bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of a vertical axis wind turbine for application in an urban/suburban area
Authors: Nguyen Lam , Metzger Meredith
Published: August 2017

The goal of this study is to investigate the effect of various design parameters on the performance of a Vertical Axis Wind Turbine (VAWT) subjected to realistic unsteady wind conditions. Thirteen turbine design configurations are examined to determine if an optimal VAWT has applications in an urban/suburban environment. The four design parameters of interest include the height-to-diameter aspect ratio (0.83≤H/D≤1.34), blade airfoil shape (NACA 0012, 0015, 0018), turbine solidity (12≤S≤25%), and turbine moment of inertia. The height and diameter of the turbine varied between 1.89 and 2.54 m, depending on the aspect ratio. The turbine moment of inertia was calculated using a computer-aided design drawing of the turbine, along with the realistic material properties of blades, shafts, and supports. The energy generated by each VAWT design configuration is simulated using a full year of actual wind speed data collected in 2009 at 9 different locations around Oklahoma City spanning an area of approximately 500 km2. The wind data were acquired from the top of traffic light posts at a height of about 9 m above the ground. In all cases, an active control strategy is used that allows the turbine to continuously adjust its rotational speed in response to the fluctuating wind. The results suggest that, for the case of operation in unsteady winds, the optimal power coefficient (Cp) versus tip speed ratio curve is not necessarily the one exhibiting the highest peak Cp value but rather the broadest shape. Of the thirteen configurations examined, the optimal wind turbine design capable of harvesting the most energy from the gusty winds was found to have an aspect ratio of H/D=1.2, a solidity of S=12%, and a blade shape using the NACA 0015 airfoil. This design also displayed the lowest moment of inertia. However, when the effects of mass were removed, this design still performed the best. The site-to-site variation in terms of energy captured relative to the available energy in the gusty winds was only about 5% on average and increased slightly with turbine moment of inertia. Four of the suburban sites studied were deemed to be economically viable locations for a small-scale VAWT. The results further indicate that, at one of these sites, the levelized cost of energy associated with the top performing turbine designs examined in the study was about 10% less than the national electricity price, meaning that wind energy provides a cheaper alternative to fossil fuel at this location. It is surmised that VAWTs could economically harvest wind energy in the urban center as well if the turbines were located higher than 9 m, such as on the rooftops of commercial/residential buildings.
Bioprinted 3D vascularized tissue model for drug toxicity analysis
Authors: Massa Solange , Sakr Mahmoud Ahmed , Seo Jungmok , Bandaru Praveen , Arneri Andrea , Bersini Simone , Zare-Eelanjegh Elaheh , Jalilian Elmira , Cha Byung-Hyun , Antona Silvia , Enrico Alessandro , Gao Yuan , Hassan Shabir , Acevedo Juan Pablo , Dokmeci Mehmet R. , Zhang Yu Shrike , Khademhosseini Ali , Shin Su Ryon
Published: August 2017

To develop biomimetic three-dimensional (3D) tissue constructs for drug screening and biological studies, engineered blood vessels should be integrated into the constructs to mimic the drug administration process in vivo. The development of perfusable vascularized 3D tissue constructs for studying the drug administration process through an engineered endothelial layer remains an area of intensive research. Here, we report the development of a simple 3D vascularized liver tissue model to study drug toxicity through the incorporation of an engineered endothelial layer. Using a sacrificial bioprinting technique, a hollow microchannel was successfully fabricated in the 3D liver tissue construct created with HepG2/C3A cells encapsulated in a gelatin methacryloyl hydrogel. After seeding human umbilical vein endothelial cells (HUVECs) into the microchannel, we obtained a vascularized tissue construct containing a uniformly coated HUVEC layer within the hollow microchannel. The inclusion of the HUVEC layer into the scaffold resulted in delayed permeability of biomolecules into the 3D liver construct. In addition, the vascularized construct containing the HUVEC layer showed an increased viability of the HepG2/C3A cells within the 3D scaffold compared to that of the 3D liver constructs without the HUVEC layer, demonstrating a protective role of the introduced endothelial cell layer. The 3D vascularized liver model presented in this study is anticipated to provide a better and more accurate in vitro liver model system for future drug toxicity testing.
An algorithm to locate optimal bond breaking points on a potential energy surface for applications in mechanochemistry and catalysis
Authors: Bofill Josep Maria , Ribas-Ariño Jordi , García Sergio Pablo , Quapp Wolfgang
Published: August 2017

The reaction path of a mechanically induced chemical transformation changes under stress. It is well established that the force-induced structural changes of minima and saddle points, i.e., the movement of the stationary points on the original or stress-free potential energy surface, can be described by a Newton Trajectory (NT). Given a reactive molecular system, a well-fitted pulling direction, and a sufficiently large value of the force, the minimum configuration of the reactant and the saddle point configuration of a transition state collapse at a point on the corresponding NT trajectory. This point is called barrier breakdown point or bond breaking point (BBP). The Hessian matrix at the BBP has a zero eigenvector which coincides with the gradient. It indicates which force (both in magnitude and direction) should be applied to the system to induce the reaction in a barrierless process. Within the manifold of BBPs, there exist optimal BBPs which indicate what is the optimal pulling direction and what is the minimal magnitude of the force to be applied for a given mechanochemical transformation. Since these special points are very important in the context of mechanochemistry and catalysis, it is crucial to develop efficient algorithms for their location. Here, we propose a Gauss-Newton algorithm that is based on the minimization of a positively defined function (the so-called σ-function). The behavior and efficiency of the new algorithm are shown for 2D test functions and for a real chemical example.
Determining the ion temperature and energy distribution in a lithium-plasma interaction test stand with a retarding field energy analyzer
Authors: Christenson M. , Stemmley S. , Jung S. , Mettler J. , Sang X. , Martin D. , Kalathiparambil K. , Ruzic D. N.
Published: August 2017

The ThermoElectric-driven Liquid-metal plasma-facing Structures (TELS) experiment at the University of Illinois is a gas-puff driven, theta-pinch plasma source that is used as a test stand for off-normal plasma events incident on materials in the edge and divertor regions of a tokamak. The ion temperatures and resulting energy distributions are crucial for understanding how well a TELS pulse can simulate an extreme event in a larger, magnetic confinement device. A retarding field energy analyzer (RFEA) has been constructed for use with such a transient plasma due to its inexpensive and robust nature. The innovation surrounding the use of a control analyzer in conjunction with an actively sampling analyzer is presented and the conditions of RFEA operation are discussed, with results presented demonstrating successful performance under extreme conditions. Such extreme conditions are defined by heat fluxes on the order of 0.8 GW m−2 and on time scales of nearly 200 μs. Measurements from the RFEA indicate two primary features for a typical TELS discharge, following closely with the pre-ionizing coaxial gun discharge characteristics. For the case using the pre-ionization pulse (PiP) and the theta pinch, the measured ion signal showed an ion temperature of 23.3 ± 6.6 eV for the first peak and 17.6 ± 1.9 eV for the second peak. For the case using only the PiP, the measured signal showed an ion temperature of 7.9 ± 1.1 eV for the first peak and 6.6 ± 0.8 eV for the second peak. These differences illustrate the effectiveness of the theta pinch for imparting energy on the ions. This information also highlights the importance of TELS as being one of the few linear pulsed plasma sources whereby moderately energetic ions will strike targets without the need for sample biasing.
Development of high sensitivity 4H–SiC detectors for fission neutron pulse shape measurements
Authors: Wu Jian , Jiang Yong , Li Meng , Zeng Lina , Li Junjie , Gao Hui , Zou Dehui , Bai Zhongxiong , Ye Cenming , Liang Wenfeng , Dai Shaofeng , Lu Yi , Rong Ru , Du Jinfeng , Fan Xiaoqiang
Published: August 2017

4H-silicon carbide (4H–SiC) detectors are well suited for measurements of fission neutron pulse shape for their compact size, excellent radiation resistance, and hydrogen free composition. The aim of this study is to improve the 4H–SiC detector’s sensitivity to fission neutron pulses. 4H–SiC detectors with varied epilayer thicknesses are fabricated and then tested in the pulsed neutron field of the Chinese Fast Burst Reactor II (CFBR II). The sensitivity of the 4H–SiC detector to the CFBR II neutron pulse is increased by 139.8%, with the enlargement of epilayer thickness from 20 μm to 120 μm. By employing the proton-recoil method, the sensitivity of the 4H–SiC detector to the CFBR II neutron pulse is further increased by 11.6%. With enhanced sensitivity to fission neutron pulses, 4H–SiC detectors are promising devices for high intensity neutron pulse measurements.
Control of vortex-induced vibration using a pair of synthetic jets: Influence of active lock-on
Authors: Wang Chenglei , Tang Hui , Yu Simon C. M. , Duan Fei
Published: August 2017

While conventional vortex-induced vibration (VIV) of bluff bodies is suppressed through reducing the strength of asymmetric vortex shedding, it can also be mitigated by shifting the vortex shedding frequency away from the natural frequency of the body structures using active lock-on. Recently Du and Sun [“Suppression of vortex-induced vibration using the rotary oscillation of a cylinder,” Phys. Fluids 27, 023603 (2015)] utilized periodical rotation to induce the lock-on of the frequency of vortex shedding from a transversely vibrating cylinder to the rotation frequency and demonstrated successful VIV suppression. However, questions were raised from this investigation: Does the occurrence of active lock-on always suppress VIV? If not, how to ensure the appropriate usage of active lock-on for VIV suppression? To address these research questions, a numerical investigation is conducted on the active VIV control of a circular cylinder using a pair of synthetic jets (SJs) at a low Reynolds number of 100. The SJ pair operates with various phase differences over a wide frequency range so that the influence of various lock-on can be investigated. It is found that the VIV control can be affected not only by the occurrence of the primary lock-on but also by the occurrence of other lock-on such as secondary and tertiary lock-on. The occurrence of lock-on does not always result in successful VIV suppression. Sometimes it even causes the augmentation of VIV. Compared to the VIV suppression using the conventional vortex-strength-reduction method, the control by the means of active lock-on seems less effective.
Total cross section of furfural by electron impact: Experiment and theory
Authors: Traoré Dubuis A. , Verkhovtsev A. , Ellis-Gibbings L. , Krupa K. , Blanco F. , Jones D. B. , Brunger M. J. , García G.
Published: August 2017

We present experimental total cross sections for electron scattering from furfural in the energy range from 10 to 1000 eV, as measured using a double electrostatic analyzer gas cell electron transmission experiment. These results are compared to theoretical data for furfural, as well as to experimental and theoretical values for the structurally similar molecules furan and tetrahydrofuran. The measured total cross section is in agreement with the theoretical results obtained by means of the independent-atom model with screening corrected additivity rule including interference method. In the region of higher electron energies, from 500 eV to 10 keV, the total electron scattering cross section is also estimated using a semi-empirical model based on the number of electrons and dipole polarizabilities of the molecular targets. Together with the recently measured differential and integral cross sections, and the furfural energy-loss spectra, the present total cross section data nearly complete the data set that is required for numerical simulation of low-energy electron processes in furfural, covering the range of projectile energies from a few electron volts up to 10 keV.
aCORN: An experiment to measure the electron-antineutrino correlation coefficient in free neutron decay
Authors: Collett B. , Bateman F. , Bauder W. K. , Byrne J. , Byron W. A. , Chen W. , Darius G. , DeAngelis C. , Dewey M. S. , Gentile T. R. , Hassan M. T. , Jones G. L. , Komives A. , Laptev A. , Mendenhall M. P. , Nico J. S. , Noid G. , Park H. , Stephenson E. J. , Stern I. , Stockton K. J. S. , Trull C. , Wietfeldt F. E. , Yerozolimsky B. G.
Published: August 2017

We describe an apparatus used to measure the electron-antineutrino angular correlation coefficient in free neutron decay. The apparatus employs a novel measurement technique in which the angular correlation is converted into a proton time-of-flight asymmetry that is counted directly, avoiding the need for proton spectroscopy. Details of the method, apparatus, detectors, data acquisition, and data reduction scheme are presented, along with a discussion of the important systematic effects.
Note: On the study of metal/oxide hybrid ferromagnets with magneto-optical techniques
Authors: Lopez-Dominguez V. , de la Presa P. , Hernando A. , García M. A.
Published: August 2017

We analyze here the magneto-optical measurements of hybrid materials containing metallic and oxide ferromagnetic phases. We show that the magnetization curves obtained with this technique can be fairly different to those obtained with standard magnetometry techniques and cannot be representative of the contribution of each phase to the magnetization of the material, due to the very different optical properties of metals and oxides. However, a proper numerical analysis of the magneto-optical measurements allows estimating the fraction of each phase present in the material.
Temperature-dependent fine structure splitting in InGaN quantum dots
Authors: Wang Tong , Puchtler Tim J. , Zhu Tongtong , Jarman John C. , Kocher Claudius C. , Oliver Rachel A. , Taylor Robert A.
Published: August 2017

We report the experimental observation of temperature-dependent fine structure splitting in semiconductor quantum dots using a non-polar (11-20) a-plane InGaN system, up to the on-chip Peltier cooling threshold of 200 K. At 5 K, a statistical average splitting of 443 ± 132 μeV has been found based on 81 quantum dots. The degree of fine structure splitting stays relatively constant for temperatures less than 100 K and only increases above that temperature. At 200 K, we find that the fine structure splitting ranges between 2 and 12 meV, which is an order of magnitude higher than that at low temperatures. Our investigations also show that phonon interactions at high temperatures might have a correlation with the degree of exchange interactions. The large fine structure splitting at 200 K makes it easier to isolate the individual components of the polarized emission spectrally, increasing the effective degree of polarization for potential on-chip applications of polarized single-photon sources.
Dynamics of electron injection in a laser-wakefield accelerator
Authors: Xu J. , Buck A. , Chou S.-W. , Schmid K. , Shen B. , Tajima T. , Kaluza M. C. , Veisz L.
Published: August 2017

The detailed temporal evolution of the laser-wakefield acceleration process with controlled injection, producing reproducible high-quality electron bunches, has been investigated. The localized injection of electrons into the wakefield has been realized in a simple way—called shock-front injection—utilizing a sharp drop in plasma density. Both experimental and numerical results reveal the electron injection and acceleration process as well as the electron bunch's temporal properties. The possibility to visualize the plasma wave gives invaluable spatially resolved information about the local background electron density, which in turn allows for an efficient suppression of electron self-injection before the controlled process of injection at the sharp density jump. Upper limits for the electron bunch duration of 6.6 fs FWHM, or 2.8 fs (r.m.s.) were found. These results indicate that shock-front injection not only provides stable and tunable, but also few-femtosecond short electron pulses for applications such as ultrashort radiation sources, time-resolved electron diffraction or for the seeding of further acceleration stages.
Magnetic and velocity fluctuations from nonlinearly coupled tearing modes in the reversed field pinch with and without the reversal surface
Authors: Craig D. , Martin D. , Den Hartog D. J. , Nornberg M. D. , Reusch J. A.
Published: August 2017

We investigate the role of poloidal mode number m = 0 fluctuations on m = 1 velocity and magnetic field fluctuations in the Reversed Field Pinch (RFP). Removing the m = 0 resonant surface in the Madison Symmetric Torus (MST), results in suppressed m = 0 activity without a reduction in m = 1 magnetic activity. However, the m = 1 velocity fluctuations and fluctuation-induced mean emf are reduced as m = 0 modes are suppressed. Velocity fluctuations are measured directly using fast Doppler spectroscopy. Similar results are seen in visco-resistive MHD simulation with the DEBS code. An artificial line-averaged velocity diagnostic is developed for DEBS simulations to facilitate direct comparisons with experimental measurements. The sensitivity of the m = 1 velocity fluctuations and corresponding emf to changes in m = 0 mode activity is a feature of tearing modes in the nonlinear regime with a spectrum of interacting modes. These results have implications for RFP sustainment strategies and inform our understanding of the role of magnetic turbulence in astrophysical contexts.
Effect of rare earth element substitution for lanthanum on structure and electrochemical characteristic of La0.8Mg0.2Ni3.3Al0.3Mo0.2 hydrogen storage alloys
Authors: Li Shucun , Guo Chengxiao , Wen Bingquan , Yin Weiqiang , Sha Ou
Published: August 2017

The microstructure and electrochemical properties of La0.8−xMg0.2RExNi3.3Al0.3Mo0.2(x = 0.1; RE = Ce, Nd, Pr, Y, Gd, and Er) hydrogen storage electrode alloys have been investigated systematically. The results of X-ray diffraction show that the matrix phase structure of the alloys is composed of the LaNi5 phase and the La2Ni7 phase. The partial substitution of Lanthanum by rare earth elements can improve the cell volume of the LaNi5 phase. The electrochemical properties of the alloys are improved obviously. The maximum discharge capacity is improved with Ce, Nd, Pr, Er, and Y substitution. Er and Y substitution promote the cyclic durability of the alloy. Nd and Pr can improve the high-rate ability of the alloy electrodes. The electrochemical impedance spectroscopy test shows that the charge-transfer resistance at the surface of the alloy electrodes decreases obviously with Nd and Pr substitution.
Optical tweezers turn hybrid to trap lightly with ultra-low power
Authors: Hall Shannon
Published: August 2017

A hybrid device could make it easier to isolate and study tiny particles.
Theoretical study on functionally graded cylindrical magnetoelectric composites using d15 shear-mode response
Authors: Shi Yang , Gao Yuanwen
Published: August 2017

In this study, a novel functionally graded cylindrical magnetoelectric (ME) composite based on d15 shear-mode response is analyzed theoretical by using the elastic mechanics model and equivalent circuit model. The composite is mounted around AC current-carrying power lines to scavenge AC magnetic field energy. For different sensing configurations, the generated magnetic fields are calculated, respectively. Then, based on the theoretical models, the dependences of the ME performances, i.e., the ME voltage and power, upon the type of the material gradation, the material constants, and geometrical parameters of the cylindrical ME composite are numerically evaluated. The results show that the ME coupling effect in the functionally graded cylindrical ME composite with special gradation is stronger than that in the homogeneous structure. The ME performance can be improved by geometrical parameters as well. The presented two models can be synthesized under the open-circuit condition, which provide a theoretical basis to understand and improve the ME property of the d15 shear-mode cylindrical ME composites operating at resonant frequency and off-resonance frequency.
Habitual sleep as a contributor to racial differences in cardiometabolic risk
Authors: Curtis David S. , Fuller-Rowell Thomas E. , El-Sheikh Mona , Carnethon Mercedes R. , Ryff Carol D.
Published: August 2017

Significance

Large differences in cardiovascular disease and diabetes prevalence exist between African American and European American adults. The US federal government has committed to reducing racial disparities in health; however, the precise mechanisms are not well understood. Sleep is one potential behavioral explanation for current racial differences in cardiometabolic conditions. We show that more than one-half of racial differences in cardiometabolic risk can be explained by sleep patterns—namely, less total sleep and lower sleep efficiency among African American than European American adults. Sleep is a malleable health behavior that is linked with characteristics of the social and physical environment and could be an effective target in national efforts to reduce racial health disparities.
Neuronal cytoskeletal gene dysregulation and mechanical hypersensitivity in a rat model of Rett syndrome
Authors: Bhattacherjee Aritra , Mu Ying , Winter Michelle K. , Knapp Jennifer R. , Eggimann Linda S. , Gunewardena Sumedha S. , Kobayashi Kazuto , Kato Shigeki , Krizsan-Agbas Dora , Smith Peter G.
Published: August 2017

Significance

Cutaneous sensitivity appears to be abnormal in Rett syndrome and other autistic disorders. Using rats with disrupted methyl-CpG binding protein 2 (MeCP2) expression characteristic of Rett syndrome, we found that MeCP2 deficiency in sensory neurons led to augmented pressure and cold sensitivity but hyposensitivity to heat, accompanied by respective changes in cutaneous innervation. Transcriptome analysis of MeCP2-deficient ganglia showed up-regulation of genes associated with actin cytoskeletal dynamics and adhesion formation; down-regulating key genes in vivo normalized both mechanical sensitivity and innervation density. These findings provide evidence that ganglion cytoskeletal genes play key roles in determining mechanosensory properties, which may contribute to altered pain sensitivity in Rett syndrome and other painful conditions.
Molecular characterization of water and surfactant AOT at nanoemulsion surfaces
Authors: Hensel Jennifer K. , Carpenter Andrew P. , Ciszewski Regina K. , Schabes Brandon K. , Kittredge Clive T. , Moore Fred G. , Richmond Geraldine L.
Published: August 2017

Significance

Nanoemulsions provide exciting opportunities for a wide range of biological, scientific, and industrial applications. The interfacial structure of nanoemulsions is crucial to their stabilization, but molecular factors contributing to their surfactant stabilization are far from understood for most systems. Much more is known about the molecular properties of their smaller micellar counterparts where model systems using surfactants such as dioctyl sodium sulfosuccinate (AOT or Aerosol-OT) have been illuminating. The studies described herein provide details about the bonding and structure of water and surfactant AOT at regular and reverse nanoemulsion curved surfaces as well as at the corresponding planar oil–water interface. This is accomplished with vibrational sum-frequency spectroscopy in its scattering and reflection geometries.
Oligomerization of the tetramerization domain of p53 probed by two- and three-color single-molecule FRET
Authors: Chung Hoi Sung , Meng Fanjie , Kim Jae-Yeol , McHale Kevin , Gopich Irina V. , Louis John M.
Published: August 2017

Significance

Intrinsically disordered proteins often form pathological oligomers implicated in various diseases. In many cases, these oligomers cannot be separated and characterizations of their sizes and conformations are difficult. We develop a single-molecule fluorescence method that can probe individual oligomers without separation and determine the equilibrium constants and oligomerization kinetics. By combining two- and three-color single-molecule FRET spectroscopy with fluorescence lifetime analysis, it is possible to determine conformations and flexibility of individual oligomers unambiguously. We apply this method to the oligomerization of the tetramerization domain of p53 and compare conformations of monomer, dimer, and tetramer. This method will be useful in exploring other protein oligomerization systems involved in important biological and disease processes.
Three Cambrian fossils assembled into an extinct body plan of cnidarian affinity
Authors: Ou Qiang , Han Jian , Zhang Zhifei , Shu Degan , Sun Ge , Mayer Georg
Published: August 2017

Significance

New material from the Chengjiang fossil Lagerstätte clarifies the identity of three early Cambrian problematica. The presumed earliest hemichordate
Galeaplumosus abilus
and the putative ancient sea pen
Chengjiangopenna wangii
are in fact fragments of
Xianguangia sinica
. Here we demonstrate that
X. sinica
possessed a polypoid body, a blind gastric cavity partitioned by septum-like structures, a holdfast that contained an additional cavity functioning as a hydroskeleton, a basal pit used for anchorage, and a radial whorl of feather-like tentacles for ciliary suspension feeding. Phylogenetic analyses based on the new findings suggest that
X. sinica
represents an extinct body plan most closely allied to cnidarians and thus sheds light on their early evolution.
Phospholipase A activity of adenylate cyclase toxin mediates translocation of its adenylate cyclase domain
Authors: González-Bullón David , Uribe Kepa B. , Martín César , Ostolaza Helena
Published: August 2017

Significance

Numerous bacterial toxins can cross cell membranes, penetrating the cytosol of their target cells, but to do so exploits cellular endocytosis or intracellular sorting machineries.
Bordetella pertussis
adenylate cyclase toxin (ACT) delivers its catalytic domain directly across the cell membrane by an unknown mechanism, and generates cAMP, which subverts the cell signaling. Here, we decipher the fundamentals of the molecular mechanism of ACT transport. We find that AC translocation and, consequently cytotoxicity, are determined by an intrinsic ACT–phospholipase A (PLA) activity, supporting a model in which in situ generation of nonlamellar lysophospholipids by ACT–PLA activity remodels the cell membrane, forming proteolipidic toroidal “holes” through which AC domain transfer may directly take place. PLA-based specific protein transport in cells is unprecedented.
Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks
Authors: Torres Mark A. , Moosdorf Nils , Hartmann Jens , Adkins Jess F. , West A. Joshua
Published: August 2017

Significance

We compile data showing that, as hypothesized previously, waters draining glaciers have solute chemistry that is distinct from nonglacial rivers and reflects different proportions of mineral weathering reactions. Elevated pyrite oxidation during glacial weathering could generate acidity, releasing carbon to the atmosphere. We show that this effect could contribute to changes in CO
2
during glacial cycles of the past million years. Over the longer, multimillion-year timescales that Earth transitions into and out of glaciated states, sustained addition of pyrite-derived sulfate to the oceans could shift the balance of the global carbon cycle toward increasing CO
2
in the ocean–atmosphere, thus providing a negative-feedback mechanism preventing runaway glaciation. This mechanism depends on oxidation and thus sufficient O
2
.
Testing inhomogeneous solvation theory in structure-based ligand discovery
Authors: Balius Trent E. , Fischer Marcus , Stein Reed M. , Adler Thomas B. , Nguyen Crystal N. , Cruz Anthony , Gilson Michael K. , Kurtzman Tom , Shoichet Brian K.
Published: August 2017

Significance

Water molecules play a crucial role in protein–ligand binding. Calculating the energetic consequences of displacing water upon ligand binding has challenged the field for many years. Inhomogeneous solvation theory (IST) is one of the most popular methods for distinguishing favorable from unfavorable water molecules, but little controlled, prospective testing at atomic resolution has been done to evaluate the method. Here we compare molecular docking screens with and without an IST term to gauge its impact on ligand discovery. We test prospective ligand-binding predictions that include an IST term, using crystallography and direct binding.
Printed droplet microfluidics for on demand dispensing of picoliter droplets and cells
Authors: Cole Russell H. , Tang Shi-Yang , Siltanen Christian A. , Shahi Payam , Zhang Jesse Q. , Poust Sean , Gartner Zev J. , Abate Adam R.
Published: August 2017

Significance

Single-cell biology requires the ability to construct experiments with single-cell precision, large numbers, and extremely small fluid volumes. To address this need, we have developed a new technology, printed droplet microfluidics, which encapsulates reagents and single cells in picoliter droplets, then actively selects and deposits desired droplets in an arrayed format on a printing substrate. This technology enables the construction of a large number of relevant single-cellular and multicellular experiments and enables new methods of detection.
Concurrent design of quasi-random photonic nanostructures
Authors: Lee Won-Kyu , Yu Shuangcheng , Engel Clifford J. , Reese Thaddeus , Rhee Dongjoon , Chen Wei , Odom Teri W.
Published: August 2017

Significance

Quasi-random nanostructures with neither periodic nor fully disordered geometries have been used for photovoltaics and light-emitting diodes because the stochastic patterns can manipulate light over a broad range of wavelengths and over wide collection angles. Although serial processes such as electron-beam lithography can fabricate nanostructures, prototype manufacturing over large areas is not possible. Moreover, trial-and-error processing optimization cannot guarantee the fabrication feasibility of the designed structures. In this paper, we report wrinkle lithography, a wafer-scale fabrication procedure whose processing steps can be integrated with concurrent design of nanostructures and function. As a proof-of-concept demonstration, we rapidly optimized three-dimensional structures for light trapping in amorphous silicon and realized >160% enhancement in light absorption over the 800–1,200-nm wavelength range.
Atomic structure of a toxic, oligomeric segment of SOD1 linked to amyotrophic lateral sclerosis (ALS)
Authors: Sangwan Smriti , Zhao Anni , Adams Katrina L. , Jayson Christina K. , Sawaya Michael R. , Guenther Elizabeth L. , Pan Albert C. , Ngo Jennifer , Moore Destaye M. , Soriaga Angela B. , Do Thanh D. , Goldschmidt Lukasz , Nelson Rebecca , Bowers Michael T. , Koehler Carla M. , Shaw David E. , Novitch Bennett G. , Eisenberg David S.
Published: August 2017

Significance

More than 170 mutations in superoxide dismutase 1 (SOD1) are linked to inherited forms of ALS, and aggregates of this protein are a pathological feature associated with this disease. Although it is accepted that SOD1 gains a toxic function in the disease state, a molecular understanding of the toxic species is lacking. Here, we identify a short segment of SOD1 that is both necessary and sufficient for toxicity to motor neurons. The crystal structure of the segment reveals an out-of-register β-sheet oligomer, providing a structural rationale for the toxic effects of mutant SOD1 in ALS.
Superresolution expansion microscopy reveals the three-dimensional organization of theDrosophilasynaptonemal complex
Authors: Cahoon Cori K. , Yu Zulin , Wang Yongfu , Guo Fengli , Unruh Jay R. , Slaughter Brian D. , Hawley R. Scott
Published: August 2017

Significance

Because inaccurate chromosome segregation during meiosis is a leading cause of miscarriage in humans, we seek to understand how homologous chromosomes segregate properly. Meiotic chromosome segregation occurs with fidelity only in the presence of the synaptonemal complex (SC), a protein structure that assembles between homologs and facilitates the occurrence of crossing over. Although some functions of the SC are evolutionarily conserved, the mechanisms underlying its multiple roles during meiosis, as well as organizational variances among different organisms, remain under investigation. Here we combine superresolution and expansion microscopy and find strong evidence that theDrosophilaSC comprises two visually distinct layers, perhaps suggesting that each layer connects one sister chromatid from each homologous chromosome.
Multiple PPR protein interactions are involved in the RNA editing system in
Arabidopsis
mitochondria and plastids
Authors: Andrés-Colás Nuria , Zhu Qiang , Takenaka Mizuki , De Rybel Bert , Weijers Dolf , Van Der Straeten Dominique
Published: August 2017

Significance

RNA editing is a posttranscriptional regulation process essential for organellar function. The PPR protein family plays a major role in RNA editing, but the precise function of each member and its interactions in editosome complexes remain unclear. This research demonstrates that three PPR proteins (SLO2, NUWA, and DYW2) interact in mitochondria and provides evidence for the following: (
i
) P-type PPR protein NUWA assists in the interaction between SLO2 and DYW2, and (
ii
) DYW2 participates in E
+
editosomes. We hypothesize that this mechanism is common in both mitochondria and chloroplasts, where the E
+
-type PPR proteins, such as SLO2, target the specific RNA sites, with DYW2 suggested to provide the editing catalytic domain and NUWA assisting the interaction between the former ones.
Light-responsive organic flashing electron ratchet
Authors: Kedem Ofer , Lau Bryan , Ratner Mark A. , Weiss Emily A.
Published: August 2017

Significance

Transport of objects in man-made systems typically relies on energy gradients that span the distance over which the particles must travel. Biological systems do not have these large-scale gradients available and instead transport particles with repeated local interactions between asymmetric structures, powered by nondirectional sources of energy like heat or chemical reactions. This process is called “ratcheting.” Here, we exploit the ratcheting mechanism to transport charge-carrying particles, electrons, through an amorphous organic film in which local structural inhomogeneities disrupt the gradients needed for typical electrical conduction to occur efficiently. This work explores basic mechanisms by which energy that is normally wasted in an electronic or photoelectrical device could be harnessed to do electrical work.
DNA damage tolerance in hematopoietic stem and progenitor cells in mice
Authors: Pilzecker Bas , Buoninfante Olimpia Alessandra , van den Berk Paul , Lancini Cesare , Song Ji-Ying , Citterio Elisabetta , Jacobs Heinz
Published: August 2017

Significance

The DNA damage response entails both DNA repair and DNA damage tolerance (DDT). DDT enables replicative bypass of fork-stalling DNA lesions and structures. Although DNA repair is known to be key in maintaining stem cells and tissue homeostasis, the contribution of DDT in stem cell maintenance remained to be defined. Using DDT-deficient

Pcna
K164R/K164R

mice we here reveal a critical role of DDT in maintaining hematopoietic stem cells (HSCs). Defective DDT results in progressive impairment of HSCs, identifying DDT as a key player in preserving HSC fitness and prohibiting premature aging.
Nitrogen-fixing trees inhibit growth of regenerating Costa Rican rainforests
Authors: Taylor Benton N. , Chazdon Robin L. , Bachelot Benedicte , Menge Duncan N. L.
Published: August 2017

Significance

Regrowing tropical forests are critical for global biodiversity conservation and carbon capture. Nitrogen availability often controls how fast these forests can regrow. Because nitrogen-fixing plants are the primary source of new nitrogen into these forests, one might expect that more nitrogen fixers lead to faster forest regrowth. However, here we show that nitrogen fixers actually slow forest regrowth. Their competitive influence on neighboring trees outweighs any growth enhancement from their nitrogen inputs at this site. Our results call for a more critical evaluation of how nitrogen fixers influence the surrounding forest, especially given the large uncertainty in global climate projections that hinges on the role of nitrogen fixers during tropical forest regeneration.
Time-resolved observation of protein allosteric communication
Authors: Buchenberg Sebastian , Sittel Florian , Stock Gerhard
Published: August 2017

Significance

Allostery describes the puzzling phenomenon of long-range communication between distant protein sites. Representing the elementary process of cell signaling, allosteric interactions also provide prime targets in pharmaceutical research. Although a number of thermodynamic models have been proposed, the dynamic process of allosteric communication itself is still not well understood. Accounting for recent time-resolved infrared spectroscopy experiments, this study uses extensive all-atom molecular dynamics simulations that envision a real-time picture of the way allostery works. Mediated by the propagation of stress, allostery is found to trigger structural and dynamical changes in a nonlinear and nonlocal fashion. Similarly as found for downhill folding, the hierarchy and exceeding structural heterogeneity of the process gives rise to strongly nonexponential kinetics.
Intraflagellar transport velocity is governed by the number of active KIF17 and KIF3AB motors and their motility properties under load
Authors: Milic Bojan , Andreasson Johan O. L. , Hogan Daniel W. , Block Steven M.
Published: August 2017

Significance

Intraflagellar transport (IFT)—cargo transport inside cilia—is mediated by two different kinesin-2 motors: the slower KIF3AB and the faster KIF17. It was not understood how ciliary cargos, called IFT trains, could attain velocities that exceed the unloaded rate of KIF3AB. We find that high IFT velocities cannot be explained by KIF3AB motors speeding up in response to being pulled forward by their KIF17 partners. Instead, IFT velocity is governed by an equilibrium between a slower state, where at least one KIF3AB motor on the train is actively participating in transport, and a faster state, where KIF3AB motors disengage, and only KIF17 motors ferry the train. The more often IFT trains access the faster state, the higher their overall velocity.
Lizards on newly created islands independently and rapidly adapt in morphology and diet
Authors: Eloy de Amorim Mariana , Schoener Thomas W. , Santoro Guilherme Ramalho Chagas Cataldi , Lins Anna Carolina Ramalho , Piovia-Scott Jonah , Brandão Reuber Albuquerque
Published: August 2017

Significance

We report for island populations of the termite-eating common gecko speciesGymnodactylus amaralirapid parallel morphological and ecological change in response to human-caused environmental disturbance. The islands were formerly part of an extensive terrestrial ecosystem; in 1997, the area was flooded to construct a reservoir, fragmenting the higher portions into separate islands. Populations on all five islands studied have proportionally larger heads than populations at five nearby mainland sites. The new island morphology is accompanied by an increase in dietary niche breadth, mainly via expansion toward larger prey. This expansion is likely due to the greater availability of such prey on the newly formed islands after the extinction there of four larger lizard species that typically also included termites in their diets.
Cytokine signature associated with disease severity in chronic fatigue syndrome patients
Authors: Montoya Jose G. , Holmes Tyson H. , Anderson Jill N. , Maecker Holden T. , Rosenberg-Hasson Yael , Valencia Ian J. , Chu Lily , Younger Jarred W. , Tato Cristina M. , Davis Mark M.
Published: August 2017

Significance

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) devastates the lives of millions of people and has remained a mystery illness despite decades of research. It has long been suspected that inflammation is central to its pathogenesis. Although only two cytokines were found to be different (TGF-β higher and resistin lower) in ME/CFS patients compared with controls, 17 cytokines correlated with ME/CFS severity. Thirteen of these cytokines are proinflammatory and may contribute to many of the symptoms these patients experience for several years. Only CXCL9 (MIG) inversely correlated with fatigue duration.
Ultralow thermal conductivity in all-inorganic halide perovskites
Authors: Lee Woochul , Li Huashan , Wong Andrew B. , Zhang Dandan , Lai Minliang , Yu Yi , Kong Qiao , Lin Elbert , Urban Jeffrey J. , Grossman Jeffrey C. , Yang Peidong
Published: August 2017

Significance

Discovery of materials with low thermal conductivity in simple, fully dense, and single-crystalline solids has proven extremely challenging. This paper reports the discovery of ultralow thermal conductivity (∼0.4 W⋅m
−1
⋅K
−1
) in single-crystalline, all-inorganic halide perovskite nanowires, which is comparable to their amorphous limit value. We attribute ultralow thermal conductivity to a cluster rattling mechanism, based on strong phonon–phonon scattering via the coexistence of collective motions involving various atom groups. These results call attention to the vital thermal transport processes and thermal management strategies for applications with all-inorganic halide perovskites. Further, CsSnI
3
shows a rare combination of ultralow thermal conductivity and high electrical conductivity, so it can be a promising material for unique applications as an electrically conductive thermal insulator.
Justice in migration
Authors: Straehle Christine
Published: August 2017

The movement of people across borders is one of the most pressing issues of our time. Yet it is still unclear how migration should be regulated to be fair to the sending societies, the host societies and the individual migrant. What is at issue? Are we discussing migration from an ethical or from a political philosophical perspective, or both? Are we discussing migration from a global justice perspective or social justice perspective? Do we consider political legitimacy and democratic self-determination as part of our analysis? How should we balance demands of justice in immigration compared to those of emigration?
Standardized Assessment of Thin-film Vitrification for Aquatic Species
Authors: Tiersch Nolan J , Tiersch Terrence R
Published: August 2017

Ultrarapid cooling under the appropriate conditions will produce vitrification, a glass-like state used to cryopreserve small sample volumes, but there are a number of major technical drawbacks impeding the application of vitrification to germplasm of aquatic species. These include a lack of suitable devices, and poor reproducibility and comparability among studies due to a lack of standardization. We used 3-D printing to produce a viewing pedestal coupled with a classification system to rapidly assess frozen film quality of vitrification loops. Classification time declined with practice from 2.1 ± 0.3 sec (mean ± SD) to 1.5 ± 0.2 sec (after 200 assessments), and assessments were consistently made in < 2.5 sec. Classifications should be reported with representative images allowing harmonization for quality control. This approach permits rapid classification and can be applied for the development of methods including the evaluation of vitrification solution components, concentrations of solutions and target cells, and configurations and volumes of new devices. Future studies should address the custom fabrication of 3-D printed vitrification devices for use with aquatic species and other applications.
On the honeycomb conjecture for a class of minimal convex partitions
Authors: Bucur Dorin , Fragalà Ilaria , Velichkov Bozhidar , Verzini Gianmaria
Published: August 2017

We prove that the planar hexagonal honeycomb is asymptotically optimal for a large class of optimal partition problems, in which the cells are assumed to be convex, and the criterion is to minimize either the sum or the maximum among the energies of the cells, the cost being a shape functional which satisfies a few assumptions. They are: monotonicity under inclusions; homogeneity under dilations; a Faber-Krahn inequality for convex hexagons; a convexity-type inequality for the map which associates with every

n
∈

N

n \in \mathbb {N}

the minimizers of

F
F

among convex

n
n

-gons with given area. In particular, our result allows us to obtain the honeycomb conjecture for the Cheeger constant and for the logarithmic capacity (still assuming the cells to be convex). Moreover, we show that, in order to get the conjecture also for the first Dirichlet eigenvalue of the Laplacian, it is sufficient to establish some facts about the behaviour of

λ
1

\lambda _1

among convex pentagons, hexagons, and heptagons with prescribed area.
Daily Shoulder Pain Among Flight Baggage Handlers and its Association With Work Tasks and Upper Arm Postures on the Same Day
Authors: Bergsten Eva L , Mathiassen Svend Erik , Kwak Lydia , Vingård Eva
Published: August 2017

Objectives

This study of flight baggage handlers aimed at examining the extent to which shoulder pain developed during single work shifts, and whether a possible development was associated with biomechanical exposures and psychosocial factors during the same shift.

Methods

Data were collected during, in total, 82 work shifts in 44 workers. Right and left shoulder pain intensity was rated just before and just after the shift (VAS scale 0–100 mm). Objective data on ‘time in extreme’ and ‘time in neutral’ upper arm postures were obtained for the full shift using accelerometers, and the baggage handlers registered the number of ‘aircrafts handled’ in a diary. During half of the shift, workers were recorded on video for subsequent task analysis of baggage handling. ‘Influence’ at work and ‘support’ from colleagues were measured by use of Copenhagen Psychosocial Questionnaire (COPSOQ). Associations between exposures and the increase in pain intensity during the shift (‘daily pain’) were analysed for the right and left shoulder separately using Generalized Estimating Equations (GEE).

Results

‘Daily pain’ was observed in approximately one third of all shifts. It was significantly associated with the number of ‘aircrafts handled’ for both the right and left shoulder. In multivariate models including both biomechanical exposures and the psychosocial factors ‘influence’ at work and ‘support’ from colleagues, ‘aircrafts handled’ was still significantly associated with ‘daily pain’ in both shoulders, and so was ‘influence’ and ‘support’, however in opposite directions.

Conclusions

‘Daily pain’ was, in general, associated with biomechanical exposures during the same shift and with general ‘influence’ and ‘support’ in the job. In an effort to reduce pain among flight baggage handlers, it may therefore be justified to consider a reduction of biomechanical exposures during handling of aircrafts, combined with due attention to psychosocial factors at work.