Optics Design and Verification for the APEX Swedish Heterodyne Facility Instrument (SHeFI)

In this paper, we present the design and verification of the optics of the Swedish Heterodyne Facility Instrument (SHeFI) receiver installed in the Atacama Pathfinder EXperiment (APEX) telescope during spring 2008. SHeFI is located in the Nasmyth instrumentation Cabin A (NCA). The receiver has been designed to have 6 frequency channels, of which four receiver channels have been built, and characterized: 211-275 GHz (Band 1), 275-370 GHz (Band 2), 385-500 GHz (Band 3), and 1250-1390 GHz (Band T2). Bands 1, 2, and T2 are installed at the telescope and are currently in operation. The optical design is driven by the requirement of frequency independent illumination of the secondary with -12 dB edge taper for each frequency channel and the limitation (beam clearance through the Nasmyth tube and the elevation encoder) imposed by the receiver position in the NCA. This paper describes the design approach, optimization, and verification of the optical system, coupling each individual receiving beam to the common optics of the telescope.     

Positron emission tomography in oncology--an introduction

Positron emission tomography has developed very much since the start in the late 1970s, especially with the development of new labelling procedures for PET-tracers. With the development of whole body imaging and the discovery that 18F-FDG allows a high sensitivity for the detection of soft tissue tumors, the clinical use has increased remarkably. The cost-effectiveness of this modality, when properly used, has been demonstrated and 18F-FDG-PET should be considered as an early alternative in patient evaluation.     

CT with different doses of the hepatocyte-specific contrast medium FP 736-03. Evaluation in a nude-rat model of experimental metastases

PURPOSE: To study the dose-response relationship in FP 736-03 (48 mg I/ml), hepatocyte-specific contrast medium for CT of the liver. MATERIAL AND METHODS: A nude-rat model of experimental hepatic metastases was used. CT of the liver was performed before and after i.v. injection of FP 736-03 at 4 different doses: 0.25, 0.5, 1.0 and 2.0 ml/kg b.w. Attenuation in the normal liver parenchyma and in the metastases was measured and plotted as a function of time. RESULTS: The enhancement of the normal liver parenchyma increased in the dose range studied. No increase was found in the metastases: the attenuation here remained constant during the observation period. The maximum enhancement values at doses of 0.25, 0.5, 1.0 and 2.0 ml/kg b.w. were (mean +/- SD) 13.5 +/- 2.7, 30.1 +/- 4.2, 33.2 +/- 4.5 and 59.7 +/- 13.1 HU respectively.     

The optx2 homeobox gene is expressed in early precursors of the eye and activates retina-specific genes

Vertebrate eye development begins at the gastrula stage, when a region known as the eye field acquires the capacity to generate retina and lens. Optx2, a homeobox gene of the sine oculis-Six family, is selectively expressed in this early eye field and later in the lens placode and optic vesicle. The distal and ventral portion of the optic vesicle are fated to become the retina and optic nerve, whereas the dorsal portion eventually loses its neural characteristics and activates the synthesis of melanin, forming the retinal pigment epithelium. Optx2 expression is turned off in the future pigment epithelium but remains expressed in the proliferating neuroblasts and differentiating cells of the neural retina. When an Optx2-expressing plasmid is transfected into embryonic or mature chicken pigment epithelial cells, these cells adopt a neuronal morphology and express markers characteristic of developing neural retina and photoreceptors. One explanation of these results is that Optx2 functions as a determinant of retinal precursors and that it has induced the transdifferentiation of pigment epithelium into retinal neurons and photoreceptors. We also have isolated optix, a Drosophila gene that is the closest insect homologue of Optx2 and Six3. Optix is expressed during early development of the fly head and eye primordia.     

A sideband separating mixer for 85-115 GHz

This paper presents the results of development and tests of a sideband separating heterodyne receiver for the 85-115 GHz band with superconducting tunnel junctions (SIS) as frequency down converters. Sideband separation is achieved by using a quadrature scheme where two identical mixer junctions are pumped by a local oscillator (LO) with 90/spl deg/ phase difference. We used an innovative mixer layout where the quadrature scheme is implemented using waveguide-based and integrated on-chip components. We employed an additional pair of SIS junctions as terminations for LO-injection directional couplers.     

Direct measurements of grain size in low-carbon steels using the laser ultrasonic technique

The laser ultrasonic technique has been used to determine grain sizes in commercial low-carbon steels. With an analysis method that employs scattering theory, absolute values of the grain size have been calculated directly from the ultrasonic traces without the need of any free-parameter fits or calibration curves between the attenuation and grain size. These results indicate that the laser ultrasonic technique may be incorporated online for direct measurements of grain size during steel production.