Comparisons of the thoracic trauma index with other models

The thoracic trauma index (TTI) provides an indication of the severity of injuries received by motor vehicle occupants in side-impact collision environments. The index was derived from results on two sets of cadaver tests. Using a variety of statistical and numerical methods, the authors reanalyzed the data from these 80+ cadaver tests to construct a better measure of injury than TTI. Indices generated by these analyses were compared with TTI using the following quantitative measures: monotonicity, overlap, percentage correct, and sensitivity. The values of these measures are broadly similar for all indices and none of the new indices consistently performs better than TTI. This suggests that TTI is as good a predictor of injury as any of the several alternative models created.     

INFLUENCE OF INTERFACIAL TENSION AND VISCOSITY ON THE BEHAVIOR OF A PACKED COLUMN IN NEAR-CRITICAL FLUID EXTRACTION

Density and viscosity of the coexisting phases and interfacial tension of the following binary systems were measured: pelargonic acid, linoleic acid, oleic acid or stearic acid as subcritical and carbon dioxide as superecritical components. Also the corresponding phase equilibria were investigated at pressures ranging from 2 to 20 MPa and temperatures from 313 K to 393 K. With increasing pressure the concentration of the supercritical component in the liquid phase increases and viscosity and liquid interfacial tension decreases. At greater activities of the dense gases the interfacial tension decreases dramatically to values less than 2 mN/m. If the pressure exceeds a certain limit, a falling film disintegrates into small droplets. The surface excess passes through a maximum at these conditions. At first appearance of instabilities on a falling film, the logarithm of the Reynolds number is a linear function of the logarithm of the film number. Independent of the type of the investigated packings, the number of theoretical stages per meter versus Hodenstein number fall all on the same curve when an extraction is carried out in the droplet regime. Also the logarithm of the capacity of a column al the flooding point versus the logarithm of the density difference between the coexisting phases is a linear function when an extraction is carried out in the droplet regime.     

Influence of dissolution rate on crack growth and fatigue of Na2O-Al2O3-B2O3 SiO2 glasses

Fracture toughness, macroscopic crack growth and dynamic fatigue of glasses of the system 15Na₂O-4Al₂O₃-xB₂O₃-(81-x)SiO₂ are studied. The fracture toughness as a function of B₂O₃ content correlates to the dependence of elastic modulus which has a maximum between 20 and 30 mol%. The shape of the crack growth curve changes characteristically. Region 1 of the curves normalized toK _Ic is shifted to higher crack growth velocities (smallerK _I/K _Ic values, respectively) for increasing B203 content. The rise of velocity correlates approximately to the dissolution rate of the glasses in water. The determination of the slope in region 1 is problematic, particularly for poorly resistant glasses. The slopen of the crack growth velocity fitted by the power law decreases above 20 mol% B₂O₃ in correspondence with the results of the dynamic fatigue (23 >n > 7). A clear fatigue limit at one fifth of the inert strength occurs in glasses with B₂O₃ content above 20 mol%.     

Use of circular cylinders as surrogates for hexagonal pristine ice crystals in scattering calculations at infrared wavelengths

We investigate the errors associated with the use of circular cylinders as surrogates for hexagonal columns in computing the optical properties of pristine ice crystals at infrared (8-12-microm) wavelengths. The equivalent circular cylinders are specified in terms of volume (V), projected area (A), and volume-to-area ratio that are equal to those of the hexagonal columns. We use the T-matrix method to compute the optical properties of the equivalent circular cylinders. We apply the finite-difference time-domain method to compute the optical properties of hexagonal ice columns smaller than 40 microm. For hexagonal columns larger than 40 microm we employ an improved geometric optics method and a stretched scattering potential technique developed in previous studies to calculate the phase function and the extinction (or absorption) efficiency, respectively. The differences between the results for circular cylinders and hexagonal columns are of the order of a few percent. Thus it is quite reasonable to use a circular cylinder geometry as a surrogate for pristine hexagonal ice columns for scattering calculations at infrared (8-12-microm) wavelengths. Although the pristine ice crystals can be approximated as circular cylinders in scattering calculations at infrared wavelengths, it is shown that optical properties of individual aggregates cannot be well approximated by those of individual finite columns or cylinders.     

Where genetic algorithms excel

We analyze the performance of a genetic algorithm (GA) we call Culling, and a variety of other algorithms, on a problem we refer to as the Additive Search Problem (ASP). We show that the problem of learning the Ising perceptron is reducible to a noisy version of ASP. Noisy ASP is the first problem we are aware of where a genetic-type algorithm bests all known competitors. We generalize ASP to k-ASP to study whether GAs will achieve "implicit parallelism" in a problem with many more schemata. GAs fail to achieve this implicit parallelism, but we describe an algorithm we call Explicitly Parallel Search that succeeds. We also compute the optimal culling point for selective breeding, which turns out to be independent of the fitness function or the population distribution. We also analyze a mean field theoretic algorithm performing similarly to Culling on many problems. These results provide insight into when and how GAs can beat competing methods.     

Microtubule structure studied by quick freezing: Cryo-electron microscopy and freeze fracture

Microtubules have been quickly frozen and examined by electron microscopy using several techniques: (1) freezing of a thin layer of solution by plunging into cryogen, followed by cryo-electron microscopy of the unstained vitrified samples; (2) freezing by the propane-jet method, followed by freeze fracturing and metal replication. The unstained frozen-hydrated microtubules show a structure in agreement with X-ray diffraction data; they differ from negatively stained particles mainly by the better preservation of cylindrical shape. Secondly, they reveal a supertwist of the profilaments that is not detected reliably by other methods. This allows a determination of the number of protofilaments and the polarity. The structural resolution of unstained microtubules is similar to that of stained ones (about 2–3 nm); it is limited by low contrast and lack of crystalline order. Propane-jet or cryo-block freezing followed by freeze fracturing reveals the structures of the inner and outer surfaces of the microtubule wall at a resolution of 4 nm or better. The outside is dominated by the longitudinal protofilaments whereas on the inside one observes tilted cross-striations. Although the freezing temperatures of the two methods are different (liquid nitrogen or helium) they yield similar results for the case of thin layers of protein solution.     

Thermal depolarization currents of regenerated cellulose films

The thermal depolarization current technique is applied to plasticized and unplasticized regenerated cellulose films. In unplasticized cellulose, two depolarization current bands are observed. The band with a current maximum occurring near 298°K (T_m), and with an activation energy, U, of 0.57 eV, is believed to be related to the second-order transition which is known to occur in dry cellulose in the vicinity of 298°K. The second band, with T_m = 215°K and U = 0.26 eV, is also present in the plasticized material, and possibly arises from primary hydroxyl group orientations. In cellulose films plasticized with glycerol, an intense band occurs at 271°K, with U = 0.51 eV, and is attributed to the plasticizer. A third band, occurring in the plasticized material near 300°K, has not been fully investigated.