2005 Vol. 29, No. S1
Display Method: |
Alamethicin is a 20-amino acid membrane-active peptide from the fungus Trichoderma viride that spontaneously inserts into lipid membranes and self-associates into transmembrane channels. It has an antimicrobial activity against fungi and Gram-positive bacteria. We have investigated the effect of the peptide on the structure of lipid membranes by X-ray scattering method. The highly aligned stacks of membranes were prepared by evaporation of organic solutions of alamethicin and 1,2-dioleoyl-sn-glycero-3-phosphocholine deposited on clean silicon surfaces and were immersed in excess ultra pure water. The in-situ X-ray measurements show that the membranes with inserted peptides become thinner and softer at high molar peptide/lipid ratio.
We report on the synchrotron small-angle X-ray scattering (SAXS) study of self-assembled complex formed by mixing short-chain DNAs with cationic phospholipids in water. The DNA/lipid complex is a sandwiched structure, consisting of alternate layers of DNAs and lipid bilayers with a periodicity of dD/L. The DNAs at the interfaces are one-dimensionally ordered with a periodicity of dDNA. When the temperature of the system is increased, the lipid bilayers become soft so that the DNAs are trapped more deeply inside the lipid bilayers. This explains why the measured dD/L decreases insignificantly with the increase of temperature.On the other hand, the value of dDNA keeps constant because of the stiffness of the DNAs.
The morphology of a series of well-defined graft copolymers of diacetate cellulose and PMMA was studied through SR-SAXS. The graft copolymer formed mono-molecular sphere in the solution of CCl2H2 and CH3OH. And the dimension of the graft copolymer increased with the increasing of the degree of polymerization of the PMMA side chains.
Encapsulated cytochrome c Sol-Gel materials was synthesis and studied by UV-vis absorption spectra and SAXS. It was illuminated that exist a lower effective pH within TMOS-derived sgel by monitoring wavelengh shifts in the peak absorption of the Soret band. The gyration radius of encapsulated cytochrome c within gel was calculation by SAXS.
The structures of [Ni70Co30(25A)/Cu(20A)]20 multilayers were investigated by X-ray anomalous scattering technique. Different structural behaviors at the Cu/Ni70Co30 and Ni70Co30/Cu interfaces were obtained respectively.For the as-deposited sample, the interfaces are asymmetrical. An 8A thick CuNi3 and a 4A thick NiCo layers are observed at the Cu/Ni70Co30 interface, however the Ni70Co30/Cu interface is sharp. For the annealed sample, the sharp Ni70Co30/Cu interface is replaced by a CuNi2Co sublayer of about 12A thick. The X-ray diffuse scattering experiments, performed with the incident X-ray energy close to the Co, Ni and Cu K edges respectively, show the distribution of Co, Ni and Cu at the interfaces is not uniform.
La0.7Ca0.3MnO3(LCMO) thin films with the thickness ranging from 5 nm to 200 nm were deposited on (001)-oriented single crystal MgO substrate by 90° off-axis radio frequency magnetron sputtering. Grazing incidence X-ray diffraction technique, combined with normal X-ray diffraction, was applied to study the lattice strain and strain relaxation in LCMO films. The magnetoresistance of films were measured by means of standard four-probe technique. The results indicated that the microstrain of LCMO/MgO film began to relax when the film thickness is less than 5 nm. The LCMO film is fully strain-relaxed with thickness larger than 100 nm and exhibit LCMO bulk-like magnetoresistance properties, i.e. with relatively lager magnetoresistance ratio and higher peak temperature of magnetoresistance.
This study systematically addresses the effect of temperature on the growth of SiGe compliant substrates. The characteristics of the films were experimentally determined by various techniques, including high resolution X-ray diffraction (HRXRD), surface diffraction, X-ray reflectivity with synchrotron radiation,transmission electron microscopy (TEM) and atomic force microscopy (AFM).In the growth temperature range from 350—600\textcelsius, X-ray diffraction shows that the film was strain relaxed with a Ge content of 32±2%, and TEM indicates that the film is free from dislocations in the temperature range, 400—500\textcelsius.AFM reveals that the optimal temperature for the growth is 450\textcelsius, with a root mean squared surface roughness of 15\AA.
Three sets of Co/W bilayers with varying Co and/or W layer thickness were prepared by d.c. magnetosputtering technique. The magnetic properties of Co/W bilayers have been investigated using ferromagnetic resonance (FMR) and vibrating sample magnetomete.Specular X-ray reflectivity and high angle X-ray diffraction were used to characterize the structure of the deposited samples. The saturation magnetization of Co increased with Co thickness but was smaller than that of bulk hcp Co. The larger interface roughness and FMR line-width for the thinner Co/W films indicate the inhomogeneity of Co and/or W layers.
Both conventional X-ray diffraction (XRD) and synchrotron radiation surface X-ray diffraction methods were used to study FeS2 films prepared by magnetron sputtering on Si (100) and glass substrates for comparison. The results show that the preferred orientation of FeS2 along (311) direction, which might be due to the well-matched crystal lattice for FeS2 and Si (100), is mistaken. The peak at about 56°with extremely strong intensity comes from the (311) crystal plane of the silicon substrate, other than the preferred orientation of FeS2. The conclusion is proved by both calculation and experimental measurements in present paper.
By means of low temperature photoluminescence and synchrotron radiation X-ray diffraction,existence of stacking faults has been determined in epitaxy lateral overgrowth GaN by metalorganic chemical vapor deposition.
Phase depth profile in NiTi shape memory alloy films made up from sputter-deposited Ni/Ti multilayers is studied by Grazing-Incidence X-Ray Diffraction. Phase depth profile is not uniform in NiTi films. Both samples show there is a multiphase mixture region of Ti3Ni4 precipitates, martensite and a little of austenite near the free surface and a uniform Martensite phase near the substrate. Diffusion and reaction take place between film and substrate. Different periodical thickness will affect the phase depth profile in the after-annealing films.
We have performed in-situ synchrotron radiation photoemission spectrum (SRPES) on a well-order surface of BaTiO3 film fabricated with laser molecular beam epitaxy. The X-ray photoemission spectrum of Ti 2p indicate the Ti ion in BaTiO3 film is Ti+4 and the epitaxy film is stoichiometric composition with less oxygen vacancies. We calculated the valence density of state of BaTiO3 in ferroelectric phase with ab-intio code wien2k. The experiment spectrum is well consistent with our calculated result.
We studied the electronic structure of SrTi1-xRuxO3 using synchrotron radiation. The Experimental used in the study were photoemission (PES) and O 1s X-ray absorption (XAS) spectroscopy. The PES and XAS spectra of SrTi1-xRuxO3showed the Ru 4d bands changed with the change of X. Compared with the results of LDA calculation, we analysis explain the experiment data.
The oil gas inclusion in the reservoir is the evident of the oil gas movement.The trace element and its distribution characteristic of oil gas inclusion indicate the feature of the oil gas when it was captured by inclusion. The trace element and its distribution of oil gas inclusion in the different layers of oil well also show the process of the movement and change of the oil gas. Therefore the analysis of trace element of oil gas inclusion can be one of the methods for the trace of the movement of oil gas. In this paper the element contents of about 50 inclusions from the oil field of Zhongyuan, Changqing and Talimu was measured, some results of the relationships between the trace elements and oil gas movement were obtained.
In this study, SRXRF method was used to analyze distribution of iron, zinc and other 5 nutrient elements in rice grain of Fe/Zn dense (IR68144) and non-dense (IR64) cultivars. The contents of iron and zinc in the dense cultivar IR68144 were 21 and 53mg/kg, respectively, while those in the non-dense cultivar IR64 being 11.2 and 23mg/kg, respectively. Iron and zinc can be detected in anywhere of the transverse section of IR 68144 grains, but cannot be detected in the center of IR64 grain. The contents of iron and zinc in seed hull of IR68144 were 3.5-fold lower than those in IR64, but higher content in endosperm cells of grain was found in IR 68144 than in IR64. Remarkable differences in the distribution of iron and zinc across rice grains section were noted between the two cultivars, however, the accumulation of Fe/Zn in rice grains was closely correlated with sulfur, calcium and manganese. The results obtained form this research can provide definite gist for further research on accumulation mechanism of iron and zinc in rice grains.
A procedure has been proposed for quantification of Fe in protein bands in polyacrylamide gel matrix with synchrotron radiation X-ray fluorescence(SRXRF)analysis. Human hemoglobin was separated with isoelectric focusing (IEF), and Fe amounts in protein bands were measured with SRXRF. Calibration standards were prepared by electrophoresis of bovine serum albumin containing known amounts of Fe with stacking gel. The calibration curves can be obtained in a range of 0—5.1ng Fe and linear relationship between dosage of metals and fluorescent intensity can be observed (R2=0.9897). The method provides detection limit of 0.63ng Fe,and the recovery of Fe determination is about 106%. The hyphenated technique of SRXRF and IEF has advantages of quantifying trace elements in proteins and identifying the proteins simultaneously. It can be employed for speciation analysis of trace elements in biological samples.
Synchrotron radiation-induced micro X-ray fluorescence analysis (μ-XRF) at BSRF(Beijing Synchrotron Radiation Facility)was used to determine the distribution of Pb and other elements in slices of bone of rat exposed to Pb. It was found that Pb was mostly located at the border of the compact bone and that Zn was mostly located at compact bone and the border of the compact bone. Additionally, Ca, P, Sr and Fe distributions were simultaneously recorded.
In order to explore the interaction and function between the ZnT3 mRNA expression and zinc elemental distribution in brain slice of mouse, zinc concentration and its distribution were determined by SRXRF and ZnT3 mRNA expression in tissue was examined by RT-PCR method. The results show that the zinc content in cerebral cortex and hippocampus was significantly higher than in other positions. The highest expression of ZnT3 mRNA was observed in cerebrum, hippocampus and testis. However, the ZnT3 mRNA was not detected in heart, liver, lung, spleen, kidney, intestine, olfactory bulb and cerebellum. Furthermore, the results suggest that ZnT3 facilitates the accumulation of zinc in synaptic vesicles and may play important roles in structuring of vesicular zinc pool.
The contents and micro distribution of iron and other trace elements in the olfactory bulb after intranasal instillation were measured by synchrotron radiation X-ray fluorescence analysis (SRXRF). The mice were intranasally instilled of fine iron oxide particles (60---200nm) at a dose of 40mg/kg b ody weight. Two weeks later, the content of iron in the olfactory bulb increased 20\% compared with the control. The elevated iron was predominately concerned in the olfactory nerve (ON), granular layer (Gl) and anterior olfactory nucleus, external part (AOE), which indicated that fine iron oxide was transported to Gl via primary olfactory nerve and further translocated in AOE via secondary olfactory nerve. Moreover, in the experiment group, the levels of Ca increased 12% and Zn decreased 17%. Similarly to Fe, the higher Ca concentration was dominantly accumulated in the ON and Gl layers as well. Although the average Cu content in the control and experimental group was similar, the distribution of Cu was obviously changed due to the exposure of fine Fe2O3 particles. In the control, Cu was primarily concerned in anterior olfactory nucleus, lateral part (AOL), AOE, accessory olfactory bulb (AOB) and granule cell layer of the accessory olfactory bulb (GrA), while the Cu content in the experimental group was significantly higher in the ON, Gl and EPl layers. In conclusion,the changes of Fe, Ca, Zn, Cu levels must be, to some extent,correlate with the oxidative stress and eurodegenerative diseases.
Nanosized TiO2 is widely used for cleaning air,antibacterial and decomposing organic in wastewater for its highly photocatalytic function. TiO2 inhalation via respiratory tracts is the most common route of its exposure in industry and environment. After inhalation by human or rodents, TiO2 can induce inflammation and pulmonary lesions, which was reported to even cause lung cancer by long-term exposure. In this paper, Synchrotron Radiation X-ray Fluorescence was employed to investigate the distribution of TiO2 in the olfactory bulb and brain of mice after inhalation of TiO2 particles suspension.The results showed that TiO2 could enter the olfactory nerve layer (ON), granular cell layer of olfactory bulb (Gro), and olfactory ventricle (OV) and further the hippocampus, thalamus,and CA3 area of the brain through the olfactory nervous system.The distribution area of microsized TiO2 was wider than that of nanosized TiO2.
In this paper, A grazing exit X-ray fluorescence spectroscopy for thin film analysis was developed by Institute of High Energy Physics, Chinese Academy of Sciences. GEXRF is a new method of instrumental analysis that not only allows determination of the film composition, but also provides information on depth distributions and densities, thickness of films. With grazing-emission X-ray fluorescence, the opposite principle of total reflection X-ray fluorescence is utilized. In this study, X-ray fluorescence (XRF) experiments have been performed for metal thin films (Ni, Ni/Ti) on silicon substrates and a mirror-polished GaAs under the grazing exit condition. The XRF intensity was measured as a function of the exit angle for nearly normal X-ray incidence. The angular dependence of the grazing exit XRF intensity showed a sharp increase at the critical angle of Kα, Kβ radiation for the metal film. The applicability of the grazing exit XRF for thin-film analysis was clearly demonstrated.
The Hg L3-edge XANES spectra of montmorillonite treated with Hg(NO3)2 0.01M aqueous solution and the mixing solution of Hg(NO3)20.01M aqueous solution and cysteine 0.01M aqueous solution have been measured at several high temperatures. The adsorption and desorption of mercury in Hg-rich montmorillonite minerals and the effect of cysteine on the adsorption of mercury by this clay mineral were studied. Our analysis shows that mercury is six fold coordinated by water molecules and the oxygen atoms of montmorillonite surface without the amino acid introduction. Mercury atoms prefer to bond with sulphur atoms of the amino acid cysteine to form more stable Hg-S bonds when the amino acid cysteine has been introduced. This result suggests that the treatment with the amino acid enhances the stability of mercury sorbed by the montmorillonite mineral and efficiently retard the release of mercury ions into the geosphere.
The PM10 samples were collected at three different sites in or out a tunnel in Shanghai. The XAFS (X-ray absorption fine structure) spectroscopy was applied for the speciation of iron and lead in the samples. The chemical components were determined by IFEFFIT program. The results show: Fe2O3, Fe3O4, Fe2(NO3)3 and FeO are presented as the main components in the samples of different sites. In the middle of the tunnel, Fe(NO3)3 and FeO are in high proportion, but outside of the tunnel, the proportion of these two components goes down, besides, the proportion of Fe2O3 increases. The main lead species are PbSO4, PbO2, Pb3(PO4)2 and a little PbO in samples of different sites. Similarly, the proportion of PbSO4 and PbO2 is higher than that of the outside. And there is a small amount of PbO out of the tunnel. There is considerable difference between the middle and outside in the two elemental species, which is caused by the different pollution source and environment.
A series of nanocrystalline Lu2O3:Eu(10%) with different sizes was studied by EXAFS. The result shows that the first coordination shells Lu-O and Eu-O have bigger coordination number and longer coordination distance with the size decreasing. The linear relation between nearest coordination distance and reciprocal value of particle diameter suggests that the system have two kinds of local structure state. One of them is noncrystal structure, which has big coordination number and long coordination distance comparing with the crystal situation. The component of noncrystal phase increases with the decreasing size and causes abnormal physical behavior such as novel luminescence property.
Single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes (DWNTs) and multi-walled carbon nanotubes (MWNTs) have been investigated using X-ray Absorption Near Edge Spectroscopy (XANES) after different thermal annealing procedures performed in ultra high vacuum. Carbon K-edge spectra show that the contaminants present on the surface of MWNTs are more sensitive to thermal treatments than those for DWNTs and SWNTs. In addition, multiple-scattering features in the XANES region shift towards low energies going from single to multi-walled nanotubes, addressing a different interaction between layers in these different nanotube systems.
The novel physical and chemical properties of endeohedral metallofullernens are very important for their potential application in electronical and medical fields and attract extensive attention from researchers.In this paper, we describe the process of efficient preparation of endeohedral metallofullernen Y@C82; we aslo investigate it by EXAFS at low temperatures (25K) and deal with the EXAFS data at different k range. The structure parameters of the first two shells are obtained and they are similar at different k range. However, there are large static disorders even at low temperature.
High pressure Energy dispersive X-ray diffraction of BeO has been studied in Beijing Synchrotron Radiation Facility (BSRF) . BeO remain hexagonal Wurtzite structure as ambient pressure phase when pressure from ambient pressure up to 42GPa, no phase transition occur, the cell volume decrease as pressure increase. The data of the Wurtzite phase ranging from 0.6 to 42GPa were fitted to the Murnaghan P-V equation of state. Assume K0' to be 4 and obtained bulk modulus K0=276GPa.
The high pressure diffraction study of SrF2 was performed using synchrotron radiation energy dispersive X-rays diffraction (EDXD). Liquid Ar was used as pressure transmitting medium in the experiment in order to produce hydrostatic pressure. The highest pressure was up to 44.2GPa. A phase transition of SrF2, from cubic to orthorhombic，occurred around 11.2GPa. By fitting the pressure-volume data, the bulk modulus of the cubic phase of SrF2 is 70.0(5.0)GPa, and the bulk modulus of the orthorhombic of SrF2 is 198.3(15.2)GPa. SrF2 was returned to the cubic phase by decreasing pressure.
We have successfully synthesized C70 rods in nano/sub-micrometers scale by evaporating solvent method. The diameter of the as grown C70 rods is ～500 nm, and the length is ～10μm. The EDXD pattern and Raman spectroscopy for as -grown sample indicate that the as grown C70 rod is in hcp structure. The pressure-induced structural phase transition has been studied by using DAC combined with EDXD and Raman spectroscopy methods under quasi-hydrostatic pressure up to 26.1GPa. It is found that hcp structure transforms into amorphous phase for C70 rods in the pressure range from 23.3 to 26.1GPa, which is higher than the transformation pressure for bulk C70 crystals. The phase transition is irreversible and it is induced by the collapse of C70 cage.
Aimed at the transformation methods and mechanism of amorphous silica on the conditions of high pressure and high temperature, we used the Changbaishan diatomite, which had been heating treated at 700°C, as the sample of amorphous silica, to carried out the in situ high pressure and high temperature synchrotron X-ray diffraction determinations (EDXD method) in the range of pressure of 0—4GPa and temperature of 1000—1300K by the diamond anvil cell apparatus and double-sided laser heating technique. The experimental results indicate that amorphous silica transform to α-quartz, but not β-quartz and cristobalite in the range of pressure of 0.8—2.4GPa and temperature of 1000—1300K. The crystalline temperature of amorphous silica under high pressure is much lower than that of ambient condition.The resluts means that the pressure is favored to low the activation energy of amorphous transform to crystalline phases,and would change the metastable phase transformation mechanism,leading to the different crystalline phases. In the range of pressure of 3—4GPa and temperature at 1300K, both amorphous silica and quartz transform to coesite.
High-pressure in situ energy dispersive X-ray diffraction (EDXRD) experiments on amorphous selenium(a-Se) have been carried out using a synchrotron X-ray source and a diamond anvil cell (DAC) up to 74.3GPa at room temperature. The pressure-induced crystallization of a-Se has been found at the pressures between 10GPa and 11GPa, and the crystal structure is confirmed to be the mixture of hexagonal phase and a new high pressure metallic phase. It is noticeable that the new phase is still stable up to 42GPa, and completely transformed to the orthorhombic phase after 42GPa. Two structure phase transitions at about 30GPa and 60GPa have also been observed, which agree very well with Mao et al and Akahama et al, respectively, whose work were starting from the material of hexagonal selenium.
Pure beta-C3N4 with symmetry group P63/M (176) and cubic C3N4 were synthesized in laser heated diamond anvil cell under high pressure and high temperature conditions. The precise XRD analysis (Rwp=2.8) was successfully performed to refine the structures of graphite C3N4 and beta-C3N4. Moreover, the structural transition from beta-C3N4 to cubic C3N4 was monitored by In-situ high pressure synchrotron X-ray diffraction analysis.
For evaluating the X-ray diffraction enhanced imaging (DEI) technology in the early diagnosis of breast cancer, the massive samples of normal breast tissue and cancerous one were imaged by DEI method using hard X-rays from 4W1A beamline at the Beijing Synchrotron Radiation Facility (BSRF). DEI images of both normal and cancerous breast tissues have been comparatively analyzed. The results show that diffraction images obtained at the top position of the rocking curve is clear enough and approximately display the structures of the soft tissue. The apparent absorption image is basically similar to the conventional mammography, and there are definite difficulties in distinguishing variant soft-tissues and its ability of finding cancerous soft-tissues is lower than the diffraction image. The inner structures of samples and the differences in shape, size, distribution and structure of the gland for normal and cancerous breast tissues can be clearly shown in refraction images. So, the DEI technology has high value in diagnosing breast cancer and may be an important complementary to early diagnostic method.
X-ray diffraction enhanced imaging (DEI) based on synchrotron radiation is effectively applied to the inspection of internal structures of weakly absorbing low-Z samples, such as soft issue. Its key problem is how to extract refractive angle images, which reflect phase gradients in samples, from DEI images. Geometric-optics approximation methods and statistical methods of multiple images are investigated in this paper. Then a new extraction method, named `statistical-geometric-optics approximation', is brought forward. It is validated by experiments at BSRF and proved that it can improve the exactness of geometric-optics approximation solutions and the Signal to Noise Ratio (SNR) of refractive angle images.
The synchrotron radiation is focused by using a combined system of a monolithic polycapillary X-ray lens and a toroidal mirror. The synchrotron radiation beam with a 2.3×26mm2 area, whose vertical divergence and transverse divergence are appropriately zero and 1.1mrad respectively, is first focused into a beam spot with a 0.9×0.3mm2 area, a 0.1mrad vertical divergence and a 1.4mrad transverse divergence by the toroidal mirror. The focused beam spot is then focused by the monolithic polycapillary X-ray lens into a focal spot with a 21.4μm diameter. The gain of power flux density in the focal spot of the polycapillary X-ray lens is 59. At 8.0keV, the transmission efficiency and focal distance of the monolithic polycapillary X-ray lens are 7.9% and 13.3mm, respectively.
After more than 30 years research and Development, Proximity X-ray lithography has matured considerably and it has many advantages, such as high resolution, long depth of focus, large process latitude, high throughout ,and so on. For X-ray mask absorber, if Au metal is selected, it can only be plated and may pollute the silicon-based integrated circuits. TaSi film can be dry etching and does not pollute the silicon-based integrated circuits, it is a potential candidate for X-ray mask absorber. In this paper , the home-made silicon nitride /TaSi X-ray mask fabrication process is described, unlike the conventional fabrication process, after e-beam exposure and development, is etched Inductively Coupled Plasma(ICP) etching based on SF6/CHF3 gas chemistries is used to pattern the TaSi film,using ZEP520 e-beam resist as the barrier layer directly. Primary experimental result demonstrated this X-ray mask fabrication process is feasible.
Different photoelectron analyzer has different detectable area and acceptance angle, the experimental count rate is up to the photon flux density in the detected area, so the size of the X-ray source used for the analyzer is very important to get the best experimental result. Due to the experimental resolution and count rate of the analyzers is not so ideal, their relation to the beam spot of the beamline is studied. Result shows the size of beam spot at the sample position is too large,which helped to decide the upgrade project for beamline 4B9B and make the beam size much more smaller. A new design for high photon energy branch of the beamline upgrade with new post-focusing mirror is finished, meanwhile the focusing of low photon energy branch is also better designed.
- A SCOAP3 participating journal - free Open Access publication for qualifying articles
- Average 24 days to first decision
- Fast-track publication for selected articles
- Subscriptions at over 3000 institutions worldwide
- Free English editing on all accepted articles
- The 2019 summer holiday-Office closure
- Editor Recruitment
- 2018 Impact Factor 5.861
- CPC Joins Committee on Publication Ethics (COPE)
- Chinese New Year-Office closure