Electromotive Force: A Guide for the Perplexed

The concept of electromotive force (emf) may be introduced in various ways in an undergraduate course of theoretical electromagnetism. The multitude of alternate expressions for the emf is often the source of confusion to the student. We summarize the main ideas, adopting a pedagogical logic that proceeds from the general to the specific. The emf of a "circuit" is first defined in the most general terms. The expressions for the emf of some familiar electrodynamical systems are then derived in a rather straightforward manner. A diversity of physical situations is thus unified within a common theoretical framework.Comment: 11 pages, 5 figures; added example & appendi

A Model for the Color Glass Condensate Versus Jet Quenching

A model for the Color Glass Condensate as opposed to jet quenching is proposed for the explanation of the presently available RHIC data. Good fits to these data are presented. A clear way to distinguish between the two possible explanations is also given.Comment: 3 pages, 1 figur

Pension Funds under Investments Constraints: An Assessment of the Opportunity Cost to the Greek Social Security System

In this paper we study the opportunity loss of the Greek social security system in terms of risk and return, caused by the inflexible investment constraints under which Greek pension funds operated in the period 1958-2000. Using data on pension fund reserves as well as on money and capital market yields, we evaluate retrospectively the risks and returns of a more pro-investment fund reserve management by analyzing an indicative number of investment scenarios in local and international money and capital markets. In order to estimate local currency yields for international investment, we generate for the entire period – covering both a fixed and a partially floating exchange rates regime – a corresponding series of exchange rate variations based on the official rate fluctuations and inflation differentials. Our results suggest that in the 43-year period, there has been a significant opportunity loss in the system both in risk and returns: first, by excluding Greek bank deposits and Greek capital market securities that would have propped returns up at acceptable levels of risk and, second, by not allowing for some degree of international diversification that would have kept overall downside risk down. This opportunity loss could have alleviated, to some extent, the current imbalance of the system, had some of the restrictive investment rules been relaxed.pension funds; financial investment

Toda Lattice and Tomimatsu-Sato Solutions

We discuss an analytic proof of a conjecture (Nakamura) that solutions of Toda molecule equation give those of Ernst equation giving Tomimatsu-Sato solutions of Einstein equation. Using Pfaffian identities it is shown for Weyl solutions completely and for generic cases partially.Comment: LaTeX 8 page

Does the electromotive force (always) represent work?

In the literature of Electromagnetism, the electromotive force of a "circuit" is often defined as work done on a unit charge during a complete tour of the latter around the circuit. We explain why this statement cannot be generally regarded as true, although it is indeed true in certain simple cases. Several examples are used to illustrate these points.Comment: 8 pages, 7 figures; various improvements; added reference

B\"acklund Transformations: Some Old and New Perspectives

B\"acklund transformations (BTs) are traditionally regarded as a tool for integrating nonlinear partial differential equations (PDEs). Their use has been recently extended, however, to problems such as the construction of recursion operators for symmetries of PDEs, as well as the solution of linear systems of PDEs. In this article, the concept and some applications of BTs are reviewed. As an example of an integrable linear system of PDEs, the Maxwell equations of electromagnetism are shown to constitute a BT connecting the wave equations for the electric and the magnetic field; plane-wave solutions of the Maxwell system are constructed in detail. The connection between BTs and recursion operators is also discussed.Comment: Review article; 15 pages; see also arXiv:0803.3688 and arXiv:1505.0709

PRELIMINARY GEOTHERMAL INVESTIGATION IN THE BASIN OF KATERINI (NORTHERN GREECE)

Η παρούσα εργασία περιγράφει τα αποτελέσματα της προκαταρκτικής γεωθερμικής έρευνας που διενεργήθηκε από το ΙΓΜΕ στην λεκάνη της Κατερίνης (Β. Ελλάδα). Οι ερευνητικές εργασίες κατά κύριο λόγο περιελάμβαναν θερμομετρήσεις στην κεφαλή 73 υπαρχουσών υδρογεωτρήσεων, μέτρηση της θερμοκρασίας σε συνάρτηση με το βάθος στο εσωτερικό πέντε (5) γεωτρήσεων και χημικές αναλύσεις 18 δειγμάτων από επιλεγμένες θέσεις. Με βάση τα στοιχεία που προέκυψαν από την κατανομή των θερμοκρασιών, διακρίνονται τρεις επιμέρους περιοχές γεωθερμικού ενδιαφέροντος. Ως σημαντικότερη κρίνεται αυτή του Κάτω Αγίου Ιωάννη (νότια τμήμα της λεκάνης), όπου μετρήθηκαν θερμοκρασίες της τάξης των 27oC σε βάθος 340m. Εν τούτοις, για τη λεπτομερή διερεύνηση των γεωθερμικών συνθηκών στη λεκάνη Κατερίνης, απαιτείται περαιτέρω συστηματική έρευνα και κατασκευή τουλάχιστον μίας ερευνητικής γεωθερμικής γεώτρησης μεγάλου βάθους.This paper describes the results of the preliminary surface geothermal exploration conducted by IGME in the basin of Katerini (Northern Greece). It mainly regards temperature measurements at the wellhead of 73 wells and in the interior of five boreholes, as well as sampling and chemical analyses from 18 selected sites. Based on the collected data, three sub-regions of geothermal interest can be distinguished, the most important of which is the area of Kato Agios Ioannis (to the south of the basin), with temperatures around 27oC at the depth of 340m. Nonetheless, the detailed geothermal investigation of this basin requires further systematic research as well as the drilling of at least one deep geothermal exploration borehole

Using e-portfolio as an online tool for L2 assessment

L2 assessment is a key moment in the process of teaching and learning of foreign languages. There are new challenges that recently have become relevant for the assessment of the online teaching and learning process. It is necessary not only to track the progress of students, but also to identify problematic aspects of the educational process and to see its subsequent adjustments. The article discusses the use of an e-portfolio as a tool for assessing the knowledge of L2 and some other relevant soft skills. The article discusses that formative e-assessment as the most reliable way to control the process of language acquisition and brings examples how e-portfolios can be used for these purposes