Device performance of p-Ge MOSFETs at liquid nitrogen temperature

The device performance of p-channel Ge MOSFETs at liquid nitrogen temperature is reported and initial results of room temperature irradiation with 2-MeV electrons on the cryogenic device performance is described. It is shown that at 77 K an increase of the drain current and g_m is observed. This increase of the g_m can be explained by considering the balance between reduced phonon scattering on the one hand and increased Coulomb scattering by interface states, on the other. After irradiation, a slight negative shift of the threshold voltage and a decrease of the drain current for input and output characteristics have been observed together with a decrease of the transconductance (g_m).     

PV1 Protein from Plasmodium falciparum Exhibits Chaperone-Like Functions and Cooperates with Hsp100s

Plasmodium falciparum parasitophorous vacuolar protein 1 (PfPV1), a protein unique to malaria parasites, is localized in the parasitophorous vacuolar (PV) and is essential for parasite growth. Previous studies suggested that PfPV1 cooperates with the Plasmodium translocon of exported proteins (PTEX) complex to export various proteins from the PV. However, the structure and function of PfPV1 have not been determined in detail. In this study, we undertook the expression, purification, and characterization of PfPV1. The tetramer appears to be the structural unit of PfPV1. The activity of PfPV1 appears to be similar to that of molecular chaperones, and it may interact with various proteins. PfPV1 could substitute CtHsp40 in the CtHsp104, CtHsp70, and CtHsp40 protein disaggregation systems. Based on these results, we propose a model in which PfPV1 captures various PV proteins and delivers them to PTEX through a specific interaction with HSP101.     

Generation of strong optical field in soft X-ray region by using high-order harmonics

For further development of a variety of applications, one of the most important issues is the improvement of output harmonic energy and conversion efficiency. We review our work on the energy scaling of high-order harmonic generation based on phase-matching using a loosely focused beam. Our harmonic energy scaling method can be universally applied to harmonic generation in the neutral rare gas target. In addition, we demonstrate a new concept for spatial separation between the high-energy pump and harmonic beam to increase the available soft X-ray energy for the applications. This method is very simple and highly useful for not only high-order harmonic generation but also longitudinally pumped X-ray lasers. By combining the high-energy high harmonic source and new spatial separation method, we successfully demonstrate focusing of the soft X-ray beam with a peak intensity of 1/spl times/10/sup 14/ W/cm/sup 2/, which is to our knowledge the highest ever reported in the soft X-ray region.     

A comparison between the journals nature and science

In this paper,Nature andScience, the two distinguished multi-disciplinary scientific journals were compared placing emphasis on their internationality. The items investigated were as follows. A general comparison: 1. number of authors per article, 2. distribution of countries to which first authors' institutions belong, 3. distribution of main discplines studied by first authors, 4. time-lag between the date of receipt of an article by the editor and the date of its publication. B. the position with regard to Japanese author: 1. number of Japanese authors, 2. relationship between the ranking of a Japanese author in the list of authors' names and the country where his institution is located, 3. relationship between the time-lag stated in A-4 and the items stated in B-2. As a result, it can be said thatNature is a more highly international journal thanScience.     

Citation analysis of physics journals: Comparison of subfields of physics

In this study, half-life, citation degree, form dispersion and title dispersion of physic journals were investigated, and they were compaired in each subfield with those in other subfields. The results from this study were that, on the whole, in physics the most preferred medium for physicists is the “journal”; however, in the subfields in which large experimental or observational devices are used, the use of “reports” and “letter journals” is going to increase.     

Evaluation of noise filter characteristics by discrete wavelet transformation

In this paper, the authors propose a wavelet analysis technique to evaluate the noise filtering characteristics of filters. To analyze noise problems, many people have used Fourier analysis. But the Fourier spectrum reveals only frequency information. Therefore, it is difficult to obtain noise waveforms from the Fourier spectrum. To overcome this difficulty, we have employed the wavelet analysis technique. Wavelet analysis makes it possible to get time domain as well as frequency domain information. It is shown that wavelet analysis is a promising methodology for noise filter characteristic evaluation. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(3): 1–8, 1997     

Design of atomic mirror for silicon atoms

Cook and Hill suggested that the gradient of an optical field can be used to reflect atoms. To reflect atoms, the repulsive dipole force is used, which comes from the interaction between the electric dipole moment of atoms and the evanescent field. The evanescent wave is generated when light is totally reflected internally at the interface of different refractive indices. Later, the way to enhance the evanescent wave with a thin dielectric waveguide has been reported. We designed the atomic mirror for silicon atoms, whose structure enhances the evanescent field that is used to repel silicon atoms. We also set up the equations of motion for silicon atoms and derive trajectories of the atoms reflected by the atomic mirror. Optical intensity, incident angle of the light, and effective detuning are described in terms of controlling the trajectory of the atom.     

Adaptively controlled supercontinuum pulse from a microstructure fiber for two-photon excited fluorescence microscopy

Selective fluorescence excitation of specific molecular species is demonstrated by using coherent control of two-photon excitation with supercontinuum pulses generated with a microstructure fiber. Pulse shaping prior to pulse propagation through the fiber is controlled by a self-learning optimization loop so that the highest fluorescence signal contrast between two fluorescent proteins is obtainable. The self-learning optimization loop successfully controls both the optical nonlinarity of the microstructure fiber and the two-photon excitation of the fluorescent proteins.     

Radiation damage of Ge-on-Si devices

The radiation damage induced by 2-MeV electrons and 70-MeV protons in p⁺n diodes and p-channel MOS transistors, fabricated in epitaxial Ge-on-Si substrates is reported for the first time. For irradiation above 5×10¹⁵ e/cm², it is noted that both the reverse and forward current increase, and that the forward current is lower after irradiation for a forward voltage larger than about 0.5 V. The reason for this might be an increased resistivity of the Ge-on-Si substrate. For p-MOSFETs, for a 1×10¹⁶ e/cm² dose, a slight negative shift of the threshold voltage and a decrease of the drain current for input and output characteristics have been observed. In addition, g_m decreases after irradiation. The degradation of the transistor performance is thought to be due to irradiation-induced positive charges in the high-κ gate dielectric. The induced lattice defects are also mainly responsible for the leakage current increase of the irradiated diodes.     

Thin film transformer and its analysis by integral equation method

We propose a thin film transformer for small electronic devices, and apply the integral equation method to analyze this transformer. Both the primary and secondary coils of the film transformer are arranged coaxially on the layer and multiply laminated. The operation principal of the transformer is based on the skin effect and the mutual effect between the coils at high frequency. Because of the coaxially arranged coils, the magnetic field of the transformer can be modeled with an axisymmetric assumption. Using the model, we evaluate the electromagnetic field and calculate the lumped circuit parameters, i.e., inductance and resistance, which are compared with experimental values