Master of Science

thesisMany of the operating system kernels we use today are monolithic. They consist of numerous file systems, device drivers, and other subsystems interacting with no isolation and full trust. As a result, a vulnerability or bug in one part of a kernel can compromise an entire machine. Our work is motivated by the following observations: (1) introducing some form of isolation into the kernel can help confine the effects of faulty code, and (2) modern hardware platforms are better suited for a decomposed kernel than platforms of the past. Platforms today consist of numerous cores, large nonuniform memories, and processor interconnects that resemble a miniature distributed system. We argue that kernels and hypervisors must eventually evolve beyond their current symmetric mulitprocessing (SMP) design toward a corresponding distributed design. But the path to this goal is not easy. Building such a kernel from scratch that has the same capabilities as an equivalent monolithic kernel could take years of effort. In this work, we explored the feasibility of incrementally isolating subsystems in the Linux kernel as a path toward a distributed kernel. We developed a design and techniques for moving kernel modules into strongly isolated domains in a way that is transparent to existing code, and we report on the feasibility of our approach

A role for jasmonates in the release of dormancy by cold stratification in wheat

Hydration at low temperatures, commonly referred to as cold stratification, is widely used for releasing dormancy and triggering germination in a wide range of species including wheat. However, the molecular mechanism that underlies its effect on germination has largely remained unknown. Our previous studies showed that methyl-jasmonate, a derivative of jasmonic acid (JA), promotes dormancy release in wheat. In this study, we found that cold-stimulated germination of dormant grains correlated with a transient increase in JA content and expression of JA biosynthesis genes in the dormant embryos after transfer to 20 (o)C. The induction of JA production was dependent on the extent of cold imbibition and precedes germination. Blocking JA biosynthesis with acetylsalicylic acid (ASA) inhibited the cold-stimulated germination in a dose-dependent manner. In addition, we have explored the relationship between JA and abscisic acid (ABA), a well-known dormancy promoter, in cold regulation of dormancy. We found an inverse relationship between JA and ABA content in dormant wheat embryos following stratification. ABA content decreased rapidly in response to stratification, and the decrease was reversed by addition of ASA. Our results indicate that the action of JA on cold-stratified grains is mediated by suppression of two key ABA biosynthesis genes, TaNCED1 and TaNCED2.This project was funded by a CSIRO Office of the Chief Executive PDF scheme

Linking goals to aspects

In RE models such as goal-oriented models, a complex system is directly described in terms of its purposes, which makes its functionality much easier to understand and to reason as compared to code-level implementations. Part of the difficulty in maintaining a stronger correspondence between requirements and code is possibly due to the sufficient modularization capabilities of traditional architectures where many functionalities do not exist in distinct modular entities. This paper reports on an investigation of how and where some distinct design requirements lead to crosscutting concerns when decomposed into code in goal models such as KAOS. We begin by matching our past experience in aspect discovery at the code level with a detailed requirements modeling of the same architecture in KAOS. The discovered patterns are validated in an independent project where the requirements modeling and the aspect identification are separately conducted. We observe that satisfying OR-decomposed subgoals in the KAOS model typically leads to tangled implementations, and agents responsible for multiple OR-refined goals should be implemented in the aspect-oriented manner

Revisiting money and labor for valuing environmental goods and services in developing countries

Many Stated Preference studies conducted in developing countries provide a low willingness to pay (WTP) for a wide range of goods and services. However, recent studies in these countries indicate that this may partly be a result of the choice of payment vehicle, not the preference for the good. Thus, low WTP may not indicate a low welfare effect for public projects in developing countries. We argue that in a setting where 1) there is imperfect substitutability between money and other measures of wealth (e.g. labor), and 2) institutions are perceived to be corrupt, including payment vehicles that are currently available to the individual and less pron to corruption may be needed to obtain valid welfare estimates. Otherwise, we risk underestimating the welfare benefit of projects. We demonstrate this through a rural household contingent valuation (CV) survey designed to elicit the value of access to reliable irrigation water in Ethiopia. Of the total average annual WTP for access to reliable irrigation service, cash contribution comprises only 24.41 %. The implication is that socially desirable projects might be rejected based on cost-benefit analysis as a result of welfare gain underestimation due to mismatch of payment vehicles choice in valuation study.Comment: There is no difference between the previous version and the current version. This version is to link with the published version DO

Rapid magma ascent recorded by water diffusion profiles in mantle olivine

Mechanisms and rates of magma ascent play a critical role in eruption dynamics but remain poorly constrained phenomena. Water, dissolved in mantle minerals as hydrogen and partitioned into the magma during ascent, may provide clues to quantifying magma ascent rates prior to eruption. We determined the dehydration profiles in olivine crystals from peridotite mantle xenoliths within the Pali-Aike alkali basalt from Patagonia, Chile. The results demonstrate that the amount of water stored in the uppermost mantle has likely been underestimated due to water loss during transport. Using experimental diffusion data for hydrogen, we estimate that the xenoliths reached the surface from 60–70 km depth in several hours, a surprisingly rapid rise comparable to ascent rates for kimberlite magmas

Resolving feature convolution in middleware systems

Middleware provides simplicity and uniformity for the development of distributed applications. However, the modularity of the architecture of middleware is starting to disintegrate and to become complicated due to the interaction of too many orthogonal concerns imposed from a wide range of application requirements. This is not due to bad design but rather due to the limitations of the conventional architectural decomposition methodologies. We introduce the principles of horizontal decomposition (HD) which addresses this problem with a mixed-paradigm middleware architecture. HD provides guidance for the use of conventional decomposition methods to implement the core functionalities of middleware and the use of aspect orientation to address its orthogonal properties. Our evaluation of the horizontal decomposition principles focuses on refactoring major middleware functionalities into aspects in order to modularize and isolate them from the core architecture. New versions of the middleware platform can be created through combining the core and the flexible selection of middleware aspects such as IDL data types, the oneway invocation style, the dynamic messaging style, and additional character encoding schemes. As a result, the primary functionality of the middleware is supported with a much simpler architecture and enhanced performance. Moreover, customization and configuration of the middleware for a wide-range of requirements becomes possible

Characterization of human immunodeficiency virus type 1 mutantswith decreased sensitivity to proteinase inhibitor Ro 31-8959

AbstractA human immunodeficiency virus type 1 (HIV-1) variant with highly reduced susceptibility to Ro 31-8959, an inhibitor of the viral proteinase, has been selected by repeated passage of wild-type virus in CEM cells in the presence of increasing concentrations of the inhibitor. Peptide sequences of the proteinase of selected virus were obtained from proviral DNA. Sequence comparison to wild-type (wt) proteinase demonstrated two amino acid substitutions in the resistant virus, a Gly to Val exchange at position 48 and a Leu to Met exchange at position 90. Furthermore, sequences of intermediate passage virus suggest contributions from positions 12, 36, 57, and 63 in early steps of resistance development. The selected virus showed a ca. 40-fold increase in 50% inhibitory concentration of Ro 31-8959. Growth kinetics of resistant virus were comparable to wild-type virus and the resistant genotype proved to be stable in the absence of inhibitor. Directed mutagenesis of the HIV-1 HXB2 proteinase at positions 48 and 90 suggested that each mutation alone led to a moderate decrease in sensitivity of the recombinant virus to proteinase inhibitor. However, a recombinant virus carrying both mutations in the proteinase gene showed a significant reduction in its sensitivity to Ro 31-8959 thus proving the importance of these exchanges for the resistance phenotype

Attention deficits in childhood-onset schizophrenia: reaction time studies

The hypothesis of continuity between childhood-onset and adult schizophrenia was tested by comparing the performance of 15 patients with childhood-onset schizophrenia and 52 age-matched controls on 2 reaction time paradigms that have been used to study adult schizophrenia. On simple reaction time to tones with regular and irregular preparatory intervals of 2, 4, and 8 s, patients showed greater effects of the length of the preparatory interval in the regular condition and greater effects of the preparatory interval (girls only) and the preceding preparatory interval in the irregular series. On simple reaction time to random lights and tones, patients were faster on ipsimodal sequences than cross-modal sequences compared with controls. Overall, patients were much slower than controls in both paradigms. The results suggest similar attention dysfunction as is found in adult schizophrenia and thus are consistent with the continuity hypothesis