Showing papers on "Rotation published in 2017"

Shaft module circuitry arrangements

Abstract: Disclosed is an apparatus and modular surgical system that allows for a user of modular surgical instruments to manipulate an end effector directly from the instrumentation contained in the handle assembly. A nozzle assembly that is detachable from a handle assembly may include an onboard circuitry board that allows for the RF generator to attach directly to the nozzle assembly and supply RF energy to the end effector, while also interfacing with a microprocessor of the handle assembly. In some aspects, the unique circuitry of the nozzle assembly also allows for shaft rotation while still supplying proper energy and functionality to the end effector.

Substrate processing apparatus

Abstract: Provided is a substrate processing apparatus, which comprises a processing chamber, a substrate sensing assembly, a rotation shaft and a driving assembly A portion of the rotation shaft is provided inside the processing chamber and the remaining portion thereof is provided outside the processing chamber The substrate sensing assembly is provided on the portion of the rotation shaft outside the processing chamber The driving assembly is fixed at the portion of the rotation shaft inside the processing chamber The driving assembly drives, when coming into contact with the substrate, the rotation shaft to rotate about its own axis along a first direction, and drives, when the substrate comes into no contact with the driving assembly, the rotation shaft to rotate about its axis along a second direction opposite to the first direction The treatment liquid does not affect the substrate sensing assembly since it is provided outside the processing chamber

Design and stable flight of a 21 g insect-like tailless flapping wing micro air vehicle with angular rates feedback control

Abstract: An insect-like tailless flapping wing micro air vehicle (FW-MAV) without feedback control eventually becomes unstable after takeoff. Flying an insect-like tailless FW-MAV is more challenging than flying a bird-like tailed FW-MAV, due to the difference in control principles. This work introduces the design and controlled flight of an insect-like tailless FW-MAV, named KUBeetle. A combination of four-bar linkage and pulley-string mechanisms was used to develop a lightweight flapping mechanism that could achieve a high flapping amplitude of approximately 190°. Clap-and-flings at dorsal and ventral stroke reversals were implemented to enhance vertical force. In the absence of a control surface at the tail, adjustment of the location of the trailing edges at the wing roots to modulate the rotational angle of the wings was used to generate control moments for the attitude control. Measurements by a 6-axis load cell showed that the control mechanism produced reasonable pitch, roll and yaw moments according to the corresponding control inputs. The control mechanism was integrated with three sub-micro servos to realize the pitch, roll and yaw controls. A simple PD feedback controller was implemented for flight stability with an onboard microcontroller and a gyroscope that sensed the pitch, roll and yaw rates. Several flight tests demonstrated that the tailless KUBeetle could successfully perform a vertical climb, then hover and loiter within a 0.3 m ground radius with small variations in pitch and roll body angles.

Rotation-supported Neutrino-driven Supernova Explosions in Three Dimensions and the Critical Luminosity Condition

Abstract: We present the first self-consistent, three-dimensional (3D) core-collapse supernova simulations performed with the Prometheus-Vertex code for a rotating progenitor star. Besides using the angular momentum of the 15 solar-mass model as obtained in the stellar evolution calculation with an angular frequency of about 0.001 rad/s (spin period of more than 6000 s) at the Si/Si-O interface, we also computed 2D and 3D cases with no rotation and with a ~300 times shorter rotation period and different angular resolutions. In 2D, only the nonrotating and slowly rotating models explode, while rapid rotation prevents an explosion within 500 ms after bounce because of lower radiated neutrino luminosities and mean energies and thus reduced neutrino heating. In contrast, only the fast rotating model develops an explosion in 3D when the Si/Si-O interface collapses through the shock. The explosion becomes possible by the support of a powerful SASI spiral mode, which compensates for the reduced neutrino heating and pushes strong shock expansion in the equatorial plane. Fast rotation in 3D leads to a "two-dimensionalization" of the turbulent energy spectrum (yielding roughly a -3 instead of a -5/3 power-law slope at intermediate wavelengths) with enhanced kinetic energy on the largest spatial scales. We also introduce a generalization of the "universal critical luminosity condition" of Summa et al. (2016) to account for the effects of rotation, and demonstrate its viability for a set of more than 40 core-collapse simulations including 9 and 20 solar-mass progenitors as well as black-hole forming cases of 40 and 75 solar-mass stars to be discussed in forthcoming papers.

Asymptotic g modes: Evidence for a rapid rotation of the solar core

Abstract: Context. Over the past 40 years, helioseismology has been enormously successful in the study of the solar interior. A shortcoming has been the lack of a convincing detection of the solar g modes, which are oscillations driven by gravity and are hidden in the deepest part of the solar body – its hydrogen-burning core. The detection of g modes is expected to dramatically improve our ability to model this core, the rotational characteristics of which have, until now, remained unknown. Aims. We present the identification of very low frequency g modes in the asymptotic regime and two important parameters that have long been waited for: the core rotation rate, and the asymptotic equidistant period spacing of these g modes. Methods. The GOLF instrument on board the SOHO space observatory has provided two decades of full-disk helioseismic data. The search for g modes in GOLF measurements has been extremely difficult because of solar and instrumental noise. In the present study, the p modes of the GOLF signal are analyzed differently: we search for possible collective frequency modulations that are produced by periodic changes in the deep solar structure. Such modulations provide access to only very low frequency g modes, thus allowing statistical methods to take advantage of their asymptotic properties. Results. For oscillatory periods in the range between 9 and nearly 48 h, almost 100 g modes of spherical harmonic degree 1 and more than 100 g modes of degree 2 are predicted. They are not observed individually, but when combined, they unambiguously provide their asymptotic period equidistance and rotational splittings, in excellent agreement with the requirements of the asymptotic approximations. When the period equidistance has been measured, all of the individual frequencies of each mode can be determined. Previously, p -mode helioseismology allowed the g -mode period equidistance parameter P 0 to be bracketed inside a narrow range, between approximately 34 and 35 min. Here, P 0 is measured to be 34 min 01 s, with a 1 s uncertainty. The previously unknown g -mode splittings have now been measured from a non-synodic reference with very high accuracy, and they imply a mean weighted rotation of 1277 ± 10 nHz (9-day period) of their kernels, resulting in a rapid rotation frequency of 1644 ± 23 nHz (period of one week) of the solar core itself, which is a factor 3.8 ± 0.1 faster than the rotation of the radiative envelope. Conclusions. The g modes are known to be the keys to a better understanding of the structure and dynamics of the solar core. Their detection with these precise parameters will certainly stimulate a new era of research in this field.

The origin and evolution of fast and slow rotators in the Illustris simulation

Abstract: Using the Illustris simulation, we follow thousands of elliptical galaxies back in time to identify how the dichotomy between fast-and slow-rotating ellipticals (FRs and SRs) develops. Comparing to the ATLAS(3D) survey, we show that Illustris reproduces similar elliptical galaxy rotation properties, quantified by the degree of ordered rotation, lambda(R). There is a clear segregation between low-mass (M-* 10(11.5) M-circle dot), which are mostly SRs, in agreement with observations. We find that SRs are very gas poor, metal rich and red in colour, while FRs are generally more gas rich and still star forming. We suggest that ellipticals begin naturally as FRs and, as they grow in mass, lose their spin and become SRs. While at z = 1, the progenitors of SRs and FRs are nearly indistinguishable, their merger and star formation histories differ thereafter. We find that major mergers tend to disrupt galaxy spin, though in rare cases can lead to a spin-up. No major difference is found between the effects of gas-rich and gas-poor mergers, and the number of minor mergers seems to have little correlation with galaxy spin. In between major mergers, lower mass ellipticals, which are mostly gas rich, tend to recover their spin by accreting gas and stars. For galaxies with M* above similar to 10(11) M-circle dot, this trend reverses;galaxies only retain or steadily lose their spin. More frequent mergers, accompanied by an inability to regain spin, lead massive ellipticals to lose most of ordered rotation and transition from FRs to SRs.

Gaia reveals a metal-rich in-situ component of the local stellar halo

Abstract: We use the first Gaia data release, combined with RAVE and APOGEE spectroscopic surveys, to investigate the origin of halo stars within -1. The orbital directions of these metal-rich halo stars are preferentially aligned with the disk rotation, in sharp contrast with the isotropic orbital distribution of the more metal-poor halo stars. We find similar properties in the Latte cosmological zoom-in simulation of a Milky Way-like galaxy from the FIRE project. In Latte, metal-rich halo stars formed primarily inside of the solar circle, while lower-metallicity halo stars preferentially formed at larger distances (extending beyond the virial radius). This suggests that metal-rich halo stars in the Solar neighborhood in fact formed in-situ within the Galactic disk rather than having been accreted from satellite systems. These stars, currently on halo-like orbits, therefore have likely undergone substantial radial migration/heating.

Rotation and mass in the Milky Way and spiral galaxies

Abstract: [PASJ Review Paper] Rotation curves are the basic tool for deriving the distribution of mass in spiral galaxies. In this review, we describe various methods to measure rotation curves in the Milky Way and spiral galaxies. We then describe two major methods to calculate the mass distribution using the rotation curve. By the direct method, the mass is calculated from rotation velocities without employing mass models. By the decomposition method, the rotation curve is deconvolved into multiple mass components by model fitting assuming a black hole, bulge, exponential disk and dark halo. The decomposition is useful for statistical correlation analyses among the dynamical parameters of the mass components. We also review recent observations and derived results. ( Full resolution copy is available at URL: this http URL )

Surface rotation of Kepler red giant stars

Abstract: Kepler allows the measurement of starspot variability in a large sample of field red giants for the first time. With a new method that combines autocorrelation and wavelet decomposition, we measure 361 rotation periods from the full set of 17 377 oscillating red giants in our sample. This represents 2.08% of the stars, consistent with the fraction of spectroscopically detected rapidly rotating giants in the field. The remaining stars do not show enough variability to allow us to measure a reliable surface rotation period. Because the stars with detected rotation periods have measured oscillations, we can infer their global properties, e.g. mass and radius, and quantitatively evaluate the predictions of standard stellar evolution models as a function of mass. Consistent with results for cluster giants when we consider only the 4881 intermediate-mass stars, M > 2.0 M ⊙ from our full red giant sample, we do not find the enhanced rates of rapid rotation expected from angular momentum conservation. We therefore suggest that either enhanced angular momentum loss or radial differential rotation must be occurring in these stars. Finally, when we examine the 575 low-mass (M ⊙ ) red clump stars in our sample, which were expected to exhibit slow (non-detectable) rotation, 15% of them actually have detectable rotation. This suggests a high rate of interactions and stellar mergers on the red giant branch.

Reconciling solar and stellar magnetic cycles with nonlinear dynamo simulations

Abstract: The magnetic fields of solar-type stars are observed to cycle over decadal periods—11 years in the case of the Sun. The fields originate in the turbulent convective layers of stars and have a complex dependency upon stellar rotation rate. We have performed a set of turbulent global simulations that exhibit magnetic cycles varying systematically with stellar rotation and luminosity. We find that the magnetic cycle period is inversely proportional to the Rossby number, which quantifies the influence of rotation on turbulent convection. The trend relies on a fundamentally nonlinear dynamo process and is compatible with the Sun’s cycle and those of other solar-type stars.

Gerstner waves in the presence of mean currents and rotation

Abstract: We present a Lagrangian analysis of nonlinear surface waves propagating zonally on a zonal current in the presence of the Earth’s rotation that shows the existence of two modes of wave motion. The first, ‘fast’ mode, one with wavelengths commonly found for wind waves and swell in the ocean, represents the wave–current interaction counterpart of the rotationally modified Gerstner waves found first by Pollard (J. Geophys. Res., vol. 75, 1970, pp. 5895–5898) that quite closely resemble Stokes waves. The second, slower, mode has a period nearly equal to the inertial period and has a small vertical scale such that very long, e.g. wavelength, waves have velocities etc. that decay exponentially from the free surface over a scale of that is proportional to the strength of the mean current. In both cases, the particle trajectories are closed in a frame of reference moving with the mean current, with particle motions in the second mode describing inertial circles. Given that the linear analysis of the governing Eulerian equations only captures the fast mode, the slow mode is a fundamentally nonlinear phenomenon in which very small free surface deflections are manifestations of an energetic current.

Galactic masers: Kinematics, spiral structure and the disk dynamic state

Abstract: We applied the currently most comprehensive version of the statistical-parallax technique to derive the kinematical parameters of the maser sample with 136 sources. Our kinematic model comprises the overall rotation of the Galactic disk and the spiral density-wave effects, and the variation of radial velocity dispersion with Galactocentric distance. The best description of the observed velocity field is provided by the model with constant radial and vertical velocity dispersions, (σU0, σW0) ≈ (9.4 ± 0.9, 5.9 ± 0.8) kms−1. The resulting Galactic rotation curve proved to be flat over the Galactocentric distance interval from 3 to 15 kpc and we find the local circular rotation velocity to be V 0 ≈ (235 − 238) ± 7 km s−1. We determine the parameters of the four-armed spiral pattern (pitch angle i ≈ −10. ◦ 4 ± 0.3◦ and the phase of the Sun χ0 ≈ 125◦ ± 10◦). The amplitudes of radial and tangential spiral perturbations are about f R ≈ −6.9 ± 1.4 km s−1, f Θ ≈ +2.8 ± 1.0 km s−1. The kinematic data yield a solar Galactocentric distance of R 0 ≈ 8.24 ± 0.12 kpc. Based on rotation curve parameters and the asymmetric drift we infer the exponential disk scale H D ≈ 2.7 ± 0.2 kpc assuming marginal stability of the intermediate-age disk, and also estimate the minimum local surface disk density, Σ(R 0) > 26 ± 3M ⊙ pc−2.

Interacting fermions in rotation: chiral symmetry restoration, moment of inertia and thermodynamics

Abstract: We study rotating fermionic matter at finite temperature in the framework of the Nambu-Jona-Lasinio model. In order to respect causality the rigidly rotating system must be bound by a cylindrical boundary with appropriate boundary conditions that confine the fermions inside the cylinder. We show the finite geometry with the MIT boundary conditions affects strongly the phase structure of the model leading to three distinct regions characterized by explicitly broken (gapped), partially restored (nearly gapless) and spontaneously broken (gapped) phases at, respectively, small, moderate and large radius of the cylinder. The presence of the boundary leads to specific steplike irregularities of the chiral condensate as functions of coupling constant, temperature and angular frequency. These steplike features have the same nature as the Shubnikov-de Haas oscillations with the crucial difference that they occur in the absence of both external magnetic field and Fermi surface. At finite temperature the rotation leads to restoration of spontaneously broken chiral symmetry while the vacuum at zero temperature is insensitive to rotation (“cold vacuum cannot rotate”). As the temperature increases the critical angular frequency decreases and the transition becomes softer. A phase diagram in angular frequency-temperature plane is presented. We also show that at fixed temperature the fermion matter in the chirally restored (gapless) phase has a higher moment of inertia compared to the one in the chirally broken (gapped) phase.

The Interior Angular Momentum of Core Hydrogen Burning Stars from Gravity-mode Oscillations

Abstract: A major uncertainty in the theory of stellar evolution is the angular momentum distribution inside stars and its change during stellar life. We compose a sample of 67 stars in the core hydrogen burning phase with a value from high-resolution spectroscopy, as well as an asteroseismic estimate of the near-core rotation rate derived from gravity-mode oscillations detected in space photometry. This assembly includes 8 B-type stars and 59 AF-type stars, covering a mass range from 1.4 to 5 M ⊙, i.e., it concerns intermediate-mass stars born with a well-developed convective core. The sample covers projected surface rotation velocities km s−1 and core rotation rates up to 26 μHz, which corresponds to 50% of the critical rotation frequency. We find deviations from rigid rotation to be moderate in the single stars of this sample. We place the near-core rotation rates in an evolutionary context and find that the core rotation must drop drastically before or during the short phase between the end of the core hydrogen burning and the onset of core helium burning. We compute the spin parameter, which is the ratio of twice the rotation rate to the mode frequency (also known as the inverse Rossby number), for 1682 gravity modes and find the majority (95%) to occur in the sub-inertial regime. The 10 stars with Rossby modes have spin parameters between 14 and 30, while the gravito-inertial modes cover the range from 1 to 15.

A Wide-Range Capacitive Sensor for Linear and Angular Displacement Measurement

Abstract: A new capacitive sensor that is suitable for measuring both linear and angular displacements of a shaft over a wide range is reported in this paper. The sensor consists of a cylindrical shaft with a semi-hollow cylinder attached in the center; the shaft is capable of moving along the axis as well as rotating about the axis. Two pairs of semi-hollow-cylindrical electrodes surround the shaft, which is grounded. The amount of linear displacement and rotation is calculated by measuring the change in the capacitance of each of the four electrodes with respect to the shaft. A prototype sensor was constructed and tested; the rms error obtained is 0.6% for the linear displacement and less than 0.6% for the angular displacement. The proposed sensor has potential applications in several robotic, industrial, and automotive fields.

Asymptotic g modes: Evidence for a rapid rotation of the solar core

Abstract: We present the identification of very low frequency g modes in the asymptotic regime and two important parameters that have long been waited for: the core rotation rate, and the asymptotic equidistant period spacing of these g modes. The GOLF instrument on board the SOHO space observatory has provided two decades of full-disk helioseismic data. In the present study, we search for possible collective frequency modulations that are produced by periodic changes in the deep solar structure. Such modulations provide access to only very low frequency g modes, thus allowing statistical methods to take advantage of their asymptotic properties. For oscillatory periods in the range between 9 and nearly 48 hours, almost 100 g modes of spherical harmonic degree 1 and more than 100 g modes of degree 2 are predicted. They are not observed individually, but when combined, they unambiguouslyprovide their asymptotic period equidistance and rotational splittings, in excellent agreement with the requirements of the asymptotic approximations. Previously, p-mode helioseismology allowed the g-mode period equidistance parameter $P_0$ to be bracketed inside a narrow range, between approximately 34 and 35 minutes. Here, $P_0$ is measured to be 34 min 01 s, with a 1 s uncertainty. The previously unknown g-mode splittings have now been measured from a non-synodic reference with very high accuracy, and they imply a mean weighted rotation of 1277 $\pm$ 10 nHz (9-day period) of their kernels, resulting in a rapid rotation frequency of 1644 $\pm$ 23 nHz (period of one week) of the solar core itself, which is a factor 3.8 $\pm$ 0.1 faster than the rotation of the radiative envelope. The g modes are known to be the keys to a better understanding of the structure and dynamics of the solar core. Their detection with these precise parameters will certainly stimulate a new era of research in this field.

Hubble Space Telescope Proper Motion (HSTPROMO) Catalogs of Galactic Globular Clusters. V. The Rapid Rotation of 47 Tuc Traced and Modeled in Three Dimensions

Abstract: High-precision proper motions of the globular cluster 47 Tuc have allowed us to measure for the first time the cluster rotation in the plane of the sky and the velocity anisotropy profile from the cluster core out to about 13'. These profiles are coupled with prior measurements along the line of sight and the surface-brightness profile, and fit all together with self-consistent models specifically constructed to describe quasi-relaxed stellar systems with realistic differential rotation, axisymmetry and pressure anisotropy. The best-fit model provides an inclination angle i between the rotation axis and the line-of-sight direction of 30 deg, and is able to simultaneously reproduce the full three-dimensional kinematics and structure of the cluster, while preserving a good agreement with the projected morphology. Literature models based solely on line-of-sight measurements imply a significantly different inclination angle (i=45 deg), demonstrating that proper motions play a key role in constraining the intrinsic structure of 47 Tuc. Our best-fit global dynamical model implies an internal rotation higher than previous studies have shown, and suggests a peak of the intrinsic V/sigma ratio of ~0.9 at around two half-light radii, with a non-monotonic intrinsic ellipticity profile reaching values up to 0.45. Our study unveils a new degree of dynamical complexity in 47 Tuc, which may be leveraged to provide new insights into the formation and evolution of globular clusters.

Evidence for photometric activity cycles in 3203 Kepler stars

Abstract: In recent years it has been claimed that the length of stellar activity cycles is determined by the stellar rotation rate. It is observed that the cycle period increases with rotation period along the so-called active and inactive sequences. In this picture the Sun occupies a solitary position in between the two sequences. Our goal is to measure cyclic variations of the stellar light curve amplitude and the rotation period using four years of Kepler data. Periodic changes of the light curve amplitude or the stellar rotation period are associated with an underlying activity cycle. Using the McQuillan et al. 2014 sample we compute the rotation period and the variability amplitude for each Kepler quarter and search for periodic variations of both time series. To test for periodicity in each stellar time series we consider Lomb-Scargle periodograms and use a selection based on a False Alarm Probability (FAP). We detect amplitude periodicities in 3203 stars between 0.5-6 years covering rotation periods between 1-40 days. Given our sample size of 23,601 stars and our selection criteria that the FAP is less than 5%, this number is almost three times higher than that expected from pure noise. We do not detect periodicities in the rotation period beyond those expected from noise. Our measurements reveal that the cycle period shows a weak dependence on rotation rate, slightly increasing for longer rotation period. We further show that the shape of the variability deviates from a pure sine curve, consistent with observations of the solar cycle. Our measurements do not support the existence of distinct sequences in the P_rot-P_cyc plane, although there is some evidence for the inactive sequence for rotation periods between 5-25 days. Unfortunately, the total observing time is too short to draw sound conclusions on activity cycles with similar length as the solar cycle.

Assessment of Elbow Torque and Other Parameters During the Pitching Motion: Comparison of Fastball, Curveball, and Change-up.

Abstract: Purpose To assess the precision of a new wearable device in detecting medial elbow torque during the pitching motion in competitive baseball pitchers and to determine the differences in torque across pitch types and thrower demographic characteristics. Methods High school and collegiate baseball pitchers were recruited from August 1, 2016, to January 31, 2017, through direct request by athletic trainers and coaches. Body dimensions and throwing arm measurements of the participants were collected. The sensor was positioned directly over the medial elbow and pitchers were instructed to throw 8 fastballs, 8 curveballs, and 8 change-ups in a standard, randomized sequence. The sensor reported elbow torque, arm speed, arm slot, and shoulder rotation, whereas a radar gun measured peak ball velocity. Precision was calculated by measuring outlier rate, and mixed model regression analysis was performed to detect differences in throwing biomechanics among pitch types. Results In total, 37 competitive baseball pitchers were included in the study. The device had a precision of 96.9% for fastballs, 96.9% for curveballs, and 97.9% for change-ups. The device was sensitive enough to distinguish pitches according to elbow torque, arm speed, arm slot, and shoulder rotation. Fastballs caused the greatest relative torque across the medial elbow (average = 45.56 N m), compared with change-ups (43.77 N m; P = .006) and curveballs (43.83 N m; P = .01). Ball velocity contributed most to medial elbow torque ( P = .003), followed by elbow circumference ( P = .021), where smaller elbow circumference predicted greater medial elbow torque. Conclusions The sensor is a precise and reproducible device for measuring torque across the medial elbow, as well as additional parameters of arm speed, arm slot, and shoulder rotation. Torque was significantly relatively higher in fastballs than curveballs and change-ups. Level of Evidence Level III, comparative study.

Novel power supply device

Abstract: The invention discloses a novel power supply device which comprises a socket part and a plug part in matching connection with the socket part. The socket part is provided with a first accommodating cavity inside. A sleeve is connected into the first accommodating cavity in a rotation fit manner. The right side of the sleeve is provided with an internal spiral thread cavity inside. The internal spiral thread cavity is internally provided with a sliding table connected in a spiral thread fit manner. The right end face of the sliding table is fixedly provided with a connecting rod extending to the right. The upper and lower sides of the connecting rod are symmetrically provided with first sliding slots. The left inner wall of the first accommodating cavity is provided with a driver inside. The right side of the driver is connected with a rotating pin. The right end face of the rotating pin is fixedly connected with the sleeve. The inner walls of the upper and lower sides of the first accommodating cavity are symmetrically provided with placement slots. Each placement slot is provided with a toothed wheel inside. The socket part is internally provided with second accommodating cavities on the left sides of the placement slots respectively. The upper and lower sides of the second accommodating cavity are provided with second sliding slots. Each second accommodating cavity is internally provided with a sliding block extending into the corresponding second sliding slots.

CO emission tracing a warp or radial flow within <~ 100 au in the HD 100546 protoplanetary disk

Abstract: We present spatially resolved Atacama Large Millimeter/submillimeter Array (ALMA) images of 12 CO J = 3−2 emission from the protoplanetary disk around the Herbig Ae star, HD 100546. We expand upon earlier analyses of this data and model the spatially-resolved kinematic structure of the CO emission. Assuming a velocity profile which prescribes a flat or flared emitting surface in Keplerian rotation, we uncover significant residuals with a peak of ≈7δv , where δv = 0.21 km s-1 is the width of a single spectral resolution element. The shape and extent of the residuals reveal the possible presence of a severely warped and twisted inner disk extending to at most 100 au. Adapting the model to include a misaligned inner gas disk with (i) an inclination almost edge-on to the line of sight, and (ii) a position angle almost orthogonal to that of the outer disk reduces the residuals to . However, these findings are contrasted by recent VLT/SPHERE, MagAO/GPI, and VLTI/PIONIER observations of HD 100546 that show no evidence of a severely misaligned inner dust disk down to spatial scales of ~ 1 au. An alternative explanation for the observed kinematics are fast radial flows mediated by (proto)planets. Inclusion of a radial velocity component at close to free-fall speeds and inwards of ≈50 au results in residuals of ≈4δv . Hence, the model including a radial velocity component only does not reproduce the data as well as that including a twisted and misaligned inner gas disk. Molecular emission data at a higher spatial resolution (of order 10 au) are required to further constrain the kinematics within ≲100 au. HD 100546 joins several other protoplanetary disks for which high spectral resolution molecular emission shows that the gas velocity structure cannot be described by a purely Keplerian velocity profile with a universal inclination and position angle. Regardless of the process, the most likely cause is the presence of an unseen planetary companion.

Circumstellar Disks and Outflows in Turbulent Molecular Cloud Cores: Possible Formation Mechanism for Misaligned Systems

Abstract: We investigate the formation of circumstellar disks and outflows subsequent to the collapse of molecular cloud cores with the magnetic field and turbulence. Numerical simulations are performed by using an adaptive mesh refinement to follow the evolution up to $\sim 1000$~yr after the formation of a protostar. In the simulations, circumstellar disks are formed around the protostars; those in magnetized models are considerably smaller than those in nonmagnetized models, but their size increases with time. The models with stronger magnetic field tends to produce smaller disks. During evolution in the magnetized models, the mass ratios of a disk to a protostar is approximately constant at $\sim 1-10$\%. The circumstellar disks are aligned according to their angular momentum, and the outflows accelerate along the magnetic field on the $10-100$~au scale; this produces a disk that is misaligned with the outflow. The outflows are classified into two types: a magneto-centrifugal wind and a spiral flow. In the latter, because of the geometry, the axis of rotation is misaligned with the magnetic field. The magnetic field has an internal structure in the cloud cores, which also causes misalignment between the outflows and the magnetic field on the scale of the cloud core. The distribution of the angular momentum vectors in a core also has a non-monotonic internal structure. This should create a time-dependent accretion of angular momenta onto the circumstellar disk. Therefore, the circumstellar disks are expected to change their orientation as well as their sizes in the long-term evolutions.

Experimental investigation of flow-induced vibration of a rotating circular cylinder

Abstract: While flow-induced vibration of bluff bodies has been extensively studied over the last half-century, only limited attention has been given to flow-induced vibration of elastically mounted rotating cylinders Since recent low-Reynolds-number numerical work suggests that rotation can enhance or suppress the natural oscillatory response, the former could find applications in energy harvesting and the latter in vibration control The present experimental investigation characterises the dynamic response and wake structure of a rotating circular cylinder undergoing vortex-induced vibration at a low mass ratio (m∗ = 578) over the reduced velocity range leading to strong oscillations The experiments were conducted in a free-surface water channel with the cylinder vertically mounted and attached to a motor that provided constant rotation Springs and an air-bearing system allow the cylinder to undertake low-damped transverse oscillations Under cylinder rotation, the normalised frequency response was found to be comparable to that of a freely vibrating non-rotating cylinder At reduced velocities consistent with the upper branch of a non-rotating transversely oscillating cylinder, the maximum oscillation amplitude increased with non-dimensional rotation rate up to α ≈ 2 Beyond this, there was a sharp decrease in amplitude Notably, this critical value corresponds approximately to the rotation rate at which vortex shedding ceases for a non-oscillating rotating cylinder Remarkably, at α = 2 there was approximately an 80% increase in the peak amplitude response compared to that of a non-rotating cylinder The observed amplitude response measured over the Reynolds-number range of (1100 Re 6300) is significantly different from numerical predictions and other experimental results recorded at significantly lower Reynolds numbers

Non-diffractive Bessel-Gauss beams for the detection of rotating object free of obstructions

Abstract: Bessel-Gauss beams carrying orbital angular momentum are widely known for their non-diffractive or self-reconstructing performance, and have been applied in lots of domains. Here we demonstrate that, by illuminating a rotating object with high-order Bessel-Gauss beams, a frequency shift proportional to the rotating speed and the topological charge is observed. Moreover, the frequency shift is still present once an obstacle exists in the path, in spite of the decreasing of received signals. Our work indicates the feasibility of detecting rotating objects free of obstructions, and has potential as obstruction-immune rotation sensors in engine monitoring, aerological sounding, and so on.

An investigation of the rotational properties of magnetic chemically peculiar stars

Abstract: The magnetic chemically peculiar (mCP) stars of the upper main sequence exhibit strong, globally organized magnetic fields that are inclined to the rotational axis and facilitate the development of surface abundance inhomogeneities resulting in photometric and spectroscopic variability. Therefore, mCP stars are perfectly suited for a direct measurement of the rotational period without the need for any additional calibrations. We have investigated the rotational properties of mCP stars based on an unprecedentedly large sample consisting of more than 500 objects with known rotational periods. Using precise parallaxes from the Hipparcos and Gaia satellite missions, well-established photometric calibrations and state-of-the-art evolutionary models, we have determined the location of our sample stars in the Hertzsprung-Russell diagram and derived astrophysical parameters such as stellar masses, effective temperature, radii, inclinations and critical rotational velocities. We have confirmed the conservation of angular momentum during the main sequence evolution; no signs of additional magnetic braking were found. The inclination angles of the rotational axes are randomly distributed, although an apparent excess of fast rotators with comparable inclination angles has been observed. We have found a rotation rate of upsilon/upsilon(crit) >= 0.5 for several stars, whose characteristics cannot be explained by current models. For the first time, we have derived the relationship between mass and rotation rate of mCP stars, and provide an analysis that links mass and rotation with magnetic field strength. Our sample is unique and offers crucial input for forthcoming evolutionary models that include the effects of magnetic fields for upper main sequence stars.

Shadow cast by rotating braneworld black holes with a cosmological constant

Abstract: In this article, we study the shadow produced by rotating black holes with a tidal charge in a Randall-Sundrum braneworld model, with a cosmological constant. We obtain the apparent shape and the corresponding observables for different values of the tidal charge and the rotation parameter, and we analyze the influence of the presence of the cosmological constant. We also discuss the observational prospects for this optical effect.

Optically driven full-angle sample rotation for tomographic imaging in digital holographic microscopy.

Abstract: This study presents a novel tomographic imaging technique for living biomedical samples using an optically driven full-angle rotation scheme based on digital holographic microscopy, in which the three-dimensional refractive index distribution inside the sample can be measured and analyzed. To accomplish the full-angle sample rotation, two optical traps are driven by highly focused spots on the top and bottom of the sample. The rim image of the sample outside the focal depth at the different rotation angles and propagation distances can be corrected and compensated, respectively, via numerical focusing; therefore, tomographic imaging of the sample can be conducted. The proposed approach shows that an entire symmetric spectrum can be acquired for tomographic reconstruction without the missing apple core problem as in traditional sample-rotation schemes. The three-dimensional refractive index of living yeast in a fluid medium is measured and verified.

Can plume-induced internal gravity waves regulate the core rotation of subgiant stars?

Abstract: Context. The seismic data provided by the space-borne missions CoRoT and Kepler enabled us to probe the internal rotation of thousands of evolved low-mass stars. Subsequently, several studies showed that current stellar evolution codes are unable to reproduce the low core rotation rates observed in these stars. These results indicate that an additional angular momentum transport process is necessary to counteract the spin up due to the core contraction during the post-main sequence evolution. For several candidates, the transport induced by internal gravity waves (IGW) could play a non-negligible role. Aims. We aim to investigate the effect of IGW generated by penetrative convection on the internal rotation of low-mass stars from the subgiant branch to the beginning of the red giant branch. Methods. A semi-analytical excitation model was used to estimate the angular momentum wave flux. The characteristic timescale associated with the angular momentum transport by IGW was computed and compared to the contraction timescale throughout the radiative region of stellar models at different evolutionary stages. Results. We show that IGW can efficiently counteract the contraction-driven spin up of the core of subgiant stars if the amplitude of the radial-differential rotation (between the center of the star and the top of the radiative zone) is higher than a threshold value. This threshold depends on the evolutionary stage and is comparable to the differential rotation rates inferred for a sample of subgiant stars observed by the satellite Kepler . Such an agreement can therefore be interpreted as the consequence of a regulation mechanism driven by IGW. This result is obtained under the assumption of a smooth rotation profile in the radiative region and holds true even if a wide range of values is considered for the parameters of the generation model. In contrast, on the red giant branch, we find that IGW remain insufficient, on their own, to explain the observations because of an excessive radiative damping. Conclusions. IGW generated by penetrative convection are able to efficiently extract angular momentum from the core of stars on the subgiant branch and accordingly have to be taken into account. Moreover, agreements with the observations reinforce the idea that their effect is essential to regulate the amplitude of the radial-differential rotation in subgiant stars. On the red giant branch, another transport mechanism must likely be invoked.