Label-free video-rate micro-endoscopy through flexible fibers via Fiber Bundle Distal Holography (FiDHo)

Fiber-based micro-endoscopes are a critically important tool for minimally-invasive deep-tissue imaging. However, the state-of-the-art micro-endoscopes cannot perform three-dimensional imaging through dynamically-bent fibers without the use of bulky optical elements such as lenses and scanners at the distal end, increasing the footprint and tissue-damage. While great efforts have been invested in developing approaches that avoid distal bulky optical elements, the fundamental barrier of dynamic optical wavefront-distortions in propagation through flexible fibers, limits current approaches to nearly-static or non-flexible fibers. Here, we present an approach that allows holographic 3D bend-insensitive, coherence-gated, micro-endoscopic imaging, using commercially available multi-core fibers (MCFs). We achieve this by adding a miniature partially-reflecting mirror to the distal fiber-tip, allowing us to perform low-coherence full-field phase-shifting holography. We demonstrate widefield diffraction-limited reflection imaging of amplitude and phase targets through dynamically bent fibers at video-rates. Our approach holds great potential for label-free investigations of dynamic samples.Comment: 28 pages, 6 figures plus 4 supplementary figures. Movies not include

Geometrical evolution of interlocked rough slip surfaces: The role of normal stress

International audienceWe study the evolution of slip surface topography using direct shear tests of perfectly mating surfaces. The tests are performed under imposed constant normal stress and constant slip rate conditions, to a sliding distance comparable to the roughness scale of the studied surfaces. Prismatic limestone blocks are fractured in tension using four-point bending and the generated surface topographies are measured using a laser profilometer. The initially rough fracture interfaces are tested in direct shear while ensuring a perfectly mating configuration at the beginning of each test. The predetermined sliding distance in all tests is 10 mm and the sliding velocity is 0.05mm/s. A constant normal stress is maintained throughout the tests using closed loop servo control. The range of normal stresses applied is between 2MPa and 15MPa. After shearing, the surface topographies are re-scanned and the geometrical evolution is analyzed. We find that surface roughness increases with increasing normal stress: under normal stresses below 5MPa the surfaces become smoother compared to the original geometry, whereas under normal stresses between 7.5 MPa and 15 MPa the surfaces clearly become rougher following shear. Statistical spectral analyses of the roughness profiles indicate that roughness increases with length-scale. Power spectral density values parallel to the slip orientation are fitted by power-law with typical power value of 2.6, corresponding to a Hurst exponent of 0.8, assuming self-affine roughness. This power value is consistent for the post-sheared surfaces and is obtained even when the original surface roughness does not follow initially a power-law form. The value of the scaling-law prefactor however increases with increasing normal stress. We find that the deformation associated with shearing initially rough interlocked surfaces extends beyond the immediate tested surface, further into the intact rock material. The intensity of the damage and its spatial distribution clearly increase with increasing normal stress. Wear loss is measured by subtracting the post-shear surface from the pre-shear surface matrices using known reference points. Our measurements indicate that wear loss and roughness evolution are both positively correlated with the mechanical shear work applied during the experiments. We argue, therefore, that normal stress plays a significant role in the evolution of interlocked surfaces, such as geological faults, and strongly affects the energy partitioning during slip

Valuations and Valuation Rings

This paper is an investigation of several basic properties of ordered Abelian groups, valuations, the relationship between valuation rings, valuations, and their value groups and valuation rings. The proofs to all theorems stated without proof can be found in Zariski and Samuel, Commutative Algebra, Vol. I, 1858. In Chapter I several basic theorems which are used in later proofs are stated without proof, and we prove several theorems on the structure of ordered Abelian groups, and the basic relationships between these groups, valuations, and their valuation rings in a field. In Chapter II we deal with valuation rings, and relate the structure of valuation rings to the structure of their value groups

Correlation calculations for the reconstruction of the Si (100) surface

Ab initio multi-reference configuration interaction calculations are performed for the Si(100) surface using a cluster approach. The convergence with respect to the cluster size is checked and the final results are taken from a $Si_{32} H_{28}$ cluster which models two dimers and six bulk layers. We find for the ideal as well as for the p($1\times 2$) reconstruction a singlet ground state consisting of several configurations. The energy gain due to forming the symmetric dimer in the p($1\times 2$) structure is 1.75 eV, the bond length of the dimer is 2.35 \AA which is very close to the bulk value. In contradiction to the LDA results and in agreement with previous correlation calculations we do not find an asymmetric p($1\times 2$) structure.Comment: 6 pages, Revtex, 3 postscript figures, to appear in Surf. S

Outline of Synthesis of Cognitive and Socio-cultural Foundations of Scientific Knowledge Evolution in Research Programs of Western Philosophy of Science

The article analyses the development of cognitive sociology of science, in the object field of which connection of cognitive and social structures of science is traced. The role of context in scientific knowledge formation is defined. It is stated that the basis for development of research program of cognitive sociology of science appeared to be reconsideration of the standard concept of science as a complex of gnoseological, epistemological and methodological interpretations of nature and morphology of the produced scientific knowledge, methods for its explanation and scientificity ideals. The difference between "strong" and «weak» varieties of scientific knowledge evolution, developed in western philosophy of science, is considered. "Social studies of science" are reviewed as a form of social constructivism and relativism, exhibiting their specific nature in macro-analytical and micro- analytical strategies of scientific knowledge evolution analysis. The thesis that multidimensionality of science cannot be adequately interpreted focusing only on conceptual history of science is proved

Master of Science

thesisBefore concentration tests were conducted on the Ontario ore for the recovery of the silver therein, specimens were studied microscopically to determine the physical characteristics of the ore and, if possible, the manner in which the silver existed. Measurements of the grains of the sulphide minerals were also made in order to determine the degree of crushing necessary to unlock the different minerals from each other. As the method of concentration will depend on the manner of association of the silver with the minerals in the ore, definite information concerning this relationship is absolutely necessary. The microscopic examination polished sections under reflected light afforded the best means for obtaining this information and was accordingly used. The silver in the ore was found as silver sulphides, presumably formed during the replacement of the silver-bearing tetrahedrite by galena. The silver minerals were closely associated with the galena and the tetrahedrite. The recovery of the silver is therefore dependent on the recovery of the lead and of the copper sulphides. No inclusions of silver minerals in either the pyrite or in the sphalerite could be found. The average size of the sulphide grains, as measured with a calibrated, net-ruled occular, was between 80 and 100 mesh (0.175 to 0.147 mm. in diameter(. Due to hte fact that the silver-bearing minerals cursh more readily than the non-silver-bearing minerals, grinding to minus 60 mesh (0.221 mm.) should be sufficient to unlock the minerals from each other and render then assemble to mechanical concentration. One possible obstacle to successful concentration of the ore is the alight alteration of galena to anglesite. This, however, was noticed in but a few sections and is probably of minor importance. The method of concentration, based on the result of this study, would involve the crushing of the ore to minus 60 mesh followed by flotation. This latter operation should recover the galena and the tetrahedrite, and therefore the silver. This material could be shipped to one of the lead smelters in the Salt Lake Valley and the full value of the silver in the concentrate could be obtained