Evaluation of Co-mo/al2o3 Catalysts for Hydrodesulfurization Prepared by the Chemical Vapor Deposition Technique and Citric Acid Addition

Sulfided Co-Mo or Ni-Mo based catalysts still have been extensively used in refinery for Hydrodesulfurization (HDS) reaction, which is so-called Co-Mo-S phase as active sites. It is proposed that to obtain near zero sulfur content of fuels in the future is by improving the performance of Co-Mo catalysts. It could be approached with enhancing the amounts of active sites, Co-Mo-S phases, for instance with a sophisticated HDS catalysts preparation such as by a Chemical Vapor Deposition (CVD) technique using Co(CO)3NO as a precursor of Co and by the citric acid addition. It is demonstrated that if MoS2/Al2O3 is exposed to Co(CO)3NO vapor and subsequently sulfided, Co-Mo-S phases form selectively when the Mo content exceeds monolayer loading. The maximum potential HDS activity of Co-Mo/Al2O3 catalysts also can be obtained by the CVD technique. With the conventional Co-Mo/Al2O3 catalysts, the edges of MoS2 particles are completely occupied by Co atoms around of 4 wt% Co, thus more addition of Co caused blocking of the active sites by overlayers of Co sulfide clusters. However, with the citric acid addition, not only the amount coverage of Co atoms is increased, but also a high content of Mo could be also well dispersed (Mo > 20 wt%) on the surface support forms monolayer. In addition, the amount of Co forming Co-Mo-S phases was estimated from the correlation between NO/Mo and Co/Mo ratio by the CVD technique

Relationships Between Landscape Features and Nutrient Concentrations in an Agricultural Watershed in Southwestern Georgia: An Integrated Geographic Information Systems Approach

This study examined the influence of landscape features on stream nutrient concentrations within the Ichawaynochaway Creek watershed in southwestern Georgia. Baseflow concentrations of both dissolved (SRP, NO3, NH4) and total (TN, TP) nutrients were measured at 17 sampling sites monthly for a period of six months (July 2012 to January 2013). A long-term dataset (January 2008 to March 2012) was also analyzed for baseflow/stormflow comparisons of dissolved nutrient concentrations. Relationships among land-use, geology, soils, physiographic features and nutrients were analyzed at both the sub-watershed and riparian corridor scales. SRP concentrations were lower and NO3 concentrations higher than reported in previous studies of the region. Due to dry conditions during the sampling period, nutrient input was likely limited to groundwater contributions and land-use effects were minimal. Trends among water quality variables varied between the upper and lower portions of the watershed, suggesting differences in nutrient transport pathways due to spatial variation

Characterization of a defective PbWO4 crystal cut along the a-c crystallographic plane: structural assessment and a novel photoelastic stress analysis

Among scintillators, the PWO is one of the most widely used, for instance in CMS calorimeter at CERN and PANDA project. Crystallographic structure and chemical composition as well as residual stress condition, are indicators of homogeneity and good quality of the crystal. In this paper, structural characterization of a defective PbWO4 (PWO) crystal has been performed by X-ray Diffraction (XRD), Energy Dispersive Spectroscopy (EDS) and Photoelasticity in the unusual a-c crystallographic plane. XRD and EDS analysis have been used to investigate crystallographic orientation and chemical composition, while stress distribution, which indicates macroscopic inhomogeneities and defects, has been obtained by photoelastic approaches, in Conoscopic and Sphenoscopic configuration. Since the sample is cut along the a-c crystallographic plane, a new method is proposed for the interpretation of the fringe pattern. The structural analysis has detected odds from the nominal lattice dimension, which can be attributed to the strong presence of Pb and W. A strong inhomogeneity over the crystal sample has been revealed by the photoelastic inspection. The results give reliability to the proposed procedure which is exploitable in crystals with other structures.Comment: 18 pages, 10 figures, revised versio

Parameterized thermal macromodeling for fast and effective design of electronic components and systems

We present a parameterized macromodeling approach to perform fast and effective dynamic thermal simulations of electronic components and systems where key design parameters vary. A decomposition of the frequency-domain data samples of the thermal impedance matrix is proposed to improve the accuracy of the model and reduce the number of the computationally costly thermal simulations needed to build the macromodel. The methodology is successfully applied to analyze the impact of layout variations on the dynamic thermal behavior of a state-of-the-art 8-finger AlGaN/GaN HEMT grown on a SiC substrate

A momentum-space representation of Green's functions with modified dispersion on ultra-static space-time

We consider the Green's functions associated to a scalar field propagating on a curved, ultra-static background, in the presence of modified dispersion relations. The usual proper-time deWitt-Schwinger procedure to obtain a series representation of the Green's functions is doomed to failure, because of higher order spatial derivatives in the Klein-Gordon operator. We show how to overcome this difficulty by considering a preferred frame, associated to a unit time-like vector. With respect to this frame, we can express the Green's functions as an integral over all frequencies of a space-dependent function. The latter can be expanded in momentum space, as a series with geometric coefficients similar to the deWitt-Schwinger's ones. By integrating over all frequencies, we finally find the expansion of the Green's function up to four derivatives of the metric tensor. The relation with the proper-time formalism is also discussed.Comment: revtex, version accepted for publication in Phys. Rev.

Bandgap Narrowing in Quantum Wires

In this paper we consider two different geometry of quasi one-dimensional semiconductors and calculate their exchange-correlation induced bandgap renormalization (BGR) as a function of the electron-hole plasma density and quantum wire width. Based on different fabrication scheme, we define suitable external confinement potential and then leading-order GW dynamical screening approximation is used in the calculation by treating electron-electron Coulomb interaction and electron-optical phonon interaction. Using a numerical scheme, screened Coulomb potential, probability of different states, profile of charge density and the values of the renormalized gap energy are calculated and the effects of variation of confinement potential width and temperature are studied.Comment: 17 Pages, 4 Figure

Prolonged Cholestatic as a Typical Manifestation of Hepatitis a Infection: Diagnosis and Management

Hepatitis A virus (HAV), a positive-strand RNA virus, is stable at moderate temperature and low pH level. These characteristics allow the virus to survive in the environment and be transmitted through fecal-oral route.Twenty-year-old male came with jaundice and itchy skin since one month before admission. He was diagnosed as hepatitis A cholestasis type according to his history taking, physical examination, and laboratory result. Blood test showed elevated total bilirubin 27.4 g/dL, direct bilirubin 21.2 g/dL, indirect bilirubin 6.2 g/dL, alanin aminotransferase (ALT) 95 U/L, aspartate transaminase (AST) 134 U/L, alkaline phosphatase (ALP) 221 U/L, and gamma-glutamyltransferase (gGT) 17 U/L. His ultrasound results showed mild, non-specific hepatomegaly without common bile duct dilatation. The patient got symptomatic therapy with ursodeoxycholic acid (UDCA) 300 mg twice daily for his itchy skin and steroid therapy 0.5-1 mg/kg per day on the tenth day. He did not vomit or feel nausea anymore. After five days of steroid therapy, his total bilirubin level became 10.83 g/dL. He was discharged home with steroid therapy and steroid was tapered off during follow-up in the clinic.Prolonged cholestasis is one of atypical manifestation of hepatitis A which is rarely found. Cholestasis increases morbidity and prolongs hospitalization. Steroid therapy decreased bilirubin level and gave clinicalimprovement to the patient