Broadband optical gain via interference in the free electron laser: principles and proposed realizations

We propose experimentally simplified schemes of an optically dispersive interface region between two coupled free electron lasers (FELs), aimed at achieving a much broader gain bandwidth than in a conventional FEL or a conventional optical klystron composed of two separated FELs. The proposed schemes can {\it universally} enhance the gain of FELs, regardless of their design when operated in the short pulsed regime

Evidence for Δ(2200)7/2−\Delta(2200)7/2^- from photoproduction and consequence for chiral-symmetry restoration at high mass

We report a partial-wave analysis of new data on the double-polarization variable $E$ for the reactions $\gamma p\to \pi^+ n$ and $\gamma p\to \pi^0 p$ and of further data published earlier. The analysis within the Bonn-Gatchina (BnGa) formalism reveals evidence for a poorly known baryon resonance, the one-star $\Delta(2200)7/2^-$. This is the lowest-mass $\Delta^*$ resonance with spin-parity $J^P=7/2^-$. Its mass is significantly higher than the mass of its parity partner $\Delta(1950)7/2^+$ which is the lowest-mass $\Delta^*$ resonance with spin-parity $J^P=7/2^+$. It has been suggested that chiral symmetry might be restored in the high-mass region of hadron excitations, and that these two resonances should be degenerate in mass. Our findings are in conflict with this prediction.Comment: 5 pages, 3 figures; Physics Letters B in pres

Quark Model and Neutral Strange Secondary Production by Neutrino and Antineutrino Beams

The experimental data on $K^0$ and $\Lambda$ production by $\nu$ and $\bar{\nu}$ beams are compared with the predictions of quark model assuming that the direct production of secondaries dominates. Disagreement of these predictions with the data allows one to suppose that there exists considerable resonance decay contribution to the multiplicities of produced secondaries.Comment: 6 pages, no figures, 2 table

Resonantly enhanced nonlinear optics in semiconductor quantum wells: An application to sensitive infrared detection

A novel class of coherent nonlinear optical phenomena, involving induced transparency in quantum wells, is considered in the context of a particular application to sensitive long-wavelength infrared detection. It is shown that the strongest decoherence mechanisms can be suppressed or mitigated, resulting in substantial enhancement of nonlinear optical effects in semiconductor quantum wells.Comment: 4 pages, 3 figures, replaced with revised versio

Communicative discourse of terminology used in gastronomical media culture

This article aims to analyze and describe the food discourse and terms of the French language, as well as to determine correlations with the French national and cultural worldview. The study also considers the current state of "gastronomical discourse" based on the French food semiotic and communicative mode

Изменение частоты неблагоприятных событий у пациентов с артериальной гипертензией II степени после перенесенной внегоспитальной пневмонии

гипертензияпневмония внегоспитальна

High-Resolution Study of the Inner Jet of M87 at 8 and 15 GHz

We present results of observation of a relativistic jet in M87 with sub-parsec resolution at 8 and 15 GHz. To obtain VLBI images, 10 Very Long Baseline Array antennas, one Very Large Array antenna (USA) and the Effelsberg telescope (Germany) were used. Synthesized images with a dynamic range higher than 20 000 : 1 clearly show a limb-brightened structure of the jet. A first reconstructed detailed spectral index map shows flattening of the spectrum along the spine of the resolved jet and at its edge. This may indicate hint at higher plasma flow velocity in the jet center an at friction between the jet edge and the surrounding material. This conclusion may support the “spine-envelope” model and explain the limb-brightening effect by the relativistic jet stratification. A measured spectrum of the faint feature in the direction of the counter jet proves that this is indeed the counter jet and not an optically thick jet origin.Представлены результаты наблюдений релятивистской струи в M87 с субпарсековым разрешением на 8 и 15 ГГц. Для получения РСДБ изображения были использованы 10 антенн Very Long Baseline Array, одна антенна Very Large Array (США) и радиотелескоп Effelsberg (Германия). Синтезированные карты демонстрируют высочайший динамический диапазон более 20 000 : 1. На них наблюдается поярчение к краю джета. Впервые полученная подробная карта распределения спектрального индекса демонстрирует уплощение радиоспектра вдоль хребта джета и у его края. Это может говорить о более высокой скорости течения плазмы в центре джета и о трении края выброса об окружающую среду. Данный вывод может служить поддержкой модели «хребет оболочка» и объяснением эффекта поярчения к краю стратификацией вещества релятивистской струи. Измеренный спектр области малой интенсивности в направлении против джета говорит в пользу того, что это именно контрджет, а не оптически толстое начало джета

First-principles Landau-like potential for BiFeO3_3 and related materials

In this work we introduce the simplest, lowest-order Landau-like potential for BiFeO$_3$ and La-doped BiFeO$_3$ as an expansion around the paraelectric cubic phase in powers of polarization, FeO$_6$ octahedral rotations and strains. We present an analytical approach for computing the model parameters from density functional theory. We illustrate our approach by computing the potentials for BiFeO$_3$ and La$_{0.25}$Bi$_{0.75}$FeO$_3$ and show that, overall, we are able to capture the first-principles results accurately. The computed models allow us to identify and explain the main interactions controlling the relative stability of the competing low-energy phases of these compounds.Comment: 12 pages, 6 figure