An exploratory study of the hard X-ray variability properties of PG quasars with RXTE

We have monitored with the RXTE PCA the variability pattern of the 2-20 keV flux in four PG quasars (QSOs) from the Laor et al. (1994) sample. Six observations of each target at regular intervals of 1 day were performed. The sample comprises objects with extreme values of Balmer line width (and hence soft X-ray steepness) and spans about one order of magnitude in luminosity. The most robust result is that the variability amplitude decreases as energy increases. Several options for a possible ultimate driver of the soft and hard X-ray variability, such as the influx rate of Comptonizing relativistic particles, instabilities in the accretion flow or the number of X-ray active sites, are consistent with our results.Comment: Contributed talk presented at the Joint MPE,AIP,ESO workshop on NLS1s, Bad Honnef, Dec. 1999, to appear in New Astronomy Reviews; also available at http://wave.xray.mpe.mpg.de/conferences/nls1-worksho

Massive Neutrinos and the Higgs Mass Window

If neutrino masses are produced by a see-saw mechanism the Standard Model prediction for the Higgs mass window (defined by upper (perturbativity) and lower (stability) bounds) can be substantially affected. Actually the Higgs mass window can close completely, which settles an upper bound on the Majorana mass for the right-handed neutrinos, $M$, ranging from $10^{13}$ GeV for three generations of quasi-degenerate massive neutrinos with $m_\nu\simeq 2$ eV, to $5\times 10^{14}$ GeV for just one relevant generation with $m_\nu\simeq 0.1$ eV. A slightly weaker upper bound on $M$, coming from the requirement that the neutrino Yukawa couplings do not develop a Landau pole, is also discussed.If neutrino masses are produced by a see-saw mechanism the Standard Model prediction for the Higgs mass window (defined by upper (perturbativity) and lower (stability) bounds) can be substantially affected. Actually the Higgs mass window can close completely, which settles an upper bound on the Majorana mass for the right-handed neutrinos, $M$, ranging from $10^{13}$ GeV for three generations of quasi-degenerate massive neutrinos with $m_\nu\simeq 2$ eV, to $5\times 10^{14}$ GeV for just one relevant generation with $m_\nu\simeq 0.1$ eV. A slightly weaker upper bound on $M$, coming from the requirement that the neutrino Yukawa couplings do not develop a Landau pole, is also discussed

Supersymmetry breaking with quasi-localized fields in orbifold field theories

We study the Scherk-Schwarz supersymmetry breaking in five-dimensional orbifold theories with five-dimensional fields which are not strictly localized on the boundaries (quasi-localized fields). We show that the Scherk-Schwarz (SS) mechanism, besides the SS parameter \omega, depends upon new parameters, e.g. supersymmetric five-dimensional odd mass terms, governing the level of localization on the boundaries of the five-dimensional fields and study in detail such a dependence. Taking into account radiative corrections, the value of \omega is dynamically allowed to acquire any value in the range 0< \omega < 1/2.Comment: 13 pages, 3 figure

The Standard Model instability and the scale of new physics

We apply a general formalism for the improved effective potential with several mass scales to compute the scale M of new physics which is needed to stabilize the Standard Model potential in the presence of a light Higgs. We find, by imposing perturbativity of the new physics, that M can be as large as one order of magnitude higher than the instability scale of the Standard Model. This implies that, with the present lower bounds on the Higgs mass, the new physics could easily (but not necessarily) escape detection in the present and future accelerators.Comment: latex2e, 12 pages, 3 figure

Anomalies in orbifold field theories

We study the constraints on models with extra dimensions arising from local anomaly cancellation. We consider a five-dimensional field theory with a U(1) gauge field and a charged fermion, compactified on the orbifold S^1/(Z_2 x Z_2'). We show that, even if the orbifold projections remove both fermionic zero modes, there are gauge anomalies localized at the fixed points. Anomalies naively cancel after integration over the fifth dimension, but gauge invariance is broken, spoiling the consistency of the theory. We discuss the implications for realistic supersymmetric models with a single Higgs hypermultiplet in the bulk, and possible cancellation mechanisms in non-minimal models.Comment: 10 pages, 2 figures, LaTex; v2: final version to be published in Phys. Lett.

Cross-correlation based high resolution electron backscatter diffraction and electron channelling contrast imaging for strain mapping and dislocation distributions in InAlN thin films

We describe the development of cross-correlation based high resolution electron backscatter diffraction (HR-EBSD) and electron channelling contrast imaging (ECCI), in the scanning electron microscope (SEM), to quantitatively map the strain variation and lattice rotation and determine the density and identify dislocations in nitride semiconductor thin films. These techniques can provide quantitative, rapid, non-destructive analysis of the structural properties of materials with a spatial resolution of order of tens of nanometers. HR-EBSD has a sensitivity to changes of strain and rotation of the order of 10−4 and 0.01° respectively, while ECCI can be used to image single dislocations up to a dislocation density of order 1010 cm−2. In the present work, we report the application of the cross-correlation based HR-EBSD approach to determine the tilt, twist, elastic strain and the distribution and type of threading dislocations in InAlN/AlN/GaN high electron mobility transistor (HEMT) structures grown on two different substrates, namely SiC and sapphire. We describe our procedure to estimate the distribution of geometrically necessary dislocations (GND) based on Nye-Kroner analysis and compare them with the direct imaging of threading dislocations (TDs) by ECCI. Combining data from HR-EBSD and ECCI observations allowed the densities of pure edge, mixed and pure screw threading dislocations to be fully separated

ИССЛЕДОВАНИЕ УСЛОВИЙ ЗАЛЕГАНИЯ, СОСТАВА И СВОЙСТВ УРАНОВЫХ МЕСТОРОЖДЕНИЙ МОНГОЛИИ

Представлены результаты промышленных и лабораторных исследований условий залегания, состава и свойств урановых месторождений Монголии. Выполнены механические, геофизические и геохимические исследования вещественных и радиологических свойств урановых ру

Culinary tourism as a cultural experience. the case study of the city of Cáceres (Spain)

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Spatiotemporal gender differences in urban vibrancy

This is the final version. Available on open access from SAGE Publications via the DOI in this recordData availability statement: The mobile phone data used in this manuscript was made openly available to researchers as part of Telecom Italia Big Data Challenge 2015. The full data set is no longer available via Telecom Italia, but aggregate data to reproduce our results can be made available from the authors upon reasonable request. OpenStreetMap data is openly available at www.openstreetmap.org. The Italian census data used here is available at www.istat.it/it/archivio/222527Urban vibrancy is the dynamic activity of humans in urban locations. It can vary with urban features and the opportunities for human interactions, but it might also differ according to the underlying social conditions of city inhabitants across and within social surroundings. Such heterogeneity in how different demographic groups may experience cities has the potential to cause gender seg regation because of differences in the preferences of inhabitants, their accessibility and oppor tunities, and large-scale mobility behaviours. However, traditional studies have failed to capture fully a high-frequency understanding of how urban vibrancy is linked to urban features, how this might differ for different genders, and how this might affect segregation in cities. Our results show that (1) there are differences between males and females in terms of urban vibrancy, (2) the differences relate to ‘Points of Interest’ as well as transportation networks, and (3) there are both positive and negative ‘spatial spillovers’ existing across each city. To do this, we use a quantitative approach using Call Detail Record data – taking advantage of the near-ubiquitous use of mobile phones – to gain high-frequency observations of spatial behaviours across Italy’s seven most prominent cities. We use a spatial model comparison approach of the direct and ‘spillover’ effects from urban features on male-female differences. Our results increase our understanding of inequality in cities and how we can make future cities fairer