Experimental observation of the trapped rainbow

We report on the first experimental demonstration of the broadband "trapped rainbow" in the visible frequency range using an adiabatically tapered waveguide. Being a distinct case of the slow light phenomenon, the trapped rainbow effect could be applied to optical computing and signal processing, and to providing enhanced light-matter interactions.Comment: 2 pages, 1 figur

Critical Point Correlation Function for the 2D Random Bond Ising Model

High accuracy Monte Carlo simulation results for 1024*1024 Ising system with ferromagnetic impurity bonds are presented. Spin-spin correlation function at a critical point is found to be numerically very close to that of a pure system. This is not trivial since a critical temperature for the system with impurities is almost two times lower than pure Ising $T_c$. Finite corrections to the correlation function due to combined action of impurities and finite lattice size are described.Comment: 7 pages, 2 figures after LaTeX fil

Preservation of pre-generation undergrowth after development of cutting areas with multi-operation equipment

Задача лесного комплекса – сохранение и преумножение лесных богатств. На возобновление леса большое влияние оказывают способы заготовки древесины. Цель данной работы – изучение сохранности подроста после разработки лесосек многооперационной техникой. Для проведения исследования были подобраны четыре участка в Алапаевском лесничестве, два из которых зимней заготовки и два летней заготовки древесины. Учет сохранности подроста проводился по следующей программе: распределение количества учтенного подроста по породному составу, высотной структуре, жизненному состоянию в зависимости от удаленности от волока в глубь пасеки. Учет подроста проводился на учетных площадках размером 2 x 2 м в количестве 25 шт. на равном расстоянии друг от друга. Расположение учетных площадок было следующее: вдоль волока (по его центру), на расстоянии 1,0 м от края волока и в глубь пасеки на 4,0 м и 6,0 м. Таким образом на каждом участке было заложено по 100 учетных площадок. Подрост делился на следующие группы высот: растения высотой до 0,5 м представляют собой категорию мелкого подроста, 0,6–1,5 м – средний подрост и выше 1,5 м – крупный подрост. При зимней заготовке на волоках присутствует подрост всех пород-лесообразователей, а при летней заготовке – только сосновый подрост. Более 2/3 всего подроста учтенного на волоках, относится к жизнеспособному. На расстоянии 2,0 м от волока количество всходов при зимней заготовке невелико – не более 1,8 тыс. шт./га, а при летней – 4–4,5 тыс. шт./га. На расстоянии 2,0 м от волока зафиксировано максимальное количество поврежденного подроста, это связано с особенностью работы лесозаготовительной техники. А именно, в этой зоне происходит обрезка кроны и распиловка ствола дерева на сортименты и укладка их в пачки. При большей удаленности от волока, 4,0 и 6,0 м, сохранность, жизнеспособность и количество подроста выше независимо от сезона заготовки.The task of the forest complex is to preserve and increase the forest resources. On renewal of the forest is greatly affected by methods of harvesting forests. The purpose of this work: to study the safety of undergrowth after the development of cutting multi-operation technique. For the study, four sites were selected in the Alapaevsky forestry, two of which are winter harvesting and two summer harvesting of wood. Accounting for the safety of undergrowth was carried out according to the following program: the distribution of the number of recorded undergrowth by breed composition, height structure, life status, depending on the distance from the portage deep into the apiary. The accounting of the undergrowth was carried out on the accounting platforms of 2 x 2 size in the amount of 25 pieces at an equal distance from each other. The location of the accounting platforms was as follows: along the portage (in its center), at a distance of 1,0 m from the edge of the portage and into the depth of the apiary at 4,0 m and 6,0 m. Thus, 100 accounting platforms were laid on each site. The undergrowth was divided into the following groups of heights, m: plants with a height of 0,1–0,5 m are a category of small undergrowth, 0,6–1,5 m-medium undergrowth and above 1,5 m-large undergrowth. At winter preparation on volokah there is an undergrowth of all breeds of forest growers, and at summer preparation only pine undergrowth. More than 2/3 of the total undergrowth accounted for on the hairs refers to the viable. At a distance of 2,0 m from the portage, the number of seedlings during winter harvesting is not large – no more than 1,8 thousand pieces/ha, and in summer – 4–4,5 thousand pieces/ha. At a distance of 2,0 m from the portage, the maximum number of damaged undergrowth is recorded, this is due to the peculiarity of logging equipment. Namely, in this zone there is a pruning of the crown and sawing the tree trunk into segments and laying them in bundles. At a greater distance from the portage, 4,0 and 6,0, the safety, viability and number of undergrowth is higher regardless of the harvesting season

Anisotropic Metamaterials Emulated by Tapered Waveguides: Application to Optical Cloaking

We demonstrate that metamaterial devices requiring anisotropic dielectric permittivity and magnetic permeability may be emulated by specially designed tapered waveguides. This approach leads to low-loss, broadband performance. Based on this technique, we demonstrate broadband electromagnetic cloaking in the visible frequency range on a scale ~100 times larger than the wavelength.Comment: 4 pages, 4 figures, corrected reference

Pseudo-epsilon expansion and the two-dimensional Ising model

Starting from the five-loop renormalization-group expansions for the two-dimensional Euclidean scalar \phi^4 field theory (field-theoretical version of two-dimensional Ising model), pseudo-\epsilon expansions for the Wilson fixed point coordinate g*, critical exponents, and the sextic effective coupling constant g_6 are obtained. Pseudo-\epsilon expansions for g*, inverse susceptibility exponent \gamma, and g_6 are found to possess a remarkable property - higher-order terms in these expansions turn out to be so small that accurate enough numerical estimates can be obtained using simple Pade approximants, i. e. without addressing resummation procedures based upon the Borel transformation.Comment: 4 pages, 4 tables, few misprints avoide

Critical behavior of two-dimensional cubic and MN models in the five-loop renormalization-group approximation

The critical thermodynamics of the two-dimensional N-vector cubic and MN models is studied within the field-theoretical renormalization-group (RG) approach. The beta functions and critical exponents are calculated in the five-loop approximation and the RG series obtained are resummed using the Borel-Leroy transformation combined with the generalized Pad\'e approximant and conformal mapping techniques. For the cubic model, the RG flows for various N are investigated. For N=2 it is found that the continuous line of fixed points running from the XY fixed point to the Ising one is well reproduced by the resummed RG series and an account for the five-loop terms makes the lines of zeros of both beta functions closer to each another. For the cubic model with N\geq 3, the five-loop contributions are shown to shift the cubic fixed point, given by the four-loop approximation, towards the Ising fixed point. This confirms the idea that the existence of the cubic fixed point in two dimensions under N>2 is an artifact of the perturbative analysis. For the quenched dilute O(M) models ($MN$ models with N=0) the results are compatible with a stable pure fixed point for M\geq1. For the MN model with M,N\geq2 all the non-perturbative results are reproduced. In addition a new stable fixed point is found for moderate values of M and N.Comment: 26 pages, 3 figure

Acute Kidney Injury after Transcatheter Aortic Valve Implantation

Aim. The aim of the study was to evaluate the incidence and predictors of acute kidney injury (AKI) associated with transcatheter aortic valve implantation (TAVI).Material and methods. 50 patients (39 women, 11 men) aged 76 (71; 80) years who underwent TAVI were examined. One day after TAVI, blood creatinine level was determined by the Jaffe method and troponin I by a highly sensitive method (hs-cTnI). Acute kidney injury (AKI) was diagnosed according to the KDIGO criteria (2012). The following hospital complications were evaluated: cases of cardiac death, intraoperative myocardial infarction (MI), stroke and transient ischemic attack, permanent pacemaker implantation, recurrent paroxysms of atrial fibrillation.Results. History of MI had 22% of patients, percutaneous coronary intervention – 38%, hypertension – 98%, chronic kidney disease – 48%, diabetes mellitus – 24%, class II NYHA of chronic heart failure (CHF) – 52%, NYHA class III – 46%, NYHA class IV – 2%. The risk of operational mortality according to EuroSCORE II was 6.3±5.4%. AKI after TAVI was registered in 6 (12%) patients (1 grade AKI – 8%, 2 grade – 2%, 3 grade – 2%). Parameters associated with AKI after TAVI were higher CHF NYHA class (p=0,020), high hs-cTnI level (p=0,013), intraoperative MI (p=0.035). The predictor of AKI after TAVI was high hs-cTnI level (odds ratio 4.0, 95% confidence interval 1.0-16.1). Among patients with AKI after TAVI in compare with patients without AKI, the cumulative frequency of cardiac death, MI, strokes and transient ischemic attacks, implantation of a permanent pacemaker, the proportion of people with paroxysmal atrial fibrillation during the hospital stay was 5,8 times higher (66.7% vs 11.4% respectively, p=0.001).Conclusion. AKI after TAVI was present in 12% of patients. The predictor for AKI development was an increase in hs-cTnI level after TAVI implantation. The hospital prognosis after TAVI is worse in patients with postoperative AKI

Critical region of the random bond Ising model

We describe results of the cluster algorithm Special Purpose Processor simulations of the 2D Ising model with impurity bonds. Use of large lattices, with the number of spins up to $10^6$, permitted to define critical region of temperatures, where both finite size corrections and corrections to scaling are small. High accuracy data unambiguously show increase of magnetization and magnetic susceptibility effective exponents $\beta$ and $\gamma$, caused by impurities. The $M$ and $\chi$ singularities became more sharp, while the specific heat singularity is smoothed. The specific heat is found to be in a good agreement with Dotsenko-Dotsenko theoretical predictions in the whole critical range of temperatures.Comment: 11 pages, 16 figures (674 KB) by request to authors: [email protected] or [email protected], LITP-94/CP-0

The stability of a cubic fixed point in three dimensions from the renormalization group

The global structure of the renormalization-group flows of a model with isotropic and cubic interactions is studied using the massive field theory directly in three dimensions. The four-loop expansions of the \bt-functions are calculated for arbitrary $N$. The critical dimensionality $N_c=2.89 \pm 0.02$ and the stability matrix eigenvalues estimates obtained on the basis of the generalized Pad$\acute{\rm e}$-Borel-Leroy resummation technique are shown to be in a good agreement with those found recently by exploiting the five-loop \ve-expansions.Comment: 18 pages, LaTeX, 5 PostScript figure