Indentation cracking and deformation mechanism of sodium aluminoborosilicate glasses

Developing less brittle oxide glasses is a grand challenge in the field of glass science and technology, as it would pave the way toward new glass applications and limit the overall raw material usage and energy consumption. However, in order to achieve this goal, more insight into the correlation between the chemical composition and material properties is required. In this work, we focus on the mechanical properties of quaternary sodium aluminoborosilicate glasses, wherein systematic changes in glass chemistry yield different resistances to indentation crack initiation. We discuss the origin of the composition dependence of indentation cracking based on an evaluation of the deformation mechanism taking place during the indentation event. To this end, we use a simple metric, the extent of indent side length recovery upon annealing, to quantify the extent of reversible volume deformation. Finally, we also compare the compositional trend in crack initiation resistance to that in crack growth resistance (fracture toughness), showing no simple correlation among the two.     

Combined-Stage Sintering Model

By focusing on the similarities between the three stages of sintering, a single equation is derived that quantifies sintering as a continuous process from beginning to end. The microstructure is characterized by two separate parameters representing geometry and scale. The dimensionless geometry parameter, denoted T, comprises five scaling factors that relate specific microstructural featuers (e.g., surface curvature) to the scale (grain diameter). Calculations of T from experimental data show (a) agreement with computer simulations of initial-stage sintering, (b) the effect of surface diffusion on T, and (c) changes in T with microstructural evolution during sintering. Application of the model to the design of firing schedules and the study of microstructural geometry effects on sintering is discussed.     

Autogenous deformation and RH-change in perspective

Autogenous deformation and change of the relative humidity (RH-change) have been described and registered for a century. However, it is only within the last decade that these phenomena have received appreciable attention. The reason for this is that autogenous deformation and autogenous RH-change are phenomena of special importance within high-strength (high-performance) concrete technology, and a significant utilisation of these concretes did not take place until the early 1980s. In the present paper an historical overview of autogenous deformation and RH-change is given. In addition, due to the present status of this research field both terminology and measuring techniques are described in detail. Finally, some expectations for future research in this field are given.     

Bilaterally Microstructured Thin Polydimethylsiloxane Film Production

Thin PDMS films with complex microstructures are used in the manufacturing of dielectric electro active polymer (DEAP) actuators, sensors and generators, to protect the metal electrode from large strains and to assure controlled actuation. The current manufacturing process at Danfoss Polypower A/S produces films with a one-sided microstructured surface only. It would be advantageous to produce a film with both surfaces microstructured, as this increases the film’s performance efficiency. The new technique introduced herein produces bilaterally microstructured film by combining an embossing method with the existing manufacturing process. In employing the new technique, films with microstructures on both surfaces are successfully made with two different liquid silicone rubber (LSR) formulations: 1) pure XLR630 and 2) XLR630 with titanium dioxide (TiO₂). The LSR films (～70 µm) are cast on a carrier web substrate using a coating blade. The carrier web, which has a sinusoidal corrugation with wave height of 7 µm and a wave period of 7 µm on its surface, imparts corrugations to the bottom surface of the film. The elastomer film on the carrier web is preheated to the gel point, where the elastomer film can retain an imprint made on it. The preheated film at gel point is embossed between the rolls of a gravure lab coater, which corrugates the top surface of the film. The films are then heated, in order to cure completely. For the LSR systems used in this process, the optimum conditions for preheating are 110°C for 4–7 s, while for embossing the temperature is 110°C with 25 psi pressure between the rolls at a speed of 1.4 rpm. Scanning electron microscope (SEM) images confirm the formation of microstructures on both the surfaces of the film.     

Marine n-3 fatty acids: Basic features and background

There is some evidence from epidemiology that intake of n-3 polyunsaturated fatty acids (PUFA) from seafood may protect against coronary artery disease (CAD). This hypothesis is further supported from animal data showing a beneficial effect of n-3 PUFA on thrombosis and atherosclerosis in animals fed fish oils in most, but not all, studies. There are several mechanisms by which an increased intake of marine n-3 PUFA may protect against CAD; the most universal finding is a reduction of plasma triglycerides. It is puzzling, however, that a very low amount of n-3 PUFA, with no known beneficial biochemical effects, seems to be cardioprotective. It has therefore been of paramount interest to perform clinical trials. Such evidence and trials are discussed in later chapters, and the results have been very encouraging.     

Isocyanate‐Free and Dual Curing of Smokeless Composite Rocket Propellants

Traditional composite rocket propellants are cured by treatment of hydroxyl‐terminated prepolymers with polyfunctional aliphatic isocyanates. For development of smokeless composite propellants containing nitramines and/or ammonium dinitramide (ADN), energetic binder systems using glycidyl azide polymer (GAP) are of particular interest. Polyfunctional alkynes are potential isocyanate‐free curing agents for GAP through thermal azide‐alkyne cycloaddition and subsequent formation of triazole crosslinkages. Propargyl succinate or closely related aliphatic derivatives have previously been reported for such isocyanate‐free curing of GAP. Herein, we present the synthesis and use of a new aromatic alkyne curing agent, the crystalline solid bisphenol A bis(propargyl ether) (BABE), as isocyanate‐free curing agent in smokeless propellants based on GAP, using either octogen (HMX) and/or prilled ADN as energetic filler materials. Thermal and mechanical properties, impact and friction sensitivity and ballistic characteristics were evaluated for these alkyne cured propellants. Improved mechanical properties could be obtained by combining isocyanate and alkyne curing agents (dual curing), a combination that imparted better mechanical properties in the cured propellants than either curing system did individually. The addition of a neutral polymeric bonding agent (NPBA) for improvement of binder‐filler interactions was also investigated using tensile testing and dynamic mechanical analysis (DMA). It was verified that the presence of isocyanates is essential for the NPBA to improve the mechanical properties of the propellants, further strengthening the attractiveness of dual cure systems.     

ER Stress in ERp57 Knockout Knee Joint Chondrocytes Induces Osteoarthritic Cartilage Degradation and Osteophyte Formation

Ageing or obesity are risk factors for protein aggregation in the endoplasmic reticulum (ER) of chondrocytes. This condition is called ER stress and leads to induction of the unfolded protein response (UPR), which, depending on the stress level, restores normal cell function or initiates apoptotic cell death. Here the role of ER stress in knee osteoarthritis (OA) was evaluated. It was first tested in vitro and in vivo whether a knockout (KO) of the protein disulfide isomerase ERp57 in chondrocytes induces sufficient ER stress for such analyses. ER stress in ERp57 KO chondrocytes was confirmed by immunofluorescence, immunohistochemistry, and transmission electron microscopy. Knee joints of wildtype (WT) and cartilage-specific ERp57 KO mice (ERp57 cKO) were analyzed by indentation-type atomic force microscopy (IT-AFM), toluidine blue, and immunofluorescence/-histochemical staining. Apoptotic cell death was investigated by a TUNEL assay. Additionally, OA was induced via forced exercise on a treadmill. ER stress in chondrocytes resulted in a reduced compressive stiffness of knee cartilage. With ER stress, 18-month-old mice developed osteoarthritic cartilage degeneration with osteophyte formation in knee joints. These degenerative changes were preceded by apoptotic death in articular chondrocytes. Young mice were not susceptible to OA, even when subjected to forced exercise. This study demonstrates that ER stress induces the development of age-related knee osteoarthritis owing to a decreased protective function of the UPR in chondrocytes with increasing age, while apoptosis increases. Therefore, inhibition of ER stress appears to be an attractive therapeutic target for OA.     

Lymphatic transport in rats of interesterified oils containing conjugated linoleic acids

In this study we examined the lymphatic transport in rats of FA after administration of interesterified oils containing CLA, with emphasis on the location of CLA and octanoic acid in the TAG. The oils were produced by enzymatic interesterification. Eight oils with different structures or FA profiles were examined in this study: MCM, CMC, OCO, and COC, where M was expected to be octanoic acid and O oleic acid. In group 1, C was CLA as a mixture of the two CLA isomers c9, t11 or t10, c12, and in group 2, C was mainly the isomer t10, c12. Rats were subjected to cannulation of the mesenteric lymph duct, and the following day they were intragastrically administered one of the oils and lymph samples were collected for 24 h. The lymphatic transport of total FA from 0 to 8 h in group 1 was significantly (P < 0.05) higher for the OCO-1 and the COC-1 oils than for the CMC-1 oil. Similarly, in group 2 the transport was higher for the OCO-2 oil than for the CMC-2 oil. The recovery of both of the CLA isomers examined was similar (50-70%) and independent of the isomer, oil structure, and FA profile, whereas more octanoic acid was recovered from the CMC oils than from the MCM oils. The results indicated that the FA profiles and the position of octanoic acid had only a minor influence on the absorption of CLA.     

Biotransformation of 2-Benzoxazolinone to 2-Amino-(3<Emphasis Type="Italic">H</Emphasis>)-Phenoxazin-3-one and 2-Acetylamino-(3<Emphasis Type="Italic">H</Emphasis>)-Phenoxazin-3-one in Soil

An alternative to the use of synthetic pesticides is to exploit the natural defense chemicals produced by cereals. An important class of allelochemicals is cyclic hydroxamic acids and related benzoxazolinones. A prolonged degradation experiment of the allelochemical compound from rye 2-benzoxazolinone (BOA) was carried out for up to 90 d at 15°C at three different concentration levels, 3, 3000, and 30,000 nmol BOA· g soil^–1, respectively, in a sandy loam soil. Two main degradation products, 2-amino-(3H)-phenoxazin-3-one (APO) and 2-acetylamino-(3H)-phenoxazin-3-one (AAPO), were identified and quantified by LC-ESI-MS-MS. The half-life of BOA increased with higher levels of BOA added to the soil. Half-lives of BOA, APO, and AAPO were determined by fitting a single first-order model to the degradation data. Half-life of BOA was determined to be 0.6 d in the 3 nmol BOA g soil^–1 treatment. Half-lives of BOA, APO, and AAPO were 3.1, 2.7, and 2.1 d, respectively, in the 3000 nmol BOA· g soil^–1 treatment. In the 30,000 nmol BOA· g soil^–1 treatment, the half-lives were 31 d for BOA and 45 d for APO. The microbial community structure was not affected by addition of BOA to the soil as investigated by analysis of signature fatty acids. The results suggest that the exploitability of BOA for crop protection is dependent on the existing concentration of BOA in the soil and the timing of incorporation of hydroxamic acid synthesizing crops into the soil.