Constant Rotation Research Articles

Extracting the Hydrolysis Rate Constant from a Single-Molecule Controlled Rotation Experimental Data on a F1-ATPase

The chemo-mechanical energy transduction of the ATP Synthase is at the heart of the biological function, and it can be elucidated by studying the water soluble F1-ATPase, focusing on the individual sub-steps of the reactions in the enzyme. In controlled rotation experiment single F1-ATPase molecules deposited on a microscope slide are rotated by magnetic tweezers. Simultaneously the individual ATP binding and ADP release events are monitored by single molecule fluorescence imaging in real time. Our goal is to extract the ATP hydrolysis and synthesis rate constants as a function of rotor angle from the single molecule binding and release data. This work requires advanced analysis because these processes occurring in the binding pocket are “hidden”, and not directly monitored. Our approach is based on the treatment of composite events developed by Volkan-Kacso and Marcus, for a constant rotation rate. We will use high-quality single-molecule trajectories provided by our experimentalist collaborator K. Adachi, who pioneered the method of controlled rotation. Preliminary results indicate that fluorescent Cy3-ATP hydrolyses about 100 times slower than the wild species (ATP), at rotor angle of 240 degrees, its rate is about 1.7 X 10⁻³ per seconds. We plan to extract the hidden hydrolysis and synthesis rates for the complete 360 degrees cycle.

Stick-slip suppression and speed tuning for a drill-string system via proportional-derivative control

This paper studies the problems of stick-slip mitigation and speed tuning for a lumped-parameter drill-string system by using a proportional-derivative feedback controller via path-following analysis. In this study, we consider two main control parameters, the weight-on-bit and the desired drill-bit speed. In particular, we determine the combinations of these two parameters for which the proposed control scheme is applicable, which is affected by the non-smooth nature of the system induced by bit-rock interaction. Our analysis using path-following techniques for non-smooth systems reveals the inherent coexistence of stick-slip vibration and constant rotation, and identifies a critical point where the drill-bit speed coincides with the desired angular speed. Furthermore, our analysis proposes a strategy that allows controlling the drill-bit speed to suppress stick-slip, by tuning the controller in a suitable manner.

Single polymer composite sheets from polypropylene nonwoven fabric and films. Influence of processing conditions on final properties

AbstractSingle polypropylene (PP) composites from a film/nonwoven fabric/film was obtained by hot calendering in order to develop recyclable, flexible, and low‐cost sheets. Processing temperature (Tp) influence on morphology and mechanical properties of developed single composites was analyzed. Two different values of roll temperature (140 and 150°C) were studied, keeping constant rotation speed and rolls distance. Results revealed notable differences in materials microstructure induced by a difference of only 10°C in Tp. Sheets obtained at 140°C presented a well‐defined film/nonwoven fabric/film structure, meanwhile the highest Tp led to a greater melting extent of external films which penetrate into the fabric, creating a more compact structure. Moreover, results confirmed that changes in Tp can induce a differential mechanical performance showing higher strength, and ductility in sheets processed at 150°C. Homogeneous sheets with good mechanical behavior, proper nonwoven fabric/films adhesion, and uniform thickness were obtained.

Delaminated Rotator Cuff Tears Showed Lower Short-term Retear Rates After Arthroscopic Double-Layer Repair Versus Bursal Layer–Only Repair: A Randomized Controlled Trial

Background: The rotator cuff is known to consist of 2 macroscopically visible layers that have different biomechanical properties. Sometimes the inferior layer may be neglected during rotator cuff repair. However, it is controversial whether double-layer (DL) repair is superior to single-layer (SL) repair in terms of retear rate and outcome. Purpose: To investigate whether DL as compared with SL repair could decrease retear rates after arthroscopic reconstruction of posterosuperior rotator cuff tears. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: A total of 70 patients were 1:1 randomized to receive an arthroscopic DL reconstruction (study group: DL suture-bridge repair) or SL reconstruction (control group: SL suture-bridge repair) for posterosuperior tears of the rotator cuff between 2.0 and 3.5 cm of the footprint detachment. Exclusion criteria were subscapularis tendon rupture (Lafosse >1°), fatty muscular infiltration >2°, and nondelaminated tendons. Tendon integrity according to Sugaya, fatty degeneration, and muscular atrophy were evaluated by magnetic resonance tomography. Pre- and postoperative evaluations included the Constant score, range of motion, American Shoulder and Elbow Surgeons score, Simple Shoulder Test, subjective shoulder value, and postoperative satisfaction with the procedure. Complications were monitored throughout the study. Results: Ninety percent of patients (n = 34, DL; n = 29, SL) were followed-up. There were no significant group differences regarding baseline characteristics and pre- and postoperative fatty degeneration of the supraspinatus and atrophy of the supraspinatus and infraspinatus. The rate of magnetic resonance–verified intact repairs (Sugaya grades 1 + 2) was significantly higher in the DL group (70.6%) than in the SL group (44.8%; P = .045). One patient in the control group with a retear underwent revision. All functional and subjective scores improved significantly pre- to postoperatively in both groups (P < .05). No significant group differences were detected regarding postoperative Constant score, forward flexion, external rotation, American Shoulder and Elbow Surgeons score, Simple Shoulder Test, subjective shoulder value, and visual analog scale and between intact and retorn tendons. The majority of patients were very satisfied or satisfied with their arthroscopic procedure (DL, 94.1%; SL, 92.9%). Conclusion: This randomized controlled trial showed significantly lower retear rates after DL repair as compared with SL repair in delaminated rotator cuff tears. Clinical short-term outcome was not different between the DL and SL repair groups. Registration: NCT003362320 (ClinicalTrials.gov identifier).

Effect of FSP process parameters with air blowing on microstructure and hardness of NiAl Bronze alloy

The present work investigates the effect of friction stir processing on microstructure evolution—grain refining and phase transformation- and hardness of NiAl bronze alloy. NiAl bronze alloys have a wide range of industrial applications especially in the marine field. The technique is based on applying friction using a rotating tool causing heat generation and material mixing. The effect of process parameters, such as; rotation speed, traverse speed, forced convection were investigated in this research. At constant traverse speed, the effect or rotation speed was studied at 800, 1000, and 1200 rpm. At constant rotation speed, the effect of traverse speed was studied at 40, 64, and 93 mm min−1. Minimum grain size was achieved at FSP conditions 800 rpm/93 mm min−1. Highest average hardness value was achieved by FSP 1200/93. At constant rotation and traverse speeds, the application of forced convection using air blowing at a rate of 4.5 m3 min−1 was studied and it was found to reduce the grain size within the SZ and to increase the average hardness value.

Optical purity, enantiomeric excess and the Horeau effect

The optical purity of an enantiomeric mixture deduced from specific rotation measurements was found by Horeau to be different from its enantiomeric excess, which came to be known as the Horeau effect. This observation had important implications in the practical use of specific rotations and has led to investigations on homochiral and heterochiral aggregation processes. In this review, dedicated to the Horeau principle, the theoretical basis for the observance of the Horeau effect and a survey of the specific rotation studies investigating the Horeau effect are provided, and possible future investigations are suggested.

Checked patterned elemental distribution in AlGaAs nanowire branches via vapor-liquid-solid growth.

Morphology, crystal defects and crystal phase can significantly affect the elemental distribution of ternary nanowires (NWs). Here, we report the synergic impact of the structure and crystal phase on the composition of branched self-catalyzed AlxGa1-xAs NWs. Branching events were confirmed to increase with Al incorporation rising, while twinning and polytypism were observed to extend from the trunk to the branches, confirming the epitaxial nature of the latter. The growth mechanism of these structures has been ascribed to Ga accumulation at the concave sites on the rough shell. This is in agreement with the ab initio calculations which reveal Ga atoms tend to segregate at the trunk/branch interface. Notably, uncommon, intricate compositional variations are exposed in these branched NWs, where Ga-rich stripes parallel to the growth direction of the branches intersect with another set of periodic arrangements of Ga-rich stripes which are perpendicular to them, leading to the realization of an elemental checked pattern. The periodic variations perpendicular to the growth direction of the branches are caused by the constant rotation of the sample during growth whilst Ga-rich stripes along the growth direction of the branches are understood to be driven by the different nucleation energies and polarities on facets of different crystal phase at the interface between the catalyst droplets and the branched NW tip. These results lead to further comprehension of phase segregation and could assist in the compositional engineering in ternary NWs via harnessing this interesting phenomenon.

Tribochemical Purification of Gases. I. The Process Model

A mathematical model of the sorption process in a tribochemical reactor with a stirrer, where monolithic granules of alkali-earth metals mutually rub in the media of the flow gas, has been built. The products of reaction of the metal with the gas impurity are continuously removed mechanically from the surface of the granules, creating new metallic regions. As a result the total area of the sorbing surface appears to be by orders of magnitude larger than that of the traditional getter materials of the same mass in the existing sorption technologies. It follows from the model that the gas purification process obeys the linear law at a constant rotation speed of the stirrer. This dependence results in a great simplification of the process control. It also makes possible replacement of a periodic mode of operation by a continuous one where the sorption capacity of the consumed chemisorbent attains theoretical limit.

I–Love–Q relations for realistic white dwarfs

ABSTRACT The space-borne gravitational wave interferometer, Laser Interferometer Space Antenna, is expected to detect signals from numerous binary white dwarfs. At small orbital separation, rapid rotation and large tidal bulges may allow for the stellar internal structure to be probed through such observations. Finite-size effects are encoded in quantities like the moment of inertia (I), tidal Love number (Love), and quadrupole moment (Q). The universal relations among them (I–Love–Q relations) can be used to reduce the number of parameters in the gravitational-wave templates. We here study I–Love–Q relations for more realistic white dwarf models than used in previous studies. In particular, we extend previous works by including (i) differential rotation and (ii) internal temperature profiles taken from detailed stellar evolution calculations. We use the publicly available stellar evolution code mesa to generate cooling models of both low- and high-mass white dwarfs. We show that differential rotation causes the I–Q relation (and similarly the Love–Q relation) to deviate from that of constant rotation. We also find that the introduction of finite temperatures causes the white dwarf to move along the zero-temperature mass sequence of I–Q values, moving towards values that suggest a lower mass. We further find that after only a few Myr, high-mass white dwarfs are well described by the zero-temperature model, suggesting that the relations with zero temperature may be good enough in most practical cases. Low-mass, He-core white dwarfs with thick hydrogen envelopes may undergo long periods of H burning which sustain the stellar temperature and allow deviations from the I–Love–Q relations for longer times.

Microstructure and mechanical properties of IF/St52 steel composite produced by friction stir lap welding

In the present research, a new composite including interstitial free (IF) steel as the outer layer and St52 as the inner layer was fabricated by friction stir lap welding (FSLW). The microstructures and mechanical properties of initial and composite samples were investigated. It was found that the quality of interfacial bonding for the tool traverse speeds of 70 and 100 mm/min was excellent due to the higher strain rate. It was observed that the microstructure of composite samples consisted of fine equiaxed ferrite, Widmanstatten ferrite, martensite, grain boundary ferrite, and aggregates of ferrite + cementite. The increase of tool traverse speed from 40 to 70 and 100 mm/min at a constant tool rotation speed of 1000 rpm decreased the cooling time leading to a higher cooling rate and the formation of martensite phase. The grain size of the composite produced by the traverse speed of 40 mm/min in the first and second HAZ regions was larger than that of the 70 mm/min due to the higher heat input and therefore lower cooling rate of the sample welded by 40 mm/min. The hardness of the center of the stirred zone (SZ) was higher than that of the advancing and retreating sides. The St52 layer of composites showed the microhardness value of ~190 HV whereas the initial St52 sheet had a microhardness around 160 HV. The composite produced by the traverse speed of 70 mm/min had the highest yield and ultimate tensile strength. This high strength achieved without a remarkable decrease in elongation due to the formation of a heterogeneous microstructure. The fracture surfaces indicated that the bonding between IF and St52 steels in the composites produced by traverse speeds of 70 and 100 mm/min was high enough strong to maintain integrity up to a high level of deformation during the tensile test. Finally, with increasing the tool traverse speed, the size and depth of dimples decreased.

Effect of rotation speed and milling time to attain Nb-10Hf-1Ti alloy powders on morphology and microstructure of Nb-10Hf-1Ti powder

The mechanical alloying process was employed to produce C103 alloy with Nb-10% Hf-1% Ti (wt.%) composition using Nb, Hf and Ti powders. The mechanical alloying process was performed in an argon atmosphere in the chamber and bullets of tungsten carbide with a ball-to-powder weight ratio (BPR) of 20:1 at rotation speed of 200, 300 and 400 rpm for 2, 5 and 8 h. At rotation speeds of 200 and 300 rpm particle size decreased and became more spherical during MA. While increasing milling time at 400 rpm caused agglomeration of particles. XRD results showed that increasing milling time at a constant rotation speed has no considerable effect on reduction of crystallite size, but the lattice strain is strongly affected by it and increased obviously with further rotation speed. The results showed that the optimum milling time and rotation speed to attain Nb-10Hf-1Ti alloy powders with the least amount of contamination and appropriate morphology are 5 h and 300 rpm, respectively.

Employing hooking and effective sheet thickness to achieve optimum failure load in lap joints of friction stir welded AA5456 aluminum

Friction stir welding process is a suitable process for joining AA5000 alloy series as it does not have associated with such problems of fusion welding especially in lap joint configuration; however, optimization of process parameters would be inevitable. In this study, the effects of tool rotation rate and welding traverse speed on the failure load of AA5456 lap joints having different sheet thicknesses were investigated. While processing, rotating tool was plunged through AA5456-H321 upper sheet (t = 5 mm) surface into AA5456-O bottom sheet (t = 2.5 mm). Rotational speeds in the range of 300–1000 rpm at constant traverse of 30 mm min−1 and traverse speeds in the range of 15–100 mm min−1 at constant rotations of 600 rpm were applied for fabrication of specimens. Macrostructure of weld cross sections were studied and for mechanical characteristics, shear-tensile tests were performed and compared in all conditions. Meanwhile, fracture surfaces of examined samples were studied using scanning electron microscope. The results of shear-tensile tests revealed that welding parameters of 600 rpm and 30 mm min−1 were the optimal combination to achieve utmost failure load in this study. Shear failure occurred in the base metal of joined materials due to employing the optimum height and orientation of hooking.

Effects of Rotation on the Multiscale Organization of Convection in a Global 2D Cloud-Resolving Model

Abstract Atmospheric convection exhibits distinct spatiotemporal variability at different latitudes. A good understanding of the effects of rotation on the multiscale organization of convection from the mesoscale to synoptic scale to planetary scale is still lacking. Here cloud-resolving simulations with fixed surface fluxes and radiative cooling are implemented with constant rotation in a two-dimensional (2D) planetary domain to simulate multiscale organization of convection from the tropics to midlatitudes. All scenarios are divided into three rotation regimes (weak, order-one, and strong) to represent the idealized ITCZ region (0°–6°N), the Indian monsoon region (6°–20°N), and the midlatitude region (20°–45°N), respectively. In each rotation regime, a multiscale asymptotic model is derived systematically and used as a diagnostic framework for energy budget analysis. The results show that planetary-scale organization of convection only arises in the weak rotation regime, while synoptic-scale organization dominates (vanishes) in the order-one (strong) rotation regime. The depletion of planetary-scale organization of convection as the magnitude of rotation increases is attributed to the reduced planetary kinetic energy of zonal winds, mainly due to the decreasing acceleration effect by eddy zonal momentum transfer from mesoscale convective systems (MCSs) and the increasing deceleration effect by the Coriolis force. Similarly, the maintenance of synoptic-scale organization is related to the acceleration effect by MCSs. Such decreasing acceleration effects by MCSs on both planetary and synoptic scales are further attributed to less favorable conditions for convection provided by weaker background vertical shear of the zonal winds, resulting from the increasing magnitude of rotation.

Fast state and trap rotation of a particle in an anisotropic potential

We study the dynamics of a quantum or classical particle in a two-dimensional rotating anisotropic harmonic potential. By a sequence of symplectic transformations for constant rotation velocity we find uncoupled normal generalized coordinates and conjugate momenta in which the Hamiltonian takes the form of two independent harmonic oscillators. The decomposition into normal-mode dynamics enables us to design fast trap-rotation processes to produce a rotated version of an arbitrary initial state, when the two normal frequencies are commensurate.

Steady sedimentation of a spherical particle under constant rotation

An analytical formula is derived for the drag force on a particle translating in a viscoelastic fluid under the influence of an externally imposed torque. A decrease of the drag force as the rotation rate of the particle increases is predicted in agreement with numerical results from the literature.

THE EFFECT OF LEEWAY ANGLE ON THE PROPELLER PERFORMANCE

One of the aspects influencing the performance of wind assisted vessels is the effect of leeway (drift) angle on the propeller performance. It is known that due to leeway the delivered propeller power and propulsive efficiency can vary significantly from the straight sailing condition. This effect of leeway angle is studied using a combination of viscous flow calculations and captive model tests for one twin screw and three single screw vessels. It is observed that the changes in mean axial velocity and pre-swirl rotation in the wakefield due to a combination of leeway angle and propeller suction are sufficient to describe the trends observed in captive model tests. This knowledge is used in a proposed prediction method to model the changes in propeller thrust and torque due to leeway angle at the design stage. The prediction model combined with a fit of the average wake parameters for the studied vessel types is finally used the show the trends in propulsive efficiency and delivered propeller power at constant propeller rotation rate and ship speed for small leeway angles.

Effect of Tool Pin Profile on the Microstructure and Tribological Properties of Friction Stir Processed Al-20 wt% Mg2Si Composite

Abstract This study was undertaken with the aim of modifying the microstructure and improving the tribological properties of in situ Al-20Mg2Si composite. For this purpose, friction stir processing (FSP) was applied on the composite at constant travel and rotation speeds of 110 mm/min and 1500 rpm, respectively, using three different tool pin profiles: threaded tapered cylindrical, triangular tapered, and triangular threaded tapered. The sliding wear tests were conducted using a pin-on-disc apparatus under the applied load of 30 N and sliding distance of 1000 m at room temperature. The results showed that FSP substantially improved tribological properties of the as-cast composite. The best result was observed in the sample processed by the threaded triangular tapered tool, where compared with the as-cast composite, its wear rate and average friction coefficient decreased by almost 40% and 18%, respectively. This improvement can be attributed to the significant refinement and uniform redistribution of Mg2Si intermetallics, especially the coarse irregular-shaped primary crystals, the formation of ultrafine grains, and elimination of casting defects from the substrate microstructure of the processed sample, which improves its hardness and increased its potential in supporting the oxide tribolayer on the composite surface.

Impact of intrafraction prostate motion on clinical target coverage in proton therapy: A simulation study of dosimetric differences in two delivery techniques.

PurposeTo investigate the dosimetric impact of prostate intrafraction motion on proton double‐scattering (DS) and uniform scanning (US) treatments using electromagnetic transponder‐based prostate tracking data in simulated treatment deliveries.MethodsIn proton DS delivery, the spread‐out Bragg peak (SOBP) is created almost instantaneously by the constant rotation of the range modulator. US, however, delivers each entire energy layer of the SOBP sequentially from distal to proximal direction in time, which can interplay with prostate intrafraction motion. This spatiotemporal interplay during proton treatment was simulated to evaluate its dosimetric impact. Prostate clinical target volume (CTV) dose was obtained by moving CTV through dose matrices of the energy layers according to prostate‐motion traces. Fourteen prostate intrafraction motion traces of each of 17 prostate patients were used in the simulated treatment deliveries. Both single fraction dose‐volume histograms (DVHs) and fraction‐cumulative DVHs were obtained for both 2 Gy per fraction and 7.25 Gy per fraction stereotactic body radiotherapy (SBRT).ResultsThe simulation results indicated that CTV dose degradation depends on the magnitude and direction of prostate intrafraction motion and is patient specific. For some individual fractions, prescription dose coverage decreased in both US and DS treatments, and hot and cold spots inside the CTV were observed in the US results. However, fraction‐cumulative CTV dose coverage showed much reduced dose degradation for both DS and US treatments for both 2 Gy per fraction and SBRT simulations.ConclusionsThis study indicated that CTV dose inhomogeneity may exist for some patients with severe prostate intrafraction motion during US treatments. However, there are no statistically significant dose differences between DS and US treatment simulations. Cumulative dose of multiple‐fractions significantly reduced dose uncertainties.

Flow Patterns, Microstructure and Mechanical Properties of AZ31/Al6061 Dissimilar Friction Stir-Welded Joints

Dissimilar joints between die-cast AZ31 and extruded Al6061-T6 were joined using friction stir welding technology at a constant transverse speed (50 mm/min) and rotation rate of 800 or 1000 rpm. The flow patterns, microstructure evolution and intermetallic compounds in dissimilar joints were studied by optical and scanning electron microscopy. The relationship between microstructure and tensile properties was analyzed. The microhardness distribution along the horizontal centerline in cross section was investigated. Local flow without obvious mixing existed between Mg and Al metals in the tool shoulder-affected zone. For the tool-pin-affected zone, two typical zones, namely, the “extrusion zone” and “flow zone” existed because of the different flow modes of the plastic metals. The phase analysis showed that intermetallic compounds, including Al12Mg17 and Al3Mg2 formed in banded structures. Phase analysis showed that a joint with welding parameters of 800 rpm and 50 mm/min (Joint-500) had good mechanical properties because of the more uniform microstructure distribution and fewer intermetallic compounds. Fracture analysis indicated some microvoids and lamellate intermetallic compounds in the fracture surface of the joint with welding parameters of 1000 rpm and 50 mm/min (Joint-1000), which deteriorated its tensile strength significantly.

Efficient triple-VENC phase-contrast MRI for improved velocity dynamic range.

To evaluate the utility of an efficient triple velocity-encoding (VENC) 4D flow MRI implementation to improve velocity unwrapping of 4D flow MRI data with the same scan time as an interleaved dual-VENC acquisition. A balanced 7-point acquisition was used to derive 3 sets of 4D flow images corresponding to 3 different VENCs. These 3 datasets were then used to unwrap the aliased lowest VENC into a minimally aliased, triple-VENC dataset. Triple-VENC MRI was evaluated and compared with dual-VENC MRI over 3 different VENC ranges (50-150, 60-150, and 60-180 cm/s) in vitro in a steadily rotating phantom as well as in a pulsatile flow phantom. In vivo, triple-VENC data of the thoracic aorta were also evaluated in 3 healthy volunteers (2 males, 26-44 years old) with VENC = 50/75/150 cm/s. Two triple-VENC (triconditional and biconditional) and 1 dual-VENC unwrapping algorithms were quantitatively assessed through comparison to a reference, unaliased, single-VENC scan. Triple-VENC 4D flow constant rotation phantom results showed high correlation with the analytical solution (intraclass correlation coefficient = 0.984-0.995, P < .001) and up to a 61% reduction in velocity noise compared with the corresponding single-VENC scans (VENC = 150, 180 cm/s). Pulsatile flow phantom experiments demonstrated good agreement between triple-VENC and single-VENC acquisitions (peak flow < 0.8% difference; peak velocity < 11.7% difference). Triconditional triple-VENC unwrapping consistently outperformed dual-VENC unwrapping, correctly unwrapping more than 83% and 46%-66% more voxels in vitro and in vivo, respectively. Triple-VENC 4D flow MRI adds no additional scan time to dual-VENC MRI and has the potential for improved unwrapping to extend the velocity dynamic range beyond dual-VENC methods.