23,593 research outputs found
The C Object System: Using C as a High-Level Object-Oriented Language
The C Object System (Cos) is a small C library which implements high-level
concepts available in Clos, Objc and other object-oriented programming
languages: uniform object model (class, meta-class and property-metaclass),
generic functions, multi-methods, delegation, properties, exceptions, contracts
and closures. Cos relies on the programmable capabilities of the C programming
language to extend its syntax and to implement the aforementioned concepts as
first-class objects. Cos aims at satisfying several general principles like
simplicity, extensibility, reusability, efficiency and portability which are
rarely met in a single programming language. Its design is tuned to provide
efficient and portable implementation of message multi-dispatch and message
multi-forwarding which are the heart of code extensibility and reusability.
With COS features in hand, software should become as flexible and extensible as
with scripting languages and as efficient and portable as expected with C
programming. Likewise, Cos concepts should significantly simplify adaptive and
aspect-oriented programming as well as distributed and service-oriented
computingComment: 18
Experiences modelling and using object-oriented telecommunication service frameworks in SDL
This paper describes experiences in using SDL and its associated tools to create telecommunication services by producing and specialising object-oriented frameworks. The chosen approach recognises the need for the rapid creation of validated telecommunication services. It introduces two stages to service creation. Firstly a software expert produces a service framework, and secondly a telecommunications ‘business consultant' specialises the framework by means of graphical tools to rapidly produce services. Here the focus is given to the underlying technology required. In particular, the advantages and disadvantages of SDL and tools for this purpose are highlighted
Studies on Resistance to Vegetative (Vip3A) and Crystal (Cry1A) Insecticidal Toxins of Bacillus thuringiensis in Heliothis virescens (Fabricius)
Bacillus thuringiensis (Bt) toxins expressed in commercial transgenic crop varieties
are all δ-endotoxins (Cry toxins) but the identification of novel vegetative insecticidal
proteins (Vip toxins) has extended the range of insecticidal proteins derived from Bt.
One such Vip toxin, Vip3A, primarily targets the midgut epithelium cells of
susceptible insects as Cry toxins do, although they appear to have different binding
sites. The present study investigated the comparative toxicity of Vip3A, Cry1Ab and
Cry1Ac against Heliothis virescens (tobacco budworm) and the impact of antibiotics
on Bt insecticidal activity. The selection of a resistant Vip3A population led to the
determination of cross-resistance, the genetics of resistance and fitness effects. There
was very little variability in the natural susceptibility to Vip3A, Cry1Ab and Cry1Ac
in the populations tested, although the toxicity of Vip3A was much lower compared to
the Cry1A toxins. A Vip3A resistant population was successfully established within
13 selected generations, with little or no cross-resistance to Cry1Ab or Cry1Ac. The
inheritance of resistance ranged from almost completely recessive to incompletely
dominant with a possible paternal influence, was polygenic and relatively stable.
Vip3A resistance showed a fitness benefit, reduced larval development time, and
fitness costs, including survival to adult eclosion, reduced egg viability and reduced
male mating success. The effects of antibiotics on H. virescens larval susceptibility to
Bt toxins varied depending on antibiotic treatment, the Bt toxin used and the larval
instar tested. Bt cotton expressing both Vip3A and Cry1Ab to provide activity against
a wide range of pest Lepidoptera, including H. virescens, a major cotton pest in the
USA is in the process of commercialisation. The present work will help to support a
suitable insecticide resistance management strategy for continued use of Bt toxin in
transgenic crops
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