bluuebunny/crossref_metadata_2025 huggingface dataset:
Learning‐goals‐driven design model: Developing curriculum materials that align with national standards and incorporate project‐based pedagogy
Authors: Krajcik Joseph , McNeill Katherine L. , Reiser Brian J.
Published: November 2007

Reform efforts in science education emphasize the importance of rigorous treatment of science standards and use of innovative pedagogical approaches to make science more meaningful and successful. In this paper, we present a learning‐goals‐driven design model for developing curriculum materials, which combines national standards and a project‐based pedagogical approach. We describe our design model in the context of the Investigating and Questioning our World through Science and Technology (IQWST) project, which is developing a three‐year coordinated series of middle grades science curriculum materials. From using this model in the development and enactment of the curriculum, we identified three important characteristics: unpacking national science standards, developing a learning performances approach to specifying learning goals, and aligning learning goals, instructional activities, and assessments. Using a case study of an IQWST unit from initial development through two cycles of enactment, we describe how these three characteristics help guide curriculum design, identify design issues in curriculum enactments, and guide the development of design solutions. The iterative use of the learning‐goals‐driven design model coupled with the analysis of multiple data sources informed our revision of the curriculum materials, resulting in substantial student learning gains for the targeted science content and scientific inquiry learning goals. © 2007 Wiley Periodicals, Inc. Sci Ed 92:1–32, 2008
Powerful learners and critical agents: The goals of five urban Caribbean youth in a conceptual physics classroom
Authors: Basu Sreyashi Jhumki
Published: November 2007

Youth from low‐income, minority backgrounds have often been marginalized from introductory courses, advanced study and careers in physics. Cultivating student agency may have the potential to improve access for diverse groups of learners. However, the implications of this lens for student learning have been minimally examined in the physics education literature. In this ethnographic study situated in a ninth‐grade conceptual physics classroom, I discuss students' critical goals—the intentions, motivations, and desires for change that youth held. These critical goals were related to learning, voice, and participation in relationships and the world. I also describe how student goals demonstrate the idea of “critical subject‐matter agency” in physics: students positioning themselves as powerful learners envisioning subject knowledge as a tool for change in their own lives and world. © 2007 Wiley Periodicals, Inc. Sci Ed 92:252–277, 2008
Determination of toxicity of subacute treatment of some plant growth regulators on rats
Authors: Celik Ismail , Tuluce Yasin
Published: November 2007

The effects of some plant growth regulators (PGRs), 2,3,5‐triiodobenzoic acid (TIBA), Naphthaleneacetic acid (NAA) and 2,4‐Dichlorofenoxyacetic acid (2,4‐D), at sublethal concentrations on antioxidant defense system [glutathione peroxidases (GPx), reduced glutathione (GSH), glutathione reductase (GR), glutathione‐S‐transferase (GST) and catalase (CAT)], immune potential enzymes [adenosine deaminase (ADA) and myeloperoxidase (MPO)], and lipid peroxidation content [Malondialdehyde, (MDA)] were investigated in lung and speen tissues of rats. Sprague‐Dawley albino rats were exposed to 0, 50, or 100 ppm (parts per million) TIBA, NAA, or 2,4‐D in drinking waterad libitumfor 25 days continuously. According to the results, MDA concentration significantly increased in the tissues treated with 100 ppm dosage of NAA or 2,4‐D without any change in the tissues of rats treated with both dosage of TIBA. The GSH depletion in the spleen tissue of rats treated with both the dosage of NAA and 2,4‐D were found to be significant. Also, GSH level in the spleen was significantly reduced with 100 ppm of 2,4‐D and NAA. The activity of antioxidant enzymes were also seriously affected by PGRs; GPx significantly decreased in the lung of rats treated with both dosages of the PGRs, whereas GPx activity in the spleen were significantly increased with 100 ppm dosage of 2,4‐D and NAA. On the other hand, CAT activity significantly decreased in the lung of rats treated with both dosages of NAA, 100 ppm of 2,4‐D and 50 ppm of TIBA, and also in the spleen treated with 50 ppm NAA and 2,4‐D. The ancillary enzyme GR activity significantly decreased in the spleen with both doses of the PGRs, also in the lung treated with both dosages of 2,4‐D, 50 ppm of NAA and 100 ppm of TIBA. The drug metabolizing enzyme GST activity significantly reduced in the lung of rats treated with both dosages of the PGRs and also in the spleen treated with 100 ppm dosage of 2,4‐D and TIBA and 50 ppm of NAA. Meanwhile, immune potential enzyme MPO activity significantly increased in the spleen of rats treated with both doses of NAA and TIBA whereas ADA activity significantly decreased in the spleen of rats treated with 100 ppm dose of NAA and TIBA. The observations presented led us to conclude that the administrations of subacute NAA, 2,4‐D, and TIBA promote MDA content, inhibit the antioxidative defense system and activate or inhibit immune potential enzymes in the rat's spleen and lung tissues. These data suggest that PGRs produced substantial organ toxicity in the lung and spleen during the period of a 25‐day subacute exposure. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 613–619, 2007.
Toxic effect of arsenate and cadmium alone and in combination on giant duckweed (Spirodela polyrrhiza L.) in response to its accumulation
Authors: Seth Chandra Shekhar , Chaturvedi Pranav Kumar , Misra Virendra
Published: November 2007

To evaluate the biological effects of wastewater samples containing heavy metals, the effects of metal Cd (II) and As (V) were studied on Spirodela polyrrhiza L. The plants were exposed at metal concentrations 0.1, 0.5, 1, 2 μM of Cd (II) and 1, 5, 10, 20 μM of As (V) for a period of 1, 4, 7 d (day) alone and in combination of both. Plants accumulated 1855 mg kg−1 dw (dry weight) Cd and 1230 mg kg−1 dw As after 7 d in alone, whereas it was 885 mg kg−1 dw Cd and 865 mg kg−1 dw As in combination. The toxicological parameters such as fresh biomass, photosynthetic pigments, and total protein contents increased up to 2 μM of Cd (II) after 1 d and 10 μM of As (V) after 4 d with respect to control (Hormesis effect), followed by gradual decline at higher concentrations and duration. In case of Cd (II) a maximum decrease of 58% in protein content, 62% in fresh biomass, and 78% in total chlorophyll was observed at 2 μM, whereas, with As (V) 38% decrease in protein content, 34% in fresh biomass, and 52% in total chlorophyll was shown at 20 μM after 7 d. The metal tolerance strategy against metal induced reactive oxygen species adopted by the plants was investigated with reference to nonprotein thiols (NP‐SH), cysteine, and ascorbic acid. The results of combined treatment revealed reduced toxicity at the level of fresh biomass, protein content, and chlorophyll; however, the amount of nonenzymatic antioxidant did not significantly (P = 0.172) increase as compared to alone treatment. Finally, it was concluded that due to high metal accumulation coupled with defense potential, the plant appears to have a potential for its use as phytoremediator species of aquatic environments. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 539–549, 2007.
Ecological relevance and sensitivity depending on the exposure time for two biomarkers
Authors: Campero Melina , Ollevier Frans , Stoks Robby
Published: November 2007

Biomarkers are widely used to assess pesticide stress, but their ecological relevance and exposure time dependent sensitivity is still heavily debated. We studied both aspects in larvae of the damselfly Coenagrion puella, comparing the impact of low doses of atrazine, carbaryl, and endosulfan on two key biomarkers (acetylcholinesterase [AChE] activity and fluctuating asymmetry [FA]) and their relationship with life history traits (mortality, development time, growth rate, and body size). Larvae exposed to the pesticides had, in general, longer development times. Size, growth rate, and mortality were not affected by any of the pesticides. In the long‐term exposure, AChE activity was diminished by atrazine treatments and stimulated by carbaryl treatments, and was not affected in the endosulfan treatments. FA decreased with increasing endosulfan concentrations and showed no reaction to atrazine or carbaryl. Overall, short‐term exposure tended to overestimate the results of long‐term exposure decreasing growth rates and enhancing inhibition of AChE activity in atrazine and carbaryl treatments. In line with its ecological relevance, relationship between biomarkers and life history traits showed that AChE inhibition was positively correlated with mortality, while FA was traded off with size. These results show that caution should be exerted when using these biomarkers to assess pesticide pollution in field situations. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 572–581, 2007.
A New Image Analysis Based Method for Measuring Electrospun Nanofiber Diameter
Authors: Ziabari Mohammad , Mottaghitalab Vahid , McGovern Scott T , Haghi AK
Published: November 2007

In this paper, a new image analysis based method for electrospun nanofiber diameter measurement has been presented. The method was tested by a simulated image with known characteristics and a real web. Mean (M) and standard deviation (STD) of fiber diameter obtained using this method for the simulated image were 15.02 and 4.80 pixels respectively, compared to the true values of 15.35 and 4.47 pixels. For the real web, applying the method resulted in M and STD of 324 and 50.4 nm which are extremely close to the values of 319 and 42 nm obtained using manual method. The results show that this approach is successful in making fast, accurate automated measurements of electrospun fiber diameters.
Melting Points and Viscosities of Fatty Acid Esters that are Potential Targets for Engineered Oilseed
Authors: Yao Linxing , Hammond Earl , Wang Tong
Published: November 2007

Our previous isolation of branched‐chain fatty acid (BCFA) methyl esters from lanolin was improved and scaled up. Also, oleate esters of isopropanol, oleyl alcohol and normal alcohols of 1–12 carbons chain lengths were prepared. Esters were made by interesterification with sodium alcoholates and by esterification with Candida antarctica lipase. It proved easier to obtain pure esters by the enzymatic synthesis. Melting points and viscosities over the range of 0–70 °C were determined in order to better identify potential lubricant targets that might be produced by genetically modified oilseed crops. Isopropyl and butyl oleate have melting points of −33 and −32 °C, respectively and viscosities that range from ~17 cp (0 °C) to ~2.5 cp (70 °C). They should have suitable stability for lubricants. BCFA esters had viscosities similar to their straight chain analogs. Viscosities increased with alcohol chain length and decreased with temperature. The dependence of viscosity on temperature was fit with an equation based on Erying’s rate equation. Some esters with branched acid or branched alcohol moieties, and some oleate esters might be utilized as biolubricants or biofuels on the basis of their melting points and viscosities.
Adapting the Fastrak® System for Three-Dimensional Measurement of the Motion of the Wrist
Authors: WIGDEROWITZ C. A. , SCOTT I. , JARIWALA A. , ARNOLD G. P. , ABBOUD R. J.
Published: November 2007

The Polhemus Fastrak® short-range miniature transmitter and mini-receivers allow wrist motion to be measured continually in three dimensions, registering patterns of motion, which until now were difficult to quantify. The current study aimed to determine the applicability and repeatability of the Fastrak® system when assessing wrist movements during a set protocol of activities. The device was found to be easy to use and repeatable; the Fastrak® system showed a mean error of up to 3° in all movements tested. Its assessment of range of motion correlated with the results in the literature. The Fastrakv® system was suitable for continuous registration of movements during the performance of set tasks in either of the wrists. It has the potential to be used for documentation of wrist motion in clinics for various pathologies and for assessing outcomes in wrist surgeries.
Closed Traumatic Rupture of the Extensor Digitorum Communis and Extensor Indicis Proprius at the Musculo-Tendinous Junction
Authors: MUDGAL C. S. , MUDGAL SHARMILA
Published: November 2007

This report describes a closed rupture of the entire extensor digitorum communis and extensor indicis proprius.
Experimental Neurotisation of the Brachial Plexus by Means of Nerve Grafting from the Corticospinal Tract of the Proximal Spinal Cord at the T3–T4 Level
Authors: BRUNELLI G. A.
Published: November 2007

This paper reports experimental work in rats in which the radial nerve was cut at its origin from the brachial plexus and connected by means of a nerve graft to the corticospinal tract of the spinal cord at the T3–T4 level. After surgery, the triceps and extensor muscles of the forearm were able to extend the elbow and the wrist and gave almost normal responses on EMG. This reinnervation was no longer cholinergic, as demonstrated by the Vecuronium test. Because of the drawbacks associated with implantation into the spinal cord, this technique could not be used in all cases of total avulsion of the brachial plexus but it might be useful in those rare cases in which avulsion of all the cervical nerves of the brachial plexus is associated with paraplegia: such cases are rare but are occasionally seen.
Mentoring trainee music teachers: beyond apprenticeship or reflection
Authors: Cain Tim
Published: November 2007

This article explores the theoretical concepts of ‘apprenticeship’ and ‘reflection’ in Initial Teacher Education music mentoring. It presents two case studies of Secondary music mentoring and relates these to the theoretical concepts. The article argues that a more integrated view of music mentoring might be provided with reference to Kolb's (1984) theory of experiential learning.
Integrating theory and practice in conservatoires: formulating holistic models for teaching and learning improvisation
Authors: Parsonage Catherine , Fadnes Petter Frost , Taylor James
Published: November 2007

Academic study has become a more significant part of a conservatoire education in recent times, but it has not always informed performance as effectively as it might. There is a need for further development of an academic curriculum that is specifically relevant to performers, in which the links between theory and practice are made explicit rather than expecting students to construct these for themselves. This article reports on research into the integration of theory and practice at Leeds College of Music, UK, using jazz improvisation as a case study. Pilot teaching sessions within two modules explored ways in which students can be encouraged to engage actively with an appropriate academic curriculum that is embedded within a holistic learning experience.
Dynamic variations of a convection flow reversal in the subauroral postmidnight sector as seen by the SuperDARN Hokkaido HF radar
Authors: Kataoka Ryuho , Nishitani Nozomu , Ebihara Yusuke , Hosokawa Keisuke , Ogawa Tadahiko , Kikuchi Takashi , Miyoshi Yoshizumi
Published: November 2007

The SuperDARN Hokkaido HF radar, capable of measuring the subauroral ionospheric plasma convection especially during storms, has been in continuous operation since the beginning of December 2006. We report the first two‐dimensional observation of a dynamic variation of convection flow reversal in subauroral postmidnight sector during the storm main phase on 29 January 2007. The flow reversal region is extended over 20° in longitude and 5° in latitude, lasting for about 10–15 min, and the maximum flow speed is about 0.5–1.0 km/s. The flow reversal structure is reasonably reproduced by the ring current simulation coupled with the ionosphere, suggesting that it is produced by the region 2 field‐aligned current associated with the ring current enhancement during the storm main phase. The dynamic variation of the flow reversal structure is interpreted as a transient eastward extension of the elongated dusk convection cell to the postmidnight and equatorward of the dawn cell, associated with the variation of the ring current whose structure is controlled by the interplanetary magnetic field and solar wind dynamic pressure. It is suggested that the ring current variation is highly coupled with the interplanetary parameters and is much more complicated than ever thought.
Single P and As dopants in the Si(001) surface
Authors: Radny M. W. , Smith P. V. , Reusch T. C. G. , Warschkow O. , Marks N. A. , Shi H. Q. , McKenzie D. R. , Schofield S. R. , Curson N. J. , Simmons M. Y.
Published: November 2007

Using first-principles density functional theory, we discuss doping of the Si(001) surface by a single substitutional phosphorus or arsenic atom. We show that there are two competing atomic structures for isolated Si–P and Si–As heterodimers, and that the donor electron is delocalized over the surface. We also show that the Si atom dangling bond of one of these heterodimer structures can be progressively charged by additional electrons. It is predicted that surface charge accumulation as a result of tip-induced band bending leads to structural and electronic changes of the Si–P and Si–As heterodimers which could be observed experimentally. Scanning tunneling microscopy (STM) measurements of the Si–P heterodimer on a n-type Si(001) surface reveal structural characteristics and a bias-voltage dependent appearance, consistent with these predictions. STM measurements for the As:Si(001) system are predicted to exhibit similar behavior to P:Si(001).
Layer-by-layer and pseudo-two-dimensional growth modes for heteroepitaxial BaTiO3 films by exploiting kinetic limitations
Authors: Shin Junsoo , Kalinin S. V. , Borisevich A. Y. , Plummer E. W. , Baddorf A. P.
Published: November 2007

Pulsed laser deposition has enabled formation of highly oxidized and strained BaTiO3 films on SrTiO3 substrates in a layer-by-layer growth mode to thicknesses of 125nm. Balancing thermodynamics and diffusion lengths enables controlled growth at the higher oxygen pressures required. Growth above 800°C produces an array of uniform pseudo-two-dimensional islands on single-step terraces which are independent of film thickness and correlated with threading dislocations. Control over growth modes is enabled by the manipulation of diffusion lengths and produces films with morphologies with broad applicability for fabrication of high-quality oxide films and self-assembled nanostructures.
Interactions between colloidal particles in amphiphilic mixtures: A density functional theory study
Authors: Egorov S. A.
Published: November 2007

We present a density functional theory study of interactions between spherical colloidal particles in amphiphile solutions. Theory is found to be in good agreement with previously published molecular dynamics simulations. It is used to analyze the effect of the amphiphile solution bulk density, the chain length, and the solvent mole fraction on the potential of mean force between the particles. The general features of the potential of mean force are rationalized in terms of formation of layers and bilayers of amphiphilic molecules in the intercolloidal gap. Theory yields the same general trends as observed in simulations and in experiments. In particular, the computed mean force changes its character from repulsive to attractive and back to repulsive as the solvent mole fraction is gradually increased.
Polycrystalline silicon thin-film transistors with location-controlled crystal grains fabricated by excimer laser crystallization
Authors: Tsai Chun-Chien , Lee Yao-Jen , Chiang Ko-Yu , Wang Jyh-Liang , Lee I-Che , Chen Hsu-Hsin , Wei Kai-Fang , Chang Ting-Kuo , Chen Bo-Ting , Cheng Huang-Chung
Published: November 2007

In this paper, location-controlled silicon crystal grains are fabricated by the excimer laser crystallization method which employs amorphous silicon spacer structure and prepatterned thin films. The amorphous silicon spacer in nanometer-sized width formed using spacer technology is served as seed crystal to artificially control superlateral growth phenomenon during excimer laser irradiation. An array of 1.8-μm-sized disklike silicon grains is formed, and the n-channel thin-film transistors whose channels located inside the artificially-controlled crystal grains exhibit higher performance of field-effect-mobility reaching 308cm2∕Vs as compared with the conventional ones. This position-manipulated silicon grains are essential to high-performance and good uniformity devices.
Quasistatic force and torque on ellipsoidal particles under generalized dielectrophoresis
Authors: Yang C. Y. , Lei U.
Published: November 2007

Analytic expressions for the quasistatic force and torque on ellipsoidal particles covered with a shell under the action of generalized dielectrophoresis have been derived using the effective moment method. Here the generalized dielectrophoresis includes traditional dielectrophoresis generated by nonuniform electric field without phase shift, electrorotation, and traveling wave dielectrophoresis. Characteristics of the results of ellipsoids are contrasted with those of spherical particles and illustrated through various examples using erythrocytes as model particles. In particular, we derived the force and torque equations in terms of electric potential, which are useful for simulating various phenomena associated with the characterization and manipulation of particles and cells in microfluidic devices.
Enhancement of yield strength in zirconium metal through high-pressure induced structural phase transition
Authors: Zhao Yusheng , Zhang Jianzhong
Published: November 2007

We report here a high-pressure phase-transition induced strengthening in ultrapure zirconium metal. The determined yield strength shows more than sixfold abrupt increase at the transition pressure of Pc=6GPa, from σyα≈180MPa in the low-pressure phase of α-Zr to σyω≈1180MPa in the high-pressure phase of ω-Zr. The observed enhancement provides an alternate route for material strengthening and is the most significant among the known strengthening techniques for metals. Our findings support the theoretical simulations of the substantial covalent bonding and “rougher” corrugation of slip planes for dislocations in the ω-phase of zirconium.
Pumping spin states of molecular magnets by strong rotating magnetic field
Authors: Hernández-Mínguez A. , Carbonell-Cortés C. , Amigó R. , Hernandez J. M. , Tejada J. , Chudnovsky E. M.
Published: November 2007

We report experiments on magnetic avalanches in a Mn12-acetate crystal at a frequency up to 50avalanches∕s, produced by a rotating magnetic field up to 1T. This method permits maintaining an elevated population of excited spin levels. It can be used for the studies of spin-phonon interactions and for a deeper understanding of the phonon bottleneck problem.
Real-time label-free quantitative monitoring of biomolecules without surface binding by floating-gate complementary metal-oxide semiconductor sensor array integrated with readout circuitry
Authors: Kim Seong-Jin , Yoo Kyutae , Shim Jeoyoung , Chung Wonseok , Ko Christopher , Im Maesoon , Kim Lee-Sup , Yoon Euisik
Published: November 2007

We report a label-free field-effect sensing array integrated with complementary metal-oxide semiconductor (CMOS) readout circuitry to detect the surface potential determined by the negative charge in DNA molecules. For real-time DNA quantification, we have demonstrated the measurements of DNA molecules without immobilizing them on the sensing surface which is composed of an array of floating-gate CMOS transistors. This nonimmobilizing technique allows the continuous monitoring of the amount of charged molecules by injecting DNA solutions sequentially. We have carried out the real-time quantitative measurement of 19bp oligonucleotides and analyzed its sensitivity as a function of pH in buffer solutions.
Separated two-phase flow regime parameter measurement by a high speed ultrasonic pulse-echo system
Authors: Masala Tatiana , Harvel Glenn , Chang Jen-Shih
Published: November 2007

In this work, a high speed ultrasonic multitransducer pulse-echo system using a four transducer method was used for the dynamic characterization of gas-liquid two-phase separated flow regimes. The ultrasonic system consists of an ultrasonic pulse signal generator, multiplexer, 10MHz (0.64cm) ultrasonic transducers, and a data acquisition system. Four transducers are mounted on a horizontal 2.1cm inner diameter circular pipe. The system uses a pulse-echo method sampled every 0.5ms for a 1s duration. A peak detection algorithm (the C-scan mode) is developed to extract the location of the gas-liquid interface after signal processing. Using the measured instantaneous location of the gas/liquid interface, two-phase flow interfacial parameters in separated flow regimes are determined such as liquid level and void fraction for stratified wavy and annular flow. The shape of the gas-liquid interface and, hence, the instantaneous and cross-sectional averaged void fraction is also determined. The results show that the high speed ultrasonic pulse-echo system provides accurate results for the determination of the liquid level within ±1.5%, and the time averaged liquid level measurements performed in the present work agree within ±10% with the theoretical models. The results also show that the time averaged void fraction measurements for a stratified smooth flow, stratified wavy flow, and annular flow qualitatively agree with the theoretical predictions.
Analysis of the contact resistance in staggered, top-gate organic field-effect transistors
Authors: Richards T. J. , Sirringhaus H.
Published: November 2007

Contact resistance effects are significant in many organic field-effect transistors. Here, we present a detailed analysis of the contact resistance in staggered, top-gate conjugated polymer field-effect transistors. A compact physical model based on the current crowding formalism has been developed. It includes gate modulation of the bulk resistivity of the semiconductor to explain the experimentally observed gate voltage dependence of the contact resistance for different thicknesses of the semiconducting film. The contact resistance is found to be Ohmic. For thick semiconducting films, we have observed a significant asymmetry between source and drain contact resistances with the drain resistances increasing more rapidly with thickness than the source resistance, reflecting the importance of diffusion at the drain contact.
Computer simulation and experimental study of elastic properties of amorphous Cu-Zr alloys
Authors: Mendelev M. I. , Rehbein D. K. , Ott R. T. , Kramer M. J. , Sordelet D. J.
Published: November 2007

Molecular-dynamics simulations were performed to determine the elastic constants of CuxZr100−x (33.3≤x≤64.5) metallic glasses at room temperature. The accuracy of the interatomic potentials used to obtain the model glass structures was tested by comparing to the total structure factors obtained from high-energy synchrotron x-ray diffraction and, more importantly, to acoustic velocities measured from melt spun ribbons. Both the simulated and measured acoustic velocities increased at comparable rates with increasing Cu concentration, but the former underestimated the latter by about 10%. Young’s moduli of the simulated models were determined by combining the ultrasonic data with densities that were obtained from simulations. In addition, the compositional dependence of Poisson’s ratio, shear modulus, and bulk modulus for this series of simulated metallic glasses was determined. Examination of partial-pair correlations deduced from simulated glass structures shows a correlation between higher bulk moduli in Cu-rich compositions and concomitant changes in Zr-Zr nearest neighbors, which exhibit a stronger sensitivity to an imposed hydrostatic stress than do Cu-Cu or Cu-Zr nearest-neighbor distances.
Electrical performance of Al2O3 gate dielectric films deposited by atomic layer deposition on 4H-SiC
Authors: Tanner Carey M. , Perng Ya-Chuan , Frewin Christopher , Saddow Stephen E. , Chang Jane P.
Published: November 2007

Stoichiometric and pure Al2O3 gate dielectric films were grown on n-type 4H-SiC by a thermal atomic layer deposition process. The electrical properties of both amorphous and epitaxial Al2O3 films were studied by capacitance-voltage and current-voltage measurements of metal-oxide-semiconductor capacitors. A dielectric constant of 9 and a flatband voltage shift of +1.3V were determined. A leakage current density of 10−3A∕cm2 at 8MV∕cm was obtained for the amorphous Al2O3 films, lower than that of any high-κ gate oxide on 4H-SiC reported to date. A Fowler-Nordheim tunneling mechanism was used to determine an Al2O3∕4H-SiC barrier height of 1.58eV. Higher leakage current was obtained for the epitaxial γ-Al2O3 films, likely due to grain boundary conduction.
Current-induced heating in quantum well and quantum wire intersubband emitter structures
Authors: Herrle Thomas , Haneder Stephan , Tranitz Hans-Peter , Reinwald Matthias , Wegscheider Werner
Published: November 2007

We discuss the influence of current-induced heating on the current-voltage (I-V) characteristics and the spectral behavior in quantum well and quantum wire intersubband emitter structures. A conventional quantum cascade laser structure in the AlGaAs∕GaAs material system with undoped cladding layers and an undoped active region is examined. This heterostructure serves as a first growth step for quantum wire intersubband emitters fabricated by the cleaved-edge overgrowth technique. We discuss the influence of electrons supplied by a remote δ-silicon doping. Duty-cycle dependent measurements on the quantum wire structures confirm the influence of current-induced heating on the I-V characteristics as well as on the emission spectra.
Zn
0.76
Mg
0.24
O
homojunction photodiode for ultraviolet detection
Authors: Liu K. W. , Shen D. Z. , Shan C. X. , Zhang J. Y. , Yao B. , Zhao D. X. , Lu Y. M. , Fan X. W.
Published: November 2007

Zn 0.76 Mg 0.24 O  p-n photodiode was fabricated on (000l) Al2O3 substrate by plasma-assisted molecular beam epitaxy. Ni∕Au and In metals deposited using vacuum evaporation were used as p-type and n-type contacts, respectively. Current-voltage measurements on the device showed weak rectifying behavior. The photodetectors exhibited a peak responsivity at around 325nm. The ultraviolet-visible rejection ratio (R325nm∕R400nm) of four orders of magnitude was obtained at 6V bias. The photodetector showed fast photoresponse with a rise time of 10ns and fall time of 150ns. In addition, the thermally limited detectivity was calculated as 1.8×1010cmHz1∕2∕W at 325nm, which corresponds to a noise equivalent power of 8.4×10−12W∕Hz1∕2 at room temperature.
Experimental study of uniaxial stress effects on Coulomb-limited mobility in p-type metal-oxide-semiconductor field-effect transistors
Authors: Kobayashi Shigeki , Saitoh Masumi , Nakabayashi Yukio , Uchida Ken
Published: November 2007

Uniaxial stress effects on Coulomb-limited mobility (μCoulomb) in Si metal-oxide-semiconductor field-effect transistors (MOSFETs) are investigated experimentally. By using the four-point bending method, uniaxial stress corresponding to 0.1% strain is applied to MOSFETs along the channel direction. It is found that μCoulomb in p-type MOSFETs is enhanced greatly by uniaxial stress; μCoulomb is as sensitive as phonon-limited mobility. The high sensitivity of μCoulomb in p-type MOSFETs to stress arises from the stress-induced change of hole effective mass.
Characterization of high-pressure capacitively coupled hydrogen plasmas
Authors: Nunomura S. , Kondo M.
Published: November 2007

Capacitively coupled very-high-frequency hydrogen plasmas have been systematically diagnosed in a wide range of a gas pressure from 5 mTorr to 10 Torr. The plasma parameters, ion species, and ion energy distributions (IEDs) are measured using a Langmuir probe, optical emission spectroscopy, and energy filtered mass spectrometer. The measurement results show that the ion species in a hydrogen plasma is determined from ionization channels and subsequent ion-molecule reactions. The ions are dominated by H2+ at a less-collisional condition of ≲20 mTorr, whereas those are dominated by H3+ at a collisional condition of ≳20 mTorr. The IED is determined by both the sheath potential drop and ion-neutral collisions in the plasma sheath. The IED is broadened for a collisional sheath at ≳0.3 Torr and the ion bombardment energy is lowered. For high-pressure discharge operated at ≈10 Torr, plasmas are characterized by a low electron temperature of ≈0.8 eV and a low ion bombardment energy of ≲15 eV.
Crystalline phases in the GeSb2Te4 alloy system: Phase transitions and elastic properties
Authors: Blachowicz T. , Beghi M. G. , Güntherodt G. , Beschoten B. , Dieker H. , Wuttig M.
Published: November 2007

Chalcogenide alloys are attracting considerable interest as phase-change materials. Their elastic properties are investigated here. A film of stoichiometric GeSb2Te4 is amorphous as deposited; under annealing at increasing temperatures it crystallizes into a cubic phase and then into a hexagonal phase. The elastic properties of the three phases have been investigated nondestructively by Brillouin light scattering. Measurements detect frequency dispersion relations of Rayleigh and Sezawa acoustic modes. All the elastic moduli can be derived: they increase, together with mass density, upon transition from the amorphous to the cubic and to the hexagonal phase. The measured moduli provide a benchmark for computational predictions of film properties.
Direct generation of charge carriers in c-Si solar cells due to embedded nanoparticles
Authors: Kirkengen M. , Bergli J. , Galperin Y. M.
Published: November 2007

It is known that silicon is an indirect band gap material, reducing its efficiency in photovoltaic applications. Using surface plasmons in metallic nanoparticles embedded in a solar cell has recently been proposed as a way to increase the efficiency of thin-film silicon solar cells. The dipole mode that dominates the plasmons in small particles produces an electric field having Fourier components with all wave numbers. In this work, we show that such a field creates electron-hole-pairs without phonon assistance, and discuss the importance of this effect compared to radiation from the particle and losses due to heating.
Random high-Q cavities in disordered photonic crystal waveguides
Authors: Topolancik J. , Vollmer F. , Ilic B.
Published: November 2007

We present direct observations of electromagnetic fields localized in disordered photonic crystal waveguides and report the modal volumes and quality factors of the confined modes. Geometrical perturbations distributed uniformly throughout the crystal lattice were introduced by changing orientations of the polygonal lattice elements. Cavities in the disordered waveguides were excited by resonant coupling through a chain of random open resonators. Localized optical resonances with sub-(λ∕n)3 modal volumes and quality factors of up to ∼150000 were observed.
High-spin ferromagnetic state observed in the Fe–Nb alloys synthesized by ion beam mixing
Authors: Tai K. P. , Wang T. L. , Liu B. X.
Published: November 2007

An fcc-structured Fe55Nb45 alloy with a large lattice constant of a≈0.408nm was synthesized by 200keV xenon ion irradiation at a dose of 3×1015Xe+∕cm2. The Fe atom in Fe55Nb45 alloy presents a distinct magnetic moment as high as 2.41μB, confirming a high-spin ferromagnetic state of fcc Fe predicted by ab initio calculation. Further irradiation, i.e., at a dose of 5×1015Xe+∕cm2, induced phase separation, resulting in fractal growth consisting of Fe72Nb28 nanoclusters embedded in Fe35Nb65 matrix. The formation mechanism of alloy phases as well as fractal pattern was discussed in terms of the atomic collision theory.
Real-time monitoring of cell death by surface infrared spectroscopy
Authors: Yamaguchi Ryo-taro , Hirano-Iwata Ayumi , Kimura Yasuo , Niwano Michio , Miyamoto Ko-ichiro , Isoda Hiroko , Miyazaki Hitoshi
Published: November 2007

We have developed a method for real-time monitoring of the cell responses to cytotoxicants using Fourier transform infrared spectroscopy with the multiple internal reflection (MIR-FTIR) geometry. To prevent cell damages induced by measurement environments, we have constructed specialized chambers, in which temperature was maintained at (37±0.5)°C and humidified air containing 5% CO2 was supplied. We monitored cell death induced by cytotoxic surfactant Tween20 using MIR-FTIR spectroscopy. It was found that cell death can be monitored by the absorption intensity of amide II band. This result suggests that our method has a potential to be applied for real-time cytotoxicity assay.
Contact-metal dependent current injection in pentacene thin-film transistors
Authors: Wang S. D. , Minari T. , Miyadera T. , Tsukagoshi K. , Aoyagi Y.
Published: November 2007

Contact-metal dependent current injection in top-contact pentacene thin-film transistors is analyzed, and the local mobility in the contact region was found to follow the Meyer-Neldel rule. An exponential trap distribution, rather than the metal/organic hole injection barrier, is proposed to be the dominant factor of the contact resistance in pentacene thin-film transistors. The variable temperature measurements revealed a much narrower trap distribution in the copper contact compared with the corresponding gold contact, and this is the origin of the smaller contact resistance for copper despite a lower work function.
An industry view of exploration in Australia
Authors: Pettingel W.W.
Published: November 2007

I felt this time last night that I must be a little brash to talk to a group of fellows like yourselves who are so deeply enmeshed in the immediate technical aspects of mining and mineral exploration and development which has so much become the keynote to the level of success that has been occurring in Australia in the last 5-10 years, and from which we can only hope that much more success will accrue than has been our good fortune to date.
Review of semi-automatic velocity analysis techniques
Authors: Crain E.R.
Published: November 2007

A large number of semi-automatic velocity techniques have been developed in the past few years. The principle of such techniques is based on computerized approximations to the familiar delta-T analysis normally done by hand. The success of these programs depends largely on the exact mathematics of the program, the quality of the data, and most important, the form of display used to present results. This review will attempt to show results from a number of different programs using different mathematical methods and various types of displays. The reader is referred to various published papers such as: (1) Schneider, Backus, et al, 1966; (2) Garotta and Michon, 1967; and (3) Taner and Koehler, 1969; for the detailed calculations of a few of these methods.
Velocity influence on seismic anomalies on continental shelf margin off coast of New Zealand
Authors: Maureira A.S.
Published: November 2007

Seismic studies carried out offshore New Zealand reveal that in certain areas the collection of velocity data is imperative for detecting lateral variations which will permit identification of time anomalies due to velocity changes instead of structural changes. Conversely, structural changes masked by velocity changes can be detected. Changes of velocity are more significant than absolute values. The variations in both are discussed.
Sign conventions in magnetometry for southern hemisphere
Authors: Shalley M.J.
Published: November 2007

There are two well known brands of vertical force fluxgate magnetometers presently in use in Australia. Both are manufactured in the northern hemisphere and the circuitry is designed to give positive anomalies over normally magnetised rock units in the northern hemisphere. This follows the convention that magnetic inclination is positive in the downward direction.
Review of gravity and magnetic data processing systems
Authors: Crain E.R.
Published: November 2007

The application of high speed computer processing and computer graphics is reviewed and discussed in relation to manipulating and present geophysical, and geological mapping data.
Professionalism and the exploration geophysicist
Authors: Leaman D.E.
Published: November 2007

The retiring editor has several times stressed the need for professionalism and the maintenance of high technical standards on the part of the exploration geophysicist. In practice there appears to be a major gulf between desirable standards and the norm.
Sampling and geophysical logging of water bores in unconsolidated sediments
Authors: Emerson D.W. , Haines B.M.
Published: November 2007

A significant proportion of Australia's groundwater is derived from aquifers in unconsolidated sediments. Because of the cost and inherent difficulties of direct sampling and testing procedures, geophysical well-logging has an important role to play in the location, definition and evaluation of these unconsolidated aquifers. Interpretation at present is semi-quantitative at best and generally qualitative. Nevertheless, with modern drilling methods, a well-logging programme and interpretation are necessary prerequisites for correct bore completion and aquifer evaluation.
Effect of seed treatment on the emergence of Cassia brewsteri and Lysiphyllum carronii seeds stored in soil
Authors: Reichman S. M. , Bellairs S. M. , Mulligan D. R.
Published: November 2007

Dormancy-breaking treatments are applied to seeds of many Australian species used for mine-site restoration in arid and semi-arid regions of Australia. Once seeds are sown, several months may pass before a rain event sufficient for germination. Therefore, it is important that treated seeds are able to survive in soil until conditions are hospitable for germination and growth. However, little is known about the effects of seed dormancy-breaking treatments on the longevity of seeds in soil. Two species that are potential candidates for use in mine site restoration programs in Queensland were trialed viz., Cassia brewsteri (F.Muell.) Benth and Lysiphyllum carronii (F.Muell.) Pedley. Untreated, boiled and acid treated seeds of the two species were sown in soil in a glasshouse. Seeds were watered immediately or kept dry for one or three months before watering and emergence was assessed. When applied to seeds incubated on filter paper in a germination cabinet, boiling and acid treatments were effective methods of breaking dormancy and increasing germination for both C. brewsteri and L. carronii seeds. However, in soil, seedling emergence from boiled seeds was the same or less than that of untreated seeds. Storage time in soil before watering had little effect on seedling emergence in the glasshouse, suggesting that most decreases in emergence compared with laboratory germination occurred after the input of water to the system. Treatments that promote germination in the laboratory can reduce seedling emergence in soil. Thus, treated seeds should be tested for survival in soil before use in mine-site restoration programs.
Monitoring changes in pastoral rangelands - the Western Australian Rangeland Monitoring System (WARMS)
Authors: Watson I. W. , Novelly P. E. , Thomas P. W. E.
Published: November 2007

The Western Australian Rangeland Monitoring System (WARMS) consists of a set of ~1620 permanent sites distributed across the pastoral rangelands of Western Australia used for commercial livestock grazing. The system is designed to provide information to government and the general community on changes in Western Australia’s rangelands, rather than to individual landholders. It is designed to report at the regional or vegetation type level by selectively sampling representative areas of the rangelands, with representation occurring at several levels. The system was fully implemented by 1999 and all sites, except a small number of ongoing replacements, have now been re-assessed at least once. Two site types are used. In grassland areas, the frequency of all perennial species is assessed, and an estimate made of crown cover of woody perennials. In shrubland areas, a direct census technique is used, with the demography and maximum canopy dimensions of all shrubs recorded. Changes in soil surface condition and patch distribution are also assessed using standard Landscape Function Analysis (LFA) techniques. The vegetation and soil surface information is used to indicate rangeland change. The system is not fixed within any single model of range dynamics and the outputs of WARMS can be interpreted in various ways, depending on the specific requirements of the end-user. The paper includes discussion of the institutional requirements for WARMS, the site stratification and selection criteria, description of the field methods used and the rationale behind its design. It also considers the implications of the site stratification and selection criteria in terms of the caveats that need to accompany reporting.
PRP4 is a spindle assembly checkpoint protein required for MPS1, MAD1, and MAD2 localization to the kinetochores
Authors: Montembault Emilie , Dutertre Stéphanie , Prigent Claude , Giet Régis
Published: November 2007

The spindle checkpoint delays anaphase onset until every chromosome kinetochore has been efficiently captured by the mitotic spindle microtubules. In this study, we report that the human pre–messenger RNA processing 4 (PRP4) protein kinase associates with kinetochores during mitosis. PRP4 depletion by RNA interference induces mitotic acceleration. Moreover, we frequently observe lagging chromatids during anaphase leading to aneuploidy. PRP4-depleted cells do not arrest in mitosis after nocodazole treatment, indicating a spindle assembly checkpoint (SAC) failure. Thus, we find that PRP4 is necessary for recruitment or maintenance of the checkpoint proteins MPS1, MAD1, and MAD2 at the kinetochores. Our data clearly identify PRP4 as a previously unrecognized kinetochore component that is necessary to establish a functional SAC.
Myc stimulates B lymphocyte differentiation and amplifies calcium signaling
Authors: Habib Tania , Park Heon , Tsang Mark , de Alborán Ignacio Moreno , Nicks Andrea , Wilson Leslie , Knoepfler Paul S. , Andrews Sarah , Rawlings David J. , Eisenman Robert N. , Iritani Brian M.
Published: November 2007

Deregulated expression of the Myc family of transcription factors (c-, N-, and L-myc) contributes to the development of many cancers by a mechanism believed to involve the stimulation of cell proliferation and inhibition of differentiation. However, using B cell–specific c-/N-myc double-knockout mice and Eμ-myc transgenic mice bred onto genetic backgrounds (recombinase-activating gene 2−/− and Btk−/− Tec−/−) whereby B cell development is arrested, we show that Myc is necessary to stimulate both proliferation and differentiation in primary B cells. Moreover, Myc expression results in sustained increases in intracellular Ca2+ ([Ca2+]i), which is required for Myc to stimulate B cell proliferation and differentiation. The increase in [Ca2+]i correlates with constitutive nuclear factor of activated T cells (NFAT) nuclear translocation, reduced Ca2+ efflux, and decreased expression of the plasma membrane Ca2+–adenosine triphosphatase (PMCA) efflux pump. Our findings demonstrate a revised model whereby Myc promotes both proliferation and differentiation, in part by a remarkable mechanism whereby Myc amplifies Ca2+ signals, thereby enabling the concurrent expression of Myc- and Ca2+-regulated target genes.