64 New York Ave Ne
Washington DC 20002
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Photophysics of Voltage Increase by Photoinduced Dipole Layers in Sensitized Solar Cells. - The journal of physical chemistry letters
Significant overpotentials between the sensitizer and both the electron and hole conductors hamper the performance of sensitized solar cells, leading to a reduced photovoltage. We show that by using properly designed type-II quantum dots (QDs) between the sensitizer and the hole conductor in thin absorber cells, it is possible to increase the open circuit voltage (Voc) by more than 100 mV. This increase is due to the formation of a photoinduced dipole (PID) layer. Photogenerated holes in the type-II QDs are retained in the core for a relatively long time, allowing for the accumulation of a positively charged layer. Negative charges are, in turn, injected and accumulated in the TiO2 anode, creating a dipole moment, which negatively shifts the TiO2 conduction band relative to the electrolyte. We study this phenomenon using a unique TiO2/CdSe/(ZnSe:Te/CdS)/polysulfide system, where the formation of a PID depends on the color of the illumination. The PID concept thus introduces a new design strategy, where the operating parameters of the solar cell can be manipulated separately.
Low-level visible light (LLVL) irradiation promotes proliferation of mesenchymal stem cells. - Lasers in medical science
Low-level visible light irradiation was found to stimulate proliferation potential of various types of cells in vitro. Stem cells in general are of significance for implantation in regenerative medicine. The aim of the present study was to investigate the effect of low-level light irradiation on the proliferation of mesenchymal stem cells (MSCs). MSCs were isolated from the bone marrow, and light irradiation was applied at energy densities of 2.4, 4.8, and 7.2Â J/cm(2). Illumination of the MSCs resulted in almost twofold increase in cell number as compared to controls. Elevated reactive oxygen species and nitric oxide production was also observed in MSCs cultures following illumination with broadband visible light. The present study clearly demonstrates the ability of broadband visible light illumination to promote proliferation of MSCs in vitro. These results may have an important impact on wound healing.
Built-in quantum dot antennas in dye-sensitized solar cells. - ACS nano
A new design of dye-sensitized solar cells involves colloidal semiconductor quantum dots that serve as antennas, funneling absorbed light to the charge separating dye molecules via nonradiative energy transfer. The colloidal quantum dot donors are incorporated into the solid titania electrode resulting in high energy transfer efficiency and significant improvement of the cell stability. This design practically separates the processes of light absorption and charge carrier injection, enabling us to optimize each of these separately. Incident photon-to-current efficiency measurements show a full coverage of the visible spectrum despite the use of a red absorbing dye, limited only by the efficiency of charge injection from the dye to the titania electrode. Time resolved luminescence measurements clearly relate this to Forster resonance energy transfer from the quantum dots to the dye. The presented design introduces new degrees of freedom in the utilization of quantum dot sensitizers for photovoltaic cells. In particular, it opens the way toward the utilization of new materials whose band offsets do not allow direct charge injection.
Protective and restorative role of AS101 in combination with chemotherapy. - Cancer research
The immunomodulator AS101 has been found previously by us to stimulate the secretion of high levels of interleukin 1 and colony stimulating factor (CSF) in vitro, as well as the production of CSF in vivo in mice models. These cytokines are known to induce proliferation and differentiation of hematopoietic progenitor cells from the spleen and bone marrow (BM) and to protect mice from DNA-damaging agents. The present studies were designed to evaluate the effects of prolonged treatment with AS101 on myelopoiesis, BM cellularity, and CSF secretion in mice treated with a sublethal dose of cyclophosphamide (CYP) and on the survival of mice undergoing treatment with lethal doses of this compound. In this model, the hematopoietic progenitors were suppressed during the overbound phase of myelopoiesis resulting from the cytotoxic effects of CYP. This allowed the detection of a significant proliferative effect of AS101 in vivo on BM colony-forming units granulocyte-macrophage progenitor cells, BM cellularity, and the secretion of CSF. Moreover, AS101 protected these animals from the lethal effects of high doses of CYP. These protective effects were demonstrable only when AS101 was administered to mice prior to CYP treatment. The only exception was CSF secretion by spleen cells that had been reconstituted when AS101 was administered both prior to and following CYP treatment. AS101 was found to have a synergistic effect with CYP in the treatment of tumor-bearing mice, suggesting that the combination of these two modalities provides a more effective treatment of their tumors. These results strongly suggest an immunoregulatory role for AS101 in counteracting the chemotherapy-induced hematopoietic suppression as well as usefulness as adjunct treatment of cancer when used in combination with CYP.
Radioprotective effects of the immunomodulator AS101. - Journal of immunology (Baltimore, Md. : 1950)
Ammonium trichloro(dioxyethylene-O-O')tellurate (AS101) is a new synthetic compound previously described by us as having immunomodulating properties and minimal toxicity. Clinical trials are currently in progress with AS101 on AIDS and cancer patients. We found that AS101 was capable of inducing spleen cells and peritoneal exudate cells to secrete high quantities of CSF and IL-1. Because IL-1 has been previously described as a radioprotector and CSF may induce in vivo the proliferation of hemopoietic cells, we designed the present study in order to evaluate the effects of prolonged in vivo injections of AS101 on protection against lethal doses of irradiation, on the recovery pattern of precursor cells, and on the functioning of bone marrow (BM) and spleen cells of mice undergoing sublethal doses of treatment. We demonstrate that pretreatment with AS101 protects mice from lethal effects of ionizing radiation. AS101 was also found to significantly increase the number of BM and spleen cells, the absolute number of granulocyte macrophage-CFU and the secretion of CSF by BM cells. All were tested 9 days after sublethal dose of irradiation was administered. AS101 was found to have all of these radioprotective effects only when administered to mice before irradiation treatment. Moreover, the compound was found to enhance the proportion of CFU-S that enters the S phase of the cell cycle. These findings indicate that AS101 may be a promising agent to be used in reducing the time needed for reconstitution of hemopoietic cells after irradiation treatment.
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