Analytical Description of Steady Magnetic Reconnection in Hall Magnetohydrodynamics

Steady magnetic reconnection in the framework of incompressible Hall magnetohydrodynamics is considered. The principal role of the Hall effect in the formation of the structure of the reconnecting current sheet is emphasized. Analytical expressions for the velocity and the magnetic field in the sheet are derived, based on the approximation of a weak two dimensionality of the planar components of the solution. The analytical solution illustrates key features of Hall magnetic reconnection, including the reconnection rate enhancement and the sheet thinning due to the Hall effect, the presence of a quadrupolar axial (out-of-the-plane) magnetic field that controls the geometry of the reconnecting planar magnetic field, and the dynamical coupling of the axial and planar components of the solution, with the coupling strength that is proportional to the ion skin depth. Scalings for the sheet thickness, width, and the reconnection inflow and outflow speeds in terms of the electric resistivity and the axial magnetic field are determined. Implications of the results for fast magnetic reconnection in a weakly collisional plasma of the solar corona are discussed

Natural enemies partially compensate for warming induced excess herbivory in an organic growth system

Predators can limit prey abundance and/or levels of activity. The magnitudes of these effects are contingent on predator and prey traits that may change with environmental conditions. Aberrant thermal regimes could disrupt pest suppression through asymmetric effects, e.g. heat-sensitive predator vs. heat-tolerant prey. To explore potential effects of warming on suppressing pests and controlling herbivory in a vegetable crop, we performed laboratory experiments exposing an important pest species to two spider predator species at different temperatures. Heat tolerance was characterised by the critical thermal maxima parameter (CTM50) of the cucumber beetle (Diabrotica undecimpunctata), wolf spider (Tigrosa helluo), and nursery web spider (Pisaurina mira). Cucumber beetles and wolf spiders were equally heat tolerant (CTM50 \u3e 40 °C), but nursery web spiders had limited heat tolerance (CTM50 = 34 °C). Inside mesocosms, beetle feeding increased with temperature, wolf spiders were always effective predators, nursery web spiders were less lethal at high temperature (38 °C). Neither spider species reduced herbivory at ambient temperature (22 °C), however, at warm temperature both species reduced herbivory with evidence of a dominant non-consumptive effect. Our experiments highlight the contingent nature of predator-prey interactions and suggest that non-consumptive effects should not be ignored when assessing the impact of temperature change

Application of the Beremin Model for Cruciform Specimen to Determine the Fracture Probability in Case of WPS

Based on large-scale experimental tests performed on cruciform specimens made of French type RPV steel, the warm prestressing (WPS) effect for LCF (load–cool–fracture) and LCTF (load–cool–transient–fracture) load cycles is studied by finite element simulation. A modified Beremin model is used to determine the fracture probability of the specimens.С использованием результатов экспериметальных иссследований крупногабаритных крестообразных образцов из реакторной стали французского производства выполнено конечно-элементное моделирование эффекта горячей опрессовки при циклической нагрузке по схемам: нагрузка–охлаждение–разрушение и нагрузка–охлаждение–переходный процесс–разрушение. Для оценки вероятности разрушения образцов использована модифицированная модель Беремина.Із використанням результатів експериментальних досліджень великогабаритних хрестоподібних зразків із реакторної сталі французького виробництва виконано скінченноелементне моделювання ефекту гарячого опресування за циклічного навантаження за схемами: навантаження–охолодження–руйнування і навантаження–охолодження–перехідний процес–руйнування. Для оцінки імовірності руйнування зразків використано модифіковану модель Береміна

Multimodal Neuroimaging Microtool for Infrared Optical Stimulation, Thermal Measurements and Recording of Neuronal Activity in the Deep Tissue

Infrared neural stimulation (INS) uses pulsed near-infrared light to generate highly controlled temperature transients in neurons, leading them to fire action potentials. Stimulation of the superficial layer of the intact brain has been presented, however, the stimulation of the deep neural tissue has larger potential in view of therapeutic use. To reveal the underlying mechanism of deep tissue stimulation properly, we present the design, the fabrication scheme and functional testing of a novel, multimodal microelectrode for future INS experiments. Three modalities—electrophysiological recording, thermal measurements and infrared waveguiding abil—were integrated based on silicon MEMS technology. Due to the advanced functionalities, a single probe is sufficient to determine safe stimulation parameters in vivo. As far as we know, this is the first multimodal microelectrode designed for INS studies in deep neural tissue. In this paper, the technology and results of chip-scale measurements are presented

Cool Headed Individuals Are Better Survivors: Non-Consumptive and Consumptive Effects of a Generalist Predator on a Sap Feeding Insect

Non-consumptive effects (NCEs) of predators are part of the complex interactions among insect natural enemies and prey. NCEs have been shown to significantly affect prey foraging and feeding. Leafhopper's (Auchenorrhyncha) lengthy phloem feeding bouts may play a role in pathogen transmission in vector species and also exposes them to predation risk. However, NCEs on leafhoppers have been scarcely studied, and we lack basic information about how anti-predator behaviour influences foraging and feeding in these species. Here we report a study on non-consumptive and consumptive predator-prey interactions in a naturally co-occurring spider-leafhopper system. In mesocosm arenas we studied movement patterns during foraging and feeding of the leafhopper Psammotettix alienus in the presence of the spider predator Tibellus oblongus. Leafhoppers delayed feeding and fed much less often when the spider was present. Foraging movement pattern changed under predation risk: movements became more frequent and brief. There was considerable individual variation in foraging movement activity. Those individuals that increased movement activity in the presence of predators exposed themselves to higher predation risk. However, surviving individuals exhibited a 'cool headed' reaction to spider presence by moving less than leafhoppers in control trials. No leafhoppers were preyed upon while feeding. We consider delayed feeding as a "paradoxical" antipredator tactic, since it is not necessarily an optimal strategy against a sit-and-wait generalist predator

Signaling and structures underpinning conducted vasodilation in human and porcine intramyocardial coronary arteries

BACKGROUND: Adequate blood flow into coronary micro-arteries is essential for myocardial function. Here we assess the mechanisms responsible for amplifying blood flow into myogenically-contracting human and porcine intramyocardial micro-arteries ex vivo using endothelium-dependent and -independent vasodilators. METHODS: Human and porcine atrial and ventricular small intramyocardial coronary arteries (IMCAs) were studied with pressure myography and imaged using confocal microscopy and serial section/3-D reconstruction EM. RESULTS: 3D rendered ultrastructure images of human right atrial (RA-) IMCAs revealed extensive homo-and hetero-cellular contacts, including to longitudinally-arranged smooth muscle cells (l-SMCs) found between the endothelial cells (ECs) and radially-arranged medial SMCs (r-SMCs). Local and conducted vasodilatation followed focal application of bradykinin in both human and porcine RA-IMCAs, and relied on hyperpolarization of SMCs, but not nitric oxide. Bradykinin initiated asynchronous oscillations in endothelial cell Ca(2+) in pressurized RA-IMCAs and, as previously shown in human RA-IMCAs, hyperpolarized porcine arteries. Immunolabelling showed small- and intermediate-conductance Ca(2+)-activated K(+) channels (K(Ca)) present in the endothelium of both species, and concentration-dependent vasodilation to bradykinin followed activation of these K(Ca) channels. Extensive electrical coupling was demonstrated between r-SMCs and l-SMCs, providing an additional pathway to facilitate the well-established myoendothelial coupling. Conducted dilation was still evident in a human RA-IMCA with poor myogenic tone, and heterocellular contacts were visible in the 3D reconstructed artery. Hyperpolarization and conducted vasodilation was also observed to adenosine which, in contrast to bradykinin, was sensitive to combined block of ATP-sensitive (K(ATP)) and inwardly rectifying (K(IR)) K(+) channels. CONCLUSIONS: These data extend our understanding of the mechanisms that coordinate human coronary microvascular blood flow and the mechanistic overlap with porcine IMCAs. The unusual presence of l-SMCs provides an additional pathway for rapid intercellular signaling between cells of the coronary artery wall. Local and conducted vasodilation follow hyperpolarization of the ECs or SMCs, and contact-coupling between l-SMCs and r-SMCs likely facilitates this vasodilation

Fracture toughness of steam turbine blades

З використанням методу J-інтеграла оцінено статичну тріщиностійкість сталі 20Х13 лопаток парових турбін у вихідному стані та після ~ 3·105 год експлуатації. На основі побудованих R-кривих для експлуатованої і неексплуатованої сталей показано відмінності між ними, пов’язані з інтенсивною деградацією металу внаслідок експлуатації. Проаналізовано поверхні зламів зразків, випробуваних на статичну тріщиностійкість, та виявлено основні фрактографічні елементи, пов’язані з деградацією сталі в експлуатаційних умовах.Using the J-integral method the static crack growth resistance of the 20Kh13 steel in the virgin state and after 3·105 h service as blades in the steam turbine was estimated. Based on the building JR-curves for the exploited and unexploited steels were shown the differences between them caused by its intensive degradation during exploitation. The fracture surfaces obtained after static crack growth resistance test of specimens were analyzed. The main fractographic elements concerned with degradation of steel in operation condition were revealed

Mi történik a Föld legmagasabban fekvő sivatagának aljzatában? - Az aktív réteg hőmérsékleti elemzése a Száraz-Andokban

Már az 1800-as évek végén (Ju et al., 1899) szembesültek azzal, hogy az elektromos áram-ellátásban alapvető szerepet játszó távvezeték-hálózatokat nagymértékben veszélyeztetik bizonyos időjárási körülmények, események. Ilyen például a villámcsapás, a viharos szél, illetve a téli jégfelhalmozódás. A jég és hó súlytöbblete, főleg ha szeles idővel társul, könnyen nagy területen okozhat vezetékszakadást. A lerakódás lehet zúzmara, ónos esőből származó jég-bevonat, vagy tapadó hó. A zúzmara a hazai éghajlati körülmények miatt ritkán éri el a kritikus súlytöbbletet, amely a vezeték elszakadásához vezethet. Ezzel szemben az ónos eső és tapadó hó gyakrabban okoz károkat. Az ónos eső kialakulási körülményeivel számos publikáció foglalkozik, amelynek Magyarországra vonatkozó vizsgálatait Fövényi (2001) végezte el. A vezetékre rakódó ónos, jeges bevonat egyszerűbben előrejelezhető, ezzel szemben a tapadó hó kialakulásának folyamata még nem ismert minden részletében, illetve előrejelzése is bonyolultabb az alkalmazott parametrizációk miatt (ISO124194, 2001). Az előrejelzések pontosítása miatt fontos megvizsgálni rádiószondás felszállások segítségével, hogy tapadó hó észlelésekor milyen a légkör vertikális állapota, a hőmérsékleti, nedvességi és szélviszonyok alakulása. A tapadó hó kialakulásához kedvező időjárási helyzetek gyakoriak hazánkban, egy téli félévben akár 35 tapadó havas napot is megfigyelhetnek (Gulyás, 2012). A legtöbb esetben néhány órán át tartó, kis csapadékintenzitású havazás tapasztalható enyhén pozitív talajközeli hőmérséklet mellett (Dalle & Admirat, 2011). Ekkor káresemény nem történik. Ezzel szemben a hevesebb, akár 5–10 órán át tartó, nagy csapadékintenzitással és erős széllel járó havazás jelenti a legnagyobb kockázatot a felsővezeték-hálózat számára (Wakahama et al., 1977, Dalle & Admirat, 2011). Magyarországon a mediterrán ciklonok átvonulásához kapcsolhatók leggyakrabban ezek az események (Gulyás, 2012). A nedves hópelyhek megjelenése összetett mikrofizikai folyamatok eredménye, amelyben jelentős szerepet játszik a légkör vertikális szerkezete, a meteorológiai, azon belül is a termo-dinamikai állapothatározók (léghőmérséklet, légnyomás, légnedvesség) alakulása. A nemzet-közi szakirodalomban a tapadó hóval kapcsolatos vizsgálatok két részre bonthatók. Egyrészt megtalálhatók a meteorológiai állomásokon mért adatokon (hőmérséklet, szélirány és szél-sebesség, látástávolság) alapuló (Makkonen, 1989; Makkonen & Wichura, 2010; Nygaard et al, 2013), másrészt a korlátos tartományú, nem-hidrosztatikus időjárás előrejelző modellek outputjaiból számított statisztikai vizsgálatok és előrejelzések (Grünewald et al., 2012; Somfalvi-Tóth et al., 2015; Lacavalla et al., 2015). Ez utóbbiak már rendkívül részletes mikrofizikai sémát használnak a téli csapadékfajták tulajdonságainak, mint például a felhőben megjelenő részecskék típusának (graupel, felhővíz, hó, eső, túlhűlt víz, stb.), a folyékony felhővíztartalomnak, a szilárd és folyékony halmazállapotú csapadékelemek arányának, vagy a hópelyhek tömegkoncetrációjának parametrizálására (Hong et al., 2004; Thompson et al., 2004; Thompson et al., 2008; Morrison et al., 2015). Ezeket a paramétereket nem mérik közvetlenül a meteorológiai állomások, ezért inicializálásuk a modellekben nem méréseken alapul, így az eredmények verifikálása is akadályokba ütközik

Altered vascular smooth muscle function in the ApoE knockout mouse during the progression of atherosclerosis

Objectives: Relaxation of vascular smooth muscle (VSM) requires re-uptake of cytosolic Ca2+ into the sarcoplasmic reticulum (SR) via the Sarco/Endoplasmic Reticulum Ca2+ ATPase (SERCA), or extrusion via the Plasma Membrane Ca2+ ATPase (PMCA) or sodium Ca2+ exchanger (NCX). Peroxynitrite, a reactive species formed in vascular inflammatory diseases, upregulates SERCA activity to induce relaxation but, chronically, can contribute to atherogenesis and altered vascular function by escalating endoplasmic reticulum stress. Our objectives were to determine if peroxynitrite-induced relaxation and Ca2+ handling processes within vascular smooth muscle cells were altered as atherosclerosis develops.<p></p> Methods: Aortae from control and ApoE−/− mice were studied histologically, functionally and for protein expression levels of SERCA and PMCA. Ca2+ responses were assessed in dissociated aortic smooth muscle cells in the presence and absence of extracellular Ca2+.<p></p> Results: Relaxation to peroxynitrite was concentration-dependent and endothelium-independent. The abilities of the SERCA blocker thapsigargin and the PMCA inhibitor carboxyeosin to block this relaxation were altered during fat feeding and plaque progression. SERCA levels were progressively reduced, while PMCA expression was upregulated. In ApoE−/− VSM cells, increases in cytosolic Ca2+ [Ca2+]c in response to SERCA blockade were reduced, while SERCA-independent Ca2+ clearance was faster compared to control.<p></p> Conclusion: As atherosclerosis develops in the ApoE−/− mouse, expression and function of Ca2+ handling proteins are altered. Up-regulation of Ca2+ removal via PMCA may offer a potential compensatory mechanism to help normalise the dysfunctional relaxation observed during disease progression