Interference-aware scheduling in the multiuser MIMO-OFDM downlink - [topics in radio communications]

With the introduction of orthogonal frequency- division multiplexing and multiple antennas in cellular networks, there are new opportunities to adapt the transmission to propagation and interference conditions. In this article we describe a practical approach using space-frequency-selective multiuser MIMO scheduling. Frequency-selective feedback is provided on achievable data rates for preferred single- and multistream transmission modes. The base station selects the best mode while providing instantaneous fairness. We observe that multiuser transmission increases the probability of using multistream transmission. Besides the benefits from optimal combining at the physical layer, there is an additional gain at the MAC layer since the estimation of achievable rates becomes more precise. Altogether, 93 percent of the theoretical throughput can be realized by synchronizing the base stations and providing cell-specific reference signals. We have implemented essential functions of the approach in real time on an experimental 3GPP LTE prototype in 20 MHz bandwidth. Feasibility of the key features is proven in laboratory and field trials.     

Pilot experiments with electrodialysis and ozonation for the production of a fertiliser from urine.

Pilot tests were performed with a process combination of electrodialysis and ozonation for the removal of micropollutants and the concentration of nutrients in urine. In continuous and batch experiments, maximum concentration factors up to 3.5 and 4.1 were obtained, respectively. The desalination capacity did not decrease significantly during continuous operation periods of several weeks. Membrane cleaning after 195 days resulted in approximately 35% increase in desalination rate. The Yeast Estrogen Screen (YES), a bioassay that selectively detects oestrogenic compounds, confirmed that about 90% of the oestrogenic activity was removed by electrodialysis. HPLC analysis showed that ibuprofen was removed to a high extent, while other micropollutants were below the detection limit. In view of the fact that ibuprofen is among the most rapidly transported micropollutants in electrodialysis processes, this result indicates that electrodialysis provides an effective barrier for micropollutants. Standardised plant growth tests were performed in the field with the salt solution resulting from the treatment by electrodialysis and subsequent ozonation. The results show that the plant height is comparable to synthetic fertilisers, but the crop yield is slightly lower. The latter is probably caused by volatilisation losses during field application, which can be prevented by improved application technologies.     

Environmental life-cycle inventory of detergent-grade surfactant sourcing and production

Life-cycle inventories were compiled to characterize natural resource requirements and environmental emissions associated with the sourcing and production of selected, detergent-grade surfactants and surfactant feedstocks. Petrochemical surfactant types examined were linear alkylbenzene sulfonate, alcohol sulfate (AS), alcohol ethoxylate (AE) and alcohol ethoxylate sulfate (AES). Oleochemical surfactants derived from palm oil, palm kernel oil and inedible tallow were AS, AE, AES and (for palm oil and tallow) methyl ester sulfonate. It was determined that natural resource requirements were primarily related to the source of feedstock and secondarily to surfactant type. Likewise, the composition and mass of atmospheric, aqueous and solid emissions were principally determined by feedstock source. Energy requirements varied as a function of both feedstock and surfactant type. The inventories do not support fundamental shifts in surfactant usage or feedstock sourcing on the basis of environmental concerns, as no single surfactant or feedstock was identified as superior across all resource and emissions criteria examined. The data provide baselines for evaluating opportunities for resource optimization, pollution prevention and waste minimization within each production technology surveyed.     

Development of a roadmap for advanced ceramics: 2010–2025

A roadmap for advanced ceramics for the period from 2010 to 2025 has been developed to provide guidelines for future investments for policy makers, scientists and industry alike. Based on questionnaires, interviews and a final workshop with well-balanced participation of members from industry and academia three roadmaps on application fields and two roadmaps on scientific areas have been developed and contrasted. The three application fields selected are: (i) electronics, information and communication; (ii) energy and environment; (iii) mechanical engineering and the two scientific fields are: (a) structural and functional properties; (b) process technology. Within these fields the tremendous growth opportunities for ceramics as an enabling technology are highlighted and manifold suggestions for future development are provided.     

New cellular ceramics from high alkane phase emulsified suspensions (HAPES)

Open porous mechanically stable ceramic foams are developed by a simple direct foaming process. The new processing route is based on the transition of a surfactant stabilized highly concentrated alkane phase homogeneously distributed in a stabilized aqueous ceramic powder suspension into high performance ceramic foams with porosities up to 90% and cell sizes ranging from 3 to 200 μm. The droplet size distribution of the high alkane phase emulsified suspensions (HAPES) is efficiently controlled by the stirring velocity during emulsification experimentally investigated for varying powder particle contents. Stable foams with tailored structural features can be prepared by adjusting the rheological characteristics of HAPES being dependent on the system and process parameters. The influence of the emulsification stirring velocity on the resulting HAPES droplet size is analysed on the basis of the Taylor model of mechanical shearing describing the stresses responsible for the fragmentation of the droplets.     

13C n.m.r. study of raw materials for carbon black

¹³C n.m.r. spectroscopy has been applied to investigate a number of coal tar and petroleum-derived carbon black feedstocks. Application of the J-modulated spin echo technique is especially rewarding, as this method renders the quaternary carbons directly detectable. Thus the quality of carbon black feedstocks can additionally be gauged on the basis of the contents of quaternary carbons, which is a direct indication of the carbon yield in the carbon black production process.     

Partial biochemical characterization of tetrazolium red‐reactive Lactobacillus plantarum mutants

One thousand colonies derived from Lactobacillus plantarum ATCC 8014 cells that survived 34–43 × 10³ ergs cm^‐2 ultraviolet irradiation were screened on media containing tetrazolium red to detect fermentative mutants. Fermentation end‐products formed from pyruvate, glucose, or lactose catabolism were determined. All 37 stable tetrazolium red‐reactive mutants had increased pyruvate utilization compared to the wild‐type strain. Only two did not produce lactate from exogenous pyruvate. When glucose or lactose were substrates, these two mutants and six other representative mutants produced lactate at levels similar to the parent strain. Although the average lactate and acetoin production from pyruvate by the mutants and wild‐type strains were similar, 25% of the mutants had increased acetoin production.     

Finite element analysis of a shear punch test

The authors present new experimental data for shear punch tests and tensile tests using four different materials. The correlation between shear punch and tensile yield stresses must be established empirically, and the procedure for doing this is discussed. The elastic-plastic deformation in a shear punch test develops gradually with increasing punch displacement and is often assumed to be simple shear. This is examined using finite element analysis to simulate the development of plasticity during the early stages of punch displacement. The simulation results are used to rationalize the empirically established yield stress correlations.     

Response of V79 cells to low doses of X-rays and negative pi-mesons: clonogenic survival and DNA strand breaks

Mammalian cells are hypersensitive to very low doses of X-rays (< 0.2 Gy), a response which is followed by increased radioresistance up to 1 Gy. Increased radioresistance is postulated to be a response to DNA damage, possibly single-strand breaks, and it appears to be a characteristic of low linear energy transfer (LET) radiation. Here we demonstrate a correspondence between the extent of the increased radioresistance and linear energy transfer of 250 kVp X-rays and plateau and Bragg peak negative pi-mesons. The results support our hypothesis since the size of the increased radioresistant response appears to correspond to the number of radiation induced single-strand breaks. Furthermore, since survival prior to the increased radioresistant response (< 0.2 Gy) was LET-independent, these data support the notion that the increased radioresistant response may dictate the overall survival response to higher doses. However, while these data provide further circumstantial evidence for the involvement of DNA strand breaks in the triggering of increased radioresistance, more direct conclusions cannot be made. The data are not accurate enough to detect structure in the single-strand break profiles, the production of single-strand breaks being apparently linear with dose.