New pyridone approach: total synthesis of mappicine ketone (nothapodytine B)

A novel synthesis of mappicine ketone, which possesses strong selective activity against the herpes viruses HSV-1 and HSV-2, including those Acyclovir-resistant, and human cytomegalovirus (HCMV) has been efficiently accomplished. The synthesis highlights a new pyridone approach that effectively combines a double, intramolecular Michael addition in a conjugated ester-conjugated amide with oxidation-decarboxylation of the resulting piperidone.     

The connection between the thermodynamics of chemisorption on semiconductor surfaces and surface scattering of carriers

An explicit theoretical relation is derived which connects the thermodynamics of chemisorption on semiconductor surfaces with the scattering rate of conduction and valence band carriers by charges localized in the chemisorption bonds.     

A unified theory of Stark broadening for hydrogenic ions—III: Results for He II Lyman-α

Calculations have been performed for He II Lyman-α using a previously developed theory (Papers I and II in this series) in which the effect of time-ordering in the required time development operator is retained. Representative results are given for an electron density of 10¹⁷ cm^-3 and a temperature of 40,000°K. Compared with non-time ordered results, these profiles are about 17% lower at line center and up to 16% higher in the wings. In addition, since the perturbing electron is speeded up by the Coulomb attraction, in comparison with neutral hydrogen the static results are not obtained until much further into the line wings. Comparison is also made to the calculations of Kepple for which good agreement is obtained, except near the line center where the difference approaches 25%.     

Epitaxial crystal growth by sputter deposition: Applications to semiconductors. Part I

The process of sputtering may be defined as the ejection of target particles due to the impingement of energetic projectile particles. The use of sputtered species as source material to deposit thin films was first reported in the literature in 1852¹ and has since enjoyed several periods of scientific and commercial interest interspersed with periods of disrepute. However, it is only recently that sufficient understanding of the complex processes occurring during, and simultaneously with. ion bombardment of solid surfaces has developed to result in the ability to reproducably and controllably use sputter deposition to grow high quality single crystal semiconducting thin films. The evolution of the branch of science concerned with ion‐surface interactions has been facilitated by the parallel development of ultra high vacuum technology and highly sensitive microanalytic techniques for identifying the state of scattered particles, sputtered species, and implanted material.     

High-accuracy optical clock via three-level coherence in neutral bosonic 88Sr

An optical atomic clock scheme is proposed that utilizes two lasers to establish coherent coupling between the 5s2 1S0 ground state of 88Sr and the first excited state, 5s5p 3P0. The coupling is mediated by the broad 5s5p 1P1 state, exploiting the phenomenon of electromagnetically induced transparency. The effective linewidth of the clock transition can be chosen at will by adjusting the laser intensity. By trapping the 88Sr atoms in an optical lattice, long interaction times with the two lasers are ensured; Doppler and recoil effects are eliminated. Based on a careful analysis of systematic errors, a clock accuracy of better than 2 x 10(-17) is expected.     

Tunneling into the normal state of Pr2-xCexCuO4

The temperature dependence of the tunneling conductance was measured for various doping levels of Pr(2-x)CexCuO4 using planar junctions. A normal state gap is seen at all doping levels studied, x=0.11 to x=0.19. We find it to vanish above a certain temperature T*. T* is greater than T(c) for the underdoped region and it follows T(c) on the overdoped side. This behavior suggests finite pairing amplitude above T(c) on the underdoped side.