Dynamic Boundaries in Asymmetric Exclusion Processes

We investigate the dynamics of a one-dimensional asymmetric exclusion process with Langmuir kinetics and a fluctuating wall. At the left boundary, particles are injected onto the lattice; from there, the particles hop to the right. Along the lattice, particles can adsorb or desorb, and the right boundary is defined by a wall particle. The confining wall particle has intrinsic forward and backward hopping, a net leftward drift, and cannot desorb. Performing Monte Carlo simulations and using a moving-frame finite segment approach coupled to mean field theory, we find the parameter regimes in which the wall acquires a steady state position. In other regimes, the wall will either drift to the left and fall off the lattice at the injection site, or drift indefinitely to the right. Our results are discussed in the context of non-equilibrium phases of the system, fluctuating boundary layers, and particle densities in the lab frame versus the frame of the fluctuating wall.Comment: 13 page

NASA Space Exploration Logistics Workshop Proceedings

As NASA has embarked on a new Vision for Space Exploration, there is new energy and focus around the area of manned space exploration. These activities encompass the design of new vehicles such as the Crew Exploration Vehicle (CEV) and Crew Launch Vehicle (CLV) and the identification of commercial opportunities for space transportation services, as well as continued operations of the Space Shuttle and the International Space Station. Reaching the Moon and eventually Mars with a mix of both robotic and human explorers for short term missions is a formidable challenge in itself. How to achieve this in a safe, efficient and long-term sustainable way is yet another question. The challenge is not only one of vehicle design, launch, and operations but also one of space logistics. Oftentimes, logistical issues are not given enough consideration upfront, in relation to the large share of operating budgets they consume. In this context, a group of 54 experts in space logistics met for a two-day workshop to discuss the following key questions: 1. What is the current state-of the art in space logistics, in terms of architectures, concepts, technologies as well as enabling processes? 2. What are the main challenges for space logistics for future human exploration of the Moon and Mars, at the intersection of engineering and space operations? 3. What lessons can be drawn from past successes and failures in human space flight logistics? 4. What lessons and connections do we see from terrestrial analogies as well as activities in other areas, such as U.S. military logistics? 5. What key advances are required to enable long-term success in the context of a future interplanetary supply chain? These proceedings summarize the outcomes of the workshop, reference particular presentations, panels and breakout sessions, and record specific observations that should help guide future efforts

Logistics Lessons Learned in NASA Space Flight

The Vision for Space Exploration sets out a number of goals, involving both strategic and tactical objectives. These include returning the Space Shuttle to flight, completing the International Space Station, and conducting human expeditions to the Moon by 2020. Each of these goals has profound logistics implications. In the consideration of these objectives,a need for a study on NASA logistics lessons learned was recognized. The study endeavors to identify both needs for space exploration and challenges in the development of past logistics architectures, as well as in the design of space systems. This study may also be appropriately applied as guidance in the development of an integrated logistics architecture for future human missions to the Moon and Mars. This report first summarizes current logistics practices for the Space Shuttle Program (SSP) and the International Space Station (ISS) and examines the practices of manifesting, stowage, inventory tracking, waste disposal, and return logistics. The key findings of this examination are that while the current practices do have many positive aspects, there are also several shortcomings. These shortcomings include a high-level of excess complexity, redundancy of information/lack of a common database, and a large human-in-the-loop component. Later sections of this report describe the methodology and results of our work to systematically gather logistics lessons learned from past and current human spaceflight programs as well as validating these lessons through a survey of the opinions of current space logisticians. To consider the perspectives on logistics lessons, we searched several sources within NASA, including organizations with direct and indirect connections with the system flow in mission planning. We utilized crew debriefs, the John Commonsense lessons repository for the JSC Mission Operations Directorate, and the Skylab Lessons Learned. Additionally, we searched the public version of the Lessons Learned Information System (LLIS) and verified that we received the same result using the internal version of LLIS for our logistics lesson searches. In conducting the research, information from multiple databases was consolidated into a single spreadsheet of 300 lessons learned. Keywords were applied for the purpose of sorting and evaluation. Once the lessons had been compiled, an analysis of the resulting data was performed, first sorting it by keyword, then finding duplication and root cause, and finally sorting by root cause. The data was then distilled into the top 7 lessons learned across programs, centers, and activities

Rounding and uncertainties in parameters determined from fits to experimental data, or a failure to round data-analysis fit parameters properly may make them useless

Almost no physically interesting physico/chemical parameter is determined directly from a measurement. Rather, they are determined by performing a least-squares fit of some model to a set of data. Unfortunately, there seems to be no commonly accepted set of `best practices' for determining how to round off such fitted parameter values to a minimum number of significant digits while ensuring that they retain the ability to reproduce the experimental data within their uncertainties. This sometimes results in lists of fitted parameters with no quoted uncertainties that have 2--3 times as many significant digits as the data being fitted, or to the results of an analysis being defined by parameters that are (unnecessarily?) quoted to more digits than normal computer double precision, which makes those results difficult or impossible to apply. Alternatively, it may also lead to fitted parameters being `over-rounded' so that the model no longer accurately represents the experimental data. This presentation describes a `best practice' to address these problems, offers a general-purpose least-squares fitting program that applies it, and provides an illustrative application of this approach in a study of the A\,^1\Sigma_u^+ - X\,^1\Sigma_g^+ system of Mg$_2$.Ope

Limiting antenatal weight gain improves maternal health outcomes in severely obese pregnant women: findings of a pragmatic evaluation of a midwife-led intervention

Background: Antenatal obesity in pregnancy is associated with complications of pregnancy and poor obstetric outcomes. Although most guidance on pregnancy weight is focused on the pre-pregnancy period, pregnancy is widely viewed as a period where women are open to lifestyle change to optimise their health. Method: The hospital-based Bumps and Beyond intervention invited all pregnant women with a BMI of over 35 kg/m2 to take part in a programme of health education around diet and exercise, accompanied by one-to-one guidance and monitoring of dietary change. This service evaluation compares 89 women who completed at a programme of 7 sessions with healthy lifestyle midwives and advisors (intervention) with a group of 89 women who chose not to attend (non-intervention). Results: Weight gain in the intervention group (4.5±4.6 kg) was less than in the non-intervention group (10.3±4.4 kg) between antenatal booking and 36 weeks gestation (<0.001). This was associated with a 95% reduction in the risk of gestational hypertension during pregnancy and a general reduction in pregnancy complications. There was no effect of the intervention upon gestational diabetes or complications in labour other than post-partum haemorrhage (reduced 55%). The impact of the intervention on gestational weight gain was greater in women with BMI over 40 kg/m2 at booking. There were no adverse effects of the intervention, even though 21% of the intervention group lost weight during their pregnancy. Conclusion: Intensive, personalised weight management intervention may be an effective strategy for prevention of hypertensive disorders during pregnancy

Limiting antenatal weight gain improves maternal health outcomes in severely obese pregnant women: findings of a pragmatic evaluation of a midwife-led intervention

Background: Antenatal obesity in pregnancy is associated with complications of pregnancy and poor obstetric outcomes. Although most guidance on pregnancy weight is focused on the pre-pregnancy period, pregnancy is widely viewed as a period where women are open to lifestyle change to optimise their health. Method: The hospital-based Bumps and Beyond intervention invited all pregnant women with a BMI of over 35 kg/m2 to take part in a programme of health education around diet and exercise, accompanied by one-to-one guidance and monitoring of dietary change. This service evaluation compares 89 women who completed at a programme of 7 sessions with healthy lifestyle midwives and advisors (intervention) with a group of 89 women who chose not to attend (non-intervention). Results: Weight gain in the intervention group (4.5±4.6 kg) was less than in the non-intervention group (10.3±4.4 kg) between antenatal booking and 36 weeks gestation (<0.001). This was associated with a 95% reduction in the risk of gestational hypertension during pregnancy and a general reduction in pregnancy complications. There was no effect of the intervention upon gestational diabetes or complications in labour other than post-partum haemorrhage (reduced 55%). The impact of the intervention on gestational weight gain was greater in women with BMI over 40 kg/m2 at booking. There were no adverse effects of the intervention, even though 21% of the intervention group lost weight during their pregnancy. Conclusion: Intensive, personalised weight management intervention may be an effective strategy for prevention of hypertensive disorders during pregnancy

Mechanisms of Fetal Programming in Hypertension

Events that occur in the early fetal environment have been linked to long-term health and lifespan consequences in the adult. Intrauterine growth restriction (IUGR), which may occur as a result of nutrient insufficiency, exposure to hormones, or disruptions in placental structure or function, may induce the fetus to alter its developmental program in order to adapt to the new conditions. IUGR may result in a decrease in the expression of genes that are responsible for nephrogenesis as nutrients are rerouted to the development of more essential organs. Fetal survival under these conditions often results in low birth weight and a deficit in nephron endowment, which are associated with hypertension in adults. Interestingly, male IUGR offspring appear to be more severely affected than females, suggesting that sex hormones may be involved. The processes of fetal programming of hypertension are complex, and we are only beginning to understand the underlying mechanisms