I-Xe analysis of a magnetic separate from Lodranite GRA95209

I-Xe dating of a magnetic mineral separate from lodranite GRA95209 suggests that peak temperatures (and therefore melt migration) occurred early, at least a few million years before closure of the I-Xe system in phosphates from Acapulco

Analytic Examples, Measurement Models and Classical Limit of Quantum Backflow

We investigate the backflow effect in elementary quantum mechanics - the phenomenon in which a state consisting entirely of positive momenta may have negative current and the probability flows in the opposite direction to the momentum. We compute the current and flux for states consisting of superpositions of gaussian wave packets. These are experimentally realizable but the amount of backflow is small. Inspired by the numerical results of Penz et al (M.Penz, G.Gr\"ubl, S.Kreidl and P.Wagner, J.Phys. A39, 423 (2006)), we find two non-trivial wave functions whose current at any time may be computed analytically and which have periods of significant backflow, in one case with a backwards flux equal to about 70 percent of the maximum possible backflow, a dimensionless number $c_{bm} \approx 0.04$, discovered by Bracken and Melloy (A.J.Bracken and G.F.Melloy, J.Phys. A27, 2197 (1994)). This number has the unusual property of being independent of $\hbar$ (and also of all other parameters of the model), despite corresponding to an obviously quantum-mechanical effect, and we shed some light on this surprising property by considering the classical limit of backflow. We discuss some specific measurement models in which backflow may be identified in certain measurable probabilities.Comment: 33 pages, 14 figures. Minor revisions. Published versio

High purity nanoparticles exceed stoichiometry limits in rebox chemistry: the nano way to cleaner water

A potentially cheaper and more effective way of cleaning wastewater has been discovered by scientists at Nazarbayev University and the University of Brighton researching nanotechnology [1]. It is well established that when particles are reduced to the nanoscale unexpected effects occur. Silver, for example, interacts with mercury ions in a fixed ratio of atoms (stoichiometry), typically 2:1, which presents a limit that has never been exceeded. In this project we used an alternative chemical procedure based on modified quartz sand to immobilise silver nanoparticles (NPs) with control over their size. We found that when the size of the silver NPs decreased below 35 nm the amount of mercury ions reacting with silver increased beyond the long-held limit and rose to a maximum of 1:1.2 for 10 nm sized silver

Interfacial Properties of Colloidal Silica Dispersions in Contact with Solutions of Fatty Amines in Hexane

Many natural phenomena and technologies are concerned with the interactions between micro- or nano-metre sized particles and surfactant molecules at liquid interfaces. Highly stable emulsions are produced by using surfactants to modify the surfaces of nanoparticles. Particle attachment to bubbles is controlled by surfactant adsorption in flotation technologies. So far, however, few experimental studies have explored the properties of these complex interfacial layers

Polyurea-Functionalized Multiwalled Carbon Nanotubes

An in situ polycondensation approach was applied to functionalize multiwalled carbon nanotubes (MWNTs), resulting in various linear or hyperbranched polycondensed polymers [e.g., polyureas, polyurethanes, and poly(urea-urethane)-bonded carbon nanotubes]. The quantity of the grafted polymer can be easily controlled by the feed ratio of monomers. As a typical example, the polyurea-functionalized MWNTs were measured and characterized in detail. The oxidized MWNTs (MWNT-COOH) were converted into acyl chloride-functionalized MWNTs (MWNT-COCl) by reaction with neat thionyl chloride (SOCl2). MWNT-COCl was reacted with excess 1,6-diaminohexane, affording amino-functionalized MWNTs (MWNT-NH2). In the presence of MWNT-NH2, the polyurea was covalently coated onto the surfaces of the nanotube by in situ polycondensation of diisocyanate [e.g., 4,4‘-methylenebis(phenylisocyanate)] and 1,6-diaminohexane, followed by the removal of free polymer via repeated filtering and solvent washing. The coated polyurea content can be controlled to some extent by adjusting the feed ratio of the isocyanato and amino groups. The structure and morphology of the resulting nanocomposites were characterized by FTIR, NMR, Raman, confocal Raman, TEM, EDS, and SEM measurements. The polyurea-coated MWNTs showed interesting self-assembled flat- or flowerlike morphologies in the solid state. The signals corresponding to that of the D and G bands of the carbon nanotubes were strongly attenuated after polyurea was chemically tethered to the MWNT surfaces. Comparative experiments showed that the grafted polymer species and structures have a strong effect on the Raman signals of polymer-functionalized MWNTs

Flow-induced dynamic surface tension effects at nanoscale

The aim of this study is to investigate flow-induced dynamic surface tension effects, similar to the well-known Marangoni phenomena, but solely generated by the nanoscale topography of the substrates. The flow-induced surface tension effects are examined on the basis of a sharp interface theory. It is demonstrated how nanoscale objects placed at the boundary of the flow domain result in the generation of substantial surface forces acting on the bulk flow

Microbial Contamination of Allende and Murchison Carbonaceous Chondrites; Developing a Protocol for Life Detection in Extraterrestrial Materials Using Biotechnology

The arguments used to refute the McKay et al., (1996) hypothesis of possible Martian life in ALH84001 failed to use contamination of the meteorite as a source. This has worrying implications for our ability to detect terrestrial microbiota in meteorites and therefore any potential extraterrestrial biosignatures in both meteorites and possible returned samples. We report on imaging and microbial culturing of both Allende and Murchison carbonaceous chondrites and on the use of molecular biology techniques on a sample of Allende. Contaminating fungi and bacteria were observed (in the case of Murchison) and cultured from both meteorites. DNA was successfully extracted and subsequent PCR showed the presence of both bacterial and fungal DNA although no Archaea were detected. These results show that it is possible to use molecular biological techniques on very small quantities (300 mg) of extraterrestrial material

Reputation Agent: Prompting Fair Reviews in Gig Markets

Our study presents a new tool, Reputation Agent, to promote fairer reviews from requesters (employers or customers) on gig markets. Unfair reviews, created when requesters consider factors outside of a worker's control, are known to plague gig workers and can result in lost job opportunities and even termination from the marketplace. Our tool leverages machine learning to implement an intelligent interface that: (1) uses deep learning to automatically detect when an individual has included unfair factors into her review (factors outside the worker's control per the policies of the market); and (2) prompts the individual to reconsider her review if she has incorporated unfair factors. To study the effectiveness of Reputation Agent, we conducted a controlled experiment over different gig markets. Our experiment illustrates that across markets, Reputation Agent, in contrast with traditional approaches, motivates requesters to review gig workers' performance more fairly. We discuss how tools that bring more transparency to employers about the policies of a gig market can help build empathy thus resulting in reasoned discussions around potential injustices towards workers generated by these interfaces. Our vision is that with tools that promote truth and transparency we can bring fairer treatment to gig workers.Comment: 12 pages, 5 figures, The Web Conference 2020, ACM WWW 202