bluuebunny/crossref_metadata_2025 huggingface dataset:
‘Jaguda boys’: pickpocketing in Ibadan, 1930–60
Authors: Heap Simon
Published: February 2009

By examining the development of pickpocketing by juveniles (jagudain Yoruba) in the later colonial era, the paper provides important information on popular urban society in the most populous city in Nigeria and tropical Africa: Ibadan. Representations of the urban experience for a group of criminally-minded citizens are detailed through explorations of street-life, public order, citizenry and neighbourhood reactions. It contributes to the emerging literature on urban patterns in colonial Africa, especially the growth of non-ethnic associations among the lower orders. The resistance of pickpockets to powerful attempts to inculcate conformist modes of behaviour through indigenous and colonial agencies of control and manipulation is highlighted. Both authority systems failed to tackle the problem of street crime beyond the banishment of offenders – a superficial, short-term solution to a well-rooted deviant urban youth culture.
Rebuilding the Chinese capital: Beijing in the early twentieth century
Authors: Shi Mingzheng
Published: February 2009

This paper studies the evolution of urban form in both physical and social manifestations through an examination of the transformation of the Chinese capital from a planned imperial city into a modern metropolis in the early twentieth century. The newly created municipal government sought to modernize Beijing through public works to improve the old urban infrastructure. Consequently, city walls and gates were reconfigured; streets were paved, widened and expanded; and new rules of urban planning and zoning were introduced. Reflecting changes in political power relations, the modernist transformation in the urban built environment was evidently brought about by a combined force of Western influences and Chinese indigenous developments, especially by a shift in ideological allegiance from imperial authority to people's rights, by the state's increasing intervention in urban affairs, and by new technologies transmitted from the West.
Civil society and the nature of urbanism: Britain, 1750–1850
Authors: Morris R.J.
Published: February 2009

The concept of civil society provides a useful means of evaluating the social and political relationships of British towns. Civil society refers to the non-prescriptive relationships that lie between the state and kin. Such relationships are associated with the existence of the free market, the rule of law and a strong voluntary associational culture. Both theoretical analysis and historical evidence link civil society with the nature of urban places, their complexity, their function as a central place and their operation as a focus for flows of information. Between 1780 and 1820 the agencies of civil society in Britain provided an arena for making choices, for reasoned informed debate and for the collective provision and consumption of services in an open and pluralist manner.
Civil society, municipal government and the state: enshrinement, empowerment and legitimacy. Scotland, 1800–1929
Authors: Morton Graeme
Published: February 2009

Civil society remains the most challenging and all-pervading of concepts, yet too rarely is it examined empirically. The potential of civil society is that it better allows understanding of local political structures as well as cross-class associational activity. Its alternatives, while many, are principally ‘public life’ and ‘influence’, both of which have their own highly respected traditions. It is argued here that civil society offers a powerful analysis of structure and action in the urban world, and that it is one mediated by municipal government. To operationalize this definition, this article will introduce three further concepts: ‘enshrinement’, ‘empowerment’ and ‘legitimacy’. Each of these is linked to the relationship of the municipal state with that at Westminster, the formal mechanism through which the stability of civil society in nineteenth-century Britain was negotiated.
Property titles and the use of British urban poll books for social analysis
Authors: Morris R. J.
Published: February 2009

The poll books produced before the Ballot Act of 1872 are a major source for political and social history. Those which have an occupational title for most or all entries have been increasingly used since Vincent's pioneering work. Others have been linked to other sources so that voting can be related to occupation. This is either time-consuming or expensive and often both. The alternative is a very selective sampling tactic guided by the directories. The use of occupational titles has been criticized because of the lack of social homogeneity within the groups designated by such titles. This is slightly unfair but a relevant warning against using such titles to do more analytical work than the meaning of the titles justifies. Those who want a more precise measure of status must link with the rate books and the census manuscripts.
Did urbanization secularize Britain?
Authors: Brown Callum G.
Published: February 2009

There are few issues in British history about which so much unsubstantiated assertion has been written as the adverse impact of industrial urbanization upon popular religiosity. Urban history undergraduates are plied each year with the well-worn secularizing interpretation of urban growth which emanated with the Victorians (mostly churchmen) and which has since been reassembled by modern investigators in forms suitable for digestion in ecclesiastical history, social history (Marxist and non-Marxist), historical sociology, and historical geography. This ‘pessimist’ school of thought has reigned virtually unchallenged since the nineteenth century, giving rise in its endless repetition to simplistic historiographical myths. Arguably, systematic inquiry has suffered because modern urban society has been regarded as inimical to religion.

An important start to disentangling the web of confusion has already been made by Jeff Cox in his admirable but underratedThe English Churches in a Secular Society, a study of Lambeth between 1870 and 1930. 'In the first and final chapters of that book, Cox commenced the assault on the ‘pessimist’ school, pointing out in necessarily blunt language the illogicality and empirical weakness in the arguments of many historians and sociologists of religion. That book should have a reserved space on every reading list dealing with this issue. The present article attempts to expand on what might be called the ‘optimist’ school of thought concerning the impact of urbanization upon religion: that the churches survived urbanization in the eighteenth and nineteenth centuries. While Cox adduced from his research on the 1870–930 period that the great decline of the churches had not occurred before then, the following pages shift the focus to a reassessment of of the evidence on the preceding 100 years.
Town histories and Victorian plaudits: some examples from Preston
Authors: Vickery A. J.
Published: February 2009

Charles Dickens visited Preston in January 1854 to report on the cotton lock-out of that year. What he saw contributed to his vision of the archetypal northern, urban industrial centre, Coketown:

It was a town of red brick or of brick that would have been red if the smoke and ashes had allowed it; but as matters stood it was a town of unnatural red and black like the painted face of a savage. It was a town of machinery and tall chimneys, out of which interminable serpents of smoke trailed themselves forever and ever and never got uncoiled.

Three years later a rather different topographical account appeared in Charles Hardwick's history of the borough:

Notwithstanding the occasional carpings of a few splenetic travellers, Preston is generally and deservedly recognized as one of the cleanest and most pleasantly situated manufacturing towns in England. The cotton factories are chiefly erected to the north and east of the old aristocratic borough …. and do not as yet materially interfere with the more ‘fashionable’ or picturesque sections of the district.

The contrast illuminates the shortcomings of the town history both as literature and historical geography; but indicates the tenor of Prestonian self-justification. It is precisely this prosaic subjectivity which makes the histories a rich source. As Peter Clark asserts, ‘even fifth-rate urban historians sometimes have an important story to tell.’

Unlike many other towns with long-established traditions of urban chronicling, history writing in Preston did not blossom until the nineteenth century.
Research in urban history: a review of recent theses
Authors: Reeder David
Published: February 2009

The annual number of completed theses which can be reasonably described as having urban themes has remained quite steady in recent years. In the lists of the Institute of Historical Research, for example, it is possible to identify 58 theses as having urban themes in the return for 1985, 41 theses in the 1986 return and 50 theses in that for 1987. It is true that in many cases such theses are not written as contributions to urban history specifically, but nevertheless they can provide much useful information and new insights on urban processes and town life even when the urban aspect of the study is incidental to the main theme. This is especially true of the selection made for this year's review which focuses more than usually on theses concerned directly or indirectly with aspects of urban society and politics in the past, and with a particular emphasis on the history of the urban working class. The review covers mostly theses completed in 1986–7 with some late additions from earlier years. It is based necessarily on the abstracts except for about a third of the theses noticed where it has been possible to examine the text. However, the aim of the review is to indicate the interest which a thesis might have for urban historians rather than to give a comprehensive assessment – which is probablynappropriate for unpublished work.
The Open University Urban Development Course
Authors: Sutcliffe Anthony
Published: February 2009

Although reviews of university lectures and courses have appeared in recent years in student newspapers on some of the more ‘progressive’ campuses of Britain and the U.S., one hopes that the practice will spread no further. Valuable though the occasional frank comment may be, nothing would normally persuade an academic to pronounce publicly on the content and presentation of a colleague's course. It was therefore with much hesitation that I agreed to follow the Open University's new course on Urban Development, and for a long time I was uncertain of my own ethical position in attempting to ‘review’ it. That this article should appear at all is the product of two considerations. Firstly, a course which is freely broadcast on radio and television can perhaps make less claim to confidentiality than a traditional university lecture course. Secondly, and this is much more important, the Urban Development course is generally so impressive that I have little but good to say of it, and with the Open University still something of a dirty word in traditional university circles, its successes deserve to be acknowledged.
Chester ceremonial: re-creation and recreation in the English ‘medieval’ town
Authors: Mills David
Published: February 2009

During the last two decades the interests of scholars of early drama and of urban historians have found common ground in the study of urban celebration and ceremonial. For the student of early drama the beginnings of this interest coincided with a redefinition of the area and nature of the study of early drama, a shift in emphasis from the textual and literary problems of the few extant dramatic texts to the circumstances and conditions of their performance. Signalled in the mid-1950s by F.M. Salter's revealing study of the production of Chester's Whitsun plays, this movement gained impetus from Glynne Wickham's investigations of the development of English stagecraft between 1300 and 1660, the first volume of which appeared in 1959, which illustrated the interdependence of a range of ostensibly disparate activities, such as plays, royal entries and tournaments. Then, in the 1970s an iconoclastic challenge to traditional theories about the staging of mystery plays was mounted by Alan H. Nelson, drawing upon various local records, and from the resulting controversies was born a new initiative, the Records of Early English Drama, whose avowed purpose is ‘to find, transcribe, and publish external evidence of dramatic, ceremonial, and minstrel activity in Great Britain before 1642’. That series is still ongoing and already constitutes a major primary resource of regional documentary transcripts for all interested in early dramatic and quasidramatic activity, suggesting a hitherto unsuspected diversity and frequency of dramatic activity throughout England.
Liquid Dissimilation in Bavarian German
Authors: Hall Tracy Alan
Published: February 2009

The present study investigates the instability of adjacent liquids in a variety of Southern Bavarian German. The focus is a synchronic process converting /r/ to [d] before or after /l/—a process argued to involve a dissimilation of the phonological feature [liquid], which itself is triggered by a specific OCP constraint, *[liquid][liquid]. In addition to providing evidence for the feature [liquid], the present article also supports a model of segment structure in which the traditional feature [sonorant] is replaced with the privative node [Sonorant Voice] (SV). The Bavarian dialect also displays a number of OCP-motivated constraints that ban other sequences of identical manner features, namely, [continuant], [nasal], [strident].*
The Marking of Gender Agreement Using Derivational Affixes in German and Dutch
Authors: Scott Alan K.
Published: February 2009

The German derivational suffix-inprimarily marks female sex on nouns that denote people. This paper investigates the attachment of the suffix to masculine noun bases that refer back to feminine nouns denoting inanimate referents in the same construction, seemingly as a means of making the gender of the two nouns match. The same phenomenon is also observed in Dutch despite the absence of a masculine/feminine distinction in the standard language. It is argued that the gender matching observed is a form of agreement. Using the evidence of corpus data and other attestations, it is concluded here that, because the inanimate referents of the subject nouns in the constructions involved all appear close to animate referents on animacy hierarchies (that is, they fall just outside the suffix's usual sphere of use), the gender agreement performed by-in(and its Dutch counterparts) is an extension of the suffix's prototypical derivational role, but resembles inflection in some respects and may indicate that the suffix is undergoing grammaticalization.*
A Bayesian network approach to knowledge integration and representation of farm irrigation: 1. Model development
Authors: Wang Q. J. , Robertson D. E. , Haines C. L.
Published: February 2009

Irrigation is important to many agricultural businesses but also has implications for catchment health. A considerable body of knowledge exists on how irrigation management affects farm business and catchment health. However, this knowledge is fragmentary; is available in many forms such as qualitative and quantitative; is dispersed in scientific literature, technical reports, and the minds of individuals; and is of varying degrees of certainty. Bayesian networks allow the integration of dispersed knowledge into quantitative systems models. This study describes the development, validation, and application of a Bayesian network model of farm irrigation in the Shepparton Irrigation Region of northern Victoria, Australia. In this first paper we describe the process used to integrate a range of sources of knowledge to develop a model of farm irrigation. We describe the principal model components and summarize the reaction to the model and its development process by local stakeholders. Subsequent papers in this series describe model validation and the application of the model to assess the regional impact of historical and future management intervention.
North‐south asymmetry in Martian crater slopes
Authors: Parsons R. A. , Nimmo F.
Published: February 2009

The presence of an extensive ice‐rich layer in the near subsurface of the Martian regolith could result in viscous creep responsible for softening of craters at middle and high latitudes. The temperature of ground ice will vary spatially within a crater owing to the effect of slope on the effective angle of insolation. The temperature at a particular latitude will also vary temporally owing to changes in Mars' obliquity. Results from numerical simulations of viscous creep indicate that these temperature variations cause the pole‐facing slopes of craters to be systematically steeper than those of equator‐facing slopes. Crater slopes should be most asymmetric between 25° and 40° latitude, depending on the thickness of the creeping layer. This slope asymmetry predicted from theoretical simulations of regolith creep is not well developed in observed Martian crater topography. Mars Orbiter Laser Altimeter (MOLA) topography of craters 16 to 40 km in diameter was analyzed for north‐south slope asymmetry within seven latitude regions ranging from 60°S to 60°N. On the basis of the lack of any systematic slope asymmetry observed in the craters, we can place a conservative upper limit of ∼150 m on the thickness of the ice‐rich creeping layer assuming a volumetric dust content of ≤70% and an exponentially decreasing regolith porosity with depth. If the creeping layer contains relatively clean ice, then the thickness of ice‐rich material is limited to ∼100 m or less. The observations also suggest that the thickness of this creeping layer is reduced by ∼30% toward the equator. These results imply a global ice‐rich regolith water volume of <∼107 km3, comparable to that proposed for a modest‐sized northern plains ocean.
Forcing of resonant modes on a fringing reef during tropical storm Man‐Yi
Authors: Péquignet A. Christine N. , Becker Janet M. , Merrifield Mark A. , Aucan Jérome
Published: February 2009

Open basin resonant modes have been observed at tidal frequencies on coastal shelves, but their excitation on coral reef platforms has only been suggested. The topography of and water depth over most fringing reefs correspond to resonant periods that are the order of tens of minutes and fall outside of the energetic part of the wave spectrum. During tropical storm Man‐Yi, low frequency near resonant oscillations dominated the variance of the sea surface elevation at the shoreline of Ipan reef, Guam. The excitation of the resonant modes resulted both from a large increase in water level over the reef due to wave setup, which increased the resonant frequencies, and the occurrence of wave group forcing with time scales commensurate with these increased resonant frequencies.
A tropical “NAT‐like” belt observed from space
Authors: Chepfer H. , Noel V.
Published: February 2009

The optical properties of cold tropical tropopause clouds are examined on a global scale, using two years of space‐borne lidar observations from CALIPSO (June 2006–May 2008). The linear depolarization ratio, color ratio and backscatter signal are analyzed in tropical clouds colder than 200 K in a way similar to recent studies of Polar Stratospheric Clouds (PSCs). It is found that the three categories of particles encountered in PSC (Ice, Sulfate Ternary Solutions or STS, and Nitric Acid Trihydrate or NAT) do also occur in tropical cold cloud layers. Particles with optical properties similar to NAT are few, but they cover the tropical belt and represent about 20% of cold cloud tropical particles. The optical behavior of these particles requires them to be small, non‐spherical, optically thin, and persistent in the TTL at temperatures colder than 200 K; NAT particles and very small ice crystals meet these criteria.
Remote sensing of aerosol water uptake
Authors: Schuster Gregory L. , Lin Bing , Dubovik Oleg
Published: February 2009

Aerosol water content is an important component of aerosol radiative forcing, but the effect of water uptake on aerosols throughout the atmospheric column is not monitored at the present time. We present a technique for retrieving the volume fraction of water in atmospheric aerosols, and apply the technique to the AERONET database. We estimate that the volume fraction of water and the geometric hygroscopic growth factor (gHGF) can be retrieved to within 0.3 using this retrieval. The growth factors we obtain are consistent with published measurements, and indicate that aerosol water uptake is high in humid continental regions (gHGF ∼ 1.3 along the U.S. East Coast in August) and low in regions dominated by desert dust (gHGF ∼ 1.04 in Saudi Arabia).
Comparison of model‐simulated and observed currents in the central Adriatic during DART
Authors: Martin P. J. , Book J. W. , Burrage D. M. , Rowley C. D. , Tudor M.
Published: February 2009

Numerical simulations of the Adriatic Sea were performed with the Navy Coastal Ocean Model (NCOM) during the Dynamics of the Adriatic in Real Time (DART) Experiments conducted between October 2005 and September 2006. Grid resolution was 1 km. Model forcing included tides, surface fluxes from the Aire Limitée Adaptation Dynamique Développement International (ALADIN) atmospheric model, relaxation to a daily satellite sea surface temperature analysis, extensive river and runoff discharges, and open boundary conditions south of Otranto specified from a global model. Currents predicted by the model were compared with currents from 12 Acoustic Doppler Current Profiler (ADCP) moorings located along a line between the Gargano Peninsula, Italy, and Split, Croatia. The nontidal comparisons were performed with detided currents. Correlations between the model and ADCP currents were highest in the Western Adriatic Current (WAC), which flows southeastward along the Italian coast. Lowest correlations were in the interior of the Adriatic, likely because of instability processes. Correlations between the ALADIN winds and the model and ADCP currents at the mooring locations were also highest in the WAC. For November 2005 through August 2006, the model and ADCP mean WAC transports were 0.321 and 0.304 Sv, respectively, with a temporal correlation of 0.79. Comparison of current variance showed best agreement near the Italian and Croatian coasts. In the interior, the NCOM current variance compared fairly well with that of the ADCPs for November–January but decreased significantly relative to the ADCPs for February–August. Spectral analyses indicate most of the difference in variance to be at periods exceeding 2 days.
Monitoring Algal Blooms in a Southwestern U.S. Reservoir System
Authors: Tarrant Philip , Neuer Susanne
Published: February 2009

In recent years, several studies have explored the potential of higher‐resolution sensor data for monitoring phytoplankton primary production in coastal areas and lakes. Landsat data have been used to monitor algal blooms [Chang et al., 2004; Vincent et al., 2004], and Moderate Resolution Imaging Spectroradiometer (MODIS) 250‐meter and Medium Resolution Imaging Spectrometer (MERIS) full‐resolution (300‐meter) bands have been utilized to detect cyanobacterial blooms [Reinart and Kutser, 2006] as well as to monitor water quality [Koponen et al., 2004].
Applying Geodesy to the Spectrum of Geosciences 2008 UNAVCO Science Workshop; Boulder, Colorado, 10–13 March 2008
Authors: Miller M. Meghan
Published: February 2009

In March 2008, 190 scientists attended an international workshop in Colorado sponsored by UNAVCO to explore research and education advances in geodesy and its spectrum of applications in geosciences. The meeting featured groundbreaking science that resulted from recent innovation, including solid Earth applications as well as emerging research focusing on the cryosphere and atmosphere, with plenary sessions on polar science and glacier dynamics, geodetic monitoring of natural hazards, seismic‐cycle geodesy, and magmatic systems.
Entropy behavior in cluster melting
Authors: Berry R. Stephen , Smirnov Boris M.
Published: February 2009

We analyze the configurational excitation of a cluster for both a microcanonical and a canonical ensemble of atoms and apply this analysis to the Lennard-Jones cluster of 13 atoms. Dividing the cluster excitations into configurational and thermal classes, we evaluate the anharmonicity coefficient of atomic vibrations and the entropy jump as a function of temperature on the basis of computer simulations of the Lennard-Jones 13-atom cluster as a canonical and a microcanonical ensemble of atoms. This analysis shows the role of anharmonicity of atomic vibrations and exhibits the importance of the temperature dependence of the entropy jump in the range of phase coexistence for cluster thermodynamics.
Finite element analysis for cooling effect of magnetic fluid with alternating magnetic field
Authors: Lee Se-Hee , Kim Young-Sun
Published: February 2009

We present a fully coupled finite element method (FEM) for analyzing a cooling effect of magnetic fluid with an alternating magnetic field driven with the power frequency, 60 Hz. There are two different heat sources with an alternating magnetic field such as the Joule’s loss in coils excited with electric input and the power dissipation corresponding to Neel and Brownian relaxation. Because the input frequency is relatively low, the Joule’s loss in coil is a dominant heat source. The heat, therefore, transfers from the coil to the magnetic fluid and the natural convection phenomena arise on the coil surfaces. To consider the natural convection phenomena, the buoyant force density was considered in a magnetic fluid. Additionally, the forced convection, magnetoconvection, results from the magnetic body force density with the magnetization as a function of magnetic field intensity and temperature. These two convection phenomena play a key role for cooling effect of magnetic fluid with an alternating magnetic field. To derive the magnetic body force density, we, here, numerically employed the continuous approach of Kelvin force density, which has been derived by introducing the virtual air-gap scheme incorporating with the FEM. The Langevin function was employed to consider the nonlinear magnetic susceptibility for evaluating the Kelvin force density and the power dissipations due to the Neel relaxation and Brownian relaxation.
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Mössbauer spectroscopy investigation of Nd3Cu4Sn4, Nd3Ag4Sn4, and Ho3Cu4Sn4
Authors: Voyer C. J. , Ryan D. H. , Cadogan J. M.
Published: February 2009

Nd 3 Cu 4 Sn 4 , Nd3Ag4Sn4, and Ho3Cu4Sn4 have been studied using S119n Mössbauer spectroscopy. Contrary to recent neutron diffraction data, Nd3Cu4Sn4 shows a clear magnetic signal at 1.6 K and has an ordering temperature of 2.0(1) K. Nd3Ag4Sn4 orders at 4.8(1) K, in agreement with neutron diffraction measurements. We observe the ordering of the Ho 2d sublattice in Ho3Cu4Sn4 at 8.2(1) K but we also see some residual magnetic splitting up to 10.5(2) K, which was not previously detected by neutron scattering.
Enhancement of tunneling magnetoresistance by optimization of capping layer thicknesses in CoFeB/MgO/CoFeB magnetic tunnel junctions
Authors: Pong Philip W. T. , Egelhoff William F.
Published: February 2009

The main focus of improving the tunneling magnetoresistance (TMR) of magnetic tunnel junctions (MTJs) has been on optimizing the structure and thickness of the MgO barrier layer [Moriyama et al., Appl. Phys. Lett. 88, 222503 (2006); Yuasa et al., Nat. Mater. 3, 868 (2004)]. However, in this paper, we found that the thicknesses of the capping layers also play an important role in TMR. We studied the influence of the capping layers above the CoFeB/MgO/CoFeB. It was intuitively believed that these capping layers did not affect the TMR because they were deposited after the critical CoFeB/MgO/CoFeB structure. Surprisingly, we found that the thicknesses of the capping Ta and Ru layers have significant influence on the TMR. The stress or strain applied onto the MgO barrier by these capping layers appear to be responsible. The results in this paper shed light on optimizing TMR of MgO MTJs.
Tunneling time of spin particle determined by the spin precession method in the Dresselhaus spin orbit semiconductor system
Authors: Wan F. , Jalil M. B. A. , Tan S. G.
Published: February 2009

We determine the traversal time τ of electrons through a semiconducting barrier by relating it to the precession of its spin due to Dresselhaus spin orbital effect. The precessional angle is obtained by performing a unitary transformation of the spin axis to the effective spin orbit coupling field and determining the change in phase of the transmitted wave function. The calculated τ exhibits counterintuitive trends with respect to barrier geometry and electron energy. The proposed clocking method based on the Dresselhaus effect might have practical advantages over the applied field and simplify experimental efforts to investigate electron tunneling in semiconductor materials.
Electrical transport and magnetism in Mo-substituted R2Ti3Ge4 (R=Tb,Er) compounds
Authors: Nirmala R. , Nagamanasa K. Hima , Bhobe P. A. , Lamsal Jagat , Nigam A. K.
Published: February 2009

The effect of Mo substitution at Ti site of orthorhombic Sm5Ge4-type R2Ti3Ge4 compounds on the magnetic and electrical transport properties has been studied. The Tb2Ti3−xMoxGe4 (x=0.3,0.75) and Er2Ti2.7Mo0.3Ge4 compounds have been synthesized and it is found that these compounds retain parent crystal structure at room temperature (space group Pnma, No. 62). Mo substitution decreases the antiferromagnetic ordering temperature (TN) of Tb2Ti3Ge4 compound from ∼18 to ∼13 and ∼10 K, respectively, for x=0.3 and 0.75. The Er2Ti2.7Mo0.3Ge4 compound shows a tendency to order at ∼2 K, whereas the parent Er2Ti3Ge4 is magnetically ordered at 3 K. Magnetization versus field data of Tb2Ti3−xMoxGe4 (x=0.3,0.75) reveal soft ferromagnetic nature. The metamagnetic transition that is present in parent Tb2Ti3Ge4 is found to disappear with Mo substitution. Magnetization value reaches ∼6.2μB/Tb3+ at 2 K in fields of 8 T, indicating incomplete ferromagnetic ordering with or without an antiferromagnetic component. Electrical resistivity of the Tb-based compounds has a linear variation with temperature from 300 to ∼50 K and shows a prominent slope change at temperatures much above TN, supporting the presence of competing short range ferromagnetic interactions.
Low damping constant for Co2FeAl Heusler alloy films and its correlation with density of states
Authors: Mizukami S. , Watanabe D. , Oogane M. , Ando Y. , Miura Y. , Shirai M. , Miyazaki T.
Published: February 2009

Gilbert damping for the epitaxial Co2FeAl Heusler alloy films was investigated. Gilbert damping constant for the films was evaluated by analyzing the data of ferromagnetic resonance measured at the frequency of 2–20 GHz. Gilbert damping constant for the film without annealing was rather large, while it decreased remarkably with postannealing. Gilbert damping constant for the film annealed at 600 °C was ≃0.001. These behavior of Gilbert damping constant can be well explained by the fact that the density of states calculated from first principles decreases with increasing the degree of B2 order.
Quantum dynamics of hydrogen interacting with single-walled carbon nanotubes
Authors: McAfee Jason L. , Poirier Bill
Published: February 2009

We perform spin-polarized density functional theory calculations for a hydrogen atom interacting exohedrally with a (5,5) single-walled carbon nanotube (SWNT). We also perform full three-dimensional (3D) quantum dynamics calculations of the H atom bound rovibrational states. We initially focus on the four sites of highest symmetry, along which we compute potential energy surface (PES) values at 33 separate, nonuniformly spaced radial values. These 132 geometries are sufficient to define the primary potential interaction regions. We find a weak physisorptive region between 2.5 and 3.5 Å from the SWNT wall, with a maximum well depth of 51 meV, relative to the desorption limit. We also find a chemisorptive region, extending from about 1.0 out to 1.5 Å from the SWNT wall. The maximum well depth of 0.755 eV occurs at 1.15 Å from the SWNT wall, nearly directly above a carbon atom. A small barrier of 54 meV lies between these two binding regions. There are also two types of transition states that lie between adjacent chemisorption wells. In addition to the high-symmetry sites, a detailed and accurate characterization of the PES requires density functional theory calculations along a large number of interstitial sites—18 in all. Using these 18×33 geometries, and exploiting the full D10h symmetry of the system, we fit a global analytical PES, using a Fourier basis in the cylindrical coordinates, with radially dependent expansion coefficients (rms error 3.8 meV). We then perform a mixed spectral basis/phase-space optimized discrete variable representation calculation of all bound rovibrational H atom eigenfunctions and energy levels. We also discuss ramifications for the possible use of SWNTs as hydrogen storage devices.
Particle blocking and carrier fluid freezing effects on the magnetic properties of Fe3O4-based ferrofluids
Authors: Morales M. B. , Phan M. H. , Pal S. , Frey N. A. , Srikanth H.
Published: February 2009

We report the systematic dc and ac susceptibility studies on the particle blocking and carrier fluid freezing effects on the magnetization and relaxation processes in two different ferrofluids composed of Fe3O4 nanoparticles (mean size of ∼14 nm) suspended in hexane and dodecane, which respectively have freezing temperatures below (178 K) and above (264 K) the blocking temperature of magnetic nanoparticles (∼200 K). Experimental results reveal that these effects play a key role in the formation of glasslike peaks and magnetic anomalies in ferrofluids. Quantitative fits of the frequency dependent ac susceptibility to the Vogel–Fulcher model τ=τo exp[Ea/k(T−To)] clearly indicate that the blocking of magnetic nanoparticles in the frozen state significantly affects the interparticle dipole-dipole interaction, causing characteristic spin-glass-like dynamics.
Achieving control of in-plane elastic waves
Authors: Brun M. , Guenneau S. , Movchan A. B.
Published: February 2009

We derive the elastic properties of a cylindrical cloak for in-plane coupled shear and pressure waves. The cloak is characterized by a rank 4 elasticity tensor with spatially varying entries, which are deduced from a geometric transform. Remarkably, the Navier equations retain their form under this transform, which is generally untrue [G. W. Milton et al., N. J. Phys. 8, 248 (2006)]. The validity of our approach is confirmed by comparison of the analytic Green’s function in homogeneous isotropic elastic space against full-wave finite element computations in a heterogeneous anisotropic elastic region surrounded by perfectly matched layers.
Magnetic properties of macroscopic colloid crystals of silica-coated FePt nanoparticles with controllable interstices for molecular separation
Authors: Lo Chester C. H. , Tsang Shik Chi , Yu Chih H. , Tam Kin
Published: February 2009

This paper reports on the magnetic properties of macroscopic colloidal crystals comprising silica-encapsulated FePt nanoparticles which assembled into three dimensional regular arrays by magnetic crystallization. The crystals have potential for magnetic separation of paramagnetic chemical or biochemical entities (e.g., proteins) by providing local magnetic fields at the interstitial sites to promote magnetic retention of the entities of interest. Structural characterizations by transmission electron microscopy and small angle x-ray scattering using a synchrotron source indicate a hcp arrangement of the nanoparticles in the colloidal crystals. The crystals have a large surface area (110.6 m2 g−1) and a sharp pore size of 15 nm which is adjustable by controlling the silica shell thickness. Under applied fields, the colloidal crystals display substantially stronger magnetic responses than the unaligned particle assembly, thus favoring removal of the colloidal crystals from the mixture by magnetic means after magnetic separation. The potential of the colloidal crystals for separating paramagnetic biological or chemical species is demonstrated in absorption experiments using two proteins with and without a paramagnetic center.
Phase transition and morphology of polydispersed ABA′ triblock copolymers determined by continuous and discrete simulations
Authors: Soldera Armand , Qi Yue , Capehart Weston T.
Published: February 2009

The purpose of this study is to consider the effect of polydispersity in triblock copolymer on its order-to-disorder phase transition and morphology, by supplementing continuous description of polymer indices carried out using random phase approximation by a discrete sampling of the polydispersity performed at the mesoscale level. Both methods confirm that the increase in polydispersity involves a greater stability of the ordered state, in agreement with published data on the effect of polydispersity on diblock copolymers. The morphology simulations reveal that longer blocks are phase segregated and shorter blocks are more or less uniformly distributed throughout the polymer. It is proposed that avoiding very short polymer chains will increase the degree of phase segregation, thus improve the mechanical and conductive properties of proton exchange membrane more efficiently.
Density functional theories of surface interactions in salt solutions
Authors: Forsman Jan
Published: February 2009

Most current density functional theories rely upon the presence of hard cores, also between ions of like charge. These hard cores should in principle reflect exchange repulsion. However, by the way in which these theories are formulated, the hard cores effectively determine the range of ion-ion correlations. This is because the mutual repulsion between like-charged ions is truncated below the corresponding hard sphere diameter. In most relevant applications, at least those related to ion correlations and surface forces in colloidal dispersions, exchange repulsion between like-charged ions is unimportant. This can easily be demonstrated by simulations. Unfortunately, the hard cores can in practice serve as fitting parameters in calculations with traditional density functional theory. In this work, we present alternative density functional theories to describe aqueous salt solutions. In these approaches, an approximation of the relevant “Coulomb hole” that results from correlations between like-charged ions is calculated for the system under study. Hence, our theories are completely free from fitting parameters, and the results are appropriately insensitive to the exchange repulsion acting between ions of like charge. The theories are evaluated by comparing predictions with simulation data, with an emphasis on ion correlations and surface interactions.
High frequency dynamics in liquids and supercritical fluids: A comparative inelastic x-ray scattering study
Authors: Bencivenga F. , Cunsolo A. , Krisch M. , Monaco G. , Ruocco G. , Sette F.
Published: February 2009

The microscopic dynamics of four prototype systems (water, ammonia, nitrogen, and neon) across the critical temperature has been investigated by means of high-resolution inelastic x-ray scattering. The experimental line shape has been described using a model based on the memory function formalism. Two main relaxations, the thermal and the structural one, were observed in all the investigated systems. We found that the microscopic mechanism driving the structural relaxation clearly changes, being mainly governed by intermolecular bond rearrangements below the critical temperature and by binary collisions above it. Moreover, we observed that the relative weight of the thermal relaxation systematically increases on approaching the critical temperature, thus allowing for the observation of a transition from an adiabatic to an isothermal regime of sound propagation. Finally, we found the presence of an additional instantaneous relaxation, likely related to the coupling between collective vibrational modes and intramolecular degrees of freedom.
Predicting the thermal conductivity of inorganic and polymeric glasses: The role of anharmonicity
Authors: Shenogin Sergei , Bodapati Arun , Keblinski Pawel , McGaughey Alan J. H.
Published: February 2009

The thermal conductivity of several amorphous solids is numerically evaluated within the harmonic approximation from Kubo linear-response theory following the formalism developed by Allen and Feldman [Phys. Rev. B 48, 12581 (1993)]. The predictions are compared to the results of molecular dynamics (MD) simulations with realistic anharmonic potentials and to experimental measurements. The harmonic theory accurately predicts the thermal conductivity of amorphous silicon, a model Lennard-Jones glass, and a bead-spring Lennard-Jones glass. For polystyrene and amorphous silica at room temperature, however, the harmonic theory underestimates the thermal conductivity by a factor of about 2. This result can be explained by the existence of additional thermal transport via anharmonic energy transfer. More surprisingly, the thermal conductivity of polystyrene and amorphous silica at low temperature (MD and experimental) are significantly below the predictions of the harmonic theory. Potential reasons for the failure of the harmonic theory of disordered solids to predict the thermal conductivity of glassy polymers are discussed.
Influence of dimensionality on thermoelectric device performance
Authors: Kim Raseong , Datta Supriyo , Lundstrom Mark S.
Published: February 2009

The role of dimensionality on the electronic performance of thermoelectric devices is clarified using the Landauer formalism, which shows that the thermoelectric coefficients are related to the transmission, T(E), and how the conducting channels, M(E), are distributed in energy. The Landauer formalism applies from the ballistic to diffusive limits and provides a clear way to compare performance in different dimensions. It also provides a physical interpretation of the “transport distribution,” a quantity that arises in the Boltzmann transport equation approach. Quantitative comparison of thermoelectric coefficients in one, two, and three dimensions shows that the channels are utilized more effectively in lower dimensions. To realize the advantage of lower dimensionality, however, the packing density must be very high, so the thicknesses of the quantum wells or wires must be small. The potential benefits of engineering M(E) into a delta function are also investigated. When compared with a bulk semiconductor, we find the potential for ∼50% improvement in performance. The shape of M(E) improves as dimensionality decreases, but lower dimensionality itself does not guarantee better performance because it is controlled by both the shape and the magnitude of M(E). The benefits of engineering the shape of M(E) appear to be modest, but approaches to increase the magnitude of M(E) could pay large dividends.
Experimental characterization and modeling of the contact resistance of Cu–Cu bonded interconnects
Authors: Leong H. L. , Gan C. L. , Made R. I. , Thompson C. V. , Pey K. L. , Li H. Y.
Published: February 2009

The effects of the surface roughness and applied loads on the specific electrical contact resistance of three-dimensional Cu–Cu bonded interconnects have been quantitatively investigated. Wafer-level thermocompression bonding was carried out on bonded Cu layers with either different surface roughness at a certain load or with similar surface roughness at different applied loads. Experimental results show that as the surface roughness of the Cu bonding layer increases or as the bonding load decreases, the specific contact resistance of the bonded interconnects increases. A model is presented which quantifies the relationship between the specific contact resistance and the true contact area (which is a function of the surface roughness and applied load). Through the true contact area, the integrity of a bonded interface may be predicted from the electrical measurement of the contact resistance.
Atomic structure imaging of L1-type FePd nanoparticles by spherical aberration corrected high-resolution transmission electron microscopy
Authors: Sato Kazuhisa , Konno Toyohiko J. , Hirotsu Yoshihiko
Published: February 2009

The atomic structure of FePd nanoparticles has been studied by spherical aberration (Cs) corrected high-resolution transmission electron microscopy. The periodic arrangement of atoms arising from chemical order is clearly seen as bright contrast due to the small negative value of corrected Cs. The amount of optimal defocus (Scherzer defocus) is markedly reduced by the small Cs value. The interface between crystalline particles and the amorphous matrix can also be observed, free of imaging artifacts, at a small defocus value. The reconstructed phase image directly shows the projected potential distribution within the specimen and reveals the elemental differences due to chemical order. The clear-cut long-range order is lost when particle size is smaller than about 5 nm, at which locally ordered mixed-phase particles begin to dominate.
Horseshoes for coupled discrete nonlinear Schrödinger equations
Authors: Shieh Shih-Feng
Published: February 2009

In this paper, we study the spatial disorder of coupled discrete nonlinear Schrödinger (CDNLS) equations with piecewise-monotone nonlinearities. By the construction of horseshoes, we show that the CDNLS equation possesses a hyperbolic invariant Cantor set on which it is topological conjugate to the full shift on N symbols. The CDNLS equation exhibits spatial disorder, resulting from the strong amplitudes and stiffness of the nonlinearities in the system. The complexity of the disorder is determined by the oscillations of the nonlinearities. We then apply our results to CDNLS equations with Kerr-like nonlinearity. We shall also show some patterns of the localized solutions of the CDNLS equation.
Temperature-dependent fluorescence decay lifetimes of the phosphor Y3(Al0.5Ga0.5)5O12:Ce 1%
Authors: Allison S. W. , Buczyna J. R. , Hansel R. A. , Walker D. G. , Gillies G. T.
Published: February 2009

The decay time of the phosphor yttrium aluminum garnet doped with cerium (YAG:Ce) is temperature dependent. Selective incorporation of gallium into the YAG:Ce matrix permits tuning the temperature at which quenching begins. Also, the size of the phosphor particle and processing method affect this characteristic. We describe one such situation in which the quenching of the combustion synthesized nanophosphor Y3(Al0.5Ga0.5)5O12:Ce 1% was observed from ambient to 125 °C. By signal averaging of laser excited fluorescence, temperature uncertainties ranged from 0.05 to 0.15 °C. The single shot temperature uncertainty at 115 °C was ±3 °C, indicating the feasibility for transient thermometry with response rate exceeding 1 MHz.
Electrical properties of low pressure chemical vapor deposited silicon nitride thin films for temperatures up to 650 °C
Authors: Tiggelaar R. M. , Groenland A. W. , Sanders R. G. P. , Gardeniers J. G. E.
Published: February 2009

The results of a study on electrical conduction in low pressure chemical vapor deposited silicon nitride thin films for temperatures up to 650 °C are described. Current density versus electrical field characteristics are measured as a function of temperature for 100 and 200 nm thick stoichiometric (Si3N4) and low stress silicon-rich (SiRN) films. For high E-fields and temperatures up to 500 °C conduction through Si3N4 can be described well by Frenkel–Poole transport with a barrier height of ∼1.10 eV, whereas for SiRN films Frenkel–Poole conduction prevails up to 350 °C with a barrier height of ∼0.92 eV. For higher temperatures, dielectric breakdown of the Si3N4 and SiRN films occurred before the E-field was reached above which Frenkel–Poole conduction dominates. A design graph is given that describes the maximum E-field that can be applied over silicon nitride films at high temperatures before electrical breakdown occurs.