Development of dual-probe atomic force microscopy system using optical beam deflection sensors with obliquely incident laser beams

We developed a dual-probe (DP) atomic force microscopy (AFM) system that has two independently controlled probes. The deflection of each cantilever is measured by the optical beam deflection (OBD) method. In order to keep a large space over the two probes for an objective lens with a large numerical aperture, we employed the OBD sensors with obliquely incident laser beams. In this paper, we describe the details of our developed DP-AFM system, including analysis of the sensitivity of the OBD sensor for detection of the cantilever deflection. We also describe a method to eliminate the crosstalk caused by the vertical translation of the cantilever. In addition, we demonstrate simultaneous topographic imaging of a test sample by the two probes and surface potential measurement on an α-sexithiophene (α-6T) thin film by one probe while electrical charges were injected by the other probe.     

Reduction of frequency noise and frequency shift by phase shifting elements in frequency modulation atomic force microscopy

We recently reported the analysis of the frequency noise in the frequency modulation atomic force microscopy (FM-AFM) both in high-Q and low-Q environments [Rev. Sci. Instrum. 80, 043708 (2009)]. We showed in the paper that the oscillator noise, the frequency fluctuation of the oscillator, becomes prominent in the modulation frequency lower than f(0)∕2Q, where f(0) and Q are the resonance frequency and Q-factor. The magnitude of the oscillator noise is determined by the slope of the phase versus frequency curve of the cantilever at f(0). However, in actual FM-AFM in liquids, the phase versus frequency curve may not be always ideal because of the existence of various phase shifting elements (PSEs). For example, the spurious resonance peaks caused by the acoustic excitation and a band-pass filter in the self-oscillation loop increase the slope of the phase versus frequency curve. Due to those PSEs, the effective Q-factor is often increased from the intrinsic Q-factor of the cantilever. In this article, the frequency noise in the FM-AFM system with the PSEs in the self-oscillation loop is analyzed to show that the oscillator noise is reduced by the increase of the effective Q-factor. It is also shown that the oscillation frequency deviates from the resonance frequency due to the increase of the effective Q-factor, thereby causing the reduction in the frequency shift signal with the same factor. Therefore the increase of the effective Q-factor does not affect the signal-to-noise ratio in the frequency shift measurement, but it does affect the quantitativeness of the measured force in the FM-AFM. Furthermore, the reduction of the frequency noise and frequency shift by the increase of the effective Q-factor were confirmed by the experiments.     

An integrated numerical simulator for thermal performance assessments of firefighters’ protective clothing

Research and development of firefighters’ protective clothing relies on a large number of fire disaster experiments in order to assess the thermal performance. It would be substantially advantageous to substitute a virtual numerical experiment for a real one in terms of time, cost and safety. The present article reports the development of an integrated numerical simulator that makes possible the estimation of burn injuries originating from fire disasters. In the simulator, a general-purpose computational fluid dynamics program computes the fluid flow and heat transfer in an in situ fire event, while a one-dimensional program calculates the radiative–conductive heat transfer through the clothing and human skin. A data interface combines the two simulations by loose coupling so as to give the real-time burn injury progress output. The predicted surface heat fluxes and burn degrees agree with experimental measurements reasonably well. Possible numerical error sources are discussed that call for potential improvements in the future.     

A new model of DLA under high magnetic field

A new Monte Carlo model is introduced to describe diffusion-limited aggregation (DLA) with extra forces arising from Lorentz's and/or Coulomb forces. Furthermore, we simulate a behavior of multiparticle diffusive aggregation to examine the resultant pattern of crystal in electrochemical deposition. Different patterns grown under various external forces are produced by Monte Carlo simulations. In the present model, the basic movement of particles is a random walk, with different transition probabilities in different directions, which characterizes stochastically the effect of extra forces. In case of assuming a high magnetic field, pattern formations which are qualitatively different from the standard DLA model are observed and they are successfully compared with preexisting experiments (Mogi et al., 1991). The present numerical results of electrochemical deposition show that the generated patterns strongly depend on the force acting on ions and their concentration (Sawada et al., 1986).     

Catheter ablation for ventricular tachycardia from a diverticulum at the right ventricular outflow tract

A case is presented of a 73-year-old man with drug resistant ventricular tachycardia that originated from the right ventricular outflow tract. A right ventriculogram showed a diverticulum in the interventricular septum at the right ventricular outflow tract. Low energy radiofrequency catheter ablation within the diverticulum was performed successfully and safely.     

Elastodynamic Doppler effects and wave energy partition by a sliding interface

Wave reflection and refraction at a sliding interface are discussed. The regular dynamic friction rule, Coulomb’s law, is assumed for the sliding interface. Doppler frequency shift is found, and it depends on the ratio of a sliding velocity to an apparent horizontal velocity of an incident wave. Wave energy partition by the sliding interface is also discussed. In the case of an incident P-wave, a transmitted/refracted P-wave gets the major part of the incident wave energy. On the other hand, in the case of an incident SV-wave, a reflected SV-wave gets most of incident wave energy. It is also found an energy supply or loss by the sliding interface. It strongly depends on the friction coefficient and on the sliding direction. Further, it is shown that there is no possibility for detecting the sliding velocity by means of Doppler frequency shift.     

Preparation of Stoichiometric Crystalline Lithium Niobate Fibers by Sol-Gel Processing with Metal Alkoxides

Homogeneous and stoichiometric crystalline LiNbO₃ fibers were successfully prepared above 450°C by sol-gel processing with metal alkoxides. Controlling the concentration of alkoxide solution and the amount of water used for partial hydrolysis made it possible to draw gel fibers having uniform diameters (10 to 100 μm) from the metal alkoxide solution. The gel fibers withdrawn crystallized directly to single-phase LiNbO₃ fibers by heating from 450° to 600°C. The density of the crystalline LiNbO₃ fibers was higher than 4.22 g/cm³, and the dielectric constant at room temperature was about 10 at 10 MHz.     

Reduction of hyperlipidemia in hepatoma-bearing rats by dietary fish oil

The effect of dietary fish oil on serum lipid levels was studied by comparing it with dietary corn oil in Donryu rats subcutaneously implanted with an ascites hepatoma cell line (AH109A). The hepatoma-bearing rats exhibited hyperlipidemia charactarized by a rise in both serum cholesterol and triglyceride levels. Increased cholesterogenesis in the host liver and decrease steroid excretion into feces are suggested to be responsible for the hepatoma-induced hypercholesterolemia, and increased fatty acid mobilization from peripheral adipose tissues and decreased triglyceride clearance from the blood circulation are considered causes for the hepatoma-induced hypertriglyceridemia. Dietary fish oil reduced the hyperfipidemia in these animals, suppressed the hepatoma-induced increase in hepatic cholesterogenesis and fatty acid mobilization from adipose tissue. Dietary fish oil also tended to increase fatty acid oxidation in the liver. Such diverse effects of fish oil may lead to the reduction of the hepatoma-induced hyperlipidemia. These results suggest that studies on dietary fish oil may be warranted in patients with cancer-related hyperlipidemia.     

Lipid synthesis and acyl-CoA synthetase in developing rice seeds

Developing rice seeds rapidly accumulated storage lipids between 5 and 12 d after flowering. The contents of palmitic, oleic, and linoleic acids increased throughout seed development, while the alpha-linolenic acid content remained low. The activity of acyl-CoA synthetase varied coincidentally during the period of lipid accumulation, and rice seeds had a sufficient capacity to supply acyl-CoA substrates for TAG synthesis. Acyl-CoA synthetase showed a broad specificity for native FA of rice seeds except for stearic acid, and pi electrons of a delta9-delta11 double bond in the C16-C18 acyl chains were required for its maximal activity.