Intrinsic
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K radioactive backgrounds from impurities of natural K in liquid scintillation cocktails have previously been demonstrated to limit their use in ultra-sensitive applications. This work ...explores two methodologies in parallel for the reduction of
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K backgrounds in the cocktails, and lays the groundwork for use in ultra-sensitive applications. In one method, alternative low-K liquid scintillation matrix constituents were identified and in the other, a simple purification method for single components and finished cocktails was developed. Both methods were verified via ICP-MS analysis. Liquid scintillation counting of selected purified cocktails demonstrated background reduction, improved stability, and enhanced performance. The best performing purified cocktail was also counted on a custom-built ultra-low background liquid scintillation counter, with results below the detector background.
Foraging segregation may play an important role in the maintenance of animal diversity, and is a proposed mechanism for promoting genetic divergence within seabird species. However, little ...information exists regarding its presence among seabird populations. We investigated genetic and foraging divergence between two colonies of endangered Hawaiian petrels (Pterodroma sandwichensis) nesting on the islands of Hawaii and Kauai using the mitochondrial Cytochrome b gene and carbon, nitrogen and hydrogen isotope values (δ¹³C, δ¹⁵N and δD, respectively) of feathers. Genetic analyses revealed strong differentiation between colonies on Hawaii and Kauai, with Φ ST = 0.50 (p < 0.0001). Coalescent-based analyses gave estimates of < 1 migration event per 1,000 generations. Hatch-year birds from Kauai had significantly lower δ¹³C and δ¹⁵N values than those from Hawaii. This is consistent with Kauai birds provisioning chicks with prey derived from near or north of the Hawaiian Islands, and Hawaii birds provisioning young with prey from regions of the equatorial Pacific characterized by elevated δ¹⁵N values at the food web base. δ¹⁵N values of Kauai and Hawaii adults differed significantly, indicating additional foraging segregation during molt. Feather 5δD varied from -69 to 53‰. This variation cannot be related solely to an isotopically homogeneous ocean water source or evaporative water loss. Instead, we propose the involvement of salt gland excretion. Our data demonstrate the presence of foraging segregation between proximately nesting seabird populations, despite high species mobility. This ecological diversity may facilitate population coexistence, and its preservation should be a focus of conservation strategies.
The performance of LSC cocktails in ultra-sensitive applications was evaluated. Backgrounds from radioactive contaminations in commercially available and in-house developed liquid scintillation ...cocktails were measured and compared to the predicted background levels of the ultra-low background liquid scintillation counter. Through the ICP-MS assay of the cocktails and their constituents, potassium impurities in the surfactant component were identified as a significant source of background, potentially limiting the use of LSC counting in ultra-sensitive applications. This work lays the groundwork for future research towards ultrapure LSC cocktails for ultrasensitive LSC counting.
Seabirds are highly vagile and can disperse up to thousands of kilometers, making it difficult to identify the factors that promote isolation between populations. The endemic Hawaiian petrel ...(Pterodroma sandwichensis) is one such species. Today it is endangered, and known to breed only on the islands of Hawaii, Maui, Lanai and Kauai. Historical records indicate that a large population formerly bred on Molokai as well, but this population has recently been extirpated. Given the great dispersal potential of these petrels, it remains unclear if populations are genetically distinct and which factors may contribute to isolation between them. We sampled petrels from across their range, including individuals from the presumably extirpated Molokai population. We sequenced 524 bp of mitochondrial DNA, 741 bp from three nuclear introns, and genotyped 18 microsatellite loci in order to examine the patterns of divergence in this species and to investigate the potential underlying mechanisms. Both mitochondrial and nuclear data sets indicated significant genetic differentiation among all modern populations, but no differentiation was found between historic samples from Molokai and modern birds from Lanai. Population-specific nonbreeding distribution and strong natal philopatry may reduce gene flow between populations. However, the lack of population structure between extirpated Molokai birds and modern birds on Lanai indicates that there was substantial gene flow between these populations and that petrels may be able to overcome barriers to dispersal prior to complete extirpation. Hawaiian petrel populations could be considered distinct management units, however, the dwindling population on Hawaii may require translocation to prevent extirpation in the near future.
The hypothesis that high temporal variability of northern spotted owl (Strix occidentalis caurina) reproductive success is a response to prey abundance remains largely untested. We evaluated this ...relationship in the Oregon Cascade Mountains. Despite similar biomass of northern flying squirrels (Glaucomys sabrinus) (169 ± 13.9 g/ha) and deer mice (Peromyscus maniculatus) (160 ± 18.8 g/ha), flying squirrels dominated the breeding season diet based on both biomass (49%) and numbers (40%). Abundance of flying squirrels and western red-backed voles (Clethrionomys californicus) was more variable spatially (
38% of process variation) than temporally (15%-24%), whereas abundance of deer mice was more similar across stands (12% spatial variation) than among years (68% temporal variation). Spotted owl reproductive success was statistically associated only with the abundance of deer mice (number of young per territory: r
2
= 0.68). However, deer mice comprised only 1.6 ± 0.5% of the biomass consumed. The low temporal variability of the dominant prey species provided evidence that simple prey relationship models were not likely to explain the highly synchronous and temporally dynamic patterns of spotted owl reproductive performance. Reproductive success was likely a result of the interaction of both weather and prey and the life history strategy of this long-lived owl.
Unlike previous spotted owl (Strix occidentalis) habitat association studies, we restricted our inquiry to the old-forest type and thus explored the association of spotted owls with habitat ...distribution as opposed to habitat type. We compared old-forest distribution around 126 northern spotted owl (S. o. caurina) nests in 70 pair territories, 14 nonreproductive spotted owl activity centers, and 104 points drawn randomly from old forest (closed canopy, >80 yr) in the central Cascade Mountains of Oregon. We quantified the percentage of old forest within 50 concentric circular plots (0.1-5.0-km radii) centered on each analyzed point, and we used logistic regression to make spatially explicit inferences. Owl nests were surrounded by more old forest in plots with 0.2-0.8-km radii (P < 0.05). Results suggested the landscape scales most pertinent to northern spotted owl nest-site positioning in this study were (in descending order) (1) the surrounding 15 ha (approx 200-m radius), (2) the surrounding 30-115 ha (approx 300-600-m radius), (3) the surrounding 200 ha (800-m radius), and (4) possibly the surrounding 700 ha (1,500-m radius). Nests were associated with higher proportions of old forest near the nest, implying that the arrangement of habitat was important for nest-site selection, positioning, or both. The 70 territories of nesting owls had more old forest on average than did the 14 nonreproductive owl sites, and the probability that a pair nested at least once during the study was positively associated with area of old-forest habitat in all radii studied. Because spotted owls in the central Cascade Mountains of Oregon are known to have home ranges that average 1,769 ha, our results apply to nest-site location on the landscape and not to the amount of habitat necessary for pair persistence or successful reproduction.
•Small particle sizes and slow crystallization exclude aggregates during freezing.•Ice exclusion processes not likely to form mm-scale spherical aggregates on Mars.•Particles become entrapped within ...the ice as aggregate size increases.•Sand and salts affected aggregation, but no mm-sized spherical aggregates formed.
The enigmatic and unexpected occurrence of coarse crystalline (gray) hematite spherules at Terra Meridiani on Mars in association with deposits of jarosite-rich sediments fueled a variety of hypotheses to explain their origin. In this study, we tested the hypothesis that freezing of aqueous hematite nanoparticle suspensions, possibly produced from low-temperature weathering of jarosite-bearing deposits, could produce coarse-grained hematite aggregate spherules. We synthesized four hematite nanoparticle suspensions with a range of sizes and morphologies and performed freezing experiments. All sizes of hematite nanoparticles rapidly aggregate during freezing. Regardless of the size or shape of the initial starting material, they rapidly collect into aggregates that are then too big to push in front of a stable advancing ice front, leading to incohesive masses of particles, rather than solid spherules. We also explored the effects of “seed” silicates, a matrix of sand grains, various concentrations of NaCl and CaCl2, and varying the freezing temperature on hematite nanoparticle aggregation. However, none of these factors resulted in mm-scale spherical aggregates. By comparing our measured freezing rates with empirical and theoretical values from the literature, we conclude that the spherules on Mars could not have been produced through the freezing of aqueous hematite nanoparticle suspensions; ice crystallization front instability disrupts the aggregation process and prevents the formation of mm-scale continuous aggregates.
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We studied the dispersal behavior of 1,475 northern spotted owls (Strix occidentalis caurina) during banding and radio-telemetry studies in Oregon and Washington in 1985-1996. The sample included 324 ...radio-marked juveniles and 1,151 banded individuals (711 juveniles, 440 non-juveniles) that were recaptured or resighted after dispersing from the initial banding location. Juveniles typically left the nest during the last week in May and the first two weeks in June (x̄ ± SE = 8 June ± 0.53 days, n = 320, range = 15 May-1 July), and spent an average of 103.7 days in the natal territory after leaving the nest (SE = 0.986 days, n = 137, range = 76-147 days). The estimated mean date that juveniles began to disperse was 19 September in Oregon (95% CI = 17-21 September) and 30 September in Washington (95% CI = 25 September-4 October). Mean dispersal dates did not differ between males and females or among years. Siblings dispersed independently. Dispersal was typically initiated with a series of rapid movements away from the natal site during the first few days or weeks of dispersal. Thereafter, most juveniles settled into temporary home ranges in late October or November and remained there for several months. In February-April there was a second pulse of dispersal activity, with many owls moving considerable distances before settling again in their second summer. Subsequent dispersal patterns were highly variable, with some individuals settling permanently in their second summer and others occupying a series of temporary home ranges before eventually settling on territories when they were 2-5 years old. Final dispersal distances ranged from 0.6-111.2 km for banded juveniles and 1.8-103.5 km for radio-marked juveniles. The distribution of dispersal distances was strongly skewed towards shorter distances, with only 8.7% of individuals dispersing more than 50 km. Median natal dispersal distances were 14.6 km for banded males, 13.5 km for radio-marked males, 24.5 km for banded females, and 22.9 km for radio-marked females. On average, banded males and females settled within 4.2 and 7.0 territory widths of their natal sites, respectively. Maximum and final dispersal distances were largely independent of the number of days that juveniles were tracked. Although statistical tests of dispersal direction based on all owls indicated that direction of natal dispersal was non-random, the mean angular deviations and 95% CI's associated with the samples were large, and r-values (vector length) were small. This lead us to conclude that significant test results were the result of large sample size and were not biologically meaningful. Our samples were not large enough to test whether dispersal direction from individual territories was random. In the sample of radio-marked owls, 22% of males and 44% of females were paired at 1 year of age, but only 1.5% of males and 1.6% of females were actually breeding at 1 year of age. At 2 years of age, 68% of males and 77% of females were paired, but only 5.4% of males and 2.6% of females were breeding. In contrast to the radio-marked owls, most juveniles that were banded and relocated at 1 or 2 years of age were paired, although few were breeding. Although recruitment into the territorial population typically occurred when owls were 1-5 years old, 9% of banded juveniles were not recaptured until they were > 5 years old. We suspect that our estimates of age at recruitment of banded owls are biased high because of the likelihood that some individuals were not recaptured in the first year that they entered the territorial population. A minimum of 6% of the banded, non-juvenile owls on our demographic study areas changed territories each year (breeding dispersal). The likelihood of breeding dispersal was higher for females, young owls, owls that did not have a mate in the previous year, and owls that lost their mate from the previous year through death or divorce. Mean and median distances dispersed by adults were shorter than for juveniles, and did not differ between the sexes or study areas (x̄ = 6.1 km, median = 3.5 km). Owls that were 1-2 years old tended to disperse farther than owls that were > 2 years old. The direction of post-natal dispersal did not differ from random. The large nonforested valleys of western Oregon (Willamette, Umpqua, Rogue Valleys) acted as barriers to dispersal between the Coast Ranges and the Cascade Mountains. However, dispersal did occur between the Coast Ranges and Cascade Mountains in the forested foothills between the non-forested valleys. Forest landscapes traversed by dispersing owls typically included a fragmented mosaic of roads, clear-cuts, non-forest areas, and a variety of forest age classes ranging from young forests on cutover areas, to old-growth forests ≥ 250 years old. Our data fit the general pattern observed in birds in that females dispersed farther than males and dispersal distances were negatively skewed towards short distance dispersers. Comparison of data from radio-marked and banded owls demonstrated that the negatively skewed distribution of dispersal distances represented the actual distribution of dispersal distances, and was not the result of small study area bias on recaptures. We found no correlation between dispersal distance and age at first breeding, which suggests that reproductive fitness is not affected by dispersal distance. We observed only 3 cases of close inbreeding (parent-offspring or sibling pairs) in thousands of pairs of spotted owls, suggesting that dispersal results in a very low incidence of close inbreeding in the spotted owl. However, inbreeding with more distant relatives was common.
To test the hypothesis that, in humans with ischemic heart disease, nifedipine is a primary dilator of the coronary circulation and in general exerts a net positive effect on the balance of ...myocardial oxygen supply and demand.
Positron-emission tomography with 13N-ammonia was used to measure myocardial blood flow in patients at rest, and during infusion of adenosine and ingestion of nifedipine (10 mg capsule, a bite-and-chew technique). Myocardial segments were defined physiologically on the basis of blood flow to adenosine as being normal or having mild, moderate, or severe impairment of dilator reserve. Myocardial systolic function was assessed under comparable physiologic conditions using gated single-photon-emission computed tomography radionuclide ventriculography.
Our study population consisted of 13 male patients and one female patient. Ingestion of nifedipine increased heart rate (from 63 +/- 11 to 80 +/- 16 beats/min, P < 0.001) and, as intended, lowered systolic arterial pressure (from 148 +/- 20 to 123 +/- 14 mmHg, P < 0.001) but had no effect on heart rate-pressure product (which changed from 9283 +/- 1576 to 9942 +/- 2162 mmHg/min). Myocardial blood flow in patients at rest in segments with mild, moderate, and severe reductions of dilator capacity (0.63 +/- 0.20, 0.67 +/- 0.25, and 0.58 +/- 0.27 ml/min per g, respectively) was less (P < 0.01) than normal (0.91 +/- 0.29 ml/min per g). Nevertheless, flow of blood was increased versus that at rest (P < 0.01) by infusion of adenosine (to 1.78 +/- 0.13, 1.29 +/- 0.16, and 0.75 +/- 0.22 ml/min per g) and ingestion of nifedipine (to 1.17 +/- 0.51, 1.06 +/- 0.36, 0.85 +/- 0.42 ml/min per g) in segments with mild, moderate, and severe reduction of dilator capacity as well as in normal segments (to 3.18 +/- 0.85 ml/min per g with adenosine and 1.68 +/- 0.65 ml/min per g with nifedipine). Global left ventricular systolic function remained unchanged versus baseline (ejection fraction 0.74 +/- 0.09) with nifedipine (0.76 +/- 0.10). Regional contraction expressed in normalized amplitude units also remained unchanged versus baseline in response to nifedipine.
Nifedipine increases myocardial blood flow in humans with ischemic heart disease in normal segments as well as in segments with mild, moderate, and severe reductions of dilator capacity, albeit to a lesser extent with increasing impairment of dilator capacity. Both global and regional left ventricular contractile function also are not adversely affected by nifedipine. These improvements in myocardial blood flow in face of no change or a decrease in myocardial demand for oxygen reflect an overall favorable effect on the balance between the supply of and demand for myocardial oxygen.
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