Manifestations of probe presence on probe dynamics in supercooled liquids

Experimental studies that follow behavior of single probes embedded in heterogeneous systems are increasingly common. The presence of probes may perturb the system, and such perturbations may or may not affect interpretation of host behavior from the probe observables typically measured. In this study, the manifestations of potential probe-induced changes to host dynamics in supercooled liquids are investigated via molecular dynamics simulations. It is found that probe dynamics do not necessarily mirror host dynamics as they exist either in the probe-free or probe-bearing systems. In particular, for a binary supercooled liquid, we find that smooth probes larger than the host particles induce increased translational diffusion in the host system; however, the diffusion is anisotropic and enhances caging of the probe, suppressing probe translational diffusion. This in turn may lead experiments that follow probe diffusion to suggest Stokes-Einstein behavior of the system even while both the probe-free and probe-bearing systems exhibit deviations from that behavior.     

Determination of the relative signs of proton spin coupling constants by double irradiation

The method of Evans [1] for determining relative signs of nuclear spin coupling constants by double irradiation experiments has been extended to the case where the three coupled nuclei are all protons. It is thus possible to demonstrate from the high resolution proton magnetic resonance spectrum of the ring protons of 2-Furoic acid that the three spin coupling constants are all of like sign.     

Continuous production of acetaldehyde by immobilized yeast within situ product trapping

Applied Biochemistry and Biotechnology - Two alternative enzymatic routes to continuous biological acetaldehyde production from ethanol by immobilized yeast were compared: ADH ofCandida utilis and...     

Self-assembled monolayers for liquid crystal alignment: simple preparation on glass using alkyltrialkoxysilanes

A simple procedure for the preparation of octadecylsiloxane self-assembled monolayers (SAMs) on float glass substrates is described. The method utilizes commercial octadecyltriethoxysilane, OTE: n-C₁₈H₃₇Si(OCH₂CH₃)₃, as the SAM precursor, with deposition accomplished in toluene solution using n-butylamine as catalyst. This synthetic approach obviates the use of the problematic trichlorosilanes typically required for the preparation of high quality SAMs, and is characterized by a wide 'process window,' utilizing off-the-shelf reagents without special handling.     

The fine structure of submicron iron particles

Summary High resolution electron micrographs are shown of samples of colloidal alpha iron. According to the conditions of manufacture the samples occur as (1) large, well-formed dendrites, (2) shorter, more fragile dendrites, (3) serrated rods, (4) needles and (5) cubic particulates. The central stem is a line-up of single cubic crystals. Representative dimensions are given for the various measurable units. A fine laminar structure in the cubic particulates, and some of the side branches and main stems is noted. The same laminar structure is observed in some of the background platelet material from the mother liquor. Stereoscopic studies show that the dendrites are three dimensional with their branches and main stem not in the same plane. X-ray diffraction detects alpha iron plus some form of Fe₂O₃ in most samples.

---

Zusammenfassung Es werden elektronenmikroskopische Aufnahmen mit hohem Aufl?sungsverm?gen von kolloiden α-Eisenteilchen gezeigt. Entsprechend den Herstellungsbedingungen fallen die Teilchen als gro\e, gut ausgebildete Dendriten, als kürzere schw?chere Dendriten, als gezackte Stangen, als Nadeln und als kubische Partikeln an. Der zentrale Stamm ist eine lineare Anordnung aus einzelnen kubischen Kristallen. Repr?sentative Dimensionen sind für die verschiedenen me\baren Einheiten eingezeichnet. Eine fein laminierte Struktur der kubischen Teilchen und von einigen Seiten?sten und Hauptachsen ist zu erkennen. Dieselbe Laminarstruktur wird teilweise an dem pl?ttchenartigen Material, das als Untergrund aus der Mutterflüssigkeit dazwischen liegt, beobachtet. Stereoskopische Aufnahmen zeigen, da\ die Dendriten dreidimensional sind und da\ Seitenzweige und Hauptachsen nicht in der gleichen Ebene liegen. R?ntgeninterferenzen lassen aufα-Eisen, sowie eine Form von Fe₂O₃ in den meisten Proben schlie\en.

---

---

The U.S. Navy Department, Bureau of Aeronautics, Industrial Planning Division, is credited with the development and sponsoring of the process for producing these fine powdered irons under contract No a (S) 52–792 C and NO a (S) 54–5190.

---

Presented in part before the Conference and Exhibit on Magnetism and Magnetic Materials held at Pittsburgh, Pennsylvania, June 14, 15 and 16, 1955 and before the annual meeting of the Electron Microscope Society of America, held at State College, Pennsylvania, October 1955; abstract, J. App. Phys.26, 1391 (1955).     

Strong resonant behaviour of the 12C + 14C reaction

Strong correlated resonances have been found in the inelastic and transfer channels of ¹²C + ¹⁴C at energies above the Coulomb barrier. It is argued that the system may be sufficiently transparent to the grazing partial waves to enable predicted resonant effects to be observed.     

Electronic structure,spin polarization and high critical fields in Chevrel compounds

Results are presented of an extensive theoretical study of the origin of high field superconductivity and/or magnetism in a number of Chevrel phase ternary compounds, MMo₆X₈ (with M=Sn, Eu, Gd and X=S and/or Se) based on self-consistent linear muffin-tin orbital (LMTO) energy band calculations using the local density approach (Hedin et al. exchange correlation) for the paramagnetic structures and local spin density formalism (Gunnarsson and Lundqvist) for the ferromagnetic structures. All electrons and all 15 atoms/cell are included with the core electrons (including the 4f's) recalculated in each iteration in a fully relativistic representation and the conduction electrons treated semirelativistically (all relativistic terms except spin-orbit). Superconductivity is found to be due to the high Mo d-band density of states (DOS) at E_F resulting from the unusual large charge transfer of Mo electrons to the chalcogen sites. There is also a large charge transfer from the metal site to the cluster (≈2 electrons in Sn and Eu) giving essentially no occupied conduction bands, for example, at the Eu site and a divalent ion isomer shift in very good agreement with the experiments of Dunlap et al. The conduction-electron DOS at the Eu site is found to be reduced by an order of magnitude from its metallic state value - in close agreement with their spin - lattice relaxation rate measurements. This low conduction-electron DOS yields very weak coupling of the 4f electrons to the conduction electrons and only a very weak Ruderman-Kittel-Kasuya-Yosida magnetic interaction showing why all the Chevrel rare-earth compounds - except Ce and Eu - are superconducting despite their having large local magnetic moments. The unusually high upper critical fields, H_c2, in these materials is found to be due to the unusully flat energy bands near F_F. The ferromagnetic (spin polarized) results for the Eu- and Gd-compounds show a net small but positive magnetic moment on the metal site and a small but negative induced spin magnetic moment on the Mo site in the Eu compound. Fermi-contact contributions to the hyperfine field are calculated and found to be in good agreement with the Eu Mössbauer results and the negative NMR Knights shift results of Fradin et al. These results demonstrate theoretically for the first time the validity of the Fischer et al. and Fradin et al. conclusion that the Jaccarino-Peter mechanism is responsible for the large increase in the H_c2 when large concentrations of Eu magnetic impurities are substituted in SnMo₆S₈. Finally, calculated Stoner factors for the paramegnetic phase and spin magnetization densities for the ferromagnetic phase are used to discuss qualitatively the origin of the different behavior observed for GdMo₆S₈ and EuMo₆S₈.