Removing Orbital Debris with Lasers

Orbital debris in low Earth orbit (LEO) are now sufficiently dense that the use of LEO space is threatened by runaway collisional cascading. A problem predicted more than thirty years ago, the threat from debris larger than about 1 cm demands serious attention. A promising proposed solution uses a high power pulsed laser system on the Earth to make plasma jets on the objects, slowing them slightly, and causing them to re-enter and burn up in the atmosphere. In this paper, we reassess this approach in light of recent advances in low-cost, light-weight modular design for large mirrors, calculations of laser-induced orbit changes and in design of repetitive, multi-kilojoule lasers, that build on inertial fusion research. These advances now suggest that laser orbital debris removal (LODR) is the most cost-effective way to mitigate the debris problem. No other solutions have been proposed that address the whole problem of large and small debris. A LODR system will have multiple uses beyond debris removal. International cooperation will be essential for building and operating such a system.Comment: 37 pages, 15 figures, in preparation for submission to Advances in Space Researc

Autofluorescence lifetime augmented reality as a means for real-time robotic surgery guidance in human patients.

Due to loss of tactile feedback the assessment of tumor margins during robotic surgery is based only on visual inspection, which is neither significantly sensitive nor specific. Here we demonstrate time-resolved fluorescence spectroscopy (TRFS) as a novel technique to complement the visual inspection of oral cancers during transoral robotic surgery (TORS) in real-time and without the need for exogenous contrast agents. TRFS enables identification of cancerous tissue by its distinct autofluorescence signature that is associated with the alteration of tissue structure and biochemical profile. A prototype TRFS instrument was integrated synergistically with the da Vinci Surgical robot and the combined system was validated in swine and human patients. Label-free and real-time assessment and visualization of tissue biochemical features during robotic surgery procedure, as demonstrated here, not only has the potential to improve the intraoperative decision making during TORS but also other robotic procedures without modification of conventional clinical protocols

Social Benefits of Niche Agricultural Products: The Case of Pasture-Based Beef in Appalachia Part 1: The Conceptual Framework

Niche agricultural products are growing in economic importance. This growth is driven mainly by the increased demand for more healthy, nutritious, fresh and locally grown food products. There is obviously a potential increase in private benefits to producers/landowners as a result of increased production of the underlying crops to satisfy this demand. What is less obvious is the potential to also generate increased social benefits, particularly as they relate to energy conservation, alternative energy or biogas development and carbon sequestration. In other words, calories and kilo-calories are becoming more linked. The objective of this analysis is to develop a conceptual framework to illustrate the linkages among production at the local level, farm-level profitability and regional economic and environmental benefits. Using an optimal control approach, we apply this framework to the case of pasture-based beef (PBB) in Appalachia. PBB is an alternative to conventional, grain-based beef production. The idea is to determine to what extent a transition to PBB would enhance farm-level profitability while enabling surrounding communities to benefit from higher quality food products, environmental improvement, economic development and, ultimately, quality of life. We expect the results to illustrate under what combination of market and policy outcomes it is optimal - from both private and social perspectives – for a given PBB farmer to switch between cattle farming, energy farming and carbon farming. This paper is the first in a three-part series, with subsequent papers devoted to: (a) integrating spatial effects into the model, and (b) model estimation and use in policy formulation. The overall effort is part of a larger, interdisciplinary multi-institutional research project funded by USDA, ARS, focusing on the development of sustainable PBB operations for Appalachia

The Integral Fast Reactor concept: Today's hope for tomorrow's electrical energy needs

Acid rain and the greenhouse effect are getting more attention as their impacts on the environment become evident around the world. Substantial evidence indicates that fossil fuel combustion for electrical energy production activities is a key cause of those problems. A change in electrical energy production policy is essential to a stable, healthy environment. That change is inevitable, it's just a matter of when and at what cost. Vision now, instead of reaction later, both in technological development and public perception, will help to limit the costs of change. The Integral Fast Reactor (IFR) is a visionary concept developed by Argonne National Laboratory that involves electrical energy production through fissioning of heavy metals by fast neutrons in a reactor cooled by liquid sodium. Physical characteristics of the coolant and fuel give the reactor impressive characteristics of inherent and passive safety. Spent fuel is pyrochemically reprocessed and returned to the reactor in the IFR's closed fuel cycle. Advantages in waste management are realized, and the reactor has the potential for breeding, i.e., producing as much or more fuel than it uses. This paper describes the IFR concept and shows how it is today's hope for tomorrow's electrical energy needs. 14 refs., 1 fig., 1 tab

Laser ablation loading of a surface-electrode ion trap

We demonstrate loading by laser ablation of $^{88}$Sr$^+$ ions into a mm-scale surface-electrode ion trap. The laser used for ablation is a pulsed, frequency-tripled Nd:YAG with pulse energies of 1-10 mJ and durations of 3-5 ns. An additional laser is not required to photoionize the ablated material. The efficiency and lifetime of several candidate materials for the laser ablation target are characterized by measuring the trapped ion fluorescence signal for a number of consecutive loads. Additionally, laser ablation is used to load traps with a trap depth (40 meV) below where electron impact ionization loading is typically successful ($\gtrsim$ 500 meV).Comment: 4 pages, 4 figure

Measurement of 30kW output from a W-band source constructed by additive manufacturing

Experimental results from the operation of an electron beam driven, mm-wave, vacuum electronic source are reported. The aim of this work is to create improved electron-beam-driven, vacuum electronic mm-wave and sub-THz sources by exploiting dispersion-engineering. Dispersion-engineered structures can be manufactured by several techniques and in this work additive manufacturing has proven to be quick, reliable and cost-effective

MoonLITE – Technological feasibility of the penetrator concept

Introduction: While the surface missions to the Moon of the 1960s and 1970s achieved a great deal, scientifically a great deal was also left unresolved. The recent plethora of lunar missions (flown or proposed) reflects resurgence in interest in the Moon, not only in its own right, but also as a record of the formation of the Earth-Moon System and the interplanetary environment at 1 AU. Results from orbiter missions have indicated the possible presense of ice within permanently shaded craters at the lunar poles [1] – a situation that, if confirmed, will have profound impacts on lunar exploration

Using chlorhexidine varnish to prevent early childhood caries in American Indian children

Objectives: To test the efficacy of 10% chlorhexidine (CHX) dental varnish applied to the mothers' dentition in preventing caries in American Indian children. Methods: This was a placebo‐controlled, double‐blind, randomized clinical trial. Mother–child pairs were enrolled when the child was 4.5‐6.0 months. Mothers received 4 weekly applications of the study treatment (CHX or placebo) followed by single applications when her child was age 12 and 18 months. Children received caries examinations at enrollment, 12, 18 and 24 months. Analyses were limited to the intent‐to‐treat (ITT) group: children whose mothers received the first study treatment and who received at least one post‐baseline exam. The outcome variable was the number of new carious surfaces (NNCS) at the child's last visit. Wilcoxon nonparametric and Fisher's exact tests were used to test differences between the active and placebo groups. Results: We randomized 414 mother–child pairs, with 367 (88.6%) included in the ITT group (active = 188, placebo = 179). The proportion of children caries‐free at their final exam was 51.1% and 50.8% for the active and placebo groups ( P  > 0.99). The mean NNCS for the active and placebo groups was 3.82 (standard deviation [SD] = 8.18) and 3.80 (SD = 6.08), respectively ( P  = 0.54). The proportion with NNCS > 6 was 18.1% for active children versus 27.9% for placebo (relative risk [RR] = 0.65, P  = 0.03). The number needed to treat to shift one child from NNCS > 6 to a lower severity was 10.2. Conclusions: In this population CHX varnish did not reduce the mean NNCS or proportion of children with caries, but did reduce the proportion with severe caries.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96744/1/jphd348.pd