bluuebunny/crossref_metadata_2025 huggingface dataset:
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effect on the stability of organic thin-film field-effect transistors
Authors: Qiu Yong , Hu Yuanchuan , Dong Guifang , Wang Liduo , Xie Junfeng , Ma Yaning
Published: August 2003

Degradation of organic thin-film field-effect transistors (OTFTs) with pentacene as the active material has been studied. It was found that the field-effect mobility of the device decreased by 30% and the on/off current ratio decreased to one fifth after the OTFTs had been stored in atmosphere for 500 h. Through surface morphology analysis by atomic force microscopy and absorption analysis by infrared spectroscopy, it was found that the adsorption of H2O on the pentacene layer was the main reason for the degradation. Remarkable improvement in the device performance was achieved by device encapsulation with UV curable resin.
Room temperature formation of half-metallic Fe3O4 thin films for the application of spintronic devices
Authors: Hong Jin Pyo , Lee Sung Bok , Jung Young Woo , Lee Jong Hyun , Yoon Kap Soo , Kim Ki Woong , Kim Chae Ok , Lee Chang Hyo , Jung Myoung Hwa
Published: August 2003

Half-metallic Fe3O4 films were prepared at room temperature using a rf sputtering system specially integrated with an external rf source. Primary emphasis was placed on obtaining a large amount of active oxygen radicals through an external electrode for efficient deposition. The insertion of an external electrode was found to be critical for room temperature growth of Fe3O4 thin films. The structural and electrical properties gave shift and broadening effects to the Verwey temperature at various powers. The magnetization could only be saturated when a 300 Oe field was applied along an easy axis of magnetization during growth. However, there was no sign of saturation up to 5 T under zero-field growth.
Midinfrared intraband electroluminescence from AlInAs quantum dots
Authors: Ulbrich N. , Bauer J. , Scarpa G. , Boy R. , Schuh D. , Abstreiter G. , Schmult S. , Wegscheider W.
Published: August 2003

Midinfrared electroluminescence from a cascade of coupled AlInAs quantum dots and GaAs quantum wells at low temperature (80 K) is demonstrated. At low injection currents, the spectra show a clear peak at 158 meV with a luminescence width of 15 meV which is associated with transitions from the s shells of a resonant subensemble of quantum dots. A Stark shift to 143 meV and spectral broadening is observed at higher injection currents which is associated with luminescence from the inhomogeneously broadened quantum-dot ensemble. The reported design is a possible solution to obtain population inversion in unipolar quantum-dot-cascade structures.
Current collapse induced in AlGaN/GaN high-electron-mobility transistors by bias stress
Authors: Mittereder J. A. , Binari S. C. , Klein P. B. , Roussos J. A. , Katzer D. S. , Storm D. F. , Koleske D. D. , Wickenden A. E. , Henry R. L.
Published: August 2003

Current collapse is observed to be induced in AlGaN/GaN high-electron-mobility transistors as a result of short-term bias stress. This effect was seen in devices grown by both metalorganic chemical vapor deposition (MOCVD) and molecular-beam epitaxy (MBE). The induced collapse appears to be permanent and can be reversed by SiN passivation. The traps responsible for the collapse have been studied by photoionization spectroscopy. For the MOCVD-grown devices, the same traps cause the collapse in both unstressed and stressed devices. These effects are thought to result from hot-carrier damage during stress.
Electronic stopping of He, B, N, and Al in SiC
Authors: Zhang Y. , Weber W. J.
Published: August 2003

Silicon carbide (SiC) is a wide-band-gap semiconductor that has attracted extensive investigations for a wide range of device applications. Accurate values of stopping powers in SiC, especially for B, N, and Al ions as dopants and for He ions used in ion-beam analysis applications, are highly desirable. In the present study, the electronic energy loss of these ions in a self-supported SiC film is directly measured in transmission geometry using a time-of-flight detection system over a continuous range of energies. The measured electronic stopping powers are parameterized, for easy implementation in other applications, and compared with the predictions of the stopping and range of ions in matter code.
Dynamic recovery of negative bias temperature instability in p-type metal–oxide–semiconductor field-effect transistors
Authors: Ershov M. , Saxena S. , Karbasi H. , Winters S. , Minehane S. , Babcock J. , Lindley R. , Clifton P. , Redford M. , Shibkov A.
Published: August 2003

An unexpected physical phenomenon—dynamic recovery of negative bias temperature instability (NBTI)—is reported. NBTI degradation in p-type metal–oxide–semiconductor field-effect transistors is significantly (by ∼40%) reduced after stress interruption. NBTI recovery dynamics includes a very fast transient (seconds time scale) followed by a slow (tens of minutes) transient, which tends to saturate. Under subsequent application of stress bias, the degradation quickly returns to its previous state. Thus, apparent NBTI degradation includes permanent and reversible components. NBTI degradation and device lifetime depend strongly on the measurement procedure and equipment due to these relaxation phenomena, which should be taken into account in analyzing the results of NBTI measurements.
High-frequency, high-sensitivity acoustic sensor implemented on ALN/Si substrate
Authors: Caliendo C. , Imperatori P.
Published: August 2003

AlN films, 1.6–6.3 μm thick, were sputtered at 200 °C on Si(100) and Si(111) substrates. The films were crack-free, uniform, and c-axis oriented. The experimental phase velocities of surface acoustic waves (SAW) propagating in the AlN/Si structures were estimated and showed only a small discrepancy (20–40 m/s) compared to the calculated theoretical values. A SAW resonator (SAWR)-based chemical sensor, operating at about 700 MHz, was implemented on AlN/Si. The SAWR surface was covered with a polymer film sensitive to relative humidity (RH) changes, already tested for RH sensing in previous works on SAW delay lines implemented on AlN/Si and ZnO/Si and operating at about 130 MHz. The RH mass sensitivity and the detection limit of the SAWR sensor improved by 38% and by one order of magnitude, respectively, compared to the delay line-based sensors previously tested.
Significant changes in the ferroelectric properties of BiFeO3 modified SrBi2Ta2O9
Authors: Srinivas A. , Kim Dong-Wan , Hong Kug Sun
Published: August 2003

The solid solution of BiFeO3 (BF)–SrBi2Ta2O9 (SBT) prepared at a concentration of 1:1 ratio, shows significant changes in the structure and dielectric properties. The obtained compound although similar to a three-layered Aurivillius phase, is noticeably a Bi and oxygen deficient SBT phase. Due to this, the unit cell shows a subtle decrease in its volume and the dielectric properties show a decline. The layered perovskite structure sustains the strain associated with the loss of Bi and oxygen. SrBi3Ta2FeO12 has been synthesized by solid-state route and the single phase was confirmed by x-ray diffraction. The Curie temperature shows a marginal increase (an increase of 20 °C) compared to that of SBT. Polarization versus electric measurements show a slim hysteresis loop with a Pmax of 4.3 μC/cm2. The electromechanical coupling coefficient “KP” values are evaluated from the resonance and antiresonance measurements.
Angular dependence of spin-transfer switching in a magnetic nanostructure
Authors: Mancoff F. B. , Dave R. W. , Rizzo N. D. , Eschrich T. C. , Engel B. N. , Tehrani S.
Published: August 2003

We measured switching of a thin film nanomagnet driven by spin-polarized current in giant magnetoresistance spin valves as small as 50 nm×100 nm. Spin-transfer reversal is observed in both dc current and magnetic field sweeps, with a switching current of ∼5 mA, for example, for a bit with ∼900 Oe switching field in zero current. We studied the dependence of spin-transfer switching on the relative angle φ between the layer magnetizations by using a magnetic field to orient the magnetization of a bulk magnetic layer at an angle to a patterned layer held in place by shape anisotropy. The critical current is a minimum for collinear magnetizations and diverges as 1/|cos φ| as φ increases to 90°, consistent with switching current calculations using the Slonczewski spin-transfer torque model.
Birefringent control and optical switching of copolymer liquid crystal film with azobenzene and photocrosslinkable side groups
Authors: Kawatsuki Nobuhiro , Uchida Emi
Published: August 2003

Photocontrol and optical switching of birefringence (Δn) in a poly(methacrylate) copolymer liquid crystal films substituted with 4-methoxyazobenzene and 4(4-methoxycinnamoyloxy)biphenyl side groups are described. Irradiating with linearly polarized 365 nm light and subsequently annealing generated uniaxial in-plane orientation of the films. Adjusting the exposure doses of nonpolarized (NP) 405 nm light regulated the generated Δn of 0.26–0.13, and after reannealing the initial value is completely restored. Optical control of the birefringence with response times of 50 ms is demonstrated when the films are exposed to NP 405 nm light at elevated temperatures.
Resonant-cavity-enhanced subwavelength metal–semiconductor–metal photodetector
Authors: Collin Stéphane , Pardo Fabrice , Pelouard Jean-Luc
Published: August 2003

We propose a resonant-cavity-enhanced subwavelength metal–semiconductor–metal structure for efficient and ultrafast photodetection. A Fabry–Pérot cavity is composed by a bottom multilayer Bragg reflector and a top subwavelength metallic grating. The structure was fabricated on a GaAs substrate with 75 nm finger width and finger spacing, and theoretical results were validated experimentally by reflection spectra and photocurrent measurements. 75% efficiency is predicted theoretically in a 40-nm-thick GaAs layer, leading to potential cutoff frequencies between 300 and 500 GHz in TE polarization.
Tunable Fresnel lens using nanoscale polymer-dispersed liquid crystals
Authors: Ren Hongwen , Fan Yun-Hsing , Wu Shin-Tson
Published: August 2003

An electrically tunable Fresnel zone plate lens is demonstrated using nanoscale polymer-dispersed liquid crystal droplets. In the voltage-off state, the zone plate behaves like a positive lens. The measured diffraction efficiency is close to the theoretical limit and is controllable by voltage. The major advantages of such a Fresnel lens are simple fabrication, large aperture size, polarization independent, and fast switching speed, although the required operating voltage is relatively high.
Field electron emission from nanostructured heterogeneous HfNxOy films
Authors: Liao M. Y. , Gotoh Y. , Tsuji H. , Ishikawa J.
Published: August 2003

Nanostructured heterogeneous HfNxOy films comprising of nanoscale conductive hafnium nitride grains embedded in a matrix of dielectric oxide or oxynitride were deposited on silicon substrate by magnetron sputtering at room temperature. Electron emission with low threshold field 25 V/μm and good current stability were reported. The field emission characteristics depend on the concentration of hafnium nitride phase, revealing the nature of heterogeneous structure. Field enhancement in HfNxOy film was explained in terms of the interaction between the conductive grains separated by dielectric layers under external electric field. The experiment is expected to open a group of nanostructured heterogeneous material consisting of stable conductive nitride and insulating oxide for field emitter, and also provide an insight into the emission mechanism of carbon films.
Time-resolved electron shadowgraphy for 300 ps laser ablation of a copper film
Authors: Okano Yasuaki , Hironaka Yoichiro , Nakamura Kazutaka G. , Kondo Ken-ichi
Published: August 2003

Time-resolved electron shadowgraphy measurement was performed in infrared 300 ps laser ablation of a copper film in order to investigate expanding plasma into vacuum with space-charge separation. The probe-electron pulse was generated by intense femtosecond laser irradiation on a tungsten bulk target. Time-resolved electron shadowgraphs showed evolving “bright” and “shadow” plumes with expanding speeds of 970 and 110 km/s, when the laser intensity was 980 G W/cm2. These are attributed to be space-charge separation field and ion plume, respectively.
Doping-induced type-II to type-I transition and interband optical gain in InAs/AlSb quantum wells
Authors: Kolokolov K. I. , Ning C. Z.
Published: August 2003

We show that proper doping of the barrier regions can convert the well-known type-II InAs/AlSb quantum wells (QWs) to type I, producing strong interband transitions comparable to regular type-I QWs. The interband gain for TM mode is as high as 4000 1/cm, thus providing an important alternative material system in the midinfrared wavelength range. We also study the TE and TM gain as functions of doping level and intrinsic electron–hole density.
Microfabricated mechanical biosensor with inherently differential readout
Authors: Savran C. A. , Burg T. P. , Fritz J. , Manalis S. R.
Published: August 2003

We report measurements with a micromachined mechanical biosensor that inherently suppresses background effects by producing a differential signal with respect to a reference. The sensor comprises two adjacent cantilevers with interdigitated fingers between them that allow interferometric detection of the differential, i.e., relative bending. We demonstrate that differential detection can efficiently suppress unspecific chemical effects that result in cantilever bending. We show that the differential deflection noise is up to an order of magnitude lower than the absolute deflection noise in the low-frequency range of 0.0003–1 Hz, where many types of biologically relevant reactions occur. We also demonstrate the sensor’s applicability to biological receptor–ligand systems by reporting experimental results on direct differential detection of biotin–streptavidin binding.
Epitaxial CuIn(1−x)GaxS2 on Si(111): A perfectly lattice-matched system for x≈0.5
Authors: Metzner H. , Cieslak J. , Eberhardt J. , Hahn Th. , Müller M. , Kaiser U. , Chuvilin A. , Reislöhner U. , Witthuhn W. , Goldhahn R. , Hudert F. , Kräußlich J.
Published: August 2003

We demonstrate the direct heteroepitaxial growth of the quaternary semiconductor CuIn(1−x)GaxS2 on Si(111) substrates by means of molecular-beam epitaxy. Using Rutherford backscattering, x-ray diffraction, transmission electron microscopy, and photoreflectance, samples of various Ga contents, x, were characterized in detail. Epitaxial growth was achieved in the whole compositional range and perfect lattice match between the epitaxial layer and substrate was obtained for x≈0.5. The epitaxial layers show the coexistence of bulk chalcopyrite and metastable CuAu-type cation ordering. Photoreflectance data reveal a linear increase of the fundamental band gap with increasing Ga content.
Crystal growth in colloidal tin oxide nanocrystals induced by coalescence at room temperature
Authors: Leite E. R. , Giraldi T. R. , Pontes F. M. , Longo E. , Beltrán A. , Andrés J.
Published: August 2003

The crystal growth process in colloidal nanocrystal systems is usually associated with the Ostwald-ripening mechanism. Here, we report on experimental evidence indicating that another crystal growth process took place in a colloidal nanocrystal system at room temperature. This crystal growth process is based on grain rotation among neighboring grains, resulting in a coherent grain–grain interface, which, by eliminating common boundaries, causes neighboring grains to coalesce, thereby forming a single larger nanocrystal. This phenomenon was observed in SnO2 nanocrystals (particle size ranging from 10 to 30 Å).
Eliminating the transit-time instability in large-area electron-beam diodes
Authors: Friedman M. , Chan Y. , Obenschain S. , Sethian J. D. , Swanekamp S. B.
Published: August 2003

The electron flow in large-area, space-charge-limited diodes is susceptible to transit time instability. The instability spatially and temporally modulates the electron beam and results in a wide, time-dependent, electron energy distribution and high-power rf emission. The electromagnetic waves that power the instability are guided and amplified in the anode–cathode (AK) region which acts as a parallel-plate transmission line with negative conductance. We investigated how to mitigate this instability in large-area rectangular electron diodes. We found that by slotting the rectangular cathode, along both its axes, with parallel grooves of predetermined depth and periodicity, the AK region was modified into a slow wave structure. The unstable electromagnetic waves are slowed down and attenuated to such an extent that the instability is eliminated and stable electron flow is achieved.
Optical properties of ZnO rods formed by metalorganic chemical vapor deposition
Authors: Zhang B. P. , Binh N. T. , Segawa Y. , Wakatsuki K. , Usami N.
Published: August 2003

High-quality ZnO rods were formed directly on sapphire (0001) substrates by metalorganic chemical vapor deposition. The rods exhibited free exciton and very sharp bound exciton emissions at low temperatures. By increasing the excitation intensity, biexciton emission was observed. Temperature dependence of the emission spectra suggested that the emission peak at ∼3.315 eV, which had been attributed to neutral acceptor-bound exciton emission, is due to donor-acceptor pairs. The acceptor binding energy was determined to be about 107 meV, which agrees well with that estimated from a hydrogen-atom-like acceptor model.
Solvation of hydroxyl ions in water
Authors: Botti A. , Bruni F. , Imberti S. , Ricci M. A. , Soper A. K.
Published: August 2003

The solvation shell of the hydroxyl ion in water is explored experimentally for the first time by using a combination of neutron diffraction with hydrogen isotope substitution and Monte Carlo simulation within the empirical potential structure refinement framework. The data are compatible with the presence of nonplanar hydrogen bonded (H9O5)− complexes. The presence of a fifth water molecule in the hydration shell of the hydroxyl ion, weakly hydrogen-bonded to the hydrogen site is also revealed. (H7O4)− complexes, which have been suggested by ab initio simulations to promote proton transfer, are not detectable in the present data, implying that, if they are present at all, they can only be formed transiently.
Ion energy and charge state distributions in zirconium nitride arc plasma
Authors: Chhowalla Manish
Published: August 2003

The charge states and ion energy distributions (IEDs) of cathodic arc zirconium (Zr) plasma in vacuum and in nitrogen are reported. The dominant charge states in vacuum and in nitrogen were found to be Zr4+ and Zr2+, respectively. In addition to Zrn+, N2+ and N+ species along with ionized zirconium nitride (ZrNn+) were also detected. The peak ion energies of all Zrn+ species in vacuum were found to be slightly higher (∼19 eV) than in nitrogen (∼15 eV). The IEDs of N2+ species exhibited two peaks, one at 2–4 eV and the other at ∼15 eV. The dual peaks in the N2+ IEDs indicate that some species are ionized in the plasma and others are emitted from, or near, the surface of the cathode. The peak energies of ZrN2+ and ZrN+ species were found to be ∼15 eV, indicating that they are emitted from the nitrided (“poisoned”) surface of the cathode or the from the dense plasma region above the arc spot.
Effects of di-butyl phthalate on in vitro morphogenesis of Arabidopsis thaliana
Authors: Wang Xiao-juan
Published: August 2003

Di-butyl phthalate (DBP) is one of the common environmental contaminants found both in terrestrial and aquatic ecosystems. However, little is known about its effects on plant morphogenesis. We report here a study examining the effects of DBP on morphogenesis of Arabidopsis thaliana. When stems and laminae of Arabidopsis were cultured on Murashige and Skoog medium supplemented with 6-benzyl aminopurine (6-BA, 2 mg L–1) and naphthalene acetic acid (NAA, 0.2 mg L–1), both produced callus and some shoots. However, the presence of 1�mg�L–1 DBP in the above medium inhibited formation of callus by stems and laminae, and eventually led to the death of the callus, indicating that DBP inhibited the de-differentiation and differentiation of Arabidopsis stem and laminae explants. Transmission electronic microscopy showed that DBP caused membrane and organelle disruption, which might explain the failure of cell division in treated tissues.
Using the short-lived isotope 11C in mechanistic studies of photosynthate transport
Authors: Minchin Peter E. H. , Thorpe Michael R.
Published: August 2003

Tracer techniques have been central in studies of transport in plants. In the case of carbon, the only readily available radioactive tracer has been 14C, although 11C was used for a short time before 14C could be made. Tracers have usually had to be measured by destructive harvesting of the plant, giving a practical limit to the data resolution in both time and space. A major advantage of the short-lived, positron-emitting tracers, of which 11C is one example, is that in vivo measurement is possible, giving detailed time series of tracer data in many locations and opening up powerful new techniques of data analysis. Medical applications of these isotopes have utilised both dynamic imaging and time courses of uptake or washout. Unfortunately, few plant biology laboratories have realised the potential of these techniques, possibly because of the large physics infrastructure needed. In this paper we review the concepts behind the use of these short-lived tracers in plant physiology, and illustrate with several cases where 11C was an essential tool.
Xylem cavitation, leaf growth and leaf water potential in Eucalyptusglobulus clones under well-watered and drought conditions
Authors: Pita Pilar , Gascó Antonio , Pardos José A.
Published: August 2003

Leaf growth, predawn leaf water potential (Ψpd), evapotranspiration, stem maximum permeability, and its percentage loss of hydraulic conductivity (PLC) were measured in rooted cuttings of selected clones of Eucalyptus globulus Labill. subjected to well-watered and drought conditions. Drought significantly reduced evapotranspiration, leaf growth and maximum permeability. E. globulus clones lost up to 70% of conductivity at values of Ψpd less negative than –1 MPa. PLC values higher than 85% could not be measured without causing leaf shedding. The coefficient related to the slope of the vulnerability curves ranged from 1.52–2.23. The lowest value was measured in the most drought-resistant clone, as estimated from field trials. Plants from this clone displayed higher drought-induced reductions in maximum permeability than plants from other clones, had significantly smaller leaves and maintained higher values of predawn leaf water potential as soil water content (SWC) declined.
Nitric oxide mediates elicitor-induced saponin synthesis in cell cultures of Panax ginseng
Authors: Hu Xiangyang , Neill Steven J. , Cai Weiming , Tang Zhangcheng
Published: August 2003

The elicitor oligogalacturonic acid (OGA) stimulated nitric oxide (NO) accumulation in the growth medium of ginseng suspension cultures and induced increased nitric oxide synthase (NOS) activity in ginseng cells. OGA also stimulated accumulation of saponin, transcription of genes encoding squalene synthase (sqs) and squalene epoxidase (sqe), two early enzymes of saponin synthesis, and the accumulation of β-amyrin synthase protein (β-AS). Saponin accumulation, sqs and sqe gene expression, and increases in β-AS content were also induced by exposure to NO via the NO donor sodium nitroprusside (SNP). Inhibitors of mammalian nitric oxide synthase reduced both OGA-induced NO accumulation and NOS activity, suggesting that OGA-induced NO production occurs via a NOS-like enzyme. OGA-induced accumulation of β-AS and saponin, and transcription of sqs and sqe, were suppressed by treatments that removed NO or inhibited its production, indicating a role for NO in mediating OGA effects on these defence responses. NO accumulation and increased NOS activity were inhibited by calcium channel inhibitors and a protein kinase inhibitor, but not by a protein phosphatase inhibitor, indicating the requirement for calcium and protein phosphorylation during OGA-induced NO production. Saponin production and transcription, and accumulation of saponin biosynthetic genes and enzymes were also suppressed by these treatments, as well as by the protein phosphatase inhibitor okadaic acid.
Short-day photoperiod induces changes in N uptake, N partitioning and accumulation of vegetative storage proteins in two Medicago sativa cultivars
Authors: Noquet Carine , Meuriot Frédéric , Caillot Sébastien , Avice Jean-Christophe , Ourry Alain , Cunningham Suzanne M. , Volenec Jeffrey J.
Published: August 2003

Our objective was to study the effect of short-day photoperiod for 28, 42 and 56 d on growth, N uptake and N partitioning, particularly vegetative storage protein (VSP) accumulation in taproots of two alfalfa (Medicago�sativa L.) cultivars (Lodi and Europe). For both varieties, the reduction of daylength from 16 h (long day,�LD) to 8 h (short day, SD) for 28 d reduced total plant growth by decreasing shoot growth. Nitrogen uptake and N distribution within the plant was determined by 15N labeling. N uptake decreased with SD treatment duration, and was 2- and 3-fold lower for Europe and Lodi, respectively, for 56 d in SD conditions when compared with LD plants. The SD treatment resulted in preferential partitioning of N to taproots in comparison with LD conditions (19�vs 9% for Lodi and 12 vs 5% for Europe after 28 d). For both cultivars, the SD-induced changes in N allocation to taproots did not significantly affect taproot soluble protein concentrations during 42 d of daylength treatment. In contrast, VSP accumulation occurred after only 28 d for plants grown in SD conditions (6.2 vs 4.8 mg g–1 DW for Lodi and 5.1 vs 1.4 mg g–1 DW for Europe). SD exposure also increased vsp 57 and vsp 32 mRNA transcript levels in Lodi and Europe (up to 2-fold higher) taproots in SD for 28 d compared with LD conditions. Overall results indicate that photoperiod modulates taproot N accumulation in alfalfa by enhancing both β-amylase (vsp 57) and vsp 32 gene expression and accumulation. The enhanced VSP accumulation by short-day photoperiod may result from altered VSP gene expression / transcript stability or occur indirectly through altered N source–sink relationships. Additionally, when SD treatment included a night break with 15 min illumination with sodium high pressure light or red light, our results suggest that the induction of vsp 57 and vsp 32 gene expressions by SD signal is mediated by the phytochrome system.
Localized breeding of the Anopheles gambiae complex (Diptera: Culicidae) along the River Gambia, West Africa
Authors: Bøgh C. , Clarke S.E. , Jawara M. , Thomas C.J. , Lindsay S.W.
Published: August 2003

A study was undertaken to identify the major larval habitats of the Anopheles gambiae (Giles) complex in rural Gambia. Mosquito larvae and pupae were sampled along transects and in specific habitats in the central region of the country during the rainy seasons of 1996 and 1997. The sampling showed that the major breeding sites were located on the flooded alluvial soils bordering the river. The largest numbers of larvae were found during September, one month after the peak rains. Polymerase chain reaction analysis of specimens showed that Anopheles melas (Theobald) was the dominant species in the flooded areas (81.5%), followed by A. gambiae sensu stricto (Giles) (18.0%) and A.arabiensis (Patton) (0.5%). By sampling in specific habitats it was evident that A.arabiensis was mainly breeding in rain-fed rice fields along the edge of the alluvial soils. Anophelesmelas and A.gambiae s.s. often coexisted but whereas A. melas were found in water with a salinity of up to 72% sea water (25.2 g NaCl l−1), A.gambiae s.s. only occurred in water with up to 30% sea water (10.5 g NaCl l−1). Anophelesmelas larvae were found in association with plant communities dominated by sedges and grasses (Eleocharis sp., Paspalum sp., Sporobolus sp.) and sea-purslane Sesuviumportulacastrum (L.) and the presence of cattle hoof prints, whereas A.gambiae s.s. larvae mainly occurred in association with Paspalum sp. and Eleocharis sp. The study showed that even during the peak rainy season, breeding of the A.gambiae complex is almost entirely restricted to the extensive alluvial areas along the river.
Quantitative description and discrimination of butterfly wing patterns using moment invariant analysis
Authors: White R.J. , Winokur L.
Published: August 2003

Studies examining and using pattern variation in insects for identification and characterization of individuals and populations have been limited by the methods available for quantifying wing patterns objectively. In this paper, differences in wing pattern are demonstrated statistically using moment invariant data sets generated automatically from digitized images of the speckled wood butterfly,Pararge aegeria(Linnaeus). Studies with other biological subjects have already shown moment invariants to work well with outline shapes and silhouettes. A pilot study with replicated monochrome photographs of a single butterfly showed the method could detect pattern differences between wing surfaces, even in the presence of simulated wing fading and damage. In a further study of the wings of 228 specimens, multivariate analyses of variance using the moment data reliably detected differences between groups of butterflies according to sex, geographical origin and culture history. Potential applications and future improvements of the moment methodology are considered.
Overwintering, soil distribution and phenology of Childers canegrub, Antitrogus parvulus (Coleoptera: Scarabaeidae) in Queensland sugarcane
Authors: Logan D.P. , Allsopp P.G. , Zalucki M.P.
Published: August 2003

In this study, the question of whether Childers canegrub, Antitrogus parvulus (Britton) overwinters in the subsoil was addressed. Irrigated fields of sugarcane were sampled during a 2-year period near Bundaberg in southern Queensland. Antitrogus parvulus overwintered as second and third instars at each of three sites. During autumn and winter third instars of different allochronic (separated in age by 12 months) populations occurred together and could not be readily separated. Field-collected third instars were reared on ryegrass and separated into two age groups based on the date of pupation. Third instars in the first year of their life cycle (young third instars) remained at shallow depth (100–200 mm) and did not overwinter in the subsoil as once thought. Minimum temperatures during winter were 13–16°C and did not prevent young third instars from feeding and gaining weight. Third instars in their second and final year moved downwards from late summer and pupated in the subsoil at 293–425 mm in spring. General phenology was as previously reported with first instar larvae occurring from January until April, second instars from January until November and third instar larvae throughout the year. Prepupae and pupae were found between October and December and adults occurred in soil during November and January. Batches of eggs occurred at a mean depth of 350 mm. First and second instars occurred predominantly at relatively shallow (100–200 mm) depths in the soil profile. All stages tended to be most common under rows of sugarcane rather than in the interrow.
Navigation of Lutzomyia longipalpis (Diptera: Psychodidae) under dusk or starlight conditions
Authors: Mellor H.E. , Hamilton J.G.C.
Published: August 2003

The responses of male and female Lutzomyia longipalpis (Lutz & Neiva) to different wavelengths of light was tested by presenting the sandflies with two light sources simultaneously, a series of test wavelengths between 350–670 nm and a 400 nm control. To test whether L. longipalpis could discriminate between the test and control, three sets of experiments were carried out in which the test wavelengths were presented at higher, equivalent or lower intensity than the control. In all three experiments, ultra-violet (350 nm) and blue-green-yellow (490–546 nm) light was more attractive to L. longipalpis than the control wavelength. However, at low intensity, UV was less attractive, than equivalent or higher intensity UV light. At intensities equivalent to or higher than the control wavelength, ultra-violet light was more attractive than blue-green. Furthermore, at low intensity, green-yellow (546 nm) light was more attractive to males whereas blue-green (490 nm) was more attractive to females. Blue-violet (400 nm) and orange-red (600–670 nm) light were least attractive in all three sets of experiments. Response function experiments indicated that the responses were dependent on both intensity and wavelength and that therefore more than one photoreceptor must be involved in the response. The results indicated that L. longipalpis can discriminate between different wavelengths at different intensities and thus have true colour vision. It also suggests that L. longipalpis may be able to navigate at dusk or under moonlight or starlight conditions using light in the blue-green-yellow part of the spectrum. The difference in response of males and females to light in this region is interesting and may indicate the different ecology of the sexes at night. Overall, these results may have important implications for sandfly trap design.
Genetic delineation of sibling species of the pest fruit fly Bactocera (Diptera: Tephritidae) using microsatellites
Authors: Wang Y. , Yu H. , Raphael K. , Gilchrist A.S.
Published: August 2003

Using a large set of microsatellites, the genetic relationships between three closely related Australian fruit fly species, Bactrocera tryoni (Froggatt), B. neohumeralis (Hardy) and B. aquilonis(May) were investigated. Bactrocera tryoni and B. neohumeralis are sympatric, while B. aquilonis is allopatric to both. The sympatric species, B. tryoni and B. neohumeralis, were found to be genetically distinct. It is likely that despite differences in mating time between these two species, some gene flow still occurs. In contrast, the sibling species B. tryoni and B. aquilonis were found to be closely related, despite allopatry. The level of genetic divergence was similar to that found within eastern Australian populations of B. tryoni. Consideration of all available genetic data suggests that this similarity is not due to recent (i.e. within the last 30 years) displacement of B. aquilonis by B. tryoni from the B. aquilonis region (north-western Australia). Instead the data suggests that, at least in the areas sampled, asymmetrical hybridization may have occurred over a longer timescale.
Prolonged Nonhydrolytic Interaction of Nucleotide with CFTR's NH2-terminal Nucleotide Binding Domain and its Role in Channel Gating
Authors: Basso Claudia , Vergani Paola , Nairn Angus C. , Gadsby David C.
Published: August 2003

CFTR, the protein defective in cystic fibrosis, functions as a Cl− channel regulated by cAMP-dependent protein kinase (PKA). CFTR is also an ATPase, comprising two nucleotide-binding domains (NBDs) thought to bind and hydrolyze ATP. In hydrolyzable nucleoside triphosphates, PKA-phosphorylated CFTR channels open into bursts, lasting on the order of a second, from closed (interburst) intervals of a second or more. To investigate nucleotide interactions underlying channel gating, we examined photolabeling by [α32P]8-N3ATP or [γ32P]8-N3ATP of intact CFTR channels expressed in HEK293T cells or Xenopus oocytes. We also exploited split CFTR channels to distinguish photolabeling at NBD1 from that at NBD2. To examine simple binding of nucleotide in the absence of hydrolysis and gating reactions, we photolabeled after incubation at 0°C with no washing. Nucleotide interactions under gating conditions were probed by photolabeling after incubation at 30°C, with extensive washing, also at 30°C. Phosphorylation of CFTR by PKA only slightly influenced photolabeling after either protocol. Strikingly, at 30°C nucleotide remained tightly bound at NBD1 for many minutes, in the form of nonhydrolyzed nucleoside triphosphate. As nucleotide-dependent gating of CFTR channels occurred on the time scale of seconds under comparable conditions, this suggests that the nucleotide interactions, including hydrolysis, that time CFTR channel opening and closing occur predominantly at NBD2. Vanadate also appeared to act at NBD2, presumably interrupting its hydrolytic cycle, and markedly delayed termination of channel open bursts. Vanadate somewhat increased the magnitude, but did not alter the rate, of the slow loss of nucleotide tightly bound at NBD1. Kinetic analysis of channel gating in Mg8-N3ATP or MgATP reveals that the rate-limiting step for CFTR channel opening at saturating [nucleotide] follows nucleotide binding to both NBDs. We propose that ATP remains tightly bound or occluded at CFTR's NBD1 for long periods, that binding of ATP at NBD2 leads to channel opening wherupon its hydrolysis prompts channel closing, and that phosphorylation acts like an automobile clutch that engages the NBD events to drive gating of the transmembrane ion pore.
The Ca-activated Cl Channel and its Control in Rat Olfactory Receptor Neurons
Authors: Reisert Johannes , Bauer Paul J. , Yau King-Wai , Frings Stephan
Published: August 2003

Odorants activate sensory transduction in olfactory receptor neurons (ORNs) via a cAMP-signaling cascade, which results in the opening of nonselective, cyclic nucleotide–gated (CNG) channels. The consequent Ca2+ influx through CNG channels activates Cl channels, which serve to amplify the transduction signal. We investigate here some general properties of this Ca-activated Cl channel in rat, as well as its functional interplay with the CNG channel, by using inside-out membrane patches excised from ORN dendritic knobs/cilia. At physiological concentrations of external divalent cations, the maximally activated Cl current was ∼30 times as large as the CNG current. The Cl channels on an excised patch could be activated by Ca2+ flux through the CNG channels opened by cAMP. The magnitude of the Cl current depended on the strength of Ca buffering in the bath solution, suggesting that the CNG and Cl channels were probably not organized as constituents of a local transducisome complex. Likewise, Cl channels and the Na/Ca exchanger, which extrudes Ca2+, appear to be spatially segregated. Based on the theory of buffered Ca2+ diffusion, we determined the Ca2+ diffusion coefficient and calculated that the CNG and Cl channel densities on the membrane were ∼8 and 62 μm−2, respectively. These densities, together with the Ca2+ diffusion coefficient, demonstrate that a given Cl channel is activated by Ca2+ originating from multiple CNG channels, thus allowing low-noise amplification of the olfactory receptor current.
Utilizing Blackboard to provide library instruction: uploading MS Word handouts with links to course specific resources
Authors: Lenholt Rob , Costello Barbara , Stryker Judson
Published: August 2003

Collaboration among three university departments resulted in a successful venture to integrate an innovative electronic element into an online course management system (Blackboard). A faculty member from the school of business and two library faculty, with assistance from the University’s Center for Information Technology, developed a unique, yet simple, method for incorporating library instruction handouts into course‐specific online classes. At the end of the semester, students were surveyed and data were collected, analyzed, and compared; the results overwhelmingly indicated that utilizing online courseware in library instruction was a useful and time saving tool for participating students. The simplicity of the method used to create these handouts lends itself to application in other areas of study, and use with online courseware other than Blackboard.
Back to basics: the role of reading in preparing young people for the information society
Authors: Eyre Gayner
Published: August 2003

Living in the information age, with its emphasis on information and communications technologies, poses special challenges. This paper raises discussion about the important role of reading in society, and examines its place in the acquisition of information capabilities among young people.
Digital reference: training and assessment for service improvement
Authors: Kawakami Alice , Swartz Pauline
Published: August 2003

This article describes the first of a series of assessments examining discrete areas of the service, needed to evaluate a digital reference program. The University of California, Los Angeles, began the first stage of a planned comprehensive evaluation with an assessment of competencies designed to reveal gaps in training that would be the starting point for a revised training program. The objectives of the first assessment were to isolate librarian‐error from user‐error, software‐error and network‐error. This assessment is the first piece of wide‐ranging evaluation that will involve all staff in the process of crafting best practices for digital reference service.
Information literacy across the wired university
Authors: Bloom Beth , Deyrup Marta
Published: August 2003

Librarians at a private Catholic university utilized a grant enabling them to team up with members of other campus constituencies to create an information literacy program aimed toward incoming students, in order to actuate a quality educational experience while improving students’ ability to do research. The participants employed various pedagogues and assessments designed to address diverse learning styles. A combination of fortunate elements: a university of optimum size, a ubiquitous computing environment, a desire to improve information literacy across the curriculum, and enthusiastic partners have promised to make this project a success.
Electronic maps: sources and techniques
Authors: Weessies Kathleen
Published: August 2003

Maps can be challenging to reference librarians, especially to those without the specialized skills needed for working with the material. Such is the same with maps found on the Internet. Finding, using, saving, or printing maps requires different strategies than those taken with other online documents. This article discusses the value of electronic maps, will help to form accurate expectations as to what one should expect to find, and cover some useful Internet sites for finding freely available general maps. Last, some strategies in working with large graphic files will assist reference librarians in putting electronic maps into the hands of their patrons.
Managing the reference desk online
Authors: Sennema Greg
Published: August 2003

Communication between reference librarians is vital for the provision of enhanced reference services. This article discusses the creation and application of three Web‐based tools that allow librarians to offer quick answers to questions posed on the library’s e‐mail reference service, to easily share news and ideas with each other between reference desk shifts, and to be actively involved in the scheduling of reference desk shifts.
Labour‐standard setting and regional trading blocs
Authors: Teague Paul
Published: August 2003

This paper examines the labour‐standard‐setting institution associated with NAFTA, the North American Agreement on Labour Cooperation (NAALC), sometimes referred to as the Labour Side Accord. The agreement is best described as a tri‐national institutional arrangement that grafts formal international procedures onto domestic labour market regimes. This feature ensures that it stands apart from the EU social policy, which is best seen as a supranational deliberative governance arrangement. The manner in which NAALC procedures have been used is documented and the main discernible pattern of action explained. The paper argues that NAALC is cumbersome and convoluted to operate. Yet it also argues that NAALC holds out interesting lessons for other regional trading blocs and other global experiments in labour market standard setting as its decentralised and “horizontal” character is more in keeping with the broad institutional design of such arrangements. The paper concludes by suggesting that NAALC will only reach its full potential when organised labour in the three participating countries adopt a more active approach to transnational collaboration inside NAFTA.
Introduction: Competitive versus non‐competitive wage differentials
Authors: Meulders Danièle , Plasman Robert , Rycx François
Published: August 2003

This paper introduces the Special Issue on competitive versus non‐competitive wage differentials, a collection of papers originally presented at the 79th Conference of the Applied Econometrics Association held in Brussels in May 2002.
Industry wage differentials: how many, big and significant are they?
Authors: Reilly Kevin T. , Zanchi Luisa
Published: August 2003

In this paper, three implementation and interpretation issues are examined associated with Krueger and Summers' method for calculating inter‐industry wage differentials. The literature tends to report a less than complete set of industry wage differentials, use the wrong standard errors, and misinterpret the meaning of the industry wage differentials. The solution to the first two issues follows from making explicit the restriction that the employment‐weighted average of all industry wage effects is zero, the same restriction that Krueger and Summers are implicitly imposing on industry wage effects. All industries have thus a wage effect relative to an average worker net of any industry effect and correct standard errors are available via the Delta method. Finally, a method is proposed for analysing inter‐industry wage differentials as actual differences between the wage levels expressed in percentage points and not as log points, which is the current misleading standard. The procedure calculates actual average percentage wage differences by industry and avoids the distortion in differences across industries that log point comparisons engender. An application is provided, using the United States Outgoing Rotation Files of the Current Population Survey for 1989 and 1996, and so updates the work by Krueger and Summers.
High potential identification policies: an empirical study among Belgian companies
Authors: Pepermans Roland , Vloeberghs Daniël , Perkisas Britt
Published: August 2003

This paper describes elements of the policies employed for identifying high potentials in their organizational context. A set of systematic research questions has been used to conceive a structured questionnaire to empirically investigate the kind of high potential competencies that companies expect when identifying high potentials and how this identification takes place. These elements of a high potential policy have been related to a number of organizational variables in 86 Belgian companies. Our empirical results indicate that the extent to which attention is paid to high potentials is linked to certain organizational characteristics (size and degree of internationalization). Moreover, the use of well‐defined competencies is not widely spread. We found ample confirmation for the identification of high potentials being a rather hierarchical process. Performance appraisals and a specific potential assessment procedure are the most popular sources of information during the identification process.