An endorsement-based approach to student modeling for planner-controlled intelligent tutoring systems

An approach is described to student modeling for intelligent tutoring systems based on an explicit representation of the tutor's beliefs about the student and the arguments for and against those beliefs (called endorsements). A lexicographic comparison of arguments, sorted according to evidence reliability, provides a principled means of determining those beliefs that are considered true, false, or uncertain. Each of these beliefs is ultimately justified by underlying assessment data. The endorsement-based approach to student modeling is particularly appropriate for tutors controlled by instructional planners. These tutors place greater demands on a student model than opportunistic tutors. Numerical calculi approaches are less well-suited because it is difficult to correctly assign numbers for evidence reliability and rule plausibility. It may also be difficult to interpret final results and provide suitable combining functions. When numeric measures of uncertainty are used, arbitrary numeric thresholds are often required for planning decisions. Such an approach is inappropriate when robust context-sensitive planning decisions must be made. A TMS-based implementation of the endorsement-based approach to student modeling is presented, this approach is compared to alternatives, and a project history is provided describing the evolution of this approach

Alien Registration- Murray, William R. (Yarmouth, Cumberland County)

https://digitalmaine.com/alien_docs/20597/thumbnail.jp

Species interactions and diversity: A unified framework using Hill numbers

Biodiversity describes the variety of organisms on planet earth. Ecologists have long hoped for a synthesis between analyses of biodiversity and analyses of biotic interactions among species, such as predation, competition, and mutualism. However, it is often unclear how to connect details of these interactions with complex modern analyses of biodiversity. To resolve this gap, we propose a unification of models of biotic interactions and measurements of diversity. We show that analyses of biodiversity obscure details about biotic interactions. For example, identical changes in biodiversity can arise from predation, competition or mutualism. Our approach indicates that traditional models of community assembly miss key facets of diversity change. Instead, we suggest that analyses of diversity change should focus on partitions, which measure mechanisms that directly shape changes in diversity, notably species level selection and immigration, rather than traditional analyses of biotic interactions

Climatic variations on Mars: 2. Evolution of carbon dioxide atmosphere and polar caps

The long-term variations in the atmospheric pressure and the polar cap temperature of Mars resulting from the obliquity oscillations (presented by W. R. Ward, 1974) are discussed. In performing these calculations, the assumption is made that the atmosphere is in equilibrium with perennial CO_2 ice deposits at the north pole, as is proposed by R. B. Leighton and B. C. Murray (1966). If heat transport by the atmosphere is neglected, the temperature of CO_2 ice at the poles ranges from ∼130°K to ∼160°K, the corresponding atmospheric pressure rising from a few tenths of a millibar to ∼30 mbar, respectively. The neglect of atmospheric heat transport probably underestimates the peak pressure. Because the altitude of the south cap is ∼2 km higher than that of the north cap, CO_2 ice is unstable there and will migrate to the north cap at a rate ∼10 g/cm^2 yr, the implication being that the south residual cap is water ice. A simplified model of the annual polar caps and pressure fluctuations is also presented. This indicates that when the obliquity is at its maximum, the annual caps may be greatly enlarged in both mass and maximum coverage. The modifications introduced by including significant atmospheric heat transport are then discussed. Finally, the implications of different past climatic conditions on the mechanism of eolian erosion are briefly considered

The amylase creatinine clearance ratio

The aims of the studies in this thesis were to evaluate the role of the amylase creatinine clearance ratio (ACCR) as a diagnostic test in British patients with acute pancreatitis and to attempt to demonstrate whether or not a significant elevation in the ACCR is related to pancreatic inflammation. In two studies in this thesis a significant elevation in the ACCR was found to be 94% accurate in diagnosing acute pancreatitis confirmed by other methods and the ACCR was found to be the most successful single-non- invasive diagnostic test for this condition. No patient without acute pancreatitis was found to have an ACCR above the upper limit of normal, including patients with acute abdominal conditions other than acute pancreatitis who had hyperamylasaemia. The ACCR was also found to have prognostic significance in acute pancreatitis being significantly related to the severity of each attack as defined by established prognostic factors and retrospective analysis of each patient*s illness. An admission ACCR of over 10% in a patient with acute pancreatitis was found to be highly suggestive of a severe attack with a mortality greater than 50%. The ACCR was found to remain abnormal for longer than serum amylase in acute pancreatitis and was judged to be of value in diagnosing acute pancreatitis in patients presenting to hospital with abdominal pain of over 48 hours duration, Post-cholecystectomy pancreatitis is well documented and significant ACCR elevations have been recorded after biliary surgery. A study was designed to confirm significant ACCR elevations after biliary surgery and demonstrate that this elevation was related to pancreatic inflammation. Intravenous Trasylol, a proteolytic enzyme inhibitor, was infused before, during and after biliary surgery in a group of patients and was found to significantly reduce the incidence of significant ACCR elevation on the first postoperative day. It has been shown in animal experiments that Trasylol can significantly modify the severity of acute pancreatitis when given prior to the induction of the pancreatitis and its failure to significantly influence the course of established acute pancreatitis in humans is almost certainly due to the fact that it is given once the inflammatory process is established. In this study it was possible to administer Trasylol prophylactically with results in keeping with the hypothesis that post- biliary surgery ACCR elevation is due to pancreatic inflammation. Acute pancreatitis and elevated ACCR values have also been recorded after cardiac surgery performed using non-pulsatile cardiopulmonary bypass. The pancreatitis developing in this situation is thought to be ischaemic in origin and it has recently been shown that pulsatile cardiopulmonary bypass can improve tissue perfusion and the functioning of several organs during bypass, ACCR changes during and after cardiac surgery performed using either non-pulsatile bypass or pulsatile bypass were studied. Significant ACCR elevation was observed in 9 out of 10 patients using non-pulsatile bypass but only 1 out of 10 patients using pulsatile bypass. The AGCR changes associated with cardiac surgery performed using cardiopulmonary bypass can therefore be significantly altered by the mode of perfusion employed. The evidence from this study suggests that the significant reduction in ACCR elevation during and after pulsatile bypass is related to normalisation of pancreatic function resulting from improved tissue perfusion. (Abstract shortened by ProQuest.)

Naturalness vs. Predictability: A Key Debate in Controlled Languages

Abstract. In this paper we describe two quite different philosophies used in developing controlled languages (CLs): A "naturalist " approach, in which CL interpretation is treated as a simpler form of full natural language processing; and a "formalist " approach, in which the CL interpretation is “deterministic” (context insensitive) and the CL is viewed more as an English-like formal specification language. Despite the philosophical and practical differences, we suggest that a synthesis can be made in which a deterministic core is embedded in a naturalist CL, and illustrate this with our own controlled language CPL. In the second part of this paper we present a fictitious debate between an ardent “naturalist ” and an ardent “formalist”, each arguing their respective positions, to illustrate the benefits and tradeoffs of these different philosophies in an accessible way. Part I: The Naturalist vs. Formalist Debate

Globular Clusters and X-ray Point Sources in Centaurus A (NGC 5128)

We detect 353 X-ray point sources, mostly low-mass X-ray binaries (LMXBs), in four Chandra observations of Centaurus A (NGC 5128), the nearest giant early-type galaxy, and correlate this point source population with the largest available ensemble of confirmed and likely globular clusters associated with this galaxy. Of the X-ray sources, 31 are coincident with 30 globular clusters that are confirmed members of the galaxy by radial velocity measurement (2 X-ray sources match one globular cluster within our search radius), while 1 X-ray source coincides with a globular cluster resolved by HST images. Another 36 X-ray point sources match probable, but spectroscopically unconfirmed, globular cluster candidates. The color distribution of globular clusters and cluster candidates in Cen A is bimodal, and the probability that a red, metal rich GC candidate contains an LMXB is at least 1.7 times that of a blue, metal poor one. If we consider only spectroscopically confirmed GCs, this ratio increases to ~3. We find that LMXBs appear preferentially in more luminous (massive) GCs. These two effects are independent, and the latter is likely a consequence of enhanced dynamical encounter rates in more massive clusters which have on average denser cores. The X-ray luminosity functions of the LMXBs found in GCs and of those that are unmatched with GCs reveal similar underlying populations, though there is some indication that fewer X-ray faint LMXBs are found in globular clusters than X-ray bright ones. Our results agree with previous observations of the connection of GCs and LMXBs in early-type galaxies and extend previous work on Centaurus A.Comment: 34 pages, 10 figures, 2 tables, Accepted for Publication in The Astrophysical Journa