educating and mentoring new investigators.
Research Ethics I: Responsible Conduct of Research (RCR)—Historical and Contemporary Issues Pertaining to Human and Animal Experimentation
Authors: Horner Jennifer , Minifie Fred D.
Published: November 2010

Purpose

In this series of articles—Research Ethics I,Research Ethics II,andResearch Ethics III—the authors provide a comprehensive review of the 9 core domains for the responsible conduct of research (RCR) as articulated by the Office of Research Integrity. InResearch Ethics I,they present a historical overview of the evolution of RCR in the United States then examine the evolution of human and animal experimentation from the birth of scientific medicine through World War II to the present day.

Method

They relied on authoritative documents, both historical and contemporary, insightful commentary, and empirical research in order to identify current issues and controversies of potential interest to both faculty and students.

Conclusions

The authors have written this article from a historical perspective because they think all readers interested in RCR should appreciate how the history of science and all the good—and harm—it has produced can inform how researchers practice responsible research in the 21st century and beyond.
Comparing Two Methods for Reducing Variability in Voice Quality Measurements
Authors: Kreiman Jody , Gerratt Bruce R.
Published: November 2010

Purpose

Interrater disagreements in ratings of quality plague the study of voice. This study compared 2 methods for handling this variability.

Method

Listeners provided multiple breathiness ratings for 2 sets of pathological voices, one including 20 male and 20 female voices unselected for quality and one including 20 breathy female voices. Ratings for each listener were averaged together, mean ratings wereztransformed, and the likelihood that 2 listeners would agree exactly in their ratings was calculated as a function of averaging and standardizing condition. Data were also multidimensionally scaled to examine similarities among listeners in perceptual strategy. Results were compared with parallel analyses of existing breathiness ratings of the same voices gathered using a method-of-adjustment task.

Results

Three-way interactions between the mean rating for a voice, standardization condition, and the number of voices averaged together were observed, but no main effect of averaging condition emerged. Multidimensional scaling revealed significant residual differences in perceptual strategy across listeners after averaging and standardizing. Ratings from the method-of-adjustment task showed both high agreement levels and consistent perceptual strategies across listeners, as theoretically predicted.

Conclusion

Averaging multiple ratings and standardizing the mean are inadequate in addressing variations in voice quality perception.
Studies of cutaneous blood flow of normal forearm skin and irritated forearm skin based on high‐resolution laser Doppler perfusion imaging (HR‐LDPI)
Authors: Fullerton Ann , Rode Birgitte , Serup Jrgen
Published: November 2010

Background/aims:  High resolution laser Doppler perfusion imaging (HR‐LDPI) is a non‐touch method used for mapping cutaneous microcirculation. The aim of the present study was to investigate the usefulness of this technique for studies of cutaneous blood flow of normal untreated forearm skin and for the assessment of weak irritant reactions induced by exposure to sodium lauryl sulphate (SLS).

Methods  12 healthy volunteers participated in the study. Initially, basal flow was measured for 6 selected test areas on the right forearm. 24 h occlusive application of 0%; 0.125%; 0.25%; 0.50% and 1.0% SLS was performed. An untreated skin area was also included. Test sites were clinically evaluated and the cutaneous blood flow was measured using HR‐ LDPI on days 2, 3 and 5.

Results and conclusions:  The results of the present study show that HR‐LDPI is a useful technique for assessing the mean cutaneous blood flow of both normal and irritated forearm skin. The rectangular region of interest (R‐ROI) method was found to be superior to the threshold region of interest (T‐ROI) method in image analysis of the mean blood flow of individual scans. The results showed that even though spatial variation within a skin region may be considerable, no intraregional differences or daily variations in mean basal flow of selected skin areas on the forearm could be found. Due to the low variability, it should not generally be necessary to include an untreated control site as each site should act as its own control. The temporal variation in skin perfusion was minor compared with the spatial variation. This was found both for normal and irritated skin. Therefore, one scan of each area of interest should normally be sufficient. Clinical irritation scores on day 3 were more evenly distributed than those on days 2 and 5. An increase in mean perfusion, as a function of the clinical irritation score, was found. However, no statistical differences could be found in mean perfusion for the selected dose levels of SLS.
Ultrabroadband dielectric spectroscopy and phonons in (Pb1−x/2Lax)(Zr0.9Ti0.1)O3
Authors: Buixaderas E. , Bovtun V. , Veljko S. , Savinov M. , Kužel P. , Gregora I. , Kamba S. , Reaney I.
Published: November 2010

The dielectric behavior of (Pb1−x/2Lax)(Zr0.9Ti0.1)O3 PLZT 100x/90/10 (0≤100x≤1) was studied in the frequency range 102–1014 Hz using dielectric, time-domain terahertz (THz), far-infrared, and Raman spectroscopy in the temperature interval 10–900 K. PZT 90/10 and PLZT 2/90/10 undergo two phase transitions, from a cubic paraelectric to a rhombohedral untilted ferroelectric (FE) phase and on further cooling to a tilted FE phase. PLZT 4/90/10 and PLZT 10/90/10 are incommensurately modulated and composed of an intergrowth of polar and antipolar cation displacements. These samples consequently demonstrate a FE soft mode which exhibits minimal frequency several tens of degrees above the nominal antiferroelectric phase transition temperature. The dielectric response of PLZT 100x/90/10 is mainly governed by a gigahertz relaxation and a soft phonon component in the THz range. As in other PbO-based perovskites, the soft mode is split into a higher-frequency component (ω∼80 cm−1) and a highly damped THz component (ω∼30 cm−1), with larger dielectric strength already in the paraelectric phase.
Effect of quantum confinement on spin transport and magnetization dynamics in dual barrier spin transfer torque magnetic tunnel junctions
Authors: Mojumder Niladri Narayan , Augustine Charles , Nikonov Dmitri E. , Roy Kaushik
Published: November 2010

Electronic transport and magnetization dynamics associated with the current induced spin torque effects in dual barrier magnetic tunnel junctions (MTJs) have been investigated using nonequilibrium Green’s Function equations solved self-consistently with Landau–Lifshitz–Gilbert–Slonczewski equation. In a dual barrier (pentalayer) MTJ, a set of geometry and band-structure parameters jointly determines the position of resonant peaks and valleys within the energy range of interest. The presence of nonmonotonic quantum well states inside the central ferromagnetic free layer significantly modifies the critical switching voltage across MTJ and tunneling magnetoresistance simultaneously depending on whether the resonant condition is satisfied. Proper choice of (i) free ferromagnetic layer thickness, (ii) tunneling barrier height, (iii) width of the tunneling barrier, and (iv) operational voltage has been found to increase both in-plane and out-of-plane spin torque efficiencies in pentalayer MTJs by approximately an order in magnitude as compared to the conventional single barrier trilayer structures. Transport simulation results are in a reasonable quantitative agreement with the existing set of trilayer MTJ experiments. Energy efficiency of pentalayer MTJ structures over that of trilayers during spin torque driven magnetization switching has also been reported quantitatively under resonance conditions.
Darboux transformations for a generalized Dirac equation in two dimensions
Authors: Pozdeeva Ekaterina , Schulze-Halberg Axel
Published: November 2010

We construct explicit Darboux transformations for a generalized, two-dimensional Dirac equation. Our results complement and generalize former findings for Dirac equations in two and three spatial dimensions. We show that as a particular case, our Darboux transformations are applicable to the two-dimensional Dirac equation in cylindrical coordinates and give several examples.
Electron induced reactions in molecular nanofilms of chlorodifluoroacetic acid (CClF2COOH): Desorption of fragment anions and formation of CO2
Authors: Orzol Mario , König-Lehmann Constanze , Illenberger Eugen , Kopyra Janina
Published: November 2010

Electron induced reactions in molecular nanofilms of chlorodifluoroacetic acid (CClF2COOH) are studied by electron stimulated desorption (ESD) of fragment anions and temperature programed thermal desorption spectroscopy (TDS). The fragment anions O−, F−, OH−, and Cl− are formed from broad resonance features in the energy range of 4–14 eV and assigned to dissociative electron attachment (DEA) of molecules or dimers at or near the surface of the film, followed by desorption. The strong low energy DEA resonances (0–2 eV) observed in a previous gas phase study [J. Kopyra et al., Int. J. Mass. Spectrom. 285, 131 (2009)] are completely suppressed in ESD. Electron irradiation at energies above 10 eV results in the formation of CO2, as revealed by TDS. The extended irradiation of a 3 ML film (25 nA, 240 min) results in a nearly completely transformation of the initial compound in favor of CO2 and other by-products.
Nanotwin domains in high-strain ferroelectric 89.5%Pb(Zn1/3Nb2/3)O3–10.5%PbTiO3 single crystal
Authors: Chang W. S. , Lim L. C. , Yang P. , Ku C.-S. , Lee H.-Y. , Tu C.-S.
Published: November 2010

High-resolution synchrotron x-ray diffraction and field emission-scanning electron microscopy were used to investigate domain structures of the unpoled (001)-oriented 89.5%Pb(Zn1/3Nb2/3)O3–10.5%PbTiO3 (PZN–10.5%PT) single crystal. The results revealed the coexistence of 180° and 90° tetragonal nanotwin domains at room temperature. Upon zero-field heating, the PZN–10.5%PT undergoes a tetragonal-to-cubic transformation near 185 °C. Tetragonal PZN–10.5%PT crystal has better thermal stability notably in the temperature range of 80–150 °C. This makes the tetragonal PZN–PT potential candidates for high temperature piezoelectric devices.
Band gap engineering of wurtzite and zinc-blende GaN/AlN superlattices from first principles
Authors: Cui X. Y. , Delley B. , Stampfl C.
Published: November 2010

Based on all-electron density functional theory calculations, we systematically investigate the electronic structure of (0001)-oriented wurtzite (wz) and (111)-, (100)-, and (110)-oriented zinc-blende (zb) GaN/AlN superlattices, where the band gap, strength of the electric field and their correlation with biaxial stain as a function of the superlattice thickness are calculated. For the polar wz-(0001) and zb-(111) systems, the band gap values are found to continuously decrease with increasing thickness of the superlattice period due to the built-in electric field. By mapping the core-level shift, we demonstrate the presence of spontaneous polarization in both wz-(0001) and zb-(111) superlattices. The built-in electric field is calculated to be about 5.1±0.3 and 1.4±0.4 MV/cm in the “free-standing” (fully relaxed) wz-(0001) and zb-(111) superlattices, respectively. Strain-induced piezoelectric polarizations are estimated to contribute only about 5% for the wz-(0001) superlattice, and about 30% for the zb-(111) systems. The zb-(100) and (110) superlattices are characterized by flat core-level bands in the well and barrier regions. The zb-(100) superlattices are predicted to have a stronger quantum confinement than the zb-(110) superlattices. In both systems, confinement effects lead to a marked band gap increase with decreasing thickness of the superlattice period.
Cosubstitution effect on the magnetic, transport, and thermoelectric properties of the electron-doped perovskite manganite CaMnO3
Authors: Okuda T. , Fujii Y.
Published: November 2010

We have investigated magnetic, transport, and thermoelecric properties of polycrystalline Ca1−xSrxMn1−yMoyO3, and have tried to optimize the n-type thermoelectric response below room temperature. The Sr substitution enlarges a Mn–O–Mn bond angle and increases a crystal symmetry, which enhances one electron transfer of the electrons doped by the Mo substitution. This effect promotes the competition between correlations of a G-type antiferromagnetic (AF) order and a C-type AF order accompanying a 3d3z2−r2 orbital order, leading to the more complicated magnetic phase diagram of Ca0.75Sr0.25Mn1−yMoyO3 than that of CaMn1−yMoyO3. A subtle balance between the effects of the enhanced one electron transfer and the introduced disorder into the A(Ca)-site upon the transport properties enhances a dimensionless thermoelectric figure-of-merit ZT up to 0.03 at room temperature. However, a correlation of the 3d3z2−r2 orbital order is also promoted by the Sr substitution, which bounds a further enhancement of ZT.
Energy considerations in a micromagnetic hysteresis model and the Preisach model
Authors: Van de Wiele Ben , Vandenbossche Lode , Dupré Luc , De Zutter Daniël
Published: November 2010

Finding the relations between the microstructural material parameters and the macroscopic hysteresis behavior is indispensable in the design of ferromagnetic materials with minimal (hysteresis) losses. Micromagnetic hysteresis simulations enable a rigorous and structured investigation of these relations since in the numerical model each material parameter can be altered independently. This paper describes a procedure to extract the Preisach distribution function, quantifying the macroscopic hysteresis properties, from micromagnetic simulations incorporating the materials’ microstructure. Furthermore, the instantaneously added, stored and dissipated energy while running through the hysteresis loop as described in the macroscopic Preisach model and in the micromagnetic hysteresis model are compared, evidencing a very good agreement. Moreover, using the micromagnetic model, the energy rearrangements between the different micromagnetic interaction terms is studied at each time point of the hysteresis loop. It is concluded that the micromagnetic hysteresis model is a valuable tool in the study of hysteresis properties and loss mechanisms in ferromagnetic materials.
Luminescence enhancement of CdTe nanostructures in LaF3:Ce/CdTe nanocomposites
Authors: Yao Mingzhen , Zhang Xing , Ma Lun , Chen Wei , Joly Alan G. , Huang Jinsong , Wang Qingwu
Published: November 2010

Radiation detection demands new scintillators with high quantum efficiency, high energy resolution, and short luminescence lifetimes. Nanocomposites consisting of quantum dots and Ce3+ doped nanophosphors may be able to meet these requirements. Here, we report the luminescence enhancement of LaF3:Ce/CdTe nanocomposites which were synthesized by a wet chemistry method. CdTe quantum dots in LaF3:Ce/CdTe nanocomposites are converted into nanowires, while in LaF3/CdTe nanocomposites no such conversion is observed. As a result, the CdTe luminescence in LaF3:Ce/CdTe nanocomposites is enhanced about five times, while in LaF3/CdTe nanocomposites no enhancement was observed. Energy transfer, light reabsorption, and defect passivation are the likely reasons for the luminescence enhancement.
Domain wall dispersions: Relaxation and resonance in Ni–Zn ferrite doped with V2O3
Authors: Herrera G.
Published: November 2010

The complex permeability dispersions: relaxation and resonance are investigated in the Ni0.7Zn0.3Fe2O4 ferrites doped with V2O3 at different weight percent. The complex permeability was measured at frequencies in the 30 kHz to 6 GHz range. The intragranular porosity plays an important role to distinguish between relaxation and resonant dispersion. The results obtained show that a tight grain size distribution leads to a resonant character, while a wide grain size distribution results in a mixed dispersion. The complex permeability results were modeled with the resonant RCL equivalent circuit formed by a series RL arrangement in parallel with a capacitor C. The experimental results and the model are in agreement.
Shape control via surface reconstruction kinetics of droplet epitaxy nanostructures
Authors: Somaschini C. , Bietti S. , Koguchi N. , Sanguinetti S.
Published: November 2010

We present the fabrication and discuss the growth dynamics of two classes of GaAs quantum nanostructures fabricated by droplet epitaxy, namely, double rings and coupled ring-disks. Their morphological differences has been investigated and found to be originated by the kinetic of the changes in the surface reconstruction around the initially formed Ga droplets during the arsenization step. The control of surface reconstruction dynamics thus permits a fine tuning of the actual nanostructure shape at the nanoscale, based on pure self-assembling techniques.
Sub 200 fs pulse generation from a graphene mode-locked fiber laser
Authors: Popa D. , Sun Z. , Torrisi F. , Hasan T. , Wang F. , Ferrari A. C.
Published: November 2010

Ultrafast fiber lasers with broad bandwidth are in great demand for a variety of applications, such as spectroscopy, biomedical diagnosis, and optical communications. Sub 200 fs pulses are required for ultrafast spectroscopy with high temporal resolution. Graphene is an ideal ultrawide-band saturable absorber. We report the generation of 174 fs pulses from a graphene-based fiber laser.
Major impacts of point defects and impurities on the carrier recombination dynamics in AlN
Authors: Chichibu S. F. , Onuma T. , Hazu K. , Uedono A.
Published: November 2010

Impacts of point defects and impurities on the carrier recombination dynamics in AlN are revealed by time-resolved spectroscopy and positron annihilation measurements. Intrinsically short low-temperature excitonic radiative lifetime (τR∼10 ps) was elongated with the increase in Al-vacancy concentration up to 530 ps, irrespective of threading dislocation density. A continuous decrease in τR with temperature rise up to 200 K for heavily doped samples revealed the carrier release from the band-tail formed due to impurities and point defects. Because room-temperature nonradiative lifetime was equally short for all samples, high temperature growth with appropriate defect management is necessary in extracting radiative nature of AlN.
Band transport and mobility edge in amorphous solution-processed zinc tin oxide thin-film transistors
Authors: Lee Chen-Guan , Cobb Brian , Dodabalapur Ananth
Published: November 2010

We report on charge transport phenomena in high-mobility solution-deposited amorphous zinc-tin oxide based thin-film transistors. At low carrier concentrations, the dominant transport mechanism is multiple trap and release, with the activation energy steadily decreasing with increasing carrier density. The activation energy decreases to zero and beyond a threshold carrier density, the mobility decreases with increasing temperature. This temperature dependence as well as the value of the mobility clearly indicates that transport is bandlike. Also observed is a clear mobility edge in accordance with the prediction of Mott’s model, which are normally observed in crystalline semiconductors.
Structure of few-layer epitaxial graphene on 6H-SiC(0001) at atomic resolution
Authors: Weng Xiaojun , Robinson Joshua A. , Trumbull Kathleen , Cavalero Randall , Fanton Mark A. , Snyder David
Published: November 2010

Using directly interpretable atomic-resolution cross-sectional scanning transmission electron microscopy, we have investigated the structure of few-layer epitaxial graphene (EG) on 6H-SiC(0001). We show that the buried interface layer possesses a lower average areal density of carbon atoms than graphene, indicating that it is not a graphenelike sheet with the 63×63R30° structure. The EG interlayer spacings are found to be considerably larger than that of the bulk graphite and the surface of the SiC(0001) substrate, often treated as relaxed, is found to be strained. Discontinuity of the graphene layers above the SiC surface steps is observed, in contradiction with the commonly believed continuous coverage.
Point-defect-mediated dehydrogenation of AlH3
Authors: Ismer Lars , Janotti Anderson , Van de Walle Chris G.
Published: November 2010

Based on hybrid density functional calculations, we propose a microscopic mechanism for the dehydrogenation of AlH3. Our results indicate that mass transport mediated by positively charged hydrogen vacancies (VH+) is likely the rate-limiting mechanism. The calculated activation energy of 1.72 eV is in good agreement with experimental values. The high formation energy and hence low concentration of VH+ explains why AlH3 does not decompose at room temperature, although it is thermodynamically unstable. Issues of maintaining charge neutrality are addressed.
Comment on Wood et al. 2008, 'Impacts of fire on forest age and runoff in mountain ash forests'
Authors: Benyon Richard , Haydon Shane , Vertessy Rob , Hatton Tom , Kuczera George , Feikema Paul , Lane Patrick
Published: November 2010

Wood et al. (2008; FPB 35) concluded their measurements of evapotranspiration (ET) in Eucalyptus regnans F.Muell. forest at Wallaby Creek, Victoria showed that ET differs only slightly between regrowth and oldgrowth, contrary to the findings of previous research. We assert that the conclusions of Wood et al. are invalid and argue that Wood et al. substantially overestimated annual transpiration and rainfall. Monthly whole-forest ET measured by Wood et al. using eddy covariance in a 296-year-old stand sum to ~700 mm year–1; consistent with rainfall of 721 mm year–1 recorded nearby by the Bureau of Meteorology. However, the Wood et al. conclusions were based on 1077 mm annual transpiration at this site, which appears to be estimated from a few months of heat pulse velocity measurements. Transpiration alone cannot be 54% higher than whole-forest ET because the latter includes transpiration, rainfall interception and evaporation from the forest floor. We believe Wood et al. made errors in scaling heat pulse velocities to whole-stand annual transpiration. Their rainfall of 1175 mm year–1 averages 62% higher than at three Bureau of Meteorology and Melbourne Water sites nearby. The paper also contains inaccuracies in reporting of the literature and numerous other errors.
Global gene expression analysis of in vitro root formation in Medicago truncatula
Authors: Holmes Peta , Djordjevic Michael A. , Imin Nijat
Published: November 2010

Medicago truncatula Gaertn. can generate roots in vitro through the formation of root stem cells from leaf explants cultured with auxin. To identify key genes involved in the early processes of root initiation, we compared gene expression in root-forming cultures (RFC) enriched for root stem cells with non-root-forming cultures (NRFC) and untreated leaves using the Affymetrix Medicago GeneChip. Comparing RFC (at 1 week, before root primordium formation) to normal leaf tissue, we identified 904 and 993 up- and downregulated probe sets. Comparing RFC and NRFC, we identified 92 and 182 up- and downregulated probe sets. By comparing all the samples we identified a set of 76 and 42 probe sets up- and downregulated that may be crucial to root stem cell formation and subsequent root initiation. Upregulated probe sets in RFC include Arabidopsis orthologs that are involved in root stem cell formation and root initiation. To validate the GeneChip results, quantitative real-time RT–PCR analysis was used to examine the expression of specific up- and downregulated genes, all of which positively correlated with the microarray data. We used bioinformatic tools developed to functionally annotate the Medicago genome array. This showed significant changes in metabolism, signalling and the expression of transcription factors including some with described roles in root organogenesis and other genes not previously linked to this process. This data facilitates the mapping of regulatory and metabolic networks in M. truncatula and provides candidates for further functional analysis of root initiation in vitro and in planta.
Buoyancy, salt tolerance and germination of coastal seeds: implications for oceanic hydrochorous dispersal
Authors: Guja Lydia K. , Merritt David J. , Dixon Kingsley W.
Published: November 2010

Many coastal plant species are widely distributed, including several pan-global species. Long-distance dispersal and physiological resilience of diaspores (i.e. the plant dispersal unit encompassing the seed and any additional surrounding or attached tissues at dispersal) to adverse environmental conditions are possible contributors to the presence of species over hundreds of kilometres of coastline. Dispersal by water (hydrochory) may occur in coastal habitats. This study investigated diaspore traits considered important for oceanic hydrochorous dispersal, including morphology, buoyancy and survival in seawater, and germination under saline conditions for 13 species common to Holocene dune communities in Western Australia. Of the diaspores of 13 species dominant in this coastal community, 11 floated in seawater, with 7 having >50% of diaspores buoyant after 14 days and some diaspores remaining buoyant for 70 days. Of the 10 species that germinated, diaspores of 9 survived exposure to seawater for up to 70 days. Germination of physiologically dormant seeds contained within indehiscent woody fruits and physically dormant seeds was least affected by time in seawater. The effects of varying concentrations of NaCl (0–500 mM) on germination differed between species, but most were able to recover and germinate when transferred to non-saline water. Three different patterns of salt response were observed. It appears likely a combination of diaspore traits, rather than a single factor, facilitate oceanic hydrochorous dispersal.
Granulocyte-colony stimulating factor promotes lung metastasis through mobilization of Ly6G+Ly6C+ granulocytes
Authors: Kowanetz Marcin , Wu Xiumin , Lee John , Tan Martha , Hagenbeek Thijs , Qu Xueping , Yu Lanlan , Ross Jed , Korsisaari Nina , Cao Tim , Bou-Reslan Hani , Kallop Dara , Weimer Robby , Ludlam Mary J. C. , Kaminker Joshua S. , Modrusan Zora , van Bruggen Nicholas , Peale Franklin V. , Carano Richard , Meng Y. Gloria , Ferrara Napoleone
Published: November 2010

Priming of the organ-specific premetastatic sites is thought to be an important yet incompletely understood step during metastasis. In this study, we show that the metastatic tumors we examined overexpress granulocyte-colony stimulating factor (G-CSF), which expands and mobilizes Ly6G+Ly6C+ granulocytes and facilitates their subsequent homing at distant organs even before the arrival of tumor cells. Moreover, G-CSF–mobilized Ly6G+Ly6C+ cells produce the Bv8 protein, which has been implicated in angiogenesis and mobilization of myeloid cells. Anti–G-CSF or anti-Bv8 antibodies significantly reduced lung metastasis. Transplantation of
Bv8
null fetal liver cells into lethally irradiated hosts also reduced metastasis. We identified an unexpected role for Bv8: the ability to stimulate tumor cell migration through activation of one of the Bv8 receptors, prokineticin receptor (PKR)-1. Finally, we show that administration of recombinant G-CSF is sufficient to increase the numbers of Ly6G+Ly6C+ cells in organ-specific metastatic sites and results in enhanced metastatic ability of several tumors.
Role of epitaxy in controlling the magnetic and magnetostrictive properties of cobalt ferrite–PZT bilayers
Authors: Mukherjee D , Dhakal T , Hyde R , Mukherjee P , Srikanth H , Witanachchi S
Published: November 2010

Epitaxial thin films of cobalt ferrite (CFO) single layer and CFO–lead zirconium titanate (PZT) bilayers were deposited on single crystal MgO (1 0 0) and SrTiO3 (STO) (1 0 0) substrates by pulsed laser deposition. The structural properties were characterized using x-ray diffraction and atomic force microscopy. The magnetic properties of the as-grown thin films were measured at 10 and 300 K in both parallel and perpendicular magnetic fields. The CFO–PZT bilayer films showed enhanced or reduced values of magnetization as compared with those of the CFO single layer films depending on the substrate of deposition. A strain compression–relaxation mechanism was proposed in order to explain the structure–property relationships in the CFO–PZT bilayer thin films.
Stabilizing the forming process in unipolar resistance switching using an improved compliance current limiter
Authors: Lee S B , Chang S H , Yoo H K , Kang B S
Published: November 2010

The high reset current I
R in unipolar resistance switching is a major obstacle to practical applications in memory devices. In particular, the first I
R value after the forming process is so high that the capacitors sometimes do not exhibit reliable unipolar resistance switching. We find that the compliance current I
comp is a critical parameter for reducing I
R values in polycrystalline Pt/NiO
w
/Pt, Pt/SrTiO
x
/Pt, Ti/SrTiO
x
/Pt, Pt/TiO
y
/Pt and Pt/FeO
z
/Pt capacitors, which show unipolar resistance switching. We therefore introduce an improved, simple and easy-to-use I
comp limiter that stabilizes the forming process by drastically decreasing the current overflow so as to precisely control the I
comp and subsequent I
R values.
Study of silicon-silicon nitride interface properties on planar (1 0 0), planar (1 1 1) and textured surfaces using deep-level transient spectroscopy
Authors: Gong Chun , Simoen Eddy , Posthuma Niels E , Van Kerschaver Emmanuel , Poortmans Jef , Mertens Robert
Published: November 2010

Deep-level transient spectroscopy (DLTS) has been applied to metal–insulator–semiconductor (MIS) capacitors fabricated on planar (1 0 0), planar (1 1 1) orientations and textured n-type silicon wafers. Low frequency direct plasma-enhanced chemical vapour deposition Si–SiN
x
interface properties with and without plasma NH3 pre-treatment, with and without rapid thermal annealing (RTA) have been investigated. It is shown that three different kinds of defect states are identified at the Si–SiN
x
interface. For the planar (1 0 0) surface, samples with plasma NH3 pre-treatment plus RTA show the lowest DLTS signals, which suggests the lowest overall interface states density. For planar (1 1 1) Si surfaces, plasma NH3 pre-treatment and RTA yield a small improvement. With the textured surface, the RTA step improves the surface passivation quality further but no obvious impact is found with plasma NH3 pre-treatment. Energy-dependent electron capture cross sections were also measured by small-pulse DLTS. The capture cross sections depend strongly on the energy level and decrease towards the conduction band edge.
Modelling of nanoparticle sintering under electrical boundary conditions
Authors: Alastalo A T , Seppä H , Leppäniemi J H , Aronniemi M J , Allen M L , Mattila T
Published: November 2010

A statistical model for sintering of solution-processed electrically conducting nanoparticle structures is developed. The model considers thermal expansion of the particles under Joule heating as the driving force of the process. The results are used to explain the fast resistance transition observed for the recently reported rapid electrical sintering process. A comparison with experimental results shows good agreement for the kinetics of the process. A heat-equation solution is also derived for a generic geometry of a printed conductor. This provides a basis for further refinements of the model to take other driving mechanisms, such as diffusion and inter-particle forces, into account. The results of this paper help in developing quantitative understanding of the physical processes that are relevant in nanoparticle sintering.
Depression and the delay between symptom onset and hospitalization in heart failure patients
Authors: Johansson Peter , Nieuwenhuis Maurice , Lesman‐Leegte Ivonne , van Veldhuisen Dirk J. , Jaarsma Tiny
Published: November 2010

Aims

Heart failure (HF) patients frequently suffer from episodes of deterioration and may need medical treatment. An adequate reaction from the patient is needed to decrease the delay between the onset of deterioration and consulting a medical professional (i.e. consulting behaviour). The aim of the present study was to evaluate whether depressive symptoms are associated with the duration of the delay between the onset of symptoms of worsening HF and hospitalization, and to examine how consulting behaviour correlates to depressive symptoms and delay in HF patients.

Methods and results

Data on the time between the onset of symptoms of worsening HF and hospitalization, depressive symptoms, and self‐care behaviour were collected in 958 HF patients (37% female; age 71 ± 11 years; New York Heart Association functional class II–IV), using validated questionnaires. The median delay time of the total sample was 72 h (ranging from 0 to 243 days). Patients with depressive symptoms delayed longer compared with those without depressive symptoms (120 vs. 54 h, P= 0.001). Patients with depressive symptoms had a 1.5 times higher risk for a delay of ≥72 h, independent of demographic and clinical variables (P= 0.008). Consulting behaviour did not correlate with depressive symptoms but was weakly associated with delay (r= −0.07, P= 0.03).

Conclusions

Heart failure patients with depressive symptoms have a significantly longer delay between HF deterioration and hospital admission. Interventions designed to improve the consulting behaviour in HF patients with depressive symptoms may have a limited effect on delay. Further research is needed to obtain more insight into the mechanisms underlying the relationship between delay and depression.