2,171 research outputs found
Self-assembly of DNA-coded nanoclusters
We present a theoretical discussion of a self-assembly scheme which makes it
possible to use DNA to uniquely encode the composition and structure of micro-
and nanoparticle clusters. These anisotropic DNA-decorated clusters can be
further used as building blocks for hierarchical self-assembly of larger
structures. We address several important aspects of possible experimental
implementation of the proposed scheme: the competition between different types
of clusters in a solution, possible jamming in an unwanted configuration, and
the degeneracy due to symmetry with respect to particle permutations.Comment: v2, 4 pages, 7 figures, added journal re
Loop realizations of quantum affine algebras
We give a simplified description of quantum affine algebras in their loop
presentation. This description is related to Drinfeld's new realization via
halves of vertex operators. We also define an idempotent version of the quantum
affine algebra which is suitable for categorification.Comment: 19 page
Revealing the visually unknown in ancient manuscripts with a similarity measure for IR-imaged inks
One of the tasks facing historians and conservationists is the authentication or dating of medieval manuscripts. To this end it is important to them to verify whether writings on the same or different manuscripts are concurrent. In this work we explore this task by capturing images of manuscript pages in infrared (IR) and modelling and then comparing the ink appearance of segmented text. The modelling of the text appearance relies on the unsupervised multimodal clustering of ink descriptors and the derived probability density functions. The similarity measure is built around the distribution of cluster labels and their proportions. We demonstrate our method by using both model inks of known composition and authentic Byzantine manuscripts
An ink texture descriptor for nir-imaged medieval documents
In this work we explore the task of authenticating and dating ancient manuscripts by capturing images of pages in nearinfrared (NIR) and modelling and then comparing the ink appearance of segmented text. We present a texture feature descriptor to characterize and recognize semi-transparent materials such as the inks found in manuscripts. These textural patterns are different in nature from perceptual entities such as textons, tokens, frequency or repeatability of textural elements. Our ink texture descriptor relates a set of ink features from various first and second-order statistics to semi-liquid and viscous image-based properties of inks. In particular, we propose eigen features from the joint gray-level probabilities and off-diagonal sums of co-occurrence matrices. We test the qualities of the features with a classifier trained with the ink descriptor to show how well it recognizes eight different inks of known composition. Presented with the very same task the human visual system would fail to spot the ink composition difference given the inks inter-class and intra-class distances are extremely short
Colloids with key-lock interactions: non-exponential relaxation, aging and anomalous diffusion
The dynamics of particles interacting by key-lock binding of attached
biomolecules are studied theoretically. Experimental realizations of such
systems include colloids grafted with complementary single-stranded DNA
(ssDNA), and particles grafted with antibodies to cell-membrane proteins.
Depending on the coverage of the functional groups, we predict two distinct
regimes. In the low coverage localized regime, there is an exponential
distribution of departure times. As the coverage is increased the system enters
a diffusive regime resulting from the interplay of particle desorption and
diffusion. This interplay leads to much longer bound state lifetimes, a
phenomenon qualitatively similar to aging in glassy systems. The diffusion
behavior is analogous to dispersive transport in disordered semiconductors:
depending on the interaction parameters it may range from a finite
renormalization of the diffusion coefficient to anomalous, subdiffusive
behavior. We make connections to recent experiments and discuss the
implications for future studies.Comment: v2: substantially revised version, new treatment of localized regime,
19 pages, 10 figure
Kinetic limitations of cooperativity based drug delivery systems
We study theoretically a novel drug delivery system that utilizes the
overexpression of certain proteins in cancerous cells for cell specific
chemotherapy. The system consists of dendrimers conjugated with "keys" (ex:
folic acid) which "key-lock" bind to particular cell membrane proteins (ex:
folate receptor). The increased concentration of "locks" on the surface leads
to a longer residence time for the dendrimer and greater incorporation into the
cell. Cooperative binding of the nanocomplexes leads to an enhancement of cell
specificity. However, both our theory and detailed analysis of in-vitro
experiments indicate that the degree of cooperativity is kinetically limited.
We demonstrate that cooperativity and hence the specificity to particular cell
type can be increased by making the strength of individual bonds weaker, and
suggest a particular implementation of this idea. The implications of the work
for optimizing the design of drug delivery vehicles are discussed.Comment: 4 pages, 4 figures, v3: minor revision
Error-proof programmable self-assembly of DNA-nanoparticle clusters
We study theoretically a new generic scheme of programmable self-assembly of
nanoparticles into clusters of desired geometry. The problem is motivated by
the feasibility of highly selective DNA-mediated interactions between colloidal
particles. By analyzing both a simple generic model and a more realistic
description of a DNA-colloidal system, we demonstrate that it is possible to
suppress the glassy behavior of the system, and to make the self-assembly
nearly error-proof. This regime requires a combination of stretchable
interparticle linkers (e.g. sufficiently long DNA), and a soft repulsive
potential. The jamming phase diagram and the error probability are computed for
several types of clusters. The prospects for the experimental implementation of
our scheme are also discussed. PACS numbers: 81.16.Dn, 87.14.Gg, 36.40.EiComment: 6 pages, 4 figures, v2: substantially revised version, added journal
re
Statistical Mechanics of DNA-Mediated Colloidal Aggregation
We present a statistical mechanical model of aggregation in colloidal systems
with DNA mediated interactions. We obtain a general result for the two-particle
binding energy in terms of the hybridization free energy of DNA and
two model dependent properties: the average number of available DNA bridges
\left and the effective DNA conccentration . We calculate
these parameters for a particular DNA bridging scheme. The fraction of all the
-mers, including the infinite aggregate, are shown to be universal functions
of a single parameter directly related to the two-particle binding energy. We
explicitly take into account the partial ergodicity of the problem resulting
from the slow DNA binding-unbinding dynamics, and introduce the concept of
angular localization of DNA linkers. In this way, we obtain a direct link
between DNA thermodynamics and the global aggregation and melting properties in
DNA-colloidal systems. The results of the theory are shown to be in
quantitative agreement with two recent experiments with particles of micron and
nanometer size.
PACS numbers: 81.16.Dn, 82.20.Db, 68.65.-k, 87.14.GgComment: 12 pages, 6 figures, v2: added reference, expanded conclusion, added
journal re
- …