Mutations in The Stator Protein PomA Affect Switching of Rotational Direction in Bacterial Flagellar Motor

The flagellar motor rotates bi-directionally in counter-clockwise (CCW) and clockwise (CW) directions. The motor consists of a stator and a rotor. Recent structural studies have revealed that the stator is composed of a pentameric ring of A subunits and a dimer axis of B subunits. The stator interacts with the rotor through conserved charged and neighboring residues, and the rotational power is generated by their interactions through a gear-like mechanism. The rotational direction is controlled by chemotaxis signaling transmitted to the rotor, with no evidence for the stator being involved. In this study, we found novel mutations that affect the switching of the rotational direction at the putative interaction site of the stator to generate rotational force. Our results highlight a novel aspect of flagellar motor function that appropriate switching of the interaction states between the stator and rotor is critical for controlling the rotational direction.

PERANCANGAN SISTEM TRANSMISI MESIN PRES BIJI KELOR DENGAN PUTARAN MESIN 1400 RPM

Abstrak Mesin pres biji kelor termasuk jenis mesin hidrolik dengan mekanisme tekan horizontal. Cara kerja mesin pres biji kelor dengan meneruskan daya putaran dari poros melalui media penghantar (fluida) menjadi daya tekan. Penelitian ini bertujuan untuk merancang sistem transmisi mesin pres biji kelor dengan putaran mesin 1400 rpm, daya 1 Hp dan kapasitas awal 100 gram. Metode penelitian berupa analisis numeric dengan variabel yang disesuaikan. Perancangan system transmisi menggunakan bahan S30C dengan kekuatan tarik 58 kg/mm2 dan tegangan geser diizinkan 4,83 kg/mm2 Mesin pres biji kelor menghasilkan kecepatan transmisi 18,70m/s dengan perkiraan waktu pemerasan 2,18 detik. Mesin pengepress biji kelor dengan mekanisme tekan horizontal memiliki hasil perasan yaitu sekitar 15,6% (100 g biji kelor = 16 ml minyak kelor) dengan gaya tarik transmisi 267,54 N. Kata kunci: Sistem transmisi, putaran mesin, daya, mesin pres Abstract Moringa seed press is a type of hydraulic machine with a horizontal pressing mechanism. The moringa seed press works by passing the rotational power from the shaft through the conveying medium (fluid) to become compressive power. This study aims to design a transmission system for the moringa seed pressing machine with an engine speed of 1400 rpm, 1 hp power, and an initial capacity of 100 grams. The research method is numerical analysis with adjusted variables. The design of the transmission system uses S30C material with tensile strength () 58 kg/mm2 and allowed shear stress () 4.83 kg/mm2. The moringa seed pressing machine produces a transmission speed of 18.70m/s with an estimated squeeze time of 2.18 seconds. The moringa seed pressing machine with a horizontal pressing mechanism has a yield of about 15.6% (100 g of moringa seeds = 16 ml of Moringa oil) with a transmission pulling force of 267.54 N.Keywords: Transmission system, engine speed, power, pressing machine

New Approach to Stiff-String Torque and Drag Modeling for Well Planning

During the process of drilling, the drillstring inadvertently comes in contact with the wellbore generating frictional losses in rotating moment (torque) and axial force (drag). These losses reduce the rotational power available at the drill bit, thus making adequate torque and drag modeling a critical piece in the drilling puzzle. The simplifying assumptions of the widely used soft-string model for torque and drag modeling make it less accurate for new complex well designs, therefore creating the need for the use of the more robust stiff-string model. This work focuses on a new approach for developing a stiff-string model that can be easily implemented for well planning. The stiff-string model addresses the pitfalls of the soft-string model by using cubic splines for its well-path trajectory and solving three coupled, non-linear ordinary differential equations that describe the motion of the drillstring at each survey point to account for the shear forces and bending stiffness. The stiff-string model is then applied to design 4 horizontal wells. In comparison with the soft-string model, results show that the stiff-string model is able to capture the extra contact loads as the drillstring goes through bends, consequently predicting higher hookload and torque values than the soft-string model. This paper also highlights how both models can be applied to well planning for improved results.

The Effect of Training in the Preparatory and Competitive Periods on Trunk Rotational Power in Canoeists, Ice-Hockey Players, and Tennis Players

This study evaluates changes in trunk rotational power at different weights and velocities after the preparatory and competitive periods in ice-hockey players, tennis players, and canoeists. The subjects performed trunk rotations to each side with a barbell of different weights placed on the shoulders (6, 10, 12, 16, 20, 22, and 26 kg) prior to and after 6 weeks of the preparatory period and 6 weeks of the competitive period. The results showed that mean power produced in the acceleration phase of trunk rotations increased significantly at weights from 10 to 26 kg or 6 to 26 kg after the preparatory and competitive periods in tennis players. The values obtained during trunk rotations with weights ≥12 kg also increased significantly after the preparatory period in ice-hockey players, whereas there were no significant changes after the competitive period. Similarly, the mean power during trunk rotations with weights ≥10 kg increased significantly only after the preparatory period in canoeists. Similar changes were observed for the peak power. These findings demonstrate that changes in trunk rotational power reflect the specificity of their training programs. This information may provide a basis for designing exercises focused on improvements of power produced during trunk rotations under loading conditions.

Theoretical concept and FEM simulations of improved shielding for round horizontal yokes for rotational power loss measurement

The paper introduces a theoretical concept of a shielding for horizontal yokes for measurements of rotational power loss and other rotational and two-dimensional properties. Apart from horizontal parts, the shielding relies on vertical pieces distributed uniformly around the sample circumference, symmetrically on both sides. The simulations in 2D and 3D FEM show significant improvement in reduction of H perpendicular to the sample surface (Hz). The gradient of the tangential H is reduced so that the extrapolation of values towards the surface might be no longer required. There is also an added benefit that the required magnetomotive force is significantly lower (20-70%) for achieving the same B in the sample, as compared to the previously used simple horizontal shields.