693 research outputs found
A versatile high resolution objective for imaging quantum gases
We present a high resolution objective lens made entirely from catalog
singlets that has a numerical aperture of 0.36. It corrects for aberrations
introduced by a glass window and has a long working distance of 35mm, making it
suitable for imaging objects within a vacuum system. This offers simple high
resolution imaging for many in the quantum gas community. The objective
achieves a resolution of 1.3{\mu}m at the design wavelength of 780nm, and a
diffraction-limited field of view of 360{\mu}m when imaging through a 5mm
window. Images of a resolution target and a pinhole show quantitative agreement
with the simulated lens performance. The objective is suitable for
diffraction-limited imaging on the D2 line of all the alkalis by changing only
the aperture diameter, retaining numerical apertures above 0.32. The design
corrects for window thicknesses of up to 15mm if the singlet spacings are
modified
Origin Destination Analysis on the London Orbital Automated Number Plate Recognition Network
The UK Highways Agency (HA) has a specific interest in understanding the actual journeys taken by drivers using the London orbital motorway (M25) in order to assist with planning and management of strategic routes. It is thought that the majority of traffic on Public Service Agreement (PSA) Routes, rather than travelling end to end is joining and leaving mid-route. We provide a tracking algorithm to detect journeys on the routes using data from the existing automated number plate recognition (ANPR) network. This network was designed for other purposes and in particular only covers subsets of lanes at sites, requiring inference of traffic behaviour in the non-covered lanes. Furthermore, its cameras translate plate numbers into nonunique hash values which give rise to many spurious matches. A full-lane calibration study was performed, and fused with induction-loop flow data to obtain parameters for such inferences
Experimental measurement of the isolated magnetic susceptibility
The isolated susceptibility may be defined as a
(non-thermodynamic) average over the canonical ensemble, but while it has often
been discussed in the literature, it has not been clearly measured. Here, we
demonstrate an unambiguous measurement of at avoided
nuclear-electronic level crossings in a dilute spin ice system, containing
well-separated holmium ions. We show that quantifies the
superposition of quasi-classical spin states at these points, and is a direct
measure of state concurrence and populations.Comment: 9 pages, & figure
A Radial Velocity Study of CTCV J1300-3052
We present time-resolved spectroscopy of the eclipsing, short period
cataclysmic variable CTCV J1300-3052. Using absorption features from the
secondary star, we determine the radial velocity semi-amplitude of the
secondary star to be K2 = 378 \pm 6 km/s, and its projected rotational velocity
to be v sin i = 125 \pm 7 km/s. Using these parameters and Monte Carlo
techniques, we obtain masses of M1 = 0.79 \pm 0.05 MSun for the white dwarf
primary and M2 = 0.198 \pm 0.029 MSun for the M-type secondary star. These
parameters are found to be in excellent agreement with previous mass
determinations found via photometric fitting techniques, supporting the
accuracy and validity of photometric mass determinations in short period CVs.Comment: Accepted for publication in MNRAS (24th January 2012). 10 pages, 9
figures (black and white
Why is it so hard to enact responsible change?: Scientists need to work more closely with other social groups to implement sustainable innovation
This is the final version. Available on open access from EMBO Press via the DOI in this record. Biotechnology and Biological Sciences Research Council (BBSRC)UK Research and Innovation | Engineering and Physical Sciences Research Council (EPSRC)Wellcome Trus
Timber gridshells: beyond the drawing board
In March 2011, a week-long workshop that invited participation from all architecture and architectural technology students at Sheffield Hallam University, UK was organised with the objective of enhancing students’ thinking and experience by construction thinking. It was aimed at creating a sense of realness to realise a design project collectively. Timber was set as the material of exploration. The students had to make use of bending to design and create a timber gridshell structure. This made use of a quality traditionally felt to be a structural weakness of the material. To do this, students form-found non-mathematically and non-digitally using paper gridmats. This paper describes the aims, activity and outcome of the timber gridshell workshop as a way of preparing architects and technologists of the future and introducing the challenges of architectural design in terms of economics and
construction process, aesthetics, effective communication and structural intuition by working with a given material –
all important aspects in achieving effective architecture
Evidence for Superhumps in the Radio Light Curve of Algol and a New Model for Magnetic Activity in Algol Systems
Extensive radio data of two Algol systems and two RS CVn binaries were
re-analyzed. We found evidence for a new periodicity that we interpret as a
superhump in Algol, in which it may have been expected according to its
semi-detached nature and low binary mass ratio. This is the first detection of
the superhump phenomenon in the radio and the first observation of superhumps
in Algol systems. According to our result, the accretion disk in Algol
precesses in spite of its non-Keplerian nature and therefore this phenomenon is
not restricted to the classical Keplerian disks in compact binaries.We propose
that in Algol systems with short orbital periods, the disk is magnetically
active as well as the secondary star. The magnetic field in the disk originates
from amplification of the seed field in the magnetized material transferred
from the secondary. The disk and stellar fields interact with each other, with
reconnection of the field lines causing flares and particle acceleration.
Relativistic particles are trapped in the field and directed toward the polar
regions of the secondary star because of the dipole structure of its magnetic
field. Our proposed model for the magnetic activity in Algol systems provides a
simple explanation to the observed properties of Algol in the radio
wavelengths, and to the presence of quiescent gyrosynchrotron emission near the
polar region of the secondary star, where electrons are difficult to be
confined if the field lines are open as in normal single magnetic stars. We
propose that the superhump variation in the radio is generated by enhanced
reconnection when the elongated side of the elliptic disk is the closest to the
cool star. This leads to flares and enhancement in particle acceleration and is
manifested as stronger gyrosynchrotron radiation.Comment: 8 pages, 5 figures, ApJ, accepted, uses apjfonts.sty and
emulateapj5.sty, full abstract in pape
Infrared Properties of Cataclysmic Variables from 2MASS: Results from the 2nd Incremental Data Release
Because accretion-generated luminosity dominates the radiated energy of most
cataclysmic variables, they have been ``traditionally'' observed primarily at
short wavelengths. Infrared observations of cataclysmic variables contribute to
the understanding of key system components that are expected to radiate at
these wavelengths, such as the cool outer disk, accretion stream, and secondary
star. We have compiled the J, H, and Ks photometry of all cataclysmic variables
located in the sky coverage of the 2 Micron All Sky Survey (2MASS) 2nd
Incremental Data Release. This data comprises 251 systems with reliably
identified near-IR counterparts and S/N > 10 photometry in one or more of the
three near-IR bands.Comment: 2 pages, including 1 figure. To appear in the proceedings of The
Physics of Cataclysmic Variables and Related Objects, Goettingen, Germany.
For our followup ApJ paper (in press), also see
http://www.ctio.noao.edu/~hoard/research/2mass/index.htm
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