bluuebunny/crossref_metadata_2025 huggingface dataset:
A stable and switchable uniform lying helix structure in cholesteric liquid crystals
Authors: Wang Chun-Ta , Wang Wei-Yuan , Lin Tsung-Hsien
Published: July 2011

This investigation demonstrates an electrically switchable uniformly lying helix (ULH) stable state in cholesteric liquid crystal. A stable ULH state can be achieved by applying the low-frequency (30 Hz) pulse electrical field via an electro-hydrodynamatic effect. The ULH state can be stably maintained with a helical pitch in the visible range (450 nm–630 nm) and exhibit a tunable uniaxial crystal wave plate property under 1 kHz electrical field. The study examines the electro-optical property of ULH state and driving scheme for switching among the three stable states. A multi-stable and electrically switchable cholesteric liquid crystal can provide various optical properties and has extensive potential applications.
Experimental assessment of quasi-binary picture of thermotropics: Induced smectic A phase in 7CB–n-heptane system
Authors: Yamaoka Yuuki , Taniguchi Yuki , Yasuzuka Syuma , Yamamura Yasuhisa , Saito Kazuya
Published: July 2011

Quasi-binary (QB) picture of thermotropics, which regards a neat thermotropic liquid crystal as a binary system consisting of (semi)rigid core and molten alkyl chain, was assessed experimentally for the most famous (and representative) thermotropic mesogenic series nCB. By adding n-heptane as solvent, the smectic A phase was induced in 7CB–n-heptane system. Small angle x-ray diffraction showed that the QB picture holds not only in the phase behavior but also in the structure. It is suggested that the melting of 8CB and 9CB to isotropic liquid via smectic and nematic liquid crystals can be understood as a thermotropic–lyotropic crossover.
Derivatives and dimers of C50-D5h and C50-D3: A comparison of two closely related but quite differently behaving fullerenes
Authors: Bihlmeier Angela
Published: July 2011

A density functional theory study on the reactivity of the energetically most stable C50 isomers, C50-D5h and C50-D3, is presented. We explore the reactivity of both fullerenes towards the addition of hydrogen and halogen atoms and towards the formation of dimers. The addition patterns of the derivatives C50X2n (X = H, F, Cl) that are preferably formed after the saturation of the most reactive sites are investigated as well. The study reveals that while the results for C50-D5h are in agreement with simple empirical rules, C50-D3 does not show the expected behaviour.
On the stationary macroscopic inertial effects for one phase flow in ordered and disordered porous media
Authors: Lasseux D. , Abbasian Arani A. A. , Ahmadi A.
Published: July 2011

We report on the controversial dependence of the inertial correction to Darcy’s law upon the filtration velocity (or Reynolds number) for one-phase Newtonian incompressible flow in model porous media. Our analysis is performed on the basis of an upscaled form of the Navier-Stokes equation requiring the solution of both the micro-scale flow and the associated closure problem. It is carried out with a special focus on the different regimes of inertia (weak and strong inertia) and the crossover between these regimes versus flow orientation and structural parameters, namely porosity and disorder. For ordered structures, it is shown that (i) the tensor involved in the expression of the correction is generally not symmetric, despite the isotropic feature of the permeability tensor. This is in accordance with the fact that the extra force due to inertia exerted on the structure is not pure drag in the general case; (ii) the Forchheimer type of correction (which strictly depends on the square of the filtration velocity) is an approximation that does not hold at all for particular orientations of the pressure gradient with respect to the axes of the structure; and (iii) the weak inertia regime always exists as predicted by theoretical developments. When structural disorder is introduced, this work shows that (i) the quadratic dependence of the correction upon the filtration velocity is very robust over a wide range of the Reynolds number in the strong inertia regime; (ii) the Reynolds number interval corresponding to weak inertia, that is always present, is strongly reduced in comparison to ordered structures. In conjunction with its relatively small magnitude, it explains why this weak inertia regime is most of the time overlooked during experiments on natural media. In all cases, the Forchheimer correction implies that the permeability is different from the intrinsic one.
Effects of silica particles on the electrical percolation threshold and thermomechanical properties of epoxy/silver nanocomposites
Authors: Nam Seungwoong , Woo Cho Hyun , Kim Taeho , Kim Daeheum , June Sung Bong , Lim Soonho , Kim Heesuk
Published: July 2011

We experimentally and theoretically demonstrated that the addition of silica particles could improve both the electrical conductivity and the thermomechanical properties of epoxy/silver nanocomposites. As silica particles were added, the electrical percolation threshold concentration of silver nanoparticles decreased and the electrical resistivity of the composite decreased by about 8 orders of magnitude. The coefficient of thermal expansion also decreased with increasing volume fraction of silica particles. Molecular simulations showed that the additional silica particles made the effective intermolecular interactions between silver nanoparticles attractive, thereby enhancing the formation of an electrical percolation network.
Folding and stacking defects of graphene flakes probed by electron nanobeam
Authors: Persichetti L. , Tombolini F. , Casciardi S. , Diociaiuti M. , Fanfoni M. , Palleschi G. , Sgarlata A. , Valentini F. , Balzarotti A.
Published: July 2011

Combining nanoscale imaging with local electron spectroscopy and diffraction has provided direct information on folding and stacking defects of graphene flakes produced by unrolled multi-walled carbon nanotubes. Structural data obtained by nanoarea electron diffraction complemented with systematic electron energy loss spectroscopy measurements of the surface plasmon losses of single flakes show the presence of flat bilayer regions coexisting with folded areas where the topology of buckled graphene resembles that of warped carbon nanostructures.
First-principles study of liquid gallium at ambient and high pressure
Authors: Yang Jianjun , Tse John S. , Iitaka Toshiaki
Published: July 2011

The static and dynamic properties of liquid Ga close to the melting line have been studied by first-principles molecular dynamics simulations at ambient and elevated pressure up to 5.8 GPa. Below 2.5 GPa, the nearest neighbor Ga-Ga separation shows little change, while the second and third coordination shells are compressed to shorter distances. This behavior is attributed to the gradual occupation of the interstitial sites. Detail analysis of the local geometry and dynamical behavior refutes the proposed existence of Ga2 dimers in the liquid state. In fact, both the structure and electronic properties of the liquid are found to closely resemble that of the underlying Ga-II and Ga-III crystalline phases.
Temperature-dependent photoluminescence from chemically and thermally reduced graphene oxide
Authors: Viet Cuong Tran , Hung Pham Viet , Woo Shin Eun , Suk Chung Jin , Hyun Hur Seung , Jung Kim Eui , Trung Tran Quang , Hung Nguyen Hoang , Kohl Paul A.
Published: July 2011

Temperature-dependent photoluminescence (PL) of graphene oxide (GO) reduced with hydrazine and heat has been measured to investigate the effect of reduction type on the bandgap of the reduced GO. Nitrogen functionalities formed in the hydrazine-treated GO were responsible for a strong localization of carriers that caused in a fluctuation in PL peak position with temperature. The intensity of C-OH peak was relatively low in the heat-treated GO, indicating that raising temperature facilitated the removal of hydroxyl groups, resulting in larger sp2 domain size and smaller bandgap energy.
Al1.3Sb3Te material for phase change memory application
Authors: Peng Cheng , Song Zhitang , Rao Feng , Wu Liangcai , Zhu Min , Song Hongjia , Liu Bo , Zhou Xilin , Yao Dongning , Yang Pingxiong , Chu Junhao
Published: July 2011

Comparing with Ge2Sb2Te5, Al1.3Sb3Te is proved to be a promising candidate for phase-change memory use because of its higher crystallization temperature (∼210 °C), larger crystallization activation energy (3.32 eV), and better data retention ability (124 °C for 10 yr). Furthermore, Al1.3Sb3Te shows fast phase change speed and crystallizes into a uniformly embedded crystal structure. As short as 10 ns width, voltage pulse can realize reversible operations for Al1.3Sb3Te based phase-change memory cell. Moreover, phase-change memory cell based on Al1.3Sb3Te material also has good endurance (∼2.5 × 104 cycles) and an enough resistance ratio of ∼102.
Communication: The formation of helium cluster cations following the ionization of helium nanodroplets: Influence of droplet size and dopant
Authors: Shepperson Benjamin , Liu Jun , Ellis Andrew M. , Yang Shengfu
Published: July 2011

The Hen+/He2+ (n ≥ 3) signal ratios in the mass spectra derived from electron impact ionization of pure helium nanodroplets are shown to increase with droplet size, reaching an asymptotic limit at an average droplet size of approximately 50 000 helium atoms. This is explained in terms of a charge hopping model, where on average the positive charge is able to penetrate more deeply into the liquid helium as the droplet size increases. The deeper the point where the charge localizes to form He2+, the greater the likelihood of collisions with the surrounding helium as the ion begins to leave the droplet, thus increasing the probability that helium will be ejected in the form of Hen+ (n ≥ 3) cluster ions rather than He2+. The addition of a dopant alters the Hen+/He2+ ratio for small helium droplets, an observation attributed to the potential energy gradient created by the cation-dopant interaction and its effect in drawing the positive charge towards the dopant in the interior of the droplet.
Effects of argon ion irradiation on nucleation and growth of silver nanoparticles in a soda-glass matrix
Authors: Gangopadhyay P. , Magudapathy P. , Srivastava S. K. , Nair K. G. M. , Panigrahi B. K.
Published: July 2011

The present article explores an experimental study for nucleation and non-equilibrium growth of silver nanoparticles in a soda-glass matrix. Ion-irradiation induced recoiling of silver atoms with argon ions (at energy 100 keV) facilitates nucleation as well as growth of the silver nanoparticles in the soda-glass matrix. Small growth of the silver nanoparticles in the soda-glass matrix has been experimentally observed after the irradiation with higher fluences of the argon ions. Role of the argon ions for the evolution of the silver nanoparticles in the soda-glass matrix has been elucidated in the present report. With increase of the argon-ion fluences, while slight athermal growth of the silver nanoparticles has been estimated, drastic increase in the optical responses and Rutherford backscattering (RBS) yields of the silver nanoparticles have been observed in the sample with the maximum fluences. Possible correlations of increase of argon-ion fluences and the observed experimental results (optical and RBS, in particular) have been explained in this article. Although it has been demonstrated using the silver metal film on a soda-glass substrate as a model example, the non-equilibrium approach of nucleation and ion-beam controlled growth of metal nanoparticles in a matrix should be applicable to other immiscible systems as well.
Spatially Varying Coefficient Models: Testing for Spatial Heteroscedasticity and Reweighting Estimation of the Coefficients
Authors: Shen Si-Lian , Mei Chang-Lin , Zhang Ying-Jian
Published: July 2011

In the framework of the geographically weighted regression technique, spatial homoscedasticity of the model error term is a common assumption when a spatially varying coefficient model is calibrated to explore spatial nonstationarity of the regression relationship. In many real-world problems, however, this assumption cannot be guaranteed. In this study we first present a residual-based test method for detecting spatial heteroscedasticity of a spatially varying coefficient model. Then, we suggest a local linear smoothing procedure to estimate the variance function of the model error when heteroscedasticity exists, on which a reweighting estimation of the regression coefficients is derived. Some numerical experiments are conducted to evaluate the performance of the test and the gain in accuracy of the coefficient estimates by using the reweighting estimation method. The results demonstrate that the test method is powerful and that the reweighting estimation can improve the accuracy of the coefficient estimates, especially when strong heteroscedasticity exists in the model error term. Finally, a real-world dataset is analyzed to demonstrate the applications of the proposed test and estimation methods.
Negotiating Intersectionality in Highly Educated Migrant Maghrebi Women's Life Stories
Authors: Kynsilehto Anitta
Published: July 2011

Through acknowledging migration as an embodied and gendered phenomenon, I problematise contemporary discourse on the migration of the highly skilled. With a focus on highly educated migrant Maghrebi women's life stories, I analyse the labour-market strategies of the women concerned and reflect these in light of macronarratives of skilled migration. I argue that the concept of intersectionality, which centres on the variety of axes of demarcation, is useful in understanding agency as conditioned by a variety of forces playing upon the individual both in enabling and in constraining ways. Paying attention to the life course via intersectionality is also helpful in understanding better the experiences of the (partially) privileged, and is necessary in order to avoid reproducing dominant representations of migrant women in positions of passivity and victimisation.
An Evolutionary Perspective on Regional Port Systems: The Role of Windows of Opportunity in Shaping Seaport Competition
Authors: Jacobs Wouter , Notteboom Theo
Published: July 2011

How do seaports evolve in relation to each other? Recent studies in port economics and transport geography have been focused on how supply-chain integration has structurally changed the competitive landscape in which individual ports and port actors operate. Port regionalization has been addressed as the corresponding new phase in the spatial and functional evolution of port systems. However, these studies lack theoretical foundations that allow us to assess empirically the role either of the institutional context or of strategic agency in the competitive (spatial and functional) evolution of regional (integrated) port systems. The authors present an evolutionary framework to analyze the development of seaports in a regional context by making use of the concept of ‘windows of opportunity’. The role of seaport-based evolution in the processes aimed at positioning market players and ports on the container scene in the Rhine–Scheldt Delta is examined.
Cities and the Unevenness of Social Movement Space: The Case of France's Immigrant Rights Movement
Authors: Nicholls Walter
Published: July 2011

This paper analyzes the formation of a ‘social movement space’ through the case of France's immigrant rights movement. Rather than this movement developing on the head of a pin, the French immigrant rights movement displays a rich and varied geography that changed over time. The movement emerged through a series of urban struggles and Paris early on became a center of these mobilizations. The complex and empowering networks developed in Paris were later deployed in a new campaign to contest restrictive national legislation passed in 1993. As this movement shifted from the urban to the national scale, networks connected the Paris hub to local struggles across the country. This network configuration, with Paris playing a centralizing role, introduced powerful geographical cleavages between center and periphery. Thus, this movement is not only conceived as a form of contentious collective action but as a distinctive spatial entity in its own right (‘social movement space’). As a spatial entity, the paper examines the processes that intersected to provide it with its own unique features, the capacities to sustain its political momentum, and the internal cleavages that would later result in its slow demise.
The Gendering of Political and Civic Participation among Colombian Migrants in London
Authors: McIlwaine Cathy , Bermúdez Anastasia
Published: July 2011

In this paper we examine how Colombian migrants participate in formal and informal political and civic activities in London. Drawing on qualitative and quantitative research conducted between 2005 and 2009, we explore how gender regimes change as people move across borders and how this affects political and civic participation. Although the gendered patterns of participation partly reflect research elsewhere, in terms of men's stronger involvement in formal and transnational activities and women's greater participation in informal politics and immigrant politics, some important differences emerged. Not only do formal and informal activities overlap, but class position and life-course stage as well as immigration status affect these processes. Although middle-class women were able to take advantage of opportunities for formal political participation in London and transnationally, working-class women gained the most from changing gender regimes, exercising increased control over their lives through their disproportionate participation with migrant-community organisations. In both cases, however, women's political engagement was easier when demands on their traditional roles, as mothers in particular, were lessened later in the life course. Working-class men emerged as the least active politically and civically, and this was related to working patterns, feelings of disempowerment and a desire to return home. Conceptually, we further challenge an unreconstructed political opportunities structure perspective for explaining migrants' political mobilisation by arguing for the need to include not only a gendered approach but also one that explicitly integrates intersectionality into any analysis. For Colombian migrants in London, although political and civic participation is far from uniform, there is evidence that engagement in such activities is important in the lives of many migrants, and especially for working-class women who appear to have been the most active in challenging hegemonic gender regimes.
Structure of the protein core of the glypican Dally-like and localization of a region important for hedgehog signaling
Authors: Kim Min-Sung , Saunders Adam M. , Hamaoka Brent Y. , Beachy Philip A. , Leahy Daniel J.
Published: July 2011

Glypicans are heparan sulfate proteoglycans that modulate the signaling of multiple growth factors active during animal development, and loss of glypican function is associated with widespread developmental abnormalities. Glypicans consist of a conserved, approximately 45-kDa N-terminal protein core region followed by a stalk region that is tethered to the cell membrane by a glycosyl-phosphatidylinositol anchor. The stalk regions are predicted to be random coil but contain a variable number of attachment sites for heparan sulfate chains. Both the N-terminal protein core and the heparan sulfate attachments are important for glypican function. We report here the 2.4-Å crystal structure of the N-terminal protein core region of the
Drosophila
glypican Dally-like (Dlp). This structure reveals an elongated, α-helical fold for glypican core regions that does not appear homologous to any known structure. The Dlp core protein is required for normal responsiveness to Hedgehog (Hh) signals, and we identify a localized region on the Dlp surface important for mediating its function in Hh signaling. Purified Dlp protein core does not, however, interact appreciably with either Hh or an Hh:Ihog complex.
Diversity in Habitat Use and Trophic Ecology of Brook Trout in Lake Superior and Tributary Streams Revealed Through Stable Isotopes
Authors: Robillard Melissa M. , McLaughlin Robert L. , Mackereth Robert W.
Published: July 2011

Two distinct types of brook troutSalvelinus fontinalishave been hypothesized to occur in Lake Superior: large fish that inhabit Lake Superior for much of the year but spawn in tributary streams, and small fish that are resident in tributary streams. The lake type has declined markedly in range and abundance, and a greater understanding of the behavior and ecology of these populations is needed to support conservation efforts. Comparisons of stable isotope (δ13C and δ15N) signatures between fish caught in the lake and those captured in streams supported the hypothesis of relatively distinct types differing in habitat use and trophic ecology. Comparisons of δ13C values for brook trout, other fishes, and aquatic invertebrates collected from stream, stream‐mouth, and lake habitats suggested that large‐type brook trout are lake specialists, whereas small‐type brook trout are stream specialists, stream–lake generalists, or some mixture of the two. Delineating the diversity in habitat use and trophic ecology of Lake Superior brook trout represents a crucial initial step toward understanding the mechanisms responsible for the observed phenotypic diversity and for developing science‐based plans to conserve or restore this diversity.
Estimation of Short‐Term Tag‐Induced Mortality in Horseshoe Crabs Limulus polyphemus
Authors: Mattei J. H. , Beekey M. A. , Potter H. R. , Bond C. S. , Woronik A. R. , Roberts J. A. , Smith K. A.
Published: July 2011

Horseshoe crabs Limulus polyphemus range along the East Coast of the United States and over 150,000 of them have been marked with U.S. Fish and Wildlife Service disk tags. It has been assumed that the tags do not harm the animals and are similar to common epibionts often found on the shells of horseshoe crabs. We investigated whether newly tagged adult female horseshoe crabs would exhibit higher short‐term mortality rates than untagged adult females. All crabs were collected from a beach in Connecticut and then were transported to a laboratory for the experiment. Tagging involved drilling a small hole through the carapace in the lower back corner of the prosoma and then inserting the tag into the hole. Overall mortality of tagged and untagged females held in flow‐through raceways for 44 d was minimal (0% mortality among 53 tagged crabs; 4% mortality among 52 untagged crabs). None of the horseshoe crabs lost or shed their disk tags over the course of the experiment. In field mark–recapture studies of horseshoe crabs, typically between 11% and 20% of the initial numbers of tagged crabs are recaptured. Crabs that are recaptured but reported dead are unlikely to have died from the initial tagging process. Our results indicate that newly tagged adult horseshoe crabs have the potential to survive as well as untagged crabs through the Connecticut spawning season (∼30–45 d). Recapture data also suggest that these crabs can survive for as long as 8–10 years with the tags in place.
Alignment of distantly related protein structures: algorithm, bound and implications to homology modeling
Authors: Wang Sheng , Peng Jian , Xu Jinbo
Published: July 2011

Motivation: Building an accurate alignment of a large set of distantly related protein structures is still very challenging.

Results: This article presents a novel method 3DCOMB that can generate a multiple structure alignment (MSA) with not only as many conserved cores as possible, but also high-quality pairwise alignments. 3DCOMB is unique in that it makes use of both local and global structure environments, combined by a statistical learning method, to accurately identify highly similar fragment blocks (HSFBs) among all proteins to be aligned. By extending the alignments of these HSFBs, 3DCOMB can quickly generate an accurate MSA without using progressive alignment. 3DCOMB significantly excels others in aligning distantly related proteins. 3DCOMB can also generate correct alignments for functionally similar regions among proteins of very different structures while many other MSA tools fail. 3DCOMB is useful for many real-world applications. In particular, it enables us to find out that there is still large improvement room for multiple template homology modeling while several other MSA tools fail to do so.

Availability: 3DCOMB is available at http://ttic.uchicago.edu/~jinbo/software.htm.

Contact:  jinboxu@gmail.com

Supplementary Information:  Supplementary data are available at Bioinformatics online.
ReplacementMatrix: a web server for maximum-likelihood estimation of amino acid replacement rate matrices
Authors: Dang Cuong Cao , Lefort Vincent , Le Vinh Sy , Le Quang Si , Gascuel Olivier
Published: July 2011

Summary: Amino acid replacement rate matrices are an essential basis of protein studies (e.g. in phylogenetics and alignment). A number of general purpose matrices have been proposed (e.g. JTT, WAG, LG) since the seminal work of Margaret Dayhoff and co-workers. However, it has been shown that matrices specific to certain protein groups (e.g. mitochondrial) or life domains (e.g. viruses) differ significantly from general average matrices, and thus perform better when applied to the data to which they are dedicated. This Web server implements the maximum-likelihood estimation procedure that was used to estimate LG, and provides a number of tools and facilities. Users upload a set of multiple protein alignments from their domain of interest and receive the resulting matrix by email, along with statistics and comparisons with other matrices. A non-parametric bootstrap is performed optionally to assess the variability of replacement rate estimates. Maximum-likelihood trees, inferred using the estimated rate matrix, are also computed optionally for each input alignment. Finely tuned procedures and up-to-date ML software (PhyML 3.0, XRATE) are combined to perform all these heavy calculations on our clusters.

Availability:  http://www.atgc-montpellier.fr/ReplacementMatrix/

Contact:  olivier.gascuel@lirmm.fr

Supplementary information:  Supplementary data are available at http://www.atgc-montpellier.fr/ReplacementMatrix/
A dynamic programming algorithm for identification of triplex-forming sequences
Authors: Lexa Matej , Martínek Tomáš , Burgetová Ivana , Kopeček Daniel , Brázdová Marie
Published: July 2011

Motivation: Current methods for identification of potential triplex-forming sequences in genomes and similar sequence sets rely primarily on detecting homopurine and homopyrimidine tracts. Procedures capable of detecting sequences supporting imperfect, but structurally feasible intramolecular triplex structures are needed for better sequence analysis.

Results: We modified an algorithm for detection of approximate palindromes, so as to account for the special nature of triplex DNA structures. From available literature, we conclude that approximate triplexes tolerate two classes of errors. One, analogical to mismatches in duplex DNA, involves nucleotides in triplets that do not readily form Hoogsteen bonds. The other class involves geometrically incompatible neighboring triplets hindering proper alignment of strands for optimal hydrogen bonding and stacking. We tested the statistical properties of the algorithm, as well as its correctness when confronted with known triplex sequences. The proposed algorithm satisfactorily detects sequences with intramolecular triplex-forming potential. Its complexity is directly comparable to palindrome searching.

Availability: Our implementation of the algorithm is available at http://www.fi.muni.cz/lexa/triplex as source code and a web-based search tool. The source code compiles into a library providing searching capability to other programs, as well as into a stand-alone command-line application based on this library.

Contact:  lexa@fi.muni.cz

Supplementary Information:  Supplementary data are available at Bioinformatics online.
VISTA Region Viewer (RViewer)—a computational system for prioritizing genomic intervals for biomedical studies
Authors: Lukashin Igor , Novichkov Pavel , Boffelli Dario , Paciorkowski Alex R. , Minovitsky Simon , Yang Song , Dubchak Inna
Published: July 2011

Summary: Current genome browsers are designed for linear browsing of individual genomic regions, but the high-throughput nature of experiments aiming to elucidate the genetic component of human disease makes it very important to develop user-friendly tools for comparing several genomic regions in parallel and prioritizing them based on their functional content. We introduce VISTA Region Viewer (RViewer), an interactive online tool that allows for efficient screening and prioritization of regions of the human genome for follow-up studies. The tool takes as input genetic variation data from different biomedical studies, determines a number of various functional parameters for both coding and non-coding sequences in each region and allows for sorting and searching the results of the analysis in multiple ways.

Availability and implementation: The tool is implemented as a web application and is freely accessible on the Web at http://rviewer.lbl.gov

Contact:  rviewer@lbl.gov; ildubchak@lbl.gov
Baseline left ventricular dP/dtmax rather than the acute improvement in dP/dtmax predicts clinical outcome in patients with cardiac resynchronization therapy
Authors: Bogaard Margot D. , Houthuizen Patrick , Bracke Frank A. , Doevendans Pieter A. , Prinzen Frits W. , Meine Mathias , van Gelder Berry M.
Published: July 2011

Aims

The maximum rate of left ventricular (LV) pressure rise (dP/dtmax) has been used to assess the acute haemodynamic effect of cardiac resynchronization therapy (CRT). We tested the hypothesis that LV dP/dtmax predicts long‐term clinical outcome after initiation of CRT.

Methods and results

This was a retrospective observational multicentre study in 285 patients in whom dP/dtmax was measured invasively following implantation of a CRT device. The minimum required follow‐up was 1 year. We analysed the relationship between dP/dtmax and time to the composite endpoint, consisting of all‐cause mortality, heart transplantation (HTX), or LV assist device (LVAD) implantation within the first year of CRT. Thirty‐four events occurred after a mean follow‐up of 160 days (range 21–359). Patients with an event had lower dP/dtmax than patients without an event both at baseline (705 ± 194 vs. 800 ± 222 mmHg/s, P= 0.018) and during CRT (894 ± 224 vs. 985 ± 244 mmHg/s, P= 0.033), but the acute increase in dP/dtmax was similar in patients with and without an event (190 ± 133 vs. 185 ± 115 mmHg/s, P= n.s.). Left ventricular dP/dtmax‐level at baseline and during CRT both predicted the clinical outcome after adjustment for gender, aetiology and New York Heart Association class: hazard ratio (HR) 0.791 [95% confidence interval (CI) 0.658–0.950, P= 0.012] and HR 0.846 (95% CI 0.723–0.991, P= 0.038), respectively.

Conclusion

Left ventricular dP/dtmax measured at baseline and during CRT are predictors of 1‐year survival free from all‐cause mortality, HTX, or LVAD implantation, but the acute improvement in dP/dtmax is not correlated to clinical outcome.
Post-allogrooming reductions in self-directed behaviour are affected by role and status in the green woodhoopoe
Authors: Radford Andrew N.
Published: July 2011

Allogrooming occurs in a wide range of species and can serve both hygienic and social functions. While the latter have long been thought to be underpinned by reductions in tension for recipients, recent work has suggested that donors may also benefit in this way. Here, I show that, in cooperatively breeding green woodhoopoes
Phoeniculus purpureus
, involvement in allogrooming is followed by a reduction in self-grooming by both recipients and donors, but that the former exhibit a greater decrease. Moreover, I demonstrate for the first time that the dominance status of the allogrooming participant is important, with subordinate group members reducing subsequent self-grooming to a greater extent than the dominant pair. If avian self-directed behaviour reflects current distress levels in the same way as found in various primates, my results would indicate that allogrooming benefits are not confined to mammals, and would have important implications both for accurate assessments of the true costs and benefits of affiliative behaviour and for our understanding of the evolution of sociality.
Biomimetic three-dimensional microenvironment for controlling stem cell fate
Authors: Zhang Hu , Dai Sheng , Bi Jingxiu , Liu Kuo-Kang
Published: July 2011

Stem cell therapy is an emerging technique which is being translated into treatment of degenerated tissues. However, the success of translation relies on the stem cell lineage commitment in the degenerated regions of interest. This commitment is precisely controlled by the stem cell microenvironment. Engineering a biomimetic three-dimensional microenvironment enables a thorough understanding of the mechanisms of governing stem cell fate. We review the individual microenvironment components, including soluble factors, extracellular matrix, cell–cell interaction and mechanical stimulation. The perspectives in creating the biomimetic microenvironments are discussed with emerging techniques.
Bond energy effects on strength, cooperativity and robustness of molecular structures
Authors: Chou Chia-Ching , Buehler Markus J.
Published: July 2011

A fundamental challenge in engineering biologically inspired materials and systems is the identification of molecular structures that define fundamental building blocks. Here, we report a systematic study of the effect of the energy of chemical bonds on the mechanical properties of molecular structures, specifically, their strength and robustness. By considering a simple model system of an assembly of bonds in a cluster, we demonstrate that weak bonding, as found for example in H-bonds, results in a highly cooperative behaviour where clusters of bonds operate synergistically to form relatively strong molecular clusters. The cooperative effect of bonding results in an enhanced robustness since the drop of strength owing to the loss of a bond in a larger cluster only results in a marginal reduction of the strength. Strong bonding, as found in covalent interactions such as disulphide bonds or in the backbone of proteins, results in a larger mechanical strength. However, the ability for bonds to interact cooperatively is lost, and, as a result, the overall robustness is lower since the mechanical strength hinges on individual bonds rather than a cluster of bonds. The systematic analysis presented here provides general insight into the interplay of bond energy, robustness and other geometric parameters such as bond spacing. We conclude our analysis with a correlation of structural data of natural protein structures, which confirms the conclusions derived from our study.
Steady-state propagation of dislocations in quasi-crystals
Authors: Radi Enrico , Mariano Paolo Maria
Published: July 2011

We analyse the steady propagation at constant speed, lower than the shear wave-speed, of a straight dislocation in an unbounded elastic quasi-crystal with five-fold symmetry. We discuss only the ideal elastic behaviour, neglecting the dissipation associated with the atomic rearrangements. Under these conditions, we provide the expressions of phonon and phason fields in closed form. Both phonon and phason stresses appear to be singular near to the dislocation core. We also find the explicit expression of the energy per unit length around a moving dislocation.
Fast and slow interaction of elastic waves with platonic clusters
Authors: Meylan Michael H. , McPhedran Ross C.
Published: July 2011

We study the scattering of elastic waves by platonic clusters in the time domain, both for plane wave excitations and for a specified initial wave profile. We show that we can use an analytical extension of our problem to calculate scattering frequencies of the solution. These allow us to calculate approximate solutions that give the flexural wave profile accurately in and around the cluster for large times. We also discuss the early-time behaviour of flexural waves in terms of the classical models of Sommerfeld and Brillouin.
Effect of surface elasticity on an interface crack in plane deformations
Authors: Kim C. I. , Schiavone P. , Ru C.-Q.
Published: July 2011

We consider the effect of surface elasticity on an interface crack between two dissimilar linearly elastic isotropic homogeneous materials undergoing plane deformations. The bi-material is subjected to either remote tension (mode-I) or in-plane shear (mode-II) with the faces of the (interface) crack assumed to be traction-free. We incorporate surface mechanics into the model of deformation by employing a version of the continuum-based surface/interface theory of Gurtin & Murdoch. Using complex variable methods, we obtain a semi-analytical solution valid throughout the entire domain of interest (including at the crack tips) by reducing the problem to a system of coupled Cauchy singular integro-differential equations, which is solved numerically using Chebychev polynomials and a collocation method. It is shown that, among other interesting phenomena, our model predicts finite stress at the (sharp) crack tips and the corresponding stress field to be size-dependent. In particular, we note that, in contrast to the results from linear elastic fracture mechanics, when the bi-material is subjected to uniform far-field stresses (either tension or in-plane shear), the incorporation of surface effects effectively eliminates the oscillatory behaviour of the solution so that the resulting stress fields no longer suffer from oscillatory singularities at the crack tips.
Electroreception in the Guiana dolphin (Sotalia guianensis)
Authors: Czech-Damal Nicole U. , Liebschner Alexander , Miersch Lars , Klauer Gertrud , Hanke Frederike D. , Marshall Christopher , Dehnhardt Guido , Hanke Wolf
Published: July 2011

Passive electroreception is a widespread sense in fishes and amphibians, but in mammals this sensory ability has previously only been shown in monotremes. While the electroreceptors in fish and amphibians evolved from mechanosensory lateral line organs, those of monotremes are based on cutaneous glands innervated by trigeminal nerves. Electroreceptors evolved from other structures or in other taxa were unknown to date. Here we show that the hairless vibrissal crypts on the rostrum of the Guiana dolphin (Sotalia guianensis), structures originally associated with the mammalian whiskers, serve as electroreceptors. Histological investigations revealed that the vibrissal crypts possess a well-innervated ampullary structure reminiscent of ampullary electroreceptors in other species. Psychophysical experiments with a male Guiana dolphin determined a sensory detection threshold for weak electric fields of 4.6 µV cm−1, which is comparable to the sensitivity of electroreceptors in platypuses. Our results show that electroreceptors can evolve from a mechanosensory organ that nearly all mammals possess and suggest the discovery of this kind of electroreception in more species, especially those with an aquatic or semi-aquatic lifestyle.
Identifying indicators of illegal behaviour: carnivore killing in human-managed landscapes
Authors: St John Freya A. V. , Keane Aidan M. , Edwards-Jones Gareth , Jones Lauren , Yarnell Richard W. , Jones Julia P. G.
Published: July 2011

Managing natural resources often depends on influencing people's behaviour, however effectively targeting interventions to discourage environmentally harmful behaviours is challenging because those involved may be unwilling to identify themselves. Non-sensitive indicators of sensitive behaviours are therefore needed. Previous studies have investigated people's attitudes, assuming attitudes reflect behaviour. There has also been interest in using people's estimates of the proportion of their peers involved in sensitive behaviours to identify those involved, since people tend to assume that others behave like themselves. However, there has been little attempt to test the potential of such indicators. We use the randomized response technique (RRT), designed for investigating sensitive behaviours, to estimate the proportion of farmers in north-eastern South Africa killing carnivores, and use a modified logistic regression model to explore relationships between our best estimates of true behaviour (from RRT) and our proposed non-sensitive indicators (including farmers' attitudes, and estimates of peer-behaviour). Farmers' attitudes towards carnivores, question sensitivity and estimates of peers' behaviour, predict the likelihood of farmers killing carnivores. Attitude and estimates of peer-behaviour are useful indicators of involvement in illicit behaviours and may be used to identify groups of people to engage in interventions aimed at changing behaviour.
Self-recognition of avatar motion: how do I know it's me?
Authors: Cook Richard , Johnston Alan , Heyes Cecilia
Published: July 2011

When motion is isolated from form cues and viewed from third-person perspectives, individuals are able to recognize their own whole body movements better than those of friends. Because we rarely see our own bodies in motion from third-person viewpoints, this self-recognition advantage may indicate a contribution to perception from the motor system. Our first experiment provides evidence that recognition of self-produced and friends' motion dissociate, with only the latter showing sensitivity to orientation. Through the use of selectively disrupted avatar motion, our second experiment shows that self-recognition of facial motion is mediated by knowledge of the local temporal characteristics of one's own actions. Specifically, inverted self-recognition was unaffected by disruption of feature configurations and trajectories, but eliminated by temporal distortion. While actors lack third-person visual experience of their actions, they have a lifetime of proprioceptive, somatosensory, vestibular and first-person-visual experience. These sources of contingent feedback may provide actors with knowledge about the temporal properties of their actions, potentially supporting recognition of characteristic rhythmic variation when viewing self-produced motion. In contrast, the ability to recognize the motion signatures of familiar others may be dependent on configural topographic cues.
Photic niche invasions: phylogenetic history of the dim-light foraging augochlorine bees (Halictidae)
Authors: Tierney Simon M. , Sanjur Oris , Grajales Grethel G. , Santos Leandro M. , Bermingham Eldredge , Wcislo William T.
Published: July 2011

Most bees rely on flowering plants and hence are diurnal foragers. From this ancestral state, dim-light foraging in bees requires significant adaptations to a new photic environment. We used DNA sequences to evaluate the phylogenetic history of the most diverse clade of Apoidea that is adapted to dim-light environments (Augochlorini:Megalopta,MegaloptidiaandMegommation). The most speciose lineage,Megalopta, is distal to the remaining dim-light genera, and its closest diurnal relative (Xenochlora) is recovered as a lineage that has secondarily reverted to diurnal foraging. Tests for adaptive protein evolution indicate that long-wavelength opsin shows strong evidence of stabilizing selection, with no more than five codons (2%) under positive selection, depending on analytical procedure. In the branch leading toMegalopta, the amino acid of the single positively selected codon is conserved among ancestral Halictidae examined, and is homologous to codons known to influence molecular structure at the chromophore-binding pocket. Theoretically, such mutations can shift photopigmentλmaxsensitivity and enable visual transduction in alternate photic environments. Results are discussed in light of the available evidence on photopigment structure, morphological specialization and biogeographic distributions over geological time.
Essential Role of Tissue-Specific Proline Synthesis and Catabolism in Growth and Redox Balance at Low Water Potential
Authors: Sharma Sandeep , Villamor Joji Grace , Verslues Paul E.
Published: July 2011

To better define the still unclear role of proline (Pro) metabolism in drought resistance, we analyzed Arabidopsis (Arabidopsis thaliana) Ɗ1-pyrroline-5-carboxylate synthetase1 (p5cs1) mutants deficient in stress-induced Pro synthesis as well as proline dehydrogenase (pdh1) mutants blocked in Pro catabolism and found that both Pro synthesis and catabolism were required for optimal growth at low water potential (ψw). The abscisic acid (ABA)-deficient mutant aba2-1 had similar reduction in root elongation as p5cs1 and p5cs1/aba2-1 double mutants. However, the reduced growth of aba2-1 but not p5cs1/aba2-1 could be complemented by exogenous ABA, indicating that Pro metabolism was required for ABA-mediated growth protection at low ψw. PDH1 maintained high expression in the root apex and shoot meristem at low ψw rather than being repressed, as in the bulk of the shoot tissue. This, plus a reduced oxygen consumption and buildup of Pro in the root apex of pdh1-2, indicated that active Pro catabolism was needed to sustain growth at low ψw. Conversely, P5CS1 expression was most highly induced in shoot tissue. Both p5cs1-4 and pdh1-2 had a more reduced NADP/NADPH ratio than the wild type at low ψw. These results indicate a new model of Pro metabolism at low ψw whereby Pro synthesis in the photosynthetic tissue regenerates NADP while Pro catabolism in meristematic and expanding cells is needed to sustain growth. Tissue-specific differences in Pro metabolism and function in maintaining a favorable NADP/NADPH ratio are relevant to understanding metabolic adaptations to drought and efforts to enhance drought resistance.
Effects of a randomized contingency management intervention on opiate abstinence and retention in methadone maintenance treatment in China
Authors: Hser Yih‐Ing , Li Jianhua , Jiang Haifeng , Zhang Ruimin , Du Jiang , Zhang Congbin , Zhang Bo , Evans Elizabeth , Wu Fei , Chang Yen‐Jung , Peng Chinyi , Huang David , Stitzer Maxine L. , Roll John , Zhao Min
Published: July 2011

Aims  Methadone maintenance treatment has been made available in China in response to the rapid spread of human immunodeficiency virus (HIV), but high rates of dropout and relapse are problematic. The aim of this study was to apply and test if a contingency management (or motivational incentives) intervention can improve treatment retention and reduce drug use.

Design  Random assignment to usual care with (n = 160) or without (n = 159) incentives during a 12‐week trial. Incentives participants earned draws for a chance to win prizes on two separate tracks targeting opiate‐negative urine sample or consecutive attendance; the number of draws increased with continuous abstinence or attendance.

Setting  Community‐based methadone maintenance clinics in Shanghai and Kunming.

Participants   The sample was 23.8% female, mean age was 38, mean years of drug use was 9.4 and 57.8% had injected drugs in the past 30 days.

Measurements  Treatment retention and negative drug urine.

Findings  Relative to the treatment‐as‐usual (control) group, better retention was observed among the incentive group in Kunming (75% versus 44%), but no difference was found in Shanghai (90% versus 86%). Submission of negative urine samples was more common among the incentive group than the usual care (74% versus 68% in Shanghai, 27% versus 18% in Kunming), as was the longest duration of sustained abstinence (7.7 weeks versus 6.5 in Shanghai, 2.5 versus 1.6 in Kunming). The average total prize amount was 371 Yuan (or $55) per participant (527 for Shanghai versus 216 in Kunming).

Conclusions   Contingency management improves treatment retention and drug abstinence in methadone maintenance treatment clinics in China, although there can be considerable site differences in magnitude of effects.