1,720 research outputs found
Simon Terrill: Crowd Theory 2004-18, Perspectives, Notes and Comments
A catalogue publication for a major survey of the monumental Crowd Theory photographs by Melbourne-born, London-based artist Simon Terrill.
The publication coincides with an exhibition bringing together all ten Crowd Theory images for the first time, at the Centre for Contemporary Photography, Melbourne. Inside are a range of responses and documents, including images and texts from the time of each event, as well as three newly commissioned essays reflecting on the project
Polymer Translocation in Crowded Environments
We study the effect of the crowded nature of the cellular cytoplasm on the
translocation of a polymer through a pore in a membrane. By systematically
treating the entropic penalty due to crowding, we show that the translocation
dynamics are significantly altered, leading to novel scaling behaviors of the
translocation time in terms of chain length. We also observe new and
qualitatively different translocation regimes depending upon the extent of
crowding, transmembrane chemical potential asymmetry, and polymer length.Comment: 4 figure
Hard Spheres in Vesicles: Curvature-Induced Forces and Particle-Induced Curvature
We explore the interplay of membrane curvature and nonspecific binding due to
excluded-volume effects among colloidal particles inside lipid bilayer
vesicles. We trapped submicron spheres of two different sizes inside a
pear-shaped, multilamellar vesicle and found the larger spheres to be pinned to
the vesicle's surface and pushed in the direction of increasing curvature. A
simple model predicts that hard spheres can induce shape changes in flexible
vesicles. The results demonstrate an important relationship between the shape
of a vesicle or pore and the arrangement of particles within it.Comment: LaTeX with epsfig; ps available at
http://dept.physics.upenn.edu/~nelson/index.shtml Phys Rev Lett in press
(1997
Depletion forces near curved surfaces
Based on density functional theory the influence of curvature on the
depletion potential of a single big hard sphere immersed in a fluid of small
hard spheres with packing fraction \eta_s either inside or outside of a hard
spherical cavity of radius R_c is calculated. The relevant features of this
potential are analyzed as function of \eta_s and R_c. There is a very slow
convergence towards the flat wall limit R_c \to \infty. Our results allow us to
discuss the strength of depletion forces acting near membranes both in normal
and lateral directions and to make contact with recent experimental results
Influences of Excluded Volume of Molecules on Signaling Processes on Biomembrane
We investigate the influences of the excluded volume of molecules on
biochemical reaction processes on 2-dimensional surfaces using a model of
signal transduction processes on biomembranes. We perform simulations of the
2-dimensional cell-based model, which describes the reactions and diffusion of
the receptors, signaling proteins, target proteins, and crowders on the cell
membrane. The signaling proteins are activated by receptors, and these
activated signaling proteins activate target proteins that bind autonomously
from the cytoplasm to the membrane, and unbind from the membrane if activated.
If the target proteins bind frequently, the volume fraction of molecules on the
membrane becomes so large that the excluded volume of the molecules for the
reaction and diffusion dynamics cannot be negligible. We find that such
excluded volume effects of the molecules induce non-trivial variations of the
signal flow, defined as the activation frequency of target proteins, as
follows. With an increase in the binding rate of target proteins, the signal
flow varies by i) monotonically increasing; ii) increasing then decreasing in a
bell-shaped curve; or iii) increasing, decreasing, then increasing in an
S-shaped curve. We further demonstrate that the excluded volume of molecules
influences the hierarchical molecular distributions throughout the reaction
processes. In particular, when the system exhibits a large signal flow, the
signaling proteins tend to surround the receptors to form receptor-signaling
protein clusters, and the target proteins tend to become distributed around
such clusters. To explain these phenomena, we analyze the stochastic model of
the local motions of molecules around the receptor.Comment: 31 pages, 10 figure
Reduced tillage, but not organic matter input, increased nematode diversity and food web stability in European long‐term field experiments
Soil nematode communities and food web indices can inform about the complexity, nutrient flows and decomposition pathways of soil food webs, reflecting soil quality. Relative abundance of nematode feeding and life‐history groups are used for calculating food web indices, i.e., maturity index (MI), enrichment index (EI), structure index (SI) and channel index (CI). Molecular methods to study nematode communities potentially offer advantages compared to traditional methods in terms of resolution, throughput, cost and time. In spite of such advantages, molecular data have not often been adopted so far to assess the effects of soil management on nematode communities and to calculate these food web indices. Here, we used high‐throughput amplicon sequencing to investigate the effects of tillage (conventional vs. reduced) and organic matter addition (low vs. high) on nematode communities and food web indices in 10 European long‐term field experiments and we assessed the relationship between nematode communities and soil parameters. We found that nematode communities were more strongly affected by tillage than by organic matter addition. Compared to conventional tillage, reduced tillage increased nematode diversity (23% higher Shannon diversity index), nematode community stability (12% higher MI), structure (24% higher SI), and the fungal decomposition channel (59% higher CI), and also the number of herbivorous nematodes (70% higher). Total and labile organic carbon, available K and microbial parameters explained nematode community structure. Our findings show that nematode communities are sensitive indicators of soil quality and that molecular profiling of nematode communities has the potential to reveal the effects of soil management on soil quality
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