Rotational Activity Around an Obstacle in 2D Cardiac Tissue in Presence of Cellular Heterogeneity

Waves of electrical excitation rotating around an obstacle is one of the important mechanisms of dangerous cardiac arrhythmias occurring in the heart damaged by post-infarction scar. Such a scar also has a border zone around it, which has electrophysiological properties different from the rest of normal myocardial tissue. Spatial patterns of wave rotation in the presence of such tissue heterogeneity are poorly studied. In this paper we perform a comprehensive numerical study of various regimes of rotation of a wave in a plane layer of the ventricular tissue around an obstacle surrounded by a gray zone. We use a TP06 cellular ionic model which reproduces the electrophysiological properties cardiomyocytes in the left ventricle of human heart. We vary the extent of obstacle and gray zone and study the pattern of wave rotation and its period. We observed different regimes of wave rotation that can be subdivided into several classes: (1) functional rotation and (2) scar rotation regimes, which were identified in the previous studies, and new (3) gray zone rotation regime: where the wave instead of rotation around the obstacle, rotates around the gray zone (an area of tissue heterogeneity) itself. For each class, the period of rotation is determined by different factors, which we discuss and quantify. We also found that due to regional pathological remodeling of myocardial tissue, we can obtain additional regimes associated with dynamical instabilities of two types which may affect or not affect the period of rotation.

A REVIEW OF FLOW CONFLICTS AND SOLUTIONS IN SOFTWARE DEFINED NETWORKS (SDN)

Software Defined Networks (SDN) are a modern networking technology introduced to simplify network management via the separation of the data and control planes. Characteristically, flow entries are propagated between the control plane layer and application or data plane layers respectively while following flow table instructions through open flow protocol. More often than not, conflicts in flows occur as a result of traffic load and priority of instructions in the data plane. Several research works have been conducted on flow conflicts in SDN to reduce the effect of conflict. The flow conflict solutions in SDN have three main limitations. First, the OpenFlow table may still cause a defect in the security module according to the priority and action matching in the open flow in the control plane. Second, flow conflict detection requires more time for flow tracking and incremental update, whereas in such a case, delay affects the efficiency of SDN. Besides, the SDN algorithm and mechanism have substantially high memory requirement for instruction and proper functioning. Third, most of the available algorithms and detection methods used to avoid flow conflicts have not fully covered the security model policy. This study reviews these limitations and suggest solutions as future open research directions. ABSTRAK: Rangkaian Perisian Tertentu (SDN) adalah teknologi rangkaian moden yang diperkenalkan bagi memudahkan pengurusan rangkaian melalui pecahan data dan kawalan permukaan. Seperti biasa, aliran kemasukan disebar luas antara lapisan permukaan kawalan dan aplikasi atau lapisan permukaan data masing-masing, sambil mengikuti arahan meja melebar melalui protokol aliran terbuka. Kebiasaannya konflik dalam aliran berlaku disebabkan oleh beban trafik dan keutamaan arahan pada permukaan data. Beberapa kajian dibuat terhadap konflik aliran SDN bagi mengurangkan kesan konflik. Solusi konflik aliran dalam SDN mempunyai tiga kekurangan besar. Pertama, jadual Aliran Terbuka mungkin masih menyebabkan kekurangan dalam modul keselamatan berdasarkan keutamaan dan tindakan persamaan dalam aliran terbuka permukaan kawalan. Kedua, pengesanan aliran konflik memerlukan lebih masa bagi pengesanan aliran dan peningkatan kemaskini, kerana setiap penangguhan memberi kesan terhadap kecekapan SDN. Selain itu, algoritma SDN dan mekanisme memerlukan memori yang agak besar bagi memproses arahan dan berfungsi dengan baik. Ketiga, kebanyakan algoritma dan kaedah pengesanan yang digunakan bagi mengelak konflik pengaliran tidak sepenuhnya dilindungi polisi model keselamatan. Oleh itu, kajian ini meneliti kekurangan dan memberi cadangan penambahbaikan bagi arah tuju kajian masa depan yang terbuka.

О теории плоской линзы из материала с отрицательным преломлением

A rigorous theory of propagation of an electromagnetic wave from a point elementary current source is considered when it is focused by a plane layer filled with a material with a negative refractive index (Veselago lens). The distributions of the electromagnetic field in the focal region are investigated and its dimensions are determined. Key theoretical questions are discussed in detail.

Cosmic-Ray Driven Outflows to Mpc Scales from L* Galaxies

We study the effects of cosmic rays (CRs) on outflows from star-forming galaxies in the circum and inter-galactic medium (CGM/IGM), in high-resolution, fully-cosmological FIRE-2 simulations (accounting for mechanical and radiative stellar feedback, magnetic fields, anisotropic conduction/viscosity/CR diffusion and streaming, and CR losses). We showed previously that massive (Mhalo ≳ 1011 M⊙), low-redshift (z ≲ 1 − 2) halos can have CR pressure dominate over thermal CGM pressure and balance gravity, giving rise to a cooler CGM with an equilibrium density profile. This dramatically alters outflows. Absent CRs, high gas thermal pressure in massive halos “traps” galactic outflows near the disk, so they recycle. With CRs injected in supernovae as modeled here, the low-pressure halo allows “escape” and CR pressure gradients continuously accelerate this material well into the IGM in “fast” outflows, while lower-density gas at large radii is accelerated in-situ into “slow” outflows that extend to >Mpc scales. CGM/IGM outflow morphologies are radically altered: they become mostly volume-filling (with inflow in a thin mid-plane layer) and coherently biconical from the disk to >Mpc. The CR-driven outflows are primarily cool (T ∼ 105 K) and low-velocity. All of these effects weaken and eventually vanish at lower halo masses (≲ 1011 M⊙) or higher redshifts (z ≳ 1 − 2), reflecting the ratio of CR to thermal+gravitational pressure in the outer halo. We present a simple analytic model which explains all of the above phenomena. We caution that these predictions may depend on uncertain CR transport physics.

Theoretical Simulation of the Near-Field Probe for Non-Invasive Measurements on Planar Layers with Biological Characteristics

The article presents the design of the near-field probe, which is a combined emitter (a combination of a symmetric dipole and an annular frame). The design of the probe allows forming a prolonged zone of the near-field. This effect can be used for in-depth penetration of the field in media with high absorption, without loss of information. Particular attention in this article is given to a detailed study of the interaction of the field created by this probe on plane-layered biological media. A theoretical analysis of the interaction of the electromagnetic field was carried out in a wide frequency band with a model plane-layer biological medium containing blood vessels of shallow depth using the proposed probe design. Conclusions are drawn about the depth of penetration of a useful signal into different media-analogs of biological tissue. This study is necessary to consider the possibility of using this probe for non-invasive measurements of blood glucose concentration. The studies were carried out using numerical simulation in the CST (Computer Simulation Technology) Microwave Studio environment. All biological tissues were simulated over a wide frequency range from 10 MHz to 10 GHz.

Atmospheric carbon dioxide and climate

Atmospheric radiative fluxes are evaluated for the line-by-line model of spectral lines in considering the atmosphere as a weakly nonuniform plane layer and altitude profiles of its parameters are taken from the model of standard atmosphere. Concepts of molecular spectroscopy are combined with the local thermodynamic equilibrium for greenhouse gases and with information from HITRAN data base for parameters of radiative transitions. In addition, the energetic balance of the Earth allows one to determine the radiative flux from clouds. As a result, the algorithm is worked out for evaluation of the atmospheric radiative flux toward the Earth depending on its composition. We below concentrate on the change of atmospheric radiative fluxes as a result of doubling of the concentration of CO2 molecules. It is shown that the change of the global temperature in this case according to the above algorithm in 5-6 times exceeds that followed from climatological models which are based on old spectral data, rather than those from HITRAN data base. These codes ignore overlapping of spectral lines of atmospheric radiators.