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Notes: Polysilicon films have been deposited at a low temperature by single and dual ion beam sputtering. The structural and electrical properties of as-deposited and annealed films have been characterized by x-ray diffraction, secondary ion mass spectroscopy, atomic force microscopy, and Hall mobility measurements. The films are microcrystalline with average grain size ranging from 200 to 400 Å. The films exposed to a low-energy secondary ion beam during sputtering from a silicon target have exhibited smoother surface topography and different electrical behavior than the films deposited without any secondary ion bombardment. Some preliminary studies on ion beam sputtered SiGe films using a compound target are also presented. © 1998 American Institute of Physics.

Notes: Electrical and structural properties of platinum monosilicide (PtSi) in deep submicron lines are reported. The sheet resistance of the silicide films was found to be rather independent of the linewidth down to dimensions as small as 0.15 μm. Plan-view and cross-sectional transmission electron microscopy was performed to study the structural properties of these films, including their gain structures and lateral growth. The insensitive nature of the electrical properties of the silicide films to the linewidths is correlated with their structural properties. © 1996 American Institute of Physics.

Notes: We measure the extent of polymerization, Φ, as a function of temperature, T, for living poly(α-methylstyrene) in the solvent tetrahydrofuran, using sodium naphthalide and cesium naphthalide as the initiating species. We compare our measurements of Φ(T) to the theoretical predictions of a mean field model and of a nonmean field model [J. C. Wheeler and P. M. Pfeuty, Phys. Rev. Lett. 71, 1653 (1993)]. We find that both models describe our observations semiquantitatively. The nonmean field model is statistically (but not dramatically) a better description for two of the samples. For the third sample, the mean field description is statistically better, probably because the concentration of monomer/polymer in solvent is the smallest for this sample. © 1995 American Institute of Physics.

Notes: We have measured the molecular weight distribution (MWD) in a case of equilibrium polymerization. We have studied the time development of the MWD of "living" bifunctional poly(α-methylstyrene) in tetrahydrofuran after a quench to 21 K below the polymerization temperature, Tp. We see an intermediate Gaussian distribution evolving toward a final exponential distribution, as expected from theoretical considerations. We see a longer equilibration time for the number average molecular weight (Mn) as well as for the weight average molecular weight (Mw) than for the monomer concentration ([M)], whereas theories predict that Mn and [M] will relax together and that Mw will take much longer. We attribute the delayed equilibration and a second peak at about Mn/4 to the effects of ionic aggregation of the living polymers. We have also studied the equilibrium MWD of this system as a function of the temperature below Tp, and thus as a function of the number average degree of polymerization (L). These measurements and the time study discussed above are the first experimental evidence that the equilibrium MWD for an organic polymer in a state of equilibrium polymerization is an exponential/Flory–Schulz distribution, and is consistent with scaling predictions. Near Tp and at low L, we observe a deviation from the exponential distribution, which may be evidence of the effect of a chain-length dependence of the equilibrium constant for polymerization, or of the effects of polydispersity on correlations due to excluded volume. In addition, the measured L is about two times less than that expected from the initiator concentration; this could result from ionic aggregation or from chain transfer reactions. © 1999 American Institute of Physics.

Notes: Atmospheric electrical conductivities have been monitored at a coastal site having a large deposit of radioactive minerals. Conductivities were also monitored at two other sites, one coastal and the other inland, both non-radioactive. The ratio of conductivity at the radioactive site to that at the others is about 6, in agreement with the ratio of radioactivity. The diurnal variation pattern at this site in May, a pre-monsoon month, agrees with the known variation of radon concentration in air. However, in June, a monsoon month, it is different, a double oscillation similar to that at the other sites. With the onset of the monsoon, conductivity at the radioactive site shows a large decrease, which is not seen at the other sites. The ratio of positive polar conductivity to negative polar conductivity shows a reduction after the onset of the monsoon rainfall. The diurnal variation pattern shows differences between pre-monsoon and monsoon periods at the radioactive site, while there is no change at the non-radioactive sites. The diurnal variation at all these sites in all seasons shows a sharp decrease starting at about 0400 hrs local time and reaching a minimum at about 0800 hrs. Such a decrease has been attributed to human activity associated with sunrise. The present results, however, suggest that this may be incorrect. Fourier analysis of the data shows that there exists a strong semi-diurnal component that is inversely correlated with the clearly seen semi-diurnal variation in pressure in the tropics.

Notes: We use new and pre-existing seismological data to study the neotectonics and the state of stress in the seismic zones of eastern Papua New Guinea and the western Solomon Sea regions. Earthquake hypocentres for the period 1964–90 were relocated, using the Joint Hypocentre Determination (JHD) technique. We show that the T axes of earthquakes in the 100–250 km depth range beneath eastern Papua New Guinea are aligned parallel to the seismic zone, with no seismicity below ≈250 km. This intermediate-depth seismic zone forms an inverted U-shaped zone, with limbs dipping to the north and south, and is interpreted to be seismicity along the subducted Solomon Sea plate. The northern and southern limbs of the seismic zone are connected by a flattened zone of seismicity which is marked by predominantly strike-slip, and a few normal, fault mechanisms. We suggest that the Solomon Sea plate at depth beneath the Finisterre mountains is no longer influenced by the tectonic forces acting at the surface, but breaking up and sinking under its own gravitational forces.A significant north-dipping seismic zone is imaged above the deeper seismic zone. This feature, characterized by thrust mechanisms, extrapolates to the surface along the Ramu Markham Valley and is attributed to the Ramu Markham Fault (RMF). The RMF has an average dip of about 40° to the north-east but its detailed geometry would appear to be complex. The RMF is interpreted to ramp steeply in the uppermost 10–20 km, flattening out sharply to a dip of ≈15° at a depth of about 20 km. The RMF marks the suture between the Finisterre Terrane and the Australia-New Guinea plate and may extend to a depth of 90 km beneath the western limit of the Finisterre mountains. There is a clear gap in seismicity between the RMF and the deeper Solomon Sea plate seismic zone beneath the Finisterre mountains, which, together with the alignment of the T axes of earthquakes along the seismic zone at depths 〉100 km, indicates that these are indeed two distinct features.The seismicity in the depth range 50–80 km, along the New Britain Arc, follows the trend of the 2000 m bathymetric contour of the New Britain Trench and the Finsch Deep far more closely than it does the trend of the surface plate boundary, indicating that the increase in the distance between the Solomon Sea/South Bismarck plate boundary and the active volcanos along the New Britain Arc, west of (6.8°S, 150.0°E) is only a shallow phenomenon, and does not reflect the geometry of the Solomon Sea plate at depths greater than 50 km.

Notes: Abstract Apexification with calcium hydroxide is a routine procedure. However, some clinical reports suggest that root completion can occur by controlling the infection without use of a catalyst. The present study investigated the use of tetracycline treatment (in root canals) on root growth in immature teeth, rendered non-vital experimentally. Incisors in 3 young baboons were exposed and canals were left open. After 2 months all canals were cleaned and treated with either tetracycline or formocresol. Some canals in each group were filed. Animals were sacrificed after 6 months. Bacterial evaluations were done before placing medications, one week later and six months after that. The number of bacteria were reduced in all treatment groups. Root growth almost near completion was observed in more teeth treated with tetracycline than in the formocresol group.