Removal of acid gases and oxides of nitrogen from space cabin atmospheres

Removal of acid gases and oxides of nitrogen from spacecraft cabin atmospheres at ambient temperature

The catalytic removal of ammonia and nitrogen oxides from spacecabin atmospheres

Investigations were made on methods for the removal of ammonia and to a lesser extent nitrogen oxides in low concentrations from air. The catalytic oxidation of ammonia was studied over a temperature range of 250 F to 600 F and a concentration range 20 ppm to 500 ppm. Of the catalysts studied, 0.5 percent ruthenium supported on alumina was found to be superior. This material is active at temperatures as low as 250 F and was found to produce much less nitrous oxide than the other two active catalysts, platinum on alumina and Hopcalite. A quantitative design model was developed which will permit the performance of an oxidizer to be calculated. The ruthenium was found to be relatively insensitive to low concentrations of water and to oxygen concentration between 21 percent and 100 percent. Hydrogen sulfide was found to be a poison when injected in relatively large quantities. The adsorption of ammonia by copper sulfate treated silica gel was investigated at temperatures of 72 F and 100 F. A quantitative model was developed for predicting adsorption bed behavior

Observation of anomalous spin-state segregation in a trapped ultra-cold vapor

We observe counter-intuitive spin segregation in an inhomogeneous sample of ultra-cold, non-condensed Rubidium atoms in a magnetic trap. We use spatially selective microwave spectroscopy to verify a model that accounts for the differential forces on two internal spin states. In any simple understanding of the cloud dynamics, the forces are far too small to account for the dramatic transient spin polarizations observed. The underlying mechanism remains to be elucidated.Comment: 5 pages, 3 figure

Optical Confinement of a Bose-Einstein Condensate

Bose-Einstein condensates of sodium atoms have been confined in an optical dipole trap using a single focused infrared laser beam. This eliminates the restrictions of magnetic traps for further studies of atom lasers and Bose-Einstein condensates. More than five million condensed atoms were transferred into the optical trap. Densities of up to $3 \times 10^{15} cm^{-3}$ of Bose condensed atoms were obtained, allowing for a measurement of the three-body decay rate constant for sodium condensates as $K_3 = (1.1 \pm 0.3) \times 10^{-30} cm^6 s^{-1}$. At lower densities, the observed 1/e lifetime was more than 10 sec. Simultaneous confinement of Bose-Einstein condensates in several hyperfine states was demonstrated.Comment: 5 pages, 4 figure

Internal state conversion in ultracold gases

We consider an ultracold gas of (non-condensed) bosons or fermions with two internal states, and study the effect of a gradient of the transition frequency between these states. When a $\pi/2$ RF pulse is applied to the sample, exchange effects during collisions transfer the atoms into internal states which depend on the direction of their velocity. This results, after a short time, in a spatial separation between the two states. A kinetic equation is solved analytically and numerically; the results agree well with the recent observations of Lewandowski et al.Comment: Accepted version, to appear in PR

On dynamic network entropy in cancer

The cellular phenotype is described by a complex network of molecular interactions. Elucidating network properties that distinguish disease from the healthy cellular state is therefore of critical importance for gaining systems-level insights into disease mechanisms and ultimately for developing improved therapies. By integrating gene expression data with a protein interaction network to induce a stochastic dynamics on the network, we here demonstrate that cancer cells are characterised by an increase in the dynamic network entropy, compared to cells of normal physiology. Using a fundamental relation between the macroscopic resilience of a dynamical system and the uncertainty (entropy) in the underlying microscopic processes, we argue that cancer cells will be more robust to random gene perturbations. In addition, we formally demonstrate that gene expression differences between normal and cancer tissue are anticorrelated with local dynamic entropy changes, thus providing a systemic link between gene expression changes at the nodes and their local network dynamics. In particular, we also find that genes which drive cell-proliferation in cancer cells and which often encode oncogenes are associated with reductions in the dynamic network entropy. In summary, our results support the view that the observed increased robustness of cancer cells to perturbation and therapy may be due to an increase in the dynamic network entropy that allows cells to adapt to the new cellular stresses. Conversely, genes that exhibit local flux entropy decreases in cancer may render cancer cells more susceptible to targeted intervention and may therefore represent promising drug targets.Comment: 10 pages, 3 figures, 4 tables. Submitte

THE ROLE OF INTERDEPENDENCE IN THE MICRO-FOUNDATIONS OF ORGANIZATION DESIGN: TASK, GOAL, AND KNOWLEDGE INTERDEPENDENCE

Interdependence is a core concept in organization design, yet one that has remained consistently understudied. Current notions of interdependence remain rooted in seminal works, produced at a time when managers’ near-perfect understanding of the task at hand drove the organization design process. In this context, task interdependence was rightly assumed to be exogenously determined by characteristics of the work and the technology. We no longer live in that world, yet our view of interdependence has remained exceedingly task-centric and our treatment of interdependence overly deterministic. As organizations face increasingly unpredictable workstreams and workers co-design the organization alongside managers, our field requires a more comprehensive toolbox that incorporates aspects of agent-based interdependence. In this paper, we synthesize research in organization design, organizational behavior, and other related literatures to examine three types of interdependence that characterize organizations’ workflows: task, goal, and knowledge interdependence. We offer clear definitions for each construct, analyze how each arises endogenously in the design process, explore their interrelations, and pose questions to guide future research

Software and Cyberinfrastructure for Astronomy III: The first SPIE software Hack Day

We report here on the software Hack Day organised at the 2014 SPIE conference on Astronomical Telescopes and Instrumentation in Montreal. The first ever Hack Day to take place at an SPIE event, the aim of the day was to bring together developers to collaborate on innovative solutions to problems of their choice. Such events have proliferated in the technology community, providing opportunities to showcase, share and learn skills. In academic environments, these events are often also instrumental in building community beyond the limits of national borders, institutions and projects. We show examples of projects the participants worked on, and provide some lessons learned for future events

The Eruption of the Candidate Young Star ASASSN-15qi

Outbursts on young stars are usually interpreted as accretion bursts caused by instabilities in the disk or the star-disk connection. However, some protostellar outbursts may not fit into this framework. In this paper, we analyze optical and near-infrared spectra and photometry to characterize the 2015 outburst of the probable young star ASASSN-15qi. The $\sim 3.5$ mag brightening in the $V$ band was sudden, with an unresolved rise time of less than one day. The outburst decayed exponentially by 1 mag for 6 days and then gradually back to the pre-outburst level after 200 days. The outburst is dominated by emission from $\sim10,000$ K gas. An explosive release of energy accelerated matter from the star in all directions, seen in a spectacular cool, spherical wind with a maximum velocity of 1000 km/s. The wind and hot gas both disappeared as the outburst faded and the source the source returned to its quiescent F-star spectrum. Nebulosity near the star brightened with a delay of 10-20 days. Fluorescent excitation of H$_2$ is detected in emission from vibrational levels as high as $v=11$, also with a possible time delay in flux increase. The mid-infrared spectral energy distribution does not indicate the presence of warm dust emission, although the optical photospheric absorption and CO overtone emission could be related to a gaseous disk. Archival photometry reveals a prior outburst in 1976. Although we speculate about possible causes for this outburst, none of the explanations are compelling