Dynamics of carbon dioxide exchange of a wheat community grown in a semi-closed environment

A wheat (Triticum aestivum Yecora Rojo) community was grown in the semi-closed conditions of the NASA/KSC Biomass Production Chamber (BPC). Experiments were conducted to determine whole community carbon dioxide exchange rates as influenced by growth and development, carbon dioxide concentration, time within the photoperiod, irradiance, and temperature. Plants were grown at a population of about 1500 per sq meter using a 20 hour light/4 hour dark daily regime. Light was supplied by HPS vapor lamps and irradiance was maintained in the range of 590 to 675 mu mol per sq meter. The temperature regime was 20 C light/16 C dark and nutrients were supplied hydroponically as a thin film. Fractional interception of PPF by the community increased rapidly during growth reaching a maximum of 0.96, 24 days after planting. This time corresponded to canopy closure and maximum rates of net photosynthesis (NP). Net daily CO2 utilization rates were calculated to day 48 and a 4th order regression equation integrated to obtain total moles of CO2 fixed by the community. This procedure may be useful for monitoring and prediction of biomass yields in a closed ecology life support system (CELSS)

Airgun pellet performance using computational fluid dynamics

Very little formal analysis has been done with respect to flow around small scale projectiles. In late 1991, a local manufacturer of airgun pellets and related equipment approached RIT to investigate the flow characteristics of two particular airgun pellet geometries. Initial work was completed with the RIT wind tunnel through the use of scaled up models of the pellets. The conclusions of this work showed many interesting results, even though only the low speed velocity range of the pellets was studied. In order to study the actual operating velocity range of the pellets, the use of a Computational Fluid Dynamics program was necessary. The results from the CFD analysis of the two airgun pellets are presented in this work

Carbon dioxide and water exchange of a soybean stand grown in the biomass production chamber

Soybean plants were grown under metal halide lamps in NASA's biomass production chamber (BPC). Experiments were conducted to determine whole stand rates of carbon dioxide exchange and transpiration as influenced by time of day, CO2 concentration, irradiance, and temperature. Plants were grown at a population of 24 plants/sq m, a daily cycle of 12 hr light/12 hr dark, and average temperature regime of 26 C light/20 C dark, and a CO2 concentration enriched and maintained at 1000 ppm during the photoperiod. A distinct diurnal pattern in the rate of stand transpiration was measured at both ambient and enriched (1000 ppm) concentration of CO2. Data generated in this study represent true whole stand responses to key developmental and environmental variables and will be valuable in database construction for future working CELSS. Crop growth studies in the BPC were conducted with a high degree of environmental control, gas tightness during growth, and have used large plant stands. These characteristics have placed it in a unique position internationally as a research tool and as a preprototype subcomponent to a fully integrated CELSS. The results from the experiments are presented

Monitoring ethylene emissions from plants cultured for a controlled ecological life support system

Emission of hydrocarbons and other volatile compounds by materials and organisms in closed environments will be a major concern in the design and management of advanced life support systems with a bioregenerative component. Ethylene, a simple hydrocarbon synthesized by plants, is involved in the elicitation of a wide range of physiological responses. In closed environments, ethylene may build up to levels which become physiologically active. In several growouts of 'Yecora Rojo' wheat in Kennedy Space Center's Biomass Production Chamber (BPC), it was observed that leaf flecking and rolling occurred in the sealed environment and was virtually eliminated when potassium permanganate was used to scrub the atmospheric environment. It was suggested that ethylene, which accumulated to about 60 ppb in the chamber and which was effectively absorbed by potassium permanganate, was responsible for the symptoms. The objectives of this work were to: (1) determine rates of ethylene evolution from lettuce (Lactuca sativa cultivar Waldemann's Green) and wheat (Triticum aestivum cultivar Yecora Rojo) plants during growth and development; (2) determine the effects of exposure of whole, vegetative stage plants to exogenous ethylene concentrations in the range of what would develop in closed environment growth chambers; and (3) develop predictive functions for changes in ethylene concentration that would develop under different cropping and closed environment configurations. Results will lead to the development of management strategies for ethylene in bioregenerative life support systems

Design of Plant Gas Exchange Experiments in a Variable Pressure Growth Chamber

Sustainable human presence in extreme environments such as lunar and martian bases will require bioregenerative components to human life support systems where plants are used for generation of oxygen, food, and water. Reduced atmospheric pressures will be used to minimize mass and engineering requirements. Few studies have assessed the metabolic and developmental responses of plants to reduced pressure and varied oxygen atmospheres. The first tests of hypobaric pressures on plant gas exchange and biomass production at the Johnson Space Center will be initiated in January 1996 in the Variable Pressure Growth Chamber (VPGC), a large, closed plant growth chamber rated for 10.2 psi. Experiments were designed and protocols detailed for two complete growouts each of lettuce and wheat to generate a general database for human life support requirements and to answer questions about plant growth processes in reduced pressure and varied oxygen environments. The central objective of crop growth studies in the VPGC is to determine the influence of reduced pressure and reduced oxygen on the rates of photosynthesis, dark respiration, evapotranspiration and biomass production of lettuce and wheat. Due to the constraint of one experimental unit, internal controls, called pressure transients, will be used to evaluate rates of CO2 uptake, O2 evolution, and H2O generation. Pressure transients will give interpretive power to the results of repeated growouts at both reduced and ambient pressures. Other experiments involve the generation of response functions to partial pressures of O2 and CO2 and to light intensity. Protocol for determining and calculating rates of gas exchange have been detailed. In order to build these databases and implement the necessary treatment combinations in short time periods, specific requirements for gas injections and removals have been defined. A set of system capability checks will include determination of leakage rates conducted prior to the actual crop growouts. Schedules of experimental events for lettuce and wheat are outlined and include replications in time of diurnal routines, pressure transients, variable pO2, pO2/pCO2 ratio, and light intensity responses

Membrane permeability of Bovine Ooctyes to Propylene Glycol and the application to the improvement of Cryopreservation

Abstract only availableIn this study, the goal was to determine the permeability parameters of bovine oocytes for water (Lp) and Propylene Glycol (PPG) at temperatures of 30, 20, 10, and 5°C. By determining permeability parameters, we can model cell volume changes during addition and removal of cryoprotectants to determine a method that will prevent osmotic damage to the cells. Individual oocytes were held stationary by a holding pipette in a Petri dish on a Nikon inverted microscope. The oocytes were initially equilibrated in propylene glycol (PG) and 0.1M Sucrose for 20 minutes and then a solution of TL-Hepes with 0.1M Sucrose was added to a drop of 1.5M PG containing the oocyte. The specific initial concentration of PG and volumes of added solutions were modified for each temperature. Then digital images were captured on a regular time scale using a Spot RT Cooled CCD Digital camera in order to record shrinking and swelling. Morphometrical analysis was then performed on each image using Adobe Photoshop to measure the radius of each oocyte at the various time points during the volume excursions. Using Microsoft Excel, we were able to fit the experimental data to a best fit curve of a theoretical model for volume change, which allowed the determination of the values of Lp and PPG. These values were used to model the cell volume changes using MLAB (Civilized Software, Inc., Bethesda, MD) to developing optimized addition and removal procedures for 3.0M CPA that would minimize potential damage of the oocyte due to shrinking and swelling, and toxicity effects of the CPA due to excessive exposure. Currently, our results for the mean values of the permeability parameters Lp and PPG at 20°C are 0.3 ± 0.03 µm-min.atm and 15 ± 7.2 µm/min, respectively (mean ± SD, n=2). Further data acquisition and analysis is in progress.NSF-REU Program in Biosystems Modeling and Analysi

Plastic Deformation and Effective Strain Hardening Coefficient of Irradiated Fe-9wt%Cr ODS Alloy by Nano-Indentation and TEM

The objective of this study is to characterize changes in the yielding, and effective strain hardening coefficient of an oxide dispersion strengthened (ODS) alloy upon exposure to irradiation. It is well known that irradiation produces a supersaturation of defects, which alters the mechanical properties of a material. In order to engineer materials for use in advanced nuclear reactors, the long-term effects of neutron irradiation on mechanical performance must be understood. However, high-dose neutron exposure is often simulated using ion bombardment. Unfortunately, ion irradiation results in a shallow damage layer that prevents traditional bulk mechanical characterization methods from being utilized. A technique with the ability to examine the thin film of irradiated damage is required to provide insight into the changes in yield stress, elastic modulus, and hardness. Nano-indentation experiments have thus become a powerful tool to analyze ion irradiated materials, but a thorough understanding of the plastic deformation that occurs during nano-indention is required to accurately interpret the results. In this work, a coupled experimental and modeling approach resulted in an understanding of the effects of irradiation on strain hardening in a model Fe-9wt%Cr ODS alloy. Nano-indentation was performed on the alloy before and after irradiation, either with 5.0 MeV Fe++ ions to 100 displacements per atom (dpa) at 400°C or with a fast neutron spectrum to 3 dpa at 500° C. Nano-hardness measurements reported similar hardening between the two conditions, which is supported by investigation of the microstructure. The size and shape of the residual plastic zone beneath nano-indents was characterized using transmission electron microscopy coupled with Automated Crystal Orientation Mapping (ACOM-TEM) techniques. A model developed from finite element analysis, using the spherical indenter approximation, was combined with the experimental results to calculate the effective strain hardening coefficient that resulted from irradiation induced defects. Results indicate a 39.2%, and 49.5% increase in strain hardening resulting from respective ion and neutron irradiation conditions, and a 10.9% between the two irradiations. The similar hardening yet slight variation in the effective strain hardening coefficient is thought to be due to the slight difference in the nature of the damage cascades developed under ion and neutron irradiation

High-entropy high-hardness metal carbides discovered by entropy descriptors

High-entropy materials have attracted considerable interest due to the combination of useful properties and promising applications. Predicting their formation remains the major hindrance to the discovery of new systems. Here we propose a descriptor - entropy forming ability - for addressing synthesizability from first principles. The formalism, based on the energy distribution spectrum of randomized calculations, captures the accessibility of equally-sampled states near the ground state and quantifies configurational disorder capable of stabilizing high-entropy homogeneous phases. The methodology is applied to disordered refractory 5-metal carbides - promising candidates for high-hardness applications. The descriptor correctly predicts the ease with which compositions can be experimentally synthesized as rock-salt high-entropy homogeneous phases, validating the ansatz, and in some cases, going beyond intuition. Several of these materials exhibit hardness up to 50% higher than rule of mixtures estimations. The entropy descriptor method has the potential to accelerate the search for high-entropy systems by rationally combining first principles with experimental synthesis and characterization.Comment: 12 pages, 2 figure

Near-Minimal Gate Set Tomography Experiment Designs

Gate set tomography (GST) provides precise, self-consistent estimates of the noise channels for all of a quantum processor's logic gates. But GST experiments are large, involving many distinct quantum circuits. This has prevented their use on systems larger than two qubits. Here, we show how to streamline GST experiment designs by removing almost all redundancy, creating smaller and more scalable experiments without losing precision. We do this by analyzing the "germ" subroutines at the heart of GST circuits, identifying exactly what gate set parameters they are sensitive to, and leveraging this information to remove circuits that duplicate other circuits' sensitivities. We apply this technique to two-qubit GST experiments, generating streamlined experiment designs that contain only slightly more circuits than the theoretical minimum bounds, but still achieve Heisenberg-like scaling in precision (as demonstrated via simulation and a theoretical analysis using Fisher information). In practical use, the new experiment designs can match the precision of previous GST experiments with significantly fewer circuits. We discuss the prospects and feasibility of extending GST to three-qubit systems using our techniques.Comment: 11 pages, 6 figures, to be published in proceedings of 2023 IEEE International Conference on Quantum Computing and Engineering (QCE