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There is a demand for further reducing NOx emissions from natural gas burners in heat and power production. For this issue, computational fluid dynamics (CFD) is a powerful tool, gaining in importance. However, because of computational efforts, there is the necessity for simplified models in order to simulate the combustion reactions and the NOx formation, respectively. In this work, different simplified models for the NOx formation, i.e., thermal NO and prompt NO formation, are validated against the predictions of a detailed chemical kinetic mechanism. NOx formation from CH4 combustion becomes relevant above ~1200 °C. For temperatures >1600 °C, thermal NO formation is dominant. At lower temperatures, the N2O/NO and NNH routes have a significant contribution. For the conditions investigated, prompt NO formation is not relevant except for fuel-rich combustion. The simplified models capture thermal NO formation quite well. The superequilibrium radical concentration in the flame zone can be modeled by the “partial equilibrium approach” for the O radical, assuming its concentration in the relevant temperature range is ~30% higher than that for the equilibrium approach. However, this model overestimates NO formation under postflame conditions. For the prompt NO model, CH4 and O2 concentrations are necessary. These are obtained from the combustion model, which can be a local thermodynamic equilibrium (mixing rate limiting), a global reaction (reaction and/or mixing rate limiting), or a simplified reaction mechanism (flamelet model¹). The prompt NO model based on these combustion calculations is able to reasonably capture the NO emissions predicted by the detailed mechanism. However, the performance of the prompt NO model is rather dependent on the combustion model. Thus, this one must be chosen carefully. Critically, it has to be stated that, although the simplified prompt NO model captures the observed trends acceptably, it lacks a physical basis. It assumes the prompt NO formation to be proportional to the fuel concentration. The detailed reaction mechanism shows that the NO formation is more strongly related to the fuel oxidation rate, i.e., the radical concentration. Moreover, the detailed mechanism shows that prompt NO formation is of secondary relevance. Low-temperature NO formation is more related to the N2O/NO and the NNH routes.

Das Disaccharid Laktose kommt als Bestandteil von Lebensmitteln einzig in Milch und Milchprodukten vor. Im Verdauungstrakt wird die Laktose mit Hilfe des Enzyms ß-Galaktosidase (Laktase) in Glukose und Galaktose aufgespalten, die sodann absorbiert werden. Außer bei den Bewohnern Nord- und Mitteleuropas und der von ihnen abstammenden Bevölkerung Nordamerikas und Australiens verschwindet bei den meisten Menschen die Laktaseaktivität in der Dünndarmmukosa zwischen dem 4. und 6. Lebensjahr. Nach Laktosezufuhr kann es bei ihnen durch die osmotische Wirksamkeit der in den Dickdarm gelangten Laktose und ihrer Fermentation durch die Dickdarmflora zu Beschwerden kommen, zur sogenannten Laktoseintoleranz. Laktoseintoleranten Personen wird undifferenziert empfohlen, auf den Verzehr von Milch und Milchprodukten zu verzichten. Meist können sie jedoch geringe Mengen Milch beschwerdefrei vertragen. Sie können ebenfalls Käse, die keine (Hart- und Halbhartkäse) oder nur wenig (10% der Weichkäse) Laktose enthalten, ohne weiteres verzehren und müssen damit nicht auf eine wichtige Kalziumquelle verzichten. Untersuchungen der letzten 10 Jahre haben gezeigt, daß Joghurt trotz seines nicht unerheblichen Laktosegehaltes von laktoseintoleranten Personen bestens vertragen wird. Dieser Vorteil wird auf die in diesem Produkt vorhandenen lebensfähigen Milchsäurebakterien, welche die sauren Bedingungen des Magens zu überstehen vermögen, sowie auf die im Joghurt enthaltene Laktase zurückgeführt. The disaccharide lactose is present as a natural component of foods only in milk and dairy products. In the gastrointestinal tract, lactose is hydrolysed by the enzyme ß-galactosidase (lactase) into glucose and galactose. These components are absorbed. With the exception of the caucasian race, the lactase activity decreases in most people at an age of 4 to 6 years. Lactose intake can cause symptoms of bloating, flatulence, abdominal pain, and diarrhea due to the lactose reaching the large intestine. This phenomenon is called lactose intolerance. It is generally recommended to those persons that they refrain from the consumption of milk and dairy products. However, most lactoseintolerant people are able to digest small amounts of milk. They can also consume cheese that contains no (hard and semi-hard) or only small amounts of lactose (present in only 10 % of soft cheeses). These products are very important sources of calcium. Compared to milk, the lactose content of yogurt is usually lower by about one third. Studies during the last 10 years have shown that in spite of its lactose content yogurt is very well tolerated by lactose intolerant persons. This advantage is ascribed to the presence of living lactic acid bacteria in fermented dairy products which survive passage through the stomach and also to the lactase present in these products.

Radiolytic loss of highly polymerized calf thymus DNA was measured by HPL-gel chromatography. Irradiation of DNA in 10-2 mol dm-3 sodium phosphate under N2 and air caused the same loss. Under N2O this loss was doubled showing that the reactions of OH radicals mainly lead to strand breakage. The stability of the double helix is decisive for the yield of double strand breaks. In this work the radiation-induced degradation was altered by different sodium phosphate concentration, by substituting phosphate for perchlorate and by changing the temperature in the radiolysis of DNA under air. A decrease of the strength of non-covalent bonds in DNA always leads to an increase of degradation of DNA. Radiosensitivity of DNA is higher at pH 7 than at pH 9 or 5.

Ripening of Emmental Cheese Wrapped in Foil with and without Addition ofLactobacillus caseisubsp.casei. II. Gaschromatographic Investigation of some Volatile Neutral Compounds using Dynamic Headspace Analysis. The present work describes the ripening of eight raw milk Swiss Emmental cheese loaves, quarters of which were packaged at 3 months in a plastic sheet. The loaves were manufactured with and without addition ofL. caseisubsp.caseito the usual starter cultures. Samples were taken at 3, 6, 9 and 12 months of ripening. The changes in content of 38 volatile neutral components (primary and secondary alcohols, mono- and diketones, aldehydes, esters, aliphatic and aromatic hydrocarbons and sulfur compound) were measured using dynamic GC-headspace analysis. Except for all aldehydes produced from a β-oxidation of unsaturated fatty acids and hydrocarbons whose concentration significantly decreased, most volatile components showed an increase in content during ripening. Addition ofL. caseisubsp.caseito the usual starter culture used for Swiss Emmental cheese showed statistically significant differences for production of ethanol, propanol-1, 2- and 3-methylbutanol-1, 2,3-pentandione, 2- and 3-methylbutanal, as well as propionic acid propylester. Of the volatiles established as flavour compounds of Swiss Emmental cheese the analytical procedure used here was sufficient to detect heptanone-2, 2,3-butandione, 2- and 3-methylbutanal, ethyl butyrate and ethyl caproate. Die vorliegende Arbeit untersucht die Reifung von 8 Schweizer Emmentaler Käsen aus Rohmilch, die nach 3 Monaten in Folien und unter Vakuum verpackt wurden. Vier Käse wurden mit und vier ohne einen Zusatz vonLactobacillus caseisubsp.caseihergestellt und nach 3, 6, 9 und 12 Monaten untersucht. Die Gehaltsänderungen von 38 neutralen, flüchtigen Komponenten (primäre und sekundäre Alkohole, Mono- und Diketone, Aldehyde, Ester, aliphatische und aromatische Kohlenwasserstoffe sowie schwefelhaltige Verbindungen) wurden mit Hilfe einer dynamischen Dampfraumanalyse mittels GC-FID/MS bestimmt. Ausser den Aldehyden, die aus der β-Oxidation der ungesättigten Fettsäuren stammen, und den Kohlenwasserstoffen, die signifikant abnahmen, erhöhte sich die Konzentration der meisten Komponenten während der Reifung. Der Zusatz vonL. caseisubsp.caseiverursachte signifikante Unterschiede bei der Bildung von Ethanol, Propanol-1, 2- und 3-Methylbutanol-1, 2,3-Pentandion, 2- und 3- Methylbutanal sowie Propionsäurepropylester. Von den flüchtigen geschmacksaktiven Komponenten in Schweizer Emmentaler Käse konnten Heptanon-2, 2,3-Butandion, 2- und 3-Methylbutanal, Buttersäure- und Capronsäureethylester mit dieser Methode erfasst werden.

Recent ethnography of minority and working-class schooling has shown how wider structural factors like class stratification, poverty, and racism influence observable patterns of failure and under achievement in the classroom. In contrast, ethnography in middle-class schools and classrooms has not seriously probed similar structural bases of middle-class children's success, instead attributing this success to a presumed equivalence between the “middle-class culture” of the children's homes and the culture of the school and its staff.This study traces the history and effects of middle-class involvement in the public elementary school of a gentrifying inner-city neighborhood in New York City. Segregated into their special classrooms with distinctive curriculum and organization, the school's middle-class children were more successful than their poor and working-class peers. Their success was not the result, in Bourdieu's terms, of the “cultural capital” afforded by their middle-class upbringing. The school staff, in fact, disapproved of many elements of the children's class culture. Rather, the children's successful standing within the school had been the object, and achievement, of their parents' long-standing political struggles against the school's staff and other parents. This case illustrates that school success is as much an active social construction—both inside and outside the school—as school failure has been shown to be.

Schimmelpilzkulturen werden bei der Herstellung von Weißschimmel— und Blauschimmelkäse verwendet. Es wird über den gegenwärtigen Stand der Kenntnisse zur Frage von Mykotoxinbildnern in Schimmelpilzkulturen der Käsefabrikation berichtet. Verschiedentlich wurde ausPenicillium roqueforti-Stämmen, die auf speziellen Medien bebrütet wurden, das PR-Toxin isoliert, auch aus P. roqueforti-Kulturen, die zur Käseherstellung verwendet werden. Doch sind die Bedingungen der Käsereifung für eine Produktion dieses Toxins nicht geeignet. Weitere Stoffwechselprodukte von P. roqueforti wie Roquefortin und Isofumigaclavin konnten in Käse aufgefunden werden, doch ist über deren toxische Wirkung wenig bekannt. Kanzerogen wirkende Mykotoxine konnten in Schimmelkäsen nicht gefunden werden, außer Aflatoxin M1, das jedoch aus der kontaminierten Milch stammen dürfte. Das Auftreten von Tumoren nach Verfütterung einer Reinkultur vonP. camemberti var. candidumließ auf eine Mykotoxinwirkung schließen. Doch haben weitere Tierversuche mit verschiedenen, bei der Käsefabrikation verwendeten Schimmelpilzstämmen diesen Befund nicht bestätigt. Es läßt sich aufgrund der gesichteten Literatur sagen, daß der Einsatz von Schimmelpilzkulturen in der Käsefabrikation kein Risiko für den Menschen darstellt, also toxikologisch unbedenklich ist. Mould cultures are used for the manufacture of soft and blue cheese. The report deals with the present stage of knowledge of the question of mycotoxin-producers in mould cultures used for cheesemaking. The PR-toxin was isolated repeatedly fromPenicillium roquefortistrains which were incubated on special media, but also from P. roqueforti cultures used for cheese manufacture. However, cheese ripening conditions do not favow the production of this toxin. Other catabolites from P. roqueforti such als roquefortine and isofumigaclavine have been found in cheese, but there is not much known about their toxic effect. No cancerogenic mycotoxins have been discovered in these types of cheese, except aflatoxin M1which might however originate from contaminated milk. It must be concluded that the occurrence of tumors after feeding of a pureP. camemberti var. candidumculture is due to the effect of mycotoxins. On the other hand, further animal experiments with various mould culture strains used for cheesemaking have not confirmed these findings. On the basis of the literature consulted it may be said that the use of mould cultures for cheesemaking does not involve any risk for human health, that means it is toxicologically harmless.

Summary Most of the duties in an incipient colony of the fungus-growing termiteMacrotermes michaelseni (Sjöstedt) are perfomed by the workers. While foraging was observed only in major workers, all of the other elements were seen in both major and minor workers. The behavioural elements were grouped as follows: (I) Alarm behaviour, shown by shaking of the whole body; (II) Building behaviour, including palpation of the inner surface of the nest, picking up of a piece of soil, transport of the soil, and deposition of the soil; (III) Procurement of food by foraging, chewing and swallowing of hay pieces, deposition of semi-liquid faecal pellets on the fungus comb, claning of the fungus comb and the fungus nodules, and feeding from fungus nodules and old fungus comb; (IV) Moisture regulation either by water intake with the hypopharynx or water release through the mouth cavity; and (V) Interindividual behaviour, consisting of cleaning all the termite castes as well as the larvæ, cleaning and moistening the eggs, feeding reproductives and larvæ with a liquid and soldiers with fungus comb material, liquid transfer between workers, faecal intake from the larvae, facilitation of hatching and moulting of the larvae.

Part IV first reports a list of acidic volatile components isolated and identified by GC-MSD in a pool of five mature, first class Swiss Gruyère cheeses. The analysis of the outer zone (including the smear-coated rind), the middle and central zones revealed concentration gradients for some of the volatile components. The compounds found were principally fatty acids such as ethanoic, butanoic, propanoic, hexanoic, 2-methylbutanoic, 2-methylpropanoic, 3-methylbutanoic, pentanoic, octanoic and decanoic acids ranked by decreasing concentration, and hydroxybenzene (phenol). Changes in the content of these acidic volatile substances were then studied in two zones of eight first class Swiss Gruyère cheese over a 12-month ripening period. Quantitative determination of main constituents were performed separately by GC-TCD for the eight loaves. Semi-quantitative analyses of minor compounds were carried out by GC-MSD or GC-FID only in a pooled sample. The content of 2-methylpropanoic, 2-methylbutanoic, 3-methylbutanoic, 4-methylpropanoic, hexanoic (particularly in the inner zone), octanoic, and decanoic acids as well as hydroxybenzene increased in an approximately exponential way during the ripening period. On the other hand, concentrations of total volatile fatty acids, ethanoic, propanoic, butanoic, pentanoic and hexanoic (particularly in the outer zone) showed a more linear increase. Some possible metabolic pathways for the formation of these cheese flavour components are reviewed. Copyright 1993, 1999 Academic Press

At intervals of 2 months over 1 year, 64 royal cells were removed from mounds of Macrotermes michaelsenito find out whether a new royal pair was produced. In five mounds replacement reproductives were found. Young reproductives from incipient laboratory colonies were never accepted as replacements if they were introduced after the removal of the primary reproductives. One out of 10 royal pairs was accepted if the royal cell was introduced immediately after removal of the original one, and three out of 10 survived if the royal cell was introduced 1 week after the removal of the original one. Replacement reproductives were only produced when nymphs or alates were in the nest at the time the primary reproductives were removed. It was not possible to find out at what time after the removal a new royal pair was accepted but measurements of the replacement queens showed that they can become fully physogastric within 7 months.

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Of the indicators of increased early-onset coronary heart disease, raised serum cholesterol is a risk factor or risk marker, but not the cause. Strategies to reduce morbidity and mortality from coronary heart diseases generally involve reduction of plasma total and low density lipoprotein cholesterol through lowering the intake of total and saturated fat and of dietary cholesterol. Several methods for the reduction of cholesterol in commonly eaten foods have been developed successfully over the past few years with the aim of lowering dietary cholesterol. These approaches are biological (microorganisms, enzymes), chemical (solid-liquid-extraction, extraction with organic solvents, complex formation) or physical processes (distillation, crystallization, supercritical fluid extraction). While the application of these procedures to animal foods, especially to dairy products, is technically feasible, the relatively small contribution of dietary cholesterol to raised plasma cholesterol does not appear to justify the costs involved or to be scientifically justified.

Der amerikanische Arzt Oster hat das Enzym Xanthinoxidase in der homogenisierten Kuhmilch beschuldigt, für das Entstehen der Arteriosklerose und von koronaren Herzkrankheiten verantwortlich zu sein. Dieses Enzym soll durch den Verzehr der zerkleinerten Fettkügelchen im Magen-Darm-Kanal absorbiert und über die Lymphe zum Herzen transportiert werden, wo es abgelagert werde. Dort zerstöre es die aus den Plasmalogenen stammenden Aldehyde. Dadurch würde die Zellmembran geschädigt, und es würden sich schlußendlich typische arteriosklerotische Läsionen in den Arterien entwickeln. In diesem Übersichtsartikel wird zu dieser Hypothese kritisch Stellung genommen. Es werden dabei diskutiert:der Einfluß der Verhältnisse im Magen und Darm auf die Xanthinoxidase-Aktivität der Milch,die Möglichkeit einer Absorption dieses Enzyms im Darm,die Antikörperbildung gegenüber absorbierter Xanthinoxidase unddas Verhalten von intravenös verabreichtem Enzym. Aufgrund der heutigen Kenntnisse ist die Beweiskraft dieser Hypothese als gering anzusehen. Oster has postulated that the enzyme xanthinoxidase in homogenized cow's milk is the cause of myocardial infarction and angina pectoris. This enzyme may be absorbed by ingestion, especially of the small particles of the fat globules, and then carried by lymph streams to the arterial vascular system, where it is deposited into the myocardium. Then it destroys the aldehydes liberated from the cell membrane-based plasmalogens. This results in the intimal damage to the cell membranes of the arterial intima and the myocardium and ultimately in the development of typical atherosclerotic lesions in the arteries. The presented review is a critical approach to this hypothesis. The following factors are discussed:the influence of conditions prevailing in the intestine and the stomach on the activity of the xanthinoxidase in milk,the possibility of this enzyme being absorbed in the intestine,the formation of antibodies against absorbed xanthinoxidase andthe behaviour of xanthinoxidase administered intravenously. Compared with present knowledge, this theory gives little evidence only.

Duration of the feeding stage and corresponding weight increase during the last larval instar of the codling moth,Laspeyresia pomonella, are controlled by JH. Larvae reared under short day conditions have a relatively high titer of JH during the last larval instar and enter diapause as mature larvae. They feed longer and become heavier than larvae reared under long day conditions, which have no JH during the last larval instar and pupate when mature. By application of the JH mimetic Altosid®during the first 2 or 3 days of the last larval instar, the duration of feeding activity of larvae reared under respectively long and short day conditions was prolongated and the larvae became significantly heavier. The feeding behaviour could only be influenced by the juvenoid as long as the feeding activity of the larvae had not yet ceased.

The present work describes the ripening of eight quarters of raw milk Swiss Emmental cheese loaves which were packaged at 3 months in a plastic sheet. The loaves were manufactured with and without addition ofL. caseisubsp.caseito the usual starter cultures. Samples were taken at 3, 6, 9 and 12 months of ripening. The following parameters were measured and statistically compared: microbial composition (propionic bacteria, enteroccoci and facultative heterofermentative lactic acid bacteria); chemical composition (water, fat, total nitrogen, water soluble nitrogen, non-protein nitrogen, ammonium, water soluble minerals, copper, volatile fatty acids, lactic, citric and succinic acid, the ortho-phthaladehyde-, p-benzoquinone- and cadmium-ninhydrin-values, free amino acids as well as biogenic amines); rheological properties (penetration depth, deformation and force at fracture, force at 33% deformation); sensorial properties such as taste (sweet, salty, acidic and bitter), odour and flavour intensity as well as other quality criteria (eye formation, body structure and consistency as well as shelf-life). Inhibition of propionic fermentation and enterococci was observed after addition ofL. caseisubsp.caseiwith a reduction in the production of tyramine without any loss of flavour properties of this cheese variety.

After the combined oral administration of tetroxoprim and sulphadiazine in 16 patients with normal or impaired renal function, a linear relationship was found between the elimination rate constant (ke) and the endogenous creatinine clearance (C1cr). The mean elimination half-life (t1/2) for tetroxoprim in patients with healthy kidneys was 6·7 h and in anuric patients 13·8 h. In the case of sulphadiazine the values were h = 10 4 h (healthy kidneys) and Zi = 25·7 h (anuria). Both drugs were influenced in the same way and in parallel with the functional condition of the kidneys. For long term administration in anuric patients a dosage interval of τ=24h is required. The relative distribution volumes Vf for both substances are independent of the degree of renal insufficiency. The mean Ff values are calculated as 0–77 ± 0·11 1/kg for tetroxoprim, and 0 36 ± 0·07 1/kg for sulphadiazine.

The present work describes the high-performance liquid chromatographic (HPLC) separation of water-soluble peptides of eight quarters of raw milk Swiss Emmental cheese loaves which were packaged at 3 months in plastic wrap. The loaves were manufactured with (n= 4) and without (n= 4) the addition ofL. caseisubsp.caseito the usual starter culture. Samples were analysed at 3, 6, 9 and 12 months of ripening. The water-soluble peptides were separated by HPLC and analysed using a UV-detector at 210 nm. More than 100 peaks could be resolved. Analysis of variance and principal component analysis of the peak heights led to the following conclusion: 15 peaks increased and seven peaks decreased during the ripening period from 3–12 months. Cheese produced withL. caseisubsp.caseishowed three larger and two smaller peaks than those produced without this adjunct. The corresponding peptide composition was not determined.

Le présent travail reconsidère les effets de certains procédés de fabrication, de conditions de stockage et de traitements à des fins culinaires de quelques produits laitiers à l'état frais du commerce susceptibles d'oxyder le cholestérol. Des fromages, des beurres fondus et un lait en poudre frais ou stockés à basse température à l'abri de la lumière et de l'oxygène ne contiennent pas ou que de faibles traces d'oxystérols. Faire fondre des fromages (raclettes) n'en génère pratiquement pas, mais porter un beurre fondu 30 min à 170–175 °C ou plus de 10 min à 205–210 °C en produit. Un stockage de fromages exposés à une lumière fluorescente (blanc froid) deux à 4 mois à 6 °C et d'un lait en poudre d'une activité en eau de 0.11 1 année à 30 °C en présence d'oxygène (660 mL/L) peut oxyder 10 à 15% du cholestérol. Ces résultats confirment la bonne stabilité du cholestérol dans les produits laitiers stockés et/ou traités dans des conditions ‘normales’, les conditions extrêmes envisagées dans ce travail correspondant en fait à des tests accélérés.

Plotnicov, Leonard, ed. American Culture: Essays on the Familiar and Unfamiliar. Pittsburgh: University of Pittsburgh Press, 1990. xii + 301 pp. including chapter bibliographies. $24.95 cloth, $12.95 paper.Moffat, Michael. Coming of Age in New Jersey: College and American Culture. New Brunswick, New Jersey: Rutgers University Press, 1989. xvii + 355 pp. including references and index. $35.00 cloth, $12.95 paper.

Whereas in last instar larvae ofL. pomonellakept under long-day-conditions (LD), the JH-titer is temporarily reduced to zero, it stays relatively high in short-day-conditioned (SD) larvae which enter diapause. Application of JH or a juvenoid to LD-larvae results in diapause, if the treated insects are kept under SD-conditions. From these results it is concluded that inL. pomonelladiapause is initiated by a relatively high titer of JH during the last larval instar.

A few months ago a Laservision-disk containing more than 43000 single pictures was created at the Faculty of Medicine of the University of Basle. The present study exploredthe applicability of this new information medium in combination with microcomputer systems to the area of medicine. It is shown that especially with the retrieval program) the end user, in only a few seconds, can get information out of a huge data and picture bank which correspond exactly to his needs. Thus, with the proper infrastructure provided, this proposed media-mix represents a future-orientated enrichment of information transfer.

No abstractCopyright 1997 Academic Press Limited