1,166 research outputs found
Abiotic and biotic processes that drive carboxylation and decarboxylation reactions
© 2020 Walter de Gruyter GmbH, Berlin/Boston 2020. Carboxylation and decarboxylation are two fundamental classes of reactions that impact the cycling of carbon in and on Earth's crust. These reactions play important roles in both long-term (primarily abiotic) and short-term (primarily biotic) carbon cycling. Long-term cycling is important in the subsurface and at subduction zones where organic carbon is decomposed and outgassed or recycled back to the mantle. Short-term reactions are driven by biology and have the ability to rapidly convert CO2 to biomass and vice versa. For instance, carboxylation is a critical reaction in primary production and metabolic pathways like photosynthesis in which sunlight provides energy to drive carbon fixation, whereas decarboxylation is a critical reaction in metabolic pathways like respiration and the tricarboxylic acid cycle. Early life and prebiotic chemistry on Earth likely relied heavily upon the abiotic synthesis of carboxylic acids. Over time, life has diversified (de)carboxylation reactions and incorporated them into many facets of cellular metabolism. Here we present a broad overview of the importance of carboxylation and decarboxylation reactions from both abiotic and biotic perspectives to highlight the importance of these reactions and compounds to planetary evolution
Maximum elastic deformations of relativistic stars
We present a method for calculating the maximum elastic quadrupolar
deformations of relativistic stars, generalizing the previous Newtonian,
Cowling approximation integral given by [G. Ushomirsky et al., Mon. Not. R.
Astron. Soc. 319, 902 (2000)]. (We also present a method for Newtonian gravity
with no Cowling approximation.) We apply these methods to the m = 2 quadrupoles
most relevant for gravitational radiation in three cases: crustal deformations,
deformations of crystalline cores of hadron-quark hybrid stars, and
deformations of entirely crystalline color superconducting quark stars. In all
cases, we find suppressions of the quadrupole due to relativity compared to the
Newtonian Cowling approximation, particularly for compact stars. For the crust
these suppressions are up to a factor ~6, for hybrid stars they are up to ~4,
and for solid quark stars they are at most ~2, with slight enhancements instead
for low mass stars. We also explore ranges of masses and equations of state
more than in previous work, and find that for some parameters the maximum
quadrupoles can still be very large. Even with the relativistic suppressions,
we find that 1.4 solar mass stars can sustain crustal quadrupoles of a few
times 10^39 g cm^2 for the SLy equation of state or close to 10^40 g cm^2 for
equations of state that produce less compact stars. Solid quark stars of 1.4
solar masses can sustain quadrupoles of around 10^44 g cm^2. Hybrid stars
typically do not have solid cores at 1.4 solar masses, but the most massive
ones (~2 solar masses) can sustain quadrupoles of a few times 10^41 g cm^2 for
typical microphysical parameters and a few times 10^42 g cm^2 for extreme ones.
All of these quadrupoles assume a breaking strain of 0.1 and can be divided by
10^45 g cm^2 to yield the fiducial "ellipticities" quoted elsewhere.Comment: 21 pages, 11 figures, version accepted by PRD, including the
corrected maximum hybrid star quadrupoles (from the erratum to the shear
modulus calculation) and the corrected binding energy computatio
Tissue distribution of enzymic methylation of glutathione S-transferase and its effects on catalytic activity. Methylation of glutathione S-transferase 11-11 inhibits conjugating activity towards 1-chloro-2,4-dinitrobenzene
Hydrogenation reactions of carbon on Earth: Linking methane, margarine, and life
Hydrogenation reactions are a major route of electron and proton flow on Earth. Interfacing geology and organic chemistry, hydrogenations occupy pivotal points in the Earth’s global geochemical cycles. Some examples of hydrogenation reactions on Earth today include the production and consumption of methane in both abiotic and biotic reactions, the reduction of protons in hydrothermal settings, and the biological synthesis and degradation of fatty acids. Hydrogenation reactions were likely important for prebiotic chemistry on the early Earth, and today serve as one of the fundamental reaction classes that enable cellular life to construct biomolecules. An understanding and awareness of hydrogenation reactions is helpful for comprehending the larger web of molecular and material inter-conversions on our planet. In this brief review we detail some important hydrogenation and dehydrogenation reactions as they relate to geology, biology, industry, and atmospheric chemistry. Such reactions have implica- tions ranging from the suite of reactions on early Earth to industrial applications like the production of hydrocarbon fuel
Gravitational Radiation from Coalescing Binary Neutron Stars
We calculate the gravitational radiation produced by the merger and
coalescence of inspiraling binary neutron stars using 3-dimensional numerical
simulations. The stars are modeled as polytropes and start out in the
point-mass limit at wide separation. The hydrodynamic integration is performed
using smooth particle hydrodynamics (SPH) with Newtonian gravity, and the
gravitational radiation is calculated using the quadrupole approximation. We
have run several simulations, varying both the neutron star radius and the
equation of state. The resulting gravitational wave energy spectra are
rich in information about the hydrodynamics of merger and coalescence. In
particular, our results demonstrate that detailed information on both
and the equation of state can in principle be extracted from the spectrum.Comment: 33 pages, LaTex with RevTex macros; 21 figures available in
compressed PostScript format via anonymous ftp to
ftp://zonker.drexel.edu/papers/ns_coll_1 ; in press, Phys. Rev. D (Nov 15,
1994 issue
Gravitational Radiation from the Coalescence of Binary Neutron Stars: Effects Due to the Equation of State, Spin, and Mass Ratio
We calculate the gravitational radiation produced by the coalescence of
inspiraling binary neutron stars in the Newtonian regime using 3-dimensional
numerical simulations. The stars are modeled as polytropes and start out in the
point-mass regime at wide separation. The hydrodynamic integration is performed
using smooth particle hydrodynamics (SPH) with Newtonian gravity, and the
gravitational radiation is calculated using the quadrupole approximation. We
have run a number of simulations varying the neutron star radii, equations of
state, spins, and mass ratio. The resulting gravitational waveforms and spectra
are rich in information about the hydrodynamics of coalescence, and show
characteristic dependence on GM/Rc^2, the equation of state, and the mass
ratio.Comment: 39 pages, uses Latex 2.09. To be published in the Dec. 15, 1996 issue
of Physical Review D. 16 Figures (bitmapped). Originals available in
compressed Postscript format at ftp://zonker.drexel.edu/papers/PAPER2
The skeletal phenotype of chondroadherin deficient mice
Chondroadherin, a leucine rich repeat extracellular matrix protein with functions in cell to matrix interactions, binds cells via their a2b1 integrin as well as via cell surface proteoglycans, providing for different sets of signals to the cell. Additionally, the protein acts as an anchor to the matrix by binding tightly to collagens type I and II as well as type VI. We generated mice with inactivated chondroadherin gene to provide integrated studies of the role of the protein. The null mice presented distinct phenotypes with affected cartilage as well as bone. At 3–6 weeks of age the epiphyseal growth plate was widened most pronounced in the proliferative zone. The proteome of the femoral head articular cartilage at 4 months of age showed some distinct differences, with increased deposition of cartilage intermediate layer protein 1 and fibronectin in the chondroadherin deficient mice, more pronounced in the female. Other proteins show decreased levels in the deficient mice, particularly pronounced for matrilin-1, thrombospondin-1 and notably the members of the a1-antitrypsin family of proteinase inhibitors as well as for a member of the bone morphogenetic protein growth factor family. Thus, cartilage homeostasis is distinctly altered. The bone phenotype was expressed in several ways. The number of bone sialoprotein mRNA expressing cells in the proximal tibial metaphysic was decreased and the osteoid surface was increased possibly indicating a change in mineral metabolism. Micro-CT revealed lower cortical thickness and increased structure model index, i.e. the amount of plates and rods composing the bone trabeculas. The structural changes were paralleled by loss of function, where the null mice showed lower femoral neck failure load and tibial strength during mechanical testing at 4 months of age. The skeletal phenotype points at a role for chondroadherin in both bone and cartilage homeostasis, however, without leading to altered longitudinal growth
Bayesian inference on compact binary inspiral gravitational radiation signals in interferometric data
Presented is a description of a Markov chain Monte Carlo (MCMC) parameter
estimation routine for use with interferometric gravitational radiational data
in searches for binary neutron star inspiral signals. Five parameters
associated with the inspiral can be estimated, and summary statistics are
produced. Advanced MCMC methods were implemented, including importance
resampling and prior distributions based on detection probability, in order to
increase the efficiency of the code. An example is presented from an
application using realistic, albeit fictitious, data.Comment: submitted to Classical and Quantum Gravity. 14 pages, 5 figure
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