42,435 research outputs found
Modified algesimeter provides accurate depth measurements
Algesimeter which incorporates a standard sensory needle with a sensitive micrometer, measures needle point depth penetration in pain tolerance research. This algesimeter provides an inexpensive, precise instrument with assured validity of recordings in those biomedical areas with a requirement for repeated pain detection or ascertaining pain sensitivity
The development of the sporozoite of Plasmodium gallinaceum (Apicomplexa Haemosporina)
Imperial Users onl
Alessi 95 and the short period Cepheid SU Cassiopeiae
The parameters for the newly-discovered open cluster Alessi 95 are
established on the basis of available photometric and spectroscopic data, in
conjunction with new observations. Colour excesses for
spectroscopically-observed B and A-type stars near SU Cas follow a reddening
relation described by E(U-B)/E(B-V)=0.83+0.02*E(B-V), implying a value of
R=Av/E(B-V)~2.8 for the associated dust. Alessi 95 has a mean reddening of
E(B-V)_(B0)=0.35+-0.02 s.e., an intrinsic distance modulus of Vo-Mv=8.16+-0.04
s.e. (+-0.21 s.d.), d=429+-8 pc, and an estimated age of 10^8.2 yr from ZAMS
fitting of available UBV, CCD BV, NOMAD, and 2MASS JHKs observations of cluster
stars. SU Cas is a likely cluster member, with an inferred space reddening of
E(B-V)=0.33+-0.02 and a luminosity of =-3.15+-0.07 s.e., consistent with
overtone pulsation (P_FM=2.75 d), as also implied by the Cepheid's light curve
parameters, rate of period increase, and Hipparcos parallaxes for cluster
stars. There is excellent agreement of the distance estimates for SU Cas
inferred from cluster ZAMS fitting, its pulsation parallax derived from the
infrared surface brightness technique, and Hipparcos parallaxes, which all
agree to within a few percent.Comment: Accepted for Publication (MNRAS
Continuously observing a dynamically decoupled spin-1 quantum gas
We continuously observe dynamical decoupling in a spin-1 quantum gas using a
weak optical measurement of spin precession. Continuous dynamical decoupling
aims to dramatically modify the character and energy spectrum of spin states to
render them insensitive to parasitic fluctuations. Continuous observation
measures this new spectrum in a single-preparation of the quantum gas. The
measured time-series contains seven tones, which spectrogram analysis parses as
splittings, coherences, and coupling strengths between the decoupled states in
real-time. With this we locate a regime where a transition between two states
is decoupled from magnetic field instabilities up to fourth order,
complementary to the parallel work at higher fields by Trypogeorgos et al.
(arXiv:1706.07876). The decoupled microscale quantum gas offers magnetic
sensitivity in a tunable band, persistent over many milliseconds: the length
scales, frequencies, and durations relevant to many applications, including
sensing biomagnetic phenomena such as neural spike trains.Comment: 5+ pages, 4 figures, 1 table; revised citation of Trypogeorgos et al.
(2017
Suspending test masses in terrestrial millihertz gravitational-wave detectors: a case study with a magnetic assisted torsion pendulum
Current terrestrial gravitational-wave detectors operate at frequencies above
10 Hz. There is strong astrophysical motivation to construct low-frequency
gravitational-wave detectors capable of observing 10 mHz - 10Hz signals. While
space-based detectors provide one means of achieving this end, one may also
consider terretrial detectors. However, there are numerous technological
challenges. In particular, it is difficult to isolate test masses so that they
are both seismically isolated and freely falling under the influence of gravity
at millihertz frequencies. We investigate the challenges of low-frequency
suspension in a hypothetical terrestrial detector. As a case study, we consider
a Magnetically Assisted Gravitational-wave Pendulum Intorsion (MAGPI)
suspension design. We construct a noise budget to estimate some of the required
specifications. In doing so, we identify what are likely to be a number of
generic limiting noise sources for terrestrial millihertz gravitational-wave
suspension systems (as well as some peculiar to the MAGPI design). We highlight
significant experimental challenges in order to argue that the development of
millihertz suspensions will be a daunting task. Any system that relies on
magnets faces even greater challenges. Entirely mechanical designs such as
Zollner pendulums may provide the best path forward.Comment: 6 pages, 4 figure
Scalar Field as Dark Matter in the Universe
We investigate the hypothesis that the scalar field is the dark matter and
the dark energy in the Cosmos, wich comprises about 95% of the matter of the
Universe. We show that this hypothesis explains quite well the recent
observations on type Ia supernovae.Comment: 4 pages REVTeX, 1 eps figure. Minor changes. To appear in Classical
and Quantum Gravit
An order (n) algorithm for the dynamics simulation of robotic systems
The formulation of an Order (n) algorithm for DISCOS (Dynamics Interaction Simulation of Controls and Structures), which is an industry-standard software package for simulation and analysis of flexible multibody systems is presented. For systems involving many bodies, the new Order (n) version of DISCOS is much faster than the current version. Results of the experimental validation of the dynamics software are also presented. The experiment is carried out on a seven-joint robot arm at NASA's Goddard Space Flight Center. The algorithm used in the current version of DISCOS requires the inverse of a matrix whose dimension is equal to the number of constraints in the system. Generally, the number of constraints in a system is roughly proportional to the number of bodies in the system, and matrix inversion requires O(p exp 3) operations, where p is the dimension of the matrix. The current version of DISCOS is therefore considered an Order (n exp 3) algorithm. In contrast, the Order (n) algorithm requires inversion of matrices which are small, and the number of matrices to be inverted increases only linearly with the number of bodies. The newly-developed Order (n) DISCOS is currently capable of handling chain and tree topologies as well as multiple closed loops. Continuing development will extend the capability of the software to deal with typical robotics applications such as put-and-place, multi-arm hand-off and surface sliding
Light forces in ultracold photoassociation
We study the time-resolved photoassociation of ultracold sodium in an optical
dipole trap. The photoassociation laser excites pairs of atoms to molecular
states of large total angular momentum at high intensities (above 20
kW/cm). Such transitions are generally suppressed at ultracold
temperatures by the centrifugal barriers for high partial waves. Time-resolved
ionization measurements reveal that the atoms are accelerated by the dipole
potential of the photoassociation beam. We change the collision energy by
varying the potential depth, and observe a strong variation of the
photoassociation rate. These results demonstrate the important role of light
forces in cw photoassociation at high intensities.Comment: 7 pages, 3 figure
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