364 research outputs found

    On the origin of the Trojan asteroids: Effects of Jupiter's mass accretion and radial migration

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    We present analytic and numerical results which illustrate the effects of Jupiter's accretion of nebular gas and the planet's radial migration on its Trojan companions. Initially, we approximate the system by the planar circular restricted three-body problem and assume small Trojan libration amplitudes. Employing an adiabatic invariant calculation, we show that Jupiter's thirty-fold growth from a 10M⊕10 M_\oplus core to its present mass causes the libration amplitudes of Trojan asteroids to shrink by a factor of about 2.5 to ∼40\sim 40% of their original size. The calculation also shows that Jupiter's radial migration has comparatively little effect on the Trojans; inward migration from 6.2 to 5.2 AU causes an increase in Trojan libration amplitudes of ∼4\sim4%. In each case, the area enclosed by small tadpole orbits, if made dimensionless by using Jupiter's semimajor axis, is approximately conserved. Similar adiabatic invariant calculations for inclined and eccentric Trojans show that Jupiter's mass growth leaves the asteroid's eccentricities and inclinations essentially unchanged, while one AU of inward migration causes an increase in both of these quantities by ∼4\sim 4%. Numerical integrations confirm and extend these analytic results. We demonstrate that our predictions remain valid for Trojans with small libration amplitudes even when the asteroids have low, butComment: Submitted to Icarus - 13 Fig

    The use of the genitive in the Arthurian section of Layamon\u27s Brut

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    New insights into the use of the genitive case in Early Middle English are possible because of the recent publication of Bruce Mitchell\u27s Old English Syntax which updates previous exhaustive grammars. Using Layamon\u27s Brut as a basis of study, it was found that Layamon employs a variety of case endings to indicate the genitive; alternatively, he uses of-periphrasis. He appears to be choosing among these grammatically acceptable possibilities in order to facilitate meter and rhyme

    High Performance Liquid Chromatography Tandem Mass Spectrometry for Trace Analysis in Environmental Samples

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    1,3-Dimethylamylamine (1,3-DMAA) is a stimulant commercially sold in a variety of dietary supplements as a chemical species derived from geranium plants (Pelargonium graveolens). Whether 1,3-DMAA naturally occurs in geranium plants or other dietary ingredients, it has important regulatory and commercial ramifications. An extraction method combined with HPLC-MS/MS is used to determine 1,3-DMAA and 1,4-dimethylamylamine (1,4-DMAA) concentrations in geranium plants with both external calibration and standard addition methods. Samples from the Changzhou, Kunming, and Guiyang regions of China during both winter and summer were analyzed. Following the detection of DMAA in the Changzhou sample, an extraction and pre-column, chiral derivatization chemistry method was developed for the separation and analysis of the four stereoisomers of 1,3-DMAA and two enantiomers for 1,4-DMAA. Two chiral derivatizing agents (CDAs) were investigated: (-)-1-(9-fluorenyl)ethyl chloroformate [(-)-FLEC] and (R)-(-)-alpha-methoxy-alpha-(trifluoromethyl) phenylacetyl [(-)-MTPA]. Optimization studies and detailed method detection limit (MDL), accuracy, and precision and linearity studies are presented for analysis of the DMAA-FLEC species in geranium plants. The DMAA-FLEC product was found to be unstable and a second, more stable CDA [(-)-MTPA] was employed. A preparatory scale HPLC separation was added prior to derivatization with (-)-MTPA to aid in the separation of all DMAA stereoisomers. The propagation of error prohibited a confident analysis of individual DMAA stereoisomers, but the DMAA-FLEC and DMAA-MTPA methods both confirmed the presence of DMAA in the Changzhou plant samples.Haloacetic acids (HAAs) are formed during the chlorination of drinking water. Previous work detected HAAs in bulk sodium hypochlorite solutions with post column reaction ion chromatography (PCR-IC). A HPLC-MS/MS method was designed to provide confirmation of the presence of HAAs in the sodium hypochlorite solutions. Detailed MDL, accuracy, and precision studies are presented for the analysis of nine haloacetic acids in sodium hypochlorite solutions. Due to the complex nature of the sample matrix a solid phase extraction step was added to the HPLC-MS/MS procedure. The HAAs monochloroacetic acid, dichloroacetic acid, and trichloroacetic acid were detected in the bulk sodium hypochlorite solutions by both the HPLC-MS/MS and the PCR-IC although the two methods disagree on reported concentrations

    Using Personality to Identify High Technology Career Preference in Military Recruits

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    Given increasing budget constraints, it is vital that employers get the most bang for their buck in recruiting efforts and that they result in hiring employees that possess the necessary skills. Nowhere is this more apparent than in the United States military which faces cutbacks while still needing to recruit soldiers who possess the skills needed to operate the modern military. This paper develops a set of propositions aimed at guiding empirical research into how military recruiters can use currently administered personality tests to ensure that they are enlisting the recruits needed to perform high technology occupations now needed

    Response to Wolf et al.: Furthering Debate over the Suitability of Trap-Neuter-Return for Stray Cat Management

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    To continue dialogue over proposed Australian trials of Trap-Neuter-Return (TNR), we applied a framework requiring identification of areas of agreement, areas of disagreement, and identification of empirical data collection required to resolve disagreements. There is agreement that Australia has a problem with stray cats, causing problems of impacts on wildlife, nuisance,disease transmission (including public health issues and exchange of diseases between stray cat and pet cat populations), poor welfare outcomes for stray cats, and an emotional burden on staff euthanising healthy stray cats. There is disagreement on whether (i) current measures are failing, leading to unacceptably high euthanasia levels, (ii) some contributors to the debate misunderstand TNR, (iii) TNR trials will reduce urban cat populations and associated problems, (iv) TNR is an ethical solution to cat overpopulation, and (v) some contributors to the debate promulgated misinformation. Although not everyone agrees that TNR trials should proceed, as a hypothetical exploration, we propose an experimental approach explicitly comparing TNR to alternatives. Trials could only be considered if other detailed and well-funded attempts at stray cat control focusing across an entire Local Government Area (LGA) prove ineffective

    A Case of Letting the Cat out of the Bag - Why Trap-Neuter-Return is Not an Ethical Solution for Stray Cat (Felis Catus) Management.

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    Trap-Neuter-Return (TNR) programs, in which stray cats are captured, neutered and returned to the environment are advocated as a humane, ethical alternative to euthanasia. We review the TNR literature in light of current debate over whether or not there should be further TNR trials in Australia. We revisit the problems arising from stray cats living in association with human habitation and estimate how many stray cats would have to be processed through a scientifically-guided TNR program to avoid high euthanasia rates. We also identify10 ethical and welfare challenges that have to be addressed: we consider the quality of life for stray cats, where they would live, whether the TNR process itself is stressful, whether TNR cats are vulnerable to injury, parasites and disease, can be medically treated, stray cats’ body condition and diet, and their impacts on people, pet cats, and urban wildlife, especially endemic fauna. We conclude that TNR is unsuitable for Australia in almost all situations because it is unlikely to resolve problems caused by stray cats or meet ethical and welfare challenges. Targeted adoption, early-age desexing, community education initiatives and responsible pet ownership have greater promise to minimize euthanasia, reduce numbers rapidly, and address the identified issues

    Pluripotent stem cell-derived hepatocyte-like cells

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    Liver disease is an important clinical problem, impacting over 30 million Americans and over 600 million people worldwide. It is the 12th leading cause of death in the United States and the 16th worldwide. Due to a paucity of donor organs, several thousand Americans die yearly while waiting for liver transplantation. Unfortunately, alternative tissue sources such as fetal hepatocytes and hepatic cell lines are unreliable, difficult to reproduce, and do not fully recapitulate hepatocyte phenotype and functions. As a consequence, alternative cell sources that do not have these limitations have been sought. Human embryonic stem (hES) cell- and induced pluripotent stem (iPS) cell-derived hepatocyte-like cells may enable cell based therapeutics, the study of the mechanisms of human disease and human development, and provide a platform for screening the efficacy and toxicity of pharmaceuticals. iPS cells can be differentiated in a step-wise fashion with high efficiency and reproducibility into hepatocyte-like cells that exhibit morphologic and phenotypic characteristics of hepatocytes. In addition, iPS-derived hepatocyte-like cells (iHLCs) possess some functional hepatic activity as they secrete urea, alpha-1-antitrypsin, and albumin. However, the combined phenotypic and functional traits exhibited by iHLCs resemble a relatively immature hepatic phenotype that more closely resembles that of fetal hepatocytes rather than adult hepatocytes. Specifically, iHLCs express fetal markers such as alpha-fetoprotein and lack key mature hepatocyte functions, as reflected by drastically reduced activity (~ 0.1%) of important detoxification enzymes (i.e. CYP2A6, CYP3A4). These key differences between iHLCs and primary adult human hepatocytes have limited the use of stem cells as a renewable source of functional adult hepatocytes for in vitro and in vivo applications. Unfortunately, the developmental pathways that control hepatocyte maturation from a fetal into an adult hepatocyte are poorly understood, which has hampered the field in its efforts to induce further maturation of iPS-derived hepatic lineage cells. This review analyzes recent developments in the derivation of hepatocyte-like cells, and proposes important points to consider and assays to perform during their characterization. In the future, we envision that iHLCs will be used as in vitro models of human disease, and in the longer term, provide an alternative cell source for drug testing and clinical therapy.National Institutes of Health (U.S.) (Roadmap for Medical Research Grant 1 R01 DK085713-01))American Gastroenterological Association (Research Scholar Award

    Body Size and Bite Force of Stray and Feral Cats - Are Bigger or Older Cats Taking the Largest or More Difficult to Handle Prey

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    As carnivorans rely heavily on their head and jaws for prey capture and handling, skull morphology and bite force can therefore reflect their ability to take larger or more difficult-to-handle prey. For 568 feral and stray cats (Felis catus), we recorded their demographics (sex and age), source location (feral or stray) and morphological measures (body mass, body condition); we estimated potential bite force from skull measurements for n = 268 of these cats, and quantified diet composition from stomach contents for n = 358. We compared skull measurements to estimate their bite force and determine how it varied with sex, age, body mass, body condition. Body mass had the strongest influence of bite force. In our sample, males were 36.2% heavier and had 20.0% greater estimated bite force (206.2 ± 44.7 Newtons, n = 168) than females (171.9 ± 29.3 Newtons, n = 120). However, cat age was the strongest predictor of the size of prey that they had taken, with older cats taking larger prey. The predictive power of this relationship was poor though (r2 \u3c 0.038, p \u3c 0.003), because even small cats ate large prey and some of the largest cats ate small prey, such as invertebrates. Cats are opportunistic, generalist carnivores taking a broad range of prey. Their ability to handle larger prey increases as the cats grow, increasing their jaw strength, and improving their hunting skills, but even the smallest cats in our sample had tackled and consumed large and potentially ‘dangerous’ prey that would likely have put up a defence

    Narrowband ultraviolet B treatment for psoriasis is highly economical and causes significant savings in cost for topical treatments

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    Background: Narrowband ultraviolet B (NB-UVB) treatment for psoriasis is considered expensive. However, existing data are based on estimates and do not consider indirect cost savings. Objectives: To define the actual costs of NB-UVB incurred by the service provider, as well as treatment-associated cost savings. Methods: We performed data linkage of (i) comprehensive treatment records and (ii) prescribing data for all NB-UVB treatment episodes spanning 6 years in a population of 420 000. We minimized data fluctuation by compiling data from four independent treatment sites, and using drug prescriptions unrelated to psoriasis as a negative control. Results: National Health Service Tayside spent an average of £257 per NB-UVB treatment course (mean 257 ± 63, range 150–286, across four independent treatment sites), contrasting sharply with the estimate of £1882 used by the U.K. National Institute for Health and Care Excellence. The cost of topical treatments averaged £128 per patient in the 12 months prior to NB-UVB, accounting for 42% of the overall drug costs incurred by these patients. This was reduced by 40% to £53 per patient over the 12-month period following NB-UVB treatment, while psoriasis-unrelated drug prescription remained unchanged, suggesting disease-specific effects of NB-UVB. The data were not due to site-specific factors, as confirmed by highly similar results observed between treatment sites operated by distinct staff. Finally, we detail all staff hours directly and indirectly involved in treatment, allowing direct translation of cost into other healthcare systems. Conclusions: NB-UVB is a low-cost treatment; cost figures currently used in health technology appraisals are an overestimate based on the data presented here. Creating or extending access to NB-UVB is likely to offer additional savings by delaying or avoiding costly third-line treatments for many patients.PostprintPeer reviewe
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