Damage Mechanisms and the Mechanical Properties of a Laminated 0/90 Ceramic/Matrix Composite

The tensile properties of a 0/90 laminated CAS matrix composite reinforced with Nicalon fibers have been measured. Some effects of notches have also been explored. Changes in modulus and permanent strain caused by matrix cracking have been measured and compared with available models. For this comparison, independent measurements have been made of the constituent properties and the residual stress. The ultimate tensile strength has also been measured and compared with a global load-sharing model. It is concluded that lower-bound matrix cracking models provide good predictability of the stresses at which various matrix cracking mechanisms first operate. Also, the ultimate tensile strength is found to be consistent with a global load-sharing model, based on the in situ strength properties of the fibers. Conversely, the evolution of matrix cracks at stresses above the lower bound has yet to be adequately modeled. In addition, a need is identified for improved models relating elastic properties and permanent strains to matrix crack spacing.     

Ketone bodies,glucose and glutamine as lipogenic precursors in human diploid fibroblasts

Incorporation of [¹⁴C] from acetoacetate, D(-)- and L(+)-3-hydroxybutyrate, glucose, glutamine, acetate and palmitate in cellular lipids were studied in cultures in human diploid fibroblasts (HDF). The results showed that acetoacetate was 2–10 times more effective as a lipogenic precursor than was either D- or L-3-hydroxybutyrate. Its extent of incorporation into lipids was 2- to 8-fold more than the other precursors examined under conditions when the overall rates of nonsaponifiable and saponi-fiable lipogenesis as measured by³H₂O incorporation were essentially unchanged. Acetoacetate supported both saponifiable and nonsaponifiable lipid syntheses with half-saturation values (K_m app.) of 185 μM and 30 μM, respectively. Glucose stimulated acetoacetate incorporation into lipids whereas, conversely, acetoacetate inhibited [¹⁴C] glucose incorporation into lipids. The presence of low density lipoproteins (LDL) cholesterol (@40 μg cholesterol/mL) inhibited the incorporation of [¹⁴C] from acetoacetate 56% into nonsaponifiable lipids; the inhibition was consistently higher (75%) when [¹⁴C] glucose or glutamine were the precrusors. The loss of 3-hydroxy-3-methyl-glutaryl CoA (HMG CoA) reductase activity upon addition of LDL-cholesterol was greater than the suppression of [¹⁴C] incorporation from acetoacetate or glucose into nonsaponifiable lipids. In the presence of glucose, [¹⁴C] acetoacetate was incorporated into 3-βOH sterols (digitonin precipitable). 7.7±1.1 times more effectively than was [¹⁴C] glucose. The results suggest that HDF would be a suitable model to investigate the effects of various precrusors of HMG CoA on the rate of cholesterol biosynthesis.     

CONFIDENCE INTERVALS FOR ROBUST ESTIMATES OF THE FIRST ORDER AUTOREGRESSIVE PARAMETER

Abstract. The confidence interval properties of several estimators of the transition parameter, φ, in the first order autoregressive model are examined by a Monte Carlo study. The least squares confidence interval estimator, as well as two forms of a proposed robust confidence interval based on a generalized M-estimator, are examined under two model alternatives to the classical time series approach: the innovations model (the time series is observed 'perfectly') and the additive effects model (the time series is observed plus an added 'effect'). Samples were generated from a number of symmetric distributions, including the Gaussian and a variety of contaminated distributions with mild to heavy contamination. Over a range of outlier models, values of φ (.25 to.9), and sample sizes (20 to 100), it was found that the GM-estimators possess desirable confidence interval robustness properties in terms of validity and efficiency. In general, the least squares confidence interval is not robust against symmetric heavy-tailed contamination in the innovations model or against the additive effects model.     

Long‐chain omega‐3 from low‐trophic‐level fish provides value to farmed seafood

Low‐trophic‐level fish are a crucial source of long‐chain (LC) omega‐3 fatty acids for farmed fish and humans. Many farm‐raised fish species have a clear need for these nutrients. Farmed fish deposit the LC omega‐3s in their flesh and transfer them up the food chain. However, the content of LC omega‐3s in farm‐raised seafood continues to decline, while the content of shorter‐chain plant‐sourced omega‐3s, and pro‐inflammtory omega‐6s continue to increase. This reduces its nutritional worth. The value of low‐trophic‐level fish is often viewed merely as its price at the dock. Some reports and metrics steer public attention towards the mass balance between quantities of low‐trophic‐level fish and farmed seafood. However, the the nutritional value of seafood is more important than its mere quantities. The role of low‐trophic‐level fish in human nutrition, health, and wellbeing is a fundamental component of its economic value to society.     

Precipitate alterations in the heat-affected zone of a Grade 100 microalloyed steel

Microalloy precipitate alterations (particularly dissolution) in the heat-affected zone (HAZ) of a Grade 100 steel, microalloyed by titanium, niobium, and vanadium and produced in the form of a plate with a thickness of 8 mm, was examined both theoretically and experimentally. For theoretical analysis of precipitate dissolution, pairs of effective peak temperature and holding time were extracted from the thermal cycles of welding, and were superimposed on the Ashby and Easterling non-equilibrium solubility curves for different fractions of precipitate dissolution. Intersections between the effective T–t curves and the non-equilibrium solubility curves gave critical pairs of effective peak temperature and holding time for dissolution of different fractions of a precipitate, which resulted in the establishment of precipitate dissolution profiles in the HAZ. Experimental analysis of precipitate alterations was carried out using carbon extraction replicas in a transmission electron microscope. The theoretical analyses were in agreement with experimental results, showing that it is the dissolution of small Nb-rich particles that paves the way to grain growth in the coarse-grained HAZ. Reprecipitation was generally suppressed in the low heat-input weld sample. There was some reprecipitation in the higher heat-input weld samples. Coarsening of TiN did not occur in the HAZ, due to the large size of these particles in the steel examined.     

黄金的电子称重成功案例

2010年5月中旬,在J.P.Morgan金库,一台全新的适用于大金条称量的电子秤正在作示范。伦敦所有金库的代表见证了这个活动过程。活动结束时,所有参加者都确信这台由赛多利斯研发的新秤,其准确性和准确度等级与短臂天平相当。至今,在伦     

The Course Thicknesses of the Great Pyramid

Eight sets of course thicknesses for the Great Pyramid are combined into one for an improved estimate of each course’s thickness and a smaller standard error than was possible before. It is found that the cubit, palm and finger were used in setting the thicknesses of the courses. Three simple patterns—slopes, ramps and flats—were used when setting the thicknesses along with some exceptions. We do not understand why this was done only that it was. This suggests a higher level of intention during the design process than was previously thought.