The production of ultrathin polyimide films for the solar sail program and Large Space Structures Technology (LSST): A feasibility study

Polyimide membranes of a thickness range from under 0.01 micron m to greater than 1 micron m can be produced at an estimated cost of 50 cents per sq m (plus the cost of the polymer). The polymer of interest is dissolved in a solvent which is solube in water. The polymer or casting solution is allowed to flow down an inclined ramp onto a water surface where a pool of floating polymer develops. The solvent dissolves into the water lowering the surface tension of the water on equently, the contact angle of the polymer pool is very low and the edge of the pool is very thin. The solvent dissolves from this thin region too rapidly to be replenished from the bulk of the pool and a solid polymer film forms. Firm formation is rapid and spontaneous and the film spreads out unaided, many feet from the leading edge of the pool. The driving force for this process is the exothermic solution of the organic solvent from the polymer solution into the water

Splittings of generalized Baumslag-Solitar groups

We study the structure of generalized Baumslag-Solitar groups from the point of view of their (usually non-unique) splittings as fundamental groups of graphs of infinite cyclic groups. We find and characterize certain decompositions of smallest complexity (`fully reduced' decompositions) and give a simplified proof of the existence of deformations. We also prove a finiteness theorem and solve the isomorphism problem for generalized Baumslag-Solitar groups with no non-trivial integral moduli.Comment: 20 pages; hyperlinked latex. Version 2: minor change

Design of agronomic experiments for plots differentiated in fertility by past treatments

With the increase in agricultural field trials in recent years, the question of the use of former sites of concluded experiments is becoming of ever increasing importance. It was the aim of the present study to define the possible methods by which areas which have been differentially treated in past experiments may be effectively utilized in new experiments and to determine the efficiency of the various methods. Methods of design were tested using the yields from a field which formed a portion of a rotation and fertilizer experiment conducted at the Iowa Agricultural Experiment Station since 1915. The possible methods of design were grouped under two heads: (a) Those in which all the treatments in the new experiment could be planted on each of the original plots; and (b) those in which the block of the new experiment comprised a number of the original plots. Reduction of the error was attempted in two ways: (a) By the grouping together of plots from different parts of the field on the basis of equal fertility (as indicated by the previous yield) to form the block of the new trial; and (b) by the application of a covariance treatment to blocks formed by the grouping of adjacent plots, using the results of the original trial as concomitant information. The efficiency of the various methods in reducing the error variance was evaluated. It was shown that on the average equal fertility grouping was little better than adjacent plot grouping. The use of covariance on the adjacent plot grouping on the basis of one year\u27s previous yield was twice as efficient as adjacent plot grouping alone. Multiple covariance on the basis of 2 previous years\u27 results was over three times as efficient in reducing the error variance. The relationship of these methods to the variable influences affecting the yield from year to year and the manner in which each did or did not utilize the available information are discussed. It was concluded that the most satisfactory method of design was to ignore the previous treatments and to form the blocks from adjacent plots in the normal manner. When the results come to hand at the end of the season the covariance adjustment should be used, supplying its own test as to its efficiency in reducing the error variance. An experiment designed so that each treatment was represented on each of the original plots was superimposed on the fertilizer trial during 1936. Three top-cross varieties of corn were tested at two rates of planting (three and four plants per hill) each of these six possible treatments being tested with normal planting as against spaced planting. The yields showed: (a) that the variety, Inbred 75 on Krug, gave the highest yields; (b) that under the dry seasonal conditions of 1936, the lower rate of planting gave the higher yield and (c) that spaced planting gave only .7 of a bushel per acre greater yield than normal planting. The error variances, both in this trial and in the case where covariance adjustments were applied to adjacent plot grouping, were comparable with the errors obtained from experiments placed on normal uniform sites, and very small differences between treatments were shown to be significant. It was shown that in certain of the suggested designs it is impossible to separate the interaction of the new treatments with the differential fertility of the original plots from the error variance and therefore such interactions may play an important part in increasing the error. In cases such as the one studied, where a variety trial was superimposed on a fertilizer trial, it is evident that this interaction, though significant, will not increase the error variance unduly. It may frequently be desirable to continue the original fertilizer trial because of its permanent nature. The bearing of the various designs on this matter is discussed and it is shown that with certain designs, the validity of the comparison of the total yields of the original plots is not disturbed by the new treatments

Used-habitat calibration plots: a new procedure for validating species distribution, resource selection, and step-selection models

“Species distribution modeling” was recently ranked as one of the top five “research fronts” in ecology and the environmental sciences by ISI's Essential Science Indicators (Renner and Warton 2013), reflecting the importance of predicting how species distributions will respond to anthropogenic change. Unfortunately, species distribution models (SDMs) often perform poorly when applied to novel environments. Compounding on this problem is the shortage of methods for evaluating SDMs (hence, we may be getting our predictions wrong and not even know it). Traditional methods for validating SDMs quantify a model's ability to classify locations as used or unused. Instead, we propose to focus on how well SDMs can predict the characteristics of used locations. This subtle shift in viewpoint leads to a more natural and informative evaluation and validation of models across the entire spectrum of SDMs. Through a series of examples, we show how simple graphical methods can help with three fundamental challenges of habitat modeling: identifying missing covariates, non-linearity, and multicollinearity. Identifying habitat characteristics that are not well-predicted by the model can provide insights into variables affecting the distribution of species, suggest appropriate model modifications, and ultimately improve the reliability and generality of conservation and management recommendations

Embedded-Cluster Calculations in a Numeric Atomic Orbital Density-Functional Theory Framework

We integrate the all-electron electronic structure code FHI-aims into the general ChemShell package for solid-state embedding (QM/MM) calculations. A major undertaking in this integration is the implementation of pseudopotential functionality into FHI-aims to describe cations at the QM/MM boundary through effective core potentials and therewith prevent spurious overpolarization of the electronic density. Based on numeric atomic orbital basis sets, FHI-aims offers particularly efficient access to exact exchange and second order perturbation theory, rendering the established QM/MM setup an ideal tool for hybrid and double-hybrid level DFT calculations of solid systems. We illustrate this capability by calculating the reduction potential of Fe in the Fe-substituted ZSM-5 zeolitic framework and the reaction energy profile for (photo-)catalytic water oxidation at TiO2(110).Comment: 12 pages, 4 figure

Stable isotope values in modern bryozoan carbonate from New Zealand and implications for paleoenvironmental interpretation

Bryozoan carbonate contains useful geochemical evidence of temperate shelf paleoenvironments. Stable isotope values were determined for 103 modern marine bryozoan skeletons representing 30 species from New Zealand. δ18O values range from -1.4 to 2.8 VPDB, while δ13C range from -4.5 to 2.8 VPDB (values uncorrected for mineralogical variation). These values are distinct from those of both tropical marine skeletons and New Zealand Tertiary fossils. Most bryozoans secrete carbonate in or near isotopic equilibrium with sea water, except for Celleporina and Steginoporella. The complex and variable mineralogies of the bryozoans reported here make correction for mineralogical effects problematic. Nevertheless, mainly aragonitic forms display higher isotope values, as anticipated. Both temperature and salinity constrain δ18O and δ13C values, and vary with latitude and water depth. Ten samples from a single branch of Cinctipora elegans from the Otago shelf cover a narrow range, although the striking difference in carbon isotope values between the endozone and exozone probably reflects different mineralisation histories. Our stable isotope results from three different laboratories on a single population from a single location are encouragingly consistent. Monomineralic bryozoans, when carefully chosen to avoid species suspected of vital fractionation, have considerable potential as geochemical paleoenvironmental indicators, particularly in temperate marine environments where bryozoans are dominant sediment producers

Electroconvulsive Therapy Practice Changes in Older Individuals Due to COVID-19: Expert Consensus Statement

© 2020 American Association for Geriatric Psychiatry The ubiquitous coronavirus 2019 (COVID-19) pandemic has required healthcare providers across all disciplines to rapidly adapt to public health guidelines to reduce risk while maintaining quality of care. Electroconvulsive therapy (ECT), which involves an aerosol-generating procedure from manual ventilation with a bag mask valve while under anesthesia, has undergone drastic practice changes in order to minimize disruption of treatment in the midst of COVID-19. In this paper, we provide a consensus statement on the clinical practice changes in ECT specific to older adults based on expert group discussions of ECT practitioners across the country and a systematic review of the literature. There is a universal consensus that ECT is an essential treatment of severe mental illness. In addition, there is a clear consensus on what modifications are imperative to ensure continued delivery of ECT in a manner that is safe for patients and Northwell Health, while maintaining the viability of ECT services. Approaches to modifications in ECT to address infection control, altered ECT procedures, and adjusting ECT operations are almost uniform across the globe. With modified ECT procedures, it is possible to continue to meet the needs of older patients while mitigating risk of transmission to this vulnerable population

Civic crowdfunding research: challenges, opportunities, and future agenda

Civic crowdfunding is a sub-type of crowdfunding through which citizens, in collaboration with government, fund projects providing a community service. Although in the early stages of development, civic crowdfunding is a promising area for both research and application due to its potential impact on citizen engagement, as well as its influence on the success of a wide range of civic projects ranging from physical structures to amenities and local services. However, the field remains under-addressed in academic research and underdeveloped in terms of the number of civic projects posted to crowdfunding platforms. Acknowledging these issues, we outline the history of civic crowdfunding and describe the current landscape, focusing on online crowdfunding platforms established specifically for the funding of civic projects (Citizinvestor, ioby, Neighbor.ly, Spacehive). The challenges and the opportunities of civic crowdfunding are examined, and its distinguishing characteristics are outlined, including a consideration of the impact of social media and platform features. We then propose a research agenda to help shape the future of this emergent field