Quantum gravitational contributions to the beta function of quantum electrodynamics

We show in a diagrammatic and regularization independent analysis that the quadratic contribution to the beta function which has been conjectured to render quantum electrodynamics asymptotically free near the Planck scale has its origin in a surface term. Such surface term is intrinsically arbitrarily valued and it is argued to vanish in a consistent treatment of the model.     

Exact Perturbative Results for the Lieb–Liniger and Gaudin–Yang Models

Journal of Statistical Physics - We present a systematic procedure to extract the perturbative series for the ground state energy density in the Lieb–Liniger and Gaudin–Yang models,...     

On universal modules with pure embeddings

We show that certain classes of modules have universal models with respect to pure embeddings: Let R be a ring, T a first-order theory with an infinite model extending the theory of R-modules and ${\mathbf{K}}^T=(Mod(T),{\le }_{\mathrm{pp}})$ (where ⩽_pp stands for “pure submodule”). Assume ${\mathbf{K}}^T$ has the joint embedding and amalgamation properties. If ${\lambda }^{|T|}=\lambda$ or $\forall \mu <\lambda ({\mu }^{|T|}<\lambda )$, then ${\mathbf{K}}^T$ has a universal model of cardinality λ. As a special case, we get a recent result of Shelah [28, 1.2] concerning the existence of universal reduced torsion-free abelian groups with respect to pure embeddings. We begin the study of limit models for classes of R-modules with joint embedding and amalgamation. We show that limit models with chains of long cofinality are pure-injective and we characterize limit models with chains of countable cofinality. This can be used to answer [18, Question 4.25]. As this paper is aimed at model theorists and algebraists an effort was made to provide the background for both.     

Chemistry of Tetradentate [C,N : C,N] Iminophosphorane Palladacycles: Preparation,Reactivity and Theoretical Calculations

A theoretical and experimental study of tetradentate [C,N : C,N] iminophosphorane palladacycles was carried out for the purpose of elucidating their behavior as compared to the parent Schiff base analogues to determine the prospect of encountering new A-frame structures for the iminophosphorane derivatives. The DFT calculations were in agreement with the experimental results regarding the performance of these ligands. New insights into the chemistry of the related dinuclear species have been obtained.     

Thermodynamic and structural study of complexation of phenylboronic acid with salicylhydroxamic acid and related ligands

Stability constants of boronate complexes with a highly efficient bioconjugation ligand salicylhydroxamic acid, its derivatives and some structurally related compounds were determined by potentiometric and spectroscopic titrations at variable pH allowing one to obtain detailed stability – pH profiles and to identify the optimum pH for complexation with each ligand. The N,O‐binding of salicylhydroxamic acid via condensation of boronic acid with phenolic OH and hydroxamic NH groups was established by crystal structure determination of isolated complexes with phenylboronic and 4‐nitrophenylboronic acids. Although this type of binding is impossible for N‐methylated salicylhydroxamic acid it still forms stable boronate complexes supposedly involving unusual 7‐membered –O‐B‐O‐ cycle supported by ¹H NMR studies. Hydroxamic acids lacking ortho‐OH group and salicyloyl hydrazide form less stable boronate complexes, which nevertheless possess stabilities similar to those of catechole complexes and may be useful for conjugation applications. In contrast to other ligands, which form tetrahedral anionic complexes, salicylamidoxime forms tetrahedral, but neutral boronate complex with high stability in weakly acid solutions. The highest affinity in neutral and acid solutions surpassing that of salicylhydroxamic acid is observed with 2,6‐dihydroxybenzhydroxamic acid (K_obs = 5.2 × 10⁴ at pH 7.4). Fairly stable mono‐ and bisboronate complexes are formed with 2,5‐dihydroxy‐1,4‐benzdihydroxamic acid, which also possesses intense fluorescence and may serve as a boronic acid sensor with detection limit 4 μM. Results presented in this study provide quantitative basis for rational applications of hydroxamic acid derivatives in bioconjugation and sensing.