bluuebunny/crossref_metadata_2025 huggingface dataset:
UNJUST ENRICHMENT AND UNLAWFUL DIVIDENDS: A STEP TOO FAR?
Authors: Tham Chee Ho
Published: April 2005

UNTIL recently, it was widely accepted that a recipient of company distributions such as dividends paid in breach of the requirements of the Companies Act 1985 (“the Act”) could only be made to repay such distributions if he knew of the illegality. Whether one looked to the Act (to wit, section 277) or beyond (to the “knowing receipt”-type liability encountered in Precision Dippings Ltd. v. Precision Dippings Marketing Ltd.), liability required knowledge. In Bairstow v. Queen’s Moat House plc, however, there appears to be the faintest of suggestions that this position may be open for re-examination. This is reinforced by Lord Nicholls’ recent speech in Criterion Properties Plc v. Stratford UK Properties LLC.
CONTRACTUAL PENALTIES IN THE KING’S COURT 1260–1360
Authors: Biancalana Joseph
Published: April 2005

CLAUSES that provided fixed monetary penalties first appeared in English contracts and conveyances in the first decade of the thirteenth century. Rather quickly thereafter penalty clauses came to be used in a wide variety of contracts and conveyances. They were used in (1) agreements over tithes, (2) settlement of disputes, (3) arbitration agreements, (4) agreements to transfer or not to transfer land, (5) marriage property agreements, (6) warranties of title to land, (7) leases, (8) agreements to pay rents and annuities, loans, and in a variety of other transactions. The penalty clause was just another clause in the agreement. At about the middle of the thirteenth century other methods of inserting a penalty clause into an agreement began to be used. A penalty clause could be made part of a recognizance on the plea rolls, the Exchequer rolls, or the Chancery rolls. The recognizance itself could be a penalty to enforce a side agreement. A money bond could serve as a penalty rendered void if the terms of a separate, conditional acquittance were met. A bond or a statute merchant could be given to a third party under an agreement to give the bond or statute merchant to the promisee if the promisor failed to carry out his agreement. By 1348 the penal bond with conditional defeasance endorsed on the back of the bond had been invented.
Rebirth of a Nation: Frederick Douglass as Postwar Founder in Life and Times
Authors: TANG EDWARD
Published: April 2005

In 1875, a year from the upcoming centennial celebrations, Frederick Douglass commemorated the African American presence in the nation's revolutionary past and Reconstruction present. “If … any man should ask me what colored people have to do with the Fourth of July, my answer is ready,” he proclaimed to a black audience in Washington, DC. “Colored people have had something to do with almost everything of vital importance in the life and progress of this great country” from its beginnings in 1776 to its greatest test in 1861 and beyond. Douglass drew upon the Revolution's legacies of liberty and democracy, urging his listeners to meet the challenge of incorporating themselves into the nation's citizenry despite sustained white resistance. Albeit a tall order, he placed this agenda in a broader perspective: “The fathers of this Republic … had their trial ninety-nine years ago. The colored citizens of this Republic are about to have their trial now.” The moment was full of possibilities: African Americans, he emphasized, faced comparable obstacles and hardships much like the founders themselves. Implied too within Douglass's invocation of the revolutionaries was the potential heroism and accomplishments of which African Americans were similarly capable, just as they had proven in the past.
“Created Space”: Mapping America as Poem in Gary Snyder's Mountains and Rivers Without End and Susan Howe's Secret History of the Dividing Line
Authors: SELBY NICK
Published: April 2005

Maps, recent cultural geographers are fond of reminding us, are products of the specific ideology from which they are written. A proper reading of a map, one that attends to it as a cultural product, can discover – even deconstruct – the ideological and cultural assumptions upon which its act of mapping is grounded. For Stephen Daniels and Denis Cosgrove, the metaphor of the map provides a crucially important analytic tool for disentangling the ways in which systems of power may be seen to work within – and through – a text. They note that, under the influence of post-structuralist theory, it has become commonplace to think of a text as a “discursive ‘terrain’ across which ‘sites’ of power may be ‘mapped’.” Clearly, then, cartographic metaphors are useful in discussing literary texts in that they can accommodate an examination of both the overt and covert operations of those texts in their representations of the cultural and ideological landscape from which they are produced. Indeed, to map the world is to make that world readable, to make it familiar; but, like any text – or, in the particular case of this essay, Gary Snyder's poetic sequence Mountains and Rivers Without End (1996) – a map does more than simply describe a discursive terrain. Such descriptions also enact the conditions of their cultural production.
Clockwork Nation: Modern Time, Moral Perfectionism and American Identity in Catharine Beecher and Henry Thoreau
Authors: ALLEN THOMAS
Published: April 2005

The economy of time, and our obligation to spend every hour for some useful end, are what few minds properly realize.
Catharine Beecher, A Treatise on Domestic Economy (1841)

There were times when I could not afford to sacrifice the bloom of the present moment to any work, whether of the head or hands.
Henry David Thoreau, Walden; Or, Life in the Woods (1854)

In his seminal 1967 essay “Time, Work-Discipline, and Industrial Capitalism,” E. P. Thompson codified the theory that modern life, characterized by capitalism and industry, would not be possible without the regulating, organizing, and disciplining power of the clock. The theory of clock time's importance to modernity, first proposed by Georg Simmel around the turn of the twentieth century and later adopted by Lewis Mumford, became conventional wisdom among social and economic historians writing after Thompson's brilliant exposition. The introduction of mechanical clocks into factories in England, Thompson argues, resulted in a “restructuring of working habits” and a concomitant change in the “inward notation of time” that led individuals to accept the industrial revolution's basic premises of quantifiable wage labor and systematic production. According to Thompson's successors, historians such as David Landes, the relationship between clocks and other forms of modernization has been recursive; advances in technology have made it possible to measure time more accurately, and this greater accuracy has in turn facilitated greater productivity, more efficient transportation networks (think of railroad timetables), and the punctuality so important to modern business. Moreover, political theorists have argued that the ubiquitous experience of precisely measured time has been fundamental to linking individuals into self-consciously modern national groups, “imagined communities” in Benedict Anderson's terms, moving forward together through a shared historical simultaneity. The result of temporal modernization, this very diverse group of thinkers agrees, has been a world made over both economically and politically to suit the clockwork rationality of the capitalist market.
Calvin Coolidge's Tragic Presidency: the Political Effects of Bereavement and Depression
Authors: GILBERT ROBERT E.
Published: April 2005

Biographers commonly describe Calvin Coolidge as having had a sound, comfortable, supportive upbringing. Fuess writes, for example, that Coolidge's early life was “simple, wholesome and unfurtive.” White and McCoy point out that the Coolidges were “aristocrats” and that Calvin was “a young prince” who was “brought up in as much luxury as could be expected in Plymouth township.”. However, a close analysis suggests strongly that the childhood years of Calvin Coolidge were marked by great sadness and dislocation. He was an extraordinarily shy boy who had few friends and often was lonely. His father, John Coolidge, was frequently absent from the household, either because of his service in the Vermont state legislature or his various business activities. As Lynch and Kilmartin point out, a father who is physically or emotionally missing from his son's life leaves scars on the boy's psychological development.
Extracting information from free-text aircraft repair notes
Authors: FARLEY BENOIT
Published: April 2005

For every problem mentioned by crew members in an aircraft
log book, an associated repair action note is entered in the
same log book by a maintenance technician after the problem
has been handled. These hand-written repair notes, subsequently
transcribed into a database, give an account of the actions
undertaken by the technicians to fix the problems. Written in
a free-text format with peculiar linguistic characteristics,
including many arbitrary abbreviations and missing auxiliaries,
they contain valuable information that can be used for decision
support methods such as case-based reasoning. We use natural
language techniques in our information extraction system to
analyze the structure and contents of these notes in order to
determine the pieces of equipment involved in a repair and what
was done to them. Lexical information and domain knowledge are
extracted from an electronic version of the illustrated parts
catalog for the particular airplane, and are used at different
stages of the process, from the morpholexical analysis to the
evaluation of the semantic expression generated by the syntactical
analyzer.
A methodology for intelligent sensor measurement, validation,
fusion, and fault detection for equipment monitoring and diagnostics
Authors: ALAG SATNAM , AGOGINO ALICE M. , MORJARIA MAHESH
Published: April 2005

In equipment monitoring and diagnostics, it is very important
to distinguish between a sensor failure and a system failure.
In this paper, we develop a comprehensive methodology based
on a hybrid system of AI and statistical techniques. The
methodology is designed for monitoring complex equipment systems,
which validates the sensor data, associates a degree of validity
with each measurement, isolates faulty sensors, estimates the
actual values despite faulty measurements, and detects incipient
sensor failures. The methodology consists of four steps: redundancy
creation, state prediction, sensor measurement validation and
fusion, and fault detection through residue change detection.
Through these four steps we use the information that can be
obtained by looking at: information from a sensor individually,
information from the sensor as part of a group of sensors, and
the immediate history of the process that is being monitored.
The advantage of this methodology is that it can detect multiple
sensor failures, both abrupt as well as incipient. It can also
detect subtle sensor failures such as drift in calibration and
degradation of the sensor. The four-step methodology is applied
to data from a gas turbine power plant.
The SACSO methodology for troubleshooting complex systems
Authors: JENSEN FINN V. , KJÆRULFF UFFE , KRISTIANSEN BRIAN , LANGSETH HELGE , SKAANNING CLAUS , VOMLEL JIŘÍ , VOMLELOVÁ MARTA
Published: April 2005

The paper describes the task of performing efficient
decision-theoretic troubleshooting of electromechanical devices.
In general, this task is NP-complete, but under fairly strict
assumptions, a greedy approach will yield an optimal sequence
of actions, as discussed in the paper. This set of assumptions
is weaker than the set proposed by Heckerman et al. (1995).
However, the printing system domain, which motivated the research
and which is described in detail in the paper, does not meet
the requirements for the greedy approach, and a heuristic method
is used. The method takes value of identification of the fault
into account and it also performs a partial two-step look-ahead
analysis. We compare the results of the heuristic method with
optimal sequences of actions, and find only minor differences
between the two.
Architecture and design of a diagnostic information fusion system
Authors: GOEBEL KAI
Published: April 2005

This paper introduces an architecture for aggregation of output
from different diagnostic tools. The diagnostic fusion tool
deals with conflict resolution, where diagnostic tools disagree;
temporal information discord, where the estimate of different
tools is separated in time; differences in information updates,
where the classifiers are updated at different rates; fault
coverage discrepancies; and integration of a priori performance
specifications. To this end, a hierarchical weight manipulation
approach is introduced which creates and successively refines
a fused output. The performance of the fusion tool is evaluated
throughout its design. This allows impact assessment of adding
heuristics and enables early tuning of parameters. Results obtained
from diagnosing on-board faults from aircraft engines are shown
which demonstrate the fusion tool's operation.
Fault prognostics using dynamic wavelet neural networks
Authors: WANG PENG , VACHTSEVANOS GEORGE
Published: April 2005

Modern industry is concerned about extending the lifetime of
its critical processes and maintaining them only when required.
Significant aspects of these trends include the ability to diagnose
impending failures, prognosticate the remaining useful lifetime
of the process and schedule maintenance operations so that uptime
is maximized. Prognosis is probably the most difficult of the
three issues leading to condition-based maintenance (CBM). This
paper attempts to address this challenging problem with
intelligence-oriented techniques, specifically dynamic wavelet
neural networks (DWNNs). DWNNs incorporate temporal information
and storage capacity into their functionality so that they can
predict into the future, carrying out fault prognostic tasks.
Such fundamental issues as the network structure, learning
algorithms, stability analysis, uncertainty management, and
performance assessment are studied in a theoretical framework.
An example is presented in which a trained DWNN successfully
prognoses a defective bearing with a crack in its inner race.
Copy but don't repeat: the conflict of dissimilation and reduplication in the Tawala durative
Authors: Kennard Catherine Hicks
Published: April 2005

In this article I provide an account of the durative aspect morpheme in Tawala, an Austronesian language spoken in Papua New Guinea. Within the framework of Optimality Theory (McCarthy & Prince 1993a, Prince & Smolensky 1993), I show that the three different reduplicant shapes, previously accounted for through the use of three separate templates, actually arise from the dynamic between the drive to copy, in terms of reduplication, and the drive to dissimilate at the level of the syllable. Central to my analysis is *REPEAT (Yip 1995, 1998), a constraint prohibiting identical adjacent syllables between the reduplicant and its stem.
A prosodic theory of laryngeal contrasts
Authors: Kehrein Wolfgang , Golston Chris
Published: April 2005

Current models of laryngeal licensing allow as many laryngeal contrasts within a syllable as there are segments, at least in principle. We show here that natural languages are much more economical in their use of laryngeal contrasts than segmental models would lead us to expect. Specifically, we show that voicing, aspiration and glottalisation occur at most once per onset, nucleus or coda in a given language, and that the order in which they are produced within onset, nucleus and coda is never contrastive. To account for these restrictions, we propose that laryngeal features are properties not of segments, but of the onsets, nuclei and codas that dominate them.
Vowel height harmony and blocking in Buchan Scots
Authors: Paster Mary
Published: April 2005

The Buchan Scots dialect of north-east Scotland exhibits a unique phonological phenomenon: vowel harmony is blocked by intervening consonants that have no secondary articulation or other obvious characteristic that should make them opaque to harmony. In this paper, I describe the harmony and blocking pattern based on new data from speakers of the modern dialect. After establishing this as a phonological rather than phonetic effect, I propose a synchronic analysis of the pattern and a phonetic explanation for the origin of this unusual sound pattern.
Sensitivity of biogenic silica oxygen isotopes to changes in surface water temperature and palaeoclimatology
Authors: Moschen Robert , Lücke Andreas , Schleser Gerhard H.
Published: April 2005

Oxygen isotope ratios of biogenic silica derived from planktonic diatoms living in the pelagial of a freshwater lake are used to determine the temperature effect on the isotope fractionation between water and biogenic silica under ecosystem conditions. Our data show a deterministic relation between seasonally changing water temperatures (4°C–22°C) and the oxygen isotope fractionation during valve formation. The temperature dependent fractionation appears to be independent of diatom cell sizes indicating a mere physical control of this process. The isotopic change induced per degree centigrade, the temperature coefficient, amounts to a value of −0.2‰/°C. This implies that previous studies have overestimated the temperature relationship of this proxy by using coefficients of up to −0.5‰/°C for climate reconstructions.
The lithosphere‐asthenosphere boundary in the Tien Shan‐Karakoram region from S receiver functions: Evidence for continental subduction
Authors: Kumar P. , Yuan X. , Kind R. , Kosarev G.
Published: April 2005

Significant S‐to‐P converted wave energy from the crust‐mantle and lithosphere‐asthenosphere boundaries (the Moho and the LAB, respectively) has been observed in the Tien Shan and Karakoram orogenic belts and used for the determination of the thickness of the crust and the mantle lithosphere. The Moho lies at depths of 45–65 km in the Tien Shan and adjacent regions and deepens to ∼70 km depth in Pamir and Karakoram. The thickness of the lithosphere varies between 90 and 120 km underneath the Tien Shan and increases to a value of 160 km beneath the Tarim Basin. To the south of the Tarim Basin the lower boundary of the Asian lithosphere can be clearly followed to a depth of 270 km beneath central Pamir and Karakoram, while the Indian lithosphere is observed beneath the Karakoram dipping from 130 km to 170 km towards the north. The observations indicate a scenario of continental collision and subduction, consistent with seismicity and the surface wave tomography results.
Kp forecast models
Authors: Wing S. , Johnson J. R. , Jen J. , Meng C.‐I. , Sibeck D. G. , Bechtold K. , Freeman J. , Costello K. , Balikhin M. , Takahashi K.
Published: April 2005

Magnetically active times, e.g., Kp > 5, are notoriously difficult to predict, precisely the times when such predictions are crucial to the space weather users. Taking advantage of the routinely available solar wind measurements at Langrangian point (L1) and nowcast Kps, Kp forecast models based on neural networks were developed with the focus on improving the forecast for active times. To satisfy different needs and operational constraints, three models were developed: (1) a model that inputs nowcast Kp and solar wind parameters and predicts Kp 1 hour ahead; (2) a model with the same input as model 1 and predicts Kp 4 hour ahead; and (3) a model that inputs only solar wind parameters and predicts Kp 1 hour ahead (the exact prediction lead time depends on the solar wind speed and the location of the solar wind monitor). Extensive evaluations of these models and other major operational Kp forecast models show that while the new models can predict Kps more accurately for all activities, the most dramatic improvements occur for moderate and active times. Information dynamics analysis of Kp suggests that geospace is more dominated by internal dynamics near solar minimum than near solar maximum, when it is more directly driven by external inputs, namely solar wind and interplanetary magnetic field (IMF).
Nonadiabatic orbit features in ion distribution functions of fast flow magnetotail configurations
Authors: Ball Bryan M. , Kaufmann Richard L. , Paterson W. R. , Frank L. A.
Published: April 2005

One of the major problems in space physics is the limitation of measurements. We present here one way to infer global characteristics of the magnetosphere from only a single satellite position. Several consistent orbit‐tracing (COT) models of fast flows in thin plasma sheets were constructed. The resulting ion distribution functions were examined to see if there are any features which can distinguish a uniform earthward flow of plasma from flows which are confined in a narrow channel in the dawn‐dusk direction. The model distribution functions during uniform flows had the appearance of an initially isotropic f(v) that had simply been shifted by the earthward flow speed. The model f(v) exhibited lima bean–shaped features when the flow was confined to a region comparable to the diameter of a cyclotron orbit based on Bz. Distribution functions observed by the Geotail satellite were examined for comparisons, and the measured distributions were found to exhibit features similar to those obtained in the COT model. We are able to demonstrate that the distributions measured by Geotail may only be reproduced in our technique if the convective electric field is confined in the dawn‐dusk direction.
Reconnection sites of spatial cusp structures
Authors: Trattner K. J. , Fuselier S. A. , Petrinec S. M. , Yeoman T. K. , Mouikis C. , Kucharek H. , Reme H.
Published: April 2005

The interconnection of the interplanetary magnetic field with the geomagnetic field is thought to be the dominant process for mass, energy, and momentum transfer from the magnetosheath into the magnetosphere. Downward precipitating ions from the reconnection site are observed in the cusp by polar orbiting satellites and exhibit sudden changes in their ion‐energy distributions, forming distinctive structures. These structures have been identified as temporal structures, most likely caused by variations of the reconnection rate at the magnetopause, as well as spatial structures caused by spatially separated flux tubes. Comparisons of spatial cusp structures observed by Cluster with simultaneously observed ionospheric convection pattern derived from SuperDARN radar observations showed that spatial cusp structures are linked with separated ionospheric convection cells. It has been suggested that these convection cells and their related spatial cusp structures are driven by multiple reconnection lines at the magnetopause. This study revisits a spatial cusp structure event and shows that the two dispersion events are indeed coming from separated reconnection lines located in different hemispheres.
Effect of upstream rotational field on the formation of magnetic depressions in a quasi‐perpendicular shock downstream
Authors: Tsubouchi K. , Matsumoto H.
Published: April 2005

One‐dimensional hybrid simulations are performed to investigate the interaction between an interplanetary rotational magnetic field (RF) and the terrestrial bow shock (a quasi‐perpendicular and supercritical regime). A magnetic depression structure called a transient density event (TDE) that is anticorrelated to the density peak is built up and is enlarged from the RF region after its entry into the magnetosheath. Contrary to the MHD view, in which such a diamagnetic structure is sandwiched by two slow or time‐dependent intermediate shocks, the TDE generation mechanism is strongly associated with effects of particle kinetics. Within the TDE, the proton temperature parallel to the ambient magnetic field Tp∥ increases to be isotropic, while the ordinary shock downstream consists of strong anisotropic protons (Tp⊥/Tp∥ > 1). This parallel heating is due to enforced conversion of the perpendicular proton motion into a parallel one by the imposed RF. The resultant intense parallel/antiparallel flows generate the field gradient at the leading and trailing edges, which act as a mirror force and reduce the magnetic intensity. In this kinetic sense, slow or Alfvén modes predicted by MHD theories are inadequate for regarding as edges of such a structure. Similar to the normal mirror mode process, particles are concentrated and trapped within the weak field region, leading to a density buildup. The trapped particles lose their energy and undergo cooling as they are bounced at the diverging mirror points. Accordingly, the TDE structure hardly collapses and endures through the magnetosheath. Compared with the mirror instability, isotropization forced by external field fluctuations works more efficiently to produce such a magnetic depression. Thus the presence of the quasi‐perpendicular shock, where large temperature anisotropy is generated, is one of the suitable situations for the TDE when interaction with the rotational field has taken place. This interaction model may also be applicable to the magnetic hole formation mechanism in the solar wind.
Calculation of pitch angle and energy diffusion coefficients with the PADIE code
Authors: Glauert Sarah A. , Horne Richard B.
Published: April 2005

We present a new computer code (PADIE) that calculates fully relativistic quasi‐linear pitch angle and energy diffusion coefficients for resonant wave‐particle interactions in a magnetized plasma. Unlike previous codes, the full electromagnetic dispersion relation is used so that interactions involving any linear electromagnetic wave mode in a predominantly cold plasma can be addressed for any ratio of the plasma‐frequency to the cyclotron frequency ωpe/∣Ωe∣. The code can be applied to problems in astrophysical, magnetospheric, and laboratory plasmas. The code is applied here to the Earth's radiation belts to calculate electron diffusion by whistler mode chorus, electromagnetic ion cyclotron (EMIC), and Z mode waves. The high‐density approximation is remarkably good for electron diffusion by whistler mode chorus for energies E ≥ 100 keV, even for ωpe/∣Ωe∣ ≈ 2 but underestimates diffusion by orders of magnitude at low energies (∼10 keV). When a realistic angular spread of propagating waves is introduced for EMIC waves, electron diffusion at ∼0.5 MeV is only slightly reduced compared with the assumption of field‐aligned propagation, but at ∼5 MeV, electron diffusion at pitch angles near 90° is reduced by a factor of 5 and increased by several orders of magnitude at pitch angles 30°–80°. Scattering by EMIC waves should contribute to flattening of the distribution function. The first results for electron diffusion by Z mode waves are presented. They show that unlike the whistler and EMIC waves, energy diffusion exceeds pitch angle diffusion over a broad range of pitch angles less than 45°. The results suggest that Z mode waves could provide a significant contribution to electron acceleration in the radiation belts during storm times.
Intensities of galactic cosmic rays of ∼1.5 GV rigidity at Earth versus the heliospheric current sheet tilt
Authors: Lockwood J. A. , Webber W. R.
Published: April 2005

In this paper we have compared the cosmic ray intensity variations at ∼1.5 GV rigidity with the corresponding time variations of the heliospheric current sheet tilt (HCST). These studies extend earlier work comparing neutron monitor variations with the HCST. In addition to the results of this earlier work we have found that (1) the delay of the cosmic ray intensity changes relative to the HCST changes is much less in 11‐year cycles starting in a negative solar magnetic cycles. (2) During the specific periods of actual changeover of the solar magnetic field from positive to negative polarity, the cosmic ray intensity decrease is ∼50% of the total 11‐year cycle intensity decrease. During the changeover from negative to positive polarity, the entire cosmic ray 11‐year decrease has almost fully occurred before the polarity changeover. (3) In 11‐year modulation cycles starting in a negative polarity period, the regression coefficient between the cosmic ray intensity and tilt is ∼0.9% per degree of tilt during both the decreasing and increasing phases. In the 11‐year modulation cycles starting in a positive polarity cycle, the regression coefficient is much smaller, only ∼0.4% per degree during much of the cycle; then it becomes much steeper toward the end of the cycle. These features are discussed in terms of current models for cosmic ray modulation that include diffusion, convection, drifts, and the wavy current sheet.
A 9‐year climatology of airstreams in East Asia and implications for the transport of pollutants and downstream impacts
Authors: Wang Kuo‐Ying
Published: April 2005

Ambient measurements of PM10 levels in Taiwan over East Asia have shown unusual decreases for the 1994–2002 period. To assess these downward trends of PM10, we develop methods for calculating climatologies of PM10 and airstreams, and a new method for quantifying airstreams and their associated impacts on PM10 and PM10‐influencing factors. These methods were verified against anomalously low PM10 levels during the 1998 ENSO, and anomalously high PM10 levels during spring 2000. Calculations show the following: 20–23% increased occurrence of airstreams from the north direction in spring 2000 coincide with 14–16% increases in ambient PM10 levels downstream over Taiwan; 60% increased occurrence of airstreams over western Pacific coincide with 10–15% drops in ambient PM10 levels downstream during the 1998 ENSO. Comparison of airstreams between 1994–1997 and 1999–2002 show a 15–29% reduction over the eastern direction and a 7–17% increase over the western direction. The most significant findings associated with these changes are the reduction in close‐to‐surface inversions, the increase in rainfall, the increase in continental outflows, and the counteracting effects between these processes. The reduction in close‐to‐surface inversions dilutes ambient particles from the surface toward the free troposphere, thereby reducing ambient PM10 levels; increases in rainfall provide efficient wet scavenging mechanisms for removing particles from the ambient air. These two processes counteract and dominate over the increase in airstreams over the northwestern direction, where continental pollutants are exported downstream, and results in the downward trends in PM10.
Physical processes in acoustic wave heating of the thermosphere
Authors: Schubert G. , Hickey M. P. , Walterscheid R. L.
Published: April 2005

Upward propagating acoustic waves heat the atmosphere at essentially all heights due to effects of viscous dissipation, sensible heat flux divergence, and Eulerian drift work. Acoustic wave‐induced pressure gradient work provides a cooling effect at all heights, but this is overwhelmed by the heating processes. Eulerian drift work and wave‐induced pressure gradient work dominate the energy balance, but they nearly cancel at most altitudes, leaving their difference, together with viscous dissipation and sensible heat flux divergence to heat the atmosphere. Acoustic waves are very different from gravity waves which cool the upper atmosphere through the effect of sensible heat flux divergence. Acoustic wave dissipation could be an important source of upper atmospheric heating.
Curie temperature and critical thickness of ferroelectric thin films
Authors: Wang Biao , Woo C. H.
Published: April 2005

The dynamic Ginzburg–Landau theory is applied to establish the critical conditions that control the transition between the paraelectric and ferroelectric states. Analytic expressions of the para-ferroelectric transition temperatures in a thin film under various electromechanical surface conditions are derived via a linear stability analysis of the evolutionary trajectory of the system for both first- and second-order transitions. Explicit expressions are then derived for the critical thickness, below which the thin film is paraelectric for all temperatures. For first-order transitions, the difference between the superheating and supercooling transition temperatures is found to be insensitive to the film thickness and surface boundary conditions. From these expressions, the relative importance on ferroelectricity in thin films due to applied mechanical constraints on the transformation strain and the depolarizing effect of surface charges is discussed and compared with experimental data.
Decay of ferroelectric domains formed in the field of an atomic force microscope
Authors: Molotskii Michel I. , Shvebelman Maria M.
Published: April 2005

Ferroelectric domains formed in the electric field of an atomic force microscope decay with time when the reversal voltage is removed. We propose a theory for this process. Dynamic equations describing the time evolution of the domain sizes are constructed and solved. It is shown that the larger the domains, the more stable they are. The time dependences of the domain length and base radius are qualitatively different. The radius of the domain decreases during the decay process, and for a large domain there is a plateau in its time dependence. In contrast to this, the length of the domain first does not decrease but rather grows significantly and then rapidly drops. We introduce the concept of critical radius for the domain stability. Only domains with a radius exceeding the critical radius have a long lifetime, which increases exponentially with the initial domain radius. The calculated value of the critical radius of stability in barium titanate is in reasonable agreement with the experiment. Possible means to stabilize the domains are proposed.
Stability of three unit charges: Necessary conditions
Authors: Gridnev D. K. , Greiner C. , Greiner W.
Published: April 2005

We consider the stability of three Coulomb charges {+1,−1,−1} with finite masses in the framework of nonrelativistic quantum mechanics. A simple physical condition on masses is derived to guarantee the absence of bound states below the dissociation thresholds. In particular this proves that certain negative muonic ions are unstable, thus extending the old result of Thirring to the actual values of all masses. The proof is done by reducing the initial problem to the question of binding of one particle in some effective potential.
The Kähler potential of Abelian Higgs vortices
Authors: Chen Heng-Yu , Manton N. S.
Published: April 2005

We calculate the Kähler potential for the Samols metric on the moduli space of Abelian Higgs vortices on R2, in two different ways. The first uses a scaling argument. The second depends on a variant of the relationship between accessory parameters and the regularized action in Liouville field theory. The Kähler potential on the moduli space of vortices on H2 is also derived, and we are led to a geometrical reinterpretation of these vortices.
Entropy generation during microcombustion
Authors: Li Z. W. , Chou S. K. , Shu C. , Yang W. M.
Published: April 2005

We use an entropy balance to formulate the entropy generation equation in a flame zone of a cylindrical microcombustor tube. In deriving this equation, we define a nondimensional radius as the ratio of the tube radius to the flame thickness, and we set up a thermal model of the flame zone by applying an energy balance for a steady flow system to the flame zone. Based on this model, we obtain a relationship between the flame temperature and the nondimensional radius. Given this relationship, the effects of the fuel, fuel-air ratio, unburned gas temperature, and tube radius on entropy generation are analyzed. The occurrence of minimum entropy generation is predicted. The efficient operating conditions of the microcombustor are suggested.
Continuum states from time-dependent density functional theory
Authors: Wasserman Adam , Maitra Neepa T. , Burke Kieron
Published: April 2005

Linear response time-dependent density functional theory is used to study low-lying electronic continuum states of targets that can bind an extra electron. Exact formulas to extract scattering amplitudes from the susceptibility are derived in one dimension. A single-pole approximation for scattering phase shifts in three dimensions is shown to be more accurate than static exchange for singlet electron-He+ scattering.
Electron density distribution in stacked benzene dimers: A new approach towards the estimation of stacking interaction energies
Authors: Zhikol Oleg A. , Shishkin Oleg V. , Lyssenko Konstantin A. , Leszczynski Jerzy
Published: April 2005

The potential energy surface for the benzene dimer in stacked conformations (84 points calculated) was computed at the MP2(FC)∕6-31+G(2d,2p) level of theory. Electron density (ED) distribution computed using the MP2(FC), B3LYP, and Hartree–Fock methods with the same basis set is studied in the frame of topological analysis. It is found that ED topology does not depend on the method of calculation. The values of the ED and its Laplacian in the cage critical point calculated using different methods are determined to be linearly dependent with the slope depending on basis set. Correlation equations based on these properties allow the interaction energy between benzene rings to be predicted with 8% mean relative error in the energy for the given region of the potential energy surface. This provides a new method for the estimation of stacking interaction energy using ED properties calculated with low level quantum-chemical methods.
Organic light-emitting devices with silicon anodes
Authors: Huang C. J. , Han S. , Grozea D. , Turak A. , Lu Z. H.
Published: April 2005

Both n and p-type Si(100) surfaces, treated by various methods, have been investigated as electrodes for hole injection in organic light-emitting devices. It was found that the Fermi level of silicon dictates the device characteristics. The surface Fermi level, which can be varied by doping and surface states, has been found to be a good reference level for controlling the hole injection barrier.
Effect of strain relaxation and exciton localization on performance of 350-nm AlInGaN quaternary light-emitting diodes
Authors: Wang T. , Raviprakash G. , Ranalli F. , Harrison C. N. , Bai J. , David J. P. R. , Parbrook P. J. , Ao J. P. , Ohno Y.
Published: April 2005

The optical and structural properties of AlInGaN quaternary single and multiple quantum-well structures have been investigated by means of photoluminescence and x-ray diffraction. This comparative study of single quantum-well (SQW) and multiple quantum-well (MQW) structures was carried out in terms of the exciton localization effect and the strain relaxation. A detailed analysis indicated that 13% strain relaxation occurs in the MQW compared to the SQW, which is assumed to be fully strained. Furthermore, the AlInGaN SQW structure showed a stronger localization effect than the MQW. Both these effects result in enhanced emission efficiency for the SQW structure, indicating that it is better suited as the active region for ultraviolet light-emitting diodes (UV-LEDs). Finally, the UV-LEDs with an emission wavelength of about 350nm based on such SQW and MQW active regions were grown. The output power of the SQW UV-LEDs is around 2.3 times higher than that of MQW UV-LEDs.
Kinetic oscillations in the NO+CO reaction on the Pt(100) surface: An alternative reaction mechanism
Authors: Alas S. J. , Cordero S. , Kornhauser I. , Zgrablich G.
Published: April 2005

Kinetic oscillations in the catalytic reduction of NO by CO on a reconstructing Pt(100) surface are simulated by using a dynamic Monte Carlo method. The simulation is based on the HS model and takes into account an alternative reaction mechanism arising from recent experimental findings for the catalytic reduction of No on Rh(111), which replaces the classical N+N recombination step by the formation of a (N–NO)* intermediary species for the production of molecular nitrogen. A synchronized mechanism and spatiotemporal patterns are observed during the oscillations. Oscillations are analyzed in terms of the controlling parameters involved in the reaction mechanism. Different values of these parameters lead to sustained, attenuated, and modulated oscillations.
A theoretical study of the gas-phase chemi-ionization reaction between uranium and oxygen atoms
Authors: Paulovič Jozef , Gagliardi Laura , Dyke John M. , Hirao Kimihiko
Published: April 2005

The U+O chemi-ionization reaction has been investigated by quantum chemical methods. Potential-energy curves have been calculated for several electronic states of UO and UO+. Comparison with the available spectroscopic and thermodynamic values for these species is reported and a mechanism for the chemi-ionization reaction U+O→UO++e− is proposed. The U+O and Sm+O chemi-ionization reactions are the first two metal-plus-oxidant chemi-ionization reactions to be studied theoretically in this way.
A dissipative particle dynamics description of liquid-crystalline phases. I. Methodology and applications
Authors: Levine Yehudi K. , Gomes Alexandre E. , Martins Assis Farinha , Polimeno Antonino
Published: April 2005

Simulations of nematic and smectic mesophases based on a dissipative particle dynamics approach are discussed. Mesogenic units are built in the form of standard semirigid bead-spring chains. It is shown that nematic phases can be formed for chains containing at least eight beads, provided that the conservative soft-repulsive potential between nonconnected beads is sufficiently strong. Smectic phases are observed only by modifying the repulsive interaction between the main-chain and terminal beads. The simulations indicate that the smectic-nematic and smectic-isotropic phase transitions take place through the buckling of the smectic layering in the system.
Decoherence effects in reactive scattering
Authors: Han Heekyung , Brumer Paul
Published: April 2005

Decoherence effects on quantum and classical dynamics in reactive scattering are examined using a Caldeira–Leggett type model. Through a study of the dynamics of the collinear H+H2 reaction and the transmission over simple one-dimensional barrier potentials, we show that decoherence leads to improved agreement between quantum and classical reactions and transmission probabilities, primarily by increasing the energy dispersion in a well-defined way. Increased potential nonlinearity is seen to require larger decoherence in order to attain comparable quantum-classical agreement.
Hole localization in [AlO4] defects in silica materials
Authors: To Judy , Sokol Alexey A. , French Samuel A. , Kaltsoyannis Nikolas , Catlow C. Richard A.
Published: April 2005

First-principles calculations based on cluster models have been performed to investigate the ground state and the optically excited states of the [AlO4]0 hole in α-quartz and in the siliceous zeolite ZSM-5. The structure and spectroscopic properties of this defect have been studied using the recently developed Becke88–Becke95 one-parameter model for kinetics (BB1K) functional of Zhao et al., [J. Phys. Chem. A 108, 2715 (2004)]. Our results show that the BB1K method is significantly more reliable and more accurate than the standard density-functional theory (DFT) functionals at reproducing the localized spin density on one oxygen atom and the hyperfine coupling constants associated with the hole. Furthermore, we find that the BB1K results are in close agreement with experiments, and with the self-interaction-free unrestricted Hartree–Fock (UHF) and unrestricted second-order Møller–Plesset perturbation theory (UMP2) calculations. For the first time, we present results of the ground-state paramagnetic properties of the Al defect in ZSM-5. Similar to the theoretical work for defective α-quartz, we find that the BB1K, UHF, UHF∕Lee–Yang–Parr, and UMP2 calculations show a localized hole on one oxygen neighboring the Al, while even the best to date thermochemically derived hybrid generalized gradient approximation density-functional, B97-2, predicts a different model where the hole is distributed over two oxygen. We have further considered the optical transitions of the [AlO4]0 center in α-quartz and ZSM-5. In both systems, our BB1K time-dependent density-functional theory (TDDFT) and configuration interaction singles (CIS) calculations predict that the most likely transition involves electron transfer from the hole-bearing oxygen to other neighboring oxygen ions. This reinforces the experimental conclusions obtained for defective α-quartz. Notably, the two lowest, most dominant excitation energies calculated by BB1K-TDDFT (1.99 and 3.03 eV) show excellent agreement with experiment (1.96 and 2.85 eV [B. K. Meyer, J.M. Spaeth, and J.A. Weil, J. Phys. C: Solid State Phys. 17, L31 (1987)]) clearly outperforming the CIS method and other DFT calculations available in the literature.
Towards automated design of quantum cascade lasers
Authors: Mirčetić Aleksandra , Indjin Dragan , Ikonić Zoran , Harrison Paul , Milanović Vitomir , Kelsall Robert W.
Published: April 2005

We present an advanced technique for the design and optimization of GaAs∕AlGaAs quantum cascade laser structures. It is based on the implementation of the simulated annealing algorithm with the purpose of determining a set of design parameters that satisfy predefined conditions, leading to an enhancement of the device output characteristics. Two important design aspects have been addressed: improved thermal behavior, achieved by the use of higher conduction band offset materials, and a more efficient extraction mechanism, realized via a ladder of three lower laser states, with subsequent pairs separated by the optical phonon energy. A detailed analysis of performance of the obtained structures is carried out within a full self-consistent rate equations model of the carrier dynamics. The latter uses wave functions calculated by the transfer matrix method, and evaluates all relevant carrier–phonon and carrier–carrier scattering rates from each quantized state to all others within the same and neighboring periods of the cascade. These values are then used to form a set of rate equations for the carrier density in each state, enabling further calculation of the current density and gain as a function of the applied field and temperature. This paper addresses the application of the described procedure to the design of λ∼9μm GaAs-based mid-infrared quantum cascade lasers and presents the output characteristics of some of the designed optimized structures.
Scaling behavior of a brush–homopolymer interface in the limit of high grafting density
Authors: Matsen M. W.
Published: April 2005

The interface between a polymer brush and a chemically equivalent homopolymer is examined using self-consistent field theory (SCFT). Focusing on ultrahigh grafting densities, we extract how the properties scale with the brush thickness, L, and compare with predictions based on strong-stretching theory (SST). Although the scaling exponents are consistent, the overall agreement is poor. We attribute this to the inaccurate way the SST-based calculation treats chain fluctuations at the extremity of the brush. This accounts for a previous disagreement between SCFT and SST in regards to autophobic dewetting, and brings into question a number of other SST predictions. Our conclusion is that SST requires a more sophisticated treatment of finite-stretching corrections, along the lines of that proposed by Likhtman and Semenov [Europhys. Lett. 51, 307 (2000)].