Crystal growth by precipitation under microgravity

The importance of understanding the mechanisms associated with defect generation during growth and the influence of gravity is stressed. An experiment is described. The advantages of adapting this experiment to the FES are then discussed. A brief survey of the ground based research under way is given

Against restructuring in modern French

Cinque (2002) examines those transparency effects that have been claimed to point to the existence of restructuring in French and concludes that quantifier and adverb climbing depend not on restructuring but, rather, on an irrealis context. In this paper, we show that restructuring does not play an active role in explaining the existence of en `of-it\u27 and y `there\u27 climbing or long movement in `easy-to-please\u27 constructions either, which leads to the conclusion that Modern French has no transparency effects of the restructuring kind. We then present three arguments against Cinque\u27s (2004) thesis that verbs of the restructuring class are universally functional verbs that appear with infinitives in a monoclausal configuration. Instead, we adopt the Cinque (2001)/Cardinaletti & Shlonsky (2004) approach according to which restructuring verbs can be merged either as lexical or functional verbs. We argue that this approach should be parametrized to yield three options that account for cross-linguistic/dialectal variation associated with restructuring

Identifying Phonologically Overt Counterparts to Silent Elements: The Case of French Exceptives

A relatively recent development in the generative framework is the hypothesis that there exist in syntax silent elements (SEs) that have a semantic content that is recovered by accessing their phonologically overt counterparts (cf. Kayne 2005, 2012 and Her and Tsai 2015, among others). In this paper, we provide a careful assessment of the two SEs that have been argued by O’Neill (2011) and Homer (2015) to be present in the French (ne)…que exceptive construction; namely silent rien ‘nothing’ and silent autre ‘other’. In doing so, we take to heart one of the main points made by Her and Tsai (2015) in relation to their criticism of Kayne (2012); namely, that for a proposed SE to be learnable, there cannot be any deviation in meaning from its overt counterpart. That is, the recoverability constraint assumed in the generative framework to be at work in, say, PF-deletion ellipsis, applies to all phonologically silent categories, including SEs. Additionally, as Her and Tsai argue, if semantic deviance between SEs and their phonologically overt counterparts were allowed, SEs would become ‘empirically intractable’. We argue that while positing a silent n-word in (ne)…que is faithful to the recoverability constraint on silent categories, the alleged second SE, namely, silent autre ‘other’, is not semantically equivalent to its phonologically overt counterpart in several respects. As we demonstrate, however, if one assumes instead that its overt counterpart is plus ‘more’, the recoverability requirement is restored

French Tough-Movement Infinitives as Deverbal Nominals

In this paper, we argue that predicates of the tough-class in French embed not a verbal infinitive but rather, a gerundive verbal noun. This hypothesis allows us to capture a number of unexpected restrictions on French tough-movement discussed by Legendre (1986). We show that these restrictions are best described as the inability of French tough-movement infinitives to be followed by complements that are disallowed in their corresponding argument-taking event nominals. Our analysis of such infinitives as nominalized elements correctly predicts that they should never be selected by auxiliaries, and that they should have suppressed external arguments in the sense of Grimshaw (1990)

Simulations of Time-Resolved X-Ray Diffraction in Laue Geometry

A method of computer simulation of Time-Resolved X-ray Diffraction (TRXD) in asymmetric Laue (transmission) geometry with an arbitrary propagating strain perpendicular to the crystal surface is presented. We present two case studies for possible strain generation by short-pulse laser irradiation: (i) a thermoelastic-like analytic model; (ii) a numerical model including effects of electron-hole diffusion, Auger recombination, deformation potential and thermal diffusion. A comparison with recent experimental results is also presented.Comment: 9 pages, 11 figure

Prediction for new magnetoelectric fluorides

We use symmetry considerations in order to predict new magnetoelectric fluorides. In addition to these magnetoelectric properties, we discuss among these fluorides the ones susceptible to present multiferroic properties. We emphasize that several materials present ferromagnetic properties. This ferromagnetism should enhance the interplay between magnetic and dielectric properties in these materials.Comment: 12 pages, 4 figures, To appear in Journal of Physics: Condensed Matte

Time dependence of Bragg forward scattering and self-seeding of hard x-ray free-electron lasers

Free-electron lasers (FELs) can now generate temporally short, high power x-ray pulses of unprecedented brightness, even though their longitudinal coherence is relatively poor. The longitudinal coherence can be potentially improved by employing narrow bandwidth x-ray crystal optics, in which case one must also understand how the crystal affects the field profile in time and space. We frame the dynamical theory of x-ray diffraction as a set of coupled waves in order to derive analytic expressions for the spatiotemporal response of Bragg scattering from temporally short incident pulses. We compute the profiles of both the reflected and forward scattered x-ray pulses, showing that the time delay of the wave $\tau$ is linked to its transverse spatial shift $\Delta x$ through the simple relationship $\Delta x = c\tau \cot\theta$, where $\theta$ is the grazing angle of incidence to the diffracting planes. Finally, we apply our findings to obtain an analytic description of Bragg forward scattering relevant to monochromatically seed hard x-ray FELs.Comment: 11 pages, 6 figure

Dynamical Diffraction Theory for Wave Packet Propagation in Deformed Crystals

We develop a theory for the trajectory of an x ray in the presence of a crystal deformation. A set of equations of motion for an x-ray wave packet including the dynamical diffraction is derived, taking into account the Berry phase as a correction to geometrical optics. The trajectory of the wave packet has a shift of the center position due to a crystal deformation. Remarkably, in the vicinity of the Bragg condition, the shift is enhanced by a factor $\omega /\Delta \omega$ ($\omega$: frequency of an x ray, $\Delta\omega$: gap frequency induced by the Bragg reflection). Comparison with the conventional dynamical diffraction theory is also made.Comment: 4 pages, 2 figures. Title change

Mn incorporation in as-grown and annealed (Ga,Mn)As layers studied by x-ray diffraction and standing-wave uorescence

A combination of high-resolution x-ray diffraction and a new technique of x-ray standing wave uorescence at grazing incidence is employed to study the structure of (Ga,Mn)As diluted magnetic semiconductor and its changes during post-growth annealing steps. We find that the film is formed by a uniform, single crystallographic phase epilayer covered by a thin surface layer with enhanced Mn concentration due to Mn atoms at random non-crystallographic positions. In the epilayer, Mn incorporated at interstitial position has a dominant effect on lattice expansion as compared to substitutional Mn. The expansion coeffcient of interstitial Mn estimated from our data is consistent with theory predictions. The concentration of interstitial Mn and the corresponding lattice expansion of the epilayer are reduced by annealing, accompanied by an increase of the density of randomly distributed Mn atoms in the disordered surface layer. Substitutional Mn atoms remain stable during the low-temperature annealing.Comment: 9 pages, 9 figure