Duality and Central Charges in Supersymmetric Quantum Mechanics

We identify a class of point-particle models that exhibit a target-space duality. This duality arises from a construction based on supersymmetric quantum mechanics with a non-vanishing central charge. Motivated by analogies to string theory, we are led to speculate regarding mechanisms for restricting the background geometry.Comment: 10 pages, 1 figure, late

An Overview of Progress and Problems in Educational Technology

Educational technologists have promised that great advances and improvements in learning and instruction would occur on account of new and emerging technologies. Some of these promises have been partially fulfilled, but many have not. The last decade of the previous century witnessed the consolidation of new approaches to learning and instruction under the banner of constructivism. This so−called new learning paradigm was really not all that new, but renewed emphasis on learners and learning effectiveness can clearly be counted as gains resulting from this constructivist consolidation within educational research. At the same time, technology was not standing still. Network technologies were increasing bandwidth, software engineering was embracing object orientation, and wireless technologies were extending accessibility. It is clear that we can now do things to improve education that were not possible twenty years ago. However, the potential gains in learning and instruction have yet to be realized on a significant global scale. Why not? Critical challenges confront instructional designers and critical problems remain with regard to learning in and about complex domains. Moreover, organizational issues required to translate advances in learning theory and educational technology into meaningful practice have yet to be addressed. The current situation in the field of educational technology is one of technification. New educational technologies are usable only by a scarce cadre of technocrats. Constructivist approaches to learning have been oversimplified to such a degree that learning effectiveness has lost meaning. As a consequence, education is generally managed in an ad hoc manner that marginalizes the potential gains offered by new learning technologies. This paper presents an overview of progress and problems in educational technology and argues that educational program management must be integrally linked with technology and theory in order for significant progress in learning and instruction to occur on a global scale.Educational technologists have promised that great advances and improvements in learning and instruction would occur on account of new and emerging technologies. Some of these promises have been partially fulfilled, but many have not. The last decade of the previous century witnessed the consolidation of new approaches to learning and instruction under the banner of constructivism. This so−called new learning paradigm was really not all that new, but renewed emphasis on learners and learning effectiveness can clearly be counted as gains resulting from this constructivist consolidation within educational research. At the same time, technology was not standing still. Network technologies were increasing bandwidth, software engineering was embracing object orientation, and wireless technologies were extending accessibility. It is clear that we can now do things to improve education that were not possible twenty years ago. However, the potential gains in learning and instruction have yet to be realized on a significant global scale. Why not? Critical challenges confront instructional designers and critical problems remain with regard to learning in and about complex domains. Moreover, organizational issues required to translate advances in learning theory and educational technology into meaningful practice have yet to be addressed. The current situation in the field of educational technology is one of technification. New educational technologies are usable only by a scarce cadre of technocrats. Constructivist approaches to learning have been oversimplified to such a degree that learning effectiveness has lost meaning. As a consequence, education is generally managed in an ad hoc manner that marginalizes the potential gains offered by new learning technologies. This paper presents an overview of progress and problems in educational technology and argues that educational program management must be integrally linked with technology and theory in order for significant progress in learning and instruction to occur on a global scale

System dynamics advances strategic economic transition planning in a developing nation

The increasingly complex environment of today's world, characterized by technological innovation and global communication, generates myriads of possible and actual interactions while limited physical and intellectual resources severely impinge on decision makers, be it in the public or private domains. At the core of the decision-making process is the need for quality information that allows the decision maker to better assess the impact of decisions in terms of outcomes, nonlinear feedback processes and time delays on the performance of the complex system invoked. This volume is a timely review on the principles underlying complex decision making, the handling of uncertainties in dynamic envrionments and of the various modeling approaches used. The book consists of five parts, each composed of several chapters: I: Complex Decision Making: Concepts, Theories and Empirical Evidence II: Tools and Techniques for Decision Making in Complex Environments and Systems III: System Dynamics and Agent-Based Modeling IV: Methodological Issues V: Future Direction

A BPS Interpretation of Shape Invariance

We show that shape invariance appears when a quantum mechanical model is invariant under a centrally extended superalgebra endowed with an additional symmetry generator, which we dub the shift operator. The familiar mathematical and physical results of shape invariance then arise from the BPS structure associated with this shift operator. The shift operator also ensures that there is a one-to-one correspondence between the energy levels of such a model and the energies of the BPS-saturating states. These findings thus provide a more comprehensive algebraic setting for understanding shape invariance.Comment: 15 pages, 2 figures, LaTe

Access to essential technologies for safe childbirth: a survey of health workers in Africa and Asia

Background: The reliable availability of health technologies, defined as equipment, medicines, and consumable supplies, is essential to ensure successful childbirth practices proven to prevent avoidable maternal and newborn mortality. The majority of global maternal and newborn deaths take place in Africa and Asia, yet few data exist that describe the availability of childbirth-related health technologies in these regions. We conducted a cross-sectional survey of health workers in Africa and Asia in order to profile the availability of health technologies considered to be essential to providing safe childbirth care. Methods: Health workers in Africa and Asia were surveyed using a web-based questionnaire. A list of essential childbirth-related health technologies was drawn from World Health Organization guidelines for preventing and managing complications associated with the major causes of maternal and newborn mortality globally. Demographic data describing each birth center were obtained and health workers reported on the availability of essential childbirth-related health technologies at their centers. Comparison analyses were conducted using Rao-Scott chi-square test statistics. Results: Health workers from 124 birth centers in 26 African and 15 Asian countries participated. All facilities exhibited gaps in the availability of essential childbirth-related health technologies. Availability was significantly reduced in birth centers that had lower birth volumes and those from lower income countries. On average across all centers, health workers reported the availability of 18 of 23 essential childbirth-related health technologies (79%; 95% CI, 74%, 84%). Low-volume facilities suffered severe shortages; on average, these centers reported reliable availability of 13 of 23 technologies (55%; 95% CI, 39%, 71%). Conclusions: Substantial gaps exist in the availability of essential childbirth-related health technologies across health sector levels in Africa and Asia. Strategies that facilitate reliable access to vital health technologies in these regions are an urgent priority

Designing on-demand education for simultaneous development of domain-specific and self-directed learning skills

On-demand education enables individual learners to choose their learning pathways according to their own learning needs. They must use self-directed learning (SDL) skills involving self-assessment and task selection to determine appropriate pathways for learning. Learners who lack these skills must develop them because SDL skills are prerequisite to developing domain-specific skills. This article describes the design of an on-demand learning environment developed to enable novices to simultaneously develop their SDL and domain-specific skills. Learners received advice on their self-assessments and their selections of subsequent learning tasks. In the domain of system dynamics – a way to model a dynamic system and draw graphs depicting the system’s behaviour over time – advice on self-assessment is provided in a scoring rubric containing relevant performance standards. Advice on task selection indicates all relevant task aspects to be taken into account, including recommendations for suitable learning tasks which meet the individual learner’s needs. This article discusses the design of the environment and the learners’ perceptions of its usefulness. Most of the times, the learners found the advice appropriate and they followed it in 78% of their task selections

La satisfaction à l’égard de la naissance parmi les couples utilisant la chambre de naissance ou la chambre traditionnelle

Distribués au hasard, deux groupes de couples cnt été comparés quant à leur sentiment de satisfaction à l'égard de la naissance de leur enfant. Le groupe O.N. a fait usage de la chambre de naissance, tandis que le groupe C.T., a utilisé la chambre traditionnelle. Le sentiment de satisfaction a été mesuré au cours des trois jours suivant la naissance et trois mois plus tard, et les moyennes des réponses obtenues pour l'ensemble des mères et des pères (chacun ayant rempli individuellement le questionnaire), ont alors été comparées. Les résultats indiquent que, immédiatement après la naissance, les mères et les pères du groupe C.N. manifestent un degré de satisfaction plus élevé que celui des couples du groupe C.T., à l'égard du lieu où le travail et l'accouchement se sont déroulés. Les mères des deux groupes C.N. et C.T. sont également satisfaites de la durée de contact avec leur nourrisson après la naissance, tandis que les pères du groupe C.N. témoignent d'une satisfaction plus élevée que celle de leur conjointe, et que celle du groupe C.T. Trois mois plus tard, les résultats sont semblables sauf que les mères du groupe C.N. se déclarent plus satisfaites que celles du groupe C.T. de la durée de leur contact avec leur bébé après sa naissance.Following a random distribution, two groups of couples, users of the B.R. (birth room) and users of the T. R. (traditional room) were compared in terms of each partner's feeling of satisfaction in relation to the giving birth process. Statistical analysis of the means of the B.R. and T.R. fathers, of the B.R. and T.R. mothers, three days after delivery and three months later, yields the following results : following birth, both fathers and mothers of the B.R. group indicate a higher feeling of satisfaction than the T.R. mothers and fathers in relation to the environment. Mothers of the B.R. and T.R. are equally satisfied in relation to the amount of time spent with their infant, whereas fathers of the B. R. are more satisfied than their spouses and more satisfied than the T.R. fathers. Three months later, the only difference to these above-mentioned results, is the higher degree of satisfaction of B.R. mothers over T.R. mothers in relation to the length of contact with their infant right after birth

Unconstraining the Unhiggs

We investigate whether or not perturbative unitarity is preserved in the Unhiggs model for the scattering process of heavy quarks and longitudinal gauge bosons $\bar q q \to V_L^+ V_L^-$. With the Yukawa coupling given in the original formulation of the Unhiggs model, the model preserves unitarity for Unhiggs scaling dimensions $d\leq 1.5$. We examine the LHC phenomenology that is implied by the Unhiggs model in this parameter range in detail and discuss to what extent the LHC can test $d$ if an excess is measured in the phenomenologically clean $ZZ$ channel in the future or if the LHC measurement remains consistent with the background. We then make use of the AdS/CFT correspondence to derive a new Yukawa coupling that is conformally invariant at high energies, and show that with this Yukawa coupling the theory is unitary for $1 \leq d < 2$.Comment: 19 pages, 10 figures; typos corrected, version published by PR

Pulsed electromagnetic energy treatment offers no clinical benefit in reducing the pain of knee osteoarthritis: a systematic review

Background The rehabilitation of knee osteoarthritis often includes electrotherapeutic modalities as well as advice and exercise. One commonly used modality is pulsed electromagnetic field therapy (PEMF). PEMF uses electro magnetically generated fields to promote tissue repair and healing rates. Its equivocal benefit over placebo treatment has been previously suggested however recently a number of randomised controlled trials have been published that have allowed a systematic review to be conducted. Methods A systematic review of the literature from 1966 to 2005 was undertaken. Relevant computerised bibliographic databases were searched and papers reviewed independently by two reviewers for quality using validated criteria for assessment. The key outcomes of pain and functional disability were analysed with weighted and standardised mean differences being calculated. Results Five randomised controlled trials comparing PEMF with placebo were identified. The weighted mean differences of the five papers for improvement in pain and function, were small and their 95% confidence intervals included the null. Conclusion This systematic review provides further evidence that PEMF has little value in the management of knee osteoarthritis. There appears to be clear evidence for the recommendation that PEMF does not significantly reduce the pain of knee osteoarthritis