Optical and atomic force microscopy measurements on the {001} form of the organic semiconductor quaterthiophene revealed interlaced spiral patterns arising from growth layers mutually rotated by 180° ...about the normal to the (001) crystal face. This bulk-surface relationship, along with the height of the exposed step ledges of the order of 10-100 nm, evidences the complex polytypic nature of these crystals in which the basic P21/c layer gives rise to several different stacking along 001, even within the same crystallite. The consequences on solid state physical properties arising from these crystal growth phenomena are briefly discussed.
We describe the Monte Carlo (MC) simulation of the Borexino detector and the agreement of its output with data. The Borexino MC “ab initio” simulates the energy loss of particles in all detector ...components and generates the resulting scintillation photons and their propagation within the liquid scintillator volume. The simulation accounts for absorption, reemission, and scattering of the optical photons and tracks them until they either are absorbed or reach the photocathode of one of the photomultiplier tubes. Photon detection is followed by a comprehensive simulation of the readout electronics response. The MC is tuned using data collected with radioactive calibration sources deployed inside and around the scintillator volume. The simulation reproduces the energy response of the detector, its uniformity within the fiducial scintillator volume relevant to neutrino physics, and the time distribution of detected photons to better than 1% between 100 keV and several MeV. The techniques developed to simulate the Borexino detector and their level of refinement are of possible interest to the neutrino community, especially for current and future large-volume liquid scintillator experiments such as Kamland–Zen, SNO+, and Juno.
A series of tetraaryl porphyrins and chlorins were synthesized and tested for photodynamic activity in human colon adenocarcinoma cells.
Photodynamic therapy (PDT) is a cancer treatment involving ...systemic administration of a tumor-localizing photosensitizer; this, when activated by the appropriate wavelength of light, interacts with molecular oxygen to form a toxic, short-lived species known as singlet oxygen, which is thought to mediate cellular death. Photofrin®, a complex mixture of porphyrin oligomers has recently received FDA approval for the photodynamic treatment of esophageal and endobronchial carcinoma, but its photodynamic and toxicity profiles are far from ideal. In the present study we evaluated a series of porphyrin-based PSs, some of which newly synthesized by our group, with the aim to identify agents with more favorable characteristics. For the most effective compounds in the porphyrin series, chlorin analogs were also synthesized; for comparison, the screening also included Photofrin®. Cytotoxicity studies were performed by the MTT assay on a cultured human colon adenocarcinoma cell line (HCT116); the results indicate that the 3,4,5-trimethoxyphenyl, 3OH- and 4OH-phenyl, and the sulfonamidophenyl derivatives are significantly more potent than Photofrin®. Flow cytometric studies and fluorescence microscopy indicate that in PDT-treated HCT116 cells death occurs mainly by apoptosis.
In summary, novel PSs described in the present study, belonging both to the porphyrin and chlorin series, have proven more effective than Photofrin® in killing colon cancer cells in vitro; extending these observation to in vivo models, particularly regarding the deeper reaching chlorin derivatives, might lead to significant advances in the development of tumor PDT.
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