Size-controlled formation of Cu nanoclusters in pulsed magnetron sputtering system

Straňák, Vítězslav; Block, Stephan; Drache, Steffen; Hubička, Zdeněk; Helm, Christiane A.; Jastrabı́k, L.; Tichý, M.; Hippler, R.

doi:10.1016/j.surfcoat.2010.10.030

Cited by 58 publications

(28 citation statements)

References 33 publications

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“…Log-normal distributions arise in the description of many phenomena that involve either growth or division mechanisms. Examples may be found in nature, social sciences, technology, biology, and medicine (15)(16)(17)(18)(19). The reason is that, for many natural processes of growth, relative growth rate is independent of size (16).…”

Section: Structural Properties Of Aegagropilaementioning

confidence: 99%

Structure and mechanics of aegagropilae fiber network

Verhille

Moulinet

Vandenberghe

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Fiber networks encompass a wide range of natural and manmade materials. The threads or filaments from which they are formed span a wide range of length scales: from nanometers, as in biological tissues and bundles of carbon nanotubes, to millimeters, as in paper and insulation materials. The mechanical and thermal behavior of these complex structures depends on both the individual response of the constituent fibers and the density and degree of entanglement of the network. A question of paramount importance is how to control the formation of a given fiber network to optimize a desired function. The study of fiber clustering of natural flocs could be useful for improving fabrication processes, such as in the paper and textile industries. Here, we use the example of aegagropilae that are the remains of a seagrass (Posidonia oceanica) found on Mediterranean beaches. First, we characterize different aspects of their structure and mechanical response, and second, we draw conclusions on their formation process. We show that these natural aggregates are formed in open sea by random aggregation and compaction of fibers held together by friction forces. Although formed in a natural environment, thus under relatively unconstrained conditions, the geometrical and mechanical properties of the resulting fiber aggregates are quite robust. This study opens perspectives for manufacturing complex fiber network materials.fiber network | fiber aggregation | Posidonia oceanica | fibrous material A egagropilae are a natural aggregate of fibers produced by the decomposition of leaves and roots of Posidonia oceanica. The fibers are entangled by sea motion until the clusters reach the shore (1) (Fig. 1). P. oceanica is an endemic plant of the Mediterranean Sea with very long and thin leaves (about 1-m long, 1-cm wide, and less than 1-mm thick). The name aegagropilae originates from the Greek [αίγαγρoς (wild goat) and πιλoς (fur)] and refers to the resemblance between the shape of these balls and those regurgitated by goats. Natural fiber clustering occurs for different species of aquatic plants, such as the so-called seaballs that can be found on the Atlantic Ocean and lake shores (2, 3).P. oceanica meadows play an important ecological role in the preservation of Mediterranean coasts. They constitute plant barriers that promote sediment trapping and oxygen production in seabed, and the accumulated remains protect the beaches from erosion. Moreover, aegagropilae fibers are suitable materials for insulation in construction and automotive industries. After submitting them to various tests, they recently landed in the marketplace under the name of Neptutherm. Beyond the curiosity that these natural objects can provoke, aegagropilae samples found on beaches raise several fundamental questions. The first set of questions is on their formation process. How can fibers be entangled and packed by a flow without any confinement? How long does it take to form a cluster? Can one explain the size distribution of these aggregates? The second set of q...

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Section: Structural Properties Of Aegagropilaementioning

confidence: 99%

Structure and mechanics of aegagropilae fiber network

Verhille

Moulinet

Vandenberghe

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…21,22 Briefly, the script scans over the images identifying the highest points within a moving 17 3 17 rectangle (supplemental Figure 1), giving the position and maximum height of the samples adsorbed to mica. To avoid cross-talk with measurement noise, a 0.9-nm threshold (the standard deviation of the background noise in the AFM images) was used in this study.…”

Section: Atomic Force Microscopymentioning

confidence: 99%

Binding of anti–platelet factor 4/heparin antibodies depends on the thermodynamics of conformational changes in platelet factor 4

Kreimann¹,

Brandt²,

Krauel³

et al. 2014

Blood

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Key Points• Besides clustering, platelet factor 4/polyanion complexes require input of energy to become immunogenic. • Minute differences in chain length determine the induction of antigenicity of PF4.The chemokine platelet factor 4 (PF4) undergoes conformational changes when complexing with polyanions. This can induce the antibody-mediated adverse drug effect of heparin-induced thrombocytopenia (HIT). Understanding why the endogenous protein PF4 becomes immunogenic when complexing with heparin is important for the development of other negatively charged drugs and may also hint toward more general mechanisms underlying the induction of autoantibodies to other proteins. By circular dichroism spectroscopy, atomic force microscopy, and isothermal titration calorimetry we characterized the interaction of PF4 with unfractionated heparin (UFH), its 16-, 8-, and 6-mer subfractions, low-molecular-weight heparin (LMWH), and the pentasaccharide fondaparinux. To bind anti-PF4/heparin antibodies, PF4/heparin complexes require (1) an increase in PF4 antiparallel b-sheets exceeding ∼30% (achieved by UFH, LMWH,, (2) formation of multimolecular complexes (UFH,, and (3) energy (needed for a conformational change), which is released by binding of ‡11-mer heparins to PF4, but not by smaller heparins. These findings may help to synthesize safer heparins. Beyond PF4 and HIT, the methods applied in the current study may be relevant to unravel mechanisms making other endogenous proteins more vulnerable to undergo conformational changes with little energy requirement (eg, point mutations and post-translational modifications) and thereby predisposing them to become immunogenic. (Blood. 2014;124(15):2442-2449 IntroductionHeparin, widely used clinically as a parenteral anticoagulant, 1-3 is a polyanion consisting of iduronic acid, glucuronic acid, and glucosamine residues carrying sulfate groups. Pharmaceutical heparin is obtained from porcine gut mucosa and, as biological material, is composed of polysaccharide chains with variable length. Degradation of unfractionated heparin (UFH) results in less polydisperse and smaller low-molecular-weight heparins (LMWHs). The pentasaccharide fondaparinux consists of the shortest sequence able to catalyze the activity of antithrombin. It was the first synthesized heparin approved for clinical use. 4 Currently, several other heparin-based, synthesized polysaccharides are in preclinical development. 5,6 Beside their anticoagulant activity, heparins have other biological effects including potential antitumor activity, 7 which, however, differs depending on the chain length. Clinically, beside bleeding, heparin-induced thrombocytopenia (HIT) is the most important adverse effect of heparin.8 HIT is a lifethreatening immune-driven adverse effect, which occurs in up to 3% of patients receiving UFH after major surgery. 9 HIT is caused by antibodies that recognize platelet factor 4 (PF4), a CXC chemokine family protein, in ultralarge multimolecular complexes with heparin. 10Several of these pathogenic antib...

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“…This concept of gas aggregation sources was modified by Haberland et al [13], who substituted evaporation cell by a magnetron, which enabled the production of nanoparticles from materials with high melting point (details related to the GAS may be found in review articles [14][15][16]). These GAS systems were already used for the fabrication of a wide variety of metallic nanoparticles such as for instance Cu, Ti, Ag, and Al [17][18][19][20][21][22][23][24][25][26][27][28].…”

Section: Introductionmentioning

confidence: 99%