bluuebunny/crossref_metadata_2025 huggingface dataset:
Unified transport scaling laws for plasma blobs and depletions
Authors: Wiesenberger M. , Held M. , Kube R. , Garcia O. E.
Published: June 2017

We study the dynamics of seeded plasma blobs and depletions in an (effective) gravitational field. For incompressible flows, the radial center of mass velocity of blobs and depletions is proportional to the square root of their initial cross-field size and amplitude. If the flows are compressible, this scaling holds only for ratios of amplitude to size larger than a critical value. Otherwise, the maximum blob and depletion velocity depends linearly on the initial amplitude and is independent of size. In both cases, the acceleration of blobs and depletions depends on their initial amplitude relative to the background plasma density and is proportional to gravity and independent of their cross-field size. Due to their reduced inertia plasma, depletions accelerate more quickly than the corresponding blobs. These scaling laws are derived from the invariants of the governing drift-fluid equations for blobs and agree excellently with numerical simulations over five orders of magnitude for both blobs and depletions. We suggest an empirical model that unifies and correctly captures the radial acceleration and maximum velocities of both blobs and depletions.
Relativistic electron-beam assisted growth of oscillating two-stream instability of a plasma wave
Authors: Yadav Pinki , Gupta D. N. , Avinash K.
Published: June 2017

Analytical formulism of oscillating two-stream instability of a plasma wave has been revisited by incorporating the effect of a relativistic electron-beam. A large-amplitude plasma wave may be susceptible to oscillating two-stream instability by decaying in a low-frequency mode and the sideband waves. The relativistic electron-beam may contribute in decaying the energy associated with the pump wave. In consequence, the growth of instability is enhanced. The findings of our calculations show that the growth of instability may be reached to a crucial level in the presence of a relativistic electron-beam. The growth of interacting waves during the instability is seriously affected by the relative motion between the beam electrons and the background plasma particles. This work may be important to understand the behavior of space and astrophysical plasmas.
Coupling of damped and growing modes in unstable shear flow
Authors: Fraser A. E. , Terry P. W. , Zweibel E. G. , Pueschel M. J.
Published: June 2017

Analysis of the saturation of the Kelvin-Helmholtz instability is undertaken to determine the extent to which the conjugate linearly stable mode plays a role. For a piecewise-continuous mean flow profile with constant shear in a fixed layer, it is shown that the stable mode is nonlinearly excited, providing an injection-scale sink of the fluctuation energy similar to what has been found for gyroradius-scale drift-wave turbulence. Quantitative evaluation of the contribution of the stable mode to the energy balance at the onset of saturation shows that nonlinear energy transfer to the stable mode is as significant as energy transfer to small scales in balancing energy injected into the spectrum by the instability. The effect of the stable mode on momentum transport is quantified by expressing the Reynolds stress in terms of stable and unstable mode amplitudes at saturation, from which it is found that the stable mode can produce a sizable reduction in the momentum flux.
Structure determination of the high-pressure phases of topological insulator Bi2Se3 using experiments and calculations
Authors: Cheng Hu , Zhang Junran , Li Yanchun , Li Gong , Li Xiaodong
Published: June 2017

The pressure-induced phase transition of bismuth selenide (Bi2Se3) was investigated by combining theoretical calculations with synchrotron powder X-ray diffraction measurements up to 57.4 GPa. We demonstrated that the ambient-pressure rhombohedral Bi2Se3 crystallized into a monoclinic structure with the space group C2/m at 9.1 GPa, and eventually to a body-centered tetragonal structure with the space group I4/mmm at about 27.2 GPa. This behavior was different from the transformation sequences of Bi2Te3 and Sb2Te3. The stabilities of five structures of Bi2Se3 were studied by density functional theory calculations. Furthermore, an unusual irreversible relaxation process was observed. We attempted to make clear the unusual structural behavior of Bi2Se3 occurring in the compression process and the relaxation process.
Electronic transition in solid Nb at high pressure and temperature
Authors: Ezenwa Innocent C. , Secco Richard A.
Published: June 2017

The electrical resistivity of high purity solid Nb has been measured at fixed pressures up to 5 GPa in a large volume press and temperatures up to ∼1900 K. The expected resistivity decrease with pressure and increase with temperature were found. A transition was observed in the temperature dependence of resistivity at high temperature. The transition is discussed in terms of the effects of pressure and temperature on the electronic band structure of Nb causing a resistivity behavior characteristic of a change from the “minus group” to the “plus group.” Extrapolation of the pressure dependence of the transition temperature suggests that Nb would show plus group behavior at room T at an estimated pressure of ∼27 ± 7 GPa. The electronic thermal conductivity was calculated using the Wiedemann-Franz law and was in very good agreement with 1 atm data. We show that the temperature dependence of the calculated electronic thermal conductivity increases with a steep slope from room temperature up to the electronic transition temperature for all fixed pressures. Above the transition temperature, the T-dependence of electronic thermal conductivity remained constant at 2 GPa and exhibited an increasingly negative slope at higher pressures. The isothermal pressure-dependence of electronic thermal conductivity is positive.
Theory of polyelectrolyte complexation—Complex coacervates are self-coacervates
Authors: Delaney Kris T. , Fredrickson Glenn H.
Published: June 2017

The complexation of mixtures of cationic and anionic polymers to produce complex-coacervate phases is a subject of fundamental importance to colloid and polymer science as well as to applications including drug delivery, sensing technologies, and bio-inspired adhesives. Unfortunately the theoretical underpinnings of complex coacervation are widely misunderstood and conceptual mistakes have propagated in the literature. Here, a simple symmetric polyelectrolyte mixture model in the absence of salt is used to discuss the salient features of the phase diagram, including the location of the critical point, binodals, and spinodals. It is argued that charge compensation by dimerization in the dilute region renders the phase diagram of an oppositely charged polyelectrolyte mixture qualitatively and quantitatively similar to that of a single-component symmetric diblock polyampholyte solution, a system capable of “self-coacervation.” The theoretical predictions are verified using fully fluctuating field-theoretic simulations for corresponding polyelectrolyte and diblock polyampholyte models. These represent the first comprehensive, approximation-free phase diagrams for coacervate and self-coacervate systems to appear in the literature.
Piezoelectricity in two-dimensional covalent organic frameworks
Authors: Xiang Hui , Xu Bo , Xia Yidong , Yin Jiang , Liu Zhiguo
Published: June 2017

First-principles calculations were used to investigate piezoelectricity in two-dimensional covalent organic frameworks, including those composed of C9H3N3 and C6H3B3O3 monolayers. We mainly studied the elastic stiffness constants and piezoelectric tensors of these networks using their clamped-ion and relaxed-ion components. Our results show that both of these organic materials are piezoelectric along the armchair direction because of their noncentrosymmetric structures. The strain effects on the bandgaps of these monolayers have almost no effect on their piezoelectric performance. Additionally, the dynamic stabilities of the C9H3N3 and C6H3B3O3 monolayers were examined. Despite their low piezoelectric coefficients, the piezoelectricity in these two-dimensional covalent organic frameworks is promising for applications such as biocompatible nanoelectromechanical systems because they offer potential for enhanced biocompatibility when compared with inorganic materials.
Analytic derivative couplings and first-principles exciton/phonon coupling constants for an ab initio Frenkel-Davydov exciton model: Theory, implementation, and application to compute triplet exciton mobility parameters for crystalline tetracene
Authors: Morrison Adrian F. , Herbert John M.
Published: June 2017

Recently, we introduced an ab initio version of the Frenkel-Davydov exciton model for computing excited-state properties of molecular crystals and aggregates. Within this model, supersystem excited states are approximated as linear combinations of excitations localized on molecular sites, and the electronic Hamiltonian is constructed and diagonalized in a direct-product basis of non-orthogonal configuration state functions computed for isolated fragments. Here, we derive and implement analytic derivative couplings for this model, including nuclear derivatives of the natural transition orbital and symmetric orthogonalization transformations that are part of the approximation. Nuclear derivatives of the exciton Hamiltonian’s matrix elements, required in order to compute the nonadiabatic couplings, are equivalent to the “Holstein” and “Peierls” exciton/phonon couplings that are widely discussed in the context of model Hamiltonians for energy and charge transport in organic photovoltaics. As an example, we compute the couplings that modulate triplet exciton transport in crystalline tetracene, which is relevant in the context of carrier diffusion following singlet exciton fission.
Flow and transport effect caused by the stalk contraction cycle of Vorticella convallaria
Authors: Zhou Jiazhong , Ryu Sangjin , Admiraal David
Published: June 2017

Vorticella convallaria is a protozoan attached to a substrate by a stalk which can contract in less than 10 ms, translating the zooid toward the substrate with a maximum Reynolds number of ∼1. Following contraction, the stalk slowly relaxes, moving the zooid away from the substrate, which results in creeping flow. Although Vorticella has long been believed to contract to evade danger, it has been suggested that its stalk may contract to enhance food transport near the substrate. To elucidate how Vorticella utilizes its contraction-relaxation cycle, we investigated water flow caused by the cycle, using a computational fluid dynamics model validated with an experimental scale model and particle tracking velocimetry. The simulated flow was visualized and analyzed by tracing virtual particles around the Vorticella. It is observed that one cycle can displace particles up to ∼190 μm with the maximum net vertical displacement of 3–4 μm and that the net transport effect becomes more evident over repeated cycles. This transport effect appears to be due to asymmetry of the contraction and relaxation phases of the flow field, and it can be more effective on motile food particles than non-motile ones. Therefore, our Vorticella model enabled investigating the fluid dynamics principle and ecological role of the transport effects of Vorticella's stalk contraction.
Tunability of the CO adsorption energy on a Ni/Cu surface: Site change and coverage effects
Authors: Vesselli Erik , Rizzi Michele , Furlan Sara , Duan Xiangmei , Monachino Enrico , Dri Carlo , Peronio Angelo , Africh Cristina , Lacovig Paolo , Baldereschi Alfonso , Comelli Giovanni , Peressi Maria
Published: June 2017

The adsorption energy of carbon monoxide on Ni ad-islands and ultra-thin films grown on the Cu(110) surface can be finely tuned via a complex interplay among diffusion, site change mechanisms, and coverage effects. The observed features of CO desorption can be explained in terms of migration of CO molecules from Cu to Ni islands, competition between bridge and on-top adsorption sites, and repulsive lateral adsorbate-adsorbate interactions. While the CO adsorption energy on clean Cu(110) is of the order of 0.5 eV, Ni-alloying allows for its controlled, continuous tunability in the 0.98-1.15 eV range with Ni coverage. Since CO is a fundamental reactant and intermediate in many heterogeneous catalytic (electro)-conversion reactions, insight into these aspects with atomic level detail provides useful information to potentially drive applicative developments. The tunability range of the CO adsorption energy that we measure is compatible with the already observed tuning of conversion rates by Ni doping of Cu single crystal catalysts for methanol synthesis from a CO2, CO, and H2 stream under ambient pressure conditions.
Large and small amplitude compressional Alfvénic shocks in an electron depleted dusty plasma
Authors: Haque Q. , Ali Sidra , Rizvi H. , Mirza Arshad M.
Published: June 2017

Compressional Dust Alfvénic Shocks (CDAS) are investigated in an electron depleted dusty plasma with dust-ion collisional effects. The large amplitude CDAS are obtained after solving the coupled nonlinear equations numerically, while small amplitude CDAS are explored through the Kortweg-de Vries Burger equation. It is pointed out that the spatio-temporal scale lengths for the formation of CDAS are different than the compressional Alfvénic shocks in an electron-ion plasma. The amplitude variation of CDAS with different parameters is shown. The transition of oscillatory shocks to monotonic shocks is presented in 3-D plots with variation in collision frequency. The importance of the results to space plasma environments is also briefly discussed.
Quadruple Beltrami fields in three component plasmas
Authors: Gondal S. M. , Iqbal M. , Khosa Ashfaq H. , Murtaza G.
Published: June 2017

A possibility of three component plasma to self-organize to Quadruple Beltrami State is explored. The Quadruple Beltrami State is characterized by four Beltarmi fields. The state emerges as a natural consequence of the contributions of all the linear and nonlinear forces present in an ideal plasma. The role of species density in the creation of relaxed structures is also investigated and found to be effective in transformation of field structures. The study will be helpful to understand formation of structures in astrophysical and laboratory plasmas.
Water structure around hydrophobic amino acid side chain analogs using different water models
Authors: Hajari Timir , Bandyopadhyay Sanjoy
Published: June 2017

The water structure around hydrophobic groups governs various biochemical processes. There is an ongoing debate on whether water molecules near hydrophobic groups are more ordered with greater participation in water-water hydrogen bonding with respect to water in the pure bulk state. The water structure around six different hydrophobic amino acid side chain analog molecules has been studied in pure water using molecular dynamics simulations. The analysis of water tetrahedral order parameter and the number of hydrogen bonds formed by the individual water molecules in the first hydration shell of the hydrophobic analogs provide evidence that both ordering and hydrogen bonds involving water molecules are to some extent reduced in the hydrophobic hydration shell. It is revealed that the water tetrahedrality in the outer part of the first hydrophobic hydration shell is equivalent to bulk water for all the water models except for the TIP4P-2005 model which shows marginally higher tetrahedrality. However, irrespective of the model employed, water tetrahedrality has always been found to be reduced in the inner part of the first hydration shell, which eventually makes the overall water tetrahedrality in the first hydrophobic hydration shell marginally lower than that observed for pure bulk water. Importantly, it is noticed that the decrease in water structuring exhibits solute size dependencies. Around a small solute like methane, the water tetrahedral ordering or hydrogen bonding propensity is quite similar to that of the bulk state. The effect, reduction in water structuring, is however more pronounced for relatively larger solutes.
Thermal expansion in FeCrCoNiGa high-entropy alloy from theory and experiment
Authors: Huang Shuo , Vida Ádám , Li Wei , Molnár Dávid , Kyun Kwon Se , Holmström Erik , Varga Béla , Károly Varga Lajos , Vitos Levente
Published: June 2017

First-principle alloy theory and key experimental techniques are applied to determine the thermal expansion of FeCrCoNiGa high-entropy alloy. The magnetic transition, observed at 649 K, is accompanied by a significant increase in the thermal expansion coefficient. The phase stability is analyzed as a function of temperature via the calculated free energies accounting for the structural, magnetic, electronic, vibrational and configurational contributions. The single- and polycrystal elastic modulus for the ferro- and paramagnetic states of the face-centered and body-centered cubic phases are presented. By combining the measured and theoretically predicted temperature-dependent lattice parameters, we reveal the structural and magnetic origin of the observed anomalous thermal expansion behavior.
Twisted graphene-assisted photocarrier transfer from HgSe colloidal quantum dots into silicon with enhanced collection and transport efficiency
Authors: Tang Xin , Wu Guang Fu , Lai King Wai Chiu
Published: June 2017

We report a strategy to realize and facilitate the photocarrier transport from mercury selenium colloidal quantum dots (HgSe CQDs) into silicon with the assistance of twisted graphene. A nanocomposite material consisting of HgSe CQDs and twisted graphene has been synthesized. By bringing the nanocomposites into contact with silicon, a HgSe CQD-twisted graphene nanocomposite/silicon junction was fabricated and demonstrated photoresponses in the long-wave infrared range. In the nanocomposites, the surface of twisted graphene was decorated with HgSe CQDs. Benefiting from the twisted structure in the nanocomposites, the active sensing area and light-matter interaction length are greatly increased. Driven by the interfacial built-in potential, photocarriers directly transfer from HgSe CQDs into the twist graphene, which serves as a fast carrier transport pathway to silicon, leading to high photocarrier collection efficiency. Compared with vertically stacked HgSe CQD film/flat graphene, the application of HgSe CQD-twisted graphene nanocomposites avoids photocarriers transporting via the hopping mechanism and over 2700% enhancement ratio of spectral responsivity was achieved, reaching 31.5 mA/W@9 μm. The interfacial energy band diagram was deduced for a better understanding of the photocarrier transfer process occurring at the interface between HgSe colloidal quantum dots, twist graphene, and silicon.
Three-phase Fe3O4/MWNT/PVDF nanocomposites with high dielectric constant for embedded capacitor
Authors: Wang Haiyun , Fu Qiong , Luo Jiangqi , Zhao Dongmei , Luo Laihui , Li Weiping
Published: June 2017

To get the dielectric material with a high dielectric constant and low dielectric loss, the modified multiwalled carbon nanotube (MWNT-S) and ferroferric oxide (Fe3O4) particles were embedded into polyvinylidene fluoride (PVDF) to fabricate the Fe3O4/MWNT-S/PVDF ternary composites. The maximum dielectric constant of these composites can be up to 3490 at a very low filler fraction, and dielectric loss can be suppressed below 0.5. The small amount of the second filler (Fe3O4) can accelerate the formation of a percolation conductive network and improve the interfacial polarization. Therefore, the excellent dielectric properties can be achieved at low loading of fillers.
An electrocaloric refrigerator with direct solid to solid regeneration
Authors: Zhang Tian , Qian Xiao-Shi , Gu Haiming , Hou Ying , Zhang Q. M.
Published: June 2017

Regenerative cooling has been used to improve the efficiency of refrigerators. Recently, exploiting the easy controlling of the electric fields, a regenerative electrocaloric (EC) cooling device with direct solid to solid regeneration has been proposed. Here, we report an experimental study of such an EC cooling device. For the EC device to be operated at a household voltage, the EC multilayer ceramic elements were first developed employing the multilayer ceramic capacitor fabrication technique. Under a voltage of 200 V, the EC multilayers with the commercial Y5V ceramic composition exhibit an electric field induced temperature change ΔT of 0.86 K. Testing results of a prototype EC device based on these EC multilayer elements show that even with only two EC rings, which is the minimum unit required to demonstrate the operation, such an EC device can generate a temperature span between hot and cold ends about three times of ΔT of the EC multilayers.
High thermoelectric figure of merit by resonant dopant in half-Heusler alloys
Authors: Chen Long , Liu Yamei , He Jian , Tritt Terry M. , Poon S. Joseph
Published: June 2017

Half-Heusler alloys have been one of the benchmark high temperature thermoelectric materials owing to their thermal stability and promising figure of merit ZT. Simonson et al. early showed that small amounts of vanadium doped in Hf0.75Zr0.25NiSn enhanced the Seebeck coefficient and correlated the change with the increased density of states near the Fermi level. We herein report a systematic study on the role of vanadium (V), niobium (Nb), and tantalum (Ta) as prospective resonant dopants in enhancing the ZT of n-type half-Heusler alloys based on Hf0.6Zr0.4NiSn0.995Sb0.005. The V doping was found to increase the Seebeck coefficient in the temperature range 300-1000 K, consistent with a resonant doping scheme. In contrast, Nb and Ta act as normal n-type dopants, as evident by the systematic decrease in electrical resistivity and Seebeck coefficient. The combination of enhanced Seebeck coefficient due to the presence of V resonant states and the reduced thermal conductivity has led to a state-of-the-art ZT of 1.3 near 850 K in n-type (Hf0.6Zr0.4)0.99V0.01NiSn0.995Sb0.005 alloys.
Periodic cycle number modulating effect on crystallization temperature in superlattice-like [Ge/Ge8Sb92]n phase-change films and exploration of mechanism
Authors: Liu Xinyi , Hu Yifeng , Lai Tianshu
Published: June 2017

Superlattice-like (SLL) phase-change films provide more controllable parameters for the optimization of the performance of phase-change films, including the thickness of each constituent layer, the thickness ratio of two constituent layers and cycle number of periodicity. The effects of the first two parameters on the performance of SLL films have been studied widely. However, the influence of last parameter, cycle number of periodicity, was studied sparsely. In this study, we have studied the period number effect on crystallization temperature of SLL [Ge/Ge8Sb92]n films, and designed and fabricated a series of superlattice-like (SLL) [Ge/Ge8Sb92]n phase-change films. Their crystallization behaviors are studied by the measurement of temperature-dependent sheet resistance. We find that crystallization temperature decreases with increasing cycle number of periodicity, revealing period-cycle-number modulation effect. However, such the effect cannot be explained by current interface effect model. We test the existence of periodic structures of the crystallized SLL films by coherent acoustic phonon (CAP) spectroscopy. Apparent folded CAP modes related to SLL nanostructures are observed, implying the existence of excellent periodic structures or no alloying within one period in crystallized SLL films. Therefore, such period number manipulation effect cannot be explained by the cooperative effects of interface and alloying effects either, implying new mechanisms to be unveiled. We tentatively propose two kinds of possible long-range effects, built-in electric field and strain effects. Based on strain effect, our results can be explained phenomenologically.
Root uptake and xylem transport of cadmium in wheat and triticale as affected by exogenous amino acids
Authors: Khodamoradi K. , Khoshgoftarmanesh A. H. , Maibody S. A. M. Mirmohammady
Published: June 2017

Organic acids exuded from plant roots significantly modify uptake and long-distance translocation of metals. Little is known about the effect of amino acids on metal ion uptake by plant roots. The present study investigated the effects of exogenous amino acids (histidine and glycine) in a nutrient solution on root uptake and xylem sap transport of cadmium (Cd) in triticale (× Triticosecale cv. Elinor) and bread wheat (Triticum aestivum L. cv. Back Cross Rushan). Plant seedlings were grown in a Cd-free modified Hoagland nutrient solution to which 1 µm Cd was added with either 50 µm histidine or 50 µm glycine or without amino acids at 4 weeks after germination. A control treatment consisted of a nutrient solution free of Cd and amino acids. In bread wheat, addition of histidine to the Cd-containing nutrient solution resulted in a higher operationally defined symplastic Cd fraction but a lower apoplastic one in the roots. In triticale, addition of either amino acid decreased the symplastic Cd fraction but increased the apoplastic one. Addition of histidine to the nutrient solution increased Cd concentration in wheat xylem sap but had no significant effect on Cd concentration in triticale xylem sap. Compared with the Cd-only treatment, the glycine-containing treatment led to significantly reduced Cd concentrations in xylem sap of both plant species. Wheat plants supplied with histidine and Cd accumulated greater amounts of Cd in their shoots than those supplied with Cd alone. Glycine had no significant effects on the Cd content of wheat shoots but decreased it in triticale shoots. Results indicate that the effects of amino acids on plant root uptake and xylem sap translocation of Cd depend on the type of amino acid supplemented. This finding is of great importance for selecting and/or breeding cultivars with Cd-toxicity tolerance.
An invasive ant distribution database to support biosecurity risk analysis in the Pacific
Authors: Gruber Monica A. M. , Cooling Meghan , Burne Allan R.
Published: June 2017

Invasive species are one of the most serious threats to biodiversity. Up-to-date and accurate information on the distribution of invasive species is an important biosecurity risk analysis tool. Several databases are available to determine the distributions of invasive and native species. However, keeping this information current is a real challenge. Ants are among the most widespread invasive species. Five species of ants are listed in the IUCN list of damaging invasive species, and many other species are also invasive in the Pacific. We sought to determine and update the distribution information for the 18 most problematic invasive ant species in the Pacific to assist Small Island Developing States with risk analysis. We compared the information on six public databases, conducted a literature review, and contacted experts on invasive ants in the Pacific region to resolve conflicting information. While most public records were accurate we found some new records had not yet been incorporated in the public databases, and some information was inaccurate. The maintenance of public databases faces an enormous challenge in balancing completeness (~15 000 ant species in this case) with accuracy (the impossibility of constantly surveying) and utility.
Interplay between tolerance mechanisms to copper and acid stress inEscherichia coli
Authors: Djoko Karrera Y. , Phan Minh-Duy , Peters Kate M. , Walker Mark J. , Schembri Mark A. , McEwan Alastair G.
Published: June 2017

Significance

Copper (Cu) is an essential trace metal nutrient in health and is increasingly recognized for its role in the control of infection. The pathogenEscherichia coliencounters host niches with mild to high acidity and elevated copper levels. Our study shows that this bacterium can alter its metabolism and harness the amino acid glutamine to suppress the effects of acid stress and copper toxicity. Given the abundance of glutamine in systemic circulation and its importance in the host immune system, our work provides a new insight into the ways in which bacterial pathogens can adapt and survive host-imposed antibacterial strategies.
Optogenetic control of mitochondrial metabolism and Ca
2+
signaling by mitochondria-targeted opsins
Authors: Tkatch Tatiana , Greotti Elisa , Baranauskas Gytis , Pendin Diana , Roy Soumitra , Nita Luliaoana I. , Wettmarshausen Jennifer , Prigge Matthias , Yizhar Ofer , Shirihai Orian S. , Fishman Daniel , Hershfinkel Michal , Fleidervish Ilya A. , Perocchi Fabiana , Pozzan Tullio , Sekler Israel
Published: June 2017

Significance

Mitochondrial functions depend on the steep H
+
electrochemical gradient (ΔμH
+
) across their inner membrane. The available tools for controlling this gradient are essentially limited to inhibitors of the respiratory chain or of the H
+
ATPase or to uncouplers, poisons plagued by important side effects and that lack both cell and spatial specificity. We show here that, by transfecting cells with the cDNA encoding channelrhodopsins specifically targeted to the inner mitochondrial membrane, we can obtain an accurate and spatially confined, light-dependent control of mitochondrial membrane potential and, as a consequence, of a series of mitochondrial activities ranging from electron transport to ATP synthesis and Ca
2+
signaling.
Energetics and dynamics of a light-driven sodium-pumping rhodopsin
Authors: Suomivuori Carl-Mikael , Gamiz-Hernandez Ana P. , Sundholm Dage , Kaila Ville R. I.
Published: June 2017

Significance

Krokinobacter eikastus
rhodopsin 2 (KR2) is the first identified light-driven Na
+
pump. Despite its recently resolved X-ray structure, the molecular mechanism of the translocation and gating of Na
+
ions during its photocycle has remained elusive. Here we use large-scale quantum and classical simulations to prepare KR2 in transient photocycle states and show how combined electrostatic, conformational, and hydration changes drive the Na
+
ions across the membrane. Our calculations identify putative ion-binding sites that can be further probed by site-directed mutagenesis experiments. The obtained results provide rational design principles to develop KR2 toward next generation optogenetic tools.
Immunoengineering nerve repair
Authors: Mokarram Nassir , Dymanus Kyle , Srinivasan Akhil , Lyon Johnathan G. , Tipton John , Chu Jason , English Arthur W. , Bellamkonda Ravi V.
Published: June 2017

Significance

Annually, more than 250,000 Americans suffer from a peripheral nerve injury, which results in a loss of function and a compromised quality of life. The current clinical gold standard to bridge long, nonhealing nerve gaps, the autograft, has several drawbacks. Therefore, there is a clear and urgent unmet clinical need for an alternative approach that can match or exceed autograft performance. Here we investigated the regenerative effect of fractalkine, a chemokine that preferentially recruits reparative monocytes in the synthetic nerve conduit. Our method of bridging gaps enhanced axonal regeneration and muscle reinnervation and showed results comparable to those observed in autografts.
Cultivating an agrarian middle class? Land reform, poverty reduction and social stratification in Southern Africa
Authors: Thebe Vusilizwe
Published: June 2017

In the past three decades, land reforms have dominated poverty and development policy debates in Southern Africa following the late attainment of independence of former settler colonies, and efforts to improve the efficiency of the agriculture sector in others. This article provides an analysis of land reforms in South Africa and Zimbabwe and proposed reforms under the new land laws in Lesotho. Based on these examples, it argues that prospects of poverty reduction through land reforms in this region are bleak. It argues that the reform process has been hamstrung by an agricultural development agenda focused on ‘farm productivity and economic returns’. Even in the cases where the poor received land, they are unlikely to benefit due to a lack of capacity both on their own part and on the part of the state. Given the evidence, the process appears to be skewed towards accumulation by an African agrarian capitalist class that will potentially result in a stratification process where the poor fail the transition to a class of modern farmers.
Population Structure of Digestive Trypsin Phenotypes in Hatcheries for Pacific White Shrimp and Their Frequencies during Growth in Commercial Culture
Authors: Aguiñaga-Cruz Jazmin Asusena , Sainz-Hernández Juan Carlos , González-Prieto Juan Manuel , Vargas-Albores Francisco , Sandoval-Castro Eduardo , Rúbio-Gastelum Damaris , Apún-Molina Juan Pablo , García-Gutiérrez Cipriano
Published: June 2017

Trypsin from Pacific white shrimp Litopenaeus vannamei is a polymorphic protein composed of three alleles (A, B, and C). The C allele is monomorphic for the first region, while A and B are allelic variations for the second region that are segregated according to Mendelian rules. These three alleles give rise to three individual trypsin phenotypes displayed in sodium dodecyl sulfate polyacrylamide gel electrophoresis: CBA, CB, and CA. The expected frequencies from mating CBA males and females resulted in offspring that consisted of 25% CB, 25% CA, and 50% CBA trypsin phenotypes. To define a management protocol for studying shrimp performance associated with the trypsin phenotype, the goal of this study was to determine if the expected proportions of the three trypsin phenotypes are represented in the population structure at breeding age in 11 hatcheries. Here, we hypothesized that the population structure of the trypsin phenotypes is represented by frequencies that are subject to selection, and it is possible to establish a management protocol to study shrimp performance. A total of 2,828 breeding shrimp from 11 hatcheries were analyzed to describe their population structure. The results showed a high frequency of CBA breeders and a near absence of the CA phenotype in the population structure. To discard the possibility that man-made selection is the cause of the trypsin phenotype frequency, the offspring of CBA breeders were cultured in nine commercial ponds, and the phenotype frequencies were monitored during 75 d. Interestingly, the CA phenotype was only present during the early stages of culture, which suggests that the population structure is not due to human selection of CBA shrimp in the hatcheries. In this condition, poslarvae production could be directed to make trials that contribute to describe the difference between the culture performance between phenotypes, but not to support the commercial production of larvae with the highest culture performance trypsin phenotype.
Caspase-8 controls the secretion of inflammatory lysyl-tRNA synthetase in exosomes from cancer cells
Authors: Kim Sang Bum , Kim Hye Rim , Park Min Chul , Cho Seongmin , Goughnour Peter C. , Han Daeyoung , Yoon Ina , Kim YounHa , Kang Taehee , Song Eunjoo , Kim Pilhan , Choi Hyosun , Mun Ji Young , Song Chihong , Lee Sangmin , Jung Hyun Suk , Kim Sunghoon
Published: June 2017

Aminoacyl-tRNA synthetases (ARSs), enzymes that normally control protein synthesis, can be secreted and have different activities in the extracellular space, but the mechanism of their secretion is not understood. This study describes the secretion route of the ARS lysyl-tRNA synthetase (KRS) and how this process is regulated by caspase activity, which has been implicated in the unconventional secretion of other proteins. We show that KRS is secreted from colorectal carcinoma cells within the lumen of exosomes that can trigger an inflammatory response. Caspase-8 cleaved the N-terminal of KRS, thus exposing a PDZ-binding motif located in the C terminus of KRS. Syntenin bound to the exposed PDZ-binding motif of KRS and facilitated the exosomic secretion of KRS dissociated from the multi-tRNA synthetase complex. KRS-containing exosomes released by cancer cells induced macrophage migration, and their secretion of TNF-α and cleaved KRS made a significant contribution to these activities, which suggests a novel mechanism by which caspase-8 may promote inflammation.
Fusion, fission, and transport control asymmetric inheritance of mitochondria and protein aggregates
Authors: Böckler Stefan , Chelius Xenia , Hock Nadine , Klecker Till , Wolter Madita , Weiss Matthias , Braun Ralf J. , Westermann Benedikt
Published: June 2017

Partitioning of cell organelles and cytoplasmic components determines the fate of daughter cells upon asymmetric division. We studied the role of mitochondria in this process using budding yeast as a model. Anterograde mitochondrial transport is mediated by the myosin motor, Myo2. A genetic screen revealed an unexpected interaction of MYO2 and genes required for mitochondrial fusion. Genetic analyses, live-cell microscopy, and simulations in silico showed that fused mitochondria become critical for inheritance and transport across the bud neck in myo2 mutants. Similarly, fused mitochondria are essential for retention in the mother when bud-directed transport is enforced. Inheritance of a less than critical mitochondrial quantity causes a severe decline of replicative life span of daughter cells. Myo2-dependent mitochondrial distribution also is critical for the capture of heat stress–induced cytosolic protein aggregates and their retention in the mother cell. Together, these data suggest that coordination of mitochondrial transport, fusion, and fission is critical for asymmetric division and rejuvenation of daughter cells.
A Pragmatist’s Guide to Epistemic Utility
Authors: Levinstein Benjamin Anders
Published: June 2017

We use a theorem from M. J. Schervish to explore the relationship between accuracy and practical success. If an agent is pragmatically rational, she will quantify the expected loss of her credence with a strictly proper scoring rule. Which scoring rule is right for her will depend on the sorts of decisions she expects to face. We relate this pragmatic conception of inaccuracy to the purely epistemic one popular among epistemic utility theorists.
Inductive McKay condition for finite simple groups of type 𝖢
Authors: Cabanes Marc , Späth Britta
Published: June 2017

We verify the inductive McKay condition for simple groups of Lie type

C

\mathsf {C}

, namely finite projective symplectic groups. This contributes to the program of a complete proof of the McKay conjecture for all finite groups via the reduction theorem of Isaacs-Malle-Navarro and the classification of finite simple groups. In an important step we use a new counting argument to determine the stabilizers of irreducible characters of a finite symplectic group in its outer automorphism group. This is completed by analogous results on characters of normalizers of Sylow

d
d

-tori in those groups.
CWENO: Uniformly accurate reconstructions for balance laws
Authors: Cravero I. , Puppo G. , Semplice M. , Visconti G.
Published: June 2017

In this paper we introduce a general framework for defining and studying essentially nonoscillatory reconstruction procedures of arbitrarily high order of accuracy, interpolating data in the central stencil around a given computational cell (

C
W
E
N
O

\mathsf {CWENO}

). This technique relies on the same selection mechanism of smooth stencils adopted in

W
E
N
O

\mathsf {WENO}

, but here the pool of candidates for the selection includes polynomials of different degrees. This seemingly minor difference allows us to compute the analytic expression of a polynomial interpolant, approximating the unknown function uniformly within a cell, instead of only at one point at a time. For this reason this technique is particularly suited for balance laws for finite volume schemes, when averages of source terms require high order quadrature rules based on several points; in the computation of local averages, during refinement in

h
h

-adaptive schemes; or in the transfer of the solution between grids in moving mesh techniques, and in general when a globally defined reconstruction is needed. Previously, these needs have been satisfied mostly by ENO reconstruction techniques, which, however, require a much wider stencil than the

C
W
E
N
O

\mathsf {CWENO}

reconstruction studied here, for the same accuracy.
Bilinear operators with homogeneous symbols, smooth molecules, and Kato-Ponce inequalities
Authors: Brummer Joshua , Naibo Virginia
Published: June 2017

We present a unifying approach to establish mapping properties for bilinear pseudodifferential operators with homogeneous symbols in the settings of function spaces that admit a discrete transform and molecular decompositions in the sense of Frazier and Jawerth. As an application, we obtain related Kato-Ponce inequalities.
Vaccines Throughout the Lifecycle
Authors: Tan Tina Q. , Flaherty John P. , Gerbie Melvin V.
Published: June 2017

Immunization schedules for infants, children, adolescents, and adults help clinicians ensure that they are administering vaccines in a timely and appropriate manner. Specific, current CDC schedules for infants, children, adolescents, and adults are presented Special attention is paid to recommendations and contraindications for the vaccination of pregnant women and women who are trying to conceive. Details for the specific illnesses, their influences on the pregnant woman and the fetus, vaccination recommendations in the pre-pregnancy, various trimesters, and post-partum periods are given. Safety concerns and Frequently Asked Questions are given significant space as patients and their families are appropriately concerned. Health Care Professionals and their staff needs are included in the recommendations.
Radiation physics, biology, and protection
Authors: Sabharwal Nikant , Arumugam Parthiban , Kelion Andrew
Published: June 2017

This chapter explains the basics of radiation physics, including an explanatory section on atoms and nuclei, and detail on radioactive decay including statistics. The interaction of X-ray and gamma photons with matter is also explained. Detail is provided on radiation exposure, including acute and late biological effects, and the principles and practical applications of radiation protection. A section on key UK legislation relevant to nuclear cardiology lists important medicines regulations and acts relating to radioactive substances.
Models of Care for Patients With HIV
Authors: Bourgeois James , Cohen Mary Ann , Grimaldi John , Levenson Jon A. , Moghimi Yavar , Fisher Weston , Tran David
Published: June 2017

Numerous contemporary clinical models for the delivery and coordination of psychiatric and other mental health care for patients with HIV within outpatient medical care settings are described in this chapter. Care for patients’ multimorbid psychiatric illness in the context of general medical care for HIV-associated conditions is a pragmatic application of the Engel biopsychosocial model and offers the opportunity for interprofessional collegiality and collaborative care in managing the clinical illnesses and other challenges faced by persons with HIV. The functional descriptions of the various care delivery models include the strengths and challenges faced in operating within these models. Detailed discussions of well-established HIV care delivery models in Boston, New York, and San Francisco are included to illustrate how to tailor the integration of psychiatric services in various institutional settings.
Psychotic Disorders and Serious Mental Illness
Authors: Thompson Alexander , Williams Daniel , Freudenreich Oliver , Angelino Andrew , Treisman Glenn
Published: June 2017

The major public health problem that is HIV/AIDS in persons with a serious mental illness is aptly described a “syndemic.” Having HIV/AIDS puts one at much greater risk for developing a serious mental illness. Conversely, having a serious mental illness, such as schizophrenia, bipolar disorder, major depressive disorder, substance use disorder, is associated with many factors that place one at greater risk for contracting and transmitting HIV. And, in both cases of serious mental illness and HIV/AIDS, each disorder creates many new challenges in the management of the other disorder. This chapter addresses these challenges, which center around being able to participate actively and adhere to medication regimens needed to manage both medical and psychiatric conditions. Fortunately, specialized models of care like comprehensive, integrated clinics and nurse care managers are ways to provide effective, satisfying, and cost-effective care to this most vulnerable population.
Psychoneuroimmunology and HIV
Authors: Carrico Adam W. , Antoni Michael H.
Published: June 2017

Psychoneuroimmunology (PNI) examines the biological and behavioral pathways whereby psychosocial factors may influence the course of chronic medical conditions, including HIV/AIDS. This chapter summarizes PNI research conducted examining the possible role of negative life events (including bereavement), stress reactivity, personality factors, cognitive appraisals, and affective states (depression) in HIV illness progression. Because much of this research was conducted in the era prior to the advent of effective antiretroviral therapy, important questions remain regarding whether there the associations of psychosocial factors with HIV illness progression are independent of medication adherence and persistence. There is also increasing recognition that chronic viral infections such as HIV have neuropsychiatric effects, and more recent PNI research has focused on studying the bidirectional communication between the immune system and central nervous system in HIV. Future research should focus on obtaining definitive answers to these questions to inform the development of novel approaches for reducing psychiatric symptoms and optimizing health outcomes among persons with HIV.
Distress in Persons with HIV and AIDS
Authors: Cohen Mary Ann , Dickerman Anna L. , Goforth Harold W.
Published: June 2017

Persons with HIV have multifactorial and multidimensional sources of distress. Distress has a profoundly negative impact on persons with HIV and their loved ones. While the term distress is more acceptable to patients and does not carry with it the stigma of a specific psychiatric diagnostic disorder, the anguish and suffering associated are still painful. This chapter explores the sources for distress utilizing a comprehensive biopsychosocial approach and presents ways to recognize distress. Related tools in assessing HIV-related distress include the Distress Thermometer (DT), Hospital Anxiety and Depression Scale (HADS), and HIV Symptom Distress Scale (SDS). An overview of the symptoms and illnesses associated with distress include biological, psychological, and social aspects including HIV stigma. Evidence-based approaches to alleviate distress in persons with HIV/AIDS are also presented in the chapter.
Integrative Treatments
Authors: Gore-Felton Cheryl , McGlynn Lawrence , Kreutzberg Andrei , Spiegel David
Published: June 2017

Many individuals seek relief from symptoms associated with HIV infection through the use of integrative medicine. Symptoms include neuropsychiatric problems such as anxiety, depression, cognitive dysfunction, and headaches, as well as somatic disorders related to viral infection and immunodysregulation, such as fatigue, diarrhea, and cardiovascular problems. As antiretroviral treatments have become increasingly effective, symptom management with minimal side effects has become more important. A variety of integrative treatments, including botanicals, vitamins, minerals, probiotics, and herbs, have been utilized, and mind–body approaches such as mindfulness, hypnosis, and movement therapy have been found to reduce symptoms and improve quality of life. This chapter examines widely used integrative medicine approaches to alleviating distressing HIV-related symptoms. Implications for clinical practice are discussed. Integrative approaches emphasize self-management of symptoms and are widely sought after and accepted, even by patients who resist other forms of medical treatment.