bluuebunny/crossref_metadata_2025 huggingface dataset:
Three-dimensional Voronoï analysis of preferential concentration of spheroidal particles in wall turbulence
Authors: Yuan Wenjun , Zhao Lihao , Andersson Helge I. , Deng Jianqiang
Published: June 2018

Three-dimensional Voronoï analysis is performed to quantify both global and local aspects of clustering of inertial spheroidal particles in wall turbulence using data sets from a direct numerical simulation coupled with a Lagrangian point-particle approach. We consider oblate and prolate spheroids and characterize their inertia and shape by means of the Stokes number St and aspect ratio λ, respectively. It is observed that particles tend to drift toward the wall, and this tendency is most prominent for St = 30. Although inertia dominates over shape on the particle clustering, intermediate asphericity (λ = 0.33 and 3) is found to promote spheroids’ flux to the wall for St ≤ 30, while heavy spheroids (St = 100) with greater departure from spheres (λ = 0.1 and 10) distribute more evenly across the channel. The tendency of inertial spheroids to concentrate locally in preferred turbulence structures decreases with the distance from the walls. Owing to the particles’ preferential distribution in lower-than-mean fluid velocity regions, the local clustering of spheroidal particles decreases with the increasing asphericity. Particles with large inertia (St ≥ 30), especially spheres and prolate spheroids, are more likely to cluster in the viscous sublayer.
Vibronic exciton theory of singlet fission. III. How vibronic coupling and thermodynamics promote rapid triplet generation in pentacene crystals
Authors: Tempelaar Roel , Reichman David R.
Published: June 2018

We extend the vibronic exciton theory introduced in our previous work to study singlet fission dynamics, in particular addressing recent indications of the importance of vibronic coupling in this process. A microscopic and non-perturbative treatment of electronic and selected vibrational degrees of freedom in combination with Redfield theory allows us to dynamically consider clusters of molecules under conditions close to those in molecular crystals that exhibit fission. Using bulk pentacene as a concrete example, our results identify a number of factors that render fission rapid and effective. Strong coupling to high-frequency Holstein modes generates resonances between the photo-prepared singlet and product triplet states. We furthermore find the large number of triplet combinations associated with bulk periodic systems to be critical to the fission process under such vibronically resonant conditions. In addition, we present results including, in an approximate manner, the effects of Peierls coupling, indicating that this factor can both enhance and suppress fission depending on its interplay with vibronic resonance and thermodynamics.
Modal model mean field self-similar solutions to the asymptotic evolution of Rayleigh-Taylor and Richtmyer-Meshkov instabilities and its dependence on the initial conditions
Authors: Elbaz Yonatan , Shvarts Dov
Published: June 2018

The evolution of Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities for incompressible and immiscible fluids and their dependence on the initial perturbation spectrum is evaluated using a new mean field formulation of the Haan-Ofer-Shvarts mode coupling model. The height of the lighter fluid bubbles penetrating into the denser fluid is shown to reach asymptotic, universal, self-similar behavior when the initial spectrum is dominated by short wavelengths and at least 3–4 mode coupling generations have occurred. For RT, the model yields h=αRTAgt2 for the bubble front penetration height, in good agreement with experimental data and 3D numerical simulations for various initial conditions. For RM, the lack of a natural length scale leads to a 2nd type self-similar solution h=αRMtθ and θ is rigorously determined from a detailed solution of the model equation, while αRM retains knowledge of the initial spectrum. The value of θRM in two dimensions is θ2D = 2/5, consistent with the Alon-Shvarts bubble-merger model and numerical simulations, and in three dimensions, it is θ3D = 1/3. We find that the smaller value θ3D ∼ 0.25 ± 0.05 obtained in numerical simulations and experiments [Dimonte and Schneider, Phys. Fluids 12, 304 (2000)] results from the lack of enough mode coupling generations needed to reach the RM asymptotic self-similar stage. The feasibility of a true self-similar RM experiment on NIF is discussed.
Research Update: Ca doping effect on the Li-ion conductivity in NASICON-type solid electrolyte LiZr2(PO4)3: A first-principles molecular dynamics study
Authors: Noda Yusuke , Nakano Koki , Otake Masanari , Kobayashi Ryo , Kotobuki Masashi , Lu Li , Nakayama Masanobu
Published: June 2018

In this work, we used a density functional theory-based molecular dynamics simulation to investigate the Ca content-dependent Li-ion conductivity of NASICON-type Li1+2xCaxZr2-x(PO4)3 (LCZP) solid electrolytes (0.063 ≤ x ≤ 0.375) which exhibit a Li-excess chemical composition. The LCZP systems show a higher room temperature Li-ion conductivity and a lower activation energy than pristine LiZr2(PO4)3 (LZP), and the tendencies of those properties agree with the experimental results. In addition, the Li-ion conduction mechanisms in LCZP were clarified by analyzing the radial distribution functions and site displacement functions obtained from our molecular dynamics simulations. For minimal Ca substitution for LZP, the Li-ion conductivity is enhanced because of the creation of interstitial Li ions by Ca doping in the LCZP systems; the frequency of collisions with Li ions dramatically increases. For substantial Ca substitution for LZP, the Li-ion conductivity gradually worsened because some Li ions were trapped at the M1 (most stable) and M2 (metastable) sites near Ca atoms.
The effect of alternative propellants on the electron drift instability in Hall-effect thrusters: Insight from 2D particle-in-cell simulations
Authors: Croes Vivien , Tavant Antoine , Lucken Romain , Martorelli Roberto , Lafleur Trevor , Bourdon Anne , Chabert Pascal
Published: June 2018

Hall-effect thrusters (HETs) operated with xenon are one of the most commonly used electric propulsion technologies for a wide range of space missions, including drag compensation in low Earth orbit, station-keeping, and orbital insertion, as access to space becomes more affordable. Although anomalous electron transport, the electron drift instability (EDI), and secondary electron emission (SEE) have been studied experimentally and numerically in xenon-based HETs, the impact of alternative propellants is still poorly characterized. In this work, a two-dimensional particle-in-cell/Monte Carlo collision code is used to model the (r – θ) plane of a HET operated separately with four different noble gases: xenon, krypton, argon, and helium. Models for electron induced secondary electron emission (SEE) and dielectric walls are implemented in order to investigate the coupling between the propellant choice and the radial thruster walls. For all conditions and propellants studied, an EDI and enhanced electron cross-field transport are observed. The frequency of the instability, as well as the electron mobility, is compared with analytical expressions from a recently developed kinetic theory. Confirming this theory, it is shown that while the frequency of the EDI depends on the propellant mass, the electron mobility appears to be almost independent of the propellant choice.
Measuring the thermal properties of anisotropic materials using beam-offset frequency domain thermoreflectance
Authors: Rahman Mizanur , Shahzadeh Mohammadreza , Braeuninger-Weimer Philipp , Hofmann Stephan , Hellwig Olav , Pisana Simone
Published: June 2018

Thermoreflectance techniques have become popular to measure the thermal properties of thin films such as thermal conductivity and thermal boundary conductance (TBC). Varying the focused spot sizes of the beams increases the sensitivity to in-plane heat transport, enabling the characterization of thermally anisotropic materials. However, this requires realignment of the optics after each spot size adjustment. Offsetting the probe beam with respect to the pump beam and modulating over a wide range of frequencies (5 kHz to 50 MHz) yield better sensitivity to the thermophysical properties of anisotropic materials without varying the spot sizes. We demonstrate how beam-offset frequency domain thermoreflectance can be used to measure the in- and out-of-plane thermal conductivity as well as the TBC simultaneously from a single data set by working at reduced spot sizes. Lowering the laser spot size allows us to detect signals over a wide range of frequencies and use larger beam offsets, thanks to the increase in the thermoreflectance signal. We measure the anisotropic thermal properties of a range of materials, including single layer Graphene on SiO2, which is of interest for novel electronic devices.
Effects of B site ions on the relaxor to normal ferroelectric transition crossover in Ba4Sm2Zr4(NbxTa1-x)6O30 tungsten bronze ceramics
Authors: Feng Wen Bin , Zhu Xiao Li , Liu Xiao Qiang , Chen Xiang Ming
Published: June 2018

Effects of B site ions on the relaxor to normal ferroelectric crossover in Ba4Sm2Zr4(NbxTa1-x)6O30 (x = 0, 0.3, 0.5, 0.7, 0.9, and 1) tungsten bronze ceramics were investigated. The tetragonal tungsten bronze structure in space group P4/mbm was confirmed for compositions of x = 0, 0.3, and 0.5, while space group P4bm was confirmed for compositions of x = 0.7, 0.9, and 1. With the increasing Nb content in the B site, the dielectric properties showed a crossover from the relaxor to normal ferroelectric behavior, accompanied with the disappearance of frequency dispersion, increased ferroelectric transition temperature, and larger dielectric constant value. The room temperature Raman spectra for compositions of x = 0 and x = 1 showed different vibration modes of the oxygen octahedral, and the temperature dependence of the integrated intensity of Raman bands indicated the different structural transition process. Unlike the effects of A site ions, the onset of the relaxor/normal ferroelectric behavior of Ba4Sm2Zr4(NbxTa1-x)6O30 was mainly caused by the different electron configuration of Nb and Ta.
Effect of membrane tension on transbilayer movement of lipids
Authors: Hasan Moynul , Saha Samiron Kumar , Yamazaki Masahito
Published: June 2018

The stretching of plasma membranes of cells and lipid bilayers of vesicles affects the physical properties of the membrane as well as the functions of proteins/peptides in the membranes. Here, we examined the effect of membrane tension on the rate constant of the transbilayer movement (kFF) of fluorescent probe-labeled lipids using a new method. Specifically, we recently reported [Hasan et al., Langmuir 34, 3349 (2018)] the development of a technique that employs giant unilamellar vesicles (GUVs) with asymmetric lipid compositions in two monolayers. In the present work, we found that the kFF greatly increased with tension without leakage of water-soluble fluorescent probes from the GUV lumen (i.e., without the formation of pores in the GUV membrane). We discussed the plausible mechanisms for the effect of tension on the transbilayer movement of lipids. As one of the mechanisms, we hypothesized that the transbilayer movement of lipids occurs through the lateral diffusion of lipids in the walls of hydrophilic pre-pores.
A study of thermal effects in superconducting terahertz modulator by low temperature scanning laser microscope
Authors: Han Chao , Li Chun , Wu Jingbo , Zhou Xianjing , Li Jun , Jin Biaobing , Wang Huabing , Wu Peiheng
Published: June 2018

We use low temperature scanning laser microscope (LTSLM) to study the Joule power distribution of superconducting (SC) terahertz (THz) modulator. The LTSLM scanning images record the SC state transformation process under different DC bias voltages. The change of THz transmission spectra can be well explained by the thermal effect in the devices observed by LTSLM. Hotspots are present in one THz modulator and the transmission spectra changes a lot after the hotspots show up. According to theoretical analysis, the appearance of hotspot may be helpful for improving the modulation speed. These results will be useful to understand the mechanism of SC THz modulator and design higher performance THz moduators.
On the use of phase correction rings on Fresnel zone plates with ultrasound piston emitters
Authors: Pérez-López Sergio , Fuster José Miguel , Candelas Pilar , Rubio Constanza , Belmar Francisco
Published: June 2018

In this work, the distortion of the Fresnel Zone Plate focusing profile generated by a piston emitter in ultrasound applications is significantly reduced through the use of phase correction rings, which compensate the effect of the piston emitter radiation diagram. Both simulation and experimental results demonstrate the improvement achieved with this design method over the conventional case.
Inclusion of nuclear quantum effects for simulations of nonlinear spectroscopy
Authors: Jung Kenneth A. , Videla Pablo E. , Batista Victor S.
Published: June 2018

The computation and interpretation of nonlinear vibrational spectroscopy is of vital importance for understanding a wide range of dynamical processes in molecular systems. Here, we introduce an approach to evaluate multi-time response functions in terms of multi-time double symmetrized Kubo transformed thermal correlation functions. Furthermore, we introduce a multi-time extension of ring polymer molecular dynamics to evaluate these Kubo transforms. Benchmark calculations show that the approximations are useful for short times even for nonlinear operators, providing a consistent improvement over classical simulations of multi-time correlation functions. The introduced methodology thus provides a practical way of including nuclear quantum effects in multi-time response functions of non-linear optical spectroscopy.
Adsorption of molecular oxygen on the Ag(111) surface: A combined temperature-programmed desorption and scanning tunneling microscopy study
Authors: Andryushechkin B. V. , Shevlyuga V. M. , Pavlova T. V. , Zhidomirov G. M. , Eltsov K. N.
Published: June 2018

The adsorption of O2 on Ag(111) between 300 and 500 K has been studied with temperature-programmed desorption (TPD) and scanning tunneling microscopy (STM). At the first stage of adsorption, the disordered local oxide phase (commonly looking in STM as an array of black spots) is formed on the surface irrespective of the substrate temperature. The maximum concentration of black spots was found to be ≈0.11 ML, which corresponds to an oxygen coverage of ≈0.66 ML. Taking into account that the nucleation of the Ag(111)-p(4 × 4)-O phase starts after the saturation of the disordered phase, one can conclude that its coverage is at least not less than 0.66 ML. The analysis of STM and TPD data shows that the thermodesorption peak (m/e = 32) at 570 K is related exclusively to the decomposition of the p(4 × 4) phase, while the local oxide phase does not contribute to desorption.
Fluid flow and heat transfer over a rotating and vertically moving disk
Authors: Turkyilmazoglu Mustafa
Published: June 2018

The object of this study is the development of the fluid flow and resultant heat transfer caused by a rotating disk moving vertically upward or downward during an unsteady flow motion. The problem is formulated such that the similarity equations governing the physical phenomenon eventually reduced to those reported in the traditional viscous pumping study of von Karman for a vertically motionless but still rotating disk. The non-rotating disk with the upward or downward motion leads to the formation of a two-dimensional flow over the disk. Otherwise, the rotation and vertical action of the disk sets up a three-dimensional flow over the surface. It is observed that the upward and downward motion of the disk exerts an effect similar to that of the injection/suction through the wall, albeit with observable differences. Moreover, the viscous pumping is found to be a jet-like radial velocity as the disk moves upward fast. Although the downward movement of the disk suppresses the velocity field, a growth in the boundary layer thickness is anticipated, contrary to the traditional wall suction. The temperature field is shown to be highly dependent on the form of the wall temperature, which is maintained at a time-varying function. Moreover, the impact of the vertical wall movement is observed to be overwhelmed by high disk rotations.
Hydrogen-Bonded Frameworks of Mercury(II) Complexes with Pyridinedicarboxylic Acids
Authors: Soldin Željka , Kukovec Boris-Marko , Matković-Čalogović Dubravka , Popović Zora
Published: June 2018

Three novel mercury(ii) coordination compounds, [HgCl(2,4-pydcH2)(2,4-pydcH)]·2H2O (1) and [HgCl(2,6-pydcH)(H2O)]·3H2O (2) that exhibit hydrogen-bonded 3D frameworks, and [Hg(2,6-pydcH)2]·2H2O (3), exhibiting only hydrogen-bonded 1D chains (2,4-pydcH2 = pyridine-2,4-dicarboxylic acid; 2,6-pydcH2 = pyridine-2,6-dicarboxylic acid), were prepared in the reactions of the corresponding pyridinedicarboxylic acid with mercury(ii) chloride or mercury(ii) acetate. Compounds 1–3 were prepared by conventional solution synthesis. Only the hydrogen-bonded 1D chain of 3 was robust enough to be prepared by mechanochemical synthesis. The crystal structures of 1–3 were determined by the single-crystal X-ray diffraction method. Neutral 2,4-pydcH2 and partially deprotonated 2,4-pydcH− act as N,O-bidentate ligands in the structure of 1 whereas crystal structure analysis reveals O,N,O′-tridentate 2,6-pydcH− ligand in the structures of 2 and 3. Compounds 1–3 were characterised by IR spectroscopy in the solid state, and compounds 1 and 2 were also characterised by 1H and 13C NMR spectroscopy in DMSO solution. Thermal properties of 1–3 were also investigated. NMR data support a collapse of the hydrogen-bonded frameworks of 1 and 2 in DMSO solution, and the existence of monomeric species in DMSO solutions.
Rayleigh–Taylor instabilities in high-energy density settings on the National Ignition Facility
Authors: Remington Bruce A. , Park Hye-Sook , Casey Daniel T. , Cavallo Robert M. , Clark Daniel S. , Huntington Channing M. , Kalantar Dan H. , Kuranz Carolyn C. , Miles Aaron R. , Nagel Sabrina R. , Raman Kumar S. , Wehrenberg Christoper E. , Smalyuk Vladimir A.
Published: June 2018

The Rayleigh–Taylor (RT) instability occurs at an interface between two fluids of differing density during an acceleration. These instabilities can occur in very diverse settings, from inertial confinement fusion (ICF) implosions over spatial scales of

∼
1

0

−
3

−
1

0

−
1

cm (10–1,000 μm) to supernova explosions at spatial scales of

∼
1

0

12

cm and larger. We describe experiments and techniques for reducing (“stabilizing”) RT growth in high-energy density (HED) settings on the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory. Three unique regimes of stabilization are described: (
i
) at an ablation front, (
ii
) behind a radiative shock, and (
iii
) due to material strength. For comparison, we also show results from nonstabilized “classical” RT instability evolution in HED regimes on the NIF. Examples from experiments on the NIF in each regime are given. These phenomena also occur in several astrophysical scenarios and planetary science [Drake R (2005)
Plasma Phys Controlled Fusion
47:B419–B440; Dahl TW, Stevenson DJ (2010)
Earth Planet Sci Lett
295:177–186].
Arthropod EVs mediate dengue virus transmission through interaction with a tetraspanin domain containing glycoprotein Tsp29Fb
Authors: Vora Ashish , Zhou Wenshuo , Londono-Renteria Berlin , Woodson Michael , Sherman Michael B. , Colpitts Tonya M. , Neelakanta Girish , Sultana Hameeda
Published: June 2018

Significance

So far, no studies have reported whether dengue virus uses arthropod extracellular vesicles (EVs) for its transmission from vector to the mammalian host. Our study reports a very significant finding on EV-mediated transmission of dengue viruses (serotypes 2 and 3) from mosquito to mammalian, including human cells, through interactions with an arthropod EV-enriched tetraspanin domain-containing glycoprotein, Tsp29Fb.
Action potential counting at giant mossy fiber terminals gates information transfer in the hippocampus
Authors: Chamberland Simon , Timofeeva Yulia , Evstratova Alesya , Volynski Kirill , Tóth Katalin
Published: June 2018

Significance

Neurons fire action potentials to transfer information through synaptic release of neurotransmitter. At presynaptic terminals, the pattern of action potential discharge is integrated through dynamic Ca
2+
signaling by the presynaptic machinery which triggers the release of neurotransmitter. It is generally accepted that the rate and the temporal precision of action potential firing support information transfer between neurons. Here, we show that in contrast to rate and temporal coding, giant mossy fiber terminals count the number of action potentials during trains to trigger CA3 pyramidal cell firing. Our results shed light on the synaptic signal transfer mechanisms supporting an additional information coding strategy in the brain.
Amyloid clearance defect in ApoE4 astrocytes is reversed by epigenetic correction of endosomal pH
Authors: Prasad Hari , Rao Rajini
Published: June 2018

Significance

Alzheimer’s disease is the most common cause of dementia in the elderly. Most cases occur sporadically, with 40–65% of patients carrying at least one copy of the E4 allele of Apolipoprotein E. Because no drug exists that can halt disease progress, there is strong interest in understanding the presymptomatic role of endosomes. We show that excessive endosomal acidification in ApoE4 astrocytes is caused by downregulation of the Na
+
/H
+
exchanger NHE6 and results in defective clearance of amyloid beta (Aβ) peptide by intracellular sequestration of the LRP1 receptor. Epigenetic modifiers restore NHE6 expression to alkalinize endosomal pH, increase surface expression of LRP1, and correct Aβ clearance in astrocytes. Thus, endosomal pH emerges as a target for the correction of amyloid disorders.
Resistance to
Plasmodium falciparum
in sickle cell trait erythrocytes is driven by oxygen-dependent growth inhibition
Authors: Archer Natasha M. , Petersen Nicole , Clark Martha A. , Buckee Caroline O. , Childs Lauren M. , Duraisingh Manoj T.
Published: June 2018

Significance

Sickle cell trait has repeatedly been identified as a major human malaria resistance factor. Despite this, the exact mechanism of resistance is unclear. These studies demonstrate how the evolutionarily significant sickle hemoglobin affects
Plasmodium falciparum
infection success and leads to a better understanding of the molecular basis and pathogenesis of malaria infection.
Cell-based screen for discovering lipopolysaccharide biogenesis inhibitors
Authors: Zhang Ge , Baidin Vadim , Pahil Karanbir S. , Moison Eileen , Tomasek David , Ramadoss Nitya S. , Chatterjee Arnab K. , McNamara Case W. , Young Travis S. , Schultz Peter G. , Meredith Timothy C. , Kahne Daniel
Published: June 2018

Significance

The outer membrane of gram-negative bacteria contains LPS on the cell surface. The presence of LPS creates an effective permeability barrier that protects gram-negative bacteria from small hydrophobic molecules. Because the entire LPS biogenesis pathway, including biosynthesis and transport, is highly conserved, proteins involved are attractive targets for antibiotic discovery. Historically, it has been challenging to target LPS biogenesis since many of the components are membrane proteins with hard-to-assay activities. Utilizing the nonessentiality of this pathway in a gram-negative pathogen, we developed a cell-based screen specific to LPS biogenesis. We identified a small-molecule inhibitor targeting an essential component of the pathway, MsbA, and validated it as an antibacterial target using a combination of genetics, biochemistry, and cellular assays.
Structural basis for recognition of human 7SK long noncoding RNA by the La-related protein Larp7
Authors: Eichhorn Catherine D. , Yang Yuan , Repeta Lucas , Feigon Juli
Published: June 2018

Significance

The 7SK ribonucleoprotein (RNP) complex regulates the activity of the kinase positive transcription elongation factor b (P-TEFb), an essential activator of RNA Polymerase II transcription. The human La-related protein group 7 (hLarp7) protein is an essential and constitutively assembled component of the 7SK RNP and is required for 7SK RNA stability and P-TEFb recruitment. We report the structure of the hLarp7 C-terminal RNA recognition motif bound to the 7SK stem-loop 4, revealing a unique binding interface. From this and other available structures, we generate a structural model of hLarp7 bound to the 7SK 3′ end. This work provides seminal insights into the unique recognition of 7SK RNA by hLarp7 and a working model for how hLarp7 assembles with 7SK to form the 7SK RNP.
Dynamically reinforced heterogeneous grain structure prolongs ductility in a medium-entropy alloy with gigapascal yield strength
Authors: Yang Muxin , Yan Dingshun , Yuan Fuping , Jiang Ping , Ma Evan , Wu Xiaolei
Published: June 2018

Significance

Back stress hardening is usually not obvious in single-phase homogeneous grains, but can be made unusually large and sustained to large tensile strains by creating an unusually heterogeneous grain structure in single-phase alloys with low stacking fault energy (SFE), as demonstrated here for the face-centered cubic CrCoNi medium-entropy alloy. The low SFE facilitates the generation of twinned nanograins and stacking faults during tensile straining, dynamically reinforcing the heterogeneity. Large uniform tensile strain can be achieved after yielding even at gigapascal stress, in the absence of heterogeneities from any second phase.
Actin filaments partition primary cilia membranes into distinct fluid corrals
Authors: Lee Sungsu , Tan Han Yen , Geneva Ivayla I. , Kruglov Aleksandr , Calvert Peter D.
Published: June 2018

Physical properties of primary cilia membranes in living cells were examined using two independent, high-spatiotemporal-resolution approaches: fast tracking of single quantum dot–labeled G protein–coupled receptors and a novel two-photon super-resolution fluorescence recovery after photobleaching of protein ensemble. Both approaches demonstrated the cilium membrane to be partitioned into corralled domains spanning 274 ± 20 nm, within which the receptors are transiently confined for 0.71 ± 0.09 s. The mean membrane diffusion coefficient within the corrals, Dm1 = 2.9 ± 0.41 µm2/s, showed that the ciliary membranes were among the most fluid encountered. At longer times, the apparent membrane diffusion coefficient, Dm2 = 0.23 ± 0.05 µm2/s, showed that corral boundaries impeded receptor diffusion 13-fold. Mathematical simulations predict the probability of G protein–coupled receptors crossing corral boundaries to be 1 in 472. Remarkably, latrunculin A, cytochalasin D, and jasplakinolide treatments altered the corral permeability. Ciliary membranes are thus partitioned into highly fluid membrane nanodomains that are delimited by filamentous actin.
Mass-conserving solutions to coagulation-fragmentation equations with nonintegrable fragment distribution function
Authors: Laurençot Philippe
Published: June 2018

Existence of mass-conserving weak solutions to the coagulation-fragmentation equation is established when the fragmentation mechanism produces an infinite number of fragments after splitting. The coagulation kernel is assumed to increase at most linearly for large sizes and no assumption is made on the growth of the overall fragmentation rate for large sizes. However, they are both required to vanish for small sizes at a rate which is prescribed by the (nonintegrable) singularity of the fragment distribution.
Ernesto Laclau and Communication Studies
Authors: Stavrakakis Yannis , Galanopoulos Antonis
Published: June 2018

Arguably one of the most important political theorists of our time, Ernesto Laclau has produced an extremely influential theoretical corpus involving a multitude of methodological and political implications. His contribution is mainly focused on three fields; discourse, hegemony, and populism, all of them highly connected with communication and mediation processes.

In particular, Ernesto Laclau has introduced, throughout his career, a complex conceptual apparatus (comprising concepts like articulation, the nodal point, dislocation, the empty signifier, etc.) as a result of the radicalization and re-elaboration of the Gramscian conceptualization of hegemony. According to this framework, elaborated for the first time in Hegemony and Socialist Strategy, co-authored with Chantal Mouffe (first published in 1985), discourse is a social practice that performatively shapes the social world. Human reality is thus articulated through discourse and obtains its meaning precisely through this discursive mediation. All social practices are therefore understood as discursive ones. To the extent, however, that processes of articulation are never taking place in a vacuum and are bound to involve different or antagonistic political orientations, the field of discursivity comes to be seen as a field marked throughout by the primacy of the political. As a result, any hegemony will be contingent, partial, and temporary.

In addition, Laclau is one of the most well known analysts of populism, to which he has (partly) devoted two of his books, Politics and Ideology in Marxist Theory (1977) and On Populist Reason (2005). Populism, for Laclau, is designated, as expected, as discourse, as a specific way to articulate and communicate social demands as well as to form popular identities, to construct “the people.” His elaborations of populism are surely critical for the analysis of a pervasive political phenomenon of our era. All in all, the thought of Ernesto Laclau remains influential in the sphere of theory and political practice, and his theoretical arsenal will be an extremely helpful tool for academics and researchers of discourse theory and political communication.
Freelancing in Journalism
Authors: Massey Brian L. , Elmore Cindy
Published: June 2018

The profession of journalism can hardly be explored today without recognizing the large number of journalists who work as freelancers rather than as organizational media direct employees. While this type of work is not new, the number of freelancers is growing as a share of all journalists as legacy media organizations lose audiences, trim workforces, and outsource labor in the context of an industrywide digital revolution. The increase in freelance journalists also comes amid a larger, postindustrial capitalist desire for flexibility and dexterity in staffing, with the resulting structural benefits for organizations. Yet there are all manner of so-called freelance journalists, and they are not easily located or defined. The most successful find opportunities and freedom in being their own boss and choosing their work. Many, however, find themselves thrust into pay-reducing competition, which engenders economic uncertainty and work volatility, the need to supplement journalism with other work, and unpaid time spent to market themselves and their work, or to get assignments (or even paid). Some freelancers find that it is not worthwhile to do time-consuming projects for which they will not receive pay commensurate with the time required.

Freelancers are used in all manner of journalism work today, throughout the world where they have been studied, and involving every media platform. Some entire content models are based mostly or entirely on freelance labor. This has implications for journalism educators, who have traditionally trained students for organizational news media jobs; and for researchers, who have not considered the freelancer in their scholarship into journalism production, culture, or journalist practices, routines, and attitudes.
Sex-Specific Regulation of Peripheral and Central Immune Responses
Authors: Klein Sabra L. , Schwarz Jaclyn M.
Published: June 2018

Sex is a biological variable that affects immune responses to both self and foreign antigens (e.g., microbial infections) in the central nervous system (CNS) as well as in peripheral organs. The sex of an individual is defined by the differential determination of the sex chromosomes, the organization of the reproductive organs, and the subsequent sex steroid hormone levels in males and females. Sex is distinct from gender, which includes self-identification as being a male or female as well as behaviors and activities that are determined by society or culture in humans. Male and female differences in immunological responses may be influenced by both sex and gender, with sex contributing to the physiological and anatomical differences that influence exposure, recognition, clearance, and even transmission of microbes in males and females. By contrast, gender may reflect behaviors that influence exposure to microbes, access to health care, or health-seeking behaviors that indirectly affect the course of infection in males and females. Though both sex and gender influence the immune response, the focus of this article is the biological factors that influence immunological differences between the sexes in both the CNS and peripheral tissues to alter the course of diseases across the life span.
Commercialization in Education
Authors: Hogan Anna , Thompson Greg
Published: June 2018

In the literature, a range of terminology is used to describe the reorganization of public education. In much critical policy sociology the terms marketization, privatization, and commercialization are used interchangeably. Our argument is that each of these denotes distinct, albeit related, characteristics of contemporary schooling and the impact of the Global Education Industry (GEI). We define marketization as the series of policy logics that aim to create quasimarkets in education; privatization as the development of quasimarkets in education that privilege parental choice, school autonomy and venture philanthropy; and commercialization as the creation, marketing, and sale of educational goods and services to schools by external providers. We explain the manifestations of each of these forms and offer two cases of actors situated within the GEI, the OECD, and Pearson PLC, to outline how commercialization and privatization proceed at the level of policy and practice.
Buddhist Religious Practice in Imperial China
Authors: Heller Natasha
Published: June 2018

Buddhist practice transformed the religious landscape in China, introducing new forms of mental cultivation and new ritual technologies within an altered cosmology of spiritual goals. Buddhist practice was carried out by individuals, but was equally as often a communal activity. A basic unit of religious practice was the family; Buddhist cultivation was also carried out by communities of practice at monasteries, which were also sites of large-scale rituals. Forms of religious practice included meditation, oral recitation, ritual performances including confession and vow making, and merit-making activities. Meditation encompassed following breath and exercises that recreated Buddhist images in the practitioner’s mind. Meditation could be carried out while sitting, or while walking, and might also incorporate recitation of scriptures, names of the Buddhas, and dhāraṇī. Indeed, meditation practices were most often embedded in liturgical sequences that included confession, vows, and merit dedication. The goal of these religious practices might be personal spiritual development; through the concept of merit transference, religious activities also worked to benefit others, especially the dead. The fundamental of components of Buddhist practice were present very early in the tradition’s history in China, and over time these elements were combined in new ways, and with reference to changing objects of devotion. The four major bodhisattvas of Mañjuśrī (Wenshu 文殊), Samantabhadra (Puxian 普賢), Kṣitigarbha (Dizang 地藏), and Avalokiteśvara (Guanyin 觀音) were especially important as objects of devotion, and also were emplaced in the Chinese landscape, where they were incorporated into pilgrimages.
The Car and the City
Authors: Blanke David
Published: June 2018

The relationship between the car and the city remains complex and involves numerous private and public forces, innovations in technology, global economic fluctuations, and shifting cultural attitudes that only rarely consider the efficiency of the automobile as a long-term solution to urban transit. The advantages of privacy, speed, ease of access, and personal enjoyment that led many to first embrace the automobile were soon shared and accentuated by transit planners as the surest means to realize the long-held ideals of urban beautification, efficiency, and accessible suburbanization. The remarkable gains in productivity provided by industrial capitalism brought these dreams within reach and individual car ownership became the norm for most American families by the middle of the 20th century. Ironically, the success in creating such a “car country” produced the conditions that again congested traffic, raised questions about the quality of urban (and now suburban) living, and further distanced the nation from alternative transit options. The “hidden costs” of postwar automotive dependency in the United States became more apparent in the late 1960s, leading to federal legislation compelling manufacturers and transit professionals to address the long-standing inefficiencies of the car. This most recent phase coincides with a broader reappraisal of life in the city and a growing recognition of the material limits to mass automobility.
Immigration to American Cities, 1925–2017
Authors: Brooks Charlotte
Published: June 2018

The Immigration Act of 1924 was in large part the result of a deep political and cultural divide in America between heavily immigrant cities and far less diverse small towns and rural areas. The 1924 legislation, together with growing residential segregation, midcentury federal urban policy, and postwar suburbanization, undermined scores of ethnic enclaves in American cities between 1925 and the 1960s. The deportation of Mexicans and their American children during the Great Depression, the incarceration of West Coast Japanese Americans during World War II, and the wartime and postwar shift of so many jobs to suburban and Sunbelt areas also reshaped many US cities in these years. The Immigration Act of 1965, which enabled the immigration of large numbers of people from Asia, Latin America, and, eventually, Africa, helped to revitalize many depressed urban areas and inner-ring suburbs. In cities and suburbs across the country, the response to the new immigration since 1965 has ranged from welcoming to hostile. The national debate over immigration in the early 21st century reflects both familiar and newer cultural, linguistic, religious, racial, and regional rifts. However, urban areas with a history of immigrant incorporation remain the most politically supportive of such people, just as they were a century ago.
The Internal Provinces of the Northern Spanish Empire
Authors: Sheridan-Prieto Cecilia
Published: June 2018

In New Spain, the 18th century was characterized by important political and administrative changes in imperial geopolicy that stemmed from the reforms introduced by Spain’s king, Charles III, which continued under the Bourbon monarchs. These so-called Bourbon Reforms sought to reduce the centralizing power of the viceroyalty’s governments, as well as that of the Royal Audiences in Spanish America. The British colonization of the Atlantic coast and the continued confrontation with Native Americans resulted in changes in New Spain’s territorial structure, especially the consolidating of the northern Provincias Internas (Internal Provinces). The project of structuring a political territory in the north originally emerged in 1751 with the aim of organizing the space into a General Command. The process began in 1776 with the appointment of José de Gálvez as the minister of the Indies. The first commanding general, Teodoro de Croix (1730–1792), who was given authorization to act independently of the viceroyalty, established the command by taking into his jurisdiction the provinces of Sonora, Sinaloa, the Californias, Nueva Vizcaya, New Mexico, Coahuila, and Tejas and, later, the New Kingdom of León and New Santander. In 1787, the Spanish government decided to modify the jurisdictions by creating provincial blocks: the Eastern Internal Provinces and the Western Internal Provinces. The jurisdiction that would experience a number of difficult changes that arose principally from the military control that began during the first years of colonization and lasted until the disappearance of viceregal power. The rest of the Spanish Empire’s territory, meanwhile, was organized into administrations ruled by a general governor or mayor who exercised powers of law, war, the treasury, public works, and the development of local economic efforts.
Artificial Languages
Authors: Libert Alan Reed
Published: June 2018

Artificial languages—languages which have been consciously designed—have been created for more than 900 years, although the number of them has increased considerably in recent decades, and by the early 21st century the total figure probably was in the thousands. There have been several goals behind their creation; the traditional one (which applies to some of the best-known artificial languages, including Esperanto) is to make international communication easier. Some other well-known artificial languages, such as Klingon, have been designed in connection with works of fiction. Still others are simply personal projects.

A traditional way of classifying artificial languages involves the extent to which they make use of material from natural languages. Those artificial languages which are created mainly by taking material from one or more natural languages are called a posteriori languages (which again include well-known languages such as Esperanto), while those which do not use natural languages as sources are a priori languages (although many a posteriori languages have a limited amount of a priori material, and some a priori languages have a small number of a posteriori components). Between these two extremes are the mixed languages, which have large amounts of both a priori and a posteriori material. Artificial languages can also be classified typologically (as natural languages are) and by how and how much they have been used.

Many linguists seem to be biased against research on artificial languages, although some major linguists of the past have been interested in them.
The Economics of Watershed Management
Authors: Haddad Brent M.
Published: June 2018

Watersheds are physical regions from which all arriving water flows to a single exit point. The shared hydrology means that other biophysical systems are linked, typically with upper-gradient regions influencing lower-gradient ones. This situation frames the challenge of managing economic and other uses of watersheds both in terms of individual activities and their influence on other connected processes and activities. Economics provides concepts and methods that help managers with decision making in the complex physical, biological, and institutional environment of a watershed. Among the important concepts and methods that help characterize watershed processes are externalities, impacts of economic activity that fall upon individuals not party to the activity, and third parties, individuals impacted without consent. Public goods and common pool resources describe categories of things or processes that by their nature are not amenable to regular market transactions. Their regulation requires special consideration and alternative approaches to markets. Benefit-cost analysis and valuation are related methods that provide a means to compare alternative uses of the same system. Each is based on the normative argument that the best use provides the greatest net benefits to society. And intergenerational equity is a value orientation that argues for preservation of watershed processes for the benefit of future generations. The need for effective watershed management methods pushed 20th-century economists to adapt their discipline to the complexity of watersheds, from which emerged subdisciplines of natural resource economics, environmental economics, and ecological economics. The field is still evolving with a growing interest in data gathering through land-based low-cost data collection systems and remote sensing, and in emerging data analysis techniques to improve management decisions.
U.S. Military Families
Authors: Dekle Judith
Published: June 2018

Social work with members of the U. S. military began during World War I and continues to evolve along with the military, its service members, and their families. This article provides an overview of the U. S. military as an organization that produces a unique culture; demographics that describe service members, military spouses, and military children; and some key indicators of the impact of military life derived from scientifically structured surveys and studies of service members and their families. It also identifies relevant professional practice and education standards for social workers who work with military families regularly and/or on a full-time basis as well as for those who are working with them for the first time and/or only on occasion. Woven together, the understanding of military families and adherence to established standards of practice discussed in this paper can provide the reader with a solid foundation for their practice when working with military families.
Logic Models
Authors: LeCroy Craig Winston
Published: June 2018

Logic models have become a critical feature of program planning and evaluation. Using a logic model framework provides a visual summary that shows the relationship between the program’s resources, activities, outputs, and outcomes. The logic model is a tool that helps individuals see the interrelationships between the different components of a program. By using logic models, program planners and evaluators can more effectively examine a program’s theory and logic. The logic model tool highlights the program’s underlying theory, the service activities, and the organizational structure for accomplishing program outcomes. The process of developing a logic model assists developers and evaluators and other stakeholders in understanding a program’s assumptions and evaluating the logical links between what programs are doing and the outcomes they hope to achieve. Because of their utility logic, models have become widely used in social service programs.
Afrocentric Social Work
Authors: Nichols Fairfax Colita
Published: June 2018

Afrocentric social work is a concept and praxis approach applicable in environmental and global settings where people of African descent are located. Using concept analysis as a methodology, this article explores Afrocentric social work theory and its applicability in the social sciences. Concept analysis is an examination of a thought or theory with the intent to create a more concise operational definition. Afrocentric social work not only is applicable to racial and social justice issues, it also is applicable to intellectual and philosophical discourses of social work, which has largely ignored Afrocentric social work as a viable theory and philosophical canon. The Walker and Avant method of concept analysis is employed in this article to provide a systemic discourse to define the attributes of Afrocentric social work, as well as its structural elements that scholars and practitioners utilize as a theory and praxis application.