19 research outputs found
Recommended from our members
Overview of DOE's field screening technology development activities
The Department of Energy (DOE) has recently created the Office of Environmental Restoration and Waste Management, into which it consolidated those activities. Within this new organization, the Office of Technology Development (OTD) is responsible for research, development, demonstration, testing, and evaluation (RDDT E) activities aimed at meeting DOE cleanup goals, while minimizing cost and risk. Site characterization using traditional drilling, sampling, and analytical methods comprises a significant part of the environmental restoration efforts in terms of both cost and time to accomplish. It can also be invasive and create additional pathways for spread of contaminants. Consequently, DOE is focusing on site characterization as one of the areas in which significant technological advances are possible which will decrease cost, reduce risk, and shorten schedules for achieving restoration goals. DOE is investing considerably in R D and demonstration activities which will improve the abilities to screen chemical, radiological, and physical parameters in the field. This paper presents an overview of the program objectives and status and reviews some of the projects which are currently underway in the area. 1 ref
The digestive performance of mammalian herbivores: why big may not be that much better
1. A traditional approach to the nutritional ecology of herbivores is that larger animals can tolerate a diet of lesser quality due to a higher digestive efficiency bestowed on them by comparatively long ingesta retention times and lower relative energy requirements.
2. There are important physiological disadvantages that larger animals must compensate for, namely a lower gut surface : gut volume ratio, larger ingesta particle size and greater losses of faecal bacterial material due to more fermentation. Compensating adaptations could include an increased surface enlargement in larger animals, increased absorption rates per unit of gut surface, and increased gut motility to enhance mixing of ingesta.
3. A lower surface : volume ratio, particularly in sacciform forestomach structures, could be a reason for the fact that methane production is of significant scope mainly in large herbivores and not in small herbivores with comparably long retention times; in the latter, the substrate for methanogenesis – the volatile fatty acids – could be absorbed faster due to a more favourable gut surface : volume ratio.
4. Existing data suggest that in herbivores, an increase in fibre digestibility is not necessarily accompanied by an increase in overall apparent dry matter digestibility. This indicates a comparative decrease of the apparent digestibility of non-fibre material, either due to a lesser utilization of non-fibre substrate or an increased loss of endogenous/bacterial substance. Quantitative research on these mechanisms is warranted in order to evaluate whether an increase in body size represents a net increase of digestive efficiency or just a shift of digestive focus