Organ donation for transplantation:a clinical study with emphasis on liver donation

The central theme of this thesis was the continuing organ shortage. Several factors have been held responsible for this shortage, including refusal of permission for organ donation by the next-of-kin, insufficient recognition of potential organ donors by the medical staff, and -unjustified- discard of donors by transplant teams either due to logistic reasons or because of medical reasons. Apart from the logistic reasons, we have explored these different causes for organ shortage. With respect to the problem of medical discard we have focused on the liver, because transplantation of a viable liver graft is an important prereguisite for patient survival due to the lack of extracorporeal liver support. In this chapter we will summarize and discuss the findings of the studies in the previous chapters. Finally, recommendations for the future are given. ... Zie: Summar

Effects of New Science Textbooks on Selected Sixth and Eighth Grade Students at Crestwood Elementary School, Paris, Illinois

This paper describes the results of a six-month field study to determine the effects of a newly adopted and implemented junior-high level science textbook series on student achievement. This study took place in the sixth, seventh, and eighth grade science classrooms of Crestwood Elementary School, Paris, Illinois, from December 1988, until May of 1989. This study compared the science achievement of two groups of students in both their sixth and eighth grade years. The Normal Curve Equivalents or NCE\u27s and letter grades as given by the junior-high level science teachers at Crestwood, were analyzed using non-independent t tests. Descriptive data was obtained by using two Likert-type surveys. The first Likert-type survey instrument was used to determine if the three junior-high science teachers varied in significant ways as to their usages and applications of the new science textbook series, in their classrooms. The second Likert-type survey instrument was used to survey the experimental group (this years eighth graders at Crestwood which were the only group of students exposed to the treatment variable) in regard to their feelings toward the new science textbook series, and as to whether or not their new science textbook series was easier to read and/or understand than the previous textbook series. Findings from the non-independent t-tests determined that the NCE\u27s and letter grades were statistically significant (with the exception of the Class of 1988\u27s NCE scores) at the pre-set level of .05. Findings from the descriptive data suggest that there is a significant amount of variation among the three junior-high science teachers at Crestwood in terms of: text usages, frequency of usage, classroom level objectives, content, ideas, concepts, and knowledges related to what is taught at the classroom level. The hypothesis suggesting that the change in textbook series was statistically significant in regard to higher NCE\u27s on standardized test scores is supported. The hypothesis suggesting that the change in textbook series was statistically significant in regard to higher grades earned by students in science is rejected

Advice On Facebook: Channel Effects On The Evaluation Of Advice

This thesis explores the evaluation of advice given in comments on Facebook status updates. To date, most research on advice has focused on dyadic, face-to-face interactions. The masspersonal channel of Facebook introduces a public into advice exchanges, including not only an audience but multiple advisors. The current study extends advice response theory by examining how advice recipients are affected by perceived consensus and tailoring in advice messages, and by the trait of conformity or the desire to conform to others\u27 opinions. Participants (N = 269) completed questionnaires about past status updates on Facebook in which they disclosed a problem and received advice in comments from friends. Hierarchical multiple regression and mediation analyses were used to test the effects of consensus, tailoring, and conformity, along with message content and advisor characteristics. Message content was the strongest predictor of intention to implement advice, and mediated the influence of advisor characteristics. Consensus was a significant independent predictor. The effect of tailoring was mediated by message content and advisor characteristics. Finally, problem seriousness had a direct effect on intention to implement advice, moderated by tailoring. Theoretical and practical implications are discussed, along with directions for future research

Sediment-moss interactions on a temperate glacier: Falljökull, Iceland

Full text of this article can be found at: http://www.igsoc.org/annals/ Copyright IGS. DOI: 10.3189/172756408784700734We present the results of preliminary investigations of globular moss growth on the surface of Falljökull, a temperate outlet glacier of the Vatnajökull ice cap, southern Iceland. Supraglacial debris has provided a basis for moss colonization, and several large (>500 m2) patches of moss growth (Racomitrium spp.) are observed on the surface of the glacier. Each area of moss-colonized supraglacial debris shows a downslope increase in sphericity and moss cushion size and a decrease in percentage surface coverage of moss-colonized and bare clasts. It is suggested that moss growth on supraglacial debris allows preferential downslope movement of clasts through an associated increase in both overall mass and sphericity. Thermal insulation by moss cushions protects the underlying ice surface from melt, and the resulting ice pedestals assist in downslope sliding and toppling of moss cushions. The morphology and life cycle of supraglacial globular mosses is therefore not only closely linked to the presence and distribution of supraglacial debris, but also appears to assist in limited down-glacier transport of this debris. This research highlights both the dynamic nature of the interaction of mosses with supraglacial sedimentary systems and the need for a detailed consideration of their role within the wider glacial ecosystem.Peer reviewe

Hyper-polynomial hierarchies and the polynomial jump

AbstractAssuming that the polynomial hierarchy (PH) does not collapse, we show the existence of ascending sequences of ptime Turing degrees of length ω1CK in PSPACE such that successors are polynomial jumps of their predecessors. Moreover these ptime degrees are all uniformly hard for PH. This is analogous to the hyperarithmetic hierarchy, which is defined similarly but with the (computable) Turing degrees. The lack of uniform least upper bounds for ascending sequences of ptime degrees causes the limit levels of our hyper-polynomial hierarchy to be inherently non-canonical. This problem is investigated in depth, and various possible structures for hyper-polynomial hierarchies are explicated, as are properties of the polynomial jump operator on the languages which are in PSPACE but not in PH

The importance of good coding practices for data scientists

Many data science students and practitioners are reluctant to adopt good coding practices as long as the code "works". However, code standards are an important part of modern data science practice, and they play an essential role in the development of "data acumen". Good coding practices lead to more reliable code and often save more time than they cost, making them important even for beginners. We believe that principled coding practices are vital for statistics and data science. To install these practices within academic programs, it is important for instructors and programs to begin establishing these practices early, to reinforce them often, and to hold themselves to a higher standard while guiding students. We describe key aspects of coding practices (both good and bad), focusing primarily on the R language, though similar standards are applicable to other software environments. The lessons are organized into a top ten list

Reduction of artefacts caused by hip implants in CT-based attenuation-corrected PET images using 2-D interpolation of a virtual sinogram on an irregular grid

Purpose: Metallic prosthetic replacements, such as hip or knee implants, are known to cause strong streaking artefacts in CT images. These artefacts likely induce over- or underestimation of the activity concentration near the metallic implants when applying CT-based attenuation correction of positron emission tomography (PET) images. Since this degrades the diagnostic quality of the images, metal artefact reduction (MAR) prior to attenuation correction is required. Methods: The proposed MAR method, referred to as virtual sinogram-based technique, replaces the projection bins of the sinogram that are influenced by metallic implants by a 2-D Clough-Tocher cubic interpolation scheme performed in an irregular grid, called Delaunay triangulated grid. To assess the performance of the proposed method, a physical phantom and 30 clinical PET/CT studies including hip prostheses were used. The results were compared to the method implemented on the Siemens Biograph mCT PET/CT scanner. Results: Both phantom and clinical studies revealed that the proposed method performs equally well as the Siemens MAR method in the regions corresponding to bright streaking artefacts and the artefact-free regions. However, in regions corresponding to dark streaking artefacts, the Siemens method does not seem to appropriately correct the tracer uptake while the proposed method consistently increased the uptake in the underestimated regions, thus bringing it to the expected level. This observation is corroborated by the experimental phantom study which demonstrates that the proposed method approaches the true activity concentration more closely. Conclusion: The proposed MAR method allows more accurate CT-based attenuation correction of PET images and prevents misinterpretation of tracer uptake, which might be biased owing to the propagation of bright and dark streaking artefacts from CT images to the PET data following the attenuation correction procedur