关于内蒙古大兴安岭林区大径材培育的探讨

文章通过对内蒙古大兴安岭林区培育大径材的目的、意义、必要性及方法等方面的分析,论述了大径级材培育是促进林区生态、经济和社会协调发展的有力措施。     

Isotopic fractionation of stratospheric nitrous oxide

We propose an isotopic fractionation mechanism, based on photolytic destruction, to explain the 15N/14N and 18O/16O fractionation of stratospheric nitrous oxide (N2O) and reconcile laboratory experiments with atmospheric observations. The theory predicts that (i) the isotopomers 15N14N16O and 14N15N16O have very different isotopic fractionations in the stratosphere, and (ii) laboratory photolysis experiments conducted at 205 nanometers should better simulate the observed isotopic fractionation of stratospheric N2O. Modeling results indicate that there is no compelling reason to invoke a significant chemical source of N2O in the middle atmosphere and that individual N2O isotopomers might be useful tracers of stratospheric air parcel motion.     

Cross-link in fibrin polymerized by factor 13: epsilon-(gamma-glutamyl)lysine

(epsilon)-((gamma)-Glutamyl)lysine has been isolated from enzymatic hydrolyzates of cross-linked human fibrin. This compound was not detected in "non-cross-linked" fibrin prepared with ethylenediaminetetraacetic acid, which inhibits factor XIII; intermediate amounts were observed when the fibrin was prepared with glycine ethyl ester, which inhibits factor XIII competitively. These and ancillary experiments furnish conclusive evidence that epsilon-(gamma-glutamyl)lysine cross-links form in human fibrin during polymerization catalyzed by factor XIII.     

Helium Flux from the Earth's Mantle as Estimated from Hawaiian Fumarolic Degassing

Averaged helium to carbon dioxide ratios measured from systematic collections of gases from Sulphur Bank fumarole. Kilauea, Hawaii, when coupled with estimates of carbon in the earth's crust, give a helium flux of 1 x 105 atoms per square centimeter per second. This is within the lower range of other estimates, and may represent the flux from deep-seated sources in the upper mantle.     

Optical studies of individual InAs quantum dots in GaAs: few-particle effects

Optical emission from individual strained indium arsenide (InAs) islands buried in gallium arsenide (GaAs) was studied. At low excitation power density, the spectra from these quantum dots consist of a single line. At higher excitation power density, additional emission lines appeared at both higher and lower energies, separated from the main line by about 1 millielectron volt. At even higher excitation power density, this set of lines was replaced by a broad emission peaking below the original line. The splittings were an order of magnitude smaller than the lowest single-electron or single-hole excited state energies, indicating that the fine structure results from few-particle interactions in the dot. Calculations of few-particle effects give splittings of the observed magnitude.     

Morpho‐physical Recording of Bovine Conceptus (Bos indicus) and Placenta from Days 20 to 70 of Pregnancy

The study is based on 141 pregnant Bos indicus cows, from days 20 to 70 post‐insemination. First, special attention was given to the macroscopically observable phenomena of attachment of the conceptus to the uterus, i.e. the implantation, from about days 20 to 30 post‐insemination up to day 70, and placentome development by growth, vascularization and increase in the number of cotyledons opposite to the endometrial caruncles. Secondly, as for the conceptuses, semiquantitative, statistical analyses were performed of the lengths of chorio‐allantois, amnion and yolk sac; and the different parts of the centre and two extremes of the yolk sacs were also analysed. Thirdly, the embryos/foetuses corresponding to their membranes were measured by their greatest length and by weight, and described by the appearance of external developmental phenomena during the investigated period like neurulation, somites, branchial arcs, brain vesicles, limb buds, C‐form, pigmented eye and facial grooves. In conclusion, all the data collected in this study from days 20 to 70 of bovine pregnancy were compared extensively with corresponding data of the literature. This resulted in an ‘embryo/foetal age‐scale’, which has extended the data in the literature by covering the first 8 to 70 days of pregnancy. This age‐scale of early bovine intrauterine development provides model for studies, even when using slaughtered cows without distinct knowledge of insemination or fertilization time, through macroscopic techniques. This distinctly facilitates research into the cow, which is now being widely used as ‘an experimental animal’ for testing new techniques of reproduction like in vitro fertilization, embryo transfer and cloning.     

Salmonellae and salmonellosis in captive reptiles.

In a survey of 150 pet reptiles submitted for necropsy, 51% of snakes, 48% of lizards and 7% of turtles were infected with Salmonella. About one third of the positive animals had died due to various manifestations of salmonellosis. Thirty-one Salmonella serotypes were identified including three isolates new to Canada. The public health implications are discussed in view of the restricted popularity of reptiles and their possible infection from domestic agricultural products.