bluuebunny/crossref_metadata_2025 huggingface dataset:
Anisotropic and inhomogeneous thermal conduction in suspended thin-film polycrystalline diamond
Authors: Sood Aditya , Cho Jungwan , Hobart Karl D. , Feygelson Tatyana I. , Pate Bradford B. , Asheghi Mehdi , Cahill David G. , Goodson Kenneth E.
Published: May 2016

While there is a great wealth of data for thermal transport in synthetic diamond, there remains much to be learned about the impacts of grain structure and associated defects and impurities within a few microns of the nucleation region in films grown using chemical vapor deposition. Measurements of the inhomogeneous and anisotropic thermal conductivity in films thinner than 10 μm have previously been complicated by the presence of the substrate thermal boundary resistance. Here, we study thermal conduction in suspended films of polycrystalline diamond, with thicknesses ranging between 0.5 and 5.6 μm, using time-domain thermoreflectance. Measurements on both sides of the films facilitate extraction of the thickness-dependent in-plane (κr) and through-plane (κz) thermal conductivities in the vicinity of the coalescence and high-quality regions. The columnar grain structure makes the conductivity highly anisotropic, with κz being nearly three to five times as large as κr, a contrast higher than that reported previously for thicker films. In the vicinity of the high-quality region, κr and κz range from 77 ± 10 W/m-K and 210 ± 50 W/m-K for the 1 μm thick film to 130 ± 20 W/m-K and 710 ± 120 W/m-K for the 5.6 μm thick film, respectively. The data are interpreted using a model relating the anisotropy to the scattering on the boundaries of columnar grains and the evolution of the grain size considering their nucleation density and spatial rate of growth. This study aids in the reduction in the near-interfacial resistance of diamond films and efforts to fabricate diamond composites with silicon and GaN for power electronics.
Crystalline-amorphous silicon nano-composites: Nano-pores and nano-inclusions impact on the thermal conductivity
Authors: Verdier M. , Termentzidis K. , Lacroix D.
Published: May 2016

The thermal conductivities of nanoporous and nanocomposite silicon with incorporated amorphous phases have been computed by molecular dynamics simulations. A systematic investigation of the porosity and the width of the amorphous shell contouring a spherical pore has been made. The impact of amorphous phase nanoinclusions in a crystalline matrix has also been studied with the same amorphous fraction as the porosity of nanoporous silicon to achieve comparison. The key parameter for all configurations with or without the amorphous phase is proved to be the interface (between the crystalline and amorphous phases or crystalline and void) to volume ratio. We obtain the sub-amorphous thermal conductivity for several configurations by combining pores, amorphous shell, and crystalline phase. These configurations are promising candidates for low cost and not toxic thermoelectric devices based on abundant semiconductors.
Depth resolved domain mapping in tetragonal SrTiO3 by micro-Laue diffraction
Authors: Merz T. A. , Noad H. , Xu R. , Inoue H. , Liu W. , Hikita Y. , Vailionis A. , Moler K. A. , Hwang H. Y.
Published: May 2016

We present depth resolved X-ray micro-Laue diffraction experiments on the low temperature domain structure of SrTiO3. At 80 K, monochromatic X-ray diffraction shows an elongated out-of-plane unit cell axis within a matrix of in-plane oriented tetragonal unit cells. Full deviatoric strain mappings from white beam diffraction show a dominance of two tetragonal domain orientations (x- and z-axes) over a large area of sample surface. This information sets an upper bound on domain wall widths and offers a method for studying 3D domain structure at low temperatures.
Honeycomb and triangular domain wall networks in heteroepitaxial systems
Authors: Elder K. R. , Chen Z. , Elder K. L. M. , Hirvonen P. , Mkhonta S. K. , Ying S.-C. , Granato E. , Huang Zhi-Feng , Ala-Nissila T.
Published: May 2016

A comprehensive study is presented for the influence of misfit strain, adhesion strength, and lattice symmetry on the complex Moiré patterns that form in ultrathin films of honeycomb symmetry adsorbed on compact triangular or honeycomb substrates. The method used is based on a complex Ginzburg-Landau model of the film that incorporates elastic strain energy and dislocations. The results indicate that different symmetries of the heteroepitaxial systems lead to distinct types of domain wall networks and phase transitions among various surface Moiré patterns and superstructures. More specifically, the results show a dramatic difference between the phase diagrams that emerge when a honeycomb film is adsorbed on substrates of honeycomb versus triangular symmetry. It is also shown that in the small deformation limit, the complex Ginzburg-Landau model reduces to a two-dimensional sine-Gordon free energy form. This free energy can be solved exactly for one dimensional patterns and reveals the role of domains walls and their crossings in determining the nature of the phase diagrams.
Stratigraphy of a diamond epitaxial three-dimensional overgrowth using doping superlattices
Authors: Lloret F. , Fiori A. , Araujo D. , Eon D. , Villar M. P. , Bustarret E.
Published: May 2016

The selective doped overgrowth of 3D mesa patterns and trenches has become an essential fabrication step of advanced monolithic diamond-based power devices. The methodology here proposed combines the overgrowth of plasma-etched cylindrical mesa structures with the sequential growth of doping superlattices. The latter involve thin heavily boron doped epilayers separating thicker undoped epilayers in a periodic fashion. Besides the classical shape analysis under the scanning electron microscope relying on the appearance of facets corresponding to the main crystallographic directions and their evolution toward slow growing facets, the doping superlattices were used as markers in oriented cross-sectional lamellas prepared by focused ion beam and observed by transmission electron microscopy. This stratigraphic approach is shown here to be applicable to overgrown structures where faceting was not detectable. Intermediate growth directions were detected at different times of the growth process and the periodicity of the superlattice allowed to calculate the growth rates and parameters, providing an original insight into the planarization mechanism. Different configurations of the growth front were obtained for different sample orientations, illustrating the anisotropy of the 3D growth. Dislocations were also observed along the lateral growth fronts with two types of Burger vector: b011¯=12[011¯] and b112=16[112]. Moreover, the clustering of these extended defects in specific regions of the overgrowth prompted a proposal of two different dislocation generation mechanisms.
Composition analysis of coaxially grown InGaN multi quantum wells using scanning transmission electron microscopy
Authors: Aschenbrenner T. , Schowalter M. , Mehrtens T. , Müller-Caspary K. , Fikry M. , Heinz D. , Tischer I. , Madel M. , Thonke K. , Hommel D. , Scholz F. , Rosenauer A.
Published: May 2016

GaN nanotubes with coaxial InGaN quantum wells were analyzed by scanning transmission electron microscopy in order to determine their structural properties as well as the indium distribution across the InGaN quantum wells. For the latter, two process steps are necessary. First, a technique to prepare cross-sectional slices out of the nanotubes has been developed. Second, an existing scanning transmission electron microscopy analysis technique has been extended with respect to the special crystallographic orientation of this type of specimen. In particular, the shape of the nanotubes, their defect structure, and the incorporation of indium on different facets were investigated. The quantum wells preferentially grow on m-planes of the dodecagonally shaped nanotubes and on semipolar top facets while no significant indium signal was found on a-planes. An averaged indium concentration of 6% to 7% was found by scanning transmission electron microscopy analysis and could be confirmed by cathodoluminescence measurements.
Hole effective masses and subband splitting in type-II superlattice infrared detectors
Authors: Ting David Z. , Soibel Alexander , Gunapala Sarath D.
Published: May 2016

We explore band structure effects to help determine the suitability of n-type type-II superlattice (T2SL) absorbers for infrared detectors. It is often assumed that the exceedingly large growth-direction band-edge curvature hole effective mass in n-type long wavelength infrared (LWIR) T2SL would lead to low hole mobility and therefore low detector collection quantum efficiency. We computed the thermally averaged conductivity effective mass and show that the LWIR T2SL hole conductivity effective mass along the growth direction can be orders of magnitude smaller than the corresponding band-edge effective mass. LWIR InAs/GaSb T2SL can have significantly smaller growth-direction hole conductivity effective mass than its InAs/InAsSb counterpart. For the InAs/InAsSb T2SL, higher Sb fraction is more favorable for hole transport. Achieving long hole diffusion length becomes progressively more difficult for the InAs/InAsSb T2SL as the cutoff wavelength increases, since its growth-direction hole conductivity effective mass increases significantly with decreasing band gap. However, this is mitigated by the fact that the splitting between the top valence subbands also increases with the cutoff wavelength, leading to reduced inter-subband scattering and increased relaxation time.
Solar photovoltaic design tool for non-residential buildings: From blueprints to arrays
Authors: Grossman Andrew , Ding Yunhua , Lunt Richard , Bénard André
Published: May 2016

In the United States, approximately 65 × 109 square-feet of underutilized rooftop space could be appropriated for the installation of solar photovoltaic systems. Although several programs are available that assist in designing a photovoltaic (PV) system, a planning tool that can take an adaptive modeling approach towards capitalizing on the complex geometry of a rooftop does not exist. We therefore focus on the development of a parametric planning tool for retrofitting rooftops with solar photovoltaic systems. The solar planning tool exploits the existing blueprint of a building's rooftop, and via image processing, the layouts of the solar photovoltaic arrays are developed based on the building's geographical location and typical weather patterns. The resulting energy generation of a PV system is estimated and is utilized to determine the leveled energy costs. The advantage of incorporating image processing in the design of a PV system not only reduces the time required for performing a robust solar PV analysis but also enables a high-level of dimensional precision when modeling the solar arrays, thus making a rooftop solar photovoltaic system installation ultimately more cost-effective. This paper demonstrates the planning tool and verifies the output array layout, sizing of the balance of system components, and expected energy generation with the existing rooftop photovoltaic systems.
The possibility of determining the spin-orbit interaction constants using scanning tunneling microscopy
Authors: Khotkevych N. V. , Vovk N. R. , Kolesnichenko Yu. A.
Published: May 2016

A study of electron tunneling from quasi-two-dimensional (surface) states with spin-orbit interaction into bulk-mode states, within the framework of a model of an infinitely thin inhomogeneous tunnel magnetic barrier between two conductors. We analyze how the scattering of quasi-two-dimensional electrons on a single magnetic defect affects the tunneling current in this system. We also obtain an analytical expression for the conductance of the tunnel point-contact, as a function of its distance from the defect. It is shown that analyzing local magnetization oscillations around the defect using spin-polarized scanning tunneling microscopy allows us to determine the spin-orbit interaction constant.
Towards a six-state magnetic memory element
Authors: Telepinsky Yevgeniy , Mor Vladislav , Schultz Moty , Hung Yu-Ming , Kent Andrew D. , Klein Lior
Published: May 2016

We pattern permalloy films into three crossing elongated ellipses with an angle of 60° between the major axes of any pair of ellipses. Planar Hall effect measurements show that the magnetization in the area of overlap of the ellipses has six stable magnetic orientations parallel to the major axes of the three ellipses. We determine the effective anisotropy field for small magnetic deviations from the easy axis and the switching field between the easy axes as a function of magnetic field orientation. We compare our results with micromagnetic simulations and present an effective Hamiltonian that captures the magnetic response. We show how such magnetic structures in a magnetic tunnel junction would result in a magnetic memory element with six distinct resistance states that could be written using spin-orbit torques.
A direct correlation of x-ray diffraction orientation distributions to the in-plane stiffness of semi-crystalline organic semiconducting films
Authors: Zhao Bingxiao , Awartani Omar , O'Connor Brendan , Zikry Mohammed A.
Published: May 2016

Large charge mobilities of semi-crystalline organic semiconducting films could be obtained by mechanically aligning the material phases of the film with the loading axis. A key element is to utilize the inherent stiffness of the material for optimal or desired alignment. However, experimentally determining the moduli of semi-crystalline organic thin films for different loading directions is difficult, if not impossible, due to film thickness and material anisotropy. In this paper, we address these challenges by presenting an approach based on combining a composite mechanics stiffness orientation formulation with a Gaussian statistical distribution to directly estimate the in-plane stiffness (transverse isotropy) of aligned semi-crystalline polymer films based on crystalline orientation distributions obtained by X-ray diffraction experimentally at different applied strains. Our predicted results indicate that the in-plane stiffness of an annealing film was initially isotropic, and then it evolved to transverse isotropy with increasing mechanical strains. This study underscores the significance of accounting for the crystalline orientation distributions of the film to obtain an accurate understanding and prediction of the elastic anisotropy of semi-crystalline polymer films.
Communication: Mode specific quantum dynamics of the F + CHD3 → HF + CD3 reaction
Authors: Qi Ji , Song Hongwei , Yang Minghui , Palma Juliana , Manthe Uwe , Guo Hua
Published: May 2016

The mode specific reactivity of the F + CHD3 → HF + CD3 reaction is investigated using an eight-dimensional quantum dynamical model on a recently developed ab initio based full-dimensional potential energy surface. Our results indicate prominent resonance structures at low collision energies and absence of an energy threshold in reaction probabilities. It was also found that excitation of the C–D stretching or CD3 umbrella mode has a relatively small impact on reactivity. On the other hand, the excitation of the C–H vibration (v1) in CHD3 is shown to significantly increase the reactivity, which, like several recent quasi-classical trajectory studies, is at odds with the available experimental data. Possible sources of the disagreement are discussed.
Oxygen vacancy defect engineering using atomic layer deposited HfAlOx in multi-layered gate stack
Authors: Bhuyian M. N. , Sengupta R. , Vurikiti P. , Misra D.
Published: May 2016

This work evaluates the defects in high quality atomic layer deposited (ALD) HfAlOx with extremely low Al (<3% Al/(Al + Hf)) incorporation in the Hf based high-k dielectrics. The defect activation energy estimated by the high temperature current voltage measurement shows that the charged oxygen vacancies, V+/V2+, are the primary source of defects in these dielectrics. When Al is added in HfO2, the V+ type defects with a defect activation energy of Ea ∼ 0.2 eV modify to V2+ type to Ea ∼ 0.1 eV with reference to the Si conduction band. When devices were stressed in the gate injection mode for 1000 s, more V+ type defects are generated and Ea reverts back to ∼0.2 eV. Since Al has a less number of valence electrons than do Hf, the change in the co-ordination number due to Al incorporation seems to contribute to the defect level modifications. Additionally, the stress induced leakage current behavior observed at 20 °C and at 125 °C demonstrates that the addition of Al in HfO2 contributed to suppressed trap generation process. This further supports the defect engineering model as reduced flat-band voltage shifts were observed at 20 °C and at 125 °C.
Anisotropic metasurface with near-unity circular polarization conversion
Authors: Wu Xiaoxiao , Meng Yan , Wang Li , Tian Jingxuan , Dai Shiwei , Wen Weijia
Published: May 2016

We demonstrate a bi-layer ultrathin anisotropic metasurface which could near-completely convert the circular-polarized electromagnetic wave to its cross polarization. The bi-layer metasurface is composed of periodic 180°-twisted double-cut split ring resonators on both sides of an F4B substrate. At resonance, cross-polarized transmission larger than 94% is observed both in simulations and experiments. The resonant frequency of the metasurface could be effectively tuned by adjusting the geometric parameters of the metasurface, while relatively high conversion efficiency is preserved. The high efficiency and ease of fabrication suggest that the ultrathin metasurface could have potential applications in telecommunications.
Wrinkled bilayer graphene with wafer scale mechanical strain
Authors: Mikael Solomon , Seo Jung-Hun , Javadi Alireza , Gong Shaoqin , Ma Zhenqiang
Published: May 2016

Wafer-scale strained bilayer graphene is demonstrated by employing a silicon nitride (Si3N4) stressor layer. Different magnitudes of compressive stress up to 840 MPa were engineered by adjusting the Si3N4 deposition recipes, and different strain conditions were analyzed using Raman spectroscopy. The strained graphene displayed significant G peak shifts and G peak splitting with 16.2 cm−1 and 23.0 cm−1 of the G band and two-dimensional band shift, which corresponds to 0.26% of strain. Raman mapping of large regions of the graphene films found that the largest shifts/splitting occurred near the bilayer regions of the graphene films. The significance of our approach lies in the fact that it can be performed in a conventional microfabrication process, i.e., the plasma enhanced chemical vapor deposition system, and thus easily implemented for large scale production.
Investigation of the effects of metal-wire resonators in sub-wavelength array based on time-reversal technique
Authors: Tu Hui-Lin , Xiao Shao-Qiu
Published: May 2016

The resonant metalens consisting of metal-wire resonators with equally finite length can break the diffraction barrier well suited for super-resolution imaging. In this study, a basic combination constructed by two metal-wire resonators with different lengths is proposed, and its resonant characteristics is analyzed using the method of moments (MoM). Based on the time reversal (TR) technique, this kind of combination can be applied to a sub-wavelength two-element antenna array with a 1/40-wavelength interval to make the elements work simultaneously with little interference in the frequency band of 1.0-1.5 GHz and 1.5-2.0 GHz, respectively. The simulations and experiments show that analysis of MoM and the application of the resonators can be used to design multi-frequency sub-wavelength antenna arrays efficiently. This general design method is convenient and can be used for many applications, such as weakening jamming effectiveness in communication systems, and sub-wavelength imaging in a broad frequency band.
A one-dimensional stochastic approach to the study of cyclic voltammetry with adsorption effects
Authors: Samin Adib J.
Published: May 2016

In this study, a one-dimensional stochastic model based on the random walk approach is used to simulate cyclic voltammetry. The model takes into account mass transport, kinetics of the redox reactions, adsorption effects and changes in the morphology of the electrode. The model is shown to display the expected behavior. Furthermore, the model shows consistent qualitative agreement with a finite difference solution. This approach allows for an understanding of phenomena on a microscopic level and may be useful for analyzing qualitative features observed in experimentally recorded signals.
Identification of kill sites from GPS clusters for jaguars (Panthera onca) in the southern Pantanal, Brazil
Authors: Gese Eric M. , Terletzky Patricia A. , Cavalcanti Sandra M. C.
Published: May 2016

Context
Understanding predator–prey relationships is important for making informed management decisions. Knowledge of jaguar (Panthera onca) predation on livestock and native prey is imperative for future conservation of jaguars in Central and South America.

Aim
As part of an investigation to determine predation patterns of jaguars in the southern Pantanal, Brazil, we examined spatial, temporal and habitat variables, which are useful in categorising location clusters as kill sites and non-kill sites.

Methods
Using GPS-collars on 10 jaguars we obtained a total of 11 784 locations, from which 877 clusters were identified, visited and examined for prey remains. Of the 877 clusters, 421 were associated with a kill and 456 clusters were not associated with a kill. We used univariate and multivariate models to examine the influence of spatial (distance to nearest: water, dense cover, road; dispersion of points), temporal (season, time, number of nights, duration) and habitat (percentage of seven habitat classes, dominant habitat class) variables on categorising clusters as kill or non-kill sites.

Key results
We found the time a jaguar spent at a cluster (duration), the dispersion of points around the centre of the cluster (dispersion) and the number of nights spent at the cluster were all reliable predictors of whether a cluster was a kill or non-kill site. The best model predicting the likelihood a cluster was a jaguar kill site was a combination of duration and dispersion. Habitat variables were not important in discriminating kills from non-kill sites.

Conclusion
We identified factors useful for discriminating between kills and non-kill sites for jaguars. We found that as a jaguar spent more time at a cluster and as the dispersion of points around the centre of the cluster increased, the higher likelihood the cluster was a jaguar kill. Similarly, as the number of nights spent at the cluster increased, the greater the probability the cluster was a kill.

Implications
Our results will increase the efficiency of field investigations of location clusters in determining predation patterns of jaguars in Central and South America. Being able to prioritise which location clusters should be investigated will assist researchers with limited time and resources.
Objects of transitive verbs in Italian as a heritage language in contact with German
Authors: Di Venanzio Laura , Schmitz Katrin , Scherger Anna-Lena
Published: May 2016

This paper seeks to close a gap in the ongoing research on heritage languages (HL), their acquisition, and the nature of transfer in HL with a study on a hitherto understudied language combination, namely Italian heritage speakers (HS) raised in Germany with two native languages. The current study compares data from spontaneous speech of these HS with speech data from native speakers of Italian who immigrated to Germany as adults with German as L2, and Italian monolinguals. Analyses of Italian objects show that the HS reflect native knowledge about lexical options of object omissions and their pragmatic identification, and of object clitic use. The results indicate no evidence for covert transfer in regards to Italian object realization types. Finally, the study leads to the conclusion that Italian HS differ in fewer investigated aspects from Italian monolinguals than L1/L2 speakers.
Objects of transitive verbs in Italian as a heritage language in contact with German
Authors: Di Venanzio Laura , Schmitz Katrin , Scherger Anna-Lena
Published: May 2016

This paper seeks to close a gap in the ongoing research on heritage languages (HL), their acquisition, and the nature of transfer in HL with a study on a hitherto understudied language combination, namely Italian heritage speakers (HS) raised in Germany with two native languages. The current study compares data from spontaneous speech of these HS with speech data from native speakers of Italian who immigrated to Germany as adults with German as L2, and Italian monolinguals. Analyses of Italian objects reveal that the HS show native knowledge about lexical options of object omissions and their pragmatic identification, and of object clitic use. The results indicate no evidence for covert transfer with regard to Italian object realization types. Finally, the study leads to the conclusion that Italian HS differ in fewer investigated aspects from Italian monolinguals than L1/L2 speakers.
RhoB controls endothelial barrier recovery by inhibiting Rac1 trafficking to the cell border
Authors: Marcos-Ramiro Beatriz , García-Weber Diego , Barroso Susana , Feito Jorge , Ortega María C. , Cernuda-Morollón Eva , Reglero-Real Natalia , Fernández-Martín Laura , Durán Maria C. , Alonso Miguel A. , Correas Isabel , Cox Susan , Ridley Anne J. , Millán Jaime
Published: May 2016

Endothelial barrier dysfunction underlies chronic inflammatory diseases. In searching for new proteins essential to the human endothelial inflammatory response, we have found that the endosomal GTPase RhoB is up-regulated in response to inflammatory cytokines and expressed in the endothelium of some chronically inflamed tissues. We show that although RhoB and the related RhoA and RhoC play additive and redundant roles in various aspects of endothelial barrier function, RhoB specifically inhibits barrier restoration after acute cell contraction by preventing plasma membrane extension. During barrier restoration, RhoB trafficking is induced between vesicles containing RhoB nanoclusters and plasma membrane protrusions. The Rho GTPase Rac1 controls membrane spreading and stabilizes endothelial barriers. We show that RhoB colocalizes with Rac1 in endosomes and inhibits Rac1 activity and trafficking to the cell border during barrier recovery. Inhibition of endosomal trafficking impairs barrier reformation, whereas induction of Rac1 translocation to the plasma membrane accelerates it. Therefore, RhoB-specific regulation of Rac1 trafficking controls endothelial barrier integrity during inflammation.
A mitotic SKAP isoform regulates spindle positioning at astral microtubule plus ends
Authors: Kern David M. , Nicholls Peter K. , Page David C. , Cheeseman Iain M.
Published: May 2016

The Astrin/SKAP complex plays important roles in mitotic chromosome alignment and centrosome integrity, but previous work found conflicting results for SKAP function. Here, we demonstrate that SKAP is expressed as two distinct isoforms in mammals: a longer, testis-specific isoform that was used for the previous studies in mitotic cells and a novel, shorter mitotic isoform. Unlike the long isoform, short SKAP rescues SKAP depletion in mitosis and displays robust microtubule plus-end tracking, including localization to astral microtubules. Eliminating SKAP microtubule binding results in severe chromosome segregation defects. In contrast, SKAP mutants specifically defective for plus-end tracking facilitate proper chromosome segregation but display spindle positioning defects. Cells lacking SKAP plus-end tracking have reduced Clasp1 localization at microtubule plus ends and display increased lateral microtubule contacts with the cell cortex, which we propose results in unbalanced dynein-dependent cortical pulling forces. Our work reveals an unappreciated role for the Astrin/SKAP complex as an astral microtubule mediator of mitotic spindle positioning.
TANGO1 and Mia2/cTAGE5 (TALI) cooperate to export bulky pre-chylomicrons/VLDLs from the endoplasmic reticulum
Authors: Santos António J.M. , Nogueira Cristina , Ortega-Bellido Maria , Malhotra Vivek
Published: May 2016

Procollagens, pre-chylomicrons, and pre–very low-density lipoproteins (pre-VLDLs) are too big to fit into conventional COPII-coated vesicles, so how are these bulky cargoes exported from the endoplasmic reticulum (ER)? We have shown that TANGO1 located at the ER exit site is necessary for procollagen export. We report a role for TANGO1 and TANGO1-like (TALI), a chimeric protein resulting from fusion of MIA2 and cTAGE5 gene products, in the export of pre-chylomicrons and pre-VLDLs from the ER. TANGO1 binds TALI, and both interact with apolipoprotein B (ApoB) and are necessary for the recruitment of ApoB-containing lipid particles to ER exit sites for their subsequent export. Although export of ApoB requires the function of both TANGO1 and TALI, the export of procollagen XII by the same cells requires only TANGO1. These findings reveal a general role for TANGO1 in the export of bulky cargoes from the ER and identify a specific requirement for TALI in assisting TANGO1 to export bulky lipid particles.
Lipoprotein secretion: It takes two to TANGO
Authors: Pfeffer Suzanne R.
Published: May 2016

An unsolved mystery in cell biology is how unusually large secretory cargoes are exported from the endoplasmic reticulum. In this issue, Santos et al. (2016. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201603072) report the function of a Mia2/cTAGE5 transcript fusion, named TALI, in the endoplasmic reticulum export of chylomicrons and very low-density lipoproteins, but not collagen XII.
Neurons let it slide
Authors: Short Ben
Published: May 2016

Study reveals how microtubule sliding affects neuronal migration and morphology.
Recent thymic emigrants are tolerized in the absence of inflammation
Authors: Friesen Travis J. , Ji Qingyong , Fink Pamela J.
Published: May 2016

T cell development requires a period of postthymic maturation. Why this is the case has remained a mystery, particularly given the rigors of intrathymic developmental checkpoints, successfully traversed by only ∼5% of thymocytes. We now show that the first few weeks of T cell residence in the lymphoid periphery define a period of heightened susceptibility to tolerance induction to tissue-restricted antigens (TRAs), the outcome of which depends on the context in which recent thymic emigrants (RTEs) encounter antigen. After encounter with TRAs in the absence of inflammation, RTEs exhibited defects in proliferation, diminished cytokine production, elevated expression of anergy-associated genes, and diminished diabetogenicity. These properties were mirrored in vitro by enhanced RTE susceptibility to regulatory T cell–mediated suppression. In the presence of inflammation, RTEs and mature T cells were, in contrast, equally capable of inducing diabetes, proliferating, and producing cytokines. Thus, recirculating RTEs encounter TRAs during a transitional developmental stage that facilitates tolerance induction, but inflammation converts antigen-exposed, tolerance-prone RTEs into competent effector cells.
Conformal Grushin spaces
Authors: Romney Matthew
Published: May 2016

We introduce a class of metrics on

R

n

\mathbb {R}^n

generalizing the classical Grushin plane. These are length metrics defined by the line element

d
s
=

d
E

(
⋅
,
Y

)

−
β

d

s
E

ds = d_E(\cdot ,Y)^{-\beta }ds_E

for a closed nonempty subset

Y
⊂

R

n

Y \subset \mathbb {R}^n

and

β
∈
[
0
,
1
)

\beta \in [0,1)

. We prove, assuming a Hölder condition on the metric, that these spaces are quasisymmetrically equivalent to

R

n

\mathbb {R}^n

and can be embedded in some larger Euclidean space under a bi-Lipschitz map. Our main tool is an embedding characterization due to Seo, which we strengthen by removing the hypothesis of uniform perfectness. In the two-dimensional case, we give another proof of bi-Lipschitz embeddability based on growth bounds on sectional curvature.
Exogenous Abscisic Acid and Gibberellic Acid Elicit Opposing Effects on Fusarium graminearum Infection in Wheat
Authors: Buhrow Leann M. , Cram Dustin , Tulpan Dan , Foroud Nora A. , Loewen Michele C.
Published: May 2016

Although the roles of salicylate (SA) and jasmonic acid (JA) have been well-characterized in Fusarium head blight (FHB)-infected cereals, the roles of other phytohormones remain more ambiguous. Here, the association between an array of phytohormones and FHB pathogenesis in wheat is investigated. Comprehensive profiling of endogenous hormones demonstrated altered cytokinin, gibberellic acid (GA), and JA metabolism in a FHB-resistant cultivar, whereas challenge by Fusarium graminearum increased abscisic acid (ABA), JA, and SA in both FHB-susceptible and -resistant cultivars. Subsequent investigation of ABA or GA coapplication with fungal challenge increased and decreased FHB spread, respectively. These phytohormones-induced effects may be attributed to alteration of the F. graminearum transcriptome because ABA promoted expression of early-infection genes, including hydrolases and cytoskeletal reorganization genes, while GA suppressed nitrogen metabolic gene expression. Neither ABA nor GA elicited significant effects on F. graminearum fungal growth or sporulation in axenic conditions, nor do these phytohormones affect trichothecene gene expression, deoxynivalenol mycotoxin accumulation, or SA/JA biosynthesis in F. graminearum-challenged wheat spikes. Finally, the combined application of GA and paclobutrazol, a Fusarium fungicide, provided additive effects on reducing FHB severity, highlighting the potential for combining fungicidal agents with select phytohormone-related treatments for management of FHB infection in wheat.
Lessons from a Phenotyping Center Revealed by the Genome-Guided Mapping of Powdery Mildew Resistance Loci
Authors: Cadle-Davidson Lance , Gadoury David , Fresnedo-Ramírez Jonathan , Yang Shanshan , Barba Paola , Sun Qi , Demmings Elizabeth M. , Seem Robert , Schaub Michelle , Nowogrodzki Anna , Kasinathan Hema , Ledbetter Craig , Reisch Bruce I.
Published: May 2016

The genomics era brought unprecedented opportunities for genetic analysis of host resistance, but it came with the challenge that accurate and reproducible phenotypes are needed so that genomic results appropriately reflect biology. Phenotyping host resistance by natural infection in the field can produce variable results due to the uncontrolled environment, uneven distribution and genetics of the pathogen, and developmentally regulated resistance among other factors. To address these challenges, we developed highly controlled, standardized methodologies for phenotyping powdery mildew resistance in the context of a phenotyping center, receiving samples of up to 140 grapevine progeny per F1 family. We applied these methodologies to F1 families segregating for REN1- or REN2-mediated resistance and validated that some but not all bioassays identified the REN1 or REN2 locus. A point-intercept method (hyphal transects) to quantify colony density objectively at 8 or 9 days postinoculation proved to be the phenotypic response most reproducibly predicted by these resistance loci. Quantitative trait locus (QTL) mapping with genotyping-by-sequencing maps defined the REN1 and REN2 loci at relatively high resolution. In the reference PN40024 genome under each QTL, nucleotide-binding site−leucine-rich repeat candidate resistance genes were identified—one gene for REN1 and two genes for REN2. The methods described here for centralized resistance phenotyping and high-resolution genetic mapping can inform strategies for breeding resistance to powdery mildews and other pathogens on diverse, highly heterozygous hosts.
Improved definition of the mouse transcriptome via targeted RNA sequencing
Authors: Bussotti Giovanni , Leonardi Tommaso , Clark Michael B. , Mercer Tim R. , Crawford Joanna , Malquori Lorenzo , Notredame Cedric , Dinger Marcel E. , Mattick John S. , Enright Anton J.
Published: May 2016

Targeted RNA sequencing (CaptureSeq) uses oligonucleotide probes to capture RNAs for sequencing, providing enriched read coverage, accurate measurement of gene expression, and quantitative expression data. We applied CaptureSeq to refine transcript annotations in the current murine GRCm38 assembly. More than 23,000 regions corresponding to putative or annotated long noncoding RNAs (lncRNAs) and 154,281 known splicing junction sites were selected for targeted sequencing across five mouse tissues and three brain subregions. The results illustrate that the mouse transcriptome is considerably more complex than previously thought. We assemble more complete transcript isoforms than GENCODE, expand transcript boundaries, and connect interspersed islands of mapped reads. We describe a novel filtering pipeline that identifies previously unannotated but high-quality transcript isoforms. In this set, 911 GENCODE neighboring genes are condensed into 400 expanded gene models. Additionally, 594 GENCODE lncRNAs acquire an open reading frame (ORF) when their structure is extended with CaptureSeq. Finally, we validate our observations using current FANTOM and Mouse ENCODE resources.
The price of associating with breeders in the cooperatively breeding chestnut‐crowned babbler: foraging constraints, survival and sociality
Authors: Sorato Enrico , Griffith Simon C. , Russell Andy F.
Published: May 2016

Understanding the costs of living with breeders might offer new insights into the factors that counter evolutionary transitions from selfish individuals to cooperative societies. While selection on early dispersal is well understood, it is less clear whether costs are also associated with remaining with family members during subsequent breeding, a prerequisite to the evolution of kin‐based cooperation.

We propose and test the hypothesis that living in groups containing breeders is costly and that such costs are exacerbated by increasing group size. For example, in group‐living central‐place foragers, group members might suffer from resource depletion when foraging in a restricted area during breeding and significant costs of repeatedly travelling between foraging patches and the site of offspring.

Using the cooperatively breeding chestnut‐crowned babbler (Pomatostomus ruficeps), for which grouping during breeding is obligatory, we show that reproduction is associated with substantially reduced foraging areas and evidence of resource depletion, particularly in larger groups. Such effects largely persisted from the onset of incubation through to offspring independence 4–5 months later. All group members, irrespective of their breeder or helper status, lost significant body mass over this period, and, in males, mass loss was associated with reduced interannual survival.

Although babblers are constrained from living outside of breeding groups due to high risks of predation and the poor success of breeding without helpers, we suggest that the effects we describe may generally select against group living during breeding attempts in species where constraints to independent breeding and costs of dispersal are less acute.
Slowing them down will make them lose: a role for attine ant crop fungus in defending pupae against infections?
Authors: Armitage Sophie A. O. , Fernández‐Marín Hermógenes , Boomsma Jacobus J. , Wcislo William T.
Published: May 2016

Fungus‐growing ants (Attini) have evolved an obligate dependency upon a basidiomycete fungus that they cultivate as their food. Less well known is that the crop fungus is also used by many attine species to cover their eggs, larvae and pupae.

The adaptive functional significance of this brood covering is poorly understood. One hypothesis to account for this behaviour is that it is part of the pathogen protection portfolio when many thousands of sister workers live in close proximity and larvae and pupae are not protected by cells, as in bees and wasps, and are immobile.

We performed behavioural observations on brood covering in the leaf‐cutting ant Acromyrmex echinatior, and we experimentally manipulated mycelial cover on pupae and exposed them to the entomopathogenic fungus Metarhizium brunneum to test for a role in pathogen resistance.

Our results show that active mycelial brood covering by workers is a behaviourally plastic trait that varies temporally, and across life stages and castes. The presence of a fungal cover on the pupae reduced the rate at which conidia appeared and the percentage of pupal surface that produced pathogen spores, compared to pupae that had fungal cover experimentally removed or naturally had no mycelial cover. Infected pupae with mycelium had higher survival rates than infected pupae without the cover, although this depended upon the time at which adult sister workers were allowed to interact with pupae. Finally, workers employed higher rates of metapleural gland grooming to infected pupae without mycelium than to infected pupae with mycelium.

Our results imply that mycelial brood covering may play a significant role in suppressing the growth and subsequent spread of disease, thus adding a novel layer of protection to their defence portfolio.
Rehabilitative bodywork: cleaning up the dirty work of homecare
Authors: Meldgaard Hansen Agnete
Published: May 2016

Care work for elderly people has been characterised as dirty work, owing to its proximity to the (dys)functions and discharges of aged bodies and the notions of disease, decay and death associated with the idea of old age. However, a wave of reform programmes in Danish municipalities promoting rehabilitative care practices aiming to empower, train and activate elderly citizens provides opportunities for homecare workers to renegotiate their status and reconstruct their work and occupational identities with a cleaner and more optimistic image. Drawing on ethnographic fieldwork in two Danish homecare units, this article analyses how rehabilitative care practices, drawing on a narrative of the third age, provide an optimistic and anti‐ageist framing of homecare work that informs the development of new occupational identities for care workers as coaches rather than carers in relation to citizens. Furthermore, rehabilitation efforts change the bodywork of care, rendering it more distanced and physically passive, and rehabilitation efforts also involve extensive motivational work aiming to help citizens to see themselves as capable, resourceful and self‐reliant. However, while rehabilitation efforts become a new resource in care workers’ taint management; they also entail potentially negative consequences in terms of responsibilising and disciplinary approaches to elderly citizens.
Estimating the Enduring Effects of Fertiliser Subsidies on Commercial Fertiliser Demand and Maize Production: Panel Data Evidence from Malawi
Authors: Ricker‐Gilbert Jacob , Jayne T. S.
Published: May 2016

Most studies of input subsidy programmes confine their analyses to measuring programme effects over a one‐year period. This article estimates the potential longer‐run or enduring effects of fertiliser subsidy programmes on smallholder farm households' demand for commercial fertiliser and maize production over time. We use four waves of panel data on 462 farm households in Malawi for whom fertiliser use can be tracked for eight consecutive seasons between 2003/2004 and 2010/2011. Panel estimation methods are used to control for potential endogeneity of subsidised fertiliser acquisition. Results indicate that farmers acquiring subsidised fertiliser in three consecutive prior years are found to purchase slightly more commercial fertiliser in the next year. This suggests a small amount of crowding in of commercial fertiliser from the receipt of subsidised fertiliser in prior years. In addition, acquiring subsidised fertiliser in a given year has a modest positive impact on increasing maize output in that same year. However, acquiring subsidised fertiliser in multiple prior years generates no statistically significant effect on maize output in the current year. These findings indicate that potential enduring effects of the Malawi fertiliser subsidy programme on maize production are limited. Additional interventions that increase soil fertility can make using inorganic fertiliser more profitable and sustainable for smallholders in sub‐Saharan Africa and thereby increase the cost‐effectiveness of input subsidy programmes.
Evaluation of habitat requirements of small rodents and effectiveness of an ecologically‐based management in a hantavirus‐endemic natural protected area in Argentina
Authors: VADELL María Victoria , GARCÍA ERIZE Francisco , GÓMEZ VILLAFAÑE Isabel Elisa
Published: May 2016

Hantavirus pulmonary syndrome is a severe cardio pulmonary disease transmitted to humans by sylvan rodents found in natural and rural environments. Disease transmission is closely linked to the ecology of animal reservoirs and abiotic factors such as habitat characteristics, season or climatic conditions. The main goals of this research were: to determine the biotic and abiotic factors affecting richness and abundance of rodent species at different spatial scales, to evaluate different methodologies for studying population of small rodents, and to describe and analyze an ecologically‐based rodent management experience in a highly touristic area. A 4‐year study of small rodent ecology was conducted between April 2007 and August 2011 in the most relevant habitats of El Palmar National Park, Argentina. Management involved a wide range of control and prevention measures, including poisoning, culling and habitat modification. A total of 172 individuals of 5 species were captured with a trapping effort of 13 860 traps‐nights (1.24 individuals/100 traps‐nights). Five rodent species were captured, including 2 hantavirus‐host species, Oligoryzomys nigripes and Akodon azarae. Oligoryzomys nigripes, host of a hantavirus that is pathogenic in humans, was the most abundant species and the only one found in all the studied habitats. Our results are inconsistent with the dilution effect hypothesis. The present study demonstrates that sylvan rodent species, including the hantavirus‐host species, have distinct local habitat selection and temporal variation patterns in abundance, which may influence the risk of human exposure to hantavirus and may have practical implications for disease transmission as well as for reservoir management.
Habitat fragmentation, vole population fluctuations, and the ROMPA hypothesis: An experimental test using model landscapes
Authors: BATZLI George O.
Published: May 2016

Increased habitat fragmentation leads to smaller size of habitat patches and to greater distance between patches. The ROMPA hypothesis (ratio of optimal to marginal patch area) uniquely links vole population fluctuations to the composition of the landscape. It states that as ROMPA decreases (fragmentation increases), vole population fluctuations will increase (including the tendency to display multi‐annual cycles in abundance) because decreased proportions of optimal habitat result in greater population declines and longer recovery time after a harsh season. To date, only comparative observations in the field have supported the hypothesis. This paper reports the results of the first experimental test. I used prairie voles, Microtus ochrogaster, and mowed grassland to create model landscapes with 3 levels of ROMPA (high with 25% mowed, medium with 50% mowed and low with 75% mowed). As ROMPA decreased, distances between patches of favorable habitat (high cover) increased owing to a greater proportion of unfavorable (mowed) habitat. Results from the first year with intensive live trapping indicated that the preconditions for operation of the hypothesis existed (inversely density dependent emigration and, as ROMPA decreased, increased per capita mortality and decreased per capita movement between optimal patches). Nevertheless, contrary to the prediction of the hypothesis that populations in landscapes with high ROMPA should have the lowest variability, 5 years of trapping indicated that variability was lowest with medium ROMPA. The design of field experiments may never be perfect, but these results indicate that the ROMPA hypothesis needs further rigorous testing.