CATALYTIC CRACKING OF RESIDUAL PETROLEUM FRACTIONS

ABSTRACT

Arabian Light crude oil vacuum bottoms has been fractionated into five high-boiling fractions by wiped film evaporation, and the fractions subjected to catalytic cracking in a fixed-fluidized bed using a commercial equilibrium cracking catalyst. Density, aromaticity, and heteroatom content generally increased with boiling point, as did metals content except for vanadium and iron which demonstrated possible bimodal distributions. The cracking response of these fractions showed increasing yields of dry gas and coke, with decreasing gasoline yields, as a function of increasing apparent boiling point as would normally be expected. Surprisingly, however, local maxima were observed for wet gas yield and total conversion, with local minima for cycle oil and slurry yields, in the region of the 1200–1263°F (650–680°C) middle fraction. All fractions showed significant response to cracking, with coke yields generally being the only negative factor observed.     

Do emerging markets matter in the world oil pricing system? Evidence of imported crude by China and India

This paper provides empirical evidence on the changing structure of world oil price system by identifying an additional driver-emerging market factor. We choose China and India as a representative of emerging markets to examine if the quantity of crude oil imported by China and India is significant in the existing oil pricing system (Kaufmann et al., 2004). Our data starts from January 2002 and ends in March 2010, which includes the oil shock of 2007–2008. We utilize cointegration and error correction model framework developed by Engle–Granger (1987) and Gregory–Hansen (1996) in the analysis. Our results indicate that demand from emerging markets has become a significant factor in the world oil pricing system since 2003. This result is significant as it lends empirical support to the widely held conjecture that the oil shock of 2007–2008 is a demand-led shock (Hamilton, 2009). Our result also has significant policy implications that go beyond the oil shock. The emerging market factor is there to stay and reflects the changing power between emerging and developed economies in the world economic system as a result of decades of fast economic development in the former. It will certainly influence policy issues related to oil and beyond.     

Evaluation and testing of analytical methods for cyanide species in municipal and industrial contaminated waters

Total cyanide analysis by distillation is used most commonly to assess cyanide content of water samples. This manual method is robust but slow and provides no information about cyanide speciation, a significant limitation in that cyanide species have substantially different toxicity characteristics. Seven alternative methods for the analysis of cyanide species or groups of species were evaluated in reagent water and five different contaminated water matrices, including five species-specific methods--weak acid dissociable (WAD) cyanide, free cyanide by microdiffusion, available cyanide, automated WAD cyanide by thin film distillation, metal cyanides by ion chromatography--and two automated techniques for total cyanide--total cyanide bythin film distillation and total cyanide by low-power UV digestion. The species-specific cyanide analytical techniques achieved low, ppb-level detection limits and exhibited satisfactory accuracy and precision for most contaminated waters. Analysis of low concentrations of cyanide species in raw wastewater was problematical for the available cyanide and ion chromatography methods, which experienced significant interference problems and/or low recoveries. There was recovery of significant diffusible cyanide in microdiffusion tests with nickel-cyanide-spiked samples, reflecting dissociation of this weak metal-cyanide complex during the test and demonstrating that the test can recover some fraction of WAD cyanide in addition to free cyanide. The automated total cyanide methods, which involve UV digestion, achieved low detection limits for most waters but exhibited low recoveries for some waters.     

Antimicrobial-resistant Salmonella serovars isolated from imported foods

A total of 187 Salmonella isolates representing 82 serotypes recovered from 4072 imported foods in the year 2000 by the U.S. Food and Drug Administration field laboratories were tested for their susceptibility to 17 antimicrobials of human and veterinary importance. Fifteen (8%) isolates were resistant to at least one antimicrobial, and five (2.7%) were resistant to three or more antimicrobials. Most of the isolates (n=9) exhibited resistance to tetracycline. Four isolates from catfish or tilapia from Taiwan or Thailand also demonstrated resistance to nalidixic acid. These nalidixic acid-resistant Salmonella isolates possessed a point mutation at the Ser83 or Asp87 position in DNA gryase, resulting in amino acid substitutions to phenylalanine, tyrosine, or asparagine. One Salmonella Derby isolated from frozen anchovies imported from Cambodia was resistant to six antimicrobials including ampicillin, amoxicillin/clavulanic acid, chloramphenicol, sulfamethoxazole, tetracycline, and trimethoprim/sulfamethoxazole. Of seven isolates displaying resistance to sulfonamides, only one S. Derby and one Salmonella Agona contained class 1 integrons that were further shown to possess the aadA and pse-1 genes conferring resistance to streptomycin and ampicillin, respectively. This study indicates that antimicrobial-resistant Salmonella are present in imported foods, primarily of seafood origin, and stresses the need for continued surveillance of foodborne zoonotic bacterial pathogens from imported foods entering the United States.     

Older versus younger treatment-seeking smokers: differences in smoking behavior, drug and alcohol use, and psychosocial and physical functioning

Quitting smoking benefits older individuals, yet few recent studies have described older smokers. The goal of this paper was to test a series of hypotheses about differences between smokers aged 50 years or older (50+) and those younger than age 50 (<50) presenting to the same treatment facility during 2002-2004 for participation in two randomized clinical trials: one exclusively for smokers aged 50+, and a second open to smokers aged 18 or older. As predicted, smokers aged 50+ were more tobacco dependent, had better psychological functioning, and had poorer physical functioning than those aged <50. Contrary to predictions, we found no differences in motivation to quit cigarette smoking or in alcohol use. Women aged 50+ were less likely to report marijuana use than women aged <50, and less likely than men to receive a positive diagnosis for alcohol abuse. Despite higher scores on measures of tobacco dependence, older smokers were less likely to be diagnosed as tobacco dependent or as having tobacco withdrawal using DSM-IV criteria. Rates of DSM-IV alcohol abuse and dependence were high in both age groups but were higher for smokers aged <50. We found no striking differences between studies in reasons for exclusion, but in both the proportion of individuals excluded due to current antidepressant use was high. Implications for the assessment and treatment of older adults are discussed.     

揭开睫毛神秘变长之谜

假设只能使用一种化妆品,你会选择什么？面对这个问题,相信99％的女人会选择睫毛膏。因为眼睛是整个面孔神采飞扬的关键,而眼部最不能省略的彩妆品就是睫毛膏（Mascara）——对,就是那种装在小管子里,能使睫毛—下子变长、变翘的粘稠状混合物。据说,当男人和女人接吻时,他的脸颊接触着她闪闪忽忽的睫毛,会有一种出奇的快感。某些敏感的男人甚至可以听到睫毛在脸颊上扫过“噗噗”的声响。那些有GF的Geek,还不快去试试？     

Convergence analysis of generalized serial message-passing schedules

Schedule is the order of passing messages between vertices of the bipartite graph defining an LDPC code in the process of decoding. Schedules affect the rate of decoding convergence. New efficient generalized serial schedules are described and analyzed, exhibiting significantly faster convergence compared to previously known schedules. For the proposed schedules, combinatorial and probabilistic analysis is presented, explaining the fast convergence observed in simulations. Using it, LDPC ensembles for which significantly better convergence rates can be achieved are identified. Specific code constructions from lifted graphs are further proposed, efficiently supporting the schedules. Examples based on regular LDPC codes are provided, in which the schedules achieve convergence speedup factors of up to 6 in comparison with the flooding schedule. Higher speedup factors are predicted by the analysis for irregular codes.     

Iridoid glycosides ofChelone glabra (Scrophulariaceae) and their sequestration by larvae of a sawfly,Tenthredo grandis (Tenthredinidae)

Analysis ofChelone glabra (Scrophulariaceae) by gas chromatography showed that leaves of this plant contained primarily the iridoid glycoside catalpol, and in a few individuals some aucubin was also detected. There was no difference in the iridoid glycoside content of damaged compared to undamaged plants, nor was there a difference between plants collected from a population in Leverett, Massachusetts, and those from plants in an experimental garden in Cambridge, Massachusetts. Larvae and prepupae of the sawfly,Tenthredo grandis (Tenthredinidae) contained catalpol sequestered from the larval host plant. The exuvia also contained catalpol, whereas the frass contained only aucubin. These results indicate that larvae of this sawfly selectively sequester catalpol, eliminating the aucubin in the frass.