|
|
Gayduchenko, I., Fedorov, G., Titova, N., Moskotin, M., Obraztsova, E., Rybin, M., et al. (2018). Towards to the development of THz detectors based on carbon nanostructures. In J. Phys.: Conf. Ser. (Vol. 1092, 012039 (1 to 4)).
Abstract: Demand for efficient terahertz radiation detectors resulted in intensive study of the carbon nanostructures as possible solution for that problem. In this work we investigate the response to sub-terahertz radiation of detectors with sensor elements based on CVD graphene as well as its derivatives – carbon nanotubes (CNTs). The devices are made in configuration of field effect transistors (FET) with asymmetric source and drain (vanadium and gold) contacts and operate as lateral Schottky diodes. We show that at 300K semiconducting CNTs show better performance up to 300GHz with responsivity up to 100V/W, while quasi-metallic CNTs are shown to operate up to 2.5THz. At 300 K graphene detector exhibit the room-temperature responsivity from R = 15 V/W at f = 129 GHz to R = 3 V/W at f = 450 GHz. We find that at low temperatures (77K) the graphene lateral Schottky diodes responsivity rises with the increasing frequency of the incident sub-THz radiation. We interpret this result as a manifestation of a plasmonic effect in the devices with the relatively long plasmonic wavelengths. The obtained data allows for determination of the most promising directions of development of the technology of nanocarbon structures for the detection of THz radiation.
|
|
|
|
Aberle, N., & Witte, U. (2003). Deep-sea macrofauna exposed to a simulated sedimentation event in the abyssal NE Atlantic: in situ pulse-chase experiments using 13C-labelled phytodetritus. Mar Ecol Prog Ser, 251, 37–47.
Abstract: Tracer experiments with 13C-labelled diatoms Thalassiosira rotula (Bacillariophycea, 98% 13C-labelled) were conducted at the Porcupine Abyssal Plain (PAP) in the NE Atlantic (BENGAL Station; 48<b0>50'N, 16<b0>30'W, 4850 m depth) during May/June 2000. In situ enrichment experiments were carried out using deep-sea benthic chamber landers: within the chambers a spring bloom was simulated and the fate of this food-pulse within the abyssal macrobenthic community was followed. In focus was the role of different macrofauna taxa and their vertical distribution within the sediment column in consuming and reworking the freshly deposited material. T. rotula is one of the most abundant pelagic diatoms in the NE Atlantic and therefore 0.2 g of freeze dried T. rotula, equivalent to 1 g algal C m-2 yr-1, was injected into each incubation chamber. Three different incubation times of 2.5, 8 and 23 d were chosen in order to follow the uptake of 13C-labelled phytodetritus by macrofauna. After only 2.5 d, 77% of all macrofauna organisms showed tracer uptake. After 23 d the highest degree of enrichment was measured and 95% of the individuals had taken up 13C from the introduced algal material. In addition to that a downward transport of organic matter was observed, even though the mixing was not very intense. The initial processing of carbon was dominated by polychaetes that made up a percentage of 52% of total macrofauna. In general macrofauna organisms that lived close to the sediment surface had higher access to the simulated food-pulse, confirming the hypothesis that individuals close to the sediment surface have the strongest impact on the decomposition of phytodetritus. In our study we observed only modest vertical entrainment of 13C tracers into the sediment. With regard to contradictory results from former 13C-enrichment experiments in bathyal regions, compared to results from our study site in the abyssal plain, we thus propose pronounced differences in feeding strategies between macrofauna communities from continental margins and abyssal plains.
|
|
|
|
Gershenzon, Y. M., Goltsman, G. N., Yelantyev, A. I., Petrova, Y. B., Ptitsina, N. G., & Filatov, V. S. (1987). Lecture demonstrations of properties of superconductors and liquid helium. USSR Rept Phys. Math. JPRS UPM, 24(7), 51.
Abstract: New demonstrations for low temperature physics courses are described. Two transparent Dewar vacuum flasks fitting one inside the other with the external flask for nitrogen and the internal flask for helium are used. The helium temperature can be regulated in the 4.2 to 1.6 K range and the effects of reducing helium to the superfluid state at 2.17 K can be shown: boiling abruptly stops and superfluid flow appears. In order to show the electric and magnetic characteristics of superconductivity, a superconducting NbTi solenoid containing nonsuperconducting wire and germanium and superconducting Nb materials with different critical temperatures is placed in the helium refrigerant vessel. The fall of the resistance at the critical temperatures can be shown. In order to show magnetic field and superconductive current flow properties a shunt of superconductive material is connected in parallel to the coil and is enclosed in a teflon container with a heater which can vary its temperature. When it is heated and not superconductive, magnetic field effects can be demonstrated and when it is unheated and superconducting a continuous current can be demonstrated.
|
|
|
|
Mandel, L. (1966). Heterodyne detection of a weak light beam. J. Opt. Society of America, 56(9), 1200–1206.
Abstract: An analysis is made of the problem of detecting a weak light beam from a distant source in the presence of a background of much greater intensity, by the photoelectric heterodyne technique. In this method the incident light is superposed on the light beam from a local laser, whose frequency can be adjusted by a feedback arrangement so as to maximize a certain “beat note” in the output of the detector. With the aid of plausible assumptions it is shown that the effectiveness of the method is largely independent of the intensity of the background light, and of the fluctuation properties of the incident light. The key parameter is the number of photoelectrons released by the signal beam in a time comparable with its coherence time.
|
|
|
|
(2006). Heterodyne detection: II. Astronomy 525. Lecture 30.
|
|
