Photonic Band Gaps of Three-Dimensional Face-Centered Cubic Lattices

We show that the photonic analogue of the Korringa-Kohn-Rostocker method is a viable alternative to the plane-wave method to analyze the spectrum of electromagnetic waves in a three-dimensional periodic dielectric lattice. Firstly, in the case of an fcc lattice of homogeneous dielectric spheres, we reproduce the main features of the spectrum obtained by the plane wave method, namely that for a sufficiently high dielectric contrast a full gap opens in the spectrum between the eights and ninth bands if the dielectric constant $\epsilon_s$ of spheres is lower than the dielectric constant $\epsilon_b$ of the background medium. If $\epsilon_s> \epsilon_b$, no gap is found in the spectrum. The maximal value of the relative band-gap width approaches 14% in the close-packed case and decreases monotonically as the filling fraction decreases. The lowest dielectric contrast $\epsilon_b/\epsilon_s$ for which a full gap opens in the spectrum is determined to be 8.13. Eventually, in the case of an fcc lattice of coated spheres, we demonstrate that a suitable coating can enhance gap widths by as much as 50%.Comment: 19 pages, 6 figs., plain latex - a section on coated spheres, two figures, and a few references adde

Photonic crystals of coated metallic spheres

It is shown that simple face-centered-cubic (fcc) structures of both metallic and coated metallic spheres are ideal candidates to achieve a tunable complete photonic bandgap (CPBG) for optical wavelengths using currently available experimental techniques. For coated microspheres with the coating width to plasma wavelength ratio $l_c/\lambda_p \leq 10$ and the coating and host refractive indices $n_c$ and $n_h$, respectively, between 1 and 1.47, one can always find a sphere radius $r_s$ such that the relative gap width $g_w$ (gap width to the midgap frequency ratio) is larger than 5% and, in some cases, $g_w$ can exceed 9%. Using different coatings and supporting liquids, the width and midgap frequency of a CPBG can be tuned considerably.Comment: 14 pages, plain latex, 3 ps figures, to appear in Europhys. Lett. For more info on this subject see http://www.amolf.nl/research/photonic_materials_theory/moroz/moroz.htm

Multiplicity Fluctuations in the Pion-Fireball Gas

The pion number fluctuations are considered in the system of pions and large mass fireballs decaying finally into pions. A formulation which gives an extension of the model of independent sources is suggested. The grand canonical and micro-canonical ensemble formulations of the pion-fireball gas are considered as particular examples.Comment: 13 pages, 4 figure

Target structure independent 7Li⃗^7\vec{Li} elastic scattering at low momentum transfers

Analyzing powers and cross sections for the elastic scattering of polarized 7Li by targets of 6Li, 7Li and 12C are shown to depend only on the properties of the projectile for momentum transfers of less than 1.0 fm-1. The result of a detailed analysis of the experimental data within the framework of the coupled channels model with ground state reorientation and transitions to the excited states of the projectile and targets included in the coupling schemes are presented. This work suggests that nuclear properties of weakly-bound nuclei can be tested by elastic scattering experiments, independent of the target used, if data are acquired for momentum transfers less than ~1.0 fm-1.Comment: 9 pages, 4 figures, 1 table, accepted in Phys. Lett.

Экспериментальные исследования ресурсных характеристик металлокомпозитных баллонов

Experimental and theoretical methods of studying life characteristics of metal-composite high-pressure cylinders are considered. It is shown that the stiffness of a load-bearing composite shell has a considerable effect on service life of the cylinders. Experimental results and their comparison with data of theoretical calculations are presented.Рассматриваются экспериментально-теоретические методы исследования ресурсных характеристик металлокомпозитных баллонов высокого давления. Показывается, что жесткость силовой композитной оболочки существенно влияет на ресурс баллонов. Приводятся экспериментальные результаты и их сопоставление с данными теоретических расчетов

Sequence Effects on DNA Entropic Elasticity

DNA stretching experiments are usually interpreted using the worm-like chain model; the persistence length A appearing in the model is then interpreted as the elastic stiffness of the double helix. In fact the persistence length obtained by this method is a combination of bend stiffness and intrinsic bend effects reflecting sequence information, just as at zero stretching force. This observation resolves the discrepancy between the value of A measured in these experiments and the larger ``dynamic persistence length'' measured by other means. On the other hand, the twist persistence length deduced from torsionally-constrained stretching experiments suffers no such correction. Our calculation is very simple and analytic; it applies to DNA and other polymers with weak intrinsic disorder.Comment: LaTeX; postscript available at http://dept.physics.upenn.edu/~nelson/index.shtm

Оценка эффективности ингаляционного колистина при нозокомиальной пневмонии

The aim of the study was the assessment of aerosolized colistin (AC) efficacy as adjunctive therapy to systemic antibiotic therapy for nosocomial pneumonia (NP).Materials and methods. This observation study included 90 NP patients under critical care. The primary criterion of therapy efficacy was NP resolution. As the secondary criteria of therapy efficacy, eradication of germs from sputum, the time to patients’ spontaneous breathing, the time in critical care unit, and mortality were evaluated. Patients were split into 2 groups: Gr.1 (n=48) — systemic antibiotics combined with AC; Gr. 2 (n=42) — systemic antibiotics cross over due to sensitivity. The groups were comparable in main characteristics. Aerosolized colistin was dosed 2 mln. U 3 times/day (Xellia Pharmaceuticals ApS, Denmark) in Gr. 1. The regimen of systemic antibiotic therapy was not changed upon AC prescription. Statistical analysis was carried out using Statistica 7.0 (M, σ, Newman—Keuls test; P<0.05).Results. This study has demonstrated efficacy of aerosolized colistin 2 mln. U 3 times/day as adjuvant therapy to systemic antibiotic therapy for NP caused by multidrug-resistant gram-negative germs: the NP resolution rate was 75% (versus 52% in Gr. 2, P=0.0295); eradication of pathogens by therapy day 7 was achieved in 80% in Gr. 1 and 60% Gr. 2 (n=12) (P>0.05); in Gr. 1, spontaneous breathing took place earlier than in Gr. 2 — 7.6±1.6 days in Gr. 1 versus 11.7±3.4 days in Gr. 2 (P=0.0000); in Gr. 1, the critical care unit duration was shorter than in Gr. 2 — 12.0±3.4 days in Gr. 1 versus 16.3±3.4 days in Gr. 2 (P=0.0000). Conclusions. Aerosolized colistin 2 mln. U 3 times a day is an effective adjuvant therapy combined with systemic antibiotic therapy for nosocomial pneumonia caused by multidrug-resistant gram-negative germs. This modified treatment assisted faster pneumonia resolution, earlier spontaneous breathing of patients, and shorter time in the intensive care unit. Addition of aerosolized colistin to systemic antibiotics should be regarded as a possible algorithm of treatment in a case of inefficient first-line antibiotic therapy.Целью исследования— оценка эффективности ингаляционного колистина (ИК) в качестве дополнения к системной антибиотикотерапии в лечении нозокомиальной пневмонии (НП).Материалы и методы. В данное обсервационное исследование было включено 90 реаниматологических пациентов с НП. В качестве основного критерия эффективности лечения оценивали разрешение НП. В качестве вторичных критериев эффективности лечения оценивали эрадикацию возбудителей из мокроты, время перевода больных на самостоятельное дыхание, время пребывания в отделении реаниматологии и летальность. Больных были разделены на 2 группы: Гр. 1 (n=48) — добавление ИК к системным антибиотикам; Гр. 2 (n=42) — смена системных антибиотиков в соответствии с чувствительностью. Группы были сравнимы по основным характеристикам. Ингаляционный колистин назначали в дозе 2 млн. ЕД 3 раза/сут. (Кселлия Фармасьютикалс АпС, Дания) в Гр. 1. Режим системной антибактериальной терапии при назначении ИК не меняли. Статистический анализ выполнили с помощью программного пакета Statistica 7.0 (M, σ, Newman—Keuls test; p<0,05).Результаты. В данном исследовании продемонстрировали эффективность ингаляционного колистина 2 млн. ЕД 3 р/сут. в качестве дополнения к системной антибактериальной терапии при лечении НП, вызванной полирезистентными грам-отрицательными возбудителями: частота разрешения ПН составила 75% (против 52% в Гр. 2, p=0.0295); эрадикация патогенных микроорганизмов к 7-м сут. лечения была достигнута у 80% в Гр. 1 и у 60% в Гр. 2 (n=12) (p>0,05); в Гр. 1 перевод на самостоятельное дыхание был выполнен раньше, чем в Гр. 2 — 7,6±1,6 сут. в Гр. 1 против 11,7±3,4 сут. в Гр. 2 (p=0.0000); в Гр. 1 сроки пребывания в отделении реаниматологии были меньше, чем в Гр. 2 — 12,0±3,4 сут. в Гр. 1 против 16,3±3,4 сут. в Гр. 2 (p=0.0000).Заключение. Применение ингаляционного колистина 2 млн. ЕД 3 р/сут. эффективно в качестве дополнения к системной антибактериальной терапии при лечении нозокомиальной пневмонии, вызванной полирезистентными грам-отрицательными возбудителями. Данное модифицированное лечение способствует более быстрому разрешению пневмонии, более раннему переводу пациентов на самостоятельное дыхание и сокращению сроков пребывания в отделении реаниматологии. Добавление ингаляционного колистина к системным антибиотикам следует рассматривать как возможный алгоритм лечения при неэффективности первой линии антибиотикотерапии

Thermal Fluctuations of Elastic Filaments with Spontaneous Curvature and Torsion

We study the effects of thermal flucutations on thin elastic filaments with spontaneous curvature and torsion. We derive analytical expressions for the orientational correlation functions and for the persistence length of helices, and find that this length varies non-monotonically with the strength of thermal fluctuations. In the weak fluctuation regime, the persistence length of a spontaneously twisted helix has three resonance peaks as a function of the twist rate. In the limit of strong fluctuations, all memory of the helical shape is lost.Comment: 1 figur