Showing papers by "National Institute of Advanced Industrial Science and Technology published in 2000"
TL;DR: Eight extracts, methanol extracts of Acacia nilotica, Boswellia carterii, Embelia schimperi, Quercus infectoria, Trachyspermum ammi and water extracts of Piper cubeba, Q. infectoria and Syzygium aromaticum were the most active.
Abstract: One hundred fifty-two methanol and water extracts of different parts of 71 plants commonly used in Sudanese traditional medicine were screened for their inhibitory effects on hepatitis C virus (HCV) protease (PR) using in vitro assay methods. Thirty-four extracts showed significant inhibitory activity (>/=60% inhibition at 100 microg/mL). Of these, eight extracts, methanol extracts of Acacia nilotica, Boswellia carterii, Embelia schimperi, Quercus infectoria, Trachyspermum ammi and water extracts of Piper cubeba, Q. infectoria and Syzygium aromaticum, were the most active (>/=90% inhibition at 100 microg/mL). From the E. schimperi extract, two benzoquinones, embelin (I) and 5-O-methylembelin (II), were isolated and found as potent HCV-PR inhibitors with IC(50) values of 21 and 46 microM, respectively. Inhibitory activities of derivatives of I against HCV-PR as well as their effects on other serine proteases were also investigated.
295 citations
TL;DR: In this article, a model in which electric fields can induce mechanical deformation in the SPM via electrokinetically induced pressure gradients, was applied to the kinetics of the bending response.
235 citations
TL;DR: In this paper, a three-way microvalve system composed of three independent one-way valve units is presented, where each valve unit has a membrane, which is actuated by external negative air pressure.
Abstract: In this paper, a three-way microvalve system composed of three independent one-way valve units is presented. Each valve unit has a membrane, which is actuated by external negative air pressure. Intervals between the valve units are smaller than 780 µm, which opens up the possibility of realizing a high-density microvalve array. The small intervals were realized by providing the system with a layer of microchannels to conduct the air pressure to the valve units. In spite of the extra layer of microchannels, the device has been fabricated through a simple process by adopting polydimethylsiloxane (PDMS) as the material for the microchannel chips as well as the membrane. In particular, a newly developed technique for wafer level transfer of a PDMS membrane has been proven to be effective. Flow characteristics of the microvalve system for water are presented. The microvalve works in an on-off manner with hysteresis. No leakage has been observed in the closed state. In the open state, measured flow resistances (pressure drops) are within the range of 1.65-2.29 kPa (µl min -1)-1, and consistent with an electric circuit model.
207 citations
TL;DR: In this article, a new series of oxides Ca3-xBixCo4O9+δ, (x = 0.0−0.75) with Ca2Co2O5-type structures were synthesized, and their structures, electrical properties, Seebeck coefficients, and thermal conductivities were measured.
Abstract: A new series of oxides Ca3-xBixCo4O9+δ, (x = 0.0−0.75) with Ca2Co2O5-type structures were synthesized, and their structures, electrical properties, Seebeck coefficients, and thermal conductivities were measured. The values of Seebeck coefficients of the new oxides are all positive, showing that they are p-type conductors. Both the electrical conductivity and Seebeck coefficients increase with the increasing Bi contents which can be attributed to the increase of carrier mobility due to the larger size of Bi ion. The electrical conductivity, Seebeck coefficient, and the calculated value of the power factor of Ca3-xBixCo4O9+δ (x = 0.5) are 105 S cm-1, 160 μV K-1, and 2.7 × 10-4 W K-2 m-1 at 700 °C, respectively. The thermal conductivity of Ca3-xBixCo4O9+δ (x = 0.5) at room temperature is 1.14 W m-1 K-1 and increase slightly with the increasing temperature. At 700 °C, the figure of merit of Ca3-xBixCo4O9+δ (x = 0.5) is 2.0 × 10-4 K-1.
204 citations
TL;DR: A new anaerobic, thermophilic, syntrophic, fatty acid-oxidizing bacterium designated strain TGB-C1T was isolated from granular sludge in a UASB reactor and the optimal temperature for growth was around 55 degrees C and growth occurred in the range 45 to 60 degrees C as mentioned in this paper.
Abstract: A new anaerobic, thermophilic, syntrophic, fatty-acid-oxidizing bacterium designated strain TGB-C1T was isolated from granular sludge in a thermophilic upflow anaerobic sludge blanket (UASB) reactor. The cells were slightly curved rods and were weakly motile. Spore formation was not observed. The optimal temperature for growth was around 55 degrees C and growth occurred in the range 45 to 60 degrees C. The pH range for growth was 5.8-7.5, and the optimum pH was 6.5-7.0. Crotonate was the only substrate that allowed the strain to grow in pure culture. However, in co-culture with the thermophilic, hydrogenotrophic Methanobacterium thermoautotrophicum strain delta H, the isolate could syntrophically oxidize saturated fatty acids with 4-10 carbon atoms, including isobutyrate. During the degradation of isobutyrate by the co-culture, isobutyrate was isomerized to butyrate, which was then oxidized. The strain was not able to utilize sulfate, sulfite, thiosulfate, nitrate, fumarate or Fe(III) as electron acceptor. The DNA base composition was 51.0 mol%. 16S rDNA sequence analysis revealed that the strain belongs to the family Syntrophomonadaceae, but it was only distantly related to other known species of beta-oxidizing syntrophs. Hence, the name Syntrophothermus lipocalidus is proposed for TGB-C1T as a new species of a new genus.
182 citations
TL;DR: In this paper, high-resolution x-ray diffraction measurements show an increase in lateral coherence length from several tens of nanometers to > 0.7μm for growth of c-oriented ZnO on the a surface as opposed to the c surface of sapphire.
Abstract: High-quality, c-oriented ZnO epitaxial films have been grown on the a surface using molecular-beam epitaxy. The use of a-oriented sapphire eliminates rotational domains and related structural defects which have limited the use of ZnO in electronic applications. The ZnO epitaxial layers are uniquely oriented with the ZnO/sapphire orientational relationship [0001]‖[1120] and 〈1120〉‖[0001]. This unique orientation is a consequence of the anisotropy of the a-sapphire surface in conjunction with a strong correlation along a single direction leading to the term uniaxial locked epitaxy. High-resolution x-ray diffraction measurements show an increase in x-ray lateral coherence length from several tens of nanometers to >0.7 μm for growth of c-oriented ZnO on the a surface as opposed to the c surface of sapphire.
176 citations
31 Oct 2000
TL;DR: The hardware design of a novel self-reconfigurable robotic system which functions as a robotic system such as a legged walking machine and its simple structure and reliable operation allows it to construct large 3D self- reconfigurable structure.
Abstract: In this paper we describe the hardware design of a novel self-reconfigurable robotic system. We have classified previous studies on self-reconfigurable robotic systems into "lattice type" composed of spatially symmetric modules and "string type" like snake robots. The proposed system has both the advantages of simple operation of self-reconfiguration of the former and motion generation ability of the latter. Its simple structure and reliable operation allows us to construct large 3D self-reconfigurable structure which functions as a robotic system such as a legged walking machine. We have examined its basic mechanical functions and verified its reliable operation of self-reconfiguration.
149 citations
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08 Dec 2000TL;DR: In this article, a biodegradable resin composition containing a polylactic acid polymer and a mamman digestion product such as a mannooligosaccharide is presented.
Abstract: The present invention provides a biodegradable resin composition with improved biodegradability or with an additional useful function (antibacterial properties), while maintaining the mechanical properties of the biodegradable resin. More specifically, the present invention provides a biodegradable resin composition containing a biodegradable resin such as a polylactic acid polymer and a mamman digestion product such as a mannooligosaccharide. The present invention further provides various biodegradable products produced by molding this biodegradable resin composition into desired shapes.
143 citations
31 Oct 2000
TL;DR: The matrix method can calculate a compliance matrix with less nodes of matrix than conventional finite element method and is well applicable to a flexure mechanism with circular notched hinges as the authors' micro parallel mechanism because it is approximate to the Rahmen structure.
Abstract: We apply the matrix method to kinematic analysis of our translational 3-DOF micro parallel mechanism for an instance of general flexure mechanisms. The matrix method has been well developed in architecture to analyze a frame structure. We found that this method is well applicable to such a flexure mechanism with circular notched hinges as our micro parallel mechanism because it is approximate to the Rahmen structure. Our matrix method can calculate a compliance matrix with less nodes of matrix than conventional finite element method. First, the compliance matrices of a circular notched hinge and some other beams are defined and the coordinate transformations of compliance matrix are introduced. Next, an analysis of our micro parallel mechanism is demonstrated.
123 citations
TL;DR: In this paper, the microstructure, wettability, and thermal stability of self-assembled monolayers (SAMs) on gold generated from semifluorinated alkanethiols F(CF2)10(CH2)nSH, where n = 2, 6, 11, 17, and 33 (F10HnSH), were examined by polarization modulation infrared reflection absoprtion spectroscopy (PM-IRRAS) and dynamic contact angle measurements.
Abstract: The microstructure, wettability, and thermal stability of self-assembled monolayers (SAMs) on gold generated from semifluorinated alkanethiols F(CF2)10(CH2)nSH, where n = 2, 6, 11, 17, and 33 (F10HnSH), were examined by polarization modulation infrared reflection absoprtion spectroscopy (PM-IRRAS) and dynamic contact angle measurements. Analysis by PM-IRRAS revealed that the length of the methylene spacer (Hn) influenced the tilt angle of the fluorocarbon segments in the semifluorinated SAMs. As the length of the methylene spacer was increased, the tilt angle of the perfluorocarbon moiety increased with respect to the surface normal. The longer methylene spacers (Hn, n = 11, 17, and 33) exhibited well-ordered trans-extended conformations as indicated by the position of the antisymmetric methylene band (νaCH2 = 2919 cm-1). Shortening the length of the methylene spacer to n = 6, however, led to a decrease in conformational order (νaCH2 = 2925 cm-1). Dynamic contact angle measurements using the Wilhelmy plat...
115 citations
TL;DR: In this article, the authors measured the thermal conductivity of carbon-bonded carbon fiber and showed that the thermal expansion anisotropy was consistent with a c-axis radial orientation of the pyrolytic carbon around the fibers in the CVI densified composite.
24 Apr 2000
TL;DR: A white-box actuator model is proposed on the basis of physicochemical hypotheses on the motion principle which are supported at present and results show higher accuracy on transient response and nonlinear characteristics in comparison with conventional models.
Abstract: The ICPF (ionic conducting polymer gel film) actuator is a new high polymer gel actuator by which revolutionary robotic mechanisms are expected. Actuator models for CAE are essential to the robotic design. However, present black/gray-box models of ICPF cannot express its nonlinear characteristics with enough accuracy. In this paper, a white-box actuator model is proposed on the basis of physicochemical hypotheses on the motion principle which are supported at present. In this model, travel of sodium ions and water molecules in the actuator membrane is modeled. Internal stress is generated by swell and contraction of the gel by water content change, electrostatic force of fixed sulfonic acid groups, and momentum conservation effect. Simulation results show higher accuracy on transient response and nonlinear characteristics in comparison with conventional models.
TL;DR: In this paper, the cumulative interactive effect of substrate, water concentration and time was studied in optimizing the hydrolysis of methyloleate using lipase from Chromobacterium viscosum immobilized on IRC-50.
Abstract: Hydrolysis of methyloleate was optimized using lipase from Chromobacterium viscosum immobilized on IRC-50. The optimization was studied by a statistical methodology using response surface methodology (RSM). The cumulative interactive effect of substrate, water concentration and time was studied in optimizing the hydrolysis of methyloleate. The interactive effect of substrate-time was found to be significant compared to substrate-water and time-water interactions. A well correlation was observed between the optimum values obtained from the response surface contour plots and from the quadratic regression model equation. The optimal values obtained for substrate, water and time were found to be in the experimental range chosen.
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20 Apr 2000TL;DR: In this paper, a method for determining a concentration of a target nucleic acid by using a probe labeled with a fluorescent dye is presented, which is capable of reducing fluorescence emission from the fluorescent dye when hybridized with the target n-acid.
Abstract: A method is provided for determining a concentration of a target nucleic acid by using a nucleic acid probe labeled with a fluorescent dye. The method comprises: providing, as the probe, a nucleic acid probe capable of reducing fluorescence emission from the fluorescent dye when hybridized with the target nucleic acid; hybridizing the probe to the target nucleic acid; and measuring a decrease in fluorescence emission from the fluorescent dye after the hybridization relative to fluorescence emission from the fluorescent dye before the hybridization.
TL;DR: In this paper, the authors investigated the propene epoxidation of propene using H2 and O2 over Au/Ti-MCM-41 at various temperatures and at a space velocity of 4000h−1.
Abstract: Vapor-phase epoxidation of propene using H2 and O2 over Au/Ti-MCM-41 with or without a promoter has been investigated at various temperatures and at a space velocity of 4000 h−1. ml/g (cat). As a promoter, CsCl was impregnated and/or physically (simple mixing) or mechanically (crushed in a mortar) mixed at various concentrations. The support, Ti-MCM-41 (Ti/Si = 3/100), was characterized by XRD, UV-Vis, FT-IR, and specific surface area measurement, whereas Au/Ti-MCM-41 with or without a promoter was characterized by TEM, XPS and ICP techniques before and/or after the catalytic tests. Au/Ti-MCM-41 as such gives propene and H2 conversions of 3.1 and 47%, respectively, with a PO selectivity of 92% at the reaction temperature of 100°C after 60 min of reaction. Physical mixing of CsCl with Au supported on Ti-MCM-41 reduces H2 consumption by about 90% and improves propene oxide (PO) selectivity up to 97% at a propene conversion of 1.7%. One constraint is that agglomeration of gold particles is caused by Cl− anions; the mean diameter of Au particles, 2.2 nm, in Au/Ti-MCM-41 increases to about 10–20 nm and some clusters are even larger than 50 nm in size due to direct contact between chloride and Au particles.
TL;DR: A new Gram-positive non-spore-forming bacterium was isolated from an activated sludge reactor showing enhanced biological phosphorus removal activity and it is proposed that a new genus and species, Micropruina glycogenica, should be created for the new isolate.
Abstract: A new Gram-positive non-spore-forming bacterium, strain Lg2T, was isolated from an activated sludge reactor showing enhanced biological phosphorus removal activity. The new isolate was a slowly growing organism and was capable of accumulating large amounts of intracellular glycogen from substrate taken up. Both oxidase and catalase were produced. The new isolate contained meso-diaminopimelic acid (DAP) in the cell wall. Complex fatty acid patterns with iso-C14:0, anteiso-C15:0, C16:0, iso-C16:0 and four other minor saturated or unsaturated straight-chain fatty acids were detected. The isolate contained a high genomic G+C content (70.5 mol%). Phylogenetic analysis based on the 16S rRNA gene sequence placed the isolate in the high G+C Gram-positive group with Microlunatus phosphovorus and Friedmanniella antarctica as the closest relatives (sequence similarities are 93 and 92 %, respectively). These three organisms shared common features in morphology, but strain Lg2T could be differentiated from the other species by its peptidoglycan type (meso-DAP), fatty acid composition, carbon source utilization profile and G+C content. On the basis of these findings, it is proposed that a new genus and species, Micropruina glycogenica, should be created for the new isolate; the type strain is strain Lg2T (= JCM 10248T).
TL;DR: In this paper, the dielectric anomaries at the phase transitions of Lu(Fe 2+ Fe 3+ )O 4, which is considered as a charge and spin frustrated system, were reported.
Abstract: We report the dielectric anomaries at the phase transitions of Lu(Fe 2+ Fe 3+ )O 4 , which is considered as a charge and spin frustrated system. Dielectric constant shows a hump, just above the transition from the high temperature two-dimensional to the low temperature three-dimensional charge ordering. A few glassy behaviors were observed at this transition. The presence of spontaneous polarization in the low temperature phase was confirmed by the measurement of pyroelectricity. A step-wise increase of the dielectric constant with increasing temperature was observed between 150 K and 250 K as in other RFe 2 O 4 . These phenomena are explained by the presence of the polar domains with the ordering of Fe 2+ and Fe 3+ and the motions of the antiphase boundaries between them.
01 Feb 2000
TL;DR: A probabilistic model of human motion is proposed which is based on motion probability grids generated from observed motion and integrated with an autonomous mobile robot system, with a laser range sensor detecting humans moving within the environment, and a path planning system.
Abstract: In order to effectively plan paths in environments inhabited by humans, robots must accurately predict human motion. Typical approaches to human prediction simply assume a constant velocity which is not always valid. This paper proposes to determine the likely navigation intent of humans and use that to predict human motion. Navigation intent is determined by the function and structure of the environment. Manually assigned functional places are combined with automatically extracted navigation way-points to define a number of likely navigation targets within the environment. To predict human motion toward these targets, a probabilistic model of human motion is proposed which is based on motion probability grids generated from observed motion. The models of human navigation intent and motion are integrated with an autonomous mobile robot system, with a laser range sensor detecting humans moving within the environment, and a path planning system. The models of human navigation intent and motion are verified using real captured human motion data from an office environment. Examples of human motion prediction are also presented.
TL;DR: In this paper, large-area mesoporous silicate thin films are reported to be formed on solid silica substrates by the simple technique of spin-coating, and the mesophase of the films can be controlled to be one-dimensional hexagonal, cubic, or lamellar by adjusting the casting solution composition, i.e., mainly the ratio of surfactant to tetraethyl orthosilicate.
Abstract: Large-area mesoporous silicate thin films are reported to be formed on solid silica substrates by the simple technique of spin-coating. The mesophase of the films can be controlled to be one-dimensional hexagonal, cubic, or lamellar by adjusting the casting solution composition, i.e., mainly the ratio of surfactant to tetraethyl orthosilicate (TEOS). The X-ray diffraction results leading to the assignment of the mesophase types are presented and reasons for the change of phase with solution composition discussed. The films are expected to have applications in catalysis, molecular separation, and sensors.
TL;DR: In this paper, an isochronal annealing experiment revealed that unrelaxed oxygen vacancies ODC(II) and interstitial oxygen were generated as dominant species during the irradiation.
Abstract: Properties of defects induced by irradiation with a near-infrared femtosecond laser beam into vitreous silica are reported. Three photoluminescence bands with photon energy of 1.9, 2.7, and 4.4 eV were observed under an excitation of 5.0 eV. An isochronal annealing experiment revealed that unrelaxed oxygen vacancies ODC(II) and interstitial oxygen were generated as dominant species during the irradiation. In the annealing, diffusion of the interstitial oxygen was thermally activated, leading to a direct reduction of oxygen-deficiency-related defects such as ODC(II) and E‘ center. The concentration of oxygen-excess-related defects such as peroxy radicals, together with nonbridging oxygen−hole centers, increased first with annealing then decreased with the exhaustion of oxygen and their precursor, the E‘ center. The recombination of oxygen vacancies with interstitial oxygen is characterized as the major process occurring during the annealing.
TL;DR: In this article, the authors showed that the catalytic activity of methanol to carbon monoxide and hydrogen can be increased with an increase in the content of nickel up to 40 wt.%.
Abstract: The decomposition of methanol to carbon monoxide and hydrogen can be catalyzed at 250°C over nickel supported on silica. The activity of the catalyst prepared by a sol–gel method increases with an increase in the content of nickel up to 40 wt.% while that for the sample prepared by an impregnation technique almost reaches a plateau at the nickel content of 10 wt.%. The activity does not relate simply to the nickel surface area of the sample, but it depends on the amounts of carbon monoxide and hydrogen strongly adsorbed on the catalyst. Small nickel particles are disadvantageous in the reaction.
TL;DR: In this article, semi-fluorinated alkanethiols (SFATs) were found to form highly ordered and densely packed self-assembled monolayers on both polycrystalline Au and Ag substrates.
Abstract: Self-assembled monolayers (SAMs) formed from semifluorinated alkanethiols (SFATs) CF3(CF2)9(CH2)nSH (F10HnSH: n = 2, 11, and 17) on poly-crystalline Au and Ag were characterized by X-ray photoelectron spectroscopy, infrared reflection absorption spectroscopy, and near edge X-ray absorption fine structure spectroscopy. SFATs were found to form highly ordered and densely packed SAMs on both substrates. The molecules are strongly bonded to the substrates via their sulfur head groups, in the same manner as conventional alkanethiol (AT) SAMs. The hydrocarbon (except for n = 2) and fluorocarbon parts of the adsorbed SFATs retain the expected planar zigzag and helical conformations of the respective bulk materials. The orientation of the fluorocarbon chains does not depend on the substrate. These entities are almost perpendicular to the substrate in F10H2S/Au and F10H2S/Ag and become slightly more tilted in SFAT SAMs with longer hydrocarbon moieties. However, the alkyl parts of the SFAT films exhibit tilt and twist angles that are similar to those of normal alkanethiol films on Ag and Au substrates despite the reduced packing density in the SFAT films as compared to normal AT SAMs. We suggest that the substrate-related differences in tilt and twist angles for both systems are associated with the different character of the head-group-substrate bonding on Au and Ag.
TL;DR: Diploid yeast cells repeatedly polarize and bud from their poles, probably because of highly stable marks of unknown composition, and Rax2, a membrane protein, was shown to behave as such a mark.
Abstract: Diploid yeast cells repeatedly polarize and bud from their poles, probably because of highly stable marks of unknown composition. Here, Rax2, a membrane protein, was shown to behave as such a mark. The Rax2 protein itself was inherited immutably at the cell cortex for multiple generations, and Rax2 was shown to have a half-life exceeding several generations. The persistent inheritance of cortical protein markers would provide a means to couple a cell's history to the future development of a precise morphogenetic form.
TL;DR: It is shown for the first time that overexpression of mot‐2 in normal human cells is able to permit their temporary escape from senescence.
Patent•
14 Sep 2000TL;DR: In this paper, a three-dimensional crosslinked silicon-oxygen structure is proposed for a proton-conducting membrane, which includes a carbon-containing compound and inorganic acid, characterized by a phase-separated structure.
Abstract: A proton-conducting membrane, excellent in resistance to heat, durability, dimensional stability and fuel barrier characteristics, and showing excellent proton conductivity at high temperature and a method for producing the same. A proton-conducting membrane includes a carbon-containing compound and inorganic acid, characterized by a phase-separated structure containing a carbon-containing phase containing at least 80% by volume of the carbon-containing compound and inorganic phase containing at least 80% by volume of the inorganic acid, the inorganic phase forming the continuous ion-conducting paths. The method for producing the above proton-conducting membrane includes steps of preparing a mixture of a carbon-containing compound (D) having one or more hydrolyzable silyl groups and inorganic acid (C), forming the above mixture into a film, and hydrolyzing/condensing the hydrolyzable silyl group contained in the mixture formed into the film, to form a three-dimensionally crosslinked silicon-oxygen structure (A). The above proton-conducting membrane is incorporated in a fuel cell.
TL;DR: In this article, the catalytic activities of Pt and Au supported on TiO2 were compared with respect to the oxidation of CO and propane, and the results are consistent with a model in which the perimeter sites have a special role in the CO oxidation reaction over Au catalysts.
Abstract: The catalytic activities of Pt and Au supported on TiO2 were compared with respect to the oxidation of CO and propane. While the Au catalysts showed higher activities for CO oxidation, the Pt catalysts were more active for propane combustion. A strong de-activation of the CO oxidation activity by SO2 was observed only over the TiO2-supported Au catalyst, indicating that SO2 can block the active sites for CO oxidation over Au catalysts. The results are consistent with a model in which the perimeter sites have a special role in the CO oxidation reaction over Au catalysts.
TL;DR: Gel polymer electrolytes based on a copolymer poly(vinylidene fluoride (VdF)/hexafluoropropylene (HFP)) and a solution of ethylene carbonate, diethyl carbonate (DEC) and as a salt LiN(CF 3 SO 2 ) 2 were prepared by changing the content of the polymer in the range 20 −80 wt%. The effects of changing the salt concentration in the solution were also explored as discussed by the authors.
03 Dec 2000
TL;DR: This work has built an experimental system to investigate the remote cooperation in MOMR teleoperation, and different coordinated control methods are proposed to cope with the collision, arising from the time delay over the network.
Abstract: Various coordinated control schemes are explored in the multi-operator-multi-robot (MOMR) tele-collaborative system through a network with time delay. Multi-robot cooperation has rapidly emerged in many possible applications such as the plant maintenance, construction, and surgery, because it would have a significant advantage over a single robot in such cases. Thus, time-delayed control of a multi-robot system is expected to play an important role in remote operations, too. However, the effect of time-delay would pose a more difficult problem to the MOMR teleoperation systems and seriously affect their performance. In this work, first, we have built an experimental system to investigate the remote cooperation in MOMR teleoperation. Then, different coordinated control methods are proposed to cope with the collision, arising from the time delay over the network. To verify the validity of the proposed schemes, we have carried out various experiments on a planar block arrangement by two slave arms employing graphic simulators and a LAN subject to a significant communication delay.
TL;DR: In this paper, the crystal structure and transition metal valancy in LiFe{sub x}Co{sub 1{minus}x}O{sub 2} cells were examined using ex situ X-ray diffraction measurements, Fe and Co K-X-ray adsorption near edge spectroscopy (XANES) and {sup 57}Fe Mossbauer spectroscope.
Abstract: Changes in the crystal structure and transition metal valancy in LiFe{sub x}Co{sub 1{minus}x}O{sub 2}(0 {le} x {le} 0.25) positive electrodes during the charge-discharge of Li/LiFe{sub x}Co{sub 1{minus}x}O{sub 2} cells were examined using ex situ X-ray diffraction measurements, Fe and Co K-X-ray adsorption near edge spectroscopy (XANES) and {sup 57}Fe Mossbauer spectroscopy. An iron-doped host material with rhombohedral symmetry was obtained up to 25% Fe per formula unit in LiCoO{sub 2} by hydrothermal reaction below 300 C from a mixture of Co{sup 3+}-Fe{sup 3+} coprecipitate (iron-doped CoOOH) and LiOH. No symmetry changes were observed during electrochemical charge-discharge tests up to the tenth cycle. The structures of Li-extracted and reinserted samples were determined by a model similar to LiCoO{sub 2} prepared at low temperature in which Li ions are located at the interstitial 6c and octahedral 3a sites. {sup 57}Fe Mossbauer and Fe and Co K-XANES spectra at 293 K indicated the presence of tetravalent Fe ions upon oxidation up to 4.3 V.