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Fracture Model for Fluid Saturated Geomaterials Implemented Via a Poro-Elasto-Plastic Cohesive Surface Finite Element
Fractures involving poromechanical fluid flow are known to exhibit a strong coupling between the behavior of the solid skeleton and the pore fluid. Though there are other ways to model this poromechanical coupling, in this thesis, fractures are modeled discretely using a quadratic, 6-noded, poromechanical cohesive surface element (CSE). The CSE has specialized behavior in both the way that fluid flow and solid mechanics are modeled. The mechanical behavior of the CSE, when activated, will go through various stages as the fracture occurs. Further, the CSE models fluid flow along the fracture (longitudinal flow) as well as fluid flow exchange between the bulk porous material and cohesive surface element (transverse flow). Specialized tools are developed using MATLAB\u27s object oriented functionality to allow for rapid generation of meshes and the associated initial conditions/boundary conditions. These tools also allow the mesh to be plotted and updated as the solution progresses. Example problems are presented to demonstrate the behavior of the poromechanical CSE as well as the close hydromechanical coupling
Does McLuhan’s Idea Stand Up for Millennials? Testing Whether the Medium is the Message in Political Organization Public Relationships
Examining McLuhan’s (1964) classic adage that the “medium is the message,” this experimental
design presented participants with the three versions of the same message content. Manipulating
medium as an online press release, blog post, or online video, the research here found that
medium does play a role in shaping the receiver’s perceived relationship with an organization.
Conversely, medium does not impact one’s assessment of credibility. Set in a digital political
public relations context, this study attempts to connect public relations’ most heuristic theory in
the examination in the state of ever-evolving digital media
Demonstration of the Zero-Crossing Phasemeter with a LISA Test-bed Interferometer
The Laser Interferometer Space Antenna (LISA) is being designed to detect and
study in detail gravitational waves from sources throughout the Universe such
as massive black hole binaries. The conceptual formulation of the LISA
space-borne gravitational wave detector is now well developed. The
interferometric measurements between the sciencecraft remain one of the most
important technological and scientific design areas for the mission.
Our work has concentrated on developing the interferometric technologies to
create a LISA-like optical signal and to measure the phase of that signal using
commercially available instruments. One of the most important goals of this
research is to demonstrate the LISA phase timing and phase reconstruction for a
LISA-like fringe signal, in the case of a high fringe rate and a low signal
level. We present current results of a test-bed interferometer designed to
produce an optical LISA-like fringe signal previously discussed in the
literature.Comment: find minor corrections in the CQG versio
Candidates for Accreditation in Public Relations: Role Enactment and the Social Media Synapse
Public relations roles have been studied for decades and around the world, but no
research published to date examines the role enactment of practitioners who choose to
sit for professional certification in public relations. This survey finds that Accreditationtrack
professionals (N = 150) align with the general-population practitioner in some
respects, such as role enactment and gender, but differ in others, such as experience
and role enactment. In determining how social media use integrates into the roles
literature, the data here support a 3-factor solution, with a social media synapse
enactment factor standing alone
Effects of Interplanetary Dust on the LISA drag-free Constellation
The analysis of non-radiative sources of static or time-dependent
gravitational fields in the Solar System is crucial to accurately estimate the
free-fall orbits of the LISA space mission. In particular, we take into account
the gravitational effects of Interplanetary Dust (ID) on the spacecraft
trajectories. The perturbing gravitational field has been calculated for some
ID density distributions that fit the observed zodiacal light. Then we
integrated the Gauss planetary equations to get the deviations from the LISA
keplerian orbits around the Sun. This analysis can be eventually extended to
Local Dark Matter (LDM), as gravitational fields are expected to be similar for
ID and LDM distributions. Under some strong assumptions on the displacement
noise at very low frequency, the Doppler data collected during the whole LISA
mission could provide upper limits on ID and LDM densities.Comment: 11 pages, 6 figures, to be published on the special issue of
"Celestial Mechanics and Dynamical Astronomy" on the CELMEC V conferenc
Technology requirements of exploration beyond Neptune by solar sail propulsion
This paper provides a set of requirements for the technology development of a solar sail propelled Interstellar Heliopause Probe mission. The mission is placed in the context of other outer solar systems missions, ranging from a Kuiper Belt mission through to an Oort cloud mission. Mission requirements are defined and a detailed parametric trajectory analysis and launch date scan performed. Through analysis of the complete mission trade space a set of critical technology development requirements are identified which include an advanced lightweight composite High-Gain Antenna, a high-efficiency Ka-band travelling-wave tube amplifier and a radioisotope thermoelectric generator with power density of approximately 12 W/kg. It is also shown that the Interstellar Heliopause Probe mission necessitates the use of a spinning sail, limiting the direct application of current hardware development activities. A Kuiper Belt mission is then considered as a pre-curser to the Interstellar Heliopause Probe, while it is also shown through study of an Oort cloud mission that the Interstellar Heliopause Probe mission is the likely end-goal of any future solar sail technology development program. As such, the technology requirements identified to enable the Interstellar Heliopause Probe must be enabled through all prior missions, with each mission acting as an enabling facilitator towards the next
Coherent interaction of laser pulses in a resonant optically dense extended medium under the regime of strong field-matter coupling
Nonstationary pump-probe interaction between short laser pulses propagating
in a resonant optically dense coherent medium is considered. A special
attention is paid to the case, where the density of two-level particles is high
enough that a considerable part of the energy of relatively weak external
laser-fields can be coherently absorbed and reemitted by the medium. Thus, the
field of medium reaction plays a key role in the interaction processes, which
leads to the collective behavior of an atomic ensemble in the strongly coupled
light-matter system. Such behavior results in the fast excitation interchanges
between the field and a medium in the form of the optical ringing, which is
analogous to polariton beating in the solid-state optics. This collective
oscillating response, which can be treated as successive beats between light
wave-packets of different group velocities, is shown to significantly affect
propagation and amplification of the probe field under its nonlinear
interaction with a nearly copropagating pump pulse. Depending on the probe-pump
time delay, the probe transmission spectra show the appearance of either
specific doublet or coherent dip. The widths of these features are determined
by the density-dependent field-matter coupling coefficient and increase during
the propagation. Besides that, the widths of the coherent features, which
appear close to the resonance in the broadband probe-spectrum, exceed the
absorption-line width, since, under the strong-coupling regime, the frequency
of the optical ringing exceeds the rate of incoherent relaxation. Contrary to
the stationary strong-field effects, the density- and coordinate-dependent
transmission spectra of the probe manifest the importance of the collective
oscillations and cannot be obtained in the framework of the single-atom model.Comment: 10 pages, 8 figures, to be published in Phys. Rev.
Scientific Exploration of Near-Earth Objects via the Crew Exploration Vehicle
The concept of a crewed mission to a Near-Earth Object (NEO) has been analyzed in depth in 1989 as part of the Space Exploration Initiative. Since that time two other studies have investigated the possibility of sending similar missions to NEOs. A more recent study has been sponsored by the Advanced Programs Office within NASA's Constellation Program. This study team has representatives from across NASA and is currently examining the feasibility of sending a Crew Exploration Vehicle (CEV) to a near-Earth object (NEO). The ideal mission profile would involve a crew of 2 or 3 astronauts on a 90 to 120 day flight, which would include a 7 to 14 day stay for proximity operations at the target NEO. One of the significant advantages of this type of mission is that it strengthens and validates the foundational infrastructure for the Vision for Space Exploration (VSE) and Exploration Systems Architecture Study (ESAS) in the run up to the lunar sorties at the end of the next decade (approx.2020). Sending a human expedition to a NEO, within the context of the VSE and ESAS, demonstrates the broad utility of the Constellation Program s Orion (CEV) crew capsule and Ares (CLV) launch systems. This mission would be the first human expedition to an interplanetary body outside of the cislunar system. Also, it will help NASA regain crucial operational experience conducting human exploration missions outside of low Earth orbit, which humanity has not attempted in nearly 40 years
Efficacy and safety of givosiran for acute hepatic porphyria: 24-month interim analysis of the randomized phase 3 ENVISION study
Background & Aims
Upregulation of hepatic delta-aminolevulinic acid synthase 1 with accumulation of potentially toxic heme precursors delta-aminolevulinic acid and porphobilinogen is fundamental to the pathogenesis of acute hepatic porphyria. Aims: evaluate long-term efficacy and safety of givosiran in acute hepatic porphyria.
Methods
Interim analysis of ongoing ENVISION study (NCT03338816), after all active patients completed their Month 24 visit. Patients with acute hepatic porphyria (≥12 years) with recurrent attacks received givosiran (2.5 mg/kg monthly) (n=48) or placebo (n=46) for 6 months (double-blind period); 93 received givosiran (2.5 mg or 1.25 mg/kg monthly) in the open-label extension (continuous givosiran, n=47/48; placebo crossover, n=46/46). Endpoints included annualized attack rate, urinary delta-aminolevulinic acid and porphobilinogen levels, hemin use, daily worst pain, quality of life, and adverse events.
Results
Patients receiving continuous givosiran had sustained annualized attack rate reduction (median 1.0 in double-blind period, 0.0 in open-label extension); in placebo crossover patients, median annualized attack rate decreased from 10.7 to 1.4. Median annualized days of hemin use were 0.0 (double-blind period) and 0.0 (open-label extension) for continuous givosiran patients and reduced from 14.98 to 0.71 for placebo crossover patients. Long-term givosiran led to sustained lowering of delta-aminolevulinic acid and porphobilinogen and improvements in daily worst pain and quality of life. Safety findings were consistent with the double-blind period.
Conclusions
Long-term givosiran has an acceptable safety profile and significantly benefits acute hepatic porphyria patients with recurrent attacks by reducing attack frequency, hemin use, and severity of daily worst pain while improving quality of life
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