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Notes: Abstract: The cellular mechanisms underlying opioid action remain to be fully determined, although there is now growing indirect evidence that some opioid receptors may be coupled to phospholipase C. Using SH-SY5Y human neuroblastoma cells (expressing both μ-and δ-opioid receptors), we demonstrated that fentanyl, a μ-preferring opioid, caused a dose-dependent (EC50= 16 nM) monophasic increase in inositol (1,4,5)trisphosphate mass formation that peaked at 15 s and returned to basal within 1–2 min. This response was of similar magnitude (25.4 ± 0.8 pmol/mg of protein for 0.1 μM fentanyl) to that found in the plateau phase (5 min) following stimulation with 1 mM carbachol (18.3 ± 1.4 pmol/mg of protein), and was naloxone-, but not naltrindole-(a δ antagonist), reversible. Further studies using [d-Ala2, MePhe4, Gly(ol)5]enkephalin and [d-Pen2,5]enkephalin confirmed that the response was specific for the μ receptor. Incubation with Ni2+ (2.5 mM) or in Ca2+-free buffer abolished the response, as did pretreatment (100 ng/ml for 24 h) with pertussis toxin (control plus 0.1 μM fentanyl, 26.9 ± 1.5 pmol/mg of protein; pertussis-treated plus 0.1 μM fentanyl, 5.1 ± 1.3 pmol/mg of protein). In summary, we have demonstrated a μ-opioid receptor-mediated activation of phospholipase C, via a pertussis toxin-sensitive G protein, that is Ca2+-dependent. This stimulatory effect of opioids on phospholipase C, and the potential inositol (1,4,5)trisphosphate-mediated rises in intracellular Ca2+, could play a part in the cellular mechanisms of opioid action.

Notes: Compression by a spherical solid liner of a gold target surrounded by a hydrogen plasma is simulated. Two-dimensional simulations that treat only a subset of the physics included in the one-dimensional code were performed in an attempt to assess multidimensional effects. A one-dimensional numerical code has been developed to study the effects of thermal radiation and conduction. Results of pressure, density, and energy deposited for different initial plasma conditions are presented and discussed. Results from both one- and two-dimensional codes show that the average target density at peak compression is 39–43 g/cm3, using the SHIVA Star facility at 90 kV discharge.

Notes: We report the observation by photoluminescence (PL) spectroscopy of cross-barrier recombination between spatially separated two-dimensional electron and hole gases confined respectively in the quantum well (QW) and collector accumulation layer of a GaAs/AlGaAs double-barrier resonant tunneling structure. At the onset of the n=3(E3) resonance in the current–voltage characteristic, the energy of the cross-barrier transition Ecr is found to coincide with that of the PL peak arising from recombination of electrons from the E3 confined level in the QW with n=1 confined hole states (E3lh recombination). Similarly, at the onset of the E4 resonance, Ecr≈E4lh. We show that this behavior arises as a consequence of the symmetrical potential distribution within the structure at the onsets of the resonances. © 1996 American Institute of Physics.

Notes: We report the measured atomic and magnetization densities of a nickel twist grain boundary averaged over its lateral dimensions as a function of distance from the interface plane. The presence of a reconstructed interface region (the grain boundary) sandwiched between two single-crystal nickel films that were hot-pressed together was confirmed with grazing incidence x-ray diffraction. From reflection data taken using unpolarized neutrons, the atomic density profile of the grain boundary was determined to be (85±5)% of the bulk density when averaged over twice the grain-boundary width of (8±1) nm. Using this information in conjunction with the reflectivity data taken from the nickel sample with polarized neutrons reflection, the magnetic moment of a nickel atom was found to be between 18% and 52% larger in the twist grain boundary than in the bulk. The enhancement of the magnetic moment at the grain boundary is believed to result from the reduced atomic density of the interface region. Owing to this reduction in density, the magnetization density of the nickel interface is only somewhat enhanced, about 10%, compared to that of bulk nickel.

Notes: Theoretical results recently obtained for polarizability of intersecting spherical particles have been compared with those for polarizability of intersecting cardioidal particles resembling the spherical shape. Calculations based on a modified Parseval Rule have been performed for a number of metals in a dielectric matrix in a quasistatic approximation. A large difference in the polarizabilities has been found in spite of a striking similarity in their shapes. An unexpected small value for both the real and the imaginary part of the polarizability of cardioidal shaped metal particles occurs at wavelengths where simple metal spheres absorb strongly. A Maxwell-Garnett model has been used to compare the optical properties of composite materials containing the cardioidal and intersecting spherical particles of interest. It has been found that a composite containing cardioid shaped particles in a dielectric matrix can have an unusual response. Its absorption is very close to zero, while the refractive index is close to that of the fully dense host. © 1996 American Institute of Physics.

Notes: The polarization of a pair of merging spheres and merging cylinders of any complex dielectric constant immersed in an external electric field has been solved. Any degree of intersection, including touching, is covered by the result. The method for cylinders is based on the solution of Laplace's equation with boundary conditions on the conjugate surfaces in a modified bicylindrical frame. The result is presented as an integral over a continuum of eigenstates. For merging spherical particles solving the boundary problem requires a Miller–Fok integral transformation. Imaginary parts of polarizabilities were calculated for aluminum cylinders and spheres to assess the spectral absorption response of small merging particles. The relative spacing has a significant influence on optical response.

Notes: We have employed Langmuir monolayers of polydimethylsiloxane-polystyrene diblock copolymers as a model system for examining layers of tethered chains under good solvent conditions. The range of surface density accessible with this system coincides with the ranges reported in the literature for chains tethered onto solid substrates from dilute solution in good solvents. We have varied both the surface density (σ) and the molecular weight (M) of the submerged polystyrene block independently, covering over a decade in each variable. Both the form of the segmental concentration profile and the variation of the layer height with σ and M are in good agreement with numerical self-consistent-field (SCF) calculations. On the other hand, we do not observe precise agreement with the scaling predictions for strongly stretched chains, in contrast to some previous reports. Through measurements of the surface pressure (Π), we present the first direct comparison between anchoring energies and differential chain energies in tethered layers. We find these to be of equal magnitude at the desorption transition. However, the chain energies reach values roughly an order of magnitude larger than can be accounted for by the osmotic interaction of the polystyrene segments in the good solvent. In addition, the dependence of Π on σ is more consistent with a model of soft spheres with hard cores than that of a semidilute polymer mesh. The hard core areas seem to be loosely related to Rg. We attribute these observations to a steric effect which limits lateral interpenetration of the submerged blocks. The sharp rise in Π with σ is of great practical importance as it limits the maximum surface coverage in this system, and may also do so for other systems. © 1995 American Institute of Physics.

Notes: Objectives To establish the relation between fetal abdominal circumference and birthweight in a large population of fetuses; to identify whether the error in estimating birthweight by abdominal circumference varied with the magnitude of abdominal circumference; and to establish whether adding femur length to abdominal circumference caused a clinically important reduction of error in predicting birthweight.Design A retrospective study.Setting The ultrasound department of a teaching maternity hospital offering a tertiary referral service.Sample From 3512 nondiabetic women with a normally formed singleton fetus, an abdominal circumference measurement of the infant was made within seven days of delivery; of these, 1213 had a femur length measurement performed at the same time.Results There was a linear relation between abdominal circumference and birthweight. There was a strong inverse correlation between the proportional error in predicting birthweight from the abdominal circumference and the magnitude of the abdominal circumference. Both the Campbell and Wilkin equation (abdominal circumference alone) and the Hadlock equation (abdominal circumference and femur length) were associated with systematic errors, especially with larger birthweight infants. The median absolute errors for the two equations were not significantly different overall (6.98% and 6.86% respectively), although the Hadlock equation was significantly more accurate in predicting birthweight in infants weighing greater than 4500 g. However, no threshold value of abdominal circumference or of estimated fetal weight using the Hadlock equation had a positive predictive value in estimating infants of 〉 4500 g of greater than 35%.Conclusions Prediction of birthweight should be by abdominal circumference alone. 〈link href="#t1"〉Table 1 presents robust estimates of the error of predicting birthweight using fetal abdominal circumference.〈tabular xml:id="t1"〉1〈title type="main"〉 The relation between fetal abdominal circumference (AC) and birthweight (BW). 〈table colsep="0" rowsep="0" frame="topbot" pgwide="0" orient="port"〉〈tgroup cols="5" align="left"〉〈colspec colnum="1" colname="col1" align="left"/〉〈colspec colnum="2" colname="col2" align="center"/〉〈colspec colnum="3" colname="col3" align="center"/〉〈colspec colnum="4" colname="col4" align="center"/〉〈colspec colnum="5" colname="col5" align="center"/〉〈thead valign="bottom"〉〈row rowsep="1"〉AC (mm)nMedian BW(g)10th-90th centile BW (g)Range BW(g)〈tbody valign="top"〉200-20913900750-1030740-1040210-219201040830-1370780-1400220–229201060750-1410650-1460230-239281255980-1470900-1860240-2493614351200-17901080-1950250-2593715801290-19251180-2260260-2695618351490-21901340-2400270-2798920001640-23201390-2620280-28913422651920-26601530-2910290-29921925302130-29001820-3100300-30935026852340-30802010-3420310-31938728502470-32902110-3650320-32948430602700-34702350-3770330-33943932602880-37002570-3980340-34942333803040-38602670-4240350-35931436153240-40402890-4460360-36924537503330-11903020-4610370-37911738403480-43603180-4790380-3896641403660-46403470-4820390-3993542903665-46753640-5000