Isotopic Composition Ratios Research Articles

Bronze Production Systems in 6-7 Centuries South Korea: Micro-Structural and Micro-Chemical Analysis of Slags

Metallurgical remains such as crucible, mould, slag and tuyere are generated in the production of bronze. The analysis of slag in particular can be used to identify the raw materials, processes and environments (temperature and condition) employed in the bronze fabrication . The Gwanbuk-ri site in Buyeo is known as the location of a royal palace during the Baekje period, in the 6-7th centuries, and crucible fragments and slags used to make bronze were excavated there. The purpose of this study is to understand the process of bronze production and the origin of the raw ores used in the Baekje period, through micro-structure and microchemical analyses. Using chemical analysis and observation of the microstructure of the crucible and slag samples, we identified evidence of the bronze alloying and melting conditions. The melting process would have taken place under a variable redox atmosphere at 1,100 oC. Cu-Sn-Pb ternary bronze might have been produced by alloying Cu-Sn metal with lead ore (galena) in the Baekje period. The lead isotope composition ratios of 2 bronze slags were located in zone 2 and zone 3 of the lead isotope map in the southern Korean peninsula, which indicates the use of galena from south Chungcheong and north Gyeongsan provinces. For efficiency and cost-effectiveness, a concentrate of lead ore might have been transported from the mine to the consumer site.

Maxwellian-averaged cross section of 181Ta (n,γ) reaction and its astrophysical implications

The neutron-capture and Maxwellian-averaged cross sections of 181Ta(n,γ) reaction have been computed making use of the TALYS code. Two main inputs of the TALYS calculation, nuclear level density (NLD) and radiative strength function (RSF), are calculated within a recent microscopic model that takes into account the exact thermal pairing plus independent-particle model and collective excitations within the phonon-damping model. A good agreement between the calculated and experimental NLD and RSF data of 182Ta was found, confirming the goodness of the microscopic nuclear model used. As the result, the deduced neutron-capture and Maxwellian-averaged cross sections of 181Ta(n,γ) reaction also agree reasonably well with the experimental and recommended data across the measured energy range. The impact of the predicted cross sections on the tantalum production in the slow neutron-capture process (s-process) is then studied by employing a recent version of FRUITY stellar evolutionary models in which the effect of magnetic fields is newly implemented. By calculating the isotopic composition ratios within the FUNS code, we obtain a slight depletion of tantalum as compared to the recommended data. The variation between the calculated and reference tungsten isotopic ratios in presolar stardust silicon carbide (SiC) grains is found to be negligible, as expected. However, the capability of our theoretical model to reproduce experimental nuclear data will allow us to investigate in detail the s-process branching points at 181W and 185W, for which experimental data from direct measurements are still unavailable.

Trophic structure of benthic communities in a Chilean fjord (45°S) influenced by salmon aquaculture: Insights from stable isotopic signatures

Benthic marine food webs, which recycle organic matter and sustain unique biodiversity, are an important component of estuarine Patagonian fjords; however, these may be heavily influenced by salmon farming activities. Under the above conditions, this study collected several food sources (sediment organic matter, suspended particulate organic matter, macroalgae) and 26 benthic invertebrate species, and analyzed them using a Bayesian mixing model. Briefly, carbon and nitrogen stable isotopes analyses revealed that the highly variable isotopic niche widths respond to food supplies from marine and terrestrial organic matter. In addition, particulate and dissolved waste from salmon farming activities were found to modify isotopic composition ratios in many suspension feeders. Particularly, our results indicate high δ15N values in the sponge Cliona chilensis and the encrusting coral Incrustatus comauensis, which appear to be potential ecological indicators for evaluating stoichiometry imbalances and trace organic pollution sources in fjord environments.

Local Structure of Li+ in Superconcentrated Aqueous LiTFSA Solutions.

It has been reported that aqueous lithium ion batteries (ALIBs) can operate beyond the electrochemical window of water by using a superconcentrated electrolyte aqueous solution. The liquid structure, particularly the local structure of the Li+, which is rather different from conventional dilute solution, plays a crucial role in realizing the ALIB. To reveal the local structure around Li+, the superconcentrated LiTFSA (TFSA: bis(trifluoromethylsulfonil)amide) aqueous solutions were investigated by means of Raman spectroscopic experiments, high-energy X-ray total scattering measurements, and the neutron diffraction technique with different isotopic composition ratios of 6Li/7Li and H/D. The Li+ local structure changes with the increase of the LiTFSA concentration; the oligomer ([Lip(TFSA)q](p-q)+ (q > 2) forms at the molar fraction of LiTFSA (xLiTFSA) > 0.25. The average structure can be determined in which two water molecules and two oxygen atoms of TFSA anion(s) coordinate to the Li+ in the superconcentrated LiTFSA aqueous solution (LiTFSA)0.25(H2O)0.75. In addition, the intermolecular interaction between the neighboring water molecules was not found, and the hydrogen-bonded interaction in the solution should be significantly weak. According to the coordination number of the oxygen atom (TFSA or H2O), a variety of TFSA- and H2O coordination manners would exist in this solution; in particular, the oligomer is formed in which the monodentate TFSA cross-links Li+.

Dual nitrogen-oxygen isotopic analysis and kinetic model for enzymatic nitrate reduction coupled with Fe(II) oxidation by Pseudogulbenkiania sp. strain 2002

While microbially mediated coupling process of nitrate reduction and Fe(II) oxidation (NRFO) plays important role in widespread nitrogen and iron biogeochemical cycles in the natural environments, the underlying mechanism of NRFO is still not clearly understood. Here, N and O isotope fractionation during microbial nitrate reduction by Pseudogulbenkiania sp. strain 2002 with or without Fe(II) were investigated. The nitrate reduction rate decreased substantially in the presence of Fe(II), and cells became encrusted with Fe(III) minerals. However, the N isotope enrichment factors (ε) with or without Fe(II) were identical within uncertainty (24.1 ± 2.4‰ and 25.1 ± 2.4‰), implying that Fe(II) oxidation had little influence on the extent of N isotope fractionation and that cell encrustation was unlikely to cause additional mass transfer limitation. Isotopic composition ratios of 18O to 15N (18ε: 15ε) were 0.73 ± 0.13 with and 0.50 ± 0.08 without Fe(II), close to reported values for nitrate reduction by periplasmic nitrate reductases, implying that enzymatic nitrate reduction mainly occurs in strain 2002's periplasmic space. A kinetic model based on elementary reactions was established, and rate constants of enzymatic nitrate reducing reactions were obtained in a living cell system. Combining dual N-O isotope fractionation analysis with kinetic modeling is a promising approach for interpreting diverse enzymatic pathways during NRFO processes.

Evaluation of photosynthetic performance and carbon isotope discrimination in perennial ryegrass (Lolium perenne L.) under allelochemicals stress

Ferulic (FA) and p-hydroxybenzoic acid (pHBA) are commonly found as phenolic compounds (PHC) in many forage and cereal crops. Although the effects of these PHC on seedling growth are relatively explored, not many information is available regarding the phytotoxicity on ecophysiological processes of perennial ryegrass adult plants. The experiment was conducted with the aim to evaluate the phytotoxic potential of PHC on the seedling growth, leaf water relation, chlorophyll fluorescence attributes and carbon isotope discrimination adult plants of perennial ryegrass (Lolium perenne L.). The results clearly indicated that PHC behaved as potent inhibitors of chlorophyll fluorescence yield (Fv/Fm) in leaves of L. perenne and plants showed poor tolerance against allelochemicals stress. Quantum yield (ΦPSII), chlorophyll fluorescence quenching (qP) and non-photochemical quenching (NPQ) were decreased following exposure to FA and pHBA. The portion of absorbed photon energy that was thermally dissipated (D) in L. perenne was decreased. Exposure of the L. perenne seedlings to FA and pHBA stress led to a decrease in fresh/dry weight, relative water content and leaf osmotic potential. Carbon isotope composition ratio (δ13C) was significantly less negative than the control following treatment with FA or pHBA. The results suggested that PHC uptake was a key step for the effectiveness of these secondary metabolites and their phytotoxicity on L. perenne adult plants was mainly due to the alteration of leaf water status accompanied by photosystem II damage. Acquisition of such knowledge may ultimately provide a better understanding about the mode of action of the tested compounds.

Guard cell-specific down-regulation of the sucrose transporter SUT1 leads to improved water use efficiency and reveals the interplay between carbohydrate metabolism and K+ accumulation in the regulation of stomatal opening

Sucrose is a key metabolite in guard cell (GC) regulation and has been proposed to form a key metabolic connection between mesophyll cells and GCs. However, the importance of sucrose transport across the GC plasma membrane in stomatal movements remains to be determined. Here, we characterized transgenic tobacco plants expressing an antisense gene construct for the SUCROSE TRANSPORTER 1 (SUT1) driven by the GC specific promoter KST1. GCs of transgenic plants contained less sucrose, more starch and had increases in K+ content. Lower GC sucrose content was associated with lower stomatal conductance that, in turn, led to a lower transpiration rate and higher carbon isotope composition ratio compared to wild type plants. Although the transgenic plants showed reduced growth under optimal water supply condition, they showed improved growth compared to wild type plants under osmotic stress and demonstrated lower water consumption that was correlated with higher relative water content under water-deficit conditions. This demonstrates the desiccation postponement phenotype of these plants together with an improved tolerance to water deficit. Taken together, our results indicate that SUT1 has an important role in stomatal movements and suggest that genetic manipulation of GC sucrose transport could be used to obtain plants with greater water use efficiency.

Biochemical, physiological and isotopic responses to natural product p-hydroxybenzoic acid in Cocksfoot (Dactylis glomerata L.)

The present study was conducted to evaluate the role of natural compound p-hydroxybenzoic acid (pHBA) on physiological, biochemical and isotopic responses of Dactylis glomerata L. Application of pHBA in the range 0.5–1.5 mM reduced the leaf fresh/dry biomass, shoot/root length, relative water content and leaf osmotic potential of D. glomerata. pHBA decreased the photosynthetic efficiency and quantum yield of photosystem II photochemistry in D. glomerata seedlings following treatment at all concentrations. Photochemical and non-photochemical fluorescence quenching were reduced after treatment with 1.5 mM pHBA. Carbon isotope composition ratio in D. glomerata leaves was significantly less negative following treatment with pHBA than the control. Carbon isotope discrimination value was declined by pHBA. The leaf protein content was lower after treatment with 1.5 mM pHBA. Our results suggest that pHBA possesses allelopathic potential against D. glomerata and this study provide new insights into the physiological, biochemical and isotopic action mechanism of pHBA.

Functional analysis of the relative growth rate, chemical composition, construction and maintenance costs, and the payback time of Coffea arabica L. leaves in response to light and water availability

In this study, the combined effects of light and water availability on the functional relationships of the relative growth rate (RGR), leaf chemical composition, construction and maintenance costs, and benefits in terms of payback time for Coffea arabica are presented. Coffee plants were grown for 8 months in 100% or 15% full sunlight and then a four-month water shortage was implemented. Plants grown under full sunlight were also transferred to shade and vice versa. Overall, most of the traits assessed were much more responsive to the availability of light than to the water supply. Larger construction costs (12%), primarily associated with elevated phenol and alkaloid pools, were found under full sunlight. There was a positive correlation between these compounds and the RGR, the mass-based net carbon assimilation rate and the carbon isotope composition ratio, which, in turn, correlated negatively with the specific leaf area. The payback time was remarkably lower in the sun than in shade leaves and increased greatly in water-deprived plants. The differences in maintenance costs among the treatments were narrow, with no significant impact on the RGR, and there was no apparent trade-off in resource allocation between growth and defence. The current irradiance during leaf bud formation affected both the specific leaf area and leaf physiology upon transferring the plants from low to high light and vice versa. In summary, sun-grown plants fixed more carbon for growth and secondary metabolism, with the net effect of an increased RGR.

Source strength increases with the increasing precociousness of fruit maturation in field-grown clones of conilon coffee (Coffea canephora) trees

In earlier-maturing coffee clones, owing to the shorter time required for fruit filling and ripening, photo- assimilates should be transported to fruits in a period shorter than that found in intermediate- or late-maturing clones. We hypothesised that at a given source-to-sink ratio, a presumably greater sink strength in early-maturing clones relative to intermediate- and late-maturing individ- uals should be correlated to increased rate of net carbon assimilation (A) and greater photo-assimilate transport to the fruits. Overall, earlier-maturing clones displayed greater A rates than the intermediate-maturing clones, which, in turn, had higher A than their late counterparts. Changes in A were largely associated with changes in stomatal conductance. Only marginal alterations occurred in the internal-to-ambient CO2 concentration ratio, the carbon isotope composition ratio, soluble sugars and chlorophyll a fluorescence parameters. Some changes in starch pools were detected among treatments. To the best of our knowledge, this is the first report showing evidence that increased precociousness of fruit growth and matura- tion results in higher A and thus increased source strength, a fact associated to a large degree with higher stomatal aperture.

THE EFFECTS OF PRUNING AT DIFFERENT TIMES ON THE GROWTH, PHOTOSYNTHESIS AND YIELD OF CONILON COFFEE (COFFEA CANEPHORA) CLONES WITH VARYING PATTERNS OF FRUIT MATURATION IN SOUTHEASTERN BRAZIL

SUMMARYThe economics of coffee plantations is intrinsically linked to pruning, which can improve the canopy architecture and thereby increase productivity. However, recommended pruning times on conilon coffee plantations have been made on an entirely empirical basis. In this study, by evaluating growth, photosynthetic gas exchanges, starch accumulation and crop productivity, the effects of pruning at different times between harvest and flowering were investigated for six conilon coffee clones with distinct stages of fruit maturation (early, intermediate and late). Clones with an early maturation stage were pruned at four different times: 0, 30, 60 and 90 days after harvest (DAH). Intermediate clones were pruned at 0, 30 and 60 DAH, and late clones were pruned at 0 and 30 DAH. Overall, the rates of shoot growth and net photosynthesis, the stomatal conductance and the crop yield were not affected by the pruning treatments in any of the clones. In addition, pruning times did not affect the concentrations of starch or the photochemical efficiency of photosystem II. The carbon isotope composition ratio was marginally affected by the treatments. These results suggest that the pruning time after harvests is relatively unimportant and pruning operations can be scheduled to optimise the use of labour, which directly impacts the production costs of coffee.

A chlorophyll fluorescence analysis of photosynthetic efficiency, quantum yield and photon energy dissipation in PSII antennae of Lactuca sativa L. leaves exposed to cinnamic acid.

This study investigated the effects of cinnamic acid (CA) on growth, biochemical and physiological responses of Lactuca sativa L. CA (0.1, 0.5, 1.0 and 1.5mM) treatments decreased plant height, root length, leaf and root fresh weight, but it did not affect the leaf water status. CA treatment (1.5mM) significantly reduced F(v), F(m), photochemical efficiency of PSII (F(v)/F(m)) and quantum yield of PSII (ΦPSII) photochemistry in L.sativa. The photochemical fluorescence quenching (qP) and non-photochemical quenching (NPQ) were reduced after treatment with 1.5mM CA. Fraction of photon energy absorbed by PS II antennae trapped by "open" PS II reaction centers (P) was reduced by CA (1.5mM) while, portion of absorbed photon energy thermally dissipated (D) and photon energy absorbed by PSII antennae and trapped by "closed" PSII reaction centers (E) was increased. Carbon isotope composition ratios (δ(13)C) was less negative (-27.10) in CA (1.5mM) treated plants as compared to control (-27.61). Carbon isotope discrimination (Δ(13)C) and ratio of intercellular CO(2) concentration (ci/ca) from leaf to air were also less in CA treated plants. CA (1.5mM) also decreased the leaf protein contents of L.sativa as compared to control.

Distinguishing between vapor- and liquid-formed ground ice in the northern martian regolith and potential for biosignatures preserved in ice bodies

In this study, various approaches that can potentially distinguish between vapor- and liquid-derived ground ice in the martian regolith (petrography, geochemistry, stable O H isotopes, CO 2 O 2 N 2 Ar gas composition) are examined using terrestrial ground ice examples. Although the stable O H isotope composition ratios can distinguish between vapor- and liquid-derived terrestrial ground ice, there might be to much mixing between the various water reservoirs on Mars to effectively use it, and, like on Earth, petrographic and geochemical approaches need to be complemented with additional supporting evidences. Of the different approaches currently being employed to determine the origin of terrestrial massive ground ice and icy sediments, it is the concentration of CO 2 and the O 2/Ar, N 2/Ar and N 2/O 2 ratios of air entrapped in the ice that has proven to be the less ambiguous and most discriminatory. This is because the molar ratios of atmospheric gases change during their dissolution in water due to differences in their relative solubilities, thus providing distinctive ratios for the dissolved gases. The gas composition of air entrapped in the ice not only distinguishes between vapor- and liquid-derived ground ice, but any deviation from the theoretical dissolved values can provide insights into potential physical and biological processes operating in the subsurface, a key component for astrobiology.

In field‐grown coffee trees source–sink manipulation alters photosynthetic rates, independently of carbon metabolism, via alterations in stomatal function

Perturbations of the source-sink balances were performed in field-grown coffee (Coffea arabica) trees to investigate the possible role of carbohydrates in feedback regulation of photosynthesis. Four treatments were applied at the whole-plant level: (i) complete defruiting and maintenance of the full leaf area, (ii) the half crop load and full leaf area, (iii) the full crop load and full leaf area and (iv) the full crop load and half leaf area. Sampling and measurements were performed twice during the phase of dry matter accumulation of fruits. Gas exchange, chlorophyll a fluorescence, carbon isotope labelling and steady-state metabolite measurements were assessed in source leaves. The average rate of net photosynthetic rate (A) and stomatal conductance (g(s)) were larger (> 50%), and carbon isotope composition ratio was lower, in trees with a full crop load and half leaf area than in defruited trees, with individuals of the other two treatments showing intermediate values. However, differences in A seem unlikely to have been caused either by photochemical impairments or a direct end-product-mediated feedback down-regulation of photosynthesis. It is proposed that the decreased A in defruited coffee trees was independent of carbon metabolism and was rather directly related to a lower CO(2) availability coupled to lower g(s).

Observation of Light-Induced Drift Effect of Rubidium by Using Two Diode Lasers for Pumping and Re-Pumping

The light-induced drift (LID) of rubidium was demonstrated by using two diode lasers for the pumping and re-pumping of rubidium atoms. The isotope composition ratio for 85 Rb and 87 Rb was estimated by measuring the absorption spectrum of the rubidium vapor.

New High-Statistical--High-Resolution Measurements of the Cosmic-Ray CNO Isotopes from a 17 Year Study Using the Voyager 1 and 2 Spacecraft

view Abstract Citations (45) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS New High-Statistical--High-Resolution Measurements of the Cosmic-Ray CNO Isotopes from a 17 Year Study Using the Voyager 1 and 2 Spacecraft Webber, W. R. ; Lukasiak, A. ; McDonald, F. B. ; Ferrando, P. Abstract We have now analyzed 17 yr of Voyager 1 and Voyager 2 data and derived isotopic composition ratios for C, N, and 0 elements in cosmic rays with a statistical accuracy exceeding that of the sum of all previously published spacecraft measurements. We have also used newly measured cross sections in the propagation calculations to derive the source composition of these elements. We find (1) the source 13C/12C ratio is 2.5 σ lower than the solar ratio of 1.1%. (2) For N we find the source 14N/16O ratio to be 5.0% and the source 15N/16O ratio to be 0.97% about 1 σ larger than the ratio of 0.37% expected for a solar composition. (3) The source 18O/16O ratio is determined to be 0.24±0.17% including both measurement and propagation errors, almost exactly the solar ratio of 0.23%. The implications of these results for cosmic-ray origin theories are discussed. Publication: The Astrophysical Journal Pub Date: January 1996 DOI: 10.1086/176743 Bibcode: 1996ApJ...457..435W Keywords: ISM: COSMIC RAYS; ISM: ABUNDANCES; SUN: ABUNDANCES full text sources ADS |

Neutron transmutation doping of isotopically engineered Ge

We report a novel approach for obtaining precise control of both p- and n-type dopant concentrations in bulk Ge single crystals. High-purity Ge single crystals of controlled 74Ge/70Ge isotope composition ratios were grown and subsequently doped by the neutron transmutation doping (NTD) technique. The resulting net-impurity concentrations and the compensation ratios were precisely determined by the thermal neutron fluence and the [74Ge]/[70Ge] ratios of the starting Ge materials, respectively. Application of NTD to seven crystals with 0≤[74Ge]/[70Ge]≤4.34 lead to p-type Ge:Ga,As with compensation ratios in the range 0–0.76. The ability to grow crystals with accurately controlled Ge isotope mixtures allows us to obtain ratios anywhere between 0 and 1 for both p- and n-type doping.

Strontium and sulphur isotope geochemistry of low-temperature barite-fluorite veins of the Catalonian Coastal Ranges (NE Spain): a fluid mixing model and age constraints

Sulphur and strontium isotope analyses from the low-temperature barite-fluorite veins of the Catalonian Coastal Ranges (NE Spain) reveal the nature and source of the ore-forming fluids and constrain the ages of the mineralizations. Sulphur isotope values in the barite δ 34S = + 15 to + 20‰) are similar to those of sulphates in nearly Triassic-Jurassic evaporites δ 34S = + 11 to + 19‰). 87 Sr 86 Sr isotopic composition ratios of barites and fluorites are 0.7094–0.7167. The variation of 87 Sr 86 Sr within individual veins suggests that the Sr had two different sources: granites rocks in the Hercynian basement and seawater or evaporites of Triassic-Early Jurassic age. Vein formation is modelled as a two-component mixing process in which the S and Sr isotopic composition of the end-members change with time. The observed difference in mean S and Sr isotopic compositions among the veins is interpreted to reflect differences in mineralization age. Ore deposition occurred between 225 and 195 Ma (Triassic to Early Jurassic) in all cases except the Berta mine which may be as young as Miocene.

Composição isotópica de carbono e oxigênio de conchas de pelecípodos do litoral brasileiro e seu significado ambiental

Carbon and oxygen isotopic compositions have been determined on modern pelecypod shells and ancient pelecypod shells whose ages had been measured by the radiocarbon method. The modern shells collected along the Brazilian coastline in order to identify possible isotopic composition trends in the shells of the pelecypods living along this coastline. The ancient pelecypod shells were collected mostly from the Cananéia-Iguape coastal plain (State of Sao Paulo). The isotopic composition ratios of these samples can be correlated with sea-level fluctuations during the Holocene, whose transgressive and regressive phases left their own typical isotopic compositions imprinted on these shells. Some samples of freshwater pelecypod shells were also analysed to establish the limites of δC13 and δO18 in fluviatile and lacustrine environments. The analytical results showed that isotopic composition can be used to distinguish between pelecypod shells in freshwater environments from those in saltwater environments, as previously has been verified elsewhere. This fact demonstrates that biological control of the isotopic fractionation mechanisms may be overriden by environmental controls.

Irrigation magnifies CAM-photosynthesis in Opuntia basilaris (Cactaceae).

Measurements of acid metabolism and gas exchange were carried out four times during a year to assess the relative importance of temperature and the accompanying seasonal change to the carbon metabolism of Opuntia basilaris Engelm. & Bigel. plants growing in situ under irrigated and natural (control) conditions. Our experiments showed that this cactus did not change its pattern of carbon assimilation when continuously irrigated under field conditions. Non-irrigated cacti had maximum acid accumulation after periods of precipitation. Maximum acid accumulation in irrigated cacti occurred when there was a large difference between day/night temperatures (i.e., 16°C), and when nighttime temperatures were moderate (14C). Irrigated cacti had greater duration of stomatal opening and lower resistance to 14CO2 uptake. When temperatures were low, daytime stomatal resistance to 14CO2 uptake decreased (to 20-40 s cm-1), but never to the level of the nocturnal resistances (5-10 s cm-1). During periods of drought, nonirrigated cycti changed to a pattern in which organic acids fluctuated. Irrigated cacti continued to have 14CO2 uptake when nighttime temperatures were as high as 33°C. 13C/12C isotope composition ratios, determined after two years of irrigation, were near -12‰ in irrigated and non-irrigated plants. Therefore, under conditions of continual irrigation, seasonal and temperature changes affected the degree of dark CO2 fixation and acid metabolism, but these cacti did not change from CAM to CO2 fixation in the light.