Spatial Patterns in Mass Balance of the Siple Coast and Amundsen Sea Sectors, West Antarctica

Local rates of change in ice-sheet thickness were calculated at IS sites in West Antarctica using the submergence velocity technique. This method entails a comparison of the vertical velocity of the ice sheet, measured using repeat global positioning system surveys of markers, and local long-term rates of snow accumulation obtained using firn-core stratigraphy. Any significant difference between these two quantities represents a thickness change with time. Measurements were conducted at sites located similar to 100-200 km apart along US ITASE traverse routes, and at several isolated locations. All but one of the sites are distributed in the Siple Coast and the Amundsen Sea basin along contours of constant elevation, along flowlines, across ice divides and close to regions of enhanced flow. Calculated rates of thickness change are different from site to site. Most of the large rates of change in ice thickness (similar to 10 cm a(-1) or larger) are observed in or close to regions of rapid flow, and are probably related to ice-dynamics effects. Near-steady-state conditions are calculated mostly at sites in the slow-moving ice-sheet interior and near the main West Antarctic ice divide. These results are consistent with regional estimates of ice-sheet change derived from remote-sensing measurements at similar locations in West Antarctica

Structures of mixed manganese ruthenium oxides (Mn1−xRux)O2(Mn_{1−x}Ru_x)O_2 crystallised under acidic hydrothermal conditions

A synthesis method for the preparation of mixed manganese–ruthenium oxides is presented along with a detailed characterisation of the solids produced. The use of 1 M aqueous sulfuric acid mediates the redox reaction between KRuO$_4$, KMnO$_4$ and Mn$^{2+}$ to form ternary oxides. At reaction temperature of 100°C the products are mixtures of α-MnO$_2$ (hollandite-type) and β-MnO$_2$ (rutile-type), with some evidence of Ru incorporation in each from their expanded unit cell volumes. At reaction temperature of 200°C solid-solutions β-Mn$_{1−x}$Ru$_x$O$_2$ are formed and materials with x ≤ 0.6 have been studied. The amount of Ru included in the oxide is greater than expected from the ratio of metals used in the synthesis, as determined by elemental analysis, implying that some Mn remains unreacted in solution. Powder X-ray diffraction (XRD) shows that while the unit cell volume expands in a linear manner, following Vegard's law, the tetragonal lattice parameters, and the a/c ratio, do not follow the extrapolated trends: this anisotropic behaviour is consistent with the different local coordination of the metals in the end members. Powder XRD patterns show increased peak broadening with increasing ruthenium content, which is corroborated by electron microscopy that shows nanocrystalline material. X-ray absorption near-edge spectra show that the average oxidation state of Mn in the solid solutions is reduced below +4 while that of Ru is increased above +4, suggesting some redistribution of charge. Analysis of the extended X-ray absorption fine structure provides complementary local structural information, confirming the formation of a solid solution, while X-ray photoelectron spectroscopy shows that the surface oxidation states of both Ru and Mn are on average lower than +4, suggesting a disordered surface layer may be present in the materials

ICESat Measurements Reveal Complex Pattern of Elevation Changes on Siple Coast Ice Streams, Antarctica

We compare ICESat data (2003-2004) to airborne laser altimetry data (1997-98 and 1999-2000) to monitor surface changes over portions of Van der Veen (VdVIS), Whillans (WIS) and Kamb ice streams (KIS) in the Ross Embayment of the West Antarctic Ice Sheet. The spatial pattern of detected surface changes is generally consistent with earlier observations. However, important changes have occurred during the past decade. For example, areas on the VdVIS and WIS, where large thinning was detected by the airborne surveys, are now closer to being in balance. The upper trunk of KIS continues to build up with thickening rates reaching 0.4 m/year. Our results provide new evidence that the overall mass balance of the region is becoming more positive, but a significant spatial variability exists. They also demonstrate the potential of ICESat data for detecting spatial patterns of surface elevation change in Antarctica

ICESat measurements reveal complex pattern of elevation changes on Siple Coast ice streams, Antarctica

This is the published version, also available here: http://dx.doi.org/10.1029/2005GL024289.We compare ICESat data (2003–2004) to airborne laser altimetry data (1997–98 and 1999–2000) to monitor surface changes over portions of Van der Veen (VdVIS), Whillans (WIS) and Kamb ice streams (KIS) in the Ross Embayment of the West Antarctic Ice Sheet. The spatial pattern of detected surface changes is generally consistent with earlier observations. However, important changes have occurred during the past decade. For example, areas on the VdVIS and WIS, where large thinning was detected by the airborne surveys, are now closer to being in balance. The upper trunk of KIS continues to build up with thickening rates reaching 0.4 m/year. Our results provide new evidence that the overall mass balance of the region is becoming more positive, but a significant spatial variability exists. They also demonstrate the potential of ICESat data for detecting spatial patterns of surface elevation change in Antarctica

Load carrying capacity of a heterogeneous surface bearing

It has been shown before that liquids can slip at a solid boundary, which prompted the idea that parallel-surfaces bearings can be achieved just by alternating slip and non-slip regions in the direction of fluid flow. The amount of slip at the wall depends on the surface tension at the liquid–solid interface, which in turn depends on the chemical state of the surface and its roughness. In the present study a heterogeneous surface was obtained by coating half of a circular glass disc with a coating repellant to glycerol. A rotating glass disc was placed at a known/calibrated distance and the gap was filled with glycerol. With the mobile surface moving from the direction of slip to non-slip region it can be theoretically shown that a pressure build up can be achieved. The pressure gradient in the two regions is constant, similar to that in a Rayleigh step bearing, with the maximum pressure at the separation line. The heterogeneous disc was placed on a holder supported by a load cell thus the force generated by this pressure increase can be measured accurately. Tests were carried out at different sliding speeds and gaps and the load carried was measured and subsequently compared with theoretical calculations. This allowed the slip coefficient to be evaluated

Novel conserved domains in proteins with predicted roles in eukaryotic cell-cycle regulation, decapping and RNA stability

BACKGROUND: The emergence of eukaryotes was characterized by the expansion and diversification of several ancient RNA-binding domains and the apparent de novo innovation of new RNA-binding domains. The identification of these RNA-binding domains may throw light on the emergence of eukaryote-specific systems of RNA metabolism. RESULTS: Using sensitive sequence profile searches, homology-based fold recognition and sequence-structure superpositions, we identified novel, divergent versions of the Sm domain in the Scd6p family of proteins. This family of Sm-related domains shares certain features of conventional Sm domains, which are required for binding RNA, in addition to possessing some unique conserved features. We also show that these proteins contain a second previously uncharacterized C-terminal domain, termed the FDF domain (after a conserved sequence motif in this domain). The FDF domain is also found in the fungal Dcp3p-like and the animal FLJ22128-like proteins, where it fused to a C-terminal domain of the YjeF-N domain family. In addition to the FDF domains, the FLJ22128-like proteins contain yet another divergent version of the Sm domain at their extreme N-terminus. We show that the YjeF-N domains represent a novel version of the Rossmann fold that has acquired a set of catalytic residues and structural features that distinguish them from the conventional dehydrogenases. CONCLUSIONS: Several lines of contextual information suggest that the Scd6p family and the Dcp3p-like proteins are conserved components of the eukaryotic RNA metabolism system. We propose that the novel domains reported here, namely the divergent versions of the Sm domain and the FDF domain may mediate specific RNA-protein and protein-protein interactions in cytoplasmic ribonucleoprotein complexes. More specifically, the protein complexes containing Sm-like domains of the Scd6p family are predicted to regulate the stability of mRNA encoding proteins involved in cell cycle progression and vesicular assembly. The Dcp3p and FLJ22128 proteins may localize to the cytoplasmic processing bodies and possibly catalyze a specific processing step in the decapping pathway. The explosive diversification of Sm domains appears to have played a role in the emergence of several uniquely eukaryotic ribonucleoprotein complexes, including those involved in decapping and mRNA stability

The synergetic effects of surface texturing and MoDDP additive applied to ball-on-disk friction subject to both flooded and starved lubrication conditions

This paper reports a novel work on the synergetic effects of microscale surface texturing and lubricant friction modifier additive of molybdenum dialkyldithiophosphate (MoDDP) subject to both flooded and starved lubrication conditions. The experiments were performed on reciprocating ball-on-disk friction in GTL8 base oil with and without MoDDP. In the flooded lubrication condition, the test results demonstrated that the presence of the MoDDP additive contributed to lower friction coefficients, and also more pronounced effect of surface textures on friction than in the case of the bare base oil. In the starved lubrication experiments, textured and texture-free surfaces in the oils with and without MoDDP additive were tested until an abrupt rising of friction coefficient was detected. The results showed that the magnitude of friction coefficient before terminating each test was the almost same for various tests, while the endurance time in different test conditions was significantly different. The textured surface exhibited longer endurance time than the texture-free surface, especially when the MoDDP additive was used. The mechanism of the synergetic effects of surface textures and MoDDP additive has been discussed based on the experimental observations in the following sections. This study provides a new idea for the application of surface texture in boundary lubrication when lubricant additive is contained in the lubricating oils

Sub-Telomere Directed Gene Expression during Initiation of Invasive Aspergillosis

Aspergillus fumigatus is a common mould whose spores are a component of the normal airborne flora. Immune dysfunction permits developmental growth of inhaled spores in the human lung causing aspergillosis, a significant threat to human health in the form of allergic, and life-threatening invasive infections. The success of A. fumigatus as a pathogen is unique among close phylogenetic relatives and is poorly characterised at the molecular level. Recent genome sequencing of several Aspergillus species provides an exceptional opportunity to analyse fungal virulence attributes within a genomic and evolutionary context. To identify genes preferentially expressed during adaptation to the mammalian host niche, we generated multiple gene expression profiles from minute samplings of A. fumigatus germlings during initiation of murine infection. They reveal a highly co-ordinated A. fumigatus gene expression programme, governing metabolic and physiological adaptation, which allows the organism to prosper within the mammalian niche. As functions of phylogenetic conservation and genetic locus, 28% and 30%, respectively, of the A. fumigatus subtelomeric and lineage-specific gene repertoires are induced relative to laboratory culture, and physically clustered genes including loci directing pseurotin, gliotoxin and siderophore biosyntheses are a prominent feature. Locationally biased A. fumigatus gene expression is not prompted by in vitro iron limitation, acid, alkaline, anaerobic or oxidative stress. However, subtelomeric gene expression is favoured following ex vivo neutrophil exposure and in comparative analyses of richly and poorly nourished laboratory cultured germlings. We found remarkable concordance between the A. fumigatus host-adaptation transcriptome and those resulting from in vitro iron depletion, alkaline shift, nitrogen starvation and loss of the methyltransferase LaeA. This first transcriptional snapshot of a fungal genome during initiation of mammalian infection provides the global perspective required to direct much-needed diagnostic and therapeutic strategies and reveals genome organisation and subtelomeric diversity as potential driving forces in the evolution of pathogenicity in the genus Aspergillus

Distinct Roles for Dectin-1 and TLR4 in the Pathogenesis of Aspergillus fumigatus Keratitis

Aspergillus species are a major worldwide cause of corneal ulcers, resulting in visual impairment and blindness in immunocompetent individuals. To enhance our understanding of the pathogenesis of Aspergillus keratitis, we developed a murine model in which red fluorescent protein (RFP)-expressing A. fumigatus (Af293.1RFP) conidia are injected into the corneal stroma, and disease progression and fungal survival are tracked over time. Using Mafia mice in which c-fms expressing macrophages and dendritic cells can be induced to undergo apoptosis, we demonstrated that the presence of resident corneal macrophages is essential for production of IL-1β and CXCL1/KC, and for recruitment of neutrophils and mononuclear cells into the corneal stroma. We found that β-glucan was highly expressed on germinating conidia and hyphae in the cornea stroma, and that both Dectin-1 and phospho-Syk were up-regulated in infected corneas. Additionally, we show that infected Dectin-1−/− corneas have impaired IL-1β and CXCL1/KC production, resulting in diminished cellular infiltration and fungal clearance compared with control mice, especially during infection with clinical isolates expressing high β-glucan. In contrast to Dectin 1−/− mice, cellular infiltration into infected TLR2−/−, TLR4−/−, and MD-2−/− mice corneas was unimpaired, indicating no role for these receptors in cell recruitment; however, fungal killing was significantly reduced in TLR4−/− mice, but not TLR2−/− or MD-2−/− mice. We also found that TRIF−/− and TIRAP−/− mice exhibited no fungal-killing defects, but that MyD88−/− and IL-1R1−/− mice were unable to regulate fungal growth. In conclusion, these data are consistent with a model in which β-glucan on A.fumigatus germinating conidia activates Dectin-1 on corneal macrophages to produce IL-1β, and CXCL1, which together with IL-1R1/MyD88-dependent activation, results in recruitment of neutrophils to the corneal stroma and TLR4-dependent fungal killing