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The title compound, C(11)H(8)O(3), was isolated from Impatiens balsamina plants (balsam, LIB) grown in our laboratory. The two six-membered rings of the naphthalene-1,4-dione unit are coplanar [maximum deviation = 0.009 (1) Å]. The O and C atoms of the meth-oxy substituent also lie close to the naphthalene plane, with deviations of 0.0090 (2) and 0.047 (2) Å, respectively.

The title compound, C(15)H(18)O(3), was isolated from Lacta-rius piperatus (Fr.) S. F. Gary collected from the Kunming area in Yunnan province, China. The central cyclo-hexyl ring adopts a chair conformation, while the furan-one ring is close to planar (r.m.s. deviation = 0.0174 Å). The remaining methyl-ene cyclo-hexene ring has a flattened chair conformation. In the crystal, mol-ecules are linked via inter-molecular O-H⋯O and C-H⋯O hydrogen bonds into zigzag chains along the a axis.

In the title compound, C(15)H(18)ClNO(4)S·H(2)O, the thia-zolidine ring displays a half-chair conformation. In the crystal, the water mol-ecules are linked to the organic acid mol-ecules via inter-molecular O-H⋯O hydrogen bonds.

In the title compound, C(15)H(18)ClNO(4)S, the thia-zolidine ring adopts a twisted conformation about the S-C(methyl-ene) bond. The dihedral angle between the five- and six-membered rings is 77.2 (3)°. In the crystal, the mol-ecules are linked by O-H⋯O hydrogen bonds, generating C(7) chains propagating in [100].

Objective: To investigate if the Ribbond polyethylene fiber has the effect of reinforcing polymethyl methacylate., Methods: 28 specimens were fabricated and divided into 3 groups: group of chemical-cured PMMA, group of chemical-cured PMMA reinforced by stainless steel wire and group of chemical-cured PMMA reinforced by Ribbond polyethylene fiber. A three-point bending test was used to measure the flexural strength and flexural modulus of specimens. Then the data were analyzed with a one-way analysis of variance., Results: The flexural strength of chemical-cured PMMA group was (51.383 +/- 2.761) MPa, the flexural modulus was (1791.2 +/- 113.760) MPa; The flexural strength of stainless steel wire reinforced group was (58.725 +/- 1.218) MPa, the flexural modulus was (2092.76 +/- 120.28) MPa; The flexural strength of Ribbond polyethylene fiber reinforced group was (80.975 +/- 2.58) MPa, the flexural modulus was (2866.53 +/- 107.51) MPa. The one-way analysis of variance showed that the results were significant (P < 0.001). Newman-Keuls method showed that the differences among all groups were significant (P < 0.05)., Conclusion: The Ribbond polyethylene fiber can raise the flexural strength and flexural modulu of polymethyl methacylate.