Kinetic modeling and simulation of high-temperature by-product formation from urea decomposition

The Selective catalytic reduction (SCR) technique is widely applied in exhaust gas after-treatment of diesel engines. Depending on operating conditions, injected urea-water solution (UWS) can form liquid films on mixer blades and the pipe wall. Evaporation and subsequent reactions in the wall film can lead to deposits of urea and by-products, respectively. Especially deposits that are not decomposed up to high temperatures are challenging for the SCR technique. Thermogravimetric experiments are conducted for these stable urea by-products, such as ammelide, ammeline and their by-products, such as cyanamide or melamine. An analysis of the evolving gases during thermal decomposition led to a more detailed understanding of the kinetics. The postulated mechanism is able to predict the thermogravimetric analyses results and the effects of variation of the experimental conditions such as initial sample mass and heating rates. The evaluated kinetics, together with the recently developed kinetics for the urea/biuret/triuret/cyanuric acid system Tischer et al. (2019), can now be integrated into CFD simulations of SCR systems to numerically simulate all relevant physical and chemical processes in UWS equipped aftertreatment systems for a wide range of conditions

Interactive effects of low molecular weight carbon compounds on N2O emissions

Low molecular weight carbon (C) compounds in hotspots such as the rhizosphere can greatly affect nitrate reduction processes. Towards a better prediction of N2O emission from denitrification, we are still lacking understanding of responses to the supply of complex C compound mixtures such as rhizodeposits versus the often examined response to individually amended C compounds. In a laboratory study, we applied three C compounds, glucose, citric acid and glutamic acid, individually or as a three-compound mixture to 14NH415NO3 amended soil at 80% water-filled pore space. For the individual C compound treatments, the substrateswere enriched in 13C-C. The mixture was enriched in 13C-C either in all constituent compounds or in one of the compounds only, resulting in four different treatments. This set-up enabled quantification of the utilization of each compound for heterotrophic respiration when applied individually and in combination, and for this to be related to the dynamics of 15N-NO3- reduction to 15N-N2O. The total 15N-N2O emission from the compound mixture over 10 days was similar to the total emission predicted from the average of the individual compound treatments This could suggest potential predictability of denitrification responses to complex mixtures of C based on knowledge of its constituents. However, immediate and simultaneous peaks of 15N-N2O and 13C-CO2 fluxes from the compound mixture contrasted with observed delays in 15N-N2O and 13C-CO2 fluxes when the compounds had been applied individually. Moreover, relative contributions of the C compounds to 13C-CO2 respiration from the compound mixture were different from the predicted contributions based on their individual application. While contributions of glutamic acid-C and citric acid-C to respiration in mixture during peak 15N-N2O emission were increased, glucose utilization in the mixture treatment was significantly lower. These findings give a glimpse of the challenges we are facing when trying to predict nitrate reduction occurring in the rhizosphere where interactions between C compounds and the soil matrix, as well as within the wider heterotrophic community, determine process rates. Given that most of our understanding of the role of C in regulating nitrate reduction, is informed from single compound studies, we require more evidence on the effects and innate interactions of compound mixtures to be able to predict responses to C sources

Cost-Effectiveness of Interferon Beta-1a, Interferon Beta-1b, and Glatiramer Acetate in Newly Diagnosed Non-primary Progressive Multiple Sclerosis

AbstractObjectiveTo perform a cost-effectiveness analysis of three immunomodulatory treatments for newly diagnosed nonprimary progressive MS: interferon beta-1a, interferon beta-1b, and glatiramer acetate.MethodsWe developed a state-transition model to estimate the health effects and costs associated with interferon beta-1a, interferon beta-1b, glatiramer acetate, and no treatment for hypothetical cohorts of men and women with non-primary progressive MS. We used the Expanded Disability Status Scale as the measure of disability and included both relapses and disease progression in the model. We evaluated treatment strategies assuming a 10-year treatment duration using the societal perspective. We elicited preferences for disability and treatment states using standard-gamble questions and modeled the disutility associated with treatment administration and side effects explicitly. Main outcome measures were net gains in quality-adjusted life expectancy and incremental cost-effectiveness ratios in dollars per quality-adjusted life year (QALY) gained.ResultsFor treatment duration of 10 years for newly diagnosed non-primary progressive MS, interferon beta-1a yielded the largest gain in quality-adjusted life expectancy with an incremental cost-effectiveness ratio of $2,200,000/QALY for women and$1,800,000/QALY for men, compared with no treatment. For a 5-year treatment duration, a “no treatment” strategy yielded more quality-adjusted life years than any of the treatment strategies. Cost-effectiveness ratios were similar for all three immunomodulatory treatments evaluated.ConclusionsCost-effectiveness results for all three immunomodulatory treatments for MS were unfavorable in the simulated study population under a wide range of assumptions. For treatment duration less than or equal to 5 years, expected benefits of treatment may not outweigh disutility associated with side effects and treatment discomfort

Physical Structure and Nature of Supernova Remnants in M101

Supernova remnant (SNR) candidates in the giant spiral galaxy M101 have been previously identified from ground-based H-alpha and [SII] images. We have used archival Hubble Space Telescope (HST) H-alpha and broad-band images as well as stellar photometry of 55 SNR candidates to examine their physical structure, interstellar environment, and underlying stellar population. We have also obtained high-dispersion echelle spectra to search for shocked high-velocity gas in 18 SNR candidates, and identified X-ray counterparts to SNR candidates using data from archival observations made by the Chandra X-ray Observatory. Twenty-one of these 55 SNR candidates studied have X-ray counterparts, although one of them is a known ultra-luminous X-ray source. The multi-wavelength information has been used to assess the nature of each SNR candidate. We find that within this limited sample, ~16% are likely remnants of Type Ia SNe and ~45% are remnants of core-collapse SNe. In addition, about ~36% are large candidates which we suggest are either superbubbles or OB/HII complexes. Existing radio observations are not sensitive enough to detect the non-thermal emission from these SNR candidates. Several radio sources are coincident with X-ray sources, but they are associated with either giant HII regions in M101 or background galaxies. The archival HST H-alpha images do not cover the entire galaxy and thus prevents a complete study of M101. Furthermore, the lack of HST [SII] images precludes searches for small SNR candidates which could not be identified by ground-based observations. Such high-resolution images are needed in order to obtain a complete census of SNRs in M101 for a comprehensive investigation of the distribution, population, and rates of SNe in this galaxy.Comment: 37 pages, 4 Tables, 7 Figures, accepted for publication in the Astronomical Journa

A statistical mechanical description of metastable states and hysteresis in the 3D soft-spin random-field model at T=0

We present a formalism for computing the complexity of metastable states and the zero-temperature magnetic hysteresis loop in the soft-spin random-field model in finite dimensions. The complexity is obtained as the Legendre transform of the free-energy associated to a certain action in replica space and the hysteresis loop above the critical disorder is defined as the curve in the field-magnetization plane where the complexity vanishes; the nonequilibrium magnetization is therefore obtained without having to follow the dynamical evolution. We use approximations borrowed from condensed-matter theory and based on assumptions on the structure of the direct correlation functions (or proper vertices), such as a local approximation for the self-energies, to calculate the hysteresis loop in three dimensions, the correlation functions along the loop, and the second moment of the avalanche-size distribution.Comment: 28 pages, 12 figure

Universal Pulse Shape Scaling Function and Exponents: A Critical Test for Avalanche Models applied to Barkhausen Noise

In order to test if the universal aspects of Barkhausen noise in magnetic materials can be predicted from recent variants of the non-equilibrium zero temperature Random Field Ising Model (RFIM), we perform a quantitative study of the universal scaling function derived from the Barkhausen pulse shape in simulations and experiment. Through data collapses and scaling relations we determine the critical exponents $\tau$ and $1/\sigma\nu z$ in both simulation and experiment. Although we find agreement in the critical exponents, we find differences between theoretical and experimental pulse shape scaling functions as well as between different experiments.Comment: 19 pages (in preprint format), 5 figures, 1 tabl

Extended versus standard lymph node dissection for urothelial carcinoma of the bladder in patients undergoing radical cystectomy

We acknowledge the support received from the author of the in-cluded study, Jürgen E. Gschwend who provided information onthe method of blinding. We are very grateful to Annemarie Uhlig, Guillaume Ploussard,Wassim Kassouf, Caroline Raw and Martin Burton for havingserved as peer reviewers. We thank Cochrane Urology, ManagingEditor Robert Lane and Cochrane Fast-Track Service, ManagingEditor Helen Wakeford, for the support we received.Peer reviewedPublisher PD

Thermal and radio-oxidation of epoxy coatings

Degradation induced by thermal (50-110 °C) and radio-oxidation of low T g epoxy-amine networks has been studied. It has been found that oxidation leads mainly to amide groups formation at the vicinity of tertiary amines whatever ageing conditions (thermal or radio-oxidation at 200 Gy h -1 ). In addition, some species as acids, peracids or formates have been revealed indicating a chain scission process. Physical modifications as T g decrease and soluble fraction increase due to chain scission process, have been correlated with chemical modifications

Modulating Myeloid Immune Cell Migration Using Multivalently Presented Monosaccharide Ligands for Advanced Immunotherapy

Due to their importance for the outcome of the inflammatory response, the motile myeloid cells are a focus of novel treatment options. The interplay of selectins and their ligands with leukocytes and endothelial cells, which mediate endothelial attachment and transmigration of immune cells, can be modulated by selectin‐binding structures. Here, a library of selectin‐targeting ligands coupled to either gold, silver, iron oxide nanospheres, or quantum dots of 5–10 nm in size is used to systematically study their impact on immune cell motility. The multivalent presentation of the carbohydrate mimetics results in very low sub‐nanomolar binding to L ‐selectin. Using human primary monocytes, granulocytes, lymphocytes, and macrophages, it is shown that the ligands exhibit only minor effects on uptake, whereas the motility of leukocytes is critically affected as observed in migration assays evaluated by flow cytometry. The carbohydrate mimetic ring structure, sulfation, in particular, and the degree of ligand presentation, are constituents which cohere in this process. Specific carbohydrate ligands can thus selectively regulate leukocyte subsets. These data form the basis for advanced immunotherapy which inhibits the amplification of inflammation by restricting leukocyte influx to injured tissue sites. Furthermore, the targeting ligands may complement existing treatment options for inflammatory diseases