1,546 research outputs found
Unfolding protein with an atomic force microscope: Force-fluctuation induced non-exponential kinetics
We show that in experimental atomic force microscopy studies of the lifetime
distribution of mechanically stressed folded proteins the effects of externally
applied fluctuations can not be distinguished from those of internally present
fluctuations. In certain circumstances this leads to artificially
non-exponential lifetime distributions which can be misinterpreted as a
signature of protein complexity. This work highlights the importance of fully
characterizing and controlling external sources of fluctuation in mechanical
studies of proteins before drawing conclusions on the physics at play on the
molecular level
Jamming Criticality Revealed by Removing Localized Buckling Excitations
Recent theoretical advances offer an exact, first-principle theory of jamming
criticality in infinite dimension as well as universal scaling relations
between critical exponents in all dimensions. For packings of frictionless
spheres near the jamming transition, these advances predict that nontrivial
power-law exponents characterize the critical distribution of (i) small
inter-particle gaps and (ii) weak contact forces, both of which are crucial for
mechanical stability. The scaling of the inter-particle gaps is known to be
constant in all spatial dimensions -- including the physically relevant
and 3, but the value of the weak force exponent remains the object of
debate and confusion. Here, we resolve this ambiguity by numerical simulations.
We construct isostatic jammed packings with extremely high accuracy, and
introduce a simple criterion to separate the contribution of particles that
give rise to localized buckling excitations, i.e., bucklers, from the others.
This analysis reveals the remarkable dimensional robustness of mean-field
marginality and its associated criticality.Comment: 12 pages, 4 figure
Let Him Hold You: Spiritual and Social Support in a Catholic Convent Infirmary
American Catholic nuns have been found to age more ‘successfully’ than their lay counterparts, living longer, healthier, and happier lives. Two of the key factors contributing to the nuns’ physical and mental wellbeing are the spiritual support they experience from the divine and the social support they provide for and receive from each other in the convent. I argue that by integrating the divine into their everyday interactions, the nuns engage in phenomenological meaning-making process through which mundane care interactions are rendered sacred. This communicative process, I argue, contributes to the nuns’ overall wellbeing by providing an enriched form of care and support, thereby enhancing their end-of-life experience
Let Him Hold You: Spiritual and Social Support in a Catholic Convent Infirmary
American Catholic nuns have been found to age more ‘successfully’ than their lay counterparts, living longer, healthier, and happier lives. Two of the key factors contributing to the nuns’ physical and mental wellbeing are the spiritual support they experience from the divine and the social support they provide for and receive from each other in the convent. I argue that by integrating the divine into their everyday interactions, the nuns engage in phenomenological meaning-making process through which mundane care interactions are rendered sacred. This communicative process, I argue, contributes to the nuns’ overall wellbeing by providing an enriched form of care and support, thereby enhancing their end-of-life experience
First Passage Time for Many Particle Diffusion in Space-Time Random Environments
The first passage time for a single diffusing particle has been studied
extensively, but the first passage time of a system of many diffusing
particles, as is often the case in physical systems, has received little
attention until recently. We consider two models for many particle diffusion --
one treats each particle as independent simple random walkers while the other
treats them as coupled to a common space-time random forcing field that biases
particles nearby in space and time in similar ways. The first passage time of a
single diffusing particle under both of these models show the same statistics
and scaling behavior. However, for many particle diffusions, the first passage
time among all particles (the `extreme first passage time') is very different
between the two models, effected in the latter case by the randomness of the
common forcing field. We develop an asymptotic (in the number of particles and
location where first passage is being probed) theoretical framework to separate
out the impact of the random environment with that of sampling trajectories
within it. We identify a new power-law describing the impact to the extreme
first passage time variance of the environment. Through numerical simulations
we verify that the predictions from this asymptotic theory hold even for
systems with widely varying numbers of particles, all the way down to 100
particles. This shows that measurements of the extreme first passage time for
many-particle diffusions provide an indirect measurement of the underlying
environment in which the diffusion is occurring
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