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In this paper, a frequency domain simulation method of magneto-acousto-electrical tomography (MAET) was proposed. This method is based on discrete Fourier transform. With this approach, the solving degrees of freedom of the simulation model can be significantly reduced. It can greatly reduce the requirements of computer hardware and improve efficiency. At the same time, the interaction between fluid and biological tissues was considered, which makes the simulation model closer to the real model. In this paper, an MAET simulation model of acoustic–solid–electromagnetic multi-physical field coupling corresponding to the actual physical world was established. It is more reasonable to adopt the fully coupled method. However, the fully coupled method needs more computational memory. To further study the memory and time required for calculation, the segregated method was used to calculate the simulation model without affecting the accuracy and tolerance in this paper. The results show that using the segregated method can significantly reduce the memory requirement of the MAET model, but the solution time will increase accordingly. Therefore, the appropriate solution method can be selected according to the simulation computer configuration and the desired solution time. We, finally, built an experimental platform to conduct MAET experiments and verified the theoretical and simulation analyses. [ABSTRACT FROM AUTHOR]

New Findings What is the central question of this study? Does antagonism of V1b receptors prevent the haemodynamic and renal sympathetic nerve responses that occur with application of exogenous vasopressin into the paraventricular nucleus (PVN) of conscious, chronically instrumented rats?, What is the main finding and its importance? Microinjection of vasopressin into the PVN increased mean arterial pressure, heart rate and renal sympathetic nerve activity, all of which were inhibited by pre-injection of the PVN with the V1b antagonist, nelivaptan. The administered vasopressin did not enter the peripheral circulation or increase plasma vasopressin. Ganglionic blockade prevented each of the responses, consistent with mediation by enhanced sympathetic output rather than an increase in circulating vasopressin., Vasopressin (VP) participates in regulation of haemodynamics and volume. Besides more classical actions as a circulating hormone, VP may act via release from axons and dendrites within the CNS. The paraventricular nucleus (PVN) possesses vasopressinergic neurons and a dense complement of VP receptors, including the V1b receptor, which has been implicated in several types of stress responses. We tested the hypothesis that antagonism of V1b receptors will prevent VP-induced increases in mean arterial pressure (MAP), heart rate (HR) and renal sympathetic nerve activity (RSNA). Studies were performed in conscious male Sprague-Dawley rats chronically instrumented with vascular catheters, renal nerve electrodes and a cannula stereotaxically directed into the PVN. Unilateral microinjection of VP into the PVN significantly increased MAP, HR and RSNA, peaking at 10 min. Pre-injection of the PVN with the selective V1b receptor antagonist, nelivaptan, did not alter baseline values but blocked the responses to VP. Ganglionic blockade with chlorisondamine decreased MAP and HR and abolished their increase in response to subsequent PVN application of VP. Injection of VP into the PVN did not alter plasma VP levels. Paraventricular nucleus injection with radiolabelled VP resulted in negligible radiolabelled VP in peripheral blood. These findings support the concept that, in basal conditions, PVN V1b receptor activation (rather than VP release into the periphery) may be implicated in the increases in MAP, HR and RSNA due to increased sympathetic outflow. While the role of V1a and oxytocin receptors cannot be excluded, these data suggest that further studies of the role of V1b receptor activation by endogenous VP during stress to effect neuroexcitation are warranted. [ABSTRACT FROM AUTHOR]

Ecological footprint (EF) and emergy analysis (EA) are two important methods in evaluating regional or system sustainability. The EF is a quantitative tool that uses material and energy flows to estimate the biophysical 'load' imposed by human populations or industrial processes on ecosystems around the world. It is a useful indicator of sustainable development that showed the size of the biologically productive area necessary for resourcing the current consumption patterns when using common technologies. Emergy Analysis (EA) is an ecological accounting method used to comprehensively account all the inputs involving energies, natural resources consumption, and financial payments for humans by using similar units (sej). EA has been proven as an effective tool to evaluate the resource flows, support both the natural system and the economic system, and also provide a useful method for measuring the sustainability of systems. Emergy Ecological Footprint (EEF), which is a combination of these two methods, is considered to be able to measure resource consumption and environmental impact more comprehensively. Using the EEF method in this paper, we evaluated the winter wheat-summer maize rotation system, which is a typical cropping system in Huantai County located in Northern China, to try to reveal the control effect of agricultural non-point source pollution in the past decade. The results showed that compared to 1996, the total emergy input decreased by 3.15% in 2012. Phosphorus fertilizer, electricity energy for water pollution treatment, and nitrogen fertilizer are the top three contributors. The emergy of phosphorus fertilizer increased while the emergy of the other two decreased. But the emergy output capacity (EOC) increased by 6.23% due to the improvement in system efficiency. The EEF ranged from 40.94 to 39.59 hm2, which decreased by 3.30%. Meanwhile, the Resource Footprint (RF) increased 2.29 hm2, whereas the Environment Footprint (EnF) decreased 3.63 hm2. The emergy carrying capacity (ECC) had little change, ranging from 2.49 to 2.51 hm2a. The value of the EEF is 16.42 times the value of the ECC in 1996 and 15.76 times the value of the ECC in 2012, and ecological deficit reached up to 38.45 hm2 and 37.08 hm2, respectively, and declined when reduced by 3.56%. From the perspective of system sustainability, the results showed that the Resource Load Index (RLI) decreased by 4.02%, Environmental Load Index (ELI) reduced by 27.90%, System Externality (SE) reduced by 8.06%, but the Sustainability Index (SI) increased by 9.64%, suggesting that the winter wheat-summer maize rotation system in Huantai County consumed less energy, while the environmental impact caused by external input was weakened, and the sustainability level was improved. These results indicate that the non-point source pollution in Huantai County has been controlled significantly in the past decade. Overall, compared to 1996, the ecological deficit of the winter wheat-summer maize system decreased in 2012 while the sustainability and efficiency of the local farmland ecosystem increased. However, the amount of resources consumption and the environmental pressure of grain production still keep high levels, which mean the control of non-point source pollution in Huantai County needs to keep going ahead in the future. EEF provided us a new way to measure ecological sustainability, and it compensated several drawbacks of EF. Nevertheless, the EEF demonstrated the ecological carrying capacity entirely from a new perspective, and the meaning of ECC has been changed. In EEF, the ECC could only be decided by local natural conditions and failed to reflect the contribution of scientific and technological progress or productivity improvement. In order to make up for it, we designed the indicators of RLI, ELI, and SI, which integrated ecological footprint, productivity, and ecological carrying capacity for a better interpretation of the system sustainability. Agricultural production highly depends on natural conditions, so EEF might be more suitable for research in the field of agriculture systems than EF. [ABSTRACT FROM AUTHOR]

Selective stimulation of inhibitory A1 and facilitatory A2a adenosine receptor subtypes located in the nucleus of the solitary tract (NTS) powerfully inhibits cardiopulmonary chemoreflex (CCR) control of regional sympathetic outputs via different mechanisms: direct inhibition of glutamate release and facilitation of an inhibitory neurotransmitter release, respectively. However, it remains unknown whether adenosine naturally released into the NTS has similar inhibitory effects on the CCR as the exogenous agonists do. Our previous study showed that adenosine is released into the NTS during severe hemorrhage and contributes to reciprocal changes of renal (decreases) and adrenal (increases) sympathetic nerve activity observed in this setting. Both A1 and A2a adenosine receptors are involved. Therefore, we tested the hypothesis that, during severe hemorrhage, CCR control of the two sympathetic outputs is attenuated by adenosine naturally released into the NTS. We compared renal and adrenal sympathoinhibitory responses evoked by right atrial injections of 5HT3 receptor agonist phenylbiguanide (2-8 μg/kg) under control conditions, during hemorrhage, and during hemorrhage preceded by blockade of NTS adenosine receptors with bilateral microinjections of 8-(p-sulfophenyl) theophylline (1 nmol/100 nl) in urethane/chloralose anesthetized rats. CCR-mediated inhibition of renal and adrenal sympathetic activity was significantly attenuated during severe hemorrhage despite reciprocal changes in the baseline activity levels, and this attenuation was removed by bilateral blockade of adenosine receptors in the caudal NTS. This confirmed that adenosine endogenously released into the NTS has a similar modulatory effect on integration of cardiovascular reflexes as stimulation of NTS adenosine receptors with exogenous agonists., (Copyright © 2014 the American Physiological Society.)

Previously we have shown that adenosine operating via the A(1) receptor subtype may inhibit glutamatergic transmission in the baroreflex arc within the nucleus of the solitary tract (NTS) and differentially increase renal (RSNA), preganglionic adrenal (pre-ASNA), and lumbar (LSNA) sympathetic nerve activity (ASNA>RSNA≥LSNA). Since the cardiopulmonary chemoreflex and the arterial baroreflex are mediated via similar medullary pathways, and glutamate is a primary transmitter in both pathways, it is likely that adenosine operating via A(1) receptors in the NTS may differentially inhibit regional sympathetic responses evoked by activation of cardiopulmonary chemoreceptors. Therefore, in urethane-chloralose-anesthetized rats (n = 37) we compared regional sympathoinhibition evoked by the cardiopulmonary chemoreflex (activated with right atrial injections of serotonin 5HT(3) receptor agonist phenylbiguanide, PBG, 1-8 μg/kg) before and after selective stimulation of NTS A(1) adenosine receptors [microinjections of N(6)-cyclopentyl adenosine (CPA), 0.033-330 pmol/50 nl]. Activation of cardiopulmonary chemoreceptors evoked differential, dose-dependent sympathoinhibition (RSNA>ASNA>LSNA), and decreases in arterial pressure and heart rate. These differential sympathetic responses were uniformly attenuated in dose-dependent manner by microinjections of CPA into the NTS. Volume control (n = 11) and blockade of adenosine receptor subtypes in the NTS via 8-(p-sulfophenyl)theophylline (8-SPT, 1 nmol in 100 nl) (n = 9) did not affect the reflex responses. We conclude that activation of NTS A(1) adenosine receptors uniformly inhibits neural and cardiovascular cardiopulmonary chemoreflex responses. A(1) adenosine receptors have no tonic modulatory effect on this reflex under normal conditions. However, when adenosine is released into the NTS (i.e., during stress or severe hypotension/ischemia), it may serve as negative feedback regulator for depressor and sympathoinhibitory reflexes integrated in the NTS.