We describe the performance of our latest generations of sensitive wide-band high-resolution digital fast Fourier transform spectrometer (FFTS). Their design, optimized for a wide range of radio astronomical applications, is presented. Developed for operation with the GREAT far infrared heterodyne spectrometer on-board SOFIA, the eXtended bandwidth FFTS (XFFTS) offers a high instantaneous bandwidth of 2.5 GHz with 88.5 kHz spectral resolution and has been in routine operation during SOFIA's Basic Science since July 2011. We discuss the advanced field programmable gate array (FPGA) signal processing pipeline, with an optimized multi-tap polyphase filter bank algorithm that provides a nearly loss-less time-to-frequency data conversion with significantly reduced frequency scallop and fast sidelobe fall-off. Our digital spectrometers have been proven to be extremely reliable and robust, even under the harsh environmental conditions of an airborne observatory, with Allan-variance stability times of several 1000 s. An enhancement of the present 2.5 GHz XFFTS will duplicate the number of spectral channels (64k), offering spectroscopy with even better resolution during Cycle 1 observations.

We present a new multi-pixel high resolution (R > ∼ 10 7 ) spectrometer for the Stratospheric Observatory for Far-Infrared Astronomy (SOFIA). The receiver uses 2 × 7-pixel subarrays in orthogonal polarization, each in an hexagonal array around a central pixel. We present the first results for this new instrument after commissioning campaigns in May and December 2015 and after science observations performed in May 2016. The receiver is designed to ultimately cover the full 1.8−2.5 THz frequency range but in its first implementation, the observing range was limited to observations of the [CII] line at 1.9 THz in 2015 and extended to 1.83−2.07 THz in 2016. The instrument sensitivities are state-of-the-art and the first scientific observations performed shortly after the commissioning confirm that the time efficiency for large scale imaging is improved by more than an order of magnitude as compared to single pixel receivers. An example of large scale mapping around the Horsehead Nebula is presented here illustrating this improvement. The array has been added to SOFIA's instrument suite already for ongoing observing cycle 4.

We present the performance of the upGREAT heterodyne array receivers on the SOFIA telescope after several years of operations. This instrument is a multi-pixel high resolution (R 10 7 ) spectrometer for the Stratospheric Observatory for Far-Infrared Astronomy (SOFIA). The receivers use 7-pixel subarrays configured in a hexagonal layout around a central pixel. The low frequency array receiver (LFA) has 2x7 pixels (dual polarization), and presently covers the 1.83-2.06 THz frequency range, which allows to observe the [CII] and [OI] lines at 158 µm and 145 µm wavelengths. The high frequency array (HFA) covers the [OI] line at 63 µm and is equipped with one polarization at the moment (7 pixels, which can be upgraded in the near future with a second polarization array). The 4.7 THz array has successfully flown using two separate quantum-cascade laser local oscillators from two different groups. NASA completed the development, integration and testing of a dual-channel closed-cycle cryocooler system, with two independently operable He compressors, aboard SOFIA in early 2017 and since then, both arrays can be operated in parallel using a frequency separating dichroic mirror. This configuration is now the prime GREAT configuration and has been added to SOFIA's instrument suite since observing cycle 6.

GLUT11 (SLC2A11) is a class II sugar transport facilitator which exhibits highest similarity with the fructose transporter GLUT5 (about 42%). Here we demonstrate that separate exons 1 (exon 1A, exon 1B, and exon 1C) of the SLC2A11 gene generate mRNAs of three GLUT11 variants (GLUT11-A, GLUT11-B, and GLUT11-C) that differ in the amino acid sequence of their N-termini. All three 5'-flanking regions of exon 1A, exon 1B and exon 1C exhibited promoter activity when expressed as luciferase fusion constructs in COS-7 cells. 5'-RACE-PCR, quantitative real-time PCR, and Northern blot analysis performed with specific probes for exon 1A, 1B and 1C demonstrated that GLUT11-A is expressed in heart, skeletal muscle, and kidney, GLUT11-B in kidney, adipose tissue, and placenta, and GLUT11-C in adipose tissue, heart, skeletal muscle, and pancreas. Surprisingly, mice and rats lack the SLC2A11 gene. When expressed in Xenopus oocytes, all three GLUT11 isoforms transport glucose and fructose but not galactose. There was no apparent difference in the subcellular distribution of the three isoforms expressed in COS-7 cells. Our data indicate that different promoters and splicing of the human SLC2A11 gene generate three GLUT11 isoforms which are expressed in a tissue specific manner but do not appear to differ in their functional characteristics.

A terahertz ͑THz͒ heterodyne spectrometer is demonstrated based on a quantum cascade laser ͑QCL͒ as a local oscillator ͑LO͒ and an NbN hot electron bolometer as a mixer, and it is used to measure high-resolution molecular spectral lines of methanol ͑CH 3 OH͒ between 2.913-2.918 THz. The spectral lines are taken from a gas cell containing methanol gas and using a single-mode QCL at 2.9156 THz as an LO, which is operated in the free running mode. By increasing the pressure of the gas, line broadening and saturation are observed. The measured spectra showed good agreement with a theoretical model. © 2010 American Institute of Physics. ͓doi:10.1063/1.3502479͔A high-resolution heterodyne spectrometer is of crucial importance for astronomical observation and atmospheric remote sensing in the terahertz ͑THz͒ frequency range. It consists of essentially a mixing detector, a local oscillator ͑LO͒, a low noise amplifier, and a GHz-band back-end spectrometer, providing both uniquely high spectral resolution ͑ / ⌬ Ͼ 10 6 , limited by the LO and back-end spectrometer, where is the frequency and ⌬ is the frequency resolution͒ and excellent sensitivity ͑e.g., receiver noise temperature of ϳ1000 K at 3 THz͒. Heterodyne receivers based on superconducting mixers and electronically tunable solid-state multiplier-chain LO sources have been realized up to 2 THz for ground based, balloon-borne, and space telescope instruments but the development of receivers at higher frequencies will be determined by the availability of suitable solid-state LO sources. Recently developed THz quantum cascade lasers 1 ͑QCLs͒ are the candidates for the LO at frequencies above 2 THz. Heterodyne receivers using a THz QCL as an LO and an NbN hot electron bolometer ͑HEB͒ as a mixer have demonstrated high sensitivity using broadband blackbody radiation ͑hot/cold loads͒ as the calibration source.2,3 A number of milestones for using a THz QCL as an LO have been demonstrated, such as phase-locking capability, 4 narrow intrinsic linewidth, 5 and excellent power stability. 2 A remaining key step is a direct measurement of spectral lines by a heterodyne spectrometer using a THz QCL as an LO. A spectroscopic measurement using a THz QCL as an active tuning source has been reported for gas phase spectroscopy. 6 However, the detection itself was not based on the heterodyne principle.In this paper we report high-resolution spectroscopic measurements using a heterodyne spectrometer with a 2.9THz QCL as an LO and an NbN HEB as a mixer. We observed simultaneously several molecular emission lines of methanol gas around 2.9 THz. By varying the pressure of the gas, we are able to follow the line broadening and also make a comparison between measured and theoretical spectra.The LO used in our experiment is a metal-metal FabryPerot ridge waveguide THz QCL, based on the resonant phonon depopulation design, 7 with cavity dimensions of 1.45 mmϫ 25 m. The QCL is mounted on the cold stage of a helium-flow cryostat, and emits a single-mode emission line at 2.9156 THz in continuous w...