bluuebunny/crossref_metadata_2025 huggingface dataset:
Uphill diffusion of ultralow-energy boron implants in preamorphized silicon and silicon-on-insulator
Authors: Ferri M. , Solmi S. , Giubertoni D. , Bersani M. , Hamilton J. J. , Kah M. , Kirkby K. , Collart E. J. H. , Cowern N. E.B.
Published: November 2007

Redistribution during annealing of low-energy boron (B) implants in silicon on insulator (SOI) structures and in bulk Si has been investigated by comparing secondary ion mass spectrometry (SIMS) and simulated profiles. All the samples have been preamorphized with Ge at different implantation energies in order to investigate the effects of the position of the damage on B diffusion. Different B doses in the range between 2×1013 and 2×1015 cm−2 and annealing temperatures between 700 and 1100 °C have been investigated. All SIMS profiles show a B pileup in the first few nanometers of the Si matrix in proximity of the Si surface. The results of our simulations, performed on samples implanted at different doses (below and above the solid solubility), indicate that the B redistribution upon annealing can be explained with a simple model which considers the presence of traps in the surface region, without considering any asymmetric behavior of the dopant diffusion. The sink region is a few monolayers (1–2 nm) for doses of 2×1013 and 2×1014 cm−2, and it extends to about 7 nm for the highest dose of 2×1015 cm−3, in the region of very high B concentration where precipitates and clusters shrink the incoming B atoms. For the two lowest B doses, the amount of B trapped at the surface is maximum at temperatures around 800 °C, when more than 80% of the implanted dopant is made immobile and electrically inactive. In our experimental conditions, i.e., preamorphization performed with constant dose and different implantation energies, the amount of trapped B increases with reducing the depth of the amorphous layer and it is higher in the bulk Si than in SOI.
Terahertz wave amplification in gases with the excitation of femtosecond laser pulses
Authors: Dai Jianming , Xie Xu , Zhang X.-C.
Published: November 2007

We report the observation of terahertz wave amplification in gases excited by femtosecond laser pulses. When a seed terahertz wave is sent into the ∼5mm long plasma created by focusing a 800nm beam and its second harmonic into nitrogen gas, a peak amplification factor of about 65% is measured with total optical excitation intensity of 8×1014W∕cm2. The amplification effect occurs within a time scale of less than 400fs of the onset of ionization processes due to the optical excitation pulse duration. Four-wave-mixing parametric processes during the plasma formation are proposed to be responsible for the amplification effect.
Enhanced circular dichroism via slow light in dispersive structured media
Authors: Pedersen Jesper , Mortensen Niels Asger
Published: November 2007

Circular dichroism (CD) is in widespread use as a means of determining enantiomeric excess. We show how slow-light phenomena in dispersive structured media allow for a reduction in the required optical path length of an order of magnitude. The same ideas may be used to enhance the sensitivity of CD measurements while maintaining the same optical path length through the sample. Finally, the sensitivity may be enhanced in frequency regimes where CD data are typically not accessible due to a modest chiral response of the enantiomers.
Production and magnetic properties of in situ oligomer coated α-Fe nanoparticles in the gas phase
Authors: Choi Byeong Ju , Lee Gang Ho
Published: November 2007

We report on the production and characterization of the magnetic properties of in situ oligomer coated α-Fe nanoparticles. Although a polymer cannot be used to in situ coat iron nanoparticles in the gas phase due to its low vapor pressure, an oligomer (i.e., a low mass polymer) may be used for this purpose because it has enough vapor pressure. Besides surface protection, functional molecules such as ligands, peptides, antibodies, and DNA can be also easily bound to an oligomer, which will be extremely useful for further advanced applications. We in situ coated α-Fe nanoparticles with a dimethylsilylenesiloxane oligomer in the gas phase by thermally decomposing Fe(CO)5 as a precursor of α-Fe nanoparticles with a resistive heater in the presence of dimethylsilylenesiloxane oligomer vapor. These core-shell nanoparticles ranging from 5 to 15 nm in core α-Fe nanoparticle diameter showed saturation magnetization as high as 68 emu/g and coercivities as large as 1338 and 381 Oe at 10 and 300 K, respectively.
Dielectric relaxation studies of nanocrystalline CuAlO2 using modulus formalism
Authors: Prakash T. , Prasad K. Padma , Kavitha R. , Ramasamy S. , Murty B. S.
Published: November 2007

Transparent semiconductor CuAlO2 in nanodimension was prepared by mechanical alloying of Cu2O and α-Al2O3 powders in toluene medium. The formation of single phase CuAlO2 with an average crystallite size of 45 nm was confirmed by x-ray diffraction analysis. The nanocrystalline nature of CuAlO2 was confirmed by atomic force microscopy. Frequency-dependent dielectric property measurements and the relaxation behavior were studied using impedance spectroscopy. Dielectric relaxation time estimated from the modulus curves was found to be decreasing with increase in temperature. The existence of stretched exponent parameter β<1 in the present nanocrystalline CuAlO2 implies non-Debye type relaxation behavior in this material.
Relationship between the optical absorption and the density of deep gap states in microcrystalline silicon
Authors: Klein Stefan , Finger Friedhelm , Carius Reinhard , Dylla Thorsten , Klomfass Josef
Published: November 2007

We have measured the subgap optical absorption of undoped microcrystalline silicon samples with photothermal deflection spectroscopy and compared it with the spin density measured by electron spin resonance. The material was prepared using the hot wire chemical vapor deposition technique with a broad range of deposition parameters, yielding materials with a wide variety of structural, optical, and electronic properties. A nearly linear correlation between the spin densities and the subgap absorption coefficient at photon energy of 0.7 eV over three orders of magnitude indicates that the optical absorption in this region is due to the dominating paramagnetic defects, likely dangling bonds. However, the structural composition of the material, determined by Raman spectroscopy, has also some influence on the optical and electronic properties, which leads to some deviation from a straightforward relationship between optical absorption and spin or defect density.
Mn doping-induced semiconducting behavior in the perovskite molybdates SrMo1−xMnxO3(≤x≤0.20)
Authors: Zhang S. B. , Sun Y. P. , Zhao B. C. , Luo X. , Hao C. Y. , Zhu X. B. , Song W. H.
Published: November 2007

The effect of Mn doping on structural, magnetic, electronic transport, and specific heat properties in 4d perovskites SrMo1−xMnxO3(0≤x≤0.20) has been investigated. The Mn doping at the Mo site does not change the space group of the samples, but increases the structural parameter a monotonically. All Mn-doped samples show Curie-Weiss paramagnetic behaviors due to the appearance of localized moment, and the magnetic susceptibility χ increases with increasing the Mn-doping content. Samples (x≥0.03) exhibit semiconducting transport behavior, while x=0.01 shows a metallic behavior with an upturn below T1. The magnitude of resistivity monotonically increases with increasing Mn-doping content. The evolution of the resistive properties is discussed according to the competition among Kondo scattering, electron-electron interaction, and the disorder effect. In addition, the electron-electron interaction intensity increases with the increasing of Mn-doping content according to the study of specific heat properties.
Two- and four-electrode, wide-bandwidth, dielectric spectrometer for conductive liquids: Theory, limitations, and experiment
Authors: Mazzeo Brian. A. , Flewitt Andrew J.
Published: November 2007

Dielectric spectroscopy is used to measure the dielectric properties of liquids. Two-electrode measurements are common but have resolution difficulties because of electrode polarization and small measured phase angles, particularly for solutions with high ionic content. Four-electrode measurements have been used in previous attempts to overcome these problems. The electrical responses of two- and four-electrode dielectric cells are derived with appropriate circuit analysis to yield expressions for the measured phase angle. The theory demonstrates that an ideal four-electrode measurement cannot resolve the permittivity of the liquid and that polarization effects will still be present in the measured characteristics. A two- and four-electrode experimental cell with a bandwidth of 100 Hz to 40 MHz was constructed and used to measure the electrical properties of water and salt solutions. Electrode polarization and conductivity effects are present in both two- and four-electrode measurements. Parasitic impedance from the potential-sensing electrodes and operational amplifiers additionally affects the four-electrode measurements.
Effect of using a high-purity Fe source on the transport properties of p-type β-FeSi2 grown by molecular-beam epitaxy
Authors: Suzuno M. , Ugajin Y. , Murase S. , Suemasu T. , Uchikoshi M. , Isshiki M.
Published: November 2007

Intentionally undoped p-type β-FeSi2 thin films were grown on Si(111) substrates by molecular-beam epitaxy using low-purity (4N) and high-purity (5N) Fe sources to investigate the effect of using a high-purity Fe source on the electrical properties of β-FeSi2. The hole mobility increased and the hole density decreased greatly as the annealing temperature and time were increased, particularly for the β-FeSi2 films produced using 5N-Fe. The observed temperature dependence of the hole mobility was reproduced well by considering various carrier scattering mechanisms due to acoustic-phonon, polar-optical phonon, nonpolar-optical phonon, and ionized impurities.
Effect of barometric pressure on sea level variations in the Pacific region
Authors: Singh A , Aung T
Published: November 2007

Barometric pressure and sea level data sets from the South Pacific Sea Level and Climate Monitoring Project funded by AusAID were analysed for twelve Tropical Pacific island countries. During mid-1997 and 1998 pressure anomalies over the Pacific region were strongly positive and sea level dropped significantly. As a consequence, sea level trends in the Pacific region suddenly changed from positive to negative. It was believed that the delayed effect of the 1997 strong El Ni�o episode was directly linked to these positive pressure anomalies. The same observations were made in 2002 and 2003 during another El Ni�o episode which was however not as strong as the previous one. The La Ni�a episode which
followed the 1997-98 El Ni�o in 1999 had opposite effects. The pressure anomalies were negative and the sea level anomalies were positive. While the thermal effect due to global warming is still the cause of sea level rise in the Pacific region, it is clearly evident that the barometric pressure effect on sea level is more abrupt and it can overshadow the other effects at least temporarily.
Human occupations of caves of the Rove peninsula, southwest Viti Levu island, Fiji
Authors: Nunn P D , Pene C , Matararaba S , Kumar R , Singh P , Dredregasa I , Gwilliam M , Heorake T , Kuilanisautabu L , Nakoro E , Narayan L , Pastorizo M R , Robinson S , Saunivalu P , Tamani F
Published: November 2007

Geoarchaeological investigations of limestone caves along the Rove Peninsula, where several Lapita-era (1150-750 BC) sites dating from the earliest period of Fiji?s human history have been found, was undertaken by a team from the University of the South Pacific and the Fiji Museum. Surface collection and excavation in the largest cave – Qaranibourewa – was hindered by large amounts of ceiling collapse and no trace of human occupation earlier than about AD 1000 was found. The second-largest cave ? Qaramatatolu ? had a cave fill 190 cm thick but this was determined to be all of recent origin, having accumulated as a result of being washed down through a hole in the cave roof from a settlement above that probably existed AD 750-1250. The shell faunal remains from the Qaramatatolu excavation all suggest an open-coast location, quite different from the mangrove forest that fronts the area today. This mangrove forest probably formed only within the last few hundred years.
Anticancer activities of constituents of kava (Piper methysticum)
Authors: Tabudravu J N , Jaspars M
Published: November 2007

Crude extracts of kava (Piper methysticum G. Forster, Piperaceae) showed good activity against ovarian tumour and leukaemia cancer cell lines. Bioassay-guided isolation resulted in the isolation of six known kava lactones and two flavokavains. The structure of the compounds were elucidated by spectroscopic techniques and by comparison with data in the literature.
Bacteriology of the fresh water bivalve clam Batissa violacea (Kai) sold in the Suva market
Authors: Hatha A A M , Christi K S , Singh R , Kumar S
Published: November 2007

Forty samples of freshwater clam (Batissa violacea), popularly known as Kai, collected from the Suva market were analysed for total aerobic plate count and total coliforms. The heterotrophic bacteria isolated by plate count were also characterised up to genera. The results indicated higher than acceptable level of plate count and coliform bacteria. While total plate count of aerobic heterotrophic bacteria ranged from 5.5 x 105 colony forming units (cfu) per gram to more than 107 cfu/ gram, total coliform load varied between 1.1 x 104 to 1.1 x 105 per 100 gm of Kai flesh. The characterisation of the heterotrophic bacteria revealed the predominance of the genera Micrococcus (34%) and Bacillus (24%). Other genera encountered included Acinetobacter, Vibrio, Aeromonas, Alcaligenes, Pseudomonas, Streptococcus and members of the family Enterobacteriaceae. The results revealed the need for depuration of the Kai in clean running water to reduce the bacterial load to acceptable levels. Temperature control soon after harvesting by proper icing and thorough cooking of the Kai before consumption is also recommended.
Nutrient characterisation and in vitro digestibility of grass and legume/browse species - based diets for beef cattle in Vanuatu
Authors: Aregheore E M , Steglar T A , Ng'ambi J W
Published: November 2007

Some grasses, Buffalo (Panicum Coloratum), Guinea (Panicum maximum), Setaria (Setaria sphacelata), Embu (Panicum maxum), Elephant (Pennisetum Purpureum), Koronivia (Brachiaria humidicola), and Signal (Brachiaria decumben); and legumes/browses Gliricidia sepium, Glycine wightii, Green desmodium and Leucaena leucocephala grazed by beef cattle
in Vanuatu were characterized for crude protein (CP), fibre fractions, macro and micro minerals (phosphorus, calcium, magnesium, potassium, copper, iron, manganese and zinc) and energy. Also in vitro digestibility study was carried out to predict the utilization of available nutrients. Data obtained were discussed in light of whether available nutrients would satisfy requirements of grazing beef cattle of different age and physiological function. The CP of grass and legume/browse species ranged from 7.9-17.8% and 10.5-23.9% respectively. L. leucocephala has a higher CP while Green leaf desmodium had the lowest CP content. DM and NDF were higher (P<0.05) in the grasses while CP was higher in the legume/browse species. Organic matter (OM) within and between the grass and legume/browse species varied. Mean concentrations of calcium (Ca) and phosphorus (P) in the grass species was 5.7 g/kg DM and 2.6 g/kg DM, respectively and this resulted in an average Ca:P ratio of 2.2:1 for the grasses while the legume /browse species had Ca:P ratio of 5.3:1. Ca was low while K was high in the grasses compared to the legume/browse species. Among the microminerals Cu was critically low in both the grass and legume/browse species. In vitro DMD, OMD and CPD between and within the grass and legume/browse species were not significantly different (P>0.05) from each other, however NDFD and ADFD were higher (P<0.05) in the grasses than in the legumes/browses. In conclusion, the results of these analyses and the in vitro digestibility study have provided information on nutrients that are adequate and/or inadequate in the grass and legume/browse species components grazed to sustain beef cattle production in Vanuatu. The very low concentration of Cu in both the grass and legume/browse species therefore demonstrates the need to supplement grazing beef cattle with mineral lick blocks to overcome its deficiency.
The potential and challenges for student teachers' learning of subject‐specific pedagogical knowledge within secondary school subject departments
Authors: Burn Katharine , Childs Ann , McNicholl Jane
Published: November 2007

This article draws on two research studies concerned with student teachers' learning of subject‐specific pedagogical knowledge: a naturalistic study within two secondary school science departments and a collaborative action research project focused on two contested aspects of the history curriculum. Both confirmed the complexity of the process by which teachers' pedagogical constructions are created and the many components they comprise.

The first study revealed rich opportunities for student teachers to observe and engage collaboratively in such processes within subject departments which have a strong geographical location in a team room, and the confidence among staff to admit problems and seek advice. In contrast, the second project's explicit focus on contested aspects of the curriculum saw mentors questioning a critical component of their pedagogical constructions. This inhibited the range of examples they shared with student teachers and their willingness to engage collaboratively with them in creating new ones. Paradoxically, close collaboration between mentors and tutors effectively restricted opportunities to learn from different conceptions of the subject held within the school department.

Together the studies raise important questions about the most effective ways of making accessible to student teachers the subject‐specific pedagogical knowledge held across the epistemic communities of subject departments.
Knowledge practices: ‘doing the subject’ in undergraduate courses
Authors: Anderson Charles , Hounsell Dai
Published: November 2007

This article addresses the themes of this special issue by examining the disciplinary dimensions of learning and teaching within undergraduate courses in the areas of biology and history. Key ways of thinking and practising that biology and history lecturers wished to foster in their students are identified. It presents a relational view of the role of these disciplinary ways of thinking and practising in undergraduate learning, and considers how domain knowledge exists in dynamic relationship with the practices that are implicated in its creation, interpretation and use. The epistemological challenges that students may face in grappling with a discipline are explored, and the intricate connection between the form and content of knowledge is highlighted. The article also points up the pedagogic actions that enabled students' affective and intellectual engagement with history.
Moving beyond physical education subject knowledge to develop knowledgeable teachers of the subject
Authors: Capel Susan
Published: November 2007

All knowledge is socially constructed, including physical education teachers' knowledge of their subject. It is acquired from other people either formally and deliberately (e.g. by being taught) or informally and casually (e.g. by interacting with physical education teachers or playing in a sports team). The social aspects of learning appear to be particularly strong in physical education. This has implications for the development of knowledge for teaching, with trainee teachers focusing on the development of subject, and particularly content, knowledge. Focusing on subject knowledge reinforces a traditional view of physical education as it is, not as it might be to meet the needs of young people today. It is argued that attention needs to be given not only to the knowledge, skills and competencies that trainee teachers ought to develop but also to the social aspects of their learning and development and the context in which they learn. Attention also needs to be given to how the ability to think critically can be developed so that trainee teachers can become reflective practitioners able to challenge and, where appropriate, change the teaching of the subject. Only by doing this can the particularly strong socialization which shapes the values and beliefs of physical education teachers begin to be challenged. However, as the process of developing knowledgeable teachers is ongoing it is also necessary to look beyond teacher training to continuing professional development.
Didactics of mathematics: an epistemological approach to mathematics education
Authors: Winsløw Carl
Published: November 2007

I present some key ideas and examples of (mainly French) work in the didactics of mathematics with the aim of identifying the didactics approach to education in relation to more general approaches. In particular I discuss three crucial features of didactics:

its epistemological character, i.e. the central focus on specific knowledge in different forms, and the conditions for enabling pupils to acquire it;

its relations to the background science (in casu, mathematics as a science);

its actual and potential roles in relation to teaching and teachers (in particular, didactics as a design science and as a part of teachers' education and professional knowledge base).
Vesicle formation by self-assembly of membrane-bound matrix proteins into a fluidlike budding domain
Authors: Shnyrova Anna V. , Ayllon Juan , Mikhalyov Ilya I. , Villar Enrique , Zimmerberg Joshua , Frolov Vadim A.
Published: November 2007

The shape of enveloped viruses depends critically on an internal protein matrix, yet it remains unclear how the matrix proteins control the geometry of the envelope membrane. We found that matrix proteins purified from Newcastle disease virus adsorb on a phospholipid bilayer and condense into fluidlike domains that cause membrane deformation and budding of spherical vesicles, as seen by fluorescent and electron microscopy. Measurements of the electrical admittance of the membrane resolved the gradual growth and rapid closure of a bud followed by its separation to form a free vesicle. The vesicle size distribution, confined by intrinsic curvature of budding domains, but broadened by their merger, matched the virus size distribution. Thus, matrix proteins implement domain-driven mechanism of budding, which suffices to control the shape of these proteolipid vesicles.
Phosphatidylethanolamine critically supports internalization of cell-penetrating protein C inhibitor
Authors: Baumgärtner Petra , Geiger Margarethe , Zieseniss Susanne , Malleier Julia , Huntington James A. , Hochrainer Karin , Bielek Edith , Stoeckelhuber Mechthild , Lauber Kirsten , Scherfeld Dag , Schwille Petra , Wäldele Katja , Beyer Klaus , Engelmann Bernd
Published: November 2007

Although their contribution remains unclear, lipids may facilitate noncanonical routes of protein internalization into cells such as those used by cell-penetrating proteins. We show that protein C inhibitor (PCI), a serine protease inhibitor (serpin), rapidly transverses the plasma membrane, which persists at low temperatures and enables its nuclear targeting in vitro and in vivo. Cell membrane translocation of PCI necessarily requires phosphatidylethanolamine (PE). In parallel, PCI acts as a lipid transferase for PE. The internalized serpin promotes phagocytosis of bacteria, thus suggesting a function in host defense. Membrane insertion of PCI depends on the conical shape of PE and is associated with the formation of restricted aqueous compartments within the membrane. Gain- and loss-of-function mutations indicate that the transmembrane passage of PCI requires a branched cavity between its helices H and D, which, according to docking studies, precisely accommodates PE. Our findings show that its specific shape enables cell surface PE to drive plasma membrane translocation of cell-penetrating PCI.
Immune synapse formation requires ZAP-70 recruitment by ezrin and CD43 removal by moesin
Authors: Ilani Tal , Khanna Chand , Zhou Ming , Veenstra Timothy D. , Bretscher Anthony
Published: November 2007

Immunological synapse (IS) formation involves receptor–ligand pair clustering and intracellular signaling molecule recruitment with a coincident removal of other membrane proteins away from the IS. As microfilament–membrane linkage is critical to this process, we investigated the involvement of ezrin and moesin, the two ezrin/radixin/moesin proteins expressed in T cells. We demonstrate that ezrin and moesin, which are generally believed to be functionally redundant, are differentially localized and have important and complementary functions in IS formation. Specifically, we find that ezrin directly interacts with and recruits the signaling kinase ZAP-70 to the IS. Furthermore, the activation of ezrin by phosphorylation is essential for this process. In contrast, moesin dephosphorylation and removal, along with CD43, are necessary to prepare a region of the cell cortex for IS. Thus, ezrin and moesin have distinct and critical functions in the T cell cortex during IS formation.
Marker development for the genetic study of natural variation inArabidopsis thaliana
Authors: Nemri Adnane , Neff Michael M. , Burrell Michael , Jones Jonathan D.G. , Studholme David J.
Published: November 2007

Summary: We report AtPRIMER, an application that automates the discovery of new polymorphic markers between ecotypes of Arabidopsis thaliana. On specifying two ecotypes and the genomic region of interest, the script retrieves all corresponding single nucleotide polymorphisms (SNPs) and generates CAPS and/or dCAPS PCR primer sequences. We show that AtPRIMER accurately found specific polymorphic markers for our linkage mapping project. AtPRIMER will therefore be useful for efficient marker development with high density and specificity.

Availability: This PERL/CGI program is available for non-commercial users at http://www.AtPRIMER.tsl.ac.uk. The web-based version is available for public use at the same URL.

Contact: adnane.nemri@tsl.ac.uk
Streamflow hydrology in the boreal region under the influences of climate and human interference
Authors: Woo Ming-ko , Thorne Robin , Szeto Kit , Yang Daqing
Published: November 2007

The boreal region has a subarctic climate that is subject to considerable inter-annual variability and is prone to impacts of future warming. Climate influences the seasonal streamflow regime which typically exhibits winter low flow, terminated by spring freshet, followed by summer flow recession. The effects of climatic variation on streamflow cannot be isolated with confidence but the impact of human regulation of rivers can greatly alter the natural flow rhythm, changing the timing of flow to suit human demands. The effect of scenario climate change on streamflow is explored through hydrological simulation. Example of a Canadian basin under warming scenario suggests that winter flow will increase, spring freshet dates will advance but peak flow will decline, as will summer flow due to enhanced evaporation. While this simulation was site specific, the results are qualitatively applicable to other boreal areas. Future studies should consider the role of human activities as their impacts on streamflow will be more profound than those due to climate change.
Potentials and limitations for human control over historic fire regimes in the boreal forest
Authors: Granström Anders , Niklasson Mats
Published: November 2007

Fire, being both a natural and cultural phenomenon, presents problems in disentangling the historical effect of humans from that of climate change. Here, we investigate the potential impact of humans on boreal fire regimes from a perspective of fuels, ignitions and culture. Two ways for a low technology culture to impact the fire regime are as follows: (i) by altering the number of ignitions and their spatial distribution and timing and (ii) by hindering fire spread. Different cultures should be expected to have quite different impacts on the fire regimes. In northern Fennoscandia, there is evidence for fire regime changes associated with the following: a reindeer herding culture associated with few ignitions above the natural; an era of cattle husbandry with dramatically increased ignitions and somewhat higher fire frequency; and a timber exploitation era with decreasing fire sizes and diminishing fire frequency. In other regions of the boreal zone, such schemes can look quite different, but we suggest that a close look at the resource extraction and land use of different cultures should be part of any analysis of past fire regimes.
Process Modeling in Laser Deposition of Multilayer SS410 Steel
Authors: Wang Liang , Felicelli Sergio
Published: November 2007

A three-dimensional finite element model was developed to predict the temperature distribution and phase transformation in deposited stainless steel 410 (SS410) during the Laser Engineered Net Shaping (LENS™) rapid fabrication process. The development of the model was carried out using the SYSWELD software package. The model calculates the evolution of temperature in the part during the fabrication of a SS410 plate. The metallurgical transformations are taken into account using the temperature-dependent material properties and the continuous cooling transformation diagram. The ferritic and martensitic transformation as well as austenitization and tempering of martensite are considered. The influence of processing parameters such as laser power and traverse speed on the phase transformation and the consequent hardness are analyzed. The potential presence of porosity due to lack of fusion is also discussed. The results show that the temperature distribution, the microstructure, and hardness in the final part depend significantly on the processing parameters.
Friction Stir Welding Lap Joint Resistance Optimization Through Gradient Techniques
Authors: Fratini L. , Corona V.
Published: November 2007

In recent years, scientific interest on friction stir welding (FSW) has grown more and more since such a joining technique allows one to weld lightweight alloys that are rather difficult to weld or even “unweldable” with the classic fusion welding operations. Furthermore, few industrial applications of the process are already known in different manufacturing fields. In this paper, the optimization problem of a FSW lap joint for automotive applications is investigated, taking into account process parameters such as the tool rotating speed and the tool feed rate; a numerical gradient technique is applied for the optimization procedure reducing the number of experimental tests to be developed.
Optimization of a Classical Stamping Progression by Modal Correction of Anisotropy Ears
Authors: Ledoux Y. , Favrelière H. , Samper S.
Published: November 2007

This work is a development from the Inetforsmep European project. We proposed to realize a global optimization of a deep drawing industrial progression (made of several stages) for a cup manufacture. The objectives of the process were the thickness decrease and the geometrical parameters (especially the height). This paper improves on this previous work in the aim of mastering the contour error. From the optimal configuration, we expect to cut down the amount of the needed material and the number of forming operations. Our action is focused on the appearance of unexpected undulations (ears) located on the rim of the cups during forming due to a nonuniform crystallographic texture. Those undulations can cause a significant amount of scraps, productivity loss, and cost during manufacture. In this paper, this phenomenon causes the use of four forming operations for the cup manufacture. The aim is to cut down from four to two forming stages by defining an optimal blank (size and shape). The advantage is to reduce the cost of the tool manufacturing and to minimize the needed material (by suppressing the part flange). The chosen approach consists in defining a particular description of the ears’ part by modal decomposition and then simulating several blank shapes and sizes generated by discrete cosine transformation (DCT). The use of a numerical simulation for the forming operation and the design of an experiment technique allow mathematical links between the ears’ formation and the DCT coefficients. An optimization is then possible by using mathematical links. This original approach leads the ears’ amplitude to be reduced by a factor of 10, with only 15 numerical experiments. Moreover, we have limited the number of forming stages from 4 to 2 with a minimal material use.
The effect of vaterite deposition on sound reception, otolith morphology, and inner ear sensory epithelia in hatchery-reared Chinook salmon (Oncorhynchus tshawytscha)
Authors: Oxman Dion S , Barnett-Johnson Rachel , Smith Michael E , Coffin Allison , Miller Diane L , Josephson Ron , Popper Arthur N
Published: November 2007

The inner ear of teleost fishes contains three calcareous structures (otoliths) that are part of the organs for hearing and balance. The largest of these structures, the sagitta, is usually composed of calcium carbonate crystals in the form of aragonite, but the calcium carbonate also occurs less frequently in a clear crystallized form called vaterite. We investigated the functional consequences of otolith crystal structure on hearing in juvenile Chinook salmon (Oncorhynchus tshawytscha) using the auditory brainstem response technique. A significant loss of sensitivity (2.5–6.5 dB) occurred within the primary hearing range (100–300 Hz) among salmon that had at least one vateritic sagitta. Auditory thresholds were not significantly different in fish with one vs. two vaterite sagittae. Crystallized sagittae were significantly larger and less dense than their aragonite counterparts. Saccular epithelium shape and hair bundle orientation patterns did not differ between saccules with different crystal types. There was, however, a propensity for the saccular epithelia from vateritic sagittae to have fewer sensory hair bundles. We conclude that significant hearing loss was associated with the occurrence of vateritic sagittae and suggest that hearing loss is caused by the lower density of the vaterite otoliths.
Fish behaviour from fishers’ knowledge: the case study of tropical tuna around drifting fish aggregating devices (DFADs)
Authors: Moreno Gala , Dagorn Laurent , Sancho Gorka , Itano David
Published: November 2007

Purse-seining for tropical tuna is one of the most technologically advanced fisheries in the world. The purpose of this study was to apply local ecological knowledge (LEK) to assist in the planning of future in situ studies of fish behaviour around drifting fish aggregating devices (DFADs) by prioritizing research topics, thereby reducing the number of potential hypotheses to explore. Interviews of fishing masters of the purse-seine fleets working in the western Indian Ocean provided an alternate, independent, and previously unexplored source of behavioural information, specifically on the attraction, retention, and departure behaviours of tuna schools in relation to DFADs. Most fishing masters agreed that the maximum attraction distance of a DFAD is approximately 10 km and generally agreed to the following statements. Tuna form distinct schools under FADs, commonly segregated by species and size. The main reasons for the departure of tuna aggregations from FADs are changes in currents or FAD movements and location in relation to physical or oceanographic features. The number of actively monitored DFADs at sea in the western Indian Ocean was estimated at approximately 2100. Incorporating fishers into the planning and design stages of future research projects will facilitate collaborative and integrated approaches.
Landscape-controlled chemistry variation affects communities and ecosystem function in headwater streams
Authors: Petrin Zlatko , McKie Brendan , Buffam Ishi , Laudon Hjalmar , Malmqvist Björn
Published: November 2007

We show that benthic freshwater communities of naturally acidic streams in boreal catchments differ depending on properties of the surrounding landscape. Although low pH usually is associated with negative impacts on species diversity and ecosystem function, here decomposition by insects and microbes as well as the abundance of leaf-eating insects were generally high at low pH and at humic sites influenced by mire-dominated compared with forest-dominated surroundings. Moreover, in situ growth experiments showed that the survival of two of the most abundant insect species was higher when they originated from mire-influenced sites, underscoring their tolerance to low pH. However, species diversity generally increased with pH and was greater at forest-influenced than at mire-influenced sites. Although less diverse, acidic and humic streams proved to be functional and supported distinct macroinvertebrate assemblages. Diversity and function in naturally acidic streams are apparently greatly influenced by the prevailing kinds of landscape-driven influences on water chemistry. In conclusion, well-known negative impacts of anthropogenic acidity on diversity and function may not apply to naturally acidic systems that are chemically and biologically heterogeneous.
A limited role for ultraviolet radiation when threespine sticklebacks (Gasterosteus aculeatus) prey uponDaphnia
Authors: Modarressie Ricarda , Bakker Theo C.M
Published: November 2007

Any trait of predatory species that enhances hunting efficiency should be favoured by natural selection. Foraging in threespine sticklebacks (Gasterosteus aculeatus) is mainly visually mediated. The visual system of sticklebacks is extended into the ultraviolet (UV) range of the spectrum. We tested, in four different experimental setups, the influence of different spectral compositions, in particular the presence and absence of ultraviolet wavelengths, on the feeding performance of threespine sticklebacks while foraging on live Daphnia magna, which absorb UV. In the three experiments with similar background reflections, the foraging behaviour of sticklebacks was unaffected by removing UV wavelengths. But in the fourth experiment, sticklebacks showed a significant difference between the rate of detecting prey against a UV-reflecting or UV-absorbing background. Sticklebacks significantly attacked prey faster when the background lacked UV reflections. Thus, the interaction of prey with its background in UV wavelengths influenced sticklebacks' prey detection. Removing long wavelengths impaired foraging rate, suggesting that long wavelengths may be more important in foraging tasks than UV wavelengths.
Do survey design and wind conditions influence survey indices?
Authors: Poulard Jean-Charles , Trenkel Verena M
Published: November 2007

Survey indices play an important role in stock assessments as they provide information on stock trends. In certain cases, large interannual variations have been observed that are unlikely to reflect true underlying stock changes but are rather outliers. When survey indices for several species appear to be outliers for the same year, the suspicion is raised that something happened during the survey of that year. This is called a year effect in survey catches. To study the potential year effect in survey catches for the French autumn groundfish survey taking place in the Bay of Biscay, several indicators for survey design and wind conditions were derived as explanatory variables, and principal component analysis was used to study the relationship between these variables. Using multiple linear regression models, we found that, on average, 20% of interannual variation in abundance indices could be explained by survey conditions for benthic species, 11% for demersal, and none for pelagic species. In contrast, survey conditions explained a smaller and decreasing part of the interannual variability in the coefficients of variations of these abundance indices and in species mean weight for benthic, demersal, and pelagic species. Thus survey indices of benthic species seemed most affected by survey design and wind conditions.
Branchial versus intestinal zinc uptake in wild yellow perch (Perca flavescens) from reference and metal-contaminated aquatic ecosystems
Authors: Niyogi Soumya , Pyle Gregory G , Wood Chris M
Published: November 2007

Zinc is an essential micronutrient for freshwater fish but can be toxic to them at elevated concentrations. Therefore, the regulation of zinc uptake is important in maintaining homeostasis when fish are chronically exposed to elevated zinc in nature. This study examined the kinetics of in vivo branchial and in vitro intestinal zinc uptake in wild yellow perch (Perca flavescens) from metal-contaminated and reference lakes in northern Ontario. The results showed that the branchial zinc uptake involves high-affinity transport sites, whereas the intestinal zinc uptake involves low-affinity transport sites. Interestingly, significant alterations in the branchial zinc uptake (reduced affinity, increased maximum transport rate) but no apparent changes in the intestinal zinc uptake characteristics were observed in the metal-impacted yellow perch population relative to the reference population. Subsequently, no differences in zinc concentrations of gill, liver, and whole body were recorded between reference and metal-impacted yellow perch populations. Overall, our study indicated that the gill, not the gut, likely plays a critical role in maintaining the zinc homeostasis in wild fish under chronic exposure.
Why do fishers fish where they fish? Using the ideal free distribution to understand the behaviour of artisanal reef fishers
Authors: Abernethy Kirsten E , Allison Edward H , Molloy Philip P , Côté Isabelle M
Published: November 2007

We used the theory of the ideal free distribution (IFD) as a framework to understand the mechanisms underlying fishing site selection by Anguillian artisanal fishers exploiting shallow-water coral reefs. Contrary to the predictions of IFD, fishers did not distribute themselves so that average reward was equal among fishers using different fishing methods or among fishers using the same method. In addition, fishing pressure did not increase with resource availability. Key assumptions of the IFD were not met. The distribution of Anguillian fishers was not "ideal" because lack of knowledge prevented fishers from choosing fishing grounds with the greatest rewards. Not all fishers sought to maximise profit. In addition, all fishers were not "free" to distribute themselves among reefs owing to variation in social, economic, and physical characteristics of fishers that constrained fisher movements and ability to extract resources. This study shows that as a null model the IFD is useful to frame studies designed to gain detailed insights into the complexity and dynamics of a small-scale fishery. Alongside ecological data, this framework may inform efficient and effective development of reef and fishery management practice.
A method for estimation of a land-cover change matrix from error-prone unit-level observations
Authors: Magnussen Steen
Published: November 2007

Coregistration and classification errors can seriously compromise direct unit-level (pixel) estimation of land-cover change from remotely sensed data. A more robust alternative to a pixel-based estimation of change is warranted. In a proposed method, spatially adjacent pixels are grouped into 3 × 3 clusters, and the change matrix is obtained from cluster-specific and land cover specific pixel counts at two points in time. The diagonal of a change matrix is estimated by combining an estimate of the temporal correlation of cover type specific, cluster-level counts with an estimate of the odds ratio of no change. Off-diagonal elements are least-squares solutions to a set of linear constraints or obtained by iterative proportional fitting under a model of quasi-independence. In a study with data from five sites, the proposed method produced less biased estimates on three sites if the mean coregistration error was in excess of 0.3–0.7 pixels and on four sites if classification accuracy dropped below 0.9.
An analysis and comparison of estimation methods for self-referencing equations
Authors: Ni Chengcai , Zhang Lianjun
Published: November 2007

Self-referencing equations (SREs) play an important role in modeling stand and individual-tree growth and yield. Over the decades, forest modelers have applied ordinary least-squares (OLS) or generalized least-squares to fit SREs (namely, the SRE method). In this article, we discuss the statistical properties of the SRE method via theoretical and empirical analyses. The SRE method has its disadvantages: (i) the parameter estimates are not the OLS estimates; (ii) the standard errors of the parameters are underestimated; (iii) the model mean squared error is overestimated; and (iv) the model random errors are always correlated and have heterogeneous variances. Thus, statistical inferences based on these model statistics may not be valid. In addition, there is no simple way to overcome these problems, because they arise from the data structures used for model fitting. This study demonstrates that the disadvantages of the SRE method can be circumvented by fitting the corresponding base model, rather than the transformed model, using two alternative methods: dummy variable regression (DVR method) and mixed effect models (MIX method). The DVR and MIX methods can efficiently account for serial autocorrelation and variance heterogeneity and, thus, produce valid model statistics for hypothesis testing and confidence intervals.
Comparative analysis of occluded branch characteristics forFraxinus excelsiorandAcer pseudoplatanuswith natural and artificial pruning
Authors: Hein Sebastian , Spiecker Heinrich
Published: November 2007

The aim of this study was to develop models on branch characteristics for Fraxinus excelsior L. (common ash) and Acer pseudoplatanus L. (sycamore maple) based on 44 and 25 sample trees, respectively. A total of 635 ash and 334 maple branches were sampled. The data set on artificial pruning was pooled among the two species with a total of 71 branches from 16 trees. The material was used to predict (i) the time for a complete occlusion, (ii) the total radius of the occluded branch inside the trunk, (iii) the branch insertion angle, and (iv) the dead branch portion of the occluded branch. In addition, the effects of species and natural versus artificial pruning were assessed. Generalized hierarchical mixed models with univariate or multivariate approaches were used in this analysis. The diameter of the occluded branch and the stem radial increment played a dominant role as predictors. Artificial pruning led to a significant reduction in occlusion time and a shorter occluded branch radius. Only few species-specific differences were found. Simulations showed a reasonable overall behaviour of the models. The residual variation was tolerable for integrating the models into a growth simulation system.