Insight into understanding magnetic transition quite sensitive to nonmagnetic impurity in a one-dimensional S = ½ regular linear chain system

Herein, we demonstrate that the antiferromagnetic couplings in a [Ni(mnt)2]− stack are realized mainly through spatial dipole–dipole type interactions.

A Semiconductive Nature of Bis(dithiolato)nickelate Radical Salt Exhibiting Broadband Photoconduction

The fractional oxidation state [M(dmit)₂] (dmit^2- = 2-thioxo-1, 3-dithiole-4, 5-dithiolate) salts have long attracted attention in the molecular metal area owing to high conductivity and even superconductivity. In this study, we achieved a mixed-valence salt (1) of [Ni(dmit)₂]^0.5- with monovalent 1,3-N,N-dimethyl-imidazolium (DiMIm⁺) by a solvent evaporation approach under ambient conditions. The mixed valence of [Ni(dmit)₂]^0.5- has been characterized by an analysis of the IR spectrum and crystal structure. In the crystal structure of 1, two [Ni(dmit)₂]^0.5- anions overlap in an eclipsed mode to form a [Ni(dmit)₂]₂^1- dimer, featuring a radical bearing an S = 1/2 spin; the dimeric radicals stack into a column along the b axis, and the adjacent columns connect together via the lateral-to-lateral S···S contacts along the a axis, and through the head-to-head S···S contacts along the [101] direction. Salt 1 shows the magnetic behavior of an S = 1/2 Heisenberg antiferromagnetic uniform linear chain with J/k_B = -47.5(4) K and a semiconducting feature with σ = 2.52 × 10^-3 S cm^-1 at 293 K, 2.32 × 10^-2 S cm^-1 at 373 K, and E_a = 0.22 eV, as well as broadband photoconductivity under irradiation of green and white lights. This study suggests the possibility of designing new photoconductors based on the mixed-valence [Ni(dmit)₂]^0.5- salt.

[Association analysis between extracurricular physical activity and dyslipidemia among primary, middle and high school students in Guangzhou]

Objective: To investigate the prevalence of dyslipidemia, and to explore the association between extracurricular physical activity and dyslipidemia among primary, middle and high school students in Guangzhou. Methods: This cross-sectional study selected primary and middle school students in Guangzhou by the stratified cluster sampling method from March to December 2019. Physical examination and blood lipid test were performed. Information about students' basic characteristics and extracurricular physical activity was collected by questionnaire. Multivariate logistic regression analysis was used to determine the association between extracurricular physical activity and dyslipidemia in this cohort. Results: A total of 7 797 participants (mean aged (12.2±2.9) years) were included (4 194 (53.79%) boys and 3 603 (46.21%) girls]. The detection rates of high total cholesterol, high triglycerides, low high-density lipoprotein cholesterol, high low-density lipoprotein cholesterol and dyslipidemia were 12.49% (974/7 797), 6.44% (502/7 797), 6.62% (516/7 797), 11.31% (882/7 797) and 23.83% (1 858/7 797), respectively. Dyslipidemia rate was lower in the junior school students (21.39% (675/3 156)) than in primary school students (25.96% (896/3 451)) and high-school students (24.12% (287/1 190)) (P<0.001). The dyslipidemia rates of boys and girls were similar (23.15% (971/4 194) vs. 24.62% (887/3 603), P>0.05). Dyslipidemia rate was lower in students with extracurricular physical activity than in students without extracurricular physical activity (22.50% (923/4 102) vs. 25.30% (935/3 695), P<0.05). Multivariate logistic regression analysis showed that extracurricular physical activity was associated with lower risk of dyslipidemia (OR=0.88, 95%CI=0.79-0.99, P=0.033). Among all types of extracurricular physical activities, participating in extracurricular large ball game was associated with 28% lower risk among junior school students (OR=0.72, 95%CI=0.57-0.91, P=0.006). Conclusion: The prevalence of dyslipidemia is high among primary, middle and high school students in Guangzhou. Extracurricular physical activity is associated with reduced risk of dyslipidemia in this cohort.

A Promising Phase Change Material with Record High Ionic Conductivity over a Wide Temperature Range of a Plastic Crystal Phase and Magnetic Thermal Memory Effect

The emerging organic ion plastic crystals (OIPCs) are the most promising candidates used as solid-state electrolytes in a range of ionic devices. To endow an OIPC with additional functionality may create a new type of material for multifunctional devices. Herein, we present an ion plastic crystal, [EMIm][Ni(mnt)₂] (1; [EMIm]⁺ = 1-ethyl-3-methylimidazolium and mnt^2- = maleonitriledithiolate), and its crystal consists of twin dimeric chains of [Ni(mnt)₂]^- anions, embraced by [EMIm]⁺ cations. A crystal-to-plastic crystal transformation with a large latent heat that occurred at ∼367/337 K on heating/cooling is confirmed by the differential scanning calorimetry (DSC) technique. The plastic crystal phase in 1, characterized by variable temperature powder X-ray diffraction (PXRD) and optical microscopy images, spans a broad temperature range with ΔT ∼123/153 K on heating/cooling (DSC measurement), and the wide ΔT is relevant to an extra stable anion chain owing to the strong antiferromagnetic (AFM) interactions protecting the chain from collapse in the plastic crystal state. 1 is a single-component ion plastic crystal with a record high ion conductivity, 0.21 S·cm^-1, at 453 K. The crystal-to-plastic crystal transformation in 1 is coupled to a bistable magnetic transition to give a multi-in-one multifunctional material. This study provides a creative thought for the design of OIPCs with striking thermal, electrical, and magnetic multifunctionality.

Multi-step structural phase transitions with novel symmetry breaking and inverse symmetry breaking characteristics in a [Ag4I6]2- cluster hybrid crystal

In this study, a multi-step phase transition hybrid composed of (Pr-dabco)2Ag4I6 clusters (Pr-dabco+ = 1-propyl-1,4-diazabicyclo[2.2.2]octan-1-ium) has been prepared and characterized by microanalysis, IR and UV-vis spectroscopy, TG and DSC techniques, etc. This hybrid is thermally stable up to ∼486 K with five phases in the temperature region below 486 K. The phase transition shows symmetry breaking (SB) character between phases II (space group P21/c) and III (space group Pa3[combining macron]), while inverse symmetry breaking (ISB) between phases II and I (space group Pbca), and it is rather exceptional for matter to exhibit simultaneously SB and ISB nature in two successive phase transitions. Most importantly, each phase transition is associated with a dielectric anomaly, and phase V appears to be a plastic crystal with extra high ac conductivity (>10-2 S cm-1). Our work opens up new avenues to find a multi-phase transition material in silver halide hybrids.

Uniaxial thermal expansion behaviors and ionic conduction in a layered (NH4)2V3O8

The zero/negative thermal expansion (ZTE/NTE), which is an intriguing physical property of solids, has been observed in a few families of materials. ZTE materials possess practical applications in specific circumstances such as space-related applications, engineering structures and precision instrument. Generally, NTE materials are used as additives to form a composite of the ZTE material with positive thermal expansion material. It is still a tremendous challenge to design new families of ZTE/NTE materials. Herein, we presented a temperature-dependent single crystal structure analysis in 110-300 K for a layered (NH4)2V3O8, which crystallizes in a tetragonal space group P4bm and comprises mixed valence [V3O82-]∞ monolayers and NH4+ residual in the interlayer spaces. Along the c-axis, (NH4)2V3O8 demonstrated uniaxial expansion behaviors, i.e., ZTE with αc = -1.10 × 10-6 K-1 in 110-170 K and NTE with αc = -16.25 × 10-6 K-1 in 170-220 K. Along the a-axis, (NH4)2V3O8 exhibited ZTE with αa = + 2.06 × 10-6 K-1 in 240-300 K. The mechanisms of ZTE and NTE were explored using structural analysis. The conduction of NH4+ ions in the interlayer space was studied, indicating that the conductivity rapidly rises with the expansion of interlayer space at temperatures of >293 K. This study discloses that layered vanadates are promising ZTE/NTE materials.

[Classification and imaging diagnosis of Lisfranc joint injuries]

OBJECTIVE

To accelerate the detection rate and accuracy of diagnosis in damage imaging of Lisfranc joint through research on the information of X-ray, CT, and MR imaging of tarsometatarsus joint (also called Lisfranc joint) damage.

METHODS

A total of 153 cases of tarsometratisus damage or Lisfranc ligamentous injury patients were chosen during November 2012 to November 2015. Lisfranc injuries were classified according to the Myerson fracture displacements classification and Nunley-Vertullo low-grade injury classification. All the treatment data was performed using SPSS 17.0 software.

RESULTS

For Myerson fracture displacements, there were 16 cases in Myerson Ⅰ type (homolateral complete), 100 cases in Myerson Ⅱ type (homolateral incomplete), and 5 cases in Myerson Ⅲ type (divergent). For the low-grade injury, there were 7 cases, 24 cases, and 1 case in Nunley-Vertullo Ⅰ, Ⅱ, Ⅲ type respectively. The probability was 14.9% (18/121) for patients that the initial survey found negative by X-ray imaging diagnosis and was confirmed by subsequent CT or MRI. It was found that the distance between the base of first (M1) and second (M2) metatarsus which was larger than 2 mm was 69.4%(84/121)from the X-ray imaging; there were small chip fractures between the base of M1 and M2 was 47.1% (57/121), and 71.2% (37/52)of small chip fractures in the inside of base of M2 from CT. On MRI, ligament disruption showed the discontinue or normal signal disappearing, and there were 15 cases in the complete disruption condition.

CONCLUSION

It should be suggested to take a CT or MRI check for the patients who have highly suspicious Lisfranc injure and the X-ray imaging diagnosis was negative, since there is a certain rate of missed diagnosis for the Lisfranc injure using X-ray imaging. For children and teenagers, the sports injuries and joint strain are common style, such as the injuries caused by jump from higher platform, football/skateboarding injures, etc. If the distance between the base of M1 and M2 is larger than 2 mm or there are small chip fractures between the M1 and M2, the patients would be suspected bone fracture or Lisfranc ligament injure. Myerson Ⅱ type is the most common Lisfranc joint injury , and MRI is best for Lisfranc ligament injury.

Rectal cancer: 3D dynamic contrast-enhanced MRI; correlation with microvascular density and clinicopathological features

PURPOSE

The primary aim of this prospective study was to evaluate the relationship between three-dimensional dynamic contrast-enhanced magnetic resonance (3D-DCE-MR) imaging parameters and clinicopathological features of rectal cancer and assess their potential as new radiological prognostic predictors.

MATERIALS AND METHODS

Three-dimensional DCE-MR was performed on 26 cases of pathologically proved rectal adenocarcinoma 1 week prior to operation. Data were analysed to calculate transfer constant (Ktrans), leakage space (Ve) and rate constant (Kep) of both tumour and normal rectal wall. Microvessel density (MVD) was evaluated by immunohistochemical staining of surgical specimens. All findings were analysed prospectively and correlated with tumour/node/metastasis (TNM) staging, Dukes staging, histological grading, presence of lymph node metastasis, serosal involvement and MVD.

RESULTS

Mean Ktrans, Ve and Kep for tumours were as follows: Ktrans 7.123±3.850/min, Ve 14.2±3.0%, Kep 49.446±20.404/min, revealing the significant difference between the tumour and normal rectal wall (p=0.001). There was a significant difference for Ktrans not only between patients with and without lymphatic involvement (p=0.000), but also among Dukes staging (p=0.04) and pTNM staging (p=0.03). Kep showed moderate correlation with TNM stages (r=0.479, p=0.02). Ve and MVD revealed no significant correlation with the clinicopathological findings described above (p>0.05).

CONCLUSION

Owing to the moderate and strong relationship between Ktrans and clinicopathological elements, Ktrans might be the prognostic indicator of rectal cancer. Threedimensional DCE high-resolution MR imaging provides a competing opportunity to assess contrast kinetics.