Seismic and gravitational studies of melting in the mantle's thermal boundary layers

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2007This thesis presents three studies which apply geophysical tools to the task of better understanding mantle melting phenomena at the upper and lower boundaries of the mantle. The first study uses seafloor bathymetry and small variations in the gravitational acceleration over the Hawaii-Emperor seamount chain to constrain the changes in the igneous production of the hot spot melting in the mantle which has created these structures over the past 80 My. The second study uses multichannel seismic reflection data to constrain the location and depth of axial magma chambers at the Endeavour Segment of the Juan de Fuca spreading ridge, and then correlates these magma chamber locations with features of the hydrothermal heat extraction system in the upper crust such as microseismicity caused by thermal cracking and high temperature hydrothermal vent systems observed on the seafloor. The third study uses two-dimensional global pseudospectral seismic wave propagation modeling to characterize the sensitivity of the SPdKS seismic phase to two-dimensional, finite-width ultra-low velocity zones (ULVZs) at the core-mantle boundary. Together these three studies highlight the dynamic complexities of melting in the mantle while offering new tools to understand that complexity.This thesis was funded by a National Science Foundation Graduate Research Fellowship, NSF grant OCE-0002551 to theWoods Hole Oceanographic Institution (WHOI), the WHOI Academic Programs Office, the Earth, Atmospheric, and Planetary Science Department at MIT, and by the WHOI Deep Ocean Exploration Institute

International Comparisons of R&D Expenditure: Does an R&D PPP Make a Difference?

Purchasing power parities (PPPs) for R&D expenditure in 19 manufacturing industries are developed for France, Germany, Japan, the Netherlands and the United Kingdom relative to the United States for the years 1997 and 1987. These PPPs are based on R&D input prices for specific cost categories and differ substantially from current practice of comparing R&D expenditure using GDP PPPs and deflators. After taking into account differences in the relative price of R&D labor and materials, separate PPPs for other R&D cost categories are less essential, and a simpler version using GDP PPPs for these other categories should suffice. Our preferred PPPs are used to compare international R&D costs and intensity. The results suggest that the efforts devoted to R&D in each country are more similar across countries than is apparent using the nominal R&D intensities that are currently the norm.

Shocking the Crowd: The Effect of Censorship Shocks on Chinese Wikipedia

Collaborative crowdsourcing has become a popular approach to organizing work across the globe. Being global also means being vulnerable to shocks -- unforeseen events that disrupt crowds -- that originate from any country. In this study, we examine changes in collaborative behavior of editors of Chinese Wikipedia that arise due to the 2005 government censor- ship in mainland China. Using the exogenous variation in the fraction of editors blocked across different articles due to the censorship, we examine the impact of reduction in group size, which we denote as the shock level, on three collaborative behavior measures: volume of activity, centralization, and conflict. We find that activity and conflict drop on articles that face a shock, whereas centralization increases. The impact of a shock on activity increases with shock level, whereas the impact on centralization and conflict is higher for moderate shock levels than for very small or very high shock levels. These findings provide support for threat rigidity theory -- originally introduced in the organizational theory literature -- in the context of large-scale collaborative crowds

Fitting the Gompertz function to dose-response data of larval tick populations

Samples of 6, 1st generation larval populations of Boophilus decoloratus, originating from field collected females, were subjected to increasing doses of the organophosphate acaricide, Dioxathion. The dose-response relationship for 3 populations showed random heterogeneity, where systematic deviations from the linear probit lines were observed for the other 3 populations. Logistic and Gompertz regressions were also fitted for all 6 populations. Probit regressions fitted best for 2 populations exhibiting heterogeneous responses. The logistic regression fitted best for 1 population with heterogeneous responses and 1 population with systematic deviating responses. The Gompertz regression fitted best for the 2 remaining populations exhibiting systematic deviating responses. The Gompertz function may be useful in describing the dose-response relationship obtained for certain acaricidal toxicity tests.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201

Quality of collaboration and information handovers in palliative care: a survey study on the perspectives of nurses in the Southwest Region of the Netherlands

Background: When patients receiving palliative care are transferred between care settings, adequate collaboration and information exchange between health care professionals is necessary to ensure continuity, efficiency and safety of care. Several studies identified deficits in communication and information exchange between care settings. Aim of this study was to get insight in the quality of collaboration and information exchange in palliative care from the perspectives of nurses. Methods: We performed a cross-sectional regional survey study among nurses working in different care settings. Nurses were approached via professional networks and media. Respondents were asked questions about collaboration in palliative care in general and about their last deceased patient. Potential associations between quality scores for collaboration and information handovers and characteristics of respondents or patients were tested with Pearson’s chi-square test. Results: A total of 933 nurses filled in the questionnaire. Nurses working in nursing homes were least positive about inter-organizational collaboration. Forty-six per cent of all nurses had actively searched for such collaboration in the last year. For their last deceased patient, 10% of all nurses had not received the information handover in time, 33% missed information they needed. An adequate information handover was positively associated with timeliness and completeness of the information and the patient being well-informed, not with procedural characteristics. Conclusion: Nurses report that collaboration between care settings and information exchange in palliative care is suboptimal. This study suggests that health care organizations should give more attention to shared professionalization towards inter-organizational collaboration among nurses in order to facilitate high-quality palliative care

On sampling tick populations : the problem of overdispersion

Data collected on both free-living and parasitic tick populations are likely to be overdispersed. The use of means from few replicate samples of overdispersed data as quantitative estimators of tick population density is in turn likely to lead to inaccurate interpretations which may be scientifically misleading. In this paper ways of estimating overdispersion are listed and suggestions for the use of correct statistical tests for handling overdispersed data are given.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201

Hyperlactatemia After Intracranial Tumor Surgery Does Not Affect 6-Month Survival: A Retrospective Case Series

BACKGROUND: Patients undergoing neurosurgery frequently exhibit hyperlactatemia. The aim of this study was to identify factors associated with hyperlactatemia and assess how hyperlactatemia impacts survival and hospital length of stay after intracranial tumor surgery. MATERIALS AND METHODS: This retrospective cohort study included 496 adult patients that underwent surgery between January 1, 2014 and December 31, 2015. We evaluated patient characteristics, surgery characteristics, pH, lactate, and blood glucose from blood samples collected on admission to the high-dependency unit and the morning after surgery, and 6-month outcome data. RESULTS: Hyperlactatemia (>2.0 mmol/L) occurred in >50% of patients, but only 7.7% had acidosis. Postoperative hyperlactatemia was not correlated with 6-month survival (P=0.987), but was correlated with (median [interquartile range]) longer hospital stays (6 [4 to 8.5] d vs. 5 [4 to 8] d; P=0.006), longer surgery duration (4:53 [4:01 to 6:18