Scattering from interface islands: enhanced lifetimes through non-linear effect of cation defects

We present quantitative calculations of scattering lifetimes associated with isovalent anion and cation defects in GaSb/InAs detector heterostructures, and identify the dependence upon the proximity of the defects to the heterointerfaces. The carrier lifetimes arising through scattering from interface islands of anion defects are shown to depend non-linearly upon the presence of additional cation defects. These weakly scattering cation defects are shown to control the larger scattering from the anion islands, enabling lifetimes to be enhanced by more than an order of magnitude through the inclusion of additional lattice imperfections.     

海宁市旅游资源特征及大桥后时代旅游业再定位

海宁市旅游资源丰富,钱江潮、鱼鳞石塘、海神庙、皮革等具有很高的知名度,但是开发深度不足,旅游形象模糊.海宁市位于浙江省杭州湾产业带核心地带,随着钱江十桥等跨海大桥的建设,海宁市的区位将进一步优化,但在今后相当长时段内,旅游业的竞争将日益加剧,海宁市旅游业的结构升级亟待解决.在充分调研的基础上,认为海宁市旅游资源要统筹规划,高标准开发,确立了海宁市作为浙北旅游增长极的地位,进行了旅游形象重新设计,并提出若干开发思路.     

Two-boundary lattice paths and parking functions

We describe an involution on a set of sequences associated with lattice paths with north or east steps constrained to lie between two arbitrary boundaries. This involution yields recursions (from which determinantal formulas can be derived) for the number and area enumerator of such paths. An analogous involution can be defined for parking functions with arbitrary lower and upper bounds. From this involution, we obtained determinantal formulas for the number and sum enumerator of such parking functions. For parking functions, there is an alternate combinatorial inclusion–exclusion approach. The recursions also yield Appell relations. In certain special cases, these Appell relations can be converted into rational or algebraic generating functions.     

The experimental study of exotic nuclear states using multi-detector arrays

This contribution outlines the work of the CHARISSA collaboration in the investigation of exotic states in nuclei. It outlines the background to the work, the techniques involved and discusses in detail an experiment to study the cluster structure of ¹²Be.     

A step toward CNO solar neutrino detection in liquid scintillators

The detection of CNO solar neutrinos in ultrapure liquid scintillator detectors is limited by the background produced by bismuth-210 nuclei that undergo β-decay to polonium-210 with a lifetime of ∼7 days. Polonium-210 nuclei are unstable and decay with a lifetime equal to ∼200 days emitting α particles that can be also detected. In this Letter, we show that the Bi-210 background can be determined by looking at the time evolution of α-decay rate of Po-210, provided that α particle detection efficiency is stable over the data acquisition period and external sources of Po-210 are negligible. A sufficient accuracy can be obtained in a relatively short time. As an example, if the initial Po-210 event rate is ∼2000 cpd/100 ton or lower, a Borexino-like detector could start discerning CNO neutrino signal from Bi-210 background in Δt∼1 yr.     

Re-evaluation of the mechanical loss factor of hydroxide-catalysis bonds and its significance for the next generation of gravitational wave detectors

New measurements of the mechanical loss factors of hydroxide-catalysis bonds have been made and these have been found to be significantly lower than previously reported. We provide the first estimate for the resulting thermal noise limitation for a practical test mass geometry for next generation gravitational wave detectors.     

Simultaneous small‐ and wide‐angle scattering at high X‐ray energies

Combined small‐ and wide‐angle X‐ray scattering (SAXS/WAXS) is a powerful technique for the study of materials at length scales ranging from atomic/molecular sizes (a few angstroms) to the mesoscopic regime (～1 nm to ～1 µm). A set‐up to apply this technique at high X‐ray energies (E > 50 keV) has been developed. Hard X‐rays permit the execution of at least three classes of investigations that are significantly more difficult to perform at standard X‐ray energies (8–20 keV): (i) in situ strain analysis revealing anisotropic strain behaviour both at the atomic (WAXS) as well as at the mesoscopic (SAXS) length scales, (ii) acquisition of WAXS patterns to very large q (>20 Å^?1) thus allowing atomic pair distribution function analysis (SAXS/PDF) of micro‐ and nano‐structured materials, and (iii) utilization of complex sample environments involving thick X‐ray windows and/or samples that can be penetrated only by high‐energy X‐rays. Using the reported set‐up a time resolution of approximately two seconds was demonstrated. It is planned to further improve this time resolution in the near future.     

Comments on generalized Heron polynomials and Robbins’ conjectures

Heron’s formula for a triangle gives a polynomial for the square of its area in terms of the lengths of its three sides. There is a very similar formula, due to Brahmagupta, for the area of a cyclic quadrilateral in terms of the lengths of its four sides. (A polygon is cyclic if its vertices lie on a circle.) In both cases if A is the area of the polygon, (4A)² is a polynomial function of the square in the lengths of its edges. David Robbins in [D.P. Robbins, Areas of polygons inscribed in a circle, Discrete Comput. Geom. 12 (2) (1994) 223-236. MR 95g:51027; David P. Robbins, Areas of polygons inscribed in a circle, Amer. Math. Monthly 102 (6) (1995) 523-530. MR 96k:51024] showed that for any cyclic polygon with n edges, (4A)² satisfies a polynomial whose coefficients are themselves polynomials in the edge lengths, and he calculated this polynomial for n=5 and n=6. He conjectured the degree of this polynomial for all n, and recently Igor Pak and Maksym Fedorchuk [Maksym Fedorchuk, Igor Pak, Rigidity and polynomial invariants of convex polytopes, Duke Math. J. 129 (2) (2005) 371-404. MR 2006f:52015] have shown that this conjecture of Robbins is true. Robbins also conjectured that his polynomial is monic, and that was shown in [V.V. Varfolomeev, Inscribed polygons and Heron polynomials (Russian. Russian summary), Mat. Sb. 194 (3) (2003) 3-24. MR 2004d:51014]. A short independent proof will be shown here.     

The boundary and the shape of binary images

In this paper we will consider an unknown binary image, of which the length of the boundary and the area of the image are given. These two values together contain some information about the general shape of the image. We will study two properties of the shape in particular. First, we will prove sharp lower bounds for the size of the largest connected component. Second, we will derive some results about the size of the largest ball containing only ones, both in the case that the connected components are all simply connected and in the general case.