bluuebunny/crossref_metadata_2025 huggingface dataset:
The 11B(3He,n0)13N Reaction
Authors: Davis JR , Din GU
Published: June 2011

The excitation function from 5�0 to 11� 5 MeV and angular distributions at 5� 2, 6� 5, 8� 0, 9�0, 10'0,11�0 and 12�0 MeV have been obtained for the "B(3He,no)13N reaction. "The data were analysed using an incoherent sum of Hauser-Feshbach and DWBA cross sections. Optical model parameters derived from elastic scattering experiments describe the direct reaction component reasonably well.
Observations of Neutral Hydrogen in Bright Southern Galaxies
Authors: Whiteoak JB , Gardner FF
Published: June 2011

Neutral hydrogen was detected in 36 out of 46 galaxies observed at 21 cm wavelength. Eighteen of the larger ones were partially mapped, and estimates of hydrogen and total mass obtained. Without correction for optical depth effects, median values of MH and MH/MT were 7�5 X 109 M0 and 0'07 respectively. These values are similar to the average values found previously for Sc-Scd galaxies (the median morphological type for the sample). The lowest MH/MT ratios were found for NGC253 and 4945, probably because of absorption of the nuclear continuum in addition to any hydrogen self-absorption.
The Molonglo Deep Sky Survey of Radio Sources. I. Declination Zone -20°
Authors: Robertson JG
Published: June 2011

Results of a deep survey made at 408 MHz with the Molonglo cross are given. The catalogue lists positions and flux densities for a total of 373 radio sources, most of which have not previously been catalogued, in a solid angle of 0�0201 Sf. This covers (with some excluded areas) right ascensions 0l h oom-06h 44m and 13h 45m-17h 19m, with a range in declination of 41'. Eighteen contour maps are given of sources that are extended or have very close companions. A thorough error analysis is given, as well as new operational definitions of completeness and reliability. The lower limit of flux density is 88 mJy, which is five times the r.m.s. error. An upper limit of 1000 mJy has also been imposed. Typical errors in positions are 15" at 100 mJy and 6" at 250 mJy.
On Space-like Geodesics in Two Special Gravitational Fields
Authors: Banerjee A , Dutta Choudhury SB
Published: June 2011

Studies are presented of space-like geodesics in the fields of a charged mass point and an uncharged static cylinder. For the first case, it is shown that circular space-like trajectories are unstable in character under radial perturbations for a physically plausible situation (82 < m2). For the second case, it is shown that no trajectories in the r-f/J plane satisfy the conditions of stability.
Australian Journal of Physics Astrophysical Supplement
Authors: E Wright Alan , Savage Ann , Bolton JG
Published: June 2011

A catalogue of 454 radio sources is presented from a 2700 MHz survey of 0�418 sr. The catalogue is essentially complete for sources with S2700 ;> 0�25 Jy, corresponding to a source density of 790 sources per steradian. Flux densities at 5000 MHz were measured for many of the sources including most of the sources with S2700 ;> o� 25 Jy. The catalogue includes the results of the examination of ESO 'quick blue' or SRC I1Ia-J survey plates at the positions of 433 sources.
The Effect of Inelastic Collisions on Diffusion Coefficients for Electron Swarms
Authors: Francey JLA , Jones DA
Published: June 2011

The effect of inelastic collisions on the ratio of the longitudinal to lateral diffusion coefficients for electrons in electrostatic fields in gases is investigated for several different momentum transfer cross sections. The effect of varying both the strength of the inelastic effects and their energy dependence is examined and the results are used to discuss some of the DL/f.l data of Wagner et al. (1967).
Nuclear Structure of 12C from an a-particle Model
Authors: Banerjee SN , Chakrabarti SN
Published: June 2011

The isoscalar levels with 1 = 0+ of the 12C nucleus have been investigated by finite-group theoretical methods using an a-particle model. An estimate has been made of the restoring force parameter in the potential between two a particles from symmetry.
The 35Ar(b+)35Cl Decay and the Anomalous Cabbibo Angle
Authors: White RE , Naylor H
Published: June 2011

The threshold energy for the 35CI(p, n)35 Ar reaction has been measured to be 6943�0 � 1 . 0 keV, the corresponding endpoint energy for the 35Ar(p+)35Cl mirror decay being 4943�4� 1�0 keV.This confirms the value 4941� 6� 1� 7 keV found by Freeman et al. (1969) and invalidates a possible explanation of the anomalous behaviour of the 35 Ar decay.
Neutron Resonance Parameters of 90Zr below 300 KeV
Authors: de L Musgrove AR , Harvey JA , Good WM
Published: June 2011

Transmission data taken at both the 80 and 200 m stations of the Oak Ridge Electron Linear Accelerator have provided resonance parameters for 90Zr to 300 keV bombarding energy. The average s-wave parameters obtained were:  = 8�6�1�6keY and So = (0�S4�0�14)x10-4 , while the average parameters for the two p-wave sequences were: for P1/2,  = 8�6 � 1 . 6 keY and SI = (3�9�1�0)x 10-4 ; for P3/2,  =o4�3�0�S keY and SI = (4�3�0�8)x 10-4 ?
The Chromium Photoneutron Cross Section
Authors: Weise Jeanette , Thompson MN , Shoda K , Tsubota H
Published: June 2011

A high resolution measurement of the total photoneutron cross section of chromium from threshold to 27 MeV has been obtained. The result is compared with an earlier measurement and an interpretation in terms of isospin effects is made.
A Study of the 42Ca(p,?)43Sc Reaction
Authors: Din GU , Heusch B
Published: June 2011

The 42Ca(p, y)43SC reaction has been studied below 2�75 MeV proton bombarding energy. Approximately 100 resonances have been identified and located in the range Ep = 2�00-2�75 MeV. Nine resonances at Ep = 1045, 1201, 1299, 1319, 2038, 2471, 2523, 2643 and 2714 keV for the 42Ca(p, y)43SC reaction were investigated with either a 54 or a 120 cm3 Ge(Li) detector. Single spectra were obtained at each of these resonances, and these were used to derive consistent y ray decay schemes and accurate level energies for the resonant and bound levels of 43Sc. Fifty-two bound levels up to an excitation energy of 4�47 MeV were observed, out of which seventeen new levels have been identified at 2�114,2� 796,2' 846,2' 860,2' 875,3 '160,3' 331,3' 374,3 '463,3;504,3' 645, 3'734,3'757,3'860,4'007,4'038 and 4�430 MeV. In addition, new results or results differing from earlier reports have been obtained for the decay properties of levels below 4�47 MeV in 43SC? The strengths of the nine resonances were measured relative to the reported strength at Ep = 2038 keV. The resonance at Ep = 2643 keV was shown for the first time to populate levels of spin> 7/2 via the proton capture reaction. A strong M1 (analogue to anti-analogue) transition from the resonance level to the level at 1� 931 MeV (9/2+) was observed. From measurements of y ray angular distributions, the following spin and parity assignments were made: 9/2+ at 7'514, 7/2+ at 4'371, >7/2 at 4'038 and 7/2 at 3�808 MeV. The resonance level at 7�514 MeV has possibly aT = 3/2 character. The low-lying excited states in 43SC are in reasonable agreement with the theoretical predictions of Johnstone (1968).
Resonant Neutron Capture in 45Sc Below 100 keV
Authors: Kenny MJ , Allen BJ , Macklin RL
Published: June 2011

The neutron capture cross section of 45SC has been measured with 0�2 % energy resolution in the range 2�S-100keV. Many new I> 0 resonances are observed and the average s- and p-wave radiative widths and standard deviations are <Γγ>s = 0�84�0�46eV and <Γγ>p = 0�S�0�3eV. No significant correlation is observed between the reduced neutron widths and radiative widths of the s-wave resonances.
Channelling of MeV H and He Ions in Alkali Halides at 'Zero Dose' Measurements
Authors: Price PB , Kelly JC
Published: June 2011

Measurements of the minimum scattering yield Xmln and the half-angle for channelling 1fI~ have been made for crystals of LiF, NaF, NaC! and KCI at very small total doses of H+ and 4He+ ions. The measured values of 1fI~ are in good agreement with theory. Comparison of the results for Xmln as a function of depth, with theories based on a linear increase of the mean square beam divergence Q2, shows that for the alkali halides studied the initial beam divergence Q o on entering the crystal is proportional to 1f11> the Lindhard characteristic channelling angle.
Theory of Melting: Thermodynamic Basis of Lindemann's Law
Authors: Stacey FD , Irvine RD
Published: June 2011

A melting equation closely resembling the differential form of Lindemann's melting law, which relates the melting point to the pressure in terms of the thermal Griineisen parameter and incompressibility, is derived from the Clausius-Clapeyron relation with the assumption that the MieGriineisen equation can be adapted directly to describe the pressure change associated with melting at constant volume. This assumption implies that melting is only a minor perturbation of the crystal structure, such that the atomic coordination is almost unaffected and that atomic bonds are merely stretched or compressed. It appears that 'normal' melting complies with this assumption reasonably closely but that departures from Lindemann's law occur when materials undergo major changes in coordination during melting. A particular merit of Lindemann's law is that it allows the extrapolation of melting points to the pressures of the Earth's deep interior. Extrapolation of data on the ironsulphur eutectic suggests a temperature of 4160 K at the boundary of the Earth's inner (solid) and outer (liquid) cores. Adiabatic extrapolation to the core-mantle boundary gives 2940 K at the base of the mantle.
A Simple Dislocation Theory of Melting
Authors: Stacey FD , Irvine RD
Published: June 2011

The ratio of volume increment to energy for the introduction of a simple dislocation to a crystal is used in the Clausius-Clapeyron equation to determine the pressure dependence of the equilibrium phase boundary between a perfect crystal and a completely dislocated crystal. It yields the Lindemann melting formula, which is thermodynamically valid for materials with central atomic forces in which melting involves no gross changes in coordination. It is concluded that melting is properly described as the free proliferation of dislocations and that melting point is the temperature at which the free energies of dislocations vanish.
Mode Coupling in the Solar Corona. IV. Magnetohydrodynamic Waves
Authors: Melrose DB , Simpson MA
Published: June 2011

A general theory for coupling between MHD waves obliquely incident on a stratified medium is developed. Coupling between the Alfvtln mode and the magnetoacoustic mode (the fast mode for VA > cs and the slow mode for VA < cs) is affected little by the finiteness of Cs/VA for VA >> Cs and the coupling becomes weaker as Cs/VA is increased towards unity. Coupling between the fast and slow modes for VA ≈ C. is discussed qualitatively using solutions of the MHD counterpart of the Booker quartic equation.
Mode Coupling in the Solar Corona. V. Reduction of the Coupled Equations
Authors: Melrose DB
Published: June 2011

A simplified version of the mode-coupling theory of Clemmow and Heading is developed by reducing the set of coupled equations to two for the magnetoionic theory and three for the MHD theory. The simplified theory reproduces known results for coupling in the neighbourhood of coupling points. It is used to treat coupling between the MHD waves, and it is found that coupling between the fast mode and the Alfven mode for VA ;?; C, is stronger than the coupling between any other pair of modes. The strongest coupling of all is between the Alfven and slow (magnetoacoustic) modes for VA ~ C,.
Generalization of Planck's Law of Radiation to Anisotropic Dispersive Media
Authors: Cole KD
Published: June 2011

The distribution of radiant energy in media which are not only dispersive but also anisotropic is derived. The distribution is found to depend on the phase velocity 1'., the group velocity V ?? and the angle oc. between them for each mode s. Planck's law is a limiting case when V. = Vas = c and oc. = 0 and applies strictly only to a vacuum.
Structural plasticity of a transmembrane peptide allows self-assembly into biologically active nanoparticles
Authors: Tarasov Sergey G. , Gaponenko Vadim , Howard O. M. Zack , Chen Yuhong , Oppenheim Joost J. , Dyba Marzena A. , Subramaniam Sriram , Lee Youngshim , Michejda Christopher , Tarasova Nadya I.
Published: June 2011

Significant efforts have been devoted to the development of nanoparticular delivering systems targeting tumors. However, clinical application of nanoparticles is hampered by insufficient size homogeneity, difficulties in reproducible synthesis and manufacturing, frequent high uptake in the liver, systemic toxicity of the carriers (particularly for inorganic nanoparticles), and insufficient selectivity for tumor cells. We have found that properly modified synthetic analogs of transmembrane domains of membrane proteins can self-assemble into remarkably uniform spherical nanoparticles with innate biological activity. Self-assembly is driven by a structural transition of the peptide that adopts predominantly a beta-hairpin conformation in aqueous solutions, but folds into an alpha-helix upon spontaneous fusion of the nanoparticles with cell membrane. A 24-amino acid peptide corresponding to the second transmembrane helix of the CXCR4 forms self-assembled particles that inhibit CXCR4 function in vitro and hamper CXCR4-dependent tumor metastasis in vivo. Furthermore, such nanoparticles can encapsulate hydrophobic drugs, thus providing a delivery system with the potential for dual biological activity.
Recruitment interactions can override catalytic interactions in determining the functional identity of a protein kinase
Authors: Won Angela P. , Garbarino Joan E. , Lim Wendell A.
Published: June 2011

The yeast
Saccharomyces cerevisae
has four distinct mitogen-activated protein kinase kinases (MAPKKs), each of which has a distinct functional identity characterized by communication with specific upstream and downstream partners to form distinct functional pathways. These four kinases belong to one family, sharing closely related catalytic domains. How have these four related kinases diverged to take on four distinct functional roles? The specificity of an enzyme for a particular substrate is often thought to reside in differences in the catalytic domain. However, many kinases, including MAPKKs, have modular interaction domains and motifs that have been shown to play an important role in determining the specificity of kinases through recruitment to specific partners and complexes. Here we probe the relative importance of catalytic domain interactions versus recruitment interactions in defining the functional identity of MAPKKs by asking whether we can use recruitment interactions to force other MAPKK catalytic domains to play the functional role of the mating MAPKK, Ste7. We find that two alternative MAPKKs, Pbs2 and Mkk2, can be forced to functionally replace the mating MAPKK Ste7, but only if the proper set of recruitment interactions are grafted onto their catalytic domains. These results show that within a family of kinases, recruitment interactions can play a dominant role in defining functional identity, and is consistent with a model in which new kinase functions can arise through recombination of existing catalytic domains with new interaction modules.
Canopy1, a positive feedback regulator of FGF signaling, controls progenitor cell clustering during Kupffer's vesicle organogenesis
Authors: Matsui Takaaki , Thitamadee Siripong , Murata Tomoko , Kakinuma Hisaya , Nabetani Takuji , Hirabayashi Yoshio , Hirate Yoshikazu , Okamoto Hitoshi , Bessho Yasumasa
Published: June 2011

The assembly of progenitor cells is a crucial step for organ formation during vertebrate development. Kupffer's vesicle (KV), a key organ required for the left–right asymmetric body plan in zebrafish, is generated from a cluster of ∼20 dorsal forerunner cells (DFCs). Although several genes are known to be involved in KV formation, how DFC clustering is regulated and how cluster formation then contributes to KV formation remain unclear. Here we show that positive feedback regulation of FGF signaling by Canopy1 (Cnpy1) controls DFC clustering. Cnpy1 positively regulates FGF signals within DFCs, which in turn promote Cadherin1-mediated cell adhesion between adjacent DFCs to sustain cell cluster formation. When this FGF positive feedback loop is disrupted, the DFC cluster fails to form, eventually leading to KV malformation and defects in the establishment of laterality. Our results therefore uncover both a previously unidentified role of FGF signaling during vertebrate organogenesis and a regulatory mechanism underlying cell cluster formation, which is an indispensable step for formation of a functional KV and establishment of the left–right asymmetric body plan.
A program of microRNAs controls osteogenic lineage progression by targeting transcription factor Runx2
Authors: Zhang Ying , Xie Rong-lin , Croce Carlo M. , Stein Janet L. , Lian Jane B. , van Wijnen Andre J. , Stein Gary S.
Published: June 2011

Lineage progression in osteoblasts and chondrocytes is stringently controlled by the cell-fate–determining transcription factor Runx2. In this study, we directly addressed whether microRNAs (miRNAs) can control the osteogenic activity of Runx2 and affect osteoblast maturation. A panel of 11 Runx2-targeting miRNAs (miR-23a, miR-30c, miR-34c, miR-133a, miR-135a, miR-137, miR-204, miR-205, miR-217, miR-218, and miR-338) is expressed in a lineage-related pattern in mesenchymal cell types. During both osteogenic and chondrogenic differentiation, these miRNAs, in general, are inversely expressed relative to Runx2. Based on 3′UTR luciferase reporter, immunoblot, and mRNA stability assays, each miRNA directly attenuates Runx2 protein accumulation. Runx2-targeting miRNAs differentially inhibit Runx2 protein expression in osteoblasts and chondrocytes and display different efficacies. Thus, cellular context contributes to miRNA-mediated regulation of Runx2. All Runx2-targeting miRNAs (except miR-218) significantly impede osteoblast differentiation, and their effects can be reversed by the corresponding anti-miRNAs. These findings demonstrate that osteoblastogenesis is limited by an elaborate network of functionally tested miRNAs that directly target the osteogenic master regulator Runx2.
Exploring the contribution and significance of animal protein in the diet of bonobos by stable isotope ratio analysis of hair
Authors: Oelze Vicky M. , Fuller Benjamin T. , Richards Michael P. , Fruth Barbara , Surbeck Martin , Hublin Jean-Jacques , Hohmann Gottfried
Published: June 2011

In primates, age, sex, and social status can strongly influence access to food resources. InPan, these criteria are assumed to influence access to vertebrate meat. However, the significance of meat in terms of its role in the nutrition ofPanis still debated. Here we present a study using stable carbon and nitrogen isotope ratios in hair samples from habituated, wild bonobos (Pan paniscus) to explore these issues. Over a period of 5 mo hair samples were collected from fresh bonobo nests at LuiKotale, Democratic Republic of Congo. Hair samples were assigned to known individuals and were of sufficient length to allow the evaluation of isotopic variation over several months. Samples of plant foods and sympatric fauna were also analyzed. The δ13C and δ15N results of the bonobo hair were remarkably homogeneous over time and for the group as a whole. There are no differences in diet between the sexes. Within the group of males, however, there was a positive correlation between dominance status and δ15N. The isotopic data indicate that the contribution of fauna to bonobo diet is marginal and that plant food is the dietary protein source. In only some cases did elevated δ15N hair values correlate with observed faunivory and not correspond to the δ15N measured in the dominant plant foods. Given the large variation in hunting and meat eating ofPanacross the African continent, the detection of seasonal changes in faunivory by elevated δ15N values in sectioned ape hair is a promising approach.
Mammary epithelial-specific disruption of c-Src impairs cell cycle progression and tumorigenesis
Authors: Marcotte Richard , Smith Harvey W. , Sanguin-Gendreau Virginie , McDonough Rosalie V. , Muller William J.
Published: June 2011

The tyrosine kinase c-Src is activated in a large proportion of breast cancers, in which it is thought to play a key role in promoting the malignant phenotype. c-Src activity is also elevated in transgenic mouse models of breast cancer, including the widely used polyomavirus middle-T antigen (PyVmT) model, which provides an opportunity to study the importance of c-Src in mammary tumorigenesis. However, germline c-Src deletion in mammary epithelial and stromal compartments complicates the interpretation of in vivo tumorigenesis studies as a result of severe defects in mammary gland development. We have therefore engineered a mouse strain in which deletion of c-Src can be targeted to the mammary epithelium. We demonstrate that mammary epithelial disruption of c-Src impairs proliferation and tumor progression driven by PyVmT in vivo. Whereas related kinases substitute for c-Src in PyVmT signaling, c-Src ablation impairs cell cycle progression with decreased cyclin expression and elevated expression of cyclin-dependent kinase inhibitors. Our data indicate that c-Src has essential and unique functions in proliferation and tumor progression in this mouse model that may also be important in certain contexts in some human breast cancers.
Minimal requirements for actin filament disassembly revealed by structural analysis of malaria parasite actin-depolymerizing factor 1
Authors: Wong Wilson , Skau Colleen T. , Marapana Danushka S. , Hanssen Eric , Taylor Nicole L. , Riglar David T. , Zuccala Elizabeth S. , Angrisano Fiona , Lewis Heather , Catimel Bruno , Clarke Oliver B. , Kershaw Nadia J. , Perugini Matthew A. , Kovar David R. , Gulbis Jacqueline M. , Baum Jake
Published: June 2011

Malaria parasite cell motility is a process that is dependent on the dynamic turnover of parasite-derived actin filaments. Despite its central role, actin's polymerization state is controlled by a set of identifiable regulators that is markedly reduced compared with those of other eukaryotic cells. In
Plasmodium falciparum
, the most virulent species that affects humans, this minimal repertoire includes two members of the actin-depolymerizing factor/cofilin (AC) family of proteins,
P
.
falciparum
actin-depolymerizing factor 1 (PfADF1) and
P
.
falciparum
actin-depolymerizing factor 2. This essential class of actin regulator is involved in the control of filament dynamics at multiple levels, from monomer binding through to filament depolymerization and severing. Previous biochemical analyses have suggested that PfADF1 sequesters monomeric actin but, unlike most eukaryotic counterparts, has limited potential to bind or depolymerize filaments. The molecular basis for these unusual properties and implications for parasite cell motility have not been established. Here we present the crystal structure of an apicomplexan AC protein, PfADF1. We show that PfADF1 lacks critical residues previously implicated as essential for AC-mediated actin filament binding and disassembly, having a substantially reduced filament-binding loop and C-terminal α4 helix. Despite this divergence in structure, we demonstrate that PfADF1 is capable of efficient actin filament severing. Furthermore, this severing occurs despite PfADF1’s low binding affinity for filaments. Comparative structural analysis along with biochemical and microscopy evidence establishes that severing is reliant on the availability of an exposed basic residue in the filament-binding loop, a conserved minimal requirement that defines AC-mediated filament disassembly across eukaryotic cells.
Neonatal Fc receptor for IgG (FcRn) regulates cross-presentation of IgG immune complexes by CD8−CD11b+dendritic cells
Authors: Baker Kristi , Qiao Shuo-Wang , Kuo Timothy T. , Aveson Victoria G. , Platzer Barbara , Andersen Jan-Terje , Sandlie Inger , Chen Zhangguo , de Haar Colin , Lencer Wayne I. , Fiebiger Edda , Blumberg Richard S.
Published: June 2011

Cross-presentation of IgG-containing immune complexes (ICs) is an important means by which dendritic cells (DCs) activate CD8+T cells, yet it proceeds by an incompletely understood mechanism. We show that monocyte-derived CD8−CD11b+DCs require the neonatal Fc receptor for IgG (FcRn) to conduct cross-presentation of IgG ICs. Consequently, in the absence of FcRn, Fcγ receptor (FcγR)-mediated antigen uptake fails to initiate cross-presentation. FcRn is shown to regulate the intracellular sorting of IgG ICs to the proper destination for such cross-presentation to occur. We demonstrate that FcRn traps antigen and protects it from degradation within an acidic loading compartment in association with the rapid recruitment of key components of the phagosome-to-cytosol cross-presentation machinery. This unique mechanism thus enables cross-presentation to evolve from an atypically acidic loading compartment. FcRn-driven cross-presentation is further shown to control cross-priming of CD8+T-cell responses in vivo such that during chronic inflammation, FcRn deficiency results in inadequate induction of CD8+T cells. These studies thus demonstrate that cross-presentation in CD8−CD11b+DCs requires a two-step mechanism that involves FcγR-mediated internalization and FcRn-directed intracellular sorting of IgG ICs. Given the centrality of FcRn in controlling cross-presentation, these studies lay the foundation for a unique means to therapeutically manipulate CD8+T-cell responses.
Monoubiquitin-dependent endocytosis of the IRON-REGULATED TRANSPORTER 1 (IRT1) transporter controls iron uptake in plants
Authors: Barberon Marie , Zelazny Enric , Robert Stéphanie , Conéjéro Geneviève , Curie Cathy , Friml Jìří , Vert Grégory
Published: June 2011

Plants take up iron from the soil using the IRON-REGULATED TRANSPORTER 1 (IRT1) high-affinity iron transporter at the root surface. Sophisticated regulatory mechanisms allow plants to tightly control the levels of IRT1, ensuring optimal absorption of essential but toxic iron. Here, we demonstrate that overexpression of
Arabidopsis thaliana
IRT1 leads to constitutive IRT1 protein accumulation, metal overload, and oxidative stress. IRT1 is unexpectedly found in
trans
-Golgi network/early endosomes of root hair cells, and its levels and localization are unaffected by iron nutrition. Using pharmacological approaches, we show that IRT1 cycles to the plasma membrane to perform iron and metal uptake at the cell surface and is sent to the vacuole for proper turnover. We also prove that IRT1 is monoubiquitinated on several cytosol-exposed residues in vivo and that mutation of two putative monoubiquitination target residues in IRT1 triggers stabilization at the plasma membrane and leads to extreme lethality. Together, these data suggest a model in which monoubiquitin-dependent internalization/sorting and turnover keep the plasma membrane pool of IRT1 low to ensure proper iron uptake and to prevent metal toxicity. More generally, our work demonstrates the existence of monoubiquitin-dependent trafficking to lytic vacuoles in plants and points to proteasome-independent turnover of plasma membrane proteins.
Abrupt Holocene climate change as an important factor for human migration in West Greenland
Authors: D’Andrea William J. , Huang Yongsong , Fritz Sherilyn C. , Anderson N. John
Published: June 2011

West Greenland has had multiple episodes of human colonization and cultural transitions over the past 4,500 y. However, the explanations for these large-scale human migrations are varied, including climatic factors, resistance to adaptation, economic marginalization, mercantile exploration, and hostile neighborhood interactions. Evaluating the potential role of climate change is complicated by the lack of quantitative paleoclimate reconstructions near settlement areas and by the relative stability of Holocene temperature derived from ice cores atop the Greenland ice sheet. Here we present high-resolution records of temperature over the past 5,600 y based on alkenone unsaturation in sediments of two lakes in West Greenland. We find that major temperature changes in the past 4,500 y occurred abruptly (within decades), and were coeval in timing with the archaeological records of settlement and abandonment of the Saqqaq, Dorset, and Norse cultures, which suggests that abrupt temperature changes profoundly impacted human civilization in the region. Temperature variations in West Greenland display an antiphased relationship to temperature changes in Ireland over centennial to millennial timescales, resembling the interannual to multidecadal temperature seesaw associated with the North Atlantic Oscillation.
Enhanced chemistry-climate feedbacks in past greenhouse worlds
Authors: Beerling David J. , Fox Andrew , Stevenson David S. , Valdes Paul J.
Published: June 2011

Trace greenhouse gases are a fundamentally important component of Earth’s global climate system sensitive to global change. However, their concentration in the pre-Pleistocene atmosphere during past warm greenhouse climates is highly uncertain because we lack suitable geochemical or biological proxies. This long-standing issue hinders assessment of their contribution to past global warmth and the equilibrium climate sensitivity of the Earth system (Ess) to CO2. Here we report results from a series of three-dimensional Earth system modeling simulations indicating that the greenhouse worlds of the early Eocene (55 Ma) and late Cretaceous (90 Ma) maintained high concentrations of methane, tropospheric ozone, and nitrous oxide. Modeled methane concentrations were four- to fivefold higher than the preindustrial value typically adopted in modeling investigations of these intervals, even after accounting for the possible high CO2-suppression of biogenic isoprene emissions on hydroxyl radical abundance. Higher concentrations of trace greenhouse gases exerted marked planetary heating (> 2 K), amplified in the high latitudes (> 6 K) by lower surface albedo feedbacks, and increasedEssin the Eocene by 1 K. Our analyses indicate the requirement for including non-CO2greenhouse gases in model-basedEssestimates for comparison with empirical paleoclimate assessments, and point to chemistry-climate feedbacks as possible amplifiers of climate sensitivity in the Anthropocene.
Unraveling the distributed neural code of facial identity through spatiotemporal pattern analysis
Authors: Nestor Adrian , Plaut David C. , Behrmann Marlene
Published: June 2011

Face individuation is one of the most impressive achievements of our visual system, and yet uncovering the neural mechanisms subserving this feat appears to elude traditional approaches to functional brain data analysis. The present study investigates the neural code of facial identity perception with the aim of ascertaining its distributed nature and informational basis. To this end, we use a sequence of multivariate pattern analyses applied to functional magnetic resonance imaging (fMRI) data. First, we combine information-based brain mapping and dynamic discrimination analysis to locate spatiotemporal patterns that support face classification at the individual level. This analysis reveals a network of fusiform and anterior temporal areas that carry information about facial identity and provides evidence that the fusiform face area responds with distinct patterns of activation to different face identities. Second, we assess the information structure of the network using recursive feature elimination. We find that diagnostic information is distributed evenly among anterior regions of the mapped network and that a right anterior region of the fusiform gyrus plays a central role within the information network mediating face individuation. These findings serve to map out and characterize a cortical system responsible for individuation. More generally, in the context of functionally defined networks, they provide an account of distributed processing grounded in information-based architectures.
Structure of transcription factor HetR required for heterocyst differentiation in cyanobacteria
Authors: Kim Youngchang , Joachimiak Grazyna , Ye Zi , Binkowski T. Andrew , Zhang Rongguang , Gornicki Piotr , Callahan Sean M. , Hess Wolfgang R. , Haselkorn Robert , Joachimiak Andrzej
Published: June 2011

HetR is an essential regulator of heterocyst development in cyanobacteria. HetR binds to a DNA palindrome upstream of the
hetP
gene. We report the crystal structure of HetR from
Fischerella
at 3.0 Å. The protein is a dimer comprised of a central DNA-binding unit containing the N-terminal regions of the two subunits organized with two helix-turn-helix motifs; two globular flaps extending in opposite directions; and a hood over the central core formed from the C-terminal subdomains. The flaps and hood have no structural precedent in the protein database, therefore representing new folds. The structural assignments are supported by site-directed mutagenesis and DNA-binding studies. We suggest that HetR serves as a scaffold for assembly of transcription components critical for heterocyst development.
Lipooligosaccharide is required for the generation of infectious elementary bodies in
Chlamydia trachomatis
Authors: Nguyen Bidong D. , Cunningham Doreen , Liang Xiaofei , Chen Xin , Toone Eric J. , Raetz Christian R. H. , Zhou Pei , Valdivia Raphael H.
Published: June 2011

Lipopolysaccharides (LPS) and lipooligosaccharides (LOS) are the main lipid components of bacterial outer membranes and are essential for cell viability in most Gram-negative bacteria. Here we show that small molecule inhibitors of LpxC [UDP-3-
O
-(
R
-3-hydroxymyristoyl)-GlcNAc deacetylase], the enzyme that catalyzes the first committed step in the biosynthesis of lipid A, block the synthesis of LOS in the obligate intracellular bacterial pathogen
Chlamydia trachomatis
. In the absence of LOS,
Chlamydia
remains viable and establishes a pathogenic vacuole (“inclusion”) that supports robust bacterial replication. However, bacteria grown under these conditions were no longer infectious. In the presence of LpxC inhibitors, replicative reticulate bodies accumulated in enlarged inclusions but failed to express selected late-stage proteins and transition to elementary bodies, a
Chlamydia
developmental form that is required for invasion of mammalian cells. These findings suggest the presence of an outer membrane quality control system that regulates
Chlamydia
developmental transition to infectious elementary bodies and highlights the potential application of LpxC inhibitors as unique class of antichlamydial agents.
Rethinking How to Tackle Binge Drinking Using Social Marketing: A Neotribal Analysis
Authors: Spotswood Fiona , Tapp Alan
Published: June 2011

In this article the authors report on primary research undertaken with young people in a deprived area of northwest England who use regular binge drinking as the lynch pin of their social group. Traditional health messaging approaches have had little success with this hard to reach group. Findings were analyzed using neotribal concepts. We found that the search for community and belonging occupied a central place in binge drinking behavior for this group. A discussion is offered of appropriate up- and downstream social marketing solutions, based on the principle that any exchange will need to offer community and other benefits equal to those currently delivered through binge drinking.
Introduction to magnetoelectric coupling and multiferroic films
Authors: Lawes G , Srinivasan G
Published: June 2011

There is an increasing understanding of the mechanisms underlying the development of magnetoelectric coupling and multiferroic order in both single-phase and composite materials. The investigations underlying this advance include a range of studies on thin films, which are expected to play an important role in the development of novel magnetoelectric devices. The properties of both single-phase and composite systems are widely studied. While single-phase materials can exhibit rich spin-charge coupling physics, the magnetizations, polarizations, and transition temperatures are often too small to be innately useful for device design. Conversely, a number of ferromagnetic–piezoelectric composites can show strong magnetoelectric coupling at ambient temperatures, which develops as a product-property mediated by elastic deformation, making these systems more directly amenable to fabricating devices. In this review, we provide a short overview of the mechanisms for magnetoelectric coupling in multiferroics, together with a discussion of how this magnetoelectric coupling is relevant for designing new multiferroic devices, including magnetic field sensors, dual electric and magnetic field tunable microwave and millimetre wave devices and miniature antennas. We present a brief summary of some of the significant results in studies on thin-film multiferroics, with an emphasis on single-phase materials, and covering systems where the magnetic and ferroelectric transitions fall at the same temperature as well as systems where they fall at different temperatures.
Micromagnetic analysis of L10-FePt/Au nanocomposite films
Authors: Feng Chun , Li Hongjia , Wei Dan , Yang Meiyin , Li Baohe , Zhan Qian , Yu Guanghua
Published: June 2011

A micromagnetic simulation analysis is systematically carried out to explore the magnetization reversal mechanism, residual stress and exchange interaction in L10-FePt/Au nanocomposite films with perpendicular magnetic anisotropy. Results show that: (1) the domain-wall pinning mode is the main mechanism responsible for magnetization reversal in L10-FePt/Au films; (2) considering the magnetoelastic energy produced by lattice mismatches between Au and FePt, the simulated out-of-plane loop matches the experimental loop very well. The residual tensile stress in the films is quantitatively described by both experimental calculations and micromagnetic simulations; (3) the exchange interaction within FePt grains of the films is strong, which allows for the coherent switching of the magnetization moments of an FePt grain.
Investigating the antifungal activity of TiO2 nanoparticles deposited on branched carbon nanotube arrays
Authors: Darbari S , Abdi Y , Haghighi F , Mohajerzadeh S , Haghighi N
Published: June 2011

Branched carbon nanotube (CNT) arrays were synthesized by plasma-enhanced chemical vapour deposition on a silicon substrate. Ni was used as the catalyst and played an important role in the realization of branches in vertically aligned nanotubes. TiO2 nanoparticles on the branched CNTs were produced by atmospheric pressure chemical vapour deposition followed by a 500 °C annealing step. Transmission and scanning electron microscopic techniques were used to study the morphology of the TiO2/branched CNT structures while x-ray diffraction and Raman spectroscopy were used to verify the characteristics of the prepared nanostructures. Their antifungal effect on Candida albicans biofilms under visible light was investigated and compared with the activity of TiO2/CNT arrays and thin films of TiO2. The TiO2/branched CNTs showed a highly improved photocatalytic antifungal activity in comparison with the TiO2/CNTs and TiO2 film. The excellent visible light-induced photocatalytic antifungal activity of the TiO2/branched CNTs was attributed to the generation of electron–hole pairs by visible light excitation with a low recombination rate, in addition to the high surface area provided for the interaction between the cells and the nanostructures. Scanning electron microscopy was used to observe the resulting morphological changes in the cell body of the biofilms existing on the antifungal samples.
Replication enhancer elements within the open reading frame of tick-borne encephalitis virus and their evolution within the Flavivirus genus
Authors: Tuplin A. , Evans D. J. , Buckley A. , Jones I. M. , Gould E. A. , Gritsun T. S.
Published: May 2011

We provide experimental evidence of a replication enhancer element (REE) within the capsid gene of tick-borne encephalitis virus (TBEV, genus Flavivirus). Thermodynamic and phylogenetic analyses predicted that the REE folds as a long stable stem–loop (designated SL6), conserved among all tick-borne flaviviruses (TBFV). Homologous sequences and potential base pairing were found in the corresponding regions of mosquito-borne flaviviruses, but not in more genetically distant flaviviruses. To investigate the role of SL6, nucleotide substitutions were introduced which changed a conserved hexanucleotide motif, the conformation of the terminal loop and the base-paired dsRNA stacking. Substitutions were made within a TBEV reverse genetic system and recovered mutants were compared for plaque morphology, single-step replication kinetics and cytopathic effect. The greatest phenotypic changes were observed in mutants with a destabilized stem. Point mutations in the conserved hexanucleotide motif of the terminal loop caused moderate virus attenuation. However, all mutants eventually reached the titre of wild-type virus late post-infection. Thus, although not essential for growth in tissue culture, the SL6 REE acts to up-regulate virus replication. We hypothesize that this modulatory role may be important for TBEV survival in nature, where the virus circulates by non-viraemic transmission between infected and non-infected ticks, during co-feeding on local rodents.
Mechanisms of Lipotoxicity in NAFLD and Clinical Implications
Authors: Ibrahim Samar H. , Kohli Rohit , Gores Gregory J.
Published: June 2011

With the epidemic of childhood obesity, nonalcoholic fatty liver disease (NAFLD) has become the most common cause of chronic liver disease in pediatrics. NAFLD is strongly associated with insulin resistance and increased level of serum free fatty acids (FFAs). FFAs have direct hepatotoxicity through the induction of an endoplasmic reticulum stress response and subsequently activation of the mitochondrial pathway of cell death. FFAs may also result in lysosomal dysfunction and alter death receptor gene expression. Lipoapoptosis is a key pathogenic process in NAFLD, and correlates with progressive inflammation, and fibrosis. Accumulation of triglyceride in the liver results from uptake and esterification of FFAs by the hepatocyte, and is less likely to be hepatotoxic per se. To date, there are no proven effective therapies that halt NAFLD progression or unfortunately improve prognosis in children. The cellular mechanisms of lipotoxicity are complex but provide potential therapeutic targets for NAFLD. In this review we discuss several potential therapeutic opportunities in detail including inhibition of apoptosis, c‐Jun‐N‐terminal kinase, and endoplasmic reticulum stress pathways.
Age-dependent inbreeding risk and offspring fitness costs in female black grouse
Authors: Soulsbury Carl D. , Alatalo Rauno V. , Lebigre Christophe , Rokka Kaisa , Siitari Heli
Published: June 2011

Dispersal is an important mechanism used to avoid inbreeding. However, dispersal may only be effective for part of an individual's lifespan since, post-dispersal individuals that breed over multiple reproductive events may risk mating with kin of the philopatric sex as they age. We tested this hypothesis in black grouseTetrao tetrix, and show that yearling females never mated with close relatives whereas older females did. However, matings were not with direct kin suggesting that short-distance dispersal to sites containing kin and subsequent overlap of reproductive lifespans between males and females were causing this pattern. Chick mass was lower when kinship was high, suggesting important fitness costs associated with inbred matings. This study shows that increased inbreeding risk might be a widespread yet rarely considered cost of ageing.
Bacteriophage selection against a plasmid-encoded sex apparatus leads to the loss of antibiotic-resistance plasmids
Authors: Jalasvuori Matti , Friman Ville-Petri , Nieminen Anne , Bamford Jaana K. H. , Buckling Angus
Published: June 2011

Antibiotic-resistance genes are often carried by conjugative plasmids, which spread within and between bacterial species. It has long been recognized that some viruses of bacteria (bacteriophage; phage) have evolved to infect and kill plasmid-harbouring cells. This raises a question: can phages cause the loss of plasmid-associated antibiotic resistance by selecting for plasmid-free bacteria, or can bacteria or plasmids evolve resistance to phages in other ways? Here, we show that multiple antibiotic-resistance genes containing plasmids are stably maintained in bothEscherichia coliandSalmonella entericain the absence of phages, while plasmid-dependent phage PRD1 causes a dramatic reduction in the frequency of antibiotic-resistant bacteria. The loss of antibiotic resistance in cells initially harbouring RP4 plasmid was shown to result from evolution of phage resistance where bacterial cells expelled their plasmid (and hence the suitable receptor for phages). Phages also selected for a low frequency of plasmid-containing, phage-resistant bacteria, presumably as a result of modification of the plasmid-encoded receptor. However, these double-resistant mutants had a growth cost compared with phage-resistant but antibiotic-susceptible mutants and were unable to conjugate. These results suggest that bacteriophages could play a significant role in restricting the spread of plasmid-encoded antibiotic resistance.
The stress of parenthood? Increased glucocorticoids in birds with experimentally enlarged broods
Authors: Bonier Frances , Moore Ignacio T. , Robertson Raleigh J.
Published: June 2011

Variation in baseline glucocorticoid (cort) levels can be attributed, at least in part, to differences in energetic demands confronting individuals. Elevated baseline cort levels are routinely interpreted as indicating individuals in poor condition, with low relative fitness. However, when greater reproductive effort increases energetic demands, individuals with high cort might paradoxically be those with the highest fitness. Here, we experimentally test the hypothesis that increased reproductive demand causes increases in baseline cort (the Cort-Adaptation hypothesis). We measured maternal baseline cort before and after experimentally enlarging and reducing brood sizes in tree swallows (
Tachycineta bicolor
). Females with experimentally enlarged broods had greater increases in baseline cort and fledged more offspring than females with reduced broods. Additionally, females with greater increases in baseline cort had higher offspring-provisioning rates than females with lower changes in cort. These findings demonstrate that increased reproductive demand can cause increased baseline cort. As yet, we do not know if these increases in cort cause increased allocation of resources towards reproduction, but the positive relationship between parental behaviour and cort suggests that increased cort does not always interfere with reproductive investment, and might instead facilitate it.