Die Messung der Gluonpolarisation durch die Produktion von Hadronpaaren mit großen Transversalimpulsen in tiefinelastischer Myonstreuung am Nukleon

Am COMPASS-Experiment am CERN-SPS wird die Spinsstruktur des Nukleons mit Hilfe der Streuung von polarisierten Myonen an polarisierten Nukleonen untersucht. Der in der inklusiven tiefinelastischen Streuung gemessene Beitrag der Quarks zum Nukleonspin reicht nicht aus, um den Spin des Nukleons zu erklären. Daher soll geklärt werden, wie die Gluonpolarisation und die Bahndrehimpulse von Quarks und Gluonen zum Gesamtspin des Nukleons beitragen. Da sich die Gluonpolarisation aus der $Q^{2}$-Abhängigkeit der Asymmetrien in der inklusiven Streuung nur abschätzen lässt, wird eine direkte Messung der Gluonpolarisation benötigt. Die COMPASS-Kollaboration bestimmt daher die Wirkungsquerschnittsasymmetrien für Photon-Gluon-Fusionprozesse, indem sie zum einen die offene Charmproduktion und zum anderen die Produktion von Hadronpaaren mit großen Transversalimpulsen verwendet. In dieser Arbeit wird die Messung der Gluonpolarisation mit den COMPASS-Daten der Jahre 2003 und 2004 vorgestellt. Für die Analyse werden die Ereignisse mit großem Impulsübertrag ($Q^{2}>1$ $GeV^{2}/c^{2}$) und mit Hadronpaaren mit großem Transversalimpuls ($p_{perp}>0.7$ $GeV/c$) verwendet. Die Photon-Nukleon-Asymmetrie wurde aus dem gewichteten Doppelverhältnis der selektierten Ereignisse bestimmt. Der Schnitt auf $p_{perp}>0.7$rn$GeV/c$ unterdrückt die Prozesse führender Ordnung und QCD-Compton Prozesse, so dass die Asymmetrie direkt mit der Gluonpolarisation über die Analysierstärke verknüpft ist. Der gemessene Wert ist sehr klein und verträglich mit einer verschwindenden Gluonpolarisation. Zur Vermeidung von falschen Asymmetrien aufgrund der Änderung der Detektorakzeptanz wurden Doppelverhältnisse untersucht, bei denen sich der Wirkungsquerschnitt aufhebt und nur die Detektorasymmetrien übrig bleiben. Es konnte gezeigt werden, dass das COMPASS-Spektrometer keine signifikante Zeitabhängigkeit aufweist. Für die Berechnung der Analysierstärke wurden Monte Carlo Ereignisse mit Hilfe des LEPTO-Generators und des COMGeant Software Paketes erzeugt. Dabei ist eine gute Beschreibung der Daten durch das Monte Carlo sehr wichtig. Dafür wurden zur Verbesserung der Beschreibung JETSET Parameter optimiert. Es ergab sich ein Wert von rn$frac{Delta G}{G}=0.054pm0.145_{(stat)}pm0.131_{(sys)}pm0.04_{(MC)}$ bei einem mittleren Impulsbruchteil von $langle x_{gluon}rangle=0.1$ und $langle Q^{2}rangle=1.9$ $GeV^{2}/c^{2}$. Dieses Ergebnis deutet auf eine sehr kleine Gluonpolarisation hin und steht im Einklang mit den Ergebnissen anderer Methoden, wie offene Charmproduktion und mit den Ergebnissen, die am doppelt polarisierten RHIC Collider am BNL erzielt wurden.

The XENON1T experiment: Monte Carlo background estimation and sensitivity curves study

Despite the scientific achievement of the last decades in the astrophysical and cosmological fields, the majority of the Universe energy content is still unknown. A potential solution to the “missing mass problem” is the existence of dark matter in the form of WIMPs. Due to the very small cross section for WIMP-nuleon interactions, the number of expected events is very limited (about 1 ev/tonne/year), thus requiring detectors with large target mass and low background level. The aim of the XENON1T experiment, the first tonne-scale LXe based detector, is to be sensitive to WIMP-nucleon cross section as low as 10^-47 cm^2. To investigate the possibility of such a detector to reach its goal, Monte Carlo simulations are mandatory to estimate the background. To this aim, the GEANT4 toolkit has been used to implement the detector geometry and to simulate the decays from the various background sources: electromagnetic and nuclear. From the analysis of the simulations, the level of background has been found totally acceptable for the experiment purposes: about 1 background event in a 2 tonne-years exposure. Indeed, using the Maximum Gap method, the XENON1T sensitivity has been evaluated and the minimum for the WIMP-nucleon cross sections has been found at 1.87 x 10^-47 cm^2, at 90% CL, for a WIMP mass of 45 GeV/c^2. The results have been independently cross checked by using the Likelihood Ratio method that confirmed such results with an agreement within less than a factor two. Such a result is completely acceptable considering the intrinsic differences between the two statistical methods. Thus, in the PhD thesis it has been proven that the XENON1T detector will be able to reach the designed sensitivity, thus lowering the limits on the WIMP-nucleon cross section by about 2 orders of magnitude with respect to the current experiments.

Music, perceived arousal, and intensity: psychophysiological reactions to Chopin's "Tristesse"

The present study investigates the relation of perceived arousal (continuous self-rating), autonomic nervous system activity (heart rate, heart rate variability) and musical characteristics (sound intensity, musical rhythm) upon listening to a complex musical piece. Twenty amateur musicians listened to two performances of Chopin's "Tristesse" with different rhythmic shapes. Besides conventional statistical methods for analyzing psychophysiological reactions (heart rate, respiration rate) and musical variables, semblance analysis was used. Perceived arousal correlated strongly with sound intensity; heart rate showed only a partial response to changes in sound intensity. Larger changes in heart rate were caused by the version with more rhythmic tension. The low-/high-frequency ratio of heart rate variability increased-whereas the high frequency component decreased-during music listening. We conclude that autonomic nervous system activity can be modulated not only by sound intensity but also by the interpreter's use of rhythmic tension. Semblance analysis enables us to track the subtle correlations between musical and physiological variables.

Cholesteryl ester accumulation and accelerated cholesterol absorption in intestine-specific hormone sensitive lipase-null mice

Hormone sensitive lipase (HSL) regulates the hydrolysis of acylglycerols and cholesteryl esters (CE) in various cells and organs, including enterocytes of the small intestine. The physiological role of this enzyme in enterocytes, however, stayed elusive. In the present study we generated mice lacking HSL exclusively in the small intestine (HSLiKO) to investigate the impact of HSL deficiency on intestinal lipid metabolism and the consequences on whole body lipid homeostasis. Chow diet-fed HSLiKO mice showed unchanged plasma lipid concentrations. In addition, feeding with high fat/high cholesterol (HF/HC) diet led to unaltered triglyceride but increased plasma cholesterol concentrations and CE accumulation in the small intestine. The same effect was observed after an acute cholesterol load. Gavaging of radioactively labeled cholesterol resulted in increased abundance of radioactivity in plasma, liver and small intestine of HSLiKO mice 4h post-gavaging. However, cholesterol absorption determined by the fecal dual-isotope ratio method revealed no significant difference, suggesting that HSLiKO mice take up the same amount of cholesterol but in an accelerated manner. mRNA expression levels of genes involved in intestinal cholesterol transport and esterification were unchanged but we observed downregulation of HMG-CoA reductase and synthase and consequently less intestinal cholesterol biosynthesis. Taken together our study demonstrates that the lack of intestinal HSL leads to CE accumulation in the small intestine, accelerated cholesterol absorption and decreased cholesterol biosynthesis, indicating that HSL plays an important role in intestinal cholesterol homeostasis.

Influence of transrectal and transabdominal ultrasound examination on salivary cortisol, heart rate, and heart rate variability in mares

Pregnancy diagnostics in equine reproduction are routinely performed using transrectal ultrasonography, although it is also possible to visualize the fetus by transabdominal ultrasound examinations from the 90th day of gestation onward. We hypothesized that ultrasound examinations may stress the mare and that the gestational stage status and lactation may influence the mare's stress reaction. To investigate the stress reaction, 25 thoroughbred mares of different age, pregnancy and lactational status underwent a transrectal examination. In pregnant mares, an additional transabdominal examination was performed. Salivary cortisol concentration, mean heart rate, and heart rate variability of mares were assessed to evaluate the reactions of hypothalamic–pituitary–adrenal (HPA) axis and of the autonomic nervous system. Significant differences were observed between lactating and nonlactating mares; with a lower responsiveness to stress in lactating mares. The transrectal ultrasound examination in nonlactating mares induced a significant increase in salivary cortisol (P < 0.05), and in the heart rate variability parameter, ratio of low to high frequencies (P < 0.05). This reflects an activation of the HPA axis and a shift to more sympathetic dominance. In contrast, a transabdominally performed pregnancy check did not induce an activation of the HPA axis over basal level but increased the mean heart rate and low to high frequency ratio. The results of this study indicate that checks of advanced pregnancies can be easily performed by transabdominal ultrasonography. With regard to animal welfare, this technique should be preferred during midgestation in nonlactating mares.

An examination of the relationship between maternal and neighborhood-level characteristics and intrauterine growth retardation in Harris County, Texas, 1999--2001

The persistence of low birth weight and intrauterine growth retardation (IUGR) in the United States has puzzled researchers for decades. Much of the work that has been conducted on adverse birth outcomes has focused on low birth weight in general and not on IUGR. Studies that have examined IUGR specifically thus far have focused primarily on individual-level maternal risk factors. These risk factors have only been able to explain a small portion of the variance in IUGR. Therefore, recent work has begun to focus on community-level risk factors in addition to the individual-level maternal characteristics. This study uses Social Ecology to examine the relationship of individual and community-level risk factors and IUGR. Logistic regression was used to establish an individual-level model based on 155, 856 births recorded in Harris County, TX during 1999-2001. IUGR was characterized using a fetal growth ratio method with race/ethnic and sex specific mean birth weights calculated from national vital records. The spatial distributions of 114,460 birth records spatially located within the City of Houston were examined using choropleth, probability and density maps. Census tracts with higher than expected rates of IUGR and high levels of neighborhood disadvantage were highlighted. Neighborhood disadvantage was constructed using socioeconomic variables from the 2000 U.S. Census. Factor analysis was used to create a unified single measure. Lastly, a random coefficients model was used to examine the relationship between varying levels of community disadvantage, given the set of individual-level risk factors for 152,997 birth records spatially located within Harris County, TX. Neighborhood disadvantage was measured using three different indices adapted from previous work. The findings show that pregnancy-induced hypertension, previous preterm infant, tobacco use and insufficient weight gain have the highest association with IUGR. Neighborhood disadvantage only slightly further increases the risk of IUGR (OR 1.12 to 1.23). Although community level disadvantage only helped to explain a small proportion of the variance of IUGR, it did have a significant impact. This finding suggests that community level risk factors should be included in future work with IUGR and that more work needs to be conducted. ^

Nosocomial infections and their relationship to non-traditional risk factors in a medical intensive care unit

Background. Nosocomial infections are a source of concern for many hospitals in the United States and worldwide. These infections are associated with increased morbidity, mortality and hospital costs. Nosocomial infections occur in ICUs at a rate which is five times greater than those in general wards. Understanding the reasons for the higher rates can ultimately help reduce these infections. The literature has been weak in documenting a direct relationship between nosocomial infections and non-traditional risk factors, such as unit staffing or patient acuity.^ Objective. To examine the relationship, if any, between nosocomial infections and non-traditional risk factors. The potential non-traditional risk factors we studied were the patient acuity (which comprised of the mortality and illness rating of the patient), patient days for patients hospitalized in the ICU, and the patient to nurse ratio.^ Method. We conducted a secondary data analysis on patients hospitalized in the Medical Intensive Care Unit (MICU) of the Memorial Hermann- Texas Medical Center in Houston during the months of March 2008- May 2009. The average monthly values for the patient acuity (mortality and illness Diagnostic Related Group (DRG) scores), patient days for patients hospitalized in the ICU and average patient to nurse ratio were calculated during this time period. Active surveillance of Bloodstream Infections (BSIs), Urinary Tract Infections (UTIs) and Ventilator Associated Pneumonias (VAPs) was performed by Infection Control practitioners, who visited the MICU and performed a personal infection record for each patient. Spearman's rank correlation was performed to determine the relationship between these nosocomial infections and the non-traditional risk factors.^ Results. We found weak negative correlations between BSIs and two measures (illness and mortality DRG). We also found a weak negative correlation between UTI and unit staffing (patient to nurse ratio). The strongest positive correlation was found between illness DRG and mortality DRG, validating our methodology.^ Conclusion. From this analysis, we were able to infer that non-traditional risk factors do not appear to play a significant role in transmission of infection in the units we evaluated.^

Diagenetic development of deep-sea carbonate sediments from DSDP Holes 30-228, 30-289 and 33-316

Laboratory measurements of ultrasonic velocity (VP, VS) and attenuation (QP**-1, QS**-1) in deep-sea carbonate sequences at DSDP Sites 288, 289 and 316 in the equatorial Pacific were made in conjunction with studies of sediment density, porosity and pore geometry in order to investigate the role of diagenesis in the development of physical properties. Bulk porosity decrease appears to be related more significantly to depth of burial than to age of strata. Both depth of burial and age, however, are important factors controlling the modal pore diameter. In deep-burial diagenesis the modification of pore geometry is influenced by the presence of silica during diagenesis. In carbonate sequences at the three DSDP sites studied, shear wave attenuation anisotropy (QSHH**-1/QSHV**-1) correlates with the shear wave velocity anisotropy. Pore orientation, resulting from overburden pressure and other deep-burial diagenetic processes, is an important factor controlling the increase of VP anisotropy with age and depth of burial. On the basis of observed minor changes in anisotropy values with increasing pressure for some samples, other contributions to VP anisotropy such as grain orientation and bedding lamination cannot be ruled out.

Age determination and paleomagnetic investigations on a sediment profile from laguna Potrok Aike

Paleomagnetic inclination, declination and relative paleointensity were reconstructed from the sediments of Laguna Potrok Aike in the framework of the International Continental scientific Drilling Program (ICDP) Potrok Aike maar lake Sediment Archive Drilling prOject (PASADO). Here we present the u-channel-based full vector paleomagnetic field reconstruction since 51.2 ka cal BP. The relative paleointensity proxy (RPI) was built by normalising the natural remanent magnetisation with the anhysteretic remanent magnetisation using the average ratio at 4 demagnetisation steps part of the ChRM interval (NRM/ARM10e40 mT). A grain size influence on the RPI was removed using a correction based on the linear relationship between the RPI and the median destructive field of the natural remanent magnetisation (MDFNRM). The new record is compared with other lacustrine and marine records and stacks from the mid- to high-latitudes of the Southern Hemisphere, revealing consistent millennial-scale variability, the identification of the Laschamp and possibly the Mono Lake geomagnetic excursions, and a direction swing possibly associated to the Hilina Pali excursion at 20 ka cal BP. Nonetheless, a global-scale comparison with other high-resolution records located on the opposite side of the Earth and with various dipole field references hint at a different behaviour of the geomagnetic field around southern South America at 46 ka cal BP.

Nd-Sr isotopic composition of foraminifera and bulk sediments

We present new isotopic data for sedimentary planktonic foraminifera, as well as for potential water column and sedimentary sources of neodymium (Nd), which confirm that the isotopic composition of the foraminifera is the same as surface seawater and very different from deep water and sedimentary Nd. The faithfulness with which sedimentary foraminifera record the isotopic signature of surface seawater Nd is difficult to explain given their variable and high Nd/Ca ratios, ratios that are often sedimentary foraminifera, ratios that are often much higher than is plausible for direct incorporation within the calcite structure. We present further data that demonstrate a similarly large range in Nd/Ca ratios in plankton tow foraminifera, a range that may be controlled by redox conditions in the water column. Cleaning experiments reveal, in common with earlier work, that large amounts of Nd are released by cleaning with both hydrazine and diethylene triamine penta-acetic acid, but that the Nd released at each step is of surface origin. While further detailed studies are required to verify the exact location of the surface isotopic signature and the key controls on foraminiferal Nd isotope systematics, these new data place the use of planktonic foraminifera as recorders of surface water Nd isotope ratios, and thus of variations in the past supply of Nd to the oceans from the continents via weathering and erosion, on a reasonably sure footing.

Benthic foraminiferal Mg/Ca ratios

Core-top samples from different ocean basins have been analyzed to refine our current understanding of the sensitivity of benthic foraminiferal calcite magnesium/calcium (Mg/Ca) to bottom water temperatures (BWT). Benthic foraminifera collected from Hawaii, Little Bahama Bank, Sea of Okhotsk, Gulf of California, NE Atlantic, Ceara Rise, Sierra Leone Rise, the Ontong Java Plateau, and the Southern Ocean covering a temperature range of 0.8 to 18°C were used to revise the Cibicidoides Mg/Ca-temperature calibration. The Mg/Ca-BWT relationship of three common Cibicidoides species is described by an exponential equation: Mg/Ca = 0.867 ± 0.049 exp (0.109 ± 0.007 * BWT) (stated errors are 95% CI). The temperature sensitivity is very similar to a previously published calibration. However, the revised calibration has a significantly different preexponential constant, resulting in different predicted absolute temperatures. We attribute this difference in the preexponential constant to an analytical issue of accuracy. Some genera, notably Uvigerina, show apparently lower temperature sensitivity than others, suggesting that the use of constant offsets to account for vital effects in Mg/Ca may not be appropriate. Downcore Mg/Ca reproducibility, as determined on replicate foraminiferal samples, is typically better than 0.1 mmol/mol (2 S.E.). Thus, considering the errors associated with the Cibicidoides calibration and the downcore reproducibility, BWT may be estimated to within ±1°C. Application of the revised core-top Mg/Ca-BWT data to Cenozoic foraminiferal Mg/Ca suggests that seawater Mg/Ca was not more than 35% lower than today in the ice-free ocean at 50 Ma.

Physical properties, velocity and attenuation characteristics, and mineralogy of gabbros from ODP Hole 176-735B

Laboratory compressional wave (Vp) and shear wave (Vs) velocities were measured as a function of confining pressure for the gabbros from Hole 735B and compared to results from Leg 118. The upper 500 m of the hole has a Vp mean value of 6895 m/s measured at 200 MPa, and at 500 meters below seafloor (mbsf), Vp measurements show a mean value of 7036 m/s. Vs mean values in the same intervals are 3840 m/s and 3857 m/s, respectively. The mean Vp and Vs values obtained from log data in the upper 600 m are 6520 and 3518 m/s, respectively. These results show a general increase in velocity with depth and the velocity gradients estimate an upper mantle depth of 3.32 km. This value agrees with previous work based on dredged samples and inversion of rare element concentrations in basalts dredged from the conjugate site to the north of the Atlantis Bank. Laboratory measurements show Vp anisotropy ranging between 0.4% and 8.8%, with the majority of the samples having values less than 3.8%. Measurements of velocity anisotropy seem to be associated with zones of high crystal-plastic deformation with predominant preferred mineral orientations of plagioclase, amphiboles, and pyroxenes. These findings are consistent with results on gabbros from the Hess Deep area and suggest that plastic deformation may play an important role in the seismic properties of the lower oceanic crust. In contrast to ophiolite studies, many of the olivine gabbros show a small degree of anisotropy. Log derived Vs anisotropy shows an average of 5.8% for the upper 600 m of Hole 735B and tends to decrease with depth where the overburden pressure and the age of the crustal section suggests closure of cracks and infilling of fractures by alteration minerals. Overall the results indicate that the average shear wave splitting in Hole 735B might be influenced by preferred structural orientations and the average value of shear wave splitting may not be a maximum because structural dips are <90°. The maximum fast-wave orientation values could be influenced by structural features striking slightly oblique to this orientation or by near-field stress concentrations. However, flexural wave dispersion analyses have not been performed to confirm this hypothesis or to indicate to what extent the near-field stresses may be influencing shear wave propagation. Acoustic impedance contrasts calculated from laboratory and logging data were used to generate synthetic seismograms that aid in the interpretation of reflection profiles. Several prominent reflections produced by these calculations suggest that Fe-Ti oxides and shear zones may contribute to the reflective nature of the lower oceanic crust. Laboratory velocity attenuation (Q) measurements from below 500 m have a mean value of 35.1, which is consistent with previous vertical seismic profile (VSP) and laboratory measurements on the upper 500 m.

Automated Tools for Layer Recognition (BMPix) and Counting (PEAK)

We present tools for rapid and quantitative detection of sediment lamination. The BMPix tool extracts color and gray-scale curves from images at pixel resolution. The PEAK tool uses the gray-scale curve and performs, for the first time, fully automated counting of laminae based on three methods. The maximum count algorithm counts every bright peak of a couplet of two laminae (annual resolution) in a smoothed curve. The zero-crossing algorithm counts every positive and negative halfway-passage of the curve through a wide moving average, separating the record into bright and dark intervals (seasonal resolution). The same is true for the frequency truncation method, which uses Fourier transformation to decompose the curve into its frequency components before counting positive and negative passages. We applied the new methods successfully to tree rings, to well-dated and already manually counted marine varves from Saanich Inlet, and to marine laminae from the Antarctic continental margin. In combination with AMS14C dating, we found convincing evidence that laminations in Weddell Sea sites represent varves, deposited continuously over several millennia during the last glacial maximum. The new tools offer several advantages over previous methods. The counting procedures are based on a moving average generated from gray-scale curves instead of manual counting. Hence, results are highly objective and rely on reproducible mathematical criteria. Also, the PEAK tool measures the thickness of each year or season. Since all information required is displayed graphically, interactive optimization of the counting algorithms can be achieved quickly and conveniently.

Maceral distribution, stratigraphic position and vitrinite reflectance at DSDP Hole 81-555

Twenty-four sediment samples from late Paleocene to early Eocene were studied for maceral content, vitrinite reflectance, and spectral fluorescence in order to determine some parameters of the origin and diagenetic history of their organic fraction. The sediments had been obtained at Site 555 of DSDP Leg 81 in the northeastern North Atlantic. The bulk of the microscopically visible fraction is made up of humic materials; inertinites follow as a distant second; and liptinites are exceedingly rare. No unequivocal evidence of marine organic matter was found. Humic materials are highly decomposed, showing signs of aerobic (frequency of sclerotinites) as well as anaerobic (abundance of and intimate association with framboidal pyrite) microbial degradation. Vitrinite reflectance values vary between 0.26 and 0.35 Ro and show a slight increase with depth. These values, indicative of a low-rank lignite stage of coalification, contrast somewhat with the sporinite fluorescence spectra, which show the configuration typical for the peat stage. In either case, the evidence for such a low stage of coalification is surprising in view of the depth and age of the sediments.

Stable oxygen isotope, UK'37, productivity, CaCO3 and XRF records from sediment core MD06-3075

Proxy records of hydrologic variability in the West Pacific Warm Pool (WPWP) have revealed wide-scale changes in past convective activity in response to orbital and sub-orbital climate forcings. However, attributing proxy responses to regional changes in WPWP hydrology versus local variations in precipitation requires independent records linking the terrestrial and marine realms. We present high-resolution stable isotope, UK'37 sea-surface temperature, X-ray fluorescence (XRF) core scanning and coccolithophore-derived paleoproductivity records covering the past 120 ka from International Marine Global Change (IMAGES) Program Core MD06-3075 (6°29' N, 125°50' E, water depth 1878 m), situated in the Davao Gulf on the southern side of Mindanao. XRF-derived log(Fe/Ca) records provide a robust proxy for runoff-driven sedimentary discharge from Mindanao, whilst past changes in local productivity are associated with variable freshwater runoff and stratification of the surface layer. Significant precessional-scale variability in sedimentary discharge occurred during Marine Isotope Stage (MIS) 5, with peaks in discharge contemporaneous with Northern Hemisphere summer insolation minima. We attribute these changes to the latitudinal migration of the Intertropical Convergence Zone (ITCZ) over the WPWP together with variability in the strength of the Walker circulation acting on precessional timescales. Between 60 and 15 ka sedimentary discharge at Mindanao was muted, displaying little orbital- or millennial-scale variability, likely in response to weakened precessional insolation forcing and lower sea level driving increased subsidence of air masses over the exposed Sunda Shelf. These results highlight the high degree of local variability in the precipitation response to past climate changes in the WPWP.