bluuebunny/crossref_metadata_2025 huggingface dataset:
Common Alzheimer's Disease Research Ontology: National Institute on Aging and Alzheimer's Association Collaborative Project
Authors: Refolo Lorenzo M. , Snyder Heather , Liggins Charlene , Ryan Laurie , Silverberg Nina , Petanceska Suzana , Carrillo Maria C.
Published: June 2012

Alzheimer's disease is recognized as a public health crisis worldwide. As public and private funding agencies around the world enhance and expand their support of Alzheimer's disease research, there is an urgent need to coordinate funding strategies and leverage resources to maximize the impact on public health and avoid duplication of effort and inefficiency. Such coordination requires a comprehensive assessment of the current landscape of Alzheimer's disease research in the United States and internationally. To this end, the National Institute on Aging at the National Institutes of Health and the Alzheimer's Association developed the Common Alzheimer's Disease Research Ontology (CADRO) as a dynamic portfolio analysis tool that can be used by funding agencies worldwide for strategic planning and coordination.
Learning from others’ misfortune: Factors influencing knowledge acquisition to reduce operational risk
Authors: Hora Manpreet , Klassen Robert D.
Published: June 2012

Risks arising from operations are increasingly being highlighted by managers, customers, and the popular press, particularly related to large‐scale (and usually low‐frequency) losses. If poorly managed, the resulting disruptions in customer service and environmental problems incur enormous recovery costs, prompt large legal liabilities, and damage customer goodwill and brand equity. Yet, despite conventional wisdom that firms should improve their own operations by observing problems that occur in others’ processes, significant operational risks appear to be ignored and similar losses recur. Using a randomized vignette‐based field experiment, we tested the influence of organization‐level factors on knowledge acquisition. Two organization‐level factors, namely perceived operational similarity, and to a lesser extent, market leadership, significantly influenced the risk manager's likelihood of acquiring knowledge about possible causes that triggered another firm's operational loss. These findings suggest that senior managers need to develop organizational systems and training to expand the screening by risk managers to enhance knowledge acquisition. Moreover, industry and trade organizations may have a role in fostering the transfer of knowledge and potential learning from operational losses of firms.
Recent changes in Arctic Ocean circulation revealed by iodine‐129 observations and modeling
Authors: Karcher Michael , Smith John N. , Kauker Frank , Gerdes Rüdiger , Smethie William M.
Published: June 2012

Anthropogenic radionuclides released into European coastal waters from nuclear fuel reprocessing plants at Sellafield (UK) and La Hague (France) flow northward through the Nordic Seas and label Atlantic Water (AW) entering the Arctic Ocean. Transport of the soluble radionuclide 129I through the Arctic Ocean has been simulated using a numerical model for the period from 1970 to 2010. The simulated tracer distributions closely conform to 129I measurements made across the Arctic Ocean during the mid‐1990s and 2000s and clearly illustrate the dramatic changes in oceanic circulation which occurred during this time. The largest changes in surface circulation were associated with the transition from a negative to a positive phase of the Arctic Oscillation in the early 1990s and the subsequent return to a weak positive phase in the late 1990s and early 2000s. Model and experimental results indicate that a new circulation regime evolved after 2004 when a period of intense, anti‐cyclonic surface stress led to a strengthening of the Beaufort Gyre. We submit that this resulted in a suppression of the cyclonic boundary current of mid‐depth Atlantic Water (AW) below the Beaufort Gyre, with upper AW in the Canada Basin showing signs of a reversal from cyclonic to anti‐cyclonic flow. These results are consistent with the development of a new AW circulation scheme involving a separation between flow at intermediate depths in the Eurasian and Canada Basins which could eventually result in modification of the Arctic intermediate water which feeds the overflows.
Direct energy estimation of the 2011 Japan tsunami using deep‐ocean pressure measurements
Authors: Tang Liujuan , Titov Vasily V. , Bernard Eddie N. , Wei Yong , Chamberlin Christopher D. , Newman Jean C. , Mofjeld Harold O. , Arcas Diego , Eble Marie C. , Moore Christopher , Uslu Burak , Pells Clint , Spillane Michael , Wright Lindsey , Gica Edison
Published: June 2012

We have developed a method to compute the total energy transmitted by tsunami waves, to the case where the earthquake source is unknown, by using deep‐ocean pressure measurements and numerical models (tsunami source functions). Based on the first wave recorded at the two closest tsunameters (Deep‐Ocean Assessment and Reporting of Tsunamis (DART)), our analysis suggests that the March 11, 2011 Tohoku‐Oki tsunami generated off Japan originated from a 300–400 km long and 100 km wide area, and the total propagated energy is 3 × 1015J (with 6% uncertainty). Measurements from 30 tsunameters and 32 coastal tide stations show excellent agreement with the forecasts obtained in real time. Our study indicates that the propagated energy and the source location are the most important source characteristics for predicting tsunami impacts. Interactions of tsunami waves with seafloor topography delay and redirect the energy flux, posing hazards from delayed and amplified waves with long duration. Seafloor topography also gives its spectral imprint to tsunami waves. Travel time forecast errors are path‐specific and correlated to the major wave scatterers in the Pacific. Numerical dissipation in the propagation modeling highlights the need of high‐resolution inundation models for accurate coastal predictions. On the other hand, it also can be used to account for physical dissipation to achieve efficiency. Our results provide guidelines for the earliest reliable tsunami forecast, warnings of long duration tsunami waves signals and enhancement of the experimental tsunami forecast system. We apply the method to quantify the energy of 15 past tsunamis, independently from earthquake magnitudes. The small tsunami to seismic radiation energy ratios, and their variability (0.01–0.8%), reinforce the importance of using deep‐ocean tsunami data, the direct measures of tsunamis, for estimates of tsunami energy and accurate forecasting.
Impact of suborbital climate changes in the North Atlantic on ice sheet dynamics at the Mid‐Pleistocene Transition
Authors: Hernández‐Almeida I. , Sierro F. J. , Cacho I. , Flores J. A.
Published: June 2012

Early and Mid‐Pleistocene climate, ocean hydrography and ice sheet dynamics have been reconstructed using a high‐resolution data set (planktonic and benthicδ18O time series, faunal‐based sea surface temperature (SST) reconstructions and ice‐rafted debris (IRD)) record from a high‐deposition‐rate sedimentary succession recovered at the Gardar Drift formation in the subpolar North Atlantic (Integrated Ocean Drilling Program Leg 306, Site U1314). Our sedimentary record spans from late in Marine Isotope Stage (MIS) 31 to MIS 19 (1069–779 ka). Different trends of the benthic and planktonic oxygen isotopes, SST and IRD records before and after MIS 25 (∼940 ka) evidence the large increase in Northern Hemisphere ice‐volume, linked to the cyclicity change from the 41‐kyr to the 100‐kyr that occurred during the Mid‐Pleistocene Transition (MPT). Beside longer glacial‐interglacial (G‐IG) variability, millennial‐scale fluctuations were a pervasive feature across our study. Negative excursions in the benthicδ18O time series observed at the times of IRD events may be related to glacio‐eustatic changes due to ice sheets retreats and/or to changes in deep hydrography. Time series analysis on surface water proxies (IRD, SST and planktonicδ18O) of the interval between MIS 31 to MIS 26 shows that the timing of these millennial‐scale climate changes are related to half‐precessional (10 kyr) components of the insolation forcing, which are interpreted as cross‐equatorial heat transport toward high latitudes during both equinox insolation maxima at the equator.
Estimating the permeability distribution and its uncertainty at the EGS demonstration reservoir Soultz‐sous‐Forêts using the ensemble Kalman filter
Authors: Vogt C. , Marquart G. , Kosack C. , Wolf A. , Clauser C.
Published: June 2012

We present an estimation of the permeability fields of the reservoir at the Enhanced Geothermal System (EGS) at Soultz‐sous‐Forêts, France, based on the data assimilation technique Ensemble Kalman Filter (EnKF). To this end, we assimilate data from a tracer circulation experiment performed in 2005. Using a 3‐D numerical simulation of fluid transport and chemical tracer dispersion, we advance the tracer in time and control the concentration. With the EnKF we obtain reliable fits for concentration data recorded in both existing production boreholes, GPK2 and GPK4. As an alternative to discrete fracture networks, our heterogeneous equivalent porous medium approach thus can also characterize the hydraulically fractured zone of the engineered geothermal system. We present best estimates for permeabilities (10−14 m2–10−12 m2for the fracture zone) and the corresponding uncertainty which is about one order of magnitude. After comparing our results to results from a massive Monte Carlo and from a gradient‐based Bayesian approach, it becomes clear that only the EnKF of this three approaches is able to fit concentrations at GPK2 and GPK4 simultaneously. Based on the EnKF estimates obtained, a long‐term performance prediction including an uncertainty analysis for the reservoir (as it was in 2005) yields no thermal breakthrough in the system within at least 50 years of operation. Our study demonstrates the efficiency of the EnKF when estimating the permeability distribution in an EGS reservoir even with sparse data available.
Satellite observations of an annual cycle in the Agulhas Current
Authors: Krug M. , Tournadre J.
Published: June 2012

Ocean models show an annual cycle in the Agulhas Current transport which has not yet been confirmed in analyses of in‐situ or satellite observations. A cross‐stream coordinate approach is used to study the variability of the Agulhas Current from 18 years of along‐track altimetry and merged altimetry and close to 7 years of high frequency Sea Surface Temperature (SST) observations. While the position and width of the Agulhas Current's dynamical core do not display an annual cycle, the geostrophic current speed at the current's core exhibits distinct seasonal variations, with a stronger flow observed in austral summer. The annual cycle dominates the frequency spectra of the current's core geostrophic velocities.
Estimating the frequency of extremely energetic solar events, based on solar, stellar, lunar, and terrestrial records
Authors: Schrijver C. J. , Beer J. , Baltensperger U. , Cliver E. W. , Güdel M. , Hudson H. S. , McCracken K. G. , Osten R. A. , Peter T. , Soderblom D. R. , Usoskin I. G. , Wolff E. W.
Published: June 2012

The most powerful explosions on the Sun – in the form of bright flares, intense storms of solar energetic particles (SEPs), and fast coronal mass ejections (CMEs) – drive the most severe space‐weather storms. Proxy records of flare energies based on SEPs in principle may offer the longest time base to study infrequent large events. We conclude that one suggested proxy, nitrate concentrations in polar ice cores, does not map reliably to SEP events. Concentrations of select radionuclides measured in natural archives may prove useful in extending the time interval of direct observations up to ten millennia, but as their calibration to solar flare fluences depends on multiple poorly known properties and processes, these proxies cannot presently be used to help determine the flare energy frequency distribution. Being thus limited to the use of direct flare observations, we evaluate the probabilities of large‐energy solar events by combining solar flare observations with an ensemble of stellar flare observations. We conclude that solar flare energies form a relatively smooth distribution from small events to large flares, while flares on magnetically active, young Sun‐like stars have energies and frequencies markedly in excess of strong solar flares, even after an empirical scaling with the mean coronal activity level of these stars. In order to empirically quantify the frequency of uncommonly large solar flares extensive surveys of stars of near‐solar age need to be obtained, such as is feasible with the Kepler satellite. Because the likelihood of flares larger than approximately X30 remains empirically unconstrained, we present indirect arguments, based on records of sunspots and on statistical arguments, that solar flares in the past four centuries have likely not substantially exceeded the level of the largest flares observed in the space era, and that there is at most about a 10% chance of a flare larger than about X30 in the next 30 years.
Functional shape of the earthquake frequency‐magnitude distribution and completeness magnitude
Authors: Mignan A.
Published: June 2012

We investigated the functional shape of the earthquake frequency‐magnitude distribution (FMD) to identify its dependence on the completeness magnitude Mc. The FMD takes the form N(m) ∝ exp(−βm)q(m) where N(m) is the event number, m the magnitude, exp(−βm) the Gutenberg‐Richter law and q(m) a detection function. q(m) is commonly defined as the cumulative Normal distribution to describe the gradual curvature of bulk FMDs. Recent results however suggest that this gradual curvature is due to Mc heterogeneities, meaning that the functional shape of the elemental FMD has yet to be described. We propose a detection function of the form q(m) = exp(κ(m − Mc)) for m < Mc and q(m) = 1 for m ≥ Mc, which leads to an FMD of angular shape. The two FMD models are compared in earthquake catalogs from Southern California and Nevada and in synthetic catalogs. We show that the angular FMD model better describes the elemental FMD and that the sum of elemental angular FMDs leads to the gradually curved bulk FMD. We propose an FMD shape ontology consisting of 5 categories depending on the Mc spatial distribution, from Mc constant to Mc highly heterogeneous: (I) Angular FMD, (II) Intermediary FMD, (III) Intermediary FMD with multiple maxima, (IV) Gradually curved FMD and (V) Gradually curved FMD with multiple maxima. We also demonstrate that the gradually curved FMD model overestimates Mc. This study provides new insights into earthquake detectability properties by using seismicity as a proxy and the means to accurately estimate Mc in any given volume.
Arctic synoptic regimes: Comparing domain‐wide Arctic cloud observations with CAM4 and CAM5 during similar dynamics
Authors: Barton Neil P. , Klein Stephen A. , Boyle James S. , Zhang Yuying Y.
Published: June 2012

Arctic cloud properties, variability, and sensitivity to surface conditions are strongly dependent on the synoptic regimes in which they exist, and proper evaluation of modeled cloud properties against observations requires that the dynamic and thermodynamic environment be carefully accounted for. In this study, a k‐means clustering algorithm is used to sort Arctic clouds observed by CALIPSO into four distinct synoptic regimes: three regimes largely associated with mid‐tropospheric subsidence or very weak uplift and separated by differences in lower tropospheric stability; and one regime associated with mid‐tropospheric uplift. Boundary layer clouds are present within the three subsidence regimes with increases in stability relating to lower altitudes of the maximum cloud percentage. In going from sea ice to open ocean, the cloud amount increases at the lowest atmospheric level for all subsidence regimes except the least stable regime, and the height of maximum low clouds rises for all subsidence regimes except the most stable regime. Within each synoptic regime, clouds diagnosed from the CALIPSO simulator in CAM4 and CAM5 forecast runs are then compared with observations. Compared with CAM4, CAM5 produces boundary layer clouds that are more similar to the observations, and more closely captures the observed sensitivity of cloud properties to the underlying surface type. However, CAM5 overestimates cloud percentages within the uplift regime. The improved boundary layer turbulence and cloud microphysical parameterizations in CAM5 yield a model that exhibits an improved sensitivity of Arctic low‐level clouds to changes in lower tropospheric stability and surface type.
A Single mri Slice Does Not Accurately Predict Visceral and Subcutaneous Adipose Tissue Changes During Weight Loss
Authors: Shen Wei , Chen Jun , Gantz Madeleine , Velasquez Gilbert , Punyanitya Mark , Heymsfield Steven B.
Published: June 2012

Earlier cross‐sectional studies found that a single magnetic resonance imaging (MRI) slice predicts total visceral and subcutaneous adipose tissue (VAT and SAT) volumes well. We sought to investigate the accuracy of trunk single slice imaging in estimating changes of total VAT and SAT volume in 123 overweight and obese subjects who were enrolled in a 24‐week CB‐1R inverse agonist clinical trial (weight change, −7.7 ± 5.3 kg; SAT change, −5.4 ± 4.9 l, VAT change, −0.8 ± 1.0 l). VAT and SAT volumes at baseline and 24 weeks were derived from whole‐body MRI images. The VAT area 5–10 cm above L4—L5 (A+5–10) (R2 = 0.59–0.70, P < 0.001) best predicted changes in VAT volume but the strength of these correlations was significantly lower than those at baseline (R2 = 0.85–0.90, P < 0.001). Furthermore, the L4—L5 slice poorly predicted VAT volume changes (R2 = 0.24–0.29, P < 0.001). Studies will require 44–69% more subjects if (A+5–10) is used and 243–320% more subjects if the L4—L5 slice is used for equivalent power of multislice total volume measurements of VAT changes. Similarly, single slice imaging predicts SAT loss less well than cross‐sectional SAT (R2 = 0.31–0.49 vs. R2 = 0.52–0.68, P < 0.05). Results were the same when examined in men and women separately. A single MRI slice 5–10 cm above L4—L5 is more powerful than the traditionally used L4—L5 slice in detecting VAT changes, but in general single slice imaging poorly predicts VAT and SAT changes during weight loss. For certain study designs, multislice imaging may be more cost‐effective than single slice imaging in detecting changes for VAT and SAT.
CRTH2 Antagonists
Authors: NATHAN TUMEY L.
Published: June 2012

Prostaglandin D2 (PGD2) plays a key role in many of the physiological markings of allergic inflammation including vasodilation, bronchoconstriction, vascular permeability and lymphocyte recruitment. The action of this molecule is elicited through its two primary receptors, DP and CRTH2. Activation of CRTH2 leads to lymphocyte chemotaxis, potentiation of histamine release from basophils, production of inflammatory cytokines (IL-4, IL-5 and IL-13) by Th2 cells, eosinophil degranulation and prevention of Th2 cell apoptosis. As such, antagonism of CRTH2 has been reported to ameliorate the symptoms associated with various allergen challenge animal models including murine antigen induced lung inflammation, murine cigarette smoke induced lung inflammation, murine allergic rhinitis, guinea pig PGD2-induced airflow obstruction, guinea pig airway hyper-responsiveness, sheep airway hyper-responsiveness and murine contact hypersensitivity. CRTH2 antagonists fall into four broad categories: tricyclic ramatroban analogues, indole acetic acids, phenyl/phenoxy acetic acids and non-acid-containing tetrahydroquinolines. Numerous CRTH2 antagonists have been advanced into the clinic and early reports from two Phase II trials suggest promising activity in the alleviation of atopic symptoms.
MAPKAP Kinase 2 (MK2) as a Target for Anti-inflammatory Drug Discovery
Authors: EDMUNDS JEREMY J. , TALANIAN ROBERT V.
Published: June 2012

Despite the success of anti-TNFα biologicals, there remains a significant unmet need for novel oral anti-inflammatory drugs for the treatment of rheumatoid arthritis and related diseases. Vigorous exploration of many potential targets for inhibition of, for example, pro-inflammatory cytokine production has led to efforts to find inhibitor leads targeting many enzymes including the p38α substrate kinase MK2. MK2 has a key role in the production of several pro-inflammatory cytokines, and studies with knockout animals and inhibitor leads support the promise of MK2 as an anti-inflammatory target. However, MK2 has additional biological roles such as in cell cycle checkpoint control, suggesting caution in the use of MK2 inhibitors for chronic non-life-threatening clinical indications such as inflammation. MK2 inhibitor lead identification and optimization efforts in several labs have resulted in a variety of potent and specific lead molecules, some of which display in-vivo activity. However, potency loss from enzyme to cell, and cell to in vivo, is commonly significant. Further, poor enzyme to cell potency correlations are also common for MK2 lead chemical series, suggesting uncontrolled confounding factors in lead inhibitor properties, or that the biological roles of MK2 and related enzymes may still be poorly understood. While further efforts in identification of MK2 inhibitors may yet yield viable drug leads, efforts to date suggest caution with this target.
CCR1
Authors: ROBERT MERRITT J. , GILCHRIST ANNETTE
Published: June 2012

CCR1 is a seven-transmembrane (7TM) protein belonging to the G-protein coupled receptor (GPCR) superfamily. As a chemokine receptor, CCR1 plays an important role in leukocyte homing in response to a number of chemotactic ligands. In addition, CCR1 has been found on a range of additional cell types (e.g. astrocytes, osteoblasts) where it may direct cell migration in response to ligand activation. As is observed for nearly all chemokine receptors, CCR1 displays a marked promiscuity of ligand binding, having at least 20 different activating ligands. CCR1 is thought to contribute to the pathogenesis of a variety of autoimmune diseases including rheumatoid arthritis, multiple sclerosis and chronic obstructive pulmonary disease. In addition, CCR1 is expressed in some cancerous cells and may play a role in multiple myeloma, prostate, breast, ovary, lung and liver cancer. Several of the small-molecule antagonists for CCR1 that have been optimized and taken into clinical trials and pre-clinical studies are presented, along with their accompanying results. However, despite numerous attempts, none of the compounds, so far, have continued beyond Phase II clinical trials. Thus, a rationale for improving CCR1 antagonists and clinical outcomes will be discussed.
The A-kinase-anchoring protein AKAP-Lbc facilitates cardioprotective PKA phosphorylation of Hsp20 on Ser16
Authors: Edwards Helen V. , Scott John D. , Baillie George S.
Published: June 2012

Hsp20 (heat-shock protein of 20 kDa; HspB6) is a cardioprotective agent which combats a number of pathophysiological processes in the heart, including hypertrophy, apoptosis and ischaemia/reperfusion injury. The cardioprotective actions of Hsp20 require its phosphorylation by PKA (cAMP-dependent protein kinase) on Ser16. Although the extracellular stimuli that promote cAMP-responsive phosphorylation of Hsp20 are well known, less is understood about the molecular processes that regulate this modification. AKAPs (A-kinase-anchoring proteins) physically compartmentalize PKA to specific locations within a cell to both direct PKA phosphorylation toward selected substrates and to orchestrate downstream signalling events. In the present study we used PKA anchoring disruptor peptides to verify that an AKAP underpins the cardioprotective phosphorylation of Hsp20. Biochemical and immunofluorescence techniques identify the cytosolic protein AKAP-Lbc (AKAP13) as the anchoring protein responsible for directing PKA phosphorylation of Hsp20 on Ser16. Gene silencing and rescue experiments establish that AKAP-Lbc-mediated PKA phosphorylation of Hsp20 is crucial to the anti-apoptotic effects of the Hsp. Thus AKAP-Lbc may serve an ancillary cardioprotective role by favouring the association of PKA with Hsp20.
Crystal structure of xenotropic murine leukaemia virus-related virus (XMRV) ribonuclease H
Authors: Kim Ju Hee , Kang Sunghyun , Jung Suk-Kyeong , Yu Keum Ran , Chung Sang J. , Chung Bong Hyun , Erikson Raymond L. , Kim Bo Yeon , Kim Seung Jun
Published: June 2012

RNase H (retroviral ribonuclease H) cleaves the phosphate backbone of the RNA template within an RNA/DNA hybrid to complete the synthesis of double-stranded viral DNA. In the present study we have determined the complete structure of the RNase H domain from XMRV (xenotropic murine leukaemia virus-related virus) RT (reverse transcriptase). The basic protrusion motif of the XMRV RNase H domain is folded as a short helix and an adjacent highly bent loop. Structural superposition and subsequent mutagenesis experiments suggest that the basic protrusion motif plays a role in direct binding to the major groove in RNA/DNA hybrid, as well as in establishing the co-ordination among modules in RT necessary for proper function.
PI3K/Akt/FoxO: a novel participant in signal transduction in bone cells under mechanical stimulation
Authors: Ma Yuanyuan , Wang Hang
Published: June 2012

FoxO (forkhead box O) transcription factors, one of the main downstream mediators of PI3K (phosphatidylinositol‐3 kinase)/Akt [also known as PKB (protein kinase B)] signal transduction pathway, play an important role in modulating cellular homoeostasis. Recent studies have revealed the significance of FoxO in bone, the interaction of FoxO with β‐catenin, along with mechanical stress‐induced inactivation of FoxO via PI3K/Akt. We hypothesize that FoxO is a novel participant in mechanotransduction of bone cells in a PI3K/Akt‐dependent way. After describing downstream targets of FoxO, we speculate that FoxO would be involved in the positive effects of mechanical stimulation on bone cells directly through its target genes. We have also concisely represented the cross‐talk between ROS (reactive oxygen species) and Wnt/β‐catenin pathway, which leads us to hypothesize that the inhibition of FoxO caused by mechanical stress acts at the cross‐roads between ROS and Wnt/β‐catenin to regulate indirectly bone metabolism.
Ultra fast x-ray streak camera for ten inch manipulator based platforms
Authors: Marley E. V. , Shepherd R. , Fulkerson S. , James L. , Emig J. , Norman D.
Published: June 2012

Ultra fast x-ray streak cameras are a staple for time resolved x-ray measurements. There is a need for a ten inch manipulator (TIM) based streak camera that can be fielded in a newer large scale laser facility. The Lawrence Livermore National Laboratory ultra fast streak camera's drive electronics have been upgraded and redesigned to fit inside a TIM tube. The camera also has a new user interface that allows for remote control and data acquisition. The system has been outfitted with a new sensor package that gives the user more operational awareness and control.
Broadband probing magnetization dynamics of the coupled vortex state permalloy layers in nanopillars
Authors: Awad A. A. , Lara A. , Metlushko V. , Guslienko K. Y. , Aliev F. G.
Published: June 2012

Broadband magnetization response of coupled vortex state magnetic dots in layered nanopillars was explored as a function of in-plane magnetic field and interlayer separation. For dipolarly coupled circular Py(25 nm)/Cu(20 nm)/Py(25 nm) nanopillars of 600 nm diameter, a small in-plane field splits the eigenfrequencies of azimuthal spin wave modes inducing an abrupt transition between in-phase and out-of-phase kinds of the low-lying coupled spin wave modes. The critical field for this splitting is determined by antiparallel chiralities of the vortices in the layers. Qualitatively similar (although more gradual) changes occur also in the exchange coupled Py(25 nm)/Cu(1 nm)/Py(25 nm) tri-layer nanopillars. These findings are in qualitative agreement with micromagnetic dynamic simulations.
Magnetoelectric relaxation in rhombohedral LiNbO3-CoFe2O4
Authors: Han Yemei , Liu Yueying , Zavalij Peter , Salamanca-Riba Lourdes , Cantando Elizabeth , Bergstrom Richard , Li Lingxia , Wuttig Manfred
Published: June 2012

We demonstrate a magnetoelectric nanocomposite, LiNbO3-CoFe2O4 (LNO-CFO), consisting of rhombohedral R3c LNO and R3m CFO phases. It is characterized by a maximum inverse magnetoelectric coefficient of 6.5 Oe cm·V−1 measured in a 106 V/m electric field, and a magnetic field dependent Vogel–Fulcher-like relaxation characterized by a relaxation time τ=τ0exp(−ΔH/k(Tm−TvfH)), τ0=29.66 s, ΔH=1.06 eV, TvfH represents the magnetic field-dependent Vogel-Fulcher temperature. The activation energy equals the activation energy of oxygen vacancy diffusion in niobate-based crystals. The room temperature electric field-induced magnetization change relaxes as τ=18.05 s.
Computer simulations of thermo-sensitive microgels: Quantitative comparison with experimental swelling data
Authors: Quesada-Pérez Manuel , Ramos Jose , Forcada Jacqueline , Martín-Molina Alberto
Published: June 2012

In this work, a quantitative comparison between experimental swelling data of thermo-sensitive microgels and computer simulation results obtained from a coarse-grained model of polyelectrolyte network and the primitive model of electrolyte is carried out. Polymer-polymer hydrophobic forces are considered in the model through a solvent-mediated interaction potential whose depth increases with temperature. The qualitative agreement between simulation and experiment is very good. In particular, our simulations predict a gradual shrinkage with temperature, which is actually observed for the microgels studied in this survey. In addition, the model can explain the swelling behavior for different contents of ionizable groups without requiring changes in the hydrophobic parameters. Our work also reveals that the abruptness of the shrinkage of charged gels is considerably conditioned by the number of monomeric units per chain. The swelling data are also analyzed with the Flory-Rhener theory, confirming some limitations of this classical formalism.
Complete nuclear motion Hamiltonian in the irreducible normal mode tensor operator formalism for the methane molecule
Authors: Rey Michaël , Nikitin Andrei V. , Tyuterev Vladimir G.
Published: June 2012

A rovibrational model based on the normal-mode complete nuclear Hamiltonian is applied to methane using our recent potential energy surface [A. V. Nikitin, M. Rey, and Vl. G. Tyuterev, Chem. Phys. Lett. 501, 179 (2011)10.1016/j.cplett.2010.11.008]. The kinetic energy operator and the potential energy function are expanded in power series to which a new truncation-reduction technique is applied. The vibration-rotation Hamiltonian is transformed systematically to a full symmetrized form using irreducible tensor operators. Each term of the Hamiltonian expansion can be thus cast in the tensor form whatever the order of the development. This allows to take full advantage of the symmetry properties for doubly and triply degenerate vibrations and vibration-rotation states. We apply this model to variational computations of energy levels for 12CH4, 13CH4, and 12CD4.
Stark coefficients for highly excited rovibrational states of H2O
Authors: Grechko M. , Aseev O. , Rizzo T. R. , Zobov N. F. , Lodi L. , Tennyson J. , Polyansky O. L. , Boyarkin O. V.
Published: June 2012

Quantum beat spectroscopy is combined with triple-resonance vibrational overtone excitation to measure the Stark coefficients (SCs) of the water molecule for 28 rovibrational levels lying from 27 600 to 41 000 cm−1. These data provide a stringent test for assessing the accuracy of the available potential energy surfaces (PESs) and dipole moment surfaces (DMSs) of this benchmark molecule in this energy region, which is inaccessible by direct absorption. SCs, calculated using the combination of a high accuracy, spectroscopically determined PES and a recent ab initio DMS, are within the 1% accuracy of available experimental data for levels below 25 000 cm−1, and within 4.5% for coefficients associated with levels up to 35 000 cm−1. However, the error in the computed coefficients is over 60% for the very high rovibrational states lying just below the lowest dissociation threshold, due, it seems, to lack of a high accuracy PES in this region. The comparative analysis suggests further steps, which may bring the theoretical predictions closer to the experimental accuracy.
Ab initio determination of the ionization potentials of water clusters (H2O)n (n = 2−6)
Authors: Segarra-Martí Javier , Merchán Manuela , Roca-Sanjuán Daniel
Published: June 2012

High-level quantum-chemical ab initio coupled-cluster and multiconfigurational perturbation methods have been used to compute the vertical and adiabatic ionization potentials of several water clusters: dimer, trimer, tetramer, pentamer, hexamer book, hexamer ring, hexamer cage, and hexamer prism. The present results establish reference values at a level not reported before for these systems, calibrating different computational strategies and helping to discard less reliable theoretical and experimental data. The systematic study with the increasing size of the water cluster allows obtaining some clues on the structure and reductive properties of liquid water.
Improvement of oxygen vacancy migration through Nb doping on Ba0.7Sr0.3TiO3 thin films for resistance switching random access memory application
Authors: Jung Chang Hwa , Park Moon Kyu , Woo Seong Ihl
Published: June 2012

Undoped and Nb-doped Ba0.7Sr0.3TiO3 (BST) thin films were fabricated by RF magnetron sputtering. The bipolar resistance switching behaviors of both thin films were observed with the stable endurance by DC voltage sweep. Nb doping in BST influenced the defect distribution and improved the uniformity of resistance switching random access memory (ReRAM) properties. The defect distribution was strongly related to the resistance switching properties and the decrease in the grain size caused by Nb doping made the oxygen migration more efficient. The oxygen migration in BST was assisted by Nb dopants which increased the concentration of the non-lattice oxygen in BST layer during ReRAM operation.
Probing quasiparticle excitations in a hybrid single electron transistor
Authors: Knowles H. S. , Maisi V. F. , Pekola J. P.
Published: June 2012

We investigate the behavior of quasiparticles in a hybrid electron turnstile with the aim of improving its performance as a metrological current source. The device is used to directly probe the density of quasiparticles and monitor their relaxation into normal metal traps. We compare different trap geometries and reach quasiparticle densities below 3 μm−3 for pumping frequencies of 20 MHz. Our data show that quasiparticles are excited both by the device operation itself and by the electromagnetic environment of the sample. Our observations can be modelled on a quantitative level with a sequential tunneling model and a simple diffusion equation.
The pattern of bioenergy utilization in China: A spatial difference analysis
Authors: Chang S. Y. , Zhao L. L.
Published: June 2012

The bioenergy utilization increased rapidly during the past few years in China. Based on provincial-level data, the geographical distributions of biomass resources and bioenergy utilization in China are evaluated in this paper. The Gini coefficient and global spatial autocorrelation are used here to carry out exploratory spatial data analysis (ESDA). The results show that (1) the biomass resource is more dispersed than bioenergy utilization. The Gini coefficients of three kinds of biomass resource considered here are all lower than 0.5 from 1999 to 2010, while that of most bioenergy are higher than 0.5. Municipal solid waste is the most dispersed one, followed by the agriculture residues and livestock and poultry excrement; (2) with strong policy support, some relatively mature bioenergy technologies show an overall country diffusion pattern. The Gini coefficient of household biogas kept on decreasing from 1999 to 2010, and that of on-grid biomass power generation decreased sharply from 2007 to September 2010; and (3) except household biogas, which is mainly located in south-western regions, most of the bioenergy applications are located in eastern regions. And there is still huge potential on technology diffusion over provinces.
Epidemic variability in hierarchical geographical networks with human activity patterns
Authors: Zhao Zhi-Dan , Liu Ying , Tang Ming
Published: June 2012

Recently, some studies have revealed that non-Poissonian statistics of human behaviors stem from the hierarchical geographical network structure. On this view, we focus on epidemic spreading in the hierarchical geographical networks and study how two distinct contact patterns (i.e., homogeneous time delay (HOTD) and heterogeneous time delay (HETD) associated with geographical distance) influence the spreading speed and the variability of outbreaks. We find that, compared with HOTD and null model, correlations between time delay and network hierarchy in HETD remarkably slow down epidemic spreading and result in an upward cascading multi-modal phenomenon. Proportionately, the variability of outbreaks in HETD has the lower value, but several comparable peaks for a long time, which makes the long-term prediction of epidemic spreading hard. When a seed (i.e., the initial infected node) is from the high layers of networks, epidemic spreading is remarkably promoted. Interestingly, distinct trends of variabilities in two contact patterns emerge: high-layer seeds in HOTD result in the lower variabilities, the case of HETD is opposite. More importantly, the variabilities of high-layer seeds in HETD are much greater than that in HOTD, which implies the unpredictability of epidemic spreading in hierarchical geographical networks.
Note: Design of a novel rotating magnetic field device
Authors: Godínez F. A. , Chávez O. , Zenit R.
Published: June 2012

A novel device to produce a rotating magnetic field was designed, constructed, and tested. The system consists of a Helmholtz coil pair which is mechanically coupled to a dc electric motor whose angular velocity is controlled. The coil pair generates a uniform magnetic field; the whole system is rotated maintaining the coils energized using brushes. The magnetic field strength is uniform (≈5.8 mT) for a workspace of about 100 mm along the rotation axis. The system remains free of undesirable high amplitude mechanical vibrations for rotation frequencies below 10 Hz. We verified the performance of the apparatus by conducting experiments with magnetic swimmers.
A new method for determining the plasma electron density using three-color interferometer
Authors: Arakawa Hiroyuki , Kawano Yasunori , Itami Kiyoshi
Published: June 2012

A new method for determining the plasma electron density using the fractional fringes on three-color interferometer is proposed. Integrated phase shift on each interferometer is derived without using the temporal history of the fractional fringes. The dependence on the fringe resolution and the electrical noise are simulated on the wavelengths of CO2 laser. Short-time integrations of the fractional fringes enhance the reliability of this method.
Inter-tube thermal conductance in carbon nanotubes arrays and bundles: Effects of contact area and pressure
Authors: Evans William J. , Shen Meng , Keblinski Pawel
Published: June 2012

We use molecular dynamics simulations to compute junction thermal conductance of carbon nanotubes as a function of crossing angle and pressure, and conductivity of arrays and bundles consisting of multiple junctions as a function of pressure. Two types of arrays are investigated: crossbar structures consisting of alternating orthogonal layers of nanotubes and close-packed bundles of parallel oriented tubes. Conductance of 90° junction increases with pressure 4 fold before saturation; cross-plane thermal conductivity of crossbar structures increases by a factor of 2. For parallel junctions pressure doubles the conductance while thermal conductivity of nanotubes bundles is more or less pressure independent.
Transport critical-current density of superconducting films with hysteretic ferromagnetic dots
Authors: Del-Valle Nuria , Navau Carles , Sanchez Alvaro , Dinner Rafael B.
Published: June 2012

Superconductor-ferromagnet hybrids present a rich and complex phenomenology. Particularly, a hysteretic behavior on the transport critical-current density, as a function of a uniform perpendicular applied field, has been experimentally found in superconducting films with some embedded ferromagnets. Here we analyze the interaction superconductor-ferromagnets by means of an iterative model based on the critical-state model with field-dependent internal critical-current density and compare the results with actual transport measurements. By using arguments of field compensation, we show how the change in the magnetization of the ferromagnetic inclusions is responsible for the observed hysteresis on the transport critical current.
Self-heterodyne mixing method of two inter-mode beat frequencies for frequency stabilization of a three-mode He-Ne laser
Authors: Lee Jeongmin , Yoon Tai Hyun
Published: June 2012

We present a robust self-heterodyne mixing method of two inter-mode beat frequencies suitable for frequency stabilization of a three longitudinal-mode (3-mode) He-Ne laser at 633 nm. A high-contrast frequency discrimination signal with a broad locking range of 244 MHz is obtained by using a self-heterodyned double balanced mixer operating at the inter-mode beat frequency of 607 MHz. We show that the central-mode frequency of the 3-mode He-Ne laser could be stabilized to the center of the gain profile with a frequency fluctuation less than ± 5 MHz for more than 12 h.
Predominant regeneration strategy results in species-specific genetic patterns in sympatric Nothofagus s.s. congeners (Nothofagaceae)
Authors: Acosta M. Cristina , Mathiasen Paula , Premoli Andrea C.
Published: June 2012

Life-history traits affect plant performance. Predominant regeneration modes, sprouting v. non-sprouting, will result in contrasting evolutionary and ecological responses that may be traced by nuclear markers. Sympatric Nothofagus Blume species provide the natural setting to test whether sprouters have a greater ability to maintain genetic diversity. In total, 28 populations along the entire distribution range of N. antarctica (G. Forst.) Oerst. were screened by eight polymorphic isozyme loci. We compared pairwise genetic patterns of the predominant sprouter N. antarctica with the mainly non-sprouter N. pumilio (Poepp. & Endl.) Krasser at 20 sympatric locations along their geographically concordant widespread range. Overall, the sprouter N. antarctica showed higher genetic variation throughout its range than did the non-sprouter N. pumilio. Mid-latitude populations of N. antarctica have maintained isozyme diversity, as inferred using genetic-landscape analysis. Despite the potential for inter-specific gene flow and past hybridisations, species identity was preserved by divergent selective forces acting on sympatric populations with distinct autoecological traits. Predominantly sprouting, as compared with mainly non-sprouting, has favoured long-term persistence of genet diversity in relatively large populations that were probably less affected by drift through time, thereby preserving molecular variants along its range. These variants, in combination with plasticity in diverse habitats, have resulted in greater resilience of N. antarctica under changing scenarios.
Characterisation of tracers for aging of α-pinene secondary organic aerosol using liquid chromatography/negative ion electrospray ionisation mass spectrometry
Authors: Yasmeen Farhat , Vermeylen Reinhilde , Maurin Nicolas , Perraudin Emilie , Doussin Jean-François , Claeys Magda
Published: June 2012

Environmental contextAmbient fine aerosol from forested sites contains secondary organic aerosol from the oxidation of monoterpenes that are emitted by the vegetation, mainly by conifers. These biogenic aerosols can have varying lifetimes in the atmosphere because they contain first-generation oxidation products of α-pinene as well as aged products formed through further photooxidation, fragmentation, hydrolysis, and dimerisation reactions. We focus on the structural characterisation of secondary organic aerosol products that are simulated in a smog chamber experiment and can serve as potential tracers for aging processes in biogenic aerosols.
AbstractSecondary organic aerosol (SOA) from the oxidation of α-pinene is a very complex and dynamic mixture containing products with a different chemical nature and physicochemical properties that are dependent on chemical evolution or aging processes. In this study, we focus on the chemical characterisation of major products that are formed upon α-pinene ozonolysis SOA and subsequent aging through OH-initiated reactions in the absence of NOx, which include known as well as unknown tracers. The mass spectrometric data obtained for selected unknown compounds that show an increased relative abundance upon aging are interpreted in detail and tentative structures for them are proposed taking into account their formation through photooxidation of α-pinene. Known tracers for α-pinene SOA aging that were identified include norpinic acid, 10-hydroxypinonic acid, diaterpenylic acid acetate, and diesters formed by esterification of pinic acid with terpenylic acid or 10-hydroxypinonic acid. Novel tracers for α-pinene SOA aging that were tentatively identified include dinorpinic acid and 8-hydroxypinonic acid. In addition, reaction mechanisms are proposed to explain the formation of the observed α-pinene SOA tracers.
Markus Grebe: Bringing plant polarity to light
Authors: Sedwick Caitlin
Published: June 2012

Grebe studies the establishment and maintenance of cell and tissue polarity in plants
CtIP-dependent DNA resection is required for DNA damage checkpoint maintenance but not initiation
Authors: Kousholt Arne Nedergaard , Fugger Kasper , Hoffmann Saskia , Larsen Brian D. , Menzel Tobias , Sartori Alessandro A. , Sørensen Claus Storgaard
Published: June 2012

To prevent accumulation of mutations, cells respond to DNA lesions by blocking cell cycle progression and initiating DNA repair. Homology-directed repair of DNA breaks requires CtIP-dependent resection of the DNA ends, which is thought to play a key role in activation of ATR (ataxia telangiectasia mutated and Rad3 related) and CHK1 kinases to induce the cell cycle checkpoint. In this paper, we show that CHK1 was rapidly and robustly activated before detectable end resection. Moreover, we show that the key resection factor CtIP was dispensable for initial ATR–CHK1 activation after DNA damage by camptothecin and ionizing radiation. In contrast, we find that DNA end resection was critically required for sustained ATR–CHK1 checkpoint signaling and for maintaining both the intra–S- and G2-phase checkpoints. Consequently, resection-deficient cells entered mitosis with persistent DNA damage. In conclusion, we have uncovered a temporal program of checkpoint activation, where CtIP-dependent DNA end resection is required for sustained checkpoint signaling.