bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantum chemistry study on B32 and B32H2–32
Authors: Feng‐Long Gu , Qian‐Shu Li , Au‐Chin Tang 
Published: September 2010

AbstractThe structures of B32 and B32H2–32 with Ih symmetry have been investigated by means of ab initio calculations at STO‐3G level. The relationship between molecular orbitals of them has been analyzed and their bonding properties have been discussed. Then the possibility of their existence, as well as the similarity and difference between B32 (B32H2–32) and C60 (C60H60) have been inferred.
A new phosphate, KMgY(PO4)2, isostructural with xenotime
Authors: Shao‐Long Tie , Qiang Su , Ya‐Qin Yu , Jian‐Fang Ma 
Published: September 2010

AbstractA new phosphate, KMgY(PO4)2, isostructural with xenotime, was firstly reported in detail. It crystallizes in tetragonal system with space group I41/amd (No. 141). The cell parameters were obtained from X‐ray powder diffraction data with a=0.6886, c=0.6025 nm, Z=2. The proposed structure of KMgY(PO4)2 was further confirmed by its vibrational spectra, IR and Raman spectra, which were also compared with those of iso‐structural YPO4.
Study on kinetics and mechanism of copper‐catalyzed oxidation of hydrazine by iron (III) in acid solution
Authors: De‐Ping Cheng , Shi‐Jun Xia 
Published: September 2010

AbstractThe copper‐catalyzed oxidation of hydrazine by iron(III) in acid solution follows the rate law ‐d[Fe(III)]/dt = kKh[Cu(II)]2/(Kh + [H+]), where Kh is the hydrolysis constant of Cu2+, k was found to be 8.8±0.8, 13.2±1.4 and 17.5±1.3 min−1 at 35, 40, and 45°C respectively and μ= 0.2 mol/L. The composition of the activated complex is Cu2+, CuOH+, N2H4, H+ or others. Perhaps several hydrazine complexes of Cu(II) participate in the reaction and one of them isolated was Cu(N2H4)2(HSO4)2. Study on the oxidation of this complex is also in conformity with the above rate law.
Synthesis and mesomorphic properties of n‐alkyl 4‐[4‐(4‐n‐octyloxybenzyloxy‐2,3,5,6‐tetrafluorophenyl)ethynyl]benzoates
Authors: Yue‐Lian Xu , Wei‐Li Wang , Qi Chen , Jian‐Xun Wen 
Published: September 2010

AbstractA new series of n‐alkyl 4‐[4‐(4‐n‐octyloxybenzyloxy‐2,3,5,6‐tetrafluorophenyl)ethynyl)benzoates have been prepared. Polarizing microscopic textural observation shows that they are liquid crystals with nematic phase.
Synthesis of key intermediates to 20(R)‐and 20(S)‐trifluoromethyl‐23,24‐dinor‐25‐hydroxy‐cholesterol and VD3 analogs
Authors: Shou‐Fu Lu , Ben‐Fang Ruan , Zhong‐Qi Wang 
Published: September 2010

AbstractSynthesis of 20(R)‐and 20(S)‐trifluoromethyl substituted steroids as the key intermediates (1a, 1b) to 23,24‐dinor‐20‐trifluoromethyl‐25‐hydroxy‐cholesterol and VD3 analogs, using trifluoromethyltrimethylsilane (CF3SiMe3) as a trifluoromethylating agent, was described.
Preparation of some new derivatives of (1R,2S)‐1,2‐diphenyl‐2‐aminoethanol and enantioselective borane reduction of propiophenone
Authors: Yao‐Zhong Jiang , Yong Qin , Ai‐Qiao Mi , Lan‐Jun Wu 
Published: September 2010

AbstractSome new methylated and N‐alkylated derivatives of (1R,2S)‐1,2‐diphenyl‐2‐amino ethanol were synthesized and applied to enantioselective borane reduction of propiophenone. The relationship between catalyst structure and enantioselectivity was discussed in detail.
Direct synthesis of 3‐fluoroalkyl‐2,6‐diethoxycarbonyl phenols
Authors: Hui‐Ping Guan , Qiao‐Sheng Hu , Chang‐Ming Hu 
Published: September 2010

AbstractCyclocondensation of α‐fluoroalkyl ketones or α‐fluoroalkyl aldehyde (1) and diethyl 1,3‐acetonedicarboxylate (2) affords 3‐fluoroalkyl‐2,6‐diethoxycarbonyl‐5‐alkyl‐phenols (3) in good yields. This provides a novel method for the preparation of meta‐fluoroalkyl polysubstituted phenols.
Comparative studies on the concerted and two‐step mechanism of ketene‐methylenimine cycloaddition
Authors: De‐Cai Fang , Xiao‐Yuan Fu 
Published: September 2010

AbstractThe concerted reaction mechanism of the ketene‐methylenimine cycloaddition reaction was reconfirmed by IRC calculation at HF/6–31G* level. Other possible reaction schemes were also studied. The cis and gauch intermediate cannot be found on the potential energy surface, and the trans intermediate can only lead to a 6‐membered ring product. Therefore, a two step mechanism to form β‐lactam is excluded for the title reaction.
Fluorescence enhancement effect and the interaction between donor and acceptor
Authors: Pin Yang , Man‐Man Yang , Bin‐Sheng Yang 
Published: September 2010

AbstractA new theoretical equation for fluorescence enhancement effect between donor and acceptor has been introduced. By using it we determined the binding constants and numbers of binding sites of five medicines, including chlorogenic acid, forsythiaside norfloxacin, Ciprofloxacin and fluorenone, to γ‐globulin.
Effect of antimony on the reduction of anodic PbO2 film on Pb‐Sb alloys in sulfuric acid solution
Authors: Wen‐Bin Cai , Yong‐Qin Wan , Hou‐Tian Liu , Wei‐Fang Zhou 
Published: September 2010

AbstractThe reduction processes of anodic PbO2 films formed on Pb‐Sb alloys in 4.5 mol.dm−3 H2SO4 solution at 1.4 V(vs. Hg/Hg2SO4) for 1 h have been investigated by photocurrent method, chronoamperometry, linear sweep voltammetry as well as X‐ray diffractometry. It was found that the reduction of most of the β‐PbO2 and part of the α‐PbO2 to PbSO4 can be completed within 1 s between 0.9 V and 1.0 V(vs. Hg/Hg2SO4) and proceeds much faster than that of the remaining α‐PbO2 into photoactive α‐PbOx (1 < x < 1.4). The presence of antimony in the alloy retards significantly the reduction of the remaining α‐PbO2 and decreases slightly the band‐gap energy of t‐PbO.
Reaction of amino acid derivatives with C60
Authors: Nai‐Xing Wang , Ji‐Sheng Li , Dao‐Ben Zhu 
Published: September 2010

AbstractAmino acid derivatives react with C60 at 110‐120°C to form adduct compounds. The products were isolated by column chromatography and were identified by FD‐MS, UV‐Vis, FT‐IR and 13C NMR spectroscopies.
Studies on the magnetic property of μ3‐oxotriiron(III) complex [Fe3O(OBz)6(CH3OH)3](NO3)(CH3OH)2 (HOBzBenzoic acid)
Authors: Guo‐Xiong Wang , Hua Zhang , Yao Chen , Tian‐Yang Yao , De‐Gang Fu 
Published: September 2010

AbstractThe magnetic property of μ3‐oxotriiron(III) complex [Fe3O(OBz)6(CH3OH)3](NP3)‐(CH3OH)2 (HOBzbenzoic acid) has been studied. We use isosceles triangle model and molecular field correction to fit the experimental magnetic susceptibility data. It shows that an intramolecular antiferromagnetic exchange interaction occurs with J = ‐31.27 cm−1, J'= ‐27.26 cm−1, and a weaker intermolecular antiferromagnetic exchange interaction occurs with zJ' = ‐ 3.76 cm−1. We give the d5‐d5‐d5 energy level diagram of triiron(III) complex as a function of J'/J. From the diagram we can get the total spin ST of the complex as 1/2 in the ground state.
HeI photoelectron spectroscopic (PES) studies of the electronic structure in ω‐heterocycle α‐cyano polyenic ethyl ester Compounds
Authors: Ying Li , Sheng Li , Ben‐Ming Chen , Dian‐Xun Wang 
Published: September 2010

AbstractHel photoelectron spectra of ω‐heterocycle α‐cyano polyenic ethyl ester compounds (1–6) have been given in this paper. Assignment of the spectra is also done with the aid of HeI photoelectron spectroscopic (PES) results of smaller molecules which have similar atomic group to the molecules studied, and the aid of MNDO molecules orbital calculations. The lowest PES experimental ionization potentials (IPs in eV) of different molecules reduce gradually with the increasing number of ethylenic group. The ‐CO2C2H5 group can be only considered as a substituent.
Electrochemically modified piezoelectric crystal biosensor for detection of Staphylococcus aureus
Authors: Shi‐Hui Si , Jin‐Hua Chen , Feng‐Jiao He , Li‐Hua Nie , Shou‐Zhuo Yao 
Published: September 2010

AbstractElectropolymerized o‐phenylenediamine film is used as a functional coating for the immobilization of anti‐S. aureus antibody on the surface of a gold‐plated piezoelectric crystal, and this piezoelectric immunosensor is applied to detect S. aureus. The frequency shift (ΔF = F20z ‐ F380z, Hz) between the frequency at the 20th second (after the addition of sample, F20Z) and that at 380 seconds later (F380z) was introduced to construct a calibration graph, and shortening of assay time was achieved. The S. aureus concentrations in the range of 105–109 cells/mL can be detected by this system.
Spectrophotometric determination of cationic surfactants by formation of ternary complexes with Fe(III) and chrome azurol
Authors: Ming Song , Shu‐Quan Liang 
Published: September 2010

AbstractAn extraction‐free spectrophotometric method for the determination of cationic surfactants, such as cetylpyridinium chloride, cetyltrimethylammonium bromide and zephiramine is proposed, which is based on the formation of ternary complexes with Fe(III) and chrome azurol S. The molar ratio of the complex is 2:1:1 (Fe(III):chrome azurol S: cationic surfactant). The method is simple, rapid and sensitive, giving an apparent molar absorptivity of 4.5×104 L·mol−1‐cm−1 and a linear range of 0.1–6.0 μmol/L cationic surfactants. The total cationic surfactant content can be determined directly in aqueous solutions by measuring the absorbance at 680 nm (pH 5.8). The method has been successfully applied to water samples.
Influence of oscillator phase on oscillation frequency and sensitivity of an electrode‐separated piezoelectric Sensor
Authors: Da‐Zhong Shen , Qi Kang , Jing‐Tian Hu 
Published: September 2010

AbstractTheoretical consideration was proposed for the influences of the oscillator phase on the response nature of an electrode‐separated piezoelectric sensor (ESPS) to liquid properties and verified experimentally. For the oscillators with different phases, the oscillation frequency of the ESPS may increase, maintain nearly constant or decrease with increasing conductivity in low conductivity solutions. The sensitivity of response to density and viscosity increases slightly with increasing oscillator phase. The response to permittivity depends hardly on the oscillator phase. In addition, the dependence of the oscillation frequency of the ESPS on the supply voltage of the oscillator was explained. The ESPS was used to determine atropine sulfate with a detection limit of 1.6·10–7 mol/L.
Nucleophilic reactions of l‐methyl‐2‐methoxy‐2‐phenyl‐3‐oxo‐2,3‐dihydroindole
Authors: Ke‐Qing Ling 
Published: September 2010

AbstractThe title compound (1) was prepared via methylene blue (MB)‐sensitized photooxy‐genation of l‐methyl‐2‐phenylindole (2d) in methanol. Acid‐catalyzed nucleophilic substitution of 1 with nucleophiles gave 1,2,2‐trisubstituted 3‐oxo‐2,3‐dihydroindoles (3–6). Reduction of 1 with lithium aluminum hydride, followed by acidic workup yielded 4d and 2d, whereas the same reduction reaction of 1, followed by neutral workup gave l‐methyl‐2‐phenyl‐3‐hydroxy‐2,3‐dihydroindole (15), together with 3. The reaction pathways of nucleophilic substitution and reduction of 1 were discussed.
Regioselective etherification of l,2‐O‐isopropylidene‐4,6‐di‐O‐benzyl myo‐inositol
Authors: Cheng‐Ye Yuan , Hai‐Xiao Zhai , Shu‐Sen Li 
Published: September 2010

AbstractDuring the etherification of 1,2‐O‐isopropylidene‐4,6‐di‐O‐benzyl myo‐inositol, the specific regioselectivity on 3‐ or 5‐hydroxyl group was showed to be determined by the nature of the O‐ alkylating agents used. As demonstrated by MM and MNDO calculation, the regioselectivity of the reaction mentioned can be rationalized by steric and/or electronic effect.
Isolation and structural elucidation of a polysaccharide with radiation‐protective activity from Spirulina platensis
Authors: Zhong‐Wu Guo , Yong‐Zheng Hui 
Published: September 2010

AbstractThe structure of a radiation‐protective sulfated polysaccharide, SP‐APS, isolated from Spirulina platensis, was investigated by methylation analysis, partial acetolysis and 1H‐NMR spectroscopy. The repeating‐unit of SP‐APS as branched structures was elucidated.
Study on the reaction of triple helix poly(A:2I) with Cu2+
Authors: Er‐Bing Hua , Pin Yang , Qing‐Shan Li , Bin‐Sheng Yang 
Published: September 2010

AbstractThe effect of Cu2+ on the triple‐stranded helical structure of poly(A:2I) was studied by means of circular dichroism spectral method with the help of ultraviolet spectral and ethidium bromide fluorescence probe methods. It was found that Cu2+ destabilizes the structure of the triple helix poly(A:2I) and induces its structural transformations, meanwhile, the transformations can be partially reversed by a higher NaCl concentration. The structural transformations may be expressed by the following scheme: poly(A:2I)·poly(A:I) + poly (I) · poly(A) + 2poly(I)
Epoxidation of styrene catalyzed by manganese (III) porphyrins supported on chloromethylated polystyrene resin bearing crown ether groups,
Authors: Jing‐Song You , You‐Fa Xiao , Xiao‐Qi Yu , Ai‐Xia Cheng , Zhong‐Wei Lan 
Published: September 2010

AbstractMetalloporphyrins and crown ether groups were simultaneously supported on chloromethylated polystyrene resin to produce a series of polymer‐supported catalysts. The synthesis of these catalysts has been studied. The influence of pH, concentrations of NaOCl and phase transfer catalysts on the epoxidation of styrene catalyzed by these catalysts has also been investigated. The experimental results show that manganese(III) porphyrin bound to chloromethylated polystyrene which bears crown ether groups is effective catalysts for the epoxidation of styrene by sodium hypochlorite. The introduction of crown ether groups increases the catalytic efficiency of supported metalloporphyrins. The kinetics of epoxidation catalyzed by supported manganese(III) porphyrins obeys Michaelis‐Menten equation—the characteristic of enzyme‐driven reaction.
Theoretical studies on the structures and reactivity of stannylenoids I. The structures and isomerization of stannylenoid H2SnLiF
Authors: Hua‐Yu Qiu , Cong‐Hao Deng 
Published: September 2010

AbstractThe structures of singlet stannylenoid H2SnLiF have been examined by ah initio MO theory. Four equilibrium states and three transition states of isomerization reaction are located. The calculation shows that the p‐complex 1 is the most stable and experimentally detectable. The other three species, three‐membered ring 2, s̀‐complex 3 and tetrahedron 4, are also local minima on the potential energy surface, but are higher in energy.
The Clar covering polynomial of hexagonal systems II. An application to resonance energy of condensed aromatic Hydrocarbons
Authors: Fu‐Ji Zhang , He‐Ping Zhang , Yu‐Ting Liu 
Published: September 2010

AbstractThe Clar covering polynomial of hexagonal systems is a recently proposed1,2 concept which contains much more topological properties of condensed aromatic hydrocarbons, such as Kekulé structure count, Clar number, first Herndon number, etc. It is shown that this polynomial can be used for calculating the resonance energy of condensed aromatic hydrocarbons with better accuracy.
New Ni(II)Cu(II)Ni(II) trinuclear complexes with an 5=3/2 high‐spin ground
Authors: Ming‐Ming State, Miao , Dai‐Zheng Liao , Zong‐Hui Jiang , Peng Cheng , Geng‐Lin Wang 
Published: September 2010

AbstractFour new heterotrinuclear complexes have been synthesized and characterized, namely {[Ni(L)2]2[Cu(opba)]}(ClO4)2, where opba denotes o‐phenylenebis(oxamato) and L stands for 1,10‐phenanthroline(phen) (1), 5‐nitro‐l,10‐phenanthroline(NO2‐phen) (2), 2,2′‐bipyridyl(bpy) (S) and 4,4′‐dimethyl‐2,2′‐bipyridyl(Me2bpy) (4). The temperature dependence of the magnetic susceptibility of {[Ni(phen)2]2[Cu(opba)]}(ClO4)23H2O has been studied in the 4–300 K range, giving the exchange integral J—109 cm−1. The HMT vs. T plot exhibits a minimum at about 100 K, characteristic of this kind of coupled polymetallic complex with an irregular spin‐state structure.
The equation of chronoamperometric current on an oblate hemispheroid microelectrode and its verification,
Authors: Guo‐Wang Diao , Liang Li , Zu‐Xun Zhang 
Published: September 2010

AbstractWith the aspect of equivalent diffusion layer an analytical chronoamperometric current equation on an oblate hemispheroid microelectrode for reversible electrochemical condition is derived. To verify this equation the chronoammograms have been obtained with benzoquinone in McIlvaine buffer solution (pH 7.0) at a mercury oblate hemispheroid microelectrode. The experimental results agree with the theoretical conclusions.
Methylene green‐mediated sensor highly sensitive to hydrogen peroxide based on entrapment of horseradish peroxidase in composite membrane of regenerated silk fibroin and poly (vinyl alcohol)
Authors: Xin‐Xin Wu , Hai‐Ying Liu , De‐Yao Qi , Yong‐Cheng Liu , Jiang‐Hong Qian , Sheng‐Hui Liu , Tong‐Yin Yu , Jia‐Qi Deng 
Published: September 2010

AbstractA novel composite membrane of poly(vinyl alcohol) and regenerated silk fibroin was employed to immobilize horseradish peroxidase (HRP) and IR was used to give a useful insight into the structure of the composite membrane before and after ethanol treatment. A methylene green‐mediated sensor sensitive to hydrogen peroxide was fabricated, based on the composite membrane as immobilization matrix for HRP. Cyclic voltammetry and amperometric measurement were for the first time utilized to demonstrate the suitability of methylene green as an electron transfer mediator between immobilized HRP and a glassy carbon electrode in bioelectrocatalytic reduction of hydrogen peroxide. Performance and characteristics of the sensor were evaluated in respect to response time, detection limit, applied potential and concentration of the mediator. The sensor possesses a variety of characteristics including good sensitivity, rapid response time and low detection of limit of 0.1 μmol/L.
Synthesis of a ball‐chain system C60 aza‐derivative
Authors: Nai‐Xing Wang , Ji‐Sheng Li , Dao‐Ben Zhu 
Published: September 2010

AbstractNitrenes generated by thermolysis of alky 1 azides were found to add to C60 in chlorobenzene solvent. The product was isolated by means of silica gel chromatography and identified by field desorption mass spectroscopy and 13C NMR spectroscopy.
A novel secondary metabolite of Chinese red alga Laurencia karlae
Authors: Long‐Mei Zeng , Yong‐Li Zhong , Jing‐Yu Su , Hou‐Ming Wu , Kan Ma 
Published: September 2010

AbstractA novel skeleton compound benkarlaol (1) was isolated from the red alga Laurencia karlae Zhang et Xia, collected from the Nansha Islands in the South China Sea. Its structure and relative stereochemistry were determined by spectroscopic data, especially extensive ID and 2D NMR experiments.
Photoisomerization of norbornadiene group in a rigid bichromophoric compound initiated by remote keto chromophore: long‐distance through‐bond triplet energy transfer
Authors: Chen‐Ho Tung , Li‐Ping Zhang , Yi Li 
Published: September 2010

AbstractA diad compound 3β(bicyclo[2,2,1]hepta‐2,5‐diene‐2‐methylcarboxylate‐3‐carboxy)‐an‐drost‐5‐en‐17‐one (NBD‐S‐ONE) was synthesized and its photochemistry was examined. Irradiation of NBD‐S‐ONE in acetonitrile at λ > 300 nm selectively excited the keto chromophore. After intersystem crossing, the triplet energy of the keto group was transferred to the NBD group with 18.6% efficiency via a through‐bond mechanism, resulting in the isomerization of the latter group to the quadricyclane group.
A sensitive xanthine oxidase electrode with silk net for estimating fish freshness
Authors: Tu‐Zhi Peng , Li‐Ju Yang , Lian‐Qing Shen 
Published: September 2010

AbstractAn enzyme biosensor was constructed using a plate platinum electrode and immobilized xanthine oxidase (XOD). Only a very small quantity of enzyme was chemically immobilized on a special silk net. Hydrogen peroxide released during the enzymatic reaction was detected by the electrode at +0.65 V (vs. Ag/AgCl). The electrode was very sensitive to hypoxanthine and its detection limit was 1×10–7 mol/L. When it was applied to the determination of fish freshness, the results agreed well with those obtained by traditional methods‐determination of total volatile basic nitrogen (TVB‐N) and microbial count. A range for estimating the freshness of river fish was suggested.
Synthesis, complexation properties and crystal structure of 4′,5‐dibromo‐o‐xylyl‐17‐crown‐5 ether
Authors: Guo‐Xiang Xiong , Qing‐Fu Zhou , Hui‐Jun Xu 
Published: September 2010

Abstract4′, 5′‐Dibromc‐o‐xylyl‐17‐crown‐5 ether (2BrB17C5) was synthesized, starting from 1,2‐dibromo‐4,5‐bis(bromomethyl)‐benzene and tetraethylene glycol, and was characterized by 1H NMR, MS and elemental analysis. Pale yellow prismatic single crystal obtained from anhydrous ethanol was investigated by X‐ray structural analysis. The complexation properties toward alkali metal ions were examined using the solvent extraction method and UV absorption spectroscopy. The crown ether was found to be conformationally deformed and oblate‐like and is highly selective for lithium ion.
The rotation and the phase transition in solid C60
Authors: Zhi‐Jin Xu , Ji‐Min Yan 
Published: September 2010

AbstractThe interaction between C60's in solid C60 has been calculated by (exp‐6–1) potential, and the cause and the controlled factor of the high rapid rotations of C60's were discussed. In order to describe the disordered degree of C60 rotation, an equivalent M is introduced. The phase transitions at the ∼260 K and at the ∼90 K are studied from the viewpoint of C60 rotation. The potential barriers of the ordered rotation below the ∼260 K and the disordered rotation above the ∼260 K have been given, and the effect of the external pressure on the temperature of phase transition has also been given.
Ab initio theoretical studies on N28, B4N24, B12N16, and B16N12 with Td symmetry
Authors: Xin‐Tian Jiang , Xu‐Guang Hu , Qian‐Shu Li 
Published: September 2010

AbstractStructures, energies and vibrational frequencies have been calculated for hollow cage clusters N28, B4N24, B12N16, and B16N12 with Td symmetry using ab initio quantum mechanical methods at the RHF/3–21G level. Each species is predicted to be both chemically and kinetically stable. Skeletal polyhedrons of all considered boron nitride hollow cage clusters are constructed from 5‐and 6‐membered rings.
Structure and magnetic properties of homobinuclear gadolinium (III) complex of isonicotinoyl hydrazone
Authors: Ruo‐Hua Zhang , Hong‐Mei Wang , Dai‐Zheng Liao , Jing‐Tang Chen , Hong‐Gen Wang , Xing‐Kan Yao 
Published: September 2010

AbstractThe crystal structure of [Gd2(μ‐L)3(H2O)2]1.5(NO3)1.5 (OH)5H2O (where L is union of N, N‐Diisonicotinoyl‐2‐hydroxy‐5‐methyl‐isophthalaldehyde dihydrazone) has been determined by X‐ray diffraction method. The complex crystallizes in the monoclinic system, space group P21/c with a=1.6654(3), b=1.6904(3), c=2.8039(6) nm, β=91.30(3), final R factor is 6.3%. The structure consists of [Gd2(μ‐L)3(H2O)2]3+ cation, one and a half nitrate and 1.5 hydroxyl anions and five water molecules. Within dinuclear cation, Gd(III)—Gd(III) is bridged by oxygen and nitrogen atoms of the three ligands, resulting in GdGd distance of 0.36353(2) nm. Gd(III) exhibits a distorted 1333 stack coordination environment. Magnetic susceptibility measurements in the temperature range 300–4 K revealed the occurrence of weak antiferromagnetic exchange interaction between two Gd(III) ions with a J value of—0.22, and g of 1.93.