Si1-xGex anode synthesis on plastic films for flexible rechargeable batteries.

SiGe is a promising anode material for replacing graphite in next generation thin-film batteries owing to its high theoretical charge/discharge capacity. Metal-induced layer exchange (LE) is a unique technique used for the low-temperature synthesis of SiGe layers on arbitrary substrates. Here, we demonstrate the synthesis of Si1-xGex (x = 0-1) layers on plastic films using Al-induced LE. The resulting SiGe layers exhibited high electrical conductivity (up to 1200 S cm-1), reflecting the self-organized doping effect of LE. Moreover, the Si1-xGex layer synthesized by the same process was adopted as the anode for the lithium-ion battery. All Si1-xGex anodes showed clear charge/discharge operation and high coulombic efficiency (≥ 97%) after 100 cycles. While the discharge capacities almost reflected the theoretical values at each x at 0.1 C, the capacity degradation with increasing current rate strongly depended on x. Si-rich samples exhibited high initial capacity and low capacity retention, while Ge-rich samples showed contrasting characteristics. In particular, the Si1-xGex layers with x ≥ 0.8 showed excellent current rate performance owing to their high electrical conductivity and low volume expansion, maintaining a high capacity (> 500 mAh g-1) even at a high current rate (10 C). Thus, we revealed the relationship between SiGe composition and anode characteristics for the SiGe layers formed by LE at low temperatures. These results will pave the way for the next generation of flexible batteries based on SiGe anodes.

Grain size dependent photoresponsivity in GaAs films formed on glass with Ge seed layers.

The strong correlation between grain size and photoresponsivity in polycrystalline GaAs films on glass was experimentally demonstrated using Ge seed layers with a wide range of grain sizes (1‒330 µm). The crystal evaluations using Raman spectroscopy, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy revealed that 500-nm-thick GaAs films epitaxially grown from the Ge seed layers at 550 °C inherited the grain boundaries and crystal orientations in Ge. With increasing grain size, the photoresponsivity corresponding to GaAs increased from 0.01 to 3 A W-1 under a bias voltage of 0.3 V. The maximum value approached that of the GaAs film formed simultaneously on a single-crystal Ge wafer, indicating the high potential of the large-grained GaAs film. Knowledge gained from this study will be essential for designing advanced solar cells based on polycrystalline III-V compound semiconductors using inexpensive substrates.

High-electron-mobility (370 cm2/Vs) polycrystalline Ge on an insulator formed by As-doped solid-phase crystallization.

High-electron-mobility polycrystalline Ge (poly-Ge) thin films are difficult to form because of their poor crystallinity, defect-induced acceptors and low solid solubility of n-type dopants. Here, we found that As doping into amorphous Ge significantly influenced the subsequent solid-phase crystallization. Although excessive As doping degraded the crystallinity of the poly-Ge, the appropriate amount of As (~1020 cm-3) promoted lateral growth and increased the Ge grain size to approximately 20 µm at a growth temperature of 375 °C. Moreover, neutral As atoms in poly-Ge reduced the trap-state density and energy barrier height of the grain boundaries. These properties reduced grain boundary scattering and allowed for an electron mobility of 370 cm2/Vs at an electron concentration of 5 × 1018 cm-3 after post annealing at 500 °C. The electron mobility further exceeds that of any other n-type poly-Ge layers and even that of single-crystal Si wafers with n ≥ 1018 cm-3. The low-temperature synthesis of high-mobility Ge on insulators will provide a pathway for the monolithic integration of high-performance Ge-CMOS onto Si-LSIs and flat-panel displays.

Fabrication of SrGe2 thin films on Ge (100), (110), and (111) substrates.

Semiconductor strontium digermanide (SrGe2) has a large absorption coefficient in the near-infrared light region and is expected to be useful for multijunction solar cells. This study firstly demonstrates the formation of SrGe2 thin films via a reactive deposition epitaxy on Ge substrates. The growth morphology of SrGe2 dramatically changed depending on the growth temperature (300-700 °C) and the crystal orientation of the Ge substrate. We succeeded in obtaining single-oriented SrGe2 using a Ge (110) substrate at 500 °C. Development on Si or glass substrates will lead to the application of SrGe2 to high-efficiency thin-film solar cells.

Quantification of suppression of bitterness using an electronic tongue.

Phospholipids, such as phosphatidic acid, suppress bitter taste without affecting other taste qualities. In the present study, we detected and quantified this suppression effect with an electronic tongue whose transducer is composed of several kinds of lipid/polymer membranes with different characteristics. We measured a phospholipid cocktail and various kinds of taste substances with five basic taste qualities. The responses to quinine hydrochloride and L-tryptophan, which have a bitter taste, were reduced as the phospholipid concentration was increased, and the responses to the other taste substances were not affected by the phospholipids, as with the human sensation test. Furthermore, the change of bitter intensity caused by phospholipid was quantified by principal component analysis and the tau scale, which expresses the relationship between taste intensity and taste substance concentration. The results are compared with those of the human sensory test and discussed.

Electronic tongue.

A taste sensor with global selectivity is composed of several kinds of lipid/polymer membranes for transforming information of taste substances into an electric signal. The output of this electronic tongue shows different patterns for chemical substances which have different taste qualities, such as saltiness and sourness. Amino acids can be classified into several groups according to their own tastes from sensor outputs. The taste of foodstuffs such as beer, sake, coffee, mineral water, milk and vegetables can be discussed quantitatively using the electronic tongue, which provides the objective scale for the human sensory expression.

Detection of suppression of bitterness by sweet substance using a multichannel taste sensor.

A multichannel taste sensor whose transducer is composed of several kinds of lipid/polymer membranes with different characteristics can detect taste in a manner similar to human gustatory sensation. Taste information is transformed into a pattern composed of electric signals of membrane potentials of the receptor part. In the present study, it was shown that the suppression of the bitterness of quinine and a drug substance by sucrose can be quantified using a multichannel taste sensor. The present method can be expected to provide a new automated method to measure the strength of bitterness of drug substance in the place of sensory evaluation.

Antitumor activity and low intestinal toxicity of S-1, a new formulation of oral tegafur, in experimental tumor models in rats.

S-1, a new oral antitumor agent, is composed of 1-(2-tetrahydrofuryl)-5-fluorouracil (Tegafur, FT), 5-chloro-2,4-dihydroxypyridine (CDHP) and potassium oxonate (Oxo) in a molar ratio of 1:0.4:1. FT which is a masked compound of 5-fluorouracil (5-FU) acts as an effector, while both CDHP and Oxo which do not have antitumor activity themselves act as modulators. In this study, the antitumor activity and intestinal toxicity of S-1 were investigated using experimental tumor models in rats, and compared with those of other oral fluoropyrimidines, namely 5-FU, FT, FCD (1 M FT/0.4 M CDHP) and UFT (combination of FT and uracil). In rats bearing subcutaneous Yoshida sarcoma, S-1 inhibited tumor growth at the lowest dose (ED50 value: S-1 5, UFT 22, FT 82, FCD 5, and 5-FU 19 mg/kg per day), and induced the least host body weight suppression, leading to the highest therapeutic index (TI) (S-1 4.5, UFT 1.4, FT 1.8, FCD 2.0, and 5-FU 1.4). S-1 also showed a higher therapeutic effect than UFT against AH-130 and Sato lung carcinoma. After administration of S-1 and UFT at equitoxic doses, S-1 showed a higher and more prolonged concentration of 5-FU than UFT both in plasma (AUC0-infinity: S-1 28 nmolh/ml, UFT 15 nmol.h/ml) and in tumor tissue (AUC0-infinity: S-1 95 nmolh/g tissue, UFT 52 nmolh/g tissue), leading to a higher 5-FU level incorporated into the RNA fraction (F-RNA level) in tumor tissue (AUC0-24: S-1 7.0 nmolh/mg RNA, UFT 4.3 nmolh/mg RNA) and 5-8% higher thymidylate synthase (TS) inhibition in tumor tissue at every time-point through 24 h. Compared with other oral fluoropyrimidines after administration of the maximal tolerable dose (MTD), S-1 caused the lowest rates of intestinal toxicities, such as diarrhea and occult blood in feces. S-1 also showed a higher antitumor effect on Yoshida sarcoma implanted intracolonically than UFT at an equitoxic dose (tumor weight: S-1 64 +/- 30 mg, UFT 133 +/- 52 mg; P < 0.05). These results suggest that CDHP, which is a potent inhibitor of 5-FU degradation, increases the antitumor activity of FT, and that Oxo, which is an inhibitor of 5-FU phosphorylation, locally protects the gastrointestinal tract from 5-FU-induced toxicity without decreasing the antitumor activity.

Change in electric characteristics of membranes in response to taste stimuli with increasing amount of lipids in membrane matrix of PVC and plasticizer.

Changes in membrane electric potential in response to taste substances were studied for membranes containing differing amounts of negatively charged lipids in the membrane matrix of polyvinyl chloride and plasticizer. Responses to quinine showing bitterness decreased systematically with increasing the quantity of charged lipids contained in the membrane, whereas the response did not depend on differences in the hydrocarbon chains of lipids. The mechanism is discussed qualitatively in terms of hydrophobicity and hydrophilicity of the membranes.

Theory of electric characteristics of the lipid/PVC/DOPP membrane and PVC/DOPP membrane in response to taste stimuli.

Electric characteristics of two kinds of membranes in response to NaCl and quinine were theoretically studied; one membrane composed of polyvinyl chloride (PVC) and dioctylphenylphosphonate (DOPP), and the other a lipid/PVC/DOPP membrane containing PVC, DOPP and a negatively charged lipid. We develop a theory by taking into account both the surface electric potential and the diffusion potential within the membrane and succeed in interpreting the observed data. On increasing the NaCl concentration, the lipid/PVC/DOPP membrane changes from weakly charged state to fully charged state by dissociation of H+ from the lipids. The hydrophobic interaction between quinine and the PVC/DOPP membrane was strong enough to overcome the electric repulsion.

Early Gravi-Electrical Responses in Bean Epicotyls.

The relationship between gravitropism and surface electrical potentials was studied using etiolated epicotyls of adzuki bean (Phaseolus angularis). Early downward curvature (or transient positive gravitropic response) was observed about 1 min after gravistimulation. The downward curvature was closely related to the speed of the subsequent upward curvature. Surface electrical potentials decreased cooperatively in a limited region on the upper side within only 0.5 to 2 min. This is the earliest event found so far to follow gravistimulation of intact epicotyls. The rapid change in the potential had a high correlation with the early downward curvature and also the subsequent negative gravitropism. It is suggested that the rapid potential change plays an important role in gravity perception.

Responses of lipid membranes of taste sensor to astringent and pungent substances.

Astringent substances and pungent substances were studied using a multichannel taste sensor with lipid membranes. The electric-potential pattern constructed of eight outputs from the membranes has information of taste quality and intensity. Pungent substances, such as capsaicin, piperine and allyl isothiocyanate, had no effect on the membrane potentials of the lipid membranes. On the other hand, astringent substances such as tannic acid, catechin, gallic acid and chlorogenic acid changed the potentials remarkably. A principal component analysis of the patterns in electric potential changes caused by the taste substances revealed the astringency is located between bitterness and sourness.

Multichannel taste sensor using electric potential changes in lipid membranes.

A taste sensor with a multichannel electrode was developed by using lipid membranes as a transducer of taste substances. The sensor can detect the taste in a similar manner to the human gustatory sensation by response patterns of electric potential to taste substances. The sensitivity, reproducibility and durability were superior to those of humans. The same taste as that elicited by some commercial aqueous drink was reproduced by making aqueous solution mixed from four kinds of basic taste substances, the concentrations of which were determined so that the electric-potential pattern of this mixed solution could agree well with the pattern by the drink. Different brands of beer were easily distinguished by the electric-potential patterns.

Dependence of the thymidylate synthase inhibition rate on the interval after the last administration of tegafur in sigmoid colon cancer patients.

The thymidylate synthase (TS) inhibition rate was measured after tegafur (FT) administration (1.5 g/day, at least 10 days) in 7 sigmoid colon cancer patients. The TS inhibition rate decreased as the interval between the time of the last administration and the time of the tumor resection increased longer. This study provides basic data for considering methods of drug administration and assessment of modification, for example, by leucovorin.

Electric current precedes emergence of a lateral root in higher plants.

Stable electrochemical patterns appear spontaneously around roots of higher plants and are closely related to growth. An electric potential pattern accompanied by lateral root emergence was measured along the surface of the primary root of adzuki bean (Phaseolus angularis) over 21 h using a microelectrode manipulated by a newly developed apparatus. The electric potential became lower at the point where a lateral root emerged. This change preceded the emergence of the lateral root by about 10 h. A theory is presented for calculating two-dimensional patterns of electric potential and electric current density around the primary root (and a lateral root) using only data on the one-dimensional electric potential measured near the surface of the primary root. The development of the lateral root inside the primary root is associated with the influx of electric current of about 0.7 muA.cm(-2) at the surface.

Electrical characteristics in an excitable element of lipid membrane.

Electrical characteristics in a membrane constructed from a porous filter adsorbed with a lipid analogue, dioleoyl phosphate (DOPH), were investigated in a situation interposed between 100 mM NaCl + 3 mM CaCl2 and 100 mM KCl. Calcium ions affected significantly the membrane characteristics. The membrane potential was negative on the KCl side, which implies the higher permeability to K+ than Na+; this tendency was increased by a tiny amount of Ca2+. While the membrane showed a low electrical resistance of several k omega . cm2 under K+/Na+ gradient, it showed several M omega . cm2 by Ca2+. The surface structure of the membrane exhibited many voids in the low-resistance state, but the surface was covered by oil droplets in the high-resistance state. Oscillations of the membrane potential appeared spontaneously with application of the electrical current from the KCl side to the NaCl + CaCl2 side. The frequency was increased with the electrical current. All these results were explained comprehensively using an electrochemical kinetic model taking account of the Ca2+ binding effect, where DOPH assemblies make a phase transition between oil droplets due to Ca2+ and multi-bilayers with excess K+. The oscillation arises from coupling of the phase transition to accumulation and release of K+ or Ca2+. This membrane can be used as an excitable element regulated by Ca2+ in neuro-computer devices.

Electrical Potentials during Gravitropism in Bean Epicotyls.

An apparatus for measuring simultaneously the surface electrical potentials along epicotyl was developed to study the largely bending situation by gravity. Potentials increased on the upper side and decreased on the lower side after the horizontal placement. The time course of electrical changes consisted of two components which correspond to growth movements observed during gravitropism.

Effect of local anesthetics on the electrical characteristics of an excitable model membrane composed of dioleyl phosphate I. Static and steady-state response.

The local anesthetics, tetracaine, procaine and lidocaine, interacted with a negatively charged lipid membrane composed of dioleyl phosphate (DOPH), which exhibited a self-sustained oscillation of the membrane potential. The anesthetics depolarized the membrane potential when present in increasing concentrations, whereas they increased the membrane resistance at low concentrations and decreased it at high concentrations. The above results were analyzed on the basis of electrochemical theory taking into account ion flux across the membrane. The electrical characteristics are affected by both the hydrophobicity and the diffusion constant of local anesthetics within the membrane.