819 research outputs found
Thermal roughening of a thin film: a new type of roughening transition
Journal ArticleThe equilibrium thermal roughening of thin Ge layers (one and two monolayers) deposited on Si(001) has been investigated with low-energy electron microscopy. A Ge-coverage-dependent roughening is observed. For two monolayers, the temperature at which imaging contrast is lost due to surface roughness is 900 ± 25 ◦C, between the roughening temperatures of Ge(001) and Si(001). Lower Ge coverages move this temperature closer to that of Si(001). The roughening is confined to the Ge overlayers. It is believed that this phenomenon represents a new type of surface roughening transition that should be generally applicable for heteroepitaxial films
Automorphisms of linear automata
AbstractRelationships between the group, Aut(M), of automorphisms of a linear automaton M and the structure of M are determined. Linear automata in which Aut(M) is a group of translations are characterized in terms of the structure of the state space of M. Also, conditions are determined as to when Aut(M) contains only linear transformations
The centralizer of a group automorphism
AbstractLet G be a finite group. The structure of the near-ring C(A) of identity preserving functions f: G → G, which commute with a given automorphism A of G, is investigated. The results are then applied to the case in which G is a finite vector space and A is an invertible linear transformation
Development of a 3-D energy-momentum analyzer for meV-scale energy electrons.
In this article, we report on the development of a time-of-flight based electron energy analyzer capable of measuring the 3-D momentum and energy distributions of very low energy (millielectronvolt-scale) photoemitted electrons. This analyzer is capable for measuring energy and 3-D momentum distributions of electrons with energies down to 1 meV with a sub-millielectronvolt energy resolution. This analyzer is an ideal tool for studying photoemission processes very close to the photoemission threshold and also for studying the physics of photoemission based electron sources
Anchored multi-phasic osteochondral construct
Disclosed are osteochondral constructs that can be utilized to encourage both bone and articular cartilage tissue repair in synovial joints. Disclosed constructs are composites including a hydrogel portion for implant in a cartilage defect site and an adjacent portion for implant in a bone defect site. The portion to be implanted in a bone defect site can include a polymeric/ceramic composite material. Disclosed constructs also include a polymeric anchor that can secure the construct at the desired site. Disclosed constructs can also include capillary channeled fibers within the bone portion of the construct that can provide improved nutrient flow to and waste flow from cells growing and developing on and in the construct
Gamow-Jordan Vectors and Non-Reducible Density Operators from Higher Order S-Matrix Poles
In analogy to Gamow vectors that are obtained from first order resonance
poles of the S-matrix, one can also define higher order Gamow vectors which are
derived from higher order poles of the S-matrix. An S-matrix pole of r-th order
at z_R=E_R-i\Gamma/2 leads to r generalized eigenvectors of order k= 0, 1, ...
, r-1, which are also Jordan vectors of degree (k+1) with generalized
eigenvalue (E_R-i\Gamma/2). The Gamow-Jordan vectors are elements of a
generalized complex eigenvector expansion, whose form suggests the definition
of a state operator (density matrix) for the microphysical decaying state of
this higher order pole. This microphysical state is a mixture of non-reducible
components. In spite of the fact that the k-th order Gamow-Jordan vectors has
the polynomial time-dependence which one always associates with higher order
poles, the microphysical state obeys a purely exponential decay law.Comment: 39 pages, 3 PostScript figures; sub2.eps may stall some printers and
should then be printed out separately; ghostview is o.
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