[Research on THz and Raman Spectra of RNA Nucleobases].

The Infrared and Raman spectra of RNA nucleobases in terahertz (THz) band (1~10 THz) were detected with Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The position of all the characteristic peaks and corresponding vibration modes of RNA nucleobase crystals were obtained with Guassian09 software and energy-based fragmentation approach under periodic boundary conditions (PBC-GEBF) method. The computational results were verified to be in accordance with experimental data, which indicated that the powder of RNA nucleobases is amorphous crystal structure. The infrared spectra demonstrated that adenine, guanine and cytosine all have 6 infrared active vibrational modes, while uracil only has 3. Comparing to experimental results, the position and intensity of the absorption peaks were nicely corroborated by the predicted spectrum, except that one weak vibrational frequency at 6.35 THz is missing and two peaks (4.83 and 5.39 THz) merge in the predicted spectrum of guanine; two peaks in 4.3 and 4.79 THz merge into a single one in the calculated spectrum of cytosine; the peaks of thymine in 3.32 and 3.82 THz merged. The computational results of Raman spectra were also verified to be in line with the experimental data. The position and intensity of the characteristics peaks were exactly simulated except that two peaks of guanine in 3.52 and 4.48 THz merged; two peaks in 7.26 and 8.03 THz merge and five peaks (3.57, 4.02, 4.49, 4.89, 5.98 THz) merge in the calculated spectrum of guanine. Through the analysis and identification of the characteristic peaks, it is indicated that the vibration modes of DNA nucleobases in 1~10 THz were derived from collective vibration of molecules in the lattice. The intermolecular hydrogen bond and the weak interaction force contribute greatly to the vibration modes. In addition, as the frequency increases to over 5.5 THz, the vibration modes will change from the atoms collective vibration to some atoms vibration. This research has important theoretical and practical reference value to reveal the effect of RNA nucleobases in the areas of RNA molecular structure constitution, biological macromolecules identification and terahertz spectra formation mechanism and biological inheritance.

Using 18F-fluorodeoxyglucose positron emission tomography/computed tomography to estimate the length of gross tumor and involvement of lymph nodes in esophagogastric junction carcinoma.

OBJECTIVE: To determine the optimal approach for estimating the length of gross tumor and involvement of the lymph nodes with 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) in esophagogastric junction carcinoma (EGJC). The result was verified with pathologic examination. MATERIALS AND METHODS: Twenty patients with diagnosed and untreated EGJC were enrolled. The length of the gross tumor was measured using different approaches with PET/CT: Standardized uptake value (SUV) 1.5-5.5 in intervals of 1.0 and 10%-50% of maximum SUV (SUVmax) on 18F-FDG PET/CT in intervals of 10%. The results were expressed as L1.0-L5.0, and L10%-L50%, respectively. The pathological length of gross tumor (Lpath) was calculated based on the shrinkage ratio of primary tumor. The measurable lymph nodes were measured on PET/CT preoperatively, labeled during operation, and examined for pathology. RESULTS: Lpath was 6.87 ± 2.25 cm, L30% and L2.5 were 6.61 ± 1.76 cm and 7.56 ± 1.89 cm, respectively. L30% was closer to Lpath than other % SUVmax, L2.5 was closer to Lpath than other absolute SUV thresholds. The diagnostic performance of 18F-FDG PET/CT for lymph nodes was best at the cutoff SUV of 2.7, providing sensitivity of 70% and a specificity of 83.7% for detecting lymph node metastases. CONCLUSIONS: The tumor length with 30% SUVmax as the threshold was closest to the actual pathological length of EGJC. The diagnostic efficiency of 18F-FDG PET/CT was best at the cutoff SUVmax of 2.7 for detecting lymph node metastases in EGJC.

[Relationship between retention PM2.5 and leaf surface AFM character of six greening trees during autumn in Beijing West Mountain.] / åŒ—äº¬è¥¿å±±ç»¿åŒ–æ ‘ç§ç§‹å­£æ»žçº³PM2.5èƒ½åŠ›åŠå ¶ä¸Žå¶è¡¨é¢AFMç‰¹å¾çš„å ³ç³».

This study investigated PM2.5 adsorption by leaves of six tree species (Pinus bungeana, Pinus tabuliformis, Salix babylonica, Acer mono, Ginkgo biloba, Populus davidiana) in the West Mountain of Beijing. An aerosol generator was used for quantitative determination of PM2.5 adsorption. Atomic force microscopy (AFM) was used to determine micro morphology characteristics on the leaf surface, including roughness parameters and the PM2.5 absorption mechanism of tree leaves. The results showed that the PM2.5 adsorption capacity per unit leaf area was as follows: P. bungeana (2.44±0.22 µg·cm-2) > P. tabuliformis (2.40±0.23 µg·cm-2) > S. babylonica (1.62±0.09 µg·cm-2) > A. mono (1.23±0.01 µg·cm-2) > G. biloba (1.00±0.07 µg·cm-2) > P. davi-diana (0.97±0.03 µg·cm-2). In autumn, PM2.5 adsorption capacity per unit leaf area was as follows: November (2.33±0.43 µg·cm-2) > October (1.62±0.64 µg·cm-2) > September (1.51±0.50 µg·cm-2). The leaves of P. bungeana and P. tabuliformis were rugged with many recesses and protrusions, large relative height difference, and high roughness, and their absorption ability of PM2.5 was strong. The leaves of S. babylonica and A. mono had folded leaf lamina and were covered by fine hairs, and their roughness was relatively high, with many protrusions and fillisters on the leaf surface. Since G. biloba and P. davidiana had smooth leaves, mostly oblong stomata and low roughness, their PM2.5 absorption ability was weaker. The ranking of average roughness on the ada-xial and abaxial side of the leaves was as follows: P. bungeana (149.91±16.38 nm) > P. tabuliformis (124.47±10.52 nm) > S. babylonica (98.85±5.36 nm) > A. mono (93.74±21.75 nm) > G. biloba (80.84±0.88 nm) > P. davidiana (67.72±8.66 nm). This accorded with PM2.5 adsorption per unit leaf area, and leaf roughness had a significant positive correlation with PM2.5 adsorption amount per unit leaf area as well (R2=0.9498). To improve the environmental effects of city vegetation, tree species with leaf surface morphology that facilitates absorption of PM2.5 and other particles should be selected.