Toward living nanomachines

2018 ◽  
Author(s):  
Christof Mast ◽  
Friederike Möller ◽  
Moritz Kreysing ◽  
Severin Schink ◽  
Benedikt Obermayer ◽  
...  
Keyword(s):  
Molecular Evolution ◽  
Thermal Gradient ◽  
Molecular Level ◽  
Minimal System ◽  
Thermal Gradients ◽  
Temperature Oscillations ◽  
Fluid Convection ◽  
Inanimate Matter ◽  
High Concentrations ◽  
Periodic Temperature

How does inanimate matter become transformed into animate matter? Living systems evolve by replication and selection at the molecular level and this chapter considers how to establish a synthetic, minimal system that can support molecular evolution and thus life. Molecular evolution cannot be explained by starting with high concentrations of activated chemicals that react toward their chemical equilibrium; persistent non-equilibria are required to maintain continuous reactivity and we especially consider thermal gradients as an early driving force for Darwinian molecular evolution. The temperature difference across water-filled compartments implements a laminar fluid convection with periodic temperature oscillations that allow for the melting and replication of DNA. Simultaneously, dissolved molecules are moved along the thermal gradient by an effect called thermophoresis. The combined result is an efficient molecule trap that exponentially favors long over short DNA and thus maintains complexity. Future experiments will reveal how thermal gradients could actively drive the Darwinian process of replication and selection.

THERMAL SOLUTIONS FOR MOLECULAR EVOLUTION

2012 ◽  
Vol 26 (32) ◽  
pp. 1230017 ◽  
Author(s):  
CHRISTOF B. MAST ◽  
NATAN OSTERMAN ◽  
DIETER BRAUN
Keyword(s):  
Molecular Evolution ◽  
Thermal Gradient ◽  
Soret Effect ◽  
Convection Flow ◽  
Thermal Gradients ◽  
Temperature Oscillations ◽  
The Origin Of Life ◽  
High Concentrations ◽  
The One ◽  
Further Development

The key requirement to solve the origin of life puzzle are disequilibrium conditions. Early molecular evolution cannot be explained by initial high concentrations of energetic chemicals since they would just react towards their chemical equilibrium allowing no further development. We argue here that persistent disequilibria are needed to increase complexity during molecular evolution. We propose thermal gradients as the disequilibrium setting which drove Darwinian molecular evolution. On the one hand the thermal gradient gives rise to laminar thermal convection flow with highly regular temperature oscillations that allow melting and replication of DNA. On the other hand molecules move along the thermal gradient, a mechanism termed Soret effect or thermophoresis. Inside a long chamber a combination of the convection flow and thermophoresis leads to a very efficient accumulation of molecules. Short DNA is concentrated thousand-fold, whereas longer DNA is exponentially better accumulated. We demonstrated both scenarios in the same micrometer-sized setting. Forthcoming experiments will reveal how replication and accumulation of DNA in a system, driven only by a thermal gradient, could create a Darwinian process of replication and selection.

Fission Gas Bubbles in Fractured UO2

1968 ◽  
Vol 26 ◽  
pp. 286-287
Author(s):  
O. M. Katz
Keyword(s):  
Electron Microscopy ◽  
Thermal Gradient ◽  
Gas Bubbles ◽  
Inert Gas ◽  
Thermal Gradients ◽  
Fission Gas ◽  
Beam Heating ◽  
Limited Application ◽  
Bubble Characteristics ◽  
Electron Beam Heating

The swelling of irradiated UO2 has been attributed to the migration and agglomeration of fission gas bubbles in a thermal gradient. High temperatures and thermal gradients obtained by electron beam heating simulate reactor behavior and lead to the postulation of swelling mechanisms. Although electron microscopy studies have been reported on UO2, two experimental procedures have limited application of the results: irradiation was achieved either with a stream of inert gas ions without fission or at depletions less than 2 x 1020 fissions/cm3 (∼3/4 at % burnup). This study was not limited either of these conditions and reports on the bubble characteristics observed by transmission and fractographic electron microscopy in high density (96% theoretical) UO2 irradiated between 3.5 and 31.3 x 1020 fissions/cm3 at temperatures below l600°F. Preliminary results from replicas of the as-polished and etched surfaces of these samples were published.

A Theoretical Study of the Temperature Gradient Effect on the Soret Coefficient in n-Pentane/n-Decane Mixtures Using Non-Equilibrium Molecular Dynamics

2020 ◽  
Vol 45 (4) ◽  
pp. 319-332
Author(s):  
Xiaoyu Chen ◽  
Ruquan Liang ◽  
Yong Wang ◽  
Ziqi Xia ◽  
Lichun Wu ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Temperature Gradient ◽  
Thermal Gradient ◽  
Linear Response ◽  
Theoretical Study ◽  
Soret Coefficient ◽  
Thermal Gradients ◽  
Gradient Effect ◽  
Non Equilibrium Molecular Dynamics ◽  
Non Equilibrium

AbstractThe effect of the temperature gradient on the Soret coefficient in n-pentane/n-decane (n-C5/n-C10) mixtures was investigated using non-equilibrium molecular dynamics (NEMD) with the heat exchange (eHEX) algorithm. n-Pentane/n-decane mixtures with three different compositions (0.25, 0.5, and 0.75 mole fractions, respectively) and the TraPPE-UA force field were used in computing the Soret coefficient ({S_{T}}) at 300 K and 1 atm. Added/removed heat quantities (ΔQ) of 0.002, 0.004, 0.006, 0.008, and 0.01 kcal/mol were employed in eHEX processes in order to study the effect of different thermal gradients on the Soret coefficient. Moreover, a phenomenological description was applied to discuss the mechanism of this effect. Present results show that the Soret coefficient values firstly fluctuate violently and then become increasingly stable with increasing ΔQ (especially in the mixture with a mole fraction of 0.75), which means that ΔQ has a smaller effect on the Soret coefficient when the temperature gradient is higher than a certain thermal gradient. Thus, a high temperature gradient is recommended for calculating the Soret coefficient under the conditions that a linear response and constant phase are ensured in the system. In addition, the simulated Soret coefficient obtained at the highest ΔQ within three different compositions is in great agreement with experimental data.

scholarly journals Changes in Quinone Profiles of Hot Spring Microbial Mats with a Thermal Gradient

1999 ◽  
Vol 65 (1) ◽  
pp. 198-205 ◽  
Author(s):  
Akira Hiraishi ◽  
Taichi Umezawa ◽  
Hiroyuki Yamamoto ◽  
Kenji Kato ◽  
Yonosuke Maki
Keyword(s):  
Thermal Gradient ◽  
Microbial Mats ◽  
Hot Springs ◽  
Hot Spring ◽  
Thermal Gradients ◽  
Cyanobacterial Mats ◽  
Dissimilarity Index ◽  
Quinone Profile ◽  
Bacterial Mats ◽  
Different Temperatures

ABSTRACT The respiratory and photosynthetic quinones of microbial mats which occurred in Japanese sulfide-containing neutral-pH hot springs at different temperatures were analyzed by spectrochromatography and mass spectrometry. All of the microbial mats that developed at high temperatures (temperatures above 68°C) were so-called sulfur-turf bacterial mats and produced methionaquinones (MTKs) as the major quinones. A 78°C hot spring sediment had a similar quinone profile.Chloroflexus-mixed mats occurred at temperatures of 61 to 65°C and contained menaquinone 10 (MK-10) as the major component together with significant amounts of either MTKs or plastoquinone 9 (PQ-9). The sunlight-exposed biomats growing at temperatures of 45 to 56°C were all cyanobacterial mats, in which the photosynthetic quinones (PQ-9 and phylloquinone) predominated and MK-10 was the next most abundant component in most cases. Ubiquinones (UQs) were not found or were detected in only small amounts in the biomats growing at temperatures of 50°C and above, whereas the majority of the quinones of a purple photosynthetic mat growing at 34°C were UQs. A numerical analysis of the quinone profiles was performed by using the following three parameters: dissimilarity index (D), microbial divergence index (MDq ), and bioenergetic divergence index (BDq ). A D matrix tree analysis showed that the hot spring mats consisting of the sulfur-turf bacteria, Chloroflexus spp., cyanobacteria, and purple phototrophic bacteria formed distinct clusters. Analyses ofMDq and BDq values indicated that the microbial diversity of hot spring mats decreased as the temperature of the environment increased. The changes in quinone profiles and physiological types of microbial mats in hot springs with thermal gradients are discussed from evolutionary viewpoints.

The reaction of the psoralens with deoxyribonucleic acid

1984 ◽  
Vol 17 (1) ◽  
pp. 1-44 ◽  
Author(s):  
John E. Hearst ◽  
Stephen T. Isaacs ◽  
David Kanne ◽  
Henry Rapoport ◽  
Kenneth Straub
Keyword(s):  
Natural Selection ◽  
Nucleic Acid ◽  
Nucleic Acids ◽  
Chemical Modification ◽  
Deoxyribonucleic Acid ◽  
Molecular Level ◽  
Virus Particles ◽  
Cross Links ◽  
High Concentrations

Psoralen photochemistry is specific for nucleic acids and is better understood at the molecular level than are all other methods of chemical modification of nucleic acids. These compounds are used both for in vivo structure analysis and for photochemotherapy since they easily penetrate both cells and virus particles. Apparently, natural selection has selected for membrane and virus penetrability during the evolution of these natural products. Most cells are unaffected by relatively high concentrations of psoralens in the absence of ultraviolet light, and the metabolites of the psoralens have thus far not created a problem. Finally, psoralens form both monoadduct and cross-links in nucleic acid helices, the yield of each being easily controlled by the conditions used during the photochemistry.

GRAVITY AIDED TEXTURE GROWTH IN CERAMIC SUPERCONDUCTORS

1989 ◽  
Vol 03 (14) ◽  
pp. 1053-1060 ◽  
Author(s):  
A. J. BOURDILLON ◽  
N. X. TAN ◽  
N. SAVVIDES ◽  
J. SHARP
Keyword(s):  
Critical Current ◽  
Grain Growth ◽  
Thermal Gradient ◽  
Thermal Gradients ◽  
Ceramic Superconductor ◽  
Downward Motion ◽  
Ceramic Superconductors ◽  
Current Densities ◽  
Molten Phase

Texture growth in incongruently melting ceramic superconductor materials, such as YBa 2 Cu 3 O 7−x, can be combined with zone refinement in thermal gradients to increase critical current densities. In gravity aided texture growth (GATEG), a vertical thermal gradient is used with downward motion of the partially molten specimen (relative to the furnace) so that the molten phase recrystallizes with grain growth.

Investigation of Heat Transfer Characteristics in a Rotating Convection System With Bi-Directional Thermal Gradients

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Ayan Kumar Banerjee ◽  
Amitabh Bhattacharya ◽  
Sridhar Balasubramanian
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Thermal Gradient ◽  
Outer Edge ◽  
Thermal Gradients ◽  
Heat Transfer Characteristics ◽  
Rotating Convection ◽  
Transfer Characteristics ◽  
Cylindrical Annulus ◽  
Inner Surface

Abstract A series of rotating convection experiments have been conducted in a novel configuration, which comprises a cylindrical annulus with spot heating on the bottom outer edge and uniform cooling on the inner surface. Such a system provides bi-directional thermal gradients in both radial and vertical directions, thereby reenacting the thermal gradient patterns encountered in the atmosphere. Bulk heat transfer characteristics are studied by quantifying the overall Nusselt number, Nu, for a range of Taylor number, Ta, heating rate, Q, and Rayleigh number, Ra. Temperature measurements are carried out at different locations with the help of thermocouples. The Nusselt number is found to be quite sensitive to the buoyancy and relatively insensitive to the rotation rate. The correlation for Nu as a function of Ra revealed different power law exponents for low and high Ta values. The varying exponent is attributed to the presence of baroclinic eddies at high Ta, which in turn is verified with the help of flow visualization. The heat transfer characteristics in this new configuration are significantly different compared to other conventional rotational convection systems, where thermal gradients are present in only one direction.

Comparison of Different Liquid Cooling Configurations for Effective Thermal Management of Li-Ion Pouch Cell for Automotive Applications

2020 ◽  
Author(s):  
Shashwat Bakhshi ◽  
Prahit Dubey ◽  
A. K. Srouji ◽  
Zenan Wu
Keyword(s):  
Thermal Management ◽  
Thermal Performance ◽  
Thermal Gradient ◽  
Battery Pack ◽  
Thermal Gradients ◽  
Liquid Cooling ◽  
Battery Thermal Management ◽  
The Face ◽  
Cooling Mechanism ◽  
Face Cooling

Abstract An effective cooling mechanism is the backbone of a good automotive battery thermal management system (BTMS). In addition to prevention of extreme events such as thermal runaway, an automotive BTMS must be able to efficiently tackle aggressive environmental temperatures, and/or discharge and charge conditions during electric vehicle operation. Moreover, electrical performance and cycle life of the battery modules and packs are closely tied to the battery temperatures and thermal gradients, which increase with increase in C-Rates. In order to keep the battery temperatures to be under the operational temperature limit, it is crucial that the selected cooling mechanism provides efficient transport of the heat generated by the battery modules and packs to the cooling media under all discharge and charge conditions. Owing to its efficient thermal performance, liquid cooling is preferred by most electric vehicle manufacturers for battery thermal management. This usually incorporates battery modules exchanging heat with a flowing coolant via cold plate or cooling channels during operation. The current work aims to investigate different liquid cooling configurations and compare their relative thermal performance during operation of a high energy density Pouch Cell. The four configurations selected for this comparison are (1) Face cooling, (2) Single-Sided cooling, (3) Double-Sided cooling, and (4) a Hybrid cooling configuration. Test setups comprising of a commercially available 9 A-h NMC Pouch cell, cold plates, pump, heat exchanger, refrigeration cooling unit, and thermal sensors are built for the above four cooling configurations. During the tests, the selected cell is discharged at different discharge rates (C-Rates), i.e., 3C, 4C, and 5C. The overall cell temperatures and thermal gradient across the cell are measured using T-type thermocouples for the four cooling configurations. In order to capture the thermal gradient across the Pouch cell accurately, several thermocouples on the face of the cell are installed using a thermal interface material. Results show the superiority of Face cooling configuration in terms of overall thermal performance under all considered test conditions. Lowest cell temperatures and thermal gradients across the cell are observed for the Face cooling configuration, while highest temperatures and thermal gradients are observed for the Single-Sided cooling configuration. Much improved thermal performance is also observed in the case of the Hybrid cooling configuration as compared to the Single and Double-Sided cooling configurations. As implementation of the Face cooling configuration at the battery pack level may result in higher weight and cost of the battery pack, owing to its good thermal performance and straightforward scaling to battery pack level, the proposed hybrid liquid cooling mechanism provides a viable alternative to Face cooling for battery thermal management.

scholarly journals The molecular evolution of feathers with direct evidence from fossils

2019 ◽  
Vol 116 (8) ◽  
pp. 3018-3023 ◽  
Author(s):  
Yanhong Pan ◽  
Wenxia Zheng ◽  
Roger H. Sawyer ◽  
Michael W. Pennington ◽  
Xiaoting Zheng ◽  
...  
Keyword(s):  
Amino Acid ◽  
Molecular Evolution ◽  
Amino Acid Composition ◽  
Acid Composition ◽  
Direct Evidence ◽  
Molecular Level ◽  
Biomechanical Properties ◽  
Deep Time ◽  
Avian Flight ◽  
Ultrastructural Evidence

Dinosaur fossils possessing integumentary appendages of various morphologies, interpreted as feathers, have greatly enhanced our understanding of the evolutionary link between birds and dinosaurs, as well as the origins of feathers and avian flight. In extant birds, the unique expression and amino acid composition of proteins in mature feathers have been shown to determine their biomechanical properties, such as hardness, resilience, and plasticity. Here, we provide molecular and ultrastructural evidence that the pennaceous feathers of the Jurassic nonavian dinosaur Anchiornis were composed of both feather β-keratins and α-keratins. This is significant, because mature feathers in extant birds are dominated by β-keratins, particularly in the barbs and barbules forming the vane. We confirm here that feathers were modified at both molecular and morphological levels to obtain the biomechanical properties for flight during the dinosaur–bird transition, and we show that the patterns and timing of adaptive change at the molecular level can be directly addressed in exceptionally preserved fossils in deep time.

Temperature selections of Anguilla japonica (L.) elvers, and their implications for migration

1991 ◽  
Vol 42 (6) ◽  
pp. 743 ◽  
Author(s):  
YL Chen ◽  
H Chen
Keyword(s):  
Thermal Gradient ◽  
Power Plants ◽  
Anguilla Japonica ◽  
Japanese Eel ◽  
Thermal Gradients ◽  
Temperature Selection ◽  
Naturally Occurring ◽  
Thermal Effluents ◽  
Stainless Steel Heat ◽  
Steel Heat

This study investigated the temperature selections of elvers of the Japanese eel, Anguilla japonica (L.), that had been acclimatized to various temperatures and salinities. The results provide information needed to assess the possible effects of thermal effluents from power plants and of naturally occurring thermal gradients on the freshwater migration and fishery harvest of elvers. A 7.14-m-long plastic pipe (i.d. 11 cm) fitted with two stainless-steel heat-exchange tubes was used for the study. The countercurrent design of the system provided a thermal gradient ranging from 11� C at one end of the pipe to 31� C at the other. Elvers could swim free of obstacles inside the pipe. They were acclimatized to 13, 15, 17, 19 or 21� C before being subjected to the thermal gradient. The distribution of elvers in the pipe was studied during a 24-h period. The results indicate that the temperature to which the elvers gravitated was higher than their acclimatization temperature for acclimatizaion temperatures between 13 and 21�C. The thermal preference of elvers acclimatized to salinities of 10 or 32 did not differ. The temperature- selection pattern of the elvers suggests that thermal effluents from power plants may not adversely affect the immigration of elvers.

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