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L Hu, R R Balusu, W-Q Zhang, O S Ajayi, Y-Y Lu, R-S Zeng, H Y Fadamiro, L Chen
Some fire ants of the genus Solenopsis have become invasive species in the southern United States displacing native species by competition. Although the displacement pattern seems clear, the mechanisms underlying competitive advantage remain unclear. The ability of ant workers to produce relatively larger amount of alarm pheromone may correspond to relative greater fitness among sympatric fire ant species. Here we report on quantitative intra-specific (i.e. inter-caste) and inter-specific differences of alarm pheromone component, 2-ethyl-3,6-dimethylpyrazine (2E36DMP), for several fire ant species...
December 10, 2017: Bulletin of Entomological Research
Agnès Gillibert
Every year, hundreds of volunteers leave their home, for few weeks or months, to provide humanitarian aid across the world. Joining a humanitarian mission, far from being a simple exotic adventure, requires, specially, a strong professional skills and personal abilities, maturely and thoughtful motivations. The work of humanitarian nurse is first and foremost a full-blown profession.
December 2017: Soins; la Revue de Référence Infirmière
A Ibañez-Justicia, A Gloria-Soria, W den Hartog, M Dik, F Jacobs, A Stroo
BACKGROUND: Air-borne introduction of exotic mosquitoes to Schiphol airport in the Netherlands has been considered plausible based upon findings of mosquitoes in aircraft cabins during 2008, 2010 and 2011. Beginning in 2013, surveillance efforts at Schiphol had focused on promptly detecting accidental introductions at the airport facilities in order to quickly react and avoid temporary proliferation or establishment of mosquito populations, identify the origin of the introductions, and avoid potential transmission of vector-borne diseases...
December 8, 2017: Parasites & Vectors
J Pérez-Rodríguez, V Martínez-Blay, A Soto, J Selfa, C Monzó, A Urbaneja, A Tena
Delottococcus aberiae De Lotto (Hemiptera: Pseudococcidae) is the latest exotic mealybug species introduced in citrus in the Mediterranean basin. It causes severe distortion and size reduction on developing fruits. Due to its first interaction with citrus, D. aberiae economic thresholds are still unknown for this crop and the current Integrated Pest Management programs have been disrupted. The objectives of this study were to determine the aggregation patterns of D. aberiae in citrus, develop an efficient sampling plan to assess its population density, and calculate its Economic and Economic Environmental Injury Levels (EIL and EEIL, respectively)...
December 5, 2017: Journal of Economic Entomology
Rachel E Mallinger, Hannah R Gaines-Day, Claudio Gratton
Managed bees are critical for crop pollination worldwide. As the demand for pollinator-dependent crops increases, so does the use of managed bees. Concern has arisen that managed bees may have unintended negative impacts on native wild bees, which are important pollinators in both agricultural and natural ecosystems. The goal of this study was to synthesize the literature documenting the effects of managed honey bees and bumble bees on wild bees in three areas: (1) competition for floral and nesting resources, (2) indirect effects via changes in plant communities, including the spread of exotic plants and decline of native plants, and (3) transmission of pathogens...
2017: PloS One
Toshihiro Sato, Martin Hohenadler, Fakher F Assaad
We consider a model of Dirac fermions in 2+1 dimensions with dynamically generated, anticommuting SO(3) Néel and Z_{2} Kekulé mass terms that permits sign-free quantum Monte Carlo simulations. The phase diagram is obtained from finite-size scaling and includes a direct and continuous transition between the Néel and Kekulé phases. The fermions remain gapped across the transition, and our data support an emergent SO(4) symmetry unifying the two order parameters. While the bare symmetries of our model do not allow for spinon-carrying Z_{3} vortices in the Kekulé mass, the emergent SO(4) invariance permits an interpretation of the transition in terms of deconfined quantum criticality...
November 10, 2017: Physical Review Letters
H Suzuki, L Sinclair, P-A Söderström, G Lorusso, P Davies, L S Ferreira, E Maglione, R Wadsworth, J Wu, Z Y Xu, S Nishimura, P Doornenbal, D S Ahn, F Browne, N Fukuda, N Inabe, T Kubo, D Lubos, Z Patel, S Rice, Y Shimizu, H Takeda, H Baba, A Estrade, Y Fang, J Henderson, T Isobe, D Jenkins, S Kubono, Z Li, I Nishizuka, H Sakurai, P Schury, T Sumikama, H Watanabe, V Werner
In this Letter, the observation of two previously unknown isotopes is presented for the first time: ^{72}Rb with 14 observed events and ^{77}Zr with one observed event. From the nonobservation of the less proton-rich nucleus ^{73}Rb, we derive an upper limit for the ground-state half-life of 81 ns, consistent with the previous upper limit of 30 ns. For ^{72}Rb, we have measured a half-life of 103(22) ns. This observation of a relatively long-lived odd-odd nucleus, ^{72}Rb, with a less exotic odd-even neighbor, ^{73}Rb, being unbound shows the diffuseness of the proton drip line and the possibility of sandbanks to exist beyond it...
November 10, 2017: Physical Review Letters
A Welker, N A S Althubiti, D Atanasov, K Blaum, T E Cocolios, F Herfurth, S Kreim, D Lunney, V Manea, M Mougeot, D Neidherr, F Nowacki, A Poves, M Rosenbusch, L Schweikhard, F Wienholtz, R N Wolf, K Zuber
The masses of the neutron-rich copper isotopes ^{75-79}Cu are determined using the precision mass spectrometer ISOLTRAP at the CERN-ISOLDE facility. The trend from the new data differs significantly from that of previous results, offering a first accurate view of the mass surface adjacent to the Z=28, N=50 nuclide ^{78}Ni and supporting a doubly magic character. The new masses compare very well with large-scale shell-model calculations that predict shape coexistence in a doubly magic ^{78}Ni and a new island of inversion for Z<28...
November 10, 2017: Physical Review Letters
Hao Zheng, Guoqing Chang, Shin-Ming Huang, Cheng Guo, Xiao Zhang, Songtian Zhang, Jiaxin Yin, Su-Yang Xu, Ilya Belopolski, Nasser Alidoust, Daniel S Sanchez, Guang Bian, Tay-Rong Chang, Titus Neupert, Horng-Tay Jeng, Shuang Jia, Hsin Lin, M Zahid Hasan
The first Weyl semimetal was recently discovered in the NbP class of compounds. Although the topology of these novel materials has been identified, the surface properties are not yet fully understood. By means of scanning tunneling spectroscopy, we find that NbP's (001) surface hosts a pair of Dirac cones protected by mirror symmetry. Through our high-resolution spectroscopic measurements, we resolve the quantum interference patterns arising from these novel Dirac fermions and reveal their electronic structure, including the linear dispersions...
November 10, 2017: Physical Review Letters
Marek Karliner, Jonathan L Rosner
Recently, the LHCb Collaboration discovered the first doubly charmed baryon Ξ_{cc}^{++}=ccu at 3621.40±0.78  MeV, very close to our theoretical prediction. We use the same methods to predict a doubly bottom tetraquark T(bbu[over ¯]d[over ¯]) with J^{P}=1^{+} at 10 389±12  MeV, 215 MeV below the B^{-}B[over ¯]^{*0} threshold and 170 MeV below the threshold for decay to B^{-}B[over ¯]^{0}γ. The T(bbu[over ¯]d[over ¯]) is therefore stable under strong and electromagnetic interactions and can only decay weakly, the first exotic hadron with such a property...
November 17, 2017: Physical Review Letters
Perttu J J Luukko, Jan-Michael Rost
Trilobites are exotic giant dimers with enormous dipole moments. They consist of a Rydberg atom and a distant ground-state atom bound together by short-range electron-neutral attraction. We show that highly polar, polyatomic trilobite states unexpectedly persist and thrive in a dense ultracold gas of randomly positioned atoms. This is caused by perturbation-induced quantum scarring and the localization of electron density on randomly occurring atom clusters. At certain densities these states also mix with an s state, overcoming selection rules that hinder the photoassociation of ordinary trilobites...
November 17, 2017: Physical Review Letters
Guoqing Chang, Su-Yang Xu, Benjamin J Wieder, Daniel S Sanchez, Shin-Ming Huang, Ilya Belopolski, Tay-Rong Chang, Songtian Zhang, Arun Bansil, Hsin Lin, M Zahid Hasan
The theoretical proposal of chiral fermions in topological semimetals has led to a significant effort towards their experimental realization. In particular, the Fermi surfaces of chiral semimetals carry quantized Chern numbers, making them an attractive platform for the observation of exotic transport and optical phenomena. While the simplest example of a chiral fermion in condensed matter is a conventional |C|=1 Weyl fermion, recent theoretical works have proposed a number of unconventional chiral fermions beyond the standard model which are protected by unique combinations of topology and crystalline symmetries...
November 17, 2017: Physical Review Letters
Peizhe Tang, Quan Zhou, Shou-Cheng Zhang
Exotic massless fermionic excitations with nonzero Berry flux, other than the Dirac and Weyl fermions, could exist in condensed matter systems under the protection of crystalline symmetries, such as spin-1 excitations with threefold degeneracy and spin-3/2 Rarita-Schwinger-Weyl fermions. Herein, by using the ab initio density functional theory, we show that these unconventional quasiparticles coexist with type-I and type-II Weyl fermions in a family of transition metal silicides, including CoSi, RhSi, RhGe, and CoGe, when spin-orbit coupling is considered...
November 17, 2017: Physical Review Letters
Shao-Kai Jian, Hong Yao
Many aspects of many-body localization (MBL) transitions remain elusive so far. Here, we propose a higher-dimensional generalization of the Sachdev-Ye-Kitaev (SYK) model and show that it exhibits a MBL transition. The model on a bipartite lattice has N Majorana fermions with SYK interactions on each site of the A sublattice and M free Majorana fermions on each site of the B sublattice, where N and M are large and finite. For r≡M/N<r_{c}=1, it describes a diffusive metal exhibiting maximal chaos. Remarkably, its diffusive constant D vanishes [D∝(r_{c}-r)^{1/2}] as r→r_{c}, implying a dynamical transition to a MBL phase...
November 17, 2017: Physical Review Letters
Dinh Loc Duong, Seok Joon Yun, Young Hee Lee
Since graphene became available by a scotch tape, a vast class of two-dimensional (2D) van der Waals (vdW) layered materials has been researched intensively. What is more intriguing is that the well-known physics and chemistry of three-dimensional bulk materials are often irrelevant, revealing exotic phenomena in 2D vdW materials. By further constructing heterostructures of these materials in the planar and vertical directions, which can be easily achieved via simple exfoliation techniques, numerous quantum mechanical devices have been demonstrated for fundamental research and technological applications...
December 8, 2017: ACS Nano
Enid Van Nieuwenhuyse, Gunnar Seemann, Alexander V Panfilov, Nele Vandersickel
Early Afterdepolarizations, EADs, are defined as the reversal of the action potential before completion of the repolarization phase, which can result in ectopic beats. However, the series of mechanisms of EADs leading to these ectopic beats and related cardiac arrhythmias are not well understood. Therefore, we aimed to investigate the influence of this single cell behavior on the whole heart level. For this study we used a modified version of the Ten Tusscher-Panfilov model of human ventricular cells (TP06) which we implemented in a 3D ventricle model including realistic fiber orientations...
2017: PloS One
Tadeusz F Molinski
This review discusses the chemistry of cyclic azole-homologated peptides (AHPs) from the marine sponges, Theonella swinhoei, other Theonella species, Calyx spp. and Plakina jamaicensis. The origin, distribution of AHPs and molecular structure elucidations of AHPs are described followed by their biosynthesis, bioactivity, and synthetic efforts towards their total synthesis. Reports of partial and total synthesis of AHPs extend beyond peptide coupling reactions and include creative construction of the non-proteinogenic amino acid components, mainly the homologated heteroaromatic and α-keto-β-amino acids...
December 6, 2017: Organic & Biomolecular Chemistry
Fangfang Huang, Richard Lankau, Shaolin Peng
Coevolution can promote long-term coexistence of two competing species if selection acts to reduce the fitness inequality between competitors and/or strengthen negative frequency dependence within each population. However, clear coevolution between plant competitors has been rarely documented. Plant invasions offer opportunities to capture the process of coevolution. Here we investigated how the developing relationship between an invasive forb, Alliaria petiolata, and a native competitor, Pilea pumila, may affect their long-term coexistence, by testing the competitive effects of populations of varying lengths of co-occurrence on each other across a chronosequence of invasion history...
December 4, 2017: New Phytologist
Rajib Biswas, Biman Bagchi
In nature, water is often found in contact with surfaces that are extended on the scale of molecule size but small on a macroscopic scale. Examples include lipid bilayers and reverse micelles as well as biomolecules like proteins, DNA and zeolites, to name a few. While the presence of surfaces and interfaces interrupts the continuous hydrogen bond network of liquid water, confinement on a mesoscopic scale introduces new features. Even when extended on a molecular scale, natural and biological surfaces often have features (like charge, hydrophobicity) that vary on the scale of the molecular diameter of water...
December 5, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
David Wragg, Maéva Angélique Techer, Kamila Canale-Tabet, Benjamin Basso, Jean-Pierre Bidanel, Emmanuelle Labarthe, Olivier Bouchez, Yves Le Conte, Johanna Clémencet, Hélène Delatte, Alain Vignal
The honeybee population of the tropical Reunion Island is a genetic admixture of the Apis mellifera unicolor subspecies, originally described in Madagascar, and of European subspecies, mainly A.m. carnica and A. m. ligustica, regularly imported to the island since the late 19th century. We took advantage of this population to study genetic admixing of the tropical-adapted indigenous and temperate-adapted European genetic backgrounds. Whole genome sequencing of 30 workers and 6 males from Reunion, compared to samples from Europe, Madagascar, Mauritius, Rodrigues and the Seychelles, revealed the Reunion honeybee population to be composed on average of 53...
November 29, 2017: Genome Biology and Evolution
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