VLT/UVES shows no cosmological variability of alpha

The cosmological variability of alpha is probed from individual observations of pairs of FeII lines. This procedure allows a better control of the systematics and avoids the influence of the spectral shifts due to ionization inhomogeneities in the absorbers and/or non-zero offsets between different exposures. Applied to the FeII lines of the metal absorption systems at zabs = 1.839 in Q1101--264 and at zabs = 1.15 in HE0515--4414 observed by means of UVES at the ESO-VLT, it provides da/a = 0.4 (+/- 1.5 stat)x10^{-6}. The result is shifted with respect to the Keck/HIRES mean da/a = -5.7(+/- 1.1 stat})x10^{-6} (Murphy et al. 2004) at a high confidence level (95%). Full details of this work are given in Levshakov et al (2005)Comment: 3 pages, 1 postscript figur

Nonlinearity Management in Optics: Experiment, Theory, and Simulation

We conduct an experimental investigation of nonlinearity management in optics using femtosecond pulses and layered Kerr media consisting of glass and air. By examining the propagation properties over several diffraction lengths, we show that wave collapse can be prevented. We corroborate these experimental results with numerical simulations of the (2+1)-dimensional focusing cubic nonlinear Schrödinger equation with piecewise constant coefficients and a theoretical analysis of this setting using a moment method

UVES radial velocity accuracy from asteroid observations. Implications for the fine structure constant variability

High resolution observations of the asteroids Iris and Juno have been performed by means of the UVES spectrograph at the ESO VLT to obtain the effective accurac y of the spectrograph's radial velocity. The knowledge of this quantity has impo rtant bearings on studies searching for a variability of the fine structure cons tant carried on with this instrument. Asteroids provide a precise radial velocit y reference at the level of 1 m/s which allows instrumental calibration and the recognition of small instrumental drifts and calibration systematics. In particu lar, radial velocity drifts due to non uniform slit illumination and slit optica l misalignment in the two UVES spectrograph arms can be investigated. The positi on of the solar spectrum reflected by the asteroids are compared with the solar wavelength positions or with that of asteroid observations at other epochs or wi th the twilight to asses UVES instrumental accuracy . Radial velocities offsets in the range 10--50 m/s are generally observed likely due to a non uniform slit illumination. However, no radial velocity patterns with wavelength are detected and the two UVES arms provide consistent radial velocities. These results suggest that the detected alpha variability by Levshakov et al. (2007) deduced from a drift of -180 (+/- 85) m/s at z =1.84, between two sets of FeII lines falling in the two UVES arms may be real or induced by other kinds of systematics than those investigated here. The proposed technique allows real time quality check of the spectrograph and should be followed for very accurate measurements.Comment: Accepted A&

Modulational instability in a layered Kerr medium: Theory and Experiment

We present the first experimental investigation of modulational instability in a layered Kerr medium. The particularly interesting and appealing feature of our configuration, consisting of alternating glass-air layers, is the piecewise-constant nature of the material properties, which allows a theoretical linear stability analysis leading to a Kronig-Penney equation whose forbidden bands correspond to the modulationally unstable regimes. We find very good {\it quantitative} agreement between theoretical, numerical, and experimental diagnostics of the modulational instability. Because of the periodicity in the evolution variable arising from the layered medium, there are multiple instability regions rather than just one as in the uniform medium.Comment: 4 pages, 4 figures, contains experimental + computational + theoretical results, to appear in Physical Review Letter

“Si Loko” sebagai Maskot PT. Kereta Api Indonesia

Upaya meningkatkan promosi dan komunikasi pemasaran, PT. Kereta Api Indonesia menetapkan Si Loko sebagai maskot PT. KAI dan juga duta yang memberikan berbagai informasi yang ingin diketahui oleh masyarakat pengguna kereta api. Si Loko adalah tokoh imajiner yang diciptakan untuk menjadi maskot PT. KAI yang digunakan untuk menyapa pelanggan dan stakeholder kereta api secara langsung. Sebagai duta PT. KAI, Si Loko juga merupakan wujud peningkatan pelayanan kepada pelanggan berkaitan dengan kebutuhan informasi produk maupun kebijakan yang dikeluarkan Perusahaan yang juga dapat digunakan sebagai media promosi dan komunikasi pemasaran. Penelitian ini bermaksud mengungkap maksud penunjukan, fungsi, dan penetapan Si Loko sebagai maskot PT Kereta Api Indonesia. Metode yang digunakan dalam penelitian ini adalah metode deskriptif kualitatif.Hasil penelitian menunjukan bahwa penetapan Si Loko Sebagai Maskot PT. Kereta Api Indonesia (Persero), dilakukan karena Perusahaan ingin menunjukkan sebuah Perubahan dimana Perusahaan tidak hanya mengembangkan sarana transportasinya saja, melainkan juga dapat memberikan harapan baru bagi pengembangan perkeretaapian di Indonesia yang semakin dekat dan peduli dengan masyarakat. Selain itu, Si Loko juga menjadi sarana mediator komunikasi antara Perusahaan dengan masyarakat