Search

High precision temperature measurements are a transversal need in a wide area of physical experiments. Space-borne gravitational wave detectors are a particularly challenging case, requiring both high precision and high stability in temperature measurement. In this contribution, we present a design able to reach 1 μ K / Hz in most of the measuring band down to 1 mHz, and reaching 20 μ K / Hz at 0.1 mHz. The scheme is based on resistive sensors in a Wheatstone bridge configuration which is AC modulated to minimize the 1/f noise. As a part of our study, we include the design of a test bench able to guarantee the high stability environment required for measurements. We show experimental results characterising both the test bench and the read-out, and discuss potential noise sources that may limit our measurement. [ABSTRACT FROM AUTHOR]

Optical metrology systems crucially rely on the dimensional stability of the optical path between their individual optical components. We present in this paper a novel adhesive bonding technology for setup of quasi-monolithic systems and compare selected characteristics to the well-established state-of-the-art technique of hydroxide-catalysis bonding. It is demonstrated that within the measurement resolution of our ultraprecise custom heterodyne interferometer, both techniques achieve an equivalent passive path length and tilt stability for time scales between 0.1 mHz and 1 Hz. Furthermore, the robustness of the adhesive bonds against mechanical and thermal inputs has been tested, making this new bonding technique in particular a potential option for interferometric applications in future space missions. The integration process itself is eased by long time scales for alignment, as well as short curing times. OCIS codes: 220.4880, 220.4830.

Marginal changes in geometrical dimensions due to temperature changes affect the performance of optical instruments. Highly dimensionally stable materials can minimize these effects since they offer low coefficients of thermal expansion (CTE). Our dilatometer, based on heterodyne interferometry, is able to determine the CTE in 1 0 − 8 K − 1 range. Here, we present the improved interferometer performance using angular measurements via differential wavefront sensing to correct for tilt-to-length coupling. The setup was tested by measuring the CTE of a single-crystal silicon at 285 K. Results are in good agreement with the reported values and show a bias of less than 1%. [ABSTRACT FROM AUTHOR]

Space applications demand light weight materials with excellent dimensional stability for telescopes, optical benches, optical resonators, etc. Glass-ceramics and composite materials can be tuned to reach very low coefficient of thermal expansion (CTE) at different temperatures. In order to determine such CTEs, very accurate setups are needed. Here we present a dilatometer that is able to measure the CTE of a large variety of materials in the temperature range of 140 K to 250 K. The dilatometer is based on a heterodyne interferometer with nanometer noise levels to measure the expansion of a sample when applying small amplitude controlled temperature signals. In this article, the CTE of a carbon fiber reinforced polymer sample has been determined with an accuracy in the 10-8 K-1 range. [ABSTRACT FROM AUTHOR]

In this article, we present the current status of our high-sensitivity compact heterodyne interferometer and highlight its application in high-accuracy dilatometry and industrial surface metrology. The linear coefficient of thermal expansion (CTE) of dimensionally highly stable carbon-fiber reinforced plastic (CFRP) was measured with 10-7 K-1 accuracy. A very compact and quasi-monolithic interferometer setup is currently developed utilizing ultra-low expansion glass material. We present first investigations on the corresponding integration technologies, hydroxide-catalysis bonding and adhesive bonding. For high resolution 3-D profilometry and surface property measurements, a low-noise actuator will be implemented in the interferometer, which enables a scan of the measurement beam over the surface under investigation. [ABSTRACT FROM AUTHOR]

We present a compact setup of a heterodyne polarizing laser interferometer for longitudinal displacement metrology combined with differential wavefront sensing for tilt measurement. This instrument serves as a demonstrator for an optical readout of the free-floating proof mass' position and tilt aboard the Laser Interferometer Space Antenna (LISA) satellites, working in the frequency band from 3 × 10-5 Hz to 1 Hz. We outline the optomechatronic system setup of our interferometer, discuss its limitations, and point out future improvements. First measurements showed noise levels below 80 pm[image omitted] and below 30 nrad[image omitted], respectively, for frequencies above 10-1 Hz. [ABSTRACT FROM AUTHOR]

Rat C‐CAM is a ubiquitous, transmembrane and carcinoembryonic antigen related cell adhesion molecule. The human counterpart is known as biliary glycoprotein (BGP) or CD66a. It is involved in different cellular functions ranging from intercellular adhesion, microbial receptor activity, signaling and tumor suppression. In the present study N‐glycosylation of C‐CAM immunopurified from rat liver was analyzed in detail. The primary sequence of rat C‐CAM contains 15 potential N‐glycosylation sites. The N‐glycans were enzymatically released from glycopeptides, fluorescently labeled with 2‐aminobenzamide, and separated by two‐dimensional HPLC. Oligosaccharide structures were characterized by enzymatic sequencing and MALDI‐TOF‐MS. Mainly bi‐ and triantennary complex structures were identified. The presence of type I and type II chains in the antennae of these glycans results in heterogeneous glycosylation of C‐CAM. Sialylation of the sugars was found to be unusual; bi‐ and triantennary glycans contained three and four sialic acid residues, respectively, and this linkage seemed to be restricted to the type I chain in the antennae. Approximately 20% of the detected sugars contain these unusual numbers of sialic acids. C‐CAM is the first transmembrane protein found to be oversialylated. [ABSTRACT FROM PUBLISHER]

The recombinant plasminogen activator (rDSPAα1) from the vampire bat Desmodus rotundus is a promising new thrombolytic agent that exhibits a superior pharmacological profile if compared to tissue-type plasminogen activator (t-PA) or streptokinase. In the present study the structures of the carbohydrate moieties at the two N-glycosylation sites (Asn-117, Asn-362) of rDSPAαI expressed in Chinese hamster ovary cells were determined. N-Linked glycans were enzymatically released from isolated tryptic glycopeptides by peptide-N4-(N-acetyl-β-glucosaminyl)asparagine amidase F digestion and separated by two-dimensional HPLC. Oligosaccharide structures were characterized by analysis of carbohydrate composition and linkage, by mass spectrometry, and by sequence analysis in which the fiuorescently labeled glycans were cleaved with an array of specific exoglycosidases. More than 30 different oligosaccharides were identified. The results revealed that Asn-117 carried a mixture of one high-mannose structure (17% of site-specific glycosylation), three hybrid glycans (26%) and predominantly biantennary complex N-glycans (54%). Glycosylation site Asn-362 was found to comprise complex glycans with biantennary (50%), 2,4- and 2,6-branched triantennary (21%, 11%), and tetraantennary structures (10%), which were fucosylated at the innermost residue of N-acetylglucosamine. Mainly neutral and monosialylated glycans, and smaller quantities of disialylated glycans, were detected at both glycosylation sites. Sialic acid was α2-3 linked to galactose exclusively. As shown in this study the N-glycans attached to Asn-117 of rDSPAα1 are more processed during biosynthesis than the high-mannose structures linked to Asn-117 of t-PA, to which the polypeptide backbone of rDSPAα1 is structurally closely related. [ABSTRACT FROM PUBLISHER]

Future space missions will benefit from highly stable and compact optical frequency references. While many promising technologies are currently under investigation, optical cavities are a well-suited technique for applications in which relative references are required. To improve the frequency stability of optical cavities, a key step in combining high performance with compactness and robustness is the further development of in-coupling optics. Here, we present our work of using a fiber-coupled circulator based in-coupling for a high-finesse optical cavity. Implementing the new, to the best of our knowledge, in-coupling board to an extensively characterized crossed cavity set-up allows us to identify possible differences to the commonly used free-beam technique. With a frequency stability of 5.5×10 -16 H z -1/2 at 1 Hz and with only a slight degradation in frequency stability below the mHz range, no circulator-caused instabilities were observed.

In this Letter, we demonstrate a method to combine a molecular iodine absolute frequency reference with a high-finesse optical cavity in a single laser to take advantage of the frequency stability properties of both systems at different time scales. The result is a laser exhibiting the long-term and short-term stability levels of the iodine frequency reference and optical cavity, respectively. The method uses frequency offset side-band locking and an acousto-optical modulator driven ac-coupled servo-loop to correct the iodine's short-term frequency fluctuations. Experimental results show cavity-limited stability at 1 Hz of 10 -15 1/ H z and iodine stability below 10 mHz of 10 -13 1/ H z . In terms of the Allan deviation, this corresponds to stability levels close to the 10 -15 at 1 s and 10 -14 for observation times >100 s .

We incorrectly cited a maximum acceleration sensitivity of the rigidly-mounted cavity of 2.5 × 10 -10  1/(m s -2 ). The correct coupling factor is a factor of 100 smaller: 2.5 × 10 -12  1/(m s -2 ).