Sample records for abrupt mass loss

  1. State survey of medical boards regarding abrupt loss of a prescriber of controlled substances.

    PubMed

    Sera, Leah; Brown, Micke; McPherson, Mary Lynn; Walker, Kathryn A; Klein-Schwartz, Wendy

    The purpose of the study was to evaluate states' experiences with abrupt changes in controlled substances (CS) prescribing, to determine whether states have action plans in place to manage such situations, and describe the components of any such plans. A survey of executive directors of 51 medical boards was conducted to evaluate states' experiences with abrupt changes in CS prescribing, the extent of consumer complaints attributed to these events, and the types of plans in place to manage these situations. Forty-six executive directors of medical boards responded. Twenty boards (43.5 percent) confirmed that their state had experienced abrupt loss of CS providers and 11 (55 percent) of these executive directors indicated that the loss resulted in increased consumer complaints. The majority of executive directors (86 percent) had no action plan. Six executive directors reported some type of action plan or process consisting of regulatory action, patient-provider connection, professional education, patient education, or public notice. Most states do not have operational plans in place. However, a few have key strategies that may be useful in addressing potential problems following abrupt loss of a CS prescriber. State medical boards can play a significant role in the development of comprehensive preparedness plans to mitigate damage from the loss of CS prescribers in the community.

  2. Mass loss

    NASA Technical Reports Server (NTRS)

    Goldberg, Leo

    1987-01-01

    Observational evidence for mass loss from cool stars is reviewed. Spectra line profiles are used for the derivation of mass-loss rates with the aid of the equation of continuity. This equation implies steady mass loss with spherical symmetry. Data from binary stars, Mira variables, and red giants in globular clusters are examined. Silicate emission is discussed as a useful indicator of mass loss in the middle infrared spectra. The use of thermal millimeter-wave radiation, Very Large Array (VLA) measurement of radio emission, and OH/IR masers are discussed as a tool for mass loss measurement. Evidence for nonsteady mass loss is also reviewed.

  3. Using SN 1987A light echoes to determine mass loss from the progenitor

    NASA Technical Reports Server (NTRS)

    Crotts, Arlin P. S.; Kunkel, William E.

    1991-01-01

    The hypothesis that the blue progenitor of SN 1987A passed through a blue supergiant phase ending with the expulsion of the outer envelope is tested. The many light echoes seen near SN 1987A were used to search for a mass flow from the progenitor and for abrupt density changes at the limits of this smooth mass flow. The progenitor needed roughly a million yr to create these structures, assuming a constant mass loss at 15 km/s. The dust in the region is small-grained and isotropically scattering. Interaction between the progenitor blue supergiant and red supergiant winds is probably contained within a roughly spherical structure 1.5 pc in diameter.

  4. Dramatic mass loss in extreme high-elevation areas of a western Himalayan glacier: observations and modeling

    NASA Astrophysics Data System (ADS)

    Zhao, Huabiao; Yang, Wei; Yao, Tandong; Tian, Lide; Xu, Baiqing

    2016-08-01

    Rapid climate change at high elevations has accelerated glacier retreat in the Himalayas and Tibetan Plateau. However, due to the lack of long-term glaciological measurements, there are still uncertainties regarding when the mass loss began and what the magnitude of mass loss is at such high elevations. Based on in situ glaciological observations during the past 9 years and a temperature-index mass balance model, this study investigates recent mass loss of the Naimona’nyi Glacier in the western Himalayas and reconstructs a 41-year (1973/74-2013/14) equilibrium line altitude (ELA) and glacier-wide mass loss. The result indicates that even at 6000 m above sea level (a.s.l.), the annual mass loss reaches ~0.73 m water equivalent (w.e.) during the past 9 years. Concordant with the abrupt climate shift in the end of 1980s, the ELA has dramatically risen from ~5969 ± 73 m a.s.l. during 1973/74-1988/89 to ~6193 ± 75 m a.s.l. during 1989/90-2013/14, suggesting that future ice cores containing uninterrupted climate records could only be recovered at least above 6200 m a.s.l. in the Naimona’nyi region. The glacier-wide mass balance over the past 41 years is averaged to be approximately -0.40 ± 0.17 m w.e., exhibiting a significant increase in the decadal average from -0.01 ± 0.15 to -0.69 ± 0.21 m w.e.

  5. Abrupt loss of MLH1 and PMS2 expression in endometrial carcinoma: molecular and morphologic analysis of 6 cases.

    PubMed

    Pai, Rish K; Plesec, Thomas P; Abdul-Karim, Fadi W; Yang, Bin; Marquard, Jessica; Shadrach, Bonnie; Roma, Andres R

    2015-07-01

    Given that endometrial cancer (EC) is often the sentinel cancer for female Lynch syndrome patients, we have successfully implemented universal screening of ECs and have previously shown that this is the preferred method to identify these patients. However, during the course of universal screening of EC, we encountered 6 cases with an unusual pattern of mismatch-repair protein immunohistochemistry that has not been previously described in this setting. In these 6 cases, there was an abrupt loss of MLH1 and PMS2 expression in a portion of the tumor. In 3 cases, marked histologic differences were identified between the areas of the tumor with retained expression and areas with loss of expression. In 2 cases, the areas with loss of expression were of higher grade (1 demonstrated solid growth and the other demonstrated increased nuclear atypia with diffuse p53 expression). In 4 tumors, histologic features associated with microsatellite instability (MSI) were present, including increased intraepithelial lymphocytes. The areas with loss of and retained MLH1/PMS2 expression were separately microdissected and assessed for MSI and MLH1 promoter methylation. The areas with loss of MLH1 and PMS2 more commonly demonstrated MSI compared with the areas with intact expression (83% vs. 33%). MLH1 promoter methylation analysis demonstrated heterogenous hypermethylation, as all areas with loss of MLH1/PMS2 expression had more extensive methylation of MLH1 compared with those areas with retained expression. In summary, we describe the histologic and molecular features of 6 cases of EC with abrupt loss of MLH1 and PMS2 expression and demonstrate that heterogenous methylation of the MLH1 promoter results in this distinct and unusual pattern of immunohistochemical expression.

  6. Fast Response of the Tropics to an Abrupt Loss of Arctic Sea Ice via Ocean Dynamics

    NASA Astrophysics Data System (ADS)

    Wang, Kun; Deser, Clara; Sun, Lantao; Tomas, Robert A.

    2018-05-01

    The role of ocean dynamics in the transient adjustment of the coupled climate system to an abrupt loss of Arctic sea ice is investigated using experiments with Community Climate System Model version 4 in two configurations: a thermodynamic slab mixed layer ocean and a full-depth ocean that includes both dynamics and thermodynamics. Ocean dynamics produce a distinct sea surface temperature warming maximum in the eastern equatorial Pacific, accompanied by an equatorward intensification of the Intertropical Convergence Zone and Hadley Circulation. These tropical responses are established within 25 years of ice loss and contrast markedly with the quasi-steady antisymmetric coupled response in the slab-ocean configuration. A heat budget analysis reveals the importance of anomalous vertical advection tied to a monotonic temperature increase below 200 m for the equatorial sea surface temperature warming maximum in the fully coupled model. Ocean dynamics also rapidly modify the midlatitude atmospheric response to sea ice loss.

  7. Abrupt shift in the observed runoff from the southwestern Greenland ice sheet

    PubMed Central

    Ahlstrøm, Andreas P.; Petersen, Dorthe; Langen, Peter L.; Citterio, Michele; Box, Jason E.

    2017-01-01

    The recent decades of accelerating mass loss of the Greenland ice sheet have arisen from an increase in both surface meltwater runoff and ice flow discharge from tidewater glaciers. Despite the role of the Greenland ice sheet as the dominant individual cryospheric contributor to sea level rise in recent decades, no observational record of its mass loss spans the 30-year period needed to assess its climatological state. We present for the first time a 40-year (1975–2014) time series of observed meltwater discharge from a >6500-km2 catchment of the southwestern Greenland ice sheet. We find that an abrupt 80% increase in runoff occurring between the 1976–2002 and 2003–2014 periods is due to a shift in atmospheric circulation, with meridional exchange events occurring more frequently over Greenland, establishing the first observation-based connection between ice sheet runoff and climate change. PMID:29242827

  8. Mass loss from solar-type stars

    NASA Technical Reports Server (NTRS)

    Hartmann, L.

    1985-01-01

    The present picture of mass loss from solar-type (low-mass) stars is described, with special emphasis on winds from pre-main-sequence stars. Attention is given to winds from T Tauri stars and to angular momentum loss. Prospects are good for further advances in our understanding of the powerful mass loss observed from young stars; ultraviolet spectra obtainable with the Space Telescope should provide better estimates of mass loss rates and a clearer picture of physical conditions in the envelopes of these stars. To understand the mass ejection from old, slowly rotating main-sequence stars, we will have to study the sun.

  9. A systematic investigation of the mass loss mechanism in dust forming long-period variable stars

    NASA Astrophysics Data System (ADS)

    Winters, J. M.; Le Bertre, T.; Jeong, K. S.; Helling, Ch.; Sedlmayr, E.

    2000-09-01

    In order to investigate the relations between the mass loss from pulsating red giants and quantities which can be obtained from observations, we have explored the behavior of theoretical models which treat the time-dependent hydrodynamics of circumstellar outflows, including a detailed treatment of the dust formation process. This approach, while ignoring effects such as a possible non-sphericity of the stellar atmospheres which are difficult to assess, accounts correctly for factors such as the grain formation and destruction which are crucial to the mass-loss mechanism. We built a grid of ~ 150 models covering a wide range of physical situations. This grid allows us to characterize the effects of different parameters, such as the stellar luminosity and temperature, the period and the amplitude of the pulsation, and the C/O element abundance ratio, on the behavior of AGB winds and on the rates of mass loss. We find two regimes for the stellar outflows. The first one (A) is characterized by stable winds with a layered structure of the circumstellar dust shell, outflow velocities in excess of 5 km s-1, and a large rate of mass loss. These outflows are dominated by radiation pressure on dust. For these models we find good correlations between near-infrared colors and the mass loss rates. In the second regime (B), the winds are slow and do not present a layered structure. The outflows displaying the second behavior come, e.g., from red giants with low luminosity, high temperature, or short period. For them there is no correlation between color and mass loss rate. The mass loss rates are low and never exceed 3 10-7 Msunyr-1. Radiation pressure on dust plays only a minor role in this regime. We have explored the effect of different parameters on the behavior of the stellar winds. We find that, in general, all other parameters been kept identical, there is a narrow range of values for each parameter within which the models abruptly change from B to A, and that once a

  10. Mass Loss during Late Stellar Evolution

    NASA Astrophysics Data System (ADS)

    Olofsson, Hans

    1999-10-01

    Extensive post-main sequence mass loss occurs for low- and intermediate-mass (up to ~8MSun) stars on the asymptotic giant branch (AGB), and for the higher-mass stars during their red supergiant evolution. These winds have a profound effect on the evolution of the stars, as well as for the enrichment of the interstellar medium with heavy elements and grain particles. The mass loss on the AGB is the by far most well studied, but a good deal of the basic processes are still not understood or cannot be described in a proper quantitative way, e.g., the mass loss mechanism itself. Furthermore, these objects provide us with fascinating systems, where intricate interplays between various physical and chemical processes take place, and their relative simplicity in terms of geometry, density distribution, and kinematics makes them excellent astrophysical laboratories. In this review we will concentrate on those aspects of AGB mass loss that are particularly well studied using a large millimetre array.

  11. Mass loss and stellar superwinds

    NASA Astrophysics Data System (ADS)

    Vink, Jorick S.

    2017-09-01

    Mass loss bridges the gap between massive stars and supernovae (SNe) in two major ways: (i) theoretically, it is the amount of mass lost that determines the mass of the star prior to explosion and (ii) observations of the circumstellar material around SNe may teach us the type of progenitor that made the SN. Here, I present the latest models and observations of mass loss from massive stars, both for canonical massive O stars, as well as very massive stars that show Wolf-Rayet type features. This article is part of the themed issue 'Bridging the gap: from massive stars to supernovae'.

  12. Mass loss and stellar superwinds.

    PubMed

    Vink, Jorick S

    2017-10-28

    Mass loss bridges the gap between massive stars and supernovae (SNe) in two major ways: (i) theoretically, it is the amount of mass lost that determines the mass of the star prior to explosion and (ii) observations of the circumstellar material around SNe may teach us the type of progenitor that made the SN. Here, I present the latest models and observations of mass loss from massive stars, both for canonical massive O stars, as well as very massive stars that show Wolf-Rayet type features.This article is part of the themed issue 'Bridging the gap: from massive stars to supernovae'. © 2017 The Author(s).

  13. Rotation and Mass Loss

    NASA Astrophysics Data System (ADS)

    Owocki, S.

    2008-06-01

    Stellar rotation can play an important role in structuring and enhancing the mass loss from massive stars. Initial 1D models focussed on the expected centrifugal enhancement of the line-driven mass flux from the equator of a rotating star, but the review here emphasizes that the loss of centrifugal support away from the stellar surface actually limits the steady mass flux to just the point-star CAK value, with models near critical rotation characterized by a slow, subcritical acceleration. Recent suggestions that such slow outflows might have high enough density to explain disks in Be or B[e] stars are examined in the context of 2D simulations of the ``Wind Compressed Disk'' (WCD) paradigm, together with a review of the tendency for poleward components of the line-driving force to inhibit WCD formation. When one accounts for equatorial gravity darkening, the net tendency is in fact for the relatively bright regions at higher latitude to drive a faster, denser ``bipolar'' outflow. I discuss the potential relevance for the bipolar form of nebulae from LBV stars like η Carinae, but emphasize that, since the large mass loss associated with the eruption of eta Carinae's Homunculus would heavily saturate line-driving, explaining its bipolar form requires development of analogous models for continuum-driven mass loss. I conclude with a discussion of how radiation seems inherently ill-suited to supporting or driving a geometrically thin, but optically thick disk or disk outflow. The disks inferred in Be and B[e] stars may instead be centrifugally ejected, with radiation inducing an ablation flow from the disk surface, and thus perhaps playing a greater role in destroying (rather than creating) an orbiting, circumstellar disk.

  14. Decreasing cloud cover drives the recent mass loss on the Greenland Ice Sheet

    PubMed Central

    Hofer, Stefan; Tedstone, Andrew J.; Fettweis, Xavier; Bamber, Jonathan L.

    2017-01-01

    The Greenland Ice Sheet (GrIS) has been losing mass at an accelerating rate since the mid-1990s. This has been due to both increased ice discharge into the ocean and melting at the surface, with the latter being the dominant contribution. This change in state has been attributed to rising temperatures and a decrease in surface albedo. We show, using satellite data and climate model output, that the abrupt reduction in surface mass balance since about 1995 can be attributed largely to a coincident trend of decreasing summer cloud cover enhancing the melt-albedo feedback. Satellite observations show that, from 1995 to 2009, summer cloud cover decreased by 0.9 ± 0.3% per year. Model output indicates that the GrIS summer melt increases by 27 ± 13 gigatons (Gt) per percent reduction in summer cloud cover, principally because of the impact of increased shortwave radiation over the low albedo ablation zone. The observed reduction in cloud cover is strongly correlated with a state shift in the North Atlantic Oscillation promoting anticyclonic conditions in summer and suggests that the enhanced surface mass loss from the GrIS is driven by synoptic-scale changes in Arctic-wide atmospheric circulation. PMID:28782014

  15. Decreasing cloud cover drives the recent mass loss on the Greenland Ice Sheet.

    PubMed

    Hofer, Stefan; Tedstone, Andrew J; Fettweis, Xavier; Bamber, Jonathan L

    2017-06-01

    The Greenland Ice Sheet (GrIS) has been losing mass at an accelerating rate since the mid-1990s. This has been due to both increased ice discharge into the ocean and melting at the surface, with the latter being the dominant contribution. This change in state has been attributed to rising temperatures and a decrease in surface albedo. We show, using satellite data and climate model output, that the abrupt reduction in surface mass balance since about 1995 can be attributed largely to a coincident trend of decreasing summer cloud cover enhancing the melt-albedo feedback. Satellite observations show that, from 1995 to 2009, summer cloud cover decreased by 0.9 ± 0.3% per year. Model output indicates that the GrIS summer melt increases by 27 ± 13 gigatons (Gt) per percent reduction in summer cloud cover, principally because of the impact of increased shortwave radiation over the low albedo ablation zone. The observed reduction in cloud cover is strongly correlated with a state shift in the North Atlantic Oscillation promoting anticyclonic conditions in summer and suggests that the enhanced surface mass loss from the GrIS is driven by synoptic-scale changes in Arctic-wide atmospheric circulation.

  16. Abrupt fire regime change may cause landscape-wide loss of mature obligate seeder forests.

    PubMed

    Bowman, David M J S; Murphy, Brett P; Neyland, Dominic L J; Williamson, Grant J; Prior, Lynda D

    2014-03-01

    Obligate seeder trees requiring high-severity fires to regenerate may be vulnerable to population collapse if fire frequency increases abruptly. We tested this proposition using a long-lived obligate seeding forest tree, alpine ash (Eucalyptus delegatensis), in the Australian Alps. Since 2002, 85% of the Alps bioregion has been burnt by several very large fires, tracking the regional trend of more frequent extreme fire weather. High-severity fires removed 25% of aboveground tree biomass, and switched fuel arrays from low loads of herbaceous and litter fuels to high loads of flammable shrubs and juvenile trees, priming regenerating stands for subsequent fires. Single high-severity fires caused adult mortality and triggered mass regeneration, but a second fire in quick succession killed 97% of the regenerating alpine ash. Our results indicate that without interventions to reduce fire severity, interactions between flammability of regenerating stands and increased extreme fire weather will eliminate much of the remaining mature alpine ash forest. © 2013 John Wiley & Sons Ltd.

  17. Abrupt tropical climate change: past and present.

    PubMed

    Thompson, Lonnie G; Mosley-Thompson, Ellen; Brecher, Henry; Davis, Mary; León, Blanca; Les, Don; Lin, Ping-Nan; Mashiotta, Tracy; Mountain, Keith

    2006-07-11

    Three lines of evidence for abrupt tropical climate change, both past and present, are presented. First, annually and decadally averaged delta(18)O and net mass-balance histories for the last 400 and 2,000 yr, respectively, demonstrate that the current warming at high elevations in the mid- to low latitudes is unprecedented for at least the last 2 millennia. Second, the continuing retreat of most mid- to low-latitude glaciers, many having persisted for thousands of years, signals a recent and abrupt change in the Earth's climate system. Finally, rooted, soft-bodied wetland plants, now exposed along the margins as the Quelccaya ice cap (Peru) retreats, have been radiocarbon dated and, when coupled with other widespread proxy evidence, provide strong evidence for an abrupt mid-Holocene climate event that marked the transition from early Holocene (pre-5,000-yr-B.P.) conditions to cooler, late Holocene (post-5,000-yr-B.P.) conditions. This abrupt event, approximately 5,200 yr ago, was widespread and spatially coherent through much of the tropics and was coincident with structural changes in several civilizations. These three lines of evidence argue that the present warming and associated glacier retreat are unprecedented in some areas for at least 5,200 yr. The ongoing global-scale, rapid retreat of mountain glaciers is not only contributing to global sea-level rise but also threatening freshwater supplies in many of the world's most populous regions.

  18. Mass loss in red giants and supergiants

    NASA Technical Reports Server (NTRS)

    Sanner, F.

    1975-01-01

    The circumstellar envelopes surrounding late-type giants and supergiants were studied using high resolution, photoelectric scans of strong optical resonance lines. A method for extracting the circumstellar from the stellar components of the lines allowed a quantitative determination of the physical conditions in the envelopes and the rates of mass loss at various positions in the red giant region of the HR diagram. The observed strengthening of the circumstellar spectrum with increasing luminosity and later spectral type is probably caused by an increase in the mass of the envelopes. The mass loss rate for individual stars is proportional to the visual luminosity; high rates for the supergiants suggest that mass loss is important in their evolution. The bulk of the mass return to the interstellar medium in the red giant region comes from the normal giants, at a rate comparable to that of planetary nebulae.

  19. Can mountain glacier melting explains the GRACE-observed mass loss in the southeast Tibetan Plateau: From a climate perspective?

    NASA Astrophysics Data System (ADS)

    Song, Chunqiao; Ke, Linghong; Huang, Bo; Richards, Keith S.

    2015-01-01

    The southeast Tibetan Plateau (SETP) includes the majority of monsoonal temperate glaciers in High Mountain Asia (HMA), which is an important source of water for the upper reaches of several large Asian river systems. Climatic change and variability has substantial impacts on cryosphere and hydrological processes in the SETP. The Gravity Recovery and Climate Experiment (GRACE) gravimetry observations between 2003 and 2009 suggest that there was an average mass loss rate of - 5.99 ± 2.78 Gigatonnes (Gt)/yr in this region. Meanwhile, the hydrological data by model calculations from the GLDAS/Noah and CPC are used to estimate terrestrial water storage (TWS) changes with a slight negative trend of about - 0.3 Gt/yr. The recent studies (Kääb et al., 2012; Gardner et al., 2013) reported the thinning rates of mountain glaciers in HMA based on the satellite laser altimetry, and an approximate estimation of the glacier mass budget in the SETP was 4.69 ± 2.03 Gt/yr during 2003-2009. This estimate accounted for a large proportion ( 78.3%) of the difference between the GRACE TWS and model-calculated TWS changes. To better understand the cause of sharp mass loss existing in the SETP, the correlations between key climatic variables (precipitation and temperature) and the GRACE TWS changes are examined at different timescales between 2003 and 2011. The results show that precipitation is the leading factors of abrupt, seasonal and multi-year undulating signals of GRACE TWS anomaly time series, but with weak correlations with the inter-annual trend and annual mass budget of GRACE TWS. In contrast, the annual mean temperature is tightly associated with the annual net mass budget (r = 0.81, p < 0.01), which indirectly suggests that the GRACE-observed mass loss in the SETP may be highly related to glacial processes.

  20. Association between fat mass, lean mass, and bone loss: the Dubbo Osteoporosis Epidemiology Study.

    PubMed

    Yang, S; Center, J R; Eisman, J A; Nguyen, T V

    2015-04-01

    Lower body fat mass is a risk factor for bone loss at lumbar spine in postmenopausal women, but not in men. Body lean mass and fat mass were not associated with femoral neck bone loss in either gender. Bone density and body mass are closely associated. Whole body lean mass (LM) and fat mass (FM) together account for approximately 95 % of body mass. Bone loss is associated with loss of body mass but which of the components of body mass (FM or LM) is related to bone loss is not well understood. Therefore, in this study, we sought to assess whether baseline FM or LM has predictive value for future relative rate of bone mineral density (BMD) changes (%/year). The present population-based cohort study was part of the ongoing Dubbo Osteoporosis Epidemiology Study (DOES). BMD, FM, and LM were measured with dual energy X-ray absorptiometry (GE-LUNAR Corp, Madison, WI). BMD measurements were taken in approximately every 2 years between 2000 and 2010. We only included the participants with at least two BMD measurements at the femoral neck and lumbar spine. In total, 717 individuals (204 men and 513 women) aged 50 years or older were studied. Rate of bone loss at femoral neck and lumbar spine was faster in women than in men (all P < 0.01). In bivariable regression analysis, each 5 kg greater FM in women was associated with 0.4 %/year (P = 0.003) lower bone loss at lumbar spine. This magnitude of association remained virtually unchanged after adjusting for LM and/or other covariates (P = 0.03). After adjusting for covariates, variation of FM accounted for ∼1.5 % total variation in lumbar spine bone loss. However, there was no significant association between FM and change in femoral neck BMD in either men or women. Lower FM was an independent but modest risk factor for greater bone loss at the lumbar spine in women but not in men. If further studies confirm our findings, FM can help predict lumbar spine bone loss in women.

  1. The BTB-zinc Finger Transcription Factor Abrupt Acts as an Epithelial Oncogene in Drosophila melanogaster through Maintaining a Progenitor-like Cell State

    PubMed Central

    Turkel, Nezaket; Sahota, Virender K.; Bolden, Jessica E.; Goulding, Karen R.; Doggett, Karen; Willoughby, Lee F.; Blanco, Enrique; Martin-Blanco, Enrique; Corominas, Montserrat; Ellul, Jason; Aigaki, Toshiro; Richardson, Helena E.; Brumby, Anthony M.

    2013-01-01

    The capacity of tumour cells to maintain continual overgrowth potential has been linked to the commandeering of normal self-renewal pathways. Using an epithelial cancer model in Drosophila melanogaster, we carried out an overexpression screen for oncogenes capable of cooperating with the loss of the epithelial apico-basal cell polarity regulator, scribbled (scrib), and identified the cell fate regulator, Abrupt, a BTB-zinc finger protein. Abrupt overexpression alone is insufficient to transform cells, but in cooperation with scrib loss of function, Abrupt promotes the formation of massive tumours in the eye/antennal disc. The steroid hormone receptor coactivator, Taiman (a homologue of SRC3/AIB1), is known to associate with Abrupt, and Taiman overexpression also drives tumour formation in cooperation with the loss of Scrib. Expression arrays and ChIP-Seq indicates that Abrupt overexpression represses a large number of genes, including steroid hormone-response genes and multiple cell fate regulators, thereby maintaining cells within an epithelial progenitor-like state. The progenitor-like state is characterised by the failure to express the conserved Eyes absent/Dachshund regulatory complex in the eye disc, and in the antennal disc by the failure to express cell fate regulators that define the temporal elaboration of the appendage along the proximo-distal axis downstream of Distalless. Loss of scrib promotes cooperation with Abrupt through impaired Hippo signalling, which is required and sufficient for cooperative overgrowth with Abrupt, and JNK (Jun kinase) signalling, which is required for tumour cell migration/invasion but not overgrowth. These results thus identify a novel cooperating oncogene, identify mammalian family members of which are also known oncogenes, and demonstrate that epithelial tumours in Drosophila can be characterised by the maintenance of a progenitor-like state. PMID:23874226

  2. Pulsation, Mass Loss and the Upper Mass Limit

    NASA Astrophysics Data System (ADS)

    Klapp, J.; Corona-Galindo, M. G.

    1990-11-01

    RESUMEN. La existencia de estrellas con masas en exceso de 100 M0 ha sido cuestionada por mucho tiempo. Lfmites superiores para la masa de 100 M0 han sido obtenidos de teorfas de pulsaci6n y formaci6n estelar. En este trabajo nosotros primero investigamos la estabilidad radial de estrellas masivas utilizando la aproximaci6n clasica cuasiadiabatica de Ledoux, la aproximaci6n cuasiadiabatica de Castor y un calculo completamente no-adiabatico. Hemos encontrado que los tres metodos de calculo dan resultados similares siempre y cuando una pequefia regi6n de las capas externas de la estrella sea despreciada para la aproximaci6n clasica. La masa crftica para estabilidad de estrellas masivas ha sido encontrada en acuerdo a trabajos anteriores. Explicamos Ia discrepancia entre este y trabajos anteriores por uno de los autores. Discunmos calculos no-lineales y perdida de masa con respecto a) lfmite superior de masa. The existence of stars with masses in excess of 100 M0 has been questioned for a very long time. Upper mass limits of 100 Me have been obtained from pulsation and star formation theories. In this work we first investigate the radial stability of massive stars using the classical Ledoux's quasiadiabatic approximation. the Castor quasiadiabatic approximation and a fully nonadiabatic calculation. We have found that the three methods of calculation give similar results provided that a small region in outer layers of the star be neglected for the classical approximation. The critical mass for stability of massive stars is found to be in agreement with previous work. We explain the reason for the discrepancy between this and previous work by one of the authors. We discuss non-linear calculations and mass loss with regard to the upper mass limit. Key words: STARS-MASS FUNCTION - STARS-MASS LOSS - STARS-PULSATION

  3. Mass-loss rates of cool stars

    NASA Astrophysics Data System (ADS)

    Katrien Els Decin, Leen

    2015-08-01

    Over much of the initial mass function, stars lose a significant fraction of their mass through a stellar wind during the late stages of their evolution when being a (super)giant star. As of today, we can not yet predict the mass-loss rate during the (super)giant phase for a given star with specific stellar parameters from first principles. This uncertainty directly impacts the accuracy of current stellar evolution and population synthesis models that predict the enrichment of the interstellar medium by these stellar winds. Efforts to establish the link between the initial physical and chemical conditions at stellar birth and the mass-loss rate during the (super)giant phase have proceeded on two separate tracks: (1) more detailed studies of the chemical and morpho-kinematical structure of the stellar winds of (super)giant stars in our own Milky Way by virtue of the proximity, and (2) large scale and statistical studies of a (large) sample of stars in other galaxies (such as the LMC and SMC) and globular clusters eliminating the uncertainty on the distance estimate and providing insight into the dependence of the mass-loss rate on the metallicity. In this review, I will present recent results of both tracks, will show how recent measurements confirm (some) theoretical predictions, but also how results from the first track admonish of common misconceptions inherent in the often more simplified analysis used to analyse the large samples from track 2.

  4. A model on CME/Flare initiation: Loss of Equilibrium caused by mass loss of quiescent prominences

    NASA Astrophysics Data System (ADS)

    Miley, George; Chon Nam, Sok; Kim, Mun Song; Kim, Jik Su

    2015-08-01

    Coronal Mass Ejections (CMEs) model should give an answer to enough energy storage for giant bulk plasma into interplanetary space to escape against the sun’s gravitation and its explosive eruption. Advocates of ‘Mass Loading’ model (e.g. Low, B. 1996, SP, 167, 217) suggested a simple mechanism of CME initiation, the loss of mass from a prominence anchoring magnetic flux rope, but they did not associate the mass loss with the loss of equilibrium. The catastrophic loss of equilibrium model is considered as to be a prospective CME/Flare model to explain sudden eruption of magnetic flux systems. Isenberg, P. A., et al (1993, ApJ, 417, 368)developed ideal magnetohydrodynamic theory of the magnetic flux rope to show occurrence of catastrophic loss of equilibrium according to increasing magnetic flux transported into corona.We begin with extending their study including gravity on prominence’s material to obtain equilibrium curves in case of given mass parameters, which are the strengths of the gravitational force compared with the characteristic magnetic force. Furthermore, we study quasi-static evolution of the system including massive prominence flux rope and current sheet below it to obtain equilibrium curves of prominence’s height according to decreasing mass parameter in a properly fixed magnetic environment. The curves show equilibrium loss behaviors to imply that mass loss result in equilibrium loss. Released fractions of magnetic energy are greater than corresponding zero-mass case. This eruption mechanism is expected to be able to apply to the eruptions of quiescent prominences, which is located in relatively weak magnetic environment with 105 km of scale length and 10G of photospheric magnetic field.

  5. Abrupt climate change and extinction events

    NASA Technical Reports Server (NTRS)

    Crowley, Thomas J.

    1988-01-01

    There is a growing body of theoretical and empirical support for the concept of instabilities in the climate system, and indications that abrupt climate change may in some cases contribute to abrupt extinctions. Theoretical indications of instabilities can be found in a broad spectrum of climate models (energy balance models, a thermohaline model of deep-water circulation, atmospheric general circulation models, and coupled ocean-atmosphere models). Abrupt transitions can be of several types and affect the environment in different ways. There is increasing evidence for abrupt climate change in the geologic record and involves both interglacial-glacial scale transitions and the longer-term evolution of climate over the last 100 million years. Records from the Cenozoic clearly show that the long-term trend is characterized by numerous abrupt steps where the system appears to be rapidly moving to a new equilibrium state. The long-term trend probably is due to changes associated with plate tectonic processes, but the abrupt steps most likely reflect instabilities in the climate system as the slowly changing boundary conditions caused the climate to reach some threshold critical point. A more detailed analysis of abrupt steps comes from high-resolution studies of glacial-interglacial fluctuations in the Pleistocene. Comparison of climate transitions with the extinction record indicates that many climate and biotic transitions coincide. The Cretaceous-Tertiary extinction is not a candidate for an extinction event due to instabilities in the climate system. It is quite possible that more detailed comparisons and analysis will indicate some flaws in the climate instability-extinction hypothesis, but at present it appears to be a viable candidate as an alternate mechanism for causing abrupt environmental changes and extinctions.

  6. Uranium isotope evidence for the abrupt onset of oceanic anoxia during the end-Guadalupian mass extinction

    NASA Astrophysics Data System (ADS)

    Song, H.; Algeo, T. J.; Romaniello, S. J.; Tong, J.; Du, Y.; Wei, H.; Shen, S.; Anbar, A. D.

    2016-12-01

    The end-Guadalupian (Middle/Late Permian) mass extinction was one of the major crises of the Phanerozoic, resulting in the disappearance of numerous shallow-marine taxa. Several hypotheses have been proposed for this catastrophe but are still under debate. Here, we undertook a high-resolution carbonate U isotopic (δ238/235U) study of the Guadalupian-Lopingian boundary (GLB) at the Penglaitan section (Guadalupian/ Lopingian GSSP) to explore the causal relationship between ocean redox changes and the mass extinction event. The Penglaitan δ238U profile shows two abrupt negative excursions, one in the uppermost Guadalupian (Beds 6j-6k) and the other in the lowermost Lopingian (lower Bed 7). The first excursion (from ‒0.30 ‰ to ‒0.50 ‰) coincided with the main extinction event, suggesting that rapid expansion of oceanic anoxia may have been a contributor to the biotic crisis. The second, larger excursion (from ‒0.25 ‰ to ‒0.65 ‰) demonstrates that the crisis interval was marked by multiple phases of expanded oceanic anoxia. A U-isotope mass balance model shows that, during these excursions, the anoxic/euxinic sink flux increased to 40 % of the total sink flux of seawater U, which is three times of the modern ocean value of 13 %. This study thus provides circumstantial evidence for a causal relationship between expansion of oceanic anoxia and the end-Guadalupian biotic crisis.

  7. Mapping Greenland’s mass loss in space and time

    PubMed Central

    Harig, Christopher; Simons, Frederik J.

    2012-01-01

    The melting of polar ice sheets is a major contributor to global sea-level rise. Early estimates of the mass lost from the Greenland ice cap, based on satellite gravity data collected by the Gravity Recovery and Climate Experiment, have widely varied. Although the continentally and decadally averaged estimated trends have now more or less converged, to this date, there has been little clarity on the detailed spatial distribution of Greenland’s mass loss and how the geographical pattern has varied on relatively shorter time scales. Here, we present a spatially and temporally resolved estimation of the ice mass change over Greenland between April of 2002 and August of 2011. Although the total mass loss trend has remained linear, actively changing areas of mass loss were concentrated on the southeastern and northwestern coasts, with ice mass in the center of Greenland steadily increasing over the decade. PMID:23169646

  8. Mass loss at Saturn: The contribution of plasmoids

    NASA Astrophysics Data System (ADS)

    Kivelson, M.; Jia, X.; Jackman, C. M.

    2017-12-01

    Jia and Kivelson (2012) showed that an MHD simulation of Saturn's magnetosphere including rotating field-aligned currents generates a plasmoid on each rotation period. For southern summer conditions, plasmoids form through reconnection in the tail near midnight at a rotation phase for which the core magnetic field perturbation points towards the planet in the LT sector of the release. After release, they move northward and outward in the post midnight sector. Mass loss is found to be dominated by plasmoid release, and to compare closely to the mass source rate; much of the outward mass flux is found in the 0300-0900 LT sector. However, studies of plasmoid signatures in Cassini magnetometer data conclude that releases do not occur each rotation period and infer mass loss rates far smaller than Saturn's mass source rate (Jackman et al., 2014). Studies based on plasma data also infer loss rates smaller than the source rate from Enceladus (Thomsen, 2013). The simulation suggests that plasmoid occurrence frequency depends strongly on local time and latitude. Indeed, in regions near the equator and near midnight, where plasmoids are present in the simulation, the occurrence frequency of plasmoid releases inferred from magnetometer data is higher than elsewhere (Jackman et al., 2016; Smith et al., 2016), with occurrence probability peaking at the phase predicted by the simulation. We consider how the observational limitations should be modified to establish mass loss rates and plasmoid occurrence frequency.

  9. Dusty Mass Loss from Galactic Asymptotic Giant Branch Stars

    NASA Astrophysics Data System (ADS)

    Sargent, Benjamin A.; Srinivasan, Sundar; Meixner, Margaret; Kastner, Joel H.

    2016-06-01

    We are probing how mass loss from Asymptotic Giant Branch (AGB) stars depends upon their metallicity. Asymptotic giant branch (AGB) stars are evolved stars that eject large parts of their mass in outflows of dust and gas in the final stages of their lives. Our previous studies focused on mass loss from AGB stars in lower metallicity galaxies: the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). In our present study, we analyze AGB star mass loss in the Galaxy, with special attention to the Bulge, to investigate how mass loss differs in an overall higher metallicity environment. We construct radiative transfer models of the spectral energy distributions (SEDs) of stars in the Galaxy identified as AGB stars from infrared and optical surveys. Our Magellanic Cloud studies found that the AGB stars with the highest mass loss rates tended to have outflows with carbon-rich dust, and that overall more carbon-rich (C-rich) dust than oxygen-rich (O-rich) was produced by AGB stars in both LMC and SMC. Our radiative transfer models have enabled us to determine reliably the dust chemistry of the AGB star from the best-fit model. For our Galactic sample, we are investigating both the dust chemistries of the AGB stars and their mass-loss rates, to compare the balance of C-rich dust to O-rich dust between the Galactic bulge and the Magellanic Clouds. We are also constructing detailed dust opacity models of AGB stars in the Galaxy for which we have infrared spectra; e.g., from the Spitzer Space Telescope Infrared Spectrograph (IRS). This detailed dust modeling of spectra informs our choice of dust properties to use in radiative transfer modeling of SEDs of Galactic AGB stars. BAS acknowledges funding from NASA ADAP grant NNX15AF15G.

  10. Mass Loss Rates of Fasting Polar Bears.

    PubMed

    Pilfold, Nicholas W; Hedman, Daryll; Stirling, Ian; Derocher, Andrew E; Lunn, Nicholas J; Richardson, Evan

    2016-01-01

    Polar bears (Ursus maritimus) have adapted to an annual cyclic regime of feeding and fasting, which is extreme in seasonal sea ice regions of the Arctic. As a consequence of climate change, sea ice breakup has become earlier and the duration of the open-water period through which polar bears must rely on fat reserves has increased. To date, there is limited empirical data with which to evaluate the potential energetic capacity of polar bears to withstand longer fasts. We measured the incoming and outgoing mass of inactive polar bears (n = 142) that were temporarily detained by Manitoba Conservation and Water Stewardship during the open-water period near the town of Churchill, Manitoba, Canada, in 2009-2014. Polar bears were given access to water but not food and held for a median length of 17 d. Median mass loss rates were 1.0 kg/d, while median mass-specific loss rates were 0.5%/d, similar to other species with high adiposity and prolonged fasting capacities. Mass loss by unfed captive adult males was identical to that lost by free-ranging individuals, suggesting that terrestrial feeding contributes little to offset mass loss. The inferred metabolic rate was comparable to a basal mammalian rate, suggesting that while on land, polar bears can maintain a depressed metabolic rate to conserve energy. Finally, we estimated time to starvation for subadults and adult males for the on-land period. Results suggest that at 180 d of fasting, 56%-63% of subadults and 18%-24% of adult males in this study would die of starvation. Results corroborate previous assessments on the limits of polar bear capacity to withstand lengthening ice-free seasons and emphasize the greater sensitivity of subadults to changes in sea ice phenology.

  11. Near-Infrared Mass Loss Diagnostics for Massive Stars

    NASA Technical Reports Server (NTRS)

    Sonneborn, George; Bouret, J. C.

    2010-01-01

    Stellar wind mass loss is a key process which modifies surface abundances, luminosities, and other physical properties of hot, massive stars. Furthermore, mass loss has to be understood quantitatively in order to accurately describe and predict massive star evolution. Two urgent problems have been identified that challenge our understanding of line-driven winds, the so-called weak-wind problem and wind clumping. In both cases, mass-loss rates are drastically lower than theoretically expected (up to a factor 1001). Here we study how the expected spectroscopic capabilities of the James Webb Space Telescope (JWST), especially NIRSpec, could be used to significantly improve constraints on wind density structures (clumps) and deep-seated phenomena in stellar winds of massive stars, including OB, Wolf-Rayet and LBV stars. Since the IR continuum of objects with strong winds is formed in the wind, IR lines may sample different depths inside the wind than UV-optical lines and provide new information about the shape of the velocity field and clumping properties. One of the most important applications of IR line diagnostics will be the measurement of mass-loss rates in massive stars with very weak winds by means of the H I Bracket alpha line, which has been identified as one of the most promising diagnostics for this problem.

  12. Mass loss from hot, luminous stars

    NASA Astrophysics Data System (ADS)

    Burnley, Adam Warwick

    A general enquiry into the physics of mass loss from hot, luminous stars is presented. Ha spectroscopy of 64 Galactic early-type stars has been obtained using the telescopes of the Isaac Newton Group (ING) and the Anglo-Australian Observatory (AAO). The sample was selected to include objects with published radio and/or mm fluxes. The Halpha observations are quantitatively modelled using a modified version of the FORSOL code developed by Puls et al. (1996). FORSOL has been coupled with the PIKAIA subroutine (Charbonneau and Knapp, 1996) to create PHALTEE (Program for Halpha Line Transfer with Eugenic Estimation), in order to search a specified parameter space for the 'best' (quasi- least-squares) model fit to the data, using a genetic algorithm. This renders Ha modelling both more objective and automated. Where possible, both mass-loss rates and velocity field beta-exponents are determined for the sample. New mm-wave observations of nineteen Galactic early-type stars, including a subset of the Halpha sample, have been obtained using the Sub-millimetre Common User Bolometer Array (SCUBA). Where possible, mean fluxes are calculated, and these data used with the results of a literature survey of mm and cm fluxes to determine mass-loss rates for a larger sample, of 53 Galactic early-type stars. The incidence of nonthermal emission is examined, with 23% of the sample exhibiting strong evidence for nonthermal flux. The occurrence of binarity and excess X-ray emission amongst the nonthermal emitters is also investigated. For the subset of 36 stars common to both the Halpha and mm/radio samples, the results permit a comparison of mass-loss rates derived using diagnostics that probe the wind conditions at different radial depths. A mean value of log (Mradio/MHalpha) = 0.02 +/- 0.05 is obtained for the thermal radio emitters. The wind-momentum-luminosity relationship (WLR) for the sample is also investigated.

  13. Spontaneous Mass and Charge Losses from Single Multi-Megadalton Ions Studied by Charge Detection Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Keifer, David Z.; Alexander, Andrew W.; Jarrold, Martin F.

    2017-03-01

    Spontaneous mass and charge losses from individual multi-megadalton ions have been observed with charge detection mass spectrometry (CDMS) by trapping single hepatitis B virus (HBV) capsids for 3 s. Gradual increases in the oscillation frequency of single ions in the ion trap are attributed mainly to mass loss (probably solvent, water, and/or salt). The total mass lost during the 3 s trapping period peaks at around 20 kDa for 4 MDa HBV T = 4 capsids. Discrete frequency drops punctuate the gradual increases in the oscillation frequencies. The drops are attributed to a sudden loss of charge. In most cases a single positive charge is lost along with some mass (on average around 1000 Da). Charge loss occurs for over 40% of the trapped ions. It usually occurs near the beginning of the trapping event, and it occurs preferentially in regions of the trap with strong electric fields, indicating that external electric fields promote charge loss. This process may contribute to the decrease in m/ z resolution that often occurs with megadalton ions.

  14. Mass loss in O-type stars - Parameters which affect it

    NASA Technical Reports Server (NTRS)

    Garmany, C. D.; Conti, P. S.

    1984-01-01

    Newly determined mass loss rates are presented for sixteen O-type stars in three open clusters. Combining the data with that already in the literature, no evidence is found that the rates are different in clusters with differing galactocentric distances and compositions, at least near the sun. There is still appreciable dispersion in the relationship between the mass loss rate and the stellar luminosity. It may be that the mass loss depends additionally on the stellar mass and/or radius, but these data cannot unequivocally indicate which physical dependence is correct. Evidence is found that a stellar wind increases as a massive star evolves from the zero-age main sequence.

  15. Evolved Late-Type Star FUV Spectra: Mass Loss and Fluorescence

    NASA Technical Reports Server (NTRS)

    Harper, Graham M.

    2005-01-01

    This proposal was for a detailed analysis of the far ultraviolet (FUV) photoionizing radiation that provides crucial input physics for mass loss studies, e.g., observations of the flux below 10448, allow us to constrain the Ca II/Ca III balance and make significant progress beyond previous optical studies on stellar mass loss and circumstellar photochemistry. Our targets selection provided good spectral-type coverage required to help unravel the Ca II/Ca III balance as the mass-loss rates increase by over three orders of magnitude from K5 III to M5 III. We also explored the relationship between the FUV radiation field and other UV diagnostics to allow us to empirically estimate the FUV radiation field for the vast majority of stars which are too faint to be observed with FUSE, and to improve upon their uncertain mass-loss rates.

  16. Surface composition changes in massive star evolution with mass loss

    NASA Technical Reports Server (NTRS)

    Noels, A.; Gabriel, M.; Vreux, J.-M.; Conti, P. S.

    1980-01-01

    A series of evolutionary models of 40-100 solar mass objects undergoing mass loss are constructed with the explicit inclusion of the surface composition of H, He, C, N, O elements. Mass loss rates similar to those observed in Of stars, 4 to 7 x 10 to the -6th solar masses/yr, result in an appearance at the surface of equilibrium CNO products, i.e. enhanced nitrogen and diminished carbon, while that star is still burning hydrogen in the core. This result obtains because the initial convection core is a relatively large fraction of the total mass and rather modest loss exposes levels of anomalous composition. It is suggested that these objects might reasonably be identified as those luminous late type WN stars still containing surface hydrogen.

  17. Polarization and studies of evolved star mass loss

    NASA Astrophysics Data System (ADS)

    Sargent, Benjamin; Srinivasan, Sundar; Riebel, David; Meixner, Margaret

    2012-05-01

    Polarization studies of astronomical dust have proven very useful in constraining its properties. Such studies are used to constrain the spatial arrangement, shape, composition, and optical properties of astronomical dust grains. Here we explore possible connections between astronomical polarization observations to our studies of mass loss from evolved stars. We are studying evolved star mass loss in the Large Magellanic Cloud (LMC) by using photometry from the Surveying the Agents of a Galaxy's Evolution (SAGE; PI: M. Meixner) Spitzer Space Telescope Legacy program. We use the radiative transfer program 2Dust to create our Grid of Red supergiant and Asymptotic giant branch ModelS (GRAMS), in order to model this mass loss. To model emission of polarized light from evolved stars, however, we appeal to other radiative transfer codes. We probe how polarization observations might be used to constrain the dust shell and dust grain properties of the samples of evolved stars we are studying.

  18. Adiabatic Mass Loss Model in Binary Stars

    NASA Astrophysics Data System (ADS)

    Ge, H. W.

    2012-07-01

    Rapid mass transfer process in the interacting binary systems is very complicated. It relates to two basic problems in the binary star evolution, i.e., the dynamically unstable Roche-lobe overflow and the common envelope evolution. Both of the problems are very important and difficult to be modeled. In this PhD thesis, we focus on the rapid mass loss process of the donor in interacting binary systems. The application to the criterion of dynamically unstable mass transfer and the common envelope evolution are also included. Our results based on the adiabatic mass loss model could be used to improve the binary evolution theory, the binary population synthetic method, and other related aspects. We build up the adiabatic mass loss model. In this model, two approximations are included. The first one is that the energy generation and heat flow through the stellar interior can be neglected, hence the restructuring is adiabatic. The second one is that he stellar interior remains in hydrostatic equilibrium. We model this response by constructing model sequences, beginning with a donor star filling its Roche lobe at an arbitrary point in its evolution, holding its specific entropy and composition profiles fixed. These approximations are validated by the comparison with the time-dependent binary mass transfer calculations and the polytropic model for low mass zero-age main-sequence stars. In the dynamical time scale mass transfer, the adiabatic response of the donor star drives it to expand beyond its Roche lobe, leading to runaway mass transfer and the formation of a common envelope with its companion star. For donor stars with surface convection zones of any significant depth, this runaway condition is encountered early in mass transfer, if at all; but for main sequence stars with radiative envelopes, it may be encountered after a prolonged phase of thermal time scale mass transfer, so-called delayed dynamical instability. We identify the critical binary mass ratio for the

  19. [FACTORS WHICH INFLUENCE THE LEAN MASS LOSS IN CANCER PATIENTS].

    PubMed

    Sánchez Sánchez, Eduardo; Muñoz Alferez, Maria José

    2015-10-01

    cancer is an important illness in the sanitary field due to phisic and functional consequences involved in it. Among these consequences there is the malnutrition which can cause a loss of lean mass and with it a decrease in the Quality of Life, an increase in hospital stays, social and health costs and so on. The aim of this research is to know which factors can influence in the loss of the lean mass. it is a cross-sectional study in a sample of 72 patients who receive a radiotherapy with curative intent during a period from February 07th and May 14th, 2014. from this pattern Of the total 64 patients were studied, of which 43.7% of the patients presented loss of lean mass, with 21.8% the percentage of patients losing < 2%, 4.7% those with a loss between 2-5% and > 5%, 17.2% of patients. Among the factors studied that can influence the loss of lean mass, only the presence of digestive symptoms have statistical significance (OR = 3.3 or 6.6, as we take as a reference the percentage loss). the aim of the health staff who are working with these patients is to avoid the consequences that accompanies the loss of lean mass. For all this, it is very important to act before the digestive symptoms, by anticipating to them, or early implementation of an individualized nutritional intervention. Copyright AULA MEDICA EDICIONES 2014. Published by AULA MEDICA. All rights reserved.

  20. The evolution of massive stars including mass loss - Presupernova models and explosion

    NASA Technical Reports Server (NTRS)

    Woosley, S. E.; Langer, Norbert; Weaver, Thomas A.

    1993-01-01

    The evolution of massive stars of 35, 40, 60, and 85 solar masses is followed through all stages of nuclear burning to the point of Fe core collapse. Critical nuclear reaction and mass-loss rates are varied. Efficient mass loss during the Wolf-Rayet (WR) stage is likely to lead to final masses as small as 4 solar masses. For a reasonable parameterization of the mass loss, there may be convergence of all WR stars, both single and in binaries, to a narrow band of small final masses. Our representative model, a 4.25 solar-mass WR presupernova derived from a 60 solar mass star, is followed through a simulated explosion, and its explosive nucleosynthesis and light curve are determined. Its properties are similar to those observed in Type Ib supernovae. The effects of the initial mass and mass loss on the presupernova structure of small mass WR models is also explored. Important properties of the presupernova star and its explosion can only be obtained by following the complete evolution starting on the main sequence.

  1. Abrupt climate shift in the Western Mediterranean Sea.

    PubMed

    Schroeder, K; Chiggiato, J; Bryden, H L; Borghini, M; Ben Ismail, S

    2016-03-11

    One century of oceanographic measurements has evidenced gradual increases in temperature and salinity of western Mediterranean water masses, even though the vertical stratification has basically remained unchanged. Starting in 2005, the basic structure of the intermediate and deep layers abruptly changed. We report here evidence of reinforced thermohaline variability in the deep western basin with significant dense water formation events producing large amounts of warmer, saltier and denser water masses than ever before. We provide a detailed chronological order to these changes, giving an overview of the new water masses and following their route from the central basin interior to the east (toward the Tyrrhenian) and toward the Atlantic Ocean. As a consequence of this climate shift, new deep waters outflowing through Gibraltar will impact the North Atlantic in terms of salt and heat input. In addition, modifications in the Mediterranean abyssal ecosystems and biogeochemical cycles are to be expected.

  2. Variation in body mass dynamics among sites in Black Brant Branta bernicla nigricans supports adaptivity of mass loss during moult

    USGS Publications Warehouse

    Fondell, Thomas F.; Flint, Paul L.; Schmutz, Joel A.; Schamber, Jason L.; Nicolai, Christopher A.

    2013-01-01

    Birds employ varying strategies to accommodate the energetic demands of moult, one important example being changes in body mass. To understand better their physiological and ecological significance, we tested three hypotheses concerning body mass dynamics during moult. We studied Black Brant in 2006 and 2007 moulting at three sites in Alaska which varied in food availability, breeding status and whether geese undertook a moult migration. First we predicted that if mass loss during moult were simply the result of inadequate food resources then mass loss would be highest where food was least available. Secondly, we predicted that if mass loss during moult were adaptive, allowing birds to reduce activity during moult, then birds would gain mass prior to moult where feeding conditions allowed and mass loss would be positively related to mass at moult initiation. Thirdly, we predicted that if mass loss during moult were adaptive, allowing birds to regain flight sooner, then across sites and groups, mass at the end of the flightless period would converge on a theoretical optimum, i.e. the mass that permits the earliest possible return to flight. Mass loss was greatest where food was most available and thus our results did not support the prediction that mass loss resulted from inadequate food availability. Mass at moult initiation was positively related to both food availability and mass loss. In addition, among sites and years, variation in mass was high at moult initiation but greatly reduced at the end of the flightless period, appearing to converge. Thus, our results supported multiple predictions that mass loss during moult was adaptive and that the optimal moulting strategy was to gain mass prior to the flightless period, then through behavioural modifications use these body reserves to reduce activity and in so doing also reduce wing loading. Geese that undertook a moult migration initiated moult at the highest mass, indicating that they were more than able to

  3. Mass loss during the RR Lyrae phase of the horizontal branch: Mass dispersion on the horizontal branch and RR Lyrae period changes

    NASA Technical Reports Server (NTRS)

    Koopmann, Rebecca A.; Lee, Young-Wook; Demarque, Pierre; Howard, Jamie M.

    1994-01-01

    Mass loss on the horizontal branch has been invoked in the literature to explain such phenomena as the color (mass) dispersion of the horizontal branch and the observed distribution of period changes in RR Lyrae stars. To test these claims, the Yale stellar evolution code was used to evolve horizontal branch models of masses 0.64, 0.66, 0.68, 0.70, and 0.72 solar mass with Z of 0.001, core mass of 0.4893, main-sequence helium abundance of 0.23, and constant mass loss rates of 0, 10(exp -10), 5 x 10(exp -10), and 10(exp -9) solar mass/yr. Mass loss was assumed to occur only in the instability strip, where a mechanism is most likely to exist. Synthetic horizontal branches, constructed from the models, show that mass loss on the horizontal branch cannot produce the observed color dispersion even for the highest mass-loss rate of 10(exp -9) solar mass/yr. Mass loss is unlikely to occur at a higher rate without significant effects on the horizontal branch morphology, which would destroy the good agreement between standard synthetic models without mass loss and observed horizontal branches. Periods and period changes were calculated for all models. The period changes are not significantly larger for models with mass loss. The effect of mass loss in clusters of other metallicities is discussed.

  4. Chromospheres and mass loss in metal-deficient giant stars

    NASA Technical Reports Server (NTRS)

    Dupree, A. K.; Hartmann, L.; Avrett, E. H.

    1984-01-01

    Semiempirical atmospheric models indicate that the characteristic emission in the wings of the H-alpha line observed in Population II giant stars can arise naturally within static chromospheres. Radial expansion gives an asymmetric, blueshifted H-alpha core accompanied by greater emission in the red line wing than in the blue wing. Wind models with extended atmospheres suggest mass loss rates much smaller than 2 x 10 to the -9th solar mass per yr. Thus H-alpha provides no evidence that steady mass loss can significantly affect the evolution of stars on the red giant branch of globular clusters.

  5. Abrupt climate change: can society cope?

    PubMed

    Hulme, Mike

    2003-09-15

    Consideration of abrupt climate change has generally been incorporated neither in analyses of climate-change impacts nor in the design of climate adaptation strategies. Yet the possibility of abrupt climate change triggered by human perturbation of the climate system is used to support the position of both those who urge stronger and earlier mitigative action than is currently being contemplated and those who argue that the unknowns in the Earth system are too large to justify such early action. This paper explores the question of abrupt climate change in terms of its potential implications for society, focusing on the UK and northwest Europe in particular. The nature of abrupt climate change and the different ways in which it has been defined and perceived are examined. Using the example of the collapse of the thermohaline circulation (THC), the suggested implications for society of abrupt climate change are reviewed; previous work has been largely speculative and has generally considered the implications only from economic and ecological perspectives. Some observations about the implications from a more social and behavioural science perspective are made. If abrupt climate change simply implies changes in the occurrence or intensity of extreme weather events, or an accelerated unidirectional change in climate, the design of adaptation to climate change can proceed within the existing paradigm, with appropriate adjustments. Limits to adaptation in some sectors or regions may be reached, and the costs of appropriate adaptive behaviour may be large, but strategy can develop on the basis of a predicted long-term unidirectional change in climate. It would be more challenging, however, if abrupt climate change implied a directional change in climate, as, for example, may well occur in northwest Europe following a collapse of the THC. There are two fundamental problems for society associated with such an outcome: first, the future changes in climate currently being

  6. Abrupt Change in Ecological Systems: Inference and Diagnosis.

    PubMed

    Ratajczak, Zak; Carpenter, Stephen R; Ives, Anthony R; Kucharik, Christopher J; Ramiadantsoa, Tanjona; Stegner, M Allison; Williams, John W; Zhang, Jien; Turner, Monica G

    2018-05-18

    Abrupt ecological changes are, by definition, those that occur over short periods of time relative to typical rates of change for a given ecosystem. The potential for such changes is growing due to anthropogenic pressures, which challenges the resilience of societies and ecosystems. Abrupt ecological changes are difficult to diagnose because they can arise from a variety of circumstances, including rapid changes in external drivers (e.g., climate, or resource extraction), nonlinear responses to gradual changes in drivers, and interactions among multiple drivers and disturbances. We synthesize strategies for identifying causes of abrupt ecological change and highlight instances where abrupt changes are likely. Diagnosing abrupt changes and inferring causation are increasingly important as society seek to adapt to rapid, multifaceted environmental changes. Copyright © 2018 Elsevier Ltd. All rights reserved.

  7. Abrupt climate shift in the Western Mediterranean Sea

    PubMed Central

    Schroeder, K.; Chiggiato, J.; Bryden, H. L.; Borghini, M.; Ben Ismail, S.

    2016-01-01

    One century of oceanographic measurements has evidenced gradual increases in temperature and salinity of western Mediterranean water masses, even though the vertical stratification has basically remained unchanged. Starting in 2005, the basic structure of the intermediate and deep layers abruptly changed. We report here evidence of reinforced thermohaline variability in the deep western basin with significant dense water formation events producing large amounts of warmer, saltier and denser water masses than ever before. We provide a detailed chronological order to these changes, giving an overview of the new water masses and following their route from the central basin interior to the east (toward the Tyrrhenian) and toward the Atlantic Ocean. As a consequence of this climate shift, new deep waters outflowing through Gibraltar will impact the North Atlantic in terms of salt and heat input. In addition, modifications in the Mediterranean abyssal ecosystems and biogeochemical cycles are to be expected. PMID:26965790

  8. A Study of the Mass Loss Rates of Symbiotic Star Systems

    NASA Technical Reports Server (NTRS)

    Korreck, K. E.; Kellogg, E.; Sokoloski, J. L.

    2007-01-01

    The amount of mass loss in symbiotic systems is investigated, specifically mass loss via the formation of jets in R Aquarii (R Aqr). The jets in R Aqr have been observed in the X-ray by Chandra over a four year time period. The jet changes on times scales of a year and new outflows have been observed. Understanding the amount of mass and the frequency of ejection further constrain the ability of the white dwarf in the system to accrete enough mass to become a Type la supernova progenitor. The details of multi-wavelength studies, such as speed, density and spatial extent of the jets will be discussed in order to understand the mass balance in the binary system. We examine other symbiotic systems to determine trends in mass loss in this class of objects.

  9. Increased protein intake reduces lean body mass loss during weight loss in athletes.

    PubMed

    Mettler, Samuel; Mitchell, Nigel; Tipton, Kevin D

    2010-02-01

    To examine the influence of dietary protein on lean body mass loss and performance during short-term hypoenergetic weight loss in athletes. In a parallel design, 20 young healthy resistance-trained athletes were examined for energy expenditure for 1 wk and fed a mixed diet (15% protein, 100% energy) in the second week followed by a hypoenergetic diet (60% of the habitual energy intake), containing either 15% (approximately 1.0 g x kg(-1)) protein (control group, n = 10; CP) or 35% (approximately 2.3 g x kg(-1)) protein (high-protein group, n = 10; HP) for 2 wk. Subjects continued their habitual training throughout the study. Total, lean body, and fat mass, performance (squat jump, maximal isometric leg extension, one-repetition maximum (1RM) bench press, muscle endurance bench press, and 30-s Wingate test) and fasting blood samples (glucose, nonesterified fatty acids (NEFA), glycerol, urea, cortisol, free testosterone, free Insulin-like growth factor-1 (IGF-1), and growth hormone), and psychologic measures were examined at the end of each of the 4 wk. Total (-3.0 +/- 0.4 and -1.5 +/- 0.3 kg for the CP and HP, respectively, P = 0.036) and lean body mass loss (-1.6 +/- 0.3 and -0.3 +/- 0.3 kg, P = 0.006) were significantly larger in the CP compared with those in the HP. Fat loss, performance, and most blood parameters were not influenced by the diet. Urea was higher in HP, and NEFA and urea showed a group x time interaction. Fatigue ratings and "worse than normal" scores on the Daily Analysis of Life Demands for Athletes were higher in HP. These results indicate that approximately 2.3 g x kg(-1) or approximately 35% protein was significantly superior to approximately 1.0 g x kg(-1) or approximately 15% energy protein for maintenance of lean body mass in young healthy athletes during short-term hypoenergetic weight loss.

  10. Banning Fisheries Discards Abruptly Has a Negative Impact on the Population Dynamics of Charismatic Marine Megafauna.

    PubMed

    Fondo, Esther N; Chaloupka, Milani; Heymans, Johanna J; Skilleter, Greg A

    2015-01-01

    Food subsidies have the potential to modify ecosystems and affect the provision of goods and services. Predictable Anthropogenic Food Subsidies (PAFS) modify ecosystems by altering ecological processes and food webs. The global concern over the effects of PAFS in ecosystems has led to development of environmental policies aimed at curbing the production or ultimately banning of PAFS. However, the effects of reducing or banning PAFS are not known. We explore the consequences of PAFS removal in a marine ecosystem under two scenarios: 1) gradual reduction, or 2) an abrupt ban, using a mass balance model to test these hypotheses-The reduction or loss of PAFS will: i) modify trophic levels and food webs through effects on foraging by opportunistic species, ii) increase the resilience of opportunistic species to food shortages, and iii) modify predator-prey interactions through shifts in prey consumption. We found that PAFS lower the trophic levels of opportunistic scavengers and increase their food pathways. Scavengers are able to switch prey when PAFS are reduced gradually but they decline when PAFS are abruptly banned. PAFS reduction to a certain minimal level causes a drop in the ecosystem's stability. We recommend gradual reduction of PAFS to a minimal level that would maintain the ecosystem's stability and allow species exploiting PAFS to habituate to the food subsidy reduction.

  11. Effects of Main-Sequence Mass Loss on Stellar and Galactic Chemical Evolution.

    NASA Astrophysics Data System (ADS)

    Guzik, Joyce Ann

    1988-06-01

    L. A. Willson, G. H. Bowen and C. Struck -Marcell have proposed that 1 to 3 solar mass stars may experience evolutionarily significant mass loss during the early part of their main-sequence phase. The suggested mass-loss mechanism is pulsation, facilitated by rapid rotation. Initial mass-loss rates may be as large as several times 10^{-9}M o/yr, diminishing over several times 10^8 years. We attempted to test this hypothesis by comparing some theoretical implications with observations. Three areas are addressed: Solar models, cluster HR diagrams, and galactic chemical evolution. Mass-losing solar models were evolved that match the Sun's luminosity and radius at its present age. The most extreme viable models have initial mass 2.0 M o, and mass-loss rates decreasing exponentially over 2-3 times 10^8 years. Compared to a constant -mass model, these models require a reduced initial ^4He abundance, have deeper envelope convection zones and higher ^8B neutrino fluxes. Early processing of present surface layers at higher interior temperatures increases the surface ^3He abundance, destroys Li, Be and B, and decreases the surface C/N ratio following first dredge-up. Evolution calculations incorporating main-sequence mass loss were completed for a grid of models with initial masses 1.25 to 2.0 Mo and mass loss timescales 0.2 to 2.0 Gyr. Cluster HR diagrams synthesized with these models confirm the potential for the hypothesis to explain observed spreads or bifurcations in the upper main sequence, blue stragglers, anomalous giants, and poor fits of main-sequence turnoffs by standard isochrones. Simple closed galactic chemical evolution models were used to test the effects of main-sequence mass loss on the F and G dwarf distribution. Stars between 3.0 M o and a metallicity -dependent lower mass are assumed to lose mass. The models produce a 30 to 60% increase in the stars to stars-plus -remnants ratio, with fewer early-F dwarfs and many more late-F dwarfs remaining on the main

  12. Risk Factors for the Loss of Lean Body Mass After Gastrectomy for Gastric Cancer.

    PubMed

    Aoyama, Toru; Sato, Tsutomu; Segami, Kenki; Maezawa, Yukio; Kano, Kazuki; Kawabe, Taiichi; Fujikawa, Hirohito; Hayashi, Tsutomu; Yamada, Takanobu; Tsuchida, Kazuhito; Yukawa, Norio; Oshima, Takashi; Rino, Yasushi; Masuda, Munetaka; Ogata, Takashi; Cho, Haruhiko; Yoshikawa, Takaki

    2016-06-01

    Lean body mass loss after surgery, which decreases the compliance of adjuvant chemotherapy, is frequently observed in gastric cancer patients who undergo gastrectomy for gastric cancer. However, the risk factors for loss of lean body mass remain unclear. The current study retrospectively examined the patients who underwent curative gastrectomy for gastric cancer between June 2010 and March 2014 at Kanagawa Cancer Center. All the patients received perioperative care for enhanced recovery after surgery. The percentage of lean body mass loss was calculated by the percentile of lean body mass 1 month after surgery to preoperative lean body mass. Severe lean body mass loss was defined as a lean body mass loss greater than 5 %. Risk factors for severe lean body mass loss were determined by both uni- and multivariate logistic regression analyses. This study examined 485 patients. The median loss of lean body mass was 4.7 %. A lean body mass loss of 5 % or more occurred for 225 patients (46.4 %). Both uni- and multivariate logistic analyses demonstrated that the significant independent risk factors for severe lean body mass loss were surgical complications with infection or fasting (odds ratio [OR] 3.576; p = 0.001), total gastrectomy (OR 2.522; p = 0.0001), and gender (OR 1.928; p = 0.001). Nutritional intervention or control of surgical invasion should be tested in future clinical trials for gastric cancer patients with these risk factors to maintain lean body mass after gastrectomy.

  13. Mass-loss Rates from Coronal Mass Ejections: A Predictive Theoretical Model for Solar-type Stars

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cranmer, Steven R.

    Coronal mass ejections (CMEs) are eruptive events that cause a solar-type star to shed mass and magnetic flux. CMEs tend to occur together with flares, radio storms, and bursts of energetic particles. On the Sun, CME-related mass loss is roughly an order of magnitude less intense than that of the background solar wind. However, on other types of stars, CMEs have been proposed to carry away much more mass and energy than the time-steady wind. Earlier papers have used observed correlations between solar CMEs and flare energies, in combination with stellar flare observations, to estimate stellar CME rates. This papermore » sidesteps flares and attempts to calibrate a more fundamental correlation between surface-averaged magnetic fluxes and CME properties. For the Sun, there exists a power-law relationship between the magnetic filling factor and the CME kinetic energy flux, and it is generalized for use on other stars. An example prediction of the time evolution of wind/CME mass-loss rates for a solar-mass star is given. A key result is that for ages younger than about 1 Gyr (i.e., activity levels only slightly higher than the present-day Sun), the CME mass loss exceeds that of the time-steady wind. At younger ages, CMEs carry 10–100 times more mass than the wind, and such high rates may be powerful enough to dispel circumstellar disks and affect the habitability of nearby planets. The cumulative CME mass lost by the young Sun may have been as much as 1% of a solar mass.« less

  14. Accelerated West Antarctic ice mass loss continues to outpace East Antarctic gains

    NASA Astrophysics Data System (ADS)

    Harig, Christopher; Simons, Frederik J.

    2015-04-01

    While multiple data sources have confirmed that Antarctica is losing ice at an accelerating rate, different measurement techniques estimate the details of its geographically highly variable mass balance with different levels of accuracy, spatio-temporal resolution, and coverage. Some scope remains for methodological improvements using a single data type. In this study we report our progress in increasing the accuracy and spatial resolution of time-variable gravimetry from the Gravity Recovery and Climate Experiment (GRACE). We determine the geographic pattern of ice mass change in Antarctica between January 2003 and June 2014, accounting for glacio-isostatic adjustment (GIA) using the IJ05_R2 model. Expressing the unknown signal in a sparse Slepian basis constructed by optimization to prevent leakage out of the regions of interest, we use robust signal processing and statistical estimation methods. Applying those to the latest time series of monthly GRACE solutions we map Antarctica's mass loss in space and time as well as can be recovered from satellite gravity alone. Ignoring GIA model uncertainty, over the period 2003-2014, West Antarctica has been losing ice mass at a rate of - 121 ± 8 Gt /yr and has experienced large acceleration of ice mass losses along the Amundsen Sea coast of - 18 ± 5 Gt /yr2, doubling the mass loss rate in the past six years. The Antarctic Peninsula shows slightly accelerating ice mass loss, with larger accelerated losses in the southern half of the Peninsula. Ice mass gains due to snowfall in Dronning Maud Land have continued to add about half the amount of West Antarctica's loss back onto the continent over the last decade. We estimate the overall mass losses from Antarctica since January 2003 at - 92 ± 10 Gt /yr.

  15. Mass Gains of the Antarctic Ice Sheet Exceed Losses

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Li, Jun; Robbins, John; Saba, Jack L.; Yi, Donghui; Brenner, Anita; Bromwich, David

    2012-01-01

    During 2003 to 2008, the mass gain of the Antarctic ice sheet from snow accumulation exceeded the mass loss from ice discharge by 49 Gt/yr (2.5% of input), as derived from ICESat laser measurements of elevation change. The net gain (86 Gt/yr) over the West Antarctic (WA) and East Antarctic ice sheets (WA and EA) is essentially unchanged from revised results for 1992 to 2001 from ERS radar altimetry. Imbalances in individual drainage systems (DS) are large (-68% to +103% of input), as are temporal changes (-39% to +44%). The recent 90 Gt/yr loss from three DS (Pine Island, Thwaites-Smith, and Marie-Bryd Coast) of WA exceeds the earlier 61 Gt/yr loss, consistent with reports of accelerating ice flow and dynamic thinning. Similarly, the recent 24 Gt/yr loss from three DS in the Antarctic Peninsula (AP) is consistent with glacier accelerations following breakup of the Larsen B and other ice shelves. In contrast, net increases in the five other DS of WA and AP and three of the 16 DS in East Antarctica (EA) exceed the increased losses. Alternate interpretations of the mass changes driven by accumulation variations are given using results from atmospheric-model re-analysis and a parameterization based on 5% change in accumulation per degree of observed surface temperature change. A slow increase in snowfall with climate waRMing, consistent with model predictions, may be offsetting increased dynamic losses.

  16. Mass Loss of Larsen B Tributary Glaciers (Antarctic Peninsula) Unabated Since 2002

    NASA Technical Reports Server (NTRS)

    Berthier, Etienne; Scambos, Ted; Shuman, Christopher A.

    2012-01-01

    Ice mass loss continues at a high rate among the large glacier tributaries of the Larsen B Ice Shelf following its disintegration in 2002. We evaluate recent mass loss by mapping elevation changes between 2006 and 201011 using differencing of digital elevation models (DEMs). The measurement accuracy of these elevation changes is confirmed by a null test, subtracting DEMs acquired within a few weeks. The overall 2006201011 mass loss rate (9.0 2.1 Gt a-1) is similar to the 2001022006 rate (8.8 1.6 Gt a-1), derived using DEM differencing and laser altimetry. This unchanged overall loss masks a varying pattern of thinning and ice loss for individual glacier basins. On Crane Glacier, the thinning pulse, initially greatest near the calving front, is now broadening and migrating upstream. The largest losses are now observed for the HektoriaGreen glacier basin, having increased by 33 since 2006. Our method has enabled us to resolve large residual uncertainties in the Larsen B sector and confirm its state of ongoing rapid mass loss.

  17. Lean Mass Loss Is Associated with Low Protein Intake during Dietary-Induced Weight Loss in Postmenopausal Women

    PubMed Central

    BOPP, MELANIE J.; HOUSTON, DENISE K.; LENCHIK, LEON; EASTER, LINDA; KRITCHEVSKY, STEPHEN B.; NICKLAS, BARBARA J.

    2013-01-01

    The health and quality-of-life implications of overweight and obesity span all ages in the United States. We investigated the association between dietary protein intake and loss of lean mass during weight loss in postmenopausal women through a retrospective analysis of a 20-week randomized, controlled diet and exercise intervention in women aged 50 to 70 years. Weight loss was achieved by differing levels of caloric restriction and exercise. The diet-only group reduced caloric intake by 2,800 kcal/week, and the exercise groups reduced caloric intake by 2,400 kcal/week and expended ~400 kcal/week through aerobic exercise. Total and appendicular lean mass was measured using dual energy x-ray absorptiometry. Linear regression analysis was used to examine the association between changes in lean mass and appendicular lean mass and dietary protein intake. Average weight loss was 10.8±4.0 kg, with an average of 32% of total weight lost as lean mass. Protein intake averaged 0.62 g/kg body weight/day (range=0.47 to 0.8 g/kg body weight/day). Participants who consumed higher amounts of dietary protein lost less lean mass and appendicular lean mass r(=0.3, P=0.01 and r=0.41, P<0.001, respectively). These associations remained significant after adjusting for intervention group and body size. Therefore, inadequate protein intake during caloric restriction may be associated with adverse body-composition changes in postmenopausal women. PMID:18589032

  18. Surface mass balance contributions to acceleration of Antarctic ice mass loss during 2003-2013

    NASA Astrophysics Data System (ADS)

    Seo, Ki-Weon; Wilson, Clark R.; Scambos, Ted; Kim, Baek-Min; Waliser, Duane E.; Tian, Baijun; Kim, Byeong-Hoon; Eom, Jooyoung

    2015-05-01

    Recent observations from satellite gravimetry (the Gravity Recovery and Climate Experiment (GRACE) mission) suggest an acceleration of ice mass loss from the Antarctic Ice Sheet (AIS). The contribution of surface mass balance changes (due to variable precipitation) is compared with GRACE-derived mass loss acceleration by assessing the estimated contribution of snow mass from meteorological reanalysis data. We find that over much of the continent, the acceleration can be explained by precipitation anomalies. However, on the Antarctic Peninsula and other parts of West Antarctica, mass changes are not explained by precipitation and are likely associated with ice discharge rate increases. The total apparent GRACE acceleration over all of the AIS between 2003 and 2013 is -13.6 ± 7.2 Gt/yr2. Of this total, we find that the surface mass balance component is -8.2 ± 2.0 Gt/yr2. However, the GRACE estimate appears to contain errors arising from the atmospheric pressure fields used to remove air mass effects. The estimated acceleration error from this effect is about 9.8 ± 5.8 Gt/yr2. Correcting for this yields an ice discharge acceleration of -15.1 ± 6.5 Gt/yr2.

  19. Surface Mass Balance Contributions to Acceleration of Antarctic Ice Mass Loss during 2003- 2013

    NASA Astrophysics Data System (ADS)

    Seo, K. W.; Wilson, C. R.; Scambos, T. A.; Kim, B. M.; Waliser, D. E.; Tian, B.; Kim, B.; Eom, J.

    2015-12-01

    Recent observations from satellite gravimetry (the GRACE mission) suggest an acceleration of ice mass loss from the Antarctic Ice Sheet (AIS). The contribution of surface mass balance changes (due to variable precipitation) is compared with GRACE-derived mass loss acceleration by assessing the estimated contribution of snow mass from meteorological reanalysis data. We find that over much of the continent, the acceleration can be explained by precipitation anomalies. However, on the Antarctic Peninsula and other parts of West Antarctica mass changes are not explained by precipitation and are likely associated with ice discharge rate increases. The total apparent GRACE acceleration over all of the AIS between 2003 and 2013 is -13.6±7.2 GTon/yr2. Of this total, we find that the surface mass balance component is -8.2±2.0 GTon/yr2. However, the GRACE estimate appears to contain errors arising from the atmospheric pressure fields used to remove air mass effects. The estimated acceleration error from this effect is about 9.8±5.8 GTon/yr2. Correcting for this yields an ice discharge acceleration of -15.1±6.5 GTon/yr2.

  20. EVOLUTIONARY MODELS OF SUPER-EARTHS AND MINI-NEPTUNES INCORPORATING COOLING AND MASS LOSS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Howe, Alex R.; Burrows, Adam, E-mail: arhowe@astro.princeton.edu, E-mail: burrows@astro.princeton.edu

    We construct models of the structural evolution of super-Earth- and mini-Neptune-type exoplanets with H{sub 2}–He envelopes, incorporating radiative cooling and XUV-driven mass loss. We conduct a parameter study of these models, focusing on initial mass, radius, and envelope mass fractions, as well as orbital distance, metallicity, and the specific prescription for mass loss. From these calculations, we investigate how the observed masses and radii of exoplanets today relate to the distribution of their initial conditions. Orbital distance and the initial envelope mass fraction are the most important factors determining planetary evolution, particularly radius evolution. Initial mass also becomes important belowmore » a “turnoff mass,” which varies with orbital distance, with mass–radius curves being approximately flat for higher masses. Initial radius is the least important parameter we study, with very little difference between the hot start and cold start limits after an age of 100 Myr. Model sets with no mass loss fail to produce results consistent with observations, but a plausible range of mass-loss scenarios is allowed. In addition, we present scenarios for the formation of the Kepler-11 planets. Our best fit to observations of Kepler-11b and Kepler-11c involves formation beyond the snow line, after which they moved inward, circularized, and underwent a reduced degree of mass loss.« less

  1. Analysis of abrupt transitions in ecological systems

    USDA-ARS?s Scientific Manuscript database

    The occurrence and causes of abrupt transitions, thresholds, or regime shifts between ecosystem states are of great concern and the likelihood of such transitions is increasing for many ecological systems. General understanding of abrupt transitions has been advanced by theory, but hindered by the l...

  2. PULSATION-TRIGGERED MASS LOSS FROM AGB STARS: THE 60 DAY CRITICAL PERIOD

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    McDonald, I.; Zijlstra, A. A., E-mail: iain.mcdonald-2@jb.man.ac.uk, E-mail: albert.zijlstra@manchester.ac.uk

    2016-06-01

    Low- and intermediate-mass stars eject much of their mass during the late, red giant branch (RGB) phase of evolution. The physics of their strong stellar winds is still poorly understood. In the standard model, stellar pulsations extend the atmosphere, allowing a wind to be driven through radiation pressure on condensing dust particles. Here, we investigate the onset of the wind, using nearby RGB stars drawn from the Hipparcos catalog. We find a sharp onset of dust production when the star first reaches a pulsation period of 60 days. This approximately coincides with the point where the star transitions to themore » first overtone pulsation mode. Models of the spectral energy distributions show stellar mass-loss rate suddenly increasing at this point, by a factor of ∼10 over the existing (chromospherically driven) wind. The dust emission is strongly correlated with both pulsation period and amplitude, indicating stellar pulsation is the main trigger for the strong mass loss, and determines the mass-loss rate. Dust emission does not strongly correlate with stellar luminosity, indicating radiation pressure on dust has little effect on the mass-loss rate. RGB stars do not normally appear to produce dust, whereas dust production by asymptotic giant branch stars appears commonplace, and is probably ubiquitous above the RGB-tip luminosity. We conclude that the strong wind begins with a step change in mass-loss rate and is triggered by stellar pulsations. A second rapid mass-loss-rate enhancement is suggested when the star transitions to the fundamental pulsation mode at a period of ∼300 days.« less

  3. Bipolar nebulae and mass loss from red giant stars

    NASA Technical Reports Server (NTRS)

    Cohen, M.

    1985-01-01

    Observations of several bipolar nebulae are used to learn something of the nature of mass loss from the probable red-giant progenitors of these nebulae. Phenomena discussed are: (1) probable GL 2688's optical molecular emissions; (2) newly discovered very high velocity knots along the axis of OH 0739 - 14, which reveal evidence for mass ejections of + or 300 km/s from the M9 III star embedded in this nebula; (3) the bipolar structure of three extreme carbon stars, and the evidence for periodic mass ejection in IRC + 30219, also at high speed (about 80 km/s); and (4) the curious cool TiO-rich region above Parsamian 13, which may represent the very recent shedding of photospheric material from a cool, oxygen-rich giant. Several general key questions about bipolar nebulae that relate to the process of mass loss from their progenitor stars are raised.

  4. Controls on the abruptness of gravel-sand transitions

    NASA Astrophysics Data System (ADS)

    Venditti, J. G.; Church, M. A.; Lamb, M. P.; Domarad, N.; Rennie, C. D.

    2014-12-01

    As gravel-bedded rivers fine downstream, they characteristically exhibit an abrupt transition from gravel- to sand-bed. This is the only abrupt transition in grain-size that occurs in the fluvial system and has attracted considerable attention. A number of competing theories have been proposed to account for the abruptness of the transition, including base-level control, attrition of ~10mm gravel to produce sand, and sediment sorting processes. The prevailing theory for the emergence of abrupt transitions is size selective sorting of bimodal sediment wherein gravel deposits due to downstream declining shear stress, fining the bedload until a sand-bed emerges. We explored this hypothesis by examining grain-size, shear stress, gravel mobility and sand suspension thresholds through the gravel-sand transition (GST) of the Fraser River, British Columbia. The Fraser GST is an arrested gravel wedge with patches of gravel downstream of the wedge forming a diffuse extension. There is an abrupt change in bed slope through the transition that leads to an abrupt change in shear stress. The GST, bed-slope change and backwater caused by the ocean are all coincident spatially, which enhances the sharpness of the GST. Interestingly, the bimodal reach of the river occurs downstream of the GST and exhibits no downstream gradients in shear stress, suspended sediment flux, gravel mobility or sand suspension thresholds. This calls into question the prevailing theory for the emergence of an abrupt GST by size selective sorting. We provide evidence, both empirical and theoretical, that suggests the emergence of an abrupt GST is caused by rapid deposition of sand when fine gravel deposits. We argue that the emergence of gravel-sand transitions is a consequence of gravel-bedded rivers adopting a steeper slope than sand-bedded rivers. The abruptness arises because the bed slope required to convey the gravel load fixes the distal location of a terminal gravel wedge, and once the river has

  5. Surface mass balance contributions to acceleration of Antarctic ice mass loss during 2003-2013.

    PubMed

    Seo, Ki-Weon; Wilson, Clark R; Scambos, Ted; Kim, Baek-Min; Waliser, Duane E; Tian, Baijun; Kim, Byeong-Hoon; Eom, Jooyoung

    2015-05-01

    Recent observations from satellite gravimetry (the Gravity Recovery and Climate Experiment (GRACE) mission) suggest an acceleration of ice mass loss from the Antarctic Ice Sheet (AIS). The contribution of surface mass balance changes (due to variable precipitation) is compared with GRACE-derived mass loss acceleration by assessing the estimated contribution of snow mass from meteorological reanalysis data. We find that over much of the continent, the acceleration can be explained by precipitation anomalies. However, on the Antarctic Peninsula and other parts of West Antarctica, mass changes are not explained by precipitation and are likely associated with ice discharge rate increases. The total apparent GRACE acceleration over all of the AIS between 2003 and 2013 is -13.6 ± 7.2 Gt/yr 2 . Of this total, we find that the surface mass balance component is -8.2 ± 2.0 Gt/yr 2 . However, the GRACE estimate appears to contain errors arising from the atmospheric pressure fields used to remove air mass effects. The estimated acceleration error from this effect is about 9.8 ± 5.8 Gt/yr 2 . Correcting for this yields an ice discharge acceleration of -15.1 ± 6.5 Gt/yr 2 .

  6. Abrupt Impacts of Climate Change: Anticipating Surprises

    NASA Astrophysics Data System (ADS)

    White, James W. C.; Alley, Richard B.; Archer, David E.; Barnosky, Anthony D.; Dunlea, Edward; Foley, Jonathan; Fu, Rong; Holland, Marika M.; Lozier, M. Susan; Schmitt, Johanna; Smith, Laurence C.; Sugihara, George; Thompson, David W. J.; Weaver, Andrew J.; Wofsy, Steven C.

    2014-05-01

    Levels of carbon dioxide and other greenhouse gases in Earth's atmosphere are exceeding levels recorded in the past millions of years, and thus climate is being forced beyond the range of the recent geological era. Lacking concerted action by the world's nations, it is clear that the future climate will be warmer, sea levels will rise, global rainfall patterns will change, and ecosystems will be altered. However, there is still uncertainty about how we will arrive at that future climate state. Although many projections of future climatic conditions have predicted steadily changing conditions giving the impression that communities have time to gradually adapt, the scientific community has been paying increasing attention to the possibility that at least some changes will be abrupt, perhaps crossing a threshold or "tipping point" to change so quickly that there will be little time to react. This presentation will synopsize the new US National Research Council Report, Abrupt Impacts of Climate Change: Anticipating Surprises, highlighting areas of increased and decreased concern, as well as areas of new concern. Emphasis is placed on not only abrupt change in physical climate, but on abrupt changes in human and natural systems that can occur as a result of a slowly changing climate. The report calls for action now on an abrupt change early warning system (ACEWS) if societies are to be resilient to climate change.

  7. The Role of the North Atlantic Oscillation (NAO) on Recent Greenland Surface Mass Loss and Mass Partitioning

    NASA Astrophysics Data System (ADS)

    Tedesco, M.; Alexander, P.; Porter, D. F.; Fettweis, X.; Luthcke, S. B.; Mote, T. L.; Rennermalm, A.; Hanna, E.

    2017-12-01

    Despite recent changes in Greenland surface mass losses and atmospheric circulation over the Arctic, little attention has been given to the potential role of large-scale atmospheric processes on the spatial and temporal variability of mass loss and partitioning of the GrIS mass loss. Using a combination of satellite gravimetry measurements, outputs of the MAR regional climate model and reanalysis data, we show that changes in atmospheric patterns since 2013 over the North Atlantic region of the Arctic (NAA) modulate total mass loss trends over Greenland together with the spatial and temporal distribution of mass loss partitioning. For example, during the 2002 - 2012 period, melting persistently increased, especially along the west coast, as a consequence of increased insulation and negative NAO conditions characterizing that period. Starting in 2013, runoff along the west coast decreased while snowfall increased substantially, when NAO turned to a more neutral/positive state. Modeled surface mass balance terms since 1950 indicate that part of the GRACE-period, specifically the period between 2002 and 2012, was exceptional in terms of snowfall over the east and northeast regions. During that period snowfall trend decreased to almost 0 Gt/yr from a long-term increasing trend, which presumed again in 2013. To identify the potential impact of atmospheric patterns on mass balance and its partitioning, we studied the spatial and temporal correlations between NAO and snowfall/runoff. Our results indicate that the correlation between summer snowfall and NAO is not stable during the 1950 - 2015 period. We further looked at changes in patterns of circulation using self organizing maps (SOMs) to identify the atmospheric patterns characterizing snowfall during different periods. We discuss potential implications for past changes and future GCM and RCM simulations.

  8. Mass loss in red giants and supergiants

    NASA Technical Reports Server (NTRS)

    Sanner, F.

    1976-01-01

    The circumstellar envelopes surrounding 13 late-type giants and supergiants have been studied using a homogeneous collection of high-resolution, photoelectric scans of strong optical resonance lines. Various properties of the envelopes, including the mass loss rate, dilution factor, hydrogen density, and degree of ionization, have been determined quantitatively.

  9. Core-powered mass-loss and the radius distribution of small exoplanets

    NASA Astrophysics Data System (ADS)

    Ginzburg, Sivan; Schlichting, Hilke E.; Sari, Re'em

    2018-05-01

    Recent observations identify a valley in the radius distribution of small exoplanets, with planets in the range 1.5-2.0 R⊕ significantly less common than somewhat smaller or larger planets. This valley may suggest a bimodal population of rocky planets that are either engulfed by massive gas envelopes that significantly enlarge their radius, or do not have detectable atmospheres at all. One explanation of such a bimodal distribution is atmospheric erosion by high-energy stellar photons. We investigate an alternative mechanism: the luminosity of the cooling rocky core, which can completely erode light envelopes while preserving heavy ones, produces a deficit of intermediate sized planets. We evolve planetary populations that are derived from observations using a simple analytical prescription, accounting self-consistently for envelope accretion, cooling and mass-loss, and demonstrate that core-powered mass-loss naturally reproduces the observed radius distribution, regardless of the high-energy incident flux. Observations of planets around different stellar types may distinguish between photoevaporation, which is powered by the high-energy tail of the stellar radiation, and core-powered mass-loss, which depends on the bolometric flux through the planet's equilibrium temperature that sets both its cooling and mass-loss rates.

  10. Probing Pre-Supernova Mass Loss With Circumstellar Dust Shells

    NASA Astrophysics Data System (ADS)

    Fox, Ori; Filippenko, Alex; Skrutskie, Mike; van Dyk, Schuyler; Kelly, Pat

    2014-12-01

    Late-time (>100 day) mid-infrared (mid-IR) observations of supernovae (SNe) offer a valuable probe of the progenitor system's mass-loss. Already, this technique has been demonstrated with the Type IIn subclass, which often have large, dusty, pre-existing shells formed in pre-SN eruptions. While other SN subclasses are thought of having relatively low density circumstellar environments, a growing number of objects in other subclasses now show evidence for significant pre-SN mass loss and similar mid-IR characteristics. Long after the SN radioactive tail fades, warm dust can stay bright at mid-IR wavelengths due to alternative heating mechanisms, such as shocks. Here we propose a SNAPSHOT survey of a well-studied and high-profile SN sample, extending over a range of subclasses, including both recent and historical events with evidence of a dense CSM and/or dust. This program will (a) discover new SNe with warm dust and (b) monitor the evolution of warm dust in previously detected SNe. Harnessing the success of our previous Spitzer programs, these observations will expand upon that work by probing the similarities in and differences between the subclasses' circumstellar environments, pre-SN mass-loss, and ultimately, the progenitors themselves.

  11. The economics of abrupt climate change.

    PubMed

    Perrings, Charles

    2003-09-15

    The US National Research Council defines abrupt climate change as a change of state that is sufficiently rapid and sufficiently widespread in its effects that economies are unprepared or incapable of adapting. This may be too restrictive a definition, but abrupt climate change does have implications for the choice between the main response options: mitigation (which reduces the risks of climate change) and adaptation (which reduces the costs of climate change). The paper argues that by (i) increasing the costs of change and the potential growth of consumption, and (ii) reducing the time to change, abrupt climate change favours mitigation over adaptation. Furthermore, because the implications of change are fundamentally uncertain and potentially very high, it favours a precautionary approach in which mitigation buys time for learning. Adaptation-oriented decision tools, such as scenario planning, are inappropriate in these circumstances. Hence learning implies the use of probabilistic models that include socioeconomic feedbacks.

  12. Mass loss in M67 giants - Evidence from isochrone fitting

    NASA Technical Reports Server (NTRS)

    Tripicco, Michael J.; Dorman, Ben; Bell, R. A.

    1993-01-01

    A comparison between the color-magnitude diagram of M67 and a new set of theoretical evolutionary models which include all phases from the unevolved main-sequence through core-helium burning and onto the AGB is presented. The present 5-Gyr solar abundance isochrone is found to yield an excellent fit to the whole of the M67 color-magnitude diagram. A differential technique that compares the gap in color between clump giants and normal red giants, on one hand, with the temperature gap between core He-burning tracks and first-ascent RGB tracks, on the other, strongly indicates that the clump giants in M67 have masses of 0.70 solar mass or less. The extremely large amount of mass loss that is deduced is well in excess of that found for globular cluster stars. Possible resolutions of this problem are that degree of mass loss increases with total stellar mass, or with metallicity.

  13. Sea-level response to abrupt ocean warming of Antarctic ice shelves

    NASA Astrophysics Data System (ADS)

    Pattyn, Frank

    2016-04-01

    Antarctica's contribution to global sea-level rise increases steadily. A fundamental question remains whether the ice discharge will lead to marine ice sheet instability (MISI) and collapse of certain sectors of the ice sheet or whether ice loss will increase linearly with the warming trends. Therefore, we employ a newly developed ice sheet model of the Antarctic ice sheet, called f.ETISh (fast Elementary Thermomechanical Ice Sheet model) to simulate ice sheet response to abrupt perturbations in ocean and atmospheric temperature. The f.ETISh model is a vertically integrated hybrid (SSA/SIA) ice sheet model including ice shelves. Although vertically integrated, thermomechanical coupling is ensured through a simplified representation of ice sheet thermodynamics based on an analytical solution of the vertical temperature profile, including strain heating and horizontal advection. The marine boundary is represented by a flux condition either coherent with power-law basal sliding (Pollard & Deconto (2012) based on Schoof (2007)) or according to Coulomb basal friction (Tsai et al., 2015), both taking into account ice-shelf buttressing. Model initialization is based on optimization of the basal friction field. Besides the traditional MISMIP tests, new tests with respect to MISI in plan-view models have been devised. The model is forced with stepwise ocean and atmosphere temperature perturbations. The former is based on a parametrised sub-shelf melt (limited to ice shelves), while the latter is based on present-day mass balance/surface temperature and corrected for elevation changes. Surface melting is introduced using a PDD model. Results show a general linear response in mass loss to ocean warming. Nonlinear response due to MISI occurs under specific conditions and is highly sensitive to the basal conditions near the grounding line, governed by both the initial conditions and the basal sliding/deformation model. The Coulomb friction model leads to significantly higher

  14. Reconstructing decades of glacial mass loss in the Canadian Arctic Archipelago

    NASA Astrophysics Data System (ADS)

    Noël, Brice; van de Berg, Willem Jan; Lhermitte, Stef; Wouters, Bert; van den Broeke, Michiel

    2017-04-01

    The Canadian Arctic Archipelago (CAA) comprises multiple small glaciers and ice caps mostly concentrated on Ellesmere and Baffin Islands situated in the north (NCAA) and south (SCAA) of the archipelago, respectively. Because they cover a relatively small area and show complex geometries, current regional climate models, generally running at 5 to 20 km horizontal resolution, struggle to accurately resolve surface mass change patterns. Here, we present a 58-year (1958-2015) reconstruction of daily, 1 km surface mass balance (SMB) of the CAA, statistically downscaled from the output of the regional climate model RACMO2.3 at 11 km. By correcting for biases in elevation and ice albedo, the downscaling method significantly improves mass loss estimates over narrow outlet glaciers and isolated ice fields through better resolved marginal meltwater runoff. During the last two decades, CAA glaciers have experienced warmer conditions (+1.1°C) resulting in continued mass loss. NCAA and SCAA mass loss accounted for -24.7 ± 18.0 Gt yr-1 and -21.9 ± 8.2 Gt yr-1 respectively, almost tripling (-8.4 Gt yr-1) and doubling (-11.8 Gt yr-1) the 1958-1995 average. Following the recent warming, enhanced meltwater production reduced the refreezing capacity of inland firn layers by about 6%. While the interior of NCAA ice caps can still buffer most of the additional melt, the lack of a perennial firn area over low-lying SCAA glaciers caused uninterrupted mass loss since the 1980s, which, in the absence of significant refreezing capacity, indicates inevitable disappearance of these highly sensitive glaciers.

  15. Mass loss from red giants - Results from ultraviolet spectroscopy

    NASA Technical Reports Server (NTRS)

    Linsky, J. L.

    1985-01-01

    New instrumentation in space, primarily the IUE spacecraft, has enabled the application of ultraviolet spectroscopic techniques to the determination of physical properties and reliable mass loss rates for red giant winds. One important result is the determination of where in the H-R diagram are found stars with hot outer atmospheres and with cool winds. So far it appears that single cool stars, except perhaps the so-called hybrid stars, have either hot outer atmospheres or cool winds but not both. The C II resonance (1335 A) and intersystem (2325 A) multiplets have been used to derive temperatures, densities, and geometrical extents for the chromospheric portions of red giant winds, with the result that the red giants and the earlier giants with hot coronae have qualitatively different chromospheres. Mass loss rates can now be derived accurately from the analysis of asymmetric emission lines, such as the Mg II resonance lines, and from P Cygni profile lines of atoms in the dominant ionization stage when a hot star is available to probe the wind of a red giant. The Zeta Aur systems, consisting of a K-M supergiant and a main sequence B star are important systems for reliable mass loss rates for the red supergiant components are becoming available.

  16. The Mass-loss Return from Evolved Stars to the Large Magellanic Cloud. VI. Luminosities and Mass-loss Rates on Population Scales

    NASA Astrophysics Data System (ADS)

    Riebel, D.; Srinivasan, S.; Sargent, B.; Meixner, M.

    2012-07-01

    We present results from the first application of the Grid of Red Supergiant and Asymptotic Giant Branch ModelS (GRAMS) model grid to the entire evolved stellar population of the Large Magellanic Cloud (LMC). GRAMS is a pre-computed grid of 80,843 radiative transfer models of evolved stars and circumstellar dust shells composed of either silicate or carbonaceous dust. We fit GRAMS models to ~30,000 asymptotic giant branch (AGB) and red supergiant (RSG) stars in the LMC, using 12 bands of photometry from the optical to the mid-infrared. Our published data set consists of thousands of evolved stars with individually determined evolutionary parameters such as luminosity and mass-loss rate. The GRAMS grid has a greater than 80% accuracy rate discriminating between oxygen- and carbon-rich chemistry. The global dust injection rate to the interstellar medium (ISM) of the LMC from RSGs and AGB stars is on the order of 2.1 × 10-5 M ⊙ yr-1, equivalent to a total mass injection rate (including the gas) into the ISM of ~6 × 10-3 M ⊙ yr-1. Carbon stars inject two and a half times as much dust into the ISM as do O-rich AGB stars, but the same amount of mass. We determine a bolometric correction factor for C-rich AGB stars in the K s band as a function of J - K s color, BC_{K_{s}} = -0.40(J-K_{s})^2 + 1.83(J-K_{s}) + 1.29. We determine several IR color proxies for the dust mass-loss rate (\\dot{M}_{d}) from C-rich AGB stars, such as log \\dot{M_{d}} = ({-18.90}/({(K_{s}-[8.0])+3.37}))-5.93. We find that a larger fraction of AGB stars exhibiting the "long-secondary period" phenomenon are more O-rich than stars dominated by radial pulsations, and AGB stars without detectable mass loss do not appear on either the first-overtone or fundamental-mode pulsation sequences.

  17. Research opportunities in loss of red blood cell mass in space flight

    NASA Technical Reports Server (NTRS)

    Talbot, J. M.; Fisher, K. D.

    1985-01-01

    Decreases of red blood cell mass and plasma volume have been observed consistently following manned space flights. Losses of red cell mass by United States astronauts have averaged 10 to 15% (range: 2 to 21%). Based on postflight estimates of total hemoglobin, Soviet cosmonauts engaged in space missions lasting from 1 to 7 months have exhibited somewhat greater losses. Restoration of red cell mass requires from 4 to 6 weeks following return to Earth, regardless of the duration of space flight.

  18. Mass Loss at Higher Metallicity: Quantifying the Mass Return from Evolved Stars in the Galactic

    NASA Astrophysics Data System (ADS)

    Sargent, Benjamin

    Bulge Mass-losing evolved stars, and in particular asymptotic giant branch (AGB) stars and red supergiant (RSG) stars, are expected to be the major producers of dust in galaxies. This dust will help form planetary systems around future generations of stars. Our ADAP program to measure the mass loss from the AGB and RSG stars in the Magellanic Clouds is nearing completion, and we wish to extend this successful study to the Galactic bulge of the Milky Way Galaxy. Metallicity should determine the amount of elements available to condense dust in the star's outflow, so evolved stars of differing metallicities should have differing mass-loss rates. Building upon our work on evolved stars in the Magellanic Clouds, we will compare the mass-loss rates from AGB and RSG stars in the older and potentially more metal-rich Bulge to the mass-loss rates of AGB and RSG stars in the Magellanic Clouds, which have lower metallicity, making for an interesting contrast. In addition, the Galactic bulge, like the Clouds, is located at a well-determined distance ( 8 kpc), thereby removing the distance ambiguities that present a major uncertainty in determining mass-loss rates and luminosities for evolved stars. To model photometric observations of outflowing dust shells around evolved stars, we have constructed the Grid of Red supergiant and Asymptotic giant branch ModelS (GRAMS; Sargent et al 2011; Srinivasan et al 2011) using the radiative transfer code 2Dust (Ueta and Meixner 2003). Our study will apply these models to the large photometric database of sources identified in the Spitzer Space Telescope GLIMPSE survey of the Milky Way and also to the various infrared spectra of Bulge AGB and RSG stars from Spitzer, ISO, etc. We have already modeled a few Galactic bulge evolved stars with GRAMS, and we will use these results as the foundation for modeling a large and representative sample of Galactic bulge evolved stars identified and measured photometrically by GLIMPSE. We will use our

  19. Determination of clothing evaporative resistance on a sweating thermal manikin in an isothermal condition: heat loss method or mass loss method?

    PubMed

    Wang, Faming; Gao, Chuansi; Kuklane, Kalev; Holmér, Ingvar

    2011-08-01

    This paper addresses selection between two calculation options, i.e heat loss option and mass loss option, for thermal manikin measurements on clothing evaporative resistance conducted in an isothermal condition (T(manikin) = T(a) = T(r)). Five vocational clothing ensembles with a thermal insulation range of 1.05-2.58 clo were selected and measured on a sweating thermal manikin 'Tore'. The reasons why the isothermal heat loss method generates a higher evaporative resistance than that of the mass loss method were thoroughly investigated. In addition, an indirect approach was applied to determine the amount of evaporative heat energy taken from the environment. It was found that clothing evaporative resistance values by the heat loss option were 11.2-37.1% greater than those based on the mass loss option. The percentage of evaporative heat loss taken from the environment (H(e,env)) for all test scenarios ranged from 10.9 to 23.8%. The real evaporative cooling efficiency ranged from 0.762 to 0.891, respectively. Furthermore, it is evident that the evaporative heat loss difference introduced by those two options was equal to the heat energy taken from the environment. In order to eliminate the combined effects of dry heat transfer, condensation, and heat pipe on clothing evaporative resistance, it is suggested that manikin measurements on the determination of clothing evaporative resistance should be performed in an isothermal condition. Moreover, the mass loss method should be applied to calculate clothing evaporative resistance. The isothermal heat loss method would appear to overestimate heat stress and thus should be corrected before use.

  20. Fat-free mass loss generated with weight loss in overweight and obese adults: What may we expect?

    PubMed

    Dixon, J B; Lambert, E A; Grima, M; Rice, T; Lambert, G W; Straznicky, N E

    2015-01-01

    There is concern that intentional weight loss may generate excessive loss of fat-free mass (FFM). Idealists target minimal loss of FFM, while others consider that FFM loss of up to 25% of weight loss is acceptable. In a cross-sectional study of 275 weight-stable, overweight or obese adults, we used whole-body dual-energy X-ray absorptiometry to measure FFM. A range of models was used to estimate the expected ΔFFM/Δweight ratio required to attain the body composition of a weight-stable individual at a lower body mass index (BMI). Higher BMI was associated linearly with higher FFM in men and women. Proportional ΔFFM/Δweight was influenced by sex, BMI and age. Direct scatter plot analysis, quadratic curve fit modelling and linear FFM-BMI modelling provided similar estimates for each model of ΔFFM/Δweight ratio, with 40% for men and 33% for women. These results show that the 25% rule is inappropriate and our estimates are higher than those generally reported after intentional weight loss indicating favourable preservation of FFM. © 2014 John Wiley & Sons Ltd.

  1. Highly reduced mass loss rates and increased litter layer in radioactively contaminated areas.

    PubMed

    Mousseau, Timothy A; Milinevsky, Gennadi; Kenney-Hunt, Jane; Møller, Anders Pape

    2014-05-01

    The effects of radioactive contamination from Chernobyl on decomposition of plant material still remain unknown. We predicted that decomposition rate would be reduced in the most contaminated sites due to an absence or reduced densities of soil invertebrates. If microorganisms were the main agents responsible for decomposition, exclusion of large soil invertebrates should not affect decomposition. In September 2007 we deposited 572 bags with uncontaminated dry leaf litter from four species of trees in the leaf litter layer at 20 forest sites around Chernobyl that varied in background radiation by more than a factor 2,600. Approximately one quarter of these bags were made of a fine mesh that prevented access to litter by soil invertebrates. These bags were retrieved in June 2008, dried and weighed to estimate litter mass loss. Litter mass loss was 40% lower in the most contaminated sites relative to sites with a normal background radiation level for Ukraine. Similar reductions in litter mass loss were estimated for individual litter bags, litter bags at different sites, and differences between litter bags at pairs of neighboring sites differing in level of radioactive contamination. Litter mass loss was slightly greater in the presence of large soil invertebrates than in their absence. The thickness of the forest floor increased with the level of radiation and decreased with proportional loss of mass from all litter bags. These findings suggest that radioactive contamination has reduced the rate of litter mass loss, increased accumulation of litter, and affected growth conditions for plants.

  2. Molecular shells in IRC+10216: tracing the mass loss history

    NASA Astrophysics Data System (ADS)

    Cernicharo, J.; Marcelino, N.; Agúndez, M.; Guélin, M.

    2015-03-01

    Thermally-pulsating AGB stars provide three-fourths of the matter returned to the interstellar medium. The mass and chemical composition of their ejecta largely control the chemical evolution of galaxies. Yet, both the mass loss process and the gas chemical composition remain poorly understood. We present maps of the extended 12CO and 13CO emissions in IRC+10216, the envelope of CW Leo, the high mass loss star the closest to the Sun. IRC+10216 is nearly spherical and expands radially with a velocity of 14.5 km s-1. The observations were made On-the-Fly with the IRAM 30 m telescope; their sensibility, calibration, and angular resolution are far higher than all previous studies. The telescope resolution at λ = 1.3 mm (11'' HPBW) corresponds to an expansion time of 500 yr. The CO emission consists of a centrally peaked pedestal and a series of bright, nearly spherical shells. It peaks on CW Leo and remains relatively strong up to rphot = 180''. Further out the emission becomes very weak and vanishes as CO gets photodissociated. As CO is the best tracer of the gas up to rphot, the maps show the mass loss history in the last 8000 yr. The bright CO shells denote over-dense regions. They show that the mass loss process is highly variable on timescales of hundreds of years. The new data, however, do not support previous claims of a strong decrease of the average mass loss in the last few thousand years. The over-dense shells are not perfectly concentric and extend farther to the N-NW. The typical shell separation is 800-1000 yr in the middle of the envelope, but seems to increase outwards. The shell-intershell brightness contrast is ≥3. All those key features can be accounted for if CW Leo has a companion star with a period ≃800 yr that increases the mass loss rate when it comes close to periastron. Higher angular resolution observations are needed to fully resolve the dense shells and measure the density contrast. The latter plays an essential role in our

  3. Greenland ice sheet surface temperature, melt and mass loss: 2000-06

    USGS Publications Warehouse

    Hall, D.K.; Williams, R.S.; Luthcke, S.B.; DiGirolamo, N.E.

    2008-01-01

    A daily time series of 'clear-sky' surface temperature has been compiled of the Greenland ice sheet (GIS) using 1 km resolution moderate-resolution imaging spectroradiometer (MODIS) land-surface temperature (LST) maps from 2000 to 2006. We also used mass-concentration data from the Gravity Recovery and Climate Experiment (GRACE) to study mass change in relationship to surface melt from 2003 to 2006. The mean LST of the GIS increased during the study period by ???0.27??Ca-1. The increase was especially notable in the northern half of the ice sheet during the winter months. Melt-season length and timing were also studied in each of the six major drainage basins. Rapid (<15 days) and sustained mass loss below 2000 m elevation was triggered in 2004 and 2005 as recorded by GRACE when surface melt begins. Initiation of large-scale surface melt was followed rapidly by mass loss. This indicates that surface meltwater is flowing rapidly to the base of the ice sheet, causing acceleration of outlet glaciers, thus highlighting the metastability of parts of the GIS and the vulnerability of the ice sheet to air-temperature increases. If air temperatures continue to rise over Greenland, increased surface melt will play a large role in ice-sheet mass loss.

  4. High Resolution Studies of Mass Loss from Massive Binary Stars

    NASA Astrophysics Data System (ADS)

    Corcoran, Michael F.; Gull, Theodore R.; Hamaguchi, Kenji; Richardson, Noel; Madura, Thomas; Post Russell, Christopher Michael; Teodoro, Mairan; Nichols, Joy S.; Moffat, Anthony F. J.; Shenar, Tomer; Pablo, Herbert

    2017-01-01

    Mass loss from hot luminous single and binary stars has a significant, perhaps decisive, effect on their evolution. The combination of X-ray observations of hot shocked gas embedded in the stellar winds and high-resolution optical/UV spectra of the cooler mass in the outflow provides unique ways to study the unstable process by which massive stars lose mass both through continuous stellar winds and rare, impulsive, large-scale mass ejections. The ability to obtain coordinated observations with the Hubble Space Telescope Imaging Spectrograph (HST/STIS) and the Chandra High-Energy Transmission Grating Spectrometer (HETGS) and other X-ray observatories has allowed, for the first time, studies of resolved line emisssion over the temperature range of 104- 108K, and has provided observations to confront numerical dynamical models in three dimensions. Such observations advance our knowledge of mass-loss asymmetries, spatial and temporal variabilities, and the fundamental underlying physics of the hot shocked outflow, providing more realistic constraints on the amount of mass lost by different luminous stars in a variety of evolutionary stages. We discuss the impact that these joint observational studies have had on our understanding of dynamical mass outflows from massive stars, with particular emphasis on two important massive binaries, Delta Ori Aa, a linchpin of the mass luminosity relation for upper HRD main sequence stars, and the supermassive colliding wind binary Eta Carinae.

  5. Abrupt tectonics and rapid slab detachment with grain damage

    PubMed Central

    Bercovici, David; Schubert, Gerald; Ricard, Yanick

    2015-01-01

    A simple model for necking and detachment of subducting slabs is developed to include the coupling between grain-sensitive rheology and grain-size evolution with damage. Necking is triggered by thickened buoyant crust entrained into a subduction zone, in which case grain damage accelerates necking and allows for relatively rapid slab detachment, i.e., within 1 My, depending on the size of the crustal plug. Thick continental crustal plugs can cause rapid necking while smaller plugs characteristic of ocean plateaux cause slower necking; oceanic lithosphere with normal or slightly thickened crust subducts without necking. The model potentially explains how large plateaux or continental crust drawn into subduction zones can cause slab loss and rapid changes in plate motion and/or induce abrupt continental rebound. PMID:25605890

  6. Abrupt tectonics and rapid slab detachment with grain damage.

    PubMed

    Bercovici, David; Schubert, Gerald; Ricard, Yanick

    2015-02-03

    A simple model for necking and detachment of subducting slabs is developed to include the coupling between grain-sensitive rheology and grain-size evolution with damage. Necking is triggered by thickened buoyant crust entrained into a subduction zone, in which case grain damage accelerates necking and allows for relatively rapid slab detachment, i.e., within 1 My, depending on the size of the crustal plug. Thick continental crustal plugs can cause rapid necking while smaller plugs characteristic of ocean plateaux cause slower necking; oceanic lithosphere with normal or slightly thickened crust subducts without necking. The model potentially explains how large plateaux or continental crust drawn into subduction zones can cause slab loss and rapid changes in plate motion and/or induce abrupt continental rebound.

  7. Heat and pregnancy-related emergencies: Risk of placental abruption during hot weather.

    PubMed

    He, Siyi; Kosatsky, Tom; Smargiassi, Audrey; Bilodeau-Bertrand, Marianne; Auger, Nathalie

    2018-02-01

    Outdoor heat increases the risk of preterm birth and stillbirth, but the association with placental abruption has not been studied. Placental abruption is a medical emergency associated with major morbidity and mortality in pregnancy. We determined the relationship between ambient temperature and risk of placental abruption in warm seasons. We performed a case-crossover analysis of 17,172 women whose pregnancies were complicated by placental abruption in Quebec, Canada from May to October 1989-2012. The main exposure measure was the maximum temperature reached during the week before abruption. We computed odds ratios (OR) and 95% confidence intervals (CI) for the association of temperature with placental abruption, adjusted for humidity and public holidays. We assessed whether associations were stronger preterm or at term, or varied with maternal age, parity, comorbidity and socioeconomic status. Compared with 15°C, a maximum weekly temperature of 30°C was associated with 1.07 times the odds of abruption (95% CI 0.99-1.16). When the timing of abruption was examined, the associations were significantly stronger at term (OR 1.12, 95% CI 1.02-1.24) than preterm (OR 0.96, 95% CI 0.83-1.10). Relationships were more prominent at term for women who were younger than 35years old, nulliparous or socioeconomically disadvantaged, but did not vary with comorbidity. Associations were stronger within 1 and 5days of abruption. Temperature was not associated with preterm abruption regardless of maternal characteristics. Elevated temperatures in warm seasons may increase the risk of abruption in women whose pregnancies are near or at term. Pregnant women may be more sensitive to heat and should consider preventive measures such as air conditioning and hydration during hot weather. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Theoretical investigation on the mass loss impact on asteroseismic grid-based estimates of mass, radius, and age for RGB stars

    NASA Astrophysics Data System (ADS)

    Valle, G.; Dell'Omodarme, M.; Prada Moroni, P. G.; Degl'Innocenti, S.

    2018-01-01

    Aims: We aim to perform a theoretical evaluation of the impact of the mass loss indetermination on asteroseismic grid based estimates of masses, radii, and ages of stars in the red giant branch (RGB) phase. Methods: We adopted the SCEPtER pipeline on a grid spanning the mass range [0.8; 1.8] M⊙. As observational constraints, we adopted the star effective temperatures, the metallicity [Fe/H], the average large frequency spacing Δν, and the frequency of maximum oscillation power νmax. The mass loss was modelled following a Reimers parametrization with the two different efficiencies η = 0.4 and η = 0.8. Results: In the RGB phase, the average random relative error (owing only to observational uncertainty) on mass and age estimates is about 8% and 30% respectively. The bias in mass and age estimates caused by the adoption of a wrong mass loss parameter in the recovery is minor for the vast majority of the RGB evolution. The biases get larger only after the RGB bump. In the last 2.5% of the RGB lifetime the error on the mass determination reaches 6.5% becoming larger than the random error component in this evolutionary phase. The error on the age estimate amounts to 9%, that is, equal to the random error uncertainty. These results are independent of the stellar metallicity [Fe/H] in the explored range. Conclusions: Asteroseismic-based estimates of stellar mass, radius, and age in the RGB phase can be considered mass loss independent within the range (η ∈ [0.0,0.8]) as long as the target is in an evolutionary phase preceding the RGB bump.

  9. THE MASS-LOSS RETURN FROM EVOLVED STARS TO THE LARGE MAGELLANIC CLOUD. VI. LUMINOSITIES AND MASS-LOSS RATES ON POPULATION SCALES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Riebel, D.; Meixner, M.; Srinivasan, S.

    We present results from the first application of the Grid of Red Supergiant and Asymptotic Giant Branch ModelS (GRAMS) model grid to the entire evolved stellar population of the Large Magellanic Cloud (LMC). GRAMS is a pre-computed grid of 80,843 radiative transfer models of evolved stars and circumstellar dust shells composed of either silicate or carbonaceous dust. We fit GRAMS models to {approx}30,000 asymptotic giant branch (AGB) and red supergiant (RSG) stars in the LMC, using 12 bands of photometry from the optical to the mid-infrared. Our published data set consists of thousands of evolved stars with individually determined evolutionarymore » parameters such as luminosity and mass-loss rate. The GRAMS grid has a greater than 80% accuracy rate discriminating between oxygen- and carbon-rich chemistry. The global dust injection rate to the interstellar medium (ISM) of the LMC from RSGs and AGB stars is on the order of 2.1 Multiplication-Sign 10{sup -5} M{sub Sun} yr{sup -1}, equivalent to a total mass injection rate (including the gas) into the ISM of {approx}6 Multiplication-Sign 10{sup -3} M{sub Sun} yr{sup -1}. Carbon stars inject two and a half times as much dust into the ISM as do O-rich AGB stars, but the same amount of mass. We determine a bolometric correction factor for C-rich AGB stars in the K{sub s} band as a function of J - K{sub s} color, BC{sub K{sub s}}= -0.40(J-K{sub s}){sup 2} + 1.83(J-K{sub s}) + 1.29. We determine several IR color proxies for the dust mass-loss rate (M-dot{sub d}) from C-rich AGB stars, such as log M-dot{sub d} = (-18.90/((K{sub s}-[8.0])+3.37) - 5.93. We find that a larger fraction of AGB stars exhibiting the 'long-secondary period' phenomenon are more O-rich than stars dominated by radial pulsations, and AGB stars without detectable mass loss do not appear on either the first-overtone or fundamental-mode pulsation sequences.« less

  10. Supercritical flow characteristics at abrupt expansion structure

    NASA Astrophysics Data System (ADS)

    Lim, Jia Jun; Puay, How Tion; Zakaria, Nor Azazi

    2017-10-01

    When dealing with the design of a hydraulic structure, lateral expansion is often necessary for flow emerging at high velocity served as a cross-sectional transition. If the abrupt expansion structure is made to diverge rapidly, it will cause the major part of the flow fail to follow the boundaries. If the transition is too gradual, it will result in a waste of structural material. A preliminary study on the flow structure near the expansion and its relationship with flow parameter is carried out in this study. A two-dimensional depth-averaged model is developed to simulate the supercritical flow at the abrupt expansion structure. Constrained Interpolation Profile (CIP) scheme (which is of third order accuracy) is adopted in the numerical model. Results show that the flow structure and flow characteristics at the abrupt expansion can be reproduced numerically. The validation of numerical result is done against analytical studies. The result from numerical simulation showed good agreement with the analytical solution.

  11. A survey of mass-loss effects in early-type stars

    NASA Technical Reports Server (NTRS)

    Snow, T. P., Jr.

    1976-01-01

    Intermediate-resolution data obtained with the Copernicus satellite are surveyed in order to define the region in the H-R diagram where mass loss occurs. The survey includes 40 stars, providing good coverage of supergiants from O4 to A2 and main-sequence stars from O4 to B7 as well as spotty coverage of late O giants and intermediate to late B stars. The spectral transitions examined are primarily resonance lines of ions of abundant elements plus some lines arising from excited states (e.g., C III at 1175.7 A and Si IV at 1122.5 A). Observed P Cygni profiles are discussed along with interesting features of some individual profiles. The data are shown to indicate that mass-loss effects occur over a wide portion of the H-R diagram, that mass ejection generally occurs when the holometric magnitude is greater than -6.0, and that the mass-ejection rate is usually high enough to produce P Cygni profile whenever the N V feature at 1240 A is present in a spectrum.

  12. The Impact of Progenitor Mass Loss on the Dynamical and Spectral Evolution of Supernova Remnants

    NASA Astrophysics Data System (ADS)

    Patnaude, Daniel J.; Lee, Shiu-Hang; Slane, Patrick O.; Badenes, Carles; Nagataki, Shigehiro; Ellison, Donald C.; Milisavljevic, Dan

    2017-11-01

    There is now substantial evidence that the progenitors of some core-collapse supernovae undergo enhanced or extreme mass loss prior to explosion. The imprint of this mass loss is observed in the spectra and dynamics of the expanding blast wave on timescales of days to years after core collapse, and the effects on the spectral and dynamical evolution may linger long after the supernova has evolved into the remnant stage. In this paper, we present, for the first time, largely self-consistent end-to-end simulations for the evolution of a massive star from the pre-main sequence, up to and through core collapse, and into the remnant phase. We present three models and compare and contrast how the progenitor mass-loss history impacts the dynamics and spectral evolution of the supernovae and supernova remnants. We study a model that only includes steady mass loss, a model with enhanced mass loss over a period of ˜5000 yr prior to core collapse, and a model with extreme mass loss over a period of ˜500 yr prior to core collapse. The models are not meant to address any particular supernova or supernova remnant, but rather to highlight the important role that the progenitor evolution plays in the observable qualities of supernovae and supernova remnants. Through comparisons of these three different progenitor evolution scenarios, we find that the mass loss in late stages (during and after core carbon burning) can have a profound impact on the dynamics and spectral evolution of the supernova remnant centuries after core collapse.

  13. Bend losses in rectangular culverts.

    DOT National Transportation Integrated Search

    2008-09-01

    This study investigated bend losses for open channel flow in rectangular channels or culverts. Laboratory experiments were performed for sub-critical flow in rectangular channels with abrupt bends. Bend angles of approximately 30, 45, 60, 75 and 90 d...

  14. Mass loss on Himalayan glacier endangers water resources

    NASA Astrophysics Data System (ADS)

    Kehrwald, Natalie M.; Thompson, Lonnie G.; Tandong, Yao; Mosley-Thompson, Ellen; Schotterer, Ulrich; Alfimov, Vasily; Beer, Jürg; Eikenberg, Jost; Davis, Mary E.

    2008-11-01

    Ice cores drilled from glaciers around the world generally contain horizons with elevated levels of beta radioactivity including 36Cl and 3H associated with atmospheric thermonuclear bomb testing in the 1950s and 1960s. Ice cores collected in 2006 from Naimona'nyi Glacier in the Himalaya (Tibet) lack these distinctive marker horizons suggesting no net accumulation of mass (ice) since at least 1950. Naimona'nyi is the highest glacier (6050 masl) documented to be losing mass annually suggesting the possibility of similar mass loss on other high-elevation glaciers in low and mid-latitudes under a warmer Earth scenario. If climatic conditions dominating the mass balance of Naimona'nyi extend to other glaciers in the region, the implications for water resources could be serious as these glaciers feed the headwaters of the Indus, Ganges, and Brahmaputra Rivers that sustain one of the world's most populous regions.

  15. Plant litter functional diversity effects on litter mass loss depend on the macro-detritivore community.

    PubMed

    Patoine, Guillaume; Thakur, Madhav P; Friese, Julia; Nock, Charles; Hönig, Lydia; Haase, Josephine; Scherer-Lorenzen, Michael; Eisenhauer, Nico

    2017-11-01

    A better understanding of the mechanisms driving litter diversity effects on decomposition is needed to predict how biodiversity losses affect this crucial ecosystem process. In a microcosm study, we investigated the effects of litter functional diversity and two major groups of soil macro-detritivores on the mass loss of tree leaf litter mixtures. Furthermore, we tested the effects of litter trait community means and dissimilarity on litter mass loss for seven traits relevant to decomposition. We expected macro-detritivore effects on litter mass loss to be most pronounced in litter mixtures of high functional diversity. We used 24 leaf mixtures differing in functional diversity, which were composed of litter from four species from a pool of 16 common European tree species. Earthworms, isopods, or a combination of both were added to each litter combination for two months. Litter mass loss was significantly higher in the presence of earthworms than in that of isopods, whereas no synergistic effects of macro-detritivore mixtures were found. The effect of functional diversity of the litter material was highest in the presence of both macro-detritivore groups, supporting the notion that litter diversity effects are most pronounced in the presence of different detritivore species. Species-specific litter mass loss was explained by nutrient content, secondary compound concentration, and structural components. Moreover, dissimilarity in N concentrations increased litter mass loss, probably because detritivores having access to nutritionally diverse food sources. Furthermore, strong competition between the two macro-detritivores for soil surface litter resulted in a decrease of survival of both macro-detritivores. These results show that the effects of litter functional diversity on decomposition are contingent upon the macro-detritivore community and composition. We conclude that the temporal dynamics of litter trait diversity effects and their interaction with

  16. Plant litter functional diversity effects on litter mass loss depend on the macro-detritivore community

    PubMed Central

    Patoine, Guillaume; Thakur, Madhav P.; Friese, Julia; Nock, Charles; Hönig, Lydia; Haase, Josephine; Scherer-Lorenzen, Michael; Eisenhauer, Nico

    2017-01-01

    A better understanding of the mechanisms driving litter diversity effects on decomposition is needed to predict how biodiversity losses affect this crucial ecosystem process. In a microcosm study, we investigated the effects of litter functional diversity and two major groups of soil macro-detritivores on the mass loss of tree leaf litter mixtures. Furthermore, we tested the effects of litter trait community means and dissimilarity on litter mass loss for seven traits relevant to decomposition. We expected macro-detritivore effects on litter mass loss to be most pronounced in litter mixtures of high functional diversity. We used 24 leaf mixtures differing in functional diversity, which were composed of litter from four species from a pool of 16 common European tree species. Earthworms, isopods, or a combination of both were added to each litter combination for two months. Litter mass loss was significantly higher in the presence of earthworms than in that of isopods, whereas no synergistic effects of macro-detritivore mixtures were found. The effect of functional diversity of the litter material was highest in the presence of both macro-detritivore groups, supporting the notion that litter diversity effects are most pronounced in the presence of different detritivore species. Species-specific litter mass loss was explained by nutrient content, secondary compound concentration, and structural components. Moreover, dissimilarity in N concentrations increased litter mass loss, probably because detritivores having access to nutritionally diverse food sources. Furthermore, strong competition between the two macro-detritivores for soil surface litter resulted in a decrease of survival of both macro-detritivores. These results show that the effects of litter functional diversity on decomposition are contingent upon the macro-detritivore community and composition. We conclude that the temporal dynamics of litter trait diversity effects and their interaction with

  17. Mass-loss evolution of close-in exoplanets: Evaporation of hot Jupiters and the effect on population

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kurokawa, H.; Nakamoto, T., E-mail: kurokawa@nagoya-u.jp

    2014-03-01

    During their evolution, short-period exoplanets may lose envelope mass through atmospheric escape owing to intense X-ray and extreme ultraviolet (XUV) radiation from their host stars. Roche-lobe overflow induced by orbital evolution or intense atmospheric escape can also contribute to mass loss. To study the effects of mass loss on inner planet populations, we calculate the evolution of hot Jupiters considering mass loss of their envelopes and thermal contraction. Mass loss is assumed to occur through XUV-driven atmospheric escape and the following Roche-lobe overflow. The runaway effect of mass loss results in a dichotomy of populations: hot Jupiters that retain theirmore » envelopes and super Earths whose envelopes are completely lost. Evolution primarily depends on the core masses of planets and only slightly on migration history. In hot Jupiters with small cores (≅ 10 Earth masses), runaway atmospheric escape followed by Roche-lobe overflow may create sub-Jupiter deserts, as observed in both mass and radius distributions of planetary populations. Comparing our results with formation scenarios and observed exoplanets populations, we propose that populations of closely orbiting exoplanets are formed by capturing planets at/inside the inner edges of protoplanetary disks and subsequent evaporation of sub-Jupiters.« less

  18. Going, Going, Gone: Localizing Abrupt Offsets of Moving Objects

    ERIC Educational Resources Information Center

    Maus, Gerrit W.; Nijhawan, Romi

    2009-01-01

    When a moving object abruptly disappears, this profoundly influences its localization by the visual system. In Experiment 1, 2 aligned objects moved across the screen, and 1 of them abruptly disappeared. Observers reported seeing the objects misaligned at the time of the offset, with the continuing object leading. Experiment 2 showed that the…

  19. Evidence for mass loss at moderate to high velocity in Be stars

    NASA Technical Reports Server (NTRS)

    Snow, T. P., Jr.; Marlborough, J. M.

    1976-01-01

    Ultraviolet spectra of intermediate resolution have been obtained with Copernicus for 12 objects classified as Be or shell stars and for 19 additional early B dwarfs. Some of these spectra show marked asymmetries in certain resonance lines, especially the Si IV doublet at 1400 A, indicating the presence in some cases of outflowing material with maximum velocities of nearly 1000 km/s. Direct evidence for mass loss at these velocities is seen for the first time in dwarf stars as late as B1.5; the only objects later than B0.5 which show this effect are Be or shell stars. Among the stars considered, there is a correlation between the presence of mass-loss effects and projected rotational velocity, suggesting that the ultraviolet flux from B1-B2 dwarfs is sufficient to drive high-velocity stellar winds only if rotational effects reduce the effective gravity near the equator. The mass-loss rate for one of the most active Be stars, 59 Cyg, is crudely estimated to be one billionth or one ten-billionth of a solar mass per year. The data suggest that the extended atmospheres associated with Be-star phenomena may be formed by mass ejection.

  20. Antarctic Mass Loss from GRACE from Space- and Time-Resolved Modeling with Slepian Functions

    NASA Astrophysics Data System (ADS)

    Simons, F. J.; Harig, C.

    2013-12-01

    The melting of polar ice sheets is a major contributor to global sea-level rise. Antarctica is of particular interest since most of the mass loss has occurred in West Antarctica, however updated glacial isostatic adjustment (GIA) models and recent mass gains in East Antarctica have reduced the continent-wide integrated decadal trend of mass loss. Here we present a spatially and temporally resolved estimation of the Antarctic ice mass change using Slepian localization functions. With a Slepian basis specifically for Antarctica, the basis functions maximize their energy on the continent and we can project the geopotential fields into a sparse set of orthogonal coefficients. By fitting polynomial functions to the limited basis coefficients we maximize signal-to-noise levels and need not perform smoothing or destriping filters common to other approaches. In addition we determine an empirical noise covariance matrix from the GRACE data to estimate the uncertainty of mass estimation. When applied to large ice sheets, as in our own recent Greenland work, this technique is able to resolve both the overall continental integrated mass trend, as well as the spatial distribution of the mass changes over time. Using CSR-RL05 GRACE data between Jan. 2003 and Jan 2013, we estimate the regional accelerations in mass change for several sub-regions and examine how the spatial pattern of mass has changed. The Amundsen Sea coast of West Antarctica has experienced a large acceleration in mass loss (-26 Gt/yr^2). While mass loss is concentrated near Pine Island and Thwaites glaciers, it has also increased along the coast further towards the Ross ice shelf.

  1. Thyroperoxidase and thyroglobulin antibodies in early pregnancy and placental abruption.

    PubMed

    Haddow, James E; McClain, Monica R; Palomaki, Glenn E; Neveux, Louis M; Lambert-Messerlian, Geralyn; Canick, Jacob A; Malone, Fergal D; Porter, T Flint; Nyberg, David A; Bernstein, Peter S; D'Alton, Mary E

    2011-02-01

    To estimate the relationship between thyroid antibodies and placental abruption. This cohort study assesses thyroperoxidase and thyroglobulin antibodies in relation to placental abruption among 10,062 women with singleton viable pregnancies (from the First and Second Trimester Risk of Aneuploidy [FaSTER] trial). A thyroperoxidase antibody cutoff of 50 international units/mL is used for comparison with published data from another cohort. Women with elevated thyroperoxidase antibody levels in the first and second trimesters have a higher rate of placental abruption than antibody-negative women. This relationship is less strong in the first trimester (1.51% compared with 0.83%; odds ratio [OR], 1.83; 95% confidence interval [CI], 0.99-3.37) than in the second trimester (1.78% compared with 0.82%; OR, 2.20; 95% CI, 1.21-3.99). A similar, but weaker, relationship is present for thyroglobulin antibodies. Sixty-four of 782 thyroperoxidase antibody-positive pregnancies without abruption become negative by the second trimester; one pregnancy with abruption becomes antibody-positive. Odds ratios for pregnancies with both thyroperoxidase and thyroglobulin antibody elevations are also higher (first trimester: OR, 2.10; 95% CI, 0.91-4.86; second trimester: OR, 2.73; 95% CI, 1.17-6.33). The present data confirm an association between thyroid antibody elevations and placental abruption described in a recent report. These findings, however, do not provide support for recommending routine testing for thyroid antibodies during pregnancy. II.

  2. Hot horizontal branch stars: Predictions for mass loss. Winds, rotation, and the low gravity problem

    NASA Astrophysics Data System (ADS)

    Vink, Jorick S.; Cassisi, Santi

    2002-09-01

    We predict mass-loss rates for the late evolutionary phases of low-mass stars, with special emphasis on the consequences for the morphology of the Horizontal Branch (HB). We show that the computed rates, as predicted by the most plausible mechanism of radiation pressure on spectral lines, are too low to produce EHB/sdB stars. This invalidates the scenario recently outlined by Yong et al. (2000) to create these objects by mass loss on the HB. We argue, however, that mass loss plays a role in the distribution of rotational velocities of hot HB stars, and may - together with the enhancement of heavy element abundances due to radiative levitation - provide an explanation for the so-called ``low gravity'' problem. The mass loss recipe derived for hot HB (and extreme HB, sdB, sdOB) stars may also be applied to post-HB (AGB-manqué, UV-bright) stars over a range in effective temperatures between 12 500-40 000 K.

  3. Mass Loss Near the Eddington Limit

    NASA Astrophysics Data System (ADS)

    Bjorkman, J. E.

    2005-09-01

    We investigate whether ``continuum'' opacity near the Fe peak at log T = 5.2 can produce the great eruption of η Car. Our simple estimates show that η Car can be super-Eddington (Γ >1) well below the photosphere. The super-Eddington region is sufficiently extended that it can drive a very large mass loss rate (a few 0.1 M⊙ yr-1) to well above the escape speed (several 100 km s-1). Furthermore once initiated, it appears plausible that continuum-driving may ``run away,'' approaching the photon tiring limit. This suggests continuum-driving may be capable of producing the great eruption.

  4. Evaluation of the significance of abrupt changes in precipitation and runoff process in China

    NASA Astrophysics Data System (ADS)

    Xie, Ping; Wu, Ziyi; Sang, Yan-Fang; Gu, Haiting; Zhao, Yuxi; Singh, Vijay P.

    2018-05-01

    Abrupt changes are an important manifestation of hydrological variability. How to accurately detect the abrupt changes in hydrological time series and evaluate their significance is an important issue, but methods for dealing with them effectively are lacking. In this study, we propose an approach to evaluate the significance of abrupt changes in time series at five levels: no, weak, moderate, strong, and dramatic. The approach was based on an index of correlation coefficient calculated for the original time series and its abrupt change component. A bigger value of correlation coefficient reflects a higher significance level of abrupt change. Results of Monte-Carlo experiments verified the reliability of the proposed approach, and also indicated the great influence of statistical characteristics of time series on the significance level of abrupt change. The approach was derived from the relationship between correlation coefficient index and abrupt change, and can estimate and grade the significance levels of abrupt changes in hydrological time series. Application of the proposed approach to ten major watersheds in China showed that abrupt changes mainly occurred in five watersheds in northern China, which have arid or semi-arid climate and severe shortages of water resources. Runoff processes in northern China were more sensitive to precipitation change than those in southern China. Although annual precipitation and surface water resources amount (SWRA) exhibited a harmonious relationship in most watersheds, abrupt changes in the latter were more significant. Compared with abrupt changes in annual precipitation, human activities contributed much more to the abrupt changes in the corresponding SWRA, except for the Northwest Inland River watershed.

  5. Prevalence of skeletal muscle mass loss and its association with swallowing function after cardiovascular surgery.

    PubMed

    Wakabayashi, Hidetaka; Takahashi, Rimiko; Watanabe, Naoko; Oritsu, Hideyuki; Shimizu, Yoshitaka

    2017-06-01

    The aim of this study was to assess the prevalence of skeletal muscle mass loss and its association with swallowing function in patients with dysphagia after cardiovascular surgery. A retrospective cohort study was performed in 65 consecutive patients with dysphagia after cardiovascular surgery who were prescribed speech therapy. Skeletal muscle index (SMI) was calculated as total psoas muscle area assessed via abdominal computed tomography divided by height squared. Cutoff values were 6.36 cm 2 /m 2 for men and 3.92 cm 2 /m 2 for women. The Food Intake Level Scale (FILS) was used to assess the swallowing function. Univariate and ordered logistic regression analyses were applied to examine the associations between skeletal muscle mass loss and dysphagia. The study included 50 men and 15 women (mean age 73 ± 8 y). The mean SMI was 4.72 ± 1.37 cm 2 /m 2 in men and 3.33 ± 1.42 cm 2 /m 2 in women. Skeletal muscle mass loss was found in 53 (82%) patients. Twelve had tracheostomy cannula. Thirteen were non-oral feeding (FILS levels 1-3), 5 were oral food intake and alternative nutrition (levels 4-6), and 47 were oral food intake alone (levels 7-9) at discharge. The FILS at discharge was significantly lower in patients with skeletal muscle mass loss. Ordered logistic regression analysis of swallowing function showed that skeletal muscle mass loss and tracheostomy cannula were associated independently with the FILS at discharge. The prevalence of skeletal muscle mass loss is very high, and skeletal muscle mass loss is associated with swallowing function. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. The association between maternal smoking and placenta abruption: a meta-analysis.

    PubMed

    Shobeiri, Fatemeh; Masoumi, Seyedeh Zahra; Jenabi, Ensiyeh

    2017-08-01

    Several epidemiological studies have determined that maternal smoking can increase the risk of placenta abruption. To date, only a meta-analysis has been performed for assessing the relationship between smoking and placenta abruption. This meta-analysis was conducted to estimate the association between smoking and the risk of placenta abruption. A literature search was conducted in major databases such as PubMed, Web of Science, and Scopus from the earliest possible year to April 2016. The heterogeneity across studies was explored by Q-test and I 2 statistic. The publication bias was assessed using Begg's and Egger's tests. The results were reported using odds ratio (OR) estimate with its 95% confidence intervals (CI) using a random effects model. The literature search yielded 1167 publications until April 2016 with 4 309 610 participants. Based on OR estimates obtained from case-control and cohort studies, there was a significant association between smoking and placenta abruption (1.80; 95% CI: 1.75, 1.85). Based on the results of cohort studies, smoking and placenta abruption had a significant association (relative risk ratio: 1.65; 95% CI: 1.51, 1.80). Based on reports in epidemiological studies, we showed that smoking is a risk factor for placenta abruption.

  7. LMC O Supergiant Mass Loss Rates Determined from P V, S V and IR Excesses

    NASA Astrophysics Data System (ADS)

    Massa, Derck; Prinja, R.; Fullerton, A.; Lennon, D.

    2012-05-01

    We use HST/STIS and FUSE spectra and Spitzer/IRAC photometry to obtain independent mass loss rates for 7 LMC O supergiants. The mass loss rates are derived from the P Cygni profiles of the P V 1118, 1128 resonance doublet, the S V 1502 and N IV 1718 excited state lines, and the IR excesses of a combination of ground based and Spitzer photometry. The different mass loss rates are compared to each other and to theoretical expectations. We discuss the causes for the differences between the various determinations.

  8. Accelerated modern human-induced species losses: Entering the sixth mass extinction.

    PubMed

    Ceballos, Gerardo; Ehrlich, Paul R; Barnosky, Anthony D; García, Andrés; Pringle, Robert M; Palmer, Todd M

    2015-06-01

    The oft-repeated claim that Earth's biota is entering a sixth "mass extinction" depends on clearly demonstrating that current extinction rates are far above the "background" rates prevailing between the five previous mass extinctions. Earlier estimates of extinction rates have been criticized for using assumptions that might overestimate the severity of the extinction crisis. We assess, using extremely conservative assumptions, whether human activities are causing a mass extinction. First, we use a recent estimate of a background rate of 2 mammal extinctions per 10,000 species per 100 years (that is, 2 E/MSY), which is twice as high as widely used previous estimates. We then compare this rate with the current rate of mammal and vertebrate extinctions. The latter is conservatively low because listing a species as extinct requires meeting stringent criteria. Even under our assumptions, which would tend to minimize evidence of an incipient mass extinction, the average rate of vertebrate species loss over the last century is up to 100 times higher than the background rate. Under the 2 E/MSY background rate, the number of species that have gone extinct in the last century would have taken, depending on the vertebrate taxon, between 800 and 10,000 years to disappear. These estimates reveal an exceptionally rapid loss of biodiversity over the last few centuries, indicating that a sixth mass extinction is already under way. Averting a dramatic decay of biodiversity and the subsequent loss of ecosystem services is still possible through intensified conservation efforts, but that window of opportunity is rapidly closing.

  9. Accelerated modern human–induced species losses: Entering the sixth mass extinction

    PubMed Central

    Ceballos, Gerardo; Ehrlich, Paul R.; Barnosky, Anthony D.; García, Andrés; Pringle, Robert M.; Palmer, Todd M.

    2015-01-01

    The oft-repeated claim that Earth’s biota is entering a sixth “mass extinction” depends on clearly demonstrating that current extinction rates are far above the “background” rates prevailing between the five previous mass extinctions. Earlier estimates of extinction rates have been criticized for using assumptions that might overestimate the severity of the extinction crisis. We assess, using extremely conservative assumptions, whether human activities are causing a mass extinction. First, we use a recent estimate of a background rate of 2 mammal extinctions per 10,000 species per 100 years (that is, 2 E/MSY), which is twice as high as widely used previous estimates. We then compare this rate with the current rate of mammal and vertebrate extinctions. The latter is conservatively low because listing a species as extinct requires meeting stringent criteria. Even under our assumptions, which would tend to minimize evidence of an incipient mass extinction, the average rate of vertebrate species loss over the last century is up to 100 times higher than the background rate. Under the 2 E/MSY background rate, the number of species that have gone extinct in the last century would have taken, depending on the vertebrate taxon, between 800 and 10,000 years to disappear. These estimates reveal an exceptionally rapid loss of biodiversity over the last few centuries, indicating that a sixth mass extinction is already under way. Averting a dramatic decay of biodiversity and the subsequent loss of ecosystem services is still possible through intensified conservation efforts, but that window of opportunity is rapidly closing. PMID:26601195

  10. Excessive loss of skeletal muscle mass in older adults with type 2 diabetes.

    PubMed

    Park, Seok Won; Goodpaster, Bret H; Lee, Jung Sun; Kuller, Lewis H; Boudreau, Robert; de Rekeneire, Nathalie; Harris, Tamara B; Kritchevsky, Stephen; Tylavsky, Frances A; Nevitt, Michael; Cho, Yong-wook; Newman, Anne B

    2009-11-01

    A loss of skeletal muscle mass is frequently observed in older adults. The aim of the study was to investigate the impact of type 2 diabetes on the changes in body composition, with particular interest in the skeletal muscle mass. We examined total body composition with dual-energy X-ray absorptiometry annually for 6 years in 2,675 older adults. We also measured mid-thigh muscle cross-sectional area (CSA) with computed tomography in year 1 and year 6. At baseline, 75-g oral glucose challenge tests were performed. Diagnosed diabetes (n = 402, 15.0%) was identified by self-report or use of hypoglycemic agents. Undiagnosed diabetes (n = 226, 8.4%) was defined by fasting plasma glucose (>or=7 mmol/l) or 2-h postchallenge plasma glucose (>or=11.1 mmol/l). Longitudinal regression models were fit to examine the effect of diabetes on the changes in body composition variables. Older adults with either diagnosed or undiagnosed type 2 diabetes showed excessive loss of appendicular lean mass and trunk fat mass compared with nondiabetic subjects. Thigh muscle CSA declined two times faster in older women with diabetes than their nondiabetic counterparts. These findings remained significant after adjusting for age, sex, race, clinic site, baseline BMI, weight change intention, and actual weight changes over time. Type 2 diabetes is associated with excessive loss of skeletal muscle and trunk fat mass in community-dwelling older adults. Older women with type 2 diabetes are at especially high risk for loss of skeletal muscle mass.

  11. Mass Loss of Coal Particles Burning in Fluidized Bed

    NASA Astrophysics Data System (ADS)

    Pełka, Piotr

    2017-06-01

    In this work many conclusions resulting from research carried out on the coal combustion process of the chosen coal type and its accompanying erosion in a two-phase flow of inert material have been presented. The purpose of this flow was to present a model of the conditions of the central and upper zone of the combustion chamber of the fluidized boiler. In the opinion of many authors (Basu, 1999; Chirone et al., 1991), the erosion process results from the contact of a fuel particle with particles of inert material that is responsible for generating fine fuel particles of less than 100 mm. If the particles are in the upper zone of the boiler where there is oxygen deficit, they can increase the loss of incomplete combustion substantially. The results of research do not confirm this common thesis, but rather indicate that the process of comminution that results from erosion under oxidative conditions contributes to the increase of substantial mass loss of a coal particle, however the increased mass loss of particle during combustion is first and foremost due to the whole process of removal of ash from the reactionary surface of a fuel particle. Nevertheless, in the conditions of oxygen deficit the comminution of particles as a result of the erosion process is negligible

  12. The association between uterine leiomyoma and placenta abruption: A meta-analysis.

    PubMed

    Jenabi, Ensiyeh; Ebrahimzadeh Zagami, Samira

    2017-11-01

    Some epidemiological studies have found that uterine leiomyoma can increase the risk of placenta abruption. To date, the meta-analysis has not been performed for assessing the relationship between uterine leiomyoma and placenta abruption. This meta-analysis was conducted to estimate the association between uterine leiomyoma and the risk of placenta abruption. A literature search was conducted out in major databases PubMed, Web of Science, and Scopus from the earliest possible year to October 2016. The heterogeneity across studies was explored by Q-test and I 2 statistic. The publication bias was assessed by Begg's and Egger's tests. The results were showed using odds ratio (OR) estimate with its 95% confidence intervals (CI) using a random-effects model. The literature search included 953 articles until October 2016 with 232,024 participants. Based on OR estimates obtained from case-control and cohort studies, there was significant association between uterine leiomyoma and placenta abruption (2.63; 95% CI: 1.38, 3.88). We showed based on reports in observational studies that uterine leiomyoma is a risk factor for placenta abruption.

  13. Use of plume mapping data to estimate chlorinated solvent mass loss

    USGS Publications Warehouse

    Barbaro, J.R.; Neupane, P.P.

    2006-01-01

    Results from a plume mapping study from November 2000 through February 2001 in the sand-and-gravel surficial aquifer at Dover Air Force Base, Delaware, were used to assess the occurrence and extent of chlorinated solvent mass loss by calculating mass fluxes across two transverse cross sections and by observing changes in concentration ratios and mole fractions along a longitudinal cross section through the core of the plume. The plume mapping investigation was conducted to determine the spatial distribution of chlorinated solvents migrating from former waste disposal sites. Vertical contaminant concentration profiles were obtained with a direct-push drill rig and multilevel piezometers. These samples were supplemented with additional ground water samples collected with a minipiezometer from the bed of a perennial stream downgradient of the source areas. Results from the field program show that the plume, consisting mainly of tetrachloroethylene (PCE), trichloroethene (TCE), and cis-1,2-dichloroethene (cis-1,2-DCE), was approximately 670 m in length and 120 m in width, extended across much of the 9- to 18-m thickness of the surficial aquifer, and discharged to the stream in some areas. The analyses of the plume mapping data show that losses of the parent compounds, PCE and TCE, were negligible downgradient of the source. In contrast, losses of cis-1,2-DCE, a daughter compound, were observed in this plume. These losses very likely resulted from biodegradation, but the specific reaction mechanism could not be identified. This study demonstrates that plume mapping data can be used to estimate the occurrence and extent of chlorinated solvent mass loss from biodegradation and assess the effectiveness of natural attenuation as a remedial measure.

  14. On Driving AGB Mass-Loss from Core-Contraction

    NASA Astrophysics Data System (ADS)

    Lewis, B. M.

    1997-12-01

    A bulk movement of mass constitutes a momentum flow. An instructive instance occurs in the radial pulsation of stars and white dwarfs, where a symmetric contraction phase implies the existence of an inwardly- directed radial momentum flow, that is followed during the subsequent expansion by an outwardly-directed flow. The key notion here is that an inward flow is effectively transmitted through the center to become in turn an outward flow: in adiabatic processes the momentum flux is not cancelled simply because it arrives at the center. However, during the radial pulsation of AGB stars momentum is cancelled in atmospheric shock-waves and consumed in work against gravity while mass is lifted far enough away from the star for dust to form, whereon radiation pressure drives it away. These momentum-dissipative conditions at the outer boundary therefore require a stellar source of radially directed momentum if pulsation is to continue in an AGB star. A sufficient source is found in the contraction of the whole of the electron-degenerate core of an AGB star under the addition of He ashes from shell-hydrogen burning. This produces an inwardly- directed radial momentum flow that must reach the center. Lewis quantifies the resulting momentum flux (http://xxx.lanl.gov/ps/astro-ph /9707233), and finds that it easily suffices to support the mass-loss of every AGB star. But it is necessary to assume that most of the inwardly directed flux is transmitted through the center to become in turn an outwardly directed flux. The AGB core maintains its virial equilibrium by exporting its excess momentum flux to the stellar envelope. This mechanism explains the dependence of the mass-loss rate from AGB stars on core mass; its generalization to objects with angular momentum and/or strong magnetic fields suggests a novel explanation for the axial symmetry exhibited by most planetary nebulae and proto planetary nebulae. Gravitational contraction can also account for the momentum flux in the

  15. Convection and mass loss through the chromosphere of Betelgeuse

    NASA Astrophysics Data System (ADS)

    Ridgway, Stephen

    2011-10-01

    Betelgeuse is well suited for detailed study of the mass loss process in a massive red supergiant. We have engaged in a multi-scale, multi-color study to trace the ejected material from the photosphere to the interstellar medium, and understand its chemical evolution {formation of molecules and dust}. Infrared interferometry already gave us a detailed image of the photosphere, compatible with large convective cells. Adaptive optics spectro-imaging {1.0-2.2 microns} allowed us to detect the presence of the CN molecule and mass loss plume structures up to at least 6 R*. At larger distances, we observed silicate-rich dust in thermal IR {8-20 microns}. From the surface to 100 R*, we therefore have a continuous coverage with multicolor imagery. The chromosphere lies at a key location, between the photosphere and the molecular envelope. As shown by STIS spatially resolved spectroscopy {Lobel & Dupree 2001}, it contains rising and falling gases. Such structure is supported by our 3D modeling of the convection. In order to probe the dynamics of the envelope and its relation to photospheric spots and mass loss plumes, we propose to obtain UV imaging with STIS at 3 epochs to complement our coordinated ground-based effort as well as the earlier HST UV snapshots. We will use this imagery to correlate structures at different radii and temperatures, and to explore the time-scales of evolution. With the support of our 3D models, this information will answer specific questions including deciding between convective and polar explanations for bright spots and plumes. Our infrared imaging observations will be repeated contemporaneously with the requested HST/STIS images.

  16. Plant diversity does not buffer drought effects on early-stage litter mass loss rates and microbial properties.

    PubMed

    Vogel, Anja; Eisenhauer, Nico; Weigelt, Alexandra; Scherer-Lorenzen, Michael

    2013-09-01

    Human activities are decreasing biodiversity and changing the climate worldwide. Both global change drivers have been shown to affect ecosystem functioning, but they may also act in concert in a non-additive way. We studied early-stage litter mass loss rates and soil microbial properties (basal respiration and microbial biomass) during the summer season in response to plant species richness and summer drought in a large grassland biodiversity experiment, the Jena Experiment, Germany. In line with our expectations, decreasing plant diversity and summer drought decreased litter mass loss rates and soil microbial properties. In contrast to our hypotheses, however, this was only true for mass loss of standard litter (wheat straw) used in all plots, and not for plant community-specific litter mass loss. We found no interactive effects between global change drivers, that is, drought reduced litter mass loss rates and soil microbial properties irrespective of plant diversity. High mass loss rates of plant community-specific litter and low responsiveness to drought relative to the standard litter indicate that soil microbial communities were adapted to decomposing community-specific plant litter material including lower susceptibility to dry conditions during summer months. Moreover, higher microbial enzymatic diversity at high plant diversity may have caused elevated mass loss of standard litter. Our results indicate that plant diversity loss and summer drought independently impede soil processes. However, soil decomposer communities may be highly adapted to decomposing plant community-specific litter material, even in situations of environmental stress. Results of standard litter mass loss moreover suggest that decomposer communities under diverse plant communities are able to cope with a greater variety of plant inputs possibly making them less responsive to biotic changes. © 2013 John Wiley & Sons Ltd.

  17. An international contrast of rates of placental abruption: an age-period-cohort analysis.

    PubMed

    Ananth, Cande V; Keyes, Katherine M; Hamilton, Ava; Gissler, Mika; Wu, Chunsen; Liu, Shiliang; Luque-Fernandez, Miguel Angel; Skjærven, Rolv; Williams, Michelle A; Tikkanen, Minna; Cnattingius, Sven

    2015-01-01

    Although rare, placental abruption is implicated in disproportionately high rates of perinatal morbidity and mortality. Understanding geographic and temporal variations may provide insights into possible amenable factors of abruption. We examined abruption frequencies by maternal age, delivery year, and maternal birth cohorts over three decades across seven countries. Women that delivered in the US (n = 863,879; 1979-10), Canada (4 provinces, n = 5,407,463; 1982-11), Sweden (n = 3,266,742; 1978-10), Denmark (n = 1,773,895; 1978-08), Norway (n = 1,780,271, 1978-09), Finland (n = 1,411,867; 1987-10), and Spain (n = 6,151,508; 1999-12) were analyzed. Abruption diagnosis was based on ICD coding. Rates were modeled using Poisson regression within the framework of an age-period-cohort analysis, and multi-level models to examine the contribution of smoking in four countries. Abruption rates varied across the seven countries (3-10 per 1000), Maternal age showed a consistent J-shaped pattern with increased rates at the extremes of the age distribution. In comparison to births in 2000, births after 2000 in European countries had lower abruption rates; in the US there was an increase in rate up to 2000 and a plateau thereafter. No birth cohort effects were evident. Changes in smoking prevalence partially explained the period effect in the US (P = 0.01) and Sweden (P<0.01). There is a strong maternal age effect on abruption. While the abruption rate has plateaued since 2000 in the US, all other countries show declining rates. These findings suggest considerable variation in abruption frequencies across countries; differences in the distribution of risk factors, especially smoking, may help guide policy to reduce abruption rates.

  18. Phase Memory Preserving Harmonics from Abruptly Autofocusing Beams.

    PubMed

    Koulouklidis, Anastasios D; Papazoglou, Dimitris G; Fedorov, Vladimir Yu; Tzortzakis, Stelios

    2017-12-01

    We demonstrate both theoretically and experimentally that the harmonics from abruptly autofocusing ring-Airy beams present a surprising property: They preserve the phase distribution of the fundamental beam. Consequently, this "phase memory" imparts to the harmonics the abrupt autofocusing behavior, while, under certain conditions, their foci coincide in space with the one of the fundamental. Experiments agree well with our theoretical estimates and detailed numerical calculations. Our findings open the way for the use of such beams and their harmonics in strong field science.

  19. Is lost lean mass from intentional weight loss recovered during weight regain in postmenopausal women?

    PubMed

    Beavers, Kristen M; Lyles, Mary F; Davis, Cralen C; Wang, Xuewen; Beavers, Daniel P; Nicklas, Barbara J

    2011-09-01

    Despite the well-known recidivism of obesity, surprisingly little is known about the composition of body weight during weight regain. The objective of this study was to determine whether the composition of body weight regained after intentional weight loss is similar to the composition of body weight lost. The design was a follow-up to a randomized controlled trial of weight loss in which body composition was analyzed and compared in 78 postmenopausal women before the intervention, immediately after the intervention, and 6 and 12 mo after the intervention. All body mass and composition variables were lower immediately after weight loss than at baseline (all P < 0.05). More fat than lean mass was lost with weight loss, which resulted in body-composition changes favoring a lower percentage of body fat and a higher lean-to-fat mass ratio (P < 0.001). Considerable interindividual variability in weight regain was noted (CV = 1.07). In women who regained ≥2 kg body weight, a decreasing trend in the lean-to-fat mass ratio was observed, which indicated greater fat mass accretion than lean mass accretion (P < 0.001). Specifically, for every 1 kg fat lost during the weight-loss intervention, 0.26 kg lean tissue was lost; for every 1 kg fat regained over the following year, only 0.12 kg lean tissue was regained. Although not all postmenopausal women who intentionally lose weight will regain it within 1 y, the data suggest that fat mass is regained to a greater degree than is lean mass in those who do experience some weight regain. The health ramifications of our findings remain to be seen.

  20. A tipping point in refreezing accelerates mass loss of Greenland's glaciers and ice caps.

    PubMed

    Noël, B; van de Berg, W J; Lhermitte, S; Wouters, B; Machguth, H; Howat, I; Citterio, M; Moholdt, G; Lenaerts, J T M; van den Broeke, M R

    2017-03-31

    Melting of the Greenland ice sheet (GrIS) and its peripheral glaciers and ice caps (GICs) contributes about 43% to contemporary sea level rise. While patterns of GrIS mass loss are well studied, the spatial and temporal evolution of GICs mass loss and the acting processes have remained unclear. Here we use a novel, 1 km surface mass balance product, evaluated against in situ and remote sensing data, to identify 1997 (±5 years) as a tipping point for GICs mass balance. That year marks the onset of a rapid deterioration in the capacity of the GICs firn to refreeze meltwater. Consequently, GICs runoff increases 65% faster than meltwater production, tripling the post-1997 mass loss to 36±16 Gt -1 , or ∼14% of the Greenland total. In sharp contrast, the extensive inland firn of the GrIS retains most of its refreezing capacity for now, buffering 22% of the increased meltwater production. This underlines the very different response of the GICs and GrIS to atmospheric warming.

  1. A tipping point in refreezing accelerates mass loss of Greenland's glaciers and ice caps

    PubMed Central

    Noël, B.; van de Berg, W. J; Lhermitte, S.; Wouters, B.; Machguth, H.; Howat, I.; Citterio, M.; Moholdt, G.; Lenaerts, J. T. M.; van den Broeke, M. R.

    2017-01-01

    Melting of the Greenland ice sheet (GrIS) and its peripheral glaciers and ice caps (GICs) contributes about 43% to contemporary sea level rise. While patterns of GrIS mass loss are well studied, the spatial and temporal evolution of GICs mass loss and the acting processes have remained unclear. Here we use a novel, 1 km surface mass balance product, evaluated against in situ and remote sensing data, to identify 1997 (±5 years) as a tipping point for GICs mass balance. That year marks the onset of a rapid deterioration in the capacity of the GICs firn to refreeze meltwater. Consequently, GICs runoff increases 65% faster than meltwater production, tripling the post-1997 mass loss to 36±16 Gt−1, or ∼14% of the Greenland total. In sharp contrast, the extensive inland firn of the GrIS retains most of its refreezing capacity for now, buffering 22% of the increased meltwater production. This underlines the very different response of the GICs and GrIS to atmospheric warming. PMID:28361871

  2. A tipping point in refreezing accelerates mass loss of Greenland's glaciers and ice caps

    NASA Astrophysics Data System (ADS)

    Noël, B.; van de Berg, W. J.; Lhermitte, S.; Wouters, B.; Machguth, H.; Howat, I.; Citterio, M.; Moholdt, G.; Lenaerts, J. T. M.; van den Broeke, M. R.

    2017-03-01

    Melting of the Greenland ice sheet (GrIS) and its peripheral glaciers and ice caps (GICs) contributes about 43% to contemporary sea level rise. While patterns of GrIS mass loss are well studied, the spatial and temporal evolution of GICs mass loss and the acting processes have remained unclear. Here we use a novel, 1 km surface mass balance product, evaluated against in situ and remote sensing data, to identify 1997 (+/-5 years) as a tipping point for GICs mass balance. That year marks the onset of a rapid deterioration in the capacity of the GICs firn to refreeze meltwater. Consequently, GICs runoff increases 65% faster than meltwater production, tripling the post-1997 mass loss to 36+/-16 Gt-1, or ~14% of the Greenland total. In sharp contrast, the extensive inland firn of the GrIS retains most of its refreezing capacity for now, buffering 22% of the increased meltwater production. This underlines the very different response of the GICs and GrIS to atmospheric warming.

  3. Limited influence of climate change mitigation on short-term glacier mass loss

    NASA Astrophysics Data System (ADS)

    Marzeion, Ben; Kaser, Georg; Maussion, Fabien; Champollion, Nicolas

    2018-04-01

    Glacier mass loss is a key contributor to sea-level change1,2, slope instability in high-mountain regions3,4 and the changing seasonality and volume of river flow5-7. Understanding the causes, mechanisms and time scales of glacier change is therefore paramount to identifying successful strategies for mitigation and adaptation. Here, we use temperature and precipitation fields from the Coupled Model Intercomparison Project Phase 5 output to force a glacier evolution model, quantifying mass responses to future climatic change. We find that contemporary glacier mass is in disequilibrium with the current climate, and 36 ± 8% mass loss is already committed in response to past greenhouse gas emissions. Consequently, mitigating future emissions will have only very limited influence on glacier mass change in the twenty-first century. No significant differences between 1.5 and 2 K warming scenarios are detectable in the sea-level contribution of glaciers accumulated within the twenty-first century. In the long-term, however, mitigation will exert strong control, suggesting that ambitious measures are necessary for the long-term preservation of glaciers.

  4. Chromospheric dust formation, stellar masers and mass loss

    NASA Technical Reports Server (NTRS)

    Stencel, R. E.

    1986-01-01

    A multistep scenario which describes a plausible mass loss mechanism associated with red giant and related stars is outlined. The process involves triggering a condensation instability in an extended chromosphere, leading to the formation of cool, dense clouds which are conducive to the formation of molecules and dust grains. Once formed, the dust can be driven away from the star by radiation pressure. Consistency with various observed phenomena is discussed.

  5. SO and SO2 in mass-loss envelopes of red giants: probes of nonequilibrium circumstellar chemistry and mass-loss rates.

    PubMed

    Sahai, R; Wannier, P G

    1992-07-20

    We have made a search for SO in the mass-loss envelopes of 24 mostly oxygen-rich red giants, using the 8(8)-7(7) (344.3 GHz), 6(5)-5(4) (219.9 GHz), 4(3)-3(2) (138.2 GHz), and 3(2)-2(1) (99.3 GHz) transitions. One or more of these transitions were detected toward 14 envelopes, including those of the supergiants VY CMa and IRC +10420. The SO envelope of IK Tau was measurably extended, and that of IRC +10420 marginally so, allowing us to determine the envelope sizes directly. The SiO (v = 0) J = 8-7, J = 5-4, and J = 3-2 lines at 347.3, 217.1, and 130.3 GHz were detected simultaneously with the 344.3, 219.9, and 138.2 GHz SO lines, respectively. From our SO data, as well as from SO2 data published elsewhere (for a few sources), we derive the circumstellar SO and SO2 abundances and compare them with theoretical predictions. We find that the photospheric abundances of SO and SO2 are insignificant, and that SO and SO2 must be produced in the circumstellar envelopes. However, the (average) SO abundances are larger than even the peak values predicted by nonequilibrium circumstellar chemistry models. The large SO abundances imply that S is not heavily depleted into grains in these envelopes, and further suggest that (i) the stellar mass-loss rates in these objects are substantially larger than accepted values, (ii) the circumstellar H/H2 abundance ratio is quite small, and (iii) the reaction of O and SH dominates over the reaction of S and OH in the production of SO. In the peculiar bipolar nebula OH 231.8+4.2, the combined SO and SO2 abundance exceeds the cosmic S abundance, if the mass-loss rate in this object is smaller than or equal to l0(-4) M solar yr-1. In IK Tau the data can only be fitted with models in which the SO is distributed in a hollow shell, as predicted by the nonequilibrium chemistry models. In another three, which have no measurable OH, the discovery of SO is difficult to explain by such models.

  6. Glaciers. Attribution of global glacier mass loss to anthropogenic and natural causes.

    PubMed

    Marzeion, Ben; Cogley, J Graham; Richter, Kristin; Parkes, David

    2014-08-22

    The ongoing global glacier retreat is affecting human societies by causing sea-level rise, changing seasonal water availability, and increasing geohazards. Melting glaciers are an icon of anthropogenic climate change. However, glacier response times are typically decades or longer, which implies that the present-day glacier retreat is a mixed response to past and current natural climate variability and current anthropogenic forcing. Here we show that only 25 ± 35% of the global glacier mass loss during the period from 1851 to 2010 is attributable to anthropogenic causes. Nevertheless, the anthropogenic signal is detectable with high confidence in glacier mass balance observations during 1991 to 2010, and the anthropogenic fraction of global glacier mass loss during that period has increased to 69 ± 24%. Copyright © 2014, American Association for the Advancement of Science.

  7. Mass Balance of the Northern Antarctic Peninsula and its Ongoing Response to Ice Shelf Loss

    NASA Astrophysics Data System (ADS)

    Scambos, T. A.; Berthier, E.; Haran, T. M.; Shuman, C. A.; Cook, A. J.; Bohlander, J. A.

    2012-12-01

    An assessment of the most rapidly changing areas of the Antarctic Peninsula (north of 66°S) shows that ice mass loss for the region is dominated by areas affected by eastern-Peninsula ice shelf losses in the past 20 years. Little if any of the mass loss is compensated by increased snowfall in the northwestern or far northern areas. We combined satellite stereo-image DEM differencing and ICESat-derived along-track elevation changes to measure ice mass loss for the Antarctic Peninsula north of 66°S between 2001-2010, focusing on the ICESat-1 period of operation (2003-2009). This mapping includes all ice drainages affected by recent ice shelf loss in the northeastern Peninsula (Prince Gustav, Larsen Inlet, Larsen A, and Larsen B) as well as James Ross Island, Vega Island, Anvers Island, Brabant Island and the adjacent west-flowing glaciers. Polaris Glacier (feeding the Larsen Inlet, which collapsed in 1986) is an exception, and may have stabilized. Our method uses ASTER and SPOT-5 stereo-image DEMs to determine dh/dt for elevations below 800 m; at higher elevations ICESat along-track elevation differencing is used. To adjust along-track path offsets between its 2003-2009 campaigns, we use a recent DEM of the Peninsula to establish and correct for cross-track slope (Cook et al., 2012, doi:10.5194/essdd-5-365-2012; http://nsidc.org/data/nsidc-0516.html) . We reduce the effect of possible seasonal variations in elevation by using only integer-year repeats of the ICESat tracks for comparison. Mass losses are dominated by the major glaciers that had flowed into the Prince Gustav (Boydell, Sjorgren, Röhss), Larsen A (Edgeworth, Bombardier, Dinsmoor, Drygalski), and Larsen B (Hektoria, Jorum, and Crane) embayments. The pattern of mass loss emphasizes the significant and multi-decadal response to ice shelf loss. Areas with shelf losses occurring 30 to 100s of years ago seem to be relatively stable or losing mass only slowly (western glaciers, northernmost areas). The

  8. A new prescription for the mass-loss rates of hydrogen-free WR stars

    NASA Astrophysics Data System (ADS)

    Tramper, Frank; Sana, Hugues; de Koter, Alex

    2017-11-01

    We present a new empirical prescription for the mass-loss rates of hydrogen-free Wolf-Rayet stars based on results of detailed spectral analyses of WC and WO stars. Compared to the prescription of Nugis & Lamers (2000), M⊙ is less sensitive to the surface helium abundance, implying a stronger mass loss at the late stages of Wolf-Rayet evolution. The winds of hydrogen-free WN stars have a strong metallicity dependence, while those of WC and WO stars have a very weak metallicity dependence.

  9. A survey of mass loss from Be and shell stars using ultraviolet data from Copernicus

    NASA Technical Reports Server (NTRS)

    Marlborough, J. M.; Snow, T. P., Jr.

    1976-01-01

    Ultraviolet spectra of intermediate resolution have been obtained with Copernicus of twelve objects classified as Be or shell stars, and an additional 19 dwarfs of spectral classes B0-B4. Some of these spectra show marked asymmetries in certain resonance lines, especially the Si IV doublet at 1400 A, indicating the presence of outflowing material with maximum velocities of nearly 1000 km/sec. Direct evidence for mass loss at these velocities is seen for the first time in dwarf stars as late as B1.5. Later than B0.5, the only survey objects showing this phenomenon are Be stars. Among the stars considered there is a correlation between the presence of mass-loss effects and projected rotational velocity, suggesting that the UV flux from B1-B3 dwarfs is sufficient to drive high-velocity stellar winds only if rotation reduces the effective gravity near the equator. The role of mass-loss in producing the Be star phenomenon and the effects of rotation on mass loss are discussed.

  10. Mass loss from interacting close binary systems

    NASA Technical Reports Server (NTRS)

    Plavec, M. J.

    1981-01-01

    The three well-defined classes of evolved binary systems that show evidence of present and/or past mass loss are the cataclysmic variables, the Algols, and Wolf-Rayet stars. It is thought that the transformation of supergiant binary systems into the very short-period cataclysmic variables must have been a complex process. The new evidence that has recently been obtained from the far ultraviolet spectra that a certain subclass of the Algols (the Serpentids) are undergoing fairly rapid evolution is discussed. It is thought probable that the remarkable mass outflow observed in them is connected with a strong wind powered by accretion. The origin of the circumbinary clouds or flat disks that probably surround many strongly interacting binaries is not clear. Attention is also given to binary systems with hot white dwarf or subdwarf components, such as the symbiotic objects and the BQ stars; it is noted that in them both components may be prone to an enhanced stellar wind.

  11. A grid of MHD models for stellar mass loss and spin-down rates of solar analogs

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cohen, O.; Drake, J. J.

    2014-03-01

    Stellar winds are believed to be the dominant factor in the spin-down of stars over time. However, stellar winds of solar analogs are poorly constrained due to observational challenges. In this paper, we present a grid of magnetohydrodynamic models to study and quantify the values of stellar mass loss and angular momentum loss rates as a function of the stellar rotation period, magnetic dipole component, and coronal base density. We derive simple scaling laws for the loss rates as a function of these parameters, and constrain the possible mass loss rate of stars with thermally driven winds. Despite the successmore » of our scaling law in matching the results of the model, we find a deviation between the 'solar dipole' case and a real case based on solar observations that overestimates the actual solar mass loss rate by a factor of three. This implies that the model for stellar fields might require a further investigation with additional complexity. Mass loss rates in general are largely controlled by the magnetic field strength, with the wind density varying in proportion to the confining magnetic pressure B {sup 2}. We also find that the mass loss rates obtained using our grid models drop much faster with the increase in rotation period than scaling laws derived using observed stellar activity. For main-sequence solar-like stars, our scaling law for angular momentum loss versus poloidal magnetic field strength retrieves the well-known Skumanich decline of angular velocity with time, Ω{sub *}∝t {sup –1/2}, if the large-scale poloidal magnetic field scales with rotation rate as B{sub p}∝Ω{sub ⋆}{sup 2}.« less

  12. Modeling of Camembert-type cheese mass loss in a ripening chamber: main biological and physical phenomena.

    PubMed

    Hélias, A; Mirade, P-S; Corrieu, G

    2007-11-01

    A model of the mass loss of Camembert-type cheese was established with data obtained from 2 experimental ripening trials carried out in 2 pilot ripening chambers. During these experiments, a cheese was continuously weighed and the relative humidity, temperature, oxygen, and carbon dioxide concentrations in the ripening chamber were recorded online. The aim was to establish a simple but accurate model that would predict cheese mass changes according to available online measurements. The main hypotheses were that 1) the cheese water activity was constant during ripening, 2) the respiratory activity of the microflora played a major role by inducing heat production, combined with important water evaporation, 3) the temperature gradient existing inside the cheese was negligible, and the limiting phenomenon was the convective transfer. The water activity and the specific heat of the cheeses were assessed by offline measurements. The others parameters in the model were obtained from the literature. This dynamic model was built with 2 state variables: the cheese mass and the surface temperature of the cheese. In this way, only the heat transfer coefficient had to be fitted, and it was strongly determined by the airflow characteristics close to the cheeses. Model efficiency was illustrated by comparing the estimated and measured mass and the mass loss rate for the 2 studied runs; the relative errors were less than 1.9 and 3.2% for the mass loss and the mass loss rate, respectively. The dynamic effects of special events, such as room defrosting or changes in chamber relative humidity, were well described by the model, especially in terms of kinetics (mass loss rates).

  13. The Roles of Tidal Evolution and Evaporative Mass Loss in the Origin of CoRoT-7 b

    NASA Technical Reports Server (NTRS)

    Jackson, Brian; Miller, Neil; Barnes, Rory; Raymond, Sean N.; Fortney, Jonathan J.; Greenberg, Richard

    2010-01-01

    CoRoT-7 b is the first confirmed rocky exoplanet, but, with an orbital semimajor axis of 0.0172 au, its origins may be unlike any rocky planet in our Solar System. In this study, we consider the roles of tidal evolution and evaporative mass loss in CoRoT-7 b's history, which together have modified the planet's mass and orbit. If CoRoT-7 b has always been a rocky body, evaporation may have driven off almost half its original mass, but the mass loss may depend sensitively on the extent of tidal decay of its orbit. As tides caused CoRoT-7 b's orbit to decay, they brought the planet closer to its host star, thereby enhancing the mass loss rate. Such a large mass loss also suggests the possibility that CoRoT-7 b began as a gas giant planet and had its original atmosphere completely evaporated. In this case, we find that CoRoT-7 b's original mass probably did not exceed 200 Earth masses (about two-third of a Jupiter mass). Tides raised on the host star by the planet may have significantly reduced the orbital semimajor axis, perhaps causing the planet to migrate through mean-motion resonances with the other planet in the system, CoRoT-7 c. The coupling between tidal evolution and mass loss may be important not only for CoRoT-7 b but also for other close-in exoplanets, and future studies of mass loss and orbital evolution may provide insight into the origin and fate of close-in planets, both rocky and gaseous.

  14. Dust Production and Mass Loss in Cool Evolved Stars

    NASA Technical Reports Server (NTRS)

    Boyer, M. L.

    2013-01-01

    Following the red giant branch phase and the subsequent core He-burning phase, the low- to intermediate-mass stars (0.8mass <8) begin to ascend the asymptotic giant branch (AGB). Pulsations levitate material from the stellar surface and provide density enhancements and shocks, which can encourage dust formation and re-processing. The dust composition depends on the atmospheric chemistry (abundance of carbon relative to oxygen), which is altered by dredging up newly formed carbon to the surface of the star. I will briefly review the current status of models that include AGB mass loss and relate them to recent observations of AGB stars from the Surveying the Agents of Galaxy Evolution (SAGE) Spitzer surveys of the Small and Large Magellanic Clouds, including measures of the total dust input to the interstellar medium from AGB stars.

  15. Investigating ice shelf mass loss processes from continuous satellite altimetry

    NASA Astrophysics Data System (ADS)

    Fricker, H. A.

    2017-12-01

    The Antarctic Ice Sheet continually gains mass through snowfall over its large area and, to remain approximately in equilibrium, it sheds most of this excess mass through two processes, basal melting and iceberg calving, that both occur in the floating ice shelves surrounding the continent. Small amounts of mass are also lost by surface melting, which occurs on many ice shelves every summer to varying degrees, and has been linked to ice-shelf collapse via hydrofracture on ice shelves that have been pre-weakened. Ice shelves provide mechanical support to `buttress' seaward flow of grounded ice, so that ice-shelf thinning and retreat result in enhanced ice discharge to the ocean. Ice shelves are susceptible to changes in forcing from both the atmosphere and the ocean, which both change on a broad range of timescales to modify mass gains and losses at the surface and base, and from internal instabilities of the ice sheet itself. Mass loss from iceberg calving is episodic, with typical intervals between calving events on the order of decades. Since ice shelves are so vast, the only viable way to monitor them is with satellites. Here, we discuss results from satellite radar and laser altimeter data from one NASA satellite (ICESat), and four ESA satellites (ERS-1, ERS-2, Envisat, CryoSat-2) to obtain estimates of ice-shelf surface height since the early 1990s. The continuous time series show accelerated losses in total Antarctic ice-shelf volume from 1994 to 2017, and allow us to investigate the processes causing ice-shelf mass change. For Larsen C, much of the variability comes from changing atmospheric conditions affecting firn state. In the Amundsen Sea, the rapid thinning is a combination of accelerated ocean-driven thinning and ice dynamics. This long-term thinning signal is, however, is strongly modulated by ENSO-driven interannual variability. However, observations of ocean variability around Antarctica are sparse, since these regions are often covered in sea ice

  16. Self-reported smoking habits and serum cotinine levels in women with placental abruption.

    PubMed

    Tikkanen, Minna; Surcel, Heljä-Marja; Bloigu, Aini; Nuutila, Mika; Ylikorkala, Olavi; Hiilesmaa, Vilho; Paavonen, Jorma

    2010-12-01

    smoking is an important risk factor for placental abruption with strong dose-dependency. Pregnant smokers often underreport tobacco use which can be objectively assessed by measuring serum cotinine levels. We examined the accuracy between self-reported smoking habits and early pregnancy serum cotinine levels in women with or without placental abruption. retrospective case-control study. university Hospital. a total of 175 women with placental abruption and 370 control women. serum samples collected during the first trimester were analyzed for serum cotinine levels. Cotinine concentration over 15 ng/ml was considered as the cutoff indicating active smoking. Smoking habits of the women and their partners were recorded at the same visit. placental abruption. of the cases of women with placental abruption, 27.4% reported smoking compared with 14.3% of the controls (p < 0.001). Based on serum cotinine levels, 30.3% of the case women and 17.6% of the control women were considered smokers (p = 0.003). Serum cotinine levels among smokers were higher in the abruption group than in the control group (median 229.5 ng/ml (interquartile range 169.8-418.1) vs. 153.5 ng/ml (56.6-241.4), p = 0.002). Self-reported number of cigarettes smoked daily correlated well with the cotinine levels (r = 0.68, p < 0.001). Of the women reporting as nonsmokers, approximately 7% were considered smokers based on cotinine testing. pregnant women with subsequent placental abruption are heavier smokers than pregnant control women. Self-reported smoking habits correlate well with serum cotinine levels in Finland. Therefore, self-reported smoking can be considered as a risk marker for placental abruption.

  17. Abrupt warming of the Red Sea

    NASA Astrophysics Data System (ADS)

    Raitsos, D. E.; Hoteit, I.; Prihartato, P. K.; Chronis, T.; Triantafyllou, G.; Abualnaja, Y.

    2011-07-01

    Coral reef ecosystems, often referred to as “marine rainforests,” concentrate the most diverse life in the oceans. Red Sea reef dwellers are adapted in a very warm environment, fact that makes them vulnerable to further and rapid warming. The detection and understanding of abrupt temperature changes is an important task, as ecosystems have more chances to adapt in a slowly rather than in a rapid changing environment. Using satellite derived sea surface and ground based air temperatures, it is shown that the Red Sea is going through an intense warming initiated in the mid-90s, with evidence for an abrupt increase after 1994 (0.7°C difference pre and post the shift). The air temperature is found to be a key parameter that influences the Red Sea marine temperature. The comparisons with Northern Hemisphere temperatures revealed that the observed warming is part of global climate change trends. The hitherto results also raise additional questions regarding other broader climatic impacts over the area.

  18. Increased consumption of dairy foods and protein during diet- and exercise-induced weight loss promotes fat mass loss and lean mass gain in overweight and obese premenopausal women.

    PubMed

    Josse, Andrea R; Atkinson, Stephanie A; Tarnopolsky, Mark A; Phillips, Stuart M

    2011-09-01

    Weight loss can have substantial health benefits for overweight or obese persons; however, the ratio of fat:lean tissue loss may be more important. We aimed to determine how daily exercise (resistance and/or aerobic) and a hypoenergetic diet varying in protein and calcium content from dairy foods would affect the composition of weight lost in otherwise healthy, premenopausal, overweight, and obese women. Ninety participants were randomized to 3 groups (n = 30/group): high protein, high dairy (HPHD), adequate protein, medium dairy (APMD), and adequate protein, low dairy (APLD) differing in the quantity of total dietary protein and dairy food-source protein consumed: 30 and 15%, 15 and 7.5%, or 15 and <2% of energy, respectively. Body composition was measured by DXA at 0, 8, and 16 wk and MRI (n = 39) to assess visceral adipose tissue (VAT) volume at 0 and 16 wk. All groups lost body weight (P < 0.05) and fat (P < 0.01); however, fat loss during wk 8-16 was greater in the HPHD group than in the APMD and APLD groups (P < 0.05). The HPHD group gained lean tissue with a greater increase during 8-16 wk than the APMD group, which maintained lean mass and the APLD group, which lost lean mass (P < 0.05). The HPHD group also lost more VAT as assessed by MRI (P < 0.05) and trunk fat as assessed by DXA (P < 0.005) than the APLD group. The reduction in VAT in all groups was correlated with intakes of calcium (r = 0.40; P < 0.05) and protein (r = 0.32; P < 0.05). Therefore, diet- and exercise-induced weight loss with higher protein and increased dairy product intakes promotes more favorable body composition changes in women characterized by greater total and visceral fat loss and lean mass gain.

  19. Finding Intervals of Abrupt Change in Earth Science Data

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Shekhar, S.; Liess, S.

    2011-12-01

    In earth science data (e.g., climate data), it is often observed that a persistently abrupt change in value occurs in a certain time-period or spatial interval. For example, abrupt climate change is defined as an unusually large shift of precipitation, temperature, etc, that occurs during a relatively short time period. A similar pattern can also be found in geographical space, representing a sharp transition of the environment (e.g., vegetation between different ecological zones). Identifying such intervals of change from earth science datasets is a crucial step for understanding and attributing the underlying phenomenon. However, inconsistencies in these noisy datasets can obstruct the major change trend, and more importantly can complicate the search of the beginning and end points of the interval of change. Also, the large volume of data makes it challenging to process the dataset reasonably fast. In earth science data (e.g., climate data), it is often observed that a persistently abrupt change in value occurs in a certain time-period or spatial interval. For example, abrupt climate change is defined as an unusually large shift of precipitation, temperature, etc, that occurs during a relatively short time period. A similar change pattern can also be found in geographical space, representing a sharp transition of the environment (e.g., vegetation between different ecological zones). Identifying such intervals of change from earth science datasets is a crucial step for understanding and attributing the underlying phenomenon. However, inconsistencies in these noisy datasets can obstruct the major change trend, and more importantly can complicate the search of the beginning and end points of the interval of change. Also, the large volume of data makes it challenging to process the dataset fast. In this work, we analyze earth science data using a novel, automated data mining approach to identify spatial/temporal intervals of persistent, abrupt change. We first

  20. The first mass and angular momentum loss measurements for a CV-like binary

    NASA Astrophysics Data System (ADS)

    Drake, Jeremy

    2015-10-01

    The period distribution of close binaries, cataclysmic variables, novae and single-degenerate SN1a progenitor candidates is largely controlled by magnetically-driven mass and angular momentum loss (AML) from the M dwarf secondary. The mass loss rates for these spun-up stars remain essentially unknown and impossible to observe directly, with likely values in the range 1e-12 to 1e-15 Msun/yr. AML presciptions for CVs differ by orders of magnitude. One way to measure the mass loss rate is to observe the dM wind accrete onto its WD companion in a pre-CV very close to Roche Lobe overflow but lacking the obscuring complications and emission from an accretion disk. The measurement can be combined with realistic MHD models to understand the accretion fraction, the mass that escapes, and the AML. The best-studied nearby pre-CV is QS Vir (48pc, P=3.6hr). However, its wind accretion rates measured from 1999 HST UV spectra of the WD metal absorption lines and 2006 XMM-Newton CCD spectroscopy differ by a factor of a thousand, pointing to either a dominant CME stochastic component, or a magnetic switch found in MHD simulations and driven by cyclic activity on the M dwarf. HST COS spectra combined with XMM-Newton monitoring on timescales from weeks to years will tease out CME vs cyclic accretion variations. UV and X-ray measurements will provide the first consistency check of both accretion rate measurement methods. MHD models tailored to the system will enable the first quasi-direct measurements of the mass loss and AML from a CV-like binary. Our project requires 6 HST/COS orbits in Cycles 22-24, and 60ksec on XMM in Cycle 22

  1. The first mass and angular momentum loss measurements for a CV-like binary

    NASA Astrophysics Data System (ADS)

    Drake, Jeremy

    2014-10-01

    The period distribution of close binaries, cataclysmic variables, novae and single-degenerate SN1a progenitor candidates is largely controlled by magnetically-driven mass and angular momentum loss (AML) from the M dwarf secondary. The mass loss rates for these spun-up stars remain essentially unknown and impossible to observe directly, with likely values in the range 1e-12 to 1e-15 Msun/yr. AML presciptions for CVs differ by orders of magnitude. One way to measure the mass loss rate is to observe the dM wind accrete onto its WD companion in a pre-CV very close to Roche Lobe overflow but lacking the obscuring complications and emission from an accretion disk. The measurement can be combined with realistic MHD models to understand the accretion fraction, the mass that escapes, and the AML. The best-studied nearby pre-CV is QS Vir (48pc, P=3.6hr). However, its wind accretion rates measured from 1999 HST UV spectra of the WD metal absorption lines and 2006 XMM-Newton CCD spectroscopy differ by a factor of a thousand, pointing to either a dominant CME stochastic component, or a "magnetic switch" found in MHD simulations and driven by cyclic activity on the M dwarf. HST COS spectra combined with XMM-Newton monitoring on timescales from weeks to years will tease out CME vs cyclic accretion variations. UV and X-ray measurements will provide the first consistency check of both accretion rate measurement methods. MHD models tailored to the system will enable the first quasi-direct measurements of the mass loss and AML from a CV-like binary. Our project requires 6 HST/COS orbits in Cycles 22-24, and 60ksec on XMM in Cycle 22

  2. The first mass and angular momentum loss measurements for a CV-like binary

    NASA Astrophysics Data System (ADS)

    Drake, Jeremy

    2016-10-01

    The period distribution of close binaries, cataclysmic variables, novae and single-degenerate SN1a progenitor candidates is largely controlled by magnetically-driven mass and angular momentum loss (AML) from the M dwarf secondary. The mass loss rates for these spun-up stars remain essentially unknown and impossible to observe directly, with likely values in the range 1e-12 to 1e-15 Msun/yr. AML presciptions for CVs differ by orders of magnitude. One way to measure the mass loss rate is to observe the dM wind accrete onto its WD companion in a pre-CV very close to Roche Lobe overflow but lacking the obscuring complications and emission from an accretion disk. The measurement can be combined with realistic MHD models to understand the accretion fraction, the mass that escapes, and the AML. The best-studied nearby pre-CV is QS Vir (48pc, P=3.6hr). However, its wind accretion rates measured from 1999 HST UV spectra of the WD metal absorption lines and 2006 XMM-Newton CCD spectroscopy differ by a factor of a thousand, pointing to either a dominant CME stochastic component, or a magnetic switch found in MHD simulations and driven by cyclic activity on the M dwarf. HST COS spectra combined with XMM-Newton monitoring on timescales from weeks to years will tease out CME vs cyclic accretion variations. UV and X-ray measurements will provide the first consistency check of both accretion rate measurement methods. MHD models tailored to the system will enable the first quasi-direct measurements of the mass loss and AML from a CV-like binary. Our project requires 6 HST/COS orbits in Cycles 22-24, and 60ksec on XMM in Cycle 22

  3. Demonstration of a Novel Method for Measuring Mass-loss Rates for Massive Stars

    NASA Astrophysics Data System (ADS)

    Kobulnicky, Henry A.; Chick, William T.; Povich, Matthew S.

    2018-03-01

    The rate at which massive stars eject mass in stellar winds significantly influences their evolutionary path. Cosmic rates of nucleosynthesis, explosive stellar phenomena, and compact object genesis depend on this poorly known facet of stellar evolution. We employ an unexploited observational technique for measuring the mass-loss rates of O and early-B stars. Our approach, which has no adjustable parameters, uses the principle of pressure equilibrium between the stellar wind and the ambient interstellar medium for a high-velocity star generating an infrared bow shock nebula. Results for 20 bow-shock-generating stars show good agreement with two sets of theoretical predictions for O5–O9.5 main-sequence stars, yielding \\dot{M} = 1.3 × 10‑6 to 2 × 10‑9 {M}ȯ {yr}}-1. Although \\dot{M} values derived for this sample are smaller than theoretical expectations by a factor of about two, this discrepancy is greatly reduced compared to canonical mass-loss methods. Bow-shock-derived mass-loss rates are factors of 10 smaller than Hα-based measurements (uncorrected for clumping) for similar stellar types and are nearly an order of magnitude larger than P4+ and some other diagnostics based on UV absorption lines. Ambient interstellar densities of at least several cm‑3 appear to be required for formation of a prominent infrared bow shock nebula. Measurements of \\dot{M} for early-B stars are not yet compelling owing to the small number in our sample and the lack of clear theoretical predictions in the regime of lower stellar luminosities. These results may constitute a partial resolution of the extant “weak-wind problem” for late-O stars. The technique shows promise for determining mass-loss rates in the weak-wind regime.

  4. Preoperative fat-free mass: a predictive factor of weight loss after gastric bypass.

    PubMed

    Robert, Maud; Pelascini, Elise; Disse, Emmanuel; Espalieu, Philippe; Poncet, Gilles; Laville, Martine; Gouillat, Christian

    2013-04-01

    Weight loss failure occurs in 8% to 40% of patients after gastric bypass (GBP). The aim of our study was to analyse the predictive factors of weight loss at 1 year so as to select the best candidates for this surgery and reduce the failures. We included 73 patients treated by laparoscopic GBP. We retrospectively analysed the predictive factors of weight loss in kilograms as well as excess weight loss in percentage (EWL%) at 1 year. The population was divided into tertiles so as to compare the sub-group with the highest weight loss with the sub-group with the least satisfactory results. The significantly predictive factors of a better weight loss in kilograms were male, higher initial weight (144 versus 118 kg, p = 0.002), a significant early weight loss and a higher preoperative percentage of fat-free mass (FFM%; p = 0.03). A higher FFM% was also associated with a better EWL% (p = 0.004). The preoperative FFM (in kilograms) was the principal factor accounting for the weight loss at 1 year regardless of age, gender, height and initial body mass index (BMI; p < 0.0001). There was a better correlation between FFM and weight loss (Spearman test, p = 0.0001) than between initial BMI and weight loss (p = 0.016). We estimated weight loss at 1 year according to initial FFM using the formula: 0.5 kg of lost weight per kilogram of initial FFM. The initial FFM appears to be a decisive factor in the success of GBP. Thus, the sarcopoenic patients would appear to be less suitable candidates for this surgery.

  5. VLA observations of mass loss from T Tauri stars

    NASA Technical Reports Server (NTRS)

    Cohen, M.; Bieging, J. H.; Schwartz, P. R.

    1982-01-01

    Six of 24 pre-main sequence stars surveyed with the VLA have been found to emit at 4.885 GHz. Radio maps of the six stars, V410 Tau, T Tau, DG Tau, LkH-alpha 101, L1551 IRS5, and Z CMa, show unresolved cores of less than 0.5 arcsec in most cases, along with 1-2 arcsec, faint, extended structures. Mass loss rates, derived under the assumption of uniform spherical winds, range from approximately 3 x 10 to the -7th to about 4 x 10 to the -5th solar masses/year. Because the flows are highly anisotropic, however, these estimates are to be taken only as likely upper limits.

  6. Rapid Weight Loss and the Body Fluid Balance and Hemoglobin Mass of Elite Amateur Boxers

    PubMed Central

    Reljic, Dejan; Hässler, Eike; Jost, Joachim; Friedmann-Bette, Birgit

    2013-01-01

    Context Dehydration is assumed to be a major adverse effect associated with rapid loss of body mass for competing in a lower weight class in combat sports. However, the effects of such weight cutting on body fluid balance in a real-life setting are unknown. Objective To examine the effects of 5% or greater loss of body mass within a few days before competition on body water, blood volume, and plasma volume in elite amateur boxers. Design Case-control study. Setting Sports medicine laboratory. Patients or Other Participants Seventeen male boxers (age = 19.2 ± 2.9 years, height = 175.1 ± 7.0 cm, mass = 65.6 ± 9.2 kg) were assigned to the weight-loss group (WLG; n = 10) or the control group (CON; n = 7). Intervention(s) The WLG reduced body mass by restricting fluid and food and inducing excessive sweat loss by adhering to individual methods. The CON participated in their usual precompetition training. Main Outcome Measure(s) During an ordinary training period (t-1), 2 days before competition (t-2), and 1 week after competition (t-3), we performed bioelectrical impedance measurements; calculated total body water, intracellular water, and extracellular water; and estimated total hemoglobin mass (tHbmass), blood volume, and plasma volume by the CO-rebreathing method. Results In the WLG, the loss of body mass (5.6% ± 1.7%) led to decreases in total body water (6.0% ± 0.9%), extracellular water (12.4% ± 7.6%), tHbmass (5.3% ± 3.8%), blood volume (7.6% ± 2.1%; P < .001), and plasma volume (8.6% ± 3.9%). The intracellular water did not change (P > .05). At t-3, total body water, extracellular water, and plasma volume had returned to near baseline values, but tHbmass and blood volume still were less than baseline values (P < .05). In CON, we found no changes (P > .05). Conclusions In a real-life setting, the loss of approximately 6% body mass within 5 days induced hypohydration, which became evident by the decreases in body water and plasma volume. The reduction in

  7. Effects of heating durations on normal concrete residual properties: compressive strength and mass loss

    NASA Astrophysics Data System (ADS)

    Nazri, Fadzli Mohamed; Shahidan, Shahiron; Khaida Baharuddin, Nur; Beddu, Salmia; Hisyam Abu Bakar, Badorul

    2017-11-01

    This study investigates the effects of high temperature with five different heating durations on residual properties of 30 MPa normal concrete. Concrete cubes were being heated up to 600°C for 30, 60, 90, 120 and 150 minutes. The temperature will keep constant for 30, 60, 90, 120 and 150 minutes. The standard temperature-time curve ISO 834 is referred to. After heating the specimen were left to cool in the furnace and removed. After cooling down to ambient temperature, the residual mass and residual compressive strength were observed. The obtained result shows that, the compressive strength of concrete decrease as the heating duration increases. This heating duration influence, might affects the loss of free water present and decomposition of hydration products in concrete. As the heating duration increases, the amount of water evaporated also increases led to loss in concrete mass. Conclusively, the percentage of mass and compressive strength loss increased as the heating duration increased.

  8. NGC 6819: testing the asteroseismic mass scale, mass loss and evidence for products of non-standard evolution

    NASA Astrophysics Data System (ADS)

    Handberg, R.; Brogaard, K.; Miglio, A.; Bossini, D.; Elsworth, Y.; Slumstrup, D.; Davies, G. R.; Chaplin, W. J.

    2017-11-01

    We present an extensive peakbagging effort on Kepler data of ∼50 red giant stars in the open star cluster NGC 6819. By employing sophisticated pre-processing of the time series and Markov chain Monte Carlo techniques we extracted individual frequencies, heights and line widths for hundreds of oscillation modes. We show that the 'average' asteroseismic parameter δν02, derived from these, can be used to distinguish the stellar evolutionary state between the red giant branch (RGB) stars and red clump (RC) stars. Masses and radii are estimated using asteroseismic scaling relations, both empirically corrected to obtain self-consistency and agreement with independent measures of distance, and using updated theoretical corrections. Remarkable agreement is found, allowing the evolutionary state of the giants to be determined exclusively from the empirical correction to the scaling relations. We find a mean mass of the RGB stars and RC stars in NGC 6819 to be 1.61 ± 0.02 and 1.64 ± 0.02 M⊙, respectively. The difference ΔM = -0.03 ± 0.01 M⊙ is almost insensitive to systematics, suggesting very little RGB mass loss, if any. Stars that are outliers relative to the ensemble reveal overmassive members that likely evolved via mass transfer in a blue straggler phase. We suggest that KIC 4937011, a low-mass Li-rich giant, is a cluster member in the RC phase that experienced very high mass loss during its evolution. Such over- and undermassive stars need to be considered when studying field giants, since the true age of such stars cannot be known and there is currently no way to distinguish them from normal stars.

  9. Ultra-wideband horn antenna with abrupt radiator

    DOEpatents

    McEwan, Thomas E.

    1998-01-01

    An ultra-wideband horn antenna transmits and receives impulse waveforms for short-range radars and impulse time-of flight systems. The antenna reduces or eliminates various sources of close-in radar clutter, including pulse dispersion and ringing, sidelobe clutter, and feedline coupling into the antenna. Dispersion is minimized with an abrupt launch point radiator element; sidelobe and feedline coupling are minimized by recessing the radiator into a metallic horn. Low frequency cut-off associated with a horn is extended by configuring the radiator drive impedance to approach a short circuit at low frequencies. A tapered feed plate connects at one end to a feedline, and at the other end to a launcher plate which is mounted to an inside wall of the horn. The launcher plate and feed plate join at an abrupt edge which forms the single launch point of the antenna.

  10. Risk of fetal death associated with maternal drug dependence and placental abruption: a population-based study.

    PubMed

    McDonald, Sarah D; Vermeulen, Marian J; Ray, Joel G

    2007-07-01

    Substance use in pregnancy is associated with placental abruption, but the risk of fetal death independent of abruption remains undetermined. Our objective was to examine the effect of maternal drug dependence on placental abruption and on fetal death in association with abruption and independent of it. To examine placental abruption and fetal death, we performed a retrospective population-based study of 1 854 463 consecutive deliveries of liveborn and stillborn infants occurring between January 1, 1995 and March 31, 2001, using the Canadian Institute for Health Information Discharge Abstract Database. Maternal drug dependence was associated with a tripling of the risk of placental abruption in singleton pregnancies (adjusted odds ratio [OR] 3.1; 95% confidence intervals [CI] 2.6-3.7), but not in multiple gestations (adjusted OR 0.88; 95% CI 0.12-6.4). Maternal drug dependence was associated with an increased risk of fetal death independent of abruption (adjusted OR 1.6: 95% CI 1.1-2.2) in singleton pregnancies, but not in multiples. Risk of fetal death was increased with placental abruption in both singleton and multiple gestations, even after controlling for drug dependence (adjusted OR 11.4 in singleton pregnancy; 95% CI 10.6-12.2, and 3.4 in multiple pregnancy; 95% CI 2.4-4.9). Maternal drug use is associated with an increased risk of intrauterine fetal death independent of placental abruption. In singleton pregnancies, maternal drug dependence is associated with an increased risk of placental abruption.

  11. Resistance training attenuates fat mass regain after weight loss in ovariectomized rats.

    PubMed

    Pighon, Abdolnaser; Paquette, Amélie; Barsalani, Razieh; Chapados, Natalie Ann; Rabasa-Lhoret, Rémi; Yasari, Siham; Prud'homme, Denis; Lavoie, Jean-Marc

    2009-09-20

    The aim of the present study was to investigate the effects of maintaining only one of the two components of a food restriction (FR)+resistance training (RT) regimen on the regain of body weight and fat mass (liver and adipocytes) in ovariectomized (Ovx) rats. Five week Ovx rats were submitted to a weight loss program consisting of a 26% FR combined with RT (OvxFR+RT) for 8 weeks. RT consisted of climbing a 1.5m vertical grid with a load attached to the tail, 20-40 times with progressively increasing loads 4 times/week. Following this weight loss intervention, OvxFR+RT rats were sub-divided into 3 groups for an additional 5 weeks: 2 groups went back to a normal ad libitum feeding with or without RT and the other group kept only FR. Combined FR+RT program in Ovx rats led to lower body mass gain, liver triacylglycerol (TAG) levels, and fat mass gain compared to sedentary normally fed Ovx rats (P<0.01). Stopping both FR and RT over a 5 week period resulted in the regain of body weight, intra-abdominal fat pad weight and liver TAG (P<0.01). When only FR was maintained, the regain of body and fat pad weight as well as liver and plasma TAG concentrations was completely prevented. However, when only RT was maintained, regain in the aforementioned parameters was attenuated but not prevented (P<0.05). It is concluded that following a FR+RT weight loss program, continuation of only RT constitutes an asset to attenuate body weight and fat mass regain in Ovx rats; although the impact is less than the maintaining FR alone. These results suggest that, in post-menopausal women, RT is a positive strategy to reduce body weight and fat mass relapse.

  12. Loss of H2 and CO from protonated aldehydes in electrospray ionization mass spectrometry.

    PubMed

    Neta, Pedatsur; Simón-Manso, Yamil; Liang, Yuxue; Stein, Stephen E

    2014-09-15

    Electrospray ionization mass spectrometry (ESI-MS) of many protonated aldehydes shows loss of CO as a major fragmentation pathway. However, we find that certain aldehydes undergo loss of H2 followed by reaction with water in the collision cell. This complicates interpretation of tandem mass (MS/MS) spectra and affects multiple reaction monitoring (MRM) results. 3-Formylchromone and other aldehydes were dissolved in acetonitrile/water/formic acid and studied by ESI-MS to record their MS(2) and MS(n) spectra in several mass spectrometers (QqQ, QTOF, ion trap (IT), and Orbitrap HCD). Certain product ions were found to react with water and the rate of reaction was determined in the IT instrument using zero collision energy and variable activation times. Theoretical calculations were performed to help with the interpretation of the fragmentation mechanism. Protonated 3-formylchromones and 3-formylcoumarins undergo loss of H2 as a major fragmentation route to yield a ketene cation, which reacts with water to form a protonated carboxylic acid. In general, protonated aldehydes which contain a vicinal group that forms a hydrogen bridge with the formyl group undergo significant loss of H2. Subsequent losses of CO and C3O are also observed. Theoretical calculations suggest mechanistic details for these losses. Loss of H2 is a major fragmentation channel for protonated 3-formychromones and certain other aldehydes and it is followed by reaction with water to produce a protonated carboxylic acid, which undergoes subsequent fragmentation. This presents a problem for reference libraries and raises concerns about MRM results. Published in 2014. This article is a U.S. Government work and is in the public domain in the USA.

  13. Anticipatory adjustments to abrupt changes of opposing forces.

    PubMed

    Rapp, Katrin; Heuer, Herbert

    2015-01-01

    Anticipatory adjustments to abrupt load changes are based on task-specific predictive information. The authors asked whether anticipatory adjustments to abrupt offsets of horizontal forces are related to expectancy. In two experiments participants held a position against an opposing force or moved against it. At force offset they had to stop rapidly. Duration of the opposing force or distance moved against it varied between blocks of trials and was constant within each block, or it varied from trial to trial. These two variations resulted in opposite changes of the expectancy of force offset with the passage of time or distance. With constant force durations or distances in each block of trials, anticipatory adjustments tended to be poorest with the longest duration or distance, but with variable force durations or distances they tended to be best with the longest duration or distance. Thus anticipatory adjustments were related to expectancy rather than time or distance per se. Anticipatory adjustments resulted in shorter peak amplitudes of the involuntary movements, accompanied by longer movement times in Experiment 1 and faster movement times in Experiment 2. Thus, for different states of the limb at abrupt dynamic changes anticipatory adjustments involve different mechanisms that modulate different mechanical characteristics.

  14. Tracers of Stellar Mass-loss. II. Mid-IR Colors and Surface Brightness Fluctuations

    NASA Astrophysics Data System (ADS)

    González-Lópezlira, Rosa A.

    2018-04-01

    I present integrated colors and surface brightness fluctuation magnitudes in the mid-infrared (IR), derived from stellar population synthesis models that include the effects of the dusty envelopes around thermally pulsing asymptotic giant branch (TP-AGB) stars. The models are based on the Bruzual & Charlot CB* isochrones; they are single-burst, range in age from a few Myr to 14 Gyr, and comprise metallicities between Z = 0.0001 and Z = 0.04. I compare these models to mid-IR data of AGB stars and star clusters in the Magellanic Clouds, and study the effects of varying self-consistently the mass-loss rate, the stellar parameters, and the output spectra of the stars plus their dusty envelopes. I find that models with a higher than fiducial mass-loss rate are needed to fit the mid-IR colors of “extreme” single AGB stars in the Large Magellanic Cloud. Surface brightness fluctuation magnitudes are quite sensitive to metallicity for 4.5 μm and longer wavelengths at all stellar population ages, and powerful diagnostics of mass-loss rate in the TP-AGB for intermediate-age populations, between 100 Myr and 2–3 Gyr.

  15. Mass loss from red giants - A simple evolutionary model for NGC 7027

    NASA Technical Reports Server (NTRS)

    Jura, M.

    1984-01-01

    NGC 7027 is a young planetary nebula with the remnants of a red giant circumstellar envelope surrounding the central, ionized region. By comparing the outer molecular envelope with the inner ionized material, it is argued that the mass loss rate has decreased by at least a factor of 3, and more probably by about a factor of 10, during the past 1000 years. From this result, it is argued that the luminosity of the central star has also decreased substantially during the same time, consistent with models for the rapid evolution of stars just after they evolve off the asymptotic giant branch. In this picture, the distance to NGC 7027 is less than 1300 pc. NGC 7027 was the last (and best) example of a star where apparently the momentum in the outflowing mass /M(dot)v/ is considerably greater than the momentum in the radiation field (L/c). With the above description of this object, the evidence is now strong that quite often the mass lost from late-type giants is ultimately driven to infinity by radiation pressure on grains. If M(dot)v is as large as L/c for asymptotic branch stars, then it is expected that the total amount of mass lost during this stage of evolution is of the same magnitude as the initial mass of the star, and therefore this mass loss can profoundly affect the star's ultimate fate.

  16. New Evidence for Mass Loss from δ Cephei from H I 21 cm Line Observations

    NASA Astrophysics Data System (ADS)

    Matthews, L. D.; Marengo, M.; Evans, N. R.; Bono, G.

    2012-01-01

    Recently published Spitzer Space Telescope observations of the classical Cepheid archetype δ Cephei revealed an extended dusty nebula surrounding this star and its hot companion HD 213307. At far-infrared wavelengths, the emission resembles a bow shock aligned with the direction of space motion of the star, indicating that δ Cephei is undergoing mass loss through a stellar wind. Here we report H I 21 cm line observations with the Very Large Array (VLA) to search for neutral atomic hydrogen associated with this wind. Our VLA data reveal a spatially extended H I nebula (~13' or 1 pc across) surrounding the position of δ Cephei. The nebula has a head-tail morphology, consistent with circumstellar ejecta shaped by the interaction between a stellar wind and the interstellar medium (ISM). We directly measure a mass of circumstellar atomic hydrogen M_H I ≈ 0.07 M_{⊙}, although the total H I mass may be larger, depending on the fraction of circumstellar material that is hidden by Galactic contamination within our band or that is present on angular scales too large to be detected by the VLA. It appears that the bulk of the circumstellar gas has originated directly from the star, although it may be augmented by material swept from the surrounding ISM. The H I data are consistent with a stellar wind with an outflow velocity V o = 35.6 ± 1.2 km s-1 and a mass-loss rate of {\\dot{M}}≈ (1.0+/- 0.8)× 10^{-6} M_{⊙} yr-1. We have computed theoretical evolutionary tracks that include mass loss across the instability strip and show that a mass-loss rate of this magnitude, sustained over the preceding Cepheid lifetime of δ Cephei, could be sufficient to resolve a significant fraction of the discrepancy between the pulsation and evolutionary masses for this star.

  17. Flow Regime Study in a High Density Circulating Fluidized Bed Riser with an Abrupt Exit

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mei, J.S.; Shadle, L.J.; Yue, P.C.

    2007-01-01

    Flow regime study was conducted in a 0.3 m diameter, 15.5 m height circulating fluidized bed (CFB) riser with an abrupt exit at the National Energy Technology Laboratory of the U.S. Department of Energy. Local particle velocities were measured at various radial positions and riser heights using an optical fiber probe. On-line measurement of solid circulating rate was continuously recorded by the Spiral. Glass beads of mean diameter 61 μm and particle density of 2,500 kg/m3 were used as bed material. The CFB riser was operated at various superficial gas velocities ranging from 3 to 7.6 m/s and solid massmore » flux from 20 to 550 kg/m2-s. At a constant riser gas velocity, transition from fast fluidization to dense suspension upflow (DSU) regime started at the bottom of the riser with increasing solid flux. Except at comparatively low riser gas velocity and solid flux, the apparent solid holdup at the top exit region was higher than the middle section of the riser. The solid fraction at this top region could be much higher than 7% under high riser gas velocity and solid mass flux. The local particle velocity showed downward flow near the wall at the top of the riser due to its abrupt exit. This abrupt geometry reflected the solids and, therefore, caused solid particles traveling downward along the wall. However, at location below, but near, the top of the riser the local particle velocities were observed flowing upward at the wall. Therefore, DSU was identified in the upper region of the riser with an abrupt exit while the fully developed region, lower in the riser, was still exhibiting core-annular flow structure. Our data were compared with the flow regime boundaries proposed by Kim et al. [1] for distinguishing the dilute pneumatic transport, fast fluidization, and DSU.« less

  18. Numerical analysis of Eucalyptus grandis × E. urophylla heat-treatment: A dynamically detecting method of mass loss during the process

    NASA Astrophysics Data System (ADS)

    Zhao, Zijian; Ma, Qing; Mu, Jun; Yi, Songlin; He, Zhengbin

    Eucalyptus particles, lamellas and boards were applied to explore a simply-implemented method with neglected heat and mass transfer to inspect the mass loss during the heat-treatment course. The results revealed that the mass loss of a certain period was theoretically the definite integration of loss rate to time in this period, and a monitoring model for mass loss speed was developed with the particles and validated with the lamellas and boards. The loss rate was correlated to the temperature and temperature-evolving speed in the model which was composed of three functions during different temperature-evolving period. The sample mass loss was calculated in the MATLAB for the lamellas and boards and the model was validated and adjusted based on the difference between the computed results and the practically measured loss values. The error ranges of the new models were -16.30% to 18.35% for wood lamellas and -9.86% to 6.80% for wood boards. This method made it possible to acquire the instantaneous loss value through continuously detecting the wood temperature evolution. This idea could provide a reference for the Eucalyptus heat-treatment to detect the treating course and control the final material characteristics.

  19. Ultra-wideband horn antenna with abrupt radiator

    DOEpatents

    McEwan, T.E.

    1998-05-19

    An ultra-wideband horn antenna transmits and receives impulse waveforms for short-range radars and impulse time-of flight systems. The antenna reduces or eliminates various sources of close-in radar clutter, including pulse dispersion and ringing, sidelobe clutter, and feedline coupling into the antenna. Dispersion is minimized with an abrupt launch point radiator element; sidelobe and feedline coupling are minimized by recessing the radiator into a metallic horn. Low frequency cut-off associated with a horn is extended by configuring the radiator drive impedance to approach a short circuit at low frequencies. A tapered feed plate connects at one end to a feedline, and at the other end to a launcher plate which is mounted to an inside wall of the horn. The launcher plate and feed plate join at an abrupt edge which forms the single launch point of the antenna. 8 figs.

  20. Abruptness of Cascade Failures in Power Grids

    NASA Astrophysics Data System (ADS)

    Pahwa, Sakshi; Scoglio, Caterina; Scala, Antonio

    2014-01-01

    Electric power-systems are one of the most important critical infrastructures. In recent years, they have been exposed to extreme stress due to the increasing demand, the introduction of distributed renewable energy sources, and the development of extensive interconnections. We investigate the phenomenon of abrupt breakdown of an electric power-system under two scenarios: load growth (mimicking the ever-increasing customer demand) and power fluctuations (mimicking the effects of renewable sources). Our results on real, realistic and synthetic networks indicate that increasing the system size causes breakdowns to become more abrupt; in fact, mapping the system to a solvable statistical-physics model indicates the occurrence of a first order transition in the large size limit. Such an enhancement for the systemic risk failures (black-outs) with increasing network size is an effect that should be considered in the current projects aiming to integrate national power-grids into ``super-grids''.

  1. Abruptness of cascade failures in power grids.

    PubMed

    Pahwa, Sakshi; Scoglio, Caterina; Scala, Antonio

    2014-01-15

    Electric power-systems are one of the most important critical infrastructures. In recent years, they have been exposed to extreme stress due to the increasing demand, the introduction of distributed renewable energy sources, and the development of extensive interconnections. We investigate the phenomenon of abrupt breakdown of an electric power-system under two scenarios: load growth (mimicking the ever-increasing customer demand) and power fluctuations (mimicking the effects of renewable sources). Our results on real, realistic and synthetic networks indicate that increasing the system size causes breakdowns to become more abrupt; in fact, mapping the system to a solvable statistical-physics model indicates the occurrence of a first order transition in the large size limit. Such an enhancement for the systemic risk failures (black-outs) with increasing network size is an effect that should be considered in the current projects aiming to integrate national power-grids into "super-grids".

  2. Mass loss of the Greenland peripheral glaciers and ice caps from satellite altimetry

    NASA Astrophysics Data System (ADS)

    Wouters, Bert; Noël, Brice; Moholdt, Geir; Ligtenberg, Stefan; van den Broeke, Michiel

    2017-04-01

    At its rapidly warming margins, the Greenland Ice Sheet is surrounded by (semi-)detached glaciers and ice caps (GIC). Although they cover only roughly 5% of the total glaciated area in the region, they are estimated to account for 15-20% of the total sea level rise contribution of Greenland. The spatial and temporal evolution of the mass changes of the peripheral GICs, however, remains poorly constrained. In this presentation, we use satellite altimetry from ICESat and Cryosat-2 combined with a high-resolution regional climate model to derive a 14 year time series (2003-2016) of regional elevation and mass changes. The total mass loss has been relatively constant during this period, but regionally, the GICs show marked temporal variations. Whereas thinning was concentrated along the eastern margin during 2003-2009, western GICs became the prime sea level rise contributors in recent years. Mass loss in the northern region has been steadily increasing throughout the record, due to a strong atmospheric warning and a deterioration of the capacity of the firn layer to buffer the resulting melt water.

  3. Mass loss of a TEOS-coated, reinforced carbon-carbon composite subjected to a simulted shuttle entry environment

    NASA Technical Reports Server (NTRS)

    Stroud, C. W.; Rummler, D. R.

    1980-01-01

    Coated, reinforced carbon-carbon (RCC) is used for the leading edges of the space shuttle. The mass loss characteristics of RCC specimens coated with tetraethyl orthosilicate (TEOS) were determine for conditions which simulated the environment expected at the lug attachment area of the leading edge. Mission simulation included simultaneous application of load, temperature, and oxygen partial pressure. Maximum specimen temperature was 900 K (1160 F). Specimens were exposed for up to 80 simulated missions. Stress levels up to 6.8 MPa (980 psi) did not significantly affect the mass loss characteristics of the TEOS-coated RCC material. Mass loss was correlated with the bulk density of the specimens.

  4. Multi-decadal mass loss of glaciers in the Everest area (Nepal Himalaya) derived from stereo imagery

    NASA Astrophysics Data System (ADS)

    Bolch, T.; Pieczonka, T.; Benn, D. I.

    2011-04-01

    Mass loss of Himalayan glaciers has wide-ranging consequences such as changing runoff distribution, sea level rise and an increasing risk of glacial lake outburst floods (GLOFs). The assessment of the regional and global impact of glacier changes in the Himalaya is, however, hampered by a lack of mass balance data for most of the range. Multi-temporal digital terrain models (DTMs) allow glacier mass balance to be calculated. Here, we present a time series of mass changes for ten glaciers covering an area of about 50 km2 south and west of Mt. Everest, Nepal, using stereo Corona spy imagery (years 1962 and 1970), aerial images and recent high resolution satellite data (Cartosat-1). This is the longest time series of mass changes in the Himalaya. We reveal that the glaciers have been significantly losing mass since at least 1970, despite thick debris cover. The specific mass loss for 1970-2007 is 0.32 ± 0.08 m w.e. a-1, however, not higher than the global average. Comparisons of the recent DTMs with earlier time periods indicate an accelerated mass loss. This is, however, hardly statistically significant due to high uncertainty, especially of the lower resolution ASTER DTM. The characteristics of surface lowering can be explained by spatial variations of glacier velocity, the thickness of the debris-cover, and ice melt due to exposed ice cliffs and ponds.

  5. Wind properties of variable B supergiants. Evidence of pulsations connected with mass-loss episodes

    NASA Astrophysics Data System (ADS)

    Haucke, M.; Cidale, L. S.; Venero, R. O. J.; Curé, M.; Kraus, M.; Kanaan, S.; Arcos, C.

    2018-06-01

    Context. Variable B supergiants (BSGs) constitute a heterogeneous group of stars with complex photometric and spectroscopic behaviours. They exhibit mass-loss variations and experience different types of oscillation modes, and there is growing evidence that variable stellar winds and photospheric pulsations are closely related. Aims: To discuss the wind properties and variability of evolved B-type stars, we derive new stellar and wind parameters for a sample of 19 Galactic BSGs by fitting theoretical line profiles of H, He, and Si to the observed ones and compare them with previous determinations. Methods: The synthetic line profiles are computed with the non-local thermodynamic equilibrium (NLTE) atmosphere code FASTWIND, with a β-law for hydrodynamics. Results: The mass-loss rate of three stars has been obtained for the first time. The global properties of stellar winds of mid/late B supergiants are well represented by a β-law with β > 2. All stars follow the known empirical wind momentum-luminosity relationships, and the late BSGs show the trend of the mid BSGs. HD 75149 and HD 99953 display significant changes in the shape and intensity of the Hα line (from a pure absorption to a P Cygni profile, and vice versa). These stars have mass-loss variations of almost a factor of 2.8. A comparison among mass-loss rates from the literature reveals discrepancies of a factor of 1 to 7. This large variation is a consequence of the uncertainties in the determination of the stellar radius. Therefore, for a reliable comparison of these values we used the invariant parameter Qr. Based on this parameter, we find an empirical relationship that associates the amplitude of mass-loss variations with photometric/spectroscopic variability on timescales of tens of days. We find that stars located on the cool side of the bi-stability jump show a decrease in the ratio V∞/Vesc, while their corresponding mass-loss rates are similar to or lower than the values found for stars on the

  6. Atmospheric mass-loss of extrasolar planets orbiting magnetically active host stars

    NASA Astrophysics Data System (ADS)

    Lalitha, Sairam; Schmitt, J. H. M. M.; Dash, Spandan

    2018-06-01

    Magnetic stellar activity of exoplanet hosts can lead to the production of large amounts of high-energy emission, which irradiates extrasolar planets, located in the immediate vicinity of such stars. This radiation is absorbed in the planets' upper atmospheres, which consequently heat up and evaporate, possibly leading to an irradiation-induced mass-loss. We present a study of the high-energy emission in the four magnetically active planet-bearing host stars, Kepler-63, Kepler-210, WASP-19, and HAT-P-11, based on new XMM-Newton observations. We find that the X-ray luminosities of these stars are rather high with orders of magnitude above the level of the active Sun. The total XUV irradiation of these planets is expected to be stronger than that of well-studied hot Jupiters. Using the estimated XUV luminosities as the energy input to the planetary atmospheres, we obtain upper limits for the total mass- loss in these hot Jupiters.

  7. Abrupt Change of the Transboundary Runoff and Its Influence on Water Security of Lanstang-Mekong River

    NASA Astrophysics Data System (ADS)

    Sang, Y. F.; Xie, P.; Ziyi, W.; Jiangyan, Z.; Qianjin, D.; Xu, L.

    2017-12-01

    As a significant manifestation of hydrological variability, abrupt change will obviously impact on the water security. To analyze what does the variation bring under changing environment, abrupt change detection should be a basic task, as well as variation level evaluation and hydrological frequency analysis. However, there lacks an effective method to reach those purposes systematically. Here we derived correlation coefficient between the original series and the jump-component series which is related to the difference degree of mean value before and after the abrupt change. Based on it, we proposed the moving-correlation-coefficient-based detection method and evaluated the significance of abrupt change as different levels related to the value of correlation coefficient. Then, with the obtained results, we calculated hydrological frequency in different situation (before and after the abrupt change). The approach above was employed to investigate the transboundary runoff of Lanstang-Mekong River at some kinds of time scale. We obtained the abrupt changes from runoff series of year, flood season and dry season which are almost the same. All the abrupt changes were significant which could reach to the moderate level. Compared with the past situation (before the abrupt change), the hydrological frequency in the current situation (after the abrupt change) indicated the water security of the water supply and flood control in the lower reaches of Lanstang-Mekong River could be guaranteed better, which is owed to the construction and operation of the water conservancy projects on the upper Lanstang-Mekong River.

  8. Equation of Motion of an Interstellar Bussard Ramjet with Radiation and Mass Losses

    ERIC Educational Resources Information Center

    Semay, Claude; Silvestre-Brac, Bernard

    2008-01-01

    An interstellar Bussard ramjet is a spaceship using the protons of the interstellar medium in a fusion engine to produce thrust. In recent papers, it was shown that the relativistic equation of motion of an ideal ramjet and that of a ramjet with radiation loss are analytical. When a mass loss appears, the limit speed of the ramjet is more strongly…

  9. Acute tubular necrosis (ATN) presenting with an unusually prolonged period of marked polyuria heralded by an abrupt oliguric phase.

    PubMed

    Ramoutar, Virin; Landa, Cristian; James, Leighton R

    2014-08-22

    A 50-year-old African-American man presented with acute tubular necrosis (ATN) secondary to hypotension from non-typhoid Salmonella gastroenteritis and bacteraemia. The oliguric phase lasted only 24 h followed by prolonged polyuria for 20 days, with urine output in excess of 16 L/day at maximum. As indexed in PubMed this is only the second published case of this nature since 1974, in which an abrupt oliguric phase of 24 h or less heralded prolonged polyuria in ATN. The diagnosis is challenging as fractional excretion of sodium early in the clinical course and rapid normalisation of serum creatinine with intravenous fluids (IVF) may point towards prerenal azotaemia resulting in a premature discharge from hospital. Patients with an abrupt oliguric phase may suffer a secondary renal insult from the profound fluid loss that is to follow and may need inpatient monitoring with supplemental IVF to prevent deleterious outcomes. 2014 BMJ Publishing Group Ltd.

  10. Acute tubular necrosis (ATN) presenting with an unusually prolonged period of marked polyuria heralded by an abrupt oliguric phase

    PubMed Central

    Ramoutar, Virin; Landa, Cristian; James, Leighton R

    2014-01-01

    A 50-year-old African-American man presented with acute tubular necrosis (ATN) secondary to hypotension from non-typhoid Salmonella gastroenteritis and bacteraemia. The oliguric phase lasted only 24 h followed by prolonged polyuria for 20 days, with urine output in excess of 16 L/day at maximum. As indexed in PubMed this is only the second published case of this nature since 1974, in which an abrupt oliguric phase of 24 h or less heralded prolonged polyuria in ATN. The diagnosis is challenging as fractional excretion of sodium early in the clinical course and rapid normalisation of serum creatinine with intravenous fluids (IVF) may point towards prerenal azotaemia resulting in a premature discharge from hospital. Patients with an abrupt oliguric phase may suffer a secondary renal insult from the profound fluid loss that is to follow and may need inpatient monitoring with supplemental IVF to prevent deleterious outcomes. PMID:25150229

  11. Mass Loss from the Nuclei of Active Galaxies

    NASA Technical Reports Server (NTRS)

    Crenshaw, Michael; Kraemer, Steven B.; George, Ian M.

    2003-01-01

    Blueshifted absorption lines in the UV and X-ray spectra of active galaxies reveal the presence of massive outflows of ionized gas from their nuclei. The intrinsic UV and X-ray absorbers show large global covering factors of the central continuum source, and the inferred mass loss rates are comparable to the mass accretion rates. Many absorbers show variable ionic column densities which are attributed to a combination of variable ionizing flux and motion of gas into and out of the line of sight . Detailed studies of the intrinsic absorbers. with the assistance of monitoring observations and photoionization models. provide constraints on their kinematics] physical conditions. and locations relative to the central continuum source. which range from the inner nucleus (approx.0.01 pc) to the galactic disk or halo (approx.10 kpc) . Dynamical models that make use of thermal winds. radiation pressure. and/or hydromagnetic flows have reached a level of sophistication that permits comparisons with the observational constraints .

  12. Protective effect of myo-inositol hexaphosphate (phytate) on bone mass loss in postmenopausal women.

    PubMed

    López-González, Angel A; Grases, Félix; Monroy, Nieves; Marí, Bartolome; Vicente-Herrero, Ma Teófila; Tur, Fernando; Perelló, Joan

    2013-03-01

    The objective of this paper was to evaluate the relationship between urinary concentrations of InsP6, bone mass loss and risk fracture in postmenopausal women. A total of 157 postmenopausal women were included in the study: 70 had low (≤0.76 μM), 42 intermediate (0.76-1.42 μM) and 45 high (≥1.42 μM) urinary phytate concentrations. Densitometry values for neck were measured at enrollment and after 12 months (lumbar spine and femoral neck), and 10-year risk fracture was calculated using the tool FRAX(®). Individuals with low InsP6 levels had significantly greater bone mass loss in the lumbar spine (3.08 ± 0.65 % vs. 0.43 ± 0.55 %) than did those with high phytate levels. Moreover, a significantly greater percentage of women with low than with high InsP6 levels showed more than 2 % of bone mass loss in the lumbar spine (55.6 vs. 20.7 %). The 10-year fracture probability was also significantly higher in the low-phytate group compared to the high-phytate group, both in hip (0.37 ± 0.06 % vs 0.18 ± 0.04 %) and major osteoporotic fracture (2.45 ± 0.24 % vs 1.83 ± 0.11 %). It can be concluded that high urinary phytate concentrations are correlated with reduced bone mass loss in lumbar spine over 12 months and with reduced 10-year probability of hip and major osteoporotic fracture, indicating that increased phytate consumption can prevent development of osteoporosis.

  13. Flow Regime Study in a Circulating Fluidized Bed Riser with an Abrupt Exit: [1] High Density Suspension

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mei, J.S.; Lee, G.T.; Seachman, S.M.

    2008-05-13

    Flow regime study was conducted in a 0.3 m diameter, 15.5 m tall circulating fluidized bed (CFB) riser with an abrupt exit at the National Energy Technology Laboratory of the U. S. Department of Energy. A statistical designed test series was conducted including four (4) operating set points and a duplicated center point (therefore a total of 6 operating set points). Glass beads of mean diameter 200 μm and particle density of 2,430 kg/m3 were used as bed material. The CFB riser was operated at various superficial gas velocities ranging from 5.6 to 7.6 m/s and solid mass flux frommore » a low of 86 to a high of 303 kg/m2-s. Results of the apparent solids fraction profile as well as the radial particle velocity profile were analyzed in order to identify the presence of Dense Suspension Upflow (DSU) conditions. DSU regime was found to exist at the bottom of the riser, while the middle section of the riser was still exhibiting core-annular flow structure. Due to the abrupt geometry of the exit, the DSU regime was also found at the top of the riser. In addition the effects of the azimuthal angle, riser gas velocity, and mass solids flux on the particle velocity were investigated and are discussed in this paper.« less

  14. Climate Stability: Pathway to understand abrupt glacial climate shifts

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Knorr, G.; Barker, S.; Lohmann, G.

    2017-12-01

    Glacial climate is marked by abrupt, millennial-scale climate changes known as Dansgaard-Oeschger (DO) cycles that have been linked to variations in the Atlantic meridional overturning circulation (AMOC). The most pronounced stadial coolings, Heinrich Stadials (HSs), are associated with massive iceberg discharges to the North Atlantic. This motivates scientists to consider that the North Atlantic freshwater perturbations is a common trigger of the associated abrupt transitions between weak and strong AMOC states. However, recent studies suggest that the Heinrich ice-surging events are triggered by ocean subsurface warming associated with an AMOC slow-down. Furthermore, the duration of ice-rafting events does not systematically coincide with the beginning and end of the pronounced cold conditions during HSs. In this context, we show that both, changes in atmospheric CO2 and ice sheet configuration can provide important control on the stability of the AMOC, using a coupled atmosphere-ocean model. Our simulations reveal that gradual changes in Northern Hemisphere ice sheet height and atmospheric CO2 can act as a trigger of abrupt glacial/deglacial climate changes. The simulated global climate responses—including abrupt warming in the North Atlantic, a northward shift of the tropical rain belts, and Southern Hemisphere cooling related to the bipolar seesaw—are generally consistent with empirical evidence. We further find that under a delicate configuration of atmospheric CO2 and ice sheet height the AMOC can be characterized by a self-oscillation (resonance) feature (Hopf Bifucation) with a 1000-year cycle that is comparable with observed small DO events during the MIS 3. This provides an alternative explanation for millennial-scale DO variability during glacial periods.

  15. Evidence for Pulsation-Driven Mass Loss from δ Cephei

    NASA Astrophysics Data System (ADS)

    Marengo, M.; Evans, N. R.; Matthews, L. D.; Bono, G.; Barmby, P.; Welch, D. L.; Romaniello, M.; Su, K. Y. L.; Fazio, G. G.; Huelsman, D.

    We found the first direct evidence that the Cepheid class namesake, δ Cephei, is currently losing mass. These observations are based on data obtained with the Spitzer Space Telescope in the infrared, and with the Very Large Array in the radio. We found that δ Cephei is associated with a vast circumstellar structure, reminiscent of a bow shock. This structure is created as the wind from the star interacts with the local interstellar medium. We measure an outflow velocity of ≈ 35. 5 km s- 1 and a mass loss rate of ≈ 10- 7-10- 6 M ⊙ year- 1. The very low dust content of the outflow suggests that the wind is possibly pulsation-driven, rather than dust-driven as common for other classes of evolved stars.

  16. The Influence of Coronal Mass Ejections on the Mass-loss Rates of Hot-Jupiters

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cherenkov, A.; Bisikalo, D.; Fossati, L.

    Hot-Jupiters are subject to extreme radiation and plasma flows coming from their host stars. Past ultraviolet Hubble Space Telescope observations, supported by hydrodynamic models, confirmed that these factors lead to the formation of an extended envelope, part of which lies beyond the Roche lobe. We use gas-dynamic simulations to study the impact of time variations in the parameters of the stellar wind, namely that of coronal mass ejections (CMEs), on the envelope of the typical hot-Jupiter HD 209458b. We consider three CMEs characterized by different velocities and densities, taking their parameters from typical CMEs observed for the Sun. The perturbationsmore » in the ram-pressure of the stellar wind during the passage of each CME tear off most of the envelope that is located beyond the Roche lobe. This leads to a substantial increase of the mass-loss rates during the interaction with the CME. We find that the mass lost by the planet during the whole crossing of a CME is of ≈10{sup 15} g, regardless of the CME taken into consideration. We also find that over the course of 1 Gyr, the mass lost by the planet because of CME impacts is comparable to that lost because of high-energy stellar irradiation.« less

  17. Abruptness of Cascade Failures in Power Grids

    PubMed Central

    Pahwa, Sakshi; Scoglio, Caterina; Scala, Antonio

    2014-01-01

    Electric power-systems are one of the most important critical infrastructures. In recent years, they have been exposed to extreme stress due to the increasing demand, the introduction of distributed renewable energy sources, and the development of extensive interconnections. We investigate the phenomenon of abrupt breakdown of an electric power-system under two scenarios: load growth (mimicking the ever-increasing customer demand) and power fluctuations (mimicking the effects of renewable sources). Our results on real, realistic and synthetic networks indicate that increasing the system size causes breakdowns to become more abrupt; in fact, mapping the system to a solvable statistical-physics model indicates the occurrence of a first order transition in the large size limit. Such an enhancement for the systemic risk failures (black-outs) with increasing network size is an effect that should be considered in the current projects aiming to integrate national power-grids into “super-grids”. PMID:24424239

  18. Empirical mass-loss rates for 25 O and early B stars, derived from Copernicus observations

    NASA Technical Reports Server (NTRS)

    Gathier, R.; Lamers, H. J. G. L. M.; Snow, T. P.

    1981-01-01

    Ultraviolet line profiles are fitted with theoretical line profiles in the cases of 25 stars covering a spectral type range from O4 to B1, including all luminosity classes. Ion column densities are compared for the determination of wind ionization, and it is found that the O VI/N V ratio is dependent on the mean density of the wind and not on effective temperature value, while the Si IV/N V ratio is temperature-dependent. The column densities are used to derive a mass-loss rate parameter that is empirically correlated against the mass-loss rate by means of standard stars with well-determined rates from IR or radio data. The empirical mass-loss rates obtained are compared with those derived by others and found to vary by as much as a factor of 10, which is shown to be due to uncertainties or errors in the ionization fractions of models used for wind ionization balance prediction.

  19. Clouds enhance Greenland ice sheet mass loss

    NASA Astrophysics Data System (ADS)

    Van Tricht, Kristof; Gorodetskaya, Irina V.; L'Ecuyer, Tristan; Lenaerts, Jan T. M.; Lhermitte, Stef; Noel, Brice; Turner, David D.; van den Broeke, Michiel R.; van Lipzig, Nicole P. M.

    2015-04-01

    Clouds have a profound influence on both the Arctic and global climate, while they still represent one of the key uncertainties in climate models, limiting the fidelity of future climate projections. The potentially important role of thin liquid-containing clouds over Greenland in enhancing ice sheet melt has recently gained interest, yet current research is spatially and temporally limited, focusing on particular events, and their large scale impact on the surface mass balance remains unknown. We used a combination of satellite remote sensing (CloudSat - CALIPSO), ground-based observations and climate model (RACMO) data to show that liquid-containing clouds warm the Greenland ice sheet 94% of the time. High surface reflectivity (albedo) for shortwave radiation reduces the cloud shortwave cooling effect on the absorbed fluxes, while not influencing the absorption of longwave radiation. Cloud warming over the ice sheet therefore dominates year-round. Only when albedo values drop below ~0.6 in the coastal areas during summer, the cooling effect starts to overcome the warming effect. The year-round excess of energy due to the presence of liquid-containing clouds has an extensive influence on the mass balance of the ice sheet. Simulations using the SNOWPACK snow model showed not only a strong influence of these liquid-containing clouds on melt increase, but also on the increased sublimation mass loss. Simulations with the Community Earth System Climate Model for the end of the 21st century (2080-2099) show that Greenland clouds contain more liquid water path and less ice water path. This implies that cloud radiative forcing will be further enhanced in the future. Our results therefore urge the need for improving cloud microphysics in climate models, to improve future projections of ice sheet mass balance and global sea level rise.

  20. Transient Mass-loss Analysis of Solar Observations Using Stellar Methods

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Crosley, M. K.; Norman, C.; Osten, R. A.

    Low-frequency dynamic spectra of radio bursts from nearby stars offer the best chance to directly detect the stellar signature of transient mass loss on low-mass stars. Crosley et al. (2016) proposes a multi-wavelength methodology to determine coronal mass ejection (CME) parameters, such as speed, mass, and kinetic energy. We test the validity and accuracy of the results derived from the methodology by using Geostationary Operational Environmental Satellite X-ray observations and Bruny Island Radio Spectrometer radio observations. These are analogous observations to those that would be found in the stellar studies. Derived results from these observations are compared to direct whitemore » light measurements of the Large Angle and Spectrometric Coronagraph. We find that, when a pre-event temperature can be determined, the accuracy of CME speeds are within a few hundred km s{sup −1}, and are reliable when specific criteria has been met. CME mass and kinetic energies are only useful in determining the approximate order of magnitude measurements when considering the large errors associated to them. These results will be directly applicable to the interpretation of any detected stellar events and the derivation of stellar CME properties.« less

  1. Abrupt climate-independent fire regime changes

    USGS Publications Warehouse

    Pausas, Juli G.; Keeley, Jon E.

    2014-01-01

    Wildfires have played a determining role in distribution, composition and structure of many ecosystems worldwide and climatic changes are widely considered to be a major driver of future fire regime changes. However, forecasting future climatic change induced impacts on fire regimes will require a clearer understanding of other drivers of abrupt fire regime changes. Here, we focus on evidence from different environmental and temporal settings of fire regimes changes that are not directly attributed to climatic changes. We review key cases of these abrupt fire regime changes at different spatial and temporal scales, including those directly driven (i) by fauna, (ii) by invasive plant species, and (iii) by socio-economic and policy changes. All these drivers might generate non-linear effects of landscape changes in fuel structure; that is, they generate fuel changes that can cross thresholds of landscape continuity, and thus drastically change fire activity. Although climatic changes might contribute to some of these changes, there are also many instances that are not primarily linked to climatic shifts. Understanding the mechanism driving fire regime changes should contribute to our ability to better assess future fire regimes.

  2. The Colorado Ultraviolet Transit Experiment (CUTE): Observing Mass Loss on Short-Period Exoplanets

    NASA Astrophysics Data System (ADS)

    Egan, Arika; Fleming, Brian; France, Kevin

    2018-06-01

    The Colorado Ultraviolet Transit Experiment (CUTE) is an NUV spectrograph packaged into a 6U CubeSat, designed to characterize the interaction between exoplanetary atmospheres and their host stars. CUTE will conduct a transit spectroscopy survey, gathering data over multiple transits on more than 12 short-period exoplanets with a range of masses and radii. The instrument will characterize the spectral properties of the transit light curves to < 1% depth sensitivity. The NUV is host to several high oscillator strength atomic and molecular absorption features predicted to exist in the upper atmospheres of these planets, including Mg I, Mg II, Fe II, and OH. The shape and evolution of these spectral light curves will be used to quantify mass loss rates, the stellar drives of that mass loss, and the possible existence of exoplanetary magnetic fiends. This poster presents the science motivation for CUTE, planned observation and data analysis methods, and expected results.

  3. Maternal sleep duration and complaints of vital exhaustion during pregnancy is associated with placental abruption.

    PubMed

    Qiu, Chunfang; Sanchez, Sixto E; Gelaye, Bizu; Enquobahrie, Daniel A; Ananth, Cande V; Williams, Michelle A

    2015-02-01

    Sleep disorders are associated with cardiovascular complications and preterm delivery (PTD). Insufficient sleep results in metabolic alterations and increased inflammation, both known to contribute to placental abruption (abruption), a determinant of PTD. We examined associations of abruption with sleep duration and complaints of vital exhaustion. The study included 164 abruption cases and 160 controls in a multicenter study in Peru. Data on habitual sleep duration and vital exhaustion during the first 6 months of pregnancy were elicited during interviews conducted following delivery. Women were categorized according to short, normal and long sleep duration (≤6, 7-8 and ≥9 h); and frequency of feeling exhausted. Odds ratios (OR) and 95% confidence intervals (CI) were calculated. Short and long sleep durations were associated with increased odds of abruption. The ORs of abruption in relation to short (≤6 h) and long (≥9 h) sleep duration were 2.0 (95% CI 1.1-3.7) and 2.1 (95% CI 1.1-4.1), compared with normal sleep duration (7-8 h). Complaints of vital exhaustion were also associated with abruption (OR = 2.37; 95% CI 1.46-3.85), and were independent of sleep duration. We extend the existing literature and support the thesis that maternal sleep habits and disorders should be assessed among pregnant women.

  4. Slowing down as an early warning signal for abrupt climate change.

    PubMed

    Dakos, Vasilis; Scheffer, Marten; van Nes, Egbert H; Brovkin, Victor; Petoukhov, Vladimir; Held, Hermann

    2008-09-23

    In the Earth's history, periods of relatively stable climate have often been interrupted by sharp transitions to a contrasting state. One explanation for such events of abrupt change is that they happened when the earth system reached a critical tipping point. However, this remains hard to prove for events in the remote past, and it is even more difficult to predict if and when we might reach a tipping point for abrupt climate change in the future. Here, we analyze eight ancient abrupt climate shifts and show that they were all preceded by a characteristic slowing down of the fluctuations starting well before the actual shift. Such slowing down, measured as increased autocorrelation, can be mathematically shown to be a hallmark of tipping points. Therefore, our results imply independent empirical evidence for the idea that past abrupt shifts were associated with the passing of critical thresholds. Because the mechanism causing slowing down is fundamentally inherent to tipping points, it follows that our way to detect slowing down might be used as a universal early warning signal for upcoming catastrophic change. Because tipping points in ecosystems and other complex systems are notoriously hard to predict in other ways, this is a promising perspective.

  5. Slowing down as an early warning signal for abrupt climate change

    PubMed Central

    Dakos, Vasilis; Scheffer, Marten; van Nes, Egbert H.; Brovkin, Victor; Petoukhov, Vladimir; Held, Hermann

    2008-01-01

    In the Earth's history, periods of relatively stable climate have often been interrupted by sharp transitions to a contrasting state. One explanation for such events of abrupt change is that they happened when the earth system reached a critical tipping point. However, this remains hard to prove for events in the remote past, and it is even more difficult to predict if and when we might reach a tipping point for abrupt climate change in the future. Here, we analyze eight ancient abrupt climate shifts and show that they were all preceded by a characteristic slowing down of the fluctuations starting well before the actual shift. Such slowing down, measured as increased autocorrelation, can be mathematically shown to be a hallmark of tipping points. Therefore, our results imply independent empirical evidence for the idea that past abrupt shifts were associated with the passing of critical thresholds. Because the mechanism causing slowing down is fundamentally inherent to tipping points, it follows that our way to detect slowing down might be used as a universal early warning signal for upcoming catastrophic change. Because tipping points in ecosystems and other complex systems are notoriously hard to predict in other ways, this is a promising perspective. PMID:18787119

  6. [Reversible catatonia after the abrupt discontinuation of clozapine: Case report].

    PubMed

    Jaafari, M; Bout, A; Rammouz, I; Aalouane, R

    2016-12-01

    In this paper, we report the case of a patient, aged 26, with schizophrenia who was admitted to psychiatric emergencies for catatonia, one week after abrupt discontinuation of clozapine. An improvement was seen after only two days of the reintroduction of clozapine alone. This catatonia is reversible and it responds magnificently to the reintroduction of clozapine. And we conclude that patients and their caregivers need to be educated about the effects of abrupt cessation of clozapine administration. Copyright © 2016 L’Encéphale, Paris. Published by Elsevier Masson SAS. All rights reserved.

  7. Corotation lag limit on mass-loss rate from Io

    NASA Astrophysics Data System (ADS)

    Huang, T. S.; Siscoe, G. L.

    1987-08-01

    Considering rapid escape of H2O from Io during an early hot evolutionary epoch, an H2O plasma torus is constructed by balancing dissociation and ionization products against centrifugally driven diffusion, including for the first time the effects of corotation lag resulting from mass loading. Two fundamental limits are found as the mass injection rate increases: (1) an 'ignition' limit of 1.1 x 10 to the 6th kg/s, beyond which the torus cannot ionize itself and photoionization dominates; and (2) the ultimate mass loading limit of 1.3 x 10 to the 7th kg/s, which occurs when neutrals newly created by charge exchange and recombination cannot leave the torus, thereby bringing magnetospherically driven transport to a halt. Connecting this limit with the variations of Io's temperature in its early evolution epoch gives an estimate of the upper limit on the total mass loss from Io, about 3.0 x 10 to the 20th kg (for high-opacity nebula) and about 8.9 x 10 to the 20th kg (for low-opacity nebula). These limits correspond to eroding 8 km and 22 km of H2O from the surface. It is concluded that compared to the other Galilean satellites, Io was created basically dry.

  8. Acute effects of self-selected regimen of rapid body mass loss in combat sports athletes.

    PubMed

    Timpmann, Saima; Oöpik, Vahur; Pääsuke, Mati; Medijainen, Luule; Ereline, Jaan

    2008-01-01

    The purpose of the study was to assess the acute effects of the self-selected regimen of rapid body mass loss (RBML) on muscle performance and metabolic response to exercise in combat sports athletes. Seventeen male athletes (20.8 ± 1.0 years; mean ± SD) reduced their body mass by 5.1 ± 1.1% within 3 days. The RBML was achieved by a gradual reduction of energy and fluid intake and mild sauna procedures. A battery of tests was performed before (Test 1) and immediately after (Test 2) RBML. The test battery included the measurement of the peak torque of knee extensors for three different speeds, assessment of total work (Wtot) performed during a 3-min intermittent intensity knee extension exercise and measurements of blood metabolites (ammonia, lactate, glucose and urea). Absolute peak torque was lower in Test 2 compared with Test 1 at angular velocities of 1.57 rad·s(-1) (218.6 ± 40.9 vs. 234.4 ± 42.2 N·m; p = 0.013) and 3.14 rad·s(-1) (100.3 ± 27.8 vs. 111.7 ± 26.2 N·m; p = 0.008). The peak torque in relation to body mass remained unchanged for any speed. Absolute Wtot was lower in Test 2 compared with Test 1 (6359 ± 2326 vs. 7452 ± 3080 J; p = 0.003) as well as Wtot in relation to body mass (89.1 ± 29.9 vs. 98.6 ± 36.4 J·kg(-1); p = 0.034), respectively. As a result of RBML, plasma urea concentration increased from 4.9 to 5.9 mmol·l(-1) (p = 0.003). The concentration of ammonia in a post-test sample in Test 2 tended to be higher in comparison with Test 1 (80.9 ± 29.1 vs. 67.6 ± 26.5 mmol·l(-1); p = 0.082). The plasma lactate and glucose responses to exercise were similar in Test 1 and Test 2. We conclude that the self-selected regimen of RBML impairs muscle performance in 3-min intermittent intensity exercise and induces an increase in blood urea concentration in experienced male combat sports athletes. Key pointsPrevious studies have revealed a negative effect of rapid body mass loss on performance. However, there are some performance

  9. Quantifying the mass loss of peripheral Greenland glaciers and ice caps (1958-2014).

    NASA Astrophysics Data System (ADS)

    Noël, Brice; van de Berg, Willem Jan; Machguth, Horst; van den Broeke, Michiel

    2016-04-01

    Since the 2000s, mass loss from Greenland peripheral glaciers and ice caps (GICs) has accelerated, becoming an important contributor to sea level rise. Under continued warming throughout the 21st century, GICs might yield up to 7.5 to 11 mm sea level rise, with increasing dominance of surface runoff at the expense of ice discharge. However, despite multiple observation campaigns, little remains known about the contribution of GICs to total Greenland mass loss. Furthermore, the relatively coarse resolutions in regional climate models, i.e. 5 km to 20 km, fail to represent the small scale patterns of surface mass balance (SMB) components over these topographically complex regions including also narrow valley glaciers. Here, we present a novel approach to quantify the contribution of GICs to surface melt and runoff, based on an elevation dependent downscaling method. GICs daily SMB components at 1 km resolution are obtained by statistically downscaling the outputs of RACMO2.3 at 11 km resolution to a down-sampled version of the GIMP DEM for the period 1958-2014. This method has recently been successfully validated over the Greenland ice sheet and is now applied to GICs. In this study, we first evaluate the 1 km daily downscaled GICs SMB against a newly available and comprehensive dataset of ablation stake measurements. Then, we investigate present-day trends of meltwater production and SMB for different regions and estimate GICs contribution to total Greenland mass loss. These data are considered valuable for model evaluation and prediction of future sea level rise.

  10. Strength and muscle mass loss with aging process. Age and strength loss.

    PubMed

    Keller, Karsten; Engelhardt, Martin

    2013-10-01

    aging process is associated with changes in muscle mass and strength with decline of muscle strength after the 30(th) life year. The aim of this study was to investigate these changes in muscle mass and strength. for this analysis 26 participants were subdivided in two groups. Group 1 comprises participants aged <40 years (n=14), group 2 those >40 years (n=12). We assessed anthropometrics, range of motions, leg circumferences and isometric strength values of the knee joints. besides comparable anthropometrics, circumferences and strength were higher in group 1 than in group 2. Circumference of upper leg (20 cm above knee articular space) showed for right leg a trend to a significant (median: 54.45 cm (1(st) quartile: 49.35/3(rd) quartile: 57.78) vs 49.80 cm (49.50/50.75), p=0.0526) and for left leg a significant 54.30 cm (49.28/58.13) vs 49.50 cm (48.00/52.53), p=0.0356) larger circumference in group 1. Isometric strength was in 60° knee flexion significantly higher in group 1 than in group 2 for right (729.88N (561.47/862.13) vs 456.92N (304.67/560.12), p=0.00448) and left leg (702.49N (581.36/983.87) vs 528.49N (332.95/648.58), p=0.0234). aging process leads to distinct muscle mass and strength loss. Muscle strength declines from people aged <40 years to those >40 years between 16.6% and 40.9%.

  11. Luminosities and mass-loss rates of Local Group AGB stars and red supergiants

    NASA Astrophysics Data System (ADS)

    Groenewegen, M. A. T.; Sloan, G. C.

    2018-01-01

    Context. Mass loss is one of the fundamental properties of asymptotic giant branch (AGB) stars, and through the enrichment of the interstellar medium, AGB stars are key players in the life cycle of dust and gas in the universe. However, a quantitative understanding of the mass-loss process is still largely lacking. Aims: We aim to investigate mass loss and luminosity in a large sample of evolved stars in several Local Group galaxies with a variety of metalliticies and star-formation histories: the Small and Large Magellanic Cloud, and the Fornax, Carina, and Sculptor dwarf spheroidal galaxies (dSphs). Methods: Dust radiative transfer models are presented for 225 carbon stars and 171 oxygen-rich evolved stars in several Local Group galaxies for which spectra from the Infrared Spectrograph on Spitzer are available. The spectra are complemented with available optical and infrared photometry to construct spectral energy distributions. A minimization procedure was used to determine luminosity and mass-loss rate (MLR). Pulsation periods were derived for a large fraction of the sample based on a re-analysis of existing data. Results: New deep K-band photometry from the VMC survey and multi-epoch data from IRAC (at 4.5 μm) and AllWISE and NEOWISE have allowed us to derive pulsation periods longer than 1000 days for some of the most heavily obscured and reddened objects. We derive (dust) MLRs and luminosities for the entire sample. The estimated MLRs can differ significantly from estimates for the same objects in the literature due to differences in adopted optical constants (up to factors of several) and details in the radiative transfer modelling. Updated parameters for the super-AGB candidate MSX SMC 055 (IRAS 00483-7347) are presented. Its current mass is estimated to be 8.5 ± 1.6 M⊙, suggesting an initial mass well above 8 M⊙ in agreement with estimates based on its large Rubidium abundance. Using synthetic photometry, we present and discuss colour-colour and

  12. Microwave continuum measurements and estimates of mass loss rates for cool giants and supergiants

    NASA Technical Reports Server (NTRS)

    Drake, S. A.; Linsky, J. L.

    1986-01-01

    Attention is given to the results of a sensitive, 6-cm radio continuum survey conducted with the NRAO VLA of 39 of the nearest single cool giants and supergiants of G0-M5 spectral types; the survey was conducted in order to obtain accurate measurements of the mass loss rates of ionized gas for a representative sample of such stars, in order to furnish constraints for, and a better understanding of, the total mass loss rates. The inferred angular diameters for the cool giant sources are noted to be twice as large as photospheric angular diameters, implying that these stars are surrounded by extended chromospheres containing warm partially ionized gas.

  13. Initial fungal colonizer affects mass loss and fungal community development in Picea abies logs 6 yr after inoculation

    Treesearch

    Daniel L. Lindner; Rimvydas Vasaitis; Ariana Kubartova; Johan Allmer; Hanna Johannesson; Mark T. Banik; Jan. Stenlid

    2011-01-01

    Picea abies logs were inoculated with Resinicium bicolor, Fomitopsis pinicola or left un-inoculated and placed in an old-growth boreal forest. Mass loss and fungal community data were collected after 6 yr to test whether simplification of the fungal community via inoculation affects mass loss and fungal community development. Three...

  14. Influence of previous body mass index and sex on regional fat changes in a weight loss intervention.

    PubMed

    Benito, Pedro J; Cupeiro, Rocio; Peinado, Ana B; Rojo, Miguel A; Maffulli, Nicola

    2017-11-01

    Men and women may lose weight in a different fashion. This study compares the changes in different anatomical regions after a well-controlled weight loss program by sex and initial BMI. A total of 180 subjects (48 overweight women, 36 overweight men, and 48 obese women and 48 obese men) were recruited to participate in a 22-week weight loss programme (diet + exercise). Regarding percentage body weight change from baseline, there was no triple interaction (BMI, sex and anatomical region), but there was interaction between BMI and anatomical region (F2,840 = 34.5; p < 0.001), and between sex and anatomical region (F2,840 = 98.8; p < 0.001). Usually, the arms and legs are the regions that lose more weight in obese participants, but men lose the highest percentage of mass from the trunk. There were differences between men and women for the areas of left trunk mass (750g), right trunk mass (700g), total mass of the trunk (1400g), android mass (350g), and finally in the total mass in overweight participants (1300g), with higher values for men than for women. The region that loses more weight and fat is the trunk, followed by the legs, and then the arms, when the loss is observed in function of the total weight or fat lost. Both BMI and sex exert a definite influence fat loss, especially in some anatomical regions.

  15. Placental abruption possibly due to parvovirus B19 infection.

    PubMed

    Kawabe, Ayaka; Takai, Yasushi; Tamaru, Jun-Ichi; Samejima, Kouki; Seki, Hiroyuki

    2016-01-01

    There is concern about the development of anemia-associated fetal hydrops associated with maternal parvovirus B19 infection. Parvovirus B19 infection occurs via the globoside (P antigen) receptor, the main glycolipid of erythroid cells, which induces apoptosis. Similar findings have been reported for the P antigen of globoside-containing placental trophoblast cells. A 32-year-old woman was infected with human parvovirus B19 at week 32 of pregnancy, and had severe anemia at week 34. At week 37, an emergency cesarean section was performed because of sudden abdominal pain and fetal bradycardia; placental abruption was found. A live male infant was delivered with no sign of fetal hydrops or fetal infection. Placental tissue was positive for parvovirus B19 according to polymerase chain reaction. Immunohistochemical analysis using caspase-related M30 CytoDEATH monoclonal antibody revealed M30 staining of the placental villous trophoblasts. Placental trophoblasts and erythroid precursor cells have been reported to express globoside (P antigen), which is necessary for parvovirus B19 infectivity, and to show apoptotic activity as a result of infection. Placentas from three other pregnancies with documented abruption showed no M30 staining. The present case strongly suggests an association between placental abruption and apoptosis resulting from parvovirus B19 infection.

  16. Merging black hole binaries: the effects of progenitor's metallicity, mass-loss rate and Eddington factor

    NASA Astrophysics Data System (ADS)

    Giacobbo, Nicola; Mapelli, Michela; Spera, Mario

    2018-03-01

    The first four gravitational wave events detected by LIGO were all interpreted as merging black hole binaries (BHBs), opening a new perspective on the study of such systems. Here we use our new population-synthesis code MOBSE, an upgraded version of BSE, to investigate the demography of merging BHBs. MOBSE includes metallicity-dependent prescriptions for mass-loss of massive hot stars. It also accounts for the impact of the electron-scattering Eddington factor on mass-loss. We perform >108 simulations of isolated massive binaries, with 12 different metallicities, to study the impact of mass-loss, core-collapse supernovae and common envelope on merging BHBs. Accounting for the dependence of stellar winds on the Eddington factor leads to the formation of black holes (BHs) with mass up to 65 M⊙ at metallicity Z ˜ 0.0002. However, most BHs in merging BHBs have masses ≲ 40 M⊙. We find merging BHBs with mass ratios in the 0.1-1.0 range, even if mass ratios >0.6 are more likely. We predict that systems like GW150914, GW170814 and GW170104 can form only from progenitors with metallicity Z ≤ 0.006, Z ≤ 0.008 and Z ≤ 0.012, respectively. Most merging BHBs have gone through a common envelope phase, but up to ˜17 per cent merging BHBs at low metallicity did not undergo any common envelope phase. We find a much higher number of mergers from metal-poor progenitors than from metal-rich ones: the number of BHB mergers per unit mass is ˜10-4 M_{⊙}^{-1} at low metallicity (Z = 0.0002-0.002) and drops to ˜10-7 M_{⊙}^{-1} at high metallicity (Z ˜ 0.02).

  17. Relationship between oxidative stress and muscle mass loss in early postmenopause: an exploratory study.

    PubMed

    Zacarías-Flores, Mariano; Sánchez-Rodríguez, Martha A; García-Anaya, Oswaldo Daniel; Correa-Muñoz, Elsa; Mendoza-Núñez, Víctor Manuel

    2018-04-09

    Endocrine changes due to menopause have been associated to oxidative stress and muscle mass loss. The study objective was to determine the relationship between both variables in early postmenopause. An exploratory, cross-sectional study was conducted in 107 pre- and postmenopausal women (aged 40-57 years). Levels of serum lipid peroxides and uric acid and enzymes superoxide dismutase and glutathione peroxidase, as well as total plasma antioxidant capacity were measured as oxidative stress markers. Muscle mass using bioelectrical impedance and muscle strength using dynamometry were also measured. Muscle mass, skeletal muscle index, fat-free mass, and body mass index were calculated. More than 90% of participants were diagnosed with overweight or obesity. Postmenopausal women had lower values of muscle mass and strength markers, with a negative correlation between lipid peroxide level and skeletal muscle index (r= -0.326, p<.05), and a positive correlation between uric acid and skeletal muscle index (r=0.295, p<.05). A multivariate model including oxidative stress markers, age, and waist circumference showed lipid peroxide level to be the main contributor to explain the decrease in skeletal muscle mass in postmenopause, since for every 0.1μmol/l increase in lipid peroxide level, skeletal muscle index decreases by 3.03 units. Our findings suggest an association between increased oxidative stress and muscle mass loss in early postmenopause. Copyright © 2018 SEEN y SED. Publicado por Elsevier España, S.L.U. All rights reserved.

  18. Role of protein and amino acids in promoting lean mass accretion with resistance exercise and attenuating lean mass loss during energy deficit in humans.

    PubMed

    Churchward-Venne, Tyler A; Murphy, Caoileann H; Longland, Thomas M; Phillips, Stuart M

    2013-08-01

    Amino acids are major nutrient regulators of muscle protein turnover. After protein ingestion, hyperaminoacidemia stimulates increased rates of skeletal muscle protein synthesis, suppresses muscle protein breakdown, and promotes net muscle protein accretion for several hours. These acute observations form the basis for strategized protein intake to promote lean mass accretion, or prevent lean mass loss over the long term. However, factors such as protein dose, protein source, and timing of intake are important in mediating the anabolic effects of amino acids on skeletal muscle and must be considered within the context of evaluating the reported efficacy of long-term studies investigating protein supplementation as part of a dietary strategy to promote lean mass accretion and/or prevent lean mass loss. Current research suggests that dietary protein supplementation can augment resistance exercise-mediated gains in skeletal muscle mass and strength and can preserve skeletal muscle mass during periods of diet-induced energy restriction. Perhaps less appreciated, protein supplementation can augment resistance training-mediated gains in skeletal muscle mass even in individuals habitually consuming 'adequate' (i.e., >0.8 g kg⁻¹ day⁻¹) protein. Additionally, overfeeding energy with moderate to high-protein intake (15-25 % protein or 1.8-3.0 g kg⁻¹ day⁻¹) is associated with lean, but not fat mass accretion, when compared to overfeeding energy with low protein intake (5 % protein or ~0.68 g kg⁻¹ day⁻¹). Amino acids represent primary nutrient regulators of skeletal muscle anabolism, capable of enhancing lean mass accretion with resistance exercise and attenuating the loss of lean mass during periods of energy deficit, although factors such as protein dose, protein source, and timing of intake are likely important in mediating these effects.

  19. Gravitational mass of positron from LEP synchrotron losses.

    PubMed

    Kalaydzhyan, Tigran

    2016-07-27

    General relativity(GR) is the current description of gravity in modern physics. One of the cornerstones of GR, as well as Newton's theory of gravity, is the weak equivalence principle (WEP), stating that the trajectory of a freely falling test body is independent of its internal structure and composition. WEP is known to be valid for the normal matter with a high precision. However, due to the rarity of antimatter and weakness of the gravitational forces, the WEP has never been confirmed for antimatter. The current direct bounds on the ratio between the gravitational and inertial masses of the antihydrogen do not rule out a repulsive nature for the antimatter gravity. Here we establish an indirect bound of 0.13% on the difference between the gravitational and inertial masses of the positron (antielectron) from the analysis of synchrotron losses at the Large Electron-Positron collider (LEP). This serves as a confirmation of the conventional gravitational properties of antimatter without common assumptions such as, e.g., coupling of gravity to virtual particles, dynamics of distant astrophysical sources and the nature of absolute gravitational potentials.

  20. A Web-Based Weight Loss Programme Including Breakfast Cereals Results in Greater Loss of Body Mass than a Standardised Web-Based Programme in a Randomised Controlled Trial

    PubMed Central

    Margaret Ashwell, Margaret; Howarth, Elaine; Chesters, David; Allan, Peter; Hoyland, Alexa; Walton, Jenny

    2014-01-01

    Objective To test the hypothesis that promoting breakfast cereal consumption, as part of a web-based programme, results in loss of body mass. Methods Single centre, single blind, randomised parallel study. Test group followed a fully interactive website (B) with ‘prescribed’ breakfast cereals. Control group followed website (A) giving standard advice on weight loss. Study site visits at 0, 4, 12 and 24 weeks for measurements of height, weight, skinfolds, body fat, waist and hip circumference. 180 subjects were randomly allocated to two equal groups. Subjects were in good health and aged 19-50 years, with a BMI ranging from 25-40 kg/m2. At baseline there was no difference in mean age or BMI between the two groups. Results The percentage change in body mass loss was greater when following website B than website A (n = 90; ITT repeated measures p = 0.013). For completers (website A: n = 62, website B: n = 64), the percentage change in body mass loss was also greater for website B than website A (repeated measures p = 0.023). Conclusion The advice and motivation offered by an interactive website, including provision and consumption of breakfast cereals, results in significantly greater loss of body mass compared to the use of a standard website. It is not possible to discern which of the three factors is responsible. PMID:25428346

  1. Catalogue of abrupt shifts in Intergovernmental Panel on Climate Change climate models

    NASA Astrophysics Data System (ADS)

    Drijfhout, Sybren; Bathiany, Sebastian; Beaulieu, Claudie; Brovkin, Victor; Claussen, Martin; Huntingford, Chris; Scheffer, Marten; Sgubin, Giovanni; Swingedouw, Didier

    2015-10-01

    Abrupt transitions of regional climate in response to the gradual rise in atmospheric greenhouse gas concentrations are notoriously difficult to foresee. However, such events could be particularly challenging in view of the capacity required for society and ecosystems to adapt to them. We present, to our knowledge, the first systematic screening of the massive climate model ensemble informing the recent Intergovernmental Panel on Climate Change report, and reveal evidence of 37 forced regional abrupt changes in the ocean, sea ice, snow cover, permafrost, and terrestrial biosphere that arise after a certain global temperature increase. Eighteen out of 37 events occur for global warming levels of less than 2°, a threshold sometimes presented as a safe limit. Although most models predict one or more such events, any specific occurrence typically appears in only a few models. We find no compelling evidence for a general relation between the overall number of abrupt shifts and the level of global warming. However, we do note that abrupt changes in ocean circulation occur more often for moderate warming (less than 2°), whereas over land they occur more often for warming larger than 2°. Using a basic proportion test, however, we find that the number of abrupt shifts identified in Representative Concentration Pathway (RCP) 8.5 scenarios is significantly larger than in other scenarios of lower radiative forcing. This suggests the potential for a gradual trend of destabilization of the climate with respect to such shifts, due to increasing global mean temperature change.

  2. Catalogue of abrupt shifts in Intergovernmental Panel on Climate Change climate models

    PubMed Central

    Drijfhout, Sybren; Bathiany, Sebastian; Beaulieu, Claudie; Brovkin, Victor; Claussen, Martin; Huntingford, Chris; Scheffer, Marten; Sgubin, Giovanni; Swingedouw, Didier

    2015-01-01

    Abrupt transitions of regional climate in response to the gradual rise in atmospheric greenhouse gas concentrations are notoriously difficult to foresee. However, such events could be particularly challenging in view of the capacity required for society and ecosystems to adapt to them. We present, to our knowledge, the first systematic screening of the massive climate model ensemble informing the recent Intergovernmental Panel on Climate Change report, and reveal evidence of 37 forced regional abrupt changes in the ocean, sea ice, snow cover, permafrost, and terrestrial biosphere that arise after a certain global temperature increase. Eighteen out of 37 events occur for global warming levels of less than 2°, a threshold sometimes presented as a safe limit. Although most models predict one or more such events, any specific occurrence typically appears in only a few models. We find no compelling evidence for a general relation between the overall number of abrupt shifts and the level of global warming. However, we do note that abrupt changes in ocean circulation occur more often for moderate warming (less than 2°), whereas over land they occur more often for warming larger than 2°. Using a basic proportion test, however, we find that the number of abrupt shifts identified in Representative Concentration Pathway (RCP) 8.5 scenarios is significantly larger than in other scenarios of lower radiative forcing. This suggests the potential for a gradual trend of destabilization of the climate with respect to such shifts, due to increasing global mean temperature change. PMID:26460042

  3. Catalogue of abrupt shifts in Intergovernmental Panel on Climate Change climate models.

    PubMed

    Drijfhout, Sybren; Bathiany, Sebastian; Beaulieu, Claudie; Brovkin, Victor; Claussen, Martin; Huntingford, Chris; Scheffer, Marten; Sgubin, Giovanni; Swingedouw, Didier

    2015-10-27

    Abrupt transitions of regional climate in response to the gradual rise in atmospheric greenhouse gas concentrations are notoriously difficult to foresee. However, such events could be particularly challenging in view of the capacity required for society and ecosystems to adapt to them. We present, to our knowledge, the first systematic screening of the massive climate model ensemble informing the recent Intergovernmental Panel on Climate Change report, and reveal evidence of 37 forced regional abrupt changes in the ocean, sea ice, snow cover, permafrost, and terrestrial biosphere that arise after a certain global temperature increase. Eighteen out of 37 events occur for global warming levels of less than 2°, a threshold sometimes presented as a safe limit. Although most models predict one or more such events, any specific occurrence typically appears in only a few models. We find no compelling evidence for a general relation between the overall number of abrupt shifts and the level of global warming. However, we do note that abrupt changes in ocean circulation occur more often for moderate warming (less than 2°), whereas over land they occur more often for warming larger than 2°. Using a basic proportion test, however, we find that the number of abrupt shifts identified in Representative Concentration Pathway (RCP) 8.5 scenarios is significantly larger than in other scenarios of lower radiative forcing. This suggests the potential for a gradual trend of destabilization of the climate with respect to such shifts, due to increasing global mean temperature change.

  4. On the formation of SMC X-1: The effect of mass and orbital angular momentum loss

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Li, Tao; Li, X.-D., E-mail: litao@nju.edu.cn, E-mail: lixd@nju.edu.cn; The Key Laboratory of Modern Astronomy and Astrophysics, Ministry of Education, Nanjing 210093

    SMC X-1 is a high-mass X-ray binary with an orbital period of 3.9 days. The mass of the neutron star is as low as ∼1M {sub ☉}, suggesting that it was likely formed through an electron-capture supernova rather than an iron-core collapse supernova. From the present system configurations, we argue that the orbital period at the supernova was ≲ 10 days. Since the mass transfer process between the neutron star's progenitor and the companion star before the supernova should have increased the orbital period to tens of days, a mechanism with efficient orbit angular momentum loss and relatively small massmore » loss is required to account for its current orbital period. We have calculated the evolution of the progenitor binary systems from zero-age main sequence to the pre-supernova stage with different initial parameters and various mass and angular momentum loss mechanisms. Our results show that the outflow from the outer Lagrangian point or a circumbinary disk formed during the mass transfer phase may be qualified for this purpose. We point out that these mechanisms may be popular in binary evolution and significantly affect the formation of compact star binaries.« less

  5. Instability, finite amplitude pulsation and mass-loss in models of massive OB-type stars

    NASA Astrophysics Data System (ADS)

    Yadav, Abhay Pratap; Glatzel, Wolfgang

    2017-11-01

    Variability and mass-loss are common phenomena in massive OB-type stars. It is argued that they are caused by violent strange mode instabilities identified in corresponding stellar models. We present a systematic linear stability analysis with respect to radial perturbations of massive OB-type stars with solar chemical composition and masses between 23 and 100 M⊙. For selected unstable stellar models, we perform non-linear simulations of the evolution of the instabilities into the non-linear regime. Finite amplitude pulsations with periods in the range between hours and 100 d are found to be the final result of the instabilities. The pulsations are associated with a mean acoustic luminosity which can be the origin of a pulsationally driven wind. Corresponding mass-loss rates lie in the range between 10-9 and 10-4 M⊙ yr-1 and may thus affect the evolution of massive stars.

  6. The Abrupt Onset of the Modern South Asian Monsoon Winds (iodp Exp. 359)

    NASA Astrophysics Data System (ADS)

    Betzler, C.; Eberli, G. P.; Kroon, D.; Wright, J. D.; Swart, P. K.; Nath, B. N.; Reijmer, J.; Alvarez Zarikian, C. A.

    2016-12-01

    The South Asian Monson (SAM) is one of the most extreme features in Earth's climate system, yet its initiation and variations are not well established. The SAM is a seasonal reversal of winds accompanied by changes in precipitation with heavy rain during the summer monsoon. It is one of the most intense annually recurring climatic elements and of immense importance in supplying moisture to the Indian subcontinent thus affecting human population and vegetation, as well as marine biota in the surrounding seas. The seasonal precipitation change is one of the SAM elements most noticed on land, whereas the reversal of the wind regime is the dominating driver of circulation in the central and northern Indian Ocean realm. New data acquired during International Ocean Discovery Program Expedition 359 from the Inner Sea of the Maldives provide a previously unread archive that reveals an abrupt onset of the SAM-linked ocean circulation pattern and its relationship to the long term Neogene climate cooling. In particular it registers ocean current fluctuations and changes of intermediate water mass properties for the last 25 myrs that are directly related to the monsoon. Dating the deposits of SAM wind-driven currents yields an age of 12.9 Ma indicating an abrupt SAM onset, over a short period of 300 kyrs. This coincided with the Indian Ocean Oxygen Minimum Zone expansion as revealed by geochemical tracers and the onset of upwelling reflected by the sediment's content of sedimentary organic matter. A weaker `proto-monsoon' existed between 12.9 and 25 Ma, as mirrored by the sedimentary signature of dust influx. Abrupt SAM initiation favors a strong influence of climate in addition to the tectonic control, and we propose that the post Miocene Climate Optimum cooling, together with increased continentalization and establishment of the bipolar ocean circulation, i.e. the beginning of the modern world, shifted the monsoon over a threshold towards the modern system.

  7. Eutrophication, microbial-sulfate reduction and mass extinctions

    PubMed Central

    Schobben, Martin; Stebbins, Alan; Ghaderi, Abbas; Strauss, Harald; Korn, Dieter; Korte, Christoph

    2016-01-01

    ABSTRACT In post-Cambrian time, life on Earth experienced 5 major extinction events, likely instigated by adverse environmental conditions. Biodiversity loss among marine taxa, for at least 3 of these mass extinction events (Late Devonian, end-Permian and end-Triassic), has been connected with widespread oxygen-depleted and sulfide-bearing marine water. Furthermore, geochemical and sedimentary evidence suggest that these events correlate with rather abrupt climate warming and possibly increased terrestrial weathering. This suggests that biodiversity loss may be triggered by mechanisms intrinsic to the Earth system, notably, the biogeochemical sulfur and carbon cycle. This climate warming feedback produces large-scale eutrophication on the continental shelf, which, in turn, expands oxygen minimum zones by increased respiration, which can turn to a sulfidic state by increased microbial-sulfate reduction due to increased availability of organic matter. A plankton community turnover from a high-diversity eukaryote to high-biomass bacterial dominated food web is the catalyst proposed in this anoxia-extinction scenario and stands in stark contrast to the postulated productivity collapse suggested for the end-Cretaceous mass extinction. This cascade of events is relevant for the future ocean under predicted greenhouse driven climate change. The exacerbation of anoxic “dead” zones is already progressing in modern oceanic environments, and this is likely to increase due to climate induced continental weathering and resulting eutrophication of the oceans. PMID:27066181

  8. ANP system activity predicts variability of fat mass reduction and insulin sensitivity during weight loss.

    PubMed

    Brachs, Maria; Wiegand, Susanna; Leupelt, Verena; Ernert, Andrea; Kintscher, Ulrich; Jumpertz von Schwarzenberg, Reiner; Decker, Anne-Marie; Bobbert, Thomas; Hübner, Norbert; Chen, Wei; Krude, Heiko; Spranger, Joachim; Mai, Knut

    2016-06-01

    In weight loss trials, a considerable inter-individual variability in reduction of fat mass and changes of insulin resistance is observed, even under standardized study conditions. The underlying mechanisms are not well understood. Given the metabolic properties of the atrial natriuretic peptide (ANP) system, we hypothesized that ANP signaling might be involved in this phenomenon by changes of ANP secretion or receptor balance. Therefore, we investigated the impact of systemic, adipose and myocellular ANP system on metabolic and anthropometric improvements during weight loss. We comprehensively investigated 143 subjects (31 male, 112 female) before and after a 3 month-standardized weight loss program. The time course of BMI, fat mass, insulin sensitivity, circulating mid-regional proANP (MR-proANP) levels as well as adipose and myocellular natriuretic receptor A (NPR-A) and C (NPR-C) mRNA expression were investigated. BMI decreased by -12.6±3.7%. This was accompanied by a remarkable decrease of adipose NPR-C expression (1005.0±488.4 vs. 556.7±465.6; p<0.001) as well as a tendency towards increased adipose NPR-A expression (4644.7±946.8 vs. 4877.6±869.8; p=0.051). Weight loss induced changes in NPR-C (ΔNPR-C) was linked to relative reduction of total fat mass (ΔFM) (r=0.281; p<0.05), reduction of BMI (r=0.277; p<0.01), and increase of free fatty acids (ΔFFA) (r=-0.258; p<0.05). Basal NPR-C expression and weight loss induced ΔNPR-C independently explained 22.7% of ΔFM. In addition, ΔMR-proANP was independently associated with improvement of insulin sensitivity (standardized ß=0.246, p<0.01). ANP receptor expression predicted the degree of weight loss induced fat mass reduction. Our comprehensive human data support that peripheral ANP signalling is involved in control of adipose tissue plasticity and function during weight loss. (Funded by the Deutsche Forschungsgemeinschaft (KFO281/2), the Berlin Institute of Health (BIH) and the German Centre for

  9. Mass loss from red giant stars. II - Carbon stars

    NASA Technical Reports Server (NTRS)

    Wannier, P. G.; Sahai, R.; Andersson, B.-G.; Johnson, H. R.

    1990-01-01

    A millimeter-wave survey has been made of bright relatively unobscured, carbon stars, chosen on the basis of their optical properties. Out of 26 program objects, (J = 2-1)CO emission is detected from 15. Most of these had not been previously detected. There are many differences among the observed objects, but one rather interesting trend emerges: a positive correlation, at moderate IR excesses, between the IR dust emission and the expansion velocity of the dense wind. A similar, positive correlation with the mass-loss rate implies that stars with larger mass fluxes also accelerate them to larger velocities. At high-IR excesses, both correlations break down, and the momentum rate may be limited by the momentum rate of the stellar radiation. All these effects could be ascribed to differences in the gas-to-dust ratio, assuming that radiation pressure initiates and accelerates the wind.

  10. Detection of abrupt changes in dynamic systems

    NASA Technical Reports Server (NTRS)

    Willsky, A. S.

    1984-01-01

    Some of the basic ideas associated with the detection of abrupt changes in dynamic systems are presented. Multiple filter-based techniques and residual-based method and the multiple model and generalized likelihood ratio methods are considered. Issues such as the effect of unknown onset time on algorithm complexity and structure and robustness to model uncertainty are discussed.

  11. Contributions of natural and anthropogenic radiative forcing to mass loss of Northern Hemisphere mountain glaciers and quantifying their uncertainties.

    PubMed

    Hirabayashi, Yukiko; Nakano, Kazunari; Zhang, Yong; Watanabe, Satoshi; Tanoue, Masahiro; Kanae, Shinjiro

    2016-07-20

    Observational evidence indicates that a number of glaciers have lost mass in the past. Given that glaciers are highly impacted by the surrounding climate, human-influenced global warming may be partly responsible for mass loss. However, previous research studies have been limited to analyzing the past several decades, and it remains unclear whether past glacier mass losses are within the range of natural internal climate variability. Here, we apply an optimal fingerprinting technique to observed and reconstructed mass losses as well as multi-model general circulation model (GCM) simulations of mountain glacier mass to detect and attribute past glacier mass changes. An 8,800-year control simulation of glaciers enabled us to evaluate detectability. The results indicate that human-induced increases in greenhouse gases have contributed to the decreased area-weighted average masses of 85 analyzed glaciers. The effect was larger than the mass increase caused by natural forcing, although the contributions of natural and anthropogenic forcing to decreases in mass varied at the local scale. We also showed that the detection of anthropogenic or natural influences could not be fully attributed when natural internal climate variability was taken into account.

  12. Contributions of natural and anthropogenic radiative forcing to mass loss of Northern Hemisphere mountain glaciers and quantifying their uncertainties

    NASA Astrophysics Data System (ADS)

    Hirabayashi, Yukiko; Nakano, Kazunari; Zhang, Yong; Watanabe, Satoshi; Tanoue, Masahiro; Kanae, Shinjiro

    2016-07-01

    Observational evidence indicates that a number of glaciers have lost mass in the past. Given that glaciers are highly impacted by the surrounding climate, human-influenced global warming may be partly responsible for mass loss. However, previous research studies have been limited to analyzing the past several decades, and it remains unclear whether past glacier mass losses are within the range of natural internal climate variability. Here, we apply an optimal fingerprinting technique to observed and reconstructed mass losses as well as multi-model general circulation model (GCM) simulations of mountain glacier mass to detect and attribute past glacier mass changes. An 8,800-year control simulation of glaciers enabled us to evaluate detectability. The results indicate that human-induced increases in greenhouse gases have contributed to the decreased area-weighted average masses of 85 analyzed glaciers. The effect was larger than the mass increase caused by natural forcing, although the contributions of natural and anthropogenic forcing to decreases in mass varied at the local scale. We also showed that the detection of anthropogenic or natural influences could not be fully attributed when natural internal climate variability was taken into account.

  13. Sex steroids, bone mass, and bone loss. A prospective study of pre-, peri-, and postmenopausal women.

    PubMed

    Slemenda, C; Longcope, C; Peacock, M; Hui, S; Johnston, C C

    1996-01-01

    Although bone loss around the time of menopause is driven by estrogen deficiency, the roles of estrogens and androgens in the preservation of skeletal mass at other stages of life are less well understood. To address this issue we studied 231 women between the ages of 32 and 77 with multiple measurements of sex steroids and bone mass over a period of 2-8 yr. In all women bone mass was negatively associated with concentrations of sex-hormone binding globulin, and positively associated with weight. Bone loss occurred from all skeletal sites in peri- and postmenopausal women, but premenopausal women lost bone only from the hip (-0.3%/yr) and had positive rates of change in the radius and spine. Bone loss was significantly associated with lower androgen concentrations in premenopausal women, and with lower estrogens and androgens in peri- and postmenopausal women. Sex steroids are important for the maintenance of skeletal integrity before menopause, and for as long as 20-25 yr afterwards.

  14. Mass loss from inhomogeneous hot star winds. I. Resonance line formation in 2D models

    NASA Astrophysics Data System (ADS)

    Sundqvist, J. O.; Puls, J.; Feldmeier, A.

    2010-01-01

    Context. The mass-loss rate is a key parameter of hot, massive stars. Small-scale inhomogeneities (clumping) in the winds of these stars are conventionally included in spectral analyses by assuming optically thin clumps, a void inter-clump medium, and a smooth velocity field. To reconcile investigations of different diagnostics (in particular, unsaturated UV resonance lines vs. Hα/radio emission) within such models, a highly clumped wind with very low mass-loss rates needs to be invoked, where the resonance lines seem to indicate rates an order of magnitude (or even more) lower than previously accepted values. If found to be realistic, this would challenge the radiative line-driven wind theory and have dramatic consequences for the evolution of massive stars. Aims: We investigate basic properties of the formation of resonance lines in small-scale inhomogeneous hot star winds with non-monotonic velocity fields. Methods: We study inhomogeneous wind structures by means of 2D stochastic and pseudo-2D radiation-hydrodynamic wind models, constructed by assembling 1D snapshots in radially independent slices. A Monte-Carlo radiative transfer code, which treats the resonance line formation in an axially symmetric spherical wind (without resorting to the Sobolev approximation), is presented and used to produce synthetic line spectra. Results: The optically thin clumping limit is only valid for very weak lines. The detailed density structure, the inter-clump medium, and the non-monotonic velocity field are all important for the line formation. We confirm previous findings that radiation-hydrodynamic wind models reproduce observed characteristics of strong lines (e.g., the black troughs) without applying the highly supersonic “microturbulence” needed in smooth models. For intermediate strong lines, the velocity spans of the clumps are of central importance. Current radiation-hydrodynamic models predict spans that are too large to reproduce observed profiles unless a very

  15. Poor vitamin D status is prospectively associated with greater muscle mass loss in middle-aged and elderly Chinese individuals.

    PubMed

    Liu, Gang; Lu, Ling; Sun, Qi; Ye, Xingwang; Sun, Liang; Liu, Xin; Zong, Geng; Jin, Qianlu; Li, Huaixing; Lin, Xu

    2014-10-01

    Poor vitamin D status can increase age-related muscle mass loss. However, existing prospective evidence is limited and controversial. This study aimed to investigate the association of plasma 25-hydroxyvitamin D [25(OH)D] with muscle mass loss in middle-aged and elderly Chinese individuals over 6 years. We conducted a prospective cohort study. This community-based study included 568 men and women aged 50 to 70 years at baseline. Baseline plasma concentrations of 25(OH)D and biomarkers of liver and kidney functions and inflammation were measured. Body composition was assessed at baseline and 6-year follow-up by dual-energy x-ray absorptiometry. Appendicular skeletal muscle mass (ASMM) and trunk lean mass were calculated and total body lean mass was defined as an overall measure of total nonfat and nonbone tissues. Descriptive statistics and multiple linear regression were applied. The 6-year loss of ASMM was 1.14 kg (5.3%) in men and 0.47 kg (3.1%) in women (all P values <0.001). Compared with the highest 25(OH)D tertile, participants in the lowest tertile had significantly more absolute loss of ASMM (-1.21 vs -1.00 kg; P for trend=0.024) after multivariate adjustments for conventional confounders, as well as protein intake. The association persisted after additional adjustment of bone mineral density and inflammatory markers (P for trend=0.017). No significant associations were detected between 25(OH)D and absolute loss of trunk lean mass or total body lean mass. Lower 25(OH)D concentrations were prospectively associated with greater ASMM loss in middle-aged and elderly Chinese individuals independent of bone mineral density, inflammation, diet, and other risk factors. Copyright © 2014 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.

  16. Strange mode instabilities and mass loss in evolved massive primordial stars

    NASA Astrophysics Data System (ADS)

    Yadav, Abhay Pratap; Kühnrich Biavatti, Stefan Henrique; Glatzel, Wolfgang

    2018-04-01

    A linear stability analysis of models for evolved primordial stars with masses between 150 and 250 M⊙ is presented. Strange mode instabilities with growth rates in the dynamical range are identified for stellar models with effective temperatures below log Teff = 4.5. For selected models, the final fate of the instabilities is determined by numerical simulation of their evolution into the non-linear regime. As a result, the instabilities lead to finite amplitude pulsations. Associated with them are acoustic energy fluxes capable of driving stellar winds with mass-loss rates in the range between 7.7 × 10-7 and 3.5 × 10-4 M⊙ yr-1.

  17. Atmospheric CO2 and abrupt climate change on submillennial timescales

    NASA Astrophysics Data System (ADS)

    Ahn, Jinho; Brook, Edward

    2010-05-01

    How atmospheric CO2 varies and is controlled on various time scales and under various boundary conditions is important for understanding how the carbon cycle and climate change are linked. Ancient air preserved in ice cores provides important information on past variations in atmospheric CO2. In particular, concentration records for intervals of abrupt climate change may improve understanding of mechanisms that govern atmospheric CO2. We present new multi-decadal CO2 records that cover Greenland stadial 9 (between Dansgaard-Oeschger (DO) events 8 and 9) and the abrupt cooling event at 8.2 ka. The CO2 records come from Antarctic ice cores but are well synchronized with Greenland ice core records using new high-resolution CH4 records,precisely defining the timing of CO2 change with respect to abrupt climate events in Greenland. Previous work showed that during stadial 9 (40~38 ka), CO2 rose by about 15~20 ppm over around 2,000 years, and at the same time temperatures in Antarctica increased. Dust proxies indicate a decrease in dust flux over the same period. With more detailed data and better age controls we now find that approximately half of the CO2 increase during stadial 9 occurred abruptly, over the course of decades to a century at ~39.6 ka. The step increase of CO2 is synchronous with a similar step increase of Antarctic isotopic temperature and a small abrupt change in CH4, and lags after the onset of decrease in dust flux by ~400 years. New atmospheric CO2 records at the well-known ~8.2 ka cooling event were obtained from Siple Dome ice core, Antarctica. Our preliminary CO2 data span 900 years and include 19 data points within the 8.2 ka cooling event, which persisted for ~160 years (Thomas et al., Quarternary Sci. Rev., 2007). We find that CO2 increased by 2~4 ppm during that cooling event. Further analyses will improve the resolution and better constrain the CO2 variability during other times in the early Holocene to determine if the variations observed

  18. VizieR Online Data Catalog: Adiabatic mass loss in binary stars. II. (Ge+, 2015)

    NASA Astrophysics Data System (ADS)

    Ge, H.; Webbink, R. F.; Chen, X.; Han, Z.

    2016-02-01

    In the limit of extremely rapid mass transfer, the response of a donor star in an interacting binary becomes asymptotically one of adiabatic expansion. We survey here adiabatic mass loss from Population I stars (Z=0.02) of mass 0.10M⊙-100M⊙ from the zero-age main sequence to the base of the giant branch, or to central hydrogen exhaustion for lower main sequence stars. The logarithmic derivatives of radius with respect to mass along adiabatic mass-loss sequences translate into critical mass ratios for runaway (dynamical timescale) mass transfer, evaluated here under the assumption of conservative mass transfer. For intermediate- and high-mass stars, dynamical mass transfer is preceded by an extended phase of thermal timescale mass transfer as the star is stripped of most of its envelope mass. The critical mass ratio qad (throughout this paper, we follow the convention of defining the binary mass ratio as q{equiv}Mdonor/Maccretor) above which this delayed dynamical instability occurs increases with advancing evolutionary age of the donor star, by ever-increasing factors for more massive donors. Most intermediate- or high-mass binaries with nondegenerate accretors probably evolve into contact before manifesting this instability. As they approach the base of the giant branch, however, and begin developing a convective envelope, qad plummets dramatically among intermediate-mass stars, to values of order unity, and a prompt dynamical instability occurs. Among low-mass stars, the prompt instability prevails throughout main sequence evolution, with qad declining with decreasing mass, and asymptotically approaching qad=2/3, appropriate to a classical isentropic n=3/2 polytrope. Our calculated qad values agree well with the behavior of time-dependent models by Chen & Han (2003MNRAS.341..662C) of intermediate-mass stars initiating mass transfer in the Hertzsprung gap. Application of our results to cataclysmic variables, as systems that must be stable against rapid mass

  19. Weight Loss Composition is One-Fourth Fat-Free Mass: A Critical Review and Critique of This Widely Cited Rule

    PubMed Central

    Heymsfield, Steven B.; Cristina Gonzalez, M. C.; Shen, Wei; Redman, Leanne; Thomas, Diana

    2014-01-01

    Maximizing fat loss while preserving lean tissue mass and function is a central goal of modern obesity treatments. A widely cited rule guiding expected loss of lean tissue as fat-free mass (FFM) states that approximately one-fourth of weight loss will be FFM (i.e., ΔFFM/ΔWeight = ~0.25) with the remaining three-fourths fat mass. This review examines the dynamic relations between FFM, fat mass, and weight changes that follow induction of negative energy balance with hypocaloric dieting and/or exercise. Historical developments in the field are traced with the “Quarter FFM Rule” used as a framework to examine evolving concepts on obesity tissue, excess weight, and what is often cited as “Forbes’ Rule”. Temporal effects in the fractional contribution of FFM to changes in body weight are examined as are lean tissue moderating effects such as aging, inactivity, and exercise that frequently accompany structured low-calorie diet weight loss protocols. Losses of lean tissue with dieting typically tend to be small, raising questions about study design, power, and applied measurement method reliability. Our review elicits important questions related to the fractional loss of lean tissues with dieting and provides a foundation for future research on this topic. PMID:24447775

  20. Abrupt contraction flow of magnetorheological fluids

    NASA Astrophysics Data System (ADS)

    Kuzhir, P.; López-López, M. T.; Bossis, G.

    2009-05-01

    Contraction and expansion flows of magnetorheological fluids occur in a variety of smart devices. It is important therefore to learn how these flows can be controlled by means of applied magnetic fields. This paper presents a first investigation into the axisymmetric flow of a magnetorheological fluid through an orifice (so-called abrupt contraction flow). The effect of an external magnetic field, longitudinal or transverse to the flow, is examined. In experiments, the pressure-flow rate curves were measured, and the excess pressure drop (associated with entrance and exit losses) was derived from experimental data through the Bagley correction procedure. The effect of the longitudinal magnetic field is manifested through a significant increase in the slope of the pressure-flow rate curves, while no discernible yield stress occurs. This behavior, observed at shear Mason numbers 10

  1. Using a mass balance to determine the potency loss during the production of a pharmaceutical blend.

    PubMed

    Mackaplow, Michael B

    2010-09-01

    The manufacture of a blend containing the active pharmaceutical ingredient (API) and inert excipients is a precursor for the production of most pharmaceutical capsules and tablets. However, if there is a net water gain or preferential loss of API during production, the potency of the final drug product may be less than the target value. We use a mass balance to predict the mean potency loss during the production of a blend via wet granulation and fluidized bed drying. The result is an explicit analytical equation for the change in blend potency a function of net water gain, solids losses (both regular and high-potency), and the fraction of excipients added extragranularly. This model predicts that each 1% gain in moisture content (as determined by a loss on drying test) will decrease the API concentration of the final blend at least 1% LC. The effect of pre-blend solid losses increases with their degree of superpotency. This work supports Quality by Design by providing a rational method to set the process design space to minimize blend potency losses. When an overage is necessary, the model can help justify it by providing a quantitative, first-principles understanding of the sources of potency loss. The analysis is applicable to other manufacturing processes where the primary sources of potency loss are net water gain and/or mass losses.

  2. Acute diabetes insipidus mediated by vasopressinase after placental abruption.

    PubMed

    Wallia, Amisha; Bizhanova, Aigerim; Huang, Wenyu; Goldsmith, Susan L; Gossett, Dana R; Kopp, Peter

    2013-03-01

    Postpartum, diabetes insipidus (DI) can be part of Sheehan's syndrome or lymphocytic hypophysitis in combination with anterior pituitary hormone deficiencies. In contrast, acute onset of isolated DI in the postpartum period is unusual. This patient presented at 33 weeks gestation with placental abruption, prompting a cesarean delivery of twins. Immediately after delivery, she developed severe DI. The DI could be controlled with the vasopressinase-resistant 1-deamino-8-D-arginine vasopressin (DDAVP), but not with arginine vasopressin (AVP), and it resolved within a few weeks. The aim of this study was to demonstrate that the postpartum DI in this patient was caused by the release of placental vasopressinase into the maternal bloodstream. Cells were transiently transfected with the AVP receptor 2 (AVPR2) and treated with either AVP or DDAVP in the presence of the patient's serum collected postpartum or 10 weeks after delivery. The response to the different treatments was evaluated by measuring the activity of a cAMP-responsive firefly luciferase reporter construct. The in vitro studies demonstrate that the patient's postpartum serum disrupts activation of the AVPR2 by AVP, but not by the vasopressinase-resistant DDAVP. Placental abruption can rarely be associated with acute postpartum DI caused by release of placental vasopressinase into the bloodstream. This clinical entity must be considered in patients with placental abruption and when evaluating patients presenting with DI after delivery.

  3. [Smoking abstinence rate and its associated factors between abrupt and gradual smoking cessation].

    PubMed

    Hao, R; Zhou, J P; Ni, L; Li, Q Y; Shi, G C

    2017-12-12

    Objective: To analyze and compare the abstinence rate of smoking quitting methods and its associated factors between abrupt and gradual smoking cessation in smokers with drug-based therapy. Methods: A prospective clinical study was conducted in patients undergoing quitting smoking intervention in Ruijin Hospital smoking cessation clinic between June 2013 and May 2016. All the subjects were randomized in a 1∶1 ratio into the abrupt smoking cessation group (smoking as usual over 3 weeks before a planned quit day, and then stopping smoking abruptly) and the gradual smoking cessation group (gradually reducing tobacco use over 3 weeks before a planned quit day, and then stopping smoking totally). The primary outcome was the complete abstinence rate, and the secondary outcomes included 1-month, 3-month and 6 month 7-day point prevalence of abstinence rates and 3 month sustained abstinence rates. Changes of body weight and drug adverse events were also compared. Results: A total of 314 moderate to severe nicotine-dependent patients were admitted in the study, including 157 patients in the abrupt smoking cessation and 157 patients in the gradual smoking cessation group. Fourteen patients fell off during the follow-up. For the complete abstinence rate, the gradual smoking cessation group was higher than the abrupt smoking cessation group(55.0% vs . 36.9%, χ(2)=9.841, P =0.002) .For 7-d smoking abstinence rate in the 1st, 3rd, 6th month, there was no significant difference between the 2 groups (all P >0.05). As for the 3-month sustained abstinence rate, a higher smoking quitting rate was seen in the gradual smoking cessation group compared to the abrupt smoking cessation group in the 6-month follow-up (17.9% vs .8.7%, χ(2)=5.441, P =0.020). The adverse drug reaction incidence was higher in the abrupt smoking cessation group than the gradual smoking cessation group (Gastrointestinal discomfort: 39.2% vs . 17.7%, χ(2)=12.336, P =0.000; Dreaminess: 40.2% vs . 13.3%, χ(2

  4. Probing the pre-PN Mass Loss Histories in the PPN Dust Shells

    NASA Astrophysics Data System (ADS)

    Ueta, T.

    2001-12-01

    Proto-planetary nebulae (PPNs) are immediate progenitors of planetary nebulae (PNs) rapidly evolving over a relatively short time scale. Unlike the full-fledged PNs, the circumstellar dust shells of PPNs have neither been photo-ionized nor been swept up by fast winds. Since the PPN shells retain pristine fossil records of mass loss histories of these stars during the pre-PN phases, these dust shells provide ideal astronomical laboratories in which to investigate the origin of complex PN structures that we observe. We have conducted imaging surveys of the PPN shells in mid-infrared and optical wavelengths, probing the dust distribution directly via mid-infrared thermal dust emission arising from the shells and indirectly via dust-scattered stellar optical emission passing through the shells. From these surveys, we have found that (1) the PPN shells are intrinsically axisymmetric due to equatorially-enhanced superwind mass loss that occurred immediately before the beginning of the PPN phase, and (2) the variable degree of equatorial enhancement in the shells, which is probably related to the progenitor mass, has resulted in different optical depths and morphologies. To characterize the PPN shell geometries, we have developed and employed a 2.5 dimensional radiative transfer code that treats dust absorption, reemission, and an/isotropic scattering in any axisymmetric system illuminated by a central energy source. In the code, the dust optical properties are derived from the laboratory-measured refractive index using Mie theory allowing a distribution of sizes for each species in each composition layer in the shell. Our numerical analysis would be able to de-project and recover 3-D geometrical quantities, such as the pole-to-equator density ratio, from the observational data. These model calculations would provide constraining parameters for hydrodynamical models intended to generate equatorial enhancements during dust mass loss as well as initial parameters for

  5. Greenland Ice Sheet Mass Balance: Distribution of Increased Mass Loss with Climate Warming; 2003-07 Versus 1992-2002

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Li, Jun; Benner, Anita C.; Beckley, Matthew; Cornejo, Helen G.; DiMarzio, John; Giovinetto, Mario B.; Neumann, Thomas A.; Robbins, John; Saba, Jack L.; hide

    2011-01-01

    We derive mass changes of the Greenland ice sheet (GIS) for 2003-07 from ICESat laser altimetry and compare them with results for 1992-2002 from ERS radar and airborne laser altimetry. The GIS continued to grow inland and thin at the margins during 2003 07, but surface melting and accelerated flow significantly increased the marginal thinning compared with the 1990s. The net balance changed from a small loss of 7 plus or minus 3 Gt a 1(sup -1) in the 1990s to 171 plus or minus 4 Gt a (sup -1) for 2003-07, contributing 0.5 mm a(sup -1) to recent global sea-level rise. We divide the derived mass changes into two components: (1) from changes in melting and ice dynamics and (2) from changes in precipitation and accumulation rate. We use our firn compaction model to calculate the elevation changes driven by changes in both temperature and accumulation rate and to calculate the appropriate density to convert the accumulation-driven changes to mass changes. Increased losses from melting and ice dynamics (17-206 Gt a(sup-1) are over seven times larger than increased gains from precipitation (10 35 Gt a(sup-1) during a warming period of approximately 2 K (10 a)(sup -1) over the GIS. Above 2000m elevation, the rate of gain decreased from 44 to 28 Gt a(sup-1), while below 2000m the rate of loss increased from 51 to 198 Gt a(sup-1). Enhanced thinning below the equilibrium line on outlet glaciers indicates that increased melting has a significant impact on outlet glaciers, as well as accelerating ice flow. Increased thinning at higher elevations appears to be induced by dynamic coupling to thinning at the margins on decadal timescales.

  6. The Influence of Mass Loss on the Eccentricity of Double Star Orbits

    NASA Astrophysics Data System (ADS)

    Docobo, J. A.; Prieto, C.; Ling, J. F.

    In this comunication we study the behaviour of the eccentricity of double star orbits (visual and wide spectroscopic binaries) according to simplified laws of mass loss. Applications to the systems WDS 05245S0224 - HD 35411, WDS 05387S0236 - HD 37468 and WDS 06154S0902 - HD 43362 are included.

  7. Population age and initial density in a patchy environment affect the occurrence of abrupt transitions in a birth-and-death model of Taylor's law

    USGS Publications Warehouse

    Jiang, Jiang; DeAngelis, Donald L.; Zhang, B.; Cohen, J.E.

    2014-01-01

    Taylor's power law describes an empirical relationship between the mean and variance of population densities in field data, in which the variance varies as a power, b, of the mean. Most studies report values of b varying between 1 and 2. However, Cohen (2014a) showed recently that smooth changes in environmental conditions in a model can lead to an abrupt, infinite change in b. To understand what factors can influence the occurrence of an abrupt change in b, we used both mathematical analysis and Monte Carlo samples from a model in which populations of the same species settled on patches, and each population followed independently a stochastic linear birth-and-death process. We investigated how the power relationship responds to a smooth change of population growth rate, under different sampling strategies, initial population density, and population age. We showed analytically that, if the initial populations differ only in density, and samples are taken from all patches after the same time period following a major invasion event, Taylor's law holds with exponent b=1, regardless of the population growth rate. If samples are taken at different times from patches that have the same initial population densities, we calculate an abrupt shift of b, as predicted by Cohen (2014a). The loss of linearity between log variance and log mean is a leading indicator of the abrupt shift. If both initial population densities and population ages vary among patches, estimates of b lie between 1 and 2, as in most empirical studies. But the value of b declines to ~1 as the system approaches a critical point. Our results can inform empirical studies that might be designed to demonstrate an abrupt shift in Taylor's law.

  8. Mass loss of TEOS-coated RCC subjected to the environment at the shuttle wing leading edge

    NASA Technical Reports Server (NTRS)

    Stroud, C. W.; Rummler, D. R.

    1981-01-01

    Coated, reinforced carbon-carbon (RCC) is used for the leading edges of the Space Shuttle. The mass loss characteristics of RCC specimens coated with tetra-ethyl-ortho-silicate (TEOS) were determined for conditions which simulated the entry environment expected at the stagnation area of the wing leading edge. Maximum specimen temperature was 1632 K. Specimens were exposed for up to 100 missions. Stress levels up to 8.274 MPa caused an average increase in oxidation of 6 percent over unstressed specimens. Experimentally determined mass losses were compared with those predicted by an existing empirical analysis.

  9. Gravitational mass of positron from LEP synchrotron losses

    DOE PAGES

    Kalaydzhyan, Tigran

    2016-07-27

    General relativity(GR) is the current description of gravity in modern physics. One of the cornerstones of GR, as well as Newton’s theory of gravity, is the weak equivalence principle (WEP), stating that the trajectory of a freely falling test body is independent of its internal structure and composition. WEP is known to be valid for the normal matter with a high precision. However, due to the rarity of antimatter and weakness of the gravitational forces, the WEP has never been confirmed for antimatter. The current direct bounds on the ratio between the gravitational and inertial masses of the antihydrogen domore » not rule out a repulsive nature for the antimatter gravity. Here we establish an indirect bound of 0.13% on the difference between the gravitational and inertial masses of the positron (antielectron) from the analysis of synchrotron losses at the Large Electron-Positron collider (LEP). As a result, this serves as a confirmation of the conventional gravitational properties of antimatter without common assumptions such as, e.g., coupling of gravity to virtual particles, dynamics of distant astrophysical sources and the nature of absolute gravitational potentials.« less

  10. Gravitational mass of positron from LEP synchrotron losses

    PubMed Central

    Kalaydzhyan, Tigran

    2016-01-01

    General relativity(GR) is the current description of gravity in modern physics. One of the cornerstones of GR, as well as Newton’s theory of gravity, is the weak equivalence principle (WEP), stating that the trajectory of a freely falling test body is independent of its internal structure and composition. WEP is known to be valid for the normal matter with a high precision. However, due to the rarity of antimatter and weakness of the gravitational forces, the WEP has never been confirmed for antimatter. The current direct bounds on the ratio between the gravitational and inertial masses of the antihydrogen do not rule out a repulsive nature for the antimatter gravity. Here we establish an indirect bound of 0.13% on the difference between the gravitational and inertial masses of the positron (antielectron) from the analysis of synchrotron losses at the Large Electron-Positron collider (LEP). This serves as a confirmation of the conventional gravitational properties of antimatter without common assumptions such as, e.g., coupling of gravity to virtual particles, dynamics of distant astrophysical sources and the nature of absolute gravitational potentials. PMID:27461548

  11. North Atlantic ocean circulation and abrupt climate change during the last glaciation.

    PubMed

    Henry, L G; McManus, J F; Curry, W B; Roberts, N L; Piotrowski, A M; Keigwin, L D

    2016-07-29

    The most recent ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3, the glacial interval 25 thousand to 60 thousand years ago. We examined climate and ocean circulation proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer protactinium/thorium (Pa/Th) with the deep water-mass tracer, epibenthic δ(13)C. These indicators suggest reduced Atlantic overturning circulation during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean's persistent, central role in abrupt glacial climate change. Copyright © 2016, American Association for the Advancement of Science.

  12. Mass loss of shuttle space suit orthofabric under simulated ionospheric atomic oxygen bombardment

    NASA Technical Reports Server (NTRS)

    Miller, W. L.

    1985-01-01

    Many polymeric materials used for thermal protection and insulation on spacecraft degrade significantly under prolonged bombardment by ionospheric atomic oxygen. The covering fabric of the multilayered shuttle space suit is composed of a loose weave of GORE-TEX fibers, Nomex and Kevlar-29, which are all polymeric materials. The complete evaluation of suit fabric degradation from ionospheric atomic oxygen is of importance in reevaluating suit lifetime and inspection procedures. The mass loss and visible physical changes of each test sample was determined. Kapton control samples and data from previous asher and flight tests were used to scale the results to reflect ionospheric conditions at about 220 km altitude. It is predicted that the orthofabric loses mass in the ionosphere at a rate of about 66% of the original orthofabric mass/yr. The outer layer of the two-layer orthofabric test samples shows few easily visible signs of degradation, even when observed at 440X. It is concluded that the orthofabric could suffer significant loss of performance after much less than a year of total exposure time, while the degradation might be undetectable in post flight visual examinations of space suits.

  13. Recommended Experimental Procedures for Evaluation of Abrupt Wing Stall Characteristics

    NASA Technical Reports Server (NTRS)

    Capone, F. J.; Hall, R. M.; Owens, D. B.; Lamar, J. E.; McMillin, S. N.

    2003-01-01

    This paper presents a review of the experimental program under the Abrupt Wing Stall (AWS) Program. Candidate figures of merit from conventional static tunnel tests are summarized and correlated with data obtained in unique free-to-roll tests. Where possible, free-to-roll results are also correlated with flight data. Based on extensive studies of static experimental figures of merit in the Abrupt Wing Stall Program for four different aircraft configurations, no one specific figure of merit consistently flagged a warning of potential lateral activity when actual activity was seen to occur in the free-to-roll experiments. However, these studies pointed out the importance of measuring and recording the root mean square signals of the force balance.

  14. Acquisition of an Underway CTD System for the Flow Encountering Abrupt Topography DRI

    DTIC Science & Technology

    2015-09-30

    Acquisition of an Underway CTD System for the Flow Encountering Abrupt Topography DRI T. M. Shaun Johnston Scripps Institution of Oceanography...westward flow in the North Equatorial Current (NEC) encounters tall, steep, submarine topography and islands. During the Flow Encountering Abrupt... Topography (FLEAT) DRI, investigators will determine: • Whether appreciable energy/momentum is lost from the large-scale NEC flow to smaller scales and

  15. The resilience of postglacial hunter-gatherers to abrupt climate change.

    PubMed

    Blockley, Simon; Candy, Ian; Matthews, Ian; Langdon, Pete; Langdon, Cath; Palmer, Adrian; Lincoln, Paul; Abrook, Ashley; Taylor, Barry; Conneller, Chantal; Bayliss, Alex; MacLeod, Alison; Deeprose, Laura; Darvill, Chris; Kearney, Rebecca; Beavan, Nancy; Staff, Richard; Bamforth, Michael; Taylor, Maisie; Milner, Nicky

    2018-05-01

    Understanding the resilience of early societies to climate change is an essential part of exploring the environmental sensitivity of human populations. There is significant interest in the role of abrupt climate events as a driver of early Holocene human activity, but there are very few well-dated records directly compared with local climate archives. Here, we present evidence from the internationally important Mesolithic site of Star Carr showing occupation during the early Holocene, which is directly compared with a high-resolution palaeoclimate record from neighbouring lake beds. We show that-once established-there was intensive human activity at the site for several hundred years when the community was subject to multiple, severe, abrupt climate events that impacted air temperatures, the landscape and the ecosystem of the region. However, these results show that occupation and activity at the site persisted regardless of the environmental stresses experienced by this society. The Star Carr population displayed a high level of resilience to climate change, suggesting that postglacial populations were not necessarily held hostage to the flickering switch of climate change. Instead, we show that local, intrinsic changes in the wetland environment were more significant in determining human activity than the large-scale abrupt early Holocene climate events.

  16. Response of seafloor ecosystems to abrupt global climate change

    PubMed Central

    Moffitt, Sarah E.; Hill, Tessa M.; Roopnarine, Peter D.; Kennett, James P.

    2015-01-01

    Anthropogenic climate change is predicted to decrease oceanic oxygen (O2) concentrations, with potentially significant effects on marine ecosystems. Geologically recent episodes of abrupt climatic warming provide opportunities to assess the effects of changing oxygenation on marine communities. Thus far, this knowledge has been largely restricted to investigations using Foraminifera, with little being known about ecosystem-scale responses to abrupt, climate-forced deoxygenation. We here present high-resolution records based on the first comprehensive quantitative analysis, to our knowledge, of changes in marine metazoans (Mollusca, Echinodermata, Arthropoda, and Annelida; >5,400 fossils and trace fossils) in response to the global warming associated with the last glacial to interglacial episode. The molluscan archive is dominated by extremophile taxa, including those containing endosymbiotic sulfur-oxidizing bacteria (Lucinoma aequizonatum) and those that graze on filamentous sulfur-oxidizing benthic bacterial mats (Alia permodesta). This record, from 16,100 to 3,400 y ago, demonstrates that seafloor invertebrate communities are subject to major turnover in response to relatively minor inferred changes in oxygenation (>1.5 to <0.5 mL⋅L−1 [O2]) associated with abrupt (<100 y) warming of the eastern Pacific. The biotic turnover and recovery events within the record expand known rates of marine biological recovery by an order of magnitude, from <100 to >1,000 y, and illustrate the crucial role of climate and oceanographic change in driving long-term successional changes in ocean ecosystems. PMID:25825727

  17. Response of seafloor ecosystems to abrupt global climate change

    NASA Astrophysics Data System (ADS)

    Moffitt, Sarah E.; Hill, Tessa M.; Roopnarine, Peter D.; Kennett, James P.

    2015-04-01

    Anthropogenic climate change is predicted to decrease oceanic oxygen (O2) concentrations, with potentially significant effects on marine ecosystems. Geologically recent episodes of abrupt climatic warming provide opportunities to assess the effects of changing oxygenation on marine communities. Thus far, this knowledge has been largely restricted to investigations using Foraminifera, with little being known about ecosystem-scale responses to abrupt, climate-forced deoxygenation. We here present high-resolution records based on the first comprehensive quantitative analysis, to our knowledge, of changes in marine metazoans (Mollusca, Echinodermata, Arthropoda, and Annelida; >5,400 fossils and trace fossils) in response to the global warming associated with the last glacial to interglacial episode. The molluscan archive is dominated by extremophile taxa, including those containing endosymbiotic sulfur-oxidizing bacteria (Lucinoma aequizonatum) and those that graze on filamentous sulfur-oxidizing benthic bacterial mats (Alia permodesta). This record, from 16,100 to 3,400 y ago, demonstrates that seafloor invertebrate communities are subject to major turnover in response to relatively minor inferred changes in oxygenation (>1.5 to <0.5 mLṡL-1 [O2]) associated with abrupt (<100 y) warming of the eastern Pacific. The biotic turnover and recovery events within the record expand known rates of marine biological recovery by an order of magnitude, from <100 to >1,000 y, and illustrate the crucial role of climate and oceanographic change in driving long-term successional changes in ocean ecosystems.

  18. Comparison of the Heat Release Rate from the Mass Loss Calorimeter to the Cone Calorimeter for Wood-based Materials

    Treesearch

    Laura E. Hasburgh; Robert H. White; Mark A. Dietenberger; Charles R. Boardman

    2015-01-01

    There is a growing demand for material properties to be used as inputs in fi re behavior models designed to address building fire safety. This comparative study evaluates using the mass loss calorimeter as an alternative to the cone calorimeter for obtaining heat release rates of wood-based materials. For this study, a modified mass loss calorimeter utilized an...

  19. Increase in transmission loss of single panels by addition of mass inclusions to a poro-elastic layer: Experimental investigation

    NASA Astrophysics Data System (ADS)

    Kidner, M. R. F.; Fuller, C. R.; Gardner, B.

    2006-06-01

    The insertion loss of standard acoustic blankets can be significantly improved at low frequencies by the addition of randomly placed mass inclusions to the poro-elastic layers. The improvement is much greater than that due to the mass effect alone. The mass inclusions act as resonant systems and so increase the structure impedance. This paper reports the results of experimental investigations into this phenomenon. Increases in insertion loss of 15 dB in the 100 Hz third octave band are reported.

  20. Unexpectedly large mass loss during the thermal pulse cycle of the red giant star R Sculptoris.

    PubMed

    Maercker, M; Mohamed, S; Vlemmings, W H T; Ramstedt, S; Groenewegen, M A T; Humphreys, E; Kerschbaum, F; Lindqvist, M; Olofsson, H; Paladini, C; Wittkowski, M; de Gregorio-Monsalvo, I; Nyman, L-A

    2012-10-11

    The asymptotic-giant-branch star R Sculptoris is surrounded by a detached shell of dust and gas. The shell originates from a thermal pulse during which the star underwent a brief period of increased mass loss. It has hitherto been impossible to constrain observationally the timescales and mass-loss properties during and after a thermal pulse--parameters that determine the lifetime of the asymptotic giant branch and the amount of elements returned by the star. Here we report observations of CO emission from the circumstellar envelope and shell around R Sculptoris with an angular resolution of 1.3″. What was previously thought to be only a thin, spherical shell with a clumpy structure is revealed to also contain a spiral structure. Spiral structures associated with circumstellar envelopes have been previously seen, leading to the conclusion that the systems must be binaries. Combining the observational data with hydrodynamic simulations, we conclude that R Sculptoris is a binary system that underwent a thermal pulse about 1,800 years ago, lasting approximately 200 years. About 3 × 10(-3) solar masses of material were ejected at a velocity of 14.3 km s(-1) and at a rate around 30 times higher than the pre-pulse mass-loss rate. This shows that about three times more mass was returned to the interstellar medium during and immediately after the pulse than previously thought.

  1. Abrupt Climate Change: the View from the Past, the Present and the Future

    NASA Astrophysics Data System (ADS)

    White, J. W. C.

    2014-12-01

    Climate is changing as humans put more and more greenhouse gases into the atmosphere. With CO2 levels today around 400ppm, we are clearly committed to far more climate change, both in the near term, and well beyond our children's future. A key question is how that change will occur. Abrupt climate changes are those that exceed our expectations, preparedness, and ability to adapt. Such changes challenge us economically, physically, and socially. This talk will draw upon results from ice core research over the past twenty years, as well as a new NRC report on abrupt climate change in order to address abrupt change, as seen in the past in ice cores, as seen today in key environmental systems upon which humans depend, and what is may be coming in the future.

  2. Rainfall-triggered shallow landslides at catchment scale: Threshold mechanics-based modeling for abruptness and localization

    NASA Astrophysics Data System (ADS)

    von Ruette, J.; Lehmann, P.; Or, D.

    2013-10-01

    Rainfall-induced shallow landslides may occur abruptly without distinct precursors and could span a wide range of soil mass released during a triggering event. We present a rainfall-induced landslide-triggering model for steep catchments with surfaces represented as an assembly of hydrologically and mechanically interconnected soil columns. The abruptness of failure was captured by defining local strength thresholds for mechanical bonds linking soil and bedrock and adjacent columns, whereby a failure of a single bond may initiate a chain reaction of subsequent failures, culminating in local mass release (a landslide). The catchment-scale hydromechanical landslide-triggering model (CHLT) was applied to results from two event-based landslide inventories triggered by two rainfall events in 2002 and 2005 in two nearby catchments located in the Prealps in Switzerland. Rainfall radar data, surface elevation and vegetation maps, and a soil production model for soil depth distribution were used for hydromechanical modeling of failure patterns for the two rainfall events at spatial and temporal resolutions of 2.5 m and 0.02 h, respectively. The CHLT model enabled systematic evaluation of the effects of soil type, mechanical reinforcement (soil cohesion and lateral root strength), and initial soil water content on landslide characteristics. We compared various landslide metrics and spatial distribution of simulated landslides in subcatchments with observed inventory data. Model parameters were optimized for the short but intense rainfall event in 2002, and the calibrated model was then applied for the 2005 rainfall, yielding reasonable predictions of landslide events and volumes and statistically reproducing localized landslide patterns similar to inventory data. The model provides a means for identifying local hot spots and offers insights into the dynamics of locally resolved landslide hazards in mountainous regions.

  3. Copernicus ultraviolet observations of mass-loss effects in O and B stars

    NASA Technical Reports Server (NTRS)

    Snow, T. P., Jr.; Morton, D. C.

    1976-01-01

    Far-UV spectra of 47 O, B, and A stars obtained with the Copernicus satellite are examined for P Cygni profiles. For all 40 stars with displaced absorption lines, values are given for the velocities of the short-wavelength edge, the line center, and the emission peak (if present). Parts of the spectra of 42 stars are reproduced, evidence for mass motions in ground-based spectra is discussed, and the best available data are summarized on the wavelengths and oscillator strengths of most lines likely to show mass-loss effects in either visual or UV spectra. The main conclusions are that: (1) the far-UV transitions, especially resonance lines, show that mass flow is present over a much wider group of stars than revealed by visible data on subordinate lines; (2) most of the line shifts imply mass motion away from the stars; (3) mass flow occurs in all but one star brighter than a bolometric magnitude of -6.0; and (4) the observed terminal velocities generally exhibit no significant correlation with temperature, luminosity, gravity, rotational velocity, or line strength.

  4. Determining Mass-Loss Rates of Evolved Stars in the Galactic Bulge from Infrared Surveys

    NASA Astrophysics Data System (ADS)

    Riley, Allyssa; Sargent, Benjamin A.; Srinivasan, Sundar; Meixner, Margaret; Kastner, Joel H.

    2018-06-01

    To investigate the relationship between mass loss from evolved stars and host galaxy metallicity, we are computing the dust mass loss budget due to red supergiant (RSG) and asymptotic giant branch (AGB) stars in the Galactic Bulge and comparing this result to that previously obtained for the Magellanic Clouds. We construct spectral energy distributions (SEDs) for our candidate RSG and AGB stars using observations from various infrared surveys, including the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE). Because Robitaille et al (2008, AJ, 136, 2413) have already identified Intrinsically Red Objects from the GLIMPSE I and II surveys, we use their method as a starting point and expand the study by using the GLIMPSE 3D survey. Because AGB stars can be variable, we also match the GLIMPSE I, II, and 3D sources to other surveys, such as DEEP GLIMPSE, WISE, VVV, and DENIS, in order to characterize the variability across the spectral energy distribution (SED) of each source. This allows us to determine the source’s average SED over multiple epochs. We use extinction curves derived from Spitzer studies of extinction in the Galaxy to determine the extinction corrections for our sample. To establish mass-loss rates of evolved stars in the Bulge, we use the Grid of Red supergiant and Asymptotic giant branch ModelS (GRAMS) of dust-enshrouded evolved stars (2011, A&A, 532, A54; 2011, ApJ, 728, 93). This allows us to determine the total mass return to the Bulge from these stars. This work has been supported by NASA ADAP grant 80NSSC17K0057.

  5. Abrupt change of Antarctic moisture origin at the end of Termination II

    PubMed Central

    Masson-Delmotte, V.; Stenni, B.; Blunier, T.; Cattani, O.; Chappellaz, J.; Cheng, H.; Dreyfus, G.; Edwards, R. L.; Falourd, S.; Govin, A.; Kawamura, K.; Johnsen, S. J.; Jouzel, J.; Landais, A.; Lemieux-Dudon, B.; Lourantou, A.; Marshall, G.; Minster, B.; Mudelsee, M.; Pol, K.; Röthlisberger, R.; Selmo, E.; Waelbroeck, C.

    2010-01-01

    The deuterium excess of polar ice cores documents past changes in evaporation conditions and moisture origin. New data obtained from the European Project for Ice Coring in Antarctica Dome C East Antarctic ice core provide new insights on the sequence of events involved in Termination II, the transition between the penultimate glacial and interglacial periods. This termination is marked by a north–south seesaw behavior, with first a slow methane concentration rise associated with a strong Antarctic temperature warming and a slow deuterium excess rise. This first step is followed by an abrupt north Atlantic warming, an abrupt resumption of the East Asian summer monsoon, a sharp methane rise, and a CO2 overshoot, which coincide within dating uncertainties with the end of Antarctic optimum. Here, we show that this second phase is marked by a very sharp Dome C centennial deuterium excess rise, revealing abrupt reorganization of atmospheric circulation in the southern Indian Ocean sector. PMID:20566887

  6. Mass Loss from Dusty AGB and Red Supergiant Stars in the Magellanic Clouds and in the Galaxy

    NASA Astrophysics Data System (ADS)

    Sargent, Benjamin A.; Srinivasan, Sundar; Meixner, Margaret; Kastner, Joel

    2016-01-01

    Asymptotic giant branch (AGB) and red supergiant (RSG) stars are evolved stars that eject large parts of their mass in outflows of dust and gas. As part of an ongoing effort to measure mass loss from evolved stars in our Galaxy and in the Magellanic Clouds, we are modeling mass loss from AGB and RSG stars in these galaxies. Our approach is twofold. We pursue radiative transfer modeling of the spectral energy distributions (SEDs) of AGB and RSG stars in the Large Magellanic Cloud (LMC), in the Small Magellanic Cloud (SMC), and in the Galactic bulge and in globular clusters of the Milky Way. We are also constructing detailed dust opacity models of AGB and RSG stars in these galaxies for which we have infrared spectra; e.g., from the Spitzer Space Telescope Infrared Spectrograph (IRS). Our sample of infrared spectra largely comes from Spitzer-IRS observations. The detailed dust modeling of spectra informs our choice of dust properties to use in radiative transfer modeling of SEDs. We seek to determine how mass loss from these evolved stars depends upon the metallicity of their host environments. BAS acknowledges funding from NASA ADAP grant NNX15AF15G.

  7. Does the Momentum Flux Generated by Gravitational Contraction Drive Asymptotic Giant Branch Mass Loss?

    NASA Astrophysics Data System (ADS)

    Lewis, B. M.

    1997-12-01

    Gravitational contraction always generates a radially directed momentum flow. A particularly simple example occurs in the electron-degenerate cores of asymptotic giant branch (AGB) stars, which contract steadily under the addition of helium ashes from shell hydrogen burning. The resulting momentum flux is quantified here. And since the cores of AGB stars lack efficient momentum-cancellation mechanisms, they can maintain equilibrium by exporting their excess momentum flux to the stellar envelope, which disposes of much of it in a low velocity wind. Gravitational contraction easily accounts for the momentum flux in the solar wind, as well as the flux required to lift mass into the dust formation zone of every AGB star, whereon radiation pressure continues its ejection as a low-velocity wind. This mechanism explains the dependence of the AGB mass-loss rate on core mass; its generalization to objects with angular momentum and/or strong magnetic fields suggests a novel explanation as to why most planetary nebulae and proto-planetary nebulae exhibit axial symmetry. Quasi-static contraction is inherently biased to the generation of the maximum possible momentum flux. Its formalism is, therefore, readily adapted to providing an upper limit to the momentum flux needed to sustain mass loss when this begins from a semicontinuous rather than an impulsive process.

  8. Using GRACE and climate model simulations to predict mass loss of Alaskan glaciers through 2100

    DOE PAGES

    Wahr, John; Burgess, Evan; Swenson, Sean

    2016-05-30

    Glaciers in Alaska are currently losing mass at a rate of ~–50 Gt a –1, one of the largest ice loss rates of any regional collection of mountain glaciers on Earth. Existing projections of Alaska's future sea-level contributions tend to be divergent and are not tied directly to regional observations. Here we develop a simple, regional observation-based projection of Alaska's future sea-level contribution. We compute a time series of recent Alaska glacier mass variability using monthly GRACE gravity fields from August 2002 through December 2014. We also construct a three-parameter model of Alaska glacier mass variability based on monthly ERA-Interimmore » snowfall and temperature fields. When these three model parameters are fitted to the GRACE time series, the model explains 94% of the variance of the GRACE data. Using these parameter values, we then apply the model to simulated fields of monthly temperature and snowfall from the Community Earth System Model, to obtain predictions of mass variations through 2100. Here, we conclude that mass loss rates may increase between –80 and –110 Gt a –1by 2100, with a total sea-level rise contribution of 19 ± 4 mm during the 21st century.« less

  9. Mass loss from red giants - Infrared spectroscopy

    NASA Technical Reports Server (NTRS)

    Wannier, P. G.

    1985-01-01

    A discussion is presented of IR spectroscopy, particularly high-resolution spectroscopy in the approximately 1-20 micron band, as it impacts the study of circumstellar envelopes. The molecular bands within this region contain an enormous amount of information, especially when observed with sufficient resolution to obtain kinematic information. In a single spectrum, it is possible to resolve lines from up to 50 different rotational/vibrational levels of a given molecule and to detect several different isotopic variants. When high resolution techniques are combined with mapping techniques and/or time sequence observations of variable stars, the resulting information can paint a very detailed picture of the mass-loss phenomenon. To date, near-IR observations have been made of 20 molecular species. CO is the most widely observed molecule and useful information has been gleaned from the observed rotational excitation, kinematics, time variability and spatial structure of its lines. Examples of different observing techniques are discussed in the following sections.

  10. Rings in Evolved Stars: Fingerprints of Their Mass-Loss History

    NASA Astrophysics Data System (ADS)

    Ramos-Larios, Gerardo; Santamaria, Edgar; Sabin, Laurence; Guerrero, Martin; Marquez-Lugo, Alejandro

    2015-08-01

    The majority of intermediate mass evolved stars i.e. asymptotic giant branch (AGB) stars, post-AGB and pre-planetary nebulae (PPN) are well known for been characterized by external structures such as knots, arcs, ansae, jets, haloes, shells and even annular enhancements in intensity -features which are commonly referred to as rings. These are well described either as spherical bubbles of periodic isotropic nuclear mass pulsations (Balick, Wilson & Hajian 2001) or projections of spherical shells onto the plane of the sky by Kwok (2001).These interesting structures are part of the AGB wind, suggesting that this wind comes in a series of semi periodic lapses, indicating that the outflow has quasi-periodic oscillations.After an extensive analysis in the Hubble Space Telescope (HST) archives we found new ring-like structures in several evolved stars. Following the image analysis procedure described by Corradi et al. (2004), and using unsharp masking techniques it was possible to enhance the ring structures, and to obtain an effective removal of the underlying halo emission.Our new findings will help first to constrain the physical processes responsible for the rings creation and then to better understand the mass loss activity in these evolved stars.

  11. The Atlantic Meridional Overturning Circulation and Abrupt Climate Change.

    PubMed

    Lynch-Stieglitz, Jean

    2017-01-03

    Abrupt changes in climate have occurred in many locations around the globe over the last glacial cycle, with pronounced temperature swings on timescales of decades or less in the North Atlantic. The global pattern of these changes suggests that they reflect variability in the Atlantic meridional overturning circulation (AMOC). This review examines the evidence from ocean sediments for ocean circulation change over these abrupt events. The evidence for changes in the strength and structure of the AMOC associated with the Younger Dryas and many of the Heinrich events is strong. Although it has been difficult to directly document changes in the AMOC over the relatively short Dansgaard-Oeschger events, there is recent evidence supporting AMOC changes over most of these oscillations as well. The lack of direct evidence for circulation changes over the shortest events leaves open the possibility of other driving mechanisms for millennial-scale climate variability.

  12. Macroclumping as solution of the discrepancy between Hα and P v mass loss diagnostics for O-type stars

    NASA Astrophysics Data System (ADS)

    Šurlan, B.; Hamann, W.-R.; Aret, A.; Kubát, J.; Oskinova, L. M.; Torres, A. F.

    2013-11-01

    Context. Recent studies of O-type stars have demonstrated that discrepant mass-loss rates are obtained when different diagnostic methods are employed. Fitting the unsaturated UV resonance lines (e.g., P v) gives drastically lower values than obtained from the Hα emission. Wind inhomogeneity (so-called "clumping") may be the main cause of this discrepancy. Aims: In a previous paper, we presented 3D Monte-Carlo calculations for the formation of scattering lines in a clumped stellar wind. In the present paper we select five O-type supergiants (from O4 to O7) and test whether the reported discrepancies can be resolved this way. Methods: In the first step, the analyses started with simulating the observed spectra with Potsdam Wolf-Rayet (PoWR) non-LTE model atmospheres. The mass-loss rates are adjusted to fit to the observed Hα emission lines best. For the unsaturated UV resonance lines (i.e., P v) we then applied our 3D Monte-Carlo code, which can account for wind clumps of any optical depths ("macroclumping"), a non-void interclump medium, and a velocity dispersion inside the clumps. The ionization stratifications and underlying photospheric spectra were adopted from the PoWR models. The properties of the wind clumps were constrained by fitting the observed resonance line profiles. Results: Our results show that with the mass-loss rates that fit Hα (and other Balmer and He ii lines), the UV resonance lines (especially the unsaturated doublet of P v) can also be reproduced with no problem when macroclumping is taken into account. There is no need to artificially reduce the mass-loss rates or to assume a subsolar phosphorus abundance or an extremely high clumping factor, unlike what was claimed by other authors. These consistent mass-loss rates are lower by a factor of 1.3 to 2.6, compared to the mass-loss rate recipe from Vink et al. Conclusions: Macroclumping resolves the previously reported discrepancy between Hα and P v mass-loss diagnostics. Based on

  13. Acceptable Risk Analysis for Abrupt Environmental Pollution Accidents in Zhangjiakou City, China.

    PubMed

    Du, Xi; Zhang, Zhijiao; Dong, Lei; Liu, Jing; Borthwick, Alistair G L; Liu, Renzhi

    2017-04-20

    Abrupt environmental pollution accidents cause considerable damage worldwide to the ecological environment, human health, and property. The concept of acceptable risk aims to answer whether or not a given environmental pollution risk exceeds a societally determined criterion. This paper presents a case study on acceptable environmental pollution risk conducted through a questionnaire survey carried out between August and October 2014 in five representative districts and two counties of Zhangjiakou City, Hebei Province, China. Here, environmental risk primarily arises from accidental water pollution, accidental air pollution, and tailings dam failure. Based on 870 valid questionnaires, demographic and regional differences in public attitudes towards abrupt environmental pollution risks were analyzed, and risk acceptance impact factors determined. The results showed females, people between 21-40 years of age, people with higher levels of education, public servants, and people with higher income had lower risk tolerance. People with lower perceived risk, low-level risk knowledge, high-level familiarity and satisfaction with environmental management, and without experience of environmental accidents had higher risk tolerance. Multiple logistic regression analysis indicated that public satisfaction with environmental management was the most significant factor in risk acceptance, followed by perceived risk of abrupt air pollution, occupation, perceived risk of tailings dam failure, and sex. These findings should be helpful to local decision-makers concerned with environmental risk management (e.g., selecting target groups for effective risk communication) in the context of abrupt environmental accidents.

  14. Acceptable Risk Analysis for Abrupt Environmental Pollution Accidents in Zhangjiakou City, China

    PubMed Central

    Du, Xi; Zhang, Zhijiao; Dong, Lei; Liu, Jing; Borthwick, Alistair G. L.; Liu, Renzhi

    2017-01-01

    Abrupt environmental pollution accidents cause considerable damage worldwide to the ecological environment, human health, and property. The concept of acceptable risk aims to answer whether or not a given environmental pollution risk exceeds a societally determined criterion. This paper presents a case study on acceptable environmental pollution risk conducted through a questionnaire survey carried out between August and October 2014 in five representative districts and two counties of Zhangjiakou City, Hebei Province, China. Here, environmental risk primarily arises from accidental water pollution, accidental air pollution, and tailings dam failure. Based on 870 valid questionnaires, demographic and regional differences in public attitudes towards abrupt environmental pollution risks were analyzed, and risk acceptance impact factors determined. The results showed females, people between 21–40 years of age, people with higher levels of education, public servants, and people with higher income had lower risk tolerance. People with lower perceived risk, low-level risk knowledge, high-level familiarity and satisfaction with environmental management, and without experience of environmental accidents had higher risk tolerance. Multiple logistic regression analysis indicated that public satisfaction with environmental management was the most significant factor in risk acceptance, followed by perceived risk of abrupt air pollution, occupation, perceived risk of tailings dam failure, and sex. These findings should be helpful to local decision-makers concerned with environmental risk management (e.g., selecting target groups for effective risk communication) in the context of abrupt environmental accidents. PMID:28425956

  15. Fire spread in chaparral: comparison of data with flame-mass loss relationships

    Treesearch

    David R. Weise; Thomas H. Fletcher; Shankar Mahalingam; Xiangyang Zhou; Lulu Sun

    2017-01-01

    The relationships between flame length, mass loss rate, and the Froude number have become well-established for many different fuels over the past 60 years. Chaparral, a mixture of shrub plants from the Mediterranean climate zone of southwestern North America, represents a fuel type—living plants—that has seldom been included in the development of these relationships....

  16. The evaluation of tissue mass loss in the incision line of prostate with benign hyperplasia performed using holmium laser and cutting electrode

    PubMed Central

    Szewczyk, Mariusz; Jesionek–Kupnicka, Dorota; Lipinski, Piotr; Różański, Waldemar

    2014-01-01

    Introduction The aim of this study is to compare the changes in the incision line of prostatic adenoma using a monopolar cutting electrode and holmium laser, as well as the assessment of associated tissue mass and volume loss of benign prostatic hyperplasia (BPH). Material and methods The material used in this study consisted of 74 preparations of prostatic adenoma obtained via open retropubic adenomectomy, with an average volume of 120.7 ml. The material obtained cut in vitro before fixation in formaldehyde. One lobe was cut using holmium laser, the other using a monopolar cutting electrode. After the incision was made, tissue mass and volume loss were evaluated. Thermocoagulation changes in the incision line were examinedunder light microscope. Results In the case of the holmium laser incision, the average tissue mass loss was 1.73 g, tissue volume loss 3.57 ml and the depth of thermocoagulation was 1.17 mm. When the monopolar cutting electrode was used average tissue mass loss was 0.807 g, tissue volume loss 2.48 ml and the depth of thermocoagulation was 0.19 mm. Conclusions Where holmium laser was used, it was observed that the layer of tissue with thermocoagulation changes was deeper than in the case of the monopolar cutting electrode. Moreover, it was noticed that holmium laser caused bigger tissue mass and volume loss than the cutting electrode. PMID:25247088

  17. The evaluation of tissue mass loss in the incision line of prostate with benign hyperplasia performed using holmium laser and cutting electrode.

    PubMed

    Szewczyk, Mariusz; Jesionek-Kupnicka, Dorota; Lipiński, Marek Ireneusz; Lipinski, Piotr; Różański, Waldemar

    2014-01-01

    The aim of this study is to compare the changes in the incision line of prostatic adenoma using a monopolar cutting electrode and holmium laser, as well as the assessment of associated tissue mass and volume loss of benign prostatic hyperplasia (BPH). The material used in this study consisted of 74 preparations of prostatic adenoma obtained via open retropubic adenomectomy, with an average volume of 120.7 ml. The material obtained cut in vitro before fixation in formaldehyde. One lobe was cut using holmium laser, the other using a monopolar cutting electrode. After the incision was made, tissue mass and volume loss were evaluated. Thermocoagulation changes in the incision line were examinedunder light microscope. In the case of the holmium laser incision, the average tissue mass loss was 1.73 g, tissue volume loss 3.57 ml and the depth of thermocoagulation was 1.17 mm. When the monopolar cutting electrode was used average tissue mass loss was 0.807 g, tissue volume loss 2.48 ml and the depth of thermocoagulation was 0.19 mm. Where holmium laser was used, it was observed that the layer of tissue with thermocoagulation changes was deeper than in the case of the monopolar cutting electrode. Moreover, it was noticed that holmium laser caused bigger tissue mass and volume loss than the cutting electrode.

  18. Exercise associated hormonal signals as powerful determinants of an effective fat mass loss.

    PubMed

    Bajer, B; Vlcek, M; Galusova, A; Imrich, R; Penesova, A

    2015-07-01

    Obesity management for achieving an effective weight loss includes dietary modification and exercise [resistance (strength), endurance (cardiovascular) or intervals training (high-intensity intermittent exercise)]. Regular exercise acutely increases fat oxidation, which induces loss of fat mass and increases energy expenditure. Moreover, it has a positive effect on the physical (improved insulin sensitivity, lipid profile, etc.) and mental health (mood, cognition, memory, sleep, etc.). Endocrine responses to muscle actions are affected by many factors, including the exercise muscle groups (lower and upper body), load/volume, time-under tension, and rest-period intervals between sets, training status, gender, and age. The aim of this review is to summarize, evaluate, and clarify the literature data focusing on the endocrine responses to different types of exercise, including the frequency, intensity, and type of movement with regard to the fat loss strategies. Many studies have investigated anabolic [growth hormone, insulin-like growth factor-1 (IGF-1), testosterone] and gluco- and appetite- regulatory (insulin, cortisol, ghrelin) hormone responses and adaptations of skeletal muscles to exercise. Muscle tissue is a critical endocrine organ, playing important role in the regulation of several physiological and metabolic events. Moreover, we are also describing the response of some other substances to exercise, such as myokines [irisin, apelin, brain-derived neurotrophic factor (BDNF), myostatin, and fibroblast growth factor 21 (FGF21)]. It is proposed that reducing intra-abdominal fat mass and increasing cardiorespiratory fitness through improving nutritional quality, reducing sedentary behavior, and increase the participation in physical activity/exercise, might be associated with clinical benefits, sometimes even in the absence of weight loss.

  19. Antarctic ice sheet mass loss estimates using Modified Antarctic Mapping Mission surface flow observations

    NASA Astrophysics Data System (ADS)

    Ren, Diandong; Leslie, Lance M.; Lynch, Mervyn J.

    2013-03-01

    The long residence time of ice and the relatively gentle slopes of the Antarctica Ice Sheet make basal sliding a unique positive feedback mechanism in enhancing ice discharge along preferred routes. The highly organized ice stream channels extending to the interior from the lower reach of the outlets are a manifestation of the role of basal granular material in enhancing the ice flow. In this study, constraining the model-simulated year 2000 ice flow fields with surface velocities obtained from InSAR measurements permits retrieval of the basal sliding parameters. Forward integrations of the ice model driven by atmospheric and oceanic parameters from coupled general circulation models under different emission scenarios provide a range of estimates of total ice mass loss during the 21st century. The total mass loss rate has a small intermodel and interscenario spread, rising from approximately -160 km3/yr at present to approximately -220 km3/yr by 2100. The accelerated mass loss rate of the Antarctica Ice Sheet in a warming climate is due primarily to a dynamic response in the form of an increase in ice flow speed. Ice shelves contribute to this feedback through a reduced buttressing effect due to more frequent systematic, tabular calving events. For example, by 2100 the Ross Ice Shelf is projected to shed 40 km3 during each systematic tabular calving. After the frontal section's attrition, the remaining shelf will rebound. Consequently, the submerged cross-sectional area will reduce, as will the buttressing stress. Longitudinal differential warming of ocean temperature contributes to tabular calving. Because of the prevalence of fringe ice shelves, oceanic effects likely will play a very important role in the future mass balance of the Antarctica Ice Sheet, under a possible future warming climate.

  20. The role of dust in mass loss from late-type stars

    NASA Technical Reports Server (NTRS)

    Jura, M.

    1986-01-01

    It is noted that, in almost all late-type stars with measured mass loss rates, there is sufficient momentum in the radiation to dominate the dynamics. The opacity of the material is sufficiently great to render radiation pressure important; the dust forms close enough to the central star for radiation pressure to account for the observed outflow velocities. Pulsations appear to be important in raising the material far enough above the photosphere for grains to condense.

  1. MTOR signaling and ubiquitin-proteosome gene expression in the preservation of fat free mass following high protein, calorie restricted weight loss

    PubMed Central

    2012-01-01

    Caloric restriction is one of the most efficient ways to promote weight loss and is known to activate protective metabolic pathways. Frequently reported with weight loss is the undesirable consequence of fat free (lean muscle) mass loss. Weight loss diets with increased dietary protein intake are popular and may provide additional benefits through preservation of fat free mass compared to a standard protein, high carbohydrate diet. However, the precise mechanism by which a high protein diet may mitigate dietary weight loss induced reductions in fat free mass has not been fully elucidated. Maintenance of fat free mass is dependent upon nutrient stimulation of protein synthesis via the mTOR complex, although during caloric restriction a decrease (atrophy) in skeletal muscle may be driven by a homeostatic shift favouring protein catabolism. This review evaluates the relationship between the macronutrient composition of calorie restricted diets and weight loss using metabolic indicators. Specifically we evaluate the effect of increased dietary protein intake and caloric restricted diets on gene expression in skeletal muscle, particularly focusing on biosynthesis, degradation and the expression of genes in the ubiquitin-proteosome (UPP) and mTOR signaling pathways, including MuRF-1, MAFbx/atrogin-1, mTORC1, and S6K1. PMID:22974011

  2. Short-term variability and mass loss in Be stars. I. BRITE satellite photometry of η and μ Centauri

    NASA Astrophysics Data System (ADS)

    Baade, D.; Rivinius, Th.; Pigulski, A.; Carciofi, A. C.; Martayan, Ch.; Moffat, A. F. J.; Wade, G. A.; Weiss, W. W.; Grunhut, J.; Handler, G.; Kuschnig, R.; Mehner, A.; Pablo, H.; Popowicz, A.; Rucinski, S.; Whittaker, G.

    2016-04-01

    Context. Empirical evidence for the involvement of nonradial pulsations (NRPs) in the mass loss from Be stars ranges from (I) a singular case (μ Cen) of repetitive mass ejections triggered by multi-mode beating to (II) several photometric reports about enormous numbers of pulsation modes that suddenly appear during outbursts and on to (III) effective single-mode pulsators. Aims: The purpose of this study is to develop a more detailed empirical description of the star-to-disk mass transfer and to check the hypothesis that spates of transient nonradial pulsation modes accompany and even drive mass-loss episodes. Methods: The BRITE Constellation of nanosatellites was used to obtain mmag photometry of the Be stars η and μ Cen. Results: In the low-inclination star μ Cen, light pollution by variable amounts of near-stellar matter prevented any new insights into the variability and other properties of the central star. In the equator-on star η Cen, BRITE photometry and Heros echelle spectroscopy from the 1990s reveal an intricate clockwork of star-disk interactions. The mass transfer is modulated with the frequency difference of two NRP modes and an amplitude three times as large as the amplitude sum of the two NRP modes. This process feeds a high-amplitude circumstellar activity running with the incoherent and slightly lower so-called Štefl frequency. The mass-loss-modulation cycles are tightly coupled to variations in the value of the Štefl frequency and in its amplitude, albeit with strongly drifting phase differences. Conclusions: The observations are well described by the decomposition of the mass loss into a pulsation-related engine in the star and a viscosity-dominated engine in the circumstellar disk. Arguments are developed that large-scale gas-circulation flows occur at the interface. The propagation rates of these eddies manifest themselves as Štefl frequencies. Bursts in power spectra during mass-loss events can be understood as the noise inherent to

  3. A laboratory scale model of abrupt ice-shelf disintegration

    NASA Astrophysics Data System (ADS)

    Macayeal, D. R.; Boghosian, A.; Styron, D. D.; Burton, J. C.; Amundson, J. M.; Cathles, L. M.; Abbot, D. S.

    2010-12-01

    An important mode of Earth’s disappearing cryosphere is the abrupt disintegration of ice shelves along the Peninsula of Antarctica. This disintegration process may be triggered by climate change, however the work needed to produce the spectacular, explosive results witnessed with the Larsen B and Wilkins ice-shelf events of the last decade comes from the large potential energy release associated with iceberg capsize and fragmentation. To gain further insight into the underlying exchanges of energy involved in massed iceberg movements, we have constructed a laboratory-scale model designed to explore the physical and hydrodynamic interactions between icebergs in a confined channel of water. The experimental apparatus consists of a 2-meter water tank that is 30 cm wide. Within the tank, we introduce fresh water and approximately 20-100 rectangular plastic ‘icebergs’ having the appropriate density contrast with water to mimic ice. The blocks are initially deployed in a tight pack, with all blocks arranged in a manner to represent the initial state of an integrated ice shelf or ice tongue. The system is allowed to evolve through time under the driving forces associated with iceberg hydrodynamics. Digitized videography is used to quantify how the system of plastic icebergs evolves between states of quiescence to states of mobilization. Initial experiments show that, after a single ‘agitator’ iceberg begins to capsize, an ‘avalanche’ of capsizing icebergs ensues which drives horizontal expansion of the massed icebergs across the water surface, and which stimulates other icebergs to capsize. A surprise initially evident in the experiments is the fact that the kinetic energy of the expanding mass of icebergs is only a small fraction of the net potential energy released by the rearrangement of mass via capsize. Approximately 85 - 90 % of the energy released by the system goes into water motion modes, including a pervasive, easily observed seich mode of the tank

  4. Empirical ionization fractions in the winds and the determination of mass-loss rates for early-type stars

    NASA Technical Reports Server (NTRS)

    Lamers, H. J. G. L. M.; Gathier, R.; Snow, T. P.

    1980-01-01

    From a study of the UV lines in the spectra of 25 stars from 04 to B1, the empirical relations between the mean density in the wind and the ionization fractions of O VI, N V, Si IV, and the excited C III (2p 3P0) level were derived. Using these empirical relations, a simple relation was derived between the mass-loss rate and the column density of any of these four ions. This relation can be used for a simple determination of the mass-loss rate from O4 to B1 stars.

  5. HRR Upgrade to mass loss calorimeter and modified Schlyter test for FR Wood

    Treesearch

    Mark A. Dietenberger; Charles R. Boardman

    2013-01-01

    Enhanced Heat Release Rate (HRR) methodology has been extended to the Mass Loss Calorimeter (MLC) and the Modified Schlyter flame spread test to evaluate fire retardant effectiveness used on wood based materials. Modifications to MLC include installation of thermopile on the chimney walls to correct systematic errors to the sensible HRR calculations to account for...

  6. Radio Photosphere and Mass-Loss Envelope of VY Canis Majoris

    NASA Astrophysics Data System (ADS)

    Lipscy, S. J.; Jura, M.; Reid, M. J.

    2005-06-01

    We have used the VLA to detect emission from the supergiant VY CMa at radio wavelengths and have constructed 3000-4500 K isothermal outer atmospheres constrained by the data. These models produce a radio photosphere at 1.5-2 R*. An extrapolation of the model can account for the observed total mass-loss rate of the star. We also present mid-infrared imaging of the supergiant which suggests that warm dust is extended in the same direction as the near-infrared reflection nebula around VY CMa. The origin of the asymmetries in the outflow remains an unsolved problem.

  7. Factor V Leiden, Prothrombin and MTHFR Mutation in Patients with Preeclamsia, Intrauterine Growth Restriction and Placental Abruption.

    PubMed

    Livrinova, Vesna; Lega, Marija Hadzi; Dimcheva, Anita Hristova; Samardziski, Igor; Isjanovska, Rozalinda

    2015-12-15

    Factor V Leiden, Prothrombin and MTHFR gene mutation, could have an influence in pregnancy with adverse outcome Preeclamsia, IUGR and Placental abruption. The aim of this study is to investigate the presence of above mentioned inherited thrombophilias and its statistical significance, distribution among the complicated and normal pregnancy, and relative risk for carrier of mutation to develop preeclampsia, IUGR and placental abruption. Prospective cohort study is implemented at University Clinic for Obstetric and Gynecology in Skopje, Republic of Macedonia. The study included 109 delivered patients: 40 with preeclapmsia, 22 with IUGR, 17 with placental abruption and 30 as control group with normal pregnancy. The amount of 3 ml venous blood has been used for detection of these point mutations using ThromboStrip -Opegen, QIAGEN kit manufactured for thrombotic risk. The highest frequency was found: in the group with preeclampsia 35% were MTHFR homozygous, IUGR -MTHFR heterozygous 45%, Placental abruption- 52.9% MTHFR heterozygous, and in the control group without thrombophilia 56.7%. There were combined thrombophilia in 3 patients. There aren`t statistical significance in presence of thrombophilia among groups (p > 0.05). Statistical significance (p < 0.05) was found between carriers of MTHFR homozygous in preeclampsia and group with placental abruption and control group. Relative risk in IUGR group for MTHFR homozygous was 5.54 (1.37abruption for Factor V Leiden heterozygous was 4.50 (0.47abruption. Further investigations with more patients are warranted.

  8. Factor V Leiden, Prothrombin and MTHFR Mutation in Patients with Preeclamsia, Intrauterine Growth Restriction and Placental Abruption

    PubMed Central

    Livrinova, Vesna; Lega, Marija Hadzi; Dimcheva, Anita Hristova; Samardziski, Igor; Isjanovska, Rozalinda

    2015-01-01

    BACKGROUND: Factor V Leiden, Prothrombin and MTHFR gene mutation, could have an influence in pregnancy with adverse outcome Preeclamsia, IUGR and Placental abruption. AIM: The aim of this study is to investigate the presence of above mentioned inherited thrombophilias and its statistical significance, distribution among the complicated and normal pregnancy, and relative risk for carrier of mutation to develop preeclampsia, IUGR and placental abruption. MATERIAL AND METHODS: Prospective cohort study is implemented at University Clinic for Obstetric and Gynecology in Skopje, Republic of Macedonia. The study included 109 delivered patients: 40 with preeclapmsia, 22 with IUGR, 17 with placental abruption and 30 as control group with normal pregnancy. The amount of 3 ml venous blood has been used for detection of these point mutations using ThromboStrip -Opegen, QIAGEN kit manufactured for thrombotic risk. RESULTS: The highest frequency was found: in the group with preeclampsia 35% were MTHFR homozygous, IUGR -MTHFR heterozygous 45%, Placental abruption- 52.9% MTHFR heterozygous, and in the control group without thrombophilia 56.7%. There were combined thrombophilia in 3 patients. There aren`t statistical significance in presence of thrombophilia among groups (p > 0.05). Statistical significance (p < 0.05) was found between carriers of MTHFR homozygous in preeclampsia and group with placental abruption and control group. Relative risk in IUGR group for MTHFR homozygous was 5.54 (1.37abruption for Factor V Leiden heterozygous was 4.50 (0.47abruption. Further investigations with more patients are warranted. PMID:27275292

  9. Constraints on Porosity and Mass Loss in O-star Winds from the Modeling of X-ray Emission Line Profile Shapes

    NASA Technical Reports Server (NTRS)

    Leutenegger, Maurice A.; Cohen, David H.; Sundqvist, Jon O.; Owocki, Stanley P.

    2013-01-01

    We fit X-ray emission line profiles in high resolution XMM-Newton and Chandra grating spectra of the early O supergiant Zeta Pup with models that include the effects of porosity in the stellar wind. We explore the effects of porosity due to both spherical and flattened clumps. We find that porosity models with flattened clumps oriented parallel to the photosphere provide poor fits to observed line shapes. However, porosity models with isotropic clumps can provide acceptable fits to observed line shapes, but only if the porosity effect is moderate. We quantify the degeneracy between porosity effects from isotropic clumps and the mass-loss rate inferred from the X-ray line shapes, and we show that only modest increases in the mass-loss rate (40%) are allowed if moderate porosity effects (h(sub infinity) less than approximately R(sub *)) are assumed to be important. Large porosity lengths, and thus strong porosity effects, are ruled out regardless of assumptions about clump shape. Thus, X-ray mass-loss rate estimates are relatively insensitive to both optically thin and optically thick clumping. This supports the use of X-ray spectroscopy as a mass-loss rate calibration for bright, nearby O stars

  10. Effects of the LBV Primary's Mass-loss Rate on the 3D Hydrodynamics of eta Carinae's Colliding Winds

    NASA Technical Reports Server (NTRS)

    Madura, Thomas I.; Gull, Theodore R.; Cocoran, M.; Okazaki, A.; Owocki, S.; Russell, C.; Hamaguchi, K.; Clementel, N; Groh, J.; Hillier, D. J.

    2013-01-01

    At the heart of eta Carinae's spectacular "Homunculus" nebula lies an extremely luminous (L(sub Total) greater than approximately 5 × 10(exp 6) solar luminosity) colliding wind binary with a highly eccentric (e approximately 0.9), 5.54-year orbit (Figure 1). The primary of the system, a Luminous Blue Variable (LBV), is our closest (D approximately 2.3 kpc) and best example of a pre-hypernova or pre-gamma ray burst environment. The remarkably consistent and periodic RXTE X-ray light curve surprisingly showed a major change during the system's last periastron in 2009, with the X-ray minimum being approximately 50% shorter than the minima of the previous two cycles1. Between 1998 and 2011, the strengths of various broad stellar wind emission lines (e.g. Halpha, Fe II) in line-of-sight (l.o.s.) also decreased by factors of 1.5 - 3 relative to the continuum2. The current interpretation for these changes is that they are due to a gradual factor of 2 - 4 drop in the primary's mass-loss rate over the last approximately 15 years1, 2. However, while a secular change is seen for a direct view of the central source, little to no change is seen in profiles at high stellar latitudes or reflected off of the dense, circumbinary material known as the "Weigelt blobs"2, 3. Moreover, model spectra generated with CMFGEN predict that a factor of 2 - 4 drop in the primary's mass-loss rate should lead to huge changes in the observed spectrum, which thus far have not been seen. Here we present results from large- (plus or minus 1620 AU) and small- (plus or minus 162 AU) domain, full 3D smoothed particle hydrodynamics (SPH) simulations of eta Car's massive binary colliding winds for three different primary-star mass-loss rates (2.4, 4.8, and 8.5 × 10(exp -4) solar mass/yr). The goal is to investigate how the mass-loss rate affects the 3D geometry and dynamics of eta Car's optically-thick wind and spatially-extended wind-wind collision (WWC) regions, both of which are known sources of

  11. Pulsations, Shocks, and Mass Loss

    NASA Technical Reports Server (NTRS)

    Bally, John

    1998-01-01

    and mass loss rates, and to probe the physics of jet collimation, and may indicate that the jet production phase of certain young stars may last more than a million years. These three discoveries provide us with fundamental new insights into the star formation process, into the physical conditions inside and near star forming clouds, and into new ways to probe the physics and chemistry of such clouds.

  12. The Necessity of Awareness of Early Symptoms of Placental Abruption Among Pregnant Japanese Women

    PubMed Central

    Suzuki, Shunji; Shinmura, Hiroki

    2016-01-01

    Background In 2012, the recommendation for immediate contact and visit to obstetric institutions by pregnant women was emphasized by The Japan Obstetric Compensation System for Cerebral Palsy (JOCSC). In this study, we examined whether or not the increased awareness has led to the improvement of perinatal outcomes of placental abruption managed at private clinics. Methods We reviewed the obstetric records of 38 singleton pregnant women complicated by placental abruption that developed at home, and were managed at private clinics from April 2008 through April 2016. Results The perinatal outcomes, specifically the rate of cases with ≥ 1 hour time interval between symptom onset and clinic visit, have not changed significantly after the intervention. Conclusion The provision of information regarding the early clinical symptoms associated with placental abruption in pregnant women has not been well documented in Japan. PMID:27540442

  13. High-resolution Greenland ice core data show abrupt climate change happens in few years.

    PubMed

    Steffensen, Jørgen Peder; Andersen, Katrine K; Bigler, Matthias; Clausen, Henrik B; Dahl-Jensen, Dorthe; Fischer, Hubertus; Goto-Azuma, Kumiko; Hansson, Margareta; Johnsen, Sigfús J; Jouzel, Jean; Masson-Delmotte, Valérie; Popp, Trevor; Rasmussen, Sune O; Röthlisberger, Regine; Ruth, Urs; Stauffer, Bernhard; Siggaard-Andersen, Marie-Louise; Sveinbjörnsdóttir, Arny E; Svensson, Anders; White, James W C

    2008-08-01

    The last two abrupt warmings at the onset of our present warm interglacial period, interrupted by the Younger Dryas cooling event, were investigated at high temporal resolution from the North Greenland Ice Core Project ice core. The deuterium excess, a proxy of Greenland precipitation moisture source, switched mode within 1 to 3 years over these transitions and initiated a more gradual change (over 50 years) of the Greenland air temperature, as recorded by stable water isotopes. The onsets of both abrupt Greenland warmings were slightly preceded by decreasing Greenland dust deposition, reflecting the wetting of Asian deserts. A northern shift of the Intertropical Convergence Zone could be the trigger of these abrupt shifts of Northern Hemisphere atmospheric circulation, resulting in changes of 2 to 4 kelvin in Greenland moisture source temperature from one year to the next.

  14. Abrupt Depletion Layer Approximation for the Metal Insulator Semiconductor Diode.

    ERIC Educational Resources Information Center

    Jones, Kenneth

    1979-01-01

    Determines the excess surface change carrier density, surface potential, and relative capacitance of a metal insulator semiconductor diode as a function of the gate voltage, using the precise questions and the equations derived with the abrupt depletion layer approximation. (Author/GA)

  15. Mass-Loss Evolution in the EUV Low Corona from SDO/AIA Data

    NASA Astrophysics Data System (ADS)

    López, Fernando M.; Hebe Cremades, M.; Nuevo, Federico A.; Balmaceda, Laura A.; Vásquez, Alberto M.

    2017-01-01

    We carry out an analysis of the mass that is ejected from three coronal dimming regions observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. The three events are unambiguously identified with white-light coronal mass ejections (CMEs) that are associated in turn with surface activity of diverse nature: an impulsive (M-class) flare, a weak (B-class) flare, and a filament eruption without a flare. The use of three AIA coronal passbands allows applying a differential emission measure technique to define the dimming regions and identify their ejected mass through the analysis of the electronic density depletion associated with the eruptions. The temporal evolution of the mass loss from the three dimmings can be approximated by an exponential equation followed by a linear fit. We determine the mass of the associated CMEs from COR2 data. The results show that the ejected masses from the low corona represent a considerable amount of the CME mass. We also find that plasma is still being ejected from the low corona at the time when the CMEs reach the COR2 field of view. The temporal evolution of the angular width of the CMEs, of the dimming regions in the low corona, and of the flux registered by GOES in soft X-rays are all in close relation with the behavior of mass ejection from the low corona. We discuss the implications of our findings toward a better understanding of the temporal evolution of several parameters associated with the analyzed dimmings and CMEs.

  16. Long-lasting X-ray emission from type IIb supernova 2011dh and mass-loss history of the yellow supergiant progenitor

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Maeda, Keiichi; Katsuda, Satoru; Bamba, Aya

    2014-04-20

    Type IIb supernova (SN) 2011dh, with conclusive detection of an unprecedented yellow supergiant (YSG) progenitor, provides an excellent opportunity to deepen our understanding on the massive star evolution in the final centuries toward the SN explosion. In this paper, we report on detection and analyses of thermal X-ray emission from SN IIb 2011dh at ∼500 days after the explosion on Chandra archival data, providing a solidly derived mass-loss rate of a YSG progenitor for the first time. We find that the circumstellar media should be dense, more than that expected from a Wolf-Rayet (W-R) star by one order of magnitude.more » The emission is powered by a reverse shock penetrating into an outer envelope, fully consistent with the YSG progenitor but not with a W-R progenitor. The density distribution at the outermost ejecta is much steeper than that expected from a compact W-R star, and this finding must be taken into account in modeling the early UV/optical emission from SNe IIb. The derived mass-loss rate is ∼3 × 10{sup –6} M {sub ☉} yr{sup –1} for the mass-loss velocity of ∼20 km s{sup –1} in the final ∼1300 yr before the explosion. The derived mass-loss properties are largely consistent with the standard wind mass-loss expected for a giant star. This is not sufficient to be a main driver to expel nearly all the hydrogen envelope. Therefore, the binary interaction, with a huge mass transfer having taken place at ≳ 1300 yr before the explosion, is a likely scenario to produce the YSG progenitor.« less

  17. Carboxylic acid functional group analysis using constant neutral loss scanning-mass spectrometry.

    PubMed

    Dron, Julien; Eyglunent, Gregory; Temime-Roussel, Brice; Marchand, Nicolas; Wortham, Henri

    2007-12-12

    The present study describes the development of a new analytical technique for the functional group determination of the carboxylic moiety using atmospheric pressure chemical ionization-mass spectrometry (APCI-MS/MS) operated in the constant neutral loss scanning (CNLS) mode. Carboxylic groups were first derivatized into their corresponding methyl esters by reacting with BF3/methanol mix and the reaction mixture was then directly injected into the APCI chamber. The loss of methanol (m/z = 32 amu) resulting from the fragmentation of the protonated methyl esters was then monitored. Applying this method together with a statistical approach to reference mixtures containing 31 different carboxylic acids at randomly calculated concentrations demonstrated its suitability for quantitative functional group measurements with relative standard deviations below 15% and a detection limit of 0.005 mmol L(-1). Its applicability to environmental matrices was also shown through the determination of carboxylic acid concentrations inside atmospheric aerosol samples. To the best of our knowledge, it is the first time that the tandem mass spectrometry was successfully applied to functional group analysis, offering great perspectives in the characterization of complex mixtures which are prevailing in the field of environmental analysis as well as in the understanding of the chemical processes occurring in these matrices.

  18. The wind speeds, dust content, and mass-loss rates of evolved AGB and RSG stars at varying metallicity

    NASA Astrophysics Data System (ADS)

    Goldman, Steven R.; van Loon, Jacco Th.; Zijlstra, Albert A.; Green, James A.; Wood, Peter R.; Nanni, Ambra; Imai, Hiroshi; Whitelock, Patricia A.; Matsuura, Mikako; Groenewegen, Martin A. T.; Gómez, José F.

    2017-02-01

    We present the results of our survey of 1612-MHz circumstellar OH maser emission from asymptotic giant branch (AGB) stars and red supergiants (RSGs) in the Large Magellanic Cloud (LMC). We have discovered four new circumstellar maser sources in the LMC, and increased the number of reliable wind speeds from infrared (IR) stars in the LMC from 5 to 13. Using our new wind speeds, as well as those from Galactic sources, we have derived an updated relation for dust-driven winds: vexp ∝ ZL0.4. We compare the subsolar metallicity LMC OH/IR stars with carefully selected samples of more metal-rich OH/IR stars, also at known distances, in the Galactic Centre and Galactic bulge. We derive pulsation periods for eight of the bulge stars for the first time by using near-IR photometry from the Vista Variables in the Via Lactea survey. We have modelled our LMC OH/IR stars and developed an empirical method of deriving gas-to-dust ratios and mass-loss rates by scaling the models to the results from maser profiles. We have done this also for samples in the Galactic Centre and bulge and derived a new mass-loss prescription which includes luminosity, pulsation period, and gas-to-dust ratio dot{M} = 1.06^{+3.5}_{-0.8} × }10^{-5 (L/10^4 L_{⊙})^{0.9± 0.1}(P/500 {d})^{0.75± 0.3} (r_gd/200)^{-0.03± 0.07} M⊙ yr-1. The tightest correlation is found between mass-loss rate and luminosity. We find that the gas-to-dust ratio has little effect on the mass-loss of oxygen-rich AGB stars and RSGs within the Galaxy and the LMC. This suggests that the mass-loss of oxygen-rich AGB stars and RSGs is (nearly) independent of metallicity between a half and twice solar.

  19. Mass loss of stars on the asymptotic giant branch. Mechanisms, models and measurements

    NASA Astrophysics Data System (ADS)

    Höfner, Susanne; Olofsson, Hans

    2018-01-01

    As low- and intermediate-mass stars reach the asymptotic giant branch (AGB), they have developed into intriguing and complex objects that are major players in the cosmic gas/dust cycle. At this stage, their appearance and evolution are strongly affected by a range of dynamical processes. Large-scale convective flows bring newly-formed chemical elements to the stellar surface and, together with pulsations, they trigger shock waves in the extended stellar atmosphere. There, massive outflows of gas and dust have their origin, which enrich the interstellar medium and, eventually, lead to a transformation of the cool luminous giants into white dwarfs. Dust grains forming in the upper atmospheric layers play a critical role in the wind acceleration process, by scattering and absorbing stellar photons and transferring their outward-directed momentum to the surrounding gas through collisions. Recent progress in high-angular-resolution instrumentation, from the visual to the radio regime, is leading to valuable new insights into the complex dynamical atmospheres of AGB stars and their wind-forming regions. Observations are revealing asymmetries and inhomogeneities in the photospheric and dust-forming layers which vary on time-scales of months, as well as more long-lived large-scale structures in the circumstellar envelopes. High-angular-resolution observations indicate at what distances from the stars dust condensation occurs, and they give information on the chemical composition and sizes of dust grains in the close vicinity of cool giants. These are essential constraints for building realistic models of wind acceleration and developing a predictive theory of mass loss for AGB stars, which is a crucial ingredient of stellar and galactic chemical evolution models. At present, it is still not fully possible to model all these phenomena from first principles, and to predict the mass-loss rate based on fundamental stellar parameters only. However, much progress has been made

  20. Precise interpolar phasing of abrupt climate change during the last ice age.

    PubMed

    2015-04-30

    The last glacial period exhibited abrupt Dansgaard-Oeschger climatic oscillations, evidence of which is preserved in a variety of Northern Hemisphere palaeoclimate archives. Ice cores show that Antarctica cooled during the warm phases of the Greenland Dansgaard-Oeschger cycle and vice versa, suggesting an interhemispheric redistribution of heat through a mechanism called the bipolar seesaw. Variations in the Atlantic meridional overturning circulation (AMOC) strength are thought to have been important, but much uncertainty remains regarding the dynamics and trigger of these abrupt events. Key information is contained in the relative phasing of hemispheric climate variations, yet the large, poorly constrained difference between gas age and ice age and the relatively low resolution of methane records from Antarctic ice cores have so far precluded methane-based synchronization at the required sub-centennial precision. Here we use a recently drilled high-accumulation Antarctic ice core to show that, on average, abrupt Greenland warming leads the corresponding Antarctic cooling onset by 218 ± 92 years (2σ) for Dansgaard-Oeschger events, including the Bølling event; Greenland cooling leads the corresponding onset of Antarctic warming by 208 ± 96 years. Our results demonstrate a north-to-south directionality of the abrupt climatic signal, which is propagated to the Southern Hemisphere high latitudes by oceanic rather than atmospheric processes. The similar interpolar phasing of warming and cooling transitions suggests that the transfer time of the climatic signal is independent of the AMOC background state. Our findings confirm a central role for ocean circulation in the bipolar seesaw and provide clear criteria for assessing hypotheses and model simulations of Dansgaard-Oeschger dynamics.

  1. Investigating Flow Features Near Abrupt Topography in the Mariana Basin

    DTIC Science & Technology

    2015-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Investigating Flow Features Near Abrupt Topography in...waves generated by flow over topography and mesoscale eddies generated by flow past islands. Having identified the prime locations in the region for such

  2. Episodic Mass Loss from the Hydrogen-deficient Central Star of the Planetary Nebula Longmore 4

    NASA Astrophysics Data System (ADS)

    Bond, Howard E.

    2014-09-01

    A spectacular transient mass-loss episode from the extremely hot, hydrogen-deficient central star of the planetary nebula (PN) Longmore 4 (Lo 4) was discovered in 1992 by Werner et al. During that event, the star temporarily changed from its normal PG 1159 spectrum to that of an emission-line low-luminosity early-type Wolf-Rayet [WCE] star. After a few days, Lo 4 reverted to its normal, predominantly absorption-line PG 1159 type. To determine whether such events recur, and if so how often, I monitored the optical spectrum of Lo 4 from early 2003 to early 2012. Out of 81 spectra taken at random dates, 4 of them revealed mass-loss outbursts similar to that seen in 1992. This indicates that the episodes recur approximately every 100 days (if the recurrence rate has been approximately constant and the duration of a typical episode is ~5 days), and that the star is in a high-mass-loss state about 5% of the time. Since the enhanced stellar wind is hydrogen-deficient, it arises from the photosphere and is unlikely to be related to phenomena such as a binary or planetary companion or infalling dust. I speculate on plausible mechanisms for these unique outbursts, including the possibility that they are related to the non-radial GW Vir-type pulsations exhibited by Lo 4. The central star of the PN NGC 246 has stellar parameters similar to those of Lo 4, and it is also a GW Vir-type pulsator with similar pulsation periods. I obtained 167 spectra of NGC 246 between 2003 and 2011, but no mass ejections were found. Based on observations with the 1.5 m telescope operated by the SMARTS Consortium at Cerro Tololo Interamerican Observatory.

  3. Abrupt GaP/Si hetero-interface using bistepped Si buffer

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ping Wang, Y., E-mail: yanping.wang@insa-rennes.fr; Kuyyalil, J.; Nguyen Thanh, T.

    We evidence the influence of the quality of the starting Si surface on the III-V/Si interface abruptness and on the formation of defects during the growth of III-V/Si heterogeneous crystal, using high resolution transmission electron microscopy and scanning transmission electron microscopy. GaP layers were grown by molecular beam epitaxy on vicinal Si (001). The strong effect of the Si substrate chemical preparation is first demonstrated by studying structural properties of both Si homoepitaxial layer and GaP/Si heterostructure. It is then shown that choosing adequate chemical preparation conditions and subsequent III-V regrowth conditions enables the quasi-suppression of micro-twins in the epilayer.more » Finally, the abruptness of GaP/Si interface is found to be very sensitive to the Si chemical preparation and is improved by the use of a bistepped Si buffer prior to III-V overgrowth.« less

  4. Modelling gas dynamics in 1D ducts with abrupt area change

    NASA Astrophysics Data System (ADS)

    Menina, R.; Saurel, R.; Zereg, M.; Houas, L.

    2011-09-01

    Most gas dynamic computations in industrial ducts are done in one dimension with cross-section-averaged Euler equations. This poses a fundamental difficulty as soon as geometrical discontinuities are present. The momentum equation contains a non-conservative term involving a surface pressure integral, responsible for momentum loss. Definition of this integral is very difficult from a mathematical standpoint as the flow may contain other discontinuities (shocks, contact discontinuities). From a physical standpoint, geometrical discontinuities induce multidimensional vortices that modify the surface pressure integral. In the present paper, an improved 1D flow model is proposed. An extra energy (or entropy) equation is added to the Euler equations expressing the energy and turbulent pressure stored in the vortices generated by the abrupt area variation. The turbulent energy created by the flow-area change interaction is determined by a specific estimate of the surface pressure integral. Model's predictions are compared with 2D-averaged results from numerical solution of the Euler equations. Comparison with shock tube experiments is also presented. The new 1D-averaged model improves the conventional cross-section-averaged Euler equations and is able to reproduce the main flow features.

  5. Prepregnancy and early adulthood body mass index and adult weight change in relation to fetal loss.

    PubMed

    Gaskins, Audrey J; Rich-Edwards, Janet W; Colaci, Daniela S; Afeiche, Myriam C; Toth, Thomas L; Gillman, Matthew W; Missmer, Stacey A; Chavarro, Jorge E

    2014-10-01

    To examine prospectively the relationships of prepregnancy body mass index (BMI), BMI at age 18 years, and weight change since age 18 years with risk of fetal loss. Our prospective cohort study included 25,719 pregnancies reported by 17,027 women in the Nurses' Health Study II between 1990 and 2009. In 1989, height, current weight, and weight at age 18 years were self-reported. Current weight was updated every 2 years thereafter. Pregnancies were self-reported, with case pregnancies lost spontaneously and comparison pregnancies ending in ectopic pregnancy, induced abortion, or live birth. Incident fetal loss was reported in 4,494 (17.5%) pregnancies. Compared with those of normal BMI, the multivariate relative risks of fetal loss were 1.07 (95% CI [confidence interval] 1.00-1.15) for overweight women, 1.10 (95% CI 0.98-1.23) for class I obese women, and 1.27 (95% CI 1.11-1.45) for class II and class III obese women (P trend ≤ .001). Body mass index at age 18 years was not associated with fetal loss (P trend=.59). Compared with women who maintained a stable weight (± 4 kg) between age 18 years and before pregnancy, women who lost weight had a 20% (95% CI 9-29%) lower risk of fetal loss. This association was stronger among women who were overweight at age 18 years. Being overweight or obese before pregnancy was associated with higher risk of fetal loss. In women overweight or obese at age 18 years, losing 4 kg or more was associated with a lower risk of fetal loss. : II.

  6. Self-assembly of electronically abrupt borophene/organic lateral heterostructures

    PubMed Central

    Liu, Xiaolong; Wei, Zonghui; Balla, Itamar; Mannix, Andrew J.; Guisinger, Nathan P.; Luijten, Erik; Hersam, Mark C.

    2017-01-01

    Two-dimensional boron sheets (that is, borophene) have recently been realized experimentally and found to have promising electronic properties. Because electronic devices and systems require the integration of multiple materials with well-defined interfaces, it is of high interest to identify chemical methods for forming atomically abrupt heterostructures between borophene and electronically distinct materials. Toward this end, we demonstrate the self-assembly of lateral heterostructures between borophene and perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA). These lateral heterostructures spontaneously form upon deposition of PTCDA onto submonolayer borophene on Ag(111) substrates as a result of the higher adsorption enthalpy of PTCDA on Ag(111) and lateral hydrogen bonding among PTCDA molecules, as demonstrated by molecular dynamics simulations. In situ x-ray photoelectron spectroscopy confirms the weak chemical interaction between borophene and PTCDA, while molecular-resolution ultrahigh-vacuum scanning tunneling microscopy and spectroscopy reveal an electronically abrupt interface at the borophene/PTCDA lateral heterostructure interface. As the first demonstration of a borophene-based heterostructure, this work will inform emerging efforts to integrate borophene into nanoelectronic applications. PMID:28261662

  7. Gradual onset and recovery of the Younger Dryas abrupt climate event in the tropics.

    PubMed

    Partin, J W; Quinn, T M; Shen, C-C; Okumura, Y; Cardenas, M B; Siringan, F P; Banner, J L; Lin, K; Hu, H-M; Taylor, F W

    2015-09-02

    Proxy records of temperature from the Atlantic clearly show that the Younger Dryas was an abrupt climate change event during the last deglaciation, but records of hydroclimate are underutilized in defining the event. Here we combine a new hydroclimate record from Palawan, Philippines, in the tropical Pacific, with previously published records to highlight a difference between hydroclimate and temperature responses to the Younger Dryas. Although the onset and termination are synchronous across the records, tropical hydroclimate changes are more gradual (>100 years) than the abrupt (10-100 years) temperature changes in the northern Atlantic Ocean. The abrupt recovery of Greenland temperatures likely reflects changes in regional sea ice extent. Proxy data and transient climate model simulations support the hypothesis that freshwater forced a reduction in the Atlantic meridional overturning circulation, thereby causing the Younger Dryas. However, changes in ocean overturning may not produce the same effects globally as in Greenland.

  8. Gain control through divisive inhibition prevents abrupt transition to chaos in a neural mass model.

    PubMed

    Papasavvas, Christoforos A; Wang, Yujiang; Trevelyan, Andrew J; Kaiser, Marcus

    2015-09-01

    Experimental results suggest that there are two distinct mechanisms of inhibition in cortical neuronal networks: subtractive and divisive inhibition. They modulate the input-output function of their target neurons either by increasing the input that is needed to reach maximum output or by reducing the gain and the value of maximum output itself, respectively. However, the role of these mechanisms on the dynamics of the network is poorly understood. We introduce a novel population model and numerically investigate the influence of divisive inhibition on network dynamics. Specifically, we focus on the transitions from a state of regular oscillations to a state of chaotic dynamics via period-doubling bifurcations. The model with divisive inhibition exhibits a universal transition rate to chaos (Feigenbaum behavior). In contrast, in an equivalent model without divisive inhibition, transition rates to chaos are not bounded by the universal constant (non-Feigenbaum behavior). This non-Feigenbaum behavior, when only subtractive inhibition is present, is linked to the interaction of bifurcation curves in the parameter space. Indeed, searching the parameter space showed that such interactions are impossible when divisive inhibition is included. Therefore, divisive inhibition prevents non-Feigenbaum behavior and, consequently, any abrupt transition to chaos. The results suggest that the divisive inhibition in neuronal networks could play a crucial role in keeping the states of order and chaos well separated and in preventing the onset of pathological neural dynamics.

  9. A Study of Hypergiant Mass Loss in the Near-To-Mid Infrared: VY CMa, IRC +10420, mu Cep and rho Cas

    NASA Astrophysics Data System (ADS)

    Shenoy, Dinesh Prabhakar

    2016-01-01

    Stars of initial mass greater than 9 M_sun become red supergiants (RSGs), a short-lived stage during which they experience mass-loss that strongly influences their post-RSG evolution and end state. The highest luminosity RSGs, referred to here as hypergiants, experience episodic mass-loss whose mechanism remains poorly understood and motivates observations to help constrain it. This thesis studies mass loss from hypergiant stars with near-to-mid infrared imaging over a range of angular scales. The recent mass-loss history of the extreme red supergiant VY Canis Majoris and the warm hypergiant star IRC +10420 are studied at the sub-arcsecond scale with adaptive optics imaging and imaging polarimetry from 1 - 5 micron using LMIRCam on the Large Binocular Telescope (LBT) and MMT-Pol at the MMT Observatory. The nebular features of VY CMa are found to be highly polarized at 1.3 and 3.1 micron, with optically thick scattering required to reproduce the observed surface brightness. The flux of VY CMa's peculiar ``Southwest Clump'' is demonstrated to be due almost entirely to optically thick scattering, with little thermal emission, and with a lower limit mass of 5E-03 M_sun in this single feature. The imaging polarimetry of IRC +10420 at 2.2 micron resolves nebular emission with intrinsic polarization of 30%, with a high surface brightness indicating optically thick scattering largely in the plane of the sky. Using the polarimetry to constrain the scattered light emission, it is shown that the nebula's the emission is mostly thermal with a color temperature well above that for typical astrophysical dust. To probe further into hypergiants' history of mass-loss, mid-IR imaging with MMT/ MIRAC and SOFIA/FORCAST is used to study VY CMa, IRC +10420 and two additional hypergiants: the RSG mu Cep and the warm hypergiant rho Cas. Using DUSTY 1-D radiative transfer models, mu Cep's mass-loss rate is found to have declined by about a factor of 5 over a 13,000 history, ranging from 5E

  10. A drop in the pond: the effect of rapid mass-loss on the dynamics and interaction rate of collisionless particles

    NASA Astrophysics Data System (ADS)

    Penoyre, Zephyr; Haiman, Zoltán

    2018-01-01

    In symmetric gravitating systems experiencing rapid mass-loss, particle orbits change almost instantaneously, which can lead to the development of a sharply contoured density profile, including singular caustics for collisionless systems. This framework can be used to model a variety of dynamical systems, such as accretion discs following a massive black hole merger and dwarf galaxies following violent early star formation feedback. Particle interactions in the high-density peaks seem a promising source of observable signatures of these mass-loss events (i.e. a possible EM counterpart for black hole mergers or strong gamma-ray emission from dark matter annihilation around young galaxies), because the interaction rate depends on the square of the density. We study post-mass-loss density profiles, both analytic and numerical, in idealized cases and present arguments and methods to extend to any general system. An analytic derivation is presented for particles on Keplerian orbits responding to a drop in the central mass. We argue that this case, with initially circular orbits, gives the most sharply contoured profile possible. We find that despite the presence of a set of singular caustics, the total particle interaction rate is reduced compared to the unperturbed system; this is a result of the overall expansion of the system dominating over the steep caustics. Finally, we argue that this result holds more generally, and the loss of central mass decreases the particle interaction rate in any physical system.

  11. Flammability properties and radiant fraction of FRT wood plastic composites using mass loss calorimeter under HRR hood

    Treesearch

    Mark A. Dietenberger; Charles R. Boardman; Nicole Stark

    2017-01-01

    A special test arrangement was used to assess the flammability of 4 different wood plastic composites (WPC), most with fire retardants, all of which has a tendency to high smoke production leading to high radiant energy losses to the apparatus walls. The mass loss calorimeter (MLC) was modified to include a thermopile on the exhaust pipe stack to compensate for radiant...

  12. The Partition Between Terminal Speed and Mass Loss: Thin, Thick, and Rotating Line-Driven Winds

    NASA Astrophysics Data System (ADS)

    Gayley, K. G.; Onifer, A. J.

    2003-01-01

    Steady-state supersonic line-driven winds are important contributors to wind-blown bubbles in star forming regions. The key input to the bubble in the energy-conserving phase is the wind kinetic-energy flux, which involves both the mass-loss rate and the terminal speed. However, these quantities are themselves self-consistent parameters of the line-driving process, so relate to each other and to the resulting wind optical depth. This complex interrelation between optical depth, mass-loss, and wind speed lies at the heart of line-driven wind theory. Drawing on the successes and insights of ``CAK'' theory, I will convey a simplified view of how to unite these processes using the concept of effective opacity, with attention to the ramifications for nonspherical nebular and wind-blown structures. Recent extensions to nongray optically thick environments such as Wolf-Rayet winds and supernovae are also discussed.

  13. Precise interpolar phasing of abrupt climate change during the last ice age

    USGS Publications Warehouse

    ,; Buizert, Christo; Adrian, Betty M.; Ahn, Jinho; Albert, Mary; Alley, Richard B.; Baggenstos, Daniel; Bauska, Thomas K.; Bay, Ryan C.; Bencivengo, Brian B.; Bentley, Charles R.; Brook, Edward J.; Chellman, Nathan J.; Clow, Gary D.; Cole-Dai, Jihong; Conway, Howard; Cravens, Eric; Cuffey, Kurt M.; Dunbar, Nelia W.; Edwards, Jon S.; Fegyveresi, John M.; Ferris, Dave G.; Fitzpatrick, Joan J.; Fudge, T. J.; Gibson, Chris J.; Gkinis, Vasileios; Goetz, Joshua J.; Gregory, Stephanie; Hargreaves, Geoffrey Mill; Iverson, Nels; Johnson, Jay A.; Jones, Tyler R.; Kalk, Michael L.; Kippenhan, Matthew J.; Koffman, Bess G.; Kreutz, Karl; Kuhl, Tanner W.; Lebar, Donald A.; Lee, James E.; Marcott, Shaun A.; Markle, Bradley R.; Maselli, Olivia J.; McConnell, Joseph R.; McGwire, Kenneth C.; Mitchell, Logan E.; Mortensen, Nicolai B.; Neff, Peter D.; Nishiizumi, Kunihiko; Nunn, Richard M.; Orsi, Anais J.; Pasteris, Daniel R.; Pedro, Joel B.; Pettit, Erin C.; Price, P. Buford; Priscu, John C.; Rhodes, Rachael H.; Rosen, Julia L.; Schauer, Andrew J.; Schoenemann, Spruce W.; Sendelbach, Paul J.; Severinghaus, Jeffrey P.; Shturmakov, Alexander J.; Sigl, Michael; Slawny, Kristina R.; Souney, Joseph M.; Sowers, Todd A.; Spencer, Matthew K.; Steig, Eric J.; Taylor, Kendrick C.; Twickler, Mark S.; Vaughn, Bruce H.; Voigt, Donald E.; Waddington, Edwin D.; Welten, Kees C.; Wendricks, Anthony W.; White, James W. C.; Winstrup, Mai; Wong, Gifford J.; Woodruff, Thomas E.

    2015-01-01

    The last glacial period exhibited abrupt Dansgaard–Oeschger climatic oscillations, evidence of which is preserved in a variety of Northern Hemisphere palaeoclimate archives1. Ice cores show that Antarctica cooled during the warm phases of the Greenland Dansgaard–Oeschger cycle and vice versa2, 3, suggesting an interhemispheric redistribution of heat through a mechanism called the bipolar seesaw4, 5, 6. Variations in the Atlantic meridional overturning circulation (AMOC) strength are thought to have been important, but much uncertainty remains regarding the dynamics and trigger of these abrupt events7, 8, 9. Key information is contained in the relative phasing of hemispheric climate variations, yet the large, poorly constrained difference between gas age and ice age and the relatively low resolution of methane records from Antarctic ice cores have so far precluded methane-based synchronization at the required sub-centennial precision2, 3,10. Here we use a recently drilled high-accumulation Antarctic ice core to show that, on average, abrupt Greenland warming leads the corresponding Antarctic cooling onset by 218 ± 92 years (2σ) for Dansgaard–Oeschger events, including the Bølling event; Greenland cooling leads the corresponding onset of Antarctic warming by 208 ± 96 years. Our results demonstrate a north-to-south directionality of the abrupt climatic signal, which is propagated to the Southern Hemisphere high latitudes by oceanic rather than atmospheric processes. The similar interpolar phasing of warming and cooling transitions suggests that the transfer time of the climatic signal is independent of the AMOC background state. Our findings confirm a central role for ocean circulation in the bipolar seesaw and provide clear criteria for assessing hypotheses and model simulations of Dansgaard–Oeschger dynamics.

  14. Ge-on-insulator tunneling FET with abrupt source junction formed by utilizing snowplow effect of NiGe

    NASA Astrophysics Data System (ADS)

    Matsumura, Ryo; Katoh, Takumi; Takaguchi, Ryotaro; Takenaka, Mitsuru; Takagi, Shinichi

    2018-04-01

    Tunneling field-effect transistors (TFETs) attract much attention for use in realizing next-generation low-power processors. In particular, Ge-on-insulator (GOI) TFETs are expected to realize low power operation with a high on-current/off-current (I on/I off) ratio, owing to their narrow bandgap. Here, to improve the performance of GOI-TFETs, a source junction with a high doping concentration and an abrupt impurity profile is essential. In this study, a snowplow effect of NiGe combined with low-energy BF2 + implantation has been investigated to realize an abrupt p+/n Ge junction for GOI n-channel TFETs. By optimizing the Ni thickness to form NiGe (thickness: 4 nm), an abrupt junction with a B profile abruptness of ˜5 nm/dec has been realized with a high doping concentration of around 1021 cm-3. The operation of GOI n-TFETs with this source junction having the abrupt B profile has been demonstrated, and the improvement of TFET properties such as the I on/I off ratio from 311 to 743 and the subthreshold slope from 368 to 239 mV/dec has been observed. This junction formation technology is attractive for enhancing the TFET performance.

  15. Involvement of human decidual cell-expressed tissue factor in uterine hemostasis and abruption.

    PubMed

    Lockwood, C J; Paidas, M; Murk, W K; Kayisli, U A; Gopinath, A; Huang, S J; Krikun, G; Schatz, F

    2009-11-01

    Vascular injury increases access and binding of plasma-derived factor VII to perivascular cell membrane-bound tissue factor (TF). The resulting TF/VIIa complex promotes hemostasis by cleaving pro-thrombin to thrombin leading to the fibrin clot. In human pregnancy, decidual cell-expressed TF prevents decidual hemorrhage (abruption). During placentation, trophoblasts remodel decidual spiral arteries into high conductance vessels. Shallow trophoblast invasion impedes decidual vascular conversion, producing an inadequate uteroplacental blood flow that elicits abruption-related placental ischemia. Thrombin induces several biological effects via cell surface protease activated receptors. In first trimester human DCs thrombin increases synthesis of sFlt-1, which elicits placental ischemia by impeding angiogenesis-related decidual vascular remodeling. During pregnacy, the fibrillar collagen-rich amnion and choriodecidua extracellular matrix (ECM) provides greater than additive tensile strength and structural integrity. Thrombin acts as an autocrine/paracrine mediator that degrades these ECMs by augmenting decidual cell expression of: 1) matrix metalloproteinases and 2) interleukin-8, a key mediator of abruption-associated decidual infiltration of neutrophils, which express several ECM degrading proteases. Among the cell types at the maternal fetal interface at term, TF expression is highest in decidual cells indicating that this TF meets the hemostatic demands of labor and delivery. TF expression in cultured term decidual cells is enhanced by progestin and thrombin suggesting that the maintenance of elevated circulating progesterone provides hemostatic protection and that abruption-generated thrombin acts in an autocrine/paracrine fashion on decidual cells to promote hemostasis via enhanced TF expression.

  16. Involvement of human decidual cell-expressed tissue factor in uterine hemostasis and abruption

    PubMed Central

    Lockwood, C.J.; Paidas, M.; Murk, W.K.; Kayisli, U.A.; Gopinath, A.; Krikun, G.; Huang, S.J.; Schatz, F.

    2009-01-01

    Vascular injury increases access and binding of plasma-derived factor VII to perivascular cell membrane-bound tissue factor (TF). The resulting TF/VIIa complex promotes hemostasis by cleaving pro-thrombin to thrombin leading to the fibrin clot. In human pregnancy, decidual cell-expressed TF prevents decidual hemorrhage (abruption). During placentation, trophoblasts remodel decidual spiral arteries into high conductance vessels. Shallow trophoblast invasion impedes decidual vascular conversion, producing an inadequate uteroplacental blood flow that elicits abruption-related placental ischemia. Thrombin induces several biological effects via cell surface protease activated receptors. In first trimester human DCs thrombin increases synthesis of sFlt-1, which elicits placental ischemia by impeding angiogenesis-related decidual vascular remodeling. During pregnacy, the fibrillar collagen-rich amnion and choriodecidua extracellular matrix (ECM) provides greater than additive tensile strength and structural integrity. Thrombin acts as an autocrine/paracrine mediator that degrades these ECMs by augmenting decidual cell expression of: 1) matrix metalloproteinases and 2) interleukin-8, a key mediator of abruption-associated decidual infiltration of neutrophils, which express several ECM degrading proteases. Our recent observations that: 1) among the cell types at the maternal fetal interface at term TF expression is highest in decidual cells indicates that this TF meets the hemostatic demands of labor and delivery; 2) TF expression in cultured term decidual cells is enhanced by progestin and thrombin suggest that maintenance of elevated circulating progesterone at term provides hemostatic protection, whereas abruption-generated thrombin can act in autocrine/paracrine fashion on DCs to promote hemostasis via enhanced TF expression. PMID:19720393

  17. ALMA observations of anisotropic dust mass loss in the inner circumstellar environment of the red supergiant VY Canis Majoris

    NASA Astrophysics Data System (ADS)

    O'Gorman, E.; Vlemmings, W.; Richards, A. M. S.; Baudry, A.; De Beck, E.; Decin, L.; Harper, G. M.; Humphreys, E. M.; Kervella, P.; Khouri, T.; Muller, S.

    2015-01-01

    The processes leading to dust formation and the subsequent role it plays in driving mass loss in cool evolved stars is an area of intense study. Here we present high resolution ALMA Science Verification data of the continuum emission around the highly evolved oxygen-rich red supergiant VY CMa. These data enable us to study the dust in its inner circumstellar environment at a spatial resolution of 129 mas at 321 GHz and 59 mas at 658 GHz, thus allowing us to trace dust on spatial scales down to 11 R⋆ (71 AU). Two prominent dust components are detected and resolved. The brightest dust component, C, is located 334 mas (61 R⋆) southeast of the star and has a dust mass of at least 2.5 × 10-4 M⊙. It has a dust emissivity spectral index of β = -0.1 at its peak, implying that it is optically thick at these frequencies with a cool core of Td ≲ 100 K. Interestingly, not a single molecule in the ALMA data has emission close to the peak of this massive dust clump. The other main dust component, VY, is located at the position of the star and contains a total dust mass of 4.0 × 10-5 M⊙. It also contains a weaker dust feature extending over 60 R⋆ to the north with the total component having a typical dust emissivity spectral index of β = 0.7. We find that at least 17% of the dust mass around VY CMa is located in clumps ejected within a more quiescent roughly spherical stellar wind, with a quiescent dust mass loss rate of 5 × 10-6 M⊙yr-1. The anisotropic morphology of the dust indicates a continuous, directed mass loss over a few decades, suggesting that this mass loss cannot be driven by large convection cells alone. Appendices are available in electronic form at http://www.aanda.org

  18. Analysis of non-enzymatically glycated peptides: neutral-loss-triggered MS3 versus multi-stage activation tandem mass spectrometry

    PubMed Central

    Zhang, Qibin; Petyuk, Vladislav A.; Schepmoes, Athena A.; Orton, Daniel J.; Monroe, Matthew E.; Yang, Feng; Smith, Richard D.; Metz, Thomas O.

    2009-01-01

    Non-enzymatic glycation of tissue proteins has important implications in the development of complications of diabetes mellitus. While electron transfer dissociation (ETD) has been shown to outperform collision-induced dissociation (CID) in sequencing glycated peptides by tandem mass spectrometry, ETD instrumentation is not yet widely available and often suffers from significantly lower sensitivity than CID. In this study, we evaluated different advanced CID techniques (i.e., neutral-loss-triggered MS3 and multi-stage activation) during liquid chromatography/multi-stage mass spectrometric (LC/MSn) analyses of Amadori-modified peptides enriched from human serum glycated in vitro. During neutral-loss-triggered MS3 experiments, MS3 scans triggered by neutral losses of 3 H2O or 3 H2O + HCHO produced similar results in terms of glycated peptide identifications. However, neutral losses of 3 H2O resulted in significantly more glycated peptide identifications during multi-stage activation experiments. Overall, the multi-stage activation approach produced more glycated peptide identifications, while the neutral-loss-triggered MS3 approach resulted in much higher specificity. Both techniques are viable alternatives to ETD for identifying glycated peptides. PMID:18763275

  19. Abrupt climate warming in East Antarctica during the early Holocene

    NASA Astrophysics Data System (ADS)

    Cremer, Holger; Heiri, Oliver; Wagner, Bernd; Wagner-Cremer, Friederike

    2007-08-01

    We report a centennial-scale warming event between 8600 and 8400 cal BP from Amery Oasis, East Antarctica, that is documented by the geochemical record in a lacustrine sediment sequence. The organic carbon content, the C/S ratio, and the sedimentation rate in this core have distinctly elevated values around 8500 y ago reflecting relatively warm and ice-free conditions that led to well-ventilated conditions in the lake and considerable sedimentation of both autochthonous and allochthonous organic matter on the lake bottom. This abrupt warming event occurred concurrently with reported warm climatic conditions in the Southern Ocean while the climate in central East Antarctic remained cold. The comparison of the spatial and temporal variability of warm climatic periods documented in various terrestrial, marine, and glacial archives from East Antarctica elucidates the uniqueness of the centennial-scale warming event in the Amery Oasis. We also discuss a possible correlation of the Amery warming event with the abrupt climatic deterioration around 8200 cal BP on the Northern Hemisphere.

  20. The abrupt onset of the modern South Asian Monsoon winds.

    PubMed

    Betzler, Christian; Eberli, Gregor P; Kroon, Dick; Wright, James D; Swart, Peter K; Nath, Bejugam Nagender; Alvarez-Zarikian, Carlos A; Alonso-García, Montserrat; Bialik, Or M; Blättler, Clara L; Guo, Junhua Adam; Haffen, Sébastien; Horozal, Senay; Inoue, Mayuri; Jovane, Luigi; Lanci, Luca; Laya, Juan Carlos; Mee, Anna Ling Hui; Lüdmann, Thomas; Nakakuni, Masatoshi; Niino, Kaoru; Petruny, Loren M; Pratiwi, Santi D; Reijmer, John J G; Reolid, Jesús; Slagle, Angela L; Sloss, Craig R; Su, Xiang; Yao, Zhengquan; Young, Jeremy R

    2016-07-20

    The South Asian Monson (SAM) is one of the most intense climatic elements yet its initiation and variations are not well established. Dating the deposits of SAM wind-driven currents in IODP cores from the Maldives yields an age of 12. 9 Ma indicating an abrupt SAM onset, over a short period of 300 kyrs. This coincided with the Indian Ocean Oxygen Minimum Zone expansion as revealed by geochemical tracers and the onset of upwelling reflected by the sediment's content of particulate organic matter. A weaker 'proto-monsoon' existed between 12.9 and 25 Ma, as mirrored by the sedimentary signature of dust influx. Abrupt SAM initiation favors a strong influence of climate in addition to the tectonic control, and we propose that the post Miocene Climate Optimum cooling, together with increased continentalization and establishment of the bipolar ocean circulation, i.e. the beginning of the modern world, shifted the monsoon over a threshold towards the modern system.

  1. Additivity of abrupt onset effects supports nonspatial distraction, not the capture of spatial attention.

    PubMed

    Folk, Charles L; Remington, Roger W; Wu, Shu-Chieh

    2009-02-01

    In a recent article, Schreij, Owens, and Theeuwes (2008) reported that abruptly onsetting distractors produce costs in performance even when spatial-cuing effects confirm the presence of a top-down set for color. The authors argued that these results show that abruptly onsetting new objects capture attention independent of a top-down set and, thus, provide conclusive evidence against the theory that attentional capture is contingent on top-down attentional control settings (Folk, Remington, & Johnston, 1992). In the following article, we argue that, contrary to the conclusion drawn by Schreij et al., their own data (1) disconfirm the claim that their abrupt onsets captured spatial attention and (2) are consistent with nonspatial interference accounts of singleton-distractor effects. In support of the nonspatial account, we show that in a paradigm similar to Schreij et al.'s, distractors that do not capture attention can nonetheless influence responses to a target. We conclude that the results of Schreij et al. do not represent a challenge to contingent capture theory.

  2. Predictors of fat-free mass loss 1 year after laparoscopic sleeve gastrectomy.

    PubMed

    Guida, B; Cataldi, M; Busetto, L; Aiello, M L; Musella, M; Capone, D; Parolisi, S; Policastro, V; Ragozini, G; Belfiore, A

    2018-03-24

    Laparoscopic sleeve gastrectomy (LSG) is one of the most frequently performed bariatric surgery interventions because of its safety and efficacy. Nevertheless, concerns have been raised on its detrimental effect on patient nutritional state that can ultimately lead to the loss of fat-free mass (FFM). There is interest in identifying predictors for the early identification of patients at risk of this highly unwanted adverse because they could benefit of nutritional preventive interventions. Therefore, we investigated whether anthropometric parameters, body composition or resting energy expenditure (REE) measured before surgery could predict FFM loss 1 year after LSG. Study design was retrospective observational. We retrieved data on body weight, BMI, body composition and REE before and 1 year after LSG from the medical files of 36 patients operated on by LSG at our institutions. Simple regression, the Oldham's method and multilevel analysis were used to identify predictors of FFM loss. Averaged percentage FFM loss 1 year after LSG was 17.0 ± 7.7% with significant differences between sexes (20.8 ± 6.6 in males and 12.2 ± 6.1% in females, p < 0.001). FFM loss was strongly predicted by pre-surgery FFM and this effect persisted also after correcting for the contribution of sex. High FFM values before surgery predict a more severe FFM loss after LSG. This factor could also account for the higher FFM loss in men than in women. Our finding could help in the early identification of patient requiring a nutritional support after LSG.

  3. Recent high-resolution Antarctic ice velocity maps reveal increased mass loss in Wilkes Land, East Antarctica.

    PubMed

    Shen, Qiang; Wang, Hansheng; Shum, C K; Jiang, Liming; Hsu, Hou Tse; Dong, Jinglong

    2018-03-14

    We constructed Antarctic ice velocity maps from Landsat 8 images for the years 2014 and 2015 at a high spatial resolution (100 m). These maps were assembled from 10,690 scenes of displacement vectors inferred from more than 10,000 optical images acquired from December 2013 through March 2016. We estimated the mass discharge of the Antarctic ice sheet in 2008, 2014, and 2015 using the Landsat ice velocity maps, interferometric synthetic aperture radar (InSAR)-derived ice velocity maps (~2008) available from prior studies, and ice thickness data. An increased mass discharge (53 ± 14 Gt yr -1 ) was found in the East Indian Ocean sector since 2008 due to unexpected widespread glacial acceleration in Wilkes Land, East Antarctica, while the other five oceanic sectors did not exhibit significant changes. However, present-day increased mass loss was found by previous studies predominantly in west Antarctica and the Antarctic Peninsula. The newly discovered increased mass loss in Wilkes Land suggests that the ocean heat flux may already be influencing ice dynamics in the marine-based sector of the East Antarctic ice sheet (EAIS). The marine-based sector could be adversely impacted by ongoing warming in the Southern Ocean, and this process may be conducive to destabilization.

  4. Investigation of the effects of shear on arc-electrode erosion using a modified arc-electrode mass loss model

    NASA Astrophysics Data System (ADS)

    Webb, Bryan T.

    The electrodes are the attachment points for an electric arc where electrons and positive ions enter and leave the gas, creating a flow of current. Electrons enter the gas at the cathode and are removed at the anode. Electrons then flow out through the leads on the anode and are replenished from the power supply through the leads on the cathode. Electric arc attachment to the electrode surface causes intensive heating and subsequent melting and vaporization. At that point a multitude of factors can contribute to mass loss, to include vaporization (boiling), material removal via shear forces, chemical reactions, evaporation, and ejection of material in jets due to pressure effects. If these factors were more thoroughly understood and could be modeled, this knowledge would guide the development of an electrode design with minimal erosion. An analytic model was developed by a previous researcher that models mass loss by melting, evaporation and boiling with a moving arc attachment point. This pseudo one-dimensional model includes surface heat flux in periodic cycles of heating and cooling to model motion of a spinning arc in an annular electrode where the arc periodically returns to the same spot. This model, however, does not account for removal of material due to shear or pressure induced effects, or the effects of chemical reactions. As a result of this, the model under-predicts material removal by about 50%. High velocity air flowing over an electrode will result in a shear force which has the potential to remove molten material as the arc melts the surface on its path around the electrode. In order to study the effects of shear on mass loss rate, the model from this previous investigator has been altered to include this mass loss mechanism. The results of this study have shown that shear is a viable mechanism for mass loss in electrodes and can account for the mismatch between theoretical and experimental rates determined by previous investigators. The results of

  5. Method for the elucidation of the elemental composition of low molecular mass chemicals using exact masses of product ions and neutral losses: application to environmental chemicals measured by liquid chromatography with hybrid quadrupole/time-of-flight mass spectrometry.

    PubMed

    Suzuki, Shigeru; Ishii, Tetsuko; Yasuhara, Akio; Sakai, Shinichi

    2005-01-01

    A method for elucidating the elemental compositions of low molecular weight chemicals, based primarily on mass measurements made using liquid chromatography (LC) with time-of-flight mass spectrometry (TOFMS) and quadrupole/time-of-flight mass spectrometry (LC/QTOFMS), was developed and tested for 113 chemicals of environmental interest with molecular masses up to approximately 400 Da. As the algorithm incorporating the method is not affected by differences in the instrument used, or by the ionization method and other ionization conditions, the method is useful not only for LC/TOFMS, but also for all kinds of mass spectra measured with higher accuracy and precision (uncertainties of a few mDa) employing all ionization methods and on-line separation techniques. The method involves calculating candidate compositions for intact ionized molecules (ionized forms of the sample molecule that have lost or gained no more than a proton, i.e., [M+H](+) or [M-H](-)) as well as for fragment ions and corresponding neutral losses, and eliminating those atomic compositions for the molecules that are inconsistent with the corresponding candidate compositions of fragment ions and neutral losses. Candidate compositions were calculated for the measured masses of the intact ionized molecules and of the fragment ions and corresponding neutral losses, using mass uncertainties of 2 and 5 mDa, respectively. Compositions proposed for the ionized molecule that did not correspond to the sum of the compositions of a candidate fragment ion and its corresponding neutral loss were discarded. One, 2-5, 6-10, 11-20, and >20 candidate compositions were found for 65%, 39%, 1%, 1%, and 0%, respectively, for the 124 ionized molecules formed from the 113 chemicals tested (both positive and negative ions were obtained from 11 of the chemicals). However, no candidate composition was found for 2% of the test cases (i.e., 3 chemicals), for each of which the measured mass of one of the product ions was in

  6. Constraints on continental crustal mass loss via chemical weathering using lithium and its isotopes

    NASA Astrophysics Data System (ADS)

    Rudnick, R. L.; Liu, X. M.

    2012-04-01

    The continental crust has an "intermediate" bulk composition that is distinct from primary melts of peridotitic mantle (basalt or picrite). This mismatch between the "building blocks" and the "edifice" that is the continental crust points to the operation of processes that preferentially remove mafic to ultramafic material from the continents. Such processes include lower crustal recycling (via density foundering or lower crustal subduction - e.g., relamination, Hacker et al., 2011, EPSL), generation of evolved melts via slab melting, and/or chemical weathering. Stable isotope systems point to the influence of chemical weathering on the bulk crust composition: the oxygen isotope composition of the bulk crust is distinctly heavier than that of primary, mantle-derived melts (Simon and Lecuyer, 2005, G-cubed) and the Li isotopic composition of the bulk crust is distinctly lighter than that of mantle-derive melts (Teng et al., 2004, GCA; 2008, Chem. Geol.). Both signatures mark the imprint of chemical weathering on the bulk crust composition. Here, we use a simple mass balance model for lithium inputs and outputs from the continental crust to quantify the mass lost due to chemical weathering. We find that a minimum of 15%, a maximum of 60%, and a best estimate of ~40% of the original juvenile rock mass may have been lost via chemical weathering. The accumulated percentage of mass loss due to chemical weathering leads to an average global chemical weathering rate (CWR) of ~ 1×10^10 to 2×10^10 t/yr since 3.5 Ga, which is about an order of magnitude higher than the minimum estimates based on modern rivers (Gaillardet et al., 1999, Chem. Geol.). While we cannot constrain the exact portion of crustal mass loss via chemical weathering, given the uncertainties of the calculation, we can demonstrate that the weathering flux is non-zero. Therefore, chemical weathering must play a role in the evolution of the composition and mass of the continental crust.

  7. Gain control through divisive inhibition prevents abrupt transition to chaos in a neural mass model

    PubMed Central

    Papasavvas, Christoforos A.; Wang, Yujiang; Trevelyan, Andrew J.; Kaiser, Marcus

    2016-01-01

    Experimental results suggest that there are two distinct mechanisms of inhibition in cortical neuronal networks: subtractive and divisive inhibition. They modulate the input-output function of their target neurons either by increasing the input that is needed to reach maximum output or by reducing the gain and the value of maximum output itself, respectively. However, the role of these mechanisms on the dynamics of the network is poorly understood. We introduce a novel population model and numerically investigate the influence of divisive inhibition on network dynamics. Specifically, we focus on the transitions from a state of regular oscillations to a state of chaotic dynamics via period-doubling bifurcations. The model with divisive inhibition exhibits a universal transition rate to chaos (Feigenbaum behavior). In contrast, in an equivalent model without divisive inhibition, transition rates to chaos are not bounded by the universal constant (non-Feigenbaum behavior). This non-Feigenbaum behavior, when only subtractive inhibition is present, is linked to the interaction of bifurcation curves in the parameter space. Indeed, searching the parameter space showed that such interactions are impossible when divisive inhibition is included. Therefore, divisive inhibition prevents non-Feigenbaum behavior and, consequently, any abrupt transition to chaos. The results suggest that the divisive inhibition in neuronal networks could play a crucial role in keeping the states of order and chaos well separated and in preventing the onset of pathological neural dynamics. PMID:26465514

  8. Extensive wildfires, climate change, and an abrupt state change in subalpine ribbon forests, Colorado.

    PubMed

    Calder, W John; Shuman, Bryan

    2017-10-01

    Ecosystems may shift abruptly when the effects of climate change and disturbance interact, and landscapes with regularly patterned vegetation may be especially vulnerable to abrupt shifts. Here we use a fossil pollen record from a regularly patterned ribbon forest (alternating bands of forests and meadows) in Colorado to examine whether past changes in wildfire and climate produced abrupt vegetation shifts. Comparing the percentages of conifer pollen with sedimentary δ 18 O data (interpreted as an indicator of temperature or snow accumulation) indicates a first-order linear relationship between vegetation composition and climate change with no detectable lags over the past 2,500 yr (r = 0.55, P < 0.001). Additionally, however, we find that the vegetation changed abruptly within a century of extensive wildfires, which were recognized in a previous study to have burned approximately 80% of the surrounding 1,000 km 2 landscape 1,000 yr ago when temperatures rose ~0.5°C. The vegetation change was larger than expected from the effects of climate change alone. Pollen assemblages changed from a composition associated with closed subalpine forests to one similar to modern ribbon forests. Fossil pollen assemblages then remained like those from modern ribbon forests for the following ~1,000 yr, providing a clear example of how extensive disturbances can trigger persistent new vegetation states and alter how vegetation responds to climate. © 2017 by the Ecological Society of America.

  9. Asymptotically simple spacetimes and mass loss due to gravitational waves

    NASA Astrophysics Data System (ADS)

    Saw, Vee-Liem

    The cosmological constant Λ used to be a freedom in Einstein’s theory of general relativity (GR), where one had a proclivity to set it to zero purely for convenience. The signs of Λ or Λ being zero would describe universes with different properties. For instance, the conformal structure of spacetime directly depends on Λ: null infinity ℐ is a spacelike, null, or timelike hypersurface, if Λ > 0, Λ = 0, or Λ < 0, respectively. Recent observations of distant supernovae have taught us that our universe expands at an accelerated rate, and this can be accounted for by choosing Λ > 0 in Einstein’s theory of GR. A quantity that depends on the conformal structure of spacetime, especially on the nature of ℐ, is the Bondi mass which in turn dictates the mass loss of an isolated gravitating system due to energy carried away by gravitational waves. This problem of extending the Bondi mass to a universe with Λ > 0 has spawned intense research activity over the past several years. Some aspects include a closer inspection on the conformal properties, working with linearization, attempts using a Hamiltonian formulation based on “linearized” asymptotic symmetries, as well as obtaining the general asymptotic solutions of de Sitter-like spacetimes. We consolidate on the progress thus far from the various approaches that have been undertaken, as well as discuss the current open problems and possible directions in this area.

  10. High-Resolution, Long-Slit Spectroscopy of VY Canis Majoris: The Evidence for Localized High Mass Loss Events

    NASA Astrophysics Data System (ADS)

    Humphreys, Roberta M.; Davidson, Kris; Ruch, Gerald; Wallerstein, George

    2005-01-01

    High spatial and spectral resolution spectroscopy of the OH/IR supergiant VY CMa and its circumstellar ejecta reveals evidence for high mass loss events from localized regions on the star occurring over the past 1000 yr. The reflected absorption lines and the extremely strong K I emission lines show a complex pattern of velocities in the ejecta. We show that the large, dusty northwest arc, expanding at ~50 km s-1 with respect to the embedded star, is kinematically distinct from the surrounding nebulosity and was ejected about 400 yr ago. Other large, more filamentary loops were probably expelled as much as 800-1000 yr ago, whereas knots and small arcs close to the star resulted from more recent events 100-200 yr ago. The more diffuse, uniformly distributed gas and dust is surprisingly stationary, with little or no velocity relative to the star. This is not what we would expect for the circumstellar material from an evolved red supergiant with a long history of mass loss. We therefore suggest that the high mass loss rate for VY CMa is a measure of the mass carried out by these specific ejections accompanied by streams or flows of gas through low-density regions in the dust envelope. VY CMa may thus be our most extreme example of stellar activity, but our results also bring into question the evolutionary state of this famous star. In a separate appendix, we discuss the origin of the very strong K I and other rare emission lines in its spectrum.

  11. On the deuterium abundance and the importance of stellar mass loss in the interstellar and intergalactic medium

    NASA Astrophysics Data System (ADS)

    van de Voort, Freeke; Quataert, Eliot; Faucher-Giguère, Claude-André; Kereš, Dušan; Hopkins, Philip F.; Chan, T. K.; Feldmann, Robert; Hafen, Zachary

    2018-06-01

    We quantify the gas-phase abundance of deuterium and fractional contribution of stellar mass loss to the gas in cosmological zoom-in simulations from the Feedback In Realistic Environments project. At low metallicity, our simulations confirm that the deuterium abundance is very close to the primordial value. The chemical evolution of the deuterium abundance that we derive here agrees quantitatively with analytical chemical evolution models. We furthermore find that the relation between the deuterium and oxygen abundance exhibits very little scatter. We compare our simulations to existing high-redshift observations in order to determine a primordial deuterium fraction of (2.549 ± 0.033) × 10-5 and stress that future observations at higher metallicity can also be used to constrain this value. At fixed metallicity, the deuterium fraction decreases slightly with decreasing redshift, due to the increased importance of mass-loss from intermediate-mass stars. We find that the evolution of the average deuterium fraction in a galaxy correlates with its star formation history. Our simulations are consistent with observations of the Milky Way's interstellar medium (ISM): the deuterium fraction at the solar circle is 85-92 per cent of the primordial deuterium fraction. We use our simulations to make predictions for future observations. In particular, the deuterium abundance is lower at smaller galactocentric radii and in higher mass galaxies, showing that stellar mass loss is more important for fuelling star formation in these regimes (and can even dominate). Gas accreting on to galaxies has a deuterium fraction above that of the galaxies' ISM, but below the primordial fraction, because it is a mix of gas accreting from the intergalactic medium and gas previously ejected or stripped from galaxies.

  12. The problem of latent attentional capture: Easy visual search conceals capture by task-irrelevant abrupt onsets.

    PubMed

    Gaspelin, Nicholas; Ruthruff, Eric; Lien, Mei-Ching

    2016-08-01

    Researchers are sharply divided regarding whether irrelevant abrupt onsets capture spatial attention. Numerous studies report that they do and a roughly equal number report that they do not. This puzzle has inspired numerous attempts at reconciliation, none gaining general acceptance. The authors propose that abrupt onsets routinely capture attention, but the size of observed capture effects depends critically on how long attention dwells on distractor items which, in turn, depends critically on search difficulty. In a series of spatial cuing experiments, the authors show that irrelevant abrupt onsets produce robust capture effects when visual search is difficult, but not when search is easy. Critically, this effect occurs even when search difficulty varies randomly across trials, preventing any strategic adjustments of the attentional set that could modulate probability of capture by the onset cue. The authors argue that easy visual search provides an insensitive test for stimulus-driven capture by abrupt onsets: even though onsets truly capture attention, the effects of capture can be latent. This observation helps to explain previous failures to find capture by onsets, nearly all of which used an easy visual search. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

  13. The Problem of Latent Attentional Capture: Easy Visual Search Conceals Capture by Task-Irrelevant Abrupt Onsets

    PubMed Central

    Gaspelin, Nicholas; Ruthruff, Eric; Lien, Mei-Ching

    2016-01-01

    Researchers are sharply divided regarding whether irrelevant abrupt onsets capture spatial attention. Numerous studies report that they do and a roughly equal number report that they do not. This puzzle has inspired numerous attempts at reconciliation, none gaining general acceptance. We propose that abrupt onsets routinely capture attention, but the size of observed capture effects depends critically on how long attention dwells on distractor items which, in turn, depends critically on search difficulty. In a series of spatial cuing experiments, we show that irrelevant abrupt onsets produce robust capture effects when visual search is difficult, but not when search is easy. Critically, this effect occurs even when search difficulty varies randomly across trials, preventing any strategic adjustments of the attentional set that could modulate probability of capture by the onset cue. We argue that easy visual search provides an insensitive test for stimulus-driven capture by abrupt onsets: even though onsets truly capture attention, the effects of capture can be latent. This observation helps to explain previous failures to find capture by onsets, nearly all of which employed an easy visual search. PMID:26854530

  14. Abrupt strategy change underlies gradual performance change: Bayesian hierarchical models of component and aggregate strategy use.

    PubMed

    Wynton, Sarah K A; Anglim, Jeromy

    2017-10-01

    While researchers have often sought to understand the learning curve in terms of multiple component processes, few studies have measured and mathematically modeled these processes on a complex task. In particular, there remains a need to reconcile how abrupt changes in strategy use can co-occur with gradual changes in task completion time. Thus, the current study aimed to assess the degree to which strategy change was abrupt or gradual, and whether strategy aggregation could partially explain gradual performance change. It also aimed to show how Bayesian methods could be used to model the effect of practice on strategy use. To achieve these aims, 162 participants completed 15 blocks of practice on a complex computer-based task-the Wynton-Anglim booking (WAB) task. The task allowed for multiple component strategies (i.e., memory retrieval, information reduction, and insight) that could also be aggregated to a global measure of strategy use. Bayesian hierarchical models were used to compare abrupt and gradual functions of component and aggregate strategy use. Task completion time was well-modeled by a power function, and global strategy use explained substantial variance in performance. Change in component strategy use tended to be abrupt, whereas change in global strategy use was gradual and well-modeled by a power function. Thus, differential timing of component strategy shifts leads to gradual changes in overall strategy efficiency, and this provides one reason for why smooth learning curves can co-occur with abrupt changes in strategy use. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  15. Revealing Abrupt and Spontaneous Ruptures of Protein Native Structure under picoNewton Compressive Force Manipulation.

    PubMed

    Chowdhury, S Roy; Cao, Jin; He, Yufan; Lu, H Peter

    2018-03-27

    Manipulating protein conformations for exploring protein structure-function relationship has shown great promise. Although protein conformational changes under pulling force manipulation have been extensively studied, protein conformation changes under a compressive force have not been explored quantitatively. The latter is even more biologically significant and relevant in revealing protein functions in living cells associated with protein crowdedness, distribution fluctuations, and cell osmotic stress. Here we report our experimental observations on abrupt ruptures of protein native structures under compressive force, demonstrated and studied by single-molecule AFM-FRET spectroscopic nanoscopy. Our results show that the protein ruptures are abrupt and spontaneous events occurred when the compressive force reaches a threshold of 12-75 pN, a force amplitude accessible from thermal fluctuations in a living cell. The abrupt ruptures are sensitive to local environment, likely a general and important pathway of protein unfolding in living cells.

  16. Conclusive evidence of abrupt coagulation inside the void during cyclic nanoparticle formation in reactive plasma

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wetering, F. M. J. H. van de; Nijdam, S.; Beckers, J.

    2016-07-25

    In this letter, we present scanning electron microscopy (SEM) results that confirm in a direct way our earlier explanation of an abrupt coagulation event as the cause for the void hiccup. In a recent paper, we reported on the fast and interrupted expansion of voids in a reactive dusty argon–acetylene plasma. The voids appeared one after the other, each showing a peculiar, though reproducible, behavior of successive periods of fast expansion, abrupt contraction, and continued expansion. The abrupt contraction was termed “hiccup” and was related to collective coagulation of a new generation of nanoparticles growing in the void using relativelymore » indirect methods: electron density measurements and optical emission spectroscopy. In this letter, we present conclusive evidence using SEM of particles collected at different moments in time spanning several growth cycles, which enables us to follow the nanoparticle formation process in great detail.« less

  17. Forest Loss and the Biodiversity Threshold: An Evaluation Considering Species Habitat Requirements and the Use of Matrix Habitats

    PubMed Central

    Estavillo, Candelaria; Pardini, Renata; da Rocha, Pedro Luís Bernardo

    2013-01-01

    Habitat loss is the main driver of the current biodiversity crisis, a landscape-scale process that affects the survival of spatially-structured populations. Although it is well-established that species responses to habitat loss can be abrupt, the existence of a biodiversity threshold is still the cause of much controversy in the literature and would require that most species respond similarly to the loss of native vegetation. Here we test the existence of a biodiversity threshold, i.e. an abrupt decline in species richness, with habitat loss. We draw on a spatially-replicated dataset on Atlantic forest small mammals, consisting of 16 sampling sites divided between forests and matrix habitats in each of five 3600-ha landscapes (varying from 5% to 45% forest cover), and on an a priori classification of species into habitat requirement categories (forest specialists, habitat generalists and open-area specialists). Forest specialists declined abruptly below 30% of forest cover, and spillover to the matrix occurred only in more forested landscapes. Generalists responded positively to landscape heterogeneity, peaking at intermediary levels of forest cover. Open area specialists dominated the matrix and did not spillover to forests. As a result of these distinct responses, we observed a biodiversity threshold for the small mammal community below 30% forest cover, and a peak in species richness just above this threshold. Our results highlight that cross habitat spillover may be asymmetrical and contingent on landscape context, occurring mainly from forests to the matrix and only in more forested landscapes. Moreover, they indicate the potential for biodiversity thresholds in human-modified landscapes, and the importance of landscape heterogeneity to biodiversity. Since forest loss affected not only the conservation value of forest patches, but also the potential for biodiversity-mediated services in anthropogenic habitats, our work indicates the importance of proactive

  18. Studies of Evolved Star Mass Loss: GRAMS Modeling of Red Supergiant and Asymptotic Giant Branch Stars in the Magellanic Clouds

    NASA Astrophysics Data System (ADS)

    Sargent, Benjamin A.; Srinivasan, S.; Riebel, D.; Boyer, M.; Meixner, M.

    2012-01-01

    As proposed in our NASA Astrophysics Data Analysis Program (ADAP) proposal, my colleagues and I are studying mass loss from evolved stars. Such stars lose their own mass in their dying stages, and in their expelled winds they form stardust. To model mass loss from these evolved stars, my colleagues and I have constructed GRAMS: the Grid of Red supergiant and Asymptotic giant branch star ModelS. These GRAMS radiative transfer models are fit to optical through mid-infrared photometry of red supergiant (RSG) stars and asymptotic giant branch (AGB) stars. I will discuss our current studies of mass loss from AGB and RSG stars in the Small Magellanic Cloud (SMC), fitting GRAMS models to the photometry of SMC evolved star candidates identified from the SAGE-SMC (PI: K. Gordon) Spitzer Space Telescope Legacy survey. This work will be briefly compared to similar work we have done for the LMC. I will also discuss Spitzer Infrared Spectrograph (IRS) studies of the dust produced by AGB and RSG stars in the LMC. BAS is grateful for support from the NASA-ADAP grant NNX11AB06G.

  19. Spatial and temporal distribution of mass loss from the Greenland Ice Sheet since AD 1900.

    PubMed

    Kjeldsen, Kristian K; Korsgaard, Niels J; Bjørk, Anders A; Khan, Shfaqat A; Box, Jason E; Funder, Svend; Larsen, Nicolaj K; Bamber, Jonathan L; Colgan, William; van den Broeke, Michiel; Siggaard-Andersen, Marie-Louise; Nuth, Christopher; Schomacker, Anders; Andresen, Camilla S; Willerslev, Eske; Kjær, Kurt H

    2015-12-17

    The response of the Greenland Ice Sheet (GIS) to changes in temperature during the twentieth century remains contentious, largely owing to difficulties in estimating the spatial and temporal distribution of ice mass changes before 1992, when Greenland-wide observations first became available. The only previous estimates of change during the twentieth century are based on empirical modelling and energy balance modelling. Consequently, no observation-based estimates of the contribution from the GIS to the global-mean sea level budget before 1990 are included in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Here we calculate spatial ice mass loss around the entire GIS from 1900 to the present using aerial imagery from the 1980s. This allows accurate high-resolution mapping of geomorphic features related to the maximum extent of the GIS during the Little Ice Age at the end of the nineteenth century. We estimate the total ice mass loss and its spatial distribution for three periods: 1900-1983 (75.1 ± 29.4 gigatonnes per year), 1983-2003 (73.8 ± 40.5 gigatonnes per year), and 2003-2010 (186.4 ± 18.9 gigatonnes per year). Furthermore, using two surface mass balance models we partition the mass balance into a term for surface mass balance (that is, total precipitation minus total sublimation minus runoff) and a dynamic term. We find that many areas currently undergoing change are identical to those that experienced considerable thinning throughout the twentieth century. We also reveal that the surface mass balance term shows a considerable decrease since 2003, whereas the dynamic term is constant over the past 110 years. Overall, our observation-based findings show that during the twentieth century the GIS contributed at least 25.0 ± 9.4 millimetres of global-mean sea level rise. Our result will help to close the twentieth-century sea level budget, which remains crucial for evaluating the reliability of models used to

  20. Spatial and temporal distribution of mass loss from the Greenland Ice Sheet since AD 1900

    NASA Astrophysics Data System (ADS)

    Kjeldsen, Kristian K.; Korsgaard, Niels J.; Bjørk, Anders A.; Khan, Shfaqat A.; Box, Jason E.; Funder, Svend; Larsen, Nicolaj K.; Bamber, Jonathan L.; Colgan, William; van den Broeke, Michiel; Siggaard-Andersen, Marie-Louise; Nuth, Christopher; Schomacker, Anders; Andresen, Camilla S.; Willerslev, Eske; Kjær, Kurt H.

    2015-12-01

    The response of the Greenland Ice Sheet (GIS) to changes in temperature during the twentieth century remains contentious, largely owing to difficulties in estimating the spatial and temporal distribution of ice mass changes before 1992, when Greenland-wide observations first became available. The only previous estimates of change during the twentieth century are based on empirical modelling and energy balance modelling. Consequently, no observation-based estimates of the contribution from the GIS to the global-mean sea level budget before 1990 are included in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Here we calculate spatial ice mass loss around the entire GIS from 1900 to the present using aerial imagery from the 1980s. This allows accurate high-resolution mapping of geomorphic features related to the maximum extent of the GIS during the Little Ice Age at the end of the nineteenth century. We estimate the total ice mass loss and its spatial distribution for three periods: 1900-1983 (75.1 ± 29.4 gigatonnes per year), 1983-2003 (73.8 ± 40.5 gigatonnes per year), and 2003-2010 (186.4 ± 18.9 gigatonnes per year). Furthermore, using two surface mass balance models we partition the mass balance into a term for surface mass balance (that is, total precipitation minus total sublimation minus runoff) and a dynamic term. We find that many areas currently undergoing change are identical to those that experienced considerable thinning throughout the twentieth century. We also reveal that the surface mass balance term shows a considerable decrease since 2003, whereas the dynamic term is constant over the past 110 years. Overall, our observation-based findings show that during the twentieth century the GIS contributed at least 25.0 ± 9.4 millimetres of global-mean sea level rise. Our result will help to close the twentieth-century sea level budget, which remains crucial for evaluating the reliability of models used to

  1. The X-Ray Lightcurve of Eta Carinae: Refinement of the Orbit and Evidence for Phase Dependent Mass Loss

    NASA Technical Reports Server (NTRS)

    Corcoran, M. F.; Ishibashi, K.; Swank, J. H.; Petre, R.; White, Nicholas E. (Technical Monitor)

    2000-01-01

    We solve the RXTE X-ray lightcurve of the extremely luminous and massive star eta Carinae with a colliding wind emission model to refine the ground-based orbital elements. The sharp decline to X-ray minimum at the end of 1997 fixes the date of the last periastron passage at 1997.95 +/- 0.05, not 1998.13 as derived from ground-based radial velocities. This helps resolve a discrepancy between the ground-based radial velocities and spatially-resolved velocity measures obtained by STIS. The X-ray data are consistent with a mass function f(M) approx. = 1.5, lower than the value f(M) approx. = 7.5 previously reported, so that the masses of eta Carinae and the companion are M(sub eta) greater than or = 80 solar mass and M(sub c) approx. 30 solar mass respectively. In addition the X-ray data suggest that the mass loss rate from eta Carinae is generally less than 3 x 10(exp -4) solar mass/yr, about a factor of 5 lower than that derived from some observations in other wavebands. We could not match the duration of the X-ray minimum with any standard colliding wind model in which the wind is spherically symmetric and the mass loss rate is constant. However we show that we can match the variations around X-ray minimum if we include an increase of a factor of approx. 20 in the mass loss rate from eta Carinae for approximately 80 days following periastron. If real, this excess in M would be the first evidence of enhanced mass flow off the primary when the two stars are close (presumably driven by tidal interactions). Our interpretation of the X-ray data suggest that the ASCA and RXTE X-ray spectra near the X-ray minimum are significantly contaminated by unresolved hard emission (E greater than or = 2 keV) from sonic other nearby source, probably associated with scattering of tile colliding wind emission by circumstellar dust. Based on the X-ray fluxes the distance to n Carinae is 2300 pc with formal uncertainties of only approx. 10%.

  2. Variability and mass loss in IA O-B-A supergiants

    NASA Technical Reports Server (NTRS)

    Schild, R. E.; Garrison, R. F.; Hiltner, W. A.

    1983-01-01

    Recently completed catalogs of MK spectral types and UBV photometry of 1227 OB stars in the southern Milky Way have been analyzed to investigate brightness and color variability among the Ia supergiants. It is found that brightness variability is common among the O9-B1 supergiants with typical amplitudes about 0.1 and time scales longer than a week and shorter than 1000 days. Among the A supergiants fluctuations in U-B color are found on similar time scales and with amplitude about 0.1. For many early Ia supergiants there is a poor correlation between Balmer jump and spectral type, as had been known previously. An attempt to correlate the Balmer jump deficiency with mass loss rate yielded uncertain results.

  3. Contributions of Weight Perceptions to Weight Loss Attempts: Differences by Body Mass Index and Gender

    PubMed Central

    Lemon, Stephenie C.; Rosal, Milagros C.; Zapka, Jane; Borg, Amy; Andersen, Victoria

    2009-01-01

    Previous studies have consistently observed that women are more likely to perceive themselves as overweight compared to men. Similarly, women are more likely than men to report trying to lose weight. Less is known about the impact that self-perceived weight has on weight loss behaviors of adults and whether this association differs by gender. We conducted a cross-sectional analysis among an employee sample to determine the association of self-perceived weight on evidence-based weight loss behaviors across genders, accounting for body mass index (BMI) and demographic characteristics. Women were more likely than men to consider themselves to be overweight across each BMI category, and were more likely to report attempting to lose weight. However, perceiving oneself to be overweight was a strong correlate for weight loss attempts across both genders. The effect of targeting accuracy of self-perceived weight status in weight loss interventions deserves research attention. PMID:19188102

  4. Abrupt cooling over the North Atlantic in modern climate models

    PubMed Central

    Sgubin, Giovanni; Swingedouw, Didier; Drijfhout, Sybren; Mary, Yannick; Bennabi, Amine

    2017-01-01

    Observations over the 20th century evidence no long-term warming in the subpolar North Atlantic (SPG). This region even experienced a rapid cooling around 1970, raising a debate over its potential reoccurrence. Here we assess the risk of future abrupt SPG cooling in 40 climate models from the fifth Coupled Model Intercomparison Project (CMIP5). Contrary to the long-term SPG warming trend evidenced by most of the models, 17.5% of the models (7/40) project a rapid SPG cooling, consistent with a collapse of the local deep-ocean convection. Uncertainty in projections is associated with the models' varying capability in simulating the present-day SPG stratification, whose realistic reproduction appears a necessary condition for the onset of a convection collapse. This event occurs in 45.5% of the 11 models best able to simulate the observed SPG stratification. Thus, due to systematic model biases, the CMIP5 ensemble as a whole underestimates the chance of future abrupt SPG cooling, entailing crucial implications for observation and adaptation policy. PMID:28198383

  5. Constraining the Post-Thermal Pulse Mass-Loss History of R Scl with SOFIA/FORCAST

    NASA Astrophysics Data System (ADS)

    Hankins, Matthew; Herter, Terry; maercker, matthias; Lau, Ryan M.; Sloan, Greg

    2018-06-01

    R Sculptoris (R Scl) is a nearby (~370 pc) carbon star with a massive circumstellar shell (Mshell∼7×10‑3 M⊙) which is thought to have been produced by a thermal pulse event ∼2200 years ago. We observed R Scl with the Faint Object InfraRed CAMera for the SOFIA Telescope (FORCAST) at 19.7, 25.2, 31.5, 34.8, and 37.1 μm to study its circumstellar dust emission. Maps of the infrared emission were used to examine the morphology and temperature structure of the spatially extended dust emission. We used the radiative transfer code DUSTY to fit the radial density profile of the circumstellar material, and find that a geometrically thin dust shell cannot reproduce the observed emission. Instead, a second dust component is needed to model the emission. This component, which lies interior to the dust shell, traces the post-thermal pulse mass loss of R Scl and is indicative of a slow decline in the star’s mass loss over thousands of years. This result is at odds with 'classical' thermal pulse models but is consistent with earlier observations of molecular gas in R Scl’s circumstellar environment.

  6. Cosmogenic nuclides in cometary materials: Implications for rate of mass loss and exposure history

    NASA Astrophysics Data System (ADS)

    Herzog, G. F.; Englert, P. A. J.; Reedy, R. C.

    As planned, the Rosetta mission will return to earth with a 10-kg core and a 1-kg surface sample from a comet. The selection of a comet with low current activity will maximize the chance of obtaining material altered as little as possible. Current temperature and level of activity, however, may not reliably indicate previous values. Fortunately, from measurements of the cosmogenic nuclide contents of cometary material, one may estimate a rate of mass loss in the past and perhaps learn something about the exposure history of the comet. Perhaps the simplest way to estimate the rate of mass loss is to compare the total inventories of several long-lived cosmogenic radionuclides with the values expected on the basis of model calculations. Although model calculations have become steadily more reliable, application to bodies with the composition of comets will require some extension beyond the normal range of use. In particular, the influence of light elements on the secondary particle cascade will need study, in part through laboratory irradiations of volatile-rich materials. In the analysis of cometary data, it would be valuable to test calculations against measurements of short-lived isotopes.

  7. Mass-loss rates, ionization fractions, shock velocities, and magnetic fields of stellar jets

    NASA Technical Reports Server (NTRS)

    Hartigan, Patrick; Morse, Jon A.; Raymond, John

    1994-01-01

    In this paper we calculate emission-line ratios from a series of planar radiative shock models that cover a wide range of shock velocities, preshock densities, and magnetic fields. The models cover the initial conditions relevant to stellar jets, and we show how to estimate the ionization fractions and shock velocities in jets directly from observations of the strong emission lines in these flows. The ionization fractions in the HH 34, HH 47, and HH 111 jets are approximately 2%, considerably smaller than previous estimates, and the shock velocities are approximately 30 km/s. For each jet the ionization fractions were found from five different line ratios, and the estimates agree to within a factor of approximately 2. The scatter in the estimates of the shock velocities is also small (+/- 4 km/s). The low ionization fractions of stellar jets imply that the observed electron densities are much lower than the total densities, so the mass-loss rates in these flows are correspondingly higher (approximately greater than 2 x 10(exp -7) solar mass/yr). The mass-loss rates in jets are a significant fraction (1%-10%) of the disk accretion rates onto young stellar objects that drive the outflows. The momentum and energy supplied by the visible portion of a typical stellar jet are sufficient to drive a weak molecular outflow. Magnetic fields in stellar jets are difficult to measure because the line ratios from a radiative shock with a magnetic field resemble those of a lower velocity shock without a field. The observed line fluxes can in principle indicate the strength of the field if the geometry of the shocks in the jet is well known.

  8. Constraining the sources of CH4 emissions during past abrupt climate change using CH4 triple isotopes mass balance from the ice core records

    NASA Astrophysics Data System (ADS)

    Dyonisius, M.; Petrenko, V. V.; Smith, A. W.; Hmiel, B.; Beck, J.; Seth, B.; Bock, M.; Hua, Q.; Yang, B.; Harth, C. M.; Beaudette, R.; Lee, J.; Erhardt, T.; Schmitt, J.; Brook, E.; Weiss, R. F.; Fischer, H.; Severinghaus, J. P.

    2017-12-01

    Methane (CH4) is the third most important greenhouse gas in the atmosphere after water vapor and CO2. Understanding how the natural CH4 budget has changed in response to changing climate in the past can provide insights on the sensitivity of the natural CH4 emissions to the current anthropogenic warming. CH4 isotopes (Δ14CH4, δ13C-CH4, and δD-CH4) from ice cores can be used to fingerprint the sources of CH4 increases in the past. We have successfully extracted 6 large volume (>1000kg) ice core samples from Taylor Glacier, Antarctica spanning the Oldest Dryas-Bølling transition ( 14.7ka) - the first abrupt warming and CH4 rise since the Last Glacial Maximum. Among the CH4 isotopes, our Δ 14CH4 data are unique in their ability to unambiguously distinguish between "old" CH4 sources (e.g. marine clathrate, geologic sources, old permafrost) and "modern" CH4 sources (e.g. tropical and boreal wetlands). Our Δ14CH4 data unambiguously rule out marine clathrate and old permafrost as the sources of the abrupt CH4 rise. Preliminary CH4 stable isotopes box modeling combined with interpolar CH4 concentration gradient from existing ice core records suggest that tropical wetlands were the dominant driver for the Oldest Dryas-Bølling CH4 rise.

  9. Parkin loss leads to PARIS-dependent declines in mitochondrial mass and respiration

    PubMed Central

    Stevens, Daniel A.; Lee, Yunjong; Kang, Ho Chul; Lee, Byoung Dae; Lee, Yun-Il; Bower, Aaron; Jiang, Haisong; Kang, Sung-Ung; Andrabi, Shaida A.; Dawson, Valina L.; Shin, Joo-Ho; Dawson, Ted M.

    2015-01-01

    Mutations in parkin lead to early-onset autosomal recessive Parkinson’s disease (PD) and inactivation of parkin is thought to contribute to sporadic PD. Adult knockout of parkin in the ventral midbrain of mice leads to an age-dependent loss of dopamine neurons that is dependent on the accumulation of parkin interacting substrate (PARIS), zinc finger protein 746 (ZNF746), and its transcriptional repression of PGC-1α. Here we show that adult knockout of parkin in mouse ventral midbrain leads to decreases in mitochondrial size, number, and protein markers consistent with a defect in mitochondrial biogenesis. This decrease in mitochondrial mass is prevented by short hairpin RNA knockdown of PARIS. PARIS overexpression in mouse ventral midbrain leads to decreases in mitochondrial number and protein markers and PGC-1α–dependent deficits in mitochondrial respiration. Taken together, these results suggest that parkin loss impairs mitochondrial biogenesis, leading to declining function of the mitochondrial pool and cell death. PMID:26324925

  10. Tunable thulium-doped fiber laser based on an abrupt-tapered in-fiber interferometer

    NASA Astrophysics Data System (ADS)

    Hernández-Arriaga, M. V.; Durán-Sánchez, M.; Ibarra-Escamilla, B.; Álvarez-Tamayo, R. I.; Santiago-Hernández, H.; Bello-Jiménez, M.; Kuzin, E. A.

    2017-11-01

    An experimental study of an all-fiber tunable thulium-doped fiber laser based on an abrupt-tapered in-fiber interferometer is presented. A microfiber filter with length of 6 mm and diameter of 20 μm is used to achieve single laser wavelength tuning in a range of 19.4 nm and dual-wavelength laser operation at 1761.8 and 1793.4 nm with a channel spacing of 31.6 nm. The abrupt-tapered structure allows multi-modal interference at the air-cladding interface. The proposed in-fiber interferometer exhibits characteristics of low cost and simple fabrication, making it suitable for practical applications in wavelength filtering and wavelength selection in all-fiber lasers.

  11. Allocation of extracellular enzymatic activity in relation to litter composition, N deposition, and mass loss

    USGS Publications Warehouse

    Sinsabaugh, R. L.; Carreiro, M.M.; Repert, D.A.

    2002-01-01

    Decomposition of plant material is a complex process that requires interaction among a diversity of microorganisms whose presence and activity is subject to regulation by a wide range of environmental factors. Analysis of extracellular enzyme activity (EEA) provides a way to relate the functional organization of microdecomposer communities to environmental variables. In this study, we examined EEA in relation to litter composition and nitrogen deposition. Mesh bags containing senescent leaves of Quercus borealis (red oak), Acer rubrum (red maple) and Cornus florida (flowering dogwood) were placed on forest floor plots in southeastern New York. One-third of the plots were sprayed monthly with distilled water. The other plots were sprayed monthly with NH4NO3 solution at dose rates equivalent to 2 or 8 g N m-2 y-1. Mass loss, litter composition, fungal mass, and the activities of eight enzymes were measured on 13 dates for each litter type. Dogwood was followed for one year, maple for two, oak for three, For each litter type and treatment, enzymatic turnover activities were calculated from regressions of LN (%mass remaining) vs. cumulative activity. The decomposition of dogwood litter was more efficient than that of maple and oak. Maple litter had the lowest fungal mass and required the most enzymatic work to decompose, even though its mass loss rate was twice that of oak. Across litter types, N amendment reduced apparent enzymatic efficiencies and shifted EEA away from N acquisition and toward P acquisition, and away from polyphenol oxidation and toward polysaccharide hydrolysis. The effect of these shifts on decomposition rate varied with litter composition: dogwood was stimulated, oak was inhibited and maple showed mixed effects. The results show that relatively small shifts in the activity of one or two critical enzymes can significantly alter decomposition rates.

  12. Comprehensive quantification of triacylglycerols in soybean seeds by electrospray ionization mass spectrometry with multiple neutral loss scans

    DOE PAGES

    Li, Maoyin; Butka, Emily; Wang, Xuemin

    2014-10-10

    Soybean seeds are an important source of vegetable oil and biomaterials. The content of individual triacylglycerol species (TAG) in soybean seeds is difficult to quantify in an accurate and rapid way. The present study establishes an approach to quantify TAG species in soybean seeds utilizing an electrospray ionization tandem mass spectrometry with multiple neutral loss scans. Ten neutral loss scans were performed to detect the fatty acyl chains of TAG, including palmitic (P, 1650), linolenic (Ln, 1853), linoleic (L, 1852), oleic (O, 1851), stearic (S, 1850), eicosadienoic (2052), gadoleic (2051), arachidic (2050), erucic (2251), and behenic (2250). The abundance ofmore » ten fatty acyl chains at 46 TAG masses (mass-to-charge ratio, m/z) were determined after isotopic deconvolution and correction by adjustment factors at each TAG mass. The direct sample infusion and multiple internal standards correction allowed a rapid and accurate quantification of TAG species. Ninety-three TAG species were resolved and their levels were determined.The most abundant TAG species were LLL, OLL, LLLn, PLL, OLLn, OOL, POL, and SLL. Many new species were detected and quantified. As a result, this shotgun lipidomics approach should facilitate the study of TAG metabolism and genetic breeding of soybean seeds for desirable TAG content and composition.« less

  13. Dust composition and mass-loss return from the luminous blue variable R71 in the LMC

    NASA Astrophysics Data System (ADS)

    Guha Niyogi, S.; Min, M.; Meixner, M.; Waters, L. B. F. M.; Seale, J.; Tielens, A. G. G. M.

    2014-09-01

    Context. We present an analysis of mid- and far-infrared (IR) spectrum and spectral energy distribution (SED) of the luminous blue variable (LBV) R71 in the Large Magellanic Cloud (LMC). Aims: This work aims to understand the overall contribution of high-mass LBVs to the total dust-mass budget of the interstellar medium (ISM) of the LMC and compare this with the contribution from low-mass asymptotic giant branch (AGB) stars. As a case study, we analyze the SED of R71. Methods: We compiled all the available photometric and spectroscopic observational fluxes from various telescopes for a wide wavelength range (0.36-250 μm). We determined the dust composition from the spectroscopic data, and derived the ejected dust mass, dust mass-loss rate, and other dust shell properties by modeling the SED of R71. We noted nine spectral features in the dust shell of R71 by analyzing Spitzer Space Telescope spectroscopic data. Among these, we identified three new crystalline silicate features. We computed our model spectrum by using 3D radiative transfer code MCMax. Results: Our model calculation shows that dust is dominated by amorphous silicates, with some crystalline silicates, metallic iron, and a very tiny amount of polycyclic aromatic hydrocarbon (PAH) molecules. The presence of both silicates and PAHs indicates that the dust has a mixed chemistry. We derived a dust mass of 0.01 M⊙, from which we arrive at a total ejected mass of ≈5 M⊙. This implies a time-averaged dust mass-loss rate of 2.5 × 10-6 M⊙ yr-1 with an explosion about 4000 years ago. We assume that the other five confirmed dusty LBVs in the LMC loose mass at a similar rate, and estimate the total contribution to the mass budget of the LMC to be ≈10-5 M⊙ yr-1, which is comparable to the contribution by all the AGB stars in the LMC. Conclusions: Based on our analysis on R71, we speculate that LBVs as a class may be an important dust source in the ISM of the LMC.

  14. Nitrogen losses from dairy manure estimated through nitrogen mass balance and chemical markers

    USGS Publications Warehouse

    Hristov, Alexander N.; Zaman, S.; Vander Pol, M.; Ndegwa, P.; Campbell, L.; Silva, S.

    2009-01-01

    Ammonia is an important air and water pollutant, but the spatial variation in its concentrations presents technical difficulties in accurate determination of ammonia emissions from animal feeding operations. The objectives of this study were to investigate the relationship between ammonia volatilization and ??15N of dairy manure and the feasibility of estimating ammonia losses from a dairy facility using chemical markers. In Exp. 1, the N/P ratio in manure decreased by 30% in 14 d as cumulative ammonia losses increased exponentially. Delta 15N of manure increased throughout the course of the experiment and ??15N of emitted ammonia increased (p < 0.001) quadratically from -31??? to -15 ???. The relationship between cumulative ammonia losses and ??15N of manure was highly significant (p < 0.001; r2 = 0.76). In Exp. 2, using a mass balance approach, approximately half of the N excreted by dairy cows (Bos taurus) could not be accounted for in 24 h. Using N/P and N/K ratios in fresh and 24-h manure, an estimated 0.55 and 0.34 (respectively) of the N excreted with feces and urine could not be accounted for. This study demonstrated that chemical markers (P, K) can be successfully used to estimate ammonia losses from cattle manure. The relationship between manure ??15N and cumulative ammonia loss may also be useful for estimating ammonia losses. Although promising, the latter approach needs to be further studied and verified in various experimental conditions and in the field. Copyright ?? 2009 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

  15. Gas Loss by Ram Pressure Stripping and Internal Feedback from Low-mass Milky Way Satellites

    NASA Astrophysics Data System (ADS)

    Emerick, Andrew; Mac Low, Mordecai-Mark; Grcevich, Jana; Gatto, Andrea

    2016-08-01

    The evolution of dwarf satellites in the Milky Way (MW) is affected by a combination of ram pressure stripping (RPS), tidal stripping, and internal feedback from massive stars. We investigate gas loss processes in the smallest satellites of the MW using three-dimensional, high-resolution, idealized wind tunnel simulations, accounting for gas loss through both ram pressure stripping and expulsion by supernova feedback. Using initial conditions appropriate for a dwarf galaxy like Leo T, we investigate whether or not environmental gas stripping and internal feedback can quench these low-mass galaxies on the expected timescales, shorter than 2 Gyr. We find that supernova feedback contributes negligibly to the stripping rate for these low star formation rate galaxies. However, we also find that RPS is less efficient than expected in the stripping scenarios we consider. Our work suggests that although RPS can eventually completely strip these galaxies, other physics is likely at play to reconcile our computed stripping times with the rapid quenching timescales deduced from observations of low-mass MW dwarf galaxies. We discuss the roles additional physics may play in this scenario, including host-satellite tidal interactions, cored versus cuspy dark matter profiles, reionization, and satellite preprocessing. We conclude that a proper accounting of these physics together is necessary to understand the quenching of low-mass MW satellites.

  16. GAS LOSS BY RAM PRESSURE STRIPPING AND INTERNAL FEEDBACK FROM LOW-MASS MILKY WAY SATELLITES

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Emerick, Andrew; Low, Mordecai-Mark Mac; Grcevich, Jana

    The evolution of dwarf satellites in the Milky Way (MW) is affected by a combination of ram pressure stripping (RPS), tidal stripping, and internal feedback from massive stars. We investigate gas loss processes in the smallest satellites of the MW using three-dimensional, high-resolution, idealized wind tunnel simulations, accounting for gas loss through both ram pressure stripping and expulsion by supernova feedback. Using initial conditions appropriate for a dwarf galaxy like Leo T, we investigate whether or not environmental gas stripping and internal feedback can quench these low-mass galaxies on the expected timescales, shorter than 2 Gyr. We find that supernovamore » feedback contributes negligibly to the stripping rate for these low star formation rate galaxies. However, we also find that RPS is less efficient than expected in the stripping scenarios we consider. Our work suggests that although RPS can eventually completely strip these galaxies, other physics is likely at play to reconcile our computed stripping times with the rapid quenching timescales deduced from observations of low-mass MW dwarf galaxies. We discuss the roles additional physics may play in this scenario, including host-satellite tidal interactions, cored versus cuspy dark matter profiles, reionization, and satellite preprocessing. We conclude that a proper accounting of these physics together is necessary to understand the quenching of low-mass MW satellites.« less

  17. Extreme temperatures, foundation species, and abrupt ecosystem change: an example from an iconic seagrass ecosystem.

    PubMed

    Thomson, Jordan A; Burkholder, Derek A; Heithaus, Michael R; Fourqurean, James W; Fraser, Matthew W; Statton, John; Kendrick, Gary A

    2015-04-01

    Extreme climatic events can trigger abrupt and often lasting change in ecosystems via the reduction or elimination of foundation (i.e., habitat-forming) species. However, while the frequency/intensity of extreme events is predicted to increase under climate change, the impact of these events on many foundation species and the ecosystems they support remains poorly understood. Here, we use the iconic seagrass meadows of Shark Bay, Western Australia--a relatively pristine subtropical embayment whose dominant, canopy-forming seagrass, Amphibolis antarctica, is a temperate species growing near its low-latitude range limit--as a model system to investigate the impacts of extreme temperatures on ecosystems supported by thermally sensitive foundation species in a changing climate. Following an unprecedented marine heat wave in late summer 2010/11, A. antarctica experienced catastrophic (>90%) dieback in several regions of Shark Bay. Animal-borne video footage taken from the perspective of resident, seagrass-associated megafauna (sea turtles) revealed severe habitat degradation after the event compared with a decade earlier. This reduction in habitat quality corresponded with a decline in the health status of largely herbivorous green turtles (Chelonia mydas) in the 2 years following the heat wave, providing evidence of long-term, community-level impacts of the event. Based on these findings, and similar examples from diverse ecosystems, we argue that a generalized framework for assessing the vulnerability of ecosystems to abrupt change associated with the loss of foundation species is needed to accurately predict ecosystem trajectories in a changing climate. This includes seagrass meadows, which have received relatively little attention in this context. Novel research and monitoring methods, such as the analysis of habitat and environmental data from animal-borne video and data-logging systems, can make an important contribution to this framework. © 2014 John Wiley

  18. Abrupt transitions to a cold North Atlantic in the late Holocene

    NASA Astrophysics Data System (ADS)

    Geirsdóttir, Áslaug; Miller, Gifford; Larsen, Darren; Florian, Christopher; Pendleton, Simon

    2015-04-01

    The Holocene provides a time interval with boundary conditions similar to present, except for greenhouse gas concentrations. Recent high-resolution Northern Hemisphere records show general cooling related to orbital terms through the late Holocene, but also highly non-linear abrupt departures of centennial scale summer cold periods. These abrupt departures are evident within the last two millennia (the transitions between the Roman Warm Period (RWP, ~2,000 yr BP), the Dark Ages Cold Period (DACP, ~500-900 years AD), the Medieval Warm Period (MWP, 1000-1200 years AD) and the Little Ice Age (LIA, ~1300-1900 AD). A series of new, high-resolution and securely dated lake records from Iceland also show abrupt climate departures over the past 2 ka, characterized by shifts to persistent cold summers and an expanded cryosphere. Despite substantial differences in catchment-specific processes that dominate the lake records, the multi-proxy reconstructions are remarkably similar. After nearly a millennium with little evidence of significant climate shifts, the beginning of the first millennium AD is characterized by renewed summer cooling that leads to an expanding cryosphere. Slow summer cooling over the first five centuries is succeeded by widespread substantial cooling, with evidence for substantial expansion of glaciers and ice caps throughout our field areas between 530 and 900 AD, and an accompanying reduction in vegetation cover across much of Iceland that led to widespread landscape instability. These data suggest that the North Atlantic system began a transition into a new cold state early in the first millennium AD, which was amplified after 500 AD, until it was interrupted by warmer Medieval times between ~1000 and 1250 AD. Although severe soil erosion in Iceland is frequently associated with human settlement dated to 871 ±2 AD our reconstructions indicate that soil erosion began several centuries before settlement, during the DACP, whereas for several centuries

  19. On the Evolutionary Phase and Mass Loss of the Wolf-Rayet--like Stars in R136a

    NASA Astrophysics Data System (ADS)

    de Koter, Alex; Heap, Sara R.; Hubeny, Ivan

    1997-03-01

    We report on a systematic study of the most massive stars, in which we analyzed the spectra of four very luminous stars in the Large Magellanic Cloud. The stars lie in the 30 Doradus complex, three of which are located in the core of the compact cluster, R136a (R136a1, R136a3, and R136a5), and the fourth (Melnick 42), located about 8" north of R136a. Low-resolution spectra (<200 km s-1) of these four stars were obtained with the GHRS and FOS spectrographs on the Hubble Space Telescope. The GHRS spectra cover the spectral range from 1200 to 1750 A, and the FOS spectra from 3200 to 6700 A. We derived the fundamental parameters of these stars by fitting the observations by model spectra calculated with the "ISA-WIND" code of de Koter et al. We find that all four stars are very hot (~45 kK), luminous, and rich in hydrogen. Their positions on the HR-diagram imply that they are stars with masses in the range 60--90 M⊙ that are 2 million years old at most, and hence, they are O-type main-sequence stars still in the core H-burning phase of evolution. Nevertheless, the spectra of two of the stars (R136a1, R136a3) mimic those of Wolf-Rayet stars in showing very strong He II emission lines. According to our calculations, this emission is a natural consequence of a very high mass-loss rate. We conjecture that the most massive stars in R136a---those with initial masses of ~100 M⊙ or more---are born as WR-like stars and that the high mass loss may perhaps be connected to the actual stellar formation process. Because the observed mass-loss rates are up to 3 times higher than assumed by evolutionary models, the main-sequence and post--main-sequence tracks of these stars will be qualitatively different from current models. The mass-loss rate is 3.5--8 times that predicted by the analytical solutions for radiation-driven winds of Kudritzki et al. (1989). However, using sophisticated Monte Carlo calculations of radiative driving in unified model atmospheres, we show that

  20. Effects of 4 weight-loss diets differing in fat, protein, and carbohydrate on fat mass, lean mass, visceral adipose tissue, and hepatic fat: results from the POUNDS LOST trial.

    PubMed

    de Souza, Russell J; Bray, George A; Carey, Vincent J; Hall, Kevin D; LeBoff, Meryl S; Loria, Catherine M; Laranjo, Nancy M; Sacks, Frank M; Smith, Steven R

    2012-03-01

    Weight loss reduces body fat and lean mass, but whether these changes are influenced by macronutrient composition of the diet is unclear. We determined whether energy-reduced diets that emphasize fat, protein, or carbohydrate differentially reduce total, visceral, or hepatic fat or preserve lean mass. In a subset of participants in a randomized trial of 4 weight-loss diets, body fat and lean mass (n = 424; by using dual-energy X-ray absorptiometry) and abdominal and hepatic fat (n = 165; by using computed tomography) were measured after 6 mo and 2 y. Changes from baseline were compared between assigned amounts of protein (25% compared with 15%) and fat (40% compared with 20%) and across 4 carbohydrate amounts (35% through 65%). At 6 mo, participants lost a mean (±SEM) of 4.2 ± 0.3 kg (12.4%) fat and 2.1 ± 0.3 kg (3.5%) lean mass (both P < 0.0001 compared with baseline values), with no differences between 25% and 15% protein (P ≥ 0.10), 40% and 20% fat (P ≥ 0.34), or 65% and 35% carbohydrate (P ≥ 0.27). Participants lost 2.3 ± 0.2 kg (13.8%) abdominal fat: 1.5 ± 0.2 kg (13.6%) subcutaneous fat and 0.9 ± 0.1 kg (16.1%) visceral fat (all P < 0.0001 compared with baseline values), with no differences between the diets (P ≥ 0.29). Women lost more visceral fat than did men relative to total-body fat loss. Participants regained ~40% of these losses by 2 y, with no differences between diets (P ≥ 0.23). Weight loss reduced hepatic fat, but there were no differences between groups (P ≥ 0.28). Dietary goals were not fully met; self-reported contrasts were closer to 2% protein, 8% fat, and 14% carbohydrate at 6 mo and 1%, 7%, and 10%, respectively, at 2 y. Participants lost more fat than lean mass after consumption of all diets, with no differences in changes in body composition, abdominal fat, or hepatic fat between assigned macronutrient amounts. This trial was registered at clinicaltrials.gov as NCT00072995.

  1. Mass ablation and magnetic flux losses through a magnetized plasma-liner wall interface

    NASA Astrophysics Data System (ADS)

    García-Rubio, F.; Sanz, J.

    2017-07-01

    The understanding of energy and magnetic flux losses in a magnetized plasma medium confined by a cold wall is of great interest in the success of magnetized liner inertial fusion (MagLIF). In a MagLIF scheme, the fuel is magnetized and subsonically compressed by a cylindrical liner. Magnetic flux conservation is degraded by the presence of gradient-driven transport processes such as thermoelectric effects (Nernst) and magnetic field diffusion. In previous publications [Velikovich et al., Phys. Plasmas 22, 042702 (2015)], the evolution of a hot magnetized plasma in contact with a cold solid wall (liner) was studied using the classical collisional Braginskii's plasma transport equations in one dimension. The Nernst term degraded the magnetic flux conservation, while both thermal energy and magnetic flux losses were reduced with the electron Hall parameter ωeτe with a power-law asymptotic scaling (ωeτe)-1/2. In the analysis made in the present paper, we consider a similar situation, but with the liner being treated differently. Instead of a cold solid wall acting as a heat sink, we model the liner as a cold dense plasma with low thermal conduction (that could represent the cryogenic fuel layer added on the inner surface of the liner in a high-gain MagLIF configuration). Mass ablation comes into play, which adds notably differences to the previous analysis. The direction of the plasma motion is inverted, but the Nernst term still convects the magnetic field towards the liner. Magnetization suppresses the Nernst velocity and improves the magnetic flux conservation. Thermal energy in the hot plasma is lost in heating the ablated material. When the electron Hall parameter is large, mass ablation scales as (ωeτe)-3/10, while both the energy and magnetic flux losses are reduced with a power-law asymptotic scaling (ωeτe)-7/10.

  2. Association between involuntary weight loss with low muscle mass and health-related quality of life in community-dwelling older adults: Nationwide surveys (KNHANES 2008-2011).

    PubMed

    Kim, Miji; Kim, Junghoon; Won, Chang Won

    2018-06-01

    To investigate the relationship between involuntary weight loss with low muscle mass and health-related quality of life in a large representative sample of older adults. A nationwide cross-sectional study based on data from the Korea National Health and Nutritional Examination Survey, 2008 to 2011. Study participants included 2249 individuals aged ≥70 years. The participants reported an unintentional weight loss >3 kg in the past year. Appendicular lean mass was measured using dual-energy X-ray absorptiometry and calculated with the appendicular lean mass index. Health-related quality of life was measured using the EuroQol-5 dimension (EQ-5D) instrument. Univariate and multivariate survey logistic regression models were used to calculate odds ratios (OR) with 95% confidence intervals (95% CI) for the lowest quintile of the EQ-5D index. In total, 39.1% of participants were male and 60.9% were female. The weighted mean age was 75.6 years (95% CI; 75.3-75.9). Clinically significant weight loss is typically 5% of one's body weight; average, 2.8 kg (3.1 kg for men; 2.7 kg, women) for our participants. Compared with the normal reference group and after adjusting for potential confounders, the ORs for the lowest quintile of the EQ-5D indices were 1.39 (95% CI, 0.92-2.10), 2.56 (95% CI, 1.56-4.18), and 3.40 (95% CI, 2.05 to 5.63) for the low muscle mass, involuntary weight loss, involuntary weight loss with low muscle mass groups, respectively. Involuntary weight loss combined with low muscle mass was more closely associated with poor quality of life than involuntary weight loss alone in community-dwelling older adults. Copyright © 2018 Elsevier Inc. All rights reserved.

  3. Dissociating the capture of attention from saccade activation by subliminal abrupt onsets.

    PubMed

    Schoeberl, Tobias; Ansorge, Ulrich

    2017-10-01

    Attentional capture and effects on saccade metrics by subliminal abrupt onset cues have been studied with peripheral cues at one out of several (two to four) display locations, swiftly followed by additional onsets at the other display locations. The lead time of the cue was too short to be seen. Here, we were interested in whether such subliminal onset cues influenced saccades primarily by way of attention or by way of direct saccade activation. In separate blocks, participants made speeded pro-saccades towards a black target or anti-saccades away from the target. Prior to the targets, an abrupt onset cue was presented either at the same side as the target (valid condition) or at the opposite side (invalid condition). If cues influenced performance by way of attentional capture, we expected facilitation of target processing in valid compared to invalid conditions (cueing effect) in the pro- as well as in the anti-saccade task. If the cues activated saccades in their direction, we expected the cueing effect to drop in the anti-saccade task compared to the pro-saccade task because in the anti-saccade task the invalid cue would activate the finally required response, whereas the valid cue would activate the alternative response, leading to interference. Results were in line with the former of these possibilities suggesting that subliminal abrupt onsets influenced saccades by way of attention with no or little direct activation of saccades.

  4. Rapid Loss of Bone Mass and Strength in Mice after Abdominal Irradiation

    PubMed Central

    Jia, Dan; Gaddy, Dana; Suva, Larry J.; Corry, Peter M.

    2011-01-01

    Localized irradiation is a common treatment modality for malignancies in the pelvic-abdominal cavity. We report here on the changes in bone mass and strength in mice 7–14 days after abdominal irradiation. Male C57BL/6 mice of 10–12 weeks of age were given a single-dose (0, 5, 10, 15 or 20 Gy) or fractionated (3 Gy × 2 per day × 7.5 days) X rays to the abdomen and monitored daily for up to 14 days. A decrease in the serum bone formation marker and ex vivo osteoblast differentiation was detected 7 days after a single dose of radiation, with little change in the serum bone resorption marker and ex vivo osteoclast formation. A single dose of radiation elicited a loss of bone mineral density (BMD) within 14 days of irradiation. The BMD loss was up to 4.1% in the whole skeleton, 7.3% in tibia, and 7.7% in the femur. Fractionated abdominal irradiation induced similar extents of BMD loss 10 days after the last fraction: 6.2% in the whole skeleton, 5.1% in tibia, and 13.8% in the femur. The loss of BMD was dependent on radiation dose and was more profound in the trabecula-rich regions of the long bones. Moreover, BMD loss in the total skeleton and the femurs progressed with time. Peak load and stiffness in the mid-shaft tibia from irradiated mice were 11.2–14.2% and 11.5–25.0% lower, respectively, than sham controls tested 7 days after a single-dose abdominal irradiation. Our data demonstrate that abdominal irradiation induces a rapid loss of BMD in the mouse skeleton. These effects are bone type- and region-specific but are independent of radiation fractionation. The radiation-induced abscopal damage to the skeleton is manifested by the deterioration of biomechanical properties of the affected bone. PMID:21859327

  5. Assessment of the Body Composition and the Loss of Fat-Free Mass through Bioelectric Impedance Analysis in Patients Who Underwent Open Gastric Bypass

    PubMed Central

    de Freitas Junior, Wilson Rodrigues; Ilias, Elias Jirjoss; Kassab, Paulo; Cordts, Roberto; Porto, Paulo Gustavo; Martins Rodrigues, Francisco Cesar; Ali Taha, Mohamed Ibrahim; Carrara, Paulo; de Carvalho Aguiar, Isabella; de Oliveira, Luis Vicente Franco; Malheiros, Carlos Alberto

    2014-01-01

    Background. Bariatric surgery is considered an effective option for the management of morbid obesity. The incidence of obesity has been gradually increasing all over the world reaching epidemic proportions in some regions of the world. Obesity can cause a reduction of up to 22% in the life expectancy of morbidly obese patients. Objective. The objective of this paper is to assess the weight loss associated with the first 6 months after bariatric surgery using bioelectric impedance analysis (BIA) for the evaluation of fat mass and fat-free mass. Method. A total of 36 morbidly obese patients were subjected to open gastric bypass surgery. The patients weight was monitored before and after the procedure using the bioelectric impedance analysis. Results. Bariatric surgery resulted in an average percentage of weight loss of 28.6% (40 kg) as determined 6 months after the procedure was performed. Analysis of the different components of body weight indicated an undesirable loss of fat-free mass along with the reduction of total body weight. Conclusion. Open gastric bypass induced a significant loss of total weight and loss of fat-free mass in patients six months after the surgery. The use of bioelectric impedance analysis resulted in an appropriate estimation of the total weight components in individuals subjected to bariatric surgery allowing a more real analysis of the variation of weight after the surgery. PMID:24523649

  6. Could gradual changes in Holocene Saharan landscape have caused the observed abrupt shift in North Atlantic dust deposition?

    NASA Astrophysics Data System (ADS)

    Egerer, Sabine; Claussen, Martin; Reick, Christian; Stanelle, Tanja

    2017-09-01

    The abrupt change in North Atlantic dust deposition found in sediment records has been associated with a rapid large scale transition of Holocene Saharan landscape. We hypothesize that gradual changes in the landscape may have caused this abrupt shift in dust deposition either because of the non-linearity in dust activation or because of the heterogeneous distribution of major dust sources. To test this hypothesis, we investigate the response of North Atlantic dust deposition to a prescribed 1) gradual and spatially homogeneous decrease and 2) gradual southward retreat of North African vegetation and lakes during the Holocene using the aerosol-climate model ECHAM-HAM. In our simulations, we do not find evidence of an abrupt increase in dust deposition as observed in marine sediment records along the Northwest African margin. We conclude that such gradual changes in landscape are not sufficient to explain the observed abrupt changes in dust accumulation in marine sediment records. Instead, our results point to a rapid large-scale retreat of vegetation and lakes in the area of significant dust sources.

  7. Abrupt intensification of the SW Indian Ocean monsoon during the last deglaciation: constraints from Th, Pa, and He isotopes

    NASA Astrophysics Data System (ADS)

    Marcantonio, Franco; Anderson, Robert F.; Higgins, Sean; Fleisher, Martin Q.; Stute, Martin; Schlosser, Peter

    2001-01-01

    Sediments from western Arabian Sea core 74KL representing the last 23 ka were analyzed for helium, thorium, and protactinium isotopes. Assuming global average fluxes of extraterrestrial 3He and 230Th, the average 3He-derived sediment mass accumulation rate (MAR) is a factor of 1.8 higher than the average 230Th-derived MAR. 3He- and 230Th-derived MARs converge, however, during the Younger Dryas (YD) and during the peak of the early Holocene humid interval. These features, not seen anywhere else in the world, probably reflect a combination of climate-driven changes in the flux of 230Th and 3He. Ratios of xs 231Pa/xs 230Th, proxies of paleoproductivity, are lowest during the last glacial maximum (LGM), and increase abruptly during the Bolling-Allerod. Later, following a sudden decrease to near-LGM values during the YD, they rise abruptly to maximum values for the entire record in the early Holocene. We hypothesize that low xs 231Pa/xs 230Th ratios reflect low productivity due to the decreased intensity of the SW monsoon, whereas the opposite is true for high ratios. The correlation between Arabian Sea productivity and monsoonal upwelling, on the one hand, and North Atlantic climate variability, on the other, suggests a linkage between high- and low-latitude climates caused by changing patterns of atmospheric circulation.

  8. EXPLAINING THE OBSERVED VELOCITY DISPERSION OF DWARF GALAXIES BY BARYONIC MASS LOSS DURING THE FIRST COLLAPSE

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gritschneder, Matthias; Lin, Douglas N. C., E-mail: gritschneder@ucolick.org

    2013-03-01

    In the widely adopted {Lambda} cold dark matter ({Lambda}CDM) scenario for galaxy formation, dwarf galaxies are the building blocks of larger galaxies. Since they formed at relatively early epochs when the background density was relatively high, they are expected to retain their integrity as satellite galaxies when they merge to form larger entities. Although many dwarf spheroidal galaxies are found in the galactic halo around the Milky Way, their phase-space density (or velocity dispersion) appears to be significantly smaller than that expected for satellite dwarf galaxies in the {Lambda}CDM scenario. In order to account for this discrepancy, we consider themore » possibility that they may have lost a significant fraction of their baryonic matter content during the first infall at the Hubble expansion turnaround. Such mass loss arises naturally due to the feedback by relatively massive stars that formed in their centers briefly before the maximum contraction. Through a series of N-body simulations, we show that the timely loss of a significant fraction of the dSphs initial baryonic matter content can have profound effects on their asymptotic half-mass radius, velocity dispersion, phase-space density, and the mass fraction between residual baryonic and dark matter.« less

  9. Atmosphere Impact Losses

    NASA Astrophysics Data System (ADS)

    Schlichting, Hilke E.; Mukhopadhyay, Sujoy

    2018-02-01

    Determining the origin of volatiles on terrestrial planets and quantifying atmospheric loss during planet formation is crucial for understanding the history and evolution of planetary atmospheres. Using geochemical observations of noble gases and major volatiles we determine what the present day inventory of volatiles tells us about the sources, the accretion process and the early differentiation of the Earth. We further quantify the key volatile loss mechanisms and the atmospheric loss history during Earth's formation. Volatiles were accreted throughout the Earth's formation, but Earth's early accretion history was volatile poor. Although nebular Ne and possible H in the deep mantle might be a fingerprint of this early accretion, most of the mantle does not remember this signature implying that volatile loss occurred during accretion. Present day geochemistry of volatiles shows no evidence of hydrodynamic escape as the isotopic compositions of most volatiles are chondritic. This suggests that atmospheric loss generated by impacts played a major role during Earth's formation. While many of the volatiles have chondritic isotopic ratios, their relative abundances are certainly not chondritic again suggesting volatile loss tied to impacts. Geochemical evidence of atmospheric loss comes from the {}3He/{}^{22}Ne, halogen ratios (e.g., F/Cl) and low H/N ratios. In addition, the geochemical ratios indicate that most of the water could have been delivered prior to the Moon forming impact and that the Moon forming impact did not drive off the ocean. Given the importance of impacts in determining the volatile budget of the Earth we examine the contributions to atmospheric loss from both small and large impacts. We find that atmospheric mass loss due to impacts can be characterized into three different regimes: 1) Giant Impacts, that create a strong shock transversing the whole planet and that can lead to atmospheric loss globally. 2) Large enough impactors (m_{cap} ≳ √{2

  10. THE DEPENDENCE OF STELLAR MASS AND ANGULAR MOMENTUM LOSSES ON LATITUDE AND THE INTERACTION OF ACTIVE REGION AND DIPOLAR MAGNETIC FIELDS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Garraffo, Cecilia; Drake, Jeremy J.; Cohen, Ofer

    Rotation evolution of late-type stars is dominated by magnetic braking and the underlying factors that control this angular momentum loss are important for the study of stellar spin-down. In this work, we study angular momentum loss as a function of two different aspects of magnetic activity using a calibrated Alfvén wave-driven magnetohydrodynamic wind model: the strengths of magnetic spots and their distribution in latitude. By driving the model using solar and modified solar surface magnetograms, we show that the topology of the field arising from the net interaction of both small-scale and large-scale field is important for spin-down rates andmore » that angular momentum loss is not a simple function of large scale magnetic field strength. We find that changing the latitude of magnetic spots can modify mass and angular momentum loss rates by a factor of two. The general effect that causes these differences is the closing down of large-scale open field at mid- and high-latitudes by the addition of the small-scale field. These effects might give rise to modulation of mass and angular momentum loss through stellar cycles, and present a problem for ab initio attempts to predict stellar spin-down based on wind models. For all the magnetogram cases considered here, from dipoles to various spotted distributions, we find that angular momentum loss is dominated by the mass loss at mid-latitudes. The spin-down torque applied by magnetized winds therefore acts at specific latitudes and is not evenly distributed over the stellar surface, though this aspect is unlikely to be important for understanding spin-down and surface flows on stars.« less

  11. Volcanic eruptions on Io - Implications for surface evolution and mass loss

    NASA Technical Reports Server (NTRS)

    Johnson, T. V.; Soderblom, L. A.

    1982-01-01

    Active volcanism on Io results in a continual resurfacing of the satellite. Analysis of required burial rates to erase impact craters, the mass production in the observed plumes, and the energy requirements for the volcanic activity suggest resurfacing rates of 0.001 to 10 cm/yr in recent geologic time. If this rate is typical of the last 4.5 Gyr, then extensive recycling of the upper crust and mantle must have occurred. The currently estimated loss rate of S, O, and Na from Io into the magnetosphere corresponds to only a small fraction of the resurfacing rate and should not have resulted in either extensive erosion or total depletion of any of the escaping species.

  12. A path model of sarcopenia on bone mass loss in elderly subjects.

    PubMed

    Rondanelli, M; Guido, D; Opizzi, A; Faliva, M A; Perna, S; Grassi, M

    2014-01-01

    Aging is associated with decreases in muscle mass, strength, power (sarcopenia) and bone mineral density (BMD). The aims of this study were to investigate in elderly the role of sarcopenia on BMD loss by a path model, including adiposity, inflammation, and malnutrition associations. Body composition and BMD were measured by dual X-ray absorptiometry in 159 elderly subjects (52 male/107 female; mean age 80.3 yrs). Muscle strength was determined with dynamometer. Serum albumin and PCR were also assessed. Structural equations examined the effect of sarcopenia (measured by Relative Skeletal Muscle Mass, Total Muscle Mass, Handgrip, Muscle Quality Score) on osteoporosis (measured by Vertebral and Femoral T-scores) in a latent variable model including adiposity (measured by Total Fat Mass, BMI, Ginoid/Android Fat), inflammation (PCR), and malnutrition (serum albumin). The sarcopenia assumed a role of moderator in the adiposity-osteoporosis relationship. Specifically, increasing the sarcopenia, the relationship adiposity-osteoporosis (β: -0.58) decrease in intensity. Adiposity also influences sarcopenia (β: -0.18). Malnutrition affects the inflammatory and the adiposity states (β: +0.61, and β: -0.30, respectively), while not influencing the sarcopenia. Thus, adiposity has a role as a mediator of the effect of malnutrition on both sarcopenia and osteoporosis. Malnutrition decreases adiposity; decreasing adiposity, in turn, increase the sarcopenia and osteoporosis. This study suggests such as in a group of elderly sarcopenia affects the link between adiposity and BMD, but not have a pure independent effect on osteoporosis.

  13. [Contribution of soil fauna to the mass loss of Betula albosinensis leaf litter at early decomposition stage of subalpine forest litter in western Sichuan].

    PubMed

    Xia, Lei; Wu, Fu-Zhong; Yang, Wan-Qin; Tan, Bo

    2012-02-01

    In order to quantify the contribution of soil fauna to the decomposition of birch (Betula albosinensis) leaf litter in subalpine forests in western Sichuan of Southwest China during freeze-thaw season, a field experiment with different mesh sizes (0.02, 0.125, 1 and 3 mm) of litterbags was conducted in a representative birch-fir (Abies faxoniana) forest to investigate the mass loss rate of the birch leaf litter from 26 October, 2010 to 18 April, 2011, and the contributions of micro-, meso- and macro-fauna to the decomposition of the leaf litter. Over the freeze-thaw season, 11.8%, 13.2%, 15.4% and 19.5% of the mass loss were detected in the litterbags with 0.02, 0. 125, 1 and 3 mm mesh sizes, respectively. The total contribution of soil fauna to the litter decomposition accounted for 39.5% of the mass loss, and the taxa and individual relative density of the soil fauna in the litterbags had the similar variation trend with that of the mass loss rate. The contribution rate of soil fauna to the leaf litter mass loss showed the order of micro- < meso- < macro-fauna, with the highest contribution of micro-fauna (7.9%), meso-fauna (11.9%), and macro-fauna (22.7%) at the onset of freezing stage, deeply frozen stage, and thawing stage, respectively. The results demonstrated that soil fauna played an important role in the litter decomposition in subalpine forests of western Sichuan during freeze-thaw season.

  14. Implementation of a method to visualize noise-induced hearing loss in mass stranded cetaceans

    NASA Astrophysics Data System (ADS)

    Morell, Maria; Brownlow, Andrew; McGovern, Barry; Raverty, Stephen A.; Shadwick, Robert E.; André, Michel

    2017-02-01

    Assessment of the impact of noise over-exposure in stranded cetaceans is challenging, as the lesions that lead to hearing loss occur at the cellular level and inner ear cells are very sensitive to autolysis. Distinguishing ante-mortem pathology from post-mortem change has been a major constraint in diagnosing potential impact. Here, we outline a methodology applicable to the detection of noise-induced hearing loss in stranded cetaceans. Inner ears from two mass strandings of long-finned pilot whales in Scotland were processed for scanning electron microscopy observation. In one case, a juvenile animal, whose ears were fixed within 4 hours of death, revealed that many sensory cells at the apex of the cochlear spiral were missing. In this case, the absence of outer hair cells would be compatible with overexposure to underwater noise, affecting the region which transduces the lowest frequencies of the pilot whales hearing spectrum. Perfusion of cochlea with fixative greatly improved preservation and enabled diagnostic imaging of the organ of Corti, even 30 hours after death. This finding supports adopting a routine protocol to detect the pathological legacy of noise overexposure in mass stranded cetaceans as a key to understanding the complex processes and implications that lie behind such stranding events.

  15. Response of the tropical Pacific to abrupt climate change 8,200 years ago

    NASA Astrophysics Data System (ADS)

    Atwood, A. R.; Battisti, D.; Bitz, C. M.; Sachs, J. P.

    2017-12-01

    The relatively stable climate of the Holocene epoch was punctuated by a period of large and abrupt climate change ca. 8,200 yr BP, when an outburst of glacial meltwater into the Labrador Sea drove large and abrupt climate changes across the globe. However, little is known about the response of the tropical Pacific to this event. We present the first evidence for large perturbations to the eastern tropical Pacific climate, based on sedimentary biomarker and hydrogen isotopic records from a freshwater lake in the Galápagos Islands. We inform these reconstructions with freshwater forcing simulations performed with the Community Climate System Model version 4. Together, the biomarker records and model simulations provide evidence for a mechanistic link between (1) a southward shift of the Intertropical Convergence Zone in the eastern equatorial Pacific and (2) decreased frequency and/or intensity of Eastern Pacific El Niño events during the 8,200 BP event. While climate theory and modeling studies support a southward shift of the ITCZ in response to a weakened AMOC, the dynamical drivers for the observed change in ENSO variability are less well developed. To explore these linkages, we perform simulations with an intermediate complexity model of the tropical Pacific. These results provide valuable insight into the controls of tropical Pacific climate variability and the mechanisms behind the global response to abrupt climate change.

  16. Minimalist coupled evolution model for stellar X-ray activity, rotation, mass loss, and magnetic field

    NASA Astrophysics Data System (ADS)

    Blackman, Eric G.; Owen, James E.

    2016-05-01

    Late-type main-sequence stars exhibit an X-ray to bolometric flux ratio that depends on {tilde{R}o}, the ratio of rotation period to convective turnover time, as {tilde{R}o}^{-ζ } with 2 ≤ ζ ≤ 3 for {tilde{R}o} > 0.13, but saturates with |ζ| < 0.2 for {tilde{R}o} < 0.13. Saturated stars are younger than unsaturated stars and show a broader spread of rotation rates and X-ray activity. The unsaturated stars have magnetic fields and rotation speeds that scale roughly with the square root of their age, though possibly flattening for stars older than the Sun. The connection between faster rotators, stronger fields, and higher activity has been established observationally, but a theory for the unified time-evolution of X-ray luminosity, rotation, magnetic field and mass loss that captures the above trends has been lacking. Here we derive a minimalist holistic framework for the time evolution of these quantities built from combining a Parker wind with new ingredients: (1) explicit sourcing of both the thermal energy launching the wind and the X-ray luminosity via dynamo produced magnetic fields; (2) explicit coupling of X-ray activity and mass-loss saturation to dynamo saturation (via magnetic helicity build-up and convection eddy shredding); (3) use of coronal equilibrium to determine how magnetic energy is divided into wind and X-ray contributions. For solar-type stars younger than the Sun, we infer conduction to be a subdominant power loss compared to X-rays and wind. For older stars, conduction is more important, possibly quenching the wind and reducing angular momentum loss. We focus on the time evolution for stars younger than the Sun, highlighting what is possible for further generalizations. Overall, the approach shows promise towards a unified explanation of all of the aforementioned observational trends.

  17. Elucidating Dynamical Processes Relevant to Flow Encountering Abrupt Topography (FLEAT)

    DTIC Science & Technology

    2015-09-30

    Encountering Abrupt Topography (FLEAT) Bo Qiu Dept of Oceanography, University of Hawaii at Manoa 1000 Pope Rd. Honolulu, HI 96822 phone: (808) 956...c) to explore relevant dynamics by using both simplified models and OGCM output with realistic topography and surface boundary conditions...scale abyssal circulation, we propose to use the Hallberg Isopycnal Model (HIM). The HIM allows sloping isopycnals to interact with bottom topography

  18. Mass loss in HR 1040 /A0 Ia/ - Analysis of Mg II lambda 2802 and H-alpha

    NASA Technical Reports Server (NTRS)

    Kunasz, P. B.; Morrison, N. D.; Spressart, B.

    1983-01-01

    It is pointed out that International Ultraviolet Explorer (IUE) data for several early A type supergiants are now available to complement the ground-based spectroscopic data available for these bright stars. An examination of the resonance doublet of Mg II in the A type supergiants reveals that HR 1040 (HD 21389) is the only star in the observational literature in which a violet-shifted, deep absorption line is present without complete saturation. From an unsaturated profile, a good estimate of Mg(+) density can be found by means of accurate radiative transfer calculations. A relation can then be derived between mass loss rate and ionization balance. When certain velocity-related quantities can be estimated from a Mg II line profile, the H-alpha provides an estimate of the mass loss rate. The present investigation is concerned with an application of these diagnostics to HR 1040.

  19. Sauna-Induced Body Mass Loss in Young Sedentary Women and Men

    PubMed Central

    Podstawski, Robert; Boraczyński, Tomasz; Boraczyński, Michał

    2014-01-01

    The aim of the study was to evaluate the relationship between body mass index (BMI) and body mass loss (BML) induced by thermal stress in a dry sauna. The study was conducted on a group of 674 sedentary students, 326 women and 348 men aged 19-20. The correlations between BMI scores and BML were determined. The subjects were placed in supine position in a dry sauna for two sessions of 10 minutes each with a 5-minute break. The influence of BMI on the amount of BML in the sauna was determined by nonlinear stepwise regression. The smallest BML was noted in underweight subjects; students with normal weight lost more weight, whereas the greatest BML was reported in overweight and obese subjects. Persons with a high BMI are at higher risk of dehydration, and they should pay particular attention to replenishing fluids during a visit to the sauna. The proposed equations for calculating BML based on a person's BMI can be useful in estimating the amount of fluids that should be replenished by both men and women during a visit to a dry sauna. PMID:25614882

  20. Effects of 4 weight-loss diets differing in fat, protein, and carbohydrate on fat mass, lean mass, visceral adipose tissue, and hepatic fat: results from the POUNDS LOST trial123

    PubMed Central

    de Souza, Russell J; Carey, Vincent J; Hall, Kevin D; LeBoff, Meryl S; Loria, Catherine M; Laranjo, Nancy M; Sacks, Frank M; Smith, Steven R

    2012-01-01

    Background: Weight loss reduces body fat and lean mass, but whether these changes are influenced by macronutrient composition of the diet is unclear. Objective: We determined whether energy-reduced diets that emphasize fat, protein, or carbohydrate differentially reduce total, visceral, or hepatic fat or preserve lean mass. Design: In a subset of participants in a randomized trial of 4 weight-loss diets, body fat and lean mass (n = 424; by using dual-energy X-ray absorptiometry) and abdominal and hepatic fat (n = 165; by using computed tomography) were measured after 6 mo and 2 y. Changes from baseline were compared between assigned amounts of protein (25% compared with 15%) and fat (40% compared with 20%) and across 4 carbohydrate amounts (35% through 65%). Results: At 6 mo, participants lost a mean (±SEM) of 4.2 ± 0.3 kg (12.4%) fat and 2.1 ± 0.3 kg (3.5%) lean mass (both P < 0.0001 compared with baseline values), with no differences between 25% and 15% protein (P ≥ 0.10), 40% and 20% fat (P ≥ 0.34), or 65% and 35% carbohydrate (P ≥ 0.27). Participants lost 2.3 ± 0.2 kg (13.8%) abdominal fat: 1.5 ± 0.2 kg (13.6%) subcutaneous fat and 0.9 ± 0.1 kg (16.1%) visceral fat (all P < 0.0001 compared with baseline values), with no differences between the diets (P ≥ 0.29). Women lost more visceral fat than did men relative to total-body fat loss. Participants regained ∼40% of these losses by 2 y, with no differences between diets (P ≥ 0.23). Weight loss reduced hepatic fat, but there were no differences between groups (P ≥ 0.28). Dietary goals were not fully met; self-reported contrasts were closer to 2% protein, 8% fat, and 14% carbohydrate at 6 mo and 1%, 7%, and 10%, respectively, at 2 y. Conclusion: Participants lost more fat than lean mass after consumption of all diets, with no differences in changes in body composition, abdominal fat, or hepatic fat between assigned macronutrient amounts. This trial was registered at clinicaltrials.gov as NCT

  1. ADIABATIC MASS LOSS IN BINARY STARS. II. FROM ZERO-AGE MAIN SEQUENCE TO THE BASE OF THE GIANT BRANCH

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ge, Hongwei; Chen, Xuefei; Han, Zhanwen

    2015-10-10

    In the limit of extremely rapid mass transfer, the response of a donor star in an interacting binary becomes asymptotically one of adiabatic expansion. We survey here adiabatic mass loss from Population I stars (Z = 0.02) of mass 0.10 M{sub ⊙}–100 M{sub ⊙} from the zero-age main sequence to the base of the giant branch, or to central hydrogen exhaustion for lower main sequence stars. The logarithmic derivatives of radius with respect to mass along adiabatic mass-loss sequences translate into critical mass ratios for runaway (dynamical timescale) mass transfer, evaluated here under the assumption of conservative mass transfer. Formore » intermediate- and high-mass stars, dynamical mass transfer is preceded by an extended phase of thermal timescale mass transfer as the star is stripped of most of its envelope mass. The critical mass ratio q{sub ad} (throughout this paper, we follow the convention of defining the binary mass ratio as q ≡ M{sub donor}/M{sub accretor}) above which this delayed dynamical instability occurs increases with advancing evolutionary age of the donor star, by ever-increasing factors for more massive donors. Most intermediate- or high-mass binaries with nondegenerate accretors probably evolve into contact before manifesting this instability. As they approach the base of the giant branch, however, and begin developing a convective envelope, q{sub ad} plummets dramatically among intermediate-mass stars, to values of order unity, and a prompt dynamical instability occurs. Among low-mass stars, the prompt instability prevails throughout main sequence evolution, with q{sub ad} declining with decreasing mass, and asymptotically approaching q{sub ad} = 2/3, appropriate to a classical isentropic n = 3/2 polytrope. Our calculated q{sub ad} values agree well with the behavior of time-dependent models by Chen and Han of intermediate-mass stars initiating mass transfer in the Hertzsprung gap. Application of our results to cataclysmic variables, as

  2. Onset of Oviposition Triggers Abrupt Reduction in Migratory Flight Behavior and Flight Muscle in the Female Beet Webworm, Loxostege sticticalis

    PubMed Central

    Cheng, Yunxia; Luo, Lizhi; Sappington, Thomas W.; Jiang, Xingfu; Zhang, Lei; Frolov, Andrei N.

    2016-01-01

    Flight and reproduction are usually considered as two life history traits that compete for resources in a migratory insect. The beet webworm, Loxostege sticticalis L., manages the costs of migratory flight and reproduction through a trade-off in timing of these two life history traits, where migratory behavior occurs during the preoviposition period. To gain insight into how migratory flight and reproduction are coordinated in the female beet webworm, we conducted experiments beginning at the end of the preoviposition period. We used flight mills to test whether flight performance and supportive flight musculature and fuel are affected by the number of eggs oviposited, or by the age of mated and unmated females after onset of oviposition by the former. The results showed that flight distance, flight velocity, flight duration, and flight muscle mass decreased abruptly at the onset of oviposition, compared to that of virgin females of the same age which did not change over the next 7 d. These results indicate that onset of oviposition triggers a decrease in flight performance and capacity in female beet webworms, as a way of actively managing reallocation of resources away from migratory flight and into egg production. In addition to the abrupt switch, there was a gradual, linear decline in flight performance, flight muscle mass, and flight fuel relative to the number of eggs oviposited. The histolysis of flight muscle and decrease of triglyceride content indicate a progressive degradation in the ability of adults to perform additional migratory flights after onset of oviposition. Although the results show that substantial, albeit reduced, long-duration flights remain possible after oviposition begins, additional long-distance migratory flights probably are not launched after the initiation of oviposition. PMID:27893835

  3. Onset of Oviposition Triggers Abrupt Reduction in Migratory Flight Behavior and Flight Muscle in the Female Beet Webworm, Loxostege sticticalis.

    PubMed

    Cheng, Yunxia; Luo, Lizhi; Sappington, Thomas W; Jiang, Xingfu; Zhang, Lei; Frolov, Andrei N

    2016-01-01

    Flight and reproduction are usually considered as two life history traits that compete for resources in a migratory insect. The beet webworm, Loxostege sticticalis L., manages the costs of migratory flight and reproduction through a trade-off in timing of these two life history traits, where migratory behavior occurs during the preoviposition period. To gain insight into how migratory flight and reproduction are coordinated in the female beet webworm, we conducted experiments beginning at the end of the preoviposition period. We used flight mills to test whether flight performance and supportive flight musculature and fuel are affected by the number of eggs oviposited, or by the age of mated and unmated females after onset of oviposition by the former. The results showed that flight distance, flight velocity, flight duration, and flight muscle mass decreased abruptly at the onset of oviposition, compared to that of virgin females of the same age which did not change over the next 7 d. These results indicate that onset of oviposition triggers a decrease in flight performance and capacity in female beet webworms, as a way of actively managing reallocation of resources away from migratory flight and into egg production. In addition to the abrupt switch, there was a gradual, linear decline in flight performance, flight muscle mass, and flight fuel relative to the number of eggs oviposited. The histolysis of flight muscle and decrease of triglyceride content indicate a progressive degradation in the ability of adults to perform additional migratory flights after onset of oviposition. Although the results show that substantial, albeit reduced, long-duration flights remain possible after oviposition begins, additional long-distance migratory flights probably are not launched after the initiation of oviposition.

  4. Bend-imitating models of abruptly bent electron waveguides

    NASA Astrophysics Data System (ADS)

    Vakhnenko, Oleksiy O.

    2011-07-01

    The fundamentals of bend-imitating approach regarding the one-electron quantum mechanics in abruptly bent ideal electron waveguides are given. In general, the theory allows to model each particular circularlike bend of a continuous quantum wire as some effective multichannel scatterer being pointlike in longitudinal direction. Its scattering ability is determined by the bending angle, mean bending radius, lateral coordinate (or coordinates) in wire cross section, time (or electronic energy), and possibly by the applied magnetic field. In an equivalent formulation, the theory gives rise to rather simple matching rules for the electron wave function and its longitudinal derivative affecting only the straight parts of a wire and thereby permitting to bypass a detailed quantum mechanical consideration of elbow domains. The proposed technique is applicable for the analytical investigation of spectral and transport electronic properties related to the ideal abruptly bent 3D wirelike structures of fixed cross section and is adaptable to the 2D wirelike structures as well as to the wirelike structures subjected to the magnetic field perpendicular to the plane of wire bending. In the framework of bend-imitating approach, the investigation of electron scattering in a singly bent 2D quantum wire and a doubly bent 2D quantum wire with S-like bend has been made and the explicit dependences of transmission and reflection coefficients on geometrical parameters of respective structure as well as on electron energy have been obtained. The total suppression of mixing between the scattering channels of S-like bent quantum wire is predicted.

  5. Direct generation of abruptly focusing vortex beams using a 3/2 radial phase-only pattern.

    PubMed

    Davis, Jeffrey A; Cottrell, Don M; Zinn, Jonathan M

    2013-03-20

    Abruptly focusing Airy beams have previously been generated using a radial cubic phase pattern that represents the Fourier transform of the Airy beam. The Fourier transform of this pattern is formed using a system length of 2f, where f is the focal length of the Fourier transform lens. In this work, we directly generate these abruptly focusing Airy beams using a 3/2 radial phase pattern encoded onto a liquid crystal display. The resulting optical system is much shorter. In addition, we can easily produce vortex patterns at the focal point of these beams. Experimental results match theoretical predictions.

  6. West African monsoon dynamics inferred from abrupt fluctuations of Lake Mega-Chad

    PubMed Central

    Armitage, Simon J.; Bristow, Charlie S.; Drake, Nick A.

    2015-01-01

    From the deglacial period to the mid-Holocene, North Africa was characterized by much wetter conditions than today. The broad timing of this period, termed the African Humid Period, is well known. However, the rapidity of the onset and termination of the African Humid Period are contested, with strong evidence for both abrupt and gradual change. We use optically stimulated luminescence dating of dunes, shorelines, and fluviolacustrine deposits to reconstruct the fluctuations of Lake Mega-Chad, which was the largest pluvial lake in Africa. Humid conditions first occur at ∼15 ka, and by 11.5 ka, Lake Mega-Chad had reached a highstand, which persisted until 5.0 ka. Lake levels fell rapidly at ∼5 ka, indicating abrupt aridification across the entire Lake Mega-Chad Basin. This record provides strong terrestrial evidence that the African Humid Period ended abruptly, supporting the hypothesis that the African monsoon responds to insolation forcing in a markedly nonlinear manner. In addition, Lake Mega-Chad exerts strong control on global biogeochemical cycles because the northern (Bodélé) basin is currently the world’s greatest single dust source and possibly an important source of limiting nutrients for both the Amazon Basin and equatorial Atlantic. However, we demonstrate that the final desiccation of the Bodélé Basin occurred around 1 ka. Consequently, the present-day mode and scale of dust production from the Bodélé Basin cannot have occurred before 1 ka, suggesting that its role in fertilizing marine and terrestrial ecosystems is either overstated or geologically recent. PMID:26124133

  7. Remote Detection and Modeling of Abrupt and Gradual Tree Mortality in the Southwestern USA

    NASA Astrophysics Data System (ADS)

    Muss, J. D.; Xu, C.; McDowell, N. G.

    2014-12-01

    Current climate models predict a warming and drying trend that has a high probability of increasing the frequency and spatial extent of tree mortality events. Field surveys can be used to identify, date, and attribute a cause of mortality to specific trees, but monetary and time constraints prevent broad-scale surveys, which are necessary to establish regional or global trends in tree mortality. This is significant because widespread forest mortality will likely lead to radical changes in evapotranspiration and surface albedo, which could compound climate change. While understanding the causes and mechanisms of tree mortality events is crucial, it is equally important to be able to detect and monitor mortality and subsequent changes to the ecosystem at broad spatial- and temporal-scales. Over the past five years our ability to remotely detect abrupt forest mortality events has improved greatly, but gradual events—such as those caused by drought or certain types of insects—are still difficult to identify. Moreover, it is virtually impossible to quantify the amount of mortality that has occurred within a mixed pixel. We have developed a system that fuses climate and satellite-derived spectral data to identify both the date and the agent of forest mortality events. This system has been used with Landsat time series data to detect both abrupt and general trends in tree loss that have occurred during the past quarter-century in northern New Mexico. It has also been used with MODIS data to identify pixels with a high likelihood of drought-caused tree mortality in the Southwestern US. These candidate pixels were then fed to ED-FRT, a coupled forest dynamics-radiative transfer model, to generate estimates of drought-induced. We demonstrate a multi-scale approach that can produce results that will be instrumental in advancing our understanding of tree mortality-climate feedbacks, and improve our ability to predict what forests could look like in the future.

  8. O Star Wind Mass-Loss Rates and Shock Physics from X-ray Line Profiles in Archival XMM RGS Data

    NASA Astrophysics Data System (ADS)

    Cohen, David

    O stars are characterized by their dense, supersonic stellar winds. These winds are the site of X-ray emission from shock-heated plasma. By analyzing high-resolution X-ray spectra of these O stars, we can learn about the wind-shock heating and X-ray production mechanism. But in addition, the X-rays can also be used to measure the mass-loss rate of the stellar wind, which is a key observational quantity whose value affects stellar evolution and energy, momentum, and mass input to the Galactic interstellar medium. We make this X-ray based mass-loss measurement by analyzing the profile shapes of the X-ray emission lines observed at high resolution with the Chandra and XMM-Newton grating spectrometers. One advantage of our method is that it is insensitive to small-scale clumping that affects density-squared diagnostics. We are applying this analysis technique to O stars in the Chandra archive, and are finding mass-loss rates lower than those traditionally assumed for these O stars, and in line with more recent independent determinations that do account for clumping. By extending this analysis to the XMM RGS data archive, we will make significant contributions to the understanding of both X-ray production in O stars and to addressing the issue of the actual mass-loss rates of O stars. The XMM RGS data archive provides several extensions and advantages over the smaller Chandra HETGS archive: (1) there are roughly twice as many O and early B stars in the XMM archive; (2) the longer wavelength response of the RGS provides access to diagnostically important lines of nitrogen and carbon; (3) the very long, multiple exposures of zeta Pup provide the opportunity to study this canonical O supergiant's X-ray spectrum in unprecedented detail, including looking at the time variability of X-ray line profiles. Our research team has developed a sophisticated empirical line profile model as well as a computational infrastructure for fitting the model to high-resolution X-ray spectra

  9. Stellar Evolution in NGC 6791: Mass Loss on the Red Giant Branch and the Formation of Low-Mass White Dwarfs

    NASA Astrophysics Data System (ADS)

    Kalirai, Jasonjot S.; Bergeron, P.; Hansen, Brad M. S.; Kelson, Daniel D.; Reitzel, David B.; Rich, R. Michael; Richer, Harvey B.

    2007-12-01

    We present the first detailed study of the properties (temperatures, gravities, and masses) of the NGC 6791 white dwarf population. This unique stellar system is both one of the oldest (8 Gyr) and most metal-rich ([Fe/H]~+0.4) open clusters in our Galaxy and has a color-magnitude diagram (CMD) that exhibits both a red giant clump and a much hotter extreme horizontal branch. Fitting the Balmer lines of the white dwarfs in the cluster using Keck/LRIS spectra suggests that most of these stars are undermassive, =0.43+/-0.06 Msolar, and therefore could not have formed from canonical stellar evolution involving the helium flash at the tip of the red giant branch. We show that at least 40% of NGC 6791's evolved stars must have lost enough mass on the red giant branch to avoid the flash and therefore did not convert helium into carbon-oxygen in their core. Such increased mass loss in the evolution of the progenitors of these stars is consistent with the presence of the extreme horizontal branch in the CMD. This unique stellar evolutionary channel also naturally explains the recent finding of a very young age (2.4 Gyr) for NGC 6791 from white dwarf cooling theory; helium-core white dwarfs in this cluster will cool ~3 times slower than carbon-oxygen-core stars, and therefore the corrected white dwarf cooling age is in fact >~7 Gyr, consistent with the well-measured main-sequence turnoff age. These results provide direct empirical evidence that mass loss is much more efficient in high-metallicity environments and therefore may be critical in interpreting the ultraviolet upturn in elliptical galaxies. Data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Based on observations obtained at the

  10. LOSS Revisited. II. The Relative Rates of Different Types of Supernovae Vary between Low- and High-mass Galaxies

    NASA Astrophysics Data System (ADS)

    Graur, Or; Bianco, Federica B.; Modjaz, Maryam; Shivvers, Isaac; Filippenko, Alexei V.; Li, Weidong; Smith, Nathan

    2017-03-01

    In Paper I of this series, we showed that the ratio between stripped-envelope (SE) supernova (SN) and Type II SN rates reveals a significant SE SN deficiency in galaxies with stellar masses ≲ {10}10 {M}⊙ . Here, we test this result by splitting the volume-limited subsample of the Lick Observatory Supernova Search (LOSS) SN sample into low- and high-mass galaxies and comparing the relative rates of various SN types found in them. The LOSS volume-limited sample contains 180 SNe and SN impostors and is complete for SNe Ia out to 80 Mpc and core-collapse SNe out to 60 Mpc. All of these transients were recently reclassified by us in Shivvers et al. We find that the relative rates of some types of SNe differ between low- and high-mass galaxies: SNe Ib and Ic are underrepresented by a factor of ˜3 in low-mass galaxies. These galaxies also contain the only examples of SN 1987A-like SNe in the sample and host about nine times as many SN impostors. Normal SNe Ia seem to be ˜30% more common in low-mass galaxies, making these galaxies better sources for homogeneous SN Ia cosmology samples. The relative rates of SNe IIb are consistent in both low- and high-mass galaxies. The same is true for broad-line SNe Ic, although our sample includes only two such objects. The results presented here are in tension with a similar analysis from the Palomar Transient Factory, especially as regards SNe IIb.

  11. False alarms: How early warning signals falsely predict abrupt sea ice loss

    NASA Astrophysics Data System (ADS)

    Wagner, Till J. W.; Eisenman, Ian

    2016-04-01

    Uncovering universal early warning signals for critical transitions has become a coveted goal in diverse scientific disciplines, ranging from climate science to financial mathematics. There has been a flurry of recent research proposing such signals, with increasing autocorrelation and increasing variance being among the most widely discussed candidates. A number of studies have suggested that increasing autocorrelation alone may suffice to signal an impending transition, although some others have questioned this. Here we consider variance and autocorrelation in the context of sea ice loss in an idealized model of the global climate system. The model features no bifurcation, nor increased rate of retreat, as the ice disappears. Nonetheless, the autocorrelation of summer sea ice area is found to increase in a global warming scenario. The variance, by contrast, decreases. A simple physical mechanism is proposed to explain the occurrence of increasing autocorrelation but not variance when there is no approaching bifurcation. Additionally, a similar mechanism is shown to allow an increase in both indicators with no physically attainable bifurcation. This implies that relying on autocorrelation and variance as early warning signals can raise false alarms in the climate system, warning of "tipping points" that are not actually there.

  12. Trilogy, an Interplanetary Constellation to Measure the Rate of Mass Loss by the Sun

    NASA Astrophysics Data System (ADS)

    Zuber, M. T.; Smith, D. E.; Mazarico, E. M.; Genova, A.; Neumann, G. A.; Sun, X.

    2017-12-01

    As the Sun slowly converts hydrogen into helium it steadily loses mass because the mass of a fused helium atom is less than that of the four original hydrogen atoms. This mass difference is released as energy in the form of electromagnetic and particle radiation. It will also affect the orbits of the planets and other bodies because the Sun's gravity is the central force that determines the sizes of their orbits. This loss of mass, believed to be of order 10-13 solar mass/ year, increases the semi-major axis of Earth's orbit by about 1.5 cm/year, with increasing magnitude with distance, e.g., over 7 cm/year at Jupiter near 5 AU. For the inner planets, where planetary orbital velocities are greatest, the largest effect is in the decrease in angular velocity as a result of the conservation of angular momentum. We will present a mission concept called Trilogy, which would establish geodetic/geophysical spacecraft around several key planetary bodies (i.e., Venus, Mars and Earth's Moon) and measure the ranges between these spacecraft down to centimeter level regularly over a period of years. The required technologies have been demonstrated on missions to the Moon and can now be applied between planets. The observations would enable the accurate determination and monitoring of the trajectories of these masses, from which the rate of decrease in solar mass could be estimated with great precision. Such a dataset would also enable the recovery of parameters key to many scientific fields, from planetary science to heliophysics to astrophysics and relativity.

  13. The role of pyridoxine as a countermeasure for in-flight loss of lean body mass

    NASA Technical Reports Server (NTRS)

    Gilbert, Joyce A.

    1992-01-01

    Ground based and in flight research has shown that humans, under conditions of microgravity, sustain a loss of lean body tissue (protein) and changes in several biological processes including, reductions in red blood cell mass, and neurotransmitters. The maintenance of muscle mass, the major component of lean body mass, is required to meet the needs of space station EVAs. Central to the biosynthesis of amino acids, the building blocks of protein, is pyridoxine (vitamin B-6). Muscle mass integrity requires the availability of vitamin B-6 for protein metabolism and neurotransmitter synthesis. Furthermore, the formation of red blood cells require pyridoxine as a cofactor in the biosynthesis of hemoglobin, a protein that carries oxygen to tissues. In its active form, pyridoxal-5'-phosphate (PLP), vitamin B-6 serves as a link between amino acid and carbohydrate metabolism through intermediates of glycolysis and the tricarboxylic acid cycle. In addition to its role in energy metabolism, PLP is involved in the biosynthesis of hemoglobin and neurotransmitter which are necessary for neurological functions. Alterations in pyridoxine metabolism may affect countermeasures designed to overcome some of these biochemical changes. The focus of this research is to determine the effects of microgravity on the metabolic utilization of vitamin B-6, integrating nutrition as an integral component of the countermeasure (exercise) to maintain lean body mass and muscle strength. The objectives are: 1) to determine whether microgravity effects the metabolic utilization of pyridoxine and 2) to quantitate changes in B-6 vitamer distribution in tissue and excreta relative to loss of lean body tissue. The rationale for this study encompasses the unique challenge to control biochemical mechanisms effected during space travel and the significance of pyridoxine to maintain and counter muscle integrity for EVA activities. This experiment will begin to elucidate the importance of biochemical

  14. Revisiting Lake Hämelsee: reconstructing abrupt Lateglacial climate transitions using state- of-the-art palaeoclimatological proxies

    NASA Astrophysics Data System (ADS)

    Engels, Stefan; Hoek, Wim; Lane, Christine; Sachse, Dirk; Wagner-Cremer, Friederike

    2015-04-01

    Lake Hämelsee (Germany) is one of the northernmost sites in NW Europe that has varved sediments throughout large parts of its Lateglacial and Early Holocene sediment sequence. Previous research on this site has shown its potential, in terms of chronological resolution and palaeoecological reconstructions, for reconstructing the abrupt transitions into and out of the Younger Dryas, the last cold period of the last glacial. The site was revisited during a 1-week summer school for Early Stage Researchers (2013), within the INTIMATE Example training and research project, supported by EU Cost Action ES0907. Two overlapping sediment sequences were retrieved from the centre of the lake during the summer school. These sediments have since formed the basis for follow-up research projects, which have sparked the collaboration of around 30 researchers in 12 laboratories across Europe. A chronological framework for the core has been composed from a combination of varve counting, radiocarbon dating and tephrochronology. Tephrostratigraphic correlations allow direct correlation and precise comparison of the record to marine and ice core records from the North Atlantic region, and other terrestrial European archives. Furthermore, the core is has been subjected to multiple sedimentological (e.g. XRF, loss-on-ignition), geochemical (e.g. lipid biomarkers, GDGTs) and palaeoecological (e.g. pollen, chironomids) proxy-based reconstructions of past environmental and climatic conditions. The results provide important insights into the nature of the abrupt climate transitions of the Lateglacial and Early Holocene, both locally and on a continental scale. The INTIMATE Example participants: Illaria Baneschi, Achim Brauer, Christopher Bronk Ramsey, Renee de Bruijn, Siwan Davies, Aritina Haliuc, Katalin Hubay, Gwydion Jones, Meike Müller, Johanna Menges, Josef Merkt, Tom Peters, Francien Peterse, Anneke ter Schure, Kathrin Schuetrumpf, Richard Staff, Falko Turner, Valerie van den Bos.

  15. An abrupt slowdown of Atlantic Meridional Overturning Circulation during 1915-1935 induced by solar forcing in a coupled GCM

    NASA Astrophysics Data System (ADS)

    Lin, P.; Song, Y.; Yu, Y.; Liu, H.

    2014-06-01

    In this study, we explore an abrupt change of Atlantic Meridional Overturning Circulation (AMOC) apparent in the historical run simulated by the second version of the Flexible Global Ocean-Atmosphere-Land System model - Spectral Version 2 (FGOALS-s2). The abrupt change is noted during the period from 1915 to 1935, in which the maximal AMOC value is weakened beyond 6 Sv (1 Sv = 106 m3 s-1). The abrupt signal first occurs at high latitudes (north of 46° N), then shifts gradually to middle latitudes (∼35° N) three to seven years later. The weakened AMOC can be explained in the following. The weak total solar irradiance (TIS) during early twentieth century decreases pole-to-equator temperature gradient in the upper stratosphere. The North polar vortex is weakened, which forces a negative North Atlantic Oscillation (NAO) phase during 1905-1914. The negative phase of NAO induces anomalous easterly winds in 50-70° N belts, which decrease the release of heat fluxes from ocean to atmosphere and induce surface warming over these regions. Through the surface ice-albedo feedback, the warming may lead to continuously melting sea ice in Baffin Bay and Davis Strait, which results in freshwater accumulation. This can lead to salinity and density reductions and then an abrupt slowdown of AMOC. Moreover, due to increased TIS after 1914, the enhanced Atlantic northward ocean heat transport from low to high latitudes induces an abrupt warming of sea surface temperature or upper ocean temperature in mid-high latitudes, which can also weaken the AMOC. The abrupt change of AMOC also appears in the PiControl run, which is associated with the lasting negative NAO phases due to natural variability.

  16. Geodetic measurements reveal similarities between post-Last Glacial Maximum and present-day mass loss from the Greenland ice sheet.

    PubMed

    Khan, Shfaqat A; Sasgen, Ingo; Bevis, Michael; van Dam, Tonie; Bamber, Jonathan L; Wahr, John; Willis, Michael; Kjær, Kurt H; Wouters, Bert; Helm, Veit; Csatho, Beata; Fleming, Kevin; Bjørk, Anders A; Aschwanden, Andy; Knudsen, Per; Munneke, Peter Kuipers

    2016-09-01

    Accurate quantification of the millennial-scale mass balance of the Greenland ice sheet (GrIS) and its contribution to global sea-level rise remain challenging because of sparse in situ observations in key regions. Glacial isostatic adjustment (GIA) is the ongoing response of the solid Earth to ice and ocean load changes occurring since the Last Glacial Maximum (LGM; ~21 thousand years ago) and may be used to constrain the GrIS deglaciation history. We use data from the Greenland Global Positioning System network to directly measure GIA and estimate basin-wide mass changes since the LGM. Unpredicted, large GIA uplift rates of +12 mm/year are found in southeast Greenland. These rates are due to low upper mantle viscosity in the region, from when Greenland passed over the Iceland hot spot about 40 million years ago. This region of concentrated soft rheology has a profound influence on reconstructing the deglaciation history of Greenland. We reevaluate the evolution of the GrIS since LGM and obtain a loss of 1.5-m sea-level equivalent from the northwest and southeast. These same sectors are dominating modern mass loss. We suggest that the present destabilization of these marine-based sectors may increase sea level for centuries to come. Our new deglaciation history and GIA uplift estimates suggest that studies that use the Gravity Recovery and Climate Experiment satellite mission to infer present-day changes in the GrIS may have erroneously corrected for GIA and underestimated the mass loss by about 20 gigatons/year.

  17. Geodetic measurements reveal similarities between post–Last Glacial Maximum and present-day mass loss from the Greenland ice sheet

    PubMed Central

    Khan, Shfaqat A.; Sasgen, Ingo; Bevis, Michael; van Dam, Tonie; Bamber, Jonathan L.; Wahr, John; Willis, Michael; Kjær, Kurt H.; Wouters, Bert; Helm, Veit; Csatho, Beata; Fleming, Kevin; Bjørk, Anders A.; Aschwanden, Andy; Knudsen, Per; Munneke, Peter Kuipers

    2016-01-01

    Accurate quantification of the millennial-scale mass balance of the Greenland ice sheet (GrIS) and its contribution to global sea-level rise remain challenging because of sparse in situ observations in key regions. Glacial isostatic adjustment (GIA) is the ongoing response of the solid Earth to ice and ocean load changes occurring since the Last Glacial Maximum (LGM; ~21 thousand years ago) and may be used to constrain the GrIS deglaciation history. We use data from the Greenland Global Positioning System network to directly measure GIA and estimate basin-wide mass changes since the LGM. Unpredicted, large GIA uplift rates of +12 mm/year are found in southeast Greenland. These rates are due to low upper mantle viscosity in the region, from when Greenland passed over the Iceland hot spot about 40 million years ago. This region of concentrated soft rheology has a profound influence on reconstructing the deglaciation history of Greenland. We reevaluate the evolution of the GrIS since LGM and obtain a loss of 1.5-m sea-level equivalent from the northwest and southeast. These same sectors are dominating modern mass loss. We suggest that the present destabilization of these marine-based sectors may increase sea level for centuries to come. Our new deglaciation history and GIA uplift estimates suggest that studies that use the Gravity Recovery and Climate Experiment satellite mission to infer present-day changes in the GrIS may have erroneously corrected for GIA and underestimated the mass loss by about 20 gigatons/year. PMID:27679819

  18. The Arctic Grand Challenge: Abrupt Climate Change

    NASA Astrophysics Data System (ADS)

    Wilkniss, P. E.

    2003-12-01

    Trouble in polar paradise (Science, 08/30/02), significant changes in the Arctic environment are scientifically documented (R.E. Moritz et al. ibid.). More trouble, lots more, "abrupt climate change," (R. B. Alley, et al. Science 03/28/03). R. Corell, Arctic Climate Impact Assessment team (ACIA), "If you want to see what will happen in the rest of the world 25 years from now just look what's happening in the Arctic," (Arctic Council meeting, Iceland, 08/03). What to do? Make abrupt Arctic climate change a grand challenge for the IPY-4 and beyond! Scientifically:Describe the "state" of the Arctic climate system as succinctly as possible and accept it as the point of departure.Develop a hypothesis and criteria what constitutes "abrupt climate change," in the Arctic that can be tested with observations. Observations: Bring to bear existing observations and coordinate new investments in observations through an IPY-4 scientific management committee. Make the new Barrow, Alaska, Global Climate Change Research Facility a major U.S. contribution and focal point for the IPY-4 in the U.S Arctic. Arctic populations, Native peoples: The people of the North are living already, daily, with wrenching change, encroaching on their habitats and cultures. For them "the earth is faster now," (I. Krupnik and D. Jolly, ARCUS, 2002). From a political, economic, social and entirely realistic perspective, an Arctic grand challenge without the total integration of the Native peoples in this effort cannot succeed. Therefore: Communications must be established, and the respective Native entities must be approached with the determination to create well founded, well functioning, enduring partnerships. In the U.S. Arctic, Barrow with its long history of involvement and active support of science and with the new global climate change research facility should be the focal point of choice Private industry: Resource extraction in the Arctic followed by oil and gas consumption, return the combustion

  19. Preserving Healthy Muscle during Weight Loss123

    PubMed Central

    Cava, Edda; Yeat, Nai Chien; Mittendorfer, Bettina

    2017-01-01

    Weight loss is the cornerstone of therapy for people with obesity because it can ameliorate or completely resolve the metabolic risk factors for diabetes, coronary artery disease, and obesity-associated cancers. The potential health benefits of diet-induced weight loss are thought to be compromised by the weight-loss–associated loss of lean body mass, which could increase the risk of sarcopenia (low muscle mass and impaired muscle function). The objective of this review is to provide an overview of what is known about weight-loss–induced muscle loss and its implications for overall physical function (e.g., ability to lift items, walk, and climb stairs). The currently available data in the literature show the following: 1) compared with persons with normal weight, those with obesity have more muscle mass but poor muscle quality; 2) diet-induced weight loss reduces muscle mass without adversely affecting muscle strength; 3) weight loss improves global physical function, most likely because of reduced fat mass; 4) high protein intake helps preserve lean body and muscle mass during weight loss but does not improve muscle strength and could have adverse effects on metabolic function; 5) both endurance- and resistance-type exercise help preserve muscle mass during weight loss, and resistance-type exercise also improves muscle strength. We therefore conclude that weight-loss therapy, including a hypocaloric diet with adequate (but not excessive) protein intake and increased physical activity (particularly resistance-type exercise), should be promoted to maintain muscle mass and improve muscle strength and physical function in persons with obesity. PMID:28507015

  20. Isoflavin-β modifies muscle oxidative stress and prevents a thyrotoxicosis-induced loss of muscle mass in rats.

    PubMed

    Marinello, Poliana C; Bernardes, Sara S; Guarnier, Flávia A; Da Silva, Thamara N X; Borges, Fernando H; Lopes, Natália M D; Simão, Andréa N C; Armani, André; Cecchini, Rubens; Cecchini, Alessandra L

    2017-11-01

    We sought to verify whether isoflavin-beta (Iso-β), a mixture of isoflavones with antioxidant properties, could prevent thyrotoxicosis-induced loss of muscle mass and the participation of oxidative stress (OS) in the mechanisms of this prevention. Two experimental periods of thyrotoxicosis induction were used in Wistar rats: 3 and 5 days to assess Iso-β effects before and after thyrotoxicosis-induced muscle wasting. After euthanasia, peritoneal fat and gastrocnemius muscle were collected, weighed, and muscle OS was assessed. Iso-β prevented the loss of gastrocnemius mass in thyrotoxic rats through the prevention of muscle OS generation during thyrotoxicosis, increasing muscle total antioxidant capacity and decreasing mitochondrial cytochrome c oxidase activity, lipid peroxidation, and protein carbonyl content. Iso-β decreased oxidative modification of proteins, which is known to exert a major role during proteolysis induction and is present in thyrotoxic myopathy, highlighting the potential action of Iso-β in this complication of the disease. Muscle Nerve 56: 975-981, 2017. © 2016 Wiley Periodicals, Inc.

  1. Mass-loss rates and luminosities of evolved stars in the Magellanic Clouds .

    NASA Astrophysics Data System (ADS)

    Groenewegen, M. A. T.; Sloan, G. C.

    Stars on the asymptotic giant branch (AGB) stars play an important role in the chemical evolution of their host galaxies and the life cycle of dust in the interstellar medium. A detailed and quantitative understanding of they lose mass and eject their envelopes remains elusive, particularly how that process depends on metallicity. Groenewegen & Sloan (2017, hereafter GS17) recently presented dust radiative transfer models for 225 carbon stars and 171 oxygen-rich evolved stars in the Magellanic Clouds and four nearby dSphs which were observed with the Infrared spectrograph on the Spitzer Space Telescope. They applied a minimisation procedure to fit models to spectral energy distributions constructed from the infrared spectra and the available optical and infrared photometry for each star to determine its luminosity and dust mass-loss rate (MLR). In this contribution two items from that paper are highlighted: an update on MSX SMC 055, which Groenewegen et al. (2009) suggested could be a super-AGB star, and a discussion of synthetic colour-colour and colour-magnitude diagrams expected from the James Webb Space Telescope.

  2. The P-factor and atomic mass systematics: Application to medium mass nuclei

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Brenner, D.S.; Haustein, P.E.; Casten, R.F.

    1988-01-01

    The P formalism was applied to atomic mass systematics for medium and heavy nuclei. The P-factor linearizes the structure-dependent part of the nuclear mass in those regions which are free from subshell effects indicating that the attractive quadrupole p-n force plays an important role in determining the binding of valence nucleons. Where marked non-linearities occur, the P-factor provides a means for recognizing subshell closures and/or other structural features not embodied in the simple assumptions of abrupt shell or subshell changes. These are thought to be regions where the monopole part of the p-n interaction is highly orbit dependent and altersmore » the underlying single-particle structure as a function of A, N or Z. Finally, in those regions where the systematics are smooth and subshells are absent, the P-factor provides a means for predicting masses of some nuclei far-from-stability by interpolation rather than by extrapolation. 5 figs.« less

  3. Rapid body mass loss affects erythropoiesis and hemolysis but does not impair aerobic performance in combat athletes.

    PubMed

    Reljic, D; Feist, J; Jost, J; Kieser, M; Friedmann-Bette, B

    2016-05-01

    Rapid body mass loss (RBML) before competition was found to decrease hemoglobin mass (Hbmass ) in elite boxers. This study aimed to investigate the underlying mechanisms of this observation. Fourteen well-trained combat athletes who reduced body mass before competitions (weight loss group, WLG) and 14 combat athletes who did not practice RBML (control group, CON) were tested during an ordinary training period (t-1), 1-2 days before an official competition (after 5-7 days RBML in WLG, t-2), and after a post-competition period (t-3). In WLG, body mass (-5.5%, range: 2.9-6.8 kg) and Hbmass (-4.1%) were significantly (P < 0.001) reduced after RBML and were still decreased by 1.6% (P < 0.05) and 2.6% (P < 0.001) at t-3 compared with t-1. After RBML, erythropoietin, reticulocytes, haptoglobin, triiodothyronine (FT3 ), and free androgen index (FAI) were decreased compared with t-1 and t-3. An increase occurred in ferritin and bilirubin. Peak treadmill-running performance and VO2peak did not change significantly, but performance at 4-mmol lactate threshold was higher after RBML (P < 0.05). In CON, no significant changes were found in any parameter. Apparently, the significant decrease in Hbmass after RBML in combat athletes was caused by impaired erythropoiesis and increased hemolysis without significant impact on aerobic performance capacity. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  4. Early 21st-Century Mass loss of the North-Atlantic Glaciers and Ice Caps (Arne Richter Award for Outstanding Young Scientists Lecture)

    NASA Astrophysics Data System (ADS)

    Wouters, Bert; Ligtenberg, Stefan; Moholdt, Geir; Gardner, Alex S.; Noel, Brice; Kuipers Munneke, Peter; van den Broeke, Michiel; Bamber, Jonathan L.

    2016-04-01

    Historically, ice loss from mountain glaciers and ice caps has been one of the largest contributors to sea level rise over the last century. Of particular interest are the glaciers and ice caps in the North-Atlantic region of the Arctic. Despite the cold climate in this area, considerable melting and runoff occurs in summer. A small increase in temperature will have an immediate effect on these processes, so that a large change in the Arctic ice volume can be expected in response to the anticipated climate change in the coming century. Unfortunately, direct observations of glaciers are sparse and are biased toward glaciers systems in accessible, mostly maritime, climate conditions. Remote sensing is therefore essential to monitor the state of the the North-Atlantic glaciers and ice caps. In this presentation, we will discuss the progress that has been made in estimating the ice mass balance of these regions, with a particular focus on measurements made by ESA's Cryosat-2 radar altimeter mission (2010-present). Compared to earlier altimeter mission, Cryosat-2 provides unprecedented coverage of the cryosphere, with a resolution down to 1 km or better and sampling at monthly intervals. Combining the Cryosat-2 measurements with the laser altimetry data from ICESat (2003-2009) gives us a 12 yr time series of glacial mass loss in the North Atlantic. We find excellent agreement between the altimetry measurements and independent observations by the GRACE mission, which directly 'weighs' the ice caps, albeit at a much lower resolution. Mass loss in the region has increased from 120 Gigatonnes per year in 2003-2009 to roughly 140 Gt/yr in 2010-2014, with an important contribution from Greenland's peripheral glaciers and ice caps. Importantly, the mass loss is not stationary, but shows large regional interannual variability, with mass loss shifting between eastern and western regions from year to year. Comparison with regional climate models shows that these shifts can be

  5. Abrupt climate change and collapse of deep-sea ecosystems

    USGS Publications Warehouse

    Yasuhara, Moriaki; Cronin, T. M.; Demenocal, P.B.; Okahashi, H.; Linsley, B.K.

    2008-01-01

    We investigated the deep-sea fossil record of benthic ostracodes during periods of rapid climate and oceanographic change over the past 20,000 years in a core from intermediate depth in the northwestern Atlantic. Results show that deep-sea benthic community "collapses" occur with faunal turnover of up to 50% during major climatically driven oceanographic changes. Species diversity as measured by the Shannon-Wiener index falls from 3 to as low as 1.6 during these events. Major disruptions in the benthic communities commenced with Heinrich Event 1, the Inter-Aller??d Cold Period (IACP: 13.1 ka), the Younger Dryas (YD: 12.9-11.5 ka), and several Holocene Bond events when changes in deep-water circulation occurred. The largest collapse is associated with the YD/IACP and is characterized by an abrupt two-step decrease in both the upper North Atlantic Deep Water assemblage and species diversity at 13.1 ka and at 12.2 ka. The ostracode fauna at this site did not fully recover until ???8 ka, with the establishment of Labrador Sea Water ventilation. Ecologically opportunistic slope species prospered during this community collapse. Other abrupt community collapses during the past 20 ka generally correspond to millennial climate events. These results indicate that deep-sea ecosystems are not immune to the effects of rapid climate changes occurring over centuries or less. ?? 2008 by The National Academy of Sciences of the USA.

  6. The association between body mass index, weight loss and physical function in the year following a hip fracture.

    PubMed

    Reider, L; Hawkes, W; Hebel, J R; D'Adamo, C; Magaziner, J; Miller, R; Orwig, D; Alley, D E

    2013-01-01

    To determine whether body mass index (BMI) at the time of hospitalization or weight change in the period immediately following hospitalization predict physical function in the year after hip fracture. Prospective observational study. Two hospitals in Baltimore, Maryland. Female hip fracture patients age 65 years or older (N=136 for BMI analysis, N=41 for analysis of weight change). Body mass index was calculated based on weight and height from the medical chart. Weight change was based on DXA scans at 3 and 10 days post fracture. Physical function was assessed at 2, 6 and 12 months following fracture using the lower extremity gain scale (LEGS), walking speed and grip strength. LEGS score and walking speed did not differ across BMI tertiles. However, grip strength differed significantly across BMI tertiles (p=0.029), with underweight women having lower grip strength than normal weight women at all time points. Women experiencing the most weight loss (>4.8%) had significantly lower LEGS scores at all time points, slower walking speed at 6 months, and weaker grip strength at 12 months post-fracture relative to women with more modest weight loss. In adjusted models, overall differences in function and functional change across all time points were not significant. However, at 12 months post fracture,women with the most weight loss had an average grip strength 7.0 kg lower than women with modest weight loss (p=0.030). Adjustment for confounders accounts for much of the relationships between BMI and function and weight change and function in the year after fracture. However, weight loss is associated with weakness during hip fracture recovery. Weight loss during and immediately after hospitalization appears to identify women at risk of poor function and may represent an important target for future interventions.

  7. The VLTI/MIDI view on the inner mass loss of evolved stars from the Herschel MESS sample

    NASA Astrophysics Data System (ADS)

    Paladini, C.; Klotz, D.; Sacuto, S.; Lagadec, E.; Wittkowski, M.; Richichi, A.; Hron, J.; Jorissen, A.; Groenewegen, M. A. T.; Kerschbaum, F.; Verhoelst, T.; Rau, G.; Olofsson, H.; Zhao-Geisler, R.; Matter, A.

    2017-04-01

    Context. The mass-loss process from evolved stars is a key ingredient for our understanding of many fields of astrophysics, including stellar evolution and the chemical enrichment of the interstellar medium (ISM) via stellar yields. Nevertheless, many questions are still unsolved, one of which is the geometry of the mass-loss process. Aims: Taking advantage of the results from the Herschel Mass loss of Evolved StarS (MESS) programme, we initiated a coordinated effort to characterise the geometry of mass loss from evolved red giants at various spatial scales. Methods: For this purpose we used the MID-infrared interferometric Instrument (MIDI) to resolve the inner envelope of 14 asymptotic giant branch stars (AGBs) in the MESS sample. In this contribution we present an overview of the interferometric data collected within the frame of our Large Programme, and we also add archive data for completeness. We studied the geometry of the inner atmosphere by comparing the observations with predictions from different geometric models. Results: Asymmetries are detected for the following five stars: R Leo, RT Vir, π1Gruis, omi Ori, and R Crt. All the objects are O-rich or S-type, suggesting that asymmetries in the N band are more common among stars with such chemistry. We speculate that this fact is related to the characteristics of the dust grains. Except for one star, no interferometric variability is detected, I.e. the changes in size of the shells of non-mira stars correspond to changes of the visibility of less than 10%. The observed spectral variability confirms previous findings from the literature. The detection of dust in our sample follows the location of the AGBs in the IRAS colour-colour diagram: more dust is detected around oxygen-rich stars in region II and in the carbon stars in region VII. The SiC dust feature does not appear in the visibility spectrum of the U Ant and S Sct, which are two carbon stars with detached shells. This finding has implications for

  8. Increased meal frequency attenuates fat-free mass losses and some markers of health status with a portion-controlled weight loss diet.

    PubMed

    Alencar, Michelle K; Beam, Jason R; McCormick, James J; White, Ailish C; Salgado, Roy M; Kravitz, Len R; Mermier, Christine M; Gibson, Ann L; Conn, Carole A; Kolkmeyer, Deborah; Ferraro, Robert T; Kerksick, Chad M

    2015-05-01

    Increased meal frequency (MF) may be associated with improvements in blood markers of health and body composition during weight loss; however, this claim has not been validated. The purpose of the study was to determine if either a 2-meal (2 MF) or 6-meal frequency (6 MF) regimen can improve body composition and blood-based markers of health while consuming a portion-controlled equihypocaloric diet. Eleven (N=11) obese women (52 ± 7 years, 101.7 ± 22.6 kg, 39.1 ± 7.6 kg/m(2)) were randomized into treatment condition (2 MF or 6 MF) for 2 weeks, completed a 2-week washout, and alternated treatment conditions. In pre/post fashion, changes in body composition, glucose, insulin, and lipid components were measured in response to a test meal. Body mass was successfully lost (P ≤ .05) under both feeding regimens (2 MF: -2.8 ± 1.5 vs 6 MF: -1.9 ± 1.5 kg). Altering MF did not impact glucose, insulin, total cholesterol, or low-density lipoprotein cholesterol (P>.05). On average, fat-free mass (FFM) decreased by -3.3% ± 2.6% following the 2 MF condition and, on average, increased by 1.2% ± 1.7% following the 6 MF condition (P ≤ .05). Fasting high-density lipoprotein cholesterol (HDL-C) percentage increased during the 2 MF condition; this was significantly greater than that in the 6 MF condition (1.3% ± 12.2% vs 0.12% ± 10.3%) (P ≤ .05). Overall, reductions in MF (2 MF) were associated with improved HDL-C levels; but the clinical significance is not clear. Alternatively, increased MF (6 MF) did appear to favorably preserve FFM during weight loss. In conclusion, caloric restriction was effective in reducing body mass and attenuating FFM changes in body composition; however, glucose, insulin, and lipid metabolism had no significant differences between MF. Copyright © 2015 Elsevier Inc. All rights reserved.

  9. Protection of total body water content and absence of hyperthermia despite 2% body mass loss ('voluntary dehydration') in soldiers drinking ad libitum during prolonged exercise in cool environmental conditions.

    PubMed

    Nolte, Heinrich W; Noakes, Timothy D; van Vuuren, Bernard

    2011-11-01

    The extent to which humans need to replace fluid losses during exercise remains contentious despite years of focused research. The primary objective was to evaluate ad libitum drinking on hydration status to determine whether body mass loss can be used as an accurate surrogate for changes in total body water (TBW) during exercise. Data were collected during a 14.6-km route march (wet bulb globe temperature of 14.1°C ). 18 subjects with an average age of 26 ± 2.5 (SD) years participated. Their mean ad libitum total fluid intake was 2.1 ± 1.4 litres during the exercise. Predicted sweat rate was 1.289 ± 0.530 l/h. There were no significant changes (p>0.05) in TBW, urine specific gravity or urine osmolality despite an average body mass loss (p<0.05) of 1.3 ± 0.45 kg during the march. Core temperature rose as a function of marching speed and was unrelated to the % change in body mass. This suggests that changes in mass do not accurately predict changes in TBW (r=-0.16) because either the body mass loss during exercise includes losses other than water or there is an endogenous body water source that is released during exercise not requiring replacement during exercise, or both. Ad libitum water replacement between 65% and 70% of sweat losses maintained safe levels of hydration during the experiment. The finding that TBW was protected by ad libitum drinking despite approximately 2% body mass loss suggests that the concept of 'voluntary dehydration' may require revision.

  10. Aerodynamic and acoustic effects of abrupt frequency changes in excised larynges.

    PubMed

    Alipour, Fariborz; Finnegan, Eileen M; Scherer, Ronald C

    2009-04-01

    To determine the aerodynamic and acoustic effects due to a sudden change from chest to falsetto register or vice versa. It was hypothesized that the continuous change in subglottal pressure and flow rate alone (pressure-flow sweep [PFS]) can trigger a mode change in the canine larynx. Ten canine larynges were each mounted over a tapered tube that supplied pressurized, heated, and humidified air. Glottographic signals were recorded during each PFS experiment, during which airflow was increased in a gradual manner for a period of 20-30 s. Abrupt changes in fundamental frequency (F(0)) and mode of vibration occurred during the PFS in the passive larynx without any change in adduction or elongation. The lower frequency mode of oscillation of the vocal folds, perceptually identified as the chest register, had relatively large amplitude oscillation, significant vocal fold contact, a rich spectral content, and a relatively loud audio signal. The higher frequency mode of oscillation, perceptually identified as falsetto, had little or no vocal fold contact and a dominant first partial. Relatively abrupt F(0) changes also occurred for gradual adduction changes, with the chest register corresponding to greater adduction, falsetto to less adduction.

  11. Abrupt Decline in Kidney Function Before Initiating Hemodialysis and All-Cause Mortality: The Chronic Renal Insufficiency Cohort (CRIC) Study.

    PubMed

    Hsu, Raymond K; Chai, Boyang; Roy, Jason A; Anderson, Amanda H; Bansal, Nisha; Feldman, Harold I; Go, Alan S; He, Jiang; Horwitz, Edward J; Kusek, John W; Lash, James P; Ojo, Akinlolu; Sondheimer, James H; Townsend, Raymond R; Zhan, Min; Hsu, Chi-Yuan

    2016-08-01

    It is not clear whether the pattern of kidney function decline in patients with chronic kidney disease (CKD) may relate to outcomes after reaching end-stage renal disease (ESRD). We hypothesize that an abrupt decline in kidney function prior to ESRD predicts early death after initiating maintenance hemodialysis therapy. Prospective cohort study. The Chronic Renal Insufficiency Cohort (CRIC) Study enrolled men and women with mild to moderate CKD. For this study, we studied 661 individuals who developed chronic kidney failure that required hemodialysis therapy initiation. The primary predictor was the presence of an abrupt decline in kidney function prior to ESRD. We incorporated annual estimated glomerular filtration rates (eGFRs) into a mixed-effects model to estimate patient-specific eGFRs at 3 months prior to initiation of hemodialysis therapy. Abrupt decline was defined as having an extrapolated eGFR≥30mL/min/1.73m(2) at that time point. All-cause mortality within 1 year after initiating hemodialysis therapy. Multivariable Cox proportional hazards. Among 661 patients with CKD initiating hemodialysis therapy, 56 (8.5%) had an abrupt predialysis decline in kidney function and 69 died within 1 year after initiating hemodialysis therapy. After adjustment for demographics, cardiovascular disease, diabetes, and cancer, abrupt decline in kidney function was associated with a 3-fold higher risk for death within the first year of ESRD (adjusted HR, 3.09; 95% CI, 1.65-5.76). Relatively small number of outcomes; infrequent (yearly) eGFR determinations; lack of more granular clinical data. Abrupt decline in kidney function prior to ESRD occurred in a significant minority of incident hemodialysis patients and predicted early death in ESRD. Copyright © 2016 National Kidney Foundation, Inc. All rights reserved.

  12. Causes and projections of abrupt climate-driven ecosystem shifts in the North Atlantic.

    PubMed

    Beaugrand, Grégory; Edwards, Martin; Brander, Keith; Luczak, Christophe; Ibanez, Frederic

    2008-11-01

    Warming of the global climate is now unequivocal and its impact on Earth' functional units has become more apparent. Here, we show that marine ecosystems are not equally sensitive to climate change and reveal a critical thermal boundary where a small increase in temperature triggers abrupt ecosystem shifts seen across multiple trophic levels. This large-scale boundary is located in regions where abrupt ecosystem shifts have been reported in the North Atlantic sector and thereby allows us to link these shifts by a global common phenomenon. We show that these changes alter the biodiversity and carrying capacity of ecosystems and may, combined with fishing, precipitate the reduction of some stocks of Atlantic cod already severely impacted by exploitation. These findings offer a way to anticipate major ecosystem changes and to propose adaptive strategies for marine exploited resources such as cod in order to minimize social and economic consequences.

  13. Abrupt treatments of hysteria during World War I, 1914-18.

    PubMed

    Macleod, Ad Sandy

    2018-06-01

    Case reports of the abrupt recovery of hysterical disorders during World War I (1914-18), though undoubtedly subject to publication bias, raise both aetiological and treatment issues regarding pseudo-neurological conversion symptoms. Published clinical anecdotes report circumstantial, psychotherapeutic, hypnotic, persuasive (and coercive) methods seemingly inducing recovery, and also responses to fright and alterations of consciousness. The ethics of modern medical practice would not allow many of these techniques, which were reported to be effective, even in the chronic cases.

  14. Effects on the equine colon ecosystem of grass silage and haylage diets after an abrupt change from hay.

    PubMed

    Muhonen, S; Julliand, V; Lindberg, J E; Bertilsson, J; Jansson, A

    2009-07-01

    The objective of this study was to investigate the effect of an abrupt change from grass hay (81% DM) to grass silage (36% DM) or grass haylage (55% DM), fed at similar DM intakes, and to compare the effects of silage and haylage on the composition and activities of the colon microflora. The forages were from the same swath harvested on the same day. Four adult colon-fistulated geldings were randomly assigned to diets in a crossover design. The study started with a preperiod when all 4 horses received the hay diet, followed by an abrupt feed change to the haylage diet for 2 horses and the silage diet for 2 horses. All 4 horses then had a new second preperiod of hay, followed by an abrupt feed change to the opposite haylage and silage diet. The periods were 21 d long, and the forage-only diets were supplemented with minerals and salt. The abrupt feed changes were made at 0800 h. Colon samples were taken before the abrupt feed change, 4 and 28 h after the feed change, and 8, 15, and 21 d after the feed change, all at 1200 h. Colon bacterial counts, VFA, pH, and DM concentrations were unchanged throughout the first 28 h after the abrupt feed change from hay to haylage and silage. Also, fecal pH and DM concentrations were unchanged during the first 28 h. During the weekly observations, colon lactobacilli counts increased (P = 0.023) in horses receiving the silage diet and were greater than on the haylage diet at 21 d. Streptococci counts decreased (P = 0.046) in horses receiving the haylage diet and were less than on the silage diet at 15 and 21 d. Total VFA concentrations and colon and fecal pH did not differ between diets and were unchanged throughout the weekly observations. The DM concentration of colon digesta and feces decreased (P = 0.030 and 0.049, respectively) on both diets during the weekly observations. The results suggest that in horses fed at the maintenance level of energy intake, an abrupt feed change from grass hay to grass silage or grass haylage from

  15. The role of MicroRNAs in COPD muscle dysfunction and mass loss: implications on the clinic.

    PubMed

    Barreiro, Esther

    2016-09-01

    Chronic obstructive pulmonary disease (COPD) is a common preventable and treatable disease and a leading cause of morbidity and mortality worldwide. In COPD, comorbidities, acute exacerbations, and systemic manifestations negatively influence disease severity, prognosis, and progression regardless of the respiratory condition. Several factors and biological mechanisms are involved in the pathophysiology of COPD muscle dysfunction. The non-coding microRNAs were shown to be differentially expressed in the respiratory and limb muscles of patients with COPD. Moreover, a differential expression profile of muscle-specific microRNAs has also been demonstrated in the lower limb muscles of COPD patients with and without muscle mass loss and weakness. All these features are reviewed herein. The most relevant articles on the topic in question were selected from PubMed to write this review. Expert commentary: MicroRNAs are excellent targets for the design of specific therapeutic interventions in patients with muscle weakness. Selective enhancers of microRNAs that promote myogenesis (proliferation and differentiation of satellite cells) should be designed to alleviate the negative impact of skeletal muscle dysfunction and mass loss in COPD regardless of the degree of the airway obstruction.

  16. Effect of fjord geometry on Greenland mass loss in a warming climate (Invited)

    NASA Astrophysics Data System (ADS)

    Nick, F. M.; Vieli, A.; Andersen, M. L.; Joughin, I. R.

    2013-12-01

    Over the past decade, ice loss from the Greenland Ice Sheet increased as a result of both increased surface melting and ice discharge through the narrow outlet glaciers. The complicated behaviour of narrow outlet glaciers has not yet been fully captured by the ice-sheet models used to predict Greenland's contribution to future sea level. Here we try to quantify the future dynamic contribution of four major marine terminating outlet glaciers to sea-level rise. We use a glacier flow line model that includes a fully dynamic treatment of marine termini to simulate behavior of Helheim, Kangerdlugssuaq, Petermann and Jakobshavn Isbræ. The contribution from these glaciers to sea-level rise is largely (80%) dynamic in origin and is caused by several episodic retreats past overdeepenings in outlet glacier troughs. Model results show that the shape of the glacier and its fjord can alter how the glacier will respond to a changing climate. Dynamic losses are mainly related to channel geometry and occur when an ice front retreats from a basal high through an overdeepening. Subsequent decelerations in retreat and mass loss mostly coincide with a decrease in water depth as the glacier retreats or re-advances to a new or previous bathymetric high. In some cases, channel narrowing may temporarily slowdown the terminus retreat even when the terminus is located on an upward bed slope.

  17. Longitudinal changes in reproductive hormones and menstrual cyclicity in cynomolgus monkeys during strenuous exercise training: abrupt transition to exercise-induced amenorrhea.

    PubMed

    Williams, N I; Caston-Balderrama, A L; Helmreich, D L; Parfitt, D B; Nosbisch, C; Cameron, J L

    2001-06-01

    Cross-sectional studies of exercise-induced reproductive dysfunction have documented a high proportion of menstrual cycle disturbances in women involved in strenuous exercise training. However, longitudinal studies have been needed to examine individual susceptibility to exercise-induced reproductive dysfunction and to elucidate the progression of changes in reproductive function that occur with strenuous exercise training. Using the female cynomolgus monkey (Macaca fascicularis), we documented changes in menstrual cyclicity and patterns of LH, FSH, estradiol, and progesterone secretion as the animals developed exercise-induced amenorrhea. As monkeys gradually increased running to 12.3 +/- 0.9 km/day, body weight did not change significantly although food intake remained constant. The time spent training until amenorrhea developed varied widely among animals (7-24 months; mean = 14.3 +/- 2.2 months) and was not correlated with initial body weight, training distance, or food intake. Consistent changes in function of the reproductive axis occurred abruptly, one to two menstrual cycles before the development of amenorrhea. These included significant declines in plasma reproductive hormone concentrations, an increase in follicular phase length, and a decrease in luteal phase progesterone secretion. These data document a high level of interindividual variability in the development of exercise-induced reproductive dysfunction, delineate the progression of changes in reproductive hormone secretion that occur with exercise training, and illustrate an abrupt transition from normal cyclicity to an amenorrheic state in exercising individuals, that is not necessarily associated with weight loss.

  18. Abrupt skin lesion border cutoff measurement for malignancy detection in dermoscopy images.

    PubMed

    Kaya, Sertan; Bayraktar, Mustafa; Kockara, Sinan; Mete, Mutlu; Halic, Tansel; Field, Halle E; Wong, Henry K

    2016-10-06

    Automated skin lesion border examination and analysis techniques have become an important field of research for distinguishing malignant pigmented lesions from benign lesions. An abrupt pigment pattern cutoff at the periphery of a skin lesion is one of the most important dermoscopic features for detection of neoplastic behavior. In current clinical setting, the lesion is divided into a virtual pie with eight sections. Each section is examined by a dermatologist for abrupt cutoff and scored accordingly, which can be tedious and subjective. This study introduces a novel approach to objectively quantify abruptness of pigment patterns along the lesion periphery. In the proposed approach, first, the skin lesion border is detected by the density based lesion border detection method. Second, the detected border is gradually scaled through vector operations. Then, along gradually scaled borders, pigment pattern homogeneities are calculated at different scales. Through this process, statistical texture features are extracted. Moreover, different color spaces are examined for the efficacy of texture analysis. The proposed method has been tested and validated on 100 (31 melanoma, 69 benign) dermoscopy images. Analyzed results indicate that proposed method is efficient on malignancy detection. More specifically, we obtained specificity of 0.96 and sensitivity of 0.86 for malignancy detection in a certain color space. The F-measure, harmonic mean of recall and precision, of the framework is reported as 0.87. The use of texture homogeneity along the periphery of the lesion border is an effective method to detect malignancy of the skin lesion in dermoscopy images. Among different color spaces tested, RGB color space's blue color channel is the most informative color channel to detect malignancy for skin lesions. That is followed by YCbCr color spaces Cr channel, and Cr is closely followed by the green color channel of RGB color space.

  19. A study of mass loss from the mid-ultraviolet spectrum of Alpha Cygni /A2 Ia/, Beta Orionis /B8 Ia/, and Eta Leonis /A0 Ib/

    NASA Technical Reports Server (NTRS)

    Lamers, H. J. G. L. M.; Stalio, R.; Kondo, Y.

    1978-01-01

    Results are presented for a study of mass loss from A and late-B supergiants based on high-resolution mid-UV spectra obtained with the echelle spectrograph of the Balloon-borne Ultraviolet Stellar Spectrometer. Spectra of Alpha Cyg, Beta Ori, Eta Leo, and Alpha Lyr are compared in selected wavelength regions; particular attention is given to previous observations of each star, the Mg II and Fe II resonance lines, lines due to other ions, and evidence for mass ejection. The results indicate that mass loss from late-B and A supergiants is variable, that a considerable fraction of envelope material is ejected in 'puffs', and that the puffs may be due to photospheric instabilities. A mass-loss rate of about 1 hundred-millionth of a solar mass per year is derived for Alpha Cyg and shown to be two orders of magnitude smaller than the value determined from the observed IR excess. This discrepancy is attributed to excess ionization in the envelope.

  20. Fast Winds and Mass Loss from Metal-Poor Field Giants

    NASA Astrophysics Data System (ADS)

    Dupree, A. K.; Smith, Graeme H.; Strader, Jay

    2009-11-01

    Echelle spectra of the infrared He I λ10830 line were obtained with NIRSPEC on the Keck 2 telescope for 41 metal-deficient field giant stars including those on the red giant branch (RGB), asymptotic giant branch (AGB), and red horizontal branch (RHB). The presence of this He I line is ubiquitous in stars with T effgsim 4500 K and MV fainter than -1.5, and reveals the dynamics of the atmosphere. The line strength increases with effective temperature for T effgsim 5300 K in RHB stars. In AGB and RGB stars, the line strength increases with luminosity. Fast outflows (gsim 60 km s-1) are detected from the majority of the stars and about 40% of the outflows have sufficient speed as to allow escape of material from the star as well as from a globular cluster. Outflow speeds and line strengths do not depend on metallicity for our sample ([Fe/H]= -0.7 to -3.0), suggesting the driving mechanism for these winds derives from magnetic and/or hydrodynamic processes. Gas outflows are present in every luminous giant, but are not detected in all stars of lower luminosity indicating possible variability. Mass loss rates ranging from ~3 × 10-10 to ~6 × 10-8 M sun yr-1 estimated from the Sobolev approximation for line formation represent values with evolutionary significance for red giants and RHB stars. We estimate that 0.2 M sun will be lost on the RGB, and the torque of this wind can account for observations of slowly rotating RHB stars in the field. About 0.1-0.2 M sun will be lost on the RHB itself. This first empirical determination of mass loss on the RHB may contribute to the appearance of extended horizontal branches in globular clusters. The spectra appear to resolve the problem of missing intracluster material in globular clusters. Opportunities exist for "wind smothering" of dwarf stars by winds from the evolved population, possibly leading to surface pollution in regions of high stellar density. Data presented herein were obtained at the W. M. Keck Observatory, which

  1. Abrupt glacial climate shifts controlled by ice sheet changes.

    PubMed

    Zhang, Xu; Lohmann, Gerrit; Knorr, Gregor; Purcell, Conor

    2014-08-21

    During glacial periods of the Late Pleistocene, an abundance of proxy data demonstrates the existence of large and repeated millennial-scale warming episodes, known as Dansgaard-Oeschger (DO) events. This ubiquitous feature of rapid glacial climate change can be extended back as far as 800,000 years before present (BP) in the ice core record, and has drawn broad attention within the science and policy-making communities alike. Many studies have been dedicated to investigating the underlying causes of these changes, but no coherent mechanism has yet been identified. Here we show, by using a comprehensive fully coupled model, that gradual changes in the height of the Northern Hemisphere ice sheets (NHISs) can alter the coupled atmosphere-ocean system and cause rapid glacial climate shifts closely resembling DO events. The simulated global climate responses--including abrupt warming in the North Atlantic, a northward shift of the tropical rainbelts, and Southern Hemisphere cooling related to the bipolar seesaw--are generally consistent with empirical evidence. As a result of the coexistence of two glacial ocean circulation states at intermediate heights of the ice sheets, minor changes in the height of the NHISs and the amount of atmospheric CO2 can trigger the rapid climate transitions via a local positive atmosphere-ocean-sea-ice feedback in the North Atlantic. Our results, although based on a single model, thus provide a coherent concept for understanding the recorded millennial-scale variability and abrupt climate changes in the coupled atmosphere-ocean system, as well as their linkages to the volume of the intermediate ice sheets during glacials.

  2. [Prelabour uterine torsion complicated by partial abruption and fetal death].

    PubMed

    Agar, N; Canis, M; Accoceberry, M; Bourdel, N; Lafaye, A-L; Gallot, D

    2014-06-01

    Uterine torsion is a rare obstetrical complication whose diagnosis remains challenging. We report a case of 180 degrees dextrogyre torsion at 36(+5) weeks of gestation complicated by partial abruption and in utero fetal death. Emergency cesarean section was performed through an unintentional posterior hysterotomy. Literature reports a few similar cases. Vertical hysterotomy should be advised in this context avoiding incision on lateral sides associated with increased risk of vascular or ureteral injury. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

  3. Switching from oral extended-release methylphenidate to the methylphenidate transdermal system: continued ADHD symptom control and tolerability after abrupt conversion

    PubMed Central

    Arnold, L. E.; Hodgkins, P.; McKay, M.; Beckett-Thurman, L.; Greenbaum, M.; Bukstein, O.; Patel, A.; Bozzolo, D. R.

    2013-01-01

    Objective To evaluate symptom control and tolerability after abrupt conversion from oral extended-release methylphenidate (ER-MPH) to methylphenidate transdermal system (MTS) via a dose-transition schedule in children with attention-deficit/hyperactivity disorder (ADHD). Methods In a 4-week, prospective, multisite, open-label study, 171 children (164 intent-to-treat) with diagnosed ADHD aged 6–12 years abruptly switched from a stable dose of oral ER-MPH to MTS in nominal dosages of 10, 15, 20, and 30 mg using a predefined dose-transition schedule. After the first week on the scheduled dose, the dose was titrated to optimal effect. The primary effectiveness outcome was the change from baseline (while taking ER-MPH) to week 4 in ADHD-Rating Scale-IV (ADHD-RS-IV) total scores. Adverse events (AEs) were assessed throughout the study. Results Most subjects (58%) remained on the initial MTS dose defined by the dose-transition schedule; 38% increased and 4% decreased their MTS dose for optimization. MTS dose optimization resulted in significantly better ADHD-RS-IV total (mean ± SD) scores at week 4 than at baseline (9.9±7.47 vs 14.1±7.48; p<0.0001). The most commonly reported AEs included headache, decreased appetite, insomnia, and upper abdominal pain. Four subjects (2.3%) discontinued because of application site reactions and 3 discontinued because of other AEs. Conclusions Abrupt conversion from a stable dose of oral ER-MPH to MTS was accomplished using a predefined dose-transition schedule without loss of symptom control; however, careful titration to optimal dose is recommended. Most AEs were mild to moderate and, with the exception of application site reactions, were similar to AEs typically observed with oral MPH. Limitations of this study included its open-label sequential design without placebo, which could result in spurious attribution of improvement to the study treatment and precluded superiority determinations of MTS over baseline ER-MPH treatment. The

  4. Correction to: Dissociating the capture of attention from saccade activation by subliminal abrupt onsets.

    PubMed

    Schoeberl, Tobias; Ansorge, Ulrich

    2018-01-01

    Attentional capture and effects on saccade metrics by subliminal abrupt onset cues have been studied with peripheral cues at one out of several (two to four) display locations, swiftly followed by additional onsets at the other display locations. The lead time of the cue was too short to be seen. Here, we were interested in whether such subliminal onset cues influenced saccades primarily by way of attention or by way of direct saccade activation. In separate blocks, participants made speeded pro-saccades towards a black target or anti-saccades away from the target. Prior to the targets, an abrupt onset cue was presented either at the same side as the target (valid condition) or at the opposite side (invalid condition). If cues influenced performance by way of attentional capture, we expected facilitation of target processing in valid compared to invalid conditions (cueing effect) in the pro- as well as in the anti-saccade task. If the cues activated saccades in their direction, we expected the cueing effect to drop in the anti-saccade task compared to the pro-saccade task because in the anti-saccade task the invalid cue would activate the finally required response, whereas the valid cue would activate the alternative response, leading to interference. Results were in line with the former of these possibilities suggesting that subliminal abrupt onsets influenced saccades by way of attention with no or little direct activation of saccades.

  5. Momentum-resolved hidden-order gap reveals symmetry breaking and origin of entropy loss in URu2Si2

    NASA Astrophysics Data System (ADS)

    Bareille, C.; Boariu, F. L.; Schwab, H.; Lejay, P.; Reinert, F.; Santander-Syro, A. F.

    2014-07-01

    Spontaneous symmetry breaking in physical systems leads to salient phenomena at all scales, from the Higgs mechanism and the emergence of the mass of the elementary particles, to superconductivity and magnetism in solids. The hidden-order state arising below 17.5 K in URu2Si2 is a puzzling example of one of such phase transitions: its associated broken symmetry and gap structure have remained longstanding riddles. Here we directly image how, across the hidden-order transition, the electronic structure of URu2Si2 abruptly reconstructs. We observe an energy gap of 7 meV opening over 70% of a large diamond-like heavy-fermion Fermi surface, resulting in the formation of four small Fermi petals, and a change in the electronic periodicity from body-centred tetragonal to simple tetragonal. Our results explain the large entropy loss in the hidden-order phase, and the similarity between this phase and the high-pressure antiferromagnetic phase found in quantum-oscillation experiments.

  6. Magnetic confinement, Alfven wave reflection, and the origins of X-ray and mass-loss 'dividing lines' for late-type giants and supergiants

    NASA Technical Reports Server (NTRS)

    Rosner, R.; An, C.-H.; Musielak, Z. E.; Moore, R. L.; Suess, S. T.

    1991-01-01

    A simple qualitative model for the origin of the coronal and mass-loss dividing lines separating late-type giants and supergiants with and without hot, X-ray-emitting corona, and with and without significant mass loss is discussed. The basic physical effects considered are the necessity of magnetic confinement for hot coronal material on the surface of such stars and the large reflection efficiency for Alfven waves in cool exponential atmospheres. The model assumes that the magnetic field geometry of these stars changes across the observed 'dividing lines' from being mostly closed on the high effective temperature side to being mostly open on the low effective temperature side.

  7. Isotopic composition of ice core air reveals abrupt Antarctic warming during and after Heinrich Event 1a

    NASA Astrophysics Data System (ADS)

    Morgan, J. D.; Bereiter, B.; Baggenstos, D.; Kawamura, K.; Shackleton, S. A.; Severinghaus, J. P.

    2017-12-01

    Antarctic temperature variations during Heinrich events, as recorded by δ18O­ice­, generally show more gradual changes than the abrupt warmings seen in Greenland ice. However, quantitative temperature interpretation of the water isotope temperature proxy is difficult as the relationship between δ18Oice and temperature is not constant through time. Fortunately, ice cores offer a second temperature proxy based on trapped gases. During times of surface warming, thermal fractionation of gases in the column of unconsolidated snow (firn) on top of the ice sheet results in isotopically heavier nitrogen (N2) and argon (Ar) being trapped in the ice core bubbles. During times of surface cooling, isotopically lighter gases are trapped. Measurements of δ15N and δ40Ar can therefore be used, in combination with a model for the height of the column of firn, to quantitatively reconstruct surface temperatures. In the WAIS Divide Ice Core, the two temperature proxies show a brief disagreement during Heinrich Stadial 1. Despite δ18Oice recording relatively constant temperature, the nitrogen and argon isotopes imply an abrupt warming between 16 and 15.8 kyr BP, manifest as an abrupt 1.25oC increase in the firn temperature gradient. To our knowledge, this would be the first evidence that such abrupt climate change has been recorded in an Antarctic climate proxy. If confirmed by more detailed studies, this event may represent warming due to an extreme southward shift of the Earth's thermal equator (and the southern hemisphere westerly wind belt), caused by the 16.1 ka Heinrich Event.

  8. Greenland Ice Sheet Surface Temperature, Melt, and Mass Loss: 2000-2006

    NASA Technical Reports Server (NTRS)

    Hall, Dorothy K.; Williams, Richard S., Jr.; Luthcke, Scott B.; DiGirolamo, Nocolo

    2007-01-01

    Extensive melt on the Greenland Ice Sheet has been documented by a variety of ground and satellite measurements in recent years. If the well-documented warming continues in the Arctic, melting of the Greenland Ice Sheet will likely accelerate, contributing to sea-level rise. Modeling studies indicate that an annual or summer temperature rise of 1 C on the ice sheet will increase melt by 20-50% therefore, surface temperature is one of the most important ice-sheet parameters to study for analysis of changes in the mass balance of the ice-sheet. The Greenland Ice Sheet contains enough water to produce a rise in eustatic sea level of up to 7.0 m if the ice were to melt completely. However, even small changes (centimeters) in sea level would cause important economic and societal consequences in the world's major coastal cities thus it is extremely important to monitor changes in the ice-sheet surface temperature and to ultimately quantify these changes in terms of amount of sea-level rise. We have compiled a high-resolution, daily time series of surface temperature of the Greenland Ice Sheet, using the I-km resolution, clear-sky land-surface temperature (LST) standard product from the Moderate-Resolution Imaging Spectroradiometer (MODIS), from 2000 - 2006. We also use Gravity Recovery and Climate Experiment (GRACE) data, averaged over 10-day periods, to measure change in mass of the ice sheet as it melt and snow accumulates. Surface temperature can be used to determine frequency of surface melt, timing of the start and the end of the melt season, and duration of melt. In conjunction with GRACE data, it can also be used to analyze timing of ice-sheet mass loss and gain.

  9. Oiling accelerates loss of salt marshes, southeastern Louisiana

    USGS Publications Warehouse

    Beland, Michael; Biggs, Trent W.; Roberts, Dar A.; Peterson, Seth H.; Kokaly, Raymond F.; Piazza, Sarai

    2017-01-01

    The 2010 BP Deepwater Horizon (DWH) oil spill damaged thousands of km2 of intertidal marsh along shorelines that had been experiencing elevated rates of erosion for decades. Yet, the contribution of marsh oiling to landscape-scale degradation and subsequent land loss has been difficult to quantify. Here, we applied advanced remote sensing techniques to map changes in marsh land cover and open water before and after oiling. We segmented the marsh shorelines into non-oiled and oiled reaches and calculated the land loss rates for each 10% increase in oil cover (e.g. 0% to >70%), to determine if land loss rates for each reach oiling category were significantly different before and after oiling. Finally, we calculated background land-loss rates to separate natural and oil-related erosion and land loss. Oiling caused significant increases in land losses, particularly along reaches of heavy oiling (>20% oil cover). For reaches with ≥20% oiling, land loss rates increased abruptly during the 2010–2013 period, and the loss rates during this period are significantly different from both the pre-oiling (p < 0.0001) and 2013–2016 post-oiling periods (p < 0.0001). The pre-oiling and 2013–2016 post-oiling periods exhibit no significant differences in land loss rates across oiled and non-oiled reaches (p = 0.557). We conclude that oiling increased land loss by more than 50%, but that land loss rates returned to background levels within 3–6 years after oiling, suggesting that oiling results in a large but temporary increase in land loss rates along the shoreline.

  10. Weight loss and bone mineral density.

    PubMed

    Hunter, Gary R; Plaisance, Eric P; Fisher, Gordon

    2014-10-01

    Despite evidence that energy deficit produces multiple physiological and metabolic benefits, clinicians are often reluctant to prescribe weight loss in older individuals or those with low bone mineral density (BMD), fearing BMD will be decreased. Confusion exists concerning the effects that weight loss has on bone health. Bone density is more closely associated with lean mass than total body mass and fat mass. Although rapid or large weight loss is often associated with loss of bone density, slower or smaller weight loss is much less apt to adversely affect BMD, especially when it is accompanied with high intensity resistance and/or impact loading training. Maintenance of calcium and vitamin D intake seems to positively affect BMD during weight loss. Although dual energy X-ray absorptiometry is normally used to evaluate bone density, it may overestimate BMD loss following massive weight loss. Volumetric quantitative computed tomography may be more accurate for tracking bone density changes following large weight loss. Moderate weight loss does not necessarily compromise bone health, especially when exercise training is involved. Training strategies that include heavy resistance training and high impact loading that occur with jump training may be especially productive in maintaining, or even increasing bone density with weight loss.

  11. Abrupt pre-Bølling-Allerød warming and circulation changes in the deep ocean.

    PubMed

    Thiagarajan, Nivedita; Subhas, Adam V; Southon, John R; Eiler, John M; Adkins, Jess F

    2014-07-03

    Several large and rapid changes in atmospheric temperature and the partial pressure of carbon dioxide in the atmosphere--probably linked to changes in deep ocean circulation--occurred during the last deglaciation. The abrupt temperature rise in the Northern Hemisphere and the restart of the Atlantic meridional overturning circulation at the start of the Bølling-Allerød interstadial, 14,700 years ago, are among the most dramatic deglacial events, but their underlying physical causes are not known. Here we show that the release of heat from warm waters in the deep North Atlantic Ocean probably triggered the Bølling-Allerød warming and reinvigoration of the Atlantic meridional overturning circulation. Our results are based on coupled radiocarbon and uranium-series dates, along with clumped isotope temperature estimates, from water column profiles of fossil deep-sea corals in a limited area of the western North Atlantic. We find that during Heinrich stadial 1 (the cool period immediately before the Bølling-Allerød interstadial), the deep ocean was about three degrees Celsius warmer than shallower waters above. This reversal of the ocean's usual thermal stratification pre-dates the Bølling-Allerød warming and must have been associated with increased salinity at depth to preserve the static stability of the water column. The depleted radiocarbon content of the warm and salty water mass implies a long-term disconnect from rapid surface exchanges, and, although uncertainties remain, is most consistent with a Southern Ocean source. The Heinrich stadial 1 ocean profile is distinct from the modern water column, that for the Last Glacial Maximum and that for the Younger Dryas, suggesting that the patterns we observe are a unique feature of the deglacial climate system. Our observations indicate that the deep ocean influenced dramatic Northern Hemisphere warming by storing heat at depth that preconditioned the system for a subsequent abrupt overturning event during the

  12. A Fast Framework for Abrupt Change Detection Based on Binary Search Trees and Kolmogorov Statistic

    PubMed Central

    Qi, Jin-Peng; Qi, Jie; Zhang, Qing

    2016-01-01

    Change-Point (CP) detection has attracted considerable attention in the fields of data mining and statistics; it is very meaningful to discuss how to quickly and efficiently detect abrupt change from large-scale bioelectric signals. Currently, most of the existing methods, like Kolmogorov-Smirnov (KS) statistic and so forth, are time-consuming, especially for large-scale datasets. In this paper, we propose a fast framework for abrupt change detection based on binary search trees (BSTs) and a modified KS statistic, named BSTKS (binary search trees and Kolmogorov statistic). In this method, first, two binary search trees, termed as BSTcA and BSTcD, are constructed by multilevel Haar Wavelet Transform (HWT); second, three search criteria are introduced in terms of the statistic and variance fluctuations in the diagnosed time series; last, an optimal search path is detected from the root to leaf nodes of two BSTs. The studies on both the synthetic time series samples and the real electroencephalograph (EEG) recordings indicate that the proposed BSTKS can detect abrupt change more quickly and efficiently than KS, t-statistic (t), and Singular-Spectrum Analyses (SSA) methods, with the shortest computation time, the highest hit rate, the smallest error, and the highest accuracy out of four methods. This study suggests that the proposed BSTKS is very helpful for useful information inspection on all kinds of bioelectric time series signals. PMID:27413364

  13. A Fast Framework for Abrupt Change Detection Based on Binary Search Trees and Kolmogorov Statistic.

    PubMed

    Qi, Jin-Peng; Qi, Jie; Zhang, Qing

    2016-01-01

    Change-Point (CP) detection has attracted considerable attention in the fields of data mining and statistics; it is very meaningful to discuss how to quickly and efficiently detect abrupt change from large-scale bioelectric signals. Currently, most of the existing methods, like Kolmogorov-Smirnov (KS) statistic and so forth, are time-consuming, especially for large-scale datasets. In this paper, we propose a fast framework for abrupt change detection based on binary search trees (BSTs) and a modified KS statistic, named BSTKS (binary search trees and Kolmogorov statistic). In this method, first, two binary search trees, termed as BSTcA and BSTcD, are constructed by multilevel Haar Wavelet Transform (HWT); second, three search criteria are introduced in terms of the statistic and variance fluctuations in the diagnosed time series; last, an optimal search path is detected from the root to leaf nodes of two BSTs. The studies on both the synthetic time series samples and the real electroencephalograph (EEG) recordings indicate that the proposed BSTKS can detect abrupt change more quickly and efficiently than KS, t-statistic (t), and Singular-Spectrum Analyses (SSA) methods, with the shortest computation time, the highest hit rate, the smallest error, and the highest accuracy out of four methods. This study suggests that the proposed BSTKS is very helpful for useful information inspection on all kinds of bioelectric time series signals.

  14. Turbulent Swirling Flow Downstream of an Abrupt Pipe Expansion -- Modeling and Experimental Measurements.

    DTIC Science & Technology

    1982-07-01

    aerospace engineering um~Ŕ" eqe~vswse 0engiee amp snry stem englnerlag. enI~e so ISaCW , meterI scienc Turbulent Swirling Flow Dowstreas of an Abrupt...With the horizontal test section and circumferentially local measurements, the extent of the influence of gravity -induced convection can be determined

  15. Effects of lorcaserin on fat and lean mass loss in obese and overweight patients without and with type 2 diabetes mellitus: the BLOSSOM and BLOOM-DM studies.

    PubMed

    Apovian, C; Palmer, K; Fain, R; Perdomo, C; Rubino, D

    2016-09-01

    Body composition was determined using dual-energy X-ray absorptiometry (DXA) in a subset of patients without (BLOSSOM) and with (BLOOM-DM) type 2 diabetes who received diet and exercise counselling along with either lorcaserin 10 mg twice daily or placebo. DXA scans were performed on study day 1 (baseline), week 24 and week 52. Baseline demographics of the subpopulations (without diabetes, n = 189; with diabetes, n = 63) were similar between studies and representative of their study populations. At week 52, patients without diabetes on lorcaserin lost significantly more fat mass relative to those on placebo (-12.06% vs -5.93%; p = 0.008). In patients with diabetes, fat mass was also decreased with lorcaserin relative to placebo (-9.87% vs -1.65%; p < 0.05). More fat mass was lost in the trunk region with lorcaserin compared with placebo (without diabetes: -3.31% vs -2.05%; with diabetes: -3.65% vs -0.36%). Weight loss with lorcaserin was associated with a greater degree of fat mass loss than lean mass loss, and most of the fat mass lost for patients without and with diabetes was from the central region of the body. © 2016 John Wiley & Sons Ltd.

  16. Controls on mass loss and nitrogen dynamics of oak leaf litter along an urban-rural land-use gradient

    Treesearch

    Richard V. Pouyat; Margaret M. Carreiro

    2003-01-01

    Using reciprocal leaf litter transplants, we investigated the effects of contrasting environments (urban vs. rural) and intraspecific variations in oak leaf litter quality on mass loss rates and nitrogen (N) dynamics along an urban-rural gradient in the New York City metropolitan area. Differences in earthworm abundances and temperature had previously been documented...

  17. THE SECRET LIVES OF CEPHEIDS: EVOLUTION, MASS-LOSS, AND ULTRAVIOLET EMISSION OF THE LONG-PERIOD CLASSICAL CEPHEID

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Neilson, Hilding R.; Engle, Scott G.; Guinan, Edward F.

    The classical Cepheid l Carinae is an essential calibrator of the Cepheid Leavitt Law as a rare long-period Galactic Cepheid. Understanding the properties of this star will also constrain the physics and evolution of massive ( M ≥ 8 M {sub ⊙}) Cepheids. The challenge, however, is precisely measuring the star's pulsation period and its rate of period change. The former is important for calibrating the Leavitt Law and the latter for stellar evolution modeling. In this work, we combine previous time-series observations spanning more than a century with new observations to remeasure the pulsation period and compute the ratemore » of period change. We compare our new rate of period change with stellar evolution models to measure the properties of l Car, but find models and observations are, at best, marginally consistent. The results imply that l Car does not have significantly enhanced mass-loss rates like that measured for δ Cephei. We find that the mass of l Car is about 8–10 M {sub ⊙}. We present Hubble Space Telescope Cosmic Origins Spectrograph observations that also differ from measurements for δ Cep and β Dor. These measurements further add to the challenge of understanding the physics of Cepheids, but do hint at the possible relation between enhanced mass-loss and ultraviolet emission, perhaps both due to the strength of shocks propagating in the atmospheres of Cepheids.« less

  18. North Pacific deglacial hypoxic events linked to abrupt ocean warming

    USGS Publications Warehouse

    Praetorius, Summer K; Mix, Alan C.; Davies, Maureen H.; Wolhowe, Matthew D; Addison, Jason A.; Prahl, Frederick G

    2015-01-01

    Marine sediments from the North Pacific document two episodes of expansion and strengthening of the subsurface oxygen minimum zone (OMZ) accompanied by seafloor hypoxia during the last deglacial transition1, 2, 3, 4. The mechanisms driving this hypoxia remain under debate1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11. We present a new high-resolution alkenone palaeotemperature reconstruction from the Gulf of Alaska that reveals two abrupt warming events of 4–5 degrees Celsius at the onset of the Bølling and Holocene intervals that coincide with sudden shifts to hypoxia at intermediate depths. The presence of diatomaceous laminations and hypoxia-tolerant benthic foraminiferal species, peaks in redox-sensitive trace metals12, 13, and enhanced 15N/14N ratio of organic matter13, collectively suggest association with high export production. A decrease in 18O/16O values of benthic foraminifera accompanying the most severe deoxygenation event indicates subsurface warming of up to about 2 degrees Celsius. We infer that abrupt warming triggered expansion of the North Pacific OMZ through reduced oxygen solubility and increased marine productivity via physiological effects; following initiation of hypoxia, remobilization of iron from hypoxic sediments could have provided a positive feedback on ocean deoxygenation through increased nutrient utilization and carbon export. Such a biogeochemical amplification process implies high sensitivity of OMZ expansion to warming.

  19. Abrupt Upper-Plate Tilting Upon Slab-Transition-Zone Collision

    NASA Astrophysics Data System (ADS)

    Crameri, F.; Lithgow-Bertelloni, C. R.

    2017-12-01

    During its sinking, the remnant of a surface plate crosses and interacts with multiple boundaries in Earth's interior. The most-prominent dynamic interaction arises at the upper-mantle transition zone where the sinking plate is strongly affected by the higher-viscosity lower mantle. Within our numerical model, we unravel, for the first time, that this very collision of the sinking slab with the transition zone induces a sudden, dramatic downward tilt of the upper plate towards the subduction trench. The slab-transition zone collision sets parts of the higher-viscosity lower mantle in motion. Naturally, this then induces an overall larger return flow cell that, at its onset, tilts the upper plate abruptly by around 0.05 degrees and over around 10 Millions of years. Such a significant and abrupt variation in surface topography should be clearly visible in temporal geologic records of large-scale surface elevation and might explain continental-wide tilting as observed in Australia since the Eocene or North America during the Phanerozoic. Unravelling this crucial mantle-lithosphere interaction was possible thanks to state-of-the-art numerical modelling (powered by StagYY; Tackley 2008, PEPI) and post-processing (powered by StagLab; www.fabiocrameri.ch/software). The new model that is introduced here to study the dynamically self-consistent temporal evolution of subduction features accurate subduction-zone topography, robust single-sided plate sinking, stronger plates close to laboratory values, an upper-mantle phase transition and, crucially, simple continents at a free surface. A novel, fully-automated post-processing includes physical model diagnostics like slab geometry, mantle flow pattern, upper-plate tilt angle and trench location.

  20. Observation and analysis of abrupt changes in the interplanetary plasma velocity and magnetic field.

    NASA Technical Reports Server (NTRS)

    Martin, R. N.; Belcher, J. W.; Lazarus, A. J.

    1973-01-01

    This paper presents a limited study of the physical nature of abrupt changes in the interplanetary plasma velocity and magnetic field based on 19 day's data from the Pioneer 6 spacecraft. The period was chosen to include a high-velocity solar wind stream and low-velocity wind. Abrupt events were accepted for study if the sum of the energy density in the magnetic field and velocity changes was above a specified minimum. A statistical analysis of the events in the high-velocity solar wind stream shows that Alfvenic changes predominate. This conclusion is independent of whether steady state requirements are imposed on conditions before and after the event. Alfvenic changes do not dominate in the lower-speed wind. This study extends the plasma field evidence for outwardly propagating Alfvenic changes to time scales as small as 1 min (scale lengths on the order of 20,000 km).

  1. Observation of an abrupt electron heating mode transition in capacitive single radio frequency discharges

    NASA Astrophysics Data System (ADS)

    Wilczek, Sebastian; Trieschmann, Jan; Schulze, Julian; Brinkmann, Ralf Peter; Mussenbrock, Thomas; Derzsi, Aranka; Korolov, Ihor; Donkó, Zoltan

    2013-09-01

    The electron heating in capacitive discharges at very low pressures (~1 Pa) is dominated by stochastic heating. In this regime electrons are accelerated by the oscillating sheaths, traverse through the plasma bulk and interact with the opposite sheath. By varying the driving frequency or the gap size of the discharge, energetic electrons reach the sheath edge at different temporal phases, i.e., the collapsing or expanding phase, or the moment of minimum sheath width. This work reports numerical experiments based on Particle-In-Cell simulations which show that at certain frequencies the discharge switches abruptly from a low density mode in a high density mode. The inverse transition is also abrupt, but shows a significant hysteresis. This behavior is explained by the complex interaction of the bulk and the sheath. This work is supported by the German Research Foundation in the frame of TRR 87.

  2. Loss of muscle mass: Current developments in cachexia and sarcopenia focused on biomarkers and treatment.

    PubMed

    Drescher, Cathleen; Konishi, Masaaki; Ebner, Nicole; Springer, Jochen

    2016-01-01

    Loss of muscle mass arises from an imbalance of protein synthesis and protein degradation. Potential triggers of muscle wasting and function are immobilization, loss of appetite, dystrophies and chronic diseases as well as aging. All these conditions lead to increased morbidity and mortality in patients, which makes it a timely matter to find new biomarkers to get a fast clinical diagnosis and to develop new therapies. This mini-review covers current developments in the field of biomarkers and drugs on cachexia and sarcopenia. Here, we reported about promising markers, e.g. tartrate-resistant acid phosphatase 5a (TRACP5a), and novel substances like Epigallocatechin-3-gallate (EGCg). In summary, the progress to combat muscle wasting is in full swing and perhaps diagnosis of muscle atrophy and of course patient treatments could be soon supported by improved and more helpful strategies. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  3. Factors which modulate the rates of skeletal muscle mass loss in non-small cell lung cancer patients: a pilot study.

    PubMed

    Atlan, Philippe; Bayar, Mohamed Amine; Lanoy, Emilie; Besse, Benjamin; Planchard, David; Ramon, Jordy; Raynard, Bruno; Antoun, Sami

    2017-11-01

    Advanced non-small cell lung cancer (NSCLC) is associated with weight loss which may reflect skeletal muscle mass (SMM) and/or total adipose tissue (TAT) depletion. This study aimed to describe changes in body composition (BC) parameters and to identify the factors unrelated to the tumor which modulate them. SMM, TAT, and the proportion of SMM to SMM + TAT were assessed with computed tomography. Estimates of each BC parameter at follow-up initiation and across time were derived from a mixed linear model of repeated measurements with a random intercept and a random slope. The same models were used to assess the independent effect of gender, age, body mass index (BMI), and initial values on changes in each BC parameter. Sixty-four patients with stage III or IV NSCLC were reviewed. The mean ± SD decreases in body weight and SMM were respectively 59 ± 3 g/week (P < 0.03) and 7 mm 2 /m 2 /week (P = 0.0003). During follow-up, no changes were identified in TAT nor in muscle density or in the proportion of SMM to SMM + TAT, estimated at 37 ± 2% at baseline. SMM loss was influenced by initial BMI (P < 0.0001) and SMM values (P = 0.0002): the higher the initial BMI or SMM values, the greater the loss observed. Weight loss was greater when the initial weight was heavier (P < 0.0001). Our results demonstrate that SMM wasting in NSCLC is lower when initial SMM and BMI values are low. These exploratory findings after our attempt to better understand the intrinsic factors associated with muscle mass depletion need to be confirmed in larger studies.

  4. Early Holocene hydroclimate of Baffin Bay: Understanding the interplay between abrupt climate change events and ice sheet fluctuations

    NASA Astrophysics Data System (ADS)

    Corcoran, M. C.; Thomas, E. K.; Castañeda, I. S.; Briner, J. P.

    2017-12-01

    Understanding the causes of ice sheet fluctuations resulting in sea level rise is essential in today's warming climate. In high-latitude ice-sheet-proximal environments such as Baffin Bay, studying both the cause and the rate of ice sheet variability during past abrupt climate change events aids in predictions. Past climate reconstructions are used to understand ice sheet responses to changes in temperature and precipitation. The 9,300 and 8,200 yr BP events are examples of abrupt climate change events in the Baffin Bay region during which there were multiple re-advances of the Greenland and Laurentide ice sheets. High-resolution (decadal-scale) hydroclimate variability near the ice sheet margins during these abrupt climate change events is still unknown. We will generate a decadal-scale record of early Holocene temperature and precipitation using leaf wax hydrogen isotopes, δ2Hwax, from a lake sediment archive on Baffin Island, western Baffin Bay, to better understand abrupt climate change in this region. Shifts in temperature and moisture source result in changes in environmental water δ2H, which in turn is reflected in δ2Hwax, allowing for past hydroclimate to be determined from these compound-specific isotopes. The combination of terrestrial and aquatic δ2Hwax is used to determine soil evaporation and is ultimately used to reconstruct moisture variability. We will compare our results with a previous analysis of δ2Hwax and branched glycerol dialkyl glycerol tetraethers, a temperature and pH proxy, in lake sediment from western Greenland, eastern Baffin Bay, which indicates that cool and dry climate occurred in response to freshwater forcing events in the Labrador Sea. Reconstructing and comparing records on both the western and eastern sides of Baffin Bay during the early Holocene will allow for a spatial understanding of temperature and moisture balance changes during abrupt climate events, aiding in ice sheet modeling and predictions of future sea level

  5. The risk of placental abruption and placenta previa in pregnant women with chronic hepatitis B viral infection: a systematic review and meta-analysis.

    PubMed

    Huang, Q T; Chen, J H; Zhong, M; Xu, Y Y; Cai, C X; Wei, S S; Hang, L L; Liu, Q; Yu, Y H

    2014-08-01

    Several epidemiological studies have found a positive association between chronic hepatitis B virus (CHB) infection and the risk of placental abruption and placenta previa, but various studies have reported conflicting findings. The objective was to systematically review the literature to determine a possible association between CHB infection and these two placental complications. We conducted a computerized search in electronic database through March 1, 2014, supplemented with a manual search of reference lists, to identify original published research on placental abruption and placenta previa rates in women with CHB infection. Data were independently extracted, and relative risks were calculated. The meta-analysis was performed using Stata version 10.0 software. Five studies involving 9088 placenta previa cases were identified. No significant association between CHB infection and placenta previa was identified (OR = 0.98, 95% CI = 0.60-1.62). Five studies involving 15571 placental abruption cases were identified. No significant association between CHB infection and placental abruption was identified (OR = 1.42, 95% CI, 0.93-2.15). The immune response against the virus represents a key factor in determining infection outcomes. No observation of significant increased risk of the placental complications could be partially explained by the complex immune response during CHB infection. Our meta-analysis found no evidence of significant associations between CHB infection and increased risk of placental abruption as well as placenta previa. Further well-designed studies were warranted to assess any potential association between CHB infection and increased risk of placental abruption as well as placenta previa. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Global-scale hydrological response to future glacier mass loss

    NASA Astrophysics Data System (ADS)

    Huss, Matthias; Hock, Regine

    2018-01-01

    Worldwide glacier retreat and associated future runoff changes raise major concerns over the sustainability of global water resources1-4, but global-scale assessments of glacier decline and the resulting hydrological consequences are scarce5,6. Here we compute global glacier runoff changes for 56 large-scale glacierized drainage basins to 2100 and analyse the glacial impact on streamflow. In roughly half of the investigated basins, the modelled annual glacier runoff continues to rise until a maximum (`peak water') is reached, beyond which runoff steadily declines. In the remaining basins, this tipping point has already been passed. Peak water occurs later in basins with larger glaciers and higher ice-cover fractions. Typically, future glacier runoff increases in early summer but decreases in late summer. Although most of the 56 basins have less than 2% ice coverage, by 2100 one-third of them might experience runoff decreases greater than 10% due to glacier mass loss in at least one month of the melt season, with the largest reductions in central Asia and the Andes. We conclude that, even in large-scale basins with minimal ice-cover fraction, the downstream hydrological effects of continued glacier wastage can be substantial, but the magnitudes vary greatly among basins and throughout the melt season.

  7. Balanced conditions or slight mass gain of glaciers in the Lahaul and Spiti region (northern India, Himalaya) during the nineties preceded recent mass loss

    NASA Astrophysics Data System (ADS)

    Vincent, C.; Ramanathan, Al.; Wagnon, P.; Dobhal, D. P.; Linda, A.; Berthier, E.; Sharma, P.; Arnaud, Y.; Azam, M. F.; Jose, P. G.; Gardelle, J.

    2013-04-01

    The volume change of the Chhota Shigri Glacier (India, 32° 20 N, 77° 30' E) between 1988 and 2010 has been determined using in situ geodetic measurements. This glacier has experienced only a slight mass loss between 1988 and 2010 (-3.8 ± 2.0 m w.e. (water equivalent) corresponding to -0.17 ± 0.09 m w.e. yr-1). Using satellite digital elevation models (DEM) differencing and field measurements, we measure a negative mass balance (MB) between 1999 and 2010 (-4.8 ± 1.8 m w.e. corresponding to -0.44 ± 0.16 m w.e. yr-1). Thus, we deduce a slightly positive or near-zero MB between 1988 and 1999 (+1.0 ± 2.7 m w.e. corresponding to +0.09 ± 0.24 m w.e. yr-1). Furthermore, satellite DEM differencing reveals that the MB of the Chhota Shigri Glacier (-0.39 ± 0.15 m w.e. yr-1) has been only slightly less negative than the MB of a 2110 km2 glaciarized area in the Lahaul and Spiti region (-0.44 ± 0.09 m w.e. yr-1) during 1999-2011. Hence, we conclude that the ice wastage is probably moderate in this region over the last 22 yr, with near equilibrium conditions during the nineties, and an ice mass loss after. The turning point from balanced to negative mass budget is not known but lies probably in the late nineties and at the latest in 1999. This positive or near-zero MB for Chhota Shigri Glacier (and probably for the surrounding glaciers of the Lahaul and Spiti region) during at least part of the 1990s contrasts with a recent compilation of MB data in the Himalayan range that indicated ice wastage since 1975. However, in agreement with this compilation, we confirm more negative balances since the beginning of the 21st century.

  8. Early Warning Signals for Abrupt Change Raise False Alarm During Sea Ice Loss

    NASA Astrophysics Data System (ADS)

    Wagner, T. J. W.; Eisenman, I.

    2015-12-01

    Uncovering universal early warning signals for critical transitions has become a coveted goal in diverse scientific disciplines, ranging from climate science to financial mathematics. There has been a flurry of recent research proposing such signals, with increasing autocorrelation and increasing variance being among the most widely discussed candidates. A number of studies have suggested that increasing autocorrelation alone may suffice to signal an impending transition, although some others have questioned this. Here, we consider variance and autocorrelation in the context of sea ice loss in an idealized model of the global climate system. The model features no bifurcation, nor increased rate of retreat, as the ice disappears. Nonetheless, the autocorrelation of summer sea ice area is found to increase with diminishing sea ice cover in a global warming scenario. The variance, by contrast, decreases. A simple physical mechanism is proposed to explain the occurrence of increasing autocorrelation but not variance in the model when there is no approaching bifurcation. Additionally, a similar mechanism is shown to allow an increase in both indicators with no physically attainable bifurcation. This implies that relying on autocorrelation and variance as early warning signals can raise false alarms in the climate system, warning of "tipping points" that are not actually there.

  9. Abrupt Climatic Change during the Latest Maastrichtian: Establishing Robust Temporal Links with the Onset of Deccan Volcanism and K/Pg Mass Extinction

    NASA Astrophysics Data System (ADS)

    Barnet, J.; Littler, K.; Kroon, D.; Leng, M. J.; Westerhold, T.; Roehl, U.; Zachos, J. C.

    2017-12-01

    A transient period of climate change, characterized by a global warming of 2.5-5°C followed by a cooling to pre-excursion conditions, occurred during the last 300 kyr of the Maastrichtian ( 66.34-66.02 Ma). This instability may have played a role in destabilizing marine and terrestrial ecosystems, priming the system for abrupt extinction at the K-Pg boundary, likely triggered by a large bolide impact. This pre-K-Pg warming event has often been linked to the main phase of Deccan Trap volcanism, however large uncertainties associated with radio-isotopic dating methods of basalts, along with low sedimentation rates and hiatuses in many studied sedimentary sequences, have long hampered a definitive correlation. To complement recent advances in dating of the traps, we have generated the first complete and highest resolution (2.5-4 kyr) benthic stable δ13C and δ18O record for the final million years of the Maastrichtian using the epifaunal foraminifera species Nuttallides truempyi from ODP Site 1262, Walvis Ridge, South Atlantic, calibrated to an updated orbitally-tuned age model. We then compare our data to other previously published geochemical data from other sites in the high, middle, and low latitudes. Our data confirms that the onset of the warming event coincides with the onset of the main phase of Deccan volcanism, strongly suggesting a causal link. Furthermore, spectral analysis of our extended late Maastrichtian-Early Eocene record suggests that the onset of the warming event corresponds to a 405-kyr eccentricity minima, in contrast to many transient warming events (hyperthermals) of the Paleogene, suggesting a control by orbital forcing alone is unlikely. A peculiar feature of the event, compared to other hyperthermals, is a muted carbon cycle response during warming, which may be related to the comparatively heavier δ13C signature of volcanogenic CO2 (-7‰), compared to other sources of light carbon invoked to explain Paleogene hyperthermals. The warming

  10. The Sodium Glucose Cotransporter 2 Inhibitor Ipragliflozin Promotes Preferential Loss of Fat Mass in Non-obese Diabetic Goto-Kakizaki Rats.

    PubMed

    Takasu, Toshiyuki; Hayashizaki, Yuka; Hirosumi, Jiro; Minoura, Hideaki; Amino, Nobuaki; Kurosaki, Eiji; Takakura, Shoji

    2017-01-01

    Sodium glucose cotransporter 2 (SGLT2) inhibitors improve hyperglycemia in patients with type 2 diabetes mellitus (T2DM) by increasing urinary glucose excretion. In addition to their antihyperglycemic effect, SGLT2 inhibitors also reduce body weight and fat mass in obese and overweight patients with T2DM. However, whether or not SGLT2 inhibitors similarly affect body composition of non-obese patients with T2DM remains unclear. In this study, we investigated the effect of the SGLT2 inhibitor ipragliflozin on body composition in a Goto-Kakizaki (GK) rat model of non-obese T2DM. GK rats were treated with ipragliflozin once daily for 9 weeks, starting at 23 weeks of age. Body composition was then analyzed using dual-energy X-ray absorptiometry. Treatment with ipragliflozin increased urinary glucose excretion, reduced hemoglobin A1c (HbA1c) levels and suppressed body weight gain as the dose increased. Body composition analysis revealed that body fat mass was lower in the ipragliflozin-treated groups than in the control group, while lean body mass and bone mineral contents were comparable between groups. Thus, an SGLT2 inhibitor ipragliflozin was found to promote preferential loss of fat mass in a rat model of non-obese T2DM. Ipragliflozin might also promote preferential loss of fat in non-obese patients with T2DM.

  11. Rapid reduction versus abrupt quitting for smokers who want to stop soon: a randomised controlled non-inferiority trial

    PubMed Central

    Lindson, Nicola; Aveyard, Paul; Ingram, Jackie T; Inglis, Jennie; Beach, Jane; West, Robert; Michie, Susan

    2009-01-01

    Background The standard way to stop smoking is to stop abruptly on a quit day with no prior reduction in consumption of cigarettes. Many smokers feel that reduction is natural and if reduction programmes were offered, many more might take up treatment. Few trials of reduction versus abrupt cessation have been completed. Most are small, do not use pharmacotherapy, and do not meet the standards necessary to obtain a marketing authorisation for a pharmacotherapy. Design/Methods We will conduct a non-inferiority randomised trial of rapid reduction versus standard abrupt cessation among smokers who want to stop smoking. In the reduction arm, participants will be advised to reduce smoking consumption by half in the first week and to 25% of baseline in the second, leading up to a quit day at which participants will stop smoking completely. This will be assisted by nicotine patches and an acute form of nicotine replacement therapy. In the abrupt arm participants will use nicotine patches only, whilst smoking as normal, for two weeks prior to a quit day, at which they will also stop smoking completely. Smokers in either arm will have standard withdrawal orientated behavioural support programme with a combination of nicotine patches and acute nicotine replacement therapy post-cessation. Outcomes/Follow-up The primary outcome of interest will be prolonged abstinence from smoking, with secondary trial outcomes of point prevalence, urges to smoke and withdrawal symptoms. Follow up will take place at 4 weeks, 8 weeks and 6 months post-quit day. Trial Registration Current Controlled Trials ISRCTN22526020 PMID:19682359

  12. Globally synchronous ice core volcanic tracers and abrupt cooling during the last glacial period

    USGS Publications Warehouse

    Bay, R.C.; Bramall, N.E.; Price, P.B.; Clow, G.D.; Hawley, R.L.; Udisti, R.; Castellano, E.

    2006-01-01

    We perform a Monte Carlo pattern recognition analysis of the coincidence between three regional volcanic histories from ice coring of Greenland and Antarctica over the period 2 to 45 ka, using SO4 anomalies in Greenland and East Antarctica determined by continuous core chemistry, together with West Antarctic volcanic ash layers determined by remote optical borehole logging and core assays. We find that the Antarctic record of volcanism correlates with Glacial abrupt climate change at a 95% to >99.8% (???3??) significance level and that volcanic depositions at the three locations match at levels exceeding 3??, likely indicating that many common horizons represent single eruptive events which dispersed material world wide. These globally coincident volcanics were associated with abrupt cooling, often simultaneous with onsets or sudden intensifications of millennial cold periods. The striking agreement between sites implies that the consistency of current timescales obtained by isotopic and glaciological dating methods is better than estimated. Copyright 2006 by the American Geogphysical Union.

  13. The nature of abrupt climate change during the last glacial period from detailed isotopic records from the NGRIP ice core

    NASA Astrophysics Data System (ADS)

    Popp, T. J.; Svensson, A.; Steffensen, J. P.; Johnsen, S. J.; White, J. W. C.

    2009-04-01

    Isotopic and chemical impurity records from Greenland ice cores with sub-annual resolution across three fast climate transitions of the last deglacial termination reveal complex patterns of environmental change for the onset of Greenland Interstadial 1 (GI-1 or Bølling), the onset of Greenland Stadial 1 (GS-1 or Younger Dryas), and the onset of the Holocene. In the NGRIP ice core each of these transitions is initiated by a 1-3 year mode shift in deuterium excess, which is a proxy for the Greenland precipitation moisture source. These mode shifts in deuterium excess are decoupled in time from the isotopic (deuterium and oxygen-18) transitions from which they are derived. In general the abrupt isotopic transitions follow the corresponding deuterium excess shifts and span decades rather than years. Similar data from GISP2 confirms the clear deuterium excess mode shifts for transitions from cold states to warm states; however the abrupt deuterium excess transition at the onset of GS-1 is not expressed in a similar way at GISP2. Ironically, it appears that this cooling at the beginning of the Younger Dryas, for which we have theories of the triggering event, is less clearly recorded than warming events, the triggering of which is still poorly understood. Along with other available paleo-data, these results indicate that the sum of an abrupt climate change is composed of multiple responses from different parts of the climate system. These responses can be separated by as little as a single year to a few decades and the collection of these responses result in a variety of abrupt transitions giving each a unique anatomy. Here we expand this type of analysis with new isotope, deuterium excess, and accumulation rate time series from NGRIP across the abrupt transitions associated with several interstadial events of the Last Glacial period (Dansgaard-Oeschger events). Indeed the temporal phasing of deuterium excess and the isotopic content of the ice can vary from one event

  14. Ultralow-loss polaritons in isotopically pure boron nitride

    NASA Astrophysics Data System (ADS)

    Giles, Alexander J.; Dai, Siyuan; Vurgaftman, Igor; Hoffman, Timothy; Liu, Song; Lindsay, Lucas; Ellis, Chase T.; Assefa, Nathanael; Chatzakis, Ioannis; Reinecke, Thomas L.; Tischler, Joseph G.; Fogler, Michael M.; Edgar, J. H.; Basov, D. N.; Caldwell, Joshua D.

    2018-02-01

    Conventional optical components are limited to size scales much larger than the wavelength of light, as changes to the amplitude, phase and polarization of the electromagnetic fields are accrued gradually along an optical path. However, advances in nanophotonics have produced ultrathin, so-called `flat' optical components that beget abrupt changes in these properties over distances significantly shorter than the free-space wavelength. Although high optical losses still plague many approaches, phonon polariton (PhP) materials have demonstrated long lifetimes for sub-diffractional modes in comparison to plasmon-polariton-based nanophotonics. We experimentally observe a threefold improvement in polariton lifetime through isotopic enrichment of hexagonal boron nitride (hBN). Commensurate increases in the polariton propagation length are demonstrated via direct imaging of polaritonic standing waves by means of infrared nano-optics. Our results provide the foundation for a materials-growth-directed approach aimed at realizing the loss control necessary for the development of PhP-based nanophotonic devices.

  15. Glacier mass loss. Dynamic thinning of glaciers on the Southern Antarctic Peninsula.

    PubMed

    Wouters, B; Martin-Español, A; Helm, V; Flament, T; van Wessem, J M; Ligtenberg, S R M; van den Broeke, M R; Bamber, J L

    2015-05-22

    Growing evidence has demonstrated the importance of ice shelf buttressing on the inland grounded ice, especially if it is resting on bedrock below sea level. Much of the Southern Antarctic Peninsula satisfies this condition and also possesses a bed slope that deepens inland. Such ice sheet geometry is potentially unstable. We use satellite altimetry and gravity observations to show that a major portion of the region has, since 2009, destabilized. Ice mass loss of the marine-terminating glaciers has rapidly accelerated from close to balance in the 2000s to a sustained rate of -56 ± 8 gigatons per year, constituting a major fraction of Antarctica's contribution to rising sea level. The widespread, simultaneous nature of the acceleration, in the absence of a persistent atmospheric forcing, points to an oceanic driving mechanism. Copyright © 2015, American Association for the Advancement of Science.

  16. [Management of sudden neurosensory hearing loss in a Primary Care Centre].

    PubMed

    Muñoz-Proto, F; Carnevale, C; Bejarano-Panadés, N; Ferrán-de la Cierva, L; Mas-Mercant, S; Sarría-Echegaray, P

    2014-04-01

    Sudden hearing loss is a rapid loss of neurosensory hearing that may occur within hours or days in an apparently healthy patient. Its origins are variable and multifactorial. Most patients do not recover hearing if not treated, and some even develop cophosis (deafness) in the affected ear. It is an otological emergency, as early therapeutic management offers a better hearing prognosis. As there is limited knowledge on this condition, it may be underdiagnosed in Primary Health Care Centers. It should be suspected in patients with abrupt hearing loss or tinnitus. Sophisticated instruments are not required for its diagnosis, just a detailed history, basic otoscopy, and proper interpretation of the hearing test. In this way, an accurate diagnosis is achieved in most cases, which is confirmed by audiometry. Copyright © 2012 Sociedad Española de Médicos de Atención Primaria (SEMERGEN). Publicado por Elsevier España. All rights reserved.

  17. Pregnancy loss managed by cervical dilatation and curettage increases the risk of spontaneous preterm birth.

    PubMed

    McCarthy, Fergus P; Khashan, Ali S; North, Robyn A; Rahma, Muna B; Walker, James J; Baker, Philip N; Dekker, Gus; Poston, Lucilla; McCowan, Lesley M E; O'Donoghue, Keelin; Kenny, Louise C

    2013-12-01

    Do women with a previous miscarriage or termination of pregnancy have an increased risk of spontaneous preterm birth and is this related to previous cervical dilatation and curettage? A single previous pregnancy loss (termination or miscarriage) managed by cervical dilatation and curettage is associated with a greater risk of SpPTB. Miscarriage affects ∼20% of pregnancies and as many as a further 20% of pregnancies undergo termination. We utilized data from 5575 healthy nulliparous women with singleton pregnancies recruited to the Screening for Pregnancy Endpoints (SCOPE) study, a prospective cohort study performed between November 2004 and January 2011. The primary outcome was spontaneous preterm birth (defined as spontaneous preterm labour or preterm premature rupture of membranes (PPROM) resulting in preterm birth <37 weeks' gestation). Secondary outcomes included PPROM, small for gestational age, birthweight, pre-eclampsia and placental abruption. Women with previous pregnancy loss (miscarriage or termination) were compared with those with no previous pregnancy loss. There were 4331 (78%) women who had no previous pregnancy loss, 974 (17.5%) who had one early previous pregnancy loss, 249 (4.5%) who had two and 21 (0.5%) who had three or four losses. Women with two to four previous losses, but not those with a single loss, had an increased risk of spontaneous preterm birth (adjusted OR 2.12; 95% CI 1.55, 2.90) and/or placental abruption (adjusted OR 2.30; 95% CI 1.36, 3.89) compared with those with no previous pregnancy. A single previous miscarriage or termination of pregnancy where the management involved cervical dilatation and curettage was associated with an increased risk of spontaneous preterm birth (adjusted OR 1.64; 95% CI 1.08, 2.50; 6% absolute risk and adjusted OR 1.83; 95% CI 1.35, 2.48; 7% absolute risk, respectively) compared with those with no previous pregnancy losses. This is in contrast with women with a single previous miscarriage or

  18. Placental Abruption and Perinatal Mortality With Preterm Delivery as a Mediator: Disentangling Direct and Indirect Effects

    PubMed Central

    Ananth, Cande V.; VanderWeele, Tyler J.

    2011-01-01

    The authors use recent methodology in causal inference to disentangle the direct and indirect effects that operate through a mediator in an exposure-response association paradigm. They demonstrate how total effects can be partitioned into direct and indirect effects even when the exposure and mediator interact. The impact of bias due to unmeasured confounding on the exposure-response association is assessed through a series of sensitivity analyses. These methods are applied to a problem in perinatal epidemiology to examine the extent to which the effect of abruption on perinatal mortality is mediated through preterm delivery. Data on over 26 million US singleton births (1995–2002) were utilized. Risks of mortality among abruption and nonabruption births were 102.7 and 6.2 per 1,000 births, respectively. Risk ratios of the natural direct and indirect (preterm delivery-mediated) effects of abruption on mortality were 10.18 (95% confidence interval: 9.80, 10.58) and 1.35 (95% confidence interval: 1.33, 1.38), respectively. The proportion of increased mortality risk mediated through preterm delivery was 28.1%, with even higher proportions associated with deliveries at earlier gestational ages. Sensitivity analyses underscore that the qualitative conclusions of some mediated effects and substantial direct effects are reasonably robust to unmeasured confounding of a fairly considerable magnitude. PMID:21430195

  19. The importance of Titan's current mass loss processes to understanding the evolution of Titan's atmosphere

    NASA Astrophysics Data System (ADS)

    Mandt, Kathleen; Waite, J. Hunter, Jr.; Bell, Jared; Mousis, Olivier

    2010-04-01

    Current isotopic ratios in planetary atmospheres have played an important role in determining how that atmosphere has evolved over geologic time scales (e.g. Donahue et al. 1997, Lunine et al. 1999). The current 12C/13C ratio in methane is a particularly useful indicator of Titan's atmospheric evolutionary history (Mandt et al. 2009). Primordial 12C/13C ratios throughout the solar system are limited to 89.01+4.45-2.67. (Alexander et al. 2007, Martins et al. 2008), while the methane 12C/13C ratio measured by GCMS and CIRS are 82.3+/-1.0 and 76.6+/-2.7 respectively (Niemann et al. 2005, Nixon et al. 2008). This is well below the primordial range, suggesting fractionation of the isotopes by atmospheric processes. A number of atmospheric mass loss processes can fractionate the isotopes over geologic time scales. Photochemistry and escape are of particular importance (Donahue et al 1997, Mandt et al. 2009). Measurements of the 12C/13C ratios in C2 hydrocarbons show evidence of fractionation due to photochemistry (Nixon et al. 2008) that is most likely due to a kinetic isotope effect (KIE). A KIE is a mildly efficient fractionating process in which reactions involving 12C occur 1.04 times faster than reactions involving 13C. A moderate time scale, on the order of 50 to 400 million years, is required to change the 12C/13C ratio of the atmospheric methane inventory. The exact length of this time scale depends directly on the methane photochemical loss rate. Titan's photochemistry is extremely complex, and although the total photochemical loss rate is photon-limited (Lorenz et al. 1997), the literature provides a range of loss rates between 4.9 x 10^9 cm-2s-1 (Wilson and Atreya 2004) and 3.4 x 10^10 cm-2s-1 (Lebonnois et al. 2003). This range can alter the time scale for fractionation in the carbon isotopes by as much as a factor of 8. INMS measurements of the methane 12C/13C ratio in the upper atmosphere show that atmospheric escape is a more efficient fractionating

  20. Effects of high protein diets on fat-free mass and muscle protein synthesis following weight loss: a randomized controlled trial

    USDA-ARS?s Scientific Manuscript database

    Context: The benefits of high protein diets for sparing lean body mass and sustaining skeletal muscle protein metabolism during short-term weight loss in normal-weight adults are not well described. Objective: Determine the effects of varying levels of dietary protein intake on body compos...

  1. Integrative Analyses of miRNA-mRNA Interactions Reveal let-7b, miR-128 and MAPK Pathway Involvement in Muscle Mass Loss in Sex-Linked Dwarf Chickens

    PubMed Central

    Luo, Wen; Lin, Shumao; Li, Guihuan; Nie, Qinghua; Zhang, Xiquan

    2016-01-01

    The sex-linked dwarf (SLD) chicken is an ideal model system for understanding growth hormone (GH)-action and growth hormone receptor (GHR) function because of its recessive mutation in the GHR gene. Skeletal muscle mass is reduced in the SLD chicken with a smaller muscle fiber diameter. Our previous study has presented the mRNA and miRNA expression profiles of the SLD chicken and normal chicken between embryo day 14 and seven weeks of age. However, the molecular mechanism of GHR-deficient induced muscle mass loss is still unclear, and the key molecules and pathways underlying the GHR-deficient induced muscle mass loss also remain to be illustrated. Here, by functional network analysis of the differentially expressed miRNAs and mRNAs between the SLD and normal chickens, we revealed that let-7b, miR-128 and the MAPK pathway might play key roles in the GHR-deficient induced muscle mass loss, and that the reduced cell division and growth are potential cellular processes during the SLD chicken skeletal muscle development. Additionally, we also found some genes and miRNAs involved in chicken skeletal muscle development, through the MAPK, PI3K-Akt, Wnt and Insulin signaling pathways. This study provides new insights into the molecular mechanism underlying muscle mass loss in the SLD chickens, and some regulatory networks that are crucial for chicken skeletal muscle development. PMID:26927061

  2. Effect of homolog doping on surface morphology and mass-loss rates from PETN crystals. Studies using atomic force microscope and thermo-gravimetric analysis

    DOE PAGES

    Bhattacharya, S. K.; Maiti, A; Gee, R. H.; ...

    2012-08-28

    Pentaerythritol tetranitrate (PETN) is an important energetic material and its performance as a secondary explosive depends strongly on the density as well as flow porosity of powdered material, which in turn is governed by the size and surface properties of the PETN crystallite particles. Historically there has been evidence that the surface properties of PETN particles can be strongly influenced by the presence of homolog impurities of PETN, in particular, dipentaerythritol hexanitrate (diPEHN) and tripentaerythritol octanitrate (triPEON), although not many systematic studies characterizing such influence exist. In this work we employ thermogravimetric analysis (TGA) to measure mass-loss rates at elevatedmore » temperatures and show that doping with a small amount of diPEHN and triPEON can reduce the mass-loss rate from PETN single-crystal surfaces by as much as 35 % as compared to undoped crystals. Arrhenius plots of mass-loss rates as a function of temperature suggest that the reduction in evaporation is not due to the change in activation barrier of the molecular evaporation process, but perhaps due to the impedance to the receding motion of the steps by the immobile impurities on the surface. Removal of surface impurities through gentle washing with ethanol leads to enhanced mass-loss rate relative to pure PETN suggesting a roughened surface morphology. Some surface roughening in doped crystals is supported by Atomic force microscopy (AFM) images of growth layers that show evidences of growth layer stacking and rough edges. Furthermore, we find that a larger amount of impurity added to the original solution does not necessarily lead to a more highly doped crystal, which could perhaps be interpreted as PETN crystals being able to accommodate only up to a certain weight percent of homolog impurities.« less

  3. Saturn’s Ring Rain: Initial Estimates of Ring Mass Loss Rates

    NASA Astrophysics Data System (ADS)

    Moore, Luke; O'Donoghue, J.; Mueller-Wodarg, I.; Mendillo, M.

    2013-10-01

    We estimate rates of mass loss from Saturn’s rings based on ionospheric model reproductions of derived H3+ column densities. On 17 April 2011 over two hours of near-infrared spectral data were obtained of Saturn using the Near InfraRed Spectrograph (NIRSPEC) instrument on the 10-m Keck II telescope. The intensity of two bright H3+ rotational-vibrational emission lines was visible from nearly pole to pole, allowing low-latitude ionospheric emissions to be studied for the first time, and revealing significant latitudinal structure, with local extrema in one hemisphere being mirrored at magnetically conjugate latitudes in the opposite hemisphere. Even more striking, those minima and maxima mapped to latitudes of increased or increased density in Saturn’s rings, implying a direct ring-atmosphere connection in which charged water group particles from the rings are guided by magnetic field lines as they “rain” down upon the atmosphere. Water products act to quench the local ionosphere, and therefore modify the observed H3+ densities. Using the Saturn Thermosphere Ionosphere Model (STIM), a 3-D model of Saturn’s upper atmosphere, we derive the rates of water influx required from the rings in order to reproduce the observed H3+ column densities. As a unique pair of conjugate latitudes map to a specific radial distance in the ring plane, the derived water influxes can equivalently be described as rates of ring mass erosion as a function of radial distance in the ring plane, and therefore also allow for an improved estimate of the lifetime of Saturn’s rings.

  4. An Abrupt Centennial-Scale Drought Event and Mid-Holocene Climate Change Patterns in Monsoon Marginal Zones of East Asia

    PubMed Central

    Li, Yu; Wang, Nai'ang; Zhang, Chengqi

    2014-01-01

    The mid-latitudes of East Asia are characterized by the interaction between the Asian summer monsoon and the westerly winds. Understanding long-term climate change in the marginal regions of the Asian monsoon is critical for understanding the millennial-scale interactions between the Asian monsoon and the westerly winds. Abrupt climate events are always associated with changes in large-scale circulation patterns; therefore, investigations into abrupt climate changes provide clues for responses of circulation patterns to extreme climate events. In this paper, we examined the time scale and mid-Holocene climatic background of an abrupt dry mid-Holocene event in the Shiyang River drainage basin in the northwest margin of the Asian monsoon. Mid-Holocene lacustrine records were collected from the middle reaches and the terminal lake of the basin. Using radiocarbon and OSL ages, a centennial-scale drought event, which is characterized by a sand layer in lacustrine sediments both from the middle and lower reaches of the basin, was absolutely dated between 8.0–7.0 cal kyr BP. Grain size data suggest an abrupt decline in lake level and a dry environment in the middle reaches of the basin during the dry interval. Previous studies have shown mid-Holocene drought events in other places of monsoon marginal zones; however, their chronologies are not strong enough to study the mechanism. According to the absolutely dated records, we proposed a new hypothesis that the mid-Holocene dry interval can be related to the weakening Asian summer monsoon and the relatively arid environment in arid Central Asia. Furthermore, abrupt dry climatic events are directly linked to the basin-wide effective moisture change in semi-arid and arid regions. Effective moisture is affected by basin-wide precipitation, evapotranspiration, lake surface evaporation and other geographical settings. As a result, the time scales of the dry interval could vary according to locations due to different

  5. An abrupt centennial-scale drought event and mid-holocene climate change patterns in monsoon marginal zones of East Asia.

    PubMed

    Li, Yu; Wang, Nai'ang; Zhang, Chengqi

    2014-01-01

    The mid-latitudes of East Asia are characterized by the interaction between the Asian summer monsoon and the westerly winds. Understanding long-term climate change in the marginal regions of the Asian monsoon is critical for understanding the millennial-scale interactions between the Asian monsoon and the westerly winds. Abrupt climate events are always associated with changes in large-scale circulation patterns; therefore, investigations into abrupt climate changes provide clues for responses of circulation patterns to extreme climate events. In this paper, we examined the time scale and mid-Holocene climatic background of an abrupt dry mid-Holocene event in the Shiyang River drainage basin in the northwest margin of the Asian monsoon. Mid-Holocene lacustrine records were collected from the middle reaches and the terminal lake of the basin. Using radiocarbon and OSL ages, a centennial-scale drought event, which is characterized by a sand layer in lacustrine sediments both from the middle and lower reaches of the basin, was absolutely dated between 8.0-7.0 cal kyr BP. Grain size data suggest an abrupt decline in lake level and a dry environment in the middle reaches of the basin during the dry interval. Previous studies have shown mid-Holocene drought events in other places of monsoon marginal zones; however, their chronologies are not strong enough to study the mechanism. According to the absolutely dated records, we proposed a new hypothesis that the mid-Holocene dry interval can be related to the weakening Asian summer monsoon and the relatively arid environment in arid Central Asia. Furthermore, abrupt dry climatic events are directly linked to the basin-wide effective moisture change in semi-arid and arid regions. Effective moisture is affected by basin-wide precipitation, evapotranspiration, lake surface evaporation and other geographical settings. As a result, the time scales of the dry interval could vary according to locations due to different geographical

  6. High resolution water stable isotope profiles of abrupt climate transitions in Greenland ice with new observations from NEEM

    NASA Astrophysics Data System (ADS)

    Popp, T. J.; White, J. W. C.; Gkinis, V.; Vinther, B. M.; Johnsen, S. J.

    2012-04-01

    In 1989 Willi Dansgaard and others, using the DYE3 ice core, showed that the abrupt termination of the Younger Dryas expressed in water stable isotope ratios and deuterium excess was completed in less than 50 years. A few years later, using the GISP2 ice core, Richard Alley and others proposed that snow accumulation at the site doubled in as little as 1-3 years across the same climate transition at the end of the Younger Dryas. Over the next two decades, in large part due to such observations from Greenland ice cores, a paradigm of linked, abrupt changes in the North Atlantic region has been developed around North Atlantic deep water formation, North Atlantic sea ice extent, and widespread atmospheric circulation changes occurring repeatedly during the last glacial period in response to changing freshwater fluxes to the region, or perhaps other causes. More recently, with the NGRIP ice core, using a suite of high resolution proxy data, and in particular deuterium excess, it was observed again that certain features in the climate system can switch modes from one year to the next, while other proxies can take from decades to centuries to completely switch modes. Thus, an event seen in the proxy records such as the abrupt end of the Younger Dryas (or other interstadial events) may comprise multiple climatic or oceanic responses with different relative timing and duration which potentially follow a predictable sequence of events, in some cases separated by only a few years. Today, the search continues for these emerging patterns through isotopic and other highly resolvable proxy data series from ice cores. With the recent completion of the drilling at NEEM, many abrupt transitions have now been measured in detail over a geographic transect with drilling sites spanning from DYE3 in Southern Greenland, GISP2 in the central summit region, and up to NGRIP and NEEM in the far north. The anatomy of abrupt climate transitions can therefore be examined both spatially and

  7. Towards Greenland Glaciation: Cumulative or Abrupt Transition?

    NASA Astrophysics Data System (ADS)

    Tan, N.; Ramstein, G.; Contoux, C.; Ladant, J. B.; Dumas, C.; Donnadieu, Y.

    2014-12-01

    The insolation evolution [Laskar 2004] from 4 to 2.5 Ma depicts a series of three summer solstice insolation minima between 2.7 and 2.6 Ma, but there are other more important summer solstice minima notably around 3.82 and 3.05 Ma. On such a time span of more than 1 Ma, data shows that there are variations in the evolution of atmospheric CO2 concentration with a local maximum around 3 Ma [Seki et al.2010; Bartoli et al. 2011], before a decrease between 3 and 2.6 Ma. The latter, suggesting an abrupt ice sheet inception around 2.7 Ma, has been shown to be a major culprit for the full Greenland Glaciation [Lunt et al. 2008]. However, a recent study [Contoux et al. 2014, in review] suggests that a lowering of CO2 is not sufficient to initiate a glaciation on Greenland and must be combined to low summer insolation, with surviving ice during insolation maximum, suggesting a cumulative process in the first place, which could further lead to full glaciation at 2.7 Ma. Through a new tri-dimensional interpolation method implemented within the asynchronous coupling between an atmosphere ocean general circulation model (IPSL-CM5A) and an ice sheet model (GRISLI), we investigate the transient evolution of Greenland ice sheet during the Pliocene to diagnose whether the ice sheet inception is an abrupt event or rather a cumulative process, involving waxing and waning of the ice sheet during several orbital cycles. ReferencesBartoli, G., Hönisch, B., & Zeebe, R. E. (2011). Atmospheric CO2 decline during the Pliocene intensification of Northern Hemisphere glaciations. Paleoceanography, 26(4). Contoux C, Dumas C, Ramstein G, Jost A, Dolan A. M. (2014) Modelling Greenland Ice sheet inception and sustainability during the late Pliocene. (in review for Earth and Planetary Science Letters.).Laskar, J., Robutel, P., Joutel, F., Gastineau, M., Correia, A. C. M., & Levrard, B. (2004). A long-term numerical solution for the insolation quantities of the Earth. Astronomy & Astrophysics, 428

  8. Inadequate protein intake after laparoscopic sleeve gastrectomy surgery is associated with a greater fat free mass loss.

    PubMed

    Sherf Dagan, Shiri; Tovim, Tali Ben; Keidar, Andrei; Raziel, Asnat; Shibolet, Oren; Zelber-Sagi, Shira

    2017-01-01

    Low postoperative protein intake may represent a modifiable risk factor that leads to fat free mass (FFM) loss postlaparoscopic sleeve gastrectomy (LSG), but data concerning this phenomenon is scarce. To evaluate the association between daily protein intake and relative FFM loss at 6 (M6) and 12 (M12) months after LSG surgery. Private hospital and university hospital. A prospective cohort study with 12 months follow-up of 77 patients who underwent LSG surgery. Anthropometrics including body composition analysis measured by multifrequency bioelectrical impedance analysis, 3-day food diaries, food intolerance, and habitual physical activity were evaluated at baseline and at M3, M6, and M12. Repeated body composition measurements and food diary were available for 77 patients (45 women) at M6 and for 68 patients at M12. Mean age was 42.7±9.4 years and mean preoperative body mass index was 42.2±4.8 kg/m 2 . A protein intake of≥60 g/d was achieved in 13.3%, 32.5% and 39.7% of the study participants at M3, M6 and M12, respectively. FFM significantly decreased at M6 and stabilized at M12. Protein intake of≥60 g/d was associated with a significantly lower relative FFM loss at M6 among women (8.9±6.5% versus 12.4±4.1%; P = .039) and this trend was also reported among men (9.5±5.5% versus 13.4±6.0%; P = .068). A logistic regression for the prediction of FFM loss of≥10% at M6, indicated that protein intake≥60 g/d is a strong protective factor (odds ratio = 0.29, 95% confidence interval .09-.96, P = .043). Our study supports the currently recommended protein intake goal of≥60 g/d as an efficient strategy for better preservation of FFM post-LSG. Copyright © 2017 American Society for Bariatric Surgery. Published by Elsevier Inc. All rights reserved.

  9. Exogenous attentional capture by subliminal abrupt-onset cues: evidence from contrast-polarity independent cueing effects.

    PubMed

    Fuchs, Isabella; Theeuwes, Jan; Ansorge, Ulrich

    2013-08-01

    In the present study, we tested whether subliminal abrupt-onset cues capture attention in a bottom-up or top-down controlled manner. For our tests, we varied the searched-for target-contrast polarity (i.e., dark or light targets against a gray background) over four experiments. In line with the bottom-up hypothesis, our results indicate that subliminal-onset cues capture attention independently of the searched-for target-contrast polarity (Experiment 1), and this effect is not stronger for targets that matched the searched-for target-contrast polarity (Experiment 2). In fact, even to-be-ignored cues associated with a no-go response captured attention in a salience-driven way (Experiment 3). For supraliminal cues, we found attentional capture only by cues with a matching contrast polarity, reflecting contingent capture (Experiment 4). The results point toward a specific role of subliminal abrupt onsets for attentional capture. 2013 APA, all rights reserved

  10. Enhanced summer warming reduces fungal decomposer diversity and litter mass loss more strongly in dry than in wet tundra.

    PubMed

    Christiansen, Casper T; Haugwitz, Merian S; Priemé, Anders; Nielsen, Cecilie S; Elberling, Bo; Michelsen, Anders; Grogan, Paul; Blok, Daan

    2017-01-01

    Many Arctic regions are currently experiencing substantial summer and winter climate changes. Litter decomposition is a fundamental component of ecosystem carbon and nutrient cycles, with fungi being among the primary decomposers. To assess the impacts of seasonal climatic changes on litter fungal communities and their functioning, Betula glandulosa leaf litter was surface-incubated in two adjacent low Arctic sites with contrasting soil moisture regimes: dry shrub heath and wet sedge tundra at Disko Island, Greenland. At both sites, we investigated the impacts of factorial combinations of enhanced summer warming (using open-top chambers; OTCs) and deepened snow (using snow fences) on surface litter mass loss, chemistry and fungal decomposer communities after approximately 1 year. Enhanced summer warming significantly restricted litter mass loss by 32% in the dry and 17% in the wet site. Litter moisture content was significantly reduced by summer warming in the dry, but not in the wet site. Likewise, fungal total abundance and diversity were reduced by OTC warming at the dry site, while comparatively modest warming effects were observed in the wet site. These results suggest that increased evapotranspiration in the OTC plots lowered litter moisture content to the point where fungal decomposition activities became inhibited. In contrast, snow addition enhanced fungal abundance in both sites but did not significantly affect litter mass loss rates. Across sites, control plots only shared 15% of their fungal phylotypes, suggesting strong local controls on fungal decomposer community composition. Nevertheless, fungal community functioning (litter decomposition) was negatively affected by warming in both sites. We conclude that although buried soil organic matter decomposition is widely expected to increase with future summer warming, surface litter decay and nutrient turnover rates in both xeric and relatively moist tundra are likely to be significantly restricted by

  11. Evaluating the impact of abrupt changes in forest policy and management practices on landscape dynamics: analysis of a Landsat image time series in the Atlantic Northern Forest.

    PubMed

    Legaard, Kasey R; Sader, Steven A; Simons-Legaard, Erin M

    2015-01-01

    Sustainable forest management is based on functional relationships between management actions, landscape conditions, and forest values. Changes in management practices make it fundamentally more difficult to study these relationships because the impacts of current practices are difficult to disentangle from the persistent influences of past practices. Within the Atlantic Northern Forest of Maine, U.S.A., forest policy and management practices changed abruptly in the early 1990s. During the 1970s-1980s, a severe insect outbreak stimulated salvage clearcutting of large contiguous tracts of spruce-fir forest. Following clearcut regulation in 1991, management practices shifted abruptly to near complete dependence on partial harvesting. Using a time series of Landsat satellite imagery (1973-2010) we assessed cumulative landscape change caused by these very different management regimes. We modeled predominant temporal patterns of harvesting and segmented a large study area into groups of landscape units with similar harvest histories. Time series of landscape composition and configuration metrics averaged within groups revealed differences in landscape dynamics caused by differences in management history. In some groups (24% of landscape units), salvage caused rapid loss and subdivision of intact mature forest. Persistent landscape change was created by large salvage clearcuts (often averaging > 100 ha) and conversion of spruce-fir to deciduous and mixed forest. In groups that were little affected by salvage (56% of landscape units), contemporary partial harvesting caused loss and subdivision of intact mature forest at even greater rates. Patch shape complexity and edge density reached high levels even where cumulative harvest area was relatively low. Contemporary practices introduced more numerous and much smaller patches of stand-replacing disturbance (typically averaging <15 ha) and a correspondingly large amount of edge. Management regimes impacted different areas to

  12. Evaluating the Impact of Abrupt Changes in Forest Policy and Management Practices on Landscape Dynamics: Analysis of a Landsat Image Time Series in the Atlantic Northern Forest

    PubMed Central

    Legaard, Kasey R.; Sader, Steven A.; Simons-Legaard, Erin M.

    2015-01-01

    Sustainable forest management is based on functional relationships between management actions, landscape conditions, and forest values. Changes in management practices make it fundamentally more difficult to study these relationships because the impacts of current practices are difficult to disentangle from the persistent influences of past practices. Within the Atlantic Northern Forest of Maine, U.S.A., forest policy and management practices changed abruptly in the early 1990s. During the 1970s-1980s, a severe insect outbreak stimulated salvage clearcutting of large contiguous tracts of spruce-fir forest. Following clearcut regulation in 1991, management practices shifted abruptly to near complete dependence on partial harvesting. Using a time series of Landsat satellite imagery (1973-2010) we assessed cumulative landscape change caused by these very different management regimes. We modeled predominant temporal patterns of harvesting and segmented a large study area into groups of landscape units with similar harvest histories. Time series of landscape composition and configuration metrics averaged within groups revealed differences in landscape dynamics caused by differences in management history. In some groups (24% of landscape units), salvage caused rapid loss and subdivision of intact mature forest. Persistent landscape change was created by large salvage clearcuts (often averaging > 100 ha) and conversion of spruce-fir to deciduous and mixed forest. In groups that were little affected by salvage (56% of landscape units), contemporary partial harvesting caused loss and subdivision of intact mature forest at even greater rates. Patch shape complexity and edge density reached high levels even where cumulative harvest area was relatively low. Contemporary practices introduced more numerous and much smaller patches of stand-replacing disturbance (typically averaging <15 ha) and a correspondingly large amount of edge. Management regimes impacted different areas to

  13. Loss of Cyclin-dependent Kinase 2 in the Pancreas Links Primary β-Cell Dysfunction to Progressive Depletion of β-Cell Mass and Diabetes*

    PubMed Central

    Kim, So Yoon; Lee, Ji-Hyeon; Merrins, Matthew J.; Gavrilova, Oksana; Bisteau, Xavier; Kaldis, Philipp; Satin, Leslie S.; Rane, Sushil G.

    2017-01-01

    The failure of pancreatic islet β-cells is a major contributor to the etiology of type 2 diabetes. β-Cell dysfunction and declining β-cell mass are two mechanisms that contribute to this failure, although it is unclear whether they are molecularly linked. Here, we show that the cell cycle regulator, cyclin-dependent kinase 2 (CDK2), couples primary β-cell dysfunction to the progressive deterioration of β-cell mass in diabetes. Mice with pancreas-specific deletion of Cdk2 are glucose-intolerant, primarily due to defects in glucose-stimulated insulin secretion. Accompanying this loss of secretion are defects in β-cell metabolism and perturbed mitochondrial structure. Persistent insulin secretion defects culminate in progressive deficits in β-cell proliferation, reduced β-cell mass, and diabetes. These outcomes may be mediated directly by the loss of CDK2, which binds to and phosphorylates the transcription factor FOXO1 in a glucose-dependent manner. Further, we identified a requirement for CDK2 in the compensatory increases in β-cell mass that occur in response to age- and diet-induced stress. Thus, CDK2 serves as an important nexus linking primary β-cell dysfunction to progressive β-cell mass deterioration in diabetes. PMID:28100774

  14. Associated among endocrine, inflammatory, and bone markers, body composition and weight loss induced bone loss

    USDA-ARS?s Scientific Manuscript database

    Weight loss reduces co-¬morbidities of obesity but decreases bone mass. Our aims were to determine whether adequate dairy intake could prevent weight loss related bone loss and to evaluate the contribution of energy-related hormones and inflammatory markers to bone metabolism. Overweight and obese w...

  15. Loss of endocytic capacity in aging Paramecium. The importance of cytoplasmic organelles

    PubMed Central

    1976-01-01

    Aged cells have significantly fewer food vacuoles and ingest fewer bacteria than young cells. Loss of food vacuoles was explained by a decreasing difference in the food vacuole formation and excretion rates; the formation rate declined more rapidly than the excretion rate, approaching equivalence at 160 fissions, when the proportion of cells with no food vacuoles, in the presence of excess food, abruptly increased. A model for cellular aging is presented in which control of organelle numbers and cyclical interactions between the nucleus and cytoplasm may be of critical importance. PMID:993263

  16. Attention capture by abrupt onsets: re-visiting the priority tag model.

    PubMed

    Sunny, Meera M; von Mühlenen, Adrian

    2013-01-01

    Abrupt onsets have been shown to strongly attract attention in a stimulus-driven, bottom-up manner. However, the precise mechanism that drives capture by onsets is still debated. According to the new object account, abrupt onsets capture attention because they signal the appearance of a new object. Yantis and Johnson (1990) used a visual search task and showed that up to four onsets can be automatically prioritized. However, in their study the number of onsets co-varied with the total number of items in the display, allowing for a possible confound between these two variables. In the present study, display size was fixed at eight items while the number of onsets was systematically varied between zero and eight. Experiment 1 showed a systematic increase in reactions times with increasing number of onsets. This increase was stronger when the target was an onset than when it was a no-onset item, a result that is best explained by a model according to which only one onset is automatically prioritized. Even when the onsets were marked in red (Experiment 2), nearly half of the participants continued to prioritize only one onset item. Only when onset and no-onset targets were blocked (Experiment 3), participants started to search selectively through the set of only the relevant target type. These results further support the finding that only one onset captures attention. Many bottom-up models of attention capture, like masking or saliency accounts, can efficiently explain this finding.

  17. A turbulent wake as a tracer of 30,000 years of Mira's mass loss history.

    PubMed

    Martin, D Christopher; Seibert, Mark; Neill, James D; Schiminovich, David; Forster, Karl; Rich, R Michael; Welsh, Barry Y; Madore, Barry F; Wheatley, Jonathan M; Morrissey, Patrick; Barlow, Tom A

    2007-08-16

    Mira is one of the first variable stars ever discovered and it is the prototype (and also the nearest example) of a class of low-to-intermediate-mass stars in the late stages of stellar evolution. These stars are relatively common and they return a large fraction of their original mass to the interstellar medium (ISM) (ref. 2) through a processed, dusty, molecular wind. Thus stars in Mira's stage of evolution have a direct impact on subsequent star and planet formation in their host galaxy. Previously, the only direct observation of the interaction between Mira-type stellar winds and the ISM was in the infrared. Here we report the discovery of an ultraviolet-emitting bow shock and turbulent wake extending over 2 degrees on the sky, arising from Mira's large space velocity and the interaction between its wind and the ISM. The wake is visible only in the far ultraviolet and is consistent with an unusual emission mechanism whereby molecular hydrogen is excited by turbulent mixing of cool molecular gas and shock-heated gas. This wind wake is a tracer of the past 30,000 years of Mira's mass-loss history and provides an excellent laboratory for studying turbulent stellar wind-ISM interactions.

  18. Spontaneous abrupt climate change due to an atmospheric blocking-sea-ice-ocean feedback in an unforced climate model simulation.

    PubMed

    Drijfhout, Sybren; Gleeson, Emily; Dijkstra, Henk A; Livina, Valerie

    2013-12-03

    Abrupt climate change is abundant in geological records, but climate models rarely have been able to simulate such events in response to realistic forcing. Here we report on a spontaneous abrupt cooling event, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The event was simulated in the preindustrial control run of a high-resolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70 °N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the event with similar abruptness to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of abrupt climate change.

  19. Spontaneous abrupt climate change due to an atmospheric blocking–sea-ice–ocean feedback in an unforced climate model simulation

    PubMed Central

    Drijfhout, Sybren; Gleeson, Emily; Dijkstra, Henk A.; Livina, Valerie

    2013-01-01

    Abrupt climate change is abundant in geological records, but climate models rarely have been able to simulate such events in response to realistic forcing. Here we report on a spontaneous abrupt cooling event, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The event was simulated in the preindustrial control run of a high-resolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70°N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the event with similar abruptness to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of abrupt climate change. PMID:24248352

  20. Influence of external forcings on abrupt millennial-scale climate changes: a statistical modelling study

    NASA Astrophysics Data System (ADS)

    Mitsui, Takahito; Crucifix, Michel

    2017-04-01

    The last glacial period was punctuated by a series of abrupt climate shifts, the so-called Dansgaard-Oeschger (DO) events. The frequency of DO events varied in time, supposedly because of changes in background climate conditions. Here, the influence of external forcings on DO events is investigated with statistical modelling. We assume two types of simple stochastic dynamical systems models (double-well potential-type and oscillator-type), forced by the northern hemisphere summer insolation change and/or the global ice volume change. The model parameters are estimated by using the maximum likelihood method with the NGRIP Ca^{2+} record. The stochastic oscillator model with at least the ice volume forcing reproduces well the sample autocorrelation function of the record and the frequency changes of warming transitions in the last glacial period across MISs 2, 3, and 4. The model performance is improved with the additional insolation forcing. The BIC scores also suggest that the ice volume forcing is relatively more important than the insolation forcing, though the strength of evidence depends on the model assumption. Finally, we simulate the average number of warming transitions in the past four glacial periods, assuming the model can be extended beyond the last glacial, and compare the result with an Iberian margin sea-surface temperature (SST) record (Martrat et al. in Science 317(5837): 502-507, 2007). The simulation result supports the previous observation that abrupt millennial-scale climate changes in the penultimate glacial (MIS 6) are less frequent than in the last glacial (MISs 2-4). On the other hand, it suggests that the number of abrupt millennial-scale climate changes in older glacial periods (MISs 6, 8, and 10) might be larger than inferred from the SST record.

  1. Temperature independent refractive index measurement using a fiber Bragg grating on abrupt tapered tip

    NASA Astrophysics Data System (ADS)

    Gomes, André D.; Silveira, Beatriz; Warren-Smith, Stephen C.; Becker, Martin; Rothhardt, Manfred; Frazão, Orlando

    2018-05-01

    A fiber Bragg grating was inscribed in an abrupt fiber taper using a femtosecond laser and phase-mask interferometer. The abrupt taper transition allows to excite a broad range of guided modes with different effective refractive indices that are reflected at different wavelengths according to Bragg's law. The multimode-Bragg reflection expands over 30 nm in the telecom-C-band. This corresponds to a mode-field overlap of up to 30% outside of the fiber, making the device suitable for evanescent field sensing. Refractive index and temperature measurements are performed for different reflection peaks. Temperature independent refractive index measurements are achieved by considering the difference between the wavelength shifts of two measured reflection peaks. A minimum refractive index sensitivity of 16 ± 1 nm/RIU was obtained in a low refractive index regime (1.3475-1.3720) with low influence of temperature (-0.32 ± 0.06 pm/°C). The cross sensitivity for this structure is 2.0 × 10-5 RIU/°C. The potential for simultaneous measurement of refractive index and temperature is also studied.

  2. The abrupt temperature changes in the plantar skin thermogram of the diabetic patient: looking in to prevent the insidious ulcers.

    PubMed

    Renero-C, Francisco-J

    2018-01-01

    Background: One of the complications of the diabetes mellitus is the amputation of the lower limbs. This complication may be developed after an insidious ulcer, that may be raised by the peripheral neuropathy or the ischaemic limb, and that the ulcer get infected. That is, to develop an ulcer, in the diabetic patient, three factors should be taken into the account, the autonomic nervous system, the blood supply and the inmune system. Methods: In this work, the thermogram is used to identify regions on the plantar skin with blood supply deficiencies and the behaviour of the thermoregulation process. Within the thermogram of the plantar skin, it can be identify local regions with low and high temperatures that corresponds to ischemic or inflammatory process on that part of the skin. Results: The findings within the 186 thermograms of diabetic patients, obtained from three hospitals and from INAOE facilities, showed, first, the thermograms of the plantar skin of two diabetic patients, acquired in two different times show that the temperature distribution and the average temperatures, vary slightly for a period of weeks. Second, the thermograms of two patients, who both developed insidious ulcers which evolved favourable, demonstrated the importance of the immune system and the drug therapy. These patients are, one who has a Charcot foot, and in the second one, the patient had loss the sensibility of the feet. Finally, the thermograms of two patients, showing abrupt temperature change within small regions in the plantar skin, are discussed. Conclusion: A diabetic patient, with an asymmetric thermogram, as physiological interpretation of the thermoregulation, may indicate a decrease of the blood supply, which may be corroborated by vascular ultrasound. The regions of abrupt temperature change, cold or hot spots, may correspond to ischaemic or inflammatory processes.

  3. The abrupt temperature changes in the plantar skin thermogram of the diabetic patient: looking in to prevent the insidious ulcers

    PubMed Central

    Renero-C, Francisco-J

    2018-01-01

    ABSTRACT Background: One of the complications of the diabetes mellitus is the amputation of the lower limbs. This complication may be developed after an insidious ulcer, that may be raised by the peripheral neuropathy or the ischaemic limb, and that the ulcer get infected. That is, to develop an ulcer, in the diabetic patient, three factors should be taken into the account, the autonomic nervous system, the blood supply and the inmune system. Methods: In this work, the thermogram is used to identify regions on the plantar skin with blood supply deficiencies and the behaviour of the thermoregulation process. Within the thermogram of the plantar skin, it can be identify local regions with low and high temperatures that corresponds to ischemic or inflammatory process on that part of the skin. Results: The findings within the 186 thermograms of diabetic patients, obtained from three hospitals and from INAOE facilities, showed, first, the thermograms of the plantar skin of two diabetic patients, acquired in two different times show that the temperature distribution and the average temperatures, vary slightly for a period of weeks. Second, the thermograms of two patients, who both developed insidious ulcers which evolved favourable, demonstrated the importance of the immune system and the drug therapy. These patients are, one who has a Charcot foot, and in the second one, the patient had loss the sensibility of the feet. Finally, the thermograms of two patients, showing abrupt temperature change within small regions in the plantar skin, are discussed. Conclusion: A diabetic patient, with an asymmetric thermogram, as physiological interpretation of the thermoregulation, may indicate a decrease of the blood supply, which may be corroborated by vascular ultrasound. The regions of abrupt temperature change, cold or hot spots, may correspond to ischaemic or inflammatory processes. PMID:29410772

  4. Variation in C-reactive protein following weight loss in obese insulin resistant postmenopausal women: is there an independent contribution of lean body mass?

    PubMed

    Barsalani, R; Riesco, É; Perreault, K; Imbeault, P; Brochu, M; Dionne, I J

    2015-03-01

    We showed that obese insulin resistant postmenopausal women are characterized by higher lean body mass and elevated C-reactive protein. Although counterintuitive, we hypothesized that losses in muscle mass following caloric restriction and increase in muscle quality will be associated with improvements in glucose homeostasis through decreases in C-reactive protein. To determine 1) if improvements in C-reactive protein concentrations occurs through losses in lean body mass; and 2) if decreases in C-reactive protein levels contribute to improvements in insulin sensitivity. 50 postmenopausal women (body mass index>26 kg/m(²)) with impaired glucose disposal (<7.5 mg/kg/min) completed a 6-month caloric restriction program. Outcome measures were: Glucose disposal rate: M value (by hyperinsulinemic-euglycemic clamp), body composition (total, trunk, and appendicluar). LBM and FM by DXA), LBM index (LBM (kg)/height (m(2)), body fat distribution (VAT and SAT by CT scan) and plasma high-sensitive C-reactive protein (hsCRP) and interleukin-6 (Il-6). Significant correlations were observed between Δ hsCRP levels with Δ Il-6 (r=0.33, p≤0.05), Δ total LBM index (r=0.44, p≤0.01), Δ trunk LBM (r=0.38, p≤0.01) Δ SAT (r=0.35, p≤0.05) and ∆ glucose disposal rate (r=- 0.44, p≤0.01). After including all the correlated variables in Stepwise linear regression model, Δ LBM index was the only independent predictor of the reduction in hsCRP levels (R(2)=0.20, p≤0.01). Losses in total lean body mass are independently associated with improvements in inflammatory state (CRP levels) in obese postmenopausal women with impaired glucose disposal. © Georg Thieme Verlag KG Stuttgart · New York.

  5. Loss of lean body mass affects low bone mineral density in patients with rheumatoid arthritis - results from the TOMORROW study.

    PubMed

    Okano, Tadashi; Inui, Kentaro; Tada, Masahiro; Sugioka, Yuko; Mamoto, Kenji; Wakitani, Shigeyuki; Koike, Tatsuya; Nakamura, Hiroaki

    2017-11-01

    Osteoporosis is one of the complications for patients with rheumatoid arthritis (RA). Rheumatoid cachexia, the loss of lean body mass, is another. However, the relationship between decreased lean body mass and reduced bone mineral density (BMD) in patients with RA has not been well studied. This study included 413 participants, comprising 208 patients with RA and 205 age- and sex-matched healthy volunteers. Clinical data, BMD, bone metabolic markers (BMM) and body composition, such as lean body mass and percent fat, were collected. Risk factors for osteoporosis in patients with RA including the relationship BMD and body composition were analyzed. Patients with RA showed low BMD and high BMM compared with controls. Moreover, lean body mass was lower and percent fat was higher in patients with RA. Lean body mass correlated positively and percent fat negatively with BMD. Lean body mass was a positive and disease duration was a negative independent factor for BMD in multivariate statistical analysis. BMD and lean body mass were significantly lower in patients with RA compared to healthy controls. Lean body mass correlated positively with BMD and decreased lean body mass and disease duration affected low BMD in patients with RA. [UMIN Clinical Trials Registry, http://www.umin.ac.jp/ctr/ , UMIN000003876].

  6. Ultralow-loss polaritons in isotopically pure boron nitride.

    PubMed

    Giles, Alexander J; Dai, Siyuan; Vurgaftman, Igor; Hoffman, Timothy; Liu, Song; Lindsay, Lucas; Ellis, Chase T; Assefa, Nathanael; Chatzakis, Ioannis; Reinecke, Thomas L; Tischler, Joseph G; Fogler, Michael M; Edgar, J H; Basov, D N; Caldwell, Joshua D

    2018-02-01

    Conventional optical components are limited to size scales much larger than the wavelength of light, as changes to the amplitude, phase and polarization of the electromagnetic fields are accrued gradually along an optical path. However, advances in nanophotonics have produced ultrathin, so-called 'flat' optical components that beget abrupt changes in these properties over distances significantly shorter than the free-space wavelength. Although high optical losses still plague many approaches, phonon polariton (PhP) materials have demonstrated long lifetimes for sub-diffractional modes in comparison to plasmon-polariton-based nanophotonics. We experimentally observe a threefold improvement in polariton lifetime through isotopic enrichment of hexagonal boron nitride (hBN). Commensurate increases in the polariton propagation length are demonstrated via direct imaging of polaritonic standing waves by means of infrared nano-optics. Our results provide the foundation for a materials-growth-directed approach aimed at realizing the loss control necessary for the development of PhP-based nanophotonic devices.

  7. Ultralow-loss polaritons in isotopically pure boron nitride

    DOE PAGES

    Giles, Alexander J.; Dai, Siyuan; Vurgaftman, Igor; ...

    2017-12-11

    Conventional optical components are limited to size scales much larger than the wavelength of light, as changes to the amplitude, phase and polarization of the electromagnetic fields are accrued gradually along an optical path. However, advances in nanophotonics have produced ultrathin, so-called ‘flat’ optical components that beget abrupt changes in these properties over distances significantly shorter than the free-space wavelength. Although high optical losses still plague many approaches, phonon polariton (PhP) materials have demonstrated long lifetimes for sub-diffractional modes in comparison to plasmon-polariton-based nanophotonics. We experimentally observe a threefold improvement in polariton lifetime through isotopic enrichment of hexagonal boron nitridemore » (hBN). Commensurate increases in the polariton propagation length are demonstrated via direct imaging of polaritonic standing waves by means of infrared nano-optics. Lastly, our results provide the foundation for a materials-growth-directed approach aimed at realizing the loss control necessary for the development of PhP-based nanophotonic devices.« less

  8. Ultralow-loss polaritons in isotopically pure boron nitride

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Giles, Alexander J.; Dai, Siyuan; Vurgaftman, Igor

    Conventional optical components are limited to size scales much larger than the wavelength of light, as changes to the amplitude, phase and polarization of the electromagnetic fields are accrued gradually along an optical path. However, advances in nanophotonics have produced ultrathin, so-called ‘flat’ optical components that beget abrupt changes in these properties over distances significantly shorter than the free-space wavelength. Although high optical losses still plague many approaches, phonon polariton (PhP) materials have demonstrated long lifetimes for sub-diffractional modes in comparison to plasmon-polariton-based nanophotonics. We experimentally observe a threefold improvement in polariton lifetime through isotopic enrichment of hexagonal boron nitridemore » (hBN). Commensurate increases in the polariton propagation length are demonstrated via direct imaging of polaritonic standing waves by means of infrared nano-optics. Lastly, our results provide the foundation for a materials-growth-directed approach aimed at realizing the loss control necessary for the development of PhP-based nanophotonic devices.« less

  9. Rapid screening of illicit additives in weight loss dietary supplements with desorption corona beam ionisation (DCBI) mass spectrometry.

    PubMed

    Wang, H; Wu, Y; Zhao, Y; Sun, W; Ding, L; Guo, B; Chen, B

    2012-08-01

    Desorption corona beam ionisation (DCBI), the relatively novel ambient mass spectrometry (MS) technique, was utilised to screen for illicit additives in weight-loss food. The five usually abused chemicals - fenfluramine, N-di-desmethyl sibutramine, N-mono-desmethyl sibutramine, sibutramine and phenolphthalein - were detected with the proposed DCBI-MS method. Fast single-sample and high-throughput analysis was demonstrated. Semi-quantification was accomplished based on peak areas in the ion chromatograms. Four illicit additives were identified and semi-quantified in commercial samples. As there was no tedious sample pre-treatment compared with conventional HPLC methods, high-throughput analysis was achieved with DCBI. The results proved that DCBI-MS is a powerful tool for the rapid screening of illicit additives in weight-loss dietary supplements.

  10. LIGHT CURVES OF CORE-COLLAPSE SUPERNOVAE WITH SUBSTANTIAL MASS LOSS USING THE NEW OPEN-SOURCE SUPERNOVA EXPLOSION CODE (SNEC)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Morozova, Viktoriya; Renzo, Mathieu; Ott, Christian D.

    We present the SuperNova Explosion Code (SNEC), an open-source Lagrangian code for the hydrodynamics and equilibrium-diffusion radiation transport in the expanding envelopes of supernovae. Given a model of a progenitor star, an explosion energy, and an amount and distribution of radioactive nickel, SNEC generates the bolometric light curve, as well as the light curves in different broad bands assuming blackbody emission. As a first application of SNEC, we consider the explosions of a grid of 15 M{sub ⊙} (at zero-age main sequence, ZAMS) stars whose hydrogen envelopes are stripped to different extents and at different points in their evolution. Themore » resulting light curves exhibit plateaus with durations of ∼20–100 days if ≳1.5–2 M{sub ⊙} of hydrogen-rich material is left and no plateau if less hydrogen-rich material is left. If these shorter plateau lengths are not seen for SNe IIP in nature, it suggests that, at least for ZAMS masses ≲20 M{sub ⊙}, hydrogen mass loss occurs as an all or nothing process. This perhaps points to the important role binary interactions play in generating the observed mass-stripped supernovae (i.e., Type Ib/c events). These light curves are also unlike what is typically seen for SNe IIL, arguing that simply varying the amount of mass loss cannot explain these events. The most stripped models begin to show double-peaked light curves similar to what is often seen for SNe IIb, confirming previous work that these supernovae can come from progenitors that have a small amount of hydrogen and a radius of ∼500 R{sub ⊙}.« less

  11. Proprioceptive recalibration in the right and left hands following abrupt visuomotor adaptation.

    PubMed

    Salomonczyk, Danielle; Henriques, Denise Y P; Cressman, Erin K

    2012-03-01

    Previous studies have demonstrated that after reaching with misaligned visual feedback of the hand, one adapts his or her reaches and partially recalibrates proprioception, such that sense of felt hand position is shifted to match the seen hand position. However, to date, this has only been demonstrated in the right (dominant) hand following reach training with a visuomotor distortion in which the rotated cursor distortion was introduced gradually. As reach adaptation has been shown to differ depending on how the distortion is introduced (gradual vs. abrupt), we sought to examine proprioceptive recalibration following reach training with a cursor that was abruptly rotated 30° clockwise relative to hand motion. Furthermore, because the left and right arms have demonstrated selective advantages when matching visual and proprioceptive targets, respectively, we assessed proprioceptive recalibration in right-handed subjects following training with either the right or the left hand. On average, we observed shifts in felt hand position of approximately 7.6° following training with misaligned visual feedback of the hand, which is consistent with our previous findings in which the distortion was introduced gradually. Moreover, no difference was observed in proprioceptive recalibration across the left and right hands. These findings suggest that proprioceptive recalibration is a robust process that arises symmetrically in the two hands following visuomotor adaptation regardless of the initial magnitude of the error signal.

  12. Does bone loss begin after weight loss ends? Results 2 years after weight loss or regain in postmenopausal women.

    PubMed

    Von Thun, Nancy L; Sukumar, Deeptha; Heymsfield, Steven B; Shapses, Sue A

    2014-05-01

    Short-term weight loss is accompanied by bone loss in postmenopausal women. The longer-term impact of weight loss on bone in reduced overweight/obese women compared with women who regained their weight was examined in this study using a case-control design. Postmenopausal women (N = 42; mean [SD] body mass index, 28.3 [2.8] kg/m; mean [SD] age, 60.7 [5.5] y) were recruited 2 years after the start of a 6-month weight loss trial; those who maintained their weight (weight loss maintainer [WL-M] group) were matched to a cohort of women who regained their weight (weight loss regainer [WL-R] group). Serum hormones and bone markers were measured in a subset. Bone mineral density (BMD) at the femoral neck, trochanter, spine, radius, and total body, and soft-tissue composition were taken at baseline, 0.5 years, and 2 years. During weight loss, both groups lost 9.3% (3.4%) of body weight, with no significant difference between the groups. After weight loss, weight change was -0.1% (2.7%) and 6.0% (3.3%) in the WL-M (n = 22) and WL-R (n = 20) groups, respectively. After 2 years, both groups lost BMD at the femoral neck and trochanter (P ≤ 0.01), whereas only the WL-M group reduced BMD at the 1/3 radius (P < 0.001). There was greater BMD loss at the trochanter (-6.8% [5.7%]) and 1/3 radius (-4.5% [3.3%]) in the WL-M group compared with the WL-R group after 2 years. Multiple linear regression showed that change in leg fat mass (but not trunk fat) contributed to trochanter BMD loss (P < 0.05). After 2 years, there is no BMD recovery of weight reduction-induced bone loss, irrespective of weight regain. These data suggest that the period after weight loss may be an important point in time to prevent bone loss for those who maintain weight and those who regain weight.

  13. Sea-level feedback lowers projections of future Antarctic Ice-Sheet mass loss

    PubMed Central

    Gomez, Natalya; Pollard, David; Holland, David

    2015-01-01

    The stability of marine sectors of the Antarctic Ice Sheet (AIS) in a warming climate has been identified as the largest source of uncertainty in projections of future sea-level rise. Sea-level fall near the grounding line of a retreating marine ice sheet has a stabilizing influence on the ice sheets, and previous studies have established the importance of this feedback on ice age AIS evolution. Here we use a coupled ice sheet–sea-level model to investigate the impact of the feedback mechanism on future AIS retreat over centennial and millennial timescales for a range of emission scenarios. We show that the combination of bedrock uplift and sea-surface drop associated with ice-sheet retreat significantly reduces AIS mass loss relative to a simulation without these effects included. Sensitivity analyses show that the stabilization tends to be greatest for lower emission scenarios and Earth models characterized by a thin elastic lithosphere and low-viscosity upper mantle, as is the case for West Antarctica. PMID:26554381

  14. Coherent Sea Ice Variations in the Nordic Seas and Abrupt Greenland Climate Changes over Dansgaard-Oeschger Cycles

    NASA Astrophysics Data System (ADS)

    Sadatzki, H.; Berben, S.; Dokken, T.; Stein, R.; Fahl, K.; Jansen, E.

    2016-12-01

    Rapid changes in sea ice extent in the Nordic Seas may have played a crucial role in controlling the abruptness of ocean circulation and climate changes associated with Dansgaard-Oeschger (D-O) cycles during the last glacial (Li et al., 2010; Dokken et al., 2013). To investigate the role of sea ice for abrupt climate changes, we produced a sea ice record from the Norwegian Sea Core MD99-2284 at a temporal resolution approaching that of ice core records, covering four D-O cycles at ca. 32-41 ka. This record is based on the sea ice diatom biomarker IP25, open-water phytoplankton biomarker dinosterol and semi-quantitative phytoplankton-IP25 (PIP25) estimates. A detailed tephrochronology of MD99-2284 corroborates the tuning-based age model and independently constrains the GS9/GIS8 transition, allowing for direct comparison between our sediment and ice core records. For cold stadials we find extremely low fluxes of total organic carbon, dinosterol and IP25, which points to a general absence of open-water phytoplankton and ice algae production under a near-permanent sea ice cover. For the interstadials, in turn, all biomarker fluxes are strongly enhanced, reflecting a highly productive sea ice edge situation and implying largely open ocean conditions for the eastern Nordic Seas. As constrained by three tephra layers, we observe that the stadial-interstadial sea ice decline was rapid and may have induced a coeval abrupt northward shift in the Greenland precipitation moisture source as recorded in ice cores. The sea ice retreat also facilitated a massive heat release through deep convection in the previously stratified Nordic Seas, generating atmospheric warming of the D-O events. We thus conclude that rapid changes in sea ice extent in the Nordic Seas amplified oceanic reorganizations and were a key factor in controlling abrupt Greenland climate changes over D-O cycles. Dokken, T.M. et al., 2013. Paleoceanography 28, 491-502 Li, C. et al., 2010. Journ. Clim. 23, 5457-5475

  15. Low-fat, high-carbohydrate (low-glycaemic index) diet induces weight loss and preserves lean body mass in obese healthy subjects: results of a 24-week study.

    PubMed

    Bahadori, B; Yazdani-Biuki, B; Krippl, P; Brath, H; Uitz, E; Wascher, T C

    2005-05-01

    The traditional treatment for obesity which is based on a reduced caloric diet has only been partially successful. Contributing factors are not only a poor long-term dietary adherence but also a significant loss of lean body mass and subsequent reduction in energy expenditure. Both low-fat, high-carbohydrate diets and diets using low-glycaemic index (GI) foods are capable of inducing modest weight loss without specific caloric restriction. The purpose of this study was to investigate the feasibility and medium-term effect of a low-fat diet with high (low GI) carbohydrates on weight loss, body composition changes and dietary compliance. Obese patients were recruited from two obesity outpatient clinics. Subjects were given advise by a dietician, then they attended biweekly for 1-hour group meetings. Bodyweight and body composition were measured at baseline and after 24 weeks. One hundred and nine (91%) patients completed the study; after 24 weeks the average weight loss was 8.9 kg (98.6 vs. 89.7 kg; p < or = 0.0001). There was a significant 15% decrease in fat mass (42.5 vs. 36.4 kg; p < or = 0.0001) and a decrease in lean body mass of 5% (56.1 vs. 53.3 kg; p < or = 0.0001). In this 6-month study, a low-fat, low-GI diet led to a significant reduction of fat mass; adherence to the diet was very good. Our results suggest that such a diet is feasible and should be evaluated in randomized controlled trials.

  16. Continuous methane record of abrupt climate change 10-68 ka: sighting Heinrich events in the ice core record

    NASA Astrophysics Data System (ADS)

    Rhodes, Rachael; Brook, Edward; Chiang, John; Blunier, Thomas; Cheng, Hai; Edwards, R. Lawrence; Maselli, Olivia; McConnell, Joseph; Romanini, Daniele; Severinghaus, Jeffrey; Sowers, Todd; Stowasser, Christopher

    2014-05-01

    The Last Glacial period was punctuated by millennial scale abrupt climate changes - Dansgaard-Oeschger (D-O) cycles and Heinrich events. Controls on the magnitude and frequency of these climate perturbations, and how they may be inter-related, remain unclear. Specific problems include the difficulty of dating Heinrich sediment layers and local bias of key paleoclimate archives. We present a highly detailed and precise record of ice core methane (CH4), a globally integrated signal, which resolves climatic features in unprecedented resolution. Abrupt CH4 increases are resolved in Heinrich Stadials (HS) 1, 2, 4 and 5 where, in contrast to all D-O cycles, there are no concurrent abrupt changes in Greenland temperature. Using modern-day tropical rainfall variability as an analog, we propose that strong cooling in the North Atlantic severely restricted the northerly range of the Intertropical Convergence Zone (ITCZ), leading to an enhanced wet season over Southern Hemisphere tropical land areas, and consequently driving production of excess CH4 in tropical wetlands. Our findings place four Heinrich events firmly within ice core chronologies and suggest maximum durations of 778 to 1606 yr. CH4 anomalies are only associated with Heinrich events of Hudson Strait provenance, indicating that the tropical impacts of Heinrich events were not uniform.

  17. Abrupt variations of Indian and East Asian summer monsoons during the last deglacial stadial and interstadial

    NASA Astrophysics Data System (ADS)

    Hong, Bing; Hong, Yetang; Uchida, Masao; Shibata, Yasuyuki; Cai, Cheng; Peng, Haijun; Zhu, Yongxuan; Wang, Yu; Yuan, Linggui

    2014-08-01

    The phase relationship between the Indian summer monsoon (ISM) and the East Asian summer monsoon (EASM) during the last deglaciation remains controversial. Here, we reconstruct a 15,000-year plant cellulose δ13C proxy record for the ISM from the Yuexi peat bog in southwestern China. The record shows that the ISM abruptly decreases during the Younger Dryas (YD) stadial and abruptly increases during the Bølling-Allerød (BA) interstadial. A comparison of the Yuexi record with other related proxy climate records reveals two types of phenomena. First, the strengths of the two Asian monsoons are inversely related during the YD stadial, i.e., the ISM strength decreases and the EASM increases. During this period, the southern Chinese mainland consisted of a wide arid zone while the northern Chinese mainland was much wetter. The arid zone in southern China resulted from two different types of monsoon processes: the abnormal northward extension of the EASM rain belt, leading to less rainfall in southeast China, or an illusion that the EASM weakened. The other process is a real weakening of the ISM. Second, during the BA interstadial, the strengths of both the ISM and EASM clearly increased. However, the maximum strengths appear to have occurred in the Allerød period. During this period, the entire Chinese mainland, both northern and southern, experienced wet conditions. The abnormal climate pattern of wet in the north and dry in the south during the YD stadial occurs because of the combined effects of the strengthened EASM, intensified westerlies, and weakened ISM, which could be attributed to the response to the abrupt cooling in the high northern latitudes and to the El Niño-like activity in the equatorial Pacific. The widespread wet climate during the BA interstadial may be related to an abrupt increase in the greenhouse gases (GHGs) concentrations in the atmosphere and to the La Niña-like activity in the equatorial Pacific. These results contribute to a better

  18. Tidal heating and mass loss in neutron star binaries - Implications for gamma-ray burst models

    NASA Technical Reports Server (NTRS)

    Meszaros, P.; Rees, M. J.

    1992-01-01

    A neutron star in a close binary orbit around another neutron star (or stellar-mass black hole) spirals inward owing to gravitational radiation. We discuss the effects of tidal dissipation during this process. Tidal energy dissipated in the neutron star's core escapes mainly as neutrinos, but heating of the crust, and outward diffusion of photons, blows off the outer layers of the star. This photon-driven mass loss precedes the final coalescence. The presence of this eject material impedes the escape of gamma-rays created via neutrino interactions. If an e(+) - e(-) fireball, created in the late stages of coalescence, were loaded with (or surrounded by) material with the mean column density of the ejecta, it could not be an efficient source of gamma-rays. Models for cosmologically distant gamma-rays burst that involve neutron stars must therefore be anisotropic, so that the fireball expands preferentially in directions where the column density of previously blown-off material is far below the spherically averaged value which we have calculated. Some possible 'scenarios' along these lines are briefly discussed.

  19. The Secret Lives of Cepheids: Evolution, Mass-Loss, and Ultraviolet Emission of the Long-period Classical Cepheid

    NASA Astrophysics Data System (ADS)

    Neilson, Hilding R.; Engle, Scott G.; Guinan, Edward F.; Bisol, Alexandra C.; Butterworth, Neil

    2016-06-01

    The classical Cepheid l Carinae is an essential calibrator of the Cepheid Leavitt Law as a rare long-period Galactic Cepheid. Understanding the properties of this star will also constrain the physics and evolution of massive (M ≥ 8 M ⊙) Cepheids. The challenge, however, is precisely measuring the star's pulsation period and its rate of period change. The former is important for calibrating the Leavitt Law and the latter for stellar evolution modeling. In this work, we combine previous time-series observations spanning more than a century with new observations to remeasure the pulsation period and compute the rate of period change. We compare our new rate of period change with stellar evolution models to measure the properties of l Car, but find models and observations are, at best, marginally consistent. The results imply that l Car does not have significantly enhanced mass-loss rates like that measured for δ Cephei. We find that the mass of l Car is about 8-10 M ⊙. We present Hubble Space Telescope Cosmic Origins Spectrograph observations that also differ from measurements for δ Cep and β Dor. These measurements further add to the challenge of understanding the physics of Cepheids, but do hint at the possible relation between enhanced mass-loss and ultraviolet emission, perhaps both due to the strength of shocks propagating in the atmospheres of Cepheids. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program #13019. This work is also based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and the USA (NASA), associated with program #060374.

  20. Loss from harlequin ducks of abdominally implanted radio transmitters equipped with percutaneous antennas

    USGS Publications Warehouse

    Mulcahy, D.M.; Esler, Daniel N.; Stoskopf, M.K.

    1999-01-01

    We documented extrusion and loss of abdominally implanted radio transmitters with percutaneous antennas from adult female Harlequin Ducks (Histrionicus histrionicus). Birds were captured during wing molt (late August to mid-September) in 1995-1997. Of 44 Harlequin Ducks implanted with radios and recaptured, 7 (16%) had lost their transmitters and 5 (11%) had radios in the process of extruding. Most (11 of 12) extrusions and losses occurred in birds implanted with radios in 1996 and recaptured in 1997. We suggest that transmitter extrusions and losses were due largely to changes in transmitter design made between 1095 and 1996. Transmitters implanted in 1996 were cylindrical rather than spherical, had a flat end with an abrupt edge, and the lower portion of the antenna was reinforced. Radio losses occurred after the 7-mo monitoring period and caused no apparent harm to the birds. Investigators using implanted radios with percutaneous antennas for long-term projects should be aware of the potential for radio extrusion and should minimize the problem by using transmitters that have no sharp edges and that are wide, rather than narrow.

  1. Less-than-expected weight loss in normal-weight women undergoing caloric restriction and exercise is accompanied by preservation of fat-free mass and metabolic adaptations.

    PubMed

    Koehler, K; De Souza, M J; Williams, N I

    2017-03-01

    Normal-weight women frequently restrict their caloric intake and exercise, but little is known about the effects on body weight, body composition and metabolic adaptations in this population. We conducted a secondary analysis of data from a randomized controlled trial in sedentary normal-weight women. Women were assigned to a severe energy deficit (SEV: -1062±80 kcal per day; n=9), a moderate energy deficit (MOD: -633±71 kcal per day; n=7) or energy balance (BAL; n=9) while exercising five times per week for 3 months. Outcome variables included changes in body weight, body composition, resting metabolic rate (RMR) and metabolic hormones associated with energy conservation. Weight loss occurred in SEV (-3.7±0.9 kg, P<0.001) and MOD (-2.7±0.8 kg; P=0.003), but weight loss was significantly less than predicted (SEV: -11.1±1.0 kg; MOD: -6.5±1.1 kg; both P<0.001 vs actual). Fat mass declined in SEV (P<0.001) and MOD (P=0.006), whereas fat-free mass remained unchanged in all groups (P>0.33). RMR decreased by -6±2% in MOD (P=0.020). In SEV, RMR did not change on a group level (P=0.66), but participants whose RMR declined lost more weight (P=0.020) and had a higher baseline RMR (P=0.026) than those whose RMR did not decrease. Characteristic changes in leptin (P=0.003), tri-iodothyronine (P=0.013), insulin-like growth factor-1 (P=0.016) and ghrelin (P=0.049) occurred only in SEV. The energy deficit and adaptive changes in RMR explained 54% of the observed weight loss. In normal-weight women, caloric restriction and exercise resulted in less-than-predicted weight loss. In contrast to previous literature, weight loss consisted almost exclusively of fat mass, whereas fat-free mass was preserved.

  2. Abrupt Greenland Ice Sheet runoff and sea water temperature changes since 1821, recorded by coralline algae

    NASA Astrophysics Data System (ADS)

    Kamenos, N.; Hoey, T.; Bedford, J.; Claverie, T.; Fallick, A. E.; Lamb, C. M.; Nienow, P. W.; O'Neill, S.; Shepherd, I.; Thormar, J.

    2012-12-01

    The Greenland Ice Sheet (GrIS) contains the largest store of fresh water in the northern hemisphere, equivalent to ~7.4m of eustatic sea level rise, but its impacts on current, past and future sea level, ocean circulation and European climate are poorly understood. Previous estimates of GrIS melt, from 26 years of satellite observations and temperature driven melt-models over 48 years, show a trend of increasing melt. There are however no runoff data of comparable duration with which to validate temperature-based runoff models, or relationships between the spatial extent of melt and runoff. Further, longer runoff records that extend GrIS melt records to centennial timescales will enable recently observed trends to be put into a better historical context. We measured Mg/Ca, δ18O and structural cell size in annual growth bands of red coralline algae to reconstruct: (1) near surface sea water temperature; and, (2) melt/runoff from the GrIS. (1) Temperature: we reconstructed the longest (1821-2009) sub-annual resolution record of water temperature in Disko Bugt (western Greenland) showing an abrupt change in temperature oscillation patterns during the 1920s which may be attributable to the interaction between atmospheric temperature and mass loss from Jakobshavn Isbrae glacier. (2) GrIS runoff: using samples from distal parts of Søndre Strømfjord we produced the first reconstruction of decadal (1939-2002) GrIS runoff. We observed significant negative relationships between historic runoff, relative salinity and marine summer temperature. Our reconstruction shows a trend of increasing reconstructed runoff since the mid 1980s. In situ summer marine temperatures followed a similar trend. We suggest that since 1939 atmospheric temperatures have been important in forcing runoff. Subject to locating in situ coralline algae samples, these methods can be applied across hundreds to thousands of years. These results show that our technique has significant potential to enhance

  3. Abrupt plate acceleration during rifted margin formation: Cause and effect

    NASA Astrophysics Data System (ADS)

    Brune, Sascha; Williams, Simon; Butterworth, Nathaniel; Müller, Dietmar

    2017-04-01

    Extension rate is known to control key processes during rifted margin formation such as crust-mantle coupling, decompression melting, magmatism, and serpentinisation. Here we build on recent advances in plate tectonic reconstructions by quantifying the extension velocity history of Earth's major rifted margins during the last 240 million years. We find that many successful rifts start with a slow phase of extension followed by rapid acceleration that introduces a fast phase. The transition from slow to fast rifting takes place long before crustal break-up: approximately half of the present day rifted margin area was created during the slow, and the other half during the fast rift phase. We reproduce the rapid transition from slow to fast extension using analytical and numerical modelling with constant force boundary conditions. In these models, rift velocities are not imposed but instead evolve naturally in response to the changing strength of the rift. Our results demonstrate that abrupt plate acceleration during continental rifting is controlled by a rift-intrinsic strength-velocity feedback. The abruptness of rift acceleration is thereby governed by the nonlinearity of lithospheric localization. Realistic brittle and power-law rheologies lead to a speed-up duration between two and ten million years. For successful rifts that generate a new ocean basin, the duration of rift speed-up is notably almost independent of the applied extensional force. Instead, the force controls the duration of the slow phase: higher forces shorten the slow phase while lower forces prolong it. If the force is too low, however, delocalisation processes prevent the rift from reaching the point of speed-up and produce a failed rift, even if the extensional system was active for many million years.

  4. Abrupt aridities in the Levant-Sahel linked with solar activities

    NASA Astrophysics Data System (ADS)

    Stein, M.; Kushnir, Y.

    2012-04-01

    Observations of 19th and 20th century precipitation in the Dead Sea watershed region display a multidecadal, anti-phase relationship to North Atlantic (NAtl) sea surface temperature (SST) variability, such that when the NAtl is relatively cold, Jerusalem experiences higher than normal precipitation and vice versa. This association is underlined by a negative correlation to precipitation in the sub-Saharan Sahel and a positive correlation to precipitation in western North America, areas that are also affected by multidecadal NAtl SST variability. These observations are consistent with broad range of Holocene hydroclimatic fluctuations from the epochal, to the millennial and centennial time scales, as displayed by the Dead Sea and Sahelian lake levels and by direct and indirect proxy indicators of NAtl SSTs. On the epochal time scale, the gradual cooling of NAtl SSTs throughout the Holocene in response to precession-driven reduction of summer insolation is associated with previously well-studied wet-to-dry transition in the Sahel and with a general increase in Dead Sea lake levels from low stands after the Younger Dryas to higher stands in the mid- to late-Holocene. On the millennial and centennial time scales there is also evidence for an antiphase relationship between Holocene variations in the Dead Sea and Sahelian lake levels and with proxy indicators of NAtl SSTs. However, the records are punctuated by abrupt lake-level drops and extensive expansion of the desert belt at ~8.1, 5.7, 3.3 and 1.4 ka cal BP, which appear to be in-phase and which occur during previously documented abrupt major cooling events in the Northern Hemisphere. We link these cooling to solar activity variations that were identified in the North Atlantic IRD and cosmogenic isotopes records.

  5. Zoledronate prevents lactation induced bone loss and results in additional post-lactation bone mass in mice.

    PubMed

    Wendelboe, Mette Høegh; Thomsen, Jesper Skovhus; Henriksen, Kim; Vegger, Jens Bay; Brüel, Annemarie

    2016-06-01

    In rodents, lactation is associated with a considerable and very rapid bone loss, which almost completely recovers after weaning. The aim of the present study was to investigate whether the bisphosphonate Zoledronate (Zln) can inhibit lactation induced bone loss, and if Zln interferes with recovery of bone mass after lactation has ceased. Seventy-six 10-weeks-old NMRI mice were divided into the following groups: Baseline, Pregnant, Lactation, Lactation+Zln, Recovery, Recovery+Zln, and Virgin Control (age-matched). The lactation period was 12days, then the pups were removed, and thereafter recovery took place for 28days. Zln, 100μg/kg, was given s.c. on the day of delivery, and again 4 and 8days later. Mechanical testing, μCT, and dynamic histomorphometry were performed. At L4, lactation resulted in a substantial loss of bone strength (-55% vs. Pregnant, p<0.01), BV/TV (-40% vs. Pregnant, p<0.01), and trabecular thickness (Tb.Th) (-29% vs. Pregnant, p<0.001). Treatment with Zln completely prevented lactation induced loss of bone strength, BV/TV, and Tb.Th at L4. Full recovery of micro-architectural and mechanical properties was found 28days after weaning in vehicle-treated mice. Interestingly, the recovery group treated with Zln during the lactation period had higher BV/TV (+45%, p<0.01) and Tb.Th (+16%, p<0.05) compared with virgin controls. Similar results were found at the proximal tibia and femur. This indicates that Zln did not interfere with the bone formation taking place after weaning. On this background, we conclude that post-lactation bone formation is not dependent on a preceding lactation induced bone loss. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. Body mass index and bone loss among postmenopausal women: the 10-year follow-up of the OSTPRE cohort.

    PubMed

    Saarelainen, Jarmo; Kiviniemi, Vesa; Kröger, Heikki; Tuppurainen, Marjo; Niskanen, Leo; Jurvelin, Jukka; Honkanen, Risto

    2012-03-01

    Obesity protects against osteoporosis, but the magnitude of this association has been difficult to assess from cross-sectional or short term studies. We examined the time course of bone loss as a function of body mass index (BMI) in early and late postmenopausal women. Our study population (n = 300) was a random sample of the population-based Kuopio Osteoporosis Risk Factor and Prevention (OSTPRE) Study, Finland. We excluded women without complete BMD results, premenopausal women during the second bone densitometry and women who had used hormone replacement therapy, bisphosphonates or calcitonin. BMI along with femoral neck and spinal bone mineral density (BMD) were assessed three times by dual-energy X-ray absorptiometry during a mean follow-up of 10.5 years (SD 0.5). The mean baseline age was 53.6 years (SD 2.8), time since menopause 2.9 years (SD 4.3) and BMI 27.3 kg/m(2) (SD 4.4). The data was analyzed by linear mixed models. Thus, we were able to approximate the bone loss up to 20 postmenopausal years. To illustrate, a woman with a baseline BMI of 20 kg/m(2) became osteopenic 2 (spine) and 4 (femoral neck) years after menopause, while obesity (BMI of 30 kg/m(2)) delayed the incidence of osteopenia by 5 (spine) and 9 (femoral neck) years, respectively. The delay was due to high baseline BMD of the obese, while bone loss rate was similar for both lean and obese subjects. This lean versus obese difference may also be partly due to altered X-ray attenuation due to fat mass.

  7. Estimation of soil loss by water erosion in the Chinese Loess Plateau using Universal Soil Loss Equation and GRACE

    NASA Astrophysics Data System (ADS)

    Schnitzer, S.; Seitz, F.; Eicker, A.; Güntner, A.; Wattenbach, M.; Menzel, A.

    2013-06-01

    For the estimation of soil loss by erosion in the strongly affected Chinese Loess Plateau we applied the Universal Soil Loss Equation (USLE) using a number of input data sets (monthly precipitation, soil types, digital elevation model, land cover and soil conservation measures). Calculations were performed in ArcGIS and SAGA. The large-scale soil erosion in the Loess Plateau results in a strong non-hydrological mass change. In order to investigate whether the resulting mass change from USLE may be validated by the gravity field satellite mission GRACE (Gravity Recovery and Climate Experiment), we processed different GRACE level-2 products (ITG, GFZ and CSR). The mass variations estimated in the GRACE trend were relatively close to the observed sediment yield data of the Yellow River. However, the soil losses resulting from two USLE parameterizations were comparatively high since USLE does not consider the sediment delivery ratio. Most eroded soil stays in the study area and only a fraction is exported by the Yellow River. Thus, the resultant mass loss appears to be too small to be resolved by GRACE.

  8. The abrupt changes in the yellowed fibril density in the Linen of Turin

    NASA Astrophysics Data System (ADS)

    Curciarello, F.; De Leo, V.; Fazio, G.; Mandaglio, G.

    2012-03-01

    The present investigation is an attempt to explain the abrupt changes in the yellowed fibril density (or image intensity) values in the dorsal part of the Shroud of Turin body image. The interested areas are the ones at the base of the shoulders and the buttocks. These rapid changes in the body image intensity are not anomalies of the linen manufacture. They can be explained with the original presence of aromas and/or burial ointments.

  9. Difficulty accepting lifestyle limitations after the abrupt onset of end-stage renal disease.

    PubMed

    Wolfson, M; Strong, C; Hamel, K; Cummings-Cosgrove, M; Brown, R

    1995-07-01

    Adjustment to the lifestyle changes imposed by end-stage renal disease is particularly difficult when the onset is abrupt and unheralded. A case of atheroembolism is presented in which living situation, dietary compliance, and family involvement are particularly problematic for the dialysis staff. Discussion by team members focuses on the evolution of a reasonable disposition through diligence and persistence, recognizing the need to compromise medical indications with individual lifestyle and available family support.

  10. Mass-loss From Evolved Stellar Populations In The Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Riebel, David

    2012-01-01

    I have conducted a study of a sample of 30,000 evolved stars in the Large Magellanic Cloud (LMC) and 6,000 in the Small Magellanic Cloud (SMC), covering their variability, mass-loss properties, and chemistry. The initial stages of of my thesis work focused on the infrared variability of Asymptotic Giant Branch (AGB) stars in the LMC. I determined the period-luminosity (P-L) relations for 6 separate sequences of 30,000 evolved star candidates at 8 wavelengths, as a function of photometrically assigned chemistry, and showed that the P-L relations are different for different chemical populations (O-rich or C-rich). I also present results from the Grid of Red supergiant and Asymptotic giant branch star ModelS (GRAMS) radiative transfer (RT) model grid applied to the evolved stellar population of the LMC. GRAMS is a pre-computed grid of RT models of RSG and AGB stars and surrounding circumstellar dust. Best-fit models are determined based on 12 bands of photometry from the optical to the mid-infrared. Using a pre-computed grid, I can present the first reasonably detailed radiative transfer modeling for tens of thousands of stars, allowing me to make statistically accurate estimations of the carbon-star luminosity function and the global dust mass return to the interstellar medium from AGB stars, both key parameters for stellar population synthesis models to reproduce. In the SAGE-Var program, I used the warm Spitzer mission to take 4 additional epochs of observations of 7500 AGB stars in the LMC and SMC. These epochs, combined with existing data, enable me to derive mean fluxes at 3.6 and 4.5 microns, that will be used for tighter constraints for GRAMS, which is currently limited by the variability induced error on the photometry. This work is support by NASA NAG5-12595 and Spitzer contract 1415784.

  11. Oceanic link between abrupt changes in the North Atlantic Ocean and the African monsoon

    NASA Astrophysics Data System (ADS)

    Chang, Ping; Zhang, Rong; Hazeleger, Wilco; Wen, Caihong; Wan, Xiuquan; Ji, Link; Haarsma, Reindert J.; Breugem, Wim-Paul; Seidel, Howard

    2008-07-01

    Abrupt changes in the African monsoon can have pronounced socioeconomic impacts on many West African countries. Evidence for both prolonged humid periods and monsoon failures have been identified throughout the late Pleistocene and early Holocene epochs. In particular, drought conditions in West Africa have occurred during periods of reduced North Atlantic thermohaline circulation, such as the Younger Dryas cold event. Here, we use an ocean-atmosphere general circulation model to examine the link between oceanographic changes in the North Atlantic Ocean and changes in the strength of the African monsoon. Our simulations show that when North Atlantic thermohaline circulation is substantially weakened, the flow of the subsurface North Brazil Current reverses. This leads to decreased upper tropical ocean stratification and warmer sea surface temperatures in the equatorial South Atlantic Ocean, and consequently reduces African summer monsoonal winds and rainfall over West Africa. This mechanism is in agreement with reconstructions of past climate. We therefore suggest that the interaction between thermohaline circulation in the North Atlantic Ocean and wind-driven currents in the tropical Atlantic Ocean contributes to the rapidity of African monsoon transitions during abrupt climate change events.

  12. Abrupt Holocene climate change as an important factor for human migration in West Greenland

    PubMed Central

    D’Andrea, William J.; Huang, Yongsong; Fritz, Sherilyn C.; Anderson, N. John

    2011-01-01

    West Greenland has had multiple episodes of human colonization and cultural transitions over the past 4,500 y. However, the explanations for these large-scale human migrations are varied, including climatic factors, resistance to adaptation, economic marginalization, mercantile exploration, and hostile neighborhood interactions. Evaluating the potential role of climate change is complicated by the lack of quantitative paleoclimate reconstructions near settlement areas and by the relative stability of Holocene temperature derived from ice cores atop the Greenland ice sheet. Here we present high-resolution records of temperature over the past 5,600 y based on alkenone unsaturation in sediments of two lakes in West Greenland. We find that major temperature changes in the past 4,500 y occurred abruptly (within decades), and were coeval in timing with the archaeological records of settlement and abandonment of the Saqqaq, Dorset, and Norse cultures, which suggests that abrupt temperature changes profoundly impacted human civilization in the region. Temperature variations in West Greenland display an antiphased relationship to temperature changes in Ireland over centennial to millennial timescales, resembling the interannual to multidecadal temperature seesaw associated with the North Atlantic Oscillation. PMID:21628586

  13. Late Frasnian mass extinction: Conodont event stratigraphy, global changes, and possible causes

    NASA Technical Reports Server (NTRS)

    Sandberg, Charles A.; Ziegler, Willi; Dreesen, Roland; Butler, Jamie L.

    1988-01-01

    Several abrupt changes in conodont biofacies are documented to occur synchronously at six primary control sections across the Frasnian-Famennian boundary in Euramerica. These changes occurred within a time-span of only about 100,000 years near the end of the latest Frasnian linguiformis Zone, which is formally named to replace the Uppermost gigas Zone. The conodont-biofacies changes are interpreted to reflect a eustatic rise followed by an abrupt eustatic fall immediately preceding the late Frasnian mass extinction. Two new conodont species are named and described. Ancyrognathus ubiquitus n.sp. is recorded only just below and above the level of late Frasnian extinction and hence is a global marker for that event. Palmatolepispraetriangularis n.sp. is the long-sought Frasnian ancestor of the formerly cryptogenic species, Pa. triangularis, indicator of the earliest Famennian Lower triangularis Zone. The actual extinction event occurred entirely within the Frasnian and is interpreted to have been of brief duration-from as long as 20,000 years to as short as several days. The eustatic rise-and-fall couplet associated with the late Frasnian mass extinction is similar to eustatic couplets associated with the demise of most Frasnian (F2h) reefs worldwide about 1 m.y. earlier and with a latest Famennian mass extinction about 9.5 m.y. later. All these events may be directly or indirectly attributable to extraterrestrial triggering mechanisms. An impact of a small bolide or a near miss of a larger bolide may have caused the earlier demise of Frasnian reefs. An impact of possibly the same larger bolide in the Southern Hemisphere would explain the late Frasnian mass extinction. Global regression during the Famennian probably resulted from Southern-Hemisphere glaciation triggered by the latest Frasnian impact. Glaciation probably was the indirect cause of the latest Famennian mass extinction.

  14. Controlling abruptly autofocusing vortex beams to mitigate crosstalk and vortex splitting in free-space optical communication.

    PubMed

    Yan, Xu; Guo, Lixin; Cheng, Mingjian; Li, Jiangting

    2018-05-14

    Orbital angular momentum (OAM) mode crosstalk induced by atmospheric turbulence is a challenging phenomenon commonly occurring in OAM-based free-space optical (FSO) communication. Recent advances have facilitated new practicable methods using abruptly autofocusing light beams for weakening the turbulence effect on the FSO link. In this work, we show that a circular phase-locked Airy vortex beam array (AVBA) with sufficient elements has the inherent ability to form an abruptly autofocusing light beam carrying OAM, and its focusing properties can be controlled on demand by adjusting the topological charge values and locations of these vortices embedded in the array elements. The performance of a tailored Airy vortex beam array (TAVBA) through atmospheric turbulence is numerically studied. In a comparison with the ring Airy vortex beam (RAVB), the results indicate that TAVBA can be a superior light source for effectively reducing the intermodal crosstalk and vortex splitting, thus leading to improvement in the FSO system performance.

  15. The role of diet and exercise for the maintenance of fat-free mass and resting metabolic rate during weight loss.

    PubMed

    Stiegler, Petra; Cunliffe, Adam

    2006-01-01

    The incidence of obesity is increasing rapidly. Research efforts for effective treatment strategies still focus on diet and exercise programmes, the individual components of which have been investigated in intervention trials in order to determine the most effective recommendations for sustained changes in bodyweight. The foremost objective of a weight-loss trial has to be the reduction in body fat leading to a decrease in risk factors for metabolic syndrome. However, a concomitant decline in lean tissue can frequently be observed. Given that fat-free mass (FFM) represents a key determinant of the magnitude of resting metabolic rate (RMR), it follows that a decrease in lean tissue could hinder the progress of weight loss. Therefore, with respect to long-term effectiveness of weight-loss programmes, the loss of fat mass while maintaining FFM and RMR seems desirable. Diet intervention studies suggest spontaneous losses in bodyweight following low-fat diets, and current data on a reduction of the carbohydrate-to-protein ratio of the diet show promising outcomes. Exercise training is associated with an increase in energy expenditure, thus promoting changes in body composition and bodyweight while keeping dietary intake constant. The advantages of strength training may have greater implications than initially proposed with respect to decreasing percentage body fat and sustaining FFM. Research to date suggests that the addition of exercise programmes to dietary restriction can promote more favourable changes in body composition than diet or physical activity on its own. Moreover, recent research indicates that the macronutrient content of the energy-restricted diet may influence body compositional alterations following exercise regimens. Protein emerges as an important factor for the maintenance of or increase in FFM induced by exercise training. Changes in RMR can only partly be accounted for by alterations in respiring tissues, and other yet-undefined mechanisms have

  16. Impacts of abrupt climate changes in the Levant from Last Glacial Dead Sea levels

    NASA Astrophysics Data System (ADS)

    Torfstein, Adi; Goldstein, Steven L.; Stein, Mordechai; Enzel, Yehouda

    2013-06-01

    A new, detailed lake level curve for Lake Lisan (the Last Glacial Dead Sea) reveals a high frequency of abrupt fluctuations during Marine Isotope Stage 3 (MIS3) compared to the relatively high stand characterizing MIS2, and the significantly lower Holocene lake. The lake level fluctuations reflect the hydrological conditions in the large watershed of the lake, which in turn reflects the hydro-climatic conditions in the central Levant region. The new curve shows that the fluctuations coincide on millennial timescales with temperature variations recorded in Greenland. Four patterns of correlation are observed through the last ice age: (1) maximum lake elevations were reached during MIS2, the coldest interval; (2) abrupt lake level drops to the lowest elevations coincided with the occurrence of Heinrich (H) events; (3) the lake returned to higher-stand conditions along with warming in Greenland that followed H-events; (4) significant lake level fluctuations coincided with virtually every Greenland stadial-interstadial cycle. Over glacial-interglacial time-scales, Northern Hemisphere glacial cooling induces extreme wetness in the Levant, with high lake levels reaching ˜160 m below mean sea level (mbmsl), approximately 240 m above typical Holocene levels of ˜400 mbmsl. These orbital time-scale shifts are driven by expansions of the European ice sheet, which deflect westerly storm tracks southward to the Eastern Mediterranean, resulting in increased sea-air temperature gradients that invoke increased cyclogenesis, and enhanced moisture delivery to the Levant. The millennial-scale lake level drops associated with Greenland stadials are most extreme during Heinrich stadials and reflect abrupt cooling of the Eastern Mediterranean atmosphere and sea-surface, which weaken the cyclogenic rain engine and cause extreme Levant droughts. During the recovery from the effect of Heinrich stadials, the regional climate configuration resumed typical glacial conditions, with enhanced

  17. Effects of Early, Abrupt Weaning on HIV-free Survival of Children in Zambia

    PubMed Central

    Kuhn, Louise; Aldrovandi, Grace M.; Sinkala, Moses; Kankasa, Chipepo; Semrau, Katherine; Mwiya, Mwiya; Kasonde, Prisca; Scott, Nancy; Vwalika, Cheswa; Walter, Jan; Bulterys, Marc; Tsai, Wei-Yann; Thea, Donald M.

    2008-01-01

    Background In low-resource settings, many programs recommend that women who are infected with the human immunodeficiency virus (HIV) stop breast-feeding early. We conducted a randomized trial to evaluate whether abrupt weaning at 4 months as compared with the standard practice has a net benefit for HIV-free survival of children. Methods We enrolled 958 HIV-infected women and their infants in Lusaka, Zambia. All the women planned to breast-feed exclusively to 4 months; 481 were randomly assigned to a counseling program that encouraged abrupt weaning at 4 months, and 477 to a program that encouraged continued breast-feeding for as long as the women chose. The primary outcome was either HIV infection or death of the child by 24 months. Results In the intervention group, 69.0% of the mothers stopped breast-feeding at 5 months or earlier; 68.8% of these women reported the completion of weaning in less than 2 days. In the control group, the median duration of breast-feeding was 16 months. In the overall cohort, there was no significant difference between the groups in the rate of HIV-free survival among the children; 68.4% and 64.0% survived to 24 months without HIV infection in the intervention and control groups, respectively (P = 0.13). Among infants who were still being breast-fed and were not infected with HIV at 4 months, there was no significant difference between the groups in HIV-free survival at 24 months (83.9% and 80.7% in the intervention and control groups, respectively; P = 0.27). Children who were infected with HIV by 4 months had a higher mortality by 24 months if they had been assigned to the intervention group than if they had been assigned to the control group (73.6% vs. 54.8%, P = 0.007). Conclusions Early, abrupt cessation of breast-feeding by HIV-infected women in a low-resource setting, such as Lusaka, Zambia, does not improve the rate of HIV-free survival among children born to HIV-infected mothers and is harmful to HIV-infected infants

  18. Heavy quark energy loss in nuclear medium

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Benr-Wei; Wang, Enke; Wang, Xin-Nian

    2003-09-16

    Multiple scattering, modified fragmentation functions and radiative energy loss of a heavy quark propagating in a nuclear medium are investigated in perturbative QCD. Because of the quark mass dependence of the gluon formation time, the medium size dependence of heavy quark energy loss is found to change from a linear to a quadratic form when the initial energy and momentum scale are increased relative to the quark mass. The radiative energy loss is also significantly suppressed relative to a light quark due to the suppression of collinear gluon emission by a heavy quark.

  19. Abrupt Increases in Amazonian Tree Mortality Due to Drought-Fire Interactions

    NASA Technical Reports Server (NTRS)

    Brando, Paulo Monteiro; Balch, Jennifer K.; Nepstad, Daniel C.; Morton, Douglas C.; Putz, Francis E.; Coe, Michael T.; Silverio, Divino; Macedo, Marcia N.; Davidson, Eric A.; Nobrega, Caroline C.; hide

    2014-01-01

    Interactions between climate and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather events could accelerate this degradation by abruptly increasing tree mortality, but this process remains poorly understood. Here we present, to our knowledge, the first field-based evidence of a tipping point in Amazon forests due to altered fire regimes. Based on results of a large-scale, longterm experiment with annual and triennial burn regimes (B1yr and B3yr, respectively) in the Amazon, we found abrupt increases in fire-induced tree mortality (226 and 462%) during a severe drought event, when fuel loads and air temperatures were substantially higher and relative humidity was lower than long-term averages. This threshold mortality response had a cascading effect, causing sharp declines in canopy cover (23 and 31%) and aboveground live biomass (12 and 30%) and favoring widespread invasion by flammable grasses across the forest edge area (80 and 63%), where fires were most intense (e.g., 220 and 820 kW x m(exp -1)). During the droughts of 2007 and 2010, regional forest fires burned 12 and 5% of southeastern Amazon forests, respectively, compared with less than 1% in nondrought years. These results show that a few extreme drought events, coupled with forest fragmentation and anthropogenic ignition sources, are already causing widespread fire-induced tree mortality and forest degradation across southeastern Amazon forests. Future projections of vegetation responses to climate change across drier portions of the Amazon require more than simulation of global climate forcing alone and must also include interactions of extreme weather events, fire, and land-use change.

  20. Abrupt increases in Amazonian tree mortality due to drought-fire interactions.

    PubMed

    Brando, Paulo Monteiro; Balch, Jennifer K; Nepstad, Daniel C; Morton, Douglas C; Putz, Francis E; Coe, Michael T; Silvério, Divino; Macedo, Marcia N; Davidson, Eric A; Nóbrega, Caroline C; Alencar, Ane; Soares-Filho, Britaldo S

    2014-04-29

    Interactions between climate and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather events could accelerate this degradation by abruptly increasing tree mortality, but this process remains poorly understood. Here we present, to our knowledge, the first field-based evidence of a tipping point in Amazon forests due to altered fire regimes. Based on results of a large-scale, long-term experiment with annual and triennial burn regimes (B1yr and B3yr, respectively) in the Amazon, we found abrupt increases in fire-induced tree mortality (226 and 462%) during a severe drought event, when fuel loads and air temperatures were substantially higher and relative humidity was lower than long-term averages. This threshold mortality response had a cascading effect, causing sharp declines in canopy cover (23 and 31%) and aboveground live biomass (12 and 30%) and favoring widespread invasion by flammable grasses across the forest edge area (80 and 63%), where fires were most intense (e.g., 220 and 820 kW ⋅ m(-1)). During the droughts of 2007 and 2010, regional forest fires burned 12 and 5% of southeastern Amazon forests, respectively, compared with <1% in nondrought years. These results show that a few extreme drought events, coupled with forest fragmentation and anthropogenic ignition sources, are already causing widespread fire-induced tree mortality and forest degradation across southeastern Amazon forests. Future projections of vegetation responses to climate change across drier portions of the Amazon require more than simulation of global climate forcing alone and must also include interactions of extreme weather events, fire, and land-use change.