bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced Nonclassical Third‐Order Spatial Intensity Correlations in Three‐Beam Interferences<
Authors: Richter Th.
Published: May 2007

The joint probability of detecting simultaneously three photons at two and three points in the superposition field of three independent plane waves with the same frequency but random phases is calculated and compared with the results of a classical wave theory. Significant differences occur for sufficiently weak fields. We find that the differences between the quantum mechanical and classical predictions concerning the third order intensity correlation functions are more pronounced in a three‐beam than in a two‐beam interference experiment.
Reduction of Higher Derivative Lagrangians
Authors: Schäfer G.
Published: May 2007

Perturbative higher time‐derivative N‐body Lagrangians are treated. By the aid of the redefinition of position variables the higher derivatives are reduced to ordinary derivatives directly on the Lagrangian level. This method clarifies the meaning of using equations and/or constants of motion in higher derivative terms in perturbative Lagrangians.
Relaxation timescales for conformational substates in disordered polymers
Authors: Fernández Ariel
Published: May 2007

We study the kinetics of interconversion of conformational substates in RNA folding by means of a Monte‐Carlo simulation. We establish a scaling law relating the size of the barriers with the length of a random uncorrelated RNA chain. The way the relaxation timescales diverge in the thermodynamic limit coincides with the behavior of nonergodic relaxation timescales for spin glasses.
Local‐moment and itinerant antiferromagnetism in the heavy‐fermion system Ce(Cu1−xNix)2Ge2
Authors: Loidl A. , Krimmel A. , Knorr K. , Sparn G. , Lang M. , Geibel C. , Horn S. , Grauel A. , Steglich F. , Welslau B. , Grewe N. , Nakotte H. , de Boer F. R. , Murani A. P.
Published: May 2007

Elastic and inelastic neutron‐scattering studies on the system Ce(Cu1−xNix)2Ge2 are reported. These measurements are complemented by measurements of the magnetic susceptibility, high‐field magnetization, heat capacity, thermal expansion, electrical resistivity and thermopower. The results reveal an interesting T‐x phase diagram consisting of two different antiferromagnetic phases for x < 0.2 and 0.2 < x < 0.75, respectively, and a heavy‐Fermi‐liquid regime at higher Ni concentrations. The experimental results are interpreted in terms of an alloying‐induced transition from local‐moment to itinerant heavy‐fermion magnetism. Fingerprints of this latter phase are a strongly reduced ordered moment and a short incommensurate ordering wave vector, in accord with theoretical predictions. A surprisingly good agreement between theory and experiment is found for x > 0.5. Further experimental evidence for different types of antiferromagnetic ordering derives from a line‐shape analysis of the quasielastic neutron‐scattering intensity, from magnetization and thermopower experiments.
Magneto‐electrogyration in cubic Sr(NO3)2, Ba(NO3)2, and Pb(NO3)2
Authors: Kaminsky W. , Fahnenstich A. , Haussühl S.
Published: May 2007

The simultaneous application of electric and magnetic fields on single crystals of Sr‐, Ba‐and Pb‐dinitrate yields an additional term to the pure electrogyration and Faraday effect. The symmetric part of the fourth‐rank tensor of this magneto‐electrogyration has been completely determined with the aid of a high‐resolution computer‐aided polarimetric device. In Pb(NO3)2 a maximum magneto‐electrogyration of about 10% of the magnitude of electrogyration is observed when a magnetic field of 1000 kA/m (1.2 Tesla) is applied along [111]. The effects in Sr(NO3)2 and Ba(NO3)2 are much smaller. Index of refraction, electrogyration, Faraday effect, and the new magneto‐electrogyration obey the same sequence: Pb(NO3)2 > Ba(NO3)2 > Sr(NO3)2.
Eigenvalue problem for arbitrary linear combinations of a boson annihilation and creation operator
Authors: Wünsche Alfred
Published: May 2007

The eigenvalue problem for arbitrary linear combinations kα + μα† of a boson annihilation operator α and a boson creation operator α† is solved. It is shown that these operators possess nondegenerate eigenstates to arbitrary complex eigenvalues. The expansion of these eigenstates into the basic set of number states | n >, (n = 0, 1, 2, …), is found. The eigenstates are normalizable and are therefore states of a Hilbert space for | ζ | < 1 with ζ  μ/k and represent in this case squeezed coherent states of minimal uncertainty product. They can be considered as states of a rigged Hilbert space for | ζ | ⩾ 1. A completeness relation for these states is derived that generalizes the completeness relation for the coherent states | α 〉. Furthermore, it is shown that there exists a dual orthogonality in the entire set of these states and a connected dual completeness of the eigenstates on widely arbitrary paths over the complex plane of eigenvalues. This duality goes over into a selfduality of the eigenstates of the hermitian operators kα + k* α† to real eigenvalues. The usually as nonexistent considered eigenstates of the boson creation operator α† are obtained by a limiting procedure. They belong to the most singular case among the considered general class of eigenstates with ζ  μ/k as a parameter.
Resonant Raman scattering from a spin density wave insulator
Authors: Kampf A. P. , Brenig W.
Published: May 2007

We present a calculation of the electronic Raman cross section for the scattering of light across the energy gap of an antiferromagnetic insulator. The antiferromagnet is described in terms of a spin density wave state for the Hubbard model at half filling. We consider the coupling of the light to the current density and the inverse mass tensor on equal footing. A comparison of the cross section for different scattering geometries is given.
Scanning tunneling microscopy with atomic resolution on ReS2 single crystals grown by vapor phase transport
Authors: Friemelt K. , Akari S. , Lux‐Steiner M.‐Ch. , Schill T. , Bucher E. , Dransfeld K.
Published: May 2007

Atomic resolution images of layered transition metal‐dichalcogenide ReS2 single‐crystals (n‐type semiconductor) were obtained using a scanning tunneling microscope with a positive tip. In most cases only unresolved clusters of four rhenium atoms could be seen. Occasional images with higher resolution showed that these bright structures consist of four separated atoms. The symmetry of the imaged atoms is identical to that of the rhenium sublattice but not to that of the sulfur atoms. We conclude therefore that the main contribution to the tunneling current is due to the rhenium atoms, although the sulfur atoms are placed by about 0.15 nm closer to the tip. Thus for our positive bias of the tip the tunneling electrons originate from occupied rhenium states in the valence band of the semiconductor.
Dissociation of doubly charged alkali metal clusters
Authors: López J. M. , Alonso J. A. , Garcias F. , Barranco M.
Published: May 2007

We have studied the competition experimentally observed between fission and neutral atom evaporation, as dissociation channels of excited doubly charged sodium clusters, using the Density Functional Theory and the jellium model. The fission barrier has been obtained from an Extended Thomas‐Fermi calculation including density gradient corrections to the kinetic energy of the electronic cloud. We discuss the influence of the coefficient of the density gradient term on the barrier height.
Localization lengths in disordered Peierls systems
Authors: Wolf M. , Fesser K.
Published: May 2007

We have studied the influence of bond‐ and site‐type impurities on the ground state properties of one‐dimensional Peierls systems. Using a functional integral formalism with both commuting and anticommuting variables we have calculated the averaged Green's function which determines the electronic density of states and localization length (Thouless formula). Some limiting cases can be solved analytically. To apply our model to doped polymers we derive the connection between doping concentration and disorder strengths Dj. For illustration we present the results with parameters appropriate for polyacetylene.
Desorption kinetics and surface diffusion of potassium, rubidium and cesium on a silicon(111)7 × 7‐surface
Authors: Storch R. , Stolz H. , Wassmuth H.‐W.
Published: May 2007

Using pulsed atomic beam technique and a surface ionization ion microscope, the desorption kinetics and the surface diffusion of the alkalis potassium, rubidium and cesium were investigated on a Si(111)7 × 7‐surface at extremely low alkali coverages.

In the temperature range 1120 … 800 K, the mean adsorption lifetime τ(T) = τ0 · exp(Edesi/kT) and the mean diffusion length x(T) ‐ defined in the equilibrium between adsorption, diffusion and desorption ‐ were measured. From these data the diffusion constant D(T) = D0 · exp(‐Ediff/kT) was obtained as D = x−2/τ. For temperatures T ⩽ 750 K, the diffusion constant was calculated from nonstationary alkali concentration profiles using the Boltzmann‐Matano method.

From the temperature dependence of these quantities the parameters of desorption (Edes,i τ0) and surface diffusion (Ediff, D0) for K, Rb and Cs on Si(111) were obtained. The values of Ediff and D0 are comparably high and may be interpreted by non‐localized diffusion according to a model proposed by Bonzel (Surf. Sci. 21 (1970) 45).
On electron screening effects in the low‐energy 3He(d, p)4He data
Authors: Langanke Karlheinz , Lukas Dirk
Published: May 2007

We have calculated the screening effects of the two electrons in the atomic 3He gas target on the low‐energy3He(d, p)4He data. The nuclear degrees of freedom have been described within the microscopic multi‐channel Resonating Group Method, while the two electrons have been treated in Born‐Oppenheimer approximation deriving the exact screening potential within the Path Integral Monte Carlo method. Our model underestimates the observed screening effects implying the need to consider the coupling of nuclear and electronic degrees of freedom.
Tunneling dynamics in stationary field emission
Authors: Gottlieb B. , Kleber M.
Published: May 2007

Stationary three‐dimensional field emission out of an ultrathin quantum well is analyzed in terms of the semiclassical Hamilton‐Jacobi theory. We compare the spatial quantum distribution of the tunneling electrons with the corresponding results obtained from real‐time tunneling trajectories. The classical‐limit trajectory method reproduces the exact quantum distribution for weak external fields. The Büttiker‐Landauer expression for the barrier crossing velocity is confirmed.
Localization and interaction in two dimensions: The disordered Tomonaga model
Authors: Fastenrath Ulrich
Published: May 2007

The effect of electron‐electron interactions on the localization behavior of two‐dimensional disordered systems is investigated in the framework of a generalized version of Tomonaga's model. The main result is a closed expression for the dynamical conductivity which allows to predict the critical electron concentration below which localization sets in as a function of microscopic parameters only. Experimental verification is possible, although difficult.
The one‐dimensional 1/4‐filled Hubbard model with alternating interactions
Authors: Japaridze G. , Khomskii D. , Müller‐Hartmann E.
Published: May 2007

The one‐dimensional Hubbard model with different on‐site interaction on the even (Ua) and odd (Ub) sites is considered within the framework of the weak coupling approach. In the case of a 1/4‐filled band the dynamical nonequivalence of sites leads to the appearance of Umklapp processes in the system and to the dynamical generation of a commensurability gap in the charge excitation spectrum for Ua ≠ Ub and Ua>0 or Ub>0. Depending on the relation between the bare coupling constants the system shows four different regimes of behaviour in the infrared limit corresponding to normal metal, nonmagnetic insulator, antiferromagnetic insulator and superconducting states. The extended model including interaction between particles on nearest and next‐nearest neighbour sites is also considered.
Near field optics and light confinement
Authors: Courjon D. , Bainier C. , Girard C. , Vigoureux J. M.
Published: May 2007

By exploring the surface of an illuminated object at a very short distance by means of a subwavelength detector, it is possible to reconstruct images whose resolution is beyond the diffraction limit. This opportunity due to the properties of near fields can be explained in terms of non radiating field detection. Such a detection is the basis of near field microscopy. In this communication emphasis will be put on some fundamental aspects of the new concept of non radiative optics such as the relation between Rayleigh criterion and Heisenberg principle and the notion of light confinement. Some proposals of non radiative transfers will be evoked.
Spin dynamics for 2d Heisenberg antiferromagnets with combined easy‐plane and Dzyaloshinsky interactions
Authors: Völkel A. R. , Mertens F. G. , Bishop A. R. , Wysin G. M.
Published: May 2007

We investigate the spin dynamics of the classical two‐dimensional easy‐plane Heisenberg antiferromagnet with an additional Dzyaloshinsky interaction, which serves as a simple model for Langmuir‐Blodgett films of Mn (C18H35O2)2. By mapping the system onto a pure easy‐plane model we discuss the corresponding spin wave and vortex dynamics. The additional Dzyaloshinsky interaction forces all spins to cant in a certain direction, which is the same for neighboring spins on different sublattices. This canting causes the presence of a second spin wave peak in the dynamical in‐plane correlation function below the Kosterlitz‐Thouless transition temperature TKT and a second vortex central peak above TKT. Using a vortex gas approach we explicitly calculate the contribution of the free vortices to several dynamical correlation functions. These results are compared to a combined Monte Carlo‐Molecular Dynamics simulation on square lattices with different sizes. We also discuss the relevance of this simple model for describing the spin dynamics of Mn (C18H35O2)2.
Far‐infrared spectrum and the soft mode of ferroelectric betaine phosphite
Authors: Koch G. , Happ H.
Published: May 2007

The far‐infrared reflection spectra of betaine phosphite single crystals in the three crystallographic directions are investigated in the range from 5 to 600 cm−1 at temperatures between 203 and 323 K using a dispersive Fourier spectrometer. The dielectric function is evaluated from the complex amplitude reflection coefficient measured. In the spectrum polarized along the ferroelectric direction a soft mode of relaxation type is observed which accounts for a large part of the relevant static dielectric constant at Tc = 210 K. Among the oscillator modes, which generally exhibit normal temperature dependence, there is a heavily overdamped mode at 58 cm−1, polarized along the crystallographia a1 axis, with anomalous damping behaviour. The damping constant decreases nearly linearly with temperature up to 323 K which is close to T = 355 K where a second phase transition is known to exist.
δ‐function perturbations and boundary problems by path integration
Authors: Grosche C.
Published: May 2007

A wide class of boundary problems in quantum mechanics is discussed by using path integrals. This includes motion in half‐spaces, radial boxes, rings, and moving boundaries. As a preparation the formalism for the incorporation of δ‐function perturbations is outlined, which includes the discussion of multiple δ‐function perturbations, δ‐function perturbations along perpendicular lines and planes, and moving δ‐function perturbations. The limiting process, where the strength of the δ‐function perturbations gets infinitely repulsive, has the effect of producing impenetrable walls at the locations of the δ‐function perturbations, i.e. a consistent description for boundary problems with Dirichlet boundary‐condition emerges. Several examples illustrate the formalism.
Discrete resistance fluctuations in pressure‐type point contacts
Authors: Kokkedee J. A. , Thier C. , Jansen A. G. M.
Published: May 2007

In high ohmic pressure‐type metallic point contacts (resistance range 50 Ω to 3 k Ω) the point‐contact resistance is observed to switch randomly between two or more discrete levels. This effect can be explained by the motion or reorientation of single defects, thereby changing their cross section for electron scattering. From the temperature‐ and voltage‐dependence of the characteristic times of the fluctuations, electromigration parameters for a defect in silver are extracted.
Quantum trajectories for nonlinear optical processes
Authors: Goetsch Peter , Graham Robert
Published: May 2007

The stochastic Schrödinger equation, a novel method for describing the dissipative dynamics of open quantum systems interacting with their environment, is applied to some nonlinear optical processes, namely nonlinear absorption and second‐harmonic generation, the latter also in the range of instabilities and classical chaotic behaviour. Where possible the results are compared with numerical simulations of the positive P representation, which in some cases are found to give unreliable results.
Flow‐equations for Hamiltonians
Authors: Wegner Franz
Published: May 2007

Flow‐equations are introduced in order to bring Hamiltonians closer to diagonalization. It is characteristic for these equations that matrix‐elements between degenerate or almost degenerate states do not decay or decay very slowly. In order to understand different types of physical systems in this framework it is probably necessary to classify various types of these degeneracies and to investigate the corresponding physical behavior.

In general these equations generate many‐particle interactions. However, for an n‐orbital model the equations for the two‐particle interaction are closed in the limit of large n. Solutions of these equations for a one‐dimensional model are considered. There appear convergency problems, which are removed, if instead of diagonalization only a block‐diagonalization into blocks with the same number of quasiparticles is performed.
Electrons with correlated hopping interaction in one dimension
Authors: Japaridze G. , Müller‐Hartmann E.
Published: May 2007

The 1D system of correlated electrons characterized in addition to the usual on‐site (U) and nearest‐neighbour (V) repulsion by a correlated‐hopping term (t*) is considered. The ground state phase diagram is studied within the framework of the weak‐coupling continuum‐limit approach. At filling v the effective interaction originating from the correlated‐hopping term which appears in the continuum‐limit theory is given by t* cos (πv). Being repulsive for v < 1/2 and attractive for v > 1/2, this interaction leads to a characteristic band‐filling dependence of the phase diagram of the system. For v ≠ 1/2, depending on the relation between the bare values of the coupling constants (U, V, t* cos (π v)) and, hence, on the band‐filling, the system shows three different phases in the infrared limit: a Luttinger metal, a nonmagnetic metal and a singlet superconducting phase. For v = 1/2, the correlated‐hopping interaction is dynamically trivial, leading only to a renormalization of the oneelectron hopping amplitude and the phase diagram of the model coincides with that of the extended Hubbard model.
Fulde‐Ferrell‐Larkin‐Ovchinnikov state in layered superconductors
Authors: Burkhardt H. , Rainer D.
Published: May 2007

The phase diagram of a layered superconductor in a large parallel magnetic field is calculated. This includes a calculation of the lower critical field beyond which the superconductor is in the FFLO‐state and possesses a spatially modulated order parameter and spin polarization. The order parameter, spin polarization, free‐energy density, and phase boundaries of this unconventional superconducting phase are evaluated numerically in the complete B–T plane. The analysis suggests that the transition at the lower critical field is of second order, and not of first order, as previously assumed. The order parameter of the FFLO‐state merges continuously into the uniform superconducting state.
On the limitation imposed by gravity on measurements of the critical viscosity of a pure fluid
Authors: Ferrell Richard A. , Moldover Michael R.
Published: May 2007

Measurements of the viscosity of a fluid by means of a parallel plate torsional oscillator are conventionally limited to a plate separation that is much larger than the viscous penetration depth of the fluid contained between the plates. Here we demonstrate that, in principle, useful measurements can be carried out in the opposite regime where the thickness is smaller than the penetration depth. An alternative method, described in the last part of this paper, for alleviating the restriction imposed by the density stratification that results from the earth's gravity, is to use electrostriction, rather than the inertial force, to drive the fluid between the plates.
Path integrals for two‐ and three‐dimensional δ‐function perturbations
Authors: Grosche Christian
Published: May 2007

The incorporation of two‐ and three‐dimensional Δ‐function perturbations into the path integral formalism is discussed. Contrary to the one‐dimensional case, a regularization prescription is needed due to the divergence of the Green function corresponding to a potential V, G(v) (x,y;E) (x, y ϵ ℝ2, ℝ3) for x→y. The known procedure to define proper self‐adjoint extensions for Hamiltonians with point‐interactions can be exploited to define the incorporation of δ‐function perturbations in the path integral. Several examples illustrate the formalism.
Spheroidally deformed sodium clusters in the selfconsistent jellium model
Authors: Hirschmann Th. , Brack M. , Meyer J.
Published: May 2007

We present the first systematic study of potential energy curves and prolate‐oblate shape transitions of sodium clusters with 8 < N < 40 atoms. The Kohn‐Sham equations are solved in the local density approximation for the jellium model with spheroidal deformations. The ionic background density is taken to have a diffuse surface of Woods‐Saxon type. The quadrupole and hexadecupole moments of the electron and jellium densities are investigated, revealing a strong hexadecupole dependence for selected clusters. Collective dipole resonances are described in the simple surface plasmon model. Shape transitions are found to occur at particle numbers 12–14 (prolate‐oblate), 18–20–22 (oblate‐spherical‐prolate) and 30–32 (prolate‐oblate), which are in good agreement with experimental results; triaxiality is predicted for Na‐36. Comparing our results with those of molecular dynamics calculations, we confirm the scheme of Kohn‐Sham levels and the gross behaviour of potentials and densities.
Event‐enhanced quantum theory and piecewise deterministic dynamics
Authors: Blanchard Ph. , Jadczyk A.
Published: May 2007

The standard formalism of quantum theory is enhanced and definite meaning is given to the concepts of experiment, measurement and event. Within this approach one obtains a uniquely defined piecewise deterministic algorithm generating quantum jumps, classical events and histories of single quantum objects. The wave‐function Monte Carlo method of Quantum Optics is generalized and promoted to the level of a fundamental process generating all the real events in Nature. The already worked out applications include SQUID‐tank model and generalized cloud chamber model with GRW spontaneous localization as a particular case. Differences between the present approach and quantum measurement theories based on environment‐induced master equations are stressed. Questions: what is classical, what is time, and what observers are addressed. Possible applications of the new approach are suggested, among them connection between the stochastic commutative geometry and Connes' noncommutative formulation of the Standard Model, as well as potential applications to the theory and practice of quantum computers.
Physical properties of dynamic force microscopies in contact and noncontact operation
Authors: Krüger D. , Anczykowski B. , Fuchs H.
Published: May 2007

In the field of Scanning Force Microscopy several dynamical contact and noncontact modes have been introduced increasing the range of detectable surface and interface properties, and allowing to detect material properties such as elasticity and mass density on the nanometer scale. A detailed understanding of tip/surface interactions and the dynamic processes involved is required to understand the origin of a material contrast using these techniques. Here a general method to solve the equation of motion of a vibrating SFM cantilever/tip system in an external force field is presented. Contact modes as well as intermittent contact modes are discussed using a single set of equations describing the cantilever/tip motion, and by varying the size of amplitudes of the vibrating cantilever/tip system. To quantitatively describe the oscillation behavior of the SFM cantilever at large amplitudes the computer simulations are based on the MYD/BHW model providing a realistic contact model with respect to the contact area, the size of the contact forces as well as the transition from repulsive to attractive forces. The results are compared with the experiment and with different approaches based on analytical and numerical models.
Discrete chaotic cryptography
Authors: Kotulski Zbigniew , Szczepański Janusz
Published: May 2007

In the paper we propose a new method of constructing cryptosystems utilising a nonpredictability property of discrete chaotic systems. We formulate the requirements for such systems to assure their safety. We also give examples of practical realisation of chaotic cryptosystems, using a generalisation of the method presented in [7]. The proposed algorithm of encryption and decryption is based on multiple iteration of a certain dynamical chaotic system. We assume that some part of the initial condition is a plain message. As the secret key we assume the system parameter(s) and additionally another part of the initial condition.
On the problem of divergences in Quantumelectrodynamics
Authors: Sünkel W. , Wildermuth K.
Published: May 2007

In a first step we have tried to show that very probably in Quantumelectrodynamics (QED) due to vacuum polarization effects the original bare charges of electrons and positrons are smeared out so much that their original divergent energy distances from the vacuum energy become finite. Furthermore, we have sketched how one has to generalize the calculations to refine the considerations presented in this paper.
The Vlasov equation for Coulomb systems and the Husimi picture
Authors: Domps A. , L'Eplattenier P. , Reinhard P. G. , Suraud E.
Published: May 2007

We explore the validity of the Vlasov equation as a semi‐classical approximation of time‐dependent Hartree‐Fock and time‐dependent LDA theories. We discuss the h → 0 limit for the propagation of quantal wavefunctions in terms of classical densities. The h → 0 limit is studied formally by means of its Wigner and Husimi phase‐space representations. We consider an application to the valence electron cloud of metal clusters and show a comparison between quantal and Vlasov dynamics in this case.
Differences between women and men in surgical treatment and case fatality rates for ruptured aortic abdominal aneurysm in England
Authors: Filipovic M , Seagroatt V , Goldacre M J
Published: May 2007

Background

Differences between women and men in treatment and outcome after admission with a ruptured abdominal aortic aneurysm (AAA) in England were studied.

Methods

Routinely collected data in Hospital Episode Statistics, linked to death records, for emergency admissions for ruptured AAA in England were analysed. The percentage of patients who underwent surgical repair was calculated, together with 30-day case fatality rates and age-adjusted odds ratios (ORs), comparing women with men.

Results

A total of 2463 women and 7615 men were admitted with a primary diagnosis of ruptured AAA (mean age 79·8 and 74·9 years respectively); 39·6 per cent of women and 66·4 per cent of men underwent surgical repair (OR 0·47 (95 per cent confidence interval 0·42 to 0·52)). Overall, 75·6 per cent of women and 61·7 per cent of men died within 30 days of admission (OR 1·36 (1·22 to 1·52)). The death rate for women and men who had surgery was similar (OR 1·01 (0·88 to 1·17)); when no operation was performed the mortality rate was higher in women, but not significantly so (OR 1·14 (0·91 to 1·42)).

Conclusion

Women with a ruptured AAA were less likely to be treated surgically than men, and their overall mortality rate was higher. Lower rates of surgery in women than in men may contribute to the higher mortality in women, but other explanations are possible.
Paired exchange programmes can expand the live kidney donor pool
Authors: Mahendran A O , Veitch P S
Published: May 2007

Background

Kidney paired donation (KPD) is an exchange of organs between two live donors, who are otherwise ABO incompatible or cross-match positive, and their intended recipients. The outcome is the generation of compatible transplants conferring an improvement in quality of life and longevity.

Methods

Medline was searched for articles on KPD using a combination of keywords. Publications focusing on protocols and policy, mathematical modelling, ethical controversies, and legal and logistical barriers were identified.

Results

Many are precluded from transplantation because of incompatibilities with their intended donors. KPD has the potential to increase the rate of transplantation by facilitating exchange transplants between otherwise incompatible donor–recipient couples. Ethical controversies surrounding paired donation include confidentiality, conditionality of donation, synchronicity of operations and the possibility of disadvantaging blood group O recipients. Logistical barriers hampering KPD programmes involve the location of donor surgery and organ transport.

Conclusion

Paired donation may expand the living donor pool by providing an alternative successful strategy for incompatible donor–recipient couples. Its widespread implementation will depend on resolving ethical and logistical constraints.
Zur Konstitution des Samandarins
Authors: Schöpf Clemens , Blödorn Hans‐Karl , Klein Dieter , Seitz Georg
Published: May 2007

Bei der Umsetzung von Samandarin mit Phenylmagnesiumbromid wurde neben dem Phenylsamandiol das stereoisomere Epiphenylsamandiol erhalten. Der Abbau des Phenylsamandiols und Phenylsamandions mit Blei(IV)‐acetat und die Untersuchung der dabei entstehenden Spaltstücke zeigt, daß die Samandiole der Teilformel XIIIa entsprechen und Samandarin demnach ein Oxazolidin der Formel XVI ist.
Zwei desmotrope Formen des 2‐Benzoyloxy‐benzylalkohols, ein neuer Fall von Ring‐Ketten‐Tautomerie
Authors: Helferich Burckhardt , Liesen Hermine
Published: May 2007

Die beiden in der Literatur beschriebenen Formen des Monobenzoyl‐saligenins werden als Desmotrop‐tautomere erkannt und charakterisiert.
Über die Einwirkung von Schwefel auf aromatische Triamine und Diaminophenole, I. Mitteilung
Authors: Jaeckel Bernhard
Published: May 2007

Es wird eine Reihe organischer Schwefelverbindungen von aromatischen Triaminen und Diaminophenolen beschrieben, welche durch Einwirkung von Schwefel auf Lösungen dieser Aminoverbindungen als Mercaptane, Disulfide, Trisulfide sowie als weitere Reaktionsprodukte unmittelbar in reiner krystallisierter Form erhalten werden.
Zur Kenntnis der Enolformen von β‐Dicarbonylverbindungen und der Katalyse von Diazomethan‐Methylierungen
Authors: Eistert Bernd , Arndt Fritz , Loewe Lotte , Ayea Ertugrul
Published: May 2007

Ätherische Lösungen von Acetylaceton reagieren mit Diazomethan bei Abwesenheit von Hydroxylverbindungen nur sehr langsam und unvollständig unter Bildung von cis‐Enoläther. Siedesteinchen oder Zusatz von wenig Methanol katalysieren die Umsetzung, wobei ebenfalls cis‐Enoläther entsteht. Methanolische Lösungen von Acetylaceton verbrauchen Diazomethan rasch, wobei nebeneinander cis‐ und trans‐Enoläther und „Polymethylene”︁ entstehen. Der Chemismus dieser Katalysen sowie die Beziehungen zwischen den verschiedenen Molekelarten β‐Diketon, cis‐Enol‐Chelat, cis‐ und trans‐Enol‐Solvaten und Halbacetalen werden erörtert.
Über die Konstitution des Triacetsäure‐lactons und seiner Derivate
Authors: Arndt Fritz , Avan Sabahat
Published: May 2007

Triacetsäure‐lacton zeigt α, γ‐Pyron‐Tautomerie; der feste Stoff ist 4‐Oxy‐6‐methyl‐α‐pyron, sein Methyl‐Derivat dagegen 2‐Methoxy‐6‐methyl‐γ‐pyron. Entsprechendes gilt von dem bei Bromierung ausschließlich entstehenden 3‐Brom‐Derivat und dem bei Nitrierung ausschließlich entstehenden 3‐Nitro‐Derivat.
Notiz über eine Tetrazoliumverbindung der Pyrimidinreihe
Authors: Ludolphy Erich
Published: May 2007

Ausgehend vom Phenylhydrazon des Uracil‐4‐aldehyds wird über das entsprechende Formazan die Tetrazoliumverbindung dargestellt. Bei der Einwirkung auf tierische Zellen zeigt diese Verbindung keine Besonderheiten und Vorteile hinsichtlich spezifischer Anfärbung, Farbtiefe und Eindringungsvermögen gegenüber den bisher verwendeten Verbindungen.
Über die Umsetzung von Alkanen mit Phosphortrichlorid und Sauerstoff
Authors: Graf Roderich
Published: May 2007

Es wurde gefunden, daß durch Einwirkung von Sauerstoff auf Gemische aus einem gesättigten aliphatischen Kohlenwasserstoff und Phosphortrichlorid neben Chlorwasserstoff und Phosphoroxychlorid in direkter Substitutionsreaktion Alkan‐phosphonsäure‐dichloride der Konstitution Alkyl‐POCl2 entstehen. Beim äthan entsteht neben äthan‐phosphonsäure‐dichlorid das Dichlorid des Phosphorsäure‐monoäthylesters. Die stark exotherme, allgemein anwendbare Reaktion verläuft im Dunkeln und selbst bei—80° noch mit sehr erheblicher Umsetzungsgeschwindigkeit. Es wird eine Deutung des Reaktionsverlaufes gegeben und auf die Umsetzungsmöglichkeiten der neuerschlossenen Körperklasse hingewiesen.
Über stereoisomere 2‐Acyl‐pyridin‐phenylhydradzone und die Darstellung von 8‐Aza‐indazolium‐Salzen
Authors: Kuhn Richard , Münzing Wolfgang
Published: May 2007

Das Phenylhydrazon des 2‐Benzoyl‐ pyridins kann in Nadeln vom Schmp. 77° und in sechsseitigen Blättchen vom Schmp. 143° erhalten werden. Nur die höher schmelzende Verbindung (syn‐Form) läßt sich durch Bleitetraacetat unter Ringschluß in 8‐Aza‐indazolium‐ Salze verwandeln, aus denen reduktiv unter Ringöffnung das Phenylhydrazon zurückgebildet wird. Entsprechende Ringschluß‐Reaktionen zu weiteren Aza‐ indazolium‐Salzen gelangen mit den Phenyl‐hydrazonen des 2‐Acetyl‐pyridins und 2‐Acetyl‐chinolins.
Kohlenwasserstoffe mit intercyclischen Doppelbindungen
Authors: Criegee Rudolf , Vogel Emanuel , Höger Herwig
Published: May 2007

Die Darstellung von drei Vertretern einer neuen Klasse von Olefinen wird beschrieben.
p‐Oxy‐styrol‐β‐d‐glucosid
Authors: Helferich Burckhardt , Höfmann Hans‐Jürgen
Published: May 2007

Es wird die Synthese des monomeren p‐Oxy‐styrol‐β‐d‐glucosids, seines Tetraacetats und deren Polymerisation beschrieben.
Über flüchtige organische Uranverbindungen
Authors: Albers Henry , Deutsch Martin , Krastinat Walter , von Osten Horst
Published: May 2007

Zur Prüfung der Flüchtigkeits‐ und Löslichkeits‐Eigenschaften organischer Uran (IV)‐ Verbindungen werden Alkoholate, 1.3‐Diketon‐Komplexe und Komplexe Alkoxoverbindungen dargestellt. Das Uran (IV)‐aluminiumisopropylat zeichnet sich durch eine relativ hohe Flüchtigkeit und Beständigkeit aus.
Zum Mechanismus der Reaktionen von Vitamin A und D. bzw. β‐Carotin mit metallhalogeniden, insbesondere Antimonchloriden, I. Mitteil.: Zusammensetzung einiger Halogenidkomplexe
Authors: Brüggemann Johanners , Krauss Walther , Tiews Jürgen
Published: May 2007

Die Vitamine A und d sowie β‐Carotin reagieren nicht, wie bisher angenommen, mit Antimontrichlorid unter Komplexbildung, sondern nur mit Antimonpentachlorid. Die stöchiometrischen Bindungsverhältnisse ergaben sich zu: 1 mol. Vitamin A oder D: 1 Mol. SbCl5 bzw. 1 Mol. β‐Carotin: Moll. SbCl5 Im handelsüblichen Antimontrichlorid sind etwa 006 Gew. % Antimonpentachlorid enthalten. Die molaren Extinktionskoeffizienten für Vitamin a und β‐Carotin bei 610 mμ und für Vitamin d bei 500 mμ wurden bestimmt. Bei Vitamin D ergibt sich, daß der i. Ggw. von Acetylchlorid bestimmte Koeffizient etwa 3 mal höher liegt als ohne Acetylchlorid. Es muß auf das Vorliegen von 2 verschiedenen Verbindungen geschlossen werden, indem vermutlich CH3CO⊕ mit Vitamin D reagiert und erst diese Verbindung den entsprechenden Komplex mit höheren Extinktions‐koeffizienten bildet. Allgemein sind nur solche Metallhalogenide zur Komplexbildung mit Vitamin A oder D geeignet, nach deren Koordinationszahl nur 1 Vitamin‐Molekül zur Ausbildung des Komplexes notwendig ist. Eisen (III)‐chlorid reagiert in kleinsten Mengen, wobei sich Farbzustände ausbilden deren Extinktionsmaxima den gleichen Schwerpunkt haben und deren Extinktionskoeffizienten ebenso mit dem der Antimonopentachlorid‐Verbindungen übereinstimmen wie die stöchiometrischen Bindungsverhältnisse. Arsen (III)‐chlorid kann nur nach vorheriger Überführung im Arsen (V)‐chlorid zur Reaktion gebracht werden.
Das an der Verholzung beteiligte Fermentsystem
Authors: Freudenberg Karl , Reznik Hans , Boesenberg Heinz , Rasenack Dietrich
Published: May 2007

An der Verholzung ist eine streng lokalisierte β‐Glucosidase beteiligt, die in Schnitten mit Indican nachgewiesen wird, das bei der Spaltung über Indoxyl Indigo bildet. Die dehydrogenierenden und oxydierenden Fermente im Gebiet des Cambiums sind wie die bisher verwendete Pilzdehydrogenase imstande, aus Coniferylalkohol ligninartige Dehydrierungspolymerisate zu bilden, Eine Deutung des Verholzungsvorganges wird gegeben.
Die Frage nach der physiologischen Funktion der Katalase im menschlichen Organismus; Notiz über die Entdeckung einer Konstitutionsanomalie „Anenzymia catalasea”︁
Authors: Kaziro Koozoo , Kikuchi Goroo , Nakamura Heizoo , Yoshiya Masaru
Published: May 2007

Ein neuer, durch das Fehlen des Ferments Katalase im Blut gekennzeichneter Typus einer Konstitutionsanomalie des Menschen wurde zuerst von Takahara und alsdann von Yoshiya aufgefunden. Unsere Untersuchungen ergaben, Daß bei dieser Anomalie, für die wir die Bezeichnung „Anenzymia catalasea”︁ vorschlagen, die Katalase nicht nur im Blut, sondern auch in den Geweben fehlt. Die Anomalie steht in engem Zusammenhang mit einer Erkrankung des Stützgewebes der Zähne, die vorläufig als „Takaharasche Krankheit”︁ bezeichnet werden soll. Die mit der Anomalie behafteten Personen sind aber im übrigen gesund und leiden an keiner Stoffwechselstörung, was physiologisch und fermentchemisch von großem Interesse ist. Angesichts der Tatsache, daß die Katalase im normalen Stoffwechsel des menschlichen Organismus offenbar entbehrlich ist, wird das. alte Problem der physiologischen Funktion der Katalase erneut diskutiert. Es wird ferner versucht, eine Erklärung für die Pathogenese der Takaharaschen Krankheit zu finden.
Purinoxydierende Fermente aus Schimmelpilzen, III. Mitteil.: Zur Kenntnis der Alternaria‐ Uricasen
Authors: Franke Wilhelm , Taha Ezz‐Eldin M.
Published: May 2007

Während die Uricase aller bisher untersuchten Alternaria‐Arten und ‐Stämme Harnsäure unter Aufnahme eines Atoms Sauerstoff zu Allantoin oxydiert, vermittelt das Ferment eines ägyptischen Alternaria tenuis ‐ Stamms (VII)1a) als einziges die doppelte Sauerstoffaufnahme. Als Zwischenprodukt läßt sich auch in diesem Falle Allantoin nachweisen, das unter NH3‐Abspaltung höchstwahrscheinlich zu Oxonsäure (Allantoxansäure) weiter oxydiert wird.
Eine neue Methode zur Darstellung langkettiger Carbonsäuren, III. Mitteil.: Darstellung einiger ungesättigter und phenylsubstituierter Carbonsäuren
Authors: Stetter Hermann , Dieriehs Wolfgang
Published: May 2007

Durch Kondensation des Dihydroresorcins mit Allylbromid, 1‐Brom‐cyclohexen‐(2), 1.4‐Dibrom‐buten‐(2) und Benzylehlorid wurden C‐alkylierte Dihydroresorcine dargestellt. Die Säurespaltung und Reduktion dieser substituierten Dihydroresorcine ergab die entsprechenden ungesättigten und phenylsubstituierten langkettigen Carbonsäuren. Durch Alkylierung von 1‐Benzyl‐cyclohexandion‐(2.6) mit Methyljodid konnte 1‐Methyl‐1‐benzyl‐cyclohexandion‐(2.6) erhalten werden. Diese Verbindung erleidet in Methanol eine Alkoholyse unter Ringöffnung zum 4‐Oxo‐5‐methyl‐6‐phenyl‐hexan‐carbonsäure‐(1)‐methylester, aus dem durch Verseifung und Reduktion 5‐Methyl‐6‐phenyl‐hexan‐carbonsäure ‐(1) erhalten werden konnte.
Über das Syringaresinol, ein Dehydrierungsprodukt des Sinapinalkohols
Authors: Freudenberg Karl , Dietrich Heinz
Published: May 2007

Sinapinalkohol (II) wird durch eine Dehydrogenase der Mandeln in das Syringaresinol verwandelt, dessen Konstitution ermittelt wurde (V). Pinoresinol (IV) gibt mit Pilzredoxase ein Dehydrierungspolymerisat.
Butadien‐Derivate aus Cyclooctatetraen
Authors: Criegee Rudolf , Hörauf Werner , Schellenberg Wolf Dietrich
Published: May 2007

Die Abbauprodukte des Cyclooctatetraens, denen man bisher die Konstitution von Dichlor‐ und Diacetoxy‐cyclobutenen zuschrieb, sind in Wirklichkeit 1.4‐disubstitutierte Butadiene.
Darstellung von Polycarbonsäuren, I. Mitteil.: Darstellung der Äthan‐1.1.2.2‐tetraessigsäure
Authors: Runge Franz , Goldann Karl
Published: May 2007

2.6‐ und 2.7‐Dioxy‐dekahydronaphthalin wurden zu Äthan‐1.1.2.2‐tetraessigsäure oxydiert. Die neue Carbonsäure wurde in ihrer Konstitution festgelegt und durch einige Derivate charakterisiert.
Notiz über die Darstellung der Propiolsäure
Authors: Wolf Viktor
Published: May 2007

Die Darstellung der Propiolsäure aus Propargylalkohol durch Oxydation mit Chromtrioxyd in schwefelsaurer Lösung wird beschrieben.
Über Acetale des Acetessigaldehyds
Authors: Franke Walter , Kraft Richard , Tietjen Diedrich , Weber Heinrich
Published: May 2007

Diacetylen lagert im alkalischen Medium 1 bzw. 2 Moll. Alkohol an zu Methoxybutenin und Butinalacetal, aus denen Acetessig‐aldehyd‐1.3‐bis‐dimethylacetal, Methoxy‐crotonaldehydacetal, Acetessigaldehyd‐dimethylacetal und Methoxybutenon gewonnen werden.
Über Bis‐[pyridyl]‐ketone. Bemerkung zur Abhandlung von Wilhelm Mathes und Walter Sauermilch: Notiz über Bis‐[α‐pyridyl]‐ketone
Authors: Wibaut J. P.
Published: May 2007

Es wird auf die vom Verfasser in den Jahren 1950 und 1951 durchgeführten Synthesen von Bis‐[pyridyl]‐ketonen hingewiesen.
Die Methylol‐Verbindungen des m‐Kresols
Authors: Reese Johannes
Published: May 2007

Die bei alkalischer Kondensation von Formaldehyd mit m‐Kresol als Primärprodukte der Verharzung entstehenden Methylol‐Verbindungen werden teils isoliert, teils werden mögliche Reaktionsprodukte auf andere Weise eindeutig synthetisiert. Die zwischen Methyl‐ und Oxygruppe befindliche ortho‐(2)‐Stellung des m‐Kresols erweist sich als weniger reaktionsfähig als die ortho‐(6)‐Stellung.
Über substituierte 6‐Aminobenzisoxazole und ihre Umwandlung in Abkömmlinge des 4‐Aminosalicylsäure‐nitrils (PAS‐Nitril)
Authors: Ried Walter , Gutjahr Heinz
Published: May 2007

Es wird die Synthese des 6‐Amino‐benzisoxazol‐carbonsäure‐(3)‐methylesters und einiger Derivate mitgeteilt. Durch Aufspaltung des Isoxazol‐Ringes werden die erhaltenen Verbindungen in Abkömmlinge des 4‐Amino‐salicylsäure‐nitrils (PAS‐Nitril) übergeführt.
Über Actinomycetenfarbstoffe, II. Mitteil.: Limocrocin, ein gelber Actinomycetenfarbstoff
Authors: Brockmann Hans , Grothe Gerhard
Published: May 2007

Aus der Kulturlösung von Streptomyces limosus wurde ein gelber, kristallisierter, stickstoffhaltiger Farbstoff, das Limocrocin, isoliert. Seine katalytische Hydrierung lieferte eine farblose, kristallisierte Verbindung C26H40O6N2.
Photochemie des Triphenylformazans
Authors: Kuhn Richard , Weitz Hans Martin
Published: May 2007

Wenn eine rote Lösung von Triphenylformazan in Toluol durch Belichten gelb und anschließend im Dunkeln wieder rot wird, spielt sich ein Kreisprozeß ab, der aus mindestens 3 Lichtreaktionen (hv) und mindestens 3 Dunkelreaktionen (D) besteht. Die sterischen Umlagerungen, die sich dabei an den ‐NN‐ und >CN‐Gruppierungen abspielen, werden folgendermaßen gedeutet:
magnified image

Es war möglich, die Halbwertszeiten der 2 langsameren Dunkelreaktionen und, aus deren Temperaturkoeffizienten, auch die Aktivierungsenergien in kgcal/Mol zu ermitteln. Die aus der Intensitäts‐Abhängigkeit der Quantenausbeuten mathematisch vorausgesagte, im Dunkeln rasch zurückreagierende Zwischenstufe der Rot→Gelb‐Umlagerung ist vermutlich die sehr kurzlebige cis‐syn‐Form. Die beiden anti‐Formen sind gelb gefärbt.
Über γ‐Pyrone und γ‐Pyridone, I. Mitteil.: Zur Konstitution der Oxy‐γ‐pyrone und Oxy‐γ‐pyridone
Authors: Heyns Kurt , Vogelsang Gerhard
Published: May 2007

Kojisäure‐monomethyläther läßt sich durch Oxydation mit Salpetersäure oder Luftsauerstoff i. Ggw. eines Platin‐Katalysators in Komensäure‐methyläther überführen. Auf einem neuen Wege wird die 5‐Stellung der Oxy‐Gruppe in den aus Mekonsäure und Kojisäure erhaltenen Pyron‐ und Pyridonderivaten bestätigt und damit eine neuerdings vertretene abweichende Auffassung widerlegt.
Über Alkalimetallverbindungen der 2.3.4.6‐Tetramethyl‐d‐glucopyranose und 1.3.4.6‐Tetramethyl‐d‐fructofuranose und ihre Verwendung zu Glykosid‐ und Disaccharid‐Synthesen
Authors: Bredereck Hellmut , Hambsch Erich
Published: May 2007

In der Tetramethyl‐d‐glucose und Tetramethyl‐d‐fructose konnte der Wasserstoff des Lactolhydroxyls durch Alkalimetall ersetzt werden. Konfiguration und Reaktionsfähigkeit der Alkalimetallverbindungen wurden durch Umsetzung mit Methyljodid und Dimethylsulfat, die zu den entsprechenden Glykosiden führte, ermittelt. Die Kalium‐Verbindung der 2.3.4.6‐Tetramethyl‐d‐glucose reagierte mit α‐1‐Tosyl‐, α‐1‐Brom‐ und β‐1‐Chlor‐2.3.4.6‐Tetramethyl‐d‐glucose unter Bildung von Disacchariden des Trehalosetypus.
Über 1.2.4‐Thiodiazole, I. Mitteil.): Darstellung und Eigenschaften der 5‐Amino‐1.2.4‐thiodiazole (Mitbearbeitet von Kurt Wember und Gerhard Worsch)
Authors: Goerdeler Joachim
Published: May 2007

Es wird eine allgemeine Methode zur Darstellung der 5‐Amino‐1.2.4‐thiodiazole beschrieben, die sich auf die Umsetzung von N‐Halogen‐amidinen mit Rhodaniden gründet. Auf die Eigenschaften dieser Stoffe, einige Derivate ‐ darunter die Sulfanilamide ‐ und Abbaureaktionen wird näher eingegangen.
Über eine Synthese partiell hydrierter Naphthalin‐dicarbonsäuren‐(1.2) und Naphthalin‐monocarbonsäuren‐(1)
Authors: Alder Kurt , Triebeneck Kurt
Published: May 2007

Die Addition von Maleinsäure‐anhydrid an α‐Brom‐styrol verläuft unter Abspaltung von Bromwasserstoff und führt in glatter Reaktion zur 1.2‐Dihydro‐naphthalin‐dicarbonsäure‐(1.2), die sich successive in die isomeren 1.4‐ und 3.4‐Dihydro‐säuren umlagern läßt. In der Literatur beschriebene und auf anderen Wegen gewonnene Präparate werden in ihrer Struktur bestätigt oder berichtigt.

Durch Einwirkung von Acrylsäure auf α‐Brom‐styrol läßt sich auf die gleiche Weise die noch unbekannte 1.2 Dihydro‐naphthoesäure‐(1) darstellen.

Versuche einer Addition von β‐Brom‐styrol, α.β‐Dibrom‐styrol und β.β‐Dibrom‐styrol an Maleinsäure‐anhydrid werden beschrieben.
Phosphoroxy‐triamid und Phosphorthio‐triamid
Authors: Klement Robert , Koch Otto
Published: May 2007

Darstellung und Eigenschaften der Triamide der Phosphorsäure und der Monothiophosphorsäure, OP(NH2)3 bzw. SP(NH2)3, werden beschrieben. Beide Verbindungen sind Nichtelektrolyte. Sie sind an trockener Luft beständig. In feuchter Luft gehen sie in Ammoniumhydrogen‐monoamidophosphat, NH4HPO3(NH2), bzw. in Diammoniumhydrogen‐monothiophosphat, (NH4)2HPO3S, über. Beim Erwärmen mit verd. Natronlauge entstehen Natriumdiamidophosphat, NaPO2(NH2)2·4H2O, bzw. Natriumdiamido‐monothiophosphat, NaPOS(NH2)2)2·4H2O. Es lassen sich also, ausgehend von Phosphoroxychlorid bzw. von Phosphorthiochlorid und Ammoniak, alle drei Amidoderivate der Orthophosphorsäure bzw. mindestens das Phosphorthio‐triamid und das Natriumsalz der Diamido‐monothio‐phosphorsäure auf verhältnismäßig einfache und rein anorganische Weise darstellen. Phosphoroxy‐triamid kann als Ligand in Komplex‐verbindungen fungieren, wie das Beispiel des Silber‐phosphoroxytriamido‐nitrats, [{OP(NH2)3}Ag]NO3, erkennen läßt.
Synthesen mit Dicarbosäuren, VII. Mitteil.: Die Einwirkung von Magnesium, Aluminium und Eisen auf halogenierte Säuren
Authors: Mayer Roland , Treibs Wilhelm
Published: May 2007

Es werden Reformatzki‐ und Grignard‐Reaktionen mit Magnesium und Aluminium und die Einwirkung von metallischem Eisen auf bromierte Adipinsäureester beschrieben.