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We investigate the consequences of the ambiguity of minimal coupling procedure for Einstein-Cartan gravity with Holst term and fermions. A new insight is provided into the nature and physical relevance of coupling procedures considered hitherto in the context of Ashtekar-Barbero-Immirzi formalism with fermions. The issue of physical effects of the Immirzi parameter in semi--classical theory is reinvestigated. We argue that the conclusive answer to the question of its measurability will not be possible until the more fundamental problem of nonuniqueness of gravity--induced fermion interaction in Einstein-Cartan theory is solved.Comment: 11 pages, typos corrected, final version, to appear in Phys. Rev.

We report a simple protocol for the synthesis of α‐fluoro‐β‐aminophosphonates by the regioselective fluorination of α‐hydroxy‐β‐aminophosphonates under mild conditions. The fluorination reactions were mediated by the PyFluor reagent and occurred with the retention of configuration. The main products of this reaction were a series of α‐fluoro‐β‐aminophosphonates, which can be used as precursors in the preparation of medicinally important compounds (e.g., dipeptide analogues).

Nucleophilic fluorination is one of the fundamental reactions in organic chemistry, as well as a convenient tool for the synthesis of fluorinated building blocks with a potential biological activity. In this minireview, diethylaminosulfur trifluoride (DAST) mediated reactions leading to valuable building blocks and bioactive compounds will be discussed. We focused on results that have been published since 2010. Transformation of βamino alcohols, heterocyclic frameworks synthesis, as well as rearrangement reactions have been described in detail.

We report on the effect of alginic acid capping on the behavior of magnetite nanoparticles. The capped nanoparticles exhibit improved crystalline structure of the surface which leads to an enhanced magnetization. The improved structure facilitates quantization of spin-wave spectrum in the finite size nanoparticles and this in turn is responsible for unconventional behavior at low temperatures. In electron magnetic resonance these anomalies are manifested as an unusual increase in the resonant field H r (T) and as a maximum of the spectroscopic splitting g eff parameter at low temperatures. This unconventional behavior leads also to pronounced upturn of magnetization at low temperatures and a deviation from the Bloch law M(T)~T 3/2 .

An elementary presentation of the methods for the canonical quantization of constraint systems with Fermi variables is given. The emphasis is on the subtleties of the construction of an appropriate classical bracket that could be consistently replaced by commutators or anti-commutators of operators, as required by canonical quantization procedure for bosonic and fermionic degrees of freedom respectively. I present a consequent canonical quantization of the Dirac field, in which the role of Poincaré invariance is made marginal. This simple example provides an introduction to the Poincaré-free quantization of spinor electrodynamics in the second part of the paper.

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