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First measurements of the differential positronium-formation cross-sections

Positrons are the antimatter version of electrons and so their fate in a matter world is ultimately to annihilate. However, prior to this, a positron may combine with an electron to form a matter-antimatter hybrid called positronium. This is akin to a hydrogen atom with the proton replaced by a positron. Fundamental to our understanding of the physical universe, positron and positronium are these days also acknowledged as being fantastically useful in practical applications such as probing material properties and medical diagnostics. However, there is still much that we do not know for sure about the details of the interactions of these particles with ordinary matter. For example if, in a collision with an atom or molecule, a positron captures an electron, in which directions is the positronium likely to travel and with what probability? More...

Published: Jun 17, 2015 12:35:19 PM

CO2 Satellite

New calculations to improve carbon dioxide monitoring from space

How light of different colours is absorbed by carbon dioxide (CO2) can now be accurately predicted using new calculations developed by a UCL-led team of scientists. This will help climate scientists studying Earth’s greenhouse gas emissions to better interpret data collected from satellites and ground stations measuring CO2. More...

Published: Jun 15, 2015 10:29:10 AM

Watt Steam Engine

On quantum scales, there are many second laws of thermodynamics

New research from UCL has uncovered additional second laws of thermodynamics which complement the ordinary second law of thermodynamics, one of the most fundamental laws of nature. These new second laws are generally not noticeable except on very small scales, at which point, they become increasingly important. More...

Published: Feb 10, 2015 11:55:53 AM

Isabel Llorente Garcia

Senior Research Fellow

Department of Physics and Astronomy

Biological Physics Group (BioP)
Atomic, Molecular, Optical and Positron Physics Group (AMOPP)

Gower Street, London WC1E 6BT




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Our new paper has been accepted:

Magneto-electrical orientation of lipid-coated graphitic micro-particles in solution in RSC Advances (April 2016). By J. Nguyen, S. Contera, and I. Llorente García.

DOI: 10.1039/C6RA07657B


This paper presents a novel method for manipulating anisotropic, lipid coated- biocompatible graphitic micro-particles in aqueous solution. The method is based on the application of two perpendicular fields: a vertical static magnetic field and a horizontal time-varying electric field oscillating at fast frequencies (MHz). We generate rotational traps to confine the orientation of the micro-particles parallel to the plane containing both fields and use measurements of random orientational fluctuations of the particles due to collisions with water molecules to calibrate the strength of the traps and measure the torque exerted on them, as well as to measure their dependence on the frequency of the applied electric field.

Our new method enables quantification of the response of the micro-particles to orienting fields in different experimental configurations for a broad range of applications. These include energy storage devices, opto-electronic devices, synthesis of artificial materials, biological and chemical sensing applications, fundamental studies in biological and medical physics, etc. Our scheme can be applied to other carbon-based micro/nano-particles, such as graphene platelets or carbon-nanotubes, has great potential for being scaled down via micro-fabrication, and can open up new ways for trapping, transporting and separating these particles with the use of time-varying fields enabling frequency-control of the magneto-electrical manipulations.

This work is in collaboration with Prof. Sonia Contera from Oxford Physics.