Estimated Residence Time Research Articles

Model-based control for column-based continuous viral inactivation of biopharmaceuticals.

Batch low-pH hold is a common processing step to inactivate enveloped viruses for biologics derived from mammalian sources. Increased interest in the transition of biopharmaceutical manufacturing from batch to continuous operation resulted in numerous attempts to adapt batch low-pH hold to continuous processing. However, control challenges with operating this system have not been directly addressed. This article describes a low-cost, column-based continuous viral inactivation system constructed with off-the-shelf components. Model-based, reaction-invariant pH controller is implemented to account for the nonlinearities with Bayesian estimation addressing variations in the operation. The residence time distribution is modeled as a plug flow reactor with axial dispersion in series with a continuously stirred tank reactor, and is periodically estimated during operation through inverse tracer experiments. The estimated residence time distribution quantifies the minimum residence time, which is used to adjust feed flow rates. Controller validation experiments demonstrate that pH and minimum residence time setpoint tracking and disturbance rejection are achieved with fast and accurate response and no instability. Viral inactivation testing demonstrates tight control of logarithmic reduction values over extended operation. This study provides tools for the design and operation of continuous viral inactivation systems in service of increasing productivity, improving product quality, and enhancing patient safety.

Non-thermal plasma-based inactivation of bacteria in water using a microfluidic reactor

Failure of conventional water treatment systems may lead to the contamination of water sources, which can cause outbreaks of waterborne healthcare associated infections. Advanced oxidation processing by non-thermal plasma has the potential to treat water without the addition of chemicals. Antibiotic resistant Pseudomonas aeruginosa and Escherichia coli were chosen to investigate the use of non-thermal plasma generated in a microfluidic reactor to disinfect bacteria contaminated water. The microfluidic reactor used in this study utilized a dielectric barrier discharge, in a gas-liquid phase annular flow regime. Microbiological analysis of water inoculated with P. aeruginosa and E. coli was carried out before and after plasma treatment. Using air as the carrier gas, effective disinfection of water was achieved. At the lowest flow rate (35 µL/min), P. aeruginosa and E. coli viability were drastically reduced, with an approximate 8 log maximum decrease in viability following an estimated residence time of 5 s of plasma treatment. Scanning electron microscopy indicated changes in cell morphology due to the plasma treatment. Live/Dead assays revealed that the membranes of the cells had been damaged after plasma treatment. This work demonstrated that non-thermal plasma has the potential to disinfect against microbial contamination in water.

Electrochemical Residence Time Distribution As a Diagnostic Tool for Electrodes in Redox Flow Batteries

Redox flow batteries (RFBs) are a burgeoning technology for use in grid-scale energy storage; however, broad adoption is stymied by large capital costs.1,2 Housed within the reactor, porous electrodes are critical components to system performance and cost, as they provide surfaces for redox reactions, void space for electrolyte passage, and conductive solids for electron transport.3 Carbon papers, cloths, and felts are commonly used in RFBs, despite their tailored design and function towards the governing physics as fuel cell gas diffusion layers. Consequently, when coupled with geometrically varying flow field structures, these carbon substrates underperform in RFBs with forced liquid advection, resulting in uneven flow and current distributions. These inhomogeneities lead to inefficient operation, motivating the investigation of electrode morphologies and flow conditions that enable more uniform reactions throughout the reactor.One promising approach to assessing electrode performance is the measurement of residence time distribution, a traditional chemical reactor efficacy metric for quantifying flow pathways and hydraulic short-circuiting.4 Currently, most residence time estimations in flow cells assess the fluid dynamic spreading of a known solution leaving a reactor, using both experiments and computational fluid dynamics.5 However, in the absence of complementary electrochemical performance measurements, hydrodynamic calculations can only serve as a proxy for possible surface accessibility. Additionally, sole measurements of the reactor effluent are susceptible to added variance, which can obscure experimental results6 as opposed to spatial quantities within the reactor.Herein, we present an electrochemical method to measure spatially averaged electrochemical residence times in a small-scale flow cell. Using two disparate flow fields each with carbon cloth and paper electrodes, we compare electrochemical residence time responses to conventional steady-state polarization measurements to capture performance scaling relationships. Further, we present complementary modeling approaches, depicting multi-scale residence time calculations to contextualize the experimental values. Together, these approaches have the potential to elucidate the effects of electrode microstructure and flow field selection on cell-level fluid dynamics and electrochemical performance, which, in turn, may be used to advance RFB reactor design.AcknowledgmentsThis work was funded by the Joint Center for Energy Storage Research, an Energy Innovation Hub of the U.S. Department of Energy, Office of Science, Basic Energy (De-AC02-06CH11357). K.M.T. recognizes additional support from the U.S. NSF Graduate Research Fellowship (1122374).References A. Z. Weber et al., J. Appl. Electrochem., 41, 1137 (2011).C. Minke, U. Kunz, and T. Turek, J. Power Sources, 361, 105–114 (2017).K. J. Kim et al., J. Mater. Chem. A, 3, 16913–16933 (2015).A. E. Rodrigues, Chem. Eng. Sci., 230, 116188 (2021).G. Aparicio-Mauricio, F. A. Rodríguez, J. J. H. Pijpers, M. R. Cruz-Díaz, and E. P. Rivero, J. Energy Storage, 29, 101337 (2020).A. Bérard, B. Blais, and G. S. Patience, Can. J. Chem. Eng., 98, 848–867 (2020).

Groundwater residence time estimates obscured by anthropogenic carbonate.

Groundwater is an important source of drinking and irrigation water. Dating groundwater informs its vulnerability to contamination and aids in calibrating flow models. Here, we report measurements of multiple age tracers (14C, 3H, 39Ar, and 85Kr) and parameters relevant to dissolved inorganic carbon (DIC) from 17 wells in California's San Joaquin Valley (SJV), an agricultural region that is heavily reliant on groundwater. We find evidence for a major mid-20th century shift in groundwater DIC input from mostly closed- to mostly open-system carbonate dissolution, which we suggest is driven by input of anthropogenic carbonate soil amendments. Crucially, enhanced open-system dissolution, in which DIC equilibrates with soil CO2, fundamentally affects the initial 14C activity of recently recharged groundwater. Conventional 14C dating of deeper SJV groundwater, assuming an open system, substantially overestimates residence time and thereby underestimates susceptibility to modern contamination. Because carbonate soil amendments are ubiquitous, other groundwater-reliant agricultural regions may be similarly affected.

Influence of Thermal Stratification on Seasonal Net Ecosystem Production and Dissolved Inorganic Carbon in a Shallow Subtropical Lake

AbstractThermal stratification is a critical physical process controlling carbon (C) flux from lakes into the atmosphere. In general, vertical water temperature profiles in shallow subtropical lakes can vary significantly because typhoons frequently induce vertical mixing across the entire lake due to strong winds and rapid flushing from river inputs. Since C fluxes are driven by dissolved inorganic C (DIC), it is necessary to understand stratification's influence on DIC dynamics in shallow subtropical lakes. Therefore, we aimed to clarify the impact of stratification on DIC in Yuan‐Yang Lake, a typical shallow subtropical mountain lake, by developing a net ecosystem production (NEP) model. We measured the vertical profile of water temperature and DIC once or twice a month from July 2004 to December 2017. We applied a three‐dimensional hydrological model to estimate residence time and NEP, which revealed that large amounts of DIC are stored in the lower layer from spring to summer due to the suppression of vertical mixing by stratification. In autumn and winter, the lake was well mixed, and DIC was evenly distributed in the water column due to vertical mixing. This was confirmed by vertical DIC profiles.

Bound2Learn: a machine learning approach for classification of DNA-bound proteins from single-molecule tracking experiments.

DNA-bound proteins are essential elements for the maintenance, regulation, and use of the genome. The time they spend bound to DNA provides useful information on their stability within protein complexes and insight into the understanding of biological processes. Single-particle tracking allows for direct visualization of protein–DNA kinetics, however, identifying whether a molecule is bound to DNA can be non-trivial. Further complications arise when tracking molecules for extended durations in processes with slow kinetics. We developed a machine learning approach, termed Bound2Learn, using output from a widely used tracking software, to robustly classify tracks in order to accurately estimate residence times. We validated our approach in silico, and in live-cell data from Escherichia coli and Saccharomyces cerevisiae. Our method has the potential for broad utility and is applicable to other organisms.

An ex-vivo model for transsynovial drug permeation of intraarticular injectables in naive and arthritic synovium

Estimation of joint residence time of a drug is a key requirement for rational development of intraarticular therapeutics. There is a great need for a predictive model to reduce the high number of animal experiments in early stage development.Here, a Franz-cell based porcine ex-vivo permeation model is proposed, and transsynovial permeation of fluorescently-labeled dextrans in the range of potential drug candidates (10–150 kDa), as well as a small molecule (fluorescein sodium) and charged dextran derivates, have been determined. In addition, a lipopolysaccharide (LPS) -induced synovitis model was assessed for inflammatory biomarker levels and its effect on permeation of the solutes.Size-dependent permeability was observed for the analytes, which distinctly differed from findings with an artificial polycarbonate membrane, which is a widely used model. LPS was found to successfully stimulate an inflammatory response and led to a reduced size selectivity of the synovial membrane. 150 kDa dextran flux was accelerated approximately 2.5-fold in the inflamed state, whereas the permeation of smaller molecules was little affected. Moreover, by varying the LPS concentrations, the ex-vivo model was shown to produce varying degrees of synovitis-like inflammation.A simple and highly relevant ex-vivo tool for investigation of transsynovial permeation was developed, offering the further advantage of mimicking synovitis-induced permeability changes. Thus, this model provides a promising method for formulation screening, while reducing the need for animal experiments.

δ13C and 14C activity of groundwater DOC and DIC in the volcanically active and arid Loa Basin of northern Chile

Organic and inorganic carbon reservoirs are investigated in surface and groundwater in the semi to hyper-arid Río Loa Basin in Northern Chile. Part of the study area is within the Andean volcanic arc, and volcanism is responsible for large inputs of 14C-depleted CO2 which hampers groundwater residence time estimations using dissolved inorganic carbon (DIC). To better understand the area’s carbon system, we investigated 14C and δ13C in dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in groundwater and surface water. DOC concentrations are low in all water samples analyzed, 16–53 μM. Fluorescence and δ13C measurements on DOC indicate that dissolved organic matter (DOM) entering groundwater has characteristics of humic compounds derived from terrestrial plants in the recharge area. Fluorescence is lost in groundwater in the lower part of the system due to microbial or abiotic degradation. Changes in 14CDOC and δ13CDOC also indicate that microbial activity contributes to DOC, possibly from geogenic CO2. While the range of 14CDIC is very large, 1.6 to >50 pmC, that of 14CDOC is restricted between 53 and 72 pmC. We estimated C residence times in the volcanic arc, based on corrected 14CDOC, are <3,200 years compared to 14CDIC estimates that range from 2,000 to 15,000 years. While uncertainties in the estimate due to sources and sinks of DOC within the different aquifers exist, the range in age is somewhat restricted, despite the large distances that separate different sampling points and the different types of aquifers sampled. This leads us to conclude that wetter climate conditions in the past increased recharge and storage of the aquifers, and DOC inputs to recharging water was enhanced by more widespread plant growth during those past wet climates.

Penerapan Geometri dalam Perencanaan Instalasi Pengolahan Air Limbah Domestik : Studi Kasus Perumahan Mutiara Sartika, Kota Kendari

Penerapan konsep geometri sederhana untuk mendesain suatu instalasi pengolahan air limbah (IPAL) domestik penting dilakukan karena mengacu pada bangun ruang tiga dimensi untuk membuat bak penampungan. Oleh sebab itu dalam penelitian ini, kami menerapkan sistem geometri sederhana untuk perencanaan desain bak penampungan yang dapat diaplikasikan dibeberapa kawasan perumahan sederhana (Perumahan Mutiara Sartika-Kota Kendari). Hasil menunjukkan bahwa dengan kebutuhan konsumsi air bersih sebesar 150 L/hari/orang dengan jumlah perumahan 68 rumah type 36 dan 5 orang/rumah maka jumlah limbah yang dihasilkan sebesar 40.8 m3/hari. Sehingga dimensi bak penampungan air limbah yang dibangun berbentuk persegi panjang dengan total volume penampungan 79,1 m3 dengan perkiraan waktu tinggal selama 29 jam memperhatikan beberapa fungsi unit pengolahan. Berdasarkan hasil penelitian ini diharapkan dapat membantu untuk mengaplikasikan desain IPAL sederhana untuk pembangunan perumahan.

Movements and occurrence in two closely related fritillary species

Mobility may affect species' distribution patterns in heterogeneous landscapes, and it might impact fitness by influencing mating success, predation avoidance, and foraging success. Here, we studied causes and consequences of mobility patterns in butterflies: Argynnis adippe, a specialist constrained to warm microhabitats within woodland landscapes, and A. aglaja, a relative generalist that also inhabits grasslands, and tolerates lower temperatures. We explored associations of movement and occurrence patterns, population size and density, niche breadth, wing size, and different types of behaviour prior to capture by conducting a mark‐release‐recapture study on the Swedish island Öland. We marked 1 935 A. aglaja and 123 A. adippe and achieved recapture rates of 9.5% (A. aglaja), and 8.9% (A. adippe). Estimated population densities were 5 066 and 814 individuals per km2, for A. aglaja and A. adippe, respectively. Argynnis aglaja was less likely to perform long‐distance flights according to estimated dispersal kernels, hinting at negative density‐dependent dispersal in these species. Although we detected the longest flight distances ever in these species in MRR studies (11.9 km for A. aglaja and 3.7 km for A. adippe), most butterflies were recaptured within 200 meters (60–80%). Low recapture rates along with low estimated residence times and the potential for long movement might indicate that many individuals left the study area, and that the species form open populations, stretching over large areas. Despite significant differences in wing size and behaviour types, mean observed flight distances were similar in these species.

Size distribution of virus laden droplets from expiratory ejecta of infected subjects

For rebooting economic activities in the ongoing COVID-19 pandemic scenario, it is important to pay detailed attention to infection transfer mechanisms during interaction of people in enclosed environments. Utmost concern is the possibility of aerosol mediated infection transfer, which is largely governed by the size distributions of virus laden droplets, termed as virusols in this work, ejected from humans. We expand on the well-known theory of Poisson fluctuations which acts as statistical barrier against formation of virusols. Analysis suggests that for viral loads < 2 × 105 RNA copies/mL, often corresponding to mild-to-moderate cases of COVID-19, droplets of diameter < 20 µm at the time of emission (equivalent to ~ 10 µm desiccated residue diameter) are unlikely to be of consequence in carrying infections. Cut-off diameters below which droplets will be practically free of contamination, are presented as a function of viral loading. The median diameters of virus laden polydisperse droplet distributions will be 1.5 to 20 times higher depending upon the geometric standard deviation. The studies have implications to risk assessment as well as residence time estimates of airborne infections in indoor environments. Additionally, it will be also helpful for performance evaluation of sanitization and control technologies to mitigate infection risks in workplaces.

Geochemical tracers in submarine groundwater discharge research: practice and challenges from a view of climate changes

Submarine groundwater discharge (SGD), the flux of porewater from permeable seabed or karst conduits to surface water bodies, delivers a significant quantity of land-borne solutes to coastal oceans. This input of land-derived solutes is frequently linked with eutrophication, harmful algae blooms, and benthic hypoxia, and hence has the potential to trigger great economic losses. Geophysical and geochemical tracers, including salinity, temperature, water stable isotopes, and radioactive elements, have been widely applied in SGD studies for more than 50 years to, amongst others, identify water sources, estimate residence times, and quantify discharge rates. Here we review advantages and shortcomings of these tracers in the study of SGD. Application requirements are outlined based on previous research and combined tracer approaches in karst environments, permeable coasts, and estuaries are illustrated under the view of climate changes. Current challenges with the use of geochemical tracers in SGD studies are highlighted and opportunities to develop these tracers for improved coastal management showcased.

Effectiveness of airborne radon progeny assessment for atmospheric studies

In this paper, measurements of short- and long-lived Radon progeny attached to atmospheric fine aerosols are reported.Hourly measurements of 222Rn short-lived decay products (i.e. 214Bi via on-line alpha spectrometry on 214Po) in the atmosphere were carried out in Milan (Italy) from 1999 to 2016; 214Bi mean concentrations ranged from 0.2 to 38.1 Bq m−3. It is noteworthy that minima occurred in springtime although the strongest convective turbulence can be expected in summer, when the highest solar radiation is available; one order of magnitude higher values were observed in winter when the Po valley experienced poor atmospheric dilution. The Theil-Sen method was applied to investigate the long-time trend in de-seasonalised data series. Results showed that - although inter/intra-annual variations in 214Bi concentrations were observed in connection with differences in atmospheric dispersion conditions – no statistically significant trend over the investigated period was detected.On a sub-set of these samples, also weekly 210Pb concentrations were determined via off-line alpha spectrometry on 210Po; atmospheric activity concentration values ranged between 0.13 and 3.05 mBq m−3. The seasonal behaviour of 210Pb concentrations followed fairly well the 214Bi temporal pattern, showing that mixing layer dynamics is paramount in determining short- and long-lived Radon progeny levels in the atmosphere.From 210Pb/214Bi activity ratio, the residence time τres of fine aerosols in the atmosphere was estimated to be on average 1 day, ranging from 11.0 to 55.3 h without any evident temporal trend. By exploiting the availability of mixing layer height data at our site, an alternative approach to estimate aerosol residence time was tested; this was based on a simple relationship relying on deposition velocity (from literature data) and mixing layer height (available at our monitoring station). Mean experimental τres resulted in 1.2 days which was comprised in the 0.6–2.0 days range estimated by the alternative method. This result brings a noteworthy contribution to the scientific debate about differences among aerosol residence time estimates obtained by different radioactive parent-daughter couple; our results show that the 210Pb/214Bi (or equivalently 210Pb/222Rn) couple provides reliable estimates.

A review of the geology and origin of CO2 in mineral water springs in east Belgium

Naturally CO2-rich mineral water springs (pouhons) in east Belgium occur in the context of the Rhenohercynian domain of the Variscan fold-and-thrust belt, mostly within the Cambro-Ordovician Stavelot-Venn Massif. The origin of the CO2 is still unclear, although different hypotheses exist. In this review study, we show pouhon waters are of the calcium bicarbonate type (~310 mg/l HCO3- on average), with notable Fe (~15 mg/l) and some Ca (~43 mg/l). Pouhon waters are primarily meteoric waters, as evidenced by H and O isotopic signature. The δ13C of CO2 varies from -7.8 to +0.8‰ and contains up to ~15% He from magmatic origin, reflecting a combination of carbonate rocks and mantle as CO2 sources at depth. Dinantian and Middle Devonian carbonates at 2–6 km depth could be potential sources, with CO2 generated by dissolution. However, carbonates below the Stavelot-Venn Massif are only predicted by structural models that assume in-sequence thrusting, not by the more generally accepted out-of-sequence thrust models. The mantle CO2 might originate from degassing of the Eifel magmatic plume or an unknown shallower magmatic reservoir. Deep rooted faults are thought to act as preferential pathways. Overall low temperatures of pouhons (~10 °C) and short estimated residence times (up to 60 years) suggest magmatic CO2 is transported upwards to meet infiltrating groundwater at shallower depths, with partial to full isotopic exchange with carbonate rocks along its path, resulting in mixed magmatic-carbonate signature. Although the precise role and interaction of the involved subsurface processes remains debatable, this review study provides a baseline for future investigations.

Determination of Residence Time Distribution in a Continuous Powder Mixing Process With Supervised and Unsupervised Modeling of In-line Near Infrared (NIR) Spectroscopic Data.

Successful implementation of continuous manufacturing processes requires robust methods to assess and control product quality in a real-time mode. In this study, the residence time distribution of a continuous powder mixing process was investigated via pulse tracer experiments using near infrared spectroscopy for tracer detection in an in-line mode. The residence time distribution was modeled by applying the continuous stirred tank reactor in series model for achieving the tracer (paracetamol) concentration profiles. Partial least squares discriminant analysis and principal component analysis of the near infrared spectroscopy data were applied to investigate both supervised and unsupervised chemometric modeling approaches. Additionally, the mean residence time for three powder systems was measured with different process settings. It was found that a significant change in the mean residence time occurred when comparing powder systems with different flowability and mixing process settings. This study also confirmed that the partial least squares discriminant analysis applied as a supervised chemometric model enabled an efficient and fast estimate of the mean residence time based on pulse tracer experiments.

A Lagrangian-to-Eulerian Metric to Identify Estuarine Pelagic Habitats

Estuaries are among the world’s most productive ecosystems, but recent natural and anthropogenic changes have stressed these ecosystems. Tools to assess estuarine pelagic habitats are important to support and maintain healthy ecosystem function. In this work, we demonstrate that estuarine pelagic habitats can be identified by a simple ratio, termed the LE ratio, that takes into account the tidal excursion along a channel (a Lagrangian length scale) and the distance along that channel (an Eulerian length scale). To develop and assess this concept, numerical simulations of the 1D advection–dispersion equation of a conservative tracer and tidal excursion estimates based on data were used to formulize a conceptual model and to define exchange zones within a tidal channel. This conceptual model was then used to predict the extent of pelagic habitats in a terminal channel network in the Sacramento–San Joaquin Delta. Exchange zones mapped onto these channels were found to be in good agreement with independent estimates of residence time. Sensitivity analyses of the numerical model suggest that productive pelagic habitats can be expanded by a factor of 2 by either increasing dispersion or increasing spring–neap variability in mean tidal velocity. Such changes can also enhance flushing in upper channel reaches. These findings are relevant for tidal marsh restoration projects that aim to expand beneficial aquatic habitats by varying exchange or residence time over the spring–neap cycle, because this variability may interact synergistically with varying rates of phytoplankton growth due to spatiotemporal changes in environmental conditions.

Estimation of reaction kinetics for aromatic and heterocycles nitration in mixed acids through computational chemistry approach

AbstractNitration of aromatic compounds and heterocycles in mixed acid environment is one of the regularly performed large‐scale reactions in the chemical industry. Although the reaction mechanism of nitration of aromatics in mixed acid is well established, the development of a methodology for the evaluation of kinetics of exothermic aromatic nitrations in a simplified and accurate way is necessary. Here we evaluate the applicability of a kinetic evaluation methodology based on Hammett's acidity function, acidity function, and empirical activity coefficient for the nitration reaction. The contributions from the functional groups on the aromatic ring and quantitative structure‐activity relationships technique are considered for these evaluations. Natural bond orbital and magnetic index nucleus independent chemical shift analyses were carried out to obtain the substitution constants. The rate constant and activation energy values were evaluated at various temperatures and sulfuric acid strengths. The results were validated by comparing with the experimental data from the literature for several molecules. The effect of various functional groups (viz carbonyl, carboxyl, methyl, and amine) substituted on the benzene ring was also evaluated. For a few identified substrates, the data were used for estimation of residence time needed for complete conversion in continuous stirred tank reactor and in a plug flow reactor to quantify the effect of substitution constant and strength of sulfuric acid. The approach will help select a suitable reactor.

Interpreting Groundwater Chemistry and Estimating Residence Time of Groundwater in the Mt. Fuji Area Based on a Dissolution Kinetics-Fluid Flow Model and Chlorofluorocarbons (CFCs) Concentration

Relationships of concentrations of elements (Ca, Mg, Si) in groundwater from the Mt. Fuji area are obtained using analytical data on groundwater. Relationships of Ca, Mg, and H4SiO4 concentrations can be explained in terms of the dissolution of basaltic glass and precipitations of secondary minerals (halloysite, allophane, montmorillonite, and α-cristobalite). The relationship between residence time and H4SiO4 concentration of groundwater is obtained based on dissolution kinetics-piston fluid flow and a perfectly mixing fluid flow model. Using this relationship, the dissolution rate constant experimentally determined in an open system (not in a closed system) (k = 10−10.7 molSi/m2 s) and analytical data on H4SiO4 in groundwater, the residence time of groundwater (Kakitagawa site, southeastern foot and Fuji Yoshida site, northern foot) is estimated to be ca. 20 years for A/M (A: surface area of rock (m2), M: mass of water (kg)) = 20 based on a dissolution kinetics-fluid flow model. This estimated residence time is roughly consistent with other methods (He isotope tritium, chlorofluorocarbons (CFCs) ages (10-40 years), indicating that the dissolution kinetics-fluid flow model using dissolved silica concentration is a potentially useful method for estimating the residence time of groundwater in a young volcanic region. It is also reported that CFCs ages are ca. 30-40 years, which are the first data obtained for the Mt. Fuji area. This suggests that CFCs data are very useful for providing the residence time of groundwater in an area at a high elevation.

More than just refuelling: lengthy stopover and selection of departure weather by sandpipers prior to transoceanic and transcontinental flights

The evolutionary and behavioural ecology of migratory birds has received much theoretical and empirical attention. We contribute to this field by contrasting the weather at departure and stopover durations of a long‐distance migratory sandpiper prior to initiating lengthy transoceanic vs. transcontinental flights of potentially variable duration. Transoceanic flights provide few if any stopover options. We predicted that transoceanic migrants should therefore be more selective of energetically favourable weather at departure and have longer stopover durations prior to departing, using time as a surrogate for cumulative fuel acquisition, compared with transcontinental migrants. We used recent advances in capture–recapture modelling to quantify how weather conditions, length of stay, including estimated residence time prior to capture, and age class correlated with daily departure probabilities of Semipalmated Sandpipers Calidris pusilla at a coastal and an inland stopover site at comparable latitude. As expected, departure probabilities from both sites were higher with increasing strength of tailwinds, and the strength of this effect was larger for birds facing transoceanic vs. transcontinental flights. Cloud cover and temperature conditions at departure converged between sites at intermediate values from different background distributions. Stopover durations at both sites were substantially longer than needed if the birds were pursuing a simple tactic of arrive–fatten–leave at the stopover site. We infer that both sites provided high levels of both food and safety relative to other stages in the birds’ annual cycle, favouring lengthy stopovers and subsequent use of lengthy flights from both sites. Our study shows that recent advances of capture–recapture models can provide additional resolution to studies of the migration strategies of birds and refine our perspective on global patterns of migration routes and stopover decisions.

Development of high-performance hybrid ANN-finite volume scheme (ANN-FVS) for simulation of pharmaceutical continuous granulation

A hybrid model was developed for simulation of continuous wet granulation of pharmaceutical formulations via twin-screw granulator. The model was based on population balance model (PBM) for prediction of particle size distribution, while artificial neural network (ANN) was used for estimation of mean residence time which is required for numerical solution of PBM. A new numerical scheme based on finite volume approach was developed for solution of one dimensional PBM to predict granule size distribution obtained in a twin-screw granulator. The model takes into account liquid and feed flow rates, and screw speed, while the granule size distribution is the model's main output. Aggregation and breakage were considered as the main mechanisms in the process, and the model was developed and solved for different zones of extruder, i.e. conveying and kneading ones. The model's predictions were validated through comparing with experimental data collected using a 12mm twin-screw extruder for granulation of microcrystalline cellulose. The results indicated that the model is facile, robust and valid, which can predict the performance of twin-screw granulator for pharmaceutical formulations.