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The sound emission pattern and the acoustical role of the noseleaf in the echolocating bat, Carollia perspicillata

Carollia perspicillata (Phyllostomidae) is a frugivorous bat that emits low-intensity, broadband, frequency-modulated echolocation pulses through nostrils surrounded by a noseleaf. The emission pattern of this bat is of interest because the ratio between the nostril spacing and the emitted wavelength varies during the pulse, causing complex interference patterns in the horizontal dimension. Sound pressures around the bat were measured using a movable microphone and were referenced to those at a stationary microphone positioned directly in front of the animal. Interference between the nostrils was confirmed by blocking one nostril, which eliminated sidelobes and minima in the emission pattern, and by comparison of real emission patterns with simple computer models. The positions of minima in the patterns indicate effective nostril spacings of over a half-wavelength. Displacement of the dorsal lancet of the noseleaf demonstrated that this structure directs sound in the vertical dimension.     

Analysis of residual stresses in cylindrically anisotropic materials

Metal-forming operations leave residual stresses in formed parts due to nonuniform deformation occurring during the process. An exact method of determining the longitudinal, radial and circumferential (tangential) residual stresses in axisymmetric specimens was proposed by Mesnager¹ and further developed by Sachs². The boring-out technique can be complemented by a similar procedure in which strains are measured on the inner surface of the tube when material is removed from the outer surface.The work proposed in this paper extends previous analyses of residual stresses to the case where the material exhibits cylindrical elastic anisotropy, i.e., the principal axes of anisotropy correspond to the longitudinal, radial and circum-ferential directions of the tube. In addition, the present analysis considers the case in which a residual-shear stress, developed by twisting the tube about its axis, exists in the tube. When such shearing stresses are present, the principal axes of the residual-stress distribution are not parallel to the principal axes of the tube.     

Folding-controlled assembly of ortho-phenylene-based macrocycles

The self-assembly of foldamers into macrocycles is a simple approach to non-biological higher-order structure. Previous work on the co-assembly of ortho-phenylene foldamers with rod-shaped linkers has shown that folding and self-assembly affect each other; that is, the combination leads to new emergent behavior, such as access to otherwise unfavorable folding states. To this point this relationship has been passive. Here, we demonstrate control of self-assembly by manipulating the foldamers'' conformational energy surfaces. A series of o-phenylene decamers and octamers have been assembled into macrocycles using imine condensation. Product distributions were analyzed by gel-permeation chromatography and molecular geometries extracted from a combination of NMR spectroscopy and computational chemistry. The assembly of o-phenylene decamers functionalized with alkoxy groups or hydrogens gives both [2 + 2] and [3 + 3] macrocycles. The mixture results from a subtle balance of entropic and enthalpic effects in these systems: the smaller [2 + 2] macrocycles are entropically favored but require the oligomer to misfold, whereas a perfectly folded decamer fits well within the larger [3 + 3] macrocycle that is entropically disfavored. Changing the substituents to fluoro groups, however, shifts assembly quantitatively to the [3 + 3] macrocycle products, even though the structural changes are well-removed from the functional groups directly participating in bond formation. The electron-withdrawing groups favor folding in these systems by strengthening arene–arene stacking interactions, increasing the enthalpic penalty to misfolding. The architectural changes are substantial even though the chemical perturbation is small: analogous o-phenylene octamers do not fit within macrocycles when perfectly folded, and quantitatively misfold to give small macrocycles regardless of substitution. Taken together, these results represent both a high level of structural control in structurally complex foldamer systems and the demonstration of large-amplitude structural changes as a consequence of a small structural effects.

The folding propensity of ortho-phenylene foldamers dictates the outcome of their self-assembly into macrocycles.     

Light element profiling using nuclear reaction analysis on tapered corrosion sections

A scanned microbeam has been used to profile tapered corrosion sections of thickness up to 500 μm. The method of beam scanning and data collection is described and selected profiles are presented for the reactions D(³He, p)α,¹²C(d, p)¹³C,¹⁴N(p, α)¹²C and¹⁸O(p, α)¹⁵N. Finally the advantages and limitations of the technique are discussed.     

Biosensor for the specific detection of a single viable B. anthracis spore

A simple membrane strip-based biosensor for the detection of viable B. anthracis spores was developed and combined with a spore germination procedure as well as a nucleic acid amplification reaction to identify as little as one viable B. anthracis spore in less than 12 h. The biosensor is based on identification of a unique mRNA sequence from the anthrax toxin activator (atxA) gene encoded on the toxin plasmid, pXO1. Preliminary work relied on plasmid vectors in both E. coli and B. thuringiensis expressing the atxA gene. Once the principle was firmly established, the vaccine strain of B. anthracis was used. After inducing germination and outgrowth of spores of B. anthracis (Sterne strain), RNA was extracted from lysed cells, amplified using nucleic acid sequence-based amplification (NASBA), and rapidly identified by the biosensor. While the biosensor assay requires only 15-min assay time, the overall process takes 12 h for the detection of as little as one viable B. anthracis spore, and is shortened significantly, if larger amounts of spores are present. The biosensor is based on an oligonucleotide sandwich-hybridization assay format. It uses a membrane flow-through system with an immobilized oligonucleotide probe that hybridizes with the target sequence. Signal amplification is provided when the target sequence hybridizes to a second oligonucleotide probe that has been coupled to dye-encapsulating liposomes. The dye in the liposomes then provides a signal that can be read visually or quantified with a hand-held reflectometer. The biosensor can detect as little as 1.5 fmol of target mRNA. Specificity analysis revealed no crossreactivity with closely related species such as B. cereus, B. megaterium, B. subtilis, B. thuringiensis etc.     

High-performance liquid chromatographic determination of carbamazepine and carbamazepine 10,11-epoxide in plasma and saliva following solid-phase sample extraction

A rapid, sensitive and simple to operate high-performance liquid chromatographic method for the simultaneous determination of carbamazepine (CBZ) and carbamazepine 10,11-epoxide (CBZ-EP) in plasma and saliva is described. The drug and its metabolite are extracted from both plasma and saliva using commercially available reversed-phase octadecylsilane bonded silica columns (Bond-Elut C18, 2.8 ml capacity). Separation of CBZ and CBZ-EP was achieved by reversed-phase chromatography, using a mobile phase consisting of acetonitrile-methanol-water (19:37:44) at a flow-rate of 1.8 ml/min in conjunction with a Nova-Pak C18 column. The analytical column, in Radial-Pak cartridge form, was used in combination with a Z-module RCSS and protected by a Guard-Pak precolumn module containing a Guard-Pak mu Bondapak C18 insert. Using ultraviolet detection at 214 nm, levels in the region of 50-100 ng/ml for CBZ and CBZ-EP can be measured with only 250 and 500 microliters of plasma and saliva, respectively. The method, which has been used to determine steady-state concentrations of the drug and its metabolite in paediatric patients receiving CBZ monotherapy, is also suitable for pharmacokinetic studies.     

The Grammar of Platonism

In this paper, based on a critical analysis of ideas of Frege, Quine and Prior, we show how Lambda Calculus and Hilbert’s Epsilon Calculus are useful to give us a good understanding of Platonic objects.