271 research outputs found
Impact and Casualty Prediction for Malfunctioning Multi-Stage Vehicles
Presented is a rather general explanation of an automated method for determining, by Monte Carlo techniques, the probabilities of impacting populated land masses and causing a casualty when a malfunctioning multi-stage vehicle deviates from its normal instantaneous earth impact pattern. The generation of this data is explained through the use of illustrative material which describes the necessary flow of information and computational operations. The economic advantages of the method discussed are compared, in terms of manpower, computer time, and total elapsed time requirements,with those of a forerunning method used to generate such data
Defects in Chiral Columnar Phases: Tilt Grain Boundaries and Iterated Moire Maps
Biomolecules are often very long with a definite chirality. DNA, xanthan and
poly-gamma-benzyl-glutamate (PBLG) can all form columnar crystalline phases.
The chirality, however, competes with the tendency for crystalline order. For
chiral polymers, there are two sorts of chirality: the first describes the
usual cholesteric-like twist of the local director around a pitch axis, while
the second favors the rotation of the local bond-orientational order and leads
to a braiding of the polymers along an average direction. In the former case
chirality can be manifested in a tilt grain boundary phase (TGB) analogous to
the Renn-Lubensky phase of smectic-A liquid crystals. In the latter case we are
led to a new "moire" state with twisted bond order. In the moire state polymers
are simultaneously entangled, crystalline, and aligned, on average, in a common
direction. In the moire state polymers are simultaneously entangled,
crystalline, and aligned, on average, in a common direction. In this case the
polymer trajectories in the plane perpendicular to their average direction are
described by iterated moire maps of remarkable complexity, reminiscent of
dynamical systems.Comment: plain TeX, (33 pages), 17 figures, some uufiled and included, the
remaining available at ftp://ftp.sns.ias.edu/pub/kamien/ or by request to
[email protected]
Buckling Instabilities of a Confined Colloid Crystal Layer
A model predicting the structure of repulsive, spherically symmetric,
monodisperse particles confined between two walls is presented. We study the
buckling transition of a single flat layer as the double layer state develops.
Experimental realizations of this model are suspensions of stabilized colloidal
particles squeezed between glass plates. By expanding the thermodynamic
potential about a flat state of confined colloidal particles, we derive
a free energy as a functional of in-plane and out-of-plane displacements. The
wavevectors of these first buckling instabilities correspond to three different
ordered structures. Landau theory predicts that the symmetry of these phases
allows for second order phase transitions. This possibility exists even in the
presence of gravity or plate asymmetry. These transitions lead to critical
behavior and phases with the symmetry of the three-state and four-state Potts
models, the X-Y model with 6-fold anisotropy, and the Heisenberg model with
cubic interactions. Experimental detection of these structures is discussed.Comment: 24 pages, 8 figures on request. EF508
Mutual shaping in the design of socially assistive robots: A case study on social robots for therapy
This paper offers a case study in undertaking a mutual shaping approach to the design of socially assistive robots. We consider the use of social robots in therapy, and we present our results regarding this application, but the approach is generalisable. Our methodology combines elements of user-centered and participatory design with a focus on mutual learning. We present it in full alongside a more general guide for application to other areas. This approach led to valuable results concerning mutual shaping effects and societal factors regarding the use of such robots early in the design process. We also measured a significant shift in participant robot acceptance pre-/post-study, demonstrating that our approach led to the two-way sharing and shaping of knowledge, ideas and acceptance
Measuring Cosmic Defect Correlations in Liquid Crystals
From the theory of topological defect formation proposed for the early
universe, the so called Kibble mechanism, it follows that the density
correlation functions of defects and anti-defects in a given system should be
completely determined in terms of a single length scale , the relevant
domain size. Thus, when lengths are expressed in units of , these
distributions should show universal behavior, depending only on the symmetry of
the order parameter, and space dimensions. We have verified this prediction by
analyzing the distributions of defects/anti-defects formed in the
isotropic-nematic phase transition in a thin layer of nematic liquid crystals.
Our experimental results confirm this prediction and are in reasonable
agreement with the results of numerical simulations.Comment: 15 pages, 4 figures, minor changes, few new references adde
Accessing HE for non-traditional students: 'Outside of my position'
Widening participation within higher education and increasing social mobility have been high on the agendas of former and current governments. This paper examines the admissions procedure of a Foundation degree in Early Years programme using Bourdieu's concept of capital as a vehicle for analysis. During the process of an admissions interview, the interviewer is required to make decisions regarding a student's suitability to fit into the existing field of the programme as they often feel it is outside of their position. The stories of three non-traditional students are explored to highlight existing capital and dispositions that they bring to the programme. Research findings showed that there are many variables that impact on a student's ability to gain entry and be successful on an HE programme, including accumulation of capital, emotional drivers and potential to acquire capital throughout the programme. © 2014 Further Education Research Association
Tracking Rotational Diffusion of Colloidal Clusters
We describe a novel method of tracking the rotational motion of clusters of
colloidal particles. Our method utilizes rigid body transfor- mations to
determine the rotations of a cluster and extends conventional proven particle
tracking techniques in a simple way, thus facilitating the study of rotational
dynamics in systems containing or composed of colloidal clusters. We test our
method by measuring dynamical properties of simulated Brownian clusters under
conditions relevant to microscopy experiments. We then use the technique to
track and describe the motions of a real colloidal cluster imaged with confocal
microscopy.Comment: 14 pages, 6 figures. Submitted to Optics Expres
A comparison of alternative assays to measure DNA damage in stallion spermatozoa: TUNEL test versus ‘Nicoletti assay’
The aberrations of sperm DNA may cause various problems and have negative consequences on fertility. These influence embryonic development or might lead to early embryo loss. Sperm Chromatin Structure Assay (SCSA) is the flow cytometric method most often used for the detection of DNA lesions; however, some studies using that method reached confusing conclusions. The aim of this pilot study was to adjust and compare two alternative tests, namely the TUNEL test and the Nicoletti assay. The above-mentioned two flow cytometric methods capable of detecting the fragmented DNA of sperm were tested on 12 frozen-thawed stallion semen samples. The TUNEL test demonstrated much higher DNA fragmentation ratio than the Nicoletti assay (mean ± SD: 30.77 ± 13.03% vs. 1.93 ± 0.89%, respectively). A fluorescent microscopic check of the samples showed that TUNEL labelled the plasma membrane and the mitochondria in a nonspecific way, rather than detecting only the fragmented DNA, thus eventually resulting in a false positive sign. The Nicoletti assay is simpler, quicker and does not detect nonspecific binding; however, further analyses are required to determine its diagnostic value
Microwave multiplexing on the Keck Array
We describe an on-sky demonstration of a microwave-multiplexing readout
system in one of the receivers of the Keck Array, a polarimetry experiment
observing the cosmic microwave background at the South Pole. During the austral
summer of 2018-2019, we replaced the time-division multiplexing readout system
with microwave-multiplexing components including superconducting microwave
resonators coupled to radio-frequency superconducting quantum interference
devices at the sub-Kelvin focal plane, coaxial-cable plumbing and amplification
between room temperature and the cold stages, and a SLAC Microresonator Radio
Frequency system for the warm electronics. In the range 5-6 GHz, a single
coaxial cable reads out 528 channels. The readout system is coupled to
transition-edge sensors, which are in turn coupled to 150-GHz slot-dipole
phased-array antennas. Observations began in April 2019, and we report here on
an initial characterization of the system performance.Comment: 9 pages, 11 figures, Accepted by the Journal of Low Temperature
Physics (Proceedings of the 18th International Workshop on Low Temperature
Detectors
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