Fiber Strength After Grain Growth in Nextel™ 610 Alumina Fiber

Nextel^? 610 alumina fiber tows were heat‐treated at 1100°C–1500°C for 1 to 100 h in air. Tensile strengths and Weibull moduli were measured for 30 filaments after each heat‐treatment. 3‐D grain size and orientation distributions were described using oblate ellipsoids. The number of grains in a 1 inch gauge length and grains with the largest major and minor ellipsoid‐axes were determined from these distributions. The grain with the largest K_EFF for mixed‐mode fracture was also determined, using the maximum energy release rate criteria from grain‐size and orientation distributions. Grain‐size dependence of tensile strength and Weibull modulus was evaluated. Strength had no obvious dependence on grain size for fibers with average major‐axes smaller than 0.25 μm. For fibers with larger grains, grain‐size dependence may involve flaws originating from clumps of grains, rather than a single grain. Possible relationships between strength and grain‐size and other causes of strength degradation after heat‐treatment are discussed.     

Contaminant blubber burdens in Atlantic bottlenose dolphins (Tursiops truncatus) from two southeastern US estuarine areas: Concentrations and patterns of PCBs, pesticides, PBDEs, PFCs, and PAHs

Polychlorinated biphenyls (PCBs), chlorinated pesticides (i.e., dichlorodiphenyltrichloroethane (DDT) and its metabolites, chlordanes (CHLs), dieldrin, hexachlorobenzene (HCB), and mirex), polybrominated diphenyl ethers (PBDEs), perfluorinated chemicals (PFCs), and polyaromatic hydrocarbons (PAHs) were measured in blubber biopsy samples collected from 139 wild bottlenose dolphins (Tursiops truncatus) during 2003-2005 in Charleston (CHS), SC and the Indian River Lagoon (IRL), FL. Dolphins accumulated a similar suite of contaminants with ∑ PCB dominating (CHS 64%, IRL 72%), followed by ∑ DDT (CHS 20%, IRL 17%), ∑ CHLs (CHS 7%; IRL 7%), ∑ PBDE (CHS 4%, IRL 2%), PAH at 2%, and dieldrin, PFCs and mirex each 1% or less. Together ∑ PCB and ∑ DDT concentrations contributed ∼ 87% of the total POCs measured in blubber of adult males. ∑ PCBs in adult male dolphins exceed the established PCB threshold of 17 mg/kg by a 5-fold order of magnitude with a 15-fold increase for many animals; 88% of the dolphins exceed this threshold. For male dolphins, CHS (93,980 ng/g lipid) had a higher ∑ PCBs geomean compared to the IRL (79,752 ng/g lipid) although not statistically different. In adult males, the PBDE geometric mean concentration was significantly higher in CHS (5920 ng/g lipid) than the IRL (1487 ng/g). Blubber ∑ PFCs concentrations were significantly higher in CHS dolphins. In addition to differences in concentration of PCB congeners, ∑ PBDE, TEQ, ∑ CHLs, mirex, dieldrin, and the ratios ∑ DDE/∑DDT and trans-nonachlor/cis-nonachlor were the most informative for discriminating contaminant loads in these two dolphin populations. Collectively, the current ∑ PCB, ∑ DDT, and ∑ PBDEs blubber concentrations found in CHS dolphins are among the highest reported values in marine mammals. Both dolphin populations, particularly those in CHS, carry a suite of organic chemicals at or above the level where adverse effects have been reported in wildlife, humans, and laboratory animals warranting further examination of the potential adverse effects of these exposures.     

Determination of 3‐D Alumina Grain Orientation,Size, Shape,and Growth Kinetics from 2‐D Data in Nextel™ 610 Fibers

Nextel^? 610 alumina fibers were heat‐treated at 1100°C–1500°C for 1–100 h in air. Grain size distributions (GSDs) and grain orientation distributions (ODs) with respect to the fiber axis were characterized by analysis of TEM images from longitudinal fiber sections. The 2‐D GSDs and ODs were characterized as ellipses. 3‐D GSDs and ODs were calculated by fitting distributions of oriented oblate ellipsoids to 2‐D GSDs and ODs formed by ellipsoid–section‐plane intersections. The standard deviations (SDs) of log‐normal GSDs consistently increased with grain size, which is not diagnostic of normal grain growth. The grain aspect ratio (α) and the tendency of the short grain axis to orient perpendicular to the fiber axis also increased with grain size, resulting in more textured fibers at larger grain sizes. Average 3‐D grain sizes were larger than 2‐D sizes for GSDs with small SDs, but smaller for GSDs with large SDs because of under sampling of small grains. 3‐D grain growth kinetics had the same 815 kJ/mol activation energy as that found by 2‐D analysis, but the grain growth exponent m of 6.0 was larger and the pre‐exponential factor much smaller. Expressions for 3‐D log‐normal GSDs as a function of heat treatment temperature and time were determined. α‐distributions and ODs were determined as a function of grain size. Methods for determining 3‐D GSDs are discussed.     

EFFICIENCY OF A CONTROLLED-CYCLE EXTRACTOR

Experimental studies were performed with a 4.0 in. (10.2 cm.) diameter extraction column containing ten dualflow type trays and operated in a controlled cycling mode. The systems methyl isobutyl ketone/acetic acid/water and toluene/acetone/water were used. The overall stage efficiency was found to be a function of the ratio of the volume of a phase transferred during a cycle to the volume of that phase held up on the tray, of the feed-to-solvent ratio, and of the phase throughput rates. A non-equilibrium model was developed to represent the experimental data. For the HIBK/acetic acid/water system, overall stage efficiencies were in the range of 30 to 38 percent, corresponding to HETS values of 0.46 to 0.55 meters. For the toluene/acetone/water system, overall stage efficiencies were in the range of 20 to 31 percent, corresponding to HETS values of 0.55 to 0.95 meters.     

A comparison of semen diluents on the in vitro and in vivo fertility of liquid bull semen

The aim of this study was to assess the effect of semen diluent on calving rate (CR) following artificial insemination with liquid bull semen stored for up to 3 d postcollection. In experiment 1, the effect of storing liquid semen maintained at a constant ambient temperature in 1 of 7 different diluents [Caprogen (homemade), OptiXcell, BioXcell, BullXcell, INRA96, NutriXcell, or AndroMed (all commercially available)] on total and progressive motility was assessed on d 0, 1, 2, and 3 postcollection. In experiment 2, the field fertility of liquid semen diluted in Caprogen, BioXcell, or INRA96 and inseminated on d 1, 2, or 3 postcollection was assessed in comparison to frozen-thawed semen (total of n = 19,126 inseminations). In experiment 3, the effect of storage temperature fluctuations (4 and 18°C) on total and progressive motility following dilution in Caprogen, BioXcell, and INRA96 was assessed on d 0, 1, 2, and 3 postcollection. In experiment 1, semen stored in Caprogen, BioXcell, and INRA96 resulted in the highest total and progressive motility on d 1, 2, and 3 of storage compared with OptiXcell, BullXcell, NutriXcell, and AndroMed. In experiment 2, an effect of diluent on CR was found as semen diluted in BioXcell had a lower CR on d 1, 2, and 3 of storage (46.3, 35.4, and 34.0%, respectively) in comparison with Caprogen (55.8, 52.0, and 51.9%, respectively), INRA96 (55.0, 55.1, and 52.2%, respectively), and frozen-thawed semen (59.7%). Effects were found of parity, cow fertility sub-index, as well as the number of days in milk on CR. In experiment 3, when the storage temperature of diluted semen fluctuated between 4 and 18°C, to mimic what occurs in the field (nighttime vs. daytime), BioXcell had the lowest total and progressive motility in comparison to Caprogen and INRA96. In conclusion, diluent significantly affected sperm motility when stored for up to 3 d. Semen diluted in INRA96 resulted in a similar CR to semen diluted in Caprogen and to frozen-thawed semen, whereas that diluted in BioXcell resulted in a decreased CR. Consistent with this finding, semen diluted in BioXcell was less tolerant of temperature fluctuations than that stored in Caprogen or INRA96. Given that it can be used directly off the shelf, INRA96 may be a suitable alternative to Caprogen for the storage of liquid bull semen.     

THE EFFECT OF RESIDUAL STRESSES INDUCED BY SHOT-PEENING ON FATIGUE CRACK PROPAGATION IN TWO HIGH STRENGTH ALUMINIUM ALLOYS

Abstract— The crack initiation lives of peened specimens of aluminium alloys 7010 and 8090 are shorter than those of unpeened specimens. This is caused by the acceleration of crack initiation due to stress concentration in the rough peened surface, especially at fold-like defects. The crack growth rate in peened specimens is significantly reduced with increasing Δ K , i.e. with increasing crack length. At a crack length of approximately 0.3 mm this trend is reversed and the crack growth rate rapidly increases and attains the same level of crack growth rate as that in unpeened specimens. The point of smallest crack growth rate roughly corresponds to the point of maximum residual stress. The crack growth rate in a peened specimen has been modelled by assuming the effect of residual stress reduces to the equivalent stress ratio. The predicted results agree well with the experimental data.     

High-order spectral- multimode codes

A new class of codes with high-order spectral s at zero frequency is introduced. The codes, called high-order spectral- multimode codes, are constructed through state-dependent encoding by use of the guided-scrambling coding technique, and result in efficiently coded sequences with good low-frequency characteristics.     

A performance metric for codes with a high-order spectral at zero frequency

Sum-variance is a well-known metric for assessing the performance of dc-free codes (first-order spectral- codes), however, as we show in this paper, it is unsuitable for comparing the magnitude of spectral components of high-order spectral- (HOSN) codes at low frequencies. In this paper, we introduce a new performance metric for evaluating the spectrum compression of arbitrarily HOSN codes around zero frequency; we call this metric the low-frequency spectrum weight (LFSW). We show that the asymptotic low-frequency spectral components of Kth-order spectral- codes (K/spl ges/1) are exclusively determined by the order K and the LFSW, and that the LFSW equals the zero-frequency value in the spectrum of the corresponding sequence of Kth-order running digital sum values. We derive this result for symbol-by-symbol encoding, and then extend it to block HOSN codes. We then derive a closed-form expression for the LFSW of HOSN codes constructed through state-independent encoding. Closed-form expressions for LFSW of first-order zero-disparity codes and for the asymptotic LSFW of maxentropic dc-free sequences are also given.