Catalytic reduction of ortho- and para-azidonitrobenzenes via tert-butoxide ion mediated electron transfer

The reduction of a range of substituted azidonitrobenzene derivatives to the corresponding aniline is described. The chemoselective reaction proceeds cleanly and in good yield, generating minimal waste products. The process involves a thiazolium salt derived species which is proposed as a radical anion relay, with tert-butoxide as the stoichiometric reductant

Modeling the Effects of Steel Catenary Riser (SCR) Wall Thickness on Its Structural and Fatigue Performances for Wave-Induced Load

The Steel Catenary Riser (SCR) exhibits significant bending and oscillation owing to undue vessel (which the riser is attached to) movements. The prevalent hydrodynamic loads (wave, current, hydrostatic pressure) are the leading causes of this structural behavior. These initiate a motion - related fatigue phenomenon. This study evaluates the feasibility of increasing the SCR Wall Thickness (WT) for better fatigue performance and structural responses when subjected to the dominant wave spectrum (Ochi Hubble) in deep water West Africa. Relevant data were acquired from an offshore facility in the study area and managed empirically through the use of marine structural analysis software- ORCAFLEX®. Following Det Norske Veritas (DNV, 2010) methodology, 4 SCRs of uniform Internal Diameters (ID) were designated (SCR1, SCR2, SCR3, SCR4), modeled with different WTs (0.0626ft, 0.1876ft, 0.3126ft, 0.4376ft) and analyzed under eight wave load cases. Before the fatigue assessments, the systems were analyzed for static and dynamic responses. Results showed that increasing the WT increases the Fatigue Life (FL) only along each riser arc length - from top to bottom. It was also observed from the systems’ structural response analyses that the effective tension at the Hang off Point (HOP) increases with increase in WT and a compromise in the capacity of the SCRs to flex alongside the hydrodynamic loads due to cumulative rise in the weight of the system. This eventually lowered the FL at the HOP below the DNV’s minimum FL for design purposes – 200 years.Keywords: Steel Catenary Riser, Wall thickness, Fatigue Performance, Ochi-Hubble, Structural response.DOI: 10.7176/ISDE/10-6-03Publication date:July 31st 201

Desiccation-Induced Volumetric Shrinkage Characteristics of Highly Expansive Tropical Black Clay Treated with Groundnut Shell Ash for Barrier Consideration

Contamination of underground water as a result of excessive crack on clay liner material is a prevalent phenomenon in an engineered landfill. Volumetric shrinkage strain (VSS) is one of the veritable properties considered for selection of materials suitable for liners and cover in waste containment systems. Material devoid of excessive shrinkage and cracking during climate change could possibly make a better barrier material that will eventually limit or control infiltration of leachate in an engineered landfill. Hence, to obtain a clay liner and covers system that are safe and robust, stabilization of such soil (expansive clay soils) becomes imperative. In order to stabilize or reduce excessive cracking and shrinkage of this soil, earlier researchers have employed cement, chemicals, and fibers. However, in recent times, the ill effects of these stabilizers on the environment have been realized, and hence their replacement with sustainable materials that are mostly agro and or industry by-products is becoming necessary. Tropical dark grey clay treated with up to 8 % Groundnut shell ash (GSA), was carried out. Specimen were compacted using British standard light (BSL) and British standard heavy (BSH) compactive efforts; at water contents between 2% dry and 4% wet of optimum. The compacted specimens were extruded and subjected to drying under laboratory conditions to evaluate its desiccation induced shrinkage and hence its suitability as a cover material in waste containment facilities. Results of this study show that changes in mass and volumetric shrinkage strain were large within the first five days of drying. Volumetric shrinkage strain increased with higher moulding water contents (MWC) and water contents relative to optimum (WRO). The effect of GSA treatment on VSS was not consistent from -2 to +2 % of optimum moisture content. For specimen prepared at +4 % of optimum moisture content, VSS decreased up to a threshold of  28% at 6 % GSA and 30% at 4% GSA for BSH and BSL compactive effort, respectively. Generally, lower compactive effort (BSL) with higher moulding water content and lower dry density produced higher VSS. A regression function was developed from the data to estimate VSS given the compaction water content relative to optimum (WRO), groundnut shell ash content (GSA), plasticity index (PI), percentage fine content (PF) and compactive effort (CE). Compaction water content relative to optimum significantly correlated with VSS, thus should be strictly regulated during field compaction to realize a durable hydraulic barrier. Keywords: Atterberg limit, compaction, desiccation, expansive soil, groundnut shell ash, statistical analysis DOI: 10.7176/CER/11-8-06 Publication date:September 30th 201

A fragment based click chemistry approach towards hybrid G-quadruplex ligands: design, synthesis and biophysical evaluation

A library of hybrid oxazole-triazole based compounds containing contiguously linked aromatic units were synthesised as G-quadruplex binding ligands. The design of these ligands was based upon combining features of our first generation of G-quadruplex bis-triazole ligands and the natural product telomestatin. The syntheses and biophysical studies of these ligands are described. © 2011 Elsevier B.V. All rights reserved

Remyelination Induced by a DNA Aptamer in a Mouse Model of Multiple Sclerosis

Multiple sclerosis (MS) is a debilitating inflammatory disease of the central nervous system (CNS) characterized by local destruction of the insulating myelin surrounding neuronal axons. With more than 200 million MS patients worldwide, the absence of treatments that prevent progression or induce repair poses a major challenge. Anti-inflammatory therapies have met with limited success only in preventing relapses. Previous screening of human serum samples revealed natural IgM antibodies that bind oligodendrocytes and promote both cell signaling and remyelination of CNS lesions in an MS model involving chronic infection of susceptible mice by Theiler’s encephalomyelitis virus and in the lysolecithin model of focal demyelination. This intriguing result raises the possibility that molecules with binding specificity for oligodendrocytes or myelin components may promote therapeutic remyelination in MS. Because of the size and complexity of IgM antibodies, it is of interest to identify smaller myelin-specific molecules with the ability to promote remyelination in vivo. Here we show that a 40-nucleotide single-stranded DNA aptamer selected for affinity to murine myelin shows this property. This aptamer binds multiple myelin components in vitro. Peritoneal injection of this aptamer results in distribution to CNS tissues and promotes remyelination of CNS lesions in mice infected by Theiler’s virus. Interestingly, the selected DNA aptamer contains guanosine-rich sequences predicted to induce folding involving guanosine quartet structures. Relative to monoclonal antibodies, DNA aptamers are small, stable, and non-immunogenic, suggesting new possibilities for MS treatment

Structural characterization of the apo form and NADH binary complex of human lactate dehydrogenase

Lactate dehydrogenase A (LDH-A) is a key enzyme in anaerobic respiration that is predominantly found in skeletal muscle and catalyses the reversible conversion of pyruvate to lactate in the presence of NADH. LDH-A is overexpressed in many tumours and has therefore emerged as an attractive target for anticancer drug discovery. Crystal structures of human LDH-A in the presence of inhibitors have been described, but currently no structures of the apo or binary NADH-bound forms are available for any mammalian LDH-A. Here, the apo structure of human LDH-A was solved at a resolution of 2.1 Å in space group P4122. The active-site loop adopts an open conformation and the packing and crystallization conditions suggest that the crystal form is suitable for soaking experiments. The soaking potential was assessed with the cofactor NADH, which yielded a ligand-bound crystal structure in the absence of any inhibitors. The structures show that NADH binding induces small conformational changes in the active-site loop and an adjacent helix. A comparison with other eukaryotic apo LDH structures reveals the conservation of intra-loop interactions. The structures provide novel insight into cofactor binding and provide the foundation for soaking experiments with fragments and inhibitors

Correspondence between solar fine-scale structures in the corona, transition region, and lower atmosphere from collaborative observations

The Soft X-Ray Imaging Payload and the High Resolution Telescope and Spectrograph (HRTS) instrument were launched from White Sands on 11 December 1987 in coordinated sounding rocket flights to investigate the correspondence of coronal and transition region structures, especially the relationship between X-ray bright points (XBPs) and transition region small spatial scale energetic events. The coaligned data from X-ray images are presented along with maps of sites of transition region energetic events observed in C IV (100,000 K), HRTS 1600 A spectroheliograms of the T sub min region and ground based magnetogram and He I 10830 A images