Collaborative Learning in Engineering Education: A Grounded Theory Analysis of a CSCL Application

This study examines how students collaborate on engineering problems and the effect of information technology on facilitating collaboration. Twenty-eight undergraduate engineering students were placed in small groups to discuss questions about mechanics of materials, either face-to-face or via a keyboard chat. Students were interviewed after completing the tasks, and the interviews were analyzed using the grounded theory approach. The resulting framework suggests that social goals as well as achievement goals are major motivations for students’ behavior in the team situation, and that technology and group characteristics were acknowledged to influence their actions during and after the cooperation

In vitro selection and characterization of cellulose-binding DNA aptamers

Many nucleic acid enzymes and aptamers have modular architectures that allow them to retain their functions when combined with other nucleotide sequences. This modular function facilitates the engineering of RNAs and DNAs that have more complex functions. We sought to create new DNA aptamers that bind cellulose to provide a module for immobilizing DNAs. Cellulose has been used in a variety of applications ranging from coatings and films to pharmaceutical preparations, and therefore DNA aptamers that bind cellulose might enable new applications. We used in vitro selection to isolate aptamers from a pool of random-sequence DNAs and subjected two distinct clones to additional rounds of mutagenesis and selection. One aptamer (CELAPT 14) was chosen for sequence minimization and more detailed biochemical analysis. CELAPT 14 aptamer variants exhibit robust binding both to cellulose powder and paper. Also, an allosteric aptamer construct was engineered that exhibits ATP-mediated cellulose binding during paper chromatography

Evaluating the Use of 3D Visualization Technology in Geology Education

Information systems can contribute to the success of students in engineering and science. In this study, 3-D visualizations that create a realistic map of rock structures are used to aid students in developing the spatial intuition to understand geological processes. This technology received positive ratings for learning outcomes and within the technology acceptance model. In addition, qualitative data provides additional detail about what features are correlated with the success of direct manipulation visualizations. The qualitative data suggest that the interface design may be a moderator of the relationship between the completeness of the visualization and how much individuals can benefit from the visualization

Developing a Grounded Theory Model on Collaboration in Learning

The purpose of this research is to develop a grounded theory model to explain the factors influencing collaborative learning in higher education, the role of technology in facilitating collaboration, and the outcome of collaboration. We assigned 28 participants to small groups to work on course-related questions; half of the groups were face-to-face groups and the other half groups were collaborating in a simulated virtual environment with the aid of information technology. Interview data was collected and analyzed following the grounded theory approach. Congruent with distributed cognition theories, the results of our study suggest that both social and technological factors were important and interlocking. We also discussed the importance of designing learning technologies that have strong social and communications features

Turhan Valide'nin saltanatı

Ömer Refi'nin Hizmet'te tefrika edilen Turhan Valide'nin Saltanatı adlı romanıArşivdeki eksikler nedeniyle romanın tam metni verilememiştir. Bkz. Tefrika bilgi form

Current-oscillator correlation and Fano factor spectrum of quantum shuttle with finite bias voltage and temperature

A general master equation is derived to describe an electromechanical single-dot transistor in the Coulomb blockade regime. In the equation, Fermi distribution functions in the two leads are taken into account, which allows one to study the system as a function of bias voltage and temperature of the leads. Furthermore, we treat the coherent interaction mechanism between electron tunneling events and the dynamics of excited vibrational modes. Stationary solutions of the equation are numerically calculated. We show current through the oscillating island at low temperature appears step like characteristics as a function of the bias voltage and the steps depend on mean phonon number of the oscillator. At higher temperatures the current steps would disappear and this event is accompanied by the emergence of thermal noise of the charge transfer. When the system is mainly in the ground state, zero frequency Fano factor of current manifests sub-Poissonian noise and when the system is partially driven into its excited states it exhibits super-Poissonian noise. The difference in the current noise would almost be removed for the situation in which the dissipation rate of the oscillator is much larger than the bare tunneling rates of electrons.Comment: 14 pages, 8 figure

Tunneling broadening of vibrational sidebands in molecular transistors

Transport through molecular quantum dots coupled to a single vibration mode is studied in the case with strong coupling to the leads. We use an expansion in the correlation between electrons on the molecule and electrons in the leads and show that the tunneling broadening is strongly suppressed by the combination of the Pauli principle and the quantization of the oscillator. As a consequence the first Frank-Condon step is sharper than the higher order ones, and its width, when compared to the bare tunneling strength, is reduced by the overlap between the groundstates of the displaced and the non-displaced oscillator.Comment: 8 pages, 3 figures. PRB, in pres

Single electron-phonon interaction in a suspended quantum dot phonon cavity

An electron-phonon cavity consisting of a quantum dot embedded in a free-standing GaAs/AlGaAs membrane is characterized in Coulomb blockade measurements at low temperatures. We find a complete suppression of single electron tunneling around zero bias leading to the formation of an energy gap in the transport spectrum. The observed effect is induced by the excitation of a localized phonon mode confined in the cavity. This phonon blockade of transport is lifted at magnetic fields where higher electronic states with nonzero angular momentum are brought into resonance with the phonon energy.Comment: 4 pages, 4 figure

Dephasing in sequential tunneling through a double-dot interferometer

We analyze dephasing in a model system where electrons tunnel sequentially through a symmetric interference setup consisting of two single-level quantum dots. Depending on the phase difference between the two tunneling paths, this may result in perfect destructive interference. However, if the dots are coupled to a bath, it may act as a which-way detector, leading to partial suppression of the phase-coherence and the reappearance of a finite tunneling current. In our approach, the tunneling is treated in leading order whereas coupling to the bath is kept to all orders (using P(E) theory). We discuss the influence of different bath spectra on the visibility of the interference pattern, including the distinction between "mere renormalization effects" and "true dephasing".Comment: 18 pages, 8 figures; For a tutorial introduction to dephasing see http://iff.physik.unibas.ch/~florian/dephasing/dephasing.htm

Filtering spin with tunnel-coupled electron wave guides

We show how momentum-resolved tunneling between parallel electron wave guides can be used to observe and exploit lifting of spin degeneracy due to Rashba spin-orbit coupling. A device is proposed that achieves spin filtering without using ferromagnets or the Zeeman effect.Comment: 4 pages, 4 figures, RevTex