Transfer Function Approximations for Large Highly Coupled Elastic Boosters with Fuel Slosh

Transfer function approximations for large highly coupled flexible body launch vehicles with liquid fuel slos

Weak refinement in Z

An important aspect in the specification of distributed systems is the role of the internal (or unobservable) operation. Such operations are not part of the user interface (i.e. the user cannot invoke them), however, they are essential to our understanding and correct modelling of the system. Various conventions have been employed to model internal operations when specifying distributed systems in Z. If internal operations are distinguished in the specification notation, then refinement needs to deal with internal operations in appropriate ways. However, in the presence of internal operations, standard Z refinement leads to undesirable implementations. In this paper we present a generalization of Z refinement, called weak refinement, which treats internal operations differently from observable operations when refining a system. We illustrate some of the properties of weak refinement through a specification of a telecommunications protocol

Formal Specification and Testing of a Management Architecture

The importance of network and distributed systems management to supply and maintain services required by users has led to a demand for management facilities. Open network management is assisted by representing the system resources to be managed as objects, and providing standard services and protocols for interrogating and manipulating these objects. This paper examines the application of formal description techniques to the specification of managed objects by presenting a case study in the specification and testing of a management architecture. We describe a formal specification of a management architecture suitable for scheduling and distributing services across nodes in a distributed system. In addition, we show how formal specifications can be used to generate conformance tests for the management architecture

Testing refinements by refining tests

One of the potential benefits of formal methods is that they offer the possibility of reducing the costs of testing. A specification acts as both the benchmark against which any implementation is tested, and also as the means by which tests are generated. There has therefore been interest in developing test generation techniques from formal specifications, and a number of different methods have been derived for state based languages such as Z, B and VDM. However, in addition to deriving tests from a formal specification, we might wish to refine the specification further before its implementation. The purpose of this paper is to explore the relationship between testing and refinement. As our model for test generation we use a DNF partition analysis for operations written in Z, which produces a number of disjoint test cases for each operation. In this paper we discuss how the partition analysis of an operation alters upon refinement, and we develop techniques that allow us to refine abstract tests in order to generate test cases for a refinement. To do so we use (and extend existing) methods for calculating the weakest data refinement of a specification

Atropselective syntheses of (-) and (+) rugulotrosin A utilizing point-to-axial chirality transfer

Chiral, dimeric natural products containing complex structures and interesting biological properties have inspired chemists and biologists for decades. A seven-step total synthesis of the axially chiral, dimeric tetrahydroxanthone natural product rugulotrosin A is described. The synthesis employs a one-pot Suzuki coupling/dimerization to generate the requisite 2,2'-biaryl linkage. Highly selective point-to-axial chirality transfer was achieved using palladium catalysis with achiral phosphine ligands. Single X-ray crystal diffraction data were obtained to confirm both the atropisomeric configuration and absolute stereochemistry of rugulotrosin A. Computational studies are described to rationalize the atropselectivity observed in the key dimerization step. Comparison of the crude fungal extract with synthetic rugulotrosin A and its atropisomer verified that nature generates a single atropisomer of the natural product.P50 GM067041 - NIGMS NIH HHS; R01 GM099920 - NIGMS NIH HHS; GM-067041 - NIGMS NIH HHS; GM-099920 - NIGMS NIH HH

Effects of negatively charged shift reagents on red blood cell morphology, lithium ion transport, and membrane potential

Lanthanide shift reagents have been used extensively in multinuclear magnetic resonance (NMR) applications in order to obtain information regarding ion distribution and transport in cellular systems. The aqueous reagents used in this study were Dy(PPP)J-, Tm( PPP)J-, Dy(TTHA)’-, Dy(PcPcP);-, and Dy(DOTP)’-, where Dy3+ and Tm3+ represent dysprosium and thulium ions and PPPs-, TTHA6-, PcPcPs-, and DOTP*- denote the triphosphate, triethylenetetraminehexaacetate, bis(dihydroxyphosphiny1- methyl)phosphinate, and I ,4,7,1 O-tetrazacyclododecane-N,N’,N”,N”’-tetrakis(methanephosphonate) ligands, respectively. The apparent size and shape of Li+-free RBCs (red blood cells), studied by both scanning electron microscopy and Coulter counter methods, were unchanged by the presence of the above shift reagents at concentrations lower than 10 mM. However, Li+ incubation changed both the shape and size of RBCs. The rates of Na+-Li+ exchange in Li+-loaded RBCs measured by 7Li NMR spectroscopy in the presence of Dy(PPP);-, TI~(PPP),~o-r, D~(PcPcP),~w-e re significantly higher than the rates measured in the absence of shift reagents by atomic absorption or in the presence of DY(TTHA)~o-r DY(DOTP)~b-y 7Li NMR spectroscopy. 31P and I9F NMR measurements of the membrane potential of Li+-free RBCs revealed that the shift reagents studied (except for Dy(TTHA)”) do change the membrane potential, with the most negatively charged reagents having the largest effect. Thus, shift reagents must be used with caution in physiological NMR studies and in particular RBC applications

A democratic dictator's success: how Chad's President Deby defeated the military opposition in three years (2008–2011)

This is an Accepted Manuscript of an article published by Taylor & Francis in The Journal of Contemporary African Studies on 26 Sep 2013, available online: http://www.tandfonline.com/10.1080/02589001.2013.840974.This article focuses on how President Deby re-gained power after a nearly successful coup d'état against him in February 2008. The analysis points towards one major external reason for success and a divided internal strategy. The international community's little interest in Chad and the desire for political stability among the few interested states are the main external reasons for Deby's success. Internally, Deby's use of violence and co-optation explain his success. Deby defeated the Chadian military opposition by combining co-optation of adversaries in Chad's patrimonial marketplace