bluuebunny/crossref_metadata_2025 huggingface dataset:
Band diagrams of layered plasmonic metamaterials
Authors: Al Shakhs Mohammed H. , Ott Peter , Chau Kenneth J.
Published: November 2014

We introduce a method to map the band diagrams, or equipotential contours (EPCs), of any layered plasmonic metamaterial using a general expression for the Poynting vector in a lossy layered medium of finite extent under plane-wave illumination. Unlike conventional methods to get band diagrams by solving the Helmholtz equation using the Floquet-Bloch theorem (an approach restricted to infinite, periodic, lossless media), our method adopts a bottom-up philosophy based on spatial-frequency decomposition of the electric and magnetic fields (an approach applicable to finite, lossy media). Equipotential contours are used to visualize phase and group velocities in a wide range of layered plasmonic systems, including the basic building block of a thin metallic layer and more complex multi-layers with unique optical properties such as negative phase velocity, super-resolution imaging, canalization, and far-field imaging. We show that a thin metallic layer can mimic a left-handed electromagnetic response at the surface plasmon resonance and that stacks of metal and dielectric layers can do the same provided that the dielectric layer is sufficiently thin. We also use EPCs to estimate resolution limits of both Pendry's silver slab lens and the Veselago lens and show that the image location and lateral image resolution of metal-dielectric layered flat lenses can be described (and tailored) by the concavity and spectral reach of the dominant band in their EPCs. Homogenization methods for describing the effective optical properties of various layered systems are validated by the extent to which they accurately mimic features in their EPCs.
One-photon mass-analyzed threshold ionization (MATI) spectroscopy of pyridine: Determination of accurate ionization energy and cationic structure
Authors: Lee Yu Ran , Kang Do Won , Kim Hong Lae , Kwon Chan Ho
Published: November 2014

Ionization energies and cationic structures of pyridine were intensively investigated utilizing one-photon mass-analyzed threshold ionization (MATI) spectroscopy with vacuum ultraviolet radiation generated by four-wave difference frequency mixing in Kr. The present one-photon high-resolution MATI spectrum of pyridine demonstrated a much finer and richer vibrational structure than that of the previously reported two-photon MATI spectrum. From the MATI spectrum and photoionization efficiency curve, the accurate ionization energy of the ionic ground state of pyridine was confidently determined to be 73 570 ± 6 cm−1 (9.1215 ± 0.0007 eV). The observed spectrum was almost completely assigned by utilizing Franck-Condon factors and vibrational frequencies calculated through adjustments of the geometrical parameters of cationic pyridine at the B3LYP/cc-pVTZ level. A unique feature unveiled through rigorous analysis was the prominent progression of the 10 vibrational mode, which corresponds to in-plane ring bending, and the combination of other totally symmetric fundamentals with the ring bending overtones, which contribute to the geometrical change upon ionization. Notably, the remaining peaks originate from the upper electronic state (2A2), as predicted by high-resolution photoelectron spectroscopy studies and symmetry-adapted cluster configuration interaction calculations. Based on the quantitatively good agreement between the experimental and calculated results, it was concluded that upon ionization the pyridine cation in the ground electronic state should have a planar structure of C2v symmetry through the C-N axis.
A multi-species exchange model for fully fluctuating polymer field theory simulations
Authors: Düchs Dominik , Delaney Kris T. , Fredrickson Glenn H.
Published: November 2014

Field-theoretic models have been used extensively to study the phase behavior of inhomogeneous polymer melts and solutions, both in self-consistent mean-field calculations and in numerical simulations of the full theory capturing composition fluctuations. The models commonly used can be grouped into two categories, namely, species models and exchange models. Species models involve integrations of functionals that explicitly depend on fields originating both from species density operators and their conjugate chemical potential fields. In contrast, exchange models retain only linear combinations of the chemical potential fields. In the two-component case, development of exchange models has been instrumental in enabling stable complex Langevin (CL) simulations of the full complex-valued theory. No comparable stable CL approach has yet been established for field theories of the species type. Here, we introduce an extension of the exchange model to an arbitrary number of components, namely, the multi-species exchange (MSE) model, which greatly expands the classes of soft material systems that can be accessed by the complex Langevin simulation technique. We demonstrate the stability and accuracy of the MSE-CL sampling approach using numerical simulations of triblock and tetrablock terpolymer melts, and tetrablock quaterpolymer melts. This method should enable studies of a wide range of fluctuation phenomena in multiblock/multi-species polymer blends and composites.
Nonlinear frequency-dependent effects in the dc magnetization of uniaxial magnetic nanoparticles in superimposed strong alternating current and direct current fields
Authors: Wei Nijun , Byrne Declan , Coffey William T. , Kalmykov Yuri P. , Titov Serguey V.
Published: November 2014

The dc component of the magnetization of noninteracting fine magnetic particles possessing simple uniaxial anisotropy and subjected to strong ac and dc bias magnetic fields is calculated via the magnetic Langevin equation. In the presence of an ac driving field, the dc component of the magnetization of uniaxial particles alters drastically leading to new nonlinear effects; in particular, it becomes frequency-dependent. In axial symmetry, where the strong ac field is parallel to the easy axis of a particle, two distinct dispersion regions in the dc magnetization at low and mid-frequencies emerge, corresponding to longitudinal overbarrier and intrawell relaxation modes. Such frequency-dependent behavior allows one to estimate the magnetization reversal time via the half-width of the low-frequency dispersion band. Otherwise, by applying the strong ac field at an angle to the easy axis of a particle so breaking the axial symmetry, a third high-frequency nonlinear resonant dispersion in the dc component of the magnetization appears accompanied by parametric resonance behavior due to excitation of transverse modes with frequencies close to the precession frequency.
The effect of shock dynamics on compressibility of ignition-scale National Ignition Facility implosions
Authors: Zylstra A. B. , Frenje J. A. , Séguin F. H. , Hicks D. G. , Dewald E. L. , Robey H. F. , Rygg J. R. , Meezan N. B. , Rosenberg M. J. , Rinderknecht H. G. , Friedrich S. , Bionta R. , Olson R. , Atherton J. , Barrios M. , Bell P. , Benedetti R. , Berzak Hopkins L. , Betti R. , Bradley D. , Callahan D. , Casey D. , Collins G. , Dixit S. , Döppner T. , Edgell D. , Edwards M. J. , Gatu Johnson M. , Glenn S. , Glenzer S. , Grim G. , Hatchett S. , Jones O. , Khan S. , Kilkenny J. , Kline J. , Knauer J. , Kritcher A. , Kyrala G. , Landen O. , LePape S. , Li C. K. , Lindl J. , Ma T. , Mackinnon A. , Macphee A. , Manuel M. J.-E. , Meyerhofer D. , Moody J. , Moses E. , Nagel S. R. , Nikroo A. , Pak A. , Parham T. , Petrasso R. D. , Prasad R. , Ralph J. , Rosen M. , Ross J. S. , Sangster T. C. , Sepke S. , Sinenian N. , Sio H. W. , Spears B. , Springer P. , Tommasini R. , Town R. , Weber S. , Wilson D. , Zacharias R.
Published: November 2014

The effects of shock dynamics on compressibility of indirect-drive ignition-scale surrogate implosions, CH shells filled with D3He gas, have been studied using charged-particle spectroscopy. Spectral measurements of D3He protons produced at the shock-bang time probe the shock dynamics and in-flight characteristics of an implosion. The proton shock yield is found to vary by over an order of magnitude. A simple model relates the observed yield to incipient hot-spot adiabat, suggesting that implosions with rapid radiation-power increase during the main drive pulse may have a 2× higher hot-spot adiabat, potentially reducing compressibility. A self-consistent 1-D implosion model was used to infer the areal density (ρR) and the shell center-of-mass radius (Rcm) from the downshift of the shock-produced D3He protons. The observed ρR at shock-bang time is substantially higher for implosions, where the laser drive is on until near the compression bang time (“short-coast”), while longer-coasting implosions have lower ρR. This corresponds to a much larger temporal difference between the shock- and compression-bang time in the long-coast implosions (∼800 ps) than in the short-coast (∼400 ps); this will be verified with a future direct bang-time diagnostic. This model-inferred differential bang time contradicts radiation-hydrodynamic simulations, which predict constant 700–800 ps differential independent of coasting time; this result is potentially explained by uncertainties in modeling late-time ablation drive on the capsule. In an ignition experiment, an earlier shock-bang time resulting in an earlier onset of shell deceleration, potentially reducing compression and, thus, fuel ρR.
Temperature and phase dynamics in superconducting weak-link
Authors: Gupta Anjan K. , Kumar Nikhil , Biswas Sourav
Published: November 2014

A time dependent thermal model for a superconducting constriction based weak-link (WL) is discussed for investigating the deterministic dynamics of its temperature and phase. A new dynamic regime is found where a non-zero voltage exists across the WL, and its temperature stabilizes between the bath temperature and superconductor's critical temperature. This regime exists over a limited bias current range and gives rise to a new hysteretic regime in current-voltage characteristics. We also discuss the effect of fluctuations on the current-voltage characteristics and experimental implications of this dynamic regime.
Sheath oscillation characteristics and effect on near-wall conduction in a krypton Hall thruster
Authors: Zhang Fengkui , Kong Lingyi , Li Chenliang , Yang Haiwei , Li Wei
Published: November 2014

Despite its affordability, the krypton Hall-effect thruster in applications always had problems in regard to performance. The reason for this degradation is studied from the perspective of the near-wall conductivity of electrons. Using the particle-in-cell method, the sheath oscillation characteristics and its effect on near-wall conduction are compared in the krypton and xenon Hall-effect thrusters both with wall material composed of BNSiO2. Comparing these two thrusters, the sheath in the krypton-plasma thruster will oscillate at low electron temperatures. The near-wall conduction current is only produced by collisions between electrons and wall, thereby causing a deficiency in the channel current. The sheath displays spatial oscillations only at high electron temperature; electrons are then reflected to produce the non-oscillation conduction current needed for the krypton-plasma thruster. However, it is accompanied with intensified oscillations.
Magnetization reversal assisted by half antivortex states in nanostructured circular cobalt disks
Authors: Lara A. , Dobrovolskiy O. V. , Prieto J. L. , Huth M. , Aliev F. G.
Published: November 2014

The half antivortex, a fundamental topological structure which determines magnetization reversal of submicron magnetic devices with domain walls, has been suggested also to play a crucial role in spin torque induced vortex core reversal in circular disks. Here, we report on magnetization reversal in circular disks with nanoholes through consecutive metastable states with half antivortices. In-plane anisotropic magnetoresistance and broadband susceptibility measurements accompanied by micromagnetic simulations reveal that cobalt (Co) disks with two and three linearly arranged nanoholes directed at 45° and 135° with respect to the external magnetic field show reproducible step-like changes in the anisotropic magnetoresistance and magnetic permeability due to transitions between different intermediate states mediated by vortices and half antivortices confined to the dot nanoholes and edges, respectively. Our findings are relevant for the development of multi-hole based spintronic and magnetic memory devices.
Low temperature photoresponse of monolayer tungsten disulphide
Authors: Cao Bingchen , Shen Xiaonan , Shang Jingzhi , Cong Chunxiao , Yang Weihuang , Eginligil Mustafa , Yu Ting
Published: November 2014

High photoresponse can be achieved in monolayers of transition metal dichalcogenides. However, the response times are inconveniently limited by defects. Here, we report low temperature photoresponse of monolayer tungsten disulphide prepared by exfoliation and chemical vapour deposition (CVD) method. The exfoliated device exhibits n-type behaviour; while the CVD device exhibits intrinsic behaviour. In off state, the CVD device has four times larger ratio of photoresponse for laser on/off and photoresponse decay–rise times are 0.1 s (limited by our setup), while the exfoliated device has few seconds. These findings are discussed in terms of charge trapping and localization.
Isothermal vortex flows in the vicinity of ferro- and diamagnetic condensation cores in magnetic fluids undergoing first-order phase transition
Authors: Ivanov A. S. , Melenev P. V.
Published: November 2014

The paper presents the system of analytical equations describing isothermal vortex flows induced in a plane magnetized ferrofluid layer by magnetophoresis of drop-like aggregates. Magnetophoresis of the aggregates is caused by configuration of a constant inhomogeneous magnetic field in the vicinity of a solid condensation core placed in the fluid. The vortex flow generated by inhomogeneous ponderomotive force drives the aggregates into the region of highest magnetic field intensity, which resembles condensation of drops at the surface of the core. The dynamic equations are written for the case of dilute magnetic fluids and take into account the dynamics of the drop-like aggregate growth. Numerical simulation based on the proposed system of equations is in qualitative agreement with the experimental data obtained in the Hele-Shaw cell.
Highly tunable quantum Hall far-infrared photodetector by use of GaAs/AlxGa1−xAs-graphene composite material
Authors: Tang Chiu-Chun , Ling D. C. , Chi C. C. , Chen Jeng-Chung
Published: November 2014

We have developed a highly tunable, narrow band far-infrared (FIR) photodetector which utilizes the characteristic merits of graphene and two-dimensional electron gas (2DEG) in GaAs/AlxGa1−xAs heterostructure in the Quantum Hall states (QHS). The heterostructure surface is covered with chemical vapor-deposited graphene, which functions as a transparent top-gate to vary the electron density of the 2DEG. FIR response observed in the vicinity of integer QH regime can be effectively tuned in a wide range of 27–102 cm−1 with a bias voltage less than −1 V. In addition, we have found that the presence of graphene can genuinely modulate the photoresponse. Our results demonstrate a promising direction for realizing a tunable long-wavelength FIR detector using QHS in GaAs 2DEG/ graphene composite material.
Room temperature ferromagnetic and ferroelectric properties of Bi1−xCaxMnO3 thin films
Authors: Pugazhvadivu K. S. , Balakrishnan L. , Mohan Rao G. , Tamilarasan K.
Published: November 2014

Bi1−xCaxMnO3 (BCMO) thin films with x = 0, 0.1, 0.2, 0.3 and 0.4 are successfully deposited on the n-type Si (100) substrate at two different temperatures of 400 °C and 800 °C using RF magnetron sputtering. The stoichiometry of the films and oxidation state of the elements have been described by X-ray photoelectron spectroscopy analysis. Dielectric measurement depicts the insulating property of BCMO films. Magnetic and ferroelectric studies confirm the significant enhancement in spin orientation as well as electric polarization at room temperature due to incorporation of Ca2+ ions into BiMnO3 films. The BCMO (x = 0.2) film grown at 400 °C shows better magnetization (Msat) and polarization (Ps)with the measured values of 869 emu / cc and 6.6 μC/ cm2 respectively than the values of the other prepared films. Thus the realization of room temperature ferromagnetic and ferroelectric ordering in Ca2+ ions substituted BMO films makes potentially interesting for spintronic device applications.
Graphene based tunable fractal Hilbert curve array broadband radar absorbing screen for radar cross section reduction
Authors: Huang Xianjun , Hu Zhirun , Liu Peiguo
Published: November 2014

This paper proposes a new type of graphene based tunable radar absorbing screen. The absorbing screen consists of Hilbert curve metal strip array and chemical vapour deposition (CVD) graphene sheet. The graphene based screen is not only tunable when the chemical potential of the graphene changes, but also has broadband effective absorption. The absorption bandwidth is from 8.9GHz to 18.1GHz, ie., relative bandwidth of more than 68%, at chemical potential of 0eV, which is significantly wider than that if the graphene sheet had not been employed. As the chemical potential varies from 0 to 0.4eV, the central frequency of the screen can be tuned from 13.5GHz to 19.0GHz. In the proposed structure, Hilbert curve metal strip array was designed to provide multiple narrow band resonances, whereas the graphene sheet directly underneath the metal strip array provides tunability and averagely required surface resistance so to significantly extend the screen operation bandwidth by providing broadband impedance matching and absorption. In addition, the thickness of the screen has been optimized to achieve nearly the minimum thickness limitation for a nonmagnetic absorber. The working principle of this absorbing screen is studied in details, and performance under various incident angles is presented. This work extends applications of graphene into tunable microwave radar cross section (RCS) reduction applications.
A Prototype-Based Resonance Model of Rhythm Categorization
Authors: Bååth Rasmus , Lagerstedt Erik , Gärdenfors Peter
Published: November 2014

Categorization of rhythmic patterns is prevalent in musical practice, an example of this being the transcription of (possibly not strictly metrical) music into musical notation. In this article we implement a dynamical systems' model of rhythm categorization based on the resonance theory of rhythm perception developed by Large (2010). This model is used to simulate the categorical choices of participants in two experiments of Desain and Honing (2003). The model accurately replicates the experimental data. Our results support resonance theory as a viable model of rhythm perception and show that by viewing rhythm perception as a dynamical system it is possible to model central properties of rhythm categorization.
Fabrication of High Efficiency Dye-Sensitised Solar Cell with Zirconia-Doped TiO2 Nanoparticle and Nanowire Composite Photoanode Film
Authors: Maheswari D. , Venkatachalam P.
Published: November 2014

Dye-sensitised solar cells (DSSCs) were fabricated based on coumarin NKX-2700 dye-sensitised zirconia-doped TiO2 nanoparticle and nanowire composite photoanode film and quasi-solid-state electrolyte, sandwiched together with cobalt sulfide-coated counter electrode. Novel photoanodes were prepared using composite mixtures of 90 wt-% TiO2 nanoparticles + 10 wt-% TiO2 nanowires (TNPWs) as base material and zirconia as doping metal. Hafnium oxide (HfO2) was applied on the zirconia-doped TNPWs (zirconia/TNPWs) film structure as a blocking layer. TiO2 nanoparticles, TiO2 nanowires, and zirconia/TNPWs were characterised by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The sensitising organic dye coumarin, NKX-2700, displayed maximum absorption wavelength (λmax) at 525 nm, which could be observed from the UV-visible spectrum. DSSC-1 built with zirconia/TNPWs-doped photoanode with blocking layer revealed enhanced photo-current efficiency (PCE) as compared with other DSSCs and illustrated photovoltaic parameters: short circuit current JSC = 20 mA m–2, open circuit voltage (VOC = 730 mV, fill factor (FF) = 68 %, and PCE (η) = 9.93 %. The electron transport and charge recombination behaviours of DSSCs were investigated by electrochemical impedance spectroscopy and the results exhibited that DSSC-1 possessed the lowest charge transfer resistance (Rrec) and longest electron lifetime (τrec) compared with other DSSCs. Therefore, from the present investigation, it could be concluded that the improved performance of DSSC-1 is ascribed to the zirconia/TNPWs-doped photoanode with the blocking layer increasing the short circuit current, electron transport, and suppressing the recombination of charge carriers at the photoanode/dye/electrolyte interface.
Overtone-based pitch selection in hermit thrush song: Unexpected convergence with scale construction in human music
Authors: Doolittle Emily L. , Gingras Bruno , Endres Dominik M. , Fitch W. Tecumseh
Published: November 2014

Significance

The song of the hermit thrush, a common North American songbird, is renowned for its apparent musicality and has attracted the attention of musicians and ornithologists for more than a century. Here we show that hermit thrush songs, like much human music, use pitches that are mathematically related by simple integer ratios and follow the harmonic series. Our findings add to a small but growing body of research showing that a preference for small-integer ratio intervals is not unique to humans and are thus particularly relevant to the ongoing nature/nurture debate about whether musical predispositions such as the preference for consonant intervals are biologically or culturally driven.
Microtubules stabilize cell polarity by localizing rear signals
Authors: Zhang Jian , Guo Wei-Hui , Wang Yu-Li
Published: November 2014

Significance

We discovered that cells on micropatterned strips change from highly persistent migration into striking oscillations upon the disassembly of microtubules. The oscillation phenomenon then allowed us to apply computer modeling to understand how the positive feedback in the local-excitation–global-inhibition (LEGI) mechanism, responsible for the persistence of migration, might be converted into negative feedback to drive oscillations upon the disassembly of microtubules. Our analyses led to the conclusion that microtubules facilitate the transport of inhibitory signals and their global distribution. Depending on the relative position of excitation and inhibitory signals, the resulting feedback in the integrated control circuit may be either positive or negative. Our finding therefore provides important insights into the role of microtubules in the control circuit of cell migration.
Probabilistic cognition in two indigenous Mayan groups
Authors: Fontanari Laura , Gonzalez Michel , Vallortigara Giorgio , Girotto Vittorio
Published: November 2014

Significance

Correct probabilistic evaluations are one of the hallmarks of rationality. Is the human ability to make them dependent on formal education, or does it emerge regardless of instruction and culture? This paper shows that preliterate and prenumerate Mayan adults are able to solve a variety of probabilistic problems. These individuals correctly use prior and posterior information, proportions and elementary combinatorial procedures to predict the occurrence of random outcomes. And they perform like Mayan school children and Western controls. The finding that adults with no formal education are able to make suitable predictions indicates that, regardless of schooling and culture, the human mind possesses a basic probabilistic knowledge.
Metabolic sensor governing bacterial virulence in
Staphylococcus aureus
Authors: Ding Yue , Liu Xing , Chen Feifei , Di Hongxia , Xu Bin , Zhou Lu , Deng Xin , Wu Min , Yang Cai-Guang , Lan Lefu
Published: November 2014

Significance

Staphylococcus aureus
is one of the most successful and adaptable human pathogens and is a major cause of hospital-acquired infections. Here we provide insight into how
S
.
aureus
uses the catabolite control protein E (CcpE) to sense its intracellular metabolic status and to regulate its virulence-associated properties. We define a key circuit of the virulence regulatory network of
S
.
aureus
and emphasize that metabolic status may be a critical element governing the virulence of this pathogen. Understanding the role of metabolites in virulence factor expression ultimately may contribute to the development of novel strategies to combat this dreaded infectious disease.
Topography's crucial role in Heinrich Events
Authors: Roberts William H. G. , Valdes Paul J. , Payne Antony J.
Published: November 2014

Significance

Heinrich Events are frequently promoted as examples of an abruptly forced climate change. Although the evidence for changes in the ice sheets, which cause these events, is clear, the pathway by which these changes can affect the climate is not. The most common explanation is that the melting icebergs released by the ice sheet cause a change in the ocean’s circulation. Here we propose that the change in the height of the ice sheet, which changes the atmospheric circulation, is just as important. We must therefore reassess the simple paradigm that the climate changes that occurred during Heinrich Events are solely the result of a change in the ocean’s circulation.
Decreased segregation of brain systems across the healthy adult lifespan
Authors: Chan Micaela Y. , Park Denise C. , Savalia Neil K. , Petersen Steven E. , Wig Gagan S.
Published: November 2014

Significance

The brain is a large-scale network, not unlike many social or technological networks. Just like social networks, brain networks contain subnetworks or systems of highly related or interacting nodes (in the case of brains, nodes may represent neurons or brain areas). Using functional MRI to measure functional correlations between brain areas during periods of rest, we describe differences in brain network organization in a large group of individuals sampled across the healthy adult lifespan (20–89 y). We characterize a measure of system segregation, reflecting the degree to which the systems share connections among one another. Increasing age is accompanied by decreasing segregation of brain systems. Importantly, system segregation is predictive of measures of long-term memory function, independent of age.
Notes on the role of dynamic DNA methylation in mammalian development
Authors: Bestor Timothy H. , Edwards John R. , Boulard Mathieu
Published: November 2014

It has been nearly 40 y since it was suggested that genomic methylation patterns could be transmitted via maintenance methylation during S phase and might play a role in the dynamic regulation of gene expression during development [Holliday R, Pugh JE (1975)
Science
187(4173):226–232; Riggs AD (1975)
Cytogenet Cell Genet
14(1):9–25]. This revolutionary proposal was justified by “... our almost complete ignorance of the mechanism for the unfolding of the genetic program during development” that prevailed at the time. Many correlations between transcriptional activation and demethylation have since been reported, but causation has not been demonstrated and to date there is no reasonable proof of the existence of a complex biochemical system that activates and represses genes via reversible DNA methylation. Such a system would supplement or replace the conserved web of transcription factors that regulate cellular differentiation in organisms that have unmethylated genomes (such as
Caenorhaditis elegans
and the Dipteran insects) and those that methylate their genomes. DNA methylation does have essential roles in irreversible promoter silencing, as in the monoallelic expression of imprinted genes, in the silencing of transposons, and in X chromosome inactivation in female mammals. Rather than reinforcing or replacing regulatory pathways that are conserved between organisms that have either methylated or unmethylated genomes, DNA methylation endows genomes with the ability to subject specific sequences to irreversible transcriptional silencing even in the presence of all of the factors required for their expression, an ability that is generally unavailable to organisms that have unmethylated genomes.
Amino acid modified Ni catalyst exhibits reversible H
2
oxidation/production over a broad pH range at elevated temperatures
Authors: Dutta Arnab , DuBois Daniel L. , Roberts John A. S. , Shaw Wendy J.
Published: November 2014

Significance

Enzymes achieve rapid and reversible H
2
oxidation catalysis by cooperative behavior between the active site and the protein scaffold. To better understand the role of the enzyme scaffold, we have attached amino acids (glycine, arginine, and arginine methyl ester) to an active functional mimic of hydrogenase to give

[

Ni

(

P
2

Cy

N
2

Amino
 
acid

)

2

]

2
+

. The resulting complexes are fully reversible catalysts with the arginine complex exhibiting high activity for both H
2
oxidation/production, functionality achieved by the addition of an outer coordination sphere.
Stable expression and function of the inositol 1,4,5-triphosphate receptor requires palmitoylation by a DHHC6/selenoprotein K complex
Authors: Fredericks Gregory J. , Hoffmann FuKun W. , Rose Aaron H. , Osterheld Hanna J. , Hess Franz M. , Mercier Frederic , Hoffmann Peter R.
Published: November 2014

Significance

The stimulation of certain surface receptors on immune cells triggers the release of calcium (Ca
2+
) stored in the endoplasmic reticulum (ER). This Ca
2+
flux is required for efficient activation and function of immune cells, and involves the ER membrane Ca
2+
channel, the inositol 1,4,5-triphosphate receptor (IP3R). We found that stable expression of IP3R requires the addition of a fatty acid through a process called palmitoylation catalyzed by an enzyme complex composed of DHHC6 (letters represent the amino acids aspartic acid, histidine, histidine, and cysteine in the catalytic domain) and selenoprotein K (Selk) proteins. These findings provide new mechanistic insight into the selenium-sensitive fine-tuning of immune cell activation through posttranslational modification of the IP3R Ca
2+
channel. This study also reveals a novel DHHC6/Selk enzyme complex responsible for regulating stable expression of the IP3R.
Excess cholesterol induces mouse egg activation and may cause female infertility
Authors: Yesilaltay Ayce , Dokshin Gregoriy A. , Busso Dolores , Wang Li , Galiani Dalia , Chavarria Tony , Vasile Eliza , Quilaqueo Linda , Orellana Juan Andrés , Walzer Dalia , Shalgi Ruth , Dekel Nava , Albertini David F. , Rigotti Attilio , Page David C. , Krieger Monty
Published: November 2014

Significance

Production of functional sperm and eggs requires a complex process called meiosis. Meiosis in mouse and human eggs pauses at a stage called metaphase II (MII) arrest until fertilization by sperm. After fertilization, eggs released from MII arrest complete meiosis and develop into new individuals. In analyzing the female infertility of genetically altered mice, we discovered that excess cholesterol can trick mouse eggs into behaving as though they were fertilized (released from arrest), thus disrupting the normal synchrony between fertilization and completion of meiosis and rendering them dysfunctional. These findings suggest that abnormal cholesterol metabolism may contribute to some forms of human female infertility.
Ventromedial prefrontal cortex supports affective future simulation by integrating distributed knowledge
Authors: Benoit Roland G. , Szpunar Karl K. , Schacter Daniel L.
Published: November 2014

Significance

Decisions concerning the future are often informed by past experiences. However, in a complex world, we frequently have to make choices for prospective scenarios that we haven’t yet encountered. The present study demonstrates a critical role for the ventromedial prefrontal cortex in simulating what it may feel like to experience such future events. We show that this region contributes to integrating knowledge related to the elements that constitute the episode (e.g., the episode’s location and protagonists). Its activation then indicates the episode’s emergent or overall anticipated affective quality. By this process, the ventromedial prefrontal cortex fundamentally supports our ability to predict possible future affective states, a mechanism that can be flexibly used to augment future oriented decisions.
The securitization of dual citizenship. National security concerns and the making of the Overseas Citizenship of India
Authors: Naujoks Daniel
Published: November 2014

When India first introduced the Overseas Citizenship of India (OCI) in 2003 under the label of “dual citizenship”, potential links between this new diasporic membership status and national security concerns were not publicly discussed, while such concerns influenced the shape of this membership policy and its limitations behind closed doors. On the other hand, during an extensive parliamentary debate on amending OCI legislation in 2005, 16 out of 34 speakers made 55 references to national security. Based on 50 interviews with Indian policy-makers and an extensive analysis of Parliamentary debates, this essay considers core tenets of the securitization framework from the emigration perspective, advancing our comprehension of discussions on diaspora membership and dual citizenship in countries of origin. Specifically, it sheds light on several security narratives in the policy-making process in the lead up to the Citizenship (Amendment) Acts of 2003 and 2005, and how perceptions of dual citizenship as a security risk, including links to terrorism, organized crime and diplomatic relations to other countries, shaped the OCI. It explores how institutional paradigms and developments in adjacent policy arenas affected the debates, and when discourse limitations led to the omission of security discussions in the positively framed diaspora engagement discourse.
Repetitive centromeric satellite RNA is essential for kinetochore formation and cell division
Authors: Rošić Silvana , Köhler Florian , Erhardt Sylvia
Published: November 2014

Chromosome segregation requires centromeres on every sister chromatid to correctly form and attach the microtubule spindle during cell division. Even though centromeres are essential for genome stability, the underlying centromeric DNA is highly variable in sequence and evolves quickly. Epigenetic mechanisms are therefore thought to regulate centromeres. Here, we show that the 359-bp repeat satellite III (SAT III), which spans megabases on the X chromosome of Drosophila melanogaster, produces a long noncoding RNA that localizes to centromeric regions of all major chromosomes. Depletion of SAT III RNA causes mitotic defects, not only of the sex chromosome but also in trans of all autosomes. We furthermore find that SAT III RNA binds to the kinetochore component CENP-C, and is required for correct localization of the centromere-defining proteins CENP-A and CENP-C, as well as outer kinetochore proteins. In conclusion, our data reveal that SAT III RNA is an integral part of centromere identity, adding RNA to the complex epigenetic mark at centromeres in flies.
A fluorescent tagging approach in Drosophila reveals late endosomal trafficking of Notch and Sanpodo
Authors: Couturier Lydie , Trylinski Mateusz , Mazouni Khallil , Darnet Léa , Schweisguth François
Published: November 2014

Signaling and endocytosis are highly integrated processes that regulate cell fate. In the Drosophila melanogaster sensory bristle lineages, Numb inhibits the recycling of Notch and its trafficking partner Sanpodo (Spdo) to regulate cell fate after asymmetric cell division. In this paper, we have used a dual GFP/Cherry tagging approach to study the distribution and endosomal sorting of Notch and Spdo in living pupae. The specific properties of GFP, i.e., quenching at low pH, and Cherry, i.e., slow maturation time, revealed distinct pools of Notch and Spdo: cargoes exhibiting high GFP/low Cherry fluorescence intensities localized mostly at the plasma membrane and early/sorting endosomes, whereas low GFP/high Cherry cargoes accumulated in late acidic endosomes. These properties were used to show that Spdo is sorted toward late endosomes in a Numb-dependent manner. This dual-tagging approach should be generally applicable to study the trafficking dynamics of membrane proteins in living cells and tissues.
Congruence formula for certain dihedral twists
Authors: Shekhar Sudhanshu , Sujatha R.
Published: November 2014

In this article we prove a congruence formula for the special values of certain dihedral twists of two primitive modular forms of weight two with isomorphic residual Galois representation at a prime

p
p

.
Inelastic and Fragmented Farm Supply Response for Second‐generation Bioenergy Feedstocks: Ex Ante Survey Evidence from Wisconsin
Authors: Mooney Daniel F. , Barham Bradford L. , Lian Chang
Published: November 2014

Second‐generation bioenergy feedstocks stand poised to become a key component of the nation's agricultural and energy sectors, yet few studies have examined farm supply response using survey information. We use contingent valuation data from farmers in southwestern Wisconsin to develop ex ante supply estimates for two prospective feedstocks—corn stover and switchgrass—in terms of farmers' extensive and intensive acreage decisions. Supply response is found to be price inelastic and spatially fragmented, making widespread production unlikely in the near‐term. However, heterogeneity in farmer reservation prices suggests that agglomerations or “hot spots” of feedstock supply could arise at local or regional levels.
Halophilic archaea on Earth and in space: growth and survival under extreme conditions
Authors: Oren Aharon
Published: November 2014

Salts are abundant on Mars, and any liquid water that is present or may have been present on the planet is expected to be hypersaline. Halophilic archaea (family Halobacteriaceae) are the microorganisms best adapted to life at extremes of salinity on Earth. This paper reviews the properties of the Halobacteriaceae that may make the group good candidates for life also on Mars. Many species resist high UV and gamma radiation levels; one species has survived exposure to vacuum and radiation during a space flight; and there is at least one psychrotolerant species. Halophilic archaea may survive for millions of years within brine inclusions in salt crystals. Many species have different modes of anaerobic metabolism, and some can use light as an energy source using the light-driven proton pump bacteriorhodopsin. They are also highly tolerant to perchlorate, recently shown to be present in Martian soils, and some species can even use perchlorate as an electron acceptor to support anaerobic growth. The presence of characteristic carotenoid pigments (
α
-bacterioruberin and derivatives) makes the Halobacteriaceae easy to identify by Raman spectroscopy. Thus, if present on Mars, such organisms may be detected by Raman instrumentation planned to explore Mars during the upcoming ExoMars mission.
Miniaturized Raman instrumentation detects carotenoids in Mars-analogue rocks from the Mojave and Atacama deserts
Authors: Vítek P. , Jehlička J. , Edwards H. G. M. , Hutchinson I. , Ascaso C. , Wierzchos J.
Published: November 2014

This study is primarily focused on proving the potential of miniaturized Raman systems to detect any biomolecular and mineral signal in natural geobiological samples that are relevant for future application of the technique within astrobiologically aimed missions on Mars. A series of evaporites of varying composition and origin from two extremely dry deserts were studied, namely Atacama and Mojave. The samples represent both dry evaporitic deposits and recent evaporitic efflorescences from hypersaline brines. The samples comprise halite and different types of sulfates and carbonates. The samples were analysed in two different ways: (i) directly as untreated rocks and (ii) as homogenized powders. Two excitation wavelengths of miniaturized Raman spectrometers were compared: 532 and 785 nm. The potential to detect carotenoids as biomarkers on Mars compared with the potential detection of carbonaceous matter using miniaturized instrumentation is discussed.
Raman spectroscopic identification of scytonemin and its derivatives as key biomarkers in stressed environments
Authors: Varnali Tereza , Edwards Howell G. M.
Published: November 2014

Raman spectroscopy has been identified as an important first-pass analytical technique for deployment on planetary surfaces as part of a suite of instrumentation in projected remote space exploration missions to detect extant or extinct extraterrestrial life signatures. Aside from the demonstrable advantages of a non-destructive sampling procedure and an ability to record simultaneously the molecular signatures of biological, geobiological and geological components in admixture in the geological record, the interrogation and subsequent interpretation of spectroscopic data from these experiments will be critically dependent upon the recognition of key biomolecular markers indicative of life existing or having once existed in extreme habitats. A comparison made with the characteristic Raman spectral wavenumbers obtained from standards is not acceptable because of shifts that can occur in the presence of other biomolecules and their host mineral matrices. In this paper, we identify the major sources of difficulty experienced in the interpretation of spectroscopic data centring on a key family of biomarker molecules, namely scytonemin and its derivatives; the parent scytonemin has been characterized spectroscopically in cyanobacterial colonies inhabiting some of the most extreme terrestrial environments and, with the support of theoretical calculations, spectra have been predicted for the characterization of several of its derivatives which could occur in novel extraterrestrial environments. This work will form the foundation for the identification of novel biomarkers and for their Raman spectroscopic discrimination, an essential step in the interpretation of potentially complex and hitherto unknown biological radiation protectants based on the scytoneman and scytonin molecular skeletons which may exist in niche geological scenarios in the surface and subsurface of planets and their satellites in our Solar System.
Mineralogical analyses of surface sediments in the Antarctic Dry Valleys: coordinated analyses of Raman spectra, reflectance spectra and elemental abundances
Authors: Bishop Janice L. , Englert Peter A. J. , Patel Shital , Tirsch Daniela , Roy Alex J. , Koeberl Christian , Böttger Ute , Hanke Franziska , Jaumann Ralf
Published: November 2014

Surface sediments at Lakes Fryxell, Vanda and Brownworth in the Antarctic Dry Valleys (ADV) were investigated as analogues for the cold, dry environment on Mars. Sediments were sampled from regions surrounding the lakes and from the ice cover on top of the lakes. The ADV sediments were studied using Raman spectra of individual grains and reflectance spectra of bulk particulate samples and compared with previous analyses of subsurface and lakebottom sediments. Elemental abundances were coordinated with the spectral data in order to assess trends in sediment alteration. The surface sediments in this study were compared with lakebottom sediments (Bishop JL
et al
. 2003
Int. J. Astrobiol
.
2
, 273–287 (
doi:10.1017/S1473550403001654
)) and samples from soil pits (Englert P
et al
. 2013 In
European Planetary Science Congress
, abstract no. 96; Englert P
et al
. 2014 In
45th Lunar and Planetary Science Conf.
, abstract no. 1707). Feldspar, quartz and pyroxene are common minerals found in all the sediments. Minor abundances of carbonate, chlorite, actinolite and allophane are also found in the surface sediments, and are similar to minerals found in greater abundance in the lakebottom sediments. Surface sediment formation is dominated by physical processes; a few centimetres below the surface chemical alteration sets in, whereas lakebottom sediments experience biomineralization. Characterizing the mineralogical variations in these samples provides insights into the alteration processes occurring in the ADV and supports understanding alteration in the cold and dry environment on Mars.
Raman spectroscopic fingerprints of scytonemin-imine: density functional theory calculations of a novel potential biomarker
Authors: Varnali Tereza , Edwards Howell G. M.
Published: November 2014

Scytonemin-imine, a novel derivative of scytonemin, has been isolated and identified very recently and proposed to serve as a photoprotective biomarker for certain bacteria growing under intense photon flux density. This study predicts theoretically the Raman spectrum of scytonemin-imine by density functional theory calculations and provides comparison of major bands to those of scytonemin, the parent compound for which both the experimentally characterized and theoretically predicted spectra exist in the literature. It is proposed to be an addendum to the collection of our previous work on scytonamin and its derivatives to facilitate recognition of the diagnostic Raman spectral signatures for scytonemin-imine.
Mobile Raman spectroscopy in astrobiology research
Authors: Vandenabeele Peter , Jehlička Jan
Published: November 2014

Raman spectroscopy has proved to be a very useful technique in astrobiology research. Especially, working with mobile instrumentation during fieldwork can provide useful experiences in this field. In this work, we provide an overview of some important aspects of this research and, apart from defining different types of mobile Raman spectrometers, we highlight different reasons for this research. These include gathering experience and testing of mobile instruments, the selection of target molecules and to develop optimal data processing techniques for the identification of the spectra. We also identify the analytical techniques that it would be most appropriate to combine with Raman spectroscopy to maximize the obtained information and the synergy that exists with Raman spectroscopy research in other research areas, such as archaeometry and forensics.
Pontibacillus salicampi sp. nov., a moderately halophilic bacterium isolated from saltern soil
Authors: Lee Jae-Chan , Kim Young-Sook , Yun Bong-Sik , Whang Kyung-Sook
Published: November 2014

A Gram-stain-positive, moderately halophilic bacterium, designated BH043T, was isolated from saltern soil of Gomso in Korea. Cells were motile rods, producing ellipsoidal endospores at a terminal position in swollen sporangia. Strain BH043T was strictly aerobic, grew at pH 6.0–10.0 (optimal growth at pH 7.5), at 10–55 °C (optimal growth at 30 °C) and at salinities of 1–20 % (w/v) NaCl, growing optimally with 7 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain BH043T belongs to the family

Bacillaceae

and was most closely related to the type strains of the five recognized species of the genus

Pontibacillus

, showing sequence similarity to

Pontibacillus yanchengensis

Y32T (97.5 % similarity),

Pontibacillus marinus

BH030004T (97.4 %),

Pontibacillus chungwhensis

BH030062T (97.0 %),

Pontibacillus litoralis

JSM 072002T (96.4 %) and

Pontibacillus halophilus

JSM 076056T (96.2 %). The major cellular fatty acids of strain BH043T were iso-C15 : 0 and anteiso-C15 : 0. The genomic DNA G+C content was 42.5 mol%. The major isoprenoid quinone was MK-7 and meso-diaminopimelic acid was present in the cell-wall peptidoglycan as the diagnostic diamino acid. The major polar lipids were phosphatidylethanolamine and phosphatidylglycerol. DNA–DNA relatedness between strain BH043T and the type strains of other species of the genus

Pontibacillus

,

P. yanchengensis

CGMCC 1.10680T and

P. marinus

KCTC 3917T and

P. chungwhensis

KCTC 3890T, was 35, 24 and 18 %, respectively. On the basis of polyphasic analysis from this study, strain BH043T represents a novel species of the genus

Pontibacillus

for which the name Pontibacillus
salicampi sp. nov. is proposed. The type strain is BH043T ( = KACC 17607T = NBRC 109831T = NCAIM B.02529T).