Experiential Learning in Virtual Worlds – A Case Study for Entrepreneurial Training

Virtual worlds offer new possibilities for computer-mediated communication and cooperation because of their threedimensional (3D)-environment, which supports immersive feelings, and because of enhanced interactive techniques. Furthermore, interfaces exist to directly connect virtual worlds with other technologies such as social software, for example wikis, blogs, social networks, and traditional e-learning tools, such as Moodle. From a didactical perspective, these characteristics greatly support innovative distance learning arrangements and are particularly suitable for transferring and gaining experiential knowledge. This paper presents a theory-based framework for the construction of learning arrangements with and in virtual worlds to impart particularly experiential learning. In order to validate the suggestions of the framework and hence, the effectiveness of virtual worlds for e-learning purposes, an e-learning concept is derived from the framework and a prototype of an experiential learning environment is set up on the basis of Second Life (SL). The learning arrangement was validated by two independent groups of students which completed the program. The evaluated satisfaction and perceived usefulness of the learning arrangement are shown and discussed in this paper

Effectiveness of strategies to increase the validity of findings from association studies: size vs. replication

<p>Abstract</p> <p>Background</p> <p>The capacity of multiple comparisons to produce false positive findings in genetic association studies is abundantly clear. To address this issue, the concept of false positive report probability (FPRP) measures "the probability of no true association between a genetic variant and disease given a statistically significant finding". This concept involves the notion of prior probability of an association between a genetic variant and a disease, making it difficult to achieve acceptable levels for the FPRP when the prior probability is low. Increasing the sample size is of limited efficiency to improve the situation.</p> <p>Methods</p> <p>To further clarify this problem, the concept of true report probability (TRP) is introduced by analogy to the positive predictive value (PPV) of diagnostic testing. The approach is extended to consider the effects of replication studies. The formula for the TRP after k replication studies is mathematically derived and shown to be only dependent on prior probability, alpha, power, and number of replication studies.</p> <p>Results</p> <p>Case-control association studies are used to illustrate the TRP concept for replication strategies. Based on power considerations, a relationship is derived between TRP after k replication studies and sample size of each individual study. That relationship enables study designers optimization of study plans. Further, it is demonstrated that replication is efficient in increasing the TRP even in the case of low prior probability of an association and without requiring very large sample sizes for each individual study.</p> <p>Conclusions</p> <p>True report probability is a comprehensive and straightforward concept for assessing the validity of positive statistical testing results in association studies. By its extension to replication strategies it can be demonstrated in a transparent manner that replication is highly effective in distinguishing spurious from true associations. Based on the generalized TRP method for replication designs, optimal research strategy and sample size planning become possible.</p

Precision of the current methods to measure the alkenone proxy UK'37 and absolute alkenone abundance in sediments : results of an interlaboratory comparison study

Measurements of the UK'37 index and the absolute abundance of alkenones in marine sediments are increasingly used in paleoceanographic research as proxies of past sea surface temperature and haptophyte (mainly coccolith-bearing species) primary productivity, respectively. An important aspect of these studies is to be able to compare reliably data obtained by different laboratories from a wide variety of locations. Hence the intercomparability of data produced by the research community is essential. Here we report results from an anonymous interlaboratory comparison study involving 24 of the leading laboratories that carry out alkenone measurements worldwide. The majority of laboratories produce data that are intercomparable within the considered confidence limits. For the measurement of alkenone concentrations, however, there are systematic biases between laboratories, which might be related to the techniques employed to quantify the components. The maximum difference between any two laboratories for any two single measurements of UK'37 in sediments is estimated, with a probability of 95%, to be <2.18C. In addition, the overall within-laboratory precision for the UK'37 temperature estimates is estimated to be <1.68C (95% probability). Similarly, from the analyses of alkenone concentrations the interlaboratory reproducibility is estimated at 32%, and the repeatability is estimated at 24%. The former is compared to a theoretical estimate of reproducibility and found to be excessively high. Hence there is certainly scope and a demonstrable need to improve reproducibility and repeatability of UK'37 and especially alkenone quantification data across the community of scientists involved in alkenone research

Über das Δ 3-Piperideyl - (3) - methylketon : (Untersuchungen zur Synthese des Merochinens)

Praca doktorska Technische Hochschule Danzig

Systematic review of the relation between smokeless tobacco and non-neoplastic oral diseases in Europe and the United States

Abstract Background How smokeless tobacco contributes to non-neoplastic oral diseases is unclear. It certainly increases risk of oral mucosal lesions, but reviewers disagree as to other conditions. In some areas, especially South-East Asia, risk is difficult to quantify due to the many products, compositions (including non-tobacco ingredients), and usage practices involved. This review considers studies from Europe (in practice mainly Scandinavia) and from the USA. Methods Experimental and epidemiological studies published in 1963–2007 were identified that related risk of oral lesions to smokeless tobacco use. Data were assessed separately for oral mucosal lesions, periodontal and gingival diseases, dental caries and tooth loss, and oral pain. Results Oral mucosal lesions: Thirty-three epidemiological studies consistently show a strong dose-related effect of current snuff on oral mucosal lesion prevalence. In Scandinavia, users have a near 100% prevalence of a characteristic "snuff-induced lesion", but prevalence of the varied lesions reported in the USA is lower. Associations with chewing tobacco are weaker. The lack of clear association with former use suggests reversibility following cessation, consistent with experimental studies showing rapid lesion regression on quitting. Periodontal and gingival diseases: Two of four studies report a significant association of snuff with attachment loss and four out of eight with gingival recession. Snuff is not clearly related to gingivitis or periodontal diseases. Limited evidence suggests chewing tobacco is unrelated to periodontal or gingival diseases. Tooth loss: Swedish studies show no association with snuff, but one US study reported an association with snuff, and another with chewing tobacco. Dental caries: Evidence from nine studies suggests a possible relationship with use of smokeless tobacco, particularly chewing tobacco, and the risk of dental caries. Oral pain: Limited evidence precludes any clear conclusion. Conclusion This review confirms the strong association of current use of smokeless tobacco, particularly snuff, with prevalence of oral mucosal lesions. It provides suggestive evidence of an association of snuff use with gingival recession and attachment loss, and of chewing tobacco with dental caries. While smokeless tobacco clearly increases risk of oral mucosal lesions, interpretation for other endpoints is limited by study weaknesses, including poor confounding control.</p