Calculating the Excitation Temperature for H_2CO Absorption Lines in Molecular Clouds

The excitation temperature T_(ex)for molecular emission and absorption lines is an essential parameter for interpreting the molecular environment.This temperature can be obtained by observing multiple molecular transitions or hyperfine structures of a single transition,but it remains unknown for a single transition without hyperfine structure lines.Earlier H_(2)CO absorption experiments for a single transition without hyperfine structures adopted a constant value of T_(ex),which is not correct for molecular regions with active star formation and H II regions.For H_(2)CO,two equations with two unknowns may be used to determine the excitation temperature T_(ex)and the optical depthτ,if other parameters can be determined from measurements.Published observational data of the4.83 GHz(λ=6 cm)H_(2)CO(1_(10)-1_(11))absorption line for three star formation regions,W40,M17 and DR17,have been used to verify this method.The distributions of T_(ex)in these sources are in good agreement with the contours of the H110αemission of the H II regions in M17 and DR17 and with the H_(2)CO(1_(10)-1_(11))absorption in W40.The distributions of T_(ex)in the three sources indicate that there can be significant variation in the excitation temperature across star formation and H II regions and that the use of a fixed(low)value results in misinterpretation.

Comparison of NH_(3) and ^(12)CO,^(13)CO,C^(18)O Molecular Lines in the Aquila Rift Cloud Complex

The observations of the Aquila Rift cloud complex at 23.708 and 115.271 GHz made using the Nanshan 26 m radio telescope and the 13.7 m millimeter-wavelength telescope are presented.We find that the CO(1-0)gas distribution is similar to the NH_(3)gas distribution in the Aquila Rift cloud complex.In some diffusion regions characterized by CO,we identified several dense clumps based on the distribution of detected ammonia molecular emission.Through the comparison of spectral line parameters for NH_(3),^(13)CO,and C^(18)O,our study reveals that the line center velocities of the NH_(3),^(13)CO,and C^(18)O lines are comparable and positively correlated,indicating that they originate from the same emission region.No significant correlation was identified for other parameters,including integrated intensity,line widths,main beam brightness temperature,as well as the column densities of NH_(3),^(13)CO,and C^(18)O.The absolute difference in line-center velocities between the^(13)CO and NH_(3)lines is less than both the average line width of NH_(3)and that of^(13)CO.This suggests that there are no significant movements of NH_(3)clumps in relation to their envelopes.The velocity deviation is likely due to turbulent activity within the clumps.

常见肝癌预后预测模型的分析与比较

肝细胞癌(hepatocellular carcinoma,HCC)占我国癌症死亡原因的第三位,同时也是世界上主要的健康问题之一。尽管HCC的早期诊断及治疗已经取得了明显的进展,但是在大多数国家的死亡率仍非常高。HCC患者的预后除了依赖于肿瘤特征,更依赖于病因、肝脏功能及个体差异。尽管世界各地提出了多个肝癌的预后预测模型,但是各个模型在肝癌预后判断方面的价值尚无统一定论。因此,对比及分析这些预后模型对肝癌预后判断及治疗指导的价值至关重要。本综述的目的是分析比较当前较为常见的8种预后预测模型(Okuda、TNM8、BCLC、JIS、CUPI、CLIP、GRETCH、CIS)的优缺点,为今后的临床及科学研究提供新思路。

Taking Mafei Powder(麻沸散)as an Example to Explore the Evidence of the Existence of Ancient Anesthesia

Anesthesia has a long history in China.Ancient doctors have already created a variety of anesthetic formulae for surgery and the most famous one is Mafei powder(麻沸散).However,there are a few literatures about Mafei powder and Mafei powder was not recorded at that time.This article tries to discuss the existence of Mafei powder by summarizing relevant records in ancient books such as San Guo Zhi(《三国志》Records of The Three Kingdoms)and Hou Han Shu(《后汉书》History of the Latter-Han D^ynasty)and analyzing the anatomical,surgical,and pharmaceutical conditions at Hua Tuo's(华佗)time.

Rationally Leveraging Polymer Chain-Length Heterogeneity for Robust Structural Engineering

The inherent uncertainty of chain length in synthetic polymers casts doubt on the explicit understanding of fundamental principles.This study quantitatively assesses the critical role of chain-length distribution in the self-assembly process,aiming to identify the point at which discernible discrepancies begin to emerge.By blending discrete diblock copolymers of varying sizes,chain-length nonuniformity can be precisely regulated while the average composition remains constant.Introducing a minor heterogeneity leads to an expansion of lattice dimension,while a phase transition occurs as the difference exceeds a threshold.Interestingly,a transition from the Frank–Kasperσphase to the body-centered cubic phase was triggered by enlarging the size difference of the corona block,while introducing heterogeneity in the core block stabilized the hexagonally close-packed spheres.A self-consistent field theory calculation reveals that the synergy between the long and short chains effectively releases packing frustration,leading to substantial changes in the free-energy landscape and stabilizing unconventional phases otherwise inaccessible.This work calls particular attention to the importance of chain-length heterogeneity and provides a robust approach to finely tuning the phase behavior and physical properties of block copolymers without altering their chemical composition.

Investigation of lubricant transfer and distribution at head/disk interface in air-helium gas mixtures

Lubricant transfer and distribution at the head/disk interface in air-helium gas mixtures is investigated using a developed model that combines an air-bearing model with a molecular dynamics model. The pressure distribution is calculated by the air-bearing model at the head/disk interface with respect to the helium content and the pressure obtained is then input to the molecular dynamics model to understand the lubricant transfer mechanism. Finally, the effects of pressure at the boundary condition and disk velocity on lubricant transfer are discussed in relation to the helium fraction within the air-helium gas mixtures. Results show there is a decrease in the pressure difference with an increase in the helium percentage, which leads to a decrease in the volume of the lubricant transferred. The results also suggest that the lubricant is not easily to transfer in gas mixtures with a high percentage of helium, even when both higher disk velocities and pressure boundary conditions are applied.