bluuebunny/crossref_metadata_2025 huggingface dataset:
R47H TREM2 variant increases risk of typical early‐onset Alzheimer's disease but not of prion or frontotemporal dementia
Authors: Slattery Catherine F. , Beck Jonathan A. , Harper Lorna , Adamson Gary , Abdi Zeinab , Uphill James , Campbell Tracy , Druyeh Ron , Mahoney Colin J. , Rohrer Jonathan D. , Kenny Janna , Lowe Jessica , Leung Kelvin K. , Barnes Josephine , Clegg Shona L. , Blair Melanie , Nicholas Jennifer M. , Guerreiro Rita J. , Rowe James B. , Ponto Claudia , Zerr Inga , Kretzschmar Hans , Gambetti Pierluigi , Crutch Sebastian J. , Warren Jason D. , Rossor Martin N. , Fox Nick C. , Collinge John , Schott Jonathan M. , Mead Simon
Published: August 2014

Background

Rare TREM2 variants are significant risk factors for Alzheimer's disease (AD).

Methods

We used next generation sequencing of the whole gene (n = 700), exon 2 Sanger sequencing (n = 2634), p.R47H genotyping (n = 3518), and genome wide association study imputation (n = 13,048) to determine whether TREM2 variants are risk factors or phenotypic modifiers in patients with AD (n = 1002), frontotemporal dementia (n = 358), sporadic (n = 2500), and variant (n = 115) Creutzfeldt‐Jakob disease (CJD).

Results

We confirm only p.R47H as a risk factor for AD (odds ratio or OR = 2.19; 95% confidence interval or CI = 1.04‐4.51; P = .03). p.R47H does not significantly alter risk for frontotemporal dementia (OR = 0.81), variant or sporadic CJD (OR = 1.06 95%CI = 0.66‐1.69) in our cohorts. Individuals with p.R47H associated AD (n = 12) had significantly earlier symptom onset than individuals with no TREM2 variants (n = 551) (55.2 years vs. 61.7 years, P = .02). We note that heterozygous p.R47H AD is memory led and otherwise indistinguishable from “typical” sporadic AD.

Conclusion

We find p.R47H is a risk factor for AD, but not frontotemporal dementia or prion disease.
Reduced cerebrovascular reactivity in young adults carrying the APOE ε4 allele
Authors: Suri Sana , Mackay Clare E. , Kelly Michael E. , Germuska Michael , Tunbridge Elizabeth M. , Frisoni Giovanni B. , Matthews Paul M. , Ebmeier Klaus P. , Bulte Daniel P. , Filippini Nicola
Published: August 2014

Background

Functional magnetic resonance imaging (MRI) studies have shown that APOE ε2‐ and ε4‐carriers have similar patterns of blood‐oxygenation‐level‐dependent (BOLD) activation suggesting that we need to look beyond the BOLD signal to link APOE's effect on the brain to Alzheimer's disease (AD)‐risk.

Methods

We evaluated APOE‐related differences in BOLD activation in response to a memory task, cerebrovascular reactivity using a CO2‐inhalation challenge (CO2‐CVR), and the potential contribution of CO2‐CVR to the BOLD signal.

Results

APOE ε4‐carriers had the highest task‐related hippocampal BOLD signal relative to non‐carriers. The largest differences in CO2‐CVR were between ε2‐ and ε4‐carriers, with the latter having the lowest values. Genotype differences in CO2‐CVR accounted for ∼70% of hippocampal BOLD differences between groups.

Conclusion

Because CO2‐CVR gauges vascular health, the differential effect of APOE in young adults may reflect a vascular contribution to the vulnerability of ε4‐carriers to late‐life pathology. Studies confirming our findings are warranted.
BMPR2 loss in fibroblasts promotes mammary carcinoma metastasis via increased inflammation
Authors: Pickup Michael W. , Hover Laura D. , Polikowsky Eleanor R. , Chytil Anna , Gorska Agnieszka E. , Novitskiy Sergey V. , Moses Harold L. , Owens Philip
Published: August 2014

Bone Morphogenetic Protein (BMP) receptors mediate a diverse range of signals to regulate both development and disease. BMP activity has been linked to both tumor promoting and suppressive functions in both tumor cells and their surrounding microenvironment. We sought to investigate the requirement for BMPR2 in stromal fibroblasts during mammary tumor formation and metastasis. We utilized FSP1 (Fibroblast Specific Protein‐1) promoter driven Cre to genetically delete BMPR2 in mice expressing the MMTV.PyVmT mammary carcinoma oncogene. We found that abrogation of stromal BMPR2 expression via FSP1 driven Cre resulted in increased tumor metastasis. Additionally, similar to epithelial BMPR2 abrogation, stromal loss of BMPR2 results in increased inflammatory cell infiltration. We proceeded to isolate and establish fibroblast cell lines without BMPR2 and found a cell autonomous increase in inflammatory cytokine secretion. Fibroblasts were co‐implanted with syngeneic tumor cells and resulted in accelerated tumor growth and increased metastasis when fibroblasts lacked BMPR2. We observed that the loss of BMPR2 results in increased chemokine expression, which facilitates inflammation by a sustained increase in myeloid cells. The chemokines increased in BMPR2 deleted cells correlated with poor outcome in human breast cancer patients. We conclude that BMPR2 has tumor suppressive functions in the stroma by regulating inflammation.
Natural coal fires in the Kuznetsk Coal Basin: geologic causes, climate, and age
Authors: Sokol E.V. , Novikova S.A. , Alekseev D.V. , Travin A.V.
Published: August 2014

The paper summarizes data on the Pleistocene combustion metamorphic complexes of the Kuznetsk Coal Basin. Paralava and clinker samples are dated by 40Ar/39Ar incremental heating. The 40Ar/39Ar ages of the combustion metamorphic rocks permit reconstructions of the succession of renewed activity of ancient faults in the Salair zone and age estimates for the evolution of the present-day drainage network. Cross sections of burned rocks from the western margin and center of the Kuznetsk Basin are compared. The geologic factors of coal ignition risks are analyzed. On the western margin of the Kuznetsk Basin, paleofires occurred in steeply dipping thick seams with predominant crushed vitrain–clarain coal, which has a high oxygen and methane adsorption capacity. Highly denuded high-temperature combustion metamorphic complexes are most often localized in the arches of slightly broken anticlines. Oxygen was supplied to the coals during the Late Cenozoic renewed fault activity and the subsequent erosion of the sediments. The natural fires in the area were a result of external rather than spontaneous ignition. The depths of the paleofires (up to 200 m) indicate that they occurred in a warm and dry climate. In the center of the Kuznetsk Basin, dispersed fire foci appeared in seams of self-igniting coals with the erosion propagation of the current drainage network. The combustion metamorphic complexes here are partly eroded and consist mostly of clinkers with a low degree of alteration. The 40Ar/39Ar ages and geological data indicate that the earliest large-scale combustion events on the western periphery of the basin occurred in the Eopleistocene (1.3–0.9 Ma). The oldest 40Ar/39Ar age of a coal fire episode (1.7 ± 0.3 Ma) might be the upper age boundary of the altitude differentiation of topography, which corresponds to the renewed activity of the Tyrgan and Afonino–Kiselevsk faults. The later synchronous combustion events on the western margin (0.2 ± 0.1 Ma) and in the center of the basin (0.13–0.02 Ma), most probably, occurred during the Kazantsevian interglacial, which gave rise to the present-day drainage network.
A-type granites and related rocks: petrogenesis and classification
Authors: Grebennikov A.V.
Published: August 2014

The problems of identification of A-type granitoids are analyzed. These rocks occur in different geodynamic settings. Owing to their mantle nature, they show distinct REE specialization. These are acid intrusive rocks, whose volcanic products are of crucial scientific and practical significance. However, neither the great number of proposed classification schemes and diagrams, including those based on expensive analytical data, nor hot scientific discussions of their identification and the ambiguity of the term A-granitoids helped to determine their classification features in full measure. A principally new discriminant diagram is proposed for the classification of igneous A-type rocks, based on the analysis of earlier obtained results and the petrochemical composition of these rocks. A comparative analysis of subdivision of granites and related felsic volcanic rocks (SiO2 > 67 wt.%), based on the ternary (Na2O + K2O)–Fe2O3*×5–(CaO + MgO)×5 and other widely applied diagrams, has shown the advantage of the proposed discriminant diagram for the classification of A-type granitoids from different geodynamic settings.
Mineral inclusions in sapphire from the basalt-related deposit in Bo Phloi, Kanchanaburi, western Thailand: indication of their genesis
Authors: Khamloet P. , Pisutha-Arnond V. , Sutthirat C.
Published: August 2014

The Bo Phloi gem field in Kanchanaburi Province, Western Thailand, is closely associated with Cenozoic basalts. Blue and yellow sapphire, black spinel, and minor zircon have been mined for over three decades. The mineral inclusions observed in sapphire samples are alkali feldspar, nepheline, hercynitic spinel, zircon, manganiferous ilmenite, silica-rich enstatite, almandine–pyrope garnet, monazite, calcite, sapphirine, biotite–phlogopite mica, and staurolite. Based on their geochemical affinity, these mineral inclusions can be categorized into two main groups: felsic alkaline and contact-metamorphic, which appear to have originated from different processes. These inclusions provide new evidence for proposing a bimodal genetic model. Felsic alkaline origin is evidenced by the occurrence of a felsic alkaline inclusion suite and the REE geochemistry of sapphire-associated zircon, which indicates that most of the sapphires crystallized from a high-alkali felsic melt (probably, in the lower crust). Contact-metamorphic origin is evidenced by the presence of a contact-metamorphic inclusion suite, suggesting that some of these sapphires might also have originated from metasomatized crustal rocks and a contaminated melt along the contact zone of a basaltic intrusion (probably, in the upper mantle or lower crust).
Evaluation of radiation dose due to naturally occurring radionuclides in rock samples of different origins collected from Azad Kashmir
Authors: Rafique M. , Khan A.R. , Jabbar A. , Rahman S.U. , Kazmi S.J.A. , Nasir T. , Arshed W. , Matiullah
Published: August 2014

The state of Azad Kashmir is rich in three types of rocks, namely, sedimentary, metamorphic, and igneous rocks. These rocks contain extensive deposits of graphite, marble, limestone, quartzite, granite, dolerite, and sandstone, which are widely used for the construction of dwellings in Azad Kashmir and Pakistan. Therefore, knowledge about the presence of natural radioactivity in these materials is desirable to assess the radiological hazards associated with it. In this context, 30 rock samples were collected from different geologic formations of the Muzaffarabad Division, Azad Kashmir. After processing the samples, the specific activities of 226Ra, 232Th, and 40K in them were measured using a P-type coaxial high-purity germanium detector. The observed highest dose rate values for sedimentary, metamorphic, and igneous rocks have been found to be 83.16 ± 1.08, 135.87 ± 1.18, and 115.98 ± 1 nGy ⋅ h–1, respectively. The radium equivalent activity (Raeq) varied from 23.76 ± 1.15 for dolerite sample (igneous rock) to 293.69 ± 2.60 Bq ⋅ kg–1 for marble (metamorphic rock). The Raeq values of all rock samples are lower than the limit mentioned in the Organization for Economic Cooperation and Development (OECD, 1979) report (370 Bq ⋅ kg–1, equivalent to γ-dose of 1.5 mSv ⋅ y–1). The values of external (Hex) and internal hazard indices (Hin) are less than unity. The mean outdoor and indoor annual effective dose equivalents are 0.073 mSv ⋅ y–1 and 0.29 mSv ⋅ y–1, respectively. The mean (over all types of rock samples) annual effective dose equivalent is reported as 0.36 mSv ⋅ y–1.
The experience of mapping of Baikal subsurface gas hydrates and gas recovery
Authors: Khlystov O.M. , Nishio Sh. , Manakov A.Yu. , Sugiyama H. , Khabuev A.V. , Belousov O.V. , Grachev M.A.
Published: August 2014

Lake Baikal is the only fresh-water lake where natural gas hydrate accumulations were found in sediments. For the recent decade, Baikal has become a natural laboratory for investigation of the properties of gas hydrates, their indicators, and recovery of gas from subsurface (subbottom) gas hydrates. We present the main results of subsurface gas hydrate mapping and gas recovery test near the delta of the Goloustnaya River.
Method for deep temperature estimation with regard to the paleoclimate influence on heat flow
Authors: Golovanova I.V. , Sal’manova R.Yu. , Tagirova Ch.D.
Published: August 2014

New results of the study of the distorting effect of paleoclimate on the formation of the thermal field of the Earth’s uppermost crust in the South Urals are presented. We discuss some consequences of taking into account the paleoclimate influence on estimates of deep heat flow and possible applications of these data. The dependence of the heat flow density on the studied depth of boreholes is considered, and deep heat loss and deep temperatures are estimated. A new method for deep temperature estimation is proposed, which takes into account the paleoclimate influence on the heat flow. The method is tested on the available high-quality temperature data for deep boreholes. Deep temperatures to a depth of –10,000 m are estimated for the platform part of the Republic of Bashkortostan using the proposed method. Isotherm schemes are constructed for elevations of –5000 and –10,000 m below sea level.

The necessity of using heat flow values corrected for the paleoclimate influence to estimate the Earth’s thermal state is justified. Some examples illustrate that underestimation of heat flow values measured in shallow boreholes might lead to underestimation of deep temperatures and global heat losses.
Instability of layered media under gravity stress
Authors: Rebetsky Yu.L.
Published: August 2014

It is proposed to consider data both on the deep density distribution (gravity instability) and the bulk modulus of elasticity on estimation of the stability of layered mountain ranges. It is shown that an increase in bulk elastic rigidity with depth is the stable state of layered media in terms of energy in the field of gravity stress. In the tectonosphere, in which the moduli of elasticity are inverted (decrease) with depth, excess energy of elastic strain of volume change is generated by body forces, and it will determine the instability of the geologic medium.
Magnetic domain structure in nanocrystalline Ni-Zn-Co spinel ferrite thin films using off-axis electron holography
Authors: Zhang D. , Ray N. M. , Petuskey W. T. , Smith D. J. , McCartney M. R.
Published: August 2014

We report a study of the magnetic domain structure of nanocrystalline thin films of nickel-zinc ferrite. The ferrite films were synthesized using aqueous spin-spray coating at low temperature (∼90 °C) and showed high complex permeability in the GHz range. Electron microscopy and microanalysis revealed that the films consisted of columnar grains with uniform chemical composition. Off-axis electron holography combined with magnetic force microscopy indicated a multi-grain domain structure with in-plane magnetization. The correlation between the magnetic domain morphology and crystal structure is briefly discussed.
Computing thermal Wigner densities with the phase integration method
Authors: Beutier J. , Borgis D. , Vuilleumier R. , Bonella S.
Published: August 2014

We discuss how the Phase Integration Method (PIM), recently developed to compute symmetrized time correlation functions [M. Monteferrante, S. Bonella, and G. Ciccotti, Mol. Phys. 109, 3015 (2011)], can be adapted to sampling/generating the thermal Wigner density, a key ingredient, for example, in many approximate schemes for simulating quantum time dependent properties. PIM combines a path integral representation of the density with a cumulant expansion to represent the Wigner function in a form calculable via existing Monte Carlo algorithms for sampling noisy probability densities. The method is able to capture highly non-classical effects such as correlation among the momenta and coordinates parts of the density, or correlations among the momenta themselves. By using alternatives to cumulants, it can also indicate the presence of negative parts of the Wigner density. Both properties are demonstrated by comparing PIM results to those of reference quantum calculations on a set of model problems.
Nondegeneracy of the ground state for nonrelativistic Lee model
Authors: Erman Fatih , Malkoç Berkin , Turgut O. Teoman
Published: August 2014

In the present work, we first briefly sketch the construction of the nonrelativistic Lee model on Riemannian manifolds, introduced in our previous works. In this approach, the renormalized resolvent of the system is expressed in terms of a well-defined operator, called the principal operator, so as to obtain a finite formulation. Then, we show that the ground state of the nonrelativistic Lee model on compact Riemannian manifolds is nondegenerate using the explicit expression of the principal operator that we obtained. This is achieved by combining heat kernel methods with positivity improving semi-group approach and then applying these tools directly to the principal operator, rather than the Hamiltonian, without using cut-offs.
Effects of surface interactions on heterogeneous ice nucleation for a monatomic water model
Authors: Reinhardt Aleks , Doye Jonathan P. K.
Published: August 2014

Despite its importance in atmospheric science, much remains unknown about the microscopic mechanism of heterogeneous ice nucleation. In this work, we perform hybrid Monte Carlo simulations of the heterogeneous nucleation of ice on a range of generic surfaces, both flat and structured, in order to probe the underlying factors affecting the nucleation process. The structured surfaces we study comprise one basal plane bilayer of ice with varying lattice parameters and interaction strengths. We show that what determines the propensity for nucleation is not just the surface attraction, but also the orientational ordering imposed on liquid water near a surface. In particular, varying the ratio of the surface's attraction and orientational ordering can change the mechanism by which nucleation occurs: ice can nucleate on the structured surface even when the orientational ordering imposed by the surface is weak, as the water molecules that interact strongly with the surface are themselves a good template for further growth. We also show that lattice matching is important for heterogeneous nucleation on the structured surface we study. We rationalise these brute-force simulation results by explicitly calculating the interfacial free energies of ice and liquid water in contact with the nucleating surface and their variation with surface interaction parameters.
Validity conditions for moment closure approximations in stochastic chemical kinetics
Authors: Schnoerr David , Sanguinetti Guido , Grima Ramon
Published: August 2014

Approximations based on moment-closure (MA) are commonly used to obtain estimates of the mean molecule numbers and of the variance of fluctuations in the number of molecules of chemical systems. The advantage of this approach is that it can be far less computationally expensive than exact stochastic simulations of the chemical master equation. Here, we numerically study the conditions under which the MA equations yield results reflecting the true stochastic dynamics of the system. We show that for bistable and oscillatory chemical systems with deterministic initial conditions, the solution of the MA equations can be interpreted as a valid approximation to the true moments of the chemical master equation, only when the steady-state mean molecule numbers obtained from the chemical master equation fall within a certain finite range. The same validity criterion for monostable systems implies that the steady-state mean molecule numbers obtained from the chemical master equation must be above a certain threshold. For mean molecule numbers outside of this range of validity, the MA equations lead to either qualitatively wrong oscillatory dynamics or to unphysical predictions such as negative variances in the molecule numbers or multiple steady-state moments of the stationary distribution as the initial conditions are varied. Our results clarify the range of validity of the MA approach and show that pitfalls in the interpretation of the results can only be overcome through the systematic comparison of the solutions of the MA equations of a certain order with those of higher orders.
Diagnostics principle of microwave cut-off probe for measuring absolute electron density
Authors: Jun Hyun-Su
Published: August 2014

A generalized diagnostics principle of microwave cut-off probe is presented with a full analytical solution. In previous studies on the microwave cut-off measurement of weakly ionized plasmas, the cut-off frequency ωc of a given electron density is assumed to be equal to the plasma frequency ωp and is predicted using electromagnetic simulation or electric circuit model analysis. However, for specific plasma conditions such as highly collisional plasma and a very narrow probe tip gap, it has been found that ωc and ωp are not equal. To resolve this problem, a generalized diagnostics principle is proposed by analytically solving the microwave cut-off condition Re[εr,eff(ω = ωc)] = 0. In addition, characteristics of the microwave cut-off condition are theoretically tested for correct measurement of the absolute electron density.
Developing a narrow-line laser spectrometer based on a tunable continuous-wave dye laser
Authors: Wang Chun , Lv Shasha , Liu Fang , Bi Jin , Li Liufeng , Chen Lisheng
Published: August 2014

We present the development of a dye-laser-based spectrometer operating at 550–600 nm. The spectrometer will be used to detect an ultra-narrow clock transition (1S0-3P0) in an Ytterbium optical lattice clock and perform high-resolution spectroscopy of iodine molecules trapped in the sub-nanometer channels of zeolite crystal (AlPO4-11). Two-stage Pound-Drever-Hall frequency stabilization is implemented on the tunable continuous-wave dye laser to obtain a reliable operation and provide stable laser radiations with two different spectral linewidths. In the first-stage frequency locking, a compact home-built intracavity electro-optic modulator is adopted for suppressing fast frequency noise. With an acquisition time of 0.1 s the 670-kHz linewidth of the free-running dye laser is reduced to 2 kHz when locked to a pre-stabilization optical cavity with a finesse of 1170. When the pre-stabilized laser is locked to a high-finesse optical cavity, a linewidth of 1.4 Hz (2 s) is observed and the frequency stability is 3.7 × 10−15 (3 s). We also measure and analyze the individual noise contributions such as those from residual amplitude modulation and electronic noise. The ongoing upgrades include improving long-term frequency stability at time scales from 10 to 100 s and implementing continuous frequency scan across 10 GHz with radio-frequency precision.
Local Wegner and Lifshitz tails estimates for the density of states for continuous random Schrödinger operators
Authors: Combes Jean-Michel , Germinet François , Klein Abel
Published: August 2014

We introduce and prove local Wegner estimates for continuous generalized Anderson Hamiltonians, where the single-site random variables are independent but not necessarily identically distributed. In particular, we get Wegner estimates with a constant that goes to zero as we approach the bottom of the spectrum. As an application, we show that the (differentiated) density of states exhibits the same Lifshitz tails upper bound as the integrated density of states.
Strong pinning in very fast grown reactive co-evaporated GdBa2Cu3O7 coated conductors
Authors: MacManus-Driscoll J. L. , Bianchetti M. , Kursumovic A. , Kim G. , Jo W. , Wang H. , Lee J. H. , Hong G. W. , Moon S. H.
Published: August 2014

We report on compositional tuning to create excellent field-performance of Jc in “self-doped,” GdBa2Cu3O7−y (GdBCO) coated conductors grown by ultrafast reactive co-evaporation. In order to give excess liquid and Gd2O3, the overall compositions were all Ba-poor and Cu-rich compared to GdBCO. The precise composition was found to be critical to the current carrying performance. The most copper-rich composition had an optimum self-field Jc of 3.2 MA cm−2. A more Gd-rich composition had the best in-field performance because of the formation of low coherence, splayed Gd2O3 nanoparticles, giving Jc (77 K, 1 T) of over 1 MA cm−2 and Jc (77 K, 5 T) of over 0.1 MA cm−2.
Concentration effects on the rates of irreversible diffusion-influenced reactions
Authors: Kim Minjung , Lee Sangyoub , Kim Ji-Hyun
Published: August 2014

We formulate a new theory of the effects of like-particle interactions on the irreversible diffusion-influenced bimolecular reactions of the type A + B → P + B by considering the evolution equation of the triplet ABB number density field explicitly. The solution to the evolution equation is aided by a recently proposed method for solving the Fredholm integral equation of the second kind. We evaluate the theory by comparing its predictions with the results of extensive computer simulations. The present theory provides a reasonable explanation of the simulation results.
Systematic investigation on topological properties of layered GaS and GaSe under strain
Authors: An Wei , Wu Feng , Jiang Hong , Tian Guang-Shan , Li Xin-Zheng
Published: August 2014

The topological properties of layered β-GaS and ε-GaSe under strain are systematically investigated by ab initio calculations with the electronic exchange-correlation interactions treated beyond the generalized gradient approximation (GGA). Based on the GW method and the Tran-Blaha modified Becke-Johnson potential approach, we find that while ε-GaSe can be strain-engineered to become a topological insulator, β-GaS remains a trivial one even under strong strain, which is different from the prediction based on GGA. The reliability of the fixed volume assumption rooted in nearly all the previous calculations is discussed. By comparing to strain calculations with optimized inter-layer distance, we find that the fixed volume assumption is qualitatively valid for β-GaS and ε-GaSe, but there are quantitative differences between the results from the fixed volume treatment and those from more realistic treatments. This work indicates that it is risky to use theoretical approaches like GGA that suffer from the band gap problem to address physical properties, including, in particular, the topological nature of band structures, for which the band gap plays a crucial role. In the latter case, careful calibration against more reliable methods like the GW approach is strongly recommended.
Relativistic coupled cluster study of diatomic compounds of Hg, Cn, and Fl
Authors: Borschevsky A. , Pershina V. , Eliav E. , Kaldor U.
Published: August 2014

The structure and energetics of eight diatomic heavy-atom molecules are presented. These include the species MAu, M2, and MHg, with M standing for the Hg, Cn (element 112), and Fl (element 114) atoms. The infinite-order relativistic 2-component Hamiltonian, known to closely reproduce 4-component results at lower computational cost, is used as framework. High-accuracy treatment of correlation is achieved by using the coupled cluster scheme with single, double, and perturbative triple excitations in large converged basis sets. The calculated interatomic separation and bond energy of Hg2, the only compound with known experimental data, are in good agreement with measurements. The binding of Fl to Au is stronger than that of Cn, predicting stronger adsorption on gold surfaces. The bond in the M2 species is strongest for Fl2, being of chemical nature; weaker bonds appear in Cn2 and Hg2, which are bound by van der Waals interactions, with the former bound more strongly due to the smaller van der Waals radius. The same set of calculations was also performed using the relativistic density functional theory approach, in order to test the performance of the latter for these weakly bound systems with respect to the more accurate coupled cluster calculations. It was found that for the MAu species the B3LYP functional provides better agreement with the coupled cluster results than the B88/P86 functional. However, for the M2 and the MHg molecules, B3LYP tends to underestimate the binding energies.
Performance and characteristics of a high pressure, high temperature capillary cell with facile construction for operando x-ray absorption spectroscopy
Authors: Bansode Atul , Guilera Gemma , Cuartero Vera , Simonelli Laura , Avila Marta , Urakawa Atsushi
Published: August 2014

We demonstrate the use of commercially available fused silica capillary and fittings to construct a cell for operando X-ray absorption spectroscopy (XAS) for the study of heterogeneously catalyzed reactions under high pressure (up to 200 bars) and high temperature (up to 280 °C) conditions. As the first demonstration, the cell was used for CO2 hydrogenation reaction to examine the state of copper in a conventional Cu/ZnO/Al2O3 methanol synthesis catalyst. The active copper component of the catalyst was shown to remain in the metallic state under supercritical reaction conditions, at 200 bars and up to 260 °C. With the coiled heating system around the capillary, one can easily change the length of the capillary and control the amount of catalyst under investigation. With precise control of reactant(s) flow, the cell can mimic and serve as a conventional fixed-bed micro-reactor system to obtain reliable catalytic data. This high comparability of the reaction performance of the cell and laboratory reactors is crucial to gain insights into the nature of actual active sites under technologically relevant reaction conditions. The large length of the capillary can cause its bending upon heating when it is only fixed at both ends because of the thermal expansion. The degree of the bending can vary depending on the heating mode, and solutions to this problem are also presented. Furthermore, the cell is suitable for Raman studies, nowadays available at several beamlines for combined measurements. A concise study of CO2 phase behavior by Raman spectroscopy is presented to demonstrate a potential of the cell for combined XAS-Raman studies.
Exact scattering matrix of graphs in magnetic field and quantum noise
Authors: Caudrelier Vincent , Mintchev Mihail , Ragoucy Eric
Published: August 2014

We consider arbitrary quantum wire networks modelled by finite, noncompact, connected quantum graphs in the presence of an external magnetic field. We find a general formula for the total scattering matrix of the network in terms of its local scattering properties and its metric structure. This is applied to a quantum ring with N external edges. Connecting the external edges of the ring to heat reservoirs, we study the quantum transport on the graph in ambient magnetic field. We consider two types of dynamics on the ring: the free Schrödinger and the free massless Dirac equations. For each case, a detailed study of the thermal noise is performed analytically. Interestingly enough, in presence of a magnetic field, the standard linear Johnson-Nyquist law for the low temperature behaviour of the thermal noise becomes nonlinear. The precise regime of validity of this effect is discussed and a typical signature of the underlying dynamics is observed.
Stochastic Euler-Poincaré reduction
Authors: Arnaudon Marc , Chen Xin , Cruzeiro Ana Bela
Published: August 2014

We prove a Euler-Poincaré reduction theorem for stochastic processes taking values on a Lie group, which is a generalization of the reduction argument for the deterministic case [J. E. Marsden and T. S. Ratiu, Introduction to Mechanics and Symmetry: A Basic Exposition of Classical Mechanical Systems, Texts in Applied Mathematics (Springer, 2003)]. We also show examples of its application to SO(3) and to the group of diffeomorphisms, which includes the Navier-Stokes equation on a bounded domain and the Camassa-Holm equation.
Note: Loading method of molecular fluorine using x-ray induced chemistry
Authors: Pravica Michael , Sneed Daniel , White Melanie , Wang Yonggang
Published: August 2014

We have successfully loaded molecular fluorine into a diamond anvil cell at high pressure using the synchrotron x-ray induced decomposition of perfluorohexane (C6F14). “White” x-ray radiation from the Advanced Photon Source was used to initiate the chemical decomposition of C6F14, which resulted in the in situ production of F2 as verified via Raman spectroscopy. Due to the toxic nature of fluorine, this method will offer significant advantages in the ability to easily load a relatively nontoxic and inert substance into a chamber (such as a diamond anvil cell) that, when sealed with other reactants and irradiate with hard x-rays (>7 keV), releases highly reactive and toxic fluorine into the sample/reaction chamber to enable novel chemical synthesis under isolated and/or extreme conditions.
Time-gated single-photon detection module with 110 ps transition time and up to 80 MHz repetition rate
Authors: Buttafava Mauro , Boso Gianluca , Ruggeri Alessandro , Dalla Mora Alberto , Tosi Alberto
Published: August 2014

We present the design and characterization of a complete single-photon counting module capable of time-gating a silicon single-photon avalanche diode with ON and OFF transition times down to 110 ps, at repetition rates up to 80 MHz. Thanks to this sharp temporal filtering of incoming photons, it is possible to reject undesired strong light pulses preceding (or following) the signal of interest, allowing to increase the dynamic range of optical acquisitions up to 7 decades. A complete experimental characterization of the module highlights its very flat temporal response, with a time resolution of the order of 30 ps. The instrument is fully user-configurable via a PC interface and can be easily integrated in any optical setup, thanks to its small and compact form factor.
In situ measurement of low-Z material coating thickness on high Z substrate for tokamaks
Authors: Mueller D. , Roquemore A. L. , Jaworski M. , Skinner C. H. , Miller J. , Creely A. , Raman P. , Ruzic D.
Published: August 2014

Rutherford backscattering of energetic particles can be used to determine the thickness of a coating of a low-Z material over a heavier substrate. Simulations indicate that 5 MeV alpha particles from an 241Am source can be used to measure the thickness of a Li coating on Mo tiles between 0.5 and 15 μm thick. Using a 0.1 mCi source, a thickness measurement can be accomplished in 2 h of counting. This technique could be used to measure any thin, low-Z material coating (up to 1 mg/cm2 thick) on a high-Z substrate, such as Be on W, B on Mo, or Li on Mo. By inserting a source and detector on a moveable probe, this technique could be used to provide an in situ measurement of the thickness of Li coating on NSTX-U Mo tiles. A test stand with an alpha source and an annular solid-state detector was used to investigate the measurable range of low-Z material thicknesses on Mo tiles.
Research on a novel two-stage direct current hybrid circuit breaker
Authors: Wu Yifei , Wu Yi , Rong Mingzhe , Yang Fei , Niu Chunping , Li Mei , Hu Yang
Published: August 2014

The DC hybrid circuit breaker based on high-speed switch (HSS) and parallel connected capacitor has been widely applied in the fault current breaking of DC system. However, when the current is commutated from HSS to the capacitor according to single-stage operation, the capacitor has to absorb a large amount of energy stored in the system inductance within very short time. Meanwhile, a high over-voltage rate of rise is especially prone to be produced between the contacts of HSS, which will lead to a failed breaking. As a result, a novel DC hybrid circuit breaker based on the two-stage operation is proposed and analyzed in this paper. By controlling the thyristors in the commutation branches, the fault current is fast commutated into the capacitor, which can not only realize the arcless open of HSS, but also decrease the over-voltage rate of rise significantly in comparison to the traditional single-stage operation. The simulation model of fault current breaking under different conditions in 10 kV medium voltage DC system is constructed. The simulated over-voltages of single-stage and two-stage operations in the case of fault current breaking are compared and analyzed. Finally, the fault current breaking test in the two-stage operation is investigated experimentally, which validates the feasibility and effectiveness of the simulation model well.
Analysis of ballistic transport in nanoscale devices by using an accelerated finite element contact block reduction approach
Authors: Li H. , Li G.
Published: August 2014

An accelerated Finite Element Contact Block Reduction (FECBR) approach is presented for computational analysis of ballistic transport in nanoscale electronic devices with arbitrary geometry and unstructured mesh. Finite element formulation is developed for the theoretical CBR/Poisson model. The FECBR approach is accelerated through eigen-pair reduction, lead mode space projection, and component mode synthesis techniques. The accelerated FECBR is applied to perform quantum mechanical ballistic transport analysis of a DG-MOSFET with taper-shaped extensions and a DG-MOSFET with Si/SiO2 interface roughness. The computed electrical transport properties of the devices obtained from the accelerated FECBR approach and associated computational cost as a function of system degrees of freedom are compared with those obtained from the original CBR and direct inversion methods. The performance of the accelerated FECBR in both its accuracy and efficiency is demonstrated.
Electron mobility calculation for graphene on substrates
Authors: Hirai Hideki , Tsuchiya Hideaki , Kamakura Yoshinari , Mori Nobuya , Ogawa Matsuto
Published: August 2014

By a semiclassical Monte Carlo method, the electron mobility in graphene is calculated for three different substrates: SiO2, HfO2, and hexagonal boron nitride (h-BN). The calculations account for polar and non-polar surface optical phonon (OP) scatterings induced by the substrates and charged impurity (CI) scattering, in addition to intrinsic phonon scattering in pristine graphene. It is found that HfO2 is unsuitable as a substrate, because the surface OP scattering of the substrate significantly degrades the electron mobility. The mobility on the SiO2 and h-BN substrates decreases due to CI scattering. However, the mobility on the h-BN substrate exhibits a high electron mobility of 170 000 cm2/(V·s) for electron densities less than 1012 cm−2. Therefore, h-BN should be an appealing substrate for graphene devices, as confirmed experimentally.
Pulsating flow driven alteration in moving contact-line dynamics on surfaces with patterned wettability gradients
Authors: Mondal Pranab Kumar , DasGupta Debabrata , Bandopadhyay Aditya , Chakraborty Suman
Published: August 2014

The contact line dynamics over surfaces patterned with wettability gradients under pulsating flow condition are of essential importance in application areas ranging from the design of smart and effective microfluidic devices to the understanding of blood flow dynamics in narrow conduits. In the present study, we probe the capillary filling dynamics in a pulsatile flow environment, in an effort to explore the underlying flow physics. Presenting the results of frequency assisted contact line motion of two immiscible fluids over surfaces patterned with wettability gradients, we show how the interfacial dynamics are affected by the interplay of both the surface characteristics and flow pulsation. Our results reveal that the competition between two control parameters, the frequency and the amplitude of the imposed flow pulsation, may effectively be tuned to control the capillary filling dynamics significantly. The study, we present here, also suggests that by suitably tuning the control parameters, it is possible to control the capillary residence time over engineered locations which may, in turn, facilitate improved mixing and/or design of chemically active reaction stations.
Engineering strain, densification, order parameter and magnetic properties of FePt thin films by dense electronic excitations
Authors: Gupta Rekha , Sehdev Neeru , Asokan K. , Kanjilal D. , Annapoorni S.
Published: August 2014

FePt films prepared by DC sputtering on Si ⟨100⟩ substrates when annealed at 600 °C for 1 h exhibited a structurally ordered and magnetically hard L10 phase. These FePt films were exposed to dense electronic excitations by using 100 MeV oxygen ions as a function of increasing fluences. Such excitations induce pressure and result in the enhancement of order parameter by increasing strain on the FePt films. Apart from this, the surface morphological images from field emission scanning electron microscopy reveal a densification of the films consequent to irradiation and are correlated with the details obtained from Rutherford back scattering analysis. The variation in the values of coercivity correlates well with the change in volume percentage of face centered tetragonal and face centered cubic phase. A coercivity of 14.7 kOe with order parameter 0.92 is achieved at a fluence of 5 × 1012 ions/cm2. The theoretical simulation of the demagnetization curve shows a strong correlation of coercivity and order parameter between the experimentally obtained values with that of simulation. The effect of irradiation induced strain, the structural ordering and coercivity of FePt films as a function of fluences have been discussed.
Metal-silicane: Stability and properties
Authors: Yang Huan-Cheng , Wang Jing , Liu Ying
Published: August 2014

The decoration of silicane using 16 different metal adatoms and the adsorption of small molecules are studied using first-principles calculations. Of the 16 metal adatoms, Li, Na, K, Ca, In, and Sc show a larger binding energy with silicane than their corresponding cohesive energy in the bulk, which suggests they can form 2D layers on the surface of silicane. The band analysis indicates that decoration with metal atoms can effectively tailor the electronic properties of silicane. The adsorption for hydrogen and carbon monoxide on Li-silicane system demonstrates that each Li atom can adsorb a maximum of five H2 or four CO molecules with the average adsorption energy of 0.18 and 0.23 eV/atom, respectively. The calculated results suggest that metal-silicane systems can provide more information for applications as hydrogen-storage or environment-protection materials.
A quantitative acoustic emission study on fracture processes in ceramics based on wavelet packet decomposition
Authors: Ning J. G. , Chu L. , Ren H. L.
Published: August 2014

We base a quantitative acoustic emission (AE) study on fracture processes in alumina ceramics on wavelet packet decomposition and AE source location. According to the frequency characteristics, as well as energy and ringdown counts of AE, the fracture process is divided into four stages: crack closure, nucleation, development, and critical failure. Each of the AE signals is decomposed by a 2-level wavelet package decomposition into four different (from-low-to-high) frequency bands (AA2, AD2, DA2, and DD2). The energy eigenvalues P0, P1, P2, and P3 corresponding to these four frequency bands are calculated. By analyzing changes in P0 and P3 in the four stages, we determine the inverse relationship between AE frequency and the crack source size during ceramic fracture. AE signals with regard to crack nucleation can be expressed when P0 is less than 5 and P3 more than 60; whereas AE signals with regard to dangerous crack propagation can be expressed when more than 92% of P0 is greater than 4, and more than 95% of P3 is less than 45. Geiger location algorithm is used to locate AE sources and cracks in the sample. The results of this location algorithm are consistent with the positions of fractures in the sample when observed under a scanning electronic microscope; thus the locations of fractures located with Geiger's method can reflect the fracture process. The stage division by location results is in a good agreement with the division based on AE frequency characteristics. We find that both wavelet package decomposition and Geiger's AE source locations are suitable for the identification of the evolutionary process of cracks in alumina ceramics.
A gold hybrid structure as optical coupler for quantum well infrared photodetector
Authors: Ding Jiayi , Chen Xiaoshuang , Li Qian , Jing Youliang , Li Zhifeng , Li Ning , Lu Wei
Published: August 2014

A hybrid structure consisting of a square lattice of gold disk arrays and an overlaying gold film is proposed as an optical coupler for a backside-illuminated quantum well infrared photodetector (QWIP). Finite difference time-domain method is used to numerically simulate the reflection spectra and the field distributions of the hybrid structure combined with the QWIP device. The results show that the electric field component perpendicular to the quantum well is strongly enhanced when the plasmonic resonant wavelength of the hybrid structure coincides with the response one of the quantum well infrared photodetector regardless of the polarization of the incident light. The effect of the diameter and thickness of an individual gold disk on the resonant wavelength is also investigated, which indicates that the localized surface plasmon also plays a role in the light coupling with the hybrid structure. The coupling efficiency can exceed 50 if the structural parameters of the gold disk arrays are well optimized.
Electrically tunable organic vertical-cavity surface-emitting laser
Authors: Chang Wendi , Wang Annie , Murarka Apoorva , Akselrod Gleb M. , Packard Corinne , Lang Jeffrey H. , Bulović Vladimir
Published: August 2014

An electrically tunable organic vertical-cavity surface-emitting laser (VCSEL) is demonstrated and characterized. A lasing wavelength tunability of Δλ = 10 nm with 6 V actuation is shown for a red laser emission tuned between λ = 637 nm and λ = 628 nm. Wavelength tuning of the VCSEL structure is enabled by electrostatic deflection of a reflective flexible membrane that is suspended over an air gap and a dielectric mirror, forming a 3λ lasing cavity. The lasing gain medium consists of an evaporated organic thin film coated on a reflective membrane, which is then additively placed over a patterned substrate containing the dielectric mirror to fabricate an array of air-gap-VCSEL structures, each 100 μm in diameter. Beyond the electrostatic actuation of these tunable lasers, the VCSEL array geometry also has the potential to be used as pressure sensors with an all-optical remote excitation and readout and a pressure sensitivity of 64 Pa/nm in the demonstrated configuration.
Magnetophoretic-based microfluidic device for DNA isolation
Authors: Hale C. , Darabi J.
Published: August 2014

This paper presents a continuous flow microfluidic device for the separation of DNA from blood using magnetophoresis for biological applications and analysis. This microfluidic bio-separation device has several benefits, including decreased sample handling, smaller sample and reagent volumes, faster isolation time, and decreased cost to perform DNA isolation. One of the key features of this device is the use of short-range magnetic field gradients, generated by a micro-patterned nickel array on the bottom surface of the separation channel. In addition, the device utilizes an array of oppositely oriented, external permanent magnets to produce strong long-range field gradients at the interfaces between magnets, further increasing the effectiveness of the device. A comprehensive simulation is performed using COMSOL Multiphysics to study the effect of various parameters on the magnetic flux within the separation channel. Additionally, a microfluidic device is designed, fabricated, and tested to isolate DNA from blood. The results show that the device has the capability of separating DNA from a blood sample with a purity of 1.8 or higher, a yield of up to 33 μg of polymerase chain reaction ready DNA per milliliter of blood, and a volumetric throughput of up to 50 ml/h.