Concentration fields near air-water interfaces during interfacial mass transport: oxygen transport and random square wave analysis

Mass transfer across a gas-liquid interface was studied theoretically and experimentally, using transfer of oxygen into water as the gas-liquid system. The experimental results support the conclusions of a theoretical description of the concentration field that uses random square waves approximations. The effect of diffusion over the concentration records was quantified. It is shown that the peak of the normalized rms concentration fluctuation profiles must be lower than 0.5, and that the position of the peak of the rms value is an adequate measure of the thickness of the diffusive layer. The position of the peak is the boundary between the regions more subject to molecular diffusion or to turbulent transport of dissolved mass

Study protocol: A comprehensive multi-method neuroimaging approach to disentangle developmental effects and individual differences in second language learning

Background While it is well established that second language (L2) learning success changes with age and across individuals, the underlying neural mechanisms responsible for this developmental shift and these individual differences are largely unknown. We will study the behavioral and neural factors that subserve new grammar and word learning in a large cross-sectional developmental sample. This study falls under the NWO (Nederlandse Organisatie voor Wetenschappelijk Onderzoek [Dutch Research Council]) Language in Interaction consortium (website: https://www.languageininteraction.nl/). Methods We will sample 360 healthy individuals across a broad age range between 8 and 25 years. In this paper, we describe the study design and protocol, which involves multiple study visits covering a comprehensive behavioral battery and extensive magnetic resonance imaging (MRI) protocols. On the basis of these measures, we will create behavioral and neural fingerprints that capture age-based and individual variability in new language learning. The behavioral fingerprint will be based on first and second language proficiency, memory systems, and executive functioning. We will map the neural fingerprint for each participant using the following MRI modalities: T1‐weighted, diffusion-weighted, resting-state functional MRI, and multiple functional-MRI paradigms. With respect to the functional MRI measures, half of the sample will learn grammatical features and half will learn words of a new language. Combining all individual fingerprints allows us to explore the neural maturation effects on grammar and word learning. Discussion This will be one of the largest neuroimaging studies to date that investigates the developmental shift in L2 learning covering preadolescence to adulthood. Our comprehensive approach of combining behavioral and neuroimaging data will contribute to the understanding of the mechanisms influencing this developmental shift and individual differences in new language learning. We aim to answer: (I) do these fingerprints differ according to age and can these explain the age-related differences observed in new language learning? And (II) which aspects of the behavioral and neural fingerprints explain individual differences (across and within ages) in grammar and word learning? The results of this study provide a unique opportunity to understand how the development of brain structure and function influence new language learning success

Stability of the replica-symmetric saddle-point in general mean-field spin-glass models

Within the replica approach to mean-field spin-glasses the transition from ergodic high-temperature behaviour to the glassy low-temperature phase is marked by the instability of the replica-symmetric saddle-point. For general spin-glass models with non-Gaussian field distributions the corresponding Hessian is a $2^n\times 2^n$ matrix with the number $n$ of replicas tending to zero eventually. We block-diagonalize this Hessian matrix using representation theory of the permutation group and identify the blocks related to the spin-glass susceptibility. Performing the limit $n\to 0$ within these blocks we derive expressions for the de~Almeida-Thouless line of general spin-glass models. Specifying these expressions to the cases of the Sherrington-Kirkpatrick, Viana-Bray, and the L\'evy spin glass respectively we obtain results in agreement with previous findings using the cavity approach

Stand Characteristics and Leaf Litter Composition of a Dry Forest Hectare in Santa Rosa National Park, Costa Rica

One hectare of tropical dry forest in Guanacaste Conservation Area, Costa Rica was mapped and all trees larger than 10 cm diameter at breast height (DBH) identified. The same hectare was sampled for leaf litter and the two data sets, forest and litter, were compared. Dominant and subdominant species of the forest are represented in the leaf litter, whereas rare tree species are highly variable in their representation in the leaf litter. Relative abundance of dominant and subdominant tree species is represented well by the litter although absolute rank-order is nor identical between source forest basal area and leaf litter mass. The litter adds a significant component to the source forest data owing to the presence of vines and lianas, and more rarely small trees or shrubs. This indicates that litter studies may be able to add depth to forest diversity surveys. The source forest also was used to test foliar physiognomic reconstructions of climate that have been proposed recently by paleobotanists as an alternative to taxonomic affinities methods. The observed climate of the area does not conform to the climatic values that were predicted by application of these new methods. RESUMEN Una hectÁrea de bosque seco tropical en el Area de ConservaciÓn de Guanacaste, Costa Rica fue mapeada, y todos los Árboles mayores de 10 cm de dap fueron identificados. En la misma hectÁrea, se tomaron muestras de hojarasca y los dos colecciones de datos. bosque y hojarasca, fueron comparadas. Se encontrÓ que las especies dominantes y subdominantes del bosque estaban representadas en las muestras de hojarasca, mientras que la presencia de especias arbÓreas raras en las muestras de mojarasca fue muy variable. La abundancia relativa de especies arbÓreas dominantesestÁ bien representada en la hojarasca aunque el Área basal del bosque de origen y la masa de hojarasca no heron idÉnticos en rangos absolutos. La hojarasca aÑade un componente significativo a los datos del bosque de origen debido a la presencia de bejucos y lianas en la hojarasca, y mÁs raramente Árboles pequeÑos y arbustos. Estos datos indican que los estudios de hojarasca pueden incrementar la precisiÓn de las estimaciones de la diversidad de los bosques. El bosque de origen fue usado tarnbien para examinar reconstrucciones del clima basados en la fisiognomia foliar recientemenre propuesras por paleobotÁnicas como una alternativa a mÉtodos de afinidad raxonÓmicas. El clima observado en el Área no corresponde con los valores climÁticos que fueron predecidos por la aplicaciÓn de estos nuevos mÉtodos.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73234/1/j.1744-7429.1997.tb00034.x.pd

Landmark Recognition in Alzheimer’s Dementia: Spared Implicit Memory for Objects Relevant for Navigation

Contains fulltext : 97074.pdf (publisher's version ) (Open Access)BACKGROUND: In spatial navigation, landmark recognition is crucial. Specifically, memory for objects placed at decision points on a route is relevant. Previous fMRI research in healthy adults showed higher medial-temporal lobe (MTL) activation for objects placed at decision points compared to non-decision points, even at an implicit level. Since there is evidence that implicit learning is intact in amnesic patients, the current study examined memory for objects relevant for navigation in patients with Alzheimer's dementia (AD). METHODOLOGY/PRINCIPAL FINDINGS: 21 AD patients participated with MTL atrophy assessed on MRI (mean MMSE = 21.2, SD = 4.0), as well as 20 age- and education-matched non-demented controls. All participants watched a 5-min video showing a route through a virtual museum with 20 objects placed at intersections (decision points) and 20 at simple turns (non-decision points). The instruction was to pay attention to the toys (half of the objects) for which they were supposedly tested later. Subsequently, a recognition test followed with the 40 previously presented objects among 40 distracter items (both toys and non-toys). Results showed a better performance for the non-toy objects placed at decision points than non-decision points, both for AD patients and controls. CONCLUSION/SIGNIFICANCE: Our findings indicate that AD patients with MTL damage have implicit memory for object information relevant for navigation. No decision point effect was found for the attended items. Possibly, focusing attention on the items occurred at the cost of the context information in AD, whereas the controls performed at an optimal level due to intact memory function.5 p

SiC substrate effects on electron transport in the epitaxial graphene layer

Cataloged from PDF version of article.Hall effect measurements on epitaxial graphene (EG) on SiC substrate have been carried out as a function of temperature. The mobility and concentration of electrons within the two-dimensional electron gas (2DEG) at the EG layers and within the underlying SiC substrate are readily separated and characterized by the simple parallel conduction extraction method (SPCEM). Two electron carriers are identified in the EG/SiC sample: one high-mobility carrier (3493 cm(2)/Vs at 300 K) and one low-mobility carrier (1115 cm(2)/Vs at 300 K). The high mobility carrier can be assigned to the graphene layers. The second carrier has been assigned to the SiC substrate

Quantum virial expansion approach to thermodynamics of 4^4He adsorbates in carbon nanotube materials: Interacting Bose gas in one dimension

I demonstrate that $^4$He adsorbates in carbon nanotube materials can be treated as one-dimensional interacting gas of spinless bosons for temperatures below 8 K and for coverages such that all the adsorbates are in the groove positions of the carbon nanotube bundles. The effects of adsorbate-adsorbate interactions are studied within the scheme of virial expansion approach. The theoretical predictions for the specific heat of the interacting adsorbed gas are given.Comment: 5 PS figure

Boron and nitrogen isotope effects on hexagonal boron nitride properties

The unique physical, mechanical, chemical, optical, and electronic properties of hexagonal boron nitride (hBN) make it a promising two-dimensional material for electronic, optoelectronic, nanophotonic, and quantum devices. Here we report on the changes in hBN's properties induced by isotopic purification in both boron and nitrogen. Previous studies on isotopically pure hBN have focused on purifying the boron isotope concentration in hBN from its natural concentration (approximately 20 at$\%$ $^{10}$B, 80 at$\%$ $^{11}$B) while using naturally abundant nitrogen (99.6 at$\%$ $^{14}$N, 0.4 at$\%$ $^{15}$N), i.e. almost pure $^{14}$N. In this study, we extend the class of isotopically-purified hBN crystals to $^{15}$N. Crystals in the four configurations, namely h$^{10}$B$^{14}$N, h$^{11}$B$^{14}$N, h$^{10}$B$^{15}$N, and h$^{11}$B$^{15}$N, were grown by the metal flux method using boron and nitrogen single isotope ($>99\%$) enriched sources, with nickel plus chromium as the solvent. In-depth Raman and photoluminescence spectroscopies demonstrate the high quality of the monoisotopic hBN crystals with vibrational and optical properties of the $^{15}$N-purified crystals at the state of the art of currently available $^{14}$N-purified hBN. The growth of high-quality h$^{10}$B$^{14}$N, h$^{11}$B$^{14}$N, h$^{10}$B$^{15}$N, and h$^{11}$B$^{15}$N opens exciting perspectives for thermal conductivity control in heat management, as well as for advanced functionalities in quantum technologies.Comment: 13 pages, 7 figure