bluuebunny/crossref_metadata_2025 huggingface dataset:
MicroRNAs encoded by Kaposi's sarcoma‐associated herpesvirus regulate viral life cycle
Authors: Lu Chih‐Chung , Li Zhonghan , Chu Chia‐Ying , Feng Jiaying , Feng Jun , Sun Ren , Rana Tariq M
Published: September 2010

Kaposi's sarcoma‐associated herpesvirus (KSHV) is linked with Kaposi's sarcoma and lymphomas. The pathogenesis of KSHV depends on the balance between two phases of the viral cycle: latency and lytic replication. In this study, we report that KSHV‐encoded microRNAs (miRNAs) function as regulators by maintaining viral latency and inhibiting viral lytic replication. MiRNAs are short, noncoding, small RNAs that post‐transcriptionally regulate the expression of messenger RNAs. Of the 12 viral miRNAs expressed in latent KSHV‐infected cells, we observed that expression of miR‐K3 can suppress both viral lytic replication and gene expression. Further experiments indicate that miR‐K3 can regulate viral latency by targeting nuclear factor I/B. Nuclear factor I/B can activate the promoter of the viral immediate‐early transactivator replication and transcription activator (RTA), and depletion of nuclear factor I/B by short hairpin RNAs had similar effects on the viral life cycle to those of miR‐K3. Our results suggest a role for KSHV miRNAs in regulating the viral life cycle.
A further case of Dop‐ing in bacterial pupylation
Authors: Bremm Anja , Komander David
Published: September 2010

Two recent studies, one in this issue of EMBO reports and one in Molecular Cell, identify Dop as a depupylase, ascribing a novel function to Dop and providing further evidence for the functional similarity of the prokaryotic Pup‐modification system and the eukaryotic ubiquitin system.
Celebrating 100 years of Drosophila research
Authors: Gilboa Lilach , Boutros Michael
Published: September 2010

The seventeenth EMBO Conference on the Molecular and Developmental Biology of Drosophila took place in Kolymbari, Crete, between 20 and 26 June 2010. The conference covered a broad range of topics and much progress was made by combining two or more fields of study. Such combinations included quantitative approaches to cell and developmental biology, dissecting interrelations of physiology and development and integrated genomic analysis.
Recombinant mammalian DNA methyltransferase activity on model transcriptional gene silencing short RNA–DNA heteroduplex substrates
Authors: Ross Jason P. , Suetake Isao , Tajima Shoji , Molloy Peter L.
Published: September 2010

The biochemical mechanism of short RNA-induced TGS (transcriptional gene silencing) in mammals is unknown. Two competing models exist; one suggesting that the short RNA interacts with a nascent transcribed RNA strand (RNA–RNA model) and the other implying that short RNA forms a heteroduplex with DNA from the unwound double helix, an R-loop structure (RNA–DNA model). Likewise, the requirement for DNA methylation to enact TGS is still controversial. In vitro assays using purified recombinant murine Dnmt (DNA methyltransferase) 1-dN (where dN indicates an N-terminal truncation), 3a and 3b enzymes and annealed oligonucleotides were designed to question whether Dnmts methylate DNA in a RNA–DNA heteroduplex context and whether a RNA–DNA heteroduplex R-loop is a good substrate for Dnmts. Specifically, model synthetic oligonucleotides were used to examine methylation of single-stranded oligonucleotides, annealed oligonucleotide duplexes, RNA–DNA heteroduplexes, DNA bubbles and R-loops. Dnmt methylation activity on the model substrates was quantified with initial velocity assays, novel ARORA (annealed RNA and DNA oligonucleotide-based methylation-sensitive restriction enzyme analysis), tBS (tagged-bisulfite sequencing) and the quantitative PCR-based method MethylQuant. We found that RNA–DNA heteroduplexes and R-loops are poor substrates for methylation by both the maintenance (Dnmt1) and de novo (Dnmt3a and Dnmt3b) Dnmts. These results suggest the proposed RNA/DNA model of TGS in mammals is unlikely. Analysis of tagged-bisulfite genomic sequencing led to the unexpected observation that Dnmt1-dN can methylate cytosines in a non-CpG context in DNA bubbles. This may have relevance in DNA replication and silencing of transcriptionally active loci in vivo.
Monitoring of heart failure: comparison of left atrial pressure with intrathoracic impedance and natriuretic peptide measurements in an experimental model of ovine heart failure
Authors: Rademaker Miriam T. , Charles Christopher J. , Melton Iain C. , Richards A. Mark , Frampton Christopher M. , Siou Jeff , Qu Fujian , Eigler Neal L. , Gutfinger Dan , Troughton Richard W.
Published: September 2010

Monitoring of HF (heart failure) with intracardiac pressure, intrathoracic impedance and/or natriuretic peptide levels has been advocated. We aimed to investigate possible differences in the response patterns of each of these monitoring modalities during HF decompensation that may have an impact on the potential for early therapeutic intervention. Six sheep were implanted with a LAP (left atrial pressure) sensor and a CRT-D (cardiac resynchronization therapy defibrillator) capable of monitoring impedance along six lead configuration vectors. An estimate of ALAP (LAP from admittance) was determined by linear regression. HF was induced by rapid ventricular pacing at 180 and 220 bpm (beats/min) for a week each, followed by a third week with daily pacing suspensions for increasing durations (1–5 h). Incremental pacing induced progressively severe HF reflected in increases in LAP (5.9 ± 0.4 to 24.5 ± 1.6 mmHg) and plasma atrial (20 ± 3 to 197 ± 36 pmol/l) and B-type natriuretic peptide (3.7 ± 0.7 to 32.7 ± 5.4 pmol/l) (all P<0.001) levels. All impedance vectors decreased in proportion to HF severity (all P<0.001), with the LVring (left ventricular)-case vector correlating best with LAP (r2=0.63, P<0.001). Natriuretic peptides closely paralleled rapid acute changes in LAP during alterations in pacing (P<0.001), whereas impedance changes were delayed relative to LAP. ALAP exhibited good agreement with LAP. In summary, impedance measured with an LV lead correlates significantly with changes in LAP, but exhibits a delayed response to acute alterations. Natriuretic peptides respond rapidly to acute LAP changes. Direct LAP, impedance and natriuretic peptide measurements all show promise as early indicators of worsening HF. ALAP provides an estimate of LAP that may be clinically useful.
Motion of a spherical particle near a planar fluid-fluid interface: The effect of surface incompressibility
Authors: Bławzdziewicz J. , Ekiel-Jeżewska M. L. , Wajnryb E.
Published: September 2010

Hydrodynamic coupling of a spherical particle to an undeformable planar fluid-fluid interface under creeping-flow conditions is discussed. The interface can be either surfactant-free or covered with an incompressible surfactant monolayer. In the incompressible surfactant limit, a uniform surfactant concentration is maintained by Marangoni stresses associated with infinitesimal surfactant redistribution. Our detailed numerical calculations show that the effect of surface incompressibility on lateral particle motion is accurately accounted for by the first reflection of the flow from the interface. For small particle-interface distances, the remaining contributions are significant, but they are weakly affected by the surface incompressibility. We show that for small particle-wall gaps, the transverse and lateral particle resistance coefficients can be rescaled onto corresponding universal master curves. The scaling functions depend on a scaling variable that combines the particle-wall gap with the viscosity ratio between fluids on both sides of the interface. A logarithmic dependence of the contact value of the lateral resistance function on the viscosity ratio is derived. Accurate numerical calculations are performed using our Cartesian-representation method.
Laser induced fluorescence measurements of the cylindrical Hall thruster plume
Authors: Spektor R. , Diamant K. D. , Beiting E. J. , Raitses Y. , Fisch N. J.
Published: September 2010

An investigation of a fully cylindrical Hall thruster was performed using laser induced fluorescence (LIF) to measure ion velocity profiles in the plume. The measurements confirm a previously reported 9% increase in the exhaust energy when the cathode keeper draws an excess current (overrun mode). Furthermore, the velocity directions in the plume remain relatively unchanged for the cusped and direct magnetic field configuration in both overrun and nonoverrun modes. Previously reported plume narrowing in the overrun mode was confirmed and found to be due to the shift of the acceleration and ionization regions toward the anode. The electric field inferred from the LIF measurements allowed calculation of the electron E×B drift. Close to the centerline of the thruster, electrons drift azimuthally with velocity decreasing away from the centerline, thus creating shear. This shear can be a source of plasma instabilities and influence electron transport. Further away from the centerline, electrons drift in the opposite direction with their velocity increasing with increasing radius. In that region, electrons rotate without shear.
Epitaxial growth and interfacial magnetism of spin aligner for remanent spin injection: [Fe/Tb]n/Fe/MgO/GaAs-light emitting diode as a prototype system
Authors: Schuster E. , Brand R. A. , Stromberg F. , Lo F.-Y. , Ludwig A. , Reuter D. , Wieck A. D. , Hövel S. , Gerhardt N. C. , Hofmann M. R. , Wende H. , Keune W.
Published: September 2010

We have successfully grown and characterized [Fe/Tb]10/Fe(001)/F57e(001)/MgO(001) multilayer contacts on a GaAs-based light emitting diode. Using F57e conversion-electron Mössbauer spectroscopy at room temperature (RT) and at 4.2 K, we provide atomistic proof of large perpendicular Fe spin components in zero external field at and below RT at the F57e(001)/MgO(001) interface. Further, indirect evidence of large interfacial Fe atomic moments is provided. Our contacts serve as a prototype spin aligner for remanent electrical spin injection at RT.
Proposed truncated Cu–Hf tight-binding potential to study the crystal-to-amorphous phase transition
Authors: Cui Yuanyuan , Li Jiahao , Dai Ye , Liu Baixin
Published: September 2010

Proposed truncated Cu–Hf tight-binding potential was constructed by fitting the physical properties of Cu, Hf, and their stable compounds, i.e., Cu5Hf, Cu8Hf3, Cu10Hf7, and CuHf2. Based on the constructed potentials, molecular dynamics simulations were carried out to compare the relative stability of the crystalline solid solution and the disordered state. Simulation results not only reveal that the physical origin of crystal-to-amorphous transition is the crystalline lattice collapsing when the solute atoms exceeding the critical concentration, but also predict that the glass forming range (GFR) of the Cu–Hf system is 21–77 at. % Cu, which covers the GFRs determined by various metallic glass-producing techniques. Ion beam mixing experiments of the Cu–Hf system were conducted using 200 keV xenon ions and the results show that a uniform amorphous phase can be obtained in the Cu23Hf77 sample, matching well with the GFR determined by the interatomic potential, which, in turn, provides additional evidence to the relevance of the constructed Cu–Hf potential.
Pinning analyses on epitaxial YBa2Cu3O7−δ films with BaZrO3 inclusions
Authors: Augieri A. , Celentano G. , Galluzzi V. , Mancini A. , Rufoloni A. , Vannozzi A. , Armenio A. Angrisani , Petrisor T. , Ciontea L. , Rubanov S. , Silva E. , Pompeo N.
Published: September 2010

The introduction of artificial pinning sites in YBa2Cu3O7−δ (YBCO) epitaxial thin films has been obtained by pulsed laser deposition (PLD) technique from YBCO-BaZrO3 (BZO) composite targets with BZO concentration ranging from 2.5 to 7 mol %. The typical critical temperature, Tc, drop observed in YBCO-secondary phase films grown by PLD has been successfully recovered by increasing the deposition temperature. Transport properties analyses revealed improved pinning force values for YBCO-BZO films for BZO concentration above 5 mol %. These films exhibited an anomalous dual peak structure which has been ascribed to the presence of two pinning contributions. The crossover field, Bm, separating these two pinning regimes has been observed to be temperature independent suggesting the occurrence of the matching field effect. The measured value of Bm agreed with the matching field value, BΦ=KndΦ0, as evaluated from transmission electron microscopy investigations. The mark of this phenomenon is retained down to 10 K, making YBCO-BZO more performing than pristine YBCO films at applied magnetic fields below Bm in all the temperature range inspected. On the contrary, in the high magnetic field range (above Bm), the effectiveness of correlated pinning is progressively reduced on lowering the temperature suggesting that at low temperatures the dominant pinning contribution arises from isotropic pinning centers.
Surprising enhancing effect of methyl group on the strength of O⋯XF and S⋯XF (X=Cl and Br) halogen bonds
Authors: Li Qingzhong , Jing Bo , Liu Zhenbo , Li Wenzuo , Cheng Jianbo , Gong Baoan , Sun Jiazhong
Published: September 2010

The role of methyl group in H2O⋯XF and H2S⋯XF (X=Cl and Br) halogen-bonded complexes has been investigated with quantum chemical calculations. The halogen bond in the H2O⋯XF complexes is stronger than that in the H2S⋯XF complexes. However, the S⋯X halogen bond is stronger than the O⋯X one with the increase of methyl number. The result shows that the methyl group in the halogen acceptor has a positive contribution to the formation of halogen bond and there is a positive nonadditivity of methyl groups. Surprisingly, the methyl groups in dimethyl sulfide causes an increase of 150% for the interaction energy of S⋯Cl halogen bond. The natural bond orbital analyses have been performed to unveil the mechanism of the methyl group in the halogen bonding formation.
Difference between resistance degradation of fixed valence acceptor (Mg) and variable valence acceptor (Mn)-doped BaTiO3 ceramics
Authors: Yoon Seok-Hyun , Randall Clive A. , Hur Kang-Heon
Published: September 2010

The difference in the resistance degradation behavior was investigated between fixed valence acceptor (Mg) and the variable valence acceptor (Mn)-doped BaTiO3 ceramics with an increase of each acceptor concentration. Coarse-grained specimens with uniform grain sizes and different acceptor concentrations were prepared. In the case of Mg-doped BaTiO3, the time to degradation systematically decreased with the increase in Mg concentration. In contrast, there is a systematically increased time to degradation with the increase in Mn concentration in Mn-doped BaTiO3. The fast degradation by the increase in Mg concentration directly corresponded to an increase in the Warburg impedance and ionic transference number (tion) associated with an increase in oxygen vacancy concentration ([VO••]). On the other hand, no distinct Warburg impedance or ionic conduction contribution could be observed with the increase in Mn concentration. It is supposed that the increase in [VO••] is negligible in spite of the increase in acceptor Mn concentration, when it is compared to Mg-doped BaTiO3. The much lower [VO••] and more dominant electron/hole trapping effect due to multivalence nature of Mn are supposed to cause such a contrary degradation behavior between Mg and Mn-doped BaTiO3. Reoxidation in a slightly reducing atmosphere (N2) showed better resistance to degradation behavior than in a oxidizing air atmosphere in both Mg and Mn-doped BaTiO3, which is anticipated to be an increase in the electron/hole trapping sites. All these behaviors could be explained by the low temperature defect chemical model that shows difference in the defect structure between Mg and Mn-doped BaTiO3, and its dependence on the oxygen partial pressure (pO2) during reoxidation and cooling. Not only the [VO••], but also the density of electron/hole trap sites, are believed to be crucial in controlling resistance degradation.
The ion capturing effect of 5° SiOx alignment films in liquid crystal devices
Authors: Huang Yi , Bos Philip J. , Bhowmik Achintya
Published: September 2010

We show that SiOx, deposited at 5° to the interior surface of a liquid crystal cell allows for a surprisingly substantial reduction in the ion concentration of liquid crystal devices. We have investigated this effect and found that this type of film, due to its surface morphology, captures ions from the liquid crystal material. Ion adsorption on 5° SiOx film obeys the Langmuir isotherm. Experimental results shown allow estimation of the ion capturing capacity of these films to be more than an order of 10 000/μm2. These types of materials are useful for new types of very low power liquid crystal devices such as e-books.
Efficient energy transfer from Si-nanoclusters to Er ions in silica induced by substrate heating during deposition
Authors: Cueff Sébastien , Labbé Christophe , Cardin Julien , Doualan Jean-Louis , Khomenkova Larysa , Hijazi Khalil , Jambois Olivier , Garrido Blas , Rizk Richard
Published: September 2010

This study investigates the influence of the deposition temperature Td on the Si-mediated excitation of Er ions within silicon-rich silicon oxide layers obtained by magnetron cosputtering. For Td exceeding 200 °C, an efficient indirect excitation of Er ions is observed for all as-deposited samples. The photoluminescence intensity improves gradually up to a maximum at Td=600 °C before decreasing for higher Td values. The effects of this “growth-induced annealing” are compared to those resulting from the same thermal budget used for the “classical” approach of postdeposition annealing performed after a room temperature deposition. It is demonstrated that the former approach is highly beneficial, not only in terms of saving time but also in the fourfold enhancement of the Er photoluminescence efficiency.
Theory of resonant sound transmission through small apertures on periodically perforated slabs
Authors: Wang Xinlong
Published: September 2010

An analytical theory for sound transmitting through apertures that are slits or holes periodically pored on one- or two-dimensional rigid panels is developed in small-aperture approximation, with all coefficients of reflection and transmission given explicitly in concise and easily calculable forms. We utilize acoustical impedance to quantitatively describe the effect of sound diffraction by both surfaces of a perforated slab on the aperture resonance. We show that diffraction induced reactance Xa, which is acoustically inertant (Xa>0) for incident wavelength λ longer than the period Λ of the perforated slab, can become infinitely large as λ approaches to Λ. We further show that the singularity of Xa not only causes the already known full reflection of acoustic waves at λ=Λ, but also drastically changes the aperture resonance leading to the extraordinary acoustical transmission that was observed in recent experiments. With this understanding, tuning the resonant transmission becomes practically feasible in applications of the resonant transmission phenomenon.
Magneto-optical enhancement in magnetophotonic crystals based on cholesteric liquid crystals
Authors: Da Hai-Xia , Huang Zi-Qiang , Li Zhen-Ya
Published: September 2010

The magneto-optical features in a one-dimensional magnetophotonic crystal based on cholesteric liquid crystals are explored theoretically by employing the Muller matrix method. It is unveiled that the intrinsic nonreciprocity-derived magneto-optical effect exhibits an enhancement, which origins from the strong photonic localization in the defect layers. Meanwhile, the oscillation behavior in the transmission spectrum with the linearly polarized angle indicates its polarization-dependent characteristic due to the breaking of time reversal symmetry in the magnetic materials. This novel scheme presents an opportunity of developing new hybrid structures for technological applications.
Characterization of dual high transition temperature superconducting quantum interference device first-order planar gradiometers on a chip
Authors: Chen Kuen-Lin , Yang Hong-Chang , Ko P. C. , Horng H. E.
Published: September 2010

The dual first-order planar gradiometers of high transition temperature (high-Tc) superconducting quantum interference devices (SQUIDs) were designed and fabricated on a 10×10 mm2 SrTiO3 bicrystal substrate. Each gradiometer consists of four bare SQUIDs which are connected to two symmetric pickup loops. Any two of the SQUIDs can be connected in series to obtain better performance. In this study, by selecting the coupling direction of SQUID, a balance resolution of 0.08% was achieved. And, a second-order electronic planar gradiometer was composed of these two first-order gradiometers. Experimental data showed that the noise performance of the second-order electronic planar gradiometer composed of two planar first-order gradiometers can reach 15 μΦ0/Hz1/2 at 1 kHz in an unshielded environment, which is comparable to the noise level of a magnetometer in a shielded environment.
A yellow phosphor K2SiF6 activated by Mn2+ ions
Authors: Arai Takahiro , Arai Yusuke , Takahashi Toru , Adachi Sadao
Published: September 2010

A unique Mn2+-activated phosphor has been synthesized by wet chemical etching of Si wafers in HF/K2Cr2O7 mixed solution with the addition of pure Mn metal. The x-ray diffraction pattern suggests that the synthesized compound is a Mn2+-activaed K2SiF6 phosphor having cubic structure (space group=Oh5−Fm3m). The Mn2+-activated K2SiF6 phosphor emits light in the yellow or yellowish green region, depending on the quantity of the Mn additive. This phosphor shows unique photoluminescent properties that have not yet been reported previously. The electronic states of the 3d5 (Mn2+) electrons in the K2SiF6:Mn2+ phosphor are identified together with those of the 3d3 (Mn4+) electrons in the conventional K2SiF6:Mn4+ red phosphor. The temperature-dependent photoluminescent properties are explained by the aid of the electronic energy-band diagram of K2SiF6 with taking into account the effects of thermal emission of electrons in the Mn2+ excited states.
In situ electron energy loss spectroscopy study of metallic Co and Co oxides
Authors: Zhao Yuan , Feltes Theresa E. , Regalbuto John R. , Meyer Randall J. , Klie Robert F.
Published: September 2010

Determining the Co valence, particularly in Co-based nanocatalysts is a longstanding experimental challenge. In this paper, we utilize in situ electron energy-loss spectroscopy and first-principles density functional theory calculations to distinguish between metallic Co, Co3O4, as well as CoO. More specifically, differences in the O K- and Co L-edges are utilized to determine the Co valence in different Co-oxide particles. We will further demonstrate that while the metallic Co L3/L2-ratio equals that of partially reduced Co3O4, the near-edge fine-structure of the metallic Co L-edge exhibits additional features not present in any Co-oxide. The origin of these features will be discussed. Based on our experimental and theoretical results, we will propose a fitting method to distinguish metallic Co from Co-oxides.
Characteristics of emission polarization in a-plane nanorods embedded with InGaN/GaN multiple quantum wells
Authors: Li J. C. , Lu T. C. , Huang H. M. , Chan W. W. , Kuo H. C. , Wang S. C.
Published: September 2010

Nonpolar (a-plane) GaN nanorod arrays with embedded InxGa1−xN/GaN (x=0.09, 0.14, 0.24, and 0.30) multiple quantum wells (MQWs) grown on r-plane sapphire have been fabricated successfully by self-assembled Ni nanomasks and subsequent inductively coupled plasma reactive-ion etching. After nanorod fabrications, the polarization ratio of the emission from MQWs with lower indium composition (x=0.09 and 0.14) slightly decreases but apparently increases by at most 79% for the samples with higher indium composition (x=0.24 and 0.30). Competition between the effect of multiple scattering, strain relaxation and reduction in localized centers, expected in a-plane MQW samples, are attributed to the variations in the polarization ratios after the nanorod formation.
Magnetoconcentration effect in intrinsic graphene ribbons
Authors: Sokolov V. N. , Kochelap V. A. , Kim K. W.
Published: September 2010

We consider transverse redistributions of the electrons and holes in intrinsic graphene ribbons under the influence of crossed electric and magnetic fields, i.e., the magnetoconcentration effect. The electron and hole transport is described from the Boltzmann kinetic equation assuming the local quasiequilibrium distributions of the carriers over energy states. The effective control of the carriers is achieved from deep depletion to accumulation modes depending on the properties of the ribbon edges, provided electron-hole recombination/generation rates at the edges are different from those inside the ribbon. The current-voltage characteristics reflect the behavior of the carrier redistributions across the ribbon. The obtained results suggest that interesting effects such as the population inversion in certain ranges of energies and the induced transparency are possible, which make them attractive for various optoelectronics applications in the terahertz spectral range.
320 fs pulse generation from an ultrafast laser inscribed waveguide laser mode-locked by a nanotube saturable absorber
Authors: Beecher S. J. , Thomson R. R. , Psaila N. D. , Sun Z. , Hasan T. , Rozhin A. G. , Ferrari A. C. , Kar A. K.
Published: September 2010

Ultrafast laser inscription is used to fabricate the gain element for a mode-locked Er-doped bismuthate glass waveguide laser. Mode-locking is initiated and stabilized by the use of a single wall carbon nanotube saturable absorber. The waveguide laser produces 320 fs pulses at 1.56 μm with a pulse repetition rate of 40 MHz and average output power of 1.25 mW.
Negative differential resistance in Gd0.5Sr0.5MnO3: A consequence of Joule heating
Authors: Wagh Aditya A. , Kumar P. S. Anil , Bhat H. L. , Elizabeth Suja
Published: September 2010

Negative differential resistance (NDR) in current-voltage (I-V) characteristics and apparent colossal electroresistance were observed in Gd0.5Sr0.5MnO3 single crystals at low temperatures. The continuous dc I-V measurements showed a marked thermal drift. In addition, temperature of the sample surface was found to be significantly higher than that of the base at high applied currents. Two different strategies namely estimation and diminution of the Joule heating (pulsed I-V measurements) were employed to investigate its role in the electric transport properties. Our experiments reveal that the NDR in Gd0.5Sr0.5MnO3 is a consequence of Joule heating rather than the melting of charge order.
Bound states in a hybrid magnetic-electric quantum dot
Authors: Song Yu , Guo Yong
Published: September 2010

We propose a hybrid magnetic-electric quantum dot defined by a missing magnetic flux and an electrostatic dot potential in a same circular region, which can be realized through an electrode-controlled (Vg) superconducting disk deposited atop a two-dimensional electron gas in a homogeneous perpendicular magnetic field (Ba). We find that when Vg/Ba=eℏ/4m∗, all ground states with m the (angular momentum) ≤0 recover the degeneracy Landau levels (LLs), although for general cases m-dependent energy deviations from the LLs happen. We also find that the magnetic-field-dependent energy spectrum exhibits quite different features for dot potentials with different signs, e.g., angular momentum transitions occurring in the positive case and coexistence of quantum-dot-kind and LL-kind levels for a small Ba in the negative one. Moreover, as the dot potential varies in a middle range, the energy spectrum shows step-type profiles, which are related to the nonmonotonous change in the probability for the electron to stay in the dot region. At the zero magnetic-field limit, the electron eigenenergy can jump between two adjacent LLs with a little change in the dot potential around special |m|-dependent values.
Structural characterization of amorphous Ta2O5 and SiO2–Ta2O5 used as solid electrolyte for nonvolatile switches
Authors: Banno Naoki , Sakamoto Toshitsugu , Iguchi Noriyuki , Matsumoto Masashi , Imai Hideto , Ichihashi Toshinari , Fujieda Shinji , Tanaka Kazuhiko , Watanabe Satoshi , Yamaguchi Shu , Hasegawa Tsuyoshi , Aono Masakazu
Published: September 2010

Diffusivity of Cu in amorphous (a-) Ta2O5 is increased by low temperature annealing above 350 °C but the increase is suppressed by adding SiO2 to Ta2O5. To clarify the reasons, we investigated the structural difference between a-Ta2O5 and a-SiO2–Ta2O5. The results show that the low temperature annealing does not cause polycrystallization of Ta2O5 but purges weakly bonded oxygen atoms from the bulk and decreases the film density. Adding SiO2 to Ta2O5 is shown to increase the coordination number of Ta–O, which results in the improved thermal stability.
Systematic study of first-row transition-metal diatomic molecules: A self-consistent DFT+U approach
Authors: Kulik Heather J. , Marzari Nicola
Published: September 2010

We present a systematic first-principles study of the equilibrium bond lengths, harmonic frequencies, dissociation energies, ground state symmetries, and spin state splittings of 22 diatomic molecules comprised of a first-row 3d transition-metal and a main-group element (H, C, N, O, or F). Diatomic molecules are building blocks of the key molecular bonding motifs in biological and inorganic catalytic systems, but, at the same time, their small size permits a thorough study by even the most computationally expensive quantum chemistry approaches. The results of several density-functional theory (DFT) approaches including hybrid, generalized-gradient, and generalized-gradient augmented with Hubbard U exchange-correlation functionals are presented. We compare these efficiently calculated DFT results with the highly accurate but computationally expensive post-Hartree–Fock approaches multireference configuration interaction (MRCI) and coupled cluster [CCSD(T)] as well as experimental values, where available. We show that by employing a Hubbard U approach, we systematically reduce average errors in state splittings and dissociation energies by a factor of 3. We are also able to reassign the ground state of four molecules improperly identified by hybrid or generalized-gradient approaches and provide correct assignment of all ground state symmetries as compared against experimental assignment and MRCI reference. By providing accuracy comparable to more expensive quantum chemistry approaches with the robust scaling of the generalized-gradient approximation, our DFT+U approach permits the study of very large scale systems with vastly improved results.
Epitaxial EuO thin films on GaAs
Authors: Swartz A. G. , Ciraldo J. , Wong J. J. I. , Li Yan , Han Wei , Lin Tao , Mack S. , Shi J. , Awschalom D. D. , Kawakami R. K.
Published: September 2010

We demonstrate the epitaxial growth of EuO on GaAs by reactive molecular beam epitaxy. Thin films are grown in an adsorption-controlled regime with the aid of an MgO diffusion barrier. Despite the large lattice mismatch, it is shown that EuO grows well on MgO(001) with excellent magnetic properties. Epitaxy on GaAs is cube-on-cube and longitudinal magneto-optic Kerr effect measurements demonstrate a large Kerr rotation of 0.57°, a significant remanent magnetization, and a Curie temperature of 69 K.
Production of hollow hemisphere shells by pure Kirkendall porosity formation in Au/Ag system
Authors: Glodán Györgyi , Cserháti Csaba , Beszeda Imre , Beke Dezső L.
Published: September 2010

Interdiffusion has been studied in Ag/Au hemispherical core-shell structures on sapphire substrate. In isothermal heat treatments first a relatively fast growth of nanovoids was observed, which was followed by a slower shrinkage process. The void formation is interpreted by pure Kirkendall-porosity formation since Ag-50%Au solid solution has been formed in the shell. In contrary, in all previous publications on hollow nanoshell formation a chemical reaction took place and the shell consisted of the reaction product (i.e., of sulphide or oxide). Furthermore, in these cases the shrinkage was observed at temperatures higher than the formation temperature.
Effect of heat shock on germination of 23 plant species in pine - oak and montane cloud forests in western Mexico
Authors: Zuloaga-Aguilar Susana , Briones Oscar , Orozco-Segovia Alma
Published: September 2010

We determined the effect of heat shock on seed germination of 23 species growing in fire-prone areas covered by pine–oak and montane cloud forests. Seeds of each species were exposed to 60, 80, 100 or 120°C for 5 or 60 min in dry and moist sand. Seeds of nine species were incubated for 15 h in moist sand and exposed to the temperature that best promoted germination. Eighteen species required heat shock for germination, and five tolerated it. Dry heat shock for 5 min promoted germination of these species; heat shock in moist sand at 100°C induced germination of 10 species. Exposure for 60 min to heat shock in dry and moist sand improved germination of 14 and 5 species respectively. Logistic models indicate that germination probabilities of most species are increased by temperatures of 70–120°C. Depending on substrate and seed hydration, heat shock increased or left unchanged the germination of most pine–oak and montane cloud forest species. Thus, montane cloud forest seeds can survive low-intensity surface fires. Most species with seeds hydrated before heat shock showed little or no germination. Prescribed burns at the end of the rainy season may therefore be harmful to pine–oak and montane cloud forest species.
Burn severity mapping using simulation modelling and satellite imagery
Authors: Karau Eva C. , Keane Robert E.
Published: September 2010

Although burn severity maps derived from satellite imagery provide a landscape view of fire impacts, fire effects simulation models can provide spatial fire severity estimates and add a biotic context in which to interpret severity. In this project, we evaluated two methods of mapping burn severity in the context of rapid post-fire assessment for four wildfires in western Montana using 64 plots as field reference: (1) an image-based burn severity mapping approach using the Differenced Normalised Burn Ratio, and (2) a fire effects simulation approach using the FIREHARM model. The image-based approach was moderately correlated with percentage tree mortality but had no relationship with percentage fuel consumption, whereas the simulation approach was moderately correlated with percentage fuel consumption and weakly correlated with percentage tree mortality. Burn severity maps produced by the two approaches had mixed results among the four sampled wildfires. Both approaches had the same overall map agreement when compared with a sampled composite burn index but the approaches generated different severity maps. Though there are limitations to both approaches and more research is needed to refine methodologies, these techniques have the potential to be used synergistically to improve burn severity mapping capabilities of land managers, enabling them to quickly and effectively meet rehabilitation objectives.
Field estimation of ash and char colour-lightness using a standard grey scale
Authors: Roy David P. , Boschetti Luigi , Maier Stefan W. , Smith Alistair M. S.
Published: September 2010

Vegetation fires produce biomass combustion residues, with colour varying from dark black char to white mineral ash. The colour-lightness of char and ash combustion residues is a qualitative parameter describing the post-fire condition of burned areas, and has been correlated with the completeness of combustion, fire intensity, and fire duration. Researchers have suggested that visual comparison of combustion residue samples with a standard grey scale would enable reliable combustion residue colour-lightness estimation. This paper describes an experiment aimed at assessing if colour-lightness can be estimated using a standard grey scale. Fifteen combustion residue samples with colour-lightness ranging from black char to white mineral ash were collected in the Northern Territory, Australia, and visually evaluated by three individuals using a grey scale. The grey-scale scores (0–19) were compared with the mean visible (390 to 830 nm) wavelength combustion residue reflectance (0–1) measured with a portable spectroradiometer. A significant linear relationship between the grey-scale scores and the mean visible combustion residue reflectance was found (R2 = 0.816 with a linear fit, R2 = 0.936 with a logarithmic-transformed fit). This finding suggests that combustion residue colour-lightness can be assessed in the field using inexpensive grey scales, and that this technique is a suitable avenue for future research on the field assessment of fire characteristics and effects.
Seasonal and Ascending Trends in the Incidence of Carriage of Extended-Spectrumβ-Lactamase–ProducingEscherichia coliandKlebsiellaSpecies in 2 German Hospitals
Authors: Dipl-Vw Klaus Kaier , Frank Uwe , Conrad Andreas , Meyer Elisabeth
Published: September 2010

Background.

Extended-spectrumβ-lactamase (ESBL)–producing strains of bacteria have become a major public health concern. In the present study, the incidence of carriage of ESBL-producing strains was analyzed for general trends and seasonality.

Methods.

Monthly data on ESBL-producing strains were collected retrospectively at 2 large university hospitals in Germany. The mean monthly temperatures for the 2 settings were collected from Germany's national meteorological service. Multivariable time series analyses were performed to explain variations in the monthly incidence densities of carriage of ESBL-producing bacteria (number of cases involving ESBL-producingEscherichia coliand/orKlebsiellaspecies per 1,000 patient days). For the final models, we incorporated variables for the ascending linear trends and other variables representing the mean monthly temperature.

Results.

Our models demonstrated that there was an increasing trend in the incidences of carriage of ESBL-producing bacteria. In addition, the incidences of carriage of all ESBL-producing bacteria responded positively to the mean temperature, meaning that during the summer, more cases involving ESBL-producing bacteria were detected than during the winter. The same methodology was also applied to the incidence of methicillin-resistantStaphylococcus aureuscarriage, but no association was found with the mean temperature.

Conclusions.

In the present study, we demonstrated that the monthly incidence of carriage of ESBL-producing bacteria was highly correlated with the mean monthly temperature, a fact that should be considered in experimental studies as an additional parameter influencing the incidence of ESBL-producing bacteria.
Realization of forming-free ZnO-based resistive switching memory by controlling film thickness
Authors: Mao Qinan , Ji Zhenguo , Xi Junhua
Published: September 2010

Cu/ZnO/n+-Si structures that show resistive switching behaviour have been successfully fabricated. The influence of ZnO thickness on resistive switching is investigated. As the ZnO thickness is reduced from 100 to 25 nm, Cu/ZnO/n+-Si cells change from forming-necessary ones to forming-free ones. Compared with the forming-necessary cells, the forming-free cells show more stable resistive switching characteristics. The underlying mechanism of the forming-free phenomenon is proposed. We infer that the oxygen vacancies pre-existing in ZnO films play an important role in the realization of forming-free cells.
Analysis of multifunctional oxycarbide and oxynitride thin films by modulated IR radiometry
Authors: Gibkes J , Vaz F , Fernandes A C , Carvalho P , Macedo F , Faria R T , Kijamnajsuk P , Pelzl J , Bein B K
Published: September 2010

Multifunctional coatings consisting of transition metal oxycarbides and oxynitrides deposited by physical vapour deposition techniques on tool steel are analysed in this work by means of modulated IR radiometry (MIRR), a non-contact non-destructive thermal wave measurement technique, with respect to the thermal transport properties relevant for time-dependent surface heating processes of coating–substrate systems. In order to interpret the measured data quantitatively, an inverse solution of the two-layer thermal wave problem is applied, which relies on the thermal wave phase lag data measured as a function of modulation frequency of the periodically modulated laser beam heating intensity. Based on these measurements and their quantitative interpretation, correlations between the thermal transport properties of the coatings and their deposition conditions have been found, which can be used to monitor deposition processes. For a second objective of this work, namely to determine the film thickness by means of MIRR, different sets of thin films of approximately constant thermal transport properties, but differing film thickness, have been measured. To discuss the limitations and error limits of these non-contact non-destructive measurements of the coating thickness, the results obtained by MIRR are compared with the coating thickness determined by destructive measurements.
Geoengineering as an optimization problem
Authors: Ban-Weiss George A , Caldeira Ken
Published: September 2010

There is increasing evidence that Earth’s climate is currently warming, primarily due to emissions of greenhouse gases from human activities, and Earth has been projected to continue warming throughout this century. Scientists have begun to investigate the potential for geoengineering options for reducing surface temperatures and whether such options could possibly contribute to environmental risk reduction. One proposed method involves deliberately increasing aerosol loading in the stratosphere to scatter additional sunlight to space. Previous modeling studies have attempted to predict the climate consequences of hypothetical aerosol additions to the stratosphere. These studies have shown that this method could potentially reduce surface temperatures, but could not recreate a low-CO2climate in a high-CO2world. In this study, we attempt to determine the latitudinal distribution of stratospheric aerosols that would most closely achieve a low-CO2climate despite high CO2levels. Using the NCAR CAM3.1 general circulation model, we find that having a stratospheric aerosol loading in polar regions higher than that in tropical regions leads to a temperature distribution that is more similar to the low-CO2climate than that yielded by a globally uniform loading. However, such polar weighting of stratospheric sulfate tends to degrade the degree to which the hydrological cycle is restored, and thus does not markedly contribute to improved recovery of a low-CO2climate. In the model, the optimal latitudinally varying aerosol distributions diminished the rms zonal mean land temperature change from a doubling of CO2by 94% and the rms zonal mean land precipitation minus evaporation change by 74%. It is important to note that this idealized study represents a first attempt at optimizing the engineering of climate using a general circulation model; uncertainties are high and not all processes that are important in reality are modeled.
Characterizing molecular adaptation: a hierarchical approach to assess the selective influence of amino acid properties
Authors: Datta Saheli , Prado Raquel , Rodríguez Abel , Escalante Ananías A.
Published: September 2010

Motivation: A number of methods for detecting positive selection in protein coding DNA sequences are based on whether each site/region has a non-synonymous to synonymous substitution rates ratio ω greater than one. However, a site/region may show a relatively large number of non-synonymous mutations that conserve a particular property. Recent methods have proposed to consider as evidence for molecular adaptations how conserving, or radically different, non-synonymous mutations are with respect to some key amino acid properties. While such methods have been useful in providing a qualitative assessment of molecular adaptation, they rely on independent statistical analyses for each amino acid property and typically do not properly adjust for multiple comparisons when selection needs to be assessed at several sites.

Results: We consider a Bayesian hierarchical model that allows us to jointly determine if a set of amino acid properties are being conserved or radically changed while simultaneously adjusting for multiple comparisons at the codon level. We illustrate how this model can be used to characterize molecular adaptation in two datasets: an alignment from six class I alleles of the human major histocompatibility complex and a sperm lysin alignment from 25 abalone species. We compare the results obtained with the proposed hierarchical models to those obtained with alternative methods. Our analyses indicate that a more complete quantitative and qualitative characterization of molecular adaptation is achieved by taking into account changes in amino acid properties.

Contact:  raquel@ams.ucsc.edu

Availability: The R code for implementing the hierarchical models is freely available at http://www.ams.ucsc.edu/∼raquel/software/.

Supplementary information:  Supplementary data are available at Bioinformatics online.
Improved quality of life in Norwegian heart failure patients after follow‐up in outpatient heart failure clinics: results from the Norwegian heart failure registry
Authors: Hole Torstein , Grundtvig Morten , Gullestad Lars , Flønæs Berit , Westheim Arne
Published: September 2010

Aims

To evaluate the quality of life in heart failure (HF) outpatients attending multidisciplinary disease management programmes at HF clinics in Norwegian hospitals.

Methods and results

Data from HF patients at 24 hospital outpatient clinics were entered in a common database; The Norwegian Heart Failure Registry. Quality of life assessment was done using Minnesota Living with Heart Failure Questionnaire (MLHF). The quality of life assessment was optional at each hospital and was done both at initial evaluation and after 6 months of stable follow‐up. A total of 3632 patients were included in the registry and 1778 patients had at least one assessment of quality of life. The mean MLHF score improved significantly from 2.1 at the initial evaluation to 1.4 six months after leaving the clinic (P < 0.001). There was a significant difference in MLHF score between hospitals and baseline MLHF score was significantly associated with NYHA functional class, hospitalizations 6 months before entering the registry, and brain natriuretic peptide; and inversely related to age and systolic blood pressure. Minnesota Living with Heart Failure score was an independent predictor of mortality in this population.

Conclusion

Quality of life assessed with MLHF improved after follow‐up at outpatient HF clinics. Minnesota Living with Heart Failure score was significantly related to functional status, laboratory and demographic variables, and was an important predictor of prognosis.