bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficient spin-filtering, magnetoresistance and negative differential resistance effects of a one-dimensional single-molecule magnet Mn(dmit)2-based device with graphene nanoribbon electrodes
Authors: Liu N. , Liu J. B. , Yao K. L.
Published: December 2017

We present first-principle spin-dependent quantum transport calculations in a molecular device constructed by one single-molecule magnet Mn(dmit)2 and two graphene nanoribbon electrodes. Our results show that the device could generate perfect spin-filtering performance in a certain bias range both in the parallel configuration (PC) and the antiparallel configuration (APC). At the same time, a magnetoresistance effect, up to a high value of 103%, can be realized. Moreover, visible negative differential resistance phenomenon is obtained for the spin-up current of the PC. These results suggest that our one-dimensional molecular device is a promising candidate for multi-functional spintronics devices.
Epitaxy of GaN in high aspect ratio nanoscale holes over silicon substrate
Authors: Wang Kejia , Wang Anqi , Ji Qingbin , Hu Xiaodong , Xie Yahong , Sun Ying , Cheng Zhiyuan
Published: December 2017

Dislocation filtering in gallium nitride (GaN) by epitaxial growth through patterned nanoscale holes is studied. GaN grown from extremely high aspect ratio holes by metalorganic chemical vapor deposition is examined by transmission electron microscopy and high-resolution transmission electron microscopy. This selective area epitaxial growth method with a reduced epitaxy area and an increased depth to width ratio of holes leads to effective filtering of dislocations within the hole and improves the quality of GaN significantly.
Geometry effect on electrokinetic flow and ionic conductance in pH-regulated nanochannels
Authors: Sadeghi Morteza , Saidi Mohammad Hassan , Moosavi Ali , Sadeghi Arman
Published: December 2017

Semi-analytical solutions are obtained for the electrical potential, electroosmotic velocity, ionic conductance, and surface physicochemical properties associated with long pH-regulated nanochannels of arbitrary but constant cross-sectional area. The effects of electric double layer overlap, multiple ionic species, and surface association/dissociation reactions are all taken into account, assuming low surface potentials. The method of analysis includes series solutions which the pertinent coefficients are obtained by applying the wall boundary conditions using either of the least-squares or point matching techniques. Although the procedure is general enough to be applied to almost any arbitrary cross section, nine nanogeometries including polygonal, trapezoidal, double-trapezoidal, rectangular, elliptical, semi-elliptical, isosceles triangular, rhombic, and isotropically etched profiles are selected for presentation. For the special case of an elliptic cross section, full analytical solutions are also obtained utilizing the Mathieu functions. We show that the geometrical configuration plays a key role in determination of the ionic conductance, surface charge density, electrical potential and velocity fields, and proton enhancement. In this respect, the net electric charge and convective ionic conductance are higher for channels of larger perimeter to area ratio, whereas the opposite is true for the average surface charge density and mean velocity; the geometry impact on the two latest ones, however, vanishes if the background salt concentration is high enough. Moreover, we demonstrate that considering a constant surface potential equal to the average charge-regulated potential provides sufficiently accurate results for smooth geometries such as an ellipse at medium-high aspect ratios but leads to significant errors for geometries having narrow corners such as a triangle.
Spatial structure of ion beams in an expanding plasma
Authors: Aguirre E. M. , Scime E. E. , Thompson D. S. , Good T. N.
Published: December 2017

We report spatially resolved perpendicular and parallel, to the magnetic field, ion velocity distribution function (IVDF) measurements in an expanding argon helicon plasma. The parallel IVDFs, obtained through laser induced fluorescence (LIF), show an ion beam with v ≈ 8000 m/s flowing downstream and confined to the center of the discharge. The ion beam is measurable for tens of centimeters along the expansion axis before the LIF signal fades, likely a result of metastable quenching of the beam ions. The parallel ion beam velocity slows in agreement with expectations for the measured parallel electric field. The perpendicular IVDFs show an ion population with a radially outward flow that increases with distance from the plasma axis. Structures aligned to the expanding magnetic field appear in the DC electric field, the electron temperature, and the plasma density in the plasma plume. These measurements demonstrate that at least two-dimensional and perhaps fully three-dimensional models are needed to accurately describe the spontaneous acceleration of ion beams in expanding plasmas.
A compensating point defect in carbon-doped GaN substrates studied with electron paramagnetic resonance spectroscopy
Authors: Willoughby W. R. , Zvanut M. E. , Paudel Subash , Iwinska M. , Sochacki T. , Bockowski M.
Published: December 2017

Electron paramagnetic resonance (EPR) spectroscopy was used to investigate a type of point defect present in 1019 cm−3 carbon-doped GaN substrates grown by hydride vapor phase epitaxy. A broad, isotropic resonance at g ∼ 1.987 was observed at 3.5 K, and the EPR intensity increased with illumination at energies greater than 2.75 eV and decreased with photon energies greater than 0.95 eV. The latter is consistent with a deep level of 0.95 eV above the valence band maximum and implies that the associated defect likely participates in donor compensation. The ionization energy for this defect is close to the predicted value for the (−/0) transition level of CN and transition levels associated with Ga vacancies such as VGa and VGa-ON-2H.
Mechanism of flow reversal during solidification of an anomalous liquid
Authors: Kumar Virkeshwar , Kumawat Mitesh , Srivastava Atul , Karagadde Shyamprasad
Published: December 2017

In a wide variety of fluidic systems involving thermal and compositional gradients, local density changes lead to the onset of natural convection that influences the process itself, for example, during phase-change phenomena and magmatic flows. Accurate knowledge of the flow characteristics is essential to quantify the impact of the flow of the processes. In this work, the first-ever demonstration of flow reversal during bottom-up solidification of water using full-field thermal and flow measurements and its direct impact on the solidifying interface is presented. Based on prior optical interferometric measurements of full-field temperature distribution in water during solidification, we use the particle image velocimetry technique to quantify and reveal the changing natural convection pattern arising solely due to the density anomaly of water between 0 °C and 4 °C. The independently captured thermal and flow fields show striking similarities and clearly elucidate the plausible mechanism explaining the formation of a curved interface at the stagnation point and the subsequent reversal of flow direction due to a changed interface morphology. A control volume analysis is further presented to estimate the energy invested in the formation of a perturbation and the resulting flip in the flow direction caused by this perturbation.
Nuclear quantum effects on the vibrational dynamics of liquid water
Authors: Ojha Deepak , Henao Andrés , Kühne Thomas D.
Published: December 2017

Based on quantum-mechanical path-integral molecular dynamics simulations, the impact of nuclear quantum effects on the vibrational and hydrogen bond dynamics in liquid water is investigated. The instantaneous fluctuations in the frequencies of the O–H stretch modes are calculated using the wavelet method of time-series analysis, while the time scales of the vibrational spectral diffusion are determined from frequency-time correlation functions, joint probability distributions, and the slope of three-pulse photon echo. We find that the inclusion of nuclear quantum effects leads not only to a redshift of the vibrational frequency distribution by around 130 cm−1 but also to an acceleration of the vibrational dynamics by as much as 30%. In addition, quantum fluctuations also entail a significantly faster decay of correlation in the initial diffusive regime, which is in agreement with recent vibrational echo experiments.
Development of compact explosively driven ferromagnetic seed source for helical magnetic flux compression generator
Authors: Liu Peng , Zhang He , Ma Shaojie , Shi Yunlei
Published: December 2017

A compact explosively driven ferromagnetic generator (FMG) is developed for seed power source of helical magnetic flux compression generator (HMFCG). The mechanism of FMG is studied by establishing a magnetoelectric conversion model. Analytical calculations and numerical simulations are conducted on the magnetostatic field of open-circuit magnet in FMG. The calculation method for the magnet’s cross-sectional magnetic flux is obtained. The pulse sources made of different materials and equipped with different initiation modes are experimentally explored. Besides, the dynamic coupling experiments of FMG and HMFCG are carried out. The results show that, N35 single-ended and double-ended initiating FMGs have an energy conversion efficiency ηt not less than 14.6% and 24.4%, respectively; FMG has an output pulse current not less than 4kA and an energy of about 3J on 320nH inductive load; HMFCG experiences energy gains of about 2-3 times. FMG and HMFCG can be coupled to form a full-blast electrical driving pulse source.
Precision and accuracy in smFRET based structural studies—A benchmark study of the Fast-Nano-Positioning System
Authors: Nagy Julia , Eilert Tobias , Michaelis Jens
Published: December 2017

Modern hybrid structural analysis methods have opened new possibilities to analyze and resolve flexible protein complexes where conventional crystallographic methods have reached their limits. Here, the Fast-Nano-Positioning System (Fast-NPS), a Bayesian parameter estimation-based analysis method and software, is an interesting method since it allows for the localization of unknown fluorescent dye molecules attached to macromolecular complexes based on single-molecule Förster resonance energy transfer (smFRET) measurements. However, the precision, accuracy, and reliability of structural models derived from results based on such complex calculation schemes are oftentimes difficult to evaluate. Therefore, we present two proof-of-principle benchmark studies where we use smFRET data to localize supposedly unknown positions on a DNA as well as on a protein-nucleic acid complex. Since we use complexes where structural information is available, we can compare Fast-NPS localization to the existing structural data. In particular, we compare different dye models and discuss how both accuracy and precision can be optimized.
Differential voltage amplification from ferroelectric negative capacitance
Authors: Khan Asif I. , Hoffmann Michael , Chatterjee Korok , Lu Zhongyuan , Xu Ruijuan , Serrao Claudy , Smith Samuel , Martin Lane W. , Hu Chenming , Ramesh Ramamoorthy , Salahuddin Sayeef
Published: December 2017

We demonstrate that a ferroelectric can cause a differential voltage amplification without needing an external energy source. As the ferroelectric switches from one polarization state to the other, a transfer of energy takes place from the ferroelectric to the dielectric, determined by the ratio of their capacitances, which, in turn, leads to the differential amplification. This amplification is very different in nature from conventional inductor-capacitor based circuits where an oscillatory amplification can be observed. The demonstration of differential voltage amplification from completely passive capacitor elements only has fundamental ramifications for next generation electronics.
Robust ferromagnetism and half-metallicity in fluorinated two-dimensional BeN2 sheets
Authors: Xin Xiaojun , Li Wanxue , Pang Rui , Wang Hongyan , Guo Chunsheng , Shi Xingqiang , Zhao Yong
Published: December 2017

Via the first-principles approach based on the hybrid functional, the stable configurations and electronic and magnetic properties of fluorinated two-dimensional BeN2 (F-BeN2) have been studied. F atoms are adsorbed on Be ion sites and each fluorine adsorbate induces robust 1 μB magnetic moment. As a result, a F-BeN2 sheet becomes a ferromagnetic half-metal from a semiconducting intrinsic BeN2. The semiconducting bandgap of the half-metallic F-BeN2 sheets varies from 2.26 to 2.92 eV with different F coverages. With external strains, F-BeN2 maintains the ferromagnetic and half-metallic features and the semiconducting bandgap changes only a little. It suggests that F-BeN2 can be a good light-element magnet with promising potential for spintronic applications.
Noise suppression and crosstalk analysis of on-chip magnetic film-type noise suppressor
Authors: Ma Jingyan , Muroga Sho , Endo Yasushi , Hashi Shuichiro , Naoe Masayuki , Yokoyama Hiroo , Hayashi Yoshiaki , Ishiyama Kazushi
Published: December 2017

This paper discusses near field, conduction and crosstalk noise suppression of magnetic films with uniaxial anisotropy on transmission lines for a film-type noise suppressor in the GHz frequency range. The electromagnetic noise suppressions of magnetic films with different permeability and resistivity were measured and simulated with simple microstrip lines. The experimental and simulated results of Co-Zr-Nb and CoPd-CaF2 films agreed with each other. The results indicate that the higher permeability leads to a better near field shielding, and in the frequency range of 2–7 GHz, a higher conduction noise suppression. It also suggests that the higher resistivity results in a better crosstalk suppression in the frequency range below 2 GHz. These results can support the design guidelines of the magnetic film-type noise suppressor used in the next generation IC chip.
Barrier breakdown mechanism in nano-scale perpendicular magnetic tunnel junctions with ultrathin MgO barrier
Authors: Lv Hua , Leitao Diana C. , Hou Zhiwei , Freitas Paulo P. , Cardoso Susana , Kämpfe Thomas , Müller Johannes , Langer Juergen , Wrona Jerzy
Published: December 2017

Recently, the perpendicular magnetic tunnel junctions (p-MTJs) arouse great interest because of its unique features in the application of spin-transfer-torque magnetoresistive random access memory (STT-MRAM), such as low switching current density, good thermal stability and high access speed. In this paper, we investigated current induced switching (CIS) in ultrathin MgO barrier p-MTJs with dimension down to 50 nm. We obtained a CIS perpendicular tunnel magnetoresistance (p-TMR) of 123.9% and 7.0 Ω·μm2 resistance area product (RA) with a critical switching density of 1.4×1010 A/m2 in a 300 nm diameter junction. We observe that the extrinsic breakdown mechanism dominates, since the resistance of our p-MTJs decreases gradually with the increasing current. From the statistical analysis of differently sized p-MTJs, we observe that the breakdown voltage (Vb) of 1.4 V is 2 times the switching voltage (Vs) of 0.7 V and the breakdown process exhibits two different breakdown states, unsteady and steady state. Using Simmons’ model, we find that the steady state is related with the barrier height of the MgO layer. Furthermore, our study suggests a more efficient method to evaluate the MTJ stability under high bias rather than measuring Vb. In conclusion, we developed well performant p-MTJs for the use in STT-MRAM and demonstrate the mechanism and control of breakdown in nano-scale ultrathin MgO barrier p-MTJs.
Co-based amorphous thin films on silicon with soft magnetic properties
Authors: Masood Ansar , McCloskey P. , Mathúna Cian Ó. , Kulkarni S.
Published: December 2017

The present work investigates the emergence of multiple modes in the high-frequency permeability spectrum of Co-Zr-Ta-B amorphous thin films. Amorphous thin films of different thicknesses (t=100-530 nm) were deposited by DC magnetron sputtering. Their static and dynamic soft magnetic properties were investigated to explore the presence of multi-magnetic phases in the films. A two-phase magnetic behavior of the thicker films (≥333 nm) was revealed by the in-plane hysteresis loops. Multiple resonance peaks were observed in the high-frequency permeability spectrum of the thicker films. The thickness dependent multiple resonance peaks below the main ferromagnetic resonance (FMR) can be attributed to the two-phase magnetic behaviors of the films.
Temperature dependence of the effective mass of the hybrid organic-inorganic perovskites CH3NH3PbI3
Authors: Lu Ying-Bo , Yang Haozhi , Cong Wei-Yan , Zhang Peng , Guo Hong
Published: December 2017

The material of methylammonium lead iodide, CH3NH3PbI3 (MAPbI3), has shown significant promise in solar cell applications. A way to infer the microscopic scattering mechanism(s) in MAPbI3 is through the measured temperature dependence of carrier mobility. To this end, how does the carrier effective mass depend on temperature, m* = m*(T), is a useful information since the mobility is a function of m*. By atomistic first principles, we report the calculated m*(T) due to the thermal expansion of MAPbI3 materials, in the experimentally relevant range of 130 K to room temperature. The calculated results suggest m* = m*(T) to be linear in T. The increase of m* versus temperature is predominantly due to the expansion of the longitudinal atomic spacing that weakens the s/p hybridization between the I/Pb atoms.
Electrically driven quantum light emission in electromechanically tuneable photonic crystal cavities
Authors: Petruzzella M. , Pagliano F. M. , Zobenica Ž. , Birindelli S. , Cotrufo M. , van Otten F. W. M. , van der Heijden R. W. , Fiore A.
Published: December 2017

A single quantum dot deterministically coupled to a photonic crystal environment constitutes an indispensable elementary unit to both generate and manipulate single-photons in next-generation quantum photonic circuits. To date, the scaling of the number of these quantum nodes on a fully integrated chip has been prevented by the use of optical pumping strategies that require a bulky off-chip laser along with the lack of methods to control the energies of nano-cavities and emitters. Here, we concurrently overcome these limitations by demonstrating electrical injection of single excitonic lines within a nano-electro-mechanically tuneable photonic crystal cavity. When an electrically driven dot line is brought into resonance with a photonic crystal mode, its emission rate is enhanced. Anti-bunching experiments reveal the quantum nature of these on-demand sources emitting in the telecom range. These results represent an important step forward in the realization of integrated quantum optics experiments featuring multiple electrically triggered Purcell-enhanced single-photon sources embedded in a reconfigurable semiconductor architecture.
Design of mechanical metamaterials for simultaneous vibration isolation and energy harvesting
Authors: Li Ying , Baker Evan , Reissman Timothy , Sun Cheng , Liu Wing Kam
Published: December 2017

Through finite element analysis and a 3D printing assisted experimental study, we demonstrate a design of mechanical metamaterials for simultaneous mechanical wave filtering and energy harvesting. The mechanical metamaterials compromise a square array of free-standing cantilevers featuring piezoelectric properties being attached to a primary structural frame. A complete bandgap has thus been created via the strong coupling of the bulk elastic wave propagating along the structural frame and the distributed local resonance associated with the square array of piezoelectrically active cantilevers. Operating within the stop-band, external vibration energy has been trapped and transferred into the kinetic energy of the cantilevers, which is further converted into electric energy through mechano-electrical conversion of its integrated piezoelectric elements. Therefore, two distinct functions, vibration isolation and energy harvesting, are achieved simultaneously through the designed mechanical metamaterials.
From properties to materials: An efficient and simple approach
Authors: Huwig Kai , Fan Chencheng , Springborg Michael
Published: December 2017

We present an inverse-design method, the poor man’s materials optimization, that is designed to identify materials within a very large class with optimized values for a pre-chosen property. The method combines an efficient genetic-algorithm-based optimization, an automatic approach for generating modified molecules, a simple approach for calculating the property of interest, and a mathematical formulation of the quantity whose value shall be optimized. In order to illustrate the performance of our approach, we study the properties of organic molecules related to those used in dye-sensitized solar cells, whereby we, for the sake of proof of principle, consider benzene as a simple test system. Using a genetic algorithm, the substituents attached to the organic backbone are varied and the best performing molecules are identified. We consider several properties to describe the performance of organic molecules, including the HOMO-LUMO gap, the sunlight absorption, the spatial distance of the orbitals, and the reorganisation energy. The results show that our method is able to identify a large number of good candidate structures within a short time. In some cases, chemical/physical intuition can be used to rationalize the substitution pattern of the best structures, although this is not always possible. The present investigations provide a solid foundation for dealing with more complex and technically relevant systems such as porphyrins. Furthermore, our “properties first, materials second” approach is not limited to solar-energy harvesting but can be applied to many other fields, as briefly is discussed in the paper.
Observation of valley-selective microwave transport in photonic crystals
Authors: Ye Liping , Yang Yuting , Hong Hang Zhi , Qiu Chunyin , Liu Zhengyou
Published: December 2017

Recently, the discrete valley degree of freedom has attracted extensive attention in condensed matter physics. Here, we present an experimental observation of the intriguing valley transport for microwaves in photonic crystals, including the bulk valley transport and the valley-projected edge modes along the interface separating different photonic insulating phases. For both cases, valley-selective excitations are realized by a point-like chiral source located at proper locations inside the samples. Our results are promising for exploring unprecedented routes to manipulate microwaves.
Spectral photovoltaic response of graphene-silicon heterojunction
Authors: Ying Xiangxiao , Li Kai , Liu Lu , Wang Jun , Jiang Yadong , Xu Jimmy , Liu Zhijun
Published: December 2017

A graphene-Si junction is an attractive system as it is both CMOS-compatible and representative of very interesting van der Waals (vdW) heterostructures. In this paper, the full spectral photoresponse of the graphene-Si heterojunction is investigated in the photovoltaic mode by using Fourier transform infrared photocurrent spectroscopy. Two photoresponse bands at 980 nm and 1550 nm are measured, which are attributed to the photocarrier generations in Si and in the graphene-Si vdW junction, respectively. Peak detectivities of the Si and the vdW junction photoresponses are measured to be 1.3 × 109 cm Hz1/2/W and 1.3 × 108 cm Hz1/2/W, respectively. The band diagram of the heterojunction suggests an indirect spatial transfer process from graphene to silicon. The results are indicative of great potential of the graphene-Si vdW junction for photodetection in the infrared region.
Modal gain characteristics of a 2 μm InGaSb/AlGaAsSb passively mode-locked quantum well laser
Authors: Li Xiang , Wang Hong , Qiao Zhongliang , Guo Xin , Ng Geok Ing , Zhang Yu , Niu Zhichuan , Tong Cunzhu , Liu Chongyang
Published: December 2017

Passive mode locking with a fundamental repetition rate at ∼18.46 GHz is demonstrated in a two-section InGaSb/AlGaAsSb quantum well laser emitting at 2 μm. Modal gain characteristics of the laser are investigated by performing the Hakki-Paoli method to gain better insight into the impact of the absorber bias voltage (Va) on the light output. The lasing action moves to longer wavelengths markedly with increasing negative Va. The light output contains more longitudinal modes in the mode locking regime if the gain bandwidth is larger at a certain Va. Our findings provide guidelines for output characteristics of the mode-locked laser.
Improved tandem mass spectrometer coupled to a laser vaporization cluster ion source
Authors: Förstel Marko , Jaeger Bertram K. A. , Schewe Wolfgang , Sporkhorst Philipp H. A. , Dopfer Otto
Published: December 2017

We describe two improvements to an existing tandem mass spectrometer coupled to a laser vaporization cluster ion source suitable for photodissociation spectroscopy: (i) cooling of the cluster source nozzle and (ii) mass selection prior to the photodissociation region via replacing an octupole ion guide by a quadrupole mass spectrometer. The improved sensitivity and transmission enable the production of larger heteroatomic clusters as well as rare gas solvated clusters. We present two examples demonstrating the new capabilities of the improved setup. In the first application, cooling of the cluster source nozzle produces Si+Arn and Si2+Arn cluster cations with n = 1-25. Magic numbers are extracted from the mass spectrum by applying a transmission function obtained via simulations. In the second example, the vibronic photodissociation spectrum of cold Au4+ cluster ions is recorded with unprecedented detail, resolution, and sensitivity. Such high-resolution optical excitation spectra of metal cluster cations may serve as a benchmark for the performance of Franck-Condon simulations based on quantum chemical calculations for excited states.
Sub-monolayer quantum dot quantum cascade mid-infrared photodetector
Authors: Huang Jian , Guo Daqian , Chen Wei , Deng Zhuo , Bai Yinghao , Wu Tinghui , Chen Yaojiang , Liu Huiyun , Wu Jiang , Chen Baile
Published: December 2017

In this work, we demonstrate a sub-monolayer quantum dot quantum cascade photodetector grown on GaAs for photovoltaic mid-infrared photo-detection. The detector shows a normal-incident peak responsivity of 1.90 mA/W at the wavelength of 6.05 μm and a resistance-area product of 1.54 × 108 Ω cm2 at 77 K. The corresponding specific detectivity is 3.22 × 1011 cm·Hz1/2/W.
High performance field emission of silicon carbide nanowires and their applications in flexible field emission displays
Authors: Cui Yunkang , Chen Jing , Di Yunsong , Zhang Xiaobing , Lei Wei
Published: December 2017

In this paper, a facile method to fabricate the flexible field emission devices (FEDs) based on SiC nanostructure emitters by a thermal evaporation method has been demonstrated. The composition characteristics of SiC nanowires was characterized by X-ray diffraction (XRD), selected area electron diffraction (SAED) and energy dispersive X-ray spectrometer (EDX), while the morphology was revealed by field emission scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The results showed that the SiC nanowires grew along the [111] direction with the diameter of ∼110 nm and length of∼30 μm. The flexible FEDs have been fabricated by transferring and screen-printing the SiC nanowires onto the flexible substrates exhibited excellent field emission properties, such as the low turn-on field (∼0.95 V/μm) and threshold field (∼3.26 V/μm), and the high field enhancement factor (β=4670). It is worth noting the current density degradation can be controlled lower than 2% per hour during the stability tests. In addition, the flexible FEDs based on SiC nanowire emitters exhibit uniform bright emission modes under bending test conditions. As a result, this strategy is very useful for its potential application in the commercial flexible FEDs.
Kinetic and Computational Studies of Rhenium Catalysis for Oxygen Atom Transfer Reactions
Authors: Ibdah Abdellatif , Bakar Heba Bani , Alduwikat Salwa
Published: December 2017

The rhenium(v)oxo dimer {MeReO(edt)}2 (edt = 1,2-ethanedithiolate) is an effective catalyst for the oxygen atom transfer (OAT) reaction from pyridine oxide and picoline oxide to triphenylarsine (Ph3As) as oxygen acceptor. Kinetics measurements were carried out by the initial rate method because of the monomerization reaction of the pyridine product with the {MeReO(edt)}2 catalysts. The derived rate is R = k[Re][NO] (where NO is picoline oxide or pyridine oxide) and independent of the Ph3As concentration. The rate constant at room temperature in chloroform is k(PicNO) = 268.1 ± 3.5 L mol−1 s−1 and k(PyNO) = 155.3 ± 2.3 L mol−1 s−1. The analogue rhenium(v)oxo dimer {MeReO(pdt)}2 (pdt = 1,3-propanedithiolate) does not monomerize with pyridine. However, {MeReO(edt)}2 rapidly monomerizes with pyridine. Density functional theory study of the enthalpy of the monomerization reaction shows that the {MeReO(edt)}2 reaction with pyridine is more thermodynamically favoured than {MeReO(pdt)}2 and this is attributed to the higher angle strain on the {MeReO(edt)}2 bridging sulfur. The computational study of the proposed slow step shows that enthalpy of activation (ΔH‡) of ReV oxidation to ReVII is unchanged by varying the substituent on the pyridine oxide.
Structure of the chlorovirus PBCV-1 major capsid glycoprotein determined by combining crystallographic and carbohydrate molecular modeling approaches
Authors: De Castro Cristina , Klose Thomas , Speciale Immacolata , Lanzetta Rosa , Molinaro Antonio , Van Etten James L. , Rossmann Michael G.
Published: December 2017

Significance

The three-dimensional structure of Vp54, the major capsid protein of the chlorovirus
Paramecium bursaria
chlorella virus (PBCV-1), was determined by combining two powerful techniques, X-ray diffraction and carbohydrate molecular modeling. This strategy resolved the limitations posed by each technique alone and increases our understanding of how glycans fold, their flexibility, and the type of interactions they exert within the protein component.
Lesion network localization of criminal behavior
Authors: Darby R. Ryan , Horn Andreas , Cushman Fiery , Fox Michael D.
Published: December 2017

Significance

Cases like that of Charles Whitman, who murdered 16 people after growth of a brain tumor, have sparked debate about why some brain lesions, but not others, might lead to criminal behavior. Here we systematically characterize such lesions and compare them with lesions that cause other symptoms. We find that lesions in multiple different brain areas are associated with criminal behavior. However, these lesions all fall within a unique functionally connected brain network involved in moral decision making. Furthermore, connectivity to competing brain networks predicts the abnormal moral decisions observed in these patients. These results provide insight into why some brain lesions, but not others, might predispose to criminal behavior, with potential neuroscience, medical, and legal implications.
Evidence of directional and stabilizing selection in contemporary humans
Authors: Sanjak Jaleal S. , Sidorenko Julia , Robinson Matthew R. , Thornton Kevin R. , Visscher Peter M.
Published: December 2017

Significance

Combining high-throughput molecular genetic data with extensive phenotyping enables the direct study of natural selection in humans. We see firsthand how and at what rates contemporary human populations are evolving. Here we demonstrate that the genetic variants associated with several traits, including age at first birth in females and body-mass index in males, are also associated with reproductive success. In addition, for several traits, we demonstrate that individuals at either extreme of the phenotypic range have reduced fitness—the hallmark of stabilizing selection. Overall, the data are indicative of a moving optimum model for contemporary evolution of human quantitative traits.
Dynamic and heterogeneous effects of sibling death on children’s outcomes
Authors: Fletcher Jason , Vidal-Fernandez Marian , Wolfe Barbara
Published: December 2017

Significance

Although childhood mortality rates have plummeted over the past century in developed countries, between 5% and 10% of the US population still experiences a sibling death. While we know a death in the family has strong and durable negative long-term effects on relatives in the long run, little is known about the development of children who experience the death of a sibling in the medium run. This is a key issue, given children’s vulnerability, the malleability of early childhood skills, and their impact on future adult health and socioeconomic outcomes. By analyzing a longitudinal dataset, this study examines how children’s cognitive and socioemotional skills and parental effort change around the time of the death of a child in the family.
Epigenetic control of pheromone MAPK signaling determines sexual fecundity in
Candida albicans
Authors: Scaduto Christine M. , Kabrawala Shail , Thomson Gregory J. , Scheving William , Ly Andy , Anderson Matthew Z. , Whiteway Malcolm , Bennett Richard J.
Published: December 2017

Significance

A central theme in biology is to understand how different signaling outputs can be accomplished by changes to signal transduction pathways. Here, we examined epigenetic differences between two cell states in the human fungal pathogen
Candida albicans
. We show that cells in the “white” state are sterile due to multiple bottlenecks in MAPK signaling relative to mating-competent “opaque” cells. Alleviation of these bottlenecks by reverse engineering effectively converts sterile white cells into sexually competent cells. These results have broad implications for understanding how epigenetic changes can impact MAPK expression and signaling output, including events associated with tumorigenesis. We also propose a model for how the white-opaque switch gained control of sexual reproduction in
Candida
during evolution.
In vivo inhibition of tryptophan catabolism reorganizes the tuberculoma and augments immune-mediated control ofMycobacterium tuberculosis
Authors: Gautam Uma S. , Foreman Taylor W. , Bucsan Allison N. , Veatch Ashley V. , Alvarez Xavier , Adekambi Toidi , Golden Nadia A. , Gentry Kaylee M. , Doyle-Meyers Lara A. , Russell-Lodrigue Kasi E. , Didier Peter J. , Blanchard James L. , Kousoulas K. Gus , Lackner Andrew A. , Kalman Daniel , Rengarajan Jyothi , Khader Shabaana A. , Kaushal Deepak , Mehra Smriti
Published: December 2017

Significance

Mycobacterium tuberculosisinduces the expression of the indoleamine 2,3-dioxygenase (IDO) enzyme, which catabolizes tryptophan. Tryptophan metabolites potently suppress host immunity. The present study demonstrates that blockade of IDO activity reduces both clinical manifestations of tuberculosis (TB) as well as microbial and pathological correlates of the human TB syndrome in macaques. In granulomas, T cells localize in the periphery, and are unable to access the core, where bacilli persist. Inhibiting IDO activity altered granuloma organization such that more T cells translocated to the lesion core and exhibited highly proliferative signatures. Our results identify a highly efficient immunosuppressive mechanism at play in the granuloma environment that aids inM. tuberculosispersistence. The ability to modulate this pathway with safe and approved compounds could, however, facilitate chemotherapy-adjunctive host-directed therapy approaches for the control of TB.
Closing the loop on impulsivity via nucleus accumbens delta-band activity in mice and man
Authors: Wu Hemmings , Miller Kai J. , Blumenfeld Zack , Williams Nolan R. , Ravikumar Vinod K. , Lee Karen E. , Kakusa Bina , Sacchet Matthew D. , Wintermark Max , Christoffel Daniel J. , Rutt Brian K. , Bronte-Stewart Helen , Knutson Brian , Malenka Robert C. , Halpern Casey H.
Published: December 2017

Significance

We reveal prominent delta oscillations in the nucleus accumbens preceding food reward in mice and use them to guide responsive neurostimulation to suppress binge-like behavior. Similar electrographic signatures are observed in human nucleus accumbens during reward anticipation as well, suggesting their translational potential in the development of a treatment for loss of impulse control in obesity and perhaps additional brain disorders.
Initial elevation bias in subjective reports
Authors: Shrout Patrick E. , Stadler Gertraud , Lane Sean P. , McClure M. Joy , Jackson Grace L. , Clavél Frederick D. , Iida Masumi , Gleason Marci E. J. , Xu Joy H. , Bolger Niall
Published: December 2017

Significance

People’s reports of their own thoughts, feelings, and behaviors are essential assessment tools in biomedical and social science. When subjective states have been studied over time, however, researchers have often observed an unpredicted and puzzling decrease with repeated assessments. Our results across multiple outcomes in four field experiments suggest that this pattern is due to an initial elevation bias. This effect is larger for reports of internal states than for behaviors and for negative mental states and physical symptoms than for positive states. This initial elevation bias needs to be considered in all types of research using subjective reports.
Bifidobacterium
can mitigate intestinal immunopathology in the context of CTLA-4 blockade
Authors: Wang Feng , Yin Qian , Chen Liang , Davis Mark M.
Published: December 2017

Significance

The major stumbling block in the use of checkpoint inhibitors for cancer treatment is the severe autoimmunity that often results. In this study, we found the toxicity of a checkpoint blockade antibody can be ameliorated via administration of
Bifidobacterium
, a widely available probiotic. These results suggest that it may be possible to mitigate the autoimmunity caused by anti–CTLA-4 and perhaps other checkpoint inhibitors by manipulating gut microbiota.
Enhancer adoption caused by genomic insertion elicits interdigital
Shh
expression and syndactyly in mouse
Authors: Mouri Kousuke , Sagai Tomoko , Maeno Akiteru , Amano Takanori , Toyoda Atsushi , Shiroishi Toshihiko
Published: December 2017

Acquisition of new
cis
-regulatory elements (CREs) can cause alteration of developmental gene regulation and may introduce morphological novelty in evolution. Although structural variation in the genome generated by chromosomal rearrangement is one possible source of new CREs, only a few examples are known, except for cases of retrotransposition. In this study, we show the acquisition of novel regulatory sequences as a result of large genomic insertion in the spontaneous mouse mutation Hammer toe (
Hm
).
Hm
mice exhibit syndactyly with webbing, due to suppression of interdigital cell death in limb development. We reveal that, in the
Hm
genome, a 150-kb noncoding DNA fragment from chromosome 14 is inserted into the region upstream of the Sonic hedgehog (
Shh
) promoter in chromosome 5. Phenotyping of mouse embryos with a series of CRISPR/Cas9-aided partial deletion of the 150-kb insert clearly indicated that two different regions are necessary for the syndactyly phenotype of
Hm
. We found that each of the two regions contains at least one enhancer for interdigital regulation. These results show that a set of enhancers brought by the large genomic insertion elicits the interdigital
Shh
expression and the
Hm
phenotype. Transcriptome analysis indicates that ectopic expression of
Shh
up-regulates Chordin (
Chrd
) that antagonizes bone morphogenetic protein signaling in the interdigital region. Indeed,
Chrd-
overexpressing transgenic mice recapitulated syndactyly with webbing. Thus, the
Hm
mutation provides an insight into enhancer acquisition as a source of creation of novel gene regulation.
Artificial antibody created by conformational reconstruction of the complementary-determining region on gold nanoparticles
Authors: Yan Gui-Hua , Wang Kun , Shao Zhuxue , Luo Lei , Song Zheng-Mei , Chen Jingqi , Jin Rong , Deng Xiaoyong , Wang Haifang , Cao Zhonglian , Liu Yuanfang , Cao Aoneng
Published: December 2017

Significance

Mimicking protein-like specific interactions and functions has been a long-pursued goal in nanotechnology. The key challenge is to precisely organize nonfunctional surface groups on nanoparticles into specific 3D conformations to function in a concerted and orchestrated manner. Here, we develop a method to graft the complementary-determining regions of natural antibodies onto nanoparticles and reconstruct their “active” conformation to create nanoparticle-based artificial antibodies that recognize the corresponding antigens. Our work demonstrates that it is possible to create functions on nanoparticles by conformational engineering, namely tuning flexible surface groups into specific conformations. Our straightforward strategy could be used further to create other artificial antibodies for various applications and provides a new tool to understand the structure and folding of natural proteins.
Nonequilibrium internal energy distributions during dissociation
Authors: Singh Narendra , Schwartzentruber Thomas
Published: December 2017

Significance

Predicting the extent of air dissociation in thin shock layers created by hypersonic vehicles is challenging due to coupling between gas internal energy and chemical reactions. Thermochemical nonequilibrium flow models, capable of predicting the heat flux and the flux of reactive atomic species to the vehicle surface, are critical for heat shield design. Whereas existing continuum models do not account for non-Boltzmann rotational and vibrational energy distributions and coupling to dissociation, we develop a model based on recent ab initio calculations that does.
Form finding in elastic gridshells
Authors: Baek Changyeob , Sageman-Furnas Andrew O. , Jawed Mohammad K. , Reis Pedro M.
Published: December 2017

Significance

Elastic gridshells arise from the buckling of an initially planar grid of rods. The interaction of elasticity and geometric constraints makes their actuated shapes difficult to predict using classical methods. However, recent progress in extreme mechanics reveals the benefits of structures that buckle by design, when exploiting underlying geometry. Here, we demonstrate the geometry-driven nature of elastic gridshells. We use a geometric model, originally for woven fabric, to rationalize their actuated shapes and describe their nonlocal response to loading. Validation is provided with precision experiments and rod-based simulations. The prominence of geometry in elastic gridshells that we identify should allow for our results to transfer across length scales from architectural structures to micro/nano–1-df mechanical actuators and self-assembly systems.
Accurate quantification of brown adipose tissue mass by xenon-enhanced computed tomography
Authors: Branca Rosa T. , McCallister Andrew , Yuan Hong , Aghajanian Amir , Faber James E. , Weimer Nicholas , Buchanan Riley , Floyd Carlos S. , Antonacci Michael , Zhang Le , Burant Alex
Published: December 2017

Significance

The search for new obesity drug targets and the rediscovery of active brown fat (brown adipose tissue; BAT) in adult humans has triggered a BAT renaissance. However, the assumption that this tissue plays a key role in energy balance in humans, as it does in rodents, is still a matter of debate. This is because BAT mass cannot be correctly quantified by current imaging techniques, as these are either nonspecific or lack the necessary sensitivity to detect BAT, especially in obese phenotypes. Here, we show that xenon-enhanced computed tomography can accurately quantify BAT mass, especially in obese mouse phenotypes in which extensive BAT hypertrophy hampers the detection of this tissue by current tomographic imaging techniques.
College completion predicts lower depression but higher metabolic syndrome among disadvantaged minorities in young adulthood
Authors: Gaydosh Lauren , Schorpp Kristen M. , Chen Edith , Miller Gregory E. , Harris Kathleen Mullan
Published: December 2017

Significance

College graduates enjoy healthier, longer lives compared with individuals who do not graduate from college. However, the health benefit of educational attainment is not as great for blacks as it is for whites. Moreover, college completion may not erase the detrimental effects of early-life disadvantage for blacks and Hispanics. We use nationally representative data on young adults to test whether American minorities experience differential returns to educational attainment. We find that college completion predicts lower rates of depression for all racial groups. It also predicts lower metabolic syndrome among whites. However, college completion predicts higher metabolic syndrome among black and Hispanic adults from disadvantaged backgrounds, suggesting upward mobility may come at a health cost to young minorities in America.
Conserved epitope on influenza-virus hemagglutinin head defined by a vaccine-induced antibody
Authors: Raymond Donald D. , Bajic Goran , Ferdman Jack , Suphaphiphat Pirada , Settembre Ethan C. , Moody M. Anthony , Schmidt Aaron G. , Harrison Stephen C.
Published: December 2017

Significance

Antigenic variation requires frequent revision of annual influenza vaccines. Next-generation vaccine design strategies aim to elicit a broader immunity by directing the human immune response toward conserved sites on the principal viral surface protein, the hemagglutinin (HA). We describe a group of antibodies that recognize a hitherto unappreciated, conserved site on the HA of H1 subtype influenza viruses. Mutations in that site, which required a change in the H1 component of the 2017 vaccine, had not previously “taken over” among circulating H1 viruses. Our results encourage vaccine design strategies that resurface a protein to focus the immune response on a specific region.
Basal resistance enhances warming tolerance of alien over indigenous species across latitude
Authors: Janion-Scheepers Charlene , Phillips Laura , Sgrò Carla M. , Duffy Grant A. , Hallas Rebecca , Chown Steven L.
Published: December 2017

Significance

How climate change and biological invasions interact to affect biodiversity is of major concern to conservation. Quantitative evidence for the nature of climate change–invasion interactions is, however, limited. For the soil ecosystem fauna, such evidence is nonexistent. Yet across the globe, soil-dwelling animals regulate belowground functioning and have pronounced influences on aboveground dynamics. Using springtails as an exemplar taxon, widely known to have species-specific effects on below- and aboveground dynamics, we show that across a wide latitudinal span (16–54°S), alien species have greater ability to tolerate climate change-associated warming than do their indigenous counterparts. The consequences of such consistent differences are profound given globally significant invasions of soil systems by springtails.
Functions of maize genes encoding pyruvate phosphate dikinase in developing endosperm
Authors: Lappe Ryan R. , Baier John W. , Boehlein Susan K. , Huffman Ryan , Lin Qiaohui , Wattebled Fabrice , Settles A. Mark , Hannah L. Curtis , Borisjuk Ljudmilla , Rolletschek Hardy , Stewart Jon D. , Scott M. Paul , Hennen-Bierwagen Tracie A. , Myers Alan M.
Published: December 2017

Significance

Mutations affecting the transcription factor encoded by the gene
o2
are important in maize agriculture because they result in improved grain nutritional quality. The mutations also cause detrimental effects by reducing kernel hardness and diminishing agronomic quality and food applications. The undesirable characteristics are not fully understood because the
o2
product regulates multiple targets that could contribute to the phenotype. This study investigated one target that had not been previously mutated, pyruvate phosphate dikinase (PPDK), and showed that PPDK deficiency in isolation causes the negative phenotype associated with reduced kernel hardness. Thus, maize improvement may be better accomplished by targeting individual metabolic pathways determining protein and amino acid balance rather than pleiotropic regulators such as the
o2
transcription factor.