54 research outputs found
On the thermodynamic path enabling a room-temperature, laser-assisted graphite to nanodiamond transformation
Nanodiamonds are the subject of active research for their potential applications in nano-magnetometry, quantum optics, bioimaging and water cleaning processes. Here, we present a novel thermodynamic model that describes a graphite-liquid-diamond route for the synthesis of nanodiamonds. Its robustness is proved via the production of nanodiamonds powders at room-temperature and standard atmospheric pressure by pulsed laser ablation of pyrolytic graphite in water. The aqueous environment provides a confinement mechanism that promotes diamond nucleation and growth, and a biologically compatible medium for suspension of nanodiamonds. Moreover, we introduce a facile physico-chemical method that does not require harsh chemical or temperature conditions to remove the graphitic byproducts of the laser ablation process. A full characterization of the nanodiamonds by electron and Raman spectroscopies is reported. Our model is also corroborated by comparison with experimental data from the literature
Large N and Bosonization in Three Dimensions
Bosonization is normally thought of as a purely two-dimensional phenomenon,
and generic field theories with fermions in D>2 are not expected be describable
by local bosonic actions, except in some special cases. We point out that 3D
SU(N) gauge theories on R^{1,1} x S^{1}_{L} with adjoint fermions can be
bosonized in the large N limit. The key feature of such theories is that they
enjoy large N volume independence for arbitrary circle size L. A consequence of
this is a large N equivalence between these 3D gauge theories and certain 2D
gauge theories, which matches a set of correlation functions in the 3D theories
to corresponding observables in the 2D theories. As an example, we focus on a
3D SU(N) gauge theory with one flavor of adjoint Majorana fermions and derive
the large-N equivalent 2D gauge theory. The extra dimension is encoded in the
color degrees of freedom of the 2D theory. We then apply the technique of
non-Abelian bosonization to the 2D theory to obtain an equivalent local theory
written purely in terms of bosonic variables. Hence the bosonized version of
the large N three-dimensional theory turns out to live in two dimensions.Comment: 30 pages, 2 tables. v2 minor revisions, references adde
Welfare effects of unbundling under different regulatory regimes in natural gas markets
In this paper, we develop a theoretical model that enriches the literature on the pros and cons of ownership unbundling vis-a`-vis lighter unbundling frameworks in the natural gas markets. For each regulatory framework, we compute equilibrium outcomes when an incumbent firm and a new entrant compete a` la Cournot in the final gas market. We find that the entrant’s contracting conditions in the upstream market and the transmission tariff are key determinants of the market structure in the downstream gas market (both with ownership and with legal unbundling). We also study how the regulator must optimally set transmission tariffs in each of the two unbundling regimes. We conclude that welfare maximizing tariffs often require free access to the transmission network (in both regulatoy regimes). However, when the regulator aims at promoting the break-even of the regulated transmission system operator, the first-best tariff is unfeasible in both regimes. Hence, we study a more realistic set-up, in which the regulator’s action is constrained by the break-even of the regulated firm (the transmission system operator). In this set-up, we find that, for a given transmission tariff, final prices in the downstream market are always higher with ownership unbundling than with legal unbundling.info:eu-repo/semantics/publishedVersio
Funzione antiossidante dei nitrati e dei nitriti nella produzione di salame Milano
The invetigation has shown that nitrites used in salarme Milano processing have a determinant antioxidant effect which is demonstrated by a decrease of TBARS values and of
cholesterol oxides. The importance of such a finding in relation with humal health is discussed
Antioxidants and oxidative processes of lipids and cholesterol in a dry fermented meat product (salame Milano)
The research, of which some preliminary results are here presented, was intended to clarify the antioxidant role of nitrates and nitrites
used in combination with or without ascorbic acid, in relation with lipid oxidative processes in a dry fermented meat product. Lipid
oxidation would be looked at in a comprehensive way covering the rancidity (TBARS), the flavour (aldehydes) and the toxic (cholesterol oxides) aspects. Only part of the results dealing with TBARS and cholesterol oxides are reported
Lipid and colour stability of Milano-type sausages: effect of packing conditions
Lipid and colour oxidative changes in Milano-type fermented sausages were studied in relation to packing conditions and
extended storage under fluorescent light. Matured sausages were sliced and packed under vacuum or in protective atmosphere
(100% N2) and exposed in a display cabinet to mimic commercial conditions of light and temperature for 2 months. Lipid oxidation
was measured by the determination of thiobarbituric acid reactive substances (TBARS) and cholesterol oxidation products (COP),
whereas the oxidation of nitrosylmyoglobin was evaluated by a trained sensory panel. Lipid oxidation and discolouration were
positively related in vacuum-packed sausages: TBARS and COP values increased significantly concurrently with increasing brown
scores. Protective atmosphere came out to be more efficient than vacuum in controlling fatty acid oxidation and, to a lesser extent,
cholesterol and pigment degradation: TBARS values remained constant during the whole storage period whereas cholesterol oxides
and brown colour scores gradually increased but remained lower than those of vacuum-packed sausages. Higher residual oxygen in
vacuum packing could be responsible for the observed differences in oxidative stability. # 2002 Elsevier Science Ltd. All rights
reserved
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