1,084 research outputs found
Theoretical study of charge exchange dynamics in He + NO collisions
We investigate the charge transfer mechanism in the collisions of helium ions
on nitric oxide using a molecular description framework with consideration of
the orientation of the projectile toward the target. The anisotropy of the
collision process has been analysed in detail in connection with the
non-adiabatic interactions around avoided crossings. Potential energy curves,
radial and rotational coupling matrix elements have been determined by means of
ab initio quantum chemical methods. The collision dynamics is performed in the
[1.-25.] keV collision energy range using a semiclassical approach, and the
total electron transfer cross sections are analysed with regard to available
experimental data.Comment: 16 pages, 3 tables, 6 figure
Tropical river fisheries valuation: a global synthesis and critical review
River fisheries / Inland fisheries / Economic impact / Cost benefit analysis / Developing countries / River basin management / Wetlands / Valuation
Groupoid Extensions of Mapping Class Representations for Bordered Surfaces
The mapping class group of a surface with one boundary component admits
numerous interesting representations including as a group of automorphisms of a
free group and as a group of symplectic transformations. Insofar as the mapping
class group can be identified with the fundamental group of Riemann's moduli
space, it is furthermore identified with a subgroup of the fundamental path
groupoid upon choosing a basepoint. A combinatorial model for this, the mapping
class groupoid, arises from the invariant cell decomposition of Teichm\"uller
space, whose fundamental path groupoid is called the Ptolemy groupoid. It is
natural to try to extend representations of the mapping class group to the
mapping class groupoid, i.e., construct a homomorphism from the mapping class
groupoid to the same target that extends the given representations arising from
various choices of basepoint.
Among others, we extend both aforementioned representations to the groupoid
level in this sense, where the symplectic representation is lifted both
rationally and integrally. The techniques of proof include several algorithms
involving fatgraphs and chord diagrams. The former extension is given by
explicit formulae depending upon six essential cases, and the kernel and image
of the groupoid representation are computed. Furthermore, this provides
groupoid extensions of any representation of the mapping class group that
factors through its action on the fundamental group of the surface including,
for instance, the Magnus representation and representations on the moduli
spaces of flat connections.Comment: 24 pages, 4 figures Theorem 3.6 has been strengthened, and Theorems
8.1 and 8.2 have been adde
Finite type invariants and fatgraphs
We define an invariant of pairs M,G, where M is a 3-manifold
obtained by surgery on some framed link in the cylinder , S is a
connected surface with at least one boundary component, and G is a fatgraph
spine of S. In effect, is the composition with the maps of
Le-Murakami-Ohtsuki of the link invariant of Andersen-Mattes-Reshetikhin
computed relative to choices determined by the fatgraph G; this provides a
basic connection between 2d geometry and 3d quantum topology. For each fixed G,
this invariant is shown to be universal for homology cylinders, i.e.,
establishes an isomorphism from an appropriate vector space
of homology cylinders to a certain algebra of Jacobi diagrams. Via
composition for any pair of fatgraph spines
G,G' of S, we derive a representation of the Ptolemy groupoid, i.e., the
combinatorial model for the fundamental path groupoid of Teichmuller space, as
a group of automorphisms of this algebra. The space comes equipped
with a geometrically natural product induced by stacking cylinders on top of
one another and furthermore supports related operations which arise by gluing a
homology handlebody to one end of a cylinder or to another homology handlebody.
We compute how interacts with all three operations explicitly in
terms of natural products on Jacobi diagrams and certain diagrammatic
constants. Our main result gives an explicit extension of the LMO invariant of
3-manifolds to the Ptolemy groupoid in terms of these operations, and this
groupoid extension nearly fits the paradigm of a TQFT. We finally re-derive the
Morita-Penner cocycle representing the first Johnson homomorphism using a
variant/generalization of .Comment: 39 page
Conventional and manipulated growth of Cu-Cu(111)
Molecular beam epitaxy of Cu on Cu(111) was studied using thermal energy He scattering, in the temperature range between 100 and 450 K. Three-dimensional growth was observed in the whole temperature range. To determine the onset of various diffusion processes, submonolayer films formed by deposition at low temperature were annealed. Annealing proceeds in two steps. The first step is interpreted as a change in island shape, the second as Ostwald-ripening. A comparison with homoepitaxy on Pt(111) and Ag(111) is made. Growth manipulation was carried out by artificially increasing the island number density via intervention in the nucleation stage of each layer. The procedures applied were temperature reduction during nucleation as well as pulsed ion bombardment. These techniques enabled the convenient growth of good quality films consisting of a large number of monolayers. Finally, the use of oxygen as a surfactant modifying the growth mode was investigated. Under some growth conditions, pre-exposure of the surface to oxygen was found to induce weak He-intensity oscillations during deposition. The quality of the films grown in this way was, however, low
Greenhouse gas emissions in the agricultural phase of wine production in the Maremma rural district (Tuscany, Italy).
In recent years, there has been an increasing interest from retailers, industries and environmental associations in estimating the life cycle of greenhouse gases emitted in the atmosphere from everyday products and services, also known as carbon footprint (CF). Life cycle assessment (LCA) is the most common methodology used to evaluate the environmental impact of a product. This approach was largely used in many industrial sectors and was also recently applied to quantify the environmental impact of the agri-food chain. Within agri-food products, wine is one of the most analysed, both for its importance in economic production and in the world distribution market. The present study is a part of the Carbon Label Project carried out in the wine production chain in the Maremma rural district (Tuscany, Italy). The project assessed the greenhouse
gas (GHG) emissions from wine production for labelling purposes.
Here, we evaluated the environmental performances of four high
quality wines for carbon labelling. The international standards ISO
14040, ISO 14044, and the Product Category Rules (PCR) Wine from Fresh Grapes (except sparkling wine) and Grape Must for the Environmental Product Declaration (EPD) certification, specifically for
Climate Declaration, were used in order to carry out our analyses. The functional unit (FU) used here was one 0.75 L bottle of wine. The system boundaries were set from the vineyard planting to the distribution and waste disposal. The global warming potential (GWP) of four investigated wines was found to lie between 0.6 and 1.3 kg CO2-eq./bottle, showing a value comparable with literature. With all the four wines analysed, the agricultural phase covered, on average, 22% of the total GWP/bottle, while the main impact was in the production of the glass bottle. The results showed that the vineyard-planting phase has a significant impact on the wine CF, thus it has to be considered in the life cycle, while in literature it is frequently omitted. On the contrary, the pre-production phase did not present a relevant impact. The use of nitrogen fertilisers, the grapes’ yield and N2O emissions were the parameters that mostly affected the carbon footprint in the agricultural phase, as underlined by the sensitivity analysis
Maturation of B Cells in the Lamina Propria of Human Gut and Bronchi in the First Months of Human Life
Little is known of the maturation of the mucosae-associated lymphoid tissue (MALT) in man,
because, for ethical reasons, tissues from newborns are not easy to obtain. We used the
opportunity provided by autopsies systematically performed in infants who died of Sudden Infant
Death Syndrome (SIDS) to study the maturation of the MALT after birth. Gut and bronchus
samples of 90 infants from postpartum to 90 months and who died from SIDS were collected and
studied by histological and immunofluorescence examination. Plasma cells, absent at birth,
appeared within a few hours after birth and initially were of the IgM isotype. IgA plasma cells
appeared at 12 days. These cells were first observed in gut and later in bronchi, indicating that
maturation of the gut precedes that of bronchi. The number of plasma cells increased rapidly over
time and IgA plasma cells became predominant after 3 weeks in the gut and 6 weeks in bronchi.
At birth, only small IgM bearing B-cell foci were seen and organized germinal centers appeared
to develop over a few days, first in the gut and only later in bronchi. These results confirm that,
in man, the MALT organization at birth is still in its fetal form and that maturation depends on
intestinal challenges and evolves over several weeks before IgA becomes the predominant
isotype secreted
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