Bent Bruun Kristensen

Chronic Thromboembolic Pulmonary Hypertension (CTEPH) Results From an International Prospective Registry

Background— Chronic thromboembolic pulmonary hypertension (CTEPH) is often a sequel of venous thromboembolism with fatal natural history; however, many cases can be cured by pulmonary endarterectomy. The clinical characteristics and current management of patients enrolled in an international CTEPH registry was investigated. Methods and Results— The international registry included 679 newly diagnosed (≤6 months) consecutive patients with CTEPH, from February 2007 until January 2009. Diagnosis was confirmed by right heart catheterization, ventilation-perfusion lung scintigraphy, computerized tomography, and/or pulmonary angiography. At diagnosis, a median of 14.1 months had passed since first symptoms; 427 patients (62.9%) were considered operable, 247 (36.4%) nonoperable, and 5 (0.7%) had no operability data; 386 patients (56.8%, ranging from 12.0%– 60.9% across countries) underwent surgery. Operable patients did not differ from nonoperable patients relative to symptoms, New York Heart Association class, and hemodynamics. A history of acute pulmonary embolism was reported for 74.8% of patients (77.5% operable, 70.0% nonoperable). Associated conditions included thrombophilic disorder in 31.9% (37.1% operable, 23.5% nonoperable) and splenectomy in 3.4% of patients (1.9% operable, 5.7% nonoperable). At the time of CTEPH diagnosis, 37.7% of patients initiated at least 1 pulmonary arterial hypertension–targeted therapy (28.3% operable, 53.8% nonoperable). Pulmonary endarterectomy was performed with a 4.7% documented mortality rate. Conclusions— Despite similarities in clinical presentation, operable and nonoperable CTEPH patients may have distinct associated medical conditions. Operability rates vary considerably across countries, and a substantial number of patients (operable and nonoperable) receive off-label pulmonary arterial hypertension–targeted treatments. # Clinical Perspective {#article-title-40}Background— Chronic thromboembolic pulmonary hypertension (CTEPH) is often a sequel of venous thromboembolism with fatal natural history; however, many cases can be cured by pulmonary endarterectomy. The clinical characteristics and current management of patients enrolled in an international CTEPH registry was investigated. Methods and Results— The international registry included 679 newly diagnosed (⩽6 months) consecutive patients with CTEPH, from February 2007 until January 2009. Diagnosis was confirmed by right heart catheterization, ventilation-perfusion lung scintigraphy, computerized tomography, and/or pulmonary angiography. At diagnosis, a median of 14.1 months had passed since first symptoms; 427 patients (62.9%) were considered operable, 247 (36.4%) nonoperable, and 5 (0.7%) had no operability data; 386 patients (56.8%, ranging from 12.0%– 60.9% across countries) underwent surgery. Operable patients did not differ from nonoperable patients relative to symptoms, New York Heart Association class, and hemodynamics. A history of acute pulmonary embolism was reported for 74.8% of patients (77.5% operable, 70.0% nonoperable). Associated conditions included thrombophilic disorder in 31.9% (37.1% operable, 23.5% nonoperable) and splenectomy in 3.4% of patients (1.9% operable, 5.7% nonoperable). At the time of CTEPH diagnosis, 37.7% of patients initiated at least 1 pulmonary arterial hypertension–targeted therapy (28.3% operable, 53.8% nonoperable). Pulmonary endarterectomy was performed with a 4.7% documented mortality rate. Conclusions— Despite similarities in clinical presentation, operable and nonoperable CTEPH patients may have distinct associated medical conditions. Operability rates vary considerably across countries, and a substantial number of patients (operable and nonoperable) receive off-label pulmonary arterial hypertension–targeted treatments.

Object-Oriented Modeling with Roles

Objects relate to each other in different ways — serving, using, and communicating with each other. From the way in which they treat one another, objects have different perspectives of each other. These perspectives define the role that an object may play towards another. The perspectives are formed as a restricted set of methods of the object, — exactly the methods that are relevant for the relations between the objects. Different roles exist for different purposes, and the roles played by an object may change over time. The role is a powerful modeling concept in object-oriented analysis, design, and programming. A graphical notation is defined to support static and dynamic description of roles. The notation supports generalization and part-whole hierarchies for roles, the extension of methods and active objects with roles, and the integration of roles and locality.

Abstraction mechanisms in the BETA programming language

The BETA programming language is developed as part of the BETAproject. The purpose of this project is to develop concepts,constructs and tools in the field of programming and programminglanguages. BETA has been developed from 1975 on and the variousstages of the language are documented in [BETA a]. The application area of BETA is programming of embedded as wellas distributed computing systems. For this reason a major goal hasbeen to develop constructs that may be efficiently implemented.Furthermore the BETA language is intended to have a few number ofbasic but general constructs. It is then necessary that theabstraction mechanisms are powerful in order to define morespecialized constructs. BETA is an object oriented language like SIMULA 67([SIMULA]) and SMALLTALK ([SMALLTALK]). By this is meant that aconstruct like the SIMULA class/subclass mechanism is fundamentalin BETA. In contrast to SMALLTALK, BETA is a language in the ALGOL60 ([ALGOL]) family. SIMULA 67 is a system description and a programming language.The DELTA language ([DELTA]) is a system description language only,allowing description of full concurrency, continuous change andcomponent interaction, developed from a SIMULA conceptual platform.BETA started from the system concepts of DELTA, but is aprogramming language, drawing upon a large number of contributionsto programming research in the 1970s. A basic idea in BETA is tobuild the language upon one, general abstraction mechanism --- thepattern ([BETA a 77]) --- covering both data, procedural andcontrol abstractions, substituting constructs like class,procedure, function and type. Correspondingly objects, procedure activation records andvariables are all regarded as special cases of the basic buildingblock of program executions: the entity. A pattern thusdescribes a category of entities with identical structure.An entity consists of a set of attributes and anaction-part. An attribute may be a data-item or apattern. The action-part is a sequence of imperatives that may beexecuted. A data-item may be an entity or a reference to an entity.A pattern may be used in a procedure like manner in the sense thatan entity (procedure activation record) described by the patternmay be generated and executed as a part of the action sequence ofanother entity. A pattern may be used to generate entities thatexecute their action-part in concurrency with other entities. Suchentities may also execute their actions interleaved in a coroutinelike manner. Entities may be organized hierarcically by means of ageneralization of the SIMULA subclass mechanism. This givespossibilities for grouping common properties of entities ofdifferent patterns. In SIMULA 67 a class may have virtual attributes(procedures, labels, and switches). This is a powerful parametermechanism that gives the possibility to delay the specification ofan attribute to a subclass specification. However, SIMULA 67 lacksthe possibility to have virtual class attributes. Furthermore it isnecessary to have a runtime check on the parameters of virtualprocedures, since it is not possible to specify the parameter listof a virtual procedure. The virtual patterns of BETA is ageneralization of the virtual concept in SIMULA 67. In this paper the sequential part of BETA will be presented. Themain purpose is to demonstrate the use of the pattern/subpatternmechanism with virtual patterns as a powerful abstractionmechanism. In addition, a further generalization of the virtualconcept based on syntactic categories will be described. Work has been initiated to design and implement an integratedprogramming system for BETA. The approach to separatecompilation of BETA modules is described in [BETA c]. This paper is organised as follows: Section 2 describesentities, patterns and imperatives. Section 3 describes thesubpattern mechanism. Virtual patterns are described in section 4.Section 5 describes the generalization of the virtual concept. Insection 6 the remaining elements of BETA not mentioned in theprevious sections are described. Finally the syntax of BETA isgiven in the appendix. Each section with a brief introduction ofthe relevant language elements whereafter a number of examples aregiven. Most of the examples are extended versions of HoaresSmallIntSet [Hoare 72]. There is a distinction between the base language (calledbasic BETA) and standard BETA. Standard BETA is basicBETA extended with a number of commonly used constructs. Theseadditional constructs may all be regarded as patterns in basicBETA, but will often be given a special syntax. This paper willmainly focus on basic BETA. Occasionally we shall use parts of astandard BETA, but this will be stated at the appropiate place.

Methods for Computing LALR( k ) Lookahead

Methods for constructing LALR(k) parsers are discussed. Algorithms for computing LALR(k) lookahead are presented together with the necessary theory to prove their correctness. First, a special algorithm for the LALR(1) case is presented. Second, a general LALR(k) algorithm with k-1 is presented. Given an item and a state, the algorithms compute their corresponding LALR lookahead during a recursive traversal of the LR(0) machine. Finally, the LALR(k) algorithm is generalized to compute LALR(k) lookahead for all items and states visited during the recursive traversal performed by the first two algorithms.

Complex associations: abstractions in object-oriented modeling

Objects model phenomena and a phenomenon is usually a component. Information characterizing a component is encapsulated and accessible only by its methods. The relations between components are modeled explicitly by means of associations or references. A relation is also a phenomenon and objects can model this type of phenomena too. Components are usually related conceptually in diverse and subtle ways: Some relations are implicitly given and some are local to other more basic relations. Such kinds of relations are important for understanding the organization and cooperation of objects and may be supported in object-oriented analysis, design, and programming: An implicit association describes a relation between an object and objects local to this enclosing object, and a complex association describes an explicit relation between local objects in different enclosing objects. Such associations are described by classes and the objects have the usual properties including methods and attributes.

Activities: Abstractions for Collective Behavior

Conventional object-oriented modeling lacks support for representing the interaction between objects in a conceptually intuitive way — often dispersing the logic/control of interplay throughout the objects. We introduce the concept of an activity as an abstraction mechanism to model the interplay between objects.

Conceptual modeling and programming languages

Modeling

Absolute, State-selective Measurements of the Photoionization Cross Sections of N+ and O+ Ions

The absolute single-photoionization cross sections of singly charged nitrogen and oxygen ions have been measured from 29-80 eV and 30-150 eV, respectively, by merging a synchrotron-radiation beam from an undulator with a 2 keV ion beam. In the case of O+, separate data sets were obtained for the 4S ground state and the 2D/2P metastable states by attenuating the target-ion beam with N2 gas, exploiting the fact that cross sections for charge exchange between O+ ions, in the 4S or in the 2D/2P states, and N2 are different. The spectral structures were very different for the ground and the metastable states, whereas the cross sections for photoionization into the continua were nearly identical. The agreement between the experimental data and data calculated using the model function by Verner et al. or obtained from R-matrix calculations performed within the Opacity and the Iron projects is rather good. Finally, double photoionization (direct) was observed for O+ ions, with an approximately linear onset at 90 eV and a maximum cross section of 0.04 Mb.

The when, why and why not of the BETA programming language

This paper tells the story of the development of BETA: a programming language with just one abstraction mechanism, instead of one abstraction mechanism for each kind of program element (classes, types, procedures, functions, etc.). The paper explains how this single abstraction mechanism, the pattern, came about and how it was designed to be so powerful that it covered the other mechanisms. In addition to describing the technical challenge of capturing all programming elements with just one abstraction mechanism, the paper also explains how the language was based upon a modeling approach, so that it could be used for analysis, design and implementation. It also illustrates how this modeling approach guided and settled the design of specific language concepts. The paper compares the BETA programming language with other languages and explains how such a minimal language can still support modeling, even though it does not have some of the language mechanisms found in other object-oriented languages. Finally, the paper tries to convey the organization, working conditions and social life around the BETA project, which turned out to be a lifelong activity for Kristen Nygaard, the authors of this paper, and many others.

LR-parsing of extended context free grammars

SummaryTo improve the readability of a grammar it is common to use extended context free grammars (ECFGs) which are context free grammars (CFGs) extended with the repetition operator (*), the alternation operator (¦) and parentheses to express the right hand sides of the productions. The topic treated here is LR-parsing of ECFGs. The LR(k) concept is generalized to ECFGs, a set of LR-preserving transformations from ECFGs to CFGs is given and finally it is shown how to construct LR-parsers directly from ECFGs.