Diffractive and refractive timescales at 4.8 GHz in PSR B0329+54

We present the results of flux density monitoring of PSR B0329+54 at the frequency of 4.8 GHz using the 32-meter TCfA radiotelescope. The observations were conducted between 2002 and 2005. The main goal of the project was to find interstellar scintillation (ISS) parameters for the pulsar at the frequency at which it was never studied in detail. To achieve this the 20 observing sessions consisted of 3-minute integrations which on average lasted 24 hours. Flux density time series obtained for each session were analysed using structure functions. For some of the individual sessions as well as for the general average structure function we were able to identify two distinctive timescales present, the timescales of diffractive and refractive scintillations. To the best of our knowledge, this is the first case when both scintillation timescales, t_DISS=42.7 minutes and t_RISS=305 minutes, were observed simultaneously in a uniform data set and estimated using the same method. The obtained values of the ISS parameters combined with the data found in the literature allowed us to study the frequency dependence of these parameters over a wide range of observing frequencies, which is crucial for understanding the ISM turbulence. We found that the Kolmogorov spectrum is not best suited for describing the density fluctuations of the ISM, and a power-law spectrum with beta =4 seems to fit better with our results. We were also able to estimate the transition frequency (transition from strong to weak scintillation regimes) as 10.1 GHz, much higher than was previously predicted. We were also able to estimate the strength of scattering parameter u=2.67$ and the Fresnel scale as 6.7x10^8 meters.Comment: 11 pages, 4 figures, accepted for publication in: Astronomy and Astrophysic

Effect of disciplinary content of a simulation on open-ended problem-solving strategies

There is a long-standing debate about so-called generic vs. domain- or context-specific problem-solving skills and strategies. To investigate this issue, we developed a pair of structurally and functionally similar computer simulations and used them in an experimental study with undergraduate students from all fields of study. One, described to users as a teaching tool based on current entomology research, featured three species of ants whose tasks could change as a result of encounters with each other. The other, which we call a non-disciplinary simulation, featured three types of abstract moving shapes whose color could change after a collision. Users received no information about the latter, not even that it was a simulation. Both simulations, which students used in succession, allowed users to change the number and types of objects, and to move them freely on the screen. We told students that the problem was to describe and explain what occurred on the screen, and asked them to explain, while they were working with the simulation, what they observed, what they did and why. We conducted a first, quantitative analysis of various “surfac

A Strategy for Teaching an Effective Undergraduate Mineralogy Course

An effective undergraduate mineralogy course provides students with a familiarity and understanding of minerals that is necessary for studying the Earth. This paper describes a strategy for integrating the disparate topics covered in a mineralogy course and for presenting them in a way that facilitates an understanding of mineralogy that enables students to apply it in subsequent courses and research. The course is organized into a well-integrated sequence of lectures, demonstrations and laboratory exercises that unfolds the material logically and at a pace that is responsive to the students’ needs. The course begins with six weeks on crystal chemistry, then five weeks covering analytical methods for characterizing minerals and ends with five weeks on the silicates. This order facilitates a progression of learning from the basic concepts to the more advanced and allows us to reinforce the concepts of crystal chemistry during the final section on the silicates. Optical mineralogy is almost entirely taught in the lab and is aided by use of a mineral identification chart developed to help students learn to identify minerals in thin section. Student performance is assessed through one technical paper and presentation as well as homework, essay exams and lab practicals. Educational levels: Graduate or professional

A Logical Verification Methodology for Service-Oriented Computing

We introduce a logical verification methodology for checking behavioural properties of service-oriented computing systems. Service properties are described by means of SocL, a branching-time temporal logic that we have specifically designed to express in an effective way distinctive aspects of services, such as, e.g., acceptance of a request, provision of a response, and correlation among service requests and responses. Our approach allows service properties to be expressed in such a way that they can be independent of service domains and specifications. We show an instantiation of our general methodology that uses the formal language COWS to conveniently specify services and the expressly developed software tool CMC to assist the user in the task of verifying SocL formulae over service specifications. We demonstrate feasibility and effectiveness of our methodology by means of the specification and the analysis of a case study in the automotive domain

The two Josephson junction flux qubit with large tunneling amplitude

In this paper we discuss solid-state nanoelectronic realizations of Josephson flux qubits with large tunneling amplitude between the two macroscopic states. The latter can be controlled via the height and wells form of the potential barrier, which is determined by quantum-state engineering of the flux qubit circuit. The simplest circuit of the flux qubit is a superconducting loop interrupted by a Josephson nanoscale tunnel junction. The tunneling amplitude between two macroscopically different states can be essentially increased, by engineering of the qubit circuit, if tunnel junction is replaced by a ScS contact. However, only Josephson tunnel junctions are particularly suitable for large-scale integration circuits and quantum detectors with preset-day technology. To overcome this difficulty we consider here the flux qubit with high-level energy separation between "ground" and "excited" states, which consists of a superconducting loop with two low-capacitance Josephson tunnel junctions in series. We demonstrate that for real parameters of resonant superposition between the two macroscopic states the tunneling amplitude can reach values greater than 1K. Analytical results for the tunneling amplitude obtained within semiclassical approximation by instanton technique show good correlation with a numerical solution.Comment: 8 pages, 4 figure

Metacognition and transfer within a course or instructional design rules and metacognition

A metacognitive strategy for doing research, included transfer, was taught in a course of nine afternoons. The success of this course raised some questions. How do the students learn? How does metacognition play a role? The course was designed in accordance with several instructional principles. The course was divided into three domains in which the strategy was introduced, practised, and applied respectively. Literature research revealed four possible metacognitive variants that correlate so it was supposed that implementing them all helped to reach the objectives of the course. The relation of the metacognitive variants with the instructional principles is described. To study learning the students were divided into three groups (weak, moderate, good) by their marks for other courses. The performance of the groups in each domain was monitored by their marks, scoring of metacognitive skills, questionnaires, observations, and time keeping. The moderate students scored as high as the good ones for the strategy in the last domain, a unique result. The metacognitive development of the other metacognitive skills was not linear. The conclusions are that the success of this course can be explained by a system of double sequencing and an interaction of all metacognitive variants, and that instructional design rules for metacognitive and cognitive objectives are differen

Representation growth and representation zeta functions of groups

We give a short introduction to the subject of representation growth and representation zeta functions of groups, omitting all proofs. Our focus is on results which are relevant to the study of arithmetic groups in semisimple algebraic groups, such as the special linear group of degree n over the ring of integers. In the last two sections we state several results which were recently obtained in joint work with N. Avni, U. Onn and C. Voll.Comment: 14 pages, submitted to Note di Matematica, survey based on a conference tal