Effect of secondary decay on isoscaling: Results from the canonical thermodynamical model

The projectile fragmentation reactions using ⁵⁸Ni and ⁶⁴Ni beams at 140 MeV/n on targets ⁹Be and ¹⁸¹Ta are studied using the canonical thermodynamical model coupled with an evaporation code. The isoscaling property of the fragments produced is studied using both the primary and the secondary fragments and it is observed that the secondary fragments also respect isoscaling though the isoscaling parameters α and β changes. The temperature needed to reproduce experimental data with the secondary fragments is less than that needed with the primary ones. The canonical model coupled with the evaporation code successfully explains the experimental data for isoscaling for the projectile fragmentation reactions.     

Distinct chemoselectivities in the platinum-catalyzed 1,2-carboalkoxylations of 5-alkoxypent-1-yn-3-ol derivatives

Two distinct Pt-catalyzed carboalkoxylations of alkynes are reported. The cycloisomerization of 5-alkoxypent-1-yn-3-ol derivatives 5 produces 2,6-dioxabicyclo[3.1.0]hexanes 6; the mechanism is postulated to involve a hydroxyl-triggered [3.3]-sigmatropic allyl rearrangement. As the same catalysis is extensible to their tertiary alcohol analogues 7, distinct dihydrofuranyl alcohols 8 were obtained through a [3.3]-allyl rearrangement that is not assisted by the hydroxyl group.     

Qualitative inequalities for squared partial correlations of a Gaussian random vector

We describe various sets of conditional independence relationships, sufficient for qualitatively comparing non-vanishing squared partial correlations of a Gaussian random vector. These sufficient conditions are satisfied by several graphical Markov models. Rules for comparing degree of association among the vertices of such Gaussian graphical models are also developed. We apply these rules to compare conditional dependencies on Gaussian trees. In particular for trees, we show that such dependence can be completely characterised by the length of the paths joining the dependent vertices to each other and to the vertices conditioned on. We also apply our results to postulate rules for model selection for polytree models. Our rules apply to mutual information of Gaussian random vectors as well.     

Soft mode and related behaviour in the SmA and SmC* phases of a ferroelectric liquid crystalline polymer by dielectric spectroscopy

Anomalous dielectric relaxation behaviour is observed in the ferroelectric liquid crystalline polymer (viz. ferroelectric copolysiloxane (R)-COPS 11-10) around the ferroelectric SmC* to paraelectric SmA phase transition. Measurements have been performed on sample of thickness ～10 μm in indium-tin-oxide coated cell in the frequency range 10 Hz to 13 MHz. With increase of temperature, a gradual shift of the soft mode frequency towards the higher frequency side was observed, while a decrease in the relaxation strength was seen with the corresponding increase in temperature. The shifts of the soft modes in the SmC* and SmA phase are considered to be due to change in the viscosity of the polymer, as an increase in viscosity increases fluctuations of the coupling between the dipoles in the network even far from the paraelectric-ferroelectric phase transition. Application of a bias field causes a shift of the critical frequency towards the higher frequency side, while the dielectric strength (δε) decreases under the bias field. The Cole-Cole fitting parameters obtained from the best fit of the dielectric constant data are found to be consistent with other similar materials. Another relaxation mode (molecular mode) was also observed which comes into play in both the smectic phases (SmC% and SmA) and contributes to the dielectric permittivity.     

Characterization of the kinetics of Fe (II) binding by the R2 protein subunit of E. coli ribonucleotide reductase

¹¹⁹Sn Mössbauer spectroscopy was used to study Sn_1???x ⁵⁷Fe _x O_2???δ and Fe _x Sb _y Sn_1???x???y O_2???δ sol–gel synthesized ferromagnetic powders. ¹¹⁹Sn Mössbauer spectra of powder samples showed envelopes characteristic of a relatively broad Sn(IV) line. Small but significant differences can be found among the spectra belonging to different compositions and heat treatments. The spectra were decomposed into two doublets, one of these with unusually high quadrupole splitting was assigned to the defects playing very important role in the realisation of ferromagnetism in these materials.     

Cover Picture: Expanding the Toolbox of Target Directed Bio-Orthogonal Synthesis: In Situ Direct Macrocyclization by DNA Templates (Angew. Chem. Int. Ed. 7/2023)

Herein, we demonstrate for the first time that noncanonical DNA can direct macrocyclization-like challenging reactions to synthesize gene modulators. The planar G-quartets present in DNA G-quadruplexes (G4s) provide a size complementary reaction platform for the bio-orthogonal macrocyclization of bifunctional azide and alkyne fragments over oligo- and polymerization. G4s immobilized on gold-coated magnetic nanoparticles have been used as target templates to enable easy identification of a selective peptidomimetic macrocycle. Structurally similar macrocycles have been synthesized to understand their functional role in the modulation of gene function. The innate fluorescence of the in situ formed macrocycle has been utilized to monitor its cellular localization using a G4 antibody and its in cell formation from the corresponding azide and alkyne fragments. The successful execution of in situ macrocyclization in vitro and in cells would open up a new dimension for target-directed therapeutic applications.