Dynamic nuclear structure emerges from chromatin crosslinks and motors

The cell nucleus houses the chromosomes, which are linked to a soft shell of lamin filaments. Experiments indicate that correlated chromosome dynamics and nuclear shape fluctuations arise from motor activity. To identify the physical mechanisms, we develop a model of an active, crosslinked Rouse chain bound to a polymeric shell. System-sized correlated motions occur but require both motor activity and crosslinks. Contractile motors, in particular, enhance chromosome dynamics by driving anomalous density fluctuations. Nuclear shape fluctuations depend on motor strength, crosslinking, and chromosome-lamina binding. Therefore, complex chromatin dynamics and nuclear shape emerge from a minimal, active chromosome-lamina system.

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Density Fluctuations and Energy Spectra of 3D Bacterial Suspensions

Soft Matter ◽

10.1039/d1sm01183a ◽

2021 ◽

Author(s):

Zhengyang Liu ◽

Wei Zeng ◽

Xiaolei Ma ◽

Xiang Cheng

Keyword(s):

Density Fluctuations ◽

Energy Spectra ◽

Nonequilibrium Dynamics ◽

Two Dimensional ◽

Anomalous Density

Giant number fluctuations are often considered as a hallmark of the emergent nonequilibrium dynamics of active fluids. However, these anomalous density fluctuations have only been reported experimentally in two-dimensional dry...

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Anomalous density fluctuations in a strange metal

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1721495115 ◽

2018 ◽

Vol 115 (21) ◽

pp. 5392-5396 ◽

Cited By ~ 30

Author(s):

M. Mitrano ◽

A. A. Husain ◽

S. Vig ◽

A. Kogar ◽

M. S. Rak ◽

...

Keyword(s):

Low Temperature ◽

Power Law ◽

High Temperature Superconductivity ◽

High Energy ◽

Energy Scale ◽

Density Fluctuations ◽

Inelastic Electron ◽

Anomalous Density ◽

Dynamic Charge ◽

New Type

A central mystery in high-temperature superconductivity is the origin of the so-called strange metal (i.e., the anomalous conductor from which superconductivity emerges at low temperature). Measuring the dynamic charge response of the copper oxides, χ″(q,ω), would directly reveal the collective properties of the strange metal, but it has never been possible to measure this quantity with millielectronvolt resolution. Here, we present a measurement of χ″(q,ω) for a cuprate, optimally doped Bi2.1Sr1.9CaCu2O8+x (Tc = 91 K), using momentum-resolved inelastic electron scattering. In the medium energy range 0.1–2 eV relevant to the strange metal, the spectra are dominated by a featureless, temperature- and momentum-independent continuum persisting to the electronvolt energy scale. This continuum displays a simple power-law form, exhibiting q2 behavior at low energy and q2/ω2 behavior at high energy. Measurements of an overdoped crystal (Tc = 50 K) showed the emergence of a gap-like feature at low temperature, indicating deviation from power law form outside the strange-metal regime. Our study suggests the strange metal exhibits a new type of charge dynamics in which excitations are local to such a degree that space and time axes are decoupled.

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Anomalous density fluctuations in a random t−J model

Physical Review B ◽

10.1103/physrevb.102.165146 ◽

2020 ◽

Vol 102 (16) ◽

Author(s):

Darshan G. Joshi ◽

Subir Sachdev

Keyword(s):

Density Fluctuations ◽

Anomalous Density

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Strain analysis with nanometer resolution using a conventional transmission electron microsopy technique: electron diffraction contrast imaging revisited

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100137215 ◽

1995 ◽

Vol 53 ◽

pp. 168-169

Author(s):

Koenraad G F Janssens ◽

Omer Van der Biest ◽

Jan Vanhellemont ◽

Herman E Maes ◽

Robert Hull

Keyword(s):

Electron Diffraction ◽

Strain Field ◽

Elastic Strain ◽

Strain Analysis ◽

Local Strain ◽

Contrast Imaging ◽

Strain Characterization ◽

Physical Mechanisms ◽

Diffraction Contrast ◽

Transmission Electron

There is a growing need for elastic strain characterization techniques with submicrometer resolution in several engineering technologies. In advanced material science and engineering the quantitative knowledge of elastic strain, e.g. at small particles or fibers in reinforced composite materials, can lead to a better understanding of the underlying physical mechanisms and thus to an optimization of material production processes. In advanced semiconductor processing and technology, the current size of micro-electronic devices requires an increasing effort in the analysis and characterization of localized strain. More than 30 years have passed since electron diffraction contrast imaging (EDCI) was used for the first time to analyse the local strain field in and around small coherent precipitates1. In later stages the same technique was used to identify straight dislocations by simulating the EDCI contrast resulting from the strain field of a dislocation and comparing it with experimental observations. Since then the technique was developed further by a small number of researchers, most of whom programmed their own dedicated algorithms to solve the problem of EDCI image simulation for the particular problem they were studying at the time.

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