245 research outputs found
Changing incentives for early retirement - Causal evidence from a cohort based pension reform
In this paper we exploit a cohort specific pension reform to estimate the causal employment effect of changes in the financial incentives to retire. In particular we analyze the effect of the introduction of pension deductions for early retirement on female employment. For the empirical analysis we use high-quality administrative data from the German Federal Pension Insurance (VSKT) and find positive and significant effects of the reform on employment
In vivo photosensitizer tomography inside the human prostate
Interstitial photodynamic therapy (IPDT) provides a promising means to treat large cancerous tumors and solid organs inside the human body. The treatment outcome is dependent on the distributions of light, photosensitizer, and tissue oxygenation. We present a scheme for reconstructing the spatial distribution of a fluorescent photosensitizer. The reconstruction is based on measurements performed in the human prostate, acquired during an ongoing IPDT clinical trial, as well as in optical phantoms. We show that in an experimental setup we can quantitatively reconstruct a fluorescent inclusion in a fluorescent background. We also show reconstructions from a patient showing a heterogeneous distribution of the photosensitizer mTHPC in the human prostate. (C) 2009 Optical Society of Americ
Comparison of spatially and temporally resolved diffuse-reflectance measurement systems for determination of biomedical optical properties
Time-resolved and spatially resolved measurements of the diffuse reflectance from biological tissue are two well-established techniques for extracting the reduced scattering and absorption coefficients. We have performed a comparison study of the performance of a spatially resolved and a time-resolved instrument at wavelengths 660 and 785 nm and also of an integrating-sphere setup at 550-800 nm. The first system records the diffuse reflectance from a diode laser by means of a fiber bundle probe in contact with the sample. The time-resolved system utilizes picosecond laser pulses and a single-photon-counting detection scheme. We extracted the optical properties by calibration using known standards for the spatially resolved system, by fitting to the diffusion equation for the time-resolved system, and by using an inverse Monte Carlo model for the integrating sphere. The measurements were performed on a set of solid epoxy tissue phantoms. The results showed less than 10% difference in the evaluation of the reduced scattering coefficient among the systems for the phantoms in the range 9-20 cm(-1), and absolute differences of less than 0.05 cm(-1) for the absorption coefficient in the interval 0.05-0.30 cm(-1). (C) 2003 Optical Society of America
Are the old International Board for Plant Genetic Resources (IBPGR) base collections available through the Plant Treaty's multilateral system of access and benefit sharing? A review
In 1975, the International Board for Plant Genetic Resources created the first internationally linked system of genebanks, known as the Registry of Base Collections (RBC), to conserve plant germplasm and make it available globally for agricultural research and development. Over time, international efforts shifted away from enhancing and building the RBC toward other means to promote the conservation and sustainable use of plant genetic resources. Perhaps the most important development in this regard was the negotiation of the International Treaty on Plant Genetic Resources for Food and Agriculture (Plant Treaty or ITPGRFA) and the development of its multilateral system for access and benefit sharing (multilateral system). Our study aimed to ascertain whether the RBC materials are still being conserved/curated in the original recipient organizations. We also sought to assess whether those materials have been included in, and are available through, the ITPGRFA's multilateral system. This outcome would be significant since, in many ways, the multilateral system reflects the spirit, commitment, and objectives of the RBC, with important additional components (e.g. obligations to share monetary benefits derived from the uses of plant genetic resources for food and agriculture). We identify four levels of probability that RBC materials are included in, and available through, the multilateral system. Ultimately, we find that there is a high level of probability that approximately 80% of the RBC materials are currently available through the multilateral system. We further identify a number of possible interventions that could be made to ensure that all RBC materials are conserved and made available through the multilateral system (or on similar terms and conditions of facilitated access and benefit sharing)
Light Scattering By Multiple Red Blood Cells
The interaction of light with multiple red blood cells was systematically investigated by the finite-different time-domain method. The simulations show that the lateral multiple scattering between red blood cells is very weak. The polarization is shown to have an almost insignificant influence on the distribution of the scattered light. The numerical results were compared with three approximate methods: the superposition approximation, the Rytov approximation and the discrete dipole approximation. The agreement was very good
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