scholarly journals Reversibly Cross-Linking Amino-Polysiloxanes by Simple Triatomic Molecules. Facile Methods for Tuning Thermal, Rheological, and Adhesive Properties

2009 ◽  
Vol 113 (27) ◽  
pp. 11546-11553 ◽  
Author(s):  
Tao Yu ◽  
Koji Wakuda ◽  
Daniel L. Blair ◽  
Richard G. Weiss
Keyword(s):  
Cross Linking ◽  
Adhesive Properties ◽  
Triatomic Molecules

Surface and Adhesive Properties of Low-Density Polyethylene after Radiation Cross-Linking

2014 ◽  
Vol 606 ◽  
pp. 265-268 ◽  
Author(s):  
Martin Bednarik ◽  
David Manas ◽  
Miroslav Manas ◽  
Martin Ovsik ◽  
Jan Navratil ◽  
...  
Keyword(s):  
Electron Beam ◽  
High Performance ◽  
Chemical Properties ◽  
Low Density Polyethylene ◽  
Cross Linking ◽  
Low Density ◽  
X Rays ◽  
Radiation Processing ◽  
Adhesive Properties ◽  
Γ Rays

Radiation cross-linking gives inexpensive commodity plastics and technical plastics the mechanical, thermal, and chemical properties of high-performance plastic. This upgrading of the plastics enables them to be used in conditions which they would not be able to with stand otherwise. The irradiation cross-linking of thermoplastic materials via electron beam or cobalt 60 (gammy rays) is performed separately, after processing. Generally, ionizing radiation includes accelerated electrons, gamma rays and X-rays. Radiation processing with an electron beam offers several distinct advantages when compared with other radiation sources, particularly γ-rays and x-rays. The process is very fast, clean and can be controlled with much precision. There is no permanent radioactivity since the machine can be switched off. In contrast to γ-rays and x-rays, the electron beam can steered relatively easily, thus allowing irradiation of a variety of physical shapes. The energy-rich beta rays trigger chemical reactions in the plastics which results in networking of molecules (comparable to the vulcanization of rubbers which has been in industrial use for so long). The energy from the rays is absorbed by the material and cleavage of chemical bonds takes place. This releases free radicals which in next phase from desired molecular bonds. This article describes the effect of radiation cross-linking on the surface and adhesive properties of low-density polyethylene.

Surface Energy of Selected Polyolefins after Radiation Cross-Linking

2015 ◽  
Vol 752-753 ◽  
pp. 342-345
Author(s):  
Martin Bednarik ◽  
David Manas ◽  
Miroslav Manas ◽  
Michal Stanek ◽  
Jan Navratil ◽  
...  
Keyword(s):  
Surface Energy ◽  
High Density Polyethylene ◽  
Beta Radiation ◽  
Low Density Polyethylene ◽  
Cross Linking ◽  
Bonded Joints ◽  
Adhesive Properties ◽  
High Quality ◽  
Measurement Results ◽  
Untreated Material

In this study there was found that radiation cross-linking increased the surface energy of high-density polyethylene (HDPE), and low-density polyethylene (LDPE). Surface energy affects the wettability of the surface and is very important for creating of high-quality bonded joints. The measurement results indicated that radiation cross-linking was a very effective tool for the improvement of adhesive properties and increased the surface energy of selected polyolefins. Surfaces of selected materials with ionizing beta radiation with doses of 0, 33, 66, 99, 132, 165, and 198 kGy were irradiated. The best results were achieved by irradiation at dose of 165 kGy. The surface energy after irradiation was increased up to 100 % compared to untreated material.

Effects of low-energy electron bombardment on the surface chemical structure and adhesive properties of polytetrafluoroethylene (PTFE)

1986 ◽  
Vol 1 (5) ◽  
pp. 717-723 ◽  
Author(s):  
J.A. Kelber ◽  
J.W. Rogers ◽  
S.J. Ward
Keyword(s):  
High Vacuum ◽  
Nitrogen Adsorption ◽  
Electron Bombardment ◽  
Polymer Chains ◽  
Ultra High Vacuum ◽  
Cross Linking ◽  
Cohesive Failure ◽  
Adhesive Properties ◽  
Rate Determining Step ◽  
Adsorption Of Nitrogen

The x-ray photoemission studies of polytetrafluoroethylene (PTFE) bombarded by lowenergy electrons in ultra-high vacuum conditions indicate that the major chemical changes induced by electron bombardment are defluorination of the surface and cross-linking of the polymer chains. The same electron bombardment process, when performed in the presence of 1×10−6 Torr ND3, also results in the adsorption of nitrogen-containing groups at the surface. The rate of nitrogen adsorption is linear for short electron bombardment times while the rates of defluorination and cross-linking are roughly exponential. However, at long bombardment times, the rates of nitrogen uptake, defluorination, and cross-linking become zero at the same time, indicating that defluorination of the surface is the rate-determining step in electron beam-induced adsorption of nitrogen-containing species. Regardless of whether the bombardment is carried out in ultra-high vacuum or in the presence of ND3, the maximum modification depth is less than 30 Å. Pull tests performed on PTFE samples bombarded by electrons in ultra-high vacuum, then removed into air and bonded to epoxy show epoxy-PTFE joint strengths of 280–360 1b/in.2 (psi), are compared to zero psi for untreated PTFE and ≃2000 psi for cohesive failure within the PTFE layer.

Double-Network Physical Cross-Linking Strategy To Promote Bulk Mechanical and Surface Adhesive Properties of Hydrogels

2019 ◽  
Vol 52 (24) ◽  
pp. 9512-9525 ◽  
Author(s):  
Li Tang ◽  
Dong Zhang ◽  
Liang Gong ◽  
Yanxian Zhang ◽  
Shaowen Xie ◽  
...  
Keyword(s):  
Cross Linking ◽  
Adhesive Properties ◽  
Double Network

Influence of Calcium Ions on the Plant Cell Surface: Membrane Fusions and Conformational Changes

1974 ◽  
Vol 32 ◽  
pp. 154-155
Author(s):  
D. James Morré ◽  
Charles E. Bracker ◽  
William J. VanDerWoude
Keyword(s):  
Cell Wall ◽  
Cell Surface ◽  
Conformational Changes ◽  
Calcium Ions ◽  
Surface Membrane ◽  
Carboxyl Groups ◽  
Cross Linking ◽  
Ultrastructural Evidence ◽  
Glycine Max L ◽  
Wall Extensibility

Calcium ions in the concentration range 5-100 mM inhibit auxin-induced cell elongation and wall extensibility of plant stems. Inhibition of wall extensibility requires that the tissue be living; growth inhibition cannot be explained on the basis of cross-linking of carboxyl groups of cell wall uronides by calcium ions. In this study, ultrastructural evidence was sought for an interaction of calcium ions with some component other than the wall at the cell surface of soybean (Glycine max (L.) Merr.) hypocotyls.

Embedding Procedure for Water Swollen Samples

1970 ◽  
Vol 28 ◽  
pp. 504-505
Author(s):  
Ann M. Thomas ◽  
Virginia Shemeley
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ion Exchange ◽  
Structural Changes ◽  
Cross Linking ◽  
Ion Exchange Resins ◽  
Transmission Electron ◽  
First Pass ◽  
Exchange Resins

Those samples which swell rapidly when exposed to water are, at best, difficult to section for transmission electron microscopy. Some materials literally burst out of the embedding block with the first pass by the knife, and even the most rapid cutting cycle produces sections of limited value. Many ion exchange resins swell in water; some undergo irreversible structural changes when dried. We developed our embedding procedure to handle this type of sample, but it should be applicable to many materials that present similar sectioning difficulties.The purpose of our embedding procedure is to build up a cross-linking network throughout the sample, while it is in a water swollen state. Our procedure was suggested to us by the work of Rosenberg, where he mentioned the formation of a tridimensional structure by the polymerization of the GMA biproduct, triglycol dimethacrylate.

The Current Situation in Chemical Stabilization of Biological Materials

1972 ◽  
Vol 30 ◽  
pp. 132-133
Author(s):  
John H. Luft
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Osmium Tetroxide ◽  
Molecular Level ◽  
Cross Linking ◽  
Chemical Stabilization ◽  
Specimen Preparation ◽  
Sufficient Condition ◽  
Radio Telescopes

With information processing devices such as radio telescopes, microscopes or hi-fi systems, the quality of the output often is limited by distortion or noise introduced at the input stage of the device. This analogy can be extended usefully to specimen preparation for the electron microscope; fixation, which initiates the processing sequence, is the single most important step and, unfortunately, is the least well understood. Although there is an abundance of fixation mixtures recommended in the light microscopy literature, osmium tetroxide and glutaraldehyde are favored for electron microscopy. These fixatives react vigorously with proteins at the molecular level. There is clear evidence for the cross-linking of proteins both by osmium tetroxide and glutaraldehyde and cross-linking may be a necessary if not sufficient condition to define fixatives as a class.

Parathyroid gland before and after cisplatin treatment

1987 ◽  
Vol 45 ◽  
pp. 860-861
Author(s):  
S.K. Aggarwal ◽  
J.M. Fadool
Keyword(s):  
Parathyroid Gland ◽  
Wistar Rats ◽  
Antitumor Agent ◽  
The Body ◽  
Cross Linking ◽  
Limiting Factor ◽  
Hormonal Changes ◽  
Primary Mechanism ◽  
Before And After ◽  
Dna Strands

Cisplatin (CDDP) a potent antitumor agent suffers from severe toxic side effects with nephrotoxicity being the major dose-limiting factor, The primary mechanism of its action has been proposed to be through its cross-linking DNA strands. It has also been shown to inactivate various transport enzymes and induce hypocalcemia and hypomagnesemia that may be the underlying cause for some of its toxicities. The present is an effort to study its influence on the parathyroid gland for any hormonal changes that control calcium levels in the body.Male Swiss Wistar rats (Crl: (WI) BR) weighing 200-300 g and of 60 days in age were injected (ip) with cisplatin (7mg/kg in normal saline). The controls received saline injections only. The animals were injected (iv) with calcium (0.5 ml of 10% calcium gluconate/day) and were killed by decapitation on day 1 through 5. Trunk blood was collected in heparinized tubes.

Large-cluster and combined fluorescent and gold immunoprobes

1996 ◽  
Vol 54 ◽  
pp. 892-893
Author(s):  
Richard D. Powell ◽  
James F. Hainfeld ◽  
Carol M. R. Halsey ◽  
David L. Spector ◽  
Shelley Kaurin ◽  
...  
Keyword(s):  
Metal Cluster ◽  
Sulfonyl Chloride ◽  
Gel Filtration ◽  
Cross Linking ◽  
Site Specific ◽  
Fab Fragments ◽  
Cluster Label ◽  
Covalently Linked ◽  
Texas Red ◽  
Fold Excess

Two new types of covalently linked, site-specific immunoprobes have been prepared using metal cluster labels, and used to stain components of cells. Combined fluorescein and 1.4 nm “Nanogold” labels were prepared by using the fluorescein-conjugated tris (aryl) phosphine ligand and the amino-substituted ligand in the synthesis of the Nanogold cluster. This cluster label was activated by reaction with a 60-fold excess of (sulfo-Succinimidyl-4-N-maleiniido-cyclohexane-l-carboxylate (sulfo-SMCC) at pH 7.5, separated from excess cross-linking reagent by gel filtration, and mixed in ten-fold excess with Goat Fab’ fragments against mouse IgG (obtained by reduction of F(ab’)2 fragments with 50 mM mercaptoethylamine hydrochloride). Labeled Fab’ fragments were isolated by gel filtration HPLC (Superose-12, Pharmacia). A combined Nanogold and Texas Red label was also prepared, using a Nanogold cluster derivatized with both and its protected analog: the cluster was reacted with an eight-fold excess of Texas Red sulfonyl chloride at pH 9.0, separated from excess Texas Red by gel filtration, then deprotected with HC1 in methanol to yield the amino-substituted label.

CRYO-Electron Microscopy of the Acto-Myosin-ATP Complex

1990 ◽  
Vol 48 (1) ◽  
pp. 248-249
Author(s):  
John Trinickt ◽  
Howard White
Keyword(s):  
Electron Microscopy ◽  
Atp Hydrolysis ◽  
Myosin Head ◽  
Bound State ◽  
Cross Linking ◽  
Weakly Bound ◽  
Cryo Electron Microscopy ◽  
Myosin Subfragment 1 ◽  
Attached State ◽  
High Fraction

The primary force of muscle contraction is thought to involve a change in the myosin head whilst attached to actin, the energy coming from ATP hydrolysis. This change in attached state could either be a conformational change in the head or an alteration in the binding angle made with actin. A considerable amount is known about one bound state, the so-called strongly attached state, which occurs in the presence of ADP or in the absence of nucleotide. In this state, which probably corresponds to the last attached state of the force-producing cycle, the angle between the long axis myosin head and the actin filament is roughly 45°. Details of other attached states before and during power production have been difficult to obtain because, even at very high protein concentration, the complex is almost completely dissociated by ATP. Electron micrographs of the complex in the presence of ATP have therefore been obtained only after chemically cross-linking myosin subfragment-1 (S1) to actin filaments to prevent dissociation. But it is unclear then whether the variability in attachment angle observed is due merely to the cross-link acting as a hinge.We have recently found low ionic-strength conditions under which, without resorting to cross-linking, a high fraction of S1 is bound to actin during steady state ATP hydrolysis. The structure of this complex is being studied by cryo-electron microscopy of hydrated specimens. Most advantages of frozen specimens over ambient temperature methods such as negative staining have already been documented. These include improved preservation and fixation rates and the ability to observe protein directly rather than a surrounding stain envelope. In the present experiments, hydrated specimens have the additional benefit that it is feasible to use protein concentrations roughly two orders of magnitude higher than in conventional specimens, thereby reducing dissociation of weakly bound complexes.

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