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• Articles  (56,227)
• 1975-1979  (56,227)
• 1970-1974
• 1978  (56,227)
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• Books  (175)
• Articles  (56,227)
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• 1975-1979  (56,227)
• 1970-1974
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• 1
Electronic Resource
Oxford, UK : Blackwell Publishing Ltd
Birth 5 (1978), S. 0
ISSN: 1523-536X
Source: Blackwell Publishing Journal Backfiles 1879-2005
Topics: Medicine
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• 2
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Oxford, UK : Blackwell Publishing Ltd
Birth 5 (1978), S. 0
ISSN: 1523-536X
Source: Blackwell Publishing Journal Backfiles 1879-2005
Topics: Medicine
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• 3
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Oxford, UK : Blackwell Publishing Ltd
Birth 5 (1978), S. 0
ISSN: 1523-536X
Source: Blackwell Publishing Journal Backfiles 1879-2005
Topics: Medicine
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• 4
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Oxford, UK : Blackwell Publishing Ltd
Birth 5 (1978), S. 0
ISSN: 1523-536X
Source: Blackwell Publishing Journal Backfiles 1879-2005
Topics: Medicine
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• 5
Electronic Resource
Oxford, UK : Blackwell Publishing Ltd
Birth 5 (1978), S. 0
ISSN: 1523-536X
Source: Blackwell Publishing Journal Backfiles 1879-2005
Topics: Medicine
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• 6
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Oxford, UK : Blackwell Publishing Ltd
Birth 5 (1978), S. 0
ISSN: 1523-536X
Source: Blackwell Publishing Journal Backfiles 1879-2005
Topics: Medicine
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• 7
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Oxford, UK : Blackwell Publishing Ltd
Birth 5 (1978), S. 0
ISSN: 1523-536X
Source: Blackwell Publishing Journal Backfiles 1879-2005
Topics: Medicine
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• 8
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Oxford, UK : Blackwell Publishing Ltd
Birth 5 (1978), S. 0
ISSN: 1523-536X
Source: Blackwell Publishing Journal Backfiles 1879-2005
Topics: Medicine
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• 9
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Oxford, UK : Blackwell Publishing Ltd
Birth 5 (1978), S. 0
ISSN: 1523-536X
Source: Blackwell Publishing Journal Backfiles 1879-2005
Topics: Medicine
Notes: : One hundred and five women who had cesarean sections were interviewed to assess their feelings about their births. Forty-one percent of the women were told they had to have a cesarean fewer than two hours before, and 35% were repeat cesareans. Statistical data are presented on women's reasons for feeling cesareans were harder, easier, or not different, including the finding that 30% felt relief at having a cesarean. Sources of stress and negative feelings after cesareans are discussed.
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• 10
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Oxford, UK : Blackwell Publishing Ltd
Birth 5 (1978), S. 0
ISSN: 1523-536X
Source: Blackwell Publishing Journal Backfiles 1879-2005
Topics: Medicine
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• 11
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Oxford, UK : Blackwell Publishing Ltd
Birth 5 (1978), S. 0
ISSN: 1523-536X
Source: Blackwell Publishing Journal Backfiles 1879-2005
Topics: Medicine
Notes: : As part of planning a new maternity wing of a Boulder, Colorado hospital, a telephone interview survey of 645 women who delivered within one year at this hospital was made to determine their preferences for 49 different options in maternity care. The sample was divided into 210 women chosen at random, 230 from La Leche League groups, and 205 women from prepared childbirth classes. The most important areas of concern to these new mothers were similar in all three groups and revolved around maintaining family closeness and obtaining help from hospital staff rather than desire for new or different facilities. Proposals resulting from this study were for the new maternity service to provide 1) combined labor-delivery-recovery rooms; 2) most post-partum rooms to be private; 3) father unrestricted in visiting throughout; 4) sibling visitation; 5) inservice training for medical and nursing staff in childbirth and breastfeeding techniques; 6) family-centered cesarean births; 7) alternative birth arrangement with early discharge.
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• 12
Electronic Resource
Oxford, UK : Blackwell Publishing Ltd
Birth 5 (1978), S. 0
ISSN: 1523-536X
Source: Blackwell Publishing Journal Backfiles 1879-2005
Topics: Medicine
Notes: : A study of the timing of first solid foods in the infant diet reveals significant differences, with bottlefeeding mothers more likely to add solid foods prior to the infant's third month than breastfeeding mothers. In addition, the type of food used was related to the timing of its introduction, with bottlefeeding mothers more likely than breastfeeding women to use commercially prepared baby foods rather than home-prepared foods. Although recommendations by established pediatric societies caution against the too-early introduction of solid foods at the expense of the amount of milk received, these recommendations have not yet filtered down to a number of parents, especially those who bottlefeed their infants.
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• 13
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Springer
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract We derive new inequalities for the plane rotator ferromagnetic model and use them to obtain the following results: 1) If the model is isotropic, the derivability of the free energy as function of the magnetic fieldh implies the existence of a unique translation invariant Gibbs state and if furthermoreh=0 all Gibbs states are invariant by rotation of the spins. 2) If the model is anisotropic the above assertion holds forh non-zero. 3) If the model is anisotropic then there are at most two extremal translation invariant Gibbs states for almost all values of the anisotropy parameter.
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• 14
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Springer
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract An abstract form of the spatially non-homogeneous Boltzmann equation is derived which includes the usual, more concrete form for any kind of potential, hard or soft, with finite cutoff. It is assumed that the corresponding “gas” is confined to a bounded domain by some sort of reflection law. The problem then considered is the corresponding initial-boundary value problem, locally in time. Two proofs of existence are given. Both are constructive, and the first, at least, provides two sequences, one converging to the solution from above, the other from below, thus producing, at the same time as existence, approximations to the solution and error bounds for the approximation. The solution is found within a space of functions bounded by a multiple of a Maxwellian, and, in this space, uniqueness is also proved.
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• 15
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Springer
Communications in mathematical physics 58 (1978), S. 195-203
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract Distribution of the zeros of absorptive differential cross section is studied. Several rigorous bounds are deduced on the slope and curvature of diffraction peak. Energy dependence of the slope of diffraction peak and location of zeros of the cross section impose a constraint on ratio of curvature and slope of diffraction peak.
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• 16
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Springer
Communications in mathematical physics 62 (1978), S. 167-171
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract Any generator of a norm continuous semigroup of completely positive normal maps on a von Neumann algebraM can be decomposed into a sum of a completely positive map and a map of the formm→x*m+mx.
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• 17
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Springer
Communications in mathematical physics 62 (1978), S. 119-136
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract We prove the existence of the limit Gibbs state for one-dimensional continuous quantum fermion systems with non-hard-core, non-negative, rapidly decreasing pair interaction potentials. Existence of the limit Gibbs state is also established for one-dimensional continuous quantum boson systems with pair interaction potentials as above which, in addition, increase sufficiently fast at small distances.
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• 18
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Springer
Communications in mathematical physics 62 (1978), S. 191-200
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract For infinite classical systems a class of spatially homogeneous perturbed states is defined, and used to give a direct proof of the fact that global thermodynamical stability implies the (classical) KMS-condition.
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• 19
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Springer
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract We describe several new techniques for obtaining detailed information on the exponential falloff of discrete eigenfunctions ofN-body Schrödinger operators. An example of a new result is the bound (conjectured by Morgan) $$\left| {\psi (x_1 \ldots x_N )} \right| \leqq C\exp ( - \sum\limits_1^N {\alpha _n r_n )}$$ for an eigenfunction ω of $$H_N = - \sum\limits_{i = 1}^N {(\Delta _i - } \left. {\frac{Z}{{\left| {x_i } \right|}}} \right) + \sum\limits_{i〈 j} {\left| {x_i - x_j } \right|^{ - 1} }$$ with energyE N . In this boundr 1 r 2...r N are the radii |x i | in increasing order and the α's are restricted by α n 〈(E n−1−E n )1/2, whereE n , forn=0, 1,...,N−1, is the lowest energy of the system described byH n . Our methods include subharmonic comparison theorems and “geometric spectral analysis”.
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• 20
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Springer
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract Frobenius theory about the cyclic structure of eigenvalues of irreducible non negative matrices is extended to the case of positive linear maps of von Neumann algebras. Semigroups of such maps and ergodic properties are also considered.
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• 21
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Springer
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract Swinney et al. (1977) have found that turbulence in rotational Couette flow results from a small number of instabilities. They have raised the question of whether these instabilities conform with the ideas of Ruelle and Takens (1971). We show that a simple model of the Couette flow yields power spectra similar to those seen in the experiments. The model is consistent with the Ruelle and Takens picture.
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• 22
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Springer
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract We study the interaction ofN classical two-dimensional massless Fermi fields through the symmetric couplings $$[\bar \psi _i \psi _i ]^2$$ or $$[\bar \psi _i \psi _i ]^2 - [\bar \psi _i \gamma _5 \psi _i ]^2$$ . We explicitly show complete integrability in the casesN=1, 2, using the inverse scattering method. The fields occuring in the associated linear eigenvalue problem and evolution equation are simply related to the fundamental fields Ψ i that satisfy the original non-linear equations. ForN〉2, calculations become very involved, but there is no doubt that the system remains completely integrable, reducing to appropriate generalizations of the sine- and sinh-Gordon equation, a situation analogous to Pohlmeyer's discussion in a somewhat similar problem: the two-dimensional non-linear σ-model. Finally, all the explicit analytic solutions that we have worked out in the present framework are identical to those found by Dashen et al., and Shei, in a semiclassical treatment of the fully quantum mechanical version of these models. This leads us to conjecture that the quantum theory also shares most of the features of completely integrable systems, like the massive Thirring model.
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• 23
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Springer
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract This paper contains a detailed study of the flow that the classical Hamiltonian $$H = \tfrac{1}{2}(x_1^2 + y_1^2 ) - \tfrac{1}{2}(x_2^2 + y_2^2 ) + \mathcal{O}_3$$ induces near the origin of its phase spaceR 4. Here the perturbation term $$\mathcal{O}_3$$ represents a convergent power series. In particular, criteria for the existence and stability of periodic orbits are developed and expressed in terms of canonical invariants that are extracted from the perturbation term.
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• 24
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Springer
Communications in mathematical physics 58 (1978), S. 113-129
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract We study some properties of the time evolution of an infinite one dimensional hard cores system with singular two body interaction. We show that the Liouville operator is essentially antiselfadjoint on the algebra of local observables. Some consequences of this result are also discussed.
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• 25
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Springer
Communications in mathematical physics 58 (1978), S. 273-290
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract We characterize equilibrium states of quantum systems by a condition of passivity suggested by the second principle of thermodynamics. Ground states and β-KMS states for all inverse temperatures β≧0 are completely passive. We prove that these states are the only completely passive ones. For the special case of states describing pure phases, assuming the passivity we reproduce the results of Haag et al.
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• 26
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Springer
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract We discuss a model of non linear quantum mechanics in which the wave equation satisfies the homogeneity condition (2.1). It is argued that in this model the set of (mixed) states is a simplex.
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• 27
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Springer
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract Examples are presented of potentialsV for which −d 2 /dr 2+V(r) inL 2(0, ∞) has singular continuous spectrum, and the physical interpretation is discussed.
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• 28
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Springer
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract The spectrum of the mass operator on the soliton sectors of the anisotropic (λ|ø|4)2—and the (λø4)2—quantum field models in the two phase region is analyzed. It is proven that, for small enough λ〉0, the mass gapm s(λ) on the soliton sector is positive, andm s(λ)=0(λ−1). This involves estimatingm s(λ) from below by a quantity τ(λ) analogous to the surface tension in the statistical mechanics of two dimensional, classical spin systems and then estimating τ(λ) by methods of Euclidean field theory. In principle, our methods apply to any two dimensional quantum field model with a spontaneously broken, internal symmetry group.
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• 29
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Springer
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract We use the holonomic character of Feynman integrals to describe their singularity structure explicitly in some simple cases. The results in §1 show that under moderate conditions Feynman amplitudes can be locally expressed essentially in terms of Legendre functions near the points where two positive-α Landau-Nakanishi surfaces meet. Related topics such as hierarchical principle in perturbation theory are also discussed in terms of holonomic systems involved. In §4 we use the concrete expressions for Feynman amplitudes obtained in §1 to discuss the validity of Sato's conjecture.
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• 30
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Springer
Communications in mathematical physics 60 (1978), S. 153-170
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract By application of the Girsanov formula for measures induced by diffusion processes with constant diffusion coefficients it is possible to define the Onsager-Machlup function as the Lagrangian for the most probable tube around a differentiable function. The absolute continuity of a measure induced by a process with process depending diffusion w.r.t. a quasi translation invariant measure is investigated. The orthogonality of these measures w.r.t. quasi translation invariant measures is shown. It is concluded that the Onsager-Machlup function cannot be defined as a Lagrangian for processes with process depending diffusion coefficients.
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• 31
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Communications in mathematical physics 60 (1978), S. 181-191
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract A representation of the pair correlation function for the rectangular Ising model in zero magnetic field is derived using a new spinor technique; this enables the scaling limit to be established, as well as several analytical properties of the scaling functions.
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• 32
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Communications in mathematical physics 60 (1978), S. 192-192
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
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• 33
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Springer
Communications in mathematical physics 60 (1978), S. 193-204
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract A 14-dimensional generalized Lorenz system of ordinary differential equations is constructed and its bifurcation sequence is then studied numerically. Several fundamental differences are found which serve to distinguish this model from Lorenz's original one, the most unexpected of which is a family of invariant two-tori whose ultimate bifurcation leads to a strange attractor. The strange attractor seems to have many of the gross features observed in Lorenz's model and therefore is an excellent candidate for a higher dimensional analogue.
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• 34
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Springer
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract We give an explicit construction of the affine Lie algebraA 1 (1) as an algebra of differential operators on ℂ[x 1,x 3,x 5, ...]. This algebra is spanned by the creation and annihilation operators and by the homogeneous components of a certain “exponential generating function” which is strikingly similar to the vertex operator in the string model.
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• 35
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Springer
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract We extend a characterisation by Lindblad of complete normal dissipations on hyperfinite von Neumann algebras to general semifinite von Neumann algebras.
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• 36
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Springer
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract We give a criterion that the two point function for a Gaussian lattice with random mass decay exponentially. The proof uses a random walk representation which may be of interest in other contexts.
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• 37
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Springer
Communications in mathematical physics 62 (1978), S. 107-118
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract It is shown that the characteristic Cauchy problem $$\left( {\frac{{\partial ^2 }}{{\partial t^2 }} - \Delta + 1} \right)$$ ·u(x,t)=0,u(x,−|x|)=f(x),x∈ℝ n ,n≧1 has a unique finite energy weak solution for allf such that ∫dx(|∇f|2+|f|2)〈∞ and all finite energy weak solutions of the equation are obtained in this way.
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• 38
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Springer
Communications in mathematical physics 62 (1978), S. 137-158
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract For any Feynman amplitude, where any subset of invariants and/or squared masses is scaled by a real parameter λ going to zero or infinity, the existence of an expansion in powers of λ and lnλ is proved, and a method is given for determining such an expansion. This is shown quite generally in euclidean metric, whatever the external momenta (exceptional or not) and the internal masses (vanishing or not) may be, and for some simple cases in minkowskian metric, assuming only finiteness of the — eventually renormalized — amplitude before scaling. The method uses what is called “Multiple Mellin representation”, the validity of which is related to a “generalized power-counting” theorem.
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• 39
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Communications in mathematical physics 62 (1978), S. 159-166
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract Upper and lower bounds are proven for the speed of propagation of general classes of physical signals in particle lattice models.
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• 40
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Communications in mathematical physics 62 (1978), S. 173-189
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract We investigate the cohomology of nets over Minkowski space and develop exact sequence techniques enabling us to compute many low-dimensional cohomologies. We examine in particular nets derived from smooth solutions of invariant partial differential equations using causal support conditions. Thus the wave equation gives a trivial second cohomology whereas the vector wave equation with Lorentz condition and Maxwell's equations give a second cohomology ℝ and ℝ×ℝ corresponding, respectively, to an electric and an electric and magnetic charge.
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• 41
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Communications in mathematical physics 62 (1978), S. 201-212
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract We discussN-body kinematics and study the Berezin-Sigal equations in configuration space. Assuming that the threshold of the continuous spectrum is zero and that the pair potentials satisfy |V(x)|≦C(1+|x|2)−Q , ϰ ∈ ℝ3 ϱ 〉 1 (together with some technical hypotheses), we show that the discrete spectrum of the hamiltonian in the center of mass system is finite. The case of negative threshold will be treated in a further publication.
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• 42
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Communications in mathematical physics 62 (1978), S. 235-245
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract This paper discusses the topological setting of the preceding paper by Callias. In particular, an alternate way of deriving his results is outlined.
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• 43
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Communications in mathematical physics 62 (1978), S. 279-302
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract Equivalence (allowing for convex combinations) of microcanonical, canonical and grandcanonical ensembles for states of classical systems is established under very mild assumptions on the limiting state. We introduce the notion of conditional equilibrium (C.E.), a property of states of infinite systems which characterizes convex combinations of limits of microcanonical ensembles. It is shown that C.E. states are, under quite general conditions, mixtures of Gibbs states.
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• 44
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Communications in mathematical physics 62 (1978), S. 247-278
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract All rotating perfect fluid configurations having two-parameter equations of state are shown to be dynamically unstable to nonaxisymmetric perturbations in the framework of general relativity. Perturbations of an equilibrium fluid are described by means of a Lagrangian displacement, and an action for the linearized field equations is obtained, in terms of which the symplectic product and canonical energy of the system can be expressed. Previous criteria governing stability were based on the sign of the canonical energy, but this functional fails to be invariant under the gauge freedom associated with a class of trivial Lagrangian displacements, whose existence was first pointed out by Schutz and Sorkin [12]. In order to regain a stability criterion, one must eliminate the trivials, and this is accomplished by restricting consideration to a class of “canonical” displacements, orthogonal to the trivials with respect to the symplectic product. There nevertheless remain perturbations having angular dependencee imφ (φ the azimuthal angle) which, for sufficiently largem, make the canonical energy negative; consequently, even slowly rotating stars are unstable to short wavelength perturbations. To show strict instability, it is necessary to assume that time-dependent nonaxisymmetric perturbations radiate energy to null infinity. As a byproduct of the work, the relativistic generalization of Ertel's theorem (conservation of vorticity in constant entropy surfaces) is obtained and shown to be Noetherrelated to the symmetry associated with the trivial displacements.
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• 45
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ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract A lattice theory of Fermi fields of massm coupled to gauge fields in the region wherem and the gauge field coupling constantg are large is studied. It is shown that the energy of some states composed of a fermion and a distant antifermion with a string in between grows at least linearly with the distance if 1〈g 6〈m〈g εlogg .
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• 46
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ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract We study the real, Euclidean, classical field equation $$(\mu ^2 + \Delta )\varphi + \lambda F(\varphi ) = f,\mu ^2 〉 0$$ where φ: ℝ d →ℝ is suitably small at infinity. We study existence and regularity assuming that λ≧0,F∈C ∞(ℝ), andaF(a)≧0∀a∈∝. These hypotheses allow strongly nonlinearF and nonunique solutions forf≠0. WhenF′≧0, we prove uniqueness, various contractivity properties, analytic dependence on the coupling constant λ, and differentiability in the external sourcef. For applications in the loop expansion in quantum field theory, it is useful to know that φ is in the Schwartz classL wheneverf is, and we provide a proof of this fact. The technical innovations of the problem lie in treating the noncompactness of R d , the strong nonlinearity ofF, and the polynomial weights in the seminorms definingL.
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• 47
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Communications in mathematical physics 63 (1978), S. 131-153
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract It is shown that the expansion in powers of 1/N characteristic of Gross-Neveu type models is of quasiclassical nature, 1/N taking part of the Planck constant. The limity classical mechanics has curved phase space that does not admit introduction of naturally canonically conjugated coordinates.
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• 48
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Communications in mathematical physics 63 (1978), S. 177-192
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract An explicit description is given for all self-dual Euclidean Yang-Mills fields and their parameter spaces in the theory with unitary gauge group of arbitrary rank.
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• 49
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Communications in mathematical physics 63 (1978), S. 193-218
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract We prove the positivity of the pressure and compressibility for neutral systems in the Thomas-Fermi theory of molecules. Our results include some new properties of the Thomas-Fermi potential and a proof that the kinetic energy is superadditive.
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• 50
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Communications in mathematical physics 63 (1978), S. 243-255
ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract We consider stationary asymptotically flat spacetimes having an ergosphere but with no horizon. In the framework of linear perturbation theory such configurations are unstable or marginally unstable to scalar and electromagnetic perturbations.
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• 51
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ISSN: 1432-0916
Source: Springer Online Journal Archives 1860-2000
Topics: Mathematics , Physics
Notes: Abstract It is shown that by a smallC 2 (resp.C ∞) perturbation of a quasiperiodic flow on the 3-torus (resp. them-torus,m〉3), one can produce strange AxiomA attractors. Ancillary results and physical interpretation are also discussed.
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• 52
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European biophysics journal 4 (1978), S. 115-128
ISSN: 1432-1017
Keywords: Adaptation ; Rod outer segment
Source: Springer Online Journal Archives 1860-2000
Topics: Biology , Physics
Notes: Abstract This model of rod outer segment adaptation is based on the hypothesis that transmitter substance released by bleached rhodopsin closes sodium channels in the outer segment plasma membrane, leading to hyperpolarization of the receptor. The outer segment adaptation processes of the model are associated with the transmitter release, the transmitter background concentration and the plasma membrane leakage. Changes in the three model parameters correspond to the three types of outer segment adaptation processes. According to the model the stimulus-response function is in every adaptational state U/U max −I/(I+I H ). The model predicts how each adaptation process affects I H and U max. Specifically, when the number of liberated transmitter molecules per isomerizing quantum decreases, the amplitude U max remains constant but I H increases. A short description of this model has been published in a paper reporting experimental results on background adaptation (HemilÄ, 1977).
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• 53
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European biophysics journal 4 (1978), S. 129-138
ISSN: 1432-1017
Keywords: Flash photolysis ; Rhodopsin ; Quantum efficiency ; Rate con stant
Source: Springer Online Journal Archives 1860-2000
Topics: Biology , Physics
Notes: Abstract Flash photolysis of rhodopsin in rabbit's retina has been analysed theoretically, and the results are found to be in good agreement with the experimental results of Hagins (1957). We have also obtained the variation of relative concentrations of rhodopsin, lumirhodopsin, isorhodopsin and metarhodopsin I during the period of the flash corresponding to two different intensities of the flash. It has been found that the quantum efficiencies of conversion of lumirhodopsin into rhodopsin and isorhodopsin will lie in the range 0.24–0.45 and 0.20–0.44 respectively; quantum efficiencies of conversion of metarhodopsin I into rhodopsin and isorhodopsin are found to have values greater than 0.52 and 0.45 respectively and the quantum efficiency of conversion of isorhodopsin into lumirhodopsin has been found to be approximately 0.865. Also the maximum value of the rate constant of the reaction metarhodopsin I→metarhodopsin II at 37
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• 54
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European biophysics journal 4 (1978), S. 159-168
ISSN: 1432-1017
Keywords: Muscle rigor ; Cross bridge slippage ; ATP analogue ; Insect fibrillar muscle ; Muscle stiffness
Source: Springer Online Journal Archives 1860-2000
Topics: Biology , Physics
Notes: Abstract Glycerol-extracted insect fibrillar muscle fibres in rigor exhibited both an elastic and a plastic phase in the length-tension diagram. The transition between these phases took place at a critical tension, the “yield point” or elastic limit. In the plastic phase the apparent static elastic modulus became zero, whereas the immediate elastic modulus (measured by rapid length changes completed within 4 ms) exhibited no abrupt change at the yield point. The tension value of the yield point (but not immediate stiffness) was lowered by addition of AMP-PNP and was partially restored by washing out AMP-PNP. The dependence of the critical tension at which plastic flow begins on cooperative cross bridge behaviour is discussed in terms of breaking and reforming acto-myosin linkages. Evidence is presented that addition of AMP-PNP induces slippage of cross bridges on the actin filament by affecting the interaction between myosin and actin.
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• 55
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European biophysics journal 4 (1978), S. 179-199
ISSN: 1432-1017
Keywords: 1/f Noise ; Biological membrane ; Synthetic membrane ; Membrane pore ; Diffusion
Source: Springer Online Journal Archives 1860-2000
Topics: Biology , Physics
Notes: Abstract The present situation of 1/f noise in the passage of ions across membranes is examined. A survey of biological and synthetic membranes is given at which a l/f frequency dependence has been observed in the spectrum of voltage or current fluctuations. Empirical relations and theories of 1/f noise in membranes are critically discussed.
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• 56
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European biophysics journal 4 (1978), S. 169-177
ISSN: 1432-1017
Keywords: Mössbauer spectra ; Halophilic bacteria ; 2 Fe-Ferredoxins ; EPR ; Localization of ferredoxin in the cell
Source: Springer Online Journal Archives 1860-2000
Topics: Biology , Physics
Notes: Abstract Recoil-free measurements were carried out on a 2 Fe-ferredoxin, which was isolated and purified from an extreme halophile, Halobacterium of the Dead Sea. The spectrum of this ferredoxin in the oxidized state at 82 K is a superposition of two quadrupole doublets, representing two non-equivalent Fe3+ sites of equal intensity. The spectrum of the reduced ferredoxin is consistent with the presence of two pure classes of iron atoms, ferric (lower isomer shift) and ferrous (higher isomer shift). Interpretations of the recoil-free spectra are discussed. Mössbauer measurements were also carried out on frozen whole bacterial cells and the resulting spectrum was found to be quite different from that observed in the isolated ferredoxin. Tentative conclusions are reached concerning the localization of this ferredoxin in the cytosol of the Halobacteria. The EPR spectrum of the reduced ferredoxin obtained at 24 K exhibits rhombic symmetry with the following g values: 1.894, 1.984 and 2.07. These values are similar to those obtained with 2 Fe-ferredoxins of the plant type, except that the g y and g z values are somewhat higher. Both from the EPR and Mössbauer data, it is deduced that the spin relaxation times in reduced halophilic ferredoxins are faster than in the reduced plant ferredoxins.
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• 57
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European biophysics journal 4 (1978), S. 139-158
ISSN: 1432-1017
Keywords: Hemoproteins ; Magnetic circular dichroism ; Heme environment ; Transition assignment ; Least squares fit
Source: Springer Online Journal Archives 1860-2000
Topics: Biology , Physics
Notes: Abstract The magnetic circular dichroism spectra (MCD) recorded for the visible and near-UV regions of high-spin ferrous derivatives of myoglobin, hemoglobin, hemoglobin dimers and isolated chains as well as of horseradish peroxidase at pH 6.8 and 11.4 have been compared at the room and liquid nitrogen temperatures. The MCD of the Q 00- and Qv-bands have been shown to be sensitive to structural differences in the heme environment of these hemoproteins. The room temperature visible MCD of native hemoglobin differs from that of myoglobin, hemoglobin dimers and isolated chains as well as from that of model pentacoordinated complex. The MCD of hemoglobin is characterized by the greater value of the MCD intensity ratio of derivative shape A-term in the Q 00-band to the A-term in the Q v-band. The evidences are presented for the existence of two pH-dependent forms of ferroperoxidase, the neutral peroxidase shows the “hemoglobin-like” MCD, while the alkaline ferroperoxidase is characterized by the “myoglobin-like” MCD spectrum in the visible region. The differences in the MCD of deoxyhemoglobin and neutral ferroperoxidase as compared with other high-spin ferrous hemoproteins are considered to result from the constraints on heme group imposed by quaternary and/or tertiary protein structure. The differences between hemoproteins which are seen at the room temperature become more pronounced at liquid nitrogen temperature. Except the peak at ∼ 580 nm in the MCD of deoxymyoglobin and reduced peroxidase at pH 11.4 the visible MCD does not show appreciable temperature dependent C-terms. The nature of the temperature dependent effect at ∼ 580 nm is not clear. The Soret MCD of all hemoproteins studied are similar and are predominantly composed of the derivative-shaped C-terms as revealed by the increase of the MCD peaks approximately in accordance with Boltzmann distribution. The interpretation of temperature-dependent MCD observed for the Soret band has been made in terms of porphyrin to Fe-ion charge-transfer electronic transition which may be assigned as b(π) → 3d. This charge-transfer band is strongly overlapped with usual B(π - π*) band resulting in diffuse Soret band. Adopting that only two normal vibrations are sinphase with charge-transfer transition the extracted C-terms of the Soret MCD have been fitted by theoretical dispersion curves.
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• 58
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European biophysics journal 4 (1978), S. 201-207
ISSN: 1432-1017
Keywords: Hemoglobin ; Oxygen binding ; Charged allosteric effectors ; Model
Source: Springer Online Journal Archives 1860-2000
Topics: Biology , Physics
Notes: Abstract A mechanism for indirect allosteric action of charged effectors on substrate binding to a macromolecule is proposed. It is accounted for by electrostatic interaction among effectors in the solution, away from their receptors. The possibility of the mechanism proposed is tested in the allosteric action of univalent salt and 2,3-diphosphoglycerate on oxygen binding to hemoglobin. A model for electrostatic interaction between these two effectors in the solution and for their overall effect on oxygen binding is introduced. The 2,3-diphosphoglycerate binding constant to deoxygenated hemoglobin as a function of univalent salt concentration and the median ligand activity as a function of the concentration of univalent salt and 2,3-diphoshoglycerate are calculated and compared with experimental data. The obtained results indicate that electrostatic interaction in the solution may significantly contribute to indirect allosteric action of charged effectors.
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• 59
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European biophysics journal 4 (1978), S. 237-249
ISSN: 1432-1017
Keywords: Conductivity ; Halobacterium
Source: Springer Online Journal Archives 1860-2000
Topics: Biology , Physics
Notes: Abstract The electrical conductivity of suspensions of two species of Halobacterium was measured at low A. C. frequency. The results obtained fromHalobacterium halobium suspensions show that the bacteria act as non-conducting particles. In contrast, the cells of a Halobacterium obtained from the Dead Sea (Halobacterium marismortui) had an apparently high conductivity which can be explained partly in terms of the cell-membrane being pierced by pores through which ions can move freely and partly in terms of highly concentrated cell ions, all of which are mobile.
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ISSN: 1432-1041
Keywords: β-Blockers ; α-blocking ; activity ; intrinsic sympathomimetic activity ; partial agonist
Source: Springer Online Journal Archives 1860-2000
Topics: Chemistry and Pharmacology , Medicine
Notes: Summary The pharmacological methods used to assess the intrinsic sympathomimetic activity (ISA) of β-blockers are discussed. The clinical relevance of ISA to respiratory function, peripheral resistance and cardiac function is reviewed. It appears doubtful whether ISA is always of predominant clinical significance and an alternative explanation is offered for many clinical effects observed with certain β-blockers, e.g. pindolol, oxprenolol, tolamolol, metoprolol, etc. Some effects of these β-blockers resemble those of labetalol, a new drug with both α- and β-blocking activity. Some clinical effects of certain β-blockers are more likely to be due to α-blocking activity than to their ISA.
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ISSN: 1432-1041
Keywords: Pindolol ; beta1-blockade ; bronchial asthma ; salbutamol ; ventilatory function
Source: Springer Online Journal Archives 1860-2000
Topics: Chemistry and Pharmacology , Medicine
Notes: Summary The effect of a single oral dose of pindolol on bronchi was studied in a double-blind cross-over trial in 20 adult patients, most of whom had moderate bronchial asthma. A single dose of pindolol 5 mg, sufficient to cause a significant fall in heart rate and blood pressure at rest, did not produce a significant fall in the forced expiratory volume (FEV1.0). However, two patients showed marked deterioration in lung function after pindolol. A conventional therapeutic dose of salbutamol by inhalation produced a significant increase in ventilatory function relative to placebo, but it did not outweigh the bronchial effect of pindolol.
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ISSN: 1432-1041
Keywords: Antiarrhythmic drug ; propafenone ; serum concentration ; atrioventricular conduction time
Source: Springer Online Journal Archives 1860-2000
Topics: Chemistry and Pharmacology , Medicine
Notes: Summary Seven patients with cardiac dysrhythmias received a single, oral, therapeutically effective dose of the antiarrhythmic drug propafenone. The serum levels correlated well with changes in atrioventricular conduction times during the postabsorptive elimination phase (r=0.6810, p〈0.001). The mean half-lives of the serum level and the electrocardiographic effect (PQ-time) were 3.6±0.2 h and 3.8±0.6 h, respectively.
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ISSN: 1432-1041
Keywords: Norethindrone ; bioavailability ; man ; competitive protein binding ; sex differences ; pharmacokinetics
Source: Springer Online Journal Archives 1860-2000
Topics: Chemistry and Pharmacology , Medicine
Notes: Summary A competitive protein binding assay for norethindrone was developed to measure plasma levels in human subjects. The plasma levels were considerably higher in women than in men, especially at low dose levels. The plasma levels were directly related to the dose in men; but greater variations in the plasma levels were observed in women. The plasma half-life was about 5 h in both sexes with single oral doses of 5 to 20 mg. A comparative bioavailability study with norethindrone from 2 different manufacturers, formulated in the same manner, showed no significant differences in absorption characteristics and provided sufficient data for pharmacokinetic analysis.
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ISSN: 1432-1041
Keywords: p-Chlorophenoxyisobutyric acid ; clofibrate ; steady-state plasma concentrations ; bioavailability ; pharmacokinetics
Source: Springer Online Journal Archives 1860-2000
Topics: Chemistry and Pharmacology , Medicine
Notes: Summary Plasma concentrations and bioavailability of clofibrinic acid have been estimated under conditions approaching the steady-state during a ten-day period of administration as clofibrate or as a calcium clofibrinate-carbonate combination (1:1 w/w) at a dosage interval of 12 h. Formulation — related differences in bioavailability were not significant, and the 95% confidence limits of these differences were within −2% to +8% of the mean for the reference formulation of clofibrate. The mean steadystate plasma concentrations of clofibrinic acid measured on the tenth day of dosing were 116 µg/ml±22 S.D. and 119 µg/ml±23 S.D. after administration of 885 mg as clofibrate and the calcium clofibrinate-carbonate combination respectively. The peaks of mean plasma concentrations were 70 µg/ml±15 S.D., 119 µg/ml±32 S.D. and 131 µg/ml±26 S.D. on the first, fifth and tenth day of dosing with clofibrate, and 62 µg/ml±13 S.D., 127 µg/ml±S.D. and 143 µg/ml±25 S.D. on the corresponding days of dosing with the calcium clofibrinate-carbonate combination. After the last dose on the tenth day of dosing, the mean apparent half-lives of elimination of clofibrinic acid from plasma were 24.2 h±4.4 S.D. and 25.5 h±3.2 S.D. after administration of clofibrate and the calcium clofibrinate-carbonate combination respectively.
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ISSN: 1432-1041
Source: Springer Online Journal Archives 1860-2000
Topics: Chemistry and Pharmacology , Medicine
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ISSN: 1432-1041
Keywords: Valproic acid ; pharmacokinetics ; liver disease
Source: Springer Online Journal Archives 1860-2000
Topics: Chemistry and Pharmacology , Medicine
Notes: Summary The disposition of valproic acid (di-n-propylacetate; VA) has been studied after a single oral dose of a solution of 450 mg in 7 patients with alcoholic cirrhosis and in 4 patients recovering from acute hepatitis. The diagnosis was based on biochemical function tests and histological findings. The pharmacokinetic parameters were compared with those reported for healthy volunteers. VA in therapeutic concentration (80 µg/ml) in plasma was less bound to plasma proteins in patients with alcoholic cirrhosis (70.7±11.3%) and in patients recovering from acute hepatitis (78.1±14.1%) than in controls (88.7±5.2%). The reduced binding affected the blood/plasma concentration ratio and the apparent distribution volume Vd(β); the latter was increased from the normal value of 0.14±0.05 l/kg to 0.22±0.09 (p〈0.05) in alcoholic cirrhotics, and to 0.20±0.07 (p=0.056) in patients recovering from acute hepatitis. The half-life of elimination T1/2 (β) (controls=12.2±3.7 h) was significantly (p〈0.05) prolonged in cirrhotics (18.9±5.1 h) and in patients recovering from acute hepatitis (17.0±3.7 h). The plasma $$\overline {Cl}$$ of total drug was not impaired, which can best be explained by the lower plasma protein binding, which might have increased the $$\overline {Cl}$$ of this drug which shows restricted clearance. In addition, the plasma $$\overline {Cl}$$ of free drug was significantly (p〈0.02) reduced in alcoholic cirrhotics. During a two day urine collection no measurable amount of unchanged VA was recovered. There was considerable excretion of VA-conjugates, which could be hydrolyzed either by HCl or by β-glucuronidase/arylsulphatase (4–23% of the dose). These percentages were in the same range as in normals (26.7±16.1%). The study indicates that elimination of VA is slightly impaired in patients with dysfunction of the liver.
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ISSN: 1432-1041
Keywords: Beta receptor blockade ; atenolol ; blood and urinary levels ; tilt ; renin ; blood pressure
Source: Springer Online Journal Archives 1860-2000
Topics: Chemistry and Pharmacology , Medicine
Notes: Summary The non-stimulant cardioselective beta adrenocepter antagonist atenolol has been studied in volunteers in order to define its pharmacokinetic characteristics. Atenolol (100 and 200 mg orally) is rapidly absorbed, reductions in heart rate and systolic pressure being observed in 30 min. The effect persists for up to 8 h. Over 85% of an intravenous dose is excreted in urine within 24 h but only 50% of an oral dose. The bioavailability of approximately 50% is due to reduced absorption. Peak blood levels are observed at 2–4 h and the half life of atenolol given orally is 5–6 h. Atenolol reduces the cardiac response to standing and head-up tilt. It does not reduce circulating levels of renin but slightly impairs the renin response to tilt. Atenolol both orally and intravenously reduces supine diastolic pressure about four hours after administration, the effect persisting for up to 24 h.
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ISSN: 1432-1041
Keywords: Digitoxin ; β-acetyldigoxin ; plasma levels ; cardiac performance ; dose-effect relationship ; 86-Rb-erythrocyte assay ; systolic time intervals
Source: Springer Online Journal Archives 1860-2000
Topics: Chemistry and Pharmacology , Medicine
Notes: Summary An inter-individual, randomized, double-blind study of digitoxin (Dt) and β-acetyl digoxin (D) was performed in 120 healthy male volunteers. Groups of 10 persons each received orally D 0, 0.1, 0.2, 0.3, 0.4, 0.5 or 0.6 mg and Dt 0.04, 0.08, 0.12, or 0.16 mg daily for 7 days; Loading doses were given for the first three days. Plasma levels were measured with an86Rb-erythrocyte assay 24 h after the last dose. ECG, carotid artery pulse and phonocardiogram were recorded prior to (b) and 24 h after (a) the last dose. QTc, amplitude of T-waves in V2 to V6, electromechanical systole (QS2c) and left ventricular ejection time (LVETc) were measured. The differences between a and b (Δ-values) reflect glycoside-induced changes in heart function. The plasma glycoside concentrations depended on dose and ranged from 0 to 2.4 ng/ml for D and from 0 to 42 ng/ml for Dt. QTc, QS2c, and LVETc were significantly shortened by the glycosides and typical parallel, sigmoid, log dose-response curves were obtained for the Δ-values. Dt was 3.8-times as potent as D in diminishing these parameters. The maximal effect of the two glycosides was almost identical at the highest doses: Δ-QTc=−45 ms, Δ-QS2c=−25 ms, Δ-LVETc=−12.5 ms. The latter two parameters showed a plateau of maximum efficacy. Both glycosides caused significant flattening of T-waves, Dt being 7.2-times as potent as D. Significant relationships between plasma concentration and cardiac effects were observed (p〈0.001)−Δ-QTc (D: r=0.7; Dt: r=0.77), Δ-QS2c (D: r=0.7; Dt: r=0.75), and Δ-LVETc (D: r=0.46; Dt: r=0.43); D correlated less well than Dt with the flattening of T (r=0.46; r=0.76, respectively). The most important conclusions were that: Dt was about 4-times as potent as D in influencing cardiac performance; the effects of D and Dt on systolic time intervals reached a plateau at “therapeutic” doses; Dt induced more pronounced flattening of the T-wave than D; and plasma glycoside levels within the “therapeutic” range corresponded to observed effects on the heart.
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ISSN: 1432-1041
Keywords: bioavailability ; diuretics ; gastrointestinal absorption ; hydrochlorothiazide ; thiazides ; food effect
Source: Springer Online Journal Archives 1860-2000
Topics: Chemistry and Pharmacology , Medicine
Notes: Summary Hydrochlorothiazide (hct) 75 mg was administered orally to eight healthy volunteers without (Study I) or together with a standardized meal (Study II), and plasma and urine concentrations of hct were analyzed by GLC. The plasma levels of hct were higher initially when the tablets were taken on an empty stomach, but after 5 h they were higher in Study II. There was no difference between the two studies in the area under plasma concentration time curves. The urinary recovery of hct totalled 55.6±4.9 mg when the drug was given with food and 47.4±6.0 when it was taken on an empty stomach. The difference is significant (p〈0.01). As the urinary recovery represents the uptake of hct, it appears that the gastrointestinal absorption of hct is enhanced when the drug is given with food.
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ISSN: 1432-1041
Keywords: Amikacin ; gentamycin ; netilmicin ; sisomicin ; tobramycin ; kidney damage ; proximal tubule ; cell membrane ; AAP
Source: Springer Online Journal Archives 1860-2000
Topics: Chemistry and Pharmacology , Medicine
Notes: Summary The effect of the aminoglycosides amikacin, gentamicin, netilmicin sisomicin and tobramycin on the proximal tubule of the human kidney was investigated in 78 healthy subjects. Fifteen adults were each given gentamicin, sisomicin or tobramycin 3 mg/kg bodyweight, 10 subjects received netilmicin 3 mg/kg or amikacin 15 mg/kg additionally seven subjects amikacin 10 mg and six subjects netilmicin 6 mg on three consecutive days. The principal enzyme of the brush border membrane of the proximal tubule, alanine aminopeptidase (AAP), was determined enzymatically and immunologically in 24-hour urines. The effects of the various aminoglycosides on the membranes were different. Less of membrane AAP was greatest after amikacin and was least after tobramycin. There was no difference between gentamicin, netilmicin, and sisomicin, which had an effect intermediate between the other two compounds. The elimination of AAP occurred at intervals whicht might possibly have been caused by impairment of cell cycles.
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ISSN: 1432-1041
Keywords: Lignocaine ; pharmacokinetics ; neonates ; metabolism ; renal excretion ; plasma concentrations
Source: Springer Online Journal Archives 1860-2000
Topics: Chemistry and Pharmacology , Medicine
Notes: Summary The pharmacokinetics and metabolism of lignocaine in premature neonates was studied after subcutaneous administration. The collection of serial urine together with a limited number of blood samples from neonates enabled simultaneous computer fitting of data to a pharmacokinetic model. The disposition kinetics of lignocaine in four neonates were compared with similar data reported for adults. Neonates had prolonged t1/2 (neonate mean: 3.16 h; adult mean: 1.80 h), and an increased total volume of distribution (neonate mean: 2.75 l/kg; adult mean: 1.11 l/kg) compared with adults. Total plasma clearance (Cltp) normalised on body weight showed no significant difference between neonates (mean: 0.610 l/h/kg) and adults (mean: 0.550 l/h/kg). The urinary excretion of lignocaine and several of its metabolites was studied in 8 neonates and 11 adults. Neonates were shown to excrete much more unchanged lignocaine (mean: 19.67%) compared with adults (mean: 4.27%) and the proportion of the dose excreted as 4-hydroxyxylidine is considerably reduced in neonates (neonate mean: 8.89%; adult mean: 63.78%). The use of the two pharmacokinetic parameters, t1/2 and Cltp, as indices of drug elimination ability are discussed.
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