Current-induced magnetic domain wall motion below intrinsic threshold triggered by Walker breakdown.

Controlling the position of a magnetic domain wall with electric current may allow for new types of non-volatile memory and logic devices. To be practical, however, the threshold current density necessary for domain wall motion must be reduced below present values. Intrinsic pinning due to magnetic anisotropy, as recently observed in perpendicularly magnetized Co/Ni nanowires, has been shown to give rise to an intrinsic current threshold J(th)(0). Here, we show that domain wall motion can be induced at current densities 40% below J(th)(0) when an external magnetic field of the order of the domain wall pinning field is applied. We observe that the velocity of the domain wall motion is the vector sum of current- and field-induced velocities, and that the domain wall can be driven against the direction of a magnetic field as large as 2,000 Oe, even at currents below J(th)(0). We show that this counterintuitive phenomenon is triggered by Walker breakdown, and that the additive velocities provide a unique way of simultaneously determining the spin polarization of current and the Gilbert damping constant.

Electric-field control of magnetic domain-wall velocity in ultrathin cobalt with perpendicular magnetization.

Controlling the displacement of a magnetic domain wall is potentially useful for information processing in magnetic non-volatile memories and logic devices. A magnetic domain wall can be moved by applying an external magnetic field and/or electric current, and its velocity depends on their magnitudes. Here we show that the applying an electric field can change the velocity of a magnetic domain wall significantly. A field-effect device, consisting of a top-gate electrode, a dielectric insulator layer, and a wire-shaped ferromagnetic Co/Pt thin layer with perpendicular anisotropy, was used to observe it in a finite magnetic field. We found that the application of the electric fields in the range of ± 2-3 MV cm(-1) can change the magnetic domain wall velocity in its creep regime (10(6)-10(3) m s(-1)) by more than an order of magnitude. This significant change is due to electrical modulation of the energy barrier for the magnetic domain wall motion.

Electrical control of the ferromagnetic phase transition in cobalt at room temperature.

Electrical control of magnetic properties is crucial for device applications in the field of spintronics. Although the magnetic coercivity or anisotropy has been successfully controlled electrically in metals as well as in semiconductors, the electrical control of Curie temperature has been realized only in semiconductors at low temperature. Here, we demonstrate the room-temperature electrical control of the ferromagnetic phase transition in cobalt, one of the most representative transition-metal ferromagnets. Solid-state field effect devices consisting of a ultrathin cobalt film covered by a dielectric layer and a gate electrode were fabricated. We prove that the Curie temperature of cobalt can be changed by up to 12 K by applying a gate electric field of about ±2 MV cm(-1). The two-dimensionality of the cobalt film may be relevant to our observations. The demonstrated electric field effect in the ferromagnetic metal at room temperature is a significant step towards realizing future low-power magnetic applications.

Observation of the intrinsic pinning of a magnetic domain wall in a ferromagnetic nanowire.

The spin transfer torque is essential for electrical magnetization switching. When a magnetic domain wall is driven by an electric current through an adiabatic spin torque, the theory predicts a threshold current even for a perfect wire without any extrinsic pinning. The experimental confirmation of this 'intrinsic pinning', however, has long been missing. Here, we give evidence that this intrinsic pinning determines the threshold, and thus that the adiabatic spin torque dominates the domain wall motion in a perpendicularly magnetized Co/Ni nanowire. The intrinsic nature manifests itself both in the field-independent threshold current and in the presence of its minimum on tuning the wire width. The demonstrated domain wall motion purely due to the adiabatic spin torque will serve to achieve robust operation and low energy consumption in spintronic devices.

Relationship between apoptosis and immunohistochemical staining for proliferating cell nuclear antigen and Ki-67 in non-small cell lung cancer.

The relationship between apoptosis and cellular proliferative activity in human non-small cell lung cancer (25 cases) was investigated using the in situ DNA nick-end labeling method and immunohistochemistry for both proliferating cell nuclear antigen (PCNA) and Ki-67 antigen. Comparison of the distribution of Ki-67-positive cells to that of apoptotic cells shows an inverse correlation in semi-serial sections. The PCNA labeling rates were closely correlated with Ki-67 labeling rates in non-small cell lung cancer. It was concluded that the immunostainings of PCNA and Ki-67 were almost equally valuable for assessing the proliferative activity in paraffin-embedded tissue from non-small cell lung cancer and that apoptosis may be related with the cell cycle in this cancer.

Hypersensitivity pneumonitis among workers cultivating Tricholoma conglobatum (shimeji).

We report five cases of hypersensitivity pneumonitis among workers cultivating Tricholoma conglobatum (shimeji). After having worked for 5 to 20 years, they began to notice symptoms of cough, sputum, and dyspnea. They were diagnosed as having a hypersensitivity pneumonitis based on clinical features, bronchoalveolar lavage and transbronchial lung biopsy. By the double immunodiffusion test, precipitating lines between shimeji spore antigen and sera were observed in all of the patients. By enzyme-linked immunosorbent assay, the antibody activities against shimeji and three species of fungi (Cladosporium sphaerospermum, Penicillium frequentans, and Scopulariopsis species) were significantly higher in the sera of the patients than in those of normal subjects who were cultivating shimeji. Although it is not clear what causes this disease, these findings may be helpful in determining the specific antigen.

StyD4I restriction-modification system of Salmonella typhi D4: cloning and sequence analysis.

A plasmid (5.4 kbp) from Salmonella Typhi D4 has been identified as encoding a restriction and modification (R-M) system. DNA fragments (2537 bp) that carried the genes for restriction endonuclease and methyltransferase encoded on the plasmid were sequenced. Two divergently arranged open reading frames of 957 bp for the restriction endonuclease consisting of 318 aa (amino acids) and 1140 bp for the DNA methyltransferase consisting of 379 aa were identified. These sequences were similar to the sequences of the SsoII R-M system, including the interspace between the two genes.

Production of New Restriction Endonuclease VpaK111BI Recognizing Sequence 5'-GGWCC-3' in a Haemolysin-less Mutant of Vibrio parahaemolyticus.

High restriction endonuclease activity was found in a haemolysin-less mutant of the Vibrio parahaemolyticus 1743-1 strain. The endonuclease, named VpaK11BI, recognized the palindromic pentanucleotide sequence of 5'-GGWCC-3' and cleaved double-stranded DNA after the first G, which is exactly the same as the specificity of AvaII. The haemolysin-less mutant of V. parahaemolyticus is now available for producing the valuable restriction endonuclease on a commercial scale.

Alternatively spliced isoform of P-selectin is present in vivo as a soluble molecule.

To demonstrate the presence of a soluble isoform of P-selectin predicted from cDNA sequencing (Johnston, G.I., Bliss, G.A., Newman, P.J., and McEver, R.P. (1990) J. Biol. Chem. 265, 21381-21385), we immunoisolated and compared structurally P-selectin from fresh frozen human plasma with that from washed intact platelets. Plasma P-selectin was reactive with rabbit antiserum to a synthesized peptide (residues 762-774 of mature P-selectin) but was significantly less reactive with antibody to a peptide (residues 747-760). In contrast, platelet P-selectin reacted with both antibodies. S-Pyridylethylated plasma P-selectin was fractionated by reversed phase-high performance liquid chromatography into two major species. From platelets, two virtually identical species were separated. Sequential digestion with Achromobacter protease I and then Staphylococcus V8 protease produced peptides assigned to the tail region of the protein including the putative spliced site. From the more hydrophilic species in both plasma and platelets, a peptide completely lacking the sequence of the putative spliced site was identified. In contrast, the more hydrophobic species yielded a peptide with an intact transmembrane sequence. Hence, these results provide direct evidence that the previously predicted soluble isoform of P-selectin is actually synthesized in vivo and is present as a circulating molecule.