Partially coherent spherical sources with spherical harmonic modes.

A class of partially coherent spherical sources is introduced whose cross-spectral density across the surface has a modal expansion made up of spherical harmonics. For such sources, the solution of the propagation problem in all the outer spaces can be written through a series of the propagated modes, which maintains the spherical harmonic structure. The main features of this class of cross-spectral densities are derived illustrating their coherence properties with examples. Attention is paid to the properties of radial coherence. In particular, it is clearly shown that sources with perfect radial coherence exist with angular coherence that is only partial.

Cylindrical partially coherent scalar sources.

Partially coherent scalar sources with cylindrical symmetry radiating outwards are introduced. Homogeneous cross-spectral densities are shown to possess angularly modulated Hankel modes, whose amplitudes are subject to a filtering process during propagation. Simple criteria for treating such sources are given. For the case of an incoherent cylinder, the number of effective modes is found and spatial coherence is shown to appear in the radiated light. The radial coherence of the radiated field is then examined. Non-homogeneous cylindrical sources are also introduced.

Polymerogenic neuroserpin causes mitochondrial alterations and activates NFκB but not the UPR in a neuronal model of neurodegeneration FENIB.

The neurodegenerative condition FENIB (familiar encephalopathy with neuroserpin inclusion bodies) is caused by heterozygous expression of polymerogenic mutant neuroserpin (NS), with polymer deposition within the endoplasmic reticulum (ER) of neurons. We generated transgenic neural progenitor cells (NPCs) from mouse fetal cerebral cortex stably expressing either the control protein GFP or human wild type, polymerogenic G392E or truncated (delta) NS. This cellular model makes it possible to study the toxicity of polymerogenic NS in the appropriated cell type by in vitro differentiation to neurons. Our previous work showed that expression of G392E NS in differentiated NPCs induced an adaptive response through the upregulation of several genes involved in the defence against oxidative stress, and that pharmacological reduction of the antioxidant defences by drug treatments rendered G392E NS neurons more susceptible to apoptosis than control neurons. In this study, we assessed mitochondrial distribution and found a higher percentage of perinuclear localisation in G392E NS neurons, particularly in those containing polymers, a phenotype that was enhanced by glutathione chelation and rescued by antioxidant molecules. Mitochondrial membrane potential and contact sites between mitochondria and the ER were reduced in neurons expressing the G392E mutation. These alterations were associated with a pattern of ER stress that involved the ER overload response but not the unfolded protein response. Our results suggest that intracellular accumulation of NS polymers affects the interaction between the ER and mitochondria, causing mitochondrial alterations that contribute to the neuronal degeneration seen in FENIB patients.

A novel approach to detect and characterize the scattering patterns of single Au nanoparticles using confocal microscopy.

We demonstrate a novel optical method for characterizing single Au nanoparticles by acquiring their scattering patterns. This technique combines confocal microscopy and higher-order laser modes for detecting the light scattered by sub-wavelength-sized nanoobjects. The optical patterns are generated by the coherent superposition of the field scattered by individual metallic particles and the excitation field reflected at the cover slide-air interface and provide information about the particles' position, orientation, size and shape. Detectable changes in the full width at half maximum (FWHM) of the signal intensity permit to distinguish between 20- and 60-nm diameter Au spheres. The confocal images are also very sensitive to the particle's geometry and polarizability, that is, Au nanospheres, Au nanorods and triangular Au nanoplates give different characteristic patterns if the excitation wavelength is varied.

Spatially modulated illumination microscopy: online visualization of intensity distribution and prediction of nanometer precision of axial distance measurements by computer simulations.

During the last years, measurements considerably beyond the conventional "Abbe-Limit" of optical resolution in far field light microscopy were realized by several light microscopical approaches. Point spread function (PSF) engineering, spectral precision distance microscopy (SPDM), and related methods were used to demonstrate the feasibility of such measurements. SPDM allows the measurement of position and multiple distances between point-like fluorescent objects of different spectral signatures far below the optical resolution criterion as defined by the full width at half maximum of the PSF. Here, we report a software method to obtain online visualization of light distribution in the lateral and axial direction of any object detected in a spatially modulated illumination (SMI) microscope. This strongly facilitates routine application of SMI microscopy. The software was developed using Microsoft Visual C++ running on Windows NT. Furthermore, some aspects of the theoretical limits of the SPDM method were studied by virtual microscopy. For the case of SMI microscopy the precision of axial distance measurements was studied, taking into account photon statistics and image analysis procedures. The results indicate that even under low fluorescence intensity conditions typical for biological structure research, precise distance measurements in the nanometer range can be determined, and that axial distances in the order of 40 nm are detectable with such precision.