Metabolic Flux Analysis—Linking Isotope Labeling and Metabolic Fluxes

Metabolic flux analysis (MFA) is an increasingly important tool to study metabolism quantitatively. Unlike the concentrations of metabolites, the fluxes, which are the rates at which intracellular metabolites interconvert, are not directly measurable. MFA uses stable isotope labeled tracers to reveal information related to the fluxes. The conceptual idea of MFA is that in tracer experiments the isotope labeling patterns of intracellular metabolites are determined by the fluxes, therefore by measuring the labeling patterns we can infer the fluxes in the network. In this review, we will discuss the basic concept of MFA using a simplified upper glycolysis network as an example. We will show how the fluxes are reflected in the isotope labeling patterns. The central idea we wish to deliver is that under metabolic and isotopic steady-state the labeling pattern of a metabolite is the flux-weighted average of the substrates’ labeling patterns. As a result, MFA can tell the relative contributions of converging metabolic pathways only when these pathways make substrates in different labeling patterns for the shared product. This is the fundamental principle guiding the design of isotope labeling experiment for MFA including tracer selection. In addition, we will also discuss the basic biochemical assumptions of MFA, and we will show the flux-solving procedure and result evaluation. Finally, we will highlight the link between isotopically stationary and nonstationary flux analysis.

Modeling the provenance of fine sediments in Parón Glacier Lake (Cordillera Blanca, Perú) by using a new procedure of tracer selection

<p>Climate warming in high altitude regions is causing rapid retreat of mountain glaciers that might likely accelerate in the near future. As much as 99 % of all tropical glaciers are in the Andes, of which approximately 70% concentrate in the Cordillera Blanca range (Perú) where Parón Lake is located at the foot of Artesonraju Glacier. In the last century the glacier surface area in the Cordillera Blanca has decreased by around one third. Melting glaciers is leading to the formation of new proglacial lakes that are increasing in number and volume playing a key role in regulating water storage and supply to glacier-fed rivers. Glacier recession results in changes in paraglacial environments where processes acting on new exposed surfaces of highly reactive rocks are highly dynamic. These processes can generate important amounts of sediments which can threaten water quality and biodiversity. Environmental concerns strengthen the need for assessing the provenance of fine sediment. To this end, in the frame of the IAEA INT5153 project a two week field survey of the Parón Lake area was carried out in October 2016 to recognize the main glacial landforms which had direct connectivity to the drainage system into the lake. The main glacial landforms, which included moraines, colluvium, glacio-fluvial terraces and alluvial fans that had developed after different stages of glacier retreat from the Last Glacial Maximum to the Little Ice Age, were mapped. For identifying the main provenance of sediments, a total of 40 composite soil and sediment samples (from 0-3cm depth) were collected as sources from representative sites on the main glacial landforms. In addition a total of 9 sediment mixtures including composite channel bed sediments and suspended sediments were collected. Channel bed mixtures were sampled along the river system between the tongue of Artesonraju Glacier and the end of Parón Lake while suspended sediment samples were also collected from the lake margin half way along its length. For applying fingerprinting methods we analysed 6 radioisotopes (2 FRNs and 4 ERNs) and a total of 28 stable elements. The preliminary unmixing results modeled with FingerPro after applying a novel procedure for tracer selection (Lizaga et al., 2020) identified different provenances in each of the sampled points depending on the proximity and connectivity of the glacial landforms. Moraines and alluvial terraces were main contributors in two of the channel mixtures while a relatively greater apportion from colluvium and alluvial fans was found in the lake sediment mixture located at the end of the Parón Lake. Unmixing results for the suspended sediments confirmed the higher contributions from glacio-fluvial terraces and colluvium in the middle part of the lake suggesting that the direct connectivity of glacial landforms was a key control of fine sediment supply to the lake. Further research is needed to assess changes of sediment sources during wet seasons or rainfall peaks in high water and flood regime to gain more comprehensive information on the temporal and climate variability of fine sediment supply.</p>

The Multi-Tracer Optimal Estimator applied to VIPERS

ABSTRACT We use mock galaxy data from the VIMOS Public Extragalactic Redshift Survey (VIPERS) to test the performance of the Multi-Tracer Optimal Estimator (MTOE) of Abramo et al. as a tool to measure the monopoles of the power spectra of multiple tracers of the large-scale structure, $P^{(0)}_\alpha (\mathbf {k})$. We show that MTOE provides more accurate measurements than the standard technique of Feldman, Kaiser & Peacock (FKP), independently of the tracer-selection strategy adopted, on both small and large scales. The largest improvements on individual $P^{(0)}_\alpha (\mathbf {k})$ are obtained on small scales, using a colour–magnitude selection, due to MTOE being naturally better equipped to deal with shot noise: we report an average error reduction with respect to FKP of $\sim 30{{\ \rm per\ cent}}$ at $0.3 \lt k \, [h$ Mpc−1] < 0.5, with improvements exceeding 40–50 ${{\ \rm per\ cent}}$ for some tracers. On large scales (k[h Mpc−1] ≲ 0.1), the gain in accuracy resulting from cosmic-variance cancellation is ∼10 ${{\ \rm per\ cent}}$ for the ratios of $P^{(0)}_\alpha (\mathbf {k})$. We have carried out a Markov chain Monte Carlo analysis to determine the impact of these gains on several quantities derived from $P^{(0)}_\alpha (\mathbf {k})$. If we pushthat the estimated power spectra are themselves the measurement to scales $0.3 \lt k \, [h$ Mpc−1] < 0.5, the average improvements are $\sim 30{{\ \rm per\ cent}}$ for the amplitudes of the monopoles, $\sim 75{{\ \rm per\ cent}}$ for the monopole ratios, and $\sim 20{{\ \rm per\ cent}}$ for the linear galaxy biases. Our results highlight the potential of MTOE to shed light upon the physics that operate both on large and small cosmological scales. The effect of MTOE on cosmological constraints using VIPERS data will be addressed in a separate paper.

Preliminary Study on Tracer of High Temperature and High Salinity Resistant

Five kinds of new tracers of high temperature and high salinity resistant were screened in order to meet tracer monitoring requirements in Tarapoa block at Dorine oilfield, these tracers were evaluated according to the tracer selection criteria, the optimal detection method was also studied in this paper. It showed that new tracers can adapt to high temperature, high salinity of the formation conditions, so as to meet adjacent multi-well groups monitoring requirements. Tracer monitoring can provide basis for the next step implementation of the program and the adjustment of measures, of a bright application future.

A Modified Tracer Selection and Tracking Procedure to Derive Winds Using Water Vapor Imagers

The remotely sensed upper-tropospheric water vapor wind information has been of increasing interest for operational meteorology. A new tracer selection based on a local image anomaly and tracking procedure, itself based on Nash–Sutcliffe model efficiency, is demonstrated here for the estimation of upper-tropospheric water vapor winds both for cloudy and cloud-free regions from water vapor images. The pressure height of the selected water vapor tracers is calculated empirically using a height assignment technique based on a genetic algorithm. The new technique shows encouraging results when compared with Meteosat-5 water vapor winds over the Indian Ocean region. The water vapor winds produced by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) from Meteosat-5 and the present algorithm are compared with collocated radiosonde observations according to Coordination Group for Meteorological Satellites guidelines. The proposed algorithm shows better accuracy in terms of mean vector difference, rms vector difference, standard deviation, speed bias, number of collocations, and mean speed and mean direction differences. Also it is found that the sensitivity of the spatial consistency check in the quality indicator is not so significant for the improvement of statistics.