Thiol–Ene Clickable Gelatin: A Platform Bioink for Multiple 3D Biofabrication Technologies

Bioprinting can be defined as the art of combining materials and cells to fabricate designed, hierarchical 3D hybrid constructs. Suitable materials, so called bioinks, have to comply with challenging rheological processing demands and rapidly form a stable hydrogel postprinting in a cytocompatible manner. Gelatin is often adopted for this purpose, usually modified with (meth‐)acryloyl functionalities for postfabrication curing by free radical photopolymerization, resulting in a hydrogel that is cross‐linked via nondegradable polymer chains of uncontrolled length. The application of allylated gelatin (GelAGE) as a thiol–ene clickable bioink for distinct biofabrication applications is reported. Curing of this system occurs via dimerization and yields a network with flexible properties that offer a wider biofabrication window than (meth‐)acryloyl chemistry, and without additional nondegradable components. An in‐depth analysis of GelAGE synthesis is conducted, and standard UV‐initiation is further compared with a recently described visible‐light‐initiator system for GelAGE hydrogel formation. It is demonstrated that GelAGE may serve as a platform bioink for several biofabrication technologies by fabricating constructs with high shape fidelity via lithography‐based (digital light processing) 3D printing and extrusion‐based 3D bioprinting, the latter supporting long‐term viability postprinting of encapsulated chondrocytes.     

一种用于实时体绘制系统的自适应采样算法

本文讨论了一种用于体绘制的、支持基于空间跳跃和自适应光线终止等优化算法的高效硬件结构及一种加速半透明物体绘制的新技术.这种硬件结构用于绘制规模为256³体元的数据时可达到70Hz的帧频,但这样的帧频只是在体元的透明度都被置为0(完全透明)或1(完全不透明)的情况下才能取得.引入新的加速技术后,绘制半透明物体的帧频也可接近上述数值.新的加速技术采用自适应采样步长减少体绘制过程中冗余的体元重采样,从而使算法的复杂度和对存储器的带宽要求大大减小.新的加速技术对半透明体数据可取得高达4.7倍的加速比.采用新的加速技术需要在开始交互绘制前对体数据进行距离编码.优化后的距离编码对有8兆体元的体数据的预处理时间仅需要8~30秒.     

Neutron detection by measuring capture gammas in a calorimetric approach

The neutron capture detector (NCD) is introduced as a novel detection scheme for thermal and epithermal neutrons that could provide large-area neutron counters by using common detector materials and proven technologies. The NCD is based on the fact that neutron captures are usually followed by prompt gamma cascades, where the sum energy of the gammas equals to the total excitation energy of typically 6-9 MeV. This large sum energy is measured in a calorimetric approach and taken as the signature of a neutron capture event. An NCD consists of a neutron converter, comprising of constituents with large elemental neutron capture cross-section like cadmium or gadolinium, which is embedded in common scintillator material. The scintillator must be large and dense enough to absorb with reasonable probability a portion of the sum energy that exceeds the energy of gammas emitted by common (natural, medical, industrial) radiation sources. An energy window, advantageously complemented with a multiplicity filter, then discriminates neutron capture signals against background. The paper presents experimental results obtained at the cold-neutron beam of the BER II research reactor, Helmholtz-Zentrum Berlin, and at other neutron sources with a prototype NCD, consisting of four BGO crystals with embedded cadmium sheets, and with a benchmark configuration consisting of two separate NaI(Tl) detectors. The detector responses are in excellent agreement with predictions of a simulation model developed for optimizing NCD configurations. NCDs could be deployed as neutron detectors in radiation portal monitors (RPMs). Advanced modular scintillation detector systems could even combine neutron and gamma sensitivity with excellent background suppression at minimum overall expense.     

Flexible time reduction method for burn-in of high-quality products

Burn-in is an effective method to screen out early failures of electronic devices. Typically, this is achieved by operating the devices under accelerated stress conditions. This paper focuses on a burn-in concept where a random sample of devices is drawn out of the running production, put to burn-in, and investigated for early failures. This procedure is called burn-in study. In parallel, as long as the burn-in study is ongoing, all other produced devices are subjected to burn-in screening. In this article, new flexible sampling plans for burn-in studies are introduced. These are based on the progress of these studies and defined quality targets. Furthermore, these sampling plans enable fast burn-in time reductions and various time reduction strategies. From a statistical point of view, this requires to combine the proportion of early failures in a population with their lifetime distribution function. The new model is illustrated by case studies and simulations. It contributes to burn-in cost reductions, while controlling quality levels at the same time.     

Gas/liquid oxygen-transfer to flowing lead alloys

For the application of liquid lead or lead-bismuth eutectic as coolant in nuclear reactors, the concentration of dissolved oxygen, determining the compatibility with steels used as construction materials, is of critical importance. In general, oxygen has to be added continuously to the liquid metal, so as to compensate for consumption by oxide formation on the surface of the reactor components. A potential method of keeping the oxygen concentration in a favourable range is transferring oxygen from an oxygen-containing gas, which is investigated on the basis of the experience from operating a gas/liquid transfer device in the CORRIDA loop. Conclusions on oxygen transfer in industrial-scale systems are drawn.     

信号路径设计

每当我们设计高速的混合信号系统时,我们最好先审视信号路径的每一环节,详细评估各区块的信号失真程度.本文主要介绍输入或接收器路径的设计.发送器或输出路径的设计将会留待以后再详细介绍.典型的接收器或仪表测量系统由信号传感器、模拟信号处理区块、数据转换器、接口及数字处理区块等多个不同环节组成(参看图1).但本文只集中讨论输入路径设计的模拟及混合信号部分.我们必须小心挑选信号路径的各个区块,才可取得预期的成效.     

Phosphate–Halide Systems: I, Constitution of NaPO3-NaF Glasses

The influence of sodium fluoride additions on the constitution of sodium metaphosphate glass has been determined by paper chromatographic techniques. Glasses with Na/P ratios varying from 1.5 to 1.22 and melted in air have been studied. It has been found that fluorine is lost from the melt during the normal preparation of glasses. When, however, the melt is quenched immediately after the components have melted into a homogeneous liquid, most of the fluorine is retained. With an increase in the melting time, the amount of fluorine retained by the melt decreases and after about 10 minutes all the fluorine is replaced by oxygen. The constitution of NaPO₃-NaF glasses with the varying Na/P ratios and with melting periods up to 15 minutes has been determined. When the glasses contain a considerable amount of fluorine, there is a breakdown in the structure of phosphate polymers. The results obtained are discussed in relation to the data reported by earlier investigators.