Life just got complicated

The fossil record of ancient life is, in general, poor. Certainly, fossils are abundant in many rock successions and may reveal remarkable details about evolution and environmental change, but they typically consist of disarticulated or broken skeletal material, such as shells, bones and teeth. Even worse, the record of entirely (or largely) soft-bodied organisms, such as jellyfish and worms, is extremely scant, despite the fact that such animals dominate modern marine environments and presumably did so in the past. The reason is obvious — such organisms are highly susceptible to post-mortem decay and typically decompose more rapidly than the ‘normal’ processes of fossilisation operate. This significantly blurs our view of ancient life, with obvious consequences for those interested in understanding evolution and past ecosystems

Antimatter propulsion, status and prospects

The use of advanced propulsion techniques must be considered if the currently envisioned launch date of the manned Mars mission were delayed until 2020 or later. Within the next thirty years, technological advances may allow such methods as beaming power to the ship, inertial-confinement fusion, or mass-conversion of antiprotons to become feasible. A propulsion system with an ISP of around 5000 s would allow the currently envisioned mission module to fly to Mars in 3 months and would require about one million pounds to be assembled in Earth orbit. Of the possible methods to achieve this, the antiproton mass-conversion reaction offers the highest potential, the greatest problems, and the most fascination. Increasing the production rates of antiprotons is a high priority task at facilities around the world. The application of antiprotons to propulsion requires the coupling of the energy released in the mass-conversion reaction to thrust-producing mechanisms. Recent proposals entail using the antiprotons to produce inertial confinement fusion or to produce negative muons which can catalyze fusion. By increasing the energy released per antiproton, the effective cost, (dollars/joule) can be reduced. These proposals and other areas of research can be investigated now. These short term results will be important in assessing the long range feasibility of an antiproton powered engine

Controlled Synthesis of Pt-Sn/Al2O3 Catalysts and Their Application in the Hydrodeoxygenation of Bio-Based Succinic Acid

As environmental and economic forces push for movement away from traditional petroleum-sourced chemical and fuel production, it becomes essential for technologies in renewable carbon resources to be developed. In particular, the production of chemical commodities from renewable lignocellulosic biomass provides a unique path away from the use of petrol. Considering the high density of functional groups present in biomass feedstocks, new technologies must be developed to selectively target the removal of functional groups through the application of supported metal catalysts. The ability to target specific functional group removal would allow for biomass feedstocks to produce higher yields of desired commodities without the production of undesired, lower value chemicals. Through the use of promoter metals, such as Sn, it is possible to shift the selectivities of noble metal catalysts (e.g. Pt, Ru, Pd, etc.), often without greatly reducing the intrinsic activity of the monometallic catalyst. While the usefulness of bimetallic catalysts has been observed in many applications, the actual mechanisms by which promoter metals alter the catalyst’s performance is largely left unknown. This gap in knowledge is largely due to the fact that the traditional methods of catalyst synthesis lack the ability to control exact compositions and geometries of surface metal complexes. The synthesis method of strong electrostatic adsorption (SEA) utilizes the surface charging properties of metal oxides to selectively adsorb promoter metals to primary metal sites, potentially allowing for greater control of the composition of metal complexes. This work employs the SEA technique to develop a realistic method for the synthesis of Pt-Sn/Al2O3 bimetallic catalysts. The addition of Sn had profound effects on the selectivity of propionic acid hydrodeoxygenation (HDO), an analog for succinic acid HDO, suppressing nearly all unwanted byproduct production. Through the use of temperature programmed reductions (TPR), ambient-pressure photoemission spectroscopy (AP-PES), chemical and physical adsorptions, and electron microprobe characterization techniques, this work shows that the changes in propionic acid HDO is likely attributed to the changes in oxidation states of Pt metal sites upon the addition of Sn

Improving Estimates of Seismic Source Parameters Using Surface-Wave Observations: Applications to Earthquakes and Underground Nuclear Explosions

We address questions related to the parameterization of two distinct types of seismic sources: earthquakes and underground nuclear explosions. For earthquakes, we focus on the improvement of location parameters, latitude and longitude, using relative measurements of spatial cluster of events. For underground nuclear explosions, we focus on the seismic source model, especially with regard to the generation of surface waves. We develop a procedure to improve relative earthquake location estimates by fitting predicted differential travel times to those measured by cross-correlating Rayleigh- and Love-wave arrivals for multiple earthquakes recorded at common stations. Our procedure can be applied to populations of earthquakes with arbitrary source mechanisms because we mitigate the phase delay that results from surface-wave radiation patterns by making source corrections calculated from the source mechanism solutions published in the Global CMT Catalog. We demonstrate the effectiveness of this relocation procedure by first applying it to two suites of synthetic earthquakes. We then relocate real earthquakes in three separate regions: two ridge-transform systems and one subduction zone. In each scenario, relocated epicenters show a reduction in location uncertainty compared to initial single-event location estimates. We apply the relocation procedure on a larger scale to the seismicity of the Eltanin Fault System which is comprised of three large transform faults: the Heezen transform, the Tharp transform, and the Hollister transform. We examine the localization of seismicity in each transform, the locations of earthquakes with atypical source mechanisms, and the spatial extent of seismic rupture and repeating earthquakes in each transform. We show that improved relative location estimates, aligned with bathymetry, greatly reduces the localization of seismicity on each of the three transforms. We also show how improved location estimates enhance the ability to use earthquake locations to address geophysical questions such as the presence of atypical earthquakes and the nature of seismic rupture along an oceanic transform fault. We investigate the physical basis for the mb-MS discriminant, which relies on differences between amplitudes of body waves and surface waves. We analyze observations for 71 well-recorded underground nuclear tests that were conducted between 1977-1989 at the Balapan test site near Semipalatinsk, Kazakhstan in the former Soviet Union. We combine revised mb values and earlier long-period surface-wave results with a new source model, which allows the vertical and horizontal forces of the explosive source to be different. We introduce a scaling factor between vertical and horizontal forces in the explosion model, to reconcile differences between body wave and surface wave observations. We find that this parameter is well correlated with the scaled depth of burial for UNEs at this test site. We use the modified source model to estimate the scaled depth of burial for the 71 UNEs considered in this study

GlyPro as a self-immolative spacer for the release of payloads from antibody-drug conjugates

Antibody-drug conjugates (ADCs) are an increasingly popular modality for targeted drug delivery in many oncological and immunological applications. The paratope of a monoclonal antibody (mAb) directs the delivery of a conjugated therapeutic payload to antigen expressing cells, resulting in a controlled transport of payload to a desired cell type. Internalization of the ADC followed by lysosomal degradation results in the release of a payload to perform its biochemical function. A chemical linker between the drug and the antibody is responsible for the stability of the conjugate in circulation alongside mediating the release of an unmodified payload under lysosomal conditions. Currently, the lead linker, ValCit-p-aminobenzyl carbamate (PABC), has demonstrated impressive extracellular integrity while maintaining susceptibility to lysosomal proteases, such as Cathepsin B, for controlled intracellular release.1 However, the well-studied ValCitPABC linker system is largely restricted to amine-containing payloads for immuno-modulating ADCs whereas there are few ADC linkage systems that are able to release alcohol containing payloads, regardless of their functional prevalence across a myriad of biologically active small molecules. We propose that upon cathepsin-mediated cleavage of our ADCs, the ValCit release of a GlyPro ester undergoes rapid cyclization to form a diketopiperazine, thereby releasing the alcohol-containing payload. The efficiency of this linker (ValCitGlyPro) was examined using a model system designed to release dexamethasone, a potent glucocorticoid. Kinetic studies demonstrated that our linker system results in rapid GlyPro-dexamethasone release in lysosomes, which undergoes rapid cyclization to release dexamethasone at neutral pH. After conjugation of the linker payload to targeted and untargeted antibodies, several cell assays show that this system is capable of targeted immune suppression of lipopolysaccharide (LPS) stimulated cells. We also report our efforts to expand the utility of this linker system for the release of anilines, and amines

Multiplicity, Invariants and Tensor Product Decomposition of Tame Representations of U(\infty)

The structure of r-fold tensor products of irreducible tame representations of the inductive limit U(\infty) of unitary groups U(n) are are described, versions of contragredient representations and invariants are realized on Bargmann-Segal-Fock spaces.Comment: 48 pages, LaTeX file, to appear in J. Math. Phy