Escher's Room

Marrink, Siewert-Jan and Herman J. C. Berendsen. "Simulation of Water Transport through a Lipid Membrane." The Journal of Physical Chemistry 98, no. 15 (1994): 4155--4168. Marrink and Berendsen describe the headgroups of DPPC as "dipolar" (p. 4161).  Phosphatidylcholine contains both a negatively charged phosphate and a positively charged choline, hence the descriptor.  Another name would be zwitterion, wherein a molecule contains both a positively charged and negatively charged group but whose net charge is neutral. Because of the polar nature of the the DPPC headgroup, they observed a "very diffuse interface between the dipolar headgroups and water" (p. 4161).

 "An investor could lose the full principal value of his/her investment within a single day if the index loses more than 33% in one day." ... Largest daily percentage losses in the S&P 500 Index since 1957 [1]  1. 1987-10-19   -20.47%  2. 1929-10-28   -12.34%  3. 2020-03-16   -11.98%  4. 1929-10-29   -10.16%  5. 1929-11-06   - 9.92%  6. 2020-03-12   - 9.51%  7. 1937-10-18   - 9.27%  8. 2008-10-15   - 9.04%  9. 2008-12-01   - 8.93% 10. 1933-07-20   - 8.88% A 33% loss in one day has not occurred since 1957.  I suppose it's unlikely to occur, but there's always a chance.  Even the worst market shock due to the recent pandemic was -12%.  What would cause a 33% loss? This is called tail risk, right? [1] "List of largest daily changes in the S&P 500 Index." Wikipedia. Last edited on 2 July 2022 11:11 CDT. https://en....

 Cohen, Jordi, Anton Arkhipov, Rosemary Braun, and Klaus Schulten. "Imaging the Migration Pathways for O2, CO, NO, and Xe Inside Myoglobin." Biophysical Journal  91, (2006): 1844-1857. In their paper, Cohen et al. introduce a method for studying gas migration pathways in proteins based on free-energy perturbation calculations called implicit ligand sampling (ILS).  They present the theoretical foundation of ILS, which calculates the Gibb's free energy cost of having a particle occupy certain positions in a molecular dynamics simulation.  This calculation provides a three-dimensional map of the potential of mean force (PMF) inside the analyzed volume.  They used the technique to study sperm whale myoglobin.  First they reported that ILS accurately predicted the xenon binding sites in the whale myoglobin by comparing the results of their ILS to crystal structures of the protein co-crystallized with xenon gas, validating the technique.  They then mapped o...

 Marrink, Siewert-Jan and Herman J. C. Berendsen. "Simulation of Water Transport through a Lipid Membrane." The Journal of Physical Chemistry  98, no. 15 (1994): 4155--4168. In their paper, Marrink and Berendsen theoretically examined water permeation across phospholipid bilayers through computational means.  They extended the homogenous solubility-diffusion model to what they call the inhomogeneous solubility-diffusion model (ISD), which relates local free energy and diffusion coefficient to permeability.  They show connections between variables in their model to experimentally measurable quantities, like hydrostatic pressure difference.  They performed atomistic molecular dynamics simulations of dipalmitoylphosphatdylcholine (DPPC) membranes and water to compute the permeability coefficient of water through the bilayer by measuring the potential of mean force and local diffusion coefficients of water through the bilayers.  Position-dependent characterizat...

Wednesday, 2021-08-04 11:04 AM CT.  The last transaction of Chi Gas on Uniswap V2 traded at a price of 1.6173e-4 Eth/Chi, paying a gas price of 76 gwei on the Ethereum network. The price of Chi continues to fall against elevated gas prices and contracting supply (2,031,988 CHI).      Chi may be falling in anticipation of the upcoming EIP-1559 upgrade, which changes the transaction fee mechanism on the Ethereum network.  Uncertainty about the continued usability of Chi after the upgrade may have users waiting to see what will happen once the upgrade launches.  The planned should occur in about 20 hours.

Monday, 2021-08-02 11:05 AM CT. The last transaction of Chi Gas on Uniswap V2 traded at a price of 1.9664e-4 Eth/Chi, paying a gas price of 42 gwei on the Ethereum network. The price of Chi has fallen in spite of seemingly elevated gas prices and contracting supply (2,101,973 CHI).      To make a transaction on the Ethereum network, users must pay a fee denominated in "gas". The amount of gas that is paid is dependent upon the complexity of the transaction. A transaction that simply transfers tokens from one address to another will require less gas than a transaction that utilizes smart contracts deployed on the Ethereum block chain.