Search results for "Particles"

Nanodiamond-Rich Layer across Three Continents Consistent with Major Cosmic Impact at 12,800 Cal BP

2014

© 2014 by The University of Chicago. All rights reserved. A major cosmic-impact event has been proposed at the onset of the Younger Dryas (YD) cooling episode at ≈12,800 ± 150 years before present, forming the YD Boundary (YDB) layer, distributed over 150 million km2 on four continents. In 24 dated stratigraphic sections in 10 countries of the Northern Hemisphere, the YDB layer contains a clearly defined abundance peak in nanodiamonds (NDs), a major cosmic-impact proxy. Observed ND polytypes include cubic diamonds, lonsdaleite-like crystals, and diamond-like carbon nanoparticles, called n-diamond and i-carbon. The ND abundances in bulk YDB sediments ranged up to ≈500 ppb (mean: 200 ppb) and…

Distribution of fullerenes (nC60) between sediment and water in freshwaters

2014

Abstract Depending on environmental conditions, fullerenes (nC 60 ) have the potential to settle to the bottom sediments. In this study the distribution of nC 60 was investigated in the labile zone between sediment and water. Three freshwater–sediment systems representing oligohumic, mesohumic, and polyhumic lakes with varying sediment composition and structure were used to investigate the target of fullerenes. The largest portion of water suspended fullerenes was found in the sediment, but a part re-suspended relatively quickly to water-stabile particles associated with natural particles. Rapid initial re-suspending was followed by a slower one offering a continuous pathway to the water ph…

Toxicity of silver nanoparticles to Lumbriculus variegatus is a function of dissolved silver and promoted by low sediment pH

2017

Toxicity of silver nanoparticles (AgNPs) to benthic organisms is a major concern. The use of AgNPs in industry and consumer products leads to increasing release of AgNPs into the aquatic environment-sediments being the major sink. Effects of sediment pH on the toxicity of AgNPs to benthic oligochaeta Lumbriculus variegatus were studied in a 23-d toxicity test. Artificially prepared sediments (pH 5 and 7) were spiked with varying concentrations of uncoated AgNP, polyvinylpyrrolidone (PVP)-coated AgNP, and silver nitrate (AgNO3 ) as dissolved Ag reference. Number of individuals and biomass change were used as endpoints for the toxicity. The toxic effects were related to the bioaccessible conc…

Toxicity Testing of Silver Nanoparticles in Artificial and Natural Sediments Using the Benthic Organism Lumbriculus variegatus

2016

The increased use of silver nanoparticles (AgNP) in industrial and consumer products worldwide has resulted in their release to aquatic environments. Previous studies have mainly focused on the effects of AgNP on pelagic species, whereas few studies have assessed the risks to benthic invertebrates despite the fact that the sediments act as a large potential sink for NPs. In this study, the toxicity of sediment-associated AgNP was evaluated using the standard sediment toxicity test for chemicals provided by the Organization of Economic Cooperation and Development. The freshwater benthic oligochaete worm Lumbriculus variegatus was exposed to sediment-associated AgNP in artificial and natural …

Topological Hopf Algebras, Quantum Groups and Deformation Quantization

2019

After a presentation of the context and a brief reminder of deformation quantization, we indicate how the introduction of natural topological vector space topologi es on Hopf algebras associated with Poisson Lie groups, Lie bialgebras and their doubles explains their dualities a nd provides a comprehensive framework. Relations with deformation quantization and applications to the deformation quantization of symmetric spaces are described.

The Inverse Seesaw Family: Dirac And Majorana

2021

After developing a general criterion for deciding which neutrino mass models belong to the category of inverse seesaw models, we apply it to obtain the Dirac analogue of the canonical Majorana inverse seesaw model. We then generalize the inverse seesaw model and obtain a class of inverse seesaw mechanisms both for Majorana and Dirac neutrinos. We further show that many of the models have double or multiple suppressions coming from tiny symmetry breaking "$\mu$-terms". These models can be tested both in colliders and with the observation of lepton flavour violating processes.

Stimulated transitions in resonant atom Majorana mixing

2018

Massive neutrinos demand to ask whether they are Dirac or Majorana particles. Majorana neutrinos are an irrefutable proof of physics beyond the Standard Model. Neutrinoless double electron capture is not a process but a virtual $\Delta L = 2$ mixing between a parent $^AZ$ atom and a daughter $^A(Z-2)$ excited atom with two electron holes. As a mixing between two neutral atoms and the observable signal in terms of emitted two-hole X-rays, the strategy, experimental signature and background are different from neutrinoless double beta decay. The mixing is resonantly enhanced for almost degeneracy and, under these conditions, there is no irreducible background from the standard two-neutrino cha…

Inhalable polymer-glycerosomes as safe and effective carriers for rifampicin delivery to the lungs

2016

Rifampicin loaded glycerosomes, vesicles composed of phospholipids, glycerol and water, were combined with trimethyl chitosan chloride (TMC) to prepare TMC-glycerosomes or, alternatively, with sodium hyaluronate (HY) to obtain HY-glycerosomes. These new hybrid nanovesicles were tested as carriers for pulmonary delivery of rifampicin. Glycerosomes without polymers were also prepared and characterized. All vesicles were similar: they were spherical, multilamellar and able to incorporate good amount of rifampicin (EE%∼55%). The addition of the polymers to the formulations allowed an increase of mean diameter. All the glycerosomes, in particular HY-glycerosomes, were able to deliver the drug to…

Gold Nanoparticles Coated with a Thermosensitive Hyperbranched Polyelectrolyte: Towards Smart Temperature and pH Nanosensors

2008

Phosphonylation Controls the Protein Corona of Multifunctional Polyglycerol-Modified Nanocarriers.

2018

Nanocarriers are a platform for modern drug delivery. In contact with blood, proteins adsorb to nanocarriers, altering their behavior in vivo. To reduce unspecific protein adsorption and unspecific cellular uptake, nanocarriers are modified with hydrophilic polymers like poly(ethylene glycol) (PEG). However, with PEG the attachment of further functional structures such as targeting units is limited. A method to introduce multifunctionality via polyglycerol (PG) while maintaining the hydrophilicity of PEG is introduced. Different amounts of negatively charged phosphonate groups (up to 29 mol%) are attached to the multifunctional PGs (Mn 2-4 kg mol-1 , Ð < 1.36) by post-modification. PGs are …