University of Portsmouth

About: University of Portsmouth is a education organization based out in Portsmouth, Portsmouth, United Kingdom. It is known for research contribution in the topics: Population & Galaxy. The organization has 5452 authors who have published 14256 publications receiving 424346 citations. The organization is also known as: Portsmouth and Gosport School of Science and Art & Portsmouth and Gosport School of Science and the Arts.

Integrability of irrotational silent cosmological models

Abstract: We revisit the issue of integrability conditions for the irrotational silent cosmological models. We formulate the problem both in 1 + 3 covariant and 1 + 3 orthonormal frame notation and show that there exists a series of constraint equations that need to be satisfied. These conditions hold identically for FLRW-linearized silent models, but not in the general exact nonlinear case. Thus there is a linearization instability and it is highly unlikely that there is a large class of silent models. We conjecture that there are no spatially inhomogeneous solutions with Weyl curvature of Petrov type I and indicate further issues that await clarification.

Expression, assembly and function of novel C-terminal truncated variants of the mouse P2X7 receptor: re-evaluation of P2X7 knockouts.

Abstract: BACKGROUND AND PURPOSE Splice variants of P2X7 receptor transcripts contribute to the diversity of receptor-mediated responses Here, we investigated expression and function of C-terminal truncated (ΔC) variants of the mP2X7 receptor, which are predicted to escape inactivation in one strain of P2X7 -/- mice (Pfizer KO) EXPERIMENTAL APPROACH Expression in wild-type (WT) and Pfizer KO tissue was investigated by reverse transcription (RT)-PCR and Western blot analysis ΔC variants were also cloned and expressed in HEK293 cells to investigate their assembly, trafficking and function KEY RESULTS RT-PCR indicates expression of a ΔC splice variant in brain, salivary gland (SG) and spleen from WT and Pfizer KO mice An additional ΔC hybrid transcript, containing sequences of P2X7 upstream of exon 12, part of exon 13 followed in-frame by the sequence of the vector used to disrupt the P2X7 gene, was also identified in the KO mice By blue native (BN) PAGE analysis and the use of cross linking reagents followed by SDS-PAGE, P2X7 trimers, dimers and monomers were detected in the spleen and SG of Pfizer KO mice The molecular mass was reduced compared with P2X7 in WT mice tissue, consistent with a ΔC variant When expressed in HEK293 cells the ΔC variants were inefficiently trafficked to the cell surface and agonist-evoked whole cell currents were small Co-expressed with P2X7A, the ΔC splice variant acted in a dominant negative fashion to inhibit function CONCLUSIONS AND IMPLICATIONS Pfizer KO mice are not null for P2X7 receptor expression but express ΔC variants with reduced function © 2011 The British Pharmacological Society

Anatomy of a world-class source rock: Distribution and depositional model of Silurian organic-rich shales in Jordan and implications for hydrocarbon potential

Abstract: Silurian organic-rich (hot) shales were the source of large amounts of hydrocarbons in northern Gondwana, with supergiant and giant fields in the Middle East and North Africa. A study of these black shales has been conducted in Jordan, where they represent the source for the Risha gas field. Two organically enriched horizons occur in the Silurian in Jordan, termed the lower hot shale and the upper hot shale. Deposition of the transgressive lower hot shale occurred during the early Llandoverian and was restricted to the earliest Silurian paleodepressions. Three lower hot shale depocenters have been identified in Jordan; they are located in the western Risha, eastern Wadi Sirhan, and Jafr areas. The eastern Risha area was part of a larger scale paleohigh covering northeast Jordan, most of Syria and Iraq, and north-central Saudi Arabia (Qusaiba area). At least in Jordan, the high coincides with the depocenter of the latest Ordovician glaciation. Sedimentation of the upper hot shale occurred around peak sea level during the late Llandoverian and/or early Wenlockian and was limited to the distal parts of the shelf (Risha area), in front of the prograding silty-sandy deltaic front.Thermal maturity increases from immature in the Southern Desert outcrops to late or postmature in northern Jordan. Organic richness and pyrolysis data deteriorate significantly with increasing thermal maturity because of hydrocarbon generation. Prior to maturation, maximum organic richness is interpreted to have considerably exceeded 10% with good S2 (remaining generative potential) yields, as reflected in the values of the immature lower hot shale in the shallow borehole BG-14 in the Southern Desert outcrop area and exploration well Hunt JF-1 in the Jafr area.Identification and isopach mapping of the lower hot shale is based on its characteristic uranium enrichment. The gamma-ray/total organic carbon correlation coefficient increases with increasing maturity, suggesting that uranium is less vulnerable to maturity effects than the organic matter itself. The gamma-ray log, therefore, can be used as a proxy for the prematuration organic richness, representing a suitable basis for cross-basin comparisons of original organic richness trends.A two-phase generation of hydrocarbons is interpreted for both the Risha and Wadi Sirhan areas, with the first as a pre-Hercynian phase in the Carboniferous and the second as a less intense generation phase during the Mesozoic to early Tertiary. In contrast, gas generation of the Silurian-sourced giant fields in the central part of the Arabian Peninsula and Iran was restricted to the post-Hercynian. In Jordan, both structural and stratigraphic play concepts are envisaged, including fault, paleohigh, and channel plays. Key elements that need attention in future exploration of the Silurian plays in Jordan are Ordovician reservoir quality and timing of maturation. Poor permeabilities have been reported from wells in both the Risha and Wadi Sirhan areas.