Average Transfer Rate Research Articles

Periodic venting of MABR lumen allows high removal rates and high gas-transfer efficiencies

The membrane-aerated biofilm reactor (MABR) is a novel treatment technology that employs gas-supplying membranes to deliver oxygen directly to a biofilm growing on the membrane surface. When operated with closed-end membranes, the MABR provides 100-percent oxygen transfer efficiencies (OTE), resulting in significant energy savings. However, closed-end MABRs are more sensitive to back-diffusion of inert gases, such as nitrogen. Back-diffusion reduces the average oxygen transfer rates (OTR), consequently decreasing the average contaminant removal fluxes (J). We hypothesized that venting the membrane lumen periodically would increase the OTR and J. Using an experimental flow cell and mathematical modeling, we showed that back-diffusion gas profiles developed over relatively long timescales. Thus, very short ventings could re-establish uniform gas profiles for relatively long time periods. Using modeling, we systematically explored the effect of the venting interval (time between ventings). At moderate venting intervals, opening the membrane for 20 s every 30 min, the venting significantly increased the average OTR and J without substantially impacting the OTEs. When the interval was short enough, in this case shorter than 20 min, the OTR was actually higher than for continuous open-end operation. Our results show that periodic venting is a promising strategy to combine the advantages of open-end and closed end operation, maximizing both the OTR and OTE.

The mass, luminosity and mass-loss rate of the donor of the V1487 Aql/GRS 1915+105 binary system

The donor in the microquasar GRS 1915+105 is a low-mass giant. Such a star consists of a degenerate helium core and a hydrogen-rich envelope. Both components are separated by a hydrogen-burning shell. The structure of such an object is relatively simple and easy to model. Making use of the observational constraints on the luminosity and the radius of the donor, we constrain the mass of this star with evolutionary models. We find a very good agreement between the constraints from those models and from the observed rotational broadening and the near-infrared magnitude. Combining the constraints, we find solutions with stripped giants of mass ≥0.28 M⊙ and of the spectral class K5 III, independent of the distance to the system, and a distance-dependent upper limit, ≲1 M⊙. We also calculate the average mass transfer rate and the duty cycle of the system as a function of the donor mass. This rate is much below the critical rate (at which the system would become persistent), and the duty cycle is less than 20 per cent.

Vascularized Fibula-Based Physis Transfer: A Follow-Up Study of Longitudinal Bone Growth and Complications.

Background:The vascularized free fibula epiphyseal transfer provides an option for the preservation of limb lengthening after resection of the proximal humerus in pediatric sarcoma patients. The purpose of this study was to provide a long-term follow-up of longitudinal growth patterns and outcomes after free fibula epiphyseal transfer in upper extremity reconstruction.Methods:A retrospective review of 4 patients who underwent free fibula epiphyseal transfer after oncologic resection of the proximal humerus for osteosarcoma was performed. Oncologic details that could affect outcomes were included in the review: primary tumor pathology, location of malignancy, and presence of recurrence. Details on the reconstruction included longitudinal growth of the flap from the time of implantation to the most recently available radiograph and postoperative complications. The length of the fibula over time was measured from the humeral head to the olecranon process.Results:All patients were alive at the start of this study. The average longitudinal growth rate of the free fibula epiphyseal transfer was 0.54 ± 0.18 cm/y, and patients demonstrated satisfactory and consistent longitudinal bone growth and hypertrophy over time. All 4 patients suffered from a complication of postoperative fibula graft fracture, and 1 of 4 patients experienced unremitting peroneal nerve damage. All patients demonstrated normal wrist and hand motion with a normal arc of elbow flexion and extension.Conclusion:This study demonstrates that the vascularized fibula epiphyseal transfer offers the ability to preserve longitudinal limb growth and hypertrophy throughout adolescence.

Enhancing Detection of SSVEPs for a High-Speed Brain Speller Using Task-Related Component Analysis.

This study proposes and evaluates a novel data-driven spatial filtering approach for enhancing steady-state visual evoked potentials (SSVEPs) detection toward a high-speed brain-computer interface (BCI) speller. Task-related component analysis (TRCA), which can enhance reproducibility of SSVEPs across multiple trials, was employed to improve the signal-to-noise ratio (SNR) of SSVEP signals by removing background electroencephalographic (EEG) activities. An ensemble method was further developed to integrate TRCA filters corresponding to multiple stimulation frequencies. This study conducted a comparison of BCI performance between the proposed TRCA-based method and an extended canonical correlation analysis (CCA)-based method using a 40-class SSVEP dataset recorded from 12 subjects. An online BCI speller was further implemented using a cue-guided target selection task with 20 subjects and a free-spelling task with 10 of the subjects. The offline comparison results indicate that the proposed TRCA-based approach can significantly improve the classification accuracy compared with the extended CCA-based method. Furthermore, the online BCI speller achieved averaged information transfer rates (ITRs) of 325.33 ± 38.17 bits/min with the cue-guided task and 198.67 ± 50.48 bits/min with the free-spelling task. This study validated the efficiency of the proposed TRCA-based method in implementing a high-speed SSVEP-based BCI. The high-speed SSVEP-based BCIs using the TRCA method have great potential for various applications in communication and control.

An Artificial-Noise-Aided Hybrid TS/PS Scheme for OFDM-Based SWIPT Systems

We propose a new artificial-noise aided hybrid time-switching/power-splitting scheme for orthogonal frequency-division multiplexing (OFDM) systems to securely transmit data and transfer energy to a legitimate receiving node. In our proposed scheme, the cyclic prefix has two more benefits in addition to the cancellation of the inter-symbol interference between the OFDM blocks. First, it enables the legitimate transmitter to send artificial-noise (AN) vectors in a way such that the interference can be canceled at the legitimate receiver prior to information decoding. Second, its power is used to energize the legitimate receiver. We optimize the cyclic prefix length, the time-switching and power-splitting parameters, and the power allocation ratio between the data and AN signals at the legitimate transmitter to maximize the average secrecy rate subject to a constraint on the average energy transfer rate at the legitimate receiver. Numerical results demonstrate that our proposed scheme can achieve up to 23% average secrecy rate gain relative to a pure power-splitting scheme.

Four Levers of Redistribution: The Impact of Tax and Transfer Systems on Inequality Reduction

Using observational micro data from the Luxembourg Income Study (LIS) we assess the redistributive impact of tax and transfer cofigurations across 22 OECD countries for the period 1999-2013. After imputing missing tax data (employer social security contributions), we measure the reduction of income inequality due to four key levers of tax and transfer systems: the average tax rate, tax progressivity, the average transfer rate, and transfer targeting. Our methodological improvements provide the following results: First, tax redistribution dominates transfer redistribution (excluding pensions) in most countries. Second, targeting explains very little of the cross-country variation in inequality reduction. In contrast, both progressivity of taxes and the average tax rate have large impacts on redistribution. Third, we observe the trace of political trade-offs. High average tax rates do not appear in conjunction with highly progressive tax systems.

A Hardware/Software Prototype of EEG-based BCI System for Home Device Control

This paper presents a design exploration of a new EEG-based embedded system for home devices control. Two main issues are addressed in this work: the first one consists of an adaptive filter design to increase the classification accuracy for motor imagery. The second issue deals with the design of an efficient hardware/software embedded architeclture integrating the entire EEG signal processing chain. In this embedded system organization, the pre-processing techniques, which are time consuming, are integrated as hardware accelerators. The remaining blocks (Intellectual Properties - IP) are developed as embedded-software running on an embedded soft-core processor. The pre-processing step is designed to be self-adjusted according to the intrinsic characteristics of each subject. The feature extraction process uses the Common Spatial Pattern (CSP) as a filter due to its effectiveness to extract the ERD/ERS (Event-Related Desynchronization/ Synchronization) effect, where the classifier is based on the Mahalanobis distance. The advantage of the proposed system lies in its simplicity and short processing time while maintaining a high performance in term of classification accuracy. A prototype of the embedded system has been implemented on an Altera FPGA-based platform (Stratix-IV). It is shown that the proposed architecture can effectively extract discriminative features for motor imagery with a maximum frequency of 150 MHz. The proposed system was validated on EEG data of twelve subjects from the BCI competition data sets. The prototype performs a fast classification within time delay of 0.399 second per trial, an accuracy average of 94.47 %, an average transfer rate over all subjects of 20.74 bits/min. The estimated power consumption of the proposed system is around 1.067 Watt (based on an integrated tool-power analysis of Altera corporation).

Application of nanodisc technology for direct electrochemical investigation of plant cytochrome P450s and their NADPH P450 oxidoreductase.

Direct electrochemistry of cytochrome P450 containing systems has primarily focused on investigating enzymes from microbes and animals for bio-sensing applications. Plant P450s receive electrons from NADPH P450 oxidoreductase (POR) to orchestrate the bio-synthesis of a plethora of commercially valuable compounds. In this report, full length CYP79A1, CYP71E1 and POR of the dhurrin pathway in Sorghum bicolor were reconstituted individually in nanoscale lipid patches, “nanodiscs”, and directly immobilized on unmodified gold electrodes. Cyclic voltammograms of CYP79A1 and CYP71E1 revealed reversible redox peaks with average midpoint potentials of 80 ± 5 mV and 72 ± 5 mV vs. Ag/AgCl, respectively. POR yielded two pairs of redox peaks with midpoint potentials of 90 ± 5 mV and −300 ± 10 mV, respectively. The average heterogeneous electron transfer rate constant was calculated to be ~1.5 s−1. POR was electro-catalytically active while the P450s generated hydrogen peroxide (H2O2). These nanodisc-based investigations lay the prospects and guidelines for construction of a simplified platform to perform mediator-free, direct electrochemistry of non-engineered cytochromes P450 under native-like conditions. It is also a prelude for driving plant P450 systems electronically for simplified and cost-effective screening of potential substrates/inhibitors and fabrication of nano-bioreactors for synthesis of high value natural products.

Fabrication and characterization of metal-packaged fiber Bragg grating sensor by one-step ultrasonic welding

A metallic packaging technique of fiber Bragg grating (FBG) sensors is developed for measurement of strain and temperature, and it can be simply achieved via one-step ultrasonic welding. The average strain transfer rate of the metal-packaged sensor is theoretically evaluated by a proposed model aiming at surface-bonded metallic packaging FBG. According to analytical results, the metallic packaging shows higher average strain transfer rate compared with traditional adhesive packaging under the same packaging conditions. Strain tests are performed on an elaborate uniform strength beam for both tensile and compressive strains; strain sensitivities of approximately 1.16 and 1.30 pm/μϵ are obtained for the tensile and compressive situations, respectively. Temperature rising and cooling tests are also executed from 50°C to 200°C, and the sensitivity of temperature is 36.59 pm/°C. All the measurements of strain and temperature exhibit good linearity and stability. These results demonstrate that the metal-packaged sensors can be successfully fabricated by one-step welding technique and provide great promise for long-term and high-precision structural health monitoring.

Conjugated Effect of Joule Heating and Magnetohydrodynamic on Laminar Convective Heat Transfer of Nanofluids Inside a Concentric Annulus in the Presence of Slip Condition

In the current study, the conjugated effect of Joule heating and magnetohydrodynamics (MHD) on the forced convective heat transfer of fully developed laminar nanofluid flows inside annular pipes, under the influence of MHD field, has been investigated. The temperature and nanoparticle distributions at both the inner and outer walls are assumed to vary in the direction of the fluid. Furthermore, owing to the nanoparticle migrations in the fluid, a slip condition becomes far more important than the no-slip condition of the fluid–solid interface, which appropriately represents the non-equilibrium region near the interface. The governing equations—obtained by employing the Buongiorno’s model for nanofluid in cylindrical coordinates—are converted into two-point ordinary boundary value differential equations and solved numerically. The effects of various controlling parameters on the flow characteristics, the average Nusselt number and the average Sherwood number have been assessed in detail. Additionally, the effect of the inner to outer diameter ratio on the heat and mass transfer rate has been studied. The results obtained indicate that, in the presence of a magnetic field when the fluid is electrically conductive, heat transfer will be reduced significantly due to the influences of Joule heating, while the average mass transfer rate experiences an opposite trend. Moreover, the increase in the slip velocity on both the walls causes the average heat transfer to rise and the average mass transfer to decrease.

Direct electrochemistry and electrocatalysis of cytochrome P450s immobilized on gold/graphene-based nanocomposites

In the present work, gold nanoparticles coated chitosan/reduced graphene oxide (Au-CS-RG) was prepared for cytochrome P450 2D6 (CYP2D6) and cytochrome P450 1A1 (CYP1A1) immobilization, investigation of the direct electrochemistry and electrochemically-driven drug metabolism. The immobilized CYP2D6 and CYP1A1 displayed respectively a pair of redox peaks with a formal potential of −492±4 and −504±6mV. The response showed a surface-controlled electrode process with an average electron transfer rate constant of 5.19±0.3s−1 for CYP2D6 and 3.24±0.4s−1 for CYP1A1 determined in the scan rate of 100mV/s. When the Au-CS-RG was treated with polyacrylic acid (PAA), the resulting nanocomposites (PAA-Au-CS-RG) changed the surface charge of Au-CS-RG from positive to negative and increased the size of the coated gold nanoparticles from ~15 to ~25nm. This led to negative-shift of the formal potential to −513±6mV for CYP2D6 and −509±5mV for CYP1A1, while the electron transfer rate constant decreased to 4.10±0.3s−1 for CYP2D6 and 2.78±0.2s−1 for CYP1A1, respectively. The immobilized CYP2D6 and CYP1A1 in both cases showed excellent electrochemically-driven drug metabolism. The LC-MS analysis demonstrated the bioconversion from tramadol or benzo[a]pyrene to o-demethyl-tramadol or 7.8-diol benzo[a]pyrene by the electrochemically-driven way, respectively. The metabolic inhibition of the quinidine and alpha-naphthoflavone to the enzymatic activity of CYP2D6 and CYP1A1 were also evaluated.

CSaaS - a multi-cloud framework for secure file storage technology using open ZFS

Many business enterprises are migrating towards multi-cloud to store the enterprise data. Multi-cloud approach overcomes various limitations faced by single cloud environment. The advantages include freedom from vendor-lock-in, and improved availability and security of the data. File storage approach supported by network attached storage NAS proves to be a better solution especially for structured database storage that needs to handle random read/write loads and virtual machine file system. In this paper, we propose a novel framework that helps the enterprises to store their data in the multi-cloud environment using file storage technology. This framework, referred to as controller for storage as a service CSaaS, comprises four modules which facilitates the clients to achieve secure data storage on multiple clouds. Performance evaluation for average data transfer rate and completion latency show that read and rand-read performance of CSaaS has been significantly improved as compared to single CSP, for file sizes up to 90 MB.

Impact of carrier filling ratio on oxygen uptake & transfer rate, volumetric oxygen transfer coefficient and energy saving potential in a lab-scale MBBR

This study investigates the effect of bio-carriers on the oxygen uptake rate (OUR) in the effluent of the reactor with an aim to provide optimized filling ratio for the practical operation of a moving bed biofilm reactor. The experimental work was carried out in seven different phases with respect to the filling ratio. In each phase, oxygen transfer efficiency and volumetric oxygen mass transfer coefficient (kla) were measured by varying the carrier filling ratio (10–70%). The effect of filling ratios, mixing intensity, hydraulic retention time and kla on OUR were observed. The value of OUR increased 2–3 times with the augmentation of carrier filling ratio but it decreased when more carriers were added inside the reactor. Secondly, efforts were also made to find ways to reduce aeration energy. Savings of energy consumption (up to 35%) were noted by providing intermittent aeration at an average oxygen transfer rate of 6mg-O2L−1h−1. Still, further scope exists to conserve more energy if the oxygen transfer rate is maintained at 4mg-O2L−1h−1.

FORMATION AND EVOLUTION OF GALACTIC INTERMEDIATE/LOW-MASS X-RAY BINARIES

We investigate the formation and evolutionary sequences of Galactic intermediate- and low-mass X-ray binaries (I/LMXBs) by combining binary population synthesis (BPS) and detailed stellar evolutionary calculations. Using an updated BPS code we compute the evolution of massive binaries that leads to the formation of incipient I/LMXBs, and present their distribution in the initial donor mass vs. initial orbital period diagram. We then follow the evolution of I/LMXBs until the formation of binary millisecond pulsars (BMSPs). We find that the birthrate of the I/LMXB population is in the range of $ 9\times10^{-6} - 3.4\times10^{-5} \, {\rm yr^{-1}}$, compatible with that of BMSPs which are thought to descend from I/LMXBs. We show that during the evolution of I/LMXBs they are likely to be observed as relatively compact binaries with orbital periods $ \lesssim $ 1 day and donor masses $\lesssim 0.3 M_{\odot}$. The resultant BMSPs have orbital periods ranging from less than 1 day to a few hundred days. These features are consistent with observations of LMXBs and BMSPs. We also confirm the discrepancies between theoretical predications and observations mentioned in the literature, that is, the theoretical average mass transfer rates ($ \sim 10^{-10} M_{\odot} $\,yr$^{-1}$) of LMXBs are considerably lower than observed, and the number of BMSPs with orbital periods $\sim 0.1-10$ day is severely underestimated. These discrepancies imply that something is missing in the modeling of LMXBs, which is likely to be related to the mechanisms of the orbital angular momentum loss.

Accurate analysis of electron transfer from quantum dots to metal oxides in quantum dot sensitized solar cells

Electron transfer rate from quantum dot (QD) to metal oxide (MO) in quantum dot sensitized solar cells (QDSSCs) has an important role in the efficiency. In this work, we analyse the electron transfer rate from CdSe, CdS and CdTe QDs to TiO2, ZnO and SnO2 MOs by extending the related equations with considering various effects, based on the Marcus theory. In this regard, the effects of QD diameter, QD–MO spacing, the crystalline defects, temperature, and the reorganizational energy, on the electron transfer rate are investigated. The results show that, the maximum electron transfer rate is achieved for CdTe QD with the mentioned three MOs. Moreover, in order to direct the designer to reach the appropriate QDs–MOs combinations for obtaining the maximum electron transfer rate, the average electron transfer rate for various combinations is calculated. For the verification of simulation method, a part of work has been compared with the previous experimental and theoretical results, which indicates the correctness of our simulation algorithm.

Emergency Department Visits for Children With Cancer

Research Article| May 01 2015 Emergency Department Visits for Children With Cancer AAP Grand Rounds (2015) 33 (5): 56. https://doi.org/10.1542/gr.33-5-56 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation Emergency Department Visits for Children With Cancer. AAP Grand Rounds May 2015; 33 (5): 56. https://doi.org/10.1542/gr.33-5-56 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search toolbar search search input Search input auto suggest filter your search All PublicationsAll JournalsAAP Grand RoundsPediatricsHospital PediatricsPediatrics In ReviewNeoReviewsAAP NewsAll AAP Sites Search Advanced Search Topics: cancer, childhood cancer, emergency service, hospital, hospital admission Source: Mueller EL, Sabbatini A, Gebremariam A, et al. Why pediatric patients with cancer visit the emergency department: United States, 2006–2010. Pediatr Blood Cancer. 2015; 62(2): 490– 549; doi: https://doi.org/10.1002/pbc.25288Google Scholar Investigators from the University of Michigan and the Hospital for Sick Children, Toronto, conducted a retrospective cohort study to determine the reasons for which children with cancer seek emergent care and the factors associated with consequent hospital admission. Using data from the Healthcare Cost and Utilization Project’s Nationwide Emergency Department Sample (NEDS), children diagnosed with cancer were selected by assessing all US pediatric emergency department (ED) encounters from 2006–2010. De-identified data included primary cancer and ED discharge, patient demographics, hospital characteristics, and inpatient data, when appropriate. Since NEDS is a national database containing a 20% stratified probability sample of all hospital-based EDs, weighted analyses were conducted to attain representative estimates of ED visits, disposition status, and factors relating to admission. Characteristics of visits that led to discharge from the ED versus hospital admission were compared using regression analysis. A total of 294,289 ED visits for children with cancer, aged 0–19 years, representing 0.2% of all nationwide pediatric ED evaluations over this 5-year period, were analyzed. Acute lymphoblastic leukemia comprised 25.9% of malignancies in this cohort, followed by central nervous system tumor (8.1%) and acute myelogenous leukemia (7.5%). Of the top 10 reasons for ED encounters, fever and febrile neutropenia (FN) represented 19.2% of the visits, blood stream infections 4.3% of visits, upper respiratory infection 2.8%, pneumonia 2.5%, and neutropenia 2.2%. Overall, 43.6% of ED visits led to admission for the child at the same hospital as the ED, with highest admission rates for FN (82.3%), neutropenia (80.1%), blood stream infection (74.7%), and pneumonia (67.8%). The average transfer rate to another hospital was 3.7% with highest transfer rates for seizures (9.9%), FN (6.5%), and neutropenia (6.2%). Approximately 0.1% of children with cancer died in the ED. Variables significantly associated with admission versus discharge included age <4 years compared to age 15–19 years, having the highest quartile of median household income compared to the lowest, and having public insurance compared to self-pay status. Children presenting to metropolitan teaching hospitals were more likely to be admitted, while children presenting to non-metropolitan hospitals were less likely to be admitted compared to those attending a metropolitan non-teaching hospital. Children presenting with FN, neutropenia only, pneumonia, and dehydration were more likely to be admitted than discharged home. The authors conclude that children with cancer present to EDs most commonly with fever and FN. Younger age, having FN or neutropenia, and socioeconomic issues were associated with hospital admission from the ED. Dr Hogan has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device. Despite improved outcomes for children diagnosed with cancer, immunosuppression remains a common and potentially lethal toxicity related to current chemotherapy, radiotherapy, and immunotherapy. In addition, surgically implanted... You do not currently have access to this content.

Transfer rates of toxic metals during decoction preparation from hebal medicines and safety evaluation of the final decoction products

Transfer rates of toxic metals during herbal decoction preparation were investigated using risk assessment tools. Decoction samples were analyzed using Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) and a mercury analyzer after microwave digestion. The average decoction transfer rate (%) for each toxic metal after boiling was 10.5 for As, 4.3 for Pb, 4.1 for Cd, and 2.7 for Hg. A risk assessment of toxic metals in decoctions was performed based on the percentage provisional tolerable weekly intake (PTWI) values for a mean value scenario and a 95th percentile value scenario. Samples were collected of 68 decoctions representing 8 types frequently prescribed by oriental medicine clinics in Seoul, Korea. Both scenarios demonstrated low PTWI values. All decoction samples were safe according to risk assessment results.

Toward the measurement of the hyperfine splitting in the ground state of muonic hydrogen

The recent Lamb shift experiment at PSI and the controversy about proton size revived the interest in measuring the hyperfine splitting in muonic hydrogen and extracting the proton Zemach radius. The efficiency of the experimental method depends on the energy dependence of the muon transfer rate to higher-Z gases in the near epithermal energy range. As long as the available experimental data only give the average transfer rate in the whole epithermal range, and the detailed theoretical calculations have not yet been verified, an experiment has been started for the measurement of the transfer rate in thermalized gas target at different temperatures and extracting from the data an estimate of the transfer rate for arbitrary energies. We outline the underlying mathematical method and estimate its accuracy.

Enhanced heat and mass transfer in alternating structure of tubes and longitudinal trough mesh packing in lithium bromide solution absorber

For enhancing the vapour absorption in LiBr solution systems, a novel absorber with tube and mesh packing alternating structure is designed and investigated. Stainless steel mesh screens are folded as the longitudinal trough mesh packing, and inserted to the gaps of horizontal tubes to make the absorbent flow through the tube and mesh packing regimes successively, thus forming an alternating heat and mass transfer absorption process. Experimental investigation is conducted to characterize the absorption performance of the absorption bodies of this alternating structure and conventional horizontal coils. The results show that the average mass transfer rate and cooling load are increased by 17.2% and 6.23% respectively, which confirms that the alternating structures can promote the absorption. The mesh packing provides extended absorption area, slows down the flow and well mingles the solution, which are all beneficial for vapour absorption.

High-Rayleigh-number convection of a reactive solute in a porous medium

AbstractWe consider two-dimensional one-sided convection of a solute in a fluid-saturated porous medium, where the solute decays via a first-order reaction. Fully nonlinear convection is investigated using high-resolution numerical simulations and a low-order model that couples the dynamic boundary layer immediately beneath the distributed solute source to the slender vertical plumes that form beneath. A transient-growth analysis of the boundary layer is used to characterise its excitability. Three asymptotic regimes are investigated in the limit of high Rayleigh number $\mathit{Ra}$, in which the domain is considered deep, shallow or of intermediate depth, and for which the Damköhler number $\mathit{Da}$ is respectively large, small or of order unity. Scaling properties of the flow are identified numerically and rationalised via the analytic model. For fully established high-$\mathit{Ra}$ convection, analysis and simulation suggest that the time-averaged solute transfer rate scales with $\mathit{Ra}$ and the plume horizontal wavenumber with $\mathit{Ra}^{1/2}$, with coefficients modulated by $\mathit{Da}$ in each case. For large $\mathit{Da}$, the rapid reaction rate limits the plume depth and the boundary layer restricts the rate of solute transfer to the bulk, whereas for small $\mathit{Da}$ the average solute transfer rate is ultimately limited by the domain depth and the convection is correspondingly weaker.