Drei neue Nickelenzyme aus anaeroben Bakterien

Until recently nickel was not considered to be an element of biological importance. Nutritional studies have shown, however, that many eucaryotic and procaryotic organisms are dependent on the transition metal for growth. Four enzymes are presently known to contain nickel: urease from plants and from bacteria; methyl CoM reductase from methanogenic bacteria; all “uptake” hydrogenases investigated so far; and carbon monoxide dehydrogenase from anaerobic bacteria. The prosthetic group of the methyl CoM reductase has been identified as a nickel tetrapyrrole, the structure of which has been elucidated.     

Product Guide/1979

The Product Guide series which appears in the Journal of the Air Pollution Control Association and the APCA Directory and Resource Book is a computer-based program. A questionnaire form provided entry into the program for responding manufacturers of emission control equipment and air pollution instrumentation. If any manufacturers or product categories have been overlooked, the omission is regretted and should be brought to the attention of the editor, JAPCA.     

Dynamics of dust explosions suppression by means of extinguishing powder in various industrial conditions

In industrial conditions, there are different kinds of installations endangered by an explosion of dust–gas mixtures. In order to prevent them from any consequences of potential explosions, active protection systems which use extinguishing powders, as the suppressing material, are more and more widely applied. It often happens that the industrial installations are additionally endangered by an action of mechanical vibrations. In the above-mentioned conditions, the extinguishing powder tends to aggregate, making the process of dispersing it in the protected areas more difficult.

The results of research into optimization of the shape, number of igniters and miniaturization of the explosive charge mass are presented. In case of occurrence of the mechanical vibrations in the installations that cause aggregation of the suppressing powder, the best solution was modification of the perforated combustion chamber located inside the extinguisher. As a result of that, a certain amount of gases generated in the course of combustion of the main charge is directed over the membrane, where the gases crash a layer of aggregated powder. Thus, the process of pushing the powder out from a container towards the dispersing head improves considerably and consequently increases the efficiency of the explosion-suppressing process.     

Are barnacle larvae able to escape from the threat of UV?

Earlier laboratory experiments suggested that environmental levels of UV-B radiation can damage the eyes of barnacle naupliar larvae and impair their phototactic behaviors. However, since barnacle larvae may avoid UV by migrating to deeper waters, it is not known whether such impairment would actually occur under field conditions. For the first time, this study provides both field and laboratory evidences to show that prevailing UV-B in the natural habitat of barnacle larvae could be an important environmental factor affecting natural barnacle populations. We here showed that although barnacle nauplii may avoid UV-B irradiation by downward migration, the amount of UV energy (9.8 × 10⁻⁶ J) received by a naupliar eye during downward migration in the natural water column is within the same order of magnitude as the total energy (7.5 × 10⁻⁶ J) sufficient to cause damages to naupliar eye and impair their phototactic responses. It is possible that solar UV-B prevailing at shallow waters would pose a similar threat to other zooplankton species over large geographic scale.     

Methanogene Bakterien

Methanogenic bacteria area diverse group of anaerobic procaryotes that ferment CO₂ plus H₂ to CH₄. Besides their unusual energy metabolism they are unique in that their cell walls do not contain murein, and in that their cell membranes are composed of isoprenoid lipids. Coenzymes occur which are not found in any other living organism. The translation apparatus differs, e.g., in not being affected by antibiotics known to be inhibitors of procaryotic protein synthesis. Most of the methanogens can grow on CO₂ as sole carbon source; autotrophic CO₂ fixation does not, however, proceed via reactions of the Calvin cycle. Molecular genealogical analysis has revealed that methanogenic bacteria constitute a grouping phylogenetically distinct from most other procaryotes.     

机场安全与危机管理

网络管理是一项很关键的技术,换句话说,为了能够满足新的无线电通讯基础结构中ATN和无线电通讯这两方面的要求,人们需要有一种新的网络管理模式。特别是新的网络管理模式必须结合ATN管理框架,此框架组成包括:相关的标准、电信管理框架,特别是国际电信联盟(ITU)制定的电信管理网络(TMN)标准。本文描述了一种新的公共空中交通情报控制与诊断系统,探讨了公共空中交通硬件和软件开发过程中的系统操作模式和诊断方法。为了提供安全的设备操作,能够快速指出错误并且评估有缺陷的系统、装置和构件至关重要。     

Natural product biomarkers as indicators of sources and transport of sedimentary organic matter in a subtropical river

The sources and transformations of sedimentary organic matter along the Harney River, a representative subtropical river of the Florida Everglades, were assessed using a natural product biomarker approach. Sediment samples were collected from the headwaters to the Continental Shelf, with characteristic vegetation dominated by freshwater marsh species, mangrove (middle to lower estuary), and seagrass as the marine end-member. A peat sample was collected inland. All sample extracts were analyzed by GC–MS as underivatized and as silylated compounds. With these total extract analyses, major compound classes can be defined: n-alkanols, n-alkanoic acids, methyl alkanoates, methyl - and ω-hydroxyalkanoates, triterpenoids, phytosterols and saccharides, with traces of hydrocarbons. In general, the peat sample extract has a different overall composition compared to the sediment extracts. The major differences include distinct carbon number maxima for the lipid series (e.g., C_max = 28 for n-alkanols) probably from sawgrass and periphyton biomass, and predominance of phytosterols (sitosterol and stigmasterol) from higher plant detritus. In contrast, river sediment extracts contain biomarkers predominantly from mangrove-derived organic matter, such as the triterpenoids taraxerol and myricadiol. Significant amounts of saccharides and ω-hydroxyalkanoates are also found. Generally, compound concentrations decrease downstream due to dilution, and alteration of organic compounds from plant waxes and coastal vegetation is obvious in both peat and sediment samples. This is confirmed by the significant low abundance of n-alkanes and n-alkenoic acids due to biodegradation, oxidation of -tocopherol to homophytanic acid γ-lactone, and presence of traces of dihydrolacunosic acid, a photochemical alteration product of taraxerol.     

Effects of the antimicrobial agent sulfamethazine on metolachlor persistence and sorption in soil

Recent monitoring investigations have shown that antimicrobial agents used in veterinary medicine can cause non-point source contamination of soils through manure spreading. In the present study, the effect of the antimicrobial agent sulfamethazine (sulfadimidine) on degradation and sorption of the herbicide metolachlor in a sandy loam soil was studied. In soil samples treated with sulfamethazine at two concentrations (15 and 150 microg kg(-1) soil), metolachlor persistence was not different than of that observed in untreated samples. These results were supported by the absence of effects of both sulfamethazine concentration levels on the size of the culturable soil bacteria population. Equilibrating soil samples with metolachlor solutions containing equivalent sulfamethazine concentrations did not lead to any significant effects on metolachlor sorption, suggesting that, under the conditions of the present experiment, sulfamethazine did not affect metolachlor bioavailability in soil. This laboratory investigation showed that concentrations of sulfamethazine in the microg kg(-1) range did not cause significant effects on metolachlor degradation and sorption thus not affecting the main processes ruling its environmental fate in soil.