Para-Grassmann Variables and Coherent States

The definitions of para-Grassmann variables and q-oscillator algebras are recalled. Some new properties are given. We then introduce appropriate coherent states as well as their dual states. This allows us to obtain a formula for the trace of a operator expressed as a function of the creation and annihilation operators.Comment: This is a contribution to the Proc. of the O'Raifeartaigh Symposium on Non-Perturbative and Symmetry Methods in Field Theory (June 2006, Budapest, Hungary), published in SIGMA (Symmetry, Integrability and Geometry: Methods and Applications) at http://www.emis.de/journals/SIGMA

Bosonization of fermions coupled to topologically massive gravity

We establish a duality between massive fermions coupled to topologically massive gravity (TGM) in $d=3$ space-time dimensions and a purely gravity theory which also will turn out to be a TGM theory but with different parameters: the original graviton mass in the TGM theory coupled to fermions picks-up a contribution from fermion bosonization. We obtain explicit bosonization rules for the fermionic currents and for the energy-momentum-tensor showing that the identifications do not depend explicitly on the parameters of the theory. These results are the gravitational analog of the results for $2+1$ Abelian and non-Abelian bosonization in flat space-time.Comment: 8 page

Bosonization of fermions coupled to topologically massive gravity

We establish a duality between massive fermions coupled to topologically massive gravity (TMG) in d = 3 space–time dimensions and a purely gravity theory which also will turn out to be a TMG theory but with different parameters: the original graviton mass in the TMG theory coupled to fermions picks up a contribution from fermion bosonization. We obtain explicit bosonization rules for the fermionic currents and for the energy–momentum tensor showing that the identifications do not depend explicitly on the parameters of the theory. These results are the gravitational analog of the results for 2 + 1 Abelian and non-Abelian bosonization in flat space–time

Stomatal control of water use in olive tree leaves

Little is known about the strategies used by olive trees to overcome the long dry periods typical of the areas where they are cropped. This makes it difficult to optimize the water supply in orchards. To study the control of water consumption by olive trees, measurements of leaf water potential (Ψ) and stomatal conductance to H2O (g) were made on 26-year-old Manzanillo olive trees under three irrigation treatments. The first treatment provided enough water to cover the crop water demand, the next treatment supplied one third of that rate, and the final treatment was no irrigation at all, typical of dry-farming conditions. Under conditions of high vapour pressure deficit of the air (D(a)), the olive trees prevented excessive water loss by closing their stomata. Leaves of the current year showed better stomatal control than did the 1-year-old leaves. The upper-bound functional relationships between g and D(a) and photon flux density (I(P)) were obtained by boundary-line analysis, based on a technique of non-linear least squares. Maximum values of g were observed at relatively low levels of I(p), from about 500 μmol m-2 s-1, and a proportional decrease in g with increasing D(a) was also found, at least for values of up to approximately 3.5 kPa. Higher values of g were observed in the morning than in the afternoon, for similar levels of I(P) and D(a). Unirrigated olive trees recovered quickly after the dry season, showing values of Ψ and g similar to those of irrigated trees after just two days.Peer Reviewe

Quasiparticle operators with non-Abelian braiding statistics

We study the gauge invariant fermions in the fermion coset representation of $SU(N)_k$ Wess-Zumino-Witten models which create, by construction, the physical excitations (quasiparticles) of the theory. We show that they provide an explicit holomorphic factorization of $SU(N)_k$ Wess-Zumino-Witten primaries and satisfy non-Abelian braiding relations.Comment: 13 pages, no figures, final version to appear in Physics Letters

Duality in deformed coset fermionic models

We study the $SU(2)_k/U(1)$-parafermion model perturbed by its first thermal operator. By formulating the theory in terms of a (perturbed) fermionic coset model we show that the model is equivalent to interacting WZW fields modulo free fields. In this scheme, the order and disorder operators of the $Z_k$ parafermion theory are constructed as gauge invariant composites. We find that the theory presents a duality symmetry that interchanges the roles of the spin and dual spin operators. For two particular values of the coupling constant we find that the theory recovers conformal invariance and the gauge symmetry is enlarged. We also find a novel self-dual point.Comment: 13 pages, LaTex. Minor corrections. One reference added. Version to appear in Nuc. Phys.

Effect of fructose-containing feedstocks on the microstructure of multicomponent coatings deposited by suspension plasma spraying

This work addressed to investigate the use of fructose as an additive in the water-based suspension feedstock of a Y-TZP/Al2O3/SiC multicomponent coating manufactured by suspension plasma spraying. The effect of fructose on suspension rheology and surface tension and on the microstructure and thermal conductivity of the resulting coatings was assessed. It was observed that addition of fructose slightly affected the rheological behaviour of the suspensions while a strong decrease in the surface tension of water occurred. The fructose addition led to the development of columnar-like structures, probably associated with its effect on surface tension. X-ray diffraction patterns in the final coating displayed that crystallinity of tetragonal zirconia formed when fructose was added whereas silicon carbide crystalline phase was practically preserved. The determination of thermal conductivity showed that the formation of a controlled columnar structure along with inter-columnar porosity can be beneficial for thermal insulation

Heat-pulse measurements of sap flow in olives for automating irrigation: tests, root flow and diagnostics of water stress

26 páginas, 10 figuras, 1 tabla, 32 referencias.-- [email protected] compensation heat-pulse method for measuring sap flow is tested here in olive trees (Olea europaea L.). We describe a rigorous three-way examination of the robustness of the technique for this species, and examine the potential of the technique for an automatic control of the irrigation system. Two tests were carried out using heat-pulse gear inserted into the stem of 12-year-old ‘Manzanilla’ olive trees. One test used forced-flow through a stem section, and the other involved measured water uptake by an excised tree. The measured sap flow in these two tests was in agreement with calculations from heat-pulse velocities when using a standard ‘wound correction’ to account for the presence of the probes and the disruption to the sap flow. Thus, this technique for monitoring transpiration can, we feel, be used with confidence in olives. The third experiment was carried out in the field, where we analysed sap flow data from two 29- year-old olive trees—one tree was under regular drip irrigation and the other was from dry-farming conditions. We use measurements of sap flow in the trunk to examine the hydraulic functioning of the tree, and to explore some diagnostics of water stress. Our heat-pulse measurements in the irrigated olive tree exhibited a profile of sap flow that was weighted towards the outer xylem of the tree trunk while the water-stressed trees in the field showed a profile of sap flow weighted towards the centre of the trunk. The loss of hydraulic functioning in the outermost section of the vascular system, as a result of water stress, we consider to be due both to stomatal control and to embolisms in the xylem vessels. The fourth experiment was also carried out in the field, in which sap flow measurements were made at three locations in the trunk as well as in two roots of another 29-year-old olive tree. The soil explored by each root, on opposite sides of the trunk, was differentially wetted by separate irrigation of each side. Our data showed that the surface roots were able to absorb water immediately after wetting, despite a reasonably prolonged period of moderate drought. Root activity quickly shifted to the regions where the soil had been wetted. A root in dry soil exhibited no flow at night, whereas sap flows of about 0.02 l h 1 were measured around midnight in the root drawing water from the wetter soil. Our observations suggest that the hydraulic behaviour of the trunk and surface roots might be used as a diagnostic of the onset, or severity, of water stress. Here there is not the imperative to replicate, for the prime goal is not transpiration estimation. Rather interpretation of the diurnal dynamics is used to infer the onset, or severity of water stress. The compensation heat-pulse seems a suitable technique for automatically controlling the irrigation system of olives, and probably other trees, based either on the estimation of the short-time dynamics of transpiration, or on changes in the hydraulic behaviour of the trees.The Comisión Interministerial de Ciencia y Tecnología of the Spanish Ministry of Education and Science financial support this project.Peer reviewe

Heat-pulse measurements of sap flow in olives for automating irrigation: tests, root flow and diagnostics of water stress

26 páginas, 10 figuras, 1 tabla, 32 referencias.-- [email protected] compensation heat-pulse method for measuring sap flow is tested here in olive trees (Olea europaea L.). We describe a rigorous three-way examination of the robustness of the technique for this species, and examine the potential of the technique for an automatic control of the irrigation system. Two tests were carried out using heat-pulse gear inserted into the stem of 12-year-old ‘Manzanilla’ olive trees. One test used forced-flow through a stem section, and the other involved measured water uptake by an excised tree. The measured sap flow in these two tests was in agreement with calculations from heat-pulse velocities when using a standard ‘wound correction’ to account for the presence of the probes and the disruption to the sap flow. Thus, this technique for monitoring transpiration can, we feel, be used with confidence in olives. The third experiment was carried out in the field, where we analysed sap flow data from two 29- year-old olive trees—one tree was under regular drip irrigation and the other was from dry-farming conditions. We use measurements of sap flow in the trunk to examine the hydraulic functioning of the tree, and to explore some diagnostics of water stress. Our heat-pulse measurements in the irrigated olive tree exhibited a profile of sap flow that was weighted towards the outer xylem of the tree trunk while the water-stressed trees in the field showed a profile of sap flow weighted towards the centre of the trunk. The loss of hydraulic functioning in the outermost section of the vascular system, as a result of water stress, we consider to be due both to stomatal control and to embolisms in the xylem vessels. The fourth experiment was also carried out in the field, in which sap flow measurements were made at three locations in the trunk as well as in two roots of another 29-year-old olive tree. The soil explored by each root, on opposite sides of the trunk, was differentially wetted by separate irrigation of each side. Our data showed that the surface roots were able to absorb water immediately after wetting, despite a reasonably prolonged period of moderate drought. Root activity quickly shifted to the regions where the soil had been wetted. A root in dry soil exhibited no flow at night, whereas sap flows of about 0.02 l h 1 were measured around midnight in the root drawing water from the wetter soil. Our observations suggest that the hydraulic behaviour of the trunk and surface roots might be used as a diagnostic of the onset, or severity, of water stress. Here there is not the imperative to replicate, for the prime goal is not transpiration estimation. Rather interpretation of the diurnal dynamics is used to infer the onset, or severity of water stress. The compensation heat-pulse seems a suitable technique for automatically controlling the irrigation system of olives, and probably other trees, based either on the estimation of the short-time dynamics of transpiration, or on changes in the hydraulic behaviour of the trees.The Comisión Interministerial de Ciencia y Tecnología of the Spanish Ministry of Education and Science financial support this project.Peer reviewe