bluuebunny/crossref_metadata_2025 huggingface dataset:
Serum Vitamin B12 Concentrations among Mothers and Newborns and Follow-up Study to Assess Implication on the Growth Velocity and the Urinary Methylmalonic Acid Excretion
Authors: Hussein Laila , Abdel Aziz Sahar , Tapouzada Salwa , Boehles
Published: June 2010

Objective:Cobalamin (B12) deficiency has been reported in infants born to mothers with low cobalamin intake. Early diagnosis of vitamin B12 deficiency in infants is critical for the prevention of neurobehavioral disorders. We investigated the relationship between serum vitamin B12 level in newborns and in their healthy mothers who consumed an omnivorous diet. Anthropometry was studied longitudinally to assess the growth velocity of the infants. Urinary methylmalonic acid (MMA) excretion of 6-month old infants was compared retrospectively as the biomarker correlated with the initial serum vitamin B12 concentrations. Methods: Serum cobalamin and blood hemoglobin were determined in 84 pairs of newborns and their mothers. Urinary MMA excretion was measured in the same subjects during the first 6 months of the post partum period. Results: At birth, median serum cobalamin levels were 152.0 pmol/L in the mothers and 296.6 pmol/L in the newborns. Maternal and neonatal serum cobalamin levels had no effect on growth velocity during the first six months of postnatal life. Serum maternal and neonatal cobalamin levels were inversely associated with urinary MMA excretion. Conclusion: Early diagnosis of vitamin B12 status in neonates and infants is crucial, particularly in nutritionally deprived areas. Biochemical measurement of plasma cobalamin or its metabolic marker MMA is highly recommended. Urinary MMA measurement in cobalamin diagnostics provides an advantage in that blood sampling is not required. A vitamin B12 taskforce should be created to alleviate vitamin deficiency and its negative consequences.
A snapshot of climate variability at Tahiti at 9.5 ka using a fossil coral from IODP Expedition 310
Authors: DeLong Kristine L. , Quinn Terrence M. , Shen Chuan‐Chou , Lin Ke
Published: June 2010

The Integrated Ocean Drilling Program (IODP) Expedition 310 recovered drill cores from the drowned reefs around the island of Tahiti (17°40′S, 149°30′W), many of which contained samples of massive corals from the genus Porites. Herein we report on one well‐preserved fossil coral sample: a 13.6 cm long Porites sp. dated by uranium series techniques at 9523 ± 33 years. Monthly δ18O and Sr/Ca determinations reveal nine clear and robust annual cycles. Coral δ18O and Sr/Ca determinations estimate a mean temperature of ∼24.3°C (∼3.2°C colder than modern) for Tahiti at 9.5 ka; however, this estimate is viewed with caution since potential sources of cold bias in coral geochemistry remain to be resolved. The interannual variability in coral δ18O is similar between the 9.5 ka coral record and a modern record from nearby Moorea. The seasonal cycle in coral Sr/Ca is approximately the same or greater in the 9.5 ka coral record than in modern coral records from Tahiti. Paired analysis of coral δ18O and Sr/Ca indicates cold/wet (warm/dry) interannual anomalies, opposite from those observed in the modern instrumental record.
Toward an explanation for the present and past locations of the poles
Authors: Steinberger B. , Torsvik T. H.
Published: June 2010

Earth's orientation relative to its spin axis is determined by its nonhydrostatic inertia tensor. We show here that the present‐day nonhydrostatic inertia tensor can be modeled by combining contributions due to large low shear velocity provinces (LLSVPs) in the lowermost mantle and due to subduction. With the first contribution only, the spin axis would be at ∼67°N, 96°E (north Siberia). The distribution of recent subduction, with largest amounts in the northwest Pacific (beneath East Asia) and the southeast Pacific (beneath South America), adds a secondary contribution which moves the spin axis toward the observed poles. We use plate reconstructions to infer subduction and inertia tensor through time, assuming that the LLSVP contribution has remained constant. Motion of the pole toward Greenland since ∼50 Ma is attributed to increased subduction beneath East Asia and South America and a decrease beneath North America since then. Motion of the pole toward Siberia before that is attributed to large amounts of subduction beneath North America between ∼120 and 50 Ma and decreasing amounts of subduction in East Asia after 60–70 Ma. Greater stability of the spin axis since ∼100 Ma can be attributed to a decrease in the amount of subduction in polar latitudes and an increase in equatorial latitudes.
Pacific‐North America plate boundary reorganization in response to a change in relative plate motion: Offshore Canada
Authors: Rohr K. M. M. , Tryon A. J.
Published: June 2010

The transition from subduction in Cascadia to the transform Queen Charlotte fault along western Canada is often drawn as a subduction zone, yet recent studies of GPS and earthquake data from northern Vancouver Island are not consistent with that model. In this paper we synthesize seismic reflection and gravity interpretations with microseismicity data in order to test models of (1) microplate subduction and (2) reorganization of the preexisting strike‐slip plate boundary. We focus on the critical region of outer Queen Charlotte Sound and the adjacent offshore. On much of the continental shelf, several million years of subsidence above thin crust are a counterindicator for subduction. An undated episode of compression uplifted the southernmost shelf, but subsidence patterns offshore show that recent subduction is unlikely to be responsible. Previously unremarked near‐vertical faults and a mix of extensional and compressional faults offshore indicate that strike‐slip faulting has been a significant mode of deformation. Seismicity in the last 18 years is dominantly strike‐slip and shows large amounts of moment release on the Revere‐Dellwood fault and its overlap with the Queen Charlotte fault. The relative plate motion between the Pacific and North American plates rotated clockwise ∼6 Ma and appears to have triggered formation of an evolving array of structures. We suggest that the paleo‐Queen Charlotte fault which had defined this continental margin retreated northward as offshore distributed shear and the newly formed Revere Dellwood fault propagated to the northwest.
A kinetic ballooning/interchange instability in the magnetotail
Authors: Pritchett P. L. , Coroniti F. V.
Published: June 2010

Three‐dimensional electromagnetic particle‐in‐cell simulations are used to investigate the stability properties of a plasma sheet equilibrium with a minimum in the magnetic normal (Bz) component. Such a configuration is found to be unstable to a ballooning/interchange type mode that is localized tailward of theBzminimum. The mode has a relatively short dawn‐dusk wavelength of the order of the ion Larmor radius in theBzfield (∼2000 km) and a phase velocity in the direction of the ion diamagnetic drift with a magnitude about one‐fifth of the drift speed. The real frequency is about 60% of the midplane ion cyclotron frequency. The dominant mode polarization isδϕ andδB∥. A linear kinetic analysis including bounce and drift resonance interactions for the electrons and an orbit average over the flux tube volume for the Boltzmann term in the ion density perturbation produces agreement with the simulation mode properties and permits identification of the mode as the low‐frequency extension of the lower hybrid drift instability in straight magnetic geometry. In its nonlinear evolution, the mode develops Rayleigh‐Taylor fingers that extend across theBzminimum and into the near‐Earth dipole region. These fingers transport magnetic flux earthward, and the flux is redistributed by electron Hall currents that flow around the fingers. This mode is likely to contribute to the nearly continuous presence of turbulence in the center of the plasma sheet.
On the relationship between coronal heating, magnetic flux, and the density of the solar wind
Authors: Riley Pete , Mikic Z. , Lionello R. , Linker J. A. , Schwadron N. A. , McComas D. J.
Published: June 2010

The stark differences between the current solar minimum and the previous one offer a unique opportunity to develop new constraints on mechanisms for heating and acceleration of the solar wind. We have used a combination of numerical simulations and analysis of remote solar and in situ observations to infer that the coronal heating rate, H, scales with the average magnetic field strength within a coronal hole, Bch. This was accomplished in three steps. First, we analyzed Ulysses measurements made during its first and third orbit southern and northern polar passes (i.e., during near‐solar minimum conditions) to deduce a linear relationship between proton number density (np) and radial magnetic field strength (Br) in the high‐speed quiescent solar wind, consistent with the results of McComas et al. (2008) and Ebert et al. (2009). Second, we used Wilcox Solar Observatory measurements of the photospheric magnetic field to show that the magnetic field strength within coronal holes (Bch) is approximately correlated with the strength of the interplanetary field at the location of Ulysses. Third, we used hydrodynamic simulations to show that np in the solar wind scales linearly with H. Taken together, these results imply the chain: H ∝ np ∝ Br ∝ Bch. We also explored ideas that the correlation between np and Br could have resulted from interplanetary processes, or from the superradial expansion of the coronal magnetic field close to the Sun, but find that neither possibility can produce the observed relationship. The derived heating relationship is consistent with (1) empirical heating laws derived for closed‐field line regions and (2) theoretical models aimed at understanding both the heating and acceleration of the solar wind.
Recurrence rates of large explosive volcanic eruptions
Authors: Deligne N. I. , Coles S. G. , Sparks R. S. J.
Published: June 2010

A global database of large explosive volcanic eruptions has been compiled for the Holocene and analyzed using extreme value theory to estimate magnitude‐frequency relationships. The database consists of explosive eruptions with magnitude (M) greater than or equal to 4. Two models are applied to the data, one assuming no underreporting of eruptions and the other taking underreporting into consideration. Results from the latter indicate that the level of underreporting is high and fairly constant from the start of the Holocene until about 1 A.D. and then decreases dramatically toward the present. Results indicate there is only a ∼20% probability that an explosive eruption of M = 6 occurring prior to 1 A.D. is recorded. Analysis of the data set in the time periods 1750 A.D. and 1900 A.D. to present (assuming no underreporting) suggests that that these periods are likely to be too short to give reliable estimates of return periods for explosive eruptions with M > 6. Analysis of the Holocene data set with corrections for underreporting bias provide robust magnitude‐frequency relationships up to M = 7. Extrapolation of the model to greater magnitudes (M > 8) gives results inconsistent with geological data, predicting eruption size upper limits much smaller than known eruptions such as the Fish Canyon Tuff. We interpret this result as the consequence of different mechanisms operating for explosive eruptions with M > 7.
Effective medium modeling of gas hydrate‐filled fractures using the sonic log in the Krishna‐Godavari basin, offshore eastern India
Authors: Ghosh Ranjana , Sain Kalachand , Ojha Maheswar
Published: June 2010

Indian National Gas Hydrate Program Expedition 01 has established that clay‐rich marine sediment from the Krishna‐Godavari (KG) basin in the eastern Indian margin hosts one of the richest gas hydrate deposits in the world. Resistivity at‐bit images and pressure cores reveal that the gas hydrate morphology in clay‐rich sediment varies from complex vein structures (grain displacing) to invisible pore filling. Existing rock physics models, which relate acoustic data to in situ gas hydrate concentrations, generally assume isotropic pore‐filling gas hydrate, which yields misleading concentration estimates for fractured fine‐grained sediments. The anisotropic KG basin sediment presents additional complications. Here we apply differential effective medium theory to incorporate grain‐displacing morphologies by which gas hydrate is included as vertical ellipsoids with aspect ratios ranging from those of thin veins up to those of nodules in an elastic anisotropic background. We have estimated gas hydrate concentrations from sonic velocities at hole 10D in the KG basin considering three basic gas hydrate morphologies: (i) pore filling, (ii) grain displacing, and (iii) a combination of grain displacing and pore filling. Average gas hydrate saturations for these three cases are 35–42%, 27–30%, and 33–41% of the total porosity, respectively, in the depth range 60–140 m below seafloor (mbsf). Saturation is highest at ∼67 mbsf for any morphology but the values differ between morphologies. For the pore‐filling morphology, the maximum gas hydrate saturation of 56% is 18–22% higher than the grain‐displacing morphology and 2–9% higher than the combined morphology. Estimates differ by ±6% of the sediment volume with rotations of gas hydrate veins from vertical to horizontal.
Aircraft measurements of vertical profiles of aerosol mixing states
Authors: Pratt Kerri A. , Prather Kimberly A.
Published: June 2010

To examine the overall impact of aerosols on climate, direct measurements of the size‐resolved mixing states of atmospheric particles are needed as a function of altitude. During the Ice in Clouds Experiment‐Layer Clouds, the recently developed aircraft aerosol time‐of‐flight mass spectrometer directly measured the vertical profiles of size‐resolved single‐particle chemistry in cloud‐free air over Wyoming and northern Colorado. These represent the first aircraft‐based, dual polarity mass spectrometry measurements, allowing a detailed examination of in situ single‐particle mixing state as a function of altitude. Measurement of both positive and negative ions for each individual particle provides the ability to identify the primary particle type/source, such as biomass burning, organic carbon, or soot, and examine the extent of mixing with secondary species, such as ammonium, nitrate, sulfate, and sulfuric acid. For the primary particle cores, biomass burning represented the largest source of submicron particles: ∼33–39% by number from 1 to 7 km. Organic carbon particles were the second most abundant type (maximum of ∼33% by number from 1.2 to 2.0 km) with elemental carbon (soot) particles comprising 14–22% by number from 1 to 7 km. In general, biomass burning, organic carbon, and soot particles were frequently internally mixed with ammonium, nitrate, and sulfate at lower altitudes, switching to sulfate and sulfuric acid mixtures at higher altitudes. Further, the number fraction of externally mixed sulfuric acid particles increased with altitude from 1 to 9%, likely because of cloud processing of SO2. The variance of particle mixing state with altitude significantly changes absorption and hygroscopic properties, and must be taken into account in models calculating aerosol direct and indirect radiative forcings.
Agriculture and resource availability in a changing world: The role of irrigation
Authors: Sauer Timm , Havlík Petr , Schneider Uwe A. , Schmid Erwin , Kindermann Georg , Obersteiner Michael
Published: June 2010

Fertile land and freshwater constitute two of the most fundamental resources for food production. These resources are affected by environmental, political, economic, and technical developments. Regional impacts may transmit to the world through increased trade. With a global forest and agricultural sector model, we quantify the impacts of increased demand for food due to population growth and economic development on potential land and water use until 2030. In particular, we investigate producer adaptation regarding crop and irrigation choice, agricultural market adjustments, and changes in the values of land and water. In the context of resource sustainability and food security, this study accounts for the spatial and operational heterogeneity of irrigation management to globally assess agricultural land and water use. Agricultural responses to population and economic growth include considerable increases in irrigated area and water use but reductions in the average water intensity. Different irrigation systems are preferred under different exogenous biophysical and socioeconomic conditions. Negligence of these adaptations would bias the burden of development on land and water scarcity. Without technical progress, substantial price adjustments for land, water, and food would be required to equilibrate supply and demand.
An upscaled model for biofilm growth in a thin strip
Authors: van Noorden T. L. , Pop I. S. , Ebigbo A. , Helmig R.
Published: June 2010

The focus of this paper is the derivation of an effective model for biofilm growth in a porous medium and its effect on fluid flow. The starting point is a pore‐scale model in which the local geometry of the pore is represented as a thin strip. The model accounts for changes in pore volume due to biomass accumulation. As the ratio of the width of the strip to its length approaches zero, we apply a formal limiting argument to derive a one‐dimensional upscaled (effective) model. For a better understanding of the terms and parameters involved in the equations derived here, we compare these equations to a well‐known core‐scale model from the literature.
Non‐volcanic CO2 Earth degassing: Case of Mefite d'Ansanto (southern Apennines), Italy
Authors: Chiodini G. , Granieri D. , Avino R. , Caliro S. , Costa A. , Minopoli C. , Vilardo G.
Published: June 2010

Mefite d'Ansanto, southern Apennines, Italy is the largest natural emission of low temperature CO2 rich gases, from non‐volcanic environment, ever measured in the Earth. The emission is fed by a buried reservoir, made up of permeable limestones and covered by clayey sediments. We estimated a total gas flux of ∼2000 tons per day. Under low wind conditions, the gas flows along a narrow natural channel producing a persistent gas river which has killed over a period of time people and animals. The application of a physical numerical model allowed us to define the zones which potentially can be affected by dangerous CO2 concentration at breathing height for humans. The geometry of the Mefite gas reservoir is similar to those designed for sequestering CO2 in geological storage projects where huge amounts of CO2 should be injected in order to reduce atmospheric CO2 concentration. The approach which we have used at Mefite to define hazardous zones for the human health can be applied also in case of large CO2 leakages from storage sites, a phenomena which, even if improbable, can not be ruled out.
Super‐refraction effects on GPS radio occultation refractivity in marine boundary layers
Authors: Xie F. , Wu D. L. , Ao C. O. , Kursinski E. R. , Mannucci A. J. , Syndergaard S.
Published: June 2010

With the combination of global coverage, high vertical resolution, and all‐weather capability, GPS radio occultation (RO) is an emerging satellite remote sensing technique that can probe the atmospheric boundary layer (ABL) on a global basis. However, a systematic negative bias (commonly referred to as N‐bias) remains in derived refractivity profiles in the ABL. In this paper we present the N‐biases in COSMIC RO soundings with respect to ECMWF analyses, which show a seasonally varying pattern clustered over the oceans where super‐refraction (SR) often occurs. A case study of coincident COSMIC RO and radiosonde sounding confirms that the N‐bias is primarily caused by SR. We also show that the high‐rate RO bending angle measurements can resolve the ABL top at a vertical resolution better than 100 m. A reconstruction method is applied to one case where SR occurs and significantly reduces the negative refractivity error in the ABL.
Role of vertical migration in biogenic ocean mixing
Authors: Dabiri John O.
Published: June 2010

Recent efforts to empirically measure and numerically simulate biogenic ocean mixing have consistently observed low mixing efficiency. This suggests that the buoyancy flux achieved by swimming animals in the ocean may be negligible in spite of the observed large kinetic energy dissipation rates. The present letter suggests that vertical migration across isopycnals may be necessary in order to generate overturning and subsequent mixing at length scales significantly larger than the individual animals. The animal‐fluid interactions are simulated here using a simplified potential flow model of solid spheres migrating vertically in a stably stratified fluid. The interaction of successive solid bodies with each parcel of fluid is shown to lead, under certain conditions, to vertical displacement of the fluid parcels over distances much larger than the individual body size. These regions of displaced fluid are unstably stratified and, hence, amenable to large‐scale overturning and efficient mixing.
Seasonal dependence of MSTIDs obtained from 630.0 nm airglow imaging at Arecibo
Authors: Martinis C. , Baumgardner J. , Wroten J. , Mendillo M.
Published: June 2010

All‐sky imaging data of 630.0 nm airglow emissions are used to study the seasonal and solar activity dependence of medium‐scale traveling ionospheric disturbances (MSTIDs) over Arecibo, Puerto Rico (18.3° N, 66.7° W, 28° N mag lat). MSTIDs are typical F‐region signatures at midlatitudes, yet limited statistical results in the American sector hindered the progress in our understanding of these dynamical structures. This study compiles data from 2002 to 2007 and shows for the first time that optically‐determined MSTIDs at Arecibo present a semiannual pattern with peak occurrence at both solstices. In the Japanese longitude sector, a similar pattern has been found, but one with a main peak during local summer. This paper explains the high occurrence rate during local winter at Arecibo via E‐layer/F‐layer coupling and inter‐hemispheric coupling, thus accounting for a consistent morphology between the two longitude sectors.
Modelling and experimental analysis of hormonal crosstalk in Arabidopsis
Authors: Liu Junli , Mehdi Saher , Topping Jennifer , Tarkowski Petr , Lindsey Keith
Published: June 2010

An important question in plant biology is how genes influence the crosstalk between hormones to regulate growth. In this study, we model POLARIS (PLS) gene function and crosstalk between auxin, ethylene and cytokinin in Arabidopsis. Experimental evidence suggests that PLS acts on or close to the ethylene receptor ETR1, and a mathematical model describing possible PLS–ethylene pathway interactions is developed, and used to make quantitative predictions about PLS–hormone interactions. Modelling correctly predicts experimental results for the effect of the pls gene mutation on endogenous cytokinin concentration. Modelling also reveals a role for PLS in auxin biosynthesis in addition to a role in auxin transport. The model reproduces available mutants, and with new experimental data provides new insights into how PLS regulates auxin concentration, by controlling the relative contribution of auxin transport and biosynthesis and by integrating auxin, ethylene and cytokinin signalling. Modelling further reveals that a bell‐shaped dose–response relationship between endogenous auxin and root length is established via PLS. This combined modelling and experimental analysis provides new insights into the integration of hormonal signals in plants.
Protein Crystallography for Metalloproteins
Authors: Gao Zengqiang , Hou Haifeng , Dong Yuhui
Published: June 2010

The structures of proteins are very essential in understanding the functions of proteins. Protein crystallography is the most wide-used and precious method for structure determination of proteins. This chapter, Protein crystallography for metalloproteins, is divided into four sections. Firstly, we introduce protein crystallography by comparing with other methods for obtaining structure, such as NMR and cryo-EM. And then the general routine for getting structures via crystallography is described, especially the phasing problem in protein structure determination. In Section 3, the most favorite phasing method, MAD, which is suitable for metallloproteins, is presented. Finally, we demonstrate one case of investigating the function of metalloprotein by obtaining the structure.
Applications of Nuclear Analytical Techniques for Iron-omics Studies
Authors: Nie Guangjun , Zhu Motao , Ning Bo
Published: June 2010

Modern nuclear analytical techniques (NATs), including neutron activation analysis (NAA), Mössbauer spectroscopy, proton-induced X-ray emission (PIXE) spectroscopy, synchronous radiation (SR) based analytical techniques and isotope-based techniques, have been successfully utilized as important tools for iron-omics studies for understanding the mechanisms of iron metabolism implicated in physiology, pathology, toxicology and pharmacology. NATs could be applied for both element bulk analysis and chemical speciation studies. For instance, SR-based method and PIXE for iron mapping at tissue, cellular and sub-cellular levels, NAA for iron quantification, Mössbauer spectroscopy for giving chemical, structural and magnetic information, have been commonly used for iron-omics studies. Furthermore, for speciation and iron-omics studies at molecular levels, a variety of physical, chemical or biological separation procedures, such as chromatography and electrophoresis, have been developed in combination with the NATs. With advantages of high sensitivity, high accuracy, sufficient detection limits, no interferences from other components and economical operating costs, iron metabolism could be studied at the tissue, cellular, subcellular or even molecular level by NATs independently or by NATs combining with pre-separation procedures. The advance of these analytical techniques will significantly increase our understanding of the roles of iron in various physiological and pathological conditions.
Application of Integrated Techniques for Micro- and Nano-imaging Towards the Study of Metallomics and Metalloproteomics in Biological Systems
Authors: Zhang Lili , Chen Chunying
Published: June 2010

Nuclear imaging techniques can provide visible information on distribution patterns of metals or metalloids in various biological tissues, cell and subcellular fractions, and even at molecular level. Since the changes of not only its concentration but also spatial distribution for a specific element may cause some physiological problems even death, it is crucial to know the exact distribution in various organisms. In this chapter we introduce some imaging techniques (here mainly refers to the two-dimensional (2D) elemental distributions in samples) that are developing or have been used for metallomics and metalloproteomics. These techniques include not only modern nuclear analytical imaging techniques such as X-ray Fluorescence (XRF) in Section 1 and Particle Induced X-ray Emission (PIXE) in Section 2, but also non-nuclear analytical techniques such as Mass spectrometry imaging (MSI) technique in Section 3. We demonstrate their applications on the elemental imaging in animal tissues, plant leaves, nematodes, mammalian cells and so on. In addition to 2D imaging techniques, in Section 4, we also briefly introduce tomography, a three-dimensional imaging technique which can be done in vivo. All these techniques have successful applications in multidisciplinary study. Finally, in Section 5 we summarize the important characteristics of these techniques. Actually, each elemental imaging technique has its own characteristics. But for those researchers who engage in metallomics and metalloproteomics, the most important thing is to make a better understanding and use of these techniques. We hope that this chapter will be helpful.
Effects of Brn‐4 on the neuronal differentiation of neural stem cells derived from rat midbrain
Authors: Tan Xue‐Feng , Qin Jian‐Bing , Jin Guo‐Hua , Tian Mei‐Ling , Li Hao‐Ming , Zhu Hui‐Xia , Zhang Xin‐Hua , Shi Jin‐Hong , Huang Zhen
Published: June 2010

NSCs (neural stem cells) provide a powerful research tool for the design and discovery of new approaches to cell replacement therapy during brain repair. However, the usefulness of this tool has been particulaly obstructed by limited neuronal differentiation of NSCs. Brn‐4, a member of the POU domain family of transcription factors, has been previously implicated in the development of neurons by expression analysis. Here, we directly investigated the effects of Brn‐4 on the neuronal differentiation and development of NSCs derived from the E13 rat midbrain. We found that Brn‐4 knockdown in NSCs resulted in a significant decrease of MAP‐2‐positive neurons with immature morphology. Overexpression of Brn‐4 in NSCs markedly increased the production and maturation of newborn neurons. These results suggest that Brn‐4 has a critical role in the neuronal differentiation of mesencephalic NSCs and the maturation of newborn neurons. Brn‐4 may be utilized to manipulate NSCs for gene and cell therapy of several neurological diseases.
Three Profiles of Language Abilities in Toddlers With an Expressive Vocabulary Delay: Variations on a Theme
Authors: Desmarais Chantal , Sylvestre Audette , Meyer François , Bairati Isabelle , Rouleau Nancie
Published: June 2010

Purpose

The presence of an expressive vocabulary delay (EVD) in the context of otherwise harmonious development has been the main criterion used to define language delay in 2-year-olds. To better understand the communicative functioning of these children, other variables must be considered. In this study, the aim was to delineate and characterize clusters of 2-year-olds with EVD by measuring other language variables in these children.

Method

Language and related variables were measured in 68 francophone children with EVD.

Results

In a cluster analysis, 2 language variables—(a) language expression and engagement in communication and (b) language comprehension—yielded 3 clusters ranging from weak language ability to high scores on both variables. Further differences were found between these clusters with regard to 2 correlates of lexical acquisition—namely, size of the expressive vocabulary and cognitive development.

Conclusion

These results shed new light on the notion of heterogeneity in toddlers who present with an EVD by proposing subgroups among them. A follow-up investigation of these participants is ongoing.
Narrative Assessment for Cantonese-Speaking Children
Authors: Kit-Sum To Carol , Stokes Stephanie F. , Cheung Hin-Tat , T’sou Benjamin
Published: June 2010

Background

This study examined the narrative skills of Cantonese-speaking school-age children to fill a need for a normative language test for school-age children.

Purpose

To provide a benchmark of the narrative skills of Cantonese-speaking children; to identify which of the microstructure components was the best predictor of age; and to determine the diagnostic accuracy of the test components.

Method and Procedure

Data were collected from 1,120 Cantonese-speaking children between the ages of 4;10 (years;months) and 12;01, using a story-retell of a 24-frame picture series. Four narrative components (syntactic complexity, semantic score, referencing, and connective use) were measured.

Outcomes and Results

Each measure reflected significant age-related differences in narrative ability. Regression analyses revealed that vocabulary and syntactic complexity were the best predictors of grade. All measures showed high sensitivity (86%–94%) but relatively low specificity (60%–90%) and modest likelihood ratio (LR) values: LR+ (2.15–9.42) and LR− (0.07–0.34).

Conclusion and Implications

Narrative assessment can be standardized to be a reliable and valid instrument to assist in the identification of children with language impairment. Syntactic complexity is not only a strong predictor of grade but was also particularly vulnerable in Cantonese-speaking children with specific language impairment. Further diagnostic research using narrative analysis is warranted.
Electrophysiological Indices of Discrimination of Long-Duration, Phonetically Similar Vowels in Children With Typical and Atypical Language Development
Authors: Datta Hia , Shafer Valerie L. , Morr Mara L. , Kurtzberg Diane , Schwartz Richard G.
Published: June 2010

Purpose

The authors investigated the neurophysiological bases of vowel perception in children with specific language impairment (SLI) compared with typical language development (TLD) controls using 250-ms phonetically similar vowels. In a previous study, children with SLI showed a poor neurophysiological response (the mismatch negativity [MMN]) to 50-ms versions of these vowels, regardless of whether attention was directed to (attend) or away (passive) from the auditory modality (V. Shafer, M. Morr, H. Datta, D. Kurtzberg, & R. Schwartz, 2005). They hypothesized that longer vowels would allow for improved speech perception.

Method

Brain responses were elicited to the vowel contrast in 2 conditions: (a) attend and (b) passive. Behavioral discrimination and identification responses were also examined.

Results

Both SLI and TLD groups showed evidence of discrimination (MMN) of the vowels in the attend and passive conditions. Only subtle differences in the scalp topography of a late negative (LN) brain component were observed between groups. The SLI compared with the TLD group showed significantly poorer identification of these long vowels, as found previously with the shorter vowels.

Conclusions

Increased vowel duration can improve discrimination in children with SLI. However, poor identification of these longer vowels by some children with SLI suggests a deficit in long-term phonological representations or accessing these representations.
Word Learning in Children With Primary Language Impairment: A Meta-Analysis
Authors: Kan Pui Fong , Windsor Jennifer
Published: June 2010

Purpose

The present study is a meta-analysis that examines the difference in novel word learning performance between children with primary language impairment (LI) and typically developing children. Participant and task characteristics were examined as variables that potentially moderated children’s word learning.

Method

Eight hundred and forty-six published studies were retrieved from conventional databases (PsycINFO, MEDLINE, and Web of Science). Of these studies, 28 met the criteria for inclusion in the meta-analysis, yielding 244 effect sizes across experimental conditions.

Results

LI groups showed significantly lower word learning performance than typical age-matched groups and equivalent performance to typical language–matched groups. Moderator analyses showed that the magnitude of the group difference relative to age peers was significantly associated with participants' chronological age, receptive language and cognitive abilities, task and novel word type, and the extent of novel word exposure.

Conclusion

The difference in novel word learning performance between children with LI and age-matched children is strongly affected by task and participant characteristics in the primary studies.
Neighborhood Density and Word Frequency Predict Vocabulary Size in Toddlers
Authors: Stokes Stephanie F.
Published: June 2010

Purpose

To document the lexical characteristics of neighborhood density (ND) and word frequency (WF) in the lexicons of a large sample of English-speaking toddlers.

Method

Parents of 222 British-English–speaking children aged 27(±3) months completed a British adaptation of the MacArthur–Bates Communicative Development Inventory: Words and Sentences (MCDI; Klee & Harrison, 2001). Child words were coded for ND and WF, and the relationships among vocabulary, ND, and WF were examined. A cut-point of −1
SD
below the mean on the MCDI classified children into one of two groups: low or high vocabulary size. Group differences on ND and WF were examined using nonparametric statistics.

Results

In a hierarchical regression, ND and WF accounted for 47% and 14% of unique variance in MCDI scores, respectively. Low-vocabulary children scored significantly higher on ND and significantly lower on WF than did high-vocabulary children, but there was more variability in ND and WF for children at the lowest points of the vocabulary continuum.

Conclusion

Children at the lowest points of a continuum of vocabulary size may be extracting statistical properties of the input language in a manner quite different from their more able age peers.
Investigating Mechanisms of Suppression in Preschool Children With Specific Language Impairment
Authors: Spaulding Tammie J.
Published: June 2010

Purpose

This study investigated 2 suppression mechanisms—(a) resistance to distracter interference and (b) inhibition of a prepotent response—in preschool children with specific language impairment (SLI) and their typically developing peers.

Method

Twenty-two preschool children with SLI and 22 typically developing controls participated in this study. The resistance to distracter interference task involved suppressing distracters (nonverbal auditory, linguistic, and visual) that were external and irrelevant to the task goal. Inhibition was assessed using a stop-signal paradigm to evaluate the ability to suppress a prepotent, conflicting response.

Results

The children with SLI exhibited decreased resistance to distracter interference regardless of distracter modality and poor inhibitory control relative to their typically developing peers.

Conclusion

These results identify suppression weaknesses in preschool-age children with SLI. Specifically, children with this disorder exhibited difficulty suppressing both irrelevant and contradictory information.
Improving the Quality and Applicability of the Dutch Scales of the Communication Profile for the Hearing Impaired Using Item Response Theory
Authors: Mokkink Lidwine B. , Knol Dirk L. , van Nispen Ruth M. A. , Kramer Sophia E.
Published: June 2010

Purpose

The aim of this study was to improve the quality and applicability of the 6 Dutch scales of the Communication Profile for the Hearing Impaired (CPHI; Demorest & Erdman, 1986, 1987, 1988) using item response theory (IRT). IRT modeling can produce precise, valid, and relatively brief instruments, resulting in minimal response burden (Edelen & Reeve, 2006).

Method

We investigated (a) whether items fit to the graded response model (GRM; Samejima, 1969) using Stone and Zhang’s (2003) procedure to test goodness of fit and (b) whether items showed differential item functioning (DIF) with the IRT log-likelihood ratio approach for 5 group variables: gender, age, living arrangement, use of hearing aids, and degree of hearing impairment. We investigated the magnitude of DIF by calculating the maximum difference between expected item scores for subgroups of the group variables of items showing DIF.

Results

In a cross-sectional study, 408 consecutive individuals with hearing impairment completed the Dutch CPHI scales. Twelve items were deleted because of misfit to GRMs, 14 items showed uniform DIF, and 2 showed nonuniform DIF. Five items showing DIF were deleted due to large magnitude of DIF. The short form of the Dutch CPHI scales contains 35 items.

Conclusions

DIF analyses showed that the short form was relatively free of DIF with respect to the 5 group variables. Hence, there is no need to make adjustments for the calculation of subgroup scores.
Modeling and simulation of anode melting pool flow under the action of high-current vacuum arc
Authors: Wang Lijun , Jia Shenli , Liu Yu , Chen Bin , Yang Dingge , Shi Zongqian
Published: June 2010

In this paper, a transient magnetohydrodynamic (MHD) model of an anode melting pool (AMP) flow (AMPF) is established. Mass equation, momentum equations along axial, radial and azimuthal directions, energy equation, and current continuity equations are considered in the model. In the momentum equations, the influence of electromagnetic force, viscosity force and Marangoni force (anode surface shear stress) are included. Joule heating is also included in the energy equations. According to the MHD model of AMPF, the influence of different heat flux densities to melting pool flow velocities (including azimuthal, radial, and axial velocity), anode temperature, fraction of liquid, melting depth, melting radius, and anode vapor flux will be analyzed. In the AMP, the azimuthal velocity is dominant, whose value approximately approaches velocity magnitude, the radial velocity is much smaller than azimuthal velocity, and the axial velocity is the smallest one compared with radial and azimuthal velocity. According to simulation results, anode surface temperature, melting width, melting depth, and anode vapor flux are increased with the increase in heat flux densities, but the increase in azimuthal velocity is not significant. Simulation results also show that the maximum anode temperature appears near 6.5–7 ms (50 Hz), but the maximum velocity of AMPF appears near 8–10 ms, which is in agreement with the experimental observation. Simulation result of AMPF swirl velocity (about 0.4 m/s) is approximately close to experimental result (about 0.6 m/s) based on high-speed camera data. Simulation results also show that the influence of joule heating and radiation on anode temperature can be neglected. The influence of Marangoni force on AMPF is significant.
Generation of inhomogeneous bulk plane acoustic modes by laser-induced thermoelastic grating near mechanically free surface
Authors: Gusev Vitalyi
Published: June 2010

The detailed theoretical description of how picosecond plane shear acoustic transients can be excited by ultrafast lasers in isotropic media is presented. The processes leading to excitation of inhomogeneous plane bulk compression/dilatation (c/d) and shear acoustic modes by transient laser interference pattern at a mechanically free surface of an elastically isotropic medium are analyzed. Both pure modes are dispersive. The modes can be evanescent or propagating. The mechanical displacement vector in both propagating modes is oriented obliquely to the mode propagation direction. Consequently the c/d mode is not purely longitudinal and shear mode is not purely transversal. Each of the propagating modes has a plane wave front parallel to the surface and the amplitude harmonically modulated along the surface. Inhomogeneous shear acoustic mode cannot be generated in isotropic medium by thermal expansion and is excited by mode conversion of laser-generated inhomogeneous c/d acoustic mode incident on the surface. The spectral transformation function of the laser radiation conversion into shear modes has one of its maxima at a frequency corresponding to transmission from laser-induced generation of propagating to laser-induced generation of evanescent c/d modes. At this particular frequency the shear waves are due to their Cherenkov emission by bulk longitudinal acoustic waves skimming along the laser-irradiated surface, which are generated by laser-induced gratings synchronously. There exists an interval of frequencies where only shear acoustic modes are launched in the material by laser-induced grating, while c/d modes generated by thermoelastic optoacoustic conversion are evanescent. Propagating picosecond plane shear acoustic fronts excited by interference pattern of fs-ps laser pulses can be applied for the determination of the shear rigidity by optoacoustic echoes diagnostics of thin films and coatings. Theoretical predictions are correlated with available results of experiments and of numerical modeling.
Effect of electric field on low temperature multisubband electron mobility in a coupled Ga0.5In0.5P/GaAs quantum well structure
Authors: Sahu Trinath , Shore K. Alan
Published: June 2010

The effect of uniform electric field on low temperature (T=0 K) multisubband electron mobility μi is analyzed by considering a barrier delta-doped Ga0.5In0.5P/GaAs coupled double quantum well structure. We consider ionized impurity scattering and interface roughness (IR) scattering. The screening of the scattering potentials is obtained by adopting the random phase approximation. Starting with a double-subband occupied system we have studied the changes in the intrasubband and intersubband scattering processes by varying the electric field F and highlight the influence of F on the intersubband effects which yields interesting results on μi. At a certain electric field, the system undergoes a transition from double subband to single subband occupancy leading to a large enhancement in mobility due to the suppression of the intersubband interactions. We show that by reversing the electric field a large change in mobility is obtained due to the asymmetric nature of the IR scattering potential. It is also gratifying to show that by varying the electric field the relative dominance of different scattering mechanisms on subband mobility changes through the intersubband interaction.
Metallic coatings of microelectromechanical structures at low temperatures: Stress, elasticity, and nonlinear dissipation
Authors: Collin E. , Kofler J. , Lakhloufi S. , Pairis S. , Bunkov Yu. M. , Godfrin H.
Published: June 2010

We present mechanical measurements performed at low temperatures on cantilever-based microelectromechanical structures coated with a metallic layer. Two very different coatings are presented in order to illustrate the capabilities of the present approach, namely (soft) aluminum and (hard) niobium oxide. The temperature is used as a control parameter to access materials properties. We benefit from low temperature techniques to extract a phase-resolved measurement of the first mechanical resonance mode in cryogenic vacuum. By repeating the experiment on the same samples, after multiple metallic depositions, we can determine accurately the contribution of the coating layers to the mechanical properties in terms of surface stress, additional mass, additional elasticity, and damping. Analytic theoretical expressions are derived and used to fit the data. Taking advantage of the extremely broad dynamic range provided by the technique, we can measure the anelasticity of the thin metallic film. The key parameters describing the metals’ dynamics are analyzed in an original way in order to provide new experimental grounds for future theoretical modelings of the underlying mechanisms.
Dispersion and temperature statistics of inertial particles in isotropic turbulence
Authors: Wetchagarun Saensuk , Riley James J.
Published: June 2010

The dispersion and temperature distribution of inertial particles are important in many turbulent, multiphase flow problems. In order to understand these better, direct numerical simulations (DNSs) are performed for inertial particles in a fluid with a constant temperature gradient and whose motion is either statistically stationary or decaying, isotropic turbulence. It is found that, for long times, the dispersion of inertial particles is the greatest when the Stokes number, Stη=τp/τη, is of order 1, where τp and τη are, respectively, the particle response time and the flow Kolmogorov time scale. A similar result is found for the long time behavior of the time rate of change of the mean-square particle temperature fluctuations, d⟨Tp′2⟩/dt. To understand the DNS results better, an evolution equation for ⟨Tp′2⟩, along with the short and long time limits, is derived analytically from the thermal energy equation for inertial particles.