Model-based simulation

  • 文章类型: Journal Article
    时间干扰(TI)刺激,一种新的非侵入性刺激策略,最近被证明可以调节活体小鼠脑深部区域的神经活动。然而,不确定这种方法是否适用于较大的大脑,以及在传统安全电流下产生的电场是否可以像在小鼠中观察到的那样穿透深部区域。尽管最近基于模型的模拟研究在宏观和微观层面提供了积极的证据,缺乏来自实际大脑的电生理数据阻碍了对TI的全面理解和潜在应用。这项研究旨在直接测量恒河猴大脑中干扰电场的时空特性,并验证TI对人脑的影响。两只猴子参与了测量,植入多个立体脑电图(SEEG)深度电极。在不同的刺激参数下使用两对表面电极对麻醉的猴子施加TI刺激。还进行了基于模型的模拟,随后与实际记录进行了比较。此外,对患有运动障碍的患者进行TI刺激以验证其对运动症状的影响。通过将计算电场模拟与经验测量相结合,确定在深中心区域中的时间干扰电场能够达到足以引起对神经信号的亚阈值调制效应的幅度。此外,TI刺激导致运动障碍改善.这项研究首次系统地测量了活体非人灵长类动物的TI电场,提供经验证据表明,TI有望作为一种更集中,更精确的方法来调节大型大脑深部区域的神经活动。这一进展为TI在治疗神经精神疾病方面的未来应用铺平了道路。
    Temporal interference (TI) stimulation, a novel non-invasive stimulation strategy, has recently been shown to modulate neural activity in deep brain regions of living mice. Yet, it is uncertain if this method is applicable to larger brains and whether the electric field produced under traditional safety currents can penetrate deep regions as observed in mice. Despite recent model-based simulation studies offering positive evidence at both macro- and micro-scale levels, the absence of electrophysiological data from actual brains hinders comprehensive understanding and potential application of TI. This study aims to directly measure the spatiotemporal properties of the interfered electric field in the rhesus monkey brain and to validate the effects of TI on the human brain. Two monkeys were involved in the measurement, with implantation of several stereo-electroencephalography (SEEG) depth electrodes. TI stimulation was applied to anesthetized monkeys using two pairs of surface electrodes at differing stimulation parameters. Model-based simulations were also conducted and subsequently compared with actual recordings. Additionally, TI stimulation was administered to patients with motor disorders to validate its effects on motor symptoms. Through the integration of computational electric field simulation with empirical measurements, it was determined that the temporally interfering electric fields in the deep central regions are capable of attaining a magnitude sufficient to induce a subthreshold modulation effect on neural signals. Additionally, an improvement in movement disorders was observed as a result of TI stimulation. This study is the first to systematically measure the TI electric field in living non-human primates, offering empirical evidence that TI holds promise as a more focal and precise method for modulating neural activities in deep regions of a large brain. This advancement paves the way for future applications of TI in treating neuropsychiatric disorders.
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  • 文章类型: Journal Article
    背景:在癫痫药物治疗中,延迟或错过剂量是不可避免的。美国食品和药物管理局(FDA)针对不依从性建议的当前补救措施是通用的,缺乏临床证据。
    目的:使用蒙特卡洛模拟评估癫痫患者延迟或错过普瑞巴林剂量的治疗策略。
    方法:使用已发表的普瑞巴林群体药代动力学模型进行蒙特卡罗模拟。通过模拟八个人群的各种不良依从性情况,评估了五个拟议的治疗方案以及FDA建议的适用性。包括肾功能不全的患者.
    结果:所有建议的治疗策略均与延迟持续时间和肾功能相关。当延迟相对较短时,建议立即定期剂量。对于轻度肾功能损害和肾功能正常的患者,采取常规剂量作为治疗方案的截止时间点为1、2、4和12h,中度肾功能损害,严重肾功能损害,和终末期肾病,分别。然而,当延迟与给药间隔密切相关时,常规剂量与部分剂量相结合证明是有效的。一般来说,在下一个预定时间补充1.3倍的常规剂量可以充分补偿错过的剂量.
    结论:基于模型的模拟为普瑞巴林剂量缺失或延迟的治疗策略的有效性和可行性提供了定量证据。
    BACKGROUND: Delayed or missed doses are inevitable in epilepsy pharmacotherapy. The current remedial measures recommended by the United States Food and Drug Administration (FDA) for non-adherence are generic and lack clinical evidence.
    OBJECTIVE: To assess remedial strategies for delayed or missed pregabalin doses in patients with epilepsy using Monte Carlo simulations.
    METHODS: Monte Carlo simulations were performed using a published population pharmacokinetic model for pregabalin. The applicability of five proposed remedial regimens as well as FDA recommendations was evaluated by simulating various poor adherence scenarios in eight populations, including those with renal dysfunction.
    RESULTS: All proposed remedial strategies were associated with delay duration and renal function. When delays are relatively short, an immediate regular dose is advised. The cut-off time points for taking the regular dose as a remedial regimen were 1, 2, 4, and 12 h for patients with mild renal impairment and normal renal function, moderate renal impairment, severe renal impairment, and end-stage renal disease, respectively. However, when delay aligns closely with a dosing interval, a regular dose combined with a partial dose proves effective. Generally, supplementing 1.3-fold the regular dose at the next scheduled time adequately compensates for the missed dose.
    CONCLUSIONS: Model-based simulations provided quantitative evidence for the effectiveness and feasibility of remedial strategies for missed or delayed pregabalin doses.
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  • 文章类型: Journal Article
    Cobotic applications require a good knowledge of human behaviour in order to be cleverly, securely and fluidly performed. For example, to make a human and a humanoid robot perform a co-navigation or a co-manipulation task, a model of human walking trajectories is essential to make the robot follow or even anticipate the human movements. This paper aims to study the Center of Mass (CoM) path during locomotion and generate human-like trajectories with an optimal control scheme. It also proposes a metric which allows to assess this model compared to the human behaviour. CoM trajectories during locomotion of 10 healthy subjects were recorded and analysed as part of this study. Inverse optimal control was used to find the optimal cost function which best fits the model to the measurements. Then, the measurements and the generated data were compared in order to assess the performance of the presented model. Even if the experiments show a great variability in human behaviours, the model presented in this study gives an accurate approximation of the average human walking trajectories. Furthermore, this model gives an approximation of human locomotion good enough to improve cobotic tasks allowing a humanoid robot to anticipate the human behaviour.
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  • 文章类型: Journal Article
    Cirrhotic patients are at a high risk of fungal infections. Voriconazole is widely used as prophylaxis and in the treatment of invasive fungal disease. However, the safety, pharmacokinetics, and optimal regimens of voriconazole are currently not well defined in cirrhotic patients.
    Retrospective pharmacokinetics study.
    Two large, academic, tertiary-care medical center.
    Two hundred nineteen plasma trough concentrations (Cmin ) from 120 cirrhotic patients and 83 plasma concentrations from 11 non-cirrhotic patients were included.
    Data pertaining to voriconazole were collected retrospectively. A population pharmacokinetics analysis was performed and model-based simulation was used to optimize voriconazole dosage regimens.
    Voriconazole-related adverse events (AEs) developed in 29 cirrhotic patients, and the threshold Cmin for AE was 5.12 mg/L. A two-compartment model with first-order elimination adequately described the data. The Child-Pugh class and body weight were the significant covariates in the final model. Voriconazole clearance in non-cirrhotic, Child-Pugh class A and B cirrhotic (CP-A/B) and Child-Pugh class C cirrhotic (CP-C) patients was 7.59, 1.86, and 0.93 L/hour, respectively. The central distribution volume and peripheral distribution volume was 100.8 and 55.2 L, respectively. The oral bioavailability was 91.6%. Model-based simulations showed that a loading dose regimen of 200 mg/12 hours intravenously or orally led to 65.0-75.7% of voriconazole Cmin in therapeutic range on day 1, and the appropriate maintenance dosage regimens were 75 mg/12 hours and 150 mg/24 hours intravenously or orally for CP-A/B patients, and 50 mg/12 hours and 100 mg/24 hours intravenously or orally for CP-C patients. The predicted probability of achieving the therapeutic target concentration for optimized regimens at steady-state was 66.8-72.3% for CP-A/B patients and 70.3-74.0% for CP-C patients.
    These results recommended that the halved loading dose regimens should be used, and voriconazole maintenance doses in cirrhotic patients should be reduced to one-fourth for CP-C patients and to one-third for CP-A/B patients compared to that for patients with normal liver function.
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  • 文章类型: Comparative Study
    The low ammonium concentration, low temperature, presence of organic matter, and large variation of influent ammonium load pose serious challenges for the application of PN/AMX (partial nitrification-anammox) reactor in the mainstream wastewater treatment. Previous mathematical simulation studies of PN/AMX granule reactor mainly concentrated on the steady-state modeling. The steady-state simulation cannot be used for developing control strategies under dynamic condition. In this study, four control strategies were evaluated on their abilities to minimize the impact of feed disturbances on autotrophic nitrogen removal in mainstream wastewater. The four control strategies included are the following: (A) direct airflow adjustment to maintain the fixed NH4+ set point, (B) fixed NH4+ set point control manipulated by DO concentration with DO limit, (C) constant DO control strategy, and (D) adaptive change of NH4+ set point control based on the feed disturbance (NH4+ set point value achieved by DO concentration manipulation with DO limit). The results indicated that the control strategy A successfully implemented for high NH4+ strength wastewater treatment cannot be directly transferred into the mainstream wastewater treatment, in which high NO2- accumulation was resulted during the NH4+ peaks at the low-temperature period. Satisfactory TN removal could be achieved by maintaining either fixed or variable bulk NH4+ set point values calculated based on the feed disturbances (control strategies B and D). The DO limit imposed on the DO concentration manipulation to derive the desired NH4+ set point values was essential for the successful implementation of control strategies B and D. The control strategy C with constant DO concentration was not feasible for the PN/AMX process under dynamic feed disturbances. The control simulation results and the control variable sensitivity analysis indicated that the NH4+ concentration was a better control variable than the DO concentration.
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