409 research outputs found

    Dust Stratification in Young Circumstellar Disks

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    We present high-resolution infrared spectra of four YSOs (T Tau N, T Tau S, RNO 91, and HL Tau). The spectra exhibit narrow absorption lines of 12CO, 13CO, and C18O as well as broad emission lines of gas phase12CO. The narrow absorption lines of CO are shown to originate from the colder circumstellar gas. We find that the line of sight gas column densities resulting from the CO absorption lines are much higher than expected for the measured extinction for each source and suggest the gas to dust ratio is measuring the dust settling and/or grain coagulation in these extended disks. We provide a model of turbulence, dust settling and grain growth to explain the results. The techniques presented here allow us to provide some observationally-motivated bounds on accretion disk alpha in protostellar systems

    CO Emission from Disks around AB Aurigae and HD 141569: Implications for Disk Structure and Planet Formation Timescales

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    We present a comparison of CO fundamental rovibrational lines (observed in the M band near 4.7 Όm) from the inner circumstellar disks around the Herbig AeBe stars AB Aur and HD 141569. The CO spatial profiles and temperatures constrain the location of the gas for both stars to a distance of less than 50 AU. The CO emission from the disk of the ~4 Myr star AB Aur shows at least two temperature components, the inner disk at a rotational temperature of 1540 ± 80 K and the outer disk at 70 ± 10 K. The hot gas is located near the hot bright inner rim of the disk and the cold gas is located in the outer disk from 8-50 AU. The relative intensities of low-J lines suggest that the cold gas is optically thick. The excitation of CO in both temperature regimes is dominated by infrared fluorescence (resonant scattering). In the more evolved disk around HD 141569, the CO is excited by UV fluorescence. The relative intensity of the CO emission lines implies a rotational temperature of 190 ± 30 K. The resulting column density is ~ 1011 cm-2, indicating approximately 1019 g of CO. The observed line profiles indicate that the inner disk has been cleared of CO gas by stellar radiation out to a minimum of 17 AU. The residual mass of CO suggests that the inner disk of HD 141569 is not in an active phase of planet building but it does not rule out the possibility that giant planet building has previously occurred

    Gaps in the Child Tuberculosis Care Cascade in 32 Rural Communities in Uganda and Kenya.

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    Background:Reducing tuberculosis (TB) deaths among children requires a better understanding of the gaps in the care cascade from TB diagnosis to treatment completion. We sought to assess the child TB care cascade in 32 rural communities in Uganda and Kenya using programmatic data. Methods:This is a retrospective cohort study of 160,851 children (ages <15 years) living in 12 rural communities in Kenya and 22 in Uganda. We reviewed national TB registries from health centers in and adjacent to the 32 communities, and we included all child TB cases recorded from January 1, 2013 to June 30, 2016. To calculate the first step of the child TB care cascade, the number of children with active TB, we divided the number of reported child TB diagnoses by the 2015 World Health Organization (WHO) child TB case detection ratio for Africa of 27%. The remaining components of the Child TB Care Cascade were ascertained directly from the TB registries and included: diagnosed with TB, started on TB treatment, and completed TB treatment. Results:In two and a half years, a total of 42 TB cases were reported among children living in 32 rural communities in Uganda and Kenya. 40% of the children were co-infected with HIV. Using the WHO child TB case detection ratio, we calculated that 155 children in this cohort had TB during the study period. Of those 155 children, 42 were diagnosed and linked to TB care, 42 were started on treatment, and 31 completed treatment. Among the 42 children who started TB treatment, reasons for treatment non-completion were loss to follow up (7%), death (5%), and un-recorded reasons (5%). Overall, 20% (31/155) of children completed the child TB care cascade. Conclusion:In 32 rural communities in Uganda and Kenya, we estimate that 80% of children with TB fell off the care cascade. Reducing morbidity and mortality from child TB requires strengthening of the child TB care cascade from diagnosis through treatment completion

    The Giardia lamblia vsp gene repertoire: characteristics, genomic organization, and evolution

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    BACKGROUND:Giardia lamblia trophozoites colonize the intestines of susceptible mammals and cause diarrhea, which can be prolonged despite an intestinal immune response. The variable expression of the variant-specific surface protein (VSP) genes may contribute to this prolonged infection. Only one is expressed at a time, and switching expression from one gene to another occurs by an epigenetic mechanism.RESULTS:The WB Giardia isolate has been sequenced at 10x coverage and assembled into 306 contigs as large as 870 kb in size. We have used this assembly to evaluate the genomic organization and evolution of the vsp repertoire. We have identified 228 complete and 75 partial vsp gene sequences for an estimated repertoire of 270 to 303, making up about 4% of the genome. The vsp gene diversity includes 30 genes containing tandem repeats, and 14 vsp pairs of identical genes present in either head to head or tail to tail configurations (designated as inverted pairs), where the two genes are separated by 2 to 4 kb of non-coding DNA. Interestingly, over half the total vsp repertoire is present in the form of linear gene arrays that can contain up to 10 vsp gene members. Lastly, evidence for recombination within and across minor clades of vsp genes is provided.CONCLUSIONS:The data we present here is the first comprehensive analysis of the vsp gene family from the Genotype A1 WB isolate with an emphasis on vsp characterization, function, evolution and contributions to pathogenesis of this important pathogen.This item is part of the UA Faculty Publications collection. For more information this item or other items in the UA Campus Repository, contact the University of Arizona Libraries at [email protected]

    Loss of Biological Diversity: A Global Crisis Requiring International Solutions: A Report to the National Science Board

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    Executive Summary Biological diversity refers to the variety and variability among living organisms and the ecological complexes in which they occur. Diversity can be defined as the number of different items and their relative frequency. For biological diversity, these items are organized at many levels, ranging from complete ecosystems to the chemical structures that are the molecular basis of heredity. Thus, the term encompasses different ecosystems, species, genes, and their relative abundance (OTA, 1987). There is an ongoing, unprecedented loss of the variety as well as absolute numbers of organisms-from the smallest microorganism to the largest and most spectacular of mammals. Loss of tropical moist forests, which contain over half the total species of organisms, has been well documented by scientists and is now widely reported in the media. Many other ecosystems are also threatened; as human populations and their support systems expand, natural ecosystems at all latitudes are altered or converted. At its meeting on October 15, 1987, the National Science Board concluded that the world\u27s decreasing biological diversity is a critical scientific issue requiring immediate attention. The National Science Board\u27s Committee on International Science was asked to study the scientific and international aspects of the decline of biological diversity and to recommend a course of action. This report describes what the National Science Foundation (NSF) can do to influence the U.S. science and education base, articulates where international scientific cooperation is needed, and suggests roles for other agencies and organizations (both national and international) which have scientific, educational, and management responsibilities. The current disappearance of biota has several causes: the destruction or degradation of entire ecosystems; the accelerating loss of individual species from communities or ecosystems as a result of human disturb;mce; and the loss of genetically distinct parts of populations due to human-induced selective pressures. Although not all parts of the planet are equally affected, the problem is global, and human activities are the primary cause. The loss of biological diversity is important because human existence depends on the biological resources of 1 the earth. Human prosperity is based very largely on the ability to utilize biological diversity: to take advantage of the properties of plants, animals, fungi, and microorganisms for food, clothing, medicine, and shelter. Scientific knowledge about the earth\u27s biological diversity has huge gaps. This lack of information hampers society\u27s ability either to estimate the magnitude of the problem or to prevent further losses. It is impossible to identify all the biological resources at risk, since there is no complete inventory of all the life forms on earth. Approximately 1.4 million species have been given scientific names, but estimates of actual numbers range from 5 million to 80 million species. Although knowledge of some taxa is extensive, the vast majority of groups are largely unknown. The current wave of extinction is destroying both known biotic resources and those still undiscovered. As is proving to be the case with most environmental problems, neither the loss of biological diversity nor its solution is the exclusive province of any one nation. International cooperation is necessary to develop both scientific knowledge and successful mitigation and management strategies. The root causes of the problem include sociological and economic processes which operate on an global scale; a thorough understanding will require investigation and elucidation of both biological and non-biological components. There are several reasons for increasing National Science Foundation (NSF) involvement in biodiversity studies: the economic and social importance of biodiversity (and the risk of opportunity lost due to accelerating extinction); the contributions such leadership can make toward to conservation of biological diversity; the important role of such studies in the international growth of science, especially in tropical countries; the potential impact of such studies on the future course of biology as a whole; and enhancing public awareness of the issues. NSF should assume a scientific leadership position with respect to agencies in the U.S. and throughout the world. By insisting on the central importance of biodiversity, the NSF could encourage collaborative support for the actions recommended below. 1. The Committee believes that the role of the NSF is clear-NSF should, as a matter of National Science Board Policy, provide leadership to undertake the inventory of the world\u27s biodiversity. 2. The scientific basis for conservation biology, restoration ecology, and environmental management must be strengthened. 3. Educational and public awareness programs related to biodiversity need increased support. 4. The economic and social aspects of the biodiversity crisis need additional study. 5. Enhance support for developing country scientists and institutions for biodiversity research and conservation

    Transcriptomic Analysis of Equine Chorioallantois Reveals Immune Networks and Molecular Mechanisms Involved in Nocardioform Placentitis

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    Nocardioform placentitis (NP) continues to result in episodic outbreaks of abortion and preterm birth in mares and remains a poorly understood disease. The objective of this study was to characterize the transcriptome of the chorioallantois (CA) of mares with NP. The CA were collected from mares with confirmed NP based upon histopathology, microbiological culture and PCR for Amycolatopsis spp. Samples were collected from the margin of the NP lesion (NPL, n = 4) and grossly normal region (NPN, n = 4). Additionally, CA samples were collected from normal postpartum mares (Control; CRL, n = 4). Transcriptome analysis identified 2892 differentially expressed genes (DEGs) in NPL vs. CRL and 2450 DEGs in NPL vs. NPN. Functional genomics analysis elucidated that inflammatory signaling, toll-like receptor signaling, inflammasome activation, chemotaxis, and apoptosis pathways are involved in NP. The increased leukocytic infiltration in NPL was associated with the upregulation of matrix metalloproteinase (MMP1, MMP3, and MMP8) and apoptosis-related genes, such as caspases (CASP3 and CASP7), which could explain placental separation associated with NP. Also, NP was associated with downregulation of several placenta-regulatory genes (ABCG2, GCM1, EPAS1, and NR3C1), angiogenesis-related genes (VEGFA, FLT1, KDR, and ANGPT2), and glucose transporter coding genes (GLUT1, GLUT10, and GLUT12), as well as upregulation of hypoxia-related genes (HIF1A and EGLN3), which could elucidate placental insufficiency accompanying NP. In conclusion, our findings revealed for the first time, the key regulators and mechanisms underlying placental inflammation, separation, and insufficiency during NP, which might lead to the development of efficacious therapies or diagnostic aids by targeting the key molecular pathways

    Establishing ZIF-8 as a reference material for hydrogen cryoadsorption: An interlaboratory study

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    Hydrogen storage by cryoadsorption on porous materials has the advantages of low material cost, safety, fast kinetics, and high cyclic stability. The further development of this technology requires reliable data on the H2 uptake of the adsorbents, however, even for activated carbons the values between different laboratories show sometimes large discrepancies. So far no reference material for hydrogen cryoadsorption is available. The metal-organic framework ZIF-8 is an ideal material possessing high thermal, chemical, and mechanical stability that reduces degradation during handling and activation. Here, we distributed ZIF-8 pellets synthesized by extrusion to 9 laboratories equipped with 15 different experimental setups including gravimetric and volumetric analyzers. The gravimetric H2 uptake of the pellets was measured at 77 K and up to 100 bar showing a high reproducibility between the different laboratories, with a small relative standard deviation of 3–4 % between pressures of 10–100 bar. The effect of operating variables like the amount of sample or analysis temperature was evaluated, remarking the calibration of devices and other correction procedures as the most significant deviation sources. Overall, the reproducible hydrogen cryoadsorption measurements indicate the robustness of the ZIF-8 pellets, which we want to propose as a reference material.M. Maiwald, J. A. Villajos, R. Balderas and M. Hirscher acknowledge the EMPIR programme from the European Union's Horizon 2020 research and innovation programme for funding. F. Cuevas and F. Couturas acknowledge support from France 2030 program under project ANR-22-PEHY-0007. D. Cazorla and A. Berenguer-Murcia thank the support by PID2021-123079OB-I00 project funded by MCIN/AEI/10.13039/501100011033, and “ERDF A way of making Europe”. K. N. Heinselman, S. Shulda and P. A. Parilla acknowledge the support from the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding provided by U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Hydrogen and Fuel Cell Technology Office through the HyMARC Energy Materials Network

    Is Aquatic Life Correlated with an Increased Hematocrit in Snakes?

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    Background: Physiological adaptations that allow air-breathing vertebrates to remain underwater for long periods mainly involve modifications of the respiratory system, essentially through increased oxygen reserves. Physiological constraints on dive duration tend to be less critical for ectotherms than for endotherms because the former have lower mass-specific metabolic rates. Moreover, comparative studies between marine and terrestrial ectotherms have yet to show overall distinct physiological differences specifically associated with oxygen reserves. Methodology/Principal Findings: We used phylogenetically informed statistical models to test if habitat affects hematocrit (an indicator of blood oxygen stores) in snakes, a lineage that varies widely in habitat use. Our results indicate that both phylogenetic position (clade) and especially habitat are significant predictors of hematocrit. Our analysis also confirms the peculiar respiratory physiology of the marine Acrochordus granulatus. Conclusion/Significance: Contrary to previous findings, marine snakes have significantly–albeit slightly–elevated hematocrit, which should facilitate increased aerobic dive times. Longer dives could have consequences for foraging, mate searching, and predation risks. Alternatively, but not exclusively, increased Hct in marine species might also help t
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