Systematic study of the thermal diffusion in associated mixtures

Polyakov, Pavel; Wiegand, Simone

doi:10.1063/1.2819672

Cited by 32 publications

(30 citation statements)

References 40 publications

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“…The change in the slope of curves at different temperatures leads to a common intersection at a weight fraction of 0.13. Such an intersection point is often found for associated mixtures (28).…”

Section: Resultsmentioning

confidence: 99%

Accumulation of formamide in hydrothermal pores to form prebiotic nucleobases

Niether

Afanasenkau

Dhont

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Formamide is one of the important compounds from which prebiotic molecules can be synthesized, provided that its concentration is sufficiently high. For nucleotides and short DNA strands, it has been shown that a high degree of accumulation in hydrothermal pores occurs, so that temperature gradients might play a role in the origin of life [Baaske P, et al. (2007) Proc Natl Acad Sci USA 104(22): 9346−9351]. We show that the same combination of thermophoresis and convection in hydrothermal pores leads to accumulation of formamide up to concentrations where nucleobases are formed. The thermophoretic properties of aqueous formamide solutions are studied by means of Infrared Thermal Diffusion Forced Rayleigh Scattering. These data are used in numerical finite element calculations in hydrothermal pores for various initial concentrations, ambient temperatures, and pore sizes. The high degree of formamide accumulation is due to an unusual temperature and concentration dependence of the thermophoretic behavior of formamide. The accumulation fold in part of the pores increases strongly with increasing aspect ratio of the pores, and saturates to highly concentrated aqueous formamide solutions of ∼85 wt% at large aspect ratios. Time-dependent studies show that these high concentrations are reached after 45-90 d, starting with an initial formamide weight fraction of 10 −3 wt % that is typical for concentrations in shallow lakes on early Earth.concentration problem | hydrothermal vents | molecular evolution | origin-of-life problem | thermophoresis T hermophoresis has been suggested as an active transport mechanism to reach high concentrations of prebiotic molecules to culminate in the formation of RNA (1). A still open question is whether thermophoresis can also be a possible mechanism to form prebiotic nucleobases from simple molecules such as hydrogen cyanide (HCN) and formamide (FA). Already for almost 50 years, FA has been discussed as an important compound from which prebiotic molecules originate (2-7). It has been shown that all known nucleobases can be synthesized from aqueous FA solutions (4). In diluted HCN solutions, polymerization of HCN to form nucleobases becomes favored over hydrolysis of HCN at concentrations of 0.03-0.3 wt % (8). To our knowledge, there are no similar studies of diluted FA solutions. Taking into account the faster hydrolysis of FA (3), we estimated that a 100-timeshigher concentration between 3 wt % and 33 wt % should be sufficient for the synthesis of prebiotic molecules in aqueous solutions. In the ocean during the early stages of Earth, the natural occurring concentrations at a low temperature (10°C) and a pH between 6 and 8 are estimated to be only on the order of 10 −9 wt %, whereas, in shallow lakes (depth 10 m), due to vaporization and FA input from the atmosphere, higher concentrations of about 10 −3 wt % are possible (3). Still, these natural concentrations are far too small compared with those required for the formation of nucleobases.In this work, we perform numerical calculations ...

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Section: Resultsmentioning

confidence: 99%

Accumulation of formamide in hydrothermal pores to form prebiotic nucleobases

Niether

Afanasenkau

Dhont

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…36 Concerning the thermal diffusion coefficient, one can observe that D T increases with increasing temperature. A similar trend has been also found in many systems, for instance, in aqueous suspensions of polystyrene spheres for different sizes of particles, 25 in water and in water/ethanol solutions of polyethylene oxide, 37 and in aqueous solutions of dextran.…”

Section: Influence Of the Temperature And Sugar Concentrationmentioning

confidence: 99%

Thermal Diffusion of Oligosaccharide Solutions: The Role of Chain Length and Structure

et al. 2010

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“…The sample behaves like an optical lens due to the change of refractive index resulting from thermal and compositional gradients. Another important method is the thermal diffusion forced Rayleigh scattering [23][24][25][26] where a grating created by the interference of two laser beams is converted into temperature grating by a chemically inert dye. A periodic temperature field induces periodic field of concentration due to the Soret effect.…”

Section: Introductionmentioning

confidence: 99%

Measurement of the Soret and diffusion coefficients for benchmark binary mixtures by means of digital interferometry

Mialdun

Shevtsova

2011

The Journal of Chemical Physics

102

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We report on the development of the optical digital interferometry (ODI) technique for measuring diffusion and Soret coefficients. The unique feature of this method is that it traces the transient path of the system in the entire two-dimensional cross section of a cell. In this way, it is applicable not only for measurements of Soret coefficients, but also for studying diffusive transport mechanism and convection. Presently, this method is not widely used and, in our view, not because of fundamental limitations but rather due to a lack of properly developed postexperimental procedures of the raw data analysis. Thus, in this paper our attention is focused on the successive analysis of different steps: the fringe analysis, the choice of reference images, the thermal design of the cell, and multiparameter fitting procedure. Using the ODI technique, we have measured the diffusion and the Soret coefficients for three binary mixtures composed of dodecane (C 12 H 26 ), isobutylbenzene, and 1,2,3,4-tetrahydronaphtalene at a mean temperature of 25 • C and 50 wt. % in each component. These measurements were compared with their benchmark values and show an agreement within less than 3%.

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Systematic study of the thermal diffusion in associated mixtures

Cited by 32 publications

References 40 publications

Accumulation of formamide in hydrothermal pores to form prebiotic nucleobases

Accumulation of formamide in hydrothermal pores to form prebiotic nucleobases

Thermal Diffusion of Oligosaccharide Solutions: The Role of Chain Length and Structure

Measurement of the Soret and diffusion coefficients for benchmark binary mixtures by means of digital interferometry

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