In vivo Laser-induced Fluorescence Imaging of a Rat Pancreatic Cancer with Pheophorbide-a

Laser-induced fluorescence (LIF) of pheophorbide-a (Ph-a) was used for imaging of a rat pancreatic tumor. Using a dimensionless function (the ratio of Ph-a fluorescence by bluish autofluorescence), the fluorescence contrasts between excised tumors and their paired pancreas were investigated up to 48 h after a 9 mg kg^-1 Ph-a intravenous administration. Among five tested excitation wavelengths, 355 and 610 nm excitations gave the best distinctive contrasts, both 48 h after dye injection. The LIF imaging of six intrapancreatic tumors and six healthy pancreas was carried out in vivo using two laser excitations: 355 nm (Nd:YAG + tripling) for bluish autofluorescence and 610 nm (rhodamine 6G dye) for reddish autofluorescence and dye emission. Images were recorded through bandpass filters at 470 and 640 nm (autofluorescence) and at 680 nm (dye + autofluorescence) with an intensified charged-coupled device camera. Autofluorescence as Ph-a fluorescence images did not allow accurate LIF diagnosis of pancreatic carcinoma. An image processing, including for each pixel a computed division of Ph-a fluorescence (after subtraction of reddish autofluorescence) by bluish autofluorescence intensity generated poorly contrasted tumor images in five of six and false tumor localization in one of three of the tumor-bearing pancreas. A fitting of the digital 640 nm autofluorescence up to the mean 680 nm fluorescence intensity in pancreas prior to subtraction allowed a safe diagnosis to be made with well-contrasted tumor images. To assess automation ability of the processing, a same fitting coefficient (mean of individual values) was applied. In this way, false-negative (one of six) and false-positive (two of six) images were present in tumor-bearing animals as false-positive in one-half of the controls. A successful standardized procedure was then applied with a normalization of 640 and 680 nm pancreas intensities to a same set threshold prior processing. In opposition to thin-layered hollow organs, such as bronchial tube or digestive tract, LIF imaging of carcinoma inserted in a compact organ is exhausting. The use of a dye excitable in the red wavelength range (610 nm for Ph-a) may partly solve this problem, rendering LIF imaging more accurate and potentially automated.     

Confinement-Driven Photophysics in Hydrazone-Based Hierarchical Materials

Confinement-imposed photophysics was probed for novel stimuli-responsive hydrazone-based compounds demonstrating a conceptual difference in their behavior within 2D versus 3D porous matrices for the first time. The challenges associated with photoswitch isomerization arising from host interactions with photochromic compounds in 2D scaffolds could be overcome in 3D materials. Solution-like photoisomerization rate constants were realized for sterically demanding hydrazone derivatives in the solid state through their coordinative immobilization in 3D scaffolds. According to steady-state and time-resolved photophysical measurements and theoretical modeling, this approach provides access to hydrazone-based materials with fast photoisomerization kinetics in the solid state. Fast isomerization of integrated hydrazone derivatives allows for probing and tailoring resonance energy transfer (ET) processes as a function of excitation wavelength, providing a novel pathway for ET modulation.     

Blue-colored donor-acceptor [2]rotaxane

[reaction: see text] A guest molecule-a bis-N-tetraethyleneglycol-substituted 3,3'-difluorobenzidine derivative-has been synthesized, and its complexation with the host, cyclobis(paraquat-p-phenylene), has been investigated. This host-guest complex was then employed in the template-directed synthesis of a blue-colored [2]rotaxane. The color of this [2]rotaxane arises from the charge-transfer absorption band between the HOMO of the guest and the LUMO of the host. This host-guest complex, and the derived [2]rotaxane, completes the donor-acceptor-based RGB (red/green/blue) color complex set.     

Decay of the 21/2− isomer in211Bi and structure of thevg 9 2/2 πh 9/2 levels

Gamma rays and conversion electrons have been measured in²¹¹Bi populated by the²⁰⁹Bi(t,p) reaction, and the near yrast levels were observed up to 21/2^?. The 21/2^? state is isomeric withT _1/2=70(5) ns. No alpha decaying isomer was found in²¹¹Bi. ObservedM1 transitions reveal mixing of the²¹⁰Pb parent states in the levels of²¹¹Bi. The levels and transitions are well reproduced by the shell model with experimental matrix elements and pure configurations.     

Toward Electrochemically Controllable Tristable Three‐Station [2]Catenanes

Encouraged by the prospect of producing an electrochemical, color‐switchable red–green–blue (RGB) dye compound, we have designed, synthesized, and characterized two three‐station [2]catenanes. Both are composed of macrocyclic polyethers containing three π‐electron‐rich stations, which act as recognition sites for a π‐electron‐deficient tetracationic cyclophane. The molecular structures of the two three‐station [2]catenanes were characterized fully by mass spectrometry and ¹H NMR spectroscopy. To anticipate the relative occupancies of the three stations in each [2]catenane by the cyclophane, model compounds with the same constitutions in the vicinity of the stations were synthesized. The relative ground‐state populations of the three stations occupied in both [2]catenanes were estimated from the thermodynamic parameters for 1:1 complexes between all these model compounds and the cyclophane, obtained from isothermal titration calorimetry (ITC). The electrochemical and electromechanical properties of the three‐station [2]catenanes were analyzed by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and spectroelectrochemistry (SEC). The first three‐station [2]catenane was found to behave like a bistable system, whereas the second can be described as a quasi‐tristable system.     

Decreasing and fast solutions for a second-order difference equation related to Fisher-Kolmogorov's equation

We prove the existence of so-called fast solutions of a second-order difference equation related to traveling wave solutions of Fisher-Kolmogorov's equation. Variational approach is used and the fast solutions are obtained as minimizers of an energy functional on a weighted Hilbert space. Numerical experiments are presented.