bluuebunny/crossref_metadata_2025 huggingface dataset:
Mesolithic cremations as secondary mortuary practices at Vlasac (Serbia)
Authors: Borić Dušan , Raičević Jelena , Stefanović Sofija
Published: December 2009

In the course of recent excavations of the Mesolithic-Neolithic site of Vlasac, new light has been shed on the mortuary practices and ritualistic behaviour of the Danube Gorges foragers on the basis of human remains with evidence of diverse treatments of dead human bodies. While the majority of burials from the site were found as articulated and some as disarticulated inhumations, there were also several cremation burials. The aim of this paper is to present the analyses of these burned remains, which were excavated in the course of 2006–2007 field seasons in the Danube Gorges. Some of the cremation pits contained calcified human bones, with charcoal and fragments of broken and burned projectile points. These contexts are compared with similar cremation pits found during the first excavations at Vlasac and other sites in the region in 1970–1971. Finally, we examine a series of plausible interpretations in order to sketch a belief system that was part of these funerary practices at Vlasac throughout the 7th millennium BC.
Representing people, constituting worlds: multiple 'Neolithics' in the Southern Balkans
Authors: Nanoglou Stratos
Published: December 2009

This paper considers the diverse iconographic landscapes of the southern Balkans, especiallythose populated by human figurines. The main premise is that material culture is a resource upon which agents draw to situate themselves in the world. In this way, regional traits are deemed particularly important for the constitution of specific subjectivities, in contrast to a generic ‘Neolithic individual’, and at the same time, for the constitution of specific local worlds as opposed to an all-encompassing world that is merely experienced differently. I attempt to provide an example of such regional traits that would have constituted different contexts for agency during the Neolithic and focus on the differences between two regions within the southern Balkans, regions that do not remain the same in the course of time.
Palaeolithic art in Slovenia
Authors: Petru Simona
Published: December 2009

This article is a review of Slovenian Palaeolithic ‘art’ objects. Most were found quite some time ago and were described as ‘art’ by their excavators, who undertook no further examination and authentication. More recent finds, like the Mousterian ‘flute’, were thoroughly examined,but in the case of the flute, there is still no uniform agreement on whether it was used as musical instrument or not. The only objects which are definitely artificial are engraved bone points, two engraved stones and three pieces of jewellery from Late Palaeolithic sites.
Lithic raw material procurement in the Moravian Neolithic: the search for extra-regional networks
Authors: Kuča Martin , Prichystal Antonín , Schenk Zdenk , Škrdla Petr , Vokác Milan
Published: December 2009

The study of lithic raw material procurement can contribute to the study of ancient networks. Petrographic analysis combined with systematic mapping of raw material outcrops has been conducted in Moravia and adjacent territories by A. Přichystal over a period of more than three decades. Combined with well excavated (including wet-screening) and 14C (radiometric) dated sites,allows us to study changes in the distribution networks of raw materials during the Mesolithic and Neolithic periods.
Neolithic\Eneolithic settlement patterns and Holocene environmental changes in Bela Krajina (south-eastern Slovenia)
Authors: Mason Phil , Andrič Maja
Published: December 2009

This paper examines the archaeological settlement pattern and vegetation history of Bela krajina region of Slovenia in order to better understand the interaction of human activities and environmental processes in the landscape. Pollen record of two small palaeoecological sites (Mlaka and Griblje) indicates that human impact on the vegetation at circa 4150 calBC was intensive (forest cutting/burning, beech decline and formation of fields, pastures, meadows) and can be associated with numerous Neolithic/Eneolithic sites, located in the Lahinja river basin and the Kolpa lowlands. Human pressure on the (lowland/riverine) environment slightly decreased between c. 3750–2850 calBC. This coincides with the appearance of a more dispersed settlement pattern, including the formation of short-term settlement/activity areas on the karst plateau. This change to a more extensive Eneolithic settlement pattern can be presumably associated with change in economy (more intensive pastoralism and transhumance, possibly also soil erosion) and is partially borne out by evidence from excavated sites in the area.
Book Reviews
Authors: Budja Mihael , Petru Simona
Published: December 2009

Book Reviews
Climate change and population dynamics during the late Mesolithic and the Neolithic transition in Iberia
Authors: López de Pablo Javier Fernández , Gómez Puche Magdalena
Published: December 2009

This paper explores how Early Holocene climate changes in the Western Mediterranean would have affected Late Mesolithic settlement distribution and subsistence strategies in Iberian Peninsula, thereby giving rise to various adaptive scenarios. The current radiocarbon data set concerning the Neolithisation process has revealed the rapidity of the spread of farming in Iberia. Considering both the implications of the last hunter-gatherers’ adaptation strategies and the population dynamics of agro-pastoral communities, we address the migration patterns underlying the Mesolithic- Neolithic transition. In conclusion, we propose that the initial colonization process was the result of two successive and spatially heterogeneous migrations: Maritime Pioneer Colonization and targeted migration to places favorable to the new economic system.
Climate fluctuations and trajectories to complexity in the Neolithic: towards a theory
Authors: Gronenborn Detlef
Published: December 2009

Theories about the emergence and spread of farming in western Eurasia have a long research history. Occasionally, climate fluctuations have served as explanations for short-term culture change. However, the entire Holocene climate fluctuation sequence has so far not been regarded. First steps towards a theory which combines the successive stages in Neolithization and early to Mid-Holocene climate fluctuations are described.
Implications of the role of Southeastern Europe in the origins and diffusion of major Eurasian paternal lineages
Authors: Rootsi Siiri
Published: December 2009

The aim of this study is to give an overview of the extent and nature of Southeastern Europe (SEE) paternal genetic variation in relation to potential episodes of gene flow during dispersals of the Upper Paleolithic and Neolithic. A survey based on studies of the paternal gene pool of the region revealed consistency with the typical European paternal gene pool, as five major haplogroups E3b1, I1b*, J2, R1a, and R1b contribute more than 70% to the total genetic variation in SEE. Comprehensive characterization and dating of major paternal lineages imply that SEE has been both an important source and recipient of gene flow.
Early Neolithic pottery dispersals and demic diffusion in southeastern Europe
Authors: Budja Mihael
Published: December 2009

The 14C gradient of pottery dispersal suggests that the sites in the southern Balkans are not significantly older than those in the northern and eastern Balkans. A gradual demic diffusion model from south to north and a millennium time span vector thus find no confirmation in the set of AMS 14C dates and associated contexts that mark pottery dispersal within Southeastern Europe. The first ‘demic event’ that was hypothesised to reshape significantly European population structure and generate a uniform process of neolithisation of southestern Europe has no confirmation in frequency of Y-chromosome subhaplogroups J2b and E3b1 distribution within modern population in Southeastern Europe.
Demographic model of the Neolithic transition in Central Europe
Authors: Galeta Patrik , Bruzek Jaroslav
Published: December 2009

Several recent lines of evidence indicate more intensive contact between LBK farmers and indigenous foragers in Central Europe (5600–5400 calBC). Strong continuity has been identified between Mesolithic and Neolithic material cultures; faunal assemblages, and isotopic analyses of diet have revealed a greater role of hunting in LBK communities; genetic analyses have suggested that the modern Central European gene pool is mainly of Palaeolithic origin. Surprisingly little attention has been paid to demographic aspects of the Neolithic transition. In our study, demographic simulations were performed to assess the demographic conditions that would allow LBK farmers to spread across central Europe without any admixture with Mesolithic foragers. We constructed a stochastic demographic model of changes in farming population size. Model parameters were constrained by data from human demography, archaeology, and human ecology. Our results indicate that the establishment of farming communities in Central Europe without an admixture with foragers was highly improbable. The demographic conditions necessary for colonization were beyond the potential of the Neolithic population. Our study supports the integrationists’ view of the Neolithic transition in Central Europe.
Modality of hyperalgesia tested, not type of nerve damage, predicts pharmacological sensitivity in rat models of neuropathic pain
Authors: Pradhan Amynah Amir Ali , Yu Xiao Hong , Laird Jennifer M.A.
Published: December 2009

Although many types of nerve damage can cause neuropathic pain, there are substantial commonalities in neuropathic pain symptoms, and patients can be divided into sub‐groups based on their symptom profile rather than etiology. Mechanism‐based treatment suggests that pharmacotherapy should be chosen be based shared commonalities of symptoms rather than etiology. The aim of the present study was to determine whether type of injury (etiology) or behavioral endpoint (symptom) is a better predictor of pharmacological responsivity in the most commonly used rodent models of neuropathic pain. We used the chronic constriction injury (CCI) model to directly compare the temporal and pharmacological characteristics of four different types of evoked stimuli; heat, pressure, acetone cooling and punctate mechanical. We then compared heat hyperalgesia and mechanical allodynia endpoints across etiologies using the spinal nerve ligation (SNL) model. Evoked pain responses in both models had strikingly different temporal characteristics. We then tested three standard therapies for neuropathic pain from different drug classes, oxycodone, gabapentin, and amitriptyline. Notably, regardless of the model tested, or the time of onset, common endpoints showed near‐identical pharmacological responses, and not all endpoints were equally sensitive to drug intervention within one model. Hypersensitivity to heat and pressure were highly responsive to oxycodone, gabapentin, and amitriptyline; whereas cold and mechanical allodynia were more difficult to reverse. Moreover, CCI‐ and SNL‐induced mechanical allodynia was completely insensitive to amitriptyline treatment. We conclude that regardless of model and time course of presentation, different symptoms of peripheral neuropathy have unique pharmacological responses.
Relationships between coping strategies and lumbar muscle activity in subjects with chronic low back pain
Authors: van der Hulst Marije , Vollenbroek‐Hutten Miriam M. , Schreurs Karlein M. , Rietman Johan S. , Hermens Hermanus J.
Published: December 2009

Background: Concerning chronic low back pain (CLBP), different cognitive–behavioral models have hypothesized that coping strategies play a role in the chronification of pain by changes in physical activity. Strategies such as avoidance – or persistent coping may be related to changes in (lumbar) muscle activity.

Aim: Investigate the different coping strategies present in CLBP and whether these are differentially related to lumbar muscle activity during walking.

Methods: In a cross sectional study, 63 subjects with CLBP walked on a treadmill at 3.8 km/h. Coping strategies were measured with the Dutch version of the Coping Strategies Questionnaire and three factors were identified with principal component analysis. Surface electromyography data of the erector spinae were obtained and smooth rectified electromyography (SRE) values were averaged per periods of swing and double support. The ratio of SRE values (swing/double support) was used as a measure of relaxation. The relation between SRE values and coping strategies was analyzed with random coefficient analysis.

Results: Three coping strategies (i.e. “catastrophizing”, “distraction” and “persistence and control”) could be discerned. “Catastrophizing” was positively related to (natural logarithm) SRE values (β = 0.06, 95% CI = 0.01–0.10; R2 = 7.7%). “Distraction” was negatively associated with SRE ratios (β = −0.03, 95% CI = −0.05 to −0.01; R2 = 7.5%). No relation was found between “persistence and control” and SRE values or ratios.

Conclusions: In CLBP, a maladaptive coping strategy like “catastrophizing” is related to increased lumbar muscle activity, and an adaptive strategy like “distraction” to increased lumbar muscle relaxation during walking.
Pain expression in children with an intellectual disability
Authors: Dubois Amandine , Capdevila Xavier , Bringuier Sophie , Pry René
Published: December 2009

Background: Children with an intellectual disability (ID) are sometimes unable to verbalize and describe their painful experience; therefore family members and health carers can assess the intensity of the pain only from the behaviour exhibited by the children.

Aim and method: The purpose of this descriptive and exploratory study was to examine the behavioural pain expression in 30 children with ID aged from 5 to 18 years in a surgical context. Children were matched with 30 typically developing children of the same chronological age and 30 typically developing children of the same developmental age.

Results: The results showed the influence of the level of expressive communication on the pain expression. Children who were able to verbalize their pain exhibited a normative pain expression with behavioural traits similar to those of typically developing children of the same developmental age. Children who were unable to verbalize their pain produced particular pain expressions with behavioural traits that were atypical and without a communicative goal.

Conclusion: Pain expression modalities are extremely different between children able to verbalize their pain and those unable to do so. This study confirmed the necessity to take into account the particularities of each child with ID in order to individualize the pain management and avoid misdiagnosis and the under treating of pain in non verbal children.
Knowledge Management and the Intranet at Field Fisher Waterhouse
Authors: Rudman Sarah
Published: December 2009

Sarah Rudman, Learning and Knowledge Management Director, describes the successful implementation by the information and knowledge management team of a new intranet in a London law firm.
Industry architecture as a determinant of successful platform strategies: a case study of the i‐mode mobile Internet service
Authors: Tee Richard , Gawer Annabelle
Published: December 2009

Abstract What factors and processes drive value appropriation and value creation in interdependent industry ecosystems? This paper explores this issue through a case study comparing the deployment of the i‐mode mobile Internet service in two countries, seeking the reasons behind its contrasting fortunes: spectacular success in Japan vs failure in Europe. The comparison between network operators NTT Docomo in Japan and KPN in the Netherlands suggests that differences in the underlying industry architectures explain why similar platform strategies led to such different outcomes. The paper contributes to the literature on industry architecture by unpacking the interaction between evolutionary processes, industry architecture, and business strategies. It also contributes to the platforms literature, by positing that firms' ability to successfully pursue platform strategies depends on industry architecture.
Knowledge integration and vertical specialization in the semiconductor industry
Authors: Dibiaggio Ludovic , Nasiriyar Maryam
Published: December 2009

Abstract We use patent data from the worldwide semiconductor industry to examine the effect of knowledge integration capabilities on firms' innovative performance, according to their role in the industry architecture. We argue that the organization of the industry knowledge base is characterized by a structure of distinct clusters of strongly coupled knowledge elements, and of interfaces between clusters considered. We find that the integration of complementary knowledge increases the innovative performance of all firms, whatever their position in the industry architecture. However, our results suggest that systems integrators play a critical role in the knowledge production process by investing more than other firms in the development of interfaces, which provide them with innovative advantage.
Building architectural advantage in the US motion picture industry: Lew Wasserman and the Music Corporation of America
Authors: Ferraro Fabrizio , Gurses Kerem
Published: December 2009

Abstract This article contributes to the literature on industry architecture by identifying the conditions that enable the emergence of architectural advantage. To understand how one firm can shape the industry architecture in its favor, we analyzed a historical case study on the role of Lew Wasserman and the Music Corporation of America (MCA) in the evolution of the motion picture industry in the United States. We focused on two major disruptive events: the 1948 Paramount Decree which forced vertically integrated movie studios to divest their theaters, and the explosion of television as a new form of entertainment in the 1950s which became an alternative for exhibiting movies. In both these cases, one company, MCA, managed to improve substantially its standing by occupying and consolidating a position of advantage in the industry or, in other terms, an ‘architectural advantage’. We show how in both cases this was the result of interactions between the Studios, constrained by the institutional logic of the industry, the regulatory framework, and MCA's introduction of novel practices. The latter consolidated its grip on talents and facilitated the growth of independent production and TV production.
Product architecture, inter‐firm vertical coordination and knowledge partitioning in the auto industry
Authors: Zirpoli Francesco , Camuffo Arnaldo
Published: December 2009

Abstract This study investigates the dynamics of knowledge partitioning, integration and coordination in vertical inter‐firm relationships by addressing the following research questions: How and to what extent does product architecture shape the allocation of design tasks and inter‐firm coordination? What variables do firms have to consider in making decisions concerning the organization of co‐design projects? Following a ‘quasi‐experimental’ research design approach, we conducted a comparative study of two similar auto component co‐development projects (air‐conditioning systems) carried out by a Japanese first‐tier supplier with two European automakers. Despite the coeteris paribus conditions defined by the research design, we observed significant cross‐firm differences in task and knowledge partitioning and in the relationship governance. The study shows that firm‐specific factors (e.g. pre‐existing technological and organizational capabilities) ‐ not product architecture per se ‐ resulted the key determinants of cross‐firm differences. From this perspective our findings contributes to the broader debate about the co‐determination of product architectures, firms' vertical scope and industry architecture.
Attofarad resolution potentiostat for electrochemical measurements on nanoscale biomolecular interfacial systems
Authors: Carminati Marco , Ferrari Giorgio , Sampietro Marco
Published: December 2009

We present an instrument that enables electrochemical measurements (cyclic voltammetry, impedance tracking, and impedance spectroscopy) on submicrometric samples. The system features a frequency range from dc to 1 MHz and a current resolution of 10 fA for a measurement time of 1 s, giving a sensitivity of few attofarads in terms of measurable capacitance with an applied voltage of only 100 mV. These performances are obtained using a low-noise wide-bandwidth integrator/differentiator stage to sense the input current and a modular approach to minimize the effect of input stray capacitances. A digitally implemented lock-in filter optimally extracts the impedance of the sample, providing time tracking and spectroscopy operating modes. This computer-based and flexible instrument is well suited for characterizing and tracking the electrical properties of biomolecules kept in the physiological solution down to the nanoscale.
Monte Carlo simulation on the size effect in ferroelectric nanostructures
Authors: Xue F. , Gao X. S. , Liu J.-M.
Published: December 2009

The ferroelectric domain structures in a two-dimensional square lattice with different lattice sizes under a set of finite boundary conditions (zero dipole and clamped strain on lattice boundaries) are investigated using Monte Carlo simulation, based on the Landau phenomenological model. Given the finite boundary conditions, the ferroelectric domain structure evolves gradually from the 90°-striped pattern into the single-vortex pattern with reducing lattice size. When the finite boundary conditions apply only onto one-dimensional boundaries, as an approach to the case of thin films, the single-domain pattern is favored with reducing lattice size. The physics underlying the evolution of domain structures with varying lattice size is discussed.
Modulation frequency dependence of the photoelectrical response of GaAs/InGaP superlattices
Authors: Parisini Antonella , Ghezzi Carlo , Tarricone Luciano , Baldini Michele , Vantaggio Salvatore , Gombia Enos
Published: December 2009

Photoelectrical measurements were taken on a nominally undoped-InGaP/GaAs superlattice, inserted between two p+ and n+ InGaP cladding layers. The sequence of InGaP/GaAs alternated layers forming the superlattice was grown lattice matched on n+-GaAs substrates through low pressure-metal organic vapor phase epitaxy, at growth conditions previously optimized for obtaining sharp interfaces and negligible ordering effects in the cation sublattice of the InGaP layers. A peculiar dependence of both the photocurrent and the photovoltaic signals on the modulation frequency of the exciting light beam was observed and then interpreted according to proper equivalent electrical circuits. The effects induced by an incomplete depletion of the nominally undoped superlattice region are analyzed in detail, and the analogies between photoelectrical investigation and admittance spectroscopy are pointed out.
Atomic force microscopic study of folate receptors in live cells with functionalized tips
Authors: Girish C M , Binulal N S , Anitha V C , Nair Shantikumar , Mony U , Prasanth R
Published: December 2009

Membrane associated folate receptors (FR) is gaining importance in cancer research. Understanding the FR density, distribution, and the strength of its interaction with ligands is crucial in cancer diagnostics and therapeutics. Here we reported the enhanced phase contrast image of FR by scanning with properly functionalized atomic force microscope (AFM) tips over live cell lines. The choice of the ligand was made for better interaction of tip with FR, expressed in the cell lines. The selectively enhanced force of interaction at the receptor molecule produced a considerable enhancement in the phase contrast between a receptor site and a nonreceptor site.
Stability of Al2O3 and Al2O3/a-SiNx:H stacks for surface passivation of crystalline silicon
Authors: Dingemans G. , Engelhart P. , Seguin R. , Einsele F. , Hoex B. , van de Sanden M. C. M. , Kessels W. M. M.
Published: December 2009

The thermal and ultraviolet (UV) stability of crystalline silicon (c-Si) surface passivation provided by atomic layer deposited Al2O3 was compared with results for thermal SiO2. For Al2O3 and Al2O3/a-SiNx:H stacks on 2 Ω cm n-type c-Si, ultralow surface recombination velocities of Seff<3 cm/s were obtained and the passivation proved sufficiently stable (Seff<14 cm/s) against a high temperature “firing” process (>800 °C) used for screen printed c-Si solar cells. Effusion measurements revealed the loss of hydrogen and oxygen during firing through the detection of H2 and H2O. Al2O3 also demonstrated UV stability with the surface passivation improving during UV irradiation.
Simplified one-dimensional calculation of 13.5 nm emission in a tin plasma including radiation transport
Authors: White J. , Dunne P. , Hayden P. , O’Sullivan G.
Published: December 2009

Many next generation lithography schemes for the semiconductor industry are based on a 13.5 nm tin plasma light source, where hundreds of thousands of 4d-4f, 4p-4d, and 4d-5p transitions from Sn5+–Sn13+ ions overlap to form an unresolved transition array. To aid computation, transition arrays are treated statistically, and Hartree–Fock results are used to calculate radiation transport in the optically thick regime with a one-dimensional Lagrangian plasma hydrodynamics code. Time-dependent spectra and conversion efficiencies of 2% in-band 13.5 nm emission to laser energy are predicted for a Nd:YAG (yttrium aluminum garnet) laser incident on a pure tin slab target as a function of laser power density and pulse duration at normal incidence. Calculated results showed a maximum conversion efficiency of 2.3% for a 10 ns pulse duration at 8.0×1010 W/cm2 and are compared to experimental data where available. Evidence for the need to include lateral expansion is presented.
Limits of the ratios of tracer diffusivities for diffusion by vacancy pairs: Application to compound semiconductors
Authors: Belova I. V. , Shaw D. , Murch G. E.
Published: December 2009

In this paper, the vacancy-pair diffusion mechanism in cubic materials is revisited with emphasis on the limits of the ratio of the tracer diffusion coefficients to demonstrate the operation of this mechanism. The vacancy-pair mechanism puts very strict upper and lower bounds on this ratio. Extensive high precision Monte Carlo simulation is used to calculate tracer correlation factor, ratios of tracer diffusivities, and percolation effects (in mixed compounds). The three major cubic lattices—NaCl, CsCl, and zinc blende structures—are analyzed, and correct limits for the ratio of the tracer diffusivities are found to be 5.6, 11.2, and 2.6, respectively. For the case of the CsCl structure correlation factors are redetermined using the matrix method to obtain good agreement with the Monte Carlo results. Self-diffusion in the compound semiconductors PbSe (NaCl structure) InSb, GaSb, CdTe, and HgCdTe (zinc blende structure) is reanalyzed. It is shown that the vacancy-pair mechanism is unlikely to contribute to self-diffusion in CdTe and HgCdTe but it remains a valid possibility for self-diffusion in PbSe, InSb, and GaSb.
Magnetization dynamics in nanopillars in the diffusive transport regime: Macrospin versus micromagnetic analysis
Authors: Jaromirska E. , Baláž P. , Díaz L. López , Barnaś J.
Published: December 2009

Current-induced spin-transfer torque in spin valve structures with magnetic layers made of different materials can exhibit a nonstandard, i.e., wavy like, angular variation. Following the diffusive spin transport model, the wavy torque was theoretically found in the Co(8nm)∕Cu(10nm)∕Py(8nm) spin valve, and later was also experimentally confirmed. However, the single domain (macrospin) approximation fails to describe some features of magnetic dynamics observed in experiments, especially the frequency agility with current and its slope for the out-of-plane precessions. Therefore, we have revisited the abovementioned pillar structure and analyzed the conditions for the appearance of the out-of-plane oscillations. In particular, we have studied the possibility of triggering these modes by means of a moderate external magnetic field. We have identified modes supported within the macrospin model and verified the results by full micromagnetic simulations, revealing numerous qualitative discrepancies. For instance, the out-of-plane oscillations have been found in the macrospin model, whereas no such precessions have been observed in micromagnetic simulations even with an external magnetic field.
Effects of aggregation on the permittivity of random media containing monodisperse spheres
Authors: Doyle Timothy E. , Tew Adam T. , Jain Rahul , Robinson David A.
Published: December 2009

Numerical simulations were used to calculate the effective permittivities of three-dimensional random particle suspensions containing up to 2440 particles and exhibiting two types of particle aggregation. The particles were modeled as 200 μm spheres that were aggregated into either large spherical clusters or into foam-type microstructures with large spherical voids. Multiple scattering of 0.01–10.0 GHz electromagnetic fields was simulated using a first-principles iterative multipole approach with matrix and particle permittivities of 1.0 and 8.5, respectively. The computational results showed both significant and highly significant trends. Aggregation into spherical clusters decreased the effective permittivity by up to 3.2±0.2%, whereas aggregation into foam-type microstructures increased the effective permittivity by up to 3.0±1.6%. The effective permittivity trends exhibited little change with frequency. These results were compared to effective medium approximations that predicted higher permittivities than those from the simulations and showed opposite trends for cluster aggregation. Three theories are proposed to explain the simulation results. The first theory invokes a waveguidelike mechanism. The simulations indicate that the wave fields propagate more through the continuous paths of greater or lesser particle density created by aggregation, rather than through the isolated particle clusters or large voids. This quasicontinuous phase, or quasimatrix, therefore behaves like a random waveguide structure in the material. A second theory is proposed where the quasicontinuous phase governs the behavior of the system by a percolationlike process. In this theory, the multipole interactions are modeled as the percolation of virtual charges tunneling from one particle to another. A third mechanism for the permittivity changes is also proposed involving collective polarization effects associated with the particle clusters or large voids. The simulation results challenge the general applicability of the quasistatic limit for heterogeneous media by showing how microstructural changes much smaller than the electromagnetic wavelength can alter the effective permittivity by a statistically significant degree. The results also provide a quantitative indication of the effects of aggregation and hierarchical microstructures on the electromagnetic properties of random media and have application to the remote and in situ sensing of soils, the rational design and nondestructive evaluation of composites, and the study of biological tissues and other random materials.
Excitation current dependent cathodoluminescence study of InGaN/GaN quantum wells grown on m-plane and c-plane GaN substrates
Authors: Lai K. Y. , Paskova T. , Wheeler V. D. , Grenko J. A. , Johnson M. A. L. , Barlage D. W. , Udwary K. , Preble E. A. , Evans K. R.
Published: December 2009

InGaN/GaN quantum wells (QWs) grown with identical conditions on m-plane and c-plane GaN substrates were studied by cathodoluminescence spectroscopy. At a low current of 10 nA, the emission intensity and wavelength of the m-plane aligned QWs were found to be about two times stronger and 19.5 nm blueshifted with respect to that of the c-plane aligned QWs. An increase in the current over three orders of magnitude was found to result in an increase in the emission intensities, with faster saturation in the m-plane aligned QWs. This was explained by the screening of quantum-confined Stark effect in the emission efficiency of the c-plane aligned QWs.
Structuring by field enhancement of glass, Ag, Au, and Co thin films using short pulse laser ablation
Authors: Ulmeanu M. , Zamfirescu M. , Rusen L. , Luculescu C. , Moldovan A. , Stratan A. , Dabu R.
Published: December 2009

Single pulse laser ablation of glass, Ag, Au, and Co thin films was experimentally investigated with a laser pulse width of 400 ps at a wavelength of 532 nm both in the far and near fields. In the far-field regime, the electromagnetic field results from a focused laser beam, while the near-field regime is realized by a combination of the focused laser beam incident on a spherical colloidal particle. For the near-field experiments we have used polystyrene colloidal particles of 700 nm diameter self-assembled or spin coated on top of the surfaces. Laser fluences applied are in the range of 0.01–10 J/cm2. The diameter and the morphologies of the ablated holes were investigated by optical microscopy, profilometry, scanning electron microscopy, and atomic force microscopy. The dependence of the shape of the holes reflects the fluence regime and the thermophysical properties, i.e., melting temperature and thermal diffusivity of the surfaces involved in the experiments. We give quantitative data about the fluence threshold, diameter, and depth ablation dependence for the far and near fields and discuss their values with respect to the enhancement factor of the intensity of the electromagnetic field due to the use of the colloidal particles. Theoretical estimations of the intensity enhancement were done using the finite-difference time-domain method by using the RSOFT software. The application of near fields allows structuring of the surfaces with structure dimension in the order of 100 nm and even below.
Bonding and magnetism in nanosized graphene molecules: Singlet states of zigzag edged hexangulenes C6m2H6m(m=2,3,…,10)
Authors: Philpott Michael R. , Kawazoe Yoshiyuki
Published: December 2009

A novel molecular phenomenon is predicted on the basis of trends identified in an ab initio density functional theory study of the electronic and geometric structure of the hexagonal shaped zigzag edged graphene hydrocarbon molecules C6m2H6m(m=2,…,10). Electrons in the interior organize to form a graphene core that grows with edge size m. Electrons in the highest occupied molecular orbital levels, localized primarily on the perimeter carbons, polarize the interior atoms with a intensity that decays rapidly with distance from the perimeter. Three distinctive bond length patterns emerge: (i) a central graphene core that grows with size m; (ii) shape-similar transverse and radial bond length patterns on interior rows close to the edges; and (iii) quinoidal bonds radiating from each apex that link adjacent edges. Concomitant with these changes are: (i) a monotonic decrease in atomic charge from center to perimeter and (ii) relegation of spin in diradical states to the outer atomic rows of the bipartite lattice.
Nonlinear vibrations of microcantilevers subjected to tip-sample interactions: Theory and experiment
Authors: Delnavaz Aidin , Mahmoodi S. Nima , Jalili Nader , Mahdi Ahadian M. , Zohoor Hassan
Published: December 2009

Improvement of microcantilever-based sensors and actuators chiefly depends on their modeling accuracy. Atomic force microscopy (AFM) is the most widespread application of microcantilever beam as a sensor, which is usually influenced by the tip-sample interaction force. Along this line of reasoning, vibration of AFM microcantilever probe is analyzed in this paper, along with analytical and experimental investigation of the influence of the sample interaction force on the microcantilever vibration. Nonlinear integropartial equation of microcantilever vibration subject to the tip-sample interaction is then derived and multiple time scales method is utilized to estimate the tip amplitude while it is vibrating near the sample. A set of experiments is performed using a commercial AFM for both resonance and nonresonance modes, and the results are compared with the theoretical results. Hysteresis, instability and amplitude drop can be identified in the experimental curves inside the particle attraction domain. They are likely related to the interaction force between the tip and sample as well as the ever-present water layer during the experiments. A fair agreement is observed between the theoretical simulations and experimental findings, which obviously demonstrates the effectiveness and applicability of the developed model.
Nanostructuring of a silicon surface by laser redeposition of Si vapor
Authors: Lugomer S. , Maksimović A. , Karacs A. , Toth A. L.
Published: December 2009

We report on the surface nanostructuring of silicon wafer by self-organization of redeposited Si nanoparticles, at various energy levels, in the vaporization regime of laser-matter interaction. By using the semiconfined configuration, a quasi-two-dimensional turbulent Si vapor field with gradients of pressure and temperature is formed. The turbulent field evolves into point vortices which condense into Si nanodroplets. At a low laser energy of ∼1.2 J (0.23 GW/cm2), the inertial instability of nanodroplets under gradients of pressure and temperature, cause their intermittent accumulation in the low-pressure regions of turbulent field. The solidification of Si nanodroplets into particles and their redeposition, cause a simple two-dimensional low density nanostructuring of Si wafer in the near periphery region, and a high density nanostructuring in the periphery region of the spot. The pattern of redeposited Si nanoparticles in these regions is equivalent to the pattern of point vortices in a two-dimensional turbulent field. Such a pattern of point vortices is obtained by numerical simulation from the two-dimensional Navier–Stokes equation for forced turbulence. The self-organization of the coherent point vortex pattern is generated by numerical simulation of the solitary turbulence model based on the nonlinear Schrödinger equation. At the high laser energy of ∼1.5 and ∼2.0 J (∼0.42 and ∼0.52 GW/cm2, respectively), the transition from simple intermittent two-dimensional nanoparticle organization into a continuous and more complex one takes place. The nanostructured pattern shows a continuous distribution of Si particles, whose size increases from the periphery toward the center without spatial intermittency, showing a gradient of particle size. In addition, the open and closed loops chain clusters appear, with morphology and fractal dimension similar to the chain clusters which grow according to the Meakin–Jullien model of cluster-cluster aggregation. At the higher power density of ∼0.52 GW/cm2, the chain clusters become connected and tend to compactification. They form a network similar to the one obtained by numerical simulation of two-dimensional turbulence at small Stokes numbers. The silicon surface nanostructured by recondensation in this case comprises only the nanometer sized particles.
Magnetic and transport properties of diluted granular multilayers
Authors: Silva H. G. , Gomes H. L. , Pogorelov Y. G. , Pereira L. M. C. , Kakazei G. N. , Sousa J. B. , Araújo J. P. , Mariano J. F. L. , Cardoso S. , Freitas P. P.
Published: December 2009

The magnetic and transport properties of Co80Fe20(t)/Al2O3(4 nm) multilayers with low nominal thicknesses t=0.7 and 0.9 nm of Co80Fe20 granular layers are studied. Magnetic studies find a superparamagnetic state above the blocking temperature Tb (of field-cooled/zero-field-cooled splitting) that grows with t and decreases with H. The low-voltage Ohmic tunnel transport passes to non-Ohmic I∝V3/2 law for applied fields above ∼500 V/cm. At fixed V, the temperature dependence of conductance reveals an anomalous dip around ∼220 K, which can be attributed to the effect of surface contamination by supercooled water. Current-in-plane tunnel magnetoresistance (MR) ratio tends, at lower t, to higher maximum values (∼8% at room temperature) but to lower field sensitivity. This may indicate growing discorrelation effect (e.g., between shrinking areas of correlated moments) in this regime and corroborates the deficit of granule magnetization estimated from the Inoue–Maekawa MR fit, compared to that from direct magnetization measurements. MR displays a mean-field-like critical behavior when t approaches the point of superparamagnetic/superferromagnetic transition (tc∼1.3 nm at room temperature) from below, different from the formerly reported percolationlike behavior at approaching it from above. With growing temperature, MR reveals, beyond the common decrease, an anomalous plateau from Tb∼30–50 K up to some higher value T∗∼150–200 K, not seen at higher t.
Multicarrier conduction and Boltzmann transport analysis of heavy hole mobility in HgCdTe near room temperature
Authors: Murthy Oruganty V. S. N. , Venkataraman V. , Sharma R. K. , Vurgaftman I. , Meyer J. R.
Published: December 2009

Magnetotransport measurements in pulsed fields up to 15 T have been performed on mercury cadmium telluride (Hg1−xCdxTe, x∼0.2) bulk as well as liquid phase epitaxially grown samples to obtain the resistivity and conductivity tensors in the temperature range 220–300 K. Mobilities and densities of various carriers participating in conduction have been extracted using both conventional multicarrier fitting (MCF) and mobility spectrum analysis. The fits to experimental data, particularly at the highest magnetic fields, were substantially improved when MCF is applied to minimize errors simultaneously on both resistivity and conductivity tensors. The semiclassical Boltzmann transport equation has been solved without using adjustable parameters by incorporating the following scattering mechanisms to fit the mobility: ionized impurity, polar and nonpolar optical phonons, acoustic deformation potential, and alloy disorder. Compared to previous estimates based on the relaxation time approximation with outscattering only, polar optical scattering and ionized impurity scattering limited mobilities are shown to be larger due to the correct incorporation of the inscattering term taking into account the overlap integrals in the valence band.
Influence of the electronic states anisotropy on the band gap pressure coefficient of InxGa1−xN alloys
Authors: Shi L. , Xu K. , Xiong K. L. , Yang H. , Ni J.
Published: December 2009

Using the first-principle methods, we investigate the structural and electronic properties of the wurtzite InxGa1−xN (0<x<1) alloys under hydrostatic pressure. We find that the pressure coefficient decreases with the In concentration and becomes constant when the In concentration is higher than some critical value, which is in agreement with experimental results. Our calculations demonstrate that the axial ratio c/a of InxGa1−xN increases with the hydrostatic pressure when x<0.25, while it decreases when x>0.25. The densities of px and py orbitals are higher than that of pz orbital at the valence band top. This anisotropy induces the pronounced bowing of the pressure coefficient.
A study on the orientation relationship between the scallop-type Cu6Sn5 grains and (011) Cu substrate using electron backscattered diffraction
Authors: Zou H. F. , Yang H. J. , Zhang Z. F.
Published: December 2009

The wetting reaction between molten Sn and (011) Cu single crystal was investigated. Based on the electron backscattered diffraction technique, the preferential orientation relationships between the scallop-type Cu6Sn5 grains and (011) Cu single crystals were detected. The strong texture of Cu6Sn5 grains was formed on the normal direction although the Sn/(011) Cu couple was aged at 170 °C for 40 days. This indicates that the Cu6Sn5 grains do not desultorily form on the (011) Cu substrate for these scallop-type Cu6Sn5 grains.
Biosensors using the Si nanochannel junction-isolated from the Si bulk substrate
Authors: Ahn Chang-Geun , Park Chan Woo , Yang Jong-Heon , Ah Chil Seong , Kim Ansoon , Kim Tae-Youb , Yu Han Young , Jang Moongyu , Kim Sang-Hoon , Baek In-Bok , Lee Seongjae , Sung Gun Yong
Published: December 2009

The biosensor using a silicon nanochannel field effect transistor has been developed on the basis of a bulk silicon substrate instead of an expensive silicon-on-insulator material, for low cost applications. “Top-down” fabricated Si nanochannels for detecting prostate specific antigen (PSA) are electrically isolated from the bulk Si substrate only by a reverse-biased p-n junction with very low reverse leakage currents. The reverse leakage current flowing through the p-n junction is small enough to be ignored, when compared with the current flowing through the p-type Si channel; roughly 100 times lower. The surface immobilization of anti-PSA has been confirmed by the specific binding test of DNA stabilized Au nanoparticles (NPs), showing 1200 NPs/μm2 and atomic force microscopy surface analysis. The injection of 10 ng/ml PSA solutions leads to a clear increase in the conductance of Si nanochannels, indicating the specific binding of PSA with the immobilized anti-PSA. The similar signal changes were observed on the injection of the 1 pg/ml PSA, very low concentration of PSA.
Mn incorporation induced changes on structure and properties of N-doped ZnO
Authors: Wu Kongping , Gu Shulin , Tang Kun , Zhu Shunming , Xu Mingxiang , Zhang Rong , Zheng Youdou
Published: December 2009

The influences of Mn doping on the electrical and optical properties of the Zn1−xMnxO:N films have been investigated. Mn incorporation occupying on the Zn site has led the lattice constants and the bandgap of the films increased with the structural quality deteriorated. The electrical properties have been found to change significantly with the content of Mn in the films, due to the changes in the amount of the NO acceptors and CN compensation centers formed in the films by Mn incorporation as revealed by x-ray photoelectron spectrometry measurements. The chemical states of Mn have been identified as Mn2+ and Mn4+, corresponding to Mn occupying on the Zn site and MnO2 second phase, respectively. The conductive type and the Mn2+ content of the films show a strong effect on the magnetic properties, which can be explained from the theoretical predication on the Mn 3d and N 2p ferromagnetic (hole) coupling on the ferromagnetism. However, uncompensated spins from nonuniform distribution of Mn atoms in ZnO may also be responsible for the observation of ferromagnetism signature at least on the high resistant samples.
MgB
2
superconductors with abnormally improved Jc sintered after autoxidation of milled original powders
Authors: Ma Zongqing , Liu Yongchang , Huo Jie , Gao Zhiming
Published: December 2009

An autoxidation treatment of short-time milled original powders was introduced for the synthesis of MgB2 superconductors and the critical current density Jc of the sintered MgB2 bulks was measured. It is unusually found that the undoped MgB2 bulks sintered with those autoxided milled original powder exhibit abnormally excellent Jc (above 1×104 A cm−2 even at 3.5 T, 20 K). Combined with the investigation of sintering process, it was found that the autoxidation treatment of the milled powders affects the subsequent sintering process dramatically and finally leads to the formation of MgB2 nanocrystalline with lots of dislocation and self-generated MgO nanoinclusions embedded in them. This unique microstructure brought up a significant improvement of Jc at high fields. Besides, the formation mechanism of this unique microstructure during the sintering process was also discussed in detail. It suggested that the MgO preformed by the reaction between Mg and B2O3 in the interface between Mg particles and B particles might serve as nuclei for the heterogeneous nucleation of the MgB2 phase and finally be included in the MgB2 grains as they grew up. The present method provides possible windows for the development of practical MgB2 superconductors without adopting expensive nanodopants.