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A woven aramid (Kevlar®)/polyvinyl butyral phenolic composite that is used in ballistic applications was subjected to a wide variety of characterization and ballistic impact tests. Characterization data obtained under various stress states were used to generate two different models of the composite. The first model utilized a mesoscale modeling approach. Individual Kevlar yarns, the surrounding matrix, and interfaces are all represented with separate finite elements, and each constituent is assigned its own unique material model. The second model utilizes a continuum-level user material subroutine where rules of mixtures to relate stresses and strains within the individual fiber and matrix constituents. Although this material model is much more complex than any of those used in the mesoscale model, the approach allows the composite to be represented in simulations using a simple interconnected finite element mesh. Ballistic tests utilizing various target thicknesses and projectile sizes were also conducted to obtain validation data. Simulations of these tests were conducted using both the mesoscale and continuum models, and the results were compared to velocity and deflection data from the tests. Simulation results suggest that the relatively large void content of the material (~ 11%) has a significant effect on the resulting impact response.

Yucca mountain is being closely studied as a possible repository for high-level radioactive waste. The rock found at the Yucca Mountain site, i.e. Nevada tuff, is, consequently, of immediate interest. Since it is difficult to obtain samples of the actual Nevada tuff the Apache Leap tuff rock, from Arizona, has been chosen as a similar alternative for this study. The Apache rock was tested in compression at low (10- 4s$^{ - 1})$and high (102 -103s$^{ - 1})$strain rates to evaluate its strain rate dependence. Some of the dynamic tests were performed with a pulse shaper. Strain in the sample was measured with strain gages. Numerical simulations of the full Hopkinson Bar with and without pulse shaper were performed with LS-DYNA. These were very useful in understanding interpretation of the experimental results. Both incident and output waves measured in the SHPB compared very well with the waves obtained from LS-DYNA simulations, confirming that the constitutive model used for the rock was a realistic one. The main conclusions from this work are: 1) The SHPB is a reliable method to obtain the constitutive model of the rock at high strain rates. 2) The pulse shaper use is advised but not compulsory to obtain reliable data, 3) the Apache tuff rock is not strongly sensitive to strain rate.

Yucca mountain is being closely studied as a possible repository for high-level radioactive waste. The rock found at the Yucca Mountain site, i.e. Nevada tuff, is, consequently, of immediate interest. Since it is difficult to obtain samples of the actual Nevada tuff the Apache Leap tuff rock, from Arizona, has been chosen as a similar alternative for this study. The Apache rock was tested in compression at low (10 - 4 s - 1) and high (102 -103 s - 1) strain rates to evaluate its strain rate dependence. Some of the dynamic tests were performed with a pulse shaper. Strain in the sample was measured with strain gages. Numerical simulations of the full Hopkinson Bar with and without pulse shaper were performed with LS-DYNA. These were very useful in understanding interpretation of the experimental results. Both incident and output waves measured in the SHPB compared very well with the waves obtained from LS-DYNA simulations, confirming that the constitutive model used for the rock was a realistic one. The main conclusions from this work are: 1) The SHPB is a reliable method to obtain the constitutive model of the rock at high strain rates. 2) The pulse shaper use is advised but not compulsory to obtain reliable data, 3) the Apache tuff rock is not strongly sensitive to strain rate.

The oxidative addition of aryl halides, ArX, to [Ph3P]3CoCH3yield ArAr and ArCH3when Ar = 4-CH3C6H4, but exclusively ArCH3for 1- and 2-bromo-naphthalene and 4-bromobiphenyl. Decomposition of the phosphine ligand in [Ph3P]3CoCH3interfers with these reactions to varying extents depending on the relative rates of the reactions; ArCl mostly gives PhPh with some ArPh and ArAr; ArI gives mostly ArAr; ArBr shows intermediate behaviour. Other cobalt compounds such as [Ph3P]3CoSi[C3]3, [Ph2PCH3]3CoCH3, [Ph2PCH3]3CoPh and [Ph2PGe(CH3)3]3CoCH3and several other organic halides examined show a low activity in the oxidative addition.

Background: The twofold aim of this experimental study was (1) to verify the correlation between the duration of ischemia and concentration of cardiac troponin I and (2) to compare the release of cardiac troponin I with histologic findings. Methods: Experiments were done on 18 rat hearts, which were perfused according to the Langendorff method, immediately after excision in group I (control group) and after immersion for 3 hours (group II) and 6 hours (group III) in St. Thomas' Hospital solution at 4@? C. During reperfusion, the release of cardiac troponin I, creatine kinase isoenzyme MB, and lactate dehydrogenase, the recovery of left ventricular pressure, and heart rates were compared among the three groups. After the experiment, three samples of myocardium (left ventricle, right ventricle, and septum) were taken for histologic examination. Results: Cardiac troponin I concentration was significantly higher in group III than in groups I and II and in group II compared with group I. Cardiac troponin I concentration increased as the ischemic period increased. The relation between cardiac troponin I release and ischemic duration tended to be linear. Creatine kinase MB and lactate dehydrogenase concentrations did not differ from one group to the other. Left ventricular pressure was not significantly different among the groups. In the control group, no heart had more than 10% of the myocytes affected. One of six hearts in group II and three of six in group III had more than 10% of myocytes affected. Conclusion: This experimental study showed (1) that cardiac troponin I is an early marker of ischemic injury and (2) that cardiac troponin I concentration increases as the ischemic period increases. Early cardiac troponin I release appears to correlate with the extent of ischemic injury in rats undergoing buffer perfusion. (J Thorac Cardiovasc Surg 1996;112:508-13)

The interpretation of coronary angiograms is indispensable in determining procedure in coronary surgery. The aim of this study was to measure the overall reliability of a group of surgeons in the interpretation of coronary angiograms, surgical procedure and the evaluation of operative risk. Ten coronary angiograms were interpreted by eight cardiac surgeons at four different medical centers. Evaluation of coding discrepancies, in this case of multiple raters applying an ordinal-scale classification scheme (0, 1, 2) with no expert yardstick available for coding, was explored by a two-way random factor analysis of variance. Reliability was substantial for the assessment of stenosis irrespective of the artery (intraclass correlation coefficient (ICC) ranging from 0.92 to 1), and good for the distal part of the artery (ICC ranging from 0.83 to 0.86) as well as for the collateral provision (ICC ranging from 0.75 to 0.94). Agreement between surgeons was good with respect to the number of bypasses to be performed (ICC = 0.88). The number of bypass per patient varied from 2.6 to 3.2 depending on the surgeon. Agreement as to whether or not to bypass was substantial for the right coronary artery (ICC = 0.92), good for the marginal artery (ICC = 0.87) and fair for the left anterior descending artery (ICC = 0.60) and the circumflex artery (ICC = 0.60). There was a higher rate of agreement concerning inferior wall motion (ICC = 0.98) than of the anterior wall motion (ICC = 0.78). Agreement was substantial for ejection fraction (ICC = 0.93), operative risk (ICC = 0.93) and the type of coronary tree (ICC = 0.85). With respect to the overall set of items, no one surgeon disagreed significantly with the rest of the group. Some disagreement regarding anatomy suitable for revascularization exists between surgeons. Surgical assessment of risk is similar. Cardiac surgeons quickly learn to assess risk in a similar manner, even though they might not always graft the same anatomic vessels or assess regional wall motion similarly.

The National Aeronautics and Space Administration (NASA) Psyche mission will visit the 226‐km diameter main belt asteroid (16) Psyche, our first opportunity to visit a metal‐rich object at close range. The unique and poorly understood nature of Psyche offers a challenge to the mission as we have little understanding of the surface morphology and composition. It is commonly accepted that the main evolutionary process for asteroid surfaces is impact cratering. While a considerable body of literature is available on collisions on rocky/icy objects, less work is available for metallic targets with compositions relevant to Psyche. Here we present a suite of impact experiments performed at the NASA Ames Vertical Gun Range facility on several types of iron meteorites and foundry‐cast ingots that have similar Fe‐Ni compositions as the iron meteorites. Our experiments were designed to better understand crater formation (e.g., size, depth), over a range of impact conditions, including target temperature and composition. We find that the target strength, as inferred from crater sizes, ranges from 700 to 1,300 MPa. Target temperature has measurable effects on strength, with cooled targets typically 10–20% stronger. Crater morphologies are characterized by sharp, raised rims and deep cavities. Further, we derive broad implications for Psyche's collisional evolution, in light of available low resolution shape models. We find that the number of large craters (>50 km) is particularly diagnostic for the overall bulk strength of Psyche. If confirmed, the number of putative large craters may indicate that Psyche's bulk strength is significantly reduced compared to that of intact iron meteorites. Many iron meteorites are thought to be remnants of the cores of melted asteroids. Some cores may have been exposed by collisions during the earliest days of Solar System history, with a few survivors possibly found today in the main asteroid belt. National Aeronautics and Space Administration (NASA) Psyche mission will be the first spacecraft to visit asteroid (16) Psyche, an object thought to be representative of these metallic asteroids. Impacts onto (16) Psyche in the past may therefore be able to tell us about the history and nature of this body. To this end, we performed high‐speed impact experiments into metallic targets in order to understand how crater formation differs from rocky bodies. These experiments revealed that impact craters into metal targets are deeper and have sharper rims than on their rocky counterparts. These results will be crucial for interpreting both the bulk properties of Psyche's interior and the modification of Psyche's surface when the Psyche mission reaches its target. We quantify morphological properties of cratering in metallic targets.We derive implications for the Psyche mission.

2‐Methylnaphthalene (I) is oxidized in acetonitrile/water solution to give 2‐methyl‐1,4‐naphthoquinone (IV) either by bis(tetrabutylammonium) dichromate or ammonium dichromate at slightly elevated temperatures.