1,884 research outputs found
The Database of Abstracts of Reviews of Effects (DARE)
Systematic reviews are useful tools for busy decision-makers because they identify, appraise and synthesise the available research evidence on a particular topic. Many thousands of systematic reviews relevant to health care have been published. However, they can be difficult to locate and their quality is variable. DARE (the Database of Abstracts of Reviews of Effects) contains summaries of systematic reviews which have met strict quality criteria. Each summary also provides a critical commentary on the quality of the review. DARE covers a broad range of health care related topics and can be used for answering questions about the effects of health care interventions, as well as for developing clinical guidelines and policy making. DARE is available free of charge on the internet (http://nhscrd.york.ac.uk), and as part of the Cochrane Library. Alternatively, DARE can be searched, on your behalf, by CRD information staff (tel: 01904 433707 or email [email protected])
Hopf instantons, Chern-Simons vortices, and Heisenberg ferromagnets
The dimensional reduction of the three-dimensional fermion-Chern-Simons model
(related to Hopf maps) of Adam et el. is shown to be equivalent to (i) either
the static, fixed--chirality sector of our non-relativistic spinor-Chern-Simons
model in 2+1 dimensions, (ii) or a particular Heisenberg ferromagnet in the
plane.Comment: 4 pages, Plain Tex, no figure
Information Services in the CGIAR
Paper by the TAC Standing Committee for External Reviews, drawing on the consultant paper by John Woolston, and several inputs from the CGIAR Secretariat concerning the role of information in the CGIAR. It argues for the centers to play a role in the development and use of a more coherent global information system for research in agriculture, forestry, and fisheries. The NARS should in the long term be able to participate in such a system as full fledged actors. The paper urges the CGIAR to take the lead in organizing a conference on global information needs and opportunities.Agenda document, TAC 56
Quantum Hall effect anomaly and collective modes in the magnetic-field-induced spin-density-wave phases of quasi-one-dimensional conductors
We study the collective modes in the magnetic-field-induced spin-density-wave
(FISDW) phases experimentally observed in organic conductors of the Bechgaard
salts family. In phases that exhibit a sign reversal of the quantum Hall effect
(Ribault anomaly), the coexistence of two spin-density waves gives rise to
additional collective modes besides the Goldstone modes due to spontaneous
translation and rotation symmetry breaking. These modes strongly affect the
charge and spin response functions. We discuss some experimental consequences
for the Bechgaard salts.Comment: Final version (LaTex, 8 pages, no figure), to be published in
Europhys. Let
Is "just-so" Higgs splitting needed for t-b-\tau Yukawa unified SUSY GUTs?
Recent renormalization group calculations of the sparticle mass spectrum in
the Minimal Supersymmetric Standard Model (MSSM) show that t-b-\tau Yukawa
coupling unification at M_{\rm GUT} is possible when the mass spectra follow
the pattern of a radiatively induced inverted scalar mass hierarchy. The
calculation is entirely consistent with expectations from SO(10) SUSY GUT
theories, with one exception: it seems to require MSSM Higgs soft term mass
splitting at M_{\rm GUT}, dubbed "just-so Higgs splitting" (HS) in the
literature, which apparently violates the SO(10) gauge symmetry. Here, we
investigate three alternative effects: {\it i}). SO(10) D-term splitting, {\it
ii}). inclusion of right hand neutrino in the RG calculation, and {\it iii}).
first/third generation scalar mass splitting. By combining all three effects
(the DR3 model), we find t-b-\tau Yukawa unification at M_{\rm GUT} can be
achieved at the 2.5% level. In the DR3 case, we expect lighter (and possibly
detectable) third generation and heavy Higgs scalars than in the model with HS.
In addition, the light bottom squark in DR3 should be dominantly a right state,
while in the HS model, it is dominantly a left state.Comment: 21 pages with 11 .eps figures; revised version added two reference
Critical Exponents of the Three Dimensional Random Field Ising Model
The phase transition of the three--dimensional random field Ising model with
a discrete () field distribution is investigated by extensive Monte
Carlo simulations. Values of the critical exponents for the correlation length,
specific heat, susceptibility, disconnected susceptibility and magnetization
are determined simultaneously via finite size scaling. While the exponents for
the magnetization and disconnected susceptibility are consistent with a first
order transition, the specific heat appears to saturate indicating no latent
heat. Sample to sample fluctuations of the susceptibilty are consistent with
the droplet picture for the transition.Comment: Revtex, 10 pages + 4 figures included as Latex files and 1 in
Postscrip
D-branes and Closed String Field Theory
We construct BRST invariant solitonic states in the OSp invariant string
field theory for closed bosonic strings. Our construction is a generalization
of the one given in the noncritical case. These states are made by using the
boundary states for D-branes, and can be regarded as states in which D-branes
or ghost D-branes are excited. We calculate the vacuum amplitude in the
presence of solitons perturbatively and show that the cylinder amplitude for
the D-brane is reproduced. The results imply that these are states with even
number of D-branes or ghost D-branes.Comment: 36 pages, 3 figures, LaTeX; typos correcte
Neutrino masses in the Lepton Number Violating MSSM
We consider the most general supersymmetric model with minimal particle
content and an additional discrete Z_3 symmetry (instead of R-parity), which
allows lepton number violating terms and results in non-zero Majorana neutrino
masses. We investigate whether the currently measured values for lepton masses
and mixing can be reproduced. We set up a framework in which Lagrangian
parameters can be initialised without recourse to assumptions concerning
trilinear or bilinear superpotential terms, CP-conservation or
intergenerational mixing and analyse in detail the one loop corrections to the
neutrino masses. We present scenarios in which the experimental data are
reproduced and show the effect varying lepton number violating couplings has on
the predicted atmospheric and solar mass^2 differences. We find that with
bilinear lepton number violating couplings in the superpotential of the order 1
MeV the atmospheric mass scale can be reproduced. Certain trilinear
superpotential couplings, usually, of the order of the electron Yukawa coupling
can give rise to either atmospheric or solar mass scales and bilinear
supersymmetry breaking terms of the order 0.1 GeV^2 can set the solar mass
scale. Further details of our calculation, Lagrangian, Feynman rules and
relevant generic loop diagrams, are presented in three Appendices.Comment: 48 pages, 7 figures, v2 references added, typos corrected, published
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