35 research outputs found
The James Webb Space Telescope
The James Webb Space Telescope (JWST) is a large (6.6m), cold (50K),
infrared-optimized space observatory that will be launched early in the next
decade. The observatory will have four instruments: a near-infrared camera, a
near-infrared multi-object spectrograph, and a tunable filter imager will cover
the wavelength range, 0.6 to 5.0 microns, while the mid-infrared instrument
will do both imaging and spectroscopy from 5.0 to 29 microns. The JWST science
goals are divided into four themes. The End of the Dark Ages: First Light and
Reionization theme seeks to identify the first luminous sources to form and to
determine the ionization history of the early universe. The Assembly of
Galaxies theme seeks to determine how galaxies and the dark matter, gas, stars,
metals, morphological structures, and active nuclei within them evolved from
the epoch of reionization to the present day. The Birth of Stars and
Protoplanetary Systems theme seeks to unravel the birth and early evolution of
stars, from infall on to dust-enshrouded protostars to the genesis of planetary
systems. The Planetary Systems and the Origins of Life theme seeks to determine
the physical and chemical properties of planetary systems including our own,
and investigate the potential for the origins of life in those systems. To
enable these observations, JWST consists of a telescope, an instrument package,
a spacecraft and a sunshield. The telescope consists of 18 beryllium segments,
some of which are deployed. The segments will be brought into optical alignment
on-orbit through a process of periodic wavefront sensing and control. The JWST
operations plan is based on that used for previous space observatories, and the
majority of JWST observing time will be allocated to the international
astronomical community through annual peer-reviewed proposal opportunities.Comment: 96 pages, including 48 figures and 15 tables, accepted by Space
Science Review
jae-f-database
A global database and âstate of the fieldâ review of research into ecosystem engineering by land animals
Formation and Dynamics of Electron-Irradiation-Induced Defects in Hexagonal Boron Nitride at Elevated Temperatures
The atomic structure,
stability, and dynamics of defects in hexagonal boron nitride (h-BN)
are investigated using an aberration-corrected transmission electron
microscope operated at 80 kV between room temperature and 1000 °C.
At temperatures above 700 °C, parallelogram- and hexagon-shaped
defects with zigzag edges become prominent, in contrast to the triangular
defects typically observed at lower temperatures. The appearance of
120° corners at defect vertices indicates the coexistence of
both N- and B-terminated zigzag edges in the same defect. In situ
dynamics studies show that the hexagonal holes grow by electron-induced
sputtering of BâN chains, and that at high temperatures these
chains can migrate from one defect corner to another. We complement
the experiments with first-principles calculation which consider the
thermal equilibrium formation energy of different defect configurations.
It is shown that, below a critical defect size, hexagonal defects
have the lowest formation energy and therefore are the more-stable
configuration, and triangular defects are energetically metastable
but can be âfrozen inâ under experimental conditions.
We also discuss the possible contributions of several dynamic processes
to the temperature-dependent defect formation
Formation and Dynamics of Electron-Irradiation-Induced Defects in Hexagonal Boron Nitride at Elevated Temperatures
The atomic structure,
stability, and dynamics of defects in hexagonal boron nitride (h-BN)
are investigated using an aberration-corrected transmission electron
microscope operated at 80 kV between room temperature and 1000 °C.
At temperatures above 700 °C, parallelogram- and hexagon-shaped
defects with zigzag edges become prominent, in contrast to the triangular
defects typically observed at lower temperatures. The appearance of
120° corners at defect vertices indicates the coexistence of
both N- and B-terminated zigzag edges in the same defect. In situ
dynamics studies show that the hexagonal holes grow by electron-induced
sputtering of BâN chains, and that at high temperatures these
chains can migrate from one defect corner to another. We complement
the experiments with first-principles calculation which consider the
thermal equilibrium formation energy of different defect configurations.
It is shown that, below a critical defect size, hexagonal defects
have the lowest formation energy and therefore are the more-stable
configuration, and triangular defects are energetically metastable
but can be âfrozen inâ under experimental conditions.
We also discuss the possible contributions of several dynamic processes
to the temperature-dependent defect formation
Clinical experience of using virtual 3D modelling for pre and intraoperative guidance during robotic-assisted partial nephrectomy
Objective: Surgical planning for robotic-assisted partial nephrectomy is widely performed using two-dimensional computed tomography images. It is unclear to what extent two-dimensional images fully simulate surgical anatomy and case complexity. To overcome these limitations, software has been developed to reconstruct three-dimensional models from computed tomography data. We present the results of a feasibility study, to explore the role and practicality of virtual three-dimensional modelling (by Innersight Labs) in the context of surgical utility for preoperative and intraoperative use, as well as improving patient involvement. /
Methods: A prospective study was conducted on patients undergoing robotic-assisted partial nephrectomy at our high volume kidney cancer centre. Approval from a research ethics committee was obtained. Patient demographics and tumour characteristics were collected. Surgical outcome measures were recorded. The value of the three-dimensional model to the surgeon and patient was assessed using a survey. The prospective cohort was compared against a retrospective cohort and cases were individually matched using RENAL (radius, exophytic/endophytic, nearness to collecting system or sinus, anterior/posterior, location relative to polar lines) scores. /
Results: This study included 22 patients. Three-dimensional modelling was found to be safe for this prospective cohort and resulted in good surgical outcome measures. The mean (standard deviation) console time was 158.6 (35) min and warm ischaemia time was 17.3 (6.3) min. The median (interquartile range) estimated blood loss was 125 (50â237.5) ml. Two procedures were converted to radical nephrectomy due to the risk of positive margins during resection. The median (interquartile range) length of stay was 2 (2â3) days. No postoperative complications were noted and all patients had negative surgical margins. Patients reported improved understanding of their procedure using the three-dimensional model. /
Conclusion: This study shows the potential benefit of three-dimensional modelling technology with positive uptake from surgeons and patients. Benefits are improved perception of vascular anatomy and resection approach, and procedure understanding by patients. A randomised controlled trial is needed to evaluate the technology further. /
Level of evidence: 2