A Lie Algebra Method for Rational Parametrization of Severi-Brauer Surfaces

It is well-known that a Severi-Brauer surface has a rational point if and only if it is isomorphic to the projective plane. Given a Severi-Brauer surface, we study the problem to decide whether such an isomorphism to the projective plane, or such a rational point, does exist; and to construct such an isomorphism or such a point in the affirmative case. We give an algorithm using Lie algebra techniques. The algorithm has been implemented in Magma.Comment: 16 pages some minor revision

Learning and Production of Movement Sequences: Behavioral, Neurophysiological, and Modeling Perspectives

A growing wave of behavioral studies, using a wide variety of paradigms that were introduced or greatly refined in recent years, has generated a new wealth of parametric observations about serial order behavior. What was a mere trickle of neurophysiological studies has grown to a more steady stream of probes of neural sites and mechanisms underlying sequential behavior. Moreover, simulation models of serial behavior generation have begun to open a channel to link cellular dynamics with cognitive and behavioral dynamics. Here we summarize the major results from prominent sequence learning and performance tasks, namely immediate serial recall, typing, 2XN, discrete sequence production, and serial reaction time. These populate a continuum from higher to lower degrees of internal control of sequential organization. The main movement classes covered are speech and keypressing, both involving small amplitude movements that are very amenable to parametric study. A brief synopsis of classes of serial order models, vis-à-vis the detailing of major effects found in the behavioral data, leads to a focus on competitive queuing (CQ) models. Recently, the many behavioral predictive successes of CQ models have been joined by successful prediction of distinctively patterend electrophysiological recordings in prefrontal cortex, wherein parallel activation dynamics of multiple neural ensembles strikingly matches the parallel dynamics predicted by CQ theory. An extended CQ simulation model-the N-STREAMS neural network model-is then examined to highlight issues in ongoing attemptes to accomodate a broader range of behavioral and neurophysiological data within a CQ-consistent theory. Important contemporary issues such as the nature of working memory representations for sequential behavior, and the development and role of chunks in hierarchial control are prominent throughout.Defense Advanced Research Projects Agency/Office of Naval Research (N00014-95-1-0409); National Institute of Mental Health (R01 DC02852

Exchange of oxygen and hydrogen isotopes between water and water vapor: Experimental results

The exchange of {dollar}\delta\sp{18}{dollar}O, {dollar}\delta{dollar}D, and tritium between water and water vapor was quantified using two methods. The first was quiescent equilibration of water samples having widely contrasting isotopic compositions, surface areas, volumes and temperatures, but similar salinities. Rates of exchange (k) depended on surface area and vapor pressure, while the end-point equilibrium was controlled by volume and isotopic composition of the exchanging waters. Values of k ranged from 0.09 to 0.19 cm/day at 22{dollar}\sp\circ{dollar}C and from 0.86 to 0.92 cm/day at 52{dollar}\sp\circ{dollar}C. The second method involved sparging 30 l of tritiated water (5,000 and 630,000 TU) with a constant 15 l/min flux of water-saturated air (TU {dollar}\u3c{dollar} 10). Half of the tritium was exchanged into the vapor effuent over 40 days; k ranged from 0.025/day to 0.030/day. Equilibration with 630,000 TU was observed over a bubble path of 20 cm, suggesting an alternative method of tritium remediation

Career paths of psychology graduates

Little is known about the employment patterns and career paths of psychology graduates following their graduation from university. The responses of 576 psychology graduates from five major metropolitan universities to a postal survey were studied in order to ascertain their career paths following graduation. Although a majority of graduates undertook studies in psychology in order to pursue a career in psychology, less than 20 per cent ultimately worked as psychologists. The remainder found careers in a wide variety of occupations and industries, mostly as professionals within the community services industry. Employment histories of three graduate cohorts were followed throughout the 1980's, in order to examine changes in the psychology labour market over time. Increasing proportions of graduates found employment as managers administrators and para-professionals, at the expense of traditional positions within the professionals sphere. Specifically, occupations in research, welfare and business increased in popularity, occupations in psychology and personnel remained steady, and clerical and teaching positions declined in popularity. Private sector employment increased steadily throughout the 1980's, whereas government and education sector employment decreased, the latter markedly. A number of factors were found to influence career paths, notably, whether the undergraduate degree was of three or four years duration, whether the graduate had subsequently undertaken higher degree studies, and the amount of workforce experience the graduate had. The gender of the graduate was not found to be significant, although it was observed that on average male graduates worked in positions with higher occupational prestige. These factors were used to model career path development for psychology graduates

A Fix for Airway Management Training?:Realism and Suitability of the Fix for Life Cadaver Model

The primary focus of this thesis was the novel Fix for Life (F4L) cadaver model and its possible role in airway management training. The following research questions were addressed: 1. Is the F4L cadaver model a suitable and realistic model for the training and teaching of different airway management techniques? 2. How suitable and realistic is the F4L cadaver model for the training of the identification of the correct anatomical spot to incise for a ‘surgical airway’ (cricothyroidotomy), i.e., the identification of the cricothyroid membrane via palpation and ultrasonography? 3. What is the effectiveness of video-assisted fibreoptic intubation versus videolaryngoscopy in an established difficult airway F4L cadaver model? The F4L cadaver models were compared to formalin-fixed cadaver models and a manikin for suitability and realism for the teaching of 3 basic airway skills: facemask ventilation, tracheal intubation via direct laryngoscopy, and laryngeal mask insertion. The F4L cadaver model was ranked best for facemask ventilation. In other rankings, the F4L cadaver model was not ranked significantly different in regard to the manikin. Both the F4L cadaver model and the manikin were ranked significantly higher than the formalin-fixed cadaver model. With the exception of the score for realism of laryngeal mask insertion, all verbal rating scores between the F4L cadaver model and the manikin were not significantly different. The formalin-fixed cadaver model received the lowest scores. We concluded that there is potential of the F4L cadaver model in airway management training, particularly for facemask ventilation. The F4L cadaver model was also assessed for two advanced airway techniques, namely tracheal intubation with videolaryngoscopy and flexible fibreoptic tracheoscopy. The results in verbal rating scores obtained in this study were very promising, as these were higher compared to the previous study, indicating that the F4L cadaver model could be more suitable for these advanced techniques. These results suggest that the F4L cadaver model could be regarded as a suitable and realistic training model for advanced airway management techniques. A following study describes the suitability and realism of the F4L cadaver model for the training of the identification of the cricothyroid membrane with palpation or ultrasonography. The F4L cadaver model received high verbal rating scores for both techniques, being 8 or higher. The rate of successful identification was significantly higher in the ultrasonography group, although the time needed to do so was longer. We conclude that the F4L cadaver model is realistic and suitable to train the identification of the cricothyroid membrane. The final study primarily compared the success rates of tracheal intubation with videolaryngoscopy versus video-assisted fibreoptic intubation in a difficult airway F4L cadaver model. The success of tracheal intubation was higher with the video-assisted fibreoptic intubation technique, probably due to the higher percentage of glottic opening. In conclusion, the F4L cadaver model was the focus of our different investigations into the possible realism and suitability for airway management training, and the comparison of two intubation techniques for the management of a difficult airway. Based on our studies, the following conclusions can be drawn: 1. The F4L cadaver model could be a suitable and realistic alternative model to the manikin for the training of basic airway maneuvers, in particular for facemask ventilation. 2. The F4L cadaver model is a suitable and realistic model for the teaching of advanced airway procedures, namely videolaryngoscopy and fibreoptic intubation. 3. The F4L cadaver model is a suitable and realistic model for the teaching of cricothyroid membrane identification via palpation and ultrasonography. 4. The higher percentage of glottic opening score obtained with the video-assisted fibreoptic intubation technique versus videolaryngoscopy, probably translates to a higher intubation success in a difficult airway

Educational inequality and state-sponsored elite education: the case of the Dutch gymnasium

In this paper the authors examine the role the Dutch gymnasium continues to play in the institutional maintenance of educational inequality. To that end they examine the relational and spatial features of state-sponsored elite education in the Dutch system: the unique identity the gymnasium seeks to cultivate; its value to its consumers; its geographic significance; and its market position amidst a growing array of other selective forms of schooling. They argue that there is a strong correlation between a higher social class background and the concern to transmit one’s cultural habitus. They further speculate on the moral implications of state-sponsored elite education, both as it concerns the specific role of the gymnasium in the reproduction of social inequality as well as the curious tendency among its supporters to rationalise the necessity of its existence

Bayesian Optimization for Probabilistic Programs

We present the first general purpose framework for marginal maximum a posteriori estimation of probabilistic program variables. By using a series of code transformations, the evidence of any probabilistic program, and therefore of any graphical model, can be optimized with respect to an arbitrary subset of its sampled variables. To carry out this optimization, we develop the first Bayesian optimization package to directly exploit the source code of its target, leading to innovations in problem-independent hyperpriors, unbounded optimization, and implicit constraint satisfaction; delivering significant performance improvements over prominent existing packages. We present applications of our method to a number of tasks including engineering design and parameter optimization

Local Ecological Knowledge and Communitybased Management of Wildlife Resources: A Study of the Mumbwa and Lupande Game Management Areas of Zambia

The aim of this study was to investigate the scope of local ecological knowledge (LEK) in the Lupande and Mumbwa Game Management Areas (GMAs) of Zambia and to assess the extent to which such knowledge has been used in the management of wildlife resources in the two areas. Quantitative and qualitative data were gathered through interviews and surveys in the two case-study areas. It was found that LEK in the study areas included taboos associated with the sustainable use of natural resources, traditional teachings that guided the local people as to the correct time to harvest their natural resources and providedknowledge of the natural distribution of plants in the two areas. Finally, it is recommended that, in order to complement modern scientific knowledge in the realisation of sustainable wildlife resource management, greater attention be paid to the LEK possessed by communities

Gedragsveronderstellingen en verzekeringen

__Samenvatting__ Verzekeringseconomieen -recht hanteren alspresumptie dat verzekerden minder voorzichtig worden als zij verzekerd zijn en dat juist diegenen die het verhoogde risico op schade lopen, een verzekering nemen. Heteerste verschijnsel wordt geduid als ‘moreel risico’en het tweede verschijnsel roept het risico van ‘antiselectie’ in het leven. Daar kan aan worden toegevoegd de presumptie dat de vraag naar verzekeringen rationeel tot stand komt: men verzekert weloverwogen wat men van waarde acht en men laat onverzekerd waar men minder aan hecht. Het recht ontwikkelt instrumenten om moreel risico en antiselectie tegen te gaan en de verzekeringseconomie baseertcompletetheorieën op de genoemde uitgangspunten. Maar empirietoont aan dat rationele keuze minder dominant is dan de presumptie veronderstelt. Dat werpteen anderlichtop moreelrisicoen antiselectie. In dit hoofdstuk wordt ditempirisch materiaal ontsloten en wordt derelevantie van het materiaal voorbeleidsmakersbinnen het verzekeringsrecht beargumenteerd