About the Second Neighborhood Problem in Tournaments Missing Disjoint Stars

Let $D$ be a digraph without digons. Seymour's second neighborhood conjecture states that $D$ has a vertex $v$ such that $d^+(v) \leq d^{++}(v)$. Under some conditions, we prove this conjecture for digraphs missing $n$ disjoint stars. Weaker conditions are required when $n = 2$ or $3$. In some cases we exhibit two such vertices

Do Large-Scale Inhomogeneities Explain Away Dark Energy?

Recently, new arguments (astro-ph/0501152, hep-th/0503117) for how corrections from super-Hubble modes can explain the present-day acceleration of the universe have appeared in the literature. However, in this letter, we argue that, to second order in spatial gradients, these corrections only amount to a renormalization of local spatial curvature, and thus cannot account for the negative deceleration. Moreover, cosmological observations already put severe bounds on such corrections, at the level of a few percent, while in the context of inflationary models, these corrections are typically limited to ~ 10^{-5}. Currently there is no general constraint on the possible correction from higher order gradient terms, but we argue that such corrections are even more constrained in the context of inflationary models.Comment: 4 Pages, no figures. Minor modifications, added reference

GaAs-based Self-Aligned Stripe Superluminescent Diodes Processed Normal to the Cleaved Facet

We demonstrate GaAs-based superluminescent diodes (SLDs) incorporating a window-like back facet in a self-aligned stripe. SLDs are realised with low spectral modulation depth (SMD) at high power spectral density, without application of anti-reflection coatings. Such application of a window-like facet reduces effective facet reflectivity in a broadband manner. We demonstrate 30mW output power in a narrow bandwidth with only 5% SMD, outline the design criteria for high power and low SMD, and describe the deviation from a linear dependence of SMD on output power as a result of Joule heating in SLDs under continuous wave current injection. Furthermore, SLDs processed normal to the facet demonstrate output powers as high as 20mW, offering improvements in beam quality, ease of packaging and use of real estate. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Draft Genome Sequence of Photorhabdus luminescens subsp. laumondii HP88, an Entomopathogenic Bacterium Isolated from Nematodes

Photorhabdus luminescens subsp. laumondii HP88 is an entomopathogenic bacterium that forms a symbiotic association with Heterorhabditis nematodes. We report here a 5.27-Mbp draft genome sequence for P. luminescens subsp. laumondii HP88, with a G+C content of 42.4% and containing 4,243 candidate protein-coding genes

Permanent Draft Genome Sequence of Photorhabdus temperata Strain Hm, an Entomopathogenic Bacterium Isolated from Nematodes

Photorhabdus temperata strain Hm is an entomopathogenic bacterium that forms a symbiotic association with Heterorhabditis nematodes. Here, we report a 5.0-Mbp draft genome sequence for P. temperata strain Hm with a G+C content of 44.1% and containing 4,226 candidate protein-encoding genes

Low Reflectivity Facet Realization in GaAs-Based Optoelectronic Devices Using Self-Aligned Stripe Process

This thesis explores the realization of low facet reflectivity using self-aligned stripe buried waveguide configuration and its implementation in optoelectronic devices such as superluminescent diodes (SLDs) and semiconductor optical amplifiers (SOAs). I explored the development of the buried waveguide in AlGaAs/GaAs material system ,since its first presentation in 1974 by Tsukada, in order to identify the problems associated with this technology. A novel window-faceted structure is demonstrated. The experimental measurements demonstrated effective reflectivity <10-14 as a result of both divergence and absorption within these window-like regions (i.e. not transparent). Its implementation to suppress lasing in tilted and normal-to-facet waveguide SLDs was thoroughly investigated in chapters 3 and 4. In the tilted devices, ~40mW output power with spectral modulation depth < 2% is demonstrated. In the latter types of SLDs, up to 16mW output power with <5% spectral modulation depth was recorded, which is the highest power demonstrated for such configurations. The performance of the two types of devices was measured without the application of anti-reflective coatings on the rear facet, which makes them inherently broadband. By incorporating a windowed facet at each end of a waveguide I could realize an SOA with window structured facet. Promising results were demonstrated in this configuration including 33dB gain and <6dB noise figure, which are comparable to the state-of-the-art. A trial was held to extend the concept of absorptive rear window to visible wavelengths available in the GaInP/AlGaInP material system. Problems associated with such devices were explored briefly and two solutions are suggested. Simulations were performed to realize design of an optimized device. Unfortunately, the experimental implementation of the design was not successful but suggestions for strategies to overcome these problems are discusse

Effect of Different Growth Conditions on Certain Biochemical Parameters of Different Cyanobacterial Strains

Aims: Variation in the traditional growth medium conditions to enhance the production of lipids, carbohydrates, protein and the free amino acids content of three cyanobacterial species. Methodology and Results: Three species of cyanobacteria (Anabaena laxa, Anabaena fertilissima and Nostoc muscorum) were collected from the culture collection of Soils, Water and Environment Research Institute, Agriculture Research Center, Giza, Egypt, to investigate their biochemical composition under different growth conditions, using BG110 (nitrogen free) as growth medium. These conditions were represented by control medium, static glucose medium with (1%, w/v), aerated medium (aerated by bubbling technique depending on CO2 normally existed in air with a concentration of 0.03%), molasses medium (0.7%, v/v) and aerated medium enriched with glucose (1%, w/v). Lipid content, total carbohydrates, soluble proteins and free amino acids were determined at the previous conditions. Glucose at 0.7% (w/v) was the most favorable for lipid production in A. laxa, where it exhibited the highest lipid content (427 μg/g fresh wt.). Increasing molasses concentration up to 0.7% (v/v) produced an increase in lipid contents of the tested cyanobacterial strains. The highest lipid content of both N. muscorum (366.2 μg/g fresh wt.) and A. laxa (357.4 μg/g fresh wt.) were recorded at molasses concentrations of 0.1 and 0.7% (v/v), respectively. A. laxa expressed high significant values for both proteins (31.6 μg/mL) and free amino acids (40.5 mg/g dry wt.) after 6 days of incubation period under aerated enriched glucose condition (1%, w/v). Also, at the same growth conditions, A. fertilissima exhibited high significant values for carbohydrates at 4th day (876.8 mg/g dry wt.). Conclusion, significance and impact of study: Aerated enriched glucose medium (1%, w/v) was the best growth medium condition used in the present study