This work presents a facile sol-gel method for the deposition of ZnO and ZnO:Mg films. The films are spin coated on silicon and quartz substrates. The impact of magnesium concentrations (0, 0.5, 1, 2 ...and 3 wt%) and post-annealing treatments (300-600 °C) on the film's structural, vibrational and optical properties is investigated. Undoped ZnO films crystallize in the wurtzite phase, with crystallite sizes ranging from 9.1 nm (300 °C) to 29.7 nm (600 °C). Mg doping deteriorates the film crystallization and shifting of 002 peak towards higher diffraction angles is observed, indicating the successful incorporation of Mg into the ZnO matrix. ZnO:Mg films (2 wt%) possess the smallest crystallite size, ranging from 6.2 nm (300 °C) to 25.2 nm (600 °C). The highest Mg concentration (3 wt%) results into a segregation of the MgO phase. Lattice constants, texture coefficients and Zn-O bond lengths are discussed. The diminution of the
lattice parameter is related to the replacement of Zn
by Mg
in the ZnO host lattice. The vibrational properties are studied by Fourier transform infrared (FTIR) spectroscopy. IR lines related to Mg-O bonds are found for ZnO:Mg films with dopant concentrations of 2 and 3 wt%. The optical characterization showed that the transmittance of ZnO:Mg thin films increased from 74.5% (undoped ZnO) to about 89.1% and the optical band gap energy from 3.24 to 3.56 eV. Mg doping leads to a higher refractive index compared to undoped ZnO films. The FESEM (field emission scanning electron microscopy) technique is used for observation of the surface morphology modification of ZnO:Mg films. The doped ZnO films possess a smoother grained surface structure, opposite to the wrinkle-type morphology of undoped sol-gel ZnO films. The smoother surface leads to improved transparency of ZnO:Mg films.
A
bstract
We consider supersymmetric field theories on compact manifolds
and obtain constraints on the parameter dependence of their partition functions
. Our primary focus is the dependence of
on ...the geometry of
, as well as background gauge fields that couple to continuous flavor symmetries. For
= 1 theories with a U(1)
R
symmetry in four dimensions,
must be a complex manifold with a Hermitian metric. We find that
is independent of the metric and depends holomorphically on the complex structure moduli. Background gauge fields define holomorphic vector bundles over
and
is a holomorphic function of the corresponding bundle moduli. We also carry out a parallel analysis for three-dimensional
= 2 theories with a U(1)
R
symmetry, where the necessary geometric structure on
is a transversely holomorphic foliation (THF) with a transversely Hermitian metric. Again, we find that
is independent of the metric and depends holomorphically on the moduli of the THF. We discuss several applications, including manifolds diffeomorphic to
S
3
× S
1
or
S
2
× S
1
, which are related to supersymmetric indices, and manifolds diffeomorphic to
S
3
(squashed spheres). In examples where
has been calculated explicitly, our results explain many of its observed properties.
•The invasive Rhododendron ponticum is considered an emergent threat in W France.•It thrives in woodlands on acidic soils and appears promoted by climate change.•It locally spreads on moister soils ...via active layering.•Its ability to establish new populations is low due to recruitment limitations.•Management should minimize soil disturbance near established populations.
Understanding the population dynamics of invasive species is essential for identifying the key parameters of their success and guiding management actions. European temperate forests of the Atlantic domain are prone to be invaded by the Pontic Rhododendron (Rhododendron ponticum L. subsp. baeticum (Boiss. & Reut.) Hand.-Mazz.), a shade-tolerate evergreen shrub native to the Iberian peninsula. While the invasion has a long history in Ireland and the British Isles, it is an emerging threat in mainland Europe. It is therefore a timely challenge to better understanding the invasive dynamics of this species in this context. We studied the population dynamics of R. ponticum in 27 invaded forests of north-western France, examining population structure, and individuals’ growth, fertility and fecundity among contrasted light conditions. All invasive populations were found on acidic soils. Irrespective of light conditions, R. ponticum exhibited a regular radial growth, with a clear increase since the 1990s. The majority of stems were younger than 38 years on average, indicating a recent increase in population density. Light availability strongly impacted R. ponticum’s canopy structure, with higher canopy cover and stem numbers under sun conditions. Despite the production of a huge number of viable seeds, the observed number of seedlings was always very low irrespective of light conditions, indicating recruitment limitation and thus a limited ability to establish new, distant populations. In contrast, vegetative propagation via intense layering at the invasion front wave ensured local population spread from initially planted individuals, especially on moist soils. We conclude that where it has been planted, R. ponticum is able to actively layer, thereby forming dense bushes in the forest understories as long as the soil is acidic and relatively moist. The establishment of new, distant populations appears a rare event since recruitment is limited to particular microhabitats related to forest management-associated disturbances. Such disturbance should thus be avoided in sites where the species has already established, unless a post-disturbance eradication of R. ponticum’s seedling can be implemented the following years. The plantation of R. ponticum in forest must be avoided when the soil is acidic and moist. Because R. ponticum’s growth performances are increasing since the 1990s, as a likely consequence of climate change, monitoring established populations is recommended to detect a possible increasing invasiveness.
Clusterin is, in its major form, a secreted heterodimeric disulfide-linked glycoprotein (75–80 kDa). It was first linked to cell death in the rat ventral prostate after androgen deprivation. Recent ...studies have demonstrated that overexpression of clusterin in prostatic cells protects them against tumor necrosis factor-α (TNFα)-induced apoptosis. However the details of this survival mechanism remain undefined. Here, we investigate how clusterin prevents cells from undergoing TNFα-induced apoptosis. We established a double-stable prostatic cell line for inducible clusterin by using the Tet-On gene expression system. We demonstrated that 50% of the cells overexpressing clusterin escaped from TNFα- and actinomycin D-induced cell death. Moreover we demonstrated that the incubation of MLL cells with conditioned medium containing the secreted clusterin or the supplementation of purified clusterin in the extracellular medium decreased the TNFα-induced apoptosis significantly. This extracellular action implicates megalin, the putative membrane receptor for clusterin to mediate survival. Indeed clusterin overexpression up-regulated the expression of megalin and induced its phosphorylation in a dose-dependent manner. We interestingly showed that clusterin overexpression is associated with the up-regulation of the phosphorylation of Akt. Activated Akt induced the phosphorylation of Bad and caused a decrease of cytochrome c release. These results enable us to pinpoint one mechanism by which secreted clusterin favors survival in androgen-independent prostate cancer cells, implicating its receptor megalin and Akt survival pathway.
A
bstract
Chern-Simons quivers for M2-branes at Calabi-Yau singularities are best understood as the low energy theory of D2-branes on a dual type IIA background. We show how the D2-brane point of ...view naturally leads to three dimensional Seiberg dualities for Chern-Simons quivers with chiral matter content: They arise from a change of brane basis (or mutation), in complete analogy with the better known Seiberg dualities for D3-brane quivers. This perspective reproduces the known rules for Seiberg dualities in Chern-Simons-Yang-Mills theories with unitary gauge groups. We provide explicit examples of dual theories for the quiver dual to the
geometries. We also comment on the string theory derivation of CS quivers dual to massive type IIA geometries.
A
bstract
We study contact terms of conserved currents and the energy-momentum tensor in three-dimensional quantum field theory. They are associated with Chern-Simons terms for background fields. ...While the integer parts of these contact terms are ambiguous, their fractional parts are meaningful physical observables. In
supersymmetric theories with a U(1)
R
symmetry some of these observables lead to an anomaly. Moreover, they can be computed exactly using localization, leading to new tests of dualities.
A
bstract
We study two-dimensional
N
=
2
,
2
supersymmetric gauged linear sigma models (GLSM) on the Ω-deformed sphere,
S
Ω
2
, which is a one-parameter deformation of the
A
-twisted sphere. We ...provide an exact formula for the
S
Ω
2
supersymmetric correlation functions using supersymmetric localization. The contribution of each instanton sector is given in terms of a Jeffrey-Kirwan residue on the Coulomb branch. In the limit of vanishing Ω-deformation, the localization formula greatly simplifies the computation of
A
-twisted correlation functions, and leads to new results for non-abelian theories. We discuss a number of examples and comment on the
ϵ
Ω
-deformation of the quantum cohomology relations. Finally, we present a complementary Higgs branch localization scheme in the special case of abelian gauge groups.
We study the quantum moduli space of
Chern-Simons quivers with generic ranks and CS levels, proving along the way exact formulas for the charges of bare monopole operators. We then derive
...Chern-Simons quiver theories dual to
M-theory backgrounds, for the whole family of Sasaki-Einstein seven-manifolds and for any value of the torsion
G
4
flux. The derivation of the gauge theories relies on the reduction to type IIA string theory, in which M2-branes become D2-branes while the conical geometry maps to RR flux and D6-branes wrapped on compact four-cycles. M5-branes on torsion cycles map to flux and wrapped D4-branes. The moduli space of the quiver is shown to contain the corresponding CY
4
cone and all its crepant resolutions.
Questions
Light availability at the forest floor affects many forest ecosystem processes, and is often quantified indirectly through easy‐to‐measure stand characteristics. We investigated how three ...such characteristics, basal area, canopy cover and canopy closure, were related to each other in structurally complex mixed forests. We also asked how well they can predict the light‐demand signature of the forest understorey (estimated as the mean Ellenberg indicator value for light “EIVLIGHT” and the proportion of “forest specialists” “%FS” within the plots). Furthermore, we asked whether accounting for the shade‐casting ability of individual canopy species could improve predictions of EIVLIGHT and %FS.
Location
A total of 192 study plots from nineteen temperate forest regions across Europe.
Methods
In each plot, we measured stand basal area (all stems >7.5 cm diameter), canopy closure (with a densiometer) and visually estimated the percentage cover of all plant species in the herb (<1 m), shrub (1–7 m) and tree layer (>7 m). We used linear mixed‐effect models to assess the relationships between basal area, canopy cover and canopy closure. We performed model comparisons, based on R2 and the Akaike Information Criterion (AIC), to assess which stand characteristics can predict EIVLIGHT and %FS best, and to assess whether canopy shade‐casting ability can significantly improve model fit.
Results
Canopy closure and cover were weakly related to each other, but showed no relation with basal area. For both EIVLIGHT and %FS, canopy cover was the best predictor. Including the share of high‐shade‐casting species in both the basal‐area and cover models improved the model fit for EIVLIGHT, but not for %FS.
Conclusions
The typically expected relationships between basal area, canopy cover and canopy closure were weak or even absent in structurally complex mixed forests. In these forests, easy‐to‐measure structural canopy characteristics were poor predictors of the understorey light‐demand signature, but accounting for compositional characteristics could improve predictions.
In contrast to observations in even‐aged homogeneous forest stands, three easy‐to‐measure forest stand characteristics (basal area, canopy cover and canopy closure) were not or only weakly related to each other in structurally complex mixed forests. Moreover, these stand characteristics were poor predictors of the understorey light requirements, but accounting for the shade‐casting ability of different canopy species improved predictions.
In an attempt to match US bankruptcy law, many European countries have reformed their insolvency laws towards a regime that fosters corporate restructuring. This paper evaluates the implications of ...these reforms. Based on a staggered difference-in-differences analysis around eight insolvency reforms in 15 European countries, this paper finds a relative increase in the cost of debt by about 50 bps in countries with such a reform. The effect is more pronounced among firms being closer to default. As a result of increased cost of debt financing, firms cut investment, innovation, and employee pay. In addition, firms are also more likely to turn into zombies post-treatment. Overall, the results are consistent with the view that creditors may be negatively affected by insolvency law reforms oriented towards restructuring and, thus, demand higher risk premia. This, in turn, causes real effects in the corporate sector.
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