Low Band Gap Donor‐Acceptor Conjugated Polymer Nanoparticles and their NIR‐mediated Thermal Ablation of Cancer Cells

Low band gap D‐A conjugated PNs consisting of 2‐ethylhexyl cyclopentadithiophene co‐polymerized with 2,1,3‐benzothiadiazole (for nano‐PCPDTBT) or 2,1,3‐benzoselenadiazole (for nano‐PCPDTBSe) have been developed. The PNs are stable in aqueous media and showed no significant toxicity up to 1 mg · mL^?1. Upon exposure to 808 nm light, the PNs generated temperatures above 50 °C. Photothermal ablation studies of the PNs with RKO and HCT116 colorectal cancer cells were performed. At concentrations above 100 µg · mL^?1 for nano‐PCPDTBSe, cell viability was less than 20%, while at concentrations above 62 µg · mL^?1 for nano‐PCPDTBT, cell viability was less than 10%. The results of this work demonstrate that low band gap D‐A conjugated polymers 1) can be formed into nanoparticles that are stable in aqueous media; 2) are non‐toxic until stimulated by IR light and 3) have a high photothermal efficiency.

     

On the evolution of states of controlled qubits

Theoretical and Mathematical Physics - We describe the interaction between the qubit and the electromagnetic field in a waveguide in accordance with the Lee model using the fact that photons in the...     

On the threshold anisotropy for unstable spherical stellar systems

The radial orbit instability generally arises in anisotropic collisionless stellar systems with the dominance of radial motions over transverse ones. Using the simplest anisotropic generalization of polytrope models for spherical clusters as an example, we show that the instability growth rates become exponentially small as the isotropic limit is approached. Given the finite lifetime of real astronomical objects, these systems should be assumed to become stable at some finite radial anisotropy.     

Travel time of a quantum particle through a given domain

A quantum field model is proposed for determining the travel time of a quantum particle through a given domain. The model involves a source and a detector of scalar particles. Using this model, the particle travel time between the source and detector, as well as the tunneling time, is determined. The travel time depends on the detector characteristics, and tunneling decreases the travel time. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 118, No. 1, pp. 51–66, January, 1999.     

Soft template synthesis of donor–acceptor conjugated polymer nanoparticles: Structural effects,stability, and photothermal studies

Donor–acceptor conjugated polymer nanoparticles and nanofibers, based on Poly[4,4‐bis(2‐ethylhexyl)‐cyclopenta[2,1‐b;3,4‐b']dithiophene‐2,6‐diyl‐alt?2,1,3‐benzoselenadiazole‐4,7‐diyl] (PCPDTBSe), were synthesized using Pluronic F127 as a template. The nanomaterials were compared to previously reported PCPDTBSe nanoparticles, which were synthesized without the use of a template. Our goal was to improve on the aqueous stability and photothermal heating efficiency of the previously synthesized PCPDTBSe nanoparticles by decreasing their size and coating them with a biocompatible surfactant. The pluronic wrapped PCPDTBSe (PW‐PCPDTBSe) nanoparticles (40–60 nm) showed excellent aqueous stability compared to the PW‐PCPDTBSe nanofibers (d = 20–60 nm, l = 200–1000 nm) and previously synthesized PCPDTBSe nanoparticles (150 nm). Under stimulation from 800 nm near infrared light (3 W, 1 min), the PW‐PCPDTBSe nanoparticles showed greater heat generation (ΔT = 47 °C) compared to bare PCPDTBSe nanoparticles and PW‐PCPDTBSe nanofibers (ΔT = 35 °C for both). Cytotoxicity studies determined that both the PW‐PCPDTBSe nanoparticles and PW‐PCPDTBSe nanofibers displayed no significant toxicity toward either noncancerous small intestinal cells (FHs 74 Int) or colorectal cancer cells (CT26). Photothermal ablation studies confirmed that both the PW‐PCPDTBSe nanoparticles and the PW‐PCPDTBSe nanofibers can be used as localized photothermal agents to eradicate colorectal cancer cells due to their excellent ablation efficiency (>95% cell death at 15 µg/mL concentration). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1622–1632     

Gravitational loss-cone instability

We study physical corollaries of the existing analogy between the simplest plasma traps (mirror traps) and star clusters surrounding massive black holes or dense galactic nuclei. There is a loss cone in the system through which plasma particles with low velocities transverse to the trap axis or, similarly, stars with low angular momenta (destroyed or absorbed by the central body) escape. The consequences of the “beam-like” deformation of the plasma distribution function in a trap are well known: a peculiar loss-cone instability producing a plasma flow into the loss cone develops as a result. We show that a similar gravitational loss-cone instability can also arise under certain conditions in the galactic case of interest to us. This instability is related to the slow precessional motions of highly elongated (nearly radial) stellar orbits and the main condition for its growth is that the precession of such orbits be retrograde (in the direction opposite to the orbital rotation of stars). Only under this condition do oscillations that can become unstable in the presence of a loss cone arise instead of the radial orbit instability (a variety of the Jeans instability in systems with highly elongated orbits) that takes place in the case of prograde precession. The instability produces a stream of stars onto the galactic center, i.e., serves as a mechanism of fueling the nuclear activity of galaxies. For a mathematical analysis, we have obtained relatively simple characteristic equations that describe small perturbations in a sphere of radially highly elongated stellar orbits. These characteristic equations are derived through a number of successive simplifications from a general linearized system of equations, including the collisionless Boltzmann kinetic equation and the Poisson equation (in action-angle variables). The central point of our analysis of the characteristic equations is preliminary detection of neutral modes (or proof of their absence in the case of stability).     

On quantization of systems with actions unbounded from below

We consider two possible approaches to the problem of the quantization of systems with actions unbounded from below: the Borel summation method applied to the perturbation expansion in the coupling constant and the method based on the kerneled Langevin equation for stochastic quantization. In the simplest case of an anharmonic oscillator, the first method produces Schwinger functions, even though the corresponding path integral diverges. The solutions of the kerneled Langevin equation are studied both analytically and numerically. The fictitious time averages are shown to have limits that can be considered as the Schwinger functions. The examples demonstrate that both methods may give the same result.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 109, No. 2, pp. 175–186, November, 1996.     

Stability of self-gravitating astrophysical disks

Criteria which guarantee the stability of self-gravitating gaseous and stellar disks toward any localized small perturbations are obtained. These criteria are formulated as inequalities of the form Q>Q _c (separately for gas and stars). The latter should be satisfied by the “stability parameter” Q, which is equal, by definition, to unity on the stability boundary of radial perturbations. The critical value of the stability parameter Q _c is appreciably greater than (although of the order of) unity, attesting to the great instability of nonaxially symmetric perturbations. It is shown that the stability criterion derived for gaseous disks is valid for disks rotating within a spheroidal component (as in spiral galaxies) or in the field of a central mass (planetary rings and accretion disks). Stellar disks are stabilized with significantly greater difficulty. This is attributable mainly to the anisotropy of the velocity distribution inherent to them, which is favorable for instability. Zh. éksp. Teor. Fiz. 112, 771–795 (September 1997)     

A linear theory of resonance structures in spiral galaxies

The resonance mechanism for the formation of galactic spirals is considered. Expressions are derived for the resonance responses of disks with circular and nearly circular stellar orbits. The spiral responses produced by the central oval-shaped structures (bars) available in many galaxies are shown to have the characteristic properties of the spirals observed in these galaxies. In the most interesting case of a quasi-steady state, the spiral responses possess a similarity property: the spiral thickness and inclination are proportional to the mean size of an epicycle (an analog of the Larmor circle in plasma).