Geochemical Control of Methanogenesis in Cape Lookout Bight, North Carolina

Hydrogen exerts thermodynamic control over the exclusion of methanogens by sulfate reducers in Cape Lookout Bight, NC, marine sediments. This has been demonstrated by previous in situ measurements, but has never been demonstrated in a batch incubation of unamended sediments and has never been combined with identification of the microorganisms involved in this process. We made triplicate anoxic incubations of sediments from the upper 3 cm of sediment over 122 days while taking weekly samples for DNA extraction, cell counts, and measurements of methane, sulfate, and hydrogen. The headspaces of the bottles were initially gassed with nitrogen and the third was subsequently gassed with methane, although the methane disappeared within the first two weeks and after that the incubation served as a third replicate. While sulfate was present, the hydrogen concentration was maintained below 2 nM. Hydrogen started to rise as sulfate concentrations fell below 3 mM, coinciding with a small increase in methane. Only when sulfate has been depleted and the hydrogen concentrations rise was methane continuously produced. Quantitative PCR (qPCR) suggests that Methanosarcinales and Methanomicrobiales increase when sulfate is depleted in all three incubations. 16s rRNA gene Miseq tag libraries support the increase of these methanogens as well as a novel archaeal group, Kazan 3A-21, and sulfur-oxidizing bacteria. qPCR and tag libraries show that the methanogen-like archaea, ANME-1, increase during early methanogenesis, but the values are near detection limits and are therefore noisy. The tag libraries suggest that sulfate-reducing bacteria maintain similar population levels throughout the sulfate reduction phase, decrease as sulfate is depleted, and then rebound during the methanogenic phase. This most likely signifies a switch from sulfate reduction to syntrophic fermentation of organic matter with methanogens. Total cell counts demonstrate a decline in cells with the decrease of sulfate until a recovery corresponding with production of methane. Our results suggest that competition for hydrogen influences what metabolic processes can occur in marine sediments and that a diversity of sulfate reducers and methanogens are involved in this competition

The time-history of a satellite around an oblate planet

Time history of satellite around oblate plane

Transient resonances in the inspirals of point particles into black holes

We show that transient resonances occur in the two body problem in general relativity, in the highly relativistic, extreme mass-ratio regime for spinning black holes. These resonances occur when the ratio of polar and radial orbital frequencies, which is slowly evolving under the influence of gravitational radiation reaction, passes through a low order rational number. At such points, the adiabatic approximation to the orbital evolution breaks down, and there is a brief but order unity correction to the inspiral rate. Corrections to the gravitational wave signal's phase due to resonance effects scale as the square root of the inverse of mass of the small body, and thus become large in the extreme-mass-ratio limit, dominating over all other post-adiabatic effects. The resonances make orbits more sensitive to changes in initial data (though not quite chaotic), and are genuine non-perturbative effects that are not seen at any order in a standard post-Newtonian expansion. Our results apply to an important potential source of gravitational waves, the gradual inspiral of white dwarfs, neutron stars, or black holes into much more massive black holes. It is hoped to exploit observations of these sources to map the spacetime geometry of black holes. However, such mapping will require accurate models of binary dynamics, which is a computational challenge whose difficulty is significantly increased by resonance effects. We estimate that the resonance phase shifts will be of order a few tens of cycles for mass ratios $\sim 10^{-6}$, by numerically evolving fully relativistic orbital dynamics supplemented with an approximate, post-Newtonian self-force.Comment: 4 pages, 1 figure, minor correction

Propagation of a laser beam in a plasma

This paper shows that for a nonabsorbing medium with a prescribed index of refraction, the effects of beam stability, line focusing, and beam distortion can be predicted from simple ray optics. When the paraxial approximation is used, diffraction effects are examined for Gaussian, Lorentzian, and square beams. Most importantly, it is shown that for a Gaussian beam, diffraction effects can be included simply by adding imaginary solutions to the paraxial ray equations. Also presented are several procedures to extend the paraxial approximation so that the solution will have a domain of validity of greater extent

The Higher Orders of the Theory of Strong Perturbations in Quantum Mechanics and the Secularity Problem

We solve the higher order equations of the theory of the strong perturbations in quantum mechanics given in M. Frasca, Phys. Rev. A 45, 43 (1992), by assuming that, at the leading order, the wave function goes adiabatically. This is accomplished by deriving the unitary operator of adiabatic evolution for the leading order. In this way it is possible to show that at least one of the causes of the problem of phase-mixing, whose effect is the polynomial increase in time of the perturbation terms normally called secularities, arises from the shifts of the perturbation energy levels due to the unperturbed part of the hamiltonian. An example is given for a two-level system that, anyway, shows a secularity at second order also in the standard theory of small perturbations. The theory is applied to the quantum analog of a classical problem that can become chaotic, a particle under the effect of two waves of different amplitudes, frequencies and wave numbers.Comment: 13 pages, Late

Colonial Necrocapitalism, State Secrecy, and the Palestinian Freedom Tunnel

Secrecy and the use of “secret information” as capital in the hands of the state is mobilised by affective racialised machineries, cultivated on “security” grounds. Securitised secrecy is an assemblage of concealed operations juxtaposing various forms of invasions and dispossessions. It is a central strategy in the politico-economic life of the state to increase its scope of domination. Secrecy is used and abused to entrap and penetrate political subjects and entities. This article explores the necrocapitalist utilisation of secrecy embedded in the coloniser’s attempt to distort the mind of the colonised. Built from the voices of those affected by secrecy’s violent psychopolitical entrapment and penetrability, we expose the ways in which secrecy manufactures colonisers’ impunity and immunity. Further, we discuss the ruins that secrecy mislays, arguing as Fanon explained, that psychic ruins are common usage of colonial violence. In fact, Fanon (1963) argued that damaged personhood was central to the colonial order and its making. We conclude by insisting that ruins can also be sites of reflection and counteractions of life against the necrocapitalist violent machinery and ideology of the settler colonial state. Building on previous critical and decolonial theories, this essay argues that the coloniser’s yearning for destruction, coupled with the use of militarised “secret information”, constitutes colonial invisible criminalities to maim (Puar, 2015) and erase (Wolf, 2006). Militarised secrecy’s necrocapitalist assemblage takes us to one of the core dimensions of settler colonial ideology “accumulation by dispossession” (Harvey, 2003), that is, the elimination of the colonised, demolition of life and the psychic in which the colonialist “trades” and “sells” the machineries of elimination as combat proven. Examining secrecy and its eliminatory machineries exposes the colonialist’s brutality and the colonised’s unending capacity for resistance and the power of life. This essay hopes to expose the politics underpinning the way securitized secrecy is imagined, implemented and resisted

Noise Effects on Synchronized Globally Coupled Oscillators

The synchronized phase of globally coupled nonlinear oscillators subject to noise fluctuations is studied by means of a new analytical approach able to tackle general couplings, nonlinearities, and noise temporal correlations. Our results show that the interplay between coupling and noise modifies the effective frequency of the system in a non trivial way. Whereas for linear couplings the effect of noise is always to increase the effective frequency, for nonlinear couplings the noise influence is shown to be positive or negative depending on the problem parameters. Possible experimental verification of the results is discussed.Comment: 6 Pages, 4 EPS figures included (RevTeX and epsfig needed). Submitted to Phys. Re

Nonlinear dynamics in one dimension: On a criterion for coarsening and its temporal law

We develop a general criterion about coarsening for a class of nonlinear evolution equations describing one dimensional pattern-forming systems. This criterion allows one to discriminate between the situation where a coarsening process takes place and the one where the wavelength is fixed in the course of time. An intermediate scenario may occur, namely `interrupted coarsening'. The power of the criterion lies in the fact that the statement about the occurrence of coarsening, or selection of a length scale, can be made by only inspecting the behavior of the branch of steady state periodic solutions. The criterion states that coarsening occurs if lambda'(A)>0 while a length scale selection prevails if lambda'(A)<0, where $lambda$ is the wavelength of the pattern and A is the amplitude of the profile. This criterion is established thanks to the analysis of the phase diffusion equation of the pattern. We connect the phase diffusion coefficient D(lambda) (which carries a kinetic information) to lambda'(A), which refers to a pure steady state property. The relationship between kinetics and the behavior of the branch of steady state solutions is established fully analytically for several classes of equations. Another important and new result which emerges here is that the exploitation of the phase diffusion coefficient enables us to determine in a rather straightforward manner the dynamical coarsening exponent. Our calculation, based on the idea that |D(lambda)|=lambda^2/t, is exemplified on several nonlinear equations, showing that the exact exponent is captured. Some speculations about the extension of the present results to higher dimension are outlined.Comment: 16 pages. Only a few minor changes. Accepted for publication in Physical Review