Mineralogy of spessartine-quartz rocks of the Sikhote-Alin

Research subject. The article is devoted to the study of spessartine-quartz rocks of the Triassic chert formation of the Sikhote-Alin. The research objects involved the outcrops of spessartine-quartz rocks of the Gornaya and Shirokaya Pad areas from Malinovka and Olga ore districts (in the Samarka and Taukha terranes respectively). Materials and methods. The selection of stone materials was performed manually. The diagnostic of minerals was performed using the microscope in transmitted and reflected light and carried out by the determination of their composion. The polished sections of the minerals were investigated at the FEGI FEB RAS using JXA8100 microanalysers. Results. Spessartine-quartz and manganese silicate rocks occupy the same position in the section of the Triassic deposits of the Taukha and Samarka terrains. This indicates a synchronous accumulation of sediments (protoliths of these rocks) in a single sedimentary basin. The rocks formed by contact metamorphism in the Late and Early Cretaceous large granitoid massifs. This process is manifested in the presence of a variety of such minerals, as spessartine, members of the ilmenite-pyrophanite series, titanite, monazite, bastnesite, allanite, apatite, zircon, baddeleyite, torianite and others. The rocks under study also include such rare minerals, as cheralite, greyite and a rare variety of fluorine-aluminous titanite. Conclusion. The occurrence (during contact metamorphism of siliceous-rhodochrosite rocks) of spessartine-quartz or manganesesilicate rocks composed mainly of pyroxenoids, was determined by both the relative amounts of carbonate and clay matter, as well as the concentrations of Ba and alkalis in the initial sediments.

Rejection of the biophoton hypothesis on the origin of photoreceptor dark noise

Rod photoreceptors of the vertebrate retina produce, in darkness, spontaneous discrete current waves virtually identical to responses to single photons. The waves comprise an irreducible source of noise (discrete dark noise) that may limit the threshold sensitivity of vision. The waves obviously originate from acts of random activation of single rhodopsin molecules. Until recently, it was generally accepted that the activation occurs due to the rhodopsin thermal motion. Yet, a few years ago it was proposed that rhodopsin molecules are activated not by heat but rather by real photons generated within the retina by chemiluminescence. Using a high-sensitive photomultiplier, we measured intensities of biophoton emission from isolated retinas and eyecups of frogs (Rana ridibunda) and fish (sterlet, Acipenser ruthenus). Retinal samples were placed in a perfusion chamber and emitted photons collected by a high-aperture quartz lens. The collected light was sent to the photomultiplier cathode through a rotating chopper so that a long-lasting synchronous accumulation of the light signal was possible. The absolute intensity of bio-emission was estimated by the response of the measuring system to a calibrated light source. The intensity of the source, in turn, was quantified by measuring rhodopsin bleaching with single-rod microspectrophotometry. We also measured the frequency of discrete dark waves in rods of the two species with suction pipette recordings. Expressed as the rate constant of rhodopsin activation, it was 1.2 × 10−11/s in frogs and 7.6 × 10−11/s in sterlets. Approximately two thirds of retinal samples of each species produced reliably measurable biophoton emissions. However, its intensity was ≥100 times lower than necessary to produce the discrete dark noise. We argue that this is just a lower estimate of the discrepancy between the hypothesis and experiment. We conclude that the biophoton hypothesis on the origin of discrete dark noise in photoreceptors must be rejected.