Experimentally tracing the key steps in the origin of life: The aromatic world

Life is generally believed to emerge on Earth, to be at least functionally similar to life as we know it today, and to be much simpler than modern life. Although minimal life is notoriously difficult to define, a molecular system can be considered alive if it turns resources into building blocks, replicates, and evolves. Primitive life may have consisted of a compartmentalized genetic system coupled with an energy-harvesting mechanism. How prebiotic building blocks self-assemble and transform themselves into a minimal living system can be broken into two questions: (1) How can prebiotic building blocks form containers, metabolic networks, and informational polymers? (2) How can these three components cooperatively organize to form a protocell that satisfies the minimal requirements for a living system? The functional integration of these components is a difficult puzzle that requires cooperation among all the aspects of protocell assembly: starting material, reaction mechanisms, thermodynamics, and the integration of the inheritance, metabolism, and container functionalities. Protocells may have been self-assembled from components different from those used in modern biochemistry. We propose that assemblies based on aromatic hydrocarbons may have been the most abundant flexible and stable organic materials on the primitive Earth and discuss their possible integration into a minimal life form. In this paper we attempt to combine current knowledge of the composition of prebiotic organic material of extraterrestrial and terrestrial origin, and put these in the context of possible prebiotic scenarios. We also describe laboratory experiments that might help clarify the transition from nonliving to living matter using aromatic material. This paper presents an interdisciplinary approach to interface state of the art knowledge in astrochemistry, prebiotic chemistry, and artificial life research.     

Spectral Energy Requirements and Adjacent-Channel Crosstalk in CAS

Four-frequency channels avoid the prior slot interference that handicaps single-frequency collision avoidance systems of equal message-slot capacity. Crosstalk between adjacent frequency channels is adequately limited If the receiver response to adjacent-channel signals is attenuated at least 52 dB. With 5-MHz channel separation, 48-dB crosstalk rejection was achieved in a test receiver by restricting the RF pulse rise time and decay time to 0.2 ?s minimum. Crosstalk resulting from biphase modulation can be effectively attenuated by limiting the minimum envelope transition time to 0.2 ?s. The effect of pulse rise time and decay time on the energy density spectrum is discussed.