Emerging Biofabrication Strategies for Engineering Complex Tissue Constructs

The demand for organ transplantation and repair, coupled with a shortage of available donors, poses an urgent clinical need for the development of innovative treatment strategies for long‐term repair and regeneration of injured or diseased tissues and organs. Bioengineering organs, by growing patient‐derived cells in biomaterial scaffolds in the presence of pertinent physicochemical signals, provides a promising solution to meet this demand. However, recapitulating the structural and cytoarchitectural complexities of native tissues in vitro remains a significant challenge to be addressed. Through tremendous efforts over the past decade, several innovative biofabrication strategies have been developed to overcome these challenges. This review highlights recent work on emerging three‐dimensional bioprinting and textile techniques, compares the advantages and shortcomings of these approaches, outlines the use of common biomaterials and advanced hybrid scaffolds, and describes several design considerations including the structural, physical, biological, and economical parameters that are crucial for the fabrication of functional, complex, engineered tissues. Finally, the applications of these biofabrication strategies in neural, skin, connective, and muscle tissue engineering are explored.     

Fatigue behaviour of additive manufactured materials: An overview of some recent experimental studies on Ti‐6Al‐4V considering various processing and loading direction effects

Although additive manufacturing (AM) has gained significant attention due to the advantages it offers and is currently a focus of much research, design of critical load carrying components utilizing such processes is still at its infancy. This is due to the fact that most of the load carrying components made by AM processes are subjected to cyclic loads, and fatigue behaviour of AM metals is far less understood as compared with those made by conventional methods, such as wrought and cast metals. To better understand the fatigue behaviour of AM metals, a wide range of issues that affect the behaviour in a synergistic manner must be considered. These include the effects of defects, residual stresses, surface finish, geometry and size, layer orientation, and heat treatment. Additionally, due to the multiaxial nature of the loading and/or complex geometries typically manufactured by AM processes, the stress state is often multiaxial including both normal and shear stresses. In this paper, the aforementioned effects influencing the fatigue resistance of AM parts, including torsion and multiaxial fatigue behaviour, are briefly discussed using some recently generated experimental data on Ti‐6Al‐4V by the authors.     

A memetic algorithm for the flexible flow line scheduling problem with processor blocking

This paper introduces an efficient memetic algorithm (MA) combined with a novel local search engine, namely, nested variable neighbourhood search (NVNS), to solve the flexible flow line scheduling problem with processor blocking (FFLB) and without intermediate buffers. A flexible flow line consists of several processing stages in series, with or without intermediate buffers, with each stage having one or more identical parallel processors. The line produces a number of different products, and each product must be processed by at most one processor in each stage. To obtain an optimal solution for this type of complex, large-sized problem in reasonable computational time using traditional approaches and optimization tools is extremely difficult. Our proposed MA employs a new representation, operators, and local search method to solve the above-mentioned problem. The computational results obtained in experiments demonstrate the efficiency of the proposed MA, which is significantly superior to the classical genetic algorithm (CGA) under the same conditions when the population size is increased in the CGA.     

尼洋河流域径流时空变化特性初步分析

尼洋河是雅鲁藏布江的5大支流之一,该流域气候温暖湿润,植被覆盖率高,虽地处青藏高原,却具有独特的温带气候特征和下垫面条件.根据尼洋河流域现有测站的径流资料对其年内分配和径流的多年变化进行了初步的分析.结果表明,尼洋河流域主汛期为6月～9月,径流量年内集中程度高,其汛期径流量占总径流量的90%左右,多年期间丰水时段和枯水时段为3～5 a.     

On Smoothed Analysis of?Quicksort?and?Hoare’s Find

We provide a smoothed analysis of Hoare’s find algorithm, and we revisit the smoothed analysis of quicksort. Hoare’s find algorithm—often called quickselect or one-sided quicksort—is an easy-to-implement algorithm for finding the k-th smallest element of a sequence. While the worst-case number of comparisons that Hoare’s find needs is Θ(n ²), the average-case number is Θ(n). We analyze what happens between these two extremes by providing a smoothed analysis. In the first perturbation model, an adversary specifies a sequence of n numbers of [0,1], and then, to each number of the sequence, we add a random number drawn independently from the interval [0,d]. We prove that Hoare’s find needs $\Theta(\frac{n}{d+1} \sqrt{n/d} + n)$ comparisons in expectation if the adversary may also specify the target element (even after seeing the perturbed sequence) and slightly fewer comparisons for finding the median. In the second perturbation model, each element is marked with a probability of p, and then a random permutation is applied to the marked elements. We prove that the expected number of comparisons to find the median is $\Omega((1-p) \frac{n}{p} \log n)$ . Finally, we provide lower bounds for the smoothed number of comparisons of quicksort and Hoare’s find for the median-of-three pivot rule, which usually yields faster algorithms than always selecting the first element: The pivot is the median of the first, middle, and last element of the sequence. We show that median-of-three does not yield a significant improvement over the classic rule.     

Molecular tracking: A concept for side-draw distillation column design

A simple approach is introduced to locate a side-draw tray for ternary and multi-component mixtures with middle boiling component(s) present in the system at trace levels. The concept is based on a probability function defined by the thermodynamic properties of the system. The advantage of this method over existing methods is the ability to quickly and efficiently provide a feasible configuration of the distillation unit without relying on rigorous optimization or trial and error approaches. Moreover, it provides an intuitive understanding of the movements of the middle boiling components in the column.     

Mechanical performance of vinyl ester—polyurethane interpenetrating polymer network composites

In this study, a carbon fiber/vinyl ester-polyurethane interpenetrating polymer network (IPN) laminate composite was fabricated and characterized for the first time. The IPN matrix, consisting of a commercially available vinyl ester and polyurethane, was synthesized via a sequential method with vinyl ester as the rigid phase and polyurethane as the flexible phase. Good compatibility between the two phases in the matrix was achieved and confirmed via differential scanning calorimetry and dynamic mechanical analysis. The thermomechanical response of the IPN matrix was compared with that of an unmodified vinyl ester resin. The presence of the more ductile polyurethane in the IPN matrix depressed the glass transition temperature (from 94 to 84°C), but also served to improve damping response at all frequencies studied. Tensile and flexural tests were performed on the carbon fiber/IPN and carbon fiber/vinyl ester composites to determine their mechanical response. The IPN composite exhibited lower tensile properties than the vinyl ester composite. However, its flexural properties were on par with those of the vinyl ester composite.     

Synthesis and Application of Titania Nanotubes and Hydrous Manganese Oxide in Heavy Metal Removal from Aqueous Solution: Characterization,Comparative Study,and Adsorption Kinetics

Theoretical Foundations of Chemical Engineering - Titania nanotube (TNT) and hydrous manganese oxide (HMO) nanoparticles were synthesized via hydrothermal synthesis and chemical coprecipitation...     

A Century of Fractionated Radiotherapy: How Mathematical Oncology Can Break the Rules

Radiotherapy is involved in 50% of all cancer treatments and 40% of cancer cures. Most of these treatments are delivered in fractions of equal doses of radiation (Fractional Equivalent Dosing (FED)) in days to weeks. This treatment paradigm has remained unchanged in the past century and does not account for the development of radioresistance during treatment. Even if under-optimized, deviating from a century of successful therapy delivered in FED can be difficult. One way of exploring the infinite space of fraction size and scheduling to identify optimal fractionation schedules is through mathematical oncology simulations that allow for in silico evaluation. This review article explores the evidence that current fractionation promotes the development of radioresistance, summarizes mathematical solutions to account for radioresistance, both in the curative and non-curative setting, and reviews current clinical data investigating non-FED fractionated radiotherapy.