218 research outputs found
Bottom-up assembly of functional intracellular synthetic organelles by droplet-based microfluidics
Bottom-up synthetic biology has directed most efforts toward the construction of artificial compartmentalized systems that recreate living cell functions in their mechanical, morphological, or metabolic characteristics. However, bottom-up synthetic biology also offers great potential to study subcellular structures like organelles. Because of their intricate and complex structure, these key elements of eukaryotic life forms remain poorly understood. Here, the controlled assembly of lipid enclosed, organelle-like architectures is explored by droplet-based microfluidics. Three types of giant unilamellar vesicles (GUVs)-based synthetic organelles (SOs) functioning within natural living cells are procedured: (A) synthetic peroxisomes supporting cellular stress-management, mimicking an organelle innate to the host cell by using analogous enzymatic modules; (B) synthetic endoplasmic reticulum (ER) as intracellular light-responsive calcium stores involved in intercellular calcium signalling, mimicking an organelle innate to the host cell but utilizing a fundamentally different mechanism; and (C) synthetic magnetosomes providing eukaryotic cells with a magnetotactic sense, mimicking an organelle that is not natural to the host cell but transplanting its functionality from other branches of the phylogenetic tree. Microfluidic assembly of functional SOs paves the way for high-throughput generation of versatile intracellular structures implantable into living cells. This in-droplet SO design may support or expand cellular functionalities in translational nanomedicine
Trajectory matching of ozonesondes and MOZAIC measurements in the UTLS – Part 2: Application to the global ozonesonde network
Both balloon-borne electrochemical ozonesondes and MOZAIC (measurements of
ozone, water vapour, carbon monoxide and nitrogen oxides by in-service Airbus
aircraft) provide very valuable data sets for ozone studies in the upper
troposphere/lower stratosphere (UTLS). Although MOZAIC's highly accurate
UV-photometers are regularly inspected and recalibrated annually, recent
analyses cast some doubt on the long-term stability of their ozone analysers.
To investigate this further, we perform a 16 yr comparison (1994–2009) of
UTLS ozone measurements from balloon-borne ozonesondes and MOZAIC. The
analysis uses fully three-dimensional trajectories computed from ERA-Interim
(European Centre for Medium-Range Weather Forecasts Re-analysis) wind fields
to find matches between the two measurement platforms. Although different
sensor types (Brewer-Mast and Electrochemical Concentration Cell ozonesondes)
were used, most of the 28 launch sites considered show considerable
differences of up to 25% compared to MOZAIC in the mid-1990s, followed
by a systematic tendency to smaller differences of around 5–10% in
subsequent years. The reason for the difference before 1998 remains unclear,
but observations from both sondes and MOZAIC require further examination to
be reliable enough for use in robust long-term trend analyses starting before
1998. According to our analysis, ozonesonde measurements at tropopause
altitudes appear to be rather insensitive to changing the type of the
Electrochemical Concentration Cell ozonesonde, provided the cathode sensing
solution strength remains unchanged. Scoresbysund (Greenland) showed
systematically 5% higher readings after changing from Science Pump
Corporation sondes to ENSCI Corporation sondes, while a 1.0% KI cathode
electrolyte was retained
Theory for the Interdependence of High-T Superconductivity and Dynamical Spin Fluctuations
The doping dependence of the superconducting state for the 2D one-band
Hubbard Hamiltonian is determined. By using an Eliashberg-type theory, we find
that the gap function has a symmetry in momentum
space and T becomes maximal for doping. Since we determine the
dynamical excitations directly from real frequency axis calculations, we obtain
new structures in the angular resolved density of states related to the
occurrence of {\it shadow states} below T. Explaining the anomalous
behavior of photoemission and tunneling experiments in the cuprates, we find a
strong interplay between -wave superconductivity and dynamical spin
fluctuations.Comment: 4 pages (REVTeX) with 4 figures (Postscript
Aspects socio-économiques de la gestion des infiltrations/exfiltrations dans les réseaux d'assainissement
Vanishing Loss Effect on the Effective ac Conductivity behavior for 2D Composite Metal-Dielectric Films At The Percolation Threshold
We study the imaginary part of the effective conductivity as well as its
distribution probability for vanishing losses in 2D composites. This
investigation showed that the effective medium theory provides only
informations about the average conductivity, while its fluctuations which
correspond to the field energy in this limit are neglected by this theory.Comment: 6 pages, 2 figures, submitted to Phys.Rev.
Remote Nanoimaging on Mars - Results of the Atomic Force Microscope Onboard NASA's Phoenix Mission
Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7-August 11, 201
C-axis electronic Raman scattering in Bi_2Sr_2CaCu_2O_{8+\delta}
We report a c-axis-polarized electronic Raman scattering study of
Bi_2Sr_2CaCu_2O_{8+\delta} single crystals. In the normal state, a resonant
electronic continuum extends to 1.5 eV and gains significant intensity as the
incoming photon energy increases. In the superconducting state, a coherence
2\Delta peak appears around 50 meV, with a suppression of the scattering
intensity at frequencies below the peak position. The peak energy, which is
higher than that seen with in-plane polarizations, signifies distinctly
different dynamics of quasiparticle excitations created with out-of-plane
polarization.Comment: 12 pages, REVTEX, 3 postscript figure
Relation between the superconducting gap energy and the two-magnon Raman peak energy in Bi2Sr2Ca{1-x}YxCu2O{8+\delta}
The relation between the electronic excitation and the magnetic excitation
for the superconductivity in Bi2Sr2Ca{1-x}YxCu2O{8+\delta} was investigated by
wide-energy Raman spectroscopy. In the underdoping region the B1g scattering
intensity is depleted below the two-magnon peak energy due to the "hot spots"
effects. The depleted region decreases according to the decrease of the
two-magnon peak energy, as the carrier concentration ncreases. This two-magnon
peak energy also determines the B1g superconducting gap energy as
from under to overdoping hole concentration.Comment: 10 pages, 4 figure
Chiral transition and monopole percolation in lattice scalar QED with quenched fermions
We study the interplay between topological observables and chiral and Higgs
transitions in lattice scalar QED with quenched fermions. Emphasis is put on
the chiral transition line and magnetic monopole percolation at strong gauge
coupling. We confirm that at infinite gauge coupling the chiral transition is
described by mean field exponents. We find a rich and complicated behaviour at
the endpoint of the Higgs transition line which hampers a satisfactory analysis
of the chiral transition. We study in detail an intermediate coupling, where
the data are consistent both with a trivial chiral transition clearly separated
from monopole percolation and with a chiral transition coincident with monopole
percolation, and characterized by the same critical exponent .
We discuss the relevance (or lack thereof) of these quenched results to our
understanding of the \chupiv\ model. We comment on the interplay of magnetic
monopoles and fermion dynamics in more general contexts.Comment: 29 pages, 13 figures included, LaTeX2e (elsart
C-axis Raman spectra of a normal plane-chain bilayer cuprate and the pseudogap
We investigate the Raman spectra in the geometry where both incident and
scattered photon polarizations are parallel to the -direction, for a
plane-chain bilayer coupled via a single-particle tunneling . The
Raman vertex is derived in the tight-binding limit and in the absence of
Coulomb screening, the Raman intensity can be separated into intraband
() and interband () transitions. In the
small- limit, the interband part dominates and a pseudogap will appear
as it does in the conductivity. Coulomb interactions bring in a two-particle
coupling and result in the breakdown of intra- and interband separation.
Nevertheless, when is small, the Coulomb screening () has little effect on the intensity to which the unscreened
interband transitions contribute most. In general, the total Raman spectra are
strongly dependent on the magnitude of .Comment: 23 pages, 6 figures, submitted to Phys. Rev.
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