Consumption over the life cycle and over the business cycle

Consumption;Models

The Flare-energy Distributions Generated by Kink-unstable Ensembles of Zero-net-current Coronal Loops

It has been proposed that the million degree temperature of the corona is due to the combined effect of barely-detectable energy releases, so called nanoflares, that occur throughout the solar atmosphere. Alas, the nanoflare density and brightness implied by this hypothesis means that conclusive verification is beyond present observational abilities. Nevertheless, we investigate the plausibility of the nanoflare hypothesis by constructing a magnetohydrodynamic (MHD) model that can derive the energy of a nanoflare from the nature of an ideal kink instability. The set of energy-releasing instabilities is captured by an instability threshold for linear kink modes. Each point on the threshold is associated with a unique energy release and so we can predict a distribution of nanoflare energies. When the linear instability threshold is crossed, the instability enters a nonlinear phase as it is driven by current sheet reconnection. As the ensuing flare erupts and declines, the field transitions to a lower energy state, which is modelled by relaxation theory, i.e., helicity is conserved and the ratio of current to field becomes invariant within the loop. We apply the model so that all the loops within an ensemble achieve instability followed by energy-releasing relaxation. The result is a nanoflare energy distribution. Furthermore, we produce different distributions by varying the loop aspect ratio, the nature of the path to instability taken by each loop and also the level of radial expansion that may accompany loop relaxation. The heating rate obtained is just sufficient for coronal heating. In addition, we also show that kink instability cannot be associated with a critical magnetic twist value for every point along the instability threshold

Particle interactions with single or multiple 3D solar reconnecting current sheets

The acceleration of charged particles (electrons and protons) in flaring solar active regions is analyzed by numerical experiments. The acceleration is modelled as a stochastic process taking place by the interaction of the particles with local magnetic reconnection sites via multiple steps. Two types of local reconnecting topologies are studied: the Harris-type and the X-point. A formula for the maximum kinetic energy gain in a Harris-type current sheet, found in a previous work of ours, fits well the numerical data for a single step of the process. A generalization is then given approximating the kinetic energy gain through an X-point. In the case of the multiple step process, in both topologies the particles' kinetic energy distribution is found to acquire a practically invariant form after a small number of steps. This tendency is interpreted theoretically. Other characteristics of the acceleration process are given, such as the mean acceleration time and the pitch angle distributions of the particles.Comment: 18 pages, 9 figures, Solar Physics, in pres

Development of Low-Cost Austenitic Stainless Gas-Turbine and Diesel Engine Components with Enhanced High-Temperature Reliability

In July of 1999, a Cooperative Research and Development Agreement (CRADA) was undertaken between Oak Ridge National Laboratory (ORNL) and Solar Turbines, Inc. and Caterpillar, Inc. (Caterpillar Technical Center) to evaluate commercial cast stainless steels for gas turbine engine and diesel engine exhaust component applications relative to the materials currently being used. If appropriate, the goal was to develop cast stainless steels with improved performance and reliability rather than switch to more costly cast Ni-based superalloys for upgraded performance. The gas-turbine components considered for the Mercury-50 engine were the combustor housing and end-cover, and the center-frame hot-plate, both made from commercial CF8C cast austenitic stainless steel (Fe-l9Cr-12Ni-Nb,C), which is generally limited to use at below 650 C. The advanced diesel engine components considered for truck applications (C10, C12, 3300 and 3400) were the exhaust manifold and turbocharger housing made from commercial high SiMo ductile cast iron with uses limited to 700-750 C or below. Shortly after the start of the CRADA, the turbine materials emphasis changed to wrought 347H stainless steel (hot-plate) and after some initial baseline tensile and creep testing, it was confirmed that this material was typical of those comprising the abundant database; and by 2000, the emphasis of the CRADA was primarily on diesel engine materials. For the diesel applications, commercial SiMo cast iron and standard cast CN12 austenitic stainless steel (Fe-25Cr-13Ni-Nb,C,N,S) baseline materials were obtained commercially. Tensile and creep testing from room temperature to 900 C showed the CN12 austenitic stainless steel to have far superior strength compared to SiMo cast iron above 550 C, together with outstanding oxidation resistance. However, aging at 850 C reduced room-temperature ductility of the standard CN12, and creep-rupture resistance at 850 C was less than expected, which triggered a focused laboratory-scale alloy development effort on modified cast austenitic stainless steels at ORNL. Isothermal fatigue testing at 700 C also showed that standard CN12 was far superior to SiMo cast iron, but somewhat less than the desired behavior. During the first year, 3 new modified CF8C heats and 8 new modified CN12 heats were made, based on compositional changes specifically designed to change the nature, dispersion and stability of the as-cast and high-temperature aging-induced microstructures that consisted of carbides and other precipitate phases. Screening of the alloys at room-temperature and at 850 C (tensile and creep-rupture) showed -a ten-fold increase in rupture life of the best modified CN12 relative to the baseline material, better room-temperature ductility after aging, caused by less precipitation in the as-cast material and much less aging-induced precipitation. The best new modified CF8C steel showed strength at tensile and creep-rupture strength comparable to standard CN12 steel at 850 C, due to a unique and very stable microstructure. The CRADA was scheduled to end in July 2001, but was extended twice until July 2002. Based on the very positive results on the newly developed modified CF8C and CN12 cast austenitic stainless steels, a new CRADA with Caterpillar has been set up to commercially scale-up, test and evaluate, and make trial components from the new steels

Excitation of standing kink oscillations in coronal loops

In this work we review the efforts that have been done to study the excitation of the standing fast kink body mode in coronal loops. We mainly focus on the time-dependent problem, which is appropriate to describe flare or CME induced kink oscillations. The analytical and numerical studies in slab and cylindrical loop geometries are reviewed. We discuss the results from very simple one-dimensional models to more realistic (but still simple) loop configurations. We emphasise how the results of the initial value problem complement the eigenmode calculations. The possible damping mechanisms of the kink oscillations are also discussed

Recent Advances in Understanding Particle Acceleration Processes in Solar Flares

We review basic theoretical concepts in particle acceleration, with particular emphasis on processes likely to occur in regions of magnetic reconnection. Several new developments are discussed, including detailed studies of reconnection in three-dimensional magnetic field configurations (e.g., current sheets, collapsing traps, separatrix regions) and stochastic acceleration in a turbulent environment. Fluid, test-particle, and particle-in-cell approaches are used and results compared. While these studies show considerable promise in accounting for the various observational manifestations of solar flares, they are limited by a number of factors, mostly relating to available computational power. Not the least of these issues is the need to explicitly incorporate the electrodynamic feedback of the accelerated particles themselves on the environment in which they are accelerated. A brief prognosis for future advancement is offered.Comment: This is a chapter in a monograph on the physics of solar flares, inspired by RHESSI observations. The individual articles are to appear in Space Science Reviews (2011

Long-term efficacy and safety of dupilumab in adolescents with moderate-to-severe atopic dermatitis : results through week 52 from a phase III open-label extension trial (LIBERTY AD PED-OLE)

Background For adolescent patients (aged ≥ 12 to < 18 years) with uncontrolled moderate-to-severe atopic dermatitis (AD), 16 weeks of treatment with dupilumab resulted in substantial clinical benefit compared with placebo, with an acceptable safety profile. However, long-term data on the approved dose regimens of dupilumab in adolescents with AD are lacking. Objectives This open-label extension study (LIBERTY AD PED-OLE, NCT02612454) reports the long-term safety, efficacy, and pharmacokinetics of dupilumab in adolescents with moderate-to-severe AD who had participated in dupilumab parent trials. Methods Patients enrolled under the original study protocol received subcutaneous dupilumab according to a weight-based regimen (2 or 4 mg/kg every week). Following protocol amendment, patients were switched to subcutaneous dupilumab 300 mg every 4 weeks (q4w) irrespective of weight, and newly enrolled patients were started on dupilumab 300 mg q4w. Patients with an inadequate clinical response (Investigator’s Global Assessment [IGA] score of 0/1 was not reached) to the q4w regimen could be uptitrated to the approved dupilumab dose regimens of 200 or 300 mg every 2 weeks (body weight < 60 or ≥ 60 kg, respectively). Patients whose IGA score of 0/1 was maintained continuously for a 12-week period after week 40 were discontinued from dupilumab, monitored for relapse, and re-initiated on dupilumab if required. Results Data for 294 patients (mean age 14.7 years) were analyzed, 102 (34.7%) of whom had completed the 52-week visit at the database lock. The dupilumab long-term safety profile was comparable to that seen in adults and consistent with the known safety profile. Most treatment-emergent adverse events were mild/moderate. By week 52, 42.7% of patients had an IGA score of 0/1 (clear/almost clear), and 93.1%, 81.2%, and 56.4%, respectively, had at least a 50%, 75%, or 90% improvement in Eczema Area and Severity Index (EASI). Most (70.9%) patients required uptitration to the approved dupilumab dose regimen. The proportions of uptitrated patients with an IGA score of 0/1 or 75% improvement in EASI increased over time, reaching 35.7% and 51.9%, respectively, 48 weeks after the first uptitration visit. By week 52, 29.4% of patients had clear/almost clear skin sustained for 12 weeks and had stopped medication; 56.7% relapsed and were subsequently re-initiated on treatment, with a mean time to re-initiation of 17.5 (± standard deviation 17.3) weeks. Conclusions Consistent with results seen with short-term treatment, long-term treatment with dupilumab showed an acceptable safety profile while providing incremental clinical benefit with continued treatment over time. The high proportion of patients who needed uptitration because of inadequate response to q4w dosing supports the q2w dose regimen as optimal for this age group. Finally, the majority of patients who stopped medication after having clear/almost clear skin sustained over 12 weeks experienced disease recurrence, suggesting the need for continued dupilumab dosing to maintain efficacy. Trial Registration ClinicalTrials.gov Identifiers: NCT02612454, NCT02407756, NCT03054428, and NCT03050151

Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at sNN=2.76\sqrt{s_{\rm NN}}=2.76 TeV

The elliptic, $v_2$, triangular, $v_3$, and quadrangular, $v_4$, azimuthal anisotropic flow coefficients are measured for unidentified charged particles, pions and (anti-)protons in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV with the ALICE detector at the Large Hadron Collider. Results obtained with the event plane and four-particle cumulant methods are reported for the pseudo-rapidity range $|\eta|<0.8$ at different collision centralities and as a function of transverse momentum, $p_{\rm T}$, out to $p_{\rm T}=20$ GeV/$c$. The observed non-zero elliptic and triangular flow depends only weakly on transverse momentum for $p_{\rm T}>8$ GeV/$c$. The small $p_{\rm T}$ dependence of the difference between elliptic flow results obtained from the event plane and four-particle cumulant methods suggests a common origin of flow fluctuations up to $p_{\rm T}=8$ GeV/$c$. The magnitude of the (anti-)proton elliptic and triangular flow is larger than that of pions out to at least $p_{\rm T}=8$ GeV/$c$ indicating that the particle type dependence persists out to high $p_{\rm T}$.Comment: 16 pages, 5 captioned figures, authors from page 11, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/186