What Do We Know About Metal Recycling Rates?

The recycling of metals is widely viewed as a fruitful sustainability strategy, but little information is available on the degree to which recycling is actually taking place. This article provides an overview on the current knowledge of recycling rates for 60 metals. We propose various recycling metrics, discuss relevant aspects of recycling processes, and present current estimates on global end‐of‐life recycling rates (EOL‐RR; i.e., the percentage of a metal in discards that is actually recycled), recycled content (RC), and old scrap ratios (OSRs; i.e., the share of old scrap in the total scrap flow). Because of increases in metal use over time and long metal in‐use lifetimes, many RC values are low and will remain so for the foreseeable future. Because of relatively low efficiencies in the collection and processing of most discarded products, inherent limitations in recycling processes, and the fact that primary material is often relatively abundant and low‐cost (which thereby keeps down the price of scrap), many EOL‐RRs are very low: Only for 18 metals (silver, aluminum, gold, cobalt, chromium, copper, iron, manganese, niobium, nickel, lead, palladium, platinum, rhenium, rhodium, tin, titanium, and zinc) is the EOL‐RR above 50% at present. Only for niobium, lead, and ruthenium is the RC above 50%, although 16 metals are in the 25% to 50% range. Thirteen metals have an OSR greater than 50%. These estimates may be used in considerations of whether recycling efficiencies can be improved; which metric could best encourage improved effectiveness in recycling; and an improved understanding of the dependence of recycling on economics, technology, and other factors.     

Internode length in Pisum. I. The effect of the Le/le gene difference on endogenous gibberellin-like substances

The allelopathic potential of the dry fruits of Washingtonia filifera (L. Linden) H. Wendl. was investigated. Leachates from fruits inhibited the germination of lettuce, wheat, red cabbage and cucumber seeds. The inhibitory effect was partly neutralized by kinetin (20 mg 1⁻¹) and gibberellic acid (50 mg 1⁻¹). The effect of kinetin was more pronounced at 25°C than at 20°C. Substances inhibiting germination were localized in the pericarp of the fruit and were resistant to high temperature.     

Socially isolated? How parents and neighbourhood adults influence youth behaviour in disadvantaged communities

William Julius Wilson’s model of adult joblessness, community disorganization and their effects on youth problem behaviour de-emphasizes the range in children’s outcomes across socially disorganized communities, and says little about the factors that influence this variation. It also does not address the processes by which family structure and relationships affect the well-being of African-American and poor youth. My work is part of a larger research agenda that has begun to address these issues by focusing on the differential rates of sexual activity among youth living in disadvantaged environments, and developing models to explain this variation. This work suggests that units of socially cohesive, stable adults exist among the social networks of successful children and families in poor neighbourhoods. It also points to the existence and functioning of alternative two-parent family structures and offers hypotheses for how family environment interacts with neighbourhood context to influence youth behaviour.     

Optimization of Antiviral Prodrug Properties Using Combinatorial Methods

Abstract

Some diacid biodegradable synthesis of aziduthymidine (AZT) were synthesized and applied to production of about 60 different derivatives.     

Mechanism of the binding of 2-(4'-hydroxyphenylazo)benzoic acid to bovine serum albumin

The mechanism of the binding of 2-(4'-hydroxyphenylazo)benzoic acid (HABA) to bovine serum albumin was studied by relaxation methods as well as the binding isotherm using gel chromatography. A single relaxation was observed over a wide range of HABA concentration except at the extremes of high concentration where another slow process was observed. The concentration dependence of the reciprocal relaxation time of the fast process decreased monotonically with increase in concentration of HABA at constant polymer concentration. The data were analyzed on the basis of Brown's domain structure model and were found to be consistent with a sequential binding mechanism. The azohydrazon tautomerism of HABA was identified with the intramolecular step of the complex. The activation parameters of the step, determined from the temperature dependence of the relaxation time of the fast process, showed that this step is rate limited by an enthalpy barrier in both forward and backward directions. Comparison of the activation parameters with those of other serum albumin-ligand systems suggests that there is an enthalpy-entropy compensation in the activation process of the intramolecular step with the compensation temperature at about 270 K; the enthalpy-entropy compensation is thought to be related to the hydrophobic nature of the ligand.     

Thermal inhibition of repair of methylmethane sulfonate-damaged DNA in chick embryo fibroblasts

Chick embryo fibroblasts were treated with the monofunctional alkylating agent methylmethane sulfonate at various concentrations for 1 h at 42°C, rinsed and then incubated post-treatment at various temperatures at which the kinetics of alkali-labile bond disappearance was followed. Growth experiments showed that these cells grew similarly at temperatures of either 37°C or 42°C. Repair as assessed by removal of alkali-labile bond was also similar for postincubation in the temperature range 37–42°C for damage due to methylmethane sulfonate treatment at concentrations less than 1.5 mM. When the postincubation temperature was raised higher than 42.5–43°C, this type of repair was stopped. The normal internal body temperature of adult chickens is about 41.6°C. Hence the present finding indicates that chick cells are much more severely restricted in DNA repair at temperatures above normal than are mammalian cells, which can function in this respect for several deg. C above 37°C.     

Sequence heterogeneity and anomalous electrophoretic mobility of kinetoplast minicircle DNA from Leishmania tarentolae

Several unit-length minicircles from the kinetoplast DNA of Leishmania tarentolae were cloned into pBR322 and into M13 phage vectors. The complete nucleotide sequences of three different partially homologous minicircles were obtained. The molecules contained a region of approx. 80% sequence homology extending for 160–270 bp and a region unique to each minicircle. A 14-mer was found to be conserved in all kinetoplast minicircle sequences reported to date. The frequency distributions of various minicircle sequence classes in L. tarentolae were obtained by quantitative gel electrophoresis and by examination of the “T ladder” patterns of minicircles randomly cloned into M13 at several sites. By these methods we could assign approx. 50% of the total minicircle DNA into a minimum of five sequence classes. A sequence-dependent polyacrylamide gel migration abnormality was observed with several minicircle fragments both cloned and uncloned. The abnormality was dependent on the presence of a portion of the conserved region of the minicircle.     

A DNA Damage Checkpoint Pathway Coordinates the Division of Dikaryotic Cells in the Ink Cap Mushroom Coprinopsis cinerea

The fungal fruiting body or mushroom is a multicellular structure essential for sexual reproduction. It is composed of dikaryotic cells that contain one haploid nucleus from each mating partner sharing the same cytoplasm without undergoing nuclear fusion. In the mushroom, the pileus bears the hymenium, a layer of cells that includes the specialized basidia in which nuclear fusion, meiosis, and sporulation occur. Coprinopsis cinerea is a well-known model fungus used to study developmental processes associated with the formation of the fruiting body. Here we describe that knocking down the expression of Atr1 and Chk1, two kinases shown to be involved in the response to DNA damage in a number of eukaryotic organisms, dramatically impairs the ability to develop fruiting bodies in C. cinerea, as well as other developmental decisions such as sclerotia formation. These developmental defects correlated with the impairment in silenced strains to sustain an appropriated dikaryotic cell cycle. Dikaryotic cells in which chk1 or atr1 genes were silenced displayed a higher level of asynchronous mitosis and as a consequence aberrant cells carrying an unbalanced dose of nuclei. Since fruiting body initiation is dependent on the balanced mating-type regulator doses present in the dikaryon, we believe that the observed developmental defects were a consequence of the impaired cell cycle in the dikaryon. Our results suggest a connection between the DNA damage response cascade, cell cycle regulation, and developmental processes in this fungus.     

A transient species of poly(A)+ RNA detected by a myosin heavy chain cDNA probe in muscle cell culture during terminal differentiation

Primary cell cultures were prepared from breast muscles of 11 day 4 hour-embryonic chicks. Cytoplasmic RNAs were isolated from the cultured cells at various time intervals from day 3 to day 8. A [P32] DNA probe complementary to messenger RNA of myosin heavy chain was used to hybridize with the RNAs after gel electrophoresis. A transient species of polyadenylated RNA with a decreased mobility in electrophoresis was detected during a period of time when contractions of syncytial fibers were first observed.