A characteristic frequency of two mutually interacting gas bubbles in an acoustic field

Transition frequencies of two spherical gas bubbles interacting in an acoustic field are discussed theoretically. In the present study, transition frequency is defined as the frequency of external sound for which the phase difference between a bubble's pulsation and the external sound is $\pi / 2$. It is shown by a linear theory that a bubble interacting with a neighboring bubble has three (or fewer) transition frequencies but only two natural frequencies. This result means that the bubble has a characteristic frequency besides the natural frequencies.Comment: 14 pages, 5 figures, elsart, "Eigenfrequency" replaced with "transition frequency" and a reference added, accepted for publication in Phys. Lett.

Exact Diagonalisation of The XY-Hamiltonian of Open Linear Chains with Periodic Coupling Constants and Its Application to Dynamics of One-Dimensional Spin Systems

A new method of diagonalisation of the XY-Hamiltonian of inhomogeneous open linear chains with periodic (in space) changing Larmor frequencies and coupling constants is developed. As an example of application, multiple quantum dynamics of an inhomogeneous chain consisting of 1001 spins is investigated. Intensities of multiple quantum coherences are calculated for arbitrary inhomogeneous chains in the approximation of the next nearest interactions. {\it Key words:} linear spin chain, nearest--neighbour approximation, three--diagonal matrices, diagonalisation, fermions, multiple--quantum NMR, multiple--quantum coherence, intensities of multiple--quantum coherences. {\it PACS numbers:} 05.30.-d; 76.20.+qComment: 21 pages + 1 figure (to download separately via ps-format

Excitation of extraordinary modes inside the source of Saturn's kilometric radiation

The electron cyclotron maser instability (ECMI) of extraordinary mode waves was investigated with the parameters observed in Saturn's kilometric radiation (SKR) sources. Previous studies employed simplified dispersion relations, and did not consider the excitation of the relativistic (R) mode. This mode is introduced by considering the relativistic effect in plasmas consisting of both cold and hot electrons. Using particle-in-cell simulations, we investigated the excitation of R and X modes based on the measured data. Using the reported value of the density ratio of energetic to total electrons $n_e/n_0=24\%$, the most unstable mode is the R mode. The escaping X-mode emissions are amplified only if the energetic electrons are dominant with $n_e/n_0 \ge 90\%$. For these cases, only the X mode is excited and the R mode disappears due to its strong coupling. The results are well in line with the linear kinetic theory of ECMI. The properties of both the R and X modes are consistent with the observed SKR emissions. This raises questions about the nature of the measured electric field fluctuations within ``presumed'' SKR sources. The study provides new insights into the ECMI process relevant to SKR emission mechanisms

Nonradiating anapole modes in dielectric nanoparticles

Nonradiating current configurations attract attention of physicists for many years as possible models of stable atoms. One intriguing example of such a nonradiating source is known as 'anapole'. An anapole mode can be viewed as a composition of electric and toroidal dipole moments, resulting in destructive interference of the radiation fields due to similarity of their far-field scattering patterns. Here we demonstrate experimentally that dielectric nanoparticles can exhibit a radiationless anapole mode in visible. We achieve the spectral overlap of the toroidal and electric dipole modes through a geometry tuning, and observe a highly pronounced dip in the far-field scattering accompanied by the specific near-field distribution associated with the anapole mode. The anapole physics provides a unique playground for the study of electromagnetic properties of nontrivial excitations of complex fields, reciprocity violation and Aharonov-Bohm like phenomena at optical frequencies.The work of A.E.M. was supported by the Australian Research Council via Future Fellowship program (FT110100037). The authors at DSI were supported by DSI core funds. Fabrication, Scanning Electron Microscope Imaging and NSOM works were carried out in facilities provided by SnFPC@DSI (SERC Grant 092 160 0139). Zhen Ying Pan (DSI) is acknowledged for SEM imaging. Yi Zhou (DSI) is acknowledged for silicon film growth. Leonard Gonzaga (DSI), Yeow Teck Toh (DSI) and Doris Ng (DSI) are acknowledged for development of the silicon nanofabrication procedure. B.N.C. acknowledges support from the Government of Russian Federation, Megagrant No. 14.B25.31.0019

Результати АВС-, VEN- та частотного аналізів фармакотерапії позалікарняної пневмонії у дітей в закладах охорони здоров’я

The comprehensive assessment of the real financial costs of pharmacotherapy of the community-acquired pneumonia in children in specific clinics of Kharkiv and Sumy has been carried out with the help of auxiliary pharmacoeconomic methods such as ABC-, VEN- and frequency analyses. In each clinic as many as 100 case histories with drug charts of patients with the community-acquired pneumonia at the age from 10 to 12 in each clinic have been analysed. The study duration was 6 months of 2012. It has been found that the main directions of pharmacotherapy in children in the clinic of Kharkiv and in the clinic of Sumy correspond to the Ukrainian clinical protocol of treating disease, but the assortment of the drugs prescribed, the number and the level of implementation of the formulary system in these clinics are different. According to the results of the “formal” VEN-analysis it has been determined that the majority of the drugs prescribed in both clinics (73.91% – Kharkov, 88.04% – Sumy) are present in the State formulary of Ukraine. With the help of the results of the integrated ABC/VEN/frequency analysis it has been found that these drugs are the most part of the doctors’ presciptions (82.78% – Kharkov, 86.55% – Sumy), the main sum of money (Kharkov – 92.37%, Sumy – 92.02%) for pharmacotherapy of the patients under study has been spent on these drugs. In general, the financial costs for pharmacotherapy of pediatric patients with the community-acquired pneumonia in the healthcare institutions studied in Kharkiv and Sumy can be considered to be rational and economically reasonable, but the approaches to pharmacotherapy require further correction in accordance with the State formulary of Ukraine.Проведена сравнительная комплексная оценка реальных финансовых затрат на фармакотерапию внебольничной пневмонии у детей в конкретных клиниках г. Харькова и г. Сумы с помощью вспомогательных фармакоэкономических методов – АВС-, VEN- и частотного анализов. В каждой клинике проанализировано по 100 историй болезни с листами назначений пациентов с внебольничной пневмонией в возрасте от 10 до 12 лет. Продолжительность исследования – 6 месяцев 2012 года. Установлено, что основные направления проведения фармакотерапии внебольничной пневмонии у детей в клинике г. Харькова и в клинике г. Сумы соответствуют украинскому клиническому протоколу лечения заболевания, но отличаются ассортиментом назначенных лекарственных препаратов, их количеством и уровнем внедрения формулярной системы в данных клиниках.По результатам «формального» VEN-анализа определено, что в обеих клиниках преимущественное большинство назначенных лекарственных препаратов (73,91% – г. Харьков, 88,04% – г. Сумы) присутствуют в Государственном формуляре Украины. С помощью интегрированного АВС/VEN/частотного анализа установлено, что указанные препараты составляют большую часть назначений врачей (82,78% – г. Харьков, 86,55% – г. Сумы) и на них потрачена основная часть денежных средств (г. Харьков – 92,37%, г. Сумы – 92,02%), связанных с фармакотерапией исследуемых пациентов. В целом финансовые затраты на фармакотерапию пациентов детского возраста с внебольничной пневмонией в исследуемых учреждениях здравоохранения г. Харькова и г. Сумы можно считать рациональными и экономически целесообразными, но подходы к фармакотерапии требуют дальнейшей коррекции в соответствии с Государственным формуляром Украины.Проведена порівняльна комплексна оцінка реальних фінансових витрат на фармакотерапію позалікарняної пневмонії у дітей у певних клініках м. Харкова та м. Суми за допомогою допоміжних фармакоекономічних методів – АВС-, VEN- та частотного аналізів. У кожній клініці проаналізовано по 100 історій хвороб з листами призначень пацієнтів з позалікарняною пневмонією віком від 10 до 12 років. Тривалість дослідження – 6 місяців 2012 року. Встановлено, що основні напрямки проведення фармакотерапії позалікарняної пневмонії у дітей в клініці м. Харкова та в клініці м. Суми відповідають українському клінічному протоколу лікування захворювання, але відрізняються асортиментом призначених лікарських препаратів, їх кількістю та рівнем впровадження формулярної системи в даних клініках. За результатами «формального» VEN-аналізу визначено, що в обох клініках переважна більшість призначених лікарських препаратів (73,91% – м. Харків, 88,04% – м. Суми) наявна в Державному формулярі України. За допомогою інтегрованого АВС/VEN/частотного аналізу встановлено, що зазначені препарати складають більшу частину лікарських призначень (82,78% – м. Харків, 86,55% – м. Суми) і на них витрачена основна частина грошових коштів (м. Харків – 92,37%, м. Суми – 92,02%), пов’язаних з фармакотерапією досліджуваних пацієнтів. У цілому фінансові витрати на фармакотерапію пацієнтів дитячого віку з позалікарняною пневмонією в досліджуваних закладах охорони здоров’я м. Харкова та м. Суми можна вважати раціональними та економічно доцільними, але підходи до фармакотерапії потребують подальшої корекції відповідно до Державного формуляра України

Search for sterile neutrinos at the DANSS experiment

DANSS is a highly segmented 1~m${}^3$ plastic scintillator detector. Its 2500 one meter long scintillator strips have a Gd-loaded reflective cover. The DANSS detector is placed under an industrial 3.1~$\mathrm{GW_{th}}$ reactor of the Kalinin Nuclear Power Plant 350~km NW from Moscow. The distance to the core is varied on-line from 10.7~m to 12.7~m. The reactor building provides about 50~m water-equivalent shielding against the cosmic background. DANSS detects almost 5000 $\widetilde\nu_e$ per day at the closest position with the cosmic background less than 3$\%$. The inverse beta decay process is used to detect $\widetilde\nu_e$. Sterile neutrinos are searched for assuming the $4\nu$ model (3 active and 1 sterile $\nu$). The exclusion area in the $\Delta m_{14}^2,\sin^22\theta_{14}$ plane is obtained using a ratio of positron energy spectra collected at different distances. Therefore results do not depend on the shape and normalization of the reactor $\widetilde\nu_e$ spectrum, as well as on the detector efficiency. Results are based on 966 thousand antineutrino events collected at 3 distances from the reactor core. The excluded area covers a wide range of the sterile neutrino parameters up to $\sin^22\theta_{14}<0.01$ in the most sensitive region.Comment: 10 pages, 13 figures, version accepted for publicatio

A Metalens with Near-Unity Numerical Aperture

The numerical aperture (NA) of a lens determines its ability to focus light and its resolving capability. Having a large NA is a very desirable quality for applications requiring small light-matter interaction volumes or large angular collections. Traditionally, a large NA lens based on light refraction requires precision bulk optics that ends up being expensive and is thus also a specialty item. In contrast, metasurfaces allow the lens designer to circumvent those issues producing high NA lenses in an ultra-flat fashion. However, so far, these have been limited to numerical apertures on the same order of traditional optical components, with experimentally reported values of NA <0.9. Here we demonstrate, both numerically and experimentally, a new approach that results in a diffraction limited flat lens with a near-unity numerical aperture (NA>0.99) and sub-wavelength thickness (~{\lambda}/3), operating with unpolarized light at 715 nm. To demonstrate its imaging capability, the designed lens is applied in a confocal configuration to map color centers in sub-diffractive diamond nanocrystals. This work, based on diffractive elements able to efficiently bend light at angles as large as 82{\deg}, represents a step beyond traditional optical elements and existing flat optics, circumventing the efficiency drop associated to the standard, phase mapping approach.Comment: 12 pages, 5 figure