Polymer Nanocomposites Containing High Aspect Ratio Particulates: Innovation in Co-Extruded Multilayer Barrier Films

Delaminated montmorillonite (MMT) clay/ maleic anhydride grafted LLDPE nanocomposite multilayer films with alternating layers of LDPE were produced through multilayer co-extrusion. The MMT concentration within the nanocomposite layers was increased through annealing the films in the melt due to a mismatch in interdiffusion rates of the polymer layers. Analysis of the nanocomposite layers upon annealing revealed that the platelets impinged upon one another resulting in significant improvement in oxygen barrier in the multilayer system, exceeding the results of bulk nanocomposites. Model analysis demonstrated that increasing the nanoplatelet aspect ratio or initial concentration in the filled layers would lead to even higher barrier. This lead to an investigation into high aspect ratio graphene nanoplatelete composites. Gas and fire barrier, mechanical, and thermal property enhancement of polyethylene/ short stack graphene nanoplatelet (xGnP) composite systems were thoroughly analyzed in bulk composites and multilayers. Through incorporation of a small amount of xGnP in LLDPE, a substantial increase in barrier and mechanical strength was observed, even without polymer/platelet modification. Composite layer shrinkage from controlled interdiffusion in the melt was confirmed and resulted in a decrease in permeability for the coextruded films that reflected barrier properties of composite multilayers with initially more GnPs. Finally, to better understand clay-polymer interactions, amorphous hyperbranched polyester (HBP)/MMT nanocomposites were studied. With increasing clay content, the composites’ glass transition (Tg) and heat capacity (∆Cp) at Tg showed behavior indicative of the suppression of the HBP’s segmental mobility. This behavior correlated to changes in intercalation interlayer spacing. The fraction of the mobile amorphous fraction (MAF), which contributed to the change in heat capacity at Tg,and corresponding rigid amorphous fraction (RAF) were calculated based on the corresponding ∆Cp. Calculation of interlayer spacings from the ∆Cp data were in agreement with those determined by x-ray diffraction. The results demonstrated that changes in the RAF and MAF content depend on both the clay volume fraction and the clay morphology. Furthermore, a novel approach to estimate MAF and RAF via positron annihilation lifetime spectroscopy (PALS) from the thermal expansivities of free volume hole sizes in the liquid and glassy states was proposed

How Do Mode and Timing of Follow-Up Surveys Affect Evaluation Success?

This article presents the analysis of evaluation methods used in a well-designed and comprehensive evaluation effort of a significant Extension program. The evaluation data collection methods were analyzed by questionnaire mode and timing of follow-up surveys. Response rates from the short- and long-term follow-ups and different questionnaire modes by occupational categories also were examined. Overall, the electronic questionnaire mode and 2-month follow-ups yielded significantly higher response rates. The findings have implications for meaningfully evaluating Extension programs operating with limited resources. The recommendations are useful to Extension educators who need to decide how to capture program outcomes but have limited resources

The Effect of a Gluten-Free Diet in Children With Difficult-to-Manage Nephrotic Syndrome

Case reports have linked childhood nephrotic syndrome to food sensitivity, including gluten. We report our experience with 8 children (6 boys, 2 girls; age at implementation of special diet 2–14 years) with difficult-to-manage nephrotic syndrome who were placed on a gluten-free diet for 3.4 ± 4.3 years (range, 0.6–14 years) and who had clinical improvement enabling reduction or discontinuation in steroid dosage

Systems Theory as the Foundation for Understanding Systems

As currently used, systems theory is lacking a universally agreed upon definition. The purpose of this paper is to offer a resolution by articulating a formal definition of systems theory. This definition is presented as a unified group of specific propositions which are brought together by way of an axiom set to form a system construct: systems theory. This construct affords systems practitioners and theoreticians with a prescriptive set of axioms by which a system must operate; conversely, any set of entities identified as a system may be characterized by this set of axioms. Given its multidisciplinary theoretical foundation and discipline-agnostic framework, systems theory, as it is presented here, is posited as a general approach to understanding system behavior. © 2013 Wiley Periodicals, Inc

The fundamental equation of eddy covariance and its application in flux measurements

A fundamental equation of eddy covariance (FQEC) is derived that allows the net ecosystem exchange (NEE) N̅s of a specified atmospheric constituent s to be measured with the constraint of conservation of any other atmospheric constituent (e.g. N2, argon, or dry air). It is shown that if the condition │N̅s│ ˃˃ │X̅s│ │N̅co2│is true, the conservation of mass can be applied with the assumption of no net ecosystem source or sink of dry air and the FQEC is reduced to the following equation and its approximation for horizontally homogeneous mass fluxes: N̅s = c̅dw’X’s│h + ∫h0 c̅d(z) ∂Xs/∂t dz + ∫h0 [X̅s (z)- X̅s (h)] ∂̅c̅d̅/∂t dz = c̅d̅(h) {w̅’X̅’s│h + ∫h0 ∂Xs/∂t dz}. Here w is vertical velocity, c molar density, t time, h eddy flux measurement height, z vertical distance and Xs= cs/cd molar mixing ratio relative to dry air. Subscripts s, d and CO2 are for the specified constituent, dry air and carbon dioxide, respectively. Primes and overbars refer to turbulent fluctuations and time averages, respectively. This equation and its approximation are derived for non-steady state conditions that build on the steady-state theory of Webb, Pearman and Leuning (WPL; Webb et al., 1980. Quart. J. R. Meteorol. Soc. 106, 85–100), theory that is widely used to calculate the eddy fluxes of CO2 and other trace gases. The original WPL constraint of no vertical flux of dry air across the EC measurement plane, which is valid only for steady-state conditions, is replaced with the requirement of no net ecosystem source or sink of dry air for non-steady state conditions. This replacement does not affect the ‘eddy flux’ term c̅d̅w̅’X̅’s s but requires the change in storage to be calculated as the ‘effective change in storage’ as follows: ∫h0 ∂̅c̅s̅/ ∂̅t̅ dz – X̅s(h) ∫h0 ∂̅c̅d̅/∂t dz = ∫h0 c̅d̅ (z) - ∂Xs/∂t dz + ∫h0 [X̅s (z)- X̅s (h)] ∂̅c̅d̅/∂t dz= c̅d (h) ∫h0 ∂Xs/∂t dz. Without doing so, significant diurnal and seasonal biases may occur. We demonstrate that the effective change in storage can be estimated accurately with a properly designed profile of mixing ratio measurements made at multiple heights. However further simplification by using a single measurement at the EC instrumentation height is shown to produce substantial biases. It is emphasized that an adequately designed profile system for measuring the effective change in storage in proper units is as important as the eddy flux term for determining NEE

Tenofovir-Associated Nephrotoxicity in Two HIV-Infected Adolescent Males

We report two cases of tenofovir (TDF)-associated nephrotoxicity in perinatally HIV-infected adolescents. The first case, a 16-year-old African American male with an absolute CD4+ cell count of 314 cells/mm3, presented with an abrupt rise in serum creatinine leading to irreversible renal failure while on TDF-containing highly active antiretroviral therapy (HAART). While the patient had evidence of underlying kidney disease, the timing of his renal failure indicates that TDF played a central role. The second case, a 16-year-old African-American male with an absolute CD4+ cell count of 895 cells/mm3, presented with rickets and hypophosphatemia while receiving TDF-based HAART. To our knowledge, these cases represent the first reports of TDF-associated irreversible renal failure and rickets in pediatric patients. We believe these cases highlight important and potentially irreversible side effects of this agent and emphasize the need for further studies of the renal safety of TDF in pediatric patients

The fundamental equation of eddy covariance and its application in flux measurements

A fundamental equation of eddy covariance (FQEC) is derived that allows the net ecosystem exchange (NEE) N̅s of a specified atmospheric constituent s to be measured with the constraint of conservation of any other atmospheric constituent (e.g. N2, argon, or dry air). It is shown that if the condition │N̅s│ ˃˃ │X̅s│ │N̅co2│is true, the conservation of mass can be applied with the assumption of no net ecosystem source or sink of dry air and the FQEC is reduced to the following equation and its approximation for horizontally homogeneous mass fluxes: N̅s = c̅dw’X’s│h + ∫h0 c̅d(z) ∂Xs/∂t dz + ∫h0 [X̅s (z)- X̅s (h)] ∂̅c̅d̅/∂t dz = c̅d̅(h) {w̅’X̅’s│h + ∫h0 ∂Xs/∂t dz}. Here w is vertical velocity, c molar density, t time, h eddy flux measurement height, z vertical distance and Xs= cs/cd molar mixing ratio relative to dry air. Subscripts s, d and CO2 are for the specified constituent, dry air and carbon dioxide, respectively. Primes and overbars refer to turbulent fluctuations and time averages, respectively. This equation and its approximation are derived for non-steady state conditions that build on the steady-state theory of Webb, Pearman and Leuning (WPL; Webb et al., 1980. Quart. J. R. Meteorol. Soc. 106, 85–100), theory that is widely used to calculate the eddy fluxes of CO2 and other trace gases. The original WPL constraint of no vertical flux of dry air across the EC measurement plane, which is valid only for steady-state conditions, is replaced with the requirement of no net ecosystem source or sink of dry air for non-steady state conditions. This replacement does not affect the ‘eddy flux’ term c̅d̅w̅’X̅’s s but requires the change in storage to be calculated as the ‘effective change in storage’ as follows: ∫h0 ∂̅c̅s̅/ ∂̅t̅ dz – X̅s(h) ∫h0 ∂̅c̅d̅/∂t dz = ∫h0 c̅d̅ (z) - ∂Xs/∂t dz + ∫h0 [X̅s (z)- X̅s (h)] ∂̅c̅d̅/∂t dz= c̅d (h) ∫h0 ∂Xs/∂t dz. Without doing so, significant diurnal and seasonal biases may occur. We demonstrate that the effective change in storage can be estimated accurately with a properly designed profile of mixing ratio measurements made at multiple heights. However further simplification by using a single measurement at the EC instrumentation height is shown to produce substantial biases. It is emphasized that an adequately designed profile system for measuring the effective change in storage in proper units is as important as the eddy flux term for determining NEE

Predictive Analytics Supporting Labor Market Success: A Career Explorer for Job Seekers and Workforce Professionals in Michigan

Career Explorer provides customized career exploration tools for workforce development staff and job seekers in Michigan. There are separate Career Explorer modules for mediated staff services and self-service by job seekers. The system was developed by the Michigan Center for Data and Analytics in collaboration with the W.E. Upjohn Institute for Employment Research and Michigan Works! Southwest. It was funded by the U.S. Department of Labor’s Office of Workforce Investment and the Schmidt Futures foundation’s Data for the American Dream (D4AD) project. In this paper, we describe specifications of the models behind the frontline-staff-mediated version of Career Explorer, which are based on program administrative data, applying data-science methods for predictive analytics. We also describe the self-service Career Explorer, which provides customized labor market information based on published Bureau of Labor Statistics data. Career Explorer became an active feature of Michigan’s online reemployment-services system in June 2021

Paradoxical enhancement of fear extinction memory and synaptic plasticity by inhibition of the histone acetyltransferase p300

It is well established that the coordinated regulation of activity-dependent gene expression by the histone acetyltransferase (HAT) family of transcriptional coactivators is crucial for the formation of contextual fear and spatial memory, and for hippocampal synaptic plasticity. However, no studies have examined the role of this epigenetic mechanism within the infralimbic prefrontal cortex (ILPFC), an area of the brain that is essential for the formation and consolidation of fear extinction memory. Here we report that a postextinction training infusion of a combined p300/CBP inhibitor (Lys-CoA-Tat), directly into the ILPFC, enhances fear extinction memory in mice. Our results also demonstrate that the HAT p300 is highly expressed within pyramidal neurons of the ILPFC and that the small-molecule p300-specific inhibitor (C646) infused into the ILPFC immediately after weak extinction training enhances the consolidation of fear extinction memory. C646 infused 6 h after extinction had no effect on fear extinction memory, nor did an immediate postextinction training infusion into the prelimbic prefrontal cortex. Consistent with the behavioral findings, inhibition of p300 activity within the ILPFC facilitated long-term potentiation (LTP) under stimulation conditions that do not evoke long-lasting LTP. These data suggest that one function of p300 activity within the ILPFC is to constrain synaptic plasticity, and that a reduction in the function of this HAT is required for the formation of fear extinction memory

Apportioning sources of organic matter in streambed sediments: An integrated molecular and compound-specific stable isotope approach

We present a novel application for quantitatively apportioning sources of organic matter in streambed sediments via a coupled molecular and compound-specific isotope analysis (CSIA) of long-chain leaf wax n-alkane biomarkers using a Bayesian mixing model. Leaf wax extracts of 13 plant species were collected from across two environments (aquatic and terrestrial) and four plant functional types (trees, herbaceous perennials, and C3 and C4 graminoids) from the agricultural River Wensum catchment, UK. Seven isotopic (δ13C27, δ13C29, δ13C31, δ13C27–31, δ2H27, δ2H29, and δ2H27–29) and two n-alkane ratio (average chain length (ACL), carbon preference index (CPI)) fingerprints were derived, which successfully differentiated 93% of individual plant specimens by plant functional type. The δ2H values were the strongest discriminators of plants originating from different functional groups, with trees (δ2H27–29 = − 208‰ to − 164‰) and C3 graminoids (δ2H27–29 = − 259‰ to − 221‰) providing the largest contrasts. The δ13C values provided strong discrimination between C3 (δ13C27–31 = − 37.5‰ to − 33.8‰) and C4 (δ13C27–31 = − 23.5‰ to − 23.1‰) plants, but neither δ13C nor δ2H values could uniquely differentiate aquatic and terrestrial species, emphasizing a stronger plant physiological/biochemical rather than environmental control over isotopic differences. ACL and CPI complemented isotopic discrimination, with significantly longer chain lengths recorded for trees and terrestrial plants compared with herbaceous perennials and aquatic species, respectively. Application of a comprehensive Bayesian mixing model for 18 streambed sediments collected between September 2013 and March 2014 revealed considerable temporal variability in the apportionment of organic matter sources. Median organic matter contributions ranged from 22% to 52% for trees, 29% to 50% for herbaceous perennials, 17% to 34% for C3 graminoids and 3% to 7% for C4 graminoids. The results presented here clearly demonstrate the effectiveness of an integrated molecular and stable isotope analysis for quantitatively apportioning, with uncertainty, plant-specific organic matter contributions to streambed sediments via a Bayesian mixing model approach