Molybdena on titania : I. Preparation and characterization by Raman and Fourier Transform Infrared spectroscopy

Titania-supported molybdenum and cobalt-molybdenum catalysts were prepared by the dry impregnation and equilibrium adsorption techniques. Raman and Fourier Transform Infrared spectroscopy were used to follow the changes the catalysts underwent during the drying and calcination stages. The results indicate that the nature of the surface species depends on the loading, pH of the starting solution and the method of catalyst loading. It was found, for coverages calculated to be less than a monolayer, that the main surface species are tetrahedral molybdates. As the loading increases, octahedrally coordinated polymeric surface species form. Above the monolayer coverage, MoO3 is also formed. After calcination the spectra of catalysts prepared by the equilibrium adsorption technique change much less than those for catalysts prepared by the dry impregnation technique. Addition of cobalt to titania-supported molybdenum catalysts suppresses the formation of bulk MoO3 and leads to the formation of a cobalt molybdate phase. The results show that surface molybdates interact strongly with the support, TiO2.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25722/1/0000279.pd

Spectroscopic and scattering investigation of isopoly-molybdate and tungstate solutions

Detailed spectroscopic and scattering investigations of isopoly-molybdate and -tungstate solutions as a function of concentration and pH were made. From scattering results the apparent molecular weights were determined as a function of time and concentration. We find that the result agree with the aggregation scheme of simple --> hepta --> octa --> [Mo36O112]-8 --> protonated polymeric species, for molybdate solutions. Tungstate solutions aggregate according to simple --> Y-polytungstate --> paratungstate-A --> paratungstate-B --> [Psi]-metatungstate. The molybdate solutions exhibited very rapid equilibration, but the tungstate solutions required several days to reach equilibrium. From the discrete changes in the Raman spectra of both systems we find that the formation of isopoly anions is not a continuous process and that only certain species are present in solution. Our results do not rule out the formation of significant quantities of the octamolybdate anion as suggested by previous investigators.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25027/1/0000454.pd

Fischer-tropsch synthesis on charcoal-supported molybdenum: The effect of preparation conditions and potassium promotion on activity and selectivity

High dispersion and high activity charcoal-supported molybdenum catalysts were prepared using incipient wetness and equilibrium adsorption methods. Activities and selectivities of these catalysts were tested after reducing the catalysts at 773 K in flowing hydrogen. It was found that all the catalysts, particularly those prepared by the equilibrium adsorption method, showed high activities in Fischer-Tropsch synthesis of C1 to C3 hydrocarbons. Potassium promotion increased the selectivity towards C2 and C3 hydrocarbons while reducing moderately the activity. Without potassium promotion, C2+ selectivities of all the catalysts with metal loading of three weight percent or higher were about 50 +/- 5% under differential reactor conditions. Promotion by potassium increased the C2+ selectivity to as much as 70%. It was found that there was a critical potassium loading at which point the activity decrease levelled off. The method of potassium addition to the catalyst also plays a major role in determining the final activity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25875/1/0000438.pd

Effect of surface modification of siliconeon Staphylococcus epidermidis adhesion and colonization

Cerebrospinal fluid (CSF) shunts for the treatment of hydrocephalus are generally made of silicone rubber. The growth of bacterial colonies on the silicone surface leads to frequent CSF shunt complications. A systematic study of the effect of the surface modification of silicone on Staphylococcus epidermidis adhesion and colonization was performed for different incubation times by means of colony counting and scanning electron microscopy (SEM). Silicone was modified with different biopolymers and silanes, including heparin, hyaluronan, octadecyltrichlorosilane (OTS), and fluoroalkylsilane (FAS) to provide a stable and biocompatible surface with different surface functional groups and degrees of hydrophobicity. The modified silicone surfaces were studied by using contact angle measurements, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). After 4 and 8 h of incubation, the FAS- and OTS-coated silicone and the hyaluronan coated OTS/silicone surfaces showed significantly reduced bacterial adhesion and colonization compared to blank silicone by both quantification methods. However, the heparin coated OTS/silicone showed significantly increased bacterial adhesion. These results indicate that the nature of the surface functional group and surface roughness determine the extent of bacterial adhesion and colonization. However, the degree of hydrophobicity of the surface did not appear to play a determining role in bacterial adhesion and colonization. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/55980/1/30952_ftp.pd

Modeling microclimatic effects of trees and green roofs/façades in ENVI-met: Sensitivity tests and proposed model library

Urban green infrastructure furnishes one of the most effective ways to mitigate and adapt to climate change and the consequent thermal environment deterioration. ENVI-met, a holistic computational fluid dynamics model with various plant modules, has become a principal simulation tool to evaluate the thermal effects of urban greenery. This study emphasized the significance of clear and accurate ENVI-met vegetation modeling, aiming to formulate strategies to boost modeling data quality, veracity and rigor of ENVI-met-based simulation studies. This study applied a two-step framework. First, a series of sensitivity tests were conducted under hot and humid meteorological conditions to identify the microclimate-sensitive parameters and their relative cooling effects at the pedestrian level. The results identified leaf area density as the most significant parameter in ENVI-met tree modeling. Some compromises on root properties' input accuracy could be tolerated since they would not considerably hamper the overall simulation quality at the pedestrian level. For green roof/façade modeling, leaf area index and leaf angle distribution were significant and should be accurately input to ensure simulation quality. Second, for the microclimate-sensitive parameters in modeling, this study used commonly-planted species in subtropical South China cities to demonstrate a systematic workflow of developing an ENVI-met vegetation model library. The library could include basic plant physical traits, plant albums, reference values of the microclimate-sensitive parameters, and recommended alternative modeling data sources. The vegetation model library could provide a helpful and actionable package from which researchers can quickly obtain accurate input values without highly specialized knowledge or instruments

Immunoregulatory Protein Profiles of Necrotizing Enterocolitis versus Spontaneous Intestinal Perforation in Preterm Infants

Necrotizing enterocolitis (NEC) and spontaneous intestinal perforation (SIP) are the most common acute surgical emergencies associated with high morbidity and mortality in preterm infants. We aimed to compare the profiles of immunoregulatory proteins and identify novel mediators in plasma of NEC and SIP infants. We also investigated the expression of target genes in resected intestinal tissues and an enterocyte cell line. Using Cytokine Antibody Array assay, we reported the first comparative profiles of immunoregulatory proteins in plasma of NEC and SIP infants, and showed that dysregulated proteins belonged to functionally diversified categories, including pro- and anti-inflammation, angiogenesis, cell growth, wound healing, anti-apoptosis, cell adhesion and extracellular matrix reorganization. Validation by ELISA confirmed significantly higher concentrations of interleukin (IL)-6, angiopoietin (Ang)-2, soluble type II interleukin-1 receptor (sIL-1RII), and soluble urokinase-type plasminogen activator receptor (suPAR) in NEC infants compared with gestational age-matched control, and a lower level of an epidermal growth factor receptor, secreted form of receptor tyrosine-protein kinase ErbB3 (sErbB3), compared with SIP infants. mRNA expressions of IL1-RII and uPAR were up-regulated in resected bowel tissues from NEC infants, indicating that immunoregulation also occurred at the cellular level. In FHs-74 Int cells, Ang-2, IL1-RII and uPAR mRNA expressions were significantly induced by the combined treatment with lipopolysaccharide (LPS) and platelet activating factor (PAF). Our study provided plasmatic signatures of immunoregulatory proteins in NEC and SIP infants, and demonstrated involvement of multiple functional pathways. The magnitude of changes in these proteins was significantly more extensive in NEC infants, reflecting the different nature of injury and/or severity of inflammation. We speculate that dysregulation of IL-6, Ang-2, IL-1RII and uPAR occurred at both systemic and cellular levels, and probably mediated via LPS and endogeneous PAF signals. Such exaggerated immunologic responses may account for the high morbidity and mortality in NEC compared with SIP patients

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Search for High-Mass Resonances Decaying to τν in pp Collisions at √s=13 TeV with the ATLAS Detector

A search for high-mass resonances decaying to τν using proton-proton collisions at √s=13 TeV produced by the Large Hadron Collider is presented. Only τ-lepton decays with hadrons in the final state are considered. The data were recorded with the ATLAS detector and correspond to an integrated luminosity of 36.1 fb−1. No statistically significant excess above the standard model expectation is observed; model-independent upper limits are set on the visible τν production cross section. Heavy W′ bosons with masses less than 3.7 TeV in the sequential standard model and masses less than 2.2–3.8 TeV depending on the coupling in the nonuniversal G(221) model are excluded at the 95% credibility level

Measurement of differential cross sections and W + /W − cross-section ratios for W boson production in association with jets at √s =8 TeV with the ATLAS detector

This paper presents a measurement of the W boson production cross section and the W + /W − cross-section ratio, both in association with jets, in proton--proton collisions at s √ =8 TeV with the ATLAS experiment at the Large Hadron Collider. The measurement is performed in final states containing one electron and missing transverse momentum using data corresponding to an integrated luminosity of 20.2 fb −1 . Differential cross sections for events with one or two jets are presented for a range of observables, including jet transverse momenta and rapidities, the scalar sum of transverse momenta of the visible particles and the missing transverse momentum in the event, and the transverse momentum of the W boson. For a subset of the observables, the differential cross sections of positively and negatively charged W bosons are measured separately. In the cross-section ratio of W + /W − the dominant systematic uncertainties cancel out, improving the measurement precision by up to a factor of nine. The observables and ratios selected for this paper provide valuable input for the up quark, down quark, and gluon parton distribution functions of the proto

Anatomy of the sign-problem in heavy-dense QCD

QCD at finite densities of heavy quarks is investigated using the density-of-states method. The phase factor expectation value of the quark determinant is calculated to unprecedented precision as a function of the chemical potential. Results are validated using those from a reweighting approach where the latter can produce a significant signalto-noise ratio. We confirm the particle–hole symmetry at low temperatures, find a strong sign problem at intermediate values of the chemical potential, and an inverse Silver Blaze feature for chemical potentials close to the onset value: here, the phase-quenched theory underestimates the density of the full theory