bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical study on interaction of hydrogen with single-walled boron nitride nanotubes. II. Collision, storage, and adsorption
Authors: Han Sang Soo , Kang Jeung Ku , Lee Hyuck Mo , van Duin Adri C. T. , Goddard William A.
Published: September 2005

Collision and adsorption of hydrogen with high incident kinetic energies on a single-walled boron nitride (BN) nanotube have been investigated. Molecular-dynamics (MD) simulations indicate that at incident energies below 14eV hydrogen bounces off the BN nanotube wall. On the other hand, at incident energies between 14 and 22eV each hydrogen molecule is dissociated at the exterior wall to form two hydrogen atoms, but only one of them goes through the wall. However, at the incident energies between 23 and 26eV all of the hydrogen atoms dissociated at the exterior wall are found to be capable of going inside the nanotube and then to recombine to form hydrogen molecules inside the nanotube. Consequently, it is determined that hydrogen should have the incident energy >22eV to go inside the nanotube. On the other hand, we find that the collisions using the incident energies >26eV could result in damaging the nanotube structures. In addition our MD simulations find that hydrogen atoms dissociated at the wall cannot bind to either boron or nitrogen atoms in the interior wall of the nanotube.
The molecular symmetry and electronic spectroscopy of 7-azaindole dimer: Its proton-transfer channels
Authors: Catalán J. , de Paz J. L. G.
Published: September 2005

The potential-energy surfaces for the proton transfer in the doubly hydrogen-bonded dimer of 7-azaindole in its lowest excited electronic states were examined. The dimer with C2h symmetry in its lowest excited electronic states, 2Ag and 1Bu, undergoes concerted double-proton transfer via transition states of the same symmetry placed at energies 4.55 and 4.70kcal∕mol higher, respectively. This suggests that the activation barriers for the double-proton transfer, if any, are lower than 1kcal∕mol. Emission from the dimers resulting from the double-proton transfer involves a Stokes shift of 5605cm−1, as theoretically estimated from the 0-0 components of the absortion and emission transitions of the dimer. Surprisingly, however, the calculations suggest that the green emission cannot arise from the 2Ag state generated by a double-proton transfer, because this structure possesses an imaginary frequency. In the 7-azaindole dimer of Cs symmetry, the first excited electronic state, a′, lies 4.9kcal∕mol below 1Bu. This excited state a′ can be the starting point for single-proton transfers giving a zwitterionic form that can dissociate into the protonated and deprotonated forms of 7-azaindole, the former being electronically excited. This situation of lower symmetry is consistent with the mutational scheme proposed by Goodman [Nature (London) 378, 237 (1995)].
Epitaxial Fe∕GaAs via electrochemistry
Authors: Bao Zhi Liang , Kavanagh Karen L.
Published: September 2005

Single-crystalline, body-centered-cubic Fe films have been electrodeposited on n-GaAs (001)-, (111)-, and (110)-oriented substrates from ferrous ammonium sulphate [Fe(NH4)2SO4] electrolytes. The purity of the epitaxial Fe films (lattice constant), and the quality of the epitaxy as indicated by x-ray diffraction and transmission electron microscopy, is comparable to vacuum-deposited films. The films nucleate as islands that strain relax before coalescing into continuous layers. The resulting interfaces are atomically abrupt and the films are magnetic with easy magnetization axes the same as that for bulk iron.
Oscillatory surface tension due to finite-size effects
Authors: Orea Pedro , López-Lemus Jorge , Alejandre José
Published: September 2005

The simulation results of surface tension at the liquid-vapor interface are presented for fluids interacting with Lennard Jones and square-well potentials. From the simulation of liquids we have reported [M. González-Melchor et al., J. Chem. Phys. 122, 4503 (2005)] that the components of pressure tensor in parallelepiped boxes are not the same when periodic boundary conditions and small transversal areas are used. This fact creates an artificial oscillatory stress anisotropy in the system with even negative values. By doing direct simulations of interfaces we show in this work that surface tension has also an oscillatory decay at small surface areas; this behavior is opposite to the monotonic decay reported previously for the Lennard Jones fluid. It is shown that for small surface areas, the surface tension of the square-well potential artificially takes negative values and even increases with temperature. The calculated surface tension using a direct simulation of interfaces might have two contributions: one from finite-size effects of interfacial areas due to box geometry and another from the interface. Thus, it is difficult to evaluate the true surface tension of an interface when small surface areas are used. Care has to be taken to use the direct simulation method of interfaces to evaluate the predicted surface tension as a function of interfacial area from capillary-wave theory. The oscillations of surface tension decay faster at temperatures close to the critical point. It is also discussed that a surface area does not show any important effect on coexisting densities, making this method reliable to calculate bulk coexisting properties using small systems.
Coulomb effects and terahertz emission in semiconductor superlattices
Authors: Cruz H. , Luis D.
Published: September 2005

We have solved the effective-mass nonlinear Schrödinger equation for an electron-hole gas in a semiconductor superlattice in space and time. Considering a Coulomb interaction between both electron-hole gases in a semiconductor superlattice we have obtained a time-varying dipole moment in the heterostructure. In this way, we have shown the possibility of another kind of terahertz electromagnetic radiation that emerges from a semiconductor superlattice after optical excitation of the sample.
Intersecting basal plane and prismatic stacking fault structures and their formation mechanisms in GaN
Authors: Bai J. , Huang X. , Dudley M. , Wagner B. , Davis R. F. , Wu L. , Sutter E. , Zhu Y. , Skromme B. J.
Published: September 2005

A systematic study of intersecting planar boundary structures observed in a GaN epifilm grown on a vicinal 6H-SiC substrate (offcut towards [12¯10]) with an AlN buffer is presented. These structures are shown to comprise stacking faults that fold back and forth from the basal plane [I1 basal plane stacking faults (BSFs)] to the prismatic plane [prismatic stacking faults (PSFs)]. The PSFs, with fault vector 12⟨101¯1⟩ nucleate at steps on the substrate surface as a consequence of the different stacking sequences exposed on either side of the step. Once nucleated, PSFs intersecting the vertical step risers in the AlN buffer and eventually in the GaN film are replicated during the predominantly step-flow growth and propagate into the growing crystal. As a consequence of the different growth rates experienced on either side of the intersection of a PSF with a vertical step riser, the PSF may be redirected onto an equivalent {112¯0} plane, leaving an I1 BSF between the bottom of the redirected section of PSF and the top of that portion of the original PSF which was below the terrace. This leads to the formation of folded PSF/BSF fault structures which exhibit various configurations. Such folded stacking fault configurations form walls which enclose domains of different stacking sequence. Stair-rod dislocations (SRDs) are observed to form at the intersections of these various faults and the Burgers vectors of some of these are discussed. In some cases, reconstruction of these SRDs occurs through the formation of partner dislocations which serve to minimize the energy associated with the lattice disconnections located at the cores of the SRDs.
Wrinkling of a two-layer polymeric coating
Authors: Basu Soumendra K. , Bergstreser Aaron M. , Francis L. F. , Scriven L. E. , McCormick A. V.
Published: September 2005

Wrinkling of a two-layer coating, comprised of a glassy polyvinyl alcohol top layer and a rubbery polyethyl acrylate bottom layer, was studied. The coatings were prepared on polyethylene terephthalate substrates by depositing and drying the layers in sequence. Fine, short-wavelength (180–200μm) wrinkles formed when the two-layer coating was exposed to humid atmosphere after the second drying treatment and coarse, long-wavelength (450–500μm) wrinkles formed when the two-layer coating was heated to a temperature above the glass transition temperature of the top layer. Both types of wrinkles must have arisen from compressive stress in the top layer. The compressive stress developed by either moisture absorption (fine wrinkles) or differential thermal expansion on heating (coarse wrinkles). When compressive stress is high enough, the top layer deforms out of plane without detaching from the bottom layer to produce wrinkles. The balance of forces in systems of three adhering layers of different thicknesses and moduli in static mechanical equilibrium was analyzed, and it was found that the layer with the highest in-plane axial stiffness, the product of elastic modulus by thickness, typically dictates the dimension of the entire composite. When the mismatch of thermal expansivities of the layers generates the compressive stress that produces wrinkling, the difference between the thermal expansivity of the top layer and the axial stiffness-weighted average thermal expansivity of the three layers governs the compressive stress in the top layer. Because polymer modulus falls abruptly at the glass transition temperature Tg, the critical compressive stress required for wrinkling falls abruptly at Tg. Therefore, the two-layer coating atop a stiff substrate is more susceptible to wrinkling when the top layer is above its Tg. When absorption of moisture in the top layer generates the compressive stress that generates wrinkling, that stress goes through a minimum because modulus falls and compressive strain rises with rising moisture content. However, the critical compressive stress for wrinkling falls because modulus falls with rising moisture content. Therefore, the two-layer coating atop a stiff substrate is more susceptible to wrinkling the greater the moisture content in the top layer. The relative humidity (RH) of the sample atmosphere was raised to raise the moisture content in the top layer. The wrinkle wavelength fell with rising RH because the modulus, and therefore the bending stiffness, of the top layer fell with rising RH. The measured wavelengths were qualitatively predicted at low humidities and quantitatively predicted at high humidities.
Clustering in high Re monodispersed bubbly flows
Authors: Figueroa-Espinoza Bernardo , Zenit Roberto
Published: September 2005

Experiments were conducted to determine the amount of clustering that occurs in bubbly flows for which the liquid motion can be described, with a certain degree of accuracy, using potential flow theory. A Hele-Shaw-type channel was used in which bubble overlap was avoided. Direct video image analysis was performed to calculate bubbles properties and identify cluster formation. Despite the significant wall influence of this configuration, it was found that the bubbles do form aggregates with a statistical horizontal tendency. The flow structure was also analyzed using the radial probability distribution, giving indications that support the clustering hypothesis.
Thermal inhibition of high-power second-harmonic generation in periodically poled LiNbO3 and LiTaO3 crystals
Authors: Louchev Oleg A. , Yu Nan Ei , Kurimura Sunao , Kitamura Kenji
Published: September 2005

A coupled thermo-optical model shows strong thermal inhibition of second-harmonic generation (SHG) in periodically poled (PP) LiNbO3 (PPLN) and stoichiometric LiTaO3 (PPSLT) crystals. Three-dimensional simulations performed for a 1.064μm fundamental wavelength pulsed nanosecond laser beam 150μm in radius show the onset of significant temperature nonuniformities along and across the irradiated zone, and strong thermal dephasing and inhibition of SHG in these crystals for input powers >10W. PPSLT is found to have a significant advantage over PPLN due to the higher heat conductance, decreasing these temperature nonuniformities and allowing one to maintain the irradiated zone within the corresponding SHG temperature tolerance range (ΔT≈3K).
Atomic-scale structure of self-assembled In(Ga)As quantum rings in GaAs
Authors: Offermans P. , Koenraad P. M. , Wolter J. H. , Granados D. , García J. M. , Fomin V. M. , Gladilin V. N. , Devreese J. T.
Published: September 2005

We present an atomic-scale analysis of the indium distribution of self-assembled In(Ga)As quantum rings (QRs) which are formed from InAs quantum dots by capping with a thin layer of GaAs and subsequent annealing. We find that the size and shape of QRs as observed by cross-sectional scanning tunneling microscopy (X-STM) deviate substantially from the ring-shaped islands as observed by atomic force microscopy on the surface of uncapped QR structures. We show unambiguously that X-STM images the remaining quantum dot material whereas the AFM images the erupted quantum dot material. The remaining dot material shows an asymmetric indium-rich crater-like shape with a depression rather than an opening at the center and is responsible for the observed electronic properties of QR structures. These quantum craters have an indium concentration of about 55% and a diameter of about 20nm which is consistent with the observed electronic radius of QR structures.
Multiple cyclin-dependent kinases signals are critical mediators of ischemia/hypoxic neuronal death
in vitro
and
in vivo
Authors: Rashidian Juliet , Iyirhiaro Grace , Aleyasin Hossein , Rios Mario , Vincent Inez , Callaghan Steven , Bland Ross J. , Slack Ruth S. , During Matthew J. , Park David S.
Published: September 2005

The mechanisms involving neuronal death after ischemic/hypoxic insult are complex, involving both rapid (excitotoxic) and delayed (apoptotic-like) processes. Recent evidence suggests that cell cycle regulators such as cyclin-dependent kinases are abnormally activated in neuropathological conditions, including stroke. However, the function of this activation is unclear. Here, we provide evidence that inhibition of the cell cycle regulator, Cdk4, and its activator, cyclinD1, plays critical roles in the delayed death component of ischemic/hypoxic stress by regulating the tumor suppressor retinoblastoma protein. In contrast, the excitotoxic component of ischemia/hypoxia is predominately regulated by Cdk5 and its activator p35, components of a cyclin-dependent kinase complex associated with neuronal development. Hence, our data both characterize the functional significance of the cell cycle Cdk4 and neuronal Cdk5 signals as well as define the pathways and circumstances by which they act to control ischemic/hypoxic damage.
Connections of thalamic modulatory centers to the vocal control system of the zebra finch
Authors: Akutagawa Eugene , Konishi Masakazu
Published: September 2005

The vocal control system of zebra finches shows auditory gating in which neuronal responses to the individual bird's own song vary with behavioral states such as sleep and wakefulness. However, we know neither the source of gating signals nor the anatomical connections that could link the modulatory centers of the brain with the song system. Two of the song-control nuclei in the forebrain, the HVC (used as the proper name) and the interfacial nucleus of the nidopallium, both show auditory gating, and they receive input from the uvaeform nucleus (Uva) in the thalamus. We used a combination of anterograde and retrograde tracing methods to show that the dorsal part of the reticular formation and the medial habenula (MHb) project to the Uva. We also show by choline acetyl transferase immunohistochemistry that the MHb is cholinergic and sends cholinergic fibers to the Uva. Our findings suggest that the Uva might serve as a hub to coordinate neuromodulatory input into the song system.
Nitrogenase reactivity with P-cluster variants
Authors: Hu Yilin , Corbett Mary C. , Fay Aaron W. , Webber Jerome A. , Hedman Britt , Hodgson Keith O. , Ribbe Markus W.
Published: September 2005

Nitrogenase is a multicomponent metalloenzyme that catalyzes the conversion of atmospheric dinitrogen to ammonia. For decades, it has been generally believed that the [8Fe-7S] P-cluster of nitrogenase component 1 is indispensable for nitrogenase activity. In this study, we identified two catalytically active P-cluster variants by activity assays, metal analysis, and EPR spectroscopic studies. Further, we showed that both P-cluster variants resemble [4Fe-4S]-like centers based on x-ray absorption spectroscopic experiments. We believe that our findings challenge the dogma that the standard P-cluster is the only cluster species capable of supporting substrate reduction at the FeMo cofactor and provide important insights into the general mechanism of nitrogenase catalysis and assembly.
Activation of MAPK is necessary for long-term memory consolidation following food-reward conditioning
Authors: Ribeiro Maria J. , Schofield Michael G. , Kemenes Ildikó , O'Shea Michael , Kemenes György , Benjamin Paul R.
Published: September 2005

Although an important role for the mitogen-activated protein kinase (MAPK)
has been established for memory consolidation in a variety of learning
paradigms, it is not known if this pathway is also involved in appetitive
classical conditioning. We address this question by using a single-trial
food-reward conditioning paradigm in the freshwater snail Lymnaea
stagnalis. This learning paradigm induces protein synthesis-dependent
long-term memory formation. Inhibition of MAPK phosphorylation blocked
long-term memory consolidation without affecting the sensory and motor
abilities of the snails. Thirty minutes after conditioning, levels of MAPK
phosphorylation were increased in extracts from the buccal and cerebral
ganglia. These ganglia are involved in the generation, modulation, and
plasticity of the feeding behavior. We also detected an increase in levels of
MAPK phosphorylation in the peripheral tissue around the mouth of the snails
where chemoreceptors are located. Although an increase in MAPK phosphorylation
was shown to be essential for food-reward conditioning, it was also detected
in snails that were exposed to the conditioned stimulus (CS) or the
unconditioned stimulus (US) alone, suggesting that phosphorylation of MAPK is
necessary but not sufficient for learning to occur.
The neural correlates of implicit and explicit sequence learning: Interacting networks revealed by the process dissociation procedure
Authors: Destrebecqz Arnaud , Peigneux Philippe , Laureys Steven , Degueldre Christian , Del Fiore Guy , Aerts Joël , Luxen André , Van Der Linden Martial , Cleeremans Axel , Maquet Pierre
Published: September 2005

In two H215O PET scan experiments, we investigated
the cerebral correlates of explicit and implicit knowledge in a serial
reaction time (SRT) task. To do so, we used a novel application of the Process
Dissociation Procedure, a behavioral paradigm that makes it possible to
separately assess conscious and unconscious contributions to performance
during a subsequent sequence generation task. To manipulate the extent to
which the repeating sequential pattern was learned explicitly, we varied the
pace of the choice reaction time task—a variable that is known to have
differential effects on the extent to which sensitivity to sequence structure
involves implicit or explicit knowledge. Results showed that activity in the
striatum subtends the implicit component of performance during recollection of
a learned sequence, whereas the anterior cingulate/mesial prefrontal cortex
(ACC/MPFC) supports the explicit component. Most importantly, we found that
the ACC/MPFC exerts control on the activity of the striatum during retrieval
of the sequence after explicit learning, whereas the activity of these regions
is uncoupled when learning had been essentially implicit. These data suggest
that implicit learning processes can be successfully controlled by conscious
knowledge when learning is essentially explicit. They also supply further
evidence for a partial dissociation between the neural substrates supporting
conscious and nonconscious components of performance during recollection of a
learned sequence.
Correlation function of the excluded volume
Authors: Kruglov Timofey
Published: September 2005

The paper introduces a correlation function of the excluded volume necessary for a real-space description of scattering from dense systems of spherical particles.
DS5: direct-searcher automatic system version 5 for small molecules running on Windows personal computers
Authors: Okada Kenji , Boochathum Ploenpit
Published: September 2005

DS5(Direct-Searcher Automatic System Version 5), for the crystal structure analysis of small molecules on personal computers (PCs), is a new program that integrates more than 18 main programs, subroutines and mathematics/graphic libraries of theDS*SYSTEM4package. Three features of note are: compatibility of input instruction data with theSHELXseries, control of calculation sequences by subprogram names that are prepared by the user, and graphical output on the PC display with Postscript/HPGL files. All functions ofDS5are inherited fromDS*SYSTEM4.
Application ofin situvapor sorption small-angle neutron scattering (SANS) to semicrystalline polymers: vapor pathway and structure evolution in semicrystalline linear polyethylene
Authors: Kim Man-Ho , Glinka Charles J.
Published: September 2005

SANS has not been successfully applied to study the structure of semicrystalline polyolefins without deuterated polymers because of the fundamental limitation of negligible contrast between the crystalline and amorphous phases in spite of the mass density difference. The proposedin situvapor sorption SANS technique circumvents this limitation and enables structural changes to be studied quantitatively with sorption of a contrast-generating vapor. The results verify the long-standing assumption that vapor selectively diffuses into the amorphous regions of semicrystalline polyethylenes. The proposed technique makes it possible to correlate the structure, sorption isotherm and diffusion coefficient, which is not possible using conventional gravimetric methods.
High-resolution X-ray diffraction of silicon-on-nothing
Authors: Servidori Marco , Ottaviani Giampiero
Published: September 2005

High-resolution multi-crystal X-ray diffraction was employed to characterize silicon-on-nothing samples consisting of a one-dimensional periodic array of buried empty channels.p- andn-type silicon starting wafers were used for sample preparation. For thep-type samples, this periodic array gives rise to well defined Fraunhofer diffraction when the channels are normal to the scattering plane. This indicates good lattice quality of the layer containing the channels. Moreover, the lattices of the surface layer and the layer with the channels were almost indistinguishable from that of perfect silicon. Conversely, then-type samples showed such lattice tilts and out-of-plane mosaic spreads in the surface and buried layers that Fraunhofer diffraction does not occur from the periodic array of the channels. The elucidation of this different behaviour is in progress and will most likely be fruitful after X-ray images of the same samples are taken.
A Swagelok-typein situcell for battery investigations using synchrotron radiation
Authors: Nikolowski Kristian , Baehtz Carsten , Bramnik Natalia N. , Ehrenberg Helmut
Published: September 2005

Anin situcell designed for synchrotron X-ray diffraction during electrochemical cycling of battery materials is presented. The cell operates in transmission mode and can be oscillated with the dedicated sample holder to improve powder statistics. It allows fast data acquisition, provides hermetic sealing and high-quality diffraction data, and is easy to assemble, since a commercially available Swagelok junction is used as the cell body. Diffraction data from the cycling of a battery using LixNi0.8Co0.2O2(0 ≤x≤ 1) as the cathode material are presented.
A comparison of methods for modeling the effect of axial divergence in powder diffraction
Authors: Prince E. , Toby B. H.
Published: September 2005

The Edgeworth series model for the modification of diffraction peak shapes because of axial divergence is compared with the peak shapes computed by a numerical convolution method that is computationally slow. It is shown that if the width of an approximately Gaussian instrumental peak shape is comparable with the width of the modifying function, a condition that is generally satisfied in fixed-wavelength neutron diffraction and in many laboratory X-ray diffraction instruments, but not with synchrotron X-ray instruments, the Edgeworth model is nearly identical to the convolution model, while the computation is much simpler.
A study of the effect of annealing on Fe-doped LiNbO3by HRXRD, XRT and FT–IR
Authors: Bhagavannarayana G. , Ananthamurthy R. V. , Budakoti G. C. , Kumar B. , Bartwal K. S.
Published: September 2005

The annealing effect on the structural perfection of Fe-doped LiNbO3single crystals has been studied by high-resolution X-ray diffractometry (HRXRD), X-ray topography (XRT) and Fourier transform infrared (FT–IR) spectroscopy. The single crystals, prepared by mixing Li2CO3and Nb2O5powders in the molar ratio 48.6:51.4 with 0.05 mol% of iron at 1415 (1) K, were grown by the Czochralski (CZ) method along the [001] direction in air and poled during crystal growth by the application of a DC field. Two low-angle (tilt angle ∼1 arc minute) structural grain boundaries were observed in as-grown specimens. FT–IR spectra revealed that these crystals contain OH−and CO32−ionic defects. Grain boundaries and CO32−ionic defects were successfully removed, while the concentration of OH−ions was considerably reduced by post-growth thermal annealing at elevated temperatures.
Investigation of the primary crystallization of Ni–17 at.% P alloy by ASAXS
Authors: Tatchev D. , Goerigk G. , Valova E. , Dille J. , Kranold R. , Armyanov S. , Delplancke J.-L.
Published: September 2005

Primary crystallization of Ni(P) particles in hypoeutectic Ni–P amorphous alloy obtained by electroless deposition has been investigated with ASAXS. The particle size distribution, the size dependence of the particle composition and the amorphous matrix composition were found simultaneously. The size distribution consists of a peak at particle radius of ∼1 nm and a tail spanning from ∼2 to 15 nm. The composition of the particles of the peak changes from ∼14 to ∼2 at.% P as their radius grows from 0.7 to about 3 nm. The particles in the tail of the size distribution (2–15 nm) have nearly constant P content in the range of 0–2 at.%. The matrix composition tends to the eutectic one at the end of the primary crystallization process.
Structure factors from pseudo-Kossel line patterns
Authors: Bortel Gabor , Tegze Miklos , Faigel Gyula
Published: September 2005

Pseudo-Kossel lines are cones of Bragg reflections that contain information on the structure of single crystals. Nevertheless, they are not used in structure determination. The feasibility of obtaining a data set of structure factor amplitudes from a pseudo-Kossel line pattern measurement is presented in this paper. The experimental setup shown allows the detection of almost the complete cone pattern around the sample. The measurement process is significantly simpler than data collection with a conventional four-circle diffractometer. The extraction of structural information from the measured pattern completely separates from the data collection phase. The process consists of three main steps: determining the crystal lattice from the geometry of the cones, calculating the integrated intensities belonging to each reflection and finally solving/refining the structure in the usual manner. As an example, the pseudo-Kossel line pattern of a C60single crystal was recorded and analysed. The extracted single-crystal data set, fitted with the face-centred cubic structure of C60, yieldedR= 4.5% andRw= 7.7%. The advantages and drawbacks of this method compared with conventional single-crystal measurements are discussed. Two variants of the detection process in the method are also compared.
Melatonin‐evoked potentiation of the juvenile rat tail artery neurogenic reactivity depends on degree of the change in the reactivity
Authors: Karachentseva O. V. , Yartsev V. N. , Dvoretsky D. P. , Zhdanova I. V.
Published: September 2005

Aim:  Dependence of the melatonin‐evoked potentiation of the rat tail artery neurogenic reactivity on degree of the change in the reactivity was studied.

Method:  Electrical field stimulation‐evoked contractile response of the juvenile rat tail artery segment under isometric conditions was recorded. 0.1 μm melatonin was administered after the change in the response produced both spontaneously and by acidification (pH 6.6) or alkalinization (pH 7.8) of the solution.

Results:  During the course of experiment, the contraction force continuously declined, being reduced by 12 ± 5, 24 ± 7 and 32 ± 6% at 20, 70, and 170 min after beginning of experiment, respectively. Melatonin applied at these time points increased the contraction by 20 ± 5, 41 ± 10, and 48 ± 8%, respectively, relative to control. This increase in potentiating effect of melatonin during the course of experiment was not because of sensitization of the segment to the hormone. Acidosis‐induced considerable decline in neurogenic contraction was counteracted by melatonin, while after alkalosis‐induced augmentation in the contraction the hormone was not effective. Melatonin increased the artery response to 0.1 μm noradrenaline.

Conclusion:  These data suggest that melatonin can restore an attenuated neurogenic reactivity of the juvenile rat tail artery. The effect is more pronounced with further decrease in reactivity and might be due to a change in sensitivity of the post‐junctional membrane to noradrenaline.
Relaxant effects of β‐adrenergic agonists on porcine and human detrusor muscle
Authors: Badawi J. K. , Uecelehan H. , Hatzinger M. , Michel M. S. , Haferkamp A. , Bross S.
Published: September 2005

Aim:  Relaxant effects of different β‐adrenoceptor agonists on porcine and human detrusor were examined. Thus, the β‐adrenoceptor subtype mainly responsible for relaxation in the detrusor muscle of pigs was characterized. Additionally, different effects of several β‐agonists in both species were shown.

Methods:  Experiments were performed on muscle strips of porcine and human detrusor suspended in a tissue bath. The relaxant effects of the non‐selective β‐agonist isoprenaline, the selective β2‐agonists procaterol, salbutamol and the selective β3‐agonists BRL 37344, CL 316 243 and CGP 12177 on potassium‐induced contraction were investigated. The inhibitory effect of different substances on the maximum contraction and the rank order of potency for endogenous catecholamines was determined in pigs. Furthermore, concentration‐relaxation curves were performed for pigs and humans.

Results:  Pigs: In the pre‐treatment experiments isoprenaline and procaterol showed similar effects. The concentration–response experiments showed that the maximum relaxation induced by procaterol and salbutamol was more than 90%, not significantly different from isoprenaline, whereas the maximum relaxations of CL 316 243, BRL 37344 and CGP 12177 amounted to 68, 70 or 30%, respectively. Rank order of potencies was isoprenaline ≥ adrenaline > noradrenaline. Humans: Isoprenaline, procaterol, salbutamol and CL 316 243 showed a maximum relaxation of 80, 41, 24 and 35% and pD2 values of 6.24, 5.65, 5.48 and 5.55, respectively.

Conclusion:  β2‐receptors play a main functional role in mediating relaxation of porcine detrusor. Selective β2‐ and β3‐agonists similarly relax the human detrusor. Effects were smaller compared with the pig.
Exhaled nitric oxide during normoxic and hypoxic exercise in endurance athletes
Authors: Verges S. , Flore P. , Favre‐Juvin A. , Lévy P. , Wuyam B.
Published: September 2005

Aim:  Endogenous nitric oxide (NO) through its relaxing effect on smooth muscle cells may be involved in pulmonary gas exchange as well as in the modulation of the hypoxic pulmonary vasoconstriction. As athletes with exercise‐induced hypoxaemia (EIH) present pulmonary gas exchange abnormalities in normoxia that could be even greater in hypoxia, we hypothesized that pulmonary NO may be lower in such athletes with EIH.

Methods:  Eleven athletes with EIH [decrease in arterial oxygen blood partial pressure (PaO2) > 12 mmHg] and 9 without EIH (NEIH) exercised at 40%, 60% (10 min) and 90% (5 min) of normoxic maximal power output (Pmax) in normoxia, and at 40% and 60% (10 min) of Pmax in hypoxia (FiO2 = 15%). Exhaled NO concentration during a constant flow exhalation (FENO0.170) and arterialized blood gases were measured at every power output.

Results:  FENO0.170 decreased from rest to exercise both in normoxia (−27.8 ± 22.8% at 90%Pmax, P < 0.001) and hypoxia (−23.8 ± 17.5% at 60%Pmax, P < 0.001). At 90%Pmax in normoxia, EIH athletes showed lower PaO2 (76.7 ± 5.4 vs. 82.8 ± 4.4 mmHg, P = 0.013) and greater FENO0.170 decrement (−37.0 ± 24.7% vs. −16.6 ± 14.6%, P = 0.042) than NEIH athletes. During hypoxic exercise, PaO2 and FENO0.170 decreases were similar in both groups (P > 0.05).

Conclusion:  The present study shows lower pulmonary NO in athletes with gas exchange abnormalities during intense exercise in normoxia, while EIH and NEIH athletes have similar decreases in blood gases and pulmonary NO during hypoxic exercise. Decreased pulmonary NO in such conditions may contribute to ventilation‐perfusion inequality and/or increase pulmonary vascular tone in athletes.
Effect of breathing low concentrations of volatile anaesthetic agents on incidence of adverse airway events
Authors: Goodwin N. , Strong P. J. , Sudhir G. , Wilkes A. R. , Hall J. E.
Published: September 2005

The effect of breathing 0.1 minimum alveolar concentrations (MAC) of desflurane or isoflurane for three minutes on the incidence of adverse airway events on a subsequent breath of 2 MAC was investigated. Twenty‐five volunteers known to develop an adverse airway event to desflurane or isoflurane took part in the study. Each volunteer was exposed to isoflurane and desflurane at least 24 h apart. Volunteers were assessed for adverse airway events while breathing 2 MAC inhalational anaesthetic following breathing 100% O2 for 3 min. This was repeated with 0.1 MAC inhalational anaesthetic in oxygen instead of 100% O2. Adverse airway events decreased from 88% to 40% when tests were conducted with desflurane (p = 0.002). With isoflurane, the reduction from 60% to 52% was not statistically significant (p = 0.774). Breathing low concentrations of desflurane decreases the incidence of adverse airway events on subsequent inhalation of higher concentration of desflurane.
Cardiac output measurement by pulse dye densitometry in cardiac surgery
Authors: Baulig W. , Bernhard E. O. , Bettex D. , Schmidlin D. , Schmid E. R.
Published: September 2005

The aim of this study was to compare the accuracy of pulse dye densitometry with that of bolus thermodilution cardiac output measurement in patients before and after elective coronary artery bypass grafting. Twenty‐eight patients were studied. Agreement between mean thermodilution and pulse dye densitometry cardiac output values was assessed by Bland‐Altman analysis. Preoperative median [range] cardiac output was 3.87 [2.37–6.0] l.min−1 by thermodilution, and 3.11 [1.7–5.45] l.min−1 by pulse dye densitometry using indocyanine green 5 mg. Pulse dye densitometry underestimated cardiac output (mean bias − 0.42 l.min−1); the limits of agreement were ± 1.91 l.min−1, and mean error was 50.3%, indicating low precision. Preoperative median [range] cardiac output was 3.85 [2.2–6.0] l.min−1 for bolus thermodilution cardiac output and 4.2 [2.0–7.2] l.min−1 for pulse dye densitometry using indocyanine green 20 mg. Mean bias was + 0.566 l.min−1, the limits of agreement were ± 2.51 l.min−1 and mean error was 60.9%. Postoperative cardiac output data were not analysed because pulse dye densitometry signals were low or absent in > 50% of the patients. We conclude that pulse dye densitometry using indocyanine green 5 mg or 20 mg is inaccurate in anaesthetised patients before coronary artery bypass surgery and cannot be used after surgery because of a high incidence of low pulse dye densitometry signal amplitudes.
Experiences of families when a relative is diagnosed brain stem dead: understanding of death, observation of brain stem death testing and attitudes to organ donation
Authors: Ormrod J. A. , Ryder T. , Chadwick R. J. , Bonner S. M.
Published: September 2005

Brain stem death may be a difficult concept for relatives to understand. Our ITU practice follows published recommendations that the use of explanatory leaflets showing CT scans and observing brain stem death testing in some cases may help relatives to understand that death has occurred. Using this strategy, we interviewed 27 relatives 12 months after bereavement following certification by brain stem testing, investigating their understanding of brain stem death, subsequent attitudes to organ donation, grief reactions and attitudes of those who had observed the tests. Most relatives understood that the brain stem death tests indicated that survival was not possible, although three relatives had not fully understood this and valued the opportunity to discuss it again. Only five relatives observed the tests, all were pleased that they had done so as this had confirmed their understanding that death had occurred; however, these relatives had more evidence of psychological distress. No relatives who agreed to organ donation regretted this but three who did not allow donation subsequently expressed regret. Several relatives thought that observing the tests would have helped them to understand that death had occurred, making easier the decision to allow organ donation.
Effect of remifentanil with and without atropine on heart rate variability and RR interval in children
Authors: Tirel O. , Chanavaz C. , Bansard J. Y. , Carré F. , Ecoffey C. , Senhadji L. , Wodey E.
Published: September 2005

Remifentanil can cause bradycardia either by parasympathetic activation or by other negative chronotropic effects. The high frequency (HF) component of heart rate variability (HRV) is a marker of parasympathetic activity. This study aimed to evaluate the effect of remifentanil on RR interval and on HRV in children. Forty children ASA I or II were studied after approval by the human studies committee and informed parental consent was obtained. After stabilisation at sevoflurane 1 MAC, they were randomly divided into two groups: one received a 20 μg.kg−1 atropine injection (AT + REMI) and the other ringer lactate solution (REMI). Three minutes later, a 1 μg.kg−1 bolus of remifentanil was administered over 1 min, followed by a continual infusion at 0.25 μg.kg−1.min−1 for 10 min increased to 0.5 μg.kg−1.min−1 for a further 10 min. A time varying, autoregressive analysis of RR sequences was used to estimate classical spectral parameters: low (0.04–0.15 Hz; LF) and high (0.15–0.45 Hz; HF) frequency, whereas the root mean square of successive differences of RR intervals (rmssd) was derived directly from the temporal sequence. Statistical analyses were conducted by means of the multiple correspondence analysis and with non parametrical tests. Remifentanil induced an RR interval lengthening, i.e. bradycardia, in both groups compared to pretreatment values and was associated with an increase of HF and rmssd only for the REMI group. The parasympathetic inhibition by atropine did not totally prevent remifentanil's negative chronotropic effect. A direct negative chronotropic effect of remifentanil is proposed.
Comparison of xenon‐based anaesthesia compared with total intravenous anaesthesia in high risk surgical patients*
Authors: Bein B. , Turowski P. , Renner J. , Hanss R. , Steinfath M. , Scholz J. , Tonner P. H.
Published: September 2005

Xenon, a noble gas with anaesthetic and analgesic properties, has gained renewed interest due to its favourable physical properties which allow a rapid emergence from anaesthesia. However, high costs limit its use to a subset of patients who may benefit from xenon, thereby offsetting its costs. To date, there are only limited data available on the performance of xenon in high risk patients. We studied 39 patients with ASA physical status III undergoing aortic surgery. The patients were randomly assigned to either a xenon (Xe, n = 20) or a TIVA (T, n = 19) group. Global cardiac performance and myocardial contractility were assessed using transoesophageal echocardiography, and myocardial cell damage with troponin T and CK‐MB. Echocardiographic measurements were made prior to xenon administration, following xenon administration, and after clamping of the abdominal aorta, after declamping and at corresponding time points in the TIVA group. Laboratory values were determined repeatedly for up to 72 h. Data were analysed using two‐way anova factoring for time and anaesthetic agent or with ancova comparing linear regression lines. No significant differences were found in global myocardial performance, myocardial contractility or laboratory values at any time during the study period. Mean (SEM) duration of stay on the ICU (xenon: 38 ± 46 vs. TIVA 25 ± 15 h) or in hospital (xenon: 14 ± 12 vs. TIVA 10 ± 6 days) did not differ significantly between the groups. Although xenon has previously been shown to exert superior haemodynamic stability, we were unable to demonstrate an advantage of xenon‐based anaesthesia compared to TIVA in high risk surgical patients.
Analysis of recessive lethality on swine chromosome 6 in a Göttingen miniature resource family
Authors: Mikawa S. , Kishi H. , Ogawa H. , Iga K. , Uenishi H. , Yasue H.
Published: September 2005

Previously, we reported recessive gene(s) that terminate fetal development on swine chromosome (SSC) 6 between SW855 and SW122. The affected alleles originated from a Göttingen miniature pig used for construction of a Göttingen miniature pig × Meishan resource population. However, it is not known when the gene(s) are activated during fetal development, which is one of the important factors in selecting candidate genes responsible for fetal death. In the present study, a second swine population consisting of 159 progeny was produced by mating pigs carrying the deleterious allele(s). This population allowed us to narrow the genetic region harbouring the affected gene(s) and to demonstrate that the region was confined between RYR1 and SW782 (5.7 cM on the National Institute of Animal Industry (NIAI) map and 100 cR on the INRA/University of Minnesota porcine radiation hybrid panel map). In order to determine when the affected gene(s) are activated and in turn terminate fetal development, embryos produced in the second population were collected at several development stages and genotyped for markers in the region. Genes in the homozygous state affected embryo development between 9 and 11 days post‐coitus.
Analysis of public single nucleotide polymorphisms in commercial pig populations
Authors: Kollers S. , Mégy K. , Rocha D.
Published: September 2005

More than 5500 pig single nucleotide polymorphisms (SNPs) were recently identified and deposited in the public domain. To test the usefulness of these public SNPs, 109 SNPs were analysed for polymorphism within six commercial pig populations. A functional polymerase chain reaction (PCR) assay was obtained for 103 SNPs and it was possible to validate c. 59% by PCR‐restriction fragment length polymorphism. Furthermore, polymorphism was found using a relatively limited number of genomic DNA samples, indicating that these polymorphisms are segregating at a useful frequency in these populations. The high percentage of validated markers demonstrates the utility of these public pig SNPs to identify loci responsible for economically important traits in commercial pig populations.
High‐resolution typing for chicken BF2 (MHC class I) alleles by automated sequencing
Authors: Livant E. J. , Ewald S. J.
Published: September 2005

Sequence‐based typing (SBT) was developed for major histocompatibility complex (MHC) class I and class II alleles in humans. We report here the development and application of a SBT method for alleles of the chicken BF2 locus (the more polymorphic of the two MHC class I loci in chickens). Exon 2 of the BF2 gene was selectively amplified from genomic DNA using a BF2 locus‐specific PCR primer. Exon 2 sequences were sufficient to identify the 21 distinct BF2 alleles described in standard B haplotypes of Leghorns and in commercial broiler‐breeder lines. Sixty‐six samples from MHC typed, pedigreed chickens were tested, including 50 different heterozygous combinations. BF2 sequences from all B homozygotes were successfully amplified, and all combinations of BF2 alleles in heterozygotes were co‐amplified equally. The two different BF2 alleles in heterozygotes could be identified unambiguously by distinct sequence motif patterns. In tests of samples of unknown B genotype in commercial broiler‐breeder flocks, we identified expected BF2 alleles as well as an allele not previously encountered in one of the lines.
Mapping of plumage colour and blood protein loci on the microsatellite linkage map of the Japanese quail
Authors: Miwa M. , Inoue‐Murayama M. , Kayang B. B. , Vignal A. , Minvielle F. , Monvoisin J. L. , Takahashi H. , Ito S.
Published: September 2005

The objective of this work was to map classical markers (plumage colours and blood proteins) on the microsatellite linkage map of the Japanese quail (Coturnix japonica). The segregation data on two plumage colours and three blood proteins were obtained from 25 three‐generation families (193 F2 birds). Linkage analysis was carried out for these five classical markers and 80 microsatellite markers. A total of 15 linkage groups that included the five classical loci and 69 of the 80 microsatellite markers were constructed. Using the BLAST homology search against the chicken genome sequence, three quail linkage groups, QL8, QL10 and QL13, were suggested to be homologous to chicken chromosomes GGA9, GGA20 and GGA24, respectively. Two plumage colour loci, black at hatch (Bh) and yellow (Y), and the three blood protein loci, transferrin (Tf), haemoglobin (Hb‐1) and prealbumin‐1 (Pa‐1), were assigned to CJA01, QL10, QL8, CJA14 and QL13, respectively.
Whole‐genome scan to detect QTL for milk production, conformation, fertility and functional traits in two US Holstein families
Authors: Schnabel R. D. , Sonstegard T. S. , Taylor J. F. , Ashwell M. S.
Published: September 2005

A genome scan was conducted in two US Holstein half‐sib families to identify quantitative trait loci (QTL) affecting milk production and conformation traits using the granddaughter design. The sires of the two studied families were related as sire and son and had 96 and 212 sons respectively. A total of 221 microsatellite loci were scored in both families. Statistical analysis was performed using two different analytical methods; half‐sib least squares regression and Bayesian Monte Carlo Markov Chain. Traits analysed included five traditional milk production traits, somatic cell count, daughter pregnancy rate, male fertility and 20 conformation traits. A total of 47 tests achieved at least genome‐wise significance. However, results from the two methods of analysis were only concordant for QTL location and level of significance in eight instances.