bluuebunny/crossref_metadata_2025 huggingface dataset:
Palm top plasma focus device as a portable pulsed neutron source
Authors: Rout R. K. , Niranjan Ram , Mishra P. , Srivastava R. , Rawool A. M. , Kaushik T. C. , Gupta Satish C.
Published: June 2013

Development of a palm top plasma focus device generating (5.2 ± 0.8) × 104 neutrons/pulse into 4π steradians with a pulse width of 15 ± 3 ns is reported for the first time. The weight of the system is less than 1.5 kg. The system comprises a compact capacitor bank, a triggered open air spark gap switch, and a sealed type miniature plasma focus tube. The setup is around 14 cm in diameter and 12.5 cm in length. The energy driver for the unit is a capacitor bank of four cylindrical commercially available electrolytic capacitors. Each capacitor is of 2 μF capacity, 4.5 cm in diameter, and 9.8 cm in length. The cost of each capacitor is less than US$ 10. The internal diameter and the effective length of the plasma focus unit are 2.9 cm and 5 cm, respectively. A DC to DC converter power supply powered by two rechargeable batteries charges the capacitor bank to the desired voltage and also provides a trigger pulse of −15 kV to the spark gap. The maximum energy of operation of the device is 100 J (8 μF, 5 kV, 59 kA) with deuterium gas filling pressure of 3 mbar. The neutrons have also been produced at energy as low as 36 J (3 kV) of operation. The neutron diagnostics are carried out with a bank of 3He detectors and with a plastic scintillator detector. The device is portable, reusable, and can be operated for multiple shots with a single gas filling.
The electrostatic response of water to neutral polar solutes: Implications for continuum solvent modeling
Authors: Muddana Hari S. , Sapra Neil V. , Fenley Andrew T. , Gilson Michael K.
Published: June 2013

Continuum solvation models are widely used to estimate the hydration free energies of small molecules and proteins, in applications ranging from drug design to protein engineering, and most such models are based on the approximation of a linear dielectric response by the solvent. We used explicit-water molecular dynamics simulations with the TIP3P water model to probe this linear response approximation in the case of neutral polar molecules, using miniature cucurbituril and cyclodextrin receptors and protein side-chain analogs as model systems. We observe supralinear electrostatic solvent responses, and this nonlinearity is found to result primarily from waters’ being drawn closer and closer to the solutes with increased solute-solvent electrostatic interactions; i.e., from solute electrostriction. Dielectric saturation and changes in the water-water hydrogen bonding network, on the other hand, play little role. Thus, accounting for solute electrostriction may be a productive approach to improving the accuracy of continuum solvation models.
High-pressure resistivity technique for quasi-hydrostatic compression experiments
Authors: Rotundu C. R. , Ćuk T. , Greene R. L. , Shen Z.-X. , Hemley Russell J. , Struzhkin V. V.
Published: June 2013

Diamond anvil cell techniques are now well established and powerful methods for measuring materials properties to very high pressure. However, high pressure resistivity measurements are challenging because the electrical contacts attached to the sample have to survive to extreme stress conditions. Until recently, experiments in a diamond anvil cell were mostly limited to non-hydrostatic or quasi-hydrostatic pressure media other than inert gases. We present here a solution to the problem by using focused ion beam ultrathin lithography for a diamond anvil cell loaded with inert gas (Ne) and show typical resistivity data. These ultrathin leads are deposited on the culet of the diamond and are attaching the sample to the anvil mechanically, therefore allowing for measurements in hydrostatic or nearly hydrostatic conditions of pressure using noble gases like Ne or He as pressure transmitting media.
Architecture, implementation, and testing of a multiple-shell gas injection system for high current implosions on the Z accelerator
Authors: Krishnan Mahadevan , Elliott Kristi Wilson , Madden Robert E. , Coleman P. L. , Thompson John R. , Bixler Alex , Lamppa D. C. , McKenney J. L. , Strizic T. , Johnson D. , Johns O. , Vigil M. P. , Jones B. , Ampleford D. J. , Savage M. E. , Cuneo M. E. , Jones M. C.
Published: June 2013

Tests are ongoing to conduct ∼20 MA z-pinch implosions on the Z accelerator at Sandia National Laboratory using Ar, Kr, and D2 gas puffs as the imploding loads. The relatively high cost of operations on a machine of this scale imposes stringent requirements on the functionality, reliability, and safety of gas puff hardware. Here we describe the development of a prototype gas puff system including the multiple-shell nozzles, electromagnetic drivers for each nozzle's valve, a UV pre-ionizer, and an inductive isolator to isolate the ∼2.4 MV machine voltage pulse present at the gas load from the necessary electrical and fluid connections made to the puff system from outside the Z vacuum chamber. This paper shows how the assembly couples to the overall Z system and presents data taken to validate the functionality of the overall system.
Laser ablation of ceramic Al2O3 at 193 nm and 248 nm: The importance of single-photon ionization processes
Authors: Peláez R. J. , Afonso C. N. , Bator M. , Lippert T.
Published: June 2013

The aim of this work is to demonstrate that single-photon photoionization processes make a significant difference in the expansion and temperature of the plasma produced by laser ablation of ceramic Al2O3 in vacuum as well as to show their consequences in the kinetic energy distribution of the species that eventually will impact on the film properties produced by pulsed laser deposition. This work compares results obtained by mass spectrometry and optical spectroscopy on the composition and features of the plasma produced by laser ablation at 193 nm and 248 nm, i.e., photon energies that are, respectively, above and below the ionization potential of Al, and for fluences between threshold for visible plasma and up to ≈2 times higher. The results show that the ionic composition and excitation of the plasma as well as the ion kinetic energies are much higher at 193 nm than at 248 nm and, in the latter case, the population of excited ions is even negligible. The comparison of Maxwell-Boltzmann temperature, electron temperatures, and densities of the plasmas produced with the two laser wavelengths suggests that the expansion of the plasma produced at 248 nm is dominated by a single population. Instead, the one produced at 193 nm is consistent with the existence of two populations of cold and hot species, the latter associated to Al+ ions that travel at the forefront and produced by single photon ionization as well as Al neutrals and double ionized ions produced by electron-ion impact. The results also show that the most energetic Al neutrals in the plasma produced at the two studied wavelengths are in the ground state.
Structure and magnetoresistance of current-perpendicular-to-plane pseudo spin valves using Co2Mn(Ga0.25Ge0.75) Heusler alloy
Authors: Takahashi Y. K. , Hase N. , Kodzuka M. , Itoh A. , Koganezawa T. , Furubayashi T. , Li S. , Varaprasad B. S. D. Ch. S. , Ohkubo T. , Hono K.
Published: June 2013

We have investigated the structure and magnetoresistance of current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) pseudo spin valves (PSVs) using Co2Mn(Ga0.25Ge0.75) (CMGG) Heusler alloy ferromagnetic layers annealed at different temperatures. Relatively large ΔRA of 6.1 mΩμm2 and MR ratio of 40.2% were obtained in the CPP-PSV annealed at 400 °C. Annealing at higher than 400 °C led to a significant deterioration of MR outputs. Detailed structure analysis using transmission electron microscopy, three-dimensional atom probe, and synchrotron x-ray diffraction showed that the degradation of MR in the over-annealed sample was due to the increase of DO3 disorder in the CMGG layer, while the layered structure of the film is fully preserved.
Carrier transport in green AlInGaN based structures on c-plane substrates
Authors: Hager T. , Binder M. , Brüderl G. , Eichler C. , Avramescu A. , Wurm T. , Gomez-Iglesias A. , Stojetz B. , Tautz S. , Galler B. , Gerhard S. , Zeisel R. , Strauss U.
Published: June 2013

In this paper, the carrier transport in (Al)InGaN based test structures with In-rich quantum wells on c-plane substrates is investigated under high current operation. To get access to the injection efficiency, the devices are processed as ridge waveguide lasers and examined above threshold. The slope efficiency reveals a slight decrease as a function of current even under pulsed operation that can be related to a reduction of the injection efficiency based on carrier leakage. As the test structure contains an InGaN detection layer on the n-side, it is possible to verify hole overflow across the active region. Moreover, by analysing the current dependence of the radiative recombination in the detection layer, the reduction of slope efficiency can be correlated to increasing hole leakage.
Super-resolution of dense nanoscale emitters beyond the diffraction limit using spatial and temporal information
Authors: Barsic Anthony , Piestun Rafael
Published: June 2013

We propose a super-resolution technique for dense clusters of blinking emitters. The method relies on two basic assumptions: the emitters are statistically independent and a model of the imaging system is known. We numerically analyze the performance limits of the method as a function of emitter density and noise level. Numerical simulations show that five closely packed emitters can be resolved and localized to a precision of 17 nm. The experimental resolution of five quantum dots located within a diffraction-limited spot confirms the applicability of this approach. Statistical tests validate the independence of our quantum dots separated by nanoscale distances.
Compressive object tracking using entangled photons
Authors: Magaña-Loaiza Omar S. , Howland Gregory A. , Malik Mehul , Howell John C. , Boyd Robert W.
Published: June 2013

We present a compressive sensing protocol that tracks a moving object by removing static components from a scene. The implementation is carried out on a ghost imaging scheme to minimize both the number of photons and the number of measurements required to form a quantum image of the tracked object. This procedure tracks an object at low light levels with fewer than 3% of the measurements required for a raster scan, permitting us to more effectively use the information content in each photon.
Dynamics of water droplet on a heated nanotubes surface
Authors: Kim Seol Ha , Seon Ahn Ho , Kim Joonwon , Kaviany Massoud , Hwan Kim Moo
Published: June 2013

This study investigated an effect of nanotubes on a heated surface onto Leidenfrost droplet through high speed visualization and momentum balance analysis. Delayed cutback phenomena and Leidenfrost Point (LFP) by dramatically high heating level were observed, and it is elucidated through wettable and spreadable features induced by nanotubes. As much delayed LFP, transient boiling regime with explosion-like dynamics of a water droplet on the nanotubes was observed. Furthermore, nanotubes required higher wall temperature to maintain non wetting cushion, due to the induced slip condition by porous features.
Enhanced vertical and lateral hole transport in high aluminum-containing AlGaN for deep ultraviolet light emitters
Authors: Cheng B. , Choi S. , Northrup J. E. , Yang Z. , Knollenberg C. , Teepe M. , Wunderer T. , Chua C. L. , Johnson N. M.
Published: June 2013

Improved p-type conductivity is demonstrated in AlGaN:Mg superlattice (SL) cladding layers with average Al composition ∼60%. The vertical conductivity ranges from 6.6 × 10−5 S/cm at a DC current of 1 mA to ∼0.1 S/cm at 550 mA and approaches the lateral conductivity that was obtained from Hall-effect measurements. The effective acceptor activation energy (EA) in the SL was determined to be 17 meV, nearly 10× smaller than EA in homogeneous p-GaN. The devices sustain current densities of 11 kA/cm2 under DC and up to 21 kA/cm2 under pulsed operation.
Coupled optical and electrical modeling of solar cell based on conical pore silicon photonic crystals
Authors: Deinega Alexei , Eyderman Sergey , John Sajeev
Published: June 2013

We compare the efficiency of thin film photonic crystal solar cells consisting of conical pores and nanowires. Solving both Maxwell's equations and the semiconductor drift-diffusion in each geometry, we identify optimal junction and contact positions and study the influence of bulk and surface recombination losses on solar cell efficiency. We find that using only 1 μm of silicon, sculpted in the form of an inverted slanted conical pore photonic crystal film, and using standard contact recombination velocities, solar power conversion efficiency of 17.5% is obtained when the carrier diffusion length exceeds 10 μm. Reducing the contact recombination velocity to 100 cm s−1 yields efficiency up to 22.5%. Further efficiency improvements are possible (with 1 μm of silicon) in a tandem cell with amorphous silicon at the top.
Active plasmonic switching at mid-infrared wavelengths with graphene ribbon arrays
Authors: Chu Hong-Son , How Gan Choon
Published: June 2013

An active plasmonic switch based on single- and few-layer doped graphene ribbon array operating in the mid-infrared spectrum is investigated with theoretical and numerical calculations. It is shown that significant resonance wavelength shifts and modulation depths can be achieved with a slight variation of the doping concentration of the graphene ribbon. The few-layer graphene ribbon array device outperforms the single-layer one in terms of the achievable modulation depth. Our simulations reveal that, by modulating the Fermi-energy level between 0.2 eV and 0.25 eV, a four-layer graphene ribbon array device can achieve a modulation depth and resonance wavelength shift of ∼13 dB and 0.94 μm, respectively, compared to ∼2.8 dB and 1.85 μm for a single-layer device. Additionally, simple fitting models to predict the modulation depth and the resonance wavelength shift are proposed. These prospects pave the way towards ultrafast active graphene-based plasmonic devices for infrared and THz applications.
Specially designed long period grating with internal geometric bending for enhanced refractive index sensitivity
Authors: Chiavaioli F. , Trono C. , Baldini F.
Published: June 2013

We propose a long period grating (LPG) characterized by specially designed refractive index (RI) profile in which each grating plane is tilted at increasing angles, as moving away from the center of symmetry of the structure towards its both edges. This internally manufactured geometric structure, which basically simulates the bending of an optical fiber, increases the RI sensitivity of an LPG to the external medium. We experimentally demonstrate a three-fold improvement in the RI sensitivity, thus providing the basis for another step forward in the field of RI sensors based on optical fiber gratings.
Fabrication of doubly resonant plasmonic nanopatch arrays on graphene
Authors: Grande M. , Stomeo T. , Bianco G. V. , Vincenti M. A. , de Ceglia D. , Petruzzelli V. , Bruno G. , De Vittorio M. , Scalora M. , D'Orazio A.
Published: June 2013

We report theoretical and experimental investigations of the optical response of two-dimensional periodic arrays of rectangular gold nanopatches grown on a monolayer graphene placed on a glass substrate. We discuss the numerical analysis and optical characterization by means of reflection spectra and show that rectangular nanopatches display a polarization-dependent response, at normal incidence, which leads to double plasmonic resonances due to the Wood anomaly. We detail the fabrication process highlighting how the resist primer and the adhesion layer can reduce and impede the graphene doping due to the environment and to the nanopatches, respectively, by means of Raman spectroscopy.
Assessing Reproductive Condition in Captive and Wild Common Snook Stocks: A Comparison between the Wet Mount Technique and Histological Preparations
Authors: Rhody N. R. , Neidig C. L. , Grier H. J. , Main K. L. , Migaud H.
Published: June 2013

We describe oocyte development in Common Snook Centropomus undecimalis and, secondarily, present results from a comparison of the wet mount technique with histological preparations of ovarian biopsies. Potential differences in ovarian development between wild and captive broodstock were investigated. Results showed that mean oocyte diameter (μm) was not statistically different between the two groups or within each defined stage and step of reproductive condition. Histological preparations were used to validate the wet mount technique as a rapid, yet accurate, low‐cost alternative for assessing reproductive condition in Common Snook. When compared with histology, the wet mount provided a precise method for determining whether female broodstock were candidates for hormone induction in aquaculture applications. However, due to the loss of fine resolution, it was not possible to identify cortical alveoli, oocyte atresia, and postovulatory follicle complexes by using the wet mount technique. Despite these limitations, findings from this study indicate that the wet mount technique may have applications in fishery biology as a noninvasive method for assessing reproductive condition in wild fish stocks.
Building inter-ethnic bridges or promoting ethno-territorial demarcation lines? Hungarian minority parties in competition
Authors: Bochsler Daniel , Szöcsik Edina
Published: June 2013

Parties of ethnic minorities are flourishing in a large number of ethnically divided democracies. While academic research has studied their emergence and success, we know little about intra-group party competition. This paper discusses the reasons for intra-group political plurality, with a focus on intra-party conflict and intra-group party competition: it explains the political orientation of ethnic minority parties and their intra-group challengers as a consequence of the inclusion of minority parties into government. The inclusion of minority parties into national governments produces an inherent conflict between pragmatic office-seekers and radical partisans. In minority parties that have governmental responsibilities, the pragmatist view overwhelms, while in those parties in opposition, radical voices dominate. The formation of two intra-Hungarian challenger parties in Romania and in Slovakia in 2007 and 2009 represents two very similar cases, which appear to be in line with our hypotheses.
One hippopotamus and eight blind analysts: a multivocal analysis of the 2012 political crisis in the divided Republic of Mali
Authors: Lecocq Baz , Mann Gregory , Whitehouse Bruce , Badi Dida , Pelckmans Lotte , Belalimat Nadia , Hall Bruce , Lacher Wolfram
Published: June 2013

This is an exercise in contemporary history that aims to give a comprehensive background and analysis to the current (2012) political crisis in Mali, generated by the start of a new Tuareg nationalist uprising against the state, complemented by a coordinated attack on the state by both international (AQIM) and local Jihadi–Salafi movements, leading to a coup d’état against the incumbent President Touré, and finallly a political stalemate of great concern to the international community. By pooling sources and analysis, a group of eight scholars tries to give a comprehensive overall picture.

[Un hippopotame et huit analystes aveugles : une analyse à plusieurs voix de la crise politique de 2012 dans la République du Mali divisée.] Cet exercice d'histoire contemporaine vise à fournir le contexte et une analyse complète de l'actuelle crise politique au Mali (2012). Initiée par l'amorce d'un nouveau soulèvement nationaliste touareg, la crise s'est aggravée suite à l'attaque coordonnée de mouvements salafistes jihadistes internationaux (Aqmi) et locaux contre l'Etat malien, conduisant à un coup d'Etat contre le président Touré en exercice, et, finalement, à une impasse politique inquiétante pour la communauté internationale. Mettant en commun sources et analyses, un groupe de huit chercheurs tente de fournir une étude complète de la situation.

Mots-clés : Mali ; Azawad ; Sahel ; djihad ; Touareg ; rébellion
Dynamic microtubules produce an asymmetric E-cadherin–Bazooka complex to maintain segment boundaries
Authors: Bulgakova Natalia A. , Grigoriev Ilya , Yap Alpha S. , Akhmanova Anna , Brown Nicholas H.
Published: June 2013

Distributing junctional components around the cell periphery is key for epithelial tissue morphogenesis and homeostasis. We discovered that positioning of dynamic microtubules controls the asymmetric accumulation of E-cadherin. Microtubules are oriented preferentially along the dorso-ventral axis in Drosophila melanogaster embryonic epidermal cells, and thus more frequently contact E-cadherin at dorso-ventral cell–cell borders. This inhibits RhoGEF2, reducing membrane recruitment of Rho-kinase, and increasing a specific E-cadherin pool that is mobile when assayed by fluorescence recovery after photobleaching. This mobile E-cadherin is complexed with Bazooka/Par-3, which in turn is required for normal levels of mobile E-cadherin. Mobile E-cadherin–Bazooka prevents formation of multicellular rosette structures and cell motility across the segment border in Drosophila embryos. Altogether, the combined action of dynamic microtubules and Rho signaling determines the level and asymmetric distribution of a mobile E-cadherin–Bazooka complex, which regulates cell behavior during the generation of a patterned epithelium.
A Wee1 checkpoint inhibits anaphase onset
Authors: Lianga Noel , Williams Elizabeth C. , Kennedy Erin K. , Doré Carole , Pilon Sophie , Girard Stéphanie L. , Deneault Jean-Sebastien , Rudner Adam D.
Published: June 2013

Cdk1 drives both mitotic entry and the metaphase-to-anaphase transition. Past work has shown that Wee1 inhibition of Cdk1 blocks mitotic entry. Here we show that the budding yeast Wee1 kinase, Swe1, also restrains the metaphase-to-anaphase transition by preventing Cdk1 phosphorylation and activation of the mitotic form of the anaphase-promoting complex/cyclosome (APCCdc20). Deletion of SWE1 or its opposing phosphatase MIH1 (the budding yeast cdc25+) altered the timing of anaphase onset, and activation of the Swe1-dependent morphogenesis checkpoint or overexpression of Swe1 blocked cells in metaphase with reduced APC activity in vivo and in vitro. The morphogenesis checkpoint also depended on Cdc55, a regulatory subunit of protein phosphatase 2A (PP2A). cdc55Δ checkpoint defects were rescued by mutating 12 Cdk1 phosphorylation sites on the APC, demonstrating that the APC is a target of this checkpoint. These data suggest a model in which stepwise activation of Cdk1 and inhibition of PP2ACdc55 triggers anaphase onset.
RNF111/Arkadia is a SUMO-targeted ubiquitin ligase that facilitates the DNA damage response
Authors: Poulsen Sara L. , Hansen Rebecca K. , Wagner Sebastian A. , van Cuijk Loes , van Belle Gijsbert J. , Streicher Werner , Wikström Mats , Choudhary Chunaram , Houtsmuller Adriaan B. , Marteijn Jurgen A. , Bekker-Jensen Simon , Mailand Niels
Published: June 2013

Protein modifications by ubiquitin and small ubiquitin-like modifier (SUMO) play key roles in cellular signaling pathways. SUMO-targeted ubiquitin ligases (STUbLs) directly couple these modifications by selectively recognizing SUMOylated target proteins through SUMO-interacting motifs (SIMs), promoting their K48-linked ubiquitylation and degradation. Only a single mammalian STUbL, RNF4, has been identified. We show that human RNF111/Arkadia is a new STUbL, which used three adjacent SIMs for specific recognition of poly-SUMO2/3 chains, and used Ubc13–Mms2 as a cognate E2 enzyme to promote nonproteolytic, K63-linked ubiquitylation of SUMOylated target proteins. We demonstrate that RNF111 promoted ubiquitylation of SUMOylated XPC (xeroderma pigmentosum C) protein, a central DNA damage recognition factor in nucleotide excision repair (NER) extensively regulated by ultraviolet (UV)-induced SUMOylation and ubiquitylation. Moreover, we show that RNF111 facilitated NER by regulating the recruitment of XPC to UV-damaged DNA. Our findings establish RNF111 as a new STUbL that directly links nonproteolytic ubiquitylation and SUMOylation in the DNA damage response.
Liprin-α2 promotes the presynaptic recruitment and turnover of RIM1/CASK to facilitate synaptic transmission
Authors: Spangler Samantha A. , Schmitz Sabine K. , Kevenaar Josta T. , de Graaff Esther , de Wit Heidi , Demmers Jeroen , Toonen Ruud F. , Hoogenraad Casper C.
Published: June 2013

The presynaptic active zone mediates synaptic vesicle exocytosis, and modulation of its molecular composition is important for many types of synaptic plasticity. Here, we identify synaptic scaffold protein liprin-α2 as a key organizer in this process. We show that liprin-α2 levels were regulated by synaptic activity and the ubiquitin–proteasome system. Furthermore, liprin-α2 organized presynaptic ultrastructure and controlled synaptic output by regulating synaptic vesicle pool size. The presence of liprin-α2 at presynaptic sites did not depend on other active zone scaffolding proteins but was critical for recruitment of several components of the release machinery, including RIM1 and CASK. Fluorescence recovery after photobleaching showed that depletion of liprin-α2 resulted in reduced turnover of RIM1 and CASK at presynaptic terminals, suggesting that liprin-α2 promotes dynamic scaffolding for molecular complexes that facilitate synaptic vesicle release. Therefore, liprin-α2 plays an important role in maintaining active zone dynamics to modulate synaptic efficacy in response to changes in network activity.
The netrin receptor DCC focuses invadopodia-driven basement membrane transmigration in vivo
Authors: Hagedorn Elliott J. , Ziel Joshua W. , Morrissey Meghan A. , Linden Lara M. , Wang Zheng , Chi Qiuyi , Johnson Sam A. , Sherwood David R.
Published: June 2013

Though critical to normal development and cancer metastasis, how cells traverse basement membranes is poorly understood. A central impediment has been the challenge of visualizing invasive cell interactions with basement membrane in vivo. By developing live-cell imaging methods to follow anchor cell (AC) invasion in Caenorhabditis elegans, we identify F-actin–based invadopodia that breach basement membrane. When an invadopodium penetrates basement membrane, it rapidly transitions into a stable invasive process that expands the breach and crosses into the vulval tissue. We find that the netrin receptor UNC-40 (DCC) specifically enriches at the site of basement membrane breach and that activation by UNC-6 (netrin) directs focused F-actin formation, generating the invasive protrusion and the cessation of invadopodia. Using optical highlighting of basement membrane components, we further demonstrate that rather than relying solely on proteolytic dissolution, the AC’s protrusion physically displaces basement membrane. These studies reveal an UNC-40–mediated morphogenetic transition at the cell–basement membrane interface that directs invading cells across basement membrane barriers.
Means to an end
Authors: Leslie Mitch
Published: June 2013

Bacteria use DNA segregation machinery to position polarity protein.
Asymptotics of generalized Galois numbers via affine Kac-Moody algebras
Authors: Kousidis Stavros
Published: June 2013

Generalized Galois numbers count the number of flags in vector spaces over finite fields. Asymptotically, as the dimension of the vector space becomes large, we give their exponential growth and determine their initial values. The initial values are expressed analytically in terms of theta functions and Euler’s generating function for the partition numbers. Our asymptotic enumeration method is based on a Demazure module limit construction for integrable highest weight representations of affine Kac-Moody algebras. For the classical Galois numbers that count the number of subspaces in vector spaces over finite fields, the theta functions are Jacobi theta functions. We apply our findings to the asymptotic number of linearqq-ary codes and conclude with some final remarks about possible future research concerning asymptotic enumerations via limit constructions for affine Kac-Moody algebras and modularity of characters of integrable highest weight representations.
Spectral geometry of cosmological and event horizons for Kerr-Newman-de Sitter metrics
Authors: Engman Martin , Santana Gerardo
Published: June 2013

We study the Laplace spectra of the intrinsic instantaneous metrics on the event and cosmological horizons of a Kerr-Newman-de Sitter space-time and prove that the spectral data from these horizons uniquely determine the metric among all such space-times. This is accomplished by exhibiting formulae relating the parameters of the space-time metric to the traces of invariant and equivariant Green’s operators associated with these Laplacians. In particular, an interesting explicit formula for the cosmological constant is found.
On the embedding of the attractor generated by Navier-Stokes equations into finite dimensional spaces
Authors: Mohebbi Mahdi
Published: June 2013

For 2-D Navier-Stokes equations on a

C
2

C^2

bounded domain

Ω
\Omega

, a class of nonlinear homeomorphisms is constructed from the attractor of Navier-Stokes to curves in

R

N

\mathbb {R}^N

for sufficiently large

N
N

. The construction uses an

ε
\varepsilon

-net on

Ω
\Omega

(so does not use the information “near” the boundary) and is more physically perceivable compared to abstract common embeddings.
Dehn fillings of knot manifolds containing essential once-punctured tori
Authors: Boyer Steven , Gordon Cameron , Zhang Xingru
Published: June 2013

In this paper we study exceptional Dehn fillings on hyperbolic knot manifolds which contain an essential once-punctured torus. Let

M
M

be such a knot manifold and let

β
\beta

be the boundary slope of such an essential once-punctured torus. We prove that if Dehn filling

M
M

with slope

α
\alpha

produces a Seifert fibred manifold, then

Δ
(
α
,
β
)
≤
5

\Delta (\alpha ,\beta )\leq 5

. Furthermore we classify the triples

(
M
;
α
,
β
)

(M; \alpha ,\beta )

when

Δ
(
α
,
β
)
≥
4

\Delta (\alpha ,\beta )\geq 4

. More precisely, when

Δ
(
α
,
β
)
=
5

\Delta (\alpha ,\beta )=5

, then

M
M

is the (unique) manifold

W
h
(
−
3

/

2
)

Wh(-3/2)

obtained by Dehn filling one boundary component of the Whitehead link exterior with slope

−
3

/

2

-3/2

, and

(
α
,
β
)

(\alpha , \beta )

is the pair of slopes

(
−
5
,
0
)

(-5, 0)

. Further,

Δ
(
α
,
β
)
=
4

\Delta (\alpha ,\beta )=4

if and only if

(
M
;
α
,
β
)

(M; \alpha ,\beta )

is the triple

(
W
h
(

−
2
n
±
1

n

)
;
−
4
,
0
)

\displaystyle (Wh(\frac {-2n\pm 1}{n}); -4, 0)

for some integer

n
n

with

|

n

|

>
1

|n|>1

. Combining this with known results, we classify all hyperbolic knot manifolds

M
M

and pairs of slopes

(
β
,
γ
)

(\beta , \gamma )

on

∂
M

\partial M

where

β
\beta

is the boundary slope of an essential once-punctured torus in

M
M

and

γ
\gamma

is an exceptional filling slope of distance

4
4

or more from

β
\beta

. Refined results in the special case of hyperbolic genus one knot exteriors in

S
3

S^3

are also given.
Infection of Onion Leaves by Pantoea ananatis Leads to Bulb Infection
Authors: Carr Eric A. , Zaid Ali M. , Bonasera Jean M. , Lorbeer James W. , Beer Steven V.
Published: June 2013

Pantoea ananatis has been identified as a cause of center rot of onion. In the field, onion leaves can become infected with P. ananatis and lead to leaf blight. Infected bulbs often are detected only after harvest; however, it has not been demonstrated experimentally that leaf infection by P. ananatis can lead to bulb infection. In this study, onion leaf infection by P. ananatis leading to bulb infection was investigated. Of 18 strains of P. ananatis isolated from symptomatic onion bulbs grown in New York, 14 were pathogenic in bulb and leaf tissue. Pathogenic strains of P. ananatis caused nonmacerated, yellow-brown coloration in fleshy bulb scales following inoculation of bulbs and incubation for 2 days at 28°C. Subepidermal inoculation of onion leaves with pathogenic strains of P. ananatis resulted in gray-white foliar lesions that extended acropetally and basipetally from the points of inoculation. In all, 16% of leaf lesions extended to the onion neck and 11% continued into the bulbs, which developed nonmacerated, yellow-brown scales. Bacteria recovered from the leading edges of lesions had microbiological and molecular characteristics of P. ananatis. This is the first experimental evidence that infection of onion leaves by P. ananatis can lead to bulb infection.
State-dependent signaling by Cav1.2 regulates hair follicle stem cell function
Authors: Yucel Gozde , Altindag Banu , Gomez-Ospina Natalia , Rana Anshul , Panagiotakos Georgia , Lara Maria Fernanda , Dolmetsch Ricardo , Oro Anthony E.
Published: June 2013

The signals regulating stem cell activation during tissue regeneration remain poorly understood. We investigated the baldness associated with mutations in the voltage-gated calcium channel (VGCC) Cav1.2 underlying Timothy syndrome (TS). While hair follicle stem cells express Cav1.2, they lack detectable voltage-dependent calcium currents. Cav1.2TS acts in a dominant-negative manner to markedly delay anagen, while L-type channel blockers act through Cav1.2 to induce anagen and overcome the TS phenotype. Cav1.2 regulates production of the bulge-derived BMP inhibitor follistatin-like1 (Fstl1), derepressing stem cell quiescence. Our findings show how channels act in nonexcitable tissues to regulate stem cells and may lead to novel therapeutics for tissue regeneration.
The methyltransferase SMYD3 mediates the recruitment of transcriptional cofactors at the myostatin and c-Met genes and regulates skeletal muscle atrophy
Authors: Proserpio Valentina , Fittipaldi Raffaella , Ryall James G. , Sartorelli Vittorio , Caretti Giuseppina
Published: June 2013

Elucidating the epigenetic mechanisms underlying muscle mass determination and skeletal muscle wasting holds the potential of identifying molecular pathways that constitute possible drug targets. Here, we report that the methyltransferase SMYD3 modulates myostatin and c-Met transcription in primary skeletal muscle cells and C2C12 myogenic cells. SMYD3 targets the myostatin and c-Met genes and participates in the recruitment of the bromodomain protein BRD4 to their regulatory regions through protein–protein interaction. By recruiting BRD4, SMYD3 favors chromatin engagement of the pause–release factor p-TEFb (positive transcription elongation factor) and elongation of Ser2-phosphorylated RNA polymerase II (PolIISer2P). Reducing SMYD3 decreases myostatin and c-Met transcription, thus protecting from glucocorticoid-induced myotube atrophy. Supporting functional relevance of the SMYD3/BRD4 interaction, BRD4 pharmacological blockade by the small molecule JQ1 prevents dexamethasone-induced myostatin and atrogene up-regulation and spares myotube atrophy. Importantly, in a mouse model of dexamethasone-induced skeletal muscle atrophy, SMYD3 depletion prevents muscle loss and fiber size decrease. These findings reveal a mechanistic link between SMYD3/BRD4-dependent transcriptional regulation, muscle mass determination, and skeletal muscle atrophy and further encourage testing of small molecules targeting specific epigenetic regulators in animal models of muscle wasting.
Development enhances hypometabolism in northern elephant seal pups (Mirounga angustirostris)
Authors: Tift Michael S. , Ranalli Elizabeth C. , Houser Dorian S. , Ortiz Rudy M. , Crocker Daniel E.
Published: June 2013

Investigation into the development of oxygen storage capacity in air‐breathing marine predators has been performed, but little is known about the development of regulatory factors that influence oxygen utilization. Strategies for efficiently using oxygen stores should enable marine predators to optimize time spent foraging underwater.

We describe the developmental patterns of oxygen use during voluntary breath‐holds in northern elephant seals (Mirounga angustirostris) at 2 and 7 weeks postweaning. We measured (i) changes in oxygen consumption (VO2) and (ii) changes in venous pH, partial pressure of oxygen (pO2), haemoglobin saturation (sO2), oxygen content (O2ct), partial pressure of carbon dioxide (pCO2), haematocrit (Hct) and total haemoglobin (tHb). To examine the effect of the dive response on the development of oxygen utilization, voluntary breath‐hold experiments were conducted in and out of water.

Suppression of VO2 during voluntary breath‐holds increased significantly between 2 and 7 weeks postweaning, reaching a maximum suppression of 53% below resting metabolic rate and 56% below Kleiber's standard metabolic rate. From 2 to 7 weeks postweaning, breath‐hold VO2 was reduced by 52%. Between the two age classes, this equates to a mean breath‐hold VO2 reduction of 16% from resting VO2. Breath‐hold VO2 also declined with increasing breath‐hold duration, but there was no direct effect of voluntary submergence on reducing VO2.

Age did not influence rates of venous pO2 depletion during breath‐holds. However, voluntary submergence did result in slower pO2 depletion rates when compared with voluntary terrestrial apnoeas. The differences in whole‐body VO2 during breath‐holds (measured at recovery) and venous pO2 (reflective of tissue O2‐use measured during breath‐holds) likely reflect metabolic suppression in hypoxic, vasoconstricted tissues.

Consistent pCO2 values at the end of all voluntary breath‐holds (59·0 ± 0·7 mmHg) suggest the physiological cue for stimulating respiration in northern elephant seal pups is the accumulation of CO2.

Oxygen storage capacity and metabolic suppression directly limit diving capabilities and may influence foraging success in low‐weaning weight seals forced to depart to sea prior to achieving full developmental diving capacity.
REVIEW: Towards a systems approach for understanding honeybee decline: a stocktaking and synthesis of existing models
Authors: Becher Matthias A. , Osborne Juliet L. , Thorbek Pernille , Kennedy Peter J. , Grimm Volker
Published: June 2013

The health of managed and wild honeybee colonies appears to have declined substantially in Europe and the United States over the last decade. Sustainability of honeybee colonies is important not only for honey production, but also for pollination of crops and wild plants alongside other insect pollinators. A combination of causal factors, including parasites, pathogens, land use changes and pesticide usage, are cited as responsible for the increased colony mortality.

However, despite detailed knowledge of the behaviour of honeybees and their colonies, there are no suitable tools to explore the resilience mechanisms of this complex system under stress. Empirically testing all combinations of stressors in a systematic fashion is not feasible. We therefore suggest a cross‐level systems approach, based on mechanistic modelling, to investigate the impacts of (and interactions between) colony and land management.

We review existing honeybee models that are relevant to examining the effects of different stressors on colony growth and survival. Most of these models describe honeybee colony dynamics, foraging behaviour or honeybee – varroa mite – virus interactions.

We found that many, but not all, processes within honeybee colonies, epidemiology and foraging are well understood and described in the models, but there is no model that couples in‐hive dynamics and pathology with foraging dynamics in realistic landscapes.

Synthesis and applications. We describe how a new integrated model could be built to simulate multifactorial impacts on the honeybee colony system, using building blocks from the reviewed models. The development of such a tool would not only highlight empirical research priorities but also provide an important forecasting tool for policy makers and beekeepers, and we list examples of relevant applications to bee disease and landscape management decisions.
Measuring activity and participation in children and adolescents with disabilities: A literature review of available instruments
Authors: Phillips Rebecca L. , Olds Tim , Boshoff Kobie , Lane Alison E.
Published: June 2013

Background/aim

This article aims to (1) identify instruments available to measure activity and participation in children with disabilities; (2) describe the reliability and validity of these instruments; and (3) consider whether the available instruments capture the extent of involvement, as well as the difficulty and satisfaction/enjoyment associated with performance in all life areas.

Method

A literature review was completed by undertaking an electronic search to identify instruments that measure activity and participation in children with disabilities. A further electronic search was conducted to obtain an adequate description of the instruments, including psychometric properties.

Results

The search identified 20 instruments purporting to measure activity and participation, however, no single instrument measured extent of involvement, difficulty and satisfaction/enjoyment in all life areas. There were instances in which each of these aspects was captured, but not within the one instrument. Instruments assessed combinations of frequency, difficulty, assistance, environment and satisfaction across varying contexts, for example, school, domestic life, recreational tasks, leisure tasks or all life areas.

Conclusions

Although a large number of instruments exist to measure varying aspects of activity and participation, there is currently no single instrument available to measure the extent of involvement, difficulty and satisfaction/enjoyment in all life areas. This finding indicates that there is the opportunity to develop a single instrument to measure activity and participation across all life areas.
The welfare cost of Japanese rice policy with home‐good preference and an endogenous import price
Authors: Fell James , MacLaren Donald
Published: June 2013

The welfare cost of Japanese rice policy is estimated in the context of a large importing country, treating domestically produced rice and imported rice as heterogeneous goods and where there is home‐good preference. Not accounting for this preference will cause the gains from liberalisation to be overestimated. The period that is analysed is 2004–2007, departing from that in previous studies, which do not cover this period of greater deregulation. Rather than use border trade flow data as is customary, we acknowledge the actions of a state trading enterprise and construct and use a unique data set which should better gauge import penetration in the Japanese market for rice. Econometric estimation fails to reject the hypothesis that the Ministry of Agriculture, Forestry and Fisheries prevents imports from affecting the price of domestically produced rice. In the absence of precisely estimated parameter values, simulations of liberalisation are conducted under a range of parameter values and the effects on social welfare calculated. The tariff equivalents of the government's support to rice producers are also estimated with values for the period in excess of 100 per cent.
World food prices and poverty in Indonesia
Authors: Warr Peter , Yusuf Arief Anshory
Published: June 2013

Spikes in international food prices in 2007–2008 worsened poverty incidence in Indonesia, both rural and urban, but only by small amounts. The paper reaches this conclusion using a multisectoral and multihousehold general equilibrium model of the Indonesian economy. The negative effect on poor consumers, operating through their living costs, outweighed the positive effect on poor farmers, operating through their incomes. Indonesia's post‐2004 rice import restrictions shielded its internal rice market from the temporary world price increases, muting the increase in poverty. But it did this only by imposing large and permanent increases in both domestic rice prices and poverty incidence. Poverty incidence increased more among rural than urban people, even though higher agricultural prices mean higher incomes for many of the rural poor. Gains to poor farmers were outweighed by the losses incurred by the large number of rural poor who are net buyers of food, and the fact that food represents a large share of their total budgets, even larger on average than for the urban poor. The main beneficiaries of higher food prices are not the rural poor, but the owners of agricultural land and capital, many of whom are urban based.
Rethinking Empirical Approaches to Racial Segregation
Authors: Kapoor Nisha
Published: June 2013

Within empirical approaches to racial residential segregation, there has been a tendency to draw on the work of or influenced by Robert E. Park and his ecological hypothesis to explore social and spatial relations between members of different ethnic and racial groups, thus framing research within a race relations paradigm. This has promoted an analysis which naturalizes racial differences but which also sidelines structural considerations. In turn this approach has also fed into political discourses on segregation, at times supporting more reactionary positions. This paper seeks to address this debate by considering whether emphasis on minority ethnic concentration sidelines the more pertinent issue of concentration in deprived areas, suggesting that neighbourhood deprivation as a measure can be more easily aligned with structural conditions which have influenced the settlement and historical experience of many ethnic minority communities. Specifically, I consider the extent to which a measure of neighbourhood deprivation is more important than the ethnic composition of an area for thinking about the distribution of inequalities in unemployment (as one example of socio-economic inequality). Using multilevel logistic regression I find neighbourhood income deprivation to be more important than levels of co-ethnic concentration for explaining ethnic differences in unemployment. The findings imply that neighbourhood deprivation is significantly more important for considering inequalities in unemployment for ethnic minorities than the ethnic composition of an area.
In Search of the Mechanisms Conducive to Class Differentials in Educational Choice: A Mixed Method Research
Authors: Boone Simon , Van Houtte Mieke
Published: June 2013

This paper inquires into the mechanisms conducive to social class differentials in educational choice in Flanders (the Northern, Dutch-speaking part of Belgium) using both quantitative data gathered from parents ( N = 1339) and qualitative data gathered during two focus groups with pupils ( N = 16). Unlike most of the previous studies, this study takes into consideration all three theoretical perspectives that have driven research on class differentials in educational choice so far, namely cultural reproduction theory, rational action theory and the notion of social capital. Logistic regression analysis shows that self-selection does also occur in Flanders and that the effect of parental SES cannot be explained by a specific measure of cultural capital centred on knowledge of the educational system, nor by measures of social capital. What emerges most clearly from this study is that pupils' perception of their choice process is powerfully framed by deep-rooted conceptions about the educational alternatives available to them. Furthermore, children's choices seem to be delimited by parents' opinions of which educational alternatives were acceptable, and which ones not. Our study calls for future research to take the wider context of decision-making processes more explicitly into account.