bluuebunny/crossref_metadata_2025 huggingface dataset:
Composition of dissolved organic matter within a lacustrine environment
Authors: McCaul Margaret V. , Sutton David , Simpson André J. , Spence Adrian , McNally David J. , Moran Brian W. , Goel Alok , O'Connor Brendan , Hart Kris , Kelleher Brian P.
Published: May 2011

Environmental contextFreshwater dissolved organic matter is a complex chemical mixture central to many environmental processes, including carbon and nitrogen cycling. Questions remain, however, as to its chemical characteristics, sources and transformation mechanisms. We studied the nature of dissolved organic matter in a lake system and found that it is influenced by anthropogenic activities. Human activities can therefore influence the huge amounts of carbon sequestered in lakes as dissolved organic matter. AbstractFreshwater dissolved organic matter (DOM) is a complex mixture of chemical components that are central to many environmental processes, including carbon and nitrogen cycling. However, questions remain as to its chemical characteristics, sources and transformation mechanisms. Here, we employ 1- and 2-D nuclear magnetic resonance (NMR) spectroscopy to investigate the structural components of lacustrine DOM from Ireland, and how it varies within a lake system, as well as to assess potential sources. Major components found, such as carboxyl-rich alicyclic molecules (CRAM) are consistent with those recently identified in marine and freshwater DOM. Lignin-type markers and protein/peptides were identified and vary spatially. Phenylalanine was detected in lake areas influenced by agriculture, whereas it is not detectable where zebra mussels are prominent. The presence of peptidoglycan, lipoproteins, large polymeric carbohydrates and proteinaceous material supports the substantial contribution of material derived from microorganisms. Evidence is provided that peptidoglycan and silicate species may in part originate from soil microbes.
Source apportionment of fine particles at a suburban site in Queensland, Australia
Authors: Friend Adrian J. , Ayoko Godwin A. , Elbagir Sohair G.
Published: May 2011

Environmental contextAirborne fine particles affect local, regional and global air quality and deteriorate the environment. Therefore comprehensive information on the locations and strengths of particle sources is critical for the development of strategies for mitigating the adverse effects of aerosols. The multivariate data analysis techniques used in this paper allowed the benefits of a previous control measure to be assessed and provided vital information for the application of further pollution reduction strategies to this and other areas of the world.
AbstractAirborne fine particles were collected at a suburban site in Queensland, Australia between 1995 and 2003. The samples were analysed for 21 elements and Positive Matrix Factorisation (PMF), Preference Ranking Organisation Methods for Enrichment Evaluation (PROMETHEE) and Graphical Analysis for Interactive Assistance (GAIA) were applied to the data. PROMETHEE provided information on the ranking of pollutant levels from the sampling years whereas PMF provided insights into the sources of the pollutants, their chemical composition, most likely locations and relative contribution to the levels of particulate pollution at the site. PROMETHEE and GAIA found that the removal of lead from fuel in the area had a significant effect on the pollution patterns whereas PMF identified six pollution sources, including railways (5.5%), biomass burning (43.3%), soil (9.2%), sea salt (15.6%), aged sea salt (24.4%) and motor vehicles (2.0%). Thus the results gave information that can assist in the formulation of mitigation measures for air pollution.
Photolysis of benzotriazole and formation of its polymerised photoproducts in aqueous solutions under UV irradiation
Authors: Liu You-Sheng , Ying Guang-Guo , Shareef Ali , Kookana Rai S.
Published: May 2011

Environmental contextBenzotriazole is an anti-corrosion agent that is widely applied in various industrial processes and in household products. It has been found persistent in various aquatic environments. Our investigation found that benzotriazole can be rapidly transformed under UV light to form several photoproducts. Photolysis rates decreased with increasing solution pH, whereas salinity had no significant effect. Metal species Cu2+ and Fe3+, and humic acid in aquatic environment could have inhibitory effects on the photolysis of benzotriazole.
AbstractBenzotriazole (BT) is an anti-corrosion agent used widely in some industrial processes and household products, and it has been detected in surface water and ground water due to its high mobility and low biodegradability. We have investigated the photolysis of benzotriazole in aqueous solutions under UV radiation at 254 nm and the effect of pH, salinity, metal species and dissolved organic matter on the photo-transformation processes. Benzotriazole was found to undergo rapid transformation to form several photoproducts. The half-lives for the photolysis of benzotriazole ranged from 2.8 to 14.3 h in various aqueous solutions containing metal ions and dissolved organic matter. Photolysis rates decreased with increasing solution pH, whereas salinity had no significant effect. Metal species Cu2+ and Fe3+, and especially humic acid had inhibitory effects on the photolysis of benzotriazole under UV light irradiation at 254 nm. We propose the formation of three major photoproducts via instantaneous polymerisation of small intermediates generated during the photolysis of benzotriazole including 2,6-diethylaniline, phenazine and 1,6-dihydroxyphenazine.
Can yield potential be increased by manipulation of reproductive partitioning in quinoa (Chenopodium quinoa)? Evidence from gibberellic acid synthesis inhibition using Paclobutrazol
Authors: Gómez M. B. , Castro P. Aguirre , Mignone C. , Bertero H. D.
Published: May 2011

One factor conditioning quinoa (Chenopodium quinoa Willd.) adoption is the need to increase yield. This paper analyses the effect that Paclobutrazol, a GA synthesis inhibitor, produces on yield, biomass, partitioning, seed number and weight in quinoa. Two experiments were conducted under field conditions: one compared a tall genotype (2-Want) with a shorter genotype (NL-6); while the other analysed seed yield and its components using the 2-Want genotype. As a consequence of Paclobutrazol application in the one-genotype experiment, plant height decreased from 197 to 138 cm, yield increased from 517 to 791 g m–2, seed numbers rose from 308 000 to 432 000 seeds per m2, and the harvest index increased from 0.282 to 0.398 g g–1. Biomass accumulation and seed weight were not affected. The leaf area index was reduced by Paclobutrazol but radiation interception was only marginally reduced; soil plant analysis development (SPAD) values and specific leaf weight were increased, but radiation use efficiency was not affected by treatments. Root biomass and lateral roots tended to increase under Paclobutrazol treatment. Genotypes were compared until the end of flowering and similar responses were obtained. Higher yields could be obtained in quinoa if reproductive partitioning was increased, turning it into a good candidate in the search for high quality protein sources.
A mutation in the purine biosynthetic enzyme ATASE2 impacts high light signalling and acclimation responses in green and chlorotic sectors of Arabidopsis leaves
Authors: Woo Nick S. , Gordon Matthew J. , Graham Stephen R. , Rossel Jan Bart , Badger Murray R. , Pogson Barry J.
Published: May 2011

In this report, we investigate the altered APX2 expression 13 (alx13) mutation of Arabidopsis thaliana, a mutation in glutamine phosphoribosyl pyrophosphate amidotransferase 2 (ATASE2), the primary isoform of the enzyme mediating the first committed step of purine biosynthesis. Light-dependent leaf variegation was exhibited by alx13 plants, with partial shading of alx13 rosettes revealing that the development of chlorosis in emerging leaves is influenced by the growth irradiance of established leaves. Chlorotic sectors arose from emerging green alx13 leaves during a phase of rapid cell division and expansion, which shows that each new cell’s fate is independent of its progenitor. In conjunction with the variegated phenotype, alx13 plants showed altered high light stress responses, including changed expression of genes encoding proteins with antioxidative functions, impaired anthocyanin production and over-accumulation of reactive oxygen species. These characteristics were observed in both photosynthetically-normal green tissues and chlorotic tissues. Chlorotic tissues of alx13 leaves accumulated mRNAs of nuclear-encoded photosynthesis genes that are repressed in other variegated mutants of Arabidopsis. Thus, defective purine biosynthesis impairs chloroplast biogenesis in a light-dependent manner and alters the induction of high light stress pathways and nuclear-encoded photosynthesis genes.
Net carbon exchange in grapevine canopies responds rapidly to timing and extent of regulated deficit irrigation
Authors: Tarara Julie M. , Peña Jorge E. Perez , Keller Markus , Schreiner R. Paul , Smithyman Russell P.
Published: May 2011

Whole-canopy net CO2 exchange (NCEC) was measured near key stages of fruit development in grapevines (Vitis vinifera L. cv. Cabernet Sauvignon) that were managed under three approaches to regulated deficit irrigation (RDI): (1) standard practice (RDIS), or weekly replacement of 60–70% of estimated evapotranspiration for well watered grapevines; (2) early additional deficit (RDIE), or one-half of RDIS applied between fruit set and the onset of ripening (veraison), followed by RDIS; and (3) RDIS followed by late additional deficit (RDIL), or one-half of RDIS applied between veraison and harvest. Summed between fruit set and harvest, nearly 40% less irrigation was applied to RDIE vines and ~20% less to RDIL vines than to those continuously under RDIS. After ~5 weeks of additional deficit, NCEC in RDIE vines was 43–46% less per day than in RDIS vines. After RDIL vines had been under additional water deficit for ~3 weeks, NCEC was ~33% less per day than in RDIS vines. Instantaneous rates of NCEC responded rapidly to irrigation delivery and elapsed time between irrigation sets. Concurrent single-leaf measurements (NCEL) reflected the relative differences in NCEC between irrigation treatments, and were linearly associated with NCEC (r2 = 0.61). Despite halving the water applied under commercial RDI, mid-day stomatal conductance values in RDIE and RDIL of ~50–125 mmol m–2 s–1 indicated that the additional deficit imposed only moderate water stress. There was no effect of additional deficit on yield or berry maturity.
Development of a novel semi-hydroponic phenotyping system for studying root architecture
Authors: Chen Ying L. , Dunbabin Vanessa M. , Diggle Art J. , Siddique Kadambot H. M. , Rengel Zed
Published: May 2011

A semi-hydroponic bin system was developed to provide an efficient phenotyping platform for studying root architecture. The system was designed to accommodate a large number of plants in a small area for screening genotypes. It was constructed using inexpensive and easily obtained materials: 240 L plastic mobile bins, clear acrylic panels covered with black calico cloth and a controlled watering system. A screening experiment for root traits of 20 wild genotypes of narrow-leafed lupin (Lupinus angustifolius L.) evaluated the reliability and efficiency of the system. Root architecture, root elongation rate and branching patterns were monitored for 6 weeks. Significant differences in both architectural and morphological traits were observed among tested genotypes, particularly for total root length, branch number, specific root length and branch density. Results demonstrated that the bin system was efficient in screening root traits in narrow-leafed lupin, allowing for rapid measurement of two-dimensional root architecture over time with minimal disturbance to plant growth and without destructive root sampling. The system permits mapping and digital measurement of dynamic growth of taproot and lateral roots. This phenotyping platform is a desirable tool for examining root architecture of deep root systems and large sets of plants in a relatively small space.
Partial rootzone drying improves almond tree leaf-level water use efficiency and afternoon water status compared with regulated deficit irrigation
Authors: Egea Gregorio , Dodd Ian C. , González-Real María M. , Domingo Rafael , Baille Alain
Published: May 2011

To determine whether partial rootzone drying (PRD) optimised leaf gas exchange and soil–plant water relations in almond (Prunus dulcis (Mill.) D.A. Webb) compared with regulated deficit irrigation (RDI), a 2 year trial was conducted on field-grown trees in a semiarid climate. Five irrigation treatments were established: full irrigation (FI) where the trees were irrigated at 100% of the standard crop evapotranspiration (ETc); three PRD treatments (PRD70, PRD50 and PRD30) that applied 70, 50 and 30% ETc, respectively; and a commercially practiced RDI treatment that applied 50% ETc during the kernel-filling stage and 100% ETc during the remainder of the growth season. Measurements of volumetric soil moisture content in the soil profile (0–100 cm), predawn leaf water potential (Ψpd), midday stem water potential (Ψms), midday leaf gas exchange and trunk diameter fluctuations (TDF) were made during two growing seasons. The diurnal patterns of leaf gas exchange and stem water potential (Ψs) were appraised during the kernel-filling stage in all irrigation regimes. When tree water relations were assessed at solar noon, PRD did not show differences in either leaf gas exchange or tree water status compared with RDI. At similar average soil moisture status (adjudged by similar Ψpd), PRD50 trees had higher water status than RDI trees in the afternoon, as confirmed by Ψs and TDF. Although irrigation placement showed no effects on diurnal stomatal regulation, diurnal leaf net photosynthesis (Al) was substantially less limited in PRD50 than in RDI trees, indicating that PRD improved leaf-level water use efficiency.
Large root systems: are they useful in adapting wheat to dry environments?
Authors: Palta Jairo A. , Chen Xing , Milroy Stephen P. , Rebetzke Greg J. , Dreccer M. Fernanda , Watt Michelle
Published: May 2011

There is little consensus on whether having a large root system is the best strategy in adapting wheat (Triticum aestivum L.) to water-limited environments. We explore the reasons for the lack of consensus and aim to answer the question of whether a large root system is useful in adapting wheat to dry environments. We used unpublished data from glasshouse and field experiments examining the relationship between root system size and their functional implication for water capture. Individual root traits for water uptake do not describe a root system as being large or small. However, the recent invigoration of the root system in wheat by indirect selection for increased leaf vigour has enlarged the root system through increases in root biomass and length and root length density. This large root system contributes to increasing the capture of water and nitrogen early in the season, and facilitates the capture of additional water for grain filling. The usefulness of a vigorous root system in increasing wheat yields under water-limited conditions maybe greater in environments where crops rely largely on seasonal rainfall, such as the Mediterranean-type environments. In environments where crops are reliant on stored soil water, a vigorous root system increases the risk of depleting soil water before completion of grain filling.
Before Babel
Authors: Disler Caroline
Published: May 2011

The biblical story of Babel has long served as a powerful image for translators in western civilization, stimulating much productive discourse about translation history, mythology, theory and practice. It is therefore interesting to note that the biblical story itself, despite its apparent antiquity and remarkable brevity, has been strongly influenced by even earlier sources stemming from societies antedating its ancient Israelite authors. This article examines some of the most interesting examples of cross-cultural and intertextual references from ancient proverbs and writings including well-known works such as the Gilgamesh epic and the Babylonian creation epic, Enûma Eliš. The delightfully subtle translingual wordplay in the name ‘Babel’ is also clarified. The biblical Tower of Babel reveals a startling complexity resulting from the wealth of intercultural and multilingual contacts that constitute the distant foundation of western tradition.
Origins and conceptual analysis of the term ‘traductologie/translatology’
Authors: Harris Brian
Published: May 2011

The term traductologie was coined in the early 1970s to correspond to the establishment of translation as a valid object of scientific and academic study. Its English equivalent is usually translation studies but sometimes translatology.
Traductologie has two conceptual levels: the metalevel of study and analysis and the object level of what is thus examined, namely translations and translating. Both levels are variegated. The metalevel can usefully be mapped into broad ‘paradigms’ or disciplinary approaches: literary, linguistic, semiotic, philosophical, historical, lexico-terminological, automated (MT), prescriptive and pedagogical, scientific-experimental, text and corpus oriented, process oriented, social etc. The object level is traditionally divided between written translation and oral translation (interpretation), and the former is often categorized by ‘text types’.
Permutations of the meta and object categories characterize different varieties of traductologie. When discoursing about it, one should be aware that a statement that is meaningful in one variety may be meaningless in another.
Occludin S408 phosphorylation regulates tight junction protein interactions and barrier function
Authors: Raleigh David R. , Boe Devin M. , Yu Dan , Weber Christopher R. , Marchiando Amanda M. , Bradford Emily M. , Wang Yingmin , Wu Licheng , Schneeberger Eveline E. , Shen Le , Turner Jerrold R.
Published: May 2011

Although the C-terminal cytoplasmic tail of the tight junction protein occludin is heavily phosphorylated, the functional impact of most individual sites is undefined. Here, we show that inhibition of CK2-mediated occludin S408 phosphorylation elevates transepithelial resistance by reducing paracellular cation flux. This regulation requires occludin, claudin-1, claudin-2, and ZO-1. S408 dephosphorylation reduces occludin exchange, but increases exchange of ZO-1, claudin-1, and claudin-2, thereby causing the mobile fractions of these proteins to converge. Claudin-4 exchange is not affected. ZO-1 domains that mediate interactions with occludin and claudins are required for increases in claudin-2 exchange, suggesting assembly of a phosphorylation-sensitive protein complex. Consistent with this, binding of claudin-1 and claudin-2, but not claudin-4, to S408A occludin tail is increased relative to S408D. Finally, CK2 inhibition reversed IL-13–induced, claudin-2–dependent barrier loss. Thus, occludin S408 dephosphorylation regulates paracellular permeability by remodeling tight junction protein dynamic behavior and intermolecular interactions between occludin, ZO-1, and select claudins, and may have therapeutic potential in inflammation-associated barrier dysfunction.
WNT-3A modulates articular chondrocyte phenotype by activating both canonical and noncanonical pathways
Authors: Nalesso Giovanna , Sherwood Joanna , Bertrand Jessica , Pap Thomas , Ramachandran Manoj , De Bari Cosimo , Pitzalis Costantino , Dell'Accio Francesco
Published: May 2011

Activation and disruption of Wnt/β-catenin signaling both result in cartilage breakdown via unknown mechanisms. Here we show that both WNT-3A and the Wnt inhibitor DKK1 induced de-differentiation of human articular chondrocytes through simultaneous activation of β-catenin–dependent and independent responses. WNT-3A activates both the β-catenin–dependent canonical pathway and the Ca2+/CaMKII noncanonical pathways, with distinct transcriptional targets. WNT-3A promotes cell proliferation and loss of expression of the chondrocyte markers COL2A1, Aggrecan, and SOX9; however, proliferation and AXIN2 up-regulation are downstream of the canonical pathway and are rescued by DKK1, whereas the loss of differentiation markers is CaMKII dependent. Finally, we showed that in chondrocytes, the Ca2+/CaMKII-dependent and β-catenin–dependent pathways are reciprocally inhibitory, thereby explaining why DKK1 can induce loss of differentiation through de-repression of the CaMKII pathway. We propose a novel model in which a single WNT can simultaneously activate different pathways with distinct and independent outcomes and with reciprocal regulation. This offers an opportunity for selective pharmacological targeting.
Regulating the transition from centriole to basal body
Authors: Kobayashi Tetsuo , Dynlacht Brian D.
Published: May 2011

The role of centrioles changes as a function of the cell cycle. Centrioles promote formation of spindle poles in mitosis and act as basal bodies to assemble primary cilia in interphase. Stringent regulations govern conversion between these two states. Although the molecular mechanisms have not been fully elucidated, recent findings have begun to shed light on pathways that regulate the conversion of centrioles to basal bodies and vice versa. Emerging studies also provide insights into how defects in the balance between centrosome and cilia function could promote ciliopathies and cancer.
Interruption of intrachromosomal looping by CCCTC binding factor decoy proteins abrogates genomic imprinting of human insulin-like growth factor II
Authors: Zhang He , Niu Beibei , Hu Ji-Fan , Ge Shengfang , Wang Haibo , Li Tao , Ling Jianqun , Steelman Brandon N. , Qian Guanxiang , Hoffman Andrew R.
Published: May 2011

Monoallelic expression of IGF2 is regulated by CCCTC binding factor (CTCF) binding to the imprinting control region (ICR) on the maternal allele, with subsequent formation of an intrachromosomal loop to the promoter region. The N-terminal domain of CTCF interacts with SUZ12, part of the polycomb repressive complex-2 (PRC2), to silence the maternal allele. We synthesized decoy CTCF proteins, fusing the CTCF deoxyribonucleic acid–binding zinc finger domain to CpG methyltransferase Sss1 or to enhanced green fluorescent protein. In normal human fibroblasts and breast cancer MCF7 cell lines, the CTCF decoy proteins bound to the unmethylated ICR and to the IGF2 promoter region but did not interact with SUZ12. EZH2, another part of PRC2, was unable to methylate histone H3-K27 in the IGF2 promoter region, resulting in reactivation of the imprinted allele. The intrachromosomal loop between the maternal ICR and the IGF2 promoters was not observed when IGF2 imprinting was lost. CTCF epigenetically governs allelic gene expression of IGF2 by orchestrating chromatin loop structures involving PRC2.
Spatial regulation of Cdc55–PP2A by Zds1/Zds2 controls mitotic entry and mitotic exit in budding yeast
Authors: Rossio Valentina , Yoshida Satoshi
Published: May 2011

Budding yeast CDC55 encodes a regulatory B subunit of the PP2A (protein phosphatase 2A), which plays important roles in mitotic entry and mitotic exit. The spatial and temporal regulation of PP2A is poorly understood, although recent studies demonstrated that the conserved proteins Zds1 and Zds2 stoichiometrically bind to Cdc55–PP2A and regulate it in a complex manner. Zds1/Zds2 promote Cdc55–PP2A function for mitotic entry, whereas Zds1/Zds2 inhibit Cdc55–PP2A function during mitotic exit. In this paper, we propose that Zds1/Zds2 primarily control Cdc55 localization. Cortical and cytoplasmic localization of Cdc55 requires Zds1/Zds2, and Cdc55 accumulates in the nucleus in the absence of Zds1/Zds2. By genetically manipulating the nucleocytoplasmic distribution of Cdc55, we showed that Cdc55 promotes mitotic entry when in the cytoplasm. On the other hand, nuclear Cdc55 prevents mitotic exit. Our analysis defines the long-sought molecular function for the zillion different screens family proteins and reveals the importance of the regulation of PP2A localization for proper mitotic progression.
Generating a Wnt switch: it’s all about the right dosage
Authors: Kestler Hans A. , Kühl Michael
Published: May 2011

Wnt proteins can activate different branches of the Wnt signaling pathway, raising the question of specificity. In this issue, Nalesso et al. (2011. J. Cell Biol. doi:10.1083/jcb.201011051) provide an answer to this conundrum by showing that different concentrations of Wnt ligands can elicit different intracellular responses. These findings not only provide new insights into the molecular mechanisms underlying Wnt signaling, but also indicate how Wnt gradients might contribute to tissue patterning during embryogenesis.
Tight embedding of subspaces of 𝐿_{𝑝} in ℓ_{𝑝}ⁿ for even 𝑝
Authors: Schechtman Gideon
Published: May 2011

Using a recent result of Batson, Spielman and Srivastava, we obtain a tight estimate on the dimension of

ℓ
p
n

\ell _p^n

,

p
p

an even integer, needed to almost isometrically contain all

k
k

-dimensional subspaces of

L
p

L_p

.
Noncancellation for contractible affine threefolds
Authors: Dubouloz Adrien , Moser-Jauslin Lucy , Poloni P.-M.
Published: May 2011

We construct two nonisomorphic contractible affine threefolds

X
X

and

Y
Y

with the property that their cylinders

X
×

A

1

X\times \mathbb {A}^{1}

and

Y
×

A

1

Y\times \mathbb {A}^{1}

are isomorphic, showing that the generalized Cancellation Problem has a negative answer in general for contractible affine threefolds. We also establish that

X
X

and

Y
Y

are actually biholomorphic as complex analytic varieties, providing the first example of a pair of biholomorphic but not isomorphic exotic

A

3

\mathbb {A}^{3}

’s.
On harmonic functions and the Schwarz lemma
Authors: Kalaj David , Vuorinen Matti
Published: May 2011

We study the Schwarz lemma for harmonic functions and prove sharp versions for the cases of real harmonic functions and the norm of harmonic mappings.
A lattice Boltzmann approach for solving scalar transport equations
Authors: Zhang Raoyang , Fan Hongli , Chen Hudong
Published: May 2011

A lattice Boltzmann (LB) approach is presented for solving scalar transport equations. In addition to the standard LB for fluid flow, a second set of distribution functions is introduced for transport scalars. This LB approach fully recovers the macroscopic scalar transport equation satisfying an exact conservation law. It is numerically stable and scalar diffusivity does not have a Courant–Friedrichs–Lewy-like stability upper limit. With a sufficient lattice isotropy, numerical solutions are independent of grid orientations. A generalized boundary condition for scalars on arbitrary geometry is also realized by a precise control of surface scalar flux. Numerical results of various benchmarks are presented to demonstrate the accuracy, efficiency and robustness of the approach.
Thermodynamic consistency in deriving lattice Boltzmann models for describing segregation in non-ideal mixtures
Authors: Philippi Paulo Cesar , Emerich Dos Santos Luis Orlando , Hegele Luiz Adolfo , Pico Ortiz Carlos Enrique , Siebert Diogo Nardelli , Surmas Rodrigo
Published: May 2011

The thermodynamic consistency of kinetic models for non-ideal mixtures in non-isothermal conditions is investigated. A kinetic model is proposed that is suitable for deriving high-order lattice Boltzmann equations by an appropriate discretization of the velocity space, satisfying the Galilean invariance condition and free of spurious terms in the first moment equations.
Rectangular lattice Boltzmann model for nonlinear convection–diffusion equations
Authors: Lu Jianhua , Chai Zhenhua , Shi Baochang , Guo Zhaoli , Hou Guoxiang
Published: May 2011

In this paper, a rectangular lattice Boltzmann model is proposed for nonlinear convection–diffusion equations (NCDEs). The model can be used to solve NCDEs with very general form by using a real/complex-valued quadric equilibrium distribution function and relaxation time. Detailed simulations on several examples are performed to validate the model. The numerical results show good agreement with the analytical solutions, and the numerical accuracy is much better than that of the models with a linear equilibrium distribution function.
Chequerboard effects on spurious currents in the lattice Boltzmann equation for two-phase flows
Authors: Guo Zhaoli , Shi Baochang , Zheng Chuguang
Published: May 2011

Spurious currents near an interface between different phases are a common undesirable feature of the lattice Boltzmann equation (LBE) method for two-phase systems. In this paper, we show that the spurious currents of a kinetic theory-based LBE have a significant dependence on the parity of the grid number of the underlying lattice, which can be attributed to the chequerboard effect. A technique that uses a Lax–Wendroff streaming is proposed to overcome this anomaly, and its performance is verified numerically.
A local lattice Boltzmann method for multiple immiscible fluids and dense suspensions of drops
Authors: Spencer Timothy J. , Halliday Ian , Care Chris M.
Published: May 2011

The lattice Boltzmann method (LBM) for computational fluid dynamics benefits from a simple, explicit, completely local computational algorithm making it highly efficient. We extend LBM to recover hydrodynamics of multi-component immiscible fluids, while retaining a completely local, explicit and simple algorithm. Hence, no computationally expensive lattice gradients, interaction potentials or curvatures, that use information from neighbouring lattice sites, need to be calculated, which makes the method highly scalable and suitable for high performance parallel computing. The method is analytical and is shown to recover correct continuum hydrodynamic equations of motion and interfacial boundary conditions. This LBM may be further extended to situations containing a high number (O(100)) of individually immiscible drops. We make comparisons of the emergent non-Newtonian behaviour with a power-law fluid model. We anticipate our method will have a range applications in engineering, industrial and biological sciences.
Endothelial shear stress from large-scale blood flow simulations
Authors: Melchionna Simone , Kaxiras Efthimios , Bernaschi Massimo , Succi Sauro
Published: May 2011

We discuss the optimal evaluation of endothelial shear stress for real-life case studies based on anatomic data acquisition. The fluid dynamic simulations require smoothing of the geometric dataset to avoid major artefacts in the flow patterns, especially in the proximity of bifurcations. A systematic series of simulations at different corrugation levels shows that, below a smoothing length of about 0.5 mm, the numerical data are insensitive to further smoothing.
Smoothed particle hydrodynamics simulation of shear-induced powder migration in injection moulding
Authors: Kauzlarić David , Pastewka Lars , Meyer Hagen , Heldele Richard , Schulz Michael , Weber Oxana , Piotter Volker , Hausselt Jürgen , Greiner Andreas , Korvink Jan G.
Published: May 2011

We present the application of the smoothed particle hydrodynamics (SPH) discretization scheme to Phillips’ model for shear-induced particle migration in concentrated suspensions. This model provides an evolution equation for the scalar mean volume fraction of idealized spherical solid particles of equal diameter which is discretized by the SPH formalism. In order to obtain a discrete evolution equation with exact conservation properties we treat in fact the occupied volume of the solid particles as the degree of freedom for the fluid particles. We present simulation results in two- and three-dimensional channel flow. The two-dimensional results serve as a verification by a comparison to analytic solutions. The three-dimensional results are used for a comparison with experimental measurements obtained from computer tomography of injection moulded ceramic microparts. We observe the best agreement of measurements with snapshots of the transient simulation for a ratio
D
c
/
D

η

=0.1 of the two model parameters.
Involving the Navier–Stokes equations in the derivation of boundary conditions for the lattice Boltzmann method
Authors: Verschaeve Joris C. G.
Published: May 2011

By means of the continuity equation of the incompressible Navier–Stokes equations, additional physical arguments for the derivation of a formulation of the no-slip boundary condition for the lattice Boltzmann method for straight walls at rest are obtained. This leads to a boundary condition that is second-order accurate with respect to the grid spacing and conserves mass. In addition, the boundary condition is stable for relaxation frequencies close to two.
New variational principles for locating periodic orbits of differential equations
Authors: Boghosian Bruce M. , Fazendeiro Luis M. , Lätt Jonas , Tang Hui , Coveney Peter V.
Published: May 2011

We present new methods for the determination of periodic orbits of general dynamical systems. Iterative algorithms for finding solutions by these methods, for both the exact continuum case, and for approximate discrete representations suitable for numerical implementation, are discussed. Finally, we describe our approach to the computation of unstable periodic orbits of the driven Navier–Stokes equations, simulated using the lattice Boltzmann equation.
A lattice Boltzmann method for dilute polymer solutions
Authors: Singh Shiwani , Subramanian Ganesh , Ansumali Santosh
Published: May 2011

We present a lattice Boltzmann approach for the simulation of non-Newtonian fluids. The method is illustrated for the specific case of dilute polymer solutions. With the appropriate local equilibrium distribution, phase-space dynamics on a lattice, driven by a Bhatnagar–Gross–Krook (BGK) relaxation term, leads to a solution of the Fokker–Planck equation governing the probability density of polymer configurations. Results for the bulk rheological characteristics for steady and start-up shear flow are presented, and compare favourably with those obtained using Brownian dynamics simulations. The new method is less expensive than stochastic simulation techniques, particularly in the range of small to moderate Weissenberg numbers (Wi).
Mesh–particle interpolations on graphics processing units and multicore central processing units
Authors: Rossinelli Diego , Conti Christian , Koumoutsakos Petros
Published: May 2011

Particle–mesh interpolations are fundamental operations for particle-in-cell codes, as implemented in vortex methods, plasma dynamics and electrostatics simulations. In these simulations, the mesh is used to solve the field equations and the gradients of the fields are used in order to advance the particles. The time integration of particle trajectories is performed through an extensive resampling of the flow field at the particle locations. The computational performance of this resampling turns out to be limited by the memory bandwidth of the underlying computer architecture. We investigate how mesh–particle interpolation can be efficiently performed on graphics processing units (GPUs) and multicore central processing units (CPUs), and we present two implementation techniques. The single-precision results for the multicore CPU implementation show an acceleration of 45–70×, depending on system size, and an acceleration of 85–155× for the GPU implementation over an efficient single-threaded C++ implementation. In double precision, we observe a performance improvement of 30–40× for the multicore CPU implementation and 20–45× for the GPU implementation. With respect to the 16-threaded standard C++ implementation, the present CPU technique leads to a performance increase of roughly 2.8–3.7× in single precision and 1.7–2.4× in double precision, whereas the GPU technique leads to an improvement of 9× in single precision and 2.2–2.8× in double precision.
Modelling thermal fluctuations in non-ideal fluids with the lattice Boltzmann method
Authors: Gross M. , Adhikari R. , Cates M. E. , Varnik F.
Published: May 2011

Recently, we proposed a theoretical framework to include thermal fluctuations into the Lattice Boltzmann (LB) method for non-ideal fluids. Here, we apply a variant thereof to a certain class of force-based non-ideal fluid LB models. We find that ideal-gas-like noise is an exact result of the fluctuation–dissipation theorem in the hydrodynamic regime. It is shown that satisfactory equilibration of the density and fluid momentum can be obtained in a simulation over a wide range of length scales.
The neuropsychology of face perception: beyond simple dissociations and functional selectivity
Authors: Atkinson Anthony P. , Adolphs Ralph
Published: May 2011

Face processing relies on a distributed, patchy network of cortical regions in the temporal and frontal lobes that respond disproportionately to face stimuli, other cortical regions that are not even primarily visual (such as somatosensory cortex), and subcortical structures such as the amygdala. Higher-level face perception abilities, such as judging identity, emotion and trustworthiness, appear to rely on an intact face-processing network that includes the occipital face area (OFA), whereas lower-level face categorization abilities, such as discriminating faces from objects, can be achieved without OFA, perhaps via the direct connections to the fusiform face area (FFA) from several extrastriate cortical areas. Some lesion, transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) findings argue against a strict feed-forward hierarchical model of face perception, in which the OFA is the principal and common source of input for other visual and non-visual cortical regions involved in face perception, including the FFA, face-selective superior temporal sulcus and somatosensory cortex. Instead, these findings point to a more interactive model in which higher-level face perception abilities depend on the interplay between several functionally and anatomically distinct neural regions. Furthermore, the nature of these interactions may depend on the particular demands of the task. We review the lesion and TMS literature on this topic and highlight the dynamic and distributed nature of face processing.
Brain systems for assessing the affective value of faces
Authors: Said Christopher P. , Haxby James V. , Todorov Alexander
Published: May 2011

Cognitive neuroscience research on facial expression recognition and face evaluation has proliferated over the past 15 years. Nevertheless, large questions remain unanswered. In this overview, we discuss the current understanding in the field, and describe what is known and what remains unknown. In §2, we describe three types of behavioural evidence that the perception of traits in neutral faces is related to the perception of facial expressions, and may rely on the same mechanisms. In §3, we discuss cortical systems for the perception of facial expressions, and argue for a partial segregation of function in the superior temporal sulcus and the fusiform gyrus. In §4, we describe the current understanding of how the brain responds to emotionally neutral faces. To resolve some of the inconsistencies in the literature, we perform a large group analysis across three different studies, and argue that one parsimonious explanation of prior findings is that faces are coded in terms of their typicality. In §5, we discuss how these two lines of research—perception of emotional expressions and face evaluation—could be integrated into a common, cognitive neuroscience framework.
From single cells to social perception
Authors: Barraclough Nick E. , Perrett David I.
Published: May 2011

Research describing the cellular coding of faces in non-human primates often provides the underlying physiological framework for our understanding of face processing in humans. Models of face perception, explanations of perceptual after-effects from viewing particular types of faces, and interpretation of human neuroimaging data rely on monkey neurophysiological data and the assumption that neurophysiological responses of humans are comparable to those recorded in the non-human primate. Here, we review studies that describe cells that preferentially respond to faces, and assess the link between the physiological characteristics of single cells and social perception. Principally, we describe cells recorded from the non-human primate, although a limited number of cells have been recorded in humans, and are included in order to appraise the validity of non-human physiological data for our understanding of human face and social perception.
The evolution of face processing in primates
Authors: Parr Lisa A.
Published: May 2011

The ability to recognize faces is an important socio-cognitive skill that is associated with a number of cognitive specializations in humans. While numerous studies have examined the presence of these specializations in non-human primates, species where face recognition would confer distinct advantages in social situations, results have been mixed. The majority of studies in chimpanzees support homologous face-processing mechanisms with humans, but results from monkey studies appear largely dependent on the type of testing methods used. Studies that employ passive viewing paradigms, like the visual paired comparison task, report evidence of similarities between monkeys and humans, but tasks that use more stringent, operant response tasks, like the matching-to-sample task, often report species differences. Moreover, the data suggest that monkeys may be less sensitive than chimpanzees and humans to the precise spacing of facial features, in addition to the surface-based cues reflected in those features, information that is critical for the representation of individual identity. The aim of this paper is to provide a comprehensive review of the available data from face-processing tasks in non-human primates with the goal of understanding the evolution of this complex cognitive skill.
Visual adaptation and face perception
Authors: Webster Michael A. , MacLeod Donald I. A.
Published: May 2011

The appearance of faces can be strongly affected by the characteristics of faces viewed previously. These perceptual after-effects reflect processes of sensory adaptation that are found throughout the visual system, but which have been considered only relatively recently in the context of higher level perceptual judgements. In this review, we explore the consequences of adaptation for human face perception, and the implications of adaptation for understanding the neural-coding schemes underlying the visual representation of faces. The properties of face after-effects suggest that they, in part, reflect response changes at high and possibly face-specific levels of visual processing. Yet, the form of the after-effects and the norm-based codes that they point to show many parallels with the adaptations and functional organization that are thought to underlie the encoding of perceptual attributes like colour. The nature and basis for human colour vision have been studied extensively, and we draw on ideas and principles that have been developed to account for norms and normalization in colour vision to consider potential similarities and differences in the representation and adaptation of faces.
Stable face representations
Authors: Jenkins Rob , Burton A. Mike
Published: May 2011

Photographs are often used to establish the identity of an individual or to verify that they are who they claim to be. Yet, recent research shows that it is surprisingly difficult to match a photo to a face. Neither humans nor machines can perform this task reliably. Although human perceivers are good at matching
familiar
faces, performance with
unfamiliar
faces is strikingly poor. The situation is no better for automatic face recognition systems. In practical settings, automatic systems have been consistently disappointing. In this review, we suggest that failure to distinguish between familiar and unfamiliar face processing has led to unrealistic expectations about face identification in applied settings. We also argue that a photograph is not necessarily a reliable indicator of facial appearance, and develop our proposal that summary statistics can provide more stable face representations. In particular, we show that image averaging stabilizes facial appearance by diluting aspects of the image that vary between snapshots of the same person. We review evidence that the resulting images can outperform photographs in both behavioural experiments and computer simulations, and outline promising directions for future research.
The many faces of research on face perception
Authors: Little Anthony C. , Jones Benedict C. , DeBruine Lisa M.
Published: May 2011

Face perception is fundamental to human social interaction. Many different types of important information are visible in faces and the processes and mechanisms involved in extracting this information are complex and can be highly specialized. The importance of faces has long been recognized by a wide range of scientists. Importantly, the range of perspectives and techniques that this breadth has brought to face perception research has, in recent years, led to many important advances in our understanding of face processing. The articles in this issue on face perception each review a particular arena of interest in face perception, variously focusing on (i) the social aspects of face perception (attraction, recognition and emotion), (ii) the neural mechanisms underlying face perception (using brain scanning, patient data, direct stimulation of the brain, visual adaptation and single-cell recording), and (iii) comparative aspects of face perception (comparing adult human abilities with those of chimpanzees and children). Here, we introduce the central themes of the issue and present an overview of the articles.
Facial attractiveness: evolutionary based research
Authors: Little Anthony C. , Jones Benedict C. , DeBruine Lisa M.
Published: May 2011

Face preferences affect a diverse range of critical social outcomes, from mate choices and decisions about platonic relationships to hiring decisions and decisions about social exchange. Firstly, we review the facial characteristics that influence attractiveness judgements of faces (e.g. symmetry, sexually dimorphic shape cues, averageness, skin colour/texture and cues to personality) and then review several important sources of individual differences in face preferences (e.g. hormone levels and fertility, own attractiveness and personality, visual experience, familiarity and imprinting, social learning). The research relating to these issues highlights flexible, sophisticated systems that support and promote adaptive responses to faces that appear to function to maximize the benefits of both our mate choices and more general decisions about other types of social partners.