909 research outputs found
Factors influencing the potency of marbofloxacin for pig pneumonia pathogens Actinobacillus pleuropneumoniae and Pasteurella multocida
For the pig respiratory tract pathogens, Actinobacillus pleuropneumoniae and Pasteurella multocida, Minimum Inhibitory Concentration (MIC) of marbofloxacin was determined in recommended broths and pig serum at three inoculum strengths. MICs in both growth matrices increased progressively from low, through medium to high starting inoculum counts, 104, 106 and 108 CFU/mL, respectively. P. multocida MIC ratios for high:low inocula were 14:4:1 for broth and 28.2:1 for serum. Corresponding MIC ratios for A. pleuropneumoniae were lower, 4.1:1 (broth) and 9.2:1 (serum). MIC high:low ratios were therefore both growth matrix and bacterial species dependent. The effect of alterations to the chemical composition of broths and serum on MIC were also investigated. Neither adjusting broth or serum pH in six increments over the range 7.0 to 8.0 nor increasing calcium and magnesium concentrations of broth in seven incremental steps significantly affected MICs for either organism. In time-kill studies, the killing action of marbofloxacin had the characteristics of concentration dependency against both organisms in both growth matrices. It is concluded that MIC and time-kill data for marbofloxacin, generated in serum, might be preferable to broth data, for predicting dosages of marbofloxacin for clinical use
Potency of marbofloxacin for pig pneumonia pathogens Actinobacillus pleuropneumoniae and Pasteurella multocida: Comparison of growth media
Pharmacodynamic properties of marbofloxacin were established for six isolates each of the pig respiratory tract pathogens, Actinobacillus pleuropneumoniae and Pasteurella multocida. Three in vitro indices of potency were determined; Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC) and Mutant Prevention Concentration (MPC). For MIC determination Clinical Laboratory Standards Institute guidelines were modified in three respects: (1) comparison was made between two growth media, an artificial broth and pig serum; (2) a high inoculum count was used to simulate heavy clinical bacteriological loads; and (3) five overlapping sets of two-fold dilutions were used to improve accuracy of determinations. Similar methods were used for MBC and MPC estimations. MIC and MPC serum:broth ratios for A. pleuropneumoniae were 0.79:1 and 0.99:1, respectively, and corresponding values for P. multocida were 1.12:1 and 1.32:1. Serum protein binding of marbofloxacin was 49%, so that fraction unbound (fu) serum MIC values were significantly lower than those predicted by correction for protein binding; fu serum:broth MIC ratios were 0.40:1 (A. pleuropneumoniae) and 0.50:1 (P. multocida). For broth, MPC:MIC ratios were 13.7:1 (A. pleuropneumoniae) and 14.2:1 (P. multocida). Corresponding ratios for serum were similar, 17.2:1 and 18.8:1, respectively. It is suggested that, for dose prediction purposes, serum data might be preferable to potency indices measured in broths
Complex WKB Analysis of a PT Symmetric Eigenvalue Problem
The spectra of a particular class of PT symmetric eigenvalue problems has
previously been studied, and found to have an extremely rich structure. In this
paper we present an explanation for these spectral properties in terms of
quantisation conditions obtained from the complex WKB method. In particular, we
consider the relation of the quantisation conditions to the reality and
positivity properties of the eigenvalues. The methods are also used to examine
further the pattern of eigenvalue degeneracies observed by Dorey et al. in
[1,2].Comment: 22 pages, 13 figures. Added references, minor revision
Finite size effects in quantum field theories with boundary from scattering data
We derive a relation between leading finite size corrections for a 1+1
dimensional quantum field theory on a strip and scattering data, which is very
similar in spirit to the approach pioneered by Luscher for periodic boundary
conditions. The consistency of the results is tested both analytically and
numerically using thermodynamic Bethe Ansatz, Destri-de Vega nonlinear integral
equation and classical field theory techniques. We present strong evidence that
the relation between the boundary state and the reflection factor one-particle
couplings, noticed earlier by Dorey et al. in the case of the Lee-Yang model
extends to any boundary quantum field theory in 1+1 dimensions.Comment: 24 pages, 1 eps figure. Clarifying comments and a reference adde
On the boundary form factor program
Boundary form factor axioms are derived for the matrix elements of local
boundary operators in integrable 1+1 dimensional boundary quantum field
theories using the analyticity properties of correlators via the boundary
reduction formula. Minimal solutions are determined for the integrable boundary
perturbations of the free boson, free fermion (Ising), Lee-Yang and sinh-Gordon
models and the two point functions calculated from them are checked against the
exact solutions in the free cases and against the conformal data in the
ultraviolet limit for the Lee-Yang model. In the case of the free boson/fermion
the dimension of the solution space of the boundary form factor equation is
shown to match the number of independent local operators. We obtain excellent
agreement which proves not only the correctness of the solutions but also
confirms the form factor axioms.Comment: 38 pages, 17 eps figures, LaTeX, References adde
Recovering From a Stalled Change Initiative: A Case of Correcting Implementation Mistakes
Amid an age of increasing technology, innovation, and global business competition, there is no question that the pace organizational changes are introduced will increase, as well. With this pace of change, organizational leaders might find themselves short on the time and resources necessary to properly create readiness by utilizing implementation strategies. Frequently, a change initiative that is not introduced properly will meet resistance within the organization. When strong resistance is encountered, the initiative is often abandoned and replaced with some other effort. However, in some situations, the initiative can not be abandoned and implementation must continue. This research effort sought to identify the barriers leaders face as change initiatives stall by thematically analyzing responses from consultants in the organization development field. Then these barriers were reaffirmed by practitioners that experienced a stalled change initiative. Furthermore, strategies to overcome these barriers were identified by the consultants and then correlated to interview excerpts from the practitioners. The results indicate that the main barriers of stalled change initiatives include distrust, cynicism, and uncertain personal consequences. The suggested strategies to overcome these barriers included communication, creation of an open and inspirational environment, alignment of policies with the change, and reevaluation of the change effort
On the Uniqueness of the effective Lagrangian for N= 2 SQCD
The low energy effective Lagrangian for N= 2 SU(2) supersymmetric Yang-Mills
theory coupled to N_F<4 massless matter fields is derived from the BPS mass
formula using asymptotic freedom and assuming that the number of strong
coupling singularities is finite.Comment: 16 pages, LaTeX, 2 figures, title changed, sections on central charge
and superconformal anomaly extende
A Symplectic Structure for String Theory on Integrable Backgrounds
We define regularised Poisson brackets for the monodromy matrix of classical
string theory on R x S^3. The ambiguities associated with Non-Ultra Locality
are resolved using the symmetrisation prescription of Maillet. The resulting
brackets lead to an infinite tower of Poisson-commuting conserved charges as
expected in an integrable system. The brackets are also used to obtain the
correct symplectic structure on the moduli space of finite-gap solutions and to
define the corresponding action-angle variables. The canonically-normalised
action variables are the filling fractions associated with each cut in the
finite-gap construction. Our results are relevant for the leading-order
semiclassical quantisation of string theory on AdS_5 x S^5 and lead to
integer-valued filling fractions in this context.Comment: 41 pages, 2 figures; added references, corrected typos, improved
discussion of Hamiltonian constraint
Large N and double scaling limits in two dimensions
Recently, the author has constructed a series of four dimensional
non-critical string theories with eight supercharges, dual to theories of light
electric and magnetic charges, for which exact formulas for the central charge
of the space-time supersymmetry algebra as a function of the world-sheet
couplings were obtained. The basic idea was to generalize the old matrix model
approach, replacing the simple matrix integrals by the four dimensional matrix
path integrals of N=2 supersymmetric Yang-Mills theory, and the Kazakov
critical points by the Argyres-Douglas critical points. In the present paper,
we study qualitatively similar toy path integrals corresponding to the two
dimensional N=2 supersymmetric non-linear sigma model with target space CP^n
and twisted mass terms. This theory has some very strong similarities with N=2
super Yang-Mills, including the presence of critical points in the vicinity of
which the large n expansion is IR divergent. The model being exactly solvable
at large n, we can study non-BPS observables and give full proofs that double
scaling limits exist and correspond to universal continuum limits. A complete
characterization of the double scaled theories is given. We find evidence for
dimensional transmutation of the string coupling in some non-critical string
theories. We also identify en passant some non-BPS particles that become
massless at the singularities in addition to the usual BPS states.Comment: 38 pages, including an introductory section that makes the paper
self-contained, two figures and one appendix; v2: typos correcte
Exact Superpotentials for Theories with Flavors via a Matrix Integral
We extend and test the method of Dijkgraaf and Vafa for computing the
superpotential of N=1 theories to include flavors in the fundamental
representation of the gauge group. This amounts to computing the contribution
to the superpotential from surfaces with one boundary in the matrix integral.
We compute exactly the effective superpotential for the case of gauge group
U(N_c), N_f massive flavor chiral multiplets in the fundamental and one massive
chiral multiplet in the adjoint, together with a Yukawa coupling. We compare up
to sixth-order with the result obtained by standard field theory techniques in
the already non trivial case of N_c=2 and N_f=1. The agreement is perfect.Comment: 7 pages, v2: typos involving signs fixed; v3: version to appear in
Phys.Rev.
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