Metal-insulator transition and the Pr3+^{3+}/Pr4+^{4+} valence shift in (Pr1−y_{1-y}Yy_{y})0.7_{0.7}Ca0.3_{0.3}CoO3_3

The magnetic, electric and thermal properties of the ($Ln_{1-y}$Y$_{y}$)$_{0.7}$Ca$_{0.3}$CoO$_3$ perovskites ($Ln$~=~Pr, Nd) were investigated down to very low temperatures. The main attention was given to a peculiar metal-insulator transition, which is observed in the praseodymium based samples with $y=0.075$ and 0.15 at $T_{M-I}=64$ and 132~K, respectively. The study suggests that the transition, reported originally in Pr$_{0.5}$Ca$_{0.5}$CoO$_3$, is not due to a mere change of cobalt ions from the intermediate- to the low-spin states, but is associated also with a significant electron transfer between Pr$^{3+}$ and Co$^{3+}$/Co$^{4+}$ sites, so that the praseodymium ions occur below $T_{M-I}$ in a mixed Pr$^{3+}$/Pr$^{4+}$ valence. The presence of Pr$^{4+}$ ions in the insulating phase of the yttrium doped samples (Pr$_{1-y}$Y$_{y}$)$_{0.7}$Ca$_{0.3}$CoO$_3$ is evidenced by Schottky peak originating in Zeeman splitting of the ground state Kramers doublet. The peak is absent in pure Pr$_{0.7}$Ca$_{0.3}$CoO$_3$ in which metallic phase, based solely on non-Kramers Pr$^{3+}$ ions, is retained down to the lowest temperature.Comment: 10 figure

Magnetism in heavy-fermion U(Pt,Pd)3 studied by mSR

We report mSR experiments carried out on a series of heavy-electron pseudobinary compounds U(Pt1-xPdx)3 (x<=0.05). For x<=0.005 the zero-field muon depolarisation is described by the Kubo-Toyabe function. However the temperature variation of the Kubo-Toyabe relaxation rate does not show any sign of the small-moment antiferromagnetic phase with TN~6 K (signalled by neutron diffraction), in contrast to previous reports. The failure to detect the small ordered moment suggests it has a fluctuating (> 10 MHz) nature, which is consistent with the interpretation of NMR data. For 0.01<=x<=0.05 the muon depolarisation in the ordered state is described by two terms of equal amplitude: an exponentially damped spontaneous oscillation and a Lorentzian Kubo-Toyabe function. These terms are associated with antiferromagnetic order with substantial moments. The Knight-shift measured in a magnetic field of 0.6 T on single-crystalline U(Pt0.95Pd0.05)3 in the paramagnetic state shows two signals for B perpendicular to c, while only one signal is observed for B||c. The observation of two signals for B perpendicular to c, while there is only one muon localisation site (0,0,0), points to the presence of two spatially distinct regions of different magnetic response.Comment: 25 pages including 12 figures (PS), J. Phys.: Condens. Matter, in prin

Hunting dark matter with X-rays

The nature of the Dark Matter is one of the biggest open questions in modern cosmology and particle physics. The work in this thesis concerns a search for the observational effects of one particular class of hypothetical Dark Matter particles, namely those that are allowed to decay. In decaying, X-ray photons are emitted and should be observable. One part of the thesis details the discovery of a potential Dark Matter decay signal in X-ray spectra of galaxies and galaxy clusters, and the subsequent efforts to identify its origin. To this end archival data and new observations are compared to the respective Dark Matter masses of the observed objects. Interpretations of the signal as an instrumental effect, or due to regular astrophysical processes are unsatisfactory. Although the Dark Matter interpretation remains plausible, definitive conclusions about the origin of the signal can not be drawn yet and will require measurements by next generation observatories. The last chapter of the thesis contains the proof-of-concept of a novel technique to search for such weak signals that combines increased statistical power with the ability to determine the physical origin of a signal, while avoiding some of the disadvantages of traditional methods.Theoretical Physic

Impurity effects in superconducting UPt3

Superconducting UPt3 is characterized by a novel and complex magnetic field‐temperature phase diagram, with two superconducting transitions at Tc1 and Tc2 in zero field. We have studied the effects of Pd and Y impurities on the zero field superconducting properties of UPt3. Resistance measurements show that both dopants increase the residual resistivity and decrease the spin fluctuation temperature in the normal state. Tc1 is depressed by both dopants, but more effectively by Pd. ‖Tc1 − Tc2‖ is essentially unaffected by Y doping, but increases dramatically with Pd doping.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70706/2/JAPIAU-69-8-5487-1.pd

Prospectively measured lifestyle factors and BMI explain differences in health-related quality of life between colorectal cancer patients with and without comorbid diabetes

Purpose This study aimed to assess the longitudinal association between lifestyle factors, body mass index (BMI), and health-related quality of life (HRQoL) among colorectal cancer patients with (CRCDM+) and without diabetes (CRCDM−). Methods Data from a longitudinal study among CRC patients diagnosed between 2000 and 2009 were used. Clinical characteristics were retrieved from the Netherlands Cancer Registry and questionnaires were sent in 2010, 2011, and 2012 using the Patient Reported Outcomes Following Initial Treatment and Long term Evaluation of Survivorship (PROFILES) registry. Lifestyle (including moderate-to-vigorous physical activity (MVPA), smoking and alcohol use), BMI, diabetes status, and HRQoL were assessed in the questionnaire. Results One thousand seven hundred thirty-nine (49 %) patients responded to ≥2 questionnaires, of whom 126 CRCDM+ and 789 CRCDM− patients were included. CRCDM+ patients had a higher BMI (29.1 ± 4.2 vs. 26.4 ± 3.7 kg/m2), whereas the number of alcohol users was lower (50 vs. 70 %, p value <0.0001) among CRCDM+ as compared to CRCDM− patients. Analyses adjusted for sociodemographic and cancer characteristics showed that CRCDM+ patients reported statistically significantly lower physical function (beta = -5.76; SE = 1.67), global QoL (beta = -4.31; SE = 1.48), and more symptoms of fatigue (beta = 5.38; SE = 1.95) than CRCDM− patients. However, these effects disappeared after adjustments for lifestyle factors and BMI which were all significant predictors of HRQoL. Additional adjustment for comorbidity further attenuated the main effect of DM on HRQoL. Conclusions Diabetes was not independently associated with HRQoL but deteriorated HRQoL among CRCDM+ patients seem to be explained by an unhealthier lifestyle and other comorbid conditions. Moreover, residual confounding cannot be ruled out.KeywordsColorectal cancer, Diabetes, Lifestyle, Health-related quality of lif

Checking the dark matter origin of a 3.53 keV line with the Milky Way center

Theoretical Physic