Hydrocarbon Molecules Research Articles

Shape-Selective Ultramicroporous Carbon Membranes for Sub-0.1nm Organic Liquid Separation.

Liquid‐phase chemical separations from complex mixtures of hydrocarbon molecules into singular components are large‐scale and energy‐intensive processes. Membranes with molecular specificity that efficiently separate molecules of similar size and shape can avoid phase changes, thereby reducing the energy intensity of the process. Here, forward osmosis molecular differentiation of hexane isomers through a combination of size‐ and shape‐based separation of molecules is demonstrated. An ultramicroporous carbon membrane produced with 6FDA‐polyimides realized the separation of isomers for different shapes of di‐branched, mono‐branched, and linear molecules. The draw solvents provide the driving force for fractionation of hexane isomers with a sub‐0.1 nm size difference at room temperature without liquid‐phase pressurization. Such membranes could perform bulk chemical separations of organic liquids to achieve major reductions in the energy intensity of the separation processes.

Response modulation of silicon nanowires-based sensor to carbon number in petroleum vapor detection

To ensure high safety level in crude oil and its distillates storage tanks, petrochemical industry needs responsive and reliable hydrocarbon vapor sensing devices. We propose here a cost-effective petroleum vapor sensor that could be used effectively in oil tanks. The fabricated device is based on silicon nanowires (SiNWs) and has a good response to petroleum vapor concentration fluctuations. The chemiresistive sensitive device is a layer of SiNWs elaborated on a Cz-Si wafer with top planar Ag-Al electrical contacts. Petroleum vapors are obtained by heating crude oil. Detection measurements are performed at temperatures ranging from the ambient (18 °C) to 70 °C and for vapor concentrations varying between the Lower Explosion Limit (LEL) ~ 10000 ppmv and the Upper Explosion Limit (UEL) ~ 60000 ppmv.By measuring the time-dependent electrical resistance of the device at a fixed temperature, multiple cycles of response-recovery are obtained. As a main finding, we report on how the response of SiNWs to carbon number (nC) of petroleum vapor could be modulated by varying the device temperature.Therefore, at room temperature, when the petroleum vapor is rich of light hydrocarbon molecules (nC ≤ 7), adsorption–desorption cycles are quasi-reversible. However, at higher temperature, when vapors substantially contain heavier hydrocarbon molecules (nC > 7), we obtain a time dependent pronounced increasing drift in the chemiresistance of the device. Interestingly we found that the carbon number of molecules in the petroleum vapor plays a key-role in the response of the sensor.

Combustion kinetics of alternative jet fuels, Part-II: Reaction model for fuel surrogate

Conventional transportation fuels used in aviation (jet fuel) or in ground transportation (gasoline, diesel) contain multitude of hydrocarbon components and are difficult to be modeled, if one has to consider each of the component present. A typical approach is the definition of a fuel surrogate with a limited number of fuel components. In this context, a single semi-detailed high temperature reaction kinetic mechanism is presented in this work, which contains all the important molecular classes required for the detailed surrogate modeling of a hydrocarbon fuel. The appeal of the mechanism is the suitability for a broad range of technical fuels covering gasoline, diesel and jet fuels. The reaction mechanism for hydrocarbon combustion is consisted of 238 species and 1814 reactions and is rigorously validated for 70 neat hydrocarbon components over a wide range of experimental conditions including combustion setups such as shock-tubes, laminar flames, jet-stirred and flow reactors.The purpose of this study is to provide a single reaction model that (1) includes variety of hydrocarbon molecules of varying degree of complexity and carbon numbers, (2) has capability to model a spectrum of different fuels, initially aviation fuels, and (3) is compact to apply both in simple (fundamental kinetic investigations) and complex geometries (CFD studies) of combustion system enabled through customized mechanism reductions. The ultimate goal is to resolve the fuel differences using the model predictions obtained from the reaction mechanism that will supply parameters for fuel design and optimization of fuels. Extensive supporting information is available in this work.

S/Se-embedded acenaphthylene-imide-containing polycyclic heteroaromatic hydrocarbon

Acenapththylene-imide (AnI), similar to naphthalene diimide (NDI), is an outstanding building block for organic functional materials and has gained a lot of research attention. Herein, Sulphur and Selenium-embedded AnI-containing polycyclic aromatic hydrocarbon molecules, AnI-SQ and AnI-SeQ, with [1,2,5]thiadiazolo[3,4-g]quinoxaline (SQ) and [1,2,5]selenadiazolo[3,4-g]quinoxaline (SeQ) are designed and synthesized with low-lying LUMO energy levels. The absorption and emission of AnI-SQ and AnI-SeQ displayed a bathochromic shift upon protonation of the C = N bond. Besides, theoretical calculation indicates remarkable rigid planar backbones for both AnI-SQ and AnI-SeQ. Through self-assembly with polymeric Pluronic® F-127, corresponding hydrophilic nanoparticles (NPs) were prepared with low cytotoxicity. And AnI-SQ NPs could be applied for in vitro two-photon fluorescence imaging.

Void-Defect Induced Magnetism and Structure Change of Carbon Material-Ⅲ: Hydrocarbon Molecules

Void-defect induced magnetism of graphene molecule was recently reported in our previous paper of this series study. This paper investigated the case of hydrogenated graphene molecule, in chemical term, polycyclic aromatic hydrocarbon (PAH). Molecular infrared spectrum obtained by density functional theory was compared with astronomical observation. Void-defect on PAH caused serious structure change. Typical example of C23H12 had two carbon pentagon rings among hexagon networks. Stable spin state was non-magnetic singlet state. This is contrary to pure carbon case of C23, which show magnetic triplet state. It was discussed that Hydrogen played an important role to diminish magnetism by creating an SP3-bond among SP2-networks. Such a structure change affected molecular vibration and finally to photoemission spectrum in infrared region. The dication-C23H12 showed featured bands at 3.2, 6.3, 7.7, 8.6, 11.2, and 12.7 micrometer. It was surprising that those calculated bands coincided well with astronomically observed bands in many planetary nebulae. To confirm our study, large size molecule of C53H18 was studied. Calculation reproduced again similar astronomical bands. Also, small size molecule of C12H8 showed good coincidence with the spectrum observed for young stars. This paper would be the first report to indicate the specific PAH in space.

Piecing Together Large Polycyclic Aromatic Hydrocarbons and Fullerenes: A Combined ChemTEM Imaging and MALDI-ToF Mass Spectrometry Approach.

Motivated by their importance in chemistry, physics, astronomy and materials science, we investigate routes to the formation of large polycyclic aromatic hydrocarbon (PAH) molecules and the fullerene C60 from specific smaller PAH building blocks. The behaviour of selected PAH molecules under electron (using transmission electron microscopy, TEM) and laser irradiation is examined, where four specific PAHs—anthracene, pyrene, perylene and coronene—are assembling into larger structures and fullerenes. This contrasts with earlier TEM studies in which large graphene flakes were shown to transform into fullerenes via a top-down route. A new combined approach is presented in which spectrometric and microscopic experimental techniques exploit the stabilisation of adsorbed molecules through supramolecular interactions with a graphene substrate and enable the molecules to be characterised and irradiated sequentially. Thereby allowing initiation of transformation and characterisation of the resultant species by both mass spectrometry and direct-space imaging. We investigate the types of large PAH molecule that can form from smaller PAHs, and discuss the potential of a “bottom-up” followed by “top-down” mechanism for forming C60.

UV-Mediated Photofunctionalization of Indirect Restorative Materials Enhances Bonding to a Resin-Based Luting Agent.

Purpose The potential of UV-mediated photofunctionalization to enhance the resin-based luting agent bonding performance to aged materials was investigated. Methods Sixty samples of each material were prepared. Yttria-stabilized zirconia (YZr) and Pd-Au alloy (Pd-Au) plates were fabricated and sandblasted. Lithium disilicate glass-ceramic (LDS) was CAD-CAM prepared and ground with #800 SiC paper. Half of the specimens were immersed in machine oil for 24 h to simulate the carbon adsorption. Then, all of the specimens (noncarbon- and carbon-adsorbed) were submitted to UV-mediated photofunctionalization with a 15 W UV-LED (265 nm, 300 mA, 7692 μW/cm2) for 0 (control groups), 5, and 15 min and subjected to contact angle (Ɵ) measurement and bonded using a resin cement (Panavia™ V5, Kuraray Noritake, Japan). The tensile bond strength (TBS) test was performed after 24 h. The Ɵ (°) and TBS (MPa) data were statistically analyzed using two-way ANOVA and Bonferroni correction tests (α = 0.05). Results In the carbon-adsorbed groups, UV-mediated photofunctionalization for 5 min significantly decreased Ɵ of all materials and increased TBS of YZr, and UV for 15 min significantly increased the TBS of LDS and Pd-Au. In noncarbon-adsorbed groups, UV-photofunctionalization did not significantly change the Ɵ or TBS except YZr specimens UV-photofunctionalized for 15 min. Conclusion UV-mediated photofunctionalization might have removed the adsorbed hydrocarbon molecules from the materials' surfaces and enhanced bond strengths of Panavia™ V5 to YZr, LDS, and Pd-Au. Additionally, UV-mediated photofunctionalization improved the overall TBS of YZr. Further investigation on the optimum conditions of UV photofunctionalization on indirect restorative materials should be conducted.

Slip length of branched hydrocarbon oils confined between iron surfaces

In this paper, the slip length of branched hydrocarbon molecules, i.e., polyalphaolefin oils, under shear in a gap between iron surfaces were investigated utilizing large-scale Molecular Dynamics (MD) simulation. The results showed the expected singularity for the slip length with variation gap height. For large gap height, h→∞, the slip length approaches a constant asymptote λ→λ∞. This study indicated that as the number of branches of the liquid molecule raise, the slip length λ→λ∞ as well as viscosity increases. For given apparent shear rate, the friction force increased with increasing temperature due to the reduction of wall slip. MD Simulations demonstrate that the slip length of the polyalphaolefin-iron system increase by decreasing the liquid temperature, indicating an Arrhenius process.

Flow of long chain hydrocarbons through carbon nanotubes (CNTs)

The pressure-driven flow of long-chain hydrocarbons in nanosized pores is important in energy, environmental, biological, and pharmaceutical applications. This paper examines the flow of hexane, heptane, and decane in carbon nanotubes (CNTs) of pore diameters 1–8 nm using molecular dynamic simulations. Enhancement of water flow in CNTs in comparison to rates predicted by continuum models has been well established in the literature. Our work was intended to observe if molecular dynamic simulations of hydrocarbon flow in CNTs produced similar enhancements. We used the OPLS-AA force field to simulate the hydrocarbons and the CNTs. Our simulations predicted the bulk densities of the hydrocarbons to be within 3% of the literature values. Molecular sizes and shapes of the hydrocarbon molecules compared to the pore size create interesting density patterns for smaller sized CNTs. We observed moderate flow enhancements for all the hydrocarbons (1–100) flowing through small-sized CNTs. For very small CNTs the larger hydrocarbons were forced to flow in a cork-screw fashion. As a result of this flow orientation, the larger molecules flowed as effectively (similar enhancements) as the smaller hydrocarbons.

Harmonic chains and the thermal diode effect.

Harmonic oscillator chains connecting two harmonic reservoirs at different constant temperatures cannot act as thermal diodes, irrespective of structural asymmetry. However, here we prove that perfectly harmonic junctions can rectify heat once the reservoirs (described by white Langevin noise) are placed under temperature gradients, which are asymmetric at the two sides, an effect that we term "temperature-gradient harmonic oscillator diodes." This nonlinear diode effect results from the additional constraint-the imposed thermal gradient at the boundaries. We demonstrate the rectification behavior based on the exact analytical formulation of steady-state heat transport in harmonic systems coupled to Langevin baths, which can describe quantum and classical transport, both regimes realizing the diode effect under the involved boundary conditions. Our study shows that asymmetric harmonic systems, such as room-temperature hydrocarbon molecules with varying side groups and end groups, or a linear lattice of trapped ions may rectify heat by going beyond simple boundary conditions.

Self-assembly of curved aromatic molecules in nanoparticles

The self-assembly and structure of nanoparticles containing curved polycyclic aromatic hydrocarbon molecules (cPAHs) are investigated using molecular modelling. These polar fullerene-like molecules are receiving increased attention recently due to the steric and electronic properties caused by the inclusion of five-membered ring(s) within their hexagonal lattice. In this work, the curPAHIP potential is extended to describe the interactions between large cPAHs. It is then used within molecular dynamics simulations to produce nanoparticles containing cPAHs. Structural and energetic metrics, including diameter, density, intermolecular spacing, coordination number, alignment angle, radial distance, and energy value, are used to analyse systems containing cPAHs of different sizes and ratios, and containing flat PAHs or ions. Homogeneous cPAH particles are more tightly packed than their flat PAH counterparts, with large cPAHs displaying stacked columnar configurations absent in nanoparticles containing small cPAHs. Mixing cPAHs of different sizes disrupts the ordered mesophase and forms a core-shell structure in which the larger molecules make up the core and the smaller molecules comprise the shell, although this partitioning is less distinct compared to flat PAHs. In addition, the presence of flat PAHs and ions within cPAH nanoparticles promotes distinct arrangements dominated by weak dispersive interactions and strong electrostatic interactions, respectively.

Accurate Atom-Dipole Interaction Model for Prediction of Electro-optical Properties: From van der Waals Aggregates to Covalently Bonded Clusters.

This work aims at the accurate estimation of the electro-optical properties of atoms and functional groups in organic crystals. A better understanding of the nature of building blocks and the way they interact with each other enables more efficient prediction of self-assembly, and thus physical properties in condensed matter. We propose a modified version of an atom-dipole interaction model that is based on atomic dipole moments calculated from the quantum theory of atoms in molecules. The method is very reliable for the prediction of various optical and electric properties in diverse chemical environments, ranging from hydrocarbon molecules bonded by dispersive interactions to polar rings connected by hydrogen bonds, or even polymeric structures whose monomers are covalently linked. Distributed polarizabilities and electrostatic potentials are compared to those obtained using a complete quantum-mechanical approach on finite-size aggregates. Our electrostatic approximation recovers isotropic polarizabilities with an accuracy of ca. 5 au and electrostatic potentials of ca. 0.05 au, even in the worst-case scenario in which polarization and charge-transfer effects are large. Functional groups are highly exportable, estimating the properties of small peptides and polyaromatics with a maximum deviation as low as ca. 15%.

The Characterization of hydrocarbon compounds in bio-oil produced by pyrolysis of biomass from the essential oil distilled residue using ZSM-5 and YSZ catalysts

The main hydrocarbon containing in petroleum and natural gas are important feedstocks for various kinds of fuel and petrochemical products, but these non-renewable resources will diminish their supply over time and that is why the development of environmentally friendly hydrocarbon resources whose more secure should be driven. One of the origins could become the residue of the distillation process of essential oils using catalytic pyrolysis that would produce the hydrocarbon distribution products. The use of acid catalysts such as ZSM-5 can improve the hydrocarbon in bio-oil. However, the use of zeolites can mainly accelerate the cracking of long molecules to make hydrocarbon molecules simpler by forming carbonium ions from the carbon-carbon chain. Thus, requiring a modification of the catalyst with adds YSZ catalyst, which can cut off oxygen from the hydrocarbon group is needed to improve the results of catalytic pyrolysis. The results of this study showed that the maximum temperature at 550 °C was able to increase the yield of steam products and the production of non-oxygenated hydrocarbon compounds. Similarly, the optimization condition of the argon gas flow rate is 100 mL/min. In that condition, the fluidization of biomass material occurs maximally, and the occurrence of the heat transfer process is very fast. While the optimum ratio of YSZ/ZSM-5 catalyst was achieved by a 3:2 ratio. YSZ is very effective at 550 °C in assisting ZSM-5 to form non-oxygenated hydrocarbon compounds. It can be proofed by GC-MS results that non-oxygenated compounds produced such a group of non-oxygenated hydrocarbon cyclic, paraffin, and aromatic compounds are dominant.

Reversible hydrogenation restores defected graphene to graphene

Graphene as a two-dimensional material is prone to hydrocarbon contaminations, which can significantly alter its intrinsic electrical properties. Herein, we implement a facile hydrogenation-dehydrogenation strategy to remove hydrocarbon contaminations and preserve the excellent transport properties of monolayer graphene. Using electron microscopy we quantitatively characterized the improved cleanness of hydrogenated graphene compared to untreated samples. In situ spectroscopic investigations revealed that the hydrogenation treatment promoted the adsorption ofytyt water at the graphene surface, resulting in a protective layer against the re-deposition of hydrocarbon molecules. Additionally, the further dehydrogenation of hydrogenated graphene rendered a more pristine-like basal plane with improved carrier mobility compared to untreated pristine graphene. Our findings provide a practical post-growth cleaning protocol for graphene with maintained surface cleanness and lattice integrity to systematically carry a range of surface chemistry in the form of a well-performing and reproducible transistor.

The Graovac-Pisanski index of connected bipartite graphs with applications to hydrocarbon molecules

The Graovac-Pisanski index, also called the modified Wiener index, was introduced in 1991 and represents an extension of the original Wiener index, because it considers beside the distances in a graph also its symmetries. Similarly as Wiener in 1947 showed the correlation of the Wiener indices of the alkane series with the boiling points, in 2018 the connection between the Graovac-Pisanski index and the melting points of some hydrocarbon molecules was established. In this paper, we prove that the Graovac-Pisanski index of any connected bipartite graph as well as of any connected graph on an even number of vertices is an integer number. These results are applied to some important families of hydrocarbon molecules. By using a computer programme, the graphs with a non-integer Graovac-Pisanski index on at most nine vertices are counted. Finally, an infinite class of unicyclic graphs with a non-integer Graovac-Pisanski index is described.

Comparison of Many-Particle Representations for Selected Configuration Interaction: II. Numerical Benchmark Calculations

The present work is the second part in our three-part series on the comparison of many-particle representations for the selected configuration interaction (CI) method. In this work, we present benchmark calculations based on our selected CI program called the iterative configuration expansion (ICE) that is inspired by the CIPSI method of Malrieu and co-workers (MalrieuJ. Chem. Phys.1973, 58, ( (12), ), 5745−5759). We describe the main parameters that enter in this algorithm and perform benchmark calculations on a set of 21 small molecules and compare ground state energies with full configuration interaction (FCI) results (FCI21 test set). The focus is the comparison of the performance of three different types of many-particle basis functions (MPBFs): (1) individual Slater determinants (DETS), (2) individual spin-adapted configuration state functions (CSFs), and (3) all CSFs of a given total spin that can be generated from spatial configurations (CFGs). An analysis of the cost of the calculation in terms of the number of wavefunction parameters and the energy error is evaluated for the DET-, CFG-, and CSF-based ICE. The main differences for the three many-particle basis representations show up in the number of wavefunction parameters and the rate of convergence toward the FCI limit with the thresholds of the ICE. Next, we analyze the best way to extrapolate the ICE energies toward the FCI results as a function of the thresholds. The efficiency of the extrapolation is investigated relative to the FCI21 test set as well as near FCI calculations on three moderately sized hydrocarbon molecules CH4, C2H4, and C4H6. Finally, we comment on the size-inconsistency error for the three many-particle representations and compare it with the error in the total energy. The implication for selected CI implementations with any of the three many-particle representations is discussed.

Compact planetary nebulae MaC 2-1 and Sp 4-1: photoionization models and dust characteristics

ABSTRACT We study the characteristics of the planetary nebulae (PNe) MaC 2-1 and Sp 4-1. We use our optical spectra taken with the 2 m Himalayan Chandra Telescope, Spitzer mid-infrared (mid-IR) spectra, HST images, and IR photometric data. These PNe have not previously been individually studied in detail. Both are in the low- to moderate-excitation class. MaC 2-1 shows the presence of silicon carbide (SiC) and magnesium sulphide (MgS) dust. Sp 4-1 hosts polycyclic aromatic hydrocarbon (PAH) molecules. We obtain the plasma properties of the PNe from the optical and mid-IR emission-line fluxes. We compute photoionization models of the PNe for the self-consistent estimation of physical parameters associated with the central star and the nebula, including nebular abundances. From the modelling of the IR data, we obtain the characteristics of dust and molecules formed in the nebulae. From our study, we estimate that the progenitors of MaC 2-1 and Sp 4-1 had masses of 1.2 and 1.55 M⊙, respectively, and both of them seem to have been born in a metal-poor environment. Both are distant PNe, with estimated distances of 16 and 18 kpc for MaC 2-1 and Sp 4-1, respectively.

Adsorption, selectivity, and phase behavior in organic nanopores for shale gas and oil development

In a shale gas and oil reservoir, hydrocarbon fluids are stored in organic nanopores with sizes on the order of ∼1–100 nm. The adsorption, selectivity, and phase behavior of hydrocarbons in the nanopores are crucial for estimating the gas-in-place and predicting the productivity. In this study, to understand the characteristics of the phase behavior of multicomponent hydrocarbon systems in shale reservoirs, the phase behavior of a CH4/n-C4H10 binary mixture in graphite nanopores was investigated by Grand Canonical Monte Carlo (GCMC) molecular simulation. The method for determining the dew-point pressure and bubble-point pressure in the nanopores was explored. The condensation phenomenon was observed owing to the difference in the adsorption selectivities of the hydrocarbon molecules on the nanopore surfaces, and hence the dew-point pressure (and bubble-point pressure) of hydrocarbon mixtures in the nanopores significantly shifted. The GCMC simulations reproduced both the higher and lower bubble-point pressures in nanopores in previous studies. This work highlights the crucial role of the selectivity in the phase behavior of hydrocarbons in nanopores.

Efficient adsorption separation of methane from CO2 and C2–C3 hydrocarbons in a microporous closo-dodecaborate [B12H12]2- pillared metal–organic framework

A closo-dodecaborate [B12H12]2- functionalized metal organic framework (MOF), BSF-3, constructed by the self-assembly of the Cu(II) cation, 1,4-di(pyridin-4-yl)benzene linker and cluster [B12H12]2- pillar was investigated for the adsorption separation of light hydrocarbons. The activated MOF exhibited efficient uptake of CO2 and C2–C3 hydrocarbons with high separation selectivity of C3H8 (138), C2H2 (205), C2H4 (23), C2H6 (13) and CO2 (9) over CH4, outperforming many popular MOFs. The practical gas separation ability for C2H2/CH4, CO2/CH4 and C3H8/C2H6/CH4 was confirmed by mixed gas breakthrough experiments with no capacity loss after 7 cycles, indicating its potential for purification of methane from natural gas and pyrolysis gas. The gas bonding sites within the framework were further studied by modelling studies, which indicated that the anionic [B12H12]2- pillar contributed the most to capturing hydrocarbon molecules by multiple B-Hδ-···Hδ+-C interactions.

A Spectroscopic View on Cosmic PAH Emission

ConspectusPolycyclic aromatic hydrocarbon molecules (PAHs) are ubiquitously present at high abundances in the Universe. They are detected through their infrared (IR) fluorescence UV pumped by nearby massive stars. Hence, their infrared emission is used to determine the star formation rate in galaxies, one of the key indicators for understanding the evolution of galaxies. Together with fullerenes, PAHs are the largest molecules found in space. They significantly partake in a variety of physical and chemical processes in space, influencing star and planet formation as well as galaxy evolution.Since the IR features from PAHs originate from chemical bonds involving only nearest neighbor atoms, they have only a weak dependence on the size and structure of the molecule, and it is therefore not possible to identify the individual PAH molecules that make up the cosmic PAH family. This strongly hampers the interpretation of their astronomical fingerprints. Despite the lack of identification, constraints can be set on the characteristics of the cosmic PAH family thanks to a joint effort of astronomers, physicists, and chemists.This Account presents the spectroscopic properties of the cosmic PAH emission as well as the intrinsic spectroscopic properties of PAHs and astronomical modeling of the PAH evolution required for the interpretation of the cosmic PAH characteristics. We discuss the observed spectral signatures tracing PAH properties such as charge, size, and structure and highlight the related challenges. We discuss the recent success of anharmonic calculations of PAH infrared absorption and emission spectra and outline the path forward. Finally, we illustrate the importance of models on PAH processing for the interpretation of the astronomical data in terms of the charge balance and PAH destruction.Throughout this Account, we emphasize that huge progress is on the horizon on the astronomical front. Indeed, the world is eagerly awaiting the launch of the James Webb Space Telescope (JWST). With its incredible improvement in spatial resolution, combined with its complete spectral coverage of the PAH infrared emission bands at medium spectral resolution and superb sensitivity, the JWST will revolutionize PAH research. Previous observations could only present spectra averaged over regions with vastly different properties, thus greatly confusing their interpretation. The amazing spatial resolution of JWST will disentangle these different regions. This will allow us to quantify precisely how PAHs are modified by the physical conditions of their host environment and thus trace how PAHs evolve across space. However, this will only be achieved when the necessary (and still missing) fundamental properties of PAHs, outlined in this Account, are known. We strongly encourage you to join this effort.