| 1. |
- Beiranvand, B., et al.
(författare)
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A distributed terahertz metasurface with cold-electron bolometers for cosmology missions
- 2021
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Ingår i: Applied Sciences (Switzerland). - : MDPI AG. - 2076-3417. ; 11:10
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Tidskriftsartikel (refereegranskat)abstract
- We developed and tested a 2D periodic array of cold-electron bolometers arranged into a wideband frequency selective metasurface that absorbs more than 70% of the incident power in the frequency range 100–800 GHz. The array had 10 × 10 unit cells, each containing four bolometers incorporated into a ring. The chip with bolometers was mounted on the back side of the silicon lens without a back-reflector. Preliminary experiments demonstrated voltage responsivity as high as 10 V/W for the current-biased series array. Simulation of the noise performance shows realization of background noise-limited performance with NEP < NEP for the optical power load P > 15 pW. Results of numerical simulation made for the unit cell of the array are presented together with the equivalent diagram based on lumped network elements. The unit cell also was developed numerically to operate in two radiation modes.
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| 2. |
- Ershova, Victoria B., et al.
(författare)
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The De Long Islands : A missing link in unraveling the Paleozoic paleogeography of the Arctic
- 2016
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Ingår i: Gondwana Research. - : Elsevier BV. - 1342-937X .- 1878-0571. ; 35, s. 305-322
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Tidskriftsartikel (refereegranskat)abstract
- The vast Laptev and East Siberian shelves in the eastern Russian Arctic, largely covered by a shallow sea and buried beneath sea ice for 9 months of the year, remain one of the least studied parts of continental crust of the Earth and represent a big unknown when performing pre-Cenozoic geodynamic reconstructions of the Arctic. The De Long islands provide a vitally important window into the geology of this area and are a key for [1] understanding the Early Paleozoic history of the Amerasian Arctic. Four of them (Jeanette, Henrietta, Bennett and Zhokhov islands) were studied using structural data, petrographic and geochemical analyses and U-Pb zircon age dating to offer the following new constraints for the Early Paleozoic paleogeography of the Arctic realm. The basement beneath the De Long Islands is of Late Neoproterozoic to earliest Cambrian age, about 670-535 Ma. In the Early Paleozoic, the De Long Islands were located along the broad Timanian margin of Baltica, with a clastic sediment provenance from the Timanian, Grenville-Sveconorwegian, and Baltic Shield domains. The Cambro-Ordovician volcaniclastic successions on Jeannette and Henrietta islands formed part of a continental margin volcanic arc with a corresponding back-arc basin located to the south (in present co-ordinates). On the continent-ward side of the back-arc basin, shallow marine shelf clastic and carbonate rocks were deposited, which are exposed today on Bennett Island in the south-west of the archipelago (in modern coordinates). The De Long Islands together with other continental blocks, such as Severnaya Zemlya, Arctic Alaska-Chukotka, and the Alexander Terrane, formed the contiguous active continental margin of Baltica during the Early Paleozoic. Today however, these terranes are spread out over a distance of 5000 km across the Arctic and eastern Pacific margins due to the subsequent opening of a series of Late Paleozoic, Mesozoic and Cenozoic oceanic basins.
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| 3. |
- Karasev, Dmitry A., et al.
(författare)
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Prediction of amino acid positions specific for functional groups in a protein family based on local sequence similarity
- 2016
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Ingår i: Journal of Molecular Recognition. - : Wiley. - 0952-3499 .- 1099-1352. ; 29:4, s. 159-169
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Tidskriftsartikel (refereegranskat)abstract
- The exchange of single amino acid residue in protein can substantially affect the specificity of molecular recognition. Many protein families can be divided into the groups based on specificity to recognized ligands. Prediction of group-discriminating residues within the certain family is extremely necessary for theoretical studies, enzyme engineering, drug design, and so on. The most existing methods use the multiple sequence alignment. They have the limitations in prediction accuracy due to the family sequence divergence and ligand-based grouping. We developed a new method SPrOS (Specificity Projection On Sequence) for estimating the specificity of residues to user-defined groups. SPrOS compares the sequence segments from the test protein and training proteins. Contrary to other segment-comparison approaches extracting the string motifs, SPrOS calculates the scores for single positions by the similarity of their surroundings. The method was evaluated on the simulated sequences and real protein families. The high-prediction accuracy was achieved for simulated sequences, in which SPrOS detected specific positions not predicted with the alignment-based method. For bacterial transcription factors (LacI/GalR) clearly divided into functional groups, the predicted specific residues corresponded to the published experimental data. In a more complicated case of protein kinases classified by inhibitor specificity, the positions predicted with high significance were located in ligand-binding areas. As the ligand specificity is not necessary coincided with phylogeny, evolutionary-coupled mutations could disturb the detection of ligand-specific residues. Excluding proximate homologs of the test protein kinase from the training set, we improved the prediction of the ligand-specific residues.
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| 4. |
- Kuzmin, Leonid, 1946, et al.
(författare)
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Multifrequency Seashell Slot Antenna With Cold-Electron Bolometers for Cosmology Space Missions
- 2016
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Ingår i: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 26:3
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Tidskriftsartikel (refereegranskat)abstract
- A novel type of the "seashell" multichroic polarized antenna is proposed for cosmology space missions. The polarized slot antennas are arranged in the compact form of a seashell with individual slots for each frequency and each polarization. Such an arrangement gives a unique opportunity for independent adjusting individual parameters of slots with microstrip lines (MSLs) and bolometers. For each frequency band, the seashell antenna contains two pairs of orthogonal slots for each polarization connected by MSLs with a bolometer in the middle for in-phase operation. To fit slots in the lambda/2 area for the best beam shape, lumped capacitances in the form of the H-slot were introduced. Ellipticity of a beam was improved to the level of better than 1%. The seashell antenna gives a unique opportunity to select the needed bandwidth using two options. The first option is the frequency selection by resonance properties of slots with MSLs and resistive cold-electron bolometer (CEB). The second option is the frequency selection by resonant CEB with an internal nanofilter organized by a kinetic inductance of the NbN superconducting nanostrip and a capacitance of the nanoscale superconductor-insulator-normal tunnel junction.
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| 5. |
- Kuzmin, Leonid, 1946, et al.
(författare)
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Single Photon Counter Based on a Josephson Junction at 14 GHz for Searching Galactic Axions
- 2018
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Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 28:7
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Tidskriftsartikel (refereegranskat)abstract
- Axions and axion-like particles appear in well-motivated extensions of the standard model of particle physics and may be the solution to the long-standing puzzle of the dark matter in our Universe. Several new experiments are foreseen in the next decade searching them in a wide range of the parameter space. In the mass region from few to several tens of microelectronvolt, detector sensitivity will be limited by the standard quantum limit of linear amplifiers and a new class of single microwave-photon detector will be needed. We have developed a single photon counter based on the voltage switching of an underdamped Josephson junction that is coupled to a coplanar waveguide. By measuring the switching voltage, we can register single photons at 14 GHz with the rate less than 1 photon per 3000 s.
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| 6. |
- Kuzmin, Leonid, 1946, et al.
(författare)
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Wideband Double-Polarized Array of Cold-Electron Bolometers for OLIMPO Balloon Telescope
- 2021
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 69:3, s. 1427-1432
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we propose a novel type of a wideband 2-D array of cold-electron bolometers (CEBs) sensitive to both polarizations of the incoming optical signal. This array was developed for osservatorio per il lontano infrarosso e le microonde su pallone orientabile (OLIMPO) balloon telescope with a requirement on bandwidth more than 10%. Sensitivity to both polarization components was achieved by a special meander-type arrangement of orthogonal L/2 dipoles. We present theoretical estimations for the optimal arrangement of 2-D arrays of CEBs, which allows achieving maximum efficiency in a wide band with the lowest noise equivalent power (NEP). A pixel layout with an optimal density of CEBs, sensitive to dual polarizations, and having more than 10% FWHM bandwidth at around 350 GHz was proposed and numerically analyzed. The layout consists of a periodic sparse array of orthogonal dipoles sensitive to both polarization components of the incoming signal. The numerical analysis confirmed that the sparse array is the most promising for a combination of high absorbing efficiency and low noise of the system and satisfying the 10% bandwidth requirements for the OLIMPO instrument. Different combinations of series and parallel connections of bolometers were considered for better noise properties to achieve the photon noise-limited level.
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| 7. |
- Mahashabde, Sumedh, 1985, et al.
(författare)
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A Frequency Selective Surface based focal plane receiver for the OLIMPO balloon-borne telescope
- 2015
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Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 5:1, s. 145-152
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Tidskriftsartikel (refereegranskat)abstract
- We describe here a focal plane array of Cold-Electron Bolometer (CEB) detectors integrated in a Frequency Selective Surface (FSS) for the 350 GHz detection band of the OLIMPO balloon-borne telescope. In our architecture, the two terminal CEB has been integrated in the periodic unit cell of the FSS structure and is impedance matched to the embedding impedance seen by it and provides a resonant interaction with the incident sub-mm radiation. The detector array has been designed to operate in background noise limited condition for incident powers of 20 pW to 80 pW, making it possible to use the same pixel in both photometric and spectrometric configurations. We present high frequency and dc simulations of our system, together with fabrication details. The frequency response of the FSS array, optical response measurements with hot/cold load in front of optical window and with variable temperature black body source inside cryostat are presented. A comparison of the optical response to the CEB model and estimations of Noise Equivalent power (NEP) is also presented.
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| 8. |
- Mahashabde, Sumedh, 1985, et al.
(författare)
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Planar Frequency Selective Bolometric Array at 350 GHz
- 2015
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Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 5:1, s. 37-43
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we describe a bolometric focal plane array consisting of the Cold Electron Bolometer integrated in a Frequency Selective Surface fabricated on a Silicon substrate with a backshort. This array is formed by a periodic pattern of conducting annular square and ring shapes and the two-terminal CEB is embedded directly in the element. The CEBs impedance has been matched to the FSS which provides resonant interaction with incident sub-millimetre radiation. A further degree of freedom for the tuning is via varying the thickness of the substrate. We've been able to design the FSS at 350 GHz with peak coupling of more than 90% as is common for FSS based filters. A prototype of such a detector has been fabricated and optical response to blackbody radiation has been measured, indicating responsivities of 2*10^9 V/W and higher at 185 mK and 3*10^8 V/W and higher at 300 mK. The details of this new concept, together with numerical simulations and optical measurements are presented.
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| 9. |
- Norberg, Stefan, 1972, et al.
(författare)
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Cation movement and phase transitions in KTP isostructures; X-ray study of sodium-doped KTP at 10.5 K
- 2003
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Ingår i: Acta Crystallographica Section B: Structural Science. - 0108-7681 .- 1600-5740. ; 59:3, s. 353-360
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Tidskriftsartikel (refereegranskat)abstract
- An accurate structure model of sodium-doped potassium titanyl phosphate, (Na0.114K0.886) K(TiO)(2)(PO4)(2), has been determined at 10.5 K by single-crystal X-ray diffraction. In addition to the low-temperature data, X-ray intensities have been collected at room temperature. When the temperature was decreased from room temperature to 10.5 K, both potassium cations moved 0.033 (2) Angstrom along the c-axis, i.e. in the polar direction within the rigid Ti-O-P network. This alkaline metal ion displacement can be related to the Abrahams-Jamieson-Kurtz T-C criteria for oxygen framework ferroelectrics. Potassium titanyl phosphate (KTP) is a well known material for second harmonic generation (SHG), and the influence of sodium dopant on the TiO6 octahedral geometry and SHG is discussed. The material studied crystallizes in the space group Pna2(1) with Z = 4, a = 12.7919 (5), b = 6.3798 (4), c = 10.5880 (7) Angstrom, V = 864.08 (9) Angstrom(3), T = 10.5 (3) K and R = 0.023.
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| 10. |
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