The AI Bus architecture for distributed knowledge-based systems

The AI Bus architecture is layered, distributed object oriented framework developed to support the requirements of advanced technology programs for an order of magnitude improvement in software costs. The consequent need for highly autonomous computer systems, adaptable to new technology advances over a long lifespan, led to the design of an open architecture and toolbox for building large scale, robust, production quality systems. The AI Bus accommodates a mix of knowledge based and conventional components, running on heterogeneous, distributed real world and testbed environment. The concepts and design is described of the AI Bus architecture and its current implementation status as a Unix C++ library or reusable objects. Each high level semiautonomous agent process consists of a number of knowledge sources together with interagent communication mechanisms based on shared blackboards and message passing acquaintances. Standard interfaces and protocols are followed for combining and validating subsystems. Dynamic probes or demons provide an event driven means for providing active objects with shared access to resources, and each other, while not violating their security

The Effect Of Vasoactive Intestinal Peptide On Pulsatile Lutenizing Hormone Release In The Ovariectomized Rat

Vasoactive intestinal peptide (VIP) affects the secretion of several pituitary hormones including LH.;The initial objective was to study in greater detail the action of VIP on pulsatile LH secretion.;Ovariectomized rats were used in this study and peptide solutions were infused into the third cerebral ventricle. Venous blood was sampled every 5 min and assayed for LH.;VIP (3.5 nmole/h) lowered the mean LH levels and the pulse frequency but had no effect on pulse amplitude.;To determine whether VIP acts within the brain or at the pituitary GnRH was injected intravenously after infusion of either VIP or saline. The amplitude of the GnRH-induced LH peak was measured. VIP did not alter the sensitivity of the pituitary to GnRH; therefore VIP exerts its action within the brain.;The possibility that an endogenous VIPergic pathway may be important for influencing the action of exogenously administered VIP was examined. It was hypothesized that the destruction of VIP cell bodies in the suprachiasmatic (SCN) or the parventricular (PVN) nuclei of the hypothalamus may result in a supersensitivity to VIP. The destruction of the SCN caused animals to respond to a normally-ineffective dose of VIP (0.4 nmole/h). The destruction of the PVN did not result in an increased sensitivity to a low dose of VIP, instead it blocked the action of VIP (3.5 nmole/h). The data of both lesion experiments were interpreted to mean that a known target area of the SCN VIPergic neurons; specifically the PVN is required for the action of VIP.;Treatment of animals with either a dopamine receptor antagonist, or an opiate receptor antagonist did not block the action of VIP; therefore VIP does not exert its action via dopaminergic or opiatergic systems.;The specificity of the action of VIP was explored by examining the action of the structurally-related peptide, secretin. Secretin (3.5 nmole/h) also lowered mean LH levels and pulse frequency but VIP was slightly more potent than secretin.;VIP inhibits LH secretion by acting within the brain at the PVN

Emotional armor

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Gravity shear waves atop the cirrus layer of intense convective storms

Recent visual satellite photographs of certain intense convective storms have revealed concentric wave patterns. A model for the generation and growth of these waves is proposed. The proposed initial generating mechanism is similar to the effect noticed when a pebble is dropped into a calm pond. The penetration of the tropopause by overshooting convection is analogous to the pebble's penetration of the water's surface. The model for wave growth involves instability due to the wind shear resulting from the cirrus outflow. This model is based on an equation for the waves' phase speed which is similar to the Helmholtz equation. It, however, does not assume an incompressible atmosphere, but rather assumes density is a logarithmic function of height. Finally, the model is evaluated on the two mid-latitude and three tropical cases. The data indicate that shearing instability may be a significant factor in the appearance of these waves

The market for equity release products: Lessons from the international experience

Home Equity Release Products (ERPs) are innovative fi nancialinstruments that enable elderly, retired people to use theirunencumbered houses as a source of income/funding whilethey continue to reside in them, thereby seeking to address theconstraints of the life cycle hypothesis. The loan and outstandingamounts are normally settled through the sale of the property, eitheron death or when the client voluntarily vacates. This research is anexploration of demand and supply issues that aff ect the suppliersof ERPs (both internationally and in South Africa). Interviews wereheld with established suppliers in Britain (where the market is moreadvanced), as well as with several fi nancial services companies inSouth Africa.The ERP industry has grown slowly over the last decade. Factors suchas increased life expectancy, decreased savings rates and changingattitudes towards debt are just some of the driving forces of demand.However, the growth of the ERP industry has consistently fallen shortof analysts’ predictions, highlighting some of the diffi culties facingthe market – not least of which is to gain the acceptance of both themarket and government as a mainstream option for the elderly, whoare often asset-rich but income-poor. A number of impediments tomarket growth are explored in detail in this research

EAGLE ISS - A modular twin-channel integral-field near-IR spectrograph

The ISS (Integral-field Spectrograph System) has been designed as part of the EAGLE Phase A Instrument Study for the E-ELT. It consists of two input channels of 1.65x1.65 arcsec field-of-view, each reconfigured spatially by an image-slicing integral-field unit to feed a single near-IR spectrograph using cryogenic volume-phase-holographic (VPH) gratings to disperse the image spectrally. A 4k x 4k array detector array records the dispersed images. The optical design employs anamorphic magnification, image slicing, VPH gratings scanned with a novel cryo-mechanism and a three-lens camera. The mechanical implementation features IFU optics in Zerodur, a modular bench structure and a number of high-precision cryo-mechanisms.Comment: 12 pages, to be published in Proc SPIE 7735: Ground-based & Airborne Instrumentation for Astronomy II

A Deep Multicolor Survey V: The M Dwarf Luminosity Function

We present a study of M dwarfs discovered in a large area, multicolor survey. We employ a combination of morphological and color criteria to select M dwarfs to a limiting magnitude in V of 22, the deepest such ground-based survey for M dwarfs to date. We solve for the vertical disk stellar density law and use the resulting parameters to derive the M dwarf luminosity and mass functions from this sample. We find the stellar luminosity function peaks at M_V = 12 and declines thereafter. Our derived mass function for stars with M < 0.6 M_sun is inconsistent with a Salpeter function at the 3 sigma level; instead, we find the mass function is relatively flat for 0.6 M_sun > M > 0.1 M_sun.Comment: Accepted for publication in AJ. 19 pages including 4 embedded postscript figures (AASTEX

Internal rotation of subdwarf B stars: limiting cases and asteroseismological consequences

Observations of the rotation rates of horizontal branch (HB) stars show puzzling systematics. In particular, cooler HB stars often show rapid rotation (with velocities in excess of 10 km/s), while hotter HB stars typically show much smaller rotation velocities. Simple models of angular momentum evolution of stars from the main sequence through the red giant branch fail to explain these effects. In general, evolutionary models in all cases preserve a rapidly rotating core. The observed angular velocities of HB stars require that some of the angular momentum stored in the core reaches the surface. To test the idea that HB stars contain such a core, one can appeal to detailed computations of trace element abundences and rotational mixing. However, a more direct probe is available to test these limiting cases of angular momentum evolution. Some of the hottest horizontal branch stars are members of the pulsating sdB class. They frequently show rich pulsation spectra characteristic of nonradially pulsating stars. Thus their pulsations probe the internal rotation of these stars, and should show the effects of rapid rotation in their cores. Using models of sdB stars that include angular momentum evolution, we explore this possibility and show that some of the sdB pulsators may indeed have rapidly rotating cores.Comment: accepted for publication in The Astrophysical Journa