Small-scale turbulent fluctuations beyond Taylor's frozen-flow hypothesis

The space-time cross-correlation function C-T(r, tau) of local temperature fluctuations in turbulent Rayleigh-Benard convection is obtained from simultaneous two-point time series measurements. The obtained C-T(r, tau) is found to have the scaling form C-T(r(E), 0) with r(E)=[(r-U tau)(2)+ V-2 tau(2)](1/2), where U and V are two characteristic velocities associated with the mean and rms velocities of the flow. The experiment verifies the theory and demonstrates its applications to a class of turbulent flows in which the requirement of Taylor's frozen flow hypothesis is not met.

IMPROMPTU: FROM PUBLISHER'S IMPULSE TO AN ESTABLISHED SMALL­ SCALE GENRE IN PIANO LITERATURE

The word 'impromptu' began to appear in music literature in the early 19th century, specifically as title for a relatively short composition written for solo piano. The first impromptus appear to have been named so by the publishers. However, the composers themselves soon embraced the title to indicate, for the most part, fairly short character pieces. Impromptus do not follow any specific structural pattern, although many are cast in ternary form. The formal design ranges from strict compound ternary in the early impromptus to through-composed and variation forms. The peak of impromptu's popularity undoubtedly came during the middle and late19th century. However, they are still being composed today, albeit much less frequently. Although there have been many variants of impromptus in relation to formal design and harmonic language over the years, the essence of impromptu remains the same: it is still a short character piece with a general feeling of spontaneity. Overall, impromptus may be categorized into several different groups: some appear as part of a larger cycle, such as Dvorak's G minor Impromptu from his Piano Pieces, B. 110; many others use an element of an additional genre that enhances the character ofthe impromptu, such as Liszt's Valse-Impromptu and Antonio Bibalo's Tango Impromptu; yet another group consists of works based on opera themes, such as Liszt's Impromptu Brillant sur des themes de Rossini et Spontini and Czerny's Impromptus et variations sur Oberon, Op. 134. My recording project includes well-known impromptus, such as Schubert's Op. 142 and the four by Chopin, as well as lesser known works that have not been performed or recorded often. There are four impromptus that have been recorded here for the first time, including those written by Leopold Godowsky, Antonio Bibalo, Altin Volaj, and Nikolay Mazhara. I personally requested the two last named composers to contribute impromptus to this project. My selection represents works by twenty composers and reflects the different types of impromptus that have been encountered through almost three hundred years of the genre's existence, from approximately 1817 (VoriSek) to 2008 (Volaj and Mazhara).

Investigation into the performance of turbulence models for fluid flow and heat transfer phenomena in electronic applications

Computational Fluid Dynamics (CFD) is gradually becoming a powerful and almost essential tool for the design, development and optimization of engineering applications. However the mathematical modelling of the erratic turbulent motion remains the key issue when tackling such flow phenomena. The reliability of CFD analysis depends heavily on the turbulence model employed together with the wall functions implemented. In order to resolve the abrupt changes in the turbulent energy and other parameters situated at near wall regions a particularly fine mesh is necessary which inevitably increases the computer storage and run-time requirements. Turbulence modelling can be considered to be one of the three key elements in CFD. Precise mathematical theories have evolved for the other two key elements, grid generation and algorithm development. The principal objective of turbulence modelling is to enhance computational procedures of efficient accuracy to reproduce the main structures of three dimensional fluid flows. The flow within an electronic system can be characterized as being in a transitional state due to the low velocities and relatively small dimensions encountered. This paper presents simulated CFD results for an investigation into the predictive capability of turbulence models when considering both fluid flow and heat transfer phenomena. Also a new two-layer hybrid kε / kl turbulence model for electronic application areas will be presented which holds the advantages of being cheap in terms of the computational mesh required and is also economical with regards to run-time.

Scale-length optimising of short pulse Cu K-alpha laser plasma sources

The authors present experimental results showing how the use of a high contrast femtosecond laser system allows better optimization of K emission from a Cu target. The shorter scale-length preformed plasma is better optimized for resonance absorption of the laser light when the laser is moved away from best focus. The experimental data show a central peak of K emission at tight focus with strong secondary peaks at large offset. The use of these secondary peaks results in a much reduced hard x-ray background and should lead to shorter K pulses than at tight focus.

Higher order statistics for lognormal small-scale fading in mobile radio channels

This letter reports the statistical characterization and modeling of the indoor radio channel for a mobile wireless personal area network operating at 868 MHz. Line of sight (LOS) and non-LOS conditions were considered for three environments: anechoic chamber, open office area and hallway. Overall, the Nakagami-m cdf best described fading for bodyworn operation in 60% of all measured channels in anechoic chamber and open office area environments. The Nakagami distribution was also found to provide a good description of Rician distributed channels which predominated in the hallway. Multipath played an important role in channel statistics with the mean recorded m value being reduced from 7.8 in the anechoic chamber to 1.3 in both the open office area and hallway.

Do dynamic work instructions provide an advantage over static instructions in a small scale assembly task?

Recent studies exploring the effects of instructional animations on learning compared to static graphics have yielded mixed results. Few studies have explored their effectiveness in portraying procedural-motor information. Opportunities exist within an applied (manufacturing) context for instructional animations to be used to facilitate build performance on an assembly line. The present study compares build time performance across successive builds when using animation, static diagrams or text instructions to convey an assembly sequence for a handheld device. Although an immediate facilitating effect of animation was found, yielding a significantly faster build time for Build 1, this advantage had disappeared by Build 3. (C) 2009 Elsevier Ltd. All rights reserved.

Small-scale Hα jets in the solar chromosphere

Aims. High temporal and spatial resolution observations from the Rapid Oscillations in the Solar Atmosphere (ROSA) multiwavelength imager on the Dunn Solar Telescope are used to study the velocities of small-scale Hα jets in an emerging solar active region.
Methods. The dataset comprises simultaneous imaging in the Hα core, Ca ii K, and G band, together with photospheric line-of-sight magnetograms. Time-distance techniques are employed to determine projected plane-of-sky velocities.
Results. The Hα images are highly dynamic in nature, with estimated jet velocities as high as 45 km s-1. These jets are one-directional, with their origin seemingly linked to underlying Ca ii K brightenings and G-band magnetic bright points.
Conclusions. It is suggested that the siphon flow model of cool coronal loops is suitable for interpreting our observations. The jets are associated with small-scale explosive events, and may provide a mass outflow from the photosphere to the corona.

Quenching small quantum gases: Genesis of the orthogonality catastrophe

We study the dynamics of two strongly interacting bosons with an additional impurity atom trapped in a harmonic potential. Using exact numerical diagonalization we are able to fully explore the dynamical evolution when the interaction between the two distinct species is suddenly switched on (quenched). We examine the behavior of the densities, the entanglement, the Loschmidt echo, and the spectral function for a large range of interspecies interactions and find that even in such small systems evidence of Anderson's orthogonality catastrophe can be witnessed.

Quiet-Sun Hα Transients and Corresponding Small-scale Transition Region and Coronal Heating

Rapid blue- and redshifted excursions (RBEs and RREs) are likely to be the on-disk counterparts of Type II spicules. Recently, heating signatures from RBEs/RREs have been detected in IRIS slit-jaw images dominated by transition region (TR) lines around network patches. Additionally, signatures of Type II spicules have been observed in Atmospheric Imaging Assembly (AIA) diagnostics. The full-disk, ever-present nature of the AIA diagnostics should provide us with sufficient statistics to directly determine how important RBEs and RREs are to the heating of the TR and corona. We find, with high statistical significance, that at least 11% of the low coronal brightenings detected in a quiet-Sun region in He ii 304 Å can be attributed to either RBEs or RREs as observed in Hα, and a 6% match of Fe IX 171 Å detected events to RBEs or RREs with very similar statistics for both types of Hα features. We took a statistical approach that allows for noisy detections in the coronal channels and provides us with a lower, but statistical significant, bound. Further, we consider matches based on overlapping features in both time and space, and find strong visual indications of further correspondence between coronal events and co-evolving but non-overlapping, RBEs and RREs.

Profiling of T-cell receptor signaling complex assembly in human CD4 T-lymphocytes using RP protein arrays.

The RP protein (RPP) array approach immobilizes minute amounts of cell lysates or tissue protein extracts as distinct microspots on NC-coated slide. Subsequent detection with specific antibodies allows multiplexed quantification of proteins and their modifications at a scale that is beyond what traditional techniques can achieve. Cellular functions are the result of the coordinated action of signaling proteins assembled in macromolecular complexes. These signaling complexes are highly dynamic structures that change their composition with time and space to adapt to cell environment. Their comprehensive analysis requires until now relatively large amounts of cells (>5 x 10(7)) due to their low abundance and breakdown during isolation procedure. In this study, we combined small scale affinity capture of the T-cell receptor (TCR) and RPP arrays to follow TCR signaling complex assembly in human ex vivo isolated CD4 T-cells. Using this strategy, we report specific recruitment of signaling components to the TCR complex upon T-cell activation in as few as 0.5 million of cells. Second- to fourth-order TCR interacting proteins were accurately quantified, making this strategy specially well-suited to the analysis of membrane-associated signaling complexes in limited amounts of cells or tissues, e.g., ex vivo isolated cells or clinical specimens.

Why Bt cotton pays for small-scale producers in South Africa

There is much debate about the potential benefits (and costs) of genetically modified (GM) crop technology for developing countries. Studies have been carried out in Argentina, China, Indonesia and most recently India1 to assess the impact of Bacillus thuringiensis (Bt) cotton on farmers in those regions.

What is wrong with the global support facility for small-scale mining?

The World Bank, United Nations and UK Department for International Development (DfID) have spearheaded a recent global drive to regularize artisanal and small-scale mining (ASM), and provide assistance to its predominantly impoverished participants. To date, millions of dollars have been pledged toward the design of industry-specific policies and regulations; implementation of mechanized equipment; extension; and the launch of alternative livelihood (AL) programmes aimed at diversifying local economies. Much of this funding, however, has failed to facilitate marked improvements, and in many cases, has exacerbated problems. This paper argues that a poor understanding of artisanal, mine-community dynamics and operators’ needs has, in a number of cases, led to the design and implementation of inappropriate industry support schemes and interventions. The discussion focuses upon experiences from sub-Saharan Africa, where ASM is in the most rudimentary of states.

'A load too heavy': Critical reflections on the child labor problem in Africa's small-scale mining sector

This paper provides an extended analysis of the child labor problem in the artisanal and small-scale mining (ASM) sector, focusing specifically on the situation in sub-Saharan Africa. In recent years, the issue of child labor in ASM has garnered significant attention from the International Labor Organization (ILO), which has been particularly active in raising public awareness of the problem; and, has proceeded to implement policies and collaborative project work aimed at Curtailing children's participation in ASM activities in a number of African countries. The analysis concludes with a critical appraisal of an ILO project recently launched in the Talensi-Nabdam District in the Upper East Region of Ghana, which sheds light on how the child labor problem is being tackled in practice in ASM communities in sub-Saharan Africa. (c) 2008 Elsevier Ltd. All rights reserved.