Abstract:In this paper we present the analysis, optimization and implementation of several Stokes polarimeter configurations based on a setup including two variable retarders. The polarimeter analysis is based on the Mueller-Stokes formalism, and as a consequence, it is suitable to deal with depolarized light. Complete Stokes polarimeters are optimized by minimizing the amplification of simulated errors into the final solution. Different indicators useful to achieve this aim, as the condition number or the equally weighted variance, are compared in this paper. Moreover, some of the optimized polarimeters are experimentally implemented and it is studied the influence of small deviations from the theoretical ones on the amplification of the Stokes component error. In addition, the benefit of using incomplete polarimeters, when detecting specific ranges of states of polarization, is discussed.

J. Neurochem. (2010) 112, 1305–1315. Abstract Frontotemporal dementia with ubiquitin‐positive inclusions (FTLD‐U) can be caused by mutations in the progranulin gene (GRN). Progranulin (PGRN) is a cysteine‐rich growth factor, which is proteolytically cleaved by elastase to produce several granulins (GRNs). All FTLD‐U mutations in GRN characterized to date result in reduced secreted PGRN protein. We recently reported a Spanish family with progressive non‐fluent aphasia and dementia in which a novel C521Y mutation segregates with disease. A second cysteine mutation (C139R) has also been reported to be disease specific. Allele‐specific mRNA expression assays in brain reveal that the C521Y mutant allele is expressed at similar levels to the wild‐type allele. Furthermore, plasma PGRN levels in C521Y carriers are comparable with non‐carrier family relatives, suggesting that the mutation does not affect PGRN protein expression and secretion in vivo. Despite normal PGRN levels C521Y and C139R mutant GRNs show reduced neurite growth‐stimulating activity in vitro. Further study revealed that these mutations also cause impaired cleavage of PGRN by elastase. Our data suggest that these mutations affect the function of full‐length PGRN as well as elastase cleavage of PGRN into GRNs, leading to neurodegeneration.

In higher organisms, dietary proteins are broken down into amino acids within the digestive tract but outside the cells, which incorporate the resulting amino acids into their metabolism. However, under certain conditions, an organism loses more nitrogen than is assimilated in the diet. This additional loss was found in the past century to come from intracellular proteins and started an intensive research that produced an enormous expansion of the field and a dispersed literature. Therefore, our purpose is to provide an updated summary of the current knowledge on the proteolytic machinery involved in intracellular protein degradation and its physiological and pathological relevance, especially addressed to newcomers in the field who may find further details in more specialized reviews. However, even providing a general overview, this is an extremely wide field and, therefore, we mainly focus on mammalian cells, while other cells will be mentioned only for comparison purposes.

Optical methods, as fluorescence microscopy or hyperspectral imaging, are commonly used for plants visualization and characterization. Another powerful collection of optical techniques is the so-called polarimetry, widely used to enhance image contrast in multiple applications. In the botanical applications framework, in spite of some works have already highlighted the depolarizing print that plant structures left on input polarized beams, the potential of polarimetric methods has not been properly exploited. In fact, among the few works dealing with polarization and plants, most of them study light scattered by plants using the Degree of Polarization (DoP) indicator. Other more powerful depolarization metrics are nowadays neglected. In this context, we highlight the potential of different depolarization metrics obtained using the Mueller matrix (MM) measurement: the Depolarization Index and the Indices of Polarimetric Purity. We perform a qualitative and quantitative comparison between DoP- and MM-based images by studying a particular plant, the Hedera maroccana. We show how Mueller-based metrics are generally more suitable in terms of contrast than DoP-based measurements. The potential of polarimetric measurements in the study of plants is highlighted in this work, suggesting they can be applied to the characterization of plants, plant taxonomy, water stress in plants, and other botanical studies.

This work evidences the suitability of applying a single twisted nematic liquid-crystal (TN-LC) device to obtain dynamic polarimeters with high accuracy and repeatability. Different Stokes polarimeter setups based on a TN-LC device are optimized, leading to the minimization of the noise propagated from intensity measurements to the Stokes vector calculations. To this aim, we revise the influence of working out of normal incidence and of performing a double pass of the light beam through the LC device. In addition, because transmissive TN-LC devices act as elliptical retarders, an extra study is performed. It analyzes the influence of projecting the light exiting from the TN-LC device over elliptical states of polarization. Finally, diverse optimized polarimeters are experimentally implemented and validated by measuring different states of partially and fully polarized light. The analysis is conducted both for monochromatic (He-Ne laser) and LED light sources, proving the potential of polarimeters based on a single TN-LC device.