644 research outputs found
A Dynamical System with Q-deformed Phase Space Represented in Ordinary Variable Spaces
Dynamical systems associated with a q-deformed two dimensional phase space
are studied as effective dynamical systems described by ordinary variables. In
quantum theory, the momentum operator in such a deformed phase space becomes a
difference operator instead of the differential operator. Then, using the path
integral representation for such a dynamical system, we derive an effective
short-time action, which contains interaction terms even for a free particle
with q-deformed phase space. Analysis is also made on the eigenvalue problem
for a particle with q-deformed phase space confined in a compact space. Under
some boundary conditions of the compact space, there arises fairly different
structures from case in the energy spectrum of the particle and in the
corresponding eigenspace .Comment: 17page, 2 figure
Perpendicularly Magnetized Ni / Pt (001) Epitaxial Superlattice
A perpendicularly magnetized ferromagnetic layer is an important building
block for recent/future highdensity spintronic memory applications. This paper
reports on the fabrication of perpendicularly magnetized Ni / Pt superlattices
and the characterization of their structures and magnetic properties. The
optimization of film growth conditions allowed us to grow epitaxial Ni / Pt
(001) superlattices on SrTiO (001) single crystal substrates. We
investigated their structural parameters and magnetic properties as a function
of the Ni layer thickness, and obtained a high uniaxial magnetic anisotropy
energy of 1.9 x 10 erg/cm for a [Ni (4.0 nm) / Pt (1.0 nm)]
superlattice. In order to elucidate the detailed mechanism on perpendicular
magnetic anisotropy for the Ni / Pt (001) superlattices, the experimental
results were compared with the first-principles calculations. It has been found
that the strain effect is a prime source of the emergence of perpendicular
magnetic anisotropy.Comment: 33 pages, 12 figure
Simulated and experimental results of dual resolution sensor based planning for hyper-redundant manipulators
This paper presents a dual-resolution local sensor based planning method for hyper-redundant robot mechanisms. Two classes of sensor feedback control methods, working at different sampling rates and different spatial resolutions, are considered: full shape modification (FSM), and partial shape modification (PSM). FSM and PSM cooperate to utilize a mechanism's hyper-redundancy to enable both local obstacle avoidance and end-effector placement in real-time. These methods have been implemented on a thirty degree of freedom hyper-redundant manipulator which has 11 ultrasonic distance measurement sensors and 20 infrared proximity sensors. The implementation of these algorithms in a dual CPU real-time control computer, an innovative sensor bus architecture, and a novel graphical control interface are described. Experimental results obtained using this test bed show the efficacy of the proposed method
Subaru FOCAS Spectroscopic Observations of High-Redshift Supernovae
We present spectra of high-redshift supernovae (SNe) that were taken with the
Subaru low resolution optical spectrograph, FOCAS. These SNe were found in SN
surveys with Suprime-Cam on Subaru, the CFH12k camera on the
Canada-France-Hawaii Telescope (CFHT), and the Advanced Camera for Surveys
(ACS) on the Hubble Space Telescope (HST). These SN surveys specifically
targeted z>1 Type Ia supernovae (SNe Ia). From the spectra of 39 candidates, we
obtain redshifts for 32 candidates and spectroscopically identify 7 active
candidates as probable SNe Ia, including one at z=1.35, which is the most
distant SN Ia to be spectroscopically confirmed with a ground-based telescope.
An additional 4 candidates are identified as likely SNe Ia from the
spectrophotometric properties of their host galaxies. Seven candidates are not
SNe Ia, either being SNe of another type or active galactic nuclei. When SNe Ia
are observed within a week of maximum light, we find that we can
spectroscopically identify most of them up to z=1.1. Beyond this redshift, very
few candidates were spectroscopically identified as SNe Ia. The current
generation of super red-sensitive, fringe-free CCDs will push this redshift
limit higher.Comment: 19 pages, 26 figures. PASJ in press. see
http://www.supernova.lbl.gov/2009ClusterSurvey/ for additional information
pertaining to the HST Cluster SN Surve
Interesting magnetic properties of FeCoSi alloys
Solid solution between nonmagnetic narrow gap semiconductor FeSi and
diamagnetic semi-metal CoSi gives rise to interesting metallic alloys with
long-range helical magnetic ordering, for a wide range of intermediate
concentration. We report various interesting magnetic properties of these
alloys, including low temperature re-entrant spin-glass like behaviour and a
novel inverted magnetic hysteresis loop. Role of Dzyaloshinski-Moriya
interaction in the magnetic response of these non-centrosymmetric alloys is
discussed.Comment: 11 pages and 3 figure
A reversible lesion of the corpus callosum splenium with adult influenza-associated encephalitis/encephalopathy: a case report
<p>ABstract</p> <p>Introduction</p> <p>Influenza virus-associated encephalitis/encephalopathy is a severe childhood illness with a poor prognosis. Adult case reports are rare and, to date, there have been no reports of adults with a mild subcortical encephalopathy with reversible lesions of the corpus callosum splenium.</p> <p>Case presentation</p> <p>A previously healthy 35-year-old man presented with acute progressive tetraplegia, transcortical motor aphasia and a mild decrease in his consciousness during his recovery after receiving oseltamivir phosphate treatment, and influenza type A antiviral medication. The initial magnetic resonance imaging study at day 1 showed symmetrical diffuse lesions in the white matter and a lesion on the central portion of the corpus callosum splenium. These findings had resolved on follow-up studies at day 8 and day 146. His neurological deficits mostly recovered within 12 hours following methylprednisolone pulse therapy. The levels of interleukin-6 and interleukin-10 in his blood and cerebrospinal fluid were initially elevated, but rapidly decreased to normal levels by day 8.</p> <p>Conclusion</p> <p>It is important for clinicians to recognize that even in adulthood, the subcortical encephalopathy observed during the therapeutic treatment for influenza type A infection can occur in conjunction with a reversible lesion of the corpus callosum, which may recover quickly. In addition, the cytokine storm in the blood system and the corticospinal cavity may play an important role in the etiology of the disease process.</p
The Hubble Space Telescope Cluster Supernova Survey: VI. The Volumetric Type Ia Supernova Rate
We present a measurement of the volumetric Type Ia supernova (SN Ia) rate out
to z ~ 1.6 from the Hubble Space Telescope Cluster Supernova Survey. In
observations spanning 189 orbits with the Advanced Camera for Surveys we
discovered 29 SNe, of which approximately 20 are SNe Ia. Twelve of these SNe Ia
are located in the foregrounds and backgrounds of the clusters targeted in the
survey. Using these new data, we derive the volumetric SN Ia rate in four broad
redshift bins, finding results consistent with previous measurements at z > 1
and strengthening the case for a SN Ia rate that is equal to or greater than
~0.6 x 10^-4/yr/Mpc^3 at z ~ 1 and flattening out at higher redshift. We
provide SN candidates and efficiency calculations in a form that makes it easy
to rebin and combine these results with other measurements for increased
statistics. Finally, we compare the assumptions about host-galaxy dust
extinction used in different high-redshift rate measurements, finding that
different assumptions may induce significant systematic differences between
measurements.Comment: 11 pages, 7 figures. Submitted to the Astrophysical Journal. Revised
version following referee comments. See the HST Cluster SN Survey website at
http://supernova.lbl.gov/2009ClusterSurvey for control time simulations in a
machine-readable table and a complete listing of transient candidates from
the surve
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