No abstract available

No abstract available

[en] The facilitation of barium enemas for even highly viscous suspensions into the colon by using a roller pump is described. An advantage of the procedure is the gentle insufflation of air

[en] The dependence of the rate constant of Rb⁺ efflux on extracellular cation concentration was measured. At low ionic strengths Rb⁺ efflux increased strongly. Permeability coefficients were calculated from the rate constants measured, using the Goldman flux equation, with and without making allowance for surface potentials. Only when allowance was made for surface potentials and the associated differences between ion concentrations in the bulk solutions and at the membrane surface, the permeability coefficient remained constant. Best agreement between experimental data and theoretically calculated values was obtained when an interior surface potential of -110 mV was assumed. When the surface charge of erythrocytes is reduced by neuraminidase, the rate constants for Rb⁺ efflux decreased, indicating a significant influence of surface potential

[en] The paper is concerned with various aspects of climatic history. Emphasis is on the spectrum of data and methods used in historical climatology. The following section is devoted to an outline of the short- and long-range climatic changes since 1500 A.D. that show how much the climate has varied in space and time. It is pointed out that climatic extremes have been an ever-recurrent phenomenon throughout history. (orig.)

[en] The present article gives an overview of climate development during the Holocene epoch. It discusses at different time scales certain methodological and substantive aspects that are relevant to the assessment of contemporary climate scenarios and therefore deserve greater consideration than they receive at present. A strong emphasis is placed on research projects on the historical perspective. After an excursion to the various data types and methods of Historical Climatology the authors present some regionally differentiated findings. This gives an idea of climate variability in an experential dimension that the human mind is able to grasp. Many of the slow climate fluctuations become particularly illuminating when considered, for example, in conjunction with the cold period between 1550 and 1850. Another point of interest are the numerous extreme periods and anomalous findings. Climate fluctuations and climate desasters, while differing in their temporal and spatial characteristics, have accompanied mankind throughout history. (orig.)

[en] The reaction of sm-bullet CH₃ free radicals with Cu^II(NH₂CH₂CO₂^-)₂ in aqueous solutions was studied. The formation of the unstable intermediate (NH₂CH₂CO₂^-)₂Cu^III-CH₃(aq) in this reaction was observed. This intermediate decomposes into Cu^III(NH₂CH₂CO₂^-)₂⁺(aq) + CH₄. The formation of Cu^III(NH₂CH₂CO₂^-)₂⁺(aq) is not observed, as this complex is short-lived under these conditions and decomposes via ligand oxidation. The sm-bullet CH₃ free radicals react with the transient complex (NH₂CH₂CO₂^-)₂Cu^III-CH₃(aq) to form ethane and Cu^II(NH₂CH₂CO₂^-)₂; the specific rate of this reaction approaches the diffusion-controlled limit. The results thus point out that aliphatic free radicals can oxidize copper(II) complexes to copper(III) complexes. The results suggest that the reactions of aliphatic free radicals with copper complexes might cause the reported radiosensitization by copper compounds. 18 refs., 3 figs., 3 tabs

[en] Two epithelia tumor cell lines were established from biopsy specimens of nasopharyngeal carcinomas (NPC). The specimens were taken from poorly differentiated squamous cell carcinomas of the nasopharynx. The tissues were prepared for cell culture and eventually two continuous epithelia cell lines were obtained and designated HONE-1 and HNE-1. Light and electron microscopic examination of these two cell lines demonstrated cells with an epithelial morphology including the presence of desmosomes. It was found that early-passage uncloned HNE-1 cells (passage 23) could be superinfected with B95-8 and NPC-EBV isolates as demonstrated by the induction of Epstein-Barr virus (EBV)-specific early antigen(s) in a small percentage of the cells; HONE-1 cells could also be superinfected with EBV. Southern blot analysis detected EBV DNA in samples from uncloned HNE-1 cells at passages 12, 17, 21, 27, and 35. However, by passage 45, EBV DNA could no longer be detected in HNE-1 cells by Southern blot analysis. The EBV genome was detected in parental HONE-1 cells at subculture 9 and in clone 40 cells up to passage 40 thus far. The data suggest that EBV genome-positive HNE-1 and HONE-1 cells were lost as the cells were cultivated in vitro and that cloning the cells at an early passage level may be critical in maintaining EBV genome-positive epithelial NPC cells. These EBV genome-positive epithelia NPC cell lines will be useful for studying the association of EBV and NPC

[en] Superhydrogenated polycyclic aromatic hydrocarbons (PAHs) may be present in H-rich and ultraviolet-poor benign regions. The addition of excess H atoms to PAHs converts the aromatic bonds into aliphatic bonds, the strongest of which falls near 3.4 μm. Therefore, superhydrogenated PAHs are often hypothesized to be a carrier of the 3.4 μm emission feature that typically accompanies the stronger 3.3 μm aromatic C–H stretching feature. To assess this hypothesis, we use density function theory to compute the infrared (IR) vibrational spectra of superhydrogenated PAHs and their ions of various sizes (ranging from benzene and naphthalene to perylene and coronene) and of various degrees of hydrogenation. For each molecule, we derive the intrinsic oscillator strengths of the 3.3 μm aromatic C–H stretch ($A_{3.3}$) and the 3.4 μm aliphatic C–H stretch ($A_{3.4}$). By comparing the computationally derived mean ratio of $⟨<!--\; ???\; -->A_{3.4}/A_{3.3}⟩<!--\; ???\; -->\approx <!--\; ???\; -->1.98$ with the mean ratio of the observed intensities $⟨<!--\; ???\; -->I_{3.4}/I_{3.3}⟩<!--\; ???\; -->\approx <!--\; ???\; -->0.12$, we find that the degree of superhydrogenation—the fraction of carbon atoms attached with extra hydrogen atoms—is only ∼2.2% for neutral PAHs, which predominantly emit the 3.3 and 3.4 μm features. We also determine for each molecule the intrinsic band strengths of the 6.2 μm aromatic C–C stretch ($A_{6.2}$) and the 6.85 μm aliphatic C–H deformation ($A_{6.85}$). We derive the degree of superhydrogenation from the mean ratio of the observed intensities $⟨<!--\; ???\; -->I_{6.85}/I_{6.2}⟩<!--\; ???\; -->\lesssim <!--\; ???\; -->0.10$ and $⟨<!--\; ???\; -->A_{6.85}/A_{6.2}⟩<!--\; ???\; -->\approx <!--\; ???\; -->1.53$ for neutrals and $⟨<!--\; ???\; -->A_{6.85}/A_{6.2}⟩<!--\; ???\; -->\approx <!--\; ???\; -->0.56$ for cations to be ≲3.1% for neutrals and ≲8.6% for cations. We conclude that astrophysical PAHs are primarily aromatic and are only marginally superhydrogenated.

[en] The so-called “unidentified” infrared emission (UIE) features at 3.3, 6.2, 7.7, 8.6, and 11.3 μm are ubiquitously seen in a wide variety of astrophysical regions. The UIE features are characteristic of the stretching and bending vibrations of aromatic hydrocarbon materials, e.g., polycyclic aromatic hydrocarbon (PAH) molecules. The 3.3 μm aromatic C–H stretching feature is often accompanied by a weaker feature at 3.4 μm. The latter is generally thought to result from the C–H stretch of aliphatic groups attached to the aromatic systems. The ratio of the observed intensity of the 3.3 μm aromatic C–H feature to that of the 3.4 μm aliphatic C–H feature allows one to estimate the aliphatic fraction of the UIE carriers, provided that the intrinsic oscillator strengths of the 3.3 μm aromatic C–H stretch ($A_{3.3}$) and the 3.4 μm aliphatic C–H stretch ($A_{3.4}$) are known. While previous studies on the aliphatic fraction of the UIE carriers were mostly based on the $A_{3.4}/A_{3.3}$ ratios derived from the mono-methyl derivatives of small PAH molecules, in this work we employ density functional theory to compute the infrared vibrational spectra of PAH molecules with a wide range of sidegroups including ethyl, propyl, butyl, and several unsaturated alkyl chains, as well as all the isomers of dimethyl-substituted pyrene. We find that, except for PAHs with unsaturated alkyl chains, the corresponding $A_{3.4}/A_{3.3}$ ratios are close to that of mono-methyl PAHs. This confirms the predominantly aromatic nature of the UIE carriers previously inferred from the $A_{3.4}/A_{3.3}$ ratio derived from mono-methyl PAHs.