The 30-kW ammonia arcjet technology

The technical results are summarized of a 30 kW class ammonia propellant arcjet technology program. Evaluation of previous arcjet thruster performance, including materials analysis of used thruster components, led to the design of an arcjet with improved performance and thermal characteristics. Tests of the new engine demonstrated that engine performance is relatively insensitive to cathode tip geometry. Other data suggested a maximum sustainable arc length for a given thruster configuration, beyond which the arc may reconfigure in a destructive manner. A flow controller calibration error was identified. This error caused previously reported values of specific impulse and thrust efficiency to be 20 percent higher than the real values. Corrected arcjet performance data are given. Duration tests of 413 and 252 hours, and several tests 100 hours in duration, were performed. The cathode tip erosion rate increased with increasing arc current. Elimination of power source ripple did not affect cathode tip whisker growth. Results of arcjet modeling, diagnostic development and mission analyses are also discussed. The 30 kW ammonia arcjet may now be considered ready for development for a flight demonstration, but widespread application of 30 kW class arcjet will require improved efficiency and lifetime

Retrodiction as a tool for micromaser field measurements

We use retrodictive quantum theory to describe cavity field measurements by successive atomic detections in the micromaser. We calculate the state of the micromaser cavity field prior to detection of sequences of atoms in either the excited or ground state, for atoms that are initially prepared in the excited state. This provides the POM elements, which describe such sequences of measurements.Comment: 20 pages, 4(8) figure

Experimental Demonstration of Optimal Unambiguous State Discrimination

We present the first full demonstration of unambiguous state discrimination between non-orthogonal quantum states. Using a novel free space interferometer we have realised the optimum quantum measurement scheme for two non-orthogonal states of light, known as the Ivanovic-Dieks-Peres (IDP) measurement. We have for the first time gained access to all three possible outcomes of this measurement. All aspects of this generalised measurement scheme, including its superiority over a standard von Neumann measurement, have been demonstrated within 1.5% of the IDP predictions

Large-uncertainty intelligent states for angular momentum and angle

The equality in the uncertainty principle for linear momentum and position is obtained for states which also minimize the uncertainty product. However, in the uncertainty relation for angular momentum and angular position both sides of the inequality are state dependent and therefore the intelligent states, which satisfy the equality, do not necessarily give a minimum for the uncertainty product. In this paper, we highlight the difference between intelligent states and minimum uncertainty states by investigating a class of intelligent states which obey the equality in the angular uncertainty relation while having an arbitrarily large uncertainty product. To develop an understanding for the uncertainties of angle and angular momentum for the large-uncertainty intelligent states we compare exact solutions with analytical approximations in two limiting cases.Comment: 20 pages, 9 figures, submitted to J. Opt. B special issue in connection with ICSSUR 2005 conferenc

Joint measurements and Bell inequalities

Joint quantum measurements of non-commuting observables are possible, if one accepts an increase in the measured variances. A necessary condition for a joint measurement to be possible is that a joint probability distribution exists for the measurement. This fact suggests that there may be a link with Bell inequalities, as these will be satisfied if and only if a joint probability distribution for all involved observables exists. We investigate the connections between Bell inequalities and conditions for joint quantum measurements to be possible. Mermin's inequality for the three-particle Greenberger-Horne-Zeilinger state turns out to be equivalent to the condition for a joint measurement on two out of the three quantum systems to exist. Gisin's Bell inequality for three co-planar measurement directions, meanwhile, is shown to be less strict than the condition for the corresponding joint measurement

Dydrogesterone and norethisterone regulate expression of lipoprotein lipase and hormones-sensitive lipase in human subcutaneous abdominal adipocytes

Aim: In premenopausal women, hyper-androgenicity is associated with central obesity and an increased cardiovascular risk. We investigated the effects of dydrogesterone (DYD)(a non-androgenic progestogen) and norethisterone (NET)(an androgenic progestogen) on lipoprotein lipase (LPL), hormone-sensitive lipase (HSL) and glycerol release in adipocytes isolated from subcutaneous abdominal adipose tissue. Methods: Adipose tissue was obtained from 12 non-diabetic women, mean age 51 years (range 37-78) and mean BMI 25.4kg/m2 (range 20.3-26.4). Adipocytes were treated with increasing doses of DYD and NET for 48 hours prior to protein extraction. Effects on lipogenesis and lipolysis were assessed using western blotting to determine the expression of key enzymes, LPL (56kDa) and HSL (84kDa) respectively. Measurement of glycerol release into the medium provided an assessment of lipolytic activity. Results: Expression of LPL was increased by DYD and NET (mean protein expression relative to control ± SEM); with greatest effect at 10-8M for DYD: 2.32±0.51(p0.05). Conclusions: DYD and NET significantly increased LPL expression relative to control whilst significantly reducing HSL expression. At the concentrations studied, similar effects were observed with the androgenic NET and the non-androgenic DYD despite differing effects on the lipid profile when taken in combination with estrogen. Further work in this area may improve knowledge about the effects of different progestogens on body fat distribution and enable progestogen use to be tailored to the individual to achieve maximal benefits

Atmospheric transmission computer program CP

A computer program is described which allows for calculation of the effects of carbon dioxide, water vapor, methane, ozone, carbon monoxide, and nitrous oxide on earth resources remote sensing techniques. A flow chart of the program and operating instructions are provided. Comparisons are made between the atmospheric transmission obtained from laboratory and spacecraft spectrometer data and that obtained from a computer prediction using a model atmosphere and radiosonde data. Limitations of the model atmosphere are discussed. The computer program listings, input card formats, and sample runs for both radiosonde data and laboratory data are included

Single-shot measurement of quantum optical phase

Although the canonical phase of light, which is defined as the complement of photon number, has been described theoretically by a variety of distinct approaches, there have been no methods proposed for its measurement. Indeed doubts have been expressed about whether or not it is measurable. Here we show how it is possible, at least in principle, to perform a single-shot measurement of canonical phase using beam splitters, mirrors, phase shifters and photodetectors.Comment: This paper was published in PRL in 2002 but, at the time, was not placed on the archive. It is included now to make accessing this paper easie