Relative acceptance of brodifacoum pellets and soft bait sachets by Polynesian rats (Rattus exulans) on Wake Atoll

Removing invasive rats from island ecosystems using rodenticides has proven conservation benefits and is an important management tool for conserving and restoring island ecosystems. However, rodenticide-based eradications can fail if not all rats consume enough bait to result in lethal toxicosis. A recent post-operational review of a failed attempt to eradicate rats from Wake Atoll suggested that some individuals may not have ingested a lethal dose of rodenticide due to potential dietary and/or sensory preferences developed via regular access to anthropogenic food sources. These food sources may be higher in fats and oils, possessing different sensory properties (e.g., softer, chewier, etc.) than the harder pellet formulation of the rodenticide Brodifacoum 25W Conservation (B-25W) used in the eradication attempt. To test this theory, we captured rats from two areas on Wake Island where they may have regular access to human food sources, as well as an uninhabited part of island where rats presumably have less access to human-based food sources and therefore are less likely to be preconditioned for these food types. We subjected them to a head-to-head two-choice bait selection trial between a “soft” sachet formulation of a brodifacoum-based bait, FINAL Soft Bait with Lumitrack® (FINAL), versus the harder pellet formulation of B-25W. Regardless of which habitat rats were captured in, rats overwhelmingly preferred the pellet formulation. No rats in the head-to-head trail consumed any of the FINAL bait, and 100% of the rats that consumed B-25W died. Of the rats in a separate no-choice trail of just FINAL bait, 5 failed to eat any bait; of the rats that did consume some of the FINAL bait, 80% died. Our results demonstrate that Polynesian rats on Wake Atoll do not prefer this soft formulation of brodifacoum-based rodenticide bait. Our results suggest that baiting strategies in the inhabited regions of the atoll, for a proposed eradication attempt, should continue to focus on utilizing traditional pellet formulations. While these results are unequivocal in our test case, we suggest caution in making inference to other situations where dietary preferences of local rodent populations may differ, and local environmental conditions may make other baiting choices more appropriate and efficacious

Advanced modulation technology development for earth station demodulator applications. Coded modulation system development

A jointly optimized coded modulation system is described which was designed, built, and tested by COMSAT Laboratories for NASA LeRC which provides a bandwidth efficiency of 2 bits/s/Hz at an information rate of 160 Mbit/s. A high speed rate 8/9 encoder with a Viterbi decoder and an Octal PSK modem are used to achieve this. The BER performance is approximately 1 dB from the theoretically calculated value for this system at a BER of 5 E-7 under nominal conditions. The system operates in burst mode for downlink applications and tests have demonstrated very little degradation in performance with frequency and level offset. Unique word miss rate measurements were conducted which demonstrate reliable acquisition at low values of Eb/No. Codec self tests have verified the performance of this subsystem in a stand alone mode. The codec is capable of operation at a 200 Mbit/s information rate as demonstrated using a codec test set which introduces noise digitally. The measured performance is within 0.2 dB of the computer simulated predictions. A gate array implementation of the most time critical element of the high speed Viterbi decoder was completed. This gate array add-compare-select chip significantly reduces the power consumption and improves the manufacturability of the decoder. This chip has general application in the implementation of high speed Viterbi decoders

The Influence of Alternate Life History Strategies and Natal Conditions on the Reproductive Performance of Adélie Penguins Breeding on Ross Island, Antarctica

A fundamental objective of ecology and population biology is to identify factors that drive population dynamics and determine the population-level consequences of their interaction with the environment. Studies of reproductive performance can illuminate population dynamic processes, including the links between organismal biology, the environment, and life history theory. A central tenent of life history theory is that organisms face trade-offs when partitioning limited resources among growth, maintenance, survival, and lifetime reproductive potential. For long-lived species that have multiple breeding attempts during their lifetime (i.e., iteroparous species), these trade-offs can be observed in the age-related variation in reproductive performance associated with alternate breeding strategies, namely, variation in the age first reproduction/recruitment into the breeding population and lifetime reproductive potential. Understanding the consequences of this variation can provide insights into population dynamics and life history theory and is critical to predicting how individuals and thus populations are likely to respond to anthropogenic and natural changes in their environment. In Chapter 2, I used generalized linear mixed models to disentangle population and within-individual processes influencing observed patterns in age-specific reproductive performance. I tested the following five distinct patterns in breeding success as predicted by various life history hypotheses: 1) linearly increasing with breeding experience; 2) increasing with low levels of experience to a plateau; 3)increasing with low levels of experience to a plateau or peak near optimum performance with intermediate levels of experience, then increasing again in older age classes; 4) increasing with low levels of experience to a plateau or peak near optimum performance with intermediate levels of experience, then decreasing; or (5) remains constant. Overall patterns of reproductive performance were similar at all three colonies. Regardless of recruitment age, breeding success improved with post-recruitment experience at all three colonies, reaching a maximum at intermediate experience (4-8 attempts), which occurred roughly 4 years earlier for younger recruits than for older recruits. At all three colonies, improvement in breeding success was most dramatic for the youngest recruits, while the oldest recruits showed the lowest overall improvement in breeding success with additional post-recruitment experience. Together, these results support the “constraint hypothesis” and suggest that individuals face trade-offs late in life based on recruitment decisions. When controlling for selective disappearance of lower quality phenotypes, I documented pronounced declines (i.e., senescence) in breeding success for the oldest recruitment cohorts at all three colonies. In Chapter 3 I decomposed age-related reproductive performance into its constituent processes at each colony. The selective appearance of new phenotypes contributed negatively (range: 20% - 54%) to overall age-related reproductive performance at all colonies. At the small- and medium-sized colonies improvements in age-related reproductive performance was driven by a combination of within-individual maturation (15% at both colonies) and selective disappearance (41% and 32%, respectively). At the largest colony, the majority of the improvement was due to within-individual maturation (67%). Comparisons of the relative contribution of each of the processes in early life versus late life stages at all three colonies revealed similar contributions early in life, but important differences at advanced ages. At the two smaller colonies, observed changes late in life were primarily driven by population level changes resulting from selective disappearance of individuals of lower phenotypic quality. However, at the largest colony, changes in performance were driven by a combination of decline due to within-individual maturation and the selective disappearance of individuals of higher phenotypic quality. This unexpected result may be due to a combination of potential trade-offs associated with differences between colonies of different sizes and associated differences between individual life history strategies. These results highlight the importance of accounting for the different processes contributing to reproductive performance and of incorporating replication into studies of age-related performance. In Chapter 4 I tested the prediction from the internal predictive adaptive response (internal PAR) hypothesis that individuals raised under poor natal predictions can mitigate those conditions and have equally productive reproductive life spans as individuals raised under better natal conditions. For five years, two giant icebergs substantially altered sea ice conditions throughout the annual cycle, including preferred penguin habitat, sea ice concentrations on the foraging grounds near breeding colonies, and increased the extent of fast ice near breeding colonies. As a result, 5 iceberg-affected cohorts experienced significantly reduced early-life conditions from other non-iceberg-affected cohorts. In accordance with predictions from the internal PAR hypothesis, iceberg cohorts entered the breeding population earlier, exhibited higher levels of breeding success, and had shorter lifespans than non-iceberg-affected cohorts. Non-iceberg-affected cohorts recruited to the breeding population later, never achieved levels of breeding success documented for iceberg-affected cohorts, and lived longer than icebergs cohorts. At the end of their lifespan iceberg-affected cohorts were nearly able to completely mitigate the fitness costs of poor natal conditions. These results support the internal PAR hypothesis and highlight the importance of accounting for early life conditions when studying life history strategies and population dynamics. Taken together, these results highlight the importance of long-term studies that incorporate sufficient spatial and temporal variability to understand how varying reproductive strategies drive population dynamics. Without the temporal scale of 20 years and spatial scale across three colonies, the quantitative analysis of age-related reproductive strategies (Chapter 1), the decomposition of reproductive success into constituent processes (Chapter 2), or the testing of hypotheses relating natal environment to life-time reproductive success (Chapter 3) would have been impossible. The results of these three studies will further guide and refine the next 20 years of research and contribute to our knowledge of life history theory and an ice-obligate species facing dramatic changes in sea ice conditions in the coming decades

Electromagnetic transitions of the helium atom in superstrong magnetic fields

We investigate the electromagnetic transition probabilities for the helium atom embedded in a superstrong magnetic field taking into account the finite nuclear mass. We address the regime \gamma=100-10000 a.u. studying several excited states for each symmetry, i.e. for the magnetic quantum numbers 0,-1,-2,-3, positive and negative z parity and singlet and triplet symmetry. The oscillator strengths as a function of the magnetic field, and in particular the influence of the finite nuclear mass on the oscillator strengths are shown and analyzed.Comment: 10 pages, 8 figure

Efficient Blue Phosphorescence in Gold(I)‐Acetylide Functionalized Coinage Metal Bis(amidinate) Complexes

The synthesis of linear symmetric ethynyl‐ and acetylide‐amidinates of the coinage metals is presented. Starting with the desilylation of the complexes [{Me$_{3}$SiC≡CC(NDipp)$_{2}$}$_{2}$M$_{2}$] (Dipp=2,6‐diisopropylphenyl) (M=Cu, Au) it is demonstrated that this compound class is suitable to serve as a versatile metalloligand. Deprotonation with n‐butyllithium and subsequent salt metathesis reactions yield symmetric tetranuclear gold(I) acetylide complexes of the form [{(PPh$_{3}$)AuC≡CC(NDipp)$_{2}$}$_{2}$M$_{2}$] (M=Cu, Au). The corresponding Ag complex [{(PPh$_{3}$)AuC≡CC(NDipp)$_{2}$}$_{2}$Ag$_{2}$] was obtained by a different route via metal rearrangement. All compounds show bright blue or blue‐green microsecond long phosphorescence in the solid state, hence their photophysical properties were thoroughly investigated in a temperature range of 20–295 K. Emission quantum yields of up to 41 % at room temperature were determined. Furthermore, similar emissions with quantum yields of 15 % were observed for the two most brightly luminescent complexes in thf solution

Alkali Metal Complexes of a Bis(diphenylphosphino)methane Functionalized Amidinate Ligand: Synthesis and Luminescence

A novel bis(diphenylphosphino)methane (DPPM) functionalized amidine ligand (DPPM−C(N-Dipp)$_{2}$H) (Dipp=2,6-diisopropylphenyl) was synthesized. Subsequent deprotonation with suitable alkali metal bases resulted in the corresponding complexes [M{DPPM−C(N-Dipp)$_{2}$}(Ln)] (M=Li, Na, K, Rb, Cs; L=thf, Et$_{2}$O). The alkali metal complexes form monomeric species in the solid state, exhibiting intramolecular metal-π-interactions. In addition, a caesium derivative [Cs{PPh$_{2}$CH$_{2}$-C(N-Dipp)$_{2}$}]$_{6}$ was obtained by cleavage of a diphenylphosphino moiety, forming an unusual six-membered ring structure in the solid state. All complexes were fully characterized by single crystal X-ray diffraction, NMR spectroscopy, IR spectroscopy as well as elemental analysis. Furthermore, the photoluminescent properties of the complexes were thoroughly investigated, revealing differences in emission with regards to the respective alkali metal. Interestingly, the hexanuclear [Cs{PPh$_{2}$CH$_{2}$-C(N-Dipp)$_{2}$}]$_{6}$ metallocycle exhibits a blue emission in the solid state, which is significantly red-shifted at low temperatures. The bifunctional design of the ligand, featuring orthogonal donor atoms (N vs. P) and a high steric demand, is highly promising for the construction of advanced metal and main group complexes

Relative palatability and efficacy of brodifacoum-25D conservation rodenticide pellets for mouse eradication on Midway Atoll

Invasive mice (Mus spp.) can negatively impact island species and ecosystems. Because fewer island rodent eradications have been attempted for mice compared to rats (Rattus spp.), less is known about efficacy and palatability of rodenticide baits for mouse eradications. We performed a series of bait acceptance and efficacy cage trials using a standard formulation of brodifacoum-based rodenticide on wild-caught mice from Sand Island, Midway Atoll, to help inform a proposed eradication there. Mice were offered ad libitum brodifacoum pellets along with various alternative food sources, and a “no choice” treatment group received only bait pellets. Mortality in the no choice trial was 100%; however, when offered alternative foods, mice preferred the alternative diets to the bait, leading to low mortality (40%). Because there was concern that the bittering agent Bitrex® in the formulation may have reduced palatability, we conducted a subsequent trial comparing brodifacoum bait with and without Bitrex. Mortality in the with-Bitrex treatment group was slightly higher, indicating that the bittering agent was not likely responsible for low efficacy. Laboratory trials cannot account for the numerous environmental and behavioral factors that influence bait acceptance nor replicate the true availability of alternative food sources in the environment, so low efficacy results from these trials should be interpreted cautiously and not necessarily as a measure of the likelihood of success or failure of a proposed eradication

Complementary roles of murine NaV1.7, NaV1.8 and NaV1.9 in acute itch signalling

Acute pruritus occurs in various disorders. Despite severe repercussions on quality of life treatment options remain limited. Voltage-gated sodium channels (NaV) are indispensable for transformation and propagation of sensory signals implicating them as drug targets. Here, NaV1.7, 1.8 and 1.9 were compared for their contribution to itch by analysing NaV-specific knockout mice. Acute pruritus was induced by a comprehensive panel of pruritogens (C48/80, endothelin, 5-HT, chloroquine, histamine, lysophosphatidic acid, trypsin, SLIGRL, β-alanine, BAM8-22), and scratching was assessed using a magnet-based recording technology. We report an unexpected stimulus-dependent diversity in NaV channel-mediated itch signalling. NaV1.7−/− showed substantial scratch reduction mainly towards strong pruritogens. NaV1.8−/− impaired histamine and 5-HT-induced scratching while NaV1.9 was involved in itch signalling towards 5-HT, C48/80 and SLIGRL. Furthermore, similar microfluorimetric calcium responses of sensory neurons and expression of itch-related TRP channels suggest no change in sensory transduction but in action potential transformation and conduction. The cumulative sum of scratching over all pruritogens confirmed a leading role of NaV1.7 and indicated an overall contribution of NaV1.9. Beside the proposed general role of NaV1.7 and 1.9 in itch signalling, scrutiny of time courses suggested NaV1.8 to sustain prolonged itching. Therefore, NaV1.7 and 1.9 may represent targets in pruritus therapy