bluuebunny/crossref_metadata_2025 huggingface dataset:
A new tuning fork-based instrument for oscillatory shear rheology of nano-confined liquids
Authors: Kapoor Karan , Kanawade Vinod , Shukla Vibham , Patil Shivprasad
Published: February 2013

We present a new method to measure rheological response of liquids confined to nano-scale which exhibit a considerable slow-down in dynamics compared to bulk liquids. The method relies on using a tuning fork force sensor that has stiffness of 5.5 × 104 N/m to avoid thermal noise. Off-resonance operation ensures application of a range of shear frequencies. This range is higher than the inverse of the system's mechanical relaxation time and allows the measurement of nonlinear effects emerging due to significant “slow down” in dynamics upon confinement. We develop necessary mathematical modelling to quantify our measurements. The instrument is a step forward towards resolving the controversies about the nature of nano-confined liquids.
Photodissociation dynamics of the methyl perthiyl radical at 248 nm via photofragment translational spectroscopy
Authors: Cole-Filipiak Neil C. , Negru Bogdan , Just Gabriel M. P. , Park Dayoung , Neumark Daniel M.
Published: February 2013

Photofragment translational spectroscopy was used to study the photodissociation of the methyl perthiyl radical CH3SS at 248 nm. The radical was produced by flash pyrolysis of dimethyl disulfide (CH3SSCH3). Two channels were observed: CH3 + S2 and CH2S + SH. Photofragment translational energy distributions indicate that CH3 + S2 results from C–S bond fission on the ground state surface. The CH2S + SH channel can proceed through isomerization to CH2SSH on the ground state surface but also may involve production of electronically excited CH2S.
The effect of InGaN underlayers on the electronic and optical properties of InGaN/GaN quantum wells
Authors: Li T. , Wei Q. Y. , Fischer A. M. , Huang J. Y. , Huang Y. U. , Ponce F. A. , Liu J. P. , Lochner Z. , Ryou J.-H. , Dupuis R. D.
Published: February 2013

The electronic and optical properties of visible InGaN quantum-well (QW) structures grown on In0.03Ga0.97N underlayers have been investigated. A significant improvement of the QW emission is observed as a result of the insertion of the underlayers, which is associated with blueshift in the emission energy, reduced recombination lifetime, increased spatial homogeneity in the QW luminescence, and weaker internal fields inside the QWs. These are explained by partial strain relaxation evidenced by reciprocal space mapping of the X-ray diffraction intensity. Electrostatic potential profiles obtained by electron holography provide evidence for enhanced carrier injection by tunneling from the underlayer into the first QW.
Single exposure three-dimensional imaging of dusty plasma clusters
Authors: Hartmann Peter , Donkó István , Donkó Zoltán
Published: February 2013

We have worked out the details of a single camera, single exposure method to perform three-dimensional imaging of a finite particle cluster. The procedure is based on the plenoptic imaging principle and utilizes a commercial Lytro light field still camera. We demonstrate the capabilities of our technique on a single layer particle cluster in a dusty plasma, where the camera is aligned and inclined at a small angle to the particle layer. The reconstruction of the third coordinate (depth) is found to be accurate and even shadowing particles can be identified.
Ion temperature gradient instability at sub-Larmor radius scales with non-zero ballooning angle
Authors: Migliano P. , Camenen Y. , Casson F. J. , Hornsby W. A. , Peeters A. G.
Published: February 2013

Linear gyro-kinetic stability calculations predict unstable toroidal ion temperature gradient modes (ITGs) with normalised poloidal wave vectors well above one (kθρi>1) for standard tokamak parameters with adiabatic electron response. These modes have a maximum amplitude at a poloidal angle θ that is shifted away from the low field side (θ≠0). The physical mechanism is clarified through the use of a fluid model. It is shown that the shift of the mode away from the low field side reduces the effective drift frequency which allows for the instability to develop. Numerical tests using the gyro-kinetic model confirm this physical mechanism. Furthermore, it is shown that modes localized away from the low field side can be important also for kθρi<1 close to the threshold of the ITG. In fact, modes with maximum amplitude at θ≠0 can exist for normalised temperature gradient lengths below the threshold of the ITG obtained for the case with the maximum at θ=0.
Space- and time-resolved Seebeck and Nernst voltages in laser-heated permalloy/gold microstructures
Authors: von Bieren Arndt , Brandl Florian , Grundler Dirk , Ansermet Jean-Philippe
Published: February 2013

Thermoelectric effects in microstructured permalloy (Py)/Au wires are investigated using space- and time-resolved measurements based on scanning focused laser heating. Supported by numerical simulations of the temperature distribution, we identify two major contributions to the laser-induced signals: (i) the Seebeck effect due to thermocouples of Py/Au and (ii) the anomalous Nernst effect (ANE) in Py with a coefficient of NANE≈1.6 μV/K. ANE-based magnetic imaging of magnetic domains and magnetization reversal is demonstrated with a lateral resolution on the μm scale.
Schottky barrier height extraction from forward current-voltage characteristics of non-ideal diodes with high series resistance
Authors: Ahmed Khaled , Chiang Tony
Published: February 2013

Forward bias current-voltage (I-V) characteristics measured at room temperature were used to extract Schottky barrier heights in sulfur-implanted PtSi/n-Si and NiGe/n-Ge contacts. It is found that I-V data claimed to support barrier height reductions of ∼700 meV and ∼500 meV are more consistent with ∼300 meV and 100 meV reductions, respectively. These estimates should better guide attempts aiming at finding physical models for the observed reductions.
Effects of ruthenium seed layer on the microstructure and spin dynamics of thin permalloy films
Authors: Jin Lichuan , Zhang Huaiwu , Tang Xiaoli , Bai Feiming , Zhong Zhiyong
Published: February 2013

The spin dynamics and microstructure properties of a sputtered 12 nm Ni81Fe19 thin film have been enhanced by the use of a ruthenium seed layer. Both the ferromagnetic resonance field and linewidth are enhanced dramatically as the thickness of ruthenium seed layer is increased. The surface anisotropy energy constant can also be largely tailored from 0.06 to 0.96 erg/cm−2 by changing the seed layer thickness. The changes to the dynamics magnetization properties are caused by both ruthenium seed layer induced changes in the Ni81Fe19 structure properties and surface topography properties. Roughness induced inhomogeneous linewidth broadening is also seen. The damping constant is highly tunable via the ruthenium thickness. This approach can be used to tailor both the structure and spin dynamic properties of thin Ni81Fe19 films over a wide range. And it may benefit the applications of spin dynamics and spin current based devices.
Hysteretic control of organic conductance due to remanent magnetic fringe fields
Authors: Macià F. , Wang F. , Harmon N. J. , Wohlgenannt M. , Kent A. D. , Flatté M. E.
Published: February 2013

Manipulation of the remanent (zero external magnetic field) magnetization state of a single ferromagnetic film is shown to control the room-temperature conductance of an organic semiconductor thin film deposited on top. For the organic semiconductor Alq3, the magnetic fringe fields from a multidomain remanent magnetization state of the film enhance the device conductance by several percent relative to its value for the magnetically saturated ferromagnetic film. The effect of fringe fields is insensitive to ferromagnetic film's thickness (which varies the fringe field magnitude proportionately) but sensitive to the magnetic domain's correlation length.
The role of the products of the decay of optical phonons
Authors: Dyson A. , Ridley B. K.
Published: February 2013

The decay of nonequilibrium longitudinal optical phonons is investigated by abandoning the usual assumption that the decay products remain in thermodynamic equilibrium. The case when only the grand-daughter modes remain in thermodynamic equilibrium is studied. The effective lifetime of the LO mode, which is the one that would be measured by experiment, is found to decrease with increasing occupancy of the LO mode.
Controlled route to the fabrication of carbon and boron nitride nanoscrolls: A molecular dynamics investigation
Authors: Perim Eric , Paupitz Ricardo , Galvão Douglas S.
Published: February 2013

Carbon nanoscrolls (graphene layers rolled up into papyrus-like tubular structures) are nanostructures with unique and interesting characteristics that could be exploited to build several new nanodevices. However, an efficient and controlled synthesis of these structures was not achieved yet, making its large scale production a challenge to materials scientists. Also, the formation process and detailed mechanisms that occur during its synthesis are not completely known. In this work, using fully atomistic molecular dynamics simulations, we discuss a possible route to nanoscrolls made from graphene layers deposited over silicon oxide substrates containing chambers/pits. The scrolling mechanism is triggered by carbon nanotubes deposited on the layers. The process is completely general and can be used to produce scrolls from other lamellar materials, like boron nitride, for instance.
Enhancement of thermoelectric performance in strontium titanate by praseodymium substitution
Authors: Kovalevsky A. V. , Yaremchenko A. A. , Populoh S. , Weidenkaff A. , Frade J. R.
Published: February 2013

In order to identify the effects of Pr additions on thermoelectric properties of strontium titanate, crystal structure, electrical and thermal conductivity, and Seebeck coefficient of Sr1−xPrxTiO3 (x = 0.02–0.30) materials were studied at 400 < T < 1180 K under highly reducing atmosphere. The mechanism of electronic transport was found to be similar up to 10% of praseodymium content, where generation of the charge carriers upon substitution resulted in significant increase of the electrical conductivity, moderate decrease in Seebeck coefficient, and general improvement of the power factor. Formation of point defects in the course of substitution led to suppression of the lattice thermal conductivity, whilst the contribution from electronic component was increasing with carrier concentration. Possible formation of layered structures and growing distortion of the perovskite lattice resulted in relatively low thermoelectric performance for Sr0.80Pr0.20TiO3 and Sr0.70Pr0.30TiO3. The maximum dimensionless figure of merit was observed for Sr0.90Pr0.10TiO3 and amounted to ∼0.23 at 670 K and ∼0.34 at 1170 K, close to the values, obtained in similar conditions for the best bulk thermoelectrics, based on rare-earth substituted SrTiO3.
Two-photon induced excited-state absorption and optical limiting properties in a chiral polymer
Authors: Zeng Yi , Wang Changshun , Zhao Fuli , Qin Mu , Zhou Yan , Huang Xiaobo
Published: February 2013

The nonlinear absorption and optical limiting properties of a chiral polymer were investigated by employing Z-scan technique in femtosecond regime. Reverse saturable absorption was observed in the polymer at 800 nm and the nonlinear absorption coefficient of 5.97 cm/GW was obtained at the irradiance of 2.75 GW/cm2. The nonlinear absorption coefficient versus the input irradiance was measured to meet a linear increasing function, giving evidence of two-photon induced excited-state absorption existing. Particularly, the chiral polymer was shown to possess a large ratio (∼251) of excited-state to ground-state absorption cross-section and a remarkable optical limiting behavior was achieved in it.
Surface doping of nitrogen atoms on graphene via molecular precursor
Authors: Hong Guo , Wu Qi-Hui , Wang Chundong , Ren Jianguo , Xu Tingting , Zhang Wenjun , Lee Shuit-Tong
Published: February 2013

Surface doping can be a powerful way to modify the electronic properties of graphene with the unique potential to retain the excellent pristine properties of graphene. Here, we report an atomic surface doping method for graphene via dissociation of adsorbed precursor molecules of tetrafluorotetracyanoquinodimethane (F4-TCNQ) induced by hydrogen plasma treatment. Significantly, the location of the dopant N atoms can be pre-determined by the location and orientation of the F4-TCNQ molecule precursor on graphene, leading in principle to site-selective doping. Furthermore, the molecular precursor is stable under ambient conditions, satisfying an important consideration for patterning processes.
Role of the anode material in the unipolar switching of TiN\NiO\Ni cells
Authors: Goux L. , Degraeve R. , Meersschaut J. , Govoreanu B. , Wouters D. J. , Kubicek S. , Jurczak M.
Published: February 2013

In this paper, we investigate the unipolar resistive-switching mechanism in TiN\NiO\Ni cells, whereby the NiO layer is deposited by metal-organic chemical vapor deposition. Irrespective of the cell size down to 80 nm, controlled unipolar switching is observed only on condition the Ni electrode is used as anode. Local elemental analyzes revealed enhanced oxygen concentration at the NiO\Ni interface after reset operation. Based on this result as well as on the quantum-mechanical modeling of the conduction for different resistance states, the reset switching is analyzed in terms of electrochemically assisted oxidation process of the conductive filament close to the Ni anode. Electrical switching results on various stack configurations confirm the major impact of the electrode materials on the reset performances, bringing important insights into the mechanisms involved in the unipolar switching of this system. Literature data are discussed on the basis of this learning, suggesting possible extension of these considerations to other oxide-based switching systems.
Lattice and grain-boundary diffusions of boron atoms in BaSi2 epitaxial films on Si(111)
Authors: Nakamura K. , Baba M. , Ajmal Khan M. , Du W. , Sasase M. , Hara K. O. , Usami N. , Toko K. , Suemasu T.
Published: February 2013

A 180-nm-thick boron (B) layer was deposited on a 300-nm-thick a-axis-oriented BaSi2 epitaxial film grown by molecular beam epitaxy on Si(111) and was annealed at different temperatures in ultrahigh vacuum. The depth profiles of B were investigated using secondary ion mass spectrometry (SIMS) with O2+, and the diffusion coefficients of B were evaluated. The B profiles were reproduced well by taking both the lattice and the grain boundary (GB) diffusions into consideration. The cross-sectional transmission electron microscopy (TEM) image revealed that the GBs of the BaSi2 film were very sharp and normal to the sample surface. The plan-view TEM image exhibited that the grain size of the BaSi2 film was approximately 0.6 μm. The temperature dependence of lattice and GB diffusion coefficients was derived from the SIMS profiles, and their activation energies were found to be 4.6 eV and 4.4 eV, respectively.
Atomic scale study of thermal reduction of nano goethite coexisting with magnetite
Authors: singh L. Herojit , Govindaraj R. , Mythili R. , Amarendra G. , Sundar C. S.
Published: February 2013

Evolution of the local structure and magnetic properties of nano particles of goethite having magnetite as a composite due to controlled annealing treatments in vacuum has been studied using Mossbauer spectroscopy. Importance of size, defect associated with structural OH- for the observed structural and magnetic properties of goethite has been emphasized in this study. Present Mossbauer results show that thermal annealing at low temperatures (420-550 K) lead to a partial conversion / reduction of orthorhombic goethite to cubic spinel oxides such as maghemite and off-stochiometric magnetite. This study further establishes that annealing treatments beyond 650 K predominantly results in topotactic conversion of goethite to haematite. Underlying physics of the transitions of goethite to iron oxides and the important role of desorbed hydrogen for the orthorhombic to cubic structural transitions has been elucidated in this study.
A method to determine the Young's modulus of thin-film elements assisted by dark-field electron holography
Authors: Reboh S. , Benzo P. , Morin P. , Cours R. , Hÿtch M. J. , Claverie A.
Published: February 2013

We present a method to determine the isotropic elastic modulus of nanometer-thick films of unknown or imprecise microstructure and composition. First, the mesoscopic stress of the film is determined using Stoney's method. Then, after fabricating film-stripes by lithography, dark-field electron holography is used to image the strain fields (3 nm spatial resolution, ∼2 × 10−4 precision) resulting from the local interactions between the stripes and an underlying silicon crystal. By comparing the experimental results with finite element method modeling, we deduce Young's modulus of the film. Silicon nitride films on Si substrates are presented as a model system.
ZnO UV photodetector with controllable quality factor and photosensitivity
Authors: Campos L. C. , Guimarães M. H. D. , Goncalves A. M. B. , de Oliveira S. , Lacerda R. G.
Published: February 2013

ZnO nanowires have an enormous potential for applications as ultra-violet (UV) photodetectors. Their mechanism of photocurrent generation is intimately related with the presence of surface states where considerable efforts, such as surface chemical modifications, have been pursued to improve their photodetection capabilities. In this work, we report a step further in this direction demonstrating that the relative photosensitivity and quality factor (Q factor) of the photodetector are entirely tunable by an applied gate voltage. This mechanism enables UV photodetection selectivity ranging from wavelengths from tens of nanometers (full width at half maximum - FWHM) down to a narrow detection of 3 nm. Such control paves the way for novel applications, especially related to the detection of elements that have very sharp luminescence.
Strain engineering in epitaxial La1−xSr1+xMnO4 thin films
Authors: Vafaee Mehran , Baghaie Yazdi Mehrdad , Radetinac Aldin , Cherkashinin Gennady , Komissinskiy Philipp , Alff Lambert
Published: February 2013

We have synthesized epitaxial thin films of La1−xSr1+xMnO4 with x = 0.0 and x = 0.5 by pulsed laser deposition on NdGaO3 and LaSrAlO4 substrates with different lattice mismatch. X-ray analysis shows that these layered doped manganites can be grown fully strained allowing to tune the lattice degrees of freedom which otherwise are a function of chemical composition x. Since the crystal structure is strongly coupled to the magnetic, orbital, and charge degrees of freedom in the doped manganites, the demonstrated strain engineering is the base for an extrinsic control of, e.g., charge-orbital order.
Curie temperature rising by fluorination for Sm2Fe17
Authors: Komuro Matahiro , Satsu Yuichi , Nishi Kazuya , Kanda Takayuki
Published: February 2013

Fluorine atoms can be introduced to Sm2Fe17 using XeF2 below 423 K. The resulting fluorinated Sm2Fe17 powders have ferromagnetic phases containing Sm2Fe17FY1(0<Y1<1), Sm2Fe17FY2 (1<Y2<4), Sm2Fe17, and α-Fe. The unit cell for Sm2Fe17 is elongated by the fluorination. The largest unit cell volume among the rhombohedral Sm2Fe17 compounds is 83.8 nm3, which is 5.8% larger than Sm2Fe17. The rhombohedral Sm2Fe17 with the largest unit cell volume is dissociated above 873 K, and fluorination increases Curie temperature from 403 K for Sm2Fe17 to 675 K. This increase can be explained by the magneto-volume effect.
Energy-loss rate of a fast particle in two-dimensional semiconductors with Rashba spin-orbit coupling
Authors: Feng W. , Tawfiq Asya , Cao J. C. , Zhang C.
Published: February 2013

The energy-loss rate (ELR) of a charged particle in a two-dimensional semiconductor with Rashba spin-orbit coupling is studied. Our model takes into account of the temperature and density dependence of the electronic properties of the Rashba system. The energy and temperature dependence of the ELR are presented. It is found that a finite Rashba spin-orbit coupling offers a mechanism of tuning the mean scattering time in narrow-gap semiconductors. With a change of Rashba parameter of around 3 times, the mean scattering time can change by one to two orders of magnitude.
Crystalline anisotropic magnetoresistance in quaternary ferromagnetic semiconductor (Ga,Mn)(As,Sb)
Authors: Howells B. , Wang M. , Edmonds K. W. , Wadley P. , Campion R. P. , Rushforth A. W. , Foxon C. T. , Gallagher B. L.
Published: February 2013

We demonstrate a strong dependence of the anisotropic magnetoresistance (AMR) on the direction of current with respect to the crystalline axes in the quaternary diluted ferromagnetic semiconductor Ga0.94Mn0.06As0.9Sb0.1. Dominant cubic and uniaxial symmetries are observed for current along the [11¯0] and [110] crystalline directions, respectively. In addition, an anomalous temperature dependence of the symmetry and magnitude of the AMR is observed. Phenomenological analysis reveals an important contribution of a crossed cubic crystalline/non-crystalline term, which is much larger than previously observed in (Ga,Mn)As films. Possible reasons for the enhancement of this term are discussed.
Tungsten oxide proton conducting films for low-voltage transparent oxide-based thin-film transistors
Authors: Zhang Hongliang , Wan Qing , Wan Changjin , Wu Guodong , Zhu Liqiang
Published: February 2013

Tungsten oxide (WOx) electrolyte films deposited by reactive magnetron sputtering showed a high room temperature proton conductivity of 1.38 × 10−4 S/cm with a relative humidity of 60%. Low-voltage transparent W-doped indium-zinc-oxide thin-film transistors gated by WOx-based electrolytes were self-assembled on glass substrates by one mask diffraction method. Enhancement mode operation with a large current on/off ratio of 4.7 × 106, a low subthreshold swing of 108 mV/decade, and a high field-effect mobility 42.6 cm2/V s was realized. Our results demonstrated that WOx-based proton conducting films were promising gate dielectric candidates for portable low-voltage oxide-based devices.
Fuzzy Clustering Analysis in Geomarketing Research
Authors: Grekousis George , Hatzichristos Thomas
Published: February 2013

In this study we use geographic information systems (GIS) and computational intelligence for geomarketing analysis. GIS technology offers a powerful set of tools for the input, management, and output of data, whereas computational intelligence is used for the analysis and the clustering of data by the use of unsupervised fuzzy clustering and the Gustafson–Kessel algorithm. The advantage of fuzzy geomarketing segmentation is that a customer is not assigned exclusively to one segment only, but rather with a membership value to each cluster. The proposed methodology is applied to the metropolitan area of Athens, Greece. A dataset describes 130 demographic, lifestyle, and economy variables, and the results are analysed and discussed.
Sedimentary constraints on the duration of the Marinoan Oxygen-17 Depletion (MOSD) event
Authors: Killingsworth Bryan A. , Hayles Justin A. , Zhou Chuanming , Bao Huiming
Published: February 2013

The ∼635 Ma Marinoan glaciation is marked by dramatic Earth system perturbations. Deposition of nonmass-dependently
17
O-depleted sulfate (SO
4
2−
) in worldwide postglacial sediments is, thus far, unique to this glaciation. It is proposed that an extremely high-
p
CO
2
atmosphere can result in highly
17
O-depleted atmospheric O
2
, or the Marinoan Oxygen-17 Depletion (MOSD) event. This anomalous
17
O signal was imparted to sulfate of oxidative weathering origin. However,
17
O-depleted sulfate occurs in limited sedimentary intervals, suggesting that Earth surface conditions conducive to the MOSD had a finite duration. An MOSD duration can, therefore, provide much needed constraint on modeling Earth system responses at that time. Unfortunately, the sulfate
17
O record is often sparse or lacks radiometric dates. Here, we report 11 barite layers from a post-Marinoan dolostone sequence at Wushanhu in the South China Block. The
17
O depletion fluctuates in magnitude in lower layers but is persistently absent up section, providing the most confident first and last sedimentary appearance of the anomaly. δ
13
C chemostratigraphy is used to correlate the Wushanhu section to two proximal sections on the same shallow platform that lack barite layers but have published U-Pb dates that occur in dolostone and shale. Assuming a similar pattern and rate for carbonate and shale deposition among the different sections, we estimate the MOSD duration at 0–0.99 My. This number can be further constrained by new radiometric dates from equivalent sequences worldwide, thus underpinning models on the nonsteady-state Earth system response in the immediate aftermath of the Marinoan meltdown.
Astrocyte-induced cortical vasodilation is mediated by
D
-serine and endothelial nitric oxide synthase
Authors: Stobart Jillian L. LeMaistre , Lu Lingling , Anderson Hope D. I. , Mori Hisashi , Anderson Christopher M.
Published: February 2013

Astrocytes play a critical role in neurovascular coupling by providing a physical linkage from synapses to arterioles and releasing vaso-active gliotransmitters. We identified a gliotransmitter pathway by which astrocytes influence arteriole lumen diameter. Astrocytes synthesize and release NMDA receptor coagonist,
D
-serine, in response to neurotransmitter input. Mouse cortical slice astrocyte activation by metabotropic glutamate receptors or photolysis of caged Ca
2+
produced dilation of penetrating arterioles in a manner attenuated by scavenging
D
-serine with
D
-amino acid oxidase, deleting the enzyme responsible for
D
-serine synthesis (serine racemase) or blocking NMDA receptor glycine coagonist sites with 5,7-dichlorokynurenic acid. We also found that dilatory responses were dramatically reduced by inhibition or elimination of endothelial nitric oxide synthase and that the vasodilatory effect of endothelial nitric oxide synthase is likely mediated by suppressing levels of the vasoconstrictor arachidonic acid metabolite, 20-hydroxy arachidonic acid. Our results provide evidence that
D
-serine coactivation of NMDA receptors and endothelial nitric oxide synthase is involved in astrocyte-mediated neurovascular coupling.
Dual role for mammalian DNA polymerase ζ in maintaining genome stability and proliferative responses
Authors: Lange Sabine S. , Bedford Ella , Reh Shelley , Wittschieben John P. , Carbajal Steve , Kusewitt Donna F. , DiGiovanni John , Wood Richard D.
Published: February 2013

Significance

In mammalian cells DNA polymerase ζ (polζ) appears critical for bypass of DNA damage and was expected to be important for UV-induced skin carcinogenesis. To investigate the response to UV radiation, we engineered mice lacking polζ in the epidermis, circumventing a requirement for embryonic development. These mice were much more sensitive to UVB radiation than predicted, failed to mount skin-regenerative responses, and did not develop UV-induced skin tumors. Even unirradiated polζ-deficient keratinocytes had a marked proliferation defect and increased chromosomal breaks. Thus in rapidly proliferating cells, polζ maintains levels of DNA breaks below a lethal threshold.
Taking Agency, Constituting Community: The Activist Rhetoric of Richard Allen
Authors: McClish Glen , Bacon Jacqueline
Published: February 2013

This study features the activist rhetoric of early African American clergyman Richard Allen. Through chronological analyses of four late eighteenth- and early nineteenth-century texts, we explore how Allen establishes individual and corporate agency and furthers an African American community consciousness. Allen's rhetoric, we argue, demonstrates the ways material and rhetorical opportunities affect textual production that, in turn, enables freedom and community to emerge. Paying particular attention to the strategy of the narrative account, we demonstrate how Allen's advocacy, which both works within and challenges the limitations imposed by white society, reflects and develops his identity as a black community leader.
Identification and Property: Burke's and Lincoln's Ratio of Act and Purpose
Authors: Kraemer Don J.
Published: February 2013

Must acts of identification via an inclusive “we” mystify the inequalities they are meant to transcend? One answer lies in this essay's reading of Abraham Lincoln's and Kenneth Burke's rhetoric, a reading that tracks (especially through Lincoln's rhetoric) the “ways of identification,” ways which Burke claimed “are in accordance with the nature of property.” Identification in Lincoln's Second Inaugural Address confirms much of Burke's theory, yet Lincoln's career of appeals to the connections between property and propriety—and in particular the specific identifications made by such appeals in the Second Inaugural—suggests that Burke's presentation of identification is itself a kind of mystification that can lead to under-reading the ways of identification.
Citizenship as Salvation: The 1963 Mississippi Freedom Vote
Authors: Lawson William H.
Published: February 2013

This essay is an attempt at primary resource recovery to inform an under-studied moment from the Civil Rights Movement—the 1963 Mississippi Freedom Vote. Analysis of these primary texts reveals how the campaign used religious narratives and discourse to create political efficacy and agency among disenfranchised voters in Mississippi. It is this rhetorical transformation that holds the key to understanding how and why over 80,000 blacks who had never before participated in any sustained and organized political campaign chose to do so in the fall of 1963. Exploring these texts and events with a nuanced eye for religious and political discourse reveals how a rhetorical transformation from religious believers to political agents came about, and why it was successful in an overshadowed moment from the Civil Rights Movement.
On certain elements in the Bernstein center of 𝐆𝐋₂
Authors: Varma Sandeep
Published: February 2013

Let

F
F

be a nonarchimedean local field of residue characteristic

p
p

, and let

r
r

be an odd natural number less than

p
p

. Using the work of Moy and Tadić, we find an element

z
z

of the Bernstein center of

G
=

G
L

2

(
F
)

G = \mathbf {GL}_2(F)

that acts on any representation

π
\pi

of

G
G

by the scalar
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="z left-parenthesis pi right-parenthesis equals trace left-parenthesis upper F r o b semicolon left-parenthesis upper S y m Superscript r Baseline ring phi Subscript pi Baseline right-parenthesis Superscript upper I Super Subscript upper F Superscript Baseline right-parenthesis">

z
(
π
)
=
tr
⁡

(
Frob
;

(

Sym
r

∘

φ

π

)

I
F

)

z(\pi ) = \operatorname {tr} \left (\operatorname {Frob} ; \left ( \operatorname {Sym}^r \circ \varphi _{\pi }\right )^{I_F} \right )

, the trace of any geometric Frobenius element

Frob
\operatorname {Frob}

of the absolute Weil group

W
F

W_F

of

F
F

, acting on the inertia-fixed points of the representation

Sym
r

∘

φ

π

\operatorname {Sym}^r \circ \varphi _{\pi }

of

W
F

W_F

, where

φ

π

:

W
F

→

G
^

\varphi _{\pi } : W_F \rightarrow \hat {G}

is the restriction to

W
F

W_F

of the Langlands parameter of

π
\pi

. This element

z
z

is specified by giving the functions obtained by convolving it with the characteristic functions of a large class of compact open subgroups of

G
G

, that includes all the groups of both the congruence and the Iwahori filtrations of

G
G

having depth at least one.
Constraining self-interacting dark matter with the Milky Way’s dwarf spheroidals
Authors: Zavala Jesús , Vogelsberger Mark , Walker Matthew G.
Published: February 2013

Self-interacting dark matter is an attractive alternative to the cold dark matter paradigm only if it is able to substantially reduce the central densities of dwarf-size haloes while keeping the densities and shapes of cluster-size haloes within current constraints. Given the seemingly stringent nature of the latter, it was thought for nearly a decade that self-interacting dark matter would be viable only if the cross-section for self-scattering was strongly velocity dependent. However, it has recently been suggested that a constant cross-section per unit mass of σT/m ∼ 0.1 cm2 g−1 is sufficient to accomplish the desired effect. We explicitly investigate this claim using high-resolution cosmological simulations of a Milky Way-size halo and find that, similarly to the cold dark matter case, such cross-section produces a population of massive subhaloes that is inconsistent with the kinematics of the classical dwarf spheroidals, in particular with the inferred slopes of the mass profiles of Fornax and Sculptor. This problem is resolved if σT/m ∼ 1 cm2 g−1 at the dwarf spheroidal scales. Since this value is likely inconsistent with the halo shapes of several clusters, our results leave only a small window open for a velocity-independent self-interacting dark matter model to work as a distinct alternative to cold dark matter.
X-ray emission from the ultramassive black hole candidate NGC 1277: implications and speculations on its origin
Authors: Fabian A. C. , Sanders J. S. , Haehnelt M. , Rees M. J. , Miller J. M.
Published: February 2013

We study the X-ray emission from NGC 1277, a galaxy in the core of the Perseus cluster, for which van den Bosch et al. have recently claimed the presence of an ultramassive black hole (UMBH) of mass $1.7\times 10^{10}{\,\mathrm{M}_{{\odot }}}$, unless the initial mass function of the stars in the stellar bulge is extremely bottom heavy. The X-rays originate in a power-law component of luminosity $1.3\times 10^{40}{\,{\rm erg}\,{\rm s}^{-1}\,}$ embedded in a 1 keV thermal minicorona which has a half-light radius of about 1.3 kpc, typical of many early-type galaxies in rich clusters of galaxies. If Bondi accretion operated on to the UMBH from the minicorona with a radiative efficiency of 10 per cent, then the object would appear as a quasar with luminosity $10^{46}{\,{\rm erg}\,{\rm s}^{-1}\,}$, a factor of almost 106 times higher than observed. The accretion flow must be highly radiatively inefficient, similar to past results on M87 and NGC 3115. The UMBH in NGC 1277 is definitely not undergoing any significant growth at the present epoch. We note that there are three UMBH candidates in the Perseus cluster and that the inferred present mean mass density in UMBHs could be $10^5{\,\mathrm{M}_{{\odot }}}\,{\rm Mpc^{-3}}$, which is 20–30 per cent of the estimated mean mass density of all BHs. We speculate on the implied growth of UMBHs and their hosts, and discuss the possibility that extreme active galactic nucleus feedback could make all UMBH host galaxies have low stellar masses at redshifts around 3. Only those which end up at the centres of groups and clusters later accrete large stellar envelopes and become brightest cluster galaxies. NGC 1277 and the other Perseus core UMBH, NGC 1270, have not, however, been able to gather more stars or gas owing to their rapid orbital motion in the cluster core.
Coleosporium tussilaginis Found on Senecio nemorensis ssp. fuchsia in Norway
Authors: Talgø Venche , Gjærum Halvor B. , Hansen Ole B.
Published: February 2013

The rust fungus Coleosporium tussilaginis occurs on several genera of Asteraceae. It is host alternating with many species of pine (Pinus spp.). In 2010, the rust was confirmed on alpine ragwort (Senecio nemorensis) in Norway.

Accepted for publication 18 December 2012. Published 17 January 2013.
Identification of a Cucumber mosaic virus Subgroup II Strain Associated with Virus-like Symptoms on Hosta in Ohio
Authors: Fisher John R.
Published: February 2013

In this brief, the authors report the identification of a Cucumber mosaic virus subgroup II strain associated with mottle and spotting symptoms on Hosta spp. 'Cynthia.’ These results represent the first confirmed report of CMV infecting Hosta in Ohio.

Accepted for publication 18 December 2012. Published 23 January 2013.
A Comparative Biomechanical Analysis of Stand Alone Versus Facet Screw and Pedicle Screw Augmented Lateral Interbody Arthrodesis
Authors: Kretzer Ryan M. , Molina Camilo , Hu Nianbin , Umekoji Hidemasa , Baaj Ali A. , Serhan Hassan , Cunningham Bryan W.
Published: February 2013

Study Design:

Cadaveric biomechanical study.

Objective:

To investigate the kinematic response of a stand-alone lateral lumbar interbody cage compared with supplemental posterior fixation with either facet or pedicle screws after lateral discectomy.

Summary of Background Data:

Lateral interbody fusion is a promising minimally invasive fixation technique for lumbar interbody arthrodesis. The biomechanical stability of stand-alone cage placement compared with supplemental posterior fixation with either facet or bilateral pedicle screws remains unclear.

Methods:

A 6-degree of freedom spine simulator was used to test flexibility in 7 human cadaveric specimens. Flexion-extension, lateral-bending, and axial-rotation were tested in the intact condition, followed by destabilization through a lateral discectomy at L2–L3 and L4–L5. Specimens were then reconstructed at both operative segments in the following sequence: (1) lateral interbody cage placement; (2) either Discovery facet screws or the Viper F2 system using a transfacet-pedicular trajectory randomized to L2–L3 or L4–L5; and (3) removal of facet screw fixation followed by placement of bilateral pedicle screw instrumentation. Acute range of motion (ROM) was quantified and analyzed.

Results:

All 4 reconstruction groups, including stand-alone interbody cage placement, bilateral Discovery facet screws, the Viper F2 system, and bilateral pedicle screw-rod stabilization, resulted in a significant decrease in acute ROM in all loading modes tested (P<0.05). There were no significant differences observed between the 4 instrumentation groups (P>0.05). Although not statistically significant, the Viper F2 system resulted in greatest reduction of acute ROM in both flexion-extension and axial rotation versus all other treatments (P>0.05).

Conclusions:

Stand-alone interbody cage placement results in a significant reduction in acute ROM at the operative segment in the absence of posterior supplemental fixation. If added fixation is desired, facet screw placement, including the Viper F2 facet screw system using an integrated compression washer and transfacet-pedicular trajectory, provides similar acute stability to the spinal segment compared with traditional bilateral pedicle screw fixation in the setting of lateral interbody cage deployment.
Using network theory to identify the causes of disease outbreaks of unknown origin
Authors: Bogich Tiffany L. , Funk Sebastian , Malcolm Trent R. , Chhun Nok , Epstein Jonathan H. , Chmura Aleksei A. , Kilpatrick A. Marm , Brownstein John S. , Hutchison O. Clyde , Doyle-Capitman Catherine , Deaville Robert , Morse Stephen S. , Cunningham Andrew A. , Daszak Peter
Published: February 2013

The identification of undiagnosed disease outbreaks is critical for mobilizing efforts to prevent widespread transmission of novel virulent pathogens. Recent developments in online surveillance systems allow for the rapid communication of the earliest reports of emerging infectious diseases and tracking of their spread. The efficacy of these programs, however, is inhibited by the anecdotal nature of informal reporting and uncertainty of pathogen identity in the early stages of emergence. We developed theory to connect disease outbreaks of known aetiology in a network using an array of properties including symptoms, seasonality and case-fatality ratio. We tested the method with 125 reports of outbreaks of 10 known infectious diseases causing encephalitis in South Asia, and showed that different diseases frequently form distinct clusters within the networks. The approach correctly identified unknown disease outbreaks with an average sensitivity of 76 per cent and specificity of 88 per cent. Outbreaks of some diseases, such as Nipah virus encephalitis, were well identified (sensitivity = 100%, positive predictive values = 80%), whereas others (e.g. Chandipura encephalitis) were more difficult to distinguish. These results suggest that unknown outbreaks in resource-poor settings could be evaluated in real time, potentially leading to more rapid responses and reducing the risk of an outbreak becoming a pandemic.
A stability-based mechanism for hysteresis in the walk–trot transition in quadruped locomotion
Authors: Aoi Shinya , Katayama Daiki , Fujiki Soichiro , Tomita Nozomi , Funato Tetsuro , Yamashita Tsuyoshi , Senda Kei , Tsuchiya Kazuo
Published: February 2013

Quadrupeds vary their gaits in accordance with their locomotion speed. Such gait transitions exhibit hysteresis. However, the underlying mechanism for this hysteresis remains largely unclear. It has been suggested that gaits correspond to attractors in their dynamics and that gait transitions are non-equilibrium phase transitions that are accompanied by a loss in stability. In the present study, we used a robotic platform to investigate the dynamic stability of gaits and to clarify the hysteresis mechanism in the walk–trot transition of quadrupeds. Specifically, we used a quadruped robot as the body mechanical model and an oscillator network for the nervous system model to emulate dynamic locomotion of a quadruped. Experiments using this robot revealed that dynamic interactions among the robot mechanical system, the oscillator network, and the environment generate walk and trot gaits depending on the locomotion speed. In addition, a walk–trot transition that exhibited hysteresis was observed when the locomotion speed was changed. We evaluated the gait changes of the robot by measuring the locomotion of dogs. Furthermore, we investigated the stability structure during the gait transition of the robot by constructing a potential function from the return map of the relative phase of the legs and clarified the physical characteristics inherent to the gait transition in terms of the dynamics.
A strong magnetic pulse affects the precision of departure direction of naturally migrating adult but not juvenile birds
Authors: Holland Richard A. , Helm Barbara
Published: February 2013

The mechanisms by which migratory birds achieve their often spectacular navigational performance are still largely unclear, but perception of cues from the Earth's magnetic field is thought to play a role. Birds that possess migratory experience can use map-based navigation, which may involve a receptor that uses ferrimagnetic material for detecting gradients in the magnetic field. Such a mechanism can be experimentally disrupted by applying a strong magnetic pulse that re-magnetizes ferrimagnetic materials. In captivity, this treatment indeed affected bearings of adult but not of naive juvenile birds. However, field studies, which expose birds to various navigational cues, yielded mixed results. Supportive studies were difficult to interpret because they were conducted in spring when all age groups navigate back to breeding areas. The present study, therefore, applied a magnetic pulse treatment in autumn to naturally migrating, radio-tagged European robins. We found that, although overall bearings were seasonally correct, orientation of adult but not juvenile robins was compromised by a pulse. Pulsed adults that departed within 10 days of treatment failed to show significant orientation and deviated more from mean migration direction than adult controls and juveniles. Thus, our data give field-based support for a possible ferrimagnetic map-sense during bird migration.
Phenotypically plastic neophobia: a response to variable predation risk
Authors: Brown Grant E. , Ferrari Maud C. O. , Elvidge Chris K. , Ramnarine Indar , Chivers Douglas P.
Published: February 2013

Prey species possess a variety of morphological, life history and behavioural adaptations to evade predators. While specific evolutionary conditions have led to the expression of permanent, non-plastic anti-predator traits, the vast majority of prey species rely on experience to express adaptive anti-predator defences. While ecologists have identified highly sophisticated means through which naive prey can deal with predation threats, the potential for death upon the first encounter with a predator is still a remarkably important unresolved issue. Here, we used both laboratory and field studies to provide the first evidence for risk-induced neophobia in two taxa (fish and amphibians), and argue that phenotypically plastic neophobia acts as an adaptive anti-predator strategy for vulnerable prey dealing with spatial and temporal variation in predation risk. Our study also illustrates how risk-free maintenance conditions used in laboratory studies may blind researchers to adaptive anti-predator strategies that are only expressed in high-risk conditions.
Aquihabitans daechungensis gen. nov., sp. nov., an actinobacterium isolated from reservoir water
Authors: Jin Long , Huy Hangsak , Kim Kwang Kyu , Lee Hyung-Gwan , Kim Hee-Sik , Ahn Chi-Yong , Oh Hee-Mock
Published: February 2013

A novel Gram-reaction-positive bacterium, strain CH22-21T, was isolated from a water sample taken from Daechung Reservoir, Republic of Korea, during the late-blooming period of cyanobacteria. Cells of strain CH22-21T were non-motile, ciliated short rods that formed creamy-white colonies on half-strength modified R2A agar. Chemotaxonomic results showed menaquinone MK-9(H6) as the predominant respiratory menaquinone, diphosphatidylglycerol, phosphatidylinositol and phosphatidylinositolmannoside as major polar lipids, 16 : 1ω5c, 16 : 0, 17 : 1ω8c and 18 : 1ω9c as major fatty acids, and a DNA G+C content of 71.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequencing indicated that the strain formed a separate lineage within the order

Acidimicrobiales

, showing similarity values of <92.3 % with its closest phylogenetic neighbours. The combined genotypic and phenotypic data showed that strain CH22-21T could be distinguished from all genera within the order

Acidimicrobiales

and represented a novel species of a new genus in the family

Iamiaceae

, for which the name Aquihabitans dachungensis gen. nov., sp. nov. is proposed. The type strain of Aquihabitans dachungensis is CH22-21T ( = KCTC 19849T = JCM 17787T).
Morphology, morphogenesis and small-subunit rRNA gene sequence of the novel brackish-water ciliate Strongylidium orientale sp. nov. (Ciliophora, Hypotrichia)
Authors: Chen Xumiao , Miao Miao , Ma Honggang , Shao Chen , Al-Rasheid Khaled A. S.
Published: February 2013

A novel stichotrich ciliate, Strongylidium orientale sp. nov., was discovered from a mangrove river in Hong Kong, southern China, and its morphology was investigated through observations in vivo and after protargol impregnation. Cells are 80–120×35–50 µm in vivo and fusiform in shape, with rounded anterior and tapered posterior ends. It is characterized by its brackish habitat and by the presence of two types of cortical granules arranged irregularly throughout the cortex. Morphogenetic events of cell division and physiological reorganization are described. The main ontogenetic features were: (i) only the posterior portion of the parental adoral zone of membranelles was renewed by dedifferentiation of the old structures; (ii) the oral primordium in the opisthe occurred apokinetally; (iii) the left and right ventral rows originated intrakinetally and the final left ventral row was spliced from two cirri from the frontoventral cirral anlage, a short cirral row from the anlage for the right ventral row and a long cirral row which was formed from the whole anlage of the left ventral row; (iv) the marginal rows developed intrakinetally; (v) the dorsal kineties replicated entirely de novo and did not fragment; and (vi) the two macronuclear nodules fused into a mass and then divided. Based on small-subunit rRNA gene sequences, phylogenetic analyses showed a close relationship with its congener Strongylidium pseudocrassum and with the genus Pseudouroleptus.