Estimating oxygen distribution from vasculature in three-dimensional tumour tissue

Regions of tissue which are well oxygenated respond better to radiotherapy than hypoxic regions by up to a factor of three. If these volumes could be accurately estimated, then it might be possible to selectively boost dose to radio-resistant regions, a concept known as dose-painting. While imaging modalities such as ¹⁸F-fluoromisonidazole positron emission tomography (PET) allow identification of hypoxic regions, they are intrinsically limited by the physics of such systems to the millimetre domain, whereas tumour oxygenation is known to vary over a micrometre scale. Mathematical modelling of microscopic tumour oxygen distribution therefore has the potential to complement and enhance macroscopic information derived from PET. In this work, we develop a general method of estimating oxygen distribution in three dimensions from a source vessel map. The method is applied analytically to line sources and quasi-linear idealized line source maps, and also applied to full three-dimensional vessel distributions through a kernel method and compared with oxygen distribution in tumour sections. The model outlined is flexible and stable, and can readily be applied to estimating likely microscopic oxygen distribution from any source geometry. We also investigate the problem of reconstructing three-dimensional oxygen maps from histological and confocal two-dimensional sections, concluding that two-dimensional histological sections are generally inadequate representations of the three-dimensional oxygen distribution.     

Feedback control method for estimating the oxygen uptake rate inactivated sludge systems

The measurement and utilization of the respiration rate or oxygen uptake rate (OUR) is very important in activated sludge system control. It provides information about the quality of the influent, activated sludge quality and can indicate the presence of toxic elements that can poison the system. The existing methods for continuously measuring and estimating the OUR have, generally, a long sampling interval of a few minutes. An alternative respiration rate meter with much shorter response time is proposed. The results of simulation studies, as well as experimental results of a microcontroller based data acquisition system connected to a PC, around a laboratory scale biological reactor are presented     

Predicting changes in oxygen concentration in the headspace of nitrogen flushed packages by the ambient oxygen ingress rate method

The ambient oxygen ingress rate (AOIR) method is an alternative/supplementary method to Ox‐Tran for measuring the oxygen transmission rates of packages. The AOIR method facilitates high‐capacity testing of packages under realistic food storage conditions, on the one hand, and on the other hand provides the possibility to predict the oxygen concentration over time in packages flushed with nitrogen at the time of packaging. The predicted oxygen concentration values showed good agreement with experimental values for flexible packages stored over a period of 91 days at 23°C and 38°C. The prediction of the oxygen concentration in­nitrogen‐flushed packages may be a useful tool, e.g. in shelf life studies, in the selection of the optimal food package as regards to oxygen protection and within quality control purposes. Copyright © 2002 John Wiley & Sons, Ltd.     

A patient-specific computational model of hypoxia-modulated radiation resistance in glioblastoma using 18F-FMISO-PET

Glioblastoma multiforme (GBM) is a highly invasive primary brain tumour that has poor prognosis despite aggressive treatment. A hallmark of these tumours is diffuse invasion into the surrounding brain, necessitating a multi-modal treatment approach, including surgery, radiation and chemotherapy. We have previously demonstrated the ability of our model to predict radiographic response immediately following radiation therapy in individual GBM patients using a simplified geometry of the brain and theoretical radiation dose. Using only two pre-treatment magnetic resonance imaging scans, we calculate net rates of proliferation and invasion as well as radiation sensitivity for a patient''s disease. Here, we present the application of our clinically targeted modelling approach to a single glioblastoma patient as a demonstration of our method. We apply our model in the full three-dimensional architecture of the brain to quantify the effects of regional resistance to radiation owing to hypoxia in vivo determined by [¹⁸F]-fluoromisonidazole positron emission tomography (FMISO-PET) and the patient-specific three-dimensional radiation treatment plan. Incorporation of hypoxia into our model with FMISO-PET increases the model–data agreement by an order of magnitude. This improvement was robust to our definition of hypoxia or the degree of radiation resistance quantified with the FMISO-PET image and our computational model, respectively. This work demonstrates a useful application of patient-specific modelling in personalized medicine and how mathematical modelling has the potential to unify multi-modality imaging and radiation treatment planning.     

Ambient oxygen ingress rate method—an alternative method to Ox‐Tran for measuring oxygen transmission rate of whole packages

The ambient oxygen ingress rate method (AOIR) is an alternative method to Ox‐Tran for measuring the oxygen transmission rates (OTR) of whole packages. The objective of the present work was (a) to compare OTR values obtained by the two methods, and (b) to evaluate the use of the AOIR method for measuring OTR at realistic food storage temperatures and humidity levels. The AOIR method gave equal OTR values compared to the Ox‐Tran method for the five different types of whole packages used in the experiment, with OTR values in the range 0.06–1.48 ml O₂/day. The repeatability of the AOIR method measured on an HDPE bottle was ±2.6% of the measured value in this experiment. This is slightly higher than the general specifications of the Ox‐Tran method (1% of reading for packages). However, the AOIR method can be considered to be a reliable, precise and cheap alternative method to the Ox‐Tran method for measuring OTR of whole packages. The capacity of the method is also high. The AOIR method showed satisfactory results when comparing OTR for packages tested under realistic food storage conditions covering 23°C/50% relative humidity (RH) and at 4°C/60% RH on the outside, combined with water (100% RH) or dry air inside the packages. Copyright © 2000 John Wiley & Sons, Ltd.     

A variational method of estimating the total measurement error of microwave-circuit analyzers

A variational method of estimating the total measurement error of microwave-circuit analyzers is considered. The method is based on the variation of the instrumental errors of the analyzer with respect to their confidence intervals, provided that the measurable and measured quantities are related by its mathematical model. Translated from Izmeritel’naya Tekhnika, No. 12, pp. 43–46, December, 2008.     

A generic tool for cost estimating in aircraft design

A methodology to estimate the cost implications of design decisions by integrating cost as a design parameter at an early design stage is presented. The model is developed on a hierarchical basis, the manufacturing cost of aircraft fuselage panels being analysed in this paper. The manufacturing cost modelling is original and relies on a genetic-causal method where the drivers of each element of cost are identified relative to the process capability. The cost model is then extended to life cycle costing by computing the Direct Operating Cost as a function of acquisition cost and fuel burn, and coupled with a semi-empirical numerical analysis using Engineering Sciences Data Unit reference data to model the structural integrity of the fuselage shell with regard to material failure and various modes of buckling. The main finding of the paper is that the traditional minimum weight condition is a dated and sub-optimal approach to airframe structural design.     

面向企业能效评估的能源消耗过程建模方法研究

针对企业能效评估对能源消耗系统模型的需求,在分析企业能耗过程的组成因素及其相互作用关系的基础上,提出了一种将企业的生产过程、物料移动、资源配置、余能回收利用等数字化的,基于模糊高级Petri网的企业能源消耗过程建模方法,并详细地给出了模型的形式化定义、运行规则以及建模原则.实例分析表明,该方法独立于特定的能源类型和用能设备,实现了能耗过程结构和动态行为方面信息的全面描述,是企业能源消耗过程分析与优化的基础.     

A deterministic model for the occurrence and dynamics of multiple mutations in hierarchically organized tissues

Cancers are rarely caused by single mutations, but often develop as a result of the combined effects of multiple mutations. For most cells, the number of possible cell divisions is limited because of various biological constraints, such as progressive telomere shortening, cell senescence cascades or a hierarchically organized tissue structure. Thus, the risk of accumulating cells carrying multiple mutations is low. Nonetheless, many diseases are based on the accumulation of such multiple mutations. We model a general, hierarchically organized tissue by a multi-compartment approach, allowing any number of mutations within a cell. We derive closed solutions for the deterministic clonal dynamics and the reproductive capacity of single clones. Our results hold for the average dynamics in a hierarchical tissue characterized by an arbitrary combination of proliferation parameters. We show that hierarchically organized tissues strongly suppress cells carrying multiple mutations and derive closed solutions for the expected size and diversity of clonal populations founded by a single mutant within the hierarchy. We discuss the example of childhood acute lymphoblastic leukaemia in detail and find good agreement between our predicted results and recently observed clonal diversities in patients. This result can contribute to the explanation of very diverse mutation profiles observed by whole genome sequencing of many different cancers.     

Density of capillaries and the oxygen diffusion model in the porous silk fibroin film

In order to obtain porous silk fibroin films (PSFFs) fit for the repair of different tissues and organs and design the configuration of the PSFFs more rationally, a model of the oxygen diffusing system of the capillary was built, and also the equations of the model were solved. Moreover, the relationships between the distribution of the oxygen concentration and each affecting factors were discussed, a method was developed to estimate the density of the capillaries in the tissue, and hereby discussed the characteristics of the oxygen diffusion in the tissues around the open capillaries.     

A comparison of methods for estimating the weld-metal cooling rate in laser welds

Microstructural transformations in 304 L stainless-steel welds as a function of welding parameters were studied using a high-power continuous CO₂ laser. The experimental results can be represented by the relation ₁ = 40 V ^–1/2 where ₁ is the primary dendrite spacing in m and V is the welding speed in mm s^–1, for different laser powers and two sample thicknesses. The cooling rates estimated by different methods have been found to be in the range 10² to 3 × 10³ Ks^–1, and the temperature gradients are in the range 10² to 9 × 10² K cm^–1. The experimental results are shown to be in very good agreement with recent dendrite-growth models. An analogy is presented between the cooling rate during melt spinning and laser welding.     

A domain transformation technique in oxygen diffusion problems with moving oxidation fronts on unbounded domains

In this paper we study numerical computations of oxygen diffusion problems with a moving oxidation front on unbounded domains of planar, cylindrical and spherical geometrical shapes. A new domain transformation technique of space variables and time variable is introduced in the application of the variable grid method for numerical computation of these problems. Some upper bound estimates of oxidation fronts are obtained. A numerical algorithm is proposed and discussed. © 1998 John Wiley & Sons, Ltd.     

全低压大型制氧机“快速制氧”操作法

介绍了“快速制氧”的原理和制氧机流程的改造。分析了氮气回收型和氮气不回收型两种“快速制氧”操作的启动方法和操作要点 ,阐述了“快速制氧”的特点及在制氧机启动和运行中的作用     

A TLM method for steady‐state convection–diffusion: Some additions and refinements

A recent paper introduced a novel and efficient scheme, based on the transmission line modelling (TLM) method, for solving steady‐state convection–diffusion problems. This paper shows how this one‐dimensional scheme can be adapted to include reaction and source terms and how it can be implemented with non‐equidistant nodes. It introduces new ways of calculating the necessary model parameters which can improve the accuracy of the scheme, shows how steady‐state solutions can be obtained directly, and compares results with those from two finite difference (FD) methods. While the cost of implementation is higher than for the FD schemes, the new TLM scheme can be significantly more accurate, especially when convection dominates. Copyright © 2008 John Wiley & Sons, Ltd.     

Quantitative assessment of the oxidation potential of sulfide-bearing aggregates in concrete using an oxygen consumption test

In the presence of oxygen and humidity, the iron sulfide minerals present in some concrete aggregates can oxidize creating damage to concrete infrastructure. An oxygen consumption test was developed to assess the oxidation potential of concrete aggregate. A compacted layer of aggregate material is exposed to oxygen (O₂) in a hermetic cell, and the O₂ consumption is monitored. Optimized parameters included a 10 cm compacted layer of aggregate material with particle size <150 μm kept at 40% saturation degree with a 10-cm headspace left at the top of the cell. The consumption of the O₂ present in the headspace is monitored over a 3-h testing period at 22 °C. The test was able to discriminate the eight sulfide-bearing and control aggregates selected when using a threshold limit of 5% O₂ consumed. This draft limit will, however, require to be confirmed through the testing of a larger number of aggregates.     

定速房间空调器制冷季节耗电量计算方法的探讨

分别采用能效比（EER）及季节能效比（SEER）作为评价指标,计算国内2009年度新增加的房间空调器的耗电量,经分析比较,指出采用SEER计算更加符合实际使用情况。     

A simple synthesis method for nanostructured Co-WC/carbon composites with enhanced oxygen reduction reaction activity

Co nanoparticles (Co NPs) and nanoscale tungsten carbide (WC) are successfully synthesized simultaneously with mesoporous structured carbon black (C) using an innovative simple method, which is known as solution plasma processing (SPP), and NPs are also loaded onto carbon black at the same time by SPP. The introduction of Co NPs led to not only superior oxygen reduction reaction (ORR) activity in terms of onset potential and peak potential, but also to a more efficient electron transfer process compared to that of pure WC. Co-WC/C also showed durability for long-term operation better than that of commercial Pt/C. These results clearly demonstrate that the presence of Co NPs significantly enhanced the ORR and charge transfer number of neighboring WC NPs in ORR activities. In addition, it was proved that SPP is a simple method (from synthesis of NPs and carbon black to loading on carbon black) for the large-scale synthesis of NP-carbon composite. Therefore, SPP holds great potential as a candidate for next-generation synthetic methods for the production of NP-carbon composites.     

A simple method for estimating the roundness of minimum zone circle

With the rapid development of micromachining technology, the feature size of object parts becomes smaller whilst the required tolerance accuracy becomes higher. The geometry of these micro-parts must be critically verified at sub-micrometer or even nanometer accuracy in three dimensions to guarantee machining quality, such as the cylindrical parts. Therefore, the method for estimating roundness error plays an increasingly important role in machining. This paper focuses on the roundness estimation based on the minimum zone circle method in a Cartesian coordinate system. An asymptotic search method is also proposed to obtain the coordinates of the concentric centre of the minimum zone circle model and to calculate the roundness error. Comparison and simulation experiments are also conducted to test the performance of the proposed method. The results demonstrate that the proposed method is effective, reliable and can meet the requirements for roundness estimation.     

A method for the calculation of the softerror rate of sub-μm dynamic logic cmos circuits

As a prerequisite for predicting the soft-error rate (SER) of CMOS circuits with dynamic registers a method to calculate the SER is presented which takes into account charge collection by drift and diffusion. It has been found that besides collection due to drift, the noise charge collected by diffusion has to be considered to accurately predict the SER of dynamic CMOS circuits. Calculated results are compared to device simulations and SER measurements.