We study the representation
D
of a simple compact Lie algebra
g
of rank
l constructed with the aid of the hermitian Dirac matrices of a (
dim
g
)-dimensional euclidean space. The irreducible ...representations of
g
contained in
D
are found by providing a general construction on suitable fermionic Fock spaces. We give full details not only for the simplest odd and even cases, namely
su(2) and
su(3) , but also for the next (
dim
g
)-even case of
su(5) . Our results are far reaching: they apply to any
g
-invariant quantum mechanical system containing
dim
g
fermions. Another reason for undertaking this study is to examine the role of the
g
-invariant fermionic operators that naturally arise. These are given in terms of products of an odd number of gamma matrices, and include, besides a cubic operator,
l−1 fermionic scalars of higher order. The latter are constructed from the Lie algebra cohomology cocycles, and must be considered to be of theoretical significance similar to the cubic operator. In the (
dim
g
)-even case, the product of all
l operators turns out to be the chirality operator
γ
q,
q=(
dim
g+1)
.
This paper shows that (anisotropic) spin chains of
XY type arise by matrix representation of the fermionic terms of hamiltonians of quantum systems whose supersymmetry involves in general no more ...than a single hermitian supercharge. It provides some background relevant to this type of supersymmetry and makes applications to such chains including those which admit quantum groups as invariance algebras.
The overall incidence of multiple births in England and Wales, which had been declining since the early 1950s, started to increase in the early 1980s in all age groups except for women under 20. This ...followed a rise in the incidence of triplet and higher order multiple births which had started in the late 1970s. Analyses of data for births between 1978 and 1983 showed that while stillbirth, perinatal, neonatal, and post-neonatal mortalities among multiple births fell considerably, they remained consistently higher than those for singleton births. Differences in the distribution of birth weight do not wholly explain these differences. Analyses of certified causes of stillbirth and death are difficult to interpret because a considerable proportion were attributed to 'multiple pregnancy'.
Background Assessors from the Confidential Enquiry into Stillbirths and Deaths in Infancy (CESDI) have cited poor communication as a contributory factor in a proportion of such deaths. This review ...assesses what research evidence exists to support or explain this. Methods A structured review was carried out, including all studies of sub-optimal care in stillbirth or infant death and studies of litigation in perinatal care. The following databases were searched: MEDLINE, PsycLIT, The Cochrane Library, BIDS Science and Social Science Citation Indexes, Cinahl and Embase. For included studies, information was extracted on the type of study, the selection criteria and number of cases studied, other methods used and results relevant to the question. Results One hundred and four studies of potential relevance to the review were identified. Of these, 52 did not meet the inclusion criteria and were excluded. Of the remaining 52 studies, 11 considered communication failure explicitly as a factor in sub-optimal care leading to stillbirth or infant death. In three out of the four studies that presented their findings in terms of numbers of cases, communication failure was noted in between 24 and 29 per cent of cases. There was some consistency across different types of study in the types of communication problems noted. Conclusion Poor communication may contribute to a proportion of stillbirths and infant deaths. However, given the small number of papers that looked explicitly at poor communication as a factor in sub-optimal care and the lack of comparative information on communication in cases that do not end in poor outcome, caution is needed in drawing conclusions based on the findings of these papers.
A theory is studied of the supersymmetric motion of a
spin-
1
2
particle with
SU(2) colour in a Wu-Yang monopole background, in which
H =
Q
0
2 relates Hamiltonian and supercharge. Two additional ...supercharges which anticommute with
Q
0 are found so that the theory possesses a hidden
N = 2 supersymmetry algebra
{Q
i, Q
j} = δ
ij
1
2
(J
2+
constant)
,
i,
j = 1, 2, where
J is the conserved total angular momentum.
We show that one-dimensional superspace is isomorphic to a nontrivial but consistent limit as
q → −1 of the braided line. Supersymmetry is identified as translational invariance along this line. The ...supertranslation generator and covariant derivative are obtained in the limit in question as the left and right derivatives of the calculus on the braided line.
The oxidation of the amino acid tyrosine to the tyrosyl radical is now known to be important in many electron transfer reactions in biology. Electron Paramagnetic Resonance (EPR) and Electron Nuclear ...Double Resonance (ENDOR) have previously been used to obtain proton hyperfine couplings for the radical in vivo. This study uses AM 1 molecular orbital calculations to provide a detailed insight into the geometry and electronic makeup of this important radical. Molecular orbital studies are first used to obtain an optimised geometry for the tyrosyl radical. This is shown to differ significantly from the unoxidised form. The extent of the singly occupied molecular orbital is then examined and a theoretical estimate of the unpaired electron spin distribution is obtained. This is then used to calculate the anisoptopic hyperfine coupling components for comparison with experimental determinations.
The statistical adequacy of all papers published in the period 1976‐80 describing clinical trials of five non‐steroidal anti‐inflammatory and two analgesic drugs introduced into the UK market in 1978 ...and 1979 has been assessed using a checklist of simple criteria. Most trials were reported to be randomised and double‐blind. Trial designs were less satisfactory in other important respects; the sample size of most trials was inadequate to demonstrate superiority of the new drug compared with an active control therapy. The period of treatment assessment was short in view of the likelihood of prolonged prescription of drugs in these classes. It is suggested that licensing authorities should demand higher standards of clinical trial evidence offered in support of new drugs.
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