Superconductivity and electronic structure of KFe2As2, RbFe2As2, and CsFe2As2 probed by thermal expansion and magnetostriction at very low temperatures

This thesis compares the iron-based superconductors KFe2As2, RbFe2As2, and CsFe2As2 based on thermal expansion and magnetostriction measurements at temperatures between 50 mK and 4 K and in magnetic fields up to 14 T. The upper critical field is paramagnetically limited for magnetic fields applied parallel to the FeAs layers. Quantum oscillations of the magnetostriction yield extremal cross-sectional areas of the Fermi surface and effective quasiparticle masses, which are enhanced considerably

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Igloo: Soundly Linking Compositional Refinement and Separation Logic for Distributed System Verification

Lighthouse projects like CompCert, seL4, IronFleet, and DeepSpec have demonstrated that full system verification is feasible by establishing a refinement between an abstract system specification and an executable implementation. Existing approaches however impose severe restrictions on the abstract system specifications due to their limited expressiveness or versatility, or on the executable code due to their use of suboptimal code extraction or inexpressive program logics. We propose a novel methodology that combines the compositional refinement of event-based models of distributed systems with the verification of full-fledged program code using expressive separation logics, which support features of realistic programming languages like heap data structures and concurrency. Our main technical contribution is a formal framework that soundly relates event-based system models to program specifications in separation logics. This enables protocol development tools to soundly interoperate with program verifiers to establish a refinement between the model and the code. We formalized our framework, Igloo, in Isabelle/HOL. We report on three case studies, a leader election protocol, a replication protocol, and a security protocol, for which we refine formal requirements into program specifications that we implement in Java and Python and prove correct using the VeriFast and Nagini tools.ISSN:2475-142

Usefulness of Serial N-Terminal Pro B-Type Natriuretic Peptide Measurements for Determining Prognosis in Patients With Pulmonary Arterial Hypertension

Previous studies have shown the prognostic benefit of N-terminal pro- brain natriuretic peptide (NT-pro-BNP) in pulmonary arterial hypertension (PAH) at time of diagnosis. However, there are only limited data on the clinical utility of serial measurements of the inactive peptide NT-pro-BNP in PAH. This study examined the value of serial NT-pro-BNP measurements in predicting prognosis PAH. We retrospectively analyzed all available NT-pro-BNP plasma samples in 198 patients who were diagnosed with World Health Organization group I PAH from January 2002 through January 2009. At time of diagnosis median NT-pro-BNP levels were significantly different between survivors (610 pg/ml, range 6 to 8,714) and nonsurvivors (2,609 pg/ml, range 28 to 9,828, p = 1,256 pg/ml as the optimal NT-pro-BNP cutoff for predicting mortality at time of diagnosis. Serial measurements allowed calculation of baseline NT-pro-BNP (i.e., intercept obtained by back-extrapolation of concentration-time graph), providing a better discrimination between survivors and nonsurvivors than NT-pro-BNP at time of diagnosis alone (p = 0.010). Furthermore, a decrease of NT-pro-BNP of >15%/year was associated with survival. In conclusion, a serum NT-pro-BNP level >= 1,256 pg/ml at time of diagnosis identifies poor outcome in patients with PAH. In addition, a decrease in NT-pro-BNP of >15%/year is associated with survival in PAH. (C) 2011 Elsevier Inc. All rights reserved. (Am J Cardiol 2011;108:1645-1650

Usefulness of Serial N-Terminal Pro B-Type Natriuretic Peptide Measurements for Determining Prognosis in Patients With Pulmonary Arterial Hypertension

Previous studies have shown the prognostic benefit of N-terminal pro- brain natriuretic peptide (NT-pro-BNP) in pulmonary arterial hypertension (PAH) at time of diagnosis. However, there are only limited data on the clinical utility of serial measurements of the inactive peptide NT-pro-BNP in PAH. This study examined the value of serial NT-pro-BNP measurements in predicting prognosis PAH. We retrospectively analyzed all available NT-pro-BNP plasma samples in 198 patients who were diagnosed with World Health Organization group I PAH from January 2002 through January 2009. At time of diagnosis median NT-pro-BNP levels were significantly different between survivors (610 pg/ml, range 6 to 8,714) and nonsurvivors (2,609 pg/ml, range 28 to 9,828, p = 1,256 pg/ml as the optimal NT-pro-BNP cutoff for predicting mortality at time of diagnosis. Serial measurements allowed calculation of baseline NT-pro-BNP (i.e., intercept obtained by back-extrapolation of concentration-time graph), providing a better discrimination between survivors and nonsurvivors than NT-pro-BNP at time of diagnosis alone (p = 0.010). Furthermore, a decrease of NT-pro-BNP of >15%/year was associated with survival. In conclusion, a serum NT-pro-BNP level >= 1,256 pg/ml at time of diagnosis identifies poor outcome in patients with PAH. In addition, a decrease in NT-pro-BNP of >15%/year is associated with survival in PAH. (C) 2011 Elsevier Inc. All rights reserved. (Am J Cardiol 2011;108:1645-1650

Active zone compaction correlates with presynaptic homeostatic potentiation

Neurotransmitter release is stabilized by homeostatic plasticity. Presynaptic homeostatic potentiation (PHP) operates on timescales ranging from minute- to life-long adaptations and likely involves reorganization of presynaptic active zones (AZs). At Drosophila melanogaster neuromuscular junctions, earlier work ascribed AZ enlargement by incorporating more Bruchpilot (Brp) scaffold protein a role in PHP. We use localization microscopy (direct stochastic optical reconstruction microscopy [dSTORM]) and hierarchical density-based spatial clustering of applications with noise (HDBSCAN) to study AZ plasticity during PHP at the synaptic mesoscale. We find compaction of individual AZs in acute philanthotoxin-induced and chronic genetically induced PHP but unchanged copy numbers of AZ proteins. Compaction even occurs at the level of Brp subclusters, which move toward AZ centers, and in Rab3 interacting molecule (RIM)-binding protein (RBP) subclusters. Furthermore, correlative confocal and dSTORM imaging reveals how AZ compaction in PHP translates into apparent increases in AZ area and Brp protein content, as implied earlier

Strain-Driven Approach to Quantum Criticality in AFe2As2 with A=K, Rb, and Cs

The iron-based superconductors AFe2As2 with A=K, Rb, Cs exhibit large Sommerfeld coefficients approaching those of heavy-fermion systems. We have investigated the magnetostriction and thermal expansion of this series to shed light on this unusual behavior. Quantum oscillations of the magnetostriction allow identifying the band-specific quasiparticle masses which by far exceed the band-structure derived masses. The divergence of the Grüneisen ratio derived from thermal expansion indicates that with increasing volume along the series a quantum critical point is approached. The critical fluctuations responsible for the enhancement of the quasiparticle masses appear to weaken the superconducting state