美国辛辛那提 兰姆特 兰迪斯集团公司来渝专题讲座

20 0 3年 12月 17日 ,美国辛辛那提兰姆特兰迪斯集团公司在重庆西亚酒店举办了C .G .I新材料的专题讲座和技术交流。重庆市有关企事业单位的专家、学者、技术人员共计 98人参加了会议。美国辛辛那提兰姆特兰迪斯集团公司副总裁RogerCope先生、瑞典SinterCast公司总裁SteveDawson先生、美国辛辛那提兰姆特兰迪斯集团公司加工专家GeorgeGerorgiou先生分别介绍了公司情况、C .G .I新材料的应用以及加工技术方面的情况。与会代表就相关技术问题进行了直接交流 ,会议气氛热烈。C .G .I材料为石墨密集型铸铁。这种材料强度高、质量轻 ,其中…     

Platinum, palladium, and rhodium in fresh snow from the Aspe Valley (Pyrenees Mountains, France)

Platinum, palladium, and rhodium have been measured in fresh snow samples from 14 locations within the Aspe Valley (Pyrenees Mountains, France) during two winter seasons, February 2003 and March 2004. Ultraclean procedures were employed for the sampling, sample treatment, and analysis in order to reduce sample contamination. Possible spectral interferences on platinum group element (PGE) analysis by inductively coupled plasma mass spectrometry (ICP-MS) were controlled and corrected. The detection limits obtained were 0.05, 0.45, and 0.075 pg g(-1) for Pt, Pd, and Rh, respectively. PGE content in fresh snow from the Pyrenees Mountains range from 0.20 to 2.51 pg g(-1) for Pt, 1.45-14.04 pg g(-1) for Pd, and 0.24-0.66 pg g(-1) for Rh. The higher PGE concentration, generally measured in sites located close to road traffic, exhibit potential resuspension of PGE-enriched particles emitted locally from the car exhaust, although no direct relationship could be observed with the number of vehicles. Measured atmospheric synoptic conditions allowed identification of the origin of air masses reaching the Aspe Valley and therefore provided information about the possible sources of platinum group elements. Higher PGE concentrations measured in 2004 samples, compared to the ones collected in 2003, indicate the influence of atmospheric synoptic conditions on the studied area. Fresh snow samples collected in 2003 could not be linked to a specific source, whereas 2004 samples could be influenced by PGE emissions from European vehicle fleet and Russian PGE-containing mining activities.     

Partitioning of metal species during an enriched fuel combustion experiment. speciation in the gaseous and particulate phases

Combustion processes are the most important source of metal in the atmosphere and need to be better understood to improve flue gas treatment and health impact studies. This combustion experiment was designed to study metal partitioning and metal speciation in the gaseous and particulate phases. A light fuel oil was enriched with 15 organometallic compounds of the following elements: Pb, Hg, As, Cu, Zn, Cd, Se, Sn, Mn, V, Tl, Ni, Co, Cr, and Sb. The resulting mixture was burnt in a pilot-scale fuel combustion boiler under controlled conditions. After filtration of the particles, the gaseous species were sampled in the stack through a heated sampling tube simultaneously by standardized washing bottles-based sampling techniques and cryogenically. The cryogenic samples were collected at -80 degrees C for further speciation analysis by LT/GC-ICPMS. Three species of selenium and two of mercury were evidenced as volatile species in the flue gas. Thermodynamic predictions and experiments suggest the following volatile metal species to be present in the flue gas: H2Se, CSSe, CSe2, SeCl2, Hg(0), and HgCl2. Quantification of volatile metal species in comparison between cryogenic techniques and the washing bottles-based sampling method is also discussed. Concerning metal partitioning, the results indicated that under these conditions, at least 60% (by weight) of the elements Pb, Sn, Cu, Co, Tl, Mn, V, Cr, Ni, Zn, Cd, and Sb mixed to the fuel were found in the particulate matter. For As and Se, 37 and 17%, respectively, were detected in the particles, and no particulate mercury was found. Direct metal speciation in particles was performed by XPS allowing the determination of the oxidation state of the following elements: Sb(V), Tl(III), Mn(IV), Cd(II), Zn(II), Cr(III), Ni(II), Co(II), V(V), and Cu(II). Water soluble species of inorganic Cr, As, and Se in particulate matter were determined by HPLC/ICP-MS and identified in the oxidation state Cr(III), As(V), and Se(IV).     

Reproducible surface-enhanced Raman scattering spectra of bacteria on aggregated silver nanoparticles

Surface-enhanced Raman scattering (SERS) is proven to be a powerful technique for rapid identification and discrimination of microorganisms. However, due to the heterogeneous nature of the samples, the acquisition of reproducible spectra hinders the further development of the technique. In this study, we demonstrate the influence of the experimental conditions on SERS spectra. Then, we report a simple sample preparation method coupled with a light microscope attached to a Raman spectrometer to find a proper spot on the sample to acquire reproducible SERS spectra. This method utilizes the excited surface plasmons of the aggregated silver nanoparticles to visualize the spots on the sample. The samples are prepared using the concentrated silver colloidal solutions. The collection time for one spectrum is 10 s and each spectrum is a very good representative of the other spectra acquired from the same sample. The nature of the surface charge of the silver nanoparticles influences the spectral features by determining the strength of the interactions between nanoparticles and bacteria and the aggregation properties of the nanoparticles. Although increasing the colloid concentration in the sample resulted in reproducible spectra from arbitrary points on the sample, a great variation from sample to sample prepared with the different colloidal solution concentrations is observed.     

Segmenting articular cartilage automatically using a voxel classification approach

We present a fully automatic method for articular cartilage segmentation from magnetic resonance imaging (MRI) which we use as the foundation of a quantitative cartilage assessment. We evaluate our method by comparisons to manual segmentations by a radiologist and by examining the interscan reproducibility of the volume and area estimates. Training and evaluation of the method is performed on a data set consisting of 139 scans of knees with a status ranging from healthy to severely osteoarthritic. This is, to our knowledge, the only fully automatic cartilage segmentation method that has good agreement with manual segmentations, an interscan reproducibility as good as that of a human expert, and enables the separation between healthy and osteoarthritic populations. While high-field scanners offer high-quality imaging from which the articular cartilage have been evaluated extensively using manual and automated image analysis techniques, low-field scanners on the other hand produce lower quality images but to a fraction of the cost of their high-field counterpart. For low-field MRI, there is no well-established accuracy validation for quantitative cartilage estimates, but we show that differences between healthy and osteoarthritic populations are statistically significant using our cartilage volume and surface area estimates, which suggests that low-field MRI analysis can become a useful, affordable tool in clinical studies.     

Discrimination of polymers by using their characteristic collision energy in tandem mass spectrometry

The characteristic collision energy to obtain 50% fragmentation, expressed as the characteristic collision voltage (CCV), was used as a tool to discriminate different classes of polymers. The CCV value of different polymers was determined in a quadrupole ion trap mass spectrometer. Good linear correlation (0.980 < R(2) < 0.999) between the CCV values and precursor ion mass was found for all polymers studied. The position of the various linear trend lines varied among the various polymers, which allowed their grouping based on the respective CCV values. The collision energy necessary to drive fragmentation was decreasing in the order of polyethers > polymethacrylates > polyesters > polysaccharides. This suggests that polysaccharides fragment most easily (low CCVs), while polyethers require the highest collision energy among the polymers studied. The effect of end group on the CCV was also studied, showing a minor influence in most cases. In addition, the applicability of CCV as discriminator was studied for a mixture of (1) polylactic acid (PLA), (2) poly(tetramethylene glycol) (PTMEG), and (3) PLA-block-PTMEG-block-PLA block copolymer. Differences between the CCV values of four nominally isobaric polymers (of which two were copolymers and two were homopolymers) were observed. These results demonstrate that the insertion of a "weak" link into a polymer chain significantly affects the energy required for fragmentation.     

遥测技术在火箭发动机过载试验中的应用

详细介绍火箭发动机过载试验台遥测系统的设计方法和设计内容。针对过载试验台遥测信道的特点,通过科学布局、合理分配系统参数,并采用适合的天线类型和信道编码技术,成功解决了火箭喷焰和多径衰落对无线电遥测信号的影响,实现了火箭发动机过载试验37种传感器参数非接触测量。     

(Tri)butyltin biotic degradation rates and pathways in different compartments of a freshwater model ecosystem

Experiments were conducted in controlled temperate freshwater ecosystems (microcosms) to determine the persistence and biogeochemical dynamic of tributyltin (TBT) and its degradation products. TBT and its derivatives were monitored simultaneously for 23 days (552 h) in sediment-water systems, with or without macroorganisms (macrophytes: Elodea canadensis and gastropods: Lymnaea stagnalis). Biphasic TBT removal from the water column was significantly enhanced by the presence of biota. The persistence of TBT in biota was assessed by a kinetic approach of the different bioaccumulation pathways and associated metabolisms adopted by the snails and the macrophytes in response to the TBT contamination. Furthermore, sediment acted for the final sink for butyltins in both types of microcosms, with more than 70% of TBT and its metabolites recovered in this compartment after two weeks of exposure. Degradation pathways in sediments of both biotic and abiotic microcosms appeared to represent a key process in TBT cycle and were characterized by half-lives in the range of one month. Specific transformation and transfer pathways of TBT as reactional mechanisms are discussed and modelled assessing in detail the role of each compartment with regards to the fate of TBT in the model aquatic ecosystems.