In the present research, the dipole moment, electronic structure, frontier orbitals energy, and aromaticity in the graphyne and Si-doped graphynes were studied with M062X quantum chemical computation. The relative energies of four possible isomers of Si-doped graphyne were calculated. Also, the ionization potential (IP) and electron affinity (EA) values of the studied molecules were reported. Frontier orbital (HOMO-LUMO) gap values were used for illustration of conductivity of these molecules. Aromaticity of the cycles of studied molecules was investigated by nucleus independent chemical shift (NICS) values and electron localization function (ELF).

The structures and properties of [n] sila-acenes (n=2-4) were investigated by density functional theory method. The results of calculations were obtained at B3LYP/6-311G (d, p) level on model species. Energetic criteria suggest that 2-1b (n=2), 3-1b (n=3), and 4-1b (n=4) isomers enjoy stabilization. By frontier orbital analysis, these systems are among the most stable of the family. Also, calculations indicate the most stable isomers have the most first hyperpolarizability values. The aromaticity of all molecules has been studied by nucleusindependent chemical shift.

Objectives: The aim of this study was to evaluate the diagnostic accuracy of chemical shift imaging in vertebral compression. Patients and Methods: Forty-nine patients with vertebral compression with suspected malignancy or history of trauma were included in this study. MRimaging of the spine with standard conventionalMRsequences and additional chemical shift imaging was done with 1. 5 Tesla MR Unit. Regions of interest (ROI) were placed on the abnormal marrow of compressed vertebrae both on the opposed phase and on the matching in phase images and signal intensity (SI) ratio values (SI out-phase/SI-in phase) were calculated. Results: Forty-nine patients had 68 spine lesions, consisting of 49 benign and 19 malignant fractures. Student t test, receiver operating characteristic (ROC) analysisandinterclass correlation test were used statistically. MeanSI ratio of benign vertebral compression (0. 68  0. 29, range 0. 13-1. 53) was significantly lower than malignant SI ratio values (1. 06  0. 10, range 0. 96-1. 35). With student t-test, there was significant difference between benign compressions compared to malignant compressions (P < 0. 001). Receiver operating characteristic (ROC) curve analysis was used to determine the optimal cut off value in malignant and benign lesion definition. The optimal SI ratio cut off value was found to be 0. 96 for separating benign and malignant vertebral compression. The area under the curve (AUC) value was observed as 0. 92 (95% confidence interval [CI] = 0. 86-0. 99). According to that cutoff value, sensitivity was 100% (95% CI = 82. 35%-100%) and the specificity was 86% (95% CI = 72. 76%-94. 06%). Interobserver reliability was studied with intraclass correlation and results were statistically significant with intraclass correlation coefficient (ICC) as 0. 85 (P < 0. 05). Conclusions: There is significant difference in signal values between benign and malignant compression fractures in chemical shift MR imaging. Chemical shift MR imaging has much additive data to conventional MRI in vertebral compression.