Gravitational lensing: a unique probe of dark matter and dark energy

I review the development of gravitational lensing as a powerful tool of the observational cosmologist. After the historic eclipse expedition organized by Arthur Eddington and Frank Dyson, the subject lay observationally dormant for 60 years. However, subsequent progress has been astonishingly rapid, especially in the past decade, so that gravitational lensing now holds the key to unravelling the two most profound mysteries of our Universe—the nature and distribution of dark matter, and the origin of the puzzling cosmic acceleration first identified in the late 1990s. In this non-specialist review, I focus on the unusual history and achievements of gravitational lensing and its future observational prospects

Decadal-centennial scale monsoon variations in the Arabian Sea during the Early Holocene

An essential prerequisite for the prediction of future climate change due to anthropogenic input is an understanding of the natural processes that control Earth's climate on timescales comparable to human-lifespan. The Early Holocene period was chosen to study the natural climate variability in a warm interval when solar insolation was at its maximum. The monsoonal system of the Tropics is highly sensitive to seasonal variations in solar insolation, and consequently marine sediments from the region are a potential monitor of past climate change. Here we show that during the Early Holocene period rapid

Orbital Magnetism in Ensembles of Parabolic Potentials

We study the magnetic susceptibility of an ensemble of non-interacting electrons confined by parabolic potentials and subjected to a perpendicular magnetic field at finite temperatures. We show that the behavior of the average susceptibility is qualitatively different from that of billiards. When averaged over the Fermi energy the susceptibility exhibits a large paramagnetic response only at certain special field values, corresponding to comensurate classical frequencies, being negligible elsewhere. We derive approximate analytical formulae for the susceptibility and compare the results with numerical calculations.Comment: 4 pages, 4 figures, REVTE

Enhanced Pro-apoptotic Effects of Fe(II)-Modified IVIG on Human Neutrophils.

Mild modification of intravenous immunoglobulin (IVIG) has been reported to result in enhanced polyspecificity and leveraged therapeutic effects in animal models of inflammation. Here, we observed that IVIG modification by ferrous ions, heme or low pH exposure, shifted the repertoires of specificities in different directions. Ferrous ions exposed Fe(II)-IVIG, but not heme or low pH exposed IVIG, showed increased pro-apoptotic effects on neutrophil granulocytes that relied on a FAS-dependent mechanism. These effects were also observed in human neutrophils primed by inflammatory mediators or rheumatoid arthritis joint fluid in vitro, or patient neutrophils ex vivo from acute Crohn's disease. These observations indicate that IVIG-mediated effects on cells can be enhanced by IVIG modification, yet specific modification conditions may be required to target specific molecular pathways and eventually to enhance the therapeutic potential

Experimental evidence for 56Ni-core breaking from the low-spin structure of the N=Z nucleus 58Cu

Low-spin states in the odd-odd N=Z nucleus 58Cu were investigated with the 58Ni(p,n gamma)58Cu fusion evaporation reaction at the FN-tandem accelerator in Cologne. Seventeen low spin states below 3.6 MeV and 17 new transitions were observed. Ten multipole mixing ratios and 17 gamma-branching ratios were determined for the first time. New detailed spectroscopic information on the 2+,2 state, the Isobaric Analogue State (IAS) of the 2+,1,T=1 state of 58Ni, makes 58Cu the heaviest odd-odd N=Z nucleus with known B(E2;2+,T=1 --> 0+,T=1) value. The 4^+ state at 2.751 MeV, observed here for the first time, is identified as the IAS of the 4+,1,T=1 state in 58Ni. The new data are compared to full pf-shell model calculations with the novel GXPF1 residual interaction and to calculations within a pf5/2 configurational space with a residual surface delta interaction. The role of the 56Ni core excitations for the low-spin structure in 58Cu is discussed.Comment: 15 pages, 7 figures, submitted to Phys. Rev.

Transition Rates between Mixed Symmetry States: First Measurement in 94Mo

The nucleus 94Mo was investigated using a powerful combination of gamma-singles photon scattering experiments and gamma-gamma-coincidence studies following the beta-decay of 94mTc. The data survey short-lived J^pi=1+,2+ states and include branching ratios, E2/M1 mixing ratios, lifetimes, and transition strengths. The mixed-symmetry (MS) 1+ scissors mode and the 2+ MS state are identified from M1 strengths. A gamma transition between MS states was observed and its rate was measured. Nine M1 and E2 strengths involving MS states agree with the O(6) limit of the interacting boson model-2 using the proton boson E2 charge as the only free parameter.Comment: 9 pages, 3 PostScript figures included, ReVTeX, accepted for publication in Physical Review Letters, tentatively scheduled for August 9, 199

Physical properties of methane-enriched plumes along the Hikurangi margin of New Zealand: Thoughts on sources and life spans of water column methane anomalies

We explored methane distribution and physical mixing processes at active areas with CTD measurements utilizing a methane sensor combined with discrete water samples collected in Niskin bottles (24 bottle carrousel). Evidence of a methane plume injection was obtained during a CTD cast. The plume injection is thought to be the result of a vertical advective flow driven by a source of buoyancy (e.g., heat flux, bubbles, high dissolved methane concentration). Thorpe scale analyses on the high-resolution temperature data allow us to locate turbulent overturns and the associated small- to large-scale temperature inversions. Thorpe displacement analysis shows substantial overturns of ca. 30 m at around 720 m depth that perfectly correspond with a large peak (ca. 600 nM) of methane. This is likely the final intrusion depth of a methane plume originating from the sea floor. However, it is inconclusive which buoyancy source(s) are driving the plume (e.g. heat flux, bubbles, etc.). In the corresponding profiles, a completely well-mixed ca. 35 m thick layer (in T and Sal) is observed at this location. This further suggests a local buoyancy source. Substantial energy input is required to maintain such a well-mixed structure. In absence of a supporting energy source, this signal would be vertically diffusively smeared within several days (t = z/Kz), and much faster horizontally. Energy balances suggest that the source and resulting upwelling are a dissolved methane-enriched thermal plume, as the number of bubbles required to produce such a plume and maintain the deep-mixed layer is too substantial

Concepts and characteristics of the 'COST Reference Microplasma Jet'

Biomedical applications of non-equilibrium atmospheric pressure plasmas have attracted intense interest in the past few years. Many plasma sources of diverse design have been proposed for these applications, but the relationship between source characteristics and application performance is not well-understood, and indeed many sources are poorly characterized. This circumstance is an impediment to progress in application development. A reference source with well-understood and highly reproducible characteristics may be an important tool in this context. Researchers around the world should be able to compare the characteristics of their own sources and also their results with this device. In this paper, we describe such a reference source, developed from the simple and robust micro-scaled atmospheric pressure plasma jet (μ-APPJ) concept. This development occurred under the auspices of COST Action MP1101 'Biomedical Applications of Atmospheric Pressure Plasmas'. Gas contamination and power measurement are shown to be major causes of irreproducible results in earlier source designs. These problems are resolved in the reference source by refinement of the mechanical and electrical design and by specifying an operating protocol. These measures are shown to be absolutely necessary for reproducible operation. They include the integration of current and voltage probes into the jet. The usual combination of matching unit and power supply is replaced by an integrated LC power coupling circuit and a 5 W single frequency generator. The design specification and operating protocol for the reference source are being made freely available

Mistargeting of aggregation prone mitochondrial proteins activates a nucleus-mediated posttranscriptional quality control pathway in trypanosomes.

Mitochondrial protein import in the parasitic protozoan Trypanosoma brucei is mediated by the atypical outer membrane translocase, ATOM. It consists of seven subunits including ATOM69, the import receptor for hydrophobic proteins. Ablation of ATOM69, but not of any other subunit, triggers a unique quality control pathway resulting in the proteasomal degradation of non-imported mitochondrial proteins. The process requires a protein of unknown function, an E3 ubiquitin ligase and the ubiquitin-like protein (TbUbL1), which all are recruited to the mitochondrion upon ATOM69 depletion. TbUbL1 is a nuclear protein, a fraction of which is released to the cytosol upon triggering of the pathway. Nuclear release is essential as cytosolic TbUbL1 can bind mislocalised mitochondrial proteins and likely transfers them to the proteasome. Mitochondrial quality control has previously been studied in yeast and metazoans. Finding such a pathway in the highly diverged trypanosomes suggests such pathways are an obligate feature of all eukaryotes

Submarine flatulence along the Hikurangi margin of New Zealand: Linking geochemical methane anomalies in the water column with hydroacoustic evidence of bubble transport

High methane concentrations of up to 3200 nM have been measured in the water column along the Hikurangi margin. The methane is a manifestation of common and wide spread cold fluid seepage that is linked to considerable gas hydrate resources. Three methods were utilised to explore for active seeps: by continuous, qualitative measurement of dissolved methane gas in the water column, using a methane sensor (METS) which was attached to a CTD; by qualitative measurement of discrete water samples collected in niskin bottles on the CTD; and by hydroacoustic detection of gas bubbles with a single beam echosounder. Prior to cruises on the TANGAROA RV in 2006 and the SONNE RV in 2007, only a few studies have been performed in this region. Here we present data of methane distribution from three different seep locations along the Hikurangi Margin. The Rock Garden seep site is in the northern part of the Hikurangi margin and occurs at the gas hydrate stability boundary (about 700m water depth in this area). The Omakere Ridge site is also in the northern Hikurangi margin, but occurs within deeper waters (1200m). The Wairarapa area is in the southern Hikurangi margin and is only 6 miles offshore (about 1200m depth) in the Cook Strait. Qualitative methane data have been obtained by onboard GC-based analyses using head-space equilibrium and vacuum extraction methods. The ability to define and corroborate by direct measurement, narrow (10-15m wide) methane anomalies in the water column was made possible only by the availability of a very responsive METS. Hydroacoustic flare imaging shows that bubble release is a common process at almost all of the 12 studied seep sites. Particularly at Rock Garden, ROV observations show pulsed bubble release with outbursts lasting minutes. The fate of methane along the Hikurangi margin will be discussed based on CTD-cast sections across seep sites and detailed sampling at seeps and in flares. The results are linked with bubble dissolution models, incorporating ADCP current data, physical water column properties, bubble-induced advection as studied by thermistor-moorings and knowledge about currents and eddies in the area