The Experts below are selected from a list of 171 Experts worldwide ranked by ideXlab platform
Jiaxu Liang - One of the best experts on this subject based on the ideXlab platform.
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a facile schiff Base Chemical approach towards molecular scale engineering of n c interface for high performance lithium sulfur batteries
Nano Energy, 2018Co-Authors: Zhichang Xiao, Debin Kong, Qi Song, Shanke Zhou, Yunbo Zhang, Amir Badshah, Jiaxu LiangAbstract:Abstract Nitrogen-doped (N-doped) carbon has great potential in lithium-sulfur (Li-S) batteries, since N-doping can not only enhance the reaction activity of the cathode but also suppress the shuttle effect. Unfortunately, the N-C interface as a critical Chemical active site is still short of a deep and detail understanding owing to the difficulty of interfacial structure engineering on the molecular scale. In this work, an interwoven coaxial cable network with ultrahigh nitrogen content of 9.56 wt% has been successfully fabricated through engineering a rationally designed Schiff-Base chemistry. This in-situ bottom-up strategy enables the targeted heteroatom doping throughout the entire networks on molecular scale. Thus, a homogenous interface between nitrogen and carbon matrix can be achieved even at such a high doping level, which is demonstrated to play the key role in facilitating the Chemical absorption of sulfur/polysulfides, and eventually improving the cycling stability of the electrode. Consequently, the composite demonstrates outstanding long cycling performance with a high specific capacity of 729 mAh g−1 after 500 cycles and a superior rate capability. The bottom-up strategy for fabricating the N-doped carbon networks will open up a new avenue for deeply understanding the critical role of interface in rational designing of N-doped carbon materials.
Eric C. Apel - One of the best experts on this subject based on the ideXlab platform.
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Missing peroxy radical sources within a summertime ponderosa pine forest
Atmospheric Chemistry and Physics, 2014Co-Authors: G M Wolfe, Christopher A. Cantrell, R L Mauldin, T Karl, Peter Harley, A. Turnipseed, W. Zheng, Frank Flocke, S. Kim, Eric C. ApelAbstract:Abstract. Organic peroxy (RO2) and hydroperoxy (HO2) radicals are key intermediates in the photoChemical processes that generate ozone, secondary organic aerosol and reactive nitrogen reservoirs throughout the troposphere. In regions with ample biogenic hydrocarbons, the richness and complexity of peroxy radical chemistry presents a significant challenge to current-generation models, especially given the scarcity of measurements in such environments. We present peroxy radical observations acquired within a ponderosa pine forest during the summer 2010 Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics and Nitrogen – Rocky Mountain Organic Carbon Study (BEACHON-ROCS). Total peroxy radical mixing ratios reach as high as 180 pptv (parts per trillion by volume) and are among the highest yet recorded. Using the comprehensive measurement suite to constrain a near-explicit 0-D box model, we investigate the sources, sinks and distribution of peroxy radicals below the forest canopy. The Base Chemical mechanism underestimates total peroxy radicals by as much as a factor of 3. Since primary reaction partners for peroxy radicals are either measured (NO) or underpredicted (HO2 and RO2, i.e., self-reaction), missing sources are the most likely explanation for this result. A close comparison of model output with observations reveals at least two distinct source signatures. The first missing source, characterized by a sharp midday maximum and a strong dependence on solar radiation, is consistent with photolytic production of HO2. The diel profile of the second missing source peaks in the afternoon and suggests a process that generates RO2 independently of sun-driven photochemistry, such as ozonolysis of reactive hydrocarbons. The maximum magnitudes of these missing sources (~120 and 50 pptv min−1, respectively) are consistent with previous observations alluding to unexpectedly intense oxidation within forests. We conclude that a similar mechanism may underlie many such observations.
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Missing peroxy radical sources within a rural forest canopy
2013Co-Authors: G M Wolfe, Christopher A. Cantrell, R L Mauldin, T Karl, Si-wan Kim, Peter Harley, A. Turnipseed, W. Zheng, Frank Flocke, Eric C. ApelAbstract:Organic peroxy (RO2) and hydroperoxy (HO2) radicals are key intermediates in the photoChemical processes that generate ozone, secondary organic aerosol and reactive nitrogen reservoirs throughout the troposphere. In regions with ample biogenic hydrocarbons, the richness and complexity of peroxy radical chemistry presents a significant challenge to current-generation models, especially given the scarcity of measurements in such environments. We present peroxy radical observations acquired within a Ponderosa pine forest during the summer 2010 Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics and Nitrogen - Rocky Mountain Organic Carbon Study (BEACHON-ROCS). Total peroxy radical mixing ratios reach as high as 180 pptv and are among the highest yet recorded. Using the comprehensive measurement suite to constrain a near-explicit 0-D box model, we investigate the sources, sinks and distribution of peroxy radicals below the forest canopy. The Base Chemical mechanism underestimates total peroxy radicals by as much as a factor of 3. Since primary reaction partners for peroxy radicals are either measured (NO) or under-predicted (HO2 and RO2, i.e. self-reaction), missing sources are the most likely explanation for this result. A close comparison of model output with observations reveals at least two distinct source signatures. The first missing source, characterized by a sharp midday maximum and a strong dependence on solar radiation, is consistent with photolytic production of HO2. The diel profile of the second missing source peaks in the afternoon and suggests a process that generates RO2 independently of sun-driven photochemistry, such as ozonolysis of reactive hydrocarbons. The maximum magnitudes of these missing sources (approximately 120 and 50 pptv min1, respectively) are consistent with previous observations alluding to unexpectedly intense oxidation within forests. We conclude that a similar mechanism may underlie many such observations.
Gregory D. Tredwell - One of the best experts on this subject based on the ideXlab platform.
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Modelling the acid/Base ^1H NMR Chemical shift limits of metabolites in human urine
Metabolomics, 2016Co-Authors: Gregory D. Tredwell, Jacob G. Bundy, Maria Iorio, Timothy M. D. EbbelsAbstract:Introduction Despite the use of buffering agents the ^1H NMR spectra of biofluid samples in metabolic profiling investigations typically suffer from extensive peak frequency shifting between spectra. These Chemical shift changes are mainly due to differences in pH and divalent metal ion concentrations between the samples. This frequency shifting results in a correspondence problem: it can be hard to register the same peak as belonging to the same molecule across multiple samples. The problem is especially acute for urine, which can have a wide range of ionic concentrations between different samples. Objectives To investigate the acid, Base and metal ion dependent ^1H NMR Chemical shift variations and limits of the main metabolites in a complex biological mixture. Methods Urine samples from five different individuals were collected and pooled, and pre-treated with Chelex-100 ion exchange resin. Urine samples were either treated with either HCl or NaOH, or were supplemented with various concentrations of CaCl_2, MgCl_2, NaCl or KCl, and their ^1H NMR spectra were acquired. Results Nonlinear fitting was used to derive acid dissociation constants and acid and Base Chemical shift limits for peaks from 33 identified metabolites. Peak pH titration curves for a further 65 unidentified peaks were also obtained for future reference. Furthermore, the peak variations induced by the main metal ions present in urine, Na^+, K^+, Ca^2+ and Mg^2+, were also measured. Conclusion These data will be a valuable resource for ^1H NMR metabolite profiling experiments and for the development of automated metabolite alignment and identification algorithms for ^1H NMR spectra.
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modelling the acid Base 1h nmr Chemical shift limits of metabolites in human urine
Metabolomics, 2016Co-Authors: Gregory D. Tredwell, Jacob G. Bundy, Maria Iorio, Timothy M. D. EbbelsAbstract:Despite the use of buffering agents the 1H NMR spectra of biofluid samples in metabolic profiling investigations typically suffer from extensive peak frequency shifting between spectra. These Chemical shift changes are mainly due to differences in pH and divalent metal ion concentrations between the samples. This frequency shifting results in a correspondence problem: it can be hard to register the same peak as belonging to the same molecule across multiple samples. The problem is especially acute for urine, which can have a wide range of ionic concentrations between different samples. To investigate the acid, Base and metal ion dependent 1H NMR Chemical shift variations and limits of the main metabolites in a complex biological mixture. Urine samples from five different individuals were collected and pooled, and pre-treated with Chelex-100 ion exchange resin. Urine samples were either treated with either HCl or NaOH, or were supplemented with various concentrations of CaCl2, MgCl2, NaCl or KCl, and their 1H NMR spectra were acquired. Nonlinear fitting was used to derive acid dissociation constants and acid and Base Chemical shift limits for peaks from 33 identified metabolites. Peak pH titration curves for a further 65 unidentified peaks were also obtained for future reference. Furthermore, the peak variations induced by the main metal ions present in urine, Na+, K+, Ca2+ and Mg2+, were also measured. These data will be a valuable resource for 1H NMR metabolite profiling experiments and for the development of automated metabolite alignment and identification algorithms for 1H NMR spectra.
Timothy M. D. Ebbels - One of the best experts on this subject based on the ideXlab platform.
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Modelling the acid/Base ^1H NMR Chemical shift limits of metabolites in human urine
Metabolomics, 2016Co-Authors: Gregory D. Tredwell, Jacob G. Bundy, Maria Iorio, Timothy M. D. EbbelsAbstract:Introduction Despite the use of buffering agents the ^1H NMR spectra of biofluid samples in metabolic profiling investigations typically suffer from extensive peak frequency shifting between spectra. These Chemical shift changes are mainly due to differences in pH and divalent metal ion concentrations between the samples. This frequency shifting results in a correspondence problem: it can be hard to register the same peak as belonging to the same molecule across multiple samples. The problem is especially acute for urine, which can have a wide range of ionic concentrations between different samples. Objectives To investigate the acid, Base and metal ion dependent ^1H NMR Chemical shift variations and limits of the main metabolites in a complex biological mixture. Methods Urine samples from five different individuals were collected and pooled, and pre-treated with Chelex-100 ion exchange resin. Urine samples were either treated with either HCl or NaOH, or were supplemented with various concentrations of CaCl_2, MgCl_2, NaCl or KCl, and their ^1H NMR spectra were acquired. Results Nonlinear fitting was used to derive acid dissociation constants and acid and Base Chemical shift limits for peaks from 33 identified metabolites. Peak pH titration curves for a further 65 unidentified peaks were also obtained for future reference. Furthermore, the peak variations induced by the main metal ions present in urine, Na^+, K^+, Ca^2+ and Mg^2+, were also measured. Conclusion These data will be a valuable resource for ^1H NMR metabolite profiling experiments and for the development of automated metabolite alignment and identification algorithms for ^1H NMR spectra.
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modelling the acid Base 1h nmr Chemical shift limits of metabolites in human urine
Metabolomics, 2016Co-Authors: Gregory D. Tredwell, Jacob G. Bundy, Maria Iorio, Timothy M. D. EbbelsAbstract:Despite the use of buffering agents the 1H NMR spectra of biofluid samples in metabolic profiling investigations typically suffer from extensive peak frequency shifting between spectra. These Chemical shift changes are mainly due to differences in pH and divalent metal ion concentrations between the samples. This frequency shifting results in a correspondence problem: it can be hard to register the same peak as belonging to the same molecule across multiple samples. The problem is especially acute for urine, which can have a wide range of ionic concentrations between different samples. To investigate the acid, Base and metal ion dependent 1H NMR Chemical shift variations and limits of the main metabolites in a complex biological mixture. Urine samples from five different individuals were collected and pooled, and pre-treated with Chelex-100 ion exchange resin. Urine samples were either treated with either HCl or NaOH, or were supplemented with various concentrations of CaCl2, MgCl2, NaCl or KCl, and their 1H NMR spectra were acquired. Nonlinear fitting was used to derive acid dissociation constants and acid and Base Chemical shift limits for peaks from 33 identified metabolites. Peak pH titration curves for a further 65 unidentified peaks were also obtained for future reference. Furthermore, the peak variations induced by the main metal ions present in urine, Na+, K+, Ca2+ and Mg2+, were also measured. These data will be a valuable resource for 1H NMR metabolite profiling experiments and for the development of automated metabolite alignment and identification algorithms for 1H NMR spectra.
Leif Johnen - One of the best experts on this subject based on the ideXlab platform.
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myrcene as a natural Base Chemical in sustainable chemistry a critical review
Chemsuschem, 2009Co-Authors: Arno Behr, Leif JohnenAbstract:Currently, a shift towards Chemical products derived from renewable, biological feedstocks is observed more and more. However, substantial differences with traditional feedstocks, such as their “hyperfunctionalization,” ethical problems caused by competition with foods, and problems with a constant qualitative/quantitative availability of the natural products, occasionally complicate the large-scale market entry of renewable resources. In this context the vast family of terpenes is often not taken into consideration, although the terpenes have been known for hundreds of years as components of essential oils obtained from leaves, flowers, and fruits of many plants. The simple acyclic monoterpenes, particularly the industrially available myrcene, provide a classical chemistry similar to unsaturated hydrocarbons already known from oil and gas. Hence, this Review is aimed at reviving myrcene as a renewable compound suitable for sustainable chemistry in the area of fine Chemicals. The versatility of the unsaturated C10-hydrocarbon myrcene, leading to products with several different areas of application, is pointed out.