A light-harvesting fluorinated fullerene donor-acceptor ensemble; long-lived charge separation

In a first example of a trannulene-based donor-acceptor dyad visible light photoexcitation generates a long-lived (870 ns) charge-separated state.     

Stable equidistant step trains during crystallization of insulin

Bunching of growth steps plagues layerwise crystallization of materials in laboratory, industrial, and geological environments, and theory predicts that equidistant step trains are unstable under a variety of conditions. Searching for an example of stable equidistant step trains, we monitored the generation and spatiotemporal evolution of step trains on length scales from 100 nm to 1 mm during the crystallization of insulin, using atomic force microscopy and phase-shifting interferometry. We show that near-equidistant step trains are generated by single and cooperating screw dislocation. The lack of step-step interaction and the overall transport-controlled growth regime further regularize the step train and ensure the stability of the obtained equidistant arrangement.     

The spectral theory for a pencil of skewsymmetrical differential operators of the third order

We consider the linear algebra of a pair of skewsymmetrical forms in the space of periodic functions defined by differential operators. By linear transform in the space of functions we reduce this pair to the simplest possible form. In this process, we prove the theorem of reduction in rather general context. © 1994 John Wiley & Sons, Inc.     

Non-uniform decay of predictability and return of skill in stochastic oscillatory models

We examine the dynamical mechanisms that lead to the loss of predictability in low-dimensional stochastic models that exhibit three main types of oscillatory behavior: damped, self-sustained, and heteroclinic. We show that the information that an initial ensemble provides about the state of the system decays non-uniformly with time. Long intervals during which the forecast provided by the ensemble does not loose any of its power are typical in all the three cases. Moreover, the information that the forecast provides about the individual variables in the model may increase, despite the fact that information about the entire system always decreases. We analyze the fully solvable case of the linear oscillator, and use it to provide a general heuristic explanation for the phenomenon. We also show that during the intervals during which the forecast loses little of its power, there is a flow of information between the marginal and conditional distributions.     

Novel NIR-Phosphorescent Ir(III) Complexes: Synthesis,Characterization and Their Exploration as Lifetime-Based O2 Sensors in Living Cells

A series of [Ir(N^C)₂(N^N)]⁺ NIR-emitting orthometalated complexes (1–7) has been prepared and structurally characterized using elemental analysis, mass-spectrometry, and NMR spectroscopy. The complexes display intense phosphorescence with vibrationally structured emission bands exhibiting the maxima in the range 713–722 nm. The DFT and TD DFT calculations showed that the photophysical characteristics of these complexes are largely determined by the properties of the metalating N^C ligands, with their major contribution into formation of the lowest S₁ and T₁ excited states responsible for low energy absorption and emission, respectively. Emission lifetimes of 1–7 in degassed methanol solution vary from 1.76 to 5.39 µs and show strong quenching with molecular oxygen to provide an order of magnitude lifetime reduction in aerated solution. The photophysics of two complexes (1 and 7) were studied in model physiological media containing fetal bovine serum (FBS) and Dulbecco’s Modified Eagle Medium (DMEM) to give linear Stern-Volmer calibrations with substantially lower oxygen-quenching constants compared to those obtained in methanol solution. These observations were interpreted in terms of the sensors’ interaction with albumin, which is an abundant component of FBS and cell media. The studied complexes displayed acceptable cytotoxicity and preferential localization, either in mitochondria (1) or in lysosomes (7) of the CHO-K1 cell line. The results of the phosphorescence lifetime imaging (PLIM) experiments demonstrated considerable variations of the sensors’ lifetimes under normoxia and hypoxia conditions and indicated their applicability for semi-quantitative measurements of oxygen concentration in living cells. The complexes’ emission in the NIR domain and the excitation spectrum, extending down to ca. 600 nm, also showed that they are promising for use in in vivo studies.     

Light propagation in linear arrays of spherical particles

A propagation of dipolar radiation in a finite length linear chain of identical dielectric spheres is investigated using the multisphere Mie scattering formalism (MSMS). A frequency pass band is shown to be formed near every Mie resonances inherent in the spheres. The manifestation of the pass band depends on the polarization of the travelling radiation. To prove this effect, a point dipole placed by the end of the chain is used as an external source of radiation. It is found that, if this dipole is directed parallel to the chain axis, the frequency pass bands exist if the refractive index of dielectric spheres is sufficiently large nr>1.9. For the dipole normal to the chain axis, the pass band can always be formed if the chain is sufficiently long. Such a distinction is due to different behavior of the far-field dipolar interaction between the spheres induced by the external source. The edges of the pass bands are defined by the guiding wave criterion based on the light-cone constraint. The criterion of creation of the pass bands correlate with condition of formation of high quality factor modes in these systems found in our previous papers. A comparison with the results available for infinite chains is made. In particular, we clarify the nature of braking down the band structure for small enough wavevectors.     

Iterative technique for analysis of periodic structures at oblique incidence in the finite-difference time-domain method

Normal incidence of a plane electromagnetic wave on a periodical structure can be simulated by the finite-difference time-domain method using a single unit cell with periodical boundary conditions imposed on its borders. For the oblique wave incidence, the boundary conditions would contain time delays and thus are difficult to implement in the time-domain method. We propose a method of oblique incidence simulation, based on an iterative algorithm. The accuracy of this method is demonstrated by comparing it with the layer Korringa-Kohn-Rostoker frequency-domain method for calculation of transmission spectra of a monolayered photonic crystal.     

Critical networks exhibit maximal information diversity in structure-dynamics relationships

Network structure strongly constrains the range of dynamic behaviors available to a complex system. These system dynamics can be classified based on their response to perturbations over time into two distinct regimes, ordered or chaotic, separated by a critical phase transition. Numerous studies have shown that the most complex dynamics arise near the critical regime. Here we use an information theoretic approach to study structure-dynamics relationships within a unified framework and show that these relationships are most diverse in the critical regime.