Marjan Zadnik

Introductory thermal concept evaluation: Assessing students' understanding

We describe a pen and paper instrument designed to provide a measure of a range of student beliefs about thermal phenomena. The trial version, administered to 478 high school and university students aged 15–18 years, was able to distinguish belief changes in two populations, year 11 and first-year university physics students. We have used the revised instrument as a pre-test and post-test for evaluating students’ conceptual change following instruction. The instrument, called the Thermal Concept Evaluation, is appended.

Student and Teacher Perceptions of the Use of Multimedia Supported Predict–Observe–Explain Tasks to Probe Understanding

This paper discusses student and teacher perceptions of a new development in the use of the predict–observe–explain (POE) strategy. This development involves the incorporation of POE tasks into a multimedia computer program that uses real-life, digital video clips of difficult, expensive, time consuming or dangerous scenarios as stimuli for these tasks. The program was created by the first author to be used by pairs of secondary physics students to elicit their conceptions of force and motion and encourage discussion about these views. In this computer learning environment, students were required to type full sentence responses that were recorded by the computer for later analysis by the researcher. Other data sources for this study included audio and video recordings of student discussions, interviews with selected students and their teachers, classroom observations, and student questionnaires. This paper will report on some findings from the study, focussing on student and teacher perceptions of the computer-mediated POE tasks. The findings have implications for the effective use of multimedia to enhance meaningful learning in science classrooms.

Unequilibrated ordinary chondrites: A tentative subclassification based on volatile-element content

For unequilibrated ordinary chondrites (= UOC), two measures of primitiveness are available: volatile content, in principle reflecting accretion conditions from the solar nebula, and metamorphism, reflecting reheating in the parent bodies. These two measures do not always correlate, and we have therefore developed a tentative classification scheme based on volatile content that complements the Searset al. (1980) scheme based on metamorphism. Like the latter, it subdivides type 3 chondrites on a scale of 3.0 to 3.9; the notation 3.4/0 indicates a meteorite that is subtype 3.4 according to metamorphism and 3.0 according to volatile content. The classification is based mainly on C and Xe—two elements that are little affected by shock-induced reheating—and to a lesser extent on Ar36,Bi,In, and Tl. Of 22 meteorites considered, the majority have concordant classifications (±0.2) on the two scales. However, 5 meteorites are richer in volatiles than their metamorphic grade indicates: Sharps 3.4/0, ALHA 77011 3.5/0, Ngawi 3.6/3, ALHA 77299 3.7/4, and Mezo-Madaras 3.7/3. It remains to be seen whether these differences indeed denote a more primitive nature. Some new clues to the formation of chondrites may eventually come from Xe and C. Their concentrations in UOCs vary by more than 5×, but the XeC ratio remains nearly constant at 3.4 × 10−3 of the solar-system ratio. Even the ratios for other chondrite classes differ only slightly from that for UOCs, e.g., C3O (1.5×) and E3,4 (0.4×). Either the 4 factors determining this ratio (T, t, P, and internal surface area of the carbon) varied in complementary fashion, or—more probably—they varied only slightly in the entire source region of chondrites.

What do students really learn from interactive multimedia? A physics case study

Interactive multimedia is promoted as an effective and stimulating medium for learning science, but students do not always interact with multimedia as intended by the designers. We discuss students’ interactions with an interactive multimedia program segment about projectile motion in the context of long jumping. Qualitative data were collected using a video camera and split-screen recorder to record each student’s image, voice, and student–program interactions. Left to themselves, students’ interactions were superficial, but when asked to explain their observations of projectile motion illustrations, they were observed to retain common intuitive conceptions. Only following researcher intervention did students develop an awareness of abstract aspects of the program. These results suggest that, despite interactivity and animated graphics, interactive multimedia may not produce the desired outcome for students learning introductory physics concepts.

REVISED ISOTOPIC COMPOSITION OF TERRESTRIAL MERCURY

A noble gas mass spectrometer has been used to remeasure the isotopic composition of mercury. The amount of mercury in the gas phase ranged over more than four orders of magnitude from approximately 0.02 to 260 pg. Isotope abundance ratios were measured in the singly charged state with an electron potential of 70 eV and the spectrometer in either the static mode (21 samples) or in the dynamic mode (nine samples), as Hg+ ions at an electron potential of 40 eV (six samples) and as doubly charged species at 70 eV (seven samples), both in the static mode. Measurements of peak heights at 19 integer and half integer mass numbers showed no evidence of contamination from hydrocarbons or from mercury hydrides in the mass number range 194–204.5. Mass fractionation lines based on Niers (1950) ratios through the heaviest six mass numbers showed a large positive departure at mass number 196 and much smaller but persistent negative departures at mass numbers 198, 200 and 201 for all four sets of measurements, suggesting that the reference abundances at these mass numbers are in error. Fitting regression lines through the 199Hg/202Hg and 204Hg/202Hg ratios only yields the following revised percentage abundances for terrestrial mercury: 196Hg 198Hg 199Hg 200Hg 201Hg 202Hg 204Hg 0.15344 9.968 16.873 23.096 13.181 29.863 6.865 ±0.00019 ±0.013 ±0.017 ±0.026 ±0.013 ±0.033 ±0.007 Full-size table Table options View in workspace Download as CSV

The Zadko Telescope: A Southern Hemisphere Telescope for Optical Transient Searches, Multi-Messenger Astronomy and Education

The new 1-m f/4 fast-slew Zadko Telescope was installed in June 2008 about 70 km north of Perth, Western Australia. It is the only metre-class optical facility at this southern latitude between the east coast of Australia and South Africa, and can rapidly image optical transients at a longitude not monitored by other similar facilities. We report on first imaging tests of a pilot program of minor planet searches, and Target of Opportunity observations triggered by the Swift satellite. In 12 months, 6 gamma-ray burst afterglows were detected, with estimated magnitudes; two of them, GRB 090205 (z = 4.65) and GRB 090516 (z = 4.11), are among the most distant optical transients imaged by an Australian telescope. Many asteroids were observed in a systematic 3-month search. In September 2009, an automatic telescope control system was installed, which will be used to link the facility to a global robotic telescope network; future targets will include fast optical transients triggered by high- energy satellites, radio transient detections, and LIGO gravitational wave candidate events. We also outline the importance of the facility as a potential tool for education, training, and public outreach.

What does a physics undergraduate education give you? A perspective from Australian physics

In a study to assess how effectively undergraduate physics studies have prepared students for the workplace, we attempted to locate and interview traditional 3-year or 4-year physics students who had graduated in the past five years (2000 to 2004), and the employers of these graduates. The study was limited to recent graduates who have majored in physics and not obtained further or concurrent degrees. Overseas studies of the destinations of physics graduates referred to in this paper have not isolated the group we interviewed as a distinct group. A major finding was that the number of these graduates was unexpectedly low. Indeed, most physics graduates have two degrees. Interviews with graduates and employers suggest that physics graduates have particular strengths in problem solving and are good at applying their skills at the workplace.

An optimal Mars Trojan asteroid search strategy

ABSTRACT Trojan asteroids are minor planets that share the orbit of a planet about the Sun andlibrate around the L4 or L5 Lagrangian points of stability. Although only three MarsTrojans have been discovered, models suggest that at least ten times this numbershould exist with diameters >1 km. We derive a model that constrains optimal skysearch areas and present a strategy for the most efficient use of telescope survey timethat maximizes the probability of detecting Mars Trojans. We show that the Gaiaspace mission could detect any Mars Trojans larger than 1 km in diameter, providedthe relative motion perpendicular to Gaia’s CCD array is less than 0.40 arcsec persecond.Keywords: methods: numerical – methods: observational – minor planets, asteroids:general – planets and satellites: general – celestial mechanics 1 INTRODUCTIONTrojan asteroids are minor planets that share the orbit ofa planet about the Sun and librate around the L4 and L5Lagrangian points of stability. The L4 and L5 points are 60

Evaluation of Students' Understanding of Thermal Concepts in Everyday Contexts

The aims of this study were to determine the underlying conceptual structure of the thermal concept evaluation (TCE) questionnaire, a pencil-and-paper instrument about everyday contexts of heat, temperature, and heat transfer, to investigate students’ conceptual understanding of thermal concepts in everyday contexts across several school years and to analyse the variables—school year, science subjects currently being studied, and science subjects previously studied in thermal energy—that influence students’ thermal conceptual understanding. The TCE, which was administered to 515 Korean students from years 10–12, was developed in Australia, using students’ alternative conceptions derived from the research literature. The conceptual structure comprised four groups—heat transfer and temperature changes, boiling, heat conductivity and equilibrium, and freezing and melting—using 19 of the 26 items in the original questionnaire. Depending on the year group, 25–55% of students experienced difficulties in applying scientific concepts in everyday contexts. Years of schooling, science subjects currently studied and physics topics previously studied correlated with development of students’ conceptual understanding, especially in topics relating to heat transfer, temperature scales, specific heat capacity, homeostasis, and thermodynamics. Although students did improve their conceptual understandings in later years of schooling, they still had difficulties in relating the scientific concepts to their experiences in everyday contexts. The study illustrates the utility of using a pencil-and-paper questionnaire to identify students’ understanding of thermal concepts in everyday situations and provides a baseline for Korean students’ achievement in terms of physics in everyday contexts, one of the objectives of the Korean national curriculum reforms.

An optimal Earth Trojan asteroid search strategy

Trojan asteroids are minor planets that share the orbit of a planet about the Sun and librate around the L4 or L5 Lagrangian points of stability. They are important solar-system fossils because they carry information on early Solar system formation, when collisions between bodies were more frequent. Discovery and study of terrestrial planet Trojans will help constrain models for the distribution of bodies and interactions in the inner Solar system. Since the discovery of the first outer planet Trojan in 1906, several thousand Jupiter Trojans have been found. Of the terrestrial planets, there are four known Mars Trojans, and one Earth Trojan has been recently discovered. We present a new model that constrains optimal search areas, and imaging cadences for narrow and wide-field survey telescopes including the Gaia satellite for the most efficient use of telescope time to maximize the probability of detecting additional Earth Trojans.