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Stone fruits are a multi-billion-dollar industry for the U.S. and Canada, one that has repeatedly suffered significant economic losses to outbreaks of the X-disease phytoplasma (Candidatus Phytoplasma pruni) over the last century. Orchards and entire production areas have been abandoned, with corresponding losses to growers, fruit packers, and consumers. The most recent outbreak, in the U.S. Pacific Northwest, caused an estimated $65 million (USD) in lost revenue between 2015 and 2020 and is only increasing in incidence. Already present across much of the continental U.S. and Canada, the phytoplasma has a broad host range beyond stone fruit and is transmitted by at least eight leafhopper species therefore stone fruit production in any state is at significant risk. This recovery plan was produced as part of the National Plant Disease Recovery System (NPDRS) and is intended to provide a review of pathogen biology, assess the status of critical recovery components, and identify disease management research, extension, and education needs.

Let G be a finite group. It has recently been proved that every nontrivial element of G is contained in a generating set of minimal size if and only if all proper quotients of G require fewer generators than G. It is natural to ask which finite groups, in addition, have the property that any two elements of G that do not generate a cyclic group can be extended to a generating set of minimal size. This note answers the question. The only such finite groups are very specific affine groups: elementary abelian groups extended by a cyclic group acting as scalars., 5 pages; to appear in Archiv der Mathematik

Candidatus Phytoplasma pruni is the causative agent of X-disease on peach (Prunus persica) trees. Infected trees exhibit premature yellowing, leaf necrosis causing a shot-hole appearance, limb dieback, and eventual death. How pathogen infection leads to these symptoms is unknown. This study undertook a modern characterization of the disease by assessing the physiological and transcriptomic consequences of phytoplasma infection. Phytoplasma titer was high in the symptomatic tissues and undetected or at low titer in asymptomatic tissues. Symptomatic leaves had a significant decrease in chlorophyll a, chlorophyll b, and carotenoids. Transcriptomic analysis showed alterations in genes related to phytohormone synthesis and signaling, circadian rhythms, lignification, and sugar synthesis and transport. Several transcripts that may be related to symptom development were identified. Collectively these data give a much clearer picture of symptom development in Ca. P. pruni infected P. persica and provide several avenues of further research in determining how Ca. P. pruni interacts with its host to elicit the observed symptoms.

Let $G$ be a finite $2$-generated non-cyclic group. The spread of $G$ is the largest integer $k$ such that for any nontrivial elements $x_1, \ldots, x_k$, there exists $y \in G$ such that $G = \langle x_i, y\rangle$ for all $i$. The more restrictive notion of uniform spread, denoted $u(G)$, requires $y$ to be chosen from a fixed conjugacy class of $G$, and a theorem of Breuer, Guralnick and Kantor states that $u(G) \geqslant 2$ for every non-abelian finite simple group $G$. For any group with $u(G) \geqslant 1$, we define the uniform domination number $\gamma_u(G)$ of $G$ to be the minimal size of a subset $S$ of conjugate elements such that for each nontrivial $x \in G$ there exists $y \in S$ with $G = \langle x, y \rangle$ (in this situation, we say that $S$ is a uniform dominating set for $G$). We introduced the latter notion in a recent paper, where we used probabilistic methods to determine close to best possible bounds on $\gamma_u(G)$ for all simple groups $G$. In this paper we establish several new results on the spread, uniform spread and uniform domination number of finite groups and finite simple groups. For example, we make substantial progress towards a classification of the simple groups $G$ with $\gamma_u(G)=2$, and we study the associated probability that two randomly chosen conjugate elements form a uniform dominating set for $G$. We also establish new results concerning the $2$-generation of soluble and symmetric groups, and we present several open problems., Comment: 60 pages; to appear in Israel Journal of Mathematics

A wide variety of Hardware Trojan countermeasures have been developed, but less work has been done to determine which are optimal for any given design. To address this, we consider not only metrics related to the performance of the countermeasure, but also the likely action of an adversary given their goals. Trojans are inserted by an adversary to accomplish an end, so these goals must be considered and quantified in order to predict these actions. The model presented here builds upon a security economic approach that models the adversary and defender motives and goals in the context of empirically derived countermeasure efficacy metrics. The approach supports formation of a two-player strategic game to determine optimal strategy selection for both adversary and defender. A game may be played in a variety of contexts, including consideration of the entire design lifecycle or only a step in product development. As a demonstration of the practicality of this approach, we present an experiment that derives efficacy metrics from a set of countermeasures (defender strategies) when tested against a taxonomy of Trojans (adversary strategies). We further present a software framework, GameRunner, that automates not only the solution to the game but also mathematical and graphical exploration of “what if” scenarios in the context of the game. GameRunner can also issue “prescriptions,” a set of commands that allows the defender to automate the application of the optimal defender strategy to their circuit of concern. Finally, we include a discussion of ongoing work to include additional software tools, a more advanced experimental framework, and the application of irrationality models to account for players who make subrational decisions.

The spread of a group $G$, written $s(G)$, is the largest $k$ such that for any nontrivial elements $x_1, \dots, x_k \in G$ there exists $y \in G$ such that $G = \langle x_i, y \rangle$ for all $i$. Burness, Guralnick and Harper recently classified the finite groups $G$ such that $s(G) > 0$, which involved a reduction to almost simple groups. In this paper, we prove an asymptotic result that determines exactly when $s(G_n) \to \infty$ for a sequence of almost simple groups $(G_n)$. We apply probabilistic and geometric ideas, but the key tool is Shintani descent, a technique from the theory of algebraic groups that provides a bijection, the Shintani map, between conjugacy classes of almost simple groups. We provide a self-contained presentation of a general version of Shintani descent, and we prove that the Shintani map preserves information about maximal overgroups. This is suited to further applications. Indeed, we also use it to study $\mu(G)$, the minimal number of maximal overgroups of an element of $G$. We show that if $G$ is almost simple, then $\mu(G) \leqslant 3$ when $G$ has an alternating or sporadic socle, but in general, unlike when $G$ is simple, $\mu(G)$ can be arbitrarily large., Comment: 30 pages; to appear in Journal of Algebra

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A group $G$ is said to be $\frac{3}{2}$-generated if every nontrivial element belongs to a generating pair. It is easy to see that if $G$ has this property then every proper quotient of $G$ is cyclic. In this paper we prove that the converse is true for finite groups, which settles a conjecture of Breuer, Guralnick and Kantor from 2008. In fact, we prove a much stronger result, which solves a problem posed by Brenner and Wiegold in 1975. Namely, if $G$ is a finite group and every proper quotient of $G$ is cyclic, then for any pair of nontrivial elements $x_1,x_2 \in G$, there exists $y \in G$ such that $G = \langle x_1, y \rangle = \langle x_2, y \rangle$. In other words, $s(G) \geqslant 2$, where $s(G)$ is the spread of $G$. Moreover, if $u(G)$ denotes the more restrictive uniform spread of $G$, then we can completely characterise the finite groups $G$ with $u(G) = 0$ and $u(G)=1$. To prove these results, we first establish a reduction to almost simple groups. For simple groups, the result was proved by Guralnick and Kantor in 2000 using probabilistic methods and since then the almost simple groups have been the subject of several papers. By combining our reduction theorem and this earlier work, it remains to handle the groups whose socles are exceptional groups of Lie type and this is the case we treat in this paper., 48 pages; to appear in Annals of Mathematics

Every finite simple group can be generated by two elements, and Guralnick and Kantor proved that, moreover, every nontrivial element is contained in a generating pair. Groups with this property are said to be 3 2-generated. Thompson’s group V was the first finitely presented infinite simple group to be discovered. The Higman–Thompson groups Vn and the Brin–Thompson groups mV are two families of finitely presented groups that generalise V. In this paper, we prove that all of the groups Vn, V0 n and mV are 3 2-generated. As far as the authors are aware, the only previously known examples of infinite noncyclic 3 2-generated groups are the pathological Tarski monsters. We conclude with several open questions motivated by our results.

A fundamental aspect of biological intelligence, from microbes to megafauna, is the ability to forage for the provisions required to sustain life. This sometimes underrated ability to seek out, identify, and use objects of interest in an environment with limited prior knowledge is an important capability that is also needed by robots. Many robotics applications can be modeled as foraging problems, such as search and rescue, wildlife tracking, crop pollination and harvesting, mining and in-situ-resource utilization, and scientific data/sample collection.

Renewable energy can address increasing energy demand while mitigating the effects of climate change. High capital costs and long payback periods require most projects to secure financing for a por...

Variability exists amongst reported levelized costs of energy (LCOEs) for wind. Wind is unique from traditional energy sources in that the fuel is free, with the majority of costs determined by capital expenses. Power purchase agreements (PPAs) are critical to the success of a project, offering a guarantee of long-term revenue. Integral to negotiating a PPA is having an accurate estimate of the LCOE for the project. This research will evaluate LCOEs for wind to uncover reasons for substantial differences. PPA ownership structures and elements will also be evaluated with consideration of how objectives, resources, and farm management will impact decisions. The importance of understanding LCOE components as they relate to PPA negotiations will be highlighted with a focus on emerging markets and case analyses using NREL's System Advisor Model (SAM). Keywords: Levelized cost of energy, Wind power, Power purchase agreement, Renewable energy, Energy economics

Let $G$ be $2$-generated group. The generating graph of $\Gamma(G)$ is the graph whose vertices are the elements of $G$ and where two vertices $g$ and $h$ are adjacent if $G=\langle g,h\rangle$. This graph encodes the combinatorial structure of the distribution of generating pairs across $G$. In this paper we study several natural graph theoretic properties related to the connectedness of $\Gamma(G)$ in the case where $G$ is a finite nilpotent group. For example, we prove that if $G$ is nilpotent, then the graph obtained from $\Gamma(G)$ by removing its isolated vertices is maximally connected and, if $|G| \geq 3$, also Hamiltonian. We pose several questions., Comment: 11 pages; to appear in Algebraic Combinatorics

The distinguishing number of $G \leqslant \sym(\Omega)$ is the smallest size of a partition of $\Omega$ such that only the identity of $G$ fixes all the parts of the partition. Extending earlier results of Cameron, Neumann, Saxl and Seress on the distinguishing number of finite primitive groups, we show that all imprimitive quasiprimitive groups have distinguishing number two, and all non-quasiprimitive semiprimitive groups have distinguishing number two, except for $\mathrm{GL}(2, 3)$ acting on the eight non-zero vectors of $\mathbb F_2^3$, which has distinguishing number three., Comment: 10 pages

We present an approach to enhance wheeled planetary rover dead-reckoning localization performance by leveraging the use of zero-type constraint equations in the navigation filter. Without external aiding, inertial navigation solutions inherently exhibit cubic error growth. Furthermore, for planetary rovers that are traversing diverse types of terrain, wheel odometry is often unreliable for use in localization, due to wheel slippage. For current Mars rovers, computer vision-based approaches are generally used whenever there is a high possibility of positioning error; however, these strategies require additional computational power, energy resources, and significantly slow down the rover traverse speed. To this end, we propose a navigation approach that compensates for the high likelihood of odometry errors by providing a reliable navigation solution that leverages non-holonomic vehicle constraints as well as state-aware pseudo-measurements (e.g., zero velocity and zero angular rate) updates during periodic stops. By using this, computationally expensive visual-based corrections could be performed less often. Experimental tests that compare against GPS-based localization are used to demonstrate the accuracy of the proposed approach. The source code, post-processing scripts, and example datasets associated with the paper are published in a public repository., 8 pages, 9 figures, Accepted to IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) 2019

Zika virus has rapidly spread through the World Health Organization's Region of the Americas since being identified in Brazil in early 2015. Transmitted primarily through the bite of infected Aedes species mosquitoes, Zika virus infection during pregnancy can cause spontaneous abortion and birth defects, including microcephaly (1,2). New York City (NYC) is home to a large number of persons who travel frequently to areas with active Zika virus transmission, including immigrants from these areas. In November 2015, the NYC Department of Health and Mental Hygiene (DOHMH) began developing and implementing plans for managing Zika virus and on February 1, 2016, activated its Incident Command System. During January 1-June 17, 2016, DOHMH coordinated diagnostic laboratory testing for 3,605 persons with travel-associated exposure, 182 (5.0%) of whom had confirmed Zika virus infection. Twenty (11.0%) confirmed patients were pregnant at the time of diagnosis. In addition, two cases of Zika virus-associated Guillain-Barré syndrome were diagnosed. DOHMH's response has focused on 1) identifying and diagnosing suspected cases; 2) educating the public and medical providers about Zika virus risks, transmission, and prevention strategies, particularly in areas with large populations of immigrants from areas with ongoing Zika virus transmission; 3) monitoring pregnant women with Zika virus infection and their fetuses and infants; 4) detecting local mosquito-borne transmission through both human and mosquito surveillance; and 5) modifying existing Culex mosquito control measures by targeting Aedes species of mosquitoes through the use of larvicides and adulticides.

Modern commercial EDA tools provide end users with a framework for application specific customizations through a general-purpose programming language interface to an underlying circuit object model. Xilinx Vivado exposes that information through Tcl. This work demonstrates an implementation of a static hardware detection algorithm utilizing this interface of Vivado.

Precision robotic pollination systems can not only fill the gap of declining natural pollinators, but can also surpass them in efficiency and uniformity, helping to feed the fast-growing human population on Earth. This paper presents the design and ongoing development of an autonomous robot named "BrambleBee", which aims at pollinating bramble plants in a greenhouse environment. Partially inspired by the ecology and behavior of bees, BrambleBee employs state-of-the-art localization and mapping, visual perception, path planning, motion control, and manipulation techniques to create an efficient and robust autonomous pollination system., Comment: Accepted at the IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2018), Madrid, Spain

A group is $\frac{3}{2}$-generated if every non-identity element is contained in a generating pair. A conjecture of Breuer, Guralnick and Kantor from 2008 asserts that a finite group is $\frac{3}{2}$-generated if and only if every proper quotient of the group is cyclic, and recent work of Guralnick reduces this conjecture to almost simple groups. In this paper, we prove a stronger form of the conjecture for almost simple symplectic and odd-dimensional orthogonal groups. More generally, we study the uniform spread of these groups, obtaining lower bounds and related asymptotics. This builds on earlier work of Burness and Guest, who established the conjecture for almost simple linear groups., 32 pages; to appear in J. Algebra

Let $G$ be a finite simple group. By a theorem of Guralnick and Kantor, $G$ contains a conjugacy class $C$ such that for each non-identity element $x \in G$, there exists $y \in C$ with $G = \langle x,y\rangle$. Building on this deep result, we introduce a new invariant $\gamma_u(G)$, which we call the uniform domination number of $G$. This is the minimal size of a subset $S$ of conjugate elements such that for each $1 \ne x \in G$, there exists $s \in S$ with $G = \langle x, s \rangle$. (This invariant is closely related to the total domination number of the generating graph of $G$, which explains our choice of terminology.) By the result of Guralnick and Kantor, we have $\gamma_u(G) \leqslant |C|$ for some conjugacy class $C$ of $G$, and the aim of this paper is to determine close to best possible bounds on $\gamma_u(G)$ for each family of simple groups. For example, we will prove that there are infinitely many non-abelian simple groups $G$ with $\gamma_u(G) = 2$. To do this, we develop a probabilistic approach, based on fixed point ratio estimates. We also establish a connection to the theory of bases for permutation groups, which allows us to apply recent results on base sizes for primitive actions of simple groups., Comment: 35 pages; to appear in Trans. Amer. Math. Soc

The purpose of this paper is twofold: (1) we study different notions of the average distance between two points of a self-similar subset of $${\mathbb {R}}$$ , and (2) we investigate the asymptotic behaviour of higher order average moments of self-similar measures on self-similar subsets of $${\mathbb {R}}$$ .

Cyber-Physical Systems improve efficiency, accuracy, and access in systems ranging from household appliances to power stations to airplanes. They also bring new risks at the intersection of physical, information, and mission assurance. This paper presents CP-SMARTS, a framework providing a means for propagating CPS assurances from planning to deployment.

The present study investigated the extent to which maternal intrusiveness and warmth during play, observed in 579 European American, 412 African American, and 110 more and 131 less acculturated Mexican American low-income families when children were approximately 15 months old, predicted 3 dimensions of the mother-toddler relationship 10 months later. Intrusiveness predicted increases in later child negativity in all 4 groups. Among African Americans only, this association was moderated by maternal warmth. Intrusiveness predicted negative change in child engagement with mothers only in European American families. Finally, near-significant trends suggested that intrusiveness predicted later decreased dyadic mutuality in European American and more acculturated Mexican American families, but not in African American or less acculturated Mexican American families.