Observation of CO and CO(2) absorption near 1.57 microm with an external-cavity diode laser

Near-IR and visible room-temperature diode lasers in broadly tunable external-cavity configurations are becoming commercially available for gas-sensing applications. Near 1.57 mum, a coincidence of overtone and combination-band transitions from CO, CO(2), OH, and H(2)O is particularly interesting for combustion and combustor emissions monitoring. We report initial observations of the room-temperature absorption of CO and CO(2) made with a commercial external-cavity diode laser.     

Spatial Distribution and Habitat Use of Spawning American Shad in the St. Johns River,Florida

American shad Alosa sapidissima populations along the Atlantic Coast of North America are near historic lows despite management actions designed to rebuild stocks. Florida's St. Johns River supports the southernmost population of this anadromous species, and as water use in the St. Johns basin increases, there is concern that their spawning may be affected. We assessed American Shad movement and habitat use in the St. Johns River during three spawning migrations (2009–2011) using acoustic telemetry. Spatial distribution patterns of telemetered shad during each year were largely similar; most shad were located within reaches from Lake Monroe (rkm 276) to just downstream of Lake Harney (rkm 308); some individuals made excursions as far upstream as Lake Poinsett (rkm 386+). Water levels varied among years (low‐water level: 2009 and 2011; higher water level: 2010), and lower water levels may have contributed to an apparent constriction of spawning grounds in 2009 and 2011. Telemetered shad selected deeper sections of river with faster currents. Our results verified that the primary spawning grounds for American shad in the St. Johns have not changed substantially in the past 50 years; thus, these areas should rank high for habitat protection. We also demonstrated linkages between American Shad distribution and habitat use and river flow that should be further developed and considered in future water withdrawal, regulation, or conservation efforts. Copyright © 2015 John Wiley & Sons, Ltd.     

Further Results on Guderley Mach Reflection and the Triple Point Paradox

Recent numerical solutions and shock tube experiments have shown the existence of a complex reflection pattern, known as Guderley Mach reflection, which provides a resolution of the von Neumann paradox of weak shock reflection. In this pattern, there is a sequence of tiny supersonic patches, reflected shocks and expansion waves behind the triple point, with a discontinuous transition from supersonic to subsonic flow across a shock at the rear of each supersonic patch. In some experiments, however, and in some numerical computations, a distinctly different structure which has been termed Guderley reflection has been found. In this structure, there appears to be a single expansion fan at the triple point, a single supersonic patch, and a smooth transition from supersonic to subsonic flow at the rear of the patch. In this work, we present numerical solutions of the compressible Euler equations written in self-similar coordinates at a set of parameter values that were used in previous computations which found the simple single patch structure described above. Our solutions are more finely resolved than these previous solutions, and they show that Guderley Mach reflection occurs at this set of parameter values. These solutions lead one to conjecture that the two patterns are not distinct: rather, Guderley reflection is actually underresolved Guderley Mach reflection.     

Platelet‐Inspired Nanocells for Targeted Heart Repair After Ischemia/Reperfusion Injury

Cardiovascular disease is the leading cause of mortality worldwide. While reperfusion therapy is vital for patient survival post‐heart attack, it also causes further tissue injury, known as myocardial ischemia/reperfusion (I/R) injury in clinical practice. Exploring ways to attenuate I/R injury is of clinical interest for improving post‐ischemic recovery. A platelet‐inspired nanocell (PINC) that incorporates both prostaglandin E2 (PGE₂)‐modified platelet membrane and cardiac stromal cell‐secreted factors to target the heart after I/R injury is introduced. By taking advantage of the natural infarct‐homing ability of platelet membrane and the overexpression of PGE₂ receptors (EPs) in the pathological cardiac microenvironment after I/R injury, the PINCs can achieve targeted delivery of therapeutic payload to the injured heart. Furthermore, a synergistic treatment efficacy can be achieved by PINC, which combines the paracrine mechanism of cell therapy with the PGE₂/EP receptor signaling that is involved in the repair and regeneration of multiple tissues. In a mouse model of myocardial I/R injury, intravenous injection of PINCs results in augmented cardiac function and mitigated heart remodeling, which is accompanied by the increase in cycling cardiomyocytes, activation of endogenous stem/progenitor cells, and promotion of angiogenesis. This approach represents a promising therapeutic delivery platform for treating I/R injury.     

Impact of Future Climate Change on Water Temperature and Thermal Habitat for Keystone Fishes in the Lower Saint John River,Canada

Water temperature is a key determinant of biological processes in rivers. Temperature in northern latitude rivers is expected to increase under climate change, with potentially adverse consequences for cold water-adapted species. In Canada, little is currently known about the timescales or magnitude of river temperature change, particularly in large (≥10⁴ km²) watersheds. However, because Canadian watersheds are home to a large number of temperature-sensitive organisms, there is a pressing need to understand the potential impacts of climate change on thermal habitats. This paper presents the results of a study to simulate the effects of climate change on the thermal regime of the lower Saint John River (SJR), a large, heavily impounded, socio-economically important watershed in eastern Canada. The CEQUEAU hydrological-water temperature model was calibrated against river temperature observations and driven using meteorological projections from a series of regional climate models. Changes in water temperature were assessed for three future periods (2030–2034, 2070–2074 and 2095–2099). Results show that mean water temperature in the SJR will increase by approximately ~1 °C by 2070–2074 and a further ~1 °C by 2095–2099, with similar findings for the maximum, minimum and standard deviation. We calculated a range of temperature metrics pertaining to the Atlantic Salmon and Striped Bass, key species within the SJR. Results show that while the SJR will become increasingly thermally-limiting for Atlantic Salmon, the Striped Bass growth season may actually lengthen under climate change. These results provide an insight into how climate change may affect thermal habitats for fish in eastern Canadian rivers.     

Catalytic Mechanism of the Hotdog‐Fold Thioesterase PA1618 Revealed by X‐ray Structure Determination of a Substrate‐Bound Oxygen Ester Analogue Complex

Thioesterase activity accounts for the majority of the activities in the hotdog‐fold superfamily. The structures and mechanisms of catalysis for many hotdog enzymes have been elucidated by X‐ray crystallography and kinetics to probe the specific substrate usage and cellular functions. However, structures of hotdog thioesterases in complexes with substrate analogues reported to date utilize ligands that either represent truncations of the substrate or include additional atoms to prevent hydrolysis. Here we present the synthesis of an isosteric and isoelectronic substrate analogue—benzoyl‐OdCoA—and the X‐ray crystal structure of a complex of the analogue with Pseudomonas aeruginosa hotdog thioesterase PA1618 (at 1.72 Å resolution). The complex is compared with that of the “imperfect” substrate analogue phenacyl‐CoA, refined to a resolution of 1.62 Å. Kinetic and structural results are consistent with Glu64 as the catalytic residue and with the involvement of Gln49 in stabilization of the transition state. Structural comparison of the two ligand‐bound structures revealed a crucial ordered water molecule coordinated in the active site of the benzoyl‐OdCoA structure but not present in the phenacyl‐CoA‐bound structure. This suggests a general base mechanism of catalysis in which Glu64 activates the coordinated water nucleophile. Together, our findings reveal the importance of a closely similar substrate analogue to determine the true substrate binding and catalytic mechanism.     

Effects of adding TiO<Subscript>2</Subscript> nanoparticles to a water-based varnish for wood applied to nine tropical woods of Costa Rica exposed to natural and accelerated weathering

The addition of titanium dioxide nanoparticles (TiO₂ nanoparticles) to a water-based varnish used for finishing tropical woods was studied. Three different concentrations of TiO₂ nanoparticles (0%, 1.0%, and 1.5%) were evaluated. The nanoparticles were characterized by means of the transmission electron microscopy and an X-ray diffractometer. The varnish prepared was evaluated for its viscosity, adhesion of the film to the wood, water absorption, and the effects of natural weathering on the color and quality of the varnish. It was found that viscosity decreases as the concentration of TiO₂ nanoparticles increases, while no variation was found in the thickness of the film. Except for Gmelina arborea and Tectona grandis, the adhesion was not statistically affected. It was found that, in the 9 species tested, incorporation of TiO₂ nanoparticles decreased the values of water absorption. The evaluation of natural weathering showed that the varnish with no added TiO₂ nanoparticles degraded completely after 1 year of weathering exposure, while the modified varnish film endured. Less color change was observed in lumber treated with the varnish containing TiO₂ nanoparticles. The best performance of the varnish in the nine tropical woods used was observed when TiO₂ nanoparticles were added at 1.5% concentration.     

Definite clause programs are canonical (over a suitable domain)

For each first-order languageL with a nonempty Herbrand universe, we construct an algebraC interpreting the function symbols ofL that is a model of the Clark equality theory with languageL and is canonical in the sense that for every definite clause programP in the languageL,T _P ^C is the greatest fixed point ofT _P ^C . The universe of individuals inC is a quotient of the set of terms ofL and is, a fortiori, countable ifL is countable. If contains at least one function symbol of arity at least 2, then the graphs of partial recursive functions onC, suitably defined, are representable in a natural way as individuals inC.Research sponsored in part by U.S. Air Force Contract F30602-85-C-0008.     

NASA multipurpose airborne DIAL system and measurements of ozone and aerosol profiles

An airborne differential absorption lidar (DIAL) system has been developed for the remote measurement of gas and aerosol profiles in the troposphere and lower stratosphere. The multipurpose DIAL system can operate from 280 to 1064 nm for measurements of ozone, sulfur dioxide, nitrogen dioxide, water vapor, temperature,pressure, and aerosol backscattering. The laser transmitter consists of two narrow linewidth Nd: YAG pumped dye lasers with automatic wavelength control. The DIAL wavelengths are transmitted with a 00-,usec temporal separation to reduce receiver system complexity. A coaxial receiver system is used to collect and optically separate the DIAL and aerosol lidar returns. Photomultiplier tubes detect the backscattered laser returns after optical filtering, and the analog signals from three tubes are digitized and stored on high-speed magnetic tape. Real-time gas concentration profiles or aerosol backscatter distributions are calculated and displayed for experiment control. Operational parameters for the airborne DIAL system are presented for measurements of ozone, water vapor, and aerosols in the 290-, 720-, and 600-nm wavelength regions, respectively. The first ozone profile measurements from an aircraft using the DIAL technique are discussed in this paper. Comparisons between DIAL and in situ ozone measurements show agreement to within +/-5 ppbv in the lower troposphere. Lidar aerosol data obtained simultaneously with DIAL ozone measurements are presented for a flight over Virginia and the Chesapeake Bay. DIAL system performance for profiling ozone in a tropopause folding experiment is evaluated, and the applications of the DIAL system to regional and global-scale tropospheric investigations are discussed.