bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal confounding in air pollution and health time‐series studies: effect on air pollution effect estimates
Authors: Touloumi G. , Samoli E. , Pipikou M. , Le Tertre A. , Atkinson R. , Katsouyanni K.
Published: September 2006

A major statistical challenge in air pollution and health time‐series studies is to adequately control for confounding effects of time‐varying covariates. Daily health outcome counts are most commonly analysed by Poisson regression models, adjusted for overdispersion, with air pollution levels included as a linear predictor and smooth functions for calendar time and weather variables to adjust for time‐varying confounders. Various smoothers have been used so far, but the optimal strategy for choosing smoothers and their degree of smoothing remains controversial. In this work, we evaluate the performance of various smoothers with different criteria for choosing the degree of smoothing in terms of bias and efficiency of the air pollution effect estimate in a simulation study. The evaluated approaches were also applied to real mortality data from 22 European cities. The simulation study imitated a multi‐city study. Data were generated from a fully parametric model. Model selection methods which optimize prediction may lead to increased biases in the air pollution effect estimate. Minimization of the absolute value of the sum of the partial autocorrelation function of the model's residuals (PACF), as a criterion to choose the degree of smoothness, gave the smallest biases. The penalized splines (PS) method with a large number of effective dfs (e.g. 8–12 per year) could be used as the basic, relatively conservative, analysis whereas the PS and natural splines in combination with PACF could be applied to provide a reasonable range of the effect estimate. Copyright © 2006 John Wiley & Sons, Ltd.
Measuring the complexity of class diagrams in reverse engineering
Authors: Sheldon Frederick T. , Chung Hong
Published: September 2006

Complexity metrics for object‐oriented systems are plentiful. Numerous studies have been undertaken to establish valid and meaningful measures of maintainability as they relate to the static structural characteristics of software. In general, these studies have lacked the empirical validation of their meaning and/or have only succeeded in evaluating partial aspects of the system. In this study we have determined, through limited empirical means, a practical and holistic view by analyzing and comparing the structural characteristics of UML class diagrams as those characteristics relate to or impact maintainability. Class diagrams are composed of three kinds of relation, association, generalization, and aggregation, which make their overall structure difficult to understand. We propose combining these three relations in such a way that enables a comprehensive measure of complexity. Theoretically, this measure is applicable among different class diagrams (including different domains, platforms or systems) to the extent that the measure is widely comparative and context free. Further, this property does not preclude comparison within a specific class diagram (or family) and is therefore very useful in evaluating a given class diagram's strengths and weaknesses. We are reporting empirical results that provide a small measure of validity to enable an objective appraisal of both complexity and maintainability without equating the two. Therefore, to evaluate our structural complexity metric, we determined the level of understandability of the system by measuring the time needed to reverse engineer source code into class diagrams including the number of errors produced while creating the diagram. The number of errors produced offers one indicator of maintainability. The results, as compared with other complexity metrics, indicate that our metric shows promise especially if proven to be scalable. Copyright © 2006 John Wiley & Sons, Ltd.
Degeneracy in Candecomp/Parafac Explained for p × p × 2 Arrays of Rank p + 1 or Higher
Authors: Stegeman Alwin
Published: September 2006

The Candecomp/Parafac (CP) model decomposes a three-way array into a prespecified number R of rank-1 arrays and a residual array, in which the sum of squares of the residual array is minimized. The practical use of CP is sometimes complicated by the occurrence of so-called degenerate solutions, in which some components are highly correlated in all three modes and the elements of these components become arbitrarily large. We consider the real-valued CP model in which p × p × 2 arrays of rank p + 1 or higher are decomposed into p rank-1 arrays and a residual array. It is shown that the CP objective function does not have a minimum in these cases, but an infimum. Moreover, any sequence of CP approximations, of which the objective value approaches the infimum, will become degenerate. This result extends Ten Berge, Kiers, & De Leeuw (1988), who consider a particular 2 × 2 × 2 array of rank 3.
In Praise of Pluralism. A Comment on Borsboom
Authors: Kane Michael
Published: September 2006

I tend to agree with Professor Borsboom that psychology, and more generally the social sciences, could benefit from better psychometric modeling. However, if psychometric developments are to have more effect on everyday practice in psychology, psychometricians probably need to pay more attention to the substantive and methodological problems in various areas of psychology. For example, Professor Borsboom is critical of the Standards for educational and psychological testing (AERA, APA, NCME, 1999) for suggesting that group differences in testcriterion relationships are relevant to test bias. He bases his criticism on the finding that predictive invariance is not the same as measurement invariance. However, he fails to acknowledge the social, political, and ethical problems associated with failures of predictive invariance in high-stakes contexts (e.g., employment and admissions testing).
When a Psychometric Advance Falls in the Forest
Authors: Clark Lee Anna
Published: September 2006

Borsboom (2006) attacks psychologists for failing to incorporate psychometric advances in their work, discusses factors that contribute to this regrettable situation, and offers suggestions for ameliorating it. This commentary applauds Borsboom for calling the field to task on this issue and notes additional problems in the field regarding measurement that he could add to his critique. It also chastises Borsboom for occasionally being unnecessarily perjorative in his critique, noting that negative rhetoric is unlikely to make converts of offenders. Finally, it exhorts psychometricians to make their work more accessible and points to Borsboom, Mellenbergh, and Van Heerden (2003) as an excellent example of how this can be done.
Measurement without Copper Instruments and Experiment without Complete Control
Authors: Heiser Willem J.
Published: September 2006

One basic reason that measurement in psychology requires statistics is that psychologists do not use copper instruments anymore, as they used to do in the nineteenth century. Instead, they determine test or total scores on the basis of miniature experiments with discrete outcomes, and use a variety of standard statististical techniques for reaching conclusions on the basis of observed data. Borsboom (2006) wants us to believe that psychologists are seriously misled in their hope that they can make progress this way, and recommends an invasion of psychometricians carrying IRT missiles and SEM guns into psychology.My prediction is that such an invasion would simply be ignored. That is not to say that whenever psychometric modeling really makes a difference, no attempts should be made to reach the mainstream of psychology. Indeed, many psychometric contributions that are obsolete according to Borsboom, like Cronbach’s alpha and exploratory factor analysis, in fact entered into the mainstream of psychology only because they tend to provide sensible answers to real problems, which cannot be easily surpassed.
Can We Bring about a Velvet Revolution in Psychological Measurement? a Rejoinder to Commentaries
Authors: Borsboom Denny
Published: September 2006

First, I thank Sijtsma, Clark, Kane, and Heiser for taking the time and effort to provide a commentary on my paper, and the Editor for allowing me to respond to them. In general, the commentators agree with the thesis that psychometrics and psychology are, to an extent that must be deemed problematic, disconnected. They further agree with the upshot of this diagnosis: Psychometricians need to work harder to make a difference in psychology, and psychologists need to develop a greater awareness of important psychometric developments. However, the commentators also raise several points of disagreement and criticism.
Sign changing bubble tower solutions in a slightly subcritical semilinear Dirichlet problem
Authors: Weth Tobias , Pistoia Angela
Published: September 2006

We consider the problem

−\mathrm{\Delta }u = |u|^{p−1−ɛ}u

in

Ω

,

u = 0

on

∂Ω

, where

Ω

is a bounded smooth domain in

\mathbb{R}^{N}

symmetric with respect to

x_{1},…,x_{N}

, which contains the origin,

N⩾3

,

p = \frac{N + 2}{N−2}

and

ɛ

is a positive parameter. As

ɛ

goes to zero, we construct sign changing solutions with multiple blow up at the origin. These solutions have, as

ɛ

goes to zero, more and more annular-shaped nodal domains.

Nous considérons le problème

−\mathrm{\Delta }u = |u|^{p−1−ɛ}u

dans

Ω

,

u = 0

sur

∂Ω

, où

Ω

est un domaine borné de

\mathbb{R}^{N}

symétrique par rapport à

x_{1},…,x_{N}

qui contient l'origine,

N⩾3

,

p = \frac{N + 2}{N−2}

et

ɛ

est un paramètre positif. Quand

ɛ\rightarrow 0

, nous construisons des solutions changeant de signe qui ressemblent à une superposition de transitoires centrées dans l'origine. Ces solutions admettent, quand

ɛ\rightarrow 0

, de plus en plus de domaines nodeaux ressemblant à un anneau.
Prescribing scalar curvature on \( S^{3} \)
Authors: Schneider Matthias
Published: September 2006

We give existence results for solutions of the prescribed scalar curvature equation on

S^{3}

, when the curvature function is a positive Morse function and satisfies an index-count condition.

Nous démontrons l'existence de solutions de l'équation courbure scalaire sur

S^{3}

, quand la courbure scalaire est une fonction de Morse positive satisfaisant à une condition d'indice.
Strong instability of solitary waves for nonlinear Klein–Gordon equations and generalized Boussinesq equations
Authors: Liu Yue , Ohta Masahito , Todorova Grozdena
Published: September 2006

We study here instability problems of standing waves for the nonlinear Klein–Gordon equations and solitary waves for the generalized Boussinesq equations. It is shown that those special wave solutions may be strongly unstable by blowup in finite time, depending on the range of the wave's frequency or the wave's speed of propagation and on the nonlinearity.

On étudie des problèmes d'instabilité des ondes stationnaires pour des équations de Klein–Gordon non linéaires et des ondes solitaires pour des équations généralisées de Boussinesq. On établit que ces solutions d'ondes spéciales peuvent être fortement instables par explosion en temps fini, selon le rang de la fréquence des ondes ou la vitesse de propagation des ondes et la non-linéarité.
Benjamin–Ono periodic bifurcating water waves in presence of an essential spectrum
Authors: Barrandon Matthieu
Published: September 2006

The mathematical study of travelling waves in the potential flow of two superposed layers of perfect fluid can be set as an ill-posed evolutionary problem, in which the horizontal unbounded space variable plays the role of “time”. In this paper we consider two problems for which the bottom layer of fluid is infinitely deep: for the first problem, the upper layer is bounded by a rigid top and there is no surface tension at the interface; for the second problem, there is a free surface with a large enough surface tension. In both problems, the linearized operator

L_{ɛ}

(where

ɛ

is a combination of the physical parameters) around 0 possesses an
essential spectrum filling the entire real line
, with in addition a simple eigenvalue in 0. Moreover, for

ɛ < 0

, there is a pair of imaginary eigenvalues which meet in 0 when

ɛ = 0

and which disappear in the essential spectrum for

ɛ > 0

. For

ɛ > 0

small enough, we prove in this paper the existence of a two parameter family of periodic travelling waves (corresponding to periodic solutions of the dynamical system). These solutions are obtained in showing that the full system can be seen as a perturbation of the Benjamin–Ono equation. The periods of these solutions run on an interval

(T_{0},\infty )

possibly except a discrete set of isolated points.

La recherche d'ondes progressives dans un système de deux couches superposées de fluides parfaits peut s'écrire comme un problème d'évolution mal posé, pour lequel la variable horizontale non bornée remplace le temps. Dans cet article, on étudie deux problèmes pour lesquels la couche inférieur de fluide est de profondeur infinie : dans le premier problème la couche supérieure est bornée par une surface rigide et il n'y a pas de tension de surface à l'interface ; pour le deuxième problème, la surface est libre mais avec une tension de surface élevée. Pour les deux problèmes, l'opérateur linéarisé à l'origine

L_{ɛ}

(où

ɛ

est une combinaison des paramètres physiques) possède, en plus d'une valeur propre simple en 0,
un spectre essentiel sur tout l'axe réel
. De plus, pour

ɛ < 0

, il y a une paire de valeurs propres imaginaires pures, qui se rencontrent à l'origine pour

ɛ = 0

, et qui disparaissent dans le spectre essentiel pour

ɛ > 0

. Pour

ɛ > 0

assez petit, on montre l'existence d'une famille à deux paramètres d'ondes progressives périodiques (qui correspondent à des solutions périodiques du système dynamique). Ces solutions sont obtenues en montrant que le système dynamique peut se réduire à une perturbation de l'équation de Benjamin–Ono. Les périodes de ces solutions appartiennent à un intervalle

(T_{0},\infty )

à l'exception possible d'un ensemble discret de points isolés.
Clustered solutions around harmonic centers to a coupled elliptic system
Authors: D'Aprile Teresa , Wei Juncheng
Published: September 2006

We study the following system of Schrödinger–Maxwell equations

ɛ^{2}\mathrm{\Delta }v−v−\omega v\phi + f(v) = 0,\:\mathrm{\Delta }\phi + \gamma v^{2} = 0\:\text{in }\Omega ,

v,\phi > 0\:\text{in }\Omega ,\:v,\phi = 0\:\text{on}\:\partial \Omega ,

where

Ω

is a smooth and bounded domain of

\mathbb{R}^{3}

. We prove that for any integer

k

the system has a family of solutions

(v_{ɛ},\phi _{ɛ})

such that the form of

v_{ɛ}

consists of

k

spikes concentrating at a harmonic center of

Ω

as

ɛ\rightarrow 0^{ + }

. Furthermore we show that the spikes approach the vertexes of a configuration which maximizes a suitable geometrical problem.

On étudie le système d'équations de Schrödinger–Maxwell suivant :

ɛ^{2}\mathrm{\Delta }v−v−\omega v\phi + f(v) = 0,\:\mathrm{\Delta }\phi + \gamma v^{2} = 0\:\text{dans }\Omega ,

v,\phi > 0\:\text{dans }\Omega ,\:v,\phi = 0\:\text{sur}\:\partial \Omega ,

où

Ω

est un ouvert borné régulier. On montre que pour tout entier

k

le système a une famille de solutions

(v_{ɛ},\phi _{ɛ})

telle que la forme de

v_{ɛ}

consiste en

k

pointes qui se concentrent sur un centre harmonique de

Ω

lorsque

ɛ\rightarrow 0^{ + }

. On montre, en plus, que les pointes approchent les sommets d'une configuration qui maximise un problème géométrique.
Defining residues involved in human rhinovirus 2A proteinase substrate recognition
Authors: Sousa Carla , Schmid Eva M. , Skern Tim
Published: September 2006

The 2A proteinase (2Apro) of human rhinoviruses (HRVs) initiates proteolytic processing by cleaving between the C‐terminus of VP1 and its own N‐terminus. It subsequently cleaves the host protein eIF4GI. HRV2 and HRV14 2Apro cleave at IITTA ∗ GPSD and DIKSY ∗ GLGP on their respective polyproteins. The HRV2 2Apro cleavage site on eIF4GI is TLSTR ∗ GPPR. We show that HRV2 2Apro can self‐process at the eIF4GI cleavage sequence whereas HRV14 2Apro cannot, due to the presence of the arginine residue at P1. The mutations A104C or A104S in HRV14 2Apro restored cleavage when arginine was present at P1, although not to wild‐type levels. These experiments define residues which determine substrate recognition in rhinoviral 2Apro.
Starter strain related effects on the biochemical and sensory properties of Cheddar cheese
Authors: Hickey Dara K , Kilcawley Kieran N , Beresford Tom P , Sheehan Elizabeth M , Wilkinson Martin G
Published: September 2006

A detailed investigation was undertaken to determine the effects of four single starter strains, Lactococcus lactis subsp. lactis 303, Lc. lactis subsp. cremoris HP, Lc. lactis subsp. cremoris AM2, and Lactobacillus helveticus DPC4571 on the proteolytic, lipolytic and sensory characteristics of Cheddar cheese. Cheeses produced using the highly autolytic starters 4571 and AM2 positively impacted on flavour development, whereas cheeses produced from the poorly autolytic starters 303 and HP developed off-flavours. Starter selection impacted significantly on the proteolytic and sensory characteristics of the resulting Cheddar cheeses. It appeared that the autolytic and/or lipolytic properties of starter strains also influenced lipolysis, however lipolysis appeared to be limited due to a possible lack of availability or access to suitable milk fat substrates over ripening. The impact of lipolysis on the sensory characteristics of Cheddar cheese was unclear, possibly due to minimal differences in the extent of lipolysis between the cheeses at the end of ripening. As anticipated seasonal milk supply influenced both proteolysis and lipolysis in Cheddar cheese. The contribution of non-starter lactic acid bacteria towards proteolysis and lipolysis over the first 8 months of Cheddar cheese ripening was negligible.
A case of mistaken identity – reappraisal of the species of canid and felid hookworms (Ancylostoma) present in Australia and India
Authors: TRAUB R. J. , HOBBS R. P. , ADAMS P. J. , BEHNKE J. M. , HARRIS P. D. , THOMPSON R. C. A.
Published: September 2006

This study serves to clarify the current status of canid and felid Ancylostoma species present in Australia. The morphological identification of A. ceylanicum from cats for the first time in Townsville, Australia, appears to be in error, together with the genetic markers provided for the species. Morphological and genetic data presented herein provide strong evidence that the hookworms from cats in Towsville are not A. ceylanicum as previously identified (i.e. the first report of this species in Australia), but are A. braziliense. Therefore the subsequent genetic markers established for A. ceylanicum in subsequent molecular studies based on these Townsville specimens should also be attributed to A. braziliense. Based on this information, a study of canine hookworm species present in northern India is also in error and it is apparent that the hookworms found in this region are those of A. ceylanicum. The distribution of A. braziliense and A. ceylanicum in the Americas and Asia Pacific region is discussed together with the importance of combining parasite morphology with genetic data for parasite diagnosis in epidemiological studies.
Jack Gray, Mao Zedong and the Political Economy of Chinese Development
Authors: Selden Mark
Published: September 2006

“Integrated village development on the basis of the employment of surplus rural labour is probably the best way forward for most poor countries.” J. Gray
The Last of the Romantics? Maoist Economic Development in Retrospect
Authors: Bramall Chris
Published: September 2006

The notion that the development strategy pursued in China after 1949 had transformed the economy of the People's Republic was a staple of Western scholarship at the close of the Maoist era. Jack Gray's work of the early 1970s stood squarely within this tradition. For him, Maoism was superior to Stalinism as a transitional path to socialism because it avoided the “urban bias” inherent in the primitive socialist accumulation suggested by Preobrazhensky, practised by Stalin, and advocated for China by (inter alia) Bo Yibo and Liu Shaoqi. Instead of extracting resources from the rural sector, the late Maoist development strategy revolved around labour accumulation: the mobilization of rural labour to carry out rural industrialization, agricultural mechanization and the extension of irrigation networks.
Culture, Revolution, and the Times of History: Mao and 20th-Century China
Authors: Karl Rebecca E.
Published: September 2006

The recent spate of English-language exposés of Mao Zedong, most prominently that written by Jung Chang and Jon Halliday, seems to announce a culmination of the tendency towards the temporal-spatial conflation of 20th-century Chinese and global history. This sense was only confirmed when the New York Times reported in late January that George W. Bush's most recent bedtime reading is Mao: The Unknown Story, or when, last month, according to a column in the British paper The Guardian, “the Council of Europe's parliamentary assembly voted to condemn the ‘crimes of totalitarian communist regimes,’ linking them with Nazism…” The conflation, then, is of the long history of the Chinese revolution with the Cultural Revolution, on the one hand; and, on the other hand, of Mao Zedong with every one of the most despicable of the 20th century's many tyrants and despots. In these conflations, general 20th-century evil has been reduced to a complicit right-wing/left-wing madness, while China's 20th century has been reduced to the ten years during which this supposed principle of madness operated as a revolutionary tyranny in its teleologically ordained fashion. In this way are the dreams of some China ideologues realized: China becomes one central node through which the trends of the 20th century as a global era are concentrated, channelled and magnified. China isglobal history, by becoming a particular universalized analytic principle, in the negative sense. That is, universality becomes a conflationary negative principle.
The High Tide in Jiangsu: A Perspective from Local Sources of the Time
Authors: Ash Robert
Published: September 2006

This essay is an attempt to recreate the events of 1955–57–the “high tide” of co-operativization – in a single province of China (Jiangsu). Whereas the other articles in this Special Issue of The China Quarterly view the same events with the benefits of hindsight, as provided by documentary materials and other evidence that have become available since the end of the Mao Era, the account given here is based on contemporary reports – above all, provincial press reports. The intention is thereby not only to give a flavour of the extraordinary atmosphere that surrounded one province's response to Mao's 31 July 1955 speech, but also to convey the tensions and policy dilemmas that emerged during the second half of the year and into 1956. Even allowing for the bias of official media reports, the evidence and analysis presented here vividly highlight the complex factors – economic and social – bearing on policy making and policy implementation during 1955–56.
Charting the State of Social Cohesion in Hong Kong
Authors: Chan Joseph , Chan Elaine
Published: September 2006

This paper reports findings from the first social cohesion survey in Hong Kong. Social cohesion is understood as a multi-dimensional concept, having a horizontal dimension which is concerned with both feelings and actions of members of society, and a vertical dimension that taps those between society and the government. It is found that horizontally, society feels cohesive but the feeling is not supported by corresponding behaviour such as participation in organizations and engagement in giving and helping. Vertically, society has much higher trust in bureaucracies of justice administration than the executive branch of the government. The level of civic engagement is respectable despite a general dissatisfaction with government performance. We conclude that however cohesively society feels, it is achieved with little institutional mediation and social engagement. We postulate that this is possible because lending support to advocacy groups, participation in small group activities and close family ties might have rendered institutional mediation less significant.
Childbirth and Posttraumatic Stress Responses
Authors: Olde Eelco , Kleber Rolf J. , van der Hart Onno , Pop Victor J.M.
Published: September 2006

Childbirth has been identified as a possible traumatic experience, leading to traumatic stress responses and even to the development of posttraumatic stress disorder (PTSD). The current study investigated the psychometric properties of the Dutch version of the Impact of Event Scale-Revised (IES-R) in a group of women who recently gave birth (N = 435). In addition, a comparison was made between the original IES and the IES-R. The scale showed high internal consistency (α = 0.88). Using confirmatory factor analysis no support was found for a three-factor structure of an intrusion, an avoidance, and a hyperarousal factor. Goodness of fit was only reasonable, even after fitting one intrusion item on the hyperarousal scale. The IES-R correlated significantly with scores on depression and anxiety self-rating scales, as well as with scores on a self-rating scale of posttraumatic stress disorder. Although the IES-R can be used for studying posttraumatic stress reactions in women who recently gave birth, the original IES proved to be a better instrument compared to the IES-R. It is concluded that adding the hyperarousal scale to the IES-R did not make the scale stronger.
Training Satisfaction Rating Scale
Authors: Holgado Tello Francisco Pablo , Chacón Moscoso Salvador , Barbero García Isabel , Sanduvete Chaves Susana
Published: September 2006

We describe the process of testing a measurement model of a satisfaction rating scale for use with training programs. The scale was developed by the Evaluation Unit of the University of Seville's Training Center. Following an initial content validity study in which we reviewed how training evaluation is modeled, a 12-item rating scale was developed and administered to a sample of 2746 subjects. The measurement model was examined through an exploratory factor analysis using polychoric correlations, the results of which were consistent with the previous dimensions obtained in the content validity study. In order to refine the model under study, a confirmatory factor analysis (also based on polychoric correlations) was then performed. The results present empirical evidence of the measurement model's validity. The scale offers simple, direct and reliable training satisfaction scores. Future development of the scale is discussed.
Measurement Invariance of the Abridged Sense of Coherence Scale in Adolescents
Authors: Zimprich Daniel , Allemand Mathias , Hornung Rainer
Published: September 2006

In the present study, the factorial structure and the degree of measurement invariance of the short form of the Sense of Coherence Scale (SOCS-13) were examined across two groups of adolescents. The sample comprised 1107 Swiss students (535 aged 14 or younger and 572 aged 15 or older). Considering a sequence of confirmatory factor models and using robust parameter estimation, results indicate that a two-factor model of sense of coherence adequately described the data. The first factor encompassed Comprehensibility and Manageability items, whereas the second factor reflected Meaningfulness. Strict measurement invariance could be established, i.e., factor loadings, latent intercepts of the manifest indicators, and residual variances were found to be equal in both age groups. In the end, students from the older age group, on average, had higher factor scores in Comprehensibility-Manageability. These findings provide support for a two-dimensional structure and complete unbiasedness of the SOCS-13 in adolescent samples differing in age.
Influence of solar variability on gravity wave structure and dissipation in the thermosphere from tropospheric convection
Authors: Vadas Sharon L. , Fritts David C.
Published: September 2006

We investigate the role convection plays in the thermosphere using deep convection and ray trace models with a general dissipative anelastic GW dispersion relation. In the absence of dissipation, a GW's vertical wavelength λz increases by , or greater if its intrinsic frequency ωIr is close to the smaller thermospheric buoyancy frequency N = N0. Here, and 0 are the asymptotic temperatures in the thermosphere and lower atmosphere, respectively, and N0 is the buoyancy frequency in the lower atmosphere. In the presence of dissipation, λz also increases in the thermosphere by a factor of ∼2–3 when ωIr > 0.2N0 and λz > 25 km during active solar conditions. GW dissipation altitudes and maximum vertical wavelengths, which increase as increases, are displayed for small‐scale and midscale GWs. GWs excited from deep convection encounter horizontal shears, which impose anisotropy on the spectrum. Along with dissipative filtering, momentum flux divergence and body forces result. The thermospheric body forces resulting from our convection model achieve maximum accelerations at z 180–200 km, extend down to z 130 km, last for the duration of deep convection, are ∼600 km × 600 km × 40–80 km in the x, y, and z directions, and are very strong with accelerations ≃0.5–0.75 m s−2 and ≃0.25–0.4 m s−2 during extreme solar minimum ( = 600 K) and active solar conditions ( = 2000 K), respectively. During extreme solar minimum, there is negligible forcing above z ≃ 230 km, whereas the forcing extends up to z ≃ 360 km during active solar conditions. These horizontal, thermospheric body forces may be a new source of large‐scale, long‐period secondary GWs and induced TIDs (traveling ionospheric disturbances) at high altitudes in the thermposphere.
Unusual mantle Poisson's ratio, subduction, and crustal structure in central Alaska
Authors: Rossi Giovannibattista , Abers Geoffrey A. , Rondenay Stephane , Christensen Douglas H.
Published: September 2006

Subduction zones alter the upper plate in a variety of ways, including metasomatism via slab‐derived fluids and accretion of exotic terranes. These processes should produce distinctive seismic signatures, as seismic velocities are sensitive to compositional variations. A new method is developed to estimates depths to interfaces and Poisson's ratio (Vp/Vs ratio) for dipping layered structures, by stacking teleseismic receiver functions. It also estimates crustal Vp/Vs and thickness. Using this method, we analyze a broadband data set from the central Alaska subduction zone, to seek evidence for mantle wedge composition. Crustal thickness varies from 27 to 45 km, and crustal Vp/Vs indicates an intermediate to mafic composition, expected for these accreted island arc terranes. Inversions for mantle structure confirm the presence of a 15–20 km thick low‐velocity zone atop of the downgoing plate to 130 km depth, perhaps subducted crust of an exotic terrane. Vp/Vs in the mantle wedge allows for 15 ± 15% serpentinization where the slab is <80 km deep and the wedge is cold. Where the slab is deeper, Vp/Vs for the mantle wedge is unusually low, <1.7. This value is lower than predicted for any common mantle mineral and may indicate significant quantities of quartz, provided that past physical properties measurements are not grossly in error. These results suggest that the mantle wedge in subduction zones can occasionally differ substantially in bulk composition from normal subcrustal mantle, perhaps because collisions of exotic terranes cause tectonic mixing of crustal material into the mantle.
Segmentation of the Levant continental margin, eastern Mediterranean
Authors: Ben‐Avraham Z. , Schattner U. , Lazar M. , Hall J. K. , Ben‐Gai Y. , Neev D. , Reshef M.
Published: September 2006

The Levant continental margin is divided into two major segments by the Carmel structure, which extends from the Dead Sea fault into the eastern Mediterranean. New seismic reflection data over the unexplored northern segment are used for completing the structural framework of the Levant area, together with existing data south of it. Inclusive depth structural maps of the area were produced for the base Pliocene and base Messinian evaporites. Previous studies indicate that differences between the two segments are well expressed in the deep crustal structure. The present study, which focuses mainly on the shallow section, shows that these differences are maintained throughout the accumulation of young sedimentary units, and even in the bathymetry. This preservation of segmentation, both in the shallow and in the deep structure, insinuates that the two segments were formed through different continental breakup processes, which continue to dictate the style of sediment accumulation.
Nocturnal jet and its effects on early morning rainfall peak over northeastern Bangladesh during the summer monsoon season
Authors: Terao Toru , Islam Md. Nazrul , Hayashi Taiichi , Oka Taro
Published: September 2006

Diurnal variations of rainfall and upper wind over Bangladesh during the summer monsoon season were investigated through the data analysis of raingauge, 4‐times‐daily rawinsonde and pilot balloon observations. Over the northeastern part where the total monsoon rainfall is heavy a rainfall peak appears at 3 to 6 local time in the early morning. In the lower troposphere, the southeasterly accelerates in the evening, and the wind direction exhibits a clockwise change at night. This feature corresponds with the nocturnal jet, which can be a cause of the midnight‐early morning rainfall peak in the northeastern part of Bangladesh through the increased wind blowing against the southern edge of the Meghalaya Mountains.
Reduced‐order 4D‐Var: A preconditioner for the Incremental 4D‐Var data assimilation method
Authors: Robert C. , Blayo E. , Verron J.
Published: September 2006

This study demonstrates how the incremental 4D‐Var data assimilation method can be applied efficiently preconditioned in an application to an oceanographic problem. The approach consists in performing a few iterations of the reduced‐order 4D‐Var prior to the incremental 4D‐Var in the full space in order to achieve faster convergence. An application performed in the tropical Pacific Ocean, with assimilation of TAO temperature data, shows the method to be both feasible and efficient. It allows the global cost of the assimilation to be reduced by a factor of 2 without affecting the quality of the solution.
Long‐range, critical‐point dynamics in oil field flow rate data
Authors: Main I. G. , Li L. , Heffer K. J. , Papasouliotis O. , Leonard T.
Published: September 2006

Earthquake triggering data exhibit long‐range spatio‐temporal correlations of the power‐law form C(l) ∼ l−α and anomalously‐slow temporal diffusion of the mean triggering distance of the form: 〈l〉 ∼ tH, with H < 0.5. We examine spatio‐temporal correlations in subsurface effective stress state caused by fluid injection and extraction at well sites in a hydrocarbon reservoir using a multivariate statistical regression model, and observe long‐range correlations in flow rate that cannot be caused by Darcy flow alone. Significantly‐correlated well pairs align with the directions of incipient horizontal‐displacement tensile and shear failure in the present‐day stress field, while the contours of the first principal component of the regression matrix closely follow the macroscopic fault pattern in the main producing horizon. The correlation function for well pairs has a power‐law form with α ≈ 0.5, and the mean correlation distance increases with H ≈ 0.33, implying a similar critical‐point response to perturbations in effective stress as the earthquake data.
Difference in seasonal variation of net precipitation between the Arctic and Antarctic regions
Authors: Oshima Kazuhiro , Yamazaki Koji
Published: September 2006

The difference in the climatological seasonal variation of the net precipitation (precipitation minus evaporation) between the Arctic and the Antarctic was evaluated using ECMWF reanalysis data. Evaluated for simplified polar caps (the regions poleward of 70°N and 67.5°S), over the Arctic, the net precipitation is large in the boreal summer, while over the Antarctic, it is large in the austral winter. The net precipitation depends strongly on the poleward transient moisture flux into the region, which is affected by both the meridional moisture gradient and eddy activity. Thus, the seasonal variation of the poleward transient moisture flux is determined by the relative amplitude of the moisture and eddy factors, that is, by the ratio of the amplitude of the seasonal variation to the annual mean. While both regions have similar relative amplitudes of the eddy factor, the moisture factor in the Arctic is much larger than in the Antarctic. The moisture factor explains the difference in the seasonal variation of the net precipitation.
Diagnosis of the summertime warm and dry bias over the U.S. Southern Great Plains in the GFDL climate model using a weather forecasting approach
Authors: Klein Stephen A. , Jiang Xianan , Boyle Jim , Malyshev Sergey , Xie Shaocheng
Published: September 2006

Weather forecasts started from realistic initial conditions are used to diagnose the large warm and dry bias over the United States Southern Great Plains simulated by the GFDL climate model. The forecasts exhibit biases in surface air temperature and precipitation within 3 days which appear to be similar to the climate bias. With the model simulating realistic evaporation but underestimated precipitation, a deficit in soil moisture results which amplifies the initial temperature bias through feedbacks with the land surface. The underestimate of precipitation may be associated with an inability of the model to simulate the eastward propagation of convection from the front‐range of the Rocky Mountains and is insensitive to an increase of horizontal resolution from 2° to 0.5° latitude.
Regulatory genes controlling cell fate choice in embryonic and adult neural stem cells
Authors: Gangemi Rosaria Maria Rita , Perera Marzia , Corte Giorgio
Published: September 2006

Neural stem cells are the most immature progenitor cells in the nervous system and are defined by their ability to self‐renew by symmetric division as well as to give rise to more mature progenitors of all neural lineages by asymmetric division (multipotentiality). The interest in neural stem cells has been growing in the past few years following the demonstration of their presence also in the adult nervous system of several mammals, including humans. This observation implies that the brain, once thought to be entirely post‐mitotic, must have at least a limited capacity for self‐renewal. This raises the possibility that the adult nervous system may still have the necessary plasticity to undergo repair of inborn defects and acquired injuries, if ways can be found to exploit the potential of neural stem cells (either endogenous or derived from other sources) to replace damaged or defective cells. A full understanding of the molecular mechanisms regulating generation and maintenance of neural stem cells, their choice between different differentiation programmes and their migration properties is essential if these cells are to be used for therapeutic applications. Here, we summarize what is currently known of the genes and the signalling pathways involved in these mechanisms.
Cholinergic modulation of microglial activation by α7 nicotinic receptors
Authors: Shytle R. Douglas , Mori Takashi , Townsend Kirk , Vendrame Martina , Sun Nan , Zeng Jin , Ehrhart Jared , Silver Archie A. , Sanberg Paul R. , Tan Jun
Published: September 2006

Almost all degenerative diseases of the CNS are associated with chronic inflammation. A central step in this process is the activation of brain mononuclear phagocyte cells, called microglia. While it is recognized that healthy neurons and astrocytes regulate the magnitude of microglia‐mediated innate immune responses and limit excessive CNS inflammation, the endogenous signals governing this process are not fully understood. In the peripheral nervous system, recent studies suggest that an endogenous ‘cholinergic anti‐inflammatory pathway’ regulates systemic inflammatory responses via α7 nicotinic acetylcholinergic receptors (nAChR) found on blood‐borne macrophages. These data led us to investigate whether a similar cholinergic pathway exists in the brain that could regulate microglial activation. Here we report for the first time that cultured microglial cells express α7 nAChR subunit as determined by RT–PCR, western blot, immunofluorescent, and immunochistochemistry analyses. Acetylcholine and nicotine pre‐treatment inhibit lipopolysaccharide (LPS)‐induced TNF‐α release in murine‐derived microglial cells, an effect attenuated by α7 selective nicotinic antagonist, α‐bungarotoxin. Furthermore, this inhibition appears to be mediated by a reduction in phosphorylation of p44/42 and p38 mitogen‐activated protein kinase (MAPK). Though preliminary, our findings suggest the existence of a brain cholinergic pathway that regulates microglial activation through α7 nicotinic receptors. Negative regulation of microglia activation may also represent additional mechanism underlying nicotine's reported neuroprotective properties.
Plasma induced laser beam smoothing below the filamentation threshold
Authors: Grech M. , Tikhonchuk V. T. , Riazuelo G. , Weber S.
Published: September 2006

This paper deals with a statistical approach for description of the laser field interaction with underdense plasmas and modification of the laser beam temporal coherence during its propagation through a plasma at power well below the filamentation threshold. The main properties of the plasma density perturbations driven by a randomized laser beam are derived from a stochastic wave equation. The laser spectral and angular broadening is shown to occur on a distance that depends essentially on the ratio of the average power in a speckle to the critical power for filamentation. The coherence time of the transmitted light is reduced to the plasma acoustic time of response to the laser. It is typically a few picoseconds. Dedicated diagnostics have been developed for the interaction code PARAX in order to analyze the laser and plasma statistical properties. The effect of the plasma length on the transmitted light coherence is found to be in good agreement with theoretical predictions. Forward stimulated Brillouin scattering is shown to play a key role in the laser coherence loss in this low-intensity regime. The limitations of the analytical model are discussed in terms of the deviation of the electric field distribution from the Gaussian statistics and creation of density-electric field correlations. This regime of laser induced incoherence is especially interesting in that the associated angular broadening is not as deleterious as observed for higher intensities. Moreover, beam smoothing can be achieved in low-density plasmas where energy losses due to absorption and backscattering are not too important.
Singlet exciton transfer and fullerene triplet formation in polymer-fullerene blend films
Authors: Cook Steffan , Ohkita Hideo , Durrant James R. , Kim Youngkyoo , Benson-Smith Jessica J. , Nelson Jenny , Bradley Donal D. C.
Published: September 2006

Photoluminescence and transient absorption measurements of poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) and 1-(3-methoxycarbonyl)propyl-1-phenyl-(6,6)C61 (PCBM) blend films reveal that optical excitation of F8BT results in formation of the singlet and triplet excited states of PCBM. These observations are assigned to rapid (>1011s−1) singlet energy transfer from F8BT to PCBM, followed by intersystem crossing to the PCBM triplet state.
Large negative magnetoresistance and strong localization in highly disordered electrospun pregraphitic carbon nanofiber
Authors: Wang Yu , Santiago-Avilés Jorge J.
Published: September 2006

A highly disordered pregraphitic carbon nanofiber with the product of its quasi-Fermi wave vector and mean free path close to 1 was fabricated using electrospinning technique. Strong localization made the conductivity vary with temperature as lnσ∝T−1∕2 from 300to5K, suggesting variable range hopping as the conductivity mechanism, and resulted in a large negative magnetoresistance from 300K down to 1.9K that can still be quantitatively described using weak localization and electron interaction models.
Necessary conditions for display and fast switching of high contrast images by antiferroelectric liquid crystal displays
Authors: Komitov Lachezar , Olsson Nils , Helgee Bertil
Published: September 2006

Antiferroelectric liquid crystals (AFLC) with 45° molecular tilt were stated to be the solution of the dark state problem in AFLC displays (AFLCDs). However, AFLCs that are available at present actually possess antiferroelectric (AF) to ferroelectric (F) transition of first order characterized by slow switching times which in turn deteriorates the dark state in AFLCDs. Here, we report on the switching behavior of a siloxane AFLC dimer with molecular tilt close to 45°. This material exhibits AF to F transition of second order at lower temperatures, something that enables display and fast switching of high contrast images in AFLCDs.
Efficiency of energy conversion by piezoelectrics
Authors: Cho J. H. , Richards R. F. , Bahr D. F. , Richards C. D. , Anderson M. J.
Published: September 2006

The efficiency of energy conversion by piezoelectric devices depends upon the quality factor Q and electromechanical coupling coefficient k2. In this study the efficiency Q and k2 are measured for a piezoelectric cantilever, a piezoelectric stack, and a micromachined piezoelectric membrane. The experimental values are compared to a model which predicts efficiency at resonance in terms of k2 and Q. Results of the experiment and model are within 2% of each other.
Control of gray scale inversion in a film-compensated twisted nematic liquid crystal display using beam steering optical film
Authors: Park Chi Hyuk , Lee Seung Hee , Jeong Jinkwan , Kim Kyoung Jin , Choi Hyun Chul
Published: September 2006

Commercially available, twisted nematic (TN), liquid crystal cells have intrinsic problems such as light leakage in the dark state, gray scale inversion, and brightness nonuniformity in gray scales when the viewing direction deviates from the normal axis. Film compensation of a TN cell has solved the first problem but the second remains unsolved, which has hindered its applications to large displays. This letter proposes the use of a beam steering film to prepare a TN cell free of gray scale inversion in wide viewing directions.
Equilibrium model for two low-pressure electronegative plasmas connected by a double layer
Authors: Chabert P. , Plihon N. , Corr C. S. , Raimbault J.-L. , Lichtenberg A. J.
Published: September 2006

Plihon et al. [J. Appl. Phys. 98, 023306 (2005)] have recently shown that double layers usually form during the expansion of a low pressure electronegative plasma. These double layers act as permeable internal boundaries between the source (upstream) plasma and the downstream expanding plasma; positive ions flow from upstream to downstream whereas negative ions flow in the opposite direction. So far, the detailed physical mechanisms leading to their formation have not been identified. In this paper, we develop a model for the two plasma equilibria, upstream and downstream, assuming that the double layer exists and couples the two plasmas. At very low pressure, typically 0.5mTorr, the coupling is strong and acts both ways. The negative ions created downstream contributes to the upstream equilibrium as well as the upstream positive ions contribute to the downstream equilibrium. As the pressure increases, the situation becomes asymmetric. The source plasma is not affected by the negative ions flowing from downstream, whereas the positive ions coming from the source control the downstream plasma equilibrium, where local ionization is negligible.