Water Dynamics in Shewanella oneidensis at Ambient and High Pressure using Quasi-Elastic Neutron Scattering

Quasielastic neutron scattering (QENS) is an ideal technique for studying water transport and relaxation dynamics at pico-to nanosecond timescales and at length scales relevant to cellular dimensions. Studies of high pressure dynamic effects in live organisms are needed to understand Earth's deep biosphere and biotechnology applications. Here we applied QENS to study water transport in Shewanella oneidensis at ambient (0.1 MPa) and high (200 MPa) pressure using H/D isotopic contrast experiments for normal and perdeuterated bacteria and buffer solutions to distinguish intracellular and transmembrane processes. The results indicate that intracellular water dynamics are comparable with bulk diffusion rates in aqueous fluids at ambient conditions but a significant reduction occurs in high pressure mobility. We interpret this as due to enhanced interactions with macromolecules in the nanoconfined environment. Overall diffusion rates across the cell envelope also occur at similar rates but unexpected narrowing of the QENS signal appears between momentum transfer values Q = 0.7-1.1 Å-1 corresponding to real space dimensions of 6-9 Å. The relaxation time increase can be explained by correlated dynamics of molecules passing through Aquaporin water transport complexes located within the inner or outer membrane structures

Pseudogap temperature as a Widom line in doped Mott insulators

The pseudogap refers to an enigmatic state of matter with unusual physical properties found below a characteristic temperature $T^*$ in hole-doped high-temperature superconductors. Determining $T^*$ is critical for understanding this state. Here we study the simplest model of correlated electron systems, the Hubbard model, with cluster dynamical mean-field theory to find out whether the pseudogap can occur solely because of strong coupling physics and short nonlocal correlations. We find that the pseudogap characteristic temperature $T^*$ is a sharp crossover between different dynamical regimes along a line of thermodynamic anomalies that appears above a first-order phase transition, the Widom line. The Widom line emanating from the critical endpoint of a first-order transition is thus the organizing principle for the pseudogap phase diagram of the cuprates. No additional broken symmetry is necessary to explain the phenomenon. Broken symmetry states appear in the pseudogap and not the other way around.Comment: 6 pages, 4 figures and supplementary information; published versio

Serum ostase in the follow-up of breast cancer patients

The present study was carried out on 152 patients divided into three groups: A) 73 underwent radical surgery for breast carcinoma without signs of metastases; B) 31 patients with radiologic and scintigraphic evidence of bone metastases originating from malignant mammary neoplasia (14 with only one and 17 with two or more localizations); C) 48 affected by simple mammary cysts. No patients had a previous history of primary or secondary bone pathologies or renal, hepatic or endocrine ones. Besides this, no patient took drugs influencing the metabolic turnover of the bony tissue in the three months preceding the study. After surgery all patients underwent standard clinical and laboratory follow-up, the latter including, every 3 months, the evaluation of serum CA 15.3, CA 27.29 MCA, and ostase. The ostase cut-off, obtained by the statistical elaboration of the serum values of the 48 patients with benign mammary cysts and the 73 disease free patients, was 17 microg./L. The mean concentration in the three groups and two subgroups was: 13.76 microg./L (patients without metastases), 31.84 (patients with metastases), 18.4 (limited bony metastases), 40.04 (diffused bony metastases) and 5,36 (mammary cists). The diagnostic sensitivity of ostase proved superior to that of CA 15.3 (84% vs 75%) except when considering the subgroup with limited metastases (71.4% vs 72.7%), while the specificity was similar (around 78%). CA 27.29 and MCA were not useful as markers of metastasis. In a longitudinal-perspective study it was possible periodically to test these markers in 13 patients, at fist, disease free and then with signs of bone progression evidence by skeletal scintigraphy. In 11 of these patients ostase and CA 15.3 showed increased values, on average 136 and 131 days respectively, before instrumental evidence of progression. None of the 13 patients, at the time of bone progression diagnosis, showed clinical, laboratory or instrumental signs of disease in other organs. The precocity of the serum increase of ostase could have a triple role: 1) accomplishment of a closer follow-up in patients at ''high risk'' of bone disease; 2) aid in the interpretation ''in a neoplastic sense'' of an ''uncertain image of hypercaptation''; 3) accomplishment of a supporting or specific oncology treatment at an earlier stage which may be of some advantage as regards quality of life

Change of the effective spin degeneracy in CeNi9−xCuxGe4 due to the interplay between Kondo and crystal field effects

Elastic and inelastic neutron scattering experiments were carried out on the heavy-fermion systems CeNi8.6Cu0.4Ge4 and CeNi8CuGe4 to study i) the influences of Ni/Cu substitution on the crystal field parameters and to identify ii) the driving forces of quantum criticality in CeNi9−xCuxGe4. The relevance of competing RKKY and Kondo interactions and changes of the crystal field parameters is discussed. The crystallographic site where the Ni replacement by copper atoms takes place is identified by neutron powder diffraction studies. Furthermore, quasi-elastic and inelastic neutron scattering studies provide detailed information regarding the Kondo properties and the changes of the crystal field parameters resulting from the Ni/Cu replacement. Hence, a reduction of the effective spin degeneracy of the crystal field ground state with increasing Cu concentration is identified as one important control parameter of quantum criticality in CeNi9−xCuxGe4. The results of these experiments are complemented by measurements of the thermopower

A Spectroscopic Investigation of Magnetic Exchange Between Highly Anisotropic Spin Centers

Structurally similar, magnetically diverse: The exchange and Zeeman parameters of two dimetallic, six-coordinate cobalt(II) compounds—i.e., with orbitally degenerate metal ions—have been determined by a combination of high-resolution EPR and INS spectroscopies, together with ab intio calculations. It is suggested that the correlation between the local crystal field about the CoII centers and the superexchange pathway controls the magnetic interaction. © 2011, Wiley-Blackwell