Magnetic and Optical properties of strained films of multiferroic GdMnO3

The effects of strain on a film of mulitferroic GdMnO3 are investigated using both magnetometry and magneto-optic spectroscopy. Optical spectra, in the energy range 1.5eV - 3.5eV, were taken in Faraday geometry in an applied magnetic field and also at remanence. This yielded rich information on the effects of strain on the spin ordering in these films. Epitaxial films of GdMnO3 were grown on SrTiO3 and LaAlO3 substrates. The LaAlO3 was twinned and so produced a highly strained film whereas the strain was less for the film grown on SrTiO3. The Ne\'el temperatures and coercive fields were measured using zero field data and hysteresis loops obtained using a SQUID magnetometer. Optical absorption data agreed with earlier work on bulk materials. The two well known features in the optical spectrum, the charge transfer transition between Mn d states at ~2eV and the band edge transition from the oxygen p band to the d states at ~3eV are observed in the magnetic circular dichroism; however they behaved very differently both as a function of magnetic field and temperature. This is interpreted in terms of the magnetic ordering of the Mn spins.Comment: 9 pages of text including figure

Direct amplitude-phase near-field observation of higher-order anapole states

Anapole states associated with the resonant suppression of electric-dipole scattering exhibit minimized extinction and maximized storage of electromagnetic energy inside a particle. Using numerical simulations, optical extinction spectroscopy and amplitude-phase near-field mapping of silicon dielectric disks, we demonstrate high-order anapole states in the near-infrared wavelength range (900-1700 nm). We develop the procedure for unambiguously identifying anapole states by monitoring the normal component of the electric near-field and experimentally detect the first two anapole states as verified by far-field extinction spectroscopy and confirmed with the numerical simulations. We demonstrate that higher order anapole states possess stronger energy concentration and narrower resonances, a remarkable feature that is advantageous for their applications in metasurfaces and nanophotonics components, such as non-linear higher-harmonic generators and nanoscale lasers

Nanometric TiO 2 as NBBs for functional organic-inorganic hybrids with efficient interfacial charge transfer

International audienceThe purpose of this work is to establish a fabrication method for new electronic materials: organic-inorganic p-MAPTMS / titanium-oxo-alkoxy hybrids. The size-selected 5.2-nm TiO 2 nanoparticles (Nano Building Blocks-NBB) are generated in a sol-gel reactor with turbulent fluids micromixing. The surface exchange between propoxy and MAPTMS groups under vacuum pumping results in a stable nanoparticulate precursor available for 2-photon laser polymerisation. The hybrids demonstrate quantum yield of photoinduced charges separation 6 % and can steadily trap photoinduced electrons at number density of 6% Ti atoms. The materials are suitable for 3D-microstructuring

Recent X-ray measurements of the accretion-powered pulsar 4U 1907+09

X-ray observations of the accreting X-ray pulsar 4U~1907+09, obtained during February 1996 with the Proportional Counter Array on the Rossi X-ray Timing Experiment (RXTE), have enabled the first measurement of the intrinsic pulse period Ppulse since 1984: Ppulse=440.341[+0.012,-0.017] s. 4U 1907+09 is in a binary system with a blue supergiant. The orbital parameters were solved and this enabled the correction for orbital delay effects of a measurement of Ppulse obtained in 1990 with Ginga. Thus, three spin down rates could be extracted from four pulse periods obtained in 1983, 1984, 1990, and 1996. These are within 8% equal to a value of dPpulse/dt=+0.225 s/yr. This suggest that the pulsar is perhaps in a monotonous spin down mode since its discovery in 1983. Furthermore, the RXTE observations show transient ~18 s oscillations during a flare that lasted about 1 hour. The oscillations may be interpreted as Keplerian motion of an accretion disk near the magnetospheric radius. This, and the notion that the co-rotation radius is much larger than any conceivable value for the magnetospheric radius (because of the long spin period), renders it unlikely that this pulsar spins near equilibrium like is suspected for other slowing accreting X-ray pulsars. We suggest as an alternative that perhaps the frequent occurrence of a retrograde transient accretion disk may be consistently slowing the pulsar down. Further observations of flares can provide more evidence of this.Comment: 26 pages, 11 figures, to be published in Astrophysical Journal part I on March 20, 199

СТАТИСТИЧЕСКИЙ АНАЛИЗ ПОВРЕЖДАЕМОСТИ РАБОЧИХ ЛОПАТОК КОМПРЕССОРОВ ДВУХКОНТУРНЫХ ТУРБОРЕАКТИВНЫХ ДВИГАТЕЛЕЙ

Aircraft gas turbine engines during the operation are exposed to damage of flowing parts. The elements of the engine design, appreciably determining operational characteristics are rotor blades. Character of typical damages for various types of engines depends on appointment and a geographical place of the aircraft operation on which one or another engine is installed. For example, the greatest problem for turboshaft engines operated in the dusty air conditions is erosive wear of a rotor blade airfoil. Among principal causes of flowing parts damages of bypass engine compressors are foreign object damages. Independently there are the damages caused by fatigue of a rotor blade material at dangerous blade mode. Pieces of the ice formed in the input unit, birds and the like can also be a source of danger. The foreign objects getting into the engine from runway are nuts, bolts, pieces of tire protectors, lock-wire, elements from earlier flying off aircraft, etc. The entry of foreign objects into the engine depends on both an operation mode (during the operation on the ground, on takeoff, on landing roll using the reverse and so on), and the aircraft engine position.Thus the foreign objects entered into the flowing path of bypass engine damage blade cascade of low and high pressure. Foreign objects entered into the flowing part of the engine with rotor blades result in dents on edges and blade shroud, deformations of edges, breakage, camber of peripheral parts and are distributed "nonlinear" on path length (steps). The article presents the results of the statistical analysis of three types engine compressors damageability over the period of more than three years. Damages are divided according to types of engines in whole and to their separate steps, depths and lengths, blades damage location. The results of the analysis make it possible to develop recommendations to carry out the optical-visual control procedures.Авиационные газотурбинные двигатели в процессе эксплуатации подвержены повреждениям проточных частей. Элементами конструкции двигателей, в значительной мере определяющими их эксплуатационные характеристики, являются рабочие лопатки. Характер типичных повреждений для различных типов двигателей зависит от назначения и места эксплуатации воздушного судна, на котором установлен тот или иной двигатель. Например, для турбовальных двигателей, эксплуатируемых в условиях запыленного воздуха, наибольшую проблему представляет эрозионный износ пера рабочих лопаток. Среди основных причин повреждений проточных частей компрессоров турбореактивных двухконтурных двигателей выделяются повреждения от попадания посторонних предметов. Особняком стоят повреждения, вызванные усталостью материала рабочих лопаток при опасных резонансных колебаниях. Посторонние предметы могут попасть в двигатель с взлетно-посадочной полосы; кроме того, опасность представляют куски льда, образовавшегося во входном устройстве, птицы и т. п. В роли предметов, попадающих в двигатель с взлетно-посадочной полосы, выступают куски бетона взлетно-посадочной полосы, льда, гайки, болты, куски протекторов шин, контровочная проволока и подобные элементы от ранее взлетавших воздушных судов. Попадание посторонних предметов в двигатель зависит как от режима работы (при работе на месте, при гонке, на взлете, при пробеге на посадке с использованием реверсивного устройства и т. п.), так и от расположения двигателя на воздушном судне.При этом предметы, попавшие в проточную чаcть двигателей, повреждают лопатки каскада как низкого, так и высокого давления. Результаты взаимодействия предметов, попавших в проточную часть двигателя, с рабочими лопатками выражаются в появлении забоин по кромкам, перу и антивибрационным полкам (при наличии) лопаток, деформациях кромок, обрывам, отгибам периферийных частей и распределяются «нелинейно» по длине тракта (ступеням).В статье приводятся результаты статистического анализа повреждаемости компрессоров двигателей трех типов за период более трех лет. Рассмотрены распределения видов повреждений по типам двигателей в целом и их отдельным ступеням, глубин и длин повреждений по кромкам внутри ступеней и положения мест повреждений от торца рабочих лопаток, в зависимости от времени года в целом по узлам и по ступеням. Результаты анализа позволяют выработать рекомендации к проведению процедур оптико-визуального контроля

Fabrication of submicron structures by three-dimensional laser lithography

As a demonstration of unique capabilities of three dimensional laser lithography, an example complex shape microobject and photonic crystals with “woodpile” structure for the infrared spectral range are fabricated by this technique. Photonic dispersion relations for the woodpile structure are calculated for different values of the permittivity contrast and the filling factor.This study was partially supported by the Government of the Russian Federation (project no. 074U01) and the Russian Foundation for Basic Research (project no. 130200186)

405-nm pumped Ce3+-doped silica fiber for broadband fluorescence from cyan to red

A pure Ce-doped silica fiber is fabricated using modified chemical vapor deposition (MCVD) technique. Fluorescence characteristics of a Ce-doped silica fiber are experimentally investigated with continuous wave pumping from 440 nm to 405 nm. Best pump absorption and broad fluorescence spectrum is observed for ~ 405 nm laser. Next, the detailed analysis of spectral response as a function of pump power and fiber length is performed. It is observed that a -10dB spectral width of ~ 280 mn can be easily achieved with different combinations of the fiber length and pump power. Lastly, we present, for the first time to the best of our knowledge, a broadband fluorescence spectrum with -10dB spectral width of 301 nm, spanning from ~ 517.36 nm to ~ 818 nm, from such fibers with non-UV pump lasers