bluuebunny/crossref_metadata_2025 huggingface dataset:
Extreme-ultraviolet polarimeter utilizing laser-generated high-order harmonics
Authors: Brimhall Nicole , Turner Matthew , Herrick Nicholas , Allred David D. , Turley R. Steven , Ware Michael , Peatross Justin
Published: October 2008

We describe an extreme-ultraviolet (EUV) polarimeter that employs laser-generated high-order harmonics as the light source. The polarimeter is designed to characterize materials and thin films for use with EUV light. Laser high harmonics are highly directional with easily rotatable linear polarization, not typically available with other EUV sources. The harmonics have good wavelength coverage, potentially spanning the entire EUV from a few to a hundred nanometers. Our instrument is configured to measure reflectances from 14 to 30 nm and has ∼180 spectral resolution (λ/Δλ). The reflection from a sample surface can be measured over a continuous range of incident angles (5°–75°). A secondary 14 cm gas cell attenuates the harmonics in a controlled way to keep signals within the linear dynamic range of the detector, comprised of a microchannel plate coupled to a phosphorous screen and charge coupled device camera. The harmonics are produced using ∼10 mJ, ∼35 fs, and ∼800 nm laser pulses with a repetition rate of 10 Hz. Per-shot energy monitoring of the laser discriminates against fluctuations. The polarimeter reflectance data agree well with data obtained at the Advanced Light Source Synchrotron (Beamline 6.3.2).
Renner–Teller interactions in the vibrational autoionization of polyatomic molecules
Authors: Jungen Ch. , Pratt S. T.
Published: October 2008

Vibrational autoionization induced by the Renner–Teller interaction in linear polyatomic molecules is considered in the context of the three-state electrostatic model developed by Gauyacq and Jungen [Mol. Phys. 41, 383 (1980)]. For small interactions, simple formulas are derived for the quantum defect matrix elements and the autoionization rates in terms of the more common Renner–Teller parameters derived from spectroscopic analyses of low-lying Rydberg states. These formulas should provide guidance for empirical fitting of quantum defect parameters to spectra of high Rydberg states. Consideration of typical values of the Renner–Teller parameters also allows the estimation of vibrational autoionization rates induced by these interactions. These estimates support the validity of the Δv=−1 propensity rule for vibrational autoionization. Constraints on the vibrational autoionization rates for the symmetric stretching vibration are also discussed. In the following paper, electron capture by polyatomic molecular ions into vibrationally autoionizing Rydberg states is considered from the same perspective, and a simple formula is derived to allow the estimation of the effect of this process on dissociative recombination cross sections.
Nonadiabatic dynamics and simulation of time resolved photoelectron spectra within time-dependent density functional theory: Ultrafast photoswitching in benzylideneaniline
Authors: Mitrić Roland , Werner Ute , Bonačić-Koutecký Vlasta
Published: October 2008

We present a theoretical approach for the nonadiabatic dynamics “on the fly” based on the combination of the time-dependent density functional theory (TDDFT) with Tully’s stochastic surface hopping method. Our formulation is based on localized Gaussian basis sets and is suitable for the simulation of ultrafast processes in complex molecular systems including all degrees of freedom. Our approach is used for the simulation of time resolved photoelectron spectra in the framework of the Wigner distribution approach. In order to illustrate the scope of the method, we study the ultrafast photoswitching dynamics of the prototype Schiff base benzylideneaniline (BAN). The nonradiative lifetime of the S1 state of BAN is determined to be ∼200 fs. The mechanism of the photoisomerization has been investigated and a connection between the time resolved photoelectron signal and the underlying nonadiabatic processes has been established.
Ion composition produced by high power impulse magnetron sputtering discharges near the substrate
Authors: Ehiasarian A. P. , Vetushka A. , Hecimovic A. , Konstantinidis S.
Published: October 2008

Plasma composition near the substrate was investigated in a high power impulse magnetron sputtering (HIPIMS) discharge using Langmuir probe analysis, mass spectroscopy, and atomic absorption spectroscopy. The HIPIMS discharge was operated in nonreactive Ar atmosphere at a pressure of 2.66 Pa and the magnetron cathode was furnished with Ti target. Plasma density, metal ion-to-neutral ratio, and gas ion-to-metal ion ratio were studied as a function of discharge current. At peak discharge current densities of ∼1 A cm−2, the results show that a dense plasma (ne∼1018 m−3) expanded from the target toward the substrate and lasted more than 330 μs after the supplied power was turned off. The shape of the time-averaged ion energy distribution function of sputtered material exhibited a transition from Thompson to Maxwellian distribution, indicating efficient energy transfer in the discharge. The metal content in the plasma monotonically increased with discharge current and the metal ion-to-neutral ratio reached approximately 1:1 in the postdischarge plasma at peak current density of 5 A cm−2.
Thermoluminescence in a scanning electron microscope
Authors: Schulz T. , Albrecht M. , Irmscher K. , Hartmann C. , Wollweber J. , Fornari R.
Published: October 2008

The capabilities of thermoluminescence (TL) performed in a scanning electron microscope using the electron beam for excitation at low temperatures are presented. This method allows spatially as well as spectrally resolved TL. In the case of low excitation densities and short excitation times, the primary electron scattering volume determines the spatial resolution of the subsequent measurement. The potential of this technique is demonstrated for the characterization of bulk and heteroepitaxial AlN.
Magnetic properties of Co/Pt multilayers on self-assembled particle arrays
Authors: Ulbrich T. C. , Assmann D. , Albrecht M.
Published: October 2008

A series of [Co(x)/Pt(0.8 nm)]8 multilayers with varying individual Co layer thickness was deposited onto self-assembled particle monolayers with particle sizes as small as 58 nm forming arrays of magnetic nanostructures. A maximal out-of-plane coercivity was observed for a Co layer thickness of 0.3 nm for all particle sizes, which decreases with further increasing Co layer thickness indicating a transition of the easy axis orientation from perpendicular to the film plane at about 0.8 nm Co layer thickness. While a single-domain state is the most favorable state after perpendicular demagnetization for a Co layer thickness of up to 0.4 nm for all particle sizes, greater Co layer thicknesses reveal a multidomain state. In addition, the angle dependent magnetization reversal behavior and the domain configurations of these magnetic nanostructures were investigated systematically. At the crossover thickness of 0.4 nm Co layer thickness, a two-domain configuration can be induced for 320 nm particles by applying a magnetic field under a critical angle of 75°.
Effect of Co interlayers in Fe/MgO/Fe magnetic tunnel junctions
Authors: Wang Yan , Han X. F. , Zhang X.-G.
Published: October 2008

The effect of Co interlayers in –Fe(001)/Co/MgO/Co/Fe– magnetic tunnel junctions is studied by first-principles calculation. We confirm that the Co layers inserted at the two Fe/MgO interfaces strongly influence the interfacial resonance (IR) states and the tunneling magnetoresistance (TMR). The effect is not monotonic. Strongest IR occurs at Co layer thickness of 0.5 monolayer (ML). With 1 ML Co, the IR is dramatically reduced and TMR ratio is maximized.
Sensitivity of the integrating pulse magnetometer with a first-order gradiometer
Authors: Trojanowski S. , Ciszek M.
Published: October 2008

Inductive magnetometers used for measurements in pulsed magnetic fields should have proper frequency characteristics. In the present work we describe the construction of an inductive magnetometer for measurements of the magnetic moment in pulsed magnetic fields, together with the calculation procedures for determination of its sensitivity. We present a method for determination of the effective coefficient of the coupling between the coils set (gradiometer) and cylindrical samples, as well as a method for calculation of the thermal noise in the measuring system. The determination of the effective coupling coefficient permits a straightforward connection of the value of the measured signal with the magnetic moment of the sample and calibration of the gradiometer in absolute units. In the work we also present, as examples, some experimental hysteresis loops of pulse magnetization measurements for some ferromagnetic samples and a single crystal of high temperature superconductor. The results were obtained using our homemade pulse magnet and magnetometer with a gradiometer designed and constructed on basis of presented here calculations.
Electrically driven single quantum dot emitter operating at room temperature
Authors: Arians R. , Gust A. , Kümmell T. , Kruse C. , Zaitsev S. , Bacher G. , Hommel D.
Published: October 2008

We present a green emitting single quantum dot light emitter integrated into a resonant-cavity diode design. Most important, electroluminescence stemming from one individual quantum dot is obtained at room temperature with a surprisingly low operation voltage of 2.6V. This demonstrates that our single quantum dot device is ideally suited for electrically driven nonclassical light generation under ambient conditions.
Electrical resistivity of individual molecular-assembly nanowires of amphiphilic bis-tetrathiafulvalene macrocycle/2,3,5,6-tetrafluoro- 7,7,8,8-tetracyano-p-quinodimethane charge transfer complex characterized by point-contact current-imaging atomic force microscopy
Authors: Tsunashima Ryo , Noda Yuki , Tatewaki Yoko , Noro Shin-ichiro , Akutagawa Tomoyuki , Nakamura Takayoshi , Matsumoto Takuya , Kawai Tomoji
Published: October 2008

Resistivity of individual molecular-assembly nanowires was characterized using the point-contact current-imaging atomic force microscope (PCI-AFM). Current images were simultaneously obtained along with topographic images, from which the mean electrical resistivity of each nanowire was deduced to be approximately 180Ωcm, which was about two orders of magnitude lower than that measured on bulk Langmuir–Blodgett films (103–105Ωcm).
The focusing effect of graded index photonic crystals
Authors: Kurt H. , Colak E. , Cakmak O. , Caglayan H. , Ozbay E.
Published: October 2008

We describe an approach to implement graded index (GRIN) structures using two-dimensional photonic crystals (PCs). The lattice spacing along the transverse direction to propagation is altered and we show, both theoretically and experimentally, that such a spatial perturbation is an effective way to obtain GRIN PC. The response of the structure to spatially wide incident beams is investigated and strong focusing behavior is observed. The large spot size conversion ratio can be attainable and is mainly limited by the finite size of the structure. The designed GRIN PC shows promise for use in optical systems that require compact and powerful focusing elements compared to the traditional bulky lenses.
Writing nanotriboelectric charge bits on insulator surface
Authors: Son J. Y. , Lee Geunhee
Published: October 2008

We demonstrated nanotriboelectric charge bits on the surface of insulating SiO2 thin film, prepared by thermo-oxidation of Si substrate with about 100 nm in thickness, by Kelvin probe force microscope. We wrote and read nanotriboelectric charge bits with the various experimental parameters such as contact force, rubbing speed, and repeat number. We could write the nanotriboelectric charge bits with the minimum line width of about 17 nm.
Room temperature magnetic stabilization of buried cobalt nanoclusters within a ferromagnetic matrix studied by soft x-ray magnetic circular dichroism
Authors: Hindmarch A. T. , Dempsey K. J. , Morgan J. P. , Hickey B. J. , Arena D. A. , Marrows C. H.
Published: October 2008

Single dusting layers of size-selected Co nanoclusters (NCs) of sizes ranging from 1.5–5.5 nm have been deposited by a gas-phase aggregation method in ultrahigh vacuum, and embedded within a NiFe matrix. Magnetic hysteresis loops have been obtained using soft x-ray magnetic circular dichroism, which shows that these Co NCs embedded in NiFe exhibit room temperature ferromagnetism with identical coercivity to the surrounding NiFe film. The strong local exchange field at the interface between NiFe and Co NCs, combined with the magnetic anisotropy of the NiFe film, allows stabilization of NC ferromagnetism which persists to room temperature.
Metaphoric Pictures Devised by an Early-Blind Adult on Her Own Initiative
Authors: Kennedy John M
Published: October 2008

EW, a totally blind adult, was encouraged to draw. Three years later, she took a sketchpad on a vacation trip to Mexico and made a series of drawings. In these pictures, objects, such as a glass or a person swimming, are drawn in a realistic manner in which lines stand for surface edges, and the shapes copy parts of the true forms of the objects. Of major interest, EW made drawings in which the lines and forms stood for the effect of the alcoholic liquid in the glass, the taste of a hot pepper, the sound of a trumpet, and the feeling of water running through the fingers of the swimmer. It is suggested that EW has invented apt metaphoric devices on her own initiative.
The effects of leaf litter characteristics on feeding and fitness of a tropical stream shredder, Anisocentropus maculatus (Trichoptera : Calamoceratidae)
Authors: Li Aggie O. Y. , Dudgeon David
Published: October 2008

Plant diversity is high in the tropics, resulting in leaf litter of differing quality in streams that may affect feeding and fitness of shredders. The effects of leaf toughness and nitrogen content on feeding and fitness (pupal weight) of a Hong Kong shredder, Anisocentropus maculatus (Trichoptera : Calamoceratidae), were investigated in laboratory feeding trials that included leaves from five plant species with contrasting characteristics. Leaf toughness adversely affected the feeding rates and fitness of A. maculatus. Feeding rates on tough leaves (Indocalamus sinicus and Pandanus furcatus) were >96% lower compared with soft leaves (Ficus fistulosa and Liquidambar formosana), whereas feeding rates on moderately tough leaves (Melaleuca quinquenervia) were intermediate. Larval mortality was >7 times higher on tough (78–100%) than softer leaves (0–11%), and resulting pupae were >71% lighter. Leaf nitrogen content was not a good determinant of feeding or fitness of A. maculatus, but larvae appeared to eat greater amounts of nitrogen-poor leaves to compensate for lower food quality. Leaf toughness was the primary determinant of feeding and fitness of A. maculatus, and the refractory leaves of many tropical plants could account for the scarcity of shredders in tropical streams.
The agistment market in the northern Australian rangelands: failings and opportunities
Authors: Reeson A. F. , McAllister R. R. J. , Whitten S. M. , Gordon I. J. , Nicholas M. , McDouall S. S.
Published: October 2008

Agistment is the practice of temporarily moving stock between properties, and is used by pastoralists both to strategically develop their enterprises and as a response to environmental heterogeneities such as variation in rainfall. This paper considers the agistment market in the northern Australian rangelands using the ‘market failure framework’. This form of economic analysis identifies failings in a market, thus, provides a rigorous basis for designing interventions intended to improve market performance. Drawing on interviews with pastoralists from the Dalrymple Shire in Queensland we conclude that, although agistment is widely used, there are several failings in the existing market which are likely to result in overall agistment activity being far less than optimal. The market failure analysis indicates that key issues relate to the lack of a common marketplace, asymmetric information on the characteristics of the other party in an agreement, and a lack of mutual expectations at the outset. Innovations with the potential to overcome these failings, while minimising the transaction costs involved in entering an agistment agreement, are discussed.
TrkB-mediated activation of geranylgeranyltransferase I promotes dendritic morphogenesis
Authors: Zhou Xiu-Ping , Wu Kong-Yan , Liang Bin , Fu Xiu-Qing , Luo Zhen-Ge
Published: October 2008

Dendrite morphogenesis is regulated by neuronal activity or neurotrophins, which may function by activating intrinsic signaling proteins, including Rho family GTPases. Here we report that activity- and brain-derived neurotrophic factor (BDNF)–dependent dendritic morphogenesis requires activation of geranylgeranyltransferase I (GGT), a prenyltransferase that mediates lipid modification of Rho GTPases. Dendritic arborization in cultured hippocampal neurons was promoted by over-expression of GGT, and reduced by inhibition or down-regulation of GGT. Furthermore, GGT was activated by neuronal depolarization or BDNF, both of which promote dendritic arborization, in cultured hippocampal neurons. Moreover, exploration of a novel environment caused activation of GGT in the mice hippocampus, suggesting that neural activity activates GGT in vivo. Interestingly, GGT was physically associated with tropomyosin-related kinase B (TrkB), the receptor for BDNF, and this association was enhanced by depolarization. Disrupting the GGT-TrkB interaction or down-regulating GGT activity attenuated depolarization- or BDNF-induced dendrite development. Finally, the GGT effect on dendrite arborization was prevented by over-expressing Rac1 with the prenylation site deleted or mutated. Thus depolarization- or BDNF-dependent dendrite development may be mediated by GGT-induced prenylation of Rho GTPases.
Osteoblastic regulation of B lymphopoiesis is mediated by G
s
α-dependent signaling pathways
Authors: Wu Joy Y. , Purton Louise E. , Rodda Stephen J. , Chen Min , Weinstein Lee S. , McMahon Andrew P. , Scadden David T. , Kronenberg Henry M.
Published: October 2008

Osteoblasts play an increasingly recognized role in supporting hematopoietic development and recently have been implicated in the regulation of B lymphopoiesis. Here we demonstrate that the heterotrimeric G protein α subunit G
s
α is required in cells of the osteoblast lineage for normal postnatal B lymphocyte production. Deletion of G
s
α early in the osteoblast lineage results in a 59% decrease in the percentage of B cell precursors in the bone marrow. Analysis of peripheral blood from mutant mice revealed a 67% decrease in the number of circulating B lymphocytes by 10 days of age. Strikingly, other mature hematopoietic lineages are not decreased significantly. Mice lacking G
s
α in cells of the osteoblast lineage exhibit a reduction in pro-B and pre-B cells. Furthermore, interleukin (IL)-7 expression is attenuated in G
s
α-deficient osteoblasts, and exogenous IL-7 is able to restore B cell precursor populations in the bone marrow of mutant mice. Finally, the defect in B lymphopoiesis can be rescued by transplantation into a WT microenvironment. These findings confirm that osteoblasts are an important component of the B lymphocyte niche and demonstrate
in vivo
that G
s
α-dependent signaling pathways in cells of the osteoblast lineage extrinsically regulate bone marrow B lymphopoiesis, at least partially in an IL-7-dependent manner.
Variable breakpoints target
PAX5
in patients with dicentric chromosomes: A model for the basis of unbalanced translocations in cancer
Authors: An Qian , Wright Sarah L. , Konn Zoë J. , Matheson Elizabeth , Minto Lynne , Moorman Anthony V. , Parker Helen , Griffiths Mike , Ross Fiona M. , Davies Teresa , Hall Andy G. , Harrison Christine J. , Irving Julie A. , Strefford Jon C.
Published: October 2008

The search for target genes involved in unbalanced acquired chromosomal abnormalities has been largely unsuccessful, because the breakpoints of these rearrangements are too variable. Here, we use the example of dicentric chromosomes in B cell precursor acute lymphoblastic leukemia to show that, despite this heterogeneity, single genes are targeted through a variety of mechanisms. FISH showed that, although they were heterogeneous, breakpoints on 9p resulted in the partial or complete deletion of
PAX5
. Molecular copy number counting further delineated the breakpoints and facilitated cloning with long-distance inverse PCR. This approach identified 5 fusion gene partners with
PAX5
:
LOC392027
(7p12.1),
SLCO1B3
(12p12),
ASXL1
(20q11.1),
KIF3B
(20q11.21), and
C20orf112
(20q11.1). In each predicted fusion protein, the DNA-binding paired domain of
PAX5
was present. Using quantitative PCR, we demonstrated that both the deletion and gene fusion events resulted in the same underexpression of
PAX5
, which extended to the differential expression of the
PAX5
target genes,
EBF1
,
ALDH1A1
,
ATP9A
, and
FLT3
. Further molecular analysis showed deletion and mutation of the homologous
PAX5
allele, providing further support for the key role of
PAX5
. Here, we show that specific gene loci may be the target of heterogeneous translocation breakpoints in human cancer, acting through a variety of mechanisms. This approach indicates an application for the identification of cancer genes in solid tumours, where unbalanced chromosomal rearrangements are particularly prevalent and few genes have been identified. It can be extrapolated that this strategy will reveal that the same mechanisms operate in cancer pathogenesis in general.
Importin-mediated retrograde transport of CREB2 from distal processes to the nucleus in neurons
Authors: Lai Kwok-On , Zhao Yali , Ch'ng Toh Hean , Martin Kelsey C.
Published: October 2008

Signals received at distal synapses of neurons must be conveyed to the nucleus to initiate the changes in transcription that underlie long-lasting synaptic plasticity. The presence of importin nuclear transporters and of select transcription factors at synapses raises the possibility that importins directly transport transcription factors from synapse to nucleus to modulate gene expression. Here, we show that cyclic AMP response element binding protein 2 (CREB2)/activating transcription factor 4 (ATF4), a transcriptional repressor that modulates long-term synaptic plasticity and memory, localizes to distal dendrites of rodent hippocampal neurons and neurites ofAplysiasensory neurons (SNs) and binds to specific importin α isoforms. Binding of CREB2 to importin α is required for its transport from distal dendrites to the soma and for its translocation into the nucleus. CREB2 accumulates in the nucleus during long-term depression (LTD) but not long-term potentiation of rodent hippocampal synapses, and during LTD but not long-term facilitation (LTF) ofAplysiasensory-motor synapses. Time-lapse microscopy of CREB2 tagged with a photoconvertible fluorescent protein further reveals retrograde transport of CREB2 from distal neurites to the nucleus ofAplysiaSN during phenylalanine-methionine-arginine-phenylalanine-amide (FMRFamide)-induced LTD. Together, our findings indicate that CREB2 is a novel cargo of importin α that translocates from distal synaptic sites to the nucleus after stimuli that induce LTD of neuronal synapses.
The genetic ablation of SRC-3 protects against obesity and improves insulin sensitivity by reducing the acetylation of PGC-1α
Authors: Coste Agnès , Louet Jean-Francois , Lagouge Marie , Lerin Carles , Antal Maria Cristina , Meziane Hamid , Schoonjans Kristina , Puigserver Pere , O'Malley Bert W. , Auwerx Johan
Published: October 2008

Transcriptional control of metabolic circuits requires coordination between specific transcription factors and coregulators and is often deregulated in metabolic diseases. We characterized here the mechanisms through which the coactivator SRC-3 controls energy homeostasis. SRC-3 knock-out mice present a more favorable metabolic profile relative to their wild-type littermates. This metabolic improvement in SRC-3
−/−
mice is caused by an increase in mitochondrial function and in energy expenditure as a consequence of activation of PGC-1α. By controlling the expression of the only characterized PGC-1α acetyltransferase GCN5, SRC-3 induces PGC-1α acetylation and consequently inhibits its activity. Interestingly, SRC-3 expression is induced by caloric excess, resulting in the inhibition of PGC-1α activity and energy expenditure, whereas caloric restriction reduces SRC-3 levels leading to enhanced PGC-1α activity and energy expenditure. Collectively, these data suggest that SRC-3 is a critical link in a cofactor network that uses PGC-1α as an effector to control mitochondrial function and energy homeostasis.
Cesarean by choice? Empirical study of public attitudes
Authors: HÖGBERG ULF , LYNÖE NIELS , WULFF MARIANNE
Published: October 2008

Objective. This study examines public attitudes towards maternal requests for cesarean delivery and its association with health care and birth experiences. In addition, this study attempts to ascertain whether gender, age and residence influence these attitudes. Design. Cross‐sectional population survey with a postal questionnaire. Setting. The counties of Stockholm and Västerbotten in Sweden. Population. Equal numbers of women and men between 20 and 80 years of age (n = 2,000) by population size and gender distribution. Methods. Descriptive statistics and content analysis. Results. Of the 1,066 women (53%) who responded, two‐thirds stated that a cesarean should be decided on for medical reasons and by a doctor. One‐third considered that a woman, without persuasion, should decide herself about mode of delivery and should be free to choose a cesarean. These respondents used arguments such as women's rights, bodily integrity and childbirth fear. The results were associated with low trust in health care, women being young or middle aged, urban living and having no children. Low trust in health care was associated with experiences of insecurity, vulnerability and perceived maltreatment. Conclusion. Public norms towards women's own decision making on mode of delivery are associated with younger age, lower trust in health care and urban living. Antenatal care will encounter more parents asking for a cesarean and demanding that health professionals provide an ethically appropriate informed consent process. Considering the risk of violating young women's trust if not respecting her wish, it seems reasonable that making decisions whether or not to perform a cesarean is part of shared decision making.
Evidence for impaired physiological decrease in the uteroplacental vascular resistance in pregnant women with familial hypercholesterolemia
Authors: KHOURY JANETTE , AMUNDSEN ÅGOT L. , TONSTAD SERENA , HENRIKSEN TORE , OSE LEIV , RETTERSTØL KJETIL , IVERSEN PER O.
Published: October 2008

Abnormal hyperlipidemia characterizes pregnancy in familial hypercholesterolemia (FH), and is associated with vascular dysfunction. Hence, we compared blood flow in the feto‐ and uteroplacental circulation in FH and healthy reference women using Doppler velocimetry. The umbilical artery pulsatility index (PI) at gestational weeks 24 and 36, and the concomitant physiological decrease in PI, was similar in FH (n = 10) and the reference group (n = 143). The decrease in mean PI of both uterine arteries from week 24 to 36 was significant in the reference group, but not among the FH women. Plasma LDL‐cholesterol measured between weeks 24 and 36 was not correlated with the decrease in umbilical PI in the FH group, or with the decrease in umbilical or mean uterine PI in the reference group. We conclude that pregnancy in FH might be associated with attenuated physiological decrease in mean PI of uterine arteries, possibly reflecting increased uteroplacental vascular resistance unrelated to plasma LDL‐cholesterol levels.
Kinetics of Turn-offs of Frog Rod Phototransduction Cascade
Authors: Astakhova Luba A. , Firsov Michael L. , Govardovskii Victor I.
Published: October 2008

The time course of the light-induced activity of phototrandsuction effector enzyme cGMP-phosphodiesterase (PDE) is shaped by kinetics of rhodopsin and transducin shut-offs. The two processes are among the key factors that set the speed and sensitivity of the photoresponse and whose regulation contributes to light adaptation. The aim of this study was to determine time courses of flash-induced PDE activity in frog rods that were dark adapted or subjected to nonsaturating steady background illumination. PDE activity was computed from the responses recorded from solitary rods with the suction pipette technique in Ca2+-clamping solution.

A flash applied in the dark-adapted state elicits a wave of PDE activity whose rising and decaying phases have characteristic times near 0.5 and 2 seconds, respectively. Nonsaturating steady background shortens both phases roughly to the same extent. The acceleration may exceed fivefold at the backgrounds that suppress ≈70% of the dark current.

The time constant of the process that controls the recovery from super-saturating flashes (so-called dominant time constant) is adaptation independent and, hence, cannot be attributed to either of the processes that shape the main part of the PDE wave. We hypothesize that the dominant time constant in frog rods characterizes arrestin binding to rhodopsin partially inactivated by phosphorylation. A mathematical model of the cascade that considers two-stage rhodopsin quenching and transducin inactivation can mimic experimental PDE activity quite well. The effect of light adaptation on the PDE kinetics can be reproduced in the model by concomitant acceleration on both rhodopsin phosphorylation and transducin turn-off, but not by accelerated arrestin binding. This suggests that not only rhodopsin but also transducin shut-off is under adaptation control.
On a class of non-dissipative materials that are not hyperelastic
Authors: Rajagopal K.R , Srinivasa A.R
Published: October 2008

The purpose of this brief note is to develop fully Eulerian, implicit constitutive equations for the mechanical response of a class of materials that do not dissipate mechanical work in any process. We show that such materials can be modelled by obtaining a form for the Helmholtz potential as a function of the current mass density, the Cauchy stress and certain other parameters that capture anisotropic response. The resulting constitutive equations are of the form

, where

and

are functions of the state variables of the system. The class of materials that can be obtained from such a constitutive relation is considerably more general than conventional Green-elastic hyperelastic materials. Such response functions may be suitable for the modelling of biological tissue where, due to the constant remodelling that takes place, there may be no physical meaning to a ‘reference configuration’.
Evolution of trust and trustworthiness: social awareness favours personality differences
Authors: McNamara John M , Stephens Philip A , Dall Sasha R.X , Houston Alasdair I
Published: October 2008

Interest in the evolution and maintenance of personality is burgeoning. Individuals of diverse animal species differ in their aggressiveness, fearfulness, sociability and activity. Strong trade-offs, mutation–selection balance, spatio-temporal fluctuations in selection, frequency dependence and good-genes mate choice are invoked to explain heritable personality variation, yet for continuous behavioural traits, it remains unclear which selective force is likely to maintain distinct polymorphisms. Using a model of trust and cooperation, we show how allowing individuals to monitor each other's cooperative tendencies, at a cost, can select for heritable polymorphisms in trustworthiness. This variation, in turn, favours costly ‘social awareness’ in some individuals. Feedback of this sort can explain the individual differences in trust and trustworthiness so often documented by economists in experimental public goods games across a range of cultures. Our work adds to growing evidence that evolutionary game theorists can no longer afford to ignore the importance of real world inter-individual variation in their models.
CLC-mediated anion transport in plant cells
Authors: De Angeli Alexis , Monachello Dario , Ephritikhine Geneviève , Frachisse Jean-Marie , Thomine Sébastien , Gambale Franco , Barbier-Brygoo Hélène
Published: October 2008

Plants need nitrate for growth and store the major part of it in the central vacuole of cells from root and shoot tissues. Based on few studies on the two model plants
Arabidopsis thaliana
and rice, members of the large
C
h
L
oride
C
hannel (CLC) family have been proposed to encode anion channels/transporters involved in nitrate homeostasis. Proteins from the
Arabidopsis
CLC family (AtClC, comprising seven members) are present in various membrane compartments including the vacuolar membrane (AtClCa), Golgi vesicles (AtClCd and AtClCf) or chloroplast membranes (AtClCe). Through a combination of electrophysiological and genetic approaches, AtClCa was shown to function as a 2NO
3
−
/1H
+
exchanger that is able to accumulate specifically nitrate into the vacuole, in agreement with the main phenotypic trait of knockout mutant plants that accumulate 50 per cent less nitrate than their wild-type counterparts. The set-up of a functional complementation assay relying on transient expression of AtClCa cDNA in the mutant background opens the way for studies on structure–function relationships of the AtClCa nitrate transporter. Such studies will reveal whether important structural determinants identified in bacterial or mammalian CLCs are also crucial for AtClCa transport activity and regulation.
The mammalian proton-coupled peptide cotransporter PepT1: sitting on the transporter–channel fence?
Authors: Meredith David
Published: October 2008

The proton-coupled di- and tripeptide transporter PepT1 (SLC15a1) is the major route by which dietary nitrogen is taken up from the small intestine, as well as being the route of entry for important therapeutic (pro)drugs such as the β-lactam antibiotics, angiotensin-converting enzyme inhibitors and antiviral and anti-cancer agents. PepT1 is a member of the major facilitator superfamily of 12 transmembrane domain transporter proteins. Expression studies in
Xenopus laevis
on rabbit PepT1 that had undergone site-directed mutagenesis of a conserved arginine residue (arginine
282
in transmembrane domain 7) to a glutamate revealed that this residue played a role in the coupling of proton and peptide transport and prevented the movement of non-coupled ions during the transporter cycle. Mutations of arginine
282
to other non-positive residues did not uncouple proton–peptide cotransport, but did allow additional ion movements when substrate was added. By contrast, mutations to positive residues appeared to function the same as wild-type. These findings are discussed in relation to the functional role that arginine
282
may play in the way PepT1 operates, together with structural information from the homology model of PepT1 based on the
Escherichia coli
lactose permease crystal structure.
Differential endocannabinoid regulation of extinction in appetitive and aversive Barnes maze tasks
Authors: Harloe John P. , Thorpe Andrew J. , Lichtman Aron H.
Published: October 2008

CB1receptor-compromised animals show profound deficits in extinguishing learned behavior from aversive conditioning tasks, but display normal extinction learning in appetitive operant tasks. However, it is difficult to discern whether the differential involvement of the endogenous cannabinoid system on extinction results from the hedonics or the required responses associated with the disparate tasks. Here, we report that the CB1receptor antagonist rimonabant disrupts extinction learning in an aversive, but not in an appetitive, Barnes maze conditioning task. Accordingly, these results provide compelling support for the hypothesis that the endogenous cannabinoid system plays a necessary role in the extinction of aversively motivated behaviors but is expendable for appetitively motivated behaviors.
Enantioselective disposition of salbutamol in man following oral and intravenous administration
Authors: BOULTON D. W. , FAWCETT J. P.
Published: October 2008

1 Salbutamol is a β2,‐adrenoceptor stimulant used clinically as a racemate where the activity resides predominantly in the (‐)R enantiomer with little or no activity attributed to the (+)S enantiomer. Salbutamol undergoes extensive pre‐systemic metabolism and active renal excretion.

2 The pharmacokinetics of the enantiomers of salbutamol have been investigated after intravenous (1.6 mg) and oral (4 mg) dosing with racemic drug to seven normal male volunteers. Plasma and urine samples were analysed by chiral h.p.1.c. after solid phase extraction.

3 The ratio of (‐)R/(+)S salbutamol in plasma and urine fobllowing intravenous administration ranged from near unity soon after dosing to about 0.66 after 8 h. The ratio remained at about 0.3 in both plasma and urine over the 8 h following an oral dose.

4 The following pharmacokinetic parameters for (+)S and (‐)R salbutamol were found to be significantly different (P <0.05) after intravenous administration (clearance 0.39±0.12vs0.62±0.18 1 h‐1kg‐1, terminal phase half‐life 2.85±0.83vs2.00±0.49 h, amount excreted unchanged in urine 55±11vs46±8%) and following oral administration (amount excreted unchanged in urine 32±11vs8±4% and bioavailability 0.71±0.09vs0.30±0.07).

5 The active (‐)R enantiomer of salbutamol undergoes significantly faster metabolism in man than the inactive (+)S enantiomer resulting in considerably lower bioavailability of the active enantiomer following oral administration.
Potential greater than additive vasorelaxant actions of milrinone and nitroglycerin on human conduit arteries
Authors: HE GUO‐WEI , YANG CHENG‐QIN , GATELY HUGH , FURNARY ANTHONY , SWANSON JEFFERY , AHMAD AFTAB , FLOTEN STORM , WOOD JAMES , STARR ALBERT
Published: October 2008

1 The mechanism of vasorelaxation for phosphodiesterase III inhibitors is mediated by increase of cAMP whereas for nitrovasodilators, cGMP. The purpose of this study was to test the hypothesis that the phosphodiesterase I inhibitor milrinone and nitroglycerin (NTG) may have greater than additive effects in human arteries.

2 Internal mammary artery segments (IMA,n= 90) taken from 23 patients were studied in organ chambers. The effect of milrinone (3 μM), NTG (10 nM), or the combination was tested in IMA rings precontracted with potassium (K+, 25 mM) or U46619 (10 nM). Concentration‐contraction curves for K+or U46619 were established in other rings treated with milrinone (70 μM), NTG (0.1 μM), or the combination for 10 min.

3 In K+‐induced contraction, the combination produced more relaxation (45.4%) than did either milrinone (7.9%, P < 0.05) or NTG (3.8%, P < 0.05) alone. This relaxation was significantly more than the theoretical overadditive effect (P < 0.05). Similar results were seen in U46619‐induced contraction (94.1% by the combinationvs70.7% by milrinone, P < 0.05, or 36.1% by NTG, P < 0.05). Pretreatment with the combination depressed contraction to a higher extend compared with milrinone alone (P < 0.05) for the K+‐induced contraction and to NTG alone (P < 0.05) in U46619‐induced contraction. Treatment with the combination also shifted EC50rightward and this shift was significantly more than that caused by treatment with NTG alone (P < O.O5).

4 We conclude that there is a greater than additive vasorelaxant effect of PDE III inhibitors and nitrovasodilators in human conduit arteries. This effect may be beneficial to patients undergoing coronary artery bypass grafting and to other patients requiring these vasodilators. Reduced doses of the vasodilators in concentration may be sufficient to produce vasodilatation similar to that produced by either of them alone at higher concentrations.
Increased systemic availability of loperamide after oral administration of loperamide and loperamide oxide with cotrimoxazole
Authors: KAMALI F. , HUANG M. L.
Published: October 2008

1 The effects of concurrent administration of cotrimoxazole on the plasma concentration‐time profiles of loperamide and its oxide were investigated in two separate studies in healthy male volunteers. Cotrimoxazole (960 mg, twice daily) was administered for 24 h before and 48 h after an oral dose of loperamide oxide (4 mg) or loperamide (4 mg).

2 Coadministration of cotrimoxazole with loperamide oxide did not alter the tmax'Cmaxand AUC of loperamide oxide, whereas the Cmax(0.32 ± 0.14 ng ml‐1without cotrimoxazole; 0.45 ± 0.18 ng ml‐1with cotrimoxazole;P< 0.05) and AUC (8.13 ± 1.91 ng ml‐1h without cotrimoxazole; 12.50 ± 4.60 ng ml‐1h with cotrimoxazole;P< 0.005) of loperamide were significantly increased.

3 Coadministration of cotrimoxazole with loperamide significantly increased the Cmax(0.74 ± 0.22 ng ml‐1without cotrimoxazole; 1.49 ± 0.81 ng ml‐1with cotrimoxazole;P< 0.01) and AUC (13.40 ± 3.80 ng ml‐1h without cotrimoxazole; 25.30 ± 11.10 ng ml‐1h with cotrimoxazole;P< 0.005) of loperamide, whilst its tmaxand t1/2, zwere not significantly altered.

4 The increase in loperamide AUC, following coadministration of either loperamide oxide or loperamide with cotrimoxazole, may be due to reduced first pass metabolism of loperamide.
Caffeine as a metabolic probe: NAT2 phenotyping
Authors: NOTARIANNI LIDIA J. , DOBROCKY P. , GODLEWSKI G. , JONES R. W. , BENNETT P. N.
Published: October 2008

1 Caffeine has been used to determine acetylator phenotype for some 15 years but the interpretation of metabolic ratios with this substance raises theoretical and methodological issues.

2 N‐acetyltransferase type 2 (NAT2) status was assessed in 23 young healthy subjects using both caffeine overnight and spot urine samples, and sulphadimidine.

3 Frequency distribution analysis of the metabolic ratios of NAT2, indicated two distinct groups for sulphadimidine, and for caffeine spot but not overnight samples. Spearman's rank correlation values were low indicating differences between the data sets for sulphadimidine and spot caffeine samples. Correlation between the two urine collection periods for caffeine was poor.

4 The complex metabolism of caffeine may compromise its value as a probe for determining acetylator phenotype until the effects of important variables are better understood.
Crossover trials are only useful when there is a positive correlation between the response to different treatment modalities
Authors: CLEOPHAS T. J. M.
Published: October 2008

1 Trials that do not allow us to reject the null hypothesis of no treatment effect may have had an inappropriate design. Trials are virtually never assessed for correlation between responses to different treatment modalities.

2 The level of correlation between responses to different treatment modalities is a major determinant of the power of crossover trials.

3 It is relevant to assess correlation levels between responses to the different treatment modalities a priori. With a negative correlation a crossover design is likely to lack power.

4 In 1991 the British Journal of Clinical Pharmacology published eight crossover trials which would have been more efficient had they been performed with a parallel groups design.
Pupillary response to topical tropicamide as a marker for Alzheimer's disease
Authors: TRELOAR ADRIAN J. , ASSIN MANDY , MACDONALD A. J. D.
Published: October 2008

The mydriatic response to eyedrops of the anticholinergic drug tropicamide at very low concentration (0.01%) was studied in subjects with Alzheimer's disease (AD, n= 10) and multi‐infarct dementia (MID, n= 10). There was no significant difference in pupillary response between the two groups. The test is unlikely to be useful in differentiating different types of dementia.
A SELF‐ALIGNING DIAPHRAGM LOAD CELL
Authors: CHAN K. S.
Published: October 2008

A description is given of the design and construction of a short, simple, self‐aligning load cell used in confined spaces. The cell, capable of very good accuracy, consists of a thick diaphragm and a self‐aligning anvil with two electrical strain gauges fixed on the underside of the diaphragm. The signal output against load characteristic is linear, and loads up to several tons can be measured.
X‐RAY TECHNIQUES FOR RESIDUAL STRESS MEASUREMENT
Authors: HUGHES H.
Published: October 2008

This paper discusses application of X‐ray techniques to measurement of residual stress in typical components.
MEASUREMENT OF STATIC STRAIN UNDER RAPID HEATING
Authors: BROAD M. S.
Published: October 2008

The behaviour of various strain gauges on unstressed aluminium under various heating rates is investigated systematically. Testing installations, gauge preparation, evaluation of tests and results are presented.
STRESS CONCENTRATIONS IN A RECTANGULAR PLATE WITH CIRCULAR PERFORATIONS ALONG ITS TWO BONDED EDGES AND SUBJECTED TO RESTRAINED SHRINKAGE
Authors: DURELLI A. J. , PARKS V. J. , CHEN T. L.
Published: October 2008

Two‐dimensional photoelasticity is used for minimising stress concentration associated with a fillet present at the end of a solid propellant rocket grain subjected to restrained shrinkage. For this purpose, successive holes were added along the bonded interface of case and propellant, but no decrease was obtained. The photoelastic method used illustrates two uncommon techniques of interest to experimental stress analysts: (1) restrained shrinkage loading and (2) a parametric stress‐analysis solution obtained with a single model.
DETERMINATION BY THREE METHODS OF YOUNG'S MODULUS OF A 0.2 MM TITANIUM ALLOY STRIP
Authors: BERGQVIST B. , SCHERLING G.
Published: October 2008

The value of Young's modulus of a 0–216 mm (0–0085 in) thick sheet of weldable titanium alloy (13% V, 11% Cr, 3% A1) was measured at room temperature by three different methods simultaneously. The results and their analysis give insight into the merits of strain measuring standards at present available at FFA and of the specialised strain measuring methods used at FFA and already described (Ref. 1).
A STRAIN GAUGE LOAD CELL FOR THE MEASUREMENT OF COMPRESSIVE LOADS UNDER
Authors: BIRKS A. W. , LUDLOW C.
Published: October 2008

The design and development of a strain gauge load cell suitable for use under high hydrostatic pressures is described and the method of bonding the resistance strain gauges is given in detail.
SOME NOTES ON THE DESIGN OF SIMPLE CANTILEVER TYPE TRANSDUCERS
Authors: WINDOW A. L.
Published: October 2008

A nomogram is derived that permits a quick selection of steel or Al‐alloy cantilever beam dimensions for the design of a transducer required to measure by means of strain gauges a given deflection or a given force. Examples show the application of the nomogram and important factors for optimum design are discussed.
THE STRAIN GAUGE: AN AID TO THE DEVELOPMENT OF MARINE TRANSPORT
Authors: BOYLE H. B.
Published: October 2008

Strain gauges measure directly strains in models and marine components and are parts of torque and thrust transducers and of force and moment balances. Six‐component balances of strut and shear‐plate design and special sliprings are described.
TRIAXIAL ANALYSIS OF THE “POKER‐CHIP” TEST
Authors: THEOCARIS P. S. , MARKETOS E.
Published: October 2008

Axial compression of thin circular discs made of plasticized epoxy resin was studied. The plane faces were cemented to platens rigid compared with the material of the discs so that the constraint due to cementing created in the discs a three‐dimensional state of stress. The internal strain distribution was measured by the moiré method which yielded enough data for an evaluation of this state of stress. The influence of the aspect‐ratio of diameter D to thickness t of the disc was investigated.