‘Factors of ignorance’ and the rationalized M.K.S.A. system of units

An attempt is made, by means of an allusive (rather than a systematic) historical account of the development of the subject, to exhibit the essentially unique character of the rationalized M.K.S.A. system of units. The establishment of this system involved one arbitrary decision—the determination to retain unaltered the size of the previously accepted unit of current. Thereafter, any choice of derived units, other than the choice actually made, would have destroyed the basic symmetry of the formulation.     

Implications of axion-like particles from the Fermi-LAT and H.E.S.S.observations of PG 1553+113 and PKS 2155−304

We investigate the axion-like particle(ALP)-photon oscillation effect in the high-energy y-ray spectra of PG 1553+113 and PK.S 2155-304 measured by Fermi-LAT and H.E.S.S.The choice of extragalactic background light(EBL)model,which induces the attenuation effect in observed y-ray spectra,affects the ALP implications.For the ordinary EBL model that prefers a null hypothesis,we set constraints on the ALP-photon coupling constant at 95% C.L.as gay 5×10^-11 GeV^-1 for the ALP mass 〜10 neV.We also consider the CIBER observation of the cosmic infrared radiation,which shows an excess at wavelengths of -1μm after the substraction of foregrounds.High-energy gamma-rays from extragalactic sources at high redshifts would suffer from a more significant attenuation effect caused by this excess.In this case,we find that the ALP-photon oscillation would improve the fit to the observed spectra of PKS 2155-304 and PG 1553+113 and find a favored parameter region at 95%CL..     

Mössbauer and N.M.R. studies of ErFe2Hx

Hydrides of Intermetallic compounds have been the object of many studies because of their potential applications/1/. Recent papers were devoted to the problem of interstitial site occupation in connection with H-H exclusion rule (d_H–H > 2.1 A). The present work deals with ErFe₂H_X, which has been investigated both by⁵⁷Fe Mössbauer Effect and by¹⁶⁷Er N.M.R. Previous studies were limited to X 2, 3.5, 4.1. Here five values of x (1.45, 1.6, 1.84, 2.6, 3.3) are considered, in order to obtain information on hydrogen location, filling and diffusion as a function of x, and also on hydrogen contribution to the electric field gradient (E.F.G.) and crystalline field at the Rare Earth.     

Theory and nonlinearity of thermoacoustics,Ⅰ. Thermoacoustics

1IntroductionThermoacousticswithpotelltialsinrefrigerationandcryogenictechnology,ha-sprogressedvigorouslyinlasttwelltyyears,asanexampleofsynchronousdevelopmentofscienceandprac-ticeofmodernsciences.Botthermoacousticphenomenawerediscoveredearlyinhistory,andittookmorethantwohundredyearsoftheeffortofscieatiststoarriveatthisperiod.Thisalsoservesasanexampleoftheduncultandtortuouswayinthecognitionofnature.Aretrthspectionoftheprogressofthermoacousticsinthelastyearsnotonlyhelpstounderstandthephysicsoft…     

Extrusions and intrusions in fatigued metals. Part 1. State of the art and history†

Current state and historical progress in experimental and theoretical studies of surface relief appertaining to persistent slip bands (PSBs) and leading to fatigue crack initiation in cyclically deformed metals is presented as a thorough critical overview. A comprehensive inventory of microscopic techniques used for this study is tabulated chronologically with emphasis to their applicability to polycrystals. The most relevant experimental characteristics concerning surface relief evolution, namely the form of extrusions and intrusions in single- and polycrystalline materials, are surveyed. Theoretical models and computational simulations of extrusion and intrusion formation and fatigue crack initiation are critically reviewed.     

Comment on ‘Structure and diffusion of clusters on Ni surfaces by C.-L. Liu and J.B. Adams’

We calculate the dissociation energy of Ni clusters containing up to 13 atoms adsorbed on Ni(111), in order to elucidate its dependence on the cluster size. As opposed to what is claimed by Liu and Adams [Surf. Sci. 268 (1992) 73] the dissociation energy of Ni/Ni(111) does not display a marked peak for N =5, its value for this cluster size being indeed very close to what is found for N = 4 and N = 6.     

Yu. N. Denisyuk’s ideas in the development of holographic methods of obtaining and projection of images

The main investigations carried out by Yuri Nikolaevich Denisyuk at the Ioffe Institute of the Russian Academy of Sciences have been presented. His investigations were aimed at developing methods of recording and projecting three-dimensional images in order to reduce the volume of information contained in the images for use in optical computers, optical interconnections, and displays.     

Quantum tunneling and the activated chemisorption of methane on tungsten: Comment on ‘activated chemisorption of methane and tunneling’ by T.-C. Lo and G. Ehrlich

Results of recent experimental studies on the dissociative chemisorption of CH₄ and CD₄ on W(211) were previously concluded to be inconsistent with earlier proposed quantum tunneling models. In this Letter we re-analyze the experimental results and show them to be entirely consistent with a tunneling mechanism. We also show that the reported inconsistency arises from the use of an oversimplified model for the tunneling transmission coefficient.     

Intermolecular Interactions. Absorption and Fluorescence Spectra of α-Naphthol

In the ground state, -naphthol interacts with water via oxygen, whereas with alcohols (ethanol and isopropanol) and acetonitrile it interacts via hydrogen from the hydroxyl group. In the excited state, -naphthol interacts much more weakly. An analysis of the dependences of positions of electronic-vibrational transitions on the solvent basicity and acidity demonstrates their nonlinearity. For the parameters describing the solvation ability of the solvent, linear dependences are observed for the following series of solvents: isopropanol, ethanol, acetonitrile, and water. The possible values of the acid number (pA*) for the excited -naphthol molecule fall within the interval from 0.4 to 1.4 depending on the chosen maximum of the absorption band. In fluorescence spectra, the band intensities differ for neutral and ionic modifications of the molecule. The fluorescence efficiency of the neutral molecule is by an order of magnitude higher than that of the ionic modification. Possible channels of quenching of the ionic modification are discussed.     

Origin of the E.S.R. hyperfine anisotropy and the cos2 θ rule of the β-fluorine couplings

The origin of the hyperfine couplings of β-fluorine nuclei in free radicals has been studied using the hyperfine tensors determined for and in single crystals. The direction of the maximum principal element of the β-fluorine coupling tensor in was found to be very close to the direction of the maximum overlap of the fluorine 2p π orbital with the half-filled carbon 2p π orbital. This means that the spin density in the fluorine 2p π orbital is mainly due to the direct overlap with the carbon 2p π orbital and the contributions from the hyperconjugation and the spin polarization mechanisms are less important. The cos²θ rule, B ₀ + B cos²θ, for the β-fluorine coupling tensor was also derived from the conformational dependence of the overlap integral. Using the ratio of B/B ₀ calculated from the overlap integral together with the observed hyperfine tensor for , the absolute values of B ₂ and B were determined and results were applied to the β-fluorine coupling tensor of the rotating CF₃ group in . The calculated tensor is in very good agreement with the one observed.     

Luminescent properties and structure of multicomponent naphthalene-β-cyclodextrin complexes. 1. Effect of adding third parties, o-carborane or/and adamantane

Luminescence spectra of water solution of β-cyclodextrin (β-CD) inclusion complexes with naphthalene have been studied in the presence of carcass compounds (CC), adamantane and ocarborane, added in solution as the third parties. It was observed that the CC structure completely determines luminescence type displayed by the three-component complex. Adding adamantane to the solution leads to the disappearance of the spontaneous excimer fluorescence observed usually along with a monomer fluorescence of naphthalene and the appearance of the long lived phosphorescence at room temperature. At the same time, introducing o-carborane in solution of β-CD inclusion complexes with naphthalene results in the dramatic growth of intensity of the excimer band at the expense of lowering intensity of monomer fluorescence. These phenomena were explained using results of the quantum-chemical calculation of the structure and complexation energies at the semi-empirical PM3 and DFT levels of theory.     

Geometric analysis of φ4 fields and Ising models. Parts I and II

We provide here the details of the proof, announced in [1], that ind>4 dimensions the (even) ⁴ Euclidean field theory, with a lattice cut-off, is inevitably free in the continuum limit (in the single phase regime). The analysis is nonperturbative, and is based on a representation of the field variables (or spins in Ising systems) as source/sink creation operators in a system of random currents — which may be viewed as the mediators of correlations. In this dual representation, the onset of long-range-order is attributed to percolation in an ensemble of sourceless currents, and the physical interaction in the ⁴ field — and other aspects of the critical behavior in Ising models — are directly related to the intersection properties of long current clusters. An insight into the criticality of the dimensiond=4 is derived from an analogy (foreseen by K. Symanzik) with the intersection properties of paths of Brownian motion. Other results include the proof that in certain respect, the critical behavior in Ising models is in exact agreement with the mean-field approximation in high dimensionsd>4, but not in the low dimensiond=2 — for which we establish the universality of hyperscaling.A. P. Sloan Foundation Research Fellow. Supported in part by the National Science Foundation Grant PHY-78-25390-A02