Observations of a mode transition in a hydrogen hollow cathode discharge using phase resolved optical emission spectroscopy

Two distinct operational modes are observed in a radio frequency (rf) low pressure hydrogen hollow cathode discharge. The mode transition is characterised by a change in total light emission and differing expansion structures. An intensified CCD camera is used to make phase resolved images of Balmer α emission from the discharge. The low emission mode is consistent with a typical γ discharge, and appears to be driven by secondary electrons ejected from the cathode surface. The bright mode displays characteristics common to an inductive discharge, including increased optical emission, power factor, and temperature of the H2 gas. The bright mode precipitates the formation of a stationary shock in the expansion, observed as a dark region adjacent to the source-chamber interface.This research was partially funded by the Australian Research Council Discovery Project (DP1096653)

MetaMesh: A hierarchical computational model for design and fabrication of biomimetic armored surfaces

Many exoskeletons exhibit multifunctional performance by combining protection from rigid ceramic components with flexibility through articulated interfaces. Structure-to-function relationships of these natural bioarmors have been studied extensively, and initial development of structural (load-bearing) bioinspired armor materials, most often nacre-mimetic laminated composites, has been conducted. However, the translation of segmented and articulated armor to bioinspired surfaces and applications requires new computational constructs. We propose a novel hierarchical computational model, MetaMesh, that adapts a segmented fish scale armor system to fit complex “host surfaces”. We define a “host” surface as the overall geometrical form on top of which the scale units are computed. MetaMesh operates in three levels of resolution: (i) locally—to construct unit geometries based on shape parameters of scales as identified and characterized in the Polypterus senegalus exoskeleton, (ii) regionally—to encode articulated connection guides that adapt units with their neighbors according to directional schema in the mesh, and (iii) globally—to generatively extend the unit assembly over arbitrarily curved surfaces through global mesh optimization using a functional coefficient gradient. Simulation results provide the basis for further physiological and kinetic development. This study provides a methodology for the generation of biomimetic protective surfaces using segmented, articulated components that maintain mobility alongside full body coverage.Massachusetts Institute of Technology. Institute for Soldier Nanotechnologies (Contract No. W911NF-13-D-0001)United States. Army Research Office (Institute for Collaborative Biotechnologies (ICB), contract no. W911NF-09-D-0001)United States. Department of Defense (National Security Science and Engineering Faculty Fellowship Program (Grant No. N00244-09-1-0064)

Anti-inflammatory and safety profile of DuP 697, a novel orally effective prostaglandin synthesis inhibitor

ABBREVIATiONS: NSAID, nonsteroidal anti-inflammatory drugs; PG. prostaglandin; RBF, renal blood flow; All, angiotensin II; POW, phenylquinon

Delayed BCG immunization does not alter antibody responses to EPI vaccines in HIV-exposed and -unexposed South African infants.

BACKGROUND: Bacille Calmette-Guérin (BCG) is routinely given at birth in tuberculosis-endemic settings due to its protective effect against disseminated tuberculosis in infants. BCG is however contraindicated in HIV-infected infants. We investigated whether delaying BCG vaccination to 14 weeks of age affected vaccine-induced antibody responses to Haemophilus influenzae type b (Hib)-conjugate, pertussis, tetanus and Hepatitis B (HBV) vaccines, in HIV-exposed uninfected (HEU) and -unexposed uninfected (HUU) infants. METHODS: Infants were randomized to receive BCG at birth or at 14 weeks of age. Blood was taken at 14, 24, and 52 weeks of age and analyzed for Hib, pertussis, tetanus and HBV specific antibodies. RESULTS: BCG was given either at birth (106 infants, 51 HEU) or at 14 weeks of age (74 infants, 50 HEU). The timing of BCG vaccination did not influence the antibody response to any antigen studied. However, in a non-randomized comparison, HEU infants had higher Hib antibody concentrations at weeks 14 and 24 (p=0.001 and <0.001, respectively) and pertussis at week 24 (p=0.003). Conversely, HEU infants had lower antibody concentrations to HBV at 14 and 52 weeks (p=0.032 and p=0.031) with no differences in tetanus titres. CONCLUSIONS: HIV exposure, but not the timing of BCG vaccination, was associated with antibody concentrations to Hib, pertussis, HBV and tetanus primary immunization. CLINICAL TRIAL REGISTRATION: DOH-27-1106-1520

Investigations of the Crust and Upper Mantle of Modern and Ancient Subduction Zones, using Pn Tomography and Seismic Receiver Functions

Advances in seismology allow us to obtain "high-resolution" images of the Earth's subsurface. This dissertation summarizes the results of three seismic studies on three different continents, with the aim of better understanding the crust and upper mantle structure of seemingly disparate yet ultimately related regions. The seismic techniques of Pn tomography and P-wave receiver function (RF) analysis are applied to central Turkey (Pn tomography), western Argentina and southwestern Wyoming, USA (RF analysis). These studies look at both a present-day convergent margin (Andean subduction zone, Argentina) and two ancient ones (Bitlis-Zagros collision zone of Arabia-Africa with Eurasia, Turkey; Farallon subduction zone, Wyoming).Using Pn tomography, we were able to detect the limit of the slab rupture edge along the Central Anatolian Fault Zone, Turkey. Slab break-off is an important process that modifies the mantle in tectonically active regions, and the limit of the oceanic Arabian slab break-off along the Bitlis-Zagros Suture Zone, thought to have begun at 11 Ma, was previously undetermined.Using RF analysis, we obtained high-resolution images of the subducting slab beneath the Sierras Pampeanas, Argentina. Continental Moho contours roughly follow terrane boundaries, suggesting that ancient terranes continue to exert control over present-day continental deformation. Overthickened oceanic crust is often cited as a cause of flat slab subduction; our RF results indicate that the crust is moderately overthickened, around 11-16 km. Further, we image offsets in the RF arrivals that indicate the subducted slab is broken or offset in along trench-subparallel fractures.The crustal structure beneath southwestern Wyoming, the location of ancient Farallon flat slab subduction, was studied using RF analysis. Looking at regional crustal structure, results include a new depth to Moho map. Coherency of the seismic signal across the dense LaBarge array (55 stations, ~250 m spacing) was investigated, with results showing that complicated shallow structure can greatly impact the resulting RF signal. Modeling of RFs using synthetics helped to separate the complex signal containing multiple primary conversions and their reverberations, which interact constructively and destructively. The dense spacing of the LaBarge array allowed unique opportunities to investigate coherency of waveforms across very short distances.Embargo: Release after 8/28/201

Modeling Fault Creep on the Hayward Fault and Implications of Seismicity for Defining Patterns of Fault Creep

The Hayward fault is considered to be one of the primary hazards in the San Francisco Bay region. Although it is documented to undergo significant creep, with some creeping patches accommodating 50% or more of the long-term fault displacement, the fault also experiences moderate to large earthquakes (most recent M ~6.8 in 1868). Under the assumption that the seismic hazard associated with a fault is related to the distribution and amount of slip deficit accumulated during interseismic periods. Therefore mapping creep patterns on a fault plane is an important component in the assessment of the seismic hazard. Combining observations of surface creep rate and the distribution of micro-seismicity, with modeling results derived from a visco-elastic finiteelement model driven by far field plate motions, we have analyzed the slip deficit that can be accumulated on the Hayward Fault. Our results show that the interaction of the fault with the surrounding lithosphere leads to a smooth transition of the creep rate from locked to fully creeping areas and implies significant slip deficit accumulation not only in fully locked zones but also in adjacent low friction areas. In order to link seismic potential to the rate at which moment accumulates on the fault plane, we need to understand the patterns and distribution of creep over time. As might be expected, the microseismicity observed on the fault produces only a negligible percentage of the seismic moment dissipated on the Hayward fault, whereas aseismic creep releases about 25% of the moment accumulating on the fault. The distribution of creep on the fault can change throughout the earthquake cycle, in particular after major seismic events. Although at present the post-seismic transients have mostly decayed, the pattern of accumulated moment is significantly different when these transients are included

Imaging Patterns of Fault Creep: Implications for Earthquakes on the Hayward Fault

The slip deficit that accumulates on a fault constrains the potential slip (and moment) for subsequent earthquakes on the fault. Fault creep will reduce the rate at which this slip deficit accumulates, at least on those patches of the fault that undergo such aseismic slip. Mapping the spatial and temporal patterns of such creep then becomes an important component of assessments of earthquake potential on a fault such as the Hayward. In regions where faults are creeping at or near the surface, the pattern of surface deformation can be used to constrain fault creep in the upper few kilometers. Determination of the patterns of creep on deeper sections of a fault is poorly constrained by near-fault surface observations. The inclusion of micro-seismicity in analyzing patterns of fault creep adds an additional constraint on locations of locked and creeping patches on the fault. A second consideration in assessing the accumulation of slip deficit is the potential for timedependent creep behavior – particularly driven by post-earthquake viscous relaxation. We are investigating the potential role of such transient behavior in both biasing observations of creep rate, and also modifying the rate at which slip deficit accumulates. Including the effects of a simulated 1868-like earthquake in our models of Hayward Fault creep indicate a significant variations in both the spatial pattern and rate of fault creep during the first 50-100 years after the earthquake

Numerical Modeling of Strike-Slip Creeping Faults and Implications for the Hayward Fault, California

The seismic potential of creeping faults such as the Hayward fault (San Francisco Bay Area, CA) depends on the rate at which moment (slip deficit) accumulates on the fault plane. Thus, it is important to evaluate how the creep rate observed at the surface is related to the slip on the fault plane. The surface creep rate (SCR) depends on the geometry of locked and free portions of the fault and on the interaction between the fault zone and the surrounding lithosphere. Using a viscoelastic finite element model, we investigate how fault zone geometries and physical characteristics such as frictionless or locked patches affect the observed surface creep when the system is driven by far field plate motions. These results have been applied to creep observations of the Hayward fault. This analysis differs from most previous fault creeping models in that the fault in our model is loaded by a distributed viscous flow induced by far field velocity boundary conditions instead of imposed slip beneath the major faults of the region. The far field velocity boundary conditions simulate the relative motion of the stable Pacific plate respect to the Rigid Sierra Nevada block, leaving the rheology, fault geometry, and mechanics (locked or free to creep patches), to determinate the patterns of fault creep. Our model results show that the fault geometry (e.g. length and depth of creeping) and the local rheology influence the surface creep rate (SCR) and the slip on the fault plane. In particular, we show that the viscoelastic layer beneath the elastic seismogenic zone plays a fundamental role in loading the fault. Additionally, the coupling with the surrounding lithosphere results in a smooth transition from regions free to creep to locked patches