Precision surveying using very long baseline interferometry

Radio interferometry measurements were used to measure the vector baselines between large microwave radio antennas. A 1.24 km baseline in Massachusetts between the 36 meter Haystack Observatory antenna and the 18 meter Westford antenna of Lincoln Laboratory was measured with 5 mm repeatability in 12 separate experiments. Preliminary results from measurements of the 3,928 km baseline between the Haystack antenna and the 40 meter antenna at the Owens Valley Radio Observatory in California are presented

Polar motion and UT1: Comparison of VLBI, lunar laser, satellite laser, satellite Doppler, and conventional astrometric determinations

Very long baseline interferometry observations made with a 3900 km baseline interferometer (Haystack Observatory in Massachusetts to Owens Valley Observation in California) were used to estimate changes in the X-component of the position of the Earth's pole and in UT1. These estimates are compared with corresponding ones from lunar laser ranging, satellite laser ranging, satellite Doppler, and stellar observations

Application of very long baseline interferometry to Astrometry and Geodesy: effects of frequency standard instability on accuracy

The accuracy of geodetic and astrometric information obtained from very long baseline interferometry (VLBI) observations is dependent upon the stability of the frequency standard, or clock, used at each site of VLBI array. The sensitivities of two hydrogen maser frequency standards of different design to pressure, temperature, and magnetic field variations were measured; and, for one of the standards, sensitivity was found to be severe enough to degrade the information content of VLBI measurements. However, the effect on the geometric and astrometric information of such clock instabilities, with time scales of hours or greater, can be sharply reduced through the use of differencing techniques

Preliminary experience with the smooth muscle troponin-like protein, calponin, as a novel biomarker for diagnosing acute aortic dissection

Aims The early diagnosis of acute aortic dissection (AD) remains challenging. We sought to determine the utility of the troponin-like protein of smooth muscle, calponin, as a diagnostic biomarker of acute AD. Methods and results Immunoassays against calponin (acidic, basic, and neutral isoforms) were developed and the levels were compared in a convenience sample of 59 patients with radiographically proven AD [34 males, age 59+15 (SD) years] vs. 158 patients suspected of having AD at presentation (116 males, age 63+15 years) but whose final diagnosis was not AD. Basic calponin, which is the most specific and abundant in smooth muscle, and acidic calponin, respectively, showed greater than two-fold and three-fold elevations in patients with acute AD. Diagnostic performance as determined by receiver-operating characteristics curve analysis showed that both acidic and basic calponin have the potential to detect AD in the first 24 h [respective areas under the curve (AUCs) 0.63 and 0.58], with superior performance of basic calponin (when compared with acidic) in the initial 6 h (respective AUCs 0.63 and 0.67). Conclusion Circulating calponin levels were elevated in acute AD compared with controls. These biomarkers have the potential for use as an early diagnostic biomarker for acute AD. Keywords Aortic dissection ? Biomarke

The fundamental constants and their variation: observational status and theoretical motivations

This article describes the various experimental bounds on the variation of the fundamental constants of nature. After a discussion on the role of fundamental constants, of their definition and link with metrology, the various constraints on the variation of the fine structure constant, the gravitational, weak and strong interactions couplings and the electron to proton mass ratio are reviewed. This review aims (1) to provide the basics of each measurement, (2) to show as clearly as possible why it constrains a given constant and (3) to point out the underlying hypotheses. Such an investigation is of importance to compare the different results, particularly in view of understanding the recent claims of the detections of a variation of the fine structure constant and of the electron to proton mass ratio in quasar absorption spectra. The theoretical models leading to the prediction of such variation are also reviewed, including Kaluza-Klein theories, string theories and other alternative theories and cosmological implications of these results are discussed. The links with the tests of general relativity are emphasized.Comment: 56 pages, l7 figures, submitted to Rev. Mod. Phy