Pd/silica cluster catalysts: synthesis and reactivity with H2 and C2H4

Silica-supported Pd clusters were characterized by in situ EXAFS spectroscopy. Clusters with an average nuclearity of six atoms were derived from either an inorganic or an organometallic precursor by reduction at 100–150C. Despite the small size of the clusters, EXAFS contributions from the metal-support interface were not detected. These clusters and larger ones formed by reduction at 320C absorb hydrogen on cooling in H₂ to 30C; the resultant interstitial hydride species decompose in vacuo at 30C. Vacuum treatment at 300C removes chemisorbed H₂ yielding bare Pd clusters. In contrast to larger crystallites, the Pd clusters do not react with C₂H₄ at 150 to form interstitial carbide species.     

Combined nonenzymatic-enzymatic method for the synthesis of simple alkyl fatty acid esters from soapstock

Soapstock (SS) is a by-product of the extraction of oilseeds to produce edible oils. Annual U.S. production exceeds one-half million tons. A representative sample of SS consists of 45.1% water, 10.0% free fatty acids, 10.1% triglycerides, 1.8% diglycerides, 3.6% phosphatidylethanolamine, 2.2% phosphatidylinositol, 2.7% phosphatidylcholine, 14.0% solvent-insolubles and 10.5% other material, which was not characterized. A process has been developed that sequentially employs a nonenzymatic and an enzymatic step to convert the lipid-linked and the free fatty acids of SS to the esters of monohydric alcohols. The first step of the process employed alcohol and potassium hydroxide to transesterify the glyceride-and phosphoglyceride-linked fatty acids of the substrate. Because water inhibited the reaction, it was necessary that the SS be dried before use. Nonetheless, even with some batches of SS with water contents below 1% (weight basis), ester hydrolysis accompanied esterification. Each of five examined simple primary alcohols participated effectively in the transesterification reaction, which proceeded rapidly at room temperature and was essentially complete within 1 h. The average ratio of transesterification to hydrolysis in four examined small primary alcohols was 4:1. However, in methanol this value was 99:1 due to the virtual absence of hydrolysis. Significant transesterification by a secondary alcohol (isopropanol) did not occur at room temperature. The minimum effective molar ratio of alcohol to lipid-linked fatty acids was 20:1. The minimum effective concentration of KOH was between 0.10 and 0.15N. The efficiency of the transesterification reaction exceeded 90% of theoretical maximum. The second step of the process involves lipase-mediated esterification of the free fatty acids in the preparation that are not esterified by the alkaline transesterfication. Of four lipase preparations examined (Novo Lipozyme IM 20 and SP435, and Amano PS30 and CE), only SP-435 catalyzed significant esterification of the free fatty acids. The reaction was not catalyzed by heat-denatured enzyme. In the pH range between 6 and 13.5, the enzyme reaction proceeded best at pH 6, although also well at pH 7. The optimal water concentration was 0.70% (vol/vol). At an enzyme dosage of 1.1% (weight basis, relative to the dry weight of SS present) under optimal conditions and at 42°C, 63% of the free fatty acids in a post-alcoholysis mixture were enzymatically esterified. The addition of molecular sieves did not increase esterification, which was probably retarded by the high viscosities of the reactions. Under the optimal conditions identified here, the degree of conversion of the fatty acids in SS to simple alkyl esters by the combined reaction scheme was 81%. Opportunities exist for further optimization of these reactions.     

SULFUR RECOVERY WITH REDUCED EMISSIONS, LOW CAPITAL INVESTMENT AND HYDROGEN CO-PRODUCTION

The main disadvantage of the Claus process is that by introducing air as oxidant a large volume of tail gas is produced. This must be treated to reduce atmospheric emissions of sulfur-containing gases. The costs of the tail-gas unit are a significant fraction of the total capital and operating costs for sulfur recovery. A new process uses thermal decomposition of hydrogen sulfide in the presence of carbon dioxide instead of air oxidation. The products of this reaction are hydrogen, carbon monoxide, elemental sulfur, water vapor and carbonyl sulfide. Carbonyl sulfide is easily converted to H₂S and C0₂ by liquid- or vapor-phase hydrolysis. Unreacted H₂S and C0₂ are recovered by absorption and recycled to the reactor. Since no air is introduced, there is no tail gas and the tail-gas unit is eliminated, giving a substantial reduction in capital investment. The concentrations of sulfur-containing gases in the product streams depend only on the operation of the absorber and stripper units and can be controlled to very low levels by increasing stripper boil-up. Process operating costs depend on the level of sulfur recovery required and can also be much lower than those of the modified Claus Process.

The process chemistry depends on a shift in the equilibrium of H₂S decomposition caused by reaction of hydrogen with C0₂ by the reverse of the water-gas-shift reaction. Catalysts for this chemistry have been identified. Reactor conversion is further improved by rapid cooling of the reactor effluent gas. Other aspects of process design and operation confer further advantages with respect to the Claus process; however, the process equipment used is similar to that used in a Claus plant. Retrofit of existing plant to the new technology can therefore be considered.     

Simultaneous Inhibition of PD-1 and Stimulation of CD40 Signaling Pathways by Anti-PD-L1/CD40L Bispecific Fusion Protein Synergistically Activate Target and Effector Cells

Bispecific antibodies (BsAbs) or fusion proteins (BsAbFPs) present a promising strategy for cancer immunotherapy. Numerous BsAbs targeting coinhibitory and costimulatory pathways have been developed for retargeting T cells and antigen presenting cells (APCs). It is challenging to assess the potency of BsAb that engages two different signaling pathways simultaneously in a single assay format, especially when the two antigen targets are expressed on different cells. To explore the potency of anti-PD-L1/CD40L BsAbFP, a fusion protein that binds to human CD40 and PD-L1, we engineered CHO cells as surrogate APCs that express T cell receptor activator and PD-L1, Jurkat cells with PD-1 and NFAT-luciferase reporter as effector T cells, and Raji cell with NFkB-luciferase that endogenously expresses CD40 as accessory B cells. A novel reporter gene bioassay was developed using these cell lines that allows anti-PD-L1/CD40L BsAbFP to engages both PD-1/PD-L1 and CD40/CD40L signaling pathways in one assay. As both reporters use firefly luciferase, the effects of activating both signaling pathways is observed as an increase in luminescence, either as a higher upper asymptote, a lower EC₅₀, or both. This dual target reporter gene bioassay system reflects potential mechanism of action and demonstrated the ability of anti-PD-L1/CD40L BsAbFP to synergistically induce biological response compared to the combination of anti-PD-L1 monovalent monoclonal antibody and agonist CD40L fusion protein, or either treatment alone. The results also showed a strong correlation between the drug dose and biological response within the tested potency range with good linearity, accuracy, precision, specificity and stability indicating properties, suggesting that this “three-cell-in-one” dual target reporter gene bioassay is suitable for assessing potency, structure-function and critical quality attributes of anti-PD-L1/CD40L BsAbFP. This approach could be used for developing dual target bioassays for other BsAbs and antibodies used for combination therapy.     

Oxytocin and Food Intake Control: Neural,Behavioral, and Signaling Mechanisms

The neuropeptide oxytocin is produced in the paraventricular hypothalamic nucleus and the supraoptic nucleus of the hypothalamus. In addition to its extensively studied influence on social behavior and reproductive function, central oxytocin signaling potently reduces food intake in both humans and animal models and has potential therapeutic use for obesity treatment. In this review, we highlight rodent model research that illuminates various neural, behavioral, and signaling mechanisms through which oxytocin’s anorexigenic effects occur. The research supports a framework through which oxytocin reduces food intake via amplification of within-meal physiological satiation signals rather than by altering between-meal interoceptive hunger and satiety states. We also emphasize the distributed neural sites of action for oxytocin’s effects on food intake and review evidence supporting the notion that central oxytocin is communicated throughout the brain, at least in part, through humoral-like volume transmission. Finally, we highlight mechanisms through which oxytocin interacts with various energy balance-associated neuropeptide and endocrine systems (e.g., agouti-related peptide, melanin-concentrating hormone, leptin), as well as the behavioral mechanisms through which oxytocin inhibits food intake, including effects on nutrient-specific ingestion, meal size control, food reward-motivated responses, and competing motivations.     

Synthesis of High Refractive Index Silicone Materials Incorporating Aromatic Moieties with Adjacent Linkage Groups for Flexible Electronic Displays

The refractive index study of copoly(arylene-siloxane)s constructed with amide, ester, or ether linkage units was conducted to synthesize a step-growth polymer for application in flexible displays. The copoly(arylene-siloxane) based materials have potential use in optical applications due to their durability, flexibility, and possession of good optical clarity properties when compared to conventional silica-filled polydimethylsiloxane-based materials. Measurement of refractive index (RI) was used as the main mode of analysis due to its direct correlation to optical clarity and material flexibility. Synthesis and characterization, including RI compiled data, was performed for six series of step-growth polymers. Effects of different linkage units, namely amides, esters, and ethers, adjacent to at least one six-membered cyclic unit (aromatic or aliphatic) were evaluated. It was observed that the refractive index of these polymers was directly proportional to the aryl content; however, the influence on RI was not equal across all types of linkage units. The highest RI copolymer, poly(4,4-methylenediphenyl diisocyanate-co-carbinol-terminated polydimethylsiloxane) (MDI-SD1.0k), yielded refractive index 1.470 and molecular weight (M_n) 16,100 g/mol; however, the copolymer poly(toluene-2,4-diisocyanate-co-carbinol-terminated polydimethylsiloxane) (TDI-SD) had the highest RI (1.462) per phenyl content. The 4,4-methylenediphenyl diisocyanate (MDI), toluene-2,4-diisocyanate (TDI), and hydrogenated methylenediphenyl-4,4-diisocyanate (HMDI) amide containing linkages best improved the refractive indices of the materials studied.     

133Cs and 23Na MAS NMR Spectroscopy of Molybdate Crystallization in Model Nuclear Glasses

Sodium borosilicate base glasses modeled on French nuclear waste materials were prepared to test the dependence of crystallization product quantity and distribution on cesium‐ and molybdenum‐loading and glass cooling rate. Scanning electron microscopy shows the presence of micrometer‐sized domains of Mo‐rich crystalline precipitates. X‐ray diffraction patterns are complex but reveal the presence of sodium molybdates and CsNaMoO₄·2H₂O. ¹³³Cs and ²³Na magic‐angle spinning NMR spectroscopy exhibit distinct peaks for glassy and crystalline phases which can be quantified to obtain the identities of the individual compounds that are formed as well as the fractions of these nuclei in particular crystalline phases. In these model systems, 1 mol% Mo can be entirely incorporated into the glassy network whereas 2.5 and 5 mol% Mo produce significant quantities of crystalline phases, with little dependence on cooling rate. Cesium content appears to have a weak influence on crystallization behavior. Sodium molybdate and sodium‐cesium molybdate hydrate are the dominant devitrification phases in all cases.     

Effectiveness of cationically modified cellulose polymers for dewatering algae

A method to flocculate algal cultures of Chlamydomonas reinhardtii using four different industrially produced polymers is presented. Starting with a 1 wt% stock polymer solution, flocculation times less than 60 min were observed for 0.1 to 0.6 g polymer per L of algae culture, while control samples took greater than 1400 min to flocculate. Cell counts showed that 99% of the cells were flocculated using the polymers compared to 73% for the control. Finally, the flocculation process was successful at both 5 and 40 mL batch sizes for one polymer; therefore, the method is efficient, effective and may be scalable.