bluuebunny/crossref_metadata_2025 huggingface dataset:
Limits for light intensification by reflection from relativistic plasma mirrors
Authors: Solodov A. A. , Malkin V. M. , Fisch N. J.
Published: September 2006

Ultraintense laser pulses might be capable of producing plasma mirrors through ultrarelativistic oscillating electrons. Two kinds of such mirrors with relativistic factors γ∼100–300 were contemplated recently as a tool for producing huge frequency upshifts 4γ2 of reflected laser pulses as well as the compressing and focusing of those pulses. The combination of these effects would result in dramatic light intensification toward the vacuum breakdown intensities (Schwinger limit) [S. V. Bulanov et al., Phys. Rev. Lett. 91, 085001 (2003) and S. Gordienko et al., Phys. Rev. Lett. 94, 103903 (2005)]. The analysis performed in these publications was limited, however, to idealized situations of cold uniform plasmas and uniform laser intensities. The analysis here of effects of electron thermal motion and random inhomogeneities in the plasma density or laser intensity indicates that the largest relativistic factors allowed within these schemes are much smaller than those assumed in the idealized models, unless essentially new physical mechanisms are adduced in addition to those already considered.
Magnetic gas sensing using a dilute magnetic semiconductor
Authors: Punnoose A. , Reddy K. M. , Hays J. , Thurber A. , Engelhard M. H.
Published: September 2006

The authors report on a magnetic gas sensing methodology to detect hydrogen using the ferromagnetic properties of a nanoscale dilute magnetic semiconductor Sn0.95Fe0.05O2. This work demonstrates the systematic variation of saturation magnetization, coercivity, and remanence of Sn0.95Fe0.05O2 with the hydrogen gas flow rate, thus providing clear experimental evidence of the concept of magnetic gas sensing (using the magnetic property of a material as a gas sensing parameter). Based on the results of using hydrogen as an example for reducing gases, it is believed that any reducing gas capable of changing the oxygen stoichiometry of Sn0.95Fe0.05O2 can be detected using this method. Furthermore, this method presents an alternative gas sensing technology without the use of the electrical contacts.
Measurements and modeling of transport and impurity radial profiles in the EXTRAP T2R reversed field pinch
Authors: Kuldkepp M. , Brunsell P. R. , Cecconello M. , Dux R. , Menmuir S. , Rachlew E.
Published: September 2006

Radial impurity profiles of oxygen in the rebuilt reversed field pinch EXTRAP T2R [P. R. Brunsell et al., Plasma Phys. Control. Fusion 43, 1457 (2001)] have been measured with a multichannel spectrometer. Absolute ion densities for oxygen peak between 1−4×1010cm−3 for a central electron density of 1×1013cm−3. Transport simulations with the one-dimensional transport code STRAHL with a diffusion coefficient of 20m2s−1 yield density profiles similar to those measured. Direct measurement of the ion profile evolution during pulsed poloidal current drive suggests that the diffusion coefficient is reduced by a factor ∼2 in the core but remains unaffected toward the edge. Core transport is not significantly affected by the radial magnetic field growth seen at the edge in discharges without feedback control. This indicates that the mode core amplitude remains the same while the mode eigenfunction increases at the edge.
Collimation of metal nanoparticle beams using aerodynamic lenses
Authors: Passig Johannes , Meiwes-Broer Karl-Heinz , Tiggesbäumker Josef
Published: September 2006

With the objective of reducing the divergence, aerodynamic lenses were applied to collimate a beam of metal nanoparticles in a size range up to 20nm. Influences of the aerodynamic devices on the particle aggregation process and the beam properties have been evaluated by time-of-flight measurements on mass filtered clusters. Additional transmission electron microscopy and atomic force microscopy studies on deposited particles complement these investigations. Perspectives for the application of aerodynamic lenses in the collimation of ultrafine particles are discussed.
Enhancement of resistivity of Czochralski silicon by deep level manganese doping
Authors: Mallik Kanad , de Groot C. H. , Ashburn P. , Wilshaw P. R.
Published: September 2006

Deep level manganese (Mn) doping has been used to fabricate very high resistivity single crystal silicon substrates grown by the Czochralski method. The Mn has been introduced by ion implantation with a dose of 1014cm−2 of Mn at 100keV followed by rapid thermal annealing at 800°C for 36s. The resistivity of the wafer is enhanced from 600Ωcm for the undoped substrate to a maximum of 10kΩcm for the Mn-doped substrate. The experimental data are corroborated using a theoretical model for doping compensation due to deep level impurities. This level of obtained resistivity is suitable for making silicon on-chip integration of radio frequency devices.
Prepulse effect on intense femtosecond laser pulse propagation in gas
Authors: Giulietti Antonio , Tomassini Paolo , Galimberti Marco , Giulietti Danilo , Gizzi Leonida A. , Koester Petra , Labate Luca , Ceccotti Tiberio , D’Oliveira Pascal , Auguste Thierry , Monot Pascal , Martin Philippe
Published: September 2006

The propagation of an ultrashort laser pulse can be affected by the light reaching the medium before the pulse. This can cause a serious drawback to possible applications. The propagation in He of an intense 60-fs pulse delivered by a Ti:sapphire laser in the chirped pulse amplification (CPA) mode has been investigated in conditions of interest for laser-plasma acceleration of electrons. The effects of both nanosecond amplified spontaneous emission and picosecond pedestals have been clearly identified. There is evidence that such effects are basically of refractive nature and that they are not detrimental for the propagation of a CPA pulse focused to moderately relativistic intensity. The observations are fully consistent with numerical simulations and can contribute to the search of a stable regime for laser acceleration.
Epitaxial orientation of III-nitrides grown on R-plane sapphire by metal-organic-vapor-phase epitaxy
Authors: Vennéguès P. , Bougrioua Z.
Published: September 2006

The absolute epitaxial relationships between III-nitride films and R-plane sapphire are investigated using convergent beam electron diffraction. The resulting relationships are found to be[1−100]III-N‖[11−20]sapphire and [0001]III-N‖[−1101]sapphire, respectively. The O–Al bonds in the sapphire surface are antiparallel to the N-III bonds in the III-N films. High-resolution transmission electron microscopy shows that the AlN nucleation layer is asymmetrically strained. Along its c direction, the AlN layer is in extension whereas it is relaxed perpendicular to c.
Resonant bending mode of Terfenol-D∕steel∕Pb(Zr,Ti)O3 magnetoelectric laminate composites
Authors: Xing Zengping , Dong Shuxiang , Zhai Junyi , Yan Li , Li Jiefang , Viehland D.
Published: September 2006

Resonant bending-mode Tb1−xDyxFe2−y∕elastic-steel∕Pb(Zr,Ti)O3 magnetoelectric (ME) laminate composites have been investigated. An elastic-steel layer with a relatively high Qm significantly increases the resonant enhancement of the ME coefficient due to an increased effective Qm of the laminate. The three-phase ME laminates have a low first-order bending frequency of ∼5kHz, with a resonance-enhanced ME coefficient of ∼40V∕cmOe.
Tunnel magnetoresistance for junctions with epitaxial full-Heusler Co2FeAl0.5Si0.5 electrodes with B2 and L21 structures
Authors: Tezuka N. , Ikeda N. , Miyazaki A. , Sugimoto S. , Kikuchi M. , Inomata K.
Published: September 2006

The tunnel magnetoresistance (TMR) effect has been investigated for magnetic tunnel junctions with epitaxial Co2FeAl0.5Si0.5 Heusler electrodes with B2 and L21 structures on a Cr-bufferd MgO substrate. The epitaxially grown Co2FeAl0.5Si0.5 has B2 structure when annealed below 400°C, and has L21 structure for annealing above 450°C. The TMR ratio of 76% at room temperature and 106% at 5K were obtained for a MgO(001)∕Cr∕B2-type Co2FeAl0.5Si0.5∕Al oxide/Co75Fe25∕IrMn∕Ta. The TMR ratio is larger than that of magnetic tunnel junction with an L21-type electrode, which may be due to the smoother surface of the B2 structure and disordered L21 structure due to the Cr atom interdiffusion.
Short-pulse laser absorption in very steep plasma density gradients
Authors: Cai Hong-bo , Yu Wei , Zhu Shao-ping , Zheng Chun-yang , Cao Li-hua , Li Bin , Chen Z. Y. , Bogerts A.
Published: September 2006

An analytical fluid model for resonance absorption during the oblique incidence by femtosecond laser pulses on a small-scale-length density plasma [k0L∊(0.1,10)] is proposed. The physics of resonance absorption is analyzed more clearly as we separate the electric field into an electromagnetic part and an electrostatic part. It is found that the characteristics of the physical quantities (fractional absorption, optimum angle, etc.) in a small-scale-length plasma are quite different from the predictions of classical theory. Absorption processes are generally dependent on the density scale length. For shorter scale length or higher laser intensity, vacuum heating tends to be dominant. It is shown that the electrons being pulled out and then returned to the plasma at the interface layer by the wave field can lead to a phenomenon like wave breaking. This can lead to heating of the plasma at the expanse of the wave energy. It is found that the optimum angle is independent of the laser intensity while the absorption rate increases with the laser intensity, and the absorption rate can reach as high as 25%.
Single vibronic level emission spectroscopic studies of the ground state energy levels and molecular structures of jet-cooled HGeBr, DGeBr, HGeI, and DGeI
Authors: Tackett Brandon S. , Li Yunjing , Clouthier Dennis J. , Pacheco Kezia L. , Schick G. Alan , Judge Richard H.
Published: September 2006

Single vibronic level dispersed fluorescence spectra of jet-cooled HGeBr, DGeBr, HGeI, and DGeI have been obtained by laser excitation of selected bands of the ÃA″1-X̃A′1 electronic transition. The measured ground state vibrational intervals were assigned and fitted to anharmonicity expressions, which allowed the harmonic frequencies to be determined for both isotopomers. In some cases, lack of a suitable range of emission data necessitated that some of the anharmonicity constants and vibrational frequencies be estimated from those of HGeCl∕DGeCl and the corresponding silylenes (HSiX). Harmonic force fields were obtained for both molecules, although only four of the six force constants could be determined. The ground state effective rotational constants and force field data were combined to calculate average (rz) and approximate equilibrium (rez) structures. For HGeBr rez(GeH)=1.593(9)Å, rez(GeBr)=2.325(21)Å, and the bond angle was fixed at our CCSD(T)/aug-cc-pVTZ ab initio value of 93.6°. For HGeI we obtained rez(GeH)=1.589(1)Å, rez(GeI)=2.525(5)Å, and bond angle=93.2°. Franck-Condon simulations of the emission spectra using ab initio Cartesian displacement coordinates reproduce the observed intensity distributions satisfactorily. The trends in structural parameters in the halogermylenes and halosilylenes can be readily understood based on the electronegativity of the halogen substituent.
Onset and duration of stigma receptivity in Kunzea pomifera (Myrtaceae)
Authors: Page T. , Moore G. M. , Will J. , Halloran G. M.
Published: September 2006

The onset and duration of stigma receptivity in K. pomifera was evaluated by observing stigma peroxidase activity, pollen-tube growth and seed set, following controlled pollination of flowers of different ages. Peroxidase activity was negligible from 1 day before to 4 days after anthesis, increasing to a peak of 65% at Day 13. The percentage of pistils bearing germinated pollen and ovaries exhibiting pollen-tube entry increased when pollen was applied to the stigma from the day before anthesis, to a maximum at Days 6 and 7 after anthesis, respectively, followed by a decline by Day 9. Under greenhouse conditions the optimum pollination period, measured as the level of set seed after pollination, ranged from 2 to 11 days after anthesis. The knowledge of this aspect of the species reproductive biology is of considerable value in controlled pollinations for its improvement as a new crop.
Similarities between female meadow voles mating during post-partum oestrus and raising two concurrent litters and females raising only one litter
Authors: delBarco-Trillo Javier , Ferkin Michael H.
Published: September 2006

In many species of small mammals, females undergo post-partum oestrus soon after delivering a litter, becoming pregnant while suckling the previous litter. Females raising two concurrent litters need to allocate many more resources to reproduction than females raising only one litter. Consequently, there may be differences between litters raised concurrently or singly. We investigated this issue in the meadow vole, Microtus pennsylvanicus, a species in which most females in the wild reproduce during post-partum oestrus. Specifically, we tested the hypothesis that the development of pups in two concurrent litters differs from that of pups in a single litter. To test this hypothesis, we measured the following variables for concurrent and singly reared litters: gestation length; litter size; sex ratio; bodyweight of males and females at different ages; total litter weight at weaning; growth rates; and intra-litter variation in body mass. Except for bodyweight of males at 60 days of age, which was higher in the first of the concurrent litters, none of the variables differed among the litters. These results indicate that females are able to adjust to differing loads of maternal care to provide equivalent resources to concurrent litters and singly reared litters.
Giant panda (Ailuropoda melanoleuca) spermatozoon decondensation in vitro is not compromised by cryopreservation
Authors: Spindler Rebecca E. , Yan Huang , Howard JoGayle , PengYan Wang , Hemin Zhang , Guiquan Zhang , Wildt David E.
Published: September 2006

Natural breeding of giant pandas in captivity is compromised, making artificial insemination and spermatozoa cryopreservation essential for genetic management. This study examined the influence of freeze–thawing on traditional parameters such as motility and spermatozoon functionality, specifically decondensation in vitro. Giant panda spermatozoa were assessed before and after rapid cryopreservation (4°C to –130°C over 2 min) in liquid nitrogen vapour. Spermatozoa pre-incubated in medium for 6 h were co-incubated with cat zonae (2 zonae μL–1) for 30 min to effect capacitation and an acrosome reaction. Spermatozoa were then mixed with mature cat oocyte cytoplasm (2 cytoplasm μL–1) for 4 h and evaluated for decondensation. Frozen spermatozoa were less motile (P < 0.05) than fresh counterparts immediately post-thawing, but not after 6 h incubation. There were more (P < 0.05) spermatozoa with completely diffused chromatin post-thaw (10.4 ± 1.3%; mean ± s.e.m.) compared to fresh counterparts (5.1 ± 1.0%). However, there was no overall difference (P > 0.05) in the incidence of decondensation between fresh (4 h, 69.8 ± 5.9%) and thawed (4 h, 71.5 ± 4.9%) spermatozoa after exposure to cat oocyte cytoplasm. It is concluded that the ‘rapid’ method now used to cryopreserve giant panda spermatozoa has little impact on spermatozoon decondensation.
Soil organic matter fractions and microaggregation in a Ultisol under cultivation and secondary forest in south-eastern Nigeria
Authors: Igwe C. A. , Nwokocha D.
Published: September 2006

The study of the role of soil organic carbon (SOC) in restoration of soil fertility and stability of soil microaggregates is of importance in soils that degrade rapidly. We studied 4 profiles in a Ultisol under secondary forest and cultivation to identify the SOC microaggregate-associated fractions and their roles in microaggregate stability. The soils are coarse-textured, deep, and low in soil nutrients and SOC, probably due to high rates of mineralisation. Microaggregate-associated SOC was also low with most of the SOC protected by the <63 µm fractions. Clay content was negatively correlated with <2, 63–2, and <63 µm associated SOC (r = –0.45*, –0.42*, –0.40*, respectively). Clay flocculation index and clay dispersion ratio were significantly correlated with <2 and 63–2 µm associated SOC, while water-stable aggregates <0.25 mm were negatively correlated with all SOC fractions determined. Principal component analysis revealed that SOC fractions associated with 2000–63 µm aggregate sizes were the SOC fractions that best explained the variance in aggregated silt + clay, indicating their contribution to microaggregate stability. This was attributed perhaps to the production of polysaccharides and materials released by microbial activities from this recently deposited or incompletely decomposed SOC. The other soil properties that in addition to SOC contributed to either dispersion or microaggregate stability of these soils were exchangeable Na+, Mg2+, and CEC.
The molecular basis for T-type Ca
2+
channel inhibition by G protein β
2
γ
2
subunits
Authors: DePuy Seth D. , Yao Junlan , Hu Changlong , McIntire William , Bidaud Isabelle , Lory Philippe , Rastinejad Fraydoon , Gonzalez Carlos , Garrison James C. , Barrett Paula Q.
Published: September 2006

Gβγ, a ubiquitous second messenger, relays external signals from G protein-coupled receptors to networks of intracellular effectors, including voltage-dependent calcium channels. Unlike high-voltage-activated Ca
2+
channels, the inhibition of low-voltage-activated Ca
2+
channels is subtype-dependent and mediated selectively by Gβ
2
-containing dimers. Yet, the molecular basis for this exquisite selectivity remains unknown. Here, we used pure recombinant Gβγ subunits to establish that the Gβ
2
γ
2
dimer can selectively reconstitute the inhibition of α
1H
channels in isolated membrane patches. This inhibition is the result of a reduction in channel open probability that is not accompanied by a change in channel expression or an alteration in active-channel gating. By exchanging residues between the active Gβ
2
subunit and the inactive Gβ
1
subunit, we identified a cluster of amino acids that functionally distinguish Gβ
2
from other Gβ subunits. These amino acids on the β-torus identify a region that is distinct from those regions that contact the Gα subunit or other effectors.
Self-assembly of receptor/signaling complexes in bacterial chemotaxis
Authors: Wolanin Peter M. , Baker Melinda D. , Francis Noreen R. , Thomas Dennis R. , DeRosier David J. , Stock Jeffry B.
Published: September 2006

Escherichia coli
chemotaxis is mediated by membrane receptor/histidine kinase signaling complexes. Fusing the cytoplasmic domain of the aspartate receptor, Tar, to a leucine zipper dimerization domain produces a hybrid, lzTar
C
, that forms soluble complexes with CheA and CheW. The three-dimensional reconstruction of these complexes was different from that anticipated based solely on structures of the isolated components. We found that analogous complexes self-assembled with a monomeric cytoplasmic domain fragment of the serine receptor without the leucine zipper dimerization domain. These complexes have essentially the same size, composition, and architecture as those formed from lzTar
C
. Thus, the organization of these receptor/signaling complexes is determined by conserved interactions between the constituent chemotaxis proteins and may represent the active form
in vivo
. To understand this structure in its cellular context, we propose a model involving parallel membrane segments in receptor-mediated CheA activation
in vivo
.
The crystal structure of human IRE1 luminal domain reveals a conserved dimerization interface required for activation of the unfolded protein response
Authors: Zhou Jiahai , Liu Chuan Yin , Back Sung Hoon , Clark Robert L. , Peisach Daniel , Xu Zhaohui , Kaufman Randal J.
Published: September 2006

The unfolded protein response (UPR) is an evolutionarily conserved mechanism by which all eukaryotic cells adapt to the accumulation of unfolded proteins in the endoplasmic reticulum (ER). Inositol-requiring kinase 1 (IRE1) and PKR-related ER kinase (PERK) are two type I transmembrane ER-localized protein kinase receptors that signal the UPR through a process that involves homodimerization and autophosphorylation. To elucidate the molecular basis of the ER transmembrane signaling event, we determined the x-ray crystal structure of the luminal domain of human IRE1α. The monomer of the luminal domain comprises a unique fold of a triangular assembly of β-sheet clusters. Structural analysis identified an extensive dimerization interface stabilized by hydrogen bonds and hydrophobic interactions. Dimerization creates an MHC-like groove at the interface. However, because this groove is too narrow for peptide binding and the purified luminal domain forms high-affinity dimers
in vitro
, peptide binding to this groove is not required for dimerization. Consistent with our structural observations, mutations that disrupt the dimerization interface produced IRE1α molecules that failed to either dimerize or activate the UPR upon ER stress. In addition, mutations in a structurally homologous region within PERK also prevented dimerization. Our structural, biochemical, and functional studies
in vivo
altogether demonstrate that IRE1 and PERK have conserved a common molecular interface necessary and sufficient for dimerization and UPR signaling.
Prolactin/growth hormone–derived antiangiogenic peptides highlight a potential role of tilted peptides in angiogenesis
Authors: Nguyen Ngoc-Quynh-Nhu , Tabruyn Sebastien P. , Lins Laurence , Lion Michelle , Cornet Anne M. , Lair Florence , Rentier-Delrue Francoise , Brasseur Robert , Martial Joseph A. , Struman Ingrid
Published: September 2006

Angiogenesis is a crucial step in many pathologies, including tumor growth and metastasis. Here, we show that tilted peptides exert antiangiogenic activity. Tilted (or oblique-oriented) peptides are short peptides known to destabilize membranes and lipid cores and characterized by an asymmetric distribution of hydrophobic residues along the axis when helical. We have previously shown that 16-kDa fragments of the human prolactin/growth hormone (PRL/GH) family members are potent angiogenesis inhibitors. Here, we demonstrate that all these fragments possess a 14-aa sequence having the characteristics of a tilted peptide. The tilted peptides of human prolactin and human growth hormone induce endothelial cell apoptosis, inhibit endothelial cell proliferation, and inhibit capillary formation both
in vitro
and
in vivo
. These antiangiogenic effects are abolished when the peptides' hydrophobicity gradient is altered by mutation. We further demonstrate that the well known tilted peptides of simian immunodeficiency virus gp32 and Alzheimer's β-amyloid peptide are also angiogenesis inhibitors. Taken together, these results point to a potential new role for tilted peptides in regulating angiogenesis.
Combinatorial activities of Akt and B-Raf/Erk signaling in a mouse model of androgen-independent prostate cancer
Authors: Gao Hui , Ouyang Xuesong , Banach-Petrosky Whitney A. , Gerald William L. , Shen Michael M. , Abate-Shen Cory
Published: September 2006

Androgen independence is responsible for most prostate cancer lethality, yet currently there are no effective clinical treatments. We have been investigating the mechanisms underlying androgen-independent prostate cancer in
Nkx3.1;Pten
mutant mice, which display salient features of the disease, including a requirement for wild-type androgen receptor (AR) signaling. We now demonstrate that the Akt and Erk MAP kinase signaling pathways are activated in androgen-independent lesions of these mice. Forced activation of either Akt or Erk signaling in an androgen-responsive prostate cancer cell line promotes hormone-independent but AR-dependent growth in culture. Although these pathways act additively in culture, they act synergistically
in vivo
to promote tumorigenicity and androgen independence in the context of the prostate microenvironment. We propose that androgen independence emerges by means of epithelial–stromal competition, in which activation of Akt and Erk promotes AR activity in the prostate epithelium while counteracting antagonistic effects of the stroma.
LET-711, theCaenorhabditis elegansNOT1 Ortholog, Is Required for Spindle Positioning and Regulation of Microtubule Length in Embryos
Authors: DeBella Leah R. , Hayashi Adam , Rose Lesilee S.
Published: September 2006

Spindle positioning is essential for the segregation of cell fate determinants during asymmetric division, as well as for proper cellular arrangements during development. In Caenorhabditis elegans embryos, spindle positioning depends on interactions between the astral microtubules and the cell cortex. Here we show that let-711 is required for spindle positioning in the early embryo. Strong loss of let-711 function leads to sterility, whereas partial loss of function results in embryos with defects in the centration and rotation movements that position the first mitotic spindle. let-711 mutant embryos have longer microtubules that are more cold-stable than in wild type, a phenotype opposite to the short microtubule phenotype caused by mutations in the C. elegans XMAP215 homolog ZYG-9. Simultaneous reduction of both ZYG-9 and LET-711 can rescue the centration and rotation defects of both single mutants. let-711 mutant embryos also have larger than wild-type centrosomes at which higher levels of ZYG-9 accumulate compared with wild type. Molecular identification of LET-711 shows it to be an ortholog of NOT1, the core component of the CCR4/NOT complex, which plays roles in the negative regulation of gene expression at transcriptional and post-transcriptional levels in yeast, flies, and mammals. We therefore propose that LET-711 inhibits the expression of ZYG-9 and potentially other centrosome-associated proteins, in order to maintain normal centrosome size and microtubule dynamics during early embryonic divisions.
A Critical Role for the Membrane-type 1 Matrix Metalloproteinase in Collagen Phagocytosis
Authors: Lee Hyejin , Overall Christopher M. , McCulloch Christopher A. , Sodek Jaro
Published: September 2006

Degradation of collagen is important for the physiological remodeling of connective tissues during growth and development as well as in wound healing, inflammatory diseases, and cancer cell invasion. In remodeling adult tissues, degradation of collagen occurs primarily through a phagocytic pathway. However, although various steps in the phagocytic pathway have been characterized, the enzyme required to initially fragment collagen fibrils for subsequent phagocytosis has not been identified. We have used laser confocal microscopy, transmission electron microscopy, and biochemical assays to show that human fibroblasts initiate degradation of collagen through the collagenase activity of the membrane-bound metalloproteinase MT1-MMP. Degradation of natural and reconstituted collagen substrates correlated with the expression of MT1-MMP, which was localized at sites of collagen cleavage at the surface of the cells and also within the cells, whereas collagen degradation was abrogated when MT1-MMP expression was blocked by small interfering RNA treatment. In contrast to MT1-MMP, the gelatinolytic activity of MMP-2 was not required for collagen phagocytosis. These studies demonstrate a pivotal role of catalytically active MT1-MMP in preparing collagen fibrils for phagocytic degradation.
On the origin of theSynodontiscatfish species flock from Lake Tanganyika
Authors: Day Julia J , Wilkinson Mark
Published: September 2006

Species flocks within Great Lakes provide unique insights into the factors affecting diversification. Lake Tanganyika (LT) is of particular interest because it contains many endemic groups for which general factors affecting diversification can be discerned. Here, we present the first phylogenetic study of the LTSynodontis(Siluriformes, Mochokidae) species flock using mtDNA sequence data. Our data reveal some previously unrecognized species diversity and indicate that the LT species flock is not monophyletic, and that two closely related clades of endemics may have independently colonized LT. Other comparable small species flocks are characterized by a single colonization event. Molecular date estimates of the timing of the initial within-lake diversification of the LT endemics, based on a fossil calibration, are comparable to those reported for other groups, suggesting that extrinsic factors maybe important common causes of clade diversification. The basal divergence in the sampledSynodontisreveals an East–West African faunal split seen in many terrestrial, but few aquatic groups, the timing of which coincides with East African rifting events.
Null trajectories for the symmetrized Hurwitz zeta function
Authors: McPhedran Ross C , Botten Lindsay C , Nicorovici Nicolae-Alexandru P
Published: September 2006

We consider the Hurwitz zeta function
ζ
(
s
,
a
) and develop asymptotic results for
a
=
p
/
q
, with
q
large, and, in particular, for
p
/
q
tending to 1/2. We also study the properties of lines along which the symmetrized parts of
ζ
(
s
,
a
),
ζ
+
(
s
,
a
) and
ζ
−
(
s
,
a
) are zero. We find that these lines may be grouped into four families, with the start and end points for each family being simply characterized. At values of
a
=1/2, 2/3 and 3/4, the curves pass through points which may also be characterized, in terms of zeros of the Riemann zeta function, or the Dirichlet functions
L
−3
(
s
) and
L
−4
(
s
), or of simple trigonometric functions. Consideration of these trajectories enables us to relate the densities of zeros of
L
−3
(
s
) and
L
−4
(
s
) to that of
ζ
(
s
) on the critical line.
New insights into neuropeptide modulation of aggression: field studies of arginine vasotocin in a territorial tropical damselfish
Authors: Santangelo Nick , Bass Andrew H
Published: September 2006

The neuropeptides arginine vasotocin (AVT) and arginine vasopressin are key modulators of affiliation and aggression among non-mammalian and mammalian vertebrates, respectively. Here, we explored AVT's effect on aggression in a wild population of beaugregory damselfish,Stegastes leucostictus, a highly territorial species. Aggression by territorial males towards ‘intruders’ (bottled fishes) was assessed before and after each male received intramuscular injections of either AVT, Manning compound (an AVT V1a receptor antagonist), isotocin (the teleost homologue of mammalian oxytocin differing from AVT by two amino acids) or saline (vehicle control). Compared to saline controls, AVT and Manning increased and decreased aggression, respectively, while isotocin had no effect. Response selectivity was further established in a dose–response study that revealed an inverted U-shaped function. Compared to saline controls, aggression levels for low and high AVT doses were similar, while medium dose treatments were significantly greater. This type of behavioural response, the first that we know of for a vertebrate neuropeptide, could depend on the binding of AVT to both V1-type and other AVT or non-AVT receptors. The pattern revealed here for damselfish may be symptomatic of species- and context-dependent specificity of AVT's modulation of aggression across teleosts, as is currently proposed for tetrapods.
Designing solution-processable air-stable liquid crystalline crosslinkable semiconductors
Authors: McCulloch Iain , Bailey Clare , Genevicius Kristijonas , Heeney Martin , Shkunov Maxim , Sparrowe David , Tierney Steven , Zhang Weimin , Baldwin Rodney , Kreouzis Theo , Andreasen Jens W , Breiby Dag W , Nielsen Martin M
Published: September 2006

Organic electronics technology, in which at least the semiconducting component of the integrated circuit is an organic material, offers the potential for fabrication of electronic products by low-cost printing technologies, such as ink jet, gravure offset lithography and flexography. The products will typically be of lower performance than those using the present state of the art single crystal or polysilicon transistors, but comparable to amorphous silicon. A range of prototypes are under development, including rollable electrophoretic displays, active matrix liquid crystal (LC) displays, flexible organic light emitting diode displays, low frequency radio frequency identification tag and other low performance electronics. Organic semiconductors that offer both electrical performance and stability with respect to storage and operation under ambient conditions are required. This work describes the development of reactive mesogen semiconductors, which form large crosslinked LC domains on polymerization within mesophases. These crosslinked domains offer mechanical stability and are inert to solvent exposure in further processing steps. Reactive mesogens containing conjugated aromatic cores, designed to facilitate charge transport and provide good oxidative stability, were prepared and their liquid crystalline properties evaluated. The organization and alignment of the mesogens, both before and after crosslinking, were probed by grazing incidence wide-angle X-ray scattering of thin films. Both time-of-flight and field effect transistor devices were prepared and their electrical characterization reported.
Silica nanocasting of lyotropic surfactant phases and organized organic matter: material science or an analytical tool?
Authors: Antonietti Markus
Published: September 2006

The synthesis of porous inorganic films and materials by templating organized organic matter with nanosized structural elements is an actual field in the cross-section of inorganic chemistry, materials chemistry and surfactant science. This discussion article will review recent experiments in this area on a variety of systems and try to evaluate the outcome of both material applications and the basic understanding of self-assembly processes of organic self-organization.
Genetic regulation of bone mass and susceptibility to osteoporosis
Authors: Ralston Stuart H. , de Crombrugghe Benoit
Published: September 2006

Osteoporosis is a common disease with a strong genetic component characterized by reduced bone mass and increased risk of fragility fractures. Twin and family studies have shown that the heritability of bone mineral density (BMD) and other determinants of fracture risk—such as ultrasound properties of bone, skeletal geometry, and bone turnover—is high, although heritability of fracture is modest. Many different genetic variants of modest effect size are likely to contribute to the regulation of these phenotypes by interacting with environmental factors such as diet and exercise. Linkage studies in rare Mendelian bone diseases have identified several previously unknown genes that play key roles in regulating bone mass and bone turnover. In many instances, subtle polymorphisms in these genes have also been found to regulate BMD in the general population. Although there has been extensive progress in identifying the genetic variants that regulate susceptibility to osteoporosis, most of the genes and genetic variants that regulate bone mass and susceptibility to osteoporosis remain to be discovered.
Identification of a novel regulatory protein (CsrD) that targets the global regulatory RNAs CsrB and CsrC for degradation by RNase E
Authors: Suzuki Kazushi , Babitzke Paul , Kushner Sidney R. , Romeo Tony
Published: September 2006

In Escherichia coli, the global regulatory protein CsrA (carbon store regulator A) binds to leader segments of target mRNAs, affecting their translation and stability. CsrA activity is regulated by two noncoding RNAs, CsrB and CsrC, which act by sequestering multiple CsrA dimers. Here, we describe a protein (CsrD) that controls the degradation of CsrB/C RNAs. The dramatic stabilization of CsrB/C RNAs in a csrD mutant altered the expression of CsrA-controlled genes in a manner predicted from the previously described Csr regulatory circuitry. A deficiency in RNase E, the primary endonuclease involved in mRNA decay, also stabilized CsrB/C, although the half-lives of other RNAs that are substrates for RNase E (rpsO, rpsT, and RyhB) were unaffected by csrD. Analysis of the decay of CsrB RNA, both in vitro and in vivo, suggested that CsrD is not a ribonuclease. Interestingly, the CsrD protein contains GGDEF and EAL domains, yet unlike typical proteins in this large superfamily, its activity in the regulation of CsrB/C decay does not involve cyclic di-GMP metabolism. The two predicted membrane-spanning regions are dispensable for CsrD activity, while HAMP-like, GGDEF, and EAL domains are required. Thus, these studies demonstrate a novel process for the selective targeting of RNA molecules for degradation by RNase E and a novel function for a GGDEF–EAL protein.
The use of an acoustic levitator to follow crystallization in small droplets by energy-dispersive X-ray diffraction
Authors: Leiterer Jork , Leitenberger Wolfram , Emmerling Franziska , Thünemann Andreas F. , Panne Ulrich
Published: September 2006

For the investigation of small sample volumes, the use of an acoustic levitator was tested as a `sample holder' for hovering droplets in a synchrotron beam. It might be advantageous to use levitated droplets instead of samples confined in solid holders, especially for the study of crystallization processes where the influence of containing walls has to be minimized. In a first experiment, the crystallization of sodium chloride in a small droplet of aqueous solution has been followed with a time resolution of 30 s. The collected diffraction peaks are compared with data in the ICSD database.
Small-angle X-ray scattering measurements of helium-bubble formation in borosilicate glass
Authors: Terekhov Alexander Y. , Heuser Brent J. , Okuniewski Maria A. , Averback Robert S. , Seifert Söenke , Jemian Pete R.
Published: September 2006

Small-angle X-ray scattering (SAXS) measurements have been performed to study helium-bubble formation in borosilicate glass. Helium was introduced by He+implantation over an energy range of 1 to 2 MeV to give a uniform distribution over ∼1 µm depth. The implanted dose was varied from 9 × 1013to 2.8 × 1016 ions cm−2, corresponding to a local concentration range of 40 to 11200 atomic parts per million (a.p.p.m.) averaged over the implantation depth. The SAXS response was fit with the Percus–Yevick hard-sphere interaction potential to account for interparticle interference. The fits yield helium-bubble radii and helium-bubble volume fractions that vary from 5 to 15 Å and from 10−3to 10−1, respectively, as the dose increased from 9 × 1013to 2.8 × 1016 cm−2. The SAXS data are also consistent with maximum helium solubility with respect to bubble formation between 40 and 200 a.p.p.m. in the borosilicate glass matrix.
SHADEweb server for estimation of hydrogen anisotropic displacement parameters
Authors: Madsen Anders Østergaard
Published: September 2006

TheSHADEweb server estimates anisotropic displacement parameters for hydrogen atoms by combining a rigid-body analysis of the non-hydrogen-atom anisotropic displacement parameters (ADPs) with a contribution from internal atomic motion. The contributions from internal mean square displacements are based on a previously compiled database derived from analysis of neutron diffraction experiments. The estimated hydrogen-atom ADPs can be used as fixed parameters in advanced applications of high-resolution X-ray diffraction, such as electron density studies using multipole modelling. The resulting electron density models have been shown to be in excellent agreement with reference models based on atomic motion derived from neutron diffraction experiments.
Socioeconomic Status and Belief in a Just World: Sentencing of Criminal Defendants1
Authors: Freeman Naomi J.
Published: September 2006

The present study investigated whether defendants' socioeconomic status (SES) and jurors' beliefs in a just world affected punishment and blame decisions. The study's 273 participants completed the Just World Scale (Rubin & Peplau, 1975) and read a case scenario describing an aggravated murder. Participants rendered a verdict and answered questions concerning confidence, responsibility, and degree of guilt. Analyses partially supported the hypothesis. High believers in a just world were more likely to assign higher degrees of guilt and to sentence low SES defendants more severely than high SES or no SES information defendants.
Scientific Jury Selection: Does It Work?
Authors: Seltzer Richard
Published: September 2006

This article describes different methodologies used to predict the likely disposition of jurors in order to guide the exercise of peremptory challenges. The actual use of these methodologies in 27 telephone surveys, 9 focus groups, and 2 studies of jurors after the case was decided is examined. It is concluded that the efficacy of scientific jury selection depends, in part, on the type of case.
Correlates of the Protestant Ethic of Hard Work: Results From a Diverse Ethno‐Religious Sample
Authors: Ghorpade Jai , Lackritz Jim , Singh Gangaram
Published: September 2006

We examine the demographic and personality correlates of the Protestant ethic and how it correlates with contemporary individual and social issues. Success is more prevalent among Christian fundamentalists, those who were born outside the United States, individualists, individuals who have a higher locus of control, and individuals who believe in a just world. Hard work is more prevalent among Asian Americans and Filipinos, women, those who have a higher internal locus of control, and those who believe in a just world. Our data show that success and hard work are correlated positively with hours worked, total hours worked, and liberalization of drug laws. No other study has examined these issues using a diverse ethno‐religious sample.
Direct and Indirect Aggression: Relationships as Social Context
Authors: Richardson Deborah S. , Green Laura R.
Published: September 2006

The studies reported in this paper examined the effect of social context—target gender and target relationship—on reports of direct and indirect aggression. In Study 1, participants completed the Richardson Conflict Response Questionnaire (RCRQ; Richardson & Green, 2003), which measured their direct and indirect aggression behavior in response to anger. Participants also selected a relationship partner to complete the RCRQ with reference to their own (i.e., participants') behavior. In Study 2, participants completed the RCRQ with reference to their behavior in response to anger with a romantic partner, a same‐sex friend, and an opposite‐sex friend. In both studies, relationship with aggression target was an important determinant of aggression, with more direct aggression occurring in romantic relationships, and more indirect aggression occurring in friendship relationships.
The Psychological Benefits of Superstitious Rituals in Top Sport: A Study Among Top Sportspersons1
Authors: Schippers Michaéla C. , Van Lange Paul A. M.
Published: September 2006

The current research addresses the psychological benefits of superstitious rituals in top sport, examining the circumstances under which top‐class sportspersons are especially committed to enacting rituals prior to a game (ritual commitment). Consistent with the hypotheses, findings revealed that ritual commitment is greater when (a) uncertainty is high rather than low; and (b) importance of the game is high rather than low. Complementary analyses revealed that the state of psychological tension mediated both effect of importance and uncertainty on ritual commitment. Moreover, players with an external locus of control exhibited greater levels of ritual commitment than did players with an internal locus of control. The results are discussed in terms of the tension‐regulation function of superstitious rituals in top sport.
Effects of Internal and External Pay Comparisons on Work Attitudes1
Authors: Shore Ted H. , Tashchian Armen , Jourdan Louis
Published: September 2006

The effects of internal and external pay comparisons on several work attitudes were assessed within an experimental design. Participants responded to hypothetical scenarios in which their pay was greater, less, or equal to an internal and external individual or group referent. As predicted, internal and external pay comparisons predicted pay satisfaction and perceived pay fairness. Also as expected, internal equity was the stronger predictor of work motivation and perceived organizational support, and external equity predicted turnover intention more strongly. Partial support was found for the hypothesis that work attitudes would be impacted more strongly when individuals made pay comparisons with a group referent than with an individual referent other. Implications for the design of compensation systems are discussed.
Differential levels of soluble angiopoietin‐2 and Tie‐2 in patients with haematological malignancies
Authors: Quartarone E. , Alonci A. , Allegra A. , Bellomo G. , Calabrò L. , D'Angelo A. , Del Fabro V. , Grasso A. , Cincotta M. , Musolino C.
Published: September 2006

The system involving angiopoietin‐2 (Ang‐2) and its receptor, Tie‐2, appears to play an important role not only in tumor angiogenesis, but also in the biology of haematological and non‐haematological malignancies. In the present study we evaluated the serum levels of soluble Ang‐2 (sAng‐2) and soluble Tie‐2 (sTie‐2) in patients with haematological malignancies. Measurements were carried out in 15 patients with chronic myeloid leukaemia (CML), 25 with essential thrombocythemia (ET), 24 with multiple myeloma (MM) and six with monoclonal gammopathy of undetermined significance (MGUS). In addition, we correlated the levels of angiopoietins with known prognostic factors. sAng‐2 and sTie‐2 were quantified with enzyme‐linked immunosorbent assay (ELISA). In patients with CML and MM the levels of sAng‐2 were significantly higher (1686.53 ± 936.41 pg/mL and 1917.82 ± 1427 pg/mL, respectively) than in controls (n = 15; 996.096 ± 414.65 pg/mL) (P < 0.01). In patients with MM sAng‐2 levels were significantly increased with increasing stage of disease, from stage I to stage III (P < 0.03) and presented a trend of correlation with Beta2‐microglobulin levels (r = 0.317) and grade of bone involvement. Furthermore, the levels of sAng‐2 determined after 6 months of chemotherapy in CML patients were significantly lower than at diagnosis in the patients who achieved haematological remission. Circulating sTie‐2 levels were increased in patients with ET (17.5 ± 9.2 vs 9 ± 3.5 ng/mL; P < 0.01) and in those with CML (16.29 ± 8.7 ng/mL; P < 0.04). In conclusion, abnormal levels of sAng‐2 and sTie‐2 are present in some haematological malignancies. These markers may play a role in the pathophysiology of these conditions and their progression.