29 research outputs found
LSST: from Science Drivers to Reference Design and Anticipated Data Products
(Abridged) We describe here the most ambitious survey currently planned in
the optical, the Large Synoptic Survey Telescope (LSST). A vast array of
science will be enabled by a single wide-deep-fast sky survey, and LSST will
have unique survey capability in the faint time domain. The LSST design is
driven by four main science themes: probing dark energy and dark matter, taking
an inventory of the Solar System, exploring the transient optical sky, and
mapping the Milky Way. LSST will be a wide-field ground-based system sited at
Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m
effective) primary mirror, a 9.6 deg field of view, and a 3.2 Gigapixel
camera. The standard observing sequence will consist of pairs of 15-second
exposures in a given field, with two such visits in each pointing in a given
night. With these repeats, the LSST system is capable of imaging about 10,000
square degrees of sky in a single filter in three nights. The typical 5
point-source depth in a single visit in will be (AB). The
project is in the construction phase and will begin regular survey operations
by 2022. The survey area will be contained within 30,000 deg with
, and will be imaged multiple times in six bands, ,
covering the wavelength range 320--1050 nm. About 90\% of the observing time
will be devoted to a deep-wide-fast survey mode which will uniformly observe a
18,000 deg region about 800 times (summed over all six bands) during the
anticipated 10 years of operations, and yield a coadded map to . The
remaining 10\% of the observing time will be allocated to projects such as a
Very Deep and Fast time domain survey. The goal is to make LSST data products,
including a relational database of about 32 trillion observations of 40 billion
objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures
available from https://www.lsst.org/overvie
Diabetes, periodontitis, and the subgingival microbiota
Both type 1 and type 2 diabetes have been associated with increased severity of periodontal disease for many years. More recently, the impact of periodontal disease on glycaemic control has been investigated. The role of the oral microbiota in this two-way relationship is at this stage unknown. Further studies, of a longitudinal nature and investigating a wider array of bacterial species, are required in order to conclusively determine if there is a difference in the oral microbiota of diabetics and non-diabetics and whether this difference accounts, on the one hand, for the increased severity of periodontal disease and on the other for the poorer glycaemic control seen in diabetics
Flame retarded poly(lactic acid) using POSS-modified cellulose. 2. Effects of intumescing flame retardant formulations on polymer degradation and composite physical properties
Atrial fibrillation genetic risk differentiates cardioembolic stroke from other stroke subtypes
Spatial and Orientation Control of Cylindrical Nanostructures in ABA Triblock Copolymer Thin Films by Raster Solvent Vapor Annealing
We present a spatially resolved approach for the solvent vapor annealing (SVA) of block copolymer thin films that permits the facile and relatively rapid manipulation of nanoscale ordering and nanostructure orientation. In our method, a localized (point) SVA zone is created through the use of a vapor delivery nozzle. This point annealing zone can be rastered across the thin film using a motorized stage to control the local nanoscale structure and orientation in a cylinder-forming ABA triblock copolymer thin film. At moderate rastering speeds (∼100 μm/s) (<i>i.e.</i>, relatively modest annealing time at a given point), the film displayed ordered cylindrical nanostructures with the cylinders oriented parallel to the substrate surface. As the rastering speed was decreased (∼10 μm/s), the morphology transformed into a surface nanostructure indicative of cylinders oriented perpendicular to the substrate surface. These perpendicular cylinder orientations also were created by rastering multiple times over the same region, and this effect was found when rastering in either retrace (overlapping) or crossed-path (orthogonal) geometries. Similar trends in nanostructure orientation and ordering were obtained from various nozzle diameters by accounting for differences in solvent flux and annealing time, illustrating the universality of this approach. Finally, we note that our “stylus-based” raster solvent vapor annealing technique allows a given point to be solvent annealed approximately 2 orders of magnitude faster than conventional “bell jar” solvent vapor annealing
Rapid fabrication of poly(DL-lactide) nanofiber scaffolds with tunable degradation for tissue engineering applications by air-brushing
Switching the Adhesive State of Catecholic Hydrogels using Phototitration
A polyacrylamide hydrogel system
that can be liquefied by remote
activation using UV irradiation is investigated as a degradable adhesive.
The linear polyacrylamide copolymer, formed by conventional free-radical
polymerization, contains biomimetic catechol–iron-mediated
cross-linkers that are sensitive to pH changes. Hydrogel films and
bulk gels are prepared by basic titration of a polymer solution doped
with a photoacid generator, diphenyliodonium chloride, generating
an ionic cross-linked network via the catechol pendant groups. Irradiation
of these hydrogels with UV light affords a viscous liquid solution,
demonstrating a gel–sol transition with a subsequent decrease
in the adhesive strength of the material. These gels may be prepared
in high throughput and require few synthetic steps with commercially
available precursors
Switching the Adhesive State of Catecholic Hydrogels using Phototitration
A polyacrylamide hydrogel system
that can be liquefied by remote
activation using UV irradiation is investigated as a degradable adhesive.
The linear polyacrylamide copolymer, formed by conventional free-radical
polymerization, contains biomimetic catechol–iron-mediated
cross-linkers that are sensitive to pH changes. Hydrogel films and
bulk gels are prepared by basic titration of a polymer solution doped
with a photoacid generator, diphenyliodonium chloride, generating
an ionic cross-linked network via the catechol pendant groups. Irradiation
of these hydrogels with UV light affords a viscous liquid solution,
demonstrating a gel–sol transition with a subsequent decrease
in the adhesive strength of the material. These gels may be prepared
in high throughput and require few synthetic steps with commercially
available precursors
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A healable supramolecular polymer blend based on aromatic π-π stacking and hydrogen bonding interactions
An elastomeric, supramolecular healable polymer blend, comprising a chain-folding polyimide and a telechelic polyurethane with pyrenyl endgroups, is compatibilised by aromatic π−π stacking between the π-electron-deficient diimide groups and the π-electron-rich pyrenyl units. This inter-polymer interaction is key to forming a tough, healable, elastomeric material. Variable temperature FTIR analysis of the bulk material also conclusively demonstrates the presence of hydrogen bonding, which complements the π–π stacking interactions. Variable temperature SAXS analysis shows that the healable polymeric blend has a nanophase-separated morphology, and that the X-ray contrast between the two types of domain increases with increasing temperature, a feature that is repeatable over several heating and cooling cycles. A fractured sample of this material reproducibly regains more than 95% of the tensile modulus, 91% of the elongation to break, and 77% of the modulus of toughness of the pristine material
Manipulating Nanoscale Morphologies in Cylinder-Forming Poly(styrene‑<i>b</i>‑isoprene‑<i>b</i>‑styrene) Thin Films Using Film Thickness and Substrate Surface Chemistry Gradients
Controlling
the nanostructure of self-assembled block copolymer
thin films is critical for applications in nanotemplate design, nanoporous
membranes, and organic optoelectronics. In this study, we employed
a gradient approach to examine the effects of substrate surface chemistry
and film thickness on the self-assembly of cylinder-forming poly(styrene-<i>b</i>-isoprene-<i>b</i>-styrene) (SIS) thin films.
Using gradients in film thickness from 85 to 120 nm (3.1<i>d</i> to 4.4<i>d</i>), we found that the thin films contained
parallel cylinders on both bare silicon substrates and benzyldimethylchlorosilane
(benzyl silane)-modified substrates regardless of film thickness,
while thin films contained surface patterns of hexagonally arranged
dots on <i>n</i>-butyldimethylchlorosilane (<i>n</i>-butyl silane)-modified substrates. These surface patterns were further
investigated using film etching, cross-sectional transmission electron
microscopy (TEM), and grazing-incidence small-angle X-ray scattering
(GISAXS) techniques. We determined that the nanostructures represented
a hexagonally perforated lamellar (HPL) morphology in which the parallel
cylinder layering was preserved during the phase transformation to
HPL. Additionally, controlled vapor deposition was used to generate
a nearly linear substrate surface chemistry gradient from benzyl silane
to <i>n</i>-butyl silane. Examination of SIS thin films
on this surface gradient revealed a morphological transformation from
parallel cylinders to HPL with changing substrate surface composition.
Thus, we demonstrated the combined usage of film thickness and monolayer
substrate surface chemistry gradients to manipulate the nanostructure
of block copolymer films, such as SIS, that possess moderate differences
in surface energy between individual blocks. Our gradients represent
a high-throughput and versatile screening tool that facilitates the
examination of new materials and furthers the understanding of block
copolymer thin film self-assembly