Dynamical Properties of Quasi One-Dimensional Correlated Electron Systems

Correlated electrons in one spatial dimension have very unusual properties such as the dynamical separation of spin and charge degrees of freedom. Typically, dynamical correlation functions of these systems are investigated with field theoretical methods that are valid in the limit of vanishingly low energies. However, there are few reliable results at finite energies which can be directly compared with spectra of scattering experiments, such as angle-resolved photoemission. It has therefore been difficult to find direct spectroscopic evidence of spin-charge separation in experimental realizations of quasi one-dimensional electron systems. The Dynamical Density-Matrix Renormalization Group can accurately determine spectral properties of correlated one-dimensional lattice models for all energy scales and interaction strengths. We use this method to determine the frequency- and momentum dependent correlation functions of extended Hubbard Hamiltonians. We obtain results for various quantities including the optical conductivity, the one-particle spectral function, dynamical charge- and spin structure factors

Quantum phase transition in the one-dimensional extended Peierls-Hubbard model

We consider the one-dimensional extended Hubbard model in the presence of an explicit dimerization $\delta$. For a sufficiently strong nearest neighbour repulsion we establish the existence of a quantum phase transition between a mixed bond-order wave and charge-density wave phase from a pure bond-order wave phase. This phase transition is in the universality class of the two-dimensional Ising model.Comment: 6 pages, 3 figure

Spectral function of the one-dimensional Hubbard model away from half filling

We calculate the photoemission spectral function of the one-dimensional Hubbard model away from half filling using the dynamical density matrix renormalization group method. An approach for calculating momentum-dependent quantities in finite open chains is presented. Comparison with exact Bethe Ansatz results demonstrates the unprecedented accuracy of our method. Our results show that the photoemission spectrum of the quasi-one-dimensional conductor TTF-TCNQ provides evidence for spin-charge separation on the scale of the conduction band width.Comment: REVTEX, 4 pages including 4 EPS figures (changed); correct chemical potential used to define excitation energies in figures and tex

The treatment of chondral and osteochondral defects of the knee with autologous matrix-induced chondrogenesis (AMIC): method description and recent developments

Purpose: Articular resurfacing by treatment of chondral defects may include chondral abrasion, autologous chondrocyte Implantation (ACI), matrix-induced chondrocyte transplantation (MACT) or osteochondral autologous transplantation (OATS). This technical note describes the method of autologous matrix-induced chondrogenesis (AMIC), a one-step procedure combining subchondral microfracture with the fixation of a collagen I/III membrane with fibrin glue or sutures. Methods: This is a technical note on the AMIC procedure and its further development. Results and conclusion: This method is applied primarily in chondral or osteochondral lesions of the knee. Indications and contraindications are provided; the technique is described. The further development of AMIC is described with an increased focus on the subchondral zone and the complex of cartilage and bone, the osteochondral unit, which receives increased attention in cartilage research. Level of evidence: I

A symptomatic sesamoid bone in the popliteus muscle (cyamella)

Sesamoid bones of the popliteus muscle, also called cyamellae, are common in primates but rare in humans. They reside as accessory bones in the tendon itself or in the intersection between tendon and bone. They should be clearly distinguished from osteochondral flakes, periosseuos calcifications, osteophytes and the fabella, a common sesamoid bone of the knee. In this case, we report a 25-year-old male with posterior lateral knee pain related to the popliteus tendon where a corresponding cyamella could be demonstrated on X-rays and MRI scans. The clinical findings may be related to the cyamella. Diagnosis and treatment of this rare pathology are discusse

Dynamical Properties of Quasi One-Dimensional Correlated Electron Systems

Correlated electrons in one spatial dimension have very unusual properties such as the dynamical separation of spin and charge degrees of freedom. Typically, dynamical correlation functions of these systems are investigated with field theoretical methods that are valid in the limit of vanishingly low energies. However, there are few reliable results at finite energies which can be directly compared with spectra of scattering experiments, such as angle-resolved photoemission. It has therefore been difficult to find direct spectroscopic evidence of spin-charge separation in experimental realizations of quasi one-dimensional electron systems. The Dynamical Density-Matrix Renormalization Group can accurately determine spectral properties of correlated one-dimensional lattice models for all energy scales and interaction strengths. We use this method to determine the frequency- and momentum dependent correlation functions of extended Hubbard Hamiltonians. We obtain results for various quantities including the optical conductivity, the one-particle spectral function, dynamical charge- and spin structure factors

We do not have evidence based methods for the treatment of cartilage defects in the knee

Purpose: The aim of this study was to perform a systematic review of studies concerning current treatment of chondral defects of the knee. Methods: The relevance for evidence based data and for successful surgical treatment of cartilage defects was evaluated. From 56,098 evaluated studies, 133 studies could be further pursued. These supplied data concerning microfracturing, the osteochondral autograft transplantation system (OATS), the autologous chondrocyte implantation (ACI) and the matrix induced chondrocyte implantation (MACI). The modified Coleman Methodical Score (CMS) and the Level of Evidence (LOE) were applied to evaluate the quality. Results: In these studies, a total of 6,920 patients were reviewed with a median of 32 patients per study and a mean follow-up of 24months. The mean CMS was 58 of 100 points. No study reached 100 points in the CMS. Three studies reached a level above 90. Ten studies were Level I, five studies reached Level II. Seven studies reached Level III, 111 studies Level IV. MRI scans to verify the clinical data were used by only 72 studies. The means in the modified CMS were for the different procedures as follows: ACI 58 points, MACI 57 points, microfracturing 68 points and OATS 50 points. 24 studies applied the Lysholm Score (LS) for clinical evaluation of cartilage surgery. All operative procedures yielded comparable improvements of the LS (n.s.) meaning that no operative procedure proved superior. Conclusion: As the majority of studies evaluated by this review is insufficient for EBM purposes more coherent studies with LOE of I or II are needed. Co-relating the systems of CMS and LOE and validating the applied scores seems desirabl