Two-step thermotropic phase transition and dielectric relaxation in 1D supramolecular lead iodide perovskite [NH4@18-crown ether]PbI3

The supramolecular lead iodide perovskite crystals, {[NH₄(18-crown-6)]PbI₃}_∞ (1), (18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane), was successfully achieved by a facile solvent evaporation strategy using a DMF solution containing equal molar quantities of PbI₂, NH₄I and 18-crown-6. The supramolecular perovskite was characterized by microanalysis for C, H and N elements, thermogravimetric (TG) analysis, differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD) and single crystal X-ray diffraction techniques. DSC measurements demonstrated that 1 experiences a two-step thermotropic phase transition around 333 K and 383 K, respectively. The phase transition is relevant to the disorder-order transformation of the 18-crown-6 molecule at ∼333 K, while both breaking-symmetry and ordered-disordered transformation of the 18-crown-6 molecule occurred at ∼383 K. In addition, the sharp change of the PbI₆ coordination octahedron distortion degree plays a synergistic role in the two-step phase transition. The dielectric relaxation occurs above 243 K in 1 and is mainly attributed to the displacement of the NH₄⁺ ions relative to the ring of the 18-crown-6 molecule and {PbI₃}_∞ chain induced by an AC electrical field.

[Analysis of incidence and risk factors for postoperative venous thromboembolism in patients with stageⅠ a non-small-cell lung cancer]

Objective: To analyze the incidence and risk factors for postoperative venous thromboembolism(VTE) in patients with stage Ⅰa non-small-cell lung cancer(NSCLC), so as to find evidence for further research of prophylactic anticoagulation. Methods: A total of 132 patients with stage Ⅰa NSCLC, 42 males and 90 females aged from 26 to 79 years with an average of (57±10) years, were retrospectively included in this study. All of them underwent surgical treatment at the Department of Thoracic Surgery of Beijing Chaoyang Hospital Affiliated with Capital Medical University from January 2017 to October 2020. A lower extremity venous ultrasound was performed before and after the operation. Participants were divided into VTE group (n=11) or non-VTE group (n=121) according to whether or not VTE occurred after operation. The surgical conditions, test indicators, imaging information, pathology information were compared between the two groups. Logistic regression analysis was performed to test the associations of VET with putative risks factors in which significant differences were observed. The independent risk factors of VET were determined by this way. Results: Postoperative VTE occurred in 11 cases (8.3%), including 10 cases (90.9%) of deep vein thrombosis (DVT) of lower limbs and 1 case (9.1%) of DVT complicated with pulmonary embolism (PE). The mean age of Patients in the VTE group was older than that in non-VTE Group ((65±9) years vs (57±10) years, P=0.009). On the fifth day after operation, patients in both groups had significantly higher D-dimer level compared with that before operation (3.18(1.55, 5.15) vs 1.54(1.09, 2.57); 2.66(1.17, 4.65) vs 1.34(0.78, 2.04))(both P<0.05). The value of neuron-specific enolase (NSE) and the number of lymph nodes removed during the operation in the VTE group were significantly higher than those in the non-VTE group ((21.54±12.37) vs (14.72±5.75); (19.7±8.2) vs (13.0±7.9)) (both P<0.05). There was no statistically significant difference in the approach of surgery, imaging features (tumor location, vascular cluster signs, etc.), and pathological information (pathological types, etc.) (all P>0.05). The logistic regression analysis showed that the number of lymph nodes removed during the operation was an independent risk factor related to the occurrence of VTE (OR=1.306, 95%CI:1.000-1.600,P<0.05). Conclusions: The incidence of postoperative VTE in patients with stage Ⅰa NSCLC is approximately 8.3%. The number of lymph nodes removed during the operation may be an independent risk factor for postoperative VTE in patients with stage Ⅰa NSCLC.

[Survey of current status of prevention of venous thromboembolism after thoracic surgery in China]

Objective: To investigate the current status of prevention and treatment of venous thromboembolism (VTE) after thoracic surgery in China. Method: Chinese thoracic surgeons were investigated by the online questionnaire which was based on the Chinese version of International VTE questionnaire added with 6 extra questions with Chinese characteristics. Results: A total of 1 150 valid questionnaires were retrieved, accounting for about 20% of all the Chinese thoracic surgeons. The surgeons participating in this survey came from all over the country, most of whom were experienced professionals with high academic titles.For lung cancer patients, 66.96% (770/1 150) of the surgeons suggested that VTE prophylaxis should start 1 day after lung cancer resection, and 64.61% (743/1 150) of the surgeons suggested extending after discharge. For esophagestomy patients, and 48.35% (514/1 063) of the surgeons suggested that there was no need for patients to extend VTE prophylaxis after discharge. More than half of the surgeons participating in this survey made decision of the method and duration of VTE prophylaxis after lung cancer resection (53.91% (620/1 150)) or esophagectomy (52.49% (558/1 063)) depending on the clinical experience.Low molecular weight heparin was the common choice of most surgeons in VTE prophylaxis. More than half of the surgeons thought that previous history of VTE, advanced age, complicated with thrombophilia, obesity (body mass index>30 kg/m²), duration of surgery longer than 6 hours and family history of VTE were key risk factors of the occurrence of postoperative VTE. Conclusions: The results of this survey are highly credible and are a good reflection of the current status of VTE prevention and treatment after thoracic surgery in China. This survey will play an important role in promoting VTE prevention and treatment in Chinese thoracic surgery department, it will also provide data support for government setting new policies, hospital construction of VTE prevention and control as well as raising physicians' awareness.

Study on crystallization and compatibility of nitrile butadiene rubber (NBR)/polyoxymethlene (POM) blends modified by a polyether polyol

Blends of nitrile butadiene rubber (NBR) and polyoxymethlene (POM) were prepared by melt mixing, with a polyether polyol (Model KGF400D) used as the compatibilizer. Scanning electron microscopy (SEM) was used to characterize the cryogenically fractured surfaces of the blends clearly, which showed that the compatibility of NBR/POM blends was significantly enhanced with the addition of KGF400D. Both differential scanning calorimetry (DSC) and rubber process analysis (RPA) results clearly indicated the mechanism of compatibility improvement. Dual functions of KGF400D within the NBR/POM blends were found: one was the lubrication effect and the other was the hydrogen bonding between the hydroxyl of KGF400D and ether oxygen group of POM or lone pair electron in the cyano group of NBR.