Non-steady State Conditions Research Articles

Clinician assessment of kidney function from plasma creatinine values during critical illness: A scenario-based international multi-professional survey

PurposeDuring critical illness interpretation of serum creatinine is affected by non-steady state conditions, reduced creatinine generation, and altered distribution. We evaluated healthcare professionals' ability to adjudicate underlying kidney function, based on simulated creatinine values. MethodsWe developed an online survey, incorporating 12 scenarios with simulated trajectories of creatinine based on profiles of muscle mass, GFR and fluid balance using bespoke kinetic modelling. Participants predicted true underlying GFR (<5, 5–14, 15–29, 30–44, 45–59, 60–90, >90 ml.min−1.1.73 m−2) and AKI stage (stages 1–3, defined as 33 %, 50 %, 66 % decrease in GFR from baseline) during the first 7-days and at ICU discharge. Results100 of 103 respondents from 16 countries, 94 completed 1 or more scenarios. 43(43 %) were senior physicians, 74(74 %) critical care and 31(31 %) nephrology physicians. Over the first 7-days, true GFR was correctly estimated 43 % of the time and underlying AKI stage in 57 % of patient days. At ICU discharge GFR was predicted 35 % of the time. At all timepoints, over and under-estimation of GFR was observed. ConclusionParticipants displayed marked variation in estimation of kidney function, suggesting difficulty in accounting for multiple confounders. There is need for alternative, unbiased measures of kidney function in critical illness to avoid misclassifying kidney disease.

Recovery of Ventilatory and Metabolic Responses to Hypoxia after Chronic Hypoxia in Neonatal Rats

Chronic hypoxia (CH) from birth blunts the hypoxic ventilatory response (HVR) in newborn rats, but there is conflicting evidence as to whether (or how quickly) the HVR recovers after these rats are returned to room air. In this study, Sprague-Dawley rats were exposed to either 21% O2 (Control) or 12% O2 (CH) for the first 3 postnatal days. Breathing and metabolism were studied using head-body plethysmography and respirometry immediately after the 3 days of CH (i.e., at P3) or after 1, 4-5, or 7 days of recovery in room air (i.e., at P4, P7-8, or P10). The early phase of the HVR was blunted in CH rats at P3 (13.7± 2.3 vs. 30.6±3.4 % increase from baseline during 12% O2), and the HVR was more biphasic in CH rats after 1 day of recovery. However, no significant differences in the HVR were observed between treatment groups after 3-4 or 7 days of recovery. Males and females showed similar patterns. Changes in ventilation during hypoxia were strongly biphasic in the younger age groups: ventilation increased initially, but this was followed by a gradual decline in ventilation towards or below baseline levels. However, when accounting for metabolic depression, all age groups continued to hyperventilate during the late phase of the HVR [i.e., the ratio of ventilation to CO2 production (CO2 convection requirement) remained elevated relative to baseline values]. The CO2 convection requirement response to hypoxia did not differ between treatment groups during the late phase of the HVR at any age, but metabolism and CO2 convection requirement could not be determined during the early phase of the HVR due to non-steady state conditions. In conclusion, 3 days of CH produces only a transient blunting of the HVR in newborn rats. Longer CH exposures may be required to elicit persistent changes in the HVR or, alternatively, this plasticity may not be revealed until after puberty. Supported by NIH grant P20 GM-103423 (Maine INBRE). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Measuring critical force in sport climbers: a validation study of the 4 min all-out test on finger flexors

PurposeThe critical force (CF) concept, differentiating steady and non-steady state conditions, extends the critical power paradigm for sport climbing. This study aimed to validate CF for finger flexors derived from the 4 min all-out test as a boundary for the highest sustainable work intensity in sport climbers.MethodsTwelve participants underwent multiple laboratory visits. Initially, they performed the 4 min intermittent contraction all-out test for CF determination. Subsequent verification visits involved finger-flexor contractions at various intensities, including CF, CF −2 kg, CF −4 kg, and CF −6 kg, lasting for 720 s or until failure, while monitoring muscle-oxygen dynamics of forearm muscles.ResultsCF, determined from the mean force of last three contractions, was measured at 20.1 ± 5.7 kg, while the end-force at 16.8 ± 5.2 kg. In the verification trials, the mean time to failure at CF was 440 ± 140 s, with only one participant completing the 720 s task. When the load was continuously lowered (−2 kg, −4 kg, and −6 kg), a greater number of participants (38%, 69%, and 92%, respectively) successfully completed the 720 s task. Changes of muscle-oxygen dynamics showed a high variability and could not clearly distinguish between exhaustive and non-exhaustive trials.ConclusionsCF, based on the mean force of the last three contractions, failed to reliably predict the highest sustainable work rate. In contrast, determining CF as the end-force of the last three contractions exhibited a stronger link to sustainable work. Caution is advised in interpreting forearm muscle-oxygen dynamics, lacking sensitivity for nuanced metabolic responses during climbing-related tasks.

Modeling Operational Flow Capacity and Evaluating Disaster Interventions for Fuel Distribution

Fuel is an essential commodity in society with an amplified role during disasters. Disasters often cause a spike in demand for fuel and impose physical and operational constraints on fuel distribution. Accordingly, public and private sector stakeholders seek disaster preparedness and response interventions to ensure an adequate supply of fuel for emergency activities. We develop models to quantify downstream operational flow capacity, i.e., the volume of fuel that can be distributed from bulk storage terminals to retail gas stations via tanker trucks. We do this for both steady state conditions and nonsteady state conditions during disasters. The operational flow capacity measures can serve as inputs to optimal relief distribution and resource allocation problems, as well as enable a cost-benefit assessment of interventions aimed at increasing system capacity. We identify the best interventions for each type of bulk storage terminal structure and determine how to prioritize bulk storage terminals for each type of intervention when resources are limited. As the downstream fuel distribution system from bulk storage terminals to retail gas stations is similar across regions, our methodology and insights are generalizable not only within the US but also in countries with comparable distribution systems. To demonstrate impact on practice, we present a case study drawn from the application of our methodology to support US federal disaster preparedness. More generally, we contribute to system level understanding of multiserver tandem cyclic queues with time-limited customers found in relief distribution systems, which is often overlooked in the disaster management literature.

Analysis of electromechanical coupling vibration characteristics of motor-gear system based on bond graph theory

In recent years, there has been a growing demand in the field of engineering systems for research on the vibration response of motor-gear systems under non-steady state conditions. However, conventional modeling and simulation techniques are primarily restricted to systems within a single energy domain. When dealing with intricate electromechanical coupling systems, the modeling process becomes increasingly intricate. Consequently, this study adopts bond graph theory as the foundation for analyzing the vibration characteristics of motor-gear coupling systems. In addressing the vibration issue of the motor-gear transmission system, a nonlinear bond graph model is established that takes into account the time-varying mesh stiffness, static errors, and tooth surface friction, among other nonlinear factors. Then, according to the coupling relationship between motor mechanical systems and electrical systems, the electromechanical coupling dynamic model of the motor-gear system is established using the method of bond graph. In addition, the state equation of the system is derived based on the bond graph model. Finally, the system is simulated using 20-sim software, and the electromechanical coupled vibration characteristics of the simulation results are analyzed. This article lays the foundation for the design and analysis of motor-gear coupling systems and multi-energy domain complex systems.

Implications of the steady-state assumption for the global vegetation carbon turnover

Vegetation carbon turnover time (τ) is a central ecosystem property to quantify the global vegetation carbon dynamics. However, our understanding of vegetation dynamics is hampered by the lack of long-term observations of the changes in vegetation biomass. Here we challenge the steady state assumption of τ by using annual changes in vegetation biomass that derived from remote-sensing observations. We evaluate the changes in magnitude, spatial patterns, and uncertainties in vegetation carbon turnover times from 1992 to 2016. We found the robustness in the steady state assumption for forest ecosystems at large spatial scales, contrasting with local larger differences at the grid cell level between τ under steady state and τ under non-steady state conditions. The observation that terrestrial ecosystems are not in a steady state locally is deemed crucial when studying vegetation dynamics and the potential response of biomass to disturbance and climatic changes.

Three-dimensional Budyko framework incorporating terrestrial water storage: Unraveling water-energy dynamics, vegetation, and ocean-atmosphere interactions

The two-dimensional steady-state Budyko framework, widely used to study water-energy dynamics in landscapes, primarily focused on the partitioning of precipitation into evapotranspiration (ET) and water yield. Though this framework has been extended by incorporating water storage changes into precipitation input for non-steady state conditions, the interactions among water-energy dynamics, vegetation covers, and ocean-atmosphere oscillations within the Budyko framework at finer spatial and temporal scales have been unexplored. This study aims to investigate the interactions of regional hydroclimatic conditions, vegetation, and climate teleconnections over the Indo-China Peninsula (ICP), a region highly vulnerable to climate change. To achieve the objective, we propose a three-dimensional Budyko framework that incorporates the ratio of Gravity Recovery and Climate Experiment (GRACE)-based terrestrial water storage (TWS) or its changes (TWSC) to precipitation (SI/SCI) as the third dimension alongside the traditional two-dimensional Budyko framework. Our findings reveal that TWS has a significant impact on the Budyko framework, particularly during the dry season. The dryness index (DI)/evaporative index (EI) and SI/SCI exhibit positive (strongly negative) linear relationships in the wet (dry) season, respectively. Vegetation covers strongly influence the three-dimensional Budyko framework, with poor performance observed in highly vegetated regions due to high ET demand. Through relative importance analysis, we identify the Silk Road Pattern (SRP) as the most influential climate teleconnection among nine different teleconnections, affecting hydroclimatic conditions over the ICP. Positive (negative) phases of SRP encourage water-limited (energy-limited) ET conditions. This demonstrates that the Budyko parameter is influenced not only by landscapes but also by climate teleconnections, offering potential benefits for Budyko parameter estimation. Furthermore, the linear relationships between DI/EI and SI/SCI in three-dimensional Budyko framework can provide a promising alternative method for evapotranspiration and groundwater estimation.

Online Broadband Impedance Identification for Lithium-Ion Batteries Based on a Nonlinear Equivalent Circuit Model

Models play a crucial role in explaining internal processes, estimating states, and managing lithium-ion batteries. Electrochemical models can effectively illustrate the battery’s mechanism; however, their complexity renders them unsuitable for onboard use in electric vehicles. On the other hand, equivalent circuit models (ECMs) utilize a simple set of circuit elements to simulate voltage–current characteristics. This approach is less complex and easier to implement. However, most ECMs do not currently account for the nonlinear impact of operating conditions on battery impedance, making it difficult to obtain accurate wideband impedance characteristics of the battery when used in online applications. This article delves into the intrinsic mechanism of batteries and discusses the influence of nonstationary conditions on impedance. An ECM designed for non-steady state conditions is presented. Online adaptive adjustment of model parameters is achieved using the forgetting factor recursive least squares (FFRLS) algorithm and varied parameters approach (VPA) algorithm. Experimental results demonstrate the impressive performance of the model and parameter identification method, enabling the accurate acquisition of online impedance.

Vertical imbalance in organic carbon budgets is indicative of a missing vertical transfer during a phytoplankton bloom near South Georgia (COMICS)

The biological carbon pump, driven principally by the surface production of sinking organic matter and its subsequent remineralization to carbon dioxide (CO2) in the deep ocean, maintains atmospheric CO2 concentrations around 200 ppm lower than they would be if the ocean were abiotic. One important driver of the magnitude of this effect is the depth to which organic matter sinks before it is remineralised, a parameter we have limited confidence in measuring given the difficulty involved in balancing sources and sinks in the ocean's interior. One solution to this imbalance might be a temporal offset in which organic carbon accumulates in the mesopelagic zone (100–1000 m depth) early in the productive season before it is consumed later. Here, we develop a novel accounting method to address non-steady state conditions by estimating fluxes of particulate organic matter into, and accumulation within, distinct vertical layers in the mesopelagic zone using high-resolution spatiotemporal vertical profiles. We apply this approach to a time series of measurements made during the declining phase of a large diatom bloom in a low-circulation region of the Southern Ocean downstream of South Georgia. Our data show that the major export event led to a significant accumulation of organic matter in the upper mesopelagic zone (100–200 m depth) which declined over the following weeks, implying that temporal offsets need to be considered when compiling budgets. However, even when accounting for this accumulation, a mismatch in the vertically resolved organic carbon budget remained, implying that there are likely widespread processes that we do not yet understand that redistribute material vertically within the mesopelagic zone.

Dynamic alpha factor prediction with operating data - a machine learning approach to model oxygen transfer dynamics in activated sludge

Aeration is an energy-intensive process of aerobic biological wastewater treatment. An accurate model of oxygen transfer dynamics in activated sludge tanks would improve design and operation of aeration systems. Such a model should consider spatial and diurnal variation of α-factor as well as site-specific conditions that impact oxygen transfer. For this dynamic prediction a machine learning approach was used for the first time. The data-driven method was based on long-term ex-situ off-gas measurements with pilot-scale reactors (5.8 m height, 8.3 m3 vol) coupled to full-scale activated sludge tanks on the sites of two conventional and a two-stage activated sludge treatment plant. The ex-situ off-gas method allowed to quantify theoretical off-gas parameters in non-aerated zones and thus consider the whole activated sludge tank. We introduced the α0-factor to compare aerated and non-aerated zones under nonsteady-state conditions. Like the established α-factor for steady-state conditions, the α0-factor describes oxygen transfer inhibiting effects in activated sludge. α0-factor was lowest in upstream denitrification zones. This indicates an anoxic elimination of oxygen transfer inhibiting wastewater contaminants which improved oxygen transfer in subsequent aerobic zones. Random Forest models predicted α0-factor reliably in all examined activated sludge tanks even for stormwater events and seasonal variation. Model development only required online sensor data already available to operators. Our results suggest that machine learning models can dynamically predict α-factors in a variety of activated sludge processes, thus considering site-specific conditions in model training without manual calibration.

Greigite Formation Modulated by Turbidites and Bioturbation in Deep‐Sea Sediments Offshore Sumatra

AbstractAuthigenic greigite may form at any time within a sediment during diagenesis. Its formation pathway, timing of formation, and geological preservation potential are key to resolving the fidelity of (paleo‐)magnetic signals in greigite‐bearing sediments. In the cored sequence of the International Ocean Discovery Program Expedition 362 (Sumatra Subduction Margin), multiple organic‐rich mudstone horizons have high magnetic susceptibilities. The high‐susceptibility horizons occur immediately below the most bioturbated intervals at the top of muddy turbidite beds. Combined mineral magnetic, microscopic, and chemical analyses on both thin sections and magnetic mineral extracts of sediments from a typical interval (∼1,103.80–1,108.80 m below seafloor) reveal the presence of coarse‐grained greigite aggregates (particles up to 50–75 μm in size). The greigite formed under nonsteady state conditions caused by the successive turbidites. Organic matter, iron (oxy)(hydr)oxides, Fe2+, and sulfides and/or sulfate were enriched in these intensively bioturbated horizons. This facilitated greigite formation and preservation within a closed diagenetic system created by the ensuing turbidite pulse, where pyritization was arrested due to insufficient sulfate supply relative to Fe (oxy)(hydr)oxide. This may represent a novel greigite formation pathway under conditions modulated by turbidites and bioturbation. Paleomagnetic analyses indicate that the early diagenetic greigite preserves primary (quasi‐)syn‐sedimentary magnetic records. The extremely high greigite content (0.06–1.30 wt% with an average of 0.50 wt% estimated from their saturation magnetization) implies that the bioturbated turbiditic deposits are an important sink for iron and sulfur. Mineral magnetic methods, thus, may offer a window to better understand the marine Fe–S–C cycle.

An Analytical Study on Trustability of Prescribed Slope Inclinations in Design Criteria

In order to investigate trustability of prescribed slope inclinations in design criteria, slope stability analyses were performed on the assumed two embankment sections. Factors of safety against dry condition for the section of 10m high and slope inclination of 1:2 and for the other section of 5m high and slope inclination of 1:1.5 were 1.93 and 2.24 respectively and those values were greater than the design criterion value of 1.50. Factors of safety which were computed through seepage analyses for steady state condition were 1.59 for the section of 10m high and 1.93 for the other section and those values were greater than design criterion value of 1.30. Non-steady state analyses under the same rainfall intensity for the steady state condition were also performed to compare with steady state analyses and it can be seen that factor of safety for the non-steady state condition was converged to the value for the steady state condition as time elapsed. Stability analyses of using piezometric line which were located on the top line of the sections were performed and computed values of factor of safety were 1.20 for the section of 10m high and 1.59 for the other section respectively and it could be seen that the factor of safety for the section of 10m is less than the criterion value of 1.30. According to the results of this study, it can be seen that the slope inclination of 1:1.5 for the slope heights less than 5m and the slope inclination of 1:2.0 for the slope heights between 5m to 10m were safe enough under dry condition and rainfall condition. Nevertheless it can be concluded that slope stability analysis should be performed for the slope over 10m high and with ground water table near the surface of the slope because the factor of safety for that situation was less than the design criterion value.

Increased bundle-sheath leakiness of CO2 during photosynthetic induction shows a lack of coordination between the C4 and C3 cycles.

Use of a complete dynamic model of NADP-malic enzyme C4 photosynthesis indicated that, during transitions from dark or shade to high light, induction of the C4 pathway was more rapid than that of C3 , resulting in a predicted transient increase in bundle-sheath CO2 leakiness (ϕ). Previously, ϕ has been measured at steady state; here we developed a new method, coupling a tunable diode laser absorption spectroscope with a gas-exchange system to track ϕ in sorghum and maize through the nonsteady-state condition of photosynthetic induction. In both species, ϕ showed a transient increase to > 0.35 before declining to a steady state of 0.2 by 1500 s after illumination. Average ϕ was 60% higher than at steady state over the first 600 s of induction and 30% higher over the first 1500 s. The transient increase in ϕ, which was consistent with model prediction, indicated that capacity to assimilate CO2 into the C3 cycle in the bundle sheath failed to keep pace with the rate of dicarboxylate delivery by the C4 cycle. Because nonsteady-state light conditions are the norm in field canopies, the results suggest that ϕ in these major crops in the field is significantly higher and energy conversion efficiency lower than previous measured values under steady-state conditions.

A New Method to Calculate the Relative Permeability of Oil and Water in Tight Oil Reservoirs by Considering the Nonlinear Flow

The theoretical research on the percolation mechanism and oil-water relative permeability of low-permeability oil reservoirs is the focus and hotspot of international researchers. Oil-water relative permeability is an important parameter that describes the characteristics of oil-water two-phase flow and is widely used in the dynamic analysis of development and numerical simulation technology in the reservoir. The traditional calculation method of oil-water relative permeability (i.e., the JBN method) is based on the Darcy flow law. When the velocity and the displacement pressure gradient do not follow the linear flow law, there are some errors in the results of oil-water relative permeability calculated by the JBN method. In this paper, the traditional JBN method is improved, and we establish a new processing method of experimental data for oil-water relative permeability considering the effects of nonlinear flow, capillary pressure, and gravity in tight oil reservoirs. The experiments on the flow characteristics of single-phase oil and oil-water relative permeability under nonsteady-state conditions were carried out. The flow velocity and displacement pressure gradient show nonlinear characteristics when single-phase oil is passed through a tight core. At the same time, when the air permeability decreases from 1.92 × 10 − 3 μ m 2 to 0.1 × 10 − 3 μ m 2 , the nonlinear characteristics are becoming more and more obvious. Compared with the traditional JBN method, when the nonlinear flow characteristics are considered, the oil phase relative permeability increases, and the water phase relative permeability is slightly lower. If nonlinear flow characteristics are considered, when the water saturation increases from 0.605 to 0.699, the difference of oil phase relative permeability calculated by the JBN method and this method is gradually decreasing and, with the increase of water saturation, decreases from 0.0029 to 0.0001. In addition, the effects of capillary pressure, gravity, and the nonlinear flow coefficient on the oil-water relative permeability in tight oil reservoirs are studied. The capillary pressure also has a great influence on the relative permeability of the oil phase, and the relative permeability of the oil phase increases with the increase in capillary pressure. In the development process of the low-permeability reservoir, the seepage characteristics of each flow area are different, and the oil-water relative permeability is also different. Therefore, the research results play an important role in guiding the understanding of seepage characteristics of low permeability of tight oil reservoirs.

Impact of High Methane Flux on the Properties of Pore Fluid and Methane-Derived Authigenic Carbonate in the ARAON Mounds, Chukchi Sea

We investigated the pore fluid and methane-derived authigenic carbonate (MDAC) chemistry from the ARAON Mounds in the Chukchi Sea to reveal how methane (CH4) seepage impacts their compositional and isotopic properties. During the ARA07C and ARA09C Expeditions, many in situ gas hydrates (GHs) and MDACs were found near the seafloor. The fluid chemistry has been considerably modified in association with the high CH4 flux and its related byproducts (GHs and MDACs). Compared to Site ARA09C-St 08 (reference site), which displays a linear SO42- downcore profile, the other sites (e.g., ARA07C-St 13, ARA07C-St 14, ARA09C-St 04, ARA09C-St 07, and ARA09C-St 12) that are found byproducts exhibit concave-up and/or kink type SO42- profiles. The physical properties and fluid pathways in sediment columns have been altered by these byproducts, which prevents the steady state condition of the dissolved species through them. Consequently, chemical zones are separated between bearing and non-bearing byproducts intervals under non-steady state condition from the seafloor to the sulfate-methane transition (SMT). GH dissociation also significantly impacts pore fluid properties (e.g., low Cl-, enriched δD and δ18O). The upward CH4 with depleted δ13C from the thermogenic origin affects the chemical signatures of MDACs. The enriched δ18O fluid from GH dissociation also influences the properties of MDACs. Thus, in the ARAON Mounds, the chemistry of the fluid and MDAC has significantly changed, most likely responding to the CH4 flux and GH dissociation through geological time. Overall, our findings will improve the understanding and prediction of the pore fluid and MDAC chemistry in the Arctic Ocean related to CH4 seepage by global climate change.

The ecohydrological effects of climate and landscape interactions within the Budyko framework under non-steady state conditions

Catchment water yield is controlled by the partitioning of precipitation into evapotranspiration, runoff, and water storage changes. As one form of the Budyko framework, Fu's equation has been widely employed to estimate the influences of climatic factors and landscape characteristics on the precipitation partitioning, with a single parameter ω reflecting the integrated ecohydrological effects of these influencing factors. However, the ecohydrological effects under non-steady state conditions are not fully understood owing to the complex hydrological and ecological processes at finer spatial and temporal scales. In addition, the finer spatial and temporal scales limit the application of the Budyko framework, since the original framework assumes that water storage changes are negligible. In this study, combining two hydrological models (the abcd model and GR2M model) and Fu's equation based on an extended Budyko framework, we estimated the ecohydrological effects of climatic factors and landscape characteristics under non-steady state conditions for 59 small catchments (≤9805 km2) in Qinba Mountains. The outputs of the two hydrological models exist good consistency with satellite-based data, with NSE exceeding 0.5 in 93% and 97% of catchments, respectively. Factors influencing the precipitation partitioning vary with timescale and exhibit greater variability at intra-annual scales. Moreover, the hydrological effects of these time-varying factors are influenced by catchment characteristics (R2 ranging from 0.01 to 0.68), implying the precipitation partitioning is controlled by the ecohydrological interactions of climate and landscape at different timescales.

The Use of Datasets for Theoretical Subjects to Validate Vitamin A–Related Methods and Experimental Designs

We review recent work in which model-based compartmental analysis has been applied to data for theoretical human subjects in order to study questions related to vitamin A kinetics and metabolism. Using model simulations in this way, one can validate experimental designs, evaluate or improve vitamin A assessment methods, study the influence of perturbations on assessment methods, and/or advance information related to retinol kinetics. We also provide some information on the rationale for assigning physiologically appropriate values for specified characteristics [e.g., plasma retinol concentration, vitamin A total body stores (TBS), vitamin A intake] to hypothetical individuals, and in addition, we outline how one might first select an appropriate compartmental model for whole-body vitamin A metabolism and then specify physiologically reasonable values for the associated retinol kinetic parameters. In the studies discussed here, the Simulation, Analysis, and Modeling software was used to simulate responses in key model compartments for hypothetical subjects so that model predictions could be compared to assigned values or projected outcomes. For example, in the case of the retinol isotope dilution (RID) method that is used to assess vitamin A status, application of this approach has provided a way to evaluate the accuracy of TBS predictions under different steady state and non-steady state conditions, thus increasing confidence about the validity of RID results obtained in the field. Although datasets for theoretical subjects have been used to evaluate protocols in pharmacokinetics, to our knowledge, other nutrition researchers have not previously used approaches such as those described here. Our results to date indicate that this strategy has the potential to provide useful information related not only to vitamin A but perhaps to other nutrients as well.

Development of calibration-free/minimal calibration wavelength selection for iterative optimization technology algorithms toward process analytical technology application

As continuous manufacturing (CM) processes are developed, process analytical technology (PAT) via NIR spectroscopy has become an integral tool in process monitoring. NIR spectroscopy requires the deployment of complex multivariate models to extract the relevant information. The model of choice for the pharmaceutical industry is Partial Least Squares (PLS). However, the development of PLS can be burdensome due to the time and resource intensive requirements of calibration. To overcome this challenge, calibration-free/minimal calibration approaches have become of increasing interest. Iterative optimization technology (IOT) algorithms are a favorable calibration-free/minimal calibration approach with only the requirement of pure component spectra for successful active pharmaceutical ingredient (API) quantification. IOT algorithms were utilized to monitor potency trends (qualitative) and API content (quantitative) in a CM system and compared to a traditional PLS model. To overcome the reduced prediction performance of IOT during non-steady state conditions, a novel wavelength method based on variable importance in projection scores was employed. Overall, the success and value of IOT algorithms for application in CM settings was demonstrated.

Tight benthic-pelagic coupling drives seasonal and interannual changes in iron‑sulfur cycling in Arctic fjord sediments (Kongsfjorden, Svalbard)

Glaciated fjords are dynamic systems dominated by seasonal events such as spring phytoplankton blooms and pulses of glacial sediment-bearing meltwater delivery. These fjords are also characterized by strong spatial gradients in environmental factors such as sedimentation rate and primary productivity from the glacier-influenced head to the marine-influenced mouth. Such seasonal variations and spatial gradients, combined with the ongoing influence of climate change, generate non-steady state conditions, which have a strong impact on the mineralization of organic carbon in the fjord sediments and the flux of nutrients from the seabed. In order to investigate the role of fjord seasonal events and variability on diagenetic cycling of iron (Fe) and sulfur (S), we sampled Kongsfjorden (Svalbard, 79°N) in the spring, mid-summer, and late summer. We investigated sediment structure and biogeochemistry, conducted laboratory experiments to determine reaction rates, and compared these findings to water column productivity and turbidity. We found that rapid sedimentation near the glacial input buried algal matter-rich layers that fueled sub-surface peaks in mineralization rates over multi-year timescales. Sulfate reduction rates were limited by organic carbon availability and competition with Fe-reducers, while Fe reduction was controlled by the availability of reactive Fe(III) oxides. Pore water Fe 2+ concentrations were influenced by sulfur cycling pathways and abiotic reactions such as carbonate precipitation and potentially reverse weathering. Seasonal changes in sedimentation and organic carbon supply caused lower sulfate reduction and sulfide production rates in spring, driving generally higher spring fluxes of Fe 2+ from the sediment. The results of this study reveal the potential for an increased benthic source of nutrients such as Fe with continued benthic remineralization over winter in Kongsfjorden. Interannual changes in primary productivity, which are likely to intensify with global warming, and shifts in glacial sediment delivery have immediate impacts on the benthic cycling of Fe and S in this tightly coupled system, with a long term trend likely toward decreased benthic Fe fluxes. With the glacial retreat and changes in productivity predicted due to climate change, glaciated fjords such as Kongsfjorden may become a less efficient carbon sink by burying less terrestrial and marine-sourced organic matter in the deep sediments. • Investigation of seasonal Fe-S-C cycling in Arctic fjord sediments and water column. • Results show benthic respiration and increased benthic Fe 2+ flux over winter. • Findings suggest that fjord sediments respond rapidly to water column changes. • With glacial retreat, fjords may produce less benthic Fe and sequester less carbon.

Application of environmental isotopes in sustainability assessment of the groundwater resources of Lagos Coastal Basin (LCB), south-west, Nigeria

Owing to the fact that groundwater is the main source of water supply for both domestic and commercial activities by the inhabitants of the Lagos Coastal Basin (LCB) in Lagos, Nigeria, detailed study with respect to recharge and Mean Residence Time (MRT) of deep groundwater samples across the area was carried out to enable proper management of this resource. The study used environmental isotopes of water particularly carbon isotope and tritium (3H) contents in the groundwater to determine the mean residence time, and stable isotope of 2H and 18O to reveal origin of the recharging water. The stable Isotope of δ18O and δ2H plot around and along the local meteoric water line indicating meteoric origin, while the tritium results range between non-detectable and 0.3 TU in the confined aquifer connote old recharged water. This agrees with the old recharged water indicated by low 14C activities that resulted in MRT range from 7400 ± 10 to 12,030 ± 10 years. Comparison of the integrated results of the shallow unconfined aquifer with the deep confined aquifers showed that the shallow aquifer was younger and recharged in Holocene to present (modern climatic condition), whereas the confined deep groundwater was older and it recharge took place during Late Pleistocene/early Holocene (more humid condition than present). Consequently, the unconfined shallow aquifer may be considered renewable while the confined deep groundwater is being mined under non-steady state condition. Therefore, increasing water demand by various economic sectors require planned intervention in groundwater resource management of the LCB to achieve sustainable development.