Ytterbium doped nano-crystalline optical fiber for reduced photodarkening

We report suppression of photodarkening in Yb-doped nano-crystalline fibers in silica host. The photodarkening induced loss reduced by 20 times compared to Yb-doped aluminosilicate fibers. The laser efficiency of the nano-crystalline fiber was 79%

Application of Replacement Theory in Determination of Pavement Design Life

This paper presents a methodology to determine the economic life of pavement based replacement theory/decision. The replacement theory is generally used for the determination of the replacement period of machines, bulbs, vehicles, equipment, buildings, T.V. parts… etc. This theory has been used to determine the economic life pavement for a road project and a bridge project with a real case study. The economic life has been found out. The economic life of flexible pavement has been found to be 15 years for national highways. This theory can be also applied to determine the economic life of new developed items/useful materials for highway projects

Strong field gravitational lensing in scalar tensor theories

Strong field gravitational lensing in the Brans-Dicke theory has been studied. The deflection angle for photons passing very close to the photon sphere is estimated for the static spherically symmetric space-time of the theory and the position and magnification of the relativistic images are obtained. Modeling the super massive central object of the galaxy by the Brans-Dicke space-time, numerical values of different strong lensing observable are estimated. It is found that against the expectation there is no significant scalar field effect in the strong field observable lensing parameters. This observation raises question on the potentiality of the strong field lensing to discriminate different gravitational theories.Comment: 20 pages, accepted in Class. Quantum Grav., final versio

On static spherically symmetric solutions of the vacuum Brans-Dicke theory

It is shown that among the four classes of the static spherically symmetric solution of the vacuum Brans-Dicke theory of gravity only two are really independent. Further by matching exterior and interior (due to physically reasonable spherically symmetric matter source) scalar fields it is found that only Brans class I solution with certain restriction on solution parameters may represent exterior metric for a nonsingular massive object. The physical viability of the black hole nature of the solution is investigated. It is concluded that no physical black hole solution different from the Schwarzschild black hole is available in the Brans-Dicke theory.Comment: 15 pages, To be published in Gen. Rel. and Grav, typos in references correcte

Testing gravity at the Second post-Newtonian level through gravitational deflection of massive particles

Expression for second post-Newtonian level gravitational deflection angle of massive particles is obtained in a model independent framework. Several of its important implications including the possibility of testing gravitational theories at that level are discussed.Comment: 5 pages, couple of equations of the previous version are correcte

Compatibility of Einstein minimally coupled self interacting scalar field theory with the solar system tests of gravity

We examine the compatibility of the Einstein minimally coupled self-interacting scalar field theory with the local tests of gravity. We find that apart from the trivial case of the Schwarzschild-de Sitter solution with constant scalar field the theory does not admit any other static solution, which is consistent with the solar system tests of gravity.Comment: 6 pages, a part of the earlier version removed, final version accepeted by CQ

Triazine functionalized porous covalent organic framework for photo-organocatalytic E–Z isomerization of olefins

Visible light-mediated photocatalytic organic transformation has drawn significant attention as an alternative process for replacing thermal reactions. Although precious metal/organic dyes based homogeneous photocatalysts have been developed, their toxic and nonreusable nature makes them inappropriate for large-scale production. Therefore, we have synthesized a triazine and a keto functionalized nonmetal based covalent organic framework (TpTt) for heterogeneous photocatalysis. As the catalyst shows significant absorption of visible light, it has been applied for the photocatalytic uphill conversion of trans-stilbene to cis-stilbene in the presence of blue light-emitting diodes with broad substrate scope via an energy transfer process

Drosophila Argonaute-1 is critical for transcriptional cosuppression and heterochromatin formation

Argonaute-1 (Ago-1) plays a crucial role in gene regulation and genome stability via biogenesis of small non-coding RNAs. Two “Argonaute” family genes, piwi and Ago-2 in Drosophila are involved in multiple silencing mechanisms in the nucleus, transgene cosuppression, long-distant chromosome interaction, nuclear organization and heterochromatin formation. To investigate whether Ago-1 also plays a similar role, we have generated a series of Ago-1 mutations by excising P element, inserted in the Ago-1 promoter (Ago-1k08121). AGO-1 protein is distributed uniformly in the nucleus and cytosol in early embryos but accumulated predominantly in the cytoplasm during the gastrulation stage. Repeat induced silencing produced by the mini-white (mw) array and transcriptional cosuppression of non-homologous transgenes Adh-w/w-Adh was disrupted by Ago-1 mutation. These effects of Ago-1 are distict from its role in microRNA processing because Dicer-1, a critical enzyme for miRNA biogenesis, has no role on the above silencing. Reduction of AGO-1 protein dislodged the POLYCOMB, EZ (enhancer of zeste) and H3me3K27 binding at the cosuppressed Adh-w transgene insertion sites suggesting its role in Polycomb dependent cosuppression. An overall reduction of methylated histone H3me2K9 and H3me3K27 from the polytene nuclei precisely from the mw promoters was also found that leads to concomitant changes in the chromatin structure. These results suggest a prominent role of Ago-1 in chromatin organization and transgene silencing and demonstrate a critical link between transcriptional transgene cosuppression, heterochromatin formation and chromatin organization. We propose Drosophila Ago-1 as a multifunctional RNAi component that interconnects at least two unrelated events, chromatin organization in the nucleus and microRNA processing in the cytoplasm, which may be extended to the other systems

Multi-wavelength fiber laser with erbium doped zirconia fiber and semiconductor optical amplifier

Multi-wavelength hybrid fiber lasers are demonstrated in both ring and linear cavities using a fabricated Erbium-doped Zirconia fiber (EDZF) and semiconductor optical amplifier (SOA) as gain media. In both configurations, the a fiber loop mirror, which is constructed using a 3 m long polarization maintaining fiber (PMF) and a polarization insensitive 3dB coupler is used as a comb filter for the fiber laser. In the ring cavity, 10 simultaneous lines with peak power above -26 dBm is obtained at 1550 nm region. This is an improvement compared to the linear cavity configuration which has only 5 simultaneous lines observed from wavelength 1556.1 nm to 1563.0 nm with the peak power above -40 dBm. Both hybrid lasers has a constant line spacing of 1.7 nm, which is suitable for wavelength division multiplexing and sensing applications and shows a stable operation at room temperature