Search results for "PLASTICS"
showing 10 items of 2724 documents
The role of the hydrophobic force in bilayer adhesion and fusion
1991
The Surface Forces Apparatus technique was used for measuring the adhesion, deformation, and fusion of bilayers supported on mica. The technique allows the molecular rearrangements to be followed in real time during the fusion process, and the most important forces involved to be identified. The adhesion between two bilayers can be increased by two orders of magnitude if they are thinned so as to expose more hydrophobic groups. For all the bilayer systems studied a single basic fusion mechanism was found in which the bilayers do not “overcome” the short-range repulsive steric-hydration forces; instead, local bilayer deformations allow these repulsive forces to be “bypassed”. The results fur…
Rheological properties of asphalt binder modified with waste polyethylene: An interlaboratory research from the RILEM TC WMR
2022
Funding Information: The RILEM Technical Committee on Valorisation of Waste and Secondary Materials for Roads (TC 279-WMR) and the members of Task Group 1 are gratefully acknowledged. The authors would also like to thank Nynas AB and Swiss company Innorecycling for supporting the interlaboratory activity by providing reference neat binder and PE-pellets, PE-shreds additives. The contribution of the Swiss National Science Foundation ( 205121_178991 ) to the Swiss partners is also acknowledged. Funding Information: The RILEM Technical Committee on Valorisation of Waste and Secondary Materials for Roads (TC 279-WMR) and the members of Task Group 1 are gratefully acknowledged. The authors would…
Rheological Behaviors of Waste Polyethylene Modified Asphalt Binder: Statistical Analysis of Interlaboratory Testing Results
2023
This article investigated the effect of waste polyethylene (PE) on the modified asphalt binders' rheological behavior from a statistical point of view. The interlaboratory testing results from the RILEM Technical Committee 279 Valorization of Waste and Secondary Materials for Roads Task Group 1 were used for this purpose. First, an unaged 70/100 penetration graded neat binder was selected as the reference material. Next, a single 5 % content of waste PE additives (PE-pellets and PE-shreds) was mixed with a 95 % neat binder to prepare two PE modified binders. Then, dynamic shear rheometer-based temperature-frequency sweep tests were performed over a wide range of temperatures and frequencies…
MRI-Visible Poly(ε-caprolactone) with Controlled Contrast Agent Ratios for Enhanced Visualization in Temporary Imaging Applications
2013
International audience; Hydrophobic macromolecular contrast agents (MMCAs) are highly desirable to provide safe and efficient magnetic resonance (MR) visibility to implantable medical devices. In this study, we report on the synthesis and evaluation of novel biodegradable poly(ε-caprolactone)-based MMCAs. Poly(α-propargyl-ε-caprolactone-co-ε-caprolactone)s containing 2, 5, and 10 mol % of propargyl groups have been prepared by ring-opening copolymerization of ε-caprolactone and the corresponding propargylated lactone. In parallel, a diazido derivative of the clinically used diethylenetriaminepentaacetic acid (DTPA)/Gd3+ complex has been synthesized. Finally, MRI-visible poly(ε-caprolactone)…
Novel polyaminoacidic copolymers as nonviral gene vectors
2000
Human gene therapy is one of the most promising methods developed in recent years, providing great potential for the treatment of a variety of diseases. Complexes formed between DNA and cationic polymers are attracting increasing attention as novel synthetic vectors for the delivery of genes. We have synthesized polycations with quaternary ammonium groups in their side chains for self-assembly with calf thymus DNA. This paper describes the functionalization of α,β-polyasparthydrazide (PAHy), a synthetic macromolecule having many potential applications in the field of biomedical sciences, with glycidyltrimethylammonuim chloride (GTA) in order to introduce positive charges into their chains. …
Synthese und Eigenschaften molekulareinheitlicher n-Paraffine bis zum C140H282
1972
Die Umsetzung von α,ω-Dihalogenalkanen mit Natrium fuhrt nach anschliesender katalytischer Hydrierung zu einem Paraffingemisch mit diskontinuierlicher Molekulargewichtsverteilung. So enthalt das aus 1.10-Dibromdecan hergestellte Produkt nur Paraffine mit 10, 20, 30 usw. C-Atomen, ein aus 1.20-Dibromeicosan hergestelltes Produkt dagegen nur die Paraffine mit 20, 40, 60 usw. C-Atomen. Diese Paraffingemische wurden gelchromatographisch in die molekulareinheitlichen Verbindungen zerlegt und Paraffine bis C140H282 isoliert. Am Beispiel des C70H142 wurde die Temperaturabhangigkeit der Rontgenkleinwinkelstreuung gemessen. Aus Intensitat und Lage der Langperiodenreflexe liesen sich die Anderungen v…
DNA Modification Induced After Metabolic Activation of the Potent Carcinogen Dibenzo[a, l]pyrene in V79 Chinese Hamster Cells Stably Expressing Singl…
2000
Abstract The polycyclic aromatic hydrocarbon (PAH) dibenzo[a, l]pyrene (DB[a, l]P) has been found to be an environmental pollutant and, considering the available data from rodent bioassays, it represents the most carcinogenic member compound of the class of PAH yet discovered. To sort out the contribution of individual cytochromes P450 (P450) in the metabolic activation of this PAH, V79 cells stably expressing a single P450 isoform were treated with DB[a, l]P or enantiomeric DB[a, l]P-11,12-dihydrodiols (diols). Subsequent analysis of the DNA adducts formed revealed substantial differences in the adduct pattern and the total DNA binding depending on the cell line used. Human P450 1B1 effect…
Species-dependent Metabolism of Benzo[c]phenanthrene and Dibenzo[a, l]pyrene by Various CYP450 Isoforms
2000
Abstract The metabolism of benzo[c]phenanthrene (B[c]Ph) and dibenzo[a, l]-pyrene (DB[a, l]P) with various CYP isoforms including rat 1A1, 1A2, 2B1, 2E1, human 1A1, 1A2, 1B1, 2A6, 3A4, 2E1 and fish 1A expressed in Chinese hamster V79 cells has been compared. Major differences in the catalytic activities and in the regioselectivity of the eleven CYP isoforms with B[c]Ph and DB[a, l]P as substrates have been observed. There have been found substantially species-specific differences between homologous CYP isoforms at least when human, rat and fish are compared, which have to be taken into account when animal experiments are extrapolated to human. In particular, complementary catalytic activiti…
Bioplastics: A new analytical challenge
2022
Even though petroleum-based plastics are advantageous in complying with the performance requirements in many applications, these are related, throughout their life cycle, to several environmental problems, including greenhouse gas emissions and persistence in marine and terrestrial environments. Therefore, the preservation of natural resources and climate change is considered worldwide, the main reason for which is necessary to reduce consumption and dependence on fossil-based materials. Biopolymers (PLA, PHAs, etc.) are examples of plastics whose use is grown exponentially over the years because of the improvements of their physical and mechanical properties using additives of various natu…
Strategies for tumor elimination by cytotoxic T lymphocytes.
1998
Despite differences in their tissue of origin, many tumors share high level expression of certain tumor-associated proteins. Our laboratory has focused on the possibility of utilizing antigenic components of these proteins as a focus for T-cell immunotherapy of cancer. The advantage of targeting such commonly expressed proteins is the fact that such therapy could be of value in eliminating many different types of tumors. A potential barrier in the identification of T-cell epitopes derived from these proteins and presented by tumor cells is the fact that these proteins are also expressed at low levels in some normal tissues, and therefore, self-tolerance may eliminate T cells that are capabl…