bluuebunny/crossref_metadata_2025 huggingface dataset:
Target fabrication for laser-ion acceleration research at the Technological Laboratory of the LMU Munich
Authors: Szerypo J. , Ma W. , Bothmann G. , Hahner D. , Haug M. , Hilz P. , Kreuzer Ch. , Lange R. , Seuferling S. , Speicher M. , Stehr F. , Stork S. , Thirolf P. G. , Schreiber J. , Wirth H.-F.
Published: May 2019

The Technological Laboratory of LMU Munich supplies various types of solid-state target for laser plasma experiments at the Centre for Advanced Laser Applications in Garching. Our main focus here is on the production of free-standing, thin foil targets, such as diamond-like-carbon foils, carbon nanotube foams (CNFs), plastic, and gold foils. The presented methods comprise cathodic arc deposition for DLC targets, chemical vapor deposition for CNFs, a droplet and spin-coating process for plastic foil production, as well as physical vapor deposition that has been optimized to provide ultrathin gold foils and tailored sacrifice layers. This paper reviews our current capabilities, which are a result of a close collaboration between target production processes and experiment, using high-power chirped pulse amplification laser systems over the past eight years.
Estimation of the magnitude of quadrupole relaxation enhancement in the context of magnetic resonance imaging contrast
Authors: Kruk Danuta , Masiewicz Elzbieta , Umut Evrim , Petrovic Andreas , Kargl Rupert , Scharfetter Hermann
Published: May 2019

Magnetic Resonance Imaging (MRI) is one of the most powerful diagnostic tools providing maps of 1H relaxation times of human bodies. The method needs, however, a contrast mechanism to enlarge the difference in the relaxation times between healthy and pathological tissues. In this work, we discuss the potential of a novel contrast mechanism for MRI based on Quadrupole Relaxation Enhancement (QRE) and estimate the achievable value of QRE under the most favorable conditions. It has turned out that the theoretically possible enhancement factors are smaller than those of typical paramagnetic contrast agents, but in turn, the field-selectivity of QRE-based agents makes them extremely sensitive to subtle changes of the electric field gradient in the tissue. So far, QRE has been observed for solids (in most cases for 14N) as a result of very slow dynamics and anisotropic spin interactions, believed to be necessary for QRE to appear. We show the first evidence that QRE can be achieved in solutions of compounds containing a high spin nucleus (209Bi) as the quadrupole element. The finding of QRE in a liquid state is explained in terms of spin relaxation theory based on the stochastic Liouville equation. The results confirm the relaxation theory and motivate further exploration of the potential of QRE for MRI.
A six-degree-of-freedom micro-vibration acoustic isolator for low-temperature radiation detectors based on superconducting transition-edge sensors
Authors: Gottardi L. , van Weers H. , Dercksen J. , Akamatsu H. , Bruijn M. P. , Gao J. R. , Jackson B. , Khosropanah P. , van der Kuur J. , Ravensberg K. , Ridder M. L.
Published: May 2019

Dilution and adiabatic demagnetization refrigerators based on pulse tube cryocoolers are nowadays used in many low temperature physics experiments, such as atomic force and scanning tunneling microscopy, quantum computing, radiation detectors, and many others. A pulse tube refrigerator greatly simplifies the laboratory activities being a cryogen-free system. The major disadvantage of a pulse tube cooler is the high level of mechanical vibrations at the warm and cold interfaces that could substantially affect the performance of very sensitive cryogenic instruments. In this paper, we describe the performance of a very simple mechanical attenuation system used to eliminate the pulse-tube-induced low frequency noise of the superconducting transition-edge sensors under development for the instruments of the next generation of infra-red and X-ray space observatories.
Generation and metastability of deep level states in β-Ga2O3 exposed to reverse bias at elevated temperatures
Authors: Ingebrigtsen M. E. , Kuznetsov A. Yu. , Svensson B. G. , Alfieri G. , Mihaila A. , Vines L.
Published: May 2019

An intriguing phenomenon of electrically active defect generation is observed in homoepitaxial β-Ga2O3 films exposed to reverse bias at elevated temperatures. In particular, heating samples up to 675 K in the course of deep level transient spectroscopy measurements, i.e., with the reverse bias and voltage pulsing applied, resulted in the generation of three new levels at ∼1, ∼1.5, and ∼2 eV below the conduction band edge (labeled as E3*, E5, and E6). The corresponding defects exhibit different thermal stabilities; E5 and E6 show stability, while E3* demonstrates a remarkable metastability—it can be generated, annealed out, and regenerated in the course of sequential temperature cycles. Combining a number of annealing tests and using different types of epitaxial materials, the levels were systematically investigated, and the most credible scenario behind the phenomenon is the evolution of already existing defect configurations provoked by the applied temperature and bias.
Clustering effect on permeability spectra of magneto-dielectric composites with conductive magnetic inclusions
Authors: Li Qifan , Chen Yajie , Harris Vincent G.
Published: May 2019

Magneto-dielectric composites, promising candidate materials for next-generation microwave communication, require high permeability and low loss, which are closely related to the particle size of the magnetic fillers. However, clustering occurs when particles physically or electrically touch each other, resulting in effective particle clusters that are much larger than the individual particle size. In this paper, we extend the effective medium theory (EMT) to include the clustering effect, which describes a more accurate prediction of the effective permeability of magneto-dielectric composites over wide ranges of both particle concentration and frequency. A Monte Carlo simulation is applied to model the agglomeration of magnetic particles suspended within a polymeric matrix. The extended formula is experimentally verified by the measurement of constitutive parameters, for iron/paraffin composites with various filler concentrations, over the frequency range from 1 MHz to 1 GHz. Considering the clustering effect, the proposed EMT model corrects the overestimation of the traditional EMT models, especially near the percolation threshold where the cluster size grows comparable to the skin depth at a given frequency.
Hydration of diblock copolymer micelles: Effects of hydrophobicity and co-solvent
Authors: Dahal Udaya R. , Prhashanna Ammu , Dormidontova Elena E.
Published: May 2019

Diblock polymer micelles dispersed in an aqueous environment are being actively investigated for various applications, but there is only a qualitative understanding of the effect of the chemical structure on the micelle hydration and water dynamics as these properties are difficult to assess experimentally. Using all-atom molecular dynamics simulations, we investigate aqueous solutions of three comparable in size diblock copolymer micelles with core-forming blocks of different hydrophobicity: polybutadiene (PB), polycaprolactone (PCL), and polytetrahydrofuran (pTHF) with the same hydrophilic block, polyethylene oxide (PEO). We found that core-block hydrophobicity and ability to form hydrogen bonds with water strongly affect the water dynamics near the core: water molecules spend considerably less time in contact with the PB block than with PCL and pTHF blocks. We obtained polymer and solvent volume fraction profiles and determined that the interfacial width systematically increases with a decrease of core block hydrophobicity with water penetration into the core being negligible for PB-PEO and PCL-PEO micelles, while for pTHF-PEO micelles the interface is more diffuse and there is a noticeable penetration of water (17% by volume). For PCL-PEO micelles, which are commonly used in biomedical applications, we also investigated tetrahydrofuran (THF) penetration into the micelles from mixed THF:water solution at early stages of micelle dissolution. We found an inhomogeneous solvent distribution with a maximum of THF volume fraction in the interfacial core-corona region and partial exclusion from the PEO corona, which slows down micelle dissolution. These results can have important implications for micelle stability and use in biomedical applications.
Split-well direct-phonon terahertz quantum cascade lasers
Authors: Albo Asaf , Flores Yuri V. , Hu Qing , Reno John L.
Published: May 2019

We present a so-called “split-well direct-phonon” active region design for terahertz quantum cascade lasers (THz-QCLs). Lasers based on this scheme profit from both elimination of high-lying parasitic bound states and resonant-depopulation of the lower laser level. Negative differential resistance is observed at room temperature, which indicates that each module behaves as a clean 3-level system. We further use this design to investigate the impact of temperature on the dephasing time of GaAs/AlGaAs THz-QCLs.
A matrix isolation ESR investigation of Mg+-N2
Authors: Hearne Thomas S. , Wild Duncan A. , McKinley Allan J.
Published: May 2019

The adducts formed between 25Mg+ with 14N2 and 25Mg+ with 15N2 have been trapped in a solid neon matrix and studied with electron spin resonance (ESR) spectroscopy. These radical species were formed through the interaction of laser ablated magnesium and nitrogen gas. The Mg+-N2 radical species was found to have a ground electronic state of 2Σ+ in a linear configuration with discrete coupling to the proximate nitrogen resolved in the spectra. Fitting the ESR spectra allowed magnetic parameters to be determined as follows: g⊥ = 2.0012(5), g∥ = 2.0015(8), A⊥(1-14N) = 32(3) MHz, A∥(1-14N) = 34(5) MHz, A⊥(1-15N) = 45(4) MHz, A∥(1-15N) = 47(6) MHz, A⊥(25Mg) = −581(5) MHz, and A∥(25Mg) = −582(5) MHz, and estimates derived for A⊥(2-14N) = 1(2) MHz, A∥(2-14N) = 2(5) MHz, A⊥(2-15N) = 2(2) MHz, and A∥(2-15N) = 4(6) MHz. Ab initio calculations using the coupled-cluster single double triple methodology showed that the linear form was 59.7 kcal mol−1 more stable than the T-shaped form. The potential energy curve around the equilibrium geometry was explored using the complete active space self-consistent field approach, and Hartree–Fock singles and double configuration interaction and multireference singles and double configuration interaction calculations of the hyperfine coupling constants were undertaken, and reasonable agreement with the experiment was observed.
Identification of the mechanism responsible for the boron oxygen light induced degradation in silicon photovoltaic cells
Authors: Vaqueiro-Contreras Michelle , Markevich Vladimir P. , Coutinho José , Santos Paulo , Crowe Iain F. , Halsall Matthew P. , Hawkins Ian , Lastovskii Stanislau B. , Murin Leonid I. , Peaker Anthony R.
Published: May 2019

Silicon solar cells containing boron and oxygen are one of the most rapidly growing forms of electricity generation. However, they suffer from significant degradation during the initial stages of use. This problem has been studied for 40 years resulting in over 250 research publications. Despite this, there is no consensus regarding the microscopic nature of the defect reactions responsible. In this paper, we present compelling evidence of the mechanism of degradation. We observe, using deep level transient spectroscopy and photoluminescence, under the action of light or injected carriers, the conversion of a deep boron-di-oxygen-related donor state into a shallow acceptor which correlates with the change in the lifetime of minority carriers in the silicon. Using ab initio modeling, we propose structures of the BsO2 defect which match the experimental findings. We put forward the hypothesis that the dominant recombination process associated with the degradation is trap-assisted Auger recombination. This assignment is supported by the observation of above bandgap luminescence due to hot carriers resulting from the Auger process.
Two-dimensional antiferromagnetic boron form first principles
Authors: Yue Chengguang , Luo Kun , Xu Bo
Published: May 2019

A new two-dimensional (2D) antiferromagnetic semiconducting boron structure, named as M-B28, is predicted using ab initio evolutionary structure searching. First-principles calculations show that M-B28 has a lower energy than other 2D magnetic boron structures and is dynamically stable. The unpaired electrons from the caps of B26 clusters lead to magnetism in M-B28, while making its highest valence band flat and isolated. The Néel temperature and mechanical properties of M-B28 are evaluated with the Ising model and strain-stress method, respectively, revealing a transition temperature of 32 K and the ideal strengths of 43.7 N/m along x direction and 38.5 N/m along y direction.
New horizons in thermoelectric materials: Correlated electrons, organic transport, machine learning, and more
Authors: Urban Jeffrey J. , Menon Akanksha K. , Tian Zhiting , Jain Anubhav , Hippalgaonkar Kedar
Published: May 2019

Thermoelectrics represent a unique opportunity in energy to directly convert thermal energy or secondary waste heat into a primary resource. The development of thermoelectric materials has improved over the decades in leaps, rather than by increments—each leap forward has recapitulated the science of its time: from the crystal growth of semiconductors, to controlled doping, to nanostructuring, and to 2D confinement. Each of those leaps forward was, arguably, more a result of materials science than physics. Thermoelectrics is now ripe for another leap forward, and many probable advances rely on new physics outside of the standard band transport model of thermoelectrics. This perspective will cover a limited selection of how thermoelectrics can benefit from new discoveries in physics: wave effects in phonon transport, correlated electron physics, and unconventional transport in organic materials. We also highlight recent developments in thermoelectrics discovery aided by machine learning that may be needed to realize some of these new concepts practically. Looking ahead, developing new thermoelectric physics will also have a concomitant domino effect on adjacent fields, furthering the understanding of nonequilibrium thermal and electronic transport in novel materials.
Dynamic absorption in optical pyrometry of hot spots in plastic-bonded triaminotrinitrobenzene
Authors: Bassett Will P. , Johnson Belinda P. , Dlott Dana D.
Published: May 2019

Herein, we demonstrate a methodology for performing optical pyrometry in environments which are disadvantageous for typical pyrometry applications by introducing additional fit parameters to account for absorption or emission which convolutes the thermal spectrum. Emission spectra from a plastic-bonded formulation of triaminotrinitrobenzene (TATB) shocked by 2–4 km s−1 impacts with Al flyer plates show significant deviations from graybody behavior. To extract reliable temperatures via optical pyrometry, we fit the spectra to a combination of a graybody and either a Gaussian absorption or emission spectrum. We found that the absorption needed to fit the data corresponds well to the known pressure-dependent absorption of TATB and that the absorption model gives temperatures and emissivities in line with other explosives. By contrast, assuming molecular emission gives temperatures too low and emissivities that decrease as more materials react. We conclude that the nonthermal part of the spectrum is dominated by the absorption of unreacted TATB and accurate pyrometry of TATB must either use our graybody plus absorption model or limit the spectral range of observation to above 650 nm.
On the optimal morphology and performance of a modeled dragonfly airfoil in gliding mode
Authors: Ansari Mohd Imran , Siddique Mohammed Hamid , Samad Abdus , Anwer Syed Fahad
Published: May 2019

Numerical investigation on the effect of wing morphology of the dragonfly Aeshna cyanea is carried out to understand its influence on the aerodynamic performance. The two-dimensional wing section has corrugation all over the surface along the chord length on both upper (suction side) and lower (pressure side) surfaces. By considering each corrugation separately on different airfoils at their different positions, 10 single corrugated airfoils were generated. Simulations are performed on these different airfoils to determine the effect of each corrugation on aerodynamic performance. The flow is modeled as incompressible, Newtonian, homogeneous, and unsteady. The angle of attack was varied from 0° to 20°, and the Reynolds number (Re) was varied from 150 to 10 000. The optimum morphology and angle of attack were predicted by using the surrogate-based optimization technique for a maximum gliding ratio at different Re. A fully corrugated pressure side gives the best performance at angles of attack of 9.79° and 14.83° at low Re. At high Re, corrugations on the pressure side which are in the middle and those near the trailing edge give a maximum gliding ratio at angles of attack 9.22° and 5.276°. The spatiotemporal dynamics indicate that corrugations near the leading edge on the upper surface and corrugations near the trailing edge for the lower surface and which are in the middle are beneficial. It is also found that shear drag due to corrugation decreases but pressure drag increases; therefore, the overall drag coefficient for a fully corrugated airfoil increases. Corrugations on the suction side have little influence, while those on the pressure side causes lift enhancement.
Ionic conduction in Li3Na(NH2)4: Study of the material design for the enhancement of ion conductivity in double-cation complex hydrides
Authors: Paik Biswajit , Oguchi Hiroyuki , Sato Toyoto , Takagi Shigeyuki , Dorai Arunkumar , Kuwata Naoaki , Kawamura Junichi , Orimo Shin-ichi
Published: May 2019

Complex hydrides have collected recent attention as a new class of solid electrolytes with potential applications in all-solid-state batteries. To improve ionic conduction in the complex hydrides, multi-cation crystal structure can be attractive. It will allow tuning the cation dynamics via structure modification depending on types and number of additional cations. However, multi-cation crystal structure struggles with the inter-cation scattering among different cations. To address this issue, understanding the conduction mechanisms in the multi-cationic crystals is indispensable. Here, we study cationic conduction in a double-cation (Li and Na) complex hydride Li3Na(NH2)4, which is formed by replacing Li (with Na) from specific lattice site of LiNH2 without altering the crystal symmetry. The nuclear magnetic resonance (NMR) measurements found that Li3Na(NH2)4 is a Li-ion conductor with negligibly small Na-ion conduction. This finding is critically important to elucidate Li-ion conduction mechanism in Li3Na(NH2)4. Enhanced Li-ion conduction in Li3Na(NH2)4 is achieved by (a) suppressing diffusion of Na cation trapped at the strategically located 2c lattice sites under deep potential well; and (b) by increasing the Li defect concentration influenced by the larger volume of the Li metastable sites due to Na substitution into LiNH2. Our study will provide the design principle for multi-cation complex hydrides, and accelerate development of superior solid electrolytes for all-solid-state batteries.
Stochastic time-dependent DFT with optimally tuned range-separated hybrids: Application to excitonic effects in large phosphorene sheets
Authors: Vlček Vojtěch , Baer Roi , Neuhauser Daniel
Published: May 2019

We develop a stochastic approach to time-dependent density functional theory with optimally tuned range-separated hybrids containing nonlocal exchange, for calculating optical spectra. The attractive electron-hole interaction, which leads to the formation of excitons, is included through a time-dependent linear-response technique with a nonlocal exchange interaction which is computed very efficiently through a stochastic scheme. The method is inexpensive and scales quadratically with the number of electrons, at almost the same (low) cost of time dependent Kohn-Sham with local functionals. Our results are in excellent agreement with experimental data, and the efficiency of the approach is demonstrated on large finite phosphorene sheets containing up to 1958 valence electrons.
All-atom molecular dynamics study on the non-solvent induced phase separation: Thermodynamics of adding water to poly(vinylidene fluoride)/N-methyl-2-pyrrolidone solution
Authors: Taddese Tseden , Kitabata Masahiro , Okazaki Susumu
Published: May 2019

The change in the thermodynamics when adding water in poly(vinylidene fluoride) (PVDF)/N-methyl-2-pyrrolidone (NMP) solution is studied from all atom molecular dynamics (MD) simulations. This is done by estimating the free energy of mixing of PVDF/NMP solution with increasing volume fraction of water (ϕw) using an appropriately chosen thermodynamic cycle and the Bennett acceptance ratio method. The MD calculations predict the thermodynamic phase separation point of water/NMP/PVDF to be at ϕw = 0.08, in close agreement with the experimental cloud point measurement (ϕw = 0.05). Examining the enthalpic and entropic components of the free energy of mixing reveals that at low concentrations of water, the enthalpy term has the most significant contribution to the miscibility of the ternary system, whereas at higher concentrations of water, the entropy term dominates. Finally, the free energy of mixing was compared with the Flory-Huggins (FH) free energy of mixing by computing the concentration-dependent interaction parameters from MD simulations. The FH model inadequately predicted the miscibility of the PVDF solution, mainly due to its negligence of the excess entropy of mixing.
Surface chemistry of 2,3-dibromosubstituted norbornadiene/quadricyclane as molecular solar thermal energy storage system on Ni(111)
Authors: Bauer U. , Fromm L. , Weiß C. , Späth F. , Bachmann P. , Düll F. , Steinhauer J. , Matysik S. , Pominov A. , Görling A. , Hirsch A. , Steinrück H.-P. , Papp C.
Published: May 2019

Dwindling fossil fuels force humanity to search for new energy production routes. Besides energy generation, its storage is a crucial aspect. One promising approach is to store energy from the sun chemically in strained organic molecules, so-called molecular solar thermal (MOST) systems, which can release the stored energy catalytically. A prototypical MOST system is norbornadiene/quadricyclane (NBD/QC) whose energy release and surface chemistry need to be understood. Besides important key parameters such as molecular weight, endergonic reaction profiles, and sufficient quantum yields, the position of the absorption onset of NBD is crucial to cover preferably a large range of sunlight’s spectrum. For this purpose, one typically derivatizes NBD with electron-donating and/or electron-accepting substituents. To keep the model system simple enough to be investigated with photoemission techniques, we introduced bromine atoms at the 2,3-position of both compounds. We study the adsorption behavior, energy release, and surface chemistry on Ni(111) using high-resolution X-ray photoelectron spectroscopy (HR-XPS), UV photoelectron spectroscopy, and density functional theory calculations. Both Br2-NBD and Br2-QC partially dissociate on the surface at ∼120 K, with Br2-QC being more stable. Several stable adsorption geometries for intact and dissociated species were calculated, and the most stable structures are determined for both molecules. By temperature-programmed HR-XPS, we were able to observe the conversion of Br2-QC to Br2-NBD in situ at 170 K. The decomposition of Br2-NBD starts at 190 K when C–Br bond cleavage occurs and benzene and methylidene are formed. For Br2-QC, the cleavage already occurs at 130 K when cycloreversion to Br2-NBD sets in.
IKKβ slows Huntington’s disease progression in R6/1 mice
Authors: Ochaba Joseph , Fote Gianna , Kachemov Marketta , Thein Soe , Yeung Sylvia Y. , Lau Alice L. , Hernandez Sarah , Lim Ryan G. , Casale Malcolm , Neel Michael J. , Monuki Edwin S. , Reidling Jack , Housman David E. , Thompson Leslie M. , Steffan Joan S.
Published: May 2019

Significance

Huntington’s disease (HD) is a devastating neurodegenerative disorder caused by expansion of a polyglutamine repeat within the huntingtin (HTT) protein. A normal function of HTT is that of a scaffold for selective autophagy, a mechanism of protein and organelle degradation by the lysosome required for neuronal health. Here, we show that the inflammatory IκB kinase (IKK) kinase subunit IKKβ may function in vivo to regulate autophagy through direct phosphorylation of HTT at serine 13 and through the activation of autophagy gene expression. IKKβ is required to slow HD behavioral progression and to suppress neurodegeneration and microglial activation in HD transgenic mice. Our work suggests that the early activation of IKK may be protective to activate autophagy, thereby slowing HD progression.
Circadian clock regulation of the glycogen synthase (
gsn
) gene by WCC is critical for rhythmic glycogen metabolism in
Neurospora crassa
Authors: Baek Mokryun , Virgilio Stela , Lamb Teresa M. , Ibarra Oneida , Andrade Juvana Moreira , Gonçalves Rodrigo Duarte , Dovzhenok Andrey , Lim Sookkyung , Bell-Pedersen Deborah , Bertolini Maria Celia , Hong Christian I.
Published: May 2019

Significance

Circadian rhythms enable organisms to anticipate daily environmental cycles and control the timing of numerous biological processes, including metabolism, to optimize the health and survival of organisms. Glycogen metabolism is a conserved glucose homeostatic process; however, the molecular mechanisms linking the circadian clock and glycogen metabolism remain largely unknown. In this report, we demonstrate that circadian clock-dependent transcriptional regulation of glycogen synthase,
gsn
, regulates circadian oscillations of GSN protein and glycogen accumulation in the model filamentous fungus,
Neurospora crassa
.
The wisdom of partisan crowds
Authors: Becker Joshua , Porter Ethan , Centola Damon
Published: May 2019

Theories in favor of deliberative democracy are based on the premise that social information processing can improve group beliefs. While research on the “wisdom of crowds” has found that information exchange can increase belief accuracy on noncontroversial factual matters, theories of political polarization imply that groups will become more extreme—and less accurate—when beliefs are motivated by partisan political bias. A primary concern is that partisan biases are associated not only with more extreme beliefs, but also with a diminished response to social information. While bipartisan networks containing both Democrats and Republicans are expected to promote accurate belief formation, politically homogeneous networks are expected to amplify partisan bias and reduce belief accuracy. To test whether the wisdom of crowds is robust to partisan bias, we conducted two web-based experiments in which individuals answered factual questions known to elicit partisan bias before and after observing the estimates of peers in a politically homogeneous social network. In contrast to polarization theories, we found that social information exchange in homogeneous networks not only increased accuracy but also reduced polarization. Our results help generalize collective intelligence research to political domains.
Rates of niche and phenotype evolution lag behind diversification in a temperate radiation
Authors: Folk Ryan A. , Stubbs Rebecca L. , Mort Mark E. , Cellinese Nico , Allen Julie M. , Soltis Pamela S. , Soltis Douglas E. , Guralnick Robert P.
Published: May 2019

Environmental change can create opportunities for increased rates of lineage diversification, but continued species accumulation has been hypothesized to lead to slowdowns via competitive exclusion and niche partitioning. Such density-dependent models imply tight linkages between diversification and trait evolution, but there are plausible alternative models. Little is known about the association between diversification and key ecological and phenotypic traits at broad phylogenetic and spatial scales. Do trait evolutionary rates coincide with rates of diversification, are there lags among these rates, or is diversification niche-neutral? To address these questions, we combine a deeply sampled phylogeny for a major flowering plant clade—Saxifragales—with phenotype and niche data to examine temporal patterns of evolutionary rates. The considerable phenotypic and habitat diversity of Saxifragales is greatest in temperate biomes. Global expansion of these habitats since the mid-Miocene provided ecological opportunities that, with density-dependent adaptive radiation, should result in simultaneous rate increases for diversification, niche, and phenotype, followed by decreases with habitat saturation. Instead, we find that these rates have significantly different timings, with increases in diversification occurring at the mid-Miocene Climatic Optimum (∼15 Mya), followed by increases in niche and phenotypic evolutionary rates by ∼5 Mya; all rates increase exponentially to the present. We attribute this surprising lack of temporal coincidence to initial niche-neutral diversification followed by ecological and phenotypic divergence coincident with more extreme cold and dry habitats that proliferated into the Pleistocene. A lack of density-dependence contrasts with investigations of other cosmopolitan lineages, suggesting alternative patterns may be common in the diversification of temperate lineages.
Derivation of simian tropic HIV-1 infectious clone reveals virus adaptation to a new host
Authors: Schmidt Fabian , Keele Brandon F. , Del Prete Gregory Q. , Voronin Dennis , Fennessey Christine M. , Soll Steven , Kane Melissa , Raymond Alice , Gifford Robert J. , KewalRamani Vineet , Lifson Jeffrey D. , Bieniasz Paul D. , Hatziioannou Theodora
Published: May 2019

To replicate in a new host, lentiviruses must adapt to exploit required host factors and evade species-specific antiviral proteins. Understanding how host protein variation drives lentivirus adaptation allowed us to expand the host range of HIV-1 to pigtail macaques. We have previously derived a viral swarm (in the blood of infected animals) that can cause AIDS in this new host. To further exploit this reagent, we generated infectious molecular clones (IMCs) from the viral swarm. We identified clones with high replicative capacity in pigtail peripheral blood mononuclear cells (PBMC) in vitro and used in vivo replication to select an individual IMC, named stHIV-A19 (for simian tropic HIV-1 clone A19), which recapitulated the phenotype obtained with the viral swarm. Adaptation of HIV-1 in macaques led to the acquisition of amino acid changes in viral proteins, such as capsid (CA), that are rarely seen in HIV-1–infected humans. Using stHIV-A19, we show that these CA changes confer a partial resistance to the host cell inhibitor Mx2 from pigtail macaques, but that complete resistance is associated with a fitness defect. Adaptation of HIV-1 to a new host will lead to a more accurate animal model and a better understanding of virus–host interactions.
Decreasing measles burden by optimizing campaign timing
Authors: Thakkar Niket , Gilani Syed Saqlain Ahmad , Hasan Quamrul , McCarthy Kevin A.
Published: May 2019

Measles remains a major contributor to preventable child mortality, and bridging gaps in measles immunity is a fundamental challenge to global health. In high-burden settings, mass vaccination campaigns are conducted to increase access to vaccine and address this issue. Ensuring that campaigns are optimally effective is a crucial step toward measles elimination; however, the relationship between campaign impact and disease dynamics is poorly understood. Here, we study measles in Pakistan, and we demonstrate that campaign timing can be tuned to optimally interact with local transmission seasonality and recent incidence history. We develop a mechanistic modeling approach to optimize timing in general high-burden settings, and we find that in Pakistan, hundreds of thousands of infections can be averted with no change in campaign cost.
In vivo evidence for dysregulation of mGluR5 as a biomarker of suicidal ideation
Authors: Davis Margaret T. , Hillmer Ansel , Holmes Sophie E. , Pietrzak Robert H. , DellaGioia Nicole , Nabulsi Nabeel , Matuskey David , Angarita Gustavo A. , Carson Richard E. , Krystal John H. , Esterlis Irina
Published: May 2019

Significance

Posttraumatic stress disorder (PTSD) is an important risk factor for suicidal ideation, attempts, and death by suicide. Understanding of the biology underlying suicidality in PTSD is limited. In this study, we used positron emission tomography to evaluate the metabotropic glutamate receptor type 5 (mGluR5) as a potential treatment target and biomarker of suicidal ideation in individuals with PTSD and major depressive disorder (MDD). We found higher availability of mGluR5 in individuals with PTSD relative to healthy control and MDD groups. Furthermore, higher mGluR5 availability was associated with scan-day suicidal ideation among individuals with PTSD, but not MDD. Findings identify mGluR5 as a biomarker for intervention and potentially suicide risk management in PTSD.
EHMT2 and SETDB1 protect the maternal pronucleus from 5mC oxidation
Authors: Zeng Tie-Bo , Han Li , Pierce Nicholas , Pfeifer Gerd P. , Szabó Piroska E.
Published: May 2019

Significance

The most important task of the mammalian zygote is to globally remodel its epigenome. Chromosomes that carried out sperm or oocyte functions are remodeled toward directing the unique totipotent state that characterizes the healthy preimplantation-stage embryo. The guiding differences in cell functions are marked on the chromosomes by interdependent epigenetic modifications including histone and DNA methylation, which both undergo global changes in the zygote. By performing genetic experiments, we found that two maternally supplied histone methyltransferase enzymes play important roles in the zygote in specifying the process of global DNA remodeling by 5-methylcytosine oxidation.
Unraveling ancestry, kinship, and violence in a Late Neolithic mass grave
Authors: Schroeder Hannes , Margaryan Ashot , Szmyt Marzena , Theulot Bertrand , Włodarczak Piotr , Rasmussen Simon , Gopalakrishnan Shyam , Szczepanek Anita , Konopka Tomasz , Jensen Theis Z. T. , Witkowska Barbara , Wilk Stanisław , Przybyła Marcin M. , Pospieszny Łukasz , Sjögren Karl-Göran , Belka Zdzislaw , Olsen Jesper , Kristiansen Kristian , Willerslev Eske , Frei Karin M. , Sikora Martin , Johannsen Niels N. , Allentoft Morten E.
Published: May 2019

The third millennium BCE was a period of major cultural and demographic changes in Europe that signaled the beginning of the Bronze Age. People from the Pontic steppe expanded westward, leading to the formation of the Corded Ware complex and transforming the genetic landscape of Europe. At the time, the Globular Amphora culture (3300–2700 BCE) existed over large parts of Central and Eastern Europe, but little is known about their interaction with neighboring Corded Ware groups and steppe societies. Here we present a detailed study of a Late Neolithic mass grave from southern Poland belonging to the Globular Amphora culture and containing the remains of 15 men, women, and children, all killed by blows to the head. We sequenced their genomes to between 1.1- and 3.9-fold coverage and performed kinship analyses that demonstrate that the individuals belonged to a large extended family. The bodies had been carefully laid out according to kin relationships by someone who evidently knew the deceased. From a population genetic viewpoint, the people from Koszyce are clearly distinct from neighboring Corded Ware groups because of their lack of steppe-related ancestry. Although the reason for the massacre is unknown, it is possible that it was connected with the expansion of Corded Ware groups, which may have resulted in competition for resources and violent conflict. Together with the archaeological evidence, these analyses provide an unprecedented level of insight into the kinship structure and social behavior of a Late Neolithic community.
Early detonation by sprouted mossy fibers enables aberrant dentate network activity
Authors: Hendricks William D. , Westbrook Gary L. , Schnell Eric
Published: May 2019

Significance

Sprouted mossy fibers are one of the hallmark histopathological findings in experimental and human temporal lobe epilepsy. These fibers form recurrent excitatory synapses onto other dentate granule cells that display profound short-term depression. Here, however, we show that although these sprouted mossy fibers weaken substantially during repetitive activation, their initial high probability of glutamate release can activate reverberant network activity. Furthermore, we find that a lack of tonic adenosine inhibition enables this high probability of release and, consequently, recurrent network activity.
Dynamic microscale flow patterning using electrical modulation of zeta potential
Authors: Paratore Federico , Bacheva Vesna , Kaigala Govind V. , Bercovici Moran
Published: May 2019

Significance

Traditional microfluidic devices make use of physical channels and mechanical actuators, in which geometries and functionalities are intimately related to one another, i.e., changing the flow field requires change at the mechanical level. In this work, we introduce a concept in which a microfluidic chamber with no preset structures or active mechanical components can be dynamically configured to produce desired flow fields.
An ammonite trapped in Burmese amber
Authors: Yu Tingting , Thomson Ulysses , Mu Lin , Ross Andrew , Kennedy Jim , Broly Pierre , Xia Fangyuan , Zhang Haichun , Wang Bo , Dilcher David
Published: May 2019

Significance

Aquatic organisms are rarely found in amber, but when they occur they provide invaluable evidence for the better understanding of amber taphonomy and past ecosystems. We report an ammonite and several marine gastropods alongside a mixed assemblage of intertidal and terrestrial forest floor organisms in mid-Cretaceous Burmese amber. Our discovery indicates that the Burmese amber forest was living near a dynamic and shifting coastal environment. The ammonite also provides supporting evidence for the age of the amber, which is still debated, and represents a rare example of dating using fossils present inside the amber.
CHD4 is essential for transcriptional repression and lineage progression in B lymphopoiesis
Authors: Arends Tessa , Dege Carissa , Bortnick Alexandra , Danhorn Thomas , Knapp Jennifer R. , Jia Haiqun , Harmacek Laura , Fleenor Courtney J. , Straign Desiree , Walton Kendra , Leach Sonia M. , Feeney Ann J. , Murre Cornelis , O’Connor Brian P. , Hagman James R.
Published: May 2019

Cell lineage specification is a tightly regulated process that is dependent on appropriate expression of lineage and developmental stage-specific transcriptional programs. Here, we show that Chromodomain Helicase DNA-binding protein 4 (CHD4), a major ATPase/helicase subunit of Nucleosome Remodeling and Deacetylase Complexes (NuRD) in lymphocytes, is essential for specification of the early B cell lineage transcriptional program. In the absence of CHD4 in B cell progenitors in vivo, development of these cells is arrested at an early pro-B-like stage that is unresponsive to IL-7 receptor signaling and unable to efficiently complete V(D)J rearrangements at
Igh
loci. Our studies confirm that chromatin accessibility and transcription of thousands of gene loci are controlled dynamically by CHD4 during early B cell development. Strikingly, CHD4-deficient pro-B cells express transcripts of many non-B cell lineage genes, including genes that are characteristic of other hematopoietic lineages, neuronal cells, and the CNS, lung, pancreas, and other cell types. We conclude that CHD4 inhibits inappropriate transcription in pro-B cells. Together, our data demonstrate the importance of CHD4 in establishing and maintaining an appropriate transcriptome in early B lymphopoiesis via chromatin accessibility.
Synthesis of polypeptides via bioinspired polymerization of in situ purified
N
-carboxyanhydrides
Authors: Song Ziyuan , Fu Hailin , Wang Jiang , Hui Jingshu , Xue Tianrui , Pacheco Lazaro A. , Yan Haoyuan , Baumgartner Ryan , Wang Zhiyu , Xia Yingchun , Wang Xuefang , Yin Lichen , Chen Chongyi , Rodríguez-López Joaquín , Ferguson Andrew L. , Lin Yao , Cheng Jianjun
Published: May 2019

Significance

Biomacromolecules are synthesized in cells with high precision, although the cellular environment contains numerous molecules and species other than the building blocks. In contrast, even the state-of-the-art chemical synthesis of macromolecules is exclusively carried out under a specific condition containing only clean, essential starting materials to minimize side reactions. Inspired by ribozyme-catalyzed protein synthesis, we report here controlled polypeptide synthesis by nonpurified
N
-carboxyanhydride monomers in an oil/water biphasic system that mediates impurity segregation and enables very fast polymerization that outpaces competing side reactions.
Conching chocolate is a prototypical transition from frictionally jammed solid to flowable suspension with maximal solid content
Authors: Blanco Elena , Hodgson Daniel J. M. , Hermes Michiel , Besseling Rut , Hunter Gary L. , Chaikin Paul M. , Cates Michael E. , Van Damme Isabella , Poon Wilson C. K.
Published: May 2019

The mixing of a powder of 10- to 50-

μ

m primary particles into a liquid to form a dispersion with the highest possible solid content is a common industrial operation. Building on recent advances in the rheology of such “granular dispersions,” we study a paradigmatic example of such powder incorporation: the conching of chocolate, in which a homogeneous, flowing suspension is prepared from an inhomogeneous mixture of particulates, triglyceride oil, and dispersants. Studying the rheology of a simplified formulation, we find that the input of mechanical energy and staged addition of surfactants combine to effect a considerable shift in the jamming volume fraction of the system, thus increasing the maximum flowable solid content. We discuss the possible microscopic origins of this shift, and suggest that chocolate conching exemplifies a ubiquitous class of powder–liquid mixing.
Long-range mobile signals mediate seasonal control of shoot growth
Authors: Miskolczi Pál , Singh Rajesh Kumar , Tylewicz Szymon , Azeez Abdul , Maurya Jay P. , Tarkowská Danuše , Novák Ondřej , Jonsson Kristoffer , Bhalerao Rishikesh P.
Published: May 2019

Significance

In perennial plants such as long-lived trees growing in boreal and temperate forest, transition from summer to winter is associated with induction of growth cessation and bud set at the shoot apex. Where in the plant these seasonal shifts are perceived and how these are communicated to the shoot apex remain unresolved. We identify leaves as a site for perception of seasonal shifts and reveal that components of floral transition such as
FLOWERING LOCUS T
(
FT
) and plant hormone GA have been recruited to function as long-range signals to communicate seasonal changes perceived in leaves to the shoot apical meristem to control its activity to synchronize bud set with the change of seasons in perennials.
Low ambient humidity impairs barrier function and innate resistance against influenza infection
Authors: Kudo Eriko , Song Eric , Yockey Laura J. , Rakib Tasfia , Wong Patrick W. , Homer Robert J. , Iwasaki Akiko
Published: May 2019

In the temperate regions, seasonal influenza virus outbreaks correlate closely with decreases in humidity. While low ambient humidity is known to enhance viral transmission, its impact on host response to influenza virus infection and disease outcome remains unclear. Here, we showed that housing Mx1 congenic mice in low relative humidity makes mice more susceptible to severe disease following respiratory challenge with influenza A virus. We find that inhalation of dry air impairs mucociliary clearance, innate antiviral defense, and tissue repair. Moreover, disease exacerbated by low relative humidity was ameliorated in caspase-1/11–deficient Mx1 mice, independent of viral burden. Single-cell RNA sequencing revealed that induction of IFN-stimulated genes in response to viral infection was diminished in multiple cell types in the lung of mice housed in low humidity condition. These results indicate that exposure to dry air impairs host defense against influenza infection, reduces tissue repair, and inflicts caspase-dependent disease pathology.
Estilo indirecto en la mediación interlingüística, intercultural y social del español al alemán
Authors: Vilar Sánchez Karin
Published: May 2019

The role of the interlinguistic-intercultural and social mediator (IISM) is acquiring increasing relevance in
societies that receive immigrants. Nevertheless, training has not yet been regulated. This article analyses the specific
linguistic needs and practices of such mediators in the context of Spanish speaking immigration to German speaking countries. It
can be observed that not only does the IISM require specialised linguistic terminology but also specialised training at the level
of communicative functions. This article examines one highly relevant example of such communicative functions, that of indirect
speech. In German, indirect speech is rich in expressive complexity and diversity. This means that from a Spanish-German
comparative viewpoint this aspect is particularly sensitive and merits special emphasis in the training of the IISM.
Commentary: Cancer Survivorship and Subclinical Myocardial Damage
Authors: Coughlin Steven S , Kapuku Gaston
Published: May 2019

The rate of cardiovascular disease among cancer survivors is higher than in the general population. This difference is due to traditional cardiovascular disease (CVD) risk factors and also to the cardiotoxicity of cancer treatment. In a population-based cohort study of 3,512 men and women who were free of CVD at visit 5 of a large, community-based cohort study, Florido et al. (Am J Epidemiol. 2019;188(12):2188–2195) evaluated the association of cancer survivorship with subclinical myocardial damage, as assessed by elevated high-sensitivity cardiac troponin T (hs-cTnT). Cancer survivors had significantly higher odds of elevated hs-cTnT (odds ratio = 1.26, 95% confidence interval: 1.03, 1.53). Results were similar for survivors of non-sex-related and colorectal cancers. There was no association between survivorship from breast and prostate cancers and elevated hs-cTnT. The findings of Florido et al. indicate that survivors of some cancers might be more likely to have elevated hs-cTnT than patients without prior cancer. These findings have important implications because identifying cancer survivors who have elevated CVD risk is of paramount importance in order to prevent CVD manifestations such as heart attack, congestive heart failure, or stroke. Additional research is needed to clarify the associations of elevated hs-cTnT levels among survivors of specific cancer sites, stage at diagnosis, and histologic types.
How are pollinators guided by colourful floral structures? A commentary on: ‘The role of pollinator preference in the maintenance of pollen colour variation’
Authors: Hempel de Ibarra Natalie , Somanathan Hema
Published: May 2019

This article comments on:

Jennifer L. Ison, Elizabeth S. L. Tuan, Matthew H. Koski, Jack S. Whalen and Laura F. Galloway. 2019. The role of pollinator preference in the maintenance of pollen colour variation. Annals of Botany 123(6): 951–960.