Some reflections on acquisition, processing and analysis of statistical data in forest soils

Beyond the classical statistical approaches (determination of basic statistics, regression analysis, ANOVA, etc.) a new set of applications of different statistical techniques has increasingly gained relevance in the analysis, processing and interpretation of data concerning the characteristics of forest soils. This is possible to be seen in some of the recent publications in the context of Multivariate Statistics. These new methods require additional care that is not always included or refered in some approaches. In the particular case of geostatistical data applications it is necessary, besides to geo-reference all the data acquisition, to collect the samples in regular grids and in sufficient quantity so that the variograms can reflect the spatial distribution of soil properties in a representative manner. In the case of the great majority of Multivariate Statistics techniques (Principal Component Analysis, Correspondence Analysis, Cluster Analysis, etc.) despite the fact they do not require in most cases the assumption of normal distribution, they however need a proper and rigorous strategy for its utilization. In this work, some reflections about these methodologies and, in particular, about the main constraints that often occur during the information collecting process and about the various linking possibilities of these different techniques will be presented. At the end, illustrations of some particular cases of the applications of these statistical methods will also be presented.

The development and implementation of math projects in a HEI: expectations, objectives, experiences and analysis

An overwhelming problem in Math Curriculums in Higher Education Institutions (HEI), we are daily facing in the last decade, is the substantial differences in Math background of our students. When you try to transmit, engage and teach subjects/contents that your “audience” is unable to respond to and/or even understand what we are trying to convey, it is somehow frustrating. In this sense, the Math projects and other didactic strategies, developed through Learning Management System Moodle, which include an array of activities that combine higher order thinking skills with math subjects and technology, for students of HE, appear as remedial but important, proactive and innovative measures in order to face and try to overcome these considerable problems. In this paper we will present some of these strategies, developed in some organic units of the Polytechnic Institute of Porto (IPP). But, how “fruitful” are the endless number of hours teachers spent in developing and implementing these platforms? Do students react to them as we would expect? Do they embrace this opportunity to overcome their difficulties? How do they use/interact individually with LMS platforms? Can this environment that provides the teacher with many interesting tools to improve the teaching – learning process, encourages students to reinforce their abilities and knowledge? In what way do they use each available material – videos, interactive tasks, texts, among others? What is the best way to assess student’s performance in these online learning environments? Learning Analytics tools provides us a huge amount of data, but how can we extract “good” and helpful information from them? These and many other questions still remain unanswered but we look forward to get some help in, at least, “get some drafts” for them because we feel that this “learning analysis”, that tackles the path from the objectives to the actual results, is perhaps the only way we have to move forward in the “best” learning and teaching direction.

Three essays on game theory and bargaining

A PhD Dissertation, presented as part of the requirements for the Degree of Doctor of Philosophy from the NOVA - School of Business and Economics

The new economy: Essays in network economics and two-sided markets

Following the Introduction, which surveys existing literature on the technology advances and regulation in telecommunications and on two-sided markets, we address specific issues on the industries of the New Economy, featured by the existence of network effects. We seek to explore how each one of these industries work, identify potential market failures and find new solutions at the economic regulation level promoting social welfare. In Chapter 1 we analyze a regulatory issue on access prices and investments in the telecommunications market. The existing literature on access prices and investment has pointed out that networks underinvest under a regime of mandatory access provision with a fixed access price per end-user. We propose a new access pricing rule, the indexation approach, i.e., the access price, per end-user, that network i pays to network j is function of the investment levels set by both networks. We show that the indexation can enhance economic efficiency beyond what is achieved with a fixed access price. In particular, access price indexation can simultaneously induce lower retail prices and higher investment and social welfare as compared to a fixed access pricing or a regulatory holidays regime. Furthermore, we provide sufficient conditions under which the indexation can implement the socially optimal investment or the Ramsey solution, which would be impossible to obtain under fixed access pricing. Our results contradict the notion that investment efficiency must be sacrificed for gains in pricing efficiency. In Chapter 2 we investigate the effect of regulations that limit advertising airtime on advertising quality and on social welfare. We show, first, that advertising time regulation may reduce the average quality of advertising broadcast on TV networks. Second, an advertising cap may reduce media platforms and firms' profits, while the net effect on viewers (subscribers) welfare is ambiguous because the ad quality reduction resulting from a regulatory cap o¤sets the subscribers direct gain from watching fewer ads. We find that if subscribers are sufficiently sensitive to ad quality, i.e., the ad quality reduction outweighs the direct effect of the cap, a cap may reduce social welfare. The welfare results suggest that a regulatory authority that is trying to increase welfare via regulation of the volume of advertising on TV might necessitate to also regulate advertising quality or, if regulating quality proves impractical, take the effect of advertising quality into consideration. 3 In Chapter 3 we investigate the rules that govern Electronic Payment Networks (EPNs). In EPNs the No-Surcharge Rule (NSR) requires that merchants charge at most the same amount for a payment card transaction as for cash. In this chapter, we analyze a three- party model (consumers, merchants, and a proprietary EPN) with endogenous transaction volumes and heterogenous merchants' transactional benefits of accepting cards to assess the welfare impacts of the NSR. We show that, if merchants are local monopolists and the network externalities from merchants to cardholders are sufficiently strong, with the exception of the EPN, all agents will be worse o¤ with the NSR, and therefore the NSR is socially undesirable. The positive role of the NSR in terms of improvement of retail price efficiency for cardholders is also highlighted.

The cloning and reconstitution of a bovine adenovirus type 2 E3 deletion mutant and the sequencing and analysis of the early 4 region

Recombinant Adenoviruses (Ads) have been shown to have potential applications in three areas: gene therapy, high level protein expression and recombinant vaccines.' At least three different locations within the Ad genome can be deleted and subsequently used for the insertion of foreign sequences. These include the Early 3 (E3), Early 1 (E1) and Early 4 (E4) regions. Viral vectors of this type have been well studied in Human Ads 2 and 5, however one has not yet been constructed for Bovine Adenovirus Type 2 (BAV2). The E3 region is located between 76.6 and 86 m.u. on the r-strand and is transcribed in a rightward direction. The gene products of the Early 3 region (E3) have been shown to be non-essential for viral replication, in vitro, but are required for host immunosurveillance. This study represents the cloning and reconstitution of a BAV2 E3 deletion mutant. A deletion of 1800bp was made within the E3 region of BAV2 and the thymidine kinase gene was subsequently inserted in the deleted area . . The plasmid pdlE3-4tk1 (23.4Kbp) was constructed and used to to facilitate homologous recombination with the wild type BAV2 to produce a mutant. Southern Blotting and Hybridization results suggest the presence of a BAV2 E3 deletion mutant with thymidine kinase sequences present. The E4 region of Human Adenovirus types 2 and 5 is located at the extreme right end of the genome (91.3 map units - 99.1 map units) and is transcribed in a leftward direction giving rise to a complicated set of differentially spliced mRNAs. Essentially there are 7 open reading frames (ORFs) encoding for at least 7 polypeptides. The gene products encoded by the E4 region have been shown to be essential for the expression of late viral genes, host cell shutoff and normal viral growth. We have cloned and sequenced the right end segment between 90.5 map units and 100 map units of the BAV2 genome. The results show several open reading frames which encode polypeptides exhibiting homology to three polypeptides encoded by the E4 region of human adenovirus type 2. These include the 14kDa protein encoded by ORF1, the 34kDa protein encoded by ORF6 and the 13kDa protein encoded by ORF3. The nucleotide sequence, restriction enzyme map, and ORF map of the E4 region could be very useful in future molecular manipulation of this region and could possibly explain the slow growth rate of BAV2 in MDBK cells.

Isolation and analysis of a corprinus cinereus DNA fragment showing homology to a fimbrial cDNA from ustilago violacea

Surface proteinaceous fibrils, termed fimbriae, were first identified on gram negative bacteria in the 1940s. Fungal fimbriae, discovered some 25 years later, are found on members of all fungal classes. In the present study, polyclonal antiserum raised against the fimbrial proteins of U. vio/acea were used in order to identify antigenically related proteins from Coprinus cinereus and Schizophy//um commune. Two polypeptides with molecular masses of 37 and 39 kDa from C. cinereus were observed and confirm earlier results. A single previously unidentified 50 kDa polypeptide in S. commune crossreacted with the antiserum. The 50 kDa protein was found to consist of 3 isoforms with isoelectric points ranging from 5.6 to 5.8. A fimbrial cDNA derived from U. vio/acea was used to identify DNA restriction fragments from C. cinereus and S. commune showing homology to the fimbrial transcript of U. vio/acea. Heterologous hybridization with this cDNA was used in order to screen a C. cinereus genomic DNA library. A single clone, A2-3A, with a 14 kbp insert showed strong homology to the pfim3-1 cDNA. The region of homology, a 700 bp Xba I fragment, was subcloned into pUG19. This plasmid was refered to as pXX8. DNA sequence determinations of pXX8 and adjacent fragments from A2-3A suggested that the cloned DNA was a portion of the rONA repeat encoding the small subunit rRNA. DNA sequence analysis of pfim3-1 yielded an incomplete open reading frame. The predicted amino acid sequence codes for a 206 amino acid, 22 kDa polypeptide which contains a domain similar to a transmembrane domain from rat leukocyte antigen, GDS3. As well, an untranslated 576 nucleotide domain showed 81 % homology to pXX8 and 830/0 homology to the 188 rRNA sequence of Ustilago maydis. This sequence was found adjacent to a region of adenine-thymine base pairs presumed to represent the polyadenylation sequence of the fimbrial transcript. The size and extent of homology is sufficient to account for the hybridization of pfim3-1 to rDNA. It is suggested that this domain represents a completely novel regulatory domain within eukaryotes that may enable the observed rapid regeneration of fimbriae in U. violacea.

A multidimensional measurement approach and analysis of children's motivation for reading, attributional style, and reading achievement

The present study investigates the usefulness of a multi-method approach to the measurement of reading motivation and achievement. A sample of 127 elementary and middle-school children aged 10 to 14 responded to measures of motivation, attributions, and achievement both longitudinally and in a challenging reading context. Novel measures of motivation and attributions were constructed, validated, and utilized to examine the relationship between ~ motivation, attributions, and achievement over a one-year period (Study I). The impact of classroom contexts and instructional practices was also explored through a study of the influence of topic interest and challenge on motivation, attributions, and persistence (Study II), as well as through interviews with children regarding motivation and reading in the classroom (Study III). Creation and validation of novel measures of motivation and attributions supported the use of a self-report measure of motivation in situation-specific contexts, and confirmed a three-factor structure of attributions for reading performance in both hypothetical and situation-specific contexts. A one-year follow up study of children's motivation and reading achievement demonstrated declines in all components of motivation beginning at age 10 through 12, and particularly strong decreases in motivation with the transition to middle school. Past perceived competence for reading predicted current achievement after controlling for past achievement, and showed the strongest relationships with reading-related skills in both elementary and middle school. Motivation and attributions were strongly related, and children with higher motivation Fulmer III displayed more adaptive attributions for reading success and failure. In the context of a developmentally inappropriate challenging reading task, children's motivation for reading, especially in terms of perceived competence, was threatened. However, interest in the story buffered some ofthe negative impacts of challenge, sustaining children's motivation, adaptive attributions, and reading persistence. Finally, children's responses during interviews outlined several emotions, perceptions, and aspects of reading tasks and contexts that influence reading motivation and achievement. Findings revealed that children with comparable motivation and achievement profiles respond in a similar way to particular reading situations, such as excessive challenge, but also that motivation is dynamic and individualistic and can change over time and across contexts. Overall, the present study outlines the importance of motivation and adaptive attributions for reading success, and the necessity of integrating various methodologies to study the dynamic construct of achievement motivation.

Comparing motives, goals and weight training behaviours of competitive and recreational weight trainers: An application of organismic integration theory and goal contents theory

The study purpose was to examine differences between competitive and recreational weight trainers on indices of motivation, goals and behaviour. Data was collected from a purposive sample of competitive (n = 177; Mage = 30.86; SDage = 11.35) and recreational (n = 196; Mage = 21.97; SDage = 6.05) weight trainers using a cross-sectional, non-experimental design. Participants completed the Behavioural Regulation in Exercise Questionnaire-2R, Exercise Motivations Inventory-2, assessment of weight training behaviour and demographic questions. Multivariate analyses of variance indicated higher endorsement of autonomous motives and mostly intrinsically-oriented goals, while independent samples t-tests indicated higher frequency of weight training behaviour among the competitive weight trainers. Group differences were independent of demographic factors. Findings suggest that autonomous motives and intrinsic goals may not be undermined by competition among competitive weight trainers. This study also provides support for the utility of organismic integration theory and goal contents theory in examining strength-based exercise.

Adult Learning in the Transformational Environments of the Digital Revolution: Connecting Theory and Practice

The purpose of this study was to investigate the learning preferences and the post-secondary educational experiences of a group of Net-Gen adult learners, aged between 18 and 35, currently working in the knowledge economy workplace, and their assessment of how adequately they were prepared to meet the requirements of the knowledge economy workplace. This study utilized an explanatory mixed-method research design. Participants completed a questionnaire providing information on their self-reported learning style preferences, their use of digital tools for formal and informal learning, their use of digital technologies in postsecondary educational experiences, and their use of digital technologies in their workplace. Four volunteers from the questionnaire respondents were selected to participate in interviews based on the diversity of their experiences in higher education, including digital environments, and the diversity of their knowledge economy workplaces. Data collected from the questionnaire were analyzed for descriptive and demographic statistics, and categorized so that common patterns could be identified from information gathered from the online questionnaire and interviews. Findings based on this study indicated that these Net-Gen adult learners were fluent with all types of digital technologies in collaborative environments, expecting their educational experiences to provide a similar experience. Participants clearly expressed an understanding that digital/collaborative aptitudes are essential to successful employment in the knowledge economy workplace. The findings of this study indicated that the majority of participants felt that their post-secondary educational experiences did not adequately prepare them to meet the expectations of this type of working environment.

Computation and Analysis of Multiple Structural-Change Models

In a recent paper, Bai and Perron (1998) considered theoretical issues related to the limiting distribution of estimators and test statistics in the linear model with multiple structural changes. In this companion paper, we consider practical issues for the empirical applications of the procedures. We first address the problem of estimation of the break dates and present an efficient algorithm to obtain global minimizers of the sum of squared residuals. This algorithm is based on the principle of dynamic programming and requires at most least-squares operations of order O(T 2) for any number of breaks. Our method can be applied to both pure and partial structural-change models. Secondly, we consider the problem of forming confidence intervals for the break dates under various hypotheses about the structure of the data and the errors across segments. Third, we address the issue of testing for structural changes under very general conditions on the data and the errors. Fourth, we address the issue of estimating the number of breaks. We present simulation results pertaining to the behavior of the estimators and tests in finite samples. Finally, a few empirical applications are presented to illustrate the usefulness of the procedures. All methods discussed are implemented in a GAUSS program available upon request for non-profit academic use.