bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiple scattering calculations for nonspherical particles based on the vector radiative transfer theory
Authors: Ishimaru A. , Lesselier D. , Yeh C.
Published: April 2008

On the basis of the vector radiative transfer equation, multiple scattering calculations were performed for an obliquely incident linearly polarized plane wave upon a plane‐parallel slab consisting of arrays of vertically oriented, uniformly distributed nonspherical spheroidal particles of identical size. Results are given in terms of the Stokes' parameters for the incoherent field. Owing to the symmetry of the particles and their orientation, decoupling of the Fourier expansion coefficients in the solution of the radiative transfer equation occurs. Each Fourier component satisfies a single equation which is then solved by the Gauss' quadrature and the eigenvalue‐eigenvector technique. The behavior of the forward scattered incoherent field is investigated for low‐loss as well as high‐loss particles, for different densities and shapes, and for various angles of incidence. Comparison with the results from the approximate first‐order theory shows good quantitative agreement for thin and sparcely populated layers.
Delay dispersion of wideband ground wave signals due to propagation over a rough ocean surface
Authors: Málaga Alfonso
Published: April 2008

The group velocity of a wave which propagates over an impedance plane (ground wave) is frequency dependent. Therefore when a narrow pulse (wideband signal) propagates over such a surface, it exhibits delay dispersion. Previous efforts to determine the delay dispersion of wideband ground wave signals have been limited to propagation over a smooth spherical earth. The analysis presented in this paper includes the effects of surface roughness and is applicable to the case of a rough ocean surface. The results are presented as a function of distance and sea state. It is shown that at short distances surface roughness tends to increase the amount of delay dispersion. Beyond a certain distance, delay dispersion depends on roughness: a small amount of roughness surprisingly causes a reduction of the delay dispersion, a large amount of roughness causes increased delay dispersion as expected.
A hybrid theory of diffraction for the RCS calculation of ogive‐like bodies
Authors: Li Shi‐Zhi , Thiele Gary A.
Published: April 2008

This hybrid theory of diffraction starts with the assumption that the dominant current on the scattering body is an optics type current close to 2
×
. Near shadow boundaries on the body or discontinuities in the surface, the current may be represented by the moment method such that the total current in the vicinity of a shadow boundary or discontinuity is the sum of the optics current and the moment method current. (In this sense the method may be equivalent to the physical theory of diffraction.) The magnetic field integral equation is then used in an iterative procedure to obtain the correct current in the asymptotic regions (away from shadow boundaries) and in the moment method region. Because the iterative process starts with a current close to the true current, convergence is rapid with one or two iterations being typical. Results will be shown for ogives of various nose angles and diameters. The implication of these results on the further development of the (new) hybrid theory of diffraction will be discussed.
Propagation and radiation characteristics of the disc‐on‐rod antenna
Authors: Olver A. D. , Dubrovka F. F. , Parini C. G.
Published: April 2008

The disc‐on‐rod antenna is analyzed as a traveling wave antenna. The propogation characteristics along the rod are predicted by modal matching, including the effect of space harmonics. The analysis is confirmed by an open resonant cavity experiment. A parametric study shows that the ratio of the inner to the outer radius is the most important factor in controlling the phase velocity of waves along the disc on rod. The far field radiation patterns are predicted by Fourier transforming the aperture fields. This enables the variation with frequency of the copolar beamwidth and the peak cross‐polar power to be studied.
Application of the Lienard‐Wiechert solution to a lightning return stroke model
Authors: Meneghini Robert
Published: April 2008

The electric and magnetic fields associated with a lossless transmission line model of the return stroke are expressed as a convolution of the current waveform shape and the fields generated by a moving charge of amplitude one (i.e., the Lienard‐Wiechert solution for a unit charge). The representation can be used to compute the fields produced by a current waveform of non‐uniform velocity that propagates along a filament of arbitrary, but finite, curvature. To study numerically the effects of linear charge acceleration and channel curvature, two simple channel models are used: the linear and the hyperbolic.
Interferometer measurements of atmospheric phase noise at 86 GHz
Authors: Bieging J. H. , Morgan J. , Welch W. J. , Vogel S. N. , Wright M. C. H.
Published: April 2008

We report measurements of the atmospheric phase noise at 86 GHz, made by using the Hat Creek millimeter wavelength interferometer. The measurements used a dual‐frequency technique to estimate the receiver noise contribution to the phase. The data, which cover projected baselines between 2000 and 40000 wavelengths, are used to derive median root mean squared (rms) phase noise as a function of baseline length. The implications of these results for the resolution limit to millimeter wavelength interferometry are discussed. We also discuss the time domain spectrum of atmospheric phase noise and consider an observing strategy that can mitigate the effects of adverse atmospheric conditions.
EHF attenuation derived from emission temperatures in light rain
Authors: Shimabukuro F. I. , Tavis M. T. , Chang D. S.
Published: April 2008

Atmospheric emission measurements have routinely been used to determine the total attenuation on an earth‐space path at the centimeter and millimeter wavelengths. In the presence of rain, scattering effects have to be taken into account at frequencies >20 GHz when interpreting emission data to derive the total attenuation. If one uses the radiometric relation to derive the attenuation assuming an absorptive medium, one finds that the predicted attenuation underestimates the true attenuation. The reason for this is that the rain scatters more emission energy out of the direct ray path than into it. Calculations of the atmospheric emission temperature and attenuation in light to moderate rain at different frequencies and rain rates are performed, taking into account molecular absorption, and varying cloud cover and ground temperature. The results show that for typically encountered meteorological conditions, the radiometric formula can be used to derive the total attenuation ( < 10 dB) from emission measurements with accuracies better than about 1 dB provided that the effective medium temperature in the radiometric formula is a function of frequency and ground temperature.
Impulse response for ionospheric reflection with a sech2 profile
Authors: Vogler Lewis E.
Published: April 2008

The impulse response for reflection from an ionospheric layer with a sech2 electron density profile is investigated. A constant electron collision frequency is assumed, and approximate results are obtained for reflection at oblique incidence under the influence of a vertical earth's magnetic field. Fast Fourier transform techniques are used to evaluate the impulse response, and an asymptotic expression is derived for the envelope of the response. Numerical examples are shown for some representative cases of E and F layer reflection.
Phase transition temperature and electrical properties of (Bi1∕2Na1∕2)TiO3–(Bi1∕2A1∕2)TiO3 (A=Li and K) lead-free ferroelectric ceramics
Authors: Hiruma Yuji , Yoshii Kazushige , Nagata Hajime , Takenaka Tadashi
Published: April 2008

( 1 − x ) ( Bi 1 ∕ 2 Na 1 ∕ 2 ) Ti O 3 – x ( Bi 1 ∕ 2 Li 1 ∕ 2 ) Ti O 3 and (1−x)(Bi1∕2Na1∕2)TiO3–x(Bi1∕2K1∕2)TiO3 (abbreviated as BNLT100x and BNKT100x, respectively) ceramics were prepared by the conventional ceramic fabrication process. In this study, the depolarization temperature Td, rhombohedral-tetragonal phase transition temperature TR-T, and the temperature of the maximum dielectric constant Tm were determined from the temperature dependences of the dielectric and piezoelectric properties. The results showed that Td of BNLT100x and BNKT100x increased to 199 and 209°C, respectively, at the rhombohedral composition. In addition, we revealed that Td is related to the magnitude of the rhombohedrality 90-α and the tetragonality c∕a. We studied the piezoelectric properties in detail, and the relationship between Td and piezoelectric properties was clarified. Moreover, we discussed the ferroelectricity of the middle phases of Td−TR-T and TR-T−Tm.
Coalescence of Tollmien–Schlichting and interfacial modes of instability in two-fluid flows
Authors: Özgen Serkan
Published: April 2008

An extensive parametric study is performed to bring out the details of the mode coalescence phenomenon in a two-fluid boundary-layer stability problem. The solution consists of numerically solving the Orr–Sommerfeld equation. The mode coalescence occurs between the Tollmien–Schlichting (TS) mode also found in the classical hydrodynamic stability theory and the interfacial mode that exists in the presence of a viscosity stratification in two-fluid flows. It was previously shown that the coalescence occurs in the unstable part of the domain when the sheared fluid thickness is sufficiently large. It was also shown that if the sheared fluid thickness is further increased, a composite mode dominates the stability problem, which carries the characteristics of the TS mode at moderate wave numbers and the interfacial mode at low and high wave numbers. In this study, the influence of sheared fluid thickness, viscosity ratio, surface tension, density stratification, and gravity on the composite mode is further elaborated. It is demonstrated that for certain parameter combinations, the mode coalescence occurs not only in the unstable part of the domain but also in the stable part. This feature had been previously reported by other researchers by using a different solution method and is now demonstrated in the Orr–Sommerfeld context as well. Moreover, mode coalescence occurs in the presence of density stratification and gravity also.
The Alzheimer’s β amyloid (Aβ1–39) monomer in an implicit solvent
Authors: Anand Priya , Nandel F. S. , Hansmann Ulrich H. E.
Published: April 2008

Results from replica-exchange and regular room temperature molecular dynamics simulations of the Alzheimer’s β amyloid (Aβ1–39) monomer in an implicit solvent are reported. Our data indicate that at room temperature, the monomer assumes random-coil and soluble conformations. No beta content is observed which therefore seems to be a product of oligomerization and aggregation of monomers.
Modeling the sorption dynamics of NaH using a reactive force field
Authors: Ojwang J. G. O. , van Santen Rutger , Kramer Gert Jan , van Duin Adri C. T. , Goddard William A.
Published: April 2008

We have parametrized a reactive force field for NaH, ReaxFFNaH, against a training set of ab initio derived data. To ascertain that ReaxFFNaH is properly parametrized, a comparison between ab initio heats of formation of small representative NaH clusters with ReaxFFNaH was done. The results and trend of ReaxFFNaH are found to be consistent with ab initio values. Further validation includes comparing the equations of state of condensed phases of Na and NaH as calculated from ab initio and ReaxFFNaH. There is a good match between the two results, showing that ReaxFFNaH is correctly parametrized by the ab initio training set. ReaxFFNaH has been used to study the dynamics of hydrogen desorption in NaH particles. We find that ReaxFFNaH properly describes the surface molecular hydrogen charge transfer during the abstraction process. Results on heat of desorption versus cluster size shows that there is a strong dependence on the heat of desorption on the particle size, which implies that nanostructuring enhances desorption process. To gain more insight into the structural transformations of NaH during thermal decomposition, we performed a heating run in a molecular dynamics simulation. These runs exhibit a series of drops in potential energy, associated with cluster fragmentation and desorption of molecular hydrogen. This is consistent with experimental evidence that NaH dissociates at its melting point into smaller fragments.
Structural characterization of annealed Si1−xCx/SiC multilayers targeting formation of Si nanocrystals in a SiC matrix
Authors: Song Dengyuan , Cho Eun-Chel , Conibeer Gavin , Huang Yidan , Flynn Chris , Green Martin A.
Published: April 2008

Amorphous Si1−xCx/SiC multilayer films were prepared by alternating deposition of Si-rich Si1−xCx and near-stoichiometric SiC layers by using magnetron sputtering. The as-deposited films were annealed at different temperatures (Ta) from 800 to 1100 °C. The influence of Ta and Si content in the Si-rich layer on the layered structural stability and on the formation of Si and/or SiC nanocrystals (NCs) is investigated by a variety of analytical techniques, including x-ray reflectivity (XRR), x-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, and Fourier transform infrared spectrometry (FTIR). XRR showed that Si1−xCx/SiC multilayers annealed at temperatures of up to 800 °C retain their layered structure. XRD revealed that Si NCs were formed in samples with a high Si content in the Si-rich layer for Ta≥800 °C. At annealing temperatures of 900 °C or greater, the formation of Si NCs was accompanied by the formation of β-SiC NCs. Additionally, the formation of Si and SiC NCs was confirmed by TEM imaging and Raman spectroscopy. The Si-NC size obtained from the TEM micrographs is within the range of 3–5 nm. The β-SiC NCs are smaller (2–3 nm) than Si NCs. Raman analysis identified an ∼9 cm−1 Raman peak shift in the Si-NC peak to a lower energy with respect to that for bulk Si. FTIR Si–C bond absorption spectra exhibited narrowing of the full width at half maximum and a peak shift toward a higher wave number with increasing Ta. This behavior can be explained by an increase in order as well as an increase in the number of Si–C bonds.
Control of a separating boundary layer with Lorentz force actuators
Authors: Dattarajan Srinivasan , Johari Hamid
Published: April 2008

The effect of time-periodic spanwise Lorentz forces on flow separation in a weakly conductive fluid is examined. An array of alternately arranged electrodes and permanent magnets constituted an electromagnetohydrodynamic actuator, which was flush mounted on a hydrofoil model with a flap that was inclined at 20° to the freestream flow in a water tunnel. Above a certain amplitude of electromagnetohydrodynamic forcing, complete reattachment of flow over the flap was seen from measured velocity fields by using particle image velocimetry. It is proposed that introduction of streamwise vorticity generated by the spanwise Lorentz forces into the flow field over the actuator surface is responsible for the reattachment of flow.
Ideal metal-decorated three dimensional covalent organic frameworks for reversible hydrogen storage
Authors: Choi Yoon Jeong , Lee Jung Woo , Choi Jung Hoon , Kang Jeung Ku
Published: April 2008

The most stable H2 adsorption on pure covalent organic frameworks (COFs) occurs near O atoms, but its binding energy (∼0.05eV) is not sufficient to satisfy the minimum value (0.24eV) required for practical applications. Meanwhile, Li and Mg ion-decorated COFs have hydrogen adsorption energies of 0.28 and 0.30eV, respectively, and their saturated hydrogen storage capacities exceed the DOE target (6.5wt%). Also the effect of some counterions on hydrogen storage has been explored. Moreover, doped ions prefer to exist as isolated elements on COFs, which is another advantage to realize hydrogen storage media.
Zeeman splitting and confinement effects in Er3+-doped nano-glass-ceramics in magnetic fields up to 50T
Authors: Saurel D. , Tikhomirov V. K. , Moshchalkov V. V. , Görller-Walrand C. , Driesen K.
Published: April 2008

A zero-phonon component of the 1.5μm emission band of Er3+ in the nano-glass-ceramics 32(SiO2)9(AlO1.5)31.5(CdF2)18.5(PbF2)5.5(ZnF2):3.5(ErF3)mol%, shifts to higher energy and splits into Zeeman doublet in external magnetic field. These effects make it possible to flatten the amplification band of the Er3+-doped amplifier. The blue photoluminescence shift can be ascribed to quantum confinement effect on the 1.5μm emission band of Er3+ in nano-glass-ceramics, where most of the Er3+ dopants are located in the PbF2 nanocrystals of about 8nm in diameter.
Self-assembly and magnetic properties of shape-controlled monodisperse CoFe2O4 nanocrystals
Authors: Bao Ningzhong , Shen Liming , Padhan Prahallad , Gupta Arunava
Published: April 2008

Ordered arrays of monodisperse cobalt ferrite (CoFe2O4) nanocrystals with highly controllable spherical or cubic shapes have been synthesized via solution-based thermolysis of an intimately mixed Co2+Fe23+-oleate precursor. The evolution from spherical to cubic morphology is achieved by simply changing the precursor concentration, thereby controlling the nanocrystal growth rate. Magnetic studies indicate that the saturation magnetization is independent of the shape and is solely determined by the size of the nanocrystal. However, the coercivity does exhibit a small shape dependence, primarily resulting from the influence of surface anisotropy.
High quality nitride based microdisks obtained via selective wet etching of AlInN sacrificial layers
Authors: Simeonov D. , Feltin E. , Altoukhov A. , Castiglia A. , Carlin J.-F. , Butté R. , Grandjean N.
Published: April 2008

The authors report a technique for selective wet chemical etching of an AlInN sacrificial layer lattice-matched to GaN for the fabrication of air-gap photonic structures. It is used to demonstrate high quality factor (Q) microdisk cavities. Whispering gallery modes are observed in the photoluminescence spectra of InGaN∕GaN quantum wells (QWs) embedded in the GaN microdisks. Q factors of up to 3500 are obtained. The measured Qs are found to be limited by the QW absorption. Room temperature laser action is achieved for a wide spectral range (409–475nm) with a threshold down to 166kW∕cm2.
Spatial mapping of the inverse decay length using scanning tunneling microscopy
Authors: de Vries R. J. , Saedi A. , Kockmann D. , van Houselt A. , Poelsema B. , Zandvliet H. J. W.
Published: April 2008

We present a scanning tunneling spectroscopy technique that allows one to make spatial maps of the characteristic length, i.e., the inverse decay length (κ), in electron tunneling. The method requires that the tunneling current i and its first and second derivative with distance di∕dz and d2i∕dz2, respectively, are simultaneously recorded. The derivatives di∕dz and d2i∕dz2 are recorded using a lock-in technique. A spatial map of κ provides valuable information on the electronic structure of surfaces, especially in case of semiconductors, nanostructured surfaces and molecules at surfaces. We have coined this spectroscopic technique κ microscopy.
Production of high-density capacitive plasma by the effects of multihollow cathode discharge and high-secondary-electron emission
Authors: Ohtsu Y. , Fujita H.
Published: April 2008

High-density capacitively coupled plasma with electron density of 1011cm−3 was produced with the effects of the multihollow cathode discharge and the high-secondary-electron emission from radio frequency (rf)-biased electrode using Ar gas. It was found that the optimum pressure was around 3–15Pa. In the case of only multihollow cathode discharge, the plasma density increased from 1.2×1010to8×1010cm−3 with the increasing distance z from the cathode electrode for 5mm<z<15mm. Moreover, plasma density increased with increasing voltage of rf-biased electrode. The rate of deposited amorphous hydrocarbon thin films of about 200nm∕min was attained with the high-density rf plasma enhanced chemical vapor deposition using CH4 gas.
Two-photon induced fabrication of gold microstructures in polystyrene sulfonate thin films using a ruthenium(II) dye as photoinitiator
Authors: Vurth Laeticia , Baldeck Patrice , Stéphan Olivier , Vitrant Guy
Published: April 2008

Gold microstructures are produced with a femtosecond laser in thin films of a polystyrene sulfonate matrix containing gold ions. Two-photon induced metal reduction is obtained by addition of 0.1wt% of ruthenium(II)tris(bipyridine) in the formulation. Laser power is reduced to 5mW, thereby limiting thermal effects. Lines of typically 150nm heights and 1μm widths are fabricated as well as freestanding bidimensional structures. An additional electroless plating step produces gold structures with conductivities only ten times smaller than the bulk metal.
Electronic structure of a potential optical crystal YBa3B9O18: Experiment and theory
Authors: Zhang Z. H. , Yang Jianjun , He Ming , Wang X. F. , Li Quan
Published: April 2008

Using valence electron energy loss spectroscopy and ab initio band structure calculations, we have studied the basic electronic structure of a potential optical crystal YBa3B9O18. Its optical band gap Eg is experimentally estimated as 6.3eV and the origins of the individual interband transitions have been identified. In addition, the theoretical calculation reveals the strong anisotropic characteristic of the material band structure, accounting for its large birefringence.
Ellipses on the Surface of a Picture
Authors: Hammad Sherief , Kennedy John M , Juricevic Igor , Rajani Shazma
Published: April 2008

Shapes on the surface of a perspective picture may be misperceived. Subjects picked a match for an ellipse depicting the circular top of a cylinder. The top was depicted as tilted forward from 5° to 85°, generating a series of ellipses on the picture surface. The matches were biased towards a circle over a wide range of midrange tilts, which suggests that, influenced by features of perspective, they were seen as in-between the shape on the surface and the shape they depicted.
Job Satisfaction in Network News: The Relationship between Producers and the News Reporters and Newsmagazine Correspondents They Supervise
Authors: Price Cindy J.
Published: April 2008

The relationship between television news producers and anchors/reporters has been studied at the local level, but it hasn't been examined at the national level. This study's authors surveyed correspondents of the traditional news offerings at ABC, CBS, CNN, PBS, and NBC and of newsmagazine offerings at ABC, CBS, and NBC. We found that most respondents reported at least a good relationship with their producers and thought the producers improved their story quality and edited the stories adequately. However, there were differences between the two groups. Newsmagazine correspondents had a better relationship with their producers and felt producers improved the quality of the product more than traditional news correspondents believed the same of their producers. Correspondents who reported a poor relationship with a producer had lower job satisfaction than those with a good relationship. In fact, more than one-fourth of the correspondents' job satisfaction was linked to the producer relationship.
An Updated Look at Trends in Content and Web Page Design in News Web Sites
Authors: Seelig Michelle I.
Published: April 2008

This research examined the similarities and differences in format and content on traditional media Web sites. A content analysis of 282 Web newspapers, 112 radio station Web sites, and 128 television station Web sites found that although traditional media have increased their presence on the Web from the mid 1990s, they're still working to move beyond imitation of format and repurposing content from their traditional media counterpart. Overall, findings show media Web sites include some type of news, sports, and weather coverage; have expanded the volume of news-related content; and have improved the design and presentation of their content. Data also indicate media Web sites still limit audience interaction to mostly e-mail and have slightly increased adoption of streaming and downloadable audio and video content.
An Extracellular Cu2+ Binding Site in the Voltage Sensor of BK and Shaker Potassium Channels
Authors: Ma Zhongming , Wong Kin Yu , Horrigan Frank T.
Published: April 2008

Copper is an essential trace element that may serve as a signaling molecule in the nervous system. Here we show that extracellular Cu2+ is a potent inhibitor of BK and Shaker K+ channels. At low micromolar concentrations, Cu2+ rapidly and reversibly reduces macrosocopic K+ conductance (GK) evoked from mSlo1 BK channels by membrane depolarization. GK is reduced in a dose-dependent manner with an IC50 and Hill coefficient of ∼2 μM and 1.0, respectively. Saturating 100 μM Cu2+ shifts the GK-V relation by +74 mV and reduces GKmax by 27% without affecting single channel conductance. However, 100 μM Cu2+ fails to inhibit GK when applied during membrane depolarization, suggesting that Cu2+ interacts poorly with the activated channel. Of other transition metal ions tested, only Zn2+ and Cd2+ had significant effects at 100 μM with IC50s > 0.5 mM, suggesting the binding site is Cu2+ selective. Mutation of external Cys or His residues did not alter Cu2+ sensitivity. However, four putative Cu2+-coordinating residues were identified (D133, Q151, D153, and R207) in transmembrane segments S1, S2, and S4 of the mSlo1 voltage sensor, based on the ability of substitutions at these positions to alter Cu2+ and/or Cd2+ sensitivity. Consistent with the presence of acidic residues in the binding site, Cu2+ sensitivity was reduced at low extracellular pH. The three charged positions in S1, S2, and S4 are highly conserved among voltage-gated channels and could play a general role in metal sensitivity. We demonstrate that Shaker, like mSlo1, is much more sensitive to Cu2+ than Zn2+ and that sensitivity to these metals is altered by mutating the conserved positions in S1 or S4 or reducing pH. Our results suggest that the voltage sensor forms a state- and pH-dependent, metal-selective binding pocket that may be occupied by Cu2+ at physiologically relevant concentrations to inhibit activation of BK and other channels.
Structure and Function of Skeletal Muscle in Zebrafish Early Larvae
Authors: Dou Ying , Andersson-Lendahl Monika , Arner Anders
Published: April 2008

Zebrafish muscles were examined at an early developmental stage (larvae 5–7 d). Using aluminum clips, preparations (∼1.5 mm length, 150 μm diameter) were mounted for force registration and small angle x-ray diffraction. Sarcomeres were oriented mainly in parallel with the preparation long axis. Electrical stimulation elicited fast and reproducible single twitch contractions. Length–force relations showed an optimal sarcomere length of 2.15 μm. x-ray diffraction revealed clear equatorial 1.1/1.0 reflections, showing that myofilaments are predominantly arranged along the preparation long axis. In contrast, reflections from older (2 mo) zebrafish showed two main filament orientations each at an ∼25° angle relative to the preparation long axis. Electrical stimulation of larvae muscles increased the 1.1/1.0 intensity ratio, reflecting mass transfer to thin filaments during contraction. The apparent lattice volume was 3.42 × 10−3 μm3, which is smaller than that of mammalian striated muscle and more similar to that of frog muscles. The relation between force and stimulation frequency showed fusion of responses at a comparatively high frequency (∼186 Hz), reflecting a fast muscle phenotype. Inhibition of fast myosin with N-benzyl-p-toluene sulphonamide (BTS) showed that the later phase of the tetanus was less affected than the initial peak. This suggests that, although the main contractile phenotype is fast, slow twitch fibers can contribute to sustained contraction. A fatigue stimulation protocol with repeated 220 ms/186 Hz tetani showed that tetanic force decreased to 50% at a train rate of 0.1 s−1. In conclusion, zebrafish larvae muscles can be examined in vitro using mechanical and x-ray methods. The muscles and myofilaments are mainly orientated in parallel with the larvae long axis and exhibit a significant fast contractile component. Sustained contractions can also involve a small contribution from slower muscle types.
Top‐down and bottom‐up control in an eelgrass–epiphyte system
Authors: Jaschinski Sybill , Sommer Ulrich
Published: April 2008

Nutrient supply and the presence of grazers can control primary producers in aquatic ecosystems, but the relative importance of bottom‐up and top‐down effects remains inconclusive. We conducted a mesocosm experiment and a field study to investigate the independent and interactive effects of nutrient enrichment and grazing on primary producers in an eelgrass bed Zostera marina. Nutrient treatments consisted of ambient or enriched (2× and 4× ambient) concentrations of inorganic nitrogen and phosphate. Grazer treatments consisted of presence or absence of field densities of the common isopod Idotea baltica. We found strong and interacting effects of nutrients and grazing on epiphytes. Epiphyte biomass and productivity were enhanced by nutrient enrichment and decreased in the presence of grazers. The absolute amount of epiphyte biomass consumed by grazers increased under high nutrient supply, and thus, nutrient effects were stronger in the absence of grazing. The effects of grazers and fertilisation on epiphyte composition were antagonistic: chain‐forming diatoms and filamentous algae profited from nutrient enrichment, but their proportions were reduced by grazing. Eelgrass growth was positively affected by grazing and by nutrient enrichment at moderate nutrient concentrations. High nutrient supply reduced eelgrass productivity compared to moderate nutrient conditions. The monthly measured field data showed a nitrogen limitation for epiphytes and eelgrass in summer, which may explain the positive effect of nutrient enrichment on both primary producers. Generally, the field data suggested the possibility of seasonally varying importance of bottom‐up and top‐down control on primary producers in this eelgrass system.
Density‐dependent sexual selection in the monogamous fish Archocentrus nigrofasciatus
Authors: Lehtonen Topi K. , Lindström Kai
Published: April 2008

To date, density‐dependent effects on sexual selection have been studied only scantly. In this study we experimentally assessed the effect of breeding site density on the size distribution of mating convict cichlids Archocentrus nigrofasciatus in the field. We found that females were larger under low than high nest density. These results are better explained by density‐dependent mate choice and mating competition than competing hypotheses of resource competition and predation pressure. We did not find differences in brood survival between the two nest density regimes. Nevertheless, convict cichlids avoided breeding in each other's close proximity, indicating that a high density of breeding pairs entails some other costs, such as energy loss through increased territorial aggression. Our results stress the importance of considering evolutionary effects of mate choice and mate competition in the context of availability of resources that determine the density of individuals that succeed to mate.
Application of the intravenous glucose tolerance test and the minimal model to patients with insulinoma: insulin sensitivity (Si) and glucose effectiveness (Sg) before and after surgical excision
Authors: Vethakkan S. R. , Walters J. M. , Gooley J. L. , Boston R. C. , Ward G. M.
Published: April 2008

Background  The unmodified frequently sampled intravenous glucose tolerance test (FSIGT) has not previously been used to assess insulin/glucose kinetics in patients with insulinoma.

Objective  To measure insulin sensitivity (Si) and glucose effectiveness (Sg) by means of the FSIGT in patients with insulinoma, before and after surgical removal of the tumour.

Subjects and methods  FSIGTs were performed in five patients, before and approximately 3 months post‐surgery, and in 11 controls. Si and Sg were estimated using Minimal Model computer analysis of dynamic glucose and insulin data.

Results  Si was lower in insulinoma patients before, compared with after surgery (3·37 ± 0·62 vs. 6·24 ± 1·09 SE [×10−4] min−1µU−1 ml, P < 0·05). Sg was similar in patients pre‐ and post‐surgery (3·0 ± 0·67 vs. 2·4 ± 0·6 [×10−2] min−1, NS).

Conclusions  Insulin sensitivity improves after excision of an insulinoma. Glucose effectiveness is not influenced by chronic hyperinsulinaemia and hypoglycaemia.
Successful surgical haemostasis in patients with von Willebrand disease with Koate®DVI
Authors: VISWABANDYA A. , MATHEWS V. , GEORGE B. , NAIR S. C. , BAIDYA S. , MAMMEN J. J. , CHANDY M. , SRIVASTAVA A.
Published: April 2008

Summary.  This report describes our experience with Koate®DVI, a factor VIII (FVIII) concentrate containing von Willebrand factor (VWF) for surgery in patients with von Willebrand’s disease (VWD). Twenty‐one patients underwent 26 procedures, 10 of which were major and 16 were minor. The median age was 27 years (3–55) and the mean weight was 52 kg (16–88). Among the ten patients (type 2–5; type 3–5) who underwent major procedures, the pre‐operative dose was 35 IU kg−1 of FVIII followed by 10–20 IU kg−1 once daily depending on FVIII:C levels. The mean total dose of FVIII used per procedures was 106 IU kg−1 (30–190) over a mean duration of 7 days (3–11). In this group, pre‐infusion FVIII:C, VWF:Ag and VWF: ristocetin cofactor (RCoF) level that were 19.5% (1–64), 20 U dL−1 (0–96) and 12% (0–66) increased to 72% (54–198), 131 U dL−1 (68–206) and 68% (27–108) postinfusion, respectively. Sixteen minor procedures were performed in 11 patients (type 1–3, type 2–6, type 3–2). The preparative dose of FVIII was 10–20 IU kg−1. The average duration of factor support was 2 days (1–3) for a mean total dose of 23 IU kg−1 (9–60). The pre‐infusion levels of FVIII:C, VWF:Ag and VWF:ristocetin cofactor (RCo) which were 31% (22–64), 25.5 U dL−1 (0–63) and 21% (0–76), respectively, increased to 76% (27–111), 73 U dL−1 (30–137) and 45% (2–106) postinfusion. Whereas surgical haemostasis was achieved in all patients, minor postoperative bleeding occurred after one procedure in each group. Both were controlled with additional doses of factor replacement. We conclude that Koate®DVI in modest doses provide adequate haemostasis for surgery in patients with VWD.
Regulatory T‐cell expansion and function do not account for the impaired alloreactivity of ex vivo‐expanded T cells
Authors: Montcuquet Nicolas , Mercier‐Letondal Patricia , Perruche Sylvain , Duperrier Anne , Couturier Mélanie , Bouchekioua Abdelghani , Bonyhadi Mark , Ferrand Christophe , Tiberghien Pierre , Robinet Eric
Published: April 2008

CD3‐ and CD28‐activated T cells expanded for 12 days ex vivo to produce suicide gene‐modified T cells are hyporesponsive to alloantigens. To investigate whether this impaired alloreactivity is a result of preferential expansion of regulatory T (Treg) cells, we compared peripheral blood mononuclear cells (PBMC) activated with CD3 and CD28 antibodies co‐immobilized on beads and expanded for 12 days with interleukin (IL)‐2 (CoCD3/CD28 cells) to the respective unactivated PBMC in terms of proliferation, cytokine production, and expression of Treg markers [cytotoxic T‐lymphocyte antigen 4 (CTLA4), glucocorticoid‐induced tumour necrosis factor receptor (GITR) and forkhead box P3 (FoxP3)] after allostimulation. Alloreactive cells were identified by carboxyfluoresceine succinimidyl ester staining dilution. Alloreactive cells in CoCD3/CD28 cells had a lower proliferative response and a lower potential for IL‐2 and interferon‐γ secretion than did those in PBMC, demonstrating a functional impairment of alloreactive cells during ex vivo expansion. Expression of Treg markers transiently increased during ex vivo expansion and was unaffected by depletion of CD25+ cells (containing Treg cells) before ex vivo PBMC expansion. Such prior CD25+ depletion did not restore the alloreactivity of CoCD3/CD28 cells. After allostimulation, expression of Treg markers was restricted to proliferative (alloreactive) cells among PBMC or CoCD3/CD28 cells. Lastly, CD4+ CD25+ cells purified from CoCD3/CD28 cells lacked suppressive activity when used as a third party, in contrast to CD4+ CD25+ cells purified from PBMC. In conclusion, the impaired alloreactivity of T cells expanded ex vivo is not a result of preferential Treg cell expansion and/or enhanced suppressive Treg activity.
Identification of two subpopulations of purified human blood B cells, CD27− CD23+ and CD27high CD80+, that strongly express cell surface Toll‐like receptor 9 and secrete high levels of interleukin‐6
Authors: Cognasse Fabrice , Hamzeh‐Cognasse Hind , Lafarge Sandrine , Chavarin Patricia , Pozzetto Bruno , Richard Yolande , Garraud Olivier
Published: April 2008

B‐cell expression of certain Toll‐like receptors (TLRs) is important in linking innate and adaptive immune responses in normal and pathological conditions. The expression of TLR9 plays a role in the recognition of conserved pathogen motifs in a manner that is dependent on B‐cell localization, deduced from B‐cell phenotype. The nature of TLR9 function is unclear. A first step in unravelling the function of this pattern recognition receptor is to discover the precise nature of the cell types that express TLR9. This study used three‐colour flow cytometry to characterize the B lymphocytes from human peripheral blood mononuclear cells (PBMCs) that express TLR9 on the surface. We sorted TLR9‐positive B and non‐B cells from the PBMC population and detected TLR9 expression on naïve and memory B cells. Moreover, we identified two discrete subpopulations of B cells: CD19+ CD27− CD23+ cells and CD19+ CD27high CD80+ cells. These subpopulations expressed high levels of membrane TLR9 and exhibited a strong in vitro response to binding a relevant CpG motif by secreting high levels of interleukin‐6 (compared to controls). Our finding that this pattern recognition receptor is expressed on a variety of cell subsets adds to the current understanding of the functional complexity of B‐cell membrane TLR9.
Lymphoid enhancer factor interacts with GATA‐3 and controls its function in T helper type 2 cells
Authors: Hossain Mohammad B. , Hosokawa Hiroyuki , Hasegawa Akihiro , Watarai Hiroshi , Taniguchi Masaru , Yamashita Masakatsu , Nakayama Toshinori
Published: April 2008

GATA‐3 is the master transcription factor for T helper 2 (Th2) cell differentiation and is critical for the expression of Th2 cytokines. Little is known, however, about the nature of the functional molecular complexes of GATA‐3. We identified a high‐mobility group (HMG)‐box type transcription factor, lymphoid enhancer factor 1 (LEF‐1), in the GATA‐3 complex present in Th2 cells using a Flag‐calmodulin‐binding peptide (CBP)‐tag based proteomics method. The interaction between GATA‐3 and LEF‐1 was confirmed by co‐immunoprecipitation experiments using LEF‐1‐introduced T‐cell lineage TG40 cells. The HMG‐box domain of LEF‐1 and two zinc finger domains of GATA‐3 were found to be important for the physical association. The introduction of LEF‐1 into developing Th2 cells resulted in the suppression of Th2 cytokine production. The suppression was significantly lower in the cells into which a HMG‐box‐deleted LEF‐1 mutant was introduced. Moreover, LEF‐1 inhibited the binding activity of GATA‐3 to the interleukin (IL)‐5 promoter. These results suggest that LEF‐1 is involved in the GATA‐3 complex, while also regulating the GATA‐3 function, such as the induction of Th2 cytokine expression via the inhibition of the DNA‐binding activity of GATA‐3.
Oral health research with children
Authors: MARSHMAN ZOE , HALL MELANIE J.
Published: April 2008

Background.  There has been a shift towards research with children and the adoption of the concept of child‐centred research. However, the majority of oral health research is conducted on children, rather than with them.

Objective.  This study aimed to provide an overview of contemporary approaches to research with children.

Considerations.  The methodological considerations of such research include: the power relationship between the adult researcher and the child participant, with important factors of language use, the setting for the research, appropriate analysis, and quality of the data; ethical factors such as the purpose and risks of the research, confidentiality, recruitment, funding, information to children and parents, consent, and dissemination; and appropriate methods. Methods suitable for oral health research with children include quantitative techniques such as questionnaires and qualitative approaches including interviews individually or in groups and participatory techniques such as time‐lines/life grids, drawings, and vignettes.

Conclusion.  There is considerable scope to access children's perspectives of their oral health and care through actively involving them in research. To conduct such research, however, requires training or collaboration with colleagues from other disciplines.
Adults with intellectual disabilities: prevalence, incidence and remission of self‐injurious behaviour, and related factors
Authors: Cooper S.‐A. , Smiley E. , Allan L. M. , Jackson A. , Finlayson J. , Mantry D. , Morrison J.
Published: April 2008

Background  Self‐injurious behaviour (SIB) is a serious condition, with implications for the person, their family and financial costs to the state providing care. The previously reported prevalence of SIB has ranged from 1.7% to 41%, or 1.7%–23.7% in community studies. There has been little study of remission rate, and incidence has not previously been reported. SIB has been reported to be individually associated with lower ability, autism and communication impairments, but given the inter‐relationships between these three factors, it is not known whether they are independently associated with SIB. This study investigates the point prevalence, incidence and remission rates of SIB among the adult population with intellectual disabilities (ID), and explores which factors are independently associated with SIB.

Method  A prospective cohort study design was used in a general community setting. The participants were all adults (16 years and over) with ID in a defined geographical area. Individual assessments were conducted with all participants.

Results  The point prevalence of SIB (as defined by DC‐LD) was 4.9%, the two‐year incidence was 0.6%, and two‐year remission rate was 38.2%. Independently related to SIB were: lower ability level, not living with a family carer, having attention deficit hyperactivity disorder, visual impairment, and not having Down syndrome. Other factors, including communication impairment, autism, and level of deprivation of the area resided within, were not related.

Conclusions  SIB is not as enduring and persistent as previously thought; a significant proportion gains remission in this time period. This should provide hope for families, paid carers and professionals, and reduce therapeutic nihilism. Our study is a first tentative step towards identifying risk‐markers for SIB, and developing aetiological hypotheses for subsequent testing. The extent to which SIB may be a relapsing‐remitting (episodic) condition requires further investigation, so does further hypothesis‐based investigation of factors that might be predictive of incidence of, and remission from, SIB.
The use of melatonin to treat sleep disorder in adults with intellectual disabilities in community settings – the evaluation of three cases using actigraphy
Authors: Dodd A. , Hare D. J. , Arshad P.
Published: April 2008

Background  Sleep disorders are known to be very prevalent in adults with intellectual disabilities (ID) but to date there has been limited objective assessment of either sleep disorders or of interventions such as the use of melatonin.

Methodology  A protocol‐driven assessment and intervention procedure was followed with three people with moderate to severe ID identified as having a possible sleep disorder. Actigraphic assessment was used to determine the nature of the sleep disorder, after which sleep hygiene advice and then individual treatment with melatonin were provided, following which further actigraphic assessment was carried out. Behavioural disturbance was formally assessed before and after the intervention phase.

Results  Following treatment with melatonin, changes in circadian rhythm were noted, together with improvements in challenging behaviour, but no significant effects were noted with regard to either quantity or quality of sleep.

Conclusions  A standardised procedure for assessment and treatment of sleep disorders in people with ID was established. Although no apparent effects on sleep quantity or quality were noted, this may reflect factors inherent in the sample, rather than the relative efficacy of melatonin treatment per se.
Oestrogen Receptor α Localisation in the Prefrontal Cortex of Three Mammalian Species
Authors: Montague D. , Weickert C. S. , Tomaskovic‐Crook E. , Rothmond D. A. , Kleinman J. E. , Rubinow D. R.
Published: April 2008

Oestrogen modulates cognitive function and affective behaviours subserved by the prefrontal cortex (PFC). Identifying and localising oestrogen receptor (ER)α, in human PFC will contribute to our understanding of the molecular mechanism of oestrogen action in this region. Inferences about the site of action of oestrogen in human brain are derived largely from studies performed in nonhuman mammalian species; however, the congruence of findings across species has not been demonstrated. Furthermore, the laminar, cellular, and subcellular localisation of ERα in the cortex is debated. Therefore, we compared the distribution of ERα in human dorsolateral prefrontal cortex (DLPFC) with that of monkey DLPFC and rat medial PFC. Immunohistochemistry performed on frontal cortex from the three species demonstrated ERα positive cells throughout all layers of the PFC, in pyramidal and nonpyramidal neurones, with both nuclear and cytoplasmic immunoreactivity. Western blot analyses and preabsorption studies confirmed that the antibody used recognised ERα and not ERβ. A strong ERα immunoreactive band corresponding to the full‐length ERα protein (65–67 kDa) in the frontal cortex of all three species matched the size of the predominant immunoreactive band detected in breast cancer cell lines known to express ERα. Additionally, other ERα immunoreactive proteins of varying molecular weight in breast cancer cells, rat ovary and mammalian brain were detected, suggesting that ERα may exist in more than one form in the mammalian frontal cortex. The present study provides evidence that ERα protein exists in neurones in mammalian PFC and that ERα is anatomically well‐positioned to directly mediate oestrogen action in these neurones.
Role of AMP‐Activated Protein Kinase in the Control of Appetite
Authors: Kola B.
Published: April 2008

AMP‐activated protein kinase is a key enzyme in the regulation of energy metabolism. Its activation has pleiotropic effects in multiple tissues, including increased fatty acid oxidation, glucose uptake and glycolysis, as well as the inhibition of fatty acid and glycogen synthesis and gluconeogenesis, and stimulation of mitochondrial biogenesis. Recently, the AMP‐activated protein kinase (AMPK) has also emerged as a regulator of appetite, contributing to the control of energy metabolism at both cell and the whole body levels. Pharmacological and genetic activation or inhibition of hypothalamic AMPK lead to increased or reduced food intake, respectively. AMPK appears to play a role in hypothalamic glucose and nutrient sensing and numerous studies have suggested a role for AMPK in mediating the orexigenic or anorexigenic effects of various endogenous and exogenous substances.