bluuebunny/crossref_metadata_2025 huggingface dataset:
Top-10 Tips for Getting Started with Magnetic Resonance Neurography
Authors: Chalian Majid , Chhabra Avneesh
Published: March 2019

Magnetic resonance neurography (MRN), also known as MR neurography, is a dedicated imaging technique for the peripheral nerves, used both in a clinical setting and research. However, like any other new diagnostic processes, there are technical, cost, and patient selection issues to overcome as well as potential imaging pitfalls to recognize before MRN can be adopted efficiently into routine clinical practice. This review focuses on the 10 most important practical tips to get started with MRN with a view to shortening the time needed for radiologists to implement this clinically useful technique into their imaging practices.
A Novel Rat Model for Comprehensive Microvascular Training of End-to-End, End-to-Side, and Side-to-Side Anastomoses
Authors: Yin Xiaoliang , Ye Gengfan , Lu Jun , Wang Lijun , Qi Peng , Wang Haifeng , Wang Junjie , Hu Shen , Yang Ximeng , Chen Kunpeng , Wang Daming
Published: March 2019

Background End-to-end, end-to-side, and side-to-side microvascular anastomoses are the main types of vascular bypass grafting used in microsurgery and neurosurgery. Currently, there has been no animal model available for practicing all three anastomoses in one operation. The aim of this study was to develop a novel animal model that utilizes the rat abdominal aorta (AA), common iliac arteries (CIAs), and the median sacral artery (MSA) for practicing these three types of anastomosis.

Methods Eight adult Sprague–Dawley rats were anesthetized and then laparotomized. The AA, MSA, and bilateral CIAs were exposed and separated from the surrounding tissues. The length and diameter of each artery were measured. The relatively long segment of the AA without major branches was selected to perform end-to-end anastomosis. One side of the CIAs (or AA) and MSA were used for end-to-side anastomosis. The bilateral CIAs were applied to a side-to-side and another end-to-side anastomosis.

Results Anatomical dissection of the AA, CIAs, and MSA was successfully performed on eight Sprague–Dawley rats; four arterial-to-arterial anastomoses were possible for each animal. The AA trunk between the left renal artery and right iliolumbar arteries was 15.60 ± 0.76 mm in length, 1.59 ± 0.15 mm in diameter, for an end-to-end anastomosis. The left CIA was 1.06 ± 0.08 mm in diameter, for an end-to-side anastomosis with the right CIA. The MSA was 0.78 ± 0.07 mm in diameter, for another end-to-side anastomosis with the right CIA or AA. After finishing end-to-side anastomosis in the proximal part of bilateral CIAs, the distal portion was juxtaposed for an average length of 5.6 ± 0.25 mm, for a side-to-side anastomosis.

Conclusion This model can comprehensively and effectively simulate anastomosis used in revascularization procedures and can provide more opportunities for surgical education, which may lead to more routine use in microvascular anastomosis training.
Length of the Tendon within the Tibial Tunnel Affects Tibial Tunnel Widening following Anatomic Anterior Cruciate Ligament Reconstruction Using a Bone–Patellar Tendon–Bone Graft
Authors: Taketomi Shuji , Inui Hiroshi , Yamagami Ryota , Kawaguchi Kohei , Nakazato Keiu , Kono Kenichi , Kawata Manabu , Nakagawa Takumi , Tanaka Sakae
Published: March 2019

The purpose of this study was to retrospectively investigate the effects of variations in the length of the tendon within the tibial tunnel on tunnel widening (TW) following anatomical anterior cruciate ligament (ACL) reconstruction using a bone–patellar tendon–bone (BTB) graft. In total, 68 patients who underwent isolated ACL reconstructions using BTB grafts were included in this study. The patients were divided into two groups according to the length of the tendon within the tibial tunnel: group S (n = 30; tendon length, < 10 mm) and group L (n = 38; tendon length, ≥ 10 mm). Tunnel aperture area was measured using three-dimensional computed tomography (3D CT) at 1 week and 1 year postoperatively, and tibial TW (%) was calculated. The correlation coefficient between the length of the tendon within the tibial tunnel and tibial TW was also calculated. Clinical assessment was performed 1 year postoperatively, corresponding to the period of CT assessment, which involved the evaluation of the Lysholm's score, measurement of anterior knee stability using a KneeLax3 arthrometer, and the pivot-shift test. A weak positive correlation was observed between the length of the tendon within the tibial tunnel and tibial TW (r = 0.270, p = 0.026). Mean tibial tunnel aperture area increased by 19.3 ± 17.4% and 35.8 ± 25.4% in the groups S and L, respectively. TW in the group L was significantly greater than that in the group S (p = 0.004). No significant difference was observed between the two groups in any clinical outcomes. In conclusion, a longer tendinous portion within the tibial tunnel resulted in a greater tibial TW following anatomical ACL reconstructions using a BTB graft.
Continuous Video-Rate Laser Speckle Imaging for Intra- and Postoperative Cutaneous Perfusion Imaging of Free Flaps
Authors: Rauh Annika , Henn Dominic , Nagel Sarah S. , Bigdeli Amir K. , Kneser Ulrich , Hirche Christoph
Published: March 2019

Background Success of free tissue transfer depends on standardized intraoperative flap design, microsurgical technique, and postoperative monitoring. We sought to investigate whether laser speckle imaging (LSI) is suitable for optimization of intraoperative flap design and postoperative monitoring of free flaps with skin paddles.

Methods Skin perfusion was assessed with LSI in 27 free flaps after dissection at the donor site, after anastomosis at the recipient site, after inset and on postoperative days (POD) 1, 5, and 10. Skin perfusion of the whole flap (ROI [region of interest]-1) and the area over the pedicle (ROI-2) were compared between patients with and without postoperative complications (POC+ and POC − , respectively). A receiver operating characteristic (ROC) analysis was performed to determine the optimal cutoff for perfusion during LSI-guided microsurgery.

Results In flaps without or only minor POC, intraoperatively measured perfusion over ROI-2 was significantly higher compared with ROI-1, whereas no significant differences were found for flaps with major POC. Perfusion of ROI-1 and 2 intraoperatively and on POD 1 was significantly lower in the POC+ compared with the POC− group (p < 0.05). ROC analysis yielded a threshold of 107 perfusion units (PU) at ROI-2 with an area under the curve (AUC) of > 0.8 for identification of flaps with major POC.

Conclusion LSI is an easy to use, noninvasive technique for identification of malperfused areas in free flaps, thus allowing for intraoperative decision-making on flap dimensions and postoperative monitoring. LSI therefore is a valuable tool for perfusion assessment with a high potential to become an established part of microsurgical practice.
Research governance and the future(s) of research assessment
Authors: Oancea Alis
Published: March 2019

This paper explores recent public debates around research assessment and its future as part of a dynamic landscape of governance discourses and practices, and organisational, professional and disciplinary cultures. Drawing reflectively on data from RAE 2001, RAE 2008 and REF 2014 (reported elsewhere), the paper highlights how recent debates around research assessment echo longer-term changes in research governance. The following changes, and several critiques of their implications, are discussed: shifts in the principles for governing research and the rise of multi-purpose assessment; the spread of performance-based funding and external accountability for research; the use of metrics and indicators in research assessment; the boundary work taking place in defining and classifying units or fields for assessment; the emphasis on research impact as a component of research value; organisational recalibration across the sector; and the specialisation of blended professional practice. These changes are underpinned by persistent tensions around accountability; evaluation; measurement; demarcation; legitimation; agency; and identity in research. Overall, such trends and the discursive shifts that made them possible have challenged established principles of funding and governance and have pushed assessment technologies into a pivot position in the political dynamics of renegotiating the relationships between universities and the state. Jointly, the directions of travel identified in this paper describe a widespread and persistent regime of research governance and policy that has become embedded in institutional and individual practices.
Stabilization of ferroelectric phase of Hf0.58Zr0.42O2 on NbN at 4 K
Authors: Henry M. D. , Smith S. W. , Lewis R. M. , Ihlefeld J. F.
Published: March 2019

Ferroelectricity in doped and alloyed hafnia thin films has been demonstrated using several different electrodes, with TiN and TaN being most prominent. In this work, we demonstrate ferroelectric Hf0.58Zr0.42O2 thin films with superconducting NbN electrodes at cryogenic temperatures. Demonstration of polarization—electric field [P(E)] response at liquid helium cryogenic temperatures, 4 K, suggests that the polarization is switchable over a wide temperature range after an initial 600 °C anneal. Further, room temperature P(E) and capacitance measurements demonstrate an expected polarization response with wake-up required to reach the steady state. Wake-up cycling at 4 K is observed to have no effect upon the ferroelectric phase suggesting an oxygen vacancy mobility freeze out whereas wake-up cycling at 294 K demonstrates close to a 3× increase in remanent polarization. This integration of a ferroelectric Hf0.58Zr0.42O2 thin film with NbN demonstrates the suitability of a highly scalable ferroelectric in applications for cryogenic technologies.
Re-entry blackout elimination and communication performance analysis based on laser-plasma-induced X-ray emission
Authors: Li Huan , Tang Xiaobin , Hang Shuang , Liu Yunpeng , Mu Junxu , Zhou Wei
Published: March 2019

X-ray communication (XCOM) offers important advantages to both civilian and military space projects. Rapid advance in high-intensity laser interaction with plasma has become a driving force for providing a new X-ray carrier generation based on the laser wakefield acceleration scheme. XCOM has the potential to eliminate RF shielding on the ground and communicate with the re-entry supersonic spacecraft during blackout occurrence. In this process, the plasma sheath is formed around the surface due to air compression and ablation, which blocks the traditional communication signals. In this paper, the hazardous substance was proactively exploited and coupled with the modulated laser. Particle-In-Cell simulation results indicate the ultra-bright controllable X-ray emission with a small angular divergence (0.04 rad×0.03 rad), a tunable X-ray energy range (4.60 keV to 321.48 keV), and high photon yields. Additionally, the data rate of the communication via the X-ray carrier during re-entry was estimated up to ∼20.7 Mbps by considering the transmission model, encoding schemes and photon information efficiency. Combined with an existing or developing X-ray detection technique, this regime can eliminate re-entry blackout and also provide a novel modulated X-ray source to acquire high-rate, low transmit power, and highly secure space-based data links.
Magnetic-field control of ionic bonds on ferroelectric surfaces
Authors: Hu Jia-Mian , Eom Chang-Beom
Published: March 2019

It is shown theoretically that applying magnetic fields can modulate the strength of ionic bonds on the surface of a ferroelectric film via field-induced strains from a magnetostrictive substrate. The ionic bonds form between oppositely charged polyelectrolytes that are bonded to the ferroelectric surface via the Coulomb interaction. The calculations show that applying a magnetic field can tune the activation energy of bond dissociation up by ∼50% or down to zero. This large modulation results from the high sensitivity of ferroelectric surface polarization to strain variation near ferroelectric phase transitions, which occur in epitaxial BaTiO3 films at experimentally accessible residual strains. Our results suggest an opportunity for tailoring the ionic bond strength on ferroelectric surfaces both statically and dynamically via strain engineering.
Microscopic and mesoscopic understanding of magnetization compensation phenomenon in ferrimagnetic Li0.5FeCr1.5O4 spinel
Authors: Ghanathe Madhu , Kumar Amit , Yusuf S. M.
Published: March 2019

Structural and magnetic properties of the spinel compound, Li0.5FeCr1.5O4, have been investigated using dc magnetization, neutron depolarization, and neutron diffraction techniques. DC magnetization measurement at 200 Oe has revealed a ferrimagnetic ordering at 417 K and a negative magnetization state between the two compensation temperatures (TComp) of 244 and 256 K. TComp varies with an applied magnetic field and two TComp merge at 256 K for magnetic fields ≥ 500 Oe. The existence of zero domain magnetization around TComp is evident from full recovery of the transmitted neutron beam polarization in a neutron depolarization study. The Rietveld refinement of the neutron diffraction pattern at 430 K reveals that the compound possesses a face centred cubic structure with Fe0.81Li0.19 and Cr1.5Li0.31Fe0.19 as cation distributions at the tetrahedral and octahedral sites, respectively. A temperature dependent neutron diffraction study reveals that the net magnetic moment changes sign near 265 K, across the spin compensation temperature. Both neutron diffraction and mean field calculation show that an asymmetric variation of the sublattice moments as a function of temperature yields a dominance of the ordered tetrahedral site moment over the octahedral site moment below TComp, and vice versa above TComp, and gives a microscopic understanding of the observed magnetization reversal phenomenon. The achieved understanding of magnetization compensation and the high coercivity near TComp have implications for possible use of such ferrimagnetic materials with finite spin polarization as effective spin polarizers/analyzers in spintronic devices.
A preconditioning scheme for minimum energy path finding methods
Authors: Makri Stela , Ortner Christoph , Kermode James R.
Published: March 2019

Popular methods for identifying transition paths between energy minima, such as the nudged elastic band and string methods, typically do not incorporate potential energy curvature information, leading to slow relaxation to the minimum energy path for typical potential energy surfaces encountered in molecular simulation. We propose a preconditioning scheme which, combined with a new adaptive time step selection algorithm, substantially reduces the computational cost of transition path finding algorithms. We demonstrate the improved performance of our approach in a range of examples including vacancy and dislocation migration modeled with both interatomic potentials and density functional theory.
Power series for normal stress differences of polymeric liquids in large-amplitude oscillatory shear flow
Authors: Poungthong P. , Giacomin A. J. , Saengow C. , Kolitawong C.
Published: March 2019

Exact solutions for normal stress differences in polymeric liquids subjected to large-amplitude oscillatory shear flow (LAOS) contain many Bessel functions, each appearing in infinite sums. For the simplest relevant model of a polymeric liquid, the corotational Maxwell fluid, Bessel functions appear 38 times in the exact solution. By relevant, we mean that higher harmonics are predicted in LAOS. By contrast, approximate analytical solutions for normal stress differences in LAOS often take the form of the first few terms of a power series in the shear rate amplitude, and without any Bessel functions at all. Perhaps the best example of this, from continuum theory, is the Goddard integral expansion (GIE) that is arrived at laboriously. There is thus practical interest in extending the GIE to an arbitrary number of terms. However, each term in the GIE requires much more work than its predecessor. For the corotational Maxwell fluid, for instance, the GIE for the normal stress differences has yet to be taken beyond the fifth power of the shear rate amplitude. In this paper, we begin with the exact solution for normal stress difference responses in corotational Maxwell fluids, then perform an expansion by symbolic computation to confirm up to the fifth power, and then to continue the GIE. In this paper, for example, we continue the GIE to the 41st power of the shear rate amplitude. We use Ewoldt grids to show that our main result is highly accurate. We also show that, except in its zero-frequency limit, the radius of convergence of the GIE is infinite. We derive the pattern for the common denominators of the GIE coefficients and also for every numerator for the zeroth harmonic coefficients. We also find that the numerators of the other harmonics appear to be patternless.
Molecular dynamics simulations for hydrogen adsorption in low energy collisions with carbon and boron-nitride nanotubes
Authors: Domínguez-Gutiérrez F. J. , Martínez-Flores C. , Cabrera-Trujillo R.
Published: March 2019

The capability of carbon nanotubes (CNTs) and boron-nitride nanotubes (BNNTs) to absorb hydrogen atoms might indicate if these materials can be used to develop an efficient and fast hydrogen nanosensor device. In this work, we carry out a theoretical study of the hydrogen adsorption mechanism by carbon and boron-nitride nanotubes irradiated by atomic hydrogen in the impact energy range of 0.25–100 eV. Hydrogen adsorption, reflection, and transmission probabilities are reported. The collision dynamics is calculated by performing quantum-classical molecular dynamics simulations within the self-consistent-charge density-functional tight-binding method. We include fitting curves for the angular distribution of reflected and transmitted H atoms by using a modified Yamamura formula. Results for CNTs follow a cosine-like law, while the majority of the projectiles tend to be scattered at angles lower than 60° for BNNTs. Based on previous studies for spherical and planar carbon-based configurations, we analyse the effect of the system’s curvature on the hydrogen adsorption on CNTs. We find that for collision energies below 5 eV, the scattering process depends on the carbon system curvature; meanwhile, the adsorption is independent for collision energies below 0.5 eV. Our results for the hydrogen adsorption rates for both types of nanotubes suggest that these materials can be used in hydrogen detector devices in a wide impact energy range.
Quantitative resonant soft x-ray reflectivity from an organic semiconductor single crystal
Authors: Capelli R. , Da Como E. , Kociok-Köhn G. , Fontanesi C. , Verna A. , Pasquali L.
Published: March 2019

Resonant soft X-ray reflectivity at the carbon K-edge was applied to a trigonal tetracene single crystal. The angular resolved reflectivity was quantitatively simulated describing the tetracene crystal in terms of its dielectric tensor, which was derived from the anisotropic absorption cross section of the single molecule, as calculated by density functional theory. A good agreement was found between the experimental and theoretically predicted reflectivity. This allows us to assess the anisotropic optical constants of the organic material, probed at the carbon K-edge, in relation to the bulk/surface structural and electronic properties of the crystal, through empty energy levels.
Evidence of electron heating at different radial locations on Proto-MPEX
Authors: Lau C. , Caneses J. F. , Bigelow T. S. , Biewer T. M. , Caughman J. B. O. , Goulding R. H. , Piotrowicz P. A. , Rapp J. , Ray H. B. , Showers M.
Published: March 2019

This paper reports on the observation of controlled underdense electron heating for high heat flux applications in the Prototype Material Plasma Exposure eXperiment. The goal of this experiment is to demonstrate the source and heating concepts to create a high intensity plasma at material targets to study plasma-material interactions in similar plasma conditions to magnetic fusion divertors. A 80 kW helicon source at 13.56 MHz is used for the plasma density production and a 15 kW microwave source at 28 GHz is used for electron heating. For electron densities ∼5 × 1018 m−3, the electron temperature at the target location increases from 2 eV to 5 eV and the core heat flux increases by a factor of 5. It is shown that the radial profile of the heat flux delivered at the target can be controlled by either the background plasma density or the magnetic field. Analysis suggests that the electron heating is due to heating near the upper-hybrid resonance layer and that this heating scenario may scale up to divertor-relevant electron densities ∼5 × 1019 m−3 by increasing the microwave driving frequency to 105 GHz.
Mean transverse energy of ultrananocrystalline diamond photocathode
Authors: Chen Gongxiaohui , Adhikari Gowri , Spentzouris Linda , Kovi Kiran Kumar , Antipov Sergey , Jing Chunguang , Andreas Schroeder W. , Baryshev Sergey V.
Published: March 2019

Nitrogen incorporated ultrananocrystalline diamond [(N)UNCD] could be an enabling material platform for injector photocathode applications due to its high emissivity. While the quantum efficiency (QE) of UNCD was reported by many groups, no experimental measurements of the intrinsic emittance/mean transverse energy (MTE) have been reported. Here, MTE measurement results for an (N)UNCD photocathode in the photon energy range from 4.41 to 5.26 eV are described. The MTE demonstrates no noticeable dependence on the photon energy, with an average value of 266 meV. This spectral behavior is shown not to be dependent upon physical or chemical surface roughness and inconsistent with low electron effective mass emission from graphitic grain boundaries but may be associated with emission from spatially confined states in the grain boundaries. The combined effect of low and constant MTE and high QE, which increases with respect to the excess laser energy, may pave the way for bright UNCD photocathodes for electron injectors.
Micro-Faraday cup matrix detector for ion beam measurements in fusion plasmas
Authors: Réfy D. I. , Zoletnik S. , Dunai D. , Anda G. , Lampert M. , Hegedűs S. , Nagy D. , Palánkai M. , Kádi J. , Leskó B. , Aradi M. , Hacek P. , Weinzettl V.
Published: March 2019

Atomic beam probe is an extension of the routinely used beam emission spectroscopy diagnostic for the plasma edge current fluctuation measurement at magnetically confined plasmas. Beam atoms ionized by the plasma are directed to a curved trajectory by the magnetic field and may be detected close to the wall of the device. The arrival location and current distribution of the ions carry information about the plasma current distribution, the density profile, and the electric potential in the plasma edge. This paper describes a micro-Faraday cup matrix detector for the measurement of the few microampere ion current distribution close to the plasma edge. The device implements a shallow Faraday cup matrix, produced by printed-circuit board technology. Secondary electrons induced by the plasma radiation and the ion bombardment are basically confined into the cups by the tokamak magnetic field. Additionally, a double mask is installed in the front face to limit the ion influx into the cups and supplement secondary electron suppression. The setup was tested in detail using a lithium ion beam in the laboratory. Switching time, cross talk, and fluctuation sensitivity test results in the lab setup are presented along with the detector setup to be installed at the COMPASS tokamak.
Ground and excited energy levels can be extracted exactly from a single ensemble density-functional theory calculation
Authors: Deur Killian , Fromager Emmanuel
Published: March 2019

Gross–Oliveira–Kohn density-functional theory (GOK-DFT) for ensembles is the DFT analog of state-averaged wavefunction-based (SA-WF) methods. In GOK-DFT, the SA (so-called ensemble) exchange-correlation (xc) energy is described by a single functional of the density which, for a fixed density, depends on the weights assigned to each state in the ensemble. We show that if a many-weight-dependent xc functional is employed, then it becomes possible to extract, in principle exactly, all individual energy levels from a single GOK-DFT calculation, exactly like in a SA-WF calculation. More precisely, starting from the Kohn–Sham energies, a global Levy–Zahariev-type shift as well as a state-specific (ensemble-based) xc derivative correction must be applied in order to reach the energy level of interest. We illustrate with the asymmetric Hubbard dimer the importance and substantial weight dependence of both corrections. A comparison with more standard extraction procedures, which rely on a sequence of ensemble calculations, is made at the ensemble exact exchange level of approximation.
Lack of an equation of state for the nonequilibrium chemical potential of gases of active particles in contact
Authors: Guioth Jules , Bertin Eric
Published: March 2019

We discuss the notion of the nonequilibrium chemical potential in gases of non-interacting active particles filling two compartments separated by a potential energy barrier. Different types of active particles are considered: run-and-tumble particles, active Brownian particles, and active Brownian particles with a stochastic reorientation along an external field. After recalling some analytical results for run-and-rumble particles in one dimension, we focus on the two-dimensional case and obtain a perturbative expression of the density profile in the limit of a fast reorientation dynamics, for the three models of active particles mentioned above. Computing the chemical potentials of the nonequilibrium systems in contact from the knowledge of the stationary probability distribution of the whole system—which agrees with a recently proposed general definition of the chemical potential in nonequilibrium systems in contact—we, generically, find that the chemical potential lacks an equation of state in the sense that it depends on the detailed shape of the potential energy barrier separating the compartments and not only on bulk properties, at odds with equilibrium. This situation is reminiscent of the properties of the mechanical pressure in active systems. We also argue that the Maxwell relation is no longer valid and cannot be used to infer the nonequilibrium chemical potential from the knowledge of the mechanical pressure.
Surface melting and breakup of metal nanowires: Theory and molecular dynamics simulation
Authors: Ridings Kannan M. , Aldershof Thomas S. , Hendy Shaun C.
Published: March 2019

We consider the surface melting of metal nanowires by solving a phenomenological two-parabola Landau model and by conducting molecular dynamics simulations of nickel and aluminum nanowires. The model suggests that surface melting will precede bulk melting when the melt completely wets the surface and the wire is sufficiently thick, as is the case for planar surfaces and sufficiently large nanoparticles. Surface melting does not occur if the melt partially wets or does not wet the surface. We test this model, which assumes that the surface energies of the wire are isotropic, using molecular dynamics simulations. For nickel, we observe the onset of anisotropic surface melting associated with each of the two surface facets present, but this gives way to uniform surface melting and the solid melts radially until the solid core eventually breaks up. For aluminum, while we observe complete surface melting of one facet, the lowest energy surface remains partially dry even up to the point where the melt completely penetrates the solid core.
Magnetoresistance and anomalous Hall effect in micro-ribbons of the magnetic Weyl semimetal Co3Sn2S2
Authors: Geishendorf K. , Schlitz R. , Vir P. , Shekhar C. , Felser C. , Nielsch K. , Goennenwein S. T. B. , Thomas A.
Published: March 2019

Magnetic Weyl semimetals exhibit intriguing transport phenomena due to their non-trivial band structure. Recent experiments in the bulk crystals of the shandite-type Co3Sn2S2 have shown that this material system is a magnetic Weyl semimetal. To access the length scales relevant to chiral transport, it is mandatory to fabricate microstructures of this fascinating compound. We therefore have cut micro-ribbons (typical size 0.3 × 3 × 50 μm3) from Co3Sn2S2 single crystals using a focused beam of Ga2+-ions and investigated the impact of the sample dimensions and possible surface doping on the magnetotransport properties. The large intrinsic anomalous Hall effect observed in the micro-ribbons is quantitatively consistent with the one in bulk samples. Our results show that focused ion beam cutting can be used for nano-patterning single crystalline Co3Sn2S2, enabling future transport experiments in complex microstructures of this Weyl semimetal.
Order in polymeric liquids under oscillatory shear flow
Authors: Kanso Mona A. , Jbara L. , Giacomin A. J. , Saengow C. , Gilbert P. H.
Published: March 2019

We examine the second order orientation tensor for the simplest molecular model relevant to a polymeric liquid in large-amplitude oscillatory shear (LAOS) flow, the rigid dumbbell suspension. For this, we use an approximate solution to the diffusion equation for rigid dumbbells, an expansion for the orientation distribution function truncated after the fourth power of the shear rate amplitude. We then calculate the second order orientation tensor, and then use this to calculate the order parameter tensor. We next examine the invariants of both the second order orientation tensor and the order parameter tensor. From the second invariant of the order parameter tensor, we calculate the scalar, the nematic order, and examine its evolution for a polymeric liquid in LAOS. We find this nematic order, our main result, to be even. We use Lissajous figures to illustrate the roles of the Weissenberg and Deborah numbers on the evolving order in LAOS. We use the low frequency limit of our main result to arrive at an expression for the nematic order in steady shear flow. Our work gives a first glimpse into macromolecular order in LAOS. Our work also provides analytical benchmarks for numerical solutions to the diffusion equation for both oscillatory and steady shear flows.
Is Tollmien-Schlichting wave necessary for transition of zero pressure gradient boundary layer flow?
Authors: Sundaram Prasannabalaji , Sengupta Tapan K. , Sengupta Soumyo
Published: March 2019

Comprehensive understanding of the routes of instability and transition for many flows is not complete yet. For a zero pressure gradient (ZPG) boundary layer, linear spatial theory predicted Tollmien-Schlichting (TS) waves, which have been experimentally verified by vortically exciting the flow by a monochromatic source. This is the well-known frequency response of dynamical system theory. Natural transition in real flows occurs due to polychromatic excitation, and to simulate such transition, the ZPG boundary layer has been excited via an impulse response in some of our recent direct numerical simulations. Such impulse responses cause transition even when TS waves are not excited. In the present exercise, we show the theoretical basis of natural transition by spatiotemporal stability analysis, as used in the work of Sengupta et al. [“Spatiotemporal growing wave fronts in spatially stable boundary layers,” Phys. Rev. Lett. 96(22), 224504 (2006)], by invoking finite start-up of the frequency response to wall excitation. There appear to be different instability mechanisms active for the frequency and the impulse responses to localized wall excitation. Here, we show that in both the frequency and impulse responses, the spatiotemporal wave-front (STWF) is the common element. Additionally, we also consider cases, where following different start-ups, the wall excitation remains constant, which also show the presence of the STWF. The presented results for the ZPG boundary layer show that the TS wave is not necessary for transition to turbulence and help us to re-evaluate our understanding of the transition mechanism for this canonical flow.
Designing a camera trap monitoring program to measure efficacy of invasive predator management
Authors: van Hespen Rosanna , Hauser Cindy E. , Benshemesh Joe , Rumpff Libby , Monfort José J. Lahoz
Published: March 2019

Context
Evaluating predator management efficacy is difficult, especially when resources are limited. Carefully designing monitoring programs in advance is critical for data collection that is sufficient to evaluate management success and to inform decisions.

Aims
The aim was to investigate how the design of camera trap studies can affect the ability to reliably detect changes in red fox (Vulpes vulpes) activity over space and time. Specifically, to examine the effect of study duration, camera cost and detection zone under various environmental and management scenarios, including different fox densities, management impacts, monitoring budgets and levels of spatial and temporal variation.

Methods
A generalised linear mixed model was used to analyse simulated datasets from control sites and sites with predator management actions implemented, following a before–after or control–impact sampling design. Statistical power analyses were conducted to evaluate whether a change in fox abundance could be detected across various environmental and management scenarios.

Key results
Results showed that a before–after sampling design is less sensitive than a control–impact sampling design to the number of cameras used for monitoring. However, a before–after sampling design requires a longer monitoring period to achieve a satisfactory level of power, due to higher sensitivity to study duration. Given a fixed budget, there can be a trade-off between purchasing a small number of high quality cameras with large detection zones, or a larger number of cameras with smaller detection zones. In a control-impact design we found that if spatial heterogeneity was high, a larger number of cameras with smaller detection zones provided more power to detect a difference in fox abundance.

Conclusion
This simulation-based approach demonstrates the importance of exploring various monitoring designs to detect the effect of predator management across plausible environmental and budgetary scenarios.

Implications
The present study informs the monitoring design of an adaptive management program that aims to understand the role of managing fox predation on malleefowl (Leipoa ocellata), a threatened Australian bird. Furthermore, this approach provides a useful guide for developing cost-effective camera trap monitoring studies to assess efficacy of conservation management programs. Power analyses are an essential step for designing efficient monitoring, and indicate the strength of ecological signals that can realistically be detected through the noise of spatial and temporal heterogeneity under various budgetary constraints.
Control of hearing sensitivity by tectorial membrane calcium
Authors: Strimbu Clark Elliott , Prasad Sonal , Hakizimana Pierre , Fridberger Anders
Published: March 2019

Significance

A new mechanism that contributes to control of hearing sensitivity is described here. We show that an accessory structure in the hearing organ, the tectorial membrane, affects the function of inner ear sensory cells by storing calcium ions. When the calcium store is depleted, by brief exposure to rock concert-level sounds or by the introduction of calcium chelators, the sound-evoked responses of the sensory cells decrease. Upon restoration of tectorial membrane calcium, sensory cell function returns. This previously unknown mechanism contributes to explaining the temporary numbness in the ear that follows from listening to sounds that are too loud, a phenomenon that most people experience at some point in their lives.
PERIOD-controlled deadenylation of the
timeless
transcript in the
Drosophila
circadian clock
Authors: Grima Brigitte , Papin Christian , Martin Béatrice , Chélot Elisabeth , Ponien Prishila , Jacquet Eric , Rouyer François
Published: March 2019

Significance

Circadian oscillators rely on transcriptional negative feedback loops. In
Drosophila
, the key transcriptional repressor PERIOD (PER) slowly accumulates during the night under the control of its partner TIMELESS (TIM). A large number of posttranslational mechanisms regulate PER and TIM stability, but no mechanisms affecting the stability of their transcripts have been described. mRNA stability depends on the length of the poly(A) tail. We show that a deadenylase, POP2, shortens
tim
mRNA poly(A) tail, thus decreasing
tim
mRNA and TIM protein levels. Moreover, POP2 activity on
tim
mRNA appears to be inhibited by PER itself. These results reveal polyadenylation control of a core clock gene transcript and suggest that the repressor of the feedback loop also acts as a posttranscriptional regulator.
Activity-dependent visualization and control of neural circuits for courtship behavior in the fly
Drosophila melanogaster
Authors: Takayanagi-Kiya Seika , Kiya Taketoshi
Published: March 2019

Significance

Immediate early genes (IEGs) are a group of genes whose expression is transiently up-regulated upon neural activity. In the present study, we established a method to label neural circuits in an activity-dependent manner, by combining the expression of an insect IEG
Hr38
and the powerful genetics of vinegar fly
Drosophila melanogaster
. With this method, we visualized neurons activated in the male brain when they interacted with a female and identified a neural cluster important for courtship persistency and successful copulation. Furthermore, by activity-dependently expressing light-activatable ion channel channelrhodopsin, we induced male courtship posture by light stimulation in an experience-dependent manner. Activity-dependent labeling can be used as a powerful tool in insects to examine neural circuits regulating innate behavior.
Renal reabsorption in 3D vascularized proximal tubule models
Authors: Lin Neil Y. C. , Homan Kimberly A. , Robinson Sanlin S. , Kolesky David B. , Duarte Nathan , Moisan Annie , Lewis Jennifer A.
Published: March 2019

Significance

Current kidney-on-chip models lack the 3D geometry, complexity, and functionality vital for recapitulating in vivo renal tissue. We report the fabrication and perfusion of 3D vascularized proximal tubules embedded within an engineered ECM that exhibit active reabsorption of solutes via tubular–vascular exchange. Using this model, we quantified albumin and glucose reabsorption over time. We also studied hyperglycemic effects in the absence and presence of a glucose transport inhibitor. Our 3D kidney tissue provides a platform for in vitro studies of kidney function, disease modeling, and pharmacology.
Jet stream dynamics, hydroclimate, and fire in California from 1600 CE to present
Authors: Wahl Eugene R. , Zorita Eduardo , Trouet Valerie , Taylor Alan H.
Published: March 2019

Moisture delivery in California is largely regulated by the strength and position of the North Pacific jet stream (NPJ), winter high-altitude winds that influence regional hydroclimate and forest fire during the following warm season. We use climate model simulations and paleoclimate data to reconstruct winter NPJ characteristics back to 1571 CE to identify the influence of NPJ behavior on moisture and forest fire extremes in California before and during the more recent period of fire suppression. Maximum zonal NPJ velocity is lower and northward shifted and has a larger latitudinal spread during presuppression dry and high-fire extremes. Conversely, maximum zonal NPJ is higher and southward shifted, with narrower latitudinal spread during wet and low-fire extremes. These NPJ, precipitation, and fire associations hold across pre–20th-century socioecological fire regimes, including Native American burning, postcontact disruption and native population decline, and intensification of forest use during the later 19th century. Precipitation extremes and NPJ behavior remain linked in the 20th and 21st centuries, but fire extremes become uncoupled due to fire suppression after 1900. Simulated future conditions in California include more wet-season moisture as rain (and less as snow), a longer fire season, and higher temperatures, leading to drier fire-season conditions independent of 21st-century precipitation changes. Assuming continuation of current fire management practices, thermodynamic warming is expected to override the dynamical influence of the NPJ on climate–fire relationships controlling fire extremes in California. Recent widespread fires in California in association with wet extremes may be early evidence of this change.
Evolution of nitric oxide regulation of gut function
Authors: Yaguchi Junko , Yaguchi Shunsuke
Published: March 2019

Significance

In vertebrate digestive tracts, pyloric sphincters play an important role in controlling the passage of food from stomach to intestine. A major regulator of sphincter relaxation is nitric oxide (NO). However, it is unknown when and how this important means of control was acquired, in part because we lack information on how nonvertebrate deuterostome sphincters are regulated. Here, we show that a NO-dependent regulatory system is present in the pyloric sphincters of sea urchin larvae. Our data suggest that NO-dependent regulation of the pyloric sphincter was present in deuterostome stem groups, and the common deuterostome ancestor had endodermally derived cells that regulated gut function.
Effect of oil spills on infant mortality in Nigeria
Authors: Bruederle Anna , Hodler Roland
Published: March 2019

Oil spills can lead to irreversible environmental degradation and are a potential hazard to human health. We study how onshore oil spills affect neonatal and infant mortality by combining spatial data from the Nigerian Oil Spill Monitor with Demographic and Health Surveys. To identify a causal effect, we compare siblings born to the same mother, conceived before and after a nearby oil spill. We find that nearby oil spills that occur before conception increase neonatal mortality by 38.3 deaths per 1,000 live births, which corresponds to an increase of around 100% on the sample mean. The effect is fairly uniform across girls and boys, socio-economic backgrounds, and locations. We show that this effect is not driven by events related to oil production or violent conflict. Rather, our results are consistent with medical and epidemiological evidence showing that exposure to hydrocarbons can pose risks to fetal development. We provide further evidence suggesting that the effects of oil spills on neonatal mortality persist for several years after the occurrence of an oil spill.
Spastin is a dual-function enzyme that severs microtubules and promotes their regrowth to increase the number and mass of microtubules
Authors: Kuo Yin-Wei , Trottier Olivier , Mahamdeh Mohammed , Howard Jonathon
Published: March 2019

Significance

Microtubule-severing enzymes are ATPases that utilize ATP hydrolysis to fragment microtubules. These enzymes play central roles in various cellular functions, including cell growth and division and neural development. In vivo studies have shown that severing enzymes can lead to an increase in microtubule mass, but how severing activity and microtubule dynamics collectively expand the microtubule network remains unclear. Here, we demonstrate that the severing enzyme spastin is a dual-microtubule regulator: in addition to its severing activity, it promotes microtubule regrowth through an ATP-independent mechanism. Using a mathematical model, we show that the modulation of dynamics is essential for increasing microtubule mass and identify quantitative criteria that must be satisfied if severing is to expand the microtubule network.
Critical symbiont signals drive both local and systemic changes in diel and developmental host gene expression
Authors: Moriano-Gutierrez Silvia , Koch Eric J. , Bussan Hailey , Romano Kymberleigh , Belcaid Mahdi , Rey Federico E. , Ruby Edward G. , McFall-Ngai Margaret J.
Published: March 2019

The colonization of an animal’s tissues by its microbial partners creates networks of communication across the host’s body. We used the natural binary light-organ symbiosis between the squid
Euprymna scolopes
and its luminous bacterial partner,
Vibrio fischeri
, to define the impact of colonization on transcriptomic networks in the host. A night-active predator,
E. scolopes
coordinates the bioluminescence of its symbiont with visual cues from the environment to camouflage against moon and starlight. Like mammals, this symbiosis has a complex developmental program and a strong day/night rhythm. We determined how symbiont colonization impacted gene expression in the light organ itself, as well as in two anatomically remote organs: the eye and gill. While the overall transcriptional signature of light organ and gill were more alike, the impact of symbiosis was most pronounced and similar in light organ and eye, both in juvenile and adult animals. Furthermore, the presence of a symbiosis drove daily rhythms of transcription within all three organs. Finally, a single mutation in
V. fischeri
—specifically, deletion of the
lux
operon, which abrogates symbiont luminescence—reduced the symbiosis-dependent transcriptome of the light organ by two-thirds. In addition, while the gills responded similarly to light-organ colonization by either the wild-type or mutant, luminescence was required for all of the colonization-associated transcriptional responses in the juvenile eye. This study defines not only the impact of symbiont colonization on the coordination of animal transcriptomes, but also provides insight into how such changes might impact the behavior and ecology of the host.
Tcf1 and Lef1 are required for the immunosuppressive function of regulatory T cells
Authors: Xing Shaojun , Gai Kexin , Li Xiang , Shao Peng , Zeng Zhouhao , Zhao Xudong , Zhao Xin , Chen Xia , Paradee William J. , Meyerholz David K. , Peng Weiqun , Xue Hai-Hui
Published: March 2019

Tcf1 and Lef1 have versatile functions in regulating T cell development and differentiation, but intrinsic requirements for these factors in regulatory T (T reg) cells remain to be unequivocally defined. Specific ablation of Tcf1 and Lef1 in T reg cells resulted in spontaneous multi-organ autoimmunity that became more evident with age. Tcf1/Lef1-deficient T regs showed reduced protection against experimentally induced colitis, indicative of diminished immuno-suppressive capacity. Transcriptomic analysis revealed that Tcf1 and Lef1 were responsible for positive regulation of a subset of T reg–overrepresented signature genes such as Ikzf4 and Izumo1r. Unexpectedly, Tcf1 and Lef1 were necessary for restraining expression of cytotoxic CD8+ effector T cell–associated genes in T reg cells, including Prdm1 and Ifng. Tcf1 ChIP-seq revealed substantial overlap between Tcf1 and Foxp3 binding peaks in the T reg cell genome, with Tcf1-Foxp3 cooccupancy observed at key T reg signature and cytotoxic effector genes. Our data collectively indicate that Tcf1 and Lef1 are critical for sustaining T reg suppressive functions and preventing loss of self-tolerance.