Advanced gearbox technology

An advanced 13,000 HP, counterrotating (CR) gearbox was designed and successfully tested to provide a technology base for future designs of geared propfan propulsion systems for both commercial and military aircraft. The advanced technology CR gearbox was designed for high efficiency, low weight, long life, and improved maintainability. The differential planetary CR gearbox features double helical gears, double row cylindrical roller bearings integral with planet gears, tapered roller prop support bearings, and a flexible ring gear and diaphragm to provide load sharing. A new Allison propfan back-to-back gearbox test facility was constructed. Extensive rotating and stationary instrumentation was used to measure temperature, strain, vibration, deflection and efficiency under representative flight operating conditions. The tests verified smooth, efficient gearbox operation. The highly-instrumented advanced CR gearbox was successfully tested to design speed and power (13,000 HP), and to a 115 percent overspeed condition. Measured CR gearbox efficiency was 99.3 percent at the design point based on heat loss to the oil. Tests demonstrated low vibration characteristics of double helical gearing, proper gear tooth load sharing, low stress levels, and the high load capacity of the prop tapered roller bearings. Applied external prop loads did not significantly affect gearbox temperature, vibration, or stress levels. Gearbox hardware was in excellent condition after the tests with no indication of distress

The 2.5-5.0 micron spectra of Io: Evidence for H2S and H2O frozen in SO2

The techniques of low temperature spectroscopy are applied to identify the constituents of the ices covering the surface of Io, a satellite of Jupiter. Infrared spectra of Io in the 4000-2000 cm exp -1 region, including new observational data, are analyzed using laboratory studies of plausible surface ices

Inter- and intragrain currents in bulk melt-grown YBaCuO rings

A simple contactless method suitable to discern between the intergrain (circular) current, which flows in the thin superconducting ring, and the intragrain current, which does not cross the weakest link, has been proposed. At first, we show that the intergrain current may directly be estimated from the magnetic flux density $B(\pm z_0)$ measured by the Hall sensor positioned in the special points $\pm z_0$ above/below the ring center. The experimental and the numerical techniques to determine the value $z_0$ are discussed. Being very promising for characterization of a current flowing across the joints in welded YBaCuO rings (its dependencies on the temperature and the external magnetic field as well as the time dissipation), the approach has been applied to study corresponding properties of the intra- and intergrain currents flowing across the $a$-twisted grain boundaries which are frequent in bulk melt-textured YBaCuO samples. We present experimental data related to the flux penetration inside a bore of MT YBaCuO rings both in the non-magnetized, virgin state and during the field reversal. The shielding properties and their dependence on external magnetic fields are also studied. Besides, we consider the flux creep effects and their influence on the current re-distribution during a dwell.Comment: 13 pages, 16 figures (EPS), RevTeX4. In the revised version, corrections to perturbing effects near the weak links are introduced, one more figure is added. lin

Visible photodissociation spectroscopy of PAH cations and derivatives in the PIRENEA experiment

The electronic spectra of gas-phase cationic polycyclic aromatic hydrocarbons (PAHs), trapped in the Fourier Transform Ion Cyclotron Resonance cell of the PIRENEA experiment, have been measured by multiphoton dissociation spectroscopy in the 430-480 nm spectral range using the radiation of a mid-band optical parametric oscillator laser. We present here the spectra recorded for different species of increasing size, namely the pyrene cation (C16H10+), the 1-methylpyrene cation (CH3-C16H9+), the coronene cation (C24H12+), and its dehydrogenated derivative C24H10+. The experimental results are interpreted with the help of time-dependent density functional theory calculations and analysed using spectral information on the same species obtained from matrix isolation spectroscopy data. A kinetic Monte Carlo code has also been used, in the case of pyrene and coronene cations, to estimate the absorption cross-sections of the measured electronic transitions. Gas-phase spectra of highly reactive species such as dehydrogenated PAH cations are reported for the first time

Five Planets Transiting a Ninth Magnitude Star

The Kepler mission has revealed a great diversity of planetary systems and architectures, but most of the planets discovered by Kepler orbit faint stars. Using new data from the K2 mission, we present the discovery of a five planet system transiting a bright (V = 8.9, K = 7.7) star called HIP 41378. HIP 41378 is a slightly metal-poor late F-type star with moderate rotation (v sin(i) = 7 km/s) and lies at a distance of 116 +/- 18 from Earth. We find that HIP 41378 hosts two sub-Neptune sized planets orbiting 3.5% outside a 2:1 period commensurability in 15.6 and 31.7 day orbits. In addition, we detect three planets which each transit once during the 75 days spanned by K2 observations. One planet is Neptune sized in a likely ~160 day orbit, one is sub-Saturn sized likely in a ~130 day orbit, and one is a Jupiter sized planet in a likely ~1 year orbit. We show that these estimates for the orbital periods can be made more precise by taking into account dynamical stability considerations. We also calculate the distribution of stellar reflex velocities expected for this system, and show that it provides a good target for future radial velocity observations. If a precise orbital period can be determined for the outer Jovian planet through future observations, it will be an excellent candidate for follow-up transit observations to study its atmosphere and measure its oblateness.Comment: Accepted by ApJL. 12 pages, 6 figures, 2 table

Collective magnetism at multiferroic vortex domain walls

Topological defects have been playgrounds for many emergent phenomena in complex matter such as superfluids, liquid crystals, and early universe. Recently, vortex-like topological defects with six interlocked structural antiphase and ferroelectric domains merging into a vortex core were revealed in multiferroic hexagonal manganites. Numerous vortices are found to form an intriguing self-organized network. Thus, it is imperative to find out the magnetic nature of these vortices. Using cryogenic magnetic force microscopy, we discovered unprecedented alternating net moments at domain walls around vortices that can correlate over the entire vortex network in hexagonal ErMnO3 The collective nature of domain wall magnetism originates from the uncompensated Er3+ moments and the correlated organization of the vortex network. Furthermore, our proposed model indicates a fascinating phenomenon of field-controllable spin chirality. Our results demonstrate a new route to achieving magnetoelectric coupling at domain walls in single-phase multiferroics, which may be harnessed for nanoscale multifunctional devices.Comment: 18 pages, 10 figure

The Role of Polycyclic Aromatic Hydrocarbons in Ultraviolet Extinction. I. Probing small molecular PAHs

We have obtained new STIS/HST spectra to search for structure in the ultraviolet interstellar extinction curve, with particular emphasis on a search for absorption features produced by polycyclic aromatic hydrocarbons (PAHs). The presence of these molecules in the interstellar medium has been postulated to explain the infrared emission features seen in the 3-13 $\mu$m spectra of numerous sources. UV spectra are uniquely capable of identifying specific PAH molecules. We obtained high S/N UV spectra of stars which are significantly more reddened than those observed in previous studies. These data put limits on the role of small (30-50 carbon atoms) PAHs in UV extinction and call for further observations to probe the role of larger PAHs. PAHs are of importance because of their ubiquity and high abundance inferred from the infrared data and also because they may link the molecular and dust phases of the interstellar medium. A presence or absence of ultraviolet absorption bands due to PAHs could be a definitive test of this hypothesis. We should be able to detect a 20 \AA wide feature down to a 3$\sigma$ limit of $\sim$0.02 A$_V$. No such absorption features are seen other than the well-known 2175 \AA bump.Comment: 16 pages, 3 figure, ApJ in pres

Coupling Classical and Quantum Variables using Continuous Quantum Measurement Theory

We propose a system of equations to describe the interaction of a quasiclassical variable $X$ with a set of quantum variables $x$ that goes beyond the usual mean field approximation. The idea is to regard the quantum system as continuously and imprecisely measured by the classical system. The effective equations of motion for the classical system therefore consist of treating the quantum variable $x$ as a stochastic c-number \x (t) the probability distibution for which is given by the theory of continuous quantum measurements. The resulting theory is similar to the usual mean field equations (in which $x$ is replaced by its quantum expectation value) but with two differences: a noise term, and more importantly, the state of the quantum subsystem evolves according to the stochastic non-linear Schrodinger equation of a continuously measured system. In the case in which the quantum system starts out in a superposition of well-separated localized states, the classical system goes into a statistical mixture of trajectories, one trajectory for each individual localized state.Comment: 11 pages, plain Tex (with revised settings for \vsize and \voffset to accommodate US paper sizes

A search for diffuse bands in the circumstellar envelopes of post-AGB stars

In this work we present the results of a systematic search for diffuse bands (DBs, hereafter) in the circumstellar envelopes of a carefully selected sample of post-AGB stars. We concentrated on the analysis of 9 of the DBs most commonly found in the interstellar medium. The strength of these features is determined using high resolution optical spectroscopy and the results obtained are compared with literature data on field stars affected only by interstellar reddening. Based on the weak features observed in the subsample of post-AGB stars dominated by circumstellar reddening we conclude that the carrier(s) of these DBs must not be present in the circumstellar environment of these sources, or at least not under the excitation conditions in which DBs are formed. The conclusion is applicable to all the post-AGB stars studied, irrespective of the dominant chemistry or the spectral type of the star considered. A detailed radial velocity analysis of the features observed in individual sources confirms this result, as the Doppler shifts measured are found to be consistent with an interstellar origin.Comment: Accepted for A&

Expression and DNA methylation of TNF, IFNG and FOXP3 in colorectal cancer and their prognostic significance.

BACKGROUND: Colorectal cancer (CRC) progression is associated with suppression of host cell-mediated immunity and local immune escape mechanisms. Our aim was to assess the immune function in terms of expression of TNF, IFNG and FOXP3 in CRC. METHODS: Sixty patients with CRC and 15 matched controls were recruited. TaqMan quantitative PCR and methylation-specific PCR was performed for expression and DNA methylation analysis of TNF, IFNG and FOXP3. Survival analysis was performed over a median follow-up of 48 months. RESULTS: TNF was suppressed in tumour and IFNG was suppressed in peripheral blood mononuclear cells (PBMCs) of patients with CRC. Tumours showed enhanced expression of FOXP3 and was significantly higher when tumour size was >38 mm (median tumour size; P=0.006, Mann-Whitney U-test). Peripheral blood mononuclear cell IFNG was suppressed in recurrent CRC (P=0.01). Methylated TNFpromoter (P=0.003) and TNFexon1 (P=0.001) were associated with significant suppression of TNF in tumours. Methylated FOXP3cpg was associated with significant suppression of FOXP3 in both PBMC (P=0.018) and tumours (P=0.010). Reduced PBMC FOXP3 expression was associated with significantly worse overall survival (HR=8.319, P=0.019). CONCLUSIONS: We have detected changes in the expression of immunomodulatory genes that could act as biomarkers for prognosis and future immunotherapeutic strategies