Current-sheet formation in incompressible electron magnetohydrodynamics

The nonlinear dynamics of axisymmetric, as well as helical, frozen-in vortex structures is investigated by the Hamiltonian method in the framework of ideal incompressible electron magnetohydrodynamics. For description of current-sheet formation from a smooth initial magnetic field, local and nonlocal nonlinear approximations are introduced and partially analyzed that are generalizations of the previously known exactly solvable local model neglecting electron inertia. Finally, estimations are made that predict finite-time singularity formation for a class of hydrodynamic models intermediate between that local model and the Eulerian hydrodynamics.Comment: REVTEX4, 5 pages, no figures. Introduction rewritten, new material and references adde

Tracking of Fluorescent Cells Based on the Wavelet Otsu Model

The mainstay of the project is to demonstrate that the proposed tracking scheme is more accurate and significantly faster than the other state-of-the-art tracking by model evolution approaches.The model is validated by comparing it to the original algorithm.The proposed tracking scheme involves two steps. First, coherence-enhancing diffusion filtering is applied on each frame to reduce the amount of noise and enhance flow-like structures. Second, the image segmentation is done by the Wavelet OTSU method in the fast level set-like and graph cut frameworks. This model evolution approach has also been extended to deal with many cells concurrently. The potential of the proposed tracking scheme and the advantages and disadvantages of both frameworks are demonstrated on 2-D and 3-D time-lapse series of mouse carcinoma cells

The Fermi-Pasta-Ulam recurrence and related phenomena for 1D shallow-water waves in a finite basin

In this work, different regimes of the Fermi-Pasta-Ulam (FPU) recurrence are simulated numerically for fully nonlinear "one-dimensional" potential water waves in a finite-depth flume between two vertical walls. In such systems, the FPU recurrence is closely related to the dynamics of coherent structures approximately corresponding to solitons of the integrable Boussinesq system. A simplest periodic solution of the Boussinesq model, describing a single soliton between the walls, is presented in an analytical form in terms of the elliptic Jacobi functions. In the numerical experiments, it is observed that depending on a number of solitons in the flume and their parameters, the FPU recurrence can occur in a simple or complicated manner, or be practically absent. For comparison, the nonlinear dynamics of potential water waves over nonuniform beds is simulated, with initial states taken in the form of several pairs of colliding solitons. With a mild-slope bed profile, a typical phenomenon in the course of evolution is appearance of relatively high (rogue) waves, while for random, relatively short-correlated bed profiles it is either appearance of tall waves, or formation of sharp crests at moderate-height waves.Comment: revtex4, 10 pages, 33 figure

Corruption dynamics in the post-crisis world

Corruption is typical for all states of the world, but its level differs significantly. In the present work, an attempt is made at spatio-temporal analysis of its changes through the period of 2012-2015 for the entire world and some particular large regions (Europe, Africa, Latin America, South-East Asia). Mean and median values of the corruption index are calculated, and specific indices reflecting the degree of differences in the distribution of corruption by countries between pairs of years are established. These specific indices are based on the correlation coefficient, the Quantified Czekanowski’s Coefficient and the Gower Index. The results of the analysis imply that the level of corruption in the world has hardly changed and remained generally high during the past four years. Some positive trends are observed only in Europe. The spatial dynamics was weak. This means that the level of corruption in the states almost did not change relatively to that in the other states. Essentially, this indicates the absence of competition between the countries for a better situation in terms of corruption. Clear tendencies are almost non-existent. Further discussion of the results suggests that the by-country distribution of corruption changed stronger in the cases of its very high and very low levels. The global financial (economic) crisis would facilitate multi-directional tendencies in the change of the corruption level and, consequently, the relatively intense dynamics. However, conclusions made in the present work point to the opposite. This may be explained by an insufficiently deep understanding of the factor of corruption and the fact that some countries with a relatively high level of corruption resisted the crisis successfully because of certain economic or geopolitical causes. Moreover, the administrative discretion that increased in the crisis times might have had its impact, too. Generally, the almost unchanged situation as regards corruption in the world does not allow for making optimistic prognoses about future economic development (also based on innovations), as well as it does not exclude the recurrence of crisis phenomena in the economy.Коррупция характерна для всех государств мира, однако ее уровень существенно различается. В настоящей работе предпринят пространственно-временной анализ его изменений за период 2012-2015 гг. для мира в целом и отдельных крупных регионов (Европа, Африка, Латинская Америка, Юго-Восточная Азия). Определялись средние и медианные значения показателя коррупции, а также рассчитывались специфические показатели, отражающие меру отличий в распределении коррупции по странам мира между двумя годами. Эти специфические показатели имеют в своей основе коэффициент корреляции, числовой коэффициент Чекановского и индекс Гоуэра. По результатам анализа установлено, что за последние четыре года уровень коррупции в мире практически не изменился и при этом остался сравнительно высоким. Некоторая позитивная тенденция отмечена лишь в Европе. Пространственная динамика была предельно слабой. Это означает, что уровень коррупции в одних государствах практически не менялся в сравнении с таковым в других. По сути это указывает на отсутствие конкуренции между странами за лучшую в отношении коррупции обстановку. Четко выраженных тенденций практически не прослеживается. Последующее обсуждение полученных результатов свидетельствует о том, что распределение коррупции по странам менялось гораздо сильнее при очень высоком и очень низком ее уровнях. Мировой финансовый (экономический) кризис должен был способствовать возникновению разнонаправленных тенденций изменения уровня коррупции в странах мира и, следовательно, достаточно интенсивной динамике. Однако сделанные в настоящей работе выводы свидетельствуют об обратном. Это может быть связано с недостаточно глубоким осознанием фактора коррупции и с тем, что целый ряд стран со сравнительно высоким уровнем коррупции в силу тех или иных экономических или геополитических причин достаточно успешно справился с кризисными явлениями. Кроме того, влияние могла оказать увеличившаяся во время кризиса управленческая дискреция. В целом практически неизменная ситуация с коррупцией в мире не позволяет делать оптимистических прогнозов в отношении будущего экономического развития (в т. ч. основанного на инновациях), равно как и не исключает повтора кризисных явлений в экономике

Fractures of the proximal humerus in children and adolescents

Background: In most children proximal humeral fractures are treated non-operatively with generally good results. The aim of the study was to evaluate the clinical outcome of closed/open reduction in children with severely displaced proximal humeral fractures. Materials and Methods: The charts of 15 patients (8 girls and 7 boys; mean age: 9.4 years) with proximal humeral fractures who were managed at our institution were reviewed from October 2011 to December 2013. Results: There were 7 metaphyseal fractures and 8 physeal injuries which were angulated according to Neer-Horowitz score as grade II (n=2), grade III(n=4) and grade IV(n=9). Associated lesions comprised open fracture with head trauma in a 2 year old female child which was operated on primarily and the 14 others by secondary intention. All patients were treated surgically with either closed (n = 5) or open (n=10) reduction and internal fixation with Kirschner wire or titanium elastic nails (TENs). They were assessed for clinical and radiological healing at a mean follow up of 1.25 years ranging from 0.5 to 2.0 years. Conclusion: Surgical option is indicated for severely displaced and unstable fractures in older children and adolescents. In addition to the periosteum , long head of the biceps, deltoid muscle, and bone fragments in combination can prevent fracture reduction. Key words: Proximal humerus fracture, Children, Open reduction, Operative

Nonlinear interfacial waves in a constant-vorticity planar flow over variable depth

Exact Lagrangian in compact form is derived for planar internal waves in a two-fluid system with a relatively small density jump (the Boussinesq limit taking place in real oceanic conditions), in the presence of a background shear current of constant vorticity, and over arbitrary bottom profile. Long-wave asymptotic approximations of higher orders are derived from the exact Hamiltonian functional in a remarkably simple way, for two different parametrizations of the interface shape.Comment: revtex, 4.5 pages, minor corrections, summary added, accepted to JETP Letter

Direct numerical simulation of a compressible boundary-layer flow past an isolated three-dimensional hump in a high-speed subsonic regime

This is the final version of the article. Available from American Physical Society via the DOI in this record.In this paper we study the boundary-layer separation produced in a high-speed subsonic boundary layer by a small wall roughness. Specifically, we present a direct numerical simulation (DNS) of a two-dimensional boundary-layer flow over a flat plate encountering a three-dimensional Gaussian-shaped hump. This work was motivated by the lack of DNS data of boundary-layer flows past roughness elements in a similar regime which is typical of civil aviation. The Mach and Reynolds numbers are chosen to be relevant for aeronautical applications when considering small imperfections at the leading edge of wings. We analyze different heights of the hump: The smaller heights result in a weakly nonlinear regime, while the larger result in a fully nonlinear regime with an increasing laminar separation bubble arising downstream of the roughness element and the formation of a pair of streamwise counterrotating vortices which appear to support themselves.This work was supported by the Laminar Flow Control Centre funded by Airbus/EADS and EPSRC under Grant No. EP/I037946 and computational resources were also provided through the UK Turbulence resource under EPSRC Grant No. EP/L000261/1. The authors would like to acknowledge the use of Imperial College High Performance Computing facility. S.J.S. would also like to acknowledge support under the RAEng Fellowship through Grant No. 10145/86

Altered lipid acyl chain length controls energy dissipation in light-harvesting complex II proteoliposomes by hydrophobic mismatch.

In plants, the major light-harvesting antenna complex (LHCII) is vital for both light harvesting and photoprotection in photosystem II. Previously, we proposed that the thylakoid membrane itself could switch LHCII into the photoprotective state, qE, via a process known as hydrophobic mismatch. The decrease in the membrane thickness that followed the formation of ΔpH was a key fact that prompted this idea. To test this, we made proteoliposomes from lipids with altered acyl chain length (ACL). Here, we show that ACL regulates the average chlorophyll fluorescence lifetime of LHCII. For liposomes made of lipids with an ACL of 18 carbons, the lifetime was ∼2 ns, like that for the thylakoid membrane. Furthermore, LHCII appears to be quenched in proteoliposomes with an ACL both shorter and longer than 18 carbons. The proteoliposomes made of short ACL lipids display structural heterogeneity revealing two quenched conformations of LHCII, each having characteristic 77 K fluorescence spectra. One conformation spectrally resembles isolated LHCII aggregates, whilst the other resembles LHCII immobilized in polyacrylamide gels. Overall, the decrease in the ACL appears to produce quenched conformations of LHCII, which renders plausible the idea that the trigger of qE is the hydrophobic mismatch