Azeotropic graft polymerizations of dienes and acrylonitrile onto poly(propylene oxide)

Graft copolymerizations of isoprene or butadiene with acrylonitrile in an approximately 2:1 weight ratio onto poly(propylene oxide) are azeotropic. These products, when vulcanized with sulfur, yield elastomers with excellent tensile properties.     

Parent-offspring relationships in apomictic guayule

The genetic base of guayule (Parthenium argentatum Gray) germ plasm that is available is narrow; yet, significant variability has been described within this germ plasm. This variability is surprising because guayule reproduces by facultative apomixis (asexual reproduction by seed), but evidence suggests that progress through selection is feasible. It has been hypothesized that this variation has arisen through periodic sexual reproduction; however, this has not been quantified. This study was designed to describe and compare eight components of yield and the expression of two isozyme systems in twenty parent plants and half-sib, open-pollinated families from each parent. Extensive variation for all characters was found among both the parents and the progeny, with fresh and dry weights being highly correlated to rubber yield. Parent-offspring regressions were not significantly different from zero. This implies low heritabilities for the major components of yield in guayule, and we believe that family selection, rather than single-plant selection, may generate higher-yielding and more genetically uniform lines at an escalated rate than single-plant selection. Periodic sexuality resulting in genetic variation was estimated by differences in isozyme expression within the half-sib families. Fifteen of the twenty progeny families were polymorphic for either esterase or peroxidase or both isozymes. This amount of sexuality is significant, and guayule must be considered an open-pollinated crop. We conclude from this study that we should rethink our breeding procedures to include controlled pollination and family selection.     

Study of boron doping in MPCVD grown homoepitaxial diamond layers based on cathodoluminescence spectroscopy, secondary ion mass spectroscopy and capacitance-voltage measurements

Boron incorporation from the gas phase was achieved in MPCVD grown (100)-oriented homoepitaxial diamond layers, either with or without a small fraction of oxygen in the gas phase, in addition to hydrogen, methane and diborane. From secondary Ion Mass Spectroscopy (SIMS), it is shown that the 0.25% of oxygen decreases the Boron concentration [B] by two orders of magnitude. In this way, we demonstrate that it becomes possible to control [B] with low levels of compensation and passivation down to the 10¹⁵ cm^− 3 range. Cathodoluminescence spectroscopy is systematically performed in seventeen samples under a 10 kV acceleration voltage at 5 K and the exciton bound to boron (BE_TO) intensity to the free exciton (FE_TO) intensity ratio is evaluated (I_BETO/I_FETO). A linear relationship between I_BETO/I_FETO and [B] with a coefficient of 3.5 × 10¹⁶ cm^− 3 is demonstrated for [B] < 3 × 10¹⁷ cm^− 3 in single crystalline diamond, irrespective of the gas phase composition during growth.     

Proposition pour une classification des graveleux latéritiques (application au cas du sénégal)

Studies of considerable data of laterite or lateritic soils to formulate a simple and reliabile predictive technique of road design or traffic specifications was vigorously advocated by investigators (CEBTP, BCEOM, the Lyon Associates and the african geotechnical laboratories). Commonly the use of lateritic soils is the basement of road paved or unpaved in the tropics. The well-known WASHOO (1955) and the AASHOO test in the USA (1956–1962), gave an estimation of the thickness of the road. The AASHOO test is derived from statistical studies for the design of road. It's based on the evaluation of the CBR index and its relation with the thickness. Peltier (1962) has shown that the relation between CBR and thickness can be approximated by the introduction of new parameters in relation with European soils and his work is the only one used in the African Tropical Countries for road pavement. The present work is derived from data complied from 1945 to 1992 by the Ministry in charge of road construction in Senegal. From these data, we proposed new specifications for road design, using statistical methods of computing. We also discuss some relations between the CBR index and some geotechnical parameters. So, it is known that the common use of the CBR index for road design is not appropriate, because the CBR may be certainly a shear strength characteristic of the soil and its relation with other parameters can be found acording to mechanical properties. Finally, the authors show that the use of a high level statistical analysis can be, supplied by the estimation of means and standard deviation. The ACP or AFD statistical methods proved that the qualitative parameters have no significant impact on the global results (without CBR evaluation): lateritic soils from Senegal have in general, the same behaviour and cannot be separated by differences from the origin of the parent rock. In fact, it is known (Gidigasu, 1976), that the composition and origin of the parent rock have a considerable influence on the soil behaviour. These results are in fact, no longer in accordance with that observation in the cases of the laterites from Senegal.     

Detection of rural electrification in Africa using DMSP-OLS night lights imagery

We report on the first systematic ground-based validation of the US Air Force Defense Meteorological Satellite Program’s Operational Linescan System (DMSP-OLS) night lights imagery to detect rural electrification in the developing world. Drawing upon a unique survey of villages in Senegal and Mali, this study compares night-time light output from the DMSP-OLS against ground-based survey data on electricity use in 232 electrified villages and additional administrative data on 899 unelectrified villages. The analysis reveals that electrified villages are consistently brighter than unelectrified villages across annual composites, monthly composites, and a time series of nightly imagery. Electrified villages appear brighter because of the presence of streetlights, and brighter villages tend to have more streetlights. By contrast, the correlation of light output with household electricity use and access is low. We further demonstrate that a detection algorithm using data on night-time light output and the geographic location of settlements can accurately classify electrified villages. This research highlights the potential to use night lights imagery for the planning and monitoring of ongoing efforts to connect the 1.4 billion people who lack electricity around the world.     

Time‐ and State‐Dependent Input Delay‐Compensated Bang‐Bang Control of a Screw Extruder for 3D Printing

In this paper, a delay‐compensated bang‐bang control design methodology for the control of the nozzle output flow rate of screw extruder‐based three‐dimensional printing processes is developed. A geometrical decomposition of the screw extruder in a partially and a fully filled regions allows to describe the material convection in the extruder chamber by a one‐dimensional hyperbolic partial differential equation (PDE) coupled with an ordinary differential equation. After solving the hyperbolic PDE by the method of characteristics, the coupled PDE–ordinary differential equation's system is transformed into a nonlinear state‐dependent input delay system. The aforementioned delay system is extended to the non‐isothermal case with the consideration of periodic fluctuations acting on the material's convection speed, which represent the process variabilities due to temperature changes in the extruder chamber, resulting to a nonlinear system with an input delay that simultaneously depends on the state and the time variable. Global exponential stability of the nonlinear delay‐free plant is established under a piecewise exponential feedback controller that is designed. By combining the nominal, piecewise exponential feedback controller with nonlinear predictor feedback, the compensation of the time‐dependent and state‐dependent input delay of the extruder model is achieved. Global asymptotic stability of the closed‐loop system under the bang‐bang predictor feedback control law is established when certain conditions related to the extruder design and the material properties, as well as to the magnitude and frequency of the materials transport speed variations, are satisfied. Simulations results are presented to illustrate the effectiveness of the proposed control design. Copyright © 2017 John Wiley & Sons, Ltd.     

Advances in network simulation

Network researchers must test Internet protocols under varied conditions to determine whether they are robust and reliable. The paper discusses the Virtual Inter Network Testbed (VINT) project which has enhanced its network simulator and related software to provide several practical innovations that broaden the conditions under which researchers can evaluate network protocols     

Derivation of supersaturation and nucleation flux during precipitation from the mixing pattern of an inert tracer in the same device: case of unmixed feed streams

Inert liquid tracer concentrations in a continuous mixer are analyzed by planar laser induced fluorescence (PLIF). Special attention is paid to the two separated entering feed streams containing the tracer solution or pure solvent. From the instantaneous tracer concentration fields, the method proposed allows one to easily calculate the instantaneous supersaturation fields, which would be obtained in the same mixing device with reagents instead of an inert tracer solution and pure solvent. A typical mixing situation in a stirred tank with separated feed streams is investigated. Maps of averaged supersaturation and averaged nucleation flux are yielded with high spatial resolution of a few tens of micrometers for each pixel. The method gives interesting indications about the ability of a given precipitator geometry to generate coarse or fine particles. However, it cannot be extended straightforward to partially premixed feed streams without the use of a mixing model.     

Isoprene emission from terrestrial ecosystems in response to global change: minding the gap between models and observations

Coupled surface-atmosphere models are being used with increased frequency to make predictions of tropospheric chemistry on a 'future' earth characterized by a warmer climate and elevated atmospheric CO2 concentration. One of the key inputs to these models is the emission of isoprene from forest ecosystems. Most models in current use rely on a scheme by which global change is coupled to changes in terrestrial net primary productivity (NPP) which, in turn, is coupled to changes in the magnitude of isoprene emissions. In this study, we conducted measurements of isoprene emissions at three prominent global change experiments in the United States. Our results showed that growth in an atmosphere of elevated CO2 inhibited the emission of isoprene at levels that completely compensate for possible increases in emission due to increases in aboveground NPP. Exposure to a prolonged drought caused leaves to increase their isoprene emissions despite reductions in photosynthesis, and presumably NPP. Thus, the current generation of models intended to predict the response of isoprene emission to future global change probably contain large errors. A framework is offered as a foundation for constructing new isoprene emission models based on the responses of leaf biochemistry to future climate change and elevated atmospheric CO2 concentrations.