Continuous catalytic decomposition of methane

Continuous catalytic decomposition of methane and application to space life support syste

Continuous catalytic decomposition of methane

Water is conserved by employing sequence of reactions whereby 75 percent of methane from Sabatier reaction is decomposed to solid carbon and hydrogen; hydrogen is then separated from residual methane and utilized in usual Sabatier reaction to reduce remaining metabolic carbon dioxide

The Y-Band at 1.035 um: Photometric Calibration and the Dwarf Stellar/Sub-Stellar Color Sequence

We define and characterize a photometric bandpass (called "Y") that is centered at 1.035 um, in between the traditionally classified ``optical'' and ``infrared'' spectral regimes. We present Y magnitudes and Y-H and Y-K colors for a sample consisting mostly of photometric and spectral standards, spanning the spectral type range sdO to T5V. Deep molecular absorption features in the near-infrared spectra of extremely cool objects are such that the Y-H and Y-K colors grow rapidly with advancing spectral type especially from late M through mid L, substantially more rapidly than J-H or H-K which span a smaller total dynamic range. Consistent with other near-infrared colors, however, Y-H and Y-K colors turn blueward in the L6-L8 temperature range with later T-type objects having colors similar to those of warmer M and L stars. Use of the Y-band filter is nonetheless promising for easy identification of low-mass stars and brown dwarfs, especially at young ages. The slope of the interstellar reddening vector within this filter is A_Y = 0.38 x A_V. Reddening moves stars nearly along the YHK dwarf color sequence making it more difficult to distinguish unambiguously very low mass candidate brown dwarf objects from higher mass stars seen, e.g. through the galactic plane or towards star-forming regions. Other diagrams involving the Y-band may be somewhat more discriminating.Comment: accepted at PAS

Subthreshold dynamics of the neural membrane potential driven by stochastic synaptic input

In the cerebral cortex, neurons are subject to a continuous bombardment of synaptic inputs originating from the network's background activity. This leads to ongoing, mostly subthreshold membrane dynamics that depends on the statistics of the background activity and of the synapses made on a neuron. Subthreshold membrane polarization is, in turn, a potent modulator of neural responses. The present paper analyzes the subthreshold dynamics of the neural membrane potential driven by synaptic inputs of stationary statistics. Synaptic inputs are considered in linear interaction. The analysis identifies regimes of input statistics which give rise to stationary, fluctuating, oscillatory, and unstable dynamics. In particular, I show that (i) mere noise inputs can drive the membrane potential into sustained, quasiperiodic oscillations (noise-driven oscillations), in the absence of a stimulus-derived, intraneural, or network pacemaker; (ii) adding hyperpolarizing to depolarizing synaptic input can increase neural activity (hyperpolarization-induced activity), in the absence of hyperpolarization-activated currents

Highly confined low-loss plasmons in graphene-boron nitride heterostructures

Graphene plasmons were predicted to possess ultra-strong field confinement and very low damping at the same time, enabling new classes of devices for deep subwavelength metamaterials, single-photon nonlinearities, extraordinarily strong light-matter interactions and nano-optoelectronic switches. While all of these great prospects require low damping, thus far strong plasmon damping was observed, with both impurity scattering and many-body effects in graphene proposed as possible explanations. With the advent of van der Waals heterostructures, new methods have been developed to integrate graphene with other atomically flat materials. In this letter we exploit near-field microscopy to image propagating plasmons in high quality graphene encapsulated between two films of hexagonal boron nitride (h-BN). We determine dispersion and particularly plasmon damping in real space. We find unprecedented low plasmon damping combined with strong field confinement, and identify the main damping channels as intrinsic thermal phonons in the graphene and dielectric losses in the h-BN. The observation and in-depth understanding of low plasmon damping is the key for the development of graphene nano-photonic and nano-optoelectronic devices