Quasi-optical SIS mixers with normal metal tuning structures

We recently reported (1996) a quasi-optical SIS mixer which used Nb/Al-oxide/Nb tunnel junctions and a normal-metal (Al) tuning circuit to achieve an uncorrected receiver noise temperature of 840 K (DSB) at 1042 GHz. Here we present results on several different device designs, which together cover the 300-1200 GHz frequency range. The mixers utilize an antireflection-coated silicon hyper-hemispherical lens, a twin-slot antenna, and a two-junction tuning circuit. The broad-band frequency response was measured using Fourier transform spectrometry (FTS), and is in good agreement with model calculations. Heterodyne tests were carried out from 400 GHz up to 1040 GHz, and these measurements agree well with the FTS results and with calculations based on Tucker's theory (1985)

Low-noise 1 THz niobium superconducting tunnel junction mixer with a normal metal tuning circuit

We describe a 1 THz quasioptical SIS mixer which uses a twin-slot antenna, an antireflection-coated silicon hyperhemispherical lens, Nb/Al-oxide/Nb tunnel junctions, and an aluminum normal-metal tuning circuit in a two-junction configuration. Since the mixer operates substantially above the gap frequency of niobium (nu >~ 2 Delta/h ~ 700 GHz), a normal metal is used in the tuning circuit in place of niobium to reduce the Ohmic loss. The frequency response of the device was measured using a Fourier transform spectrometer and agrees reasonably well with the theoretical prediction. At 1042 GHz, the uncorrected double-sideband receiver noise temperature is 840 K when the physical temperature of the mixer is 2.5 K. This is the first SIS mixer which outperforms GaAs Schottky diode mixers by a large margin at 1 THz

Characterization of low-noise quasi-optical SIS mixers for the submillimeter band

We report on the development of low-noise quasi-optical SIS mixers for the frequency range 400-850 GHz. The mixers utilize twin-slot antennas, two-junction tuning circuits, and Nb-trilayer junctions. Fourier-transform spectrometry has been used to verify that the frequency response of the devices is well predicted by computer simulations. The 400-850 GHz frequency band can be covered with four separate fixed-tuned mixers. We measure uncorrected double-sideband receiver noise temperatures around 5hν/kB to 700 GHz, and better than 540 K at 808 GHz. These results are among the best reported to date for broadband heterodyne receivers

Characterization of submillimetre quasi-optical twin-slot double-junction SIS mixers

We report on the continuing development of submillimetre quasi-optical slot antenna SIS mixers, which use two-junction tuning circuits. Direct and heterodyne Fourier transform spectrometer measurements have been performed to compare device performance with predictions. Demonstrated double-sideband receiver noise temperatures of better than 540 K at 808 GHz make these SIS mixers substantially better than GaAs Schottky receivers for the astronomically important CI and CO transitions near 810 GHz

Low-noise slot antenna SIS mixers

We describe quasi-optical SIS mixers operating in the submillimeter band (500-750 GHz) which have very low noise, around 5 h/spl nu//k/sub B/ for the double-sideband receiver noise temperature. The mixers use a twin-slot antenna, Nb/Al-Oxide/Nb tunnel junctions fabricated with optical lithography, a two-junction tuning circuit, and a silicon hyperhemispherical lens with a novel antireflection coating to optimize the optical efficiency. We have flown a submillimeter receiver using these mixers on the Kuiper Airborne Observatory, and have detected a transition of H/sub 2//sup 18/O at 745 GHz. This directly confirms that SIS junctions are capable of low-noise mixing above the gap frequency

Piotras Stolypinas ir tautinis klausimas Rusijos imperijoje 1906-1911 metais. Naujausios rusų istoriografijos tendencijos

The article covers the research on the contribution of Russian historiography of the last two decades into studying the life, political ideas, and activities of Piotr Stolypin. Attention is focused on the biographical genre and on the issue how the national policy of P. Stolypin and the government under his leadership in the "national outskirts" of the Russian Empire in 1906–1911 is revealed in such type of works. A formal analysis of the Russian historiography of the last two decades, aimed at P. Stolypin and his national policy in 1906–1911, enables to draw a conclusion that the research of biographical nature lacks a closer and broader reflection on P. Stolypin\u27s political plans and steps in all "national outskirts" of the Russian Empire. The collection of subjects and problems, inherited from the Soviet historiography, is reconsidered and reinterpreted, thereby acquiring the form of opposition to the Soviet historiographical tradition. Territorially, the historians research P. Stolypin\u27s actions only in the Western Provinces, the Kingdom of Poland, and the Grand Duchy of Finland. Therefore, the policy of P. Stolypin\u27s government is totally unrevealed in other territories governed by the Russian Empire: the Baltic governorates, the Caucasus, Transcaucasia (South Caucasus), Central Asia, and Bessarabia. Problematically, not the general government policy, but individual, though substantial, aspects thereof, such as introduction of municipalities of Russian governorates and counties (zemstvo), legal restriction of Finnish autonomy, violation of territorial integrity of the Kingdom of Poland, change of the legal status of the Jewish community, consideration of a draft law on confessions are studied in the regions at issue. Thus, both territorially and problematically, the problem is not exhausted as yet and, with reference to hitherto prevailing Russian historiography, we cannot propose a thorough and exhaustive comparative picture of P. Stolypin\u27s national policy in the Russian Empire. Even though the base of sources on this matter is expanding, it is not analyzed by historians in more detail but simply mastered in an uncritical manner

Lietuvos aukštuomenės lojalumo manifestacija Jekaterinos II paminklo atidengimo Vilniuje proga

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LIETUVOS DIDŽIOSIOS KUNIGAIKŠTYSTĖS PAVELDO IR ATMINTIES AKTUALUMAS (KONFERENCIJĄ PRISIMENANT)

2013 m. baigiasi mokslinis projektas „LDK tradicija, vaizdinys ir modernūs tapatumai“, kurį vykdė Vilniaus universiteto Istorijos fakultetas, o spiritus movens buvo Profesorius Alfredas Bumblauskas. Nors formaliai projektas prasidėjo 2010 m., idėjos ištakas ir pirmuosius darbus galime drąsiai nukelti keleriais metais anksčiau, kai buvo sėkmingai įgyvendintos dvi „LDK paveldo dalybų“ projekto dalys (2007–2009 m.) ir šio projekto metu organizuotų konferencijų pranešimų pagrindu išleisti du reikšmingi mokslinių straipsnių rinkiniai