Toxics or Lures? Biological and Behavioral Effects of Plant Essential Oils on Tephritidae Fruit Flies

The family Tephritidae (Diptera) includes species that are highly invasive and harmful to crops. Due to globalization, international trade, and human displacement, their spread is continuously increasing. Unfortunately, the control of tephritid flies is still closely linked to the use of synthetic insecticides, which are responsible for detrimental effects on the environment and human health. Recently, research is looking for alternative and more eco-friendly tools to be adopted in Integrated Pest Management (IPM) programs. In this regard, essential oils (EOs) and their main compounds represent a promising alternative to chemical insecticides. EOs are made up of phytoconstituents formed from the secondary metabolism of many plants and can act as attractants or toxics, depending on the dose. Because of this unique characteristic, EOs and their main constituents are promising tools that can be used both in Sterile Insect Technique (SIT) programs and in the “lure and kill” technique, exploiting the attractiveness of the product in the former case and its toxicity in the latter. In this article, current knowledge on the biological and behavioral effects of EOs and their main constituents on tephritid fruit flies is reviewed, mainly focusing on species belonging to the Anastrepha, Bactrocera, Ceratitis, and Zeugodacus genera. The mechanisms of action of EOs, their real-world applications, and challenges related to their use in IPM are critically discussed.     

On the equivalence of two variational problems

We consider the following problems where is a convex function, is an open bounded subset of is a closed convex subset of such that and and are suitable obstacles. We give conditions on the function {\it g} under which the two problems are equivalent. Received March 24, 1999/ Accepted January 14, 2000 / Published online June 28, 2000     

Kinetic modeling of the thermal degradation of polyethylene and polystyrene mixtures

One possible process for recovering valuable chemical and petrochemical products from plastic waste is the stepwise thermal degradation of polymer mixtures. This potentially allows the step by step simultaneous separation of the different product fractions generated by the polymers of the blend. The aim of this paper is to investigate the effect of the mixing scale of the polymers and their interactions in the melt. Several thermogravimetric analyses were performed on small samples of polyethylene (PE) and polystyrene (PS) mixtures. Two types of operating conditions were adopted: the first one is a dynamic analysis with a linear increase of the temperature over time, the latter consists of two sequential isothermal steps. The experimental results confirm that if the mixing scale is poor, the decomposition of each polymer behaves independently of the presence of the other one. Conversely, when the mixing of the two polymers reaches the molecular scale, a co-pyrolysis takes place with partial interactions. A two phase system is assumed: one phase characterized by a larger PS fraction, the other one by a prevailing PE amount. In order to properly predict the kinetic interactions typical of the mixed phases, it was necessary to extend the detailed kinetic model already developed and validated for the single polymers. The resulting two phase model gives a satisfactory explanation of several experimental data from the thermal degradation of PE–PS mixtures.     

The complexity of a minimum reload cost diameter problem

We consider the minimum diameter spanning tree problem under the reload cost model which has been introduced by Wirth and Steffan [H.-C. Wirth, J. Steffan, Reload cost problems: Minimum diameter spanning tree, Discrete Appl. Math. 113 (2001) 73-85]. In this model an undirected edge-coloured graph G is given, together with a nonnegative symmetrical integer matrix R specifying the costs of changing from a colour to another one. The reload cost of a path in G arises at its internal nodes, when passing from the colour of one incident edge to the colour of the other. We prove that, unless P=NP, the problem of finding a spanning tree of G having a minimum diameter with respect to reload costs, when restricted to graphs with maximum degree 4, cannot be approximated within any constant α<2 if the reload costs are unrestricted, and cannot be approximated within any constant β<5/3 if the reload costs satisfy the triangle inequality. This solves a problem left open by Wirth and Steffan [H.-C. Wirth, J. Steffan, Reload cost problems: minimum diameter spanning tree, Discrete Appl. Math. 113 (2001) 73-85].     

O–O2 state-to-state vibrational relaxation and dissociation rates based on quasiclassical calculations

A complete set of V–T (vibration–translation) relaxation rates and of dissociation coefficients for the system O–O₂ have been obtained by using quasiclassical trajectories on the Varandas and Pais potential energy surface. The results, averaged on a Boltzmann rotational distribution, cover the whole range of the vibrational ladder and are reproduced in closed form ready to be implemented in state-to-state kinetic models. The accuracy of the results has been tested by comparing them with available experimental and theoretical values (ASI-CAST project is acknowledged).     

Theoretical expectations for σtot at the large hadron collider

In this note, we summarize and compare various model predictions forpp total cross-section σ _tot ^pp , giving an estimate of the range of predictions for the total cross-section, σ _tot ^pp expected at the LHC. We concentrate on the results for σ _tot ^pp obtained in a particular QCD based model of the energy dependence of the total cross-section, including the effect of soft gluon radiation. We obtain the range of predictions in this model by exploring the allowed range of model parameters. We further give a handy parametrisation of these results which incidentally spans the range of various other available predictions at the LHC as well     

3-Quasi-Sasakian manifolds

In the present article we carry on a systematic study of 3-quasi-Sasakian manifolds. In particular, we prove that the three Reeb vector fields generate an involutive distribution determining a canonical totally geodesic and Riemannian foliation. Locally, the leaves of this foliation turn out to be Lie groups: either the orthogonal group or an abelian one. We show that 3-quasi-Sasakian manifolds have a well-defined rank, obtaining a rank-based classification. Furthermore, we prove a splitting theorem for these manifolds assuming the integrability of one of the almost product structures. Finally, we show that the vertical distribution is a minimum of the corrected energy.      

Melting of lithium hydride under pressure

We have computed the melting line of lithium hydride up to 200 GPa using the two-phase simulation technique coupled with first-principles molecular dynamics. Our predicted melting temperature at high pressures varies slowly with compression, ranging from 2000 to 2450 K at 50-200 GPa pressures. The compressed fluid close to the melting line retains the ionic character of the low pressure molten state, while at higher temperatures dynamical hydrogen clustering processes are observed, which are accompanied by changes in the electronic structure.     

Reactivity of titanium oxo ethoxo cluster [Ti16O16(OEt)32]. Versatile precursor of nanobuilding block-based hybrid materials

Oxo alcoxo metallic clusters can be employed as inorganic nanobuilding blocks to obtain well-defined organic-inorganic hybrid materials. A better understanding of the surface reactivity of the clusters should allow optimization of the elaboration of hybrid materials through a better control of the hybrid interface. The oxo alcoxo cluster Ti(16)O(16)(OEt)32 presents a shell of labile ethoxy groups that can be selectively transalcoholyzed with preservation of the titanium oxo core, leading to new oxo alcoxo clusters Ti(16)O(16)(OEt)32-x(OR)x (R: alkyl, phenyl, styrenic, etc. groups). The reactivity of the Ti(16)O(16)(OEt)32 cluster toward aliphatic and aromatic alcohols is investigated to determine both the kinetics and the number of substituted titanium atoms, which are strongly dependent on the nature of the alcohol. Characterization of the organic modification of the cluster is performed in situ by liquid (13)C NMR measurements, using the molecular structures of two new clusters, Ti(16)O(16)(OEt)28(OnPr)4 and Ti(16)O(16)(OEt)(24)(OnPr)(8) (OnPr = propoxy groups), as references. The structures of these clusters have been established using single-crystal X-ray diffraction. Moreover, a complete spectroscopic assignment of each ethoxy group is proposed after combining crystallographic data, (13)C NMR T(1) relaxation measurements, and (1)H-(1)H, (1)H-(13)C 2D NMR experiments. Finally, the cluster is functionalized with polymerizable ligands via transalcoholysis and transesterification reactions using hydroxystyrene and acetoxystyrene.