Origins Of Heterospory And The Seed Habit: The Role Of Heterochrony

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149713/1/tax04577.pd

Neuro-cognitive mechanisms of conscious and unconscious visual perception: From a plethora of phenomena to general principles

Psychological and neuroscience approaches have promoted much progress in elucidating the cognitive and neural mechanisms that underlie phenomenal visual awareness during the last decades. In this article, we provide an overview of the latest research investigating important phenomena in conscious and unconscious vision. We identify general principles to characterize conscious and unconscious visual perception, which may serve as important building blocks for a unified model to explain the plethora of findings. We argue that in particular the integration of principles from both conscious and unconscious vision is advantageous and provides critical constraints for developing adequate theoretical models. Based on the principles identified in our review, we outline essential components of a unified model of conscious and unconscious visual perception. We propose that awareness refers to consolidated visual representations, which are accessible to the entire brain and therefore globally available. However, visual awareness not only depends on consolidation within the visual system, but is additionally the result of a post-sensory gating process, which is mediated by higher-level cognitive control mechanisms. We further propose that amplification of visual representations by attentional sensitization is not exclusive to the domain of conscious perception, but also applies to visual stimuli, which remain unconscious. Conscious and unconscious processing modes are highly interdependent with influences in both directions. We therefore argue that exactly this interdependence renders a unified model of conscious and unconscious visual perception valuable. Computational modeling jointly with focused experimental research could lead to a better understanding of the plethora of empirical phenomena in consciousness research

Tackling antibiotic resistance: the environmental framework

Antibiotic resistance is a threat to human and animal health worldwide, and key measures are required to reduce the risks posed by antibiotic resistance genes that occur in the environment. These measures include the identification of critical points of control, the development of reliable surveillance and risk assessment procedures, and the implementation of technological solutions that can prevent environmental contamination with antibiotic resistant bacteria and genes. In this Opinion article, we discuss the main knowledge gaps, the future research needs and the policy and management options that should be prioritized to tackle antibiotic resistance in the environment

The thermal polymerization of amino acids revisited; Synthesis and structural characterization of hyperbranched polymers from L-lysine

This contribution reports on the synthesis of hyperbranched polylysines via thermal polymerization of L-lysine hydrochloride. Polymerization of L-lysine hydrochloride in the presence of one equivalent KOH at 150°C resulted in polymers with a number-average molecular weight of 4600 g/mol and a polydispersity of 2.6 after 48 h. The rate of polymerization could be significantly enhanced and the polymer molecular weight improved by carrying out the polymerization with 3 mol % of an amidation catalyst. Among the different catalysts that were investigated Zr(OnBu)4 was found to be the most effective. Unequivocal support for the branched architecture of the polymers was obtained from 1H NMR spectroscopy, which allowed the identification and quantification of the four different structural units that constitute the polymer, viz. Nα and Nε linked linear units, dendritic units and terminal units. The structure of the polymers was found to be relatively independent of the reaction conditions. The degree of branching and the average number of branches varied between 0.35-0.45 and 0.15-0.25, respectively. © 2007 Wiley Periodicals, Inc

Controlling polymer architecture in the thermal hyperbranched polymerization of L-lysine

Because of the unequal reactivity of the two amine groups of L-lysine hydrochloride, thermal polymerization of this asymmetrical AB2 monomer results in hyperbranched polymers, which contain ?2.5 times more N?-linked linear compared to N?-linked linear structural units. This report discusses the feasibility of three approaches to control polymer architecture during the thermal hyperbranched polymerization of L-lysine hydrochloride. The reactivity of the more reactive ?-NH 2 group was modulated by introducing temporary protective groups that preferentially block the ?-NH2 position. This was achieved by (i) addition of o-vanillin to the polymerization, (ii) copolymerization of N?-benzylidene-L-lysine, and (iii) copolymerization of ?-amino-?-caprolactam. Analysis of the degree of branching (DB) and the average number of branches (ANB) of the obtained polymers did not provide evidence for any significant structural changes. Analysis of the distribution of structural units, in contrast, revealed major structural changes and indicated a rearrangement from N?-linked linear structural units to N ?-linked linear structural units upon addition of o-vanillin and N?-benzylidene-L-lysine. Unlike o-vanillin and N ?-benzylidene-L-lysine, ?-amino-?-caprolactam was found to be rather ineffective in modulating polymer architecture. © 2007 American Chemical Society