Search

X-linked dyskeratosis congenita, a rare inherited bone-marrow failure syndrome in which 80%+ of the patients die, is in the main the result of DKC1 gene missense mutations. The X-linked form of the disease is known to be caused by mutations in DKC1, which encodes a 514-amino-acid protein homologous to a Saccharomyces cerevisiae protein and a rat protein. The DKC1 gene is made up of 15 exons and has been screened for mutation in genomic DNA. Mutations included 11 different single-nucleotide substitutions resulting in 10 missense mutations.

In the context of experimental advances in the realization of artificial magnetic fields in quantum gases, we discuss feasible schemes to extend measurements of the Hall polarization to a study of the Hall voltage, allowing for direct comparison with solid state systems. Specifically, for the paradigmatic example of interacting flux ladders, we report on characteristic zero crossings and a remarkable robustness of the Hall voltage with respect to interaction strengths, particle fillings, and ladder geometries, which is unobservable in the Hall polarization. Moreover, we investigate the site-resolved Hall response in spatially inhomogeneous quantum phases.

We explore the ground-state physics of two-dimensional spin-1/2 U(1) quantum link models, one of the simplest nontrivial lattice gauge theories with fermionic matter within experimental reach for quantum simulations. Whereas in the large mass limit we observe Neél-like vortex-antivortex and striped crystalline phases, for small masses there is a transition from the striped phases into a disordered phase whose properties resemble those at the Rokhsar-Kivelson point of the quantum dimer model. This phase is characterized on ladders by boundary Haldane-like properties, such as vanishing parity and finite string ordering. Moreover, from studies of the string tension between gauge charges, we find that, whereas the striped phases are confined, the novel disordered phase present clear indications of being deconfined. Our results open exciting perspectives of studying highly nontrivial physics in quantum simulators, such as spin-liquid behavior and confinement-deconfinement transitions, without the need of explicitly engineering plaquette terms.

We study the Hall response of two-dimensional lattice systems of charged fermions in a transverse magnetic field, in the ballistic coherent limit. We identify a setup in which this response vanishes over wide regions of parameter space: the "Landauer-Büttiker" setup commonly studied for coherent quantum transport, consisting of a strip contacted to biased ideal reservoirs of charges. We show that this effect does not rely on particle-hole symmetry, and is robust to a variety of perturbations including variations of the transverse magnetic field, chemical potential, and temperature. We trace this robustness back to a topological property of the Fermi surface: the number of Fermi points with positive velocity of the system. We argue that the mechanism leading to a vanishing Hall response applies to noninteracting and interacting systems alike, which we verify in concrete examples using density-matrix renormalization group simulations.

We theoretically study the Hall effect on interacting M-leg ladder systems, comparing different measures and properties of the zero temperature Hall response in the limit of weak magnetic fields. Focusing on SU(M) symmetric interacting bosons and fermions, as relevant for, e.g., typical synthetic dimensional quantum gas experiments, we identify an extensive regime in which the Hall imbalance Δ_{H} is universal and corresponds to a classical Hall resistivity R_{H}=-1/n for a large class of quantum phases. Away from this high symmetry point we observe interaction driven phenomena such as sign reversal and divergence of the Hall response.

Raman-assisted hopping may be used to realize the anyon Hubbard model in one-dimensional optical lattices. We propose a feasible scenario that significantly improves the proposal of T. Keilmann et al. [Nat. Commun. 2, 361 (2011)], allowing as well for an exact realization of the two-body hard-core constraint, and for controllable effective interactions without the need of Feshbach resonances. We show that the combination of anyonic statistics and two-body hard-core constraint leads to a rich ground-state physics, including Mott insulators with attractive interactions, pair superfluids, dimer phases, and multicritical points. Moreover, the anyonic statistics results in a novel two-component superfluid of holon and doublon dimers, characterized by a large but finite compressibility and a multipeaked momentum distribution, which may be easily revealed experimentally.

Recent experiments show that periodic modulations of cold atoms in optical lattices may be used to engineer and explore interesting models. We show that double modulation combining lattice shaking and modulated interactions allows for the engineering of a much broader class of lattice with correlated hopping, which we study for the particular case of one-dimensional systems. We show, in particular, that by using this double modulation it is possible to study Hubbard models with asymmetric hopping, which, contrary to the standard Hubbard model, present insulating phases with both parity and string order. Moreover, double modulation allows for the simulation of lattice models in unconventional parameter regimes, as we illustrate for the case of the spin-1/2 Fermi-Hubbard model with correlated hopping, a relevant model for cuprate superconductors.

Precise volumetry of the cerebellum still remains challenging, due to thin sulci and gyri. We present a new fast and reliable sulcus-corrected approach for quantitative assessment of cerebellar atrophy, evaluated on patients with spinocerebellar ataxia (SCA). Thin-sliced T1-weighted magnetic resonance images (MPRAGE) were acquired in 11 genetically confirmed SCA6 patients and in a group of age-matched control subjects (n=14). Post-processing involves a morphological image segmentation pipeline as a basis for a sulcus-corrected cerebellar volume measurement. Cerebellar volumes and intra-rater, inter-rater and scan-rescan reproducibility were quantified. Reliability of the measurements was validated using an anatomical preparation of the cerebellum. Repeatability coefficients (RC: intra-rater/inter-rater/scan-rescan) of the method were 1.07%/1.11%/1.35%. Absolute cerebellar volumes showed good agreement with the actual volume of the anatomical preparation. The cerebellar volume of the SCA 6 was 96.3±12.1ml (mean±S.D.), which was significantly lower than the results of the corresponding control groups. The cerebellar volume correlated significantly to clinical dysfunction in SCA6. This is the first study to demonstrate the feasibility of a new sulcus-corrected approach to assess cerebellar volume. In contrast to currently used methods, this new approach may be more sensitive even to small atrophic changes affecting sulcal widening., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Objectives: To determine the feasibility of ex situ prostate cancer detection by triple spectroscopy. A positive surgical margin following radical prostatectomy is an adverse factor for recurrence-free survival. Detection of residual cancer cells in vivo would be the most useful, allowing the resection of such tissue during the procedure. Aside from the use of frozen sections, the ability to detect positive surgical margins is limited. Laser-induced autofluorescence, white-light remission, and high-frequency impedance spectroscopy are methods that allow discrimination of tissues of different dignities based on their specific signature. We tested whether the combination of these techniques can differentiate malignant and benign prostate tissue ex vivo., Materials and Methods: In preparation for future in vivo measurements, an ex vivo study was performed to detect characteristics of prostate tissue. Ninety-five tissue samples from 32 patients undergoing radical prostatectomy for clinically localized prostate cancer were taken immediately after removal of the prostate and stored in liquid nitrogen. Tissue samples were thawed for laser-induced autofluorescence, white-light remission, and high-frequency impedance spectroscopy. Based on these results, a computerized algorithm was developed for tissue differentiation., Results: The statistical analysis of laser-induced autofluorescence and white-light remission data demonstrated a differentiation of benign and malignant prostate tissue with a sensitivity of 87.5% and a specificity of 87.3%. By adding the acquired high-frequency impedance data to the statistical analysis, sensitivity and specificity were increased to 93.8% and 92.4%., Conclusion: A highly accurate differentiation of prostate tissue was achieved in an ex vivo model. In vivo studies need to be performed to evaluate whether this technique can be successful in an intraoperative setting to detect positive surgical margins.

The cytochrome P-450 LM2 spin state relaxation kinetics has been resolved by means of laser temperature-jump techniques. The first order rate constants amount to about 10(6) S-1 in the substrate-free and the substrate-bound protein, respectively. Evidence is provided that the spin equilibrium preequilibrates the P-450 reduction but is not rate-limiting. Additional capacitor discharge temperature-jump studies elucidate substrate dependent perturbations.

MCD spectra of reduced cytochromes P-450 and P-420 have been recorded in the spectral region 350-800 nm at temperatures 4.2-290 K and were compared with the respective low-temperature photolysed CO-complexes at 4.2 K. The MCD data are consistent with the suggestions that: the heme iron is high-spin in the reduced proteins and in the photolysed species; mercaptide is the protein-derived ligand of the heme iron in the reduced cytochrome P-450, as well as in its CO-complex; imidazole of histidine is the fifth ligand of the heme iron both in the reduced P-420 and its CO-complex; structural changes in the heme iron coordination sphere occur at CO-binding.

Magnetic circular dichroism (MCD) spectra of reduced cytochromes P450 and P420 in equilibrium and non-equilibrium protein conformations are compared at 4.2 K for the 350-800 spectral region. Non-equilibrium forms have been produced by photolysis of CO-complexes at 4.2 K. The differences between MCD spectra of proteins in equilibrium and non-equilibrium conformations, in particular for the visible region, show clearly the structural changes in the heme iron coordination sphere to occur on ligand binding. The comparison of the Soret MCD spectra of reduced proteins in their equilibrium and non-equilibrium forms with those of other high-spin ferrous hemoproteins suggest that mercaptide (RS-) is the protein ligand of the heme iron in reduced P450, as well as in its CO-complex, and that imidazole of histidine is the fifth ligand of the iron both in reduced P420 and its CO-complex. The thermal recombination of the photoproducts with CO have been studied. When temperature rises from 4.2 to 77 K for two hours both proteins have similar temperature characteristics during the recombination processes. The recombination begins at T approximately equal to 10 K and is completed at approximately equal to 50 K. The temperature at which half of the total photolyzed molecules are restored to the CO-form is equal to 25 K. For products of photolysis of CO-complexes of myoglobin and hemoglobin under the same heating conditions these temperatures are equal to 35 and 23 K respectively. Thus, the photoproducts of P450, P420 and hemoglobin have similar parameters of low-temperature recombination and the kinetics of this process is faster than for photodissociated myoglobin.