6,041 research outputs found
Microfluidic generation of networked droplet collections and lipid membrane constructs
We report on microfluidic strategies to generate several multi-compartment membrane-based structures, including droplet interface bilayer networks and multi-compartment vesicles. These developments allow the current status quo— where microdroplets are used as isolated vessels— to be changed. By linking droplets together with lipid membranes, higher order systems can be generated, with particular ramifications for bottom-up synthetic biology and for functional droplet-based microreactors and biodevices
Measuring Fundamental Galactic Parameters with Stellar Tidal Streams and SIM PlanetQuest
Extended halo tidal streams from disrupting Milky Way satellites offer new
opportunities for gauging fundamental Galactic parameters without challenging
observations of the Galactic center. In the roughly spherical Galactic
potential tidal debris from a satellite system is largely confined to a single
plane containing the Galactic center, so accurate distances to stars in the
tidal stream can be used to gauge the Galactic center distance, R_0, given
reasonable projection of the stream orbital pole on the X_GC axis.
Alternatively, a tidal stream with orbital pole near the Y_GC axis, like the
Sagittarius stream, can be used to derive the speed of the Local Standard of
Rest (\Theta_LSR). Modest improvements in current astrometric catalogues might
allow this measurement to be made, but NASA's Space Interferometry Mission (SIM
PlanetQuest) can definitively obtain both R_0 and \Theta_LSR using tidal
streams.Comment: 8 pages, 4 figures, accepted for publication in ApJ Letters (minor
text revisions). Version with high resolution figures available at
http://www.astro.caltech.edu/~drlaw/Papers/GalaxyParameters.pd
Engineering swollen cubosomes using cholesterol and anionic lipids
Dispersions of non-lamellar lipid membrane assemblies are gaining increasing interest for drug delivery and protein therapeutic application. A key bottleneck has been the lack of rational design rules for these systems linking different lipid species and conditions to defined lattice parameters and structures. We have developed robust methods to form cubosomes (nanoparticles with a porous internal structure) with water channel diameters of up to 171 Ă… which are over 4 times larger than archetypal cubosome structures. The water channel diameter can be tuned via the incorporation of cholesterol and the charged lipids DOPA, DOPG or DOPS. We have found that large molecules can be incorporated into the porous cubosome structure and these molecules can interact with the internal cubosome membrane. This offers huge potential for accessible encapsulation and protection of biomolecules, and development of confined interfacial reaction environments
Nitrous oxide emissions from the Arabian Sea: A synthesis
We computed high-resolution (1Âş latitude x 1Âş longitude) seasonal and annual nitrous oxide (N2O) concentration fields for the Arabian Sea surface layer using a database containing more than 2400 values measured between December 1977 and July 1997. N2O concentrations are highest during the southwest (SW) monsoon along the southern Indian continental shelf. Annual emissions range from 0.33 to 0.70 Tg N2O and are dominated by fluxes from coastal regions during the SW and northeast monsoons. Our revised estimate for the annual N2O flux from the Arabian Sea is much more tightly constrained than the previous consensus derived using averaged in-situ data from a smaller number of studies. However, the tendency to focus on measurements in locally restricted features in combination with insufficient seasonal data coverage leads to considerable uncertainties of the concentration fields and thus in the flux estimates, especially in the coastal zones of the northern and eastern Arabian Sea. The overall mean relative error of the annual N2O emissions from the Arabian Sea was estimated to be at least 65%
Zooming into the coexisting regime of ferromagnetism and superconductivity in ErRh4B4 single crystals
High resolution measurements of the dynamic magnetic susceptibility are
reported for ferromagnetic re-entrant superconductor, ErRhB.
Detailed investigation of the coexisting regime reveals unusual
temperature-asymmetric and magnetically anisotropic behavior. The
superconducting phase appears via a series of discontinuous steps upon warming
from the ferromagnetic normal phase, whereas the ferromagnetic phase develops
via a gradual transition. A model based on local field inhomogeneity is
proposed to explain the observations
Adaptive optics in high-contrast imaging
The development of adaptive optics (AO) played a major role in modern
astronomy over the last three decades. By compensating for the atmospheric
turbulence, these systems enable to reach the diffraction limit on large
telescopes. In this review, we will focus on high contrast applications of
adaptive optics, namely, imaging the close vicinity of bright stellar objects
and revealing regions otherwise hidden within the turbulent halo of the
atmosphere to look for objects with a contrast ratio lower than 10^-4 with
respect to the central star. Such high-contrast AO-corrected observations have
led to fundamental results in our current understanding of planetary formation
and evolution as well as stellar evolution. AO systems equipped three
generations of instruments, from the first pioneering experiments in the
nineties, to the first wave of instruments on 8m-class telescopes in the years
2000, and finally to the extreme AO systems that have recently started
operations. Along with high-contrast techniques, AO enables to reveal the
circumstellar environment: massive protoplanetary disks featuring spiral arms,
gaps or other asymmetries hinting at on-going planet formation, young giant
planets shining in thermal emission, or tenuous debris disks and micron-sized
dust leftover from collisions in massive asteroid-belt analogs. After
introducing the science case and technical requirements, we will review the
architecture of standard and extreme AO systems, before presenting a few
selected science highlights obtained with recent AO instruments.Comment: 24 pages, 14 figure
Microfluidic generation of droplet interface bilayer networks incorporating real-time size sorting in linear and non-linear configurations
In this study, a novel droplet based microfluidic method for the generation of different sized droplet interface bilayers is reported. A microfluidic platform was designed, which allows the generation and packing of picoliter lipid coated water droplets. Droplets were generated by hydrodynamic focusing coupled with selective transport along grooves according to their size. A trapping structure at the end of the groove and a fine control of the flow pressures allowed for the droplets to be successfully trapped and aligned on demand. This technology facilitates the fine control of droplet size production as well as the generation of extended networks from a variety of lipids including 1,2-diphytanoyl-sn-glycero-3-phosphocholine and 1,2-dioleoyl-sn-glycero-3-phosphocholine in linear and non-linear configurations, which is vital to the application of Droplet Interface Bilayers to biological network construction on-chip
Quantum optics of a Bose-Einstein condensate coupled to a quantized light field
We consider the interaction between a Bose-Einstein condensate and a
single-mode quantized light field in the presence of a strong far off-resonant
pump laser. The dynamics is characterized by an exponential instability, hence
the system acts as an atom-photon parametric amplifier. Triggered by a small
injected probe field, or simply by quantum noise, entangled atom-photon pairs
are created which exhibit non-classical correlations similar to those seen
between photons in the optical parametric amplifier. In addition, the quantum
statistics of the matter and light fields depend strongly on the initial state
which triggers the amplifier. Thus by preparing different initial states of the
light field, one can generate matter waves in a variety of quantum states,
demonstrating optical control over the quantum statistics of matter waves
A transparent 3D printed device for assembling droplet hydrogel bilayers (DHBs)
We report a new approach for assembling droplet hydrogel bilayers (DHBs) using a transparent 3D printed device. We characterise the transparency of our platform, confirm bilayer formation using electrical measurements and show that single-channel recordings can be obtained using our reusable rapid prototyped device. This method significantly reduces the cost and infrastructure required to develop devices for DHB assembly and downstream study
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