Mass spectrometry-based metabolomics: accelerating the characterization of discriminating signals by combining statistical correlations and ultrahigh resolution

A strategy combining autocorrelation matrices and ultrahigh resolution mass spectrometry (MS) was developed to optimize the characterization of discriminating ions highlighted by metabolomics. As an example, urine samples from rats treated with phenobarbital (PB) were analyzed by ultrahigh-pressure chromatography with two different eluting conditions coupled to time-of-flight mass spectrometric detection in both the positive and negative electrospray ionization modes. Multivariate data analyses were performed to highlight discriminating variables from several thousand detected signals: a few hundred signals were found to be affected by PB, whereas a few tenths of them were linked to its metabolism. Autocorrelation matrices were then applied to eliminate adduct and fragment ions. Finally, the characterization of the ions of interest was performed with ultrahigh-resolution mass spectrometry and sequential MS(n) experiments, by using a LC-LTQ-Orbitrap system. The use of different eluting conditions was shown to drastically impact on the chromatographic retention and ionization of compounds, thus providing a way to obtain more exhaustive metabolic fingerprints, whereas autocorrelation matrices allowed one to focus the identification work on the most relevant ions. By using such an approach, 14 PB metabolites were characterized in rat urines, some of which have not been reported in the literature.     

Mechanical testing of titanium/aluminium–silicon interfaces by push-out

Mechanical properties of Ti/Al–7Si assemblies produced by insert moulding were studied with a classical push-out test and a variant that is the circular-bending test. Special care has been taken for controlling both the reactivity at the Ti/Al–7Si interface and the metallurgical health of the Al–7Si matrix. Mechanical tests until complete debonding have been completed with interrupted tests, metallographic characterizations and FEM analysis of elastic stress state. A mean shear strength of the interface of about 120 MPa was obtained. When the Ti insert is solely fretted in the matrix, without chemical interaction between Ti and the Al–7Si alloy, the mean shear strength is significantly lower (48 MPa). This result clearly shows that chemical interaction at the interface (formation of a thin TiSi layer at the Ti side and a thick Al₃Ti(Si) layer at the Al–7Si alloy side) improves the mechanical properties of the assembly. It is also shown that the failure sequence is characterized both by crack propagation from bottom to top and matrix yielding from top to bottom. Actually, interface damaging begins by crack initiation at the specimen bottom face (not at the top face and under the indenter) in a nearly pure mode I solicitation at a radial tensile stress of about 100 MPa.     

316L不锈钢粉末注射成形件的烧结致密化行为

为了控制粉末注射成形零件的最终尺寸精度和力学性能,对316L不锈钢粉末注射成形件的烧结致密化行为进行了试验研究,分析了烧结温度和升温速率对试件致密化行为以及烧结件力学性能的影响.试验结果表明,致密化过程始于1080℃左右,主要在1200～1300℃的升温过程中快速进行,致密化速率随着升温速率的升高而升高.烧结件的抗拉强度、抗弯强度以及延伸率,不但取决于致密化程度,而且与微观结构有关.分析表明,将基于扩散控制和强度控制的烧结理论结合,可以有效地解释316L不锈钢粉末的致密化行为,需在现有的烧结模型中考虑强度影响因素,才能更真实地模拟烧结过程.     

NO ions as IR probes for the location of OH groups and Na ions in main channels and side pockets of mordenite

NO⁺, generated from NO and O₂, is an infrared probe for the differentiation of Brønsted sites in the main channels and side pockets of mordenites, and for the location and accessibility of sodium ions in the structure. Na⁺ ions in cationic positions in the main channels are replaced by NO⁺, and sodium nitrate is formed. The band assignment was checked by isotopic experiments.     

Arsenic removal by a waste metal (hydr)oxide entrapped into calcium alginate beads

In this work, a solid waste material from an electroplating industrial plant has been investigated for As(III) and As(V) sorption. This sorbent, a mixture of mainly Fe(III) and Ni(II) (hydr)oxides, has been used both in its native form and entrapped in calcium alginate. The effect of sorbent concentration in the gel bead, solution pH, contact time and As(III) and As(V) concentration on sorption has been studied. Furthermore the effect of the gel matrix has been investigated. A 10% (w/v) of (hydr)oxide in the gel beads was found to provide both spherical beads shape and good sorption performance. Solution pH was found to exert a stronger influence in As(V) than in As(III) sorption. The optimum pH range resulted to be within 5-10 for As(III) and within 6-9 for As(V). Taking into account these results, pH 8 was chosen for further sorption experiments. Equilibrium was reached after 48 h contact time for the studied systems. Kinetics data of both As(III) and As(V) onto native (hydr)oxide (O) and entrapped in calcium alginate beads (10% O-CA) were successfully modelled according to pseudo-first and pseudo-second order equations. Sorption equilibrium data were evaluated by the Langmuir isotherm model and the maximum capacity q(max) were 77.4 and 126.5 mg g(-1) for As(III) on O and 10% O-CA, and 26.8 and 41.6 mg g(-1) for As(V) on O and 10% O-CA, respectively. The entrapment of the (hydr)oxide in a calcium alginate gel matrix improved the As(III) and As(V) sorption by 60%.     

Aluminum drinking water treatment residuals (Al-WTRs) as sorbent for mercury: Implications for soil remediation

The potential of readily available and non-hazardous waste material, aluminum drinking water treatment residuals (Al-WTRs), to efficiently sorb and immobilize mercury (Hg) from aqueous solutions was evaluated. Al-WTR samples with average specific surface area of 48m(2)/g and internal micropore surface area of 120m(2)/g were used in a series of batch sorption experiments. Obtained sorption isotherms indicated a strong affinity of Hg for Al-WTRs. Using the Langmuir adsorption model, a relatively high maximum sorption capacity of 79mg Hg/g Al-WTRs was determined. Sorption kinetic data was best fit to a pseudo-first-order model, while the use of the Weber-Morris and Bangham models suggested that the intraparticle diffusion could be the rate-limiting step. Also, Al-WTRs effectively immoblized Hg in the pH range of 3-8. The results from these short-term experiments demonstrate that Al-WTRs can be effectively used to remove Hg from aqueous solutions. This ability points to the potential of Al-WTRs as a sorbent in soil remediation techniques based on Hg-immobilization.     

Cytocompatibility of titanium metal injection molding with various anodic oxidation post-treatments

Metal injection molding (MIM) is a near net shape manufacturing method that allows for the production of components of small to moderate size and complex shape. MIM is a cost-effective and flexible manufacturing technique that provides a large innovative potential over existing methods for the industry of implantable devices. Commercially pure titanium (CP-Ti) samples were machined to the same shape as a composite feedstock with titanium and polyoxymethylene, and these metals were injected, debinded and sintered to assess comparative biological properties. Moreover, we treated MIM-Ti parts with BIOCOAT®, BIODIZE® and BIOCER®, three different anodic oxidation techniques that treat titanium using acid, alkaline and anion enriched electrolytes, respectively. Cytocompatibility as well as morphological and chemical features of surfaces was comparatively assessed on each sample, and the results revealed that MIM-Ti compared to CP-Ti demonstrated a specific surface topography with a higher roughness. MIM-Ti and BIOCER® samples significantly enhanced cell proliferation, cell adhesion and cell differentiation compared to CP-Ti. Interestingly, in the anodization post-treatment established in this study, we demonstrated the ability to improve osseointegration through anionic modification treatment. The excellent biological response we observed with MIM parts using the injection molding process represents a promising manufacturing method for the future implantable devices in direct contact with bones.     

Sensitivity of CFP/YFP and GFP/mCherry pairs to donor photobleaching on FRET determination by fluorescence lifetime imaging microscopy in living cells

Fluorescent protein-based FRET is a powerful method for visualizing protein-protein interactions and biochemical reactions in living cells. It can be difficult, however, to avoid photobleaching when observing fluorescent cells under the microscope, especially those expressing CFP. We compared the sensitivity of two protein-based FRET pairs to light-induced fluorescence changes in the donor, on FRET determination by fluorescence lifetime imaging microscopy (FLIM). Thanks to the very low excitation light levels of the time- and space-correlated single photon counting (TSCSPC) method, FLIM acquisitions were achieved without donor photobleaching. Here, we show that photobleaching of CFP by a mercury lamp under the microscope induced a decrease in the mean fluorescence lifetime, which interfered with FRET determination between CFP and YFP. Importantly, the range of light-induced variation of the mean fluorescence lifetime of CFP was not proportional to the decrease in the steady state fluorescence intensity and varied from cell to cell. The choice of the CFP/YFP pair therefore requires that the cells be observed and analyzed at very low light levels during the whole FRET experiment. In contrast, the GFP/mCherry pair provided an accurate FRET measurement by FLIM, even if some GFP photobleaching took place. We thus demonstrate that CFP can be an unreliable donor for FRET determination in living cells, due to its photosensitivity properties. We demonstrate that the GFP/mCherry pair is better suited for FRET measurement by FLIM in living cells than the CFP/YFP pair.     

Study of an aramid surface reactivity: Modification with a cold plasma or an electron beam followed by a postgrafting reaction

Different modes of activation are described for a postgrafting reaction of acrylic acid on poly(p-phenylene terephthalamid) (PPTA)mitrogen plasma or electron-beam irradiation. Both lead to surface radical formation, and these species are able to initiate grafting. The Functionalization through amino group attachment is characteristic of plasma treatment. Degradation initiated by UV-visible emission of plasma is noticed, leading to the amide clivage. The surface grafting is more important when the PPTA is irradiated with a cold plasma and if water is used as the solvent. The polymer crystallinity degree reduces the grafting of the electron beam-irradiated PPTA even with a high radical concentration. © 1994 John Wiley & Sons, Inc.