A resilience approach to the design of future moon base power systems

This paper proposes a novel approach to the design of complex engineering systems which maximise performance, and global system resilience. The approach is applied to the system level design of the power system for future Moon bases. The power system is modelled as a network, where each node represents a specific power unit: energy storage, power distribution, power generation, power regulation. The performance and resilience of each power unit is defined by a mathematical model that depends on a set of design (control) and uncertain variables. The interrelationship among nodes is defined by functional links. The combination of multiple interconnected nodes defines the performance and resilience of the whole system. An optimisation procedure is then used to find the optimal values of the design parameters. The optimal solution maximises global system resilience where an optimal resilient solution is either robust, i.e. it is not subject to disruptive failures, or recovers from failures to achieve a functioning state, albeit different from the starting one, after a contingency occurs. The power system supports a Lunar base developed within the ESA-lab initiative, IGLUNA, led by the Swiss Space Centre. The power system, developed at the University of Strathclyde as part of the PowerHab project, is composed of nine interconnected elements: a hydrogen fuel cell energy storage system, a thermal mass storage system, a lithium-ion battery storage system, a constellation of solar power satellites (SPS) working in conjunction with a microwave wireless power transmission system, a reflecting satellite constellation and a ground-based solar power array. Distinct space and ground segments are identifiable, with orbit, AOCS and reflecting satellite nodes cooperating to provide optimal performance of the SPS constellation. The ground segment encompasses the ground-based solar array, energy storage systems, Lunar habitation module and the power transmission lines connecting these elements. Power generation is predominantly supplied by the ground-based array, with the SPS constellation and energy storage systems complementing this source; as well as providing redundancy and a reliable power supply during the Lunar night period

Megawatt solar power systems for lunar surface operations

Lunar surface operations require habitation, transportation, life support, scientific, and manufacturing systems, all of which require some form of power. As an alternative to nuclear power, the development of a modular one megawatt solar power system is studied, examining both photovoltaic and dynamic cycle conversion methods, along with energy storage, heat rejection, and power backup subsystems. For photovoltaic power conversion, two systems are examined. First, a substantial increase in photovoltaic conversion efficiency is realized with the use of new GaAs/GaSb tandem photovoltaic cells, offering an impressive overall array efficiency of 23.5 percent. Since these new cells are still in the experimental phase of development, a currently available GaAs cell providing 18 percent efficiency is examined as an alternate to the experimental cells. Both Brayton and Stirling cycles, powered by linear parabolic solar concentrators, are examined for dynamic cycle power conversion. The Brayton cycle is studied in depth since it is already well developed and can provide high power levels fairly efficiently in a compact, low mass system. The dynamic conversion system requires large scale waste heat rejection capability. To provide this heat rejection, a comparison is made between a heat pipe/radiative fin system using advanced composites, and a potentially less massive liquid droplet radiator system. To supply power through the lunar night, both a low temperature alkaline fuel cell system and an experimental high temperature monolithic solid-oxide fuel cell system are considered. The reactants for the fuel cells are stored cryogenically in order to avoid the high tankage mass required by conventional gaseous storage. In addition, it is proposed that the propellant tanks from a spent, prototype lunar excursion vehicle be used for this purpose, therefore resulting in a significant overall reduction in effective storage system mass

Comparative analysis of solar power satellite systems to support a moon base

This paper compares different concepts for a space-based power system to support a lunar base: a solar power satellite (SPS) with a microwave wireless power transmission system (WPT), a hybrid configuration where two solar reflector satellites (SRS) fly in formation with the SPS and concentrate sunlight onto the SPS, and the CASSIOPeiA SPS system. Sizing of the transmitting and receiving antennae is conducted for a WPT concept utilising high frequency microwaves. Design of the microwave generator is based on gyrotron technology, with parabolic reflectors, and an array of rectifying patch antennae. The WPT solution consists of a number of satellites with solar arrays and transmission capabilities to provide continuous power to the receiving array. Solar reflectors alleviate the issue of day-night cycles, for ground-based solar arrays, by providing constant sunlight. This concept could be extended by increasing the irradiance provided by the reflecting satellite, thus decreasing the size of the ground solar array required. However, reflective satellites struggle with efficiency stemming from the size of the footprint they create, which is dependent on the angular subtense of the Sun. This paper demonstrates that a hybrid design, utilizing both the reflector satellites and the WPT, would provide the greatest power to weight ratio - decreasing the size of the solar array required. An important aspect in the effectiveness of solar powered satellites are their distance from the ground receiver, determined directly by their orbit. Smaller orbits allow for reduced distances between the satellite and ground; reducing receiver sizes. However, larger orbits increase transmission windows, reducing the required energy transfer rate. Another important consideration is the stability of the orbit. Stability is affected by the Solar Radiation Pressure, the gravitational pull of the Earth, and the effects of the non-spherical gravity field of the Moon. Thus, when designing the orbit, these effects have been considered alongside the trade-off between larger and smaller orbits. The solutions have been scaled and compared to the CASSIOPeiA concept architecture of a similar nature which has been investigated to demonstrate the effectiveness of the concept provided

Protocol for an open label: phase I trial within a cohort of foetal cell transplants in people with Huntington’s disease

Huntington’s disease is a progressive neurodegenerative disorder characterised by motor, cognitive and psychiatric symptoms. Currently, no disease-modifying therapies are available to slow or halt disease progression. Huntington’s disease is characterised by relatively focal and specific loss of striatal medium spiny neurons, which makes it suitable for cell replacement therapy, a process involving the transplantation of donor cells to replace those lost due to disease. TRIDENT (TRIal DEsigns for delivery of Novel Therapies in neurodegeneration) is a phase I Trial Within a Cohort (TWiC) designed to assess safety and feasibility of transplanting human fetalstriatal cells into the striatum of people with Huntington’s disease. A minimum of 18 participants will be enrolled in the study cohort, and up to five eligible participants will be randomly selected to undergo transplantation of 12-22 million fetal cells in a dose escalation paradigm. Independent reviewers will assess safety outcomes (lack of significant infection, bleeding or new neurological deficit) four weeks after surgery, and ongoing safety will be established before conducting each subsequent surgery. All participants will undergo detailed clinical and functional assessment at baseline, 6 and 12 months. Surgery will be performed one month after baseline, and transplant participants will undergo regular clinical follow-up for at least 12 months. Evaluation of trial processes will also be undertaken. Transplant participants and their carers will be interviewed approximately one month before and after surgery. Interviews will also be conducted with non-transplanted participants and healthcare staff delivering the intervention and involved in the clinical care of participants. Evaluation of clinical and functional efficacy outcomes and intervention costs will be carried out to explore plausible trial designs for subsequent randomised controlled trials aimed at evaluating efficacy and cost-effectiveness of cell replacement therapy. TRIDENT will enable the assessment of the safety, feasibility, acceptability and cost of fetalcell transplants in people with Huntington’s disease. The data collected will inform trial designs for complex intracranial interventions in a range of neurodegenerative conditions and facilitate the development of stable surgical pipelines for delivery of future stem cell trials

Efficient generation of vesicular stomatitis virus (VSV)-pseudotypes bearing morbilliviral glycoproteins and their use in quantifying virus neutralising antibodies

Morbillivirus neutralising antibodies are traditionally measured using either plaque reduction neutralisation tests (PRNTs) or live virus microneutralisation tests (micro-NTs). While both test formats provide a reliable assessment of the strength and specificity of the humoral response, they are restricted by the limited number of viral strains that can be studied and often present significant biological safety concerns to the operator. In this study, we describe the adaptation of a replication-defective vesicular stomatitis virus (VSVΔG) based pseudotyping system for the measurement of morbillivirus neutralising antibodies. By expressing the haemagglutinin (H) and fusion (F) proteins of canine distemper virus (CDV) on VSVΔG pseudotypes bearing a luciferase marker gene, neutralising antibody titres could be measured rapidly and with high sensitivity. Further, by exchanging the glycoprotein expression construct, responses against distinct viral strains or species may be measured. Using this technique, we demonstrate cross neutralisation between CDV and peste des petits ruminants virus (PPRV). As an example of the value of the technique, we demonstrate that UK dogs vary in the breadth of immunity induced by CDV vaccination; in some dogs the neutralising response is CDV-specific while, in others, the neutralising response extends to the ruminant morbillivirus PPRV. This technique will facilitate a comprehensive comparison of cross-neutralisation to be conducted across the morbilliviruses

Co-constructing intersubjectivity with artificial conversational agents: people are more likely to initiate repairs of misunderstandings with agents represented as human

This article explores whether people more frequently attempt to repair misunderstandings when speaking to an artificial conversational agent if it is represented as fully human. Interactants in dyadic conversations with an agent (the chat bot Cleverbot) spoke to either a text screen interface (agent's responses shown on a screen) or a human body interface (agent's responses vocalized by a human speech shadower via the echoborg method) and were either informed or not informed prior to interlocution that their interlocutor's responses would be agent-generated. Results show that an interactant is less likely to initiate repairs when an agent-interlocutor communicates via a text screen interface as well as when they explicitly know their interlocutor's words to be agent-generated. That is to say, people demonstrate the most “intersubjective effort” toward establishing common ground when they engage an agent under the same social psychological conditions as face-to-face human-human interaction (i.e., when they both encounter another human body and assume that they are speaking to an autonomously-communicating person). This article's methodology presents a novel means of benchmarking intersubjectivity and intersubjective effort in human-agent interaction

Understanding Sensory Nerve Mechanotransduction through Localized Elastomeric Matrix Control

BACKGROUND: While neural systems are known to respond to chemical and electrical stimulation, the effect of mechanics on these highly sensitive cells is still not well understood. The ability to examine the effects of mechanics on these cells is limited by existing approaches, although their overall response is intimately tied to cell-matrix interactions. Here, we offer a novel method, which we used to investigate stretch-activated mechanotransduction on nerve terminals of sensory neurons through an elastomeric interface. METHODOLOGY/PRINCIPAL FINDINGS: To apply mechanical force on neurites, we cultured dorsal root ganglion neurons on an elastic substrate, polydimethylsiloxane (PDMS), coated with extracellular matrices (ECM). We then implemented a controlled indentation scheme using a glass pipette to mechanically stimulate individual neurites that were adjacent to the pipette. We used whole-cell patch clamping to record the stretch-activated action potentials on the soma of the single neurites to determine the mechanotransduction-based response. When we imposed specific mechanical force through the ECM, we noted a significant neuronal action potential response. Furthermore, because the mechanotransduction cascade is known to be directly affected by the cytoskeleton, we investigated the cell structure and its effects. When we disrupted microtubules and actin filaments with nocodozale or cytochalasin-D, respectively, the mechanically induced action potential was abrogated. In contrast, when using blockers of channels such as TRP, ASIC, and stretch-activated channels while mechanically stimulating the cells, we observed almost no change in action potential signalling when compared with mechanical activation of unmodified cells. CONCLUSIONS/SIGNIFICANCE: These results suggest that sensory nerve terminals have a specific mechanosensitive response that is related to cell architecture

Mechanism for microbial population collapse in a fluctuating resource environment.

Managing trade-offs through gene regulation is believed to confer resilience to a microbial community in a fluctuating resource environment. To investigate this hypothesis, we imposed a fluctuating environment that required the sulfate-reduce

A new multicompartmental reaction-diffusion modeling method links transient membrane attachment of E. coli MinE to E-ring formation

Many important cellular processes are regulated by reaction-diffusion (RD) of molecules that takes place both in the cytoplasm and on the membrane. To model and analyze such multicompartmental processes, we developed a lattice-based Monte Carlo method, Spatiocyte that supports RD in volume and surface compartments at single molecule resolution. Stochasticity in RD and the excluded volume effect brought by intracellular molecular crowding, both of which can significantly affect RD and thus, cellular processes, are also supported. We verified the method by comparing simulation results of diffusion, irreversible and reversible reactions with the predicted analytical and best available numerical solutions. Moreover, to directly compare the localization patterns of molecules in fluorescence microscopy images with simulation, we devised a visualization method that mimics the microphotography process by showing the trajectory of simulated molecules averaged according to the camera exposure time. In the rod-shaped bacterium _Escherichia coli_, the division site is suppressed at the cell poles by periodic pole-to-pole oscillations of the Min proteins (MinC, MinD and MinE) arising from carefully orchestrated RD in both cytoplasm and membrane compartments. Using Spatiocyte we could model and reproduce the _in vivo_ MinDE localization dynamics by accounting for the established properties of MinE. Our results suggest that the MinE ring, which is essential in preventing polar septation, is largely composed of MinE that is transiently attached to the membrane independently after recruited by MinD. Overall, Spatiocyte allows simulation and visualization of complex spatial and reaction-diffusion mediated cellular processes in volumes and surfaces. As we showed, it can potentially provide mechanistic insights otherwise difficult to obtain experimentally

A protocol for a randomised controlled, double-blind feasibility trial investigating fluoxetine treatment in improving memory and learning impairments in patients with mesial temporal lobe epilepsy: Fluoxetine, Learning and Memory in Epilepsy (FLAME trial)

Background People with temporal lobe epilepsy (TLE) report significant problems with learning and memory. There are no effective therapies for combatting these problems in people with TLE, resulting in an unmet therapeutic need. The lack of treatment is, in part, due to a poor understanding of the neurobiology underlying these memory deficits. We know that hippocampal neurogenesis, a process believed to be important in learning and memory formation, is permanently reduced in chronic TLE, and this may go some way to explain the learning and memory impairments seen in people with TLE. The common anti-depressant drug fluoxetine has been shown to stimulate neurogenesis both in the healthy brain and in neurological diseases where neurogenesis is impaired. In an animal model of TLE, administration of fluoxetine was found to restore neurogenesis and improve learning on a complex spatial navigational task. We now want to test this effect in humans by investigating whether administration of fluoxetine to people with TLE can improve learning and memory. Methods This is a single-centre randomised controlled, double-blind feasibility trial. We plan to recruit 20 participants with a diagnosis of TLE and uni-lateral hippocampal sclerosis, confirmed by 3T MRI. Eligible participants will undergo baseline assessments of learning and memory prior to being randomised to either 20 mg/day fluoxetine or matching placebo for 60 days. Follow-up assessments will be conducted after 60 days of trial medication and then again at 60 days after cessation of trial medication. Feasibility will be assessed on measures of recruitment, retention and adherence against pre-determined criteria. Discussion This trial is designed to determine the feasibility of conducting a double-blind randomised controlled trial of fluoxetine for the treatment of learning and memory impairments in people with TLE. Data collected in this trial will inform the design and utility of any future efficacy trial involving fluoxetine for the treatment of learning and memory in people with TLE