Comment on "From the summation-by-parts algorithm to Pi"

Comments on the paper by Mosig (IEEE Antennas and Propagation Magazine, vol.47, p.38-40, 2005 December). The paper by Mosig discussed acceleration of convergence of series. Without commenting on either the validity or efficiency of his method, the present author would like to draw attention to an existing method, published long ago by D. Shanks (1955). Briefly stated, this method takes a sequence and defines partial sums, which is described in this paper.     

Local structural characterization of Zn:Cd:Se ternary semiconductors

We have studied the local atomic structure around Zn and Cd, in CdSe, ZnSe, and ordered and disordered Zn_0.5Cd_0.5Se thin films, grown by molecular beam epitaxy (MBE) and atomic layer epitaxy (ALE) using X-ray absorption spectroscopy (XAS). Zn K-shell X-ray absorption fine structure (XAFS) shows that the Zn–Se pair nearest neighbor distance is the same in both ordered and disordered ternary samples. This result shows that the ordered (or disordered growth) does not have a significant effect in the nearest neighbor Zn environment. However, results from K-shell Cd XAFS show that the Cd–Se pair nearest neighbor distance in the Zn_0.5Cd_0.5Se ordered film exhibits a contraction compared to the same pair distance in the disordered Zn_0.5Cd_0.5Se sample and the binary CdSe compound. This suggests that the shortest Zn–Se nearest neighbor distance regulates the Cd–Se nearest neighbor distance in the ternary compounds, when these are grown in an ordered, layer by layer, fashion.     

Switching and PI control of walking motions of planar biped walkers

A companion paper has addressed the problem of designing controllers that induce exponentially stable, periodic walking motions at a fixed walking rate for a planar, biped robot with one degree of underactuation. This note provides two additional control features: 1) the ability to compose such controllers to obtain walking at several discrete walking rates with guaranteed stability during the transitions; and 2) the ability to regulate the average walking rate to a continuum of values.     

Practical implementation of possibilistic probability mass functions

 Probability assessments of events are often linguistic in nature. We model them by means of possibilistic probabilities (a version of Zadeh's fuzzy probabilities with a behavioural interpretation) with a suitable shape for practical implementation (on a computer). Employing the tools of interval analysis and the theory of imprecise probabilities we argue that the verification of coherence for these possibilistic probabilities, the corrections of non-coherent to coherent possibilistic probabilities and their extension to other events and gambles can be performed by finite and exact algorithms. The model can furthermore be transformed into an imprecise first-order model, useful for decision making and statistical inference.     

Synchronized world embedding in virtual environments

We introduce a novel distributed approach that lets users copy a given CVE section and keep it consistent with all its other copies and its original CVE area. Although 3D world modeling tools such as Alias' Maya and Discreet's 3DS Max already use object embedding, our method is the first to introduce it in a functioning CVE system. We also expand the traditional object-embedding concept by introducing a mutual synchronization function between the source and destination worlds. The mutual synchronization scheme propagates events $such as changes in an object's color, shape, or position - to other copies of a world. This synchronized world embedding thus offers a new way to expand worlds. Our method is built on existing CVE functionality, which lets us deploy it without significantly interfering with existing CVE designs. We've also altered the method so that it's usable when consistency needs are more relaxed.     

A reconfigurable high-frequency phase-locked loop

Reconfigurable phase-locked loops (PLLs) present the advantage of fast-frequency acquisition combined with narrow-noise bandwidth, since their parameters can be dynamically adjusted. High-frequency PLLs are generally implemented by means of analog circuits which are not easily reconfigured during operation. However, the five-port technique allows the discrimination of the phase difference between two microwave signals using a mixed circuit. In this paper the design of a PLL comprising a five-port based phase detector is presented. This system benefits from the phase-detector digital circuit to carry out the loop filtering. Simulation results for different conditions of noise and frequency acquisition are shown. We also present measurement results to confirm the simulations.     

Can porous polymeric scaffolds be functionalized by stem cells leading to osteogenic differentiation? A systematic review of in vitro studies

The aim of this study was to analyze the influence of nanoporous structure of polymeric biomaterials on the in vitro osteogenic induction of human stem cells. An electronic search in three databases (MEDLINE, SCOPUS, and Web of Science) was performed for articles that were published before May 2018. In vitro studies were included if they met the following criteria: (1) the use of polymeric scaffolds (natural or synthetic); (2) the co-culture of human stem cells with the scaffold; and (3) cell viability, proliferation, and osteogenic differentiation assays. The main characteristics of the published studies were summarized, and a quality assessment tool was used to analyze methodological features. Eighty-eight potential articles were firstly retrieved. Thirteen were eligible for qualitative analysis. Only three studies characterized cell stemness. Nanostructure of the scaffolds showed a significant influence on viability, proliferation, and osteogenic differentiation of human stem cells. Combination of porosity between 72 and 93% and a large range diameter between 50 and 224 μm resulted in more remarkable cellular proliferation and differentiation. Porous polymeric scaffolds can be functionalized by stem cells leading to osteogenic induction. High standards of laboratory practice and accurate methodological reporting are essential for the credibility of the results.     

List partitions

By definition, apartition of a list is a division of that list into nonempty contiguous segments. Many programming and operations research problems can be specified in terms of list partitions, and we present a hierarchy of theorems for deriving programs from such specifications. Throughout, reasoning is conducted in an equational style using the calculus for program synthesis developed by Bird and Meertens.Supported by a BP research studentship.