Showing papers by "Tokyo University of Science published in 2002"
TL;DR: X-ray diffraction and absorption is used to show that LaFe0.05O3, one of the perovskite-based catalysts investigated for catalytic converter applications since the early 1970s, retains its high metal dispersion owing to structural responses to the fluctuations in exhaust-gas composition that occur in state-of-the-art petrol engines.
Abstract: Catalytic converters are widely used to reduce the amounts of nitrogen oxides, carbon monoxide and unburned hydrocarbons in automotive emissions. The catalysts are finely divided precious-metal particles dispersed on a solid support. During vehicle use, the converter is exposed to heat, which causes the metal particles to agglomerate and grow, and their overall surface area to decrease. As a result, catalyst activity deteriorates. The problem has been exacerbated in recent years by the trend to install catalytic converters closer to the engine, which ensures immediate activation of the catalyst on engine start-up, but also places demanding requirements on the catalyst's heat resistance. Conventional catalyst systems thus incorporate a sufficient excess of precious metal to guarantee continuous catalytic activity for vehicle use over 50,000 miles (80,000 km). Here we use X-ray diffraction and absorption to show that LaFe0.57Co0.38Pd0.05O3, one of the perovskite-based catalysts investigated1,2,3,4 for catalytic converter applications since the early 1970s, retains its high metal dispersion owing to structural responses to the fluctuations in exhaust-gas composition that occur in state-of-the-art petrol engines5. We find that as the catalyst is cycled between oxidative and reductive atmospheres typically encountered in exhaust gas, palladium (Pd) reversibly moves into and out of the perovskite lattice. This movement appears to suppress the growth of metallic Pd particles, and hence explains the retention of high catalyst activity during long-term use and ageing.
971 citations
TL;DR: In this article, the authors showed that the activity of a photocatalyst with antimony and chromium was remarkably higher than that of one with only chromium and that the charge balance was kept by codoping of Sb5+ and Cr3+ ions, resulting in the suppression of formation of Cr6+ ions and oxygen defects in the lattice.
Abstract: TiO2 and SrTiO3 codoped with antimony and chromium showed intense absorption bands in the visible light region and possessed 2.2 and 2.4 eV of energy gaps, respectively. TiO2 codoped with antimony and chromium evolved O2 from an aqueous silver nitrate solution under visible light irradiation, while SrTiO3 codoped with antimony and chromium evolved H2 from an aqueous methanol solution. The activity of TiO2 photocatalyst codoped with antimony and chromium was remarkably higher than that of TiO2 doped with only chromium. It was due to that the charge balance was kept by codoping of Sb5+ and Cr3+ ions, resulting in the suppression of formation of Cr6+ ions and oxygen defects in the lattice which should work as effectively nonradiative recombination centers between photogenerated electrons and holes.
782 citations
TL;DR: In this paper, the authors investigated the photocatalytic properties of perovskite-type materials AgMO3 (M: Ta and Nb) consisting of Ag+ and d0 ions and found that the band gaps of AgTaO3 and AgNbO3 were 3.4 and 2.8 eV, respectively.
Abstract: Photophysical and photocatalytic properties of perovskite-type materials AgMO3 (M: Ta and Nb) consisting of Ag+ and d0 ions were investigated. The band gaps of AgTaO3 and AgNbO3 were 3.4 and 2.8 eV, respectively, being 0.6 eV smaller than the band gaps of NaTaO3 (4.0 eV) and NaNbO3, even if the crystal structures of AgMO3 were similar to those of NaMO3. It was found from the electronic band structure study, using the plane-wave-based density functional method, that a hybrid orbital of Ag 4d and O 2p formed a valence band at a more negative level than O 2p orbitals. AgTaO3 showed photocatalytic activity for pure water splitting into H2 and O2 under UV-light irradiation. AgNbO3 has arisen as a new visible-light-driven photocatalyst possessing the ability to evolve H2 or O2 from water in the presence of sacrificial reagents.
432 citations
TL;DR: The results indicate that Pin1 positively regulates cyclin D1 function at the transcriptional level, and also through posttranslational stabilization, which together explain why Pin1 loss-of-function phenotypes in the mouse resemble cyclIn D1-null phenotypes.
Abstract: Phosphorylation of proteins on serine/threonine residues preceding proline is a key signaling mechanism. The conformation and function of a subset of these phosphorylated proteins is regulated by the prolyl isomerase Pin1 through isomerization of phosphorylated Ser/Thr-Pro bonds. Although young Pin1−/− mice have been previously shown to develop normally, we show here that they displayed a range of cell-proliferative abnormalities, including decreased body weight and testicular and retinal atrophies. Furthermore, in Pin1−/− adult females, the breast epithelial compartment failed to undergo the massive proliferative changes associated with pregnancy. Interestingly, many of these Pin1-deficient phenotypes such as retinal hypoplasia and mammary gland impairment are also the characteristic of cyclin D1-deficient mice. Cyclin D1 levels were significantly reduced in many tissues in Pin1-deficient mice, including retina and breast epithelial cells from pregnant mice. Moreover, Pin1 directly bound to cyclin D1 phosphorylated on Thr-286–Pro increased cyclin D1 in the nucleus and stabilized cyclin D1. These results indicate that Pin1 positively regulates cyclin D1 function at the transcriptional level, as demonstrated previously, and also through posttranslational stabilization, which together explain why Pin1 loss-of-function phenotypes in the mouse resemble cyclin D1-null phenotypes. Our results provide genetic evidence for an essential role of Pin1 in maintaining cell proliferation and regulating cyclin D1 function.
336 citations
TL;DR: In this paper, a variety of lactones were prepared in high yields at room temperature from the corresponding ω-hydroxycarboxylic acids using 2-methyl-6-nitrobenzoic anhydride in the presence of 4-(dimethylamino)pyridine.
229 citations
TL;DR: It is shown that during Th1 differentiation a reduction in the association of Janus kinase 1 with the IL-4 receptor (IL-4R) correlated with the appearance of the suppressor of cytokine signaling-5 (SOCS5), which resulted in the inhibition of IL- 4-mediated signal transducer and activator of transcription-6 activation.
Abstract: The development of helper T (Th) cell subsets, which secrete distinct cytokines, plays an important role in determining the type of immune response. The IL-4-mediated Janus kinase–signal transducer and activator of transcription signaling pathway is crucial for mediating Th2 cell development. Notably, this pathway is selectively impaired in Th1 cells, although the molecular basis of this impairment remains unclear. We show here that during Th1 differentiation a reduction in the association of Janus kinase 1 with the IL-4 receptor (IL-4R) correlated with the appearance of the suppressor of cytokine signaling-5 (SOCS5). SOCS5 protein was preferentially expressed in committed Th1 cells and interacted with the cytoplasmic region of the IL-4Rα chain irrespective of receptor tyrosine phosphorylation. This unconventional interaction of SOCS5 protein with the IL-4R resulted in the inhibition of IL-4-mediated signal transducer and activator of transcription-6 activation. T cells from transgenic mice constitutively expressing SOCS5 exhibited a significant reduction of IL-4-mediated Th2 development. Therefore, the induced SOCS5 protein in Th1 differentiation environment may play an important role by regulating Th1 and Th2 balance.
213 citations
TL;DR: A modified LCM system was used and successfully applied to target and isolate phloem cells of rice leaf tissue whose morphology is apparently different from the surrounding cells and the results proved the effectiveness of construction of a specialized cDNA library from the specific plant cells.
Abstract: Laser capture microdissection (LCM) is a powerful system which allows the isolation of selectively targeted cells from a tissue section for the analysis of gene-expression profiles of individual cells. The technique has been successfully used for the isolation of specific mammalian cells, mainly cancer cells. However, LCM has never been reported to be applied to the gene expression analysis of plant cells. We used a modified LCM system and successfully applied it to target and isolate phloem cells of rice leaf tissue whose morphology is apparently different from the surrounding cells. Total RNA was extracted from microdissected (approximately 150) phloem cells and the isolated RNA was used for the construction of a cDNA library following the T7 RNA polymerase amplification. Sequence analysis of 413 randomly chosen clones from the library revealed that there was a high level of redundancy in the population and the clones could be subclassified into 124 different groups that contained related sequences. Approximately 37% of both the redundant population and the non-redundant subgroups had novel components while approximately 63% were either homologues to the known genes reported to be localized in phloem of different plant species, or were homologues to other known genes. In situ hybridization revealed that putative amino acid permease, one of the non-redundant clones, was specifically expressed in the phloem. The results proved the effectiveness of construction of a specialized cDNA library from the specific plant cells.
200 citations
10 Dec 2002
TL;DR: In this article, a method for fast calculation of radial force and torque of a bearingless switched reluctance motor operating in a region of magnetic saturation is proposed, which is shown experimentally that the proposed method is effective in calculating the radial forces and the torque under conditions of magnetic saturations.
Abstract: Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed These motors are characterized by integration of switched reluctance motors and magnetic bearings It is essential for a control system to consider magnetic saturation in real time in order to realize stable operation at a full torque load Thus, this paper proposes a method for fast calculation of radial force and torque of a bearingless switched reluctance motor operating in a region of magnetic saturation It is shown experimentally that the proposed method is effective in calculating the radial force and the torque under conditions of magnetic saturation
183 citations
TL;DR: Domain search analyses led to the classification of the Arabidopsis F-box proteins into at least 19 groups based on their domain structures, including Kelch repeats, LRRs and WD40 repeats, which are implicated in protein-protein interactions.
Abstract: ;F-box proteins regulate diverse cellular processes, including cell cycle transition, transcriptional regulation and signal transduction, by playing roles in Skp1p-cullin-Fbox protein (SCF) complexes or non-SCF complexes. F-box proteins are encoded by a large gene family. Our database search revealed that at least 568 F-box protein genes are present in the Arabidopsis thaliana (Arabidopsis) genome. Domain search analysis using SMART and Pfam-A databases revealed that 67 of the F-box proteins contained Kelch repeats and 29 contained leucine-rich repeats (LRRs). Interestingly only two F-box proteins contained WD40 repeats that are found in many F-box proteins of other organisms. Kelch repeats, LRRs and WD40 repeats are implicated in protein–protein interactions. This analysis also resulted in the finding of several unique functional domains; however, 448 of the F-box proteins did not contain any known domains. Therefore, these proteins were used to search the Pfam-B database to find novel domains, and three putative ones were found. These domain search analyses led us to classify the Arabidopsis F-box proteins into at least 19 groups based on their domain structures. Macro array analysis showed that several F-box protein genes are expressed in a tissue-specific manner.
179 citations
TL;DR: In this paper, an all-electron implementation of the local density approximation (LDA) was presented and applied to wurtzite ZnO, and the frequency dependence of the dielectric function was computed within the random phase approximation (RPA), without a plasmonpole approximation.
Abstract: We present an all-electron implementation of the $\mathrm{GW}$ approximation and apply it to wurtzite ZnO. Eigenfunctions computed in the local-density approximation (LDA) by the full-potential linearized augmented-plane-wave or the linearized muffin-tin-orbital method supply the input for generating the Green function G and the screened Coulomb interaction W. A mixed basis is used for the expansion of W, consisting of plane waves in the interstitial region and augmented-wave-function products in the augmentation-sphere regions. The frequency dependence of the dielectric function is computed within the random-phase approximation (RPA), without a plasmon-pole approximation. The Zn $3d$ orbitals are treated as valence states within the LDA; both core and valence states are included in the self-energy calculation. The calculated band gap is smaller than experiment by $\ensuremath{\sim}1\mathrm{eV},$ in contrast to previously reported $\mathrm{GW}$ results. Self-energy corrections are orbital dependent and push down the deep O $2s$ and Zn $3d$ levels by $\ensuremath{\sim}1\mathrm{eV}$ relative to the LDA. The d level shifts closer to experiment but the size of shift is underestimated, suggesting that the RPA overscreens localized states.
163 citations
TL;DR: In this paper, a cyclic triaxial test apparatus was used to examine the liquefaction resistance of partially saturated sand, with which it was possible to first measure the longitudinal and shear wave velocities and then to conduct cyclic loading tests on the same specimens under p-constant conditions.
TL;DR: It is shown that the intracellular signaling molecule SMAD1, acting downstream of bone morphogenetic protein (BMP) receptors, is required for the commitment of germ cell lineage from epiblast in early mouse embryos.
TL;DR: In this article, the photocatalytic activity of SNT for the water decomposition was greatly improved by loading NiO as a cocatalyst for a whole range of x, even when the amount of Nb was small.
Abstract: Phase-pure solid solutions with the composition of Sr2NbxTa2-xO7 (SNT, x = 0−2) were prepared at 900 °C for 5 h by the Pechini-type polymerizable complex (PC) technique, based upon polymerization between citric acid and ethylene glycol. The two end compounds, Sr2Ta2O7 (x = 0) and Sr2Nb2O7 (x = 2), produced H2 and O2 in a stoichiometric ratio from pure water under UV light irradiation without a NiO cocatalyst. The photocatalytic activity of SNT for the water decomposition was greatly improved by loading NiO as a cocatalyst for a whole range of x. The photocatalytic activity was dramatically decreased approximately by 1 order of magnitude once Ta has been replaced by Nb, even when the amount of Nb was small. For all of the NiO-loaded SNT samples, water was stoichiometrically decomposed into H2 and O2. While samples prior to the complete crystallization showed very low activities despite their high surface area, the corresponding photocatalytic activities of well-crystallized samples depended primarily on th...
TL;DR: From the results of quantum chemical calculations of various radical intermediates derived from the model compound N-vanillylacetamide, and the findings that vanillin and 8-methyl-6-noneamide were major reaction products of Capsaicin with DPPH radicals, it was concluded that the radical scavenging site of capsaicin is the C7-benzyl carbon.
TL;DR: First-principles calculations on field emission (FE) from graphitic ribbons within the time-dependent density-functional theory find that dangling bond states localized at clean edges are major contributors to FE current.
Abstract: We have performed first-principles calculations on field emission (FE) from graphitic ribbons within the time-dependent density-functional theory. An important finding is that dangling bond states localized at clean edges are major contributors to FE current. H termination makes the FE current small due to the disappearance of the dangling-bond states. FE is found not to occur from the edge state of a H-terminated zigzag ribbon even when the state is at the Fermi level. The results of the FE current from graphitic ribbons give approximately 1 microA for maximum of FE current from a circular edge of graphitic sheets with approximately 1 nm diameter of an open-ended multiwalled carbon nanotube under a high electric field of approximately 1 V/A.
TL;DR: In this paper, the total energy of solids is calculated by an ab initio method based on the Green's-function theory, which is constructed from one-body wave functions and eigenvalues obtained in the local density approximation (LDA) to density-functional theory, and the correlation energy is estimated within the random phase approximation.
Abstract: Total energies of solids are calculated by an ab initio method based on the Green's-function theory. Green's function is constructed from one-body wave functions and eigenvalues obtained in the local-density approximation (LDA) to density-functional theory, and the correlation energy is estimated within the random-phase approximation. The scheme is applied to Na and Si. In both cases, the equilibrium lattice constants are in reasonable agreement with experiments. The role of the exchange-correlation energy in the total-energy curve is discussed in detail in comparison with the LDA.
TL;DR: It is concluded that the induction of endogenous glutathione in living cells immediately after low-dose γ irradiation is at least partially responsible for the appearance of enhanced NK activity.
Abstract: Kojima, S., Ishida, H., Takahashi, M. and Yamaoka, K. Elevation of Glutathione Induced by Low-Dose Gamma Rays and its Involvement in Increased Natural Killer Activity. Radiat. Res. 157, 275 – 280 (2002). We examined the relationship between the induction of an increase in the level of glutathione and the elevation of natural killer (NK) activity in mouse splenocytes by a low dose of γ rays. The glutathione levels in mouse splenocytes increased significantly between 2 h and 6 h after whole-body γ irradiation at 0.5 Gy, peaked at 4 h, and then decreased almost to the level before irradiation by 12 h postirradiation. A significant enhancement of NK activity was found in the splenocytes obtained from whole-body-irradiated mice between 4 and 6 h postirradiation. Reduced glutathione (GSH) added exogenously to splenocytes obtained from normal mice enhanced both the total cellular glutathione content and the NK activity in a dose-dependent manner. Other precursors of de novo GSH synthesis, such as cystei...
TL;DR: Though structurally epoxyquinols A and B have a highly functionalized and complicated heptacyclic ringsystem containing 12 stereocenters, biosynthetically it is proposed they are formed by an unusual oxidative dimeriza-tion of the much simpler epoxycyclohexenone 3.
Abstract: which show anti-angiogenic activity,but have different structuralproperties from the knownangiogenesis inhibitors. To facilitate elucidation of themechanism of action of epoxyquinols A and B, the develop-ment of a method for their totalsynthesis and derivatization ishighly desirable. Though structurally epoxyquinols A and Bhave a highly functionalized and complicated heptacyclic ringsystem containing 12 stereocenters, biosynthetically it isproposed they are formed by an unusualoxidative dimeriza-tion of the much simpler epoxycyclohexenone 3(Scheme 1).
TL;DR: Asymmetric autocatalysis provides a unique method for the discrimination of chiral compounds and crystals as well as discriminating the chirality of inorganic crystals such as quartz and sodium chlorate.
TL;DR: In this article, an order parameter is proposed to characterize valence-bond-solid (VBS) states in quantum spin chains, given by the ground-state expectation value of a unitary operator appearing in the Lieb-Schultz-Mattis argument.
Abstract: We propose an order parameter to characterize valence-bond-solid (VBS) states in quantum spin chains, given by the ground-state expectation value of a unitary operator appearing in the Lieb-Schultz-Mattis argument. We show that the order parameter changes the sign according to the number of valence bonds (broken valence bonds) at the boundary for periodic (open) systems. This allows us to determine the phase transition point in between different VBS states. We demonstrate this theory in the successive dimerization transitions of the bond-alternating Heisenberg chains, using the quantum Monte Carlo method.
TL;DR: In this paper, the authors find evidence that is consistent with the hypothesis that daily mutual fund flows may be instruments for investor sentiment about the stock market, and they use this finding to construct a new index of investor sentiment, and validate this index using data from both the United States and Japan.
Abstract: We find evidence that is consistent with the hypothesis that daily mutual fund flows may be instruments for investor sentiment about the stock market. We use this finding to construct a new index of investor sentiment, and validate this index using data from both the United States and Japan. In both markets exposure to this factor is priced, and in the Japanese case, we document evidence of negative correlations between "Bull" and "Bear" domestic funds. The flows to bear foreign funds in Japan display some evidence of negative correlation to foreign bull and equity funds. They appear to be independent of domestic bull and bear fund flows, suggesting that there is a foreign vs. domestic sentiment factor in Japan that does not appear in the contemporaneous U.S. data. By contrast, U.S. mutual fund investors appear to regard domestic and foreign equity mutual funds as economic complements.
TL;DR: In this paper, the electronic structure of the valence-band photoemission spectra has been investigated by using the Hund's rule energy stabilization, and a double-peak feature has been observed near the Fermi level.
Abstract: We have investigated the electronic structure of ${\mathrm{Sr}}_{2}{\mathrm{FeMoO}}_{6}$ by photoemission spectroscopy and band-structure calculations within the local-density $\mathrm{approximation}+U$ $(\mathrm{LDA}+U)$ scheme In valence-band photoemission spectra, a distinct double-peak feature has been observed near the Fermi level ${(E}_{F})$ A photon-energy dependence of the spectra and the $\mathrm{LDA}+U$ band-structure calculation have revealed that the first peak crossing ${E}_{F}$ consists of the (Fe+Mo) ${t}_{2g\ensuremath{\downarrow}}$ states and the second peak well below ${E}_{F}$ is dominated by the Fe ${e}_{g\ensuremath{\uparrow}}$ states This clearly shows that only the down-spin states contribute to the ${E}_{F}$ intensity, thus the half-metallic density of states (DOS) is realized We point out that the observed half-metallic DOS can be attributed to the strong Hund's rule energy stabilization due to the high-spin ${3d}^{5}$ configuration at the Fe site
TL;DR: In this article, the photocatalytic activity for H2 evolution from an aqueous K2SO3 solution under visible light irradiation (λ>420 nm) was investigated.
Abstract: NaInS2 which consisted of anion layers of InS2− with a 23 eV band gap showed the photocatalytic activity for H2 evolution from an aqueous K2SO3 solution under visible light irradiation (λ>420 nm)
TL;DR: In this paper, a catalytic and stereoselective glycosylation of various types of acceptors, such as methyl glycosides, thioglycosides and a disarmed glyco-fluoride, with benzyl-protected armed glycoly fluoride was successfully carried out by using various protic acids in the presence of MS 5A.
Abstract: A catalytic and stereoselective glycosylation of various glycosyl acceptors, such as methyl glycosides, thioglycosides, or a disarmed glycosyl fluoride, with benzyl-protected armed glycosyl fluoride was successfully carried out by using various protic acids in the presence of MS 5A In the cases when trifluoromethanesulfonic acid (TfOH) or perchloric acid (HClO4) was used in diethyl ether (Et2O), α-glycosides were obtained as major products, while β-stereoselectivity was observed when tetrakis(pentafluorophenyl)boric acid [HB(C6F5)4] was used in a mixed solvent of trifluoromethylbenzene (BTF)–pivalonitrile (tBuCN) = 5 : 1 Stereoselectivity of this glycosylation was controlled by the properties of counter anions of the catalyst as well as by those of solvents Also, one-pot trisaccharide synthesis was performed by successive addition of NIS and third-sugar to afford Glcα or β1–6Glcβ1–6Glc and Glcα or β1–6GlcNβ1–6Glc in excellent yields
TL;DR: In this paper, a promising approach to obtain epitaxial films of oxide semiconductors was demonstrated, namely helicon-wave-excited-plasma sputtering epitaxy.
Abstract: A promising approach to obtain epitaxial films of oxide semiconductors was demonstrated, namely helicon-wave-excited-plasma sputtering epitaxy. Due to the surface-damage-free nature, completely a-axis-locked c(0001)-orientation ZnO epilayers were successfully grown on sapphire (0001) substrates having ultrasmooth surfaces with atomic steps. The ZnO epilayer exhibited a dominant near-band-edge photoluminescence (PL) peak at 300 K. Since the PL was considered to be due to the recombination of excitons bound to an impurity or a defect and certain tilting and twisting of the films were observed when Ar/O2 were used as sputtering gases, purification and optimization of the overall process are necessary to obtain improved epilayer qualities.
TL;DR: The synthesized compounds efficiently suppress the cytotoxicity of Abeta against IMR-32 neuroblastoma cells in vitro and the compound DDX3 is an especially effective inhibitor.
TL;DR: Results indicate that the whole-mouth gustatory test procedure employed in this study may be useful for evaluating gustatory function clinically, and confirmed that sweet, salty, sour and bitter are indeed the four basic tastes.
Abstract: Gustatory testing using the whole-mouth method was performed in 123 healthy young male and female subjects. The average thresholds for detection and recognition of the four basic tastes were not greatly different from the normal thresholds previously reported in Japan: a 0.0165 M solution of sucrose for sweet taste, a 0.0316 M solution of table salt for salty taste, a 0.000743 M solution of tartaric acid for sour taste and a 0.0000203 M solution of quinine hydrochloride for bitter taste. These results indicate that the whole-mouth gustatory test procedure employed in this study may be useful for evaluating gustatory function clinically. Principal components analysis confirmed that sweet, salty, sour and bitter are indeed the four basic tastes and revealed that the sensation of taste is detected before the specific taste is recognized, regardless of the specific taste tested.
TL;DR: Growth processes of hydrocarbon droplets in oil/water emulsions under surfactant-free conditions were examined by dynamic light scattering and freeze-fracture electron microscopy (FFEM) as discussed by the authors.
Abstract: Growth processes of hydrocarbon droplets (C6−C16: n-hexane, cyclohexane, n-octane, n-decane, n-dodecane, n-tetradecane, and n-hexadecane) in oil/water emulsions under surfactant-free conditions were examined by dynamic light scattering (DLS) and freeze-fracture electron microscopy (FFEM). DLS results showed that the growth rate of droplet size decreased with increase in hydrocarbon chain length. For example, n-hexane droplets grew within 1 h from submicrometer to micrometer droplets, while n-hexadecane droplets with sizes of several tens of nanometers kept their dispersibility for 24 h. We determined the growth processes as coalescence and molecular diffusion (Ostwald ripening) in terms of the Lifshitz−Slyozov−Wagner theory and the Smoluchowski equation. Furthermore, FFEM was used to examine the growth mechanism in detail. Direct imaging of n-hexane and cyclohexane droplets by FFEM allowed us to observe very fine oil droplets (∼10 nm in diameter) though DLS could not detect these droplets, suggesting tha...
TL;DR: In this paper, the reaction cross sections for 12,16 C have been measured at the energy of 83 A MeV by a new experimental method and the larger enhancement of the 16 C reaction cross section at low energy has been used to study the density distribution of 16 C. The analysis suggests that 16 C mainly has a 14 C(core) + 2n structure and shows a strong contribution of (2s 1/2)2 for valence neutrons.