Electronic energy levels of point defects at the GaSb (110) surface

Deep energy levels are predicted for substitutional sp³-bonded defects at the (110) surface of GaSb.     

Some linked subsets of posets

Recently Frank Tall has introduced the notion of a poset being “endowed” which is used in a forcing and reflection type proof to show that certain properties are preserved by forcing with such a poset. Subsequently Bill Fleissner introduced the property of a boolean algebra having a “lynx” and used this in an “Axiom and combinatorics” type proof of the same result. The two notions are basically the same thing. In this paper we prove that some of the usual Cohen algebras have lynxes, that it is consistent that nearly all of them have lynxes and investigate more generally the notion of lynxes. Research supported by NSERC of Canada.     

Surface electronic states in GaAs1−xPx>

The intrinsic electronic surface states of (110) GaAs_1?xP_x> are predicted as functions of alloy composition x. For x >x_c ≈ 0.05, intrinsic states are found within the fundamental gap. The minimum energy of the surface band is primarily determined by the bulk electronic structure, not by the atomic relaxation at the surface.     

Remote points under the continuum hypothesis

We show that, under CH, (i) every ccc, non-pseudocompact space of weight at most ω₂ has remote points, and (ii) if X_i, for i ∈ I, is a completely regular ccc topological space of weight ω₁ and if X := Π_{i ∈ I} X_i is ccc and non-pseudocompact, then X has remote points. Received July 21, 2006; accepted in final form October 16, 2008.     

Embedding in R-closed spaces

Some problems in the theory of R-closed spaces are solved by showing that every regular space can be embedded in a minimal regular space and there is an R-closed space with no coarser minimal regular topology. A class of spaces is found so that when fed into the Jone's machinery for producing non-Tychonoff, regular spaces, the output is non-tychonoff R-closed and minimal regular spaces. Also, an example of a strongly minimal regular space that is not locally R-closed is given.     

Model calculations of the spectra of rare-gas impurities in alkali hosts

Summary The spectra of rare-gas impurities in alkali hosts are evaluated for a change of mean-field (ΔMF) model. The model produces absorption and emission edge anomalies and asymmetric X-ray photoemission line shapes, but the threshold shapes are different from those observed by Tilton, Phelps and Flynn. The resolution of the discrepancy between theory and experiment appears to lie beyond this ΔMF model.

---

Riassunto Si sono calcolati gli spettri di impurità di gas rari in ospiti alcalini per un cambiamento del modello di campo medio (ΔMF). Il modello produce anomalie di bordo di assorbimento ed emissione e forme della linea di emissione dei raggi X asimmetriche, ma le forme sulla soglia sono differenti da quelle osservate da Tilton, Phelps e Flynn. La risoluzione della discrepanza tra teoria ed esperimenti appare al di là di questo modello ΔMF.

---

Резюме Оцениваются спектры разреженных газовых примесей в щелочных кристаллах для изменения модели среднего поля (ΔMF). Предложенная моделъ дает поглощение и аномалии края испускания и асимметричнЫе формы линии фотоиспускания ренттеновского излучения, но формы порогов отличаются от резуљтатов, полчч∈нных Тилтоном Фелпсом и Флином. Возможностя разрешения расхождений между теорией и зкспериментом, оказьивается, лежит за пределами зтой ΔMF модели.

     

Optimal cupolas of uniform strength: Spherical M-shells and axisymmetric T-shells

Summary The first part of this paper is concerned with the optimal design of spherical cupolas obeying the von Mises yield condition. Five different load combinations, which all include selfweight, are investigated. The second part of the paper deals with the optimal quadratic meridional shape of cupolas obeying the Tresca yield condition, considering selfweight plus the weight of a non-carrying uniform cover. It is established that at long spans some non-spherical Tresca cupolas are much more economical than spherical ones.

---

Optimale Kuppeln gleicher Festigkeit: Kugelschalen und axialsymmetrische Schalen

Übersicht Im ersten Teil dieser Arbeit wird der optimale Entwurf sphärischer Kuppeln behandelt, wobei die von Misessche Fließbewegung zugrunde gelegt wird. Fünf verschiedene Lastkombinationen werden untersucht. Der zweite Teil befaßt sich mit der optimalen quadratischen Form des Meridians von Kuppeln, die der Fließbedingung von Tresca folgen.

---

List of Symbols a_k, b_k, c_k, A_k, B_k, C_k coefficients used in series solutions - A, B constants in the nondimensional equation of the meridional curve - normal component of the load per unit area of the middle surface - meridional and circumferential forces per unit width - radial pressure per unit area of the middle surface, - skin weight per unit area of the middle surface, - vertical external load per unit horizontal area, - base radius, - R radius of convergence - s - cupola thickness, - u, w subsidiary functions for quadratic cupolas - vertical component of the load per unit area of middle surface - resultant vertical force on a cupola segment - structural weight of cupola, - combined weight of cupola and skin, - distance from the axis of rotation, - vertical distance from the shell apex, - z auxiliary variable in series solutions - specific weight of structural material of cupola - radius of the middle surface, - uniaxial yield stress - meridional stress, - circumferential stress, - _a, _b, _c, _d, _e subsidiary variables used in evaluating the meridional stress - auxiliary function used in series solutions This paper constitutes the third part of a study of shell optimization which was initiated and planned by the late Prof. W. Prager     

Saturated boolean algebras and their stone spaces

For an infinite cardinal κ, we call a compact zero-dimensional space a κ-Parovicenko space if its boolean algebra of clopen sets is κ-saturated and has cardinality κ^<κ. We answer some questions about these spaces which were posed in [14]. For instance, it is shown that a κ⁺-Parovicenko spacé can be a Stone-Cech remainder in a natural way. We show that some of the results in [14] which used the assumption κ^<κ=κ, do indeed require this assumption. We also show that if 2^κ=κ⁺ then each compact F_κ⁺-space with weight κ⁺ can be embedded into a κ⁺-Parovicenko space (and so into an extremally disconnected space).