State multiplicity in CSTR-separator-recycle polymerisation systems

This article continues earlier work (Comput. Chem. Eng. 24 (2000) 209) concerning the design and control of isothermal reactor-separator-recycle systems. The multiplicity behaviour of six reaction systems of increasing complexity, from one-reactant, first-order reaction to chain-growth polymerisation, is investigated. Below a critical value of the plant Damkohler number, Da<Da^cr, the only steady state involves infinite flow rates. Feasible steady states become possible if the critical value is exceeded, Da>Da^cr. For one-reaction systems, one stable steady state is born at a transcritical bifurcation. For consecutive-reaction systems, including polymerisation, a fold bifurcation can lead to two feasible steady states. Moreover, the transcritical bifurcation is destroyed when two reactants are involved. If the gel-effect is included, a maximum of four steady states are possible. When multiple steady states exist, the achievable conversion is constrained by the instability of the low-conversion branch. This has practical importance for polymerisation systems when the radicals’ quasi-steady state assumption is not valid or the gel effect is significant.     

A bootstrap approach for lower injury levels of the risk curves

Survival analysis is widely applied to develop injury risk curves from biomechanical data. To obtain more accurate estimation of confidence intervals of parameters, bootstrap method was evaluated by a designed simulation process. Four censoring schemes and various sample sizes were considered to investigate failure time parameters corresponding to low-level injury probabilities. In the numerical simulations, the confidence interval ranges developed by bootstrapping were about two-third of the corresponding ranges calculated by asymptotical normal approximation and showed highest reduction for censored datasets with smaller sample size (≤ 40). In analysis of two experimental datasets with reduced sample sizes and mixed censored data, it was shown that the bootstrapping reduce significantly the confidence intervals as well. The results presented in this study recommend using bootstrapping in development of more accurate confidence intervals for risk curves in injury biomechanics, which consequently will lead to better regulations and safer vehicle designs.     

Human, rhesus macaque, and feline sequences highly similar to mouse mammary tumor virus sequences

Sequences highly similar (>95%) to the mouse mammary tumor virus (MMTV) env gene have been amplified from human DNA samples, including DNA samples from patients with breast cancer (BC) and persons who did not have BC. The sequences from human DNA were distinct from the MMTV sequences used as controls in these PCR reactions, indicating that these results are not simply due to contamination. In addition to both, mouse and human-related sequences were also amplified from some monkey and cat genomic DNA samples. These products were shown to be distinct from, but highly related to, the MMTV env gene, whereas, testing of other sources (lambda phage, snake, cockroach, sea urchin, chicken, or dog) demonstrated no specific amplification. A sequence 90% similar to the MMTV group antigen gene (gag) was amplified from cat DNA. These results indicate that DNA from vertebrate species other than rodents, including some but not all humans, monkeys, and cats, can contain sequences closely related to MMTV.     

Cyclic distillation technology – a mini‐review

Process intensification in distillation systems has received much attention during past decades, with the aim of increasing both energy and separation efficiency. Various techniques, such as internal heat‐integrated distillation, membrane distillation, rotating packed bed, dividing‐wall columns and reactive distillation were studied and reported in the literature. All these techniques employ the conventional continuous counter‐current contact of vapor and liquid phases. Cyclic distillation technology is based on an alternative operating mode using separate phase movement which leads to key practical advantages in both chemical and biochemical processes. This article provides a mini‐review of cyclic distillation technology. The topics covered include the working principle, design and control methods, main benefits and limitations as well as current industrial applications. Cyclic distillation can be rather easily implemented in existing columns by simply changing the internals and the operating mode, thus bringing new life to old distillation towers by significantly increasing the column throughput, reducing the energy requirements and offering better separation performance. © 2016 Society of Chemical Industry     

A review of biodiesel production by integrated reactive separation technologies

Biodiesel is a biodegradable and renewable fuel, emerging as a viable alternative to petroleum diesel. Conventional biodiesel processes still suffer from problems associated with the use of homogeneous catalysts and the limitations imposed by the chemical reaction equilibrium, thus leading to severe economic and environmental penalties. This work provides a detailed review—illustrated with relevant examples—of novel reactive separation technologies used in biodiesel production: reactive distillation/absorption/extraction, and membrane reactors. Reactive separation offers new and exciting opportunities for manufacturing the fatty acid alkyl esters involved in the industrial production of biodiesel and specialty chemicals. The integration of reaction and separation into one operating unit overcomes equilibrium limitations and provides major benefits such as low capital investment and operating costs. These reactive separation processes can be further enhanced by heat‐integration and powered by heterogeneous catalysts, to eliminate all conventional catalyst related operations, using efficiently the raw materials and the reaction volume, while offering higher conversion and selectivity, as well as significant energy savings compared with conventional biodiesel processes. Remarkable, in spite of the high degree of integration, such integrated reactive‐separation processes are still very well controllable as illustrated by the included examples. Copyright © 2012 Society of Chemical Industry     

The yeast rRNA biosynthesis factor Ebp2p is also required for efficient nuclear division

Molecular genetic analysis of the yeast Ebp2 protein has revealed that it is an essential, nucleolar protein that functions in the rRNA biosynthesis pathway. Temperature-sensitive ebp2-1 mutants are defective in the processing of the 27 SA precursor rRNA, and the point substitutions that disrupt this activity cluster towards the central, more highly conserved region of the Ebp2 protein. We report here that other ebp2 mutants exhibit deficiencies associated with defects in chromosome segregation. Yeast cells bearing a 50 amino acid C-terminal truncation allele (ebp2 delta C50) display a slow-growth phenotype and exhibit an increased percentage of cells with the nucleus positioned at the bud neck. The ebp2-1 and ebp2 delta C50 alleles genetically complement each other, and ebp2 delta C50 mutants exhibit nuclear division defects that are distinct from the rRNA biosynthesis-related phenotypes of ebp2-1 mutants. Cytological and FACS analysis of the ebp2 delta C50 deletion mutants indicate that the chromosome segregation related activities of the Ebp2 protein are monitored by Mad2p, a mitotic checkpoint protein. The finding that yeast Ebp2p functions in nuclear division is consistent with the growing body of evidence that supports the role that human EBP2 plays in chromosome segregation.     

Generational status: A Canadian response to the editors' consortium statement with regard to race/ethnicity.

In response to the American Editors' Consortium Statement (1996) with regard to a minimal classification scheme for describing race/ethnicity, the present study investigated a potential supplementary scheme. Having reviewed the conceptual, theoretical, and methodological concerns about the Consortium's scheme, data from 1,071 Canadian university students (mean age 19.23 yrs) were examined with regard to demographics, relationships with parents, and psychological well-being. Ss revealed 94 countries of origin, 69 languages spoken at home, identification with 203 cultural or ethnic groups, and an idiosyncratic use of the term "visible minority". The supplementary classification scheme proposed is based on immigrant Generational Status-Canadian (GS-C) . The data were analyzed according to both the race/ethnicity and GS-C schemes. Results indicate that GS-C differentiated meaningful significant differences on 10 nondemographic variables. Race/ethnicity confounded with GS-C and, when the confound was addressed, only produced 1 significant difference. According to data, the GS-C seems to be the more meaningful way of summarizing the demographic data from a racially/ethnically/culturally diverse population. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Observations on isovolemic hemodilution in acute ischemic stroke

The reduction of blood viscosity is an alternative of the improvement of the cerebral flow during an acute ischemic stroke (AIS). We studied 18 patients with AIS, ranging in age from 44 to 72 years (mean age 57 years), 11 females and 7 males. We applied an isovolemic hemodilution for 2 days starting with an emission of 250 or 500 ml blood, followed by the infusion of an equal amount of 6% HAES-steryl solution. We made determination of hematocrit, plasma density, plasma viscosity 1, 3 and 6 hours before and after the infusion; a decrease was noted in all the studied hemorheologic parameters, and the short term clinical course was an improvement. In conclusion, the isovolemic hemodilution using 6% HAES solution reduced hematocrit, plasma density, plasma viscosity but no changes were noted in the hemodynamic parameters; isovolemic hemodilution as the single therapeutic method in AIS does not solve the therapy, involving only one pathogenetic link, i.e., the microcirculation.