bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of cloud layer structure in Shouxian, China using RS92 radiosonde aided by 95 GHz cloud radar
Authors: Zhang Jinqiang , Chen Hongbin , Li Zhanqing , Fan Xuehua , Peng Liang , Yu Yu , Cribb Maureen
Published: December 2010

The Atmospheric Radiation Measurement Mobile Facility (AMF) was deployed in Shouxian, Anhui Province, China from 14 May to 28 December 2008. Radiosonde data obtained during the AMF campaign are used to analyze cloud vertical structure over this area by taking advantage of the first direct measurements of cloud vertical layers from the 95 GHz radar. Single‐layer, two‐layer, and three‐layer clouds account for 28.0%, 25.8%, and 13.9% of all cloud configurations, respectively. Low, middle, high and deep convective clouds account for 20.1%, 19.3%, 59.5%, and 1.1% of all clouds observed at the site, respectively. The average cloud base height, cloud top height, and cloud thickness for all clouds are 5912, 7639, and 1727 m, respectively. Maximum cloud top height and cloud thickness occurred at 1330 local standard time (LST) for single‐layer clouds and the uppermost layer of multiple layers of cloud. For lower layer clouds in multiple‐layer cloud systems, maximum cloud top height and cloud thickness occurred at 1930 LST. Diurnal variations in the thickness of upper level clouds are larger than those of lower level clouds. Multilayer clouds occurred more frequently in the summer. The absolute differences in cloud base heights from radiosonde and micropulse lidar/ceilometer comparisons are less than 500 m for 77.1%/68.4% of the cases analyzed.
Determining the modal mineralogy of Martian soils
Authors: McSween Harry Y. , McGlynn Ian O. , Rogers A. Deane
Published: December 2010

A method for identifying the major and minor minerals and quantifying their proportions (by weight) in soils at the Mars Exploration Rovers landing sites is presented. The procedure utilizes modeled Mössbauer data for iron‐bearing minerals, chemical calculations of Alpha Particle X‐ray Spectrometer data for iron‐absent minerals, and modeling of MiniTES thermal infrared spectra for silica and clays. Two models are formulated, using different assumptions about the mineralogy of sulfur and chlorine: sulfate + chloride, or incorporated in or adsorbed onto schwertmannite + akaganeite. The actual soil mineralogy may be bracketed by these results. Using either model, average dark soils on the Gusev crater plains and on Meridiani Planum are shown to be composed of a mixture of igneous (olivine, pyroxene, plagioclase, Fe‐Ti‐Cr spinels, phosphate) and alteration (amorphous silica, hematite, nanophase oxides, clays, plus sulfate + chloride or oxysulfate + oxychloride) minerals. This assemblage suggests that soil alteration did not occur in situ and that the igneous and alteration components were likely derived from different sources. The (model dependent) mixing ratio of igneous and alteration components is identical at the two sites on opposite sides of the planet, implying that Martian soils may provide a representative mineralogical sampling of the exposed crust.
High within‐canopy variation in isoprene emission potentials in temperate trees: Implications for predicting canopy‐scale isoprene fluxes
Authors: Niinemets Ülo , Copolovici Lucian , Hüve Katja
Published: December 2010

Isoprene emission potential (ES) varies in tree canopies, and such variations have potentially major implications for predicting canopy level emissions. So far, quantitative relationships of ES with irradiance are missing, and interspecific variation in ES plasticity and potential effects on canopy level emissions have not been characterized. ES, foliage structural, chemical, and photosynthetic characteristics were studied relative to integrated within‐canopy daily quantum flux density (Qint) in temperate deciduous tree species Quercus robur, Populus tremula, Salix alba, and Salix caprea, and canopy isoprene emissions were calculated considering observed variation in ES and under different simplifying assumptions. Strong positive curvilinear relationships between nitrogen and dry mass per unit area, photosynthetic potentials and ES per area with Qint were observed. Structural, chemical, and photosynthetic traits varied 1.5‐fold to 4‐fold and ES per area 3‐fold to 27‐fold within the canopy. ES variation reflected accumulation of mesophyll cell layers and greater emission capacity of average cells. Species with largest structural and photosynthetic plasticity had greatest plasticity in ES. Relative to the simulation considering within‐canopy variation in ES, the bias from assuming a constant ES varied between −8% and +68%, and it scaled positively with ES plasticity. The bias of big‐leaf simulations varied between −22% and −35%, and it scaled negatively with ES plasticity. A generalized canopy response function of ES developed for all species resulted in the lowest bias between −11% and 6% and can be recommended for practical applications. The results highlight huge within‐canopy and interspecific variation in ES and demonstrate that ignoring these variations strongly biases canopy emission predictions.
Enhanced detection of groundwater contamination from a leaking waste disposal site by microbial community profiles
Authors: Mouser Paula J. , Rizzo Donna M. , Druschel Gregory K. , Morales Sergio E. , Hayden Nancy , O'Grady Patrick , Stevens Lori
Published: December 2010

Groundwater biogeochemistry is adversely impacted when municipal solid waste leachate, rich in nutrients and anthropogenic compounds, percolates into the subsurface from leaking landfills. Detecting leachate contamination using statistical techniques is challenging because well strategies or analytical techniques may be insufficient for detecting low levels of groundwater contamination. We sampled profiles of the microbial community from monitoring wells surrounding a leaking landfill using terminal restriction fragment length polymorphism (T‐RFLP) targeting the 16S rRNA gene. Results show in situ monitoring of bacteria, archaea, and the family Geobacteraceae improves characterization of groundwater quality. Bacterial T‐RFLP profiles showed shifts correlated to known gradients of leachate and effectively detected changes along plume fringes that were not detected using hydrochemical data. Experimental sediment microcosms exposed to leachate‐contaminated groundwater revealed a shift from aβ‐Proteobacteria and Actinobacteria dominated community to one dominated by Firmicutes andδ‐Proteobacteria. This shift is consistent with the transition from oxic conditions to an anoxic, iron‐reducing environment as a result of landfill leachate‐derived contaminants and associated redox conditions. We suggest microbial communities are more sensitive than hydrochemistry data for characterizing low levels of groundwater contamination and thus provide a novel source of information for optimizing detection and long‐term monitoring strategies at landfill sites.
River‐to‐lake connectivities, water renewal, and aquatic habitat diversity in the Mackenzie River Delta
Authors: Lesack Lance F. W. , Marsh Philip
Published: December 2010

Past and ongoing investigations have established that lakes in the Mackenzie River Delta collectively represent gradients in water transparency, nutrient regime, and biotic communities, each strongly linked to the sill elevations of the lakes. Analysis of 40 years of water levels in East Channel of the central delta, in combination with a floodplain geometry model to estimate river water volumes added to lake waters at the annual flood peak, permitted direct estimation of annual river‐to‐lake connection times, lake water renewal, and interannual variabilities in nine lakes spanning the full range of sill elevations in the delta. Results have revealed a broad range of river‐to‐lake connectivities and river water renewals that are temporally dynamic and vary considerably among the lakes of this river delta system. Lakes with short and variable connection times plus low and variable river water renewal yield groups of lakes with high degrees of individuality because they are strongly influenced by particular sequences of antecedent years (legacy effects) that may result in lakes simultaneously containing residual waters from multiple river inundation events separated by more than a decade. Lakes with long and less varying connection times plus high river water renewal with multiple possible river water resets per year yield lakes with high degrees of similarity. The full combination of lakes arranged in an intermittently connected continuum, creating variable connectivity for aquatic organisms and water intermixing, may be an important mechanism driving the collectively distinctive habitat productivity and biodiversity of aquatic communities in this system, relative to lakes on the surrounding landscape.
A spatial‐temporal point process model with a continuous distribution of storm types
Authors: Cowpertwait Paul S. P.
Published: December 2010

A point process rainfall model is further developed that has storm origins occurring in space‐time according to a Poisson process, where each storm origin has a random radius so that storms occur as circular regions in two‐dimensional space, where the storm radii are taken to be independent exponential random variables. Each storm origin is of random type z, where z follows a continuous probability distribution. Cell origins occur in a further spatial Poisson process and have arrival times that follow a Neyman‐Scott point process. Each cell origin has a radius so that cells form discs in two‐dimensional space, where the cell radii are independent exponential random variables. Each cell has a random lifetime and an intensity that remains constant over both the cell lifetime and cell disk area. Statistical properties up to third order are given for the model. Using these properties, the model is fitted to 10 min series taken from 23 sites across the Rome region, Italy. Distributional properties of the observed annual maxima are compared to equivalent values sampled from series that are simulated using the fitted model. The results indicate that the model will be of use in urban drainage projects for the Rome region.
MRI Estimation of Global Brain Oxygen Consumption Rate
Authors: Jain Varsha , Langham Michael C , Wehrli Felix W
Published: December 2010

Journal of Cerebral Blood Flow & Metabolism (2010) 30, 1598–1607; doi:10.1038/jcbfm.2010.49; published online 21 April 2010

Following the publication of this issue, the editors noticed that the cover figure for the September 2010 issue was incorrect. The correct version appears below. Please note that this figure was created by the authors of the above article and is credited to them in the issue.
Acute Hepatocyte Growth Factor Treatment Induces Long-Term Neuroprotection and Stroke Recovery via Mechanisms Involving Neural Precursor Cell Proliferation and Differentiation
Authors: Doeppner Thorsten R , Kaltwasser Britta , ElAli Ayman , Zechariah Anil , Hermann Dirk M , Bähr Mathias
Published: December 2010

Hepatocyte growth factor (HGF) is an interesting candidate for acute stroke treatment as shown by continuous infusion or gene delivery protocols. However, little is known about HGF-mediated long-term effects. The present study therefore analyzed long-term effects of an acute intrastriatal HGF treatment (5 μg) after a 45-minute stroke, with regard to brain injury and neurologic recovery. Hepatocyte growth factor induced long-term neuroprotection as assessed by infarct volume and neuronal cell death analysis for as long as 4 weeks after stroke, which was associated with sustained neurologic recovery as evidenced by corner-turn and tight-rope tests. Analyzing underlying mechanisms of HGF-induced sustained neuroprotection, enhanced cell proliferation followed by increased neuronal differentiation of neural precursor cells (NPCs) was observed in the ischemic striatum of HGF-treated mice, which persisted for up to 4 weeks. In line with this, HGF promoted neurosphere formation as well as proliferation of NPC and decreased caspase-3-dependent hypoxic injury in vitro. Preservation of blood—brain barrier integrity 24 hours after stroke was furthermore noticed in animals receiving HGF, which was associated with the inhibition of matrix metalloproteases (MMP)-2 and MMP-9 at 4 and 24 hours, respectively. We suggest that sustained recruitment of proliferating cells together with improved neurovascular remodeling provides an explanation for HGF-induced long-term neuroprotection.
Lysosomal membrane proteins: life between acid and neutral conditions
Authors: Saftig Paul , Schröder Bernd , Blanz Judith
Published: December 2010

Whereas we have a profound understanding about the function and biogenesis of the protein constituents in the lumen of the lysosomal compartment, much less is known about the functions of proteins of the lysosomal membrane. Proteomic analyses of the lysosomal membrane suggest that, apart from the well-known lysosomal membrane proteins, additional and less abundant membrane proteins are present. The identification of disease-causing genes and the in-depth analysis of knockout mice leading to mutated or absent membrane proteins of the lysosomal membrane have demonstrated the essential role of these proteins in lysosomal acidification, transport of metabolites resulting from hydrolytic degradation and interaction and fusion with other cellular membrane systems. In addition, trafficking pathways of lysosomal membrane proteins are closely linked to the biogenesis of this compartment. This is exemplified by the recent finding that LIMP-2 (lysosomal integral membrane protein type-2) is responsible for the mannose 6-phosphate receptor-independent delivery of newly synthesized β-glucocerebrosidase to the lysosome. Similar to LIMP-2, which could also be linked to vesicular transport processes in certain polarized cell types, the major constituents of the lysosomal membrane, the glycoproteins LAMP (lysosome-associated membrane protein)-1 and LAMP-2 are essential for regulation of lysosomal motility and participating in control of membrane fusion events between autophagosomes or phagosomes with late endosomes/lysosomes. Our recent investigations into the role of these proteins have not only increased our understanding of the endolysosomal system, but also supported their major role in cell physiology and the development of different diseases.
NAADP as an intracellular messenger regulating lysosomal calcium-release channels
Authors: Galione Antony , Morgan Anthony J. , Arredouani Abdelilah , Davis Lianne C. , Rietdorf Katja , Ruas Margarida , Parrington John
Published: December 2010

Recent studies into the mechanisms of action of the Ca2+-mobilizing messenger NAADP (nicotinic acid–adenine dinucleotide phosphate) have demonstrated that a novel family of intracellular Ca2+-release channels termed TPCs (two-pore channels) are components of the NAADP receptor. TPCs appear to be exclusively localized to the endolysosomal system. These findings confirm previous pharmacological and biochemical studies suggesting that NAADP targets acidic Ca2+ stores rather than the endoplasmic reticulum, the major site of action of the other two principal Ca2+-mobilizing messengers, InsP3 and cADPR (cADP-ribose). Studies of the messenger roles of NAADP and the function of TPCs highlight the novel role of lysosomes and other organelles of the endocytic pathway as messenger-regulated Ca2+ stores which also affects the regulation of the endolysosomal system.
Lysosomal compromise and brain dysfunction: examining the role of neuroaxonal dystrophy
Authors: Walkley Steven U. , Sikora Jakub , Micsenyi Matthew , Davidson Cristin , Dobrenis Kostantin
Published: December 2010

Lysosomal diseases are a family of over 50 disorders caused by defects in proteins critical for normal function of the endosomal/lysosomal system and characterized by complex pathogenic cascades involving progressive dysfunction of many organ systems, most notably the brain. Evidence suggests that compromise in lysosomal function is highly varied and leads to changes in multiple substrate processing and endosomal signalling, in calcium homoeostasis and endoplasmic reticulum stress, and in autophagocytosis and proteasome function. Neurons are highly vulnerable and show abnormalities in perikarya, dendrites and axons, often in ways seemingly unrelated to the primary lysosomal defect. A notable example is NAD (neuroaxonal dystrophy), which is characterized by formation of focal enlargements (spheroids) containing diverse organelles and other components consistent with compromise of retrograde axonal transport. Although neurons may be universally susceptible to NAD, GABAergic neurons, particularly Purkinje cells, appear most vulnerable and ataxia and related features of cerebellar dysfunction are a common outcome. As NAD is found early in disease and thus may be a contributor to Purkinje cell dysfunction and death, understanding its link to lysosomal compromise could lead to therapies designed to prevent its occurrence and thereby ameliorate cerebellar dysfunction.
The neuronal ceroid lipofuscinoses: the same, but different?
Authors: Cooper Jonathan D.
Published: December 2010

The NCLs (neuronal ceroid lipofuscinoses) (also known as Batten disease) are a group of at least ten fatal inherited storage disorders. Despite the identification of many of the disease-causing genes, very little is known about the underlying disease mechanisms. However, now that we have mouse or large-animal models for most forms of NCL, we can investigate pathogenesis and compare what happens in the brain in different types of the disease. Broadly similar neuropathological themes have emerged, including the highly selective nature of neuron loss, early effects upon the presynaptic compartment, together with an early and localized glial activation. These events are especially pronounced within the thalamocortical system, but it is clear that where and when they occur varies markedly between different forms of NCL. It is now becoming apparent that, despite having pathological endpoints that resemble one another, these are reached by a sequence of events that is specific to each subtype of NCL.
mRNA-specific regulation of translation by poly(A)-binding proteins
Authors: Burgess Hannah M. , Gray Nicola K.
Published: December 2010

The regulation of translation has emerged as a major determinant of gene expression and is critical for both normal cellular function and the development of disease. Numerous studies have highlighted the diverse, and sometimes related, mechanisms which underlie the regulation of global translation rates and the translational control of specific mRNAs. In the present paper, we discuss the emerging roles of the basal translation factor PABP [poly(A)-binding protein] in mRNA-specific translational control in metazoa which suggest that PABP function is more complex than first recognized.
Cytoplasmic deadenylation: regulation of mRNA fate
Authors: Wiederhold Katrin , Passmore Lori A.
Published: December 2010

The poly(A) tail of mRNA has an important influence on the dynamics of gene expression. On one hand, it promotes enhanced mRNA stability to allow production of the protein, even after inactivation of transcription. On the other hand, shortening of the poly(A) tail (deadenylation) slows down translation of the mRNA, or prevents it entirely, by inducing mRNA decay. Thus deadenylation plays a crucial role in the post-transcriptional regulation of gene expression, deciding the fate of individual mRNAs. It acts both in basal mRNA turnover, as well as in temporally and spatially regulated translation and decay of specific mRNAs. In the present paper, we discuss mRNA deadenylation in eukaryotes, focusing on the main deadenylase, the Ccr4–Not complex, including its composition, regulation and functional roles.
Cutting the nonsense: the degradation of PTC-containing mRNAs
Authors: Nicholson Pamela , Mühlemann Oliver
Published: December 2010

In eukaryotes, mRNAs harbouring PTCs (premature translation-termination codons) are recognized and eliminated by NMD (nonsense-mediated mRNA decay). In addition to its quality-control function, NMD constitutes a translation-dependent post-transcriptional pathway to regulate the expression levels of physiological mRNAs. In contrast with PTC recognition, little is known about the mechanisms that trigger the rapid degradation of mammalian nonsense mRNA. Studies have shown that mammalian NMD targets can be degraded via both an SMG6 (where SMG is suppressor of morphological defects on genitalia)-dependent endonucleolytic pathway and a deadenylation and decapping-dependent exonucleolytic pathway, with the possible involvement of SMG5 and SMG7. In contrast, Drosophila melanogaster NMD is confined to the former and Saccharomyces cerevisiae NMD to the latter decay pathway. Consistent with this conclusion, mammals possess both SMG6 and SMG7, whereas D. melanogaster lacks an SMG7 homologue and yeast have no SMG6 equivalent. In the present paper, we review what is known about the degradation of PTC-containing mRNAs so far, paying particular attention to the properties of the NMD-specific factors SMG5–SMG7 and to what is known about the mechanism of degrading mRNAs after they have been committed to the NMD pathway.
Getting through anaphase: splitting the sisters and beyond
Authors: Oliveira Raquel A. , Nasmyth Kim
Published: December 2010

Sister-chromatid cohesion, thought to be primarily mediated by the cohesin complex, is essential for chromosome segregation. The forces holding the two sisters resist the tendency of microtubules to prematurely pull sister DNAs apart and thereby prevent random segregation of the genome during mitosis, and consequent aneuploidy. By counteracting the spindle pulling forces, cohesion between the two sisters generates the tension necessary to stabilize microtubule–kinetochore attachments. Upon entry into anaphase, however, the linkages that hold the two sister DNAs must be rapidly destroyed to allow physical separation of chromatids. Anaphase cells must therefore possess mechanisms that ensure faithful segregation of single chromatids that are now attached stably to the spindle in a manner no longer dependent on tension. In the present review, we discuss the nature of the cohesive forces that hold sister chromatids together, the mechanisms that trigger their physical separation, and the anaphase-specific changes that ensure proper segregation of single chromatids during the later stages of mitosis.
Mechanisms of metal-induced centrosome amplification
Authors: Holmes Amie L. , Wise John Pierce
Published: December 2010

Exposure to toxic and carcinogenic metals is widespread; however, their mechanisms of action remain largely unknown. One potential mechanism for metal-induced carcinogenicity and toxicity is centrosome amplification. Here we review the mechanisms for metal-induced centrosome amplification, including arsenic, chromium, mercury and nano-titanium dioxide.
Ran control of mitosis in human cells: gradients and local signals
Authors: Roscioli Emanuele , Bolognesi Alessio , Guarguaglini Giulia , Lavia Patrizia
Published: December 2010

Roles of the GTPase Ran in cell life and division rely on a largely conserved mechanism, i.e. Ran's ability to interact with transport vectors. Modes of control of downstream factors, however, are diversified at particular times of the cell cycle. Specificity and fine-tuning emerge most clearly during mitosis. In the present article, we focus on the distinction between global mitotic control by the chromosomal Ran gradient and specific spatial and temporal control operated by localized Ran network members at sites of the mitotic apparatus in human cells.
“Shhhh! Alex Has Something To Say”: AAC-SGD Use in the Classroom Setting
Authors: Mellman Lisa M. , DeThorne Laura S. , Hengst Julie A.
Published: December 2010

The present qualitative study was designed to examine augmentative and alternative communication (AAC) practices, particularly surrounding speech-generating devices (SGDs), in the classroom setting. We focused on three key child participants, their classroom teachers, and associated speech-language pathologists across three different schools. In addition to semi-structured interviews of all participants, six classroom observations per child were completed. Data were coded according to both pre-established and emergent themes. Four broad themes emerged: message-focused AAC use, social interactions within the classroom community, barriers to successful AAC-SGD use, and missed opportunities. Findings revealed a lack of SGD use in the classroom for two children as well as limited social interaction across all cases. We conclude by highlighting the pervasive sense of missed opportunities across these classroom observations and yet, at the same time, the striking resiliency of communicative effort in these cases.
Maternal Responsiveness to AAC
Authors: Medeiros Kara F. , Cress Cynthia J.
Published: December 2010

How a mother responds to her young child's early communication behavior has been found to contribute to the children's scores on cognitive and language measures. This effect has been found in both children with and without developmental disabilities. Aided augmentative and alternative communication (AAC) is a communication strategy used with young children with developmental disabilities. Currently, there have been no studies addressing how a mother's play with her children may change when an aided AAC device is added. In this study 25 dyads participated in familiar and unfamiliar to play with and without a BIGmack present. Mothers' responsive and directive behaviors were coded and compared across both types of play. When the two conditions were compared, mothers showed more overall responsiveness to their children's communication when the BIGmack was present. Mothers did not increase their directive behaviors significantly between the two conditions.
Disaster Preparedness
Authors: Quinn Emily , Stuart Sheela L.
Published: December 2010

Individuals with complex communication needs are particularly vulnerable in disaster situations. This paper will describe a community outreach program developed to provide emergency preparedness training for children with complex communication needs. Goals are to acquaint participants with the challenges faced by individuals who used AAC in previous disasters, describe how community education has increased the capacity of stakeholders, and facilitate discussion regarding the application of training programs in additional communities.
Complex Decisions Involving Gastrostomy Feeding Tubes: When You’re Never Right or Wrong
Authors: Leslie Paula , Coyle James
Published: December 2010

Clinical decision-making in most cases of dysphagia is neither black nor white. Risk factors predisposing a person to pneumonia, malnutrition, or dehydration can never be reduced to zero chance. Clinicians often believe that patients they consider as “unsafe for oral intake” will somehow have the best outcome if they eliminate aspiration while swallowing by using a feeding tube. In many cases, there is no evidence or reasonable expectation that a feeding tube will maintain or improve the patient's quality of life, health, or life expectancy. Feeding tubes can increase discomfort, worsen outcomes, or result in earlier mortality. Clinical decisions must integrate best clinical judgment, patient values and expectations, and best external evidence of a patient's whole health status not just dysphagia. We must carefully consider ethical imperatives governing health care practice, especially when a feeding tube is a possible intervention choice.
Use of Group Treatment With Pediatric and Adolescent Populations in an Acute Rehabilitation Hospital Setting
Authors: Paustian Glenn
Published: December 2010

Purpose: Pediatric and adolescent treatment in group settings has unique benefits for effective delivery of speech language treatment. This article advocates for the use of group treatment models in acute rehabilitation settings in which speech language treatment is offered for pediatric and adolescent populations.

Considerations for Group Practice: Effective and efficient ways to orchestrate group treatment, including planning, execution, and documentation of group treatment, are outlined. Support for such delivery of care is consistent with the World Health Organization International Classification of Disability, Functioning, and Health (Threats, 2008), which is endorsed by the American Speech-Language-Hearing Association (ASHA Practice Act 2007).

Conclusions: Examples are provided for the integration of group treatment into an acute rehabilitation setting. A variety of group treatment experiences are described, including types of group treatment, daily scheduled group treatment, and integration of group treatment with other disciplines. It is concluded by the author that group treatment is a viable and important treatment type.
The Increasing Popularity of Aphasia Groups: Some Reasons Why
Authors: Elman Roberta J.
Published: December 2010

The number of aphasia groups and programs, consistent with a social approach to aphasia intervention, has grown dramatically over the past 20 years. This article discusses how current scientific evidence, service delivery changes, and a variety of other factors may help to explain this trend. One conclusion reached is that offering group treatment to people with aphasia is extremely important, given the amount of social isolation that often results.
Retrospect and Prospect: Information Systems Research in the Last and Next 25 Years
Authors: Lee Allen S
Published: December 2010

To its detriment, past research in information systems (IS) has taken for granted many of its own key concepts, including ‘information,’ ‘theory,’ ‘system,’ ‘organization,’ and ‘relevance.’ This essay examines these concepts, shows how they have been neglected, and offers the prospect in which research in IS no longer models itself on the research disciplines found in the natural and social sciences, but Instead charts a course for its future development by modeling itself on the research disciplines found in the professions, such as medicine, engineering, architecture, and law.
Resonances of quantum mechanical scattering systems and Lax–Phillips scattering theory
Authors: Baumgärtel Hellmut
Published: December 2010

For selected classes of quantum mechanical scattering systems a canonical association of a decay semigroup is presented. The spectrum of the generator of this semigroup is a pure eigenvalue spectrum and it coincides with the set of all resonances. The essential condition for the results is the meromorphic continuability of the scattering matrix onto \documentclass[12pt]{minimal}\begin{document}$\mathbb {C}\setminus (-\infty,0]$\end{document}C∖(−∞,0] and the rims \documentclass[12pt]{minimal}\begin{document}$\mathbb {R}_{-}\pm i0$\end{document}R−±i0. Further finite multiplicity is assumed. The approach is based on an adaption of the Lax–Phillips scattering theory to semibounded Hamiltonians. It is applied to trace class perturbations with analyticity conditions. A further example is the potential scattering for central-symmetric potentials with compact support and angular momentum 0.
Explicitly correlated equation-of-motion coupled-cluster methods for excited and electron-attached states
Authors: Bokhan Denis , Ten-no Seiichiro
Published: December 2010

Based on the linearly approximated F12 coupled cluster singles and doubles [CCSD(F12)] model, equation-of-motion [EOM-CCSD(F12)] methods for electron affinities (EAs) and excitation energies (EEs) have been formulated and implemented. Extended electron-attachment and excitation operators are introduced for balanced descriptions of both neutral and electron-attached (or excited) states. In our implementation the cusp conditions are used for the definition of extended electron-attachment (excitation) operators. It is shown that EA-EOM-CCSD(F12) provides vertical electron affinities accurate to 0.1 eV compared to those in the complete basis set limit. Numerical tests conducted on a selection of small molecules have also shown notable improvement in Rydberg excitation energies compared to valence ones by the use of correlation factors.

This article is being retracted effective 8 March 2011.
Contact line motion in confined liquid–gas systems: Slip versus phase transition
Authors: Xu Xinpeng , Qian Tiezheng
Published: December 2010

In two-phase flows, the interface intervening between the two fluid phases intersects the solid wall at the contact line. A classical problem in continuum fluid mechanics is the incompatibility between the moving contact line and the no-slip boundary condition, as the latter leads to a nonintegrable stress singularity. Recently, various diffuse-interface models have been proposed to explain the contact line motion using mechanisms missing from the sharp-interface treatments in fluid mechanics. In one-component two-phase (liquid–gas) systems, the contact line can move through the mass transport across the interface while in two-component (binary) fluids, the contact line can move through diffusive transport across the interface. While these mechanisms alone suffice to remove the stress singularity, the role of fluid slip at solid surface needs to be taken into account as well. In this paper, we apply the diffuse-interface modeling to the study of contact line motion in one-component liquid–gas systems, with the fluid slip fully taken into account. The dynamic van der Waals theory has been presented for one-component fluids, capable of describing the two-phase hydrodynamics involving the liquid–gas transition [A. Onuki, Phys. Rev. E 75, 036304 (2007)]. This theory assumes the local equilibrium condition at the solid surface for density and also the no-slip boundary condition for velocity. We use its hydrodynamic equations to describe the continuum hydrodynamics in the bulk region and derive the more general boundary conditions by introducing additional dissipative processes at the fluid–solid interface. The positive definiteness of entropy production rate is the guiding principle of our derivation. Numerical simulations based on a finite-difference algorithm have been carried out to investigate the dynamic effects of the newly derived boundary conditions, showing that the contact line can move through both phase transition and slip, with their relative contributions determined by a competition between the two coexisting mechanisms in terms of entropy production. At temperatures very close to the critical temperature, the phase transition is the dominant mechanism, for the liquid–gas interface is wide and the density ratio is close to 1. At low temperatures, the slip effect shows up as the slip length is gradually increased. The observed competition can be interpreted by the Onsager principle of minimum entropy production.
Dynamics and stability of radiation-driven double ablation front structures
Authors: Drean V. , Olazabal-Loumé M. , Sanz J. , Tikhonchuk V. T.
Published: December 2010

The dynamics of double ablation front (DAF) structures is studied for planar targets with moderate atomic number ablators. These structures are obtained in hydrodynamic simulations for various materials and laser intensities and are qualitatively characterized during the acceleration stage of the target. The importance of the radiative transport for the DAF dynamics is then demonstrated. Simulated hydrodynamic profiles are compared with a theoretical model, showing the consistency of the model and the relevant parameters for the dynamics description. The stability of DAF structures with respect to two-dimensional perturbations is studied using two different approaches: one considers the assumptions of the theoretical model and the other one a more complete physics. The numerical simulations performed with both approaches demonstrate good agreement of dispersion curves.
Kinetics of water filling the hydrophobic channels of narrow carbon nanotubes studied by molecular dynamics simulations
Authors: Wu Kefei , Zhou Bo , Xiu Peng , Qi Wenpeng , Wan Rongzheng , Fang Haiping
Published: December 2010

The kinetics of water filling narrow single-walled carbon nanotubes was studied using molecular dynamics simulations. The time required to fully fill a nanotube was linear with respect to the tube length. We observed that water molecules could enter into nanotubes of different lengths, either from one end or from both ends. The probability of having a nanotube filled completely from both ends increased exponentially with the tube length. For short tubes, filling usually proceeded from only one end. For long tubes, filling generally proceeded from both tube ends over three stages, i.e., filling from one end, filling from both ends, and filling from both ends with the dipole reorientation of water molecules to give a concerted ordering within the fully filled tube. The water molecules in the partially filled nanotube were hydrogen bonded similarly to those in the fully filled nanotube. Simulations for the reference Lennard-Jones fluid without hydrogen bonds were also performed and showed that the filling behavior of water molecules can be attributed to strong intermolecular hydrogen bonding.
Spatial anisotropy of the acousto-optical efficiency in lithium niobate crystals
Authors: Andrushchak A. S. , Chernyhivsky E. M. , Gotra Z. Yu. , Kaidan M. V. , Kityk A. V. , Andrushchak N. A. , Maksymyuk T. A. , Mytsyk B. G. , Schranz W.
Published: December 2010

We report the spatial anisotropy of the acousto-optic (AO) figure of merit M2 in LiNbO3 crystals. The analysis is based on the indicative surfaces being calculated for several geometries of the AO diffraction. Basing on these results the most efficient geometries of AO cells made of LiNbO3 crystals are determined. It is revealed that the cells made of certain nondirect crystal cuts provide several times better AO diffraction efficiency comparing to the traditional ones, i.e., made of direct cuts of LiNbO3. The obtained results present considerable practical interest since may be useful in a designing of highly efficient AO cells made of LiNbO3 crystals. The methodology developed in the present work may be applied to other crystal materials as well.
Flux-closure pattern in a two-dimensional NbN–Fe superconductor-ferromagnet nanocomposite: Anisotropy of the angular magnetoresistance
Authors: Bose S. K. , Budhani R. C.
Published: December 2010

The angular dependence of magnetoresistance (MR) of distributed NbN–Fe–NbN Josephson-junctions in the out-of-plane and in-plane magnetic field geometries shows a striking anisotropy on the polarity of the current (I+/I−) and its direction with respect to the applied field. The origin of this anisotropy is suggested to be the difference in the degree of spin polarization of electrons injected from Fe nanoplaquettes into the superconducting NbN for I+ and I−. Such a conclusion is based on the topography of flux-closure domains in Fe plaquettes. The anisotropy of MR is suppressed at high fields as the flux-closure domains transform into a single-domain structure.
Electrical resistivity of nanocrystalline Al-doped zinc oxide films as a function of Al content and the degree of its segregation at the grain boundaries
Authors: Nasr B. , Dasgupta S. , Wang D. , Mechau N. , Kruk R. , Hahn H.
Published: December 2010

Highly transparent and conducting Al-doped ZnO (AZO) films are prepared via sol-gel method with a broad range of nominal Al-doping. The film porosity and morphology is determined by the rate of temperature ramping during the drying of the gel phase. The minimum resistivity is observed to occur around 1.5–2 at. % Al-doped films, irrespective of the morphology and microstructure. It is found by local chemical analysis that Al tends to segregate at the grain boundaries and above a critical concentration, the segregated Al starts to dominate the electronic transport in nanocrystalline AZO. The optical measurements corroborate these findings showing a systematic increase in carrier density only up to 1.5–2 at. % Al-doping. It is concluded that the presence of the resistivity minimum is not merely determined by a solubility limit but is a result of the interplay between the changing carrier concentration and carrier scattering at the segregated Al.
Generation and annihilation of boron–oxygen-related recombination centers in compensated p- and n-type silicon
Authors: Lim Bianca , Rougieux Fiacre , Macdonald Daniel , Bothe Karsten , Schmidt Jan
Published: December 2010

The impact of boron–oxygen-related recombination centers as well as their defect kinetics have been intensely studied in boron-doped oxygen-rich p-type crystalline silicon. Experimental data for the defect in simultaneously boron- and phosphorus-doped compensated p- and n-type silicon, however, is sparse. In this study, we present time-resolved carrier lifetime measurements on Czochralski-grown silicon (Cz-Si) doped with both boron and phosphorus under illumination at 30 °C (defect generation) as well as at 200 °C in the dark (defect annihilation). The defect generation in compensated n-type Cz-Si is found to proceed on a similar time scale as the defect generation in (compensated) p-type Cz-Si. However, the shape of the carrier lifetime reduction during defect generation in compensated n-type silicon differs considerably from that in (compensated) p-type Cz-Si. The defect annihilation in compensated n-type Cz-Si is found to take up to 1000 times longer than in (compensated) p-type Cz-Si. In addition, we confirm a linear dependence of the normalized defect concentration Nt∗ on the net doping concentration p0 as well as a proportionality between the defect generation rate Rgen and the square of the net doping concentration p02 in compensated p-type Cz-Si. These results cannot be explained by the established BsO2i defect model, however, they agree with a recently proposed defect model in which the defect is composed of one interstitial boron atom and an interstitial oxygen dimer (BiO2i).
Communication: κ-dynamics—An exact method for accelerating rare event classical molecular dynamics
Authors: Lu Chun-Yaung , Makarov Dmitrii E. , Henkelman Graeme
Published: December 2010

κ-dynamics is an accelerated molecular dynamics method for systems with slow transitions between stable states. Short trajectories are integrated from a transition state separating a reactant state from products. The first trajectory found that leads directly to a product without recrossing the transition state and starts in the reactant state is followed. The transition time is drawn from a distribution given by the transition state theory rate and the number of attempted trajectories. Repeating this procedure from each state visited gives a statistically exact state-to-state trajectory.
A quasicore-shell structure of FeCo and FeNi nanoparticles
Authors: Meng L. J. , Peng X. Y. , Tang C. , Zhang K. W. , Stocks G. M. , Zhong J. X.
Published: December 2010

Based on semiempirical generalized embedded atom method (GEAM), we carried out molecular dynamics and Monte Carlo simulations to study the structural properties of FeCo and FeNi nanoparticles. It is found that these two kinds of nanoparticles possess a new stable quasicore-shell structure, no matter whether they are in molten or condensed state and whether they are prepared by annealing or quenching. In FeCo (FeNi) nanoparticles of various sizes and atom compositions, the quasicore-shell structure is always preferred, with the shell formed only by Fe atoms and the core formed by randomly distributed Co(Ni) and Fe atoms. We have also investigated the formation mechanism of the quasicore-shell structure by energy difference analysis of the pure and doped icosahedra structure of FeCo and FeNi nanoparticles.
Single particle detection: Phase control in submicron Hall sensors
Authors: Di Michele Lorenzo , Shelly Connor , Gallop John , Kazakova Olga
Published: December 2010

We present a phase-sensitive ac-dc Hall magnetometry method which allows a clear and reliable separation of real and parasitic magnetic signals of a very small magnitude. High-sensitivity semiconductor-based Hall crosses are generally accepted as a preferential solution for non-invasive detection of superparamagnetic nanobeads used in molecular biology, nanomedicine, and nanochemistry. However, detection of such small beads is often hindered by inductive pick-up and other spurious signals. The present work demonstrates an unambiguous experimental route for detection of small magnetic moments and provides a simple theoretical background for it. The reliability of the method has been tested for a variety of InSb Hall sensors in the range 600 nm–5 μm. Complete characterization of empty devices, involving Hall coefficients and noise measurements, has been performed and detection of a single FePt bead with diameter of 140 nm and magnetic moment of μ≈108 μB has been achieved with a 600 nm-wide sensor.
Effects of using As2 and As4 on the optical properties of InGaAs quantum rods grown by molecular beam epitaxy
Authors: Li L. H. , Patriarche G. , Linfield E. H. , Khanna S. P. , Davies A. G.
Published: December 2010

We investigate the effect of the arsenic source (As2 and As4) on the optical properties of InGaAs quantum rods (QRs) grown by molecular beam epitaxy. Owing to differences in the In and Ga diffusion lengths under As2 and As4 fluxes, photoluminescence (PL) peak energies of the QR samples depend strongly on the As source when similar growth conditions are used. A marked improvement in the PL intensities from QR samples grown using As4 is achieved. However, for both As2 and As4, an increase of the As overpressure results in a PL intensity degradation, probably due to the formation of nonradiative recombination centers.
Calculations of the low-lying excited states of the TiO2 molecule
Authors: Taylor Daniel J. , Paterson Martin J.
Published: December 2010

We present calculations of the lowest excited electronic states of the TiO2 molecule. These are computed using several correlated wavefunction response based methods, as well as time-dependent density functional response theory using a range of functionals. Surprisingly lower cost wavefunction based methods, in particular the second-order CC2 and CIS(D) methods, completely fail to describe the lowest 1B2 and 1A2 states of the molecule. Density functional methods fare better but still show considerable variation amongst functionals. Thus TiO2 provides a strenuous test for correlated excited state methods.
Microdroplet target synthesis for kilohertz ultrafast lasers
Authors: Chvykov Pavel , Ongg Wise , Easter James , Hou Bixue , Nees John , Krushelnick Karl
Published: December 2010

We have developed a method for producing spatially stable micron-scale liquid targets of flexible shapes at kilohertz repetition rate for use in air and vacuum, by perturbing 5 and 30 μm diameter streams with femtosecond laser pulses and monitoring the temporal development of the perturbation. Using water, we have produced features such as 2.1 μm diameter droplet and 1.3 μm diameter neck with less than ±0.3 μm shot-to-shot variation, with prospects for further reduction in size and variability. The use of such micron-scale targets can be expected to prevent conductive heat dissipation, enhance field strength for ion acceleration and allow spatially-deterministic laser-cluster experiments.