Ferroelectricity in Non-Stoichiometric SrTiO\u3csub\u3e3\u3c/sub\u3e Films Studied by Ultraviolet Raman Spectroscopy

Homoepitaxial Sr1+xTiO3+δ films with -0.2 ≤ x ≤ 0.25 grown by reactive molecular-beam epitaxy on SrTiO3 (001) substrates have been studied by ultraviolet Raman spectroscopy. Non-stoichiometry for strontium- deficient compositions leads to the appearance of strong first-order Raman scattering at low temperatures, which decreases with increasing temperature and disappears at about 350 K. This indicates the appearance of a spontaneous polarization with a paraelectric-to-ferroelectric transition temperature above room temperature. Strontium-rich samples also show a strong first-order Raman signal, but the peaks are significantly broader and exhibit a less pronounced temperature dependence, indicating a stronger contribution of the disorder- activated mechanism in Raman scattering

Damage and repair classification in reinforced concrete beams using frequency domain data

This research aims at developing a new vibration-based damage classification technique that can efficiently be applied to a real-time large data. Statistical pattern recognition paradigm is relevant to perform a reliable site-location damage diagnosis system. By adopting such paradigm, the finite element and other inverse models with their intensive computations, corrections and inherent inaccuracies can be avoided. In this research, a two-stage combination between principal component analysis and Karhunen-Loéve transformation (also known as canonical correlation analysis) was proposed as a statistical-based damage classification technique. Vibration measurements from frequency domain were tested as possible damage-sensitive features. The performance of the proposed system was tested and verified on real vibration measurements collected from five laboratory-scale reinforced concrete beams modelled with various ranges of defects. The results of the system helped in distinguishing between normal and damaged patterns in structural vibration data. Most importantly, the system further dissected reasonably each main damage group into subgroups according to their severity of damage. Its efficiency was conclusively proved on data from both frequency response functions and response-only functions. The outcomes of this two-stage system showed a realistic detection and classification and outperform results from the principal component analysis-only. The success of this classification model is substantially tenable because the observed clusters come from well-controlled and known state conditions

LIGHT PHOTINOS AS DARK MATTER

There are good reasons to consider models of low-energy supersymmetry with very light photinos and gluinos. In a wide class of models the lightest $R$-odd, color-singlet state containing a gluino, the $\r0$, has a mass in the 1-2 GeV range and the slightly lighter photino, \pho, would survive as the relic $R$-odd species. For the light photino masses considered here, previous calculations resulted in an unacceptable photino relic abundance. But we point out that processes other than photino self-annihilation determine the relic abundance when the photino and $R^0$ are close in mass. Including \r0\longleftrightarrow\pho processes, we find that the photino relic abundance is most sensitive to the $\r0$-to-\pho mass ratio, and within model uncertainties, a critical density in photinos may be obtained for an $\r0$-to-\pho mass ratio in the range 1.2 to 2.2. We propose photinos in the mass range of 500 MeV to 1.6 GeV as a dark matter candidate, and discuss a strategy to test the hypothesis.Comment: uuencoded compressed tar file containing 32 page LaTeX file and eight postscript figure

Construction and Exploitation of a Bacterial Artificial Chromosome (BAC) Library for \u3cem\u3eLolium Perenne\u3c/em\u3e (Perennial Ryegrass)

BAC libraries are an important tool in genomics, enabling physical maps, genome sequencing, marker development and map based cloning strategies. A BAC library has therefore been generated for the temperate grass species Lolium perenne (perennial ryegrass) which compliments an existing BAC library of the closely related species, Festuca pratensis also generated by IGER. Moreover the L. perenne BAC library will provide a useful tool for grass comparative genomics to compliment the existing BAC libraries of cereal crops including rice, wheat, barley, Sorghum and maize. In particular it will allow a comparison of micro-synteny between this large genome forage crop species and the model small genome monocot species Orzya sativa

Comment on "Correlation between Compact Radio Lout Quasars and Ultrahigh Energy Cosmic Rays"

In a recent paper, Farrar and Biermann argue that there is a strong correlation between the direction of the five highest-energy cosmic-ray events and compact, radio-loud quasars. This Comment shows that this analysis contains several inconsistencies and errors so that the significance of any such correlation is certainly greatly overestimated and perhaps nonexistent.Comment: 2 pages, REVTE

New constraints on R-parity violation from \mu-e conversion in nuclei

We derive new constraints on the products of explicitly R-parity violating couplings $\lambda$ and $\lambda'$ in MSSM from searches for \mu-e conversion in nuclei. We concentrate on the loop induced photonic coherent conversion mode. For the combinations $|\lambda\lambda|$ which in \mu-e conversion can be probed only at loop level our constraints are in many cases more stringent than the previous ones due to the enhancement of the process by large $\ln(m^2_f/m^2_{\tilde f}).$ For the combinations of $|\lambda'\lambda'|$ the tree-level \mu-e conversion constraints are usually more restrictive than the loop ones except for two cases which involve the third generation. With the expected improvements in the experimental sensitivity, the \mu-e conversion will become the most stringent test for all the involved combinations of couplings.Comment: 15 pages, one figure included, needs elsart.st

Experiments to Find or Exclude a Long-Lived, Light Gluino

Gluinos in the mass range ~1 1/2 - 3 1/2 GeV are absolutely excluded. Lighter gluinos are allowed, except for certain ranges of lifetime. Only small parts of the mass-lifetime parameter space are excluded for larger masses unless the lifetime is shorter than ~ 2 10^{-11} (m_{gluino}/ GeV) sec. Refined mass and lifetime estimates for R-hadrons are given, present direct and indirect experimental constraints are reviewed, and experiments to find or definitively exclude these possibilities are suggested.Comment: 27 pp, latex with 1 uufiled figure, RU-94-35. New version amplifies discussion of some points and corresponds to version for Phys. Rev.

Correlation between Compact Radio Quasars and Ultra-High Energy Cosmic Rays

Some proposals to account for the highest energy cosmic rays predict that they should point to their sources. We study the five highest energy events (E>10^20 eV) and find they are all aligned with compact, radio-loud quasars. The probability that these alignments are coincidental is 0.005, given the accuracy of the position measurements and the rarity of such sources. The source quasars have redshifts between 0.3 and 2.2. If the correlation pointed out here is confirmed by further data, the primary must be a new hadron or one produced by a novel mechanism.Comment: 8 pages, 3 tables, revtex. with some versions of latex it's necessary to break out the tables and latex them separately using article.sty rather than revtex.st

Reconstructing f(R) model from Holographic DE: Using the observational evidence

We investigate the corresponding relation between $f(R)$ gravity and an interacting holographic dark energy. By obtaining conditions needed for some observational evidence such as, positive acceleration expansion of universe, crossing the phantom divide line and validity of thermodynamics second law in an interacting HDE model and corresponding it with $f(R)$ mode of gravity we find a viable $f(R)$ model which can explain the present universe. We also obtain the explicit evolutionary forms of the corresponding scalar field, potential and scale factor of universe.Comment: 11page. phys. Scr (2012