4,029 research outputs found
The epidemiological type identification of Serratia marcescens from outbreaks of infection in hospitals
A study of serological, bacteriocine and phage typing of Serratia marcescens was made. Specific O-antisera of adequate titre were relatively simple to prepare but H-antisera exhibited many heterologous agglutination reactions amongst the type strains. Most of these cross-reactions were not reproduced when immobilization tests with H-sera were performed. Direct haemagglutination tests were used to establish the presence of fimbriae amongst the H-type strains and the results of agglutination tests with non-fimbriate variants of strains indicated that fimbrial antibody in high titre was present in some sera. Replicate typing of 100 pairs of cultures by the phage-typing method indicated that small variations in pattern were common and that larger variations occurred occasionally. Therefore differences in pattern of less than two strong reactions should not be taken as evidence that strains can be distinguished. Cultures of S. marcescens, 273 in total, from six outbreaks of infection in British and European hospitals were typed by O-serology, H agglutination and immobilization tests, phage typing and bacteriocine susceptibility by a cross-streaking method. The typability of strains by each method was high but the results suggested that no single method was sufficiently discriminating to be used alone for typing. Comparison of the H-type and typing patterns of members of the same O serogroup from incidents of infection showed that reliable results were obtained by H-typing or by phage and bacteriocine typing after the application of the appropriate ‘difference' rule. The greatest discrimination between strains of the same 0-group was obtained by the use of H-typing or phage typin
Bubble fluctuations in inflation
In the context of the open inflationary universe, we calculate the amplitude
of quantum fluctuations which deform the bubble shape. These give rise to
scalar field fluctuations in the open Friedman-Robertson-Walker universe which
is contained inside the bubble. One can transform to a new gauge in which
matter looks perfectly smooth, and then the perturbations behave as tensor
modes (gravitational waves of very long wavelength). For , where
is the density parameter, the microwave temperature anisotropies
produced by these modes are of order . Here, is the expansion rate during inflation, is
the intrinsic radius of the bubble at the time of nucleation, is the
bubble wall tension and labels the different multipoles (). The
gravitational backreaction of the bubble has been ignored. In this
approximation, , and the new effect can be much larger than the
one due to ordinary gravitational waves generated during inflation (unless, of
course, gets too close to one, in which case the new effect
disappears).Comment: 17 pages, 3 figs, LaTeX, epsfig.sty, available at
ftp://ftp.ifae.es/preprint/ft/uabft387.p
Development of microsatellite loci in the European Dipper, Cinclus cinclus
Eighteen polymorphic microsatellite DNA loci were isolated in the Central European subspecies of the European Dipper (Cinclus cinclus aquaticus). The loci were tested for polymorphism using a test panel of 24 breeding birds. Numbers of alleles ranged from 2 to 21 per locus and expected heterozygosities varied between 0.47 and 0.83. Two loci (Cici10 and Cici12) proved to be Z-linked. Some pairs of loci exhibited significant linkage disequilibrium but not the two loci that are located on the Z-chromosome. This pattern suggests that demographic effects rather than physical linkage are likely responsible for the observed levels of linkage disequilibrium. These loci will be useful for applied conservation projects and for investigations of the dispersal and mating patterns of European and other dipper
Field-dependent specific heat and multiple superconducting phases in UPt_3
We have measured the specific heat, C, of single-crystal UPt_3 in the superconducting regime as a function of temperature, T, and magnetic field, H, parallel to the c axis. We find that C(T) at fixed H<H_(c2) shows no evidence for different superconducting states. In contrast, our field-sweep data, C(H) at fixed T, have sharp changes in slope at H≊H_(c2)/2. The phase diagram deduced from these features agrees with neutron-scattering and torsional-oscillator results on the same samples. These thermodynamic measurements as a function of magnetic field constrain theories of exotic superconductivity in UPt_3
Gravity Waves from Instantons
We perform a first principles computation of the spectrum of gravity waves
produced in open inflationary universes. The background spacetime is taken to
be the continuation of an instanton saddle point of the Euclidean no boundary
path integral. The two-point tensor correlator is computed directly from the
path integral and is shown to be unique and well behaved in the infrared. We
discuss the tensor contribution to the cosmic microwave background anisotropy
and show how it may provide an observational discriminant between different
types of primordial instantons.Comment: 19 pages, RevTex file, including two postscript figure file
Self Excitation of the Tunneling Scalar Field in False Vacuum Decay
A method to determine the quantum state of a scalar field after
-symmetric bubble nucleation has been developed recently. The method has
an advantage that it concisely gives us a clear picture of the resultant
quantum state. In particular, one may interpret the excitations as a particle
creation phenomenon just as in the case of particle creation in curved
spacetime. As an application, we investigate in detail the spectrum of quantum
excitations of the tunneling field when it undergoes false vacuum decay. We
consider a tunneling potential which is piece-wise quadratic, hence is simple
enough to allow us an analytical treatment. We find a strong dependence of the
excitation spectrum upon the shape of the potential on the true vacuum side. We
then discuss features of the excitation spectrum common to general tunneling
potentials not restricted to our simple model.Comment: 24 pages, uuencoded compressed postscript fil
SO(10) Cosmic Strings and SU(3) Color Cheshire Charge
Certain cosmic strings that occur in GUT models such as can carry a
magnetic flux which acts nontrivially on objects carrying
quantum numbers. We show that such strings are non-Abelian Alice strings
carrying nonlocalizable colored ``Cheshire" charge. We examine claims made in
the literature that strings can have a long-range, topological
Aharonov-Bohm interaction that turns quarks into leptons, and observe that such
a process is impossible. We also discuss flux-flux scattering using a
multi-sheeted formalism.Comment: 37 Pages, 8 Figures (available upon request) phyzzx, iassns-hep-93-6,
itp-sb-93-6
Holographic analysis of diffraction structure factors
We combine the theory of inside-source/inside-detector x-ray fluorescence
holography and Kossel lines/x ray standing waves in kinematic approximation to
directly obtain the phases of the diffraction structure factors. The influence
of Kossel lines and standing waves on holography is also discussed. We obtain
partial phase determination from experimental data obtaining the sign of the
real part of the structure factor for several reciprocal lattice vectors of a
vanadium crystal.Comment: 4 pages, 3 figures, submitte
Cosmological Perturbations Generated in the Colliding Bubble Braneworld Universe
We compute the cosmological perturbations generated in the colliding bubble
braneworld universe in which bubbles filled with five-dimensional anti-de
Sitter space (AdS5)expanding within a five dimensional de Sitter space (dS5) or
Minkowski space (M5) collide to form a (3+1) dimensional local brane on which
the cosmology is virtually identical to that of the Randall-Sundrum model. The
perturbation calculation presented here is valid to linear order but treats the
fluctuations of the expanding bubbles as (3+1) dimensional fields localized on
the bubble wall. We find that for bubbles expanding in dS5 the dominant
contribution to the power spectrum is `red' but very small except in certain
cases where the fifth dimension is not large or the bubbles have expanded to
far beyond the dS5 apparent horizon length. This paper supersedes a previous
version titled "Exactly Scale-Invariant Cosmological Perturbations From a
Colliding Bubble Braneworld Universe" in which we erroneously claimed that a
scale-invariant spectrum results for the case of bubbles expanding in M5. This
present paper corrects the errors of the previous version and extends the
analysis to the more interesting and general case of bubbles expanding in dS5.Comment: 29 pages Latex with eps figures. Major errors in the original version
of the paper corrected and analysis extended to bubbles expanding in dS
Magnetic Behavior in RRhX (R = rare earths; X=B, C) Compounds
We report on the magnetic behavior of RRhB (R = La, Ce, Pr, Nd, Gd, Tb and
Tm) and RRhC (R = La, Ce, Pr and Gd) compounds crystallizing in the cubic
perovskite type structure with space group Pm3m. The heat capacity data on
Pauli-paramagnetic LaRhB and LaRhC indicate a high frequency vibrating motion
of boron and carbon atoms in the unit cell. Ce is in -like nonmagnetic state in
both the compounds. Pr compounds show a dominant crystal field effect with a
nonmagnetic singlet ground state in PrRhB and a nonmagnetic quadrupolar doublet
in PrRhC. Compounds with other rare earths order ferromagnetically at low
temperatures except TmRhB in which the zero field evolution of magnetic
interactions is relatively more complicated. The electrical resistivity of
GdRhB decreases with increasing temperature in the paramagnetic state in the
vicinity of T, which is rarely seen in ferromagnets. The behavior is discussed
to be arising due to the short range spin fluctuation and a possible
contribution from Fermi surface geometry.Comment: 14 Figs and a text fil
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