The VOL-CALPUFF model for atmospheric ash dispersal: 1. Approach and physical formulation

We present a new modeling tool, named VOL-CALPUFF, that is able to simulate the transient and three-dimensional transport and deposition of volcanic ash under the action of realistic meteorological and volcanological conditions throughout eruption duration. The new model derives from the CALPUFF System, a software program widely used in environmental applications of pollutant dispersion, that describes the dispersal process in both the proximal and distal regions and also in the presence of complex orography. The main novel feature of the model is its capability of coupling a Eulerian description of plume rise with a Lagrangian representation of ash dispersal described as a series of diffusing packets of particles or puffs. The model is also able to describe the multiparticle nature of the mixture as well as the tilting effects of the plume due to wind action. The dispersal dynamics and ash deposition are described by using refined orography-corrected meteorological data with a spatial resolution up to 1 km or less and a temporal step of 1 h. The modeling approach also keeps the execution time to a few minutes on common PCs, thus making VOL-CALPUFF a possible tool for the production of ash dispersal forecasts for hazard assessment. Besides the model formulation, this paper presents the type of outcomes produced by VOL-CALPUFF, shows the effect of main model parameters on results, and also anticipates the fundamental control of atmospheric conditions on the ash dispersal processes. In the companion paper, Barsotti and Neri present a first thorough application of VOL-CALPUFF to the simulation of a weak plume at Mount Etna (Italy) with the specific aim of comparing model predictions with independent observations

The VOL-CALPUFF model for atmospheric ash dispersal. I. Approach and physical formulation

We present a new modeling tool, named VOL-CALPUFF able to simulate the transient and three-dimensional transport and deposition of volcanic ash under the action of realistic meteorological and volcanological conditions throughout eruption duration. The new model derives from the CALPUFF System, a software program widely-used in environmental applications of pollutant dispersion, that describes the dispersal process both in the proximal and distal regions and also in presence of complex orography. The main novel feature of the model is its capability of coupling a Eulerian description of plume rise with a Lagrangian representation of ash dispersal described as a series of diffusing packets of particles or puffs. The model is also able to describe the multiparticle nature of the mixture as well as the tilting effects of the plume due to wind action. The dispersal dynamics and ash deposition are described by using refined orography-corrected meteorological data with a spatial resolution up to 1 km or less and a temporal step of 1 hour. The modeling approach also keeps the execution time to a few minutes on common PCs, thus making VOL-CALPUFF a possible tool for the production of ash dispersal forecasts for hazard assessment. Besides the model formulation, the paper presents the type of outcomes produced by VOL-CALPUFF, shows the effect of main model parameters on results, and also anticipates the fundamental control of atmospheric conditions on the ash dispersal processes. In the companion paper (\cite{barsotti}, this issue) a first thorough application of VOL-CALPUFF to the simulation of a weak plume at Mount Etna (Italy) is presented with the specific aim of comparing model predictions with independent observations

Decoherence and degradation of squeezed states in quantum filter cavities

Squeezed states of light have been successfully employed in interferometric gravitational-wave detectors to reduce quantum noise, thus becoming one of the most promising options for extending the astrophysical reach of the generation of detectors currently under construction worldwide. In these advanced instruments, quantum noise will limit sensitivity over the entire detection band. Therefore, to obtain the greatest benefit from squeezing, the injected squeezed state must be filtered using a long-storage-time optical resonator, or “filter cavity,” so as to realize a frequency-dependent rotation of the squeezed quadrature. While the ultimate performance of a filter cavity is determined by its storage time, several practical decoherence and degradation mechanisms limit the experimentally achievable quantum noise reduction. In this paper we develop an analytical model to explore these mechanisms in detail. As an example, we apply our results to the 16 m filter cavity design currently under consideration for the Advanced LIGO interferometers.National Science Foundation (U.S.) (Laser Interferometer Gravitational Wave Observatory Cooperative Agreement PHY-0757058

Stretch-induced Calcium Release in Smooth Muscle

Smooth muscle cells undergo substantial increases in length, passively stretching during increases in intraluminal pressure in vessels and hollow organs. Active contractile responses to counteract increased transmural pressure were first described almost a century ago (Bayliss, 1902) and several mechanisms have been advanced to explain this phenomenon. We report here that elongation of smooth muscle cells results in ryanodine receptor–mediated Ca2+ release in individual myocytes. Mechanical elongation of isolated, single urinary bladder myocytes to ∼120% of slack length (ΔL = 20) evoked Ca2+ release from intracellular stores in the form of single Ca2+ sparks and propagated Ca2+ waves. Ca2+ release was not due to calcium-induced calcium release, as release was observed in Ca2+-free extracellular solution and when free Ca2+ ions in the cytosol were strongly buffered to prevent increases in [Ca2+]i. Stretch-induced calcium release (SICR) was not affected by inhibition of InsP3R-mediated Ca2+ release, but was completely blocked by ryanodine. Release occurred in the absence of previously reported stretch-activated currents; however, SICR evoked calcium-activated chloride currents in the form of transient inward currents, suggesting a regulatory mechanism for the generation of spontaneous currents in smooth muscle. SICR was also observed in individual myocytes during stretch of intact urinary bladder smooth muscle segments. Thus, longitudinal stretch of smooth muscle cells induces Ca2+ release through gating of RYR. SICR may be an important component of the physiological response to increases in luminal pressure in smooth muscle tissues

Effects of Mitochondria-Targeted Antioxidants on Real-time Blood Nitric Oxide and Hydrogen Peroxide Release in Hind Limb Ischemia and Reperfusion

In the body, reperfusion of ischemic tissue with blood causes the release of reactive oxygen species (ROS), in part, from damaged mitochondria leading to endothelial and organ dysfunction. Endothelial dysfunction occurs within 5 min of reperfusion, is common to all vascular beds, and is characterized by increased hydrogen peroxide (H2O2) and decreased nitric oxide (NO) levels in the blood that further exacerbate reperfusion injury. Previous studies have shown that promoting endothelial NO synthase coupling during reperfusion increases blood NO and decreases blood H2O2 levels in hind limb I/R and attenuates myocardial I/R injury (1). This study specifically examines the effects mitochondria-targeted antioxidants, mitoquinone (mitoQ; Fig. 1), a cell permeable coenzyme Q analogue or SS-31 ((D-Arg)-Dmt-Lys-Phe-Amide; Genemed Synthesis, San Antonio, TX) (Fig.1), a cell permeable peptide, on inhibiting H2O2 release and increasing NO bioavailability in hind limb I/R. MitoQ (2) and SS-31 (3,4) are able to concentrate into the inner mitochondrial membrane via an electrical potential gradient or selective diffusion respectively, where they attenuate superoxide and subsequent H2O2 production thus allowing a concurrent increase in NO bioavailability

Nanomanufacturing for biological sensing applications

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007."February 2007."Includes bibliographical references (leaves 219-226).Over the past 10-15 years, there have been tremendous research efforts in the synthesis of nanomaterials with unique electronic properties. Much less work, however, has focused on the incorporation of the nanomaterials into electronic devices. In order for nanomaterials to have a technological impact in electronic devices, nanomanufacturing techniques must be established for the reliable and reproducible creation of devices with nanomaterials as the active component. In this thesis, the incorporation of 3-20 nm diameter ligand coated gold nanoparticles into an electronic device is studied. Ligand coated nanoparticles provide great control over their solubility and electronic properties through the choice of protecting ligand molecule. The use of an isolated nanoparticle in electronic devices presents two major difficulties which are studied in detail in this work. In order to use the electrical properties of a single particle or a few particles, insulating gaps in metallic electrodes must be fabricated with dimensions of 5-50 nm. Several methods including direct patterning with electron beam lithography, physical methods of gap formation, and electrical methods of gap formation are described, studied and evaluated for use in nanomanufacturing.(cont.) A second major challenge is the specific assembly of nanoparticles into the nanogaps. The use of chemically directed assembly to pattern particles on templates generated by Dip Pen Nanolithography is described using several different surface chemistries. An electrical based method, dielectrophoresis, is found to be better suited for assembly of particles into the gaps and the forces which affect assembly are studied in detail. Electrical characterizations of networks of 10-200 nanoparticles are studied as a function of protecting ligand molecule. Preliminary results on the use of nanomanufactured devices consisting of gold nanoparticles-oglionucleotide conjugates bridging a nano-gap for DNA sensing are presented.by Robert J. Barsotti, Jr.Ph.D

Ultrathin, Ultra‐Conformable, and Free‐Standing Tattooable Organic Light‐Emitting Diodes

A novel tattooable, ultrathin, green organic light‐emitting diode (OLED) fabricated on top of commercial temporary tattoo paper, is demonstrated. The transfer mechanism relies on dissolution of the sacrificial layer typically incorporated in paper‐tattoos. The ready‐to‐use device can be stored on the tattoo substrate and released on the target surface at a later time, simply by a slight wetting of the tattoo paper with water. This approach provides a quick and easy method of transferring OLEDs on virtually any surface. This is particularly appealing, in perspective, for on‐skin and disposable electronic applications. The proof of concept demonstrates, for the very first time, the feasibility of ultrathin operational OLED tattoos. While the performance of such devices is not yet comparable with that of OLEDs on rigid or flexible non‐tattooable substrates, the results show the potential for an OLED tattoo technology in integrated conformable electronic circuits

The role of endothelial nitric oxide synthase (eNOS) uncoupling in acute hyperglycemia – induced oxidative stress and vascular endothelial dysfunction by measuring blood nitric oxide and hydrogen peroxide in real-time

Acute hyperglycemia can impair vascular endothelial function in non-diabetic subjects in addition to diabetic patients. Decreased eNOS derived nitric oxide (NO) bioavailability and increased reactive oxygen species (ROS), such as superoxide (SO) and hydrogen peroxide (H2O2), are the major characteristics of vascular endothelial dysfunction. Furthermore, eNOS can change from coupled to an uncoupled status resulting in SO production instead of NO production. The role of eNOS uncoupling in acute hyperglycemia induced vascular dysfunction is unclear in vivo. In this study we hypothesized that acute hyperglycemia (200 mg/dL) would increase H2O2 and decrease NO release in blood relative to saline control. By contrast, 5,6,7,8-tetrahydrobiopterin (BH4, an essential cofactor of coupled eNOS) (MW=241.247 g/mol, 6.5 mg/kg) or L-arginine (the substrate of coupled eNOS) (MW=210.66 g/mol, 600 mg/kg) would attenuate acute hyperglycemia-induced blood NO/H2O2 change. However, 7,8-dihydrobiopterin (BH2, an oxidized form of BH4 and serves as a cofactor for uncoupled eNOS) (MW=239.231 g/mol, 4 mg/kg) will exacerbate acute hyperglycemia-induced blood NO/H2O2 change. Blood NO or H2O2 levels were measured simultaneously using calibrated NO or H2O2 microsensors (100 µm WPI Inc.) by placing them into the femoral veins of male Sprague-Dawley rats. The electrical traces were recorded at baseline and throughout 3 hours of infusion with saline or 20% D-glucose with or without a drug and converted into concentration based on the calibration curve. We found that acute hyperglycemia (200 mg/dL) significantly increased H2O2 (n=6) and reduced NO (n=6) blood levels compared to the saline group (n=7, p2 exacerbated hyperglycemia– induced increased H2O2 levels (n=7) and decreased NO levels (n=4) (p4 (n=6), significantly attenuated hyperglycemia– induced increased H2O2 levels and decreased NO levels (p2O2 (n=5) and NO (n=6) blood levels as BH4, showing significant reduction of blood H2O2 and enhancement of blood NO (p2O2 and reduced NO blood levels. Uncoupled eNOS serves as a significant source mediating acute hyperglycemia-induced vascular dysfunction. Therefore, promotion of eNOS coupling may be effective in protecting vascular endothelial function from hyperglycemic insult