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排序方式: 共有321条查询结果,搜索用时 390 毫秒
131.
Efficient and Rapid Synthesis of Radioactive Gold Nanoparticles by Dielectric Barrier Discharge 下载免费PDF全文
Mathieu Bouchard Myriam Laprise‐Pelletier Stéphane Turgeon Marc‐André Fortin 《Particle & Particle Systems Characterization》2017,34(2)
A compact bench‐top system based on a dielectric barrier plasma discharge (DBD), enables the rapid, automatable, and continuous‐flow synthesis of gold nanoparticles (AuNPs) and radioactive gold nanoparticles (198AuNPs). AuNPs are used as radiosensitizers in oncology, and 198AuNPs (half‐life: 2.7 d) have been suggested as potential cancer brachytherapy sources. Plasma applied at the surface of a liquid containing gold ions (AuCl4?) and dextran induces the production of AuNPs directly in water. This synthesis is monitored in real time by UV–visible spectrometry: the change of absorbance of the solution provides new insights on the growth dynamics of AuNPs by plasma synthesis. By balancing gold ions and surfactant molecules, particles with a diameter lying in the optimal range for radiosensitizing applications (28 ± 9 nm) are produced. The method yields a reduction of more than 99% of the gold ions within only 30 min of plasma treatment. A postsynthesis ripening of the AuNPs is revealed, monitored by UV–visible spectrometry, and quantified within the first few hours following plasma treatment. Radioactive 198AuNPs are also produced by DBD synthesis and characterized by electron microscopy and single‐photon emission computed tomography imaging. The results confirm the efficiency of DBD reactors for AuNPs synthesis in oncology applications. 相似文献
132.
Raybaut M Godard A Haïdar R Lefebvre M Kupecek P Lemasson P Rosencher E 《Optics letters》2006,31(2):220-222
We report what we believe to be the first demonstration of mid-infrared generation (approximately 9 microm) by self-difference frequency generation in Fresnel birefringence quasi-phase-matched Cr:ZnSe laser slabs. 相似文献
133.
Tenni R Sonaggere M Viola M Bartolini B Tira ME Rossi A Orsini E Ruggeri A Ottani V 《Micron (Oxford, England : 1993)》2006,37(7):640-647
Several properties of fibrillar collagens depend on abundance and position of ionic amino acids. We recently demonstrated that N-methylation and N-acetylation of Lys/Hyl amino group did not significantly alter the thermal stability of the triple helical conformation and that the binding of modified collagens I and II to decorin is lost only on N-acetylation. The positive charge at physiological pH of Lys/Hyl side chains is preserved only by N-methylation. We report here the new aspect of the influence of the same modifications on collagen self-aggregation in neutral conditions. Three collagen preparations are very differently affected by N-methylation: acid-soluble type I collagen maintains the ability to form banded fibrils with 67-nm periodicity, whereas almost no structured aggregates were detected for pepsin-soluble type I collagen; pepsin-soluble type II collagen forms a very different supramolecular species, known as segment long spacing (SLS). N-acetylation blocks the formation of banded fibrils in neutral conditions (as did all other chemical modifications reported in the literature), demonstrating that the positive charge of Lys/Hyl amino groups is essential for self-aggregation. Kinetic measurements by turbidimetry showed a sizeable increase of absorbance only for the two N-methylated samples forming specific supramolecular aggregates; however, the derivatization affects aggregation kinetics by increasing lag time and decreasing maximum slope of absorbance variation, and lowers aggregation competency. We discuss that the effects of N-methylation on self-aggregation are caused by fewer or weaker salt bridges and by decrease of hydrogen bonding potential and conclude that protonated Lys side chains are involved in the fibril formation process. 相似文献
134.
Tommi Tervonen Igor Linkov José Rui Figueira Jeffery Steevens Mark Chappell Myriam Merad 《Journal of nanoparticle research》2009,11(4):757-766
Various stakeholders are increasingly interested in the potential toxicity and other risks associated with nanomaterials throughout
the different stages of a product’s life cycle (e.g., development, production, use, disposal). Risk assessment methods and
tools developed and applied to chemical and biological materials may not be readily adaptable for nanomaterials because of
the current uncertainty in identifying the relevant physico-chemical and biological properties that adequately describe the
materials. Such uncertainty is further driven by the substantial variations in the properties of the original material due
to variable manufacturing processes employed in nanomaterial production. To guide scientists and engineers in nanomaterial
research and application as well as to promote the safe handling and use of these materials, we propose a decision support
system for classifying nanomaterials into different risk categories. The classification system is based on a set of performance
metrics that measure both the toxicity and physico-chemical characteristics of the original materials, as well as the expected
environmental impacts through the product life cycle. Stochastic multicriteria acceptability analysis (SMAA-TRI), a formal
decision analysis method, was used as the foundation for this task. This method allowed us to cluster various nanomaterials
in different ecological risk categories based on our current knowledge of nanomaterial physico-chemical characteristics, variation
in produced material, and best professional judgments. SMAA-TRI uses Monte Carlo simulations to explore all feasible values
for weights, criteria measurements, and other model parameters to assess the robustness of nanomaterial grouping for risk
management purposes. 相似文献
135.
Myriam Bouhadid Nathalie Redon Hervé Plaisance Jacques Desbrières Stéphanie Reynaud 《Macromolecular Symposia》2008,268(1):9-13
Summary: The effect of humidity on the ammonia gas (NH3) detection of conducting composite films was investigated. The first results showed that the presence of humidity, acting as interference gas, modifies the behaviour of sensors in the presence of ammonia. However, the behaviour study at atmosphere without ammonia of our materials in controlled temperature and humidity allowed distinguishing atmospheric effect from NH3 pollution. 相似文献
136.
Since their formulation almost 100 years ago, the von Kármán (vK) plate equations have been frequently used both by engineers
and by analysts to study thin elastic bodies, in particular their stability behaviour under applied loads. At the same time
the derivation of these equations met some harsh criticism and their precise mathematical status has been unclear until very
recently. Following up on a recent variational derivation of the vK theory by Friesecke, James and Müller from three-dimensional
nonlinear elasticity we study the predictions and the validity of the vK equation in the presence of in-plane compressive
forces. The first main result is a stability alternative: either the load leads to instability already in the nonlinear bending
theory of plates (Kirchhoff–Love theory), or it leads to an instability in a geometrically linear KL theory (‘linearized instability’),
or vK theory is valid. The second main result states that under suitable conditions the critical loads for nonlinear stability
and linearized instability coincide. The third main result asserts this critical load also agrees with the load beyond which
the infimum of the vK functional is −∞. The main ingredients are a sharp rigidity estimate for maps with low elastic energy
and a study of the properties of isometric immersions from a set in to and their geometrically linear counterparts. 相似文献
137.
The two-dimensional (2D) iron trimellitate [Fe(H(2)O)(2)(C(9)O(6)H(4))].H(2)O, labeled MIL-67, has been obtained under hydrothermal conditions (473 K, 48 h). In the 2D structure of MIL-67, the Fe(2+) ions display two different octahedral environments: [FeO(4)(H(2)O)(2)] and [FeO(2)(H(2)O)(4)]. These octahedra share an apical water molecule to form infinite chains. The chains are linked by partly deprotonated C(9)O(6)H(4)(2-) anions to give hybrid organic-inorganic layers; the remaining acidic-CO(2)H group is dangling in the interlayer space. Below 8(1) K, MIL-67 displays a canted antiferromagnetic behavior, according to analyses via magnetic measurements and M?ssbauer spectroscopy. Crystal data for MIL-67 are as follows: triclinic; space group P1 (No. 2), with a = 6.9671(2) A, b = 7.3089(3) A, c = 12.5097(3) A, alpha = 78.758(1) degrees, beta = 89.542(2) degrees, and gamma = 65.197(1) degrees; volume V = 565.21(3) A(3); and Z = 2. 相似文献
138.
Crosnier de Bellaistre M Renaud L Kleimann P Morin P Randon J Rocca JL 《Electrophoresis》2004,25(18-19):3086-3091
The electroosmotic flow created in zirconia-modified capillaries has been previously investigated. In this paper, we compared the electroosmotic data set with streaming current measurements and we related all these data through zeta-potential. Streaming current measurements give an excellent indication on the direction and the value of the electroosmotic mobility of an electrolyte/capillary system for a large set of experimental conditions: 2 < pH < 12, 0 < ACN < 80 %, 10(-4) M < [SO(2- )4 ] < 4 x 10(-2) M. A good correlation between zeta-potential from streaming current measurements and zeta-potential from electroosmotic mobility measurements was observed (r2 = 0.95). However, the values obtained from streaming current were always slightly lower than the one calculated from electroosmotic mobility (slope = 0.86, sigma = 0.06). In zirconia-coated capillaries the zeta-potential can be tuned from -50 to +100 mV depending on the composition of the electrolyte. 相似文献
139.
Cañada-Cañada F Kasselouri A Prognon P Maillard P Grierson DS Descroix S Taverna M 《Journal of chromatography. A》2005,1068(1):123-130
The nonaqueous capillary electrophoresis mode which includes a preconcentration step based on a transient pseudo-isotachophoresis to the simultaneous separation of seven glucoconjugated and hydroxylated porphyrins and chlorins, exhibiting very close structures, is reported. A high methanol content, of the buffer solution, was necessary in order to prevent self-assembly of the compounds and to enhance their solubility during separation. With the addition of 66% (v/v) methanol and 1% (w/v) NaCl in the aqueous sample solution, large volumes could be injected (44% capillary volume) without a loss in resolution. Sensitivity of detection was therefore improved by a 100-fold factor with regard to the method employing normal injection (2% capillary volume). Optimum electrophoretic conditions, in terms of sensitivity and performance, were obtained by using 20 mM phosphoric acid buffer, pH 2.2 and 50% methanol. The method was validated and applied to qualitative analysis of glucoconjugates in serum samples. 相似文献
140.
Myriam Mikhael Sara N. Alektiar Charles S. Yeung Zachary K. Wickens 《Angewandte Chemie (International ed. in English)》2023,62(30):e202303264
The rapid preparation of complex three-dimensional (3D) heterocyclic scaffolds is a key challenge in modern medicinal chemistry. Despite the increased probability of clinical success for small molecule therapeutic candidates with increased 3D complexity, new drug targets remain dominated by flat molecules due to the abundance of coupling reactions available for their construction. In principle, heteroarene hydrofunctionalization reactions offer an opportunity to transform readily accessible planar molecules into more three-dimensionally complex analogs through the introduction of a single molecular vector. Unfortunately, dearomative hydrofunctionalization reactions remain limited. Herein, we report a new strategy to enable the dearomative hydrocarboxylation of indoles and related heterocycles. This reaction represents a rare example of a heteroarene hydrofunctionalization that meets the numerous requirements for broad implementation in drug discovery. The transformation is highly chemoselective, broad in scope, operationally simple, and readily amenable to high-throughput experimentation (HTE). Accordingly, this process will allow existing libraries of heteroaromatic compounds to be translated into diverse 3D analogs and enable exploration of new classes of medicinally relevant molecules. 相似文献