The depth profiling of TiO2 pigmented coil coatings using step scan phase modulation photoacoustic FTIR

The depth distribution of a TiO₂ pigment within the polyurethane (PU) coil coatings is investigated using step scan phase modulation photoacoustic (SS-PM-PA) FTIR. Coil coatings with different pigment contents were prepared and the modulation frequency (MF) of the SS-PM-PA FTIR varied to record the depth distribution of the pigment within the coating. The TiO₂ pigment was shown to contribute significantly to the SS-PM-PA FTIR signal. A TiO₂ aggregated region within the topcoat is found close to the topcoat-primer interface and further away from the topcoat surface. A deeper TiO₂ aggregated region can be identified when pigment content is relatively low. The SS-PM-PA FTIR signal shows a considerable contribution from the primer originated signal, provided the TiO₂ pigment content is sufficiently high and the modulation frequency applied is relatively low. SEM cross-section imaging results show a strong correlation of the TiO₂ depth distribution with SS-PM-PA FTIR results, which confirms the applicability of the SS-PM-PA FTIR technique to the depth profiling study of TiO₂ pigmented coil coatings.     

Chemistry of Leichhardt's Grasshopper, Petasida ephippigera, and its Host Plants, Pityrodia jamesii, P. ternifolia, and P. pungens

Investigation of the strikingly aposematic Leichhardt's grasshopper revealed a number of host-plant-derived components. Chemical study of the three known host plants revealed a diverse array of components. Pityrodia ternifolia and P. pungens contain predominantly sesquiterpenes and sesquiterpene glycosides and P. jamesii is rich in cineole, dihydrochalcones, chalcones, and monoterpene glycosides. Feces from grasshoppers feeding on P. jamesii contain a mixture of hydroxycineoles, of which 3-hydroxycineole is the predominant isomer (68%). No evidence for previously suspected "alkaloidal" toxins was found in either the insect or host plant.     

REVLD: A coarse-grained model for polymers

A new model for polymers is presented. REVLD (Rigid, Excluded Volume, Langevin Dynamics) is similar to the coarse-grained, bead spring model for linear chains except that the inter-bead distance is rigidly constrained instead of using an inter-bead potential to encapsulate the connectivity. Static and dynamic results support that REVLD accurately reproduces the single-chain behavior of real polymers known from experiment, theory, and published data from existing models. Additionally, a time step can be used that is at least comparable to simulations using a FENE potential without introducing any computational overhead for accessing longer time scale modes. REVLD, and more simply the idea of using constraints in Cartesian coordinates for large simulations, was made computationally viable through the recent development of the algorithm MILC SHAKE. We expect it to improve established techniques and aid in the development of new models of import to large scale simulations that were not practicable before.     

On Refinement-Closed Security Properties and Nondeterministic Compositions

Refinement-closed security properties allow the verification of systems for all possible implementations. Some systems, however, have refinements that do not represent possible implementations. In particular, real instantiations of abstract systems comprising security-critical components surrounded by maximally hostile unrefined components are often characterised only by compositions of refinements of the abstract system's components, rather than all refinements of the abstract system. In this case, refinement-closed security properties that examine multiple behaviours of a system at once can be falsely violated by the presence of inconsistent pairs of behaviour arising from different, incompatible refinements of the system's components.We show how to weaken a class of such properties, which includes both information flow and causation properties, to allow them to be applied to these sorts of abstract systems. The weakened properties ignore all pairs of inconsistent behaviour that would have violated the original property from which they are derived. We also show how to adapt existing automated tests for these properties to allow them to be used to test for their weakened counterparts instead. This enables greater flexibility in the application of these sorts of properties to compositions of nondeterministic components.     

Experimental automobile-pedestrian injuries

Fifteen fresh cadaver impacts were conducted in simulation of pedestrian-automobile accidents. The test sled configuration simulated an automobile bumper and hood in "standard" and "nosedive" situations as well as "hard" and "soft" impact surfaces. Instrumentation and film demonstrated large axial compression forces in the struck leg and considerable angular velocity of the torso in all modes. Dissection revealed primary injury at the impact site at low velocities with added remote injury at high velocities. Fracture of the lateral tibial plateau was most common. Lowering the bumper height offered the greatest protection against injury at moderate impact velocities.     

Autoantibodies to the insulin receptor. Effect on the insulin-receptor interaction in IM-9 lymphocytes

The serum of some patients with insulin-resistant "diabetes" contains antibodies that bind to and block the cell membrane receptors for insulin. In this report, we have characterized the effects of the antireceptor antibodies on the interaction of (125)I-insulin with its receptor on the human lymphoblastoid cell line IM-9. Up to 95% of specific insulin binding can be inhibited by pretreatment of the cells with these immunoglobulins. The onset of the inhibitory effect is time- and temperature-dependent, and the effect is reversed extremely slowly if the cells are suspended in a large excess of antibody-free buffer. These features of antibody binding can be easily distinguished from those for insulin binding to its receptor. The inhibitory effect of the antibodies can be reversed by exposure of the cells to conditions known to elute surface immunoglobulins. The three antireceptor sera studied appear to alter the insulin-receptor interaction in different ways. Two antisera markedly reduce receptor affinity through combined effects on the insulin association and dissociation rates, and, additionally, have smaller effects on available receptor number. A third antiserum primarily affects available receptor number and has little effect on receptor affinity. All three antisera inhibit the capacity of insulin to promote negatively cooperative site-site interactions among insulin receptors. The data suggest that these autoantibodies to the insulin receptor bind to different determinants on the receptor and may therefore be useful as unique probes of insulin receptor structure and function.     

Cholesterol-dependent human complement activation resulting in damage to liposomal model membranes

Human (but not guinea pig) complement-mediated damage. It was concluded that human complement was activated spontaneously by liposomes containing a high concentration (71 mol %) of cholesterol. This occurred in the absence of any recognizable antigen or antibody, and did not occur at a low concentration (43 mol %) of cholesterol. Activation of complement resulted in membrane damage and release of trapped liposomal glucose. The complement activity was inhibited by preheating (56 degrees C, 30 min), 10 mM Mg2EDTA3 or EGTA, and by prior adsorption with insoluble immune complexes. Almost all human sera had some reactivity, but it ranged from very low levels (less than 7% liposomal glucose release) to very high levels (greater than 50% glucose release). Complement activation appeared to be mediated by a serum factor which could be removed by adsorption and which was partially heat labile. The factor was transferred by adding heated high reacting human serum to unheated low reacting human serum, or to guinea pig serum. The serum factor, although quantitatively diminished in potency due to heat lability, caused equal activation of each of these two latter complement sources in the presence of high cholesterol liposomes. It did not cause activation of C4-deficient guinea pig complement. These data suggested that the classical complement pathway was activated. The liposomal membrane composition had an influence on this phenomenon. Activities of about half of the human sera were enhanced when galactosyl ceramide, or ceramide alone, was present in the liposomes. Activity was enhanced by longer fatty acyl chain lengths of lecithin when dimyristoyl-, dipalmitoyl-, or distearoyllecithin was employed in the liposomes. Liposomes containing sphingomyelin as the only phospholipid were not sensitive to cholesterol-dependent complement-mediated damage. It was concluded that human complement was activated in the presence of high concentrations of membrane cholesterol and that this was caused by an uncharacterized serum factor and was influenced by the lipid composition of the membrane.