Predictive Capability of Cardiopulmonary and Exercise Parameters From Day 1 to 6 Months After Acute Pulmonary Embolism

We hypothesized that the slope of relation ventilation to carbon dioxide output (V'E/V'CO2-slope) could be predictive already during the very first days after submassive pulmonary embolism (PE) to right ventricular systolic pressure (RVsys by echocardiography) after 6 months. We evaluated 21 hemodynamically stable patients at admittance, at days 3, 7, 90, and 180 by cardiopulmonary exercise testing and echocardiography. V'E/V'CO2-slope (48.4 ± 10.8) decreased within the first week (43.0 ± 9.8 at day 7) and normalized until follow-up at 6 months (35.0 ± 11.3; P < 10-4), p(a-ET)CO2 remained abnormal between days 1 and 3 (5.0 ± 3.9 to 6.7 ± 5.3 mmHg). RVsys declined from 41.7 ± 14.3 to 26.3±13.1 mmHg (P < 10-4) at 6 months. V'E/V'CO2-slope (r²= 0.27; P < .02) and RVsys (r² = 0.28; P = .03) at day 7 correlated with RVsys at 6 months. p(a-ET)CO2, p(a-ET)O2, V'D/V'T were not related to RVsys after 6 months. RVsys 6 months after acute PE is positively correlated with the V'E/V'CO2-slope at day 7.

Microsecond Structural Rheology

The relationship between the local structure of complex liquids and their response to shear is generally not well understood. This concerns, in particular, the formation of particle strings in the flow direction or hydroclusters, both important for the understanding of shear thinning and thickening phenomena. Here, we present results of a microfocus X-ray scattering experiment on spherical silica colloids in a liquid jet at high shear rates. Along and across the jet, we observe direction-dependent modifications of the structure factor of the suspension, suggesting the formation of differently ordered clusters in compression lines and as particle strings. With increasing distance from the orifice, the structure relaxes to the unsheared case with a typical relaxation 10 times larger as the time scale of Brownian motion. These results provide the first experimental flow characterization of a complex fluid at high shear rates detecting cluster formation and relaxation with micrometer and microsecond resolution.

Temperature dependence of the hydrogen bond network in trimethylamine N-oxide and guanidine hydrochloride–water solutions

We present an X-ray Compton scattering study on aqueous trimethylamine N-oxide (TMAO) and guanidine hydrochloride solutions (GdnHCl) as a function of temperature.

A liquid jet setup for x-ray scattering experiments on complex liquids at free-electron laser sources

In this paper we describe a setup for x-ray scattering experiments on complex fluids using a liquid jet. The setup supports Small and Wide Angle X-ray Scattering (SAXS/WAXS) geometries. The jet is formed by a gas-dynamic virtual nozzle (GDVN) allowing for diameters ranging between 1 μm and 20 μm at a jet length of several hundred μm. To control jet properties such as jet length, diameter, or flow rate, the instrument is equipped with several diagnostic tools. Three microscopes are installed to quantify jet dimensions and stability in situ. The setup has been used at several beamlines performing both SAXS and WAXS experiments. As a typical example we show an experiment on a colloidal dispersion in a liquid jet at the X-ray Correlation Spectroscopy instrument at the Linac Coherent Light Source free-electron laser.

Intramolecular structure and energetics in supercooled water down to 255 K

We studied the structure and energetics of supercooled water by means of X-ray Raman and Compton scattering. Under supercooled conditions down to 255 K, the oxygen K-edge measured by X-ray Raman scattering suggests an increase of tetrahedral order similar to the conventional temperature effect observed in non-supercooled water. Compton profile differences indicate contributions beyond the theoretically predicted temperature effect and provide a deeper insight into local structural changes. These contributions suggest a decrease of the electron mean kinetic energy by 3.3 ± 0.7 kJ (mol K)(-1) that cannot be modeled within established water models. Our surprising results emphasize the need for water models that capture in detail the intramolecular structural changes and quantum effects to explain this complex liquid.

Nano-beam X-ray microscopy of dried colloidal films

We report on a nano-beam small angle X-ray scattering study on densely-packed, dried binary films made out of spherical silica particles with radii of 11.2 and 19.3 nm. For these three-dimensional thin films prepared by drop casting, only a finite number of colloidal particles contributes to the scattering signal due to the small beam size of 400 × 400 nm(2). By scanning the samples, the structure and composition of the silica particle films are determined spatially resolved revealing spatial heterogeneities in the films. Three different types of domains were identified: regions containing mainly large particles, regions containing mainly small particles, and regions where both particle species are mixed. Using the new angular X-ray cross-correlations analysis (XCCA) approach, spatial maps of the local type and degree of orientational order within the silica particle films are obtained. Whereas the mixed regions have dominant two-fold order, weaker four-fold and marginal six-fold order, regions made out of large particles are characterized by an overall reduced orientational order. Regions of small particles are highly ordered showing actually crystalline order. Distinct differences in the local particle order are observed by analyzing sections through the intensity and XCCA maps. The different degree of order can be understood by the different particle size polydispersities. Moreover, we show that preferential orientations of the particle domains can be studied by cross-correlation analysis yielding information on particle film formation. We find patches of preferential order with an average size of 8-10 μm. Thus, by this combined X-ray cross-correlation microscopy (XCCM) approach the structure and orientational order of films made out of nanometer sized colloids can be determined. This method will allow to reveal the local structure and order of self-assembled structures with different degree of order in general.

Single shot speckle and coherence analysis of the hard X-ray free electron laser LCLS

The single shot based coherence properties of hard x-ray pulses from the Linac Coherent Light Source (LCLS) were measured by analyzing coherent diffraction patterns from nano-particles and gold nanopowder. The intensity histogram of the small angle x-ray scattering ring from nano-particles reveals the fully transversely coherent nature of the LCLS beam with a number of transverse mode 〈Ms〉 = 1.1. On the other hand, the speckle contrasts measured at a large wavevector yields information about the longitudinal coherence of the LCLS radiation after a silicon (111) monochromator. The quantitative agreement between our data and the simulation confirms a mean coherence time of 2.2 fs and a x-ray pulse duration of 29 fs. Finally the observed reduction of the speckle contrast generated by x-rays with pulse duration longer than 30 fs indicates ultrafast dynamics taking place at an atomic length scale prior to the permanent sample damage.

Single shot spatial and temporal coherence properties of the SLAC Linac Coherent Light Source in the hard x-ray regime

We measured the transverse and longitudinal coherence properties of the Linac Coherent Light Source (LCLS) at SLAC in the hard x-ray regime at 9 keV photon energy on a single shot basis. Speckle patterns recorded in the forward direction from colloidal nanoparticles yielded the transverse coherence properties of the focused LCLS beam. Speckle patterns from a gold nanopowder recorded with atomic resolution allowed us to measure the shot-to-shot variations of the spectral properties of the x-ray beam. The focused beam is in the transverse direction fully coherent with a mode number close to 1. The average number of longitudinal modes behind the Si(111) monochromator is about 14.5 and the average coherence time τ(c)=(2.0±1.0) fc. The data suggest a mean x-ray pulse duration of (29±14)  fs behind the monochromator for (100±14) fc electron pulses.

Hyperfine spectroscopy of the 1s(5)-2p(9) transition of 39Ar

We report on the first experimental determination of the hyperfine structure of the 1s(5)-2p(9) transition in (39)Ar. We give a detailed description of the sample preparation, spectroscopy cell cleaning, and spectroscopic setup. The resulting set of parameters consists of the hyperfine constants of the levels involved and the isotopic shift between (39)Ar and (40)Ar. With the achieved precision all laser frequencies necessary for the implementation of atom trap trace analysis for (39)Ar, i.e., laser cooling and repumping frequencies, are now known.

On the power of plotless density estimators for statistical comparisons of plant populations

Reliable density estimations of plant populations and their statistical comparison are fundamental in many ecological studies. Typical sampling methods are plotless density estimators (PDE) and plot counts. A simulation study was performed to examine the power of these sampling methods for the statistical comparison of the densitiesof two plant populations. The variable area transect estimator, the ordered distance estimator, and Byth’s T-square estimator were considered and compared with the quadrat count estimator. The relative root-mean-squared error and the relative bias were used to explore the quality of the estimators, and robust confidence intervals and standard deviation estimators were given. Tests were developed to compare the population densities of two independent populations, and the performance of the tests was examined. All simulations were run for spatially random and aggregate data patterns. For completely random data, all estimators and all tests behaved well if they were based on the same sampling intensity. For the aggregate pattern, all PDE’s were negatively biased, but the quadrat count estimator was unbiased. Nonparametric confidence intervals had the most robust performance for aggregate data. The results of the presented simulation study demonstrate that plant ecologists should avoid PDE for both density estimation and statistical testing except when the pattern of a population is known to follow a completely random spatial pattern. Instead, the use of the plot count estimator is recommended.