Lower Spin Research Articles

The Dynamical Complexity of Surface Mass Shedding from a Top-shaped Asteroid Near the Critical Spin Limit

Abstract The regolith transport near the surface of an asteroid is inherently sensitive to the local topography. In this paper, conditions of surface mass shedding and the subsequent evolution of the shedding material are studied for the primary of 65803 Didymos, serving as a representative for a large group of top-shaped asteroids that rotate near their critical spin limits. We considered the influences of an asymmetric shape and a non-spherical gravity, and demonstrate that these asymmetries play a significant role in the shedding process as well as in the subsequent orbital motion. The mass shedding conditions are given as a function of the geological coordinates, and show a clear-cut dependency on the local topographic features. We find that at different stages of the Yarkovsky–O’Keefe–Radzievskii–Paddack spin-up, the bulged areas exhibit a uniform superior advantage of enabling mass shedding over the depressed areas. “Dead zones” free from mass shedding are found around the polar sites. Numerical simulations show that the orbital motion of the shedding material experiences a drastic change as the spin rate is approaching the critical limit. The “mass leaking” effect is reinforced as the spin rate increases; the lower spin rates correspond to a higher capability of trapping the lofted particles in the vicinity of the asteroid, which statistically improves the probability of collisional growth in orbit. We also find that the topological transition of the equilibrium point can in practice lead to rapid clearance of the shedding material and transport of their orbits to larger distances from the surface.

P13. Semi-automatic, machine-learning based segmentation of peripheral nerves for quantitative morphometry: Comparison of low- and high-resolution MR neurography

Background Current state-of-the-art to diagnose peripheral neuropathy are neurological examination and electrodiagnostic studies. However, deeply situated nerves and plexus remain difficult to assess using these techniques, hence magnetic resonance neurography (MRN) emerged as a complementary method. MRN remains a qualitative approach and quantification, in terms of extraction of imaging biomarkers is needed to facilitate diagnosis and for follow-up examinations. Towards a multi-parametric quantitative imaging approach, accurate nerve segmentation needs to be performed first. Hampered by time-consuming manual annotation, we developed a semi-automatic, time-effective, hence clinically feasible segmentation approach based on machine-learning algorithms. In this study, we compared its performance on low- and high-resolution MRN. Materials and methods We acquired images of 9 healthy volunteers at the upper leg using 3 MRN sequences: lower resolution turbo inversion recovery magnitude (TIRM, voxel size of 78 × 78 × 4.0 mm3), lower resolution spin echo T2-weighted (T2, voxel size .52 × .52 × 4.0 mm3), and high resolution, fat-suppressed spin echo T2-weighted (hrT2, voxel size .25 × .25 × 3.3 mm3). An expert manually segmented the sciatic nerve on the T2 and hrT2 images (ground truth, GT). Our segmentation algorithm is based on a decision forest with context- and intensity-based descriptors. We split the images into two sets: a multi-modal low-resolution (TIRM and T2), and a mono-modal high-resolution (hrT2). We perform a leave-one-out cross-validation for both sets and calculate the Dice coefficient to the manually annotated GT. Cross-sectional areas (CSA) were calculated from the middle slice of the image stack. Results Dice coefficients of 0.723 ± 0.202 and 0.735 ± 0.080 are achieved for the low- and high-resolution MRN images (p = 0.858, CI 95 %). Segmentation results and 3-D renderings of the same nerve segmented in low- and high-resolution are shown in Fig. 1 . CSA for GT were 34.0 ± 5.5 mm2 (T2), and 35.4 ± 8.5 mm2 (hrT2), using semi-automatic segmentation 24.8 ± 7.6 mm2 (T2), and 25.7 ± 10.6 mm2 (hrT2). Discussion and conclusion Semi-automatic, hence fast peripheral nerve segmentation is feasible in both low- and high-resolution MRN images of the upper leg, providing image-based quantitative morphometric data. The equal performance of the low-resolution images might be due to the multi-modal setting, which possibly provides more discriminative descriptors for nerve. The lower CSA using semi-automatic segmentation is due to more rigorous segmentation constraints. Future work will include the application of our method to localize and quantify nerve lesions in images of patients diagnosed with peripheral neuropathy.

The prevalence of type III disc breaks in H i-rich and low-spin galaxies

We investigate the origin of the type III (up-bending) discs based on a sample of 1808 galaxies from SDSS and a sub-sample of 286 galaxies with HI data from ALFALFA. We examine how the type III fraction f3, the fraction of disc galaxies which host up-bending disc breaks, depends on other galactic properties. We confirm that f3 strongly depends on the stellar concentration of galaxies. We find that HI-rich galaxies with low spins tend to have significantly more type III disc breaks than control galaxies, which are matched in concentration and stellar mass. This trend is independent of the existence of strong bars or environment of the galaxies. This result is broadly consistent with predictions from theoretical simulations, and indicates in-situ star formation fueled by gas accretion to be an important mechanism that builds the outer discs of type III galaxies.

The MASSIVE Survey – X. Misalignment between kinematic and photometric axes and intrinsic shapes of massive early-type galaxies

We use spatially resolved two-dimensional stellar velocity maps over a $107"\times 107"$ field of view to investigate the kinematic features of 90 early-type galaxies above stellar mass $10^{11.5}M_\odot$ in the MASSIVE survey. We measure the misalignment angle $\Psi$ between the kinematic and photometric axes and identify local features such as velocity twists and kinematically distinct components. We find 46% of the sample to be well aligned ($\Psi < 15^{\circ}$), 33% misaligned, and 21% without detectable rotation (non-rotators). Only 24% of the sample are fast rotators, the majority of which (91%) are aligned, whereas 57% of the slow rotators are misaligned with a nearly flat distribution of $\Psi$ from $15^{\circ}$ to $90^{\circ}$. 11 galaxies have $\Psi \gtrsim 60^{\circ}$ and thus exhibit minor-axis ("prolate") rotation in which the rotation is preferentially around the photometric major axis. Kinematic misalignments occur more frequently for lower galaxy spin or denser galaxy environments. Using the observed misalignment and ellipticity distributions, we infer the intrinsic shape distribution of our sample and find that MASSIVE slow rotators are consistent with being mildly triaxial, with mean axis ratios of $b/a=0.88$ and $c/a=0.65$. In terms of local kinematic features, 51% of the sample exhibit kinematic twists of larger than $20^{\circ}$, and 2 galaxies have kinematically distinct components. The frequency of misalignment and the broad distribution of $\Psi$ reported here suggest that the most massive early-type galaxies are mildly triaxial, and that formation processes resulting in kinematically misaligned slow rotators such as gas-poor mergers occur frequently in this mass range.

Dependence of the prompt fission γ-ray spectrum on the entrance channel of compound nucleus: Spontaneous vs. neutron-induced fission

Prompt γ-ray spectra were measured for the spontaneous fission of 240,242Pu and the neutron-induced fission of 239,241Pu with incident neutron energies ranging from thermal to about 100 keV. Measurements were made using the Detector for Advanced Neutron Capture Experiments (DANCE) array in coincidence with the detection of fission fragments using a parallel-plate avalanche counter. The unfolded prompt fission γ-ray energy spectra can be reproduced reasonably well by Monte Carlo Hauser–Feshbach statistical model for the neutron-induced fission channel but not for the spontaneous fission channel. However, this entrance-channel dependence of the prompt fission γ-ray emission can be described qualitatively by the model due to the very different fission-fragment mass distributions and a lower average fragment spin for spontaneous fission. The description of measurements and the discussion of results under the framework of a Monte Carlo Hauser–Feshbach statistical approach are presented.

Interaction of supersymmetric nonlinear sigma models with external higher spin superfields via higher spin supercurrents

We consider a four dimensional generalized Wess-Zumino model formulated in terms of an arbitrary Kähler potential mathcal{K}left(varPhi, overline{varPhi}right) and an arbitrary chiral superpotential mathcal{W}left(varPhi right) . A general analysis is given to describe the possible interactions of this theory with external higher spin gauge superfields of the (s + 1, s + 1/2) supermultiplet via higher spin supercurrents. It is shown that such interactions do not exist beyond supergravity (s ≥ 2) for any mathcal{K} and mathcal{W} . However, we find three exceptions, the theory of a free massless chiral, the theory of a free massive chiral and the theory of a free chiral with linear superpotential. For the first two, the higher spin supercurrents are known and for the third one we provide the explicit expressions. We also discuss the lower spin supercurrents. As expected, a coupling to (non-minimal) supergravity (s = 1) can always be found and we give the generating supercurrent and supertrace for arbitrary mathcal{K} and mathcal{W} . On the other hand, coupling to the vector supermultiplet (s = 0) is possible only if mathcal{K} = mathcal{K}left(overline{varPhi}varPhi right) and mathcal{W}=0 .

Dewetting of Swollen Poly(3-hexylthiophene) Films during Spin-Coating Processes: Implications for Device Fabrication

Poly(3-hexylthiophene) (P3HT) films have been usually prepared by spin-coating for the applications of electronic devices such as organic photovoltaic devices (OPV) and organic field-effect transistors (OFETs). The wetting and dewetting behaviors of the swollen P3HT films during the spin-coating processes, however, are still poorly understood. In this work, we investigate the dewetting behaviors of P3HT thin films and the formation of ring structures during the spin-coating process by controlling the spin rates and the solution temperatures. Quantitative studies of the dewetting phenomena are conducted by measuring the sizes of the ring structures of the dewetting patterns. It is observed that the sizes of the ring structures are larger at lower spin rates because of the longer dewetting times allowed during the spin-coating processes. More importantly, the dewetting behaviors of the P3HT films are discovered to be affected by the formation of the P3HT nanowhiskers (nanowires). This work offers a deeper u...

Observation of low-lying electronic states of NiD with multi-isotope analysis

Resolved laser induced fluorescence spectra of 58NiD, recorded at Doppler resolution between 11000 and 18000 cm−1 have established >200 term energies in two of the three strongly interacting, low-lying states (2Δ, 2Π, 2Σ+) of NiD, associated with an Ni+(3d9)D− configuration. Our observations span v = 0–5 in the lowest spin–orbit component of the ground state, X 2Δ5/2, v = 0–3 in X 2Δ3/2 and v = 0–1 in the lower component of the W 2Π3/2 state. Collisional processes populate several neighbouring excited states, allowing us also to locate the first rotational levels of A(Ω = 5/2) v = 1, I(Ω = 3/2) v = 0 and E(Ω = 3/2) v = 1 at 16664.8, 17367.3 and 17508.1 cm−1 respectively. Spin-orbit and rotation-electronic interactions are strong in NiD (as in NiH), and with no direct observation of either of the Ω = 1/2 states, meaningful representations of the low-lying energy levels is difficult. We have therefore attempted a global, multi-isotope fit to reproduce the term energies of the known term energies of NiD and 58,60,62NiH (where some Ω″ = 1/2 levels are known). Dunham-type parameters have been used to represent the unperturbed 2Δ, 2Π and 2Σ+ states, with off-diagonal matrix elements (treating spin–orbit, L- and S-uncoupling effects) based on Ni+ atomic properties. Born-Oppenheimer breakdown terms were included in the model. The equilibrium bond lengths for 58NiH/58NiD are 1.4545(1)/1.4559(1) Å for the X 2Δ state and 1.5094(2)/1.5083(2) Å for the W 2Π state.

Determination of the ground state of an Au-supported FePc film based on the interpretation of Fe K - and L -edge x-ray magnetic circular dichroism measurements

We determine the magnetic ground state of the FePc molecule on Au-supported thin films based on the observed values of orbital anisotropy and spectroscopic x-ray magnetic circular dichroism (XMCD) measurements at the Fe $K$ and $L$ edges. Starting from ab initio molecular orbital multiplet calculations for the isolated molecule, we diagonalize the spin-orbit interaction in the subspace spanned by the three lowest spin triplet states of ${}^{3}{A}_{2g}$ and ${}^{3}{E}_{g}$ symmetry in the presence of a saturating magnetic field at a polar angle $\ensuremath{\theta}$ with respect to the normal to the plane of the film, plus an external perturbation representing the effect of the molecules in the stack on the FePc molecule under consideration. We find that the orbital moment of the ground state strongly depends on the magnetic field direction in agreement with the sum rule analysis of the ${L}_{23}$-edge XMCD data. We calculate integrals over the XMCD spectra at the Fe $K$ and ${L}_{23}$ edges as used in the sum rules and explicitly show that they agree with the expectation values of the orbital moment and effective spin moment of the ground state. On the basis of this analysis, we can rule out alternative candidates proposed in the literature.

Binary black hole mergers within the LIGO horizon: statistical properties and prospects for detecting electromagnetic counterparts

Binary black holes (BBHs) are one of the endpoints of isolated binary evolution, and their mergers a leading channel for gravitational wave events. Here, using the evolutionary code \textsc{StarTrack}, we study the statistical properties of the BBH population from isolated binary evolution for a range of progenitor star metallicities and BH natal kicks. We compute the mass function and the distribution of the primary BH spin $a$ as a result of mass accretion during the binary evolution, and find that this is not an efficient process to spin up BHs, producing an increase by at most $a\sim$~0.2--0.3 for very low natal BH spins. We further compute the distribution of merger sites within the host galaxy, after tracking the motion of the binaries in the potentials of a massive spiral, a massive elliptical, and a dwarf galaxy. We find that a fraction of 70-90\% of mergers in massive galaxies and of 40-60\% in dwarfs (range mostly sensitive to the natal kicks) is expected to occur inside of their hosts. The number density distribution at the merger sites further allows us to estimate the broadband luminosity distribution that BBH mergers would produce, \textit{if} associated with a kinetic energy release in an outflow, {which, as a reference, we assume at the level inferred for the \textit{Fermi} GBM counterpart to GW150914, with the understanding that current limits from the O1 and O2 runs would require such emission to be produced within a jet of angular size within $\lesssim 50^\circ$.}

Note: Force- and torque-detection of high frequency electron spin resonance using a membrane-type surface-stress sensor.

We developed a practical useful method for force- and torque-detected electron spin resonance (FDESR/TDESR) spectroscopy in the millimeter wave frequency region. This method uses a commercially available membrane-type surface-stress (MSS) sensor. The MSS is composed of a silicon membrane supported by four beams in which piezoresistive paths are integrated for detecting the deformation of the membrane. Although this device has a lower spin sensitivity than a microcantilever, it offers several distinct advantages, including mechanical strength, ease of use, and versatility. These advantages make this device suitable for practical applications that require FDESR/TDESR.

Sparsity of the wavefunction from the generalized Pauli exclusion principle.

Electron occupations that arise from pure quantum states are restricted by a stringent set of conditions that are said to generalize the Pauli exclusion principle. These generalized Pauli constraints (GPCs) define the boundary of the set of one-electron reduced density matrices (1-RDMs) that are derivable from at least one N-electron wavefunction. In this paper, we investigate the sparsity of the Slater-determinant representation of the wavefunction that is a necessary, albeit not sufficient, condition for its 1-RDM to lie on the boundary of the set of pure N-representable 1-RDMs or in other words saturate one of the GPCs. The sparse wavefunction, we show, is exact not only for 3 electrons in 6 orbitals but also for 3 electrons in 8 orbitals. For larger numbers of electrons and/or orbitals in the lowest spin state, the exact wavefunction does not generally saturate one of the GPCs, and hence, the sparse representation is typically an approximation. Because the sparsity of the wavefunction is a necessary but not sufficient condition for saturation of one of the GPCs, optimization of the sparse wavefunction Ansatz to minimize the ground-state energy does not necessarily produce a wavefunction whose 1-RDM exactly saturates one of the GPCs. While the sparse Ansatz can be employed with arbitrary orbitals or optimized orbitals, in this paper, we explore the Ansatz with the natural orbitals from full configuration interaction, which yields an upper bound to the ground-state energy that equals the exact energy for a given basis set if the full-configuration-interaction wavefunction saturates the Ansatz's GPC. With calculations on the boron isoelectronic sequence, the dinitrogen cation N2+, hydrogen chains, and cyclic conjugated π systems, we examine the quality of the sparse wavefunction Ansatz from the amount of correlation energy recovered.

DFT Studies on AlSe Nano Clusters

The present study of AlnSen clusters for (n =1 to 3) is based upon density functional theory (DFT). The ground state structures are obtained with preferred lower spin multiplicities. The various electronic parameters such as HOMO-LUMO gap or band gap, Ionization potential (IP), electron affinity (EA), chemical hardness (η) and absolute electronegativitty (χ) and minimum frequency are also calculated and discussed in the present study.

FR0CAT: a FIRST catalog of FR 0 radio galaxies

With the aim of exploring the properties of the class of FR 0 radio galaxies, we selected a sample of 108 compact radio sources, called FR0CAT, by combining observations from the NVSS, FIRST, and SDSS surveys. We included in the catalog sources with redshift ≤0.05, with a radio size ≲5 kpc, and with an optical spectrum characteristic of low-excitation galaxies. Their radio luminosities at 1.4 GHz are in the range 1038 ≲ νL1.4 ≲ 1040 erg s-1. The FR0CAT hosts are mostly (86%) luminous (−21 ≳ Mr ≳ −23) red early-type galaxies with black hole masses 108 ≲ MBH ≲ 109M⊙. These properties are similar to those seen for the hosts of FR I radio galaxies, but they are on average a factor ~1.6 less massive. The number density of FR0CAT sources is ~5 times higher than that of FR Is, and thus they represent the dominant population of radio sources in the local Universe. Different scenarios are considered to account for the smaller sizes and larger abundance of FR 0s with respect to FR Is. An age-size scenario that considers FR 0s as young radio galaxies that will all eventually evolve into extended radio sources cannot be reconciled with the large space density of FR 0s. However, the radio activity recurrence, with the duration of the active phase covering a wide range of values and with short active periods strongly favored with respect to longer ones, might account for their large density number. Alternatively, the jet properties of FR 0s might be intrinsically different from those of the FR Is, the former class having lower bulk Lorentz factors, possibly due to lower black hole spins. Our study indicates that FR 0s and FR I/IIs can be interpreted as two extremes of a continuous population of radio sources that is characterized by a broad distribution of sizes and luminosities of their extended radio emission, but shares a single class of host galaxies.

Proposal of a Single Nano-Magnet Memory Device

We propose a non-volatile memory device using ferromagnetic (FM) contacts fabricated on a channel exhibiting spin-momentum locking observed in diverse materials with spin-orbit coupling like heavy metals and topological insulators. The writing is enabled by the current induced spin–orbit torque, which has been used previously to switch the storage layer of a magnetic tunnel junction (MTJ). The reading is enabled by a relatively lower current-induced spin voltage measurement through the FM contact, which is high or low depending on the magnetization direction for a particular current direction. This new read mechanism significantly reduces the fabrication difficulties compared with MTJ-based designs. Simpler interconnects and control circuits can be used, since both read and write currents share the same path. Our proposal offers on-cell reference voltage generation with a normal metal contacton the channel at thesame position as theFM, which is expected to improve the performance in a large array. The estimated read signal based on available materials is smaller compared with MTJ, but the noise is also expected to be smaller in our metallic device compared with those involving tunnel barriers.

Shape coexistence and shape transition in self-conjugate nucleus 72Kr and the tensor force

Oblate-prolate shape-coexistence is well-known in the N = Z nucleus 72Kr. Furthermore, recent experimental data implies that there is a rapid shape transition at very low spins in this nucleus. We reinvestigate this problem by using large-scale shell-model calculations with the monopole interactions derived from the monopole-based universal force that contains the tensor force in the Hamiltonian. We show that in 72Kr, states with nucleon-quartet excitation from the pf shell to the – orbits, which favor large prolate deformation, compete with those having the pf shell as the main configuration with oblate deformation. These shapes can coexist if the two types of states reside closely in excitation energy. In 72Kr the tensor force is found to provide precisely such a coexistence condition near the ground state. As the tensor effect changes dynamically with orbital occupation when the nucleus rotates, a rapid shape transition can occur.

Quantifying the impact of mergers on the angular momentum of simulated galaxies

AbstractWe use eagle to quantify the effect galaxy mergers have on the stellar specific angular momentum of galaxies, jstars. We split mergers into dry (gas-poor)/wet (gas-rich), major/minor and different spin alignments and orbital parameters. Wet (dry) mergers have an average neutral gas-to-stellar mass ratio of 1.1 (0.02), while major (minor) mergers are those with stellar mass ratios ≥0.3 (0.1–0.3). We correlate the positions of galaxies in the jstars–stellar mass plane at z = 0 with their merger history, and find that galaxies of low spins suffered dry mergers, while galaxies of normal/high spins suffered predominantly wet mergers, if any. The radial jstars profiles of galaxies that went through dry mergers are deficient by ≈0.3 dex at r ≲ 10 r50 (with r50 being the half-stellar mass radius), compared to galaxies that went through wet mergers. Studying the merger remnants reveals that dry mergers reduce jstars by ≈30 per cent, while wet mergers increase it by ≈10 per cent, on average. The latter is connected to the build-up of the bulge by newly formed stars of high rotational speed. Moving from minor to major mergers accentuates these effects. When the spin vectors of the galaxies prior to the dry merger are misaligned, jstars decreases by a greater magnitude, while in wet mergers corotation and high orbital angular momentum efficiently spun-up galaxies. We predict what would be the observational signatures in the jstars profiles driven by dry mergers: (i) shallow radial profiles and (ii) profiles that rise beyond ≈10 r50, both of which are significantly different from spiral galaxies.

Large deflection model for nonlinear flexural vibration analysis of a highly flexible rotor-bearing system

Investigation of critical speeds and nonlinear free vibration analysis of a highly flexible rotor system have been studied. The rotary inertia and gyroscopic effect combined with inextensible geometric condition for pinned-guided shaft element have been taken into account to develop the governing equation of motion. The closed-form mathematical expressions have been derived for determining both linear and nonlinear natural frequencies and their behavioral patterns have been simultaneously demonstrated through time histories, FFTs and Poincare’s maps upon changing the control parameters. The nonlinear natural frequencies have been found to be higher by about 4–6% as compared to the findings obtained via linear analysis. For lower spin speed of the shaft, both linear and nonlinear forward natural frequencies have been found to be dominant. The influence of rotary inertia on natural frequencies by considering Euler and Rayleigh beam elements, separately has been reported. The system response has been observed to be either periodic or quasi-periodic depending on the spin speed. Outcomes which were not explored earlier enable significant theoretical understanding of free vibration analysis and whirling speeds of rotating system which are of great practical importance for investigating further dynamic performance.

Isobar model for kaon photoproduction with spin- 7/2 and - 9/2 nucleon resonances

We have investigated the effects of spin-7/2 and -9/2 nucleon resonances in the kaon photoproduction process γp→K+Λ. To this end, the corresponding propagators were derived from the generalized spin projection operators. To remove the lower spin backgrounds in the scattering amplitude, we used the vertex factors obtained from the consistent interaction Lagrangians inspired by Pascalutsa and Vrancx et al. The scattering amplitude was included in our previous isobar model, and the effects of four nucleon resonances with spins 7/2 and 9/2 listed by the Particle Data Group were investigated by making use of all available kaon photoproduction data. A significant improvement to our previous model has been observed in all observables, especially in the beam-recoil double-polarization observables Cx, Cz, Ox′, and Oz′.

Nuclear Data Sheets for A=193

Evaluated spectroscopic data and level schemes from radioactive decay and nuclear reaction studies are presented for 193Ta, 193W, 193Re, 193Os, 193Ir, 193Pt, 193Au, 193Hg, 193Tl, 193Pb, 193Bi, 193Po, 193At, and 193Rn. This evaluation for A=193 supersedes the earlier one by E. Achterberg, et. al. (2006Ac01).Highlights of this evaluation are the following:Based on γγ-coincidence measurements by 2005Za15, excited levels 848.93 and 849.083 in 193Ir have been merged.Proposed new spin-parity assignments for 2213.8+x(Jπ=23/2+), 2426.7+x(Jπ=25/2+), and 2584.8+x(Jπ=27/2+) by 2011Ba02 (28Si,5nγ) indicate 1ħ lower spin assignments for many of the excited levels in the 193Pb Adopted Levels including the Magnetic dipole band 1 based on 2584.8+x level.2015He27 identified many new structures in 193Bi close to the yrast line. Many new states have been added, significantly extending the previously known level scheme of 193Bi, including several new rotational bands.