First Time-dependent Study of H2 and H3+ Ortho-Para Chemistry in the Diffuse Interstellar Medium: Observations Meet Theoretical Predictions

The chemistry in the diffuse interstellar medium initiates the gradual increase of molecular complexity during the life cycle of matter. A key molecule that enables build-up of new molecular bonds and new molecules via proton-donation is H3+. Its evolution is tightly related to molecular hydrogen and thought to be well understood. However, recent observations of ortho and para lines of H2 and H3+ in the diffuse ISM showed a puzzling discrepancy in nuclear spin excitation temperatures and populations between these two key species. H3+, unlike H2, seems to be out of thermal equilibrium, contrary to the predictions of modern astrochemical models. We conduct the first time-dependent modeling of the para-fractions of H2 and H3+ in the diffuse ISM and compare our results to a set of line-of-sight observations, including new measurements presented in this study. We isolate a set of key reactions for H3+ and find that the destruction of the lowest rotational states of H3+ by dissociative recombination largely control its ortho/para ratio. A plausible agreement with observations cannot be achieved unless a ratio larger than 1:5 for the destruction of (1,1)- and (1,0)-states of H3+ is assumed. Additionally, an increased CR ionization rate to 10(-15) 1/s further improves the fit whereas variations of other individual physical parameters, such as density and chemical age, have only a minor effect on the predicted ortho/para ratios. Thus our study calls for new laboratory measurements of the dissociative recombination rate and branching ratio of the key ion H3+ under interstellar conditions.Comment: 27 pages, 6 figures, 3 table

Investigating Potential Bioactive Compounds from Rhodococcus and Their Effects on MCF7 Breast Cancer Cells

Many drugs used in the treatment of various cancers are derived from or influenced by compounds from nature. The soil bacterium Rhodococcus is of interest because of its identified secondary metabolic pathways and the production of novel natural antibiotics from several strains. In this study, a solid agar extraction method was used to collect compounds from strains of Rhodococcus. These bacterial compound extracts were then tested using a MTT assay in order to evaluate their effectiveness in augmenting MCF7 breast cancer cell death. The results of two way ANOVA analyses revealed 18 compound extracts from 15 strains of Rhodococcus that showed significant p-values when assayed with MCF7 breast cancer cells but nonsignificant interaction p-values when assayed with the healthy cell control. These results prompt further identification of specific compounds present in the bacterial extract that caused cell death as well as a mechanism of interaction with the breast cancer cells

Performance-Metric Driven Atmospheric Compensation for Robust Free-Space Laser Communication

The effect of turbulence on laser propagation is a significant challenge to current electro-optical systems. While atmospheric compensation techniques in space object imaging and high-energy laser weapons have been thoroughly investigated, optimizing these techniques for Laser Communication (LaserCom) has not been examined to the same degree. Average Strehl ratio is the typical design metric for current atmospheric compensation systems. However, fade probability is the relevant metric for LaserCom. This difference motivated the investigation into metric-driven atmospheric compensation. Metric-based tracking techniques for fade mitigation is the first major focus of this research. In a moderate range air-to-air scenario, focal plane spot breakup is the dominant failure mechanism. Although the impact of spot breakup on average Strehl is small, spot breakup considerably increases fade probability. This result demonstrates that optimization of an atmospheric compensation system requires consideration of the metric of interest. Metric-driven design led to exploration of peak intensity tracking, which reduces fade probability by greater than 50% over conventional centroid trackers and Adaptive Optics (AO) systems for scenarios studied. An investigation of atmospheric compensation requirements based on deep fade phenomenology is the second major focus of this research. Fades are classified based on complexity of the required compensation technique. For compensation techniques studied, regions of superior performance, in terms of fade probability, are identified. Peak tracking is shown to outperform AO for thresholds below approximately 4% of the unabberated intensity. Furthermore, the boundary between superior performance regions is nearly invariant to turbulence strength. This boundary invariance simplifies operation of a composite system which is able to adaptively select compensation methodology in near real-time

Solar energy conversion

If solar energy is to become a practical alternative to fossil fuels, we must have efficient ways to convert photons into electricity, fuel, and heat. The need for better conversion technologies is a driving force behind many recent developments in biology, materials, and especially nanoscience

Chemical physics and astrochemistry of H3+ and sub Doppler mid infrared spectroscopy of molecular ions

Molecular ions are known to be key reactive intermediates in interstellar environments, and H3+ in particular is responsible for initiating a network of chemical reactions that ultimately results in the formation of the ~170 molecules detected so far in space. Yet fundamental questions about the interstellar abundances of the two nuclear spin configurations of H3+ (ortho-H3+, I=3/2; and para-H3+, I=1/2) remain. In this thesis, experiments to measure the nuclear spin dependence of the chemical reactions of H3+ with electrons and with molecular hydrogen at astronomically relevant temperatures are described. The results of these laboratory measurements are included into a model of the hydrogenic chemistry of diffuse molecular clouds, in which an excess of para-H3+ is observed relative to its expected abundance at the measured cloud temperature. The model suggests that the ortho:para ratio is likely controlled by a competition between the aforementioned chemical reactions of H3+ with electrons and molecular hydrogen. Other molecular ions may similarly be useful for constraining the physical and chemical conditions of astronomical environments, but such insight can only be derived if laboratory spectroscopy of these ions has been performed. However, for many ionic species, insufficient laboratory data are available, and this is primarily because of difficulties in producing sufficient quantities of ions for traditional spectroscopic techniques. This thesis discusses the development of instrumentation to overcome the challenge of ion production. First, a continuous supersonic expansion discharge source is described that allows for the production of internally cold molecular ions in modest abundance, thereby maximizing population in the lowest-lying energy states relevant for astronomical spectroscopy. Then, an instrument for performing sub-Doppler spectroscopy of molecular ions in a liquid nitrogen cooled plasma is discussed. This instrument offers ultra high sensitivity, and sufficient accuracy and precision that rotational frequencies suitable for observational astronomy can be inferred. As a case study of the performance and capabilities of this instrument, the high resolution sub-Doppler spectrum of H3+ is presented

Searching for music: understanding the discovery, acquisition, processing and organization of music in a domestic setting for design

This series of studies make it clear that a wide range of both physical and digital resources are involved in domestic music consumption. The selection of digital resources is particularly evident, and it can be observed that domestic music consumption is a fragmented business, taking advantage of many different "channels'' for getting, using and preparing music. While there are not a series of common channels, each home displayed a variety of methods in respect to using metadata in multiple different modalities: regardless, the activities involved in getting, using and preparing music cohere through a noticeable, emergent set of workflows. We find that not only does metadata support searching, as one might expect, but also it pervades all parts of the workflow and is used in real-time as a reflexive artifact and in terms of its future perceived/prescribed use. The findings of the research raise a series of possibilities and issues that form the basis for understanding and designing for metadata use

05. Book II, Vol. 2: Events following the Watergate break-in, June 17, 1972 - February 9, 1973 (allegations involving Presidential interference with the official Department of Justice investigation)

https://digitalcommons.law.scu.edu/watergate/1004/thumbnail.jp