Chemical CEBs

A typical UF pilot plant has been used in this study. Examples of application for these membranes can be found in the literature [40, 58]. The UF unit woks in deadend mode (2.5 m h ) and it can be operated in filtration, backwash and chemically enhanced backwash (CEB) modes as described in the literature for similar UF systems [40]. The specifications of the hollow fiber UF modules and the operating conditions are summarized in Table 5. 

Waters M, Boorman G, Bushel P, Cunningham M, Irwin R, Merrick A, et al. Systems toxicology and the Chemical Effects in Biological Systems (CEBS) knowledge base. EHP Toxicogenomics 2003 111 15-28. 

Fostel J, Choi D, Zwickl C, Morrison N, Rashid A, Hasan A, et al. Chemical Effects in Biological Systems—Data Dictionary (CEBS-DD) a compendium of terms for the capture and integration of biological study design description, conventional phenotypes and omics data. Toxicol Sci 2005 88 585-601. 

With emission source chemical signatures and corresponding aerosol or rainwater sample measurements PLS can be used Co calculate a chemical element mass balance (CEB). Exact emission profiles for the copper smelter and for a power plant located further upwind were not available for calculation of source contributions to Western Washington rainwater composition. This type of calculation Is more difficult for rainwater Chan for aerosol samples due Co atmospheric gas to particle conversion of sulfur and nitrogen species and due Co variations In scavenging efficiencies among species. Gatz (14) has applied Che CEB to rainwater samples and discussed Che effect of variable solubility on the evaluation of Che soil or road dust factor. 

We start from the chemical element balance (CEB) method Z) of source resolution as a reference approach although it is not necessary to all of the discussion which follows. 

Chemical Species Balances Decay Factors for Reactive Species The CEB method can be extended to families of chemical compounds, such as polycyclic aromatic hydrocarbons (PAH), while taking chemical reaction into account. Formally this can be done by writing chemical species balances in a somewhat different fashion from the CEB formulation ... 

The CEB method can be extended to chemically reactive species by introducing decay factors into the mass balances for the chemical species. The decay factors can be evaluated from data for the composition of emissions and of the ambient aerosol. They can be related to first order reaction rate coefficients measured in the laboratory by means of an appropriate atmospheric model. 

A critical requirement for the success of receptor models for atmospheric particles Is that the compositions of particles from all major sources in an area be accurately known. Chemical element balances (CEBs) of 130 samples taken In Washington, D.C. and analyzed for 40 elements yielded nearly the same source strengths when 28 elements are used In the least-squares fit as when only nine carefully chosen elements are used. Certain elements are important to the stability of CEB fits (Na, Ca, V, Mn, As and Pb) and should be measured carefully In particles from sources. For three of the nine elements (Al, Fe and Zn), other elements can serve as surrogates (many lithophlles for Al and Fe, Sb and Cd for Zn). Measurements on many more sources of each Important type should be done In order that trends can be observed that will allow one to predict compositions of particles from unmeasured sources. Instack measurements should Include collections of at least two size fractions of particles plus vapor-phase species. Measurements of at least 20 elements plus some classes of carbonaceous material should be made. 

This result may be deceptive, however, as we had to eliminate the many studies from Cols. 2 and 3 that contained no size Information, so the two sets of averages are not for the same populations of plants. A further problem with these data may also be the Inclusion of particles up to 2.5-pm dlam, whereas, recent studies (44, 46) indicate that the large changes of composition occur below about 0.5-pm dlam. Thus, our "fine" particles In Table IV Include particulate mass between 0.5 and 2.5 ym that Is chemically similar to larger particles, which reduces the Rvalues. We made the cut at 2.5 ym to develop components for separate CEBs of fine and coarse particles In ambient air, which are commonly divided at about that point. 

CEBS Chemical Effects in Biological Systems cebs.niehs.nih.gov... 

Appendix 5.1 Descriptions of Selected-omics Technologies 129 Appendix 5.2 Chemical Effects in Biological Systems (CEBS)... 

APPENDIX 5.2 CHEMICAL EFFECTS IN BIOLOGICAL SYSTEMS (CEBS) KNOWLEDGEBASE... 

Xirasagar S, Gustafson SF, Huang CC, Pan Q, Fostel J, Boyer P, Merrick BA, Tomer KB, Chan DD, Yost KJ, III, Choi D, Xiao N, Stasiewicz S, Bushel P, Waters MD. Chemical effects in biological systems (CEBS) object model for toxicology data, SysTox-OM Design and application. Bioinformatics 2006 22(7) 874-82. 

Waters, M., G. Boorman, P. Bushel, M. Cunningham, R. Irwin, A. Merrick, K. Olden, R. Paules, J. Selkirk, S. Stasiewicz, B. Weis, B. Van Houten, N. Walker and R. Tennant. Systems toxicology and the chemical effects in biological systems (CEBS) knowledge base. Environ. Health Perspect. Toxicogenomics 111 15-28, 2003. 

Environmental Protection Agency, Options for Revising CEB s Method for Screen-Level Estimates of Dermal Exposure, Chemical Engineering Branch, June 2003, Washington, D.C. 

Waters, M., Stasiewicz, S., and Merrick, B. A. 2008. CEBS—Chemical effects in biological systems A public data repository integrating study design and toxicity data with microarray and proteomics data. Nucleic Acids Res. 36 D892-D900. 

Sanches L, Domingues SH, Marino CEB, Mascaro LH (2004) Characterization of electro-chemically deposited Ni-Mo alloy coatings. Electrochem Cranm 6 543-548... 

Solid state metal borides are characteristically extremely hard, involatUe, high melting and chemically inert materials which are industrially important with uses as refractory materials and in rocket cones and turbine blades, i.e. components that must withstand extreme stress, shock and high temperatures. The borides LaBg and CeB are excellent thermionic electron emission sources, and single crystals are used as cathode materials in electron microscopes (see Box 13.8). 

Chemical enhanced backwashes (CEB) are also used to minimize the cleaning frequency of hollow fiber membranes. Chemical enhanced backwashes include the use of chemicals, such as hypochlorite, acid, and caustic in relatively high doses, to affect a mini chemical clean of the membranes without a full membrane cleaning. Concentrations of up to 1000 ppm acid, 500 ppm caustic, and 1000 ppm hypochlorite are typically used in a CEB. 

The simulation results of the one-dimensional model were found to be in fair agreement with the two-dimensional model considering the chemical conversion of the reactor, as is also utilized by the Kunii-Levenspiel type of modeis [85]. Moreover, with extended conductive fluxes, fair temperature profiles can be predicted with the one-dimensional model. On the other hand, the flow pattern, i.e., the phasic fractions and gas phase velocity, were associated with the largest uncertainty in the current model. However, the internal flow details did not have signiflcant influence on the chemical process performance. Thus, the current one-dimensional model was considered to have good potentials for further CEB model developments in order to study interconnected fluidized bed reactors with a dynamic solid flux transferred between the reactor units. 

---