Reading M87's DNA: A Double Helix Revealing a Large-scale Helical Magnetic Field

We present unprecedented high-fidelity radio images of the M87 jet. We analyzed Jansky Very Large Array broadband full-polarization radio data from 4 to 18 GHz. The observations were taken with the most extended configuration (A configuration), which allows the study of the emission of the jet up to kiloparsec scales with a linear resolution of ∼10 pc. The high sensitivity and resolution of our data allow us to resolve the jet width. We confirm a double-helix morphology of the jet material between ∼300 pc and ∼1 kpc. We found a gradient of the polarization degree with a minimum at the projected axis and maxima at the jet edges and a gradient in the Faraday depth with opposite signs at the jet edges. We also found that the behavior of the polarization properties along the wide range of frequencies is consistent with internal Faraday depolarization. All of these characteristics strongly support the presence of a helical magnetic field in the M87 jet up to 1 kpc from the central black hole, although the jet is most likely particle-dominated at these large scales. Therefore, we propose a plausible scenario in which the helical configuration of the magnetic field has been maintained to large scales thanks to the presence of Kelvin–Helmholtz instabilities.

Self-supported rhodium catalysts based on a microporous metal–organic framework for polymerization of phenylacetylene and its derivatives

Highly efficient, cis-selective, stable, recyclable and reusable heterogeneous single-site MOF-supported rhodium catalysts polymerize PA and its derivatives, producing cis-transoidal PPAs and their functional derivatives having a helical configuration or AIE properties.

Structure of the Cdc48 segregase in the act of unfolding an authentic substrate

The cellular machine Cdc48 functions in multiple biological pathways by segregating its protein substrates from a variety of stable environments such as organelles or multi-subunit complexes. Despite extensive studies, the mechanism of Cdc48 has remained obscure, and its reported structures are inconsistent with models of substrate translocation proposed for other AAA+ ATPases (adenosine triphosphatases). Here, we report a 3.7-angstrom–resolution structure of Cdc48 in complex with an adaptor protein and a native substrate. Cdc48 engages substrate by adopting a helical configuration of substrate-binding residues that extends through the central pore of both of the ATPase rings. These findings indicate a unified hand-over-hand mechanism of protein translocation by Cdc48 and other AAA+ ATPases.

Single-Pass Four-Throw Technique for Pupilloplasty

Purpose To describe a surgical technique for performing pupilloplasty. Methods In this surgical technique for pupilloplasty, after a single pass of needle through the edges of iris defect along the pupillary margin, the suture end is passed through the loop with 4 throws, creating a helical configuration in modified Siepser slipknot technique that is self-retaining and self-locking. Results The technique was performed in 27 cases and the loop did not open in any of the cases in the 6-month follow-up period. No case of iritis was seen. The iris tissue was seen well approximated to each other in all cases. Conclusions The single-pass 4-throw technique serves as an effective method to perform pupilloplasty.

Investigation of Inducing Vibration to Reduce Friction of Coiled Tubing in Deep Drilling Operations

This work examines the buckling behavior of constrained horizontal tubular in a cylinder subjected to axial compression force. Such configurations are of interest to coiled tubing (CT) and conventional hydrocarbon drilling. When compression force is applied beyond a critical value the coiled tubing (CT) will buckle forming sinusoidal wave and with increasing the load the CT ultimately goes into a helical configuration. The friction is introduced due to the contact between the CT and the borehole wall. Increasing the CT friction eventually leads to lock-up length beyond which the drilling cannot proceed further. Vibration is a well-known technique to reduce friction between contacting bodies in many engineering systems. An in-house experimental setup is developed to imitate the wellbore being drilled with the presence of drilling fluids and vibrating facility that has the capability to vibrate the CT axially. The setup is employed to examine the effects of amplitude and frequency of vibration on the axial force transfer and weight on bit (WOB) at normal and high temperature environments. Results show that both amplitude and frequency have significant effects in reducing the friction and they alter the buckling behavior on both normal and high temperature.

Experimental Evaluations for the Effects of Amplitude and Frequency of Vibration on the Friction of Coiled Tubing in Hydrocarbon Drilling Operations

In a hydrocarbon drilling operations, when an axial load is applied beyond a critical value the coiled tubing (CT) will buckle forming sinusoidal wave and with increasing the axial load the CT ultimately goes into a helical configuration. The higher number of contacts between the CT and the wellbore the more friction is introduced. Increasing the CT friction, due to increasing the area of contact with the wellbore, eventually leads to lock-up length beyond which the drilling cannot proceed further. Vibration is understood to be a well-known technique to reduce friction between contacting bodies in many engineering systems. An in-house experimental setup is developed to imitate the wellbore being drilled with the presence of vibrating facility that has the capability to vibrate the CT axially. The setup is employed to examine the effects of amplitude and frequency of vibration on the friction force, between the CT and the wellbore, and on the axial load transfer or the weight on bit (WOB) of the CT. Response surface methodology is used to produce a prediction model to determine the effects of various amplitudes and frequencies the WOB of the CT. The investigations have shown that both amplitude and frequency of vibration have positive effects on reducing friction force and increasing WOB. The actual and predicted optimal designs are also presented in this work.