Aging and the Law

https://digitalcommons.nyls.edu/fac_books/1138/thumbnail.jp

So near and yet so far: Harmonic radar reveals reduced homing ability of nosema infected honeybees

Pathogens may gain a fitness advantage through manipulation of the behaviour of their hosts. Likewise, host behavioural changes can be a defence mechanism, counteracting the impact of pathogens on host fitness. We apply harmonic radar technology to characterize the impact of an emerging pathogen - Nosema ceranae (Microsporidia) - on honeybee (Apis mellifera) flight and orientation performance in the field. Honeybees are the most important commercial pollinators. Emerging diseases have been proposed to play a prominent role in colony decline, partly through sub-lethal behavioural manipulation of their hosts. We found that homing success was significantly reduced in diseased (65.8%) versus healthy foragers (92.5%). Although lost bees had significantly reduced continuous flight times and prolonged resting times, other flight characteristics and navigational abilities showed no significant difference between infected and non-infected bees. Our results suggest that infected bees express normal flight characteristics but are constrained in their homing ability, potentially compromising the colony by reducing its resource inputs, but also counteracting the intra-colony spread of infection. We provide the first high-resolution analysis of sub-lethal effects of an emerging disease on insect flight behaviour. The potential causes and the implications for both host and parasite are discussed

So near and yet so far: Harmonic radar reveals reduced homing ability of nosema infected honeybees

Pathogens may gain a fitness advantage through manipulation of the behaviour of their hosts. Likewise, host behavioural changes can be a defence mechanism, counteracting the impact of pathogens on host fitness. We apply harmonic radar technology to characterize the impact of an emerging pathogen - Nosema ceranae (Microsporidia) - on honeybee (Apis mellifera) flight and orientation performance in the field. Honeybees are the most important commercial pollinators. Emerging diseases have been proposed to play a prominent role in colony decline, partly through sub-lethal behavioural manipulation of their hosts. We found that homing success was significantly reduced in diseased (65.8%) versus healthy foragers (92.5%). Although lost bees had significantly reduced continuous flight times and prolonged resting times, other flight characteristics and navigational abilities showed no significant difference between infected and non-infected bees. Our results suggest that infected bees express normal flight characteristics but are constrained in their homing ability, potentially compromising the colony by reducing its resource inputs, but also counteracting the intra-colony spread of infection. We provide the first high-resolution analysis of sub-lethal effects of an emerging disease on insect flight behaviour. The potential causes and the implications for both host and parasite are discussed

Examining the Effects of Monomer and Catalyst Structure on the Mechanism of Ruthenium-Catalyzed Ring-Opening Metathesis Polymerization

The mechanism of Ru-catalyzed ring-opening metathesis polymerization (ROMP) is studied in detail using a pair of third generation ruthenium catalysts with varying sterics of the N-heterocyclic carbene (NHC) ligand. Experimental evidence for polymer chelation to the Ru center is presented in support of a monomer-dependent mechanism for polymerization of norbornene monomers using these fast-initiating catalysts. A series of kinetic experiments, including rate measurements for ROMP, rate measurements for initiation, monomer-dependent kinetic isotope effects, and activation parameters were useful for distinguishing chelating and nonchelating monomers and determining the effect of chelation on the polymerization mechanism. The formation of a chelated metallacycle is enforced by both the steric bulk of the NHC and by the geometry of the monomer, leading to a ground-state stabilization that slows the rate of polymerization and also alters the reactivity of the propagating Ru center toward different monomers in copolymerizations. The results presented here add to the body of mechanistic work for olefin metathesis and may inform the continued design of catalysts for ROMP to access new polymer architectures and materials

Diffractive imaging of dissociation and ground state dynamics in a complex molecule

We have investigated the structural dynamics in photoexcited 1,2-diiodotetrafluoroethane molecules (C2F4I2) in the gas phase experimentally using ultrafast electron diffraction and theoretically using FOMO-CASCI excited state dynamics simulations. The molecules are excited by an ultra-violet femtosecond laser pulse to a state characterized by a transition from the iodine 5p orbital to a mixed 5p|| hole and CF2 antibonding orbital, which results in the cleavage of one of the carbon-iodine bonds. We have observed, with sub-Angstrom resolution, the motion of the nuclear wavepacket of the dissociating iodine atom followed by coherent vibrations in the electronic ground state of the C2F4I radical. The radical reaches a stable classical (non-bridged) structure in less than 200 fs.Comment: 13 pages, 11 figure

Surface modification to improve in vitro attachment and proliferation of human urinary tract cells

To evaluate the attachment and proliferation of cultured human urinary tract cells to culture plates surface-modified by photochemical immobilization of extracellular matrix (ECM) proteins. MATERIALS AND METHODS Human uroepithelial (UEC) and smooth muscle (SMC) cells were harvested from ureter and expanded in culture; 24-well culture plates surface-modified by photochemical covalent immobilization of ECM proteins were then seeded with UEC or SMC. To characterize cellular attachment, cells were incubated on surface-modified plates for 30 and 90 min. For proliferation assays the cells were incubated for 3 12 days. Standard tissue culture plates with no surface modification and sham-modified plates served as controls. Differential attachment and proliferation on the various surfaces were assessed using analysis of variance with Fisher's posthoc test for multiple comparisons. RESULTS Attachment at 30 and 90 min of both UEC and SMC on plates surface-modified with ECM proteins was significantly greater than in control plates. Surface-modification with collagen resulted in significantly greater cellular attachment than with either laminin or fibronectin. UEC proliferation was also significantly greater than in control plates by surface-modification with collagen and fibronectin, but not with laminin. SMC proliferation was significantly better after surface modification than on sham- modified plates, but was no better than standard plates. CONCLUSIONS Covalent photochemical immobilization of ECM proteins to potential growth surfaces enhances the attachment of cultured UEC and SMC and the proliferation of UEC. This technique might be useful in modifying surface properties of synthetic polymer-based materials in a controlled and defined manner, giving them the capacity to promote and sustain the growth of urinary tract cells. This may lead to development of alternative methods of tissue engineering in the urinary tract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73750/1/j.1464-410X.2003.04418.x.pd

A Spitzer IRAC Census of the Asymptotic Giant Branch Populations in Local Group Dwarfs. II. IC 1613

We present Spitzer Space Telescope IRAC photometry of the Local Group dwarf irregular galaxy IC 1613. We compare our 3.6, 4.5, 5.8, and 8.0 micron photometry with broadband optical photometry and find that the optical data do not detect 43% and misidentify an additional 11% of the total AGB population, likely because of extinction caused by circumstellar material. Further, we find that a narrowband optical carbon star study of IC 1613 detects 50% of the total AGB population and only considers 18% of this population in calculating the carbon to M-type AGB ratio. We derive an integrated mass-loss rate from the AGB stars of 0.2-1.0 x 10^(-3) solar masses per year and find that the distribution of bolometric luminosities and mass-loss rates are consistent with those for other nearby metal-poor galaxies. Both the optical completeness fractions and mass-loss rates in IC 1613 are very similar to those in the Local Group dwarf irregular, WLM, which is expected given their similar characteristics and evolutionary histories.Comment: Accepted by ApJ, 26 pages, 10 figures, version with high-resolution figures available at: http://webusers.astro.umn.edu/~djackson

UO2 CORROSION IN HIGH SURFACE-AREA-TO-VOLUME BATCH EXPERIMENTS

Unsaturated drip tests have been used to investigate the alteration of unirradiated UO{sub 2} and spent UO{sub 2} fuel in an unsaturated environment, such as may be expected in the proposed repository at Yucca Mountain. In these tests, simulated groundwater is periodically injected onto a sample at 90 C in a steel vessel. The solids react with the dripping groundwater and water condensed on surfaces to form a suite of U(VI) alteration phases. Solution chemistry is determined from leachate at the bottom of each vessel after the leachate stops interacting with the solids. A more detailed knowledge of the compositional evolution of the leachate is desirable. By providing just enough water to maintain a thin film of water on a small quantity of fuel in batch experiments, we can more closely monitor the compositional changes to the water as it reacts to form alteration phases