Showing papers by "Uppsala University published in 1970"

Molecular Spectroscopy by Means of ESCA III. Carbon compounds

Abstract: Carbon 1s energies are measured by ESCA for a series of aliphatic saturated compounds, carbonyl compounds, and some aromatic compounds. For convenient use in chemical structure analysis the binding energy shifts are correlated with a charge parameter obtained from electronegativity considerations. The shifts are also analyzed in terms of group shifts from which group electronegativities are derived. A comparison is made between the shifts in solid and gaseous samples and it is shown that solid state effects are small for non-ionic compounds. The observed shifts are then compared with results of semi-empirical and ab initio molecular orbital calculations on free molecules. The theoretical calculations are simplified by use of an electrostatic potential model.

Bedforms of the Tana River, Norway

Abstract: The greater part of the water and sediment discharge in the Tana River takes place in the weeks following the ice break-up and flood. During this time the river discharge changes rapidly with an ov...

Significance of Protein A Production by Staphylococci

Abstract: Of 700 coagulase-positive staphylococcal strains isolated from humans, 692 (98.9%) produced protein A. Of 100 coagulase-negative strains, 2 were protein A-positive.

Band Structure of Transition Metals Studied by ESCA

Abstract: The position and shape of the energy bands of the following transition metals have been studied by ESCA: Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, Au. The Fermi levels of the metals with unfilled d-bands are found in the high-energy flanks of the valence band spectra. For the noble metals the Fermi level is shifted toward higher energies. These observations are in general accordance with the overlap of d- and sp-bands in transition metals. An increase in band width is noted between corresponding elements in each series of transition metals. A comparison is drawn between band widths obtained in the present study and those deduced from cohesive energy data. An observed splitting in some of the bands seems to be much too large to be attributable to spin-orbit interaction. Core electron lines are recorded for the purpose of obtaining an energy calibration, estimating the contribution to the observed band spectra from inelastically scattered electrons, and checking the chemical state of the sample. The photoexcitation process and the energy losses of the electrons due to single-particle and plasmon excitations are discussed.

Blood Flow and Oxygen Extraction in the Cat Uvea at Normal and High Intraocular Pressures

Abstract: The rate of blood flow through the uvea and the arterio-venous O2 difference across the uveal tract were determined in cats. The normal rate of blood flow was 1.14 ± 0.23 ml/min and the normal a-v O2 difference was 1.02 ± 0.16 volume per cent. The O2 extraction was 8.0 ± 0.6 μl NTP/min. The arterial O2 saturation, Po2, Pco2, and pH were 95.6 ± 0.3 per cent, 93 ± 3 mm Hg, 25.8 ± 1.0 mm Hg, and 7.44 ± 0.01 units, respectively. An artificial rise in eye pressure reduced the rate of uveal blood flow and increased the a-v O2 difference. The O2 extraction was relatively constant at blood flow rates above 0.3–0.5 ml/min. At lower flow rates the O2 extraction decreased in spite of a high venous O2 concentration. Blood collected from the choroidal veins had a slightly higher O2 concentration than blood collected from the intrascleral venous plexus. A reduction in uveal blood flow, produced by a reduction in the mean arterial blood pressure, reduced the O2 content both in blood collected from the choroid and in blood leaving the anterior uvea. The results suggest that at low perfusion pressures there is anoxia in some tissue supplied by the uveal vessels, in spite of a relatively well oxygenated venous blood.

Ionic polysaccharides. 3. Dilute solution properties of hyaluronic acid fractions.

Abstract: Molecular weights by osmometry (Mn), light scattering (Mw), and sedimentation-diffusion (MsD) were determined for selected fractions and unfractionated samples of hyaluronic acid in the molecular weight range 3 × 104−1.7 × 106. For the determination of MsD from the sedimentation coefficient s, a calibration procedure based on the data of Laurent, Ryan, and Pietruszkiewicz gave the following relations in 0.2M NaCl: log (s−1)0 = 14.681 − 0.413 log MsD and log D0 = −3.828 − 0.568 log MsD, where subscript, zero refers to zero concentration and D is the diffusion coefficient. The average Mandelkern-Flory parameter β in 0.2M NaCl is 3.0 × 106. Data for the intrinsic viscosity [η] may be fitted for M > 105 by [η] = K′Ma, where K′, a are in 0.2M NaCl, 0.0228, 0.816; in 0.5M NaCl, 0.0318, 0.777; in 0.1 M HCl, 0.0279, 0.763, respectively. Below M = 105, [η] appears to fall below the values calculated, possibly due to non-Gaussian behavior of short chains. The second virial coefficient A2 in 0.5M NaCl approaches the ideal Donnan value, decreasing slightly with increasing molecular weight. The friction parameter P is about 20% smaller than that of uncharged polymers of similar dimensions. The flexible coiling nature of this polymer is confirmed.

Drivers and road signs.

Abstract: The function of the road sign system as an information channel for car drivers was investigated. The data were gathered from more than 5,000 car drivers stopped after passing a road sign on a Swedish highway. The main results are as follows. 1. The overall probability of a road sign being noticed on passing is not higher than about 0·5. 2. The different signs studied form a scale of recording probability of perception extending from a low group with a probability of being perceived of about 0·25 up to a group with probabilities between 0·60-0·75. The rank order of the signs is consistent between occasions. 3. The results verified the outcome of a previous investigation by Johansson and Rumar, 1966. The main conclusion must be that the road sign system to a high degree does not achieve its purpose.

Accumulation of Chorio-retinotoxic Drugs in the Foetal Eye

Abstract: USING whole body autoradiography1 we have found a selective accumulation and retention of certain drugs-in the eyes of mouse foetuses These drugs are known to cause ocular damage in adult humans and experimental animals The injury (toxic retinopathy), which is not seen in albino animals, has been related to the affinity of the drugs for the melanin structures of the eye2 The risk of foetal ocular damage appears to have been neglected in the past

Electron Spectroscopic Investigation of Auger Processes in Bromine Substituted Methanes and Some Hydrocarbons

Abstract: Auger spectra in gaseous CH4, CH3Br, CH2Br2, CHBr3, CBr4, C2H6, and C6H6 are excited by electron impact at about 5 keV energy and observed by means of a spherical electrostatic spectrometer at 90° to the primary electron beam. Besides the energies and the intensities of the Auger lines and the chemical shifts, the analysis of the spectra gives the energies and the lifetimes of the doubly ionized molecules. The line widths together with energy considerations indicate that some of these doubly ionized molecules rapidly dissociate. Comparisons are also made between the bromine and the carbon spectra.

Chemical fixation of chymotrypsin to water-insoluble crosslinked dextran (sephadex) and solubilization of the enzyme derivatives by means of dextranase.

Abstract: Catalytically active chymotrypsin derivatives can be synthesized from cyanogen bromide-activated Sephadex G200. In most cases the apparent catalytic activity of the covalently fixed enzyme appears to be considerably decreased in comparison to the activity of the free enzyme. However, by proper choice of the reaction conditions for the activation, enzyme conjugates with high activity, even toward a high molecular substrate, can be synthesized. These latter derivatives may be of practical value for the digestion of proteins. Crosslinked dextran as carrier was chosen because of the possbility, of digesting it enzymatically by dextranase. Sephadex G200, if activated at or below pH 10.3, will combine with chymotrypsin to yield digestable products. Changes of apparent kinetic properties of the fixed enzyme can accordingly be studied during the degradation process. On the solubilization of the insoluble conjugate, a total recovery of activity of the fixed enzyme can be obtained in cases the carrier has been activated by a sufficiently mild procedure. The high apparent Michaelis constant Km of insoluble chymotrypsin–Sephadex toward N-acetyl-L-tyrosine ethyl ester shifts back on solubilization to the value of free chymotrypsin. We therefore propose that the decreased activity of an insoluble chymotrypsin–Sephadex is due to diffusional effects shown by the gel matrix toward the substrate. Similarly observed shifts in optimum pH are explained by accumulation of hydrogen ions in the gel. The organic chemical reaction used for coupling the enzyme to the polymer can therefore be performed without decreasing the inherent catalytic activity of the enzyme. The route described for fixing chymotrypsin to Sephadex followed by solubilization of the products may be useful as a synthetic method for binding proteins, peptides, and other amino group-containing substances to soluble carriers, e.g., for the modification of pharmaceuticals.

Asymptotic Double-Photoexcitation Cross Sections of the Helium Atom

Abstract: A relative cross section for simultaneous excitation and ionization of the helium atom is derived from the sudden approximation. It is shown to agree with that obtained from the velocity form of the cross section in the Coulomb approximation. It is connected to the asymptotic cross section of Kabir and Salpeter through the cusp condition at the nucleus. An analysis of the influence of ground-state correlations on the asymptotic double-excitation cross section is carried out.

Electron spectroscopy for chemical analysis (e.s.c.a.)

Abstract: The electronic structure of matter has so far been studied almost exclusively by means of the electromagnetic radiation which is being emitted (or absorbed) at excitation. Apart from some early attempts, the electrons themselves were not directly detected. The various energy levels which could be studied by different modes of excitations were observed as photons being emitted (or absorbed) when electrons were making quantum jumps between two levels. Over a long period of time spectroscopy in the visible, infrared, ultraviolet, and X-ray parts of the electromagnetic spectrum was gradually perfected and extensively used in many kinds of applications. More recently, other and in some cases more sophisticated techniques, like n.m.r., e.p.r. and microwave spectroscopy, have been added to previously existing spectroscopic tools. During the last decade serious attempts have been made to explore the possibility of developing a spectroscopy based on the direct observation of the electrons. The results are encouraging. Despite many initial experimental difficulties it now seems evident that these can be solved in a surprisingly satisfactory way. Moreover, new types of information have become accessible and the fields of application are numerous.

Reversion of a streptomycin-dependent strain of Escherichia coli.

Abstract: A streptomycin dependent, spectinomycin resistant mutant ofEscherichia coli was used to select spontaneous phenotypic revertants to non-dependence on streptomycin. The ribosomes from one such revertant, which is inhibited by both streptomycin and spectinomycin, were analyzedin vitro. The altered protein responsible for the suppression of the streptomycin dependent phenotype was identified; this protein is 30S-10. The genetic locus for this mutation is a newly identified locus and it has been positioned close to thestr locus. The identification of the altered component responsible for the suppression of the spectinomycin resistant phenotype may be the same as that for the streptomycin dependent phenotype, but this is unproven.

A method for the simultaneous determination of 5-hydroxy-3-indole-acetic acid (5-HIAA) and 5-hydroxytryptamine (5-HT) in brain tissue and cerebrospinal fluid.

Abstract: A method is described for the isolation of 5-HIAA in brain tissue extracts or cerebrospinal fluid by use of a Sephadex G-10 column. The eluate is taken for fluorimetric determination of 5-HIAA in 3 M hydrochloric acid. Tissue blanks are obtained by destruction of 5-HIAA with potassium ferricyanide plus UV irradiation or with hydrogen peroxide. Recovery of 5-HI.4A from brain extracts was above 90 %. The sensitivity of the method allows quantitative determination of about 50 ng of 5-HIAA in a tissue extract. 5-HT in the effluent and washings from the Sephadex G-10 column was isolated on a weak cation exchange resin and determined fluorimetrically (AndCn and Magnusson 1967). Recovery of 5-HT added to brain extracts was 85 %. Determination of 5-HIAA in 3–5 ml samples of human cerebrospinal fluid could be performed with the present method with a recovery of 83 %.