507 research outputs found
Linearisation of Universal Field Equations
The Universal Field Equations, recently constructed as examples of higher
dimensional dynamical systems which admit an infinity of inequivalent
Lagrangians are shown to be linearised by a Legendre transformation. This
establishes the conjecture that these equations describe integrable systems.
While this construction is implicit in general, there exists a large class of
solutions for which an explicit form may be written.Comment: 11pp., DTP-92/47, NI-92/01
Good images, effective messages? Working with students and educators on academic practice understanding
Work at Northumbria University has focussed on activity that extends opportunities for students to engage directly with the skills development necessary for sound academic practice. This has included highly visual campaigns on the "Plagiarism trap", providing access to Turnitin plagiarism detection software, guides and sessions to highlight use of associated referencing tools. Sessions on a variety of topics, such as supporting study skills and reading originality reports, have been provided for students on taught, undergraduate and postgraduate programmes. This provision has included students working on collaborative partners' sites and also those on research programmes. Alongside the activities with students, "designing out" approaches have been embedded in staff development within the educator community at Northumbria. Formative use of Turnitin is integrated throughout programmes and academic practice development is formally recognised within the University Learning and Teaching Strategy's focus on information literacy. This article outlines and reviews these activities in a critical institutional context and evaluates responses from a variety of students and educators to determine how effective these measures have been
The role of individual and social variables in task performance.
This paper reports on a data-based study in which we explored - as part of a larger-scale British-Hungarian research project - the effects of a number of affective and social variables on foreign language (L2) learners’ engagement in oral argumentative tasks. The assumption underlying the investigation was that students’ verbal behaviour in oral task situations is partly determined by a number of non-linguistic and non-cognitive factors whose examination may constitute a potentially fruitful extension of existing task-based research paradigms. The independent variables in the study included various aspects of L2 motivation and several factors characterizing the learner groups the participating students were members of (such as group cohesiveness and intermember relations), as well as the learners’ L2 proficiency and ‘willingness to communicate’ in their L1. The dependent variables involved objective measures of the students’ language output in two oral argumentative tasks (one in the learners’ L1, the other in their L2): the quantity of speech and the number of turns produced by the speakers. The results provide insights into the interrelationship of the multiple variables determining the learners’ task engagement, and suggest a multi-level construct whereby some independent variables only come into force when certain conditions have been met
Strange Decays of Nonstrange Baryons
The strong decays of excited nonstrange baryons into the final states Lambda
K, Sigma K, and for the first time into Lambda(1405) K, Lambda(1520) K,
Sigma(1385) K, Lambda K*, and Sigma K*, are examined in a relativized quark
pair creation model. The wave functions and parameters of the model are fixed
by previous calculations of N pi and N pi pi, etc., decays. Our results show
that it should be possible to discover several new negative parity excited
baryons and confirm the discovery of several others by analyzing these final
states in kaon production experiments. We also establish clear predictions for
the relative strengths of certain states to decay to Lambda(1405) K and
Lambda(1520) K, which can be tested to determine if a three-quark model of the
Lambda(1405) K is valid. Our results compare favorably with the results of
partial wave analyses of the limited existing data for the Lambda K and Sigma K
channels. We do not find large Sigma K decay amplitudes for a substantial group
of predicted and weakly established negative-parity states, in contrast to the
only previous work to consider decays of these states into the strange final
states Lambda K and Sigma K.Comment: 25 pages, 8 figures, RevTe
Zanamivir susceptibility monitoring and characterization of influenza virus clinical isolates obtained during phase II clinical efficacy studies
Zanamivir is a highly selective neuraminidase (NA) inhibitor with
demonstrated clinical efficacy against influenza A and B virus infections.
In phase II clinical efficacy trials (NAIB2005 and NAIB2008), virological
substudies showed mean reductions in virus shedding after 24 h of
treatment of 1.5 to 2.0 log(10) 50% tissue culture infective doses
compared to a placebo, with no reemergence of virus after the completion
of therapy. Paired isolates (n = 41) obtained before and during therapy
with zanamivir demonstrated no shifts in susceptibility to zanamivir when
measured by NA assays, although for a few isolates NA activity was too low
to evaluate. In plaque reduction assays in MDCK cells, the susceptibility
of isolates to zanamivir was extremely variable even at baseline and did
not correlate with the speed of resolution of virus shedding. Isolates
with apparent limited susceptibility to zanamivir by plaque reduction
proved highly susceptible in vivo in the ferret model. Further sequence
analysis of paired isolates revealed no changes in the hemagglutinin and
NA genes in the majority of isolates. The few changes observed were all
natural variants. No amino acid changes that had previously been
identified in vitro as being involved with reduced susceptibility to
zanamivir were observed. These studies highlighted problems associated
with monitoring susceptibility to NA inhibitors in the clinic, in that no
reliable cell-based assay is available. At present the NA assay is the
best available predictor of susceptibility to NA inhibitors in vivo, as
measured in the validated ferret model of infection
The reaction pi+ p --> K+ Sigma+ in a unitary coupled-channels model
Elastic pi N scattering and the reaction pi+ p --> K+ Sigma+ are described
simultaneously in a unitary coupled-channels approach which respects
analyticity. SU(3) flavor symmetry is used to relate the t- and u-channel
exchanges that drive the meson-baryon interaction in the different channels.
Angular distributions, polarizations, and spin-rotation parameters are compared
with available experimental data. The pole structure of the amplitudes is
extracted from the analytic continuation.Comment: 43 pages, 15 figures, Version accepted for publication in Nuclear
Physics
Discriminatory optical force for chiral molecules
We suggest that the force F exerted upon a chiral molecule by light assumes the form F = a∇w + b∇h under appropriate circumstances, where a and b pertain to the molecule whilst w and h are the local densities of electric energy and helicity in the optical field; the gradients ∇ of these quantities thus governing the molecule’s centre-of-mass motion. Whereas a is identical for the mirror- image forms or enantiomers of the molecule, b has opposite signs; the associated contribution to F therefore pointing in opposite directions. A simple optical field is presented for which ∇w vanishes but ∇h does not, so that F is absolutely discriminatory. We then present two potential applications: a Stern–Gerlach-type deflector capable of spatially separating the enantiomers of a chiral molecule and a diffraction grating to which chiral molecules alone are sensitive; the resulting diffraction patterns thus encoding information about their chiral geometry
Comparison of Lambda and Sigma(0) Threshold Production in Proton-Proton Collisions
Threshold measurements of the associated strangeness production reactions pp
--> p K(+) Lambda and pp --> p K(+) Sigma(0) are presented. Although slight
differences in the shapes of the excitation functions are observed, the most
remarkable feature of the data is that at the same excess energy the total
cross section for the Sigma(0) production appears to be about a factor of 28
smaller than the one for the Lambda particle. It is concluded that strong
Sigma(0)-p final state interactions, and in particular the Sigma-N --> Lambda-p
conversion reaction, are the likely cause of the depletion for the yield in the
Sigma signal. This hypothesis is in line with other experimental evidence in
the literature.Comment: 13 pages, 3 figures, 1 tabl
P-wave excited baryons from pion- and photo-induced hyperon production
We report evidence for , , ,
, , and , and find
indications that might have a companion state at 1970\,MeV. The
controversial is not seen. The evidence is derived from a
study of data on pion- and photo-induced hyperon production, but other data are
included as well. Most of the resonances reported here were found in the
Karlsruhe-Helsinki (KH84) and the Carnegie-Mellon (CM) analyses but were
challenged recently by the Data Analysis Center at GWU. Our analysis is
constrained by the energy independent scattering amplitudes from either
KH84 or GWU. The two amplitudes from KH84 or GWU, respectively, lead to
slightly different branching ratios of contributing resonances but the
debated resonances are required in both series of fits.Comment: 22 pages, 28 figures. Some additional sets of data are adde
Search for CP Violation in the Decay Z -> b (b bar) g
About three million hadronic decays of the Z collected by ALEPH in the years
1991-1994 are used to search for anomalous CP violation beyond the Standard
Model in the decay Z -> b \bar{b} g. The study is performed by analyzing
angular correlations between the two quarks and the gluon in three-jet events
and by measuring the differential two-jet rate. No signal of CP violation is
found. For the combinations of anomalous CP violating couplings, and , limits of \hat{h}_b < 0.59h^{\ast}_{b} < 3.02$ are given at 95\% CL.Comment: 8 pages, 1 postscript figure, uses here.sty, epsfig.st
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