Thermodynamics, transition dynamics, and texturing in polymer-dispersed liquid crystals with mesogens exhibiting a direct isotropic/smectic-A transition

Experimental and modeling/simulation studies of phase equilibrium and growth morphologies of novel polymer-dispersed liquid crystal (PDLC) mixtures of PS (polystyrene) and liquid crystals that exhibit a direct isotropic/smectic-A (lamellar) mesophase transition were performed for PS/10CB (decyl- cyanobiphenyl) and PS/12CB (dodecyl-cyanobiphenyl). Partial phase diagrams were determined using polarized optical microscopy (POM) and differential scanning calorimetry (DSC) for different compositions of both materials, determining both phase separation (liquid/liquid demixing) and phase ordering (isotropic/smectic-A transition) temperatures. The Flory-Huggins theory of isotropic mixing and Maier-Saupe-McMillan theory for smectic-A liquid crystalline ordering were used to computationally determine phase diagrams for both systems, showing good agreement with the experimental results. In addition to thermodynamic observations, growth morphology relations were found depending on phase transition sequence, quench rate, and material composition. Three stages of liquid crystal-rich domain growth morphology were observed: spherical macroscale domain growth ("stage I"), highly anisotropic domain growth ("stage II"), and sub-micron spheroid domain growth ("stage III"). Nano-scale structure of spheroidal and spherocylindrical morphologies were then determined via two-dimensional simulation of a high-order Landau-de Gennes model. Morphologies observed during stage II growth are typical of di- rect isotropic/smectic-A phase transitions, such as highly anisotropic "batonnets" and filaments. These morphologies, which are found to be persistent in direct isotropic/smectic-A PDLCs, could provide new functionality and applications for these functional materials.Comment: First Revision, 21 pages, 11 figures, submitted to Macromolecules as an article 17JUL200

An alternate algorithm for correction of the scanning multichannel microwave radiometer polarization radiances using Nimbus-7 observed data

The manner in which Nimbus-7 scanning multichannel microwave radiometer (SMMR) scan radiance data was used to determine its operational characteristics is described. The predicted SMMR scan radiance was found to be in disagreement at all wavelengths with a large area of average measured ocean radiances. A modified model incorporating a different phase shift for each of the SMMR horizontal and vertical polarization channels was developed and found to provide good data correlation. Additional study is required to determine the validity and accuracy of this model

RISK, GOVERNMENT PROGRAMS, AND THE ENVIRONMENT

Nearly all farm business ventures involve financial risk. In some instances, private and public tools used to manage financial risks in agriculture may influence farmers' production decisions. These decisions, in turn, can influence environmental quality. This bulletin summarizes research and provides some perspective on private and public attempts to cope with financial risks and their unintended environmental consequences. Specifically, it examines the conceptual underpinnings of risk-related research, challenges involved with measuring the consequences of risk for agricultural production decisions, government programs that influence the risk and return of farm businesses, and how production decisions influence both the environment and the risk and average returns to farming.risk, agricultural production, government programs, environment, Agricultural and Food Policy, Environmental Economics and Policy, Risk and Uncertainty,

Bryozoa from the Arctic Alaskan Coast

Lists 11, mostly common species of bryozoans collected in Aug. 1953 between 145 14 and 155 48 W; manner of occurrence and general distribution are noted. Location of each of the 12 stations, depth and sediment type from which material was collected, also presence of kelp are indicated

RESOURCE QUALITY AND AGRICULTURAL PRODUCTIVITY: A MULTI-COUNTRY COMPARISON

This paper builds on earlier studies of agricultural productivity by incorporating spatially referenced soil and climate data combined with high-resolution land-cover data. Econometric analysis of these data, along with panel data on agricultural inputs and outputs from 110 countries for 1961-1997, quantifies the significant impact that differences in land quality have on agricultural productivity.Productivity Analysis,

Ectoprocta

18 p. : ill. ; 24 cm.Includes bibliographical references (p. 17-18)

Multiple interfaces in diffusional phase transitions in binary mesogen-non-mesogen mixtures undergoing metastable phase separations

Theory and simulations of simultaneous chemical demixing and phase ordering are performed for a mixed order parameter system with an isotropic-isotropic (I-I) phase separation that is metastable with respect to an isotropic-nematic (I-N) phase ordering transition. Under certain conditions, the disordered phase transforms into an ordered phase via the motion of a double front containing a metastable phase produced by I-I demixing, a thermodynamically driven mechanism not previously reported. Different kinetic regimes are found depending on the location of the initial conditions in the thermodynamic phase diagram and the ratio between diffusional and nematic phase ordering mobilities. For a diffusional process, depending if the temperature is above or below the critical co-dissolution point, an inflection point or a phase separation takes place in the depletion layer. This phase separation leads to the formation of a second interface where the separation of the two metastable isotropic phases grows monotonically with time. The observed deviations from the typical Fickian concentration profiles are associated with strong positive deviations of the mixture from ideality due to couplings between concentration and nematic ordering. Although systems of interest include liquid crystalline nanocomposites, this novel mechanism may apply to any mixture that can undergo an order-disorder transition and demix.Comment: 24 pages, 8 figures, final accepted authors version, published version in http://pre.aps.org/abstract/PRE/v86/i1/e01160

Monogenetic near-island seamounts in the Galapagos Archipelago

Author Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 21(12), (2020): e2020GC008914, https://doi.org/10.1029/2020GC008914.Rarely have small seamounts on the flanks of hotspot derived ocean‐island volcanoes been the targets of sampling, due to sparse high‐resolution mapping near ocean islands. In the Galápagos Archipelago, for instance, sampling has primarily targeted the subaerial volcanic edifices, with only a few studies focusing on large‐volume submarine features. Sampling restricted to these large volcanic features may present a selection bias, potentially resulting in a skewed view of magmatic and source processes because mature magmatic systems support mixing and volcanic accretion that overprints early magmatic stages. We demonstrate how finer‐scale sampling of satellite seamounts surrounding the volcanic islands in the Galápagos can be used to lessen this bias and thus, better constrain the evolution of these volcanoes. Seamounts were targeted in the vicinity of Floreana and Fernandina Islands, and between Santiago and Santa Cruz. In all regions, individual seamounts are typically monogenetic, but each seamount field requires multigenerational magmatic episodes to account for their geochemical variability. This study demonstrates that in the southern and eastern regions the seamounts are characterized by greater geochemical variability than the islands they surround but all three regions have (Sr‐Nd‐He) isotopic signatures that resemble neighboring islands. Variations in seamount chemistry from alkalic to tholeiitic near Fernandina support the concept that islands along the center of the hotspot track undergo greater mean depths of melting, as predicted by plume theory. Patterns of geochemical and isotopic enrichment of seamounts within each region support fine‐scale mantle heterogeneities in the mantle plume sourcing the Galápagos hotspot.This work was carried out with funding from National Science Foundation Division of Ocean Sciences (OCE‐1634952 to V. D. Wanless, OCE‐1634685 to S. A. Soule). The authors have no competing interests to declare. We thank Sally Gibson and three anonymous reviewers for providing detailed and critical feedback on this manuscript.2021-05-0