bluuebunny/crossref_metadata_2025 huggingface dataset:
Altered inhibition‐related frontolimbic connectivity in obsessive–compulsive disorder
Authors: van Velzen Laura S. , de Wit Stella J. , Ćurĉić‐Blake Branislava , Cath Daniëlle C. , de Vries Froukje E. , Veltman Dick J. , van der Werf Ysbrand D. , van den Heuvel Odile A.
Published: July 2015

Background

Recent studies have shown that response inhibition is impaired in patients with obsessive–compulsive disorder and their unaffected siblings, suggesting that these deficits may be considered a cognitive endophenotype of obsessive–compulsive disorder. Structural and functional neural correlates of altered response inhibition have been identified in patients and siblings. This study aims to examine the functional integrity of the response inhibition network in patients with obsessive–compulsive disorder and their unaffected siblings.

Methods

Forty‐one unmedicated patients with obsessive–compulsive disorder, 17 of their unaffected siblings and 37 healthy controls performed a stop signal task during functional magnetic resonance imaging. Psycho‐physiological interaction analysis was used to examine functional connectivity between the following regions of interest: the bilateral inferior frontal gyri, presupplementary motor area, subthalamic nuclei, inferior parietal lobes, anterior cingulate cortex, and amygdala. We then used dynamic causal modeling to investigate the directionality of the networks involved.

Results

Patients, and to a lesser extent also their unaffected siblings, show altered connectivity between the inferior frontal gyrus and the amygdala during response inhibition. The follow‐up dynamic causal modeling suggests a bottom‐up influence of the amygdala on the inferior frontal gyrus in healthy controls, whereas processing occurs top‐down in patients with obsessive–compulsive, and in both directions in siblings.

Conclusions

Our findings suggest that amygdala activation in obsessive–compulsive disorder interferes differently with the task‐related recruitment of the inhibition network, underscoring the role of limbic disturbances in cognitive dysfunctions in obsessive–compulsive disorder. Hum Brain Mapp 36:4064–4075, 2015. © 2015 Wiley Periodicals, Inc.
South Africa's Emerging Black Middle Class: A Harbinger of Political Change?
Authors: Mattes Robert
Published: July 2015

While South Africa has seen a significant increase in the post‐apartheid period in the size of the Black middle class, the attitudinal consequences of indicators of the middle class, as of 2011, are inconsistent and modest in size. While they are no more likely to hold democratic values than other Black South Africans, they are more likely to want the government to secure ‘higher‐order’ rather than basic survival needs. They are less likely to identify with the governing African National Congress and to turn out to vote. They are also less likely to ‘voice’ their concerns by contacting officials or joining in conventional or unconventional forms of collective action. Yet while intra‐racial class differences amongst Black people remain muted, intra‐class racial differences amongst South Africa's middle class are still substantial. © 2015 The Authors. Journal of International Development published by John Wiley & Sons Ltd.
Effects of potassium titanate whiskers on the mechanical and thermal properties of poly (para‐phenylene terephthalamide) paper sheet
Authors: Yang Bin , Zhang Meiyun , Lu Zhaoqing
Published: July 2015

In this work, poly(para‐phenylene terephthalamide) (PPTA) paper sheets composed of PPTA fibers and PPTA fibrids filled with highly crystalline and high ratio of length to diameter potassium titanate whiskers (PTW) were investigated in view of possible employment as reinforcement and cost‐reducing materials. The morphological characteristics and the role of PPTA fibrids, the influence of PTW on the mechanical properties, interfacial adhesion, and thermal stability of the PPTA paper sheets were discussed. The results showed that the ductile, flexible and rough morphological characteristics of PPTA fibrids are helpful to improve the properties of PPTA paper. PTTA fibrids strongly wrapped PTW in the PPTA paper sheet was observed, which largely enhanced the retention rate of PTW and further improved the interfacial combination. The presence of PTW improved the mechanical properties and thermal stability of PPTA paper sheets. This research demonstrated the improvement of thermal and mechanical performances of PPTA paper sheets by incorporating of PTW, suggesting a significant cost‐reducing potential for the production of PPTA paper composite materials. POLYM. COMPOS., 38:1390–1395, 2017. © 2015 Society of Plastics Engineers
Pipes, pools, and filters: How collaboration networks affect innovative performance
Authors: Singh Harpreet , Kryscynski David , Li Xinxin , Gopal Ram
Published: July 2015

Research summary: Innovation requires inventors to have both new knowledge and the ability to combine and configure knowledge (i.e., combinatory knowledge), and such knowledge may flow through networks. We argue that both combinatory knowledge and new knowledge are accessed through collaboration networks, but that inventors' abilities to access such knowledge depends on its location in the network. Combinatory knowledge transfers from direct contacts, but not easily from indirect contacts. In contrast, new knowledge transfers from both direct and indirect contacts, but is far more likely to be new and useful when it comes from indirect contacts. Exploring knowledge flows in 69,476 patents and 89,930 unique inventors reveals evidence that combinatory knowledge from direct contacts and new knowledge from indirect contacts significantly affects innovative performance.

Managerial summary: Inventors often combine ideas to create innovations. To do this, they need ideas to combine and they need the ability to combine those ideas. Inventors can get ideas to combine as well as the ability to combine ideas through prior co‐workers. Prior co‐workers can share ideas that may be relevant for the inventor's project and can tell the inventor about other things that other people are working on, especially people the inventor may not know. This can help inventors easily learn about ideas from friends‐of‐friends. The ability to combine ideas, however, is much harder to pass on. Prior co‐workers must carefully work with the inventor to teach him or her the complex processes of combining ideas. This means that it is very hard to learn how to combine knowledge from a friend‐of‐a‐friend, but it may be possible to learn from prior co‐workers. We explore this phenomenon in the social relationships of software inventors. Copyright © 2015 John Wiley & Sons, Ltd.
Establishing an Evolutionary Learning Laboratory for Improving the Quality of Life of Vietnamese Women in Small‐scale Agriculture: Part II – Systemic Interventions
Authors: Ha Tuan M. , Bosch Ockie J. H. , Nguyen Nam C.
Published: July 2015

This study applies a systems thinking approach by using the seven‐step Evolutionary Learning Laboratory (ELLab) framework to identify the most economically, environmentally, culturally and socially appropriate systemic solutions to improving the quality of life for women smallholders in rural Haiphong (Northern Vietnam), with a special focus on the perceived (visible) problem of labour constraints. This paper focuses on the first five steps of the ELLab. Income, production efficiency (leading to less work pressure) and health were found to be the major contributing factors for improving the quality of life of the women farmers. The systemic interventions that will have the most effect on achieving the aforementioned leverages were defined, and the first integrated management plan was formulated to improve the quality of life of the women farmers. Although not part of this paper, further refinement and validation of the plan will be carried out in the next two steps of the ELLab process. The outcomes and lessons learned from this research will be shared with other case studies via a globally established ‘sharing platform’ in the Access Hub of the web‐based think2impact(http://think2impact.org) package. The purpose of this process is not only to improve the local knowledge and systemic management plans to help the women in agriculture in Haiphong but also to contribute to enhancing the global knowledge pool on dealing with complex issues in rural areas of many countries around the world. Copyright © 2015 John Wiley & Sons, Ltd.
The Effects of Blinding on the Outcomes of Psychotherapy and Pharmacotherapy for Adult Depression: a Meta-Analysis
Authors: Cuijpers P. , Karyotaki E. , Andersson G. , Li J. , Mergl R. , Hegerl U.
Published: July 2015

Background

Randomized trials with antidepressants are often run under double blind placebo-controlled conditions, whereas those with psychotherapies are mostly unblinded. This can introduce bias in favor of psychotherapy when the treatments are directly compared. In this meta-analysis, we examine this potential source of bias.

Methods

We searched Pubmed, PsycInfo, Embase and the Cochrane database (1966 to January 2014) by combining terms indicative of psychological treatment and depression, and limited to randomized trials. We included 35 trials (with 3721 patients) in which psychotherapy and pharmacotherapy for adult depression were directly compared with each other. We calculated effect sizes for each study indicating the difference between psychotherapy and pharmacotherapy at post-test. Then, we examined the difference between studies with a placebo condition and those without in moderator analyses.

Results

We did not find a significant difference between the studies with and those without a placebo condition. The studies in which a placebo condition was included indicated no significant difference between psychotherapy and pharmacotherapy (g = −0.07; NNT = 25). Studies in which no placebo condition was included (and patients and clinicians in both conditions were not blinded), resulted in a small, but significant difference between psychotherapy and pharmacotherapy in favor of pharmacotherapy (g = −0.13; NNT = 14).

Conclusions

Studies comparing psychotherapy and pharmacotherapy in which both groups of patients (and therapists) are not blinded (no placebo condition is included) result in a very small, but significantly higher effect for pharmacotherapy.
Epigenetic harnessing of HCV via modulating the lipid droplet‐protein, TIP47, in HCV cell models
Authors: El-Ekiaby Nada M. , Mekky Radwa Y. , El Sobky Shereen A. , Elemam Noha M. , El-Sayed Mohammed , Esmat Gamal , Abdelaziz Ahmed I.
Published: July 2015

Bioinformatics analysis revealed that miR‐148a and miR‐30a potentially target TIP47. Expression profiling showed that both microRNAs were downregulated, while TIP47 was upregulated in liver biopsies of HCV‐infected patients. Forcing the expression of both microRNAs in JFH‐I infected, oleic acid‐treated Huh7 cells, significantly suppressed TIP47 expression and reduced cellular LDs with marked decrease in viral RNA. This study shows that miR‐148a and miR‐30a, regulate TIP47 expression and LDs in HCV infected cells.
Change in heat capacity accurately predicts vibrational coupling in enzyme catalyzed reactions
Authors: Arcus Vickery L. , Pudney Christopher R.
Published: July 2015

The temperature dependence of kinetic isotope effects (KIEs) have been used to infer the vibrational coupling of the protein and or substrate to the reaction coordinate, particularly in enzyme‐catalyzed hydrogen transfer reactions. We find that a new model for the temperature dependence of experimentally determined observed rate constants (macromolecular rate theory, MMRT) is able to accurately predict the occurrence of vibrational coupling, even where the temperature dependence of the KIE fails. This model, that incorporates the change in heat capacity for enzyme catalysis, demonstrates remarkable consistency with both experiment and theory and in many respects is more robust than models used at present.
A Meta-analytic Investigation of the Role of Valence in Online Reviews
Authors: Purnawirawan Nathalia , Eisend Martin , De Pelsmacker Patrick , Dens Nathalie
Published: July 2015

Based on a meta-analysis, this study aims to clarify the influence of online review valence (i.e., whether reviews in a review set are predominantly positive or negative) on various dependent variables, in particular on perceived usefulness of the reviews and on attitudes toward the product. The findings suggest that review valence affects perceived usefulness in a different way than it affects attitudes. We find an optimum impact level for perceived usefulness and a ceiling effect for attitudes. Primarily negative review sets that include few positive reviews show the strongest effect on perceived usefulness, while positive review sets that include few or no negative reviews are most successful in influencing attitudes. Additionally, review valence has a stronger influence on perceived usefulness when the reviews refer to experience (rather than search) products, and it has a stronger influence on attitudes for unfamiliar (rather than familiar) brands. Finally, the strongest influence of review valence refers to recommendation intentions. These findings provide several implications for researchers and practitioners.
Extraterrestrial factors and their role in the Earth’s tectonic evolution in the Early Precambrian
Authors: Glukhovskii M.Z. , Kuz’min M.I.
Published: July 2015

The paper is focused on the fundamental problem of influence of extraterrestrial factors on the Earth’s geologic and tectonic evolution. Extraterrestrial factors played a decisive role in the Earth’s genesis, the formation of the first Hadean continental crust, and the beginning of the Archean era. Their significant influence persisted in the later epochs: Even in the Phanerozoic, extraterrestrial factors might have had a considerable influence on the environment. The sialic cores of protocontinental crust (4.4–3.9 Ga) with first-generation greenstone zones (3.8–3.2 Ga) and the global system of granite–greenstone belts (3.1–2.7 Ga) formed in the rotation–plume regime, mainly in the subequatorial hot belt. The formation of these global structures was, to a large extent, influenced by asteroid impacts, which caused the impact-triggered genesis of mantle plumes. Dramatic changes in the subsequent geologic history began at 2.7–2.0 Ga; at 2.0 Ga they terminated with the Moon’s transition to an orbit similar to the present-day one (50 ± 3 Earth’s radii), accompanied by the abrupt slowdown of the Earth’s axial rotation, the termination of formation of the layer D″, and the start of recent plate tectonics, which is accompanied by the plume tectonics.
Early Precambrian Earth history: plate and plume tectonics and extraterrestrial controls
Authors: Dobretsov N.L. , Turkina O.M.
Published: July 2015

The Hadean and Archean geologic history of the Earth is discussed in the context of available knowledge from different sources: space physics and comparative planetology; isotope geochronology; geology and petrology of Archean greenstone belts (GB) and tonalite-trondhjemite-granodiorite (TTG) complexes; and geodynamic modeling review to analyse plate-tectonic, plume activity, and impact processes. Correlation between the age peaks of terrestrial Hadean–Early Archean zircons and late heavy bombardment events on the Moon, as well as the Hf isotope composition of zircons indicating their mostly mafic sources, hint to an important role of impact processes in the Earth’s history between 4.4 and 3.8 Ga. The earliest continental crust (TTG complexes) formed at 4.2 Ga (Acasta gneisses), while its large-scale recycling left imprint in Hf isotope signatures after 3.75 Ga. The associations and geochemistry of rocks suggest that Archean greenstone belts formed in settings of rifting, ocean floor spreading, subduction, and plume magmatism generally similar to the present respective processes. The Archean history differed in the greater extent of rocks derived from mantle plumes (komatiites and basalts), boninites, and adakites as well as in shorter subduction cycles recorded in alternation of typical calc-alkaline andesite-dacite-rhyolite and adakite series that were generated in a hotter mantle with more turbulent convection and unsteady subduction. The Archean is interpreted as a transient period of small plate tectonics.
Bottom sediments and near-bottom currents in the Southwestern Atlantic
Authors: Emelyanov E.M.
Published: July 2015

On the basis of the author’s data on the composition of sediments and seismic cross sections, together with literature data, the bottom topography was described and the main structural features of the top 10–100 m thick sedimentary sequence in the Southwestern Atlantic (Brazil Basin) were identified. The presence of a heavy northward flow of Antarctic bottom water (AABW) and its active erosive activity were confirmed. The AABW caused the erosion or redeposition of red pelagic clays and hemipelagic clays, which accumulated in the Brazil Basin in the Holocene and Pleistocene; the clays contain abundant redeposited Pleistocene diatoms and Neogene and Paleogene discoasters. In most of the sediment cores of the Brazil Basin, the red pelagic clays are of Pleistocene age. Contourites and sandy microlayers have been found in the sediments at the foot of the continental slope of South America; this is the effect of the Deep Western Boundary Current on the ocean floor. The AABW transfers Antarctic diatom species along the continental slope of South America to 10°–5° S. The presence of the Equatorial Midocean Channel with a relative depth of 149 m in the western pelagic equatorial part of the Atlantic was confirmed, and new channels, such as Vavilov and Akademik Ioffe, have been found. The AABW flows northward along the Equatorial Mid-Ocean Channel. Apparently, the Akademik Ioffe Channel is not a proper midocean channel. At 20° S (at a depth of 5000 m), Pleistocene diatomic (Ethmodiscus rex) ooze containing up to 74% amorphous SiO2 was detected. On the Amazon–Mid-Atlantic Ridge profile, the AABW flows into the Guyana Basin through only one valley of the Nara Plain, with a depth of 4620 m. Near the Ceara Rise and on the Amazon Fan, no geologic traces of the AABW flow into the Guyana Basin were found. Near the Rio Grande Rise, the AABW might have appeared in the Eocene. The formation of the Vema Channel, which separates the Rio Grande Rise from South America, also began at that time. The AABW flows were the heaviest before the largest glaciations (particularly at isotopic stages 7/6 and 3/2).
Mobility of elements in a continental subduction zone: evidence from the UHP metamorphic complex of the Kokchetav massif
Authors: Shatsky V.S. , Skuzovatov S.Yu. , Ragozin A.L. , Sobolev N.V.
Published: July 2015

We studied clastics of high-alumina garnet–kyanite–mica schists and garnet–kyanite–quartz granofelses, including diamond-bearing ones, found in the eluvial sediments near Lake Barchi. In contents of major elements the studied rocks correspond to argillaceous shales. The garnet–kyanite–quartz granofelses are poorer in K (0.49–1.35 wt.% K2O) than the garnet–kyanite–mica schists (4.9–2.2 wt.% K2O) but have the same contents of other major components. The REE patterns of most of the garnet–kyanite–phengite schists are similar to those of the Post-Archean Australian Shale (PAAS) (x¯La/Yb=13). All garnet–kyanite–quartz rocks are much stronger depleted in LREE (x¯La/Yb=1.4) and other incompatible elements. Our studies show that allanite and monazite are the main concentrators of LREE and Th in the garnet–kyanite–phengite rocks of the Barchi site. Monazite, occurring as inclusions in garnet, contains not only LREE but also Th, U, and Pb. Rutile of the nondepleted rocks is enriched in Fe and Nb impurities only. The garnet–kyanite–quartz granofelses bear rutile, apatite, and xenotime as accessory phases. Rutile of the depleted rocks shows wide variations in contents of Nb, Ta, and V impurities. In places, the contents of Nb and Ta reach 10.5 and 2.3 wt.%, respectively. The rutile decomposes into rutile with Nb (1.4 wt.%) and Fe (0.87 wt.%) impurities and titanium oxide rich in Fe (6.61 wt.%), Nb (up to 20.8 wt.%), and Ta (up to 2.81%) impurities. Based on the measured contents of incompatible elements in differently depleted high-alumina rocks, the following series of element mobility during UHP metamorphism has been established: Th > Ce > La > Pr > Nd > K > Ba > Rb > Cs > Sm > Eu. The contents of U, P, and Zr in the depleted rocks are similar to those in the nondepleted rocks. The studies have shown that metapelites subducted to the depths with diamond stability conditions can be depleted to different degrees. This might be either due to their exhumation from different depths of the subduction zone or to the presence of an external source of water controlling the temperature of dissolution of phengite and the formation of supercritical fluid/melt.
Polygenesis of mafic–ultramafic complexes: Isotope-geochronological and geochemical evidence from zircons of the Berezovka massif rocks (Sakhalin Island)
Authors: Lesnov F.P. , V.V Khlestov , Gal’versen V.G. , Sergeev S.A.
Published: July 2015

Results of comprehensive isotope-geochronological (U–Pb dating; SHRIMP II) and geochemical (LA–ICP-MS) studies of zircons from different rocks of the Berezovka polygenetic mafic–ultramafic massif of the East Sakhalin ophiolite association are presented. The massif includes three proximal but genetically autonomous structure-lithologic complexes of different ages: protrusion of ultramafic rocks of restite nature, gabbroid intrusion breaking through it, and contact reaction zone located along their boundaries. The isotopic age of zircons in the massif as a whole and in its individual rocks varies over a broad range of values. The zircons belong to several populations according to their age (Ma) and other features: relict and xenogenous (∼ 3100–990, 70–410, and ∼ 395–210) and syngenetic (∼ 200–100, ∼ 90–65, and ∼ 30–20). They differ in grain size and morphology, optical and cathodoluminescence images, and trace-element patterns. By morphology, the grains are divided into short-prismatic crystals with well-developed faces and edges, long-prismatic crystals with well-developed faces and edges, prismatic crystals with slightly resorbed faces and edges, prismatic crystals with strongly resorbed faces and edges, and intensely resorbed grains totally or partly lacking faceting. The ages of zircons depend inversely on the contents of La, Ce, and Yb, total contents of REE, (Ce/Ce*)n, and (Eu/Eu*)n. Some grains are characterized by abnormal REE and trace-element patterns due to their epigenetic redistribution. The wide scatter of the intermediate ages of relict and xenogenous zircon grains, their resorption and disturbed optical and geochemical features are probably due to the nonuniform rejuvenation of their isotope systems and variations in other parameters, caused by the effect of younger mafic melt and its fluids, whose crystallization gave rise to a gabbroid intrusion dated at 170–150 Ma. The obtained data on the isotopic age and other properties of zircons from the rocks of the Berezovka massif agree with the geological model of its polygenesis.
Relics of biolipids in kerogen of Cambrian Siberian Platform oil shale
Authors: Savel’ev V.V. , Kam’yanov V.F. , Golovko A.K.
Published: July 2015

Products of thermal cracking of kerogen of Lower–Middle Cambrian oil shale are studied by modern instrumental analytical methods (FTIR, gas chromatography, mass spectrometry, etc.). The analyses demonstrate that the geopolymer kerogen matrix inherited fragments of lipids synthesized by living organisms, including aliphatic fat acids, both free or bounded into glycerol esters, i.e., animal or vegetable fats. It is shown that vegetable pigments (carotenes and xanthophylls) play a crucial role in the formation of monocyclic structures (including molecular alkylbenzene, alkylphenol, and phenylalkane fragments) in kerogen. Since the studied kerogen is rich in esters, it is worth performing alkaline hydrolysis of its macromolecules (ester saponification) before their thermolysis, which inevitably distorts the initial structure of molecular skeletons.
Dielectric permittivity spectra of oil–water-saturated sandy-clayey rocks of different mineralogical compositions and relaxation properties of water in these rocks
Authors: Bobrov P.P. , Mironov V.L. , Repin A.V.
Published: July 2015

Experimental measurements of the dielectric permittivity and equivalent conductivity of sandy-clayey samples (a mixture of river sand with bentonite or kaolin) saturated with salt-solution–diesel-fuel emulsions were performed in the frequency range from 10 kHz to 1 GHz at temperatures of 25–65 °C. It is shown that when the content of the salt solution in the saturating fluid does not exceed 10%, the dielectric permittivity in the frequency range from 1 MHz to 1 GHz depends little on the mineral composition of the sample and on the concentration of the saturating solution. When the portion of water is 33.3% or higher, increasing the concentration of the salt solution leads to an increase in the equivalent conductivity and the real part of the complex dielectric permittivity. Using the refractive model of the complex dielectric permittivity, we have estimated the dielectric properties of bound water, which depend on temperature and the type of clay (bentonite or kaolin) in the sand–clay mixture but are independent of the water saturation and the amount of clay in the sample.
Long-term prediction for seismic hazard for radioactive waste disposal
Authors: Kochkin B.T. , Petrov V.A.
Published: July 2015

We consider possible approaches to the long-term prediction for seismic hazard in relation to the practical need for the safety of geological disposal of long-lived radioactive waste. The required period of prediction significantly exceeds the one reflected in the set of maps of General Seismic Zoning of the territory of the Russian Federation (GSZ-97). The first geological repository in Russia is planned to be set up in the Nizhnii Kan granite massif in the Krasnoyarsk Krai. This region is an intraplate territory with a relatively high seismic activity. We summarize the analysis of the known empirical generalizations and theoretical principles underlying the seismic hazard prediction. Real seismic events constantly violate forward-looking statements even for relatively short periods of time. These and other arguments suggest that the hypothesis of stationarity of the seismic regime, which is the basis of long-term prediction today, has limited and uncertain applicability in time. Intraplate earthquake prediction is especially uncertain because of the uncertainty in the factor responsible for generating tectonic stresses in these regions. The short horizon of the prediction, based on statistical methods, can be attributed to the nonlinearity of seismic geodynamic processes. Fundamental laws of tectonic processes should be used as the scientific basis for long-term predictions for seismic hazard at the sites chosen for geological disposal of long-lived radioactive waste. These processes can be reflected in models for the migration of the seismically active boundaries of lithospheric plates and the occurrence of seismic activity in intraplate regions.
Accounting for near-surface inhomogeneities over a horizontally layered section in magnetotelluric sounding
Authors: Plotkin V.V. , Gubin D.I.
Published: July 2015

This paper presents a numerical model for the effect of near-surface inhomogeneities over a one-dimensional horizontally layered geoelectric section and the distortions they cause during magnetotelluric sounding (MTS). The electromagnetic field within the layer of near-surface inhomogeneities is calculated using the Trefftz method. Expressions are derived for the boundary conditions on the day surface and on the roof of the underlying inhomogeneity of a horizontally layered medium. These boundary conditions allow for the excitation of TM-mode fields by subsurface inhomogeneities and their penetration into the atmosphere and the underlying medium. The spatial distribution and characteristics of galvanic and inductive distortions over different time periods during MTS have been studied. Experimental data show that accounting for galvanic distortions is possible with synchronous recording of the distribution of components of the electric and magnetic fields in a limited area of the Earth’s surface.
Local pressure lows as possible sinks of fluids in geologic structures
Authors: Sibiryakov B.P. , Sibiryakov E.B.
Published: July 2015

Local pressure lows in layered sections perturbed by anticlinal structures are studied analytically using equations for pressure change across interfaces. They are simple equations of pressure difference for low-angle structures and boundary integral equations for steeply dipping anticlines. Pressure may decrease locally near the crests of anticlines, as well as away from them at distances commensurate to the anticline height. Predicting stress patterns, which are specific for different groups of geologic structures, is a difficult task. However, some components of the stress field, such as low-pressure zones which may act as sinks for fluids, are relatively easy to constrain. Stress in these zones depends on the dip of anticlines and their curvature at each surface point. Negative curvature causes additional lateral extension and promotes further decrease of overburden pressure around the crests.
Mechanisms of plasma disruption and runaway electron losses in the TEXTOR tokamak
Authors: Abdullaev S. S. , Finken K. H. , Wongrach K. , Tokar M. , Koslowski H. R. , Willi O. , Zeng L. ,   the TEXTOR team
Published: July 2015

Based on the analysis of data from the numerous dedicated experiments on plasma disruptions in the TEXTOR tokamak the mechanisms of the formation of runaway electron (RE) beams and their losses are proposed. The plasma disruption is caused by a strong stochastic magnetic field formed due to nonlinearly excited low-mode-number magneto-hydro-dynamics (MHD) modes. It is hypothesized that the RE beam is formed in the central plasma region confined by an intact magnetic surface due to the acceleration of electrons by the inductive toroidal electric field. In the case of plasmas with the safety factor $q(0)<1$ the most stable RE beams are formed by the outermost intact magnetic surface located between the magnetic surface $q=1$ and the closest low-order rational surface $q=m/n>1~(q=5/4,q=4/3,\dots )$. The thermal quench (TQ) time caused by the fast electron transport in a stochastic magnetic field is calculated using the collisional transport model. The current quench (CQ) stage is due to the particle transport in a stochastic magnetic field. The RE beam current is modelled as a sum of a toroidally symmetric part and a small-amplitude helical current with a predominant $m/n=1/1$ component. The REs are lost due to two effects: (i) by outward drift of electrons in a toroidal electric field until they touch the wall and (ii) by the formation of a stochastic layer of REs at the beam edge. Such a stochastic layer for high-energy REs is formed in the presence of the $m/n=1/1$ MHD mode. It has a mixed topological structure with a stochastic region open to the wall. The effect of external resonant magnetic perturbations on RE loss is discussed. A possible cause of the sudden MHD signals accompanied by RE bursts is explained by the redistribution of runaway current during the resonant interaction of high-energetic electron orbits with the $m/n=1/1$ MHD mode.
Radiation reaction induced non-monotonic features in runaway electron distributions
Authors: Hirvijoki E. , Pusztai I. , Decker J. , Embréus O. , Stahl A. , Fülöp T.
Published: July 2015

Runaway electrons, which are generated in a plasma where the induced electric field exceeds a certain critical value, can reach very high energies in the MeV range. For such energetic electrons, radiative losses will contribute significantly to the momentum space dynamics. Under certain conditions, due to radiative momentum losses, a non-monotonic feature – a ‘bump’ – can form in the runaway electron tail, creating a potential for bump-on-tail-type instabilities to arise. Here, we study the conditions for the existence of the bump. We derive an analytical threshold condition for bump appearance and give an approximate expression for the minimum energy at which the bump can appear. Numerical calculations are performed to support the analytical derivations.
Regular and chaotic dynamics of non-spherical bodies. Zeldovich’s pancakes and emission of very long gravitational waves
Authors: Bisnovatyi-Kogan G. S. , Tsupko O. Yu.
Published: July 2015

In this paper we review a recently developed approximate method for investigation of dynamics of compressible ellipsoidal figures. Collapse and subsequent behaviour are described by a system of ordinary differential equations for time evolution of semi-axes of a uniformly rotating, three-axis, uniform-density ellipsoid. First, we apply this approach to investigate dynamic stability of non-spherical bodies. We solve the equations that describe, in a simplified way, the Newtonian dynamics of a self-gravitating non-rotating spheroidal body. We find that, after loss of stability, a contraction to a singularity occurs only in a pure spherical collapse, and deviations from spherical symmetry prevent the contraction to the singularity through a stabilizing action of nonlinear non-spherical oscillations. The development of instability leads to the formation of a regularly or chaotically oscillating body, in which dynamical motion prevents the formation of the singularity. We find regions of chaotic and regular pulsations by constructing a Poincaré diagram. A real collapse occurs after damping of the oscillations because of energy losses, shock wave formation or viscosity. We use our approach to investigate approximately the first stages of collapse during the large scale structure formation. The theory of this process started from ideas of Ya. B. Zeldovich, concerning the formation of strongly non-spherical structures during nonlinear stages of the development of gravitational instability, known as ‘Zeldovich’s pancakes’. In this paper the collapse of non-collisional dark matter and the formation of pancake structures are investigated approximately. Violent relaxation, mass and angular momentum losses are taken into account phenomenologically. We estimate an emission of very long gravitational waves during the collapse, and discuss the possibility of gravitational lensing and polarization of the cosmic microwave background by these waves.
Energetic electron transport in the presence of magnetic perturbations in magnetically confined plasmas
Authors: Papp G. , Drevlak M. , Pokol G. I. , Fülöp T.
Published: July 2015

The transport of energetic electrons is sensitive to magnetic perturbations. By using three-dimensional numerical simulation of test particle drift orbits we show that the transport of untrapped electrons through an open region with magnetic perturbations cannot be described by a diffusive process. Based on our test particle simulations, we propose a model that leads to an exponential loss of particles.
Image processing of argon glow discharge plasma using interferometry
Authors: Hamed A. M. , Saudy M. A.
Published: July 2015

In this paper, a method of processing argon plasma images, obtained from the DC pseudo glow discharge technique, using two- and multiple-beam interference is suggested. This method is based on measuring the image fringe shift from the background interference fringes. Hence, this mapping of intensity shift is related to the electron density distribution of the argon plasma. Also, the refractive index of the plasma is computed from the electron density values. The contrast of the interferometer images in presence of plasma shift is investigated in both cases of two- and multiple-beam interference.
Small-amplitude Langmuir pulse excited by a planar grid electrode in a flowing plasma
Authors: Podesta John J.
Published: July 2015

The generation and propagation of a small-amplitude Langmuir pulse excited by a planar grid electrode in a spatially uniform collisionless plasma with a constant flow velocity is studied by solving the linearized Vlasov–Poisson equations. The electrode is transparent to the flow of particles, like a screen or a wire mesh. The particles are assumed to have a Kappa velocity distribution, a reasonable approximation for electron distribution functions in the solar wind. Exact, closed-form solutions are obtained for ${\it\kappa}=1$, the Lorentzian distribution, and for ${\it\kappa}=2$. The explicit form of the solution in the case ${\it\kappa}=2$ has not, to our knowledge, appeared in the literature before. The properties of the solutions are investigated and a practical technique for measuring the bulk flow velocity in plasma experiments is proposed that may be useful for high-accuracy, high-time-resolution measurements of the bulk flow velocity in the solar wind.
Monte Carlo particle-in-cell methods for the simulation of the Vlasov–Maxwell gyrokinetic equations
Authors: Bottino A. , Sonnendrücker E.
Published: July 2015

The particle-in-cell (PIC) algorithm is the most popular method for the discretisation of the general 6D Vlasov–Maxwell problem and it is widely used also for the simulation of the 5D gyrokinetic equations. The method consists of coupling a particle-based algorithm for the Vlasov equation with a grid-based method for the computation of the self-consistent electromagnetic fields. In this review we derive a Monte Carlo PIC finite-element model starting from a gyrokinetic discrete Lagrangian. The variations of the Lagrangian are used to obtain the time-continuous equations of motion for the particles and the finite-element approximation of the field equations. The Noether theorem for the semi-discretised system implies a certain number of conservation properties for the final set of equations. Moreover, the PIC method can be interpreted as a probabilistic Monte Carlo like method, consisting of calculating integrals of the continuous distribution function using a finite set of discrete markers. The nonlinear interactions along with numerical errors introduce random effects after some time. Therefore, the same tools for error analysis and error reduction used in Monte Carlo numerical methods can be applied to PIC simulations.
Hamiltonian magnetic reconnection with parallel electron heat flux dynamics
Authors: Grasso D. , Tassi E.
Published: July 2015

We analyse, both analytically and numerically, a two-dimensional six-field fluid model for collisionless magnetic reconnection, accounting for temperature and heat flux fluctuations along the direction of the magnetic guide field. We show that the model possesses a Hamiltonian structure with a non-canonical Poisson bracket. This bracket is characterized by the presence of six infinite families of Casimirs, associated with Lagrangian invariants. This reveals that the model can be reformulated as a system of advection equations, thus generalizing previous results obtained for Hamiltonian isothermal fluid models for reconnection. Numerical simulations indicate that the presence of heat flux and temperature fluctuations yields slightly larger growth rates and similar saturated island amplitudes, with respect to the isothermal models. For values of the sonic Larmor radius much smaller than the electron skin depth, heat flux fluctuations tend to be suppressed and temperature fluctuations follow density fluctuations. Increasing the sonic Larmor radius results in an increasing fraction of magnetic energy converted into heat flux, at the expense of temperature fluctuations. In particular, heat flux fluctuations tend to become relevant along the magnetic island separatrices. The qualitative structures associated with the electron field variables are also reinterpreted in terms of the rotation of the Lagrangian invariants of the system.
Complex astrophysical experiments relating to jets, solar loops, and water ice dusty plasma
Authors: Bellan P. M. , Zhai X. , Chai K. B. , Ha B. N.
Published: July 2015

Recent results of three astrophysically relevant experiments at Caltech are summarized. In the first experiment magnetohydrodynamically driven plasma jets simulate astrophysical jets that undergo a kink instability. Lateral acceleration of the kinking jet spawns a Rayleigh–Taylor instability, which in turn spawns a magnetic reconnection. Particle heating and a burst of waves are observed in association with the reconnection. The second experiment uses a slightly different setup to produce an expanding arched plasma loop which is similar to a solar corona loop. It is shown that the plasma in this loop results from jets originating from the electrodes. The possibility of a transition from slow to fast expansion as a result of the expanding loop breaking free of an externally imposed strapping magnetic field is investigated. The third and completely different experiment creates a weakly ionized plasma with liquid nitrogen cooled electrodes. Water vapour injected into this plasma forms water ice grains that in general are ellipsoidal and not spheroidal. The water ice grains can become quite long (up to several hundred microns) and self-organize so that they are evenly spaced and vertically aligned.
Fluctuation dynamos at finite correlation times using renewing flows
Authors: Bhat Pallavi , Subramanian Kandaswamy
Published: July 2015

Fluctuation dynamos are generic to turbulent astrophysical systems. The only analytical model of the fluctuation dynamo, due to Kazantsev, assumes the velocity to be delta-correlated in time. This assumption breaks down for any realistic turbulent flow. We generalize the analytic model of fluctuation dynamos to include the effects of a finite correlation time,${\it\tau}$, using renewing flows. The generalized evolution equation for the longitudinal correlation function$M_{L}$leads to the standard Kazantsev equation in the${\it\tau}\rightarrow 0$limit, and extends it to the next order in${\it\tau}$. We find that this evolution equation also involves third and fourth spatial derivatives of$M_{L}$, indicating that the evolution for finite-${\it\tau}$will be non-local in general. In the perturbative case of small-${\it\tau}$(or small Strouhal number), it can be recast using the Landau–Lifschitz approach, to one with at most second derivatives of$M_{L}$. Using both a scaling solution and the WKBJ approximation, we show that the dynamo growth rate is reduced when the correlation time is finite. Interestingly, to leading order in${\it\tau}$, we show that the magnetic power spectrum preserves the Kazantsev form,$M(k)\propto k^{3/2}$, in the large-$k$limit, independent of${\it\tau}$.
Saturation of Zeldovich stretch–twist–fold map dynamos
Authors: Seta Amit , Bhat Pallavi , Subramanian Kandaswamy
Published: July 2015

Zeldovich’s stretch–twist–fold (STF) dynamo provided a breakthrough in conceptual understanding of fast dynamos, including the small-scale fluctuation dynamos. We study the evolution and saturation behaviour of two types of generalized Baker’s map dynamos, which have been used to model Zeldovich’s STF dynamo process. Using such maps allows one to analyse dynamos at much higher magnetic Reynolds numbers $\mathit{Re}_{M}$ as compared to direct numerical simulations. In the two-strip map dynamo there is constant constructive folding, while the four-strip map dynamo also allows the possibility of a destructive reversal of the field. Incorporating a diffusive step parametrized by $\mathit{Re}_{M}$ into the map, we find that the magnetic field $B(x)$ is amplified only above a critical $\mathit{Re}_{M}=R_{\mathit{crit}}\sim 4$ for both types of dynamos. The growing $B(x)$ approaches a shape-invariant eigenfunction independent of initial conditions, whose fine structure increases with increasing $\mathit{Re}_{M}$. Its power spectrum $M(k)$ displays sharp peaks reflecting the fractal nature of $B(x)$ above the diffusive scale. We explore the saturation of these dynamos in three ways: via a renormalized reduced effective $\mathit{Re}_{M}$ (case I) or due to a decrease in the efficiency of the field amplification by stretching, without changing the map (case IIa), or changing the map (case IIb), and a combination of both effects (case III). For case I, we show that $B(x)$ in the saturated state, for both types of maps, approaches the marginal eigenfunction, which is obtained for $\mathit{Re}_{M}=R_{\mathit{crit}}$ independent of the initial $\mathit{Re}_{M}=R_{M0}$. On the other hand, in case II, for the two-strip map, we show that $B(x)$ saturates, preserving the structure of the kinematic eigenfunction. Thus the energy is transferred to larger scales in case I but remains at the smallest resistive scales in case II, as can be seen from both $B(x)$ and $M(k)$. For the four-strip map, $B(x)$ oscillates with time, although with a structure similar to the kinematic eigenfunction. Interestingly, the saturated state in case III shows an intermediate behaviour, with $B(x)$ similar to the kinematic eigenfunction at an intermediate $\mathit{Re}_{M}=R_{\mathit{sat}}$, with $R_{M0}>R_{\mathit{sat}}>R_{\mathit{crit}}$. The $R_{\mathit{sat}}$ value is determined by the relative importance of the increased diffusion versus the reduced stretching. These saturation properties are akin to the range of possibilities that have been discussed in the context of fluctuation dynamos.
Self-focusing and self-channelling of short circularly laser pulses propagating in a magnetized plasma channel
Authors: Hassanpour Davood , Ghorbanalilu Mohammad
Published: July 2015

In this study, non-paraxial nonlinear propagation of a relativistic laser pulse with linear and circular polarization in a preformed plasma channel having a parabolic density profile is investigated. The circular laser spot size variation in the absence/presence of an external longitudinal magnetic field is separately analysed and the results are compared. The amplitude of oscillation is decreased in the relativistic case, but it is changed in the presence of an external field. The right-turn circular pulse behaviour is completely opposite to that of the left-turn circular pulse in the presence of an external field, because the right-turn pulse is focused later than the left-turn pulse. The effect of nonlinearities on oscillations of spot size is analysed and the nonlinear critical channel depth required for propagation of a self-trapped laser pulse is evaluated. The laser field amplitude is derived for a matched pulse and it is shown that the group velocity dispersion effect causes broadening of the pulse length.
Modified Zakharov–Kuznetsov equation for a non-uniform electron–positron–ion magnetoplasma with kappa-distributed electrons
Authors: Ahmad Ali , Masood W.
Published: July 2015

We investigate the low-frequency (by comparison with the ion Larmor frequency) electrostatic solitary structures in a spatially non-uniform electron–positron–ion (e–p–i) magnetoplasma with non-Maxwellian electrons. A linear dispersion relation for the obliquely propagating ion acoustic drift wave is derived and it is shown that the non-Maxwellian electron population modifies the dispersion characteristics of the wave under consideration. We also carry out a nonlinear analysis and derive the modified Zakharov–Kuznetsov (MZK) equation for the coupled drift acoustic wave in a non-uniform magnetized plasma. We highlight the differences between the MZK equation and its homogeneous counterpart. We also find the solution of the MZK equation using the tangent hyperbolic method. It is observed that the electron spectral index ${\it\kappa}$, positron concentration, and propagation angle ${\it\alpha}$ alter the structure of the ion acoustic drift solitary waves. The results obtained in this paper may be beneficial to understanding the propagation characteristics of electrostatic drift solitary structures in the interstellar medium and in laboratory experiments where electron–positron plasmas have recently been created by impinging ultra-intense laser pulses on a solid density target at the Lawrence Livermore National Laboratory (LLNL).