用SAS迭代及蒙特卡罗模拟优化美罗培南的使用

目的:筛选出针对临床上不同MIC值细菌时美罗培南的最优的药物剂量和点滴方式,同时比较传统、延长及优化两步点滴法的药效学。方法:首先用SAS迭代的方法筛选出在不同的MIC值时美罗培南两步点滴法时最优的药物剂量和点滴方式,然后使用蒙特卡罗模拟计算传统、延长及优化两步点滴法时的%T>MIC的值和达标概率。结果:在SAS迭代时,MIC为1、2、4μg/mL及CL和Vd取均数时,分别按500mg,0.25h/100mg+2.75h/400 mg;500mg,0.25h/250mg+2.75h/250mg和1000mg;0.25h/400mg+2.75h/600mg的优化两步点滴法的模型最优。在不同的MIC时,蒙特卡罗模拟均显示出在延长点滴和优化两步点滴法比传统点滴法有更高的%T>MIC和达标概率,优化两步点滴法比延长点滴法的达峰时间更短。结论:SAS迭代可以用来筛选出最优的药物剂量和点滴方式,同时蒙特卡罗模拟可以用来比较不同点滴方式的药效学。结果显示优化两步点滴法是更好的治疗临床严重感染的方法。

Computer-assisted optimization of mobile phase compositions and development distance selectivity in gradient two-step development high-performance thin-layer chromatography

A computer-assisted method is presented for optimization of mobile phase compositions and development distance in gradient two-step development HPTLC. The method is based on a system which can predict the final R(f) values for gradient two-step development from values measured using five preliminary runs. The statistical scanning method is then used for optimization, using R(f) difference as the selection criterion. The method was evaluated using a mixture of eight components. Excellent agreement was obtained between predicted and experimental results.

Nuclear design of an integrated small modular reactor based on the APR-1400 for RO desalination purposes

The United Arab Emirates lacks conventional water resources and relies primarily on desalination plants powered by fossil fuels to produce fresh water.Nuclear desalination is a proven technology,cost-competitive,and sustainable option capable of integrating the existing largescale desalination plants to produce both freshwater and electricity.However,Small Modular Reactors(SMRs)are promising designs with advanced simplified configurations and inherent safety features.In this study,an Integrated Desalination SMR that produces thermal energy compatible with the capacity of a fossil fuel-powered desalination plant in the UAE was designed.First,the APR-1400 reactor core was used to investigate two 150 MWthconceptual SMR core designs,core A and core B,based on two-dimensional parameters,radius,and height.Then,the CASMO-4 lattice code was used to generate homogenized few-group constants for optimized fuel assembly loading patterns.Finally,to find the best core configuration,SIMULATE-3 was used to calculate the core key physics parameters such as power distribution,reactivity coefficients,and critical boron concentration.In addition,different reflector materials were investigated to compensate for the expected high leakage of the small-sized SMR cores.The pan shape core B model(142.6132 cm diameter,100 cm height,and radially reflected by Stainless Steel)was selected as the best core configuration based on its calculated physics parameters.Core B met the design and safety criteria and indicated low total neutron leakage of 11.60%and flat power distribution with 1.50 power peaking factor.Compared to core A,it has a more negative MTC value of-6.93 pcm/°F with lower CBC.In a 2-batch scheme,the fuel is discharged at 42.25 GWd/MTU burnup after a long cycle length of 1.58 years.The core B model offers the highest specific power of 36.56 kW/kgU while utilizing the smallest heavy metal mass compared with the SMART and NuScale models.

Dosimetric evaluation of CR, 3DCRT and two types of IMRT for breast cancer after conservative surgery

Objective: The purpose of this study was to compare the dose distribution and dose volume histogram (DVH) of the planning target volume (PTV) and organs at risk (OARs) among conventional radiation therapy (CR), three-dimensional conformal radiation therapy (3DCRT), two-step intensity-modulated radiation therapy (TS-IMRT) and direct machine parameter optimization intensity-modulated radiation therapy (DMPO-IMRT) after breast-conserving surgery. Methods: For each of 20 randomly chosen patients, 4 plans were designed using 4 irradiation techniques. The prescribed dose was 50 Gy/2 Gy/25 f, 95% of the planning target volume received this dose. The cumulated DVHs and 3D dose distributions of CR, 3DCRT, TS-IMRT and DMPO-IMRT plans were compared. Results: For the homogeneity indices, no statistically significant difference was observed among CR, 3DCRT, TS-IMRT and DMPO-IMRT while the difference of the conformality indices were statistically significant. With regard to the organs at risk, IMRT and 3DCRT showed a significantly fewer exposure dose to the ipsilateral lung than CR in the high-dose area while in the low-dose area, IMRT demonstrated a significant increase of exposure dose to ipsilateral lung, heart and contralateral breast compared with 3DCRT and CR. In addition, the monitor units (MUs) for DMPO-IMRT were approximately 26% more than those of TS-IMRT and the segments of the former were approximately 24% less than those of the latter. Conclusion: Compared with CR, 3DCRT and IMRT improved the homogeneity and conformity of PTV, reduced the irradiated volume of OARs in high dose area but IMRT increased the irradiated volume of OARs in low dose area. DMPO-IMRT plan has fewer delivery time but more MUs than TS-IMRT.

A Gradient-Based Optimization Method for the Design of Layered Phononic Band-Gap Materials

Phononic materials with specific band-gap characteristics at desired frequency ranges are in great demand for vibration and noise isolation, elastic wave filters, and acoustic devices. The attenuation coefficient curve depicts both the frequency range of band gap and the attenuation of elastic wave, where the frequency ranges corresponding to the none-zero attenuation coefficients are band gaps. Therefore, the band-gap characteristics can be achieved through maximizing the attenuation coefficient at the corresponding frequency or within the corresponding frequency range. Because the attenuation coefficient curve is not smooth in the frequency domain, the gradient-based optimization methods cannot be directly used in the design optimization of phononic band-gap materials to achieve the maximum attenuation within the desired frequency range. To overcome this difficulty, the objective of maximizing the attenuation coefficient is transformed into maximizing its Cosine, and in this way, the objective function is smoothed and becomes differentiable. Based on this objective function, a novel gradient-based optimization approach is proposed to open the band gap at a prescribed frequency range and to further maximize the attenuation efficiency of the elastic wave at a specific frequency or within a prescribed frequency range. Numerical results demonstrate the effectiveness of the proposed gradient-based optimization method for enhancing the wave attenuation properties.

Fully discrete two-step mixed element method for the symmetric regularized long wave equation

A numerical method based on the explicit two-step method in time direction and the mixed finite element method in spatial direction is presented for the symmetric regularized long wave(SRLW)equation.The optimal a priori error estimates(O((∆t)^(2)+h^(m+1)+h^(k+1)))for fully discrete explicit two-step mixed scheme are derived.Moreover,a numerical example is provided to confirm our theoretical results.

ESTIMATION ON SEMIVARYING COEFFICIENT MODELS WITH DIFFERENT DEGREES OF SMOOTHNESS

Semivarying coefficient models are frequently used in statistical models.In this paper,under the condition that the coefficient functions possess different degrees of smoothness,a two-stepmethod is proposed.In the case,one-step method for the smoother coefficient functions cannot beoptimal.This drawback can be repaired by using the two-step estimation procedure.The asymptoticmean-squared error for the two-step procedure is obtained and is shown to achieve the optimal rate ofconvergence.A few simulation studies are conducted to evaluate the proposed estimation methods.