A Primer to Relativistic MOND Theory

We first review the nonrelativistic lagrangian theory as a framework for the MOND equation. Obstructions to a relativistic version of it are discussed leading up to TeVeS, a relativistic tensor-vector-scalar field theory which displays both MOND and Newtonian limits. The whys for its particular structure are discussed and its achievements so far are summarized.Comment: 6 pages, LaTeX, 1 figure, to appear in proceedings of IAP05 in Paris: Mass Profiles and Shapes of Cosmological Structures, G. Mamon, F. Combes, C. Deffayet and B. Fort (eds), (EDP-Sciences 2005

Transient [3,3] Cope rearrangement of 3,3-dicyano-1,5-dienes: computational analysis and 2-step synthesis of arylcycloheptanes.

A simple and modular route to arylcycloheptene scaffolds is reported. The two-step route from Knoevenagel adducts and allylic electrophiles is made possible through the design of a Cope rearrangement that utilizes a "traceless" activating group to promote an otherwise thermodynamically unfavorable transformation. Experimentally, the [3,3] rearrangement occurrs transiently at room temperature with a computed barrier of 19.5 kcal mol-1, which ultimately allows for three-component bis-allylation. Ring-closing metathesis delivers the arylcycloheptane and removes the activating group. This report describes the design and optimization of the methodology, scope and mechanistic studies, and computational analysis

Do Newton's G and Milgrom's a_0 vary with cosmological epoch ?

In the scalar tensor gravitational theories Newton's constant G_N evolves in the expanding universe. Likewise, it has been speculated that the acceleration scale a_0 in Milgrom's modified Newtonian dynamics (MOND) is tied to the scale of the cosmos, and must thus evolve. With the advent of relativistic implementations of the modified dynamics, one can address the issue of variability of the two gravitational ''constants'' with some confidence. Using TeVeS, the Tensor-Vector-Scalar gravitational theory, as an implementation of MOND, we calculate the dependence of G_N and a_0 on the TeVeS parameters and the coeval cosmological value of its scalar field, \phi_c. We find that G_N, when expressed in atomic units, is strictly nonevolving, a result fully consistent with recent empirical limits on the variation of G_N. By contrast, we find that a_0 depends on \phi_c and may thus vary with cosmological epoch. However, for the brand of TeVeS which seems most promising, a_0 variation occurs on a timescale much longer than Hubble's, and should be imperceptible back to redshift unity or even beyond it. This is consistent with emergent data on the rotation curves of disk galaxies at significants redshifts.Comment: 9 pages, RevTe

TeVeS/MOND is in harmony with gravitational redshifts in galaxy clusters

Wojtak, Hansen and Hjorth have recently claimed to confirm general relativity and to rule out the tensor-vector-scalar (TeVeS) gravitational theory based on an analysis of the gravitational redshifts of galaxies in 7800 clusters. But their ubiquitous modeling of the sources of cluster gravitational fields with Navarro-Frenk-White mass profiles is neither empirically justified out to the necessary radii in clusters, nor germane in the case of TeVeS. Using MONDian isothermal sphere models consistently constructed within MOND (equivalent to TeVeS models), we can fit the determined redshifts no worse than does general relativity with dark halos. Wojtak, Hansen and Hjorth's work is further marred by confusion between the primitive mu-function of TeVeS and the MOND interpolation function.Comment: 7 pages, 2 pdf figure

Application of Compressed Sensing to the Simulation of Atomic Systems

Compressed sensing is a method that allows a significant reduction in the number of samples required for accurate measurements in many applications in experimental sciences and engineering. In this work, we show that compressed sensing can also be used to speed up numerical simulations. We apply compressed sensing to extract information from the real-time simulation of atomic and molecular systems, including electronic and nuclear dynamics. We find that, compared to the standard discrete Fourier transform approach, for the calculation of vibrational and optical spectra the total propagation time, and hence the computational cost, can be reduced by approximately a factor of five.Chemistry and Chemical Biolog

The thermodynamic landscape of carbon redox biochemistry

Redox biochemistry plays a key role in the transduction of chemical energy in all living systems. Observed redox reactions in metabolic networks represent only a minuscule fraction of the space of all possible redox reactions. Here we ask what distinguishes observed, natural redox biochemistry from the space of all possible redox reactions between natural and non-natural compounds. We generate the set of all possible biochemical redox reactions involving linear chain molecules with a fixed numbers of carbon atoms. Using cheminformatics and quantum chemistry tools we analyze the physicochemical and thermodynamic properties of natural and non-natural compounds and reactions. We find that among all compounds, aldose sugars are the ones with the highest possible number of connections (reductions and oxidations) to other molecules. Natural metabolites are significantly enriched in carboxylic acid functional groups and depleted in carbonyls, and have significantly higher solubilities than non-natural compounds. Upon constructing a thermodynamic landscape for the full set of reactions as a function of pH and of steady-state redox cofactor potential, we find that, over this whole range of conditions, natural metabolites have significantly lower energies than the non-natural compounds. For the set of 4-carbon compounds, we generate a Pourbaix phase diagram to determine which metabolites are local energetic minima in the landscape as a function of pH and redox potential. Our results suggest that, across a set of conditions, succinate and butyrate are local minima and would thus tend to accumulate at equilibrium. Our work suggests that metabolic compounds could have been selected for thermodynamic stability, and yields insight into thermodynamic and design principles governing nature’s metabolic redox reactions.https://www.biorxiv.org/content/10.1101/245811v1Othe

Effects of a Mycobacterium smegmatis-related Strain on the Inflammatory Signaling of BV-2 Murine Microglia Assessed via the NanoString Platform

Individuals residing in high-income, industrialized countries are facing higher rates of inflammatory disease and stress-linked psychiatric disorders for which inflammation is a risk factor. The &ldquo;Old Friends&rdquo; Hypothesis asserts that this trend exists in part due to reduced exposure to commensal microorganisms&nbsp;(Rook et al., 2013).&nbsp;Mycobacterium vaccae&nbsp;NCTC 11659, a strain of soil-derived and non-pathogenic bacterium, has been shown to attenuate inflammation and stress-linked behavior in murine studies&nbsp;(Reber et al., 2016). Analyzing the effects of related bacterial strains on immune tissue provides information on the yet undiscovered molecular mechanisms at play and can help determine which species have the strongest immunoregulatory effects.&nbsp; &nbsp; This experiment investigates the effects of a yet unnamed species of&nbsp;Mycobacterium, closely related to&nbsp;M. vaccae&nbsp;and&nbsp;M. smegmatis, on BV-2 murine microglia. Microglia, which reside in the central nervous system, are not typically exposed to bacteria and must be able to defend neural tissue when necessary. Due to their functional niche, the BV-2 cells are expected to exhibit a pro-inflammatory response after bacterial contact, along with possible strain-specific responses&nbsp;(Loane &amp; Byrnes, 2010). Cultured BV-2 cells were divided into 12 samples (three replicates of four conditions) and each condition received doses of an inflammatory agent (lipopolysaccharide, LPS), the novel mycobacterial strain, and/or growth media. Extraction of mRNA using Qiagen RNeasy kits permitted NanoString transcript sequencing, where relative levels of mRNA transcripts are measured and compared. Although one replicate in the LPS +&nbsp;M. smegmatis-related strain group could not be included in statistical analysis, the data do not indicate any strong immunomodulatory effects from treatment with the novel strain, and instead suggest that it generates a mild inflammatory phenotype in microglia.&nbsp;</p