Effect of microstructure of graphite on the nonreductive thermal ion emission in thermal ionization mass spectrometry.

The emission behavior of polyatomic ions in the ionization source of thermal ionization mass spectrometry (TIMS) was investigated. The results suggest that the presence of a graphite promoter plays a key role for the formation and stable emission of polyatomic ions, such as M(2)X(+), M(2)BO(2)(+), Cs(2)NO(2)(+), and Cs(2)CNO(+). Our data further implied that the intensity of M(2)X(+) and M(2)BO(2)(+) increases and the emission temperature decreases with increasing cationic and anionic radius. During the boron isotopic measurement using the Cs(2)BO(2)(+)-graphite-PTIMS method, the isobaric interference ion Cs(2)CNO(+) cannot be transformed from nitrate or organic compounds containing an amide group but can be induced by the existence of trace amounts of boron because of its special electron-deficiency property (B(3+)). Characterization on the planar crystalline structure of various graphite samples with SEM, TEM, and Raman spectroscopy confirmed the relationship of the emission capacity of polyatomic ions and the crystal microstructure of graphite and provides direct evidence that graphite with a perfect parallel and equidistant layer orientation shows a beneficial effect on the emission of polyatomic ions in TIMS. The mechanism study on the formation of polyatomic ions opens the possibility to establish high precision methods for isotopic composition analysis of more nonmetal elements with the TIMS technique.

Influence of air-sea fluxes on chlorine isotopic composition of ocean water: implications for constancy in delta37Cl--a statistical inference.

The behaviors of chlorine isotopes in relation to air-sea flux variables have been investigated through multivariate statistical analyses (MSA). The MSA technique provides an approach to reduce the data set and was applied to a set of 7 air-sea flux variables to supplement and describe the variation in chlorine isotopic compositions (delta37Cl) of ocean water. The variation in delta37Cl values of surface ocean water from 51 stations in 4 major world oceans--the Pacific, Atlantic, Indian and the Southern Ocean has been observed from -0.76 to +0.74 per thousand (av. 0.039+/-0.04 per thousand). The observed delta37Cl values show basic homogeneity and indicate that the air-sea fluxes act differently in different oceanic regions and help to maintain the balance between delta37Cl values of the world oceans. The study showed that it is possible to model the behavior of chlorine isotopes to the extent of 38-73% for different geographical regions. The models offered here are purely statistical in nature; however, the relationships uncovered by these models extend our understanding of the constancy in delta37Cl of ocean water in relation to air-sea flux variables.

Emission of M2X+ cluster ions in thermal ionization mass spectrometry in the presence of graphite.

The emission of M2X+ cluster ions in thermal ionization mass spectrometry when graphite is loaded on the heating filaments was studied. The emission model of non-reductive thermal ionization of graphite was preliminarily discussed and factors influencing the thermal emission of M2X+ ions were investigated. The results show that the intensities of M2X+ cluster ions are related to ionic radius and crystal lattice energy, and possibly also to the solvation energies of ions. The intensities of M2Cl+ (M stands for K, Rb, and Cs) cluster ions, the M2Cl+/M+ ratios, and the 37Cl/35Cl ratios determined from M2Cl+ ion measurement usually increase with measurement time. The variation of the 37Cl/35Cl ratios determined from Cs2Cl+ ion measurement is lower than those based on K2Cl+ and Rb2Cl+ ion measurement, indicating the lowest isotopic fractionation.

Pre- and postoperative sequential study on the immunosuppressive activity of serum and cell-free skin bleb fluid of patients with lung cancer and esophageal cancer.

Serial changes of immunosuppressive activity of serum and cell-free skin bleb fluid that can suppress the activity of acid a-naphthyl acetate esterase (ANAE) of lymphocytes and phagocytosis of macrophages were detected by immunoregulatory tests in vitro in 50 lung cancer and 42 esophageal cancer patients. In comparing these tests with those of 53 cases of noncancerous thoracic lesion and 69 normal adults, the immunosuppressive activity of serum and skin bleb fluid from cancer patients is significantly higher than that of noncancerous thoracic lesions and normal individuals (P less than .01). The activity is related to the stages of cancer, the size of primary tumor, the presence of lymph node metastasis, and tumor resect-ability, but not to histological classification, sex, and age. The immunosuppressive activity of serum and skin bleb fluid decreased gradually after the removal of the tumor and was eliminated on the 30th postoperative day. These results suggest that serum and skin bleb fluid from cancer patients may contain immunosuppressive factors that can suppress the immune responsive functions of lymphocytes and macrophages in vitro in a manner similar to that seen in vivo. Therefore, complete surgical removal of cancer is likely the most effective immunotherapy.

[Scanning electron microscopic observations on adults of Angiostrongylus cantonensis].

Scanning electron microscopic observations were made on adult Angiostrongylus cantonensis, The apex of the head has a round mouth with two rows of 6 sensory papillae each around it. The papillae of the outer row are more rudimentary and inconspicuous. A pair of amphidial pores are visible on the external side of lateral papillae of the inner row. The surface of the body is covered with a circular striated cuticle and short longitudinal ridges lying between two circular cuticles. The two copulatory spicules at the posterior end of male worms are obviously different in morphology. According to their morphological characteristics, we named them "tube-like" copulatory spicule and "grooves-like" copulatory spicule. The former, when enclosed in the latter, appeared as a single one. The copulatory bursa of the males and the structures of the tail part of the female are also described.