979 research outputs found
Insecticide Resistance in the Bed Bug Comes with a Cost
Adaptation to new environmental stress is often associated with an alteration of one or more life history parameters. Insecticide resistant populations of insects often have reduced fitness relative to susceptible populations in insecticide free environments. Our previous work showed that three populations of bed bugs, Cimex lectularius L., evolved significantly increased levels of resistance to one product containing both β-cyfluthrin and imidacloprid insecticides with only one generation of selection, which gave us an opportunity to explore potential tradeoffs between life history parameters and resistance using susceptible and resistant strains of the same populations. Life history tables were compiled by collecting weekly data on mortality and fecundity of bugs from each strain and treatment throughout their lives. Selection led to a male-biased sex ratio, shortened oviposition period, and decreased life-time reproductive rate. Generation time was shortened by selection, a change that represents a benefit rather than a cost. Using these life history characteristics we calculated that there would be a 90% return to pre-selection levels of susceptibility within 2- 6.5 generations depending on strain. The significant fitness costs associated with resistance suggest that insecticide rotation or utilization of non-insecticidal control tactics could be part of an effective resistance management strategy
Microfabricated Surfaces for the Physical Capture of Insects
Novel devices and methods of capturing, controlling and preventing infestation of insects using microfabricated surfaces are provided. In particular, a mechanism of insect capture inspired by the microstructures of the leaf surfaces of plants and the key features of those surfaces with respect to the capture and control of pests have been determined and engineered into a variety of microfabricated surfaces capable of reproducing the effectiveness of these physical capture methods
Microfabricated Sufaces for the Physical Capture of Insects
Novel devices and methods of capturing, controlling and preventing infestation of insects using microfabricated surfaces are provided. In particular, a mechanism of insect capture inspired by the microstructures of the leaf surfaces of plants and the key features of those surfaces with respect to the capture and control of pests have been determined and engineered into a variety of microfabricated surfaces capable of reproducing the effectiveness of these physical capture methods
Population Variation In and Selection For Resistance to Pyrethroid-Neonicotinoid Insecticides in the Bed Bug
Pyrethroid resistance in bed bugs, Cimex lectularius, has prompted a change to combination products that include a pyrethroid and a neonicotinoid. Ten populations of bed bugs were challenged with two combination products (Temprid SC and Transport GHP). Susceptibility of these populations varied, with the correlated response of the two products indicating cross resistance. We imposed selection on three populations using label rate Temprid, and then reared progeny from unselected and selected strains. All selected strains were significantly less susceptible to Temprid SC than unselected strains. Temprid selected strains were also less susceptible to Transport. The pyrethroid component of Temprid showed a significantly higher LD50 in selected strains, but susceptibility to the neonicotinoid remained unchanged. Taken together these results indicate resistance to combination insecticides is present in field populations at levels that should be of concern, and that short-term selection affecting existing variance in susceptibility can quickly increase resistance
The Impact of Program Context on Motivational System Activation and Subsequent Effects on Processing a Fear Appeal
This manuscript reports three experiments investigating the impact of television programming context on the processing of a fear-appeal message. This is done using a dual-motivation system theory conceptualizing emotion as arising from activation of the appetitive and/or aversive motivational systems. Results show that, as predicted, sad programming activates viewers\u27 aversive motivational systems, whereas comedic programming activates their appetitive motivational systems. Furthermore, by activating these systems through programming context, we were able to predict both retrospective self-report and real-time physiological reactions to a persuasive message employing a fear-appeal strategy. Theoretical and practical implications are discussed, as are suggestions for future experiments using the dual-motivation approach
Uncoupled evolution of the Polycomb system and deep origin of non-canonical PRC1
Polycomb group proteins, as part of the Polycomb repressive complexes, are essential in gene repression through chromatin compaction by canonical PRC1, mono-ubiquitylation of histone H2A by non-canonical PRC1 and tri-methylation of histone H3K27 by PRC2. Despite prevalent models emphasizing tight functional coupling between PRC1 and PRC2, it remains unclear whether this paradigm indeed reflects the evolution and functioning of these complexes. Here, we conduct a comprehensive analysis of the presence or absence of cPRC1, nPRC1 and PRC2 across the entire eukaryotic tree of life, and find that both complexes were present in the Last Eukaryotic Common Ancestor (LECA). Strikingly, ~42% of organisms contain only PRC1 or PRC2, showing that their evolution since LECA is largely uncoupled. The identification of ncPRC1-defining subunits in unicellular relatives of animals and fungi suggests ncPRC1 originated before cPRC1, and we propose a scenario for the evolution of cPRC1 from ncPRC1. Together, our results suggest that crosstalk between these complexes is a secondary development in evolution.</p
Uncoupled evolution of the Polycomb system and deep origin of non-canonical PRC1
Polycomb group proteins, as part of the Polycomb repressive complexes, are essential in gene repression through chromatin compaction by canonical PRC1, mono-ubiquitylation of histone H2A by non-canonical PRC1 and tri-methylation of histone H3K27 by PRC2. Despite prevalent models emphasizing tight functional coupling between PRC1 and PRC2, it remains unclear whether this paradigm indeed reflects the evolution and functioning of these complexes. Here, we conduct a comprehensive analysis of the presence or absence of cPRC1, nPRC1 and PRC2 across the entire eukaryotic tree of life, and find that both complexes were present in the Last Eukaryotic Common Ancestor (LECA). Strikingly, ~42% of organisms contain only PRC1 or PRC2, showing that their evolution since LECA is largely uncoupled. The identification of ncPRC1-defining subunits in unicellular relatives of animals and fungi suggests ncPRC1 originated before cPRC1, and we propose a scenario for the evolution of cPRC1 from ncPRC1. Together, our results suggest that crosstalk between these complexes is a secondary development in evolution
Thermodynamics of statistically interacting quantum gas in D dimensions
We present the exact thermodynamics (isochores, isotherms, isobars, response
functions) of a statistically interacting quantum gas in D dimensions. The
results in D=1 are those of the thermodynamic Bethe ansatz for the nonlinear
Schroedinger model, a gas with repulsive two-body contact potential. In all
dimensions the ideal boson and fermion gases are recovered in the weak-coupling
and strong-coupling limits, respectively. For all nonzero couplings ideal
fermion gas behavior emerges for D>>1 and, in the limit D->infinity, a phase
transition occurs at T>0. Significant deviations from ideal quantum gas
behavior are found for intermediate coupling and finite D.Comment: 12 pages and 19 figure
Hubble Space Telescope NICMOS Observations of T Dwarfs: Brown Dwarf Multiplicity and New Probes of the L/T Transition
We present the results of a Hubble Space Telescope NICMOS imaging survey of
22 T-type field brown dwarfs. Five are resolved as binary systems with angular
separations of 0"05-0"35, and companionship is established on the basis of
component F110W-F170M colors (indicative of CH4 absorption) and low
probabilities of background contamination. Prior ground-based observations show
2MASS 1553+1532AB to be a common proper motion binary. The properties of these
systems - low multiplicity fraction (11[+7][-3]% resolved, as corrected for
sample selection baises), close projected separations (a = 1.8-5.0 AU) and
near-unity mass ratios - are consistent with previous results for field brown
dwarf binaries. Three of the binaries have components that span the
poorly-understood transition between L dwarfs and T dwarfs. Spectral
decomposition analysis of one of these, SDSS 1021-0304AB, reveals a peculiar
flux reversal between its components, as its T5 secondary is ~30% brighter at
1.05 and 1.27 micron than its T1 primary. This system, 2MASS 0518-2828AB and
SDSS 1534+1615AB all demonstrate that the J-band brightening observed between
late-type L to mid-type T dwarfs is an intrinsic feature of this spectral
transition, albeit less pronounced than previously surmised. We also find that
the resolved binary fraction of L7 to T3.5 dwarfs is twice that of other L and
T dwarfs, an anomaly that can be explained by a relatively rapid evolution of
brown dwarfs through the L/T transition, perhaps driven by dynamic
(nonequilibrium) depletion of photospheric condensates.Comment: ~40 pages, 17 figures, accepted for publication to ApJ. Note that
emulateapj style file cuts off part of Table
A Survey for Circumstellar Disks Around Young Substellar Objects
(Abridged) We have completed the first systematic survey for disks around
spectroscopically identified young brown dwarfs and very low mass stars. We
have obtained L'-band (3.8 um) imaging for 38 very cool objects in IC 348 and
Taurus. Our targets span spectral types from M6 to M9.5 (~100 to ~15 Mjup).
Using the objects' measured spectral types and extinctions, we find that most
of our sample (77%+/-15%) possess intrinsic IR excesses, indicative of disks.
Because the excesses are modest, conventional analyses using only IR colors
would have missed most of the sources with excesses. The observed IR excesses
are correlated with Halpha emission, consistent with a common accretion disk
origin. The excesses can be explained by disk reprocessing of starlight alone;
the implied accretion rates are at least an order of magnitude below typical
values for classical T Tauri stars. The observed distribution of IR excesses
suggests the presence of inner disk holes. The disk frequency appears to be
independent of the mass and age. In the same star-forming regions, disks around
brown dwarfs are at least as long-lived (~3 Myr) as disks around the T Tauri
stars. Altogether, the frequency and properties of young circumstellar disks
appear to be similar from the stellar regime down to the substellar and
planetary-mass regime. This provides prima facie evidence of a common origin
for most stars and brown dwarfs.Comment: ApJ, in press, 28 pages. Minor change to the online, abridged version
of the abstract. No change to the actual pape
- …