67,621 research outputs found
Microscopic analysis of the octupole phase transition in Th isotopes
A shape phase transition between stable octupole deformation and octupole
vibrations in Th nuclei is analyzed in a microscopic framework based on nuclear
density functional theory. The relativistic functional DD-PC1 is used to
calculate axially-symmetric quadrupole-octupole constrained energy surfaces.
Observables related to order parameters are computed using an interacting-boson
Hamiltonian, with parameters determined by mapping the microscopic energy
surfaces to the expectation value of the Hamiltonian in the boson condensate.
The systematics of constrained energy surfaces and low-energy excitation
spectra point to the occurrence of a phase transition between octupole-deformed
shapes and shapes characterized by octupole-soft potentials.Comment: 6 pages, 5 figures, accepted for publication in Physical Review C,
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From Electrons to Finite Elements: A Concurrent Multiscale Approach for Metals
We present a multiscale modeling approach that concurrently couples quantum
mechanical, classical atomistic and continuum mechanics simulations in a
unified fashion for metals. This approach is particular useful for systems
where chemical interactions in a small region can affect the macroscopic
properties of a material. We discuss how the coupling across different scales
can be accomplished efficiently, and we apply the method to multiscale
simulations of an edge dislocation in aluminum in the absence and presence of H
impurities.Comment: 4 page
Microfluidically fabricated pH-responsive anionic amphiphilic microgels for drug release
© 2016 The Royal Society of Chemistry. Amphiphilic microgels of different composition based on the hydrophilic, pH-responsive acrylic acid (AA) and the hydrophobic, non-ionic n-butyl acrylate (BuA) were synthesised using a lab-on-a-chip device. Hydrophobic droplets were generated via a microfluidic platform that contained a protected form of AA, BuA, the hydrophobic crosslinker, ethylene glycol dimethacrylate (EGDMA), and a free radical initiator in an organic solvent. These hydrophobic droplets were photopolymerised within the microfluidic channels and subsequently hydrolysed, enabling an integrated platform for the rapid, automated, and in situ production of anionic amphiphilic microgels. The amphiphilic microgels did not feature the conventional core-shell structure but were instead based on random amphiphilic copolymers of AA and BuA and hydrophobic crosslinks. Due to their amphiphilic nature they were able to encapsulate and deliver both hydrophobic and hydrophilic moieties. The model drug delivery and the swelling ability of the microgels were influenced by the pH of the surrounding aqueous solution and the hydrophobic content of the microgels
Tailoring pH-responsive acrylic acid microgels with hydrophobic crosslinks for drug release
Amphiphilic microgels based on the hydrophilic acrylic acid (AA) and hydrophobic crosslinks of different compositions were synthesised using a lab-on-a-chip device. The microgels were formed by polymerising hydrophobic droplets. The droplets were generated via a microfluidic platform and contained a protected form of AA, a hydrophobic crosslinker (ethylene glycol dimethacrylate, EGDMA) and a free radical initiator in an organic solvent. Following photopolymerisation and subsequent hydrolysis, AA based microgels of amphiphilic nature were produced and it was demonstrated that they can successfully deliver both hydrophilic as well as hydrophobic moieties. The model drug delivery and the swelling ability of the microgels were influenced by the pH of the aqueous solution as well as the crosslinking density and hydrophobic content of the microgels
Herschel photometric observations of the low metallicity dwarf galaxy NGC 1705
We present Herschel SPIRE and PACS photometeric observations of the low metallicity (Z ~ 0.35 Z_â) nearby dwarf galaxy, NGC 1705, in six wavelength bands as part of the Dwarf Galaxy Survey guaranteed time Herschel key program. We confirm the presence of two dominant circumnuclear IR-bright regions surrounding the central super star cluster that had been previously noted at mid-IR wavelengths and in the sub-mm by LABOCA. On constructing a global spectral energy distribution using the SPIRE and PACS photometry, in conjunction with archival IR measurements, we note the presence of an excess at sub-mm wavelengths. This excess suggests the presence of a significant cold dust component within NGC 1705 and was modeled as an additional cold component in the SED. Although alternative explanations for the sub-mm excess beyond 350 ÎŒm, such as changes to the dust emissivity cannot be ruled out, the most likely explanation for the observed submillimetre excess is that of an additional cold dust component
Quantum Layers over Surfaces Ruled Outside a Compact Set
In this paper, we proved the quantum layer over a surface which is ruled
outside a compact set, asymptotically flat but not totally geodesic admits
ground states
On the discrete spectrum of quantum layers
Consider a quantum particle trapped between a curved layer of constant width
built over a complete, non-compact, smooth surface embedded in
. We assume that the surface is asymptotically flat in the sense
that the second fundamental form vanishes at infinity, and that the surface is
not totally geodesic. This geometric setting is known as a quantum layer. We
consider the quantum particle to be governed by the Dirichlet Laplacian as
Hamiltonian. Our work concerns the existence of bound states with energy
beneath the essential spectrum, which implies the existence of discrete
spectrum. We first prove that if the Gauss curvature is integrable, and the
surface is weakly -parabolic, then the discrete spectrum is non-empty.
This result implies that if the total Gauss curvature is non-positive, then the
discrete spectrum is non-empty. We next prove that if the Gauss curvature is
non-negative, then the discrete spectrum is non-empty. Finally, we prove that
if the surface is parabolic, then the discrete spectrum is non-empty if the
layer is sufficiently thin.Comment: Clarifications and corrections to previous version, conjecture from
previous version is proven here (Theorem 1.5), additional references include
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Novel Microgels Fabricated On Microfluidic Devices
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Microgels are micrometer sized particles consisting of a polymer network that show potential for the
delivery of both hydrophilic and hydrophobic drugs. Microfluidic devices provide an excellent format for the
generation of monodispersed droplets due to the precise manipulation of fluids and flow rates within the
microchannels. Microfluidic droplet generation chips were therefore designed using T-junction and flow
focusing geometries in glass. For microgel synthesis, monomers, crosslinker and initiator were added to the
dispersed phase and water was used as the continuous phase. Controlled formation of monodisperse droplets
was achieved with both geometries and droplets were collected off-chip for photopolymerisation. Three types
of microgel were formed using this setup: poly(ethylene glycol) diacrylate, poly(propylene glycol) diacrylate,
and tetrahydropyran acrylate - ethylene glycol dimethacrylate (THPA-EGDMA) microgels. THPA is a novel
material for microgels that can be turned from hydrophobic to amphiphilic by hydrolysation. THPA-EGDMA
microgels in particular demonstrated a strong response to pH changes due to the build-up of electrostatic force
under high pH, showing potential for the encapsulation and release of drugs
Radial distribution of gas and dust in spiral galaxies: The case of Mâ99 (NGCâ4254) and Mâ100 (NGCâ4321)
By combining Herschel-SPIRE data with archival Spitzer, Hâiâ, and CO maps, we investigate the spatial distribution of gas and dust in the two famous grand-design spirals Mâ99 and Mâ100 in the Virgo cluster. Thanks to the unique resolution and sensitivity of the Herschel-SPIRE photometer, we are for the first time able to measure the distribution and extent of cool, submillimetre (submm)-emitting dust inside and beyond the optical radius. We compare this with the radial variation in both the gas mass and the metallicity. Although we adopt a model-independent, phenomenological approach, our analysis provides important insights. We find the dust extending to at least the optical radius of the galaxy and showing breaks in its radial profiles at similar positions as the stellar distribution. The colour indices f350/f500 and f250/f350 decrease radially consistent with the temperature decreasing with radius. We also find evidence of an increasing gas to dust ratio with radius in the outer regions of both galaxies
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