The design of the SCENT automated advisor

The SCENT (Student Computing ENvironmenT) project is concerned with building an intelligent tutoring system to help student programmers debug their LISP programs. The major thrust of current SCENT investigations is into the design of the SCENT advisor which is meant to provide debugging assistance to novice students. Six conceptual levels constitute the advisor. At the lowest level is the "raw data," consisting of the student's (possibly buggy) program. This can be interpreted by a "program behaviour" level which can produce traces, cross-reference charts, etc. from the student's program. These traces, etc. can be analyzed by "observers" for interesting patterns. At the next level are "strategy judges" and "diagnosticians" which determine which strategy the student has used in his/her program and bugs in this strategy. A "task expert" provides task-specific input into the process of analyzing the student's solution, and a "student-knowledge component" provides student-specific input into this process. Information from the six levels interacts in a variety of ways and control is similarly hierarchical. This necessitates a blackboard-style scheme to coordinate information dissemination and control flow.
This paper discusses the objectives of SCENT and focusses on organizing the process of debugging student programs. A complete example is given to illustrate how entities at the six levels interact and to indicate the kinds of information sharing that occur in the SCENT advisor. The paper concludes with an evaluation of the strengths and weaknesses of this approach to automated debugging, and suggestions about directions for further exploration.     

Resuscitation from hemorrhagic shock with diaspirin cross-linked hemoglobin, blood, or hetastarch

BACKGROUND: An oxygen-transporting hemoglobin solution should be more effective than a nonhemoglobin solution for resuscitation from hemorrhagic shock. A way to evaluate this effectiveness is to determine whether a hemoglobin solution can reverse the base deficit accumulated during hemorrhage at a faster rate than a nonhemoglobin solution. Using this criterion, we compared the resuscitative powers of autologous blood, hetastarch (Het), and diaspirin cross-linked hemoglobin (DCLHb). METHODS: Fifteen sedated, spontaneously breathing sheep (37.5 +/- 10.2 kg) were bled until base deficits fell to -5 to -10 mEq/L, and plasma lactate concentrations rose to 6 to 9 mg/L. The animals were resuscitated with autologous blood (n = 5), Het (n = 5), or DCLHb (n = 5) (3.5-4.0 mL/kg every 15 minutes) until base deficits returned to prehemorrhage baseline. RESULTS: Exsanguination to target base deficits required removal of an average of 41.4 +/- 5.5 mL blood/kg (estimated total blood volume, 80 mL/kg). Resuscitation required 18 +/- 3, 38 +/- 2 (different from blood), and 35 +/- 1 (different from blood) mL/kg of autologous blood, Het and DCLHb, respectively, over periods of 78 +/- 8, 163 +/- 10 (different from blood), and 129 +/- 9 minutes (different from blood and different from Het (p < or = 0.05)). Based on regression analysis, autologous blood, Het, and DCLHb corrected the base deficit at rates of, respectively, 0.074 (different from Het (p < or = 0.05)), 0.016, and 0.056 (different from Het (P < or = 0.05)) mEq/L/min. CONCLUSIONS: Based on the rate of base deficit correction and the volume of solution required, autologous blood was the most effective resuscitation solution. However, DCLHb was more effective than Het. DCLHb may be an attractive alternative to blood for resuscitation from hemorrhagic shock.     

Preparation and Electrochemical Properties of bis-2.2′-(4.5-Dimethyl-1.3-dithiolium)-1.4-phenylene-bis-perchlorate

The title compound C₁₆H₁₆S₄(ClO₄)₂, hereafter called (TMCHDT) (ClO₄)₂, has been synthesized by a simple two-step reaction sequence. Its electrochemical behaviour was studied by cyclic volammetry under superdry conditions. Different results were obtained depending on the nature of the solvent. In propionitrile, the voltammograms showed an irreversible two-electron transfer wave at E_p = +0.050 V vs. Ag/AgCl. In methylenechloride, however, two separate, reversible one-electron transfer waves were observed at half wave potentials of E^I_1/2 = −0.107 V and E^II_1/2 = −0.321 vs. Ag/AgCl, respectively.     

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Changes in the activation markers of blood coagulation and fibrinolysis in the neonatal period

BACKGROUND: Activation markers of the clotting and fibrinolytic systems are elevated immediately after birth and decline to near adult levels during the first 24 hours of life. The aims of this study were to investigate, whether the activation of both clotting and fibrinolysis is dependent on the mode of delivery, and to measure activation markers in newborns with infection beyond the first days of life. PATIENTS: We have studied activation markers thrombin-antithrombin III complex, prothrombin fragment 1 + 2, D-dimer and plasmin-antiplasmin complex by use of commercially available ELISA techniques in 20 newborns after elective Cesarean sections because of previous sections, in 20 newborns after Cesarean sections and a trial of labor with uterine contractions over a period of > 20 hours and in 20 newborns (34.-41. gestational week) aged 10-25 days with infection. 20 healthy adults served as controls. RESULTS: A significant elevation of all activation markers was observed both in the newborns after Cesarean sections and in the 10-25 days old children with infection. There were no differences among newborns after elective sections compared to newborns after section and a trial of labor with uterine contractions over a period of > 20 hours. CONCLUSIONS: The clotting and fibrinolytic systems reveal increased activation immediately after delivery, but uterine contractions over a period of > 20 hours seem not to make a difference. During infection, the activation markers of the hemostatic system in newborns aged 10-25 days behaves similarly to the mature adult system.     

A study of the nonorthogonal FDTD method versus the conventionalFDTD technique for computing resonant frequencies of cylindricalcavities

The nonorthogonal finite-difference-time-domain (FDTD) technique is used to compute the resonant frequencies of dielectric-filled cylindrical cavities. Because the method is based on the nonorthogonal coordinate system, it is not restricted to specific geometries, e.g. rectangular or axially symmetric geometries, and is suitable for analyzing cavities of arbitrary shape. The advantages of this technique over the conventional FDTD algorithm with a staircase grid are shown in a convergence study, where the two methods are used to compute the dominant resonant frequency of a cylindrical cavity. The accuracy of the technique for calculating the resonant frequencies of the first few modes is demonstrated by comparing the results obtained with this technique with those derived by using two versions of the finite element method in the frequency domain     

The nuclear heated steam reformer — Design and semitechnical operating experiences

Good operating experiences of the EVA I- and EVA II-plant have been described. Therin the comparison of the different catalyst concepts has been given. Further the behaviour of the bundle of EVA II plant by isolation of individual reformer tubes as well as the performance of the bundle under transient conditions have been explained.Different design concepts for a nuclear heated steam reformer based on the concentric tubes and baffles have been given. Main points of studies are constructional details, thermohydraulic of the bundle and stress analysis. It can be shown that the present standard of knowledge allows the application of the steam reformer for coal refinement with nuclear heat.     

Identification of the active site histidine in the corrinoid protein MtrA of the energy-conserving methyltransferase complex from Methanobacterium thermoautotrophicum

The energy-conserving corrinoid-containing MtrA-H complex from Methanobacterium thermoautotrophicum is composed of eight different subunits of which MtrA harbors the corrinoid prosthetic group. EPR spectroscopic evidence has recently been presented for a histidine residue as a cobalt ligand of the cobamide [Harms, U. & Thauer, R. K. (1996a) Eur. J. Biochem. 241, 149-154]. This active site histidine was now identified by site-directed mutagenesis to be His84 in the MtrA sequence that contains three histidines. This result was substantiated by sequence comparison of MtrA from M. thermoautotrophicum, Methanococcus jannaschii, and Methanopyrus kandleri and of MtxA from Methanosarcina harkeri showing that only His84 is conserved. For comparison, the DNA sequences of the mtrEDCBAGH operon in M. kandleri and of the mtxXAH operon in M. barkeri were determined.     

The current contribution of molecular factors to risk estimation in neuroblastoma patients

The association of molecular characteristics with prognosis has been reported, but not their relationship with each other and their impact in the context of known clinical risk factors. In this study, data of 1249 consecutive intent-to-treat-neuroblastoma patients with more than 1 year follow-up were examined by multivariate analysis using loglinear and Cox proportional hazard regression models on a stage-related basis (stages 1-3: 600, 4S: 116, 4: 533). In a first step, risk factors were identified from 18 selected clinical variables, and risk groups defined. The second step investigated whether molecular characteristics (MYCN, LOH 1p, del 1p, CD44, N-ras, NGF-R, bcl-2, APO-1 (CD95)) contributed additional prognostic information to the model. The loglinear model demonstrated several interactions between clinical factors. By the Cox regression model, seven independent clinical risk factors were found for stages 1-3, seven for stage 4 and two for stage 4S. By subsequent introduction of all molecular variables, MYCN amplification only added significant prognostic information to the clinical factors in localised and stage 4 neuroblastoma. The models allowed the definition of risk groups for stages 1-3 patients by age (e beta = 5.09) and MYCN (e beta = 4.26), for stage 4 by MYCN (e beta = 2.78) and number of symptoms (e beta = 2.44) and for stage 4S by platelet count (e beta = 3.91) and general condition (e beta = 2.99). Molecular factors and in particular MYCN contribute significantly to risk estimation. In conjunction with clinical factors, they are powerful tools to define risk groups in neuroblastoma.     

The utilization of sodium in sodium zeolite A by broilers

Two identical experiments were conducted with 1-d-old broiler chicks to determine whether the Na in sodium zeolite A (SZA) was utilizable. Three male and three female chicks were randomly assigned to each of eight replicate pens per treatment. A corn-soybean meal basal diet was formulated to contain supplemental levels of 0, .02, .04, .06, .08, and .16% Na from either SZA or NaCl. The diets were isocaloric and isonitrogenous. The Cl level within each dietary Na level was kept constant. Feed and deionized water were offered for ad libitum consumption throughout each 21-d experiments. In both experiments, broiler body weight was increased with each addition of Na from either NaCl or SZA. In Experiment 1, the addition of Na, whether from NaCl or SZA, resulted in an improvement in feed consumption and feed conversion compared with birds fed the control diet. In Experiment 2, body weights of birds fed .04 to .08% Na from SZA were heavier than those fed the same levels from NaCl. Overall the addition of Na from SZA or NaCl resulted in an improvement in body weight, increased feed consumption, and improved feed conversion. Data from these experiments indicated that the Na in SZA was able to be utilized by broilers as efficiently as the Na from NaCl.