Hyperspectral colour imaging and spectrophotometric instrumentation

The trichromatic nature of commercial photography is strictly connected with the nature of human colour vision, although the characteristics of usual colour imaging devices are quite different from the human visual system. The increase in the number of colour channels for spectral (either multispectral or hyperspectral) imaging is an active field of research with many potential applications in different fields. Each element of the captured scene is specified in the spectral image by the spectral reflectance factor. This measurement is independent of the particular illumination of the scene and allows the colorimetric computation in a device-independent colour space for any chosen illuminant and any observer. This thesis describes the project and construction of a compact spectrophotometric camera, which can be used in both portable and in-situ applications. The compactness is made possible by a suitable image spectral scanning based on an Induced Transmission Filter (ITF). This filter is made by a set of thin-film coatings of dielectric materials with high and low refraction index, whose shape like a wedge induces a wavelength selective transmittance, continuously variable along one direction and uniform in the perpendicular direction. Such a filter, classified as Linearly Variable Filter (LVF), operates continuously from 430nm to 940nm and allows hyperspectral imaging. In traditional scanners the whole apparatus is moved along a path as long as the scene, whereas in this instrument the camera body is still and the LVF is the only moving part. The sequence of operations for wavelength and radiometric calibrations are discussed. The expected acquisition times and number of images as a function of the spectral sampling step are considered. The resulting properties make the instrument easy to use and with short acquisition times. Moreover, overviews of the historic evolution of colour vision fundamentals, colour spaces and spectral imaging technology are given for introducing the reader to the essential concepts useful for the understanding of the text

Nuclear lipid microdomains regulate daunorubicin resistance in hepatoma cells

Daunorubicin is an anticancer drug, and cholesterol is involved in cancer progression, but their relationship has not been defined. In this study, we developed a novel experimental model that utilizes daunorubicin, cholesterol, and daunorubicin plus cholesterol in the same cells (H35) to search for the role of nuclear lipid microdomains, rich in cholesterol and sphingomyelin, in drug resistance. We find that the daunorubicin induces perturbation of nuclear lipid microdomains, localized in the inner nuclear membrane, where active chromatin is anchored. As changes of sphingomyelin species in nuclear lipid microdomains depend on neutral sphingomyelinase activity, we extended our studies to investigate whether the enzyme is modulated by daunorubicin. Indeed the drug stimulated the sphingomyelinase activity that induced reduction of saturated long chain fatty acid sphingomyelin species in nuclear lipid microdomains. Incubation of untreated-drug cells with high levels of cholesterol resulted in the inhibition of sphingomyelinase activity with increased saturated fatty acid sphingomyelin species. In daunodubicin-treated cells, incubation with cholesterol reversed the action of the drug by acting via neutral sphingomyelinase. In conclusion, we suggest that cholesterol and sphingomyelin-forming nuclear lipid microdomains are involved in the drug resistance

A portable Spectro-photo/radio-metric Camera with Spatial Filtering for VIS-NIR Imaging

This work proposes the design of a miniaturized spectrophoto/radio-metric camera with spatial filtering of the light for measuring the spectral reflectance factor and the spectral radiance of the objects of a scene

Small dimensions portable instruments for in-situ multispectral imaging

The design of a compact spectrometer for analysis of artworks is presented. Its operation is based on the use of a variable transmission filter associated with an array detector. The instrument allows the measurement of the spectral reflectance factor and combines the acquisition of data in a continuous spectrum with the small dimension that is of primary importance for in-situ spectral imaging. Keywords: compact spectrometers, image spectrometry, optical filter

Spatial filtering of visible light in a spectrophotometric camera for artwork imaging

The preservation and reproduction of a still artwork needs the knowledge of its spectral reflectance, obtainable in laboratory by spectrophotometric scanners. This work proposes the design of a miniaturized spectrophotometric camera with spatial filtering of the light for measuring the spectral reflectance factor and the spectral radiance of the objects of a scene

Modal demultiplexing properties of tapered and nanostructured optical fibers for in vivo optogenetic control of neural activity

Optogenetic approaches to manipulate neural activity have revolutionized the ability of neuroscientists to uncover the functional connectivity underlying brain function. At the same time, the increasing complexity of in vivo optogenetic experiments has increased the demand for new techniques to precisely deliver light into the brain, in particular to illuminate selected portions of the neural tissue. Tapered and nanopatterned gold-coated optical fibers were recently proposed as minimally invasive multipoint light delivery devices, allowing for site-selective optogenetic stimulation in the mammalian brain [Pisanello , Neuron82, 1245 (2014)]. Here we demonstrate that the working principle behind these devices is based on the mode-selective photonic properties of the fiber taper. Using analytical and ray tracing models we model the finite conductance of the metal coating, and show that single or multiple optical windows located at specific taper sections can outcouple only specific subsets of guided modes injected into the fiber

Optical fiber technologies for in-vivo light delivery and optogenetics

In optogenetics, light-sensitive proteins are genetically targeted into specific classes of neurons in living animal models (typically mice), making possible to control their neural activity by means of visible light delivered into the brain tissue. In this paper, recent advances on techniques for in-vivo optical stimulation and inhibition of neuronal activity in optogenetic experiments are reported, with particular emphasis on new a new generation of fiber-optic technologies