Recycling Factor Research Articles

Wastewater recycling and environmental constraints at a base metal mine and process facilities

In temperate areas of abundant freshwater there is seldom an urgency to recycle. The statutory protection of inland waters for beneficial uses such as drinking, food processing and game fishing is requiring industries to choose recycling. A European success in this trend is a base metal mining/milling industry which, since 1977, is implementing hydraulic, hydrological, treatment and ecological studies with wastewaters and mine tailings. A model activity, located 50 km from Dublin is considered. Zinc and lead concentrates produced and exported to smelters ultimately yield approximately 194,000 t and 54,000 t of these respective metals (32 and 21 percent of European production). Water use as originally planned would have been approximately 6m3/t of ore milled. While ore milling increased by 25 percent to 8,500t/d in 1993, water use declined by 33 percent to 4m3/t. The components making up this reduction range from milling technology efficiency to greater recycling from the 165 ha tailings pond. Environmental standards, based on framework regulations originating in EU Directives, have been instrumental in achieving wastewater savings. A conclusion is the value of integrating water quantity, quality, recycling, storage, production and other factors early in project planning.

Wastewater recycling and environmental constraints at a base metal mine and process facilities

In temperate areas of abundant freshwater there is seldom an urgency to recycle. The statutory protection of inland waters for beneficial uses such as drinking, food processing and game fishing is requiring industries to choose recycling. A European success in this trend is a base metal mining/milling industry which, since 1977, is implementing hydraulic, hydrological, treatment and ecological studies with wastewaters and mine tailings. A model activity, located 50 km from Dublin is considered. Zinc and lead concentrates produced and exported to smelters ultimately yield approximately 194,000 t and 54,000 t of these respective metals (32 and 21 percent of European production). Water use as originally planned would have been approximately 6m3/t of ore milled. While ore milling increased by 25 percent to 8,500t/d in 1993, water use declined by 33 percent to 4m3/t. The components making up this reduction range from milling technology efficiency to greater recycling from the 165 ha tailings pond. Environmental standards, based on framework regulations originating in EU Directives, have been instrumental in achieving wastewater savings. A conclusion is the value of integrating water quantity, quality, recycling, storage, production and other factors early in project planning.

Ribosome recycling by ribosome recycling factor (RRF) — An important but overlooked step of protein biosynthesis

Ribosome recycling by ribosome recycling factor (RRF) — An important but overlooked step of protein biosynthesis

Dual functions of ribosome recycling factor in protein biosynthesis: Disassembling the termination complex and preventing translational errors

We summarize in this communication the data supporting the two functions of ribosome recycling factor (RRF, originally called ribosome releasing factor). The first described role involves the disassembly of the termination complex which consists of mRNA, tRNA and the ribosome bound to the mRNA at the termination codon. This process is catalyzed by two factors, elongation factor G (EF-G) and RRF. RRF stimulated protein synthesis as much as eight-fold in the in vitro lysozyme synthesis system, when ribosomes were limiting. In the absence of RRF, ribosomes remain mRNA-bound at the termination codon and translate downstream codons. In the in vitro system, the site of reinitiation is the triplet codon 3′ to the termination codon. RRF is an essential protein for bacterial life. Temperature sensitive (ts) RRF mutants were isolated and in vivo translational reinitiation due to inactivation of ts RRF was demonstrated using the β-galactosidase reporter gene placed downstream from the termination codon. A second function of RRF involves preventing errors in translation. In polyphenylalanine synthesis programmed by polyuridylic acid, misincorporation of isoleucine, leucine or a mixture of amino acids was stimulated upto 17-fold when RRF was omitted from the in vitro system. RRF did not influence the large error (10-fold increase) induced by streptomycin. This means that RRF participates not only in the disassembly of the termination complex but also in peptide elongation. Extending this concept and its conventional role for releasing ribosomes from mRNA, involvement of RRF in the reinitiation in the 3A′ system (a construct using S aureus protein A, a collaborative work with Dr Isaksson), in programmed frame shifting, in trans-translation with 10Sa RNA (collaborative work with Dr Muto), and in the reinitiation downstream from the ORF A of the IS 3 (insertion sequence of a transposon, collaborative work with Dr Sekine) are discussed on the basis of preliminary data to be published elsewhere. Finally, we review the known RRF sequences from various organisms including eukaryotes and discuss the possible mechanism for disassembly of the eukaryotic termination complex.

New protein functions in yeast chromosome VIII

The analysis of the 269 open reading frames of yeast chromosome VIII by computational methods has yielded 24 new significant sequence similarities to proteins of known function. The resulting predicted functions include three particularly interesting cases of translation-associated proteins: peptidyl-tRNA hydrolase, a ribosome recycling factor homologue, and a protein similar to cytochrome b translational activator CBS2. The methodological limits of the meaningful transfer of functional information between distant homologues are discussed.

Characterization of photon recycling in thin crystalline GaAs light emitting diodes

Gallium arsenide light emitting diodes (LEDs) were fabricated using molecular beam epitaxial films on GaAs substrates and removed by epitaxial lift-off (ELO). Lifted off devices were then mounted on a Si wafer using a Pd/Au/Cr contact layer, which also served as a back surface reflector. Devices were characterized by electrical and optical measurements, and the results for devices on the GaAs substrate were compared to those for ELO devices. ELO LEDs coated with a ZnS/MgF2 antireflection coating exhibited an optical output that was up to six times that of LEDs on GaAs substrates. At the same time, the measured current-voltage characteristics of the ELO devices displayed a lower n=1 current component. ELO LEDs with efficiencies up to 12.5% were realized. We attribute these results to photon recycling enhanced by the back-surface reflector in the ELO LEDs. The luminescence versus current and current versus voltage characteristics of the LEDs were analyzed to obtain the nonradiative minority carrier lifetimes and the photon recycling factors. The results demonstrate that the measured characteristics are well described by photon recycling theory. ELO LEDs may prove useful for characterizing recombination processes in LEDs, and thin-crystalline structures could provide substantial efficiency enhancements for LEDs and solar cells.

Designing a green policy

A pressing area of concern is the future competitiveness of the electronics industry. Design For Environment (DFE) is a method by which environmental considerations and constraints can be integrated into existing process and product design practices. It involves considering the environmental impact of all materials and processes that are involved in the entire life-cycle of the product. The life-cycle of a product is from materials extraction to production, use, and disposal. DFE can be broken into smaller subgroups involving designing for such things as pollution prevention, product disassembly and recyclability, environmentally sound processing, materials recyclability, maintainability, and other factors. Accounting practices and organizational issues need to be addressed as well in order to fully implement DFE within a corporation. A company that institutes DFE in its practices minimizes waste, energy, materials, and hazardous substances in its product and its manufacturing, and maximizes overall environmental friendliness in its design.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Ribosome recycling factor (ribosome releasing factor) is essential for bacterial growth.

Ribosome releasing factor, product of the frr gene in Escherichia coli, is responsible for dissociation of ribosomes from mRNA after the termination of translation. It functions to "recycle" ribosomes and is renamed ribosome recycling factor in this paper. An E. coli strain was constructed (MC1061-2), which carried frame-shifted frr in the chromosome and wild-type frr on a temperature-sensitive plasmid. MC1061-2 is temperature-sensitive in its growth and does not segregate its frr-carrying plasmid under the plasmid incompatibility pressure. In contrast, isogenic E. coli carrying wild-type frr in the chromosome and mutated frr on the temperature-sensitive plasmid is not temperature-sensitive in its growth and segregates its plasmid from incompatible plasmids. All spontaneously formed thermoresistant colonies derived from MC1061-2 carried wild-type frr that resided either in the bacterial chromosome by re-exchange or in the plasmid, which became temperature-resistant. These observations establish that frr is an essential gene for cell growth.

Requirements for intercistronic distance and level of eukaryotic initiation factor 2 activity in reinitiation on GCN4 mRNA vary with the downstream cistron.

Translational control of the GCN4 gene in response to amino acid availability is mediated by four short open reading frames in the GCN4 mRNA leader (uORFs) and by phosphorylation of eukaryotic initiation factor 2 (eIF-2). We have proposed that reducing eIF-2 activity by phosphorylation of its alpha subunit or by a mutation in the eIF-2 recycling factor eIF-2B allows ribosomes which have translated the 5'-proximal uORF1 to bypass uORF2 to uORF4 and reinitiate at GCN4 instead. In this report, we present two lines of evidence that all ribosomes which synthesize GCN4 have previously translated uORF1, resumed scanning, and reinitiated at the GCN4 start site. First, GCN4 expression was abolished when uORF1 was elongated to make it overlap the beginning of the GCN4 coding region. Second, GCN4 expression was reduced as uORF1 was moved progressively closer to GCN4, decreasing to only 5% of the level seen in the absence of all uORFs when only 32 nucleotides separated uORF1 from GCN4. We additionally found that inserting small synthetic uORFs between uORF4 and GCN4 inhibited GCN4 expression under derepressing conditions, confirming the idea that reinitiation at GCN4 under conditions of diminished eIF-2 activity is proportional to the distance of the reinitiation site downstream from uORF1. While uORF4 and GCN4 appear to be equally effective at capturing ribosomes scanning downstream from the 5' cap of mRNA, these two ORFs differ greatly in their ability to capture reinitiating ribosomes scanning from uORF1. When the active form of eIF-2 is present at high levels, reinitiation appears to be much more efficient at uORF4 than at GCN4 when each is located very close to uORF1. Under conditions of reduced recycling of eIF-2, reinitiation at uORF4 is substantially suppressed, which allows ribosomes to reach the GCN4 start site; in contrast, reinitiation at GCN4 in constructs lacking uORF4 is unaffected by decreasing the level of eIF-2 activity. This last finding raises the possibility that time-dependent binding to ribosomes of a second factor besides the eIF-2-GTP-Met-tRNA(iMet) ternary complex is rate limiting for reinitiation at GCN4. Moreover, our results show that the efficiency of translational reinitiation can be strongly influenced by the nature of the downstream cistron as well as the intercistronic distance.

Requirements for intercistronic distance and level of eukaryotic initiation factor 2 activity in reinitiation on GCN4 mRNA vary with the downstream cistron.

Translational control of the GCN4 gene in response to amino acid availability is mediated by four short open reading frames in the GCN4 mRNA leader (uORFs) and by phosphorylation of eukaryotic initiation factor 2 (eIF-2). We have proposed that reducing eIF-2 activity by phosphorylation of its alpha subunit or by a mutation in the eIF-2 recycling factor eIF-2B allows ribosomes which have translated the 5'-proximal uORF1 to bypass uORF2 to uORF4 and reinitiate at GCN4 instead. In this report, we present two lines of evidence that all ribosomes which synthesize GCN4 have previously translated uORF1, resumed scanning, and reinitiated at the GCN4 start site. First, GCN4 expression was abolished when uORF1 was elongated to make it overlap the beginning of the GCN4 coding region. Second, GCN4 expression was reduced as uORF1 was moved progressively closer to GCN4, decreasing to only 5% of the level seen in the absence of all uORFs when only 32 nucleotides separated uORF1 from GCN4. We additionally found that inserting small synthetic uORFs between uORF4 and GCN4 inhibited GCN4 expression under derepressing conditions, confirming the idea that reinitiation at GCN4 under conditions of diminished eIF-2 activity is proportional to the distance of the reinitiation site downstream from uORF1. While uORF4 and GCN4 appear to be equally effective at capturing ribosomes scanning downstream from the 5' cap of mRNA, these two ORFs differ greatly in their ability to capture reinitiating ribosomes scanning from uORF1. When the active form of eIF-2 is present at high levels, reinitiation appears to be much more efficient at uORF4 than at GCN4 when each is located very close to uORF1. Under conditions of reduced recycling of eIF-2, reinitiation at uORF4 is substantially suppressed, which allows ribosomes to reach the GCN4 start site; in contrast, reinitiation at GCN4 in constructs lacking uORF4 is unaffected by decreasing the level of eIF-2 activity. This last finding raises the possibility that time-dependent binding to ribosomes of a second factor besides the eIF-2-GTP-Met-tRNA(iMet) ternary complex is rate limiting for reinitiation at GCN4. Moreover, our results show that the efficiency of translational reinitiation can be strongly influenced by the nature of the downstream cistron as well as the intercistronic distance.

Mutations in the alpha subunit of eukaryotic translation initiation factor 2 (eIF-2 alpha) that overcome the inhibitory effect of eIF-2 alpha phosphorylation on translation initiation.

Phosphorylation of eIF-2 alpha in Saccharomyces cerevisiae by the protein kinase GCN2 leads to inhibition of general translation initiation and a specific increase in translation of GCN4 mRNA. We isolated mutations in the eIF-2 alpha structural gene that do not affect the growth rate of wild-type yeast but which suppress the toxic effects of eIF-2 alpha hyperphosphorylation catalyzed by mutationally activated forms of GCN2. These eIF-2 alpha mutations also impair translational derepression of GCN4 in strains expressing wild-type GCN2 protein. All four mutations alter single amino acids within 40 residues of the phosphorylation site in eIF-2 alpha; however, three alleles do not decrease the level of eIF-2 alpha phosphorylation. We propose that these mutations alter the interaction between eIF-2 and its recycling factor eukaryotic translation initiation factor 2B (eIF-2B) in a way that diminishes the inhibitory effect of phosphorylated eIF-2 on the essential function of eIF-2B in translation initiation. These mutations may identify a region in eIF-2 alpha that participates directly in a physical interaction with the GCN3 subunit of eIF-2B.

Why recycle? A comparison of recycling motivations in four communities

Four Illinois communities with different sociode-mographic compositions and at various stages of planning for solid waste management were surveyed to determine the influence of sociodemographic variables and planning stages on the factors that motivate recycling behavior. A factor analysis of importance ratings of reasons for recycling and for not recycling yielded five factors interpreted as altruism, personal inconvenience, social influences, economic incentives, and household storage. The four communities were shown to be significantly different in multivariate analyses of the five motivational factors. However, attempts to explain these community differences with regression analyses, which predicted the motivational factors with dummy codes for planning stages, a measure of self-reported recycling behavior, and sociodemographic measures were unsatisfactory. Contrary to expectation, the solid waste management planning stages of the cities (curbside pickup, recycling dropoff center, and planning in progress) contributed only very slightly to the prediction of motivational factors for recycling. Community differences were better explained by different underlying motivational structures among the four communities. Altruistic reasons for recycling (e.g., conserving resources) composed the only factor which was similar across the four communities. This factor was also perceived to be the most important reason for recycling by respondents from all four communities. The results of the study supported the notion that convenient, voluntary recycling programs that rely on environmental concern and conscience for motivation are useful approaches to reducing waste.

Morphometry and sedimentation as regulating factors for nutrient recycling and trophic state in coastal waters

Morphometry and sedimentation as regulating factors for nutrient recycling and trophic state in coastal waters

On Fusion/Fission Chain Reactions in the Fleischmann-Pons “Cold Fusion” Experiment

In this paper the possibility of fusion/fission chain reactions following d-d source reactions in electrochemical cold fusion experiments have been investigated. The recycling factors for the charged particles in fusion reactions with consumable nuclei deuteron, {sup 6}Li nd {sup 7}Li, are estimated. It is concluded that, based on the established nuclear fusion cross sections and electronic stopping power, the recycling factor is four to five orders of magnitude less than required for close to critical conditions. It is argued that the cross generation of charged particles by neutrons does not play a significant role in this process, even if increased densities at the surface of electrodes do occur.

A simplified recycling model for the dosimetry of radioiodide

Following the administration of radioiodide, a process of recycling takes place in which part of the radioiodide taken up and organified by the thyroid is subsequently released to re-enter the cycle. The convolution method has been applied to a simplified three-compartment model to predict individual cycles and overall cycling effects in the compartments and to illustrate the influence of various parameters on the effects of recycling. For example, a turnover half-time of 80 d in the thyroid is increased, as a result of recycling, to about 110 d if the thyroid uptake fraction is 0.3, and to about 153 d if the uptake increases to 0.55. An equation is derived for calculating a recycling factor based on values of the model parameters. The factor, which is common to the three compartments of the model, permits calculation of cumulated activities in the compartments allowing for the effects of recycled radioiodide. It is shown how differences in values of thyroid uptake fraction and discharge rate and of the physical half-lives of iodine radioisotopes affect the value of the recycling factor. Dose calculations for 125I, administered as radioiodide, are used to illustrate the above techniques and to examine the effects of recycling on dosimetry. Although recycling can lead to large increases in the doses to some body organs, the thyroid dose greatly exceeds the dose to any other organ and alone accounts for nearly all the effective dose equivalent.

Ammonium regeneration in eutrophicated coastal waters of Sweden

Rates of ammonium regeneration were measured in the Kattegat and Laholm Bay, a shallow, eutrophicated embayment in the southeastern Kattegat. Over the year, average rates in the central outer part of Laholm Bay were 51 nmol 1-' h-' and near the outlet of the River Nissan 49 nmol 1-' h-'. Elevated rates were observed during the peak of the spring bloom, and rates increased with depth throughout spring (contrary to autumn, when rates decreased with depth). Die1 variations were more pronounced in March (wlth rates during night and early morning 7 times higher than those in the evening) than in September when variations were within the error of the method. Rates measured during autumn in the central outer part were 2.5 times h g h e r than in spnng. Correcting these for the observed die1 variations resulted in 1.5 times higher rate of ammonium regeneration during autumn. In a transect extending outwards from the River Nissan, a positive correlation between the recycling factor (r) and the ammonium regeneration rate was found, even if the ammonium regeneration contributed only to part of the ammonlum uptake (due to allochthonous ammonlum input from the river) Ammonium regeneration rates (R) were generally found to exceed those of ammonium uptake (U), resulting in ratios of U: R being < 1, and should be considered as potential rates.

Preliminary experimental results of gas recycling subsystems except carbon dioxide concentration

Oxygen concentration and separation is an essential factor for air recycling in a CELSS. Furthermore, if the value of the plant assimilatory quotient is not coincident with that of the animal respiratory quotient, the recovery of O 2 from the concentrated CO 2 through chemical methods will become necessary to balance the gas contents in a CELSS. Therefore, oxygen concentration and separation equipment using Salcomine and O 2 recovery equipment, such as Sabatier and Bosch reactors, were experimentally developed and tested.

Eukaryotic initiation factor 2 from rat liver: no apparent function for the β-subunit in the formation of initiation complexes

Eukaryotic protein synthesis initiation factor 2 (eIF-2) from rat liver has been resolved into two subfractions by anion-exchange chromatography on DEAE-cellulose. One of these contained all three components (eIF-2α, eIF-2β, eIF-2γ) characteristic of mammalian eIF-2, whilst the other fraction contained only two. By a number of criteria these were shown to be eIF-2α and eIF-2γ. The absence of eIF-2β from this fraction was not due to its proteolytic degradation during purification since it was unaffected by the inclusion of a range of proteinase inhibitors in the isolation media. The properties of eIF-2 containing or lacking eIF-2β have been directly compared. It was found that eIF-2β was not required for the binding of guanine nucleotides to eIF-2 or for formation of ternary initiation complexes with GTP and the initiator tRNA. eIF-2 lacking eIF-2β was able to form 40 S initiation complexes and the presence of eIF-2β was also unnecessary for the stimulation of eIF-2 activity by the recycling factor, eIF-2B. Some of these findings are at variance with previous reports in which eIF-2β was removed proteolytically. The role of eIF-2β in the overall physiological function of eIF-2 remains to be elucidated.

Impurity recycling and retention on Au and C surfaces exposed to the scrape-off layer of the TCA tokamak

In addition to impurity trapping, surfaces exposed to the boundary layer of a tokamak and other fusion devices are subjected to erosion phenomena. On local surface regions which do not experience unipolar arcing, these processes are due to the energetic fluxes of impurity and plasma particles which induce sputtering. Data are presented on collection probe experiments in the TCA tokamak which demonstrate that this erosion behavior may be evaluated from a knowledge of the shot dependence of the areal concentrations and impact energies of the trapped particles within the surface. Furthermore, a semiempirical parameter, which we call the ‘‘impurity recycling factor’’ (k), can be used to describe impurity retention and sputtering behavior for local plasma-surface interactions. Data on impurity retention and reemission are presented with respect to the impurity recycling factor as a function of the distance from the plasma edge.

Regulation of protein synthesis in eukaryotes. Eukaryotic initiation factor eIF-2 and eukaryotic recycling factor eRF from neuroblastoma cells

eIF-2 purified from neuroblastoma cells consists of three subunits, which appear to be of molecular weight identical to those of the subunits of rabbit reticulocyte eIF-2. A protein fraction has been isolated from neuroblastoma cells with characteristics similar to eRF from reticulocytes: stimulation of amino acid incorporation in a hemin-deprived reticulocyte lysate, the removal of GDP from eIF-2-GDP complexes, a 4–5-fold stimulatory effect in a two-step reaction measuring 40 S preinitiation complex formation and a 3–3.5-fold stimulation in the methionyl-puromycin synthesis. In the methionyl-puromycin-synthesizing system phosphorylated eIF-2 is not responsive to the addition of this fraction from neuroblastoma cells. The protein fraction contains eRF which seems to be similar to the eRF isolated from Ehrlich ascites tumor cells and somewhat distinct from the reticulocyte factor. Incubation of neuroblastoma cell lysate in the presence of [γ- 32P]ATP results in the phosphorylation of a protein of M r 36 000, migrating on SDS-polyacrylamide gels to the position of eIF-2α. This protein is also phosphorylated in vitro by HRI from reticulocytes. These results may reflect a common underlying principle for the quantitative regulation of protein synthesis in eukaryotic cells.