Tolerance to Stretching in Thiol-Terminated Single-Molecule Junctions Characterized by Surface-Enhanced Raman Scattering

We investigated the change in the metal-molecule interaction in a 1,4-benzenedithiol (BDT) single-molecule junction using a combination of surface-enhanced Raman scattering spectra and current-voltage curves. During the stretching process, the conductance of the junction systematically decreased, accompanied by an increase in the vibrational energy of the CC stretching mode. By analyzing the current-voltage curves and Raman spectra, we found that the interaction between the π orbital of BDT and the electronic states of Au was diminished by the orientation change of BDT during the stretching process. A comparison with a 4,4'-bipyridine single-molecule junction revealed that the reduction of coupling of the Au-S contacts was smaller than that of Au-pyridine contacts. Therefore, the electronic states originating from the contact geometry are responsible for the tolerance to the stretching of thiol-terminated molecular junctions.

Investigation of Ag and Cu Filament Formation Inside the Metal Sulfide Layer of an Atomic Switch Based on Point-Contact Spectroscopy

The atomic switches have attracted wide attention owing to their applications in nonvolatile electric devices. The atomic switch is operated by the formation and dissipation of a metallic filament inside a metal sulfide film, which is controlled by a solid electrochemical reaction. Although the metallic filament is considered to consist of metal atoms, the chemical species of the metallic filament are difficult to be identified due to challenges in observing the metallic filament inside the solid. In this study, we report the investigation on the metallic filament in the atomic switch with metal sulfide based on point-contact spectroscopy (PCS). By cooling the atomic switch, the switch voltage increased to 1 V, which allowed for the PCS measurement. The PCS revealed that the metallic filament was composed of Ag atoms in the case of the Pt/Ag₂S/Ag atomic switch. We applied this technique to the Pt/Cu₂S/Ag and Pt/Ag₂S/Cu atomic switches to uncover the formation process of the metallic filament. In both atomic switches, the chemical species of the metallic filament were Ag. The metal atoms were supplied from both the metal electrode and the sulfide layer.

Stretch dependent electronic structure and vibrational energy of the bipyridine single molecule junction

Change in the molecular orbital energy and vibrational energy of the bipyridine single molecule junction as a function of stretch distance.

Nutritional assessment using stable isotope ratios of carbon and nitrogen in the scalp hair of geriatric patients who received enteral and parenteral nutrition formulas

BACKGROUND & AIMS

The δ¹³C and δ¹⁵N values in the scalp hair of geriatric patients in Japan who received the enteral or parenteral nutrition formula were measured to assess nutritional status.

METHODS

The relations among δ¹³C, δ¹⁵N, calorie intake, BMI, albumin concentration, total cholesterol (T-CHO) and geriatric nutritional risk index (GNRI) in the patients were investigated. Furthermore, the enrichment of δ¹³C and δ¹⁵N from the nutrients to the hair was investigated.

RESULTS

The δ¹³C values in the hair of patients who received enteral nutrition decreased with decreases in the calories received, while the δ¹⁵N values increased, suggesting malnutrition in some patients with a low calorie intake due to a negative nitrogen balance. The distribution of patients with a low calorie intake (below 20 kcal/kg/day) when δ¹³C was plotted against δ¹⁵N differed from that of control subjects, but the distribution of patients with a high calorie intake (above 20 kcal/kg/day) was similar to that of control subjects. No significant differences were observed in BMI, albumin concentration, T-CHO or GNRI between the low and high calorie groups. The enrichment of δ¹³C and δ¹⁵N from the enteral nutrients to the hair were inversely correlated with the δ¹³C and δ¹⁵N in the enteral nutrients. The enrichment levels of δ¹³C and δ¹⁵N tended to be higher and lower, respectively, in the high calorie group. On the other hand, the δ¹³C and δ¹⁵N values in the hair of patients who received parenteral nutrition were higher and lower than those in the control subjects and in the patients who received enteral nutrition, respectively, reflecting the higher δ¹³C and lower δ¹⁵N contents of the parenteral nutrients.

CONCLUSIONS

The δ¹³C and δ¹⁵N values in the hair of patients who received enteral nutrition may be effective indicators for evaluating the long-term nutritional status of geriatric patients. A calorie intake of 20 kcal/kg/day may be a cut-off value for malnutrition in Japanese geriatric patients receiving enteral nutrition. However, caution is necessary when dealing with patients switching from parental nutrition as parenteral nutrition resulted in different changes in δ¹³C and δ¹⁵N. The enrichment levels of δ¹³C and δ¹⁵N from the enteral nutrients to the hair may be inversely correlated with the δ¹³C and δ¹⁵N values of enteral nutrients and vary according to the calorie intake.

High-performance top-gated monolayer SnS2 field-effect transistors and their integrated logic circuits

Two-dimensional (2D) layered semiconductors are very promising for post-silicon ultrathin channels and flexible electronics due to the remarkable dimensional and mechanical properties. Besides molybdenum disulfide (MoS2), the first recognized 2D semiconductor, it is also important to explore the wide spectrum of layered metal chalcogenides (LMCs) and to identify possible compounds with high performance. Here we report the fabrication of high-performance top-gated field-effect transistors (FETs) and related logic gates from monolayer tin disulfide (SnS2), a non-transition metal dichalcogenide. The measured carrier mobility of our monolayer devices reaches 50 cm(2) V(-1) s(-1), much higher than that of the back-gated counterparts (~1 cm(2) V(-1) s(-1)). Based on a direct-coupled FET logic technique, advanced Boolean logic gates and operations are also implemented, with a voltage gain of 3.5 and output swing of >90% for the NOT and NOR gates, respectively. The superior electrical and integration properties make monolayer SnS2 a strong candidate for next-generation atomic electronics.

Toward sub-20 nm hybrid nanofabrication by combining the molecular ruler method and electron beam lithography

It is of great interest and importance to develop new nanofabrication processes to fabricate sub-20 nm structures with sub-2 nm resolution for next-generation nanoelectronic devices. A combination of electron beam lithography (EBL) and a molecular ruler is one of the promising methods to make these fine structures. Here we successfully develop a hybrid method to fabricate sub-20 nm nanogap devices at the desired positions with a complex structure by developing a post-EBL process, which enabled us to avoid damaging the molecular ruler with the high-energy electron beam, and to fully utilize the EBL resolution. It was found that slight etching of the Ti adhesion layer of the parent metal (Pt) by ACT935J solution assisted the removal of molecular rulers, resulting in improved enhancement in the product yield (over 70%) of nanogap devices.

In-crystal and surface charge transport of electric-field-induced carriers in organic single-crystal semiconductors

Gate-voltage dependence of carrier mobility is measured in high-performance field-effect transistors of rubrene single crystals by simultaneous detection of the longitudinal conductivity sigma(square) and Hall coefficient R(H). The Hall mobility mu(H) (identical with sigma(square)R(H)) reaches nearly 10 cm(2)/V s when relatively low-density carriers (<10(11) cm(-2)) distribute into the crystal. mu(H) rapidly decreases with higher-density carriers as they are essentially confined to the surface and are subjected to randomness of the amorphous gate insulators. The mechanism to realize high carrier mobility in the organic transistor devices involves intrinsic-semiconductor character of the high-purity organic crystals and diffusive bandlike carrier transport in the bulk.

Consideration on peak shape in a batch-type chemiluminescence detection cell for capillary electrophoresis

Peak areas, peak heights, and apparent theoretical plate numbers were examined as a function of sample injection times by use of the batch-type CL detection cell. Comparing the experimental data with those obtained by absorption detector, some considerations were carried out about the peak shape. The peak shape in CL detection was influenced by not only concentration distribution of sample in a sample zone but also sample diffusion and CL reaction at the capillary outlet. The sample injection time of ca. 35 s was recommended for the present CE with CL detector. The injection time much influenced peak shape as well as sensitivity in the CL detection cell.

Sensitive determination of metal ions by liquid chromatography with tris(2,2'-bipyridine) ruthenium (II) complex electrogenerated chemiluminescence detection

Emetine dithiocarbamate metal complex, which is prepared from emetine, carbon disulfide, and metal (II), was found to indicate a large chemiluminescence intensity on the electrogenerated chemiluminescence of tris(2,2'-bipyridine)ruthenium(II). Liquid chromatography equipped with the chemiluminescence detection was developed for analyzing trace metal ions by use of the metal complex formation. The mixture of the Cu(II) and Co(II) complexes as a model sample was injected into the LC system. The two metal complexes and an excess emetine were successfully separated. The Cu(II) and Co(II) complexes were determined over the range 1-300 nM (the detection limit of 650 fg) and 30-5000 nM (the detection limit of 17 pg), respectively.

Microchip capillary electrophoresis using on-line chemiluminescence detection

Chemiluminescence detection was used in capillary electrophoresis integrated on a microchip. Quartz microchips have two main channels and four reservoirs. Dansyl-lysine and -glycine were separated and detected with bis[(2-(3,6,9-trioxadecanyloxycarbony)-4-nitrophenyl]oxalate as peroxyoxalate chemiluminescent reagent. These dansyl amino acids came into contact with the chemiluminescence reagent to produce visible light at the interface between the separation channel and chemiluminescence reagent-containing reservoir. The detection limit (S/N = 3) for dansyl-lysine was 1 x 10(-5) M, which corresponded to the very small mass detection limit of ca. 0.4 fmol. However, the concentration sensitivity in the present system was approximately two orders of magnitude lower than that in the conventional capillary electrophoresis-chemiluminescence detection system. The relative standard deviations of migration time and peak height for dansyl-lysine were 4.2 and 4.5%, respectively. A channel conditioning before every run and an appropriate control of voltages were needed for the reproducible results. The present system had advantages in rapid separation time (within 40 s), small (several 10 pI) and accurate sample injection method using a cross-shaped injector, and simplification and miniaturization of the detection device.

Chemiluminescence detection of heme proteins separated by capillary isoelectric focusing

Chemiluminescence detection was combined with capillary isoelectric focusing to perform protein analysis with high sensitivity. Luminol-H2O2 chemiluminescence was utilized, and heme proteins such as cytochrome c, myoglobin and peroxidase were analyzed. The proteins were focused by use of Pharmalyte 3-10 as ampholytes. Hydroxypropylmethyl-cellulose was added to the sample solution in order to easily reduce protein interactions with the capillary wall as well as the electroendoosmotic flow. The focused proteins were transported by salt mobilization to chemiluminescence detection cell equipped with an optical fiber. The present method showed significantly high sensitivity and wide dynamic range; the detection limit for cytochrome c was 6 x 10(-9) M and the linear dynamic range was greater than two-orders of magnitude (up to 2 x 10(-6) M).

Setting up an automated system for evaluation of bone age

The "Tanner-Whitehouse 2" method is the most popular in evaluating skeletal maturation, but this method has some inherent weak points. We therefore developed the new system to automatically evaluate the skeletal maturation of Japanese children by means of a personal computer. The subjects of this study were 318 healthy Japanese boys and 199 girls ranging from 2 to 15 years of age. The bone age was calculated by multiple regression analysis with parameters for the epiphysis and metaphysis. Successful automatic evaluation was about 80-90% on each phalanx. There was a significant correlation between chronological age and the ratio of epiphyseal width to metaphyseal width. The system developed in this study was useful for evaluating the skeletal maturation.

Standard RUS skeletal maturation of Tokyo children

A total of 704 girls and 753 boys, all healthy, from 3 to 18 years of age, from Tokyo and its suburbs, were radiographed on the left hand and wrist in 1986. Their RUS (TW2) skeletal maturity was estimated, the 50th-centile skeletal maturity scores were obtained, and the smoothed RUS maturity curves were determined applying the cubic spline function to the 50th-centile scores. On this maturity curve the score at each 0.1 year of chronological age was obtained and allocated as a given RUS skeletal age. This set of scores and ages we termed the TW2-J RUS, i.e. the Japanese TW2 RUS maturity standard. Comparing this RUS standard with the British standard, the Belgian, the southern Chinese, and the northern Indian, it became clear that Japanese children's RUS skeletal maturity progresses rapidly during puberty (after ages 9 in girls and 11 in boys), and that the maximum score difference between neighbouring age groups was observed at ages 12.5 in girls and 14.5 in boys on the spline-smoothed curve. Japanese children attain the adult stage 1 or 2 years earlier than other groups of children (at ages 15 in girls and 16 in boys).

Aberrant expression of a hemidesmosomal protein, bullous pemphigoid antigen 2, in human squamous cell carcinoma

Through yet unidentified mechanisms, squamous epithelial cells become committed to terminal differentiation after detachment from the basement membrane. In squamous cell carcinoma, these mechanisms seem to be disturbed. A murine monoclonal antibody, designated NCC-Lu-226 (IgG1, K), which recognizes an antigen expressed in basal cells of squamous epithelium at the epithelio-connective tissue border, was obtained. A cDNA clone encoding the antigen was isolated from a cDNA library by immunoselection. DNA sequencing and a database search revealed that this cDNA clone was identical to a hemidesmosomal transmembrane protein, bullous pemphigoid antigen 2 (BPA-2; also known as BPAG2, BP180, or type XVII collagen). Immunoelectron microscopy validated the specific reactivity of this monoclonal antibody with skin hemidesmosomes. Enhanced expression and abnormal distribution of BPA-2 was revealed immunohistochemically in various precancerous and cancerous tissues, including solar keratosis (4 of 5), Bowen's disease (3 of 5), invasive squamous cell carcinoma (7 of 7) of the skin, and squamous cell carcinoma of the lung (14 of 14), esophagus (12 of 13), and cervix (14 of 17). The specific expression of BPA-2 protein in squamous cell carcinoma was confirmed by RT-PCR and Northern hybridization. BPA-2 has possible phosphorylation sites and is actually phosphorylated in cultured keratinocytes and squamous cell carcinoma. The aberrant expression of BPA-2 may reflect dysfunction of the hemidesmosome that occurs as a relatively early event in multistep carcinogenesis of squamous epithelium.

[Ferruginous bodies in the lungs of the general population during a 45-year period and mineralogical examination]

In order to determine the level of asbestos pollution in the lungs of members of the general population in and around Tokyo, the incidence of ferruginous bodies in autopsied or resected lungs during 5 periods over the 45 years from 1937 to 1981 was studied by a light microscopy. Core fibres, after removal of their ferruginous coatings with oxalic acid, and uncoated fibres were analyzed using a scanning electron microscope equipped with a Kevex energy-dispersive X-ray spectrometer. The incidence of ferruginous bodies in 5 g (wet) of digested lung tissue was shown to be 10% in period I (1937-1941), 18% in period II (1947-1951), 70% in period III (1958-1963), 74.4% in period IV (1970-1973) and 81.0% in period V (1980-1981). The major types of core fibres of ferruginous bodies were found to be asbestos, including amosite, crocidolite, chrysotile and the tremolite-actiolite series, but a small number of fibers of materials other than asbestos were also detected. In contrast, a large number of short fibers less than 5 microns in length in 1 g of wet lung tissue were classified as belonging to Mg + Si fibers (the ratio of Mg to Si components being 30% or over) and presumed to be chrysotile. Thus an annual increase in asbestos deposition in lungs of people living in and around Tokyo has been demonstrated and fine chrysotile fibers less than 5 microns in length seem to be the main type of deposited fibers.

Effects of KCl, MgCl2, and CaCl2 concentrations on the monomer-polymer equilibrium of actin in the presence and absence of cytochalasin D

Critical metal concentrations of KCl, MgCl2, and CaCl2 below which actin cannot exist in filamentous form at equilibrium were estimated to be approximately 8 mM, 0.2 mM, and 0.4 mM, respectively, when actin, 0.5 mg/ml, was incubated for a long time at pH 8.0 and 25 degrees C. These values were obtained by viscosity, UV absorbance and pyrene-labeled actin fluorescence measurements. In the case of CaCl2, viscosity measurements resulted in a larger critical concentration, 0.7 mM. It turned out that actin filaments formed in a low concentration of CaCl2 were easily fragmented by shearing force. The higher the actin concentration, the lower the critical metal concentration was. The critical concentrations of actin above which actin can exist as a polymer at equilibrium became larger as the KCl, MgCl2, and CaCl2 concentrations were lower. It is advisable to add 0.05-0.1 mM CaCl2 to a depolymerization solution to obtain a concentrated monomeric solution. In the presence of cytochalasin D, which preferentially blocks the elongation at the barbed end of actin filaments, the critical concentrations of KCl and CaCl2 were the same as in its absence. On the other hand, the critical concentration of MgCl2 was increased and the extent of polymerization was decreased by cytochalasin D. In the presence of 50 mM KCl and 1 microM cytochalasin D, 0.01-0.1 mM MgCl2 markedly decreased the extent of polymerization of actin at equilibrium, where the critical actin concentration was tenfold increased. It is suggested that Mg2+ enhances dissociation of actin monomers at the pointed end of an actin filament.

Are amorphous aggregates of actin formed at the initial stage of polymerization?

Amorphous aggregates of actin of various sizes were observed under an electron microscope, when actin polymerization was inhibited or retarded by EDTA or by low salt concentration. It was first thought that these aggregates could be intermediate complexes of actin in the process of polymerization. These aggregates were, however, present in usual G-actin solution as well as column-chromatographed or highly clarified samples. In the samples prefixed with glutaraldehyde, the aggregates were also observed. Moreover, similar aggregates were seen in denatured actin samples. Hence it is concluded that these aggregates of actin are artefact products due to the treatment with uranyl acetate used for negative staining.

Effect of alteration of pheripheral blood flow on the central circulation in man during supine cycling in different ambient temperatures

Whether the alteration of peripheral circulation caused by changing ambient temperature (Ta) affects central circulatory changes in man during supine cycling was investigated in four well-trained men, who exercised at two levels (117.7 or 176.6 W). Exercise metabolic rate (VO2) in cold (0 degree C or 10 degrees C) was the same as it was at 20 degrees C, whereas the cardiac output (CO; CO2 rebreathing technique) and heart rate were significantly lower (e.g.,176.6 W at 0 degree C, both p < 0.01). In heat (30 degrees C or 40 degrees C), the VO2 reduced with falling CO and mean arterial blood pressure from those at 20 degrees C (e.g., 176.6 W at 40 degrees C, all cases p < 0.01), whereas the peak post-exercise calf blood (CBFp) increased (p < 0.01). The VO2 and stroke volume (SV) were inversely proportional to the ratio of CBFp to CO/kg body weight (CBFp/CO) (r > -0.78, p < 0.001). Total peripheral resistance (TPR) was related to arteriovenous oxygen difference (A-VO2 difference) (r > 0.78, p < 0.001). The TPR and A-VO2 difference decreased as Ta rose, while CBFp/CO was almost the same. As CBFp/CO had exceeded 50 and further progressed, however, the two parameters elevated until the same level as that at 0 degree C. The present results suggest that during moderately prolonged (16--60 min) supine cycling in different Ta's the central circulatory changes are mainly affected by the altered peripheral blood flow in competing between skin and muscle for blood flow.