Femtosecond laser structuring of titanium implants

In this study we perform the first femtosecond laser surface treatment of titanium in order to determine the potential of this technology for surface structuring of titanium implants. We find that the femtosecond laser produces a large variety of nanostructures (nanopores, nanoprotrusions) with a size down to 20 nm, multiple parallel grooved surface patterns with a period on the sub-micron level, microroughness in the range of 1-15 μm with various configurations, smooth surface with smooth micro-inhomogeneities, and smooth surface with sphere-like nanostructures down to 10 nm. Also, we have determined the optimal conditions for producing these surface structural modifications. Femtosecond laser treatment can produce a richer variety of surface structures on titanium for implants and other biomedical applications than long-pulse laser treatments.     

Comparative dissociation of peptide polyanions by electron impact and photo-induced electron detachment

We compare product-ion mass spectra produced by electron detachment dissociation (EDD) and electron photodetachment dissociation (EPD) of multi-deprotonated peptides on a Fourier transform and a linear ion trap mass spectrometer, respectively. Both methods, EDD and EPD, involve the electron emission-induced formation of a radical oxidized species from a multi-deprotonated precursor peptide. Product-ion mass spectra display mainly fragment ions resulting from backbone cleavages of C_α-C bond ruptures yielding a and x ions. Fragment ions originating from N-C_α backbone bond cleavages are also observed, in particular by EPD. Although EDD and EPD methods involve the generation of a charge-reduced radical anion intermediate by electron emission, the product ion abundance distributions are drastically different. Both processes seem to be triggered by the location and the recombination of radicals (both neutral and cation radicals). Therefore, EPD product ions are predominantly formed near tryptophan and histidine residues, whereas in EDD the negative charge solvation sites on the backbone seem to be the most favorable for the nearby bond dissociation.     

Cover-free codes and separating system codes

A set \(T\subset {GF(q)}\), \(q=p^h\) is a super-Vandermonde set if \(\sum _{y\in T} y^k=0\) for \(0< k <|T|\). We determine the structure of super-Vandermonde sets of size \(p+1\) (almost small) and size \(q/p-1\) (almost large).     

Study of the mechanism of the reaction 2H(π−, π−p)n at relatively high neutron momenta

The ²H(π^?, π^? p)n reaction is experimentally studied at 1 GeV/c for spectator neutron momenta up to 200 MeV/c. The spectator momentum and polar angle distributions and the Treiman-Yang angle distribution are in good agreement with theoretical calculations allowing for the diagrams in which the initial pion rescatters on the nucleons inside the deuteron not more than twice. We conclude that our understanding of the mechanism of the nucleon knock-out from a deuteron is correct. The simple example of the reaction on a deuteron confirms the possibility of describing direct processes with a small number of Feynman diagrams.     

Measurement of the Weinberg Angle in an Experiment at the Super Charm Tau Factory with a Polarized Beam

Physics of Atomic Nuclei - Measurement of the effective weak mixing angle $${\theta_{\textrm{eff}}}$$ in an experiment at the Super Charm Tau Factory is discussed for the case of a longitudinal...     

Measurement of the Angular Distributions of Fission Fragments from the Neutron-Induced Fission of 240Pu Nuclei in the Energy Range of 1–200 MeV and Their Model Analysis

JETP Letters - The measured angular distributions of fission fragments of 240Pu nuclei have been presented and theoretically analyzed. Measurements at energies above 10 MeV have been performed for...     

Dynamics of relaxation processes in a triglycine selenate single crystal in a ferroelectric phase

The deviation of the relaxation spectrum from the Debye type is studied experimentally and the presence of the non-Debye relaxation is shown, which is defined in different temperature ranges either by proton multiposition transitions below the Curie point T _c or relaxation domain and interphase boundaries in the vicinity of T _c. For triglycine selenate, the methods of analysis of dielectric non-Debye spectra are used.     

Reactivity of Selected Mono- and Dimethylpyridines under Conditions of Oxidative Ammonolysis

Russian Journal of General Chemistry - The reactivity of 3-methyl-, 4-methyl-, 2,3-dimethyl-, and 3,4-dimethylpyridines under the oxidative ammonolysis on vanadium oxide catalysts has been studied....     

Radical Stability Directs Electron Capture and Transfer Dissociation of β‐Amino Acids in Peptides

We report on the characteristics of the radical‐ion‐driven dissociation of a diverse array of β‐amino acids incorporated into α‐peptides, as probed by tandem electron‐capture and electron‐transfer dissociation (ECD/ETD) mass spectrometry. The reported results demonstrate a stronger ECD/ETD dependence on the nature of the amino acid side chain for β‐amino acids than for their α‐form counterparts. In particular, only aromatic (e.g., β‐Phe), and to a substantially lower extent, carbonyl‐containing (e.g., β‐Glu and β‐Gln) amino acid side chains, lead to N? C_β bond cleavage in the corresponding β‐amino acids. We conclude that radical stabilization must be provided by the side chain to enable the radical‐driven fragmentation from the nearby backbone carbonyl carbon to proceed. In contrast with the cleavage of backbones derived from α‐amino acids, ECD of peptides composed mainly of β‐amino acids reveals a shift in cleavage priority from the N? C_β to the C_α? C bond. The incorporation of CH₂ groups into the peptide backbone may thus drastically influence the backbone charge solvation preference. The characteristics of radical‐driven β‐amino acid dissociation described herein are of particular importance to methods development, applications in peptide sequencing, and peptide and protein modification (e.g., deamidation and isomerization) analysis in life science research.