Logical, mechanical and historical time in economics

Within the economic theory different notions of time imply alternative analytical structures. This article discusses and rejects the methodological dichotomy between ‘temporal’ and ‘a-temporal’ models (equilibrium and disequilibrium models) in economics. Different notions of time are identified –logical, mechanical and historical time- which enable to specify corresponding sequential methods and to address different questions within the economic theory. Some analytical implications are examined. In the light of the proposed methodological distinction different theories of the rate of interest are evaluated and new light is thrown on the important debate on finance which arose in the ‘30s among Keynes, Robertson and representatives of the Swedish School (Ohlin).Time and causality in economics; Keynes,Robertson and the Swedish School on finance

“Spot, Bilateral and Futures Trading in Electricity Markets. Implications for Stability”

The design of wholesale electricity markets in the transition towards liberalization presents significant differences from country to country. Some spot markets have imposed the concentration of transactions to ensure market liquidity. Other markets are based on bilateral trading. The debate about the optimal trading mechanism mainly concentrates on how to deal with the trade off between the liquidity of the market and the stability of the system. The solution chosen by some market is a mandatory pool with a regulated market for electricity derivatives, that allows to hedge price volatility and to mitigate market power. This paper investigates whether, in the presence of a futures market, spot and bilateral trading can operate together and what are possible outcomes in terms of liquidity of the spot market and stability of the system. The paper extends existing literature on the role of futures market on the behavior of spot market prices, developing a multi-period model in which electricity consumers can choose whether to trade on the spot market or negotiate bilateral contracts. Results suggest that a spot market with futures contracts and a market for bilateral contracts are not necessarily alternative ways to manage stability problems, but may co-exist with positive and synergic outcomes on price behaviors and market power.Derivatives, Electricity, Market power, Hedging

The Role of Diction and Gesture in Italian Baroque opera

Early Italian Baroque opera (ca. 1600-ca. 1770) was drama-oriented; Monteverdi and the composers of the Camerata emphasized diction and gesture or acting in the portrayal of characters. Singers such as Anna Renzi were praised for their interpretive skills as much as for their singing. The anonymous treatise Il corago (ca. 1630) gives detailed instructions on acting in opera. Although later Italian opera moved toward the concert on stage, writers and critics remained enthusiastic in their emphasis on dramatic interpretation and became ever more critical in their assessment of current performance practices (Francesco Algarotti, Giovanni Antonio Bianchi, Pier Francesco Tosi, and Giambattista Mancini, among others.

River-bed erosion due to changing boundary conditions: performance of a protective measure

Due to the introduction of man-made sediment barriers along a river, the amount of sediment load entering the downstream river reach is different to that leaving the reach, and erosion processes occur downstream of the barrier itself. Designers are often required to take into account the scouring process and to include adequate protective measures against the local scour. This paper addresses the performance of bio-engineering protective measures against the erosion process. In particular, a green carpet, realized with real flexible vegetation, has been used as the protective measure against erosion processes downstream of a rigid bed. Analyses are based on experimental work carried out in a straight channel constructed at the laboratory of the Dipartimento di Ingegneria Civile, Ambientale, Aereospaziale, dei Materiali, Palermo University (Italy)

Pedagogical approaches to surface phenomena in liquids: Investigation-based laboratory and modelling activities to improve students’ learning

Paperclips can float on water, mercury drops do not spread on solid surfaces, and fluids can flow against gravity in capillary tubes. Surface tension can be used to explain these phenomena that are macroscopic manifestations of microscopic molecular interactions. At both school and university levels, surface phenomena are introduced through traditional macroscopic or microscopic approaches. However, since explanations based on microscopic models are often in conflict with common macroscopic interpretations, the traditional teaching of the basic concepts related to surface phenomena can be unclear and can prevent students from an effective understanding of the topic. However, since surface phenomena applications are important in physics and other applied disciplines, it may be worth to reconstruct this content based on research results in Physics Education. Research demonstrates that models constructed at an intermediate scale (i.e., mesoscopic scale) can be used effectively in science education. Particularly, the literature recognizes mesoscopic models as valuable for efficiently introducing topics such as solid friction and fluid statics. These models have the benefits of the microscopic model. Particularly, they foster understanding based on the recognition of a “mechanism of functioning”, that is at the basis of the development of explicative lines or reasoning. Furthermore, these models do not require a significant amount of computer resources to execute simulations implementing the models. On the basis of these observations, we asked ourselves how we could contribute to improve the teaching and learning of this topic. We hypothesised that choosing an appropriate modelling scale to introduce a given topic would appreciably enhance the teaching/learning processes at both school and university levels. On the basis of our research hypothesis, we decided to study how and to what extent different didactical approaches based on macroscopic and mesoscopic description, respectively, can foster the teaching and learning of surface phenomena at secondary school level. We designed two teaching-learning sequences (TLSs), one based on macroscopic modelling, and the other on mesoscopic modelling, which were trialled each with a group of upper secondary school students. Each TLS was based on an inquiry-based approach and was planned to involve students in active learning practices. The main goal of the trialling was not to identify which group highlights the best learning depending on the different modelling approach, but to verify the aspects of each approach that can be considered truly relevant in promoting learning. The planning and implementation of the two TLSs were guided by the general research question “which aspects of each approach can be considered relevant in promoting students’ scientific learning?”. The data collected during the trialling of the TLSs (student worksheets, interviews, students’ answers to questionnaires etc.) were studied by means of qualitative and/or quantitative analysis methodologies. Resuming some results, after the instruction students who followed the macroscopic approach, appear more capable than students who followed the mesoscopic approach, in describing complex phenomena involving liquid-solid interaction, as capillarity. However, a close analysis of their answers to questionnaires, shows that they acquired a quite superficial knowledge, as they simply memorized notions and information on the topic, but did not reach a proper awareness of it. On the other hand, after the instruction students who followed the mesoscopic approach seem more capable of building explanation than students who followed the macroscopic approach. We can infer that mesoscopic modelling activities can support the development of explanation-oriented reasoning lines more than macroscopic traditional ones. We found that students who followed the mesoscopic approach understood more deeply than students who followed the macroscopic approach the analysed topics. This, however, often happens with respect to simple physical situations like the ones involving liquid-liquid interactions. These students found it difficult to understand more complex physical situations as those involved in liquid-solid interactions. In general, both groups show comparable levels of well-being in learning. This indicates that the inquiry-type approach proposed through the two TLSs has been welcomed by most of students. The mesoscopic approach promoted the development of the willingness to extend studies and research more than the macroscopic approach and this led students to reinforce beliefs and acquire behaviours characteristic of a growth mindset. On the other hand, students who followed the macroscopic approach developed the ability of generalization of what has been learned more than students who followed the mesoscopic approach

Examining Risk Factors for Anxiety and Negative College Adjustment in First-Year College Students

College is a major transitional period for young adults as they move off into the world on their own and mental health problems are increasing within this population. The present study examined distance from students’ hometown to campus, the number of times students visit campus prior to starting classes, and the level of social and academic pressure students perceive as potential risk factors for risky drinking behaviors, anxiety, and negative college adjustment in a sample of first-year college students. Distance from students’ hometown to campus was also examined as a risk factor for hazardous drinking behaviors. Participants (N= 108) took part in a longitudinal study, completing a battery of measures as part of an online survey, at three time points throughout their first semester at college. Among other results, a one-way analysis of covariance revealed distance from hometown as a risk factor for risky drinking behaviors and the number of times students visited campus was found to be a risk factor for social anxiety symptoms. Perceived social pressure was identified as a risk factor negative college adjustment, social anxiety, and anxious mood symptoms, while perceived academic pressure was a risk factor for negative college adjustment and anxious mood symptoms. Risky drinking behavior was also found to be a risk factor for negative college adjustment. Implications for interventions and public education about risk factors for anxiety and negative college adjustment that future college students may face are discussed

Bank Erosion and Secondary Circulation in a Meandering Laboratory Flume

AbstractThis paper reports peculiar results of experimental investigation on the secondary circulation motion of flow along a meander wave. Experiments were conducted in a large amplitude meandering laboratory channel for two values of the width-to-depth ratio. Here attention is focalized on how secondary motion affects the bank shear stress distribution, influencing the stability of the outer bank. The analysis essentially highlights that, especially for small width-to-depth ratio, as the channel curvature increases, besides the classical central-region secondary circulation cell a counter-rotating circulation cell forms in the outer-bank region. Such counter-rotating circulation cell allows the bank shear stress to obtain small values at the outer bank