bluuebunny/crossref_metadata_2025 huggingface dataset:
Local electronic properties and magnetism of (Cd,Mn)Te quantum wells
Authors: Sangaletti L. , Mozzati M. C. , Drera G. , Aguekian V. , Floreano L. , Morgante A. , Goldoni A. , Karczewski G.
Published: April 2010

The electronic properties of heterostructures containing (Cd,Mn)Te quantum wells are probed by soft x-ray spectroscopies. We provide experimental evidence that Mn ions are in the Mn2+ (3d5) electronic configuration, and rule out the possibility that charge transfer and crystal field effects can reduce the magnetic moment of each Mn ion to the value (0.61) extracted from the fitting of the magnetization curve with a Brillouin function. These results confirm that the observed magnetic behavior can be correctly explained by assuming an antiferromagnetic coupling between nearest-neighbor S=5/2 Mn2+ ions, rather than a paramagnetic response from an ensemble of low-spin Mn ions.
Electric field induced anisotropy modification in (Ga,Mn)As: A strategy for the precessional switching of the magnetization
Authors: Balestriere P. , Devolder T. , Wunderlich J. , Chappert C.
Published: April 2010

We propose a scheme for the precessional switching of the magnetization in the magnetic semiconductor (Ga,Mn)As using cubic anisotropy field reduction triggered by electric field and a small assisting magnetic field. We identify magnetic field regions for toggle switching and direct-overwrite of the magnetization and discuss the toggle switching critical curve dependence on the cubic anisotropy field decrease. We also determine the half-precession period of the magnetization and propose field conditions for magnetization trajectories which are optimally immune to external noise and damping.
The effects of wet surface clean and in situ interlayer on In0.52Al0.48As metal-oxide-semiconductor characteristics
Authors: Kobayashi Masaharu , Thareja Gaurav , Sun Yun , Goel Niti , Garner Mike , Tsai Wilman , Pianetta Piero , Nishi Yoshio
Published: April 2010

The effect of the surface passivation with ex situ wet clean as well as insertion of an III-V in situ grown interlayer, on the HfO2/In0.52Al0.48As interface characteristics was investigated with capacitance/conductance measurements, and synchrotron radiation photoemission spectroscopy. A very thin aluminum oxide passivation layer grown after In0.52Al0.48As surface clean improves the In0.52Al0.48As metal-oxide-semiconductor characteristics compared to native oxide covered interface, giving an interface state density (Dit) 3.8×1012 cm−2 eV−1 at 0.31 eV from conduction band edge. Furthermore, insertion of a thin In0.53Ga0.47As cap layer effectively prevented Al oxidation further improving electrical properties, such as frequency dispersion, hysteresis, Dit (2.7×1012 cm−2 eV−1) and capacitive equivalent oxide thickness.
Comment on “Note on the relation between thermophoresis and slow uniform flow problems for a rarefied gas” [Phys. Fluids 21, 112001 (2009)]
Authors: Sharipov Felix
Published: April 2010

This comment responds to the unjustified criticisms by Takata [Phys. Fluids 21, 112001 (2009)] to papers by Sharipov on the Onsager–Casimir reciprocal relations. It is shown that such relations obtained by Sharipov [Physica A 203, 437 (1994)], where the thermophoresis problem is not considered, are correct in the frame of assumptions made in the paper.
Stable, self-ballasting field emission from zinc oxide nanowires grown on an array of vertically aligned carbon nanofibers
Authors: Li C. , Zhang Y. , Mann M. , Hiralal P. , Unalan H. E. , Lei W. , Wang B. P. , Chu D. P. , Pribat D. , Amaratunga G. A. J. , Milne W. I.
Published: April 2010

A structure composed of zinc oxide nanowires (ZNWs) grown hydrothermally on an array of vertically aligned carbon nanofibers (CNFs) was fabricated and its field emission properties determined and compared with bare CNF arrays. The combination produced a macroscopic turn-on field of 1.2 V/μm which was found to be the lowest reported from ZNWs deposited on a two-dimensional substrate and much less than the equivalent CNFs array (5.2 V/μm). Crucially, field emission was found to be much more stable at higher pressures of 5×10−6 mbar without exhibiting current degradation for a fixed external field, while emitting with a current density of 1 mA/cm2, the current density typically required for backlighting and field emission displays. We propose a self-ballasting mechanism, in which the low carrier density in the zinc oxide prevents current runaway in the presence of adsorbed species.
Singlet-triplet transition in a few-electron lateral In0.75Ga0.25As/In0.75Al0.25As quantum dot
Authors: Deon F. , Pellegrini V. , Carillo F. , Giazotto F. , Biasiol G. , Sorba L. , Beltram F.
Published: April 2010

The magnetic-field evolution of Coulomb blockade peaks in lateral In0.75Ga0.25As/In0.75Al0.25As quantum dots in the few-electron regime is reported. Quantum dots are defined by gates evaporated onto a 60-nm-thick hydrogen silsesquioxane insulating film. A gyromagnetic factor g∗≈4.4 is measured via zero-bias spin spectroscopy and a transition from singlet to triplet spin configuration is found at an in-plane magnetic field B=0.7 T. This observation opens the way to the manipulation of singlet and triplet states at moderate fields and its relevance for quantum information applications will be discussed.
Opposite bias polarity dependence of resistive switching in n-type Ga-doped-ZnO and p-type NiO thin films
Authors: Kinoshtia Kentaro , Okutani Takumi , Tanaka Hayato , Hinoki Toshio , Yazawa Kenji , Ohmi Koutoku , Kishida Satoru
Published: April 2010

A hypothesis based on the model that explains the resistance change effect of resistive random access memory by redox reaction is proposed. This hypothesis leads to the conclusion that the relationship between the polarity of the applied bias voltage and the resultant resistance change in p-type semiconductors is opposite to that for n-type semiconductors. The bias polarity dependence of the resultant resistance change in ZnO and Ga-doped ZnO (GZO), which are n-type semiconductors, and that in NiO, which is a p-type semiconductor, were investigated using conducting atomic force microscopy. Opposite bias polarity was confirmed to induce GZO and NiO into the same resistance state, which is consistent with the hypothesis.
Strong vortex pinning in Co-doped BaFe2As2 single crystal thin films
Authors: Tarantini C. , Lee S. , Zhang Y. , Jiang J. , Bark C. W. , Weiss J. D. , Polyanskii A. , Nelson C. T. , Jang H. W. , Folkman C. M. , Baek S. H. , Pan X. Q. , Gurevich A. , Hellstrom E. E. , Eom C. B. , Larbalestier D. C.
Published: April 2010

We report the field and angular dependences of Jc of truly epitaxial Co-doped BaFe2As2 thin films grown on SrTiO3/(La,Sr)(Al,Ta)O3 with different SrTiO3 template thicknesses. The films show Jc comparable to single crystals and a maximum pinning force Fp(0.6Tc)>5 GN/m3 at H/Hirr∼0.5 indicative of strong high-field vortex pinning. Due to the strong correlated c-axis pinning, Jc for field along the c-axis exceeds Jc for H∥ab plane, inverting the expectation of the Hc2 anisotropy. High resolution transmission electron microscopy reveals that the strong vortex pinning is due to a high density of nanosize columnar defects.
Unexpected magnetic behavior of Cu-doped CeO2
Authors: Slusser Paul , Kumar Dhananjay , Tiwari Ashutosh
Published: April 2010

In this paper, we are reporting the magnetic behavior of Cu-doped CeO2 films grown on single crystal LaAlO3(001) substrates. The Ce1−xCuxO2 films with x=0.03 and 0.15 were deposited by a pulsed laser deposition technique and were thoroughly characterized using high resolution x-ray diffraction, x-ray photospectroscopy, ultraviolet-visible absorption spectroscopy, and magnetic property measurements. All the characterization experiments showed the films to be of high quality, epitaxial, and free of any secondary phases. Detailed structure-property correlation analysis revealed the observed ferromagnetic property to be the intrinsic property of the material.
Characterization of fast charge trapping in bias temperature instability in metal-oxide-semiconductor field effect transistor with high dielectric constant
Authors: Jo Minseok , Kim Seonghyun , Lee Joonmyoung , Jung Seungjae , Park Ju-Bong , Jung Hyung-Suk , Choi Rino , Hwang Hyunsang
Published: April 2010

We used pulse bias temperature instability measurements to investigate the energy distributions of fast charge trapping sources to understand the origin of fast charge traps in an HfO2 device. The trap energy level was extracted using a trap-to-band tunneling model by changing the measurement delay time. The fast electron traps in an n-channel metal oxide semiconductor field effect transistors (MOSFET) exist in a 1 eV range below the bottom of the HfO2 conduction band. In the case of a p-channel MOSFET, the fast hole traps exist in the range 1–2 eV above the top of the HfO2 valence band, which could be attributed to a formation of negatively charged NO defects.
External control of the scattering properties of a single optical nanoantenna
Authors: Huang C. , Bouhelier A. , Berthelot J. , des-Francs G. Colas , Finot E. , Weeber J.-C. , Dereux A. , Kostcheev S. , Baudrion A.-L. , Plain J. , Bachelot R. , Royer P. , Wiederrecht G. P.
Published: April 2010

We present a mechanism to control the scattering properties of individual optical nanoantennas by applying an external electric field. We find that by electrically tuning an anisotropic load medium the scattered intensity becomes voltage-dependent. We also demonstrate that the scattering diagram of the antenna can be externally adjusted. This on-demand command opens up the possibility to tune an antenna without changing its geometrical parameters.
Ferroelectric BaTiO3 single crystal under superstrong electric fields up to 55 MV/m: A comparative experimental and theoretical study
Authors: Leontyev I. N. , Fesenko O. E. , Leontyev N. G. , Dkhil B.
Published: April 2010

We investigated the effect of huge electric field up to E=55 MV/m on tetragonal ferroelectric phase of BaTiO3 single crystal. Both lattice parameters and the dielectric susceptibility along the polar axis were determined. The induced polarization shows a continuous increase up to 20% of the spontaneous polarization. The longitudinal d33 and transverse d31 piezoelectric coefficients were also determined. The experimental data are described by a phenomenological approach. Interestingly, an intermediate critical electric field value of E∼25 MV/m was evidenced suggesting that the physics below and above this value are different.
Electronic properties of strained Si/Ge core-shell nanowires
Authors: Peng Xihong , Logan Paul
Published: April 2010

We investigated the electronic properties of strained Si/Ge core-shell nanowires along the [110] direction using first principles calculations based on density-functional theory. The diameter of the studied core-shell wire is up to 5 nm. We found the band gap of the core-shell wire is smaller than that of both pure Si and Ge wires with the same diameter. This reduced band gap is ascribed to the intrinsic strain between Ge and Si layers, which partially counters the quantum confinement effect. The external strain is further applied to the nanowires for tuning the band structure and band gap. By applying sufficient tensile strain, we found the band gap of Si-core/Ge-shell nanowire with diameter larger than ∼3 nm experiences a transition from direct to indirect gap.
Genetic (co)variances between wrinkle score and absence of breech strike in mulesed and unmulesed Merino sheep, using a threshold model
Authors: Scholtz A. J. , Cloete S. W. P. , van Wyk J. B. , Misztal I. , du Toit E. , van der Linde T. C. de K.
Published: April 2010

Heritability estimates for, and genetic correlations among neck wrinkle score, body wrinkle score, breech wrinkle score and the absence of breech strike were determined on 2918 16-month hoggets from a selection experiment with South African Merinos. Data were obtained from the lamb drops of 9 years between 1998 and 2007, born as the progeny of 247 sires and 1250 dams. All progeny born until 2002 were subjected to the Modified Mules operation as lambs (n = 1799). However, due to international pressure to phase out the Mules operation, animals from 2003 onwards were not mulesed (n = 1119). During both periods, the experimental animals were maintained in single flocks (separated on sex) after weaning. Progeny were subjected to visual appraisal of wrinkle scores (range) on the neck (1–6), body (1–5) and breech (1–6) at an age of ~16 months. The occurrence of blowfly strike in the breech area (breech strike) was recorded in all animals during the wool growth period of a year from shearing as weaners. Two four-trait animal models were fitted to obtain (co)variance components and ratios from the separate datasets with neck wrinkle score; body wrinkle score, breech wrinkle score and the absence of breech strike, all defined as threshold traits. Estimates of heritability for breech wrinkle score amounted to 0.27 and 0.45 for the mulesed and unmulesed groups, respectively. The absence of breech strike on the underlying scale was also heritable for the mulesed (0.33) and unmulesed (0.46) groups; translating to heritability estimates of 0.074 and 0.157, respectively, on the observed scale. The genetic correlations of wrinkle scores with absence of breech strike were generally favourable, but significant only for neck wrinkle score (–0.57) and breech wrinkle score (–0.45) in the unmulesed group. It was concluded that South African Merino sheep would respond to selection against breech strike under conditions of adequate challenge. Based on results from unmulesed sheep, selection for plainer sheep is also expected to result in a favourable correlated response in breech strike.
Influence of divergent selection for reproduction on the occurrence of breech strike in mature Merino ewes
Authors: Scholtz A. J. , Cloete S. W. P. , van Wyk J. B. , Kruger A. C. M. , van der Linde T. C. de K.
Published: April 2010

Divergent selection resulted in Merino lines that differ markedly for reproduction. These lines were selected from the same base population from 1986 to 2009. Selection was initially based on maternal ranking values for reproduction in both ewe and ram progeny. The maternal ranking scores were augmented by breeding values from a single-trait repeatability model since 2003. The site and severity of flystrike were recorded for mature breeding ewes in the flock from 2007 to 2009. The following details were captured: animal number, site of the strike (body or breech) and the severity of the strike (1 = mild to 5 = severe). Breech strikes amounted to 92.1% of all strikes and this trend was consistent across years. High-line ewes were less likely (P < 0.05) than low-line ewes to be suffering from breech strike. Ewes that suffered from breech strike during a reference year were more likely to be struck again during subsequent years, when compared with contemporaries not affected by breech strike in the reference year. When breech strike and body strike were assessed in a joint preliminary analysis, it seemed that body strike was generally more severe when diagnosed than breech strike. It was concluded that Merino sheep selected for improved reproduction for >20 years were less likely to be affected by breech strike than contemporaries selected for low reproduction.
Molecular basis for peptidoglycan recognition by a bactericidal lectin
Authors: Lehotzky Rebecca E. , Partch Carrie L. , Mukherjee Sohini , Cash Heather L. , Goldman William E. , Gardner Kevin H. , Hooper Lora V.
Published: April 2010

RegIII proteins are secreted C-type lectins that kill Gram-positive bacteria and play a vital role in antimicrobial protection of the mammalian gut. RegIII proteins bind their bacterial targets via interactions with cell wall peptidoglycan but lack the canonical sequences that support calcium-dependent carbohydrate binding in other C-type lectins. Here, we use NMR spectroscopy to determine the molecular basis for peptidoglycan recognition by HIP/PAP, a human RegIII lectin. We show that HIP/PAP recognizes the peptidoglycan carbohydrate backbone in a calcium-independent manner via a conserved “EPN” motif that is critical for bacterial killing. While EPN sequences govern calcium-dependent carbohydrate recognition in other C-type lectins, the unusual location and calcium-independent functionality of the HIP/PAP EPN motif suggest that this sequence is a versatile functional module that can support both calcium-dependent and calcium-independent carbohydrate binding. Further, we show HIP/PAP binding affinity for carbohydrate ligands depends on carbohydrate chain length, supporting a binding model in which HIP/PAP molecules “bind and jump” along the extended polysaccharide chains of peptidoglycan, reducing dissociation rates and increasing binding affinity. We propose that dynamic recognition of highly clustered carbohydrate epitopes in native peptidoglycan is an essential mechanism governing high-affinity interactions between HIP/PAP and the bacterial cell wall.
Experimental snapshots of a protein-DNA binding landscape
Authors: Sánchez Ignacio E. , Ferreiro Diego U. , Dellarole Mariano , de Prat-Gay Gonzalo
Published: April 2010

Protein recognition of DNA sites is a primary event for gene function. Its ultimate mechanistic understanding requires an integrated structural, dynamic, kinetic, and thermodynamic dissection that is currently limited considering the hundreds of structures of protein-DNA complexes available. We describe a protein-DNA-binding pathway in which an initial, diffuse, transition state ensemble with some nonnative contacts is followed by formation of extensive nonnative interactions that drive the system into a kinetic trap. Finally, nonnative contacts are slowly rearranged into native-like interactions with the DNA backbone. Dissimilar protein-DNA interfaces that populate along the DNA-binding route are explained by a temporary degeneracy of protein-DNA interactions, centered on “dual-role” residues. The nonnative species slow down the reaction allowing for extended functionality.
Temporal delays among place cells determine the frequency of population theta oscillations in the hippocampus
Authors: Geisler Caroline , Diba Kamran , Pastalkova Eva , Mizuseki Kenji , Royer Sebastien , Buzsáki György
Published: April 2010

Driven either by external landmarks or by internal dynamics, hippocampal neurons form sequences of cell assemblies. The coordinated firing of these active cells is organized by the prominent “theta” oscillations in the local field potential (LFP): place cells discharge at progressively earlier theta phases as the rat crosses the respective place field (“phase precession”). The faster oscillation frequency of active neurons and the slower theta LFP, underlying phase precession, creates a paradox. How can faster oscillating neurons comprise a slower population oscillation, as reflected by the LFP? We built a mathematical model that allowed us to calculate the population activity analytically from experimentally derived parameters of the single neuron oscillation frequency, firing field size (duration), and the relationship between within-theta delays of place cell pairs and their distance representations (“compression”). The appropriate combination of these parameters generated a constant frequency population rhythm along the septo–temporal axis of the hippocampus, while allowing individual neurons to vary their oscillation frequency and field size. Our results suggest that the faster-than-theta oscillations of pyramidal cells are inherent and that phase precession is a result of the coordinated activity of temporally shifted cell assemblies, relative to the population activity, reflected by the LFP.
High performance shape memory polymer networks based on rigid nanoparticle cores
Authors: Xu Jianwen , Song Jie
Published: April 2010

Smart materials that can respond to external stimuli are of widespread interest in biomedical science. Thermal-responsive shape memory polymers, a class of intelligent materials that can be fixed at a temporary shape below their transition temperature (T
trans
) and thermally triggered to resume their original shapes on demand, hold great potential as minimally invasive self-fitting tissue scaffolds or implants. The intrinsic mechanism for shape memory behavior of polymers is the freezing and activation of the long-range motion of polymer chain segments below and above T
trans
, respectively. Both T
trans
and the extent of polymer chain participation in effective elastic deformation and recovery are determined by the network composition and structure, which are also defining factors for their mechanical properties, degradability, and bioactivities. Such complexity has made it extremely challenging to achieve the ideal combination of a T
trans
slightly above physiological temperature, rapid and complete recovery, and suitable mechanical and biological properties for clinical applications. Here we report a shape memory polymer network constructed from a polyhedral oligomeric silsesquioxane nanoparticle core functionalized with eight polyester arms. The cross-linked networks comprising this macromer possessed a gigapascal-storage modulus at body temperature and a T
trans
between 42 and 48 °C. The materials could stably hold their temporary shapes for > 1 year at room temperature and achieve full shape recovery ≤ 51 °C in a matter of seconds. Their versatile structures allowed for tunable biodegradability and biofunctionalizability. These materials have tremendous promise for tissue engineering applications.
Enhanced synaptic connectivity and epilepsy in C1q knockout mice
Authors: Chu Yunxiang , Jin Xiaoming , Parada Isabel , Pesic Alexei , Stevens Beth , Barres Ben , Prince David A.
Published: April 2010

Excessive CNS synapses are eliminated during development to establish mature patterns of neuronal connectivity. A complement cascade protein, C1q, is involved in this process. Mice deficient in C1q fail to refine retinogeniculate connections resulting in excessive retinal innervation of lateral geniculate neurons. We hypothesized that C1q knockout (KO) mice would exhibit defects in neocortical synapse elimination resulting in enhanced excitatory synaptic connectivity and epileptiform activity. We recorded spontaneous and evoked field potential activity in neocortical slices and obtained video-EEG recordings from implanted C1q KO and wild-type (WT) mice. We also used laser scanning photostimulation of caged glutamate and whole cell recordings to map excitatory and inhibitory synaptic connectivity. Spontaneous and evoked epileptiform field potentials occurred at multiple sites in neocortical slices from C1q KO, but not WT mice. Laser mapping experiments in C1q KO slices showed that the proportion of glutamate uncaging sites from which excitatory postsynaptic currents (EPSCs) could be evoked (“hotspot ratio”) increased significantly in layer IV and layer V, although EPSC amplitudes were unaltered. Density of axonal boutons was significantly increased in layer V pyramidal neurons of C1q KO mice. Implanted KO mice had frequent behavioral seizures consisting of behavioral arrest associated with bihemispheric spikes and slow wave activity lasting from 5 to 30 s. Results indicate that epileptogenesis in C1q KO mice is related to a genetically determined failure to prune excessive excitatory synapses during development.
Spatial learning sculpts the dendritic arbor of adult-born hippocampal neurons
Authors: Tronel Sophie , Fabre Annabelle , Charrier Vanessa , Oliet Stéphane H. R. , Gage Fred H. , Abrous Djoher Nora
Published: April 2010

Neurogenesis in the hippocampus is characterized by the birth of thousand of cells that generate neurons throughout life. The fate of these adult newborn neurons depends on life experiences. In particular, spatial learning promotes the survival and death of new neurons. Whether learning influences the development of the dendritic tree of the surviving neurons (a key parameter for synaptic integration and signal processing) is unknown. Here we show that learning accelerates the maturation of their dendritic trees and their integration into the hippocampal network. We demonstrate that these learning effects on dendritic arbors are homeostatically regulated, persist for several months, and are specific to neurons born during adulthood. Finally, we show that this dendritic shaping depends on the cognitive demand and relies on the activation of NMDA receptors. In the search for the structural changes underlying long-term memory, these findings lead to the conclusion that shaping neo-networks is important in forming spatial memories.
Trs85 directs a Ypt1 GEF, TRAPPIII, to the phagophore to promote autophagy
Authors: Lynch-Day Molly A. , Bhandari Deepali , Menon Shekar , Huang Ju , Cai Huaqing , Bartholomew Clinton R. , Brumell John H. , Ferro-Novick Susan , Klionsky Daniel J.
Published: April 2010

Macroautophagy (hereafter autophagy) is a ubiquitous process in eukaryotic cells that is integrally involved in various aspects of cellular and organismal physiology. The morphological hallmark of autophagy is the formation of double-membrane cytosolic vesicles, autophagosomes, which sequester cytoplasmic cargo and deliver it to the lysosome or vacuole. Thus, autophagy involves dynamic membrane mobilization, yet the source of the lipid that forms the autophagosomes and the mechanism of membrane delivery are poorly characterized. The TRAPP complexes are multimeric guanine nucleotide exchange factors (GEFs) that activate the Rab GTPase Ypt1, which is required for secretion. Here we describe another form of this complex (TRAPPIII) that acts as an autophagy-specific GEF for Ypt1. The Trs85 subunit of the TRAPPIII complex directs this Ypt1 GEF to the phagophore assembly site (PAS) that is involved in autophagosome formation. Consistent with the observation that a Ypt1 GEF is directed to the PAS, we find that Ypt1 is essential for autophagy. This is an example of a Rab GEF that is specifically targeted for canonical autophagosome formation.
Autophagic Cell Death inDictyosteliumRequires the Receptor Histidine Kinase DhkM
Authors: Giusti Corinne , Luciani Marie-Françoise , Ravens Sarina , Gillet Alexandre , Golstein Pierre
Published: April 2010

Dictyostelium constitutes a genetically tractable model for the analysis of autophagic cell death (ACD). During ACD, Dictyostelium cells first transform into paddle cells and then become round, synthesize cellulose, vacuolize, and die. Through random insertional mutagenesis, we identified the receptor histidine kinase DhkM as being essential for ACD. Surprisingly, different DhkM mutants showed distinct nonvacuolizing ACD phenotypes. One class of mutants arrested ACD at the paddle cell stage, perhaps through a dominant-negative effect. Other mutants, however, progressed further in the ACD program. They underwent rounding and cellulose synthesis but stopped before vacuolization. Moreover, they underwent clonogenic but not morphological cell death. Exogenous 8-bromo-cAMP restored vacuolization and death. A role for a membrane receptor at a late stage of the ACD pathway is puzzling, raising questions as to which ligand it is a receptor for and which moieties it phosphorylates. Together, DhkM is the most downstream-known molecule required for this model ACD, and its distinct mutants genetically separate previously undissociated late cell death events.
Involvement of the Cytoskeleton in Controlling Leading-Edge Function during Chemotaxis
Authors: Lee Susan , Shen Zhouxin , Robinson Douglas N. , Briggs Steven , Firtel Richard A.
Published: April 2010

In response to directional stimulation by a chemoattractant, cells rapidly activate a series of signaling pathways at the site closest to the chemoattractant source that leads to F-actin polymerization, pseudopod formation, and directional movement up the gradient. Ras proteins are major regulators of chemotaxis in Dictyostelium; they are activated at the leading edge, are required for chemoattractant-mediated activation of PI3K and TORC2, and are one of the most rapid responders, with activity peaking at ∼3 s after stimulation. We demonstrate that in myosin II (MyoII) null cells, Ras activation is highly extended and is not restricted to the site closest to the chemoattractant source. This causes elevated, extended, and spatially misregulated activation of PI3K and TORC2 and their effectors Akt/PKB and PKBR1, as well as elevated F-actin polymerization. We further demonstrate that disruption of specific IQGAP/cortexillin complexes, which also regulate cortical mechanics, causes extended activation of PI3K and Akt/PKB but not Ras activation. Our findings suggest that MyoII and IQGAP/cortexillin play key roles in spatially and temporally regulating leading-edge activity and, through this, the ability of cells to restrict the site of pseudopod formation.
Why is age determination of Baltic cod (Gadus morhua) so difficult?
Authors: Hüssy Karin
Published: April 2010

Hüssy, K. 2010. Why is age determination of Baltic cod (Gadus morhua) so difficult? – ICES Journal of Marine Science, 67: 1198–1205. The aim of this study was to evaluate the consistency of three methods for assigning annuli in adult Baltic cod otoliths. The methods examined were (i) daily increment patterns, (ii) opacity profiles, and (iii) traditional age reading. Frequency distributions of the distance from the nucleus to the different zones showed that the first annulus of traditional age reading missed the first zone of both increment and opacity methods, but overlapped with the second zone identified by these methods. This pattern did not continue over subsequent zones. Frequency distributions of increment patterns were similar to opacity patterns. However, within individual fish, the co-occurrence of overlap between the two patterns was random. In cases where there was overlap, translucent zone formation started just before the disappearance of visible increments. Overlap in 1 year did not necessarily lead to a consistent pattern the following year, and overlap was not influenced by sex or fish size. The results suggest that otolith opacity in Baltic cod is not associated with seasonal patterns in daily increment structure and that traditional age determination based on otolith opacity yields highly uncertain estimates of age.
Variation Among Physical, Compositional, and Wet‐Milling Characteristics of the F1 Generation of Corn Hybrids of Introgressed Exotic and Adapted Inbred Lines
Authors: Taboada‐Gaytan Oswaldo , Pollak Linda M. , Johnson Lawrence A. , Fox Steven R. , Montgomery Kevin T.
Published: April 2010

Hybrids with high grain yield and higher starch, protein, or oil content are available to corn growers; however, they result from crossing adapted Corn Belt inbred lines that rarely include exotic germplasm. This study was conducted to determine whether Corn Belt lines introgressed with exotic materials from Argentina, Chile, Uruguay, Cuba, and Florida have appropriate wet‐milling characteristics in their hybrids. Ten lines from the Germplasm Enhancement of Maize (GEM) project with different starch contents were crossed to three adapted inbred lines used as testers. The B73×Mo17 hybrid was used as a control. The F1 generation of these 30 experimental hybrids was analyzed using both near‐infrared transmittance (NIT) technology and a 100‐g modified wet‐milling procedure, and measuring test and 1,000‐kernel weight. There was great variation among physical, compositional, and wet‐milling characteristics of the experimental hybrids, suggesting that exotic germplasm can be used to improve wet‐milling characteristics of Corn Belt hybrids.
Abdominal Tuberculosis in Children
Authors: Tinsa Faten , Essaddam Leila , Fitouri Zohra , Brini Ines , Douira Wiem , Becher Saida Ben , Boussetta Khadija , Bousnina Souad
Published: April 2010

Background:

Abdominal tuberculosis (TB) includes infection of the gastrointestinal tract, peritoneum, mesentery, abdominal lymph nodes, liver, spleen, and pancreas. The most common forms of abdominal TB in children are adhesive peritonitis and nodal disease.

Patients and Methods:

We report our experience with abdominal TB treated in our hospital from 1995 to 2008.

Results:

Thirteen patients (3 boys and 10 girls) of mean age 9.8 years were diagnosed as having abdominal TB. Eight patients presented with abdominal distension and abdominal pain. Fever was seen in 4 patients. One patient had surgical abdominal pain and 2 had abdominal mass. Two patients had coexisting pleural effusion and 1 of them had multifocal TB. Abdominal TB involved peritoneum in 9, abdominal lymph nodes in 7, gastrointestinal tract in 3, spleen in 2 patients, and liver in 1. Ascitic fluid analysis of 9 patients showed exudative fluid with predominately lymphocytes. Laparotomy was performed in 3 patients. The diagnosis of abdominal TB was confirmed histopathologically in 5 patients and microbiologically in 3. The remaining patients had been diagnosed by ascitic fluid diagnostic features, abdominal imaging, tuberculin skin test, history of exposure, and a positive response to antituberculous treatment. Twelve patients completed the antituberculous therapy without any complications. One patient with multifocal TB had neurological sequelae.

Conclusions:

In the areas with a high prevalence of tuberculosis and confirmatory investigations are inadequately available, treatment may be initiated, based on strong clinical diagnosis and supportive investigations. In such situations, it is the response to therapy that indirectly proves the diagnosis.
Antioxidant Properties of Breast Milk in a Novel In Vitro Digestion/Enterocyte Model
Authors: Yao Li , Friel James K , Suh Miyoung , Diehl‐Jones William L
Published: April 2010

Objectives:

There is good evidence to suggest that human breast milk has antioxidant properties. Our primary goal was to investigate the antioxidant properties of human milk in a combined in vitro digestion/cell culture model that more closely replicates conditions in the gastrointestinal system of the preterm infant.

Materials and Methods:

An in vitro digestion model was developed that incorporates both gastric and intestinal phases, based on reported luminal pH, digestive enzyme levels, and transit times observed in preterm infants. To mimic the human intestinal mucosa, 2 cell lines—Caco‐2BBE and HT29‐MTX—were cocultured on Matrigel, an artificial basement membrane substrate. Intracellular oxidative stress was measured with 2 broadly selective oxidant‐sensitive dyes, and oxidative DNA damage was assessed by means of single‐cell gel electrophoresis.

Results:

Enterocyte differentiation and mucin secretion were observed by 14 seeding of cultures. Direct exposure to digested milk resulted in a loss of transepithelial electrical resistance; however, exogenous mucin mitigated this loss. Data suggested that both milk and digested milk alleviated oxidative stress in the coculture, and both reduced hydrogen peroxide–induced oxidative DNA damage, as demonstrated by the comet assay.

Conclusions:

Our results support the hypothesis that breast milk reduces oxidative stress in a cell culture model representative of the intestinal mucosa, and also confirmed the suitability of this combined in vitro digestion/cell culture system for investigating the physiologic effects of enteral nutrients such as breast milk, under conditions similar to those existing in the gastrointestinal system of the preterm infant.
Feeding After Percutaneous Endoscopic Gastrostomy in Children: Early Feeding Trial
Authors: Corkins Mark R , Fitzgerald Joseph F , Gupta Sandeep K
Published: April 2010

Background:

Percutaneous endoscopic placement of a gastrostomy tube is a common procedure to provide feeding access in children. The practice has been to withhold the initial feeding for a prescribed length of time because of safety concerns. The shortest reported time to feeding in pediatric patients is 6 hours.

Patients and Methods:

A prospective randomized trial was devised to compare the tolerance of feedings at 3 and 6 hours after percutaneous endoscopic gastrostomy placement. The change in abdominal girth before and 1 hour after the initial feeding, any vomiting, and the gastric residual volume before the next feeding were recorded. The length of stay was also documented.

Results:

Forty successive patients who met the entry criteria were enrolled, with 20 in each group. There were no statistical differences between the groups for age or sex distribution. There were no significant differences in the recorded episodes of emesis from either group (median value 0 in both groups, P = 0.82). The changes in abdominal girths were also similar and statistically not significantly different (median values 0 for 3 hours vs 0.5 cm for 6 hours, P = 0.29). Gastric residual volumes were low overall and not different depending on the time that feedings were started (median value 0 in both groups, P = 0.47). The length of stay was statistically the same between the 3‐ and 6‐hour feeding groups (median values 30.7 hours for 3 hours vs 30.0 hours for 6 hours, P = 0.92).

Conclusions:

Feedings after percutaneous endoscopic gastrostomy placement can be started as soon as 3 hours after the procedure is completed with no increase in complications.
A spectacular new Philippine monitor lizard reveals a hidden biogeographic boundary and a novel flagship species for conservation
Authors: Welton Luke J. , Siler Cameron D. , Bennett Daniel , Diesmos Arvin , Duya M. Roy , Dugay Roldan , Rico Edmund Leo B. , Van Weerd Merlijn , Brown Rafe M.
Published: April 2010

As humans continue to explore the last uncharted regions of the planet, discoveries of previously unknown species of large vertebrates have become infrequent. Here, we report on the discovery of a spectacular new species of giant, secretive, frugivorous, forest monitor lizard (Genus:
Varanus
) from the forests of the northern Philippines. Using data from morphology and mitochondrial and nuclear DNA sequences, we demonstrate the taxonomic distinctiveness of this new 2 m long species and provide insight into its historical biogeography and systematic affinities. Our molecular phylogenetic analyses indicate that the new species is closely related to
Varanus olivaceus
(from southern Luzon and nearby islands), but it differs from this and other varanids with respect to characteristics of scalation, colour pattern, body size, anatomy of the reproductive organs and genetic divergence. The new species appears to be restricted to forests of the central and northern Sierra Madre mountain range; it is separated from the range of
V. olivaceus
by a more than 150 km stretch that includes at least three low-elevation river valley barriers to dispersal. This discovery identifies a seldom-perceived biogeographic boundary and emphasizes the need for continued biodiversity research in the megadiverse conservation hotspot of the Philippines. It is anticipated that the new species will serve as an important flagship species for conservation efforts aimed at preserving the remaining forests of northern Luzon.
Economically optimal timing for crop disease control under uncertainty: an options approach
Authors: Mbah Martial L. Ndeffo , Forster Graeme A. , Wesseler Justus H. , Gilligan Christopher A.
Published: April 2010

Severe large-scale disease and pest infestations in agricultural regions can cause significant economic damage. Understanding if and when disease control measures should be taken in the presence of risk and uncertainty is a key issue. We develop a framework to examine the economically optimal timing of treatment. The decision to treat should only be undertaken when the benefits exceed the costs by a certain amount and not if they are merely equal to or greater than the costs as standard net-present-value (NPV) analysis suggests. This criterion leads to a reduction in fungicide use. We investigate the effect of the model for disease progress on the value required for immediate treatment by comparing two standard models for disease increase (exponential and logistic growth). Analyses show that the threshold value of benefits required for immediate release of treatment varies significantly with the relative duration of the agricultural season, the intrinsic rate of increase of the disease and the level of uncertainty in disease progression. In comparing the performance of the delay strategy introduced here with the conventional NPV approach, we show how the degree of uncertainty affects the benefits of delaying control.
Cellular automata and integrodifferential equation models for cell renewal in mosaic tissues
Authors: Bloomfield J. M. , Sherratt J. A. , Painter K. J. , Landini G.
Published: April 2010

Mosaic tissues are composed of two or more genetically distinct cell types. They occur naturally, and are also a useful experimental method for exploring tissue growth and maintenance. By marking the different cell types, one can study the patterns formed by proliferation, renewal and migration. Here, we present mathematical modelling suggesting that small changes in the type of interaction that cells have with their local cellular environment can lead to very different outcomes for the composition of mosaics. In cell renewal, proliferation of each cell type may depend linearly or nonlinearly on the local proportion of cells of that type, and these two possibilities produce very different patterns. We study two variations of a cellular automaton model based on simple rules for renewal. We then propose an integrodifferential equation model, and again consider two different forms of cellular interaction. The results of the continuous and cellular automata models are qualitatively the same, and we observe that changes in local environment interaction affect the dynamics for both. Furthermore, we demonstrate that the models reproduce some of the patterns seen in actual mosaic tissues. In particular, our results suggest that the differing patterns seen in organ parenchymas may be driven purely by the process of cell replacement under different interaction scenarios.
Fluorescence-based transient state monitoring for biomolecular spectroscopy and imaging
Authors: Widengren Jerker
Published: April 2010

To increase read-out speed, sensitivity or specificity, an often applied strategy in fluorescence-based biomolecular spectroscopy and imaging is to simultaneously record two or more of the fluorescence parameters: intensity, lifetime, polarization or wavelength. This review highlights how additional, to-date largely unexploited, information can be extracted by monitoring long-lived, photo-induced transient states of organic dyes and their dynamics. Two major approaches are presented, where the transient state information is obtained either from fluorescence fluctuation analysis or by recording the time-averaged fluorescence response to a time-modulated excitation. The two approaches combine the detection sensitivity of the fluorescence signal with the environmental sensitivity of the long-lived transient states. For both techniques, proof-of-principle experiments are reviewed, and advantages, limitations and possible applications for biomolecular cellular biology studies are discussed.
‘Dialectical materialism and modern physics’, an unpublished text by Max Born
Authors: Freire Olival , Lehner Christoph
Published: April 2010

A previously unpublished manuscript by the physicist Max Born, one of the creators of quantum mechanics, is presented. The manuscript was addressed to Born's colleague Léon Rosenfeld and criticized his attempt to show that Niels Bohr's doctrine of complementarity was an example of dialectical materialism and as such in perfect agreement with Marxist philosophy. Besides illustrating the deep political divisions among defenders of the ‘Copenhagen spirit’ in quantum physics, the manuscript is also a valuable source illuminating Max Born's philosophical position about scientific methodology and epistemology.
Stokes flows past gaps in a wall
Authors: Crowdy Darren , Samson Ophir
Published: April 2010

This paper presents a conformal mapping approach to the study of planar Stokes flows near a wall with either one or two gaps. The technique reproduces, in a unified fashion, analytical solutions for various Stokes flows past a single gap in a wall found by previous authors using different methods. These include purely pressure-driven flows, shear flows and stagnation point flows near a gap in a wall. It is then shown how the conformal mapping method can be generalized to find new analytical solutions for the analogous flows when there are two gaps in the wall. Features of the new two-gap solutions are studied in detail.
Spatial representation of alarm pheromone information in a secondary olfactory centre in the ant brain
Authors: Yamagata Nobuhiro , Mizunami Makoto
Published: April 2010

Pheromones play major roles in intraspecific communication in many animals. Elaborated communication systems in eusocial insects provide excellent materials to study neural mechanisms for social pheromone processing. We previously reported that alarm pheromone information is processed in a specific cluster of glomeruli in the antennal lobe of the antCamponotus obscuripes. However, representation of alarm pheromone information in a secondary olfactory centre is unknown in any animal. Olfactory information in the antennal lobe is transmitted to secondary olfactory centres, including the lateral horn, by projection neurons (PNs). In this study, we compared distributions of terminal boutons of alarm pheromone-sensitive and -insensitive PNs in the lateral horn of ants. Distributions of their dendrites largely overlapped, but there was a region where boutons of pheromone-sensitive PNs, but not those of pheromone-insensitive PNs, were significantly denser than in the rest of the lateral horn. Moreover, most of a major type of pheromone-sensitive efferent neurons from the lateral horn extended dendritic branches in this region, suggesting specialization of this region for alarm pheromone processing. This study is the first study to demonstrate the presence of specialized areas for the processing of a non-sexual, social pheromone in the secondary olfactory centre in any animal.
Disrupting the experience of control in the human brain: pre-supplementary motor area contributes to the sense of agency
Authors: Moore James W. , Ruge Diane , Wenke Dorit , Rothwell John , Haggard Patrick
Published: April 2010

The feeling of controlling events through one's actions is fundamental to human experience, but its neural basis remains unclear. This ‘sense of agency’ (SoA) can be measured quantitatively as a temporal linkage between voluntary actions and their external effects. We investigated the brain areas underlying this aspect of action awareness by using theta-burst stimulation to locally and reversibly disrupt human brain function. Disruption of the pre-supplementary motor area (pre-SMA), a key structure for preparation and initiation of a voluntary action, was shown to reduce the temporal linkage between a voluntary key-press action and a subsequent electrocutaneous stimulus. In contrast, disruption of the sensorimotor cortex, which processes signals more directly related to action execution and sensory feedback, had no significant effect. Our results provide the first direct evidence of a pre-SMA contribution to SoA.