Showing papers by "Chalmers University of Technology published in 1982"

Structure of methylene blue-DNA complexes studied by linear and circular dichroism spectroscopy.

Abstract: Bradley et al. [(1972) Biopolymers11, 645–652] used electro-optical measurements to show that methylene blue (MB), like acridine orange, in its DNA complex is oriented more or less perpendicular to the helix axis as expected if intercalated. High-precision flow linear dichroism (LD) here confirms that MB is coplanar with the DNA bases at low dye/DNA binding ratios and low ionic strengths. CD shows two origins of induced optical activity for the transition of lowest energy (polarized parallel to the long-axis of the dye molecule): at low binding ratios (r 300 mM Na+ or >0.4 mM Mg2+). Nondegenerate coupled-oscillator theory can explain the CD in terms of interactions of transition moments of the dye and the nearest nucleotide bases and indicates a change between two intercalation geometries: a Lerman type of mode, denoted γ−, and an orthogonal mode, denoted γ+. This rotation of MB in the base-pair pocket is accomplished at Na+ and Mg2+ concentrations when the phosphates are effectively screened and the result suggests a more localized bonding of Mg2+ than is expected from simple polyelectrolyte models. The exciton effect at high binding ratios, observed both in CD and in LD, can be interpreted in terms of an interaction between an intercalated and a nonintercalated MB. The geometry of this “accidental” dimer is consistent with a location of the nonintercalated MB in the minor groove, bridging the strands by the positively charged amino groups directed towards phosphate groups. The dihedral angle of the MB pairs, corresponding to a left-handed helix, is opposite to that with acridine orange and proflavine on DNA, indicating that the latter ligands bind to DNA in a different way.

Diel and depth variations in dissolved free amino acids and ammonium in the Baltic Sea determined by shipboard HPLC analysis1

Abstract: A precolumn fluorimetric labeling method was tested for shipboard HPLC analysis of dissolved free amino acids (DFAA) in natural waters. No sample preparation is required and all naturally occurring amino acids plus ammonium are sufficiently separated within 30 min. Striking diel trends were observed to a depth of at least 60 m, with maximal DFAA concentrations (200–400 nM) in the late evening and minimal concentrations (30–40 nM) in the early day. Concurrent with the evening concentration maxima were elevated relative abundances of basic amino acids (especially ornithine and lysine) and ammonium. During the day very low levels of amino acids were found in the upper water. The magnitude of the night-to-day drop in total DFAA suggests a net heterotrophic uptake rate of up to 6 µg AA·liter−1 h−1. A pronounced amino acid maximum at the O2−HS− interface in the water column was presumably derived from microbial populations inhabiting this region. Pronounced, coincidental minima in amino acid and ammonium concentrations just above this interface may be related either to scavaging by precipitating metal oxyhydroxides or to enhanced heterotrophic utilization.

The Composition of the Surface during Passivation of Stainless Steels

Abstract: Molybdenum alloyed austenitic stainless steels were exposed in 0.1M HCI + 0.4M NaCl and polarized in the active and passive regions of the alloys. The treated surfaces were analyzed by uti...

Transcutaneous electrical nerve stimulation in severe angina pectoris.

Abstract: The pain-relieving effect of transcutaneous electrical nerve stimulation (TENS) was studied in 10 male patients with angina pectoris of functional class III or IV. All patients had been stabilized on long-term maximal oral treatment for at least six months. The effects of the TENS treatment were measured by means of repeated bicycle ergometer tests. All patients had an increased working capacity (16–85%) and decreased ST depression and reduced recovery time during TENS. No adverse effects were observed.

Observation of Rotational Transitions for H 2 , D 2 , and HD Adsorbed on Cu(100)

Abstract: Energy losses observed when low-energy electrons were scattered from a Cu(100) surface exposed at $T\ensuremath{\sim}15$ K to ${\mathrm{H}}_{2}$ (and ${\mathrm{D}}_{2}$,HD) lie close to rotational and rotational-vibrational transitions (${\mathrm{H}}_{2}$,${\mathrm{D}}_{2}$) of the free molecules. Both $o$- and $p$-${\mathrm{H}}_{2}$ and -${\mathrm{D}}_{2}$ physisorb on the surface, with negligible conversion on the time scale of the experiment. The relative populations were different from those characteristic of the adsorbing gas, suggesting a $j$-dependent sticking coefficient.

Radiative cooling computed for model atmospheres

Abstract: Calculations of spectral radiance are reported from several model atmospheres appropriate to different climatic conditions by use of the LOWTRAN 5 computer code. From these data we evaluate the radiative cooling power and the temperature drop below ambient temperature for horizontal surfaces that radiate toward the sky. The surfaces are ideal blackbodies or have ideal infrared-selective properties with zero reflectance in the 8-13-microm range and unity reflectance elsewhere. For freely radiating surfaces, the cooling power at ambient temperature lies between 58 Wm(-2) and 113 Wm(-2) for the different surfaces and model atmospheres. The maximum temperature difference for a device with a nonradiative heat transfer coefficient of 1 Wm(-2) K(-1) is between 11 and 21 degrees C for a blackbody and between 18 and 33 degrees C for an infrared-selective surface. For radiators arranged so that they intercept only the atmospheric zenith radiance, the cooling powers and temperature differences are higher than for freely radiating surfaces, the increase being largest for humid atmospheres. The influence of altered contents of water vapor was found to affect strongly the radiative cooling, whereas changes in ozone and aerosol abundance were less important. The significance of these results to different cooling applications is briefly discussed.

Breakdown of one-electron pictures in photoelectron spectra

Abstract: The purpose of this review is to describe some spectacular effects of many-electron interactions in certain core levels in heavy atoms, as well as to give an overview of closely related phenomena in molecules, solids and adsorbates. The central concept will be what we shall call giant Coster-Kronig (gCK) fluctuation and decay of a hole level, involving ineraction of a single hole with configurations with primarily two holes and one excited electron. In systems with an open “valence shell” structure. i.e. with empty levels spacially as compact as the occupied ones, the interaction process can become extremely strong and lead to a breakdown of the one-electron picture. In some cases, there is even a complete breakdown of the quasi-particle picture, in which case the spectral strength has no prominent discret features and rather shows a continuum-like distribution.

Mortality among the widowed in Sweden

Abstract: This study consists of three parts In the first part the risk of death for widowed persons is studied as a function of time interval since the day of bereavement The effects of bereavement on mortality are investigated in all widowed people in Sweden (about 360 000) from 1968 to 1978 Among widowers above 65 years of age there are nine deaths per 1000 in excess compared with married men during the first 3 months after bereavement In comparison with married people in the age group 70-74 it is found that among widows there is an increased mortality by 22% and among widowers by 48% during the first 3 months after bereavement Further observation, during a period of altogether 11 years, showed that excess mortality continues, though at a lower level In the second part, causes of death in the age group 70-74, divided according to marital status, are studied on the basis of data from the National Central Bureau of Statistics The excess in mortality is due mainly to cancer and cardiovascular deaths, but also accidents, suicides and cirrhosis of the liver The third part deals with differences between marital status groups with respect to tobacco smoking and alcohol abuse by using data from the population study of "70-year-olds in Goteborg" (H 70) By using data from central registers together with data from the population study it is possible to show that life style factors have an impact on the difference in mortality pattern between married and widowed people in Sweden

Positivity Improving Operators and Hypercontractivity

Abstract: Here (1.1) is the famous Nelson hypercontractivity inequality [14], which has proved to be extremely useful in Euclidean quantum field theory (see e.g. [16]). Like (1.1) the estimate (1.2) follows very easily from the It6 calculus of Brownian motion [3]. Here, in order to make the paper self-contained and to introduce the reader to some general principles of interest, we submit a new proof of (1.2) by mimicing a standard proof of (1.1). We should like to add that (1.2) has at least a formal resemblance to the familiar correlation inequalities from statistical mechanics (see e.g. [11, 12, 16]). Using (1.1) and (1.2) it is simple to obtain similar estimates for the biquantization of a linear contraction on Hilbert space (Sect. 4). Now suppose A is a self-adjoint operator on L 2 of a probability space and set A(A)=maxspec(A)-sup(spec(A)\{maxspec(A)}), where spec(A) denotes the spectrum of A. Below we will state conditions that guarantee that the gap A (A) is proper. In fact, a simplified version of our main result (Theorem 5.3) gives a positive numerical lower bound of A (A) if (i) A is positivity preserving, (ii) sup { IlZf I1~; [I f [12 = 1 } = K 2, and (iii) inf{ [IZfllp/~v_~; I l f l l , = 1, f>0} = k > 0 some 0 < p < 1. Here (i)-(iii) imply that A has a unique ground state. It shall be empha-

Electrical conductivity and activation volume of the solid electrolyte phase α -AgI and the high-pressure phase fcc AgI

Abstract: The $\ensuremath{\alpha}$ phase of silver iodide which is stable between 147 and 555\ifmmode^\circ\else\textdegree\fi{}C at normal pressure is a classical example of a solid electrolyte. In this investigation the temperature and pressure dependences of the electrical conductivity in $\ensuremath{\alpha}$-AgI have been studied for pressures up to 0.9 GPa. This phase is characterized by a large electrical conductivity, a low migration enthalpy of 0.098 eV, and a low activation volume of 0.8-0.9 ${\mathrm{cm}}^{3}$ ${\mathrm{mole}}^{\ensuremath{-}1}$. For pressures between 0.4 and 10 GPa a rocksalt-structure phase fcc AgI is stable at room temperature. The temperature and pressure dependences of the electrical conductivity in this phase have been studied for pressures up to 1.0 GPa and for temperatures between room temperature and 330\ifmmode^\circ\else\textdegree\fi{}C. The electrical conductivity resembles that in AgCl and AgBr, and it is indicated that Frenkel defects dominate also in fcc AgI. At high temperature and pressure, however, a gradual increase of the electrical conductivity takes place in fcc AgI, similar to the gradual transitions that have been reported for many materials with the fluorite structure. The electrical conductivity in this temperature and pressure range of fcc AgI is approximately 1 ${\mathrm{\ensuremath{\Omega}}}^{\ensuremath{-}1}$ ${\mathrm{cm}}^{\ensuremath{-}1}$, i.e., only slightly less than the electrical conductivity in the $\ensuremath{\alpha}$ phase.

Solubilities of actinides in neutral or basic solutions

Abstract: The solubility of actinides in environmental waters is largely determined by complexes formed with inorganic anions (OH−, CO32−, HPO42−, F−, SO42−) and organic complexing agents. Measured and estimated complex formation quotients have been summarized for the actinides, U, Np, Pu and Am. Speciation and solubility of these elements are largely determined by hydrolysis and formation of carbonate and possibly fluoride and phosphate complexes. Solubilities in the pH-range 5-11 have been calculated, considering formation of hydroxy and carbonate complexes only, and compared with data from the literature. Experimentally determined solubilities are rarely equal to values calculated from thermodynamic data. What appears to be oversaturated solutions can be obtained due to slow kinetics in the formation of e.g. thermodynamically stable oxides, or due to the existence of colloidal particulates not in true solutions. By the presence of oxide or silicate surfaces, on the other hand, species in solution will be adsorbed in certain pH-ranges, leading to a lower concentration in solution than predicted. Due to the lack of accurate thermodynamic data for some of the dominating reactions in environmental waters, calculated solubilities must in general be considered as somewhat speculative.

Synthesis of Schiff Bases Forming the First Room Temperature Ferroelectric Liquid Crystal—The Mora Series

Abstract: Condensation of chiral S-4-(6-methyl)octyloxy-2-hydroxybenzaldehyde (S-4-0- (6-methyl)octylresorcylaldehyde) with 4-alkylanilines (the MORA series, 3) gives low-melting Schiff bases showing chiral smectic C phases at or slightly above room temperature. The previously known MBRA series (4'-0- (2-methyl)-butyl- resorcylidene-4-alkylanilines, 1) has been extended by MBRA 4 and 12, both showing low-temperature smectic phases. Bis (S, S-4'-(2-methylbutyloxy-2-hydroxybenzylidene)-2-chloro-1,4-phenylene-diamine shows a cholesteric blue phase between 174 and 175 °C.

Linear dichroism studies of nucleic acids. II. Calculation of reduced dichroism curves of A-and B-form DNA†

Abstract: We have calculated the uv linear dichroism for the A- and B-forms of DNA using π-π* transition moments and band components determined from the free DNA bases. The reduced dichroism (LDR) as a function of wavelength is estimated is in the 220–300-nm region, for both the oriented-gas model and a simple exciton model. For B-form DNA, LDR is obtained to −1.48S (S being the orientation factor) over the whole wavelenth region by both models. For A-form DNA, LDR is not constant, but changes monotonically from about −1.15S at 220 nm to about −1.35S to −1.45S at 300 nm, depending on base combination and degree of interaction (−1.35S for the oriented gas). It is emphasized that a common assumption of a single “effective” transition moment of the principal band at 260 nm may not generally be made because of the extensive overlap of differently polarized bands. The possibility of using the reduced dichroism curve for characterizing the secondary structure of DNA is discussed.

Vibrational Damping of Adsorbed Molecules: Methoxide on Cu(100)

Abstract: The lifetimes of the C-H and C-D stretch vibrational modes of methoxide adsorbed on Cu(100) have been measured by infrared spectroscopy. It is shown that the damping of these vibrational states is caused by excitation of electron-hole pairs in a region very close to the vibrating molecule. It is argued that the electron-hole pairs are excited because a resonance around the Fermi level fills and empties during the vibration.

A New Explanation of the High Effective Temperatures in Pulsar Radioemissions

Abstract: A new nonlinear process, which can explain the high effective temperatures of pulsar radio emissions, is proposed. It is due to the excitation of low frequency Alfven waves by waves resonantly interacting with the electrons and positrons in the pulsar ultrarelativistic plasma.