bluuebunny/crossref_metadata_2025 huggingface dataset:
Population frequencies of transposable elements in selfing and outcrossingCaenorhabditisnematodes
Authors: DOLGIN ELIE S. , CHARLESWORTH BRIAN , CUTTER ASHER D.
Published: October 2008

Population genetics theory predicts that differences in breeding systems should be an important factor in the dynamics of selfish genetic elements, because of different intensities of selection on both hosts and elements. We examined population frequencies of transposable elements (TEs) in natural populations of the self-fertilizing nematodeCaenorhabditis elegansand its outcrossing relativeCaenorhabditis remanei. We identified a Tc1-like class of elements in theC. remaneigenome with homology to the terminal inverted repeats of theC. elegansTc1 transposon, which we name mTcre1. We measured levels of insertion polymorphism for all 32 Tc1 elements present in the genome sequence of theC. elegansN2 strain, and 16 mTcre1 elements from the genome sequence of theC. remaneiPB4641 strain. We show that transposons are less polymorphic and segregate at higher frequencies inC. eleganscompared withC. remanei. Estimates of the intensity of selection based on the population frequencies of polymorphic elements suggest that transposons are selectively neutral inC. elegans, but subject to purifying selection inC. remanei. These results are consistent with a reduced efficacy of natural selection against TEs in selfing populations, but may in part be explained by non-equilibrium TE dynamics.
Intra-individual and intra-species heterogeneity in nuclear rDNA ITS region ofVignaspecies from subgenusCeratotropis
Authors: SAINI AJAY , REDDY SREENIVASULU K. , JAWALI NARENDRA
Published: October 2008

The extent of intra-individual and intra-species heterogeneity in the nuclear rDNA internal transcribed spacer (ITS) was investigated among the ‘AsiaticVigna’ species (subgenusCeratotropis). High intra- and inter-individual ITS polymorphism was observed amongVigna radiataaccessions, where multiple ITS length variants ranging from ~700 to ~770 bp were detected on PCR amplification. Subsequent analysis revealed that the variants are ‘heteroduplex ITS fragments’ generated during the PCR process. Analysis of ITS from wild and cultivated forms of tenVignaspecies from subgenusCeratotropisrevealed substantial intra-species divergence in four species:Vigna umbellata,Vigna trilobata,V. radiataandVigna minima. However, no other species analysed showed intra-individual ITS heterogeneity as observed inV. radiata. The results demonstrate differential evolution of ITS sequence among wild and cultivated forms ofV. radiata. Evidence indicates that intra-species hybridization and a slow ‘molecular drive’ are responsible for this phenomenon. Sequence analysis of 5·8S, ITS1 and ITS2 and secondary-structure analysis of ITS regions indicate that the ITS variants do not belong to pseudogenic rDNA repeat units. Further, reverse transcriptase-PCR (RT-PCR) analysis showed that rDNA repeat units harbouring certain intra-individual ITS variants were transcriptionally inactive, indicating the regulation of these loci by epigenetic gene silencing. TheV. radiataITS variants, when analysed together, did not cause any phylogenetic errors at the species level.
Minimum dissipative relaxed states applied to laboratory and space plasmas
Authors: DASGUPTA B. , SHAIKH DASTGEER , HU Q. , ZANK G. P.
Published: October 2008

The usual theory of plasma relaxation, based on the selective decay of magnetic energy over the (global) magnetic helicity, predicts a force-free state for a plasma. Such a force-free state is inadequate to describe most realistic plasma systems occurring in laboratory and space plasmas as it produces a zero pressure gradient and cannot couple magnetic fields with flow. A different theory of relaxation has been proposed by many authors, based on a well-known principle of irreversible thermodynamics, the principle of minimum entropy production rate which is equivalent to the minimum dissipation rate of energy. We demonstrate the applicability of minimum dissipative relaxed states to various self-organized systems of magnetically confined plasma in the laboratory and in the astrophysical context. Such relaxed states are shown to produce a number of basic characteristics of laboratory plasma confinement systems and solar arcade structure.
The dangers and limitations of equality agendas as means for tackling old-age prejudice
Authors: DUNCAN COLIN
Published: October 2008

This paper presents a critique of both the concept of age equality and of the limited scope it offers as a means for challenging old-age prejudice. The equality constructs that feature in anti-ageism initiatives and in current discourses on intergenerational equity have proved susceptible to political and ideological manipulation, which has led to the illegitimate dissociation of ageism from older age and promoted damaging notions of age equivalence. The consequence has been that old-age prejudice has been de-prioritised, and older people have been de-legitimised socially and as a welfare constituency. The corrective is best sought outside the confines of age equality frameworks, although legal remedies may play a useful role if human dignity is incorporated as an equality criterion. This paper also assesses other approaches to tackling old-age prejudice that avoid the constraints of equality constructs and engage more firmly with its roots. The notion of the ‘third age’ with new social roles merits reconsideration as an affordable alternative to current policies of work obligation and pension retrenchment. Radical interventions in the labour market in favour of older people may also be needed. Age activism and advocacy will increasingly influence policy on prejudice and well-being in older age, but changed emphases are needed, as from defensive strategies and the ideologies of generational interdependence and solidarity, towards the promotion of organisational, financial and social autonomy in older age.
The experience of social and emotional loneliness among older people in Ireland
Authors: DRENNAN JONATHAN , TREACY MARGARET , BUTLER MICHELLE , BYRNE ANNE , FEALY GERARD , FRAZER KATE , IRVING KATE
Published: October 2008

This paper reports a study of the risk factors for social and emotional loneliness among older people in Ireland. Using the ‘Social and Emotional Scale for Adults’, the social and emotional dimensions of loneliness were measured. Emotional loneliness was conceptualised as having elements of both family loneliness and romantic loneliness. The data were collected through a national telephone survey of loneliness in older people conducted in 2004 that completed interviews with 683 people aged 65 or more years. It was found that levels of social and family loneliness were low, but that romantic loneliness was relatively high. Predictors for social loneliness were identified as greater age, poorer health, living in a rural area, and lack of contact with friends. Living in a rural setting, gender (male), having a lower income, being widowed, no access to transport, infrequent contact with children and relatives and caring for a spouse or relative at home were significant predictors of family loneliness. Romantic loneliness was predicted by marital status, in particular being widowed. Never having married or being divorced or separated were also significant predictors for romantic loneliness. The findings indicate that loneliness for older people is variable, multi-dimensional and experienced differently according to life events, with, for example, the death of a partner being followed by the experience of emotional loneliness, or the loss of friends or declining health leading to social loneliness.
Facts on Law and Ageing Quiz: older people's knowledge of their legal rights
Authors: DORON ISRAEL , WERNER PERLA
Published: October 2008

Until now, no attempt has been made to develop a research tool to provide a broad descriptive picture of the actual knowledge that older people have of their legal rights. This article will describe a first attempt, conducted in Israel, to create such a tool, known as theFacts on Law and Ageing Quiz (FoLAQ). This quiz was developed to provide a short and standardised tool for assessing older people's knowledge of their legal rights in Israel. It is also intended to serve as a research platform for similar studies in other countries worldwide. The research was designed using a quantitative approach. The research population consisted of adult Jews, aged 50 or more years, living in the community in Israel. Using a computer-assisted telephone interview (CATI), a randomly chosen sample of 227 persons aged 50 and over was asked 20 multiple-choice questions on central legal issues, and 13 closed questions on their socio-demographic background. The findings revealed that, in general, the majority of older persons in Israel know little about their legal rights. Specifically, the most vulnerable groups in this context were the less educated, the poor, the older-old, and women. Finally, the findings also showed that knowledge gaps were particularly obvious with regard to (1) national legal schemes covering social security in old age, and (2) the rights of older people regarding Israel's national health insurance scheme.
Uniqueness of standing waves for nonlinear Schrödinger equations
Authors: Byeon Jaeyoung , Oshita Yoshihito
Published: October 2008

For m > 0 and p ∈ (1, (N + 2)/(N − 2)), we show the uniqueness and a linearized non-degeneracy of solutions for the following problem:
Stationary surfaces in Lorentz–Minkowski space
Authors: López Rafael
Published: October 2008

Consider a space-like plane Π in Minkowski space. Under the presence of a uniform time-like potential directed towards Π, this paper analyses the configurations of shapes that show a space-like surface supported in Π with prescribed volume and show that it is a critical point of the energy of this system. Such a surface is called stationary and it is determined by the condition that the mean curvature is a linear function of the distance from Π and the fact that the angle of contact with the plate Π is constant. We prove that the surface must be rotational symmetric with respect to an axis orthogonal to Π. Next, we show existence and uniqueness of symmetric solutions for a prescribed angle of contact with Π. Finally, we study the shapes that a stationary surface can adopt in terms of its size. We thus derive estimates of its height and the enclosed volume by surface with the support plane.
A simulation model for diarrhoea and other common recurrent infections: a tool for exploring epidemiological methods
Authors: SCHMIDT W.-P. , GENSER B. , CHALABI Z.
Published: October 2008

The measurement and analysis of common recurrent conditions such as diarrhoea, respiratory infections or fever pose methodological challenges with regard to case definition, disease surveillance and statistical analysis. In this paper we describe a flexible and robust model that can generate simulated longitudinal datasets for a range of recurrent infections, reflecting the stochastic processes that underpin the data collected in the field. It can be used to evaluate and compare alternative disease definitions, surveillance strategies and statistical methods under ‘controlled conditions’. Parameters in the model include: characterizing the distributions of the individual disease incidence and the duration of disease episodes; allowing the average disease duration to depend on an individual's number of episodes (simulating a correlation between incidence and duration); making the individual risk of disease depend on the occurrence of previous episodes (simulating autocorrelation of successive episodes); finally, incorporating seasonal variation of disease.
Converging methods in studying attention-deficit/hyperactivity disorder: What can we learn from neuroimaging and genetics?
Authors: Durston Sarah
Published: October 2008

This paper discusses how converging methods may form a powerful tool in unraveling the neurobiology of attention-deficit/hyperactivity disorder (ADHD). Integrating findings from multiple disciplines can inform us on how different neurobiological and cognitive mechanisms tie together in both typical and atypical development. Examples are discussed of this approach: combining family and genetic approaches with anatomical neuroimaging illustrates how mapping familial effects can bring us closer to understanding the neurobiology of ADHD. Functional neuroimaging has convincingly linked cognitive problems in this disorder with frontostriatal functioning, but also shows that other systems may be involved in some of the symptoms of ADHD. Combining these findings has suggested new avenues for investigation, such as the role of frontocerebellar networks. Furthermore, findings may have practical applications: this paper discusses an example of how converging evidence of striatal dysregulation in ADHD suggests possible directions for treatment that are now being explored in functional imaging studies.
The development of antisocial behavior: What can we learn from functional neuroimaging studies?
Authors: Crowe S. L. , Blair R. J. R.
Published: October 2008

The recent development of low-risk imaging technologies, such as functional magnetic resonance imaging (fMRI), have had a significant impact on the investigation of psychopathologies in children and adolescents. This review considers what we can infer from fMRI work regarding the development of conduct disorder (CD) and oppositional defiant disorder (ODD). We make two central assumptions that are grounded in the empirical literature. First, the diagnoses of CD and ODD identify individuals with heterogeneous pathologies; that is, different developmental pathologies can receive a CDD or ODD diagnosis. This is indicated by the comorbidities associated with CD/ODD, some of which appear to be mutually exclusive at the biological level (e.g., posttraumatic stress disorder [PTSD] and psychopathic tendencies). Second, two populations of antisocial individuals can be identified: those that show an increased risk for only reactive aggression and those that show an increased risk for both reactive and instrumental aggression. We review the fMRI data indicating that particular comorbidities of CD/ODD (i.e., mood and anxiety conditions such as childhood bipolar disorder and PTSD) are associated with either increased responsiveness of neural regions implicated in the basic response to threat (e.g., the amygdala) or decreased responsiveness in regions of frontal cortex (e.g., ventromedial frontal cortex) that are implicated in the regulation of the basic threat response. We suggest why such pathology would increase the risk for reactive aggression and, in turn, lead to the association with a CD/ODD diagnosis. We also review the literature on psychopathic tendencies, a condition where the individual is at significantly elevated risk for both reactive and instrumental aggression. We show that in individuals with psychopathic tendencies, the functioning of the amygdala in stimulus-reinforcement learning and of the ventromedial frontal cortex in the representation of reinforcement expectancies is impaired. We suggest why such pathology would increase the risk for reactive and instrumental aggression and thus also lead to the association with a CD/ODD diagnosis.
Altered amygdala and hippocampus function in adolescents with hypercortisolemia: A functional magnetic resonance imaging study of Cushing syndrome
Authors: Maheu Françoise S. , Mazzone Luigi , Merke Deborah P. , Keil Margaret F. , Stratakis Constantine A. , Pine Daniel S. , Ernst Monique
Published: October 2008

Chronic elevations of endogenous cortisol levels have been shown to alter medial temporal cortical structures and to be accompanied by declarative memory impairments and depressive symptoms in human adults. These effects of elevated endogenous levels of cortisol have not been directly studied in adolescents. Because adolescents with Cushing syndrome show endogenous elevations in cortisol, they represent a unique natural model to study the effects of prolonged hypercortisolemia on brain function, and memory and affective processes during this developmental stage. Using functional magnetic resonance imaging (fMRI), we compared 12 adolescents with Cushing syndrome with 22 healthy control adolescents on amygdala and anterior hippocampus activation during an emotional faces encoding task. None of these adolescents manifested depressive symptoms. Encoding success was assessed using a memory recognition test performed after the scan. The fMRI analyses followed an event-related design and were conducted using the SPM99 platform. Compared to healthy adolescents, patients with Cushing syndrome showed greater left amygdala and right anterior hippocampus activation during successful face encoding. Memory performance for faces recognition did not differ between groups. This first study of cerebral function in adolescents with chronic endogeneous hypercortisolemia due to Cushing syndrome demonstrates the presence of functional alterations in amygdala and hippocampus, which are not associated with affective or memory impairments. Such findings need to be followed by work examining the role of age and related brain maturational stage on these effects, as well as the identification of possible protective factors conferring resilience to affective and cognitive consequences in this disease and/or during this stage of cerebral development.
Linear, bounded, functional pretty-printing
Authors: SWIERSTRA S. DOAITSE , CHITIL OLAF
Published: October 2008

We present two implementations of Oppen's pretty-printing algorithm in Haskell that meet the efficiency of Oppen's imperative solution but have a simpler and a clear structure. We start with an implementation that uses lazy evaluation to simulate two co-operating processes. Then we present an implementation that uses higher-order functions for delimited continuations to simulate co-routines with explicit scheduling.
Creation of an intraatrial tunnel to produce a total cavo-pulmonary connection in a patient with dominant right ventricle, totally anomalous pulmonary venous connection, and pulmonary atresia with non-confluent pulmonary arteries
Authors: Sughimoto Koichi , Aoki Mitsuru , Fujiwara Tadashi
Published: October 2008

The surgical strategy for patients having a functionally single ventricle associated with totally anomalous pulmonary venous connection and pulmonary atresia with non-confluent pulmonary artery has yet to be agreed. We created an intraatrial tunnel to produce a total cavo-pulmonary connection in such a patient, also creating a confluence for the pulmonary arteries. By minimizing the use of the GoreTex patch, the patient was able to discontinue the use of warfarin.
A practical and transferable new protocol for treadmill testing of children and adults*
Authors: Dubowy Karl-Otto , Baden Winfried , Bernitzki Stefan , Peters Brigitte
Published: October 2008

Background

It is just as vital to have an exact overview of the physical fitness of young and growing people as it is for adults. The currently used exercise protocols have limitations in healthy small children, and in senior citizens. In particular with chronically ill patients, regardless of their age, there is a need for an exercise protocol that permits observations over the long term. With this need in mind, we have designed a new transferable standardised exercise protocol, constructing reference values based on improved assessments on a treadmill that permitted stepwise increases of speed and gradient every 90 seconds – the so called treadmill protocol from the German Society of Paediatric Cardiology.

Objectives

We investigated the exercise performance in a healthy Caucasian population ranging in age from 4 to 75 years.

Methods

We measured, using a prospective study design, the distance run, the endurance, and the consumption of oxygen in 548 females and 647 males undergoing an enhanced spiroergometric treadmill protocol in two centres.

Results and conclusions

Until puberty, boys and girls have the same indicators of exercise performance. Subsequent to puberty, uptake of oxygen and distance run differ, with males showing higher uptake of oxygen. There is still an age-dependent dynamic of peak uptake of oxygen related to body surface area. Using these new reference values, covering the whole range of age, it proves possible to compare performance during growth and aging of the individual. In this fashion, we have calculated centiles for all recorded variables. External calibration, validation and quality control ensures transferability of our data to other spiroergometry units.
Some questions concerning Hrushovski's amalgamation constructions
Authors: Hasson Assaf
Published: October 2008

In order to construct a counterexample to Zilber's conjecture—that a strongly minimal set has a degenerate, affine or field-like geometry—Ehud Hrushovski invented an amalgamation technique which has yielded all the exotic geometries so far. We shall present a framework for this construction in the language of standard geometric stability and show how some of the recent constructions fit into this setting. We also ask some fundamental questions concerning this method.
La fusion libre : le cas simple
Authors: Hils Martin
Published: October 2008

We construct the free fusion of two geometric thories over a common ω-categorical strongly minimal reduct. If the two theories are supersimple of rank 1 (and satisfy an additional hypothesis true in particular for stable theories or trivial reduct), the completions of the free fusion are supersimple of rank at most ω.
Begabungsdiagnostik mit dem Grundintelligenztest (CFT 20-R)
Authors: Kuhn Jörg-Tobias , Holling Heinz , Freund Philipp Alexander
Published: October 2008

Zusammenfassung. Der CFT 20-R ist ein in der psychologischen Praxis häufig eingesetzter Test zur Diagnostik der fluiden Intelligenz. Er dient damit auch zur Diagnose von Hochbegabung. Gegenstand dieses Artikels ist die psychometrische Überprüfung der Kurzform 1 des Grundintelligenztests (CFT 20-R; Weiß, 2006 ) hinsichtlich der Messäquivalenz des Verfahrens zwischen normal- und höher begabten Schülern. Berichtet werden Ergebnisse auf Item- sowie Subtestebene. Eine Stichprobe von insgesamt N = 1886 Haupt-, Real- sowie Gymnasialschülern beiderlei Geschlechts bearbeitete die Kurzform 1 des CFT 20-R. Mittels DIF-Analysen (Itemebene) kann beim Vergleich von höher (IQ ≥ 120) sowie normal begabten Schülern (IQ < 120) gezeigt werden, dass größtenteils Messäquivalenz hinsichtlich der Itemschwierigkeiten, weniger hinsichtlich der Trennschärfen vorliegt. Die Messäquivalenz auf der Ebene der Subtests ist hoch. Das Verfahren kann damit im Rahmen eines ersten (Hoch-)Begabungsscreenings gut eingesetzt werden.
Dependence of size‐resolved CCN spectra on the mixing state of nonvolatile cores observed in Tokyo
Authors: Kuwata Mikinori , Kondo Yutaka
Published: October 2008

Size‐resolved cloud condensation nuclei (CCN) spectra and volatility tandem differential mobility analyzer (VTDMA) measurements were made simultaneously in Tokyo in wintertime 2007 to characterize CCN activity near the urban center. Ambient particles with mobility diameters of 30–200 nm were investigated at supersaturations (SSs) of 0.32, 0.60, and 0.88%. The size distributions of the nonvolatile cores of size‐selected particles measured by the VTDMA were bimodal; one mode showed relatively small changes (<10%) in peak diameter by volatilization, and the other mode showed significant changes in diameter (>10% in peak diameter). The former mode is referred to as less volatile (LV), and the latter mode is called more volatile (MV). The main component of nonvolatile cores in Tokyo is known to be black carbon (BC). Therefore, it is likely that LV particles correspond to soot particles. The size‐resolved CCN spectra were broader than those of (NH4)2SO4, indicating that the observed particles were not uniformly mixed. In addition, CCN/CN (CN: condensation nuclei) ratios were smaller than unity after the stepwise increase. A CCN‐LV correlation analysis shows that for small (<80 nm) particles, the slopes of the correlations were smaller than unity, although the correlations were significant. This indicates that CCN‐inactive fractions are explained by LV particles and particles coemitted with LV particles (likely primary organic aerosol particles). For larger particles (>100 nm), the CCN‐inactive fractions were close to the LV particle fractions, suggesting that CCN‐inactive particles were composed of fresh soot.
p/CAF modulates the activity of the transcription factor p48/Ptf1a involved in pancreatic acinar differentiation
Authors: Rodolosse Annie , Campos Maria-Luisa , Rooman Ilse , Lichtenstein Mathieu , Real Francisco X.
Published: October 2008

p48, also called Ptf1a (pancreas-specific transcription factor 1a), is a tissue-restricted bHLH (basic helix loop helix) transcription factor which is critical for pancreatic commitment during development and for the activation and maintenance of the acinar differentiation programme in the exocrine pancreas. High-level expression of exocrine digestive enzymes, a hallmark of mature acinar cells, depends largely on the trimeric complex PTF1, formed by p48, RBP-L (recombination signal-binding protein 1-like) and a class A bHLH protein. In addition, p48 induces cell-cycle exit by controlling G1/S-phase progression. However, the mechanisms that mediate PTF1-dependent gene activation are poorly understood. In the present study, we report that p48 increases transcription through two activation domains located in its N-terminal region by recruiting transcriptional co-activators. The histone acetyltransferase cofactor p/CAF {p300/CBP [CREB (cAMP-response-element-binding protein)-binding protein]-associated factor} interacts with p48 in acinar cells in vivo and is associated with the promoter region of acinar genes targeted by the PTF1 complex. p/CAF potentiates PTF1 transcriptional activity by enhancing selectively the p48 transactivation activity. p/CAF promotes the nuclear accumulation of p48 and its in vivo acetylation in Lys200. The K200R mutation abolishes the transcriptional activity of p48, as well as its capacity to functionally co-operate with RBP-L to ensure effective PTF1-driven transcription, indicating that p/CAF-mediated acetylation of p48 is required for the full transcriptional activity of PTF1. In contrast, p/CAF did not co-operate with p48 in its growth regulatory effects. These results support a critical and selective role of p/CAF in PTF1-dependent gene activation during acinar differentiation.
Language Outcomes of Late Talking Toddlers at Preschool and Beyond
Authors: Roos Elizabeth M. , Weismer Susan Ellis
Published: October 2008

Toddlers who demonstrate delayed onset and progression of expressive language in conjunction with otherwise age-appropriate development are often referred to as “late talkers.” For speech-language pathologists who provide early identification and intervention of children who are late talkers, the ability to ascertain whether children ultimately recover or go on to experience difficulties throughout their school years into adulthood is of significant interest. This article summarizes criteria for the identification of late talkers based on research to date, and considers outcomes of late talking toddlers in preschool, kindergarten, and beyond.
The Aerodigestive Clinic: Multidisciplinary Management of Pediatric Dysphagia
Authors: Haibeck Laura , Mandell David L.
Published: October 2008

The purposes of this article are (a) to explore the relationship between pediatric upper airway obstruction and dysphagia and (b) to highlight the benefits of using a multidisciplinary approach when assessing infants and children with upper respiratory and swallowing disorders. The functions of breathing and swallowing are tightly coordinated in infants and young children, and pediatric upper airway disorders can often adversely affect the swallowing mechanism and may even predispose the individual to aspiration. Some of the more common causes of pediatric airway obstruction seen in this setting are laryngomalacia, vocal fold paralysis, laryngeal cleft, and Pierre Robin's sequence. In the setting of all of these disorders, associations may also exist with gastroesophageal reflux (GER) and laryngopharyngeal reflux, and this topic is also reviewed. In the multidisciplinary assessment of young children with aerodigestive disorders, fiberoptic flexible endoscopic evaluation of swallowing has gained traction as a useful test for simultaneous evaluation of pediatric upper airway obstruction and dysphagia and has provided complimentary information to the more traditional pediatric videofluoroscopic swallowing evaluation. A representative case study is provided that illustrates the relationship between pediatric upper airway obstruction and dysphagia and demonstrates the effectiveness of a multidisciplinary approach.
Response to Intervention: My Perspective
Authors: Schussler Kelly Farquharson
Published: October 2008

Implementing new programs within a school system is a challenge often faced by educators, but one that can be successfully addressed through discussions among faculty both within and outside one's school system. It is never easy to make a change in procedures, but, with the help of our colleagues, it can sometimes go more smoothly. The purpose of this article is to provide the reader with insight into one school system's journey through the Response to Intervention (RTI) initiative.
A View From the Field: Early Intervening and RTI
Authors: Fitzgerald Mary Dale , Driggins Sylvia B.
Published: October 2008

This article describes the evolution of the early intervention process for children with speech and language needs in Tennessee and the impact of recent legislative changes in IDEA-2004 and NCLB on this process. Response to intervention (RTI) models have dramatically influenced new service delivery models and the roles of school-based clinicians. Future challenges for educational speech-language pathologists in developing collaborative partnerships and problem-solving team approaches with general and special educators are considered.
Phase separation and optical properties in oxygen-rich InN films
Authors: Dixit A. , Sudakar C. , Naik R. , Lawes G. , Thakur J. S. , McCullen E. F. , Auner G. W. , Naik V. M.
Published: October 2008

We have investigated the properties of sputter deposited InN thin films prepared from an In-metal (InN-MT) and an In2O3 target (InN-OT). The excess oxygen present in the InN-OT films alters the microstructure by introducing additional disorder. Depth dependent x-ray photoelectron spectroscopy measurements indicate the presence of higher concentrations of oxygen in InN-OT. Raman spectra show evidence for the presence of an In2O3 secondary phase in both samples. Although the InN-OT film has a higher oxygen concentration, both films show similar electrical and optical properties.
A numerical study of the electrostatic properties of two finite-width charged dielectric slabs in water
Authors: Jho Y. S. , Kim M. W. , Pincus P. A. , Brown Frank L. H.
Published: October 2008

A numerical algorithm based on the image charge method is introduced to calculate the electrostatic potential, energy, and forces present in systems involving multiple point charges embedded in an inhomogeneous dielectric environment composed of five parallel dielectric slabs. The methodology is implemented within Monte Carlo simulations to calculate the thermal properties of two charged dielectric plates of finite thickness immersed in water.
Prediction of effective permittivity of diphasic dielectrics using an equivalent capacitance model
Authors: Patil S. K. , Koledintseva M. Y. , Schwartz R. W. , Huebner W.
Published: October 2008

An analytical model based on an equivalent capacitance circuit for expressing a static effective permittivity of a composite dielectric with complex-shaped inclusions is presented. The dielectric constant of 0–3 composites is investigated using this model. The geometry of the capacitor containing a composite dielectric is discretized into partial parallel-plate capacitor elements, and the effective permittivity of the composite is obtained from the equivalent capacitance of the structure. First, an individual cell diphasic dielectric (a high-permittivity spherical inclusion enclosed in a lower permittivity parallelepiped) is considered. The capacitance of this cell is modeled as a function of an inclusion radius/volume fraction. The proposed approach is extended over a periodic three-dimensional structure comprised of multiple individual cells. The results of modeling are compared with results obtained using different effective medium theories, including Maxwell Garnett, logarithmic, Bruggeman, series, and parallel mixing rules. It is found that the model predictions are in good agreement with the experimental data. The equivalent capacitance model may be applied to composites containing inclusions of any geometry and size. Although the method presented is at static electric field, it can be easily generalized for prediction of frequency-dependent effective permittivity.
Electronic structure and optical properties of freestanding [0001] oriented GaN nanowires and nanotubes
Authors: Persson M. P. , Di Carlo A.
Published: October 2008

We report on a theoretical study of the electronic and optical properties of freestanding, [0001] oriented wurtzite GaN nanowires and nanotubes based on an atomistic tight binding approach. The developments of band structure, optical properties, and effective mass are studied as functions of nanowire size. It is shown that the valence band structure of the nanowire depends on the lateral size of the nanowire and that the order between the first two valence bands is reversed above a critical size. The fundamental optical transition is found to be strong for nanowire sizes below, and weak for nanowire sizes above, this critical size. The first strong optical transition is found to have a very large optical polarization anisotropy with the dominant component parallel to the nanowire axis. It is also shown that there is a simple functional relationship between the conduction band effective mass and the subband energy, while no such general relation can be found for the valence bands. For the nanotubes the change in energy compared to the solid nanowire is found to be strongly related to the distribution of the original nanowire state wave function. The incorporation of a hole in the nanowire will force a change in the ordering between the first two valence band states compared to a below critical size nanowire.
Optical properties of dislocations in wurtzite ZnO single crystals introduced at elevated temperatures
Authors: Ohno Y. , Koizumi H. , Taishi T. , Yonenaga I. , Fujii K. , Goto H. , Yao T.
Published: October 2008

Optical properties of wurtzite ZnO bulk single crystals in which an arbitrary number (typically 109–1010 cm−2) of fresh dislocations were introduced intentionally by the plastic deformation at elevated temperatures (923–1073 K) were examined. Deformed specimens showed excitonic light emission with photon energies of 3.100 and 3.345 eV, as well as their LO phonon replicas at 11 K. The light intensities increased with increasing dislocation density. The activation energy for a thermal quenching of the 3.100 or 3.345 eV emission band, which corresponds to the depth of the localized energy level associated with the emission band, was estimated to be 0.3±0.1 or 0.05±0.01 eV, respectively. The origin of the energy levels was proposed as point defect complexes involving dislocations. The introduction of the dislocations at the elevated temperatures above 923 K did not influence the intensities of the emission bands except the dislocation-related emission bands.
Antiferroelectric dielectric relaxation processes and the interlayer interaction in antiferroelectric liquid crystals
Authors: Song Jang-Kun , Manna U. , Fukuda A. , Vij J. K.
Published: October 2008

Antiphase relaxation process of antiferroelectric phase is investigated in binary mixtures of antiferroelectric and ferroelectric liquid crystalline compounds. It is found that the frequency of the antiphase mode ranges from 2to4MHz, being one of the fastest collective processes reported so far. This can be exploited in a photonic switch with a submicrosecond response time. However, the frequency of the antiphase mode decreases by the mixing ratio of the ferroelectric compound. The decrease in the frequency is shown to be due to a reduction in the elastic constant in between the adjacent layers.
Network structure and thermal stability study of high temperature seal glass
Authors: Lu K. , Mahapatra M. K.
Published: October 2008

High temperature seal glass has stringent requirement on glass thermal stability, which is dictated by glass network structures. In this study, a SrO–La2O3–Al2O3–B2O3–SiO2 based glass system was studied using nuclear magnetic resonance, Raman spectroscopy, and x-ray diffraction for solid oxide cell application purpose. Glass structural unit neighboring environment and local ordering were evaluated. Glass network connectivity as well as silicon and boron glass former coordination were calculated for different B2O3:SiO2 ratios. Thermal stability of the borosilicate glasses was studied after thermal treatment at 850 °C. The study shows that high B2O3 content induces BO4 and SiO4 structural unit ordering, increases glass localized inhomogeneity, decreases glass network connectivity, and causes devitrification. Glass modifiers interact with either silicon- or boron-containing structural units and form different devitrified phases at different B2O3:SiO2 ratios. B2O3-free glass shows the best thermal stability among the studied compositions, remaining stable after thermal treatment for 200 h at 850 °C.
Second-order elastic constants of pentaerythritol tetranitrate and cyclotrimethylene trinitramine using impulsive stimulated thermal scattering
Authors: Sun B. , Winey J. M. , Hemmi N. , Dreger Z. A. , Zimmerman K. A. , Gupta Y. M. , Torchinsky Darius H. , Nelson Keith A.
Published: October 2008

Impulsive stimulated thermal scattering (ISTS) was used to determine the complete set of second-order elastic constants for pentaerythritol tetranitrate (PETN) and cyclotrimethylene trinitramine (RDX) single crystals. Despite the weak scattering efficiency of these materials, excellent signal quality was obtained by using an optical heterodyne detection approach. The elastic constants for PETN agree well with previous values obtained from ultrasonic velocity measurements. The elastic constants for RDX are consistent with previous values obtained from ultrasonic velocity measurements and from resonant ultrasound spectroscopy, but show significant differences with values obtained from Brillouin scattering data. The present results demonstrate that the ISTS method, with optical heterodyne detection, provides a useful and accurate approach for determining the elastic constants of energetic crystals.
Invited Article: Time accurate mass flow measurements of solid-fueled systems
Authors: Olliges Jordan D. , Lilly Taylor C. , Joslyn Thomas B. , Ketsdever Andrew D.
Published: October 2008

A novel diagnostic method is described that utilizes a thrust stand mass balance (TSMB) to directly measure time-accurate mass flow from a solid-fuel thruster. The accuracy of the TSMB mass flow measurement technique was demonstrated in three ways including the use of an idealized numerical simulation, verifying a fluid mass calibration with high-speed digital photography, and by measuring mass loss in more than 30 hybrid rocket motor firings. Dynamic response of the mass balance was assessed through weight calibration and used to derive spring, damping, and mass moment of inertia coefficients for the TSMB. These dynamic coefficients were used to determine the mass flow rate and total mass loss within an acrylic and gaseous oxygen hybrid rocket motor firing. Intentional variations in the oxygen flow rate resulted in corresponding variations in the total propellant mass flow as expected. The TSMB was optimized to determine mass losses of up to 2.5 g and measured total mass loss to within 2.5% of that calculated by a NIST-calibrated digital scale. Using this method, a mass flow resolution of 0.0011 g/s or 2% of the average mass flow in this study has been achieved.
Photoelectron spectroscopy and theoretical studies of [Com(pyrene)n]− (m=1,2 and n=1,2) complexes
Authors: Kandalam Anil K. , Jena Puru , Li Xiang , Eustis Soren N. , Bowen Kit H.
Published: October 2008

Anion photoelectron spectroscopic experiments and density functional theory based calculations have been used to investigate the structural, electronic, and magnetic properties of neutral and anionic [Com(pyrene)n] (m,n=1–2) complexes. The calculated electron affinities and vertical transition energies of Com(pyrene)n are in good agreement with the measured values. Our results provide clear evidence for dimerization of Co atoms and formation of sandwich structures in these complexes. While the calculated spin magnetic moments of neutral Co2(pyrene)n complexes suggest a preference for ferromagnetic coupling between Co atoms, the spin magnetic moment of Co atom in Co(pyrene) and Co(pyrene)2 complexes was reduced to 1μB.
Dynamic treatment of vibrational energy relaxation in a heterogeneous and fluctuating environment
Authors: Fujisaki Hiroshi , Stock Gerhard
Published: October 2008

A computational approach to describe the energy relaxation of a high-frequency vibrational mode in a fluctuating heterogeneous environment is outlined. Extending previous work [H. Fujisaki, Y. Zhang, and J. E. Straub, J. Chem. Phys. 124, 144910 (2006)], second-order time-dependent perturbation theory is employed which includes the fluctuations of the parameters in the Hamiltonian within the vibrational adiabatic approximation. This means that the time-dependent vibrational frequencies along a molecular dynamics trajectory are obtained via a partial geometry optimization of the solute with fixed solvent and a subsequent normal mode calculation. Adopting the amide I mode of N-methylacetamide in heavy water as a test problem, it is shown that the inclusion of dynamic fluctuations may significantly change the vibrational energy relaxation. In particular, it is found that relaxation occurs in two phases, because for short times (≲200 fs) the spectral density appears continuous due to the frequency-time uncertainty relation, while at longer times the discrete nature of the bath becomes apparent. Considering the excellent agreement between theory and experiment, it is speculated if this behavior can explain the experimentally obtained biphasic relaxation the amide I mode of N-methylacetamide.
Phase diagrams for model heteronuclear dimers confined in narrow slitlike pores
Authors: Rżysko W.
Published: October 2008

Monte Carlo simulation is used to study the phase behavior of a model of heteronuclear dimers on a lattice. The calculations are carried out for two- and three-dimensional bulk systems and for dimers confined in slitlike pores of different widths and for different segment-wall interactions. The calculations recover a rich variety of phase behaviors that includes transitions between gaslike and liquidlike phases, the latter being ordered or disordered. The topology of the obtained diagrams depends on the energy of interactions between segments forming a dimer, on the segment-wall interaction, and on the pore width.
Conformational dependence of DNA ballistic conductivity
Authors: Starikov E. B. , Quintilla A. , Lee K. H. , Wenzel W.
Published: October 2008

With the atomistic Kubo–Verges method we calculate the ballistic conductance of various conformers of DNA (A,B,Z), as well as intermediate and composite conformations, using experimental structures and model complexes. For duplexes with 6 and 15 base pairs, we find that the valence band conductivity near the Fermi edge varies dramatically between the different conformations, most notably for the B-to-Z transition. The latter conductivity differences are largely unchanged both in the presence and in the absence of trimethylthiol linkers between DNA and gold electrodes in vacuo, but become much less drastic when explicit molecular dynamics and water-counterion surrounding of B- and Z-DNA are taken into account. Based on atomistic structural models, we argue that changes in the electrostatic energy in the presence of an applied external electric field can induce conformational switching that may be exploited in novel DNA-based memory devices of high packing density.
A first-principles study of NO adsorption and oxidation on Au(111) surface
Authors: Zhang Wenhua , Li Zhenyu , Luo Yi , Yang Jinlong
Published: October 2008

Density functional theory and slab models are employed to study NO molecule adsorption and reaction on clean and atomic oxygen precovered Au(111) surfaces. While clean Au(111) surface is catalytically inert and can only weakly adsorb NO, an atomic oxygen precovered Au(111) surface is found to be very active to NO. On the clean surface, NO prefers to bond at the onefold on-top surface site with a tilted geometry. On 0.33 ML (monolayer) oxygen precovered surface NO reacts with chemisorbed oxygen to form chemisorbed NO2 by conquering a small energy barrier about 0.18 eV, and the desorption energy of NO2 is 0.64 eV. On 1.0 ML oxygen coverage surface, no barrier is found while NO reacts with precovered oxygen. The desorption energy of NO2 is 0.03 eV. The desorption of NO2 is the rate determining step on both surfaces and the overall reaction barriers are 0.64 and 0.03 eV, respectively. The activation energies depend on the initial coverage of oxygen, which compare favorably with experiments on Au surface with different oxygen coverages.
On the electron correlation effects on electronic and vibrational hyperpolarizability of merocyanine dyes
Authors: Zaleśny Robert , Papadopoulos Manthos G. , Bartkowiak Wojciech , Kaczmarek Anna
Published: October 2008

Using various ab initio methods (including many-body perturbation theory and coupled cluster method), the full tensor of electronic and vibrational contributions to the first-order hyperpolarizability (β) for three molecules belonging to the group of merocyanine dyes was computed. Unexpectedly large correlation effects were observed in the electronic counterpart of nonlinear optical response. The analysis of the electronic structure, performed for one of the investigated molecules, reveals that it is the polarity of the low-lying excited state that is affected most upon inclusion of the electron correlation. The vibrational contributions to β are not significantly influenced by the applied level of theory.
Realization and characterization of tetra(tert-butyl) zinc phtalocyanine poly(methyl methacrylate) films for optical limiting applications
Authors: Larciprete M. C. , Mangialardo S. , Belardini A. , Sibilia C. , Bertolotti M.
Published: October 2008

We investigated optical limiting effects in films of tetra(tert-butyl) zinc phtalocyanine dissolved into poly(methyl methacrylate) within a 0.15% maximum weight ratio. Spectroscopic analysis was performed on the realized films in order to retrieve the corresponding linear optical absorption coefficient, whose interpolation according to a model including a set of three Lorentzian oscillators enabled the evaluation of the degrees of monomer and dimer concentrations. Thereafter, nonlinear transmission measurements were carried out at two different wavelengths, 532 and 634 nm. All the investigated films showed a nonlinear optical response, which was found to increase as the resonant condition was approached.