bluuebunny/crossref_metadata_2025 huggingface dataset:
Multivariate analysis of toxicological and environmental properties of soil nematicides
Authors: Sánchez‐Moreno Sara , Alonso‐Prados Elena , Alonso‐Prados J Luis , García‐Baudín José M
Published: September 2008

BACKGROUND: In intensive agriculture, the use of pesticides and soil fumigants is necessary to produce economically viable crops worldwide. However, this practice may involve undesirable effects on human health and the environment. In 1995, methyl bromide was restricted by the Montreal Protocol because of possible ozone depletion. The objective of this study was to compare intrinsic environmental and toxicological properties of 11 active substances with nematicidal properties, some of them recognized as methyl bromide alternatives.

RESULTS: Four groups of active substances were discriminated by a series of principal component analyses (PCAs): (a) high toxicity to non‐target fauna, humans and animals and medium persistence in the environment (cadusafos, ethoprophos and fenamiphos); (b) high toxicity to humans, animals and non‐target fauna and high persistence (carbofuran and fosthiazate); (c) low toxicity to non‐target fauna, humans and animals and low persistence (carbosulfan, benfuracarb and oxamyl); (d) low toxicity to humans, animals and non‐target fauna and medium persistence in the environment (1,3‐dichloropropene, chloropicrin and methyl bromide).

CONCLUSION: Evaluating the multiple aspects of toxicological and environmental properties of active substances through PCA is proposed as a helpful tool for initially comparing the complex toxicological behaviour of active substances as plant protection products. Copyright © 2008 Society of Chemical Industry
Brief exposure ofBlattella germanica(Blattodea) to insecticides formulated in various microcapsule sizes and applied on porous and non‐porous surfaces
Authors: Stejskal Vaclav , Aulicky Radek , Pekar Stano
Published: September 2008

BACKGROUND:The authors explored how microcapsule size and brief exposure affected the bioavailability of five microencapsulated insecticide formulations, chlorpyrifos 23.1 g L−1CS (Detmol‐PRO), chlorpyrifos 20 g L−1CS (Empire 20), fenitrothion 20 g L−1CS (Detmol‐Mic), cyphenothrin 10 g L−1CS (Detmol‐CAP) and diazinon 30 g L−1CS (Diacap), toBlattella germanicaL. on porous and non‐porous surfaces. The hypothesis was tested that microencapsulated (CS) insecticides comprising larger microcapsules show higher efficacy on porous surfaces than formulations with smaller microcapsules.

RESULTS:Brief exposure was accomplished by allowingB. germanicato cross a 0.3 m insecticide barrier in 30 s (1.01 cm s−1). Such short exposure did not lead to 100% mortality in any formulation or surface tested. Significant differences in bioavailability on the porous and the non‐porous surfaces were found: the largest difference was observed in Empire 20 and Detmol CAP, while bioavailability of Detmol MIC did not differ on porous and non‐porous surfaces. Comparison of their microcapsule size spectra revealed that formulations containing larger microcapsules had higher efficacy on porous surfaces than formulations with smaller microcapsules. In order to explain the difference in efficacy, the variance of microcapsule sizes was regressed on the efficacy ratio on porous versus non‐porous surfaces. Although negative correlation was evident between size of capsules and the efficacy ratio on porous and non‐porous surfaces, the difference in the slope parameter was not statistically significant.

CONCLUSION:Brief contact ofB. germanicawith insecticide spray residues, which is common in barrier treatment, may lead to low efficacy, especially on porous surfaces. The latter should be preferably treated with CS insecticides containing a fraction with large capsules. In addition to the size of the microcapsules, the role of other factors, such as wall capsule thickness and chemical composition, on CS insecticide activity on various surfaces should be examined in future work. Copyright © 2008 Society of Chemical Industry
Radiation force mediated by exciton of a carbon nanotube
Authors: Ajiki Hiroshi , Ishikawa Takahiro , Iida Takuya , Ishihara Hajime
Published: September 2008

Resonant radiation force exerted on a single‐walled carbon nanotube is theoretically studied. Even under weak laser irradiation at room temperature, the acceleration of a nanotube caused by a radiation force becomes significantly large in the resonant excitation conditions of an exciton.

The spectral peak frequencies of the acceleration are sensitive to the diameter of nanotubes and to the light polarization. These features are quite useful for nondestructive remote sorting and collection of nanotubes with desired structure and alignment. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pump‐energy dependence of usual and unusual Bloch oscillations in a GaAs/AlAs superlattice
Authors: Hasegawa T. , Mizoguchi K. , Nakayama M.
Published: September 2008

We have systematically investigated the wave‐packet dynamics of Bloch oscillations (BOs) from the viewpoint of the characteristics of the Wannier‐Stark (WS) localization states in a GaAs (6.8 nm)/AlAs (0.9 nm) superlattice embedded in a p ‐i ‐n diode structure. The coherent oscillations were detected with a reflection‐type pump‐probe technique. It is clearly confirmed that the unusual BO with the frequency of 2eFD/h occurs in a weak localization regime in addition to the usual BO with eFD/h in a strong localization regime, where F is the applied electric field, and D is the superlattice period. The systematic results of the pump‐probe measurements as a function of pump energy indicate that the intensity of the unusual BO is drastically changed with pump energy, while a gradual change of that of the usual BO is observed. These results demonstrate that the quantum interference leading to the unusual BO with 2eFD/h is much sensitive to the pump energy compared with that of the usual BO. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Single NN pair luminescence and single photon generation in nitrogen δ‐doped GaP
Authors: Ikezawa Michio , Sakuma Yoshiki , Watanabe Masato , Masumoto Yasuaki
Published: September 2008

Luminescence from individual nitrogen pairs (NN) were studied in nitrogen δ‐doped gallium phosphide. Density of NN pairs (NN3,4,5,6) were directly measured by counting the spot density in μ‐photoluminescence images in samples with different nitrogen densities. It was found that all the NN densities depend on the square of nitrogen sheet density suggesting that NN3∼6 definitely consists of two nitrogen atoms, although quantitative discrepancy was found for NN5 and NN6. In high resolution polarized spectrum of single NN4, two different polarization patterns due to different N‐N orientation were observed. Single photon generation from a single NN4 was demonstrated under pulsed optical excitation at 30 K. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical fabrication of wide‐gap semiconductor nanoparticles in superfluid helium
Authors: Inaba Kazuhiro , Saito Takuji , Saito Yasuhiko , Ichimiya Masayoshi , Ashida Masaaki , Ichikawa Satoshi , Takeda Seiji , Itoh Tadashi
Published: September 2008

The nanoparticles have been fabricated from CuCl powder by laser ablation in superfluid helium. We found that most of nanoparticles are CuCl nanocrystals with single‐crystal quality by means of electron diffraction and high‐resolution transmission electron microscope. Moreover, we performed cathodoluminescence spectroscopy of single nanoparticle prepared by laser ablation with use of a scanning electron microscope. I1 bound exciton luminescence which is characteristic in the bulk CuCl was clearly observed in the nanoparticle at 15 K. In addition, we found that the cathodoluminescence spectrum changes by the electron beam irradiation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exciton coherence in semiconductor quantum dots
Authors: Ishi‐Hayase Junko , Akahane Kouichi , Yamamoto Naokatsu , Kujiraoka Mamiko , Ema Kazuhiro , Sasaki Masahide
Published: September 2008

The coherent dynamics of excitons in InAs quantum dots (QDs) was investigated in the telecommunication wavelength range using a transient four‐wave mixing technique. The sample was fabricated on an InP(311)B substrate using strain compensation to control the emission wavelength. This technique also enabled us to fabricate a 150‐layer stacked QD structure for obtaining a high S/N in the four‐wave mixing measurements, although no high‐sensitive heterodyne detection was carried out. The dephasing time and transition dipole moment were precisely estimated from the polarization dependence of signals, taking into account their anisotropic properties.

The population lifetimes of the excitons were also measured by using a polarization‐dependent pumpprobe technique. A quantitative comparison of these anisotropies demonstrates that in our QDs, non‐radiative population relaxation, polarization relaxation and pure dephasing are considerably smaller than the radiative relaxation. A comparison of the results of the four‐wave mixing and pump‐probe measurements revealed that the pure dephasing could be directly estimated with an accuracy of greater than 0.1 meV by comparing the results of four‐wave mixing and pump‐probe measurements. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Molecular Evolution of a Steroid Hydroxylating Cytochrome P450 Using a Versatile Steroid Detection System for Screening
Authors: Virus Cornelia , Bernhardt Rita
Published: September 2008

Molecular evolution is a powerful tool for improving or changing activities of enzymes for their use in biotechnological processes. Cytochromes P450 are highly interesting enzymes for biotechnological purposes because they are able to hydroxylate a broad variety of substrates with high regio‐ and stereoselectivity. One promising steroid hydroxylating cytochrome P450 for biotechnological applications is CYP106A2 from Bacillus megaterium ATCC 13368. It is one of a few known bacterial cytochromes P450 able to transform steroids such as progesterone and 11‐deoxycortisol. CYP106A2 can be easily expressed in Escherichia coli with a high yield and can be reconstituted using the adrenal redox proteins, adrenodoxin and adrenodoxin reductase. We developed a simple screening assay for this system and performed random mutagenesis of CYP106A2, yielding variants with improved 11‐deoxycortisol and progesterone hydroxylation activity. After two generations of directed evolution, we were able to improve the kcat/Km of the 11‐deoxycortisol hydroxylation by a factor of more than four. At the same time progesterone conversion was improved about 1.4‐fold. Mapping the mutations identified in catalytically improved CYP106A2 variants into the structure of a CYP106A2 model suggests that these mutations influence the mobility of the F/G loop, and the interaction with the redox partner adrenodoxin. The results show the evolution of a soluble steroid hydroxylase as a potential new catalyst for the production of steroidogenic compounds.
Pliocene dinoflagellate cyst stratigraphy, palaeoecology and sequence stratigraphy of the Tunnel-Canal Dock, Belgium
Authors: DE SCHEPPER STIJN , HEAD MARTIN J. , LOUWYE STEPHEN
Published: September 2008

Dinoflagellate cysts and sequence stratigraphy are used to date accurately the Tunnel-Canal Dock section, which contains the most complete record of marine Pliocene deposits in the Antwerp harbour area. The Zanclean Kattendijk Formation was deposited between 5.0 and 4.4 Ma during warm-temperate conditions on a shelf influenced by open-marine waters. The overlying Lillo Formation is divided into four members. The lowest is the Luchtbal Sands Member, estimated to have been deposited between 3.71 and 3.21 Ma, under cooler conditions but with an open-water influence. The Oorderen Sands, Kruisschans Sands and Merksem Sands members of the Lillo Formation are considered a single depositional sequence, and biostratigraphically dated between 3.71 andc. 2.6 Ma, with the Oorderen Sands Member no younger than 2.72–2.74 Ma. Warm-temperate conditions had returned, but a cooling event is noted within the Oorderen Sands Member. Shoaling of the depositional environment is also evidenced, with the transgressive Oorderen Sands Member passing upwards into (near-)coastal high-stand deposits of the Kruisschans Sands and Merksem Sands members, as accommodation space decreased. Applying sequence stratigraphy to our section implies that the Kattendijk/Lillo Formation boundary corresponds to the sequence boundary (SB) Za2 (4.04 Ma), the Luchtbal/Oorderen sands boundary to SB Pia1 (3.21 Ma), and the top of the Merksem Sands to SB Pia2 (2.76 Ma). Finally, the Belgian deposits are compared with marine Pliocene deposits of eastern England.
Primitive divisors in arithmetic dynamics
Authors: INGRAM PATRICK , SILVERMAN JOSEPH H.
Published: September 2008

Let ϕ(z) ∈ (z) be a rational function of degree d ≥ 2 with ϕ(0) = 0 and such that ϕ does not vanish to order d at 0. Let α ∈ have infinite orbit under iteration of ϕ and write ϕn(α) = An/Bn as a fraction in lowest terms. We prove that for all but finitely many n ≥ 0, the numerator An has a primitive divisor, i.e., there is a prime p such that p | An and p ∤ Ai for all i < n. More generally, we prove an analogous result when ϕ is defined over a number field and 0 is a preperiodic point for ϕ.
Acceptance and Commitment Therapy (ACT): A Third Wave Behaviour Therapy
Authors: Cullen Chris
Published: September 2008

This paper introduces Acceptance and commitment Therapy (ACT) as one of the newer contextualist behaviour therapies. A brief history of the development of ACT is outlined. The concepts of equivalence and laterality and the important relationship between Relational Frame Theory and ACT are then described. The “hexagram” summary of the six core linked processes in ACT is presented and, finally, the research evidence to support the effectiveness of ACT applied to a range of clinical conditions and client groups is summarized.
Si cycle in the Cariaco Basin, Venezuela: Seasonal variability in silicate availability and the Si:C:N composition of sinking particles
Authors: Thunell Robert , Benitez‐Nelson Claudia , Muller‐Karger Frank , Lorenzoni Laura , Fanning Kent , Scranton Mary , Varela Ramon , Astor Yrene
Published: September 2008

A 9‐year time series of water column and sediment trap measurements was used to examine silicon cycling within the anoxic Cariaco Basin. The dynamic hydrographic regime within Cariaco Basin results in strong seasonal changes in nutrient availability and the Si:C:N of sinking particles. Upwelling in early winter injects silicic acid (Si(OH)4= ) and nitrate (NO3−) rich waters into the photic zone which stimulates primary production and results in opal fluxes in excess of 4 mmol Si m−2 d−1. However, even during upwelling, surface waters tend to be depleted (<1 μM) in both Si(OH)4= and NO3− as a result of rapid utilization. In most years, the upper water column during winter and spring is marked by Si(OH)4= :NO3− and Si* values of less than 1. This indicates that silicate limitation in Cariaco Basin is most severe during upwelling and may restrict diatom production. Conversely, during the summer and fall when upwelling is reduced, Si(OH)4= :NO3− ratios in the upper 50 m of the water column exceed 10, implying that nitrate rather than silicate is acting to limit production during this time of year. On average, sinking particles collected at 150‐m depth in the Cariaco Basin have Si:C and Si:N values of 0.17 ± 0.01 and 1.14 ± 0.10, respectively. These ratios increase with depth to 400 m and then remain relatively constant, suggesting minimal selective removal of elements with remineralization in the anoxic portion of the water column. Similar depth‐dependent changes in these ratios are seen in surface sediments from the basin. Seasonally, particulate Si:C and Si:N are highest during the early part of the year when upwelling is most intense, while both ratios decrease to their lowest values during summer and fall. The observed seasonal variability in these ratios is due to changes in both nutrient utilization by diatoms and the contribution of diatoms to the total phytoplankton. The high ratios during upwelling suggest enhanced export of Si relative to C and N during this time of year.
Spatial and temporal dependence of clouds and their radiative impacts on the large‐scale vertical velocity profile
Authors: Yuan Jian , Hartmann Dennis L.
Published: September 2008

The structure of tropical large‐scale vertical velocity from the European Centre for Medium‐Range Weather Forecasts Re‐Analysis is compared with simultaneous satellite measurements of precipitation, top of atmosphere radiation, and clouds from the Tropical Rainfall Measuring Mission (TRMM) on timescales ranging from hours to months. The first two empirical orthogonal functions of the vertical velocity profile represent the traditional deep circulation (PC1) and a shallower circulation (PC2) associated with middle‐level divergence. Together they explain 90% of total variance and can distinguish two types of upward and downward motion: “top heavy” and “bottom heavy.” Cloud and radiation budget quantities measured on TRMM have coherent relationships to PC1 and PC2 on all timescales from simultaneous to long‐term means. The relative importance of PC2 is greater on short temporal and small spatial scales. “Top heavy” ascent is associated with deep cloud systems, more intense precipitation, lower outgoing long‐wave radiation, stronger cloud long‐wave forcing, and extensive anvils. Cloud short‐wave forcing depends primarily on PC1, while the net cloud forcing depends more on PC2. High‐thin clouds are less correlated with short‐term variations of the vertical velocity. Shallow precipitation measured by TRMM precipitation radar is associated with “bottom heavy” upward motion. Temporal compositing with respect to intense precipitating events shows that strong upward motions tend to develop in the lower atmosphere first and then change to the more “top heavy” type of upward motion. The associated cloud systems show consistent temporal changes in which high‐thick clouds develop first and extensive anvil clouds develop later. These results suggest that the elevated latent heating from stratiform precipitation and the development of “top heavy” upward motion profiles in the tropics are related to each other. The coherent relationships shown here between large‐scale vertical velocity and independently measured cloud and precipitation data can be used to test the performance of climate models.
Vertical structure of anthropogenic zonal‐mean atmospheric circulation change
Authors: Woollings Tim
Published: September 2008

The atmospheric circulation changes predicted by climate models are often described using sea level pressure, which generally shows a strengthening of the mid‐latitude westerlies. Recent observed variability is dominated by the Northern Annular Mode (NAM) which is equivalent barotropic, so that wind variations of the same sign are seen at all levels. However, in model predictions of the response to anthropogenic forcing, there is a well‐known enhanced warming at low levels over the northern polar cap in winter. This means that there is a strong baroclinic component to the response. The projection of the response onto a NAM‐like zonal index varies with height. While at the surface most models project positively onto the zonal index, throughout most of the depth of the troposphere many of the models give negative projections. The response to anthropogenic forcing therefore has a distinctive baroclinic signature which is very different to the NAM.
Role of the stratosphere on the predictability of medium‐range weather forecast: A case study of winter 2003–2004
Authors: Kuroda Yuhji
Published: September 2008

The role of the stratosphere on the predictability of medium‐range weather forecast during the northern hemisphere winter is examined using numerical experiments with a middle atmosphere climate model of the Meteorological Research Institute. It is found that in the winter of 2003/04 when the stratosphere exhibited a large variability called the Polar‐night Jet Oscillation (PJO), the predictability of the model tended to be very good for large‐scale zonal variability if the prediction is performed just before the occurrence of stratospheric sudden warmings (SSWs). The role of the stratosphere is examined by comparing experiments for the 2002/03 year and using the model with and without the stratosphere included. The results of the study suggest that taking account of the role of stratospheric variability (PJO) is crucial for improving the predictability of medium‐range weather forecast in certain winters.
Surface‐coupled three‐dimensional geothermal model for study of permafrost geothermal regime in a building environment
Authors: Zhou Fuqun , Li Robert , Zhang Aining , Zhu Lichun
Published: September 2008

In many Canadian northern communities the stability of building foundation systems relies on the strength of the underlying permafrost. Building deterioration owing to the loss of this strength or stability would profoundly affect the economies and well‐being of the surrounding communities. Although studies of permafrost geothermal regime in natural conditions have been conducted for a long time, studies of ground temperature and its spatial pattern and trend in a building environment are limited. The need for the study is more pressing with the projection of climate warming. Detailed information about the pattern and trend of ground temperature and active layer thickness dynamics under climate warming is essential for examination of potential permafrost degradation, as well as its impacts on buildings that are built on/in it. To quantify geothermal responses, and then permafrost degradation, to climatic change in different locations underneath a building, a surface‐coupled three‐dimensional geothermal model was developed. The model is physical process–based and couples heat and water processes at ground surface and subsurface with simulation of incoming solar radiation and precipitation distributions surrounding and underneath a building by accounting for the effect of the building's dimensions and orientation on the energy and water balance processes at the ground surface. This paper describes the theoretical basis upon which the model is built, the specific factors, and processes considered to represent the permafrost environment surrounding and below buildings, as well as the testing of the model with two different data sets and a theoretical model.
Friedel-like oscillations in carbon nanotube quantum dots
Authors: Ayuela A. , Jaskólski W. , Pelc M. , Santos H. , Chico L.
Published: September 2008

The interface states of all-metallic carbon nanotube quantum dots are studied based on a tight-binding approach and a Green’s function matching technique. We have found that depending on the type of metallic tube, the energy of interface states may show an oscillatory behavior. We identify these as steamming from Friedel oscillations. We comment on the possible implications of this finding on other physical properties, such as stability during the growth of nanotube junctions and magnetic interaction through carbon nanotubes.
Self-aligned patterns of multiple biomolecules printed in one step
Authors: Chalmeau J. , Thibault C. , Carcenac F. , Vieu C.
Published: September 2008

We describe an adaptation of the microcontact printing technique for generating self-aligned patterns of two different molecules in one printing step. Elastomeric stamps exhibiting different levels of topography are designed and fabricated so that, by external pressure, their deformation enables two planes, selectively inked with two different molecules, to contact the surface. The fabrication of 1 μm wide biomolecular patterns aligned into 5 μm wide patterns of another biomolecule is demonstrated through fluorescence imaging and atomic force microscopy.
Measurement of the optical absorption spectra of epitaxial graphene from terahertz to visible
Authors: Dawlaty Jahan M. , Shivaraman Shriram , Strait Jared , George Paul , Chandrashekhar Mvs , Rana Farhan , Spencer Michael G. , Veksler Dmitry , Chen Yunqing
Published: September 2008

We present experimental results on the optical absorption spectra of epitaxial graphene from the visible to the terahertz frequency range. In the terahertz range, the absorption is dominated by intraband processes with a frequency dependence similar to the Drude model. In the near-IR range, the absorption is due to interband processes and the measured optical conductivity is close to the theoretical value of e2/4ℏ. We extract values for the carrier densities, the number of carbon atom layers, and the intraband scattering times from the measurements.
Structure and interface bonding of GeO2∕Ge∕In0.15Ga0.85As heterostructures
Authors: Molle Alessandro , Spiga Sabina , Andreozzi Andrea , Fanciulli Marco , Brammertz Guy , Meuris Marc
Published: September 2008

The structural and chemical details of GeO2∕Ge layers grown on In0.15Ga0.85As substrates by molecular beam deposition were studied in situ by diffraction and spectroscopic techniques. The formation of semiconductor-oxygen bonds at the Ge∕In0.15Ga0.85As interface, which may play a decisive role in dictating the quality of the Ge passivation, was assessed after using two different surface preparations, namely Ar sputtering and atomic hydrogen cleaning.
Transverse mode competition effects on the dynamics of gain-switched vertical-cavity surface-emitting lasers
Authors: Valle A. , Arizaleta M. , Thienpont H. , Panajotov K. , Sciamanna M.
Published: September 2008

An experimental analysis of the nonlinear dynamics of a multi-transverse-mode vertical-cavity surface-emitting laser (VCSEL) when subject to a high-frequency current modulation is performed. Regular periodic dynamics—with periods equal to the modulation period or twice the modulation period—and irregular pulsating dynamics are obtained. Our results show that the irregular pulsating dynamics in multimode VCSELs subject to large-signal current modulation is due to the competition between different transverse modes.
Wavelength controlled multilayer-stacked linear InAs quantum dot arrays on InGaAsP/InP (100) by self-organized anisotropic strain engineering: A self-ordered quantum dot crystal
Authors: Sritirawisarn N. , van Otten F. W. M. , Eijkemans T. J. , Nötzel R.
Published: September 2008

Multilayer-stacked linear InAs quantum dot (QD) arrays are created on InAs/InGaAsP superlattice templates formed by self-organized anisotropic strain engineering on InP (100) substrates in chemical beam epitaxy. Stacking of the QD arrays with identical emission wavelength in the 1.55 μm region at room temperature is achieved through the insertion of ultrathin GaAs interlayers beneath the QDs with increasing interlayer thickness in successive layers. The increment in the GaAs interlayer thickness compensates the QD size/wavelength increase during strain correlated stacking. This is the demonstration of a three-dimensionally self-ordered QD crystal with fully controlled structural and optical properties.
The Context Sensitivity of Visual Size Perception Varies across Cultures
Authors: Doherty Martin J , Tsuji Hiromi , Phillips William A
Published: September 2008

There is evidence that East Asian cultures have more context-sensitive styles of reasoning, memory, attention, and scene perception than Western cultures. Lower levels of the perceptual hierarchy seem likely to be similar in all cultures, however, so we compared context sensitivity in Japan with that in the UK using a rigorous psychophysical measure of the effects of centre – surround contrast on size discrimination. In both cultures context sensitivity was greater for females working in the social sciences than for males working in the mathematical sciences. More surprisingly, context sensitivity was also much greater in Japan than in the UK. These findings show that, even at low levels of the visual-processing hierarchy, context sensitivity varies across cultures, and they raise important issues for both vision scientists and cross-cultural psychologists.
Robust dynamic classes revealed by measuring the response function of a social system
Authors: Crane Riley , Sornette Didier
Published: September 2008

We study the relaxation response of a social system after endogenous and exogenous bursts of activity using the time series of daily views for nearly 5 million videos on YouTube. We find that most activity can be described accurately as a Poisson process. However, we also find hundreds of thousands of examples in which a burst of activity is followed by an ubiquitous power-law relaxation governing the timing of views. We find that these relaxation exponents cluster into three distinct classes and allow for the classification of collective human dynamics. This is consistent with an epidemic model on a social network containing two ingredients: a power-law distribution of waiting times between cause and action and an epidemic cascade of actions becoming the cause of future actions. This model is a conceptual extension of the fluctuation-dissipation theorem to social systems [Ruelle, D (2004)
Phys Today
57:48–53] and [Roehner BM,
et al.
, (2004)
Int J Mod Phys C
15:809–834], and provides a unique framework for the investigation of timing in complex systems.
The “Cheshire Cat” escape strategy of the coccolithophoreEmiliania huxleyiin response to viral infection
Authors: Frada Miguel , Probert Ian , Allen Michael J. , Wilson William H. , de Vargas Colomban
Published: September 2008

The coccolithophoreEmiliania huxleyiis one of the most successful eukaryotes in modern oceans. The two phases in its haplodiploid life cycle exhibit radically different phenotypes. The diploid calcified phase forms extensive blooms, which profoundly impact global biogeochemical equilibria. By contrast, the ecological role of the noncalcified haploid phase has been completely overlooked. Giant phycodnaviruses (Emiliania huxleyiviruses, EhVs) have been shown to infect and lyse diploid-phase cells and to be heavily implicated in the regulation of populations and the termination of blooms. Here, we demonstrate that the haploid phase ofE. huxleyiis unrecognizable and therefore resistant to EhVs that kill the diploid phase. We further show that exposure of diploidE. huxleyito EhVs induces transition to the haploid phase. Thus we have clearly demonstrated a drastic difference in viral susceptibility between life cycle stages with different ploidy levels in a unicellular eukaryote. Resistance of the haploid phase ofE. huxleyiprovides an escape mechanism that involves separation of meiosis from sexual fusion in time, thus ensuring that genes of dominant diploid clones are passed on to the next generation in a virus-free environment. These “Cheshire Cat” ecological dynamics release host evolution from pathogen pressure and thus can be seen as an opposite force to a classic “Red Queen” coevolutionary arms race. InE. huxleyi, this phenomenon can account for the fact that the selective balance is tilted toward the boom-and-bust scenario of optimization of both growth rates of calcifyingE. huxleyicells and infectivity of EhVs.
Generation Number One: Politics and Popular Music in Yugoslavia in the 1950s
Authors: Vuletic Dean
Published: September 2008

Popular music is one of the cultural phenomena that has been most shared among the peoples inhabiting the territory of the former Yugoslavia; indeed, considering the persistence of a common popular music culture there even after the break up of the Yugoslav federation in 1991, there is perhaps little in cultural life that unites them more. It was in the 1950s that a Yugoslav popular music culture emerged through the development of local festivals, radio programs and a recording industry, at a time when popular music was also referred to as “dance,” “entertainment” or “light” music, and when jazz, pop and, by the end of the decade, rock and roll were the styles of it that were being listened to in Yugoslavia and around the world. However, the development of a Yugoslav popular music culture at this time was rooted not only in international cultural trends but was also shaped by the domestic and foreign policies that were pursued by the ruling Communist Party of Yugoslavia (CPY), which was renamed the League of Communists of Yugoslavia (LCY) in 1952. Through its cultural, economic and foreign policies, the party sought to define Yugoslavia's position in Cold War international relations, develop a sense of Yugoslav identity among its multinational citizenry, and reconstruct and modernize a country that had suffered some of the greatest losses in Europe in the Second World War—and which had, just before it, been one of the Continent's least developed states, not only economically but also in terms of cultural infrastructure. In the cultural sphere, investments were needed immediately after the war to redress the facts that Yugoslavia had high rates of illiteracy and low rates of radio ownership by European standards, that cultural activities beyond folklore remained the purview of a small urban elite, and that it lacked musical artists, schools and instruments—with great disparities in all of these measures existing between its more developed northern areas (Slovenia, Croatia and northern Serbia) and the poorer south (Bosnia-Herzegovina, Macedonia, Montenegro and southern Serbia). For example, with regards to radio ownership, in 1946 the number of individuals per radio ranged from 40 in Slovenia, 48 in Croatia and 91 in Serbia to 137 in Macedonia, 288 in Bosnia-Herzegovina and 702 in Montenegro, with the average for all of Yugoslavia being 78.
Learning awareness: constructing formative assessment in the classroom, in the school and across schools
Authors: Blanchard John
Published: September 2008

This article gives details of the Portsmouth Learning Community Assessment for Learning (AfL) project from 2002 to 2007. A context of research is given and a reframing of formative assessment suggested. Qualitative, positive effects are indicated resulting from teachers' collaborative action research and learners' involvement in classroom experimentation and curriculum design. Classroom and institutional cultures are characterised as more or less open to decision‐making by learners and stakeholders. A heuristic, hermeneutic framework is presented, outlining what teachers and learners, as well as stakeholders, managers and leaders, can make explicit for any phase of activity. Conditions thought essential to sustainable development are noted.
Unconventional serine proteases: Variations on the catalytic Ser/His/Asp triad configuration
Authors: Ekici Özlem Doğan , Paetzel Mark , Dalbey Ross E.
Published: September 2008

Serine proteases comprise nearly one‐third of all known proteases identified to date and play crucial roles in a wide variety of cellular as well as extracellular functions, including the process of blood clotting, protein digestion, cell signaling, inflammation, and protein processing. Their hallmark is that they contain the so‐called “classical” catalytic Ser/His/Asp triad. Although the classical serine proteases are the most widespread in nature, there exist a variety of “nonclassical” serine proteases where variations to the catalytic triad are observed. Such variations include the triads Ser/His/Glu, Ser/His/His, and Ser/Glu/Asp, and include the dyads Ser/Lys and Ser/His. Other variations are seen with certain serine and threonine peptidases of the Ntn hydrolase superfamily that carry out catalysis with a single active site residue. This work discusses the structure and function of these novel serine proteases and threonine proteases and how their catalytic machinery differs from the prototypic serine protease class.
Year‐to‐year variation in the topology of a plant–pollinator interaction network
Authors: Alarcón Ruben , Waser Nickolas M. , Ollerton Jeff
Published: September 2008

Vigorous discussion of the degree of specialization in pollination interactions, combined with advances in the analysis of complex networks, has revitalized the study of entire plant–pollinator communities. Noticeably rare, however, are attempts to quantify temporal variation in the structure of plant–pollinator networks, and to determine whether the status of species as specialists or generalists is stable. Here we show that network structure varied through time in a montane meadow community from southern California, USA, in that pollinator species did not form the same links with plant species across years. Furthermore, composition of the generalized core group of species in the network varied among summers, as did the identity of those species involved in relationships that appeared to be reciprocally specialized within any one summer. These differences appear to be related to severe drought conditions experienced in the second summer of the 3 year study. In contrast to this variation, the pollinator community remained similarly highly nested in all three summers, even though species were packed into the nested matrix differently from year to year. These results suggest that plant–pollinator networks vary in detail through time, while retaining some basic topological properties. This dynamic aspect of community‐scale interactions has implications for both ecological and evolutionary inferences about pollination mutualisms.
Characterization of Bacillus anthracis iron‐regulated surface determinant (Isd) proteins containing NEAT domains
Authors: Gat Orit , Zaide Galia , Inbar Izhak , Grosfeld Haim , Chitlaru Theodor , Levy Haim , Shafferman Avigdor
Published: September 2008

Three iron‐regulated surface determinant (Isd) proteins, containing NEAr Transporter (NEAT) domains (GBAA4789‐7), constitute part of an eight‐member Bacillus anthracis operon. GBAA4789 (IsdC), previously characterized by others as a haem‐binding protein, and two novel Isd proteins characterized in this study, GBAA4788 (IsdJ) and GBAA4787 (IsdK) proteins, can be translated from two alternative overlapping transcriptional units. The three NEAT‐containing Isd proteins are shown to be expressed in vivo during B. anthracis infection. Expression in vitro is regulated by iron ions independent of the virulence plasmids pXO1 and pXO2, yet their presence affects the range of response to iron ion concentration. The expression of IsdC, J and K is strongly repressed under high CO2 tension, conditions that are optimal for B. anthracis toxin and capsule expression, suggesting that these Isd proteins are elements of a B. anthracis‘air‐regulon’. Deletion mutants of isdC, isdK or the entire isdCJK locus are as virulent and pathogenic to guinea pigs as the fully virulent wild‐type Vollum strain. The isdC‐deleted mutant is defective in sequestration of haemin, consistent with previous biochemical observations, while the ΔisdK mutant is defective in haemoglobin uptake. Studies with recombinant IsdK demonstrate specific binding to haemoglobin.
Rsd family proteins make simultaneous interactions with regions 2 and 4 of the primary sigma factor
Authors: Yuan Andy H. , Gregory Brian D. , Sharp Josh S. , McCleary Katherine D. , Dove Simon L. , Hochschild Ann
Published: September 2008

Bacterial anti‐σ factors typically regulate σ factor function by restricting the access of their cognate σ factors to the RNA polymerase (RNAP) core enzyme. The Escherichia coli Rsd protein forms a complex with the primary σ factor, σ70, inhibits σ70‐dependent transcription in vitro, and has been proposed to function as a σ70‐specific anti‐σ factor, thereby facilitating the utilization of alternative σ factors. In prior work, Rsd has been shown to interact with conserved region 4 of σ70, but it is not known whether this interaction suffices to account for the regulatory functions of Rsd. Here we show that Rsd and the Rsd orthologue AlgQ, a global regulator of gene expression in Pseudomonas aeruginosa, interact with conserved region 2 of σ70. We show further that Rsd and AlgQ can interact simultaneously with regions 2 and 4 of σ70. Our findings establish that the abilities of Rsd and AlgQ to interact with σ70 region 2 are important determinants of their in vitro and in vivo activities.
An HLA‐B27 polymorphism (B*2710) that is critical for T‐cell recognition has limited effects on peptide specificity
Authors: García R , Rognan D. , Lamas J.R. , Marina A. , de Castro J.A. López
Published: September 2008

Abstract: The B*2710 subtype differs from the HLA‐B27 prototype (B*2705) only by having Glu instead of Val at position 152, in the α2 helix of the peptide‐binding site. In spite of its structural similarity most allore‐active CTL raised against B*2705 fail to cross‐react with B*2710. Indeed, of the residues that are polymorphic among HLA‐B27 subtypes, the Val> Glu152 change has the greatest influence on HLA‐B27 T‐cell antigenicity. The molecular basis for this antigenic disparity was analyzed in this study. Sequence analysis indicated that B*2710‐bound peptides have very similar motifs to B*2705‐bound ones both at the main and auxiliary anchor positions. In addition, most of the individual ligands sequenced from B*2710 were previously found in B*2705. Together these results indicate that both subtypes have largely overlapping peptide repertoires. Molecular dynamics simulations of a common ligand in complex with either B*2710 or B*2705 failed to detect significant conformational changes in the peptidic main chain or in solvent accessibility of the side chains. In addition, modeling of the Val>Glu152 change into the MHC‐peptide‐TCR structure suggested a direct role of residue 152 in interaction with the TCR. Thus, the large differences in T‐cell recognition between B*2710 and B*2705 are not explained by an effect of the Glu152 change on peptide specificity or conformation, but by different direct interactions with the TCR.
Residue 67 in the DR β1*0101 and DR β1*0103 chains strongly influences antigen presentation and DR‐peptide molecular complex conformation
Authors: L'Faqihi F.‐E. , Praud C. , Yassine‐Diab B. , Enault G. , Lakhdar‐Ghazal F. , de Préval C. , Coppin H.
Published: September 2008

Abstract: Two closely‐related molecules, DR(α,β*0101) and DR(α,β*0103), whose β chains only differ by three amino acids at positions 67, 70, and 71, and six intermediate molecules obtained by site‐directed mutagenesis were used to ascertain the respective roles of the three polymorphic residues. Substitutions at positions 70 (D→Q), 71 (E→R) and 67 (I or L→F) strongly affected HA 306–318‐specific T‐cell recognition. The consequences of the substitution of residue 67 by a phenylalanine depended on the modified HLA‐DR molecule. Although this substitution completely inhibited peptide‐specific DR1‐restricted T‐cell recognition, its manifestations on the DR103‐restricted T‐cell response were variable (abolishing proliferation of some cell lines and not others), no matter what the peptide presented was (HA 306–319 or HIV P25 peptides). We also observed that inhibition of the proliferation of an alloreactive anti‐DR103 T‐cell clone, caused by a substitution at position 70, was completely canceled by substitution of residue 67 by a phenylalanine. The observations based on functional experiments, thus, suggest that residue 67 plays an important role in determining conformation of the peptide presented to the T cells. Molecular modeling was used to predict changes induced by amino acid substitutions and highly supports functional data. Substitution of residue 67 by a phenylalanine could have repercussions on the structure of HLA‐DR molecule/peptide complexes and affect T‐cell recognition.
HLA class I and class II DNA typing and the origin of Basques
Authors: Comas D. , Mateu E. , Calafell F. , Pérez‐Lezaun A. , Bosch E. , Martínez‐Arias R. , Bertranpetit J.
Published: September 2008

Abstract:Seven HLA class I and class II loci (HLA‐A, B, C, DRB1, DQA1, DPA1 and DPB1) were typed at the DNA level in two populations of the Iberian Peninsula (100 Basque and 88 Catalan individuals) in order to unravel their genetic relationship and to compare these results with other European and Mediterranean populations. For the first time,‐ the frequencies of alleles and haplotypes for the class I HLA loci at the DNA level in these populations are presented. The most frequent haplotype in both populations is A*29‐Cw*1601‐B*44‐DRB1*0701‐DQA1*0201‐DPA1*0103‐DPB1*0401. Neither population differed markedly from the highly homogeneous European and Mediterranean genetic landscape. The Basques, a European outlier population according to classical genetic markers, appear to lie within the genetic European variation with a slight uniqueness and show no clear relationship to North African populations, as has been postulated in some previous HLA studies. Here, the range of possibilities provided by the highly polymorphic HLA system is stressed by using genetic distances, phylogenetic trees and principal component analyses in order to reconstruct population history.
Comparison of serological and molecular typing for HLA‐A and ‐B on cord blood lymphocytes
Authors: Poli F. , Scalamogna M. , Crespiatico L. , Macchi B. , Mistò R. , Nocco A. , Rossini G. , Scarpino C. , Sioli V. , Sirchia G.
Published: September 2008

Abstract: HLA class I typing by standard microcytotoxicity testing has been unsatisfactory for 14.5% of 1644 cord blood samples. In this study, we evaluated the capacity of PCR‐SSP in solving problems in HLA‐A,B typing with serological methods. With this aim we have compared serology with PCR‐SSP in 100 cord blood samples with doubtful or unreliable HLA‐A,B typing. PCR‐SSP was successful in amplifying HLA‐A,B alleles in all 100 cord blood samples. Forty‐six typings gave discrepant results with the 2 methods (serology and PCR‐SSP). Typings were considered discrepant also in the case of inability to define a split. For 19 specimens, no serological conclusion was drawn due to high mortality of the cell suspension, while PCR‐SSP allowed the definition of a clear typing. In 6 cases it was necessary to infer information from serology to define the current typing. Finally, in 3 other cases it was impossible to exclude or attribute the antigen/allele B67 or B4802. PCR‐SSP for HLA‐A,B can improve the overall reliability of HLA‐A,B typing requiring a small amount of blood although, with the set of sequence specific primers adopted, a number of alleles are still poorly defined.
High‐resolution HLA typing for the DQB1 gene by sequence‐based typing
Authors: Voorter C.E.M. , Kik M.C. , van den Berg‐Loonen E.M.
Published: September 2008

Abstract: The ideal high‐resolution typing strategy for polymorphic genes is sequence‐based typing. SBT of genomic DNA has been developed for the HLA class H genes DRB1, DRB3/4/5 and DPB1. For the DQB1 gene the sequence‐based typing method was shown to cause a number of problems. To resolve those problems, different primers to amplify and sequence exon 2 of DQB1 were designed and tested. With several primer combinations, preferential amplification was observed in individuals heterozygous for DQB1*02/*03 and DQB1*02/*04. The preference was for DQB1*02 in many instances but could also be demonstrated for DQB1*03 or *04 and resulted occasionally in allelic drop‐out. The best primer combination was selected and successfully used to type individuals heterozygous for DQB1*02, *03 and*04. To distinguish DQB1*0201 and *0202, primers for amplification and sequencing of exon 3 were developed and correct subtyping was obtained. The ambiguous typing DQB1*0301/*0302 and DQB1*0303/*0304 was resolved by allele‐specifk amplification and sequencing. A total of 258 individuals were fully typed for their DQB1 subtypes. All samples had been previously typed by PCR‐SSP and serology. Concordant typing results were obtained for all individuals tested. The DQB1 alleles detected included *0501, *0502, *0503, *0601, *0602, *0603, *0604, *0609, *0201, *0202, *0301, *0302, *0303, *0304, *0401 and *0402. Sequence‐based typing of the DQB1 gene proved a reliable typing strategy for assignment of the different DQB1 alleles after intensive selection of primers and test conditions.