A biomechanical approach to iris normalization

The richness of the iris texture and its variability across individuals make it a useful biometric trait for personal authentication. One of the key stages in classical iris recognition is the normalization process, where the annular iris region is mapped to a dimensionless pseudo-polar coordinate system. This process results in a rectangular structure that can be used to compensate for differences in scale and variations in pupil size. Most iris recognition methods in the literature adopt linear sampling in the radial and angular directions when performing iris normalization. In this paper, a biomechanical model of the iris is used to define a novel nonlinear normalization scheme that improves iris recognition accuracy under different degrees of pupil dilation. The proposed biomechanical model is used to predict the radial displacement of any point in the iris at a given dilation level, and this information is incorporated in the normalization process. Experimental results on the WVU pupil light reflex database (WVU-PLR) indicate the efficacy of the proposed technique, especially when matching iris images with large differences in pupil size.

From the genius of man to the man of genius, part two: Inheriting (ideas about) genius

In Part One of ʻFrom the Genius of the Man to the Man of Geniusʼ I argued that classical and medieval inscriptions of genius figures suggest a coevalence between characters in their respective cosmologies, making it relatively more difficult to delineate Man from “spirits” and “other organisms”. The labour that genii performed flowed around two significant tropes of production and reproduction whose specificities were inflected in and across sources. In medieval poetry, for instance, genius figures took up a new role in regard to the reproduction trope, as promoter of virtue (in the form of censuring the seven deadly sins) and condemner of vice (in the form of prohibition against same sex intercourse). The sedimentation (complex processes of character-formation), directionality (patterns of descent) and sexual ecology (emergence of a field of ethics) that the medieval literature embodies also indexes an opening disarticulation of Man from universe and the possibility of grounding “morality” in and as His love choices. Through a series of narrative structures, binary concepts and new sources of authority under Christianity the figure now referred to in philosophy as “the subject” is given early grounds upon which to form in the medieval poems.

Crystal engineering in two dimensions: An approach to molecular nanopatterning

We describe a surprising cooperative adsorption process observed by scanning tunneling microscopy (STM) at the liquid−solid interface. The process involves the association of a threefold hydrogen-bonding unit, trimesic acid (TMA), with straight-chain aliphatic alcohols of varying length (from C7 to C30), which coadsorb on highly oriented pyrolytic graphite (HOPG) to form linear patterns. In certain cases, the known TMA “flower pattern” can coexist temporarily with the linear TMA−alcohol patterns, but it eventually disappears. Time-lapsed STM imaging shows that the evolution of the flower pattern is a classical ripening phenomenon. The periodicity of the linear TMA−alcohol patterns can be modulated by choosing alcohols with appropriate chain lengths, and the precise structure of the patterns depends on the parity of the carbon count in the alkyl chain. Interactions that lead to this odd−even effect are analyzed in detail. The molecular components of the patterns are achiral, yet their association by hydrogen bonding leads to the formation of enantiomeric domains on the surface. The interrelation of these domains and the observation of superperiodic structures (moiré patterns) are rationalized by considering interactions with the underlying graphite surface and within the two-dimensional crystal of the adsorbed molecules. Comparison of the observed two-dimensional structures with the three-dimensional crystal structures of TMA−alcohol complexes determined by X-ray crystallography helps reveal the mechanism of molecular association in these two-component systems.

Modified Stranski–Krastanov growth in Ge/Si heterostructures via nanostenciled pulsed laser deposition

The combination of nanostenciling with pulsed laser deposition (PLD) provides a flexible, fast approach for patterning the growth of Ge on Si. Within each stencilled site, the morphological evolution of the Ge structures with deposition follows a modified Stranski–Krastanov (SK) growth mode. By systematically varying the PLD parameters (laser repetition rate and number of pulses) on two different substrate orientations (111 and 100), we have observed corresponding changes in growth morphology, strain and elemental composition using scanning electron microscopy, atomic force microscopy and μ-Raman spectroscopy. The growth behaviour is well predicted within a classical SK scheme, although the Si(100) growth exhibits significant relaxation and ripening with increasing coverage. Other novel aspects of the growth include the increased thickness of the wetting layer and the kinetic control of Si/Ge intermixing via the PLD repetition rate.

Growth curves with explanatory variables and estimation of the effect of tagging

The von Bertalanffy growth model is extended to incorporate explanatory variables. The generalized model includes the switched growth model and the seasonal growth model as special cases, and can also be used to assess the tagging effect on growth. Distribution-free and consistent estimating functions are constructed for estimation of growth parameters from tag-recapture data in which age at release is unknown. This generalizes the work of James (1991, Biometrics 47 1519-1530) who considered the classical model and allowed for individual variability in growth. A real dataset from barramundi (Lates calcarifer) is analysed to estimate the growth parameters and possible effect of tagging on growth.