Detection of CO in Triton's atmosphere and the nature of surface-atmosphere interactions

Triton possesses a thin atmosphere, primarily composed of nitrogen, sustained by the sublimation of surface ices. The goal is to determine the composition of Triton's atmosphere and to constrain the nature of surface-atmosphere interactions. We perform high-resolution spectroscopic observations in the 2.32-2.37 $\mu$m range, using CRIRES at the VLT. From this first spectroscopic detection of Triton's atmosphere in the infrared, we report (i) the first observation of gaseous methane since its discovery in the ultraviolet by Voyager in 1989 and (ii) the first ever detection of gaseous CO in the satellite. The CO atmospheric abundance is remarkably similar to its surface abundance, and appears to be controlled by a thin, CO-enriched, surface veneer resulting from seasonal transport and/or atmospheric escape. The CH$_4$ partial pressure is several times larger than inferred from Voyager. This confirms that Triton's atmosphere is seasonally variable and is best interpreted by the warming of CH$_4$-rich icy grains as Triton passed southern summer solstice in 2000. The presence of CO in Triton's atmosphere also affects its temperature, photochemistry and ionospheric composition. An improved upper limit on CO in Pluto's atmosphere is also reported.Comment: 11 pages, including 4 figures and 2 on-line figures Astronomy and Astrophysics, in press (accepted March 13, 2010

Improved Randomization Tests for a Class of Single-Case Intervention Designs

Forty years ago, Eugene Edgington developed a single-case AB intervention design-and-analysis procedure based on a random determination of the point at which the B phase would start. In the present simulation studies encompassing a variety of AB-type contexts, it is demonstrated that by also randomizing the order in which the A and B phases are administered, a researcher can markedly increase the procedure’s statistical power

An Improved Two Independent-Samples Randomization Test for Single-Case AB-Type Intervention Designs: A 20-Year Journey

Detailed is a 20-year arduous journey to develop a statistically viable two-phase (AB) single-case two independent-samples randomization test procedure. The test is designed to compare the effectiveness of two different interventions that are randomly assigned to cases. In contrast to the unsatisfactory simulation results produced by an earlier proposed randomization test, the present test consistently exhibited acceptable Type I error control under various design and effect-type configurations, while at the same time possessing adequate power to detect moderately sized intervention-difference effects. Selected issues, applications, and a multiple-baseline extension of the two-sample test are discussed

Imaging benign inflammatory syndromes

AbstractBenign mastitis is a rare disease and its management is difficult. The diagnostic challenge is to distinguish it from carcinomatous mastitis. We make a distinction between acute mastitis secondary to an infection, to inflammation around a benign structure or to superficial thrombophlebitis, and chronic, principally plasma cell and idiopathic granulomatous mastitis. Imaging is often non-specific but we need to know and look for certain ultrasound, mammogram or magnetic resonance imaging (MRI) signs to give a pointer as early as possible towards a benign aetiology. A biopsy should be undertaken systematically where there is the slightest diagnostic doubt, to avoid failing to recognise a carcinomatous mastitis

Deficiency of the bone mineralization inhibitor NPP1 protects against obesity and diabetes

The emergence of bone as an endocrine regulator has prompted a re-evaluation of the role of bone mineralization factors in the development of metabolic disease. Ectonucleotide pyrophosphatase/phosphodiesterase-1 (NPP1) controls bone mineralization through the generation of pyrophosphate, and levels of NPP1 are elevated both in dermal fibroblast cultures and muscle of individuals with insulin resistance. We investigated the metabolic phenotype associated with impaired bone metabolism in mice lacking the gene that encodes NPP1 (Enpp1−/− mice). Enpp1−/− mice exhibited mildly improved glucose homeostasis on a normal diet but showed a pronounced resistance to obesity and insulin resistance in response to chronic high-fat feeding. Enpp1−/− mice had increased levels of the insulin-sensitizing bone-derived hormone osteocalcin but unchanged insulin signalling within osteoblasts. A fuller understanding of the pathways of NPP1 could inform the development of novel therapeutic strategies for treating insulin resistance

The Stargazin-Related Protein {gamma}7 Interacts with the mRNA-Binding Protein Heterogeneous Nuclear Ribonucleoprotein A2 and Regulates the Stability of Specific mRNAs, Including CaV2.2

The role(s) of the novel stargazin-like {gamma}-subunit proteins remain controversial. We have shown previously that the neuron-specific {gamma}7 suppresses the expression of certain calcium channels, particularly CaV2.2, and is therefore unlikely to operate as a calcium channel subunit. We now show that the effect of {gamma}7 on CaV2.2 expression is via an increase in the degradation rate of CaV2.2 mRNA and hence a reduction of CaV2.2 protein level. Furthermore, exogenous expression of {gamma}7 in PC12 cells also decreased the endogenous CaV2.2 mRNA level. Conversely, knockdown of endogenous {gamma}7 with short-hairpin RNAs produced a reciprocal enhancement of CaV2.2 mRNA stability and an increase in endogenous calcium currents in PC12 cells. Moreover, both endogenous and expressed {gamma}7 are present on intracellular membranes, rather than the plasma membrane. The cytoplasmic C terminus of {gamma}7 is essential for all its effects, and we show that {gamma}7 binds directly via its C terminus to a heterogeneous nuclear ribonucleoprotein (hnRNP A2), which also binds to a motif in CaV2.2 mRNA, and is associated with native CaV2.2 mRNA in PC12 cells. The expression of hnRNP A2 enhances CaV2.2 IBa, and this enhancement is prevented by a concentration of {gamma}7 that alone has no effect on IBa. The effect of {gamma}7 is selective for certain mRNAs because it had no effect on {alpha}2{delta}-2 mRNA stability, but it decreased the mRNA stability for the potassium-chloride cotransporter, KCC1, which contains a similar hnRNP A2 binding motif to that in CaV2.2 mRNA. Our results indicate that {gamma}7 plays a role in stabilizing CaV2.2 mRNA

New SOS diode pumping circuit based on an all-solid-state spiral generator for high-voltage nanosecond applications

Semiconductor opening switch (SOS) diodes are capable to switch currents with a density of more than 1 kA/cm 2 and withstand nanosecond pulses with an amplitude of up to 1 MV. SOS diodes, however, require a specific pumping circuit that must simultaneously provide forward and reverse pumping currents with a time of ∼ 500 and ∼ 100 ns, respectively. Such a pumping circuit with energies > 1 J typically requires a gas-discharge switch or a low-efficient solid-state solution. This study proposes a novel approach to pumping SOS diodes based on a spiral generator (SG) (also known as a vector inversion generator). Due to its wave characteristics, the SG produces a bipolar current discharge that meets the time duration and current amplitude required to pump an SOS diode. Moreover, the initial pulse from the spiral typically has a relatively low current amplitude compared to the opposite polarity secondary pulse, so the SOS diode can operate at very high efficiencies. This idea has been tested using an all-solid-state SG coupled with large-area SOS diodes (1 cm 2 ). With this combination, a voltage pulse of 62 kV having a rise time of only 11 ns was obtained on an open circuit load (3 pF, 1 M Ω ). The experiments were highly repeatable, with no damage to the components despite multiple tests. There is significant scope to further improve the results, with simple alterations to the SG