103 research outputs found
Swelling of positronium confined in a small cavity
The electron density at the positron (contact density) in the ground state positronium (Ps) formed in condensed matter is generally found to be lower than in vacuum. This is usually attributed to microscopic electric fields which polarize Ps, by acting on the two particles of the atom. In this paper we quantitatively investigate an opposite effect. It is due to the confinement of Ps in small cavities existing in the host solid (e.g. free volume in polymers), which increases the contact density. Although this phenomenon is greater, the smaller is the size of the cavity, Ps polarization seems to play anyway a predominant role
An Air-well sparging minifermenter system for high-throughput protein production.
BackgroundOver the last few years High-Throughput Protein Production (HTPP) has
played a crucial role for functional proteomics. High-quality, high yield and
fast recombinant protein production are critical for new HTPP technologies.
Escherichia coli is usually the expression system of choice in protein production
thanks to its fast growth, ease of handling and high yields of protein produced.
Even though shake-flask cultures are widely used, there is an increasing need for
easy to handle, lab scale, high throughput systems.ResultsIn this article we
described a novel minifermenter system suitable for HTPP. The Air-Well
minifermenter system is made by a homogeneous air sparging device that includes
an air diffusion system, and a stainless steel 96 needle plate integrated with a
96 deep well plate where cultures take place. This system provides aeration to
achieve higher optical density growth compared to classical shaking growth
without the decrease in pH value and bacterial viability. Moreover the yield of
recombinant protein is up to 3-fold higher with a considerable improvement in the
amount of full length proteins.ConclusionsHigh throughput production of hundreds
of proteins in parallel can be obtained sparging air in a continuous and
controlled manner. The system used is modular and can be easily modified and
scaled up to meet the demands for HTPP
Preparation of a sepia melanin and poly(ethylene-alt-maleic anhydride) hybrid material as an adsorbent for water purification
Meeting the increasing demand of clean water requires the development of novel efficient adsorbent materials for the removal of organic pollutants. In this context the use of natural, renewable sources is of special relevance and sepia melanin, thanks to its ability to bind a variety of organic and inorganic species, has already attracted interest for water purification. Here we describe the synthesis of a material obtained by the combination of sepia melanin and poly(ethylene-alt-maleic anhydride) (P(E-alt-MA)). Compared to sepia melanin, the resulting hybrid displays a high and fast adsorption efficiency towards methylene blue (a common industrial dye) for a wide pH range (from pH 2 to 12) and under high ionic strength conditions. It is easily recovered after use and can be reused up to three times. Given the wide availability of sepia melanin and P(E-alt-MA), the synthesis of our hybrid is simple and affordable, making it suitable for industrial water purification purposes
Convenient Preparation of Graphene Oxide from Expandable Graphite and Its Characterization by Positron Annihilation Lifetime Spectroscopy
Graphene oxide (GO) is conveniently prepared from expandable graphite using a
simplified Hummers\u2019 method. The product is thoroughly characterized by usual techniques (UV-vis,
Fourier-transform infrared (FTIR) and Raman spectroscopies, zeta potential, electron microscopy,
X-ray diffraction, nitrogen adsorption) to confirm the success of synthesis. Positron annihilation
lifetime spectroscopy (PALS) is then used to extract information on the microenvironment in between
the layers of graphene oxid
Proposal for the AEGIS experiment at the CERN antiproton decelerator (Antimatter Experiment: Gravity, Interferometry, Spectroscopy)
Proposed antimatter gravity measurement with an antihydrogen beam
The principle of the equivalence of gravitational and inertial mass is one of the cornerstones of general relativity. Considerable efforts have been made and are still being made to verify its validity. A quantum-mechanical formulation of gravity allows for non-Newtonian contributions to the force which might lead to a difference in the gravitational force on matter and antimatter. While it is widely expected that the gravitational interaction of matter and of antimatter should be identical, this assertion has never been tested experimentally. With the production of large amounts of cold antihydrogen at the CERN Antiproton Decelerator, such a test with neutral antimatter atoms has now become feasible. For this purpose, we have proposed to set up the AEGIS experiment at CERN/AD, whose primary goal will be the direct measurement of the Earth's gravitational acceleration on antihydrogen with a classical Moiré deflectometer. © 2007 Elsevier B.V. All rights reserved
A comparison between the magnetic quenching of positronium in atactic polypropylene and that in isotactic polypropylene
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