Dendrimer intercalation in layered double hydroxides

New organic/inorganic (O/I) hybrid assemblies based on Layered Double Hydroxide (LDH) with polyamide amine dendrimer (PAMAM, generation −0.5 and generation +0.5) were prepared by two different routes using either the direct coprecipitation at constant pH or the anion exchange procedure in double surfactant S⁺S⁻ phases. The obtained materials were characterized by means of powder X-ray diffraction, thermal gravimetric analysis associated with mass spectrometry, and Fourier-transform infrared spectroscopy. X-ray powder diffraction pattern of the O/I LDH assembly exhibit characteristic profiles of LDH-based materials with basal spacing depending on the nature of the dendrimer. Indeed, for both synthetic procedures, interleaved PAMAM −0.5 gives rise to an interlayer space in agreement with a perpendicular molecular arrangement against the layer of the host structure. For PAMAM+0.5, considering its spherical dimension, a much smaller basal spacing was observed. This observation was interpreted as shrinkage of the molecule to accommodate the interlayer LDH gap, which was rendered possible by the bond angle twisting within PAMAM−0.5. FTIR spectra confirm the presence of both moieties inside both Zn₂Al/PAMAM G−0.5 and Zn₂Al/PAMAM G+0.5 assemblies. Finally, thermal analysis associated with mass spectrometry confirm this composition, and in situ temperature XRD data reveal that the highly constrained arrangement for the generation +0.5 is not accompanied by a gain in thermal structural stability; in fact, the assembly prepared from PAMAM −0.5 is more stable. Both O/I PAMAM LDH assemblies constitute well-defined materials which are candidate for catalytic applications.     

Micro Solid Oxide Fuel Cells on Glass Ceramic Substrates

Miniaturized solid oxide fuel cells are fabricated on a photostructurable glass ceramic substrate (Foturan) by thin film and micromachining techniques. The anode is a sputtered platinum film and the cathode is made of a spray pyrolysis (SP)‐deposited lanthanum strontium cobalt iron oxide (LSCF), a sputtered platinum film and platinum paste. A single‐layer of yttria‐stabilized zirconia (YSZ) made by pulsed laser deposition (PLD) and a bilayer of PLD–YSZ and SP–YSZ are used as electrolytes. The total thickness of all layers is less than 1 µm and the cell is a free‐standing membrane with a diameter up to 200 µm. The electrolyte resistance and the sum of polarization resistances of the anode and cathode are measured between 400 and 600 °C by impedance spectroscopy and direct current (DC) techniques. The contribution of the electrolyte resistance to the total cell resistance is negligible for all cells. The area‐specific polarization resistance of the electrodes decreases for different cathode materials in the order of Pt paste > sputtered Pt > LSCF. The open circuit voltages (OCVs) of the single‐layer electrolyte cells ranges from 0.91 to 0.56 V at 550 °C. No electronic leakage in the PLD–YSZ electrolyte is found by in‐plane and cross‐plane electrical conductivity measurements and the low OCV is attributed to gas leakage through pinholes in the columnar microstructure of the electrolyte. By using a bilayer electrolyte of PLD–YSZ and SP–YSZ, an OCV of 1.06 V is obtained and the maximum power density reaches 152 mW cm⁻² at 550 °C.     

A model for capturing and representing the engineering design process

This paper presents a Collaborative Model for capturing and representing the engineering Design process (CoMoDe). CoMoDe is a deductive object-oriented model that, in relation to an engineering design process, is able to capture the different elements that participate in a design process in an integrated fashion. In particular, it is able to represent (i) the activities, operations, and actors that have generated each design product, (ii) the imposed requirements, and (iii) the rationale behind each decision. Furthermore, it also offers an explicit mechanism to represent and trace the different model versions that have participated in the design process. On such a basis, this proposal introduces specific procedures to handle various situations appearing in cooperative environments. They are: (i) different design teams perform independent concurrent activities on “a priori” independent parts of the artefact being designed and afterwards their results need to be made consistent; (ii) distinct teams concurrently work on slightly coupled parts of the artefact being designed and conflict handling must be addressed along their “parallel” course of actions.     

Enhanced HAPEX topography: Comparison of osteoblast response to established cement

The use of poly(methylmethacrylate) PMMA cement by Charnley in the 1960s revolutionized orthopaedic medicine. Since this time, however, little has changed. The development of bioactive composites, such as HAPEX (a composite of 40% vol hydroxyapatite (HA) in a polyethylene matrix) have potential in orthopaedic applications. The composite has been shown to allow direct bone bonding in vivo, and in vitro studies have shown preferential attachment to HA exposed on the composite surface. In vitro study has also shown that altering the topography HAPEX can enhance osteoblast response. This study uses microscopical investigation of osteoblast cytoskeleton, and biochemical measurement of proliferation (by thymidine incorporation) and phenotype (by alkaline phosphatase activity) to compare primary human osteoblast (HOB) activity on HAPEX and PMMA cement. The study shows large increases in HOB response to the new generation material compared to PMMA, the current implant standard.     

Surface topography and HA filler volume effect on primary human osteoblasts in vitro

HAPEX^TM, a bone analog material, with similar properties to cortical bone, has been studied in vitro with particular reference to the effect of surface topography. The stimulation of a favorable bone response by this composite depends on optimization of the hydroxyapatite (HA) content in relation to the material bioactivity without compromising the mechanical characteristics. In this study we have started to investigate the effects of surface topography on cell attachment and subsequent cellular behavior in relation to proliferation. Different volumes of HA (20% and 40%) were added to a high density polyethylene (HDPE) matrix to produce the test materials. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were used to examine cell morphology on HAPEX^TM, and the surface characteristics produced by different machining protocols. The measurement of cellular DNA and tritiated thymidine ([³H]-TdR) incorporation has been used to asses cell proliferation upon the materials. The results show that the material surface topography has a large influence on cell proliferation and attachment, and with a controled material topography the 40% vol HA/HDPE composite gives the greater biological response compared to the 20% vol HA/HDPE composite.     

Detection and quantification of lanthanide complexes in cell lysates by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Gadolinium (III) complexes are under intense scrutiny as contrast agents for magnetic resonance imaging. Although currently used mainly as extracellular agents, there is a growing interest to exploit their contrast enhancing ability in the intracellular environment. To ascertain the preservation of their chemical integrity upon the intracellular entrapment, it is necessary to have a method for their dosage in the cell lysates. Herein, a mass spectrometric method for detection and quantification of gadolinium complexes in cell lysates is reported. The detection by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was carried out by using a non-acidic matrix (2,4,6-trihydroxyacetophenone), which does not allow any leakage of gadolinium from the complex. Quantification has been possible by using as an internal standard an ytterbium complex with the same ligand of the analyte. Ytterbium was chosen because, among the lanthanides, it is the one with the isotopic distribution pattern the most similar to that of gadolinium. Sensitivity was enough to detect low micromolar quantities of a cationic complex and high micromolar quantities of a neutral complex in cell lysates of rat hepatoma cells. In the case of anionic complexes, sensitivity was too low for quantitative analysis. To the best of our knowledge, this is the first report concerning the quantification of metal complexes by MALDI-TOF-MS.     

钢中夹杂物的常规定性分析(英文)

对于钢中夹杂物的研究,目前大多数工作是采用光学显微镜测量抛光的钢样表面的方法实现的。今后若干年里,脉冲分布解析原子发射光谱法(PDA-OES)的分辩率有望得到提高,可以获得夹杂物的尺寸、颗粒数以及空间分布的信息。在应用电子探针微区分析(EPMA)或PDA-OES技术的自动监控过程中,是对抛光的钢表面进行扫描分析。虽然可以获得夹杂物的截面面积及其边界信息,但是这些夹杂物形状的成因却不明显。由于夹杂物的形状和表面特性可以揭示出某类夹杂物的形成过程,因此获知夹杂物的形成过程就可以得到夹杂物的形成、生长和演变等相     

Nine million book items and eleven million citations: a study of book-based scholarly communication using OpenCitations

Scientometrics - Books have been widely used to share information and contribute to human knowledge. However, the quantitative use of books as a method of scholarly communication is relatively...     

Tailoring brushite for in situ setting bone cements

Current strategies in developing calcium phosphate bone substitutes are focused towards in situ setting of the cements under physiological conditions with adequate mechanical properties, which can be tailored to be resorbable by controlling structure and composition. In this study we report the formulation of brushite cements at both physiological and ambient temperature and its effect on the structure and properties. In addition the influence of using both, an alkaline and acidic retardant on the setting and ageing of the cements are reported. Monosodium citrate (pH 3.5 ± 0.1) or trisodium citrate (pH 8.3 ± 0.1) solutions were used at retardants at 23 °C and 37 °C, which clearly indicated that both these parameters influenced strength and microstructure. The ageing of the cements indicated some conversion to monetite, which was predominant in cements formulated at physiological temperature. The results clearly show that the microstructure, resorbability and strength of these in situ setting cements can be manipulated by compositional and temperature ranges to provide wider application as bone substitute materials.