bluuebunny/crossref_metadata_2025 huggingface dataset:
Sulfur 1s near-edge x-ray absorption fine structure (NEXAFS) of thiol and thioether compounds
Authors: Behyan Shirin , Hu Yongfeng , Urquhart Stephen G.
Published: June 2011

The speciation and quantification of sulfur species based on sulfur K-edge x-ray absorption spectroscopy is of wide interest, particularly for biological and petroleum science. These tasks require a firm understanding of the sulfur 1s near-edge x-ray absorption fine structure (NEXAFS) spectra of relevant species. To this end, we have examined the gas phase sulfur 1s NEXAFS spectra of a group of simple thiol and thioether compounds. These high-resolution gas phase spectra are free of solid-state broadening, charging, and saturation effects common in the NEXAFS spectra of solids. These experimental data have been further analyzed with the aid of improved virtual orbital Hartree–Fock ab initio calculations. The experimental sulfur 1s NEXAFS spectra show fine features predicted by calculation, and the combination of experiment and calculation has been used to improve assignment of spectroscopic features relevant for the speciation and quantification of the sulfur compounds.
The oxidation of Al atoms embedded in water clusters: A dynamical study of the relay (Grotthuss-like) mechanism
Authors: Álvarez-Barcia S. , Flores J. R.
Published: June 2011

The dynamics of the oxidation of micro-hydrated Al atoms has been studied taking into account the effect of tunneling. Neutral aggregates of the type Al·(H2O)n, n = {1–8} and Al·(H2O)n·m(H2O) have been considered, where Al·(H2O)n has been treated by density functional theory (DFT) theory and the other m = {52, 56} waters have been represented by an effective fragment potential (EFP). The results indicate that oxidation may take place quite fast by a relay-type mechanism occurring within a ring of water molecules which involves the Al atom, in which a H atom is transferred. The inclusion of water molecules to form the ring from n = 1 to n = 3 tends to reduce the barrier height but results in lower tunneling transmission factors. The “optimal” ring is the one containing three waters; the four-water one produces lower rates. Coordination of additional waters to Al forming a second ring does not appear to have a further catalytic effect. The inclusion of many additional waters as EFPs, to simulate larger aggregates, increases the rates significantly. The extrapolation to bulk conditions and the possible impact of ionic mechanisms have also been discussed.
A simply designed cell for thermal conductivity measurements of low vapor-pressure liquids
Authors: Bonetti M. , Nakamae S. , Roger M.
Published: June 2011

We have built a simply designed cell for the measurement of the thermal conductivity of liquids under steady state conditions from room temperature to about 60 °C. Thermal conductivities measured in the range between 0.2 and 0.7 Wm−1 K−1 show deviations of a few percent from reference thermal-conductivity data. The cell is made of two concentric parallel plates separated by a 0.44 mm thick sample. It is easily assembled and loaded with the sample for a quick and routine use.
Sensitive Faraday rotation measurement with auto-balanced photodetection
Authors: Chang Chia-Yu , Wang Likarn , Shy Jow-Tsong , Lin Chu-En , Chou Chien
Published: June 2011

A magneto-optic polarimetry based on auto-balanced photodetection is investigated. In this experiment, a commercial auto-balanced photoreceiver is adopted to measure the Faraday rotation of air. With a proper setup to utilize its noise cancellation capability, the measurement can be flexible and sensitive. The angular sensitivity is 2.99×10−8 rad Hz−1/2, which is about 2.7 times the shot noise limit. The measured Verdet constant of air is +1.39×10−9 rad G−1 cm−1 at 634.8 nm. Significantly we applied a small AC current to induce the magnetic field, so there was no heating in the coil. In addition, a double current modulation scheme was used to demonstrate that there was no zero drift and amplifier instability in the measurement. The possibility of improvement of the angular sensitivity and the potential applications are also discussed.
Omnidirectional absorption enhancement in hybrid waveguide-plasmon system
Authors: Zhang Jing , Bai Wenli , Cai Likang , Chen Xi , Song Guofeng , Gan Qiaoqiang
Published: June 2011

We investigate the omnidirectional absorption enhancement induced by the excitation of the localized surface plasmon in the hybrid system consisting of a gold nanowire array embedded in a slab waveguide. Assisted by the waveguide layer, the hybrid system can support the localized waveguide-plasmon resonances for a wide range of incident angles. Theoretical and experimental results are both presented to demonstrate the omnidirectional absorption enhancement which could find important applications on plasmonic-assisted photovoltaic devices or photodetectors.
Observation of coherently enhanced tunable narrow-band terahertz transition radiation from a relativistic sub-picosecond electron bunch train
Authors: Piot P. , Sun Y.-E , Maxwell T. J. , Ruan J. , Lumpkin A. H. , Rihaoui M. M. , Thurman-Keup R.
Published: June 2011

We experimentally demonstrate the production of narrow-band (δf/f≈20% at f≈0.5 THz) transition radiation with tunable frequency over [0.37, 0.86] THz. The radiation is produced as a train of sub-picosecond relativistic electron bunches transits at the vacuum-aluminum interface of an aluminum converter screen. The bunch train is generated via a transverse-to-longitudinal phase space exchange technique. We also show a possible application of modulated beams to extend the dynamical range of a popular bunch length diagnostic technique based on the spectral analysis of coherent radiation.
Performing Research Capability Building in New Zealand's Social Sciences: Capacity–Capability Insights from Exploring the Work of BRCSS's ‘sustainability’ Theme, 2004–09
Authors: Le Heron Erena , Le Heron Richard , Lewis Nick
Published: June 2011

Many governments are seeking to ‘mature’ social science through research capability. The Building Research Capability in the Social Sciences (BRCSS) experiment gave New Zealand's social science community a chance to mature itself through capability building. We examine the emergence of BRCSS's ‘sustainability’ research theme. Selected as one of five key research themes because of its public good investment priority and the level of social science interest, the meanings and purpose of the theme emerged in practice. We present the theme as a series of performances through the life of BRCSS, itself an emergent assemblage of changing theoretical projects, research and policy priorities, and research capability. Reading the experiment reflexively from the inside, we consolidate the experience of performing new research practices into existence to reconceptualise and theorise research capability. We conclude that any fresh engagement in substantive issues must confront how knowledge production might be done differently, and that experimentation around capacities and capabilities for knowledge production begins to open up substantive concerns in fresh and generative ways.
‘We're a Rich City with Poor People’: Municipal Strategies of New-Build Gentrification in Rotterdam and Glasgow
Authors: Doucet Brian , van Kempen Ronald , van Weesep Jan
Published: June 2011

Gentrification—the creation of affluent space—has evolved from a sporadic and spontaneous process focusing on individual households into a municipal goal in and of itself, either in existing neighbourhoods, or in new-build developments. This is increasingly being done through flagship new-build gentrification projects. This paper examines why and how this strategy has been implemented in Rotterdam and Glasgow through a study of two projects: the Kop van Zuid and Glasgow Harbour. By using a comparative approach, it sheds further light on reasons for pursuing this municipal goal, and examines how large new-build flagship gentrification is used to help realise these aims. It reveals a discourse in which the rationale of this policy is linked to the attraction and retention of affluent households, a lack of which, it is believed by policy makers, hurts urban competitiveness. It shows that this discourse is present and influences these two projects despite the different compositions of actors involved (the municipally led Kop van Zuid and the developer-led Glasgow Harbour). However, the ways in which this goal is implemented vary according to the local contexts and the different roles ascribed to the various stakeholders.
When Local Interaction Does Not Suffice: Sources of Firm Innovation in Urban Norway
Authors: Fitjar Rune Dahl , Rodríguez-Pose Andrés
Published: June 2011

The geographical sources of innovation of firms have been hotly debated. While the traditional view is that physical proximity within city-regions is key for the innovative capacity of firms, the literature on ‘global pipelines’ has been stressing the importance of establishing communication channels to the outside world. This paper uses a specifically tailored survey of the level of innovation of 1604 firms of more than ten employees located in the five largest Norwegian city-regions (Oslo, Bergen, Stavanger, Trondheim, and Kristiansand) in order to determine (a) the geographical dimension of the sources of innovation, and (b) the factors behind the propensity to innovate in Norwegian firms. The results stress that, while interaction with a multitude of partners within Norwegian city-regions or with other national partners has a negligible effect on firm innovation, those firms with a greater diversity of international partners tend to innovate more and introduce more radical innovations. The results also highlight that the roots of this greater innovative capacity lie in a combination of firm (size of firms, share of foreign ownership, and sector) and cultural (the level of open-mindedness of managers) characteristics.
Membrane tension regulates motility by controlling lamellipodium organization
Authors: Batchelder Ellen L. , Hollopeter Gunther , Campillo Clément , Mezanges Xavier , Jorgensen Erik M. , Nassoy Pierre , Sens Pierre , Plastino Julie
Published: June 2011

Many cell movements proceed via a crawling mechanism, where polymerization of the cytoskeletal protein actin pushes out the leading edge membrane. In this model, membrane tension has been seen as an impediment to filament growth and cell motility. Here we use a simple model of cell motility, the
Caenorhabditis elegans
sperm cell, to test how membrane tension affects movement and cytoskeleton dynamics. To enable these analyses, we create transgenic worm strains carrying sperm with a fluorescently labeled cytoskeleton. Via osmotic shock and deoxycholate treatments, we relax or tense the cell membrane and quantify apparent membrane tension changes by the membrane tether technique. Surprisingly, we find that membrane tension reduction is correlated with a decrease in cell displacement speed, whereas an increase in membrane tension enhances motility. We further demonstrate that apparent polymerization rates follow the same trends. We observe that membrane tension reduction leads to an unorganized, rough lamellipodium, composed of short filaments angled away from the direction of movement. On the other hand, an increase in tension reduces lateral membrane protrusions in the lamellipodium, and filaments are longer and more oriented toward the direction of movement. Overall we propose that membrane tension optimizes motility by streamlining polymerization in the direction of movement, thus adding a layer of complexity to our current understanding of how membrane tension enters into the motility equation.
Taste-independent detection of the caloric content of sugar in
Drosophila
Authors: Dus Monica , Min SooHong , Keene Alex C. , Lee Ga Young , Suh Greg S. B.
Published: June 2011

Feeding behavior is influenced primarily by two factors: nutritional needs and food palatability. However, the role of food deprivation and metabolic needs in the selection of appropriate food is poorly understood. Here, we show that the fruit fly,
Drosophila melanogaster
, selects calorie-rich foods following prolonged food deprivation in the absence of taste-receptor signaling. Flies mutant for the sugar receptors Gr5a and Gr64a cannot detect the taste of sugar, but still consumed sugar over plain agar after 15 h of starvation. Similarly,
pox-neuro
mutants that are insensitive to the taste of sugar preferentially consumed sugar over plain agar upon starvation. Moreover, when given a choice between metabolizable sugar (sucrose or
d
-glucose) and nonmetabolizable (zero-calorie) sugar (sucralose or
l
-glucose), starved
Gr5a; Gr64a
double mutants preferred metabolizable sugars. These findings suggest the existence of a taste-independent metabolic sensor that functions in food selection. The preference for calorie-rich food correlates with a decrease in the two main hemolymph sugars, trehalose and glucose, and in glycogen stores, indicating that this sensor is triggered when the internal energy sources are depleted. Thus, the need to replenish depleted energy stores during periods of starvation may be met through the activity of a taste-independent metabolic sensing pathway.
Myosin-II inhibition and soft 2D matrix maximize multinucleation and cellular projections typical of platelet-producing megakaryocytes
Authors: Shin Jae-Won , Swift Joe , Spinler Kyle R. , Discher Dennis E.
Published: June 2011

Cell division, membrane rigidity, and strong adhesion to a rigid matrix are all promoted by myosin-II, and so multinucleated cells with distended membranes—typical of megakaryocytes (MKs)—seem predictable for low myosin activity in cells on soft matrices. Paradoxically, myosin mutations lead to defects in MKs and platelets. Here, reversible inhibition of myosin-II is sustained over several cell cycles to produce 3- to 10-fold increases in polyploid MK and a number of other cell types. Even brief inhibition generates highly distensible, proplatelet-like projections that fragment readily under shear, as seen in platelet generation from MKs in vivo. The effects are maximized with collagenous matrices that are soft and 2D, like the perivascular niches in marrow rather than 3D or rigid, like bone. Although multinucleation of other primary hematopoietic lineages helps to generalize a failure-to-fission mechanism, lineage-specific signaling with increased polyploidy proves possible and novel with phospho-regulation of myosin-II heavy chain. Label-free mass spectrometry quantitation of the MK proteome uses a unique proportional peak fingerprint (ProPF) analysis to also show upregulation of the cytoskeletal and adhesion machinery critical to platelet function. Myosin-inhibited MKs generate more platelets in vitro and also in vivo from the marrows of xenografted mice, while agonist stimulation activates platelet spreading and integrin αIIbβ3. Myosin-II thus seems a central, matrix-regulated node for MK-poiesis and platelet generation.
Overlapping activation-induced cytidine deaminase hotspot motifs in Ig class-switch recombination
Authors: Han Li , Masani Shahnaz , Yu Kefei
Published: June 2011

Ig class-switch recombination (CSR) is directed by the long and repetitive switch regions and requires activation-induced cytidine deaminase (AID). One of the conserved switch-region sequence motifs (AGCT) is a preferred site for AID-mediated DNA-cytosine deamination. By using somatic gene targeting and recombinase-mediated cassette exchange, we established a cell line-based CSR assay that allows manipulation of switch sequences at the endogenous locus. We show that AGCT is only one of a family of four WGCW motifs in the switch region that can facilitate CSR. We go on to show that it is the overlap of AID hotspots at WGCW sites on the top and bottom strands that is critical. This finding leads to a much clearer model for the difference between CSR and somatic hypermutation.
Sugar-regulated cation channel formed by an insect gustatory receptor
Authors: Sato Koji , Tanaka Kana , Touhara Kazushige
Published: June 2011

Insects sense the taste of foods and toxic compounds in their environment through the gustatory system. Genetic studies using fruit flies have suggested that putative seven-transmembrane gustatory receptors (Grs) expressed in gustatory sensory neurons are required for responses to specific tastants. We reconstituted sugar responses of
Bombyx mori
Gr-9 (BmGr-9), a silkworm Gr, in two heterologous expression systems.
Xenopus
oocytes or HEK293T cells expressing BmGr-9 selectively responded to
d
-fructose with an influx of extracellular Ca
2+
and a nonselective cation current conductance in a G protein-independent manner. Outside-out patch-clamp recording of BmGr-9–expressing cell membranes provides evidence supporting the hypothesis that BmGr-9 constitutes a ligand-gated ion channel. The fructose-activated current associated with BmGr-9 was suppressed by other hexoses, including glucose and sorbose. The activation and inhibition of insect Gr ion channels may be the molecular basis for the decoding system that discriminates subtle differences in sweet taste. Finally,
Drosophila melanogaster
Gr43a (DmGr43a), a BmGr-9 ortholog, also responded to
d
-fructose, suggesting that DmGr43a relatives appear to compose the family of fructose receptors.
Epidermal ablation of Dlx3 is linked to IL-17–associated skin inflammation
Authors: Hwang Joonsung , Kita Ryosuke , Kwon Hyouk-Soo , Choi Eung Ho , Lee Seung Hun , Udey Mark C. , Morasso Maria I.
Published: June 2011

In an effort to understand the role of Distal-less 3 (Dlx3) in cutaneous biology and pathophysiology, we generated and characterized a mouse model with epidermal ablation of Dlx3. K14cre;Dlx3
Kin/f
mice exhibited epidermal hyperproliferation and abnormal differentiation of keratinocytes. Results from subsequent analyses revealed cutaneous inflammation that featured accumulation of IL-17–producing CD4
+
T, CD8
+
T, and γδ T cells in the skin and lymph nodes of K14cre;Dlx3
Kin/f
mice. The gene expression signature of K14cre;Dlx3
Kin/f
skin shared features with lesional psoriatic skin, and Dlx3 expression was markedly and selectively decreased in psoriatic skin. Interestingly, cultured Dlx3 null keratinocytes triggered cytokine production that is potentially linked to inflammatory responses in K14cre;Dlx3
Kin/f
mice. Thus, Dlx3 ablation in epidermis is linked to altered epidermal differentiation, barrier development, and IL-17–associated skin inflammation. This model provides a platform that will allow the systematic exploration of the contributions of keratinocytes to cutaneous inflammation.
Many-body interactions in quasi-freestanding graphene
Authors: Siegel David A. , Park Cheol-Hwan , Hwang Choongyu , Deslippe Jack , Fedorov Alexei V. , Louie Steven G. , Lanzara Alessandra
Published: June 2011

The Landau–Fermi liquid picture for quasiparticles assumes that charge carriers are dressed by many-body interactions, forming one of the fundamental theories of solids. Whether this picture still holds for a semimetal such as graphene at the neutrality point, i.e., when the chemical potential coincides with the Dirac point energy, is one of the long-standing puzzles in this field. Here we present such a study in quasi-freestanding graphene by using high-resolution angle-resolved photoemission spectroscopy. We see the electron–electron and electron–phonon interactions go through substantial changes when the semimetallic regime is approached, including renormalizations due to strong electron–electron interactions with similarities to marginal Fermi liquid behavior. These findings set a new benchmark in our understanding of many-body physics in graphene and a variety of novel materials with Dirac fermions.
Gene flow increases fitness at the warm edge of a species’ range
Authors: Sexton Jason P. , Strauss Sharon Y. , Rice Kevin J.
Published: June 2011

According to theory, gene flow to marginal populations may stall or aid adaptation at range limits by swamping peripheral populations with maladaptive gene flow or by enhancing genetic variability and reducing inbreeding depression, respectively. We tested these contrasting predictions by manipulating patterns of gene flow of the annual plant,Mimulus laciniatus, at its warm range limit. Gene flow was experimentally applied by using crosses within warm-limit populations (selfed and outcrossed), between warm-limit populations, and between warm-limit and central range populations across two elevational transects. We measured the fitness of offspring in a common garden at the warm-edge species range limit. All sources of gene flow increased seedling emergence at the range limit, suggesting local inbreeding depression at both range limit populations; however, lifetime reproductive success only increased significantly when pollen originated from another warm-limit population. Center–to–warm-edge gene flow was maladaptive by delaying time to development at this warm, fast-drying range limit, whereas edge-to-edge gene flow hastened emergence time and time to reproduction. By empirically testing theory on the effects of gene flow on the formation of geographic range limits, we find benefits of gene flow among populations to be greatest when gene flow is between populations occupying the same range limit. Our results emphasize the overlooked importance of gene flow among populations occurring near the same range limit and highlight the potential for prescriptive gene flow as a conservation option for populations at risk from climate change.
Statistical structure of host–phage interactions
Authors: Flores Cesar O. , Meyer Justin R. , Valverde Sergi , Farr Lauren , Weitz Joshua S.
Published: June 2011

Interactions between bacteria and the viruses that infect them (i.e., phages) have profound effects on biological processes, but despite their importance, little is known on the general structure of infection and resistance between most phages and bacteria. For example, are bacteria–phage communities characterized by complex patterns of overlapping exploitation networks, do they conform to a more ordered general pattern across all communities, or are they idiosyncratic and hard to predict from one ecosystem to the next? To answer these questions, we collect and present a detailed metaanalysis of 38 laboratory-verified studies of host–phage interactions representing almost 12,000 distinct experimental infection assays across a broad spectrum of taxa, habitat, and mode of selection. In so doing, we present evidence that currently available host–phage infection networks are statistically different from random networks and that they possess a characteristic nested structure. This nested structure is typified by the finding that hard to infect bacteria are infected by generalist phages (and not specialist phages) and that easy to infect bacteria are infected by generalist and specialist phages. Moreover, we find that currently available host–phage infection networks do not typically possess a modular structure. We explore possible underlying mechanisms and significance of the observed nested host–phage interaction structure. In addition, given that most of the available host–phage infection networks examined here are composed of taxa separated by short phylogenetic distances, we propose that the lack of modularity is a scale-dependent effect, and then, we describe experimental studies to test whether modular patterns exist at macroevolutionary scales.
OUROBOROS
is a master regulator of the gametophyte to sporophyte life cycle transition in the brown alga
Ectocarpus
Authors: Coelho Susana M. , Godfroy Olivier , Arun Alok , Le Corguillé Gildas , Peters Akira F. , Cock J. Mark
Published: June 2011

The brown alga
Ectocarpus siliculosus
has a haploid–diploid life cycle that involves an alternation between two distinct generations, the sporophyte and the gametophyte. We describe a mutant,
ouroboros
(
oro
), in which the sporophyte generation is converted into a functional, gamete-producing gametophyte. The life history of the mutant thus consists of a continuous reiteration of the gametophyte generation. The
oro
mutant exhibited morphological features typical of the gametophyte generation and accumulated transcripts of gametophyte generation marker genes. Genetic analysis showed that
oro
behaved as a single, recessive, Mendelian locus that was unlinked to the
IMMEDIATE UPRIGHT
locus, which has been shown to be necessary for full expression of the sporophyte developmental program. The data presented here indicate that
ORO
is a master regulator of the gametophyte-to-sporophyte life cycle transition and, moreover, that
oro
represents a unique class of homeotic mutation that results in switching between two developmental programs that operate at the level of the whole organism.
Myosin VIIa and sans localization at stereocilia upper tip-link density implicates these Usher syndrome proteins in mechanotransduction
Authors: Grati M’hamed , Kachar Bechara
Published: June 2011

In the most accepted model for hair cell mechanotransduction, a cluster of myosin motors located at the stereocilia upper tip-link density (UTLD) keeps the tip-link under tension at rest. Both myosin VIIa (MYO7A) and myosin 1c have been implicated in mechanotransduction based on functional studies. However, localization studies are conflicting, leaving open the question of which myosin localizes at the UTLD and generates the tip-link resting tension. Using immunofluorescence, we now show that MYO7A and sans, a MYO7A-interacting protein, cluster at the UTLD. Analysis of the immunofluorescence intensity indicates that eight or more MYO7A molecules are present at each UTLD, consistent with a direct role for MYO7A in maintaining tip-link tension. MYO7A and sans localization at the UTLD is confirmed by transfection of hair cells with GFP-tagged constructs for these proteins. Cotransfection studies in a heterologous system show that MYO7A, sans, and the UTLD protein harmonin-b form a tripartite complex and that each protein is capable of interacting with one another independently. We propose that MYO7A, sans, and harmonin-b form the core components of the UTLD molecular complex. In this complex, MYO7A is likely the motor element that pulls on CDH23 to exert tension on the tip-link.
Dehydro-α-lapachone, a plant product with antivascular activity
Authors: Garkavtsev Igor , Chauhan Vikash P. , Wong Hon Kit , Mukhopadhyay Arpita , Glicksman Marcie A. , Peterson Randall T. , Jain Rakesh K.
Published: June 2011

Antivascular agents have become a standard of treatment for many malignancies. However, most of them target the VEGF pathway and lead to refractoriness. To improve the diversity of options for antivascular therapy, we applied a high-throughput screen for small molecules targeting cell adhesion. We then assayed the resulting antiadhesion hits in a transgenic zebrafish line with endothelial expression of EGFP (

Tg(fli1:EGFP)
y1

) to identify nontoxic molecules with antivascular activity selective to neovasculature. This screen identified dehydro-α-lapachone (DAL), a natural plant product. We found that DAL inhibits vessel regeneration, interferes with vessel anastomosis, and limits plexus formation in zebrafish. Furthermore, DAL induces vascular pruning and growth delay in orthotopic mammary tumors in mice. We show that DAL targets cell adhesion by promoting ubiquitination of the Rho-GTPase Rac1, which is frequently up-regulated in many different cancers.
Three-dimensional nanometer-scale optical cavities of indefinite medium
Authors: Yao Jie , Yang Xiaodong , Yin Xiaobo , Bartal Guy , Zhang Xiang
Published: June 2011

Miniaturization of optical cavities has numerous advantages for enhancing light–matter interaction in quantum optical devices, low-threshold lasers with minimal power consumption, and efficient integration of optoelectronic devices at large scale. However, the realization of a truly nanometer-scale optical cavity is hindered by the diffraction limit of the nature materials. In addition, the scaling of the photon life time with the cavity size significantly
reduces
the quality factor of small cavities. Here we theoretically present an approach to achieve ultrasmall optical cavities using indefinite medium with hyperbolic dispersion, which allows propagation of electromagnetic waves with wave vectors much larger than those in vacuum enabling extremely small 3D cavity down to (
λ
/20)
3
. These cavities exhibit size-independent resonance frequencies and anomalous scaling of quality factors in contrast to the conventional cavities, resulting in nanocavities with both high
Q
/
V

m

ratio and broad bandwidth.
Habitat fragmentation reduces nest survival in an Afrotropical bird community in a biodiversity hotspot
Authors: Newmark William D. , Stanley Thomas R.
Published: June 2011

Ecologists have long hypothesized that fragmentation of tropical landscapes reduces avian nest success. However, this hypothesis has not been rigorously assessed because of the difficulty of finding large numbers of well-hidden nests in tropical forests. Here we report that in the East Usambara Mountains in Tanzania, which are part of the Eastern Arc Mountains, a global biodiversity hotspot, that daily nest survival rate and nest success for seven of eight common understory bird species that we examined over a single breeding season were significantly lower in fragmented than in continuous forest, with the odds of nest failure for these seven species ranging from 1.9 to 196.8 times higher in fragmented than continuous forest. Cup-shaped nests were particularly vulnerable in fragments. We then examined over six breeding seasons and 14 study sites in a multivariable survival analysis the influence of landscape structure and nest location on daily nest survival for 13 common species representing 1,272 nests and four nest types (plate, cup, dome, and pouch). Across species and nest types, area, distance of nest to edge, and nest height had a dominant influence on daily nest survival, with area being positively related to nest survival and distance of nest to edge and nest height being both positively and negatively associated with daily nest survival. Our results indicate that multiple environmental factors contribute to reduce nest survival within a tropical understory bird community in a fragmented landscape and that maintaining large continuous forest is important for enhancing nest survival for Afrotropical understory birds.
Highly selective synthesis of conjugated dienoic and trienoic esters via alkyne elementometalation–Pd-catalyzed cross-coupling
Authors: Wang Guangwei , Mohan Swathi , Negishi Ei-ichi
Published: June 2011

All four stereoisomers (
7
–
10
) of ethyl undeca-2,4-dienoate were prepared in ≥98% isomeric purity by Pd-catalyzed alkenylation (Negishi coupling) using ethyl (
E
)- and (
Z
)-
β
-bromoacrylates. Although the stereoisomeric purity of the 2
Z
,4
E
-isomer (
8
) prepared by Suzuki coupling using conventional alkoxide and carbonate bases was ≤ 95%, as reported earlier, the use of CsF or

n

Bu
4
NF as a promoter base has now been found to give all of
7
–
10
in ≥98% selectivity. Other widely known methods reveal considerable limitations. Heck alkenylation was satisfactory for the syntheses of the 2
E
,4
E
and 2
E
,4
Z
isomers of ≥98% purity, but the purity of the 2
Z
,4
E
isomer was ≤ 95%. Mutually complementary Horner–Wadsworth–Emmons and Still–Gennari (SG) olefinations are also of considerably limited scopes. Neither 2
E
,4
Z
nor 2
Z
,4
Z
isomer is readily prepared in ≥90% selectivity. In addition to (2
Z
,4
E
)-dienoic esters, some (2
Z
,4
E
,6
E
)- and (2
Z
,4
E
,6
Z
)-trienoic esters have been prepared in ≥98% selectivity by a newly devised Pd-catalyzed alkenylation–SG olefination tandem process. As models for conjugated higher oligoenoic esters, all eight stereoisomers for ethyl trideca-2,4,6-trienoate (
23
–
30
) have been prepared in ≥98% overall selectivity.
Cyclin D1 promotes neurogenesis in the developing spinal cord in a cell cycle-independent manner
Authors: Lukaszewicz Agnès I. , Anderson David J.
Published: June 2011

Neural stem and progenitor cells undergo an important transition from proliferation to differentiation in the G1 phase of the cell cycle. The mechanisms coordinating this transition are incompletely understood. Cyclin D proteins promote proliferation in G1 and typically are down-regulated before differentiation. Here we show that motoneuron progenitors in the embryonic spinal cord persistently express Cyclin D1 during the initial phase of differentiation, while down-regulating Cyclin D2. Loss-of-function and gain-of-function experiments indicate that Cyclin D1 (but not D2) promotes neurogenesis in vivo, a role that can be dissociated from its cell cycle function. Moreover, reexpression of Cyclin D1 can restore neurogenic capacity to D2-expressing glial-restricted progenitors. The neurogenic function of Cyclin D1 appears to be mediated, directly or indirectly, by Hes6, a proneurogenic basic helic-loop-helix transcription factor. These data identify a cell cycle-independent function for Cyclin D1 in promoting neuronal differentiation, along with a potential genetic pathway through which this function is exerted.
Lte1 promotes mitotic exit by controlling the localization of the spindle position checkpoint kinase Kin4
Authors: Falk Jill E. , Chan Leon Y. , Amon Angelika
Published: June 2011

For a daughter cell to receive a complete genomic complement, it is essential that the mitotic spindle be positioned accurately within the cell. In budding yeast, a signaling system known as the spindle position checkpoint (SPOC) monitors spindle position and regulates the activity of the mitotic exit network (MEN), a GTPase signaling pathway that promotes exit from mitosis. The protein kinase Kin4 is a central component of the spindle position checkpoint. Kin4 primarily localizes to the mother cell and associates with spindle pole bodies (SPBs) located in the mother cell to inhibit MEN signaling. In contrast, the kinase does not associate with the SPB in the bud. Thus, only when a MEN bearing SPB leaves the mother cell and the spindle is accurately positioned along the mother–bud axis can MEN signaling occur and cell division proceed. Here, we describe a mechanism ensuring that Kin4 only associates with mother cell-located SPBs. The bud-localized MEN regulator Lte1, whose molecular function has long been unclear, prevents Kin4 that escapes into the bud from associating with SPBs in the daughter cell.
Suppression of immune responses by nonimmunogenic oligodeoxynucleotides with high affinity for high-mobility group box proteins (HMGBs)
Authors: Yanai Hideyuki , Chiba Shiho , Ban Tatsuma , Nakaima Yukana , Onoe Takashi , Honda Kenya , Ohdan Hideki , Taniguchi Tadatsugu
Published: June 2011

The activation of innate immune responses by nucleic acids is central to the generation of host responses against pathogens; however, nucleic acids can also trigger the development and/or exacerbation of pathogenic responses such as autoimmunity. We previously demonstrated that the selective activation of nucleic acid-sensing cytosolic and Toll-like receptors is contingent on the promiscuous sensing of nucleic acids by high-mobility group box proteins (HMGBs). From this, we reasoned that nonimmunogenic nucleotides with high-affinity HMGB binding may function as suppressing agents for HMGB-mediated diseases, particularly those initiated and/or exacerbated by nucleic acids. Here we characterize an array of HMGB-binding, nonimmunogenic oligodeoxynucleotides (ni-ODNs). Interestingly, we find that binding affinity is rather independent of nucleotide sequence, but is instead dependent on length and structure of the deoxyribose backbone. We further show that these ni-ODNs can strongly suppress the activation of innate immune responses induced by both classes of nucleic acid-sensing receptors. We also provide evidence for the suppressive effect of an ni-ODN, termed ISM ODN, on the induction of adaptive immune responses and in mouse models of sepsis and autoimmunity. We discuss our findings in relation to the critical role of HMGBs in initiating immune responses and the possible use of these ni-ODNs in therapeutic interventions.
Naturally transmitted segmented filamentous bacteria segregate with diabetes protection in nonobese diabetic mice
Authors: Kriegel Martin A. , Sefik Esen , Hill Jonathan A. , Wu Hsin-Jung , Benoist Christophe , Mathis Diane
Published: June 2011

Vertebrates typically harbor a rich gastrointestinal microbiota, which has coevolved with the host over millennia and is essential for several host physiological functions, in particular maturation of the immune system. Recent studies have highlighted the importance of a single bacterial species, segmented filamentous bacteria (SFB), in inducing a robust T-helper cell type 17 (Th17) population in the small-intestinal lamina propria (SI-LP) of the mouse gut. Consequently, SFB can promote IL-17–dependent immune and autoimmune responses, gut-associated as well as systemic, including inflammatory arthritis and experimental autoimmune encephalomyelitis. Here, we exploit the incomplete penetrance of SFB colonization of NOD mice in our animal facility to explore its impact on the incidence and course of type 1 diabetes in this prototypical, spontaneous model. There was a strong cosegregation of SFB positivity and diabetes protection in females, but not in males, which remained relatively disease-free regardless of the SFB status. In contrast, insulitis did not depend on SFB colonization. SFB-positive, but not SFB-negative, females had a substantial population of Th17 cells in the SI-LP, which was the only significant, repeatable difference in the examined T-cell compartments of the gut, pancreas, or systemic lymphoid tissues. Th17-signature transcripts dominated the very limited SFB-induced molecular changes detected in SI-LP CD4
+
T cells. Thus, a single bacterium, and the gut immune system alterations associated with it, can either promote or protect from autoimmunity in predisposed mouse models, probably reflecting their variable dependence on different Th subsets.
Structural and functional diversity of cadherin at the adherens junction
Authors: Oda Hiroki , Takeichi Masatoshi
Published: June 2011

Adhesion between cells is essential to the evolution of multicellularity. Indeed, morphogenesis in animals requires firm but flexible intercellular adhesions that are mediated by subcellular structures like the adherens junction (AJ). A key component of AJs is classical cadherins, a group of transmembrane proteins that maintain dynamic cell–cell associations in many animal species. An evolutionary reconstruction of cadherin structure and function provides a comprehensive framework with which to appreciate the diversity of morphogenetic mechanisms in animals.
miR669a and miR669q prevent skeletal muscle differentiation in postnatal cardiac progenitors
Authors: Crippa Stefania , Cassano Marco , Messina Graziella , Galli Daniela , Galvez Beatriz G. , Curk Tomaz , Altomare Claudia , Ronzoni Flavio , Toelen Jaan , Gijsbers Rik , Debyser Zeger , Janssens Stefan , Zupan Blaz , Zaza Antonio , Cossu Giulio , Sampaolesi Maurilio
Published: June 2011

Postnatal heart stem and progenitor cells are a potential therapeutic tool for cardiomyopathies, but little is known about the mechanisms that control cardiac differentiation. Recent work has highlighted an important role for microribonucleic acids (miRNAs) as regulators of cardiac and skeletal myogenesis. In this paper, we isolated cardiac progenitors from neonatal β-sarcoglycan (Sgcb)–null mouse hearts affected by dilated cardiomyopathy. Unexpectedly, Sgcb-null cardiac progenitors spontaneously differentiated into skeletal muscle fibers both in vitro and when transplanted into regenerating muscles or infarcted hearts. Differentiation potential correlated with the absence of expression of a novel miRNA, miR669q, and with down-regulation of miR669a. Other miRNAs are known to promote myogenesis, but only miR669a and miR669q act upstream of myogenic regulatory factors to prevent myogenesis by directly targeting the MyoD 3′ untranslated region. This finding reveals an added level of complexity in the mechanism of the fate choice of mesoderm progenitors and suggests that using endogenous cardiac stem cells therapeutically will require specially tailored procedures for certain genetic diseases.
SPARC promotes pericyte recruitment via inhibition of endoglin-dependent TGF-β1 activity
Authors: Rivera Lee B. , Brekken Rolf A.
Published: June 2011

Pericytes migrate to nascent vessels and promote vessel stability. Recently, we reported that secreted protein acidic and rich in cysteine (SPARC)–deficient mice exhibited decreased pericyte-associated vessels in an orthotopic model of pancreatic cancer, suggesting that SPARC influences pericyte behavior. In this paper, we report that SPARC promotes pericyte migration by regulating the function of endoglin, a TGF-β1 accessory receptor. Primary SPARC-deficient pericytes exhibited increased basal TGF-β1 activity and decreased cell migration, an effect blocked by inhibiting TGF-β1. Furthermore, TGF-β–mediated inhibition of pericyte migration was dependent on endoglin and αV integrin. SPARC interacted directly with endoglin and reduced endoglin interaction with αV integrin. SPARC deficiency resulted in endoglin-mediated blockade of pericyte migration, aberrant association of endoglin in focal complexes, an increase in αV integrins present in endoglin immunoprecipitates, and enhanced αV integrin–mediated activation of TGF-β. These results demonstrate that SPARC promotes pericyte migration by diminishing TGF-β activity and identify a novel function for endoglin in controlling pericyte behavior.
Cohesin, condensin, and the intramolecular centromere loop together generate the mitotic chromatin spring
Authors: Stephens Andrew D. , Haase Julian , Vicci Leandra , Taylor Russell M. , Bloom Kerry
Published: June 2011

Sister chromatid cohesion provides the mechanistic basis, together with spindle microtubules, for generating tension between bioriented chromosomes in metaphase. Pericentric chromatin forms an intramolecular loop that protrudes bidirectionally from the sister chromatid axis. The centromere lies on the surface of the chromosome at the apex of each loop. The cohesin and condensin structural maintenance of chromosomes (SMC) protein complexes are concentrated within the pericentric chromatin, but whether they contribute to tension-generating mechanisms is not known. To understand how pericentric chromatin is packaged and resists tension, we map the position of cohesin (SMC3), condensin (SMC4), and pericentric LacO arrays within the spindle. Condensin lies proximal to the spindle axis and is responsible for axial compaction of pericentric chromatin. Cohesin is radially displaced from the spindle axis and confines pericentric chromatin. Pericentric cohesin and condensin contribute to spindle length regulation and dynamics in metaphase. Together with the intramolecular centromere loop, these SMC complexes constitute a molecular spring that balances spindle microtubule force in metaphase.
Time-dependent changes in membrane excitability during glucose-induced bursting activity in pancreatic β cells
Authors: Cha Chae Young , Santos Enrique , Amano Akira , Shimayoshi Takao , Noma Akinori
Published: June 2011

In our companion paper, the physiological functions of pancreatic β cells were analyzed with a new β-cell model by time-based integration of a set of differential equations that describe individual reaction steps or functional components based on experimental studies. In this study, we calculate steady-state solutions of these differential equations to obtain the limit cycles (LCs) as well as the equilibrium points (EPs) to make all of the time derivatives equal to zero. The sequential transitions from quiescence to burst–interburst oscillations and then to continuous firing with an increasing glucose concentration were defined objectively by the EPs or LCs for the whole set of equations. We also demonstrated that membrane excitability changed between the extremes of a single action potential mode and a stable firing mode during one cycle of bursting rhythm. Membrane excitability was determined by the EPs or LCs of the membrane subsystem, with the slow variables fixed at each time point. Details of the mode changes were expressed as functions of slowly changing variables, such as intracellular [ATP], [Ca2+], and [Na+]. In conclusion, using our model, we could suggest quantitatively the mutual interactions among multiple membrane and cytosolic factors occurring in pancreatic β cells.
An investigation of the origin of junction magnetoresistance in La0.7Sr0.3MnO3/SiO2/p-Si heterostructures
Authors: Chattopadhyay S , Nath T K
Published: June 2011

A detail experimental investigation on magnetic field-dependent electronic transport across p-silicon (Si)/La0.7Sr0.3MnO3 (LSMO) junction in which the LSMO and silicon are separated by different thin interfacial silicon dioxide (SiO2) layers through in situ fabrication has been reported here. All LSMO/SiO2/Si heterostructures exhibit diode-like behaviour at all temperatures. The ideality factor, reverse saturation current, series resistances and turn-on voltages have been estimated for all the heterojunctions at different operating temperatures. The current–voltage characteristics at all temperatures conclusively show the reasonably high sensitivity of the junction under magnetic field showing reasonably high junction magnetoresistance (JMR ∼ 56% at 120 K). The JMR is positive and strongly depends on temperature and applied forward bias voltages. It is also found that the JMR depends upon the leakage current which is generated due to defects present in the oxide and interfacial layer of such heterostructures.
On self-heating in piezoresistive microcantilevers with short piezoresistor
Authors: Ansari Mohd Zahid , Cho Chongdu
Published: June 2011

This work presents an analytical model for studying the effects of short piezoresistors on self-heating phenomena in piezoresistive microcantilevers. The model is verified using commercial finite element software for predicting the temperature profile in the 4-layer silicon dioxide cantilever with silicon piezoresistor commonly used in biosensors. The numerical analysis involved thermo-electric, thermal and surface-stress studies on the cantilever models. Results show good agreement between analytical and numerical results with average deviation about 3%. Further, the temperatures increase more rapidly with the width than the length of the piezoresistor and narrow piezoresistors are helpful in reducing resistance change due to self-heating.
New proofs and extensions of Sylvester’s and Johnson’s inertia theorems to non-Hermitian matrices
Authors: Kwong Man , Zettl Anton
Published: June 2011

We present a new proof and extension of the classical Sylvester Inertia Theorem to a pair of non-Hermitian matrices which satisfies the property that any real linear combination of the pair has only real eigenvalues. In the proof, we embed the given problem in a one-parameter family of related problems and examine the eigencurves of the family. The proof requires only elementary matrix theory and the Intermediate Value Theorem. The same technique is then used to extend Johnson’s extension of Sylvester’s Theorem on possible values of the inertia of a product of two matrices.