| Records |
| Author |
Ovchinnikov, Yu. N.; Varlamov, A. A. |
| Title |
Fluctuation-dissipative phenomena in a narrow superconducting channel carrying current below critical |
Type |
Journal Article |
| Year |
2009 |
Publication |
arXiv |
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| Volume |
0910.2659v1 |
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Pages |
1-4 |
| Keywords |
superconducting nanowire, resistance calculation |
| Abstract |
The theory of current transport in a narrow superconducting channel accounting for thermal fluctuations is developed. These fluctuations result in the appearance of small but finite dissipation in the sample. The value of corresponding voltage is found as the function of temperature (close to transition temperature) and arbitrary bias current. It is demonstrated that the value of the activation energy (exponential factor in the Arrenius law) when current approaches to the critical one is proportional to (1-J/Jc)^(5/4). This result is in concordance with the one for the affine phenomenon of the Josephson current decay due to the thermal phase fluctuations, where the activation energy proportional (1-J/J_c)^(3/2)(the difference in the exponents is related to the additional current dependence of the order parameter). Found dependence of the activation energy on current explains the enormous discrepancy between the theoretically predicted before and the experimentally observed broadening of the resistive transition. |
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arXiv:0910.2659v1; 4 pages, 3 figures |
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931 |
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| Author |
Esteban, Eduin; Serna, Hernandez |
| Title |
Quantum key distribution protocol with private-public key |
Type |
Journal Article |
| Year |
2009 |
Publication |
arXiv |
Abbreviated Journal |
arXiv |
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Issue |
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Pages |
3 |
| Keywords |
quantum cryptography; QKD; protocol |
| Abstract |
A quantum cryptographic protocol based in public key cryptography combinations and private key cryptography is presented. Unlike the BB84 protocol 1 and its many variants 2,3 two quantum channels are used. The present research does not make reconciliation mechanisms of information to derive the key. A three related system of key distribution are described. |
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arXiv: 0908.2146 |
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RPLAB @ gujma @ |
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756 |
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Venkatasubramanian, Chandrasekaran; Cabarcos, Orlando M.; Allara, David L. Horn, Mark W.; Ashok, S. |
| Title |
Correlation of temperature response and structure of annealed VOx thin films for IR detector applications |
Type |
Journal Article |
| Year |
2009 |
Publication |
J. Vac. Sci. Technol. A |
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| Volume |
27 |
Issue |
4 |
Pages |
6 |
| Keywords |
Annealing |
| Abstract |
The effects of thermal annealing on vanadium oxide (VOx) thin films prepared by pulsed-dc magnetron sputtering were studied to explore methods of improving the efficiency of uncooled IR imaging microbolometers, particularly with respect to maximizing the temperature coefficients of resistance (TCR) (typically ~2%) while minimizing resistivity values (typically 0.05–5 Ω cm). Since high TCR values are usually associated with high resistivities, the experiments were designed to find processing conditions that provide an optimal balance in these properties and to then determine the underlying structural correlations which would enable rational design of thin films for this specific application. VOx films of different compositions were deposited by pulsed-dc reactive sputtering from a vanadium target at different oxygen flow rates. The deposited films were further modified by annealing in inert (nitrogen) and oxidizing (oxygen) atmospheres at four different temperatures for 10, 20, or 30 min at a time. The resistivities of the as-deposited films ranged from 0.2 to 13 Ω cm and the TCR values varied from –1.6% to –2.2%. Depending on the exact annealing conditions, several orders of magnitude change in resistance and significant variations in TCR were observed. Optimal results were obtained with annealing in a nitrogen atmosphere. Structural characterization by x-ray diffraction, field emission scanning electron microscopy, atomic force microscopy, and Raman spectroscopy indicated changes in the film crystallinity and phase for annealing conditions over 300 °C with the onset and extent of the changes dependent on which annealing atmosphere was used. |
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Annealing |
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RPLAB @ gujma @ |
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690 |
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Treuttel, J.; Thomas, B.; Maestrini, A.; Wang, H.; Alderman, B.; Siles, J.V.; Davis, S.; Narhi, T. |
| Title |
A 380 GHz sub-harmonic mixer using MMIC foundry based Schottky diodes transferred onto quartz substrate |
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Conference Article |
| Year |
2009 |
Publication |
Proc. 20th Int. Symp. Space Terahertz Technol. |
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Schottky |
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Charlottesville, Virginia, USA |
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no |
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586 |
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Meledin, Denis; Pavolotsky, Alexey; Desmaris, Vincent.; Lapkin, Igor; Risacher, Christophe; Perez, Victor; Henke, Douglas; Nystrom, Olle; Sundin, Erik; Dochev, Dimitar; Pantaleev, Miroslav; Fredrixon, Mathias; Strandberg, Magnus; Voronov, Boris; Goltsman, Gregory; Belitsky, Victor |
| Title |
A 1.3-THz balanced waveguide HEB mixer for the APEX telescope |
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Journal Article |
| Year |
2009 |
Publication |
IEEE Trans. Microw. Theory Techn. |
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57 |
Issue |
1 |
Pages |
89-98 |
| Keywords |
HEB, mixer, waveguide, balanced, NbN |
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In this paper, we report about the development, fabrication, and characterization of a balanced waveguide hot electron bolometer (HEB) receiver for the Atacama Pathfinder EXperiment telescope covering the frequency band of 1.25–1.39 THz. The receiver uses a quadrature balanced scheme and two HEB mixers, fabricated from 4- to 5-nm-thick NbN film deposited on crystalline quartz substrate with an MgO buffer layer in between. We employed a novel micromachining method to produce all-metal waveguide parts at submicrometer accuracy (the main-mode waveguide dimensions are 90×180 μm). We present details on the mixer design and measurement results, including receiver noise performance, stability and “first-light†at the telescope site. The receiver yields a double-sideband noise temperature averaged over the RF band below 1200 K, and outstanding stability with a spectroscopic Allan time more than 200 s. |
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0018-9480 |
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no |
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RPLAB @ lobanovyury @ |
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554 |
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Ryabchun, Sergey; Tong, Cheuk-Yu Edward; Blundell, Raymond; Gol'tsman, Gregory |
| Title |
Stabilization scheme for hot-electron bolometer receivers using microwave radiation |
Type |
Journal Article |
| Year |
2009 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
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19 |
Issue |
1 |
Pages |
14-19 |
| Keywords |
HEB, mixer, Allan variance, stabilization, radiometer equation |
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We present the results of a stabilization scheme for terahertz receivers based on NbN hot-electron bolometer (HEB) mixers that uses microwave radiation with a frequency much lower than the gap frequency of NbN to compensate for mixer current fluctuations. A feedback control loop, which actively controls the power level of the injected microwave radiation, has successfully been implemented to stabilize the operating point of the HEB mixer. This allows us to increase the receiver Allan time to 10 s and also improve the temperature resolution of the receiver by about 30% in the total power mode of operation. |
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1051-8223 |
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no |
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RPLAB @ lobanovyury @ |
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559 |
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Lieberzeit, Peter A.; Dickert, Franz L. |
| Title |
Chemosensors in environmental monitoring: challenges in ruggedness and selectivity |
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Journal Article |
| Year |
2009 |
Publication |
Analytical and Bioanalytical Chemistry |
Abbreviated Journal |
Anal Bioanal Chem |
| Volume |
393 |
Issue |
2 |
Pages |
467-472 |
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environmental monitoring, in situ sensing, artificial recognition materials, real-life application, molecular imprinting, QCM |
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Environmental analysis is a potential key application for chemical sensors owing to their inherent ability to detect analytes on-line and in real time in distributed systems. Operating a chemosensor in a natural environment poses substantial challenges in terms of ruggedness, long-term stability and calibration. This article highlights current trends of achieving both the necessary selectivity and ruggedness: one way is deploying sensor arrays consisting of robust broadband sensors and extracting information via chemometrics. If using only a single sensor is desired, molecularly imprinted polymers offer a straightforward way for designing artificial recognition materials. Molecularly imprinted polymers can be utilized in real-life environments, such as water and air, aiming at detecting analytes ranging from small molecules to entire cells. |
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1618-2642 |
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no |
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564 |
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Parrott, Edward P. J.; Zeitler, J. Axel; Fris<cc><152>c<cc><152>ic<cc><81>, Tomislav; Pepper, Michael; Jones, William; Day, Graeme M.; Gladden, Lynn F. |
| Title |
Testing the sensitivity of terahertz spectroscopy to changes in molecular and supramolecular structure: a study of structurally similar cocrystals |
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Journal Article |
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2009 |
Publication |
Crystal Growth & Design |
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Crystal Growth & Design |
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9 |
Issue |
3 |
Pages |
1452-1460 |
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supramolecular recognition, infrared, terahertz, IR, THz, TDS |
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Terahertz time-domain-spectroscopy (THz-TDS) has emerged as a versatile spectroscopic technique, and an alternative to powder X-ray diffraction in the characterization of molecular crystals. We tested the ability of terahertz spectroscopy to distinguish between chiral and racemic hydrogen-bonded cocrystals that are similar in molecular and supramolecular structure. Terahertz spectroscopy readily distinguished between the isostructural cocrystals of theophylline with chiral and racemic forms of malic acid which are almost identical in molecular structure and supramolecular architecture. Similarly, the cocrystals of theophylline with chiral and racemic forms of tartaric acid, which are similar at the molecular level but dissimilar in crystal packing, were distinguished unequivocally. The investigation of the same cocrystals using X-ray powder diffraction and Raman spectroscopy suggested that THz-TDS is comparable in sensitivity to diffraction methods and more sensitive than Raman spectroscopy to changes in cocrystal architecture. The differences in spectra acquired by THz-TDS could be further enhanced by cooling the samples to 109 K. |
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1528-7483 |
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no |
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567 |
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Минаева, Ольга Вячеславовна |
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Быстродействующий однофотонный детектор на основе тонкой сверхпроводниковой пленки NbN |
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Manuscript |
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2009 |
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М. МПГУ |
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SSPD |
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Ph.D. thesis |
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russian |
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no |
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585 |
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Ryabchun, S. A.; Tretyakov, I. V.; Finkel, M. I.; Maslennikov, S. N.; Kaurova, N. S.; Seleznev, V. A.; Voronov, B. M.; Gol'tsman, G. N. |
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NbN phonon-cooled hot-electron bolometer mixer with additional diffusion cooling |
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Conference Article |
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2009 |
Publication |
Proc. 20th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 20th ISSTT |
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151-154 |
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HEB, mixer, bandwidth, noise temperatue, in-situ contacts, in situ contacts |
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Charlottesville, USA |
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no |
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590 |
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