Evolutionary history of Wolbachia infections in the fire ant Solenopsis invicta

BACKGROUND: Wolbachia are endosymbiotic bacteria that commonly infect numerous arthropods. Despite their broad taxonomic distribution, the transmission patterns of these bacteria within and among host species are not well understood. We sequenced a portion of the wsp gene from the Wolbachia genome infecting 138 individuals from eleven geographically distributed native populations of the fire ant Solenopsis invicta. We then compared these wsp sequence data to patterns of mitochondrial DNA (mtDNA) variation of both infected and uninfected host individuals to infer the transmission patterns of Wolbachia in S. invicta. RESULTS: Three different Wolbachia (wsp) variants occur within S. invicta, all of which are identical to previously described strains in fire ants. A comparison of the distribution of Wolbachia variants within S. invicta to a phylogeny of mtDNA haplotypes suggests S. invicta has acquired Wolbachia infections on at least three independent occasions. One common Wolbachia variant in S. invicta (wSinvictaB) is associated with two divergent mtDNA haplotype clades. Further, within each of these clades, Wolbachia-infected and uninfected individuals possess virtually identical subsets of mtDNA haplotypes, including both putative derived and ancestral mtDNA haplotypes. The same pattern also holds for wSinvictaA, where at least one and as many as three invasions into S. invicta have occurred. These data suggest that the initial invasions of Wolbachia into host ant populations may be relatively ancient and have been followed by multiple secondary losses of Wolbachia in different infected lineages over time. Finally, our data also provide additional insights into the factors responsible for previously reported variation in Wolbachia prevalence among S. invicta populations. CONCLUSION: The history of Wolbachia infections in S. invicta is rather complex and involves multiple invasions or horizontal transmission events of Wolbachia into this species. Although these Wolbachia infections apparently have been present for relatively long time periods, these data clearly indicate that Wolbachia infections frequently have been secondarily lost within different lineages. Importantly, the uncoupled transmission of the Wolbachia and mtDNA genomes suggests that the presumed effects of Wolbachia on mtDNA evolution within S. invicta are less severe than originally predicted. Thus, the common concern that use of mtDNA markers for studying the evolutionary history of insects is confounded by maternally inherited endosymbionts such as Wolbachia may be somewhat unwarranted in the case of S. invicta

Dustbuster: a compact impact-ionization time-of-flight mass spectrometer for in situ analysis of cosmic dust

We report on the design and testing of a compact impact-ionization time-of-flight mass spectrometer for analysis of cosmic dust, suitable for use on deep space missions. The instrument, Dustbuster, incorporates a large target area with a reflectron, simultaneously optimizing mass resolution, particle detection, and ion collection. Dust particles hit the 65-cm2 target plate and are partially ionized by the impact. The resulting ions, with broad energy and angular distributions, are accelerated through a modified reflectron, focusing ions of specific m/z in space and time to produce high-resolution mass spectra. The cylindrically symmetric instrument is 10 cm in diameter and 20 cm in length, considerably smaller than previous in situ dust analyzers, and can be easily scaled as needed for specific mission requirements. Laser desorption ionization of metal and mineral samples embedded in the impact plate simulated particle impacts for evaluations of instrument performance. Mass resolution in these experiments ranged from 60–180, permitting resolution of isotopes. The mass spectrometer can be combined with other instrument components to determine dust particle trajectories and sizes

Collective Bargaining Agreements, Arbitration Provisions and Employment Discrimination Claims: Compulsory Arbitration or Judicial Remedy - Johnson v. Bodine Electric Co.

This casenote addresses the effect of mandatory arbitration provisions in collective bargaining agreements (CBA) upon statutory anti-discrimination claims. Disputes in this area arise when an employee joins a union, thus becoming subject to a CBA negotiated between the union and the employees. What often happens is that the CBA will generally contain a clause calling for arbitration of all claims arising under the agreement. Later, if the employee believes he has been subjected to discriminatory practices on the part of the employer and seeks remedies under anti-discrimination laws, such as Title VII, the employer will move to compel arbitration. The issue in such cases is whether an employee loses the right to pursue a judicial remedy by joining a union governed by a CBA

Non-Union Member Complaints to Calculation of Agency Shop Fees: Arbitration or Judicial Relief - Air Line Pilots Ass\u27n v. Miller

Free rider problems plague any group or association that provides general benefits for its participants. Members may pay a fee, but nonmembers can reap the benefits without expenditure. Labor unions address this disparity through the use of agency shop fees contained in collective bargaining agreements. These fee agreements call for those employees who choose not to join the union to pay their share of the costs of collective bargaining. Labor unions have developed extensive mechanisms in order to calculate the amount of the fee. Employees, who do not want to subsidize activities they do not support, can file complaints with the union to protest the calculation and collection of the agency fee. In order to protect the interests of the objecting nonmember, the United States Supreme Court ordered unions to develop internal remedies, usually in the form of arbitration, to address these complaints. This Casenote addresses the effect of a union\u27s arbitration remedy for agency fee complaints on an employee\u27s right to pursue judicial remedies of his claim. The union argues that if it must develop the internal remedy, it should be allowed to insist that workers pursue it before seeking a judicial remedy. Prior to the instant decision, the Supreme Court had not taken up the issue. However, six federal circuits have addressed this question. Four circuits held that workers were not required to pursue the union remedy first.\u27 Two circuits sided with the union and required exhaustion of the union\u27s remedy before pursuit in court.\u27 Certiorari was granted in this case to provide a definitive answer to this issue

From AMANDA to IceCube

The first string of the neoteric high energy neutrino telescope IceCube successfully began operating in January 2005. It is anticipated that upon completion the new detector will vastly increase the sensitivity and extend the reach of AMANDA to higher energies. A discussion of the IceCube's discovery potential for extra-terrestrial neutrinos, together with the prospects of new physics derived from the ongoing AMANDA research will be the focus of this paper. Preliminary results of the first antarctic high energy neutrino telescope AMANDA searching in the muon neutrino channel for localized and diffuse excess of extra-terrestrial neutrinos will be reviewed using data collected between 2000 and 2003. Neutrino flux limits obtained with the all-flavor dedicated UHE and cascade analyses will be described. A first neutrino spectrum above one TeV in agreement with atmospheric neutrino flux expectations and no extra-terrestrial contribution will be presented, followed by a discussion of a limit for neutralino CDM candidates annihilating in the center of the Sun.Comment: 15 pages, 8 figures Invited talk contribution at 5th International Conference on Non-accelerator New Physics (NANP 05), Dubna, Russia, 20-25 Jun 200

Fabrication of X-Graded H13 and Cu Powder Mix Using High Power Pulsed Nd:YAG Laser

The manufacturing of Functionally Graded Material (FGM) parts using Solid Free Form manufacturing technologies has been carried out since early 1980. At present, most of the powder manufacturing techniques are being focused on layering powder with different powder blend compositions with Z gradients (graded in direction of layer build). Although, there are a few researchers working on multi powder feeder and deposition system, the study of laser fusion of the deposited powder (by a powder deposition system) is minimum or not known to date. Consequently, the manufacturing of functionally graded structures is still geometry limited. This work was focused on the manufacturing of X-graded (graded along the powder bed plane) specimens with H13 tool steel and Cu mix. Five bimodal powder blends were used with a multi-container feed hopper to spread powder layers for the selective laser fusion of the powder. The powder was fused using a high power Nd:YAG pulsed laser using a specific scanning strategy to reduce porosity. Specimens were produced with graded Cu within the H13 matrix. The specimens were analysed for dimensional accuracy, microstructure, porosity, cracks and micro hardness of the FGM.Mechanical Engineerin

Extended Initiality for Typed Abstract Syntax

Initial Semantics aims at interpreting the syntax associated to a signature as the initial object of some category of 'models', yielding induction and recursion principles for abstract syntax. Zsid\'o proves an initiality result for simply-typed syntax: given a signature S, the abstract syntax associated to S constitutes the initial object in a category of models of S in monads. However, the iteration principle her theorem provides only accounts for translations between two languages over a fixed set of object types. We generalize Zsid\'o's notion of model such that object types may vary, yielding a larger category, while preserving initiality of the syntax therein. Thus we obtain an extended initiality theorem for typed abstract syntax, in which translations between terms over different types can be specified via the associated category-theoretic iteration operator as an initial morphism. Our definitions ensure that translations specified via initiality are type-safe, i.e. compatible with the typing in the source and target language in the obvious sense. Our main example is given via the propositions-as-types paradigm: we specify propositions and inference rules of classical and intuitionistic propositional logics through their respective typed signatures. Afterwards we use the category--theoretic iteration operator to specify a double negation translation from the former to the latter. A second example is given by the signature of PCF. For this particular case, we formalize the theorem in the proof assistant Coq. Afterwards we specify, via the category-theoretic iteration operator, translations from PCF to the untyped lambda calculus

Critical behavior of the Random-Field Ising model at and beyond the Upper Critical Dimension

The disorder-driven phase transition of the RFIM is observed using exact ground-state computer simulations for hyper cubic lattices in d=5,6,7 dimensions. Finite-size scaling analyses are used to calculate the critical point and the critical exponents of the specific heat, magnetization, susceptibility and of the correlation length. For dimensions d=6,7 which are larger or equal to the assumed upper critical dimension, d_u=6, mean-field behaviour is found, i.e. alpha=0, beta=1/2, gamma=1, nu=1/2. For the analysis of the numerical data, it appears to be necessary to include recently proposed corrections to scaling at and beyond the upper critical dimension.Comment: 8 pages and 13 figures; A consise summary of this work can be found in the papercore database at http://www.papercore.org/Ahrens201