bluuebunny/crossref_metadata_2025 huggingface dataset:
Bimodal dynamics of mechanically constrained hydrogen bonds revealed by vibrational photon echoes
Authors: Bodis Pavol , Yeremenko Sergiy , Berná José , Buma Wybren J. , Leigh David A. , Woutersen Sander
Published: April 2011

We have investigated the dynamics of the hydrogen bonds that connect the components of a [2]rotaxane in solution. In this rotaxane, the amide groups in the benzylic-amide macrocycle and the succinamide thread are connected by four equivalent N−H⋅⋅⋅O=C hydrogen bonds. The fluctuations of these hydrogen bonds are mirrored by the frequency fluctuations of the NH-stretch modes, which are probed by means of three-pulse photon-echo peak shift spectroscopy. The hydrogen-bond fluctuations occur on three different time scales, with time constants of 0.1, 0.6, and ⩾200 ps. Comparing these three time scales to the ones found in liquid formamide, which contains the same hydrogen-bonded amide motif but without mechanical constraints, we find that the faster two components, which are associated with small-amplitude fluctuations in the strength of the N−H⋅⋅⋅O=C hydrogen bonds, are very similar in the liquid and the rotaxane. However, the third component, which is associated with the breaking and subsequent reformation of hydrogen bonds, is found to be much slower in the rotaxane than in the liquid. It can be concluded that the mechanical bonding in a rotaxane does not influence the amplitude and time scale of the small-amplitude fluctuations of the hydrogen bonds, but strongly slows down the complete dissociation of these hydrogen bonds. This is probably because in a rotaxane breaking of the macrocycle–axle contacts is severely hindered by the mechanical constraints. The hydrogen-bond dynamics in rotaxane-based molecular machines can therefore be regarded as liquidlike on a time scale 1 ps and less, but structurally frozen on longer (up to at least 200 ps) time scales.
Influence of indium composition in the prestrained InGaN interlayer on the strain relaxation of InGaN/GaN multiple quantum wells in laser diode structures
Authors: Liu Lei , Wang Lei , Li Ding , Liu Ningyang , Li Lei , Cao Wenyu , Yang Wei , Wan Chenghao , Chen Weihua , Du Weimin , Hu Xiaodong , Feng Zhe Chuan
Published: April 2011

Prestrained InGaN layers with different indium composition were grown by metalorganic chemical vapor deposition as an interlayer before the growth of InGaN/GaN multiple quantum wells (MQWs) in laser diode structures. The strain relaxation of the MQWs with different indium composition prestrained InGaN interlayer was investigated by the grazing incidence x-ray diffraction method. Comparing to the low indium composition (about 3%) case, the strain relaxation occurred in the sample with high indium composition (about 10%) prestrained interlayer. The piezoelectric field in the MQW is also proved to be much smaller after inserting a high indium composition prestrained InGaN interlayer by a measurement of photoluminescence (PL) peak shift as a function of reverse bias voltage, indicating a reduction of the quantum-confined Stark effect (QCSE). Room temperature PL and temperature-dependent PL measurements showed that the PL intensity at 300 K and the internal quantum efficiency of the MQW sample with high indium composition prestrained interlayer were increased by 123% and 177%, respectively, compared with the low indium composition case. Therefore, the prestrained InGaN interlayer containing high indium composition is beneficial to the strain relaxation in the MQW layer and the enhancement of light emission efficiency due to the reduction of QCSE.
Simulation of nucleation in almost hard-sphere colloids: The discrepancy between experiment and simulation persists
Authors: Filion L. , Ni R. , Frenkel D. , Dijkstra M.
Published: April 2011

In this paper we examine the phase behavior of the Weeks–Chandler–Andersen (WCA) potential with βε = 40. Crystal nucleation in this model system was recently studied by Kawasaki and Tanaka [Proc. Natl. Acad. Sci. U.S.A. 107, 14036 (2010)]10.1021/pr100656u, who argued that the computed nucleation rates agree well with experiment, a finding that contradicted earlier simulation results. Here we report an extensive numerical study of crystallization in the WCA model, using three totally different techniques (Brownian dynamics, umbrella sampling, and forward flux sampling). We find that all simulations yield essentially the same nucleation rates. However, these rates differ significantly from the values reported by Kawasaki and Tanaka and hence we argue that the huge discrepancy in nucleation rates between simulation and experiment persists. When we map the WCA model onto a hard-sphere system, we find good agreement between the present simulation results and those that had been obtained for hard spheres [L. Filion, M. Hermes, R. Ni, and M. Dijkstra, J. Chem. Phys. 133, 244115 (2010)10.1063/1.3506838; S. Auer and D. Frenkel, Nature 409, 1020 (2001)10.1038/35059035].
Temperature dependence of single twin boundary motion in Ni–Mn–Ga martensite
Authors: Straka L. , Hänninen H. , Heczko O.
Published: April 2011

Magnetic-field-induced reorientation in Ni–Mn–Ga five-layered martensite (10 M) mediated by the motion of single twin boundary was evaluated from magnetization measurements between 20 and 300 K. At 300 K, the single twin boundary moved in an exceptionally small field of 25 kA/m. Twinning stress, as a measure of the twin boundary mobility, was determined from the magnetization curves using a magnetic-energy-based model; it increased from ≈0.1 MPa at 300 K to ≈0.8 MPa at 20 K. The dependence is discussed in terms of thermal activation and the effect of intermartensitic transformation is considered.
High operating temperature midwave infrared photodiodes and focal plane arrays based on type-II InAs/GaSb superlattices
Authors: Pour S. Abdollahi , Huang E. K. , Chen G. , Haddadi A. , Nguyen B.-M. , Razeghi M.
Published: April 2011

The dominant dark current mechanisms are identified and suppressed to improve the performance of midwave infrared InAs/GaSb type-II superlattice photodiodes at high temperatures. The optimized heterojunction photodiode exhibits a quantum efficiency of 50% for 2 μm thick active region without any bias dependence. At 150 K, R0A of 5100 Ω cm2 and specific detectivity of 1.05×1012 cm Hz0.5/W are demonstrated for a 50% cutoff wavelength of 4.2μm. Assuming 300 K background temperature and 2π field of view, the performance of the detector is background limited up to 180 K, which is improved by 25 °C compared to the homojunction photodiode. Infrared imaging using f/2.3 optics and an integration time of 10.02 ms demonstrates a noise equivalent temperature difference of 11 mK at operating temperatures below 120 K.
Heat transport in amorphous silicon: Interplay between morphology and disorder
Authors: He Yuping , Donadio Davide , Galli Giulia
Published: April 2011

We present a theoretical study of the thermal conductivity (κ) of amorphous silicon (a-Si) based on molecular and lattice dynamics. We find that the majority of heat carriers are quasi-stationary modes; however the small proportion (≃3%) of propagating vibrations contributes to about half of the value of κ. We show that in bulk samples the mean free path of several long-wavelength modes is on the order of microns; this value may be substantially decreased either in thin films or in systems with etched holes, resulting in a smaller thermal conductivity. Our results provide a unified explanation of several experiments and show that kinetic theory cannot be applied to describe thermal transport in a-Si at room temperature.
Two-dimensional broadband distributed-feedback quantum cascade laser arrays
Authors: Mujagić Elvis , Schwarzer Clemens , Yao Yu , Chen Jianxin , Gmachl Claire , Strasser Gottfried
Published: April 2011

We present two-dimensional broadband quantum cascade laser arrays based on distributed-feedback (DFB) ring cavity surface emitting lasers. The 16-element arrays exhibit a linear tuning range of 180 cm−1 centered at a wavelength of 8.2 μm when operated in pulsed mode at room temperature. The devices show single-mode emission with a side mode suppression ratio of 30 dB. Given by the facetless nature of the single emitters, the spectral dependent threshold current densities and optical power reflect the gain profile of the incorporated material and are not impaired by the diversity of underlying DFB designs.
Reactive hydroxyl radical-driven oral bacterial inactivation by radio frequency atmospheric plasma
Authors: Kang Sung Kil , Choi Myeong Yeol , Koo Il Gyo , Kim Paul Y. , Kim Yoonsun , Kim Gon Jun , Mohamed Abdel-Aleam H. , Collins George J. , Lee Jae Koo
Published: April 2011

We demonstrated bacterial (Streptococcus mutans) inactivation by a radio frequency power driven atmospheric pressure plasma torch with H2O2 entrained in the feedstock gas. Optical emission spectroscopy identified substantial excited state •OH generation inside the plasma and relative •OH formation was verified by optical absorption. The bacterial inactivation rate increased with increasing •OH generation and reached a maximum 5-log10 reduction with 0.6% H2O2 vapor. Generation of large amounts of toxic ozone is drawback of plasma bacterial inactivation, thus it is significant that the ozone concentration falls within recommended safe allowable levels with addition of H2O2 vapor to the plasma.
Electronic structure of cation-codoped TiO2 for visible-light photocatalyst applications from hybrid density functional theory calculations
Authors: Long Run , English Niall J.
Published: April 2011

The electronic structures of Mg/Ca- and/or Mo/W- (mono- and co-) doped anatase TiO2 have been investigated via generalized Kohn–Sham theory with the Heyd–Scuseria–Ernzerhof hybrid functional for exchange-correlation {J. Heyd et al., [J. Chem. Phys. 118, 8207 (2003)], J. Heyd et al., [J. Chem. Phys. 124, 219906 (2006)], and J. Paier et al., [J. Chem. Phys. 125, 249901 (2006)]}, in the context of density functional theory. Gap narrowing is small for monodoping, which also creates impuritiy bands in the “forbidden gap,” either as acceptor or donor states, limiting possible utility as visible-light photocatalysts. However, codoping of Mg/Ca and Mo/W not only induces appreciable gap narrowing, but also serves to passivate the impurity bands, which can harvest visible-light to a greater extent. Considering ionic radii, Mg and Mo should constitute the best cation-pair.
Quantum and quasiclassical state-to-state dynamics of the NH + H reaction: Competition between abstraction and exchange channels
Authors: Li Zheng , Xie Changjian , Jiang Bin , Xie Daiqian , Liu Lan , Sun Zhigang , Zhang Dong Hui , Guo Hua
Published: April 2011

Quantum and quasiclassical state-to-state dynamics for the NH + H′ reaction at high collision energies up to 1.6 eV was studied on an accurate ab initio potential energy surface. Both of the endothermic abstraction (NH + H′ → N + HH′) and thermoneutral exchange (NH + H′ → H + NH′) channels were investigated from the same set of wave packets using an efficient coordinate transformation method. It is found that the abstraction represents a minor reaction channel in the energy range studied, primarily due to endothermicity. The cross section for the abstraction reaction increases monotonically with the collision energy, while that for the exchange reaction is relatively energy insensitive. As a result, the thermal rate constant for the abstraction reaction follows the Arrhenius law, where that for the exchange reaction is nearly temperature independent. Finally, it is shown that the quantum mechanical results can be reasonably reproduced by the Gaussian-binning quasiclassical trajectory method and to a lesser extent by a quantum statistical model.
Band-edge and random lasing in paintable liquid crystal emulsions
Authors: Hands P. J. W. , Gardiner D. J. , Morris S. M. , Mowatt C. , Wilkinson T. D. , Coles H. J.
Published: April 2011

Lasing mechanisms within paintable dye-doped chiral liquid crystal emulsions are investigated. Evidence shows that by variation in liquid crystal droplet size, by simple control of mechanical mixing speeds, a change in the lasing mechanism from band-edge lasing (large droplets) to diffuse nonresonant random lasing (small droplets) can be facilitated. This approach represents a facile technique for the variation in lasing mechanism, within a self-organizing, flexible, and conformable system, and offers the opportunity of developing controllable linewidth laser sources.
Role of nanoadditive blended biodiesel emulsion fuel on the working characteristics of a diesel engine
Authors: Sadhik Basha J. , Anand R. B.
Published: April 2011

Biodiesel emulsions are considered as the propitious alternative fuels for diesel engines. The need of biodiesel emulsion fuels for the diesel engines is to curtail the dependency on the fossil fuels in context to the world energy oil crisis. Henceforth, the present study provides a tangible pathway to prepare and to ameliorate the biodiesel emulsion fuel on incorporating potential alumina nanoparticles. The biodiesel emulsion fuel is prepared by emulsification technique comprising of 83% of jatropha biodiesel, 15% of water, and 2% of surfactants (Span80 and Tween80) with the aid of a mechanical agitator. The prepared biodiesel emulsion fuel is mixed with the alumina nanoparticles in the mass fractions of say 25, 50, and 100 ppm with the help of an ultrasonicator. The whole investigation is carried out in a constant speed diesel engine in three phases using jatropha biodiesel, jatropha biodiesel emulsion fuel, and alumina nanoparticle blended jatropha biodiesel emulsion fuels. The experimental results revealed a substantial enhancement in the performance and a reduction in harmful emissions for the biodiesel emulsion fuels compared to those of neat biodiesel. In addition, the incorporation of nanoparticles in the biodiesel emulsion fuel has also revealed an incremental better performance and reduced emissions than that of biodiesel emulsion fuel and biodiesel. Furthermore, the significance of shorten ignition delay effect associated with the nanoparticle blended biodiesel emulsion fuels has been investigated and asserted upon conducting a hot-plate evaporation study.
Universal stress-defect correlation at (100)semiconductor/oxide interfaces
Authors: Houssa M. , Scarrozza M. , Pourtois G. , Afanas’ev V. V. , Stesmans A.
Published: April 2011

Interface models between various group IV and III-V (100)semiconductors and their oxides are generated from first-principles molecular dynamics simulations. The tensile strain at the interface (from the semiconductor side) is estimated, by comparing bond lengths at/near the interface and in the bulk semiconductor phase. A linear relationship between the calculated interface stress and the density of interface defects observed at such interfaces is revealed. These results suggest that the interface stress due to the volume mismatch between the semiconductor and its oxide likely plays an important role in the creation of interface defects. These findings can explain recent results pertaining to the passivation of various high-mobility channels for their integration in high-performance metal-oxide-semiconductor field-effect transistors.
The origin of different magnetic properties in nanosized Ca0.82La0.18MnO3: Wires versus particles
Authors: Wang Yang , Fan Hong Jin
Published: April 2011

A comparative investigation has been conducted on the nanowires and nanoparticles (both in the size range of 20–35 nm) of Ca0.82La0.18MnO3, finding that the nanowires have similar magnetic properties to the bulk, whereas the nanoparticles behave evidently different. In the nanoparticles, charge ordering and antiferromagnetic phase disappear; instead, a ferromagnetic transition is observed. Analysis of the crystal structure indicates that, for nanosized manganite systems, whether charge ordering is suppressed and ferromagnetism is developed as the size scales down depends on the level of intrinsic structural distortions; nanodimensional effect or surface effect is not determinant.
Controlling droplet incubation using close-packed plug flow
Authors: Mary Pascaline , Abate Adam R. , Agresti Jeremy J. , Weitz David A.
Published: April 2011

Controlling droplet incubation is critical for droplet-based microfluidic applications; however, current techniques are either of limited precision or place strict limits on the incubation times that can be achieved. Here, we present a simple technique to control incubation time by exploiting close-packed plug flow. In contrast to other techniques, this technique is applicable to very short and very long incubation times.
Simulation of streamers propagating along helium jets in ambient air: Polarity-induced effects
Authors: Naidis G. V.
Published: April 2011

Results of modeling of streamer propagation along helium jets for both positive and negative polarities of applied voltage are presented. Obtained patterns of streamer dynamics and structure in these two cases are similar to those observed in experiments with plasma jets.
Applying the Helmholtz Illusion to Fashion: Horizontal Stripes Won't Make You Look Fatter
Authors: Thompson Peter , Mikellidou Kyriaki
Published: April 2011

A square composed of horizontal lines appears taller and narrower than an identical square made up of vertical lines. Reporting this illusion, Hermann von Helmholtz noted that such illusions, in which filled space seems to be larger than unfilled space, were common in everyday life, adding the observation that ladies' frocks with horizontal stripes make the figure look taller. As this assertion runs counter to modern popular belief, we have investigated whether vertical or horizontal stripes on clothing should make the wearer appear taller or fatter. We find that a rectangle of vertical stripes needs to be extended by 7.1% vertically to match the height of a square of horizontal stripes and that a rectangle of horizontal stripes must be made 4.5% wider than a square of vertical stripes to match its perceived width. This illusion holds when the horizontal or vertical lines are on the dress of a line drawing of a woman. We have examined the claim that these effects apply only for 2-dimensional figures in an experiment with 3-D cylinders and find no support for the notion that horizontal lines would be ‘fattening’ on clothes. Significantly, the illusion persists when the horizontal or vertical lines are on pictures of a real half-body mannequin viewed stereoscopically. All the evidence supports Helmholtz's original assertion.
Measuring 3D Point Configurations in Pictorial Space
Authors: Wagemans Johan , Van Doorn Andrea J , Koenderink Jan J
Published: April 2011

We propose a novel method to probe the depth structure of the pictorial space evoked by paintings. The method involves an exocentric pointing paradigm that allows one to find the slope of the geodesic connection between any pair of points in pictorial space. Since the locations of the points in the picture plane are known, this immediately yields the depth difference between the points. A set of depth differences between all pairs of points from an N-point ( N > 2) configuration then yields the configuration in depth up to an arbitrary depth offset. Since an N-point configuration implies N( N-1) (ordered) pairs, the number of observations typically far exceeds the number of inferred depths. This yields a powerful check on the geometrical consistency of the results. We report that the remaining inconsistencies are fully accounted for by the spread encountered in repeated observations. This implies that the concept of ‘pictorial space’ indeed has an empirical significance. The method is analyzed and empirically verified in considerable detail. We report large quantitative interobserver differences, though the results of all observers agree modulo a certain affine transformation that describes the basic cue ambiguities. This is expected on the basis of a formal analysis of monocular optical structure. The method will prove useful in a variety of potential applications.
Conditional reduction of adult neurogenesis impairs bidirectional hippocampal synaptic plasticity
Authors: Massa Federico , Koehl Muriel , Wiesner Theresa , Grosjean Noelle , Revest Jean-Michel , Piazza Pier-Vincenzo , Abrous Djoher Nora , Oliet Stéphane H. R.
Published: April 2011

Adult neurogenesis is a process by which the brain produces new neurons once development has ceased. Adult hippocampal neurogenesis has been linked to the relational processing of spatial information, a role attributed to the contribution of newborn neurons to long-term potentiation (LTP). However, whether newborn neurons also influence long-term depression (LTD), and how synaptic transmission and plasticity are affected as they incorporate their network, remain to be determined. To address these issues, we took advantage of a genetic model in which a majority of adult-born neurons can be selectively ablated in the dentate gyrus (DG) and, most importantly, in which neurogenesis can be restored on demand. Using electrophysiological recordings, we show that selective reduction of adult-born neurons impairs synaptic transmission at medial perforant pathway synapses onto DG granule cells. Furthermore, LTP and LTD are largely compromised at these synapses, probably as a result of an increased induction threshold. Whereas the deficits in synaptic transmission and plasticity are completely rescued by restoring neurogenesis, these synapses regain their ability to express LTP much faster than their ability to express LTD. These results demonstrate that both LTP and LTD are influenced by adult neurogenesis. They also indicate that as newborn neurons integrate their network, the ability to express bidirectional synaptic plasticity is largely improved at these synapses. These findings establish that adult neurogenesis is an important process for synaptic transmission and bidirectional plasticity in the DG, accounting for its role in efficiently integrating novel incoming information and in forming new memories.
Understanding the online therapeutic alliance through the eyes of adolescent service users
Authors: Hanley Terry
Published: April 2011

Aims: The therapeutic alliance is a concept that has received a great deal of attention within face‐to‐face counselling. Furthermore, links have been made between the creation of strong alliances and successful therapeutic outcomes. This study examines the therapeutic alliance when counselling services are offered online to young people. Method: Fifteen young people took part in online interviews (utilising synchronous and asynchronous methods), and Grounded Theory techniques were utilised to analyse the data. Findings: A core category of ‘Client‐Service Match’ and three subcategories pertinent to the individuals’ experiences of creating good quality relationships with the counsellors were identified: (1) initial engagement, (2) developing rapport, and (3) establishing control. Discussion: The themes elicited are all relevant to the matching process and viewed as a chronological process similar to face‐to‐face counselling. However, unlike face‐to‐face work, specific nuances related to the online work arise that counsellors should be mindful of, including the rationale behind each individual's choice to approach services online, their own computer‐mediated communication skills, technical hurdles, and the perceived ‘power’ of the counsellor.
Practice‐based supervision research: A network of researchers using a common toolkit
Authors: Wheeler Sue , Aveline Mark , Barkham Michael
Published: April 2011

Aim: Given that various systematic reviews of supervision literature have revealed how little is known about supervision, that studies are not usually routed in practice, and that a multitude of diverse measures are used, the primary aim of this project was to support and encourage practitioner research related to supervision using a prescribed common set of instruments. Method: Funded by the British Association for Counselling and Psychotherapy (BACP), a Supervision Research Practice Network (SuPReNet) was established. A toolkit (a series of measures) that could be used routinely by practitioners was selected following the assembly of available measures of supervision and an assessment of them. Findings: The appraisal, conducted by the three authors, yielded five core measures, free for anyone to use, and accessible through the SuPReNet website. The measures are being piloted through a practice research network at a university counselling and psychotherapy research clinic where supervision data are being collected through a special module of CORE Net. Discussion: The potential yield from this initiative for practitioners, researchers, and the developing evidence‐base is discussed and a model proposed for the next generation of research on supervision.
Therapists’ and clients’ perceptions of routine outcome measurement in the NHS: A qualitative study
Authors: Unsworth Gisela , Cowie Helen , Green Anita
Published: April 2011

Primary objective: This is the first qualitative study that elicited the perceptions of both psychological therapists and their clients in the use of Clinical Outcomes in Routine Evaluation with computer software (CORE‐Net), where instant visual feedback for session tracking was given on a computer screen in the therapy room at each therapy session. The study also examined how therapists viewed its potential value in supervision and provides suggestions for improving training. Research design: The study adopted a convenience sample of four therapists in a primary care counselling setting (PCC – General Practitioner referrals) who were experienced in using CORE‐Net, and five therapists in an NHS employee/occupational support counselling service (OH) who had just begun to use CORE‐Net for session tracking with 10 of their clients. Method: A qualitative methodology was used and interview data were collected from the therapists via focus groups; the clients were interviewed individually face to face. All data was analysed inductively. Findings: The study identified six overarching themes: (i) therapists were initially anxious and resistant; (ii) therapists adapt ‘creatively’; (iii) outcome measures help the client/therapist relationship; (iv) clients perceive visual measures as helpful; (v) CORE scores inform supervision; and (vi) proper and ongoing training/support of therapists is necessary. The main limitations are comparability of data and the generalisabilty of results. Conclusions: The implementation of routine outcome measurement (ROM) is a challenge but can be made easier with proper training and supervision. Clients appear happier than their therapists when routine outcome measurement is used.
Kinetochores feel the pull
Authors: Leslie Mitch
Published: April 2011

Researchers detail how kinetochores respond to force from spindle.
Runx1 modulates adult hair follicle stem cell emergence and maintenance from distinct embryonic skin compartments
Authors: Osorio Karen M. , Lilja Karin C. , Tumbar Tudorita
Published: April 2011

Runx1 controls hematopoietic stem cell emergence and hair follicle stem cell (HFSC) activation and proliferation in adult skin. Here we use lineage tracing and mouse genetic manipulation to address the role of Runx1 in the embryonic development of HFSCs. We find Runx1 is expressed in distinct classes of embryonic skin precursors for short-term HF progenitors, adult HFSCs, and mesenchymal progenitors. Runx1 acts in the embryonic epithelium for timely emergence of adult HFSCs and short-term progenitors, but is dispensable for both of them. In contrast, Runx1 is strictly needed in the embryonic mesenchyme for proper adult HFSC differentiation and long-term skin integrity. Our data implicate Runx1 in epithelial cell adhesion and migration and in regulation of paracrine epithelial–mesenchymal cross talk. The latter involves Lef1 and Wnt signaling modulation in opposing directions from two distinct skin compartments. Thus, a master regulator of hematopoiesis also controls HFSC emergence and maintenance via modulation of bidirectional cross talking between nascent stem cells and their niche.
Integrins traffic rapidly via circular dorsal ruffles and macropinocytosis during stimulated cell migration
Authors: Gu Zhizhan , Noss Erika H. , Hsu Victor W. , Brenner Michael B.
Published: April 2011

During cell migration, integrins are redistributed from focal adhesions undergoing disassembly at the cell’s trailing edges to new focal adhesions assembling at leading edges. The initial step of integrin redistribution is thought to require clathrin-mediated endocytosis. However, whether clathrin-mediated endocytosis functions in different contexts, such as basal versus stimulated migration, has not been determined. In this paper, we examine the spatial and temporal redistribution of integrins from focal adhesions upon stimulation by growth factors. Four-dimensional confocal live-cell imaging along with functional analysis reveals that surface integrins do not undergo significant endocytosis at ventral focal adhesions upon cell stimulation with the platelet-derived growth factor. Rather, they abruptly redistribute to dorsal circular ruffles, where they are internalized through macropinocytosis. The internalized integrins then transit through recycling endosomal compartments to repopulate newly formed focal adhesions on the ventral surface. These findings explain why integrins have long been observed to redistribute through both surface-based and internal routes and identify a new function for macropinocytosis during growth factor–induced cell migration.
The chromosomal passenger complex and centralspindlin independently contribute to contractile ring assembly
Authors: Lewellyn Lindsay , Carvalho Ana , Desai Arshad , Maddox Amy S. , Oegema Karen
Published: April 2011

The chromosomal passenger complex (CPC) and centralspindlin are conserved cytokinesis regulators that localize to the spindle midzone, which forms between the separating chromosomes. Previous work placed the CPC and centralspindlin in a linear pathway that governs midzone formation. Using Caenorhabditis elegans embryos, we test whether there is a similar linear relationship between centralspindlin and the CPC in contractile ring constriction during cytokinesis. We show that simultaneous inhibition of the CPC kinase Aurora BAIR-2 and the centralspindlin component MKLP1ZEN-4 causes an additive constriction defect. Consistent with distinct roles for the proteins, inhibition of filamentous septin guanosine triphosphatases alleviates constriction defects in Aurora BAIR-2–inhibited embryos, whereas inhibition of Rac does so in MKLP1ZEN-4-inhibited embryos. Centralspindlin and the CPC are not required to enrich ring proteins at the cell equator but instead regulate formation of a compact mature ring. Therefore, in contrast to the linear midzone assembly pathway, centralspindlin and the CPC make independent contributions to control transformation of the sheet-like equatorial band into a ribbon-like contractile ring at the furrow tip.
Peroxisome assembly: matrix and membrane protein biogenesis
Authors: Ma Changle , Agrawal Gaurav , Subramani Suresh
Published: April 2011

The biogenesis of peroxisomal matrix and membrane proteins is substantially different from the biogenesis of proteins of other subcellular compartments, such as mitochondria and chloroplasts, that are of endosymbiotic origin. Proteins are targeted to the peroxisome matrix through interactions between specific targeting sequences and receptor proteins, followed by protein translocation across the peroxisomal membrane. Recent advances have shed light on the nature of the peroxisomal translocon in matrix protein import and the molecular mechanisms of receptor recycling. Furthermore, the endoplasmic reticulum has been shown to play an important role in peroxisomal membrane protein biogenesis. Defining the molecular events in peroxisome assembly may enhance our understanding of the etiology of human peroxisome biogenesis disorders.
Spindle microtubules generate tension-dependent changes in the distribution of inner kinetochore proteins
Authors: Suzuki Aussie , Hori Tetsuya , Nishino Tatsuya , Usukura Jiro , Miyagi Atsushi , Morikawa Kosuke , Fukagawa Tatsuo
Published: April 2011

The kinetochore forms a dynamic interface with microtubules from the mitotic spindle. Live-cell light microscopy–based observations on the dynamic structural changes within the kinetochore suggest that molecular rearrangements within the kinetochore occur upon microtubule interaction. However, the source of these rearrangements is still unclear. In this paper, we analyze vertebrate kinetochore ultrastructure by immunoelectron microscopy (EM) in the presence or absence of tension from spindle microtubules. We found that the inner kinetochore region defined by CENP-A, CENP-C, CENP-R, and the C-terminal domain of CENP-T is deformed in the presence of tension, whereas the outer kinetochore region defined by Ndc80, Mis12, and CENP-E is not stretched even under tension. Importantly, based on EM, fluorescence microscopy, and in vitro analyses, we demonstrated that the N and C termini of CENP-T undergo a tension-dependent separation, suggesting that CENP-T elongation is at least partly responsible for changes in the shape of the inner kinetochore.
HP1α recruitment to DNA damage by p150CAF-1 promotes homologous recombination repair
Authors: Baldeyron Céline , Soria Gaston , Roche Danièle , Cook Adam J. L. , Almouzni Geneviève
Published: April 2011

Heterochromatin protein 1 (HP1), a major component of constitutive heterochromatin, is recruited to DNA damage sites. However, the mechanism involved in this recruitment and its functional importance during DNA repair remain major unresolved issues. Here, by characterizing HP1α dynamics at laser-induced damage sites in mammalian cells, we show that the de novo accumulation of HP1α occurs within both euchromatin and heterochromatin as a rapid and transient event after DNA damage. This recruitment is strictly dependent on p150CAF-1, the largest subunit of chromatin assembly factor 1 (CAF-1), and its ability to interact with HP1α. We find that HP1α depletion severely compromises the recruitment of the DNA damage response (DDR) proteins 53BP1 and RAD51. Moreover, HP1α depletion leads to defects in homologous recombination–mediated repair and reduces cell survival after DNA damage. Collectively, our data reveal that HP1α recruitment at early stages of the DDR involves p150CAF-1 and is critical for proper DNA damage signaling and repair.
Nonzero positive solutions of systems of elliptic boundary value problems
Authors: Lan K.
Published: April 2011

A new result on existence of nonzero positive solutions of systems of second order elliptic boundary value problems is obtained under some sublinear conditions involving the principle eigenvalues of the corresponding linear systems. Results on eigenvalue problems of such elliptic systems are derived and generalize some previous results on the eigenvalue problems of systems of Laplacian elliptic equations. Applications of our results are given to two such systems with specific nonlinearities.
The HrpN Effector of Erwinia amylovora, Which Is Involved in Type III Translocation, Contributes Directly or Indirectly to Callose Elicitation on Apple Leaves
Authors: Boureau Tristan , Siamer Sabrina , Perino Claude , Gaubert Stéphane , Patrit Oriane , Degrave Alexandre , Fagard Mathilde , Chevreau Elisabeth , Barny Marie-Anne
Published: April 2011

Erwinia amylovora is responsible for fire blight of apple and pear trees. Its pathogenicity depends on a type III secretion system (T3SS) mediating the translocation of effectors into the plant cell. The DspA/E effector suppresses callose deposition on apple leaves. We found that E. amylovora and Pseudomonas syringae DC3000 tts mutants or peptide flg22 do not trigger callose deposition as strongly as the dspA/E mutant on apple leaves. This suggests that, on apple leaves, callose deposition is poorly elicited by pathogen-associated molecular patterns (PAMPs) such as flg22 or other PAMPs harbored by tts mutants and is mainly elicited by injected effectors or by the T3SS itself. Callose elicitation partly depends on HrpW because an hrpW-dspA/E mutant elicits lower callose deposition than a dspA/E mutant. Furthermore, an hrpN-dspA/E mutant does not trigger callose deposition, indicating that HrpN is required to trigger this plant defense reaction. We showed that HrpN plays a general role in the translocation process. Thus, the HrpN requirement for callose deposition may be explained by its role in translocation: HrpN could be involved in the translocation of other effectors inducing callose deposition. Furthermore, HrpN may also directly contribute to the elicitation process because we showed that purified HrpN induces callose deposition.
Why genetically modified crops?
Authors: Jones Jonathan D. G.
Published: April 2011

This paper is intended to convey the message of the talk I gave at the Theo Murphy meeting at the Kavli Centre in July 2010. It, like the talk, is polemical, and conveys the exasperation felt by a practitioner of genetically modified (GM) plant science at its widespread misrepresentation. I argue that sustainable intensification of agriculture, using GM as well as other technologies, reduces its environmental impact by reducing pesticide applications and conserving soil carbon by enabling low till methods. Current technologies (primarily insect resistance and herbicide tolerance) have been beneficial. Moreover, the near-term pipeline of new GM methods and traits to enhance our diet, increase crop yields and reduce losses to disease is substantial. It would be perverse to spurn this approach at a time when we need every tool in the toolbox to ensure adequate food production in the short, medium and long term.
Towards sustainable photovoltaics: the search for new materials
Authors: Peter L. M.
Published: April 2011

The opportunities for photovoltaic (PV) solar energy conversion are reviewed in the context of projected world energy demands for the twenty-first century. Conventional single-crystal silicon solar cells are facing increasingly strong competition from thin-film solar cells based primarily on polycrystalline absorber materials, such as cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS). However, if PVs are to make a significant contribution to satisfy global energy requirements, issues of sustainability and cost will need to be addressed with increased urgency. There is a clear need to expand the range of materials and processes that is available for thin-film solar cell manufacture, placing particular emphasis on low-energy processing and sustainable non-toxic raw materials. The potential of new materials is exemplified by copper zinc tin sulphide, which is emerging as a viable alternative to the more toxic CdTe and the more expensive CIGS absorber materials.
How urban societies can adapt to resource shortage and climate change
Authors: Satterthwaite David
Published: April 2011

With more than half the world’s population now living in urban areas and with much of the world still urbanizing, there are concerns that urbanization is a key driver of unsustainable resource demands. Urbanization also appears to contribute to ever-growing levels of greenhouse gas (GHG) emissions. Meanwhile, in much of Africa and Asia and many nations in Latin America and the Caribbean, urbanization has long outstripped local governments’ capacities or willingness to act as can be seen in the high proportion of the urban population living in poor quality, overcrowded, illegal housing lacking provision for water, sanitation, drainage, healthcare and schools. But there is good evidence that urban areas can combine high living standards with relatively low GHG emissions and lower resource demands. This paper draws on some examples of this and considers what these imply for urban policies in a resource-constrained world. These suggest that cities can allow high living standards to be combined with levels of GHG emissions that are much lower than those that are common in affluent cities today. This can be achieved not with an over-extended optimism on what new technologies can bring but mostly by a wider application of what already has been shown to work.
Oil shortages, climate change and collective action
Authors: Newbery David
Published: April 2011

Concerns over future oil scarcity might not be so worrying but for the high carbon content of substitutes, and the limited capacity of the atmosphere to absorb additional CO
2
from burning fuel. The paper argues that the tools of economics are helpful in understanding some of the key issues in pricing fossil fuels, the extent to which pricing can be left to markets, the need for, and design of, international agreements on corrective carbon pricing, and the potential Prisoners’ Dilemma in reaching such agreements, partly mitigated in the case of oil by current taxes and the probable incidence of carbon taxes on the oil price. The ‘Green Paradox’, in which carbon pricing exacerbates climate change, is theoretically possible, but empirically unlikely.
Biomedical and social contributions to sustainability
Authors: Wilmut Ian , Wongtawan Tuempong , Quigley Mindy , Sullivan Gareth
Published: April 2011

Over the past two or three centuries, biomedical advances have provided methods to prevent and treat infectious diseases. These changes have greatly reduced human suffering and enhanced sustainability by allowing people to live longer and healthier lives. The challenge for the coming centuries will be to ensure that these longer, healthier lives are also more productive lives. We must build on the gains of the past by translating new discoveries in regenerative medicine into therapies for degenerative and genetic diseases. Stem cells may be used to identify drugs that prevent the development of symptoms or to replace cells that have either died or lost their physiological function. In the case of genetic diseases, it may be possible to correct the genetic error. While most conditions that might be treated in these ways are common to all communities, some are more prevalent in specific races. Provision of these and other benefits depends not only on attainment of the research objectives, but also upon our ability to make treatment opportunities available throughout both developed and developing communities. The long history of researching and treating infectious diseases shows that it may take many decades to reap the full benefit of the new biological understanding.
Challenges for pharmaceutical industry: new partnerships for sustainable human health
Authors: Hunter Jackie
Published: April 2011

The healthcare burden is increasing in both the developed and the developing world and there is widespread acceptance that the historical pharmaceutical business model is not sustainable. In order to meet the healthcare challenge, companies and academia need to develop new business models to increase the probability of success and decrease the cost of failure. New partnerships have already emerged in the area of neglected diseases and other models for diseases of the developed world are emerging.
Towards a sustainable energy future: realities and opportunities
Authors: Armstrong Lynda
Published: April 2011

My purpose in this paper is threefold. First, I would like to examine why the world needs us to produce more energy. Second, I will look at the range of energy sources available for a sustainable future. A number of myths have grown up around the various energy sources and their relative contribution to addressing the global energy challenge: I will seek to dispel some of those. Third, I want to highlight what I see as an urgent need: for more informed decision making and more action in this complex area.
Morphological differences in parr of Atlantic salmon Salmo salar from three regions in Norway
Authors: Solem Ø. , Berg O. K.
Published: April 2011

Morphological characters were compared in parr (total length 33–166 mm) of Atlantic salmon Salmo salar sampled from eight wild populations in three regions, three in northern, two in the middle and three in southern Norway, covering a distance of 1700 km (from 70° N to 58° N). On the basis of morphological characters 94·6% of the individuals were correctly classified into the three regions. Discrimination between populations within these three regions also had a high degree of correct classification (89·0–95·8%). Principle component analysis identified largest differences to be in head characters, notably eye diameter and jawbone, with the smallest diameter and head size among the northernmost populations. Fish from the southern rivers had a deeper body form whereas fish from the middle region had larger heads and pectoral fins. This illustrates that S. salar already in the early parr stage has morphological traits, which can be used in discrimination between regions and populations and that these differences are discernible in spite of the volume of escaped farmed fish spawning in Norwegian rivers during the past 30 years.
CD133 is a marker of gland‐forming cells in gastric tumors and Sox17 is involved in its regulation
Authors: Fukamachi Hiroshi , Shimada Shu , Ito Kosei , Ito Yoshiaki , Yuasa Yasuhito
Published: April 2011

CD133 is a universal marker of tissue stem/progenitor cells as well as cancer stem cells, but its physiological significance remains to be elucidated. Here we examined the relationship between expression of CD133 and features of gastric epithelial cells, and found that CD133‐positive (CD133[+]) tumor cell lines formed well‐differentiated tumors while CD133‐negative (CD133[−]) lines formed poorly differentiated ones when subcutaneously injected into nude mice. We also found that CD133(+) and CD133(−) cell populations co‐existed in some cell lines. FACS analysis showed that CD133(+) cells were mother cells because CD133(+) cells formed both CD133(+) and CD133(−) cells, but CD133(−) cells did not form CD133(+) cells. In these cell lines, CD133(+) cells formed well‐differentiated tumors while CD133(−) cells formed poorly differentiated ones. In human gastric cancers, CD133 was exclusively expressed on the luminal surface membrane of gland‐forming cells, and it was never found on poorly differentiated diffuse‐type cells. Considering that poorly differentiated tumors often develop from well‐differentiated tumors during tumor progression, these results suggest that loss of expression of CD133 might be related to gastric tumor progression. Microarray analysis showed that CD133(+) cells specifically expressed Sox17, a tumor suppressor in gastric carcinogenesis. Forced expression of SOX17 induced expression of CD133 in CD133(−) cells, and reduction of SOX17 caused by siRNA in CD133(+) cells induced a reduction in the level of CD133. These results indicate that Sox17 might be a key transcription factor controlling CD133 expression, and that it might also play a role in the control of gastric tumor progression. (Cancer Sci 2011; 102: 1313–1321)