Logic Program Synthesis via Proof Planning

We propose a novel approach to automating the synthesis of logic programs: Logic programs are synthesized as a by-product of the planning of a verification proof. The approach is a two-level one: At the object level, we prove program verification conjectures in a sorted, first-order theory. The conjectures are of the form $\forall \vec{args}. \; prog(\vec{args}) \leftrightarrow spec(\vec{args})$. At the meta-level, we plan the object-level verification with an unspecified program definition. The definition is represented with a (second-order) meta-level variable, which becomes instantiated in the course of the planning. This technique is an application of the Clam proof planning system. Clam is currently powerful enough to plan verification proofs for given programs. We show that, if Clam's use of middle-out reasoning is extended, it will also be able to synthesize programs

Chirped pulse Raman amplification in warm plasma: towards controlling saturation

Stimulated Raman backscattering in plasma is potentially an efficient method of amplifying laser pulses to reach exawatt powers because plasma is fully broken down and withstands extremely high electric fields. Plasma also has unique nonlinear optical properties that allow simultaneous compression of optical pulses to ultra-short durations. However, current measured efficiencies are limited to several percent. Here we investigate Raman amplification of short duration seed pulses with different chirp rates using a chirped pump pulse in a preformed plasma waveguide. We identify electron trapping and wavebreaking as the main saturation mechanisms, which lead to spectral broadening and gain saturation when the seed reaches several millijoules for durations of 10's - 100's fs for 250 ps, 800 nm chirped pump pulses. We show that this prevents access to the nonlinear regime and limits the efficiency, and interpret the experimental results using slowly-varying-amplitude, current-averaged particle-in-cell simulations. We also propose methods for achieving higher efficiencies.close0

Entropic Tension in Crowded Membranes

Unlike their model membrane counterparts, biological membranes are richly decorated with a heterogeneous assembly of membrane proteins. These proteins are so tightly packed that their excluded area interactions can alter the free energy landscape controlling the conformational transitions suffered by such proteins. For membrane channels, this effect can alter the critical membrane tension at which they undergo a transition from a closed to an open state, and therefore influence protein function \emph{in vivo}. Despite their obvious importance, crowding phenomena in membranes are much less well studied than in the cytoplasm. Using statistical mechanics results for hard disk liquids, we show that crowding induces an entropic tension in the membrane, which influences transitions that alter the projected area and circumference of a membrane protein. As a specific case study in this effect, we consider the impact of crowding on the gating properties of bacterial mechanosensitive membrane channels, which are thought to confer osmoprotection when these cells are subjected to osmotic shock. We find that crowding can alter the gating energies by more than $2\;k_BT$ in physiological conditions, a substantial fraction of the total gating energies in some cases. Given the ubiquity of membrane crowding, the nonspecific nature of excluded volume interactions, and the fact that the function of many membrane proteins involve significant conformational changes, this specific case study highlights a general aspect in the function of membrane proteins.Comment: 20 pages (inclduing supporting information), 4 figures, to appear in PLoS Comp. Bio

Nutritional correlates of koala persistence in a low-density population

It is widely postulated that nutritional factors drive bottom-up, resource-based patterns in herbivore ecology and distribution. There is, however, much controversy over the roles of different plant constituents and how these influence individual herbivores and herbivore populations. The density of koala (Phascolarctos cinereus) populations varies widely and many attribute population trends to variation in the nutritional quality of the eucalypt leaves of their diet, but there is little evidence to support this hypothesis. We used a nested design that involved sampling of trees at two spatial scales to investigate how leaf chemistry influences free-living koalas from a low-density population in south east New South Wales, Australia. Using koala faecal pellets as a proxy for koala visitation to trees, we found an interaction between toxins and nutrients in leaves at a small spatial scale, whereby koalas preferred trees with leaves of higher concentrations of available nitrogen but lower concentrations of sideroxylonals (secondary metabolites found exclusively in eucalypts) compared to neighbouring trees of the same species. We argue that taxonomic and phenotypic diversity is likely to be important when foraging in habitats of low nutritional quality in providing diet choice to tradeoff nutrients and toxins and minimise movement costs. Our findings suggest that immediate nutritional concerns are an important priority of folivores in low-quality habitats and imply that nutritional limitations play an important role in constraining folivore populations. We show that, with a careful experimental design, it is possible to make inferences about populations of herbivores that exist at extremely low densities and thus achieve a better understanding about how plant composition influences herbivore ecology and persistence.IW and WF received a grant from New South Wales (NSW) Department of Environment, Climate Change & Water

Theorizing compassion and empathy in educational contexts: what are compassion and empathy and why are they important?

The world is in constant change with growing inequality and access. When you watch the news, you are confronted with national disasters, wars/conflicts, waves of refugees and other crimes against humanity. At a national level, many countries have a changing political landscape that has seen a rise in fundamentalist nationalist parties leading to a discourse of 'problematic immigrants'. We also witness the decline of democratic ideals and the ethos of supporting people in society as politicians are influenced by capitalist ideals and individual gain. In essence, the world appears to be becoming meaner, with little understanding shown to others. When did values change

Comparison of two methods based on cross-sectional data for correcting corpus uterine cancer incidence and probabilities

BACKGROUND: Two methods are presented for obtaining hysterectomy prevalence corrected estimates of invasive cancer incidence rates and probabilities of the corpus uterine. METHODS: The first method involves cross-sectional hysterectomy data from the Utah Hospital Discharge Data Base and mortality data applied to life-table methods. The second involves hysterectomy prevalence estimates obtained directly from the Utah Behavior Risk Factor Surveillance System (BRFSS) survey. RESULTS: Hysterectomy prevalence estimates based on the first method are lower than those obtained from the second method through age 74, but higher in the remaining ages. Correction for hysterectomy prevalence is greatest among women ages 75–79. In this age group, the uncorrected rate is 125 (per 100,000) and the corrected rate based on the life-table method is 223 using 1995–97 data, 243 using 1992–94 data, and 228 from the survey method. The uncorrected lifetime probability of developing corpus uterine cancer is 2.6%; the corrected probability from the life-table method using 1995–97 data is 4.2%, using 1992–94 data is 4.5%; and based on prevalence data from the survey method is 4.6%. CONCLUSIONS: Both methods provide reasonable hysterectomy prevalence estimates for correcting corpus uterine cancer rates and probabilities. Because of declining trends in hysterectomy in recent decades, corrected estimates from the life-table method are less pronounced than those based on the survey method. These methods may be useful for obtaining corrected uterine cancer rates and probabilities in areas of the world that do not have sufficient years of hysterectomy data to directly compute prevalence

Cooperative breeding by the Galápagos mockingbird, Nesomimus parvulus

The costs and benefits of helping behavior were analyzed for 36 pairs of the Galápagos mockingbird, Nesomimus parvulus , and their associates. Helping at the nest is usually done by sons or males suspected to be offspring of the breeders. Costs and benefits to breeders were assessed by comparison of pairs with and without helpers, and costs and benefits to helpers were assessed by comparison of birds which help and those which establish themselves as novice breeders.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46866/1/265_2004_Article_BF00296397.pd

The withdrawal from oncogenetic counselling and testing for hereditary and familial breast and ovarian cancer. A descriptive study of an Italian sample

<p>Abstract</p> <p>Background</p> <p>Oncogenetic counselling is seldom followed through, even when individuals are eligible according to the test criteria. The basic variables which influence the decision to undergo the genetic counselling process are: risk perception, expected benefit or limitations of genetic testing, general psychological distress or cancer-specific distress, lack of trust in one's emotional reactions when faced with negative events, expected level of family support and communications within the family. The aim of this study was to describe the psychosocial variables of an Italian sample that forgoes genetic counselling.</p> <p>Methods</p> <p>From May 2002 to December 2006 a psychological questionnaire was sent out to one hundred and six subjects, who freely requested a first genetic informative consultation, and never asked to have a second visit and the family tree drawn up in order to inquire about their eligibility for genetic testing. Statistical analysis was performed by Pearson chi-square test, t-test and Spearman RHO coefficient.</p> <p>Results</p> <p>The survey presents a lack of emotional cohesion and structured roles and rules within the family system and a positive correlation between the number of children, anxiety and risk perception. The main reasons for giving up on counselling were a sense that testing was a waste of time and the inability to emotionally handle the negative consequences of the test outcome. The subjects who maintained that test and an early diagnosis were a "waste of time" experienced more anxiety.</p> <p>Conclusion</p> <p>The study revealed the importance to ac knowledging the whole persona and their family system as well as provide information highlighting usefulness of early diagnosis.</p