New full evolutionary sequences of H and He atmosphere massive white dwarf stars using MESA

We explore the evolution of hydrogen-rich and hydrogen-deficient white dwarf stars with masses between 1.012 and 1.307 Msun, and initial metallicity of Z=0.02. These sequences are the result of main sequence stars with masses between 8.8 and 11.8 Msun. The simulations were performed with MESA, starting at the zero-age main sequence, through thermally pulsing and mass-loss phases, ending at the white dwarfs cooling sequence. We present reliable chemical profiles for the whole mass range considered, covering the different expected central compositions, i.e. C/O, O/Ne and Ne/O/Mg, and its dependence with the stellar mass. In addition, we present detailed chemical profiles of hybrid C/O-O/Ne core white dwarfs, found in the mass range between 1.024 and 1.15 Msun. We present the initial-to-final mass relation, mass-radius relation, and cooling times considering the effects of atmosphere and core composition.Comment: 17 pages, 16 figures, 3 tables, accepted for publication in MNRAS. Cooling tracks available at ftp://cdsarc.u-strasbg.fr/pub/cats/J/MNRAS/480/154

Asteroseismology of PG 1541++651 and BPM 31594 with TESS

We present the photometric data from TESS for two known ZZ Ceti stars, PG 1541+651 and BPM 31594. Before TESS, both objects only had observations from short runs from ground-based facilities, with three and one period detected, respectively. The TESS data allowed the detection of multiple periodicities, 12 for PG 1541$+$651, and six for BPM 31594, which enables us to perform a detailed asteroseismological study. For both objects we found a representative asteroseismic model with canonical stellar mass ~ 0.61 Msun and thick hydrogen envelopes, thicker than 10^(-5.3) M_*. The detection of triplets in the Fourier transform also allowed us to estimate mean rotation periods, being ~22 h for PG 1541+651 and 11.6 h for BPM 31594, which is consistent with range of values reported for other ZZ Ceti stars.Comment: 12 pages, 11 figures. Accepted for publication in MNRA

MRI sensing based on the displacement of paramagnetic ions from chelated complexes

We introduce a mechanism for ion sensing by MRI in which analytes compete with paramagnetic ions for binding to polydentate chelating agents. Displacement of the paramagnetic ions results in alteration of solvent interaction parameters and consequent changes in relaxivity and MRI contrast. The MRI changes can be tuned by the choice of chelator. As an example, we show that calcium-dependent displacement of Mn[superscript 2+] ions bound to EGTA and BAPTA results in a T[subscript 1]-weighted MRI signal increase, whereas displacement from calmodulin results in a signal decrease. The changes are ion selective and can be explained using relaxivity theory. The ratio of T[subscript 2] to T[subscript 1] relaxivity is also calcium-dependent, indicating the feasibility of “ratiometric” analyte detection, independent of the probe concentration. Measurement of paramagnetic ion displacement effects could be used to determine analyte ion concentrations with spatial resolution in opaque specimens.National Institutes of Health (U.S.) (grant DP2-OD2441)National Institutes of Health (U.S.) (grant R01-GM65519)McGovern Institute for Brain Research at MIT. Neurotechnology (MINT) Progra

Mapping of functionalized regions on carbon nanotubes by scanning tunneling microscopy

Scanning tunneling microscopy (STM) gives us the opportunity to map the surface of functionalized carbon nanotubes in an energy resolved manner and with atomic precision. But this potential is largely untapped, mainly due to sample stability issues which inhibit reliable measurements. Here we present a simple and straightforward solution that makes away with this difficulty, by incorporating the functionalized multiwalled carbon nanotubes (MWCNT) into a few layer graphene - nanotube composite. This enabled us to measure energy resolved tunneling conductance maps on the nanotubes, which shed light on the level of doping, charge transfer between tube and functional groups and the dependence of defect creation or functionalization on crystallographic orientation.Comment: Keywords: functionalization, carbon nanotubes, few layer graphene, STM, CITS, ST

Gut Hormones and Appetite Control: A Focus on PYY and GLP-1 as Therapeutic Targets in Obesity

The global obesity epidemic has resulted in significant morbidity and mortality. However, the medical treatment of obesity is limited. Gastric bypass is an effective surgical treatment but carries significant perioperative risks. The gut hormones, peptide tyrosine tyrosine (PYY) and glucagon-like peptide 1 (GLP-1), are elevated following gastric bypass and have been shown to reduce food intake. They may provide new therapeutic targets. This review article provides an overview of the central control of food intake and the role of PYY and GLP-1 in appetite control. Key translational animal and human studies are reviewed

Hydroxy double salts intercalated with Mn(II) complexes as potential contrast agents

A series of Mn(II) aminophosphonate complexes were successfully synthesized and intercalated into the hydroxy double salt [Zn5(OH)8]Cl2·yH2O. Complex incorporation led to an increase in the interlayer spacing from 7.8 to 10–12 Å. Infrared spectroscopy showed the presence of the characteristic vibration peaks of the Mn(II) complexes in the intercalates' spectra, indicating successful incorporation. The complex-loaded composites had somewhat lower proton relaxivities than the pure complexes. Nevertheless, these intercalates may have use as MRI contrast agents for patients with poor kidney function, where traditional Gd(III)-based contrast agents cause severe renal failure