Combinatorial Properties of Triangle-Free Rectangle Arrangements and the Squarability Problem

We consider arrangements of axis-aligned rectangles in the plane. A geometric arrangement specifies the coordinates of all rectangles, while a combinatorial arrangement specifies only the respective intersection type in which each pair of rectangles intersects. First, we investigate combinatorial contact arrangements, i.e., arrangements of interior-disjoint rectangles, with a triangle-free intersection graph. We show that such rectangle arrangements are in bijection with the 4-orientations of an underlying planar multigraph and prove that there is a corresponding geometric rectangle contact arrangement. Moreover, we prove that every triangle-free planar graph is the contact graph of such an arrangement. Secondly, we introduce the question whether a given rectangle arrangement has a combinatorially equivalent square arrangement. In addition to some necessary conditions and counterexamples, we show that rectangle arrangements pierced by a horizontal line are squarable under certain sufficient conditions.Comment: 15 pages, 13 figures, extended version of a paper to appear at the International Symposium on Graph Drawing and Network Visualization (GD) 201

3-(6-Methyl-2-pyrid­yl)-2-phenyl-3,4-dihydro-1,3,2-benzoxaza­phosphinine 2-oxide

In the title compound, C19H17N2O2P, the six-membered 1,3,2-oxaza­phosphinine ring adopts a boat conformation with the phosphoryl O atom in an equatorial position. The dihedral angle between the 6-methyl-2-pyridyl and phenyl groups is 75.5 (1)°. These substituents are trans to each other, and are oriented at angles of 57.2 (1) and 74.8 (1)°, respectively, to the benzene ring. The crystal structure is stabilized by intra- and inter­molecular hydrogen bonds. The phosphoryl O atom participates in inter­molecular C—H⋯O inter­actions with the neighbouring mol­ecules, forming centrosymmetric R 2 2(14) dimers

Frege on the Generality of Logical Laws

Frege claims that the laws of logic are characterized by their “generality,” but it is hard to see how this could identify a special feature of those laws. I argue that we must understand this talk of generality in normative terms, but that what Frege says provides a normative demarcation of the logical laws only once we connect it with his thinking about truth and science. He means to be identifying the laws of logic as those that appear in every one of the scientific systems whose construction is the ultimate aim of science, and in which all truths have a place. Though an account of logic in terms of scientific systems might seem hopelessly antiquated, I argue that it is not: a basically Fregean account of the nature of logic still looks quite promising

Diamagnetically Levitated MEMS Accelerometers

We introduce the theory and a proof-of-concept design for MEMS-based, diamagnetically-levitated accelerometers. The theory includes an equation for determining the diamagnetic force above a checkerboard configuration of magnets. We demonstrate both electronic probing and a rapid MEMS-based interferometer technique for position sensing of the proof mass. Through a proof-of-concept design, we show electrostatic-measurement sensitivity achieving 34 μg at a 0.1 V sense signal and interferometer-measurement sensitivity achieving 6 μg for in-plane vibrations at 5 Hz. We conclude by outlining batch-fabrication steps to produce levitated accelerometers

Diethyl [(4-bromo­phen­yl)(5-chloro-2-hydroxy­anilino)meth­yl]phospho­nate

In the title compound, C17H20BrClNO4P, inter­molecular C—H⋯O and N—H⋯O hydrogen bonds form centrosymmetric R 2 2(10) dimers linked through O—H⋯O inter­molecular hydrogen bonds, which form centrosymmetric R 2 2(16) dimers. All these hydrogen bonds form chains along [010]. In addition, the crystal structure is stabilized by weak C—H⋯Br hydrogen bonds. The very weak intramolecular N—H⋯O interaction forms a five-membered ring

Governed by history: Institutional analysis of a contested biofuel innovation system in Tanzania

Initially hailed as a miracle crop for biofuel production, Jatropha has recently attracted criticism for competing with food production, causing adverse biodiversity impacts, and jeopardizing land access by rural populations in tropical countries. This paper analyzes the contested development of Jatropha biofuel sector in Tanzania by anchoring two new concepts of ‘organizational models’ and ‘institutional arrangements’ to the sectoral systems of innovation perspective. The notion of ‘organizational models’ brings into relief the heterogeneity of actors in an innovation system and the ways in which the actors form networks, within and across national borders, to organize innovative activities. The concept of ‘institutional arrangements’ refers to the ensemble of formal and informal institutions assembled during Tanzania’s colonial and post-colonial eras, which directly govern innovative activities in specific organizational models. Based on a location-specific and historically-grounded institutional analysis within the innovation system framework, implications are drawn for the future development of Tanzania’s Jatropha sector including its links with European markets and for the regulation of ‘next-generation’ biofuels

Decomposing Service Definition in Predicate/Transition-Nets for Designing Distributed Systems

In this paper, we propose a new algorithm for the derivation of a protocol specification in Pr/T-nets, which is the specification of communicating N entities (N can be given), from a given service specification in Pr/T-nets and an allocation of the places of the service specification to the N entities. Our algorithm decomposes each transition of the service specification into a set of communicating Pr/T-subnets running on the N entities. Moreover, for the efficient control of conflict of shared resources, we present a timestamp-based mutual exclusion algorithm and incorporate it into the derivation algorithm

Why do herbivorous mites suppress plant defenses?

Plants have evolved numerous defensive traits that enable them to resist herbivores. In turn, this resistance has selected for herbivores that can cope with defenses by either avoiding, resisting or suppressing them. Several species of herbivorous mites, such as the spider mites Tetranychus urticae and Tetranychus evansi, were found to maximize their performance by suppressing inducible plant defenses. At first glimpse it seems obvious why such a trait will be favored by natural selection. However, defense suppression appeared to readily backfire since mites that do so also make their host plant more suitable for competitors and their offspring more attractive for natural enemies. This, together with the fact that spider mites are infamous for their ability to resist (plant) toxins directly, justifies the question as to why traits that allow mites to suppress defenses nonetheless seem to be relatively common? We argue that this trait may facilitate generalist herbivores, like T. urticae, to colonize new host species. While specific detoxification mechanisms may, on average, be suitable only on a narrow range of similar hosts, defense suppression may be more broadly effective, provided it operates by targeting conserved plant signaling components. If so, resistance and suppression may be under frequency-dependent selection and be maintained as a polymorphism in generalist mite populations. In that case, the defense suppression trait may be under rapid positive selection in subpopulations that have recently colonized a new host but may erode in relatively isolated populations in which host-specific detoxification mechanisms emerge. Although there is empirical evidence to support these scenarios, it contradicts the observation that several of the mite species found to suppress plant defenses actually are relatively specialized. We argue that in these cases buffering traits may enable such mites to mitigate the negative side effects of suppression in natural communities and thus shield this trait from natural selection