The Cope Rearrangement of 1,5-Dimethylsemibullvalene-2(4)-d1 : Experimental Evidence for Heavy-Atom Tunneling

2017 ◽  
Vol 129 (36) ◽  
pp. 10886-10889 ◽  
Author(s):  
Tim Schleif ◽  
Joel Mieres-Perez ◽  
Stefan Henkel ◽  
Melanie Ertelt ◽  
Weston Thatcher Borden ◽  
...  
Keyword(s):  
Experimental Evidence ◽  
Heavy Atom ◽  
Cope Rearrangement

The Cope Rearrangement of 1,5-Dimethylsemibullvalene-2(4)-d1 : Experimental Evidence for Heavy-Atom Tunneling

2017 ◽  
Vol 56 (36) ◽  
pp. 10746-10749 ◽  
Author(s):  
Tim Schleif ◽  
Joel Mieres-Perez ◽  
Stefan Henkel ◽  
Melanie Ertelt ◽  
Weston Thatcher Borden ◽  
...  
Keyword(s):  
Experimental Evidence ◽  
Heavy Atom ◽  
Cope Rearrangement

scholarly journals Experimental Evidence for Heavy-Atom Tunneling in the Ring-Opening of Cyclopropylcarbinyl Radical from Intramolecular12C/13C Kinetic Isotope Effects

2010 ◽  
Vol 132 (36) ◽  
pp. 12548-12549 ◽  
Author(s):  
Ollie M. Gonzalez-James ◽  
Xue Zhang ◽  
Ayan Datta ◽  
David A. Hrovat ◽  
Weston Thatcher Borden ◽  
...  
Keyword(s):  
Experimental Evidence ◽  
Ring Opening ◽  
Isotope Effects ◽  
Heavy Atom ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope

scholarly journals The internal conversion of γ-rays

1927 ◽  
Vol 116 (774) ◽  
pp. 491-500 ◽  
Keyword(s):  
Quantum Mechanics ◽  
Potential Energy ◽  
Experimental Evidence ◽  
Internal Conversion ◽  
Heavy Atom ◽  
The State ◽  
Characteristic Functions ◽  
Positive Energy ◽  
X Ray ◽  
Γ Rays

Ellis and Wooster have discussed in two recent papers the experimental evidence for the absorption of γ-rays in the X-ray levels of the atom in which they are emitted. In the present paper this absorption will be investigated on the lines of quantum mechanics. The problem is that of the perturbation of a heavy atom by a Hertzian doublet placed at its centre. It will be assumed that the characteristic functions corresponding to the orbits considered are those of a hydrogen-like atom. The normalised expressions for all these functions are given by Oppenheimer. If A be the perturbing term in the potential energy it may be shown by an extension of an argument given by Dirac, that the increase in the number of systems in a given state r (or in the case of positive energies in an interval of length 2π h ) from time —T to T, where T is large compared with the periods of the atom, is ΔN ( r ) = 1/ h 2 (Σ s + ∫) (N ( s ) - N ( r ) | ∫ T -T A ( rs ) dt | 2 , (1) where N( s ) and N( r ) are the numbers of systems initially in the states r and s , and h is here (Planck’s constant)/2π. Of these the number of transitions from the state s to an interval of positive energy (E r , E r - d E r ) is, supposing N ( r ) = 0.

How do memory modules differentially contribute to familiarity and recollection?

2019 ◽  
Vol 42 ◽  
Author(s):  
Olya Hakobyan ◽  
Sen Cheng
Keyword(s):  
Recognition Memory ◽  
Experimental Evidence ◽  
Subjective Experience ◽  
Target Article ◽  
Memory Modules ◽  
Familiarity And Recollection ◽  
Memory Contents

Abstract We fully support dissociating the subjective experience from the memory contents in recognition memory, as Bastin et al. posit in the target article. However, having two generic memory modules with qualitatively different functions is not mandatory and is in fact inconsistent with experimental evidence. We propose that quantitative differences in the properties of the memory modules can account for the apparent dissociation of recollection and familiarity along anatomical lines.

Redox Reactions in Lipid Membranes as a Model for Primordial Energy-Conserving Systems

1997 ◽  
Vol 161 ◽  
pp. 437-442
Author(s):  
Salvatore Di Bernardo ◽  
Romana Fato ◽  
Giorgio Lenaz
Keyword(s):  
Experimental Evidence ◽  
Lipid Membranes ◽  
Energy Supply ◽  
Redox Reactions ◽  
Living Systems ◽  
Asymmetric Distribution ◽  
Conservation Of Energy ◽  
Asymmetrical Distribution ◽  
Energy Conserving ◽  
Living Organisms

AbstractOne of the peculiar aspects of living systems is the production and conservation of energy. This aspect is provided by specialized organelles, such as the mitochondria and chloroplasts, in developed living organisms. In primordial systems lacking specialized enzymatic complexes the energy supply was probably bound to the generation and maintenance of an asymmetric distribution of charged molecules in compartmentalized systems. On the basis of experimental evidence, we suggest that lipophilic quinones were involved in the generation of this asymmetrical distribution of charges through vectorial redox reactions across lipid membranes.

Isomorphous replacement in electron diffraction of wet crystals of rat hemoglobin

1983 ◽  
Vol 41 ◽  
pp. 446-447
Author(s):  
William F. Tivol ◽  
Murray Vernon King ◽  
D. F. Parsons
Keyword(s):  
Electron Diffraction ◽  
Heavy Atom ◽  
Isomorphous Substitution ◽  
X Ray Diffraction ◽  
Salt Solutions ◽  
X Ray ◽  
Isomorphous Replacement ◽  
Structure Factors ◽  
Diffraction Structure ◽  
The Mean

Feasibility of isomorphous substitution in electron diffraction is supported by a calculation of the mean alteration of the electron-diffraction structure factors for hemoglobin crystals caused by substituting two mercury atoms per molecule, following Green, Ingram & Perutz, but with allowance for the proportionality of f to Z3/4 for electron diffraction. This yields a mean net change in F of 12.5%, as contrasted with 22.8% for x-ray diffraction.Use of the hydration chamber in electron diffraction opens prospects for examining many proteins that yield only very thin crystals not suitable for x-ray diffraction. Examination in the wet state avoids treatments that could cause translocation of the heavy-atom labels or distortion of the crystal. Combined with low-fluence techniques, it enables study of the protein in a state as close to native as possible.We have undertaken a study of crystals of rat hemoglobin by electron diffraction in the wet state. Rat hemoglobin offers a certain advantage for hydration-chamber work over other hemoglobins in that it can be crystallized from distilled water instead of salt solutions.

A Method for Setting the Clearance Angle

1972 ◽  
Vol 30 ◽  
pp. 388-389
Author(s):  
Michael T. Bucek ◽  
Howard J. Arnott
Keyword(s):  
Experimental Evidence ◽  
Light Source ◽  
Black Spot ◽  
Critical Factor ◽  
Clearance Angle ◽  
Crude Approximation ◽  
Ultrathin Sections

It is believed by the authors, with supporting experimental evidence, that as little as 0.5°, or less, knife clearance angle may be a critical factor in obtaining optimum quality ultrathin sections. The degree increments located on the knife holder provides the investigator with only a crude approximation of the angle at which the holder is set. With the increments displayed on the holder one cannot set the clearance angle precisely and reproducibly. The ability to routinely set this angle precisely and without difficulty would obviously be of great assistance to the operator. A device has been contrived to aid the investigator in precisely setting the clearance angle. This device is relatively simple and is easily constructed. It consists of a light source and an optically flat, front surfaced mirror with a minute black spot in the center. The mirror is affixed to the knife by placing it permanently on top of the knife holder.

A Base Specific Single Heavy Atom Stain for Electron Microscopy

1972 ◽  
Vol 30 ◽  
pp. 184-185
Author(s):  
J. P. Langmore ◽  
N. R. Cozzarelli ◽  
A. V. Crewe
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
High Resolution ◽  
Elastic Scattering ◽  
Heavy Atom ◽  
High Vacuum ◽  
Heavy Atoms ◽  
Large Movement ◽  
Base Sequencing ◽  
Scanning Electron

A system has been developed to allow highly specific derivatization of the thymine bases of DNA with mercurial compounds wich should be visible in the high resolution scanning electron microscope. Three problems must be completely solved before this staining system will be useful for base sequencing by electron microscopy: 1) the staining must be shown to be highly specific for one base, 2) the stained DNA must remain intact in a high vacuum on a thin support film suitable for microscopy, 3) the arrangement of heavy atoms on the DNA must be determined by the elastic scattering of electrons in the microscope without loss or large movement of heavy atoms.

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