Manipulating particle trajectories with phase-control in surface acoustic wave microfluidics

We present a 91 MHz surface acoustic wave resonator with integrated microfluidics that includes a flow focus, an expansion region, and a binning region in order to manipulate particle trajectories. We demonstrate the ability to change the position of the acoustic nodes by varying the electronic phase of one of the transducers relative to the other in a pseudo-static manner. The measurements were performed at room temperature with 3 μm diameter latex beads dispersed in a water-based solution. We demonstrate the dependence of nodal position on pseudo-static phase and show simultaneous control of 9 bead streams with spatial control of −0.058 μm/deg ± 0.001 μm/deg. As a consequence of changing the position of bead streams perpendicular to their flow direction, we also show that the integrated acoustic-microfluidic device can be used to change the trajectory of a bead stream towards a selected bin with an angular control of 0.008 deg/deg ± 0.000(2) deg/deg.     

New product introduction and product tenure: What effects on firm growth?

This study contributes to the recent empirical literature on the innovation-firm performance relationship by investigating the effect of product introduction on firm growth in a sample of Italian firms from 2000 to 2006. We adopted a novel approach that exploits the interpretative content of the tenure of the last product introduced (i.e., the number of years since its first introduction) as an additional variable into the explanatory scheme of firm sales growth rate. This variable aims to capture peculiar characteristics of new goods, such as their novelty and complexity. The estimated results confirmed the relevance of this model specification and helps in understanding the reason why previous studies have failed to find a statistically robust relationship between product innovation and growth. Moreover, we found the following: first, the release of a new product enhances growth opportunity among multiproduct firms; second, product development promotes the growth of firms belonging to sectors with stronger commitment to research and development; and third, new product development enhances firm growth substantially in those sectors that absorb externally originated patents.     

Microtextural and microchemical studies of hydraulic ancient mortars: Two analytical approaches to understand pre-industrial technology processes

Two different analytical approaches have been taken into account to investigate the role of Si-rich phases in enhance hydraulic reactions of bedding mortar mixtures from San Lorenzo Church in Milan (Northern Italy) and from the Medicean Aqueduct in Pisa (Central Italy). In the first case, mortars show clear hydraulic type reactions in the form of coronal layers between the reacting additive and the binder mass. In the second one, the hydraulic reactions do not develop visible mineral phases and processes have been inferred from chemical, mineralogical analyses and mass balance calculation. The microstructural studies not always are sufficient to understand the complex dynamics of reaction attained during pre-industrial manufacturing processing of mortars and related binders. In fact, if the reacting raw materials are fine-grained and/or have remarkable chemical reactivity, no relicts are preserved by mortar microtextures.     

Secondary students’ modelling conceptualisation in situations related to particle dynamics: a clinical perspective

This study investigates the modelling conceptualisation of secondary school students in two situations related to particle dynamics: pendulum’s motion and horizontal motion. We performed in-depth clinical interviews with secondary school students (N?=?10). Participants’ ideas about properties which are not ‘given’ in empirical observations were explored in order to investigate signs of abstractions and idealisations in their reasoning processes. We proposed contributions to modelling in science education based on Mario Bunge’s epistemology and we employed his basic concepts as the axis to analyse our results: (1) abstractions and idealisations, considered as thought processes required to build conceptual counterparts of concrete objects; (2) theoretical models, meaning hypothetico-deductive systems concerning those conceptual objects; and (3) general theoretical frameworks that allow us to derive those theoretical models. We developed our analysis viewing the ideas presented by participants as concepts-in-action and theorems-in-action as regarded by Gérard Vergnaud’s Theory of Conceptual Fields. Results indicated a gradation in the concepts-in-action mobilised in terms of levels of idealisation and showed that participants do not spontaneously recognise the use of a general theory as a possible way to obtain a theoretical model. These results suggest that science education practices must pay better attention to make abstractions and idealisations explicit in scientific concepts formation, as well as to the heuristic role of theories in model construction.     

CONCEPT MAPPING: AN ALTERNATIVE STRATEGY FOR EVALUATION

Concept maps are proposed as an alternative tool for evaluation in higher education and examples of concept maps, drawn by college students performing evaluation tasks, are presented in the areas of physics and literature.     

Real and perceived employability: a comparison among Italian graduates

The research undertaken for this article aims to analyse the correspondence between perceived employability and the actual national employment rate among Italian students and graduates undertaking different courses in a large Italian university. Data were collected through a cross-sectional survey of 2087 students in 19 faculties, and compared with the national indicators of employment rate for each faculty. Using faculty as unit of analysis, the results indicated a significant correlation between participants’ perceived employability and national employment rate. This trend was similar for both genders. However, the results showed a difference between bachelor’s and master’s degrees: the correlation between perceived and actual employability was not significant among bachelor’s participants while it remained significant among master’s participants. The results suggest that graduates are only partially aware of their possibility to enter the labour market and this, in turn, highlights that universities have only partially met the goal to increase awareness about the chances of finding a job among students and graduates.