3,667 research outputs found
Introduction of CAA into a mathematics course for technology students to address a change in curriculum requirements
The mathematical requirements for engineering, science and technology students has been debated for many years and concern has been expressed about the mathematical preparedness of students entering higher education. This paper considers a mathematics course that has been specifically designed to address some of these issues for technology education students. It briefly chronicles the changes that have taken place over its lifetime and evaluates the introduction of Computer Assisted Assessment (CAA) into a course already being delivered using Computer Aided Learning (CAL).
Benefits of CAA can be categorised into four main areas.
1. Educational – achieved by setting short, topic related, assessments, each of which has to be passed, thereby increasing curriculum coverage.
2. Students – by allowing them to complete assessments at their own pace removing the stress of the final examination.
3. Financial – increased income to the institution, by broadening access to the course. Improved retention rate due to self-paced learning.
4. Time – staff no longer required to set and mark exams.
Most students preferred this method of assessment to traditional exams, because it increased confidence and reduced stress levels. Self-paced working, however, resulted in a minority of students not completing the tests by the deadline
Radio-frequency dressed lattices for ultracold alkali atoms
Ultracold atomic gases in periodic potentials are powerful platforms for exploring quantum physics in regimes dominated by many-body effects as well as for developing applications that benefit from quantum mechanical effects. Further advances face a range of challenges including the realization of potentials with lattice constants smaller than optical wavelengths as well as creating schemes for effective addressing and manipulation of single sites. In this paper we propose a dressed-based scheme for creating periodic potential landscapes for ultracold alkali atoms with the capability of overcoming such difficulties. The dressed approach has the advantage of operating in a low-frequency regime where decoherence and heating effects due to spontaneous emission do not take place. These results highlight the possibilities of atom-chip technology in the future development of quantum simulations and quantum technologies, and provide a realistic scheme for starting such an exploration
Exact Quantum Monte Carlo Process for the Statistics of Discrete Systems
We introduce an exact Monte Carlo approach to the statistics of discrete
quantum systems which does not rely on the standard fragmentation of the
imaginary time, or any small parameter. The method deals with discrete objects,
kinks, representing virtual transitions at different moments of time. The
global statistics of kinks is reproduced by explicit local procedures, the key
one being based on the exact solution for the biased two-level system.Comment: 4 pages, latex, no figures, English translation of the paper
Variational Density Matrix Method for Warm Condensed Matter and Application to Dense Hydrogen
A new variational principle for optimizing thermal density matrices is
introduced. As a first application, the variational many body density matrix is
written as a determinant of one body density matrices, which are approximated
by Gaussians with the mean, width and amplitude as variational parameters. The
method is illustrated for the particle in an external field problem, the
hydrogen molecule and dense hydrogen where the molecular, the dissociated and
the plasma regime are described. Structural and thermodynamic properties
(energy, equation of state and shock Hugoniot) are presented.Comment: 26 pages, 13 figures. submitted to Phys. Rev. E, October 199
The binary near-Earth asteroid (175706) 1996 FG3 - An observational constraint on its orbital evolution
Using our photometric observations taken between 1996 and 2013 and other
published data, we derived properties of the binary near-Earth asteroid
(175706) 1996 FG3 including new measurements constraining evolution of the
mutual orbit with potential consequences for the entire binary asteroid
population. We also refined previously determined values of parameters of both
components, making 1996 FG3 one of the most well understood binary asteroid
systems. We determined the orbital vector with a substantially greater accuracy
than before and we also placed constraints on a stability of the orbit.
Specifically, the ecliptic longitude and latitude of the orbital pole are
266{\deg} and -83{\deg}, respectively, with the mean radius of the uncertainty
area of 4{\deg}, and the orbital period is 16.1508 +/- 0.0002 h (all quoted
uncertainties correspond to 3sigma). We looked for a quadratic drift of the
mean anomaly of the satellite and obtained a value of 0.04 +/- 0.20 deg/yr^2,
i.e., consistent with zero. The drift is substantially lower than predicted by
the pure binary YORP (BYORP) theory of McMahon and Scheeres (McMahon, J.,
Scheeres, D. [2010]. Icarus 209, 494-509) and it is consistent with the theory
of an equilibrium between BYORP and tidal torques for synchronous binary
asteroids as proposed by Jacobson and Scheeres (Jacobson, S.A., Scheeres, D.
[2011]. ApJ Letters, 736, L19). Based on the assumption of equilibrium, we
derived a ratio of the quality factor and tidal Love number of Q/k = 2.4 x 10^5
uncertain by a factor of five. We also derived a product of the rigidity and
quality factor of mu Q = 1.3 x 10^7 Pa using the theory that assumes an elastic
response of the asteroid material to the tidal forces. This very low value
indicates that the primary of 1996 FG3 is a 'rubble pile', and it also calls
for a re-thinking of the tidal energy dissipation in close asteroid binary
systems.Comment: Many changes based on referees comment
Functional characterization of the water-soluble organic carbon of size-fractionated aerosol in the southern Mississippi Valley
The chemical content of water-soluble organic carbon (WSOC) as a function of
particle size was characterized in Little Rock, Arkansas in winter and spring
2013. The objectives of this study were to (i) compare the functional
characteristics of coarse, fine and ultrafine WSOC and (ii) reconcile the
sources of WSOC for periods when carbonaceous aerosol was the most abundant
particulate component. The WSOC accounted for 5% of particle mass for
particles with <i>d</i><sub>p</sub> > 0.96 μm and 10%
of particle mass for particles with
<i>d</i><sub>p</sub> < 0.96 μm. Non-exchangeable aliphatic
(H–C), unsaturated aliphatic (H–C–C=), oxygenated saturated aliphatic
(H–C–O), acetalic (O–CH–O) and aromatic (Ar–H) protons were determined
by proton nuclear magnetic resonance (<sup>1</sup>H-NMR). The total
non-exchangeable organic hydrogen concentrations varied from
4.1 ± 0.1 nmol m<sup>−3</sup> for particles with
1.5 < <i>d</i><sub>p</sub> < 3.0 μm to
73.9 ± 12.3 nmol m<sup>−3</sup> for particles with
<i>d</i><sub>p</sub> < 0.49 μm. The molar H / C ratios varied
from 0.48 ± 0.05 to 0.92 ± 0.09, which were comparable to those
observed for combustion-related organic aerosol. The R–H was the most
abundant group, representing about 45% of measured total
non-exchangeable organic hydrogen concentrations, followed by H–C–O
(27%) and H–C–C= (26%). Levoglucosan, amines, ammonium and
methanesulfonate were identified in NMR fingerprints of fine particles.
Sucrose, fructose, glucose, formate and acetate were associated with coarse
particles. These qualitative differences of <sup>1</sup>H-NMR profiles for
different particle sizes indicated the possible contribution of biological
aerosols and a mixture of aliphatic and oxygenated compounds from biomass
burning and traffic exhausts. The concurrent presence of ammonium and amines
also suggested the presence of ammonium/aminium nitrate and sulfate secondary
aerosol. The size-dependent origin of WSOC was further corroborated by the
increasing δ<sup>13</sup>C abundance from −26.81 ± 0.18‰ for
the smallest particles to −25.93 ± 0.31‰ for the largest
particles and the relative distribution of the functional groups as compared
to those previously observed for marine, biomass burning and secondary
organic aerosol. The latter also allowed for the differentiation of urban
combustion-related aerosol and biological particles. The five types of
organic hydrogen accounted for the majority of WSOC for particles with
<i>d</i><sub>p</sub> > 3.0 μm and
<i>d</i><sub>p</sub> < 0.96 μm
Pathogenic Potential to Humans of Bovine Escherichia coli O26, Scotland
Escherichia coli O26 and O157 have similar overall prevalences in cattle in Scotland, but in humans, Shiga toxin–producing E. coli O26 infections are fewer and clinically less severe than E. coli O157 infections. To investigate this discrepancy, we genotyped E. coli O26 isolates from cattle and humans in Scotland and continental Europe. The genetic background of some strains from Scotland was closely related to that of strains causing severe infections in Europe. Nonmetric multidimensional scaling found an association between hemolytic uremic syndrome (HUS) and multilocus sequence type 21 strains and confirmed the role of stx<sub>2</sub> in severe human disease. Although the prevalences of E. coli O26 and O157 on cattle farms in Scotland are equivalent, prevalence of more virulent strains is low, reducing human infection risk. However, new data on E. coli O26–associated HUS in humans highlight the need for surveillance of non-O157 enterohemorrhagic E. coli and for understanding stx<sub>2</sub> phage acquisition
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