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This work presents a novel technique for constructing spatially resolved ion densities from Transient Insertion Langmuir Probe (TIL Probe) measurements in a flame. Similar to a tomographic transformation, this technique is used to deduce the spatial distribution of ions in a flame from many individual measurements that are integrated along a probe's length. We demonstrate the approach in the oxyfuel cutting torch preheat flame, which presents two severe challenges for electrical measurements: (1) temperatures over 3,000K destroy most probes made from alloys with appropriate chemical stability, and (2) the relevant length scales are on the order 0.15 mm. Presented here are (1) a Fourier series formulation for the current density, (2) a least-square problem for calculating the coefficients, (3) criteria for the highest wavenumber allowed in the expansion, (4) description of an experiment used to measure probe currents in an oxyfuel cutting torch preheat flame, (5) solution for spatially resolved current density in the oxyfuel cutting torch flame. Images of ion current density are produced with a resolution of 0.15 mm (0.0059 in), exhibiting peak current densities around 14 $\mu$A/mm. It is found that low-signal regions in the ``shadow'' of high-signal regions can suffer from signal-to-noise ratio problems due to natural fluctuations in the flame, and improvements are proposed to mitigate the effect. It is found that the numerical cost of setting up the resulting Hermitian-matrix linear problem far exceeds the numerical cost of inversion. High-level packages like Python and MATLAB are far too slow, so a multi-threaded algorithm is implemented in C, and the LAPACKE C library is used for efficient linear algebra support. 

This work presents a novel technique for constructing spatially resolved ion densities from Transient Insertion Langmuir Probe (TIL Probe) measurements in a flame. Similar to a tomographic transformation, this technique is used to deduce the spatial distribution of ions in a flame from many individual measurements that are integrated along a probe's length. We demonstrate the approach in the oxyfuel cutting torch preheat flame, which presents two severe challenges for electrical measurements: (1) temperatures over 3,000K destroy most probes made from alloys with appropriate chemical stability, and (2) the relevant length scales are on the order 0.15 mm. Presented here are (1) a Fourier series formulation for the current density, (2) a least-square problem for calculating the coefficients, (3) criteria for the highest wavenumber allowed in the expansion, (4) description of an experiment used to measure probe currents in an oxyfuel cutting torch preheat flame, (5) solution for spatially resolved current density in the oxyfuel cutting torch flame. Images of ion current density are produced with a resolution of 0.15 mm (0.0059 in), exhibiting peak current densities around 14 $\mu$A/mm. It is found that low-signal regions in the ``shadow'' of high-signal regions can suffer from signal-to-noise ratio problems due to natural fluctuations in the flame, and improvements are proposed to mitigate the effect. It is found that the numerical cost of setting up the resulting Hermitian-matrix linear problem far exceeds the numerical cost of inversion. High-level packages like Python and MATLAB are far too slow, so a multi-threaded algorithm is implemented in C, and the LAPACKE C library is used for efficient linear algebra support. 

ABSTRACT We describe the discovery of an archaeal virus, one that infects archaea, tentatively named Thermoproteus spherical piliferous virus 1 (TSPV1), which was purified from a Thermoproteales host isolated from a hot spring in Yellowstone National Park (USA). TSPV1 packages an 18.65-kb linear double-stranded DNA (dsDNA) genome with 31 open reading frames (ORFs), whose predicted gene products show little homology to proteins with known functions. A comparison of virus particle morphologies and gene content demonstrates that TSPV1 is a new member of the Globuloviridae family of archaeal viruses. However, unlike other Globuloviridae members, TSPV1 has numerous highly unusual filaments decorating its surface, which can extend hundreds of micrometers from the virion. To our knowledge, similar filaments have not been observed in any other archaeal virus. The filaments are remarkably stable, remaining intact across a broad range of temperature and pH values, and they are resistant to chemical denaturation and proteolysis. A major component of the filaments is a glycosylated 35-kDa TSPV1 protein (TSPV1 GP24). The filament protein lacks detectable homology to structurally or functionally characterized proteins. We propose, given the low host cell densities of hot spring environments, that the TSPV1 filaments serve to increase the probability of virus attachment and entry into host cells. IMPORTANCE High-temperature environments have proven to be an important source for the discovery of new archaeal viruses with unusual particle morphologies and gene content. Our isolation of Thermoproteus spherical piliferous virus 1 (TSPV1), with numerous filaments extending from the virion surface, expands our understanding of viral diversity and provides new insight into viral replication in high-temperature environments. 

The close synergy between peptides and nucleic acids in current biology is suggestive of a functional co-evolution between the two polymers. Here we show that cationic proto-peptides (depsipeptides and polyesters), either produced as mixtures from plausibly prebiotic dry-down reactions or synthetically prepared in pure form, can engage in direct interactions with RNA resulting in mutual stabilization. Cationic proto-peptides significantly increase the thermal stability of folded RNA structures. In turn, RNA increases the lifetime of a depsipeptide by >30-fold. Proto-peptides containing the proteinaceous amino acids Lys, Arg, or His adjacent to backbone ester bonds generally promote RNA duplex thermal stability to a greater magnitude than do analogous sequences containing non-proteinaceous residues. Our findings support a model in which tightly-intertwined biological dependencies of RNA and protein reflect a long co-evolutionary history that began with rudimentary, mutually-stabilizing interactions at early stages of polypeptide and nucleic acid co-existence.

 

The mass of the top quark is measured in 36.3$$\,\text {fb}^{-1}$$${\text{fb}}^{-1}$of LHC proton–proton collision data collected with the CMS detector at$$\sqrt{s}=13\,\text {Te}\hspace{-.08em}\text {V} $$$\sqrt{s}=13\text{Te}\text{V}$. The measurement uses a sample of top quark pair candidate events containing one isolated electron or muon and at least four jets in the final state. For each event, the mass is reconstructed from a kinematic fit of the decay products to a top quark pair hypothesis. A profile likelihood method is applied using up to four observables per event to extract the top quark mass. The top quark mass is measured to be$$171.77\pm 0.37\,\text {Ge}\hspace{-.08em}\text {V} $$$171.77\pm 0.37\text{Ge}\text{V}$. This approach significantly improves the precision over previous measurements.