bluuebunny/crossref_metadata_2025 huggingface dataset:
Removal of Mitochondria-Generated Reactive Oxygen Species Delays Age-Associated Disk Degeneration
Authors: Vo N. A. , Nasto L. A. , Robinson A. , Sowa G. , Wipf P. , Robbins P. , Kang J. , Niedernhofer L.
Published: June 2012

Introduction

Reactive oxygen species (ROS) and free radicals are byproducts of oxidative metabolism that cause cellular damage and are implicated in the pathogenesis of age-related diseases. Mitochondria are the main cellular sites of ROS production. Recent studies reported a positive correlation between mitochondria dysfunction and age-associated disk cellular senescence and apoptosis. Hence, we hypothesize that reducing mitochondria-generated ROS would slow the onset of age-related intervertebral disk degeneration (IDD). We tested this hypothesis by chronically treating the Errc1-/D mouse model of accelerated aging with XJB-5-131, a mitochondria-targeted free radical scavenger previously demonstrated to be therapeutic in rodent models of hemorrhagic shock and sepsis.

Materials and Methods

Pairs of 5-week-old siblings of Ercc1-/▵ mice were treated with XJB-5-131 or oil carrier control (intraperitoneal injections, 2 mg/Kg, 3×/week, 15 weeks). Total proteoglycan content (safranin-O histology, DMMB assay) and synthesis (35S-sulfate incorporation) were measured. Transmission electron microscopy (TEM) was performed to assess disk mitochondria number and morphology in Ercc1-/▵ mice and wild-type littermates.

Results

TEM showed greater mitochondrial death in discs of Ercc1-/▵ mice compared to their wild-type littermates. Compared to oil-treated Ercc1-/▵ controls, disks from XJB-5-131 treated Ercc1-/▵mice showed greater (1.3×) proteoglycan matrix content and higher (1.9×) rate of proteoglycan synthesis.

Conclusion

Errc1-/Dmouse model of a human progeria had previously established as an accurate model of spine aging. Treatment of Errc1-/Dmice with a mitochondria-targeted ROS scavenger decreased disk proteoglycan loss. This result is consistent with our in vitro studies which showed XJB-5-131 is able to rescue reduced proteoglycan synthesis mediated by oxidative stress in human disk cells grown at high oxygen (20 vs. 5% oxygen). The findings in this study suggest that oxidative damage originating from mitochondria dysfunction plays an important role in disk health. The mitochondrial-targeted ROS free radical scavenger XJB-5-131 is potentially therapeutic in delaying the onset of age-related IDD. I confirm having declared any potential conflict of interest for all authors listed on this abstract Yes Disclosure of Interest None declared
The Evaluation of Digital Rectal Examination for Assessment of Anal Tone
Authors: Sherlock K. E. , Turner W. , Elsayed S. , Bagouri E. , Baha L. , Boszczyk B. M. , McNally D.
Published: June 2012

Introduction

Cauda equina syndrome represents the constellation of symptoms and signs resulting from compression of lumbosacral nerve routes. Combined with subjective neurological findings, a reduction in anal tone is an important sign deeming further imaging necessary. Digital rectal examination (DRE) is an invasive procedure used to assess anal tone despite debated accuracy. Our main objective was to investigate the validity of DRE for assessment of anal tone.

Materials and Methods

Total 75 doctors completed a questionnaire documenting their grade, especiality, and experience in performing DRE. A model anus, using a pressure transducer surrounding an artificial canal, was assembled and calibrated. Participants performed four DREs on the model (with a break between attempts), and predicted tone as “reduced” or “normal” (35 and 60 mm Hg respectively), followed by a “squeeze” test. Total 30 health care assistants (HCAs) partook as a control group with no training in DRE.

Results

In each attempt 60, 61, 63, and 72% of doctors correctly identified the anal tone, respectively (average accuracy: 64%). HCAs had an identical average accuracy of 64%. Total 100% of participants correctly felt the squeeze test. For doctors no correlation was found between confidence in assessing anal tone using DRE and a correct result. Total 71% had received previous training in DRE with 64% of these taught how to assess anal tone. Total 43% of doctors felt that further training would be beneficial.

Conclusion

The results demonstrate that accuracy in assessing anal tone using DRE is limited with overall correctness of 64%. Poor correlation exists between perceived level of skill and study result. Doctors were not significantly more able than HCAs to detect correct tone. Therefore, DRE for the assessment of anal tone is not a wholly accurate tool. A squeeze test may be of greater value if interpreted correctly. I confirm having declared any potential conflict of interest for all authors listed on this abstract Yes Disclosure of Interest None declared
Minimum 2-Year Follow-Up of the Mobility and Disk Changes at the Index Level Stabilized by Isobar Hybrid Stabilization
Authors: Fu L. , Zhang P.
Published: June 2012

Introduction

To test whether the application of Isobar could prevent degeneration at the index and adjacent level.

Materials and Methods

Total 27 patients underwent decompressive discectomy and stabilized with transforaminal lumbar interbody fusion (TLIF) using Isobar. The mobility and disk changes by MRI were evaluated radiologically after a minimum follow-up of 2 years.

Results

All patients finished a mean follow-up of 39 months (range: 24 to 50 months). Clinical outcomes showed significant improvement in mean postoperative visual analog scale score by 38.3 points ( p < 0.01) and Oswestry disability index by 20.9 points ( p < 0.01). Disk height ratio and intervertebral angle were maintained at the index level and adjacent level ( p > 0.05). Range of motion averaged 2.81° at the index level, and range of motion at the adjacent level remained unchanged ( p > 0.05). The wooden score at the index level showed no statistically changes. No reoperation or screw loosening was recorded.

Conclusion

Hybird Isobar stabilization leads to excellent clinical and radiological results in a minimum follow-up of 2 years. I confirm having declared any potential conflict of interest for all authors listed on this abstract Yes Disclosure of Interest None declared Athiviraham A, Wali ZA, Yen D. Predictive factors influencing clinical outcome with operative management of lumbar spinal stenosis . Spine 2011;11:613–617 Caputy AJ, Spence CA, Bejjani GK, et al. The role of spinal fusion in surgery for lumbar spinal stenosis: a review . Neurosurgical Focus 1997;3:e3; discussion 1 p following e4 Herkowitz HN, Sidhu KS. Lumbar spine fusion in the treatment of degenerative conditions: current indications and recommendations . Journal of American Academy of Orthopedic Surgeon 1995;3:123–135 Sonntag VK, Marciano FF. Is fusion indicated for lumbar spinal disorders? Spine (Phila Pa 1976) 1995;20:138S-142S Bridwell KH, Sedgewick TA, O'Brien MF, et al. The role of fusion and instrumentation in the treatment of degenerative spondylolisthesis with spinal stenosis . Journal of Spinal Disorder 1993;6:461–472
Cervical Arthroplasty with Prodisc-C System: Our Experience
Authors: Grasso G. , Certo F. , Pirrone A. G. , Iacopino D.
Published: June 2012

Introduction

The Prodisc-C system (Synthes, USA), used in cervical arthroplasty, has been revealed as valid alternative to arthrodesis. Artificial disk replacement has the aim to preserve the physiological motion segment of the cervical spine and to decrease the kinematic strain on the adjacent levels. However, to date, with existing prostheses, the risk of adjacent segment disease and heterotopic ossification have not been proven to be definitively reduced by using artificial disk replacement. In this study, we present our experience over 5 years follow-up. The heterotopic ossification rate (HO), range of motion of the segments operated, as well as the strain of the adjacent levels, and the clinical outcome of patients following cervical arthroplasty are shown.

Materials and Methods

In our study, 35 consecutive patients (20 male, 15 female) were included. Patients presenting with clinical symptoms of degenerative disorders of the cervical spine-axial and radicular pain or radicular compromise and their corresponding signs on MRI-soft disk hernia or spondylosis, undergone surgical procedure. The following parameters were assessed before the procedure and 6 months, and each year postoperatively. Clinical condition (NDI and SF36), axial pain and radicular pain scores (VAS), and x-ray findings were assessed.

Results

Total 5 years following the surgical procedure, significant improvement in NDI, cervical, and radicular pain were assessed. HO was detected in 30% of the segments operated and a complete loss of the arthroplasty mobility in 5% of the cases.

Conclusion

The Prodisc-C system seems to favor a prompt improvement of the clinical and neurological symptoms. Although, in our experience, the system preserved the motion segment, further studies with longer follow-up are necessary to assess the long-term efficacy of this system and its advantage with respect to arthrodesis. I confirm having declared any potential conflict of interest for all authors listed on this abstract No Disclosure of Interest None declared
Acceleration of laser-driven ion bunch from double-layer thin foils
Authors: Wang X. , Yu W. , Liang E. , Yu M. Y.
Published: June 2012

Generation of monoenergetic ion bunch from a double-layer thin-foil target irradiated by an intense linearly polarized laser pulse is investigated using two-dimensional particle-in-cell simulation. The protons in the front low-density hydrogen target layer accelerated by the space-charge field of the laser-driven hot electrons can penetrate through the high-Z high-mass and high-density ion layer, resulting in an energetic proton bunch. A part of the latter is further accelerated by the space-charge field of the hot electrons in the vacuum behind the high-Z ion layer. With this scheme, quasi-monoenergetic proton bunches can be produced using presently available laser pulses of moderate contrast and duration.
Four pi calibration and modeling of a bare germanium detector in a cylindrical field source
Authors: Dewberry R. A. , Young J. E.
Published: June 2012

In this paper we describe a 4π cylindrical field acquisition configuration surrounding a bare (unshielded, uncollimated) high purity germanium detector. We perform an efficiency calibration with a flexible planar source and model the configuration in the 4π cylindrical field. We then use exact calculus to model the flux on the cylindrical sides and end faces of the detector. We demonstrate that the model accurately represents the experimental detection efficiency compared to that of a point source and to Monte Carlo N-particle (MCNP) calculations of the flux. The model sums over the entire source surface area and the entire detector surface area including both faces and the detector's cylindrical sides. Agreement between the model and both experiment and the MCNP calculation is within 8%.
Calculations of nonlocal electron energy transport in laser produced plasmas in one and two dimensions using the velocity dependent Krook model
Authors: Manheimer Wallace , Colombant Denis , Schmitt Andrew J.
Published: June 2012

This paper extends the velocity dependent Krook (VDK) model, developed at NRL over the last 4 years, to two dimensions and presents a variety of calculations. One dimensional spherical calculations presented here investigate shock ignition. Comparing VDK calculations to a flux limit calculation shows that the laser profile has to be retuned and some gain is sacrificed due to preheat of the fuel. However, preheat is by no means a show stopper for laser fusion. The recent foil acceleration experiments at the University of Rochester Laboratory for Laser Energetics are modeled with two-dimensional simulations. The radial loss is very important to consider in modeling the foil acceleration. Once this is done, the VDK model gives the best agreement with the experiment.
Computational characterization of cutoff probe system for the measurement of electron density
Authors: Na Byung-Keun , Kim Dae-Woong , Kwon Jun-Hyuk , Chang Hong-Young , Kim Jung-Hyung , You Shin-Jae
Published: June 2012

The wave cutoff probe, a precise measurement method for measuring the electron density, was recently proposed. To characterize the cutoff probe system, in this paper, the microwave simulations of a cutoff probe system were performed at various configurations of the cutoff probe system. The influence of the cutoff probe spectrum stemming from numerous parametric elements such as the probe tip length, probe tip distance, probe tip plane orientation, chamber volume/geometry, and coaxial cable length is presented and discussed. This article is expected to provide qualitative and quantitative insight into cutoff probe systems and its optimization process.
First principle nonlinear quantum dynamics using a correlation-based von Neumann entropy
Authors: Westermann Till , Manthe Uwe
Published: June 2012

A new concept to describe the quantum dynamics in complex systems is suggested. It extends established schemes based on the Dirac-Frenkel variation principle, e.g., the multi-configurational time-dependent Hartree (MCTDH) approach. The concept is based on a correlation-based von Neumann entropy (CvN-entropy) definition measuring the complexity of the wavefunction. Equations of motion are derived using a CvN-entropy constraint in the variational principle and result in a generally applicable effective Hamiltonian. It consists of the standard Hamilton operator and an additional nonlinear operator which limits the complexity of the wavefunction. Effectively, this nonlinear operator absorbs complex structures which are emerging in the wavefunction and allows one to introduce non-norm conserving equations of motion. Important aspects of the new concept are outlined studying the wave packet propagation on the diabatic B2 potential energy surfaces of NO2. First, it is demonstrated that during standard wave packet propagation the CvN-entropy increases strongly with time roughly independent of the coordinate systems employed. Second, one finds that employing CvN-entropy constrained MCTDH propagation yields improved wave function accuracy on longer time scales while compromising on the short time accuracy. Third, the loss of the wavefunction's norm is directly related to the overlap with the exact wavefunction. This provides an error estimate available without knowing an exact reference.
Pinned and unpinned epitaxial graphene layers on SiC studied by Raman spectroscopy
Authors: Grodecki K. , Blaszczyk J. A. , Strupinski W. , Wysmolek A. , Stępniewski R. , Drabinska A. , Sochacki M. , Dominiak A. , Baranowski J. M.
Published: June 2012

The study of epitaxial graphene layers grown on SiC by two techniques, namely, the traditional Si sublimation method and the recent chemical vapor deposition (CVD) using temperature induced shift of the Raman 2D line, is presented. The measurements of thermal shift rate of 2D line on 4 H-SiC(0001) allowed us to determine notable differences in interaction of graphene with SiC substrate. The obtained results show that graphene layers grown by Si sublimation of 4 H-SiC(0001) are pinned strongly to the substrate. In contrast, the layers of graphene grown on 4 H-SiC(0001) substrates by CVD showed much weaker pinning. It was found that the film consisting of two or three graphene layers grown by CVD was already unpinned and thus showing Raman shift expected for freestanding graphene. The obtained differences in pinning of epitaxial graphene layers are explained in terms of basic growth mechanism differences between these two methods: graphene growth by Si sublimation is a “bottom-up” process and by CVD—a “top-down” process. The obtained results show that the CVD method of growth is an alternative technology for producing high quality graphene structures on SiC.
Thermal expansions of Ln2Zr2O7 (Ln = La, Nd, Sm, and Gd) pyrochlore
Authors: Feng J. , Xiao B. , Zhou R. , Pan W.
Published: June 2012

The thermal expansions of the rare earth zirconate (Ln2Zr2O7, Ln = La, Nd, Sm, and Gd) pyrochlore were studied by the Debye and quasi harmonic approximation combined with the first principles calculations. The difference between CV and CP was obtained. The temperature dependence of thermal expansions is mainly caused by the restoration of thermal energy due to phonon excitations at relatively a low temperature. When the temperature is much higher than Debye temperature, i.e., above 600 K for Ln2Zr2O7 compounds, the volumetric coefficient is increased linearly by increasing the temperature. The calculations are in good agreement with the experiments.
Accuracy of second order perturbation theory in the polaron and variational polaron frames
Authors: Lee Chee Kong , Moix Jeremy , Cao Jianshu
Published: June 2012

In the study of open quantum systems, the polaron transformation has recently attracted a renewed interest as it offers the possibility to explore the strong system-bath coupling regime. Despite this interest, a clear and unambiguous analysis of the regimes of validity of the polaron transformation is still lacking. Here we provide such a benchmark, comparing second order perturbation theory results in the original untransformed frame, the polaron frame, and the variational extension with numerically exact path integral calculations of the equilibrium reduced density matrix. Equilibrium quantities allow a direct comparison of the three methods without invoking any further approximations as is usually required in deriving master equations. It is found that the second order results in the original frame are accurate for weak system-bath coupling; the results deteriorate when the bath cut-off frequency decreases. The full polaron results are accurate for the entire range of coupling for a fast bath but only in the strong coupling regime for a slow bath. The variational method is capable of interpolating between these two methods and is valid over a much broader range of parameters.
Semiclassical perturbation theory for diffraction in heavy atom surface scattering
Authors: Miret-Artés Salvador , Daon Shauli , Pollak Eli
Published: June 2012

The semiclassical perturbation theory formalism of Hubbard and Miller [J. Chem. Phys. 78, 1801 (1983)] for atom surface scattering is used to explore the possibility of observation of heavy atom diffractive scattering. In the limit of vanishing ℏ the semiclassical theory is shown to reduce to the classical perturbation theory. The quantum diffraction pattern is sensitive to the characteristics of the beam of incoming particles. Necessary conditions for observation of quantum diffraction are derived for the angular width of the incoming beam. An analytic expression for the angular distribution as a function of the angular and momentum variance of the incoming beam is obtained. We show both analytically and through some numerical results that increasing the angular width of the incident beam leads to decoherence of the quantum diffraction peaks and one approaches the classical limit. However, the incoherence of the beam in the parallel direction does not destroy the diffraction pattern. We consider the specific example of Ar atoms scattered from a rigid LiF(100) surface.
Analysis of the Heyd-Scuseria-Ernzerhof density functional parameter space
Authors: Moussa Jonathan E. , Schultz Peter A. , Chelikowsky James R.
Published: June 2012

The Heyd-Scuseria-Ernzerhof (HSE) density functionals are popular for their ability to improve upon the accuracy of standard semilocal functionals such as Perdew-Burke-Ernzerhof (PBE), particularly for semiconductor band gaps. They also have a reduced computational cost compared to hybrid functionals, which results from the restriction of Fock exchange calculations to small inter-electron separations. These functionals are defined by an overall fraction of Fock exchange and a length scale for exchange screening. We systematically examine this two-parameter space to assess the performance of hybrid screened exchange (sX) functionals and to determine a balance between improving accuracy and reducing the screening length, which can further reduce computational costs. Three parameter choices emerge as useful: “sX-PBE” is an approximation to the sX-LDA screened exchange density functionals based on the local density approximation (LDA); “HSE12” minimizes the overall error over all tests performed; and “HSE12s” is a range-minimized functional that matches the overall accuracy of the existing HSE06 parameterization but reduces the Fock exchange length scale by half. Analysis of the error trends over parameter space produces useful guidance for future improvement of density functionals.
Optical actuation of microelectromechanical systems using photoelectrowetting
Authors: Gaudet Matthieu , Arscott Steve
Published: June 2012

We demonstrate a proof-of-concept that microelectromechanical systems (MEMS) can be optically actuated using photoelectrowetting. A 30 µm thick aluminium cantilever is actuated using an ordinary white light source via the modulation of capillary forces in a liquid bridge on a Teflon® coated commercial silicon wafer. A deflection of 58 µm is observed using a light power of 100 mW at a bias of 7 V. The deflection of the cantilever relies on the photoelectrowetting effect [S. Arscott, Sci. Rep. 1, 184 (2011)]. Such wireless actuation could be useful for optical addressing and control of autonomous wireless sensors, MEMS, and microsystems.
Magnetostatic detection using magnetoresistive sensors with vertical motion flux modulation
Authors: Hu Jiafei , Pan Mengchun , Tian Wugang , Chen Dixiang , Zhao Jianqiang
Published: June 2012

Recently, the flux modulation has been presented to deal with the 1/f noise of magnetoresistive (MR) sensors. However, the efficiency of most flux modulation schemes with simple micro- electromechanical-system (MEMS) actuators is not satisfying yet. In this paper, the vertical motion flux modulation (VMFM) is proposed to improve the modulation efficiency. In VMFM, the soft magnetic film driven by a MEMS actuator vibrates vertically above the MR sensors with a pair of flux concentrators. Consequently, the detected magnetostatic field is modulated to the higher frequency where the 1/f noise is much lower. A VMFM prototype based on AA002 (multi-layered giant magnetoresistive sensors) was fabricated and its flux modulation efficiency can reach 18.7%, which exceeds most achieved efficiency with other schemes. Also, the magnetostatic detection ability is improved to 530 pT/√Hz.
Size effects on the impact response of copper nanobeams
Authors: Chen Zhen , Jiang Shan , Gan Yong , Oloriegbe Y. S. , Sewell Thomas D. , Thompson Donald L.
Published: June 2012

Molecular dynamics simulations are performed to study size effects on the impact response of copper nanobeam targets subjected to impacts by copper nanobeam flyers with different impact velocities. It is found that the Hugoniot response is size-dependent, while the aspect ratio – that is, the ratio of flyer and target nanobeam heights – has a small effect. It is also observed that the propagation speed of a disordering front generated at the impact surface is close to the shock wave speed initially, but decreases as dislocations form. The thermal gradient in the target is mainly due to the quasi-temperature difference (transient spatial localization of kinetic energy) between hexagonal-close-packed atoms and face-centered-cubic atoms. The findings for the impact stress, defect evolution, and quasi-temperature could be useful for better understanding the responses of nanosystems to extreme loading conditions.
Superconducting fluctuations and anomalous phonon renormalization much above superconducting transition temperature in Ca4Al2O5.7Fe2As2
Authors: Kumar Pradeep , Bera A. , Muthu D. V. S , Shirage P. M. , Iyo A. , Sood A. K.
Published: June 2012

Raman studies on Ca4Al2O5.7Fe2As2 superconductor in the temperature range of 5 K to 300 K, covering the superconducting transition temperature Tc = 28.3 K, reveal that the Raman mode at ∼230 cm−1 shows a sharp jump in frequency by ∼2% and linewidth increases by ∼175% at To ∼ 60 K. Below To, anomalous softening of the mode frequency and a large decrease by ∼10 cm−1 in the linewidth are observed. These precursor effects at T0 (∼2Tc) are attributed to significant superconducting fluctuations, possibly enhanced due to reduced dimensionality arising from weak coupling between the well separated (∼15 Å) Fe-As layers in the unit cell. A large blue-shift of the mode frequency between 300 K and 60 K (∼7%) indicates strong spin-phonon coupling in this superconductor.
Surface instability of binary compounds caused by sputter yield amplification
Authors: Mark Bradley R.
Published: June 2012

It is demonstrated that the flat surface of a binary material that is subjected to normal-incidence ion bombardment can be unstable even if the curvature dependence of the sputter yields is negligibly small. This unforeseen instability is brought about by sputter yield amplification, and it results in the formation of a disordered array of nanodots with the lighter of the two atomic species concentrated at the peaks of the dots.
Structural phase separation and optical and magnetic properties of BaTi1−xMnxO3 multiferroics
Authors: Dang N. V. , Phan The-Long , Thanh T. D. , Lam V. D. , Hong L. V.
Published: June 2012

Our work studies the influences of the Mn doping on structural characterization and optical and magnetic properties of BaTi1−xMnxO3 (x = 0.0–0.12) prepared by conventional solid-state reaction. Detailed analyses of XRD patterns and Raman scattering spectra indicate an incorporation of Mn dopants into the Ti sites of BaTiO3 host lattices, and the tetragonal-hexagonal transformation taking place at a threshold concentration of xc ≈ 0.01. An increase of Mn-doping content in BaTi1-xMnxO3 introduces more electronic levels associated with lattice defects and Mn ions to the forbidden gap and thus reduces luminescent intensity in the visible region. Magnetic data recorded at room temperature reveal that all the samples exhibit ferromagnetic order, and there is a phase separation in magnetism as varying x values. Particularly, the samples with x = 0.5–0.7 have a coexistence of two ferromagnetic phases with different coercivities, which are associated with tetragonal and hexagonal Mn-doped BaTiO3 structures. The nature of ferromagnetism is explained by means of the results of structural and optical analyses, where Mn3+ and Mn4+ ions play a crucial role.
White House, Congress mull future of scientific journals
Authors: Kramer David
Published: June 2012

Publishers tout actions they have taken to increase public access to their journals, but libraries complain about mounting subscription costs.
Transformations from WISE to 2MASS, SDSS and BVI Photometric Systems: II. Transformation Equations for Red-Clump Stars
Authors: Bilir S. , Karaali S. , Dağtekin N. D. , Önal Ö. , Ak S. , Ak T. , Cabrera-Lavers A.
Published: June 2012

We present colour transformations for the conversion of Wide-Field Survey Explorer W1, W2, and W3 magnitudes to the Johnson–Cousins BVIc, Sloan Digital Sky Survey gri, and Two Micron All Sky Survey JHKs photometric systems, for red clump (RC) stars. RC stars were selected from the Third Radial Velocity Experiment Data Release. The apparent magnitudes were collected by matching the coordinates of this sample with different photometric catalogues. The final sample (355 RC stars) was used to obtain metallicitydependent and free-of-metallicity transformations. These transformations combined with known absolute magnitudes at shorter wavelengths can be used in space density determinations for the Galactic (thin and thick) discs at distances larger than the ones evaluated with JHKs photometry alone, hence providing a powerful tool in the analysis of Galactic structure.
Leaf traits and persistence of relict and endangered tree species in a rare plant community
Authors: Liao Jian X. , Chen Juan , Jiang Ming X. , Huang Han D.
Published: June 2012

The rare plant communities, located in Houhe Nature Reserve, Hubei, China, are remnant evergreen and deciduous mixed broadleaved forest where many tree species have been identified as Tertiary relict and endangered plants and environmental conditions are typically characterised by low light and high rainfall. Knowledge of their patterns of leaf traits would contribute to our understanding of persistence of relict and endangered species. Here, we measured leaf mass per unit area (LMA), mass-based photosynthetic capacity (Amass), nitrogen content (Nmass), construction cost (CCmass) and photosynthetic nitrogen-use efficiency (PNUE) of 20 major tree species in a typical rare plant community. Correlations among leaf traits in the community were consistent with those from the global dataset, but they had lower Amass at any given Nmass and lower Amass and PNUE at any given LMA. Such results suggested the capacity and efficiency of photosynthetic gain from a unit investment in leaf tissue tend to be lower in the community. Moreover, they had lower LMA, CCmass and PNUE but higher Nmass than global broadleaved tree species. For relict and endangered species, the common limited factors (such as low light and high rainfall), similar leaf traits as coexisting deciduous non-endangered species and significant leaf trait relationships may allow them to persist in the community.
Do experimental methods affect estimates of pollen digestion by birds?
Authors: Fleming Patricia A. , Moore Tracey L.
Published: June 2012

Pollen protoplasts may supply important nutritional resources for birds; however, they are locked up within the mechanically strong and biochemically complex pollen wall. Previous studies of pollen digestion in birds have yielded highly variable and often contradictory results. We tested whether these differences could reflect the vastly different methodologies that have been used. We used a standard method to investigate digestion of Banksia grandis (Proteaceae) pollen in New Holland honeyeaters (Phylidonyris novaehollandiae). Four types of B. grandis pollen were examined: fresh, frozen for a week, stored in conditions to stimulate pregermination for 24 h, or collected by honeybees. Our data indicate that although pollen treatment may influence digestibility of the pollen grains, these differences do not reach statistical significance because they are dwarfed by a high degree of variability between birds fed the same diet as well as variability in gut transit time (generally more pollen grains were digested over longer transit times). Similar patterns were observed for red wattlebirds (Anthochaera carunculata) fed bee-collected pollen. We believe that feeding behaviour or gut transit time may explain the marked differences between previous studies of pollen digestion by nectarivores, particularly the conflicting results for New Holland honeyeaters.
Dissociating activity in the lateral intraparietal area from value using a visual foraging task
Authors: Mirpour Koorosh , Bisley James W.
Published: June 2012

We make decisions about where to look approximately three times per second in normal viewing. It has been suggested that eye movements may be guided by activity in the lateral intraparietal area (LIP), which is thought to represent the relative value of objects in space. However, it is not clear how values for saccade goal selection are prioritized while free-viewing in a cluttered visual environment. To address this question, we compared the neural responses of LIP neurons in two subjects with their saccadic behavior and three estimates of stimulus value. These measures were extracted from the subjects’ performance in a visual foraging task, in which we parametrically controlled the number of objects on the screen. We found that the firing rates of LIP neurons did not correlate well with the animals’ behavior or any of our estimated measures of value. However, if the LIP activity was further normalized, it became highly correlated with the animals’ decisions. These data suggest that LIP activity does not represent value in complex environments, but that the value can easily be extracted with one further step of processing. We propose that activity in LIP represents attentional priority and that the downstream normalization of this activity is an essential process in guiding action.
Structural basis of histidine kinase autophosphorylation deduced by integrating genomics, molecular dynamics, and mutagenesis
Authors: Dago Angel E. , Schug Alexander , Procaccini Andrea , Hoch James A. , Weigt Martin , Szurmant Hendrik
Published: June 2012

Signal transduction proteins such as bacterial sensor histidine kinases, designed to transition between multiple conformations, are often ruled by unstable transient interactions making structural characterization of all functional states difficult. This study explored the inactive and signal-activated conformational states of the two catalytic domains of sensor histidine kinases, HisKA and HATPase. Direct coupling analyses, a global statistical inference approach, was applied to >13,000 such domains from protein databases to identify residue contacts between the two domains. These contacts guided structural assembly of the domains using MAGMA, an advanced molecular dynamics docking method. The active conformation structure generated by MAGMA simultaneously accommodated the sequence derived residue contacts and the ATP-catalytic histidine contact. The validity of this structure was confirmed biologically by mutation of contact positions in the
Bacillus subtilis
sensor histidine kinase KinA and by restoration of activity in an inactive KinA(HisKA):KinD(HATPase) hybrid protein. These data indicate that signals binding to sensor domains activate sensor histidine kinases by causing localized strain and unwinding at the end of the C-terminal helix of the HisKA domain. This destabilizes the contact positions of the inactive conformation of the two domains, identified by previous crystal structure analyses and by the sequence analysis described here, inducing the formation of the active conformation. This study reveals that structures of unstable transient complexes of interacting proteins and of protein domains are accessible by applying this combination of cross-validating technologies.
Influence of cobalamin scarcity on diatom molecular physiology and identification of a cobalamin acquisition protein
Authors: Bertrand Erin M. , Allen Andrew E. , Dupont Christopher L. , Norden-Krichmar Trina M. , Bai Jing , Valas Ruben E. , Saito Mak A.
Published: June 2012

Diatoms are responsible for ∼40% of marine primary production and are key players in global carbon cycling. There is mounting evidence that diatom growth is influenced by cobalamin (vitamin B
12
) availability. This cobalt-containing micronutrient is only produced by some bacteria and archaea but is required by many diatoms and other eukaryotic phytoplankton. Despite its potential importance, little is known about mechanisms of cobalamin acquisition in diatoms or the impact of cobalamin scarcity on diatom molecular physiology. Proteomic profiling and RNA-sequencing transcriptomic analysis of the cultured diatoms
Phaeodactylum tricornutum
and
Thalassiosira pseudonana
revealed three distinct strategies used by diatoms to cope with low cobalamin: increased cobalamin acquisition machinery, decreased cobalamin demand, and management of reduced methionine synthase activity through changes in folate and S-adenosyl methionine metabolism. One previously uncharacterized protein, cobalamin acquisition protein 1 (CBA1), was up to 160-fold more abundant under low cobalamin availability in both diatoms. Autologous overexpression of CBA1 revealed association with the outside of the cell and likely endoplasmic reticulum localization. Cobalamin uptake rates were elevated in strains overexpressing CBA1, directly linking this protein to cobalamin acquisition. CBA1 is unlike characterized cobalamin acquisition proteins and is the only currently identified algal protein known to be implicated in cobalamin uptake. The abundance and widespread distribution of transcripts encoding CBA1 in environmental samples suggests that cobalamin is an important nutritional factor for phytoplankton. Future study of CBA1 and other molecular signatures of cobalamin scarcity identified here will yield insight into the evolution of cobalamin utilization and facilitate monitoring of cobalamin starvation in oceanic diatom communities.
Feature binding and attention in working memory: A resolution of previous contradictory findings
Authors: Allen Richard J. , Hitch Graham J. , Mate Judit , Baddeley Alan D.
Published: June 2012

We aimed to resolve an apparent contradiction between previous experiments from different laboratories, using dual-task methodology to compare effects of a concurrent executive load on immediate recognition memory for colours or shapes of items or their colour–shape combinations. Results of two experiments confirmed previous evidence that an irrelevant attentional load interferes equally with memory for features and memory for feature bindings. Detailed analyses suggested that previous contradictory evidence arose from limitations in the way recognition memory was measured. The present findings are inconsistent with an earlier suggestion that feature binding takes place within a multimodal episodic buffer Baddeley, (2000) and support a subsequent account in which binding takes place automatically prior to information entering the episodic buffer Baddeley, Allen, & Hitch, (2011). Methodologically, the results suggest that different measures of recognition memory performance ( A′, d′, corrected recognition) give a converging picture of main effects, but are less consistent in detecting interactions. We suggest that this limitation on the reliability of measuring recognition should be taken into account in future research so as to avoid problems of replication that turn out to be more apparent than real.
Rapid communication: When far becomes near: Shared environments activate action simulation
Authors: Griffiths Debra , Tipper Steven P.
Published: June 2012

It has been proposed that one means of understanding a person's current behaviour and predicting future actions is by simulating their actions. That is, when another person's actions are observed, similar motor processes are activated in the observer. For example, after observing a reach over an obstacle, a person's subsequent reach trajectory is more curved, reflecting motor priming. Importantly, such motor states are only activated if the observed action is in near (peripersonal) space. However, we demonstrate that when individuals share action environments, simulation of another person's obstacle avoiding reach path takes place even when the action is in far (extrapersonal) space. We propose that action simulation is influenced by factors such as ownership. When an “owned” object is a potential future obstacle, even when it is viewed beyond current action space, simulations are evoked, and these leave a more stable memory capable of influencing future behaviour.
The Cauchy problem for 𝑝-evolution equations
Authors: Cicognani Massimo , Colombini Ferruccio
Published: June 2012

In this paper we deal with the Cauchy problem for evolution equations with real characteristics. We show that the problem is well-posed in Sobolev spaces assuming a suitable decay of the coefficients as the space variable

x
→
∞

x\to \infty

. In some cases, such a decay may also compensate a lack of regularity with respect to the time variable

t
t

.
Inequalities for eigenvalues of selfadjoint operators
Authors: Hook Stephen M.
Published: June 2012

We establish several inequalities for eigenvalues of selfadjoint operators in Hilbert space. The results are quite general. In particular, let

Ω
\Omega

be a region in

R

n

,
∂
Ω

{{\mathbf {R}}^n},\partial \Omega

its boundary and

Δ
\Delta

the Laplace operator in

R

n

{{\mathbf {R}}^n}

. Let

p
(
x
)

p(x)

be a polynomial of degree

m
m

having nonnegative real coefficients. We show that if the problems (1)

−
Δ
u
=
λ
u

- \Delta u = \lambda u

in

Ω
;
u
=
0

\Omega ;u = 0

on

∂
Ω

\partial \Omega

; (2)

p
(
−
Δ
)
υ
=
μ
υ

p( - \Delta )\upsilon = \mu \upsilon

in

Ω
;
υ

\Omega ;\upsilon

and its first

m
−
1
derivatives
=
0
on
∂
Ω

m - 1 \text {derivatives}=0 \text {on} \partial \Omega

; and (3)

(
−
Δ

)
m

w
=
v
w

{( - \Delta )^m}w = vw

in

Ω
;
w

\Omega ;w

and its first

m
−
1
derivatives
=
0
on
∂
Ω

m - 1 \text {derivatives}=0 \text {on} \partial \Omega

are selfadjoint with discrete spectra of finite multiplicity

λ
1

≤

λ
2

≤
⋯

{\lambda _1} \leq {\lambda _2} \leq \cdots

etc. then (4)
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="p left-parenthesis normal upper Gamma Subscript i Superscript 1 slash m Baseline right-parenthesis greater-than-or-equal-to mu Subscript i Baseline greater-than-or-equal-to p left-parenthesis lamda Subscript i Baseline right-parenthesis">

p
(

Γ
i

1

/

m

)
≥

μ
i

≥
p
(

λ
i

)

p(\Gamma _i^{1/m}) \geq {\mu _i} \geq p({\lambda _i})

for each index

i
i

. The set of problems (1), (2), (3) and the result (4) is only one example of our more general result. The above problems (1), (2), and (3) can be thought of as related through the single operator given by the Laplacian. We also establish results for eigenvalues for unrelated operators. Let

A
A

,

B
B

and

A
+
B

A + B

be selfadjoint on domains

D
A

,

D
B

{D_A},{D_B}

, and

D

A
+
B

{D_{A + B}}

with

D

A
+
B

⊆

D
A

∩

D
B

{D_{A + B}} \subseteq {D_A} \cap {D_B}

. If

A
A

,

B
B

, and

A
+
B

A + B

have discrete spectra

{

λ
i

}

i
=
1

∞

,
{

μ
i

}

i
=
1

∞

\{ {\lambda _i}\} _{i = 1}^\infty ,\{ {\mu _i}\} _{i = 1}^\infty

and

{

Γ
i

}

i
=
1

∞

\{ {\Gamma _i}\} _{i = 1}^\infty

arranged in ascending order, as above, then inequality (5)
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="sigma-summation Underscript i equals 1 Overscript n Endscripts normal upper Gamma Subscript i Baseline greater-than-or-equal-to sigma-summation Underscript i equals 1 Overscript n Endscripts left-parenthesis lamda Subscript i Baseline plus v Subscript i Baseline right-parenthesis">

∑

i
=
1

n

Γ
i

≥

∑

i
=
1

n

(

λ
i

+

v
i

)

\sum \nolimits _{i = 1}^n {{\Gamma _i}} \geq \sum \nolimits _{i = 1}^n {({\lambda _i} + {v_i})}

is established for each positive integer

n
n

.
On the Dirichlet space for finitely connected regions
Authors: Chan Kit Chak
Published: June 2012

This paper is devoted to the study of the Dirichlet space

Dir
⁡
(
G
)

\operatorname {Dir} (G)

for finitely connected regions

G
G

; we are particularly interested in the algebra of bounded multiplication operators on this space. Results in different directions are obtained. One direction deals with the structure of closed subspaces invariant under all bounded multiplication operators. In particular, we show that each such subspace contains a bounded function. For regions with circular boundaries we prove that a finite codimensional closed subspace invariant under multiplication by

z
z

must be invariant under all bounded multiplication operators, and furthermore it is of the form

p
Dir
⁡
(
G
)

p\operatorname {Dir} (G)

, where

p
p

is a polynomial with all its roots lying in

G
G

. Another direction is to study cyclic and noncyclic vectors for the algebra of all bounded multiplication operators. Typical results are: if

f
∈
Dir
⁡
(
G
)

f \in \operatorname {Dir} (G)

and

f
f

is bounded away from zero then

f
f

is cyclic; on the other hand, if the zero set of the radial limit function of

f
f

on the boundary has positive logarithmic capacity, then

f
f

is not cyclic. Also, some other sufficient conditions for a function to be cyclic are given. Lastly, we study transitive operator algebras containing all bounded multiplication operators; we prove that they are dense in the algebra of all bounded operators in the strong operator topology.
The method of negative curvature: the Kobayashi metric on 𝑃₂ minus 4 lines
Authors: Cowen Michael J.
Published: June 2012

Bloch, and later H. Cartan, showed that if

H
1

,
…
,

H

n
+
2

{H_1}, \ldots ,{H_{n + 2}}

are

n
+
2

n + 2

hyperplanes in general position in complex projective space

P

n

{{\mathbf {P}}_n}

, then

P

n

−

H
1

∪
⋯
∪

H

n
+
2

{{\mathbf {P}}_n} - {H_1} \cup \cdots \cup {H_{n + 2}}

is (in current terminology) hyperbolic modulo

Δ
\Delta

, where

Δ
\Delta

is the union of the hyperplanes
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="left-parenthesis upper H Subscript Sub Superscript 1 Subscript Baseline intersection midline-horizontal-ellipsis intersection upper H Subscript k Baseline right-parenthesis circled-plus left-parenthesis upper H Subscript k plus 1 Baseline intersection midline-horizontal-ellipsis intersection upper H Subscript n plus 2 Baseline right-parenthesis">

(

H

1

∩
⋯
∩

H
k

)
⊕
(

H

k
+
1

∩
⋯
∩

H

n
+
2

)

({H_{^1}} \cap \cdots \cap {H_k}) \oplus ({H_{k + 1}} \cap \cdots \cap {H_{n + 2}})

for

2
⩽
k
⩽
n

2 \leqslant k \leqslant n

and all permutations of the

H
i

{H_i}

. Their results were purely qualitative. For

n
=
1

n = 1

, the thrice-punctured sphere, it is possible to estimate the Kobayashi metric, but no estimates were known for

n
⩾
2

n \geqslant 2

. Using the method of negative curvature, we give an explicit model for the Kobayashi metric when

n
=
2

n = 2

.
The number of solutions of norm form equations
Authors: Schmidt Wolfgang M.
Published: June 2012

A norm form is a form

F
(

X
1

,
…
,

X
n

)

F({X_1}, \ldots ,{X_n})

with rational coefficients which factors into linear forms over

C

{\mathbf {C}}

but is irreducible or a power of an irreducible form over

Q

{\mathbf {Q}}

. It is known that a nondegenerate norm form equation

F
(

x
1

,
…
,

x
n

)
=
m

F({x_1}, \ldots ,{x_n}) = m

has only finitely many solutions

(

x
1

,
…
,

x
n

)
∈

Z

n

({x_1}, \ldots ,{x_n}) \in {{\mathbf {Z}}^n}

. We derive explicit bounds for the number of solutions. When

F
F

has coefficients in

Z

{\mathbf {Z}}

, these bounds depend only on

n
n

,

m
m

and the degree of

F
F

, but are independent of the size of the coefficients of

F
F

.
Dichromatic link invariants
Authors: Hoste Jim , Kidwell Mark E.
Published: June 2012

We investigate the skein theory of oriented dichromatic links in

S
3

{S^3}

. We define a new chromatic skein invariant for a special class of dichromatic links. This invariant generalizes both the two-variable Alexander polynomial and the twisted Alexander polynomial. Alternatively, one may view this new invariant as an invariant of oriented monochromatic links in

S
1

×

D
2

{S^1} \times {D^2}

, and as such it is the exact analog of the twisted Alexander polynomial. We discuss basic properties of this new invariant and applications to link interchangeability. For the full class of dichromatic links we show that there does not exist a chromatic skein invariant which is a mutual extension of both the two-variable Alexander polynomial and the twisted Alexander polynomial.
Butler groups of infinite rank. II
Authors: Dugas Manfred , Hill Paul , Rangaswamy K. M.
Published: June 2012

A torsion-free abelian group

G
G

is called a Butler group if

Bext
⁡
(
G
,
T
)
=
0.

\operatorname {Bext} (G,T) = 0.

for any torsion group

T
T

. We show that every Butler group

G
G

of cardinality

ℵ
1

{\aleph _1}

is a

B
2

{B_2}

-group; i.e.,

G
G

is a union of a smooth ascending chain of pure subgroups

G
α

{G_\alpha }

where

G

α
+
1

=

G
α

+

B
α

,

B
α

{G_{\alpha + 1}} = {G_\alpha } + {B_\alpha },{B_\alpha }

a Butler group of finite rank. Assuming the validity of the continuum hypothesis (CH), we show that every Butler group of cardinality not exceeding

ℵ
ω

{\aleph _\omega }

is a

B
2

{B_2}

-group. Moreover, we are able to prove that the derived functor

Bext
2

(
A
,
T
)
=
0

{\operatorname {Bext} ^2}(A,T) = 0

for any torsion group

T
T

and any torsion-free

A
A

with

|

A

|

⩽

ℵ
ω

|A| \leqslant {\aleph _\omega }

. This implies that under CH all balanced subgroups of completely decomposable groups of cardinality

⩽

ℵ
ω

\leqslant {\aleph _\omega }

are

B
2

{B_2}

-groups.