The Phase Diagram of 1-in-3 Satisfiability Problem

We study the typical case properties of the 1-in-3 satisfiability problem, the boolean satisfaction problem where a clause is satisfied by exactly one literal, in an enlarged random ensemble parametrized by average connectivity and probability of negation of a variable in a clause. Random 1-in-3 Satisfiability and Exact 3-Cover are special cases of this ensemble. We interpolate between these cases from a region where satisfiability can be typically decided for all connectivities in polynomial time to a region where deciding satisfiability is hard, in some interval of connectivities. We derive several rigorous results in the first region, and develop the one-step--replica-symmetry-breaking cavity analysis in the second one. We discuss the prediction for the transition between the almost surely satisfiable and the almost surely unsatisfiable phase, and other structural properties of the phase diagram, in light of cavity method results.Comment: 30 pages, 12 figure

Sensitivity of nonlinear photoionization to resonance substructure in collective excitation

Collective behaviour is a characteristic feature in many-body systems, important for developments in fields such as magnetism, superconductivity, photonics and electronics. Recently, there has been increasing interest in the optically nonlinear response of collective excitations. Here we demonstrate how the nonlinear interaction of a many-body system with intense XUV radiation can be used as an effective probe for characterizing otherwise unresolved features of its collective response. Resonant photoionization of atomic xenon was chosen as a case study. The excellent agreement between experiment and theory strongly supports the prediction that two distinct poles underlie the giant dipole resonance. Our results pave the way towards a deeper understanding of collective behaviour in atoms, molecules and solid-state systems using nonlinear spectroscopic techniques enabled by modern short-wavelength light sources

Plant Oils and Products of Their Hydrolysis as Substrates for Polyhydroxyalkanoate Synthesis

Plant oils could provide a sustainable source of carbon for polyhydroxyalkanoate production as they are both renewable and inexpensive. No study to our knowledge has undertaken a comparative study of the use of major European and global commodity plants oils and products of their hydrolysis as substrates for medium chain length polyhydroxyalkanoate (mcl-PHA) production. There have been several studies which have investigated the use of plant oils and their hydrolysis products for short chain length PHA (scl-PHA) production, therefore, in this study, we have focused specifically on mcl-PHA-producing organisms. A comparison between direct growth on oils and the products of their hydrolysis is described here for several mcl-PHA-producing Pseudomonas strains. Pseudomonas putida KT2440, CA-3, GO16, Pseudomonas chlororaphis 555 were screened for their ability to utilize a range of common plant oils (olive, sunflower, rapeseed, and palm) and their hydrolysis products as sole sources of carbon and energy for growth and PHA accumulation. When the oils were supplied in shaken flask experiments, P. putida CA-3 and P. putida KT2440 showed little or no growth, while P. putida GO16 reached a cell dry weight of between 0.33 and 0.56 g L–1, and accumulated mcl-PHA to between 12 and 25 % of CDW, P. chlororaphis 555 reached a cell dry weight of between 0.67 and 0.86 g L–1, and accumulated mcl-PHA to between 27 and 34 % CDW in 48 h. In contrast, when the hydrolyzed fatty acid mixtures were supplied, all 4 strains tested grew and accumulated mcl-PHA. P. putida CA-3 and GO16 achieved the highest biomass (1.02 – 1.06 g L–1) with the majority of the hydrolyzed plant oil fatty acids, however P. chlororaphis 555 accumulated similar levels of PHA as these two strains. Despite being the strain of choice for mcl-PHA accumulation, for the majority of studies, P. putida KT2440 achieved less biomass and accumulated less PHA than other strains tested with the majority of oil-derived fatty acids. It is important to note that both biomass and PHA levels varied significantly across strain and hydrolyzed oil type. Due to the fact that P. chlororaphis 555 was able to grow and accumulate PHA from both plant oils and hydrolyzed oil fatty acids, it was selected for bioreactor trials to try to achieve high cell density and high PHA productivity using rapeseed oil and hydrolyzed rapeseed oil fatty acids. Rapeseed oil (RO) and its hydrolysis product (HROFA) were chosen for these experiments because P. chlororaphis 555 accumulated approximately 30 % mcl-PHA from both substrates, and as this oil can be produced globally, it would offer less barriers to scale-up than Palm oil. The mcl-PHA volumetric productivity with RO as the substrate was 0.53 g L–1 h–1 after 25 h with a yield of 0.22 g PHA g–1 oil, while the volumetric productivity with HROFA as the substrate was 0.54 g L–1 h–1 after 25 h with again a lower yield of 0.15 g PHA g–1 HROFA. Thus, under the fermentation conditions tested, HROFA was an inferior substrate for PHA production when compared to RO

A Theoretical Analysis of Two-Stage Recommendation for Cold-Start Collaborative Filtering

In this paper, we present a theoretical framework for tackling the cold-start collaborative filtering problem, where unknown targets (items or users) keep coming to the system, and there is a limited number of resources (users or items) that can be allocated and related to them. The solution requires a trade-off between exploitation and exploration as with the limited recommendation opportunities, we need to, on one hand, allocate the most relevant resources right away, but, on the other hand, it is also necessary to allocate resources that are useful for learning the target's properties in order to recommend more relevant ones in the future. In this paper, we study a simple two-stage recommendation combining a sequential and a batch solution together. We first model the problem with the partially observable Markov decision process (POMDP) and provide an exact solution. Then, through an in-depth analysis over the POMDP value iteration solution, we identify that an exact solution can be abstracted as selecting resources that are not only highly relevant to the target according to the initial-stage information, but also highly correlated, either positively or negatively, with other potential resources for the next stage. With this finding, we propose an approximate solution to ease the intractability of the exact solution. Our initial results on synthetic data and the Movie Lens 100K dataset confirm the performance gains of our theoretical development and analysis

Allocation in Practice

How do we allocate scarcere sources? How do we fairly allocate costs? These are two pressing challenges facing society today. I discuss two recent projects at NICTA concerning resource and cost allocation. In the first, we have been working with FoodBank Local, a social startup working in collaboration with food bank charities around the world to optimise the logistics of collecting and distributing donated food. Before we can distribute this food, we must decide how to allocate it to different charities and food kitchens. This gives rise to a fair division problem with several new dimensions, rarely considered in the literature. In the second, we have been looking at cost allocation within the distribution network of a large multinational company. This also has several new dimensions rarely considered in the literature.Comment: To appear in Proc. of 37th edition of the German Conference on Artificial Intelligence (KI 2014), Springer LNC

High-spatial-resolution observations of NH3 and CH3OH towards the massive twin cores NGC6334 I & I(N)

Molecular line observations of NH3 (J,K)=(1,1), (2,2) and CH3OH at 24.93GHz taken with the Australian Telescope Compact Array (ATCA) toward the massive twin cores NGC6334 I & I(N) reveal significant variations in the line emission between the two massive cores. The UCHII region/hot core NGC6334 I exhibits strong thermal NH3 and CH3OH emission adjacent to the UCHII region and coincident with two mm continuum peaks observed by Hunter et al. (in prep.). In contrast, we find neither compact NH3 nor thermal CH3OH line emission toward NGC6334 I(N). There, the NH3 emission is distributed over a broad region (>1') without a clear peak, and we find Class I CH3OH maser emission with peak brightness temperatures up to 7000K. The maser emission peaks appear to be spatially associated with the interfaces between the molecular outflows and the ambient dense gas. Peak NH3(1,1) line brightness temperatures >= 70K in both regions indicate gas temperatures of the same order. NH3 emission is also detected toward the outflow in NGC6334 I resulting in an estimated rotational temperature of Trot~19K. Furthermore, we observe CH3OH and NH3 absorption toward the UCHII region, the velocity structure is consistent with expanding molecular gas around the UCHII region. Thermal and kinematic effects possibly imposed from the UCHII region on the molecular core are also discussed.Comment: Accepted for the Astrophysical Journa

ReDeCheck: An Automatic Layout Failure Checking Tool for Responsively Designed Web Pages

Since people frequently access websites with a wide variety of devices (e.g., mobile phones, laptops, and desktops), developers need frameworks and tools for creating layouts that are useful at many viewport widths. While responsive web design (RWD) principles and frameworks facilitate the development of such sites, there is a lack of tools supporting the detection of failures in their layout. Since the quality assurance process for responsively designed websites is often manual, time-consuming, and error-prone, this paper presents ReDeCheck, an automated layout checking tool that alerts developers to both potential unintended regressions in responsive layout and common types of layout failure. In addition to summarizing ReDeCheck’s benefits, this paper explores two different usage scenarios for this tool that is publicly available on GitHub

Inverse-kinematics one-neutron pickup with fast rare-isotope beams

New measurements and reaction model calculations are reported for single neutron pickup reactions onto a fast \nuc{22}{Mg} secondary beam at 84 MeV per nucleon. Measurements were made on both carbon and beryllium targets, having very different structures, allowing a first investigation of the likely nature of the pickup reaction mechanism. The measurements involve thick reaction targets and $\gamma$-ray spectroscopy of the projectile-like reaction residue for final-state resolution, that permit experiments with low incident beam rates compared to traditional low-energy transfer reactions. From measured longitudinal momentum distributions we show that the \nuc{12}{C} (\nuc{22}{Mg},\nuc{23}{Mg}+\gamma)X reaction largely proceeds as a direct two-body reaction, the neutron transfer producing bound \nuc{11}{C} target residues. The corresponding reaction on the \nuc{9}{Be} target seems to largely leave the \nuc{8}{Be} residual nucleus unbound at excitation energies high in the continuum. We discuss the possible use of such fast-beam one-neutron pickup reactions to track single-particle strength in exotic nuclei, and also their expected sensitivity to neutron high-$\ell$ (intruder) states which are often direct indicators of shell evolution and the disappearance of magic numbers in the exotic regime.Comment: 8 pages, 5 figure