12,305 research outputs found
Interpolation Properties and SAT-based Model Checking
Craig interpolation is a widespread method in verification, with important
applications such as Predicate Abstraction, CounterExample Guided Abstraction
Refinement and Lazy Abstraction With Interpolants. Most state-of-the-art model
checking techniques based on interpolation require collections of interpolants
to satisfy particular properties, to which we refer as "collectives"; they do
not hold in general for all interpolation systems and have to be established
for each particular system and verification environment. Nevertheless, no
systematic approach exists that correlates the individual interpolation systems
and compares the necessary collectives. This paper proposes a uniform
framework, which encompasses (and generalizes) the most common collectives
exploited in verification. We use it for a systematic study of the collectives
and of the constraints they pose on propositional interpolation systems used in
SAT-based model checking
Binary-Binary Interactions and the Formation of the PSR B1620-26 Triple System in M4
The hierarchical triple system containing the millisecond pulsar PSR B1620-26
in M4 is the first triple star system ever detected in a globular cluster. Such
systems should form in globular clusters as a result of dynamical interactions
between binaries. We propose that the triple system containing PSR B1620-26
formed through an exchange interaction between a wide primordial binary and a
{\it pre-existing\/} binary millisecond pulsar. This scenario would have the
advantage of reconciling the yr timing age of the pulsar with the
much shorter lifetime of the triple system in the core of M4.Comment: 13 pages, uuencoded compressed postscript with figures, IASSNS-AST
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The relationship between the insulin-like growth factor-1 axis, weight loss, an inflammation-based score and survival in patients with inoperable non-small cell lung cancer
<b>Background & aims:</b>
The involvement of a systemic inflammatory response, as evidenced by the Glasgow Prognostic Score (GPS), is associated with weight loss and poor outcome in patients with non-small cell lung cancer. There is good evidence that nutritional and functional decline in patients with advanced malignant disease is associated with catabolic changes in metabolism. However, defects in anabolism may also contribute towards nutritional decline in patients with cancer. The aim of the present study was to examine the relationship between IGF-1 and IGFBP-3, performance status, mGPS and survival in patients with inoperable NSCLC.
<b>Methods:</b>
56 patients with inoperable NSCLC were studied. The plasma concentrations of IGF-1, IGFBP-3 and leptin were measured using ELISA and RIA.
<b>Results:</b>
The patients were predominantly male (61%), over 60 years old (80%), with advanced (stage III or IV) disease (98%), with a BMI≥20 (84%), an ECOG-ps of 0 or 1 (79%), a haemoglobin (59%) and white cell count (79%) in the reference range. On follow-up 43 patients died of their cancer. On univariate analysis, BMI (p<0.05), Stage (p<0.05), ECOG-ps (p<0.05), haemoglobin (p<0.05), white cell count (p<0.05) and mGPS (p<0.05) were associated with cancer specific survival. There was no association between age, sex, treatment, IGF-1, IGFBP-3, IGF-1:IGFBP-3 ratio, or leptin and cancer specific survival. With an increasing mGPS concentrations of haemoglobin (p<0.005) and IGFBP-3 (p<0.05) decreased. mGPS was not associated with either IGF-1(p>0.20), or leptin (p>0.20).
<b>Conclusions:</b>
In summary, the results of this study suggest that anabolism (IGF-1 axis) does not play a significant role in the relationship between nutritional and functional decline, systemic inflammation and poor survival in patients with inoperable NSCLC
CLIMATE AND SCALE IN ECONOMIC GROWTH
This paper introduces new data on climatic conditions to empirical tests of growth theories. We find that, since 1960, temperate countries have converged towards high levels of income while tropical nations have converged towards various income levels associated with economic scale and the extent of the market. These results hold for a wide range of tests. A plausible explanation is that temperate regions' growth was assisted by their climate, perhaps historically for their transition out of agriculture into sectors whose productivity converges across countries, while tropical countries' growth is relatively more dependent on gains from specialization and trade.International Development,
Africa's Growth Trap: A Political-Economy Model of Taxation, R&D and Investment
Why do so many African governments consistently impose high tax rates and make little investment in productive public goods, when alternative policies could yield greater tax revenues and higher national income? We posit and test an intertemporal political economy model in which the government sets tax and R&D levels while investors respond with production. Equilibrium policy and growth rates depend on initial cost structure. We find that in many (but not all) African countries, low tax/high investment regimes would be time-inconsistent. For pro-growth policies to become sustainable, commitment mechanisms or new production techniques would be needed.time consistency, agricultural policy, economic growth
Africa's growth trap: a political-economy model of taxation, R&D and investment.
Why do so many African governments consistently impose high tax rates and make little investment in productive public goods when alternative policies could yield greater tax revenues and higher national income? We posit and test an intertemporal political economy model in which the government sets tax and R&D levels while investors respond with production. Equilibrium policy and growth rates depend on initial cost structure. We find that in many (but not all) African countries, low tax/high investment regimes would be time-inconsistent. For progrowth policies to become sustainable, commitment mechanisms or new production techniques would be needed.time consistency, agricultural policy, tax regimes and growth.
AN AFRICAN GROWTH TRAP: PRODUCTION TECHNOLOGY AND THE TIME-CONSISTENCY OF AGRICULTURAL TAXATION, R&D AND INVESTMENT
Why do so many African governments consistently impose high tax rates and make little investment in productive public goods, when alternative policies could yield greater tax revenues and higher national income? We posit and test an intertemporal political economy model in which the government sets tax and R&D levels while investors respond with production. Equilibrium policy and growth rates depend on initial cost structure. We find that in many (but not all) African countries, low tax/high investment regimes would be time-inconsistent, primarily because production technology requires relatively large sunk costs. For pro-growth policies to become sustainable, commitment mechanisms or new production techniques would be needed.International Development, Research and Development/Tech Change/Emerging Technologies,
Splitting Proofs for Interpolation
We study interpolant extraction from local first-order refutations. We
present a new theoretical perspective on interpolation based on clearly
separating the condition on logical strength of the formula from the
requirement on the com- mon signature. This allows us to highlight the space of
all interpolants that can be extracted from a refutation as a space of simple
choices on how to split the refuta- tion into two parts. We use this new
insight to develop an algorithm for extracting interpolants which are linear in
the size of the input refutation and can be further optimized using metrics
such as number of non-logical symbols or quantifiers. We implemented the new
algorithm in first-order theorem prover VAMPIRE and evaluated it on a large
number of examples coming from the first-order proving community. Our
experiments give practical evidence that our work improves the state-of-the-art
in first-order interpolation.Comment: 26th Conference on Automated Deduction, 201
Climate and scale in economic growth.
This paper introduces new data on climatic conditions to empirical tests of growth theories. We find that, since 1960, temperate countries have converged towards high levels of income while tropical nations have converged towards various income levels associated with economic scale and the extent of the market. These results hold for a wide range of tests. A plausible explanation is that temperate regions' growth was assisted by their climate, perhaps historically for their transition out of agriculture into sectors whose productivity converges across countries, while tropical countries' growth is relatively more dependent on gains from specialization and trade.growth accounting, empirical growth models, endogenous growth
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