Separation of III-N partially-coalesced nanowire arrays from Si substrate

In modern optoelectronics, arrays or single nanowires (NWs) of III-N materials, in particular InGaN, separated from the original substrates are used to fabricate light-emitting diodes or single photon sources. This work describes a technology of separation super-dense arrays or arrays of partially-coalesced InGaN nanowires and single nanowires from a Si substrate by chemical etching in HF:HNO3 solution, which allows preserving the optical properties of the structure for further use.

Extreme suction attachment performance from specialised insects living in mountain streams (Diptera: Blephariceridae)

Suction is widely used by animals for strong controllable underwater adhesion but is less well understood than adhesion of terrestrial climbing animals. Here we investigate the attachment of aquatic insect larvae (Blephariceridae), which cling to rocks in torrential streams using the only known muscle-actuated suction organs in insects. We measured their attachment forces on well-defined rough substrates and found that their adhesion was less reduced by micro-roughness than that of terrestrial climbing insects. In vivo visualisation of the suction organs in contact with microstructured substrates revealed that they can mould around large asperities to form a seal. We have shown that the ventral surface of the suction disc is covered by dense arrays of microtrichia, which are stiff spine-like cuticular structures that only make tip contact. Our results demonstrate the impressive performance and versatility of blepharicerid suction organs and highlight their potential as a study system to explore biological suction mechanisms.

RNA polymerase backtracking results in the accumulation of fission yeast condensin at active genes

The mechanisms leading to the accumulation of the SMC complexes condensins around specific transcription units remain unclear. Observations made in bacteria suggested that RNA polymerases (RNAPs) constitute an obstacle to SMC translocation, particularly when RNAP and SMC travel in opposite directions. Here we show in fission yeast that gene termini harbour intrinsic condensin-accumulating features whatever the orientation of transcription, which we attribute to the frequent backtracking of RNAP at gene ends. Consistent with this, to relocate backtracked RNAP2 from gene termini to gene bodies was sufficient to cancel the accumulation of condensin at gene ends and to redistribute it evenly within transcription units, indicating that RNAP backtracking may play a key role in positioning condensin. Formalization of this hypothesis in a mathematical model suggests that the inclusion of a sub-population of RNAP with longer dwell-times is essential to fully recapitulate the distribution profiles of condensin around active genes. Taken together, our data strengthen the idea that dense arrays of proteins tightly bound to DNA alter the distribution of condensin on chromosomes.

A shallow Vs model from full wave inversion for hydraulic fracturing site

<p>In recent years, small dense arrays with inter-station distances ~1-km are widely deployed for various geotechnical proposes, including exploring the subsurface geothermal reservoirs, monitoring the hydraulic fracturing, and estimate the local seismic hazards. Those small-dense arrays record several hours or days microtremor datasets and can be used to extract noise H/V ratio and short-period Rayleigh wave dispersion curve. To fulfill those geotechnical purposes, the extracted H/V ratio and Rayleigh wave dispersive curves are used to invert for 1-D layered velocity structures based on traditional ray theory, ignoring the 3-D Rayleigh wave propagating effects. In the present-day, with advances in computational power, 3-D numerical seismic wave propagation in realistic Earth models has become feasible and this has led to efforts to invert full waveforms. However, as H/V ratios from microtremors are produced by multiple random sources close to the surface with complex scattering effects, they are still unrealistic to be simulated by 3-D numerical seismic wave simulations. In this study, we use a strategy to incorporate the theories of H/V ratios from microtremor and the 3-D waveform simulations to invert for shallow sub-surface speed model using a small array. The details of the strategy are that we first use the traditional method to build an initial speed model by jointly inverting the Rayleigh wave dispersion curves and H/V ratios, and then, we further update the initial model with full-wave inversion of the Rayleigh waveforms calculated from ambient noise cross-correlations. The small array used here was composed of 21 broadband seismic stations, aimed to monitor the underground hydraulic fracturing. Therefore, the newly build model has important geotechnical usages of locating stimulated micro-seismic events and diagnose the hydraulic fracturing effects.</p>

RNA polymerase backtracking drives the accumulation of fission yeast condensin at active genes

The mechanisms leading to the accumulation of the SMC complex condensin around specific transcription units in mitosis remain unclear. Observations made in bacteria suggested that RNA polymerases (RNAP) constitute an obstacle to SMC translocation, particularly when RNAP and SMC travel in opposite directions. Whether this also applies to eukaryotic condensin remains unclear. Here we show in fission yeast that condensin remains focused at the 3’ end of an RNAP2-transcribed gene after flipping its orientation, suggesting that gene termini harbor intrinsic condensin-positioning features whatever the orientation of transcription. Consistent with this, we provide evidence that transcription termination mechanisms position condensin whatever the RNAP involved. Moreover, to stabilize backtracked RNAP2 polymerases within gene bodies was sufficient to cancel the accumulation of condensin at gene termini and to redistribute it evenly within transcription units. Altogether, our results suggest that RNAP backtracking, which is frequent at gene termini, plays a key role in positioning condensin and strengthen the idea that dense arrays of proteins tightly-bound to DNA alter the distribution of condensin on mitotic chromosomes.