464 research outputs found
The Event Calculus Assessed
The range of applicability of the Full Event Calculus is proven to be the Ksp-IA class in the Features and Fluents taxonomy. The proof is given with respect to the original definition of this preference logic, where no adjustments of the language or reasoning method were necessary. The result implies that the claims on the expressiveness and
problem-solving power of this logic were indeed correct
Features and Fluents for Logic Programming: Non-simulative Algebraic Semantics
A Non-simulative Algebraic Semantics is defined and its range of applicability
is proven to be the K-RACi class of the Features and Fluents framework.
The comparative assessment reveals the semantics epistemologically equivalent
and ontologically stronger than the Abductive Logic Programming, the
Action Description Language A and the PMON entailment. The semantics
is shown to be decidable
On the peritidal cycles and their diagenetic evolution in the Lower Jurassic carbonates of the Calcare Massiccio Formation (Central Apennines)
This paper shows the environmental changes and high-frequency cyclicity recorded by Lower Jurassic shallow- water carbonates known as the Calcare Massiccio Formation which crop out in the central Apennines of Italy. Three types of sedimentary cycle bounded by subaerial erosion have been recognized: Type I consists of a shallowing upward cycle with oncoidal floatstones to rudstones passing gradationally up into peloidal packstone alternating with cryptoalgal laminites and often bounded by desiccation cracks and pisolitic-peloidal wackestones indicating a period of
subaerial exposure. Type II shows a symmetrical trend in terms of facies arrangement with peloidal packstones and cryptoalgal laminites present both at the base and in the upper portion of the cycle, separated by oncoidal floatstones to rudstones. Type III displays a shallowing upward trend with an initial erosion surface overlain by oncoidal floatstones to rudstones that, in turn, are capped by pisolitic-peloidal wackestones and desiccation sheet cracks. Sheet cracks at the top of cycles formed during the initial phase of subaerial exposure were successively enlarged by dissolution during prolonged subaerial exposure. The following sea-level fall produced dissolution cavities in subtidal facies, while the
successive sea-level rise resulted in the precipitation of marine cements in dissolution cavities. Spectral analysis revealed six peaks, five of which are consistent with orbital cycles. While a tectonic control cannot be disregarded, the main signal recorded by the sedimentary succession points toward a main control related to orbital forcing. High frequency sea-level fluctuations also controlled diagenetic processes
Modelling causal reasoning
PhDAlthough human causal reasoning is widely acknowledged as an object
of scientific enquiry, there is little consensus on an appropriate measure
of progress. Up-to-date evidence of the standard method of research in
the field shows that this method has been rejected at the birth of modern
science.
We describe an instance of the standard scientific method for modelling
causal reasoning (causal calculators). The method allows for uniform
proofs of three relevant computational properties: correctness of the model
with respect to the intended model, full abstraction of the model (function)
with respect to the equivalence of reasoning scenarios (input), and formal
relations of equivalence and subsumption between models. The method
extends and exploits the systematic paradigm [Handbook of Logic in Artificial
Intelligence and Logic Programming, volume IV, p. 439-498, Oxford 1995] to
fit with our interpretation of it.
Using the described method, we present results for some major models,
with an updated summary spanning seventy-two years of research in the
field
Investigation of the C-Terminal Helix of HIV-1 Matrix: A Region Essential for Multiple Functions in the Viral Life Cycle: A Dissertation
Since the first cases were reported over thirty years ago, great strides have been made to control disease progression in people living with HIV/AIDS. However, current estimates report that there are about 34 million individuals infected with HIV worldwide. Critical in the ongoing fight against this pandemic is the continuing development of highly active anti-retroviral therapies, ideally those with novel mechanisms of action. Currently, there are no medications approved for use that exploit the HIV-1 MA protein, despite its central role in multiple stages of the virus life cycle.
This thesis sought to examine whether a highly conserved glutamate residue at position 99 in the understudied C-terminal helix of MA is required for HIV-1 replication. I characterized a panel of mutant viruses that contain different amino acid substitutions at this position using viral infectivity studies, virus-cell fusion assays, and immunoblotting. In doing so, I found that substitution of this glutamate with either a valine (E99V) or lysine (E99K) residue disrupted Env incorporation into nascent HIV particles, and abrogated their ability to fuse with target-cell membranes. In determining that the strain of HIV could affect the magnitude of E99V-associated defects, I identified a compensatory substitution at MA residue 84 that rescued both E99V- and E99K-associated impairments.
I further characterized the MA E99V and E99K mutations by truncating HIV Env and pseudotyping with heterologous envelope proteins in an attempt to overcome the Env incorporation defect. Unexpectedly, I found that facilitating fusion at the plasma membrane was not sufficient to reverse the severe impairments in virus infectivity. Using quantitative PCR, I determined that an early post-entry step is disrupted in these particles that contain the E99V or E99K MA substitutions. However, allowing entry of mutant virus particles into cells through an endosomal route conferred a partial rescue in infectivity. As the characterization of this post-entry defect was limited by established virological methods, I designed a novel technique to analyze post-fusion events in retroviral infection. Thus, I present preliminary data regarding the development of a novel PCR-based assay that monitors trafficking of the viral reverse transcription complex (RTC) in an infected cell.
The data presented in this thesis indicate that a single residue in MA, E99, has a previously unsuspected and key role in multiple facets of HIV-1 MA function. The pleiotropic defects that arise from specific substitutions of this amino acid implicate a hydrophobic pocket in MA in Env incorporation and an early post-entry function of the protein. These findings suggest that this understudied region of MA could be an important target in the development of a novel antiretroviral therapy
La Capra sarda: 2.: i caratteri riproduttivi e produttivi
In this second paper, the Authors report on the results of a study
concerning the reproductive and productive characters of the Sardinian
goat (Italy); they have surveyed the reproducibility (fecondity, prolificity,
fertility, mortality and survival), the milk production (lactation and daily
yield, lactation lenght, fat and protein content) and meat production (birth
and slaughter weight, daily gain and carcass yield). These results were
obtained with goats from 9 herds of 3 different Sardinian areas
La Capra sarda: 1.: i caratteri morfologici
In this first paper, the Authors illustrate the importance of the goat
breeding in Sardinia (Italy) and report on the results of a study concerning
the morphological characters of the Sardinian goat; they surveyed 19 somatic
measurements, 7 body indexes, the live weight, the udder type and other
secondary characters. These resu1ts were obtained with males and females
aged 3,5 and more, 2,5 and 1,5 years. The goats were from 90 typical herds
of 15 different Sardinian areas; by hierarchical analysis of variance, the
Authors identified 3 sub-populations in the whole Sardinian goat population
La Capra sarda: 3.: le caratteristiche dell'allevamento
In this third paper, the Authors report on the results of a study concerning
the Sardinian goat; they have surveyed the demographic (geographic
distribution, size and composition of herds), technical (management sistems,
reproductive techniques and feeding) and economical (gross scalable production,
net production and nel income) characteristics. These results were
obtained with herds from 3 tipical Sardinian areas (Italy)
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