Sublimation as a function of diffusion

Purification of large organic molecules in a tubular sublimator occurs by a combination of laminar flow, Knudsen diffusion, and volume diffusion. For laminar flow, the amount purified per area per driving force varies with pd², where p is pressure and d is tube diameter. For Knudsen diffusion, it varies with d and is not a function of pressure. For volume diffusion, it is constant, consistent with experiment. This volume diffusion mechanism may offer an alternative explanation to slip flow for dilute gas transport of both organic semiconductors and common low molecular weight gases. © 2015 American Institute of Chemical Engineers AIChE J, 62: 861–867, 2016     

Carbon Nanotube Multilayer Nanocoatings Prevent Flame Spread on Flexible Polyurethane Foam

In an effort to protect polyurethane foam (commonly used as cushioning in upholstered furniture) from fire using environmentally benign chemistries, nanocomposite thin films are deposited using water‐based solutions of cationic‐ and anionic‐stabilized multiwalled carbon nanotubes (MWCNTs). The open‐celled foam is coated using layer‐by‐layer (LbL) assembly to produce uniform protective layers up to 600 nm thick, comprised of cationic polyethylenimine modified with pyrene (PEI‐Py), anionic poly(acrylic acid) (PAA), and MWCNT. Film thickness is found to rely heavily on the PAA‐stabilized MWCNT solution. Coatings of only six [PEI‐Py/PAA+MWCNT] bilayers (BL) show tremendous reductions in peak heat release rate (up to 67%) and total smoke release (up to 80%) for the polyurethane foam. This same coating significantly improves the performance of the polyurethane when exposed to horizontal and vertical flame tests. With 9 BL, the foam successfully withstands a vertical burn test, self‐extinguishing immediately after removal of the test flame. These dramatic reductions in foam flammability are unprecedented and are attributed to the protective nature of the carbon‐based char formed from the coating that acts as a protective barrier.

     

Characterization of volatile organic compounds in human leukocyte antigen heterologous expression systems: a cell's "chemical odor fingerprint"

The major histocompatibility complex (MHC), or human leukocyte antigen (HLA) gene‐coding region in humans, plays a significant role in infectious disease response, autoimmunity, and cellular recognition. This super locus is essential in mate selection and kin recognition because of the organism‐specific odor which can be perceived by other individuals. However, how the unique MHC genetic combination of an organism correlates with generation of the organism‐specific odor is not well understood. In the present work, we have shown that human B‐cells produce a set of volatile organic compounds (VOCs) that can be measured by GC‐MS. More importantly, our results show that specific HLA alleles are related to production of selected VOCs, and that this leads to a cell‐specific odor “fingerprint”. We used a C1R HLA class I A and B locus negative cell line, along with C1R cell lines that were stably transfected with specific A and B alleles. Our work demonstrates for the first time that HLA alleles can directly influence production of specific odor compounds at the cellular level. Given that the resulting odor fingerprint depends on expression of specific HLA sequences, it may yield information on unique human scent profiles, composition of exhaled breath, as well as immune response states in future studies.     

Polyphenylenepyridyl dendrimers as stabilizing and controlling agents for CdS nanoparticle formation

Semiconductor nanoparticles (NPs) are being actively explored for applications in medical diagnostics and therapy and numerous electronic devices including solar cells. In this paper we demonstrate the influence of the third generation rigid polyphenylenepyridyl dendrimers (PPPDs) of a different architecture on the formation of well-defined CdS NPs. A high temperature approach to the synthesis of novel CdS/PPPD nanocomposites is feasible due to the high thermal stability of PPPDs. The PPPD architecture affects the CdS NP formation: larger NPs are obtained in the presence of dendrimers with 1,3,5-triphenylbenzene cores compared to those with tetrakis(4-ethynylphen-1-yl)methane cores. The reaction conditions such as concentrations of PPPDs and NP precursors and the temperature regime also influence the CdS NP sizes. For the first time, we elucidated a mechanism of CdS NP formation in a non-coordinating solvent through the CdO redispersion in the presence of PPPDs. Interesting optical properties of these CdS/PPPD nanocomposites make them promising candidates for imaging applications.     

Raman Spectroscopic Mapping of the Carbon and PTFE Distribution in Gas Diffusion Layers

Raman microspectroscopy was used to gather spatially resolved chemical information on the carbon and poly(tetrafluoroethylene) (PTFE) distribution of fuel cell gas diffusion layers (GDL). GDLs with varying PTFE content were imaged over areas of 1,000 μm × 1,000 μm and it was found that the distribution of concentrated PTFE regions on the surface of the GDLs and morphology of the carbon fibre paper was readily observed. Spectroscopic measurements with point‐by‐point resolutions varying between 10 and 500 μm were performed on samples having 1.8–44 wt.% PTFE before and after the PTFE was sintered. The average PTFE signal detected on the surface of the GDLs increased monotonically for both unsintered and sintered GDLs with increasing bulk PTFE loading. The unsintered GDLs had higher PTFE signals on their surface compared to sintered GDLs and showed more concentrated PTFE regions in the mapping experiments.     

Foodways Transmission in the Standing Rock Nation

Effective foodways transmission is critical to maintain the food sovereignty of indigenous peoples. In order to determine their own foodways, indigenous communities have developed diverse systems to convey knowledge related to the procurement, preparation, distribution, and consumption of food. In recent years, community organizations are taking a more active role in facilitating foodways transmission. In the Standing Rock Nation of the northern Great Plains, several community organizations, including tribal government agencies, are creating opportunities for elders to share their knowledge about traditional foods. The impetus for these activities comes from elders themselves, who attribute high rates of diet-related diseases to a loss of knowledge about traditional foods. We conducted eighteen semi-structured interviews with elders and organizers in the midst of these activities to reflect on processes of foodways transmission, including the implications of facilitation by community organizations. Interviews were focused on four human ecological concepts: perception and diversity; human ecological relations; context; and practical wisdom. Insights generated through our discussions were immediately applicable to the ongoing activities in Standing Rock and can inform elders and community organizations leading similar efforts in other communities.     

Regulation of hepatic cytochrome P450 2C11 by transforming growth factor-beta, hepatocyte growth factor, and interleukin-11

Injection of rats with bacterial lipopolysaccharide down-regulates P450 (P450) 2C11 (2C11) mRNA to about 20% of its control levels after only 6 hr, and this level is maintained for at least 48 hr. Although we and others have demonstrated that this effect may be at least partially mediated by the cytokines interleukin-1, interleukin-6, and tumor necrosis factor-alpha, as well as by glucocorticoids, the time courses and potencies of 2C11 repression by each single mediator suggested that no cytokine alone is responsible for the entire time course of 2C11 suppression during inflammation. Here, we show that transforming growth factor-beta, hepatocyte growth factor, and interleukin-11 are potent inhibitors of 2C11 expression. In all three cases, 0.1 ng/ml was enough to down-regulate 2C11 mRNA levels to 50% of control. Interleukin-8, a cytokine that is secreted during the acute phase response but does not influence the liver acute phase response, did not affect 2C11 expression. The various mediators have different time courses of 2C11 down-regulation, indicating that the roles of each may be different at different phases of the response.     

Chemical Composition of Metapleural Gland Secretions of Fungus-Growing and Non-fungus-growing Ants

The metapleural gland is exclusive to ants, and unusual among exocrine glands in having no mechanism for closure and retention of secretion. As yet, no clear conclusion has been reached as to the function of metapleural gland secretion. Metapleural gland secretions were investigated for fungus-growing ants representing the derived attines Trachymyrmex fuscus, Atta laevigata, and Acromyrmex coronatus, the basal attines Apterostigma pilosum and Mycetarotes parallelus, and non-fungus-growing ants of the tribes Ectatommini (Ectatomma brunneum) and Myrmicini (Pogonomyrmex naegeli). Our results showed that the secretions of leaf-cutting ants (A. laevigata and A. coronatus) and the derived attine, T. fuscus, contain a greater variety and larger quantities of volatile compounds than those of myrmicine and ectatommine ants. The most abundant compounds found in the metapleural glands of A. laevigata and A. coronatus were hydroxyacids, and phenylacetic acid (only in A. laevigata). Indole was present in all groups examined, while skatole was found in large quantities only in attines. Ketones and aldehydes are present in the secretion of some attines. Esters are present in the metapleural gland secretion of all species examined, although mainly in A. laevigata, A. coronatus, and T. fuscus. Compared with basal attines and non-fungus-growing ants, the metapleural glands of leaf-cutting ants produce more acidic compounds that may have an antibiotic or antifungal function.