Control Of Exchange Research Articles

Control of the Redox Activity of PbS Quantum Dots by Tuning Electrostatic Interactions at the Quantum Dot/Solvent Interface.

This paper describes the control of electron exchange between a colloidal PbS quantum dot (QD) and a negatively charged small molecule (9,10-anthraquinone-2-sulfonic acid sodium salt, AQ), through tuning of the charge density in the ligand shell of the QD, within an aqueous dispersion. The probability of electron exchange, measured through steady-state and time-resolved optical spectroscopy, is directly related to the permeability of the protective ligand shell, which is a mixed monolayer of negatively charged 6-mercaptohexanoate (MHA) and neutral 6-mercaptohexanol (MHO), to AQ. The composition of the ligand shell is quantitatively characterized by (1)H NMR. The dependence of the change in Gibbs free energy, ΔGobs, for the diffusion of AQ through the charged ligand shell and its subsequent adsorption to the QD surface is well-described with an electrostatic double-layer model for the QD/solvent interface. Fits of the optical data to this model yield an increase in the free energy for transfer of AQ from bulk solution to the surface of the QD (where it exchanges electrons with the QD) of 154 J/mol upon introduction of each additional charged MHA ligand to the ligand shell. This work expands the set of chemical parameters useful for controlling the redox activity of QDs via surface modification and suggests strategies for the use of nanoparticles for molecular and biomolecular recognition within chemically complex environments and for design of chemically stable nanoparticles for aqueous photocatalytic systems.

Highly tunable exchange in donor qubits in silicon

AbstractIn this article we have investigated the electrical control of the exchange coupling (J) between donor-bound electrons in silicon with a detuning gate bias, crucial for the implementation of the two-qubit gate in a silicon quantum computer. We found that the asymmetric 2P–1P system provides a highly tunable exchange curve with mitigated J-oscillation, in which 5 orders of magnitude change in the exchange coupling can be achieved using a modest range of electric field (3 MV/m) for ~15-nm qubit separation. Compared with the barrier gate control of exchange in the Kane qubit, the detuning gate design reduces the gate density by a factor of ~2. By combining large-scale atomistic tight-binding method with a full configuration interaction technique, we captured the full two-electron spectrum of gated donors, providing state-of-the-art calculations of exchange energy in 1P–1P and 2P–1P qubits.

Tablets, Sealings and Weights at Ebla: Administrative and Economic Procedures at the beginning of the Archaic State in Syria

ment and movement of goods is recorded by the use of cylinder seals on sealings and on pottery vessels. In the palace were found around two hundred clay sealings with cylinder-seal impressions and more than fifty storage jars with seal impressions. Cretulae come from various functional contexts, with significant concentrations only in the northern storerooms and central archive, whilst seal-impressed jars were scattered in various quarters, including the northern warehouse, the units of the Central Quarter devoted to processing foodstuffs, and the ‘ kitchen’ which opened at the bottom of the Ceremonial Staircase. The third category of indicators of administrative management of goods is represented by balance weights, a fundamental tool enabling the palace administration to check and record disbursement and incoming quantities of precious materials and objects. More than forty stone weights were retrieved in the palace, with at least two significant concentrations that permit the localization The extraordinary state of preservation of the Royal Palace G of Ebla (c. 2400-2300 BC) with a large amount of materials sealed by the destruction levels and the presence of central and temporary archives in several rooms of the official wings of the palatial complex allow a detailed analysis of the distribution and types of the various indicators of exchange and the control of exchange. Economic written documents, sealings (cretulae, bullae and jar-sealings) and balance weights attest to the economic activities conducted within the palace and provide integrated information regarding administrative procedures. Together with these indicators, unworked precious materials (in particular lapis lazuli), imported items, and objects manufactured from imported materials show the palace administration’s control over luxury goods production and Ebla’s extended interregional exchange network. In addition to the administrative archives (with thousands of tablets), the manage- of weight sets. The evaluation of the archaeological indicators, based on the distribution and associations of these various categories of object, makes readily identifiable the ‘ places’ appointed to house single or multiple parts of the procedural chain of administrative activity : the final stage in the codification of economic transactions consisted of written cuneiform texts on clay tablets ; the interim level of recording is represented by the cretulae used to seal goods of various sorts ; and the most crucial steps in recording, when goods enter or leave the palace, are distinguished by various forms of weighing operation.

Performance Analysis of a Speed Sensor-Less Grid Connected DFIG based Wind Energy Conversion System using Nine Switch Converter

This paper presents the performance study of a Double Fed Induction Generator (DFIG) based Wind Energy Conversion System (WECS) by using the Nine Switch Converter and a new phase locked loop based slip speed estimator is also proposed to obtain speed sensor-less stator field oriented vector control operation. The Nine switch converter having two sets of independent three phase output terminals at two different frequency levels, one set is connected to the rotor winding through slip ring and brushes and other set is connected to the grid through interfacing inductors and a PLL based slip estimator is incorporated with nine switch converter controller for speed sensor-less operation of variable speed wind energy conversion system. The nine switch converter based DFIG system is used for decoupled control of stator active and reactive power exchange between the stator of the DFIG and the grid to ensure maximizing the power generation at unity power factor under varying wind speed and speed sensor-less vector control is incorporated with optimal speed tracking and optimal pitch angle controllers to capture maximum wind energy when wind speed remains within the rated range; and to restrict the captured wind energy to the turbine’s rated level when speed crosses the rated limit to prevent overloading and outage of the wind turbine respectively like convetional back-to-back converter. As compared to conventional back-to-back ac/ac converters, the numbers of power semiconductor switches are reduced in the proposed nine switch converter. The proposed topology has the advantages of reduced cost, more efficient (reduced switching loss) and reduced installation area over back-to-back converter. Simulation has been carried out in MATLAB/Simulink environment and results have been analyzed. Results show that the proposed speed sensor-less DFIG based wind turbine using nine-switch converter can operate at its optimum energy level for a wide range of wind speed and is capable to control active and reactive power independently and reduces the number of switching devices thereby minimizing the cost of the system.

Plant water stress: Associations between ethylene and abscisic acid response

Agriculture is severely impacted by water stress due either to excess (hypoxia/anoxia) or deficit of water availability. Hypoxia/anoxia is associated with oxygen (O2) deficiency or depletion, inducing several anatomical, morphological, physiological, and molecular changes. The majority of these alterations are adaptive mechanisms to cope with low O2 availability; among them, alterations in shoot length, aerenchyma formation and adventitious roots have been described in several studies. The aim of this review was to address the association between abscisic acid (ABA) and ethylene in function of water availability in plants. The major physiological responses to low O2 are associated with changes in root respiration, stomatal conductance, photosynthesis, and fermentation pathways in roots. In addition, several changes in gene expression have been associated with pathways that are not present under normal O2 supply. The expression of ethylene receptor genes is up-regulated by low O2, and ethylene seems to have a crucial role in anatomical and physiological effects during hypoxia/anoxia. During O2 depletion, ethylene accumulation down-regulates ABA by inhibiting rate-limiting enzymes in ABA biosynthesis and by activating ABA breakdown to phaseic acid. With regard to water deficit, drought is primarily sensed by the roots, inducing a signal cascade to the shoots via xylem causing physiological and morphological changes. Several genes are regulated up or down with osmotic stress; the majority of these responsive genes can be driven by either an ABA-dependent or ABA-independent pathway. Some studies suggest that ethylene shuts down leaf growth very fast after the plant senses limited water availability. Ethylene accumulation can antagonize the control of gas exchange and leaf growth upon drought and ABA accumulation.

Using Activated Transport in Parallel Nanowires for Energy Harvesting and Hot-Spot Cooling

We study arrays of parallel doped semiconductor nanowires in a temperature range where the electrons propagate through the nanowires by phonon assisted hops between localized states. By solving the Random Resistor Network problem, we compute the thermopower $S$, the electrical conductance $G$, and the electronic thermal conductance $K^e$ of the device. We investigate how those quantities depend on the position -- which can be tuned with a back gate -- of the nanowire impurity band with respect to the equilibrium electrochemical potential. We show that large power factors can be reached near the band edges, when $S$ self-averages to large values while $G$ is small but scales with the number of wires. Calculating the amount of heat exchanged locally between the electrons inside the nanowires and the phonons of the environment, we show that phonons are mainly absorbed near one electrode and emitted near the other when a charge current is driven through the nanowires near their band edges. This phenomenon could be exploited for a field control of the heat exchange between the phonons and the electrons at submicron scales in electronic circuits. It could be also used for cooling hot spots.

Using geochemical investigations for determining the interaction between groundwater and saline water in arid areas: case of the Wadi Ouazzi basin (Morocco)

Abstract. The characteristics of the Essaouira basin water resources are a semi-arid climate, which is severely impacted by the climate (quantity and quality). Considering the importance of the Essaouira aquifer in the groundwater supply of the region, a study was conducted in order to understand groundwater evolution in this aquifer. The Essaouira aquifer is a coastal aquifer located on the Atlantic coastline of southern Morocco, corresponding to a sedimentary basin with an area of nearly 200 km2. The control of the fluid exchange and the influence of mixing zones between the groundwater and saline water was investigated by sampling from 20 wells, drillings and sources belonging to the Plio-Quaternary and Turonian aquifers. It is hypothesized that groundwater major ions chemistry can be employed to determine the interaction between the groundwater and saline water (coastal aquifers). Groundwater samples examined for electric conductivity and temperature showed that waters belonging to the Plio-Quaternary and Turonian aquifers present very variable electric conductivities, from 900 μs/cm to 3880 μs/cm. Despite this variability, they are from the same family and are characterized by sodium-chloride facies. However, a good correlation exists between the electrical conductivity and chloride and sodium contents. The lower electrical conductivities are situated in the North quarter immediately to the south of the Wadi Ouazzi.

Control of Breathing and Adaptation to High‐altitude Hypoxia in Deer Mice (Peromyscus maniculatus)

High‐altitude environments pose multiple challenges, such as cold temperatures and low partial pressures of oxygen. This study compared the control of breathing and pulmonary gas exchange in populations of deer mice with highland and lowland ancestry to determine the physiological specializations important for living in high‐altitude environments. The hypoxic ventilatory response was measured using whole‐body plethysmography in response to step‐wise decreases in inspired oxygen fraction, from 21% to 8%, in mice acclimated to normoxia or hypobaric hypoxia (simulating the hypoxia at ~4300 m elevation). Total ventilation was similar between populations, but highland mice acclimated to normoxia had a more effective breathing pattern than lowland mice acclimated to normoxia, characterized by deeper less frequent breaths at a given total ventilation. Hypoxia acclimation had no effect on breathing pattern in highland mice, but it increased tidal volume and decreased breathing frequency in lowland mice. Highland ancestry and hypoxia acclimation also affected respiratory water loss and thermoregulatory responses to hypoxia. Therefore, both highland ancestry and hypoxia acclimation influence the control of breathing and pulmonary gas exchange in deer mice. Supported by NSERC of Canada.

Zebrafish as a model for apolipoprotein biology: comprehensive expression analysis and a role for ApoA-IV in regulating food intake.

Improved understanding of lipoproteins, particles that transport lipids throughout the circulation, is vital to developing new treatments for the dyslipidemias associated with metabolic syndrome. Apolipoproteins are a key component of lipoproteins. Apolipoproteins are proteins that structure lipoproteins and regulate lipid metabolism through control of cellular lipid exchange. Constraints of cell culture and mouse models mean that there is a need for a complementary model that can replicate the complex in vivo milieu that regulates apolipoprotein and lipoprotein biology. Here, we further establish the utility of the genetically tractable and optically clear larval zebrafish as a model of apolipoprotein biology. Gene ancestry analyses were implemented to determine the closest human orthologs of the zebrafish apolipoprotein A-I (apoA-I), apoB, apoE and apoA-IV genes and therefore ensure that they have been correctly named. Their expression patterns throughout development were also analyzed, by whole-mount mRNA in situ hybridization (ISH). The ISH results emphasized the importance of apolipoproteins in transporting yolk and dietary lipids: mRNA expression of all apolipoproteins was observed in the yolk syncytial layer, and intestinal and liver expression was observed from 4–6 days post-fertilization (dpf). Furthermore, real-time PCR confirmed that transcription of three of the four zebrafish apoA-IV genes was increased 4 hours after the onset of a 1-hour high-fat feed. Therefore, we tested the hypothesis that zebrafish ApoA-IV performs a conserved role to that in rat in the regulation of food intake by transiently overexpressing ApoA-IVb.1 in transgenic larvae and quantifying ingestion of co-fed fluorescently labeled fatty acid during a high-fat meal as an indicator of food intake. Indeed, ApoA-IVb.1 overexpression decreased food intake by approximately one-third. This study comprehensively describes the expression and function of eleven zebrafish apolipoproteins and serves as a springboard for future investigations to elucidate their roles in development and disease in the larval zebrafish model.

Bringing Color into the Picture: Using Digital Repeat Photography to Investigate Phenology Controls of the Carbon Dioxide Exchange in a Boreal Mire

Mire vegetation phenology is closely linked to the ecosystem carbon cycle but rarely monitored and quantified with high temporal resolution. In this study, we use digital repeat photography to explore phenology as a control of the carbon dioxide (CO2) exchange measured by eddy covariance (EC) in a minerogenic boreal mire in northern Sweden over 2 years (2011–2012). Strong correlations and seasonal hysteresis effects were observed between the green chromatic coordinate (g cc) derived from the digital image archive and leaf area index, day length, and growing degree-day sum (GDDS). Differences in GDDS between the 2 years were the main control on the between-year variations in the spring patterns of g cc. Periods with lower water table level coincided with an increase of the red chromatic coordinate. The onset and magnitudes of EC-derived photosynthetic CO2 uptake (that is, gross ecosystem production, GEP) and net ecosystem CO2 exchange (NEE) during the spring green-up of vascular plants were more closely related to those of g cc than to those of air temperature and photosynthetically active radiation. In contrast, abiotic variables controlled GEP during the summer period when vascular plant canopy cover was fully developed. Stepwise regression analysis suggested that g cc contributed substantially in explaining variations in GEP during spring and autumn. Over both growing seasons, g cc was well correlated with GEP (r 2 = 0.68), NEE (r 2 = 0.58), and ecosystem respiration (r 2 = 0.50). Overall, we show that digital repeat photography provides an inexpensive and effective method for the continuous quantification of the phenological patterns of the vascular plant community in mire ecosystems. Our results suggest that vegetation phenology is an important control of the mire CO2 exchange and should be considered in both experimental and modeling studies to better account for the separate effects of phenology and abiotic drivers on mire carbon dynamics.

Helicity-dependent three-dimensional optical trapping of chiral microparticles.

The rule of thumb of tailored optical forces consists in the control of linear momentum exchange between light and matter. This may be done by appropriate selection of the interaction geometry, optical modes or environmental characteristics. Here we reveal that the interplay of the helicity of light and the chirality of matter turns the photon spin angular momentum into an efficient tool for selective trapping of chiral particles. This is demonstrated, both experimentally and theoretically, by exploring the three-dimensional optical trapping of chiral liquid crystal microspheres with circularly polarized Gaussian or Laguerre-Gaussian beams. These results suggest the development of novel optomechanical strategies that rely on the photon helicity towards selective trapping and manipulation of chiral objects by chiral light.

Carbon isotope discrimination during branch photosynthesis of Fagus sylvatica: field measurements using laser spectrometry

On-line measurements of photosynthetic carbon isotope discrimination ((13)Δ) under field conditions are sparse. Hence, experimental verification of the natural variability of instantaneous (13)Δ is scarce, although (13)Δ is, explicitly and implicitly, used from leaf to global scales for inferring photosynthetic characteristics. This work presents the first on-line field measurements of (13)Δ of Fagus sylvatica branches, at hourly resolution, using three open branch bags and a laser spectrometer for CO₂ isotopologue measurements (QCLAS-ISO). Data from two August/September field campaigns, in 2009 and 2010, in a temperate forest in Switzerland are shown. Diurnal variability of (13)Δ was substantial, with mean diurnal amplitudes of ~9‰ and maximum diurnal amplitudes of ~20‰. The highest (13)Δ were generally observed during early morning and late afternoon, and the lowest (13)Δ during midday. An assessment of propagated standard deviations of (13)Δ demonstrated that the observed diurnal variation of (13)Δ was not a measurement artefact. Day-to-day variations of (13)Δ were summarized with flux-weighted daily means of (13)Δ, which ranged from 15‰ to 23‰ in 2009 and from 18‰ to 29‰ in 2010, thus displaying a considerable range of 8-11‰. Generally, (13)Δ showed the expected negative relationship with intrinsic water use efficiency. Diurnal and day-to-day variability of (13)Δ was, however, always better predicted by that of net CO₂ assimilation, especially in 2010 when soil moisture was high and vapour pressure deficit was low. Stomatal control of leaf gas exchange, and consequently (13)Δ, could only be identified under drier conditions in 2009.

Environmental control of daytime net ecosystem exchange of carbon dioxide in switchgrass

Net ecosystem CO2 exchange (NEE) over a young switchgrass (Panicum virgatum) stand was measured with the eddy covariance technique across two growing seasons in the southern Great Plains of the United States at Chickasha, OK. The objectives of the study were to characterize the effects of environmental factors on daytime NEE and to explore the underlying mechanisms. Photosynthetic photon flux density (PPFD) was the most significant driver of NEE and explained over 90% of the NEE variation during optimum environmental conditions. The light-response curve showed hysteresis as carbon uptake by the ecosystem decreased up to 62% (monthly average) from morning to afternoon at similar light levels because of the stomatal closure control of photosynthesis at high vapor pressure deficit (VPD). This resultant large hysteresis led to the failure of the rectangular hyperbolic light-response function in explaining the NEE–PPFD relationship. The NEE exhibited an optimum temperature range of 28–34°C and decreased markedly beyond 35°C. Our results demonstrated that warm temperature and high VPD altered the NEE–PPFD relationship and thereby affected the ecosystem light-response parameters (respiration, quantum yield, and light saturated photosynthetic capacity). Thus, it is essential to incorporate the effects of temperature and VPD on ecosystem light-response into both empirical and mechanistic models. This study also suggests including the VPD effect in the NEE flux partitioning technique can account for the systematic presence of NEE hysteresis during non-optimal environmental conditions. The results of this study are useful for the modeling community to develop, improve, and validate the models for global change studies, and for the eddy covariance community to develop more robust gap filling methods.

Stomatal Size, Speed, and Responsiveness Impact on Photosynthesis and Water Use Efficiency

The control of gaseous exchange between the leaf and bulk atmosphere by stomata governs CO₂ uptake for photosynthesis and transpiration, determining plant productivity and water use efficiency. The balance between these two processes depends on stomatal responses to environmental and internal cues and the synchrony of stomatal behavior relative to mesophyll demands for CO₂. Here we examine the rapidity of stomatal responses with attention to their relationship to photosynthetic CO₂ uptake and the consequences for water use. We discuss the influence of anatomical characteristics on the velocity of changes in stomatal conductance and explore the potential for manipulating the physical as well as physiological characteristics of stomatal guard cells in order to accelerate stomatal movements in synchrony with mesophyll CO₂ demand and to improve water use efficiency without substantial cost to photosynthetic carbon fixation. We conclude that manipulating guard cell transport and metabolism is just as, if not more likely to yield useful benefits as manipulations of their physical and anatomical characteristics. Achieving these benefits should be greatly facilitated by quantitative systems analysis that connects directly the molecular properties of the guard cells to their function in the field.

Flavescence dorée phytoplasma deregulates stomatal control of photosynthesis in Vitis vinifera

AbstractFlavescence dorée (FD) is among the major grapevine diseases causing high management costs; curative methods against FD are unavailable. In FD‐infected plants, decrease in photosynthesis is usually recorded, but deregulation in stomatal control of leaf gas exchange during FD infection and recovery is unknown. We measured the seasonal time course of gas exchange rates in two cultivars (‘Barbera’ and ‘Nebbiolo’) during the term of 1 year when grapevines experienced a water stress and another with no drought, with difference in gas exchange rates in response to FD infection and recovery as assessed by symptom observation and phytoplasma detection through PCR analysis. Chlorophyll fluorescence was also evaluated at the time of maximum symptom severity in ‘Barbera’, the cultivar showing the most severe stress response to FD infection, causing the highest damage in vineyards of north‐western Italy. In FD‐infected plants, net photosynthesis and transpiration gradually decreased during the season, more during the no drought year than during drought. During recovery, healthy (PCR negative) plants infected 2 years before, but not those infected an year before, regained the gas exchange performances to the level as measured before infection. The relationships between stomatal conductance and the residual leaf intercellular CO2 concentration (ci) discriminated healthy versus FD‐infected and recovered plants; at the same ci, FD‐infected leaves had higher non‐photochemical quenching than healthy ones. We conclude that metabolic, not stomatal, leaf gas exchange limitation in FD‐infected and recovered grapevines is the basis of plant response to FD disease. In addition, we also suggest that such response is dependent upon water stress, by showing that water stress superimposes on FD infection in terms of stomatal and metabolic non‐stomatal limitations to carbon assimilation.

Control of gas exchange during cultivation of phototrophic microorganisms

Questions on optimal control of the cultivation of phototrophic microorganisms, particularly microalgae, are currently relevant as for solving the problem of disposing of excess carbon dioxide emitted into the atmosphere by burning fossil fuels as for production of biofuels on the basis of phototrophic biomass.

Tensile Lattice Strain Accelerates Oxygen Surface Exchange and Diffusion in La1–xSrxCoO3−δ Thin Films

The influence of lattice strain on the oxygen exchange kinetics and diffusion in oxides was investigated on (100) epitaxial La1–xSrxCoO3−δ (LSC) thin films grown by pulsed laser deposition. Planar tensile and compressively strained LSC films were obtained on single-crystalline SrTiO3 and LaAlO3. 18O isotope exchange depth profiling with ToF-SIMS was employed to simultaneously measure the tracer surface exchange coefficient k* and the tracer diffusion coefficient D* in the temperature range 280–475 °C. In accordance with recent theoretical findings, much faster surface exchange (∼4 times) and diffusion (∼10 times) were observed for the tensile strained films compared to the compressively strained films in the entire temperature range. The same strain effect—tensile strain leading to higher k* and D*—was found for different LSC compositions (x = 0.2 and x = 0.4) and for surface-etched films. The temperature dependence of k* and D* is discussed with respect to the contributions of strain states, formation enthalpy of oxygen vacancies, and vacancy mobility at different temperatures. Our findings point toward the control of oxygen surface exchange and diffusion kinetics by means of lattice strain in existing mixed conducting oxides for energy conversion applications.

System Design and Analysis of a Directly Air-Assisted Turbocharged SI Engine with Camshaft Driven Valves

The availability of compressed air in combination with downsizing and turbocharging is a promising approach to improve the fuel economy and the driveability of internal combustion engines. The compressed air is used to boost and start the engine. It is generated during deceleration phases by running the engine as a piston compressor. In this paper, a camshaft-driven valve is considered for the control of the air exchange between the tank and the combustion chamber. Such a valve system is cost-effective and robust. Each pneumatic engine mode is realized by a separate cam. The air mass transfer in each mode is analyzed. Special attention is paid to the tank pressure dependence. The air demand in the boost mode is found to increase with the tank pressure. However, the dependence on the tank pressure is small in the most relevant operating region. The air demand of the pneumatic start shows a piecewise continuous dependence on the tank pressure. Finally, a tank sizing method is proposed which uses a quasi-static simulation. It is applied to a compact class vehicle, for which a tank volume of less than 10 L is sufficient. A further reduction of the tank volume is limited by the specifications imposed on the pneumatic start.

Use of an Automatic System for Optimum Control of Vulcanization in Order to Improve Rubberized Coating Quality

An automatic system is developed for optimum control of heat exchange with a rubberized coating. Vulcanizing is carried out by means of an inert granular heat-transfer agent, simple convection, and in a vulcanizing heater. Free distribution of sulfur is obtained, which specifies the degree of vulcanizing, with use of an automated control system (ACS), and this is compared with data obtained without its use.

Reversible brain inactivation induces discontinuous gas exchange in cockroaches

Many insects at rest breathe discontinuously, alternating between brief bouts of gas exchange and extended periods of breath-holding. The association between discontinuous gas exchange cycles (DGCs) and inactivity has long been recognised, leading to speculation that DGCs lie at one end of a continuum of gas exchange patterns, from continuous to discontinuous, linked to metabolic rate (MR). However, the neural hypothesis posits that it is the downregulation of brain activity and a change in the neural control of gas exchange, rather than low MR per se, which is responsible for the emergence of DGCs during inactivity. To test this, Nauphoeta cinerea cockroaches had their brains inactivated by applying a Peltier-chilled cold probe to the head. Once brain temperature fell to 8°C, cockroaches switched from a continuous to a discontinuous breathing pattern. Re-warming the brain abolished the DGC and re-established a continuous breathing pattern. Chilling the brain did not significantly reduce the cockroaches' MR and there was no association between the gas exchange pattern displayed by the insect and its MR. This demonstrates that DGCs can arise due to a decrease in brain activity and a change in the underlying regulation of gas exchange, and are not necessarily a simple consequence of low respiratory demand.