arXiv subjects

Igor Khmelinskii

Publications and source records attributed to Igor Khmelinskii.

7 recordsLinked to original sources

arXiv2018

Optical transparency and electrical conductivity of single-wall carbon nanotubes and of intermediate filaments of porcine Müller cells

In the present study, we continue investigation of the high-contrast vision in the inverted retina of the vertebrates eyes. We report a method of separation and purification of porcine (Sus scrofa domestica) intermediate filaments (IFs), extracted from the retinal Müller cells (MCs). We also report experimental and theoretical methods of measurements and calculations of the reduced resistivity and light transmission by the IFs and single-wall carbon nanotubes (SWCNTs). The measured reduced resistivity values were (3.1+-0.3)*10^-4 and (2.8+-0.2)*10^-4 Ohm m^-1 cm^2, respectively, being quite close to those of typical metals. We report a method for measuring the light energy transmission by the intermediate filaments and single-wall carbon nanotubes. We found that these structures efficiently transfer light energy along its axis, with the light reemitted at the other end of the structure. We also report spectral selectivity of the IFs. The reported results demonstrate that the assumptions we made in deducing the theory of high-contrast vision in an inverted retina were correct and fully supported by the presently reported experimental results.

cond-mat.mes-hall↗

arXiv2017

Mechanism of light energy transport in the avian retina

We studied intermediate filaments (IFs) in the retina of the Pied flycatcher (Ficedula hypoleuca) in the foveolar zone. Single IFs span Müller cells (MC) lengthwise; cylindrical bundles of IFs (IFBs) appear inside the cone inner segment (CIS) at the outer limiting membrane (OLM) level. IFBs adjoin the cone cytoplasmatic membrane, following lengthwise regularly spaced, forming a skeleton of the CIS, located above the OLM. IFBs follow along the cone outer segment (COS), with single IFs separating from the IFB, touching and entering in-between the light-sensitive disks of the cone membrane. We propose a mechanism of exciton transfer from the inner retinal surface to the visual pigments in the photoreceptor cells. This includes excitation transfer in donor-acceptor systems, from the IF donors to the rhodopsin acceptors, with theoretic efficiency over 80%. This explains high image contrast in fovea and foveola in daylight, while the classical mechanism that describes Müller cells as optical lightguides operates in night vision, with loss of resolution traded for sensitivity. Our theory receives strong confirmation in morphology and function of the cones and pigment cells. In daylight the lateral surface of the photosensor disks is blocked from the (scattered or oblique) light by the pigment cells. Thus the light energy can only get to the cone via intermediate filaments that absorb photons in the Müller cell endfeet and conduct excitons to the cone. Thus, the disks are consumed at their lateral surfaces, moving to the apex of the cone, with new disks produced below. An alternative hypothesis of direct light passing through the cone with its organelles and hitting the lowest disk contradicts morphological evidence, as thus all of the other disks would have no useful function in daylight vision.

physics.bio-ph↗

arXiv2015

Transverse Quantum Confinement in Metal Nanofilms: Optical Spectra

We report optical absorption and photoluminescence spectra of Au, Fe, Co and Ni polycrystalline nanofilms in the UV-Vis-NIR range, featuring discrete bands resulting from transverse quantum confinement. The film thickness ranged from 1.1 to 15.6 nm, depending on the material. The films were deposited on fused silica substrates by sputtering and thermo-evaporation, with Fe, Co and Ni protected by a SiO2 film deposited on top. The results are interpreted within the particle-in-a-box model, with the box width equal to the mass thickness of the nanofilm. The transverse-quantized energy levels and transition energies scale as the inverse square of the film thickness. The calculated values of the effective electron mass are 0.93 (Au), 0.027 (Fe), 0.21 (Co) and 0.16 (Ni), in units of the mass of the free electron, being independent on the film thickness. The uncertainties in the effective mass values are ca. 2.5%, determined by the film thickness calibration. The second calculated model parameter, the quantum number n of the HOMO, was thickness-independent in Au (5) and Fe (6), and increased with the film thickness in Co (from 7 to 9) and Ni (from 7 to 11). The transitions observed in absorbance all start at the level n and correspond to Δn = +1, +2, +3, etc. The photoluminescence bands exhibit large Stokes shifts, shifting to higher energies with the increased excitation energy. The photoluminescence quantum yields grow linearly with the excitation energy, showing evidence of multiple exciton generation. A prototype Fe-SnO2 nanofilm photovoltaic cell demonstrated at least 90% quantum yield of photoelectrons at 77K.

cond-mat.mes-hall↗

arXiv2015

On the Mechanism of Light Transmission by Müller Cells

We report that Müller cells contain bundles of long specialized intermediate filaments about 10 nm in diameter; most likely, these filaments are the channels providing light transmission to photoreceptor cells in mammalian and avian retinas. We interpret transmission of light in such channels using the notions of quantum confinement, describing energy transport in structures with electro-conductive walls and diameter much smaller than the wavelength of the respective photons. Model calculations produce photon transmission efficiency in such channels exceeding 0.8, in optimized geometry. We infer that protein molecules make up the channels, proposing a qualitative mechanism of light transmission by such structures.

physics.optics↗

arXiv2014

Climate Change Policies for the XXIst Century: Mechanisms, Predictions and Recommendations

Recent experimental works demonstrated that the Anthropogenic Global Warming (AGW) hypothesis, embodied in a series of Intergovernmental Panel on Climate Change (IPCC) global climate models, is erroneous. These works prove that atmospheric carbon dioxide contributes only very moderately to the observed warming, and that there is no climatic catastrophe in the making, independent on whether or not carbon dioxide emissions will be reduced. In view of these developments, we discuss climate predictions for the XXIst century. Based on the solar activity tendencies, a new Little Ice Age is predicted by the middle of this century, with significantly lower global temperatures. We also show that IPCC climate models can't produce any information regarding future climate, due to essential physical phenomena lacking in those, and that the current budget deficit in many EU countries is mainly caused by the policies promoting renewable energies and other AGW-motivated measures. In absence of any predictable adverse climate consequences of carbon dioxide emissions, and with no predictable shortage of fossil fuels, we argue for recalling of all policies aimed at reducing carbon dioxide emissions and usage of expensive renewable energy sources. The concepts of carbon credits, green energy and green fuels should be abandoned in favor of productive, economically viable and morally acceptable solutions.

physics.gen-ph↗

arXiv2014

Transverse Quantum Confinement in Semiconductor Nanofilms: Optical Spectra and Multiple Exciton Generation

We report absorption and photoluminescence spectra of Si and SnO$_2$ polycrystalline nanofilms in the UV-Vis-NIR range, featuring discrete bands resulting from transverse quantum confinement. The film thickness ranged 3.9 nm to 12.2 nm, depending on the material. The results are interpreted within the particle-in-a-box model, with the box width equal to the layer mass thickness. The energy levels and transitions scale as the inverse square of the film thickness. The calculated values of the effective electron mass are independent on the film thickness and equal to 0.17m$_o$ (Si) and 0.21m$_o$ (SnO$_2$), with m$_o$ the mass of the free electron. The uncertainties in the effective mass values are ca. 2.5%, determined by the film thickness calibration. The second calculated model parameter, the quantum number $n$ of the HOMO, was also thickness-independent: 8.00 (Si) and 7.00 (SnO$_2$). This indicates that the Fermi level should also scale as the inverse square of the film thickness in these nanofilms. The observed transitions all start at the level $n$ and correspond to Δ$n$ = 1, 2, 3, etc. The photoluminescence bands exhibit large Stokes shifts, moving to higher energies with increased excitation energy. The photoluminescence quantum yields exceed unity, showing evidence of multiple exciton generation from each absorbed photon. A prototype Si-SnO$_2$ nanofilm photovoltaic cell demonstrated an increase of the photoelectron yield with the photon energy, showing evidence of multiple exciton generation.

cond-mat.mes-hall↗

arXiv2013

Phase relation between global temperature and atmospheric carbon dioxide

The primary ingredient of Anthropogenic Global Warming hypothesis is the assumption that atmospheric carbon dioxide variations are the cause for temperature variations. In this paper we discuss this assumption and analyze it on basis of bi-centenary measurements and using a relaxation model which causes phase shifts and delays.

physics.ao-ph↗