Cu precipitation in a prestrained Fe-1.5 wt pct Cu alloy during isothermal aging

The control of Cu precipitation at low temperatures, e.g., bake hardening of Cu bearing steels, has recently attracted considerable attention due to the potential of achieving good formability and high strength. An Fe-1.5 wt pct Cu alloy, solution treated and 10 pct prestrained, exhibits a two-step age-hardening behavior, i.e., a smaller, but substantial hardening around 200 °C to 300 °C and a major hardening around 500 °C, while only the latter hardening occurs in undeformed specimens. The precipitation behavior of nanoscale Cu particles or bcc Cu clusters that plays a major role in age hardening was simulated by Cahn-Hilliard nonclassical nucleation theory and the Langer-Schwartz model. Simulation results are compared with the distribution of Cu particles observed under three-dimensional atom probe field ion microscope (3-D APFIM) and transmission electron microscope (TEM), and age hardening behavior as well. The increase in hardness in prestrained specimens at low temperatures (≤400 °C) can be ascribed to Cu particles nucleated preferentially at dislocations or to Cu particles that were formed in the matrix as early as at dislocations presumably due to excess vacancies introduced by prestraining.     

Study of micromanipulation using stereoscopic microscope

In this paper, we describe a visual feedback system using a stereoscopic microscope that controls a micromanipulator so that a needle may pierce a target with as much length as desired. First, in order to achieve the manipulation at a realistic rate, we proposed a strategy for moving the needle head. Next, we developed an algorithm for prediction of the tip position of the needle head within the target. Before the needle pierces the target, the shape of the needle head is preserved as a reference pattern. After the needle pierces the target, the shape of the needle head within the target is predicted using the reference pattern, and the tip position of the needle head can be detected. Experimental results indicate that the proposed system may be useful in micromanipulation such as microinjection to seeds     

Fluorescence energy transfer of complexes of skeletal muscle troponin C and melittin derivatives

We studied Ca2+-dependent structural change of rabbit skeletal troponin C (TnC)-melittin (ME) complex as a model of TnC-troponin I complex. In previous study, we found that the distance between Met-25 and Cys-98 of TnC in TnC-ME complex increased upon binding of Ca2+ to TnC [H. Sano and T. Iio (1995) J. Biochem. 118, 996-1000]. In this study, we used a fluorescence energy transfer method. As a fluorescent donor, we used the tryptophan residue in four melittin derivatives, in which residue 2, 5, 8, or 13 was replaced with tryptophan. As acceptor, we used dansylaziridine (DANZ) bound to Met-25 of TnC, or N-iodoacetyl-N'-(5-sulfo-1-naphthyl)ethylenediamine (1,5-I-AEDANS) bound to Cys-98 of TnC. For all TnCDANZ-ME complexes, the donor-acceptor distance (11.9-17.7 A) did not remarkably depend on Mg2+ or Ca2+ binding of TnC or on the position of tryptophan in ME derivatives. The same results were obtained for TnCAEDANS-ME complexes in the absence of Ca2+ (distance 15.2-21.7 A). But in the presence of Ca2+, tryptophan residues in the central region of ME were near to Cys-98 of TnC (distance much less than 10.4 A). Based on these results, we conclude that ME is enfolded by the N- and C-lobes of TnC, and the ME rod is almost perpendicular to a line connecting Met-25 and Cys-98 of TnC. The position of the ME rod shifts upon binding of Ca2+ to TnC.     

On discrete random dopant modeling in drift-diffusion simulations: physical meaning of ‘atomistic' dopants

We investigate the physics behind the ‘atomistic' dopant model widely used in drift-diffusion (DD) simulators for the study of statistical threshold voltage variations in ultra-small MOSFETs. It is found that the conventional dopant model, when extended to the extreme atomistic regime, becomes physically inconsistent with the concepts of electric potential presumed in DD device simulations. The split of the Coulomb potential between the long-range and short-range parts associated with discretized dopants is critical for the device simulations under the atomistic regime. A new dopant model to overcome such problems for 3-dimensional DD simulations is proposed by employing this idea.     

Simple and Efficient Nonparametric Method for Estimating the Number of Signals Without Eigendecomposition

Inspired by the computational simplicity and numerical stability of QR decomposition, a nonparametric method for estimating the number of signals without eigendecomposition (MENSE) is proposed for the coherent narrowband signals impinging on a uniform linear array (ULA). By exploiting the array geometry and its shift invariance property to decorrelate the coherency of signals through subarray averaging, the number of signals is revealed in the rank of the QR upper-trapezoidal factor of the autoproduct of a combined Hankel matrix formed from the cross correlations between some sensor data. Since the infection of additive noise is defused, signal detection capability is improved. A new detection criterion is then formulated in terms of the row elements of the QR upper-triangular factor when finite array data are available, and the number of signals is determined as a value of the running index for which this ratio criterion is maximized, where the QR decomposition with column pivoting is also used to improve detection performance. The statistical analysis clarifies that the MENSE detection criterion is asymptotically consistent. Furthermore, the proposed MENSE algorithm is robust against the array uncertainties including sensor gain and phase errors and mutual coupling and against the deviations from the spatial homogeneity of noise model. The effectiveness of the MENSE is verified through numerical examples, and the simulation results show that the MENSE is superior in detecting closely spaced signals with a small number of snapshots and/or at relatively low signal-to-noise ratio (SNR)     

NO is not involved in the simvastatin induced cell division and differentiation in PC12 cells

Simvastatin, a potent 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor has been reported to inhibit cell division and induce neurite-like outgrowth in PC12 cells [Sato-Suzuki, I. and Murota, S., Neurosci. Lett., 220 (1996) 21-24]. In the present paper, we examined whether the induced nitric oxide (NO) in the simvastatin-treated PC12 cells is involved in the growth arrest and differentiation as reported in nerve growth factor (NGF) treated PC12 cells. Treatment of PC12 cells with simvastatin caused peripherin formation and enhanced NO production just like NGF-treated PC12 cells. Different from NGF, however, NO synthase inhibitors could not affect the growth arrest and differentiation in simvastatin-treated PC12 cells. In conclusion, NO had nothing to do with cell division and differentiation in simvastatin-treated PC12 cells.     

In‐situ Observation of Penetration of Molten Slag into Solid Lime at High Temperature

The phenomena of penetration of liquid slag into solid bulk lime and into the cracks of the lime body have been investigated by in‐situ X‐ray direct observation. The lime samples were immersed into CaO‐SiO₂‐Fe_tO‐MgO molten slag at 1350, 1450 and 1550°C. It was found from the results that the height of slag penetration into the lime bulk linearly proportional to the penetration time. The rate of penetration at high temperature is much greater than that at low temperature whereas the slag penetration into a crack in the lime body slows down gradually and the penetration reaches an equilibrium height in the course of the experiments. Higher T.Fe content and temperature are favourable to lime dissolution into molten slag and thus to the penetration into both lime body and cracks. Molten slag with high FeO can completely wet solid lime.     

Two (Z)-dehydrobutyrine-containing microcystins from a hepatotoxic bloom of Oscillatoria agardhii from Soulseat Loch, Scotland

Two (Z)-dehydrobutyrine(Dhb)-containing microcystins, [d-Asp3, (Z)-Dhb7]microcystin-HtyR (1) and [d-Asp3, (Z)-Dhb7]microcystin-LR (2), were isolated from a hepatotoxic bloom of the cyanobacterium Oscillatoria agardhii from a freshwater lake in Scotland. The geometrical structure of the Dhb units in the microcystins was determined as Z on the basis of NOE and ROESY experiments.