Approach to Steady State in Completely Mixed Flow Reactors

Environmental engineers frequently employ the assumption that steady-state conditions are approximated after three hydraulic residence times. In this paper, the conditions under which this assumption is valid are elucidated. For well-mixed systems, the time to approach steady state depends on the kinetic order of removal mechanisms, the initial pollutant concentration in the control volume (=C0), and the kinetic rate constant. The assumption of three hydraulic residence times to steady state was found to be conservative if C0 = 0. However, if C0 equals the influent concentration, then more than three hydraulic residence times may be required to approach steady-state conditions with some zero-order reactions.     

Catalytic steam reforming of bio-oil

Hydrogen and synthesis gas can be produced in an environmentally friendly and sustainable way through steam reforming (SR) of bio-oil and this review presents the state-of-the-art of SR of bio-oil and model compounds hereof. The possible reactions, which can occur in the SR process and the influence of operating conditions will be presented along with the catalysts and processes investigated in the literature.     

Monoamine- and histamine-synthesizing enzymes and neurotransmitters within neurons of adult human cardiac ganglia

BACKGROUND: Cardiac ganglia were originally thought to contain only cholinergic neurons relaying parasympathetic information from preganglionic brain stem neurons to the heart. Accumulating evidence, however, suggests that cardiac ganglia contain a heterogeneous population of neurons that synthesize or respond to several different neurotransmitters and neuropeptides. Reports regarding monoamine and histamine synthesis and neurotransmission within cardiac ganglia, however, present conflicting information or are limited in number. Furthermore, very few studies have examined the neurochemistry of adult human cardiac ganglia. The purpose of this study was, therefore, to determine whether monoamine- and histamine-synthesizing enzymes and neurotransmitters exist within neurons of adult human cardiac ganglia. METHODS AND RESULTS: Human heart tissue containing cardiac ganglia was obtained during autopsies of patients without cardiovascular pathology. Avidin-biotin complex immunohistochemistry was used to demonstrate tyrosine hydroxylase, L-dopa decarboxylase, dopamine beta-hydroxylase, phenylethanolamine-N-methyltransferase, tryptophan hydroxylase, and histidine decarboxylase immunoreactivity within neurons of cardiac ganglia. Dopamine, norepinephrine, serotonin, and histamine immunoreactivity was also found in ganglionic neurons. Omission or preadsorption of primary antibodies from the antisera and subsequent incubation with cardiac ganglia abolished specific staining in all cases examined. CONCLUSIONS: Our results suggest that neurons within cardiac ganglia contain enzymes involved in the synthesis of monoamines and histamine and that they contain dopamine, norepinephrine, serotonin, and histamine immunoreactivity. Our findings suggest a putative role for monoamine and histamine neurotransmission within adult human cardiac ganglia. Additional, functional evidence will be necessary to evaluate what the physiological role of monoamines and histamine may be in neural control of the adult human heart.     

Temporal entity-relationship models-a survey

The entity-relationship (ER) model, using varying notations and with some semantic variations, is enjoying a remarkable and increasing popularity in both the research community-the computer science curriculum-and in industry. In step with the increasing diffusion of relational platforms, ER modeling is growing in popularity. It has been widely recognized that temporal aspects of database schemas are prevalent and difficult to model using the ER model. As a result, how to enable the ER model to properly capture time-varying information has, for a decade and a half, been an active area in the database research community. This has led to the proposal of close to a dozen temporally enhanced ER models. This paper surveys all temporally enhanced ER models known to the authors. It provides a comprehensive overview of temporal ER modeling and it thus meets a need for consolidating and providing easy access to the research in temporal ER modeling. In the presentation of each model, the paper examines how the time-varying information is captured in the model and presents the new concepts and modeling constructs of the model. A total of 19 different design properties for temporally enhanced ER models are defined, and each model is characterized according to these properties     

Unexpected cross-reaction with Fusobacterium necrophorum in a PCR for detection of mycoplasmas

Cross-reactions with Fusobacterium necrophorum were found in a PCR designed for detection of a wide range of mycoplasma species. Twenty-five strains of Fusobacterium were examined; all 14 F. necrophorum strains reacted positively, whereas all 7 Fusobacterium nucleatum strains reacted negatively. Two strains that were not F. necrophorum yielded variable results.     

Dietary exposure assessment of Danish consumers to dithiocarbamate residues in food: a comparison of the deterministic and probabilistic approach.

Probabilistic and deterministic estimates of the acute and chronic exposure of the Danish populations to dithiocarbamate residues were performed. The Monte Carlo Risk Assessment programme (MCRA 4.0) was used for the probabilistic risk assessment. Food consumption data were obtained from the nationwide dietary survey conducted in 2000--02. Residue data for 5721 samples from the monitoring programme conducted in the period 1998--2003 were used for dithiocarbamates, which had been determined as carbon disulphide. Contributions from 26 commodities were included in the calculations. Using the probabilistic approach, the daily acute intakes at the 99.9% percentile for adults and children were 11.2 and 28.2 microg kg(-1) body weight day(-1), representing 5.6% and 14.1% of the ARfD for maneb, respectively. When comparing the point estimate approach with the probabilistic approach, the outcome of the point estimate calculations was generally higher or comparable with the outcome of the probabilistic approach at the 99.9 percentile (consumers only). The chronic exposures for adults and children were 0.35 and 0.76 microg kg(-1) body weight day(-1) at the 99.9 percentile, representing 0.7% and 1.5%, respectively, of the acceptable daily intake for mancozeb and maneb at 50 microg kg(-1) body weight.     

100 GHz+ Gain-Bandwidth Differential Amplifiers in a Wafer Scale Heterogeneously Integrated Technology Using 250 nm InP DHBTs and 130 nm CMOS

Differential amplifiers incorporating the advantages of both Si and III-V technologies have been fabricated in a wafer scale, heterogeneously integrated, process using both 250 nm InP DHBTs and 130 nm CMOS. These ICs demonstrated gain-bandwidth product of 40-130 GHz and low frequency gain > 45 dB . The use of InP DHBTs supports a > 6.9 V differential output swing and a slew rate > 4 times 10⁴V/mus to be achieved with as low as 40 mW dissipated power. A novel on-chip buffer circuit is used to facilitate the on-wafer characterization of these amplifiers. To the authors' knowledge, this is the first demonstration of a high performance IC building block in a heterogeneously integrated process technology.