12,947 research outputs found
The Superconducting Proximity Effect as a Tool to Investigate Metal Films and Interfaces
052The superconducting
proximity effect is measured in sandwiches of thin Pb films and the alkali
metals Cs, Rb, K and Na. The -dependence provides information about the
interface barriers between Pb and the alkalis. Such a barrier is particularly
large in Pb/Cs sandwiches. It is not due to impurities or oxydation. In the
presence of a sufficiently strong barrier a special form of the Cooper limit
can be applied to calculate the transition temperature of the sandwich
Exchange Enhancement of the Electron-Phonon Pair Interaction
The critical temperature of high- superconductors is determined, at
least in part, by the electron-phonon coupling. We include the effect of an
exchange interaction between the electrons and calculate the renormalization of
the bare phonon frequencies and the electron-phonon verticies in a random phase
approximation and obtain a strongly enhanced attractive phonon-induced
electron-electron interaction. Using Fast Fourier Transform techniques, the
weak-coupling selfconsistency equation for the order parameter is solved in the
2D first Brillouin zone for the Emery tight-binding band with different band
fillings. The enhancement of arises primarily from the softening of the
phonon frequencies rather than the vertex renormalization.Comment: (2 pages, postscript file, hardcopies available from the authors
The Meservey-Tedrov effect in FSF double tunneling junctions
Double tunneling junctions of ferromagnet-superconductor-ferromagnet
electrodes (FSF) show a jump in the conductance when a parallel magnetic field
reverses the magnetization of one of the ferromagnetic electrodes. This change
is generally attributed to the spin-valve effect or to pair breaking in the
superconductor because of spin accumulation. In this paper it is shown that the
Meservey-Tedrov effect causes a similar change in the conductance since the
magnetic field changes the energy spectrum of the quasi-particles in the
superconductor. A reversal of the bias reverses the sign in the conductance
jump
The Spectral Energy Distribution of Normal, Starburst and Active Galaxies
We present the results of an extensive literature search of multiwavelength
data for a sample of 59 galaxies, consisting of 26 Starbursts, 15 Seyfert 2's,
5 LINER's, 6 normal spirals and 7 normal elliptical galaxies. The data include
soft X-ray fluxes, ultraviolet and optical spectra, near, mid/far infrared
photometry and radio measurements, selected to match as closely as possible the
IUE aperture (10" X 20"). The galaxies are separated into 6 groups with similar
characteristics, namely, Ellipticals, Spirals, LINER's, Seyfert 2's, Starbursts
of Low and High reddening, for which we create average spectral energy
distributions (SED). The individual groups SED's are normalized to the
7000\AA flux and compared, looking for similarities and differences
among them.The bolometric fluxes of different types of galaxies were calculated
integrating their SED's. These values are compared with individual waveband
flux densities, in order to determine the wavebands which contribute most to
the bolometric flux. Linear regressions were performed between the bolometric
and individual band fluxes for each kind of galaxy. These fits can be used in
the calculation of the bolometric flux for other objects of similar activity
type, but with reduced waveband information. We have also collected
multiwavelength data for 4 HII regions, a thermal supernova remnant, and a
non-thermal supernova remnant (SNR), which are compared with the Starburst
SED's.Comment: 29 pages, 13 postscript figures and 10 tables. To appear in The
Astronomical Journa
Population synthesis of HII galaxies
We study the stellar population of galaxies with active star formation,
determining ages of the stellar components by means of spectral population
synthesis of their absorption spectra. The data consist of optical spectra of
185 nearby () emission line galaxies. They are mostly HII
galaxies, but we also include some Starbursts and Seyfert 2s, for comparison
purposes. They were grouped into 19 high signal-to-noise ratio template
spectra, according to their continuum distribution, absorption and emission
line characteristics. The templates were then synthesized with a star cluster
spectral base. The synthesis results indicate that HII galaxies are typically
age-composite stellar systems, presenting important contribution from
generations up to as old as 500 Myr. We detect a significant contribution of
populations with ages older than 1 Gyr in two groups of HII galaxies. The age
distributions of stellar populations among Starbursts can vary considerably
despite similarities in the emission line spectra. In the case of Seyfert 2
groups we obtain important contributions of old population, consistent with a
bulge. From the diversity of star formation histories, we conclude that typical
HII galaxies in the local universe are not systems presently forming their
first stellar generation.Comment: 12 pages, 4 figures, MNRAS in pres
Computer Science Principles with Java
This textbook is intended to be used for a first course in computer science, such as the College Board’s Advanced Placement course known as AP Computer Science Principles (CSP). This book includes all the topics on the CSP exam, plus some additional topics. It takes a breadth-first approach, with an emphasis on the principles which form the foundation for hardware and software. No prior experience with programming should be required to use this book. This version of the book uses the Java programming language.https://rdw.rowan.edu/oer/1018/thumbnail.jp
Computer Science Principles with Python
This textbook is intended to be used for a first course in computer science, such as the College Board’s Advanced Placement course known as AP Computer Science Principles (CSP). This book includes all the topics on the CSP exam, plus some additional topics. It takes a breadth-first approach, with an emphasis on the principles which form the foundation for hardware and software. No prior experience with programming should be required to use this book. This version of the book uses the Python programming language.https://rdw.rowan.edu/oer/1024/thumbnail.jp
Computer Science Principles with C++
This textbook is intended to be used for a first course in computer science, such as the College Board’s Advanced Placement course known as AP Computer Science Principles (CSP). This book includes all the topics on the CSP exam, plus some additional topics. It takes a breadth-first approach, with an emphasis on the principles which form the foundation for hardware and software. No prior experience with programming should be required to use this book. This version of the book uses the C++ programming language.https://rdw.rowan.edu/oer/1025/thumbnail.jp
Compiler Design: Theory, Tools, and Examples
Compiler design is a subject which many believe to be fundamental and vital to computer science. It is a subject which has been studied intensively since the early 1950’s and continues to be an important research field today. Compiler design is an important part of the undergraduate curriculum for many reasons: (1) It provides students with a better understanding of and appreciation for programming languages. (2) The techniques used in compilers can be used in other applications with command languages. (3) It provides motivation for the study of theoretic topics. (4) It is a good vehicle for an extended programming project.
There are several compiler design textbooks available today, but most have been written for graduate students. Here at Rowan University, our students have had difficulty reading these books. However, I felt it was not the subject matter that was the problem, but the way it was presented. I was sure that if concepts were presented at a slower pace, with sample problems and diagrams to illustrate the concepts, that our students would be able to master the concepts. This is what I have attempted to do in writing this book.https://rdw.rowan.edu/oer/1001/thumbnail.jp
- …