Theoretical investigations of the perylene electronic structure: Monomer,dimers, and excimers

The structural and electronic properties of perylene molecule, dimers, and excimers have been computationally studied. The present work represents the first systematic study of perylene molecule and dimer forms by means of long‐range corrected time‐dependent density functional theory (TDDFT) approaches. Initially, the study explores the photophysical properties of the molecular species. Vertical transitions to many excited singlet states have been computed and rationalized with different exchange‐correlation functionals. Differences between excitation energies are discussed and compared to the absorption spectrum of perylene in gas phase and diluted solution. De‐excitation energy from the relaxed geometry of the lowest excited singlet is in good agreement with the experimental fluorescence emission. Optimization of several coplanar forms of the perylene pair prove that, contrary to generalized gradient approximation (GGA) and hybrid exchange‐correlation functionals, corrected TDDFT is able to bind the perylene dimer in the ground state. Excitation energies from different dimer conformers point to dimer formation prior to photoexcitation. The fully relaxed excimer geometry belongs to the perfectly eclipsed conformation with D_2h symmetry. The excimer equilibrium intermolecular distance is shorter than the separation found for the ground state, which is an indication of stronger interchromophore interaction in the excimer state. Excimer de‐excitation energy is in rather good agreement with the excimer band of perylene in concentrated solution. The study also scans the energy profiles of the ground and lowest excited states along several geometrical distortions. The nature of the interactions responsible for the excimer stabilization is explored in terms of excitonic and charge resonance contributions. © 2015 Wiley Periodicals, Inc.     

Locally recoverable J-affine variety codes

A locally recoverable (LRC) code is a code over a finite field ${\mathbb{F}}_q$ such that any erased coordinate of a codeword can be recovered from a small number of other coordinates in that codeword. We construct LRC codes correcting more than one erasure, which are subfield-subcodes of some J-affine variety codes. For these LRC codes, we compute localities $(r,\delta )$ that determine the minimum size of a set $\bar{R}$ of positions so that any $\delta -1$ erasures in $\bar{R}$ can be recovered from the remaining r coordinates in this set. We also show that some of these LRC codes with lengths $n\gg q$ are $(\delta -1)$-optimal.     

Principles of electrostatic interactions and self-assembly in lipid/peptide/DNA systems: Applications to gene delivery

Recently, great progress has been achieved in development of a wide variety of formulations for gene delivery in vitro and in vivo, which include lipids, peptides and DNA (LPD). Additionally, application of natural histone–DNA complexes (chromatin) in combination with transfection lipids has been suggested as a potential route for gene delivery (chromofection). However, the thermodynamic mechanisms responsible for formation of the ternary lipid–peptide–DNA supramolecular structures have rarely been analyzed. Using recent experimental studies on LPD complexes (including mixtures of chromatin with cationic lipids) and general polyelectrolyte theory, we review and analyze the major determinants defining the internal structure, particle composition and size, surface charge and ultimately, transfection properties of the LPD formulations.     

LRC电路谐振法应用的设计性实验

根据LRC电路的谐振原理，通过设计几种不同的实验方案，自制一些必要的实验装置，来解决实际应用中的问题，从而提高学生的学习兴趣，开拓学生的创新思路。