Scientists and the Science Educators: Collaborating to Develop Conceptual Change Teaching Strategies

Research in science education has identified conceptual change teaching strategies that may enhance pre-service teachers’ understanding of scientific concepts and processes. These strategies, supported by constructivist learning theory in the social and cognitive sciences, include the use of discrepant events to engage students’ prior knowledge, the learning cycle, and collaborative learning. Science educators have used these strategies to challenge alternative conceptions of pre-service K-8 teachers in methods courses in an effort to facilitate learning scientific concepts. Pre-service K-8 teachers, motivated to explore scientific phenomena and clarify their own understandings, gain confidence in their ability to learn science and are better prepared to use similar strategies with children. In redesigning innovative courses for pre-service teachers in university science departments, scientists and science educators would benefit from a mutual collaboration to develop instructional strategies informed by constructivist learning theory. In this partnership, scientists, experts in content and scientific research, would work with science educators to develop curriculum in both science and science methods courses that challenges pre-service teachers’ existing knowledge and facilitates more authentic understandings of science. A more seamless transition would thus be possible between science courses and science methods courses

Microwave saturation of the Rydberg states of electrons on helium

We present measurements of the resonant microwave excitation of the Rydberg energy levels of surface state electrons on superfluid helium. The temperature dependent linewidth agrees well with theoretical predictions and is very small below 300 mK. Absorption saturation and power broadening were observed as the fraction of electrons in the first excited state was increased to 0.49, close to the thermal excitation limit of 0.5. The Rabi frequency was determined as a function of microwave power. The high values of the ratio of the Rabi frequency to linewidth confirm this system as an excellent candidate for creating qubits.Comment: 4 pages, 4 figure

Intersubband plasmons in quasi-one-dimensional electron systems on a liquid helium surface

The collective excitation spectra are studied for a multisubband quasi-one-dimensional electron gas on the surface of liquid helium. Different intersubband plasmon modes are identified by calculating the spectral weight function of the electron gas within a 12 subband model. Strong intersubband coupling and depolarization shifts are found. When the plasmon energy is close to the energy differences between two subbands, Landau damping in this finite temperature system leads to plasmon gaps at small wavevectors.Comment: To be published as a Rapid Communication in Phys. Rev.

Thermally excited tunneling from a metastable electronic state in a single-Cooper-pair transistor

International audienceMetastable electron traps and two-level systems are common in solid-state devices and lead to background charge movement and charge noise in single-electron and singleCooper-pair transistors. We present measurements of the real-time capture and escape of individual electrons in metastable trapped states at very low temperatures, leading to charge offsets close to 1e. The charge movement exhibits thermal excitation to a hysteretic tunneling transition. The temperature dependence and hysteresis can be explained by the coupling of a two-level system to a quasiparticle trap

Counting Individual Electrons on Liquid Helium

We show that small numbers of electrons, including a single electron, can be held in a novel electrostatic trap above the surface of superfluid helium. A potential well is created using microfabricated electrodes in a 5 micron diameter pool of helium. Electrons are injected into the trap from an electron reservoir on a helium microchannel. They are individually detected using a superconducting single-electron transistor (SET) as an electrometer. A Coulomb staircase is observed as electrons leave the trap one-by-one until the trap is empty. A design for a scalable quantum information processor using arrays of electron traps is presentedComment: 15 pages, 5 figure

Thermal excitation of large charge offsets in a single-Cooper-pair transistor

International audienceCharge offsets and two-level fluctuators are common in single-electron transistors (SET) with a typical magnitude |∆Q| < 0.1e. We now present measurements in a 2e-periodic single-Cooper-pair transistor (SCPT) which exhibited hysteretic charge offsets close to 1e. The real-time capture and escape of individual electrons in metastable trapped states was measured at very low temperatures. This enabled the dynamics of the transitions to be investigated in detail, demonstrating thermal excitation to a hysteretic tunneling transition. We also show that, allowing for the hysteresis, the metastable states are in thermal equilibrium with each other. The observed temperature dependence and hysteresis can be explained by the coupling of a two-level fluctuator to a quasiparticle trap

Unrestricted Hartree-Fock theory of Wigner crystals

We demonstrate that unrestricted Hartree-Fock theory applied to electrons in a uniform potential has stable Wigner crystal solutions for $r_s \geq 1.44$ in two dimensions and $r_s \geq 4.5$ in three dimensions. The correlation energies of the Wigner crystal phases are considerably smaller than those of the fluid phases at the same density.Comment: 4 pages, 5 figure

Reducing green tape or rolling back IA in Australia: What are found jurisdictions up to?

EIA has been practiced in Australia and the rest of the world for over 40 years, but despite its successes, EIA may now be facing its biggest challenge since it came into being in 1970 with the US National Environmental Policy Act. As Morgan (2012, 11) notes: “As governments look to stimulate economic growth and create employment in response to the current financial crisis, many are promoting a major expansion of physical infrastructure, encouraging resource development projects, and generally seeking to speed decision-making about development projects. Both EIA and SEA should be even more important in such circumstances, yet the moves taken in some countries to speed up decision-making may weaken the provisions for environmental protection, including impact assessment.” In this political and economic environment, EIA is under scrutiny. Proposed changes to the EU directive on EIA released in October 2012 contain ten changes to the Articles of the Directive, with six of these referring to either ‘streamlining’ EIA or introducing specific timeframes for parts of the EIA process (European Commission 2012). This scrutiny has not been restricted to economies in recession, but includes those that have avoided recession because of strong resources sectors. The same appears to be happening in Australia, and this paper reports on these and other possible ‘efficiency’ changes to EIA in Australia at both national and sub-national levels. We attempt to critically examine the nature of such changes and the risks that may be associated with their implementation. Changes to three of the sub-national EIA processes are reviewed in detail, as well as the proposed changes to the national EIA process. There is always room for more timely assessments, but a critical examination of the potential consequences of these “reforms” on the conduct of EIAs is needed, including whether these efficiency changes will deliver sound environmental management and sustainability-oriented decision-making