- Award ID(s):
- Publication Date:
- NSF-PAR ID:
- Journal Name:
- Photonics Conference (IPC), 2016 IEEE
- Page Range or eLocation-ID:
- 339 to 340
- Sponsoring Org:
- National Science Foundation
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ABSTRACT: Biochar has been proposed as a soil amendment in agricultural applications due to its advantageous adsorptive properties, high porosity, and low cost. These properties allow biochar to retain soil nutrients, yet the effects of biochar on bacterial growth remain poorly understood. To examine how biochar influences microbial metabolism, Escherichia coli was grown in a complex, well-defined media and treated with either biochar or activated carbon. The concentration of metabolites in the media were then quantified at several time points using NMR spectroscopy. Several metabolites were immediately adsorbed by the char, including L-asparagine, L-glutamine, and L-arginine. However, we find that biochar quantitatively adsorbs less of these metabolic precursors when compared to activated carbon. Electron microscopy reveals differences in surface morphology after cell culture, suggesting that Escherichia coli can form biofilms on the surfaces of the biochar. An examination of significant compounds in the tricarboxylic acid cycle and glycolysis reveals that treatment with biochar is less disruptive than activated carbon throughout metabolism. While both biochar and activated carbon slowed growth compared to untreated media, Escherichia coli in biochartreated media grew more efficiently, as indicated by a longer logarithmic growth phase and a higher final cell density. This work suggests that biocharmore »
Reactivity of industrial wastes as measured through ICP‐OES: A case study on siliceous Indian biomass ash
An untapped source of amorphous SiO2, industrially generated Indian biomass ash (SA)—90% amorphous, with composition of ~60% SiO2and ~20% unburnt carbon—can be used to produce cementitious and alkali‐activated binders. This study reports dissolution of amorphous Si from SA in 0.5 mol/L and 1 mol/L aqueous NaOH, with and without added Ca(OH)2, at SA:Ca(OH)2wt% ratios of 100:0, 87.5:12.5, and 82.5:17.5. Monitoring of elemental dissolution and subsequent/simultaneous product uptake by ICP‐OES offers an effective process for evaluating utility of industrial wastes in binder‐based systems. After 28 days in solution, up to 68% of total Si is dissolved from SA in 1 mol/L NaOH, with values as much as 38% lower in the presence of Ca(OH)2, due to the formation of tobermorite‐like C‐S‐H. FTIR,29Si MAS‐NMR, and XRD are used to characterize solid reaction products and observe reaction progress. Product chemistries calculated from ICP‐OES results and verified by selective dissolution in EDTA/NaOH—namely, Ca/Si of 0.6‐1 and Na adsorption of 1‐2 mmol/g—are found to be consistent with those indicated by aforementioned techniques. This indicates the efficacy of ICP‐OES in estimating product chemistry via such a methodology.
Stereoregularity significantly influences the crystallization, mechanical, and thermal properties of polymers. In this work, we investigate crystallization behaviors and molecular dynamics of atactic (a)-, isotactic (i)-, and syndiotactic (s)-hydrogenated poly(norbornene) (hPNB)s by using small-angle X-ray scattering and solid-state (ss) NMR. a-hPNB exhibits a much higher crystallinity (Φc) (82%) and long period (L) (80 nm) than i- and s-hPNB (50–55% and 17–21 nm). Moreover, in the s-hPNB crystalline region, chain dynamics is not thermally activated up to the melting temperature (Tm), while in the crystalline regions of i- and a-hPNB, small amplitude motions occur in a slow dynamic regime of 10–2–102 s. The molecular dynamics follows Arrhenius behavior in a-hPNB up to the crystal–crystal transition temperature (Tcc), while these dynamics are surprisingly saturated in i-hPNB under these conditions. Temperature dependence of the molecular dynamics leads to different crystal–crystal transitions between i- and a-hPNBs: i-hPNB changes the trans conformation to the gauche one due to the localized bond rotations where chain dynamics is restricted, whereas a-hPNB keeps a nearly trans conformation and conducts fast chain dynamics due to the amplified C–C bond rotations in the high-temperature phase. Such fast chain dynamics leads to unique crystallization behaviors of hPNB, specifically in the atacticmore »
Unambiguous Stereochemical Assignment of Cyclo(Phe-Pro), Cyclo(Leu-Pro), and Cyclo(Val-Pro) by Electronic Circular Dichroic Spectroscopy2,5-diketopiperazines (DKPs) are cyclic dipeptides ubiquitously found in nature. In particular, cyclo(Phe-Pro), cyclo(Leu-Pro), and cyclo(Val-Pro) are frequently detected in many microbial cultures. Each of these DKPs has four possible stereoisomers due to the presence of two chirality centers. However, absolute configurations of natural DKPs are often ambiguous due to the lack of a simple, sensitive, and reproducible method for stereochemical assignment. This is an important problem because stereochemistry is a key determinant of biological activity. Here, we report a synthetic DKP library containing all stereoisomers of cyclo(Phe-Pro), cyclo(Leu-Pro), and cyclo(Val-Pro). The library was subjected to spectroscopic characterization using mass spectrometry, NMR, and electronic circular dichroism (ECD). It turned out that ECD can clearly differentiate DKP stereoisomers. Thus, our ECD dataset can serve as a reference for unambiguous stereochemical assignment of cyclo(Phe-Pro), cyclo(Leu-Pro), and cyclo(Val-Pro) samples from natural sources. The DKP library was also subjected to a biological screening using assays for E. coli growth and biofilm formation, which revealed distinct biological effects of cyclo(D-Phe-L-Pro).
Synthesis, structural characterization and NMR studies of group 10 metal complexes with macrocyclic amine N-heterocyclic carbene ligandsA series of Ni( ii ), Pd( ii ) and Pt( ii ) complexes [ML][PF 6 ] 2 [L = L 1 , M = Ni ( 1 ), Pd ( 2 ), Pt ( 3 ); L = L 2 , M = Ni ( 4 ), Pd ( 5 ), Pt ( 6 )] and [Pt(L 2 )(acac)] ( 7 ) have been prepared by the reactions of two tetradentate macrocyclic amine-NHC ligand precursors, [H 2 L 1 ][PF 6 ] 2 and [H 2 L 2 ][PF 6 ] 2 , with Ni(OAc) 2 ·4H 2 O, Pd(OAc) 2 and Pt(acac) 2 in the presence of NaOAc. Complex 7 is isolated along with 6 from the same reaction between [H 2 L 2 ][PF 6 ] 2 and Pt(acac) 2 . There are two atropisomers in 1–3 and two achiral conformers in 4–6 . The crystal structures of 1–3 and one conformer of 4–6 ( 4a–6a ) have been determined by single-crystal X-ray diffraction studies. The metal ion is found to reside in the cavity of the macrocyclic ring and adopts a square-planar configuration. Detailed NMR studies including variable-temperature NMR spectroscopy reveal a dynamic interconverting process betweenmore »