Distribution of transuranic elements in a freshwater pond ecosystem

Preliminary results are reported from a study initiated on the Hanford Reservation concerning the ecological behavior of $sup 238$Pu, $sup 239$Pu, $sup 240$Pu, and $sup 241$Am in a freshwater environment. This study involves a waste pond which has been receiving Pu processing wastes for about 30 years. The pond has a sufficiently established ecosystem to provide an excellent location for limnological characterization. In addition, the ecological distribution of Pu and Am was investigated. The pond is also highly enriched with nutrients, thus supporting a high level of algal and macrophyte production. Seston (30 percent diatoms) appears to be the principal concentrators of Pu transuranics in the pond system. The major sink for Pu and Am in this system is the sediments. Organic floc, overlaying the pond sediments, is also a major concentrator of transuranics in this system. Aside from the seston and floc, no other ecological components of the pond appear to have concentrations significantly greater than those of the sediment. Dragonfly, larvae, watercress, and snails show concentrations which approximate those of the sediments but nearly all other food web components have levels of Pu and Am which are lower than those of the sediments, thus, Pu and Am seem to be relatively immobile in the aquatic ecosystem. (CH

Incipient toxicity of lithium to freshwater organisms representing a salmonid habitat

Because the eventual development of fusion power reactors could increase the mining, use and disposal of lithium five-fold by the year 2000, potential effects from unusual amounts of lithium in aquatic environments were investigated. Freshwater oganisms representing a Pacific Northwest salmonid habitat were exposed to elevated conentrations of lithium. Nine parameters were used to determine the incipient toxicity of lithium to rainbow trout (Salmo gairdneri), insect larvae (Chironomus sp.), and Columbia River periphyton. All three groups of biota were incipiently sensitive to lithium at concentrations ranging between 0.1 and 1 mg/L. These results correspond with the incipient toxicity of beryllium, a chemically similar component of fusion reactor cores. A maximum lithium concentration of 0.01 mg/L occurs naturally in most freshwater environments (beryllium is rarer). Therefore, a concentration range of 0.01 to 0.1 mg/L may be regarded as approaching toxic concentrations when assessing the hazards of lithium in freshwaters

Hybrid toolboxes: Conceptual and empirical analysis of blending patterns in application of hybrid media / Hibridinės žiniasklaidos modelių taikymo konceptuali ir empirinė analizė

Hybrid media concepts, i.e. especially combinations of face‐to‐face instruments and electronic media, represent a standard in many fields of application for quite a long time. Such combinations of diverse, and thus hybrid instruments are meanwhile quite commonly used, for example, in marketing, in retail business, for communication in virtual enterprises, in internal communication processes, in human resource development and in higher education. By combining strengths of two or more media and by mutually compensating their weaknesses, hybrid media concepts aim at enhancing performance with respect to effectiveness and efficiency. So far, however, scientific discussion lacks a common understanding of the architecture of hybrid media concepts as well as empirical evidence on the application of hybrid media in practice. Hence, it is unclear to what extent the performance potential of hybrid media concepts is utilized in different application fields and what the drivers of the use and performance of hybrid media concepts are. This article presents and discusses both a conceptualization of hybrid media in terms of diversity, proportions and coupling of hybrid concepts and empirical evidence on hybrid media concepts in two typical application fields: internal communication in change management and blended learning in higher education. Santrauka Jau gana seniai hibridinė žiniasklaida, t. y. tiesioginio bendravimo priemonės ir elektroninė žiniasklaida, paplitusi daugelyje veiklos sričių. Ivairūs hibridines žiniasklaidos priemonių deriniai dažnai naudojami marketinge, mažmenineje prekyboje, virtualiujų įmonių veikloje, vidaus komunikacijos procesuose, žmogiškuju išteklių plėtros ir aukštojo mokslo srityse. Derinant dvi ar daugiau žniasklaidos priemones, sustiprinami jų privalumai ir kompensuojami trūkumai. Taigi hibridine žiniasklaida yra veiksmingesnė. Tačiau iki šiol trūksta mokslines diskusijos apie hibridines žiniasklaidos koncepcijas, ju praktinį taikymą. Taigi nera aišku, kokiu mastu naudojamos hibridinės žiniasklaidos priemonės ir kas yra ju naudotojai. Straipsnyje pateikiamos hibridines žiniasklaidos koncepcijos ir ju praktinio taikymo pavyzdžiai vidaus ryšiu valdymo ir aukštojo mokslo srityse. First published online: 21 Oct 2010 Reikšminiai žodžiai: hibridinės žiniasklaidos koncepcijos, hibridinio valdymo koncepcijos, mišrūs mokymąsis, elektroninis komunikavimas, pokyčių valdymas, e. mokymasis, aukštasis moksla