Encouraging versatile thinking in algebra using the computer

In this article we formulate and analyse some of the obstacles to understanding the notion of a variable, and the use and meaning of algebraic notation, and report empirical evidence to support the hypothesis that an approach using the computer will be more successful in overcoming these obstacles. The computer approach is formulated within a wider framework ofversatile thinking in which global, holistic processing complements local, sequential processing. This is done through a combination of programming in BASIC, physical activities which simulate computer storage and manipulation of variables, and specific software which evaluates expressions in standard mathematical notation. The software is designed to enable the user to explore examples and non-examples of a concept, in this case equivalent and non-equivalent expressions. We call such a piece of software ageneric organizer because if offers examples and non-examples which may be seen not just in specific terms, but as typical, or generic, examples of the algebraic processes, assisting the pupil in the difficult task of abstracting the more general concept which they represent. Empirical evidence from several related studies shows that such an approach significantly improves the understanding of higher order concepts in algebra, and that any initial loss in manipulative facility through lack of practice is more than made up at a later stage

The Ontology of Intentional Agency in Light of Neurobiological Determinism: Philosophy Meets Folk Psychology

The moot point of the Western philosophical rhetoric about free will consists in examining whether the claim of authorship to intentional, deliberative actions fits into or is undermined by a one-way causal framework of determinism. Philosophers who think that reconciliation between the two is possible are known as metaphysical compatibilists. However, there are philosophers populating the other end of the spectrum, known as the metaphysical libertarians, who maintain that claim to intentional agency cannot be sustained unless it is assumed that indeterministic causal processes pervade the action-implementation apparatus employed by the agent. The metaphysical libertarians differ among themselves on the question of whether the indeterministic causal relation exists between the series of intentional states and processes, both conscious and unconscious, and the action, making claim for what has come to be known as the event-causal view, or between the agent and the action, arguing that a sort of agent causation is at work. In this paper, I have tried to propose that certain features of both event-causal and agent-causal libertarian views need to be combined in order to provide a more defendable compatibilist account accommodating deliberative actions with deterministic causation. The ‘‘agent-executed-eventcausal libertarianism’’, the account of agency I have tried to develop here, integrates certain plausible features of the two competing accounts of libertarianism turning them into a consistent whole. I hope to show in the process that the integration of these two variants of libertarianism does not challenge what some accounts of metaphysical compatibilism propose—that there exists a broader deterministic relation between the web of mental and extra-mental components constituting the agent’s dispositional system—the agent’s beliefs, desires, short-term and long-term goals based on them, the acquired social, cultural and religious beliefs, the general and immediate and situational environment in which the agent is placed, etc. on the one hand and the decisions she makes over her lifetime on the basis of these factors. While in the ‘‘Introduction’’ the philosophically assumed anomaly between deterministic causation and the intentional act of deciding has been briefly surveyed, the second section is devoted to the task of bridging the gap between compatibilism and libertarianism. The next section of the paper turns to an analysis of folk-psychological concepts and intuitions about the effects of neurochemical processes and prior mental events on the freedom of making choices. How philosophical insights can be beneficially informed by taking into consideration folk-psychological intuitions has also been discussed, thus setting up the background for such analysis. It has been suggested in the end that support for the proposed theory of intentional agency can be found in the folk-psychological intuitions, when they are taken in the right perspective

A proof by graphical construction of the no-pumping theorem of stochastic pumps

A stochastic pump is a Markov model of a mesoscopic system evolving under the control of externally varied parameters. In the model, the system makes random transitions among a network of states. For such models, a "no-pumping theorem" has been obtained, which identifies minimal conditions for generating directed motion or currents. We provide a derivation of this result using a simple graphical construction on the network of states

Polymer depletion interaction between two parallel repulsive walls

The depletion interaction between two parallel repulsive walls confining a dilute solution of long and flexible polymer chains is studied by field-theoretic methods. Special attention is paid to self-avoidance between chain monomers relevant for polymers in a good solvent. Our direct approach avoids the mapping of the actual polymer chains on effective hard or soft spheres. We compare our results with recent Monte Carlo simulations [A. Milchev and K. Binder, Eur. Phys. J. B 3, 477 (1998)] and with experimental results for the depletion interaction between a spherical colloidal particle and a planar wall in a dilute solution of nonionic polymers [D. Rudhardt, C. Bechinger, and P. Leiderer, Phys. Rev. Lett. 81, 1330 (1998)].Comment: 17 pages, 3 figures. Final version as publishe

Dangerous work: The gendered nature of bullying in the context of higher education

This paper discusses results from a research project which set out to investigate gender differences in the nature and experience of bullying within the higher education sector. Gender differences emerged in the form and perception of bullying as well as in target response. Results also indicate that, irrespective of gender, bullies can capture and subvert organizational structures and procedures (official hierarchies, mentoring systems, probationary reviews) to further their abuse of the target and to conceal aggressive intent. These outcomes are discussed in relation to gendered assumptions behind management practices and in relation to the masculinist ethic that underpins many higher education management initiatives. Overall, results indicate that bullying cannot be divorced from gender and that such behaviour needs to be seen in a gendered context

Histologische, funktionelle und spezifische Regeneration nach Durchtrennung der Fila olfactoria beim Goldfisch ( Carassius auratus )

1. Alter dissection of the olfactory libres (fila olfactoria, Fig. 1) in the goldfisch, histological (Fig. 5) as well as functional regeneration takes place. When regeneration of the olfactory fibres was complete, no differences in training and learning behaviour between operated and untreated control animals could be observed (Fig. 2). Specific regeneration could also be proved after dissection of the olfactory fibres: Preoperatively trained discriminative behaviour returned (Figs. 3, 4) when histological regeneration had reached an advanced state (Figs. 6, 7). Higher concentrations of all substances used for odour training were capable of exciting the taste receptors or other struktures outside the olfactory mucosa. The concentrations used for olfactory training, however, were below the thresholds for non-olfactory perception. Neither the surgical procedure nor the anesthesia influenced the memory function. 1. Goldfische können die durchschnittenen Bahnen der Fila olfactoria anatomisch und funktionell regenerieren.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47102/1/359_2004_Article_BF00340911.pd

Quantum Theory and Time Asymmetry

The relation between quantum measurement and thermodynamically irreversible processes is investigated. The reduction of the state vector is fundamentally asymmetric in time and shows an observer-relatedness which may explain the double interpretation of the state vector as a representation of physical states as well as of information about them. The concept of relevance being used in all statistical theories of irreversible thermodynamics is shown to be based on the same observer-relatedness. Quantum theories of irreversible processes implicitly use an objectivized process of state vector reduction. The conditions for the reduction are discussed, and I speculate that the final (subjective) observer system might even be carried by a spacetime point.Comment: Latex version of a paper published in 1979 (with minor revisions), 18 page

Acute Trauma Factor Associations With Suicidality Across the First 5 Years After Traumatic Brain Injury

AbstractObjectiveTo determine whether severity of head and extracranial injuries (ECI) is associated with suicidal ideation (SI) or suicide attempt (SA) after traumatic brain injury (TBI).DesignFactors associated with SI and SA were assessed in this inception cohort study using data collected 1, 2, and 5 years post-TBI from the National Trauma Data Bank and Traumatic Brain Injury Model Systems (TBIMS) databases.SettingLevel I trauma centers, inpatient rehabilitation centers, and the community.ParticipantsParticipants with TBI from 15 TBIMS Centers with linked National Trauma Data Bank trauma data (N=3575).InterventionsNot applicable.Main Outcome MeasuresSI was measured via the Patient Health Questionnaire 9 (question 9). SA in the last year was assessed via interview. ECI was measured by the Injury Severity Scale (nonhead) and categorized as none, mild, moderate, or severe.ResultsThere were 293 (8.2%) participants who had SI without SA and 109 (3.0%) who had SA at least once in the first 5 years postinjury. Random effects logit modeling showed a higher likelihood of SI when ECI was severe (odds ratio=2.73; 95% confidence interval, 1.55–4.82; P=.001). Drug use at time of injury was also associated with SI (odds ratio=1.69; 95% confidence interval, 1.11–2.86; P=.015). Severity of ECI was not associated with SA.ConclusionsSevere ECI carried a nearly 3-fold increase in the odds of SI after TBI, but it was not related to SA. Head injury severity and less severe ECI were not associated with SI or SA. These findings warrant additional work to identify factors associated with severe ECI that make individuals more susceptible to SI after TBI

Accumulation of xylem transported protein at pit membranes and associated reductions in hydraulic conductance

Proteins and traces of polysaccharide are the only polymeric colloids consistently transported in the xylem sap of plants. The hypothesis that such proteins could have physical inhibitory effects on xylem water transport was investigated. Ovalbumin, with a molecular weight of 45 kDa and a molecular diameter of 5.4 nm, is an inert, water-soluble protein that is midway along the size range of endogenous xylem sap proteins. Solutions of ovalbumin conjugated to a fluorescent marker and supplied to transpiring shoot explants of tobacco (Nicotiana tabacum L.) and olive (Olea europaea L.) were shown by confocal laser scanning microscopy to accumulate specifically at wall-based pit membranes that connect neighbouring xylem conduits. In addition, pressure-induced perfusion of micro-filtered ovalbumin solutions, at concentrations similar to those of endogenous xylem sap proteins, through the xylem of tobacco stem or olive twig segments resulted in the retention of c. 40% of the ovalbumin and reductions in the axial hydraulic conductance of the xylem. Smaller molecules such as Texas Red 3000 (MW 3 kDa) and Alexafluor 488–cadaverin conjugates (MW 0.64 kDa) did not show similar characteristics. The partial reduction in xylem hydraulic conductance appeared to be related to the accumulation of ovalbumin at xylem pit membranes and the consequent fouling of trans-membrane water-conducting pores with smaller diameters than those of the ovalbumin molecules. Potential implications of these novel findings for whole-plant water relations are considered

Associations Between High-Density Lipoprotein Particles and Ischemic Events by Vascular Domain, Sex, and Ethnicity A Pooled Cohort Analysis

Background: High-density lipoprotein (HDL) cholesterol concentration (HDL-C) is an established atheroprotective marker, in particular for coronary artery disease; however, HDL particle concentration (HDL-P) may better predict risk. The associations of HDL-C and HDL-P with ischemic stroke and myocardial infarction (MI) among women and Blacks have not been well studied. We hypothesized that HDL-P would consistently be associated with MI and stroke among women and Blacks compared with HDL-C. Methods: We analyzed individual-level participant data in a pooled cohort of 4 large population studies without baseline atherosclerotic cardiovascular disease: DHS (Dallas Heart Study; n=2535), ARIC (Atherosclerosis Risk in Communities; n=1595), MESA (Multi-Ethnic Study of Atherosclerosis; n=6632), and PREVEND (Prevention of Renal and Vascular Endstage Disease; n=5022). HDL markers were analyzed in adjusted Cox proportional hazard models for MI and ischemic stroke. Results: In the overall population (n=15 784), HDL-P was inversely associated with the combined outcome of MI and ischemic stroke, adjusted for cardiometabolic risk factors (hazard ratio [HR] for quartile 4 [Q4] versus quartile 1 [Q1], 0.64 [95% CI, 0.52-0.78]), as was HDL-C (HR for Q4 versus Q1, 0.76 [95% CI, 0.61-0.94]). Adjustment for HDL-C did not attenuate the inverse relationship between HDL-P and atherosclerotic cardiovascular disease, whereas adjustment for HDL-P attenuated all associations between HDL-C and events. HDL-P was inversely associated with the individual end points of MI and ischemic stroke in the overall population, including in women. HDL-P was inversely associated with MI among White participants but not among Black participants (HR for Q4 versus Q1 for Whites, 0.49 [95% CI, 0.35-0.69]; for Blacks, 1.22 [95% CI, 0.76-1.98];P-interaction=0.001). Similarly, HDL-C was inversely associated with MI among White participants (HR for Q4 versus Q1, 0.53 [95% CI, 0.36-0.78]) but had a weak direct association with MI among Black participants (HR for Q4 versus Q1, 1.75 [95% CI, 1.08-2.83];P-interactio