927 research outputs found
Gas Kinematics and Excitation in the Filamentary IRDC G035.39-00.33
Some theories of dense molecular cloud formation involve dynamical
environments driven by converging atomic flows or collisions between
preexisting molecular clouds. The determination of the dynamics and physical
conditions of the gas in clouds at the early stages of their evolution is
essential to establish the dynamical imprints of such collisions, and to infer
the processes involved in their formation. We present multi-transition 13CO and
C18O maps toward the IRDC G035.39-00.33, believed to be at the earliest stages
of evolution. The 13CO and C18O gas is distributed in three filaments
(Filaments 1, 2 and 3), where the most massive cores are preferentially found
at the intersecting regions between them. The filaments have a similar
kinematic structure with smooth velocity gradients of ~0.4-0.8 km s-1 pc-1.
Several scenarios are proposed to explain these gradients, including cloud
rotation, gas accretion along the filaments, global gravitational collapse, and
unresolved sub-filament structures. These results are complemented by HCO+,
HNC, H13CO+ and HN13C single-pointing data to search for gas infall signatures.
The 13CO and C18O gas motions are supersonic across G035.39-00.33, with the
emission showing broader linewidths toward the edges of the IRDC. This could be
due to energy dissipation at the densest regions in the cloud. The average H2
densities are ~5000-7000 cm-3, with Filaments 2 and 3 being denser and more
massive than Filament 1. The C18O data unveils three regions with high CO
depletion factors (f_D~5-12), similar to those found in massive starless cores.Comment: 20 pages, 14 figures, 6 tables, accepted for publication in MNRA
Meshfree finite differences for vector Poisson and pressure Poisson equations with electric boundary conditions
We demonstrate how meshfree finite difference methods can be applied to solve
vector Poisson problems with electric boundary conditions. In these, the
tangential velocity and the incompressibility of the vector field are
prescribed at the boundary. Even on irregular domains with only convex corners,
canonical nodal-based finite elements may converge to the wrong solution due to
a version of the Babuska paradox. In turn, straightforward meshfree finite
differences converge to the true solution, and even high-order accuracy can be
achieved in a simple fashion. The methodology is then extended to a specific
pressure Poisson equation reformulation of the Navier-Stokes equations that
possesses the same type of boundary conditions. The resulting numerical
approach is second order accurate and allows for a simple switching between an
explicit and implicit treatment of the viscosity terms.Comment: 19 pages, 7 figure
Laser Applications
Contains research objectives and reports on five research projects.U. S. Air Force - Office of Scientific Research(Contract F44620-71-C-0051)Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DAAB07-71-C-0300Naval Air Systems Comman
Capability engineering -an analysis of perspectives
The terms "capability" and "capability engineering" are now widely used across industry and in government procurement, but it is clear that different communities use the terms with similar, but distinctly different meanings. Using a soft systems methodological approach, an INCOSE UK working group has identified eight perspectives of capability, which have been related to Ring"s value cycle and the Hitchins" five layer model of systems engineering. It is asserted that capability is the ability to do something and that capability engineering is the overarching approach that links value, purpose, and solution of a systems problem. It is equivalent to layers 1-4 of Hitchins" Five Layer Model and is equivalent to an holistic perspective of systems engineering. There are significant practice and examples of capability engineering from (at least) the UK rail provision, defence, and Information Services and it is the view of the working group that further INCOSE guidance may be needed to ensure engineers are properly equipped to deal with capability and capability engineering.©2011 by Michael Henshaw, Duncan Kemp, Peter Lister, Andrew Daw, Alan Harding, Andrew Farncombe, Malcolm Touchin. Published and used by INCOSE with permission
The three-dimensional structure of Galactic molecular cloud complexes out to 2.5 kpc
Knowledge of the three-dimensional structure of Galactic molecular clouds is
important for understanding how clouds are affected by processes such as
turbulence and magnetic fields and how this structure effects star formation
within them. Great progress has been made in this field with the arrival of the
Gaia mission, which provides accurate distances to stars.
Combining these distances with extinctions inferred from optical-IR, we recover
the three-dimensional structure of 16 Galactic molecular cloud complexes at
pc resolution using our novel three-dimensional dust mapping algorithm
\texttt{Dustribution}. Using \texttt{astrodendro} we derive a catalogue of
physical parameters for each complex. We recover structures with aspect ratios
between 1 and 11, i.e.\ everything from near-spherical to very elongated
shapes. We find a large variation in cloud environments that is not apparent
when studying them in two-dimensions. For example, the nearby California and
Orion A clouds look similar on-sky, but we find California to be more
sheet-like, and massive, which could explain their different star-formation
rates. In Carina, our most distant complex, we observe evidence for dust
sputtering, which explains its measured low dust mass. By calculating the total
mass of these individual clouds, we demonstrate that it is necessary to define
cloud boundaries in three-dimensions in order to obtain an accurate mass;
simply integrating the extinction overestimates masses. We find that Larson's
relationship on mass vs radius holds true whether you assume a spherical shape
for the cloud or take their true extents.Comment: accepted for publication by MNRAS, 23 pages, 9 figures, 3 table
13C dynamic nuclear polarization in diamond via a microwave-free 'integrated' cross effect
Color-center-hosting semiconductors are emerging as promising source
materials for low-field dynamic nuclear polarization (DNP) at or near room
temperature, but hyperfine broadening, susceptibility to magnetic field
heterogeneity, and nuclear spin relaxation induced by other paramagnetic
defects set practical constraints difficult to circumvent. Here, we explore an
alternate route to color-center-assisted DNP using nitrogen-vacancy (NV)
centers in diamond coupled to substitutional nitrogen impurities, the so-called
P1 centers. Working near the level anti-crossing condition - where the P1
Zeeman splitting matches one of the NV spin transitions - we demonstrate
efficient microwave-free 13C DNP through the use of consecutive magnetic field
sweeps and continuous optical excitation. The amplitude and sign of the
polarization can be controlled by adjusting the low-to-high and high-to-low
magnetic field sweep rates in each cycle so that one is much faster than the
other. By comparing the 13C DNP response for different crystal orientations, we
show that the process is robust to magnetic field/NV misalignment, a feature
that makes the present technique suitable to diamond powders and settings where
the field is heterogeneous. Applications to shallow NVs could capitalize on the
greater physical proximity between surface paramagnetic defects and outer
nuclei to efficiently polarize target samples in contact with the diamond
crystal
Clinical pharmacokinetics and pharmacodynamics of cerliponase alfa, enzyme replacement therapy for CLN2 disease by intracerebroventricular administration
Cerliponase alfa is recombinant human TPP1 delivered by intracerebroventricular (ICV) infusion for CLN2, a pediatric neurodegenerative disease caused by deficiency in lysosomal enzyme TPP1. We report the PK and PD of cerliponase alfa, the first ICV enzyme replacement therapy, characterized in a Phase 1/2 study. Escalating doses (30-300 mg every two weeks, Q2W) followed by 300 mg Q2W for ≥48 weeks were administered in 24 patients aged ≥3 years. Concentrations peaked in CSF at the end of ~4-hour ICV infusion and 8 hours thereafter in plasma. Plasma exposure was 300-1000 fold lower than in CSF, with no correlation in the magnitude of Cmax or AUC between body sites. There was no apparent accumulation in CSF or plasma exposure with Q2W dosing. Inter- and intra-patient variability of AUC, respectively, were 31-49% and 24% in CSF versus 59-103% and 80% in plasma. PK variability was not explained by baseline demographics, as gender, age, weight, and CLN2 disease severity score did not appear to impact CSF or plasma PK. No apparent correlation was noted between CSF or plasma PK and incidence of adverse events (pyrexia, hypersensitivity, seizure, and epilepsy) or presence of antidrug antibodies in CSF and serum. There was no relationship between magnitude of CSF exposure and efficacy (change in CLN2 score from baseline), indicating maximum benefit was obtained across the range of exposures with 300 mg Q2W. Data from this small trial of ultra-rare disease were leveraged to adequately profile cerliponase alfa and support 300 mg ICV Q2W for CLN2 treatment
Widespread deuteration across the IRDC G035.39-00.33
© 2016 The Authors. Infrared Dark Clouds (IRDCs) are cold, dense regions that are usually found within Giant Molecular Clouds. Ongoing star formation within IRDCs is typically still deeply embedded within the surrounding molecular gas. Characterizing the properties of relatively quiescent IRDCs may therefore help us to understand the earliest phases of the star formation process. Studies of local molecular clouds have revealed that deuterated species are enhanced in the earliest phases of star formation. In this paper, we test this towards IRDC G035.39-00.33. We present an 80 arcsec by 140 arcsec map of the J = 2 → 1 transition of N2D+, obtained with the Institut de Radioastronomie Millimétrique 30 m telescope telescope. We find that N2D+ is widespread throughout G035.39-00.33. Complementary observations of N2H+ (1 - 0) are used to estimate the deuterium fraction, DN2H+ frac ≡ N(N2D+)/N(N2H+). We report a mean DN2H+ frac = 0.04 ± 0.01, with a maximum of DN2H+ frac = 0.09 ± 0.02. The mean deuterium fraction is ~3 orders of magnitude greater than the interstellar [D]/[H] ratio. High angular resolution observations are required to exclude beam dilution effects of compact deuterated cores. Using chemical modelling, we find that the average observed values of DN2H+ frac are in agreement with an equilibrium deuterium fraction, given the general properties of the cloud. This implies that the IRDC is at least ~3 Myr old, which is ~8 times longer than the mean free-fall time of the observed deuterated region
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