215,810 research outputs found
Programmable interactions with biomimetic DNA linkers at fluid membranes and interfaces
At the heart of the structured architecture and complex dynamics of
biological systems are specific and timely interactions operated by
biomolecules. In many instances, biomolecular agents are spatially confined to
flexible lipid membranes where, among other functions, they control cell
adhesion, motility and tissue formation. Besides being central to several
biological processes, \emph{multivalent interactions} mediated by reactive
linkers confined to deformable substrates underpin the design of
synthetic-biological platforms and advanced biomimetic materials. Here we
review recent advances on the experimental study and theoretical modelling of a
heterogeneous class of biomimetic systems in which synthetic linkers mediate
multivalent interactions between fluid and deformable colloidal units,
including lipid vesicles and emulsion droplets. Linkers are often prepared from
synthetic DNA nanostructures, enabling full programmability of the
thermodynamic and kinetic properties of their mutual interactions. The coupling
of the statistical effects of multivalent interactions with substrate fluidity
and deformability gives rise to a rich emerging phenomenology that, in the
context of self-assembled soft materials, has been shown to produce exotic
phase behaviour, stimuli-responsiveness, and kinetic programmability of the
self-assembly process. Applications to (synthetic) biology will also be
reviewed.Comment: 63 pages, revie
Binary superlattice design by controlling DNA-mediated interactions
Most binary superlattices created using DNA functionalization or other
approaches rely on particle size differences to achieve compositional order and
structural diversity. Here we study two-dimensional (2D) assembly of
DNA-functionalized micron-sized particles (DFPs), and employ a strategy that
leverages the tunable disparity in interparticle interactions, and thus
enthalpic driving forces, to open new avenues for design of binary
superlattices that do not rely on the ability to tune particle size (i.e.,
entropic driving forces). Our strategy employs tailored blends of complementary
strands of ssDNA to control interparticle interactions between micron-sized
silica particles in a binary mixture to create compositionally diverse 2D
lattices. We show that the particle arrangement can be further controlled by
changing the stoichiometry of the binary mixture in certain cases. With this
approach, we demonstrate the abil- ity to program the particle assembly into
square, pentagonal, and hexagonal lattices. In addition, different particle
types can be compositionally ordered in square checkerboard and hexagonal -
alternating string, honeycomb, and Kagome arrangements.Comment: 4 figures in the main text. 5 figures in the supplementary
informatio
Dark Matter in the Coming Decade: Complementary Paths to Discovery and Beyond
In this report we summarize the many dark matter searches currently being
pursued through four complementary approaches: direct detection, indirect
detection, collider experiments, and astrophysical probes. The essential
features of broad classes of experiments are described, each with their own
strengths and weaknesses. The complementarity of the different dark matter
searches is discussed qualitatively and illustrated quantitatively in two
simple theoretical frameworks. Our primary conclusion is that the diversity of
possible dark matter candidates requires a balanced program drawing from all
four approaches.Comment: Report prepared for the Community Summer Study (Snowmass) 2013, on
behalf of Cosmic Frontier Working Groups 1-4 (CF1: WIMP Dark Matter Direct
Detection, CF2: WIMP Dark Matter Indirect Detection, CF3: Non-WIMP Dark
Matter, and CF4: Dark Matter Complementarity); published versio
Supernova / Acceleration Probe: A Satellite Experiment to Study the Nature of the Dark Energy
The Supernova / Acceleration Probe (SNAP) is a proposed space-based
experiment designed to study the dark energy and alternative explanations of
the acceleration of the Universe's expansion by performing a series of
complementary systematics-controlled measurements. We describe a
self-consistent reference mission design for building a Type Ia supernova
Hubble diagram and for performing a wide-area weak gravitational lensing study.
A 2-m wide-field telescope feeds a focal plane consisting of a 0.7
square-degree imager tiled with equal areas of optical CCDs and near infrared
sensors, and a high-efficiency low-resolution integral field spectrograph. The
SNAP mission will obtain high-signal-to-noise calibrated light-curves and
spectra for several thousand supernovae at redshifts between z=0.1 and 1.7. A
wide-field survey covering one thousand square degrees resolves ~100 galaxies
per square arcminute. If we assume we live in a cosmological-constant-dominated
Universe, the matter density, dark energy density, and flatness of space can
all be measured with SNAP supernova and weak-lensing measurements to a
systematics-limited accuracy of 1%. For a flat universe, the
density-to-pressure ratio of dark energy can be similarly measured to 5% for
the present value w0 and ~0.1 for the time variation w'. The large survey area,
depth, spatial resolution, time-sampling, and nine-band optical to NIR
photometry will support additional independent and/or complementary dark-energy
measurement approaches as well as a broad range of auxiliary science programs.
(Abridged)Comment: 40 pages, 18 figures, submitted to PASP, http://snap.lbl.go
Towards Autopoietic Computing
A key challenge in modern computing is to develop systems that address
complex, dynamic problems in a scalable and efficient way, because the
increasing complexity of software makes designing and maintaining efficient and
flexible systems increasingly difficult. Biological systems are thought to
possess robust, scalable processing paradigms that can automatically manage
complex, dynamic problem spaces, possessing several properties that may be
useful in computer systems. The biological properties of self-organisation,
self-replication, self-management, and scalability are addressed in an
interesting way by autopoiesis, a descriptive theory of the cell founded on the
concept of a system's circular organisation to define its boundary with its
environment. In this paper, therefore, we review the main concepts of
autopoiesis and then discuss how they could be related to fundamental concepts
and theories of computation. The paper is conceptual in nature and the emphasis
is on the review of other people's work in this area as part of a longer-term
strategy to develop a formal theory of autopoietic computing.Comment: 10 Pages, 3 figure
US Cosmic Visions: New Ideas in Dark Matter 2017: Community Report
This white paper summarizes the workshop "U.S. Cosmic Visions: New Ideas in
Dark Matter" held at University of Maryland on March 23-25, 2017.Comment: 102 pages + reference
Hybrid Coding Technique for Pulse Detection in an Optical Time Domain Reflectometer
The paper introduces a novel hybrid coding technique for improved pulse detection in an optical time domain reflectometer. The hybrid schemes combines Simplex codes with signal averaging to articulate a very sophisticated coding technique that considerably reduces the processing time to extract specified coding gains in comparison to the existing techniques. The paper quantifies the coding gain of the hybrid scheme mathematically and provide simulative results in direct agreement with the theoretical performance. Furthermore, the hybrid scheme has been tested on our self-developed OTDR
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