Sheet Fragments Research Articles

Universal Rim Thickness in Unsteady Sheet Fragmentation.

Unsteady fragmentation of a fluid bulk into droplets is important for epidemiology as it governs the transport of pathogens from sneezes and coughs, or from contaminated crops in agriculture. It is also ubiquitous in industrial processes such as paint, coating, and combustion. Unsteady fragmentation is distinct from steady fragmentation on which most theoretical efforts have been focused thus far. We address this gap by studying a canonical unsteady fragmentation process: the breakup from a drop impact on a finite surface where the drop fluid is transferred to a free expanding sheet of time-varying properties and bounded by a rim of time-varying thickness. The continuous rim destabilization selects the final spray droplets, yet this process remains poorly understood. We combine theory with advanced image analysis to study the unsteady rim destabilization. We show that, at all times, the rim thickness is governed by a local instantaneous Bond number equal to unity, defined with the instantaneous, local, unsteady rim acceleration. This criterion is found to be robust and universal for a family of unsteady inviscid fluid sheet fragmentation phenomena, from impacts of drops on various surface geometries to impacts on films. We discuss under which viscous and viscoelastic conditions the criterion continues to govern the unsteady rim thickness.

Limiting Size of Monolayer Graphene Flakes Grown on Silicon Carbide or via Chemical Vapor Deposition on Different Substrates

The maximum size of homogeneous monolayer graphene flakes that form during the high-temperature evaporation of silicon from a surface of SiC or during graphene synthesis via chemical vapor deposition is estimated, based on the theoretical calculations developed in this work. Conditions conducive to the fragmentation of a monolayer graphene sheet to form discrete fragments or terrace-type structures in which excess energy due to dangling bonds at the edges is compensated for by the lack of internal stress are indentified and described. The results from calculations for the sizes of graphene structures are compared with experimental findings for the most successful graphene syntheses reported in the literature.

Numerical studies of the Kelvin-Hemholtz instability in a coronal jet

Kelvin-Hemholtz (K-H) instability in a coronal EUV jet is studied via 2.5D MHD numerical simulations. The jet results from magnetic reconnection due to the interaction of the newly emerging magnetic field and the pre-existing magnetic field in the corona. Our results show that the Alfvén Mach number along the jet is about 5–14 just before the instability occurs, and it is even higher than 14 at some local areas. During the K-H instability process, several vortex-like plasma blobs with high temperature and high density appear along the jet, and magnetic fields have also been rolled up and the magnetic configuration including anti-parallel magnetic fields forms, which leads to magnetic reconnection at many X-points and current sheet fragments inside the vortex-like blob. After magnetic islands appear inside the main current sheet, the total kinetic energy of the reconnection outflows decreases, and cannot support the formation of the vortex-like blob along the jet any longer, then the K-H instability eventually disappears. We also present the results about how the guide field and flux emerging speed affect the K-H instability. We find that a strong guide field inhibits shock formation in the reconnecting upward outflow regions but helps secondary magnetic islands appear earlier in the main current sheet, and then apparently suppresses the K-H instability. As the speed of the emerging magnetic field decreases, the K-H instability appears later, the highest temperature inside the vortex blob gets lower and the vortex structure gets smaller.

Monolithic Crystalline Swelling of Graphite Oxide: A Bridge to Ultralarge Graphene Oxide with High Scalability

The large-scale preparation of ultralarge graphene oxide (ULGO) is urgently needed for developing advanced devices and high-performance nanocomposites. However, it is extremely difficult to produce ULGO in an industrially viable, high-efficiency manner because of the inevitable sheet fragmentation and significant gelation behavior occurred in existing methods. We propose a stationary oxidation-monolithic crystalline swelling strategy that can completely convert graphite to ULGO. This new stationary oxidation method minimizes the sheet fracture and prevents the exfoliation of oxidized layers without sacrificing the oxidation rate, resulting in oxidized flakes with high crystalline and lateral sizes the same as raw graphite. The oxidized graphite flakes undergo a monolithic crystalline swelling during the purification, leading to the formation of a three-dimensional ordered structure without peeling. This enables graphite oxide to be purified by spontaneous sedimentation within 1 h as gelation is avoided an...

Binding MoSe2 with carbon constrained in carbonous nanosphere towards high-capacity and ultrafast Li/Na-ion storage

Most of the reported MoSe2 electrode materials are suffered from tended stacking, large volume expansion and relatively low capacity. As shown the experiences of Li/Na-Se batteries, the encapsulating of the exfoliated MoSe2 into carbon nanospheres are successfully constructed with the introduction of C-O-Mo bonds and larger layer distance (0.89 nm). Interestingly, the C-O-Mo bonds stayed on the surface of the Se-O insulation layer can improve the rate of ions transfer and also promote the reversible conversion of MoSe2. The first-principles calculations demonstrated that the frontier molecular orbitals of C-O-Mo interface structure are mainly localized on the MoSe2 sheet fragment with an appropriate HOMO-LUMO gap (<4 eV), proving that its conductivity is being greatly enhanced with higher stability. Utilized as an anode for LIBs, it delivers Li-storage capacities of 1208 mAh g−1 after 150 cycles at 1.0 A g−1 and 519 mAh g−1 after 200 cycles at 4.0 A g−1. Also note that the Na-storage capacities are found to be 543, 491 mAh g−1 after 120 cycles at 0.1, 1.0 A g−1, respectively. Through the analysis of CV, the reduced particles might improve the capacitive behaviors, further leading to the higher rate performances. Ex-situ techniques showed that the emerging Se during the electrochemical process was constrained uniformly in the carbon matrix. More greatly, the controlling of by-product Se plays key roles in achieving high-rate capability and cycling stability, which would open up a potential avenue for these metal-selenide anodes designs of battery storage systems.

Bad Sovereign or Bad Balance Sheets? Euro Interbank Market Fragmentation and Monetary Policy, 2011-2015

We measure the relative role of sovereign-dependence risk and balance sheet (credit) risk in euro area interbank market fragmentation from 2011 to 2015. We combine bank-to-bank loan data with detailed supervisory information on banks’ cross-border and cross-sector exposures. We study the impact of the credit risk on banks’ balance sheets on their access to, and the price paid for, interbank liquidity, controlling for sovereign-dependence risk and lenders’ liquidity shocks. We find that (i) high non-performing loan ratios on the GIIPS portfolio hinder banks’ access to the interbank market throughout the sample period; (ii) large sovereign bond holdings are priced in interbank rates from mid-2011 until the announcement of the OMT; (iii) the OMT was successful in closing this channel of cross-border shock transmission; it reduced sovereign-dependence and balance sheet fragmentation alike.

Thermosensitive, Stretchable, and Piezoelectric Substrate for Generation of Myogenic Cell Sheet Fragments from Human Mesenchymal Stem Cells for Skeletal Muscle Regeneration

AbstractIn a native muscle microenvironment, electrical and mechanical stimuli exist in the form of action potentials and muscle contraction. Here, a cell culture system is developed that can mimic the in vivo microenvironment and provide these stimuli to cultured cells, and it is tested whether the stimulation can promote myogenic differentiation of human umbilical cord blood mesenchymal stem cells (hUCBMSCs). A thermosensitive, stretchable, and piezoelectric substrate (TSPS) is fabricated by polydimethylsiloxane spin‐coating of aligned ZnO nanorods and subsequent poly(N‐isopropylacrylamide) grafting on the polydimethylsiloxane surface. Pulsatile mechanoelectrical cues are provided to hUCBMSCs cultured on the TSPS by subjecting the TSPS to cyclic stretching and bending, resulting in significant promotion of myogenic differentiation of hUCBMSCs as well as intracellular signaling related to the differentiation. After differentiation ex vivo, the cells are detached from the TSPS in the form of cell sheet fragments. Injection of the cell sheet fragments of differentiated cells into injured mouse skeletal muscle shows improved cell retention and muscle regeneration as compared to injection of either undifferentiated cells or differentiated dissociated cells. This system may serve as a tool for research on the electrical and mechanical regulation of stem cells and may be used to potentiate stem cell therapies.

Deglaciation of the North Cascade Range, Washington and British Columbia, from the Last Glacial Maximum to the Holocene

Glacial retreat from the North Cascade Range after the Last Glacial Maximum (LGM) at approximately 21 ka until the end of the Pleistocene at 11.6 ka was complex and included both continental and alpine glaciers. Alpine valley glaciers reached their maximum extent before 21.4 ka, then underwent a punctuated retreat to valley heads. In the south, beyond the reach of ice sheet glaciation, several end moraines were deposited after the LGM. Moraines marking a re-advance of alpine glaciers to &lt;5 km below modern glaciers were deposited from 13.7 to 11.6 ka.The Cordilleran Ice Sheet flowed south from near 52° north latitude in British Columbia into the North Cascades. At its maximum size the ice sheet covered more than 500 km2 and had a surface elevation of 2200 m in upper Skagit valley. Deglaciation commenced about 16 ka by frontal retreat of ice flanking the mountains. Surface lowering eventually exposed regional hydrologic divides and stranded ice masses more than 1000 m thick in valleys. Isolated fragments of the ice sheet disintegrated rapidly from 14.5 to 13.5 ka, with the pattern of deglaciation in each valley controlled by valley orientation, topography, and climate. Like alpine glaciers to the south, retreat of the ice sheet remnants was slowed by millennial scale climate fluctuations that produced at least one large recessional moraine, and multiple lateral moraines and kame terraces from elevations of 200-1400 m in most valleys. Large volumes of glacial meltwater flowed through the North Cascades and was concentrated in the Skagit and Methow rivers. Outburst floods from deep proglacial lakes spilled across divides and down steep canyons, depositing coarse gravel terraces and alluvial fans at valley junctions.Climate at the LGM was characterized by a mean summer temperature 6 to 7 ºC cooler than today, and 40% lower mean annual precipitation. Persistence of this climate for thousands of years before the LGM caused a 750-1000 m decrease in alpine glacier equilibrium line altitudes (ELA). In the southern North Cascades at 16 ka, glacial ELAs were 500-700 m lower than today, and during advances from 13.7 to 11.6 ka alpine glacier ELAs were 200-400 m lower.

ID:4005 Injectable Cell Delivery Constructs for Myocardial Tissue Engineering

Cell transplantation via direct intramuscular injection is a promising therapy for patients with ischemic diseases. However, following injections, retention of transplanted cells in engrafted areas remains problematic, and can be deleterious to cell-transplantation therapy. In this presentation, a thermo-responsive hydrogel system composed of aqueous methylcellulose (MC) blended with phosphate-buffered saline is constructed to grow cell sheet fragments and cell bodies for the treatment of ischemic diseases. The as-prepared MC hydrogel system undergoes a sol–gel reversible transition upon heating or cooling at approximately 32 °C. Via this unique property, the grown cell sheet fragments (cell bodies) can be harvested without using proteolytic enzymes; consequently, their inherent extracellular matrices (ECMs) and integrative adhesive agents remain well preserved. In animal studies using rats and pigs with experimentally created myocardial infarction, the injected cell sheet fragments (cell bodies) become entrapped in the interstices of muscular tissues and adhere to engraftment sites, while a minimal number of cells exist in the group receiving dissociated cells. Moreover, transplantation of cell sheet fragments (cell bodies) significantly increases vascular density, thereby improving the function of an infarcted heart.&#x0D; These experimental results demonstrate that cell sheet fragments (cell bodies) function as a cell-delivery construct by providing a favorable ECM environment to retain transplanted cells locally and consequently, improving the efficacy of therapeutic cell transplantation

Scaffold-Based Delivery of Bone Marrow Mesenchymal Stem Cell Sheet Fragments Enhances New Bone Formation In Vivo

Stem cell therapy is becoming a potent strategy to shorten the consolidation time and reduce potential complications during distraction osteogenesis (DO). However, the conventional local injection or scaffold-based delivery of bone marrow mesenchymal stem cell (BMSC) suspension deprives the cells of their endogenous extracellular matrix, which might dampen cell differentiation and tissue regeneration after implantation. Therefore, in our study, a BMSC sheet was established and was then minced into fragments and loaded onto a hydroxyapatite (HA) scaffold for grafting. The purified and characterized BMSCs were grown into a cell sheet, and bone formation and mineralization capacity, as well as the cell sheet composition, were analyzed. Afterward, the invivo osteogenic ability of cell sheet fragments (CSFs) was evaluated in immunocompromised mouse and rabbit models of DO. The BMSC sheet exhibited higher alkaline phosphatase activity than osteogenic cell suspension cultures. Alkaline phosphatase activity and mineral particles in the cell sheet increased further after osteogenic induction. Moreover, calcium and phosphorus were present only in the osteogenic cell sheet, along with the common elements carbon, oxygen, chlorine, sodium, and sulfur, as indicated by x-ray photoelectron spectroscopy analysis. In a mouse model, the CSF-HA complex was injected subcutaneously. Micro-computed tomography analysis showed that the osteogenic CSF-HA complex led to a considerably higher bone volume than the BMSC-HA or CSF-HA complex. The osteogenic CSF-HA specimens showed increased angiogenesis and deposition of type I collagen compared with the non-osteogenic CSF-HA or BMSC-HA specimens. Moreover, the osteogenic CSF-HA markedly improved bone consolidation and increased bone mass in DO rabbits. Collectively, the incorporation of osteogenic BMSC sheets into HA particles greatly promoted bone regeneration, which offers therapeutic alternatives for DO.

Process modeling pressure-swirl-gas-atomization for metal powder production

The paper aims at integral process modeling and simulation of the pressure-swirl-gas-atomization process for metal powder production. A numerical analysis is applied in this way to the atomization and spray process of a molten metal for metal powder production. The primary disintegration process of swirling conical sheets of the molten metal is described by the Volume of Fluid (VOF) approach, while the subsequent droplet spray process is simulated through the Eulerian-Lagrangian approach by taking the secondary breakup of produced droplets as well as in-flight spray phenomena such as drag and droplet solidification into account. The characteristics of liquid sheet fragmentation such as primary droplet size and velocity are derived and compared with measurements. The coupled simulation is realized by setting the outcomes of liquid sheet fragmentation as the initial conditions for the droplet spray process simulation. An assessment of classical secondary breakup models is shown in comparison with measurements. The droplet solidification behaviour in a spray process is investigated. Finally, the powder particle size distribution will be derived from the process modeling and simulation.

MHD simulations of three-dimensional resistive reconnection in a cylindrical plasma column

Magnetic reconnection is a plasma phenomenon where a topological rearrangement of magnetic field lines with opposite polarity results in dissipation of magnetic energy into heat, kinetic energy and particle acceleration. Such a phenomenon is considered as an efficient mechanism for energy release in laboratory and astrophysical plasmas. An important question is how to make the process fast enough to account for observed explosive energy releases. The classical model for steady state magnetic reconnection predicts reconnection times scaling as $S^{1/2}$ (where $S$ is the Lundquist number) and yields times scales several order of magnitude larger than the observed ones. Earlier two-dimensional MHD simulations showed that for large Lundquist number the reconnection time becomes independent of $S$ ("fast reconnection" regime) due to the presence of the secondary tearing instability that takes place for $S \gtrsim 1 \times 10^4$. We report on our 3D MHD simulations of magnetic reconnection in a magnetically confined cylindrical plasma column under either a pressure balanced or a force-free equilibrium and compare the results with 2D simulations of a circular current sheet. We find that the 3D instabilities acting on these configurations result in a fragmentation of the initial current sheet in small filaments, leading to enhanced dissipation rate that becomes independent of the Lundquist number already at $S \simeq 1\times 10^3$.

An orthotropic viscoelastic model for the passive myocardium: continuum basis and numerical treatment

This study deals with the viscoelastic constitutive modeling and the respective computational analysis of the human passive myocardium. We start by recapitulating the locally orthotropic inner structure of the human myocardial tissue and model the mechanical response through invariants and structure tensors associated with three orthonormal basis vectors. In accordance with recent experimental findings the ventricular myocardial tissue is assumed to be incompressible, thick-walled, orthotropic and viscoelastic. In particular, one spring element coupled with Maxwell elements in parallel endows the model with viscoelastic features such that four dashpots describe the viscous response due to matrix, fiber, sheet and fiber-sheet fragments. In order to alleviate the numerical obstacles, the strictly incompressible model is altered by decomposing the free-energy function into volumetric-isochoric elastic and isochoric-viscoelastic parts along with the multiplicative split of the deformation gradient which enables the three-field mixed finite element method. The crucial aspect of the viscoelastic formulation is linked to the rate equations of the viscous overstresses resulting from a 3-D analogy of a generalized 1-D Maxwell model. We provide algorithmic updates for second Piola–Kirchhoff stress and elasticity tensors. In the sequel, we address some numerical aspects of the constitutive model by applying it to elastic, cyclic and relaxation test data obtained from biaxial extension and triaxial shear tests whereby we assess the fitting capacity of the model. With the tissue parameters identified, we conduct (elastic and viscoelastic) finite element simulations for an ellipsoidal geometry retrieved from a human specimen.

Epitope location for two monoclonal antibodies against human cystatin C, representing opposite aggregation inhibitory properties.

Human cystatin C (hCC), like many other amyloidogenic proteins, dimerizes and possibly makes aggregates by subdomain swapping. Inhibition of the process should suppress the fibrillogenesis leading to a specific amyloidosis (hereditary cystatin C amyloid angiopathy, HCCAA). It has been reported that exogenous agents like monoclonal antibodies against cystatin C are able to suppress formation of cystatin C dimers and presumably control the neurodegenerative disease. We have studied in detail two monoclonal antibodies (mAbs) representing very different aggregation inhibitory potency, Cyst10 and Cyst28, to find binding sites in hCC sequence responsible for the immunocomplex formation and pave the way for possible immunotherapy of HCCAA. We used the epitope extraction/excision mass spectrometry approach with the use of different enzymes complemented by affinity studies with synthetic hCC fragments as a basic technique for epitope identification. The results were analyzed in the context of hCC structure allowing us to discuss the binding sites for both antibodies. Epitopic sequences for clone Cyst28 which is a highly potent dimerization inhibitor were found in N-terminus, loop 1 and 2 (L1, L2) and fragments of β2 and β3 strands. The crucial difference between conformational epitope sequences found for both mAbs seems to be the lack of interactions with hCC via N-terminus and the loop 1 in the case of mAb Cyst10. Presumably the interactions of mAbs with hCC via L1 and β sheet fragments make the hCC structure rigid and unable to undergo the swapping process.

Routization Problem Complicated by the Dependence of Costs Functions and «Current» Restrictions From the Tasks List

The problem of a routization of the movements complicated by the restrictions of different type (preceding conditions, the restrictions on the attainability of states by each movement and others) is considered. A multivariance at the movement step is permitted, it is naturally resulted in the problem about the visiting of megalopolises. The costs of movements and jobs executed when visiting megalopolises may depend on the list of tacks. This list may correspond to performed or unperformed tasks. ”Current” restrictions (on movements) may depend on the aforementioned list of tasks. The considered setting is oriented to the application with regard to a nuclear power engineering problems (the problem of decreasing irradiation of the nuclear power station staff when executing a complex of tasks under high radiation intensity) and the machine building. In the second case, which consists in controling a machine for the sheet cutting of details by the numerical program control machines, ”current” restrictions on movements may be conditioned by temperature tolerance relative to the fragments of sheet which have already been ”visited” by the cutting machine. The scheme of constructing the optimal solution based on the widely understood dynamic programming is considered in this article. The used algorithm is realized on a personal computer; the results of its application are illustrated by the modelling examples.

The importance of multidisciplinary work within archaeological conservation projects: assembly of the Staffordshire Hoard die-impressed sheets

AbstractThe Anglo-Saxon Staffordshire Hoard contains, alongside the well-publicised gold and silver objects, a large collection of over 1000 fragments of die-impressed silver sheet or foil. The majority of these fragments probably decorated one high-status helmet, but were removed from it before burial. These fragments constitute a significant element of the collection, and their conservation, analysis and reassembly forms a major strand of the wider Staffordshire Hoard research project. This paper provides a background to the die-impressed sheets as a class of object within the hoard, and examines the multidisciplinary approach taken by the archaeological conservation team to this challenging but interesting body of material. It explores how this approach has contributed significantly to the results that are being delivered, particularly by the recognition of the dies used to create the impressed sheets, and from this, the development of their overall interpretation.

BRACTEATE PENDANT FROM THE LINNAKSE HOARD: ARCHAEOMETRIC DISCUSSION OF THE SILVER ARTEFACT

Introduction In the late summer of 2010, a history enthusiast Erkki Heinsalu discovered a Late Viking Age (tpq 1059) hoard from a field in the northern part of the Linnakse village in central Harjumaa. 1311 coins, two small silver bars, some silver beads and pieces of hack silver had been placed into a hand-made clay vessel with a narrow opening and lay as a rather compact assemblage amongst the vessel fragments at the depth of 25-30 cm in a soil without any traces of a cultural layer (Kiudsoo & Russow 2011, 225 f., fig. 3). Archaeological investigations of the find location revealed that a large burial ground had been on the same field with both cremation and un-cremated burials from the 3rd-4th century until the 12th-13th century. The silver hoard had been hidden in the vicinity of the earliest burial site the tarand grave (Tamla et al. 2011). This allows us to conclude that the Linnakse hoard is so far the only one from the Late Iron Age hoards in Estonia where the find context, proved by facts, refers clearly to connections with an old burial place (Leimus et al. 2014). The article concentrates on the study and research results of a piece of silver from the Linnakse hoard. It is important to note that the small item that was initially considered to be part of a widely used Late Viking Age silver coin proved, at closer inspection, to be a fragment of a rare decoration. Since such items had previously never been found in Estonia, I considered it necessary to publish an article about this item and so pass information about it on to scientific circles. An archaeometric study method was applied to reconstruct the whole item from its fragment and to establish the original shape, function and origin of the decoration. In the process I delved into the production technologies of analogous items. Archaeometry is the application of scientific methods and techniques to archaeological investigation and often looked upon as a link between the so-called traditional science of archaeology and other research areas (Murray 2001, 105). The objective of archaeometric studies is to use techniques from other scientific fields to obtain as much information as possible about the materials and techniques used for the production of archaeological items, about the craftsmen and their skills, tools, working environments, specialization, etc. and to learn about the production, trade and cultural environment of the time on a broader scale (Olin 1982; Yellen 1982; Aspinall 1986; Wisseman & Williams 1993; Killick & Young 1997; Edwards & Vandenabeele 2012). To establish the possible origin of the item I looked for parallels in archaeological collections in the neighbouring countries as well as more distant regions. The analysis of the material composition of the fragment was made at the Science Centre of Materials Research of the Tallinn University of Technology (Analysis report 2015). External observation of the item and conclusions about its production The 19 x 12 mm and 1 mm thick fragment of silver sheet with three straight and one curved side originates from a decoration, where a profiled wire with a 1.8 mm diameter has been soldered to the curved side (Fig. 1). It is most likely that the fragile item had been cut with a knife or shears for trading purposes. Unlike with chopping or tearing, the edge of a soft and thin silver sheet remains straight only if cut with a knife or shears. The barely perceptible yellowish sheen on the surface of the fragment could indicate worn gilt. If the item had been gilded, probably amalgamating was used--i.e. an ancient art of goldsmithing that became widely used in the first centuries of our era, when it replaced the method that used forging a thin sheet of gold to an item or applying glue like e.g. egg white for fastening sheet gold. The essence of amalgamating is fairly straightforward: gold is dissolved in mercury at 375 [degrees]C which produces the mass of amalgam that is then spread over the item to be gilded. …

Nanoporous-Carbon as a Potential Host Material for Reversible Mg Ion Intercalation

We study nanoporous-carbon (NPC) grown via pulsed laser deposition (PLD) as an electrically conductive anode host material for Mg2+ intercalation. NPC has high surface area, and an open, accessible pore structure tunable via mass density that can improve diffusion. We fabricate 2032 coin cells using NPC coated stainless-steel disk anodes, metallic Mg cathodes, and a Grignard-based electrolyte. NPC mass density is controlled during growth, ranging from 0.06–1.3 g/cm3. The specific surface area of NPC increases linearly from 1,000 to 1,700 m2/g as mass density decreases from 1.3 to 0.26 g/cm3, however, the surface area falls off dramatically at lower mass densities, implying a lack of mechanical integrity in such nanostructures. These structural characterizations correlate directly with coin cell electrochemical measurements. In particular, cyclic voltammetry (CV) scans for NPC with density ∼0.5 g/cm3 and BET surface area ∼1500 m2/g infer the possibility of reversible Mg-ion intercalation. Higher density NPC yields capacitive behavior, most likely resulting from the smaller interplanar spacings between graphene sheet fragments and tighter domain boundaries; lower density NPC results in asymmetrical CV scans, consistent with the likely structural degradation resulting from mass transport through soft, low-density carbon materials.

Coronal heating in multiple magnetic threads

Context. Heating the solar corona to several million degrees requires the conversion of magnetic energy into thermal energy. In this paper, we investigate whether an unstable magnetic thread within a coronal loop can destabilise a neighbouring magnetic thread. Aims. By running a series of simulations, we aim to understand under what conditions the destabilisation of a single magnetic thread can also trigger a release of energy in a nearby thread. Methods. The 3D magnetohydrodynamics code, Lare3d, is used to simulate the temporal evolution of coronal magnetic fields during a kink instability and the subsequent relaxation process. We assume that a coronal magnetic loop consists of non-potential magnetic threads that are initially in an equilibrium state. Results. The non-linear kink instability in one magnetic thread forms a helical current sheet and initiates magnetic reconnection. The current sheet fragments, and magnetic energy is released throughout that thread. We find that, under certain conditions, this event can destabilise a nearby thread, which is a necessary requirement for starting an avalanche of energy release in magnetic threads. Conclusions. It is possible to initiate an energy release in a nearby, non-potential magnetic thread, because the energy released from one unstable magnetic thread can trigger energy release in nearby threads, provided that the nearby structures are close to marginal stability.

Sandstone-matrix mélanges, architectural subdivision, and geologic history of accretionary complexes: A sedimentological and structural perspective from the Franciscan Complex of Sonoma and Marin counties, California, USA

Understanding details of accretionary complex architecture is essential to understanding construction of oceanic “outer” sides of orogens. The architecture of the Franciscan Complex (California), considered by many to be the “type” accretionary complex, is widely viewed in the context of terranes or belts delimited by reconnaissance mapping that reveals neither regional variations within terranes nor critical details of stratigraphy and structure. The architectural importance of Franciscan melanges is recognized, but the importance of sandstone-matrix melanges and olistostromal sandstones is not. Large-scale mapping in Sonoma and Marin counties, California, shows that Franciscan rocks are deformed, submarine-fan units of Facies A–E, plus Facies F olistolith-bearing submarine channel sandstones and olistostromal sandstone- and shale-matrix melanges. Some melanges are polygenetic with a sedimentary origin and a tectonic overprint. Glaucophane schists were recycled into conglomerates and olistostromes. Mappable units constitute members, broken and dismembered formations, and melanges. Considering the stratigraphy and structure evident at the 1:24,000 scale, accretion via a subduction channel mechanism is impossible. The Sonoma-Marin Central belt or Central terrane (melange) is not a monolithic shale-matrix melange and lacks this characteristic of rocks assigned the same name to the north. Franciscan rocks here structurally underlie thrust-faulted fragments of a regional ultramafic sheet and, locally, an underlying exotic block-bearing serpentinite-matrix melange. The detailed mapping shows that regional relations among and within Franciscan terranes and belts are poorly understood and suggests that such mapping is needed to clarify accretionary complex architecture and history. The implication for accretionary complex studies, in general, is that, while terrane or belt designations provide a general picture of the collage nature of accretionary complexes and clarification of regional relationships, only large-scale structural and stratigraphic studies can elucidate the architectural details of these orogenic complexes.