Mössbauer study of the Jilin and Xinyang meteorites

The Xinyang and Jilin meteorites were investigated using Mössbauer spectroscopy. In addition to troilites and silicates, the Jilin meteorite contains taenite and kamacite, while the Xinyang meteorite contains kamacite only. The Mössbauer data of these two meteorites confirm them as ordinary H chondrites. The Mössbauer parameters can be interpreted by a model based on the cooling history of these meteorites.     

Simple sound power measurements

A simple method of measuring sound power is described. Noise is added from a second calibrated source until the room sound pressure level is increased by 3 dB. The noise output of the device is then equal to the added power. A simple loudspeaker, modified to reduce the effect of the environment on the sound power output, is used as the calibrated source of sound power. Checks show that the sound power readings are substantially independent of the room in which they are made.     

The Mössbauer effect data center: A report

The Mössbauer Effect Data Center is unique in its operation and the kind of information services that it provides. It is probably the only user-supported information center in the basic sciences. This has been primarily possible due to the broad support and encouragement the center receives from the international Mössbauer community. This report also discusses the demographics of the Mössbauer community: identifying such items as the most active areas of research in Mössbauer Spectroscopy, where is this research being done and who is doing it. Also, examined is where Mössbauer research investigations are being published. BITNET and other forms of electronic mail are being widely used in the scientific community. This is also the case in the Mössbauer community. Directories and list-servers are being established.     

Polymer solid electrolytes from the PEG-PMMA-LiCF3SO3 system

Highly conductive solid polymeric electrolytes based upon low molecular weight poly(ethylene glycol) and ethylene oxide/propylene oxide copolymers blended with up to 50% by volume of poly(methyl methacrylate) have been synthesized using LiCF₃SO₃ (25:1 ether oxygen to cation ratio). Room-temperature ionic conductivities were measured to be in the range 10^?4 to 10^?5 S/cm for poly(methyl methacrylate) concentrations up to 30% by volume. In some cases, the addition of the poly(methyl methacrylate) enhanced the conductivity. All of the electrolytes studied were either amorphous or crystallized below 0°C. The variation of conductivity with temperature and polymer composition was measured and the results were analyzed in terms of effective medium theory and semiempirical considerations. Ionic transport is coupled to the structural relaxation of the polymer segments. At lower temperatures activated processes were required. Both charge carrier mobility and charge concentration were found to contribute to conduction. The effective medium theory quantitatively describes conductivities of amorphous heterogenous systems of limited miscibility (microphase separation) quite well. For miscible or partially crystalline systems other effects not incorporated in this theory play an important role, and conductivities are measured to be higher than theoretically predicted. © 1994 John Wiley & Sons, Inc.     

Tiegelloses Zonenschmelzen hochschmelzender Metalle mit Hilfe von punktfokussierten Elektronenstrahlen

Summary In conventional systems for floating-zone melting with electron bombardment the use of ring-cathode electron guns is widely spread. However, little is known about the applicability of point-focus electron-beams for floating-zone melting. To study this type of process a floating-zone melting device with a horizontal specimen position and a single point-focus electron-beam has been constructed. The experiment showed that in spite of sagging of the molten zone due to gravity, it is possible to melt rods of all refractory metals with rod diameters up to 5 mm with well controllable operating characteristics. This method easily allows the growth of exactly oriented crystals of W, Ta, Mo and Nb using a goniometric holder with a seed crystal on one side. Some characteristics of this type of zone melting and some preliminary results of an investigation of the single crystals grown in this way are discussed.

---

---

Gekürzte deutsche Fassung eines Vortrages, gehalten an «Second Internat. Conf. on Electron and Ion Beam Science and Technology», New York, April 1966.     

ACTION SPECTRA FOR PHOTOREACTIONS I AND II OF PHOTOSYNTHESIS IN THE BLUE-GREEN ALGA ANACYSTIS NIDULANS

Abstract— Action spectra for photoreactions I and II of photosynthesis were obtained for Anacystis nidulans and three of its variants which had altered chlorophyll/phycocyanin ratios. The spectra are properly scaled to each other. They provide information on contributions of phycocyanin and chlorophyll to initial absorption and final distribution of excitation energy to reaction centers I and II. In normally pigmented cells the light harvesting pigments for photoreaction I include about 40% of the phycocyanin and 84% of the chlorophyll. Both in normal cells and in cells with altered pigmentation excitation energy from phycocyanin is delivered to photoreaction II via a small number of chlorophylls. In response to alterations in chlorophyll/phycocyanin ratio Action I spectra showed large variations whereas Action II spectra were essentially invariant. The result is taken to mean that alteration in chlorophyll components in Anacystis is attended by a special restriction: there are only small changes in amount of chlorophyll accessible to photoreaction II in the face of large changes in amount committed to photoreaction I.     

Mono- and poly-ligated complexes of Zn2+: An ab initio analysis of the metal–ligand interaction energy

Detailed investigation of the binding energetics of Zn²⁺ to biologically relevant model ligands has been performed by large basis set restricted Hartree-Fock computations. This list includes neutral and anionic ligands that model the sidechains of the amino acid residues of proteins as well as those involved in binding to the metal during enzymatic activation: water, formaldehyde, formamide, imadazole, methylthiol, and the formate, hydroxyl, methoxy, methylthiolate anions. The decomposition of the intermolecular interaction energy into its components (Coulomb, exchange, polarization, and charge transfer) has been done within the frozen fragment reduced variational space procedure (RVS) developed by Stevens and Fink [W. J. Stevens and W. H. Fink, Chem. Phys. Lett., 139 , 15 (1987)]. The use of the RVS procedure was dictated by the very large magnitudes of the second-order interaction energy terms in the divalent cation complexes and the need to obtain polarization and charge-transfer contributions in a variational sense. The behavior of the interaction energy with radial and angular variation of the approach of the metal to the ligand is explored. In addition, the nonadditive behavior of polyligated complexes is studied for water and formate. This will also provide the data for a subsequent fit to a molecular mechanics procedure that considers the second-order interactions. © 1995 by John Wiley & Sons, Inc.