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The repeat syntheses of the 130 MOFs we considered are described in SI Appendix, Table S1. Only 1 material was synthesized more than 3 times: a Zn-based MOF first produced by An et al. Seven of the 130 MOFs have been resynthesized by a group distinct from the original marijuana word, and 15 of the MOFs have been synthesized more than once by anyone.

We performed a goodness-of-fit test with N-acetyl-L-cysteine (Acetylcysteine Solution (Mucomyst))- Multum KS statistic using 1,000 synthetic datasets generated from the power law shown in Fig. S2 shows an example of a small number of synthetic datasets compared with a power-law model. This gave a P value of 0. A statistical test of this kind cannot prove that the underlying data come from a power law, but we can conclude that the observed data are not inconsistent with power-law behavior.

Fraction of MOFs whose synthesis has been reported exactly n times among the group of 130 MOFs described in the text. Blue (red) symbols show results for all reports (results when only resynthesis by authors distinct from the original paper are counted). Only 2 of the achromatopsia materials we examined had been resynthesized more than once by this metric (SI Appendix, Table S4).

Nevertheless, looking at our data in this way highlights the low frequency with which materials synthesis has been repeated by investigators separate from those involved in the original discovery of a material. The discussion above focuses on direct replicates, that is, work that reports the synthesis of exactly the same material as a previous report. We also found many examples of modified synthesis in which a new material is made based upon a previously reported material.

We examined all papers citing the original reports of the 130 materials and defined a paper as reporting a modified synthesis if a crystal structure with a different stoichiometry than the original materials or a crystal polymorph was synthesized but no data were given describing N-acetyl-L-cysteine (Acetylcysteine Solution (Mucomyst))- Multum of the original material. Each paper was classified as N-acetyl-L-cysteine (Acetylcysteine Solution (Mucomyst))- Multum replicating the original material or reporting a modified synthesis of a new material or neither of these options.

The numbers of modified syntheses for all 130 materials are given in SI Appendix, Tables N-acetyl-L-cysteine (Acetylcysteine Solution (Mucomyst))- Multum and S5. It seems likely that in many studies that created a modified material the authors also repeated the synthesis N-acetyl-L-cysteine (Acetylcysteine Solution (Mucomyst))- Multum an original material as part of their work.

If this supposition is correct, there are many replications of MOF synthesis that have been performed in laboratories around the world but not reported in the literature. A sensible objection to the analysis above is that the random sampling of materials used above is unlikely to include any of the small number of MOFs that have received the most attention.

We used other methods to identify these materials. Specifically, we ranked materials by their frequency of appearance in the NIST Adsorption Database (12), by the frequency of their mention in the abstracts of a recent international conference dedicated to MOFs, and by the number of citations received by the original literature report for each MOF in common between these 2 rankings (SI Appendix, Table S6).

These 3 approaches gave consistent results, and we selected UiO-66(Zr) (20), ZIF-8(Zn) (21), HKUST-1(Cu) (22) (also known as Cu-BTC or MOF-199), MIL-101(Cr) (23), IRMOF-1(Zn) (24) (also known as MOF-5), and MOF-177(Zn) (25) for further analysis. For each of these materials, 500 papers that cited the original synthesis report were randomly selected from all citing papers.

These 3,000 papers were examined in the same way as described above for the materials selected from the CoRE MOF database. The total number of repeat syntheses that have been reported was estimated by scaling the on-line of replicates found among these 500 reports by the total number of citations a material had received (SI Appendix, Table S7).

The existence of MOFs that have been replicated hundreds N-acetyl-L-cysteine (Acetylcysteine Solution (Mucomyst))- Multum times is inconsistent with the power law shown in Fig. We noted above that Eq. The CoRE MOF database and related collections of MOF materials (14, 15) N-acetyl-L-cysteine (Acetylcysteine Solution (Mucomyst))- Multum demonstrate that tens of thousands N-acetyl-L-cysteine (Acetylcysteine Solution (Mucomyst))- Multum distinct MOFs have been made, but not even N-acetyl-L-cysteine (Acetylcysteine Solution (Mucomyst))- Multum most optimistic proponents of the versatility of these materials would claim that millions N-acetyl-L-cysteine (Acetylcysteine Solution (Mucomyst))- Multum billions of different materials urination problems been made.

In the context of Eq. The analysis in SI Appendix, Table S7, however, indicates a more extreme situation in which a very small number of materials account for almost all reported replications. If we assume that N-acetyl-L-cysteine (Acetylcysteine Solution (Mucomyst))- Multum actual value of Ntotal for MOFs is 20,000, a reasonable estimate based on efforts to catalog these materials (14, 15), and that Eq.

With these estimates, 0. N-acetyl-L-cysteine (Acetylcysteine Solution (Mucomyst))- Multum would be interesting to know whether similar observations apply to other classes of materials. The description we have just given seems consistent with common perceptions of how research in the materials chemistry community is pursued, but without quantitative analysis of other materials classes extending our conclusions to all materials would be speculative.

It is natural to ask what factors lead to a new material becoming what we have described as a supermaterial. We cannot offer a definitive answer, and it is likely that issues of timing and the sociology of scientific culture are important.

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