Covariant representations of the relativistic Brueckner T-matrix and the nuclear matter problem

We investigate nuclear matter properties in the relativistic Brueckner approach. The in-medium on-shell T-matrix is represented covariantly by five Lorentz invariant amplitudes from which we deduce directly the nucleon self-energy. We discuss the ambiguities of this approach and the failure of previously used covariant representations in reproducing the nucleon self-energies on the Hartree-Fock level. To enforce correct Hartree-Fock results we develop a subtraction scheme which treats the bare nucleon-nucleon potential exactly in accordance to the different types of meson exchanges. For the remaining ladder kernel, which contains the higher order correlations, we employ then two different covariant representations in order to study the uncertainty inherent in the approach. The nuclear matter bulk properties are only slightly sensitive on the explicit representation used for the kernel. However, we obtain new Coester lines for the various Bonn potentials which are shifted towards the empirical region of saturation. In addition the nuclear equation-of-state turns out to be significantly softer in the new approach.Comment: 39 pages Latex using Elsevier style, 16 PS figure

Mapping the Wigner distribution function of the Morse oscillator into a semi-classical distribution function

The mapping of the Wigner distribution function (WDF) for a given bound-state onto a semiclassical distribution function (SDF) satisfying the Liouville equation introduced previously by us is applied to the ground state of the Morse oscillator. Here we give results showing that the SDF gets closer to the corresponding WDF as the number of levels of the Morse oscillator increases. We find that for a Morse oscillator with one level only, the agreement between the WDF and the mapped SDF is very poor but for a Morse oscillator of ten levels it becomes satisfactory.Comment: Revtex, 27 pages including 13 eps figure

Multilinear Wavelets: A Statistical Shape Space for Human Faces

We present a statistical model for $3$D human faces in varying expression, which decomposes the surface of the face using a wavelet transform, and learns many localized, decorrelated multilinear models on the resulting coefficients. Using this model we are able to reconstruct faces from noisy and occluded $3$D face scans, and facial motion sequences. Accurate reconstruction of face shape is important for applications such as tele-presence and gaming. The localized and multi-scale nature of our model allows for recovery of fine-scale detail while retaining robustness to severe noise and occlusion, and is computationally efficient and scalable. We validate these properties experimentally on challenging data in the form of static scans and motion sequences. We show that in comparison to a global multilinear model, our model better preserves fine detail and is computationally faster, while in comparison to a localized PCA model, our model better handles variation in expression, is faster, and allows us to fix identity parameters for a given subject.Comment: 10 pages, 7 figures; accepted to ECCV 201

The Relativistic Dirac-Brueckner Approach to Asymmetric Nuclear Matter

The properties of asymmetric nuclear matter have been investigated in a relativistic Dirac-Brueckner-Hartree-Fock framework using the Bonn A potential. The components of the self-energies are extracted by projecting on Lorentz invariant amplitudes. Furthermore, the optimal representation scheme for the $T$ matrix, the subtracted $T$ matrix representation, is applied and the results are compared to those of other representation schemes. Of course, in the limit of symmetric nuclear matter our results agree with those found in literature. The binding energy $E_b$ fulfills the quadratic dependence on the asymmetry parameter and the symmetry energy is 34 MeV at saturation density. Furthermore, a neutron-proton effective mass splitting of $m_n^* < m_p^*$ is found. In addition, results are given for the mean-field effective coupling constants.Comment: 28 pages, 7 figures, to appear in Nucl. Phys. A, added additional reference

Scalar and vector decomposition of the nucleon self-energy in the relativistic Brueckner approach

We investigate the momentum dependence of the nucleon self-energy in nuclear matter. We apply the relativistic Brueckner-Hartree-Fock approach and adopt the Bonn A potential. A strong momentum dependence of the scalar and vector self-energy components can be observed when a commonly used pseudo-vector choice for the covariant representation of the T-matrix is applied. This momentum dependence is dominated by the pion exchange. We discuss the problems of this choice and its relations to on-shell ambiguities of the T-matrix representation. Starting from a complete pseudo-vector representation of the T-matrix, which reproduces correctly the pseudo-vector pion-exchange contributions at the Hartree-Fock level, we observe a much weaker momentum dependence of the self-energy. This fixes the range of the inherent uncertainty in the determination of the scalar and vector self-energy components. Comparing to other work, we find that extracting the self-energy components by a fit to the single particle potential leads to even more ambiguous results.Comment: 35 pages RevTex, 7 PS figures, replaced by a revised and extended versio

Genetic alterations on chromosome 16 and 17 are important features of ductal carcinoma in situ of the breast and are associated with histologic type

We analysed the involvement of known and putative tumour suppressor- and oncogene loci in ductal carcinoma in situ (DCIS) by microsatellite analysis (LOH), Southern blotting and comparative genomic hybridization (CGH). A total of 78 pure DCIS cases, classified histologically as well, intermediately and poorly differentiated, were examined for LOH with 76 markers dispersed along all chromosome arms. LOH on chromosome 17 was more frequent in poorly differentiated DCIS (70%) compared to well-differentiated DCIS (17%), whereas loss on chromosome 16 was associated with well- and intermediately differentiated DCIS (66%). For a subset we have done Southern blot- and CGH analysis. C-erbB2/neu was amplified in 30% of poorly differentiated DCIS. No amplification was found of c-myc, mdm2, bek, flg and the epidermal growth factor (EGF)-receptor. By CGH, most frequent alterations in poorly differentiated DCIS were gains on 8q and 17q22–24 and deletion on 17p, whereas in well-differentiated DCIS amplification on chromosome 1q and deletion on 16q were found. In conclusion, our data indicates that inactivation of a yet unknown tumour suppressor gene on chromosome 16q is implicated in the development of most well and intermediately differentiated DCIS whereas amplification and inactivation of various genes on chromosome 17 are implicated in the development of poorly differentiated DCIS. Furthermore these data show that there is a genetic basis for the classification of DCIS in a well and poorly differentiated type and support the evidence of different genetic routes to develop a specific type of carcinoma in situ of the breast. © 1999 Cancer Research Campaig

Preventing carbon nanoparticle-induced lung inflammation reduces antigen-specific sensitization and subsequent allergic reactions in a mouse model

BACKGROUND: Exposure of the airways to carbonaceous nanoparticles can contribute to the development of immune diseases both via the aggravation of the allergic immune response in sensitized individuals and by adjuvant mechanisms during the sensitization against allergens. The cellular and molecular mechanisms involved in these adverse pathways are not completely understood. We recently described that the reduction of carbon nanoparticle-induced lung inflammation by the application of the compatible solute ectoine reduced the aggravation of the allergic response in an animal system. In the current study we investigated the influence of carbon nanoparticles on the sensitization of animals to ovalbumin via the airways. Ectoine was used as a preventive strategy against nanoparticle-induced neutrophilic lung inflammation. METHODS: Balb/c mice were repetitively exposed to the antigen ovalbumin after induction of airway inflammation by carbon nanoparticles, either in the presence or in the absence of ectoine. Allergic sensitization was monitored by measurement of immunoglobulin levels and immune responses in lung and lung draining lymph nodes after challenge. Furthermore the role of dendritic cells in the effect of carbon nanoparticles was studied in vivo in the lymph nodes but also in vitro using bone marrow derived dendritic cells. RESULTS: Animals exposed to antigen in the presence of carbon nanoparticles showed increased effects with respect to ovalbumin sensitization, to the allergic airway inflammation after challenge, and to the specific T(H)2 response in the lymph nodes. The presence of ectoine during the sensitization significantly reduced these parameters. The number of antigen-loaded dendritic cells in the draining lymph nodes was identified as a possible cause for the adjuvant effect of the nanoparticles. In vitro assays indicate that the direct interaction of the particles with dendritic cells is not able to trigger CCR7 expression, while this endpoint is achieved by lung lavage fluid from nanoparticle-exposed animals. CONCLUSIONS: Using the intervention strategy of applying ectoine into the airways of animals we were able to demonstrate the relevance of neutrophilic lung inflammation for the adjuvant effect of carbon nanoparticles on allergic sensitization. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12989-015-0093-5) contains supplementary material, which is available to authorized users

Off shell behaviour of the in medium nucleon-nucleon cross section

The properties of nucleon-nucleon scattering inside dense nuclear matter are investigated. We use the relativistic Brueckner-Hartree-Fock model to determine on-shell and half off-shell in-medium transition amplitudes and cross sections. At finite densities the on-shell cross sections are generally suppressed. This reduction is, however, less pronounced than found in previous works. In the case that the outgoing momenta are allowed to be off energy shell the amplitudes show a strong variation with momentum. This description allows to determine in-medium cross sections beyond the quasi-particle approximation accounting thereby for the finite width which nucleons acquire in the dense nuclear medium. For reasonable choices of the in-medium nuclear spectral width, i.e. $\Gamma\leq 40$ MeV, the resulting total cross sections are, however, reduced by not more than about 25% compared to the on-shell values. Off-shell effect are generally more pronounced at large nuclear matter densities.Comment: 31 pages Revtex, 12 figures, typos corrected, to appear in Phys. Rev.

On the Lorentz structure of the symmetry energy

We investigate in detail the density dependence of the symmetry energy in a relativistic description by decomposing the iso-vector mean field into contributions with different Lorentz covariant properties. We find important effects of the iso-vector, scalar channel (i.e. $\delta$-meson like) on the high density behavior of the symmetry energy. Applications to static properties of finite nuclei and to dynamic situations of heavy ion collisions are explored and related to each other. The nuclear structure studies show only moderate effects originating from the virtual $\delta$ meson. At variance, in heavy ion collisions one finds important contributions on the reaction dynamics arising from the different Lorentz structure of the high density symmetry energy when a scalar iso-vector $\delta$ field is introduced. Particularly interesting is the related neutron/proton effective mass splitting for nucleon transport effects and for resonance and particle production around the threshold. We show that the $\delta$-like channel turns out to be essential for the production of pions, when comparing with experimental data, in particular for high momentum selections.Comment: 30 pages, 12 figures (.eps

Relativistic Brueckner-Hartree-Fock calculations with explicit intermediate negative energy states

In a relativistic Brueckner-Hartree-Fock calculation we include explicit negative-energy states in the two-body propagator. This is achieved by using the Gross spectator-equation, modified by medium effects. Qualitatively our results compare well with other RBHF calculations. In some details significant differences occur, e.g, our equation of state is stiffer and the momentum dependence of the self-energy components is stronger than found in a reference calculation without intermediate negative energy states.Comment: 13 pages Revtex, 5 figures included seperatel