The origin of the strings in the outer regions of Eta Carinae

The narrow optical filaments (`strings' or `spikes') emerging from the Homunculus of Eta Carinae are modelled as resulting from the passage of ballistic `bullets' of material through the dense circumstellar environment. In this explanation, the string is the decelerating flow of ablated gas from the bullet. An archive HST image and new forbidden line profiles of the most distinct of the strings are presented and discussed in terms of this simple model.Comment: 5 pages, 4 figure

Studies on the Energy Metabolism of Herpetomonads

Herpetomonas ingenoplastis is an intriguing and unusual trypanosomatid with many anaerobic features, including the lack of a complete cytochrome chain, the presence of an acristate mitochondrion and the ability to grow equally well under aerobic and anaerobic conditions. In this study, I compared the glucose catabolism of H. ingenoplastis and the aerobic H. muscarum , with the aim of providing greater insight into the mechanisms whereby H. ingenoplastis manages to meet its energetic requirements under aerobic and anaerobic conditions. The results of this study showed that both H. ingenoplastis and H. muscarum can consume glucose. This correlates with the discovered presence of enzymes of both the Embden-Meyerhof pathway and the pentose-phosphate shunt. The activities of these enzymes are similar in the two organisms. In both species the specific activities of the Embden-Meyerhof pathway enzymes, hexokinase (HK), phosphoglucoseisomerase (PGI) and phosphofructokinase (PFK), were found to be much higher than the activities of two enzymes of the pentose-phosphate shunt, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. Glucose consumption varied with gaseous conditions. Anaerobic conditions caused a reduction in glucose consumption, compared with aerobic conditions, in the case of H. muscarum. The addition of CO2 caused an increase in the rate of glucose consumption from that under argon (anaerobic) alone. Similarly for H. ingenoplastis, glucose consumption was reduced under anaerobic conditions compared with aerobic conditions and was stimulated by the presence of CO2. Herpetomonas muscarum was found to produce succinate and acetate as major excretory products of glucose catabolism, and ethanol and propionate as minor excretory products. Compared with aerobic conditions succinate production increased under aerobic conditions in the presence of CO2 by about 2-fold and up to 6-fold in the case of anaerobic conditions in the presence of CO2. Acetate production increased slightly under the two conditions containing high CO2. Herpetomonas ingenoplastis produced propionate as a major end product of glucose catabolism, along with succinate, acetate and ethanol. Ethanol production was found to be greatest under aerobic and aerobic plus CO2 conditions, while succinate and propionate were found to be produced in the greatest quantities under anaerobic plus CO2 conditions. The possibility that propionate production may help supply the energy needs of H. ingenoplastis is discussed. One factor that may be important in the energy metabolism of both herpetomonads are the CO2-fixation pathways. Two CO2-fixing enzymes, 'malic' enzyme (ME) and phosphoenolpyruvate carboxykinase (PEPCK), were found at high activities in both organisms. This correlated with succinate production in the presence of CO2. There were differences between the two species with respect to the tricarboxylic acid (TCA) cycle enzymes. Notable was the presence of fumarate reductase (FR) and the absence of succinate dehydrogenase (SDH), in the case of H. ingenoplastis. Evidence produced suggests that the TCA cycle of H. ingenoplastis operates primarily in the reverse direction. Herpetomomas muscarum was found to have both FR and SDH, suggesting flux through the TCA cycle in both directions. Succinate dehydrogenase/fumarate reductase ratios of 5. 02 and <0. 08 for H. muscarum and H. ingenoplastis, respectively, suggest that H. ingenoplastis is an organism that prefers anaerobic conditions, while H. muscarum is a facultative anaerobe. Differences between H. muscarum and H. ingenoplastis were also found at the subcellular level with respect to studies on the possible presence of glycosomes in the two herpetomonads. Some evidence was obtained for the presence of glycosomes in H. muscarum, in that HK, PGI and malate dehydrogenase (MDH) all were recovered, in part, in the particulate fraction. The distribution of the enzymes of H. ingenoplastis was found to be very different, suggesting that either this organism lacks glycosomes or that the glycosomes are much more labile that those of H. muscarum. Both FR and SDH were found to be particulate in H. muscarum which is consistent with a location in the mitochondrial membrane, perhaps as part of the electron transport chain. The FR activity in H. ingenoplastis seemed to be approximately equally divided between the soluble and particulate fractions. Pyruvate kinase is possibly the major site of glycolytic control in H. ingenoplastis. This enzyme requires MgCI2 to function and is activated by fructose-1,6-bisphosphate (F-1,6-P2) and fructose-2,6-bisphosphate (F-2,6-P2). The enzyme has an apparent Km for ADP of 1.3 mM, much higher than that of other trypanosomatids, and the activity shows sigmoid kinetics with respect to phosphoenolpyruvate (PEP) concentration. (Abstract shortened by ProQuest.)

Using Chemistry to Unveil the Kinematics of Starless Cores: Complex Radial Motions in Barnard 68

We present observations of 13CO, C18O, HCO+, H13CO+, DCO+ and N2H+ line emission towards the Barnard 68 starless core. The line profiles are interpreted using a chemical network coupled with a radiative transfer code in order to reconstruct the radial velocity profile of the core. Our observations and modeling indicate the presence of complex radial motions, with the inward motions in the outer layers of the core but outward motions in the inner part, suggesting radial oscillations. The presence of such oscillation would imply that B68 is relatively old, typically one order of magnitude older than the age inferred from its chemical evolution and statistical core lifetimes. Our study demonstrates that chemistry can be used as a tool to constrain the radial velocity profiles of starless cores.Comment: 12 pages, 3 figures, to appear in the Astrophysical Journal Letter

A high-speed bi-polar outflow from the archetypical pulsating star Mira A

Optical images and high-dispersion spectra have been obtained of the ejected material surrounding the pulsating AGB star Mira A. The two streams of knots on either side of the star, found in far ultra-viollet (FUV) GALEX images, have now been imaged clearly in the light of Halpha. Spatially resolved profiles of the same line reveal that the bulk of these knots form a bi-polar outflow with radial velocity extremes of +- 150 km/s with respect to the central star. The South stream is approaching and the North stream receding from the observer. A displacement away from Mira A between the position of one of the South stream knots in the new Halpha image and its position in the previous Palomar Observatory Sky Survey (POSS I) red plate has been noted. If interpreted as a consequence of expansion proper motions the bipolar outflow is tilted at 69deg +- 2deg to the plane of the sky, has an outflow velocity of 160 +- 10 km/s and is ~1000 y old.Comment: 8 pages, 5 figures. Accepted for pubication by A&

An Overview of Innovation in the Arab Gulf States: From Origins and Five-Year Plans to New Cities and Indices

This study first contextualizes and then examines the innovation initiatives currently being undertaken by the states of the Gulf Cooperation Council (GCC). The data presented are a qualitative analysis based on government planning documents from GCC members, which is followed by an assessment of innovation in the GCC using a composite index (Global Innovation Index) and an individual indicator. The pathways toward innovation in the GCC are traced at local policy‐making levels, but giving meaning to the quantification of these efforts and their results is confounded by the fact that innovation can be an inexact concept with imprecise measurements. This overview of innovation in the GCC shows how it is being conceptualized and executed as statecraft; however, innovation might be better gauged for the GCC if indigenous socioeconomic conditions—like the welfare models and disproportionate public and service sectors—can be taken into account

COMSAT Laboratories' on-board baseband switch development

Work performed at COMSAT Laboratories to develop a prototype on-board baseband switch is summarized. The switch design is modular to accommodate different service types, and the architecture features a high-speed optical ring operating at 1 Gbit/s to route input (up-link) channels to output (down-link) channels. The switch is inherently a packet switch, but can process either circuit-switched or packet-switched traffic. If the traffic arrives at the satellite in a circuit-switched mode, the input processor packetizes it and passes it on to the switch. The main advantage of the packet approach lies in its simplified control structure. Details of the switch architecture and design, and the status of its implementation, are presented

Champagne Flutes and Brandy Snifters: Modelling Protostellar Outflow-Cloud Chemical Interfaces

A rich variety of molecular species has now been observed towards hot cores in star forming regions and in the interstellar medium. An increasing body of evidence from millimetre interferometers suggests that many of these form at the interfaces between protostellar outflows and their natal molecular clouds. However, current models have remained unable to explain the origin of the observational bias towards wide-angled "brandy snifter" shaped outflows over narrower "champagne flute" shapes in carbon monoxide imaging. Furthermore, these wide-angled systems exhibit unusually high abundances of the molecular ion HCO$^+$. We present results from a chemo-dynamic model of such regions where a rich chemistry arises naturally as a result of turbulent mixing between cold, dense molecular gas and the hot, ionized outflow material. The injecta drives a rich and rapid ion-neutral chemistry in qualitative and quantitative agreement with the observations. The observational bias towards wide-angled outflows is explained naturally by the geometry-dependent ion injection rate causing rapid dissociation of CO in the younger systems.Comment: Accepted to MNRAS. 12 pages, 8 Figure

Reduction of computer usage costs in predicting unsteady aerodynamic loadings caused by control surface motions: Computer program description

A digital computer program was developed to calculate unsteady loadings caused by motions of lifting surfaces with leading edge and trailing edge controls based on the subsonic kernel function approach. The pressure singularities at hinge line and side edges were extracted analytically as a preliminary step to solving the integral equation of collocation. The program calculates generalized aerodynamic forces for user supplied deflection modes. Optional intermediate output includes pressure at an array of points, and sectional generalized forces. From one to six controls on the half span can be accomodated

Understanding sensitivity to BH3 mimetics: ABT-737 as a case study to foresee the complexities of personalized medicine.

BH3 mimetics such as ABT-737 and navitoclax bind to the BCL-2 family of proteins and induce apoptosis through the intrinsic apoptosis pathway. There is considerable variability in the sensitivity of different cells to these drugs. Understanding the molecular basis of this variability will help to determine which patients will benefit from these drugs. Furthermore, this understanding aids in the design of rational strategies to increase the sensitivity of cells which are otherwise resistant to BH3 mimetics. We discuss how the expression of BCL-2 family proteins regulates the sensitivity to ABT-737. One of these, MCL-1, has been widely described as contributing to resistance to ABT-737 which might suggest a poor response in patients with cancers that express levels of MCL-1. In some cases, resistance to ABT-737 conferred by MCL-1 is overcome by the expression of pro-apoptotic proteins that bind to apoptosis inhibitors such as MCL-1. However, the distribution of the pro-apoptotic proteins amongst the various apoptosis inhibitors also influences sensitivity to ABT-737. Furthermore, the expression of both pro- and anti-apoptotic proteins can change dynamically in response to exposure to ABT-737. Thus, there is significant complexity associated with predicting response to ABT-737. This provides a paradigm for the multiplicity of intricate factors that determine drug sensitivity which must be considered for the full implementation of personalized medicine