Dynamics of Vortex Core Switching in Ferromagnetic Nanodisks

Dynamics of magnetic vortex core switching in nanometer-scale permalloy disk, having a single vortex ground state, was investigated by micromagnetic modeling. When an in-plane magnetic field pulse with an appropriate strength and duration is applied to the vortex structure, additional two vortices, i.e., a circular- and an anti-vortex, are created near the original vortex core. Sequentially, the vortex-antivortex pair annihilates. A spin wave is created at the annihilation point and propagated through the entire element; the relaxed state for the system is the single vortex state with a switched vortex core.Comment: to appear in Appl. Phys. Let

The measurement of lubricant-film thickness using ultrasound

Ultrasound is reflected from a liquid layer between two solid bodies. This reflection depends on the ultrasonic frequency, the acoustic properties of the liquid and solid, and the layer thickness. If the wavelength is much greater than the liquid-layer thickness, then the response is governed by the stiffness of the layer. If the wavelength and layer thickness are similar, then the interaction of ultrasound with the layer is controlled by its resonant behaviour. This stiffness governed response and resonant response can be used to determine the thickness of the liquid layer, if the other parameters are known. In this paper, ultrasound has been developed as a method to determine the thickness of lubricating films in bearing systems. An ultrasonic transducer is positioned on the outside of a bearing shell such that the wave is focused on the lubricant-film layer. The transducer is used to both emit and receive wide-band ultrasonic pulses. For a particular lubricant film, the reflected pulse is processed to give a reflection-coefficient spectrum. The lubricant-film thickness is then obtained from either the layer stiffness or the resonant frequency. The method has been validated using fluid wedges at ambient pressure between flat and curved surfaces. Experiments on the elastohydrodynamic film formed between a sliding ball and a flat surface were performed. Film-thickness values in the range 50-500 nm were recorded, which agreed well with theoretical film-formation predictions. Similar measurements have been made on the oil film between the balls and outer raceway of a deep-groove ball bearing

Controls on the width of tropical precipitation and its contraction under global warming

AD and ARA were funded by the National Science Foundation Paleo Perspective on Climate Change (P2C2) Grant number AGS-1702827.Climate models robustly and unanimously simulate narrowing of the intense tropical precipitation under greenhouse gas forcing. We argue that the meridional width of tropical precipitation is controlled by the seasonal meridional range of the intertropical convergence zone (ITCZ). The contraction of tropical precipitation under greenhouse forcing results from a reduced seasonal range of ITCZ migration. An energetic theory -- similar to the energetic theory for ITCZ shifts based on the hemispheric contrast of energy input to the atmosphere-- is developed. The meridional width of tropical precipitation is proportional to the seasonal range of the inter-hemispheric contrast in atmospheric heating divided by the efficiency of atmospheric cross-equatorial heat transport. Climate models are biased toward overly expansive tropical precipitation resulting from an exaggerated seasonal atmospheric heating. The robust contraction of tropical precipitation under global warming results from increased efficiency of inter-hemispheric energy transport consistent with enhanced gross moist stability of the tropical atmosphere.Publisher PDFPeer reviewe

Pressure Tuning of the Charge Density Wave in the Halogen-Bridged Transition-Metal (MX) Solid Pt2Br6(NH3)4Pt_2Br_6(NH_3)_4

We report the pressure dependence up to 95 kbar of Raman active stretching modes in the quasi-one-dimensional MX chain solid $Pt_2Br_6(NH_3)_4$. The data indicate that a predicted pressure-induced insulator-to-metal transition does not occur, but are consistent with the solid undergoing either a three-dimensional structural distortion, or a transition from a charge-density wave to another broken-symmetry ground state. We show that such a transition cacan be well-modeled within a Peierls-Hubbard Hamiltonian. 1993 PACS: 71.30.+h, 71.45.Lr, 75.30.Fv, 78.30.-j, 81.40.VwComment: 4 pages, ReVTeX 3.0, figures available from the authors on request (Gary Kanner, [email protected]), to be published in Phys Rev B Rapid Commun, REVISION: minor typos corrected, LA-UR-94-246

Multimode simulations of a wide field of view double-Fourier far-infrared spatio-spectral interferometer

In the absence of 50-m class space-based observatories, subarcsecond astronomy spanning the full far-infrared wavelength range will require space-based long-baseline interferometry. The long baselines of up to tens of meters are necessary to achieve subarcsecond resolution demanded by science goals. Also, practical observing times command a field of view toward an arcminute (1′) or so, not achievable with a single on-axis coherent detector. This paper is concerned with an application of an end-to-end instrument simulator PyFIInS, developed as part of the FISICA project under funding from the European Commission’s seventh Framework Programme for Research and Technological Development (FP7). Predicted results of wide field of view spatio–spectral interferometry through simulations of a long-baseline, double-Fourier, far-infrared interferometer concept are presented and analyzed. It is shown how such an interferometer, illuminated by a multimode detector can recover a large field of view at subarcsecond angular resolution, resulting in similar image quality as that achieved by illuminating the system with an array of coherent detectors. Through careful analysis, the importance of accounting for the correct number of higher-order optical modes is demonstrated, as well as accounting for both orthogonal polarizations. Given that it is very difficult to manufacture waveguide and feed structures at sub-mm wavelengths, the larger multimode design is recommended over the array of smaller single mode detectors. A brief note is provided in the conclusion of this paper addressing a more elegant solution to modeling far-infrared interferometers, which holds promise for improving the computational efficiency of the simulations presented here

Surgical management of ambiguous genitalia in the infant and child

Proper gender assignment to a neonate born with ambiguous genitalia is a social emergency of the newborn period. Once an appropriate sex assignment has been made, the next critical step is performance, if needed, of a reconstructive procedure in a timely fashion. In an attempt to evaluate our experience with this unique group of patients, we have retrospectively reviewed the course of 69 children with ambiguous genitalia managed surgically at this institution between 1974 and 1989. This series consists of 32 genotypic females with congenital adrenal hyperplasia (CAH), 10 children with mixed gonadal dysgenesis (MGD), 10 male pseudohermaphrodites, 3 true hermaphrodites, 8 genotypic females with urogenital sinus anomalies (UGS), and 6 genotypic males with bilateral undescended testes and penoscrotal hypospadius. All newborns initially seen at this institution received proper sex assignment within the first week of life. Prior to 1980, 17 of the children with CAH underwent clitorectomy and vaginoplasty and three underwent clitoral recession and vaginoplasty. After 1980, 10 patients with CAH were managed with clitoral recession and vaginoplasty and 2 with vaginoplasty alone. Eight of 10 cases of MGD were given a female sex assignment and all 8 underwent gonadectomy due to the high risk of gonadoblastoma; the other 2 children were raised as males. There were 3 true hermaphrodites of which 2 were assigned female gender roles and were managed with a clitoral recession and vaginoplasty. All 10 male pseudohermaphrodites were raised as females and all underwent bilateral orchidectomy. The 8 children with UGS were raised as females and underwent vaginal reconstruction. Six genotypic males with penoscrotal hypospadius and bilateral undescended testes were raised as males and underwent hypospadius repair and bilateral orchidopexy. This retrospective review underscores the complexities of assessment and management of ambiguous genitalia in infants and children. It also reconfirms the data from other series showing that the vast majority of infants born with the four most common forms of ambiguous genitalia (CAH, MGD, male pseudoher-maphroditism, and true hermaphroditism) must be raised as females because of inadequacy of the phallus.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29268/1/0000327.pd

Digital circuits using universal logic gates

According to the invention, a digital circuit design embodied in at least one of a structural netlist, a behavioral netlist, a hardware description language netlist, a full-custom ASIC, a semi-custom ASIC, an IP core, an integrated circuit, a hybrid of chips, one or more masks, a FPGA, and a circuit card assembly is disclosed. The digital circuit design includes first and second sub-circuits. The first sub-circuits comprise a first percentage of the digital circuit design and the second sub-circuits comprise a second percentage of the digital circuit design. Each of the second sub-circuits is substantially comprised of one or more kernel circuits. The kernel circuits are comprised of selection circuits. The second percentage is at least 5%. In various embodiments, the second percentage could be at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 95%