Relative Abundance In Nature Research Articles

The impact of earth-abundant metals as a replacement for Pd in cross coupling reactions.

Substitution of one metal catalyst for another is not as straightforward as simply justifying this change based on the availability and/or cost of the metals. Methodologies to properly assess options for reaction design, including multiple factors like a metal's availability, cost, or environmental indicators have not advanced at the pace needed, leaving decisions to be made along these lines more challenging. Isolated indicators can lead to conclusions being made in too hasty a fashion. Therefore, an extensive life cycle-like assessment was performed documenting that the commonly held view that methods using earth-abundant metals (and in this case study, Ni) are inherently green replacements for methods using palladium in cross-coupling reactions, and Suzuki-Miyaura couplings, in particular, is an incomplete analysis of the entire picture. This notion can be misleading, and unfortunately derives mainly from the standpoint of price, and to some degree, relative natural abundance associated with the impact of mining of each metal. A more accurate picture emerges when several additional reaction parameters involved in the compared couplings are considered. The analysis points to the major impact that use of organic solvents has in these couplings, while the metals themselves actually play subordinate roles in terms of CO2-release into the environment and hence, the overall carbon footprint (i.e., climate change). The conclusion is that a far more detailed analysis is required than that typically being utilized.

Experimental determinations of carbon and hydrogen isotope fractionations and methane clumped isotope compositions associated with ethane pyrolysis from 550 to 600 °C

Methane clumped isotope compositions signify the relative natural abundances of rare, doubly substituted isotopic species of methane (13CH3D and 12CH2D2) and have emerged as a new isotopic tool to trace the sources, sinks, and lifecycles of methane in the environment. Such measurements can identify equilibration (or re-equilibration) temperatures if found to be in isotopic equilibrium or non-equilibrium processes (e.g., kinetically controlled reactions or mixing) if not in isotopic equilibrium. Naturally occurring thermogenic methane—formed by the thermally activated breakdown of larger organic molecules—has been found to have clumped isotope compositions consistent with equilibrium at reasonable gas formation temperatures in some settings and non-equilibrium processes occurring during either formation, migration, storage, or extraction in others. To explore the potential controls on the isotopic composition of thermogenic methane, we conducted isothermal time-series ethane pyrolysis experiments at 550 and 600 °C to measure methane and ethane 13C/12C and D/H fractionations and methane clumped isotope compositions (resolved 13CH3D and 12CH2D2). We explore the effects of modifying the initial clumped isotope composition of ethane and the addition of water vapor to pyrolysis experiments. We observe that ethane and methane 13C/12C are controlled by kinetic isotope effects and Rayleigh distillation processes. In contrast, ethane and methane D/H and methane clumped isotope compositions appear to be controlled by a combination of these processes and hydrogen isotope exchange. The hydrogen isotope exchange processes lead to isotopic equilibrium as reaction completion is approached for both D/H (ethane/methane) and methane clumped isotope compositions. We develop a chemical model based on a mass balance approach that accounts for inheritance vs. hydrogen-abstraction formation pathways for singly and doubly substituted isotopologues of ethane and methane that is compared to the experimental data. The model allows the determination of carbon and hydrogen kinetic isotope effects associated with ethane cracking and hydrogen abstraction reactions that, where applicable, we compare to prior theoretical constraints. From the comparison of the model to the experimental data, we infer that the kinetically controlled ethane and methane bulk isotope compositions and methane clumped isotope compositions are controlled by kinetic isotope effects (both primary and secondary) associated with both CC bond and CH bond cleavage reactions. Specifically, the methane clumped isotope compositions likely result from a combination of clumped isotope effects associated with ethane breakdown and/or assembly of methane isotopologues (expressed in terms of γ-factor parameters ≠ 1) and combinatorial effects that arise probabilistically. We discuss our experimental results in the context of recent pyrolysis experiments and observations of naturally occurring thermogenic methane. We consider a proposal consistent with observations from nature that the hydrogen isotope exchange reactions that promote equilibration of methane isotopic molecules at or near formation temperature may be facilitated by free radicals generated by pyrolysis reactions. In this framework, isotope exchange effectively ceases when pyrolysis effectively ceases locking in compositions that can be consistent with peak formation temperatures.

Co-activation for enhanced K-ion storage in battery anodes.

The relative natural abundance of potassium and potentially high energy density has established potassium-ion batteries as a promising technology for future large-scale global energy storage. However, the anodes' low capacity and high discharge platform lead to low energy density, which impedes their rapid development. Herein, we present a possible co-activation mechanism between bismuth (Bi) and tin (Sn) that enhances K-ion storage in battery anodes. The co-activated Bi-Sn anode delivered a high capacity of 634mAhg-1, with a discharge plateau as low as 0.35V, and operated continuously for 500 cycles at a current density of 50mA g-1, with a high Coulombic efficiency of 99.2%. This possible co-activation strategy for high potassium storage may be extended to other Na/Zn/Ca/Mg/Al ion battery technologies, thus providing insights into how to improve their energy storage ability.

Preparation of N,F,B-Doped Carbon Materials for High-Performance Electric Double Layer Capacitors

The incorporating heteroatom species into carbon materials give opportunities for improving electrochemical properties. Single N-doping strategies are widely studied because of easy preparations and relative abundance in nature. However, facile synthetic methods of multiple-heteroatom-doped carbons are urgent for high-performance supercapacitors. In this study, we propose N,F,B-doped carbons for electric double layer capacitors derived from polyamic acid mixed with boric acid using pyrolysis process. Fluorinated polyamic acid is applied for a N,F-doping source and boric acid acts as a B-doping source. The synthesized carbon materials exhibit excellent electrochemical performances because of the synergetic effects of each N, F, and B atoms. The N and F atoms improve electronegativity property and also low doped B atoms improve redox reactivity in the carbon. The electrode is fabricated by direct pyrolysis process with carbon fabrics, which is an advantage for binder-free type electrodes and flexibility. The morphology and surface properties of the fabricated electrodes are studied by SEM, XPS, Raman, sheet resistance, and contact angle measurement. Furthermore, the flexible symmetric device with PVA-1M H2SO4 gel electrolyte fabricated from the N,F,B-doped carbon indicates a high volumetric capacitance and an energy density as well as mechanical stabilities under various deformations. These results are expected that the synthesized N,F,B-heteroatom-doped carbons offer great potentials as electrode materials for supercapacitor applications.

A review of biodegradable films from industrial by-products for food packaging

Food packaging plays an important role in maintaining the quality of packaged food from any chemical, physical and environmental damage. Conventionally, plastic material is commonly used in the food industry due to large availability and excellent mechanical performance at a low cost. However, the usage of plastic packaging in huge amount creates the environmental and health issues. Since the availability of industrial by-products are relative abundance in nature at low cost, reusing of these by-products had gained high interest for researchers to develop new materials that meets food protection and preservation requirements. The addition of a natural bioactive compound such as antioxidant, antimicrobial and pigment also increase the functionality of the film and providing intelligent communication with the consumer. This review will be focusing on the utilisation of agricultural and pharmaceutical by-products as the source of biopolymer and additives in the development of biodegradable packaging film.

A review of biodegradable films from industrial by-products for food packaging

Food packaging plays an important role in maintaining the quality of packaged food from any chemical, physical and environmental damage. Conventionally, plastic material is commonly used in the food industry due to large availability and excellent mechanical performance at a low cost. However, the usage of plastic packaging in huge amount creates the environmental and health issues. Since the availability of industrial by-products are relative abundance in nature at low cost, reusing of these by-products had gained high interest for researchers to develop new materials that meets food protection and preservation requirements. The addition of a natural bioactive compound such as antioxidant, antimicrobial and pigment also increase the functionality of the film and providing intelligent communication with the consumer. This review will be focusing on the utilisation of agricultural and pharmaceutical by-products as the source of biopolymer and additives in the development of biodegradable packaging film.

Downcycling in automobile recycling process: A thermodynamic assessment

Current metal recycling techniques for end-of-life vehicles (ELV) are based on mechanical treatments to mainly recover steel, aluminum, copper, and zinc alloys. Such techniques facilitate compliance with the ELV European Directive (2000/53/EC) target of achieving recyclability quotes of up to 85%. However, a vehicle can use more than 60 metals, some of them considered critical by international institutions, which end up downcycled as part of alloys or ultimately in landfills. This paper undertakes an assessment of the downcycling degree of minor metals in conventional vehicles using a SEAT Leon III model as a case study. Downcycling is assessed from a thermodynamic point of view using thermodynamic rarity, an indicator that is used as a weighting factor for the metals used in the car. The thermodynamic rarity of metals is a function of the quality of the minerals from which they stem, considering their relative abundance in Nature and the energy intensity required to extract and process them. The results demonstrated that, even if the quantity of downcycled metals only represents 4.5% of the total metal weight of the vehicle, in rarity terms, this figure increases to approximately 27%. This indicates that an important portion of high-quality metals becomes functionally lost. The most downcycled vehicle subsystems are in order: (1) accessories, (2) electrical and electronic equipment, (3) exhaust system, and (4) engine. Further, the most downcycled parts are: speed sensor, control unit, antenna amplifier, airbag circuit, temperature and rain sensors, front pipe, particle filter, and turbo parts.

Zeeman slowers for strontium based on permanent magnets

We present the design, construction, and characterization of longitudinal- and transverse-field Zeeman slowers, based on arrays of permanent magnets, for slowing thermal beams of atomic Sr. The slowers are optimized for operation with deceleration related to the local laser intensity (by the parameter ϵ), which uses more effectively the available laser power, in contrast to the usual constant deceleration mode. Slowing efficiencies of up to ≈18% are realized and compared to those predicted by modelling. We highlight the transverse-field slower, which is compact, highly tunable, light-weight, and requires no electrical power, as a simple solution to slowing Sr, well-suited to space-borne application. For 88Sr we achieve a slow-atom flux of around 6 × 109 atoms s−1 at 30 ms−1, loading approximately 5 × 108 atoms in to a magneto-optical-trap, and capture all isotopes in approximate relative natural abundances.

Crystal structure refinement and vibrational analysis of Y[Co(CN)6]·4H2O and its thermal decomposition products

Studies on Y[Co(CN)6]·4H2O by means of thermal analysis, IR and Raman spectroscopy and X-ray powder diffraction were carried out. The complex Y[Co(CN)6]·4H2O crystallizes in the orthorhombic crystal system, space group Cmcm. Y3+ ion is eight-coordinated forming bicapped distorted trigonal prism YN6O2 and Co3+ ion is octahedrally coordinated to six CN groups. The IR spectrum shows well-resolved bands in the CN stretching region due to the presence of 13C and 15N in relative natural abundance. The Raman spectrum of the complex shows two distinct set of bands of the CN stretching vibration: one is a singlet and the other is split due to the low symmetry of the Y3+ ion compared to the pentahydrate complex. The thermal decomposition was studied in order to investigate the formation of YCoO3. The crystal structure of YCoO3 was refined by means of Rietveld analysis using PXRD data. We found that it was slightly deficient in Y3+, which is in agreement with the small amount of Y2O3 found as impurity in the sample. The formula of the mixed oxide obtained by this method of synthesis is Y0.961CoO3.

Crystal structure refinement, spectroscopic study and magnetic properties of yttrium hexacyanoferrate (III)

Y[Fe(CN) 6]·4H 2O has been synthesized and characterized. The crystal structure was refined by Rietveld analysis using X-ray powder diffraction data. Y[Fe(CN) 6]·4H 2O crystallizes in the orthorhombic crystal system, space group Cmcm. Y 3+ ion is eight-coordinated forming a bicapped distorted trigonal prism YN 6O 2. Fe 3+ ion is six-coordinated in the form of an irregular octahedra FeC 6 group and cyanide linkages between YN 6O 2 and FeC 6 groups build an infinite polymeric array. The vibrational spectrum shows two bands corresponding to antisymmetric and symmetric stretching 12C 14N in the CN stretching region. These bands are accompanied by four weak isotopic bands at lower frequency due to the presence of 13C and 15N in relative natural abundance. The HOH bending band split into three bands around 1600 cm −1 due to the presence of two kinds of water molecules in the structure. The thermal decomposition has been followed by thermogravimetric and differential thermal analysis, IR spectroscopy and powder XRD. The size and morphology of the complex and its thermal decomposition products were evaluated by scanning electron microscopy. The magnetic measurements confirm that Y[Fe(CN) 6]·4H 2O shows an antiferromagnetic order at low temperatures.

오미자 (Schisandra chinensis Baillon)로 부터 추출한 리그난이 고추종자의 발아에 미치는 영향

In this study, the effects of dibenzocyclooctadiene on seed germination were investigated in pepper. Four C 18 dibenzocyclooctadiene lignans - schisandrin (1143.7 ㎎), schisandrin C (317.3 ㎎), gomisin A (261.4 ㎎) and gomisin N (213.4 ㎎) - were isolated from hexane extracts of the fruits of Schisandra chinensis. The molecular structures of the four lignans were elucidated based on spectroscopic analyses including 1D NMR experiments, and by comparing their spectroscopic data with those of previous literatures. Seeds were immersed in 10 -5 M schisandrin, 10 -6 M schisandrin C, and 10 -7 M gomisin A and gomisin N for 1 hr and incubated at 25℃ in the dark for germination. Compared to untreated control, treatment with schisandrin C and gomisin A suppressed seed germination at 48 hrs after incubation, whereas treatment with gomisin N increased germination rate at 48 hrs after incubation. The results of the germination activity of the lignans from S. chinensis confirm their potential plant growth role, and the relative natural abundances of these metabolites suggest their potential use as natural plant growth regulators.

αADα Hybrids of Cryptococcus neoformans: Evidence of Same-Sex Mating in Nature and Hybrid Fitness

Cryptococcus neoformans is a ubiquitous human fungal pathogen that causes meningoencephalitis in predominantly immunocompromised hosts. The fungus is typically haploid, and sexual reproduction involves two individuals with opposite mating types/sexes, α and a. However, the overwhelming predominance of mating type (MAT) α over a in C. neoformans populations limits α–a mating in nature. Recently it was discovered that C. neoformans can undergo same-sex mating under laboratory conditions, especially between α isolates. Whether same-sex mating occurs in nature and contributes to the current population structure was unknown. In this study, natural αADα hybrids that arose by fusion between two α cells of different serotypes (A and D) were identified and characterized, providing definitive evidence that same-sex mating occurs naturally. A novel truncated allele of the mating-type-specific cell identity determinant SXI1α was also identified as a genetic factor likely involved in this process. In addition, laboratory-constructed αADα strains exhibited hybrid vigor both in vitro and in vivo, providing a plausible explanation for their relative abundance in nature despite the fact that AD hybrids are inefficient in meiosis/sporulation and are trapped in the diploid state. These findings provide insights on the origins, genetic mechanisms, and fitness impact of unisexual hybridization in the Cryptococcus population.

Microscale detection of polychlorinated biphenyls using two-step laser mass spectrometry

Microprobe two-step laser desorption/laser ionization mass spectrometry (μL2MS) is used as a new analytical technique for the detection of polychlorinated biphenyls (PCBs). Three standard Aroclor solutions (Aroclor 1232, 1242, and 1262) and three samples of activated carbon spiked with Aroclor 1242 are examined. All the PCBs present in the Aroclor solutions are clearly identified using μL2MS. The distribution of the peaks follows the relative natural abundances of the carbon and chlorine isotopes. μL2MS analyses of the spiked particles of activated carbon reveal the presence of PCBs and an abundance of polycyclic aromatic hydrocarbons. The detection limit for PCBs on solid surfaces is determined to be between 1 and 10 ppm. Because the spatial resolution of the μL2MS instrument varies between 10 and 40 microns, PCB information at the sub-particle scale can be obtained.

Correction of 13C mass isotopomer distributions for natural stable isotope abundance.

Metabolism of singly or multiply 13C-labeled substrates leads to the production of molecules that contain 13C atoms at various positions. Molecules differing only in the number of isotopic atoms incorporated are referred to as mass isotopomers. The distribution of mass isotopomers of many molecules can be measured by gas chromatography/ mass spectrometry after chemical derivatization. Quantification of metabolite mass isotopomer abundance resulting from biological processes necessitates correction of the measured mass isotopomer distribution of the derivatized metabolite for contributions due to naturally occurring isotopes of its elements. This correction must take into account differences in the relative natural abundance distribution of each mass isotopomer (skewing). An IBM-compatible computer program was developed which (i) calculates the natural abundance mass isotopomer distribution of unlabeled and labeled standards given the molecular formula of the derivatized molecule or fragment ion, and (ii) calculates the natural abundance mass isotopomer distribution of the singly and multiply labeled molecule or fragment via non-linear fitting to the measured mass isotopomer distribution of the unlabeled molecule or fragment. The output of this program is used to correct measured mass isotopomer distributions for contributions from natural isotope abundances and to verify measured values for theoretical consistency. Differences between predicted and measured unlabeled and 13C-labeled isotopomer distributions for hydroxamate di-t-butyl-dimethylsilyl (di-TBDMS) derivatized pyruvate were measured. The program was applied to the mass isotopomer distribution of glucose labeled from [U-13C3]glycerol and of fatty acids labeled from [U-13C6]glucose and either [2-13C2] acetate or [U-13C2]acetate. In some of these cases, the measured mass isotopomer distributions corrected by the program were different from those corrected by the classical technique. Implications of these differences including those on the calculation of glucose production due to gluconeogenesis in isolated perfused rat liver are discussed.

Prey Selection by Urban-Breeding Merlins

-We identified 1,332 items belonging to 36 vertebrate species from prey remains collected near 65 Merlin (Falco columbarius) nests in Saskatoon, Saskatchewan from May to July 1987-1990. Principal prey of breeding Merlins was the House Sparrow (Passer domesticus). They along with the Horned Lark (Eremophilia alpestris) were usually taken more frequently than expected from their relative abundance. Other potential prey species were usually taken in proportion to their relative abundance, or less often than expected. Proportions of adult House Sparrows in the diet decreased while juveniles increased significantly as the Merlin breeding season progressed. During incubation and nestling phases, male and female House Sparrows were taken as expected. In the fledgling phase, Merlins took adult House Sparrows less often and juveniles more often than expected. The relative availability of different species positively correlated with that in the diet during the incubation and nestling phases. Merlins selected prey based on relative availability, independent of prey mass, but not independent of relative abundance. Our data supported the prediction that increase in absolute abundance of selected prey species increased the degree of prey selectivity. Received 12 March 1992, accepted 25 November 1992. STUDIES OF prey selection in carnivorous predators have concluded that predators either take prey according to their relative abundances (e.g. Jaksic et al. 1981, Nilsson 1981, Turner 1982, Village 1982), or take prey based presumably on relative profitabilities (e.g. Korpimaki 1985, Hunter et al. 1988, Steenhof and Kochert 1988, Canova 1989, Derting and Cranford 1989, Bochenski 1990, Brigham 1990). Predators following the former strategy are called opportunistic feeders, while those following the latter are known as selective feeders (Jaksic 1989). Studies evaluating the species of prey taken usually have considered only prey abundance. Furthermore, few data are available on the sex, age, and size of prey selected by carnivorous predators. There are many reports of the diet of breeding Merlins (Falco columbarius) from North America (Oliphant and McTaggart 1977, Hodson 1978, Becker 1985, Knapton and Sanderson 1985, Laing 1985, James and Smith 1987), but the studies all suffer from small number of nests sampled or a sporadic collection schedule. Better documentation of diet of breeding Merlins comes from Britain (Newton et al. 1984, Bibby 1987). Baker and Bibby (1987) compared relative 3 Present address: Department of Zoology, University of Alberta, Edmonton T6G 2E9, Canada. abundance of birds (based on questionnaire surveys) in habitats frequented by Merlins with relative consumption of those species by Merlins. They concluded that breeding Merlins took birds in order of their relative abundance. We had three objectives. First, we described the diet of urban-breeding Merlins based on systematic collection of prey remains. Second, we tested the null hypothesis that Merlins would take prey species according to their relative abundance in nature. The alternative hypothesis, based on classical optimal-foraging theory, states that a predator should not take prey species in relation to their relative abundances, but should use cues such as relative profitability (i.e. net energy intake) for prey selection (Emlen 1966, Pulliam 1974). According to the relativeprofitability hypothesis, we predicted that Merlins would not take prey species according to their relative abundances. Also, we considered the effect of relative prey availability (percentage of individuals of each prey species outside of cover) on Merlin prey selection. Third, we examined whether Merlins show prey selectivity according to the sex and age of their primary prey (i.e. House Sparrow as shown in Table 1). Finally, we examined two qualitative predictions of the foraging-theory prey model, which have been tested in previous studies of other animals (e.g. Schluter 1981, Steenhof and Ko-

Rotational effects on pyrazine S 1 ( 1B 3u) dynamics. II. Rotational temperature effects on experimental observables from a “single rotational transition”

The increase of the rotational temperature induced a large increase in the amplitude ratio of the short to long component ( A +/ A −) in the time-resolved emission of pyrazine upon excitation of a single rotational transition as R 2, R 4 and P 2. This increased A +/ A − was accompanied by a large increase of the absorption background between transitions. The inverse J′ dependence of the emission quantum yield Y was eroded as the rotational temperature was increased. We have located the 13C isotope labeled pyrazine (about 5% relative natural abundance) at + 6.4 cm −1 from the origin. A computer simulation is presented based on the vibrational crossing (VC) model. This simulation reproduced qualitatively and quantitatively the experimental results presented in this and the previous paper. Two free parameters are used, the temperature and the Coriolis coupling parameter, which is extracted. The rotational temperature effects on a single rotational transition are interpreted in terms of invasion of high J′ transitions of the Q branch, which are broadened due to Coriolis interactions and invade to the R branch. The 13C labeled pyrazine is also found to be important in this respect as its high P-branch transitions are located in the vicinity of the low R-branch transitions. Based on our results and the computer simulation, we are capable of resolving most of the existing experimental debates emerging from different results obtained at various laboratories under seemingly identical conditions. In addition, we discuss the properties and nature of the Coriolis coupling, the nature and origin of the triplet states involved in the intra-triplet dynamics and other properties of the VC model.

Trace metal levels in some Nigerian mosses used as indicators of atmospheric pollution

Seventeen moss species from different sites within Ibadan city and some rural areas of Nigeria have been analysed for lead, zinc, copper, cadmium, nickel, manganese, magnesium and iron. There was no defined gradient in lead levels for the samples collected from areas of varying traffic densities within Ibadan, but a distinct gradient was observed when lead levels of samples from all other sites within the city were compared with those from the University Botanical Garden. Lead values for mosses collected from the rural areas of the country were significantly lower than those of Ibadan. No definite trend was observed for all other trace metals and analysed, except that their general levels reflect the ratio of their relative abundance in nature.

Relative abundance of intermediate members of the oceanic basalt-trachyte association: Evidence from clarion and Socorro Islands, Revillagigedo Islands, Mexico

Chayes [1963] showed that published analyses of oceanic lavas have a strongly bimodal frequency distribution when arranged according to compositional criteria. Criticism of Chayes' conclusions inevitably centers upon the supposed impropriety of assuming that the relative frequency of analysis of a rock is proportional to its relative abundance in nature. Ideally, estimates of abundance should be based upon mapped area and thickness, but data of this sort are not available for most of the oceanic islands. Geologic mapping recently completed on Clarion and Socorro islands in the eastern Pacific has provided a basis for accurate volumetric estimates, and the results provide strong support for the views expressed by Chayes.