13,429 research outputs found
A new H.E.L.P kit for teaching practical AC electronics to undergraduate distance students
An important part of educating students in electronics and electrical engineering is laboratory practicals. Providing effective practical experience to students by distance education has always been a significant challenge to the engineering educator. Deakin University has for many years taught practicals in basic digital electronics to off-campus students by means of a kit. The same students have performed related exercises in analogue electronics, which require generating and measuring AC signals, by means of either software simulations or on-campus attendance at lab classes. This year, for the first time, off-campus students are being provided with a new kit, which contains a low-cost, battery-powered AC signal generator, and an interface that allows a PC to be used as an oscilloscope. This kit allows the off-campus student further flexibility in learning basic electronics.<br /
Product Groups, Discrete Symmetries, and Grand Unification
We study grand unified theories based on an SU(5)xSU(5) gauge group in which
the GUT scale, M_{GUT}, is the VEV of an exact or approximate modulus, and in
which fast proton decay is avoided through a combination of a large triplet
mass and small triplet couplings. These features are achieved by discrete
symmetries. In many of our models, M_{GUT} is generated naturally by the
balance of higher dimension terms that lift the GUT modulus potential, and soft
supersymmetry breaking masses. The theories often lead to interesting patterns
of quark and lepton masses. We also discuss some distinctions between grand
unified theories and string unification.Comment: 23 pages; no figures; revtex
Gauge-Fermion Unification and Flavour Symmetry
After we study the 6-dimensional supersymmetry breaking
and symmetry breaking on , we construct two supersymmetric models on where is
broken down to by orbifold projection. In Model I, three
families of the Standard Model fermions arise from the zero modes of bulk
vector multiplet, and the symmetry
can be considered as flavour symmetry. This may explain why there are three
families of fermions in the nature. In Model II, the first two families come
from the zero modes of bulk vector multiplet, and the flavour symmetry is
similar. In these models, the anomalies can be cancelled, and we have very good
fits to the SM fermion masses and mixings. We also comment on the supersymmetric models on and ,
SU(9) models on , and SU(8) models on orbifolds.Comment: Latex, 33 pages, minor change
Flipping SU(5) Towards Five Dimensional Unification
It is shown that embedding of flipped SU(5) in a five-dimensional SO(10)
enables exact unification of the gauge coupling constants. The demand for the
unification uniquely determines both the compactification scale and the cutoff
scale. These are found to be 5.5 \times 10^{14} GeV and 1.0 \times 10^{17} GeV
respectively. The theory explains the absence of d=5 proton-decay operators
through the implementation of the missing partner mechanism. On the other hand,
the presence of d=6 proton-decay operators points towards the bulk localization
of the first and the second family of matter fields.Comment: 21 pages, references added, 3 Postscript figures, ReVTeX
A pragmatic randomised controlled trial of hydrotherapy and land exercises on overall well being and quality of life in rheumatoid arthritis
Background \ud
Hydrotherapy is highly valued by people with rheumatoid arthritis yet few studies have compared the benefits of exercises in heated water against exercises on land. In particular, data on quality of life is rarely reported. This is especially important because patients treated with hydrotherapy often report an enhanced sense of well-being. We report a randomised controlled trial in which we compared the effects of hydrotherapy with exercises on land on overall response to treatment, physical function and quality of life in patients with rheumatoid arthritis. \ud
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Methods \ud
One hundred and fifteen patients with RA were randomised to receive a weekly 30-minute session of hydrotherapy or similar exercises on land for 6 weeks. Our primary outcome was a self-rated global impression of change â a measure of treatment effect on a 7-point scale ranging from 1(very much worse) to 7 (very much better) assessed immediately on completion of treatment. Secondary outcomes including EuroQol health related quality of life, EuroQol health status valuation, HAQ, 10 metre walk time and pain scores were collected at baseline, after treatment and 3 months later. Binary outcomes were analysed by Fisher's exact test and continuous variables by Wilcoxon or Mann-Whitney tests. \ud
\ud
Results \ud
Baseline characteristics of the two groups were comparable. Significantly more patients treated with hydrotherapy (40/46, 87%) were much better or very much better than the patients treated with land exercise (19/40, 47.5%), p < 0.001 Fisher's exact test. Eleven patients allocated land exercise failed to complete treatment compared with 4 patients allocated hydrotherapy (p = 0.09). Sensitivity analyses confirmed an advantage for hydrotherapy if we assumed non-completers would all not have responded (response rates 70% versus 38%; p < 0.001) or if we assumed that non-completers would have had the same response as completers (response rates 82% versus 55% p = 0.002). Ten metre walk time improved after treatment in both cases (median pre-treatment time for both groups combined 10.9 seconds, post-treatment 9.1 s, and 3 months later 9.6 s). There was however no difference between treatment groups. Similarly there were no significant differences between groups in terms of changes to HAQ, EQ-5D utility score, EQ VAS and pain VAS. \ud
\ud
Conclusion \ud
Patients with RA treated with hydrotherapy are more likely to report feeling much better or very much better than those treated with land exercises immediately on completion of the treatment programme. This perceived benefit was not reflected by differences between groups in 10-metre walk times, functional scores, quality of life measures and pain scores
Multigluon tree amplitudes with a pair of massive fermions
We consider the calculation of n-point multigluon tree amplitudes with a pair
of massive fermions in QCD. We give the explicit transformation rules of this
kind of massive fermion-pair amplitudes with respect to different reference
momenta and check the correctness of them by SUSY Ward identities. Using these
rules and onshell BCFW recursion relation, we calculate the analytic results of
several n-point multigluon amplitudes.Comment: 15page
The Minimal Solution to the mu/B_mu Problem in Gauge Mediation
We provide a minimal solution to the mu/B_mu problem in the gauge mediated
supersymmetry breaking by introducing a Standard Model singlet filed S with a
mass around the messenger scale which couples to the Higgs and messenger
fields. This singlet is nearly supersymmetric and acquires a relatively small
Vacuum Expectation Value (VEV) from its radiatively generated tadpole term.
Consequently, both mu and B_mu parameters receive the tree-level and one-loop
contributions, which are comparable due to the small S VEV. Because there
exists a proper cancellation in such two kinds of contributions to B_mu, we can
have a viable Higgs sector for electroweak symmetry breaking.Comment: 15 pages, 2 figures, version published on JHE
A Complete Model of Low-Scale Gauge Mediation
Recent signs of a Standard Model-like Higgs at 125 GeV point towards large
A-terms in the MSSM. This presents special challenges for gauge mediation,
which by itself predicts vanishing A-terms at the messenger scale. In this
paper, we review the general problems that arise when extending gauge mediation
to achieve large A-terms, and the mechanisms that exist to overcome them. Using
these mechanisms, we construct weakly-coupled models of low-scale gauge
mediation with extended Higgs-messenger couplings that generate large A-terms
at the messenger scale and viable mu/B_mu-terms. Our models are simple,
economical, and complete realizations of supersymmetry at the weak scale.Comment: 33 pages; v2: refs added, minor change
Exponentially Small Supersymmetry Breaking from Extra Dimensions
The supersymmetric ``shining'' of free massive chiral superfields in extra
dimensions from a distant source brane can trigger exponentially small
supersymmetry breaking on our brane of order e^{-2 pi R}, where R is the radius
of the extra dimensions. This supersymmetry breaking can be transmitted to the
superpartners in a number of ways, for instance by gravity or via the standard
model gauge interactions. The radius R can easily be stabilized at a size O(10)
larger that the fundamental scale. The models are extremely simple, relying
only on free, classical bulk dynamics to solve the hierarchy problem.Comment: RevTex, 1 figure. Comment on mu problem adde
The Reach of the Fermilab Tevatron and CERN LHC for Gaugino Mediated SUSY Breaking Models
In supersymmetric models with gaugino mediated SUSY breaking (inoMSB), it is
assumed that SUSY breaking on a hidden brane is communicated to the visible
brane via gauge superfields which propagate in the bulk. This leads to GUT
models where the common gaugino mass is the only soft SUSY breaking
term to receive contributions at tree level. To obtain a viable phenomenology,
it is assumed that the gaugino mass is induced at some scale beyond the
GUT scale, and that additional renormalization group running takes place
between and as in a SUSY GUT. We assume an SU(5) SUSY GUT above
the GUT scale, and compute the SUSY particle spectrum expected in models with
inoMSB. We use the Monte Carlo program ISAJET to simulate signals within the
inoMSB model, and compute the SUSY reach including cuts and triggers approriate
to Fermilab Tevatron and CERN LHC experiments. We find no reach for SUSY by the
Tevatron collider in the trilepton channel. %either with or without %identified
tau leptons. At the CERN LHC, values of (1160) GeV can be probed
with 10 (100) fb of integrated luminosity, corresponding to a reach in
terms of of 2150 (2500) GeV. The inoMSB model and mSUGRA can likely
only be differentiated at a linear collider with sufficient energy to
produce sleptons and charginos.Comment: 17 page revtex file with 9 PS figure
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