Shared-memory Graph Truss Decomposition

We present PKT, a new shared-memory parallel algorithm and OpenMP implementation for the truss decomposition of large sparse graphs. A k-truss is a dense subgraph definition that can be considered a relaxation of a clique. Truss decomposition refers to a partitioning of all the edges in the graph based on their k-truss membership. The truss decomposition of a graph has many applications. We show that our new approach PKT consistently outperforms other truss decomposition approaches for a collection of large sparse graphs and on a 24-core shared-memory server. PKT is based on a recently proposed algorithm for k-core decomposition.Comment: 10 pages, conference submissio

Kinetic model of carbonate dissolution in Martian meteorite ALH84001

The magnetites and sulfides located in the rims of carbonate globules in the Martian meteorite ALH84001 have been claimed as evidence of past life on Mars. Here, we consider the possibility that the rims were formed by dissolution and reprecipitation of the primary carbonate by the action of water. To estimate the rate of these solution-precipitation reactions, a kinetic model of magnesite-siderite carbonate dissolution was applied and used to examine the physicochemical conditions under which these rims might have formed. The results indicate that the formation of the rims could have taken place in < 50 yr of exposure to small amounts of aqueous fluids at ambient temperatures. Plausible conditions pertaining to reactions under a hypothetical ancient Martian atmosphere (1 bar CO2), the modern Martian atmosphere (8 mbar CO2), and the present terrestrial atmosphere (0.35 mbar CO2) were explored to constrain the site of the process. The results indicated that such reactions likely occurred under the latter two conditions. The possibility of Antarctic weathering must be entertained, which, if correct, would imply that the plausibly biogenic minerals (single-domain magnetite of characteristic morphology and sulfide) reported from the rims may be the products of terrestrial microbial activity. This model is discussed in terms of the available isotope data and found to be compatible with the formation of ALH84001 rims. Particularly, anticorrelated variations of radiocarbon with δ13C indicate that carbonate in ALH84001 was affected by solution-precipitation reactions immediately after its initial fall (ca. 13,000 yr ago) and then again during its recent exposure prior to collection

Effects of Human Capital on Farm and Non-Farm Productivity and Occupational Stratification in Rural Pakistan

This paper investigates the effects of human capital on productivity using micro panel data of rural households in the NorthWest Frontier Province, Pakistan, where a substantial job stratification is observed in terms of income and education. To clarify the mechanism underlying this stratification, the human capital effects are estimated for wages(individual level) and for self-employed activities(household level), and for farm and non-farm sectors. Estimation results show a clear contrast between farm and non-farm sectors - wages and productivity in non-farm activities rise with education at an increasing rate, whereas those in agriculture respond only to the primary education.human capital, returns to education, non-farm employment, self-employment

Structural and biochemical characterization of eukaryotic mRNA decapping activators

In eukaryotes, mRNA turnover starts with the truncation of 3′ poly(A) tail and proceeds with either 3′-to-5′ degradation by the exosome complex or with decapping followed by 5′-to-3′ degradation by Xrn1. mRNA decapping is catalyzed by the decapping enzyme complex Dcp1-Dcp2 and is regulated by a highly conserved set of decapping activator proteins, including Pat1, Dhh1, Edc3 and the heptameric Lsm1-7 complex. The mechanisms regarding the interplay of mRNA decapping activators remains elusive owing to limited structural and biochemical understanding. My doctoral research was focused on elucidating the structural and functional roles of mRNA decapping activators involved in mRNA decay. Pat1 has a modular domain architecture that allows it to interact with multiple decapping activators simultaneously. Pat1 acts as a bridging factor between the 3′-end and the 5′-end of the mRNA by interacting with multiple proteins involved in decapping. The interaction of S. cerevisiae Pat1 N-terminus with the DEAD-box protein Dhh1 was characterized by biochemical pull-down assays and binding affinities were determined quantitatively by isothermal titration calorimetery. Based on these experiments, the crystal structure of Dhh1 bound to Pat1 was determined at 2.8 Å resolution. The structure reveals that Pat1 wraps around RecA2 domain of Dhh1 via evolutionary conserved interactions. This conserved surface of Dhh1 is also implicated in interaction with another decapping activator, Edc3, rationalizing why Pat1 and Edc3 binding to Dhh1 is mutually exclusive. These interactions were supported by testing mutations in in vitro assays with the yeast proteins and in co-immunoprecipitation assays with the corresponding human orthologs. Furthermore, structural analysis combined with RNA pull-down assays and a crosslinking mass spectrometry based approach gave definitive evidence that Dhh1 engages with Pat1, Edc3 and RNA in a mutually exclusive manner. The Lsm1-7 complex is another important activator of mRNA decapping. It protects the mRNA transcripts from 3′-end degradation and enhances the mRNA decapping. I determined the crystal structure of the Lsm1-7 complex at 2.3 Å resolution showing a hetero-heptameric complex of Lsm1-7 proteins that make a ring-like overall topology. Furthermore, an unusual helical structure of Lsm1 C-terminal extension and protrudes into the central channel of the heptameric ring, explaining how it is modulates the RNA binding properties of the complex. The Lsm1-7 complex interacts with the C-terminal domain of Pat1. Structure determination of this octameric Lsm1-7-Pat1 complex at 3.7 Å gave insights into the interaction of Pat1 with Lsm1-7 complex. Unexpectedly, Pat1 binds to Lsm2 and Lsm3 but not with the cytoplasmic specific subunit Lsm1. The Pat1 C-terminus makes a super-helical structure consisting of HEAT-like repeats of anti-parallel helices similar to the structure of its human ortholog. Structure based mutagenesis analysis by in vitro pull-downs showed that these interactions are conserved. This doctoral thesis gives structural and mechanistic insight into the role of multi-domain protein Pat1 and how it engages at two distinct ends of mRNA by interacting with Dhh1 at 5′-end and with Lsm1-7 complex that at 3′-end. Combining these results present a model of dynamic interplay of these activators and gives a better understanding of protein-protein and protein-RNA interaction network in the decapping machinery

Los ataques terroristas de Londres: impacto del 7-J en los musulmanes británicos

Este análisis examina las implicaciones de los ataques terroristas perpetrados en Londres el 7 de julio para los musulmanes británicos. El presente análisis examina las implicaciones de los atentados terroristas perpetrados en Londres el 7 de julio de 2005 para los musulmanes británicos, y plantea las distintas reacciones y percepciones suscitadas entre las comunidades musulmanas británicas en el período inmediatamente posterior a la consumación de tales atrocidades. Analiza el impacto emergente de los atentados en los musulmanes británicos, así como las modalidades de respuesta a sus inquietudes por parte de las autoridades británicas

Handheld forward-imaging needle endoscope for ophthalmic optical coherence tomography inspection

We report the narrowest to-date (21 gauge, 820-µm-diam) handheld forward-imaging optical coherence tomography (OCT) needle endoscope and demonstrate its feasibility for ophthalmic OCT inspection. The probe design is based on paired-angle-rotation scanning (PARS), which enables a linear B-scan pattern in front of the probe tip by using two counterrotating angle polished gradient-index (GRIN) lenses. Despite its small size, the probe can provide a numerical apertune (NA) of 0.22 and an experimental sensitivity of 92 dB at 0.5 frames. The feasibility of retinal imaging is tested on enucleated ex vivo porcine eyes, where structural features including remnant vitreous humor, retina, and choroid can be clearly distinguished. Due to its imaging quality comparable to a commercial OCT system and compatibility with the current ophthalmic surgery standard, the probe can potentially serve as a better alternative to traditional visual inspection by white light illumination during vitreoretinal surgery (e.g., vitrectomy)