Recent Progress in Direct Introduction of Fluorinated Groups on Alkenes and Alkynes by means of CH Bond Functionalization

The direct introduction of fluorine and fluorinated building blocks has recently attracted a lot of attention and particularly the direct functionalization of alkenes and alkynes. This review will highlight the major progress recently made in that field, with a focus on photocatalyzed transformations, base‐promoted processes, and transition metal‐catalyzed functionalization of alkenes and alkynes. Special attention will be paid to explanations of the reaction mechanisms.     

Deformations of duality-symmetric theories

We prove that a sum of free non-covariant duality-symmetric actions does not allow consistent, continuous and local self-interactions that deform the gauge transformations. For instance, non-abelian deformations are not allowed, even in 4 dimensions where Yang–Mills type interactions of 1-forms are allowed in the non-manifestly duality-symmetric formulation. This suggests that non-abelian duality should require to leave the standard formalism of perturbative local field theories. The analyticity of self-interactions for a single duality-symmetric gauge field in four dimensions is also analyzed.     

Indirect interactions between localized magnetic moments in intrinsic semiconductors

The indirect interaction between localized magnetic moments in insulators and semiconductors is investigated at T = 0°K. This interaction arises from virtual excitations of the valence electrons to the conduction band and is oscillatory as a function of distance. The passage from the case of small gap semiconductors to insulators is studied in detail, as a function of the energy gap and the effective masses. The Bloembergen-Rowland interaction is derived as a limiting case for insulators. Possible applications are also discussed.     

Molecular depth profiling of organic and biological materials

Atomic depth profiling using secondary ion mass spectrometry, SIMS, is common in the field micro-electronics; however, the generation of molecular information as a function of sample depth is difficult due to the accumulation of damage both on and beneath the sample surface. The introduction of polyatomic ion beams such as SF₅ and C₆₀ have raised the possibility of overcoming this problem as they deposit the majority of their energy in the upper surface of the sample resulting in increased sputter yields but with a complimentary reduction in sub-surface damage accumulation. In this paper we report the depth profile analysis of the bio-polymer polycaprolactone, PCL, using the polyatomic ions and and the monoatomic Au⁺. Results are compared to recent analysis of a similar sample using . depth profiling of cellulose is also demonstrated, an experiment that has been reported as unsuccessful when attempted with implications for biological analysis are discussed.     

Hidrogeochemical study in South Amazon region using Photoacoustic Spectroscopy

In this study we demonstrate the usefulness of the Photoacoustic Spectroscopy (PAS) in the investigation of water collected from a natural site located within the Amazon region, Brazil, during the wet to dry seasons transition (May/2006). The water samples were collected from different stages along a hydrologic pathway including precipitation water (Prec), groundwater (GW), through flow water (TF), overland flow water (OF), and stream flow water (SW). The observed photoacoustic spectral features, in the 0.3 to 1.0 μm wavelength region, fall within three distinct bands (C, S, and L). We found band-C, band-S and band-L occurring in the spectral range of 0.30 to 0.40 μm, 0.40 to 0.45 μm and 0.45 to 1.0 μm regions, respectively. The photoacoustic features shift peak positions and change intensities for all samples investigated, thus supporting the proposal of PAS as a useful technique to investigate water samples from natural environments.     

Variations de champs gaussiens stationnaires: application a l'identification

Summary Let be a stationary Gaussian random field, with covariance R. For d=1 and d=2, families of variations are described. The convergence in mean square of these variations and a subsequent identification of a model for X are studied. Under suitable glocal conditions for R, the behaviour of these variations depends on the local behaviour of R near the origin. The differences between the case d=1 and d=2 are particularly emphasised: for d=1, there exists only one variation; for d=2, several families of variations are available which provided a useful tool for identifying different models: for example, Orstein-Uhlenbeck processes can be identified in mean square on , but not on .

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Variations de champs gaussiens stationnaires: application a l'identification

     

A Note on the Morozov Principle via Lagrange Duality

Considering a general linear ill-posed equation, we explore the duality arising from the requirement that the discrepancy should take a given value based on the estimation of the noise level, as is notably the case when using the Morozov principle. We show that, under reasonable assumptions, the dual function is smooth, and that its maximization points out the appropriate value of Tikhonov’s regularization parameter. The numerical relevance of our approach is established by means of an illustrative example from nonparametric instrumental regression, a standard problem in statistics.     

Effective magnetic monopoles and universal conductance fluctuations

The observation of isolated positive and negative charges, but not isolated magnetic north and south poles, is an old puzzle. Instead, evidence of effective magnetic monopoles has been found in the abstract momentum space. Apart from Hall-related effects, few observable consequences of these abstract monopoles are known. Here, we show that it is possible to manipulate the monopoles by external magnetic fields and probe them by universal conductance fluctuation measurements in ferromagnets with strong spin-orbit coupling. The observed fluctuations are not noise, but reproducible quasiperiodic oscillations as a function of magnetization direction, a novel Berry phase fingerprint of the magnetic monopoles.