Nanometer‐Scale Mapping of Elastic Modules in Biogenic Composites: The Nacre of Mollusk Shells

In this study, a newly developed nanoscale modulus mapping is applied in order to visualize the 2D‐distribution of mechanical characteristics in the aragonitic nacre layer of Perna canaliculus (green mussel) shells. Modulus maps provide lateral resolution of about 10 nm. They allow the aragonitic mineral (CaCO₃) tablets and the interfaces between them to be clearly resolved, which are filled by an organic substance (mainly beta‐chitin). The experimental data are compared with finite element simulations that also take into account the tip radius of curvature and the thickness of organic layers, as measured by means of scanning electron microscopy with back‐scattered electrons. Based on this comparison, the Young modulus of beta‐chitin is extracted. The obtained number, E_β = 40 GPa, is higher than previously evaluated. The collected maps reveal that the elastic modules in the nacre layer change gradually across the ceramic/organic interfaces within a spatial range four times wider than the thickness of the organic layers. This is possibly due to inhomogeneous distribution of organic macromolecules within ceramic tablets. According to the data, the concentration of macromolecules gradually increases when approaching the organic/ceramic interfaces. A behavior of this type is unique to biogenic materials and distinguishes them from synthetic composite materials. Finally, three possible mechanisms that attempt to explain why gradual changes of elastic modules significantly enhance the overall resistance to fracture of the nacre layer are briefly discussed. The experimental findings support the idea that individual ceramic tablets, comprising the nacre, are built of the compositionally and functionally graded ceramic material. This sheds additional light on the origin of the superior mechanical properties of biogenic composites.     

AFM characterization of the structure of Au-colloid monolayers and their chemical etching

Modification of a glass support with triethoxy propylaminosilane yields an active interface for the assembly of Au colloids. The colloids are imaged by AFM using a low applied load (0.5–0.7 nN). The lateral Au-colloid dimensions, 33±3 nm, deviate from the particle dimensions determined by TEM (19±2 nm) and absorption spectroscopy (15 nm). This deviation is attributed to the intrinsic curvature of the AFM tip. Application of higher loads on the tip (3 nN) results in the sweeping of Au colloids from the monolayer. The Au colloid monolayer is etched in the presence of CN⁻. The etching proceeds by the initial coincidental etching of Au particles followed by the kinetically favored etching of particles at the edges of the etched domains. This provides means for the micro machining and the chemical manipulation of Au colloids of controlled spatial arrangement.     

Heat pump assisted distillation. IV: An experimental comparison of R114 and R11 as the working fluid in an external heat pump

An experimental study has been carried out on a continuously operated pilot fractional distillation column equipped with an external heat pump. The distillation column was a 15 cm internal diameter glass unit containing eleven single bubble cap plates. A methanol-water mixture was fed to the column. After operating the heat pumps with R114 as the working fluid, further experiments have been conducted with R11 as the working fluid. Plots of pressure against enthalpy, condensation pressure and latent heat of vaporization against condensation temperature and theoretical Rankine coefficient of performance against gross temperature lift and condensation temperature are presented for both R114 and R11. R11 has correspondingly higher theoretical Rankine coefficients of performance than R114. The experiments show that the actual coefficients are also higher for R11 than for R114. A maximum actual coefficient of performance of 5.3 was obtained using R11 as the working fluid with a gross temperature lift of 38.4°C. The experimental data for R11 were found to be reproducible during operation over a number of weeks. This showed that the relative thermal instability of R11 compared to R114 had not apparently affected the performance of the system.     

Similarity solutions for slender dry patches with thermocapillarity

The lubrication approximation is used to investigate slender dry patches in an infinitely wide film of viscous fluid flowing steadily on an inclined plane that is either heated or cooled relative to the surrounding atmosphere. Four non-isothermal situations in which thermocapillary effects play a significant role are considered.Similarity solutions describing a thermocapillary-driven flow with a dry patch that is widening or narrowing due to either gravitational or surface-tension effects on a non-uniformly heated or cooled substrate are obtained, and examples of these solutions, when the substrate temperature gradient depends on the longitudinal coordinate according to a general power law, are presented. When gravitational effects are strong, the solution contains a free parameter, and for each value of this parameter there is a unique solution representing both a narrowing pendent dry patch and a widening sessile dry patch, whose transverse profile has a monotonically increasing shape. When surface-tension effects are strong, the solution also contains a free parameter, and for each value of this parameter there is both a unique solution representing a narrowing dry patch, whose transverse profile has a monotonically increasing shape, and a one-parameter family of solutions representing a widening dry patch, whose transverse profile has a capillary ridge near the contact line and decays in an oscillatory manner far from it.Similarity solutions are also obtained for both a gravity-driven and a constant-surface-shear-stress-driven flow with a dry patch that is widening or narrowing due to thermocapillarity on a uniformly heated or cooled substrate. The solutions in both cases contain a free parameter, and for each value of this parameter there is a unique solution representing both a narrowing dry patch on a heated substrate and a widening dry patch on a cooled substrate, whose transverse profile has a monotonically increasing shape.     

Temporal generalization of treatment effects over a three-year period for a parent training program: Directive Parental Counseling (DPC).

Assessed the permanence of the treatment effects (temporal generalization) obtained by a parent-training program, Directive Parental Counseling (DPC), developed by the 2nd author (1983). 20 parents who participated in the program completed the Walker Problem Behavior Identification Checklist and the Missouri Children's Behavior Checklist at pretreatment, treatment termination, 3 mo posttreatment, and 3 yrs posttreatment. The parents were part of a larger treatment group of 36 Ss who demonstrated superiority in altering targeted behaviors of their children (mean age 6 yrs 11 mo), in contrast to a waiting-control group, at the completion of a 10-wk program. The positive changes noted on the behavior rating scales obtained from the parents in the treatment group at the posttreatment period were still evident at the 3-mo follow-up and continued to increase over the 3-yr interval. Results are discussed in light of the issues surrounding temporal generalization and the structure of the DPC program. (French abstract) (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heat transfer studies in a climbing film evaporator Part II: Heat transfer regions

There are three sections in an evaporator tube; liquid heating, foam and climbing film. A technique is presented for estimating the lengths of these three sections and the overall heat transfer coefficients in each of them. The lower the liquid feed temperature, the longer the liquid heating length. The length of the foam section does not depend on the liquid feed temperature. In these studies it was estimated to be more than half the length of the evaporator tube. Only at the higher liquid feed temperatures was a climbing film found to exist.     

Narp regulates long-term aversive effects of morphine withdrawal.

Although long-lasting effects of drug withdrawal are thought to play a key role in motivating continued drug use, the mechanisms mediating this type of drug-induced plasticity are unclear. Because Narp is an immediate early gene product that is secreted at synaptic sites and binds to alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, it has been implicated in mediating enduring forms of synaptic plasticity. In previous studies, the authors found that Narp is selectively induced by morphine withdrawal in the extended amygdala, a group of limbic nuclei that mediate aversive behavioral responses. Accordingly, in this study, the authors evaluate whether long-term aversive effects of morphine withdrawal are altered in Narp knockout (KO) mice. The authors found that acute physical signs of morphine withdrawal are unaffected by Narp deletion. However, Narp KO mice acquire and sustain more aversive responses to the environment conditioned with morphine withdrawal than do wild type (WT) controls. Paradoxically, Narp KO mice undergo accelerated extinction of this heightened aversive response. Taken together, these studies suggest that Narp modulates both acquisition and extinction of aversive responses to morphine withdrawal and, therefore, may regulate plasticity processes underlying drug addiction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The AMPTE Charge Composition Explorer Science Data System

The CCE Science Data Center at The Johns Hopkins University Applied Physics Laboratory is a facility that supplies the computing needs of United States science investigators in their support of the AMPTE mission. This well-focused purpose has given the Science Data Center uniqueness and special characteristics in design, implementation, and operations.