Estimating causal effects from multiple cycle data in studies of in vitro fertilization

Prospective studies of reproductive outcomes frequently record data at multiple cycles. For example, studies of in vitro fertilization and embryo transfer (IVF-ET) follow women or couples for possibly several IVF cycles and record outcomes such as pregnancy status and embryo implantation. Several time-varying covariates, such as age and diagnostic markers, typically are available as well. When attention is focused on measurement of exposure effects, the use of multiple cycle data poses several complications. If the study is observational, the exposure probability may depend on subject characteristics. Moreover, attrition rates in IVF-ET can be substantial, and the attrition process can be expected to depend heavily on prior outcome. In fact, both success (pregnancy) and failure (lack of embryo implantations) can be prognostic of dropout. In this paper, we illustrate the use of causal modeling for multiple cycle data. Key assumptions are reviewed, and inference based on weighted estimating equations is described in detail. The methods are applied to a study of the effects of hydrosalpinx among women with tubal disease undergoing IVF-ET.     

Review: functional foods and ingredients derived from milk

The objective of this paper is to review the main research works related to functional foods and ingredients derived from milk. Research in functional foods has increased during last twelve years with the intention of increasing life expectancy and improving human health conditions. Probiotics, prebiotics, bioactive peptides or proteins, dietetic fibers and fatty acids, as well as the addition of fitochemical compounds in dairy products and a record of some allergic compounds are also discussed. The demand of this kind of products is increasing due to intense advertising campaigns posted in many countries. Basically, these campaigns promise better health and/or the prevention of certain illnesses. Milk contains diverse constituents with physiological functionality, which might change the traditional view point that we have about drugs. The topic of functional foods in general, and specifically that from milk and dairy products, has still not been completely exploited, and in the future it will be found that the best work has not been carried out in this area.     

AN ITERATIVE FILTERING ALGORITHM FOR NON-FOURIER FREQUENCY ESTIMATION

Abstract. We study an iterative filtering method to estimate frequencies of random Gaussian sinusoids in white noise. The method uses higher order crossings and takes advantage of a fixed point to guide the use of bandpass filtering in an attempt effectively to increase the signal-to-noise ratio. At each iteration the expected zero-crossing rate is estimated from independent time series. Convergence occurs with any prespecified probability less than one.     

Continuous-time approaches for short-term scheduling of network batch processes: Small-scale and medium-scale problems

Two time representation approaches, discrete-time and continuous-time approaches, have been developed for short-term scheduling of batch process in small-scale and medium-scale during the last two decades. As usually establishing advantages over discrete-time approaches in the scheduling problems, continuous-time approaches have gained increasing attention in the last 10 years. The reported continuous-time approaches can be divided into four categories: global event-based, unit-specific event-based, slot-based and precedence-based models. In this paper, more complex processes, network batch processes in small and medium scales, are considered. Six models based on different continuous-time representations are compared in several benchmark examples from the literature. The compared items include problem size, computational times and model convergence. Moreover, two intermediate storage policies (limited and unlimited intermediate storage) and two objective functions (maximization of profit and minimization of makespan) are addressed.     

Collisional energy transfer in polyatomic molecules in the gas phase

This paper is an attempt to present an overall view of energy transfer between excited polyatomic molecules and polyatomic and monatomic bath, based on results obtained by classical trajectory calculations. It is not a general review of the subject but a summary based on work done by us in the last few years. We report average energies transferred in a collision and collisional energy transfer probability density functions for various collision partners as a function of various system parameters: temperature, vibrational and rotational energies of the hot and cold molecule, and relative translational energies. Various mechanisms for energy transfer are proposed, their dependence on the system parameters is explored, and the relevance of empirical numerical models to computational results is discussed.     

双蒸发器流化冰制冰机试验研究与分析

分析了流化冰制冰机在制冰溶液预冷工况与制冰工况下的理论循环,发现传统的基于制冰工况设计的单蒸发器（冰晶器）在制冰溶液预冷工况下,不能很好匹配压缩机性能,导致制冰溶液预冷工况效能低,为此提出了双蒸发器的优化方案。对单、双蒸发器机组在不同的制冰溶液流量下进行了性能试验,结果表明采用双蒸发器的制冰机在制冰溶液流量为2000 L·h^-1与2500 L·h^-1情况下,制冰溶液从9.5℃降温至0℃的速度较单蒸发器提高了34%与56%,制冷系数提高了9%与54%,同时改善了从常温到制取流化冰全过程的制冰效率。研究发现在制冰溶液流量较大的情况下,采用双蒸发器时制冰溶液预冷工况降温速度及制冷系数提高更多,优化效果更好。     

Cryopreservation of Mesenchymal Stem Cells Using Medical Grade Ice Nucleation Inducer

Mesenchymal stem cells (MSCs) can differentiate into multiple different tissue lineages and have favourable immunogenic potential making them an attractive prospect for regenerative medicine. As an essential part of the manufacturing process, preservation of these cells whilst maintaining potential is of critical importance. An uncontrolled area of storage remains the rate of change of temperature during freezing and thawing. Controlled-rate freezers attempted to rectify this; however, the change of phase from liquid to solid introduces two extreme phenomena; a rapid rise and a rapid fall in temperature in addition to the intended cooling rate (normally −1 °C/min) as a part of the supercooling event in cryopreservation. Nucleation events are well known to initiate the freezing transition although their active use in the form of ice nucleation devices (IND) are in their infancy in cryopreservation. This study sought to better understand the effects of ice nucleation and its active instigation with the use of an IND in both a standard cryotube with MSCs in suspension and a high-throughput adhered MSC 96-well plate set-up. A potential threshold nucleation temperature for best recovery of dental pulp MSCs may occur around −10 °C and for larger volume cell storage, IND and fast thaw creates the most stable process. For adhered cells, an IND with a slow thaw enables greatest metabolic activity post-thaw. This demonstrates a necessity for a medical grade IND to be used in future regenerative medicine manufacturing with the parameters discussed in this study to create stable products for clinical cellular therapies.     

基于适应策略差分进化算法的化工反应动力学参数估值

为了更准确地通过煤烟气成分推测汞元素氧化程度,建立精确的汞氧化过程动力学模型至关重要。目前已有的汞氧化过程动力学模型中存在一些难以确定的未知参数,为了确定模型中这些参数的最优值,本文提出一种改进的适应策略差分进化算法（ASDE）。该算法引入变异策略、缩放因子（F）和交叉参数（CR）候选集合,同时为集合中每个候选参数赋予一定的选择概率。在进化搜索过程中,以历史成功搜索信息为基础,实时更新每个候选集合中各参数对应的选择概率,并根据选择概率自适应为下一时刻进化群体中每个个体分配变异策略和对应控制参数。将改进算法用于汞氧化过程动力学参数估值问题,实验结果显示,相对其他6种算法,改进算法ASDE求解得到模型更加接近实际,是一种求解化工反应动力学参数估值问题的有效方法。     

A THREE-PHASE MODEL FOR SORPTION ISOTHERM IN ZEOLITE ADSORBENTS

A three-phase model for adsorption in zeolite cavities is proposed. The adsorbed molecules are taken to be distributed between a surface layer and a dense phase filling the rest of the cavity volume. This model is a more realistic representation of molecules in zeolite cages especially at high pressures. The equation for the adsorption isotherm, based on this model, has two contributions: a surface term and a dense phase term. The dense phase contribution was estimated from a simple equation that obeys the limiting values at low and high pressures. The surface contribution can be estimated from the existing surface adsorption models. When all model parameters are estimated from molecular and literature data, the combination of the two terms was found to be an improvement over traditional treatment of adsorption data of a number of gases in zeolite-A for a wide range of pressures. However, new models for the adsorbed phase that account for sorbate-sorbate repulsive forces correctly are needed for accurate prediction of adsorption data.     

High-Temperature Mechanical Properties of Si-B-C-N-Precursor-Derived Amorphous Ceramics and the Applicability of Deformation Models Developed for Metallic Glasses

The characterization of Si-B-C-N amorphous ceramics using isothermal compression creep testing in the temperature range of 1200°–1500°C is reported. The deformation rate contains a stress-dependent component that is proportional to the applied stress, which indicates that this portion of the deformation mechanism is based on viscous flow. An increase in the creep resistance is observed, following either preliminary annealing or hot isostatic pressing, which may be explained by a reduction of free volume in the amorphous material. The application of two deformation models that are used to predict similar deformation behavior in metallic glasses also is discussed. Although both models accurately predict the time dependence of the deformation rate of precursor-derived amorphous ceramics, the free-volume model fits the observed temperature dependence better than the "two-step" rearrangement model.     

Mechanism for Salt Scaling

Over the past 60 years, concrete infrastructure in cold climates has deteriorated by "salt scaling," which is superficial damage that occurs during freezing in the presence of saline water. It reduces mechanical integrity and necessitates expensive repair or replacement. The phenomenon can be demonstrated by pooling a solution on a block of concrete and subjecting it to freeze/thaw cycles. The most remarkable feature of salt scaling is that the damage is absent if the pool contains pure water, it becomes serious at concentrations of a few weight percent, and then stops at concentrations above about 6 wt%. In spite of a wealth of research, the mechanism responsible for this damage has only recently been identified. In this article, we show that salt scaling is a consequence of the fracture behavior of ice. The stress arises from thermal expansion mismatch between ice and concrete, which puts the ice in tension as the temperature drops. Considering the mechanical and viscoelastic properties of ice, it is shown that this mismatch will not cause pure ice to crack, but moderately concentrated solutions are expected to crack. Cracks in the brine ice penetrate into the substrate, resulting in superficial damage. At high concentrations, the ice does not form a rigid enough structure to result in significant stress, so no damage occurs. The morphology of cracking is predicted by fracture mechanics.     

Fuzzy modeling of signal transduction networks

This work proposes a fuzzy modeling-based approach for describing signal transduction networks. Many key steps in signal transduction mechanisms have been investigated and described qualitatively in the literature, however, only little quantitative information is available. Fuzzy models can make use of this situation as fuzzy rules can be based upon the qualitative information that is found in the literature whereas training of the model can be performed with data that is available. This combination of a fuzzy rule set based upon qualitative information with parameters to be determined from data can result in models where fewer parameters need to be estimated than if fundamental or black-box models were used. The presented fuzzy modeling procedure is used to describe two signal transduction pathways, one for IL-6 and one for TNF-α signaling. It is shown that the resulting models are capable of capturing the dynamics of key components of both signal transduction pathways.     

A new generic approach for the modeling of fluid catalytic cracking (FCC) riser reactor

A new kinetic model for the fluid catalytic cracking (FCC) riser is developed. An elementary reaction scheme, for the FCC, based on cracking of a large number of lumps in the form of narrow boiling pseudocomponents is proposed. The kinetic parameters are estimated using a semi-empirical approach based on normal probability distribution. The correlation proposed for the kinetic parameters’ estimation contains four parameters that depend on the feed characteristics, catalyst activity, and coke forming tendency of the feed. This approach eliminates the need of determining a large number of rate constants required for conventional lumped models. The model seems to be more versatile than existing models and opens up a new dimension for making generic models suitable for the analysis and control studies of FCC units. The model also incorporates catalyst deactivation and two-phase flow in the riser reactor. Predictions of the model compare well with the yield pattern of industrial scale plant data reported in literature.     

Three characterization techniques coupled with adsorption for studying the nanoporosity of supported films and membranes

Three characterization techniques are described for studying the open nanoporosity, i.e. the open free volume, the microporosity, the mesoporosity and the thickness variation of thin deposited films during gas adsorption and condensation. They are all based on the coupling of the sorption of a probe gaseous molecule at room temperature and a physical characterization tool of thin deposited films: the quartz crystal microbalance, ellipsometry and X-ray reflectometry, giving the mass uptake, the refractive index variation and the electronic density variation, respectively, of the film due to the adsorbate intrusion inside the open free volume and pores. The film thickness evolution during the sorption can also be followed by the two last techniques. These techniques are complementary because each one can bring specific properties and can validate the results of another one. Both static and dynamic measurements can be carried out to characterize the porosity, the contraction or the swelling of the film and the penetration rate of the gas.     

Compression and deformation of soft spherical particles

In order to model geometric property variation and investigate different compression behaviors between compressible (variable volume) and incompressible (invariable volume) soft spherical particles, two compression models based on different shapes of the lateral surface (non-contacted surface of the particle) of the compressed particles are proposed. The shape profiles in various compression degrees calculated by the models showed good agreement with the experimental data. The models can be also used to estimate the surface area and volume of the soft particles. Additionally, according to particle shape profiles, the particle structures, porous or dense, show great influences on the compression behavior for both compressible and incompressible soft particles, where the dense incompressible particle performs a higher degree of lateral extension during compression. This is because its volume can be transferred more completely from the compressed portion to the lateral surface, which is without loading contact on it.     

Universal correlation for gas hydrates suppression temperature of inhibited systems: IV. Water activity

In Parts I, II, and III, the Hu-Lee-Sum (HLS) correlation was demonstrated to be a robust method for determining the hydrate suppression temperatures for structure I and II hydrates containing inorganic salts and organic inhibitors. Here, Part IV introduces two different approaches to estimate the water activity for systems containing inhibitors: ice melting point and activity coefficient models. The ice melting point is translated into the water activity changes, which can then be directly used for the hydrate suppression temperatures. The great benefit of this method is its applicability to any inhibited systems with unknown compositions of inhibitors. The activity coefficient model is based on widely available models. These methods for determining the water activity allow for a simple yet reliable prediction of hydrate suppression temperatures for inhibited systems, which advocate for their use in place of the more traditional methods known to be less reliable and less accurate.     

Die Volume‐of‐Fluid‐Methode,ein Verfahren zur Simulation von Zweiphasenströmung

The computational fluid dynamics has gained a growing importance in the last decades. This has been achieved, on the one hand, through the continuously increasing speed of computers, on the other hand, through the development of mathematical‐physical models and numerical algorithms that allow a reality‐close simulation of complex flow processes. In this work, the volume of fluid method is used to simulate a two‐phase flow in a tube. The effects of the contact angle, the temperature and the mass flow of the gas phase on the form of the liquid phase are investigated.     

A comparison of chemorheological models for thermoset cure

A chemorheological study of a thermoset system consisting of diglycidyl ether of bisphenol-A (DGEBA) epoxy resin and a mixture of two armoatic amine curing agents; 4,4′ methylenedianiline (MDA) and m-phenylene diamine (m-PDA), was conducted. Experimentally obtained viscosity data were checked against the predictions of two different viscosity models; one based on a phenomenological equation obtained by modification of the classical Williams–Landel–Ferry (WLF) equation and the other based on an extension of the branching theory originally proposed by Flory. In general, the predictions of both models were in excellent agreement with experimentally obtained isothermal and dynamic viscosity data. The branching theory model was found to have a slight advantage over the phenomenological equation model in describing the viscosity prior to gelation in a fast heating cure cycle.     

Review and extension of normal force models for the Discrete Element Method

For the simulation of dense granular systems the Discrete Element Method based on a soft-sphere approach is commonly used. In such simulations collisions between particles take a finite time. The equations of motion are applied for each particle and solved numerically. Therefore models for the forces acting between particles in contact need to be specified. In this paper the focus is set on normal contacts. Based on macroscopic and microscopic accessible parameters like coefficient of restitution, collision time, force, displacement and displacement rate a wide range of commonly used force schemes are reviewed. Results obtained from these commonly used models are compared to experimental data on collisions of different metal alloys, ice and marble as reported in literature. Due to obvious limitations extensions are presented. The new extended models based on linear and non-linear models are compared to experimental data and their accuracy and applicability are discussed.     

Multi-mode resource constrained project scheduling under resource disruptions

Over the last few decades, research on resource constrained project scheduling has focused on the development of mathematical programming based approaches for the generation of a nominal schedule under a deterministic environment. During the implementation phase, however, the nominal schedule may need to be revised when one or more resources are disrupted for a length of time. In this paper, we formulate two discrete time based models to deal with two different disruption scenarios for multi-mode resource constrained problems. We propose a reactive re-scheduling procedure for a single, as well as a series of disruptions, without having any disruption information in advance. To test the proposed approaches, sets of ten, twenty and thirty-activity multi-mode test instances from Project Scheduling Library (PSLIB) were used after introducing randomly generated disruption events. The experimental studies were also carried out to determine the effect of different factors related to the disruption recovery process.