Heat- and Pressure-driven Room-temperature Polymorphic Transition Accompanied with Switchable SHG Signal in a New Chiral Hexagonal Perovskite.

Endowing room-temperature polymorphs with both long-term stability and easy interconvertibility is a big challenge due to the complexity of intermolecular interactions. Herein, we present a chiral hexagonal perovskite (R-3-hydroxy-1-methylpiperidinium)[CdCl3 ] having two room-temperature crystalline forms featuring obviously distinct second-harmonic-generation (SHG) signals with a high switching contrast of ~18 times. The two room-temperature forms could be long-term stable yet easily interconvertible through an irreversible thermal-induced phase transition and a pressure-driven backward transition, by switching hydrogen bonds via collective reorientation of ordered homochiral cations. Based on the essential role of homochiral organic cations in inducing switchable hydrogen bond linkages, this present instance provides good evidence that relatively irregular organic cations could induce more obvious inorganic chain deformations, thus endowing polymorphs with significantly different SHG signals at room temperature.

An unprecedented hexagonal double perovskite organic-inorganic hybrid ferroelastic material: (piperidinium)2[KBiCl6].

An unprecedented A2MIMIIIX6-type double perovskite adopting a fully hexagonal BaNiO3-type structure, (piperidinium)2[KBiCl6], undergoes a 2/mF1[combining macron] ferroelastic phase transition at 285 K with a spontaneous strain of 0.0615, arising from the order-disorder transition of organic cations together with the synchronous displacement of inorganic chains.

[Vacuum-assisted biopsy and wire localization for the diagnosis of non-palpable breast lesions].

OBJECTIVE: To compare the effectiveness and accuracy of the use of vacuum-assisted biopsy (VAB) versus wire localization (WL) in the diagnosis of non-palpable breast lesions (NPBL). METHODS: Ninety-seven consecutive women with NPBL were randomized into VAB group and WL group. All specimens were identified by mammography. The patients were requested to score the cosmetic appearance of their breast after operation, and a numerical rating scale was used to measure pain on the first postoperative day. Underestimation rates for atypical ductal hyperplasia (ADH) and ductal carcinoma in situ (DCIS) were recorded if open surgical biopsy revealed DCIS and invasive cancer, respectively. Clear margins were also recorded in the two groups. RESULTS: VAB and WL located all the NPBL successfully. In the VAB group, the specimen volume was smaller than that of the WL group (2.3 cm(3) vs. 18.4 cm(3), P = 0.03). Underestimation rates of ADH and DCIS in the VAB group were 16.7% and 11.1%, respectively. The diagnostic accordance rate of VAB was 97.9%, the false negative rate was 2.1%, and there was no false positive case. The means of the numerical rating pain scale were different in both groups (1.7 for VAB vs. 2.5 for WL, P = 0.02). When cosmetic results were taken into account, 40 VAB patients had excellent outcomes and 8 good outcomes, compared with 25 excellent and 24 good for the WL group. There were better cosmetic outcomes with the VAB procedure (P < 0.05). CONCLUSION: VAB is highly reliable and may avoid diagnostic open surgery in the majority of patients with benign lesions. However, because of the underestimation of histologic diagnosis and tumor margin involvement, VAB can not be used to completely substitute wire localization.

Switching hydrogen bonds to readily interconvert two room-temperature long-term stable crystalline polymorphs in chiral molecular perovskites.

It is challenging to endow polymorphs with both long-term stability and easy interconvertibility. We demonstrate an interesting example that two room-temperature polymorphs could be long-term stable yet easily interconvertible, at a pressure of ∼4.8 MPa and a temperature of 120 °C, by switching hydrogen bonds via collective reorientation of organic cations in chiral molecular perovskites.