Asymmetric Membranes and Crimestop

Dec 27, 2022
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In the scientific literature, there are countless statements of this kind:

"Asymmetric diffusion appears in studies of ion transport across membranes (1–12), and in the context of osmosis (13, 14). Ion pores in biological membranes often act as effective rectifiers, blocking the passage of a particular ion in one direction while allowing free flow in the other. Explanations of these phenomena emphasize electrostatic effects or conformational changes...Here, we demonstrate that asymmetric diffusion can occur with no ionic binding, in a fixed pore geometry." https://www.pnas.org/doi/10.1073/pnas.0703280104

Blocking the passage in one direction while allowing free flow in the other is a Maxwell demon function par excellence, which goes against the second law of thermodynamics. However authors don't even think of that, let alone mentioning it in their papers:

George Orwell: "Crimestop means the faculty of stopping short, as though by instinct, at the threshold of any dangerous thought. It includes the power of not grasping analogies, of failing to perceive logical errors, of misunderstanding the simplest arguments if they are inimical to Ingsoc, and of being bored or repelled by any train of thought which is capable of leading in a heretical direction. Crimestop, in short, means protective stupidity."

Here the crimestop is somewhat relaxed:

"...concentration difference is generated internally by a chemically-asymmetric membrane that drives anisotropic diffusion of electrolyte ions, rather than being provided by an external source." https://www.sciencedirect.com/science/article/pii/S2213138822002466#b0005

The authors don't mention the Maxwell's demon but still discuss the violation of the second law of thermodynamics, even though in an ambiguous way that would calm down fierce thermodynamicists:

"This behavior is thermodynamically intriguing. The repeated reversion from
pH = 0.00 to pH = - 0.01 indicates a spontaneous sorting of hydrogen ions from a maximum entropy state – one in which [H+] is the same in both chambers – to a lower entropy state, one in which they are 2% different. On its face, this spontaneous reduction in entropy without work input seems at odds with traditional understandings of entropy and the second law [25] but, of course, there is actually no conflict when the entropy changes associated with the walls and membrane are combined with those of the solutions...The pHs and the resultant electrical power appear to be derived from the thermal diffusion of hydrogen ions, hence from purely thermal energy. At first glance this seems at odds with the second law of thermodynamics; however, as specified by the cell half-reactions, the anode continuously grows (precipitating AgCl) at the expense of the cathode, which will eventually disappear and bring the AMCC to a halt. Further investigation of AMCC thermodynamics seems warranted."
 
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"Diffusion rates through a membrane can be asymmetric, if the diffusing particles are spatially extended and the pores in the membrane have asymmetric structure...In its extreme form, this effect will rapidly seal off flow in one direction through a membrane, while allowing free flow in the other direction. The system thus relaxes to disequilibrium, with very different densities of the permeable species on each side of the membrane." https://arxiv.org/ftp/cond-mat/papers/0412/0412626.pdf

Theoretical physicists, does this have anything to do with the second law of thermodynamics?

Theoretical physicists: Who cares?
 
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"Concentration Cell Powered by a Chemically Asymmetric Membrane...The cell employs two electrolyte-filled chambers partitioned by a chemically asymmetric membrane, which drives anisotropic diffusion of electrolyte ions; the resulting concentration difference powers a concentration cell." https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4112190

The crucial question is:

Is such an asymmetric membrane possible?

If it is, then that's the end of the second law of thermodynamics. Calming down fierce defenders of the second law may be politically useful but in terms of scientific truth it is irrelevant and misleading:

"Although the AMS solution is rechargeable, the full AMCC is not. As noted above, the AMCC is a case of controlled corrosion (CGC). The electrodes do not reconstitute themselves; rather the anode continually precipitates Cl− as AgCl, adding mass, while the cathode continually loses mass. As a result, the AMCC’s operation does not constitute a thermodynamic cycle, nor does it undercut the second law."
 
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"In biological systems, ion transport across the cell membrane is mostly directional, an embodiment of ionic rectification. Unidirectional ion transport is related to an asymmetric biological nanopore structure, in which the ionic flow in one direction is almost totally suppressed...To realize such extraordinary ion transport properties in technical systems, many nanostructures based on different materials have been fabricated by various techniques, such as asymmetric nanochannels, heterogeneous membranes, and self-assembled two-dimensional materials. The realization of unidirectional ion transport in these examples involves breaking the symmetry of the geometry, surface charge distribution, chemical composition, or channel wall wettability, separately or simultaneously. Despite massive efforts in this field, it is still a challenge to replicate the functionality of biological nanopores and push unidirectional ion transport further for applications. One reason is that ionic rectification in synthetic nanofluidic systems still shows a performance inferior to that of their natural counterparts: The rectification ratio in artificial systems is always on the order of a few hundred while biological systems almost completely suppress the ion diffusion in one direction." https://www.nature.com/articles/s41467-021-24947-3

Is it sane to discuss this without mentioning the Maxwell demon and the second law of thermodynamics? Post-truth or post-sanity science?
 
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"In her November 2021 article , Katie Robertson presents an elegant synthesis of Maxwell’s, Loschmidt’s, and Laplace’s demons. Implicit in the text—and explicit in the conclusion—is the thesis that the second law of thermodynamics remains above reproach. Although that might have appeared to be the case at the close of the 19th and 20th centuries, it is not in the 21st. Since the mid 1990s, at least three dozen potent second-law challenges have advanced into the literature, some with strong experimental support, more than the total proposed during the previous century and a half. One example involves two opposing filaments, each formed from a different material, in a diatomic gas atmosphere at uniform temperature. Due to the different dissociation rates for the diatomic gas at the two surfaces, permanent gradients in pressure and temperature are formed, in apparent conflict with the second law. The most successful of the newer demons do not suffer the ailments of their ancestors: They are macroscopic in size rather than microscopic, they operate on molecules wholesale rather than individually, and they don’t think too much. Typically, they involve thermodynamic spatial asymmetries by which macroscopic energy reservoirs, which are regenerable thermally or by other means, are created at one or more of the system boundaries, standard hallmarks of discontinuities in chemical potential. Evidence for such demons should not be overlooked here, especially considering that they undercut the primary thesis of the work." https://physicstoday.scitation.org/doi/10.1063/PT.3.5186

Thermodynamicists:

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